Python 說明文件內容

Python 有什麼新功能？

Python 3.14 有什麼新功能

發布重點摘要

新增功能

PEP 649 & PEP 749: Deferred evaluation of annotations

PEP 734: Multiple interpreters in the standard library

PEP 750: Template string literals

PEP 768: Safe external debugger interface

A new type of interpreter

Free-threaded mode improvements

改善錯誤訊息

PEP 784：標準函式庫中的 Zstandard 支援

Asyncio introspection capabilities

Concurrent safe warnings control

其他語言更動

Built-ins

命令列與環境

PEP 758: Allow except and except* expressions without brackets

PEP 765: Control flow in finally blocks

Incremental garbage collection

Default interactive shell

新增模組

改進的模組

argparse

ast

asyncio

calendar

concurrent.futures

configparser

contextvars

ctypes

curses

datetime

decimal

difflib

dis

errno

faulthandler

fnmatch

fractions

functools

getopt

getpass

graphlib

heapq

hmac

http

imaplib

inspect

io

json

linecache

logging.handlers

math

mimetypes

multiprocessing

operator

os

os.path

pathlib

pdb

pickle

platform

pydoc

re

socket

ssl

struct

symtable

sys

sys.monitoring

sysconfig

tarfile

threading

tkinter

turtle

types

typing

unicodedata

unittest

urllib

uuid

webbrowser

zipfile

最佳化

asyncio

base64

bdb

difflib

gc

io

pathlib

pdb

textwrap

uuid

zlib

已移除

argparse

ast

asyncio

email

importlib.abc

itertools

pathlib

pkgutil

pty

sqlite3

urllib

已棄用

New deprecations

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

Python 3.17 中待移除的項目

Python 3.18 中待移除的項目

Python 3.19 中待移除的項目

未來版本中的待移除項目

CPython 位元組碼變更

Pseudo-instructions

C API 變更

Python 配置 C API

C API 中的新功能

Limited C API changes

被移除的 C API

已棄用的 C API

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

Python 3.18 中待移除的項目

未來版本中的待移除項目

建置變更

build-details.json

Discontinuation of PGP signatures

Free-threaded Python is officially supported

Binary releases for the experimental just-in-time compiler

移植至 Python 3.14

Python API 的變更

Changes in annotations (PEP 649 and PEP 749)

Implications for annotated code

Implications for readers of __annotations__

Related changes

from __future__ import annotations

C API 中的改動

Python 3.14.1 中顯著的變更

Python 3.13 有什麼新功能

發布重點摘要

新增功能

A better interactive interpreter

改善錯誤訊息

Free-threaded CPython

An experimental just-in-time (JIT) compiler

Defined mutation semantics for locals()

對行動平台的支援

其他語言更動

新增模組

改進的模組

argparse

array

ast

asyncio

base64

compileall

concurrent.futures

configparser

copy

ctypes

dbm

dis

doctest

email

enum

fractions

glob

importlib

io

ipaddress

itertools

marshal

math

mimetypes

mmap

multiprocessing

os

os.path

pathlib

pdb

queue

random

re

shutil

site

sqlite3

ssl

statistics

subprocess

sys

tempfile

time

tkinter

traceback

types

typing

unicodedata

venv

warnings

xml

zipimport

最佳化

被移除的模組和 API

PEP 594：從標準函式庫中移除「用完的電池」

2to3

builtins

configparser

importlib.metadata

locale

opcode

optparse

pathlib

re

tkinter.tix

turtle

typing

unittest

urllib

webbrowser

New Deprecations

Python 3.14 中待移除的項目

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

Python 3.17 中待移除的項目

Python 3.18 中待移除的項目

Python 3.19 中待移除的項目

未來版本中的待移除項目

CPython 位元組碼變更

C API 變更

新增功能

Changed C APIs

Limited C API Changes

移除的 C API

器用的 C API

Python 3.14 中待移除的項目

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

Python 3.18 中待移除的項目

未來版本中的待移除項目

建置變更

移植至 Python 3.13

Python API 的變更

C API 中的改動

迴歸測試的變更

Python 3.12 有什麼新功能

發布重點摘要

新增功能

PEP 695：型別參數語法

PEP 701: Syntactic formalization of f-strings

PEP 684：直譯器各別持有的 GIL

PEP 669: Low impact monitoring for CPython

PEP 688：使緩衝區協定可在 Python 中存取

PEP 709: Comprehension inlining

改善錯誤訊息

型別提示相關的新特性

PEP 692: Using TypedDict for more precise **kwargs typing

PEP 698：覆蓋靜態型別的裝飾器

其他語言更動

新增模組

改進的模組

array

asyncio

calendar

csv

dis

fractions

importlib.resources

inspect

itertools

math

os

os.path

pathlib

platform

pdb

random

shutil

sqlite3

statistics

sys

tempfile

threading

tkinter

tokenize

types

typing

unicodedata

unittest

uuid

最佳化

CPython 位元組碼變更

Demos and Tools

已棄用

Python 3.13 中待移除的項目

Python 3.14 中待移除的項目

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

Python 3.17 中待移除的項目

未來版本中的待移除項目

已移除

asynchat 和 asyncore

configparser

distutils

ensurepip

enum

ftplib

gzip

hashlib

importlib

imp

io

locale

smtpd

sqlite3

ssl

unittest

webbrowser

xml.etree.ElementTree

zipimport

其他

移植至 Python 3.12

Python API 的變更

建置變更

C API 變更

新增功能

移植至 Python 3.12

已棄用

Python 3.14 中待移除的項目

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

未來版本中的待移除項目

已移除

Python 3.11 有什麼新功能

發布重點摘要

新增功能

PEP 657：回溯 (traceback) 中更細緻的錯誤位置

PEP 654：例外群組與 except*

PEP 678：運用例外註解使其更加詳盡

Windows py.exe 啟動程式 (launcher) 的改進

型別提示相關的新特性

PEP 646：可變參數泛型 (variadic generics)

PEP 655：標記獨立 TypedDict 項目為必要或不必要

PEP 673：Self 型別

PEP 675：任意的文本字串型別 (Arbitrary literal string type)

PEP 681：資料類別轉換 (Data class transforms)

PEP 563 可能不是未來

其他語言更動

其他 CPython 實作更動

新增模組

改進的模組

asyncio

contextlib

dataclasses

datetime

enum

fcntl

fractions

functools

gzip

hashlib

IDLE 和 idlelib

inspect

locale

logging

math

operator

os

pathlib

re

shutil

socket

sqlite3

string

sys

sysconfig

tempfile

threading

time

tkinter

traceback

typing

unicodedata

unittest

venv

warnings

zipfile

最佳化

更快的 CPython

更快的啟動

凍結引入 (Frozen imports) / 靜態程式碼物件 (Static code objects)

更快的運行程式

所需資源更少 (cheaper) 且惰性的 (lazy)) Python 幀 (frame)

行內 Python 函式呼叫

PEP 659：特化的適應性直譯器

雜項

FAQ

我該如何在程式碼中取得這些加速？

Python 3.11 會不會使用更多記憶體？

我在我的程式當中沒感覺到任何加速，為什麼？

有用到 JIT 編譯器嗎？

關於

CPython 位元組碼變更

新增 opcode

被取代的操作碼 (opcode)

有更動/被移除的 opcode

已棄用

語言/內建

模組

標準函式庫

Python 3.12 中待決議的移除項目

已移除

移植至 Python 3.11

建置變更

C API 變更

新增功能

移植至 Python 3.11

已棄用

Python 3.12 中待決議的移除項目

已移除

Python 3.11.4 中顯著的變更

tarfile

Python 3.11.5 中顯著的變更

OpenSSL

Python 3.10 有什麼新功能

發布重點摘要

新增功能

帶括號的情境管理器

更好的錯誤訊息

SyntaxErrors

IndentationErrors

AttributeErrors

NameErrors

PEP 626：用於除錯和其他工具的精確列號

PEP 634：結構模式匹配

語法和操作

宣告式方法 (Declarative approach)

簡單模式：與字面值匹配

沒有萬用字元 (wildcard) 的行為

具有字面值和變數的模式

模式和類別

具有位置參數的模式

巢狀模式

複雜模式和萬用字元

Guard

其他主要功能

可選的 EncodingWarning 和 encoding="locale" 選項

與型別提示相關的新功能

PEP 604：新型聯集運算子

PEP 612：參數規範變數

PEP 613：型別別名 (TypeAlias)

PEP 647：使用者定義的型別防護

其他語言更動

新模組

改進的模組

asyncio

argparse

array

asynchat, asyncore, smtpd

base64

bdb

bisect

codecs

collections.abc

contextlib

curses

dataclasses

__slots__

僅限關鍵字欄位 (Keyword-only fields)

distutils

doctest

encodings

enum

fileinput

faulthandler

gc

glob

hashlib

hmac

IDLE 和 idlelib

importlib.metadata

inspect

itertools

linecache

os

os.path

pathlib

platform

pprint

py_compile

pyclbr

shelve

statistics

site

socket

ssl

sqlite3

sys

_thread

threading

traceback

types

typing

unittest

urllib.parse

xml

zipimport

最佳化

已棄用

已刪除

移植到 Python 3.10

Python 語法的變化

Python API 的變更

C API 中的改動

CPython 位元組碼變更

建置變更

C API 變更

PEP 652：維護穩定 ABI

新增功能

移植到 Python 3.10

已棄用

已刪除

Python 3.10.7 中顯著的安全性功能

Python 3.10.8 中顯著的安全性功能

Python 3.10.12 中顯著的變更

tarfile

Python 3.9 有什麼新功能

發布重點摘要

You should check for DeprecationWarning in your code

新增功能

Dictionary Merge & Update Operators

New String Methods to Remove Prefixes and Suffixes

Type Hinting Generics in Standard Collections

新型剖析器

其他語言更動

新模組

zoneinfo

graphlib

改進的模組

ast

asyncio

compileall

concurrent.futures

curses

datetime

distutils

fcntl

ftplib

gc

hashlib

http

IDLE 和 idlelib

imaplib

importlib

inspect

ipaddress

math

multiprocessing

nntplib

os

pathlib

pdb

poplib

pprint

pydoc

random

signal

smtplib

socket

time

sys

tracemalloc

typing

unicodedata

venv

xml

最佳化

已棄用

已移除

移植至 Python 3.9

Python API 的變更

C API 中的改動

CPython 位元組碼變更

建置變更

C API 變更

新增功能

移植至 Python 3.9

已移除

Python 3.9.1 中顯著的變更

typing

macOS 11.0 (Big Sur) and Apple Silicon Mac support

Python 3.9.2 中顯著的變更

collections.abc

urllib.parse

Python 3.9.3 中顯著的變更

Python 3.9.5 中顯著的變更

urllib.parse

Python 3.9.14 中顯著的安全性功能

Python 3.9.17 中顯著的變更

tarfile

Python 3.8 有什麼新功能

發布重點摘要

新增功能

Assignment expressions

Positional-only parameters

Parallel filesystem cache for compiled bytecode files

Debug build uses the same ABI as release build

f-strings support = for self-documenting expressions and debugging

PEP 578: Python Runtime Audit Hooks

PEP 587: Python Initialization Configuration

PEP 590: Vectorcall: a fast calling protocol for CPython

Pickle protocol 5 with out-of-band data buffers

其他語言更動

新增模組

改進的模組

ast

asyncio

builtins（內建）

collections

cProfile

csv

curses

ctypes

datetime

functools

gc

gettext

gzip

IDLE 和 idlelib

inspect

io

itertools

json.tool

logging

math

mmap

multiprocessing

os

os.path

pathlib

pickle

plistlib

pprint

py_compile

shlex

shutil

socket

ssl

statistics

sys

tarfile

threading

tokenize

tkinter

time

typing

unicodedata

unittest

venv

weakref

xml

xmlrpc

最佳化

建置和 C API 變更

已棄用

API 與功能的移除

移植至 Python 3.8

Python 行為的改變

Python API 的變更

C API 中的改動

CPython 位元組碼變更

Demos and Tools

Python 3.8.1 中顯著的變更

Python 3.8.2 中顯著的變更

Python 3.8.3 中顯著的變更

Python 3.8.8 中顯著的變更

Python 3.8.9 中顯著的變更

Python 3.8.10 中顯著的變更

macOS 11.0 (Big Sur) and Apple Silicon Mac support

Python 3.8.10 中顯著的變更

urllib.parse

Python 3.8.12 中顯著的變更

Python API 的變更

Python 3.8.14 中顯著的安全性功能

Python 3.8.17 中顯著的變更

tarfile

Python 3.7 有什麼新功能

發布重點摘要

新增功能

PEP 563：延後評估註釋

PEP 538: Legacy C Locale Coercion

PEP 540: Forced UTF-8 Runtime Mode

PEP 553：內建的 breakpoint()

PEP 539: New C API for Thread-Local Storage

PEP 562: Customization of Access to Module Attributes

PEP 564: New Time Functions With Nanosecond Resolution

PEP 565：在 __main__ 中顯示 DeprecationWarning

PEP 560：對 typing 模組與泛用型別的核心支援

PEP 552：基於雜湊值的 .pyc 檔案

PEP 545：Python 文件翻譯

Python 開發模式（-X dev）

其他語言更動

新模組

contextvars

dataclasses

importlib.resources

改進的模組

argparse

asyncio

binascii

calendar

collections

compileall

concurrent.futures

contextlib

cProfile

crypt

datetime

dbm

decimal

dis

distutils

enum

functools

gc

hmac

http.client

http.server

idlelib 與 IDLE

importlib

io

ipaddress

itertools

locale

logging

math

mimetypes

msilib

multiprocessing

os

pathlib

pdb

py_compile

pydoc

queue

re

signal

socket

socketserver

sqlite3

ssl

string

subprocess

sys

time

tkinter

tracemalloc

types

unicodedata

unittest

unittest.mock

urllib.parse

uu

uuid

warnings

xml

xml.etree

xmlrpc.server

zipapp

zipfile

C API 變更

建置變更

最佳化

Other CPython Implementation Changes

已棄用的 Python 行為

已棄用的 Python 模組、函式和方法

aifc

asyncio

collections

dbm

enum

gettext

importlib

locale

macpath

threading

socket

ssl

sunau

sys

wave

Deprecated functions and types of the C API

Platform Support Removals

API 與功能的移除

Module Removals

Windows-only Changes

移植至 Python 3.7

Python 行為的改變

Python API 的變更

C API 中的改動

CPython 位元組碼變更

Windows-only Changes

Other CPython implementation changes

Python 3.7.1 中顯著的變更

Python 3.7.2 中顯著的變更

Python 3.7.6 中顯著的變更

Python 3.7.10 中顯著的變更

Python 3.7.11 中顯著的變更

Python 3.7.14 中顯著的安全性功能

Python 3.6 有什麼新功能

發布重點摘要

新增功能

PEP 498: Formatted string literals

PEP 526: Syntax for variable annotations

PEP 515: Underscores in Numeric Literals

PEP 525: Asynchronous Generators

PEP 530: Asynchronous Comprehensions

PEP 487: Simpler customization of class creation

PEP 487: Descriptor Protocol Enhancements

PEP 519: Adding a file system path protocol

PEP 495: Local Time Disambiguation

PEP 529: Change Windows filesystem encoding to UTF-8

PEP 528: Change Windows console encoding to UTF-8

PEP 520: Preserving Class Attribute Definition Order

PEP 468: Preserving Keyword Argument Order

New dict implementation

PEP 523: Adding a frame evaluation API to CPython

PYTHONMALLOC environment variable

DTrace and SystemTap probing support

其他語言更動

新模組

secrets

改進的模組

array

ast

asyncio

binascii

cmath

collections

concurrent.futures

contextlib

datetime

decimal

distutils

email

encodings

enum

faulthandler

fileinput

hashlib

http.client

idlelib 與 IDLE

importlib

inspect

json

logging

math

multiprocessing

os

pathlib

pdb

pickle

pickletools

pydoc

random

re

readline

rlcompleter

shlex

site

sqlite3

socket

socketserver

ssl

statistics

struct

subprocess

sys

telnetlib

time

timeit

tkinter

traceback

tracemalloc

typing

unicodedata

unittest.mock

urllib.request

urllib.robotparser

venv

warnings

winreg

winsound

xmlrpc.client

zipfile

zlib

最佳化

建置和 C API 變更

其他改進

已棄用

新關鍵字

已棄用的 Python 行為

已棄用的 Python 模組、函式和方法

asynchat

asyncore

dbm

distutils

grp

importlib

os

re

ssl

tkinter

venv

xml

C API 的已棄用函式和型別

已棄用的建置選項

已移除

API 與功能的移除

移植至 Python 3.6

'python' 命令的行為變更

Python API 的變更

C API 中的改動

CPython 位元組碼變更

Python 3.6.2 中顯著的變更

新增 make regen-all 建置目標

移除 make touch 建置目標

Python 3.6.4 中顯著的變更

Python 3.6.5 中顯著的變更

Python 3.6.7 中顯著的變更

Python 3.6.10 中顯著的變更

Python 3.6.13 中顯著的變更

Python 3.6.14 中顯著的變更

Python 3.5 有什麼新功能

發布重點摘要

新增功能

PEP 492 - 使用 async 和 await 語法的協程

PEP 465 - A dedicated infix operator for matrix multiplication

PEP 448 - Additional Unpacking Generalizations

PEP 461 - percent formatting support for bytes and bytearray

PEP 484 - 型別提示

PEP 471 - os.scandir() function -- a better and faster directory iterator

PEP 475: Retry system calls failing with EINTR

PEP 479: Change StopIteration handling inside generators

PEP 485: A function for testing approximate equality

PEP 486: Make the Python Launcher aware of virtual environments

PEP 488: Elimination of PYO files

PEP 489: Multi-phase extension module initialization

其他語言更動

新增模組

typing

zipapp

改進的模組

argparse

asyncio

bz2

cgi

cmath

code

collections

collections.abc

compileall

concurrent.futures

configparser

contextlib

csv

curses

dbm

difflib

distutils

doctest

email

enum

faulthandler

functools

glob

gzip

heapq

http

http.client

idlelib 與 IDLE

imaplib

imghdr

importlib

inspect

io

ipaddress

json

linecache

locale

logging

lzma

math

multiprocessing

operator

os

pathlib

pickle

poplib

re

readline

selectors

shutil

signal

smtpd

smtplib

sndhdr

socket

ssl

記憶體 BIO 支援

Application-Layer Protocol Negotiation Support

其他變更

sqlite3

subprocess

sys

sysconfig

tarfile

threading

time

timeit

tkinter

traceback

types

unicodedata

unittest

unittest.mock

urllib

wsgiref

xmlrpc

xml.sax

zipfile

其他模組層級的變更

最佳化

建置和 C API 變更

已棄用

新關鍵字

已棄用的 Python 行為

不支援的作業系統

已棄用的 Python 模組、函式和方法

已移除

API 與功能的移除

移植至 Python 3.5

Python 行為的改變

Python API 的變更

C API 中的改動

Python 3.5.4 中顯著的變更

新增 make regen-all 建置目標

移除 make touch 建置目標

Python 3.4 有什麼新功能

發布重點摘要

新增功能

PEP 453: Explicit Bootstrapping of PIP in Python Installations

Bootstrapping pip By Default

文件更動

PEP 446: Newly Created File Descriptors Are Non-Inheritable

編解碼器處理的改進

PEP 451：用於引入系統的 ModuleSpec 型別

其他語言更動

新模組

asyncio

ensurepip

enum

pathlib

selectors

statistics

tracemalloc

改進的模組

abc

aifc

argparse

audioop

base64

collections

colorsys

contextlib

dbm

dis

doctest

email

filecmp

functools

gc

glob

hashlib

hmac

html

http

idlelib 與 IDLE

importlib

inspect

ipaddress

logging

marshal

mmap

multiprocessing

operator

os

pdb

pickle

plistlib

poplib

pprint

pty

pydoc

re

resource

select

shelve

shutil

smtpd

smtplib

socket

sqlite3

ssl

stat

struct

subprocess

sunau

sys

tarfile

textwrap

threading

traceback

types

urllib

unittest

venv

wave

weakref

xml.etree

zipfile

CPython 實作變更

PEP 445: Customization of CPython Memory Allocators

PEP 442: Safe Object Finalization

PEP 456: Secure and Interchangeable Hash Algorithm

PEP 436: Argument Clinic

其他建置和 C API 變更

其他改進

顯著最佳化

已棄用

已棄用的 Python API

已棄用功能

已移除

不再支援的作業系統

API 與功能的移除

程式碼的清除

移植至 Python 3.4

Changes in 'python' Command Behavior

Python API 的變更

C API 中的改動

3.4.3 中的變更

PEP 476: Enabling certificate verification by default for stdlib http clients

Python 3.3 有什麼新功能

發布重點摘要

PEP 405：虛擬環境

PEP 420: Implicit Namespace Packages

PEP 3118: New memoryview implementation and buffer protocol documentation

功能

API 變更

PEP 393: Flexible String Representation

功能性

性能和資源使用情況

PEP 397：適用於 Windows 的 Python 啟動器

PEP 3151: Reworking the OS and IO exception hierarchy

PEP 380: Syntax for Delegating to a Subgenerator

PEP 409: Suppressing exception context

PEP 414: Explicit Unicode literals

PEP 3155: Qualified name for classes and functions

PEP 412: Key-Sharing Dictionary

PEP 362：函式簽名物件

PEP 421：新增 sys.implementation

SimpleNamespace

使用 importlib 作為 import 的實作

新 API

明顯的變更

其他語言更動

A Finer-Grained Import Lock

內建函式和型別

新模組

faulthandler

ipaddress

lzma

改進的模組

abc

array

base64

binascii

bz2

codecs

collections

contextlib

crypt

curses

datetime

decimal

功能

API 變更

email

Policy Framework

Provisional Policy with New Header API

其他 API 變更

ftplib

functools

gc

hmac

http

html

imaplib

inspect

io

itertools

logging

math

mmap

multiprocessing

nntplib

os

pdb

pickle

pydoc

re

sched

select

shlex

shutil

signal

smtpd

smtplib

socket

socketserver

sqlite3

ssl

stat

struct

subprocess

sys

tarfile

tempfile

textwrap

threading

time

types

unittest

urllib

webbrowser

xml.etree.ElementTree

zlib

最佳化

建置和 C API 變更

已棄用

不支援的作業系統

已棄用的 Python 模組、函式和方法

C API 中已棄用的函式和型別

已棄用的功能

移植到 Python 3.3

移植 Python 程式碼

Porting C code

Building C extensions

命令列開關更改

Python 3.2 有什麼新功能

PEP 384: Defining a Stable ABI

PEP 389: Argparse 命令列剖析模組

PEP 391: Dictionary Based Configuration for Logging

PEP 3148：concurrent.futures 模組

PEP 3147: PYC Repository Directories

PEP 3149: ABI Version Tagged .so Files

PEP 3333: Python Web Server Gateway Interface v1.0.1

其他語言更動

New, Improved, and Deprecated Modules

email

elementtree

functools

itertools

collections

threading

datetime 和 time

math

abc

io

reprlib

logging

csv

contextlib

decimal and fractions

ftp

popen

select

gzip 和 zipfile

tarfile

hashlib

ast

os

shutil

sqlite3

html

socket

ssl

nntp

certificates

imaplib

http.client

unittest

random

poplib

asyncore

tempfile

inspect

pydoc

dis

dbm

ctypes

site

sysconfig

pdb

configparser

urllib.parse

mailbox

turtledemo

Multi-threading

最佳化

Unicode

編解碼器

文件

IDLE

Code Repository

建置和 C API 變更

移植至 Python 3.2

Python 3.1 有什麼新功能

PEP 372：有序字典

PEP 378: Format Specifier for Thousands Separator

其他語言更動

新增、改進和棄用的模組

最佳化

IDLE

建置和 C API 變更

移植至 Python 3.1

Python 3.0 有什麼新功能

Common Stumbling Blocks

Print 是一個函式

Views And Iterators Instead Of Lists

Ordering Comparisons

整數

Text Vs. Data Instead Of Unicode Vs. 8-bit

語法變更概要

新增語法

語法變更

已被移除的語法

Changes Already Present In Python 2.6

函式庫變更

PEP 3101: A New Approach To String Formatting

Changes To Exceptions

Miscellaneous Other Changes

Operators And Special Methods

Builtins

建置和 C API 變更

效能

Porting To Python 3.0

Python 2.7 有什麼新功能

Python 2.x 的未來

Changes to the Handling of Deprecation Warnings

Python 3.1 Features

PEP 372: Adding an Ordered Dictionary to collections

PEP 378: Format Specifier for Thousands Separator

PEP 389: The argparse Module for Parsing Command Lines

PEP 391: Dictionary-Based Configuration For Logging

PEP 3106: Dictionary Views

PEP 3137: The memoryview Object

其他語言更動

Interpreter Changes

最佳化

New and Improved Modules

新模組：importlib

新模組：sysconfig

ttk: Themed Widgets for Tk

改進模組：unittest

改進模組：ElementTree 1.3

建置和 C API 變更

Capsules

Port-Specific Changes: Windows

Port-Specific Changes: Mac OS X

Port-Specific Changes: FreeBSD

Other Changes and Fixes

移植至 Python 2.7

New Features Added to Python 2.7 Maintenance Releases

偵錯模式下的兩個新環境變數

PEP 434: IDLE Enhancement Exception for All Branches

PEP 466: Network Security Enhancements for Python 2.7

PEP 477: Backport ensurepip (PEP 453) to Python 2.7

Bootstrapping pip By Default

文件更動

PEP 476: Enabling certificate verification by default for stdlib http clients

PEP 493: HTTPS verification migration tools for Python 2.7

新增 make regen-all 建置目標

移除 make touch 建置目標

致謝

Python 2.6 有什麼新功能

Python 3.0

Changes to the Development Process

New Issue Tracker: Roundup

新文件格式：使用 Sphinx 的 reStructuredText

PEP 343：'with' 陳述式

Writing Context Managers

contextlib 模組

PEP 366: Explicit Relative Imports From a Main Module

PEP 370: Per-user site-packages Directory

PEP 371: The multiprocessing Package

PEP 3101: Advanced String Formatting

PEP 3105: print As a Function

PEP 3110: Exception-Handling Changes

PEP 3112: Byte Literals

PEP 3116：新 I/O 函式庫

PEP 3118：修訂緩衝協定

PEP 3119: Abstract Base Classes

PEP 3127: Integer Literal Support and Syntax

PEP 3129: Class Decorators

PEP 3141: A Type Hierarchy for Numbers

The fractions Module

其他語言更動

最佳化

Interpreter Changes

New and Improved Modules

ast 模組

future_builtins 模組

The json module: JavaScript Object Notation

The plistlib module: A Property-List Parser

ctypes Enhancements

Improved SSL Support

Deprecations and Removals

建置和 C API 變更

Port-Specific Changes: Windows

Port-Specific Changes: Mac OS X

Port-Specific Changes: IRIX

Porting to Python 2.6

致謝

Python 2.5 有什麼新功能

PEP 308: Conditional Expressions

PEP 309: Partial Function Application

PEP 314: Metadata for Python Software Packages v1.1

PEP 328: Absolute and Relative Imports

PEP 338: Executing Modules as Scripts

PEP 341: Unified try/except/finally

PEP 342: New Generator Features

PEP 343：'with' 陳述式

Writing Context Managers

contextlib 模組

PEP 352: Exceptions as New-Style Classes

PEP 353: Using ssize_t as the index type

PEP 357: The '__index__' method

其他語言更動

Interactive Interpreter Changes

最佳化

New, Improved, and Removed Modules

ctypes 套件

ElementTree 套件

hashlib 套件

sqlite3 套件

wsgiref 套件

建置和 C API 變更

Port-Specific Changes

Porting to Python 2.5

致謝

Python 2.4 有什麼新功能

PEP 218: Built-In Set Objects

PEP 237: Unifying Long Integers and Integers

PEP 289：產生器運算式

PEP 292: Simpler String Substitutions

PEP 318: Decorators for Functions and Methods

PEP 322: Reverse Iteration

PEP 324: New subprocess Module

PEP 327：Decimal 資料型別

為什麼需要 Decimal？

Decimal 型別

Context 型別

PEP 328: Multi-line Imports

PEP 331: Locale-Independent Float/String Conversions

其他語言更動

最佳化

New, Improved, and Deprecated Modules

cookielib

doctest

建置和 C API 變更

Port-Specific Changes

Porting to Python 2.4

致謝

Python 2.3 有什麼新功能

PEP 218: A Standard Set Datatype

PEP 255：簡單產生器

PEP 263: Source Code Encodings

PEP 273: Importing Modules from ZIP Archives

PEP 277: Unicode file name support for Windows NT

PEP 278: Universal Newline Support

PEP 279：enumerate()

PEP 282: The logging Package

PEP 285：布林型別

PEP 293: Codec Error Handling Callbacks

PEP 301: Package Index and Metadata for Distutils

PEP 302: New Import Hooks

PEP 305: Comma-separated Files

PEP 307: Pickle Enhancements

Extended Slices

其他語言更動

String Changes

最佳化

New, Improved, and Deprecated Modules

Date/Time Type

The optparse Module

Pymalloc: A Specialized Object Allocator

建置和 C API 變更

Port-Specific Changes

Other Changes and Fixes

Porting to Python 2.3

致謝

Python 2.2 有什麼新功能

簡介

PEPs 252 and 253: Type and Class Changes

舊的和新的類別

描述器

Multiple Inheritance: The Diamond Rule

Attribute Access

相關連結

PEP 234：疊代器

PEP 255：簡單產生器

PEP 237: Unifying Long Integers and Integers

PEP 238: Changing the Division Operator

Unicode 變更

PEP 227: Nested Scopes

New and Improved Modules

直譯器的變更與修正

其他改動與修正

致謝

Python 2.1 有什麼新功能

簡介

PEP 227: Nested Scopes

PEP 236: __future__ Directives

PEP 207: Rich Comparisons

PEP 230：警告框架

PEP 229: New Build System

PEP 205: Weak References

PEP 232：函式屬性

PEP 235: Importing Modules on Case-Insensitive Platforms

PEP 217: Interactive Display Hook

PEP 208: New Coercion Model

PEP 241: Metadata in Python Packages

New and Improved Modules

其他變更與修正

致謝

Python 2.0 有什麼新功能

簡介

Python 1.6 呢？

新的開發流程

Unicode

串列綜合運算（List Comprehension）

擴增賦值（Augmented Assignment）

字串方法

循環的垃圾回收

其他核心變更

次要語言變更

內建函式的變更

移植到 2.0

擴充/嵌入變更

Distutils：讓模組安裝變簡單

XML 模組

SAX2 支援

DOM 支援

與 PyXML 的關係

模組變更

新增模組

IDLE 改進

已刪除和已棄用的模組

致謝

Changelog（更動日誌）

Python next

Windows

Tools/Demos

Tests

Security

Library

IDLE

Documentation

Core and Builtins

C API

Build

Python 3.14.2 final

Security

Library

Core and Builtins

Library

Python 3.14.1 final

Windows

Tools/Demos

Tests

Security

Library

IDLE

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 final

macOS

Windows

Tools/Demos

Security

Library

Python 3.14.0 release candidate 3

Windows

Tools/Demos

Security

Library

Core and Builtins

Python 3.14.0 release candidate 2

macOS

Windows

Library

Documentation

Core and Builtins

C API

Build

Python 3.14.0 release candidate 1

Tools/Demos

Security

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 beta 4

Tools/Demos

Tests

Security

Library

Documentation

Core and Builtins

C API

Build

Python 3.14.0 beta 3

Windows

Tests

Security

Library

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 beta 2

Windows

Tools/Demos

Tests

Security

Library

Core and Builtins

C API

Build

Python 3.14.0 beta 1

Windows

Tools/Demos

Tests

Security

Library

IDLE

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

C API

Build

Python 3.14.0 alpha 7

macOS

Windows

Tools/Demos

Tests

Security

Library

Documentation

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 alpha 6

macOS

Windows

Tools/Demos

Tests

Security

Library

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 alpha 5

macOS

Tools/Demos

Tests

Security

Library

IDLE

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

C API

Build

Python 3.14.0 alpha 4

macOS

Tools/Demos

Tests

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 alpha 3

Windows

Tools/Demos

Tests

Security

Library

Documentation

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.14.0 alpha 2

Windows

Tools/Demos

Tests

Security

Library

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

C API

Build

Python 3.14.0 alpha 1

macOS

Windows

Tools/Demos

Tests

Security

Library

IDLE

Documentation

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

C API

Build

Python 3.13.0 beta 1

Security

Core and Builtins

Library

Core and Builtins

Library

Documentation

Build

Windows

macOS

IDLE

C API

Python 3.13.0 alpha 6

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

C API

Python 3.13.0 alpha 5

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.13.0 alpha 4

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.13.0 alpha 3

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.13.0 alpha 2

Core and Builtins

Library

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.13.0 alpha 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.12.0 beta 1

Security

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.12.0 alpha 7

Core and Builtins

Library

Core and Builtins

Build

Core and Builtins

Library

Documentation

Tests

Build

Windows

Tools/Demos

C API

Python 3.12.0 alpha 6

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

C API

Python 3.12.0 alpha 5

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

Python 3.12.0 alpha 4

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

Tools/Demos

C API

Python 3.12.0 alpha 3

Security

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

Tools/Demos

C API

Python 3.12.0 alpha 2

Security

Core and Builtins

Build

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

C API

Python 3.12.0 alpha 1

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.11.0 beta 1

Security

Core and Builtins

Library

Core and Builtins

Build

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

Tools/Demos

C API

Python 3.11.0 alpha 7

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

Tools/Demos

C API

Python 3.11.0 alpha 6

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

IDLE

C API

Python 3.11.0 alpha 5

Core and Builtins

Library

Core and Builtins

Library

Build

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.11.0 alpha 4

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

C API

Python 3.11.0 alpha 3

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

C API

Python 3.11.0 alpha 2

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.11.0 alpha 1

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.10.0 beta 1

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.10.0 alpha 7

Security

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

IDLE

C API

Python 3.10.0 alpha 6

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.10.0 alpha 5

Security

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.10.0 alpha 4

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

macOS

Tools/Demos

C API

Python 3.10.0 alpha 3

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.10.0 alpha 2

Security

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.10.0 alpha 1

Security

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.9.0 beta 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

Tools/Demos

C API

Python 3.9.0 alpha 6

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.9.0 alpha 5

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.9.0 alpha 4

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

IDLE

C API

Python 3.9.0 alpha 3

Core and Builtins

Library

Documentation

Build

IDLE

C API

Python 3.9.0 alpha 2

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

C API

Python 3.9.0 alpha 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.8.0 beta 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.8.0 alpha 4

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.8.0 alpha 3

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

IDLE

Tools/Demos

C API

Python 3.8.0 alpha 2

Core and Builtins

Library

Documentation

Tests

Windows

IDLE

Python 3.8.0 alpha 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.7.0 final

Library

C API

Python 3.7.0 release candidate 1

Core and Builtins

Library

Documentation

Build

Windows

IDLE

Python 3.7.0 beta 5

Core and Builtins

Library

Documentation

Tests

Build

macOS

IDLE

Python 3.7.0 beta 4

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

Python 3.7.0 beta 3

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.7.0 beta 2

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

Python 3.7.0 beta 1

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

C API

Python 3.7.0 alpha 4

Core and Builtins

Library

Documentation

Tests

Windows

Tools/Demos

C API

Python 3.7.0 alpha 3

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.7.0 alpha 2

Core and Builtins

Library

Documentation

Build

IDLE

C API

Python 3.7.0 alpha 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

IDLE

Tools/Demos

C API

Python 3.6.6 final

Python 3.6.6 release candidate 1

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.6.5 final

Tests

Build

Python 3.6.5 release candidate 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.6.4 final

Python 3.6.4 release candidate 1

Core and Builtins

Library

Documentation

Tests

Build

Windows

macOS

IDLE

Tools/Demos

C API

Python 3.6.3 final

Library

Build

Python 3.6.3 release candidate 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

IDLE

Tools/Demos

Python 3.6.2 final

Python 3.6.2 release candidate 2

Security

Python 3.6.2 release candidate 1

Security

Core and Builtins

Library

IDLE

C API

Build

Documentation

Tools/Demos

Tests

Windows

Python 3.6.1 final

Core and Builtins

Build

Python 3.6.1 release candidate 1

Core and Builtins

Library

IDLE

Windows

C API

Documentation

Tests

Build

Python 3.6.0 final

Python 3.6.0 release candidate 2

Core and Builtins

Tools/Demos

Windows

Build

Python 3.6.0 release candidate 1

Core and Builtins

Library

C API

Documentation

Tools/Demos

Python 3.6.0 beta 4

Core and Builtins

Library

Documentation

Tests

Build

Python 3.6.0 beta 3

Core and Builtins

Library

Windows

Build

Tests

Python 3.6.0 beta 2

Core and Builtins

Library

Windows

C API

Build

Tests

Python 3.6.0 beta 1

Core and Builtins

Library

IDLE

C API

Tests

Build

Tools/Demos

Windows

Python 3.6.0 alpha 4

Core and Builtins

Library

IDLE

Tests

Windows

Build

Python 3.6.0 alpha 3

Security

Core and Builtins

Library

IDLE

C API

Build

Tools/Demos

Documentation

Tests

Python 3.6.0 alpha 2

Security

Core and Builtins

Library

IDLE

Documentation

Tests

Windows

Build

C API

Tools/Demos

Python 3.6.0 alpha 1

Security

Core and Builtins

Library

IDLE

Documentation

Tests

Build

Windows

Tools/Demos

C API

Python 3.5.5 final

Python 3.5.5 release candidate 1

Security

Core and Builtins

Library

Python 3.5.4 final

Library

Python 3.5.4 release candidate 1

Security

Core and Builtins

Library

Documentation

Tests

Build

Windows

C API

Python 3.5.3 final

Python 3.5.3 release candidate 1

Security

Core and Builtins

Library

IDLE

C API

Documentation

Tests

Tools/Demos

Windows

Build

Python 3.5.2 final

Core and Builtins

Tests

IDLE

Python 3.5.2 release candidate 1

Security

Core and Builtins

Library

IDLE

Documentation

Tests

Build

Windows

Tools/Demos

Python 3.5.1 final

Core and Builtins

Windows

Python 3.5.1 release candidate 1

Core and Builtins

Library

IDLE

Documentation

Tests

Build

Windows

Tools/Demos

Python 3.5.0 final

Build

Python 3.5.0 release candidate 4

Library

Build

Python 3.5.0 release candidate 3

Core and Builtins

Library

Python 3.5.0 release candidate 2

Core and Builtins

Library

Python 3.5.0 release candidate 1

Core and Builtins

Library

IDLE

Documentation

Tests

Python 3.5.0 beta 4

Core and Builtins

Library

Build

Python 3.5.0 beta 3

Core and Builtins

Library

Tests

Documentation

Build

Python 3.5.0 beta 2

Core and Builtins

Library

Python 3.5.0 beta 1

Core and Builtins

Library

IDLE

Tests

Documentation

Tools/Demos

Python 3.5.0 alpha 4

Core and Builtins

Library

Build

Tests

Tools/Demos

C API

Python 3.5.0 alpha 3

Core and Builtins

Library

Build

Tests

Tools/Demos

Python 3.5.0 alpha 2

Core and Builtins

Library

Build

C API

Windows

Python 3.5.0 alpha 1

Core and Builtins

Library

IDLE

Build

C API

Documentation

Tests

Tools/Demos

Windows

Python 教學

1. 淺嘗滋味

2. 使用 Python 直譯器

2.1. 啟動直譯器

2.1.1. 傳遞引數

2.1.2. 互動模式

2.2. 直譯器與它的環境

2.2.1. 原始碼的字元編碼 (encoding)

3. 一個非正式的 Python 簡介

3.1. 把 Python 當作計算機使用

3.1.1. 數字 (Number)

3.1.2. 文字

3.1.3. List（串列）

3.2. 初探程式設計的前幾步

4. 深入了解流程控制

4.1. if 陳述式

4.2. for 陳述式

4.3. range() 函式

4.4. break 和 continue 陳述式

4.5. 迴圈的 else 子句

4.6. pass 陳述式

4.7. match 陳述式

4.8. 定義函式 (function)

4.9. 深入了解函式定義

4.9.1. 預設引數值

4.9.2. 關鍵字引數

4.9.3. 特殊參數

4.9.3.1. 位置或關鍵字引數 (Positional-or-Keyword Arguments)

4.9.3.2. 僅限位置參數 (Positional-Only Parameters)

4.9.3.3. 僅限關鍵字引數 (Keyword-Only Arguments)

4.9.3.4. 函式範例

4.9.3.5. 回顧

4.9.4. 任意引數列表 (Arbitrary Argument Lists)

4.9.5. 拆解引數列表（Unpacking Argument Lists）

4.9.6. Lambda 運算式

4.9.7. 說明文件字串 (Documentation Strings)

4.9.8. 函式註釋 (Function Annotations)

4.10. 間奏曲：程式碼風格 (Coding Style)

5. 資料結構

5.1. 進一步了解 List（串列）

5.1.1. 將 List 作為 Stack（堆疊）使用

5.1.2. 將 List 作為 Queue（佇列）使用

5.1.3. List Comprehensions（串列綜合運算）

5.1.4. 巢狀的 List Comprehensions

5.2. del 陳述式

5.3. Tuples 和序列 (Sequences)

5.4. 集合 (Sets)

5.5. 字典（Dictionary）

5.6. 迴圈技巧

5.7. 深入了解條件 (Condition)

5.8. 序列和其他資料類型之比較

6. 模組 (Module)

6.1. 深入了解模組

6.1.1. 把模組當作腳本執行

6.1.2. 模組的搜尋路徑

6.1.3. 「編譯」Python 檔案

6.2. 標準模組

6.3. dir() 函式

6.4. 套件 (Package)

6.4.1. 從套件中 import *

6.4.2. 套件內引用

6.4.3. 多目錄中的套件

7. 輸入和輸出

7.1. 更華麗的輸出格式

7.1.1. 格式化的字串文本 (Formatted String Literals)

7.1.2. 字串的 format() method

7.1.3. 手動格式化字串

7.1.4. 格式化字串的舊方法

7.2. 讀寫檔案

7.2.1. 檔案物件的 method

7.2.2. 使用 json 儲存結構化資料

8. 錯誤和例外

8.1. 語法錯誤 (Syntax Error)

8.2. 例外 (Exception)

8.3. 處理例外

8.4. 引發例外

8.5. 例外鏈接 (Exception Chaining)

8.6. 使用者自定的例外

8.7. 定義清理動作

8.8. 預定義的清理動作

8.9. 引發及處理多個無關的例外

8.10. 用註解使例外更詳細

9. Class（類別）

9.1. 關於名稱與物件的一段話

9.2. Python 作用域 (Scope) 及命名空間 (Namespace)

9.2.1. 作用域和命名空間的範例

9.3. 初見 class

9.3.1. Class definition（類別定義）語法

9.3.2. Class 物件

9.3.3. 實例物件

9.3.4. Method 物件

9.3.5. Class 及實例變數

9.4. 隨意的備註

9.5. 繼承 (Inheritance)

9.5.1. 多重繼承

9.6. 私有變數

9.7. 補充說明

9.8. 疊代器 (Iterator)

9.9. 產生器 (Generator)

9.10. 產生器運算式

10. Python 標準函式庫概覽

10.1. 作業系統介面

10.2. 檔案之萬用字元 (File Wildcards)

10.3. 命令列引數

10.4. 錯誤輸出重新導向與程式終止

10.5. 字串樣式比對

10.6. 數學相關

10.7. 網路存取

10.8. 日期與時間

10.9. 資料壓縮

10.10. 效能量測

10.11. 品質控管

10.12. 標準模組庫

11. Python 標準函式庫概覽——第二部份

11.1. 輸出格式化 (Output Formatting)

11.2. 模板化 (Templating)

11.3. 二進制資料記錄編排 (Binary Data Record Layouts)

11.4. 多執行緒 (Multi-threading)

11.5. 日誌記錄 (Logging)

11.6. 弱引用 (Weak References)

11.7. 使用於 List 的工具

11.8. 十進制浮點數運算 (Decimal Floating-Point Arithmetic)

12. 虛擬環境與套件

12.1. 簡介

12.2. 建立虛擬環境

12.3. 用 pip 管理套件

13. 現在可以來學習些什麼？

14. 互動式輸入編輯和歷史記錄替換

14.1. Tab 鍵自動完成 (Tab Completion) 和歷史記錄編輯 (History Editing)

14.2. 互動式直譯器的替代方案

15. 浮點數運算：問題與限制

15.1. 表示法誤差 (Representation Error)

16. 附錄

16.1. 互動模式

16.1.1. 錯誤處理

16.1.2. 可執行的 Python 腳本

16.1.3. 互動式啟動檔案

16.1.4. 客製化模組

Python 的設置與使用

1. 命令列與環境

1.1. 命令列

1.1.1. 介面選項

1.1.2. Generic options

1.1.3. Miscellaneous options

1.1.4. Controlling color

1.2. 環境變數

1.2.1. 除錯模式變數

2. 在 Unix 平臺上使用 Python

2.1. 獲得並安裝 Python 的最新版本

2.1.1. 在 Linux 上

2.1.1.1. 安裝 IDLE

2.1.2. 在 FreeBSD 和 OpenBSD 上

2.2. 建置 Python

2.3. 與 Python 相關的路徑和檔案

2.4. 雜項

2.5. 客製化 OpenSSL

3. 配置 Python

3.1. 建置需求

3.1.1. 可選模組的需求

3.2. 產生的檔案

3.2.1. 設定腳本

3.3. 設定選項

3.3.1. 一般選項

3.3.2. C 編譯器選項。

3.3.3. Linker options

3.3.4. Options for third-party dependencies

3.3.5. WebAssembly 選項

3.3.6. 安裝選項

3.3.7. 效能選項

3.3.8. Python Debug Build

3.3.9. 偵錯選項

3.3.10. Linker options

3.3.11. 函式庫選項

3.3.12. 安全性選項

3.3.13. macOS 選項

3.3.14. iOS 選項

3.3.15. Cross Compiling Options

3.4. Python 建置系統

3.4.1. 建置系統的主要檔案

3.4.2. 主要建置步驟

3.4.3. 主要 Makefile 目標

3.4.3.1. make

3.4.3.2. make platform

3.4.3.3. make profile-opt

3.4.3.4. make clean

3.4.3.5. make distclean

3.4.3.6. make install

3.4.3.7. make test

3.4.3.8. make ci

3.4.3.9. make buildbottest

3.4.3.10. make regen-all

3.4.4. C 擴充模組

3.5. Compiler and linker flags

3.5.1. 預處理器旗標

3.5.2. 編譯器旗標

3.5.3. Linker flags

4. 在 Windows 上使用 Python

4.1. Python 安裝管理員

4.1.1. 安裝

4.1.2. 基本使用

4.1.3. Command help

4.1.4. 列出 runtimes

4.1.5. 安裝 runtimes

4.1.6. 離線安裝

4.1.7. 解除安裝 runtimes

4.1.8. 設定

4.1.9. Shebang lines

4.1.10. 進階安裝

4.1.11. Administrative configuration

4.1.12. Installing free-threaded binaries

4.1.13. Troubleshooting

4.2. The embeddable package

4.2.1. Python 應用程式

4.2.2. 嵌入 Python

4.3. nuget.org 套件

4.3.1. Free-threaded packages

4.4. Alternative bundles

4.5. Supported Windows versions

4.6. Removing the MAX_PATH limitation

4.7. UTF-8 模式

4.8. 找尋模組

4.9. 額外的模組

4.9.1. PyWin32

4.9.2. cx_Freeze

4.10. 編譯 Python 在 Windows

4.11. The full installer (deprecated)

4.11.1. 安裝步驟

4.11.2. Removing the MAX_PATH limitation

4.11.3. 無使用者介面安裝

4.11.4. 無下載安裝

4.11.5. Modifying an install

4.11.6. Installing free-threaded binaries

4.12. Python launcher for Windows (deprecated)

4.12.1. 開始

4.12.1.1. From the command-line

4.12.1.2. 虛擬環境（Virtual environment）

4.12.1.3. From a script

4.12.1.4. 從檔案關聯

4.12.2. Shebang lines

4.12.3. Arguments in shebang lines

4.12.4. Customization

4.12.4.1. Customization via INI files

4.12.4.2. Customizing default Python versions

4.12.5. Diagnostics

4.12.6. Dry run

4.12.7. 安裝隨選

4.12.8. Return codes

5. 於 macOS 使用 Python

5.1. Using Python for macOS from python.org

5.1.1. 安裝步驟

5.1.2. 如何執行 Python 腳本

5.2. Alternative Distributions

5.3. 安裝額外的 Python 套件

5.4. 開發 GUI 程式

5.5. 進階主題

5.5.1. Installing Free-threaded Binaries

5.5.2. 使用命令列安裝

5.5.3. 發行 Python 應用程式

5.5.4. App Store Compliance

5.6. 其他資源

6. 在 Android 上使用 Python

6.1. 將 Python 加入 Android 應用程式

6.2. 建置用於 Android 的 Python 套件

7. 在 iOS 上使用 Python

7.1. Python at runtime on iOS

7.1.1. iOS version compatibility

7.1.2. Platform identification

7.1.3. Standard library availability

7.1.4. Binary extension modules

7.1.5. Compiler stub binaries

7.2. Installing Python on iOS

7.2.1. Tools for building iOS apps

7.2.2. Adding Python to an iOS project

7.2.3. Testing a Python package

7.3. App Store Compliance

7.3.1. Incompatible code in the standard library

7.3.2. Privacy manifests

8. 編輯器與 IDE

8.1. IDLE --- Python 編輯器與 shell

8.2. 其他編輯器與 IDE

Python 語言參考手冊

1. 簡介

1.1. 可選實作

1.2. 標示法

1.2.1. 詞法和語法定義

2. 詞法分析

2.1. Line structure

2.1.1. Logical lines

2.1.2. Physical lines

2.1.3. Comments

2.1.4. Encoding declarations

2.1.5. Explicit line joining

2.1.6. Implicit line joining

2.1.7. Blank lines

2.1.8. Indentation

2.1.9. Whitespace between tokens

2.1.10. End marker

2.2. Other tokens

2.3. Names (identifiers and keywords)

2.3.1. 關鍵字

2.3.2. 軟關鍵字

2.3.3. Reserved classes of identifiers

2.3.4. 名稱中的非 ASCII 字元

2.4. Literals

2.5. String and Bytes literals

2.5.1. 三引號字串

2.5.2. String prefixes

2.5.3. Formal grammar

2.5.4. 跳脫序列

2.5.4.1. Ignored end of line

2.5.4.2. 跳脫字元

2.5.4.3. 八進位字元

2.5.4.4. 十六進位字元

2.5.4.5. Named Unicode character

2.5.4.6. 十六進位 Unicode 字元

2.5.4.7. 無法辨識的跳脫序列

2.5.5. 位元組常數

2.5.6. 原始字串常數

2.5.7. f-string（f 字串）

2.5.8. t-string（t 字串）

2.5.9. Formal grammar for f-strings

2.6. Numeric literals

2.6.1. Integer literals

2.6.2. 浮點數常數 (Floating-point literals)

2.6.3. Imaginary literals

2.7. Operators and delimiters

3. 資料模型

3.1. 物件、數值和型別

3.2. 標準型別階層

3.2.1. None

3.2.2. NotImplemented

3.2.3. Ellipsis

3.2.4. numbers.Number

3.2.4.1. numbers.Integral

3.2.4.2. numbers.Real (float)

3.2.4.3. numbers.Complex (complex)

3.2.5. Sequences

3.2.5.1. Immutable sequences

3.2.5.2. 可變序列

3.2.6. Set（集合）型別

3.2.7. 對映

3.2.7.1. 字典

3.2.8. 可呼叫型別

3.2.8.1. 自訂函式

3.2.8.1.1. 特殊唯讀屬性

3.2.8.1.2. 特殊可寫屬性

3.2.8.2. 實例方法

3.2.8.3. 產生器函式

3.2.8.4. Coroutine（協程）函式

3.2.8.5. 非同步產生器函式

3.2.8.6. 內建函式

3.2.8.7. 內建方法

3.2.8.8. Classes

3.2.8.9. 類別實例

3.2.9. 模組

3.2.9.1. Import-related attributes on module objects

3.2.9.2. 模組物件的其他可寫入屬性

3.2.9.3. 模組字典

3.2.10. Custom classes

3.2.10.1. 特殊屬性

3.2.10.2. 特殊方法

3.2.11. 類別實例

3.2.11.1. 特殊屬性

3.2.12. I/O objects (also known as file objects)

3.2.13. Internal types

3.2.13.1. 程式碼物件

3.2.13.1.1. 特殊唯讀屬性

3.2.13.1.2. 用於程式碼物件的方法

3.2.13.2. Frame objects

3.2.13.2.1. 特殊唯讀屬性

3.2.13.2.2. 特殊可寫屬性

3.2.13.2.3. Frame object methods

3.2.13.3. Traceback objects

3.2.13.4. Slice objects

3.2.13.5. Static method objects

3.2.13.6. Class method objects

3.3. Special method names

3.3.1. Basic customization

3.3.2. Customizing attribute access

3.3.2.1. Customizing module attribute access

3.3.2.2. 實作描述器

3.3.2.3. Invoking Descriptors

3.3.2.4. __slots__

3.3.3. Customizing class creation

3.3.3.1. Metaclasses

3.3.3.2. Resolving MRO entries

3.3.3.3. Determining the appropriate metaclass

3.3.3.4. Preparing the class namespace

3.3.3.5. Executing the class body

3.3.3.6. Creating the class object

3.3.3.7. Uses for metaclasses

3.3.4. Customizing instance and subclass checks

3.3.5. Emulating generic types

3.3.5.1. The purpose of __class_getitem__

3.3.5.2. __class_getitem__ versus __getitem__

3.3.6. Emulating callable objects

3.3.7. Emulating container types

3.3.8. Emulating numeric types

3.3.9. With 陳述式的情境管理器

3.3.10. Customizing positional arguments in class pattern matching

3.3.11. Emulating buffer types

3.3.12. Annotations

3.3.13. Special method lookup

3.4. 協程

3.4.1. Awaitable Objects

3.4.2. 協程物件

3.4.3. Asynchronous Iterators

3.4.4. Asynchronous Context Managers

4. 執行模型

4.1. Structure of a program

4.2. Naming and binding

4.2.1. Binding of names

4.2.2. Resolution of names

4.2.3. 註釋作用域 (annotation scopes)

4.2.4. Lazy evaluation

4.2.5. Builtins and restricted execution

4.2.6. Interaction with dynamic features

4.3. 例外

4.4. Runtime Components

4.4.1. General Computing Model

4.4.2. Python Runtime Model

5. 模組引入系統

5.1. importlib

5.2. 套件

5.2.1. 一般套件

5.2.2. 命名空間套件

5.3. 搜尋

5.3.1. 模組快取

5.3.2. 尋檢器 (Finder) 與載入器 (Loader)

5.3.3. 引入掛鉤 (Import hooks)

5.3.4. 元路徑

5.4. 載入

5.4.1. 載入器

5.4.2. 子模組

5.4.3. 模組規格

5.4.4. __path__ attributes on modules

5.4.5. Module reprs

5.4.6. Cached bytecode invalidation

5.5. The Path Based Finder

5.5.1. Path entry finders

5.5.2. Path entry finder protocol

5.6. Replacing the standard import system

5.7. Package Relative Imports

5.8. Special considerations for __main__

5.8.1. __main__.__spec__

5.9. References

6. 運算式

6.1. Arithmetic conversions

6.2. Atoms

6.2.1. Identifiers (Names)

6.2.1.1. Private name mangling

6.2.2. Literals

6.2.2.1. String literal concatenation

6.2.3. Parenthesized forms

6.2.4. Displays for lists, sets and dictionaries

6.2.5. List displays

6.2.6. Set displays

6.2.7. Dictionary displays

6.2.8. Generator expressions

6.2.9. Yield expressions

6.2.9.1. Generator-iterator methods

6.2.9.2. 模組

6.2.9.3. 非同步產生器函式

6.2.9.4. Asynchronous generator-iterator methods

6.3. Primaries

6.3.1. Attribute references

6.3.2. Subscriptions

6.3.3. Slicings

6.3.4. Calls

6.4. Await expression

6.5. The power operator

6.6. Unary arithmetic and bitwise operations

6.7. Binary arithmetic operations

6.8. Shifting operations

6.9. Binary bitwise operations

6.10. Comparisons

6.10.1. Value comparisons

6.10.2. Membership test operations

6.10.3. Identity comparisons

6.11. Boolean operations

6.12. Assignment expressions

6.13. Conditional expressions

6.14. Lambdas

6.15. Expression lists

6.16. Evaluation order

6.17. Operator precedence

7. 簡單陳述式

7.1. Expression statements

7.2. Assignment statements

7.2.1. 擴增賦值陳述式

7.2.2. 註釋賦值陳述式

7.3. assert 陳述式

7.4. pass 陳述式

7.5. del 陳述式

7.6. return 陳述式

7.7. yield 陳述式

7.8. raise 陳述式

7.9. break 陳述式

7.10. continue 陳述式

7.11. import 陳述式

7.11.1. Future statements

7.12. global 陳述式

7.13. nonlocal 陳述式

7.14. type 陳述式

8. 複合陳述式

8.1. if 陳述式

8.2. while 陳述式

8.3. for 陳述式

8.4. try 陳述式

8.4.1. except 子句

8.4.2. except* 子句

8.4.3. else 子句

8.4.4. finally 子句

8.5. with 陳述式

8.6. match 陳述式

8.6.1. Overview

8.6.2. Guards

8.6.3. Irrefutable Case Blocks

8.6.4. Patterns

8.6.4.1. OR Patterns

8.6.4.2. AS Patterns

8.6.4.3. Literal Patterns

8.6.4.4. Capture Patterns

8.6.4.5. Wildcard Patterns

8.6.4.6. Value Patterns

8.6.4.7. Group Patterns

8.6.4.8. Sequence Patterns

8.6.4.9. Mapping Patterns

8.6.4.10. Class Patterns

8.7. 函式定義

8.8. 類別定義

8.9. 協程

8.9.1. 協程函式定義

8.9.2. async for 陳述式

8.9.3. async with 陳述式

8.10. Type parameter lists

8.10.1. Generic functions

8.10.2. Generic classes

8.10.3. Generic type aliases

8.11. 註釋

9. 最高層級元件

9.1. 完整的 Python 程式

9.2. 檔案輸入

9.3. 互動式輸入

9.4. 運算式輸入

10. 完整的文法規格書

Python 標準函式庫 (Standard Library)

簡介

可用性之標註

WebAssembly 平台

行動平台

內建函式

內建常數

由 site module（模組）所添增的常數

內建型別

真值檢測

Boolean（布林）運算 --- and, or, not

比較運算

數值型別 --- int、float、complex

整數型別的位元運算

整數型別的附加方法

浮點數的附加方法

複數的附加方法

數值型別的雜湊

Boolean 型別 - bool

疊代器型別

Generator Types

Sequence Types --- list, tuple, range

Common Sequence Operations

不可變序列型別

可變序列型別

List（串列）

Tuple（元組）

Ranges

Text and Binary Sequence Type Methods Summary

Text Sequence Type --- str

字串方法

Formatted String Literals (f-strings)

Debug specifier

Conversion specifier

Format specifier

模板字串字面值 (t-strings)

printf-style String Formatting

Binary Sequence Types --- bytes, bytearray, memoryview

Bytes Objects

Bytearray 物件

Bytes 和 Bytearray 的操作

printf-style Bytes Formatting

Memory Views

Set Types --- set, frozenset

Mapping Types --- dict

字典視圖物件

情境管理器型別

型別註釋的型別 --- 泛型別名 (Generic Alias)、聯合 (Union)

泛型別名型別

標準泛型類別

GenericAlias 物件的特殊屬性

聯合型別 (Union Type)

其他內建型別

模組

類別與類別實例

函式

方法

程式碼物件

Type Objects

Null 物件

Ellipsis 物件

NotImplemented 物件

內部物件

特殊屬性

Integer string conversion length limitation

受影響的 API

設定限制

建議的配置

內建的例外

例外的情境

繼承自內建的例外

基底類別 (base classes)

實體例外

作業系統例外

警告

例外群組

例外階層

文本處理 (Text Processing) 服務

string --- 常見的字串操作

字串常數

自訂字串格式

格式化文字語法

格式規格 (Format Specification) 迷你語言

格式範例

模板字串 ($-strings)

輔助函式

string.templatelib --- 對模板字串字面值的支援

模板字串

Types

Helper functions

re --- 正規表示式 (regular expression) 操作

正規表示式語法

模組內容

旗標

函式

例外

正規表示式物件

Match Objects

Regular Expression Examples

Checking for a Pair

模擬 scanf()

search() vs. match()

Making a Phonebook

Text Munging

Finding all Adverbs

Finding all Adverbs and their Positions

Raw String Notation

Writing a Tokenizer

difflib --- 計算差異的輔助工具

SequenceMatcher 物件

SequenceMatcher 範例

Differ Objects

Differ Example

difflib 的命令列介面

ndiff 範例：

textwrap --- 文字包裝與填充

unicodedata --- Unicode 資料庫

stringprep --- 網際網路字串的準備

readline --- GNU readline 介面

Init file

Line buffer

History file

History list

Startup hooks

Completion

範例

rlcompleter --- GNU readline 的補全函式

二進位資料服務

struct --- 將位元組直譯為打包起來的二進位資料

函式與例外

格式字串

位元組順序、大小和對齊

格式字元

範例

應用

原生格式

標準格式

類別

codecs --- 編解碼器註冊表和基底類別

Codec Base Classes

Error Handlers

Stateless Encoding and Decoding

Incremental Encoding and Decoding

IncrementalEncoder 物件

IncrementalDecoder 物件

串流編碼和解碼

StreamWriter 物件

StreamReader 物件

StreamReaderWriter 物件

StreamRecoder 物件

編碼和 Unicode

標準編碼

Python Specific Encodings

Text Encodings

Binary Transforms

Standalone Codec Functions

Text Transforms

encodings --- Encodings package

encodings.idna --- Internationalized Domain Names in Applications

encodings.mbcs --- Windows ANSI 碼頁

encodings.utf_8_sig --- UTF-8 codec with BOM signature

資料型別

datetime --- 日期與時間的基本型別

Aware and Naive Objects

常數

Available Types

常見屬性

Determining if an Object is Aware or Naive

timedelta 物件

用法範例：timedelta

date 物件

用法範例：date

datetime 物件

用法範例：datetime

time 物件

用法範例：time

tzinfo 物件

timezone 物件

strftime() 與 strptime() 的行為

strftime() 與 strptime() 格式碼

技術細節

zoneinfo --- IANA 時區支援

使用 ZoneInfo

資料來源

設定資料來源

編譯時期設定

環境設定

Runtime 設定

ZoneInfo 類別

字串表示

封裝（Pickle）序列化

函式

全域變數

例外與警告

calendar --- 日曆相關函式

命令列用法

collections --- 容器資料型別

ChainMap 物件

ChainMap 範例和用法

Counter 物件

deque 物件

deque 用法

defaultdict 物件

defaultdict 範例

namedtuple() 擁有具名欄位之 tuple 的工廠函式

OrderedDict 物件

OrderedDict 範例與用法

UserDict 物件

UserList 物件

UserString 物件

collections.abc --- 容器的抽象基底類別

Collections Abstract Base Classes

集合抽象基底類別的詳細描述

Examples and Recipes

heapq --- 堆積佇列 (heap queue) 演算法

基礎範例

Other Applications

優先佇列實作細節

原理

bisect --- 陣列二分演算法 (Array bisection algorithm)

效能考量

搜尋一個已排序的 list

範例

array --- 高效率的數值型陣列

weakref --- 弱參照

弱參照物件

範例

最終化器物件

最終化器與 __del__() 方法的比較

types --- 動態型別建立與內建型別名稱

Dynamic Type Creation

Standard Interpreter Types

Additional Utility Classes and Functions

Coroutine Utility Functions

copy --- 淺層 (shallow) 和深層 (deep) 複製操作

pprint --- 資料美化列印器

函式

PrettyPrinter 物件

範例

reprlib --- repr() 的替代實作

Repr 物件

Subclassing Repr Objects

enum --- 對列舉的支援

模組內容

資料型別

支援的 __dunder__ 名稱

支援的 _sunder_ 名稱

通用項目與裝飾器

備註

graphlib —-- 使用類圖 (graph-like) 結構進行操作的功能

例外

數值與數學模組

numbers --- 數值的抽象基底類別

數值的階層

給型別實作者的註記

加入更多數值 ABC

實作算術操作

math --- 數學函式

數論函式

浮點數算術運算

浮點數操作函式

次方、指數與對數函式

總和與乘積函式

角度轉換

三角函式

雙曲函式

特殊函式

常數

cmath --- 複數的數學函式

轉換到極座標和從極座標做轉換

冪函數和對數函數

三角函數

雙曲函數

分類函式

常數

decimal --- 十進位固定點和浮點運算

Quick-start tutorial

Decimal objects

Logical operands

Context objects

常數

Rounding modes

Signals

Floating-point notes

Mitigating round-off error with increased precision

特殊值

Working with threads

Recipes

Decimal FAQ

fractions --- 有理數

random --- 產生偽隨機數

簿記函式 (bookkeeping functions)

回傳位元組的函式

回傳整數的函式

回傳序列的函式

離散分布

實數分布

替代產生器

關於 Reproducibility（復現性）的注意事項

範例

使用方案

命令列用法

命令列範例

statistics --- 數學統計函式

平均值與中央位置量數

離度 (spread) 的測量

兩個輸入之間的關係統計

函式細節

例外

NormalDist 物件

範例與錦囊妙計

經典機率問題

用於模擬的蒙地卡羅 (Monte Carlo) 輸入

近似二項分布

單純貝氏分類器 (Naive bayesian classifier)

函式程式設計模組

itertools --- 建立產生高效率迴圈之疊代器的函式

Itertool 函式

Itertools 應用技巧

functools --- 可呼叫物件上的高階函式與操作

partial 物件

operator --- 標準運算子替代函式

運算子與函式間的對映

原地 (in-place) 運算子

檔案與目錄存取

pathlib --- 物件導向檔案系統路徑

基本用法

例外

純路徑

通用屬性

運算子

對個別組成的存取

方法與屬性

實體路徑

剖析和產生 URI

擴展和解析路徑

查詢檔案類型和狀態

讀取和寫入檔案

讀取目錄

建立檔案和目錄

複製、移動和刪除

權限和所有權

模式語言 (pattern language)

與 glob 模組的比較

與 os 和 os.path 模組的比較

對應工具

Protocols

os.path --- 常見的路徑名操作

stat --- 直譯 stat() 的結果

filecmp --- 檔案與目錄比較

The dircmp class

tempfile --- 生成臨時檔案和目錄

範例

已棄用的函式和變數

glob --- Unix 風格的路徑名稱模式擴展

範例

fnmatch --- Unix 檔案名稱模式比對

linecache --- 隨機存取文字列

shutil — 高階檔案操作

目錄和檔案操作

Platform-dependent efficient copy operations

copytree 範例

rmtree 範例

Archiving operations

Archiving example

Archiving example with base_dir

Querying the size of the output terminal

資料持久性 (Data Persistence)

pickle --- Python 物件序列化

和其他 Python 模組的關係

和 marshal 的比較

和 json 的比較

資料串流格式

模組介面

哪些物件能或不能被封裝、拆封？

Pickling 類別實例

外部物件持久化

調度表

處裡紀錄大量狀態的物件

針對型別、函式或特定物件定製縮減函式

帶外（Out-of-band）資料緩衝區

供給者 API

消費者 API

範例

限制全域物件

效能

範例

命令列介面

copyreg --- 註冊 pickle 支援函式

範例

shelve --- Python object persistence

Restrictions

範例

marshal --- 內部 Python 物件序列化

dbm --- Unix "databases" 的介面

dbm.sqlite3 --- dbm 的 SQLite 後端

dbm.gnu --- GNU 資料庫管理器

dbm.ndbm --- 新資料庫管理器

dbm.dumb --- 可攜式 DBM 實作

sqlite3 --- SQLite 資料庫的 DB-API 2.0 介面

教學

Reference

Module functions

Module constants

Connection 物件

Cursor 物件

Row 物件

Blob 物件

PrepareProtocol 物件

例外

SQLite and Python types

Default adapters and converters (deprecated)

命令列介面

How-to guides

How to use placeholders to bind values in SQL queries

How to adapt custom Python types to SQLite values

How to write adaptable objects

How to register adapter callables

How to convert SQLite values to custom Python types

Adapter and converter recipes

How to use connection shortcut methods

How to use the connection context manager

How to work with SQLite URIs

How to create and use row factories

如何處理非 UTF-8 的文字編碼

解釋

Transaction control

Transaction control via the autocommit attribute

Transaction control via the isolation_level attribute

資料壓縮與保存

compression 套件

compression.zstd --- 與 Zstandard 格式相容的壓縮

例外

Reading and writing compressed files

Compressing and decompressing data in memory

Zstandard 字典

Advanced parameter control

Miscellaneous

範例

zlib --- 相容於 gzip 的壓縮

gzip --- gzip 檔案的支援

用法範例

命令列介面

命令列選項

bz2 --- bzip2 壓縮的支援

(De)compression of files

Incremental (de)compression

One-shot (de)compression

用法範例

lzma --- 使用 LZMA 演算法進行壓縮

Reading and writing compressed files

Compressing and decompressing data in memory

Miscellaneous

Specifying custom filter chains

範例

zipfile --- 處理 ZIP 封存檔案

ZipFile 物件

Path 物件

PyZipFile 物件

ZipInfo 物件

命令列介面

命令列選項

解壓縮的陷阱

來自檔案本身

檔案系統限制

資源限制

中斷

解壓縮的預設行為

tarfile --- 讀取與寫入 tar 封存檔案

TarFile 物件

TarInfo 物件

解壓縮篩選器

預設具名篩選器

篩選器錯誤

進一步驗證的提示

支援舊版 Python

有狀態的解壓縮篩選器範例

命令列介面

命令列選項

範例

讀取範例

寫入範例

支援的 tar 格式

Unicode 議題

檔案格式

csv --- CSV 檔案讀取及寫入

模組內容

Dialect 與格式參數

讀取器物件

寫入器物件

範例

configparser --- 設定檔剖析器

Quick Start

Supported Datatypes

Fallback Values

支援的 INI 檔案結構

Unnamed Sections

Interpolation of values

Mapping Protocol Access

Customizing Parser Behaviour

Legacy API Examples

ConfigParser 物件

RawConfigParser 物件

例外

tomllib --- 剖析 TOML 檔案

範例

轉換表

netrc --- netrc 檔案處理

netrc 物件

plistlib --- 產生和剖析 Apple .plist 檔案

範例

加密服務

hashlib --- 安全雜湊與訊息摘要

雜湊演算法

用法

建構函式

屬性

雜湊物件

SHAKE 可變長度摘要

檔案雜湊

密鑰的生成

BLAKE2

建立雜湊物件

常數

範例

簡單雜湊

使用不同的摘要大小

密鑰雜湊 (Keyed hashing)

隨機雜湊 (Randomized hashing)

個人化

樹狀模式

製作人員

hmac --- 基於金鑰雜湊的訊息驗證

secrets --- 產生用於管理機密的安全亂數

亂數

產生權杖（token）

權杖應當使用多少個位元組？

其他函式

應用技巧和典範實務（best practices）

通用作業系統服務

os --- 各種作業系統介面

File Names, Command Line Arguments, and Environment Variables

Python UTF-8 模式

行程參數

File Object Creation

File Descriptor Operations

Querying the size of a terminal

Inheritance of File Descriptors

Files and Directories

計時器檔案描述器

Linux extended attributes

行程管理

排程器介面

Miscellaneous System Information

Random numbers

io — 處理資料串流的核心工具

總覽

文字 I/O

二進位 (Binary) I/O

原始 (Raw) I/O

文字編碼

選擇性加入的編碼警告

高階模組介面

類別階層

I/O 基礎類別

原始檔案 I/O

Buffered Streams

文字 I/O

Static Typing

Performance

二進位 (Binary) I/O

文字 I/O

Multi-threading

Reentrancy

time --- 時間存取與轉換

函式

時鐘 ID 常數

時區常數

logging --- Python 的日誌記錄工具

Logger 物件

Logging Levels

Handler Objects

Formatter Objects

Filter Objects

LogRecord 物件

LogRecord 屬性

LoggerAdapter 物件

執行緒安全

模組層級函式

模組層級屬性

Integration with the warnings module

logging.config --- 日誌記錄配置

Configuration functions

Security considerations

Configuration dictionary schema

Dictionary Schema Details

Incremental Configuration

Object connections

User-defined objects

Handler configuration order

Access to external objects

Access to internal objects

Import resolution and custom importers

Configuring QueueHandler and QueueListener

Configuration file format

logging.handlers --- 日誌紀錄處理器

StreamHandler

FileHandler

NullHandler

WatchedFileHandler

BaseRotatingHandler

RotatingFileHandler

TimedRotatingFileHandler

SocketHandler

DatagramHandler

SysLogHandler

NTEventLogHandler

SMTPHandler

MemoryHandler

HTTPHandler

QueueHandler

QueueListener

platform --- 對底層平臺識別資料的存取

跨平台

Java 平台

Windows 平台

macOS 平台

iOS 平台

Unix 平台

Linux 平台

Android 平台

命令列用法

errno --- 標準 errno 系統符號

ctypes --- 用於 Python 的外部函式庫

ctypes 教學

Loading dynamic link libraries

Accessing functions from loaded dlls

呼叫函式

Fundamental data types

Calling functions, continued

Calling variadic functions

Calling functions with your own custom data types

Specifying the required argument types (function prototypes)

Return types

Passing pointers (or: passing parameters by reference)

Structures and unions

Structure/union layout, alignment and byte order

Bit fields in structures and unions

Arrays

指標

Thread safety without the GIL

Type conversions

Incomplete Types

回呼函式

Accessing values exported from dlls

Surprises

Variable-sized data types

ctypes reference

Finding shared libraries

Listing loaded shared libraries

Loading shared libraries

Foreign functions

Function prototypes

Utility functions

Data types

Fundamental data types

Structured data types

Arrays and pointers

Exceptions

命令列介面函式庫

argparse --- 命令列選項、引數和子命令的剖析器

ArgumentParser 物件

prog

usage

description

epilog

parents

formatter_class

prefix_chars

fromfile_prefix_chars

argument_default

allow_abbrev

conflict_handler

add_help

exit_on_error

suggest_on_error

color

add_argument() 方法

name or flags

action

nargs

const

default

type

choices

required

help

metavar

dest

deprecated

Action 類別

parse_args() 方法

Option value syntax

無效引數

包含 - 的引數

引數縮寫 (前綴匹配)

sys.argv 之外

命名空間物件

Other utilities

子命令

FileType 物件

引數群組

Mutual exclusion

Parser defaults

印出幫助訊息

Partial parsing

Customizing file parsing

Exiting methods

Intermixed parsing

Registering custom types or actions

例外

Argparse 教學

概念

基本用法

位置引數的介紹

可選引數的介紹

短選項

組合位置引數和可選引數

更進階一點

指定不明確的引數

相互衝突的選項

如何翻譯 argparse 輸出

自訂型別轉換器

結論

將 optparse 程式碼遷移到 argparse

optparse --- 命令列選項剖析器

選擇一個命令列參數剖析函式庫

Introduction

背景

術語

What are options for?

What are positional arguments for?

教學

Understanding option actions

The store action

Handling boolean (flag) options

Other actions

預設值

Generating help

Grouping Options

Printing a version string

How optparse handles errors

Putting it all together

Reference Guide

建立剖析器

Populating the parser

定義選項

選項屬性

標準選項動作

Standard option types

剖析引數

Querying and manipulating your option parser

Conflicts between options

Cleanup

其他方法

Option Callbacks

Defining a callback option

How callbacks are called

Raising errors in a callback

Callback example 1: trivial callback

Callback example 2: check option order

Callback example 3: check option order (generalized)

Callback example 4: check arbitrary condition

Callback example 5: fixed arguments

Callback example 6: variable arguments

Extending optparse

Adding new types

Adding new actions

例外

getpass --- 可攜式密碼輸入工具

fileinput --- 逐列疊代多個輸入串流

curses --- 字元儲存格顯示的終端處理

函式

Window Objects

Constants

curses.textpad --- Text input widget for curses programs

Textbox objects

curses.ascii --- ASCII 字元的工具程式

curses.panel --- curses 的面板堆疊擴充

函式

Panel Objects

cmd --- 以列為導向的命令直譯器支援

Cmd 物件

Cmd 範例

並行執行 (Concurrent Execution)

threading --- 基於執行緒的平行性

Introduction

GIL and performance considerations

Reference

Thread-local data

Thread 物件

Lock 物件

RLock 物件

Condition objects

Semaphore 物件

Semaphore 範例

Event objects

Timer 物件

Barrier 物件

Using locks, conditions, and semaphores in the with statement

multiprocessing --- 以行程為基礎的平行性

簡介

Process 類別

Contexts and start methods

Exchanging objects between processes

Synchronization between processes

Sharing state between processes

Using a pool of workers

Reference

Global start method

Process 與例外

Pipes and Queues

Miscellaneous

Connection Objects

Synchronization primitives

共享的 ctypes 物件

multiprocessing.sharedctypes 模組

Managers

Customized managers

Using a remote manager

Proxy Objects

Cleanup

Process Pools

Listeners and Clients

Address Formats

Authentication keys

Logging

multiprocessing.dummy 模組

Programming guidelines

All start methods

The spawn and forkserver start methods

範例

multiprocessing.shared_memory --- 對於共享記憶體的跨行程直接存取

concurrent 套件

concurrent.futures --- 啟動平行任務

Executor 物件

ThreadPoolExecutor

ThreadPoolExecutor 範例

InterpreterPoolExecutor

ProcessPoolExecutor

ProcessPoolExecutor 範例

Future 物件

模組函式

例外類別

concurrent.interpreters --- 在同一個行程中使用多個直譯器

Key details

Introduction

Multiple Interpreters and Isolation

Running in an Interpreter

Concurrency and Parallelism

直譯器之間的溝通

"Sharing" Objects

Reference

Interpreter objects

例外

在直譯器之間溝通

基本用法

subprocess --- 子行程管理

Using the subprocess Module

Frequently Used Arguments

Popen Constructor

例外

安全性注意事項

Popen Objects

Windows Popen Helpers

Windows Constants

Older high-level API

Replacing Older Functions with the subprocess Module

Replacing /bin/sh shell command substitution

Replacing shell pipeline

取代 os.system()

Replacing the os.spawn family

取代 os.popen()

Legacy Shell Invocation Functions

註解

Timeout Behavior

Converting an argument sequence to a string on Windows

停用 posix_spawn()

sched --- 事件排程器

排程器物件

queue --- 同步佇列 (synchronized queue) 類別

佇列物件

Waiting for task completion

Terminating queues

SimpleQueue 物件

contextvars --- 情境變數

情境變數

手動情境管理

對 asyncio 的支援

_thread --- 低階執行緒 API

網路與行程間通訊

asyncio --- 非同步 I/O

Runners (執行器)

運行一個 asyncio 程式

Runner context manager

Handling Keyboard Interruption

協程與任務

協程

Awaitables

Creating Tasks

Task Cancellation

Task Groups

Terminating a Task Group

Sleeping

Running Tasks Concurrently

Eager Task Factory

Shielding From Cancellation

Timeouts

Waiting Primitives

Running in Threads

Scheduling From Other Threads

Introspection

Task 物件

串流

StreamReader

StreamWriter

範例

使用串流的 TCP echo 用戶端

使用串流的 TCP echo 伺服器

取得 HTTP 標頭

註冊一個使用串流來等待資料的開放 socket

同步化原始物件 (Synchronization Primitives)

Lock

Event

Condition

Semaphore

BoundedSemaphore

Barrier

子行程

建立子行程

常數

與子行程互動

子行程與執行緒

範例

佇列 (Queues)

Queue

Priority Queue（優先佇列）

LIFO Queue

例外

範例

例外

Call Graph Introspection

低階工具函式

事件迴圈

事件迴圈方法

啟動和停止迴圈

排程回呼函式

排程延遲的回呼函式

建立 Futures 和 Tasks

打開網路連線

建立網路伺服器

傳輸檔案

TLS 升級

監視檔案描述器

直接使用 socket 物件

DNS

使用管道

Unix 訊號

在執行緒池或行程池中執行程式碼

錯誤處理 API

啟用除錯模式

運行子行程

回呼處理

Server 物件

事件迴圈實作

範例

使用 call_soon() 的 Hello World 範例

使用 call_later() 顯示目前日期

監聽檔案描述器以進行讀取事件

設定 SIGINT 和 SIGTERM 的訊號處理程式

Futures

Future 函式

Future 物件

傳輸與協定

Transports

Transports Hierarchy

Base Transport

Read-only Transports

Write-only Transports

Datagram Transports

Subprocess Transports

Protocols

Base Protocols

Base Protocol

Streaming Protocols

Buffered Streaming Protocols

Datagram Protocols

Subprocess Protocols

範例

TCP Echo Server

TCP Echo Client

UDP Echo Server

UDP Echo Client

Connecting Existing Sockets

loop.subprocess_exec() and SubprocessProtocol

Policies

Getting and Setting the Policy

Policy Objects

Custom Policies

平臺支援

所有平台

Windows

Windows 的子行程支援

macOS

擴充

Writing a Custom Event Loop

Future and Task private constructors

Task lifetime support

高階 API 索引

任務 (Tasks)

佇列 (Queues)

子行程 (Subprocesses)

串流 (Streams)

同步化 (Synchronization)

例外

低階 API 索引

取得事件迴圈

事件迴圈方法

傳輸

協定

事件迴圈 Policies

使用 asyncio 開發

除錯模式

並行性和多執行緒 (Concurrency and Multithreading)

執行阻塞的程式

日誌記錄

偵測從未被等待的 (never-awaited) 協程

偵測從未被取得的 (never-retrieved) 例外

socket — 低階網路介面

Socket 系列家族

模組內容

例外

常數

函式

建立 sockets

其他函式

Socket 物件

Notes on socket timeouts

Timeouts and the connect method

Timeouts and the accept method

範例

ssl --- socket 物件的 TLS/SSL 包裝器

函式、常數與例外

Socket 建立

語境建立

例外

隨機產生

認證處理

常數

SSL Sockets

SSL Contexts

Certificates

Certificate chains

CA certificates

Combined key and certificate

Self-signed certificates

範例

Testing for SSL support

Client-side operation

伺服器端操作

Notes on non-blocking sockets

記憶體 BIO 支援

SSL session

Security considerations

Best defaults

手動設定

驗證憑證

協定版本

Cipher selection

Multi-processing

TLS 1.3

select --- 等待 I/O 完成

/dev/poll Polling Objects

Edge and Level Trigger Polling (epoll) Objects

Polling Objects

Kqueue Objects

Kevent Objects

selectors --- 高階 I/O 多工

簡介

Classes

範例

signal --- 設定非同步事件的處理函式

一般規則

Python 訊號處理程式的執行

訊號和執行緒

模組內容

範例

關於 SIGPIPE 的說明

訊號處理程式與例外的說明

mmap --- 記憶體對映檔案的支援

MADV_* 常數

MAP_* 常數

網際網路資料處理

email --- 郵件和 MIME 處理套件

email.message：表示電子郵件訊息

email.parser：剖析電子郵件訊息

FeedParser API

Parser API

Additional notes

email.generator：產生 MIME 文件

email.policy: Policy Objects

email.errors：例外和缺陷類別

email.headerregistry：自訂標頭物件

email.contentmanager：管理 MIME 內容

Content Manager Instances

email：範例

email.message.Message: Representing an email message using the compat32 API

email.mime：從頭開始建立電子郵件和 MIME 物件

email.header：國際化標頭

email.charset：字元集合的表示

email.encoders：編碼器

email.utils：雜項工具

email.iterators：疊代器

json --- JSON 編碼器與解碼器

基本用法

編碼器與解碼器

例外

合規性與互通性（Interoperability）

字元編碼格式

正負無限與非數值

物件內重複的名稱

位於頂層的非物件及非列表值

實作限制

命令列介面

命令列選項

mailbox --- 以各種格式操作郵件信箱

Mailbox 物件

Mailbox 物件

mbox 物件

MH 物件

Babyl 物件

MMDF 物件

Message 物件

MaildirMessage 物件

mboxMessage 物件

MHMessage 物件

BabylMessage 物件

MMDFMessage 物件

例外

範例

mimetypes --- 將檔案名稱對映到 MIME 類型

MimeTypes 物件

命令列用法

Command-line example

base64 --- Base16、Base32、Base64、Base85 資料編碼

RFC 4648 編碼

Base85 編碼

舊版介面

安全性注意事項

binascii --- 在二進位制和 ASCII 之間轉換

quopri --- 編碼和解碼 MIME 可列印字元資料

結構化標記處理工具

html --- 超文本標記語言 (HTML) 支援

html.parser --- 簡單的 HTML 和 XHTML 剖析器

HTML 剖析器應用程式範例

HTMLParser 方法

範例

html.entities --- HTML 一般實體的定義

XML 處理模組

XML 安全性

xml.etree.cElementTree --- ElementTree XML API

教學

XML tree and elements

剖析 XML

Pull API for non-blocking parsing

Finding interesting elements

改動 XML 檔案

建立 XML 文件

Parsing XML with Namespaces

XPath 支援

範例

支援的 XPath 語法

Reference

函式

XInclude support

範例

Reference

函式

Element 物件

ElementTree 物件

QName 物件

TreeBuilder 物件

XMLParser 物件

XMLPullParser 物件

例外

xml.dom --- Document 物件模型 API

模組內容

Objects in the DOM

DOMImplementation 物件

Node Objects

NodeList 物件

DocumentType 物件

Document Objects

Element Objects

Attr Objects

NamedNodeMap 物件

Comment Objects

Text and CDATASection Objects

ProcessingInstruction 物件

例外

Conformance

Type Mapping

Accessor Methods

xml.dom.minidom --- 最小的 DOM 實作

DOM 物件

DOM 範例

minidom 和 DOM 標準

xml.dom.pulldom --- 支援建置部分 DOM 樹

DOMEventStream 物件

xml.sax --- SAX2 剖析器支援

SAXException 物件

xml.sax.handler --- SAX 處理函式的基本類別

ContentHandler 物件

DTDHandler 物件

EntityResolver 物件

ErrorHandler 物件

LexicalHandler 物件

xml.sax.saxutils --- SAX 工具程式

xml.sax.xmlreader --- XML 剖析器的介面

XMLReader 物件

IncrementalParser 物件

Locator Objects

InputSource 物件

The Attributes Interface

The AttributesNS Interface

xml.parsers.expat --- 使用 Expat 進行快速 XML 剖析

XMLParser 物件

ExpatError 例外

範例

Content Model Descriptions

Expat 錯誤常數

網路協定 (Internet protocols) 及支援

webbrowser --- 方便的網頁瀏覽器控制器

命令列介面

瀏覽器控制器物件

wsgiref --- WSGI 工具與參考實作

wsgiref.util -- WSGI 環境工具

wsgiref.headers -- WSGI 回應標頭工具

wsgiref.simple_server -- 一個簡單的 WSGI HTTP 伺服器

wsgiref.validate --- WSGI 符合性檢查

wsgiref.handlers -- 伺服器 / 閘道基本類別

wsgiref.types -- 用於靜態型別檢查的 WSGI 型別

範例

urllib --- URL 處理模組

urllib.request --- 用來開啟 URLs 的可擴充函式庫

Request 物件

OpenerDirector 物件

BaseHandler 物件

HTTPRedirectHandler 物件

HTTPCookieProcessor 物件

ProxyHandler 物件

HTTPPasswordMgr 物件

HTTPPasswordMgrWithPriorAuth 物件

AbstractBasicAuthHandler 物件

HTTPBasicAuthHandler 物件

ProxyBasicAuthHandler 物件

AbstractDigestAuthHandler 物件

HTTPDigestAuthHandler 物件

ProxyDigestAuthHandler 物件

HTTPHandler 物件

HTTPSHandler 物件

FileHandler 物件

DataHandler 物件

FTPHandler 物件

CacheFTPHandler 物件

UnknownHandler 物件

HTTPErrorProcessor 物件

範例

遺留介面

urllib.request 限制

urllib.response --- Response classes used by urllib

urllib.parse --- 將 URL 剖析成元件

URL Parsing

URL parsing security

Parsing ASCII Encoded Bytes

Structured Parse Results

URL Quoting

urllib.error --- urllib.request 引發的例外類別

urllib.robotparser --- robots.txt 的剖析器

http --- HTTP 模組

HTTP 狀態碼

HTTP 狀態分類

HTTP 方法

http.client --- HTTP 協定用戶端

HTTPConnection 物件

HTTPResponse 物件

範例

HTTPMessage 物件

ftplib --- FTP 協定用戶端

參考

FTP 物件

FTP_TLS 物件

模組變數

poplib --- POP3 協定用戶端

POP3 物件

POP3 範例

imaplib --- IMAP4 協定用戶端

IMAP4 物件

IMAP4 範例

smtplib --- SMTP 協定用戶端

SMTP 物件

SMTP 範例

uuid --- RFC 9562 定義的 UUID 物件

命令列的用法

範例

命令列的範例

socketserver --- 用於網路伺服器的框架

Server Creation Notes

Server Objects

Request Handler Objects

範例

socketserver.TCPServer 範例

socketserver.UDPServer 範例

Asynchronous Mixins

http.server — HTTP 伺服器

命令列介面

安全性注意事項

http.cookies --- HTTP 狀態管理

Cookie 物件

Morsel 物件

範例

http.cookiejar --- HTTP 用戶端的 Cookie 處理

CookieJar 與 FileCookieJar 物件

FileCookieJar 子類別及與網頁瀏覽器的合作

CookiePolicy 物件

DefaultCookiePolicy 物件

Cookie 物件

範例

xmlrpc --- XMLRPC 伺服器與用戶模組

xmlrpc.client --- XML-RPC 用戶端存取

ServerProxy 物件

日期時間物件

Binary Objects

Fault Objects

ProtocolError 物件

MultiCall 物件

便捷的函式

Example of Client Usage

Example of Client and Server Usage

xmlrpc.server --- 基本 XML-RPC 伺服器

SimpleXMLRPCServer 物件

SimpleXMLRPCServer 範例

CGIXMLRPCRequestHandler

記錄 XMLRPC 伺服器

DocXMLRPCServer 物件

DocCGIXMLRPCRequestHandler

ipaddress --- IPv4/IPv6 操作函式庫

Convenience factory functions

IP Addresses

Address objects

Conversion to Strings and Integers

運算子

比較運算子

算術運算子

IP Network definitions

Prefix, net mask and host mask

Network objects

運算子

Logical operators

疊代

Networks as containers of addresses

Interface objects

運算子

Logical operators

Other Module Level Functions

Custom Exceptions

多媒體服務

wave --- 讀寫 WAV 檔案

Wave_read 物件

Wave_write 物件

colorsys --- 顏色系統間的轉換

國際化

gettext --- 多語言國際化服務

GNU gettext API

Class-based API

The NullTranslations class

The GNUTranslations class

Solaris message catalog support

The Catalog constructor

Internationalizing your programs and modules

Localizing your module

Localizing your application

Changing languages on the fly

Deferred translations

致謝

locale --- 國際化服務

Background, details, hints, tips and caveats

Locale names

For extension writers and programs that embed Python

Access to message catalogs

以 Tk 打造圖形使用者介面 (Graphical User Interfaces)

tkinter --- Tcl/Tk 的 Python 介面

架構

Tkinter 模組

Tkinter 應急指南

一個 Hello World 程式

重要的 Tk 概念

了解 Tkinter 如何包裝 Tcl/Tk

我該如何...？哪個選項可以...？

瀏覽 Tcl/Tk 參考手冊

執行緒模型

實用參考

設定選項

Packer 佈局管理器

Packer 選項

耦合元件變數

視窗管理器

Tk 選項資料型別

繫結與事件

index 參數

圖片

檔案處理常式

tkinter.colorchooser --- 顏色選擇對話框

tkinter.font --- Tkinter 字型包裝器

Tkinter 對話框

tkinter.simpledialog --- 標準 Tkinter 輸入對話框

tkinter.filedialog --- 檔案選擇對話框

Native Load/Save Dialogs

tkinter.commondialog --- Dialog window templates

tkinter.messagebox --- Tkinter 訊息提示

tkinter.scrolledtext --- 捲動文字小工具

tkinter.dnd --- 拖放支援

tkinter.ttk --- Tk 主題化小工具

使用 Ttk

Ttk Widgets

Widget

標準選項

Scrollable Widget Options

Label Options

相容性選項

Widget States

ttk.Widget

Combobox

選項

Virtual events

ttk.Combobox

Spinbox

選項

Virtual events

ttk.Spinbox

Notebook

選項

Tab Options

Tab Identifiers

虛擬事件

ttk.Notebook

Progressbar

選項

ttk.Progressbar

Separator

選項

Sizegrip

Platform-specific notes

Bugs

Treeview

選項

Item Options

Tag Options

Column Identifiers

虛擬事件

ttk.Treeview

Ttk Styling

Layouts

IDLE --- Python 編輯器與 shell

目錄

File menu (Shell and Editor)

Edit menu (Shell and Editor)

Format menu (Editor window only)

Run menu (Editor window only)

Shell menu (Shell window only)

Debug menu (Shell window only)

Options menu (Shell and Editor)

Window menu (Shell and Editor)

Help menu (Shell and Editor)

Context menus

Editing and Navigation

Editor windows

Key bindings

Automatic indentation

Search and Replace

Completions

Calltips

Format block

Code Context

Shell window

Text colors

Startup and Code Execution

命令列用法

Startup failure

Running user code

User output in Shell

Developing tkinter applications

Running without a subprocess

Help and Preferences

Help sources

設定偏好

macOS 上的 IDLE

Extensions

idlelib --- implementation of IDLE application

turtle --- 龜圖學 (Turtle graphics)

介紹

Get started

教學

啟動一個烏龜環境

基本繪圖

Pen control

The turtle's position

Making algorithmic patterns

How to...

Get started as quickly as possible

Automatically begin and end filling

Use the turtle module namespace

Use turtle graphics in a script

Use object-oriented turtle graphics

Turtle graphics reference

Turtle methods

Methods of TurtleScreen/Screen

Methods of RawTurtle/Turtle and corresponding functions

Turtle motion

Tell Turtle's state

Settings for measurement

Pen control

Drawing state

Color control

Filling

More drawing control

Turtle state

Visibility

Appearance

Using events

Special Turtle methods

Compound shapes

Methods of TurtleScreen/Screen and corresponding functions

Window control

Animation control

Using screen events

Input methods

Settings and special methods

Methods specific to Screen, not inherited from TurtleScreen

Public classes

解釋

Help and configuration

How to use help

Translation of docstrings into different languages

How to configure Screen and Turtles

turtledemo --- Demo scripts

自 Python 2.6 以來的變更

自 Python 3.0 以來的變更

開發工具

typing --- 支援型別提示

Python 型別系統的技術規範

型別別名

NewType

註釋 callable 物件

泛型

註釋元組 (tuple)

類別物件的型別

Annotating generators and coroutines

使用者定義泛型型別

Any 型別

標稱 (nominal) 子型別 vs 結構子型別

模組內容

特別型別原語 (primitive)

特別型別

特別型式

Building generic types and type aliases

Other special directives

協定

ABCs and Protocols for working with I/O

函式與裝飾器

Introspection helpers

常數

棄用的別名

內建型別的別名

collections 中型別的別名

Aliases to other concrete types

collections.abc 中容器 ABC 的別名

collections.abc 中非同步 ABC 的別名

Aliases to other ABCs in collections.abc

contextlib ABC 的別名

主要功能的棄用時程表

pydoc --- 文件產生器與線上幫助系統

Python 開發模式

Python 開發模式的影響

ResourceWarning 範例

檔案描述器的錯誤範例

doctest --- 測試互動式 Python 範例

Simple Usage: Checking Examples in Docstrings

Simple Usage: Checking Examples in a Text File

命令列用法

運作方式

Which Docstrings Are Examined?

How are Docstring Examples Recognized?

What's the Execution Context?

What About Exceptions?

可選旗標

Directives

警告

基礎 API

Unittest API

Advanced API

DocTest 物件

Example 物件

DocTestFinder 物件

DocTestParser 物件

TestResults 物件

DocTestRunner 物件

OutputChecker 物件

偵錯

Soapbox

unittest --- 單元測試框架

簡單範例

命令列介面

命令列模式選項

Test Discovery（測試探索）

Organizing test code

Re-using old test code

Skipping tests and expected failures

Distinguishing test iterations using subtests

類別與函式

Test cases

Grouping tests

Loading and running tests

load_tests 協定

Class and Module Fixtures

setUpClass 和 tearDownClass

setUpModule 和 tearDownModule

Signal Handling

unittest.mock — mock 物件函式庫

快速導引

Mock 類別

呼叫

刪除屬性

Mock 名稱與名稱屬性

如同屬性一般附加 mock

Patchers

patch

patch.object

patch.dict

patch.multiple

patch 方法：啟動與停止

patch 內建函式

TEST_PREFIX

巢狀使用 Patch 裝飾器

該 patch 何處

Patch 描述器與代理物件 (Proxy Objects)

MagicMock 以及魔術方法支援

Mock 魔術方法

Magic Mock

輔助函式

sentinel（哨兵）

DEFAULT

call

create_autospec

ANY

FILTER_DIR

mock_open

Autospeccing（自動規格）

密封 mock

side_effect、return_value 和 wraps 的優先順序

unittest.mock --- 入門指南

使用 Mock 的方式

使用 Mock 來 patching 方法

對物件的方法呼叫使用 mock

Mock 類別

命名你的 mock

追蹤所有呼叫

設定回傳值和屬性

透過 mock 引發例外

Side effect 函式以及可疊代物件

Mock 非同步可疊代物件

Mock 非同步情境管理器

從現有物件建立 mock

使用 side_effect 回傳各別檔案內容

Patch 裝飾器

更多範例

Mock 鍊接呼叫

部分 mocking

Mock 產生器方法

對每個測試方法應用相同的 patch

Mock Unbound Methods （未繫結方法）

使用 mock 檢查多個呼叫

應對可變引數

巢狀使用 Patch

使用 MagicMock 來 mock 字典

Mock 子類別及其屬性

使用 patch.dict 來 mock import

追蹤呼叫順序與更簡潔的呼叫斷言

更複雜的引數匹配

test --- Python 的回歸測試 (regression tests) 套件

撰寫 test 套件的單元測試

使用命令列介面執行測試

test.support --- Python 測試套件的工具

test.support.socket_helper --- 用於 socket 測試的工具

test.support.script_helper --- 用於 Python 執行測試的工具

test.support.bytecode_helper --- 用於測試位元組碼能正確產生的支援工具

test.support.threading_helper --- Utilities for threading tests

test.support.os_helper --- 用於 os 測試的工具

test.support.import_helper --- 用於 import 測試的工具

test.support.warnings_helper --- 用於 warnings 測試的工具

除錯與效能分析

稽核事件表

bdb --- 偵錯器框架

faulthandler --- 傾印 Python 回溯

Dumping the traceback

Dumping the C stack

C Stack Compatibility

Fault handler state

Dumping the tracebacks after a timeout

Dumping the traceback on a user signal

Issue with file descriptors

範例

pdb --- Python 偵錯器

命令列介面

Debugger commands

Python 的分析器

分析器簡介

Instant User's Manual

profile 與 cProfile 模組參考文件

Stats 類別

What Is Deterministic Profiling?

限制

校正

Using a custom timer

timeit --- 測量小量程式片段的執行時間

基礎範例

Python 介面

命令列介面

範例

trace --- 追蹤或追查 Python 陳述式執行

命令列用法

主要選項

修飾子（Modifier）

篩選子（Filter）

程式介面

tracemalloc --- 追蹤記憶體配置

範例

Display the top 10

Compute differences

Get the traceback of a memory block

Pretty top

Record the current and peak size of all traced memory blocks

API

函式

DomainFilter

Filter

Frame

Snapshot

Statistic

StatisticDiff

Trace

Traceback

軟體封裝與發布

ensurepip --- pip 安裝器的初始建置 (bootstrapping)

命令列介面

模組 API

venv --- 建立虛擬環境

建立虛擬環境

虛擬環境如何運作

API

一個擴展 EnvBuilder 的範例

zipapp —-- 管理可執行的 Python zip 封存檔案

基本範例

命令列介面

Python API

範例

指定直譯器

使用 zipapp 建立獨立應用程式

注意事項

Python Zip 應用程式封存檔案格式

Python Runtime 服務

sys --- 系統特定的參數與函式

sys.monitoring --- 執行事件監控

工具識別器

註冊和使用工具

事件

區域事件

已棄用的事件

附屬事件 (ancillary events)

其他事件

STOP_ITERATION 事件

開啟和關閉事件

全域設定事件

各別程式碼物件事件

停用事件

註冊回呼函式

回呼函式引數

sysconfig --- 提供 Python 設定資訊的存取

Configuration variables

Installation paths

User scheme

posix_user

nt_user

osx_framework_user

Home scheme

posix_home

Prefix scheme

posix_prefix

nt

安裝路徑函式

其他函式

命令列用法

builtins --- 內建物件

__main__ --- 頂層程式碼環境

__name__ == '__main__'

什麼是「頂層程式碼環境」？

慣用 (Idiomatic) 用法

打包時須考慮的事情

Python 套件中的 __main__.py

慣用 (Idiomatic) 用法

import __main__

warnings --- 警告控制

警告類別

警告過濾器

重複警告的抑制標準

描述警告過濾器

預設警告過濾器

覆寫預設過濾器

暫時抑制警告

測試警告

為新版相依套件更新程式碼

可用的函式

可用的情境管理器

情境管理器的並行安全性

dataclasses --- Data Classes

模組內容

Post-init processing

類別變數

Init-only variables

凍結實例

繼承

Re-ordering of keyword-only parameters in __init__()

預設工廠函式

可變預設值

Descriptor-typed fields

contextlib --- with 陳述式工具程式

Utilities

Examples and Recipes

Supporting a variable number of context managers

Catching exceptions from __enter__ methods

Cleaning up in an __enter__ implementation

Replacing any use of try-finally and flag variables

Using a context manager as a function decorator

Single use, reusable and reentrant context managers

Reentrant context managers

Reusable context managers

abc --- 抽象基底類別

atexit --- 退出處理函式

atexit 範例

traceback --- 列印或取得堆疊回溯 (stack traceback)

Module-Level Functions

TracebackException 物件

StackSummary 物件

FrameSummary 物件

Examples of Using the Module-Level Functions

TracebackException 的使用範例

__future__ --- Future 陳述式定義

模組內容

gc --- 垃圾回收器介面 (Garbage Collector interface)

inspect --- 檢視活動物件

Types and members

取得原始碼

Introspecting callables with the Signature object

類別與函式

直譯器堆疊

Fetching attributes statically

Current State of Generators, Coroutines, and Asynchronous Generators

Code Objects Bit Flags

Buffer flags

命令列介面

annotationlib --- 用於自我檢查註釋的功能

Annotation semantics

Classes

Functions

Recipes

Using annotations in a metaclass

STRING 格式的限制

FORWARDREF 格式的限制

Security implications of introspecting annotations

site --- Site-specific configuration hook

sitecustomize

usercustomize

Readline configuration

模組內容

命令列介面

自訂 Python 直譯器

code --- 直譯器基底類別

互動式直譯器物件

互動式控制台物件

codeop --- 編譯 Python 程式碼

引入模組

zipimport --- 從 Zip 封存檔案匯入模組

zipimporter 物件

範例

pkgutil --- 套件擴充工具程式

modulefinder --- 搜尋腳本所使用的模組

ModuleFinder 的用法範例

runpy --- 定位並執行 Python 模組

importlib --- import 的實作

簡介

函式

importlib.abc -- Abstract base classes related to import

importlib.machinery -- Importers and path hooks

importlib.util -- Utility code for importers

範例

Importing programmatically

Checking if a module can be imported

Importing a source file directly

Implementing lazy imports

Setting up an importer

Approximating importlib.import_module()

importlib.resources -- 套件資源的讀取、開啟與存取

Functional API

importlib.resources.abc -- 資源的抽象基底類別

importlib.metadata -- 存取套件的元資料

Overview

Functional API

Entry points

Distribution metadata

Distribution versions

Distribution files

Distribution requirements

Mapping import to distribution packages

Distributions

Distribution Discovery

Implementing Custom Providers

範例

sys.path 模組搜尋路徑的初始化

虛擬環境

_pth 檔案

Embedded Python

Python 語言服務

ast --- 抽象語法樹 (Abstract Syntax Trees)

抽象文法 (Abstract Grammar)

節點 (Node) 類別

根節點

文本 (Literals)

變數

運算式

下標 (Subscripting)

綜合運算式 (comprehensions)

陳述式

引入 (imports)

流程控制

模式匹配 (pattern matching)

型別註釋

型別參數 (type parameters)

函式和類別定義

async 和 await

ast 輔助程式

編譯器旗標

命令列用法

symtable --- 存取編譯器的符號表

產生符號表

檢查符號表

命令列用法

token --- 與 Python 剖析樹一起使用的常數

keyword --- 檢驗 Python 關鍵字

tokenize --- Tokenizer for Python source

Tokenizing Input

命令列用法

範例

tabnanny --- 偵測不良縮排

pyclbr --- Python 模組瀏覽器支援

函式物件

類別物件

py_compile — 編譯 Python 來源檔案

命令列介面

compileall --- 位元組編譯 Python 函式庫

Command-line use

Public functions

dis --- Python bytecode 的反組譯器

命令列介面

Bytecode analysis

分析函式

Python 位元組碼指令

Opcode collections

pickletools --- pickle 開發者的工具

命令列用法

命令列選項

程式化介面

MS Windows 特有服務

msvcrt --- MS VC++ runtime 提供的有用例程

File Operations

Console I/O

Other Functions

winreg --- Windows 註冊表存取

函式

常數

HKEY_* Constants

Access Rights

64-bit Specific

Value Types

Registry Handle Objects

winsound --- Windows 的音效播放介面

Unix 特有服務

shlex --- 簡單的語法分析

shlex 物件

Parsing Rules

Improved Compatibility with Shells

posix --- 最常見的 POSIX 系統呼叫

對大檔案 (Large File) 的支援

值得注意的模組內容

pwd --- 密碼資料庫

grp --- 群組資料庫

termios --- POSIX 風格 tty 控制

範例

tty --- 終端機控制函式

pty --- 偽終端工具

範例

fcntl --- fcntl 和 ioctl 系統呼叫

resource --- 資源使用資訊

Resource Limits

Resource Usage

syslog --- Unix syslog 函式庫例程

範例

簡單範例

模組命令列介面

已被取代的模組

getopt --- 用於命令列選項的 C 風格剖析器

已移除的模組

安全性注意事項

擴充和嵌入 Python 直譯器

推薦的第三方工具

不使用第三方工具建立擴充

1. 以 C 或 C++ 擴充 Python

1.1. 一個簡單範例

1.2. 插曲：錯誤與例外

1.3. 回到範例

1.4. 模組的方法表和初始化函式

1.5. Compilation and Linkage

1.6. Calling Python Functions from C

1.7. Extracting Parameters in Extension Functions

1.8. Keyword Parameters for Extension Functions

1.9. Building Arbitrary Values

1.10. 參照計數

1.10.1. Python 中的參照計數

1.10.2. Ownership Rules

1.10.3. Thin Ice

1.10.4. NULL 指標

1.11. Writing Extensions in C++

1.12. Providing a C API for an Extension Module

2. 擴充型別定義教學

2.1. The Basics

2.2. Adding data and methods to the Basic example

2.3. Providing finer control over data attributes

2.4. Supporting cyclic garbage collection

2.5. Subclassing other types

3. Defining Extension Types: Assorted Topics

3.1. Finalization and De-allocation

3.2. Object Presentation

3.3. Attribute Management

3.3.1. Generic Attribute Management

3.3.2. Type-specific Attribute Management

3.4. Object Comparison

3.5. Abstract Protocol Support

3.6. Weak Reference Support

3.7. More Suggestions

4. 建立 C 與 C++ 擴充套件

4.1. 用 setuptools 建置 C 與 C++ 擴充套件

5. 建置 Windows 上的 C 和 C++ 擴充

5.1. A Cookbook Approach

5.2. Differences Between Unix and Windows

5.3. Using DLLs in Practice

在更大的應用程式中嵌入 CPython 運行環境 (runtime)

1. 在其它 App 內嵌入 Python

1.1. 非常高階的嵌入

1.2. 超越非常高階嵌入：概觀

1.3. 純嵌入

1.4. 擴充嵌入式 Python

1.5. 在 C++ 中嵌入 Python

1.6. 在類 Unix 系統下編譯和連結

Python/C API 參考手冊

簡介

語言版本相容性

編寫標準

引入檔案 (include files)

有用的巨集

物件、型別和參照計數

參照計數

參照計數詳細資訊

型別

例外

嵌入式Python

除錯建置

建議的第三方工具

C API 穩定性

不穩定的 C API

穩定的應用程式二進位介面

受限 C API

穩定 ABI

受限 API 範圍和性能

受限 API 注意事項

平台注意事項

受限 API 的內容

The Very High Level Layer

可用的起始符號

Stack Effects

參照計數

例外處理

Printing and clearing

引發例外

發出警告

Querying the error indicator

訊號處理

例外類別

例外物件

Unicode 例外物件

遞迴控制

例外和警告型別

例外型別

OSError 別名

警告型別

Tracebacks

Defining extension modules

Multiple module instances

Initialization function

Multi-phase initialization

Legacy single-phase initialization

工具

作業系統工具

系統函式

行程控制

引入模組

資料 marshal 操作的支援

剖析引數與建置數值

剖析引數

字串與緩衝區

數字

其他物件

API 函式

建置數值

字串轉換與格式化

Character classification and conversion

PyHash API

Reflection

編解碼器註冊表和支援函式

編解碼器查找 API

用於 Unicode 編碼錯誤處理程式的註冊 API

Codec utility variables

PyTime C API

型別

時鐘函式

原始時鐘函式

轉換函式

對 Perf Map 的支援

抽象物件層 (Abstract Objects Layer)

物件協定

呼叫協定 (Call Protocol)

tp_call 協定

Vectorcall 協定

遞迴控制

Vectorcall 支援 API

物件呼叫 API

呼叫支援 API

數字協定

序列協定

對映協定

疊代器協定

緩衝協定 (Buffer Protocol)

緩衝區結構

Buffer request types

request-independent fields

readonly, format

shape, strides, suboffsets

contiguity requests

compound requests

Complex arrays

NumPy 風格：形狀與步幅

PIL-style: shape, strides and suboffsets

與緩衝相關的函式

具體物件層

基礎物件

型別物件

Creating Heap-Allocated Types

None 物件

數值物件

整數物件

匯出 API

PyLongWriter API

已棄用的 API

Boolean（布林）物件

浮點數（Floating-Point）物件

打包和解包函式

打包函式

解包函式

複數物件

作為 C 結構的複數

作為 Python 物件的複數

序列物件

位元組物件 (Bytes Objects)

位元組陣列物件 (Byte Array Objects)

型別檢查巨集

直接 API 函式

巨集

Unicode 物件與編解碼器

Unicode 物件

Unicode 型別

Unicode Character Properties

Creating and accessing Unicode strings

Locale Encoding

檔案系統編碼

wchar_t 支援

內建編解碼器

泛用編解碼器

UTF-8 編解碼器

UTF-32 編解碼器

UTF-16 編解碼器

UTF-7 編解碼器

Unicode-Escape Codecs

Raw-Unicode-Escape Codecs

Latin-1 編解碼器

ASCII 編解碼器

Character Map Codecs

Windows 的 MBCS 編解碼器

Methods and Slot Functions

PyUnicodeWriter

已棄用的 API

Tuple（元組）物件

結構序列物件

List（串列）物件

容器物件

字典物件

字典視圖物件

有序字典

集合物件

已棄用的 API

函式物件

函式物件 (Function Objects)

實例方法物件 (Instance Method Objects)

方法物件 (Method Objects)

Cell 物件

程式碼物件

程式碼物件旗標

額外資訊

其他物件

檔案物件 (File Objects)

已棄用的 API

模組物件

模組定義

模組槽 (Module slots)

Creating extension modules dynamically

支援的函式

Module lookup (single-phase initialization)

疊代器（Iterator）物件

Range 物件

內建疊代器型別

其他疊代器物件

Descriptor（描述器）物件

內建描述器

切片物件

Ellipsis 物件

MemoryView 物件

Pickle buffer objects

弱參照物件

Capsules

Frame 物件

Frame Locals Proxies

Legacy Local Variable APIs

Internal Frames

產生器 (Generator) 物件

非同步產生器 (Asynchronous Generator) 物件

已棄用的 API

Coroutine（協程）物件

情境變數物件（Context Variables Objects）

型別提示物件

擴充模組的 C API

Curses C API

內部資料

DateTime 物件

內部資料

初始化、終結化與執行緒

Python 初始化之前

Global configuration variables

Initializing and finalizing the interpreter

Process-wide parameters

Thread State and the Global Interpreter Lock

Detaching the thread state from extension code

Non-Python created threads

Supporting subinterpreters in non-Python threads

Cautions about fork()

Cautions regarding runtime finalization

高階 API

低階 API

Sub-interpreter support

直譯器各別持有的 GIL

Bugs and caveats

Asynchronous Notifications

Profiling and Tracing

Reference tracing

Advanced Debugger Support

Thread Local Storage Support

Thread Specific Storage (TSS) API

Dynamic Allocation

方法

執行緒局部儲存 (Thread Local Storage, TLS) API：

Synchronization Primitives

Python Critical Section API

Legacy Locking APIs

Operating System Thread APIs

Python 初始化設定

PyInitConfig C API

範例

建立設定

錯誤處理

Get Options

Set Options

模組

初始化 Python

Configuration Options

Runtime Python configuration API

PyConfig C API

範例

PyWideStringList

PyStatus

PyPreConfig

Preinitialize Python with PyPreConfig

PyConfig

Initialization with PyConfig

Isolated Configuration

Python Configuration

Python 路徑配置

Py_GetArgcArgv()

Delaying main module execution

記憶體管理

總覽

Allocator Domains

Raw Memory Interface

記憶體介面

已棄用的別名

Object allocators

Default Memory Allocators

Customize Memory Allocators

Debug hooks on the Python memory allocators

The pymalloc allocator

Customize pymalloc Arena Allocator

The mimalloc allocator

tracemalloc C API

範例

物件實作支援

在 heap 上分配物件

被棄用的別名

物件生命週期

生命事件

Cyclic Isolate Destruction

函式

通用物件結構

Base object types and macros

實作函式與方法

Accessing attributes of extension types

Member flags

Member types

Defining Getters and Setters

型別物件結構

Quick Reference

"tp slots"

sub-slots

slot typedefs

PyTypeObject Definition

PyObject Slots

PyVarObject Slots

PyTypeObject Slots

靜態型別

堆積型別

Number Object Structures

對映物件結構

序列物件結構

緩衝區物件結構

非同步物件結構

Slot Type typedefs

範例

循環垃圾回收的支援

Controlling the Garbage Collector State

Querying Garbage Collector State

API 和 ABI 版本管理

Build-time version constants

Run-time version

Bit-packing macros

監控 C API

Generating Execution Events

Managing the Monitoring State

安裝 Python 模組

關鍵術語

基本用法

我該如何...？

...在 Python 3.4 之前的 Python 版本中安裝 pip？

...只為目前的使用者安裝套件？

...安裝科學的 Python 套件？

...平行安裝多個 Python 版本並使用它們？

常見的安裝問題

在 Linux 上安裝套件至系統 Python

未安裝 pip

安裝二進制擴充 (binary extension)

Python 如何達成任務

Python 常見問題

一般的 Python 常見問答集

一般資訊

在真實世界中的 Python

程式開發常見問答集

常見問題

核心語言

數字和字串

效能

序列（元組/串列）

物件

模組

設計和歷史常見問答集

為什麼 Python 使用縮排將陳述式進行分組？

為什麼我會從簡單的數學運算得到奇怪的結果？

為何浮點數運算如此不精確？

為什麼 Python 字串不可變動？

為何「self」在方法 (method) 定義和呼叫時一定要明確使用？

為何我不能在運算式 (expression) 中使用指派運算？

為何 Python 對於一些功能實作使用方法（像是 list.index()），另一些使用函式（像是 len(list)）？

為何 join() 是字串方法而非串列 (list) 或元組 (tuple) 方法？

例外處理有多快？

為什麼 Python 內沒有 switch 或 case 陳述式？

為何不能在直譯器上模擬執行緒，而要使用作業系統的特定實作方式？

為何 lambda 運算式不能包含陳述式？

Python 可以被編譯成機器語言、C 語言或其他種語言嗎？

Python 如何管理記憶體？

為何 CPython 不使用更多傳統的垃圾回收機制？

當 CPython 結束時，為何所有的記憶體不會被釋放？

為何要把元組 (tuple) 和串列 (list) 分成兩個資料型別？

串列 (list) 在 CPython 中是怎麼實作的？

字典 (dictionaries) 在 CPython 中是怎麼實作的？

為何字典的鍵一定是不可變的？

為何 list.sort() 不是回傳排序過的串列？

如何在 Python 中指定和強制使用一個介面規範 (interface spec)？

為何沒有 goto 語法？

為何純字串 (r-string) 不能以反斜線結尾？

為何 Python 沒有屬性賦值的 with 陳述式？

為何產生器 (generator) 不支援 with 陳述式？

為何 if、while、def、class 陳述式裡需要冒號？

為何 Python 允許在串列和元組末端加上逗號？

函式庫和擴充功能的常見問題

常見函式問題

常見課題

執行緒

輸入與輸出

網路 (Network)/網際網路 (Internet) 程式

資料庫

數學和數值

擴充/嵌入常見問題集

我可以在 C 中建立自己的函式嗎？

我可以在 C++ 中建立自己的函式嗎？

寫 C 很難；還有其他選擇嗎？

如何從 C 執行任意 Python 陳述式？

如何計算來自 C 的任意 Python 運算式？

如何從 Python 物件中提取 C 值？

如何使用 Py_BuildValue() 建立任意長度的元組？

如何從 C 呼叫物件的方法？

我如何捕捉 PyErr_Print() 的輸出（或任何印出到 stdout/stderr 的東西）？

如何從 C 存取用 Python 編寫的模組？

我如何從 Python 介接到 C++ 物件？

我使用安裝檔案新增了一個模組，但 make 失敗了；為什麼？

如何為擴充套件除錯？

我想在我的 Linux 系統上編譯一個 Python 模組，但是缺少一些檔案。為什麼？

如何從「無效輸入」區分出「不完整輸入」？

如何找到未定義的 g++ 符號 __builtin_new 或 __pure_virtual？

我可以用一些用 C 實作的方法和用 Python 實作的其他方法（例如透過繼承）建立一個物件類別嗎？

在 Windows 使用 Python 的常見問答集

如何在 Windows 作業系統裡運行 Python 程式？

如何使 Python 腳本可以執行？

為什麼 Python 有時需要這麼長的時間才能開始？

如何從 Python 腳本製作可執行檔？

*.pyd 檔是否與 DLL 相同？

如何將 Python 嵌入 Windows 應用程式中？

如何防止編輯器在我的 Python 原始碼中插入 tab？

如何在不阻塞的情況下檢查 keypress？

如何解決遺漏 api-ms-win-crt-runtime-l1-1-0.dll 的錯誤？

圖形使用者介面常見問答集

圖形使用者介面 (GUI) 的常見問題

Python 有哪些 GUI 套件？

Tkinter 的問答

「為什麼 Python 被安裝在我的機器上？」常見問答集

什麼是 Python？

為什麼 Python 被安裝在我的機器上?

我能夠自行刪除 Python 嗎？

已棄用項目

Python 3.15 中待移除的項目

Python 3.16 中待移除的項目

Python 3.17 中待移除的項目

Python 3.18 中待移除的項目

Python 3.19 中待移除的項目

未來版本中的待移除項目

C API 的棄用項目

Python 3.15 中待移除的項目

Python 3.18 中待移除的項目

未來版本中的待移除項目

術語表

關於這份說明文件

Python 文件的貢獻者們

處理錯誤 (Bug)

說明文件的錯誤

使用 Python 問題追蹤系統

開始讓自己貢獻 Python

版權宣告

沿革與授權

軟體沿革

關於存取或以其他方式使用 Python 的合約條款

PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2

BEOPEN.COM LICENSE AGREEMENT FOR PYTHON 2.0

CNRI LICENSE AGREEMENT FOR PYTHON 1.6.1

CWI LICENSE AGREEMENT FOR PYTHON 0.9.0 THROUGH 1.2

ZERO-CLAUSE BSD LICENSE FOR CODE IN THE PYTHON DOCUMENTATION

被收錄軟體的授權與致謝

Mersenne Twister

Sockets

非同步 socket 服務

Cookie 管理

執行追蹤

UUencode 與 UUdecode 函式

XML 遠端程序呼叫

test_epoll

Select kqueue

SipHash24

strtod 與 dtoa

OpenSSL

expat

libffi

zlib

cfuhash

libmpdec

W3C C14N 測試套件

mimalloc

asyncio

Global Unbounded Sequences (GUS)

Zstandard bindings

Python 有什麼新功能？

「Python 有什麼新功能」這系列的說明是讓使用者知道 Python 各個主要更新版本之間的重大改變的地方。對於希望在新版本釋出時立即了解版本差異的使用者們來說，這些說明被歸類為「必讀」的等級。

Python 3.14 有什麼新功能

發布重點摘要

新增功能

其他語言更動

新增模組

改進的模組

最佳化

已移除

已棄用

CPython 位元組碼變更

C API 變更

建置變更

移植至 Python 3.14

Python 3.14.1 中顯著的變更

Python 3.13 有什麼新功能

發布重點摘要

新增功能

其他語言更動

新增模組

改進的模組

最佳化

被移除的模組和 API

New Deprecations

CPython 位元組碼變更

C API 變更

建置變更

移植至 Python 3.13

迴歸測試的變更

Python 3.12 有什麼新功能

發布重點摘要

新增功能

型別提示相關的新特性

其他語言更動

新增模組

改進的模組

最佳化

CPython 位元組碼變更

Demos and Tools

已棄用

已移除

移植至 Python 3.12

建置變更

C API 變更

Python 3.11 有什麼新功能

發布重點摘要

新增功能

型別提示相關的新特性

其他語言更動

其他 CPython 實作更動

新增模組

改進的模組

最佳化

更快的 CPython

CPython 位元組碼變更

已棄用

Python 3.12 中待決議的移除項目

已移除

移植至 Python 3.11

建置變更

C API 變更

Python 3.11.4 中顯著的變更

Python 3.11.5 中顯著的變更

Python 3.10 有什麼新功能

發布重點摘要

新增功能

與型別提示相關的新功能

其他語言更動

新模組

改進的模組

最佳化

已棄用

已刪除

移植到 Python 3.10

CPython 位元組碼變更

建置變更

C API 變更

Python 3.10.7 中顯著的安全性功能

Python 3.10.8 中顯著的安全性功能

Python 3.10.12 中顯著的變更

Python 3.9 有什麼新功能

發布重點摘要

You should check for DeprecationWarning in your code

新增功能

其他語言更動

新模組

改進的模組

最佳化

已棄用

已移除

移植至 Python 3.9

建置變更

C API 變更

Python 3.9.1 中顯著的變更

Python 3.9.2 中顯著的變更

Python 3.9.3 中顯著的變更

Python 3.9.5 中顯著的變更

Python 3.9.14 中顯著的安全性功能

Python 3.9.17 中顯著的變更

Python 3.8 有什麼新功能

發布重點摘要

新增功能

其他語言更動

新增模組

改進的模組

最佳化

建置和 C API 變更

已棄用

API 與功能的移除

移植至 Python 3.8

Python 3.8.1 中顯著的變更

Python 3.8.2 中顯著的變更

Python 3.8.3 中顯著的變更

Python 3.8.8 中顯著的變更

Python 3.8.9 中顯著的變更

Python 3.8.10 中顯著的變更

Python 3.8.10 中顯著的變更

Python 3.8.12 中顯著的變更

Python 3.8.14 中顯著的安全性功能

Python 3.8.17 中顯著的變更

Python 3.7 有什麼新功能

發布重點摘要

新增功能

其他語言更動

新模組

改進的模組

C API 變更

建置變更

最佳化

Other CPython Implementation Changes

已棄用的 Python 行為

已棄用的 Python 模組、函式和方法

Deprecated functions and types of the C API

Platform Support Removals

API 與功能的移除

Module Removals

Windows-only Changes

移植至 Python 3.7

Python 3.7.1 中顯著的變更

Python 3.7.2 中顯著的變更

Python 3.7.6 中顯著的變更

Python 3.7.10 中顯著的變更

Python 3.7.11 中顯著的變更

Python 3.7.14 中顯著的安全性功能

Python 3.6 有什麼新功能

發布重點摘要

新增功能

其他語言更動

新模組

改進的模組

最佳化

建置和 C API 變更

其他改進

已棄用

已移除

移植至 Python 3.6

Python 3.6.2 中顯著的變更

Python 3.6.4 中顯著的變更

Python 3.6.5 中顯著的變更

Python 3.6.7 中顯著的變更

Python 3.6.10 中顯著的變更

Python 3.6.13 中顯著的變更

Python 3.6.14 中顯著的變更

Python 3.5 有什麼新功能

發布重點摘要

新增功能

其他語言更動

新增模組

改進的模組

其他模組層級的變更

最佳化

建置和 C API 變更

已棄用

已移除

移植至 Python 3.5

Python 3.5.4 中顯著的變更

Python 3.4 有什麼新功能

發布重點摘要

新增功能

新模組

改進的模組

CPython 實作變更

已棄用

已移除

移植至 Python 3.4

3.4.3 中的變更

Python 3.3 有什麼新功能

發布重點摘要

PEP 405：虛擬環境

PEP 420: Implicit Namespace Packages

PEP 3118: New memoryview implementation and buffer protocol documentation

PEP 393: Flexible String Representation

PEP 397：適用於 Windows 的 Python 啟動器

PEP 3151: Reworking the OS and IO exception hierarchy

PEP 380: Syntax for Delegating to a Subgenerator

PEP 409: Suppressing exception context

PEP 414: Explicit Unicode literals

PEP 3155: Qualified name for classes and functions

PEP 412: Key-Sharing Dictionary

PEP 362：函式簽名物件

PEP 421：新增 sys.implementation

使用 importlib 作為 import 的實作

其他語言更動

A Finer-Grained Import Lock

內建函式和型別

新模組

改進的模組

最佳化

建置和 C API 變更

已棄用

移植到 Python 3.3

Python 3.2 有什麼新功能

PEP 384: Defining a Stable ABI

PEP 389: Argparse 命令列剖析模組

PEP 391: Dictionary Based Configuration for Logging

PEP 3148：concurrent.futures 模組

PEP 3147: PYC Repository Directories

PEP 3149: ABI Version Tagged .so Files

PEP 3333: Python Web Server Gateway Interface v1.0.1

其他語言更動

New, Improved, and Deprecated Modules

Multi-threading

最佳化

Unicode

編解碼器

文件

IDLE

Code Repository

建置和 C API 變更

移植至 Python 3.2

Python 3.1 有什麼新功能

PEP 372：有序字典

PEP 378: Format Specifier for Thousands Separator

其他語言更動

新增、改進和棄用的模組

最佳化

IDLE

建置和 C API 變更

移植至 Python 3.1

Python 3.0 有什麼新功能

Common Stumbling Blocks

語法變更概要

Changes Already Present In Python 2.6

函式庫變更

PEP 3101: A New Approach To String Formatting

Changes To Exceptions

Miscellaneous Other Changes

建置和 C API 變更

效能

Porting To Python 3.0

Python 2.7 有什麼新功能

Python 2.x 的未來

Changes to the Handling of Deprecation Warnings

Python 3.1 Features

PEP 372: Adding an Ordered Dictionary to collections

PEP 378: Format Specifier for Thousands Separator

PEP 389: The argparse Module for Parsing Command Lines

PEP 391: Dictionary-Based Configuration For Logging

PEP 3106: Dictionary Views

PEP 3137: The memoryview Object

其他語言更動

New and Improved Modules

建置和 C API 變更

Other Changes and Fixes

移植至 Python 2.7

New Features Added to Python 2.7 Maintenance Releases

致謝

Python 2.6 有什麼新功能

Python 3.0

Changes to the Development Process

PEP 343：'with' 陳述式

PEP 366: Explicit Relative Imports From a Main Module

PEP 370: Per-user site-packages Directory

PEP 371: The multiprocessing Package

PEP 3101: Advanced String Formatting

PEP 3105: print As a Function

PEP 3110: Exception-Handling Changes

PEP 3112: Byte Literals

PEP 3116：新 I/O 函式庫

PEP 3118：修訂緩衝協定

PEP 3119: Abstract Base Classes

PEP 3127: Integer Literal Support and Syntax

PEP 3129: Class Decorators

PEP 3141: A Type Hierarchy for Numbers

其他語言更動

New and Improved Modules

Deprecations and Removals

建置和 C API 變更

Porting to Python 2.6

致謝

Python 2.5 有什麼新功能

PEP 308: Conditional Expressions

PEP 309: Partial Function Application

PEP 314: Metadata for Python Software Packages v1.1

PEP 328: Absolute and Relative Imports

PEP 338: Executing Modules as Scripts

PEP 341: Unified try/except/finally

PEP 342: New Generator Features

PEP 343：'with' 陳述式

PEP 352: Exceptions as New-Style Classes

PEP 353: Using ssize_t as the index type

PEP 357: The '__index__' method

其他語言更動

New, Improved, and Removed Modules

建置和 C API 變更

Porting to Python 2.5

致謝

Python 2.4 有什麼新功能

PEP 218: Built-In Set Objects

PEP 237: Unifying Long Integers and Integers

PEP 289：產生器運算式

PEP 292: Simpler String Substitutions

PEP 318: Decorators for Functions and Methods

PEP 322: Reverse Iteration

PEP 324: New subprocess Module

PEP 327：Decimal 資料型別

PEP 328: Multi-line Imports

PEP 331: Locale-Independent Float/String Conversions

其他語言更動

New, Improved, and Deprecated Modules

建置和 C API 變更

Porting to Python 2.4

致謝

Python 2.3 有什麼新功能

PEP 218: A Standard Set Datatype

PEP 255：簡單產生器

PEP 263: Source Code Encodings

PEP 273: Importing Modules from ZIP Archives

PEP 277: Unicode file name support for Windows NT

PEP 278: Universal Newline Support

PEP 279：enumerate()

PEP 282: The logging Package

PEP 285：布林型別

PEP 293: Codec Error Handling Callbacks

PEP 301: Package Index and Metadata for Distutils

PEP 302: New Import Hooks

PEP 305: Comma-separated Files

PEP 307: Pickle Enhancements

Extended Slices

其他語言更動

New, Improved, and Deprecated Modules

Pymalloc: A Specialized Object Allocator

建置和 C API 變更

Other Changes and Fixes

Porting to Python 2.3

致謝

Python 2.2 有什麼新功能

簡介

PEPs 252 and 253: Type and Class Changes

PEP 234：疊代器

PEP 255：簡單產生器

PEP 237: Unifying Long Integers and Integers

PEP 238: Changing the Division Operator

Unicode 變更

PEP 227: Nested Scopes

New and Improved Modules

直譯器的變更與修正

其他改動與修正

致謝

Python 2.1 有什麼新功能

簡介

PEP 227: Nested Scopes

PEP 236: __future__ Directives

PEP 207: Rich Comparisons

PEP 230：警告框架

PEP 229: New Build System

PEP 205: Weak References

PEP 232：函式屬性

PEP 235: Importing Modules on Case-Insensitive Platforms

PEP 217: Interactive Display Hook

PEP 208: New Coercion Model

PEP 241: Metadata in Python Packages

New and Improved Modules

其他變更與修正

致謝

Python 2.0 有什麼新功能

簡介

Python 1.6 呢？

新的開發流程

Unicode

串列綜合運算（List Comprehension）

擴增賦值（Augmented Assignment）

字串方法

循環的垃圾回收

其他核心變更

移植到 2.0

擴充/嵌入變更

Distutils：讓模組安裝變簡單

XML 模組

模組變更

新增模組

IDLE 改進

已刪除和已棄用的模組

致謝

「Changelog（更動日誌）」是從 Misc/NEWS.d [https://github.com/python/cpython/tree/3.14/Misc/NEWS.d] 目錄樹內容檔案建置 [https://pypi.org/project/blurb/]的一個 HTML 版本，其中包含了 Python 目前版本中的所有重要變更。

Changelog（更動日誌）

Python next

Python 3.14.2 final

Python 3.14.1 final

Python 3.14.0 final

Python 3.14.0 release candidate 3

Python 3.14.0 release candidate 2

Python 3.14.0 release candidate 1

Python 3.14.0 beta 4

Python 3.14.0 beta 3

Python 3.14.0 beta 2

Python 3.14.0 beta 1

Python 3.14.0 alpha 7

Python 3.14.0 alpha 6

Python 3.14.0 alpha 5

Python 3.14.0 alpha 4

Python 3.14.0 alpha 3

Python 3.14.0 alpha 2

Python 3.14.0 alpha 1

Python 3.13.0 beta 1

Python 3.13.0 alpha 6

Python 3.13.0 alpha 5

Python 3.13.0 alpha 4

Python 3.13.0 alpha 3

Python 3.13.0 alpha 2

Python 3.13.0 alpha 1

Python 3.12.0 beta 1

Python 3.12.0 alpha 7

Python 3.12.0 alpha 6

Python 3.12.0 alpha 5

Python 3.12.0 alpha 4

Python 3.12.0 alpha 3

Python 3.12.0 alpha 2

Python 3.12.0 alpha 1

Python 3.11.0 beta 1

Python 3.11.0 alpha 7

Python 3.11.0 alpha 6

Python 3.11.0 alpha 5

Python 3.11.0 alpha 4

Python 3.11.0 alpha 3

Python 3.11.0 alpha 2

Python 3.11.0 alpha 1

Python 3.10.0 beta 1

Python 3.10.0 alpha 7

Python 3.10.0 alpha 6

Python 3.10.0 alpha 5

Python 3.10.0 alpha 4

Python 3.10.0 alpha 3

Python 3.10.0 alpha 2

Python 3.10.0 alpha 1

Python 3.9.0 beta 1

Python 3.9.0 alpha 6

Python 3.9.0 alpha 5

Python 3.9.0 alpha 4

Python 3.9.0 alpha 3

Python 3.9.0 alpha 2

Python 3.9.0 alpha 1

Python 3.8.0 beta 1

Python 3.8.0 alpha 4

Python 3.8.0 alpha 3

Python 3.8.0 alpha 2

Python 3.8.0 alpha 1

Python 3.7.0 final

Python 3.7.0 release candidate 1

Python 3.7.0 beta 5

Python 3.7.0 beta 4

Python 3.7.0 beta 3

Python 3.7.0 beta 2

Python 3.7.0 beta 1

Python 3.7.0 alpha 4

Python 3.7.0 alpha 3

Python 3.7.0 alpha 2

Python 3.7.0 alpha 1

Python 3.6.6 final

Python 3.6.6 release candidate 1

Python 3.6.5 final

Python 3.6.5 release candidate 1

Python 3.6.4 final

Python 3.6.4 release candidate 1

Python 3.6.3 final

Python 3.6.3 release candidate 1

Python 3.6.2 final

Python 3.6.2 release candidate 2

Python 3.6.2 release candidate 1

Python 3.6.1 final

Python 3.6.1 release candidate 1

Python 3.6.0 final

Python 3.6.0 release candidate 2

Python 3.6.0 release candidate 1

Python 3.6.0 beta 4

Python 3.6.0 beta 3

Python 3.6.0 beta 2

Python 3.6.0 beta 1

Python 3.6.0 alpha 4

Python 3.6.0 alpha 3

Python 3.6.0 alpha 2

Python 3.6.0 alpha 1

Python 3.5.5 final

Python 3.5.5 release candidate 1

Python 3.5.4 final

Python 3.5.4 release candidate 1

Python 3.5.3 final

Python 3.5.3 release candidate 1

Python 3.5.2 final

Python 3.5.2 release candidate 1

Python 3.5.1 final

Python 3.5.1 release candidate 1

Python 3.5.0 final

Python 3.5.0 release candidate 4

Python 3.5.0 release candidate 3

Python 3.5.0 release candidate 2

Python 3.5.0 release candidate 1

Python 3.5.0 beta 4

Python 3.5.0 beta 3

Python 3.5.0 beta 2

Python 3.5.0 beta 1

Python 3.5.0 alpha 4

Python 3.5.0 alpha 3

Python 3.5.0 alpha 2

Python 3.5.0 alpha 1

Python 3.14 有什麼新功能

編輯者:

Adam Turner 和 Hugo van Kemenade

本文介紹了 Python 3.14 與 3.13 相比多了哪些新功能。Python 3.14 已於 2025 年 10 月 7 日發布。完整詳情請見 changelog。

也參考

PEP 745 [https://peps.python.org/pep-0745/] - Python 3.14 發佈時程

發布重點摘要

Python 3.14 是 Python 程式語言的最新穩定版本，包含了語言、實作和標準函式庫的各種變更。最大的變更包括模板字串字面值、延遲型別註解的求值，以及標準函式庫中對子直譯器的支援。

The library changes include significantly improved capabilities for introspection in asyncio, support for Zstandard via a new compression.zstd module, syntax highlighting in the REPL, as well as the usual deprecations and removals, and improvements in user-friendliness and correctness.

This article doesn't attempt to provide a complete specification of all new features, but instead gives a convenient overview. For full details refer to the documentation, such as the Library Reference and Language Reference. To understand the complete implementation and design rationale for a change, refer to the PEP for a particular new feature; but note that PEPs usually are not kept up-to-date once a feature has been fully implemented. See Porting to Python 3.14 for guidance on upgrading from earlier versions of Python.

直譯器的改進：

PEP 649 [https://peps.python.org/pep-0649/] and PEP 749 [https://peps.python.org/pep-0749/]: Deferred evaluation of annotations

PEP 734 [https://peps.python.org/pep-0734/]: Multiple interpreters in the standard library

PEP 750 [https://peps.python.org/pep-0750/]: Template strings

PEP 758 [https://peps.python.org/pep-0758/]: Allow except and except* expressions without brackets

PEP 765 [https://peps.python.org/pep-0765/]: Control flow in finally blocks

PEP 768 [https://peps.python.org/pep-0768/]: Safe external debugger interface for CPython

A new type of interpreter

Free-threaded mode improvements

Improved error messages

Incremental garbage collection

標準函式庫中的顯著改進

PEP 784 [https://peps.python.org/pep-0784/]: Zstandard support in the standard library

Asyncio introspection capabilities

Concurrent safe warnings control

Syntax highlighting in the default interactive shell, and color output in several standard library CLIs

C API 改進：

PEP 741 [https://peps.python.org/pep-0741/]: Python 配置 C API

平台支援：

PEP 776 [https://peps.python.org/pep-0776/]: Emscripten is now an officially supported platform, at tier 3 [https://peps.python.org/pep-0011/#tier-3].

Release changes:

PEP 779 [https://peps.python.org/pep-0779/]: Free-threaded Python is officially supported

PEP 761 [https://peps.python.org/pep-0761/]: PGP signatures have been discontinued for official releases

Windows and macOS binary releases now support the experimental just-in-time compiler

Binary releases for Android are now provided

新增功能

PEP 649 [https://peps.python.org/pep-0649/] & PEP 749 [https://peps.python.org/pep-0749/]: Deferred evaluation of annotations

The annotations on functions, classes, and modules are no longer evaluated eagerly. Instead, annotations are stored in special-purpose annotate functions and evaluated only when necessary (except if from __future__ import annotations is used).

This change is designed to improve performance and usability of annotations in Python in most circumstances. The runtime cost for defining annotations is minimized, but it remains possible to introspect annotations at runtime. It is no longer necessary to enclose annotations in strings if they contain forward references.

The new annotationlib module provides tools for inspecting deferred annotations. Annotations may be evaluated in the VALUE format (which evaluates annotations to runtime values, similar to the behavior in earlier Python versions), the FORWARDREF format (which replaces undefined names with special markers), and the STRING format (which returns annotations as strings).

This example shows how these formats behave:

>>> from annotationlib import get_annotations, Format
>>> def func(arg: Undefined):
...     pass
>>> get_annotations(func, format=Format.VALUE)
Traceback (most recent call last):
  ...
NameError: name 'Undefined' is not defined
>>> get_annotations(func, format=Format.FORWARDREF)
{'arg': ForwardRef('Undefined', owner=<function func at 0x...>)}
>>> get_annotations(func, format=Format.STRING)
{'arg': 'Undefined'}

The porting section contains guidance on changes that may be needed due to these changes, though in the majority of cases, code will continue working as-is.

（由 Jelle Zijlstra 於 PEP 749 [https://peps.python.org/pep-0749/] 和 gh-119180 [https://github.com/python/cpython/issues/119180] 貢獻；PEP 649 [https://peps.python.org/pep-0649/] 由 Larry Hastings 撰寫。）

也參考

PEP 649 [https://peps.python.org/pep-0649/]

Deferred Evaluation Of Annotations Using Descriptors

PEP 749 [https://peps.python.org/pep-0749/]

實作 PEP 649

PEP 734 [https://peps.python.org/pep-0734/]: Multiple interpreters in the standard library

The CPython runtime supports running multiple copies of Python in the same process simultaneously and has done so for over 20 years. Each of these separate copies is called an 'interpreter'. However, the feature had been available only through the C-API.

That limitation is removed in Python 3.14, with the new concurrent.interpreters module.

There are at least two notable reasons why using multiple interpreters has significant benefits:

they support a new (to Python), human-friendly concurrency model

true multi-core parallelism

For some use cases, concurrency in software improves efficiency and can simplify design, at a high level. At the same time, implementing and maintaining all but the simplest concurrency is often a struggle for the human brain. That especially applies to plain threads (for example, threading), where all memory is shared between all threads.

With multiple isolated interpreters, you can take advantage of a class of concurrency models, like Communicating Sequential Processes (CSP) or the actor model, that have found success in other programming languages, like Smalltalk, Erlang, Haskell, and Go. Think of multiple interpreters as threads but with opt-in sharing.

Regarding multi-core parallelism: as of Python 3.12, interpreters are now sufficiently isolated from one another to be used in parallel (see PEP 684 [https://peps.python.org/pep-0684/]). This unlocks a variety of CPU-intensive use cases for Python that were limited by the GIL.

Using multiple interpreters is similar in many ways to multiprocessing, in that they both provide isolated logical "processes" that can run in parallel, with no sharing by default. However, when using multiple interpreters, an application will use fewer system resources and will operate more efficiently (since it stays within the same process). Think of multiple interpreters as having the isolation of processes with the efficiency of threads.

While the feature has been around for decades, multiple interpreters have not been used widely, due to low awareness and the lack of a standard library module. Consequently, they currently have several notable limitations, which are expected to improve significantly now that the feature is going mainstream.

Current limitations:

starting each interpreter has not been optimized yet

each interpreter uses more memory than necessary (work continues on extensive internal sharing between interpreters)

there aren't many options yet for truly sharing objects or other data between interpreters (other than memoryview)

many third-party extension modules on PyPI are not yet compatible with multiple interpreters (all standard library extension modules are compatible)

the approach to writing applications that use multiple isolated interpreters is mostly unfamiliar to Python users, for now

The impact of these limitations will depend on future CPython improvements, how interpreters are used, and what the community solves through PyPI packages. Depending on the use case, the limitations may not have much impact, so try it out!

Furthermore, future CPython releases will reduce or eliminate overhead and provide utilities that are less appropriate on PyPI. In the meantime, most of the limitations can also be addressed through extension modules, meaning PyPI packages can fill any gap for 3.14, and even back to 3.12 where interpreters were finally properly isolated and stopped sharing the GIL. Likewise, libraries on PyPI are expected to emerge for high-level abstractions on top of interpreters.

Regarding extension modules, work is in progress to update some PyPI projects, as well as tools like Cython, pybind11, nanobind, and PyO3. The steps for isolating an extension module are found at 隔離擴充模組. Isolating a module has a lot of overlap with what is required to support free-threading, so the ongoing work in the community in that area will help accelerate support for multiple interpreters.

Also added in 3.14: concurrent.futures.InterpreterPoolExecutor.

（由 Eric Snow 於 gh-134939 [https://github.com/python/cpython/issues/134939] 貢獻。）

也參考

PEP 734 [https://peps.python.org/pep-0734/]

PEP 750 [https://peps.python.org/pep-0750/]: Template string literals

Template strings are a new mechanism for custom string processing. They share the familiar syntax of f-strings but, unlike f-strings, return an object representing the static and interpolated parts of the string, instead of a simple str.

To write a t-string, use a 't' prefix instead of an 'f':

>>> variety = 'Stilton'
>>> template = t'Try some {variety} cheese!'
>>> type(template)
<class 'string.templatelib.Template'>

Template objects provide access to the static and interpolated (in curly braces) parts of a string before they are combined. Iterate over Template instances to access their parts in order:

>>> list(template)
['Try some ', Interpolation('Stilton', 'variety', None, ''), ' cheese!']

It's easy to write (or call) code to process Template instances. For example, here's a function that renders static parts lowercase and Interpolation instances uppercase:

from string.templatelib import Interpolation

def lower_upper(template):
    """Render static parts lowercase and interpolations uppercase."""
    parts = []
    for part in template:
        if isinstance(part, Interpolation):
            parts.append(str(part.value).upper())
        else:
            parts.append(part.lower())
    return ''.join(parts)

name = 'Wenslydale'
template = t'Mister {name}'
assert lower_upper(template) == 'mister WENSLYDALE'

Because Template instances distinguish between static strings and interpolations at runtime, they can be useful for sanitising user input. Writing a html() function that escapes user input in HTML is an exercise left to the reader! Template processing code can provide improved flexibility. For instance, a more advanced html() function could accept a dict of HTML attributes directly in the template:

attributes = {'src': 'limburger.jpg', 'alt': 'lovely cheese'}
template = t'<img {attributes}>'
assert html(template) == '<img src="limburger.jpg" alt="lovely cheese" />'

Of course, template processing code does not need to return a string-like result. An even more advanced html() could return a custom type representing a DOM-like structure.

With t-strings in place, developers can write systems that sanitise SQL, make safe shell operations, improve logging, tackle modern ideas in web development (HTML, CSS, and so on), and implement lightweight custom business DSLs.

(Contributed by Jim Baker, Guido van Rossum, Paul Everitt, Koudai Aono, Lysandros Nikolaou, Dave Peck, Adam Turner, Jelle Zijlstra, Bénédikt Tran, and Pablo Galindo Salgado in gh-132661 [https://github.com/python/cpython/issues/132661].)

也參考

PEP 750 [https://peps.python.org/pep-0750/]。

PEP 768 [https://peps.python.org/pep-0768/]: Safe external debugger interface

Python 3.14 introduces a zero-overhead debugging interface that allows debuggers and profilers to safely attach to running Python processes without stopping or restarting them. This is a significant enhancement to Python's debugging capabilities, meaning that unsafe alternatives are no longer required.

The new interface provides safe execution points for attaching debugger code without modifying the interpreter's normal execution path or adding any overhead at runtime. Due to this, tools can now inspect and interact with Python applications in real-time, which is a crucial capability for high-availability systems and production environments.

For convenience, this interface is implemented in the sys.remote_exec() function. For example:

import sys
from tempfile import NamedTemporaryFile

with NamedTemporaryFile(mode='w', suffix='.py', delete=False) as f:
    script_path = f.name
    f.write(f'import my_debugger; my_debugger.connect({os.getpid()})')

# 在 PID 1234 的行程中執行
print('Behold! An offering:')
sys.remote_exec(1234, script_path)

This function allows sending Python code to be executed in a target process at the next safe execution point. However, tool authors can also implement the protocol directly as described in the PEP, which details the underlying mechanisms used to safely attach to running processes.

The debugging interface has been carefully designed with security in mind and includes several mechanisms to control access:

A PYTHON_DISABLE_REMOTE_DEBUG environment variable.

A -X disable-remote-debug command-line option.

A --without-remote-debug configure flag to completely disable the feature at build time.

(Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic in gh-131591 [https://github.com/python/cpython/issues/131591].)

也參考

PEP 768 [https://peps.python.org/pep-0768/]。

A new type of interpreter

A new type of interpreter has been added to CPython. It uses tail calls between small C functions that implement individual Python opcodes, rather than one large C case statement. For certain newer compilers, this interpreter provides significantly better performance. Preliminary benchmarks suggest a geometric mean of 3-5% faster on the standard pyperformance benchmark suite, depending on platform and architecture. The baseline is Python 3.14 built with Clang 19, without this new interpreter.

This interpreter currently only works with Clang 19 and newer on x86-64 and AArch64 architectures. However, a future release of GCC is expected to support this as well.

This feature is opt-in for now. Enabling profile-guided optimization is highly recommendeded when using the new interpreter as it is the only configuration that has been tested and validated for improved performance. For further information, see --with-tail-call-interp.

備註

This is not to be confused with tail call optimization [https://en.wikipedia.org/wiki/Tail_call] of Python functions, which is currently not implemented in CPython.

This new interpreter type is an internal implementation detail of the CPython interpreter. It doesn't change the visible behavior of Python programs at all. It can improve their performance, but doesn't change anything else.

(Contributed by Ken Jin in gh-128563 [https://github.com/python/cpython/issues/128563], with ideas on how to implement this in CPython by Mark Shannon, Garrett Gu, Haoran Xu, and Josh Haberman.)

Free-threaded mode improvements

CPython's free-threaded mode (PEP 703 [https://peps.python.org/pep-0703/]), initially added in 3.13, has been significantly improved in Python 3.14. The implementation described in PEP 703 has been finished, including C API changes, and temporary workarounds in the interpreter were replaced with more permanent solutions. The specializing adaptive interpreter (PEP 659 [https://peps.python.org/pep-0659/]) is now enabled in free-threaded mode, which along with many other optimizations greatly improves its performance. The performance penalty on single-threaded code in free-threaded mode is now roughly 5-10%, depending on the platform and C compiler used.

From Python 3.14, when compiling extension modules for the free-threaded build of CPython on Windows, the preprocessor variable Py_GIL_DISABLED now needs to be specified by the build backend, as it will no longer be determined automatically by the C compiler. For a running interpreter, the setting that was used at compile time can be found using sysconfig.get_config_var().

The new -X context_aware_warnings flag controls if concurrent safe warnings control is enabled. The flag defaults to true for the free-threaded build and false for the GIL-enabled build.

A new thread_inherit_context flag has been added, which if enabled means that threads created with threading.Thread start with a copy of the Context() of the caller of start(). Most significantly, this makes the warning filtering context established by catch_warnings be "inherited" by threads (or asyncio tasks) started within that context. It also affects other modules that use context variables, such as the decimal context manager. This flag defaults to true for the free-threaded build and false for the GIL-enabled build.

(Contributed by Sam Gross, Matt Page, Neil Schemenauer, Thomas Wouters, Donghee Na, Kirill Podoprigora, Ken Jin, Itamar Oren, Brett Simmers, Dino Viehland, Nathan Goldbaum, Ralf Gommers, Lysandros Nikolaou, Kumar Aditya, Edgar Margffoy, and many others. Some of these contributors are employed by Meta, which has continued to provide significant engineering resources to support this project.)

改善錯誤訊息

The interpreter now provides helpful suggestions when it detects typos in Python keywords. When a word that closely resembles a Python keyword is encountered, the interpreter will suggest the correct keyword in the error message. This feature helps programmers quickly identify and fix common typing mistakes. For example:

>>> whille True:
...     pass
Traceback (most recent call last):
  File "<stdin>", line 1
    whille True:
    ^^^^^^
SyntaxError: invalid syntax. Did you mean 'while'?

While the feature focuses on the most common cases, some variations of misspellings may still result in regular syntax errors. (Contributed by Pablo Galindo in gh-132449 [https://github.com/python/cpython/issues/132449].)

elif statements that follow an else block now have a specific error message. (Contributed by Steele Farnsworth in gh-129902 [https://github.com/python/cpython/issues/129902].)

>>> if who == "me":
...     print("It's me!")
... else:
...     print("It's not me!")
... elif who is None:
...     print("Who is it?")
File "<stdin>", line 5
  elif who is None:
  ^^^^
SyntaxError: 'elif' block follows an 'else' block

If a statement is passed to the Conditional expressions after else, or one of pass, break, or continue is passed before if, then the error message highlights where the expression is required. (Contributed by Sergey Miryanov in gh-129515 [https://github.com/python/cpython/issues/129515].)

>>> x = 1 if True else pass
Traceback (most recent call last):
  File "<string>", line 1
    x = 1 if True else pass
                       ^^^^
SyntaxError: expected expression after 'else', but statement is given

>>> x = continue if True else break
Traceback (most recent call last):
  File "<string>", line 1
    x = continue if True else break
        ^^^^^^^^
SyntaxError: expected expression before 'if', but statement is given

When incorrectly closed strings are detected, the error message suggests that the string may be intended to be part of the string. (Contributed by Pablo Galindo in gh-88535 [https://github.com/python/cpython/issues/88535].)

>>> "The interesting object "The important object" is very important"
Traceback (most recent call last):
SyntaxError: invalid syntax. Is this intended to be part of the string?

When strings have incompatible prefixes, the error now shows which prefixes are incompatible. (Contributed by Nikita Sobolev in gh-133197 [https://github.com/python/cpython/issues/133197].)

>>> ub'abc'
  File "<python-input-0>", line 1
    ub'abc'
    ^^
SyntaxError: 'u' and 'b' prefixes are incompatible

Improved error messages when using as with incompatible targets in:

Imports: import ... as ...

From imports: from ... import ... as ...

Except handlers: except ... as ...

Pattern-match cases: case ... as ...

(Contributed by Nikita Sobolev in gh-123539 [https://github.com/python/cpython/issues/123539], gh-123562 [https://github.com/python/cpython/issues/123562], and gh-123440 [https://github.com/python/cpython/issues/123440].)

Improved error message when trying to add an instance of an unhashable type to a dict or set. (Contributed by CF Bolz-Tereick and Victor Stinner in gh-132828 [https://github.com/python/cpython/issues/132828].)

>>> s = set()
>>> s.add({'pages': 12, 'grade': 'A'})
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    s.add({'pages': 12, 'grade': 'A'})
    ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: cannot use 'dict' as a set element (unhashable type: 'dict')
>>> d = {}
>>> l = [1, 2, 3]
>>> d[l] = 12
Traceback (most recent call last):
  File "<python-input-4>", line 1, in <module>
    d[l] = 12
    ~^^^
TypeError: cannot use 'list' as a dict key (unhashable type: 'list')

Improved error message when an object supporting the synchronous context manager protocol is entered using async with instead of with, and vice versa for the asynchronous context manager protocol. (Contributed by Bénédikt Tran in gh-128398 [https://github.com/python/cpython/issues/128398].)

PEP 784 [https://peps.python.org/pep-0784/]：標準函式庫中的 Zstandard 支援

The new compression package contains modules compression.lzma, compression.bz2, compression.gzip and compression.zlib which re-export the lzma, bz2, gzip and zlib modules respectively. The new import names under compression are the preferred names for importing these compression modules from Python 3.14. However, the existing modules names have not been deprecated. Any deprecation or removal of the existing compression modules will occur no sooner than five years after the release of 3.14.

The new compression.zstd module provides compression and decompression APIs for the Zstandard format via bindings to Meta's zstd library [https://facebook.github.io/zstd/]. Zstandard is a widely adopted, highly efficient, and fast compression format. In addition to the APIs introduced in compression.zstd, support for reading and writing Zstandard compressed archives has been added to the tarfile, zipfile, and shutil modules.

Here's an example of using the new module to compress some data:

from compression import zstd
import math

data = str(math.pi).encode() * 20
compressed = zstd.compress(data)
ratio = len(compressed) / len(data)
print(f"Achieved compression ratio of {ratio}")

As can be seen, the API is similar to the APIs of the lzma and bz2 modules.

(Contributed by Emma Harper Smith, Adam Turner, Gregory P. Smith, Tomas Roun, Victor Stinner, and Rogdham in gh-132983 [https://github.com/python/cpython/issues/132983].)

也參考

PEP 784 [https://peps.python.org/pep-0784/]。

Asyncio introspection capabilities

Added a new command-line interface to inspect running Python processes using asynchronous tasks, available via python -m asyncio ps PID or python -m asyncio pstree PID.

The ps subcommand inspects the given process ID (PID) and displays information about currently running asyncio tasks. It outputs a task table: a flat listing of all tasks, their names, their coroutine stacks, and which tasks are awaiting them.

The pstree subcommand fetches the same information, but instead renders a visual async call tree, showing coroutine relationships in a hierarchical format. This command is particularly useful for debugging long-running or stuck asynchronous programs. It can help developers quickly identify where a program is blocked, what tasks are pending, and how coroutines are chained together.

For example given this code:

import asyncio

async def play_track(track):
    await asyncio.sleep(5)
    print(f'🎵 Finished: {track}')

async def play_album(name, tracks):
    async with asyncio.TaskGroup() as tg:
        for track in tracks:
            tg.create_task(play_track(track), name=track)

async def main():
    async with asyncio.TaskGroup() as tg:
        tg.create_task(
          play_album('Sundowning', ['TNDNBTG', 'Levitate']),
          name='Sundowning')
        tg.create_task(
          play_album('TMBTE', ['DYWTYLM', 'Aqua Regia']),
          name='TMBTE')

if __name__ == '__main__':
    asyncio.run(main())

Executing the new tool on the running process will yield a table like this:

python -m asyncio ps 12345

tid        task id              task name            coroutine stack                                    awaiter chain                                      awaiter name    awaiter id
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1935500    0x7fc930c18050       Task-1               TaskGroup._aexit -> TaskGroup.__aexit__ -> main                                                                       0x0
1935500    0x7fc930c18230       Sundowning           TaskGroup._aexit -> TaskGroup.__aexit__ -> album   TaskGroup._aexit -> TaskGroup.__aexit__ -> main    Task-1          0x7fc930c18050
1935500    0x7fc93173fa50       TMBTE                TaskGroup._aexit -> TaskGroup.__aexit__ -> album   TaskGroup._aexit -> TaskGroup.__aexit__ -> main    Task-1          0x7fc930c18050
1935500    0x7fc93173fdf0       TNDNBTG              sleep -> play                                      TaskGroup._aexit -> TaskGroup.__aexit__ -> album   Sundowning      0x7fc930c18230
1935500    0x7fc930d32510       Levitate             sleep -> play                                      TaskGroup._aexit -> TaskGroup.__aexit__ -> album   Sundowning      0x7fc930c18230
1935500    0x7fc930d32890       DYWTYLM              sleep -> play                                      TaskGroup._aexit -> TaskGroup.__aexit__ -> album   TMBTE           0x7fc93173fa50
1935500    0x7fc93161ec30       Aqua Regia           sleep -> play                                      TaskGroup._aexit -> TaskGroup.__aexit__ -> album   TMBTE           0x7fc93173fa50

or a tree like this:

python -m asyncio pstree 12345

└── (T) Task-1
    └──  main example.py:13
        └──  TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:72
            └──  TaskGroup._aexit Lib/asyncio/taskgroups.py:121
                ├── (T) Sundowning
                │   └──  album example.py:8
                │       └──  TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:72
                │           └──  TaskGroup._aexit Lib/asyncio/taskgroups.py:121
                │               ├── (T) TNDNBTG
                │               │   └──  play example.py:4
                │               │       └──  sleep Lib/asyncio/tasks.py:702
                │               └── (T) Levitate
                │                   └──  play example.py:4
                │                       └──  sleep Lib/asyncio/tasks.py:702
                └── (T) TMBTE
                    └──  album example.py:8
                        └──  TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:72
                            └──  TaskGroup._aexit Lib/asyncio/taskgroups.py:121
                                ├── (T) DYWTYLM
                                │   └──  play example.py:4
                                │       └──  sleep Lib/asyncio/tasks.py:702
                                └── (T) Aqua Regia
                                    └──  play example.py:4
                                        └──  sleep Lib/asyncio/tasks.py:702

If a cycle is detected in the async await graph (which could indicate a programming issue), the tool raises an error and lists the cycle paths that prevent tree construction:

python -m asyncio pstree 12345

ERROR: await-graph contains cycles - cannot print a tree!

cycle: Task-2 → Task-3 → Task-2

(Contributed by Pablo Galindo, Łukasz Langa, Yury Selivanov, and Marta Gomez Macias in gh-91048 [https://github.com/python/cpython/issues/91048].)

Concurrent safe warnings control

The warnings.catch_warnings context manager will now optionally use a context variable for warning filters. This is enabled by setting the context_aware_warnings flag, either with the -X command-line option or an environment variable. This gives predictable warnings control when using catch_warnings combined with multiple threads or asynchronous tasks. The flag defaults to true for the free-threaded build and false for the GIL-enabled build.

（由 Neil Schemenauer 和 Kumar Aditya 於 gh-130010 [https://github.com/python/cpython/issues/130010] 貢獻。）

其他語言更動

All Windows code pages are now supported as 'cpXXX' codecs on Windows. (Contributed by Serhiy Storchaka in gh-123803 [https://github.com/python/cpython/issues/123803].)

Implement mixed-mode arithmetic rules combining real and complex numbers as specified by the C standard since C99. (Contributed by Sergey B Kirpichev in gh-69639 [https://github.com/python/cpython/issues/69639].)

More syntax errors are now detected regardless of optimisation and the -O command-line option. This includes writes to __debug__, incorrect use of await, and asynchronous comprehensions outside asynchronous functions. For example, python -O -c 'assert (__debug__ := 1)' or python -O -c 'assert await 1' now produce SyntaxErrors. (Contributed by Irit Katriel and Jelle Zijlstra in gh-122245 [https://github.com/python/cpython/issues/122245] & gh-121637 [https://github.com/python/cpython/issues/121637].)

When subclassing a pure C type, the C slots for the new type are no longer replaced with a wrapped version on class creation if they are not explicitly overridden in the subclass. (Contributed by Tomasz Pytel in gh-132284 [https://github.com/python/cpython/issues/132284].)

Built-ins

The bytes.fromhex() and bytearray.fromhex() methods now accept ASCII bytes and bytes-like objects. (Contributed by Daniel Pope in gh-129349 [https://github.com/python/cpython/issues/129349].)

Add class methods float.from_number() and complex.from_number() to convert a number to float or complex type correspondingly. They raise a TypeError if the argument is not a real number. (Contributed by Serhiy Storchaka in gh-84978 [https://github.com/python/cpython/issues/84978].)

Support underscore and comma as thousands separators in the fractional part for floating-point presentation types of the new-style string formatting (with format() or f-string（f 字串）). (Contributed by Sergey B Kirpichev in gh-87790 [https://github.com/python/cpython/issues/87790].)

The int() function no longer delegates to __trunc__(). Classes that want to support conversion to int() must implement either __int__() or __index__(). (Contributed by Mark Dickinson in gh-119743 [https://github.com/python/cpython/issues/119743].)

The map() function now has an optional keyword-only strict flag like zip() to check that all the iterables are of equal length. (Contributed by Wannes Boeykens in gh-119793 [https://github.com/python/cpython/issues/119793].)

The memoryview type now supports subscription, making it a generic type. (Contributed by Brian Schubert in gh-126012 [https://github.com/python/cpython/issues/126012].)

Using NotImplemented in a boolean context will now raise a TypeError. This has raised a DeprecationWarning since Python 3.9. (Contributed by Jelle Zijlstra in gh-118767 [https://github.com/python/cpython/issues/118767].)

Three-argument pow() now tries calling __rpow__() if necessary. Previously it was only called in two-argument pow() and the binary power operator. (Contributed by Serhiy Storchaka in gh-130104 [https://github.com/python/cpython/issues/130104].)

super objects are now copyable and pickleable. (Contributed by Serhiy Storchaka in gh-125767 [https://github.com/python/cpython/issues/125767].)

命令列與環境

The import time flag can now track modules that are already loaded ('cached'), via the new -X importtime=2. When such a module is imported, the self and cumulative times are replaced by the string cached.

Values above 2 for -X importtime are now reserved for future use.

（由 Noah Kim 和 Adam Turner 於 gh-118655 [https://github.com/python/cpython/issues/118655] 貢獻。）

The command-line option -c now automatically dedents its code argument before execution. The auto-dedentation behavior mirrors textwrap.dedent(). (Contributed by Jon Crall and Steven Sun in gh-103998 [https://github.com/python/cpython/issues/103998].)

-J is no longer a reserved flag for Jython [https://www.jython.org/], and now has no special meaning. (Contributed by Adam Turner in gh-133336 [https://github.com/python/cpython/issues/133336].)

PEP 758: Allow except and except* expressions without brackets

The except and except* expressions now allow brackets to be omitted when there are multiple exception types and the as clause is not used. For example:

try:
    connect_to_server()
except TimeoutError, ConnectionRefusedError:
    print('The network has ceased to be!')

（由 Pablo Galindo 和 Brett Cannon 於 PEP 758 [https://peps.python.org/pep-0758/] 和 gh-131831 [https://github.com/python/cpython/issues/131831] 貢獻。）

PEP 765: Control flow in finally blocks

The compiler now emits a SyntaxWarning when a return, break, or continue statement have the effect of leaving a finally block. This change is specified in PEP 765 [https://peps.python.org/pep-0765/].

In situations where this change is inconvenient (such as those where the warnings are redundant due to code linting), the warning filter can be used to turn off all syntax warnings by adding ignore::SyntaxWarning as a filter. This can be specified in combination with a filter that converts other warnings to errors (for example, passing -Werror -Wignore::SyntaxWarning as CLI options, or setting PYTHONWARNINGS=error,ignore::SyntaxWarning).

Note that applying such a filter at runtime using the warnings module will only suppress the warning in code that is compiled after the filter is adjusted. Code that is compiled prior to the filter adjustment (for example, when a module is imported) will still emit the syntax warning.

（由 Irit Katriel 於 gh-130080 [https://github.com/python/cpython/issues/130080] 貢獻。）

Incremental garbage collection

The cycle garbage collector is now incremental. This means that maximum pause times are reduced by an order of magnitude or more for larger heaps.

There are now only two generations: young and old. When gc.collect() is not called directly, the GC is invoked a little less frequently. When invoked, it collects the young generation and an increment of the old generation, instead of collecting one or more generations.

The behavior of gc.collect() changes slightly:

gc.collect(1): Performs an increment of garbage collection, rather than collecting generation 1.

Other calls to gc.collect() are unchanged.

（由 Mark Shannon 於 gh-108362 [https://github.com/python/cpython/issues/108362] 貢獻。）

Default interactive shell

The default interactive shell now highlights Python syntax. The feature is enabled by default, save if PYTHON_BASIC_REPL or any other environment variable that disables colour is set. See Controlling color for details.

The default color theme for syntax highlighting strives for good contrast and exclusively uses the 4-bit VGA standard ANSI color codes for maximum compatibility. The theme can be customized using an experimental API _colorize.set_theme(). This can be called interactively or in the PYTHONSTARTUP script. Note that this function has no stability guarantees, and may change or be removed.

（由 Łukasz Langa 於 gh-131507 [https://github.com/python/cpython/issues/131507] 貢獻。）

The default interactive shell now supports import auto-completion. This means that typing import co and pressing <Tab> will suggest modules starting with co. Similarly, typing from concurrent import i will suggest submodules of concurrent starting with i. Note that autocompletion of module attributes is not currently supported. (Contributed by Tomas Roun in gh-69605 [https://github.com/python/cpython/issues/69605].)

新增模組

annotationlib: For introspecting annotations. See PEP 749 for more details. (Contributed by Jelle Zijlstra in gh-119180 [https://github.com/python/cpython/issues/119180].)

compression (including compression.zstd): A package for compression-related modules, including a new module to support the Zstandard compression format. See PEP 784 for more details. (Contributed by Emma Harper Smith, Adam Turner, Gregory P. Smith, Tomas Roun, Victor Stinner, and Rogdham in gh-132983 [https://github.com/python/cpython/issues/132983].)

concurrent.interpreters: Support for multiple interpreters in the standard library. See PEP 734 for more details. (Contributed by Eric Snow in gh-134939 [https://github.com/python/cpython/issues/134939].)

string.templatelib: Support for template string literals (t-strings). See PEP 750 for more details. (Contributed by Jim Baker, Guido van Rossum, Paul Everitt, Koudai Aono, Lysandros Nikolaou, Dave Peck, Adam Turner, Jelle Zijlstra, Bénédikt Tran, and Pablo Galindo Salgado in gh-132661 [https://github.com/python/cpython/issues/132661].)

改進的模組

argparse

The default value of the program name for argparse.ArgumentParser now reflects the way the Python interpreter was instructed to find the __main__ module code. (Contributed by Serhiy Storchaka and Alyssa Coghlan in gh-66436 [https://github.com/python/cpython/issues/66436].)

Introduced the optional suggest_on_error parameter to argparse.ArgumentParser, enabling suggestions for argument choices and subparser names if mistyped by the user. (Contributed by Savannah Ostrowski in gh-124456 [https://github.com/python/cpython/issues/124456].)

Enable color for help text, which can be disabled with the optional color parameter to argparse.ArgumentParser. This can also be controlled by environment variables. (Contributed by Hugo van Kemenade in gh-130645 [https://github.com/python/cpython/issues/130645].)

ast

Add compare(), a function for comparing two ASTs. (Contributed by Batuhan Taskaya and Jeremy Hylton in gh-60191 [https://github.com/python/cpython/issues/60191].)

Add support for copy.replace() for AST nodes. (Contributed by Bénédikt Tran in gh-121141 [https://github.com/python/cpython/issues/121141].)

Docstrings are now removed from an optimized AST in optimization level 2. (Contributed by Irit Katriel in gh-123958 [https://github.com/python/cpython/issues/123958].)

The repr() output for AST nodes now includes more information. (Contributed by Tomas Roun in gh-116022 [https://github.com/python/cpython/issues/116022].)

When called with an AST as input, the parse() function now always verifies that the root node type is appropriate. (Contributed by Irit Katriel in gh-130139 [https://github.com/python/cpython/issues/130139].)

Add new options to the command-line interface: --feature-version, --optimize, and --show-empty. (Contributed by Semyon Moroz in gh-133367 [https://github.com/python/cpython/issues/133367].)

asyncio

The function and methods named create_task() now take an arbitrary list of keyword arguments. All keyword arguments are passed to the Task constructor or the custom task factory. (See set_task_factory() for details.) The name and context keyword arguments are no longer special; the name should now be set using the name keyword argument of the factory, and context may be None.

This affects the following function and methods: asyncio.create_task(), asyncio.loop.create_task(), asyncio.TaskGroup.create_task().

（由 Thomas Grainger 於 gh-128307 [https://github.com/python/cpython/issues/128307] 貢獻。）

There are two new utility functions for introspecting and printing a program's call graph: capture_call_graph() and print_call_graph(). See Asyncio introspection capabilities for more details. (Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa in gh-91048 [https://github.com/python/cpython/issues/91048].)

calendar

By default, today's date is highlighted in color in calendar's command-line text output. This can be controlled by environment variables. (Contributed by Hugo van Kemenade in gh-128317 [https://github.com/python/cpython/issues/128317].)

concurrent.futures

Add a new executor class, InterpreterPoolExecutor, which exposes multiple Python interpreters in the same process ('subinterpreters') to Python code. This uses a pool of independent Python interpreters to execute calls asynchronously.

This is separate from the new interpreters module introduced by PEP 734. (Contributed by Eric Snow in gh-124548 [https://github.com/python/cpython/issues/124548].)

On Unix platforms other than macOS, 'forkserver' is now the default start method for ProcessPoolExecutor (replacing 'fork'). This change does not affect Windows or macOS, where 'spawn' remains the default start method.

If the threading incompatible fork method is required, you must explicitly request it by supplying a multiprocessing context mp_context to ProcessPoolExecutor.

See forkserver restrictions for information and differences with the fork method and how this change may affect existing code with mutable global shared variables and/or shared objects that can not be automatically pickled.

（由 Gregory P. Smith 於 gh-84559 [https://github.com/python/cpython/issues/84559] 貢獻。）

Add two new methods to ProcessPoolExecutor, terminate_workers() and kill_workers(), as ways to terminate or kill all living worker processes in the given pool. (Contributed by Charles Machalow in gh-130849 [https://github.com/python/cpython/issues/130849].)

Add the optional buffersize parameter to Executor.map to limit the number of submitted tasks whose results have not yet been yielded. If the buffer is full, iteration over the iterables pauses until a result is yielded from the buffer. (Contributed by Enzo Bonnal and Josh Rosenberg in gh-74028 [https://github.com/python/cpython/issues/74028].)

configparser

configparser will no longer write config files it cannot read, to improve security. Attempting to write() keys containing delimiters or beginning with the section header pattern will raise an InvalidWriteError. (Contributed by Jacob Lincoln in gh-129270 [https://github.com/python/cpython/issues/129270].)

contextvars

Support the context manager protocol for Token objects. (Contributed by Andrew Svetlov in gh-129889 [https://github.com/python/cpython/issues/129889].)

ctypes

The layout of bit fields in Structure and Union objects is now a closer match to platform defaults (GCC/Clang or MSVC). In particular, fields no longer overlap. (Contributed by Matthias Görgens in gh-97702 [https://github.com/python/cpython/issues/97702].)

The Structure._layout_ class attribute can now be set to help match a non-default ABI. (Contributed by Petr Viktorin in gh-97702 [https://github.com/python/cpython/issues/97702].)

The class of Structure/Union field descriptors is now available as CField, and has new attributes to aid debugging and introspection. (Contributed by Petr Viktorin in gh-128715 [https://github.com/python/cpython/issues/128715].)

On Windows, the COMError exception is now public. (Contributed by Jun Komoda in gh-126686 [https://github.com/python/cpython/issues/126686].)

On Windows, the CopyComPointer() function is now public. (Contributed by Jun Komoda in gh-127275 [https://github.com/python/cpython/issues/127275].)

Add memoryview_at(), a function to create a memoryview object that refers to the supplied pointer and length. This works like ctypes.string_at() except it avoids a buffer copy, and is typically useful when implementing pure Python callback functions that are passed dynamically-sized buffers. (Contributed by Rian Hunter in gh-112018 [https://github.com/python/cpython/issues/112018].)

Complex types, c_float_complex, c_double_complex, and c_longdouble_complex, are now available if both the compiler and the libffi library support complex C types. (Contributed by Sergey B Kirpichev in gh-61103 [https://github.com/python/cpython/issues/61103].)

Add ctypes.util.dllist() for listing the shared libraries loaded by the current process. (Contributed by Brian Ward in gh-119349 [https://github.com/python/cpython/issues/119349].)

Move ctypes.POINTER() types cache from a global internal cache (_pointer_type_cache) to the _CData.__pointer_type__ attribute of the corresponding ctypes types. This will stop the cache from growing without limits in some situations. (Contributed by Sergey Miryanov in gh-100926 [https://github.com/python/cpython/issues/100926].)

The py_object type now supports subscription, making it a generic type. (Contributed by Brian Schubert in gh-132168 [https://github.com/python/cpython/issues/132168].)

ctypes now supports free-threading builds. (Contributed by Kumar Aditya and Peter Bierma in gh-127945 [https://github.com/python/cpython/issues/127945].)

curses

Add the assume_default_colors() function, a refinement of the use_default_colors() function which allows changing the color pair 0. (Contributed by Serhiy Storchaka in gh-133139 [https://github.com/python/cpython/issues/133139].)

datetime

Add the strptime() method to the datetime.date and datetime.time classes. (Contributed by Wannes Boeykens in gh-41431 [https://github.com/python/cpython/issues/41431].)

decimal

Add Decimal.from_number() as an alternative constructor for Decimal. (Contributed by Serhiy Storchaka in gh-121798 [https://github.com/python/cpython/issues/121798].)

Expose IEEEContext() to support creation of contexts corresponding to the IEEE 754 (2008) decimal interchange formats. (Contributed by Sergey B Kirpichev in gh-53032 [https://github.com/python/cpython/issues/53032].)

difflib

Comparison pages with highlighted changes generated by the HtmlDiff class now support 'dark mode'. (Contributed by Jiahao Li in gh-129939 [https://github.com/python/cpython/issues/129939].)

dis

Add support for rendering full source location information of instructions, rather than only the line number. This feature is added to the following interfaces via the show_positions keyword argument:

dis.Bytecode

dis.dis()

dis.distb()

dis.disassemble()

This feature is also exposed via dis --show-positions. (Contributed by Bénédikt Tran in gh-123165 [https://github.com/python/cpython/issues/123165].)

Add the dis --specialized command-line option to show specialized bytecode. (Contributed by Bénédikt Tran in gh-127413 [https://github.com/python/cpython/issues/127413].)

errno

Add the EHWPOISON error code constant. (Contributed by James Roy in gh-126585 [https://github.com/python/cpython/issues/126585].)

faulthandler

Add support for printing the C stack trace on systems that support it via the new dump_c_stack() function or via the c_stack argument in faulthandler.enable(). (Contributed by Peter Bierma in gh-127604 [https://github.com/python/cpython/issues/127604].)

fnmatch

Add filterfalse(), a function to reject names matching a given pattern. (Contributed by Bénédikt Tran in gh-74598 [https://github.com/python/cpython/issues/74598].)

fractions

A Fraction object may now be constructed from any object with the as_integer_ratio() method. (Contributed by Serhiy Storchaka in gh-82017 [https://github.com/python/cpython/issues/82017].)

Add Fraction.from_number() as an alternative constructor for Fraction. (Contributed by Serhiy Storchaka in gh-121797 [https://github.com/python/cpython/issues/121797].)

functools

Add the Placeholder sentinel. This may be used with the partial() or partialmethod() functions to reserve a place for positional arguments in the returned partial object. (Contributed by Dominykas Grigonis in gh-119127 [https://github.com/python/cpython/issues/119127].)

Allow the initial parameter of reduce() to be passed as a keyword argument. (Contributed by Sayandip Dutta in gh-125916 [https://github.com/python/cpython/issues/125916].)

getopt

Add support for options with optional arguments. (Contributed by Serhiy Storchaka in gh-126374 [https://github.com/python/cpython/issues/126374].)

Add support for returning intermixed options and non-option arguments in order. (Contributed by Serhiy Storchaka in gh-126390 [https://github.com/python/cpython/issues/126390].)

getpass

Support keyboard feedback in the getpass() function via the keyword-only optional argument echo_char. Placeholder characters are rendered whenever a character is entered, and removed when a character is deleted. (Contributed by Semyon Moroz in gh-77065 [https://github.com/python/cpython/issues/77065].)

graphlib

Allow TopologicalSorter.prepare() to be called more than once as long as sorting has not started. (Contributed by Daniel Pope in gh-130914 [https://github.com/python/cpython/issues/130914].)

heapq

The heapq module has improved support for working with max-heaps, via the following new functions:

heapify_max()

heappush_max()

heappop_max()

heapreplace_max()

heappushpop_max()

hmac

Add a built-in implementation for HMAC (RFC 2104 [https://datatracker.ietf.org/doc/html/rfc2104.html]) using formally verified code from the HACL* [https://github.com/hacl-star/hacl-star/] project. This implementation is used as a fallback when the OpenSSL implementation of HMAC is not available. (Contributed by Bénédikt Tran in gh-99108 [https://github.com/python/cpython/issues/99108].)

http

Directory lists and error pages generated by the http.server module allow the browser to apply its default dark mode. (Contributed by Yorik Hansen in gh-123430 [https://github.com/python/cpython/issues/123430].)

The http.server module now supports serving over HTTPS using the http.server.HTTPSServer class. This functionality is exposed by the command-line interface (python -m http.server) through the following options:

--tls-cert <path>: Path to the TLS certificate file.

--tls-key <path>: Optional path to the private key file.

--tls-password-file <path>: Optional path to the password file for the private key.

（由 Semyon Moroz 於 gh-85162 [https://github.com/python/cpython/issues/85162] 貢獻。）

imaplib

Add IMAP4.idle(), implementing the IMAP4 IDLE command as defined in RFC 2177 [https://datatracker.ietf.org/doc/html/rfc2177.html]. (Contributed by Forest in gh-55454 [https://github.com/python/cpython/issues/55454].)

inspect

signature() takes a new argument annotation_format to control the annotationlib.Format used for representing annotations. (Contributed by Jelle Zijlstra in gh-101552 [https://github.com/python/cpython/issues/101552].)

Signature.format() takes a new argument unquote_annotations. If true, string annotations are displayed without surrounding quotes. (Contributed by Jelle Zijlstra in gh-101552 [https://github.com/python/cpython/issues/101552].)

Add function ispackage() to determine whether an object is a package or not. (Contributed by Zhikang Yan in gh-125634 [https://github.com/python/cpython/issues/125634].)

io

Reading text from a non-blocking stream with read may now raise a BlockingIOError if the operation cannot immediately return bytes. (Contributed by Giovanni Siragusa in gh-109523 [https://github.com/python/cpython/issues/109523].)

Add the Reader and Writer protocols as simpler alternatives to the pseudo-protocols typing.IO, typing.TextIO, and typing.BinaryIO. (Contributed by Sebastian Rittau in gh-127648 [https://github.com/python/cpython/issues/127648].)

json

Add exception notes for JSON serialization errors that allow identifying the source of the error. (Contributed by Serhiy Storchaka in gh-122163 [https://github.com/python/cpython/issues/122163].)

Allow using the json module as a script using the -m switch: python -m json. This is now preferred to python -m json.tool, which is soft deprecated. See the JSON command-line interface documentation. (Contributed by Trey Hunner in gh-122873 [https://github.com/python/cpython/issues/122873].)

By default, the output of the JSON command-line interface is highlighted in color. This can be controlled by environment variables. (Contributed by Tomas Roun in gh-131952 [https://github.com/python/cpython/issues/131952].)

linecache

getline() can now retrieve source code for frozen modules. (Contributed by Tian Gao in gh-131638 [https://github.com/python/cpython/issues/131638].)

logging.handlers

QueueListener objects now support the context manager protocol. (Contributed by Charles Machalow in gh-132106 [https://github.com/python/cpython/issues/132106].)

QueueListener.start now raises a RuntimeError if the listener is already started. (Contributed by Charles Machalow in gh-132106 [https://github.com/python/cpython/issues/132106].)

math

Added more detailed error messages for domain errors in the module. (Contributed by Charlie Zhao and Sergey B Kirpichev in gh-101410 [https://github.com/python/cpython/issues/101410].)

mimetypes

Add a public command-line for the module, invoked via python -m mimetypes. (Contributed by Oleg Iarygin and Hugo van Kemenade in gh-93096 [https://github.com/python/cpython/issues/93096].)

Add several new MIME types based on RFCs and common usage:

Microsoft and RFC 8081 [https://datatracker.ietf.org/doc/html/rfc8081.html] MIME types for fonts

Embedded OpenType: application/vnd.ms-fontobject

OpenType Layout (OTF) font/otf

TrueType: font/ttf

WOFF 1.0 font/woff

WOFF 2.0 font/woff2

RFC 9559 [https://datatracker.ietf.org/doc/html/rfc9559.html] MIME types for Matroska audiovisual data container structures

audio with no video: audio/matroska (.mka)

video: video/matroska (.mkv)

stereoscopic video: video/matroska-3d (.mk3d)

Images with RFCs

RFC 1494 [https://datatracker.ietf.org/doc/html/rfc1494.html]: CCITT Group 3 (.g3)

RFC 3362 [https://datatracker.ietf.org/doc/html/rfc3362.html]: Real-time Facsimile, T.38 (.t38)

RFC 3745 [https://datatracker.ietf.org/doc/html/rfc3745.html]: JPEG 2000 (.jp2), extension (.jpx) and compound (.jpm)

RFC 3950 [https://datatracker.ietf.org/doc/html/rfc3950.html]: Tag Image File Format Fax eXtended, TIFF-FX (.tfx)

RFC 4047 [https://datatracker.ietf.org/doc/html/rfc4047.html]: Flexible Image Transport System (.fits)

RFC 7903 [https://datatracker.ietf.org/doc/html/rfc7903.html]: Enhanced Metafile (.emf) and Windows Metafile (.wmf)

Other MIME type additions and changes

RFC 2361 [https://datatracker.ietf.org/doc/html/rfc2361.html]: Change type for .avi to video/vnd.avi and for .wav to audio/vnd.wave

RFC 4337 [https://datatracker.ietf.org/doc/html/rfc4337.html]: Add MPEG-4 audio/mp4 (.m4a)

RFC 5334 [https://datatracker.ietf.org/doc/html/rfc5334.html]: Add Ogg media (.oga, .ogg and .ogx)

RFC 6713 [https://datatracker.ietf.org/doc/html/rfc6713.html]: Add gzip application/gzip (.gz)

RFC 9639 [https://datatracker.ietf.org/doc/html/rfc9639.html]: Add FLAC audio/flac (.flac)

RFC 9512 [https://datatracker.ietf.org/doc/html/rfc9512.html] application/yaml MIME type for YAML files (.yaml and .yml)

Add 7z application/x-7z-compressed (.7z)

Add Android Package application/vnd.android.package-archive (.apk) when not strict

Add deb application/x-debian-package (.deb)

Add glTF binary model/gltf-binary (.glb)

Add glTF JSON/ASCII model/gltf+json (.gltf)

Add M4V video/x-m4v (.m4v)

Add PHP application/x-httpd-php (.php)

Add RAR application/vnd.rar (.rar)

Add RPM application/x-rpm (.rpm)

Add STL model/stl (.stl)

Add Windows Media Video video/x-ms-wmv (.wmv)

De facto: Add WebM audio/webm (.weba)

ECMA-376 [https://ecma-international.org/publications-and-standards/standards/ecma-376/]: Add .docx, .pptx and .xlsx types

OASIS [https://docs.oasis-open.org/office/v1.2/cs01/OpenDocument-v1.2-cs01-part1.html#Appendix_C]: Add OpenDocument .odg, .odp, .ods and .odt types

W3C [https://www.w3.org/TR/epub-33/#app-media-type]: Add EPUB application/epub+zip (.epub)

(Contributed by Sahil Prajapati and Hugo van Kemenade in gh-84852 [https://github.com/python/cpython/issues/84852], by Sasha "Nelie" Chernykh and Hugo van Kemenade in gh-132056 [https://github.com/python/cpython/issues/132056], and by Hugo van Kemenade in gh-89416 [https://github.com/python/cpython/issues/89416], gh-85957 [https://github.com/python/cpython/issues/85957], and gh-129965 [https://github.com/python/cpython/issues/129965].)

multiprocessing

On Unix platforms other than macOS, 'forkserver' is now the default start method (replacing 'fork'). This change does not affect Windows or macOS, where 'spawn' remains the default start method.

If the threading incompatible fork method is required, you must explicitly request it via a context from get_context() (preferred) or change the default via set_start_method().

See forkserver restrictions for information and differences with the fork method and how this change may affect existing code with mutable global shared variables and/or shared objects that can not be automatically pickled.

（由 Gregory P. Smith 於 gh-84559 [https://github.com/python/cpython/issues/84559] 貢獻。）

multiprocessing's 'forkserver' start method now authenticates its control socket to avoid solely relying on filesystem permissions to restrict what other processes could cause the forkserver to spawn workers and run code. (Contributed by Gregory P. Smith for gh-97514 [https://github.com/python/cpython/issues/97514].)

The multiprocessing proxy objects for list and dict types gain previously overlooked missing methods:

clear() and copy() for proxies of list

fromkeys(), reversed(d), d | {}, {} | d, d |= {'b': 2} for proxies of dict

（由 Roy Hyunjin Han 於 gh-103134 [https://github.com/python/cpython/issues/103134] 貢獻。）

Add support for shared set objects via SyncManager.set(). The set() in Manager() method is now available. (Contributed by Mingyu Park in gh-129949 [https://github.com/python/cpython/issues/129949].)

Add the interrupt() to multiprocessing.Process objects, which terminates the child process by sending SIGINT. This enables finally clauses to print a stack trace for the terminated process. (Contributed by Artem Pulkin in gh-131913 [https://github.com/python/cpython/issues/131913].)

operator

Add is_none() and is_not_none() as a pair of functions, such that operator.is_none(obj) is equivalent to obj is None and operator.is_not_none(obj) is equivalent to obj is not None. (Contributed by Raymond Hettinger and Nico Mexis in gh-115808 [https://github.com/python/cpython/issues/115808].)

os

Add the reload_environ() function to update os.environ and os.environb with changes to the environment made by os.putenv(), by os.unsetenv(), or made outside Python in the same process. (Contributed by Victor Stinner in gh-120057 [https://github.com/python/cpython/issues/120057].)

Add the SCHED_DEADLINE and SCHED_NORMAL constants to the os module. (Contributed by James Roy in gh-127688 [https://github.com/python/cpython/issues/127688].)

Add the readinto() function to read into a buffer object from a file descriptor. (Contributed by Cody Maloney in gh-129205 [https://github.com/python/cpython/issues/129205].)

os.path

The strict parameter to realpath() accepts a new value, ALLOW_MISSING. If used, errors other than FileNotFoundError will be re-raised; the resulting path can be missing but it will be free of symlinks. (Contributed by Petr Viktorin for CVE 2025-4517 [https://www.cve.org/CVERecord?id=CVE-2025-4517].)

pathlib

Add methods to pathlib.Path to recursively copy or move files and directories:

copy() copies a file or directory tree to a destination.

copy_into() copies into a destination directory.

move() moves a file or directory tree to a destination.

move_into() moves into a destination directory.

（由 Barney Gale 於 gh-73991 [https://github.com/python/cpython/issues/73991] 貢獻。）

Add the info attribute, which stores an object implementing the new pathlib.types.PathInfo protocol. The object supports querying the file type and internally caching stat() results. Path objects generated by iterdir() are initialized with file type information gleaned from scanning the parent directory. (Contributed by Barney Gale in gh-125413 [https://github.com/python/cpython/issues/125413].)

pdb

The pdb module now supports remote attaching to a running Python process using a new -p PID command-line option:

python -m pdb -p 1234

This will connect to the Python process with the given PID and allow you to debug it interactively. Notice that due to how the Python interpreter works attaching to a remote process that is blocked in a system call or waiting for I/O will only work once the next bytecode instruction is executed or when the process receives a signal.

This feature uses PEP 768 and the new sys.remote_exec() function to attach to the remote process and send the PDB commands to it.

（由 Matt Wozniski and Pablo Galindo 於 gh-131591 [https://github.com/python/cpython/issues/131591] 貢獻。）

Hardcoded breakpoints (breakpoint() and set_trace()) now reuse the most recent Pdb instance that calls set_trace(), instead of creating a new one each time. As a result, all the instance specific data like display and commands are preserved across hardcoded breakpoints. (Contributed by Tian Gao in gh-121450 [https://github.com/python/cpython/issues/121450].)

Add a new argument mode to pdb.Pdb. Disable the restart command when pdb is in inline mode. (Contributed by Tian Gao in gh-123757 [https://github.com/python/cpython/issues/123757].)

A confirmation prompt will be shown when the user tries to quit pdb in inline mode. y, Y, <Enter> or EOF will confirm the quit and call sys.exit(), instead of raising bdb.BdbQuit. (Contributed by Tian Gao in gh-124704 [https://github.com/python/cpython/issues/124704].)

Inline breakpoints like breakpoint() or pdb.set_trace() will always stop the program at calling frame, ignoring the skip pattern (if any). (Contributed by Tian Gao in gh-130493 [https://github.com/python/cpython/issues/130493].)

<tab> at the beginning of the line in pdb multi-line input will fill in a 4-space indentation now, instead of inserting a \t character. (Contributed by Tian Gao in gh-130471 [https://github.com/python/cpython/issues/130471].)

Auto-indent is introduced in pdb multi-line input. It will either keep the indentation of the last line or insert a 4-space indentation when it detects a new code block. (Contributed by Tian Gao in gh-133350 [https://github.com/python/cpython/issues/133350].)

$_asynctask is added to access the current asyncio task if applicable. (Contributed by Tian Gao in gh-124367 [https://github.com/python/cpython/issues/124367].)

pdb.set_trace_async() is added to support debugging asyncio coroutines. await statements are supported with this function. (Contributed by Tian Gao in gh-132576 [https://github.com/python/cpython/issues/132576].)

Source code displayed in pdb will be syntax-highlighted. This feature can be controlled using the same methods as the default interactive shell, in addition to the newly added colorize argument of pdb.Pdb. (Contributed by Tian Gao and Łukasz Langa in gh-133355 [https://github.com/python/cpython/issues/133355].)

pickle

Set the default protocol version on the pickle module to 5. For more details, see pickle protocols.

Add exception notes for pickle serialization errors that allow identifying the source of the error. (Contributed by Serhiy Storchaka in gh-122213 [https://github.com/python/cpython/issues/122213].)

platform

Add invalidate_caches(), a function to invalidate cached results in the platform module. (Contributed by Bénédikt Tran in gh-122549 [https://github.com/python/cpython/issues/122549].)

pydoc

Annotations in help output are now usually displayed in a format closer to that in the original source. (Contributed by Jelle Zijlstra in gh-101552 [https://github.com/python/cpython/issues/101552].)

re

Support \z as a synonym for \Z in regular expressions. It is interpreted unambiguously in many other regular expression engines, unlike \Z, which has subtly different behavior. (Contributed by Serhiy Storchaka in gh-133306 [https://github.com/python/cpython/issues/133306].)

\B in regular expression now matches the empty input string, meaning that it is now always the opposite of \b. (Contributed by Serhiy Storchaka in gh-124130 [https://github.com/python/cpython/issues/124130].)

socket

Improve and fix support for Bluetooth sockets.

Fix support of Bluetooth sockets on NetBSD and DragonFly BSD. (Contributed by Serhiy Storchaka in gh-132429 [https://github.com/python/cpython/issues/132429].)

Fix support for BTPROTO_HCI on FreeBSD. (Contributed by Victor Stinner in gh-111178 [https://github.com/python/cpython/issues/111178].)

Add support for BTPROTO_SCO on FreeBSD. (Contributed by Serhiy Storchaka in gh-85302 [https://github.com/python/cpython/issues/85302].)

Add support for cid and bdaddr_type in the address for BTPROTO_L2CAP on FreeBSD. (Contributed by Serhiy Storchaka in gh-132429 [https://github.com/python/cpython/issues/132429].)

Add support for channel in the address for BTPROTO_HCI on Linux. (Contributed by Serhiy Storchaka in gh-70145 [https://github.com/python/cpython/issues/70145].)

Accept an integer as the address for BTPROTO_HCI on Linux. (Contributed by Serhiy Storchaka in gh-132099 [https://github.com/python/cpython/issues/132099].)

Return cid in getsockname() for BTPROTO_L2CAP. (Contributed by Serhiy Storchaka in gh-132429 [https://github.com/python/cpython/issues/132429].)

Add many new constants. (Contributed by Serhiy Storchaka in gh-132734 [https://github.com/python/cpython/issues/132734].)

ssl

Indicate through the HAS_PHA Boolean whether the ssl module supports TLSv1.3 post-handshake client authentication (PHA). (Contributed by Will Childs-Klein in gh-128036 [https://github.com/python/cpython/issues/128036].)

struct

Support the float complex and double complex C types in the struct module (formatting characters 'F' and 'D' respectively). (Contributed by Sergey B Kirpichev in gh-121249 [https://github.com/python/cpython/issues/121249].)

symtable

Expose the following Symbol methods:

is_comp_cell()

is_comp_iter()

is_free_class()

（由 Bénédikt Tran 於 gh-120029 [https://github.com/python/cpython/issues/120029] 貢獻。）

sys

The previously undocumented special function sys.getobjects(), which only exists in specialized builds of Python, may now return objects from other interpreters than the one it's called in. (Contributed by Eric Snow in gh-125286 [https://github.com/python/cpython/issues/125286].)

Add sys._is_immortal() for determining if an object is immortal. (Contributed by Peter Bierma in gh-128509 [https://github.com/python/cpython/issues/128509].)

On FreeBSD, sys.platform no longer contains the major version number. It is always 'freebsd', instead of 'freebsd13' or 'freebsd14'. (Contributed by Michael Osipov in gh-129393 [https://github.com/python/cpython/issues/129393].)

Raise DeprecationWarning for sys._clear_type_cache(). This function was deprecated in Python 3.13 but it didn't raise a runtime warning.

Add sys.remote_exec() to implement the new external debugger interface. See PEP 768 for details. (Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic in gh-131591 [https://github.com/python/cpython/issues/131591].)

Add the sys._jit namespace, containing utilities for introspecting just-in-time compilation. (Contributed by Brandt Bucher in gh-133231 [https://github.com/python/cpython/issues/133231].)

sys.monitoring

Add two new monitoring events, BRANCH_LEFT and BRANCH_RIGHT. These replace and deprecate the BRANCH event. (Contributed by Mark Shannon in gh-122548 [https://github.com/python/cpython/issues/122548].)

sysconfig

Add ABIFLAGS key to get_config_vars() on Windows. (Contributed by Xuehai Pan in gh-131799 [https://github.com/python/cpython/issues/131799].)

tarfile

data_filter() now normalizes symbolic link targets in order to avoid path traversal attacks. (Contributed by Petr Viktorin in gh-127987 [https://github.com/python/cpython/issues/127987] and CVE 2025-4138 [https://www.cve.org/CVERecord?id=CVE-2025-4138].)

extractall() now skips fixing up directory attributes when a directory was removed or replaced by another kind of file. (Contributed by Petr Viktorin in gh-127987 [https://github.com/python/cpython/issues/127987] and CVE 2024-12718 [https://www.cve.org/CVERecord?id=CVE-2024-12718].)

extract() and extractall() now (re-)apply the extraction filter when substituting a link (hard or symbolic) with a copy of another archive member, and when fixing up directory attributes. The former raises a new exception, LinkFallbackError. (Contributed by Petr Viktorin for CVE 2025-4330 [https://www.cve.org/CVERecord?id=CVE-2025-4330] and CVE 2024-12718 [https://www.cve.org/CVERecord?id=CVE-2024-12718].)

extract() and extractall() no longer extract rejected members when errorlevel() is zero. (Contributed by Matt Prodani and Petr Viktorin in gh-112887 [https://github.com/python/cpython/issues/112887] and CVE 2025-4435 [https://www.cve.org/CVERecord?id=CVE-2025-4435].)

threading

threading.Thread.start() now sets the operating system thread name to threading.Thread.name. (Contributed by Victor Stinner in gh-59705 [https://github.com/python/cpython/issues/59705].)

tkinter

Make tkinter widget methods after() and after_idle() accept keyword arguments. (Contributed by Zhikang Yan in gh-126899 [https://github.com/python/cpython/issues/126899].)

Add ability to specify a name for tkinter.OptionMenu and tkinter.ttk.OptionMenu. (Contributed by Zhikang Yan in gh-130482 [https://github.com/python/cpython/issues/130482].)

turtle

Add context managers for turtle.fill(), turtle.poly(), and turtle.no_animation(). (Contributed by Marie Roald and Yngve Mardal Moe in gh-126350 [https://github.com/python/cpython/issues/126350].)

types

types.UnionType is now an alias for typing.Union. See below for more details. (Contributed by Jelle Zijlstra in gh-105499 [https://github.com/python/cpython/issues/105499].)

typing

The types.UnionType and typing.Union types are now aliases for each other, meaning that both old-style unions (created with Union[int, str]) and new-style unions (int | str) now create instances of the same runtime type. This unifies the behavior between the two syntaxes, but leads to some differences in behavior that may affect users who introspect types at runtime:

Both syntaxes for creating a union now produce the same string representation in repr(). For example, repr(Union[int, str]) is now "int | str" instead of "typing.Union[int, str]".

Unions created using the old syntax are no longer cached. Previously, running Union[int, str] multiple times would return the same object (Union[int, str] is Union[int, str] would be True), but now it will return two different objects. Use == to compare unions for equality, not is. New-style unions have never been cached this way. This change could increase memory usage for some programs that use a large number of unions created by subscripting typing.Union. However, several factors offset this cost: unions used in annotations are no longer evaluated by default in Python 3.14 because of PEP 649 [https://peps.python.org/pep-0649/]; an instance of types.UnionType is itself much smaller than the object returned by Union[] was on prior Python versions; and removing the cache also saves some space. It is therefore unlikely that this change will cause a significant increase in memory usage for most users.

在過去，舊式聯集是使用私有類別 typing._UnionGenericAlias 實作的。這個類別不再被需要，但為了向後相容性而保留，並計劃將在 Python 3.17 中移除。使用者應該改用文件中記錄的自我檢查輔助函式，例如 get_origin() 和 typing.get_args()，或者依賴私有實作細節。

It is now possible to use typing.Union itself in isinstance() checks. For example, isinstance(int | str, typing.Union) will return True; previously this raised TypeError.

The __args__ attribute of typing.Union objects is no longer writable.

It is no longer possible to set any attributes on Union objects. This only ever worked for dunder attributes on previous versions, was never documented to work, and was subtly broken in many cases.

（由 Jelle Zijlstra 於 gh-105499 [https://github.com/python/cpython/issues/105499] 貢獻。）

TypeAliasType now supports star unpacking.

unicodedata

The Unicode database has been updated to Unicode 16.0.0.

unittest

unittest output is now colored by default. This can be controlled by environment variables. (Contributed by Hugo van Kemenade in gh-127221 [https://github.com/python/cpython/issues/127221].)

unittest discovery supports namespace package as start directory again. It was removed in Python 3.11. (Contributed by Jacob Walls in gh-80958 [https://github.com/python/cpython/issues/80958].)

A number of new methods were added in the TestCase class that provide more specialized tests.

assertHasAttr() and assertNotHasAttr() check whether the object has a particular attribute.

assertIsSubclass() and assertNotIsSubclass() check whether the object is a subclass of a particular class, or of one of a tuple of classes.

assertStartsWith(), assertNotStartsWith(), assertEndsWith() and assertNotEndsWith() check whether the Unicode or byte string starts or ends with particular strings.

（由 Serhiy Storchaka 於 gh-71339 [https://github.com/python/cpython/issues/71339] 貢獻。）

urllib

Upgrade HTTP digest authentication algorithm for urllib.request by supporting SHA-256 digest authentication as specified in RFC 7616 [https://datatracker.ietf.org/doc/html/rfc7616.html]. (Contributed by Calvin Bui in gh-128193 [https://github.com/python/cpython/issues/128193].)

Improve ergonomics and standards compliance when parsing and emitting file: URLs.

In url2pathname():

Accept a complete URL when the new require_scheme argument is set to true.

Discard URL authority if it matches the local hostname.

Discard URL authority if it resolves to a local IP address when the new resolve_host argument is set to true.

Discard URL query and fragment components.

Raise URLError if a URL authority isn't local, except on Windows where we return a UNC path as before.

In pathname2url():

Return a complete URL when the new add_scheme argument is set to true.

Include an empty URL authority when a path begins with a slash. For example, the path /etc/hosts is converted to the URL ///etc/hosts.

On Windows, drive letters are no longer converted to uppercase, and : characters not following a drive letter no longer cause an OSError exception to be raised.

（由 Barney Gale 於 gh-125866 [https://github.com/python/cpython/issues/125866] 貢獻。）

uuid

Add support for UUID versions 6, 7, and 8 via uuid6(), uuid7(), and uuid8() respectively, as specified in RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html]. (Contributed by Bénédikt Tran in gh-89083 [https://github.com/python/cpython/issues/89083].)

NIL and MAX are now available to represent the Nil and Max UUID formats as defined by RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html]. (Contributed by Nick Pope in gh-128427 [https://github.com/python/cpython/issues/128427].)

Allow generating multiple UUIDs simultaneously on the command-line via python -m uuid --count. (Contributed by Simon Legner in gh-131236 [https://github.com/python/cpython/issues/131236].)

webbrowser

Names in the BROWSER environment variable can now refer to already registered browsers for the webbrowser module, instead of always generating a new browser command.

This makes it possible to set BROWSER to the value of one of the supported browsers on macOS.

zipfile

Added ZipInfo._for_archive, a method to resolve suitable defaults for a ZipInfo object as used by ZipFile.writestr. (Contributed by Bénédikt Tran in gh-123424 [https://github.com/python/cpython/issues/123424].)

ZipFile.writestr() now respects the SOURCE_DATE_EPOCH environment variable in order to better support reproducible builds. (Contributed by Jiahao Li in gh-91279 [https://github.com/python/cpython/issues/91279].)

最佳化

The import time for several standard library modules has been improved, including annotationlib, ast, asyncio, base64, cmd, csv, gettext, importlib.util, locale, mimetypes, optparse, pickle, pprint, pstats, shlex, socket, string, subprocess, threading, tomllib, types, and zipfile.

(Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli Schwartz, Hugo van Kemenade, Jelle Zijlstra, and others in gh-118761 [https://github.com/python/cpython/issues/118761].)

The interpreter now avoids some reference count modifications internally when it's safe to do so. This can lead to different values being returned from sys.getrefcount() and Py_REFCNT() compared to previous versions of Python. See below for details.

asyncio

Standard benchmark results have improved by 10-20% following the implementation of a new per-thread doubly linked list for native tasks, also reducing memory usage. This enables external introspection tools such as python -m asyncio pstree to introspect the call graph of asyncio tasks running in all threads. (Contributed by Kumar Aditya in gh-107803 [https://github.com/python/cpython/issues/107803].)

The module now has first class support for free-threading builds. This enables parallel execution of multiple event loops across different threads, scaling linearly with the number of threads. (Contributed by Kumar Aditya in gh-128002 [https://github.com/python/cpython/issues/128002].)

base64

b16decode() is now up to six times faster. (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in gh-118761 [https://github.com/python/cpython/issues/118761].)

bdb

The basic debugger now has a sys.monitoring-based backend, which can be selected via the passing 'monitoring' to the Bdb class's new backend parameter. (Contributed by Tian Gao in gh-124533 [https://github.com/python/cpython/issues/124533].)

difflib

The IS_LINE_JUNK() function is now up to twice as fast. (Contributed by Adam Turner and Semyon Moroz in gh-130167 [https://github.com/python/cpython/issues/130167].)

gc

The new incremental garbage collector means that maximum pause times are reduced by an order of magnitude or more for larger heaps.

Because of this optimization, the meaning of the results of get_threshold() and set_threshold() have changed, along with get_count() and get_stats().

For backwards compatibility, get_threshold() continues to return a three-item tuple. The first value is the threshold for young collections, as before; the second value determines the rate at which the old collection is scanned (the default is 10, and higher values mean that the old collection is scanned more slowly). The third value is now meaningless and is always zero.

set_threshold() now ignores any items after the second.

get_count() and get_stats() continue to return the same format of results. The only difference is that instead of the results referring to the young, aging and old generations, the results refer to the young generation and the aging and collecting spaces of the old generation.

In summary, code that attempted to manipulate the behavior of the cycle GC may not work exactly as intended, but it is very unlikely to be harmful. All other code will work just fine.

（由 Mark Shannon 於 gh-108362 [https://github.com/python/cpython/issues/108362] 貢獻。）

io

Opening and reading files now executes fewer system calls. Reading a small operating system cached file in full is up to 15% faster. (Contributed by Cody Maloney and Victor Stinner in gh-120754 [https://github.com/python/cpython/issues/120754] and gh-90102 [https://github.com/python/cpython/issues/90102].)

pathlib

Path.read_bytes now uses unbuffered mode to open files, which is between 9% and 17% faster to read in full. (Contributed by Cody Maloney in gh-120754 [https://github.com/python/cpython/issues/120754].)

pdb

pdb now supports two backends, based on either sys.settrace() or sys.monitoring. Using the pdb CLI or breakpoint() will always use the sys.monitoring backend. Explicitly instantiating pdb.Pdb and its derived classes will use the sys.settrace() backend by default, which is configurable. (Contributed by Tian Gao in gh-124533 [https://github.com/python/cpython/issues/124533].)

textwrap

Optimize the dedent() function, improving performance by an average of 2.4x, with larger improvements for bigger inputs, and fix a bug with incomplete normalization of blank lines with whitespace characters other than space and tab.

uuid

uuid3() and uuid5() are now both roughly 40% faster for 16-byte names and 20% faster for 1024-byte names. Performance for longer names remains unchanged. (Contributed by Bénédikt Tran in gh-128150 [https://github.com/python/cpython/issues/128150].)

uuid4() is now c. 30% faster. (Contributed by Bénédikt Tran in gh-128150 [https://github.com/python/cpython/issues/128150].)

zlib

On Windows, zlib-ng [https://github.com/zlib-ng/zlib-ng] is now used as the implementation of the zlib module in the default binaries. There are no known incompatibilities between zlib-ng and the previously-used zlib implementation. This should result in better performance at all compression levels.

It is worth noting that zlib.Z_BEST_SPEED (1) may result in significantly less compression than the previous implementation, whilst also significantly reducing the time taken to compress.

（由 Steve Dower 於 gh-91349 [https://github.com/python/cpython/issues/91349] 貢獻。）

已移除

argparse

Remove the type, choices, and metavar parameters of BooleanOptionalAction. These have been deprecated since Python 3.12. (Contributed by Nikita Sobolev in gh-118805 [https://github.com/python/cpython/issues/118805].)

Calling add_argument_group() on an argument group now raises a ValueError. Similarly, add_argument_group() or add_mutually_exclusive_group() on a mutually exclusive group now both raise ValueErrors. This 'nesting' was never supported, often failed to work correctly, and was unintentionally exposed through inheritance. This functionality has been deprecated since Python 3.11. (Contributed by Savannah Ostrowski in gh-127186 [https://github.com/python/cpython/issues/127186].)

ast

Remove the following classes, which have been deprecated aliases of Constant since Python 3.8 and have emitted deprecation warnings since Python 3.12:

Bytes

Ellipsis

NameConstant

Num

Str

As a consequence of these removals, user-defined visit_Num, visit_Str, visit_Bytes, visit_NameConstant and visit_Ellipsis methods on custom NodeVisitor subclasses will no longer be called when the NodeVisitor subclass is visiting an AST. Define a visit_Constant method instead.

（由 Alex Waygood 於 gh-119562 [https://github.com/python/cpython/issues/119562] 貢獻。）

Remove the following deprecated properties on ast.Constant, which were present for compatibility with the now-removed AST classes:

Constant.n

Constant.s

改用 Constant.value。（由 Alex Waygood 於 gh-119562 [https://github.com/python/cpython/issues/119562] 貢獻。）

asyncio

Remove the following classes, methods, and functions, which have been deprecated since Python 3.12:

AbstractChildWatcher

FastChildWatcher

MultiLoopChildWatcher

PidfdChildWatcher

SafeChildWatcher

ThreadedChildWatcher

AbstractEventLoopPolicy.get_child_watcher()

AbstractEventLoopPolicy.set_child_watcher()

get_child_watcher()

set_child_watcher()

（由 Kumar Aditya 於 gh-120804 [https://github.com/python/cpython/issues/120804] 貢獻。）

asyncio.get_event_loop() now raises a RuntimeError if there is no current event loop, and no longer implicitly creates an event loop.

（由 Kumar Aditya 於 gh-126353 [https://github.com/python/cpython/issues/126353] 貢獻。）

有一些使用 asyncio.get_event_loop() 的模式，其中大多數可以用 asyncio.run() 取代。

如果你正在運行非同步函式，只需使用 asyncio.run()。

之前是：

async def main():
    ...

loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(main())
finally:
    loop.close()

之後是：

async def main():
    ...

asyncio.run(main())

如果你需要啟動某些東西然後永遠運行，像是監聽 socket 的伺服器，請使用 asyncio.run() 和 asyncio.Event。

之前是：

def start_server(loop): ...

loop = asyncio.get_event_loop()
try:
    start_server(loop)
    loop.run_forever()
finally:
    loop.close()

之後是：

def start_server(loop): ...

async def main():
    start_server(asyncio.get_running_loop())
    await asyncio.Event().wait()

asyncio.run(main())

如果你需要在事件迴圈中運行某些東西，然後在其周圍運行一些阻塞程式碼，請使用 asyncio.Runner。

之前是：

async def operation_one(): ...
def blocking_code(): ...
async def operation_two(): ...

loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(operation_one())
    blocking_code()
    loop.run_until_complete(operation_two())
finally:
    loop.close()

之後是：

async def operation_one(): ...
def blocking_code(): ...
async def operation_two(): ...

with asyncio.Runner() as runner:
    runner.run(operation_one())
    blocking_code()
    runner.run(operation_two())

email

Remove email.utils.localtime()'s isdst parameter, which was deprecated in and has been ignored since Python 3.12. (Contributed by Hugo van Kemenade in gh-118798 [https://github.com/python/cpython/issues/118798].)

importlib.abc

移除已棄用的 importlib.abc 類別：

ResourceReader（請改用 TraversableResources）

Traversable（請改用 Traversable）

TraversableResources（請改用 TraversableResources）

（由 Jason R. Coombs 和 Hugo van Kemenade 貢獻於 gh-93963 [https://github.com/python/cpython/issues/93963]。）

itertools

Remove support for copy, deepcopy, and pickle operations from itertools iterators. These have emitted a DeprecationWarning since Python 3.12. (Contributed by Raymond Hettinger in gh-101588 [https://github.com/python/cpython/issues/101588].)

pathlib

Remove support for passing additional keyword arguments to Path. In previous versions, any such arguments are ignored. (Contributed by Barney Gale in gh-74033 [https://github.com/python/cpython/issues/74033].)

Remove support for passing additional positional arguments to PurePath.relative_to() and is_relative_to(). In previous versions, any such arguments are joined onto other. (Contributed by Barney Gale in gh-78707 [https://github.com/python/cpython/issues/78707].)

pkgutil

Remove the get_loader() and find_loader() functions, which have been deprecated since Python 3.12. (Contributed by Bénédikt Tran in gh-97850 [https://github.com/python/cpython/issues/97850].)

pty

Remove the master_open() and slave_open() functions, which have been deprecated since Python 3.12. Use pty.openpty() instead. (Contributed by Nikita Sobolev in gh-118824 [https://github.com/python/cpython/issues/118824].)

sqlite3

Remove version and version_info from the sqlite3 module; use sqlite_version and sqlite_version_info for the actual version number of the runtime SQLite library. (Contributed by Hugo van Kemenade in gh-118924 [https://github.com/python/cpython/issues/118924].)

Using a sequence of parameters with named placeholders now raises a ProgrammingError, having been deprecated since Python 3.12. (Contributed by Erlend E. Aasland in gh-118928 [https://github.com/python/cpython/issues/118928] and gh-101693 [https://github.com/python/cpython/issues/101693].)

urllib

Remove the Quoter class from urllib.parse, which has been deprecated since Python 3.11. (Contributed by Nikita Sobolev in gh-118827 [https://github.com/python/cpython/issues/118827].)

Remove the URLopener and FancyURLopener classes from urllib.request, which have been deprecated since Python 3.3.

myopener.open() can be replaced with urlopen(). myopener.retrieve() can be replaced with urlretrieve(). Customisations to the opener classes can be replaced by passing customized handlers to build_opener(). (Contributed by Barney Gale in gh-84850 [https://github.com/python/cpython/issues/84850].)

已棄用

New deprecations

在 complex() 建構函式中將複數作為 real 或 imag 引數傳遞現在已被棄用；複數應該只作為單個位置引數傳遞。 (由 Serhiy Storchaka 於 gh-109218 [https://github.com/python/cpython/issues/109218] 貢獻。)

argparse：

將未以文件記錄的關鍵字引數 prefix_chars 傳遞給 add_argument_group() 的做法現在已被棄用。（由 Savannah Ostrowski 於 gh-125563 [https://github.com/python/cpython/issues/125563] 貢獻。）

Deprecated the argparse.FileType type converter. Anything relating to resource management should be handled downstream, after the arguments have been parsed. (Contributed by Serhiy Storchaka in gh-58032 [https://github.com/python/cpython/issues/58032].)

asyncio：

asyncio.iscoroutinefunction() 已被棄用並將在 Python 3.16 中移除；請改用 inspect.iscoroutinefunction()。（由 Jiahao Li 和 Kumar Aditya 於 gh-122875 [https://github.com/python/cpython/issues/122875] 貢獻。）

asyncio 策略系統已被棄用並將在 Python 3.16 中移除。特別是以下類別和函式已被棄用：

asyncio.AbstractEventLoopPolicy

asyncio.DefaultEventLoopPolicy

asyncio.WindowsSelectorEventLoopPolicy

asyncio.WindowsProactorEventLoopPolicy

asyncio.get_event_loop_policy()

asyncio.set_event_loop_policy()

使用者應該使用 asyncio.run() 或 asyncio.Runner 搭配 loop_factory 引數來使用所需的事件迴圈實作。

例如在 Windows 上使用 asyncio.SelectorEventLoop：

import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

（由 Kumar Aditya 於 gh-127949 [https://github.com/python/cpython/issues/127949] 貢獻。）

codecs: codecs.open() 函式已被棄用，並將在未來的 Python 版本中移除。請改用 open()。（由 Inada Naoki 於 gh-133036 [https://github.com/python/cpython/issues/133036] 貢獻。）

ctypes：

On non-Windows platforms, setting Structure._pack_ to use a MSVC-compatible default memory layout is now deprecated in favor of setting Structure._layout_ to 'ms', and will be removed in Python 3.19. (Contributed by Petr Viktorin in gh-131747 [https://github.com/python/cpython/issues/131747].)

Calling ctypes.POINTER() on a string is now deprecated. Use incomplete types for self-referential structures. Also, the internal ctypes._pointer_type_cache is deprecated. See ctypes.POINTER() for updated implementation details. (Contributed by Sergey Myrianov in gh-100926 [https://github.com/python/cpython/issues/100926].)

functools: 使用 function 或 sequence 關鍵字引數呼叫 functools.reduce() 的 Python 實作已被棄用；這些參數將在 Python 3.16 中變為僅限位置引數。（由 Kirill Podoprigora 於 gh-121676 [https://github.com/python/cpython/issues/121676] 貢獻。）

logging: 對具有 strm 引數的自訂日誌記錄處理函式的支援已被棄用，並計劃在 Python 3.16 中移除。請改為使用 stream 引數來定義處理函式。（由 Mariusz Felisiak 於 gh-115032 [https://github.com/python/cpython/issues/115032] 貢獻。）

mimetypes: 有效的副檔名為空字串或對 mimetypes.MimeTypes.add_type() 以 '.' 開頭。未加點的副檔名已被棄用，並將在 Python 3.16 中引發 ValueError。（由 Hugo van Kemenade 於 gh-75223 [https://github.com/python/cpython/issues/75223] 貢獻。）

nturl2path: This module is now deprecated. Call urllib.request.url2pathname() and pathname2url() instead. (Contributed by Barney Gale in gh-125866 [https://github.com/python/cpython/issues/125866].)

os: The os.popen() and os.spawn* functions are now soft deprecated. They should no longer be used to write new code. The subprocess module is recommended instead. (Contributed by Victor Stinner in gh-120743 [https://github.com/python/cpython/issues/120743].)

pathlib: pathlib.PurePath.as_uri() is now deprecated and scheduled for removal in Python 3.19. Use pathlib.Path.as_uri() instead. (Contributed by Barney Gale in gh-123599 [https://github.com/python/cpython/issues/123599].)

pdb: The undocumented pdb.Pdb.curframe_locals attribute is now a deprecated read-only property, which will be removed in a future version of Python. The low overhead dynamic frame locals access added in Python 3.13 by PEP 667 [https://peps.python.org/pep-0667/] means the frame locals cache reference previously stored in this attribute is no longer needed. Derived debuggers should access pdb.Pdb.curframe.f_locals directly in Python 3.13 and later versions. (Contributed by Tian Gao in gh-124369 [https://github.com/python/cpython/issues/124369] and gh-125951 [https://github.com/python/cpython/issues/125951].)

symtable: Deprecate symtable.Class.get_methods() due to the lack of interest, scheduled for removal in Python 3.16. (Contributed by Bénédikt Tran in gh-119698 [https://github.com/python/cpython/issues/119698].)

tkinter: The tkinter.Variable methods trace_variable(), trace_vdelete() and trace_vinfo() are now deprecated. Use trace_add(), trace_remove() and trace_info() instead. (Contributed by Serhiy Storchaka in gh-120220 [https://github.com/python/cpython/issues/120220].)

urllib.parse: Accepting objects with false values (like 0 and []) except empty strings, bytes-like objects and None in parse_qsl() and parse_qs() is now deprecated. (Contributed by Serhiy Storchaka in gh-116897 [https://github.com/python/cpython/issues/116897].)

Python 3.15 中待移除的項目

引入系統 (import system)：

在模組上設定 __cached__ 而沒有設定 __spec__.cached 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __cached__。(gh-97879 [https://github.com/python/cpython/issues/97879])

在模組上設定 __package__ 而沒有設定 __spec__.parent 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __package__。(gh-97879 [https://github.com/python/cpython/issues/97879])

ctypes：

自 Python 3.13 起，未記錄的 ctypes.SetPointerType() 函式已被棄用。

http.server：

過時且很少使用的 CGIHTTPRequestHandler 自 Python 3.13 起已被棄用。不存在直接的替代。任何東西都比 CGI 更好地將 Web 伺服器與請求處理程序介接起來。

自 Python 3.13 起，python -m http.server 命令列介面的 --cgi 旗標已被棄用。

importlib：

load_module() method：請改用 exec_module()。

locale：

getdefaultlocale() 已在 Python 3.11 中被棄用，原本計劃在 Python 3.13 中移除 (gh-90817 [https://github.com/python/cpython/issues/90817])，但被延後至 Python 3.15。請改用 getlocale()、setlocale() 和 getencoding()。 (由 Hugo van Kemenade 於 gh-111187 [https://github.com/python/cpython/issues/111187] 貢獻。)

pathlib：

PurePath.is_reserved() 已自 Python 3.13 被棄用。請用 os.path.isreserved() 來偵測 Windows 上的保留路徑。

platform：

自 Python 3.13 起，java_ver() 已被棄用。此函式僅對 Jython 支援有用，具有令人困惑的 API，基本上未經測試。

sysconfig：

sysconfig.is_python_build() 的 check_home 引數自 Python 3.12 起已被棄用。

threading：

RLock() 在 Python 3.15 中將不接受任何引數。自 Python 3.14 起，傳遞任何引數的用法已被棄用，因為 Python 版本不允許任何引數，但 C 版本允許任意數量的位置或關鍵字引數，並忽略每個引數。

types：

types.CodeType：自 3.10 起，存取 co_lnotab 已在 PEP 626 [https://peps.python.org/pep-0626/] 中被棄用，並計劃在 3.12 中移除，但只在 3.12 中於適當時發出 DeprecationWarning。可能在 3.15 中移除。（由 Nikita Sobolev 於 gh-101866 [https://github.com/python/cpython/issues/101866] 貢獻。）

typing：

用於建立 NamedTuple 類別的未以文件記錄之關鍵字引數語法 (Point = NamedTuple("Point", x=int, y=int)) 已自 Python 3.13 棄用。請改用基於類別的語法或函式語法 (functional syntax)。

當使用 TypedDict 的函式語法時，未傳遞值給 fields 參數 (TD = TypedDict("TD")) 或傳遞 None (TD = TypedDict("TD", None)) 的做法自 Python 3.13 起已被棄用。請使用 class TD(TypedDict): pass 或 TD = TypedDict("TD", {}) 來建立具有零個欄位的 TypedDict。

自 Python 3.13 起，typing.no_type_check_decorator() 裝飾器函式已被棄用。在 typing 模組中使用了八年之後，它尚未得到任何主要型別檢查器的支援。

wave：

已棄用 Wave_read 和 Wave_write 類別的 getmark()、setmark() 和 getmarkers() 方法自 Python 3.13 被棄用。

zipimport：

load_module() 自 Python 3.10 被棄用。請改用 exec_module()。（由 Jiahao Li 於 gh-125746 [https://github.com/python/cpython/issues/125746] 貢獻。）

Python 3.16 中待移除的項目

引入系統 (import system)：

在模組上設定 __loader__ 而沒有設定 __spec__.loader 的做法將於 Python 3.16 被棄用。在 Python 3.16 中，引入系統或標準函式庫將不再設定或考慮 __loader__。

array：

自 Python 3.3 起，'u' 格式碼 (wchar_t) 在文件中已被棄用，自 Python 3.13 起在 runtime 已被棄用。請使用 'w' 格式碼 (Py_UCS4) 來取代 Unicode 字元。

asyncio：

asyncio.iscoroutinefunction() 已被棄用並將在 Python 3.16 中移除；請改用 inspect.iscoroutinefunction()。（由 Jiahao Li 和 Kumar Aditya 於 gh-122875 [https://github.com/python/cpython/issues/122875] 貢獻。）

asyncio 策略系統已被棄用並將在 Python 3.16 中移除。特別是以下類別和函式已被棄用：

asyncio.AbstractEventLoopPolicy

asyncio.DefaultEventLoopPolicy

asyncio.WindowsSelectorEventLoopPolicy

asyncio.WindowsProactorEventLoopPolicy

asyncio.get_event_loop_policy()

asyncio.set_event_loop_policy()

使用者應該使用 asyncio.run() 或 asyncio.Runner 搭配 loop_factory 來使用所需的事件迴圈實作。

例如在 Windows 上使用 asyncio.SelectorEventLoop：

import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

（由 Kumar Aditya 於 gh-127949 [https://github.com/python/cpython/issues/127949] 貢獻。）

builtins：

自 Python 3.12 起，布林型別的位元反轉 ~True 或 ~False 已被棄用，因為它會產生不預期且不直觀的結果（-2 和 -1）。使用 not x 代替布林值的邏輯否定。在極少數情況下，你需要對底層的整數進行位元反轉，請明確轉換為 ~int(x) (~int(x))。

functools：

自 Python 3.14 起，使用 function 或 sequence 關鍵字引數呼叫 functools.reduce() 的 Python 實作已被棄用。

logging：

對具有 strm 引數的自訂日誌記錄處理函式的支援已被棄用，並計劃在 Python 3.16 中移除。請改用 stream 引數。（由 Mariusz Felisiak 於 gh-115032 [https://github.com/python/cpython/issues/115032] 貢獻。）

mimetypes：

有效的副檔名以 '.' 開頭或對 mimetypes.MimeTypes.add_type() 為空字串。未加點的副檔名已被棄用，並將在 Python 3.16 中引發 ValueError。（由 Hugo van Kemenade 於 gh-75223 [https://github.com/python/cpython/issues/75223] 貢獻。）

shutil：

自 Python 3.14 起，ExecError 例外已被棄用。自 Python 3.4 以來，它尚未被 shutil 中的任何函式使用，現在是 RuntimeError 的別名。

symtable：

自 Python 3.14 起，Class.get_methods 方法已被棄用。

sys：

自 Python 3.13 起，_enablelegacywindowsfsencoding() 函式已被棄用。請改用 PYTHONLEGACYWINDOWSFSENCODING 環境變數。

sysconfig：

自 Python 3.14 起，sysconfig.expand_makefile_vars() 函式已被棄用。請改用 sysconfig.get_paths() 的 vars 引數。

tarfile：

自 Python 3.13 起，未以文件記錄和未被使用的 TarFile.tarfile 屬性已被棄用。

Python 3.17 中待移除的項目

collections.abc：

collections.abc.ByteString 預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

typing：

在 Python 3.14 之前，舊式聯集是使用私有類別 typing._UnionGenericAlias 實作的。這個類別不再被需要，但為了向後相容性而保留，並計劃將在 Python 3.17 中移除。使用者應該改用文件中記錄的內省輔助函式，例如 typing.get_origin() 和 typing.get_args()，或者依賴私有實作細節。

typing.ByteString 自 Python 3.9 起已被棄用，預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

Python 3.18 中待移除的項目

decimal：

非標準且無文件記載的 Decimal 格式說明符號 'N'，僅在 decimal 模組的 C 實作中被支援，自 Python 3.13 起已被棄用。（由 Serhiy Storchaka 於 gh-89902 [https://github.com/python/cpython/issues/89902] 中貢獻。）

Python 3.19 中待移除的項目

ctypes：

在非 Windows 平台上，透過設定 _pack_ 而沒有設定 _layout_ 來隱式地切換到與 MSVC 相容的結構佈局。

未來版本中的待移除項目

以下 API 將在未來被移除，雖然目前尚未安排移除日期。

argparse：

巢狀引數群組和巢狀互斥群組已被棄用。

將未以文件記錄的關鍵字引數 prefix_chars 傳遞給 add_argument_group() 的做法現在已被棄用。

argparse.FileType 型別轉換器已被棄用。

builtins：

產生器：throw(type, exc, tb) 和 athrow(type, exc, tb) 簽名已被棄用：請改用 throw(exc) 和 athrow(exc)，為單引數簽名。

目前 Python 接受數值字面值後面立即接關鍵字，例如 0in x、1or x、0if 1else 2。它讓運算式模糊且容易混淆，如 [0x1for x in y]（可以解釋為 [0x1 for x in y] 或 [0x1f or x in y]）。如果數值字面值後立即接 and、else、for、if、in、is 和 or 之一的關鍵字，則會引發語法警告。在未來版本中，它將被更改為語法錯誤。(gh-87999 [https://github.com/python/cpython/issues/87999])

__index__() 和 __int__() 方法回傳非 int 型別的支援：這些方法將需要回傳 int 的嚴格子類別實例。

回傳 float 嚴格子類別 __float__() 方法的支援：這些方法將需要回傳 float 的實例。

回傳 complex 嚴格子類別 __complex__() 方法的支援：這些方法將需要回傳 complex 的實例。

將 int() 委派給 __trunc__() 方法。

在 complex() 建構子中將複數作為 real 或 imag 引數傳遞現在已被棄用；它應該只作為單個位置引數傳遞。 (由 Serhiy Storchaka 於 gh-109218 [https://github.com/python/cpython/issues/109218] 貢獻。)

calendar：calendar.January 和 calendar.February 常數已被棄用並被 calendar.JANUARY 和 calendar.FEBRUARY 取代。 (由 Prince Roshan 於 gh-103636 [https://github.com/python/cpython/issues/103636] 貢獻。)

codecs：請改用 open() 而非 codecs.open()。(gh-133038 [https://github.com/python/cpython/issues/133038])

codeobject.co_lnotab：請改用 codeobject.co_lines() 方法。

datetime：

utcnow()：請改用 datetime.datetime.now(tz=datetime.UTC)。

utcfromtimestamp()：請改用 datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)。

gettext：複數值必須是整數。

importlib：

cache_from_source() debug_override 參數已被棄用：請改用 optimization 參數。

importlib.metadata：

EntryPoints 元組介面。

回傳值上的隱式 None。

logging：自 Python 3.3 起，warn() 方法已被棄用，請改用 warning()。

mailbox：已棄用 StringIO 輸入和文本模式，請改用 BytesIO 和二進位模式。

os：在多執行緒行程中呼叫 os.register_at_fork()。

pydoc.ErrorDuringImport：exc_info 參數的元組值已被棄用，請用例外實例。

re：現在對正規表示式中的數值群組參照和群組名稱用了更嚴格的規則。現在只有 ASCII 數碼序列被接受作為數值參照。位元組模式和替換字串中的群組名稱現在只能包含 ASCII 字母、數碼和底線。（由 Serhiy Storchaka 於 gh-91760 [https://github.com/python/cpython/issues/91760] 貢獻。）

sre_compile、sre_constants 和 sre_parse 模組。

shutil：rmtree() 的 onerror 參數在 Python 3.12 中已被棄用；請改用 onexc 參數。

ssl 選項和協定：

不帶協定引數的 ssl.SSLContext 已被棄用。

ssl.SSLContext：set_npn_protocols() 和 selected_npn_protocol() 已被棄用：請改用 ALPN。

ssl.OP_NO_SSL* 選項

ssl.OP_NO_TLS* 選項

ssl.PROTOCOL_SSLv3

ssl.PROTOCOL_TLS

ssl.PROTOCOL_TLSv1

ssl.PROTOCOL_TLSv1_1

ssl.PROTOCOL_TLSv1_2

ssl.TLSVersion.SSLv3

ssl.TLSVersion.TLSv1

ssl.TLSVersion.TLSv1_1

threading 方法：

threading.Condition.notifyAll()：請用 notify_all()。

threading.Event.isSet()：請用 is_set()。

threading.Thread.isDaemon()、threading.Thread.setDaemon()：請用 threading.Thread.daemon 屬性。

threading.Thread.getName()、threading.Thread.setName()：請用 threading.Thread.name 屬性。

threading.currentThread()：請用 threading.current_thread()。

threading.activeCount()：請用 threading.active_count()。

typing.Text (gh-92332 [https://github.com/python/cpython/issues/92332])。

內部類別 typing._UnionGenericAlias 不再用於實作 typing.Union。為了保持與此私有類別使用者的相容性，直到至少 Python 3.17 都將提供一個相容性 shim。（由 Jelle Zijlstra 於 gh-105499 [https://github.com/python/cpython/issues/105499] 貢獻。）

unittest.IsolatedAsyncioTestCase：從測試案例中回傳非 None 的值已被棄用。

urllib.parse 已棄用函式：請改用 urlparse()。

splitattr()

splithost()

splitnport()

splitpasswd()

splitport()

splitquery()

splittag()

splittype()

splituser()

splitvalue()

to_bytes()

wsgiref：SimpleHandler.stdout.write() 不應該進行部分寫入。

xml.etree.ElementTree：已棄用對 Element 的真值測試。在未來版本中，它將始終回傳 True。請改用明確的 len(elem) 或 elem is not None 測試。

sys._clear_type_cache() 已被棄用：請改用 sys._clear_internal_caches()。

CPython 位元組碼變更

Replaced the opcode BINARY_SUBSCR by the BINARY_OP opcode with the NB_SUBSCR oparg. (Contributed by Irit Katriel in gh-100239 [https://github.com/python/cpython/issues/100239].)

Add the BUILD_INTERPOLATION and BUILD_TEMPLATE opcodes to construct new Interpolation and Template instances, respectively. (Contributed by Lysandros Nikolaou and others in gh-132661 [https://github.com/python/cpython/issues/132661]; see also PEP 750: Template strings).

Remove the BUILD_CONST_KEY_MAP opcode. Use BUILD_MAP instead. (Contributed by Mark Shannon in gh-122160 [https://github.com/python/cpython/issues/122160].)

Replace the LOAD_ASSERTION_ERROR opcode with LOAD_COMMON_CONSTANT and add support for loading NotImplementedError.

Add the LOAD_FAST_BORROW and LOAD_FAST_BORROW_LOAD_FAST_BORROW opcodes to reduce reference counting overhead when the interpreter can prove that the reference in the frame outlives the reference loaded onto the stack. (Contributed by Matt Page in gh-130704 [https://github.com/python/cpython/issues/130704].)

Add the LOAD_SMALL_INT opcode, which pushes a small integer equal to the oparg to the stack. The RETURN_CONST opcode is removed as it is no longer used. (Contributed by Mark Shannon in gh-125837 [https://github.com/python/cpython/issues/125837].)

Add the new LOAD_SPECIAL instruction. Generate code for with and async with statements using the new instruction. Removed the BEFORE_WITH and BEFORE_ASYNC_WITH instructions. (Contributed by Mark Shannon in gh-120507 [https://github.com/python/cpython/issues/120507].)

Add the POP_ITER opcode to support 'virtual' iterators. (Contributed by Mark Shannon in gh-132554 [https://github.com/python/cpython/issues/132554].)

Pseudo-instructions

Add the ANNOTATIONS_PLACEHOLDER pseudo instruction to support partially executed module-level annotations with deferred evaluation of annotations. (Contributed by Jelle Zijlstra in gh-130907 [https://github.com/python/cpython/issues/130907].)

Add the BINARY_OP_EXTEND pseudo instruction, which executes a pair of functions (guard and specialization functions) accessed from the inline cache. (Contributed by Irit Katriel in gh-100239 [https://github.com/python/cpython/issues/100239].)

Add three specializations for CALL_KW; CALL_KW_PY for calls to Python functions, CALL_KW_BOUND_METHOD for calls to bound methods, and CALL_KW_NON_PY for all other calls. (Contributed by Mark Shannon in gh-118093 [https://github.com/python/cpython/issues/118093].)

Add the JUMP_IF_TRUE and JUMP_IF_FALSE pseudo instructions, conditional jumps which do not impact the stack. Replaced by the sequence COPY 1, TO_BOOL, POP_JUMP_IF_TRUE/FALSE. (Contributed by Irit Katriel in gh-124285 [https://github.com/python/cpython/issues/124285].)

Add the LOAD_CONST_MORTAL pseudo instruction. (Contributed by Mark Shannon in gh-128685 [https://github.com/python/cpython/issues/128685].)

Add the LOAD_CONST_IMMORTAL pseudo instruction, which does the same as LOAD_CONST, but is more efficient for immortal objects. (Contributed by Mark Shannon in gh-125837 [https://github.com/python/cpython/issues/125837].)

Add the NOT_TAKEN pseudo instruction, used by sys.monitoring to record branch events (such as BRANCH_LEFT). (Contributed by Mark Shannon in gh-122548 [https://github.com/python/cpython/issues/122548].)

C API 變更

Python 配置 C API

Add a PyInitConfig C API to configure the Python initialization without relying on C structures and the ability to make ABI-compatible changes in the future.

Complete the PEP 587 [https://peps.python.org/pep-0587/] PyConfig C API by adding PyInitConfig_AddModule() which can be used to add a built-in extension module; a feature previously referred to as the "inittab".

Add PyConfig_Get() and PyConfig_Set() functions to get and set the current runtime configuration.

PEP 587 [https://peps.python.org/pep-0587/] 'Python Initialization Configuration' unified all the ways to configure Python's initialization. This PEP also unifies the configuration of Python's preinitialization and initialization in a single API. Moreover, this PEP only provides a single choice to embed Python, instead of having two 'Python' and 'Isolated' choices (PEP 587), to further simplify the API.

The lower level PEP 587 PyConfig API remains available for use cases with an intentionally higher level of coupling to CPython implementation details (such as emulating the full functionality of CPython's CLI, including its configuration mechanisms).

（由 Victor Stinner 於 gh-107954 [https://github.com/python/cpython/issues/107954] 貢獻。）

也參考

PEP 741 [https://peps.python.org/pep-0741/] 和 PEP 587 [https://peps.python.org/pep-0587/]

C API 中的新功能

Add Py_PACK_VERSION() and Py_PACK_FULL_VERSION(), two new macros for bit-packing Python version numbers. This is useful for comparisons with Py_Version or PY_VERSION_HEX. (Contributed by Petr Viktorin in gh-128629 [https://github.com/python/cpython/issues/128629].)

Add PyBytes_Join(sep, iterable) function, similar to sep.join(iterable) in Python. (Contributed by Victor Stinner in gh-121645 [https://github.com/python/cpython/issues/121645].)

新增用於操作目前 runtime Python 直譯器配置的函式（PEP 741：Python 配置 C API）：

PyConfig_Get()

PyConfig_GetInt()

PyConfig_Set()

PyConfig_Names()

（由 Victor Stinner 於 gh-107954 [https://github.com/python/cpython/issues/107954] 貢獻。）

新增用於配置 Python 初始化的函式（PEP 741：Python 配置 C API）：

Py_InitializeFromInitConfig()

PyInitConfig_AddModule()

PyInitConfig_Create()

PyInitConfig_Free()

PyInitConfig_FreeStrList()

PyInitConfig_GetError()

PyInitConfig_GetExitCode()

PyInitConfig_GetInt()

PyInitConfig_GetStr()

PyInitConfig_GetStrList()

PyInitConfig_HasOption()

PyInitConfig_SetInt()

PyInitConfig_SetStr()

PyInitConfig_SetStrList()

（由 Victor Stinner 於 gh-107954 [https://github.com/python/cpython/issues/107954] 貢獻。）

Add Py_fopen() function to open a file. This works similarly to the standard C fopen() function, instead accepting a Python object for the path parameter and setting an exception on error. The corresponding new Py_fclose() function should be used to close a file. (Contributed by Victor Stinner in gh-127350 [https://github.com/python/cpython/issues/127350].)

Add Py_HashBuffer() to compute and return the hash value of a buffer. (Contributed by Antoine Pitrou and Victor Stinner in gh-122854 [https://github.com/python/cpython/issues/122854].)

Add PyImport_ImportModuleAttr() and PyImport_ImportModuleAttrString() helper functions to import a module and get an attribute of the module. (Contributed by Victor Stinner in gh-128911 [https://github.com/python/cpython/issues/128911].)

Add PyIter_NextItem() to replace PyIter_Next(), which has an ambiguous return value. (Contributed by Irit Katriel and Erlend Aasland in gh-105201 [https://github.com/python/cpython/issues/105201].)

Add PyLong_GetSign() function to get the sign of int objects. (Contributed by Sergey B Kirpichev in gh-116560 [https://github.com/python/cpython/issues/116560].)

Add PyLong_IsPositive(), PyLong_IsNegative() and PyLong_IsZero() for checking if PyLongObject is positive, negative, or zero, respectively. (Contributed by James Roy and Sergey B Kirpichev in gh-126061 [https://github.com/python/cpython/issues/126061].)

Add new functions to convert C <stdint.h> numbers to/from Python int objects:

PyLong_AsInt32()

PyLong_AsInt64()

PyLong_AsUInt32()

PyLong_AsUInt64()

PyLong_FromInt32()

PyLong_FromInt64()

PyLong_FromUInt32()

PyLong_FromUInt64()

（由 Victor Stinner 於 gh-120389 [https://github.com/python/cpython/issues/120389] 貢獻。）

Add a new import and export API for Python int objects (PEP 757 [https://peps.python.org/pep-0757/]):

PyLong_GetNativeLayout()

PyLong_Export()

PyLong_FreeExport()

PyLongWriter_Create()

PyLongWriter_Finish()

PyLongWriter_Discard()

（由 Sergey B Kirpichev 和 Victor Stinner 於 gh-102471 [https://github.com/python/cpython/issues/102471] 貢獻。）

Add PyMonitoring_FireBranchLeftEvent() and PyMonitoring_FireBranchRightEvent() for generating BRANCH_LEFT and BRANCH_RIGHT events, respectively. (Contributed by Mark Shannon in gh-122548 [https://github.com/python/cpython/issues/122548].)

Add PyType_Freeze() function to make a type immutable. (Contributed by Victor Stinner in gh-121654 [https://github.com/python/cpython/issues/121654].)

Add PyType_GetBaseByToken() and Py_tp_token slot for easier superclass identification, which attempts to resolve the type checking issue mentioned in PEP 630 [https://peps.python.org/pep-0630/#type-checking]. (Contributed in gh-124153 [https://github.com/python/cpython/issues/124153].)

Add a new PyUnicode_Equal() function to test if two strings are equal. The function is also added to the Limited C API. (Contributed by Victor Stinner in gh-124502 [https://github.com/python/cpython/issues/124502].)

Add a new PyUnicodeWriter API to create a Python str object, with the following functions:

PyUnicodeWriter_Create()

PyUnicodeWriter_DecodeUTF8Stateful()

PyUnicodeWriter_Discard()

PyUnicodeWriter_Finish()

PyUnicodeWriter_Format()

PyUnicodeWriter_WriteASCII()

PyUnicodeWriter_WriteChar()

PyUnicodeWriter_WriteRepr()

PyUnicodeWriter_WriteStr()

PyUnicodeWriter_WriteSubstring()

PyUnicodeWriter_WriteUCS4()

PyUnicodeWriter_WriteUTF8()

PyUnicodeWriter_WriteWideChar()

（由 Victor Stinner 於 gh-119182 [https://github.com/python/cpython/issues/119182] 貢獻。）

The k and K formats in PyArg_ParseTuple() and similar functions now use __index__() if available, like all other integer formats. (Contributed by Serhiy Storchaka in gh-112068 [https://github.com/python/cpython/issues/112068].)

Add support for a new p format unit in Py_BuildValue() that produces a Python bool object from a C integer. (Contributed by Pablo Galindo in bpo-45325 [https://bugs.python.org/issue?@action=redirect&bpo=45325].)

Add PyUnstable_IsImmortal() for determining if an object is immortal, for debugging purposes. (Contributed by Peter Bierma in gh-128509 [https://github.com/python/cpython/issues/128509].)

Add PyUnstable_Object_EnableDeferredRefcount() for enabling deferred reference counting, as outlined in PEP 703 [https://peps.python.org/pep-0703/].

Add PyUnstable_Object_IsUniquelyReferenced() as a replacement for Py_REFCNT(op) == 1 on free threaded builds. (Contributed by Peter Bierma in gh-133140 [https://github.com/python/cpython/issues/133140].)

Add PyUnstable_Object_IsUniqueReferencedTemporary() to determine if an object is a unique temporary object on the interpreter's operand stack. This can be used in some cases as a replacement for checking if Py_REFCNT() is 1 for Python objects passed as arguments to C API functions. (Contributed by Sam Gross in gh-133164 [https://github.com/python/cpython/issues/133164].)

Limited C API changes

In the limited C API version 3.14 and newer, Py_TYPE() and Py_REFCNT() are now implemented as an opaque function call to hide implementation details. (Contributed by Victor Stinner in gh-120600 [https://github.com/python/cpython/issues/120600] and gh-124127 [https://github.com/python/cpython/issues/124127].)

Remove the PySequence_Fast_GET_SIZE, PySequence_Fast_GET_ITEM, and PySequence_Fast_ITEMS macros from the limited C API, since they have always been broken in the limited C API. (Contributed by Victor Stinner in gh-91417 [https://github.com/python/cpython/issues/91417].)

被移除的 C API

Creating immutable types with mutable bases was deprecated in Python 3.12, and now raises a TypeError. (Contributed by Nikita Sobolev in gh-119775 [https://github.com/python/cpython/issues/119775].)

Remove PyDictObject.ma_version_tag member, which was deprecated in Python 3.12. Use the PyDict_AddWatcher() API instead. (Contributed by Sam Gross in gh-124296 [https://github.com/python/cpython/issues/124296].)

Remove the private _Py_InitializeMain() function. It was a provisional API added to Python 3.8 by PEP 587 [https://peps.python.org/pep-0587/]. (Contributed by Victor Stinner in gh-129033 [https://github.com/python/cpython/issues/129033].)

Remove the undocumented APIs Py_C_RECURSION_LIMIT and PyThreadState.c_recursion_remaining. These were added in 3.13 and have been removed without deprecation. Use Py_EnterRecursiveCall() to guard against runaway recursion in C code. (Removed by Petr Viktorin in gh-133079 [https://github.com/python/cpython/issues/133079], see also gh-130396 [https://github.com/python/cpython/issues/130396].)

已棄用的 C API

The Py_HUGE_VAL macro is now soft deprecated. Use Py_INFINITY instead. (Contributed by Sergey B Kirpichev in gh-120026 [https://github.com/python/cpython/issues/120026].)

The Py_IS_NAN, Py_IS_INFINITY, and Py_IS_FINITE macros are now soft deprecated. Use isnan, isinf and isfinite instead, available from math.h since C99. (Contributed by Sergey B Kirpichev in gh-119613 [https://github.com/python/cpython/issues/119613].)

Non-tuple sequences are now deprecated as argument for the (items) format unit in PyArg_ParseTuple() and other argument parsing functions if items contains format units which store a borrowed buffer or a borrowed reference. (Contributed by Serhiy Storchaka in gh-50333 [https://github.com/python/cpython/issues/50333].)

The _PyMonitoring_FireBranchEvent function is now deprecated and should be replaced with calls to PyMonitoring_FireBranchLeftEvent() and PyMonitoring_FireBranchRightEvent().

The previously undocumented function PySequence_In() is now soft deprecated. Use PySequence_Contains() instead. (Contributed by Yuki Kobayashi in gh-127896 [https://github.com/python/cpython/issues/127896].)

Python 3.15 中待移除的項目

PyImport_ImportModuleNoBlock()：請改用 PyImport_ImportModule()。

PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT()：請改用 PyWeakref_GetRef()。可以使用 pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]來為 Python 3.12 和更早版本取得 PyWeakref_GetRef()。

Py_UNICODE 型別與 Py_UNICODE_WIDE 巨集：請改用 wchar_t。

PyUnicode_AsDecodedObject()：請改用 PyCodec_Decode()。

PyUnicode_AsDecodedUnicode()：請改用 PyCodec_Decode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 str 的型別，例如 bytes。

PyUnicode_AsEncodedObject()：請改用 PyCodec_Encode()。

PyUnicode_AsEncodedUnicode()：請改用 PyCodec_Encode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 bytes 的型別，例如 str。

Python 初始化函式，自 Python 3.13 起已被棄用：

Py_GetPath()：請改用 PyConfig_Get("module_search_paths") (sys.path)。

Py_GetPrefix()：請改用 PyConfig_Get("base_prefix") (sys.base_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("prefix") (sys.prefix)。

Py_GetExecPrefix()：請改用 PyConfig_Get("base_exec_prefix") (sys.base_exec_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("exec_prefix") (sys.exec_prefix)。

Py_GetProgramFullPath()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetProgramName()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetPythonHome()：請改用 PyConfig_Get("home") 或 PYTHONHOME 環境變數。

pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/] 可以用來為 Python 3.13 和更早版本取得 PyConfig_Get()。

用於配置 Python 初始化的函式，自 Python 3.11 起已被棄用：

PySys_SetArgvEx()：請改用 PyConfig.argv。

PySys_SetArgv()：請改用 PyConfig.argv。

Py_SetProgramName()：請改用 PyConfig.program_name。

Py_SetPythonHome()：請改用 PyConfig.home。

PySys_ResetWarnOptions()：請改為清除 sys.warnoptions 和 warnings.filters。

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API。

全域配置變數：

Py_DebugFlag：請改用 PyConfig.parser_debug 或 PyConfig_Get("parser_debug")。

Py_VerboseFlag：請改用 PyConfig.verbose 或 PyConfig_Get("verbose")。

Py_QuietFlag：請改用 PyConfig.quiet 或 PyConfig_Get("quiet")。

Py_InteractiveFlag：請改用 PyConfig.interactive 或 PyConfig_Get("interactive")。

Py_InspectFlag：請改用 PyConfig.inspect 或 PyConfig_Get("inspect")。

Py_OptimizeFlag：請改用 PyConfig.optimization_level 或 PyConfig_Get("optimization_level")。

Py_NoSiteFlag：請改用 PyConfig.site_import 或 PyConfig_Get("site_import")。

Py_BytesWarningFlag：請改用 PyConfig.bytes_warning 或 PyConfig_Get("bytes_warning")。

Py_FrozenFlag：請改用 PyConfig.pathconfig_warnings 或 PyConfig_Get("pathconfig_warnings")。

Py_IgnoreEnvironmentFlag：請改用 PyConfig.use_environment 或 PyConfig_Get("use_environment")。

Py_DontWriteBytecodeFlag：請改用 PyConfig.write_bytecode 或 PyConfig_Get("write_bytecode")。

Py_NoUserSiteDirectory：請改用 PyConfig.user_site_directory 或 PyConfig_Get("user_site_directory")。

Py_UnbufferedStdioFlag：請改用 PyConfig.buffered_stdio 或 PyConfig_Get("buffered_stdio")。

Py_HashRandomizationFlag：請改用 PyConfig.use_hash_seed 和 PyConfig.hash_seed 或 PyConfig_Get("hash_seed")。

Py_IsolatedFlag：請改用 PyConfig.isolated 或 PyConfig_Get("isolated")。

Py_LegacyWindowsFSEncodingFlag：請改用 PyPreConfig.legacy_windows_fs_encoding 或 PyConfig_Get("legacy_windows_fs_encoding")。

Py_LegacyWindowsStdioFlag：請改用 PyConfig.legacy_windows_stdio 或 PyConfig_Get("legacy_windows_stdio")。

Py_FileSystemDefaultEncoding、Py_HasFileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding 或 PyConfig_Get("filesystem_encoding")。

Py_FileSystemDefaultEncodeErrors：請改用 PyConfig.filesystem_errors 或 PyConfig_Get("filesystem_errors")。

Py_UTF8Mode：請改用 PyPreConfig.utf8_mode 或 PyConfig_Get("utf8_mode")。（請參閱 Py_PreInitialize()）

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API 來設定這些選項。或者也可以使用 PyConfig_Get() 在執行時取得這些選項。

Python 3.16 中待移除的項目

libmpdecimal 的打包副本 (bundled copy)。

Python 3.18 中待移除的項目

以下私有函式已被棄用，並計劃在 Python 3.18 中移除：

_PyBytes_Join()：請改用 PyBytes_Join()。

_PyDict_GetItemStringWithError()：請改用 PyDict_GetItemStringRef()。

_PyDict_Pop()：請改用 PyDict_Pop()。

_PyLong_Sign()：請改用 PyLong_GetSign()。

_PyLong_FromDigits() 和 _PyLong_New()：請改用 PyLongWriter_Create()。

_PyThreadState_UncheckedGet()：請改用 PyThreadState_GetUnchecked()。

_PyUnicode_AsString()：請改用 PyUnicode_AsUTF8()。

_PyUnicodeWriter_Init()：將 _PyUnicodeWriter_Init(&writer) 替換為 writer = PyUnicodeWriter_Create(0)。

_PyUnicodeWriter_Finish()：將 _PyUnicodeWriter_Finish(&writer) 替換為 PyUnicodeWriter_Finish(writer)。

_PyUnicodeWriter_Dealloc()：將 _PyUnicodeWriter_Dealloc(&writer) 替換為 PyUnicodeWriter_Discard(writer)。

_PyUnicodeWriter_WriteChar()：將 _PyUnicodeWriter_WriteChar(&writer, ch) 替換為 PyUnicodeWriter_WriteChar(writer, ch)。

_PyUnicodeWriter_WriteStr()：將 _PyUnicodeWriter_WriteStr(&writer, str) 替換為 PyUnicodeWriter_WriteStr(writer, str)。

_PyUnicodeWriter_WriteSubstring()：將 _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) 替換為 PyUnicodeWriter_WriteSubstring(writer, str, start, end)。

_PyUnicodeWriter_WriteASCIIString()：將 _PyUnicodeWriter_WriteASCIIString(&writer, str) 替換為 PyUnicodeWriter_WriteASCII(writer, str)。

_PyUnicodeWriter_WriteLatin1String()：將 _PyUnicodeWriter_WriteLatin1String(&writer, str) 替換為 PyUnicodeWriter_WriteUTF8(writer, str)。

_PyUnicodeWriter_Prepare()：（無替代方案）。

_PyUnicodeWriter_PrepareKind()：（無替代方案）。

_Py_HashPointer()：請改用 Py_HashPointer()。

_Py_fopen_obj()：請改用 Py_fopen()。

可以使用 pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] 來取得這些於 Python 3.13 及更早版本的新公開函式。（由 Victor Stinner 在 gh-128863 [https://github.com/python/cpython/issues/128863] 貢獻）

未來版本中的待移除項目

下列 API 已被棄用並將會被移除，不過目前尚未訂定移除日期。

Py_TPFLAGS_HAVE_FINALIZE：自 Python 3.8 起不再需要

PyErr_Fetch()：請改用 PyErr_GetRaisedException()。

PyErr_NormalizeException()：請改用 PyErr_GetRaisedException()。

PyErr_Restore()：請改用 PyErr_SetRaisedException()。

PyModule_GetFilename()：請改用 PyModule_GetFilenameObject()。

PyOS_AfterFork()：請改用 PyOS_AfterFork_Child()。

PySlice_GetIndicesEx()：請改用 PySlice_Unpack() 和 PySlice_AdjustIndices()。

PyUnicode_READY()：自 Python 3.12 起不再需要

PyErr_Display()：請改用 PyErr_DisplayException()。

_PyErr_ChainExceptions()：請改用 _PyErr_ChainExceptions1。

PyBytesObject.ob_shash 成員：請改為呼叫 PyObject_Hash()。

執行緒局部儲存 (Thread Local Storage, TLS) API：

PyThread_create_key()：請改用 PyThread_tss_alloc()。

PyThread_delete_key()：請改用 PyThread_tss_free()。

PyThread_set_key_value()：請改用 PyThread_tss_set()。

PyThread_get_key_value()：請改用 PyThread_tss_get()。

PyThread_delete_key_value()：請改用 PyThread_tss_delete()。

PyThread_ReInitTLS()：自 Python 3.7 起不再需要。

建置變更

PEP 776 [https://peps.python.org/pep-0776/]: Emscripten is now an officially supported platform at tier 3 [https://peps.python.org/pep-0011/#tier-3]. As a part of this effort, more than 25 bugs in Emscripten libc [https://emscripten.org/docs/porting/emscripten-runtime-environment.html] were fixed. Emscripten now includes support for ctypes, termios, and fcntl, as well as experimental support for the new default interactive shell. (Contributed by R. Hood Chatham in gh-127146 [https://github.com/python/cpython/issues/127146], gh-127683 [https://github.com/python/cpython/issues/127683], and gh-136931 [https://github.com/python/cpython/issues/136931].)

Official Android binary releases are now provided on python.org [https://www.python.org/downloads/android/].

GNU Autoconf 2.72 is now required to generate configure. (Contributed by Erlend Aasland in gh-115765 [https://github.com/python/cpython/issues/115765].)

wasm32-unknown-emscripten is now a PEP 11 [https://peps.python.org/pep-0011/] tier 3 platform. (Contributed by R. Hood Chatham in gh-127146 [https://github.com/python/cpython/issues/127146], gh-127683 [https://github.com/python/cpython/issues/127683], and gh-136931 [https://github.com/python/cpython/issues/136931].)

#pragma-based linking with python3*.lib can now be switched off with Py_NO_LINK_LIB. (Contributed by Jean-Christophe Fillion-Robin in gh-82909 [https://github.com/python/cpython/issues/82909].)

CPython now enables a set of recommended compiler options by default for improved security. Use the --disable-safety configure option to disable them, or the --enable-slower-safety option for a larger set of compiler options, albeit with a performance cost.

The WITH_FREELISTS macro and --without-freelists configure option have been removed.

The new configure option --with-tail-call-interp may be used to enable the experimental tail call interpreter. See A new type of interpreter for further details.

To disable the new remote debugging support, use the --without-remote-debug configure option. This may be useful for security reasons.

iOS and macOS apps can now be configured to redirect stdout and stderr content to the system log. (Contributed by Russell Keith-Magee in gh-127592 [https://github.com/python/cpython/issues/127592].)

The iOS testbed is now able to stream test output while the test is running. The testbed can also be used to run the test suite of projects other than CPython itself. (Contributed by Russell Keith-Magee in gh-127592 [https://github.com/python/cpython/issues/127592].)

build-details.json

Installations of Python now contain a new file, build-details.json. This is a static JSON document containing build details for CPython, to allow for introspection without needing to run code. This is helpful for use-cases such as Python launchers, cross-compilation, and so on.

build-details.json must be installed in the platform-independent standard library directory. This corresponds to the 'stdlib' sysconfig installation path, which can be found by running sysconfig.get_path('stdlib').

也參考

PEP 739 [https://peps.python.org/pep-0739/] -- build-details.json 1.0 -- a static description file for Python build details

Discontinuation of PGP signatures

PGP (Pretty Good Privacy) signatures will not be provided for releases of Python 3.14 or future versions. To verify CPython artifacts, users must use Sigstore verification materials [https://www.python.org/downloads/metadata/sigstore/]. Releases have been signed using Sigstore [https://www.sigstore.dev/] since Python 3.11.

This change in release process was specified in PEP 761 [https://peps.python.org/pep-0761/].

Free-threaded Python is officially supported

The free-threaded build of Python is now supported and no longer experimental. This is the start of phase II [https://discuss.python.org/t/37075] where free-threaded Python is officially supported but still optional.

The free-threading team are confident that the project is on the right path, and appreciate the continued dedication from everyone working to make free-threading ready for broader adoption across the Python community.

With these recommendations and the acceptance of this PEP, the Python developer community should broadly advertise that free-threading is a supported Python build option now and into the future, and that it will not be removed without a proper deprecation schedule.

Any decision to transition to phase III [https://discuss.python.org/t/37075], with free-threading as the default or sole build of Python is still undecided, and dependent on many factors both within CPython itself and the community. This decision is for the future.

也參考

PEP 779 [https://peps.python.org/pep-0779/]

PEP 779 的接受 [https://discuss.python.org/t/84319/123]

Binary releases for the experimental just-in-time compiler

The official macOS and Windows release binaries now include an experimental just-in-time (JIT) compiler. Although it is not recommended for production use, it can be tested by setting PYTHON_JIT=1 as an environment variable. Downstream source builds and redistributors can use the --enable-experimental-jit=yes-off configuration option for similar behavior.

The JIT is at an early stage and still in active development. As such, the typical performance impact of enabling it can range from 10% slower to 20% faster, depending on workload. To aid in testing and evaluation, a set of introspection functions has been provided in the sys._jit namespace. sys._jit.is_available() can be used to determine if the current executable supports JIT compilation, while sys._jit.is_enabled() can be used to tell if JIT compilation has been enabled for the current process.

Currently, the most significant missing functionality is that native debuggers and profilers like gdb and perf are unable to unwind through JIT frames (Python debuggers and profilers, like pdb or profile, continue to work without modification). Free-threaded builds do not support JIT compilation.

Please report any bugs or major performance regressions that you encounter!

也參考

PEP 744 [https://peps.python.org/pep-0744/]

移植至 Python 3.14

本節列出了前面描述的更改以及可能需要更改程式碼的其他錯誤修復。

Python API 的變更

On Unix platforms other than macOS, forkserver is now the default start method for multiprocessing and ProcessPoolExecutor, instead of fork.

See (1) and (2) for details.

If you encounter NameErrors or pickling errors coming out of multiprocessing or concurrent.futures, see the forkserver restrictions.

This change does not affect Windows or macOS, where 'spawn' remains the default start method.

functools.partial is now a method descriptor. Wrap it in staticmethod() if you want to preserve the old behavior. (Contributed by Serhiy Storchaka and Dominykas Grigonis in gh-121027 [https://github.com/python/cpython/issues/121027].)

The garbage collector is now incremental, which means that the behavior of gc.collect() changes slightly:

gc.collect(1): Performs an increment of garbage collection, rather than collecting generation 1.

Other calls to gc.collect() are unchanged.

The locale.nl_langinfo() function now temporarily sets the LC_CTYPE locale in some cases. This temporary change affects other threads. (Contributed by Serhiy Storchaka in gh-69998 [https://github.com/python/cpython/issues/69998].)

types.UnionType is now an alias for typing.Union, causing changes in some behaviors. See above for more details. (Contributed by Jelle Zijlstra in gh-105499 [https://github.com/python/cpython/issues/105499].)

The runtime behavior of annotations has changed in various ways; see above for details. While most code that interacts with annotations should continue to work, some undocumented details may behave differently.

As part of making the mimetypes CLI public, it now exits with 1 on failure instead of 0 and 2 on incorrect command-line parameters instead of 1. Error messages are now printed to stderr.

The \B pattern in regular expression now matches the empty string when given as the entire pattern, which may cause behavioural changes.

On FreeBSD, sys.platform no longer contains the major version number.

Changes in annotations (PEP 649 [https://peps.python.org/pep-0649/] and PEP 749 [https://peps.python.org/pep-0749/])

This section contains guidance on changes that may be needed to annotations or Python code that interacts with or introspects annotations, due to the changes related to deferred evaluation of annotations.

In the majority of cases, working code from older versions of Python will not require any changes.

Implications for annotated code

If you define annotations in your code (for example, for use with a static type checker), then this change probably does not affect you: you can keep writing annotations the same way you did with previous versions of Python.

You will likely be able to remove quoted strings in annotations, which are frequently used for forward references. Similarly, if you use from __future__ import annotations to avoid having to write strings in annotations, you may well be able to remove that import once you support only Python 3.14 and newer. However, if you rely on third-party libraries that read annotations, those libraries may need changes to support unquoted annotations before they work as expected.

Implications for readers of __annotations__

If your code reads the __annotations__ attribute on objects, you may want to make changes in order to support code that relies on deferred evaluation of annotations. For example, you may want to use annotationlib.get_annotations() with the FORWARDREF format, as the dataclasses module now does.

The external typing_extensions [https://pypi.org/project/typing_extensions/] package provides partial backports of some of the functionality of the annotationlib module, such as the Format enum and the get_annotations() function. These can be used to write cross-version code that takes advantage of the new behavior in Python 3.14.

Related changes

The changes in Python 3.14 are designed to rework how __annotations__ works at runtime while minimizing breakage to code that contains annotations in source code and to code that reads __annotations__. However, if you rely on undocumented details of the annotation behavior or on private functions in the standard library, there are many ways in which your code may not work in Python 3.14. To safeguard your code against future changes, only use the documented functionality of the annotationlib module.

In particular, do not read annotations directly from the namespace dictionary attribute of type objects. Use annotationlib.get_annotate_from_class_namespace() during class construction and annotationlib.get_annotations() afterwards.

In previous releases, it was sometimes possible to access class annotations from an instance of an annotated class. This behavior was undocumented and accidental, and will no longer work in Python 3.14.

from __future__ import annotations

In Python 3.7, PEP 563 [https://peps.python.org/pep-0563/] introduced the from __future__ import annotations future statement, which turns all annotations into strings.

However, this statement is now deprecated and it is expected to be removed in a future version of Python. This removal will not happen until after Python 3.13 reaches its end of life in 2029, being the last version of Python without support for deferred evaluation of annotations.

In Python 3.14, the behavior of code using from __future__ import annotations is unchanged.

C API 中的改動

Py_Finalize() now deletes all interned strings. This is backwards incompatible to any C extension that holds onto an interned string after a call to Py_Finalize() and is then reused after a call to Py_Initialize(). Any issues arising from this behavior will normally result in crashes during the execution of the subsequent call to Py_Initialize() from accessing uninitialized memory. To fix, use an address sanitizer to identify any use-after-free coming from an interned string and deallocate it during module shutdown. (Contributed by Eddie Elizondo in gh-113601 [https://github.com/python/cpython/issues/113601].)

The Unicode Exception Objects C API now raises a TypeError if its exception argument is not a UnicodeError object. (Contributed by Bénédikt Tran in gh-127691 [https://github.com/python/cpython/issues/127691].)

The interpreter internally avoids some reference count modifications when loading objects onto the operands stack by borrowing references when possible. This can lead to smaller reference count values compared to previous Python versions. C API extensions that checked Py_REFCNT() of 1 to determine if an function argument is not referenced by any other code should instead use PyUnstable_Object_IsUniqueReferencedTemporary() as a safer replacement.

被提升為公開 C API 的私有函式：

_PyBytes_Join(): PyBytes_Join()

_PyLong_IsNegative(): PyLong_IsNegative()

_PyLong_IsPositive(): PyLong_IsPositive()

_PyLong_IsZero(): PyLong_IsZero()

_PyLong_Sign(): PyLong_GetSign()

_PyUnicodeWriter_Dealloc(): PyUnicodeWriter_Discard()

_PyUnicodeWriter_Finish(): PyUnicodeWriter_Finish()

_PyUnicodeWriter_Init(): 使用 PyUnicodeWriter_Create()

_PyUnicodeWriter_Prepare(): (無替代方案)

_PyUnicodeWriter_PrepareKind(): (無替代方案)

_PyUnicodeWriter_WriteChar(): PyUnicodeWriter_WriteChar()

_PyUnicodeWriter_WriteStr(): PyUnicodeWriter_WriteStr()

_PyUnicodeWriter_WriteSubstring(): PyUnicodeWriter_WriteSubstring()

_PyUnicode_EQ(): PyUnicode_Equal()

_PyUnicode_Equal(): PyUnicode_Equal()

_Py_GetConfig(): PyConfig_Get() 和 PyConfig_GetInt()

_Py_HashBytes(): Py_HashBuffer()

_Py_fopen_obj(): Py_fopen()

PyMutex_IsLocked() : PyMutex_IsLocked()

pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] 可以用來在 Python 3.13 和更早版本中獲得這些新函式。

Python 3.14.1 中顯著的變更

Add PyUnstable_ThreadState_SetStackProtection() and PyUnstable_ThreadState_ResetStackProtection() functions to set the stack protection base address and stack protection size of a Python thread state. (Contributed by Victor Stinner in gh-139653 [https://github.com/python/cpython/issues/139653].)

Python 3.13 有什麼新功能

編輯者:

Adam Turner 和 Thomas Wouters

本文介紹了 Python 3.13 與 3.12 相比多了哪些新功能。Python 3.13 已於 2024 年 10 月 7 日發布。完整詳情請見 changelog。

也參考

PEP 719 [https://peps.python.org/pep-0719/] -- Python 3.13 發佈時程

發布重點摘要

Python 3.13 is a stable release of the Python programming language, with a mix of changes to the language, the implementation and the standard library. The biggest changes include a new interactive interpreter, experimental support for running in a free-threaded mode (PEP 703 [https://peps.python.org/pep-0703/]), and a Just-In-Time compiler (PEP 744 [https://peps.python.org/pep-0744/]).

Error messages continue to improve, with tracebacks now highlighted in color by default. The locals() builtin now has defined semantics for changing the returned mapping, and type parameters now support default values.

The library changes contain removal of deprecated APIs and modules, as well as the usual improvements in user-friendliness and correctness. Several legacy standard library modules have now been removed following their deprecation in Python 3.11 (PEP 594 [https://peps.python.org/pep-0594/]).

This article doesn't attempt to provide a complete specification of all new features, but instead gives a convenient overview. For full details refer to the documentation, such as the Library Reference and Language Reference. To understand the complete implementation and design rationale for a change, refer to the PEP for a particular new feature; but note that PEPs usually are not kept up-to-date once a feature has been fully implemented. See Porting to Python 3.13 for guidance on upgrading from earlier versions of Python.

直譯器改進：

A greatly improved interactive interpreter and improved error messages.

PEP 667 [https://peps.python.org/pep-0667/]: The locals() builtin now has defined semantics when mutating the returned mapping. Python debuggers and similar tools may now more reliably update local variables in optimized scopes even during concurrent code execution.

PEP 703 [https://peps.python.org/pep-0703/]: CPython 3.13 has experimental support for running with the global interpreter lock disabled. See Free-threaded CPython for more details.

PEP 744 [https://peps.python.org/pep-0744/]: A basic JIT compiler was added. It is currently disabled by default (though we may turn it on later). Performance improvements are modest -- we expect to improve this over the next few releases.

Color support in the new interactive interpreter, as well as in tracebacks and doctest output. This can be disabled through the PYTHON_COLORS and NO_COLOR [https://no-color.org/] environment variables.

Python 資料模型改進：

__static_attributes__ stores the names of attributes accessed through self.X in any function in a class body.

__firstlineno__ records the first line number of a class definition.

標準函式庫中的顯著改進

Add a new PythonFinalizationError exception, raised when an operation is blocked during finalization.

The argparse module now supports deprecating command-line options, positional arguments, and subcommands.

The new functions base64.z85encode() and base64.z85decode() support encoding and decoding Z85 data [https://rfc.zeromq.org/spec/32/].

The copy module now has a copy.replace() function, with support for many builtin types and any class defining the __replace__() method.

新的 dbm.sqlite3 模組現在是預設的 dbm 後端。

The os module has a suite of new functions for working with Linux's timer notification file descriptors.

現在 random 模組有一個命令列介面。

安全性改進：

ssl.create_default_context() sets ssl.VERIFY_X509_PARTIAL_CHAIN and ssl.VERIFY_X509_STRICT as default flags.

C API 改進：

The Py_mod_gil slot is now used to indicate that an extension module supports running with the GIL disabled.

The PyTime C API has been added, providing access to system clocks.

PyMutex is a new lightweight mutex that occupies a single byte.

There is a new suite of functions for generating PEP 669 [https://peps.python.org/pep-0669/] monitoring events in the C API.

新增型別特性：

PEP 696 [https://peps.python.org/pep-0696/]: Type parameters (typing.TypeVar, typing.ParamSpec, and typing.TypeVarTuple) now support defaults.

PEP 702 [https://peps.python.org/pep-0702/]: The new warnings.deprecated() decorator adds support for marking deprecations in the type system and at runtime.

PEP 705 [https://peps.python.org/pep-0705/]: typing.ReadOnly can be used to mark an item of a typing.TypedDict as read-only for type checkers.

PEP 742 [https://peps.python.org/pep-0742/]: typing.TypeIs provides more intuitive type narrowing behavior, as an alternative to typing.TypeGuard.

平台支援：

PEP 730 [https://peps.python.org/pep-0730/]: Apple's iOS is now an officially supported platform, at tier 3 [https://peps.python.org/pep-0011/#tier-3].

PEP 738 [https://peps.python.org/pep-0738/]: Android is now an officially supported platform, at tier 3 [https://peps.python.org/pep-0011/#tier-3].

wasm32-wasi 現在作為 tier 2 [https://peps.python.org/pep-0011/#tier-2] 平台支援。

wasm32-emscripten 不再是官方支援的平台。

重要的移除：

PEP 594: 剩下的 19 個 "dead batteries" （遺留標準函式庫模組）已自標準函式庫中移除：aifc、audioop、cgi、cgitb、chunk、crypt、imghdr、mailcap、msilib、nis、nntplib、ossaudiodev、pipes、sndhdr、spwd、sunau、telnetlib、uu 和 xdrlib.

Remove the 2to3 tool and lib2to3 module (deprecated in Python 3.11).

移除 tkinter.tix 模組（在 Python 3.6 中已棄用）。

移除 locale.resetlocale() 函式。

移除 typing.io 和 typing.re 命名空間。

Remove chained classmethod descriptors.

Release schedule changes:

PEP 602 [https://peps.python.org/pep-0602/] ("Annual Release Cycle for Python") has been updated to extend the full support ('bugfix') period for new releases to two years. This updated policy means that:

Python 3.9--3.12 have one and a half years of full support, followed by three and a half years of security fixes.

Python 3.13 and later have two years of full support, followed by three years of security fixes.

新增功能

A better interactive interpreter

Python now uses a new interactive shell by default, based on code from the PyPy project [https://pypy.org/]. When the user starts the REPL from an interactive terminal, the following new features are now supported:

Multiline editing with history preservation.

Direct support for REPL-specific commands like help, exit, and quit, without the need to call them as functions.

Prompts and tracebacks with color enabled by default.

Interactive help browsing using F1 with a separate command history.

History browsing using F2 that skips output as well as the >>> and ... prompts.

"Paste mode" with F3 that makes pasting larger blocks of code easier (press F3 again to return to the regular prompt).

To disable the new interactive shell, set the PYTHON_BASIC_REPL environment variable. For more on interactive mode, see 互動模式.

(Contributed by Pablo Galindo Salgado, Łukasz Langa, and Lysandros Nikolaou in gh-111201 [https://github.com/python/cpython/issues/111201] based on code from the PyPy project. Windows support contributed by Dino Viehland and Anthony Shaw.)

改善錯誤訊息

The interpreter now uses color by default when displaying tracebacks in the terminal. This feature can be controlled via the new PYTHON_COLORS environment variable as well as the canonical NO_COLOR [https://no-color.org/] and FORCE_COLOR [https://force-color.org/] environment variables. (Contributed by Pablo Galindo Salgado in gh-112730 [https://github.com/python/cpython/issues/112730].)

A common mistake is to write a script with the same name as a standard library module. When this results in errors, we now display a more helpful error message:

$ python random.py
Traceback (most recent call last):
  File "/home/me/random.py", line 1, in <module>
    import random
  File "/home/me/random.py", line 3, in <module>
    print(random.randint(5))
          ^^^^^^^^^^^^^^
AttributeError: module 'random' has no attribute 'randint' (consider renaming '/home/me/random.py' since it has the same name as the standard library module named 'random' and prevents importing that standard library module)

Similarly, if a script has the same name as a third-party module that it attempts to import and this results in errors, we also display a more helpful error message:

$ python numpy.py
Traceback (most recent call last):
  File "/home/me/numpy.py", line 1, in <module>
    import numpy as np
  File "/home/me/numpy.py", line 3, in <module>
    np.array([1, 2, 3])
    ^^^^^^^^
AttributeError: module 'numpy' has no attribute 'array' (consider renaming '/home/me/numpy.py' if it has the same name as a library you intended to import)

（由 Shantanu Jain 在 gh-95754 [https://github.com/python/cpython/issues/95754] 中貢獻。）

The error message now tries to suggest the correct keyword argument when an incorrect keyword argument is passed to a function.

>>> "Better error messages!".split(max_split=1)
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    "Better error messages!".split(max_split=1)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
TypeError: split() got an unexpected keyword argument 'max_split'. Did you mean 'maxsplit'?

（由 Pablo Galindo Salgado 和 Shantanu Jain 於 gh-107944 [https://github.com/python/cpython/issues/107944] 中貢獻。）

Free-threaded CPython

CPython now has experimental support for running in a free-threaded mode, with the global interpreter lock (GIL) disabled. This is an experimental feature and therefore is not enabled by default. The free-threaded mode requires a different executable, usually called python3.13t or python3.13t.exe. Pre-built binaries marked as free-threaded can be installed as part of the official Windows and macOS installers, or CPython can be built from source with the --disable-gil option.

Free-threaded execution allows for full utilization of the available processing power by running threads in parallel on available CPU cores. While not all software will benefit from this automatically, programs designed with threading in mind will run faster on multi-core hardware. The free-threaded mode is experimental and work is ongoing to improve it: expect some bugs and a substantial single-threaded performance hit. Free-threaded builds of CPython support optionally running with the GIL enabled at runtime using the environment variable PYTHON_GIL or the command-line option -X gil=1.

To check if the current interpreter supports free-threading, python -VV and sys.version contain "experimental free-threading build". The new sys._is_gil_enabled() function can be used to check whether the GIL is actually disabled in the running process.

C-API extension modules need to be built specifically for the free-threaded build. Extensions that support running with the GIL disabled should use the Py_mod_gil slot. Extensions using single-phase init should use PyUnstable_Module_SetGIL() to indicate whether they support running with the GIL disabled. Importing C extensions that don't use these mechanisms will cause the GIL to be enabled, unless the GIL was explicitly disabled with the PYTHON_GIL environment variable or the -X gil=0 option. pip 24.1 or newer is required to install packages with C extensions in the free-threaded build.

This work was made possible thanks to many individuals and organizations, including the large community of contributors to Python and third-party projects to test and enable free-threading support. Notable contributors include: Sam Gross, Ken Jin, Donghee Na, Itamar Oren, Matt Page, Brett Simmers, Dino Viehland, Carl Meyer, Nathan Goldbaum, Ralf Gommers, Lysandros Nikolaou, and many others. Many of these contributors are employed by Meta, which has provided significant engineering resources to support this project.

也參考

PEP 703 [https://peps.python.org/pep-0703/] "Making the Global Interpreter Lock Optional in CPython" contains rationale and information surrounding this work.

Porting Extension Modules to Support Free-Threading [https://py-free-threading.github.io/porting/]: A community-maintained porting guide for extension authors.

An experimental just-in-time (JIT) compiler

When CPython is configured and built using the --enable-experimental-jit option, a just-in-time (JIT) compiler is added which may speed up some Python programs. On Windows, use PCbuild/build.bat --experimental-jit to enable the JIT or --experimental-jit-interpreter to enable the Tier 2 interpreter. Build requirements and further supporting information are contained at [https://github.com/python/cpython/blob/main/Tools/jit/README.md] Tools/jit/README.md.

The --enable-experimental-jit option takes these (optional) values, defaulting to yes if --enable-experimental-jit is present without the optional value.

no: Disable the entire Tier 2 and JIT pipeline.

yes: Enable the JIT. To disable the JIT at runtime, pass the environment variable PYTHON_JIT=0.

yes-off: Build the JIT but disable it by default. To enable the JIT at runtime, pass the environment variable PYTHON_JIT=1.

interpreter: Enable the Tier 2 interpreter but disable the JIT. The interpreter can be disabled by running with PYTHON_JIT=0.

The internal architecture is roughly as follows:

We start with specialized Tier 1 bytecode. See What's new in 3.11 for details.

When the Tier 1 bytecode gets hot enough, it gets translated to a new purely internal intermediate representation (IR), called the Tier 2 IR, and sometimes referred to as micro-ops ("uops").

The Tier 2 IR uses the same stack-based virtual machine as Tier 1, but the instruction format is better suited to translation to machine code.

We have several optimization passes for Tier 2 IR, which are applied before it is interpreted or translated to machine code.

There is a Tier 2 interpreter, but it is mostly intended for debugging the earlier stages of the optimization pipeline. The Tier 2 interpreter can be enabled by configuring Python with --enable-experimental-jit=interpreter.

When the JIT is enabled, the optimized Tier 2 IR is translated to machine code, which is then executed.

The machine code translation process uses a technique called copy-and-patch. It has no runtime dependencies, but there is a new build-time dependency on LLVM.

也參考

PEP 744 [https://peps.python.org/pep-0744/]

(JIT by Brandt Bucher, inspired by a paper by Haoran Xu and Fredrik Kjolstad. Tier 2 IR by Mark Shannon and Guido van Rossum. Tier 2 optimizer by Ken Jin.)

Defined mutation semantics for locals()

Historically, the expected result of mutating the return value of locals() has been left to individual Python implementations to define. Starting from Python 3.13, PEP 667 [https://peps.python.org/pep-0667/] standardises the historical behavior of CPython for most code execution scopes, but changes optimized scopes (functions, generators, coroutines, comprehensions, and generator expressions) to explicitly return independent snapshots of the currently assigned local variables, including locally referenced nonlocal variables captured in closures.

This change to the semantics of locals() in optimized scopes also affects the default behavior of code execution functions that implicitly target locals() if no explicit namespace is provided (such as exec() and eval()). In previous versions, whether or not changes could be accessed by calling locals() after calling the code execution function was implementation-dependent. In CPython specifically, such code would typically appear to work as desired, but could sometimes fail in optimized scopes based on other code (including debuggers and code execution tracing tools) potentially resetting the shared snapshot in that scope. Now, the code will always run against an independent snapshot of the local variables in optimized scopes, and hence the changes will never be visible in subsequent calls to locals(). To access the changes made in these cases, an explicit namespace reference must now be passed to the relevant function. Alternatively, it may make sense to update affected code to use a higher level code execution API that returns the resulting code execution namespace (e.g. runpy.run_path() when executing Python files from disk).

To ensure debuggers and similar tools can reliably update local variables in scopes affected by this change, FrameType.f_locals now returns a write-through proxy to the frame's local and locally referenced nonlocal variables in these scopes, rather than returning an inconsistently updated shared dict instance with undefined runtime semantics.

See PEP 667 [https://peps.python.org/pep-0667/] for more details, including related C API changes and deprecations. Porting notes are also provided below for the affected Python APIs and C APIs.

(PEP and implementation contributed by Mark Shannon and Tian Gao in gh-74929 [https://github.com/python/cpython/issues/74929]. Documentation updates provided by Guido van Rossum and Alyssa Coghlan.)

對行動平台的支援

PEP 730 [https://peps.python.org/pep-0730/]: iOS is now a PEP 11 [https://peps.python.org/pep-0011/] supported platform, with the arm64-apple-ios and arm64-apple-ios-simulator targets at tier 3 (iPhone and iPad devices released after 2013 and the Xcode iOS simulator running on Apple silicon hardware, respectively). x86_64-apple-ios-simulator (the Xcode iOS simulator running on older x86_64 hardware) is not a tier 3 supported platform, but will have best-effort support. (PEP written and implementation contributed by Russell Keith-Magee in gh-114099 [https://github.com/python/cpython/issues/114099].)

PEP 738 [https://peps.python.org/pep-0738/]: Android is now a PEP 11 [https://peps.python.org/pep-0011/] supported platform, with the aarch64-linux-android and x86_64-linux-android targets at tier 3. The 32-bit targets arm-linux-androideabi and i686-linux-android are not tier 3 supported platforms, but will have best-effort support. (PEP written and implementation contributed by Malcolm Smith in gh-116622 [https://github.com/python/cpython/issues/116622].)

也參考

PEP 730 [https://peps.python.org/pep-0730/]、PEP 738 [https://peps.python.org/pep-0738/]

其他語言更動

The compiler now strips common leading whitespace from every line in a docstring. This reduces the size of the bytecode cache (such as .pyc files), with reductions in file size of around 5%, for example in sqlalchemy.orm.session from SQLAlchemy 2.0. This change affects tools that use docstrings, such as doctest.

>>> def spam():
...     """
...         This is a docstring with
...           leading whitespace.
...
...         It even has multiple paragraphs!
...     """
...
>>> spam.__doc__
'\nThis is a docstring with\n  leading whitespace.\n\nIt even has multiple paragraphs!\n'

（由 Inada Naoki 在 gh-81283 [https://github.com/python/cpython/issues/81283] 中貢獻。）

Annotation scopes within class scopes can now contain lambdas and comprehensions. Comprehensions that are located within class scopes are not inlined into their parent scope.

class C[T]:
    type Alias = lambda: T

（由 Jelle Zijlstra 在 gh-109118 [https://github.com/python/cpython/issues/109118] 和 gh-118160 [https://github.com/python/cpython/issues/118160] 中貢獻。）

Future statements are no longer triggered by relative imports of the __future__ module, meaning that statements of the form from .__future__ import ... are now simply standard relative imports, with no special features activated. (Contributed by Jeremiah Gabriel Pascual in gh-118216 [https://github.com/python/cpython/issues/118216].)

global declarations are now permitted in except blocks when that global is used in the else block. Previously this raised an erroneous SyntaxError. (Contributed by Irit Katriel in gh-111123 [https://github.com/python/cpython/issues/111123].)

Add PYTHON_FROZEN_MODULES, a new environment variable that determines whether frozen modules are ignored by the import machinery, equivalent to the -X frozen_modules command-line option. (Contributed by Yilei Yang in gh-111374 [https://github.com/python/cpython/issues/111374].)

Add support for the perf profiler working without frame pointers [https://en.wikipedia.org/wiki/Call_stack] through the new environment variable PYTHON_PERF_JIT_SUPPORT and command-line option -X perf_jit. (Contributed by Pablo Galindo in gh-118518 [https://github.com/python/cpython/issues/118518].)

The location of a .python_history file can be changed via the new PYTHON_HISTORY environment variable. (Contributed by Levi Sabah, Zackery Spytz and Hugo van Kemenade in gh-73965 [https://github.com/python/cpython/issues/73965].)

Classes have a new __static_attributes__ attribute. This is populated by the compiler with a tuple of the class's attribute names which are assigned through self.<name> from any function in its body. (Contributed by Irit Katriel in gh-115775 [https://github.com/python/cpython/issues/115775].)

The compiler now creates a __firstlineno__ attribute on classes with the line number of the first line of the class definition. (Contributed by Serhiy Storchaka in gh-118465 [https://github.com/python/cpython/issues/118465].)

The exec() and eval() builtins now accept the globals and locals arguments as keywords. (Contributed by Raphael Gaschignard in gh-105879 [https://github.com/python/cpython/issues/105879])

The compile() builtin now accepts a new flag, ast.PyCF_OPTIMIZED_AST, which is similar to ast.PyCF_ONLY_AST except that the returned AST is optimized according to the value of the optimize argument. (Contributed by Irit Katriel in gh-108113 [https://github.com/python/cpython/issues/108113]).

Add a __name__ attribute on property objects. (Contributed by Eugene Toder in gh-101860 [https://github.com/python/cpython/issues/101860].)

Add PythonFinalizationError, a new exception derived from RuntimeError and used to signal when operations are blocked during finalization. The following callables now raise PythonFinalizationError, instead of RuntimeError:

_thread.start_new_thread()

os.fork()

os.forkpty()

subprocess.Popen

（由 Victor Stinner 在 gh-114570 [https://github.com/python/cpython/issues/114570] 中貢獻。）

允許 str.replace() 的 count 引數為關鍵字。（由 Hugo van Kemenade 在 gh-106487 [https://github.com/python/cpython/issues/106487] 中貢獻。）

Many functions now emit a warning if a boolean value is passed as a file descriptor argument. This can help catch some errors earlier. (Contributed by Serhiy Storchaka in gh-82626 [https://github.com/python/cpython/issues/82626].)

Added name and mode attributes for compressed and archived file-like objects in the bz2, lzma, tarfile, and zipfile modules. (Contributed by Serhiy Storchaka in gh-115961 [https://github.com/python/cpython/issues/115961].)

新增模組

dbm.sqlite3: An SQLite backend for dbm. (Contributed by Raymond Hettinger and Erlend E. Aasland in gh-100414 [https://github.com/python/cpython/issues/100414].)

改進的模組

argparse

Add the deprecated parameter to the add_argument() and add_parser() methods, to enable deprecating command-line options, positional arguments, and subcommands. (Contributed by Serhiy Storchaka in gh-83648 [https://github.com/python/cpython/issues/83648].)

array

Add the 'w' type code (Py_UCS4) for Unicode characters. It should be used instead of the deprecated 'u' type code. (Contributed by Inada Naoki in gh-80480 [https://github.com/python/cpython/issues/80480].)

Register array.array as a MutableSequence by implementing the clear() method. (Contributed by Mike Zimin in gh-114894 [https://github.com/python/cpython/issues/114894].)

ast

The constructors of node types in the ast module are now stricter in the arguments they accept, with more intuitive behavior when arguments are omitted.

If an optional field on an AST node is not included as an argument when constructing an instance, the field will now be set to None. Similarly, if a list field is omitted, that field will now be set to an empty list, and if an expr_context field is omitted, it defaults to Load(). (Previously, in all cases, the attribute would be missing on the newly constructed AST node instance.)

In all other cases, where a required argument is omitted, the node constructor will emit a DeprecationWarning. This will raise an exception in Python 3.15. Similarly, passing a keyword argument to the constructor that does not map to a field on the AST node is now deprecated, and will raise an exception in Python 3.15.

These changes do not apply to user-defined subclasses of ast.AST unless the class opts in to the new behavior by defining the AST._field_types mapping.

(Contributed by Jelle Zijlstra in gh-105858 [https://github.com/python/cpython/issues/105858], gh-117486 [https://github.com/python/cpython/issues/117486], and gh-118851 [https://github.com/python/cpython/issues/118851].)

ast.parse() now accepts an optional argument optimize which is passed on to compile(). This makes it possible to obtain an optimized AST. (Contributed by Irit Katriel in gh-108113 [https://github.com/python/cpython/issues/108113].)

asyncio

asyncio.as_completed() now returns an object that is both an asynchronous iterator and a plain iterator of awaitables. The awaitables yielded by asynchronous iteration include original task or future objects that were passed in, making it easier to associate results with the tasks being completed. (Contributed by Justin Arthur in gh-77714 [https://github.com/python/cpython/issues/77714].)

asyncio.loop.create_unix_server() will now automatically remove the Unix socket when the server is closed. (Contributed by Pierre Ossman in gh-111246 [https://github.com/python/cpython/issues/111246].)

DatagramTransport.sendto() will now send zero-length datagrams if called with an empty bytes object. The transport flow control also now accounts for the datagram header when calculating the buffer size. (Contributed by Jamie Phan in gh-115199 [https://github.com/python/cpython/issues/115199].)

Add Queue.shutdown and QueueShutDown to manage queue termination. (Contributed by Laurie Opperman and Yves Duprat in gh-104228 [https://github.com/python/cpython/issues/104228].)

Add the Server.close_clients() and Server.abort_clients() methods, which more forcefully close an asyncio server. (Contributed by Pierre Ossman in gh-113538 [https://github.com/python/cpython/issues/113538].)

Accept a tuple of separators in StreamReader.readuntil(), stopping when any one of them is encountered. (Contributed by Bruce Merry in gh-81322 [https://github.com/python/cpython/issues/81322].)

Improve the behavior of TaskGroup when an external cancellation collides with an internal cancellation. For example, when two task groups are nested and both experience an exception in a child task simultaneously, it was possible that the outer task group would hang, because its internal cancellation was swallowed by the inner task group.

In the case where a task group is cancelled externally and also must raise an ExceptionGroup, it will now call the parent task's cancel() method. This ensures that a CancelledError will be raised at the next await, so the cancellation is not lost.

An added benefit of these changes is that task groups now preserve the cancellation count (cancelling()).

In order to handle some corner cases, uncancel() may now reset the undocumented _must_cancel flag when the cancellation count reaches zero.

(Inspired by an issue reported by Arthur Tacca in gh-116720 [https://github.com/python/cpython/issues/116720].)

When TaskGroup.create_task() is called on an inactive TaskGroup, the given coroutine will be closed (which prevents a RuntimeWarning about the given coroutine being never awaited). (Contributed by Arthur Tacca and Jason Zhang in gh-115957 [https://github.com/python/cpython/issues/115957].)

The function and methods named create_task have received a new **kwargs argument that is passed through to the task constructor. This change was accidentally added in 3.13.3, and broke the API contract for custom task factories. Several third-party task factories implemented workarounds for this. In 3.13.4 and later releases the old factory contract is honored once again (until 3.14). To keep the workarounds working, the extra **kwargs argument still allows passing additional keyword arguments to Task and to custom task factories.

This affects the following function and methods: asyncio.create_task(), asyncio.loop.create_task(), asyncio.TaskGroup.create_task(). (Contributed by Thomas Grainger in gh-128307 [https://github.com/python/cpython/issues/128307].)

base64

Add z85encode() and z85decode() functions for encoding bytes as Z85 data [https://rfc.zeromq.org/spec/32/] and decoding Z85-encoded data to bytes. (Contributed by Matan Perelman in gh-75299 [https://github.com/python/cpython/issues/75299].)

compileall

The default number of worker threads and processes is now selected using os.process_cpu_count() instead of os.cpu_count(). (Contributed by Victor Stinner in gh-109649 [https://github.com/python/cpython/issues/109649].)

concurrent.futures

The default number of worker threads and processes is now selected using os.process_cpu_count() instead of os.cpu_count(). (Contributed by Victor Stinner in gh-109649 [https://github.com/python/cpython/issues/109649].)

configparser

ConfigParser now has support for unnamed sections, which allows for top-level key-value pairs. This can be enabled with the new allow_unnamed_section parameter. (Contributed by Pedro Sousa Lacerda in gh-66449 [https://github.com/python/cpython/issues/66449].)

copy

The new replace() function and the replace protocol make creating modified copies of objects much simpler. This is especially useful when working with immutable objects. The following types support the replace() function and implement the replace protocol:

collections.namedtuple()

dataclasses.dataclass

datetime.datetime、datetime.date、datetime.time

inspect.Signature、inspect.Parameter

types.SimpleNamespace

程式碼物件

Any user-defined class can also support copy.replace() by defining the __replace__() method. (Contributed by Serhiy Storchaka in gh-108751 [https://github.com/python/cpython/issues/108751].)

ctypes

As a consequence of necessary internal refactoring, initialization of internal metaclasses now happens in __init__ rather than in __new__. This affects projects that subclass these internal metaclasses to provide custom initialization. Generally:

Custom logic that was done in __new__ after calling super().__new__ should be moved to __init__.

To create a class, call the metaclass, not only the metaclass's __new__ method.

See gh-124520 [https://github.com/python/cpython/issues/124520] for discussion and links to changes in some affected projects.

ctypes.Structure objects have a new _align_ attribute which allows the alignment of the structure being packed to/from memory to be specified explicitly. (Contributed by Matt Sanderson in gh-112433 [https://github.com/python/cpython/issues/112433])

dbm

Add dbm.sqlite3, a new module which implements an SQLite backend, and make it the default dbm backend. (Contributed by Raymond Hettinger and Erlend E. Aasland in gh-100414 [https://github.com/python/cpython/issues/100414].)

Allow removing all items from the database through the new clear() methods of the GDBM and NDBM database objects. (Contributed by Donghee Na in gh-107122 [https://github.com/python/cpython/issues/107122].)

dis

Change the output of dis module functions to show logical labels for jump targets and exception handlers, rather than offsets. The offsets can be added with the new -O command-line option or the show_offsets argument. (Contributed by Irit Katriel in gh-112137 [https://github.com/python/cpython/issues/112137].)

get_instructions() no longer represents cache entries as separate instructions. Instead, it returns them as part of the Instruction, in the new cache_info field. The show_caches argument to get_instructions() is deprecated and no longer has any effect. (Contributed by Irit Katriel in gh-112962 [https://github.com/python/cpython/issues/112962].)

doctest

doctest output is now colored by default. This can be controlled via the new PYTHON_COLORS environment variable as well as the canonical NO_COLOR [https://no-color.org/] and FORCE_COLOR [https://force-color.org/] environment variables. See also Controlling color. (Contributed by Hugo van Kemenade in gh-117225 [https://github.com/python/cpython/issues/117225].)

The DocTestRunner.run() method now counts the number of skipped tests. Add the DocTestRunner.skips and TestResults.skipped attributes. (Contributed by Victor Stinner in gh-108794 [https://github.com/python/cpython/issues/108794].)

email

Headers with embedded newlines are now quoted on output. The generator will now refuse to serialize (write) headers that are improperly folded or delimited, such that they would be parsed as multiple headers or joined with adjacent data. If you need to turn this safety feature off, set verify_generated_headers. (Contributed by Bas Bloemsaat and Petr Viktorin in gh-121650 [https://github.com/python/cpython/issues/121650].)

getaddresses() and parseaddr() now return ('', '') pairs in more situations where invalid email addresses are encountered instead of potentially inaccurate values. The two functions have a new optional strict parameter (default True). To get the old behavior (accepting malformed input), use strict=False. getattr(email.utils, 'supports_strict_parsing', False) can be used to check if the strict parameter is available. (Contributed by Thomas Dwyer and Victor Stinner for gh-102988 [https://github.com/python/cpython/issues/102988] to improve the CVE 2023-27043 [https://www.cve.org/CVERecord?id=CVE-2023-27043] fix.)

enum

公開 EnumDict 以更好地支援 EnumType 的子類別。

fractions

Fraction objects now support the standard format specification mini-language rules for fill, alignment, sign handling, minimum width, and grouping. (Contributed by Mark Dickinson in gh-111320 [https://github.com/python/cpython/issues/111320].)

glob

Add translate(), a function to convert a path specification with shell-style wildcards to a regular expression. (Contributed by Barney Gale in gh-72904 [https://github.com/python/cpython/issues/72904].)

importlib

The following functions in importlib.resources now allow accessing a directory (or tree) of resources, using multiple positional arguments (the encoding and errors arguments in the text-reading functions are now keyword-only):

is_resource()

open_binary()

open_text()

path()

read_binary()

read_text()

These functions are no longer deprecated and are not scheduled for removal. (Contributed by Petr Viktorin in gh-116608 [https://github.com/python/cpython/issues/116608].)

contents() remains deprecated in favor of the fully-featured Traversable API. However, there is now no plan to remove it. (Contributed by Petr Viktorin in gh-116608 [https://github.com/python/cpython/issues/116608].)

io

The IOBase finalizer now logs any errors raised by the close() method with sys.unraisablehook. Previously, errors were ignored silently by default, and only logged in Python Development Mode or when using a Python debug build. (Contributed by Victor Stinner in gh-62948 [https://github.com/python/cpython/issues/62948].)

ipaddress

Add the IPv4Address.ipv6_mapped property, which returns the IPv4-mapped IPv6 address. (Contributed by Charles Machalow in gh-109466 [https://github.com/python/cpython/issues/109466].)

Fix is_global and is_private behavior in IPv4Address, IPv6Address, IPv4Network, and IPv6Network. (Contributed by Jakub Stasiak in gh-113171 [https://github.com/python/cpython/issues/113171].)

itertools

batched() has a new strict parameter, which raises a ValueError if the final batch is shorter than the specified batch size. (Contributed by Raymond Hettinger in gh-113202 [https://github.com/python/cpython/issues/113202].)

marshal

Add the allow_code parameter in module functions. Passing allow_code=False prevents serialization and de-serialization of code objects which are incompatible between Python versions. (Contributed by Serhiy Storchaka in gh-113626 [https://github.com/python/cpython/issues/113626].)

math

The new function fma() performs fused multiply-add operations. This computes x * y + z with only a single round, and so avoids any intermediate loss of precision. It wraps the fma() function provided by C99, and follows the specification of the IEEE 754 "fusedMultiplyAdd" operation for special cases. (Contributed by Mark Dickinson and Victor Stinner in gh-73468 [https://github.com/python/cpython/issues/73468].)

mimetypes

Add the guess_file_type() function to guess a MIME type from a filesystem path. Using paths with guess_type() is now soft deprecated. (Contributed by Serhiy Storchaka in gh-66543 [https://github.com/python/cpython/issues/66543].)

mmap

mmap is now protected from crashing on Windows when the mapped memory is inaccessible due to file system errors or access violations. (Contributed by Jannis Weigend in gh-118209 [https://github.com/python/cpython/issues/118209].)

mmap has a new seekable() method that can be used when a seekable file-like object is required. The seek() method now returns the new absolute position. (Contributed by Donghee Na and Sylvie Liberman in gh-111835 [https://github.com/python/cpython/issues/111835].)

The new UNIX-only trackfd parameter for mmap controls file descriptor duplication; if false, the file descriptor specified by fileno will not be duplicated. (Contributed by Zackery Spytz and Petr Viktorin in gh-78502 [https://github.com/python/cpython/issues/78502].)

multiprocessing

The default number of worker threads and processes is now selected using os.process_cpu_count() instead of os.cpu_count(). (Contributed by Victor Stinner in gh-109649 [https://github.com/python/cpython/issues/109649].)

os

Add process_cpu_count() function to get the number of logical CPU cores usable by the calling thread of the current process. (Contributed by Victor Stinner in gh-109649 [https://github.com/python/cpython/issues/109649].)

cpu_count() and process_cpu_count() can be overridden through the new environment variable PYTHON_CPU_COUNT or the new command-line option -X cpu_count. This option is useful for users who need to limit CPU resources of a container system without having to modify application code or the container itself. (Contributed by Donghee Na in gh-109595 [https://github.com/python/cpython/issues/109595].)

Add a low level interface to Linux's timer file descriptors [https://manpages.debian.org/timerfd_create(2)] via timerfd_create(), timerfd_settime(), timerfd_settime_ns(), timerfd_gettime(), timerfd_gettime_ns(), TFD_NONBLOCK, TFD_CLOEXEC, TFD_TIMER_ABSTIME, and TFD_TIMER_CANCEL_ON_SET (Contributed by Masaru Tsuchiyama in gh-108277 [https://github.com/python/cpython/issues/108277].)

lchmod() and the follow_symlinks argument of chmod() are both now available on Windows. Note that the default value of follow_symlinks in lchmod() is False on Windows. (Contributed by Serhiy Storchaka in gh-59616 [https://github.com/python/cpython/issues/59616].)

fchmod() and support for file descriptors in chmod() are both now available on Windows. (Contributed by Serhiy Storchaka in gh-113191 [https://github.com/python/cpython/issues/113191].)

On Windows, mkdir() and makedirs() now support passing a mode value of 0o700 to apply access control to the new directory. This implicitly affects tempfile.mkdtemp() and is a mitigation for CVE 2024-4030 [https://www.cve.org/CVERecord?id=CVE-2024-4030]. Other values for mode continue to be ignored. (Contributed by Steve Dower in gh-118486 [https://github.com/python/cpython/issues/118486].)

posix_spawn() now accepts None for the env argument, which makes the newly spawned process use the current process environment. (Contributed by Jakub Kulik in gh-113119 [https://github.com/python/cpython/issues/113119].)

posix_spawn() can now use the POSIX_SPAWN_CLOSEFROM attribute in the file_actions parameter on platforms that support posix_spawn_file_actions_addclosefrom_np(). (Contributed by Jakub Kulik in gh-113117 [https://github.com/python/cpython/issues/113117].)

os.path

Add isreserved() to check if a path is reserved on the current system. This function is only available on Windows. (Contributed by Barney Gale in gh-88569 [https://github.com/python/cpython/issues/88569].)

On Windows, isabs() no longer considers paths starting with exactly one slash (\ or /) to be absolute. (Contributed by Barney Gale and Jon Foster in gh-44626 [https://github.com/python/cpython/issues/44626].)

realpath() now resolves MS-DOS style file names even if the file is not accessible. (Contributed by Moonsik Park in gh-82367 [https://github.com/python/cpython/issues/82367].)

pathlib

Add UnsupportedOperation, which is raised instead of NotImplementedError when a path operation isn't supported. (Contributed by Barney Gale in gh-89812 [https://github.com/python/cpython/issues/89812].)

Add a new constructor for creating Path objects from 'file' URIs (file:///), Path.from_uri(). (Contributed by Barney Gale in gh-107465 [https://github.com/python/cpython/issues/107465].)

Add PurePath.full_match() for matching paths with shell-style wildcards, including the recursive wildcard "**". (Contributed by Barney Gale in gh-73435 [https://github.com/python/cpython/issues/73435].)

Add the PurePath.parser class attribute to store the implementation of os.path used for low-level path parsing and joining. This will be either posixpath or ntpath.

Add recurse_symlinks keyword-only argument to Path.glob() and rglob(). (Contributed by Barney Gale in gh-77609 [https://github.com/python/cpython/issues/77609].)

Path.glob() and rglob() now return files and directories when given a pattern that ends with "**". Previously, only directories were returned. (Contributed by Barney Gale in gh-70303 [https://github.com/python/cpython/issues/70303].)

Add the follow_symlinks keyword-only argument to Path.is_file, Path.is_dir, Path.owner(), and Path.group(). (Contributed by Barney Gale in gh-105793 [https://github.com/python/cpython/issues/105793] and Kamil Turek in gh-107962 [https://github.com/python/cpython/issues/107962].)

pdb

breakpoint() and set_trace() now enter the debugger immediately rather than on the next line of code to be executed. This change prevents the debugger from breaking outside of the context when breakpoint() is positioned at the end of the context. (Contributed by Tian Gao in gh-118579 [https://github.com/python/cpython/issues/118579].)

sys.path[0] is no longer replaced by the directory of the script being debugged when sys.flags.safe_path is set. (Contributed by Tian Gao and Christian Walther in gh-111762 [https://github.com/python/cpython/issues/111762].)

zipapp is now supported as a debugging target. (Contributed by Tian Gao in gh-118501 [https://github.com/python/cpython/issues/118501].)

Add ability to move between chained exceptions during post-mortem debugging in pm() using the new exceptions [exc_number] command for Pdb. (Contributed by Matthias Bussonnier in gh-106676 [https://github.com/python/cpython/issues/106676].)

Expressions and statements whose prefix is a pdb command are now correctly identified and executed. (Contributed by Tian Gao in gh-108464 [https://github.com/python/cpython/issues/108464].)

queue

Add Queue.shutdown and ShutDown to manage queue termination. (Contributed by Laurie Opperman and Yves Duprat in gh-104750 [https://github.com/python/cpython/issues/104750].)

random

Add a command-line interface. (Contributed by Hugo van Kemenade in gh-118131 [https://github.com/python/cpython/issues/118131].)

re

Rename re.error to PatternError for improved clarity. re.error is kept for backward compatibility.

shutil

Support the dir_fd and follow_symlinks keyword arguments in chown(). (Contributed by Berker Peksag and Tahia K in gh-62308 [https://github.com/python/cpython/issues/62308])

site

.pth files are now decoded using UTF-8 first, and then with the locale encoding if UTF-8 decoding fails. (Contributed by Inada Naoki in gh-117802 [https://github.com/python/cpython/issues/117802].)

sqlite3

A ResourceWarning is now emitted if a Connection object is not closed explicitly. (Contributed by Erlend E. Aasland in gh-105539 [https://github.com/python/cpython/issues/105539].)

Add the filter keyword-only parameter to Connection.iterdump() for filtering database objects to dump. (Contributed by Mariusz Felisiak in gh-91602 [https://github.com/python/cpython/issues/91602].)

ssl

The create_default_context() API now includes VERIFY_X509_PARTIAL_CHAIN and VERIFY_X509_STRICT in its default flags.

備註

VERIFY_X509_STRICT may reject pre-RFC 5280 [https://datatracker.ietf.org/doc/html/rfc5280.html] or malformed certificates that the underlying OpenSSL implementation might otherwise accept. Whilst disabling this is not recommended, you can do so using:

import ssl

ctx = ssl.create_default_context()
ctx.verify_flags &= ~ssl.VERIFY_X509_STRICT

（由 William Woodruff 在 gh-112389 [https://github.com/python/cpython/issues/112389] 中貢獻。）

statistics

Add kde() for kernel density estimation. This makes it possible to estimate a continuous probability density function from a fixed number of discrete samples. (Contributed by Raymond Hettinger in gh-115863 [https://github.com/python/cpython/issues/115863].)

Add kde_random() for sampling from an estimated probability density function created by kde(). (Contributed by Raymond Hettinger in gh-115863 [https://github.com/python/cpython/issues/115863].)

subprocess

The subprocess module now uses the posix_spawn() function in more situations.

Notably, when close_fds is True (the default), posix_spawn() will be used when the C library provides posix_spawn_file_actions_addclosefrom_np(), which includes recent versions of Linux, FreeBSD, and Solaris. On Linux, this should perform similarly to the existing Linux vfork() based code.

A private control knob subprocess._USE_POSIX_SPAWN can be set to False if you need to force subprocess to never use posix_spawn(). Please report your reason and platform details in the issue tracker if you set this so that we can improve our API selection logic for everyone. (Contributed by Jakub Kulik in gh-113117 [https://github.com/python/cpython/issues/113117].)

sys

Add the _is_interned() function to test if a string was interned. This function is not guaranteed to exist in all implementations of Python. (Contributed by Serhiy Storchaka in gh-78573 [https://github.com/python/cpython/issues/78573].)

tempfile

On Windows, the default mode 0o700 used by tempfile.mkdtemp() now limits access to the new directory due to changes to os.mkdir(). This is a mitigation for CVE 2024-4030 [https://www.cve.org/CVERecord?id=CVE-2024-4030]. (Contributed by Steve Dower in gh-118486 [https://github.com/python/cpython/issues/118486].)

time

On Windows, monotonic() now uses the QueryPerformanceCounter() clock for a resolution of 1 microsecond, instead of the GetTickCount64() clock which has a resolution of 15.6 milliseconds. (Contributed by Victor Stinner in gh-88494 [https://github.com/python/cpython/issues/88494].)

On Windows, time() now uses the GetSystemTimePreciseAsFileTime() clock for a resolution of 1 microsecond, instead of the GetSystemTimeAsFileTime() clock which has a resolution of 15.6 milliseconds. (Contributed by Victor Stinner in gh-63207 [https://github.com/python/cpython/issues/63207].)

tkinter

Add tkinter widget methods: tk_busy_hold(), tk_busy_configure(), tk_busy_cget(), tk_busy_forget(), tk_busy_current(), and tk_busy_status(). (Contributed by Miguel, klappnase and Serhiy Storchaka in gh-72684 [https://github.com/python/cpython/issues/72684].)

The tkinter widget method wm_attributes() now accepts the attribute name without the minus prefix to get window attributes, for example w.wm_attributes('alpha') and allows specifying attributes and values to set as keyword arguments, for example w.wm_attributes(alpha=0.5). (Contributed by Serhiy Storchaka in gh-43457 [https://github.com/python/cpython/issues/43457].)

wm_attributes() can now return attributes as a dict, by using the new optional keyword-only parameter return_python_dict. (Contributed by Serhiy Storchaka in gh-43457 [https://github.com/python/cpython/issues/43457].)

Text.count() can now return a simple int when the new optional keyword-only parameter return_ints is used. Otherwise, the single count is returned as a 1-tuple or None. (Contributed by Serhiy Storchaka in gh-97928 [https://github.com/python/cpython/issues/97928].)

Support the "vsapi" element type in the element_create() method of tkinter.ttk.Style. (Contributed by Serhiy Storchaka in gh-68166 [https://github.com/python/cpython/issues/68166].)

Add the after_info() method for Tkinter widgets. (Contributed by Cheryl Sabella in gh-77020 [https://github.com/python/cpython/issues/77020].)

Add a new copy_replace() method to PhotoImage to copy a region from one image to another, possibly with pixel zooming, subsampling, or both. (Contributed by Serhiy Storchaka in gh-118225 [https://github.com/python/cpython/issues/118225].)

Add from_coords parameter to the PhotoImage methods copy(), zoom() and subsample(). Add zoom and subsample parameters to the PhotoImage method copy(). (Contributed by Serhiy Storchaka in gh-118225 [https://github.com/python/cpython/issues/118225].)

Add the PhotoImage methods read() to read an image from a file and data() to get the image data. Add background and grayscale parameters to the write() method. (Contributed by Serhiy Storchaka in gh-118271 [https://github.com/python/cpython/issues/118271].)

traceback

Add the exc_type_str attribute to TracebackException, which holds a string display of the exc_type. Deprecate the exc_type attribute, which holds the type object itself. Add parameter save_exc_type (default True) to indicate whether exc_type should be saved. (Contributed by Irit Katriel in gh-112332 [https://github.com/python/cpython/issues/112332].)

Add a new show_group keyword-only parameter to TracebackException.format_exception_only() to (recursively) format the nested exceptions of a BaseExceptionGroup instance. (Contributed by Irit Katriel in gh-105292 [https://github.com/python/cpython/issues/105292].)

types

SimpleNamespace can now take a single positional argument to initialise the namespace's arguments. This argument must either be a mapping or an iterable of key-value pairs. (Contributed by Serhiy Storchaka in gh-108191 [https://github.com/python/cpython/issues/108191].)

typing

PEP 705 [https://peps.python.org/pep-0705/]: Add ReadOnly, a special typing construct to mark a TypedDict item as read-only for type checkers.

PEP 742 [https://peps.python.org/pep-0742/]: Add TypeIs, a typing construct that can be used to instruct a type checker how to narrow a type.

Add NoDefault, a sentinel object used to represent the defaults of some parameters in the typing module. (Contributed by Jelle Zijlstra in gh-116126 [https://github.com/python/cpython/issues/116126].)

Add get_protocol_members() to return the set of members defining a typing.Protocol. (Contributed by Jelle Zijlstra in gh-104873 [https://github.com/python/cpython/issues/104873].)

Add is_protocol() to check whether a class is a Protocol. (Contributed by Jelle Zijlstra in gh-104873 [https://github.com/python/cpython/issues/104873].)

ClassVar can now be nested in Final, and vice versa. (Contributed by Mehdi Drissi in gh-89547 [https://github.com/python/cpython/issues/89547].)

unicodedata

Update the Unicode database to version 15.1.0 [https://www.unicode.org/versions/Unicode15.1.0/]. (Contributed by James Gerity in gh-109559 [https://github.com/python/cpython/issues/109559].)

venv

Add support for creating source control management (SCM) ignore files in a virtual environment's directory. By default, Git is supported. This is implemented as opt-in via the API, which can be extended to support other SCMs (EnvBuilder and create()), and opt-out via the CLI, using --without-scm-ignore-files. (Contributed by Brett Cannon in gh-108125 [https://github.com/python/cpython/issues/108125].)

warnings

PEP 702 [https://peps.python.org/pep-0702/]: The new warnings.deprecated() decorator provides a way to communicate deprecations to a static type checker and to warn on usage of deprecated classes and functions. A DeprecationWarning may also be emitted when a decorated function or class is used at runtime. (Contributed by Jelle Zijlstra in gh-104003 [https://github.com/python/cpython/issues/104003].)

xml

Allow controlling Expat >=2.6.0 reparse deferral (CVE 2023-52425 [https://www.cve.org/CVERecord?id=CVE-2023-52425]) by adding five new methods:

xml.etree.ElementTree.XMLParser.flush()

xml.etree.ElementTree.XMLPullParser.flush()

xml.parsers.expat.xmlparser.GetReparseDeferralEnabled()

xml.parsers.expat.xmlparser.SetReparseDeferralEnabled()

xml.sax.expatreader.ExpatParser.flush()

（由 Sebastian Pipping 在 gh-115623 [https://github.com/python/cpython/issues/115623] 中貢獻。）

Add the close() method for the iterator returned by iterparse() for explicit cleanup. (Contributed by Serhiy Storchaka in gh-69893 [https://github.com/python/cpython/issues/69893].)

zipimport

Add support for ZIP64 [https://en.wikipedia.org/wiki/Zip_(file_format)#ZIP64] format files. Everybody loves huge data, right? (Contributed by Tim Hatch in gh-94146 [https://github.com/python/cpython/issues/94146].)

最佳化

Several standard library modules have had their import times significantly improved. For example, the import time of the typing module has been reduced by around a third by removing dependencies on re and contextlib. Other modules to enjoy import-time speedups include email.utils, enum, functools, importlib.metadata, and threading. (Contributed by Alex Waygood, Shantanu Jain, Adam Turner, Daniel Hollas, and others in gh-109653 [https://github.com/python/cpython/issues/109653].)

textwrap.indent() is now around 30% faster than before for large input. (Contributed by Inada Naoki in gh-107369 [https://github.com/python/cpython/issues/107369].)

The subprocess module now uses the posix_spawn() function in more situations, including when close_fds is True (the default) on many modern platforms. This should provide a notable performance increase when launching processes on FreeBSD and Solaris. See the subprocess section above for details. (Contributed by Jakub Kulik in gh-113117 [https://github.com/python/cpython/issues/113117].)

被移除的模組和 API

PEP 594：從標準函式庫中移除「用完的電池」

PEP 594 [https://peps.python.org/pep-0594/] 提議從標準函式庫中移除因為歷史、過時或不安全狀態而被稱為「用完的電池 (dead batteries)」的 19 個模組。以下所有模組在 Python 3.11 中已被棄用，現在已被移除：

aifc

standard-aifc [https://pypi.org/project/standard-aifc/]：PyPI 上的 aifc 函式庫重新發布版。

audioop

audioop-lts [https://pypi.org/project/audioop-lts/]：PyPI 上的 audioop-lts 函式庫。

chunk

standard-chunk [https://pypi.org/project/standard-chunk/]：PyPI 上的 chunk 函式庫重新發布版。

cgi 和 cgitb

cgi.FieldStorage，在於 GET 和 HEAD 請求中通常可以被 urllib.parse.parse_qsl() 取代，而在於 POST 和 PUT 請求中可以被 email.message 模組或 multipart [https://pypi.org/project/multipart/] 函式庫取代。

cgi.parse() 能夠以在所需的查詢字串上直接呼叫 urllib.parse.parse_qs() 來取代，除非輸入為 multipart/form-data，而這種情況則應該如下所述地將 cgi.parse_multipart() 給替換掉。

cgi.parse_header() can be replaced with the functionality in the email package, which implements the same MIME RFCs. For example, with email.message.EmailMessage:

from email.message import EmailMessage

msg = EmailMessage()
msg['content-type'] = 'application/json; charset="utf8"'
main, params = msg.get_content_type(), msg['content-type'].params

cgi.parse_multipart() 可以被 email 函式庫中實作相同 MIME RFCs 的功能取代，或者可以被 multipart [https://pypi.org/project/multipart/] 函式庫取代，例如 email.message.EmailMessage 和 email.message.Message 類別。

standard-cgi [https://pypi.org/project/standard-cgi/] 和 standard-cgitb [https://pypi.org/project/standard-cgitb/]：PyPI 上的 cgi 和 cgitb 函式庫重新發布版。

crypt and the private _crypt extension. The hashlib module may be an appropriate replacement when simply hashing a value is required. Otherwise, various third-party libraries on PyPI are available:

bcrypt [https://pypi.org/project/bcrypt/]：適用於你的軟體與伺服器的現代密碼雜湊演算法。

argon2-cffi [https://pypi.org/project/argon2-cffi/]：安全的 Argon2 密碼雜湊演算法。

legacycrypt [https://pypi.org/project/legacycrypt/]：對 POSIX crypt 函式庫呼叫及相關功能的 ctypes 包裝。

crypt_r [https://pypi.org/project/crypt_r/]：對 crypt 模組的分支 (fork)，對 crypt_r(3) [https://manpages.debian.org/crypt_r(3)] 函式庫呼叫及相關功能的包裝。

standard-crypt [https://pypi.org/project/standard-crypt/] 和 deprecated-crypt-alternative [https://pypi.org/project/deprecated-crypt-alternative/]：PyPI 上的 crypt 函式庫重新發布版和 _crypt 函式庫的重新實作。

imghdr：請改用 filetype [https://pypi.org/project/filetype/]、puremagic [https://pypi.org/project/puremagic/] 或 python-magic [https://pypi.org/project/python-magic/] 函式庫。例如 puremagic.what() 函式可以取代 imghdr 過去所支援所有文件格式的 imghdr.what() 函式。

standard-imghdr [https://pypi.org/project/standard-imghdr/]：PyPI 上的 imghdr 函式庫重新發布版。

mailcap：請改用 mimetypes 模組。

standard-mailcap [https://pypi.org/project/standard-mailcap/]：PyPI 上的 mailcap 函式庫重新發布版。

msilib

nis

nntplib：請改用 PyPI 上的 pynntp [https://pypi.org/project/pynntp/] 函式庫。

standard-nntplib [https://pypi.org/project/standard-nntplib/]：PyPI 上的 nntplib 函式庫重新發布版。

ossaudiodev：音訊播放方面，請改用 PyPI 上的 pygame [https://pypi.org/project/pygame/] 函式庫。

pipes：請改用 subprocess 模組。使用 shlex.quote() 來取代未以文件紀錄的 pipes.quote 函式。

standard-pipes [https://pypi.org/project/standard-pipes/]：PyPI 上的 pipes 函式庫重新發布版。

sndhdr：請改用 filetype [https://pypi.org/project/filetype/]、puremagic [https://pypi.org/project/puremagic/] 或 python-magic [https://pypi.org/project/python-magic/] 函式庫。

standard-sndhdr [https://pypi.org/project/standard-sndhdr/]：PyPI 上的 sndhdr 函式庫重新發布版。

spwd：請改用 PyPI 上的 python-pam [https://pypi.org/project/python-pam/] 函式庫。

sunau

standard-sunau [https://pypi.org/project/standard-sunau/]：PyPI 上的 sunau 函式庫重新發布版。

telnetlib：請改用 PyPI 上的 telnetlib3 [https://pypi.org/project/telnetlib3/] 或 Exscript [https://pypi.org/project/Exscript/] 函式庫。

standard-telnetlib [https://pypi.org/project/standard-telnetlib/]：PyPI 上的 telnetlib 函式庫重新發布版。

uu：請改用 base64 模組來作為當代的替代方案。

standard-uu [https://pypi.org/project/standard-uu/]：PyPI 上的 uu 函式庫重新發布版。

xdrlib

standard-xdrlib [https://pypi.org/project/standard-xdrlib/]：PyPI 上的 xdrlib 函式庫重新發布版。

（由 Victor Stinner 和 Zachary Ware 在 gh-104773 [https://github.com/python/cpython/issues/104773] 和 gh-104780 [https://github.com/python/cpython/issues/104780] 中貢獻。）

2to3

Remove the 2to3 program and the lib2to3 module, previously deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104780 [https://github.com/python/cpython/issues/104780].)

builtins

Remove support for chained classmethod descriptors (introduced in gh-63272 [https://github.com/python/cpython/issues/63272]). These can no longer be used to wrap other descriptors, such as property. The core design of this feature was flawed and led to several problems. To "pass-through" a classmethod, consider using the __wrapped__ attribute that was added in Python 3.10. (Contributed by Raymond Hettinger in gh-89519 [https://github.com/python/cpython/issues/89519].)

Raise a RuntimeError when calling frame.clear() on a suspended frame (as has always been the case for an executing frame). (Contributed by Irit Katriel in gh-79932 [https://github.com/python/cpython/issues/79932].)

configparser

Remove the undocumented LegacyInterpolation class, deprecated in the docstring since Python 3.2, and at runtime since Python 3.11. (Contributed by Hugo van Kemenade in gh-104886 [https://github.com/python/cpython/issues/104886].)

importlib.metadata

Remove deprecated subscript (__getitem__()) access for EntryPoint objects. (Contributed by Jason R. Coombs in gh-113175 [https://github.com/python/cpython/issues/113175].)

locale

Remove the locale.resetlocale() function, deprecated in Python 3.11. Use locale.setlocale(locale.LC_ALL, "") instead. (Contributed by Victor Stinner in gh-104783 [https://github.com/python/cpython/issues/104783].)

opcode

Move opcode.ENABLE_SPECIALIZATION to _opcode.ENABLE_SPECIALIZATION. This field was added in 3.12, it was never documented, and is not intended for external use. (Contributed by Irit Katriel in gh-105481 [https://github.com/python/cpython/issues/105481].)

Remove opcode.is_pseudo(), opcode.MIN_PSEUDO_OPCODE, and opcode.MAX_PSEUDO_OPCODE, which were added in Python 3.12, but were neither documented nor exposed through dis, and were not intended to be used externally. (Contributed by Irit Katriel in gh-105481 [https://github.com/python/cpython/issues/105481].)

optparse

This module is no longer considered soft deprecated. While argparse remains preferred for new projects that aren't using a third party command line argument processing library, there are aspects of the way argparse works that mean the lower level optparse module may provide a better foundation for writing argument processing libraries, and for implementing command line applications which adhere more strictly than argparse does to various Unix command line processing conventions that originate in the behaviour of the C getopt() function . (Contributed by Alyssa Coghlan and Serhiy Storchaka in gh-126180 [https://github.com/python/cpython/issues/126180].)

pathlib

Remove the ability to use Path objects as context managers. This functionality was deprecated and has had no effect since Python 3.9. (Contributed by Barney Gale in gh-83863 [https://github.com/python/cpython/issues/83863].)

re

Remove the undocumented, deprecated, and broken re.template() function and re.TEMPLATE / re.T flag. (Contributed by Serhiy Storchaka and Nikita Sobolev in gh-105687 [https://github.com/python/cpython/issues/105687].)

tkinter.tix

Remove the tkinter.tix module, deprecated in Python 3.6. The third-party Tix library which the module wrapped is unmaintained. (Contributed by Zachary Ware in gh-75552 [https://github.com/python/cpython/issues/75552].)

turtle

Remove the RawTurtle.settiltangle() method, deprecated in the documentation since Python 3.1 and at runtime since Python 3.11. (Contributed by Hugo van Kemenade in gh-104876 [https://github.com/python/cpython/issues/104876].)

typing

Remove the typing.io and typing.re namespaces, deprecated since Python 3.8. The items in those namespaces can be imported directly from the typing module. (Contributed by Sebastian Rittau in gh-92871 [https://github.com/python/cpython/issues/92871].)

Remove the keyword-argument method of creating TypedDict types, deprecated in Python 3.11. (Contributed by Tomas Roun in gh-104786 [https://github.com/python/cpython/issues/104786].)

unittest

移除以下在 Python 3.11 中已被棄用的 unittest 函式：

unittest.findTestCases()

unittest.makeSuite()

unittest.getTestCaseNames()

改用 TestLoader 方法：

loadTestsFromModule()

loadTestsFromTestCase()

getTestCaseNames()

（由 Hugo van Kemenade 在 gh-104835 [https://github.com/python/cpython/issues/104835] 中貢獻。）

Remove the untested and undocumented TestProgram.usageExit() method, deprecated in Python 3.11. (Contributed by Hugo van Kemenade in gh-104992 [https://github.com/python/cpython/issues/104992].)

urllib

Remove the cafile, capath, and cadefault parameters of the urllib.request.urlopen() function, deprecated in Python 3.6. Use the context parameter instead with an SSLContext instance. The ssl.SSLContext.load_cert_chain() function can be used to load specific certificates, or let ssl.create_default_context() select the operating system's trusted certificate authority (CA) certificates. (Contributed by Victor Stinner in gh-105382 [https://github.com/python/cpython/issues/105382].)

webbrowser

Remove the untested and undocumented MacOSX class, deprecated in Python 3.11. Use the MacOSXOSAScript class (introduced in Python 3.2) instead. (Contributed by Hugo van Kemenade in gh-104804 [https://github.com/python/cpython/issues/104804].)

Remove the deprecated MacOSXOSAScript._name attribute. Use the MacOSXOSAScript.name attribute instead. (Contributed by Nikita Sobolev in gh-105546 [https://github.com/python/cpython/issues/105546].)

New Deprecations

使用者定義函式：

Deprecate assignment to a function's __code__ attribute, where the new code object's type does not match the function's type. The different types are: plain function, generator, async generator, and coroutine. (Contributed by Irit Katriel in gh-81137 [https://github.com/python/cpython/issues/81137].)

array：

Deprecate the 'u' format code (wchar_t) at runtime. This format code has been deprecated in documentation since Python 3.3, and will be removed in Python 3.16. Use the 'w' format code (Py_UCS4) for Unicode characters instead. (Contributed by Hugo van Kemenade in gh-80480 [https://github.com/python/cpython/issues/80480].)

ctypes：

Deprecate the undocumented SetPointerType() function, to be removed in Python 3.15. (Contributed by Victor Stinner in gh-105733 [https://github.com/python/cpython/issues/105733].)

Soft-deprecate the ARRAY() function in favour of type * length multiplication. (Contributed by Victor Stinner in gh-105733 [https://github.com/python/cpython/issues/105733].)

decimal：

Deprecate the non-standard and undocumented Decimal format specifier 'N', which is only supported in the decimal module's C implementation. Scheduled to be removed in Python 3.18. (Contributed by Serhiy Storchaka in gh-89902 [https://github.com/python/cpython/issues/89902].)

dis：

Deprecate the HAVE_ARGUMENT separator. Check membership in hasarg instead. (Contributed by Irit Katriel in gh-109319 [https://github.com/python/cpython/issues/109319].)

gettext：

Deprecate non-integer numbers as arguments to functions and methods that consider plural forms in the gettext module, even if no translation was found. (Contributed by Serhiy Storchaka in gh-88434 [https://github.com/python/cpython/issues/88434].)

glob：

Deprecate the undocumented glob0() and glob1() functions. Use glob() and pass a path-like object specifying the root directory to the root_dir parameter instead. (Contributed by Barney Gale in gh-117337 [https://github.com/python/cpython/issues/117337].)

http.server：

Deprecate CGIHTTPRequestHandler, to be removed in Python 3.15. Process-based CGI HTTP servers have been out of favor for a very long time. This code was outdated, unmaintained, and rarely used. It has a high potential for both security and functionality bugs. (Contributed by Gregory P. Smith in gh-109096 [https://github.com/python/cpython/issues/109096].)

Deprecate the --cgi flag to the python -m http.server command-line interface, to be removed in Python 3.15. (Contributed by Gregory P. Smith in gh-109096 [https://github.com/python/cpython/issues/109096].)

mimetypes：

Soft-deprecate file path arguments to guess_type(), use guess_file_type() instead. (Contributed by Serhiy Storchaka in gh-66543 [https://github.com/python/cpython/issues/66543].)

re：

Deprecate passing the optional maxsplit, count, or flags arguments as positional arguments to the module-level split(), sub(), and subn() functions. These parameters will become keyword-only in a future version of Python. (Contributed by Serhiy Storchaka in gh-56166 [https://github.com/python/cpython/issues/56166].)

pathlib：

Deprecate PurePath.is_reserved(), to be removed in Python 3.15. Use os.path.isreserved() to detect reserved paths on Windows. (Contributed by Barney Gale in gh-88569 [https://github.com/python/cpython/issues/88569].)

platform：

Deprecate java_ver(), to be removed in Python 3.15. This function is only useful for Jython support, has a confusing API, and is largely untested. (Contributed by Nikita Sobolev in gh-116349 [https://github.com/python/cpython/issues/116349].)

pydoc：

Deprecate the undocumented ispackage() function. (Contributed by Zackery Spytz in gh-64020 [https://github.com/python/cpython/issues/64020].)

sqlite3：

Deprecate passing more than one positional argument to the connect() function and the Connection constructor. The remaining parameters will become keyword-only in Python 3.15. (Contributed by Erlend E. Aasland in gh-107948 [https://github.com/python/cpython/issues/107948].)

Deprecate passing name, number of arguments, and the callable as keyword arguments for Connection.create_function() and Connection.create_aggregate() These parameters will become positional-only in Python 3.15. (Contributed by Erlend E. Aasland in gh-108278 [https://github.com/python/cpython/issues/108278].)

Deprecate passing the callback callable by keyword for the set_authorizer(), set_progress_handler(), and set_trace_callback() Connection methods. The callback callables will become positional-only in Python 3.15. (Contributed by Erlend E. Aasland in gh-108278 [https://github.com/python/cpython/issues/108278].)

sys：

Deprecate the _enablelegacywindowsfsencoding() function, to be removed in Python 3.16. Use the PYTHONLEGACYWINDOWSFSENCODING environment variable instead. (Contributed by Inada Naoki in gh-73427 [https://github.com/python/cpython/issues/73427].)

tarfile：

Deprecate the undocumented and unused TarFile.tarfile attribute, to be removed in Python 3.16. (Contributed in gh-115256 [https://github.com/python/cpython/issues/115256].)

traceback：

Deprecate the TracebackException.exc_type attribute. Use TracebackException.exc_type_str instead. (Contributed by Irit Katriel in gh-112332 [https://github.com/python/cpython/issues/112332].)

typing：

Deprecate the undocumented keyword argument syntax for creating NamedTuple classes (e.g. Point = NamedTuple("Point", x=int, y=int)), to be removed in Python 3.15. Use the class-based syntax or the functional syntax instead. (Contributed by Alex Waygood in gh-105566 [https://github.com/python/cpython/issues/105566].)

Deprecate omitting the fields parameter when creating a NamedTuple or typing.TypedDict class, and deprecate passing None to the fields parameter of both types. Python 3.15 will require a valid sequence for the fields parameter. To create a NamedTuple class with zero fields, use class NT(NamedTuple): pass or NT = NamedTuple("NT", ()). To create a TypedDict class with zero fields, use class TD(TypedDict): pass or TD = TypedDict("TD", {}). (Contributed by Alex Waygood in gh-105566 [https://github.com/python/cpython/issues/105566] and gh-105570 [https://github.com/python/cpython/issues/105570].)

棄用 typing.no_type_check_decorator() 裝飾器函式。將在 Python 3.15 中移除。在 typing 模組中經過八年後，它至今仍未被任何主要的型別檢查器所支援。（由 Alex Waygood 在 gh-106309 [https://github.com/python/cpython/issues/106309] 中貢獻。）

Deprecate typing.AnyStr. In Python 3.16, it will be removed from typing.__all__, and a DeprecationWarning will be emitted at runtime when it is imported or accessed. It will be removed entirely in Python 3.18. Use the new type parameter syntax instead. (Contributed by Michael The in gh-107116 [https://github.com/python/cpython/issues/107116].)

wave：

Deprecate the getmark(), setmark(), and getmarkers() methods of the Wave_read and Wave_write classes, to be removed in Python 3.15. (Contributed by Victor Stinner in gh-105096 [https://github.com/python/cpython/issues/105096].)

Python 3.14 中待移除的項目

argparse：argparse.BooleanOptionalAction 的 type、choices 和 metavar 參數已被棄用，將在 3.14 中移除。 (由 Nikita Sobolev 於 gh-92248 [https://github.com/python/cpython/issues/92248] 貢獻。)

ast：自 Python 3.8 起，下列功能已在文件中被棄用，現在在存取或使用時會於 runtime 發出 DeprecationWarning，並將在 Python 3.14 中移除：

ast.Num

ast.Str

ast.Bytes

ast.NameConstant

ast.Ellipsis

請改用 ast.Constant。（由 Serhiy Storchaka 於 gh-90953 [https://github.com/python/cpython/issues/90953] 貢獻。）

asyncio：

已棄用並將在 Python 3.14 中移除的 child watcher 類別：asyncio.MultiLoopChildWatcher、asyncio.FastChildWatcher、asyncio.AbstractChildWatcher 和 asyncio.SafeChildWatcher。 (由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。)

asyncio.set_child_watcher()、asyncio.get_child_watcher()、asyncio.AbstractEventLoopPolicy.set_child_watcher() 和 asyncio.AbstractEventLoopPolicy.get_child_watcher() 已被棄用並將在 Python 3.14 中移除。（由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。）

預設事件迴圈策略的 get_event_loop() 方法現在會在沒有設定目前事件迴圈且決定建立一個時發出 DeprecationWarning。 (由 Serhiy Storchaka 和 Guido van Rossum 於 gh-100160 [https://github.com/python/cpython/issues/100160] 貢獻。)

email：已棄用 email.utils.localtime() 中的 isdst 參數。（由 Alan Williams 於 gh-72346 [https://github.com/python/cpython/issues/72346] 貢獻。）

importlib.abc 的已棄用類別：

importlib.abc.ResourceReader

importlib.abc.Traversable

importlib.abc.TraversableResources

請改用 importlib.resources.abc 類別：

importlib.resources.abc.Traversable

importlib.resources.abc.TraversableResources

（由 Jason R. Coombs 和 Hugo van Kemenade 貢獻於 gh-93963 [https://github.com/python/cpython/issues/93963]。）

itertools 有不以文件記錄、效率低下、過去常有 bug 且不一致的 copy、deepcopy 和 pickle 操作支援。將在 3.14 中移除以大幅減少程式碼量和維護負擔。 (由 Raymond Hettinger 於 gh-101588 [https://github.com/python/cpython/issues/101588] 貢獻。)

multiprocessing：預設的啟動方法將在 Linux、BSD 和其他非 macOS POSIX 平台上更改為更安全的 方法，目前 'fork' 是預設值 (gh-84559 [https://github.com/python/cpython/issues/84559])。對此增加一個 runtime 警告被認為太過擾人，因為 大多數程式碼不會在意。請使用 get_context() 或 set_start_method() API 來明確指定你的程式碼何時需要 'fork'。請參閱 Contexts and start methods。

pathlib：已棄用 is_relative_to() 和 relative_to()：額外引數的傳遞已被棄用。

pkgutil：pkgutil.find_loader() 和 pkgutil.get_loader() 現在會引發 DeprecationWarning；請改用 importlib.util.find_spec()。 (由 Nikita Sobolev 於 gh-97850 [https://github.com/python/cpython/issues/97850] 貢獻。)

pty：

master_open()：請用 pty.openpty()。

slave_open()：請用 pty.openpty()。

sqlite3：

version 和 version_info。

execute() 和 executemany()，如果使用 named placeholders 且 parameters 是序列而不是 dict。

urllib：urllib.parse.Quoter 已被棄用：它並非預期的公開 API。(由 Gregory P. Smith 於 gh-88168 [https://github.com/python/cpython/issues/88168] 貢獻。)

Python 3.15 中待移除的項目

引入系統 (import system)：

在模組上設定 __cached__ 而沒有設定 __spec__.cached 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __cached__。(gh-97879 [https://github.com/python/cpython/issues/97879])

在模組上設定 __package__ 而沒有設定 __spec__.parent 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __package__。(gh-97879 [https://github.com/python/cpython/issues/97879])

ctypes：

自 Python 3.13 起，未記錄的 ctypes.SetPointerType() 函式已被棄用。

http.server：

過時且很少使用的 CGIHTTPRequestHandler 自 Python 3.13 起已被棄用。不存在直接的替代。任何東西都比 CGI 更好地將 Web 伺服器與請求處理程序介接起來。

自 Python 3.13 起，python -m http.server 命令列介面的 --cgi 旗標已被棄用。

importlib：

load_module() method：請改用 exec_module()。

locale：

getdefaultlocale() 已在 Python 3.11 中被棄用，原本計劃在 Python 3.13 中移除 (gh-90817 [https://github.com/python/cpython/issues/90817])，但被延後至 Python 3.15。請改用 getlocale()、setlocale() 和 getencoding()。 (由 Hugo van Kemenade 於 gh-111187 [https://github.com/python/cpython/issues/111187] 貢獻。)

pathlib：

PurePath.is_reserved() 已自 Python 3.13 被棄用。請用 os.path.isreserved() 來偵測 Windows 上的保留路徑。

platform：

自 Python 3.13 起，java_ver() 已被棄用。此函式僅對 Jython 支援有用，具有令人困惑的 API，基本上未經測試。

sysconfig：

sysconfig.is_python_build() 的 check_home 引數自 Python 3.12 起已被棄用。

threading：

RLock() 在 Python 3.15 中將不接受任何引數。自 Python 3.14 起，傳遞任何引數的用法已被棄用，因為 Python 版本不允許任何引數，但 C 版本允許任意數量的位置或關鍵字引數，並忽略每個引數。

types：

types.CodeType：自 3.10 起，存取 co_lnotab 已在 PEP 626 [https://peps.python.org/pep-0626/] 中被棄用，並計劃在 3.12 中移除，但只在 3.12 中於適當時發出 DeprecationWarning。可能在 3.15 中移除。（由 Nikita Sobolev 於 gh-101866 [https://github.com/python/cpython/issues/101866] 貢獻。）

typing：

用於建立 NamedTuple 類別的未以文件記錄之關鍵字引數語法 (Point = NamedTuple("Point", x=int, y=int)) 已自 Python 3.13 棄用。請改用基於類別的語法或函式語法 (functional syntax)。

當使用 TypedDict 的函式語法時，未傳遞值給 fields 參數 (TD = TypedDict("TD")) 或傳遞 None (TD = TypedDict("TD", None)) 的做法自 Python 3.13 起已被棄用。請使用 class TD(TypedDict): pass 或 TD = TypedDict("TD", {}) 來建立具有零個欄位的 TypedDict。

自 Python 3.13 起，typing.no_type_check_decorator() 裝飾器函式已被棄用。在 typing 模組中使用了八年之後，它尚未得到任何主要型別檢查器的支援。

wave：

已棄用 Wave_read 和 Wave_write 類別的 getmark()、setmark() 和 getmarkers() 方法自 Python 3.13 被棄用。

zipimport：

load_module() 自 Python 3.10 被棄用。請改用 exec_module()。（由 Jiahao Li 於 gh-125746 [https://github.com/python/cpython/issues/125746] 貢獻。）

Python 3.16 中待移除的項目

引入系統 (import system)：

在模組上設定 __loader__ 而沒有設定 __spec__.loader 的做法將於 Python 3.16 被棄用。在 Python 3.16 中，引入系統或標準函式庫將不再設定或考慮 __loader__。

array：

自 Python 3.3 起，'u' 格式碼 (wchar_t) 在文件中已被棄用，自 Python 3.13 起在 runtime 已被棄用。請使用 'w' 格式碼 (Py_UCS4) 來取代 Unicode 字元。

asyncio：

asyncio.iscoroutinefunction() 已被棄用並將在 Python 3.16 中移除；請改用 inspect.iscoroutinefunction()。（由 Jiahao Li 和 Kumar Aditya 於 gh-122875 [https://github.com/python/cpython/issues/122875] 貢獻。）

asyncio 策略系統已被棄用並將在 Python 3.16 中移除。特別是以下類別和函式已被棄用：

asyncio.AbstractEventLoopPolicy

asyncio.DefaultEventLoopPolicy

asyncio.WindowsSelectorEventLoopPolicy

asyncio.WindowsProactorEventLoopPolicy

asyncio.get_event_loop_policy()

asyncio.set_event_loop_policy()

使用者應該使用 asyncio.run() 或 asyncio.Runner 搭配 loop_factory 來使用所需的事件迴圈實作。

例如在 Windows 上使用 asyncio.SelectorEventLoop：

import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

（由 Kumar Aditya 於 gh-127949 [https://github.com/python/cpython/issues/127949] 貢獻。）

builtins：

自 Python 3.12 起，布林型別的位元反轉 ~True 或 ~False 已被棄用，因為它會產生不預期且不直觀的結果（-2 和 -1）。使用 not x 代替布林值的邏輯否定。在極少數情況下，你需要對底層的整數進行位元反轉，請明確轉換為 ~int(x) (~int(x))。

functools：

自 Python 3.14 起，使用 function 或 sequence 關鍵字引數呼叫 functools.reduce() 的 Python 實作已被棄用。

logging：

對具有 strm 引數的自訂日誌記錄處理函式的支援已被棄用，並計劃在 Python 3.16 中移除。請改用 stream 引數。（由 Mariusz Felisiak 於 gh-115032 [https://github.com/python/cpython/issues/115032] 貢獻。）

mimetypes：

有效的副檔名以 '.' 開頭或對 mimetypes.MimeTypes.add_type() 為空字串。未加點的副檔名已被棄用，並將在 Python 3.16 中引發 ValueError。（由 Hugo van Kemenade 於 gh-75223 [https://github.com/python/cpython/issues/75223] 貢獻。）

shutil：

自 Python 3.14 起，ExecError 例外已被棄用。自 Python 3.4 以來，它尚未被 shutil 中的任何函式使用，現在是 RuntimeError 的別名。

symtable：

自 Python 3.14 起，Class.get_methods 方法已被棄用。

sys：

自 Python 3.13 起，_enablelegacywindowsfsencoding() 函式已被棄用。請改用 PYTHONLEGACYWINDOWSFSENCODING 環境變數。

sysconfig：

自 Python 3.14 起，sysconfig.expand_makefile_vars() 函式已被棄用。請改用 sysconfig.get_paths() 的 vars 引數。

tarfile：

自 Python 3.13 起，未以文件記錄和未被使用的 TarFile.tarfile 屬性已被棄用。

Python 3.17 中待移除的項目

collections.abc：

collections.abc.ByteString 預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

typing：

在 Python 3.14 之前，舊式聯集是使用私有類別 typing._UnionGenericAlias 實作的。這個類別不再被需要，但為了向後相容性而保留，並計劃將在 Python 3.17 中移除。使用者應該改用文件中記錄的內省輔助函式，例如 typing.get_origin() 和 typing.get_args()，或者依賴私有實作細節。

typing.ByteString 自 Python 3.9 起已被棄用，預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

Python 3.18 中待移除的項目

decimal：

非標準且無文件記載的 Decimal 格式說明符號 'N'，僅在 decimal 模組的 C 實作中被支援，自 Python 3.13 起已被棄用。（由 Serhiy Storchaka 於 gh-89902 [https://github.com/python/cpython/issues/89902] 中貢獻。）

Python 3.19 中待移除的項目

ctypes：

Implicitly switching to the MSVC-compatible struct layout by setting _pack_ but not _layout_ on non-Windows platforms.

未來版本中的待移除項目

以下 API 將在未來被移除，雖然目前尚未安排移除日期。

argparse：

巢狀引數群組和巢狀互斥群組已被棄用。

將未以文件記錄的關鍵字引數 prefix_chars 傳遞給 add_argument_group() 的做法現在已被棄用。

argparse.FileType 型別轉換器已被棄用。

builtins：

產生器：throw(type, exc, tb) 和 athrow(type, exc, tb) 簽名已被棄用：請改用 throw(exc) 和 athrow(exc)，為單引數簽名。

目前 Python 接受數值字面值後面立即接關鍵字，例如 0in x、1or x、0if 1else 2。它讓運算式模糊且容易混淆，如 [0x1for x in y]（可以解釋為 [0x1 for x in y] 或 [0x1f or x in y]）。如果數值字面值後立即接 and、else、for、if、in、is 和 or 之一的關鍵字，則會引發語法警告。在未來版本中，它將被更改為語法錯誤。(gh-87999 [https://github.com/python/cpython/issues/87999])

__index__() 和 __int__() 方法回傳非 int 型別的支援：這些方法將需要回傳 int 的嚴格子類別實例。

回傳 float 嚴格子類別 __float__() 方法的支援：這些方法將需要回傳 float 的實例。

回傳 complex 嚴格子類別 __complex__() 方法的支援：這些方法將需要回傳 complex 的實例。

將 int() 委派給 __trunc__() 方法。

在 complex() 建構子中將複數作為 real 或 imag 引數傳遞現在已被棄用；它應該只作為單個位置引數傳遞。 (由 Serhiy Storchaka 於 gh-109218 [https://github.com/python/cpython/issues/109218] 貢獻。)

calendar：calendar.January 和 calendar.February 常數已被棄用並被 calendar.JANUARY 和 calendar.FEBRUARY 取代。 (由 Prince Roshan 於 gh-103636 [https://github.com/python/cpython/issues/103636] 貢獻。)

codecs：請改用 open() 而非 codecs.open()。(gh-133038 [https://github.com/python/cpython/issues/133038])

codeobject.co_lnotab：請改用 codeobject.co_lines() 方法。

datetime：

utcnow()：請改用 datetime.datetime.now(tz=datetime.UTC)。

utcfromtimestamp()：請改用 datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)。

gettext：複數值必須是整數。

importlib：

cache_from_source() debug_override 參數已被棄用：請改用 optimization 參數。

importlib.metadata：

EntryPoints 元組介面。

回傳值上的隱式 None。

logging：自 Python 3.3 起，warn() 方法已被棄用，請改用 warning()。

mailbox：已棄用 StringIO 輸入和文本模式，請改用 BytesIO 和二進位模式。

os：在多執行緒行程中呼叫 os.register_at_fork()。

pydoc.ErrorDuringImport：exc_info 參數的元組值已被棄用，請用例外實例。

re：現在對正規表示式中的數值群組參照和群組名稱用了更嚴格的規則。現在只有 ASCII 數碼序列被接受作為數值參照。位元組模式和替換字串中的群組名稱現在只能包含 ASCII 字母、數碼和底線。（由 Serhiy Storchaka 於 gh-91760 [https://github.com/python/cpython/issues/91760] 貢獻。）

sre_compile、sre_constants 和 sre_parse 模組。

shutil：rmtree() 的 onerror 參數在 Python 3.12 中已被棄用；請改用 onexc 參數。

ssl 選項和協定：

不帶協定引數的 ssl.SSLContext 已被棄用。

ssl.SSLContext：set_npn_protocols() 和 selected_npn_protocol() 已被棄用：請改用 ALPN。

ssl.OP_NO_SSL* 選項

ssl.OP_NO_TLS* 選項

ssl.PROTOCOL_SSLv3

ssl.PROTOCOL_TLS

ssl.PROTOCOL_TLSv1

ssl.PROTOCOL_TLSv1_1

ssl.PROTOCOL_TLSv1_2

ssl.TLSVersion.SSLv3

ssl.TLSVersion.TLSv1

ssl.TLSVersion.TLSv1_1

threading 方法：

threading.Condition.notifyAll()：請用 notify_all()。

threading.Event.isSet()：請用 is_set()。

threading.Thread.isDaemon()、threading.Thread.setDaemon()：請用 threading.Thread.daemon 屬性。

threading.Thread.getName()、threading.Thread.setName()：請用 threading.Thread.name 屬性。

threading.currentThread()：請用 threading.current_thread()。

threading.activeCount()：請用 threading.active_count()。

typing.Text (gh-92332 [https://github.com/python/cpython/issues/92332])。

內部類別 typing._UnionGenericAlias 不再用於實作 typing.Union。為了保持與此私有類別使用者的相容性，直到至少 Python 3.17 都將提供一個相容性 shim。（由 Jelle Zijlstra 於 gh-105499 [https://github.com/python/cpython/issues/105499] 貢獻。）

unittest.IsolatedAsyncioTestCase：從測試案例中回傳非 None 的值已被棄用。

urllib.parse 已棄用函式：請改用 urlparse()。

splitattr()

splithost()

splitnport()

splitpasswd()

splitport()

splitquery()

splittag()

splittype()

splituser()

splitvalue()

to_bytes()

wsgiref：SimpleHandler.stdout.write() 不應該進行部分寫入。

xml.etree.ElementTree：已棄用對 Element 的真值測試。在未來版本中，它將始終回傳 True。請改用明確的 len(elem) 或 elem is not None 測試。

sys._clear_type_cache() 已被棄用：請改用 sys._clear_internal_caches()。

CPython 位元組碼變更

The oparg of YIELD_VALUE is now 1 if the yield is part of a yield-from or await, and 0 otherwise. The oparg of RESUME was changed to add a bit indicating if the except-depth is 1, which is needed to optimize closing of generators. (Contributed by Irit Katriel in gh-111354 [https://github.com/python/cpython/issues/111354].)

C API 變更

新增功能

Add the PyMonitoring C API for generating PEP 669 [https://peps.python.org/pep-0669/] monitoring events:

PyMonitoringState

PyMonitoring_FirePyStartEvent()

PyMonitoring_FirePyResumeEvent()

PyMonitoring_FirePyReturnEvent()

PyMonitoring_FirePyYieldEvent()

PyMonitoring_FireCallEvent()

PyMonitoring_FireLineEvent()

PyMonitoring_FireJumpEvent()

PyMonitoring_FireBranchEvent

PyMonitoring_FireCReturnEvent()

PyMonitoring_FirePyThrowEvent()

PyMonitoring_FireRaiseEvent()

PyMonitoring_FireCRaiseEvent()

PyMonitoring_FireReraiseEvent()

PyMonitoring_FireExceptionHandledEvent()

PyMonitoring_FirePyUnwindEvent()

PyMonitoring_FireStopIterationEvent()

PyMonitoring_EnterScope()

PyMonitoring_ExitScope()

（由 Irit Katriel 在 gh-111997 [https://github.com/python/cpython/issues/111997] 中貢獻。）

Add PyMutex, a lightweight mutex that occupies a single byte, and the new PyMutex_Lock() and PyMutex_Unlock() functions. PyMutex_Lock() will release the GIL (if currently held) if the operation needs to block. (Contributed by Sam Gross in gh-108724 [https://github.com/python/cpython/issues/108724].)

Add the PyTime C API to provide access to system clocks:

PyTime_t。

PyTime_MIN 和 PyTime_MAX。

PyTime_AsSecondsDouble()。

PyTime_Monotonic()。

PyTime_MonotonicRaw()。

PyTime_PerfCounter()。

PyTime_PerfCounterRaw()。

PyTime_Time()。

PyTime_TimeRaw()。

（由 Victor Stinner 和 Petr Viktorin 在 gh-110850 [https://github.com/python/cpython/issues/110850] 中貢獻。）

Add the PyDict_ContainsString() function with the same behavior as PyDict_Contains(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*. (Contributed by Victor Stinner in gh-108314 [https://github.com/python/cpython/issues/108314].)

Add the PyDict_GetItemRef() and PyDict_GetItemStringRef() functions, which behave similarly to PyDict_GetItemWithError(), but return a strong reference instead of a borrowed reference. Moreover, these functions return -1 on error, removing the need to check PyErr_Occurred(). (Contributed by Victor Stinner in gh-106004 [https://github.com/python/cpython/issues/106004].)

Add the PyDict_SetDefaultRef() function, which behaves similarly to PyDict_SetDefault(), but returns a strong reference instead of a borrowed reference. This function returns -1 on error, 0 on insertion, and 1 if the key was already present in the dictionary. (Contributed by Sam Gross in gh-112066 [https://github.com/python/cpython/issues/112066].)

Add the PyDict_Pop() and PyDict_PopString() functions to remove a key from a dictionary and optionally return the removed value. This is similar to dict.pop(), though there is no default value, and KeyError is not raised for missing keys. (Contributed by Stefan Behnel and Victor Stinner in gh-111262 [https://github.com/python/cpython/issues/111262].)

Add the PyMapping_GetOptionalItem() and PyMapping_GetOptionalItemString() functions as alternatives to PyObject_GetItem() and PyMapping_GetItemString() respectively. The new functions do not raise KeyError if the requested key is missing from the mapping. These variants are more convenient and faster if a missing key should not be treated as a failure. (Contributed by Serhiy Storchaka in gh-106307 [https://github.com/python/cpython/issues/106307].)

Add the PyObject_GetOptionalAttr() and PyObject_GetOptionalAttrString() functions as alternatives to PyObject_GetAttr() and PyObject_GetAttrString() respectively. The new functions do not raise AttributeError if the requested attribute is not found on the object. These variants are more convenient and faster if the missing attribute should not be treated as a failure. (Contributed by Serhiy Storchaka in gh-106521 [https://github.com/python/cpython/issues/106521].)

Add the PyErr_FormatUnraisable() function as an extension to PyErr_WriteUnraisable() that allows customizing the warning message. (Contributed by Serhiy Storchaka in gh-108082 [https://github.com/python/cpython/issues/108082].)

Add new functions that return a strong reference instead of a borrowed reference for frame locals, globals, and builtins, as part of PEP 667:

PyEval_GetFrameBuiltins() 取代 PyEval_GetBuiltins()

PyEval_GetFrameGlobals() 取代 PyEval_GetGlobals()

PyEval_GetFrameLocals() 取代 PyEval_GetLocals()

（由 Mark Shannon 和 Tian Gao 在 gh-74929 [https://github.com/python/cpython/issues/74929] 中貢獻。）

Add the Py_GetConstant() and Py_GetConstantBorrowed() functions to get strong or borrowed references to constants. For example, Py_GetConstant(Py_CONSTANT_ZERO) returns a strong reference to the constant zero. (Contributed by Victor Stinner in gh-115754 [https://github.com/python/cpython/issues/115754].)

Add the PyImport_AddModuleRef() function as a replacement for PyImport_AddModule() that returns a strong reference instead of a borrowed reference. (Contributed by Victor Stinner in gh-105922 [https://github.com/python/cpython/issues/105922].)

Add the Py_IsFinalizing() function to check whether the main Python interpreter is shutting down. (Contributed by Victor Stinner in gh-108014 [https://github.com/python/cpython/issues/108014].)

Add the PyList_GetItemRef() function as a replacement for PyList_GetItem() that returns a strong reference instead of a borrowed reference. (Contributed by Sam Gross in gh-114329 [https://github.com/python/cpython/issues/114329].)

Add the PyList_Extend() and PyList_Clear() functions, mirroring the Python list.extend() and list.clear() methods. (Contributed by Victor Stinner in gh-111138 [https://github.com/python/cpython/issues/111138].)

Add the PyLong_AsInt() function. It behaves similarly to PyLong_AsLong(), but stores the result in a C int instead of a C long. (Contributed by Victor Stinner in gh-108014 [https://github.com/python/cpython/issues/108014].)

Add the PyLong_AsNativeBytes(), PyLong_FromNativeBytes(), and PyLong_FromUnsignedNativeBytes() functions to simplify converting between native integer types and Python int objects. (Contributed by Steve Dower in gh-111140 [https://github.com/python/cpython/issues/111140].)

Add PyModule_Add() function, which is similar to PyModule_AddObjectRef() and PyModule_AddObject(), but always steals a reference to the value. (Contributed by Serhiy Storchaka in gh-86493 [https://github.com/python/cpython/issues/86493].)

Add the PyObject_GenericHash() function that implements the default hashing function of a Python object. (Contributed by Serhiy Storchaka in gh-113024 [https://github.com/python/cpython/issues/113024].)

Add the Py_HashPointer() function to hash a raw pointer. (Contributed by Victor Stinner in gh-111545 [https://github.com/python/cpython/issues/111545].)

Add the PyObject_VisitManagedDict() and PyObject_ClearManagedDict() functions. which must be called by the traverse and clear functions of a type using the Py_TPFLAGS_MANAGED_DICT flag. The pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] can be used to use these functions with Python 3.11 and 3.12. (Contributed by Victor Stinner in gh-107073 [https://github.com/python/cpython/issues/107073].)

Add the PyRefTracer_SetTracer() and PyRefTracer_GetTracer() functions, which enable tracking object creation and destruction in the same way that the tracemalloc module does. (Contributed by Pablo Galindo in gh-93502 [https://github.com/python/cpython/issues/93502].)

Add the PySys_AuditTuple() function as an alternative to PySys_Audit() that takes event arguments as a Python tuple object. (Contributed by Victor Stinner in gh-85283 [https://github.com/python/cpython/issues/85283].)

Add the PyThreadState_GetUnchecked() function as an alternative to PyThreadState_Get() that doesn't kill the process with a fatal error if it is NULL. The caller is responsible for checking if the result is NULL. (Contributed by Victor Stinner in gh-108867 [https://github.com/python/cpython/issues/108867].)

Add the PyType_GetFullyQualifiedName() function to get the type's fully qualified name. The module name is prepended if type.__module__ is a string and is not equal to either 'builtins' or '__main__'. (Contributed by Victor Stinner in gh-111696 [https://github.com/python/cpython/issues/111696].)

Add the PyType_GetModuleName() function to get the type's module name. This is equivalent to getting the type.__module__ attribute. (Contributed by Eric Snow and Victor Stinner in gh-111696 [https://github.com/python/cpython/issues/111696].)

Add the PyUnicode_EqualToUTF8AndSize() and PyUnicode_EqualToUTF8() functions to compare a Unicode object with a const char* UTF-8 encoded string and 1 if they are equal or 0 otherwise. These functions do not raise exceptions. (Contributed by Serhiy Storchaka in gh-110289 [https://github.com/python/cpython/issues/110289].)

Add the PyWeakref_GetRef() function as an alternative to PyWeakref_GetObject() that returns a strong reference or NULL if the referent is no longer live. (Contributed by Victor Stinner in gh-105927 [https://github.com/python/cpython/issues/105927].)

Add fixed variants of functions which silently ignore errors:

PyObject_HasAttrWithError() 取代 PyObject_HasAttr()。

PyObject_HasAttrStringWithError() 取代 PyObject_HasAttrString()。

PyMapping_HasKeyWithError() 取代 PyMapping_HasKey()。

PyMapping_HasKeyStringWithError() 取代 PyMapping_HasKeyString()。

The new functions return -1 for errors and the standard 1 for true and 0 for false.

（由 Serhiy Storchaka 在 gh-108511 [https://github.com/python/cpython/issues/108511] 中貢獻。）

Changed C APIs

The keywords parameter of PyArg_ParseTupleAndKeywords() and PyArg_VaParseTupleAndKeywords() now has type char *const* in C and const char *const* in C++, instead of char**. In C++, this makes these functions compatible with arguments of type const char *const*, const char**, or char *const* without an explicit type cast. In C, the functions only support arguments of type char *const*. This can be overridden with the PY_CXX_CONST macro. (Contributed by Serhiy Storchaka in gh-65210 [https://github.com/python/cpython/issues/65210].)

PyArg_ParseTupleAndKeywords() now supports non-ASCII keyword parameter names. (Contributed by Serhiy Storchaka in gh-110815 [https://github.com/python/cpython/issues/110815].)

The PyCode_GetFirstFree() function is now unstable API and is now named PyUnstable_Code_GetFirstFree(). (Contributed by Bogdan Romanyuk in gh-115781 [https://github.com/python/cpython/issues/115781].)

The PyDict_GetItem(), PyDict_GetItemString(), PyMapping_HasKey(), PyMapping_HasKeyString(), PyObject_HasAttr(), PyObject_HasAttrString(), and PySys_GetObject() functions, each of which clears all errors which occurred when calling them now reports these errors using sys.unraisablehook(). You may replace them with other functions as recommended in the documentation. (Contributed by Serhiy Storchaka in gh-106672 [https://github.com/python/cpython/issues/106672].)

Add support for the %T, %#T, %N and %#N formats to PyUnicode_FromFormat():

%T: Get the fully qualified name of an object type

%#T: As above, but use a colon as the separator

%N: Get the fully qualified name of a type

%#N: As above, but use a colon as the separator

See PEP 737 [https://peps.python.org/pep-0737/] for more information. (Contributed by Victor Stinner in gh-111696 [https://github.com/python/cpython/issues/111696].)

You no longer have to define the PY_SSIZE_T_CLEAN macro before including Python.h when using # formats in format codes. APIs accepting the format codes always use Py_ssize_t for # formats. (Contributed by Inada Naoki in gh-104922 [https://github.com/python/cpython/issues/104922].)

If Python is built in debug mode or with assertions, PyTuple_SET_ITEM() and PyList_SET_ITEM() now check the index argument with an assertion. (Contributed by Victor Stinner in gh-106168 [https://github.com/python/cpython/issues/106168].)

Limited C API Changes

The following functions are now included in the Limited C API:

PyMem_RawMalloc()

PyMem_RawCalloc()

PyMem_RawRealloc()

PyMem_RawFree()

PySys_Audit()

PySys_AuditTuple()

PyType_GetModuleByDef()

（由 Victor Stinner 貢獻於 gh-85283 [https://github.com/python/cpython/issues/85283] 和 gh-116936 [https://github.com/python/cpython/issues/116936]。）

Python built with --with-trace-refs (tracing references) now supports the Limited API. (Contributed by Victor Stinner in gh-108634 [https://github.com/python/cpython/issues/108634].)

移除的 C API

Remove several functions, macros, variables, etc with names prefixed by _Py or _PY (which are considered private). If your project is affected by one of these removals and you believe that the removed API should remain available, please open a new issue to request a public C API and add cc: @vstinner to the issue to notify Victor Stinner. (Contributed by Victor Stinner in gh-106320 [https://github.com/python/cpython/issues/106320].)

Remove old buffer protocols deprecated in Python 3.0. Use 緩衝協定 (Buffer Protocol) instead.

PyObject_CheckReadBuffer(): Use PyObject_CheckBuffer() to test whether the object supports the buffer protocol. Note that PyObject_CheckBuffer() doesn't guarantee that PyObject_GetBuffer() will succeed. To test if the object is actually readable, see the next example of PyObject_GetBuffer().

PyObject_AsCharBuffer()、PyObject_AsReadBuffer()：請改用 PyObject_GetBuffer() 和 PyBuffer_Release()。

Py_buffer view;
if (PyObject_GetBuffer(obj, &view, PyBUF_SIMPLE) < 0) {
    return NULL;
}
// Use `view.buf` and `view.len` to read from the buffer.
// You may need to cast buf as `(const char*)view.buf`.
PyBuffer_Release(&view);

PyObject_AsWriteBuffer()：請改用 PyObject_GetBuffer() 和 PyBuffer_Release()。

Py_buffer view;
if (PyObject_GetBuffer(obj, &view, PyBUF_WRITABLE) < 0) {
    return NULL;
}
// Use `view.buf` and `view.len` to write to the buffer.
PyBuffer_Release(&view);

（由 Inada Naoki 貢獻於 gh-85275 [https://github.com/python/cpython/issues/85275]。）

Remove various functions deprecated in Python 3.9:

PyEval_CallObject()、PyEval_CallObjectWithKeywords()：請改用 PyObject_CallNoArgs() 或 PyObject_Call()。

警告

In PyObject_Call(), positional arguments must be a tuple and must not be NULL, and keyword arguments must be a dict or NULL, whereas the removed functions checked argument types and accepted NULL positional and keyword arguments. To replace PyEval_CallObjectWithKeywords(func, NULL, kwargs) with PyObject_Call(), pass an empty tuple as positional arguments using PyTuple_New(0).

PyEval_CallFunction()：請改用 PyObject_CallFunction()。

PyEval_CallMethod()：請改用 PyObject_CallMethod()。

PyCFunction_Call()：請改用 PyObject_Call()。

（由 Victor Stinner 貢獻於 gh-105107 [https://github.com/python/cpython/issues/105107]。）

移除以下設定 Python 初始化的舊函式，這些函式在 Python 3.11 中已被棄用：

PySys_AddWarnOptionUnicode()：請改用 PyConfig.warnoptions。

PySys_AddWarnOption()：請改用 PyConfig.warnoptions。

PySys_AddXOption()：請改用 PyConfig.xoptions。

PySys_HasWarnOptions()：請改用 PyConfig.xoptions。

PySys_SetPath()：請改用 PyConfig.module_search_paths。

Py_SetPath()：請改用 PyConfig.module_search_paths。

Py_SetStandardStreamEncoding()：請改用 PyConfig.stdio_encoding 並設定可能的 PyConfig.legacy_windows_stdio（在 Windows 上）。

_Py_SetProgramFullPath()：請改用 PyConfig.executable。

請改用 Python 初始化設定的新 PyConfig API (PEP 587 [https://peps.python.org/pep-0587/])，這是在 Python 3.8 中新增的。（由 Victor Stinner 於 gh-105145 [https://github.com/python/cpython/issues/105145] 貢獻。）

移除 PyEval_AcquireLock() 和 PyEval_ReleaseLock() 函式，這些函式在 Python 3.2 中已被廢棄。它們不會更新目前的執行緒狀態。可以用以下函式取代：

PyEval_SaveThread() 和 PyEval_RestoreThread()；

低階的 PyEval_AcquireThread() 和 PyEval_RestoreThread()；

或 PyGILState_Ensure() 與 PyGILState_Release()。

（由 Victor Stinner 貢獻於 gh-105182 [https://github.com/python/cpython/issues/105182]。）

移除在 Python 3.9 中已被棄用的 PyEval_ThreadsInitialized() 函式。自 Python 3.7 起，Py_Initialize() 總是會建立 GIL：呼叫 PyEval_InitThreads() 不會有任何作用，而 PyEval_ThreadsInitialized() 總是會回傳非零值。（由 Victor Stinner 於 gh-105182 [https://github.com/python/cpython/issues/105182] 貢獻。）

移除 _PyInterpreterState_Get() 這個對 PyInterpreterState_Get() 的別名，這個別名是為了與 Python 3.8 的向後相容性而保留的。pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]可以用於在 Python 3.8 和更舊的版本中取得 PyInterpreterState_Get()。（由 Victor Stinner 於 gh-106320 [https://github.com/python/cpython/issues/106320] 貢獻。）

移除私有的 _PyObject_FastCall() 函式：請改用自 Python 3.8 起可用的 PyObject_Vectorcall() 函式（PEP 590 [https://peps.python.org/pep-0590/]）。（由 Victor Stinner 於 gh-106023 [https://github.com/python/cpython/issues/106023] 貢獻。）

移除只包含私有函式的 cpython/pytime.h 標頭檔。（由 Victor Stinner 於 gh-106316 [https://github.com/python/cpython/issues/106316] 貢獻。）

Remove the undocumented PY_TIMEOUT_MAX constant from the limited C API. (Contributed by Victor Stinner in gh-110014 [https://github.com/python/cpython/issues/110014].)

移除舊的垃圾桶巨集 Py_TRASHCAN_SAFE_BEGIN 和 Py_TRASHCAN_SAFE_END。請將兩者都替換為新的巨集 Py_TRASHCAN_BEGIN 和 Py_TRASHCAN_END。（由 Irit Katriel 在 gh-105111 [https://github.com/python/cpython/issues/105111] 中貢獻。）

器用的 C API

棄用舊的 Python 初始化函式：

PySys_ResetWarnOptions()：請改為清除 sys.warnoptions 和 warnings.filters。

Py_GetExecPrefix()：請改用 sys.exec_prefix。

Py_GetPath()：請改用 sys.path。

Py_GetPrefix()：請改用 sys.prefix。

Py_GetProgramFullPath()：請改用 sys.executable。

Py_GetProgramName()：請改用 sys.executable。

Py_GetPythonHome()：請改用 PyConfig.home 或 PYTHONHOME 環境變數。

（由 Victor Stinner 在 gh-105145 [https://github.com/python/cpython/issues/105145] 中貢獻。）

軟性棄用 PyEval_GetBuiltins()、PyEval_GetGlobals() 和 PyEval_GetLocals() 函式，這些函式會回傳一個借用參照。（作為 PEP 667 [https://peps.python.org/pep-0667/] 一部分的軟性棄用。）

棄用 PyImport_ImportModuleNoBlock() 函式，這只是自 Python 3.3 起的 PyImport_ImportModule() 的別名。（由 Victor Stinner 在 gh-105396 [https://github.com/python/cpython/issues/105396] 中貢獻。）

軟性棄用 PyModule_AddObject() 函式。應該改用 PyModule_Add() 或 PyModule_AddObjectRef()。（由 Serhiy Storchaka 在 gh-86493 [https://github.com/python/cpython/issues/86493] 中貢獻。）

棄用舊的 Py_UNICODE 和 PY_UNICODE_TYPE 型別以及 Py_UNICODE_WIDE 定義。請直接使用 wchar_t 型別。自 Python 3.3 起，Py_UNICODE 和 PY_UNICODE_TYPE 只是 wchar_t 的別名。（由 Victor Stinner 在 gh-105156 [https://github.com/python/cpython/issues/105156] 中貢獻。）

棄用 PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT() 函式，這些函式會回傳一個借用參照。請改用新的 PyWeakref_GetRef() 函式，這個函式會回傳一個強參照。pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]可以用於在 Python 3.12 和更舊的版本中取得 PyWeakref_GetRef()。（由 Victor Stinner 在 gh-105927 [https://github.com/python/cpython/issues/105927] 中貢獻。）

Python 3.14 中待移除的項目

PyDictObject 中的 ma_version_tag 欄位，用於擴充模組 (PEP 699 [https://peps.python.org/pep-0699/]；gh-101193 [https://github.com/python/cpython/issues/101193])。

使用可變基底建立不可變型別 (gh-95388 [https://github.com/python/cpython/issues/95388])。

Python 3.15 中待移除的項目

PyImport_ImportModuleNoBlock()：請改用 PyImport_ImportModule()。

PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT()：請改用 PyWeakref_GetRef()。可以使用 pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]來為 Python 3.12 和更早版本取得 PyWeakref_GetRef()。

Py_UNICODE 型別與 Py_UNICODE_WIDE 巨集：請改用 wchar_t。

PyUnicode_AsDecodedObject()：請改用 PyCodec_Decode()。

PyUnicode_AsDecodedUnicode()：請改用 PyCodec_Decode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 str 的型別，例如 bytes。

PyUnicode_AsEncodedObject()：請改用 PyCodec_Encode()。

PyUnicode_AsEncodedUnicode()：請改用 PyCodec_Encode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 bytes 的型別，例如 str。

Python 初始化函式，自 Python 3.13 起已被棄用：

Py_GetPath()：請改用 PyConfig_Get("module_search_paths") (sys.path)。

Py_GetPrefix()：請改用 PyConfig_Get("base_prefix") (sys.base_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("prefix") (sys.prefix)。

Py_GetExecPrefix()：請改用 PyConfig_Get("base_exec_prefix") (sys.base_exec_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("exec_prefix") (sys.exec_prefix)。

Py_GetProgramFullPath()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetProgramName()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetPythonHome()：請改用 PyConfig_Get("home") 或 PYTHONHOME 環境變數。

pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/] 可以用來為 Python 3.13 和更早版本取得 PyConfig_Get()。

用於配置 Python 初始化的函式，自 Python 3.11 起已被棄用：

PySys_SetArgvEx()：請改用 PyConfig.argv。

PySys_SetArgv()：請改用 PyConfig.argv。

Py_SetProgramName()：請改用 PyConfig.program_name。

Py_SetPythonHome()：請改用 PyConfig.home。

PySys_ResetWarnOptions()：請改為清除 sys.warnoptions 和 warnings.filters。

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API。

全域配置變數：

Py_DebugFlag：請改用 PyConfig.parser_debug 或 PyConfig_Get("parser_debug")。

Py_VerboseFlag：請改用 PyConfig.verbose 或 PyConfig_Get("verbose")。

Py_QuietFlag：請改用 PyConfig.quiet 或 PyConfig_Get("quiet")。

Py_InteractiveFlag：請改用 PyConfig.interactive 或 PyConfig_Get("interactive")。

Py_InspectFlag：請改用 PyConfig.inspect 或 PyConfig_Get("inspect")。

Py_OptimizeFlag：請改用 PyConfig.optimization_level 或 PyConfig_Get("optimization_level")。

Py_NoSiteFlag：請改用 PyConfig.site_import 或 PyConfig_Get("site_import")。

Py_BytesWarningFlag：請改用 PyConfig.bytes_warning 或 PyConfig_Get("bytes_warning")。

Py_FrozenFlag：請改用 PyConfig.pathconfig_warnings 或 PyConfig_Get("pathconfig_warnings")。

Py_IgnoreEnvironmentFlag：請改用 PyConfig.use_environment 或 PyConfig_Get("use_environment")。

Py_DontWriteBytecodeFlag：請改用 PyConfig.write_bytecode 或 PyConfig_Get("write_bytecode")。

Py_NoUserSiteDirectory：請改用 PyConfig.user_site_directory 或 PyConfig_Get("user_site_directory")。

Py_UnbufferedStdioFlag：請改用 PyConfig.buffered_stdio 或 PyConfig_Get("buffered_stdio")。

Py_HashRandomizationFlag：請改用 PyConfig.use_hash_seed 和 PyConfig.hash_seed 或 PyConfig_Get("hash_seed")。

Py_IsolatedFlag：請改用 PyConfig.isolated 或 PyConfig_Get("isolated")。

Py_LegacyWindowsFSEncodingFlag：請改用 PyPreConfig.legacy_windows_fs_encoding 或 PyConfig_Get("legacy_windows_fs_encoding")。

Py_LegacyWindowsStdioFlag：請改用 PyConfig.legacy_windows_stdio 或 PyConfig_Get("legacy_windows_stdio")。

Py_FileSystemDefaultEncoding、Py_HasFileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding 或 PyConfig_Get("filesystem_encoding")。

Py_FileSystemDefaultEncodeErrors：請改用 PyConfig.filesystem_errors 或 PyConfig_Get("filesystem_errors")。

Py_UTF8Mode：請改用 PyPreConfig.utf8_mode 或 PyConfig_Get("utf8_mode")。（請參閱 Py_PreInitialize()）

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API 來設定這些選項。或者也可以使用 PyConfig_Get() 在執行時取得這些選項。

Python 3.16 中待移除的項目

libmpdecimal 的打包副本 (bundled copy)。

Python 3.18 中待移除的項目

以下私有函式已被棄用，並計劃在 Python 3.18 中移除：

_PyBytes_Join()：請改用 PyBytes_Join()。

_PyDict_GetItemStringWithError()：請改用 PyDict_GetItemStringRef()。

_PyDict_Pop()：請改用 PyDict_Pop()。

_PyLong_Sign()：請改用 PyLong_GetSign()。

_PyLong_FromDigits() 和 _PyLong_New()：請改用 PyLongWriter_Create()。

_PyThreadState_UncheckedGet()：請改用 PyThreadState_GetUnchecked()。

_PyUnicode_AsString()：請改用 PyUnicode_AsUTF8()。

_PyUnicodeWriter_Init()：將 _PyUnicodeWriter_Init(&writer) 替換為 writer = PyUnicodeWriter_Create(0)。

_PyUnicodeWriter_Finish()：將 _PyUnicodeWriter_Finish(&writer) 替換為 PyUnicodeWriter_Finish(writer)。

_PyUnicodeWriter_Dealloc()：將 _PyUnicodeWriter_Dealloc(&writer) 替換為 PyUnicodeWriter_Discard(writer)。

_PyUnicodeWriter_WriteChar()：將 _PyUnicodeWriter_WriteChar(&writer, ch) 替換為 PyUnicodeWriter_WriteChar(writer, ch)。

_PyUnicodeWriter_WriteStr()：將 _PyUnicodeWriter_WriteStr(&writer, str) 替換為 PyUnicodeWriter_WriteStr(writer, str)。

_PyUnicodeWriter_WriteSubstring()：將 _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) 替換為 PyUnicodeWriter_WriteSubstring(writer, str, start, end)。

_PyUnicodeWriter_WriteASCIIString()：將 _PyUnicodeWriter_WriteASCIIString(&writer, str) 替換為 PyUnicodeWriter_WriteASCII(writer, str)。

_PyUnicodeWriter_WriteLatin1String()：將 _PyUnicodeWriter_WriteLatin1String(&writer, str) 替換為 PyUnicodeWriter_WriteUTF8(writer, str)。

_PyUnicodeWriter_Prepare()：（無替代方案）。

_PyUnicodeWriter_PrepareKind()：（無替代方案）。

_Py_HashPointer()：請改用 Py_HashPointer()。

_Py_fopen_obj()：請改用 Py_fopen()。

可以使用 pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] 來取得這些於 Python 3.13 及更早版本的新公開函式。（由 Victor Stinner 在 gh-128863 [https://github.com/python/cpython/issues/128863] 貢獻）

未來版本中的待移除項目

下列 API 已被棄用並將會被移除，不過目前尚未訂定移除日期。

Py_TPFLAGS_HAVE_FINALIZE：自 Python 3.8 起不再需要

PyErr_Fetch()：請改用 PyErr_GetRaisedException()。

PyErr_NormalizeException()：請改用 PyErr_GetRaisedException()。

PyErr_Restore()：請改用 PyErr_SetRaisedException()。

PyModule_GetFilename()：請改用 PyModule_GetFilenameObject()。

PyOS_AfterFork()：請改用 PyOS_AfterFork_Child()。

PySlice_GetIndicesEx()：請改用 PySlice_Unpack() 和 PySlice_AdjustIndices()。

PyUnicode_READY()：自 Python 3.12 起不再需要

PyErr_Display()：請改用 PyErr_DisplayException()。

_PyErr_ChainExceptions()：請改用 _PyErr_ChainExceptions1。

PyBytesObject.ob_shash 成員：請改為呼叫 PyObject_Hash()。

執行緒局部儲存 (Thread Local Storage, TLS) API：

PyThread_create_key()：請改用 PyThread_tss_alloc()。

PyThread_delete_key()：請改用 PyThread_tss_free()。

PyThread_set_key_value()：請改用 PyThread_tss_set()。

PyThread_get_key_value()：請改用 PyThread_tss_get()。

PyThread_delete_key_value()：請改用 PyThread_tss_delete()。

PyThread_ReInitTLS()：自 Python 3.7 起不再需要。

建置變更

arm64-apple-ios and arm64-apple-ios-simulator are both now PEP 11 [https://peps.python.org/pep-0011/] tier 3 platforms. (PEP 730 written and implementation contributed by Russell Keith-Magee in gh-114099 [https://github.com/python/cpython/issues/114099].)

aarch64-linux-android and x86_64-linux-android are both now PEP 11 [https://peps.python.org/pep-0011/] tier 3 platforms. (PEP 738 written and implementation contributed by Malcolm Smith in gh-116622 [https://github.com/python/cpython/issues/116622].)

wasm32-wasi is now a PEP 11 [https://peps.python.org/pep-0011/] tier 2 platform. (Contributed by Brett Cannon in gh-115192 [https://github.com/python/cpython/issues/115192].)

wasm32-emscripten 不再是 PEP 11 [https://peps.python.org/pep-0011/] 支援的平台。（由 Brett Cannon 在 gh-115192 [https://github.com/python/cpython/issues/115192] 貢獻。）

Building CPython now requires a compiler with support for the C11 atomic library, GCC built-in atomic functions, or MSVC interlocked intrinsics.

Autoconf 2.71 and aclocal 1.16.5 are now required to regenerate the configure script. (Contributed by Christian Heimes in gh-89886 [https://github.com/python/cpython/issues/89886] and by Victor Stinner in gh-112090 [https://github.com/python/cpython/issues/112090].)

SQLite 3.15.2 or newer is required to build the sqlite3 extension module. (Contributed by Erlend Aasland in gh-105875 [https://github.com/python/cpython/issues/105875].)

CPython now bundles the mimalloc library [https://github.com/microsoft/mimalloc/] by default. It is licensed under the MIT license; see mimalloc license. The bundled mimalloc has custom changes, see gh-113141 [https://github.com/python/cpython/issues/113141] for details. (Contributed by Dino Viehland in gh-109914 [https://github.com/python/cpython/issues/109914].)

The configure option --with-system-libmpdec now defaults to yes. The bundled copy of libmpdec will be removed in Python 3.16.

Python built with configure --with-trace-refs (tracing references) is now ABI compatible with the Python release build and debug build. (Contributed by Victor Stinner in gh-108634 [https://github.com/python/cpython/issues/108634].)

On POSIX systems, the pkg-config (.pc) filenames now include the ABI flags. For example, the free-threaded build generates python-3.13t.pc and the debug build generates python-3.13d.pc.

The errno, fcntl, grp, md5, pwd, resource, termios, winsound, _ctypes_test, _multiprocessing.posixshmem, _scproxy, _stat, _statistics, _testconsole, _testimportmultiple and _uuid C extensions are now built with the limited C API. (Contributed by Victor Stinner in gh-85283 [https://github.com/python/cpython/issues/85283].)

移植至 Python 3.13

This section lists previously described changes and other bugfixes that may require changes to your code.

Python API 的變更

PEP 667 introduces several changes to the semantics of locals() and f_locals:

Calling locals() in an optimized scope now produces an independent snapshot on each call, and hence no longer implicitly updates previously returned references. Obtaining the legacy CPython behavior now requires explicit calls to update the initially returned dictionary with the results of subsequent calls to locals(). Code execution functions that implicitly target locals() (such as exec and eval) must be passed an explicit namespace to access their results in an optimized scope. (Changed as part of PEP 667 [https://peps.python.org/pep-0667/].)

Calling locals() from a comprehension at module or class scope (including via exec or eval) once more behaves as if the comprehension were running as an independent nested function (i.e. the local variables from the containing scope are not included). In Python 3.12, this had changed to include the local variables from the containing scope when implementing PEP 709 [https://peps.python.org/pep-0709/]. (Changed as part of PEP 667 [https://peps.python.org/pep-0667/].)

Accessing FrameType.f_locals in an optimized scope now returns a write-through proxy rather than a snapshot that gets updated at ill-specified times. If a snapshot is desired, it must be created explicitly with dict or the proxy's .copy() method. (Changed as part of PEP 667 [https://peps.python.org/pep-0667/].)

functools.partial now emits a FutureWarning when used as a method. The behavior will change in future Python versions. Wrap it in staticmethod() if you want to preserve the old behavior. (Contributed by Serhiy Storchaka in gh-121027 [https://github.com/python/cpython/issues/121027].)

An OSError is now raised by getpass.getuser() for any failure to retrieve a username, instead of ImportError on non-Unix platforms or KeyError on Unix platforms where the password database is empty.

The value of the mode attribute of gzip.GzipFile is now a string ('rb' or 'wb') instead of an integer (1 or 2). The value of the mode attribute of the readable file-like object returned by zipfile.ZipFile.open() is now 'rb' instead of 'r'. (Contributed by Serhiy Storchaka in gh-115961 [https://github.com/python/cpython/issues/115961].)

mailbox.Maildir 現在會忽略以點號 (.) 開頭的檔案。 (由 Zackery Spytz 在 gh-65559 [https://github.com/python/cpython/issues/65559] 貢獻。)

pathlib.Path.glob() and rglob() now return both files and directories if a pattern that ends with "**" is given, rather than directories only. Add a trailing slash to keep the previous behavior and only match directories.

The threading module now expects the _thread module to have an _is_main_interpreter() function. This function takes no arguments and returns True if the current interpreter is the main interpreter.

Any library or application that provides a custom _thread module must provide _is_main_interpreter(), just like the module's other "private" attributes. (gh-112826 [https://github.com/python/cpython/issues/112826].)

C API 中的改動

Python.h no longer includes the <ieeefp.h> standard header. It was included for the finite() function which is now provided by the <math.h> header. It should now be included explicitly if needed. Remove also the HAVE_IEEEFP_H macro. (Contributed by Victor Stinner in gh-108765 [https://github.com/python/cpython/issues/108765].)

Python.h no longer includes these standard header files: <time.h>, <sys/select.h> and <sys/time.h>. If needed, they should now be included explicitly. For example, <time.h> provides the clock() and gmtime() functions, <sys/select.h> provides the select() function, and <sys/time.h> provides the futimes(), gettimeofday() and setitimer() functions. (Contributed by Victor Stinner in gh-108765 [https://github.com/python/cpython/issues/108765].)

On Windows, Python.h no longer includes the <stddef.h> standard header file. If needed, it should now be included explicitly. For example, it provides offsetof() function, and size_t and ptrdiff_t types. Including <stddef.h> explicitly was already needed by all other platforms, the HAVE_STDDEF_H macro is only defined on Windows. (Contributed by Victor Stinner in gh-108765 [https://github.com/python/cpython/issues/108765].)

If the Py_LIMITED_API macro is defined, Py_BUILD_CORE, Py_BUILD_CORE_BUILTIN and Py_BUILD_CORE_MODULE macros are now undefined by <Python.h>. (Contributed by Victor Stinner in gh-85283 [https://github.com/python/cpython/issues/85283].)

The old trashcan macros Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END were removed. They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END.

有舊巨集的 tp_dealloc 函式，例如：

static void
mytype_dealloc(mytype *p)
{
    PyObject_GC_UnTrack(p);
    Py_TRASHCAN_SAFE_BEGIN(p);
    ...
    Py_TRASHCAN_SAFE_END
}

應該改為使用新的巨集，如下所示：

static void
mytype_dealloc(mytype *p)
{
    PyObject_GC_UnTrack(p);
    Py_TRASHCAN_BEGIN(p, mytype_dealloc)
    ...
    Py_TRASHCAN_END
}

Note that Py_TRASHCAN_BEGIN has a second argument which should be the deallocation function it is in. The new macros were added in Python 3.8 and the old macros were deprecated in Python 3.11. (Contributed by Irit Katriel in gh-105111 [https://github.com/python/cpython/issues/105111].)

PEP 667 introduces several changes to frame-related functions:

The effects of mutating the dictionary returned from PyEval_GetLocals() in an optimized scope have changed. New dict entries added this way will now only be visible to subsequent PyEval_GetLocals() calls in that frame, as PyFrame_GetLocals(), locals(), and FrameType.f_locals no longer access the same underlying cached dictionary. Changes made to entries for actual variable names and names added via the write-through proxy interfaces will be overwritten on subsequent calls to PyEval_GetLocals() in that frame. The recommended code update depends on how the function was being used, so refer to the deprecation notice on the function for details.

Calling PyFrame_GetLocals() in an optimized scope now returns a write-through proxy rather than a snapshot that gets updated at ill-specified times. If a snapshot is desired, it must be created explicitly (e.g. with PyDict_Copy()), or by calling the new PyEval_GetFrameLocals() API.

PyFrame_FastToLocals() and PyFrame_FastToLocalsWithError() no longer have any effect. Calling these functions has been redundant since Python 3.11, when PyFrame_GetLocals() was first introduced.

PyFrame_LocalsToFast() no longer has any effect. Calling this function is redundant now that PyFrame_GetLocals() returns a write-through proxy for optimized scopes.

Python 3.13 removed many private functions. Some of them can be replaced using these alternatives:

_PyDict_Pop()：PyDict_Pop() 或 PyDict_PopString()；

_PyDict_GetItemWithError()：PyDict_GetItemRef()；

_PyErr_WriteUnraisableMsg()：PyErr_FormatUnraisable()；

_PyEval_SetTrace()：PyEval_SetTrace() 或 PyEval_SetTraceAllThreads()；

_PyList_Extend()：PyList_Extend()；

_PyLong_AsInt()：PyLong_AsInt()；

_PyMem_RawStrdup()：strdup()；

_PyMem_Strdup()：strdup()；

_PyObject_ClearManagedDict()：PyObject_ClearManagedDict()；

_PyObject_VisitManagedDict()：PyObject_VisitManagedDict()；

_PyThreadState_UncheckedGet()：PyThreadState_GetUnchecked()；

_PyTime_AsSecondsDouble()：PyTime_AsSecondsDouble()；

_PyTime_GetMonotonicClock()：PyTime_Monotonic() 或 PyTime_MonotonicRaw()；

_PyTime_GetPerfCounter()：PyTime_PerfCounter() 或 PyTime_PerfCounterRaw()；

_PyTime_GetSystemClock()：PyTime_Time() 或 PyTime_TimeRaw()；

_PyTime_MAX：PyTime_MAX；

_PyTime_MIN：PyTime_MIN；

_PyTime_t：PyTime_t；

_Py_HashPointer()：Py_HashPointer()；

_Py_IsFinalizing()：Py_IsFinalizing()。

可以使用 pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]來在 Python 3.12 及更舊的版本中取用大部分的這些新函式。

迴歸測試的變更

使用 configure --with-pydebug 建置的 Python 現在支援 -X presite=package.module 命令列選項。如果使用它就會指定一個應該在直譯器生命週期的早期階段、在執行 site.py 之前被引入的模組。(由 Łukasz Langa 在 gh-110769 [https://github.com/python/cpython/issues/110769] 中貢獻。)

Python 3.12 有什麼新功能

編輯者:

Adam Turner

本文介紹了 Python 3.12 與 3.11 相比多了哪些新功能。 Python 3.12 於 2023 年 10 月 2 日發布。完整詳情請見 changelog。

也參考

PEP 693 [https://peps.python.org/pep-0693/] -- Python 3.12 發佈時程

發布重點摘要

Python 3.12 是 Python 程式語言的穩定版本，包含了語言和標準函式庫的綜合變更。標準函式庫的變更主要集中在清理棄用的 API、可用性和正確性。值得注意的是，distutils 套件已從標準函式庫中移除。os 和 pathlib 中的檔案系統支援進行了許多改進，並且有數個模組得到更好的效能。

語言變更主要集中在可用性，因為 f-字串已經移除了許多限制，並且持續改進 'Did you mean ...' 建議。新的型別參數語法和 type 陳述式改進了泛型型別和型別別名在與靜態型別檢查器一起使用上的效率。

這篇文章並不試圖提供所有新功能的完整規格，而是提供一個方便的概覽。完整詳情應參考文件，如標準函式庫參考和語言參考。如果你想了解某個新功能的完整實作和設計理念，請參考該功能的 PEP；但請注意 PEP 通常在功能完全實作後就不再更新。

新增語法特性：

PEP 695，型別參數語法和 type 陳述式

新增語法特性：

PEP 701，文法中的 f-字串

直譯器改進：

PEP 684，直譯器各別持有的 GIL

PEP 669，低影響監控

Improved 'Did you mean ...' suggestions for NameError, ImportError, and SyntaxError exceptions

Python 資料模型改進：

PEP 688, using the buffer protocol from Python

標準函式庫中的顯著改進

pathlib.Path 類別現在支援子類別化

os 模組在 Windows 支援上有了數項改進

一個命令列介面已被加入 sqlite3 模組中

isinstance() checks against runtime-checkable protocols enjoy a speed up of between two and 20 times

asyncio 套件進行了許多效能改進，一些基準測試顯示速度提高了 75%。

一個命令列介面已被加入 uuid 模組中

Due to the changes in PEP 701, producing tokens via the tokenize module is up to 64% faster.

安全性改進：

Replace the builtin hashlib implementations of SHA1, SHA3, SHA2-384, SHA2-512, and MD5 with formally verified code from the HACL* [https://github.com/hacl-star/hacl-star/] project. These builtin implementations remain as fallbacks that are only used when OpenSSL does not provide them.

C API 改進：

PEP 697，不穩定 C API 層

PEP 683, immortal objects

CPython 實作改進：

PEP 709, comprehension inlining

CPython support for the Linux perf profiler

Implement stack overflow protection on supported platforms

新增型別特性：

PEP 692、使用 TypedDict 來標註 **kwargs

PEP 698、typing.override() 裝飾器

重要的棄用、刪除或限制：

PEP 623 [https://peps.python.org/pep-0623/]: Remove wstr from Unicode objects in Python's C API, reducing the size of every str object by at least 8 bytes.

PEP 632 [https://peps.python.org/pep-0632/]: Remove the distutils package. See the migration guide [https://peps.python.org/pep-0632/#migration-advice] for advice replacing the APIs it provided. The third-party Setuptools [https://setuptools.pypa.io/en/latest/deprecated/distutils-legacy.html] package continues to provide distutils, if you still require it in Python 3.12 and beyond.

gh-95299 [https://github.com/python/cpython/issues/95299]：不再於以 venv 建立的虛擬環境中預先安裝 setuptools。這意味著 distutils、setuptools、pkg_resources 和 easy_install 將預設不可用；若要使用這些工具，請在已啟用的虛擬環境中執行 pip install setuptools。

asynchat、asyncore 和 imp 模組以及幾個 unittest.TestCase 的方法別名已被刪除。

新增功能

PEP 695：型別參數語法

Generic classes and functions under PEP 484 [https://peps.python.org/pep-0484/] were declared using a verbose syntax that left the scope of type parameters unclear and required explicit declarations of variance.

PEP 695 [https://peps.python.org/pep-0695/] introduces a new, more compact and explicit way to create generic classes and functions:

def max[T](args: Iterable[T]) -> T:
    ...

class list[T]:
    def __getitem__(self, index: int, /) -> T:
        ...

    def append(self, element: T) -> None:
        ...

In addition, the PEP introduces a new way to declare type aliases using the type statement, which creates an instance of TypeAliasType:

type Point = tuple[float, float]

型別別名也可以是泛型：

type Point[T] = tuple[T, T]

The new syntax allows declaring TypeVarTuple and ParamSpec parameters, as well as TypeVar parameters with bounds or constraints:

type IntFunc[**P] = Callable[P, int]  # ParamSpec
type LabeledTuple[*Ts] = tuple[str, *Ts]  # TypeVarTuple
type HashableSequence[T: Hashable] = Sequence[T]  # 帶有邊界的 TypeVar
type IntOrStrSequence[T: (int, str)] = Sequence[T]  # 帶有限制的 TypeVar

The value of type aliases and the bound and constraints of type variables created through this syntax are evaluated only on demand (see lazy evaluation). This means type aliases are able to refer to other types defined later in the file.

Type parameters declared through a type parameter list are visible within the scope of the declaration and any nested scopes, but not in the outer scope. For example, they can be used in the type annotations for the methods of a generic class or in the class body. However, they cannot be used in the module scope after the class is defined. See Type parameter lists for a detailed description of the runtime semantics of type parameters.

In order to support these scoping semantics, a new kind of scope is introduced, the annotation scope. Annotation scopes behave for the most part like function scopes, but interact differently with enclosing class scopes. In Python 3.13, annotations will also be evaluated in annotation scopes.

詳情請見 PEP 695 [https://peps.python.org/pep-0695/]。

（PEP 由 Eric Traut 撰寫。由 Jelle Zijlstra、Eric Traut 和其他人在 gh-103764 [https://github.com/python/cpython/issues/103764] 中實作。）

PEP 701: Syntactic formalization of f-strings

PEP 701 [https://peps.python.org/pep-0701/] lifts some restrictions on the usage of f-strings. Expression components inside f-strings can now be any valid Python expression, including strings reusing the same quote as the containing f-string, multi-line expressions, comments, backslashes, and unicode escape sequences. Let's cover these in detail:

Quote reuse: in Python 3.11, reusing the same quotes as the enclosing f-string raises a SyntaxError, forcing the user to either use other available quotes (like using double quotes or triple quotes if the f-string uses single quotes). In Python 3.12, you can now do things like this:

>>> songs = ['Take me back to Eden', 'Alkaline', 'Ascensionism']
>>> f"This is the playlist: {", ".join(songs)}"
'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'

Note that before this change there was no explicit limit in how f-strings can be nested, but the fact that string quotes cannot be reused inside the expression component of f-strings made it impossible to nest f-strings arbitrarily. In fact, this is the most nested f-string that could be written:

>>> f"""{f'''{f'{f"{1+1}"}'}'''}"""
'2'

As now f-strings can contain any valid Python expression inside expression components, it is now possible to nest f-strings arbitrarily:

>>> f"{f"{f"{f"{f"{f"{1+1}"}"}"}"}"}"
'2'

Multi-line expressions and comments: In Python 3.11, f-string expressions must be defined in a single line, even if the expression within the f-string could normally span multiple lines (like literal lists being defined over multiple lines), making them harder to read. In Python 3.12 you can now define f-strings spanning multiple lines, and add inline comments:

>>> f"This is the playlist: {", ".join([
...     'Take me back to Eden',  # My, my, those eyes like fire
...     'Alkaline',              # Not acid nor alkaline
...     'Ascensionism'           # Take to the broken skies at last
... ])}"
'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'

Backslashes and unicode characters: before Python 3.12 f-string expressions couldn't contain any \ character. This also affected unicode escape sequences (such as \N{snowman}) as these contain the \N part that previously could not be part of expression components of f-strings. Now, you can define expressions like this:

>>> print(f"This is the playlist: {"\n".join(songs)}")
This is the playlist: Take me back to Eden
Alkaline
Ascensionism
>>> print(f"This is the playlist: {"\N{BLACK HEART SUIT}".join(songs)}")
This is the playlist: Take me back to Eden♥Alkaline♥Ascensionism

詳情請見 PEP 701 [https://peps.python.org/pep-0701/]。

As a positive side-effect of how this feature has been implemented (by parsing f-strings with the PEG parser [https://peps.python.org/pep-0617/]), now error messages for f-strings are more precise and include the exact location of the error. For example, in Python 3.11, the following f-string raises a SyntaxError:

>>> my_string = f"{x z y}" + f"{1 + 1}"
  File "<stdin>", line 1
    (x z y)
     ^^^
SyntaxError: f-string: invalid syntax. Perhaps you forgot a comma?

but the error message doesn't include the exact location of the error within the line and also has the expression artificially surrounded by parentheses. In Python 3.12, as f-strings are parsed with the PEG parser, error messages can be more precise and show the entire line:

>>> my_string = f"{x z y}" + f"{1 + 1}"
  File "<stdin>", line 1
    my_string = f"{x z y}" + f"{1 + 1}"
                   ^^^
SyntaxError: invalid syntax. Perhaps you forgot a comma?

(Contributed by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou, Cristián Maureira-Fredes and Marta Gómez in gh-102856 [https://github.com/python/cpython/issues/102856]. PEP written by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou and Marta Gómez).

PEP 684：直譯器各別持有的 GIL

PEP 684 [https://peps.python.org/pep-0684/] 引入了直譯器各別持有的 GIL，因此子直譯器現在可以使用各個直譯器特有的 GIL 來建立。這使得 Python 程式可以充分利用多個 CPU 核心。目前這僅透過 C-API 使用，不過 Python API 預計在 3.13 中釋出 [https://peps.python.org/pep-0554/]。

Use the new Py_NewInterpreterFromConfig() function to create an interpreter with its own GIL:

PyInterpreterConfig config = {
    .check_multi_interp_extensions = 1,
    .gil = PyInterpreterConfig_OWN_GIL,
};
PyThreadState *tstate = NULL;
PyStatus status = Py_NewInterpreterFromConfig(&tstate, &config);
if (PyStatus_Exception(status)) {
    return -1;
}
/* 新的直譯器現在會在目前執行緒中啟用。 */

For further examples how to use the C-API for sub-interpreters with a per-interpreter GIL, see Modules/_xxsubinterpretersmodule.c.

（由 Eric Snow 於 gh-104210 [https://github.com/python/cpython/issues/104210] 等貢獻。）

PEP 669: Low impact monitoring for CPython

PEP 669 [https://peps.python.org/pep-0669/] defines a new API for profilers, debuggers, and other tools to monitor events in CPython. It covers a wide range of events, including calls, returns, lines, exceptions, jumps, and more. This means that you only pay for what you use, providing support for near-zero overhead debuggers and coverage tools. See sys.monitoring for details.

（由 Mark Shannon 於 gh-103082 [https://github.com/python/cpython/issues/103082] 中貢獻。）

PEP 688：使緩衝區協定可在 Python 中存取

PEP 688 [https://peps.python.org/pep-0688/] introduces a way to use the buffer protocol from Python code. Classes that implement the __buffer__() method are now usable as buffer types.

The new collections.abc.Buffer ABC provides a standard way to represent buffer objects, for example in type annotations. The new inspect.BufferFlags enum represents the flags that can be used to customize buffer creation. (Contributed by Jelle Zijlstra in gh-102500 [https://github.com/python/cpython/issues/102500].)

PEP 709: Comprehension inlining

Dictionary, list, and set comprehensions are now inlined, rather than creating a new single-use function object for each execution of the comprehension. This speeds up execution of a comprehension by up to two times. See PEP 709 [https://peps.python.org/pep-0709/] for further details.

Comprehension iteration variables remain isolated and don't overwrite a variable of the same name in the outer scope, nor are they visible after the comprehension. Inlining does result in a few visible behavior changes:

There is no longer a separate frame for the comprehension in tracebacks, and tracing/profiling no longer shows the comprehension as a function call.

The symtable module will no longer produce child symbol tables for each comprehension; instead, the comprehension's locals will be included in the parent function's symbol table.

Calling locals() inside a comprehension now includes variables from outside the comprehension, and no longer includes the synthetic .0 variable for the comprehension "argument".

A comprehension iterating directly over locals() (e.g. [k for k in locals()]) may see "RuntimeError: dictionary changed size during iteration" when run under tracing (e.g. code coverage measurement). This is the same behavior already seen in e.g. for k in locals():. To avoid the error, first create a list of keys to iterate over: keys = list(locals()); [k for k in keys].

（由 Carl Meyer 和 Vladimir Matveev 於 PEP 709 [https://peps.python.org/pep-0709/] 中貢獻。）

改善錯誤訊息

Modules from the standard library are now potentially suggested as part of the error messages displayed by the interpreter when a NameError is raised to the top level. (Contributed by Pablo Galindo in gh-98254 [https://github.com/python/cpython/issues/98254].)

>>> sys.version_info
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'sys' is not defined. Did you forget to import 'sys'?

Improve the error suggestion for NameError exceptions for instances. Now if a NameError is raised in a method and the instance has an attribute that's exactly equal to the name in the exception, the suggestion will include self.<NAME> instead of the closest match in the method scope. (Contributed by Pablo Galindo in gh-99139 [https://github.com/python/cpython/issues/99139].)

>>> class A:
...    def __init__(self):
...        self.blech = 1
...
...    def foo(self):
...        somethin = blech
...
>>> A().foo()
Traceback (most recent call last):
  File "<stdin>", line 1
    somethin = blech
               ^^^^^
NameError: name 'blech' is not defined. Did you mean: 'self.blech'?

Improve the SyntaxError error message when the user types import x from y instead of from y import x. (Contributed by Pablo Galindo in gh-98931 [https://github.com/python/cpython/issues/98931].)

>>> import a.y.z from b.y.z
Traceback (most recent call last):
  File "<stdin>", line 1
    import a.y.z from b.y.z
    ^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Did you mean to use 'from ... import ...' instead?

ImportError exceptions raised from failed from <module> import <name> statements now include suggestions for the value of <name> based on the available names in <module>. (Contributed by Pablo Galindo in gh-91058 [https://github.com/python/cpython/issues/91058].)

>>> from collections import chainmap
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?

型別提示相關的新特性

本節涵蓋了影響型別提示 [https://peps.python.org/pep-0484/]和 typing 模組的主要變更。

PEP 692: Using TypedDict for more precise **kwargs typing

Typing **kwargs in a function signature as introduced by PEP 484 [https://peps.python.org/pep-0484/] allowed for valid annotations only in cases where all of the **kwargs were of the same type.

PEP 692 [https://peps.python.org/pep-0692/] specifies a more precise way of typing **kwargs by relying on typed dictionaries:

from typing import TypedDict, Unpack

class Movie(TypedDict):
  name: str
  year: int

def foo(**kwargs: Unpack[Movie]): ...

詳情請見 PEP 692 [https://peps.python.org/pep-0692/]。

（由 Franek Magiera 於 gh-103629 [https://github.com/python/cpython/issues/103629] 中貢獻。）

PEP 698：覆蓋靜態型別的裝飾器

A new decorator typing.override() has been added to the typing module. It indicates to type checkers that the method is intended to override a method in a superclass. This allows type checkers to catch mistakes where a method that is intended to override something in a base class does not in fact do so.

範例：

from typing import override

class Base:
  def get_color(self) -> str:
    return "blue"

class GoodChild(Base):
  @override  # ok：覆寫 Base.get_color
  def get_color(self) -> str:
    return "yellow"

class BadChild(Base):
  @override  # 型別檢查錯誤：未覆寫 Base.get_color
  def get_colour(self) -> str:
    return "red"

詳情請見 PEP 698 [https://peps.python.org/pep-0698/]。

（由 Steven Troxler 於 gh-101561 [https://github.com/python/cpython/issues/101561] 中貢獻。）

其他語言更動

The parser now raises SyntaxError when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670 [https://github.com/python/cpython/issues/96670].)

A backslash-character pair that is not a valid escape sequence now generates a SyntaxWarning, instead of DeprecationWarning. For example, re.compile("\d+\.\d+") now emits a SyntaxWarning ("\d" is an invalid escape sequence, use raw strings for regular expression: re.compile(r"\d+\.\d+")). In a future Python version, SyntaxError will eventually be raised, instead of SyntaxWarning. (Contributed by Victor Stinner in gh-98401 [https://github.com/python/cpython/issues/98401].)

Octal escapes with value larger than 0o377 (ex: "\477"), deprecated in Python 3.11, now produce a SyntaxWarning, instead of DeprecationWarning. In a future Python version they will be eventually a SyntaxError. (Contributed by Victor Stinner in gh-98401 [https://github.com/python/cpython/issues/98401].)

Variables used in the target part of comprehensions that are not stored to can now be used in assignment expressions (:=). For example, in [(b := 1) for a, b.prop in some_iter], the assignment to b is now allowed. Note that assigning to variables stored to in the target part of comprehensions (like a) is still disallowed, as per PEP 572 [https://peps.python.org/pep-0572/]. (Contributed by Nikita Sobolev in gh-100581 [https://github.com/python/cpython/issues/100581].)

Exceptions raised in a class or type's __set_name__ method are no longer wrapped by a RuntimeError. Context information is added to the exception as a PEP 678 [https://peps.python.org/pep-0678/] note. (Contributed by Irit Katriel in gh-77757 [https://github.com/python/cpython/issues/77757].)

When a try-except* construct handles the entire ExceptionGroup and raises one other exception, that exception is no longer wrapped in an ExceptionGroup. Also changed in version 3.11.4. (Contributed by Irit Katriel in gh-103590 [https://github.com/python/cpython/issues/103590].)

The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead of object allocations. The GC can also run when PyErr_CheckSignals() is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically. (Contributed by Pablo Galindo in gh-97922 [https://github.com/python/cpython/issues/97922].)

All builtin and extension callables expecting boolean parameters now accept arguments of any type instead of just bool and int. (Contributed by Serhiy Storchaka in gh-60203 [https://github.com/python/cpython/issues/60203].)

memoryview now supports the half-float type (the "e" format code). (Contributed by Donghee Na and Antoine Pitrou in gh-90751 [https://github.com/python/cpython/issues/90751].)

slice objects are now hashable, allowing them to be used as dict keys and set items. (Contributed by Will Bradshaw, Furkan Onder, and Raymond Hettinger in gh-101264 [https://github.com/python/cpython/issues/101264].)

sum() now uses Neumaier summation to improve accuracy and commutativity when summing floats or mixed ints and floats. (Contributed by Raymond Hettinger in gh-100425 [https://github.com/python/cpython/issues/100425].)

ast.parse() now raises SyntaxError instead of ValueError when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670 [https://github.com/python/cpython/issues/96670].)

The extraction methods in tarfile, and shutil.unpack_archive(), have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See tarfile extraction filters for details. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in PEP 706 [https://peps.python.org/pep-0706/].)

types.MappingProxyType instances are now hashable if the underlying mapping is hashable. (Contributed by Serhiy Storchaka in gh-87995 [https://github.com/python/cpython/issues/87995].)

透過新的環境變數 PYTHONPERFSUPPORT 和命令列選項 -X perf 以及新的 sys.activate_stack_trampoline()、sys.deactivate_stack_trampoline() 和 sys.is_stack_trampoline_active() 函式，新增對效能分析器的支援。（由 Pablo Galindo 設計。由 Pablo Galindo 和 Christian Heimes 貢獻，Gregory P. Smith [Google] 和 Mark Shannon 在 gh-96123 [https://github.com/python/cpython/issues/96123] 中也有貢獻。）

新增模組

無。

改進的模組

array

The array.array class now supports subscripting, making it a generic type. (Contributed by Jelle Zijlstra in gh-98658 [https://github.com/python/cpython/issues/98658].)

asyncio

The performance of writing to sockets in asyncio has been significantly improved. asyncio now avoids unnecessary copying when writing to sockets and uses sendmsg() if the platform supports it. (Contributed by Kumar Aditya in gh-91166 [https://github.com/python/cpython/issues/91166].)

Add asyncio.eager_task_factory() and asyncio.create_eager_task_factory() functions to allow opting an event loop in to eager task execution, making some use-cases 2x to 5x faster. (Contributed by Jacob Bower & Itamar Oren in gh-102853 [https://github.com/python/cpython/issues/102853], gh-104140 [https://github.com/python/cpython/issues/104140], and gh-104138 [https://github.com/python/cpython/issues/104138])

On Linux, asyncio uses asyncio.PidfdChildWatcher by default if os.pidfd_open() is available and functional instead of asyncio.ThreadedChildWatcher. (Contributed by Kumar Aditya in gh-98024 [https://github.com/python/cpython/issues/98024].)

The event loop now uses the best available child watcher for each platform (asyncio.PidfdChildWatcher if supported and asyncio.ThreadedChildWatcher otherwise), so manually configuring a child watcher is not recommended. (Contributed by Kumar Aditya in gh-94597 [https://github.com/python/cpython/issues/94597].)

Add loop_factory parameter to asyncio.run() to allow specifying a custom event loop factory. (Contributed by Kumar Aditya in gh-99388 [https://github.com/python/cpython/issues/99388].)

Add C implementation of asyncio.current_task() for 4x-6x speedup. (Contributed by Itamar Oren and Pranav Thulasiram Bhat in gh-100344 [https://github.com/python/cpython/issues/100344].)

asyncio.iscoroutine() now returns False for generators as asyncio does not support legacy generator-based coroutines. (Contributed by Kumar Aditya in gh-102748 [https://github.com/python/cpython/issues/102748].)

asyncio.wait() and asyncio.as_completed() now accepts generators yielding tasks. (Contributed by Kumar Aditya in gh-78530 [https://github.com/python/cpython/issues/78530].)

calendar

Add enums calendar.Month and calendar.Day defining months of the year and days of the week. (Contributed by Prince Roshan in gh-103636 [https://github.com/python/cpython/issues/103636].)

csv

Add csv.QUOTE_NOTNULL and csv.QUOTE_STRINGS flags to provide finer grained control of None and empty strings by reader and writer objects.

dis

Pseudo instruction opcodes (which are used by the compiler but do not appear in executable bytecode) are now exposed in the dis module. HAVE_ARGUMENT is still relevant to real opcodes, but it is not useful for pseudo instructions. Use the new dis.hasarg collection instead. (Contributed by Irit Katriel in gh-94216 [https://github.com/python/cpython/issues/94216].)

Add the dis.hasexc collection to signify instructions that set an exception handler. (Contributed by Irit Katriel in gh-94216 [https://github.com/python/cpython/issues/94216].)

fractions

Objects of type fractions.Fraction now support float-style formatting. (Contributed by Mark Dickinson in gh-100161 [https://github.com/python/cpython/issues/100161].)

importlib.resources

importlib.resources.as_file() 現在支援資源目錄。（由 Jason R. Coombs 於 gh-97930 [https://github.com/python/cpython/issues/97930] 中貢獻。）

將 importlib.resources.files() 的第一個參數重新命名為 anchor。（由 Jason R. Coombs 於 gh-100598 [https://github.com/python/cpython/issues/100598] 中貢獻。）

inspect

新增 inspect.markcoroutinefunction() 以標記會回傳 coroutine 的同步函式，以供 inspect.iscoroutinefunction() 使用。（由 Carlton Gibson 於 gh-99247 [https://github.com/python/cpython/issues/99247] 中貢獻。）

新增 inspect.getasyncgenstate() 和 inspect.getasyncgenlocals() 以確定非同步產生器的目前狀態。（由 Thomas Krennwallner 於 gh-79940 [https://github.com/python/cpython/issues/79940] 中貢獻。）

inspect.getattr_static() 的效能已大幅改善。大多數對該函式的呼叫應該比 Python 3.11 中快至少 2 倍。（由 Alex Waygood 於 gh-103193 [https://github.com/python/cpython/issues/103193] 中貢獻。）

itertools

新增 itertools.batched() 以將元素收集到大小均等的元組中，其中最後一批次可能比其他的少。（由 Raymond Hettinger 於 gh-98363 [https://github.com/python/cpython/issues/98363] 中貢獻。）

math

新增 math.sumprod() 以計算乘積總和。（由 Raymond Hettinger 於 gh-100485 [https://github.com/python/cpython/issues/100485] 中貢獻。）

Extend math.nextafter() to include a steps argument for moving up or down multiple steps at a time. (Contributed by Matthias Goergens, Mark Dickinson, and Raymond Hettinger in gh-94906 [https://github.com/python/cpython/issues/94906].)

os

Add os.PIDFD_NONBLOCK to open a file descriptor for a process with os.pidfd_open() in non-blocking mode. (Contributed by Kumar Aditya in gh-93312 [https://github.com/python/cpython/issues/93312].)

os.DirEntry now includes an os.DirEntry.is_junction() method to check if the entry is a junction. (Contributed by Charles Machalow in gh-99547 [https://github.com/python/cpython/issues/99547].)

Add os.listdrives(), os.listvolumes() and os.listmounts() functions on Windows for enumerating drives, volumes and mount points. (Contributed by Steve Dower in gh-102519 [https://github.com/python/cpython/issues/102519].)

os.stat() and os.lstat() are now more accurate on Windows. The st_birthtime field will now be filled with the creation time of the file, and st_ctime is deprecated but still contains the creation time (but in the future will return the last metadata change, for consistency with other platforms). st_dev may be up to 64 bits and st_ino up to 128 bits depending on your file system, and st_rdev is always set to zero rather than incorrect values. Both functions may be significantly faster on newer releases of Windows. (Contributed by Steve Dower in gh-99726 [https://github.com/python/cpython/issues/99726].)

os.path

新增 os.path.isjunction() 以檢查給定路徑是否為連結點 (junction)。（由 Charles Machalow 於 gh-99547 [https://github.com/python/cpython/issues/99547] 中貢獻。）

新增 os.path.splitroot() 以將路徑分割為三元組 (drive, root, tail)。（由 Barney Gale 於 gh-101000 [https://github.com/python/cpython/issues/101000] 中貢獻。）

pathlib

Add support for subclassing pathlib.PurePath and pathlib.Path, plus their Posix- and Windows-specific variants. Subclasses may override the pathlib.PurePath.with_segments() method to pass information between path instances.

Add pathlib.Path.walk() for walking the directory trees and generating all file or directory names within them, similar to os.walk(). (Contributed by Stanislav Zmiev in gh-90385 [https://github.com/python/cpython/issues/90385].)

Add walk_up optional parameter to pathlib.PurePath.relative_to() to allow the insertion of .. entries in the result; this behavior is more consistent with os.path.relpath(). (Contributed by Domenico Ragusa in gh-84538 [https://github.com/python/cpython/issues/84538].)

Add pathlib.Path.is_junction() as a proxy to os.path.isjunction(). (Contributed by Charles Machalow in gh-99547 [https://github.com/python/cpython/issues/99547].)

Add case_sensitive optional parameter to pathlib.Path.glob(), pathlib.Path.rglob() and pathlib.PurePath.match() for matching the path's case sensitivity, allowing for more precise control over the matching process.

platform

Add support for detecting Windows 11 and Windows Server releases past 2012. Previously, lookups on Windows Server platforms newer than Windows Server 2012 and on Windows 11 would return Windows-10. (Contributed by Steve Dower in gh-89545 [https://github.com/python/cpython/issues/89545].)

pdb

Add convenience variables to hold values temporarily for debug session and provide quick access to values like the current frame or the return value. (Contributed by Tian Gao in gh-103693 [https://github.com/python/cpython/issues/103693].)

random

新增 random.binomialvariate()。（由 Raymond Hettinger 於 gh-81620 [https://github.com/python/cpython/issues/81620] 中貢獻。）

將預設值 lambd=1.0 加入至 random.expovariate() 中。（由 Raymond Hettinger 在 gh-100234 [https://github.com/python/cpython/issues/100234] 中貢獻。）

shutil

shutil.make_archive() now passes the root_dir argument to custom archivers which support it. In this case it no longer temporarily changes the current working directory of the process to root_dir to perform archiving. (Contributed by Serhiy Storchaka in gh-74696 [https://github.com/python/cpython/issues/74696].)

shutil.rmtree() now accepts a new argument onexc which is an error handler like onerror but which expects an exception instance rather than a (typ, val, tb) triplet. onerror is deprecated. (Contributed by Irit Katriel in gh-102828 [https://github.com/python/cpython/issues/102828].)

shutil.which() now consults the PATHEXT environment variable to find matches within PATH on Windows even when the given cmd includes a directory component. (Contributed by Charles Machalow in gh-103179 [https://github.com/python/cpython/issues/103179].)

shutil.which() will call NeedCurrentDirectoryForExePathW when querying for executables on Windows to determine if the current working directory should be prepended to the search path. (Contributed by Charles Machalow in gh-103179 [https://github.com/python/cpython/issues/103179].)

shutil.which() will return a path matching the cmd with a component from PATHEXT prior to a direct match elsewhere in the search path on Windows. (Contributed by Charles Machalow in gh-103179 [https://github.com/python/cpython/issues/103179].)

sqlite3

新增命令列介面。（由 Erlend E. Aasland 於 gh-77617 [https://github.com/python/cpython/issues/77617] 中貢獻。）

Add the sqlite3.Connection.autocommit attribute to sqlite3.Connection and the autocommit parameter to sqlite3.connect() to control PEP 249 [https://peps.python.org/pep-0249/]-compliant transaction handling. (Contributed by Erlend E. Aasland in gh-83638 [https://github.com/python/cpython/issues/83638].)

Add entrypoint keyword-only parameter to sqlite3.Connection.load_extension(), for overriding the SQLite extension entry point. (Contributed by Erlend E. Aasland in gh-103015 [https://github.com/python/cpython/issues/103015].)

Add sqlite3.Connection.getconfig() and sqlite3.Connection.setconfig() to sqlite3.Connection to make configuration changes to a database connection. (Contributed by Erlend E. Aasland in gh-103489 [https://github.com/python/cpython/issues/103489].)

statistics

Extend statistics.correlation() to include as a ranked method for computing the Spearman correlation of ranked data. (Contributed by Raymond Hettinger in gh-95861 [https://github.com/python/cpython/issues/95861].)

sys

Add the sys.monitoring namespace to expose the new PEP 669 monitoring API. (Contributed by Mark Shannon in gh-103082 [https://github.com/python/cpython/issues/103082].)

Add sys.activate_stack_trampoline() and sys.deactivate_stack_trampoline() for activating and deactivating stack profiler trampolines, and sys.is_stack_trampoline_active() for querying if stack profiler trampolines are active. (Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon in gh-96123 [https://github.com/python/cpython/issues/96123].)

Add sys.last_exc which holds the last unhandled exception that was raised (for post-mortem debugging use cases). Deprecate the three fields that have the same information in its legacy form: sys.last_type, sys.last_value and sys.last_traceback. (Contributed by Irit Katriel in gh-102778 [https://github.com/python/cpython/issues/102778].)

sys._current_exceptions() now returns a mapping from thread-id to an exception instance, rather than to a (typ, exc, tb) tuple. (Contributed by Irit Katriel in gh-103176 [https://github.com/python/cpython/issues/103176].)

sys.setrecursionlimit() and sys.getrecursionlimit(). The recursion limit now applies only to Python code. Builtin functions do not use the recursion limit, but are protected by a different mechanism that prevents recursion from causing a virtual machine crash.

tempfile

tempfile.NamedTemporaryFile 函式新增了一個選擇性參數 delete_on_close （由 Evgeny Zorin 於 gh-58451 [https://github.com/python/cpython/issues/58451] 中貢獻。）

tempfile.mkdtemp() 現在總是會傳回絕對路徑，即使提供給 dir 參數的引數是相對路徑。

threading

Add threading.settrace_all_threads() and threading.setprofile_all_threads() that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in gh-93503 [https://github.com/python/cpython/issues/93503].)

tkinter

tkinter.Canvas.coords() now flattens its arguments. It now accepts not only coordinates as separate arguments (x1, y1, x2, y2, ...) and a sequence of coordinates ([x1, y1, x2, y2, ...]), but also coordinates grouped in pairs ((x1, y1), (x2, y2), ... and [(x1, y1), (x2, y2), ...]), like create_*() methods. (Contributed by Serhiy Storchaka in gh-94473 [https://github.com/python/cpython/issues/94473].)

tokenize

The tokenize module includes the changes introduced in PEP 701 [https://peps.python.org/pep-0701/]. (Contributed by Marta Gómez Macías and Pablo Galindo in gh-102856 [https://github.com/python/cpython/issues/102856].) See 移植至 Python 3.12 for more information on the changes to the tokenize module.

types

Add types.get_original_bases() to allow for further introspection of 使用者定義泛型型別 when subclassed. (Contributed by James Hilton-Balfe and Alex Waygood in gh-101827 [https://github.com/python/cpython/issues/101827].)

typing

isinstance() checks against runtime-checkable protocols now use inspect.getattr_static() rather than hasattr() to lookup whether attributes exist. This means that descriptors and __getattr__() methods are no longer unexpectedly evaluated during isinstance() checks against runtime-checkable protocols. However, it may also mean that some objects which used to be considered instances of a runtime-checkable protocol may no longer be considered instances of that protocol on Python 3.12+, and vice versa. Most users are unlikely to be affected by this change. (Contributed by Alex Waygood in gh-102433 [https://github.com/python/cpython/issues/102433].)

The members of a runtime-checkable protocol are now considered "frozen" at runtime as soon as the class has been created. Monkey-patching attributes onto a runtime-checkable protocol will still work, but will have no impact on isinstance() checks comparing objects to the protocol. For example:

>>> from typing import Protocol, runtime_checkable
>>> @runtime_checkable
... class HasX(Protocol):
...     x = 1
...
>>> class Foo: ...
...
>>> f = Foo()
>>> isinstance(f, HasX)
False
>>> f.x = 1
>>> isinstance(f, HasX)
True
>>> HasX.y = 2
>>> isinstance(f, HasX)  # 沒有改變，即便 HasX 現在有 "y" 屬性
True

This change was made in order to speed up isinstance() checks against runtime-checkable protocols.

The performance profile of isinstance() checks against runtime-checkable protocols has changed significantly. Most isinstance() checks against protocols with only a few members should be at least 2x faster than in 3.11, and some may be 20x faster or more. However, isinstance() checks against protocols with many members may be slower than in Python 3.11. (Contributed by Alex Waygood in gh-74690 [https://github.com/python/cpython/issues/74690] and gh-103193 [https://github.com/python/cpython/issues/103193].)

All typing.TypedDict and typing.NamedTuple classes now have the __orig_bases__ attribute. (Contributed by Adrian Garcia Badaracco in gh-103699 [https://github.com/python/cpython/issues/103699].)

新增 frozen_default 參數至 typing.dataclass_transform()。（由 Erik De Bonte 於 gh-99957 [https://github.com/python/cpython/issues/99957] 中貢獻。）

unicodedata

The Unicode database has been updated to version 15.0.0. (Contributed by Benjamin Peterson in gh-96734 [https://github.com/python/cpython/issues/96734]).

unittest

新增 --durations 命令列選項，顯示 N 個最慢的測試案例：

python3 -m unittest --durations=3 lib.tests.test_threading
.....
Slowest test durations
----------------------------------------------------------------------
1.210s     test_timeout (Lib.test.test_threading.BarrierTests)
1.003s     test_default_timeout (Lib.test.test_threading.BarrierTests)
0.518s     test_timeout (Lib.test.test_threading.EventTests)

(0.000 durations hidden.  Use -v to show these durations.)
----------------------------------------------------------------------
Ran 158 tests in 9.869s

OK (skipped=3)

（由 Giampaolo Rodola 於 gh-48330 [https://github.com/python/cpython/issues/48330] 中貢獻。）

uuid

新增一個命令列介面。（由 Adam Chhina 於 gh-88597 [https://github.com/python/cpython/issues/88597] 中貢獻。）

最佳化

Remove wstr and wstr_length members from Unicode objects. It reduces object size by 8 or 16 bytes on 64bit platform. (PEP 623 [https://peps.python.org/pep-0623/]) (Contributed by Inada Naoki in gh-92536 [https://github.com/python/cpython/issues/92536].)

Add experimental support for using the BOLT binary optimizer in the build process, which improves performance by 1-5%. (Contributed by Kevin Modzelewski in gh-90536 [https://github.com/python/cpython/issues/90536] and tuned by Donghee Na in gh-101525 [https://github.com/python/cpython/issues/101525])

Speed up the regular expression substitution (functions re.sub() and re.subn() and corresponding re.Pattern methods) for replacement strings containing group references by 2--3 times. (Contributed by Serhiy Storchaka in gh-91524 [https://github.com/python/cpython/issues/91524].)

透過延遲運算較繁重的字串格式化來加速 asyncio.Task 的建立。（由 Itamar Oren 於 gh-103793 [https://github.com/python/cpython/issues/103793] 中貢獻。）

The tokenize.tokenize() and tokenize.generate_tokens() functions are up to 64% faster as a side effect of the changes required to cover PEP 701 [https://peps.python.org/pep-0701/] in the tokenize module. (Contributed by Marta Gómez Macías and Pablo Galindo in gh-102856 [https://github.com/python/cpython/issues/102856].)

Speed up super() method calls and attribute loads via the new LOAD_SUPER_ATTR instruction. (Contributed by Carl Meyer and Vladimir Matveev in gh-103497 [https://github.com/python/cpython/issues/103497].)

CPython 位元組碼變更

移除 LOAD_METHOD 指令。它已經合併至 LOAD_ATTR。LOAD_ATTR 現在會像舊的 LOAD_METHOD 指令一樣行為，如果其 oparg 的低位元 (low bit) 有被設定。（由 Ken Jin 於 gh-93429 [https://github.com/python/cpython/issues/93429] 中貢獻。）

移除 JUMP_IF_FALSE_OR_POP 和 JUMP_IF_TRUE_OR_POP 指令。（由 Irit Katriel 於 gh-102859 [https://github.com/python/cpython/issues/102859] 中貢獻。）

移除 PRECALL 指令。（由 Mark Shannon 於 gh-92925 [https://github.com/python/cpython/issues/92925] 中貢獻。）

新增 BINARY_SLICE 和 STORE_SLICE 指令。（由 Mark Shannon 於 gh-94163 [https://github.com/python/cpython/issues/94163] 中貢獻。）

新增 CALL_INTRINSIC_1 指令。（由 Mark Shannon 於 gh-99005 [https://github.com/python/cpython/issues/99005] 中貢獻。）

新增 CALL_INTRINSIC_2 指令。（由 Irit Katriel 於 gh-101799 [https://github.com/python/cpython/issues/101799] 中貢獻。）

新增 CLEANUP_THROW 指令。（由 Brandt Bucher 於 gh-90997 [https://github.com/python/cpython/issues/90997] 中貢獻。）

新增 END_SEND 指令。（由 Mark Shannon 於 gh-103082 [https://github.com/python/cpython/issues/103082] 中貢獻。）

新增 LOAD_FAST_AND_CLEAR 指令作為 PEP 709 [https://peps.python.org/pep-0709/] 實作的一部分。（由 Carl Meyer 於 gh-101441 [https://github.com/python/cpython/issues/101441] 中貢獻。）

新增 LOAD_FAST_CHECK 指令。（由 Dennis Sweeney 於 gh-93143 [https://github.com/python/cpython/issues/93143] 中貢獻。）

新增 LOAD_FROM_DICT_OR_DEREF、LOAD_FROM_DICT_OR_GLOBALS 和 LOAD_LOCALS 操作碼作為 PEP 695 [https://peps.python.org/pep-0695/] 實作的一部分。移除 LOAD_CLASSDEREF 操作碼，可以用 LOAD_LOCALS 加上 LOAD_FROM_DICT_OR_DEREF 來取代。（由 Jelle Zijlstra 於 gh-103764 [https://github.com/python/cpython/issues/103764] 中貢獻。）

新增 LOAD_SUPER_ATTR 指令。（由 Carl Meyer 和 Vladimir Matveev 於 gh-103497 [https://github.com/python/cpython/issues/103497] 中貢獻。）

新增 RETURN_CONST 指令。（由 Wenyang Wang 於 gh-101632 [https://github.com/python/cpython/issues/101632] 中貢獻。）

Demos and Tools

Remove the Tools/demo/ directory which contained old demo scripts. A copy can be found in the old-demos project [https://github.com/gvanrossum/old-demos]. (Contributed by Victor Stinner in gh-97681 [https://github.com/python/cpython/issues/97681].)

Remove outdated example scripts of the Tools/scripts/ directory. A copy can be found in the old-demos project [https://github.com/gvanrossum/old-demos]. (Contributed by Victor Stinner in gh-97669 [https://github.com/python/cpython/issues/97669].)

已棄用

argparse：argparse.BooleanOptionalAction 的 type、choices 和 metavar 參數已被棄用，將在 3.14 中移除。 (由 Nikita Sobolev 於 gh-92248 [https://github.com/python/cpython/issues/92248] 貢獻。)

ast：以下 ast 功能自 Python 3.8 起已在文件中被棄用，現在在存取或使用時會在 runtime 發出 DeprecationWarning，並將在 Python 3.14 中移除：

ast.Num

ast.Str

ast.Bytes

ast.NameConstant

ast.Ellipsis

請改用 ast.Constant。（由 Serhiy Storchaka 於 gh-90953 [https://github.com/python/cpython/issues/90953] 貢獻。）

asyncio：

已棄用並將在 Python 3.14 中移除的 child watcher 類別：asyncio.MultiLoopChildWatcher、asyncio.FastChildWatcher、asyncio.AbstractChildWatcher 和 asyncio.SafeChildWatcher。 (由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。)

asyncio.set_child_watcher()、asyncio.get_child_watcher()、asyncio.AbstractEventLoopPolicy.set_child_watcher() 和 asyncio.AbstractEventLoopPolicy.get_child_watcher() 已被棄用並將在 Python 3.14 中移除。（由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。）

預設事件迴圈策略的 get_event_loop() 方法現在會在沒有設定目前事件迴圈且決定建立一個時發出 DeprecationWarning。 (由 Serhiy Storchaka 和 Guido van Rossum 於 gh-100160 [https://github.com/python/cpython/issues/100160] 貢獻。)

calendar：calendar.January 和 calendar.February 常數已被棄用並被 calendar.JANUARY 和 calendar.FEBRUARY 取代。 (由 Prince Roshan 於 gh-103636 [https://github.com/python/cpython/issues/103636] 貢獻。)

collections.abc：棄用 collections.abc.ByteString。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

datetime: datetime.datetime's utcnow() and utcfromtimestamp() are deprecated and will be removed in a future version. Instead, use timezone-aware objects to represent datetimes in UTC: respectively, call now() and fromtimestamp() with the tz parameter set to datetime.UTC. (Contributed by Paul Ganssle in gh-103857 [https://github.com/python/cpython/issues/103857].)

email：棄用 email.utils.localtime() 中的 isdst 參數。（由 Alan Williams 於 gh-72346 [https://github.com/python/cpython/issues/72346] 中貢獻。）

importlib.abc：棄用下列類別，預定於 Python 3.14 中移除：

importlib.abc.ResourceReader

importlib.abc.Traversable

importlib.abc.TraversableResources

請改用 importlib.resources.abc 類別：

importlib.resources.abc.Traversable

importlib.resources.abc.TraversableResources

（由 Jason R. Coombs 和 Hugo van Kemenade 貢獻於 gh-93963 [https://github.com/python/cpython/issues/93963]。）

itertools: Deprecate the support for copy, deepcopy, and pickle operations, which is undocumented, inefficient, historically buggy, and inconsistent. This will be removed in 3.14 for a significant reduction in code volume and maintenance burden. (Contributed by Raymond Hettinger in gh-101588 [https://github.com/python/cpython/issues/101588].)

multiprocessing: In Python 3.14, the default multiprocessing start method will change to a safer one on Linux, BSDs, and other non-macOS POSIX platforms where 'fork' is currently the default (gh-84559 [https://github.com/python/cpython/issues/84559]). Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care. Use the get_context() or set_start_method() APIs to explicitly specify when your code requires 'fork'. See contexts and start methods.

pkgutil：pkgutil.find_loader() 和 pkgutil.get_loader() 已被棄用並將在 Python 3.14 中移除；請改用 importlib.util.find_spec()。（由 Nikita Sobolev 於 gh-97850 [https://github.com/python/cpython/issues/97850] 中貢獻。）

pty: The module has two undocumented master_open() and slave_open() functions that have been deprecated since Python 2 but only gained a proper DeprecationWarning in 3.12. Remove them in 3.14. (Contributed by Soumendra Ganguly and Gregory P. Smith in gh-85984 [https://github.com/python/cpython/issues/85984].)

os：

The st_ctime fields return by os.stat() and os.lstat() on Windows are deprecated. In a future release, they will contain the last metadata change time, consistent with other platforms. For now, they still contain the creation time, which is also available in the new st_birthtime field. (Contributed by Steve Dower in gh-99726 [https://github.com/python/cpython/issues/99726].)

On POSIX platforms, os.fork() can now raise a DeprecationWarning when it can detect being called from a multithreaded process. There has always been a fundamental incompatibility with the POSIX platform when doing so. Even if such code appeared to work. We added the warning to raise awareness as issues encountered by code doing this are becoming more frequent. See the os.fork() documentation for more details along with this discussion on fork being incompatible with threads [https://discuss.python.org/t/concerns-regarding-deprecation-of-fork-with-alive-threads/33555] for why we're now surfacing this longstanding platform compatibility problem to developers.

When this warning appears due to usage of multiprocessing or concurrent.futures the fix is to use a different multiprocessing start method such as "spawn" or "forkserver".

shutil：shutil.rmtree() 的 onerror 引數已被棄用，請改用 onexc。（由 Irit Katriel 於 gh-102828 [https://github.com/python/cpython/issues/102828] 中貢獻。）

sqlite3：

default adapters and converters are now deprecated. Instead, use the Adapter and converter recipes and tailor them to your needs. (Contributed by Erlend E. Aasland in gh-90016 [https://github.com/python/cpython/issues/90016].)

In execute(), DeprecationWarning is now emitted when named placeholders are used together with parameters supplied as a sequence instead of as a dict. Starting from Python 3.14, using named placeholders with parameters supplied as a sequence will raise a ProgrammingError. (Contributed by Erlend E. Aasland in gh-101698 [https://github.com/python/cpython/issues/101698].)

sys：sys.last_type、sys.last_value 和 sys.last_traceback 欄位已被棄用。請改用 sys.last_exc。（由 Irit Katriel 於 gh-102778 [https://github.com/python/cpython/issues/102778] 中貢獻。）

tarfile: Extracting tar archives without specifying filter is deprecated until Python 3.14, when 'data' filter will become the default. See 解壓縮篩選器 for details.

typing：

typing.Hashable and typing.Sized, aliases for collections.abc.Hashable and collections.abc.Sized respectively, are deprecated. (gh-94309 [https://github.com/python/cpython/issues/94309].)

自 Python 3.9 起已被棄用的 typing.ByteString 現在在使用時會發出 DeprecationWarning。（由 Alex Waygood 於 gh-91896 [https://github.com/python/cpython/issues/91896] 中貢獻。）

xml.etree.ElementTree: The module now emits DeprecationWarning when testing the truth value of an xml.etree.ElementTree.Element. Before, the Python implementation emitted FutureWarning, and the C implementation emitted nothing. (Contributed by Jacob Walls in gh-83122 [https://github.com/python/cpython/issues/83122].)

The 3-arg signatures (type, value, traceback) of coroutine throw(), generator throw() and async generator throw() are deprecated and may be removed in a future version of Python. Use the single-arg versions of these functions instead. (Contributed by Ofey Chan in gh-89874 [https://github.com/python/cpython/issues/89874].)

DeprecationWarning is now raised when __package__ on a module differs from __spec__.parent (previously it was ImportWarning). (Contributed by Brett Cannon in gh-65961 [https://github.com/python/cpython/issues/65961].)

Setting __package__ or __cached__ on a module is deprecated, and will cease to be set or taken into consideration by the import system in Python 3.14. (Contributed by Brett Cannon in gh-65961 [https://github.com/python/cpython/issues/65961].)

The bitwise inversion operator (~) on bool is deprecated. It will throw an error in Python 3.16. Use not for logical negation of bools instead. In the rare case that you really need the bitwise inversion of the underlying int, convert to int explicitly: ~int(x). (Contributed by Tim Hoffmann in gh-103487 [https://github.com/python/cpython/issues/103487].)

自 3.10 起，於程式碼物件存取 co_lnotab 的功能已在 PEP 626 [https://peps.python.org/pep-0626/] 中被棄用，但只在 3.12 中於適時發出 DeprecationWarning。可能在 3.15 中移除。（由 Nikita Sobolev 於 gh-101866 [https://github.com/python/cpython/issues/101866] 貢獻。）

Python 3.13 中待移除的項目

模組（請見 PEP 594 [https://peps.python.org/pep-0594/]）：

aifc

audioop

cgi

cgitb

chunk

crypt

imghdr

mailcap

msilib

nis

nntplib

ossaudiodev

pipes

sndhdr

spwd

sunau

telnetlib

uu

xdrlib

其他模組：

lib2to3 和 2to3 程式 (gh-84540 [https://github.com/python/cpython/issues/84540])

API：

configparser.LegacyInterpolation (gh-90765 [https://github.com/python/cpython/issues/90765])

locale.resetlocale() (gh-90817 [https://github.com/python/cpython/issues/90817])

turtle.RawTurtle.settiltangle() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.findTestCases() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.getTestCaseNames() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.makeSuite() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.TestProgram.usageExit() (gh-67048 [https://github.com/python/cpython/issues/67048])

webbrowser.MacOSX (gh-86421 [https://github.com/python/cpython/issues/86421])

classmethod 描述器鏈接 (gh-89519 [https://github.com/python/cpython/issues/89519])

Python 3.14 中待移除的項目

argparse：argparse.BooleanOptionalAction 的 type、choices 和 metavar 參數已被棄用，將在 3.14 中移除。 (由 Nikita Sobolev 於 gh-92248 [https://github.com/python/cpython/issues/92248] 貢獻。)

ast：自 Python 3.8 起，下列功能已在文件中被棄用，現在在存取或使用時會於 runtime 發出 DeprecationWarning，並將在 Python 3.14 中移除：

ast.Num

ast.Str

ast.Bytes

ast.NameConstant

ast.Ellipsis

請改用 ast.Constant。（由 Serhiy Storchaka 於 gh-90953 [https://github.com/python/cpython/issues/90953] 貢獻。）

asyncio：

已棄用並將在 Python 3.14 中移除的 child watcher 類別：asyncio.MultiLoopChildWatcher、asyncio.FastChildWatcher、asyncio.AbstractChildWatcher 和 asyncio.SafeChildWatcher。 (由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。)

asyncio.set_child_watcher()、asyncio.get_child_watcher()、asyncio.AbstractEventLoopPolicy.set_child_watcher() 和 asyncio.AbstractEventLoopPolicy.get_child_watcher() 已被棄用並將在 Python 3.14 中移除。（由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。）

預設事件迴圈策略的 get_event_loop() 方法現在會在沒有設定目前事件迴圈且決定建立一個時發出 DeprecationWarning。 (由 Serhiy Storchaka 和 Guido van Rossum 於 gh-100160 [https://github.com/python/cpython/issues/100160] 貢獻。)

email：已棄用 email.utils.localtime() 中的 isdst 參數。（由 Alan Williams 於 gh-72346 [https://github.com/python/cpython/issues/72346] 貢獻。）

importlib.abc 的已棄用類別：

importlib.abc.ResourceReader

importlib.abc.Traversable

importlib.abc.TraversableResources

請改用 importlib.resources.abc 類別：

importlib.resources.abc.Traversable

importlib.resources.abc.TraversableResources

（由 Jason R. Coombs 和 Hugo van Kemenade 貢獻於 gh-93963 [https://github.com/python/cpython/issues/93963]。）

itertools 有不以文件記錄、效率低下、過去常有 bug 且不一致的 copy、deepcopy 和 pickle 操作支援。將在 3.14 中移除以大幅減少程式碼量和維護負擔。 (由 Raymond Hettinger 於 gh-101588 [https://github.com/python/cpython/issues/101588] 貢獻。)

multiprocessing：預設的啟動方法將在 Linux、BSD 和其他非 macOS POSIX 平台上更改為更安全的 方法，目前 'fork' 是預設值 (gh-84559 [https://github.com/python/cpython/issues/84559])。對此增加一個 runtime 警告被認為太過擾人，因為 大多數程式碼不會在意。請使用 get_context() 或 set_start_method() API 來明確指定你的程式碼何時需要 'fork'。請參閱 Contexts and start methods。

pathlib：已棄用 is_relative_to() 和 relative_to()：額外引數的傳遞已被棄用。

pkgutil：pkgutil.find_loader() 和 pkgutil.get_loader() 現在會引發 DeprecationWarning；請改用 importlib.util.find_spec()。 (由 Nikita Sobolev 於 gh-97850 [https://github.com/python/cpython/issues/97850] 貢獻。)

pty：

master_open()：請用 pty.openpty()。

slave_open()：請用 pty.openpty()。

sqlite3：

version 和 version_info。

execute() 和 executemany()，如果使用 named placeholders 且 parameters 是序列而不是 dict。

urllib：urllib.parse.Quoter 已被棄用：它並非預期的公開 API。(由 Gregory P. Smith 於 gh-88168 [https://github.com/python/cpython/issues/88168] 貢獻。)

Python 3.15 中待移除的項目

引入系統 (import system)：

在模組上設定 __cached__ 而沒有設定 __spec__.cached 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __cached__。(gh-97879 [https://github.com/python/cpython/issues/97879])

在模組上設定 __package__ 而沒有設定 __spec__.parent 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __package__。(gh-97879 [https://github.com/python/cpython/issues/97879])

ctypes：

自 Python 3.13 起，未記錄的 ctypes.SetPointerType() 函式已被棄用。

http.server：

過時且很少使用的 CGIHTTPRequestHandler 自 Python 3.13 起已被棄用。不存在直接的替代。任何東西都比 CGI 更好地將 Web 伺服器與請求處理程序介接起來。

自 Python 3.13 起，python -m http.server 命令列介面的 --cgi 旗標已被棄用。

importlib：

load_module() method：請改用 exec_module()。

locale：

getdefaultlocale() 已在 Python 3.11 中被棄用，原本計劃在 Python 3.13 中移除 (gh-90817 [https://github.com/python/cpython/issues/90817])，但被延後至 Python 3.15。請改用 getlocale()、setlocale() 和 getencoding()。 (由 Hugo van Kemenade 於 gh-111187 [https://github.com/python/cpython/issues/111187] 貢獻。)

pathlib：

PurePath.is_reserved() 已自 Python 3.13 被棄用。請用 os.path.isreserved() 來偵測 Windows 上的保留路徑。

platform：

自 Python 3.13 起，java_ver() 已被棄用。此函式僅對 Jython 支援有用，具有令人困惑的 API，基本上未經測試。

sysconfig：

sysconfig.is_python_build() 的 check_home 引數自 Python 3.12 起已被棄用。

threading：

RLock() 在 Python 3.15 中將不接受任何引數。自 Python 3.14 起，傳遞任何引數的用法已被棄用，因為 Python 版本不允許任何引數，但 C 版本允許任意數量的位置或關鍵字引數，並忽略每個引數。

types：

types.CodeType：自 3.10 起，存取 co_lnotab 已在 PEP 626 [https://peps.python.org/pep-0626/] 中被棄用，並計劃在 3.12 中移除，但只在 3.12 中於適當時發出 DeprecationWarning。可能在 3.15 中移除。（由 Nikita Sobolev 於 gh-101866 [https://github.com/python/cpython/issues/101866] 貢獻。）

typing：

用於建立 NamedTuple 類別的未以文件記錄之關鍵字引數語法 (Point = NamedTuple("Point", x=int, y=int)) 已自 Python 3.13 棄用。請改用基於類別的語法或函式語法 (functional syntax)。

當使用 TypedDict 的函式語法時，未傳遞值給 fields 參數 (TD = TypedDict("TD")) 或傳遞 None (TD = TypedDict("TD", None)) 的做法自 Python 3.13 起已被棄用。請使用 class TD(TypedDict): pass 或 TD = TypedDict("TD", {}) 來建立具有零個欄位的 TypedDict。

自 Python 3.13 起，typing.no_type_check_decorator() 裝飾器函式已被棄用。在 typing 模組中使用了八年之後，它尚未得到任何主要型別檢查器的支援。

wave：

已棄用 Wave_read 和 Wave_write 類別的 getmark()、setmark() 和 getmarkers() 方法自 Python 3.13 被棄用。

zipimport：

load_module() 自 Python 3.10 被棄用。請改用 exec_module()。（由 Jiahao Li 於 gh-125746 [https://github.com/python/cpython/issues/125746] 貢獻。）

Python 3.16 中待移除的項目

引入系統 (import system)：

在模組上設定 __loader__ 而沒有設定 __spec__.loader 的做法將於 Python 3.16 被棄用。在 Python 3.16 中，引入系統或標準函式庫將不再設定或考慮 __loader__。

array：

自 Python 3.3 起，'u' 格式碼 (wchar_t) 在文件中已被棄用，自 Python 3.13 起在 runtime 已被棄用。請使用 'w' 格式碼 (Py_UCS4) 來取代 Unicode 字元。

asyncio：

asyncio.iscoroutinefunction() 已被棄用並將在 Python 3.16 中移除；請改用 inspect.iscoroutinefunction()。（由 Jiahao Li 和 Kumar Aditya 於 gh-122875 [https://github.com/python/cpython/issues/122875] 貢獻。）

asyncio 策略系統已被棄用並將在 Python 3.16 中移除。特別是以下類別和函式已被棄用：

asyncio.AbstractEventLoopPolicy

asyncio.DefaultEventLoopPolicy

asyncio.WindowsSelectorEventLoopPolicy

asyncio.WindowsProactorEventLoopPolicy

asyncio.get_event_loop_policy()

asyncio.set_event_loop_policy()

使用者應該使用 asyncio.run() 或 asyncio.Runner 搭配 loop_factory 來使用所需的事件迴圈實作。

例如在 Windows 上使用 asyncio.SelectorEventLoop：

import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

（由 Kumar Aditya 於 gh-127949 [https://github.com/python/cpython/issues/127949] 貢獻。）

builtins：

自 Python 3.12 起，布林型別的位元反轉 ~True 或 ~False 已被棄用，因為它會產生不預期且不直觀的結果（-2 和 -1）。使用 not x 代替布林值的邏輯否定。在極少數情況下，你需要對底層的整數進行位元反轉，請明確轉換為 ~int(x) (~int(x))。

functools：

自 Python 3.14 起，使用 function 或 sequence 關鍵字引數呼叫 functools.reduce() 的 Python 實作已被棄用。

logging：

對具有 strm 引數的自訂日誌記錄處理函式的支援已被棄用，並計劃在 Python 3.16 中移除。請改用 stream 引數。（由 Mariusz Felisiak 於 gh-115032 [https://github.com/python/cpython/issues/115032] 貢獻。）

mimetypes：

有效的副檔名以 '.' 開頭或對 mimetypes.MimeTypes.add_type() 為空字串。未加點的副檔名已被棄用，並將在 Python 3.16 中引發 ValueError。（由 Hugo van Kemenade 於 gh-75223 [https://github.com/python/cpython/issues/75223] 貢獻。）

shutil：

自 Python 3.14 起，ExecError 例外已被棄用。自 Python 3.4 以來，它尚未被 shutil 中的任何函式使用，現在是 RuntimeError 的別名。

symtable：

自 Python 3.14 起，Class.get_methods 方法已被棄用。

sys：

自 Python 3.13 起，_enablelegacywindowsfsencoding() 函式已被棄用。請改用 PYTHONLEGACYWINDOWSFSENCODING 環境變數。

sysconfig：

自 Python 3.14 起，sysconfig.expand_makefile_vars() 函式已被棄用。請改用 sysconfig.get_paths() 的 vars 引數。

tarfile：

自 Python 3.13 起，未以文件記錄和未被使用的 TarFile.tarfile 屬性已被棄用。

Python 3.17 中待移除的項目

collections.abc：

collections.abc.ByteString 預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

typing：

在 Python 3.14 之前，舊式聯集是使用私有類別 typing._UnionGenericAlias 實作的。這個類別不再被需要，但為了向後相容性而保留，並計劃將在 Python 3.17 中移除。使用者應該改用文件中記錄的內省輔助函式，例如 typing.get_origin() 和 typing.get_args()，或者依賴私有實作細節。

typing.ByteString 自 Python 3.9 起已被棄用，預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

未來版本中的待移除項目

以下 API 將在未來被移除，雖然目前尚未安排移除日期。

argparse：

巢狀引數群組和巢狀互斥群組已被棄用。

將未以文件記錄的關鍵字引數 prefix_chars 傳遞給 add_argument_group() 的做法現在已被棄用。

argparse.FileType 型別轉換器已被棄用。

builtins：

產生器：throw(type, exc, tb) 和 athrow(type, exc, tb) 簽名已被棄用：請改用 throw(exc) 和 athrow(exc)，為單引數簽名。

目前 Python 接受數值字面值後面立即接關鍵字，例如 0in x、1or x、0if 1else 2。它讓運算式模糊且容易混淆，如 [0x1for x in y]（可以解釋為 [0x1 for x in y] 或 [0x1f or x in y]）。如果數值字面值後立即接 and、else、for、if、in、is 和 or 之一的關鍵字，則會引發語法警告。在未來版本中，它將被更改為語法錯誤。(gh-87999 [https://github.com/python/cpython/issues/87999])

__index__() 和 __int__() 方法回傳非 int 型別的支援：這些方法將需要回傳 int 的嚴格子類別實例。

回傳 float 嚴格子類別 __float__() 方法的支援：這些方法將需要回傳 float 的實例。

回傳 complex 嚴格子類別 __complex__() 方法的支援：這些方法將需要回傳 complex 的實例。

將 int() 委派給 __trunc__() 方法。

在 complex() 建構子中將複數作為 real 或 imag 引數傳遞現在已被棄用；它應該只作為單個位置引數傳遞。 (由 Serhiy Storchaka 於 gh-109218 [https://github.com/python/cpython/issues/109218] 貢獻。)

calendar：calendar.January 和 calendar.February 常數已被棄用並被 calendar.JANUARY 和 calendar.FEBRUARY 取代。 (由 Prince Roshan 於 gh-103636 [https://github.com/python/cpython/issues/103636] 貢獻。)

codecs：請改用 open() 而非 codecs.open()。(gh-133038 [https://github.com/python/cpython/issues/133038])

codeobject.co_lnotab：請改用 codeobject.co_lines() 方法。

datetime：

utcnow()：請改用 datetime.datetime.now(tz=datetime.UTC)。

utcfromtimestamp()：請改用 datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)。

gettext：複數值必須是整數。

importlib：

cache_from_source() debug_override 參數已被棄用：請改用 optimization 參數。

importlib.metadata：

EntryPoints 元組介面。

回傳值上的隱式 None。

logging：自 Python 3.3 起，warn() 方法已被棄用，請改用 warning()。

mailbox：已棄用 StringIO 輸入和文本模式，請改用 BytesIO 和二進位模式。

os：在多執行緒行程中呼叫 os.register_at_fork()。

pydoc.ErrorDuringImport：exc_info 參數的元組值已被棄用，請用例外實例。

re：現在對正規表示式中的數值群組參照和群組名稱用了更嚴格的規則。現在只有 ASCII 數碼序列被接受作為數值參照。位元組模式和替換字串中的群組名稱現在只能包含 ASCII 字母、數碼和底線。（由 Serhiy Storchaka 於 gh-91760 [https://github.com/python/cpython/issues/91760] 貢獻。）

sre_compile、sre_constants 和 sre_parse 模組。

shutil：rmtree() 的 onerror 參數在 Python 3.12 中已被棄用；請改用 onexc 參數。

ssl 選項和協定：

不帶協定引數的 ssl.SSLContext 已被棄用。

ssl.SSLContext：set_npn_protocols() 和 selected_npn_protocol() 已被棄用：請改用 ALPN。

ssl.OP_NO_SSL* 選項

ssl.OP_NO_TLS* 選項

ssl.PROTOCOL_SSLv3

ssl.PROTOCOL_TLS

ssl.PROTOCOL_TLSv1

ssl.PROTOCOL_TLSv1_1

ssl.PROTOCOL_TLSv1_2

ssl.TLSVersion.SSLv3

ssl.TLSVersion.TLSv1

ssl.TLSVersion.TLSv1_1

threading 方法：

threading.Condition.notifyAll()：請用 notify_all()。

threading.Event.isSet()：請用 is_set()。

threading.Thread.isDaemon()、threading.Thread.setDaemon()：請用 threading.Thread.daemon 屬性。

threading.Thread.getName()、threading.Thread.setName()：請用 threading.Thread.name 屬性。

threading.currentThread()：請用 threading.current_thread()。

threading.activeCount()：請用 threading.active_count()。

typing.Text (gh-92332 [https://github.com/python/cpython/issues/92332])。

內部類別 typing._UnionGenericAlias 不再用於實作 typing.Union。為了保持與此私有類別使用者的相容性，直到至少 Python 3.17 都將提供一個相容性 shim。（由 Jelle Zijlstra 於 gh-105499 [https://github.com/python/cpython/issues/105499] 貢獻。）

unittest.IsolatedAsyncioTestCase：從測試案例中回傳非 None 的值已被棄用。

urllib.parse 已棄用函式：請改用 urlparse()。

splitattr()

splithost()

splitnport()

splitpasswd()

splitport()

splitquery()

splittag()

splittype()

splituser()

splitvalue()

to_bytes()

wsgiref：SimpleHandler.stdout.write() 不應該進行部分寫入。

xml.etree.ElementTree：已棄用對 Element 的真值測試。在未來版本中，它將始終回傳 True。請改用明確的 len(elem) 或 elem is not None 測試。

sys._clear_type_cache() 已被棄用：請改用 sys._clear_internal_caches()。

已移除

asynchat 和 asyncore

These two modules have been removed according to the schedule in PEP 594 [https://peps.python.org/pep-0594/], having been deprecated in Python 3.6. Use asyncio instead. (Contributed by Nikita Sobolev in gh-96580 [https://github.com/python/cpython/issues/96580].)

configparser

根據 gh-89336 [https://github.com/python/cpython/issues/89336]，已移除了在 3.2 中被 configparser 棄用的幾個名稱：

configparser.ParsingError 不再具有 filename 屬性或引數。請改用 source 屬性和引數。

configparser 不再具有 SafeConfigParser 類別。請改用較短的 ConfigParser 名稱。

configparser.ConfigParser 不再具有 readfp 方法。請改用 read_file()。

distutils

Remove the distutils package. It was deprecated in Python 3.10 by PEP 632 [https://peps.python.org/pep-0632/] "Deprecate distutils module". For projects still using distutils and cannot be updated to something else, the setuptools project can be installed: it still provides distutils. (Contributed by Victor Stinner in gh-92584 [https://github.com/python/cpython/issues/92584].)

ensurepip

Remove the bundled setuptools wheel from ensurepip, and stop installing setuptools in environments created by venv.

pip (>= 22.1) 不需要在環境中安裝 setuptools。基於 setuptools（以及基於 distutils）的套件仍然可以透過 pip install 來使用，因為 pip 會在其用於建置套件的建置環境中提供 setuptools。

以 venv 建立或以 ensurepip 啟動引導的環境中不再預設提供 easy_install、pkg_resources、setuptools 和 distutils，因為它們是 setuptools 套件的一部分。對於在 runtime 依賴這些工具的專案，應將 setuptools 專案宣告為相依套件並單獨安裝（通常使用 pip）。

（由 Pradyun Gedam 於 gh-95299 [https://github.com/python/cpython/issues/95299] 中貢獻。）

enum

移除 enum 的 EnumMeta.__getattr__，對於列舉屬性的存取不再會需要它。

ftplib

移除 ftplib 的 FTP_TLS.ssl_version 類別屬性：請改用 context 參數。（由 Victor Stinner 於 gh-94172 [https://github.com/python/cpython/issues/94172] 中貢獻。）

gzip

Remove the filename attribute of gzip's gzip.GzipFile, deprecated since Python 2.6, use the name attribute instead. In write mode, the filename attribute added '.gz' file extension if it was not present. (Contributed by Victor Stinner in gh-94196 [https://github.com/python/cpython/issues/94196].)

hashlib

Remove the pure Python implementation of hashlib's hashlib.pbkdf2_hmac(), deprecated in Python 3.10. Python 3.10 and newer requires OpenSSL 1.1.1 (PEP 644 [https://peps.python.org/pep-0644/]): this OpenSSL version provides a C implementation of pbkdf2_hmac() which is faster. (Contributed by Victor Stinner in gh-94199 [https://github.com/python/cpython/issues/94199].)

importlib

現已完成清理 importlib 中許多過去已經棄用的東西：

對 module_repr() 的參照和支援已刪除。（由 Barry Warsaw 在 gh-97850 [https://github.com/python/cpython/issues/97850] 中貢獻。）

importlib.util.set_package、importlib.util.set_loader 和 importlib.util.module_for_loader 已全部刪除。（由 Brett Cannon 和 Nikita Sobolev 在 gh-65961 [https://github.com/python/cpython/issues/65961] 和 gh-97850 [https://github.com/python/cpython/issues/97850] 貢獻。）

對 find_loader() 和 find_module() API 的支援已被刪除。（由 Barry Warsaw 在 gh-98040 [https://github.com/python/cpython/issues/98040] 中貢獻。）

importlib.abc.Finder、pkgutil.ImpImporter 和 pkgutil.ImpLoader 已被刪除。（由 Barry Warsaw 在 gh-98040 [https://github.com/python/cpython/issues/98040] 中貢獻。）

imp

imp 模組已被移除。（由 Barry Warsaw 在 gh-98040 [https://github.com/python/cpython/issues/98040] 中貢獻。）

要遷移的話請參考以下對應表：

imp

importlib

imp.NullImporter

將 None 插入 sys.path_importer_cache

imp.cache_from_source()

importlib.util.cache_from_source()

imp.find_module()

importlib.util.find_spec()

imp.get_magic()

importlib.util.MAGIC_NUMBER

imp.get_suffixes()

importlib.machinery.SOURCE_SUFFIXES、importlib.machinery.EXTENSION_SUFFIXES 和 importlib.machinery.BYTECODE_SUFFIXES

imp.get_tag()

sys.implementation.cache_tag

imp.load_module()

importlib.import_module()

imp.new_module(name)

types.ModuleType(name)

imp.reload()

importlib.reload()

imp.source_from_cache()

importlib.util.source_from_cache()

imp.load_source()

見下文

用以下取代 imp.load_source()：

import importlib.util
import importlib.machinery

def load_source(modname, filename):
    loader = importlib.machinery.SourceFileLoader(modname, filename)
    spec = importlib.util.spec_from_file_location(modname, filename, loader=loader)
    module = importlib.util.module_from_spec(spec)
    # 此模組都會被執行且不會被快取於 sys.modules。
    # 要快取模組的話可以把下面一行取消註解
    # sys.modules[module.__name__] = module
    loader.exec_module(module)
    return module

移除 imp 函式和屬性、沒有替代方案：

未以文件記錄的函式：

imp.init_builtin()

imp.load_compiled()

imp.load_dynamic()

imp.load_package()

imp.lock_held(), imp.acquire_lock(), imp.release_lock(): the locking scheme has changed in Python 3.3 to per-module locks.

imp.find_module() 常數：SEARCH_ERROR、PY_SOURCE、PY_COMPILED、C_EXTENSION、PY_RESOURCE、PKG_DIRECTORY、C_BUILTIN、PY_FROZEN、PY_CODERESOURCE、IMP_HOOK。

io

Remove io's io.OpenWrapper and _pyio.OpenWrapper, deprecated in Python 3.10: just use open() instead. The open() (io.open()) function is a built-in function. Since Python 3.10, _pyio.open() is also a static method. (Contributed by Victor Stinner in gh-94169 [https://github.com/python/cpython/issues/94169].)

locale

Remove locale's locale.format() function, deprecated in Python 3.7: use locale.format_string() instead. (Contributed by Victor Stinner in gh-94226 [https://github.com/python/cpython/issues/94226].)

smtpd

根據 PEP 594 [https://peps.python.org/pep-0594/] 的時間表移除 smtpd 模組，它在 Python 3.4.7 和 3.5.4 中已被棄用。請改用 PyPI 上的 aiosmtpd [https://pypi.org/project/aiosmtpd/] 模組或任何其他基於 asyncio 的伺服器。

sqlite3

以下未以文件記錄的 sqlite3 功能已在 Python 3.10 中被棄用、現在已被移除：

sqlite3.enable_shared_cache()

sqlite3.OptimizedUnicode

If a shared cache must be used, open the database in URI mode using the cache=shared query parameter.

The sqlite3.OptimizedUnicode text factory has been an alias for str since Python 3.3. Code that previously set the text factory to OptimizedUnicode can either use str explicitly, or rely on the default value which is also str.

（由 Erlend E. Aasland 於 gh-92548 [https://github.com/python/cpython/issues/92548] 中貢獻。）

ssl

移除 ssl 的 ssl.RAND_pseudo_bytes() 函式，該函式自 Python 3.6 起已被棄用：請改用 os.urandom() 或 ssl.RAND_bytes()。（由 Victor Stinner 於 gh-94199 [https://github.com/python/cpython/issues/94199] 中貢獻。）

移除 ssl.match_hostname() 函式。該函式自 Python 3.7 起已被棄用。自 Python 3.7 起，OpenSSL 會執行主機名稱比對，Python 不再使用 ssl.match_hostname() 函式。（由 Victor Stinner 於 gh-94199 [https://github.com/python/cpython/issues/94199] 中貢獻。）

移除 ssl.wrap_socket() 函式，該函式自 Python 3.7 起已被棄用：請改為建立一個 ssl.SSLContext 物件並呼叫其 ssl.SSLContext.wrap_socket 方法。任何仍在使用 ssl.wrap_socket() 的套件都是有問題且不安全的。該函式既不傳送 SNI TLS 擴充，也不驗證伺服器主機名稱。程式碼會受到 CWE 295 [https://cwe.mitre.org/data/definitions/295.html]（不當的憑證驗證）影響。（由 Victor Stinner 於 gh-94199 [https://github.com/python/cpython/issues/94199] 中貢獻。）

unittest

移除許多 unittest 中被棄用已久的功能：

許多 TestCase 方法別名：

已棄用的別名

方法名稱

已棄用於

failUnless

assertTrue()

3.1

failIf

assertFalse()

3.1

failUnlessEqual

assertEqual()

3.1

failIfEqual

assertNotEqual()

3.1

failUnlessAlmostEqual

assertAlmostEqual()

3.1

failIfAlmostEqual

assertNotAlmostEqual()

3.1

failUnlessRaises

assertRaises()

3.1

assert_

assertTrue()

3.2

assertEquals

assertEqual()

3.2

assertNotEquals

assertNotEqual()

3.2

assertAlmostEquals

assertAlmostEqual()

3.2

assertNotAlmostEquals

assertNotAlmostEqual()

3.2

assertRegexpMatches

assertRegex()

3.2

assertRaisesRegexp

assertRaisesRegex()

3.2

assertNotRegexpMatches

assertNotRegex()

3.5

你可以使用 https://github.com/isidentical/teyit 來自動現代化你的單元測試。

未以文件記錄且已失效的 TestCase 方法 assertDictContainsSubset（自 Python 3.2 起已棄用）。

Undocumented TestLoader.loadTestsFromModule parameter use_load_tests (deprecated and ignored since Python 3.5).

對 TextTestResult 類別的別名：_TextTestResult（自 Python 3.2 起已棄用）。

（由 Serhiy Storchaka 於 gh-89325 [https://github.com/python/cpython/issues/89325] 中貢獻。）

webbrowser

Remove support for obsolete browsers from webbrowser. The removed browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone, Iceape, Firebird, and Firefox versions 35 and below (gh-102871 [https://github.com/python/cpython/issues/102871]).

xml.etree.ElementTree

Remove the ElementTree.Element.copy() method of the pure Python implementation, deprecated in Python 3.10, use the copy.copy() function instead. The C implementation of xml.etree.ElementTree has no copy() method, only a __copy__() method. (Contributed by Victor Stinner in gh-94383 [https://github.com/python/cpython/issues/94383].)

zipimport

Remove zipimport's find_loader() and find_module() methods, deprecated in Python 3.10: use the find_spec() method instead. See PEP 451 [https://peps.python.org/pep-0451/] for the rationale. (Contributed by Victor Stinner in gh-94379 [https://github.com/python/cpython/issues/94379].)

其他

Remove the suspicious rule from the documentation Makefile and Doc/tools/rstlint.py, both in favor of sphinx-lint [https://github.com/sphinx-contrib/sphinx-lint]. (Contributed by Julien Palard in gh-98179 [https://github.com/python/cpython/issues/98179].)

Remove the keyfile and certfile parameters from the ftplib, imaplib, poplib and smtplib modules, and the key_file, cert_file and check_hostname parameters from the http.client module, all deprecated since Python 3.6. Use the context parameter (ssl_context in imaplib) instead. (Contributed by Victor Stinner in gh-94172 [https://github.com/python/cpython/issues/94172].)

移除數個標準函式庫模組與測試中的 Jython 相容性修補程式。（由 Nikita Sobolev 於 gh-99482 [https://github.com/python/cpython/issues/99482] 中貢獻。）

移除 ctypes 模組中的 _use_broken_old_ctypes_structure_semantics_ 旗標。（由 Nikita Sobolev 於 gh-99285 [https://github.com/python/cpython/issues/99285] 中貢獻。）

移植至 Python 3.12

This section lists previously described changes and other bugfixes that may require changes to your code.

Python API 的變更

More strict rules are now applied for numerical group references and group names in regular expressions. Only sequence of ASCII digits is now accepted as a numerical reference. The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore. (Contributed by Serhiy Storchaka in gh-91760 [https://github.com/python/cpython/issues/91760].)

Remove randrange() functionality deprecated since Python 3.10. Formerly, randrange(10.0) losslessly converted to randrange(10). Now, it raises a TypeError. Also, the exception raised for non-integer values such as randrange(10.5) or randrange('10') has been changed from ValueError to TypeError. This also prevents bugs where randrange(1e25) would silently select from a larger range than randrange(10**25). (Originally suggested by Serhiy Storchaka gh-86388 [https://github.com/python/cpython/issues/86388].)

argparse.ArgumentParser changed encoding and error handler for reading arguments from file (e.g. fromfile_prefix_chars option) from default text encoding (e.g. locale.getpreferredencoding(False)) to filesystem encoding and error handler. Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.

Remove the asyncore-based smtpd module deprecated in Python 3.4.7 and 3.5.4. A recommended replacement is the asyncio-based aiosmtpd [https://pypi.org/project/aiosmtpd/] PyPI module.

shlex.split(): Passing None for s argument now raises an exception, rather than reading sys.stdin. The feature was deprecated in Python 3.9. (Contributed by Victor Stinner in gh-94352 [https://github.com/python/cpython/issues/94352].)

The os module no longer accepts bytes-like paths, like bytearray and memoryview types: only the exact bytes type is accepted for bytes strings. (Contributed by Victor Stinner in gh-98393 [https://github.com/python/cpython/issues/98393].)

syslog.openlog() and syslog.closelog() now fail if used in subinterpreters. syslog.syslog() may still be used in subinterpreters, but now only if syslog.openlog() has already been called in the main interpreter. These new restrictions do not apply to the main interpreter, so only a very small set of users might be affected. This change helps with interpreter isolation. Furthermore, syslog is a wrapper around process-global resources, which are best managed from the main interpreter. (Contributed by Donghee Na in gh-99127 [https://github.com/python/cpython/issues/99127].)

The undocumented locking behavior of cached_property() is removed, because it locked across all instances of the class, leading to high lock contention. This means that a cached property getter function could now run more than once for a single instance, if two threads race. For most simple cached properties (e.g. those that are idempotent and simply calculate a value based on other attributes of the instance) this will be fine. If synchronization is needed, implement locking within the cached property getter function or around multi-threaded access points.

sys._current_exceptions() now returns a mapping from thread-id to an exception instance, rather than to a (typ, exc, tb) tuple. (Contributed by Irit Katriel in gh-103176 [https://github.com/python/cpython/issues/103176].)

When extracting tar files using tarfile or shutil.unpack_archive(), pass the filter argument to limit features that may be surprising or dangerous. See 解壓縮篩選器 for details.

The output of the tokenize.tokenize() and tokenize.generate_tokens() functions is now changed due to the changes introduced in PEP 701 [https://peps.python.org/pep-0701/]. This means that STRING tokens are not emitted any more for f-strings and the tokens described in PEP 701 [https://peps.python.org/pep-0701/] are now produced instead: FSTRING_START, FSTRING_MIDDLE and FSTRING_END are now emitted for f-string "string" parts in addition to the appropriate tokens for the tokenization in the expression components. For example for the f-string f"start {1+1} end" the old version of the tokenizer emitted:

1,0-1,18:           STRING         'f"start {1+1} end"'

while the new version emits:

1,0-1,2:            FSTRING_START  'f"'
1,2-1,8:            FSTRING_MIDDLE 'start '
1,8-1,9:            OP             '{'
1,9-1,10:           NUMBER         '1'
1,10-1,11:          OP             '+'
1,11-1,12:          NUMBER         '1'
1,12-1,13:          OP             '}'
1,13-1,17:          FSTRING_MIDDLE ' end'
1,17-1,18:          FSTRING_END    '"'

Additionally, there may be some minor behavioral changes as a consequence of the changes required to support PEP 701 [https://peps.python.org/pep-0701/]. Some of these changes include:

The type attribute of the tokens emitted when tokenizing some invalid Python characters such as ! has changed from ERRORTOKEN to OP.

Incomplete single-line strings now also raise tokenize.TokenError as incomplete multiline strings do.

Some incomplete or invalid Python code now raises tokenize.TokenError instead of returning arbitrary ERRORTOKEN tokens when tokenizing it.

Mixing tabs and spaces as indentation in the same file is not supported anymore and will raise a TabError.

The threading module now expects the _thread module to have an _is_main_interpreter attribute. It is a function with no arguments that returns True if the current interpreter is the main interpreter.

Any library or application that provides a custom _thread module should provide _is_main_interpreter(). (See gh-112826 [https://github.com/python/cpython/issues/112826].)

建置變更

Python no longer uses setup.py to build shared C extension modules. Build parameters like headers and libraries are detected in configure script. Extensions are built by Makefile. Most extensions use pkg-config and fall back to manual detection. (Contributed by Christian Heimes in gh-93939 [https://github.com/python/cpython/issues/93939].)

va_start() with two parameters, like va_start(args, format), is now required to build Python. va_start() is no longer called with a single parameter. (Contributed by Kumar Aditya in gh-93207 [https://github.com/python/cpython/issues/93207].)

CPython now uses the ThinLTO option as the default link time optimization policy if the Clang compiler accepts the flag. (Contributed by Donghee Na in gh-89536 [https://github.com/python/cpython/issues/89536].)

Add COMPILEALL_OPTS variable in Makefile to override compileall options (default: -j0) in make install. Also merged the 3 compileall commands into a single command to build .pyc files for all optimization levels (0, 1, 2) at once. (Contributed by Victor Stinner in gh-99289 [https://github.com/python/cpython/issues/99289].)

Add platform triplets for 64-bit LoongArch:

loongarch64-linux-gnusf

loongarch64-linux-gnuf32

loongarch64-linux-gnu

（由 Zhang Na 於 gh-90656 [https://github.com/python/cpython/issues/90656] 中貢獻。）

PYTHON_FOR_REGEN 現在需要 Python 3.10 或更新的版本。

Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate configure. (Contributed by Christian Heimes in gh-89886 [https://github.com/python/cpython/issues/89886].)

Windows builds and macOS installers from python.org now use OpenSSL 3.0.

C API 變更

新增功能

PEP 697 [https://peps.python.org/pep-0697/]: Introduce the Unstable C API tier, intended for low-level tools like debuggers and JIT compilers. This API may change in each minor release of CPython without deprecation warnings. Its contents are marked by the PyUnstable_ prefix in names.

程式碼物件建構函式：

PyUnstable_Code_New()（自 PyCode_New 重新命名）

PyUnstable_Code_NewWithPosOnlyArgs()（自 PyCode_NewWithPosOnlyArgs 重新命名）

程式碼物件的額外儲存 (PEP 523 [https://peps.python.org/pep-0523/])：

PyUnstable_Eval_RequestCodeExtraIndex()（自 _PyEval_RequestCodeExtraIndex 重新命名）

PyUnstable_Code_GetExtra()（自 _PyCode_GetExtra 重新命名）

PyUnstable_Code_SetExtra()（自 _PyCode_SetExtra 重新命名）

原始名稱將可繼續使用，直到相應的 API 發生變更。

（由 Petr Viktorin 於 gh-101101 [https://github.com/python/cpython/issues/101101] 中貢獻。）

PEP 697 [https://peps.python.org/pep-0697/]: Add an API for extending types whose instance memory layout is opaque:

PyType_Spec.basicsize 可以為零或負數來指定繼承或擴充基底類別大小。

PyObject_GetTypeData() and PyType_GetTypeDataSize() added to allow access to subclass-specific instance data.

Py_TPFLAGS_ITEMS_AT_END and PyObject_GetItemData() added to allow safely extending certain variable-sized types, including PyType_Type.

Py_RELATIVE_OFFSET added to allow defining members in terms of a subclass-specific struct.

（由 Petr Viktorin 於 gh-103509 [https://github.com/python/cpython/issues/103509] 中貢獻。）

Add the new limited C API function PyType_FromMetaclass(), which generalizes the existing PyType_FromModuleAndSpec() using an additional metaclass argument. (Contributed by Wenzel Jakob in gh-93012 [https://github.com/python/cpython/issues/93012].)

API for creating objects that can be called using the vectorcall protocol was added to the Limited API:

Py_TPFLAGS_HAVE_VECTORCALL

PyVectorcall_NARGS()

PyVectorcall_Call()

vectorcallfunc

The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class's __call__() method is reassigned. This makes vectorcall safe to use with mutable types (i.e. heap types without the immutable flag, Py_TPFLAGS_IMMUTABLETYPE). Mutable types that do not override tp_call now inherit the Py_TPFLAGS_HAVE_VECTORCALL flag. (Contributed by Petr Viktorin in gh-93274 [https://github.com/python/cpython/issues/93274].)

The Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF flags have been added. This allows extensions classes to support object __dict__ and weakrefs with less bookkeeping, using less memory and with faster access.

API for performing calls using the vectorcall protocol was added to the Limited API:

PyObject_Vectorcall()

PyObject_VectorcallMethod()

PY_VECTORCALL_ARGUMENTS_OFFSET

This means that both the incoming and outgoing ends of the vector call protocol are now available in the Limited API. (Contributed by Wenzel Jakob in gh-98586 [https://github.com/python/cpython/issues/98586].)

Add two new public functions, PyEval_SetProfileAllThreads() and PyEval_SetTraceAllThreads(), that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in gh-93503 [https://github.com/python/cpython/issues/93503].)

Add new function PyFunction_SetVectorcall() to the C API which sets the vectorcall field of a given PyFunctionObject. (Contributed by Andrew Frost in gh-92257 [https://github.com/python/cpython/issues/92257].)

The C API now permits registering callbacks via PyDict_AddWatcher(), PyDict_Watch() and related APIs to be called whenever a dictionary is modified. This is intended for use by optimizing interpreters, JIT compilers, or debuggers. (Contributed by Carl Meyer in gh-91052 [https://github.com/python/cpython/issues/91052].)

Add PyType_AddWatcher() and PyType_Watch() API to register callbacks to receive notification on changes to a type. (Contributed by Carl Meyer in gh-91051 [https://github.com/python/cpython/issues/91051].)

Add PyCode_AddWatcher() and PyCode_ClearWatcher() APIs to register callbacks to receive notification on creation and destruction of code objects. (Contributed by Itamar Oren in gh-91054 [https://github.com/python/cpython/issues/91054].)

Add PyFrame_GetVar() and PyFrame_GetVarString() functions to get a frame variable by its name. (Contributed by Victor Stinner in gh-91248 [https://github.com/python/cpython/issues/91248].)

新增 PyErr_GetRaisedException() 和 PyErr_SetRaisedException() 以用於儲存和復原目前的例外。這些函式回傳並接受單一例外物件，而非現已棄用的 PyErr_Fetch() 和 PyErr_Restore() 的三元引數。這樣做較不容易出錯且效率稍高。（由 Mark Shannon 於 gh-101578 [https://github.com/python/cpython/issues/101578] 中貢獻。）

新增 _PyErr_ChainExceptions1，它接受一個例外實例，以取代現已棄用的舊版 API _PyErr_ChainExceptions。（由 Mark Shannon 於 gh-101578 [https://github.com/python/cpython/issues/101578] 中貢獻。）

新增 PyException_GetArgs() 和 PyException_SetArgs() 作為便捷函式，用於取得和修改傳遞給例外建構函式的 args。（由 Mark Shannon 於 gh-101578 [https://github.com/python/cpython/issues/101578] 中貢獻。）

新增 PyErr_DisplayException()，它接受一個例外實例，以取代舊版 API PyErr_Display()。（由 Irit Katriel 於 gh-102755 [https://github.com/python/cpython/issues/102755] 中貢獻。）

PEP 683 [https://peps.python.org/pep-0683/]: Introduce Immortal Objects, which allows objects to bypass reference counts, and related changes to the C-API:

_Py_IMMORTAL_REFCNT：定義物件的參照計數

as immortal.

_Py_IsImmortal Checks if an object has the immortal reference count.

PyObject_HEAD_INIT 這現在將初始化參照計數

_Py_IMMORTAL_REFCNT（與 Py_BUILD_CORE 一起使用時）。

SSTATE_INTERNED_IMMORTAL 駐留的 (interned) unicode 物件的識別字

那是不滅的。

SSSTATE_INTERNED_IMMORTAL_STATIC 駐留的 unicode 的識別字

不滅且靜態的物體

sys.getunicodeinternedsize 這會回傳 unicode 的總數

objects that have been interned. This is now needed for refleak.py to correctly track reference counts and allocated blocks

（由 Eddie Elizondo 於 gh-84436 [https://github.com/python/cpython/issues/84436] 中貢獻。）

PEP 684 [https://peps.python.org/pep-0684/]：新增新的 Py_NewInterpreterFromConfig() 函式和 PyInterpreterConfig，它們可用於建立具有自己的 GIL 的子直譯器。（有關更多資訊，請參閱 PEP 684：直譯器各別持有的 GIL。）（由 Eric Snow 在 gh-104110 [https://github.com/python/cpython/issues/104110] 中貢獻。）

In the limited C API version 3.12, Py_INCREF() and Py_DECREF() functions are now implemented as opaque function calls to hide implementation details. (Contributed by Victor Stinner in gh-105387 [https://github.com/python/cpython/issues/105387].)

移植至 Python 3.12

Legacy Unicode APIs based on Py_UNICODE* representation has been removed. Please migrate to APIs based on UTF-8 or wchar_t*.

Argument parsing functions like PyArg_ParseTuple() doesn't support Py_UNICODE* based format (e.g. u, Z) anymore. Please migrate to other formats for Unicode like s, z, es, and U.

tp_weaklist for all static builtin types is always NULL. This is an internal-only field on PyTypeObject but we're pointing out the change in case someone happens to be accessing the field directly anyway. To avoid breakage, consider using the existing public C-API instead, or, if necessary, the (internal-only) _PyObject_GET_WEAKREFS_LISTPTR() macro.

This internal-only PyTypeObject.tp_subclasses may now not be a valid object pointer. Its type was changed to void* to reflect this. We mention this in case someone happens to be accessing the internal-only field directly.

To get a list of subclasses, call the Python method __subclasses__() (using PyObject_CallMethod(), for example).

Add support of more formatting options (left aligning, octals, uppercase hexadecimals, intmax_t, ptrdiff_t, wchar_t C strings, variable width and precision) in PyUnicode_FromFormat() and PyUnicode_FromFormatV(). (Contributed by Serhiy Storchaka in gh-98836 [https://github.com/python/cpython/issues/98836].)

An unrecognized format character in PyUnicode_FromFormat() and PyUnicode_FromFormatV() now sets a SystemError. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded. (Contributed by Serhiy Storchaka in gh-95781 [https://github.com/python/cpython/issues/95781].)

Fix wrong sign placement in PyUnicode_FromFormat() and PyUnicode_FromFormatV(). (Contributed by Philip Georgi in gh-95504 [https://github.com/python/cpython/issues/95504].)

Extension classes wanting to add a __dict__ or weak reference slot should use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead of tp_dictoffset and tp_weaklistoffset, respectively. The use of tp_dictoffset and tp_weaklistoffset is still supported, but does not fully support multiple inheritance (gh-95589 [https://github.com/python/cpython/issues/95589]), and performance may be worse. Classes declaring Py_TPFLAGS_MANAGED_DICT must call _PyObject_VisitManagedDict() and _PyObject_ClearManagedDict() to traverse and clear their instance's dictionaries. To clear weakrefs, call PyObject_ClearWeakRefs(), as before.

The PyUnicode_FSDecoder() function no longer accepts bytes-like paths, like bytearray and memoryview types: only the exact bytes type is accepted for bytes strings. (Contributed by Victor Stinner in gh-98393 [https://github.com/python/cpython/issues/98393].)

The Py_CLEAR, Py_SETREF and Py_XSETREF macros now only evaluate their arguments once. If an argument has side effects, these side effects are no longer duplicated. (Contributed by Victor Stinner in gh-98724 [https://github.com/python/cpython/issues/98724].)

The interpreter's error indicator is now always normalized. This means that PyErr_SetObject(), PyErr_SetString() and the other functions that set the error indicator now normalize the exception before storing it. (Contributed by Mark Shannon in gh-101578 [https://github.com/python/cpython/issues/101578].)

_Py_RefTotal is no longer authoritative and only kept around for ABI compatibility. Note that it is an internal global and only available on debug builds. If you happen to be using it then you'll need to start using _Py_GetGlobalRefTotal().

The following functions now select an appropriate metaclass for the newly created type:

PyType_FromSpec()

PyType_FromSpecWithBases()

PyType_FromModuleAndSpec()

Creating classes whose metaclass overrides tp_new is deprecated, and in Python 3.14+ it will be disallowed. Note that these functions ignore tp_new of the metaclass, possibly allowing incomplete initialization.

Note that PyType_FromMetaclass() (added in Python 3.12) already disallows creating classes whose metaclass overrides tp_new (__new__() in Python).

Since tp_new overrides almost everything PyType_From* functions do, the two are incompatible with each other. The existing behavior -- ignoring the metaclass for several steps of type creation -- is unsafe in general, since (meta)classes assume that tp_new was called. There is no simple general workaround. One of the following may work for you:

If you control the metaclass, avoid using tp_new in it:

If initialization can be skipped, it can be done in tp_init instead.

If the metaclass doesn't need to be instantiated from Python, set its tp_new to NULL using the Py_TPFLAGS_DISALLOW_INSTANTIATION flag. This makes it acceptable for PyType_From* functions.

Avoid PyType_From* functions: if you don't need C-specific features (slots or setting the instance size), create types by calling the metaclass.

If you know the tp_new can be skipped safely, filter the deprecation warning out using warnings.catch_warnings() from Python.

PyOS_InputHook and PyOS_ReadlineFunctionPointer are no longer called in subinterpreters. This is because clients generally rely on process-wide global state (since these callbacks have no way of recovering extension module state).

This also avoids situations where extensions may find themselves running in a subinterpreter that they don't support (or haven't yet been loaded in). See gh-104668 [https://github.com/python/cpython/issues/104668] for more info.

PyLongObject has had its internals changed for better performance. Although the internals of PyLongObject are private, they are used by some extension modules. The internal fields should no longer be accessed directly, instead the API functions beginning PyLong_... should be used instead. Two new unstable API functions are provided for efficient access to the value of PyLongObjects which fit into a single machine word:

PyUnstable_Long_IsCompact()

PyUnstable_Long_CompactValue()

Custom allocators, set via PyMem_SetAllocator(), are now required to be thread-safe, regardless of memory domain. Allocators that don't have their own state, including "hooks", are not affected. If your custom allocator is not already thread-safe and you need guidance then please create a new GitHub issue and CC @ericsnowcurrently.

已棄用

In accordance with PEP 699 [https://peps.python.org/pep-0699/], the ma_version_tag field in PyDictObject is deprecated for extension modules. Accessing this field will generate a compiler warning at compile time. This field will be removed in Python 3.14. (Contributed by Ramvikrams and Kumar Aditya in gh-101193 [https://github.com/python/cpython/issues/101193]. PEP by Ken Jin.)

棄用全域配置變數：

Py_DebugFlag：請改用 PyConfig.parser_debug

Py_VerboseFlag：請改用 PyConfig.verbose

Py_QuietFlag：請改用 PyConfig.quiet

Py_InteractiveFlag：請改用 PyConfig.interactive

Py_InspectFlag：請改用 PyConfig.inspect

Py_OptimizeFlag：請改用 PyConfig.optimization_level

Py_NoSiteFlag：請改用 PyConfig.site_import

Py_BytesWarningFlag：請改用 PyConfig.bytes_warning

Py_FrozenFlag：請改用 PyConfig.pathconfig_warnings

Py_IgnoreEnvironmentFlag：請改用 PyConfig.use_environment

Py_DontWriteBytecodeFlag：請改用 PyConfig.write_bytecode

Py_NoUserSiteDirectory：請改用 PyConfig.user_site_directory

Py_UnbufferedStdioFlag：請改用 PyConfig.buffered_stdio

Py_HashRandomizationFlag：請改用 PyConfig.use_hash_seed 和 PyConfig.hash_seed

Py_IsolatedFlag：請改用 PyConfig.isolated

Py_LegacyWindowsFSEncodingFlag：請改用 PyPreConfig.legacy_windows_fs_encoding

Py_LegacyWindowsStdioFlag：請改用 PyConfig.legacy_windows_stdio

Py_FileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding

Py_HasFileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding

Py_FileSystemDefaultEncodeErrors：請改用 PyConfig.filesystem_errors

Py_UTF8Mode：請改用 PyPreConfig.utf8_mode（參見 Py_PreInitialize()）

Py_InitializeFromConfig() API 應改為與 PyConfig 一起使用。（由 Victor Stinner 於 gh-77782 [https://github.com/python/cpython/issues/77782] 中貢獻。）

Creating immutable types with mutable bases is deprecated and will be disabled in Python 3.14. (gh-95388 [https://github.com/python/cpython/issues/95388])

structmember.h 標頭已棄用，但仍可使用，且還沒有移除它的計畫。

現在只需包含 Python.h 即可使用其內容，如果缺少，則新增 Py 前綴：

PyMemberDef、PyMember_GetOne() 和 PyMember_SetOne()

型別巨集，如 Py_T_INT、Py_T_DOUBLE 等（以前為 T_INT、 T_DOUBLE 等）

Py_READONLY（先前為 READONLY）和 Py_AUDIT_READ（先前全大寫）旗標

數個項目不再從 Python.h 中公開：

T_OBJECT（請改用 Py_T_OBJECT_EX）

T_NONE（先前未記錄於文件上，且相當古怪）

不做任何事的巨集 WRITE_RESTRICTED。

RESTRICTED 和 READ_RESTRICTED 這兩個巨集，相當於 Py_AUDIT_READ。

In some configurations, <stddef.h> is not included from Python.h. It should be included manually when using offsetof().

The deprecated header continues to provide its original contents under the original names. Your old code can stay unchanged, unless the extra include and non-namespaced macros bother you greatly.

（由 Petr Viktorin 在 gh-47146 [https://github.com/python/cpython/issues/47146] 中貢獻，其基於 Alexander Belopolsky 和 Matthias Braun 的前期工作。）

PyErr_Fetch() and PyErr_Restore() are deprecated. Use PyErr_GetRaisedException() and PyErr_SetRaisedException() instead. (Contributed by Mark Shannon in gh-101578 [https://github.com/python/cpython/issues/101578].)

PyErr_Display() 已棄用，請改用 PyErr_DisplayException()。（由 Irit Katriel 於 gh-102755 [https://github.com/python/cpython/issues/102755] 中貢獻。）

_PyErr_ChainExceptions 已棄用，請改用 _PyErr_ChainExceptions1。（由 Irit Katriel 於 gh-102192 [https://github.com/python/cpython/issues/102192] 中貢獻。）

使用 PyType_FromSpec()、PyType_FromSpecWithBases() 或 PyType_FromModuleAndSpec() 建立一個其元類別覆寫 tp_new 的類別已被棄用。請改為呼叫元類別。

Python 3.14 中待移除的項目

PyDictObject 中的 ma_version_tag 欄位，用於擴充模組 (PEP 699 [https://peps.python.org/pep-0699/]；gh-101193 [https://github.com/python/cpython/issues/101193])。

使用可變基底建立不可變型別 (gh-95388 [https://github.com/python/cpython/issues/95388])。

Python 3.15 中待移除的項目

PyImport_ImportModuleNoBlock()：請改用 PyImport_ImportModule()。

PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT()：請改用 PyWeakref_GetRef()。可以使用 pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]來為 Python 3.12 和更早版本取得 PyWeakref_GetRef()。

Py_UNICODE 型別與 Py_UNICODE_WIDE 巨集：請改用 wchar_t。

PyUnicode_AsDecodedObject()：請改用 PyCodec_Decode()。

PyUnicode_AsDecodedUnicode()：請改用 PyCodec_Decode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 str 的型別，例如 bytes。

PyUnicode_AsEncodedObject()：請改用 PyCodec_Encode()。

PyUnicode_AsEncodedUnicode()：請改用 PyCodec_Encode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 bytes 的型別，例如 str。

Python 初始化函式，自 Python 3.13 起已被棄用：

Py_GetPath()：請改用 PyConfig_Get("module_search_paths") (sys.path)。

Py_GetPrefix()：請改用 PyConfig_Get("base_prefix") (sys.base_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("prefix") (sys.prefix)。

Py_GetExecPrefix()：請改用 PyConfig_Get("base_exec_prefix") (sys.base_exec_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("exec_prefix") (sys.exec_prefix)。

Py_GetProgramFullPath()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetProgramName()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetPythonHome()：請改用 PyConfig_Get("home") 或 PYTHONHOME 環境變數。

pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/] 可以用來為 Python 3.13 和更早版本取得 PyConfig_Get()。

用於配置 Python 初始化的函式，自 Python 3.11 起已被棄用：

PySys_SetArgvEx()：請改用 PyConfig.argv。

PySys_SetArgv()：請改用 PyConfig.argv。

Py_SetProgramName()：請改用 PyConfig.program_name。

Py_SetPythonHome()：請改用 PyConfig.home。

PySys_ResetWarnOptions()：請改為清除 sys.warnoptions 和 warnings.filters。

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API。

全域配置變數：

Py_DebugFlag：請改用 PyConfig.parser_debug 或 PyConfig_Get("parser_debug")。

Py_VerboseFlag：請改用 PyConfig.verbose 或 PyConfig_Get("verbose")。

Py_QuietFlag：請改用 PyConfig.quiet 或 PyConfig_Get("quiet")。

Py_InteractiveFlag：請改用 PyConfig.interactive 或 PyConfig_Get("interactive")。

Py_InspectFlag：請改用 PyConfig.inspect 或 PyConfig_Get("inspect")。

Py_OptimizeFlag：請改用 PyConfig.optimization_level 或 PyConfig_Get("optimization_level")。

Py_NoSiteFlag：請改用 PyConfig.site_import 或 PyConfig_Get("site_import")。

Py_BytesWarningFlag：請改用 PyConfig.bytes_warning 或 PyConfig_Get("bytes_warning")。

Py_FrozenFlag：請改用 PyConfig.pathconfig_warnings 或 PyConfig_Get("pathconfig_warnings")。

Py_IgnoreEnvironmentFlag：請改用 PyConfig.use_environment 或 PyConfig_Get("use_environment")。

Py_DontWriteBytecodeFlag：請改用 PyConfig.write_bytecode 或 PyConfig_Get("write_bytecode")。

Py_NoUserSiteDirectory：請改用 PyConfig.user_site_directory 或 PyConfig_Get("user_site_directory")。

Py_UnbufferedStdioFlag：請改用 PyConfig.buffered_stdio 或 PyConfig_Get("buffered_stdio")。

Py_HashRandomizationFlag：請改用 PyConfig.use_hash_seed 和 PyConfig.hash_seed 或 PyConfig_Get("hash_seed")。

Py_IsolatedFlag：請改用 PyConfig.isolated 或 PyConfig_Get("isolated")。

Py_LegacyWindowsFSEncodingFlag：請改用 PyPreConfig.legacy_windows_fs_encoding 或 PyConfig_Get("legacy_windows_fs_encoding")。

Py_LegacyWindowsStdioFlag：請改用 PyConfig.legacy_windows_stdio 或 PyConfig_Get("legacy_windows_stdio")。

Py_FileSystemDefaultEncoding、Py_HasFileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding 或 PyConfig_Get("filesystem_encoding")。

Py_FileSystemDefaultEncodeErrors：請改用 PyConfig.filesystem_errors 或 PyConfig_Get("filesystem_errors")。

Py_UTF8Mode：請改用 PyPreConfig.utf8_mode 或 PyConfig_Get("utf8_mode")。（請參閱 Py_PreInitialize()）

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API 來設定這些選項。或者也可以使用 PyConfig_Get() 在執行時取得這些選項。

Python 3.16 中待移除的項目

libmpdecimal 的打包副本 (bundled copy)。

未來版本中的待移除項目

下列 API 已被棄用並將會被移除，不過目前尚未訂定移除日期。

Py_TPFLAGS_HAVE_FINALIZE：自 Python 3.8 起不再需要

PyErr_Fetch()：請改用 PyErr_GetRaisedException()。

PyErr_NormalizeException()：請改用 PyErr_GetRaisedException()。

PyErr_Restore()：請改用 PyErr_SetRaisedException()。

PyModule_GetFilename()：請改用 PyModule_GetFilenameObject()。

PyOS_AfterFork()：請改用 PyOS_AfterFork_Child()。

PySlice_GetIndicesEx()：請改用 PySlice_Unpack() 和 PySlice_AdjustIndices()。

PyUnicode_READY()：自 Python 3.12 起不再需要

PyErr_Display()：請改用 PyErr_DisplayException()。

_PyErr_ChainExceptions()：請改用 _PyErr_ChainExceptions1。

PyBytesObject.ob_shash 成員：請改為呼叫 PyObject_Hash()。

執行緒局部儲存 (Thread Local Storage, TLS) API：

PyThread_create_key()：請改用 PyThread_tss_alloc()。

PyThread_delete_key()：請改用 PyThread_tss_free()。

PyThread_set_key_value()：請改用 PyThread_tss_set()。

PyThread_get_key_value()：請改用 PyThread_tss_get()。

PyThread_delete_key_value()：請改用 PyThread_tss_delete()。

PyThread_ReInitTLS()：自 Python 3.7 起不再需要。

已移除

移除 token.h 標頭檔案。從未有任何公開的 tokenizer C API。token.h 標頭檔案的設計是僅限用於 Python 內部。（由 Victor Stinner 於 gh-92651 [https://github.com/python/cpython/issues/92651] 中貢獻。）

Legacy Unicode APIs have been removed. See PEP 623 [https://peps.python.org/pep-0623/] for detail.

PyUnicode_WCHAR_KIND

PyUnicode_AS_UNICODE()

PyUnicode_AsUnicode()

PyUnicode_AsUnicodeAndSize()

PyUnicode_AS_DATA()

PyUnicode_FromUnicode()

PyUnicode_GET_SIZE()

PyUnicode_GetSize()

PyUnicode_GET_DATA_SIZE()

移除 PyUnicode_InternImmortal() 函式巨集。（由 Victor Stinner 於 gh-85858 [https://github.com/python/cpython/issues/85858] 中貢獻。）

Python 3.11 有什麼新功能

編輯者:

Pablo Galindo Salgado

此文章解釋了 Python 3.11 和 3.10 相比多了哪些新功能。Python 3.11 於 2022 年 10 月 24 日發布。完整細節請見 Changelog（更動日誌）。

發布重點摘要

Python 3.11 比 Python 3.10 快了 10-60%。我們使用了標準基準量測套裝軟體 (benchmark suite) 測得平均加速了 1.25x。細節請見更快的 CPython。

新增語法特性：

PEP 654：例外群組與 except*

新的內建功能：

PEP 678：運用例外註解使其更加詳盡

新增標準函式庫模組：

PEP 680 [https://peps.python.org/pep-0680/]：tomllib — 在標準函式庫中支援 TOML [https://toml.io/] 檔案的剖析

直譯器的改進：

PEP 657：回溯 (traceback) 中更細緻的錯誤位置

新增 -P 命令列選項和 PYTHONSAFEPATH 環境變數以停用自動於 sys.path 的開頭加上一個有潛在安全問題的路徑

新增型別特性：

PEP 646：可變參數泛型 (variadic generics)

PEP 655：標記獨立 TypedDict 項目為必要或不必要

PEP 673：Self 型別

PEP 675：任意的文本字串型別 (Arbitrary literal string type)

PEP 681：資料類別轉換 (Data class transforms)

重要的棄用、移除與限制：

PEP 594 [https://peps.python.org/pep-0594/]：許多標準函式庫中的遺留模組已被棄用且將於 Python 3.13 移除

PEP 624 [https://peps.python.org/pep-0624/]：Py_UNICODE 編碼器 API 已被移除

PEP 670 [https://peps.python.org/pep-0670/]：轉換為靜態行內函式的巨集

新增功能

PEP 657：回溯 (traceback) 中更細緻的錯誤位置

當要印出回溯，直譯器現在會指出造成錯誤的確切運算式，而非只說明是哪一行。例如：

Traceback (most recent call last):
  File "distance.py", line 11, in <module>
    print(manhattan_distance(p1, p2))
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "distance.py", line 6, in manhattan_distance
    return abs(point_1.x - point_2.x) + abs(point_1.y - point_2.y)
                           ^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'x'

前一版本的直譯器只會標明是哪一行，無法辨認哪一個物件是 None。當處理多層的巢狀 dict 物件和多個函式呼叫時，這種強化錯誤提示也可能非常有用：

Traceback (most recent call last):
  File "query.py", line 37, in <module>
    magic_arithmetic('foo')
  File "query.py", line 18, in magic_arithmetic
    return add_counts(x) / 25
           ^^^^^^^^^^^^^
  File "query.py", line 24, in add_counts
    return 25 + query_user(user1) + query_user(user2)
                ^^^^^^^^^^^^^^^^^
  File "query.py", line 32, in query_user
    return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
                               ~~~~~~~~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable

在複雜的計算運算式中也是：

Traceback (most recent call last):
  File "calculation.py", line 54, in <module>
    result = (x / y / z) * (a / b / c)
              ~~~~~~^~~
ZeroDivisionError: division by zero

此外，強化回溯特性所使用的資訊可以透過一般的 API 來取得，以用來使 bytecode 指示 (instruction)與原始碼位置相互關聯。此項資訊可以用以下方式取得：

Python 中的 codeobject.co_positions() 方法。

C API 中的 PyCode_Addr2Location() 函式。

詳情請見 PEP 657 [https://peps.python.org/pep-0657/]。（由 Pablo Galindo、Batuhan Taskaya 與 Ammar Askar 於 bpo-43950 [https://bugs.python.org/issue?@action=redirect&bpo=43950] 中所貢獻。）

備註

這個特性必須要將欄的位置 (column position) 儲存於 程式碼物件，這可能會導致直譯器用於編譯 Python 檔案的記憶體使用量與硬碟使用量增加。為了避免儲存多餘的資訊且停用印出多餘的回溯資訊，請用 -X no_debug_ranges 命令列選項或是 PYTHONNODEBUGRANGES 環境變數。

PEP 654：例外群組與 except*

PEP 654 [https://peps.python.org/pep-0654/] 引入了新的的語言特性，可讓程式同時引發並處理多個相互無關的例外。內建型別 ExceptionGroup 和 BaseExceptionGroup 使得程式可為多個例外組成群組並同時引發，新的 except* 語法也將 except 泛用化、能夠比對例外群組的子群組。

詳情請見 PEP 654 [https://peps.python.org/pep-0654/]。

（由 Irit Katriel 於 bpo-45292 [https://bugs.python.org/issue?@action=redirect&bpo=45292] 中所貢獻。PEP 由 Irit Katriel、Yury Selivanov 與 Guido van Rossum 撰寫。）

PEP 678：運用例外註解使其更加詳盡

新增 add_note() 方法到 BaseException。當上下文資訊在例外被引發時無法被取得，這個方法就可以用來為例外添加更多資訊。被添加的註解會在預設回溯中出現。

詳情請見 PEP 678 [https://peps.python.org/pep-0678/]。

（由 Irit Katriel 於 bpo-45607 [https://bugs.python.org/issue?@action=redirect&bpo=45607] 中所貢獻。PEP 由 Zac Hatfield-Dodds 所撰寫）

Windows py.exe 啟動程式 (launcher) 的改進

Python 3.11 所包含的 Python 安裝管理員 複製品有了顯著的改善。它現在支援 PEP 514 [https://peps.python.org/pep-0514/] 所定義的公司/標籤 (tag) 語法，可用 -V:<company>/<tag> 引數來取代受限的 -<major>.<minor>。這允許了 python.org [https://www.python.org] 上的 PythonCore 以外的發行版本發布。

使用 -V: 選擇器時，可以省略公司或標籤，但會搜尋所有安裝。例如，-V:OtherPython/ 將選擇 OtherPython 註冊的「最佳」標籤，而 -V:3.11 或 -V:/3.11 將選擇帶有 3.11 標籤的「最佳」發行版。

當使用遺留的 -<major>、-<major>.<minor>、-<major>-<bitness> 或 -<major>.<minor>-<bitness> 引數時，所有過去版本的行為都應該保留下來，且只有 PythonCore 中的發布版本會被選用。然而，-64 後綴現在暗示了「非 32-bit」（不用一定要是 x86-64），因為現在有多個支援 64-bit 的平台。32-bit 運行程式會在檢查運行程式之標籤是否帶有 -32 後綴時被偵測出來。所有 Python 3.5 以後發布版本的 32-bit 建置中都有這個行為。

型別提示相關的新特性

這個部分涵蓋影響 PEP 484 [https://peps.python.org/pep-0484/] 型別提示 (type hints) 與 typing 模組的重大變更。

PEP 646：可變參數泛型 (variadic generics)

PEP 484 [https://peps.python.org/pep-0484/] 先前引入了 TypeVar，開啟了帶有單一型別的泛型參數化。PEP 646 [https://peps.python.org/pep-0646/] 新增 TypeVarTuple，開啟了帶有任意數量型別的參數化 (parameterisation)。換句話說，TypeVarTuple 是可變的型別變數，啟用了可變的泛型。

這使其有非常多用例，特別是它允許了像是 NumPy 和 Tensorflow 的數值運算函式庫中類似陣列結構的型別可用 shape 陣列來被參數化。靜態型別檢查工具現在也能夠為使用這些函式庫的程式捕捉到維度相關的錯誤。

詳情請見 PEP 646 [https://peps.python.org/pep-0646/]。

（由 Matthew Rahtz 於 bpo-43224 [https://bugs.python.org/issue?@action=redirect&bpo=43224] 中所貢獻，由 Serhiy Storchaka 與 Jelle Zijlstra 協助。PEP 由 Mark Mendoza、Matthew Rahtz、Pradeep Kumar Srinivasan 與 Vincent Siles 所撰寫）

PEP 655：標記獨立 TypedDict 項目為必要或不必要

Required 與 NotRequired 提供了標記一個獨立項目在 TypedDict 中是否必須存在的直覺方法。在這之前，這只有透過繼承才有可能做得到。

所有欄位都預設為是必要的，除非 total 參數有被設為 False，那麼所有欄位就會是非必要的。例如，這個範例指定了要有一個必要鍵與一個非必要鍵的 TypedDict：

class Movie(TypedDict):
   title: str
   year: NotRequired[int]

m1: Movie = {"title": "Black Panther", "year": 2018}  # OK
m2: Movie = {"title": "Star Wars"}  # OK (year is not required)
m3: Movie = {"year": 2022}  # ERROR (missing required field title)

以下定義等同於：

class Movie(TypedDict, total=False):
   title: Required[str]
   year: int

詳情請見 PEP 655 [https://peps.python.org/pep-0655/]。

（由 David Foster 與 Jelle Zijlstra 於 bpo-47087 [https://bugs.python.org/issue?@action=redirect&bpo=47087] 中所貢獻。PEP 由 David Foster 所撰寫）

PEP 673：Self 型別

新的 Self 標註提供了一種簡單直觀的方法來標註那些會回傳其類別實例的方法。這與 PEP 484 [https://peps.python.org/pep-0484/#annotating-instance-and-class-methods] 中指定的基於 TypeVar 的方法相同，但更簡潔且更易於遵循。

常見用例包括作為 classmethod 的替代建構函式和會回傳 self 的 __enter__() 方法：

class MyLock:
    def __enter__(self) -> Self:
        self.lock()
        return self

    ...

class MyInt:
    @classmethod
    def fromhex(cls, s: str) -> Self:
        return cls(int(s, 16))

    ...

Self 也可用於標註與其封閉類類別 (enclosing class) 相同的方法參數或屬性。

詳情請見 PEP 673 [https://peps.python.org/pep-0673/]。

（由 James Hilton-Balfe 於 bpo-46534 [https://bugs.python.org/issue?@action=redirect&bpo=46534] 中所貢獻。PEP 由 Pradeep Kumar Srinivasan 與 James Hilton-Balfe 所撰寫）

PEP 675：任意的文本字串型別 (Arbitrary literal string type)

新的 LiteralString 標註可用於標示一個函式參數可為任何文本字串型別 (literal string type)。這允許函式接受任意的文本字串型別，以及從其他文本字串建立的字串。型別檢查器就可以強制需審慎處理的函式（例如會執行 SQL 陳述式或 shell 命令的函式）僅會以靜態引數呼叫，從而提供針對注入攻擊的保護。

例如一個 SQL 查詢函式 (query function) 可以被標註為：

def run_query(sql: LiteralString) -> ...
    ...

def caller(
    arbitrary_string: str,
    query_string: LiteralString,
    table_name: LiteralString,
) -> None:
    run_query("SELECT * FROM students")       # ok
    run_query(query_string)                   # ok
    run_query("SELECT * FROM " + table_name)  # ok
    run_query(arbitrary_string)               # 型別檢查器錯誤
    run_query(                                # 型別檢查器錯誤
        f"SELECT * FROM students WHERE name = {arbitrary_string}"
    )

詳情請見 PEP 675 [https://peps.python.org/pep-0675/]。

（由 Jelle Zijlstra 於 bpo-47088 [https://bugs.python.org/issue?@action=redirect&bpo=47088] 中所貢獻。PEP 由 Pradeep Kumar Srinivasan 與 Graham Bleaney 所撰寫）

PEP 681：資料類別轉換 (Data class transforms)

dataclass_transform 可以用來裝飾一個類別、元類別 (metaclass)、或是一個本身就是裝飾器的函式。@dataclass_transform() 的存在會讓一個靜態型別檢查器知道被裝飾物件會在運行程式做出轉換類別的「魔法」，賦予其類似 dataclass 的行為。

舉例來說：

# create_model 裝飾器是由一個函式庫定義。
@typing.dataclass_transform()
def create_model(cls: Type[T]) -> Type[T]:
    cls.__init__ = ...
    cls.__eq__ = ...
    cls.__ne__ = ...
    return cls

# create_model 裝飾器現在可以被用來建立新的模型類別：
@create_model
class CustomerModel:
    id: int
    name: str

c = CustomerModel(id=327, name="Eric Idle")

詳情請見 PEP 681 [https://peps.python.org/pep-0681/]。

（由 Jelle Zijlstra 於 gh-91860 [https://github.com/python/cpython/issues/91860] 中所貢獻。PEP 由 Erik De Bonte 與 Eric Traut 所撰寫）

PEP 563 可能不是未來

PEP 563 [https://peps.python.org/pep-0563/] 推遲對註釋的求值 (Postponed Evaluation of Annotations)（from __future__ import annotations future 陳述式）最初計劃在 Python 3.10 中發布，但已被無限期擱置。請參閱來自指導委員會 (Steering Counsil) 的訊息 [https://mail.python.org/archives/list/python-dev@python.org/message/VIZEBX5EYMSYIJNDBF6DMUMZOCWHARSO/]以獲得更多資訊。

其他語言更動

星號拆解 (starred unpacking) 運算式現在可以在 for 陳述式中使用。（詳情請見 bpo-46725 [https://bugs.python.org/issue?@action=redirect&bpo=46725]。）

非同步綜合運算 (comprehension) 現在允許在非同步函式中的內部綜合運算 (inside comprehension)。在這種情況下，外部綜合運算 (outer comprehension) 隱晦地變成了非同步的了。（由 Serhiy Storchaka 在 bpo-33346 [https://bugs.python.org/issue?@action=redirect&bpo=33346] 中貢獻。）

現在在不支援 context manager 協定的物件上使用 with 陳述式和 contextlib.ExitStack.enter_context() 或在不支援 asynchronous context manager 協定的物件上使用 async with 陳述式和 contextlib.AsyncExitStack.enter_async_context()，會引發 TypeError 而不是 AttributeError。（由 Serhiy Storchaka 在 bpo-12022 [https://bugs.python.org/issue?@action=redirect&bpo=12022] 和 bpo-44471 [https://bugs.python.org/issue?@action=redirect&bpo=44471] 中貢獻。）

Added object.__getstate__(), which provides the default implementation of the __getstate__() method. copying and pickleing instances of subclasses of builtin types bytearray, set, frozenset, collections.OrderedDict, collections.deque, weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes implemented as slots. This change has an unintended side effect: It trips up a small minority of existing Python projects not expecting object.__getstate__() to exist. See the later comments on gh-70766 [https://github.com/python/cpython/issues/70766] for discussions of what workarounds such code may need. (Contributed by Serhiy Storchaka in bpo-26579 [https://bugs.python.org/issue?@action=redirect&bpo=26579].)

新增了一個 -P 命令列選項和一個 PYTHONSAFEPATH 環境變數，它們禁用了當使用 -c 和 -m 以在運行腳本或目前目錄時自動添加到腳本目錄的 sys.path。這確保只有 stdlib 和已安裝的模組會被 import 取用，以避免不小心或被惡意地將模組與本地（通常是使用者可寫入的）目錄中的模組重疊。（由 Victor Stinner 在 gh-57684 [https://github.com/python/cpython/issues/57684] 中貢獻。）

"z" 選項被新增到 格式規格 (Format Specification) 迷你語言，它會強迫負的 0 在進位到格式精度後成為正的。更多詳情請見 PEP 682 [https://peps.python.org/pep-0682/]。（由 John Belmonte 於 gh-90153 [https://github.com/python/cpython/issues/90153] 中貢獻。）

sys.path 不再接受位元組。支援已在 Python 3.2 和 3.6 之間的某個時間停止，直到 Python 3.10.0 發布後才引起人們的注意。此外，由於混合使用 str 和 bytes 鍵時 -b 和 sys.path_importer_cache 會出現的交互作用，恢復這項支援會出現問題。（由 Thomas Grainger 在 gh-91181 [https://github.com/python/cpython/issues/91181] 中貢獻。）

其他 CPython 實作更動

為支援 typing.SupportsComplex 與 typing.SupportsBytes 協定，實作了 complex 與 bytes 的特殊方法 __complex__() 與 __bytes__()。（由 Mark Dickinson 和 Donghee Na 於 bpo-24234 [https://bugs.python.org/issue?@action=redirect&bpo=24234] 中所貢獻。）

新增 siphash13 以作為內部的雜湊演算法，它有與 siphash24 相似的安全特性，但是在處理較長的輸入時會更快一些。現在是 str、bytes 和一些其他型別的 hash() 預設演算法。PEP 552 [https://peps.python.org/pep-0552/] 基於雜湊的 .pyc 檔案 現在也使用 siphash13。（由 Inada Naoki 於 bpo-29410 [https://bugs.python.org/issue?@action=redirect&bpo=29410] 中貢獻。）

當一個仍有效的例外被 raise 陳述式在沒有參數的情況下重新引發，被附於該例外的追蹤資訊現在都會是 sys.exc_info()[1].__traceback__。這代表對於目前 except 子句的追蹤上做的改動會反映在被重複引發的例外上。（由 Irit Katriel 於 bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711] 中貢獻。）

有被處理的例外在直譯器狀態的表示（也就是 exc_info 或 _PyErr_StackItem）現在只會有 exc_value 欄位；exc_type 和 exc_traceback 已被移除，現在只能透過 exc_value 來取得它們。（由 Irit Katriel 於 bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711] 中貢獻。）

新增命令列選項 AppendPath，已增加於 Windows 安裝程式。它的行為類似於 PrependPath，但在安裝和腳本目錄後面附加而非新增於它們前面。（由 Bastian Neuburger 在 bpo-44934 [https://bugs.python.org/issue?@action=redirect&bpo=44934] 中貢獻。）

初始化中若是要用 PyConfig.module_search_paths 來初始化 sys.path，則現在 PyConfig.module_search_paths_set 必須被設為 1。否則，初始化會重新計算路徑並取代所有被加到 module_search_paths 的值。

--help 選項的輸出現在會在 50 列、80 欄的大小之內，Python 環境變數和 -X 選項的資訊現在能夠分別透過 --help-env 和 --help-xoptions 旗標與 --help-all 一起使用來取得。（由 Éric Araujo 於 bpo-46142 [https://bugs.python.org/issue?@action=redirect&bpo=46142] 中貢獻。）

在除 2（binary、二進制）、4、8（octal、八進制）、16（hexadecimal、十六進制）或 32 以外的基數中，例如以 10（decimal、十進制）為基數，進行 int 和 str 之間的轉換且字串形式的位數超過限制，現在會引發 ValueError，以避免由於演算法複雜性而導致的潛在阻斷服務攻擊 (denial of service attacks)。這是針對 CVE 2020-10735 [https://www.cve.org/CVERecord?id=CVE-2020-10735] 的緩解措施，可以透過環境變數、命令列旗標或 sys API 來設定或禁用此限制。請參閱整數字串轉換長度限制 文件。預設限制為字串形式的 4300 位數字。

新增模組

tomllib：用於剖析 TOML [https://toml.io/]。詳情請見 PEP 680 [https://peps.python.org/pep-0680/]。（由 Taneli Hukkinen 於 bpo-40059 [https://bugs.python.org/issue?@action=redirect&bpo=40059] 中所貢獻。）

wsgiref.types：WSGI [https://peps.python.org/pep-3333/] 限定型別，用於靜態型別檢查。（Sebastian Rittau 於 bpo-42012 [https://bugs.python.org/issue?@action=redirect&bpo=42012] 中所貢獻。）

改進的模組

asyncio

添加了 TaskGroup 類別，為一個會持有任務群組並在退出時等待全部完成的非同步情境管理器 (asynchronous context manager)。對於新程式碼，建議直接使用 create_task() 和 gather()。（由 Yury Selivanov 和其他人在 gh-90908 [https://github.com/python/cpython/issues/90908] 中貢獻。）

新增 timeout()，是一個用來為一個非同步操作設置超時的非同步情境管理器，新的程式建議直接使用它以取代 wait_for()。（由 Andrew Svetlov 於 gh-90927 [https://github.com/python/cpython/issues/90927] 貢獻。）

新增 Runner 類別，它會對外公布了 run() 的使用機制。（由 Andrew Svetlov 於 gh-91218 [https://github.com/python/cpython/issues/91218] 貢獻。）

於 asyncio 函式庫的同步化原始物件中新增 Barrier 類別與和其相關的 BrokenBarrierError 例外。（由 Yves Duprat 和 Andrew Svetlov in gh-87518 [https://github.com/python/cpython/issues/87518] 貢獻。）

在 asyncio.loop.create_connection() 新增關鍵字引數 all_errors，這樣多個連接錯誤就可以一起用一個 ExceptionGroup 來引發。

新增 asyncio.StreamWriter.start_tls() 方法，用來將已存在的串流連線升級至 TLS。（由 Ian Good 於 bpo-34975 [https://bugs.python.org/issue?@action=redirect&bpo=34975] 中貢獻。）

在事件迴圈增加原始資料元 (raw datagram) socket 函式：sock_sendto()、sock_recvfrom() 和 sock_recvfrom_into()。以上在 SelectorEventLoop 和 ProactorEventLoop 中都有實作。（由 Alex Grönholm 在 bpo-46805 [https://bugs.python.org/issue?@action=redirect&bpo=46805] 中貢獻。）

於 Task 新增 cancelling() 和 uncancel() 方法。這些預期是只用於內部，尤其是 TaskGroup。

contextlib

添加了非平行安全的 chdir() 情境管理器來更改目前工作目錄，然後在退出時恢復它。chdir() 的簡單包裝器。（由 Filipe Laíns 在 bpo-25625 [https://bugs.python.org/issue?@action=redirect&bpo=25625] 中貢獻）

dataclasses

更改欄位預設的可變性檢查 (mutability check)，僅允許預設值是 hashable 而不是任何非 dict、list 或 set 實例的物件。（由 Eric V. Smith 在 bpo-44674 [https://bugs.python.org/issue?@action=redirect&bpo=44674] 中貢獻。）

datetime

新增 datetime.UTC，一個 datetime.timezone.utc 的方便別名。（由 Kabir Kwatra 於 gh-91973 [https://github.com/python/cpython/issues/91973] 所貢獻。）

datetime.date.fromisoformat()、datetime.time.fromisoformat() 和 datetime.datetime.fromisoformat() 現在可以用來剖析大部分的 ISO 8601 格式（除了那些支援分數形式的小時與分鐘）。（由 Paul Ganssle 於 gh-80010 [https://github.com/python/cpython/issues/80010] 中所貢獻。）

enum

EnumMeta 更名為 EnumType（EnumMeta 保留為別名）。

增加 StrEnum，列舉 (enum) 內的成員必須是字串。

新增 ReprEnum，它只修改成員的 __repr__()，同時回傳成員的文本值 (literal value)（而不是名稱），以用於（為 str()、format() 和 f-string 所使用的）__str__() 和 __format__()。

改變了 Enum.__format__() （被 format()、str.format() 和 f-string 預設使用），以使其與 enum.Enum.__str__ 產生相同結果：對於繼承自 ReprEnum 的列舉，這會是成員之值；而其他的列舉會是列舉與成員名稱（例如 Color.RED）。

新增 boundary 類別參數與其選項到 Flag 列舉和 FlagBoundary 列舉以控制處理超出範圍旗標數值的方法。

新增了 verify() 列舉裝飾器和 EnumCheck 列舉及其選項，以根據幾個特定限制檢查列舉類別。

新增 member() 與 nonmember() 裝飾器以確保被裝飾的物件會/不會被轉換成一個列舉成員。

新增 property() 裝飾器，它的作用類似 property() 但是是用於列舉，用以替代 types.DynamicClassAttribute()。

新增 global_enum() 列舉裝飾器，用來調整 __repr__() 和 __str__() 以模組成員形式而非列舉類別來顯示值。例如，re.RegexFlag 的 ASCII 成員的 're.ASCII'，而非 'RegexFlag.ASCII'。

強化 Flag 以支援使用 len()、疊代 (iteration) 和 in/not in 於其成員。例如，以下程式現在能夠作用了：len(AFlag(3)) == 2 and list(AFlag(3)) == (AFlag.ONE, AFlag.TWO)

更改了 Enum 和 Flag 以在呼叫 __init_subclass__() 之前就定義成員；dir() 現在包括來自混合資料型別的方法。

更改 Flag 以僅考慮主要值（2 的次方）規範，而複合值（3、6、10 等）被視為別名；倒置旗標 (inverted flags) 會被強制轉換為正等價的值。

fcntl

FreeBSD 上，F_DUP2FD 和 F_DUP2FD_CLOEXEC 旗標分別有被支援，前者等同於 dup2 用法，而後者設定了 FD_CLOEXEC 旗標。

fractions

支援有 PEP 515 [https://peps.python.org/pep-0515/] 風格的 Fraction 以字串初始化。（Sergey B Kirpichev 於 bpo-44258 [https://bugs.python.org/issue?@action=redirect&bpo=44258] 中所貢獻。）

Fraction 現在有實作了一個 __int__ 方法，因此 isinstance(some_fraction, typing.SupportsInt) 的檢查會通過。（由 Mark Dickinson 在 bpo-44547 [https://bugs.python.org/issue?@action=redirect&bpo=44547] 中貢獻。）

functools

functools.singledispatch() 現在支援 types.UnionType 和 typing.Union 作為調度 (dispatch) 引數的標註。

>>> from functools import singledispatch
>>> @singledispatch
... def fun(arg, verbose=False):
...     if verbose:
...         print("Let me just say,", end=" ")
...     print(arg)
...
>>> @fun.register
... def _(arg: int | float, verbose=False):
...     if verbose:
...         print("Strength in numbers, eh?", end=" ")
...     print(arg)
...
>>> from typing import Union
>>> @fun.register
... def _(arg: Union[list, set], verbose=False):
...     if verbose:
...         print("Enumerate this:")
...     for i, elem in enumerate(arg):
...         print(i, elem)
...

（由 Yurii Karabas 於 bpo-46014 [https://bugs.python.org/issue?@action=redirect&bpo=46014] 中所貢獻。）

gzip

The gzip.compress() function is now faster when used with the mtime=0 argument as it delegates the compression entirely to a single zlib.compress() operation. There is one side effect of this change: The gzip file header contains an "OS" byte in its header. That was traditionally always set to a value of 255 representing "unknown" by the gzip module. Now, when using compress() with mtime=0, it may be set to a different value by the underlying zlib C library Python was linked against. (See gh-112346 [https://github.com/python/cpython/issues/112346] for details on the side effect.)

hashlib

hashlib.blake2b() 與 hashlib.blake2s() 現在偏好使用 libb2 [https://www.blake2.net/] 多於 Python 自發行版的複製。（由 Christian Heimes 於 bpo-47095 [https://bugs.python.org/issue?@action=redirect&bpo=47095] 中所貢獻。）

帶有 SHA3 和 SHAKE 演算法的內部 _sha3 模組現在使用 tiny_sha3 而不是 Keccak 程式碼套件來減少程式碼和二進位檔案大小。hashlib 模組更喜歡來自 OpenSSL 的 SHA3 和 SHAKE 最佳化實作。此更改僅影響沒有 OpenSSL 支援的安裝。（由 Christian Heimes 在 bpo-47098 [https://bugs.python.org/issue?@action=redirect&bpo=47098] 中貢獻。）

新增 hashlib.file_digest()，是個能夠為檔案或類檔案物件做高效率雜湊的幫助函式。（由 Christian Heimes 於 gh-89313 [https://github.com/python/cpython/issues/89313] 中貢獻。）

IDLE 和 idlelib

在 .pyi 檔案施用語法突顯 (syntax highlight)。（由 Alex Waygood 與 Terry Jan Reedy 於 bpo-45447 [https://bugs.python.org/issue?@action=redirect&bpo=45447] 中所貢獻。）

當帶有輸入與輸出地儲存 Shell 時，也會包含提示字元。（由 Terry Jan Reedy 於 gh-95191 [https://github.com/python/cpython/issues/95191] 中所貢獻。）

inspect

添加 getmembers_static() 以回傳所有成員，而不會透過描述器協定 (descriptor protocol) 觸發動態查找。（由 Weipeng Hong 在 bpo-30533 [https://bugs.python.org/issue?@action=redirect&bpo=30533] 中貢獻。）

新增 inspect.ismethodwrapper()，用來檢查一個物件的型別是否為 MethodWrapperType。（由 Hakan Çelik 於 bpo-29418 [https://bugs.python.org/issue?@action=redirect&bpo=29418] 中所貢獻。）

更改 inspect 模組中與幀相關的函式以回傳新的 FrameInfo 和 Traceback 類別實例（向後相容之前類似於 named tuple 的介面），包括擴充的 PEP 657 [https://peps.python.org/pep-0657/] 位置資訊（結束行號、欄和結束欄）。受影響的功能是：

inspect.getframeinfo()

inspect.getouterframes()

inspect.getinnerframes(),

inspect.stack()

inspect.trace()

（由 Pablo Galindo 於 gh-88116 [https://github.com/python/cpython/issues/88116] 中所貢獻。）

locale

新增 locale.getencoding() 以取得目前的區域編碼 (locale encoding)。和 locale.getpreferredencoding(False) 類似但不考慮 Python UTF-8 模式。

logging

新增 getLevelNamesMapping() 以回傳一個日誌級別名稱（例如 'CRITICAL'）指到對應的 Logging Levels 數值（例如，預設為 50）的對映。（由 Andrei Kulakovin 於 gh-88024 [https://github.com/python/cpython/issues/88024] 中貢獻。）

添加了一個 createSocket() 方法到 SysLogHandler，以匹配 SocketHandler.createSocket() 。如果沒有已啟用的 socket，它會在處理程式初始化期間和發出一個事件時自動呼叫。（由 Kirill Pinchuk 在 gh-88457 [https://github.com/python/cpython/issues/88457] 中貢獻。）

math

新增 math.exp2()：回傳 2 的 x 次方。（由 Gideon Mitchell 於 bpo-45917 [https://bugs.python.org/issue?@action=redirect&bpo=45917] 中所貢獻。）

新增 math.cbrt()：回傳 x 的立方根。（由 Ajith Ramachandran 於 bpo-44357 [https://bugs.python.org/issue?@action=redirect&bpo=44357] 中所貢獻。）

為了與 IEEE 754 規範保持一致，更改了兩個 math.pow() 邊角案例 (corner case) 的行為。math.pow(0.0, -math.inf) 和 math.pow(-0.0, -math.inf) 現在回傳 inf，之前它們會引發 ValueError。（由 Mark Dickinson 在 bpo-44339 [https://bugs.python.org/issue?@action=redirect&bpo=44339] 中貢獻。）

math.nan 現為隨時可用。（由 Victor Stinner 於 bpo-46917 [https://bugs.python.org/issue?@action=redirect&bpo=46917] 中所貢獻。）

operator

新增 operator.call 函式，使得 operator.call(obj, *args, **kwargs) == obj(*args, **kwargs)。（由 Antony Lee 於 bpo-44019 [https://bugs.python.org/issue?@action=redirect&bpo=44019] 中所貢獻。）

os

在 Windows 上，os.urandom() 現在使用 BCryptGenRandom() 以取代被棄用的 CryptGenRandom()。（由 Donghee Na 於 bpo-44611 [https://bugs.python.org/issue?@action=redirect&bpo=44611] 中所貢獻。）

pathlib

如果 pattern 以路徑名稱元件分隔符號 sep 或 altsep 結尾，glob() 和 rglob() 只回傳目錄。（由 Eisuke Kawasima 於 bpo-22276 [https://bugs.python.org/issue?@action=redirect&bpo=22276] 與 bpo-33392 [https://bugs.python.org/issue?@action=redirect&bpo=33392] 中所貢獻。）

re

現在正規表示式 (regular expression) 是有支援原子性群組 (atomic grouping) ((?>...)) 和佔有性量詞 (possessive quantifier) (*+, ++, ?+, {m,n}+) 的。（由 Jeffrey C. Jacobs 和 Serhiy Storchaka 在 bpo-433030 [https://bugs.python.org/issue?@action=redirect&bpo=433030] 中貢獻。）

shutil

新增 shutil.rmtree() 的可選參數 dir_fd。（由 Serhiy Storchaka 於 bpo-46245 [https://bugs.python.org/issue?@action=redirect&bpo=46245] 中所貢獻。）

socket

新增 NetBSD 對於 CAN Socket 的支援。（由 Thomas Klausner 於 bpo-30512 [https://bugs.python.org/issue?@action=redirect&bpo=30512] 中所貢獻。）

當連接失敗時，create_connection() 有個選項可以引發一個包含所有錯誤的 ExceptionGroup，而非只引發最後一個錯誤。（由 Irit Katriel 於 bpo-29980 [https://bugs.python.org/issue?@action=redirect&bpo=29980] 中貢獻。）

sqlite3

現在可以透過將 None 傳遞給 set_authorizer() 來停用 authorizer。（由 Erlend E. Aasland 於 bpo-44491 [https://bugs.python.org/issue?@action=redirect&bpo=44491] 中貢獻。）

定序 (collation) 名稱 create_collation() 現在可以包含任何 Unicode 字元。帶有無效字元的定序名稱現在會引發 UnicodeEncodeError 而不是 sqlite3.ProgrammingError。（由 Erlend E. Aasland 在 bpo-44688 [https://bugs.python.org/issue?@action=redirect&bpo=44688] 中貢獻。）

sqlite3 例外現在包含 SQLite 擴充錯誤碼和 SQLite 錯誤名稱（分別為 sqlite_errorcode 和 sqlite_errorname）。（由 Aviv Palivoda、Daniel Shahaf 和 Erlend E. Aasland 在 bpo-16379 [https://bugs.python.org/issue?@action=redirect&bpo=16379] 和 bpo-24139 [https://bugs.python.org/issue?@action=redirect&bpo=24139] 中貢獻。）

將 setlimit() 和 getlimit() 新增到 sqlite3.Connection 以根據連線來設定和取得 SQLite 限制。（由 Erlend E. Aasland 在 bpo-45243 [https://bugs.python.org/issue?@action=redirect&bpo=45243] 中貢獻。）

sqlite3 現在會基於底層 SQLite 函式庫編譯時所使用的預設執行緒模式來設定 sqlite3.threadsafety。（由 Erlend E. Aasland 在 bpo-45613 [https://bugs.python.org/issue?@action=redirect&bpo=45613] 中貢獻。）

sqlite3 如果啟用回呼回溯 (callback traceback)，C 回呼現在使用無法被引發的例外。使用者現在可以註冊一個無法被引發的掛鈎處理程式 (unraisable hook handler) 來改善他們的除錯體驗。（由 Erlend E. Aasland 在 bpo-45828 [https://bugs.python.org/issue?@action=redirect&bpo=45828] 中貢獻。）

跨越不同回滾 (rollback) 的拿取動作不再引發 InterfaceError，我們將其留給 SQLite 函式庫來處理這些情況。（由 Erlend E. Aasland 在 bpo-44092 [https://bugs.python.org/issue?@action=redirect&bpo=44092] 中貢獻。）

將 serialize() 和 deserialize() 新增到 sqlite3.Connection 以用於序列化和反序列化資料庫。（由 Erlend E. Aasland 在 bpo-41930 [https://bugs.python.org/issue?@action=redirect&bpo=41930] 中貢獻。）

於 sqlite3.Connection 加入 create_window_function() 已建立聚合視窗函式 (aggregate window function)。（由 Erlend E. Aasland 於 bpo-34916 [https://bugs.python.org/issue?@action=redirect&bpo=34916] 中貢獻。）

在 sqlite3.Connection 新增 blobopen()。 sqlite3.Blob 允許對 blob 進行增量 I/O 操作 (incremental I/O operations)。（由 Aviv Palivoda 和 Erlend E. Aasland 在 bpo-24905 [https://bugs.python.org/issue?@action=redirect&bpo=24905] 中貢獻。）

string

新增 get_identifiers() 和 is_valid() 於 string.Template，分別能夠回傳所有合格的預留位置 (placeholder) 與是否有任何不合格的預留位置存在。（由 Ben Kehoe 於 gh-90465 [https://github.com/python/cpython/issues/90465] 中貢獻。）

sys

sys.exc_info() 現在從 value（例外實例）衍生出 type 和 traceback 欄位，因此當例外在處理過程中被修改時，變更會反映在 exc_info() 後續呼叫的結果中。（由 Irit Katriel 在 bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711] 中貢獻。）

新增會回傳活躍例外實例 (active exception instance) 的 sys.exception()（等價於 sys.exc_info()[1]）。（由 Irit Katriel 於 bpo-46328 [https://bugs.python.org/issue?@action=redirect&bpo=46328] 中所貢獻。）

新增 sys.flags.safe_path 旗標。（由 Victor Stinner 於 gh-57684 [https://github.com/python/cpython/issues/57684] 中所貢獻。）

sysconfig

新增了三個安裝方案（posix_venv、nt_venv 和 venv），它們在 Python 建立新的虛擬環境或在虛擬環境中執行環境使用。前兩個方案（posix_venv 和 nt_venv）是非 Windows 和 Windows 作業系統所特有的，venv 本質上會根據 Python 運行的作業系統來做為其中之一的別名。這對修改 sysconfig.get_preferred_scheme() 的下游發布者很有用。建立新虛擬環境的第三方程式碼應該使用新的 venv 安裝方案來確定路徑，就像 venv 一樣。（由 Miro Hrončok 在 bpo-45413 [https://bugs.python.org/issue?@action=redirect&bpo=45413] 中貢獻。）

tempfile

SpooledTemporaryFile 物件現在完整實作了 io.BufferedIOBase 或 io.TextIOBase 的方法（取決於檔案模式），這使它們能夠正確地使用需要類檔案物件的 API，例如壓縮模組。（由 Carey Metcalfe 在 gh-70363 [https://github.com/python/cpython/issues/70363] 中貢獻。）

threading

在 Unix 上，如果 sem_clockwait() 函式在 C 函式庫（glibc 2.30 與其更新的版本）中可被使用，則 threading.Lock.acquire() 方法現在會使用單調時鐘 (time.CLOCK_MONOTONIC) 用於超時 (timeout)，而不是使用系統時鐘 (time.CLOCK_REALTIME)，以免受系統時鐘變化的影響。 由 Victor Stinner 在 bpo-41710 [https://bugs.python.org/issue?@action=redirect&bpo=41710] 中貢獻。）

time

在 Unix 上，如果可用的話，time.sleep() 現在會使用 clock_nanosleep() 或 nanosleep() 函式，其解析度為 1 納秒（10⁻⁹ 秒），而不是使用解析度為 1 微秒（10⁻⁶ 秒）的 select()。（由 Benjamin Szőke 和 Victor Stinner 在 bpo-21302 [https://bugs.python.org/issue?@action=redirect&bpo=21302] 中貢獻。）

在 Windows 8.1 或更新的平台上，time.sleep() 現在使用了一個基於高解析度計時器 [https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/high-resolution-timers]的可等待 (waitable) 計時器，解析度為 100 奈秒（即 10⁻⁷ 秒）。在這之前，它只有 1 微秒（10⁻³ 秒） 的解析度。（由 Benjamin Szőke、Donghee Na、Eryk Sun 和 Victor Stinner 於 bpo-21302 [https://bugs.python.org/issue?@action=redirect&bpo=21302] 與 bpo-45429 [https://bugs.python.org/issue?@action=redirect&bpo=45429] 中貢獻。）

tkinter

新增了 info_patchlevel() 方法，它會回傳 Tcl 函式庫的確切版本以作為類似於 sys.version_info 的附名元組。（由 Serhiy Storchaka 在 gh-91827 [https://github.com/python/cpython/issues/91827] 中貢獻。）

traceback

新增 traceback.StackSummary.format_frame_summary() 以允許使用者覆蓋回溯中出現的幀及它們的格式。（由 Ammar Askar 在 bpo-44569 [https://bugs.python.org/issue?@action=redirect&bpo=44569] 中貢獻。）

新增 traceback.TracebackException.print()，它會印出格式化的 TracebackException 實例至一個檔案。（由 Irit Katriel 在 bpo-33809 [https://bugs.python.org/issue?@action=redirect&bpo=33809] 中貢獻。）

typing

重大變更請見 型別提示相關的新特性。

新增 typing.assert_never() 和 typing.Never。 typing.assert_never() 可用於要型別檢查器確認某行程式碼是否不可觸及。在執行環境，它會引發 AssertionError。（由 Jelle Zijlstra 在 gh-90633 [https://github.com/python/cpython/issues/90633] 中貢獻。）

新增 typing.reveal_type()，這可用於請求型別檢查器為給定運算式推斷出什麼型別。在執行環境它會印出接收到的值的型別。（由 Jelle Zijlstra 在 gh-90572 [https://github.com/python/cpython/issues/90572] 中貢獻。）

新增 typing.assert_type()，這可用於要型別檢查器確認它為給定運算式推斷的型別是否與給定型別相符。在執行環境，它只會回傳接收到的值。（由 Jelle Zijlstra 在 gh-90638 [https://github.com/python/cpython/issues/90638] 中貢獻。）

typing.TypedDict 型別現可為泛型。（由 Samodya Abeysiriwardane 於 gh-89026 [https://github.com/python/cpython/issues/89026] 中所貢獻。）

NamedTuple 型別現可為泛型。（由 Serhiy Storchaka 於 bpo-43923 [https://bugs.python.org/issue?@action=redirect&bpo=43923] 中所貢獻。）

允許繼承 typing.Any，這能有效避免與高度動態類別（例如 mock）相關的型別檢查器錯誤。（由 Shantanu Jain 在 gh-91154 [https://github.com/python/cpython/issues/91154] 中貢獻。）

typing.final() 裝飾器現在會在被裝飾的物件上設定 __final__ 屬性。（由 Serhiy Storchaka 於 gh-90500 [https://github.com/python/cpython/issues/90500] 中所貢獻。）

typing.get_overloads() 函式可用於自我檢查 (introspect) 一個函式的過載 (overload)。typing.clear_overloads() 可用於清除一個函式的所有已註冊過載。（由 Jelle Zijlstra 在 gh-89263 [https://github.com/python/cpython/issues/89263] 中貢獻。）

Protocol 子類別的 __init__() 方法現在被保留。（由 Adrian Garcia Badarasco 在 gh-88970 [https://github.com/python/cpython/issues/88970] 中貢獻。）

空元組型別 (Tuple[()]) 的表示法得到簡化，這會影響自我檢查 (introspection)，例如 get_args(Tuple[()]) 的求值現在會是 () 而不是 ((),)。（由 Serhiy Storchaka 在 gh-91137 [https://github.com/python/cpython/issues/91137] 中貢獻。）

透過刪除私有 typing._type_check 函式中的可呼叫檢查，放寬型別標註的執行環境要求。（由 Gregory Beauregard 在 gh-90802 [https://github.com/python/cpython/issues/90802] 中貢獻。）

作為PEP 585 泛化別名中的前向參照，typing.get_type_hints() 現支援了為字串求值 (evaluate)。（由 Niklas Rosenstein 在 gh-85542 [https://github.com/python/cpython/issues/85542] 中貢獻。）

typing.get_type_hints() 不再將 Optional 新增到預設為 None 的參數中。（由 Nikita Sobolev 在 gh-90353 [https://github.com/python/cpython/issues/90353] 中貢獻。）

typing.get_type_hints() 現在支援為無修飾 (bare) 字串化 (stringified) 的 ClassVar 標註來求值。（由 Gregory Beauregard 在 gh-90711 [https://github.com/python/cpython/issues/90711] 中貢獻。）

typing.no_type_check() 不再修改外部類別和函式。它現在也正確地將類別方法標記為不需進行型別檢查。（由 Nikita Sobolev 在 gh-90729 [https://github.com/python/cpython/issues/90729] 中貢獻。）

unicodedata

Unicode 資料庫被更新為 14.0.0 版本。（Benjamin Peterson 於 bpo-45190 [https://bugs.python.org/issue?@action=redirect&bpo=45190] 中所貢獻。）

unittest

新增 TestCase 類別的 enterContext() 與 enterClassContext() 方法、 IsolatedAsyncioTestCase 類別 的 enterAsyncContext() 方法、unittest.enterModuleContext() 函式。（由 Serhiy Storchaka 於 bpo-45046 [https://bugs.python.org/issue?@action=redirect&bpo=45046] 貢獻。）

venv

建立新的 Python 虛擬環境時，venv sysconfig 安裝方案會被用於確定環境內的路徑。當 Python 在虛擬環境中運行時，預設使用相同的安裝方案。這意味著下游發布者可以在不改變虛擬環境行為的情況下更改預設的 sysconfig 安裝方案。建立新虛擬環境的第三方程式碼也應該這樣做。（由 Miro Hrončok 在 bpo-45413 [https://bugs.python.org/issue?@action=redirect&bpo=45413] 中貢獻。）

warnings

warnings.catch_warnings() 現在接受 warnings.simplefilter() 的引數，提供了一種更簡潔的方法來在本地端忽略警告或將它們轉換為錯誤。（由 Zac Hatfield-Dodds 在 bpo-47074 [https://bugs.python.org/issue?@action=redirect&bpo=47074] 中貢獻。）

zipfile

新增了對指定成員名稱編碼的支援，以便在 ZipFile 的目錄和檔案標頭中讀取元資料 (metadata)。（由 Stephen J. Turnbull 和 Serhiy Storchaka 在 bpo-28080 [https://bugs.python.org/issue?@action=redirect&bpo=28080] 中貢獻。）

新增 ZipFile.mkdir() 以在 ZIP 歸檔中建立新的目錄。（由 Sam Ezeh 於 gh-49083 [https://github.com/python/cpython/issues/49083] 貢獻。）

於 zipfile.Path 新增 stem、suffix 和 suffixes。（由 Miguel Brito 於 gh-88261 [https://github.com/python/cpython/issues/88261] 貢獻。）

最佳化

這個部分會涵蓋到特定的最佳化，但獨立於擁有自己一個說明的更快的 CPython 計畫。

編譯器現在對僅包含格式程式碼 %s、%r 和 %a 的字串文本 (string literal) 進行簡單的 printf 風格 % 格式化 (printf-style % formatting) 最佳化並使其與相應的 f-string 運算式一樣快。（由 Serhiy Storchaka 在 bpo-28307 [https://bugs.python.org/issue?@action=redirect&bpo=28307] 中貢獻。）

整數除法 (//) 為了編譯器最佳化而被調校過。現在將 int 除以小於 2**30 的值時，在 x86-64 上快了大約 20%。（由 Gregory P. Smith 和 Tim Peters 在 gh-90564 [https://github.com/python/cpython/issues/90564] 中貢獻。）

針對小於 2**30 的整數，sum() 現在快了將近 30%。（由 Stefan Behnel 於 gh-68264 [https://github.com/python/cpython/issues/68264] 中所貢獻。）

調整 list 大小在常見情況下增進了效能，為 list.append() 加快了約 15% 並為簡單的 list comprehension 加快了高達 20-30%（由 Dennis Sweeney 在 gh-91165 [https://github.com/python/cpython/issues/91165] 中貢獻。）

當所有鍵都是 Unicode 物件時，字典不儲存雜湊值，減少了 dict 的大小。例如，sys.getsizeof(dict.fromkeys("abcdefg")) 在 64-bit 平台上從 352 位元組減少到 272 位元組（減少 23%）。（由 Inada Naoki 在 bpo-46845 [https://bugs.python.org/issue?@action=redirect&bpo=46845] 中貢獻。）

使用 asyncio.DatagramProtocol 以透過 UDP 傳輸大文件時，現在速度提高了幾個數量級，傳輸 ≈60 MiB 檔案的速度提高了 100 多倍。（由 msoxzw 在 gh-91487 [https://github.com/python/cpython/issues/91487] 中貢獻。）

math 函式 comb() 和 perm() 針對較大引數現在快了 ≈10 倍（對於更大的 k 有更大的加速）。（由 Serhiy Storchaka 在 bpo-37295 [https://bugs.python.org/issue?@action=redirect&bpo=37295] 中貢獻。）

statistics 函式 mean()、variance() 和 stdev() 現在會一次性的消耗疊代器，而不是先將它們轉換為 list，這讓速度提升為兩倍並可以節省大量記憶體空間。（由 Raymond Hettinger 在 gh-90415 [https://github.com/python/cpython/issues/90415] 中貢獻。）

unicodedata.normalize() 現在在常數時間內規範化 (normalize) 純 ASCII 字串。（由 Donghee Na 在 bpo-44987 [https://bugs.python.org/issue?@action=redirect&bpo=44987] 中貢獻。）

更快的 CPython

當使用基準量測套裝軟體 pyperformance [https://github.com/python/pyperformance] 量測並以 GCC 於 Ubuntu Linux 上編譯，Python 3.11 平均比 Python 3.10 快了 25% [https://github.com/faster-cpython/ideas#published-results]。根據程式工作量可能有所不同，整體加速程度可達 10-60%。

此計畫專注在 Python 的 更快的啟動 和 更快的運行程式。不在此專案內的最佳化被獨立列出在 最佳化。

更快的啟動

凍結引入 (Frozen imports) / 靜態程式碼物件 (Static code objects)

Python 將位元組碼於 __pycache__ 目錄中存為快取來加速模組的載入。

在先前的 3.10 中，執行 Python 模組會像是這樣：

Read __pycache__ -> Unmarshal -> Heap allocated code object -> Evaluate

在 Python 3.11 中，核心模組在 Python 啟動時必須被「凍結」，這意味著它們的程式碼物件（和位元組碼）是由直譯器靜態分配的。這將模組執行過程中的步驟減少為：

Statically allocated code object -> Evaluate

在 Python 3.11 中直譯器啟動速度快了 10-15%。這對於使用 Python 所撰寫的短暫程式有著巨大影響。

（由 Eric Snow、Guido van Rossum 與 Kumar Aditya 於多個 issue 中貢獻。）

更快的運行程式

所需資源更少 (cheaper) 且惰性的 (lazy)) Python 幀 (frame)

每當 Python 呼叫 Python 函式時，就會建立保存執行資訊的 Python 幀。以下是針對幀而做的新最佳化：

使幀的建立過程更有效率。

在 C 堆疊 (stack) 中盡量重複利用幀的空間來避免記憶體分配。

讓內部幀結構只包含必要資訊，使其更加精簡。在過去，幀必須帶有額外的偵錯與記憶體管理的資訊。

舊式幀物件現在僅在除錯器或 Python 自我檢查函式（例如 sys._getframe() 或 inspect.currentframe()）請求時才建立。對於大多數使用者程式碼，根本不會建立任何幀物件。結果幾乎所有 Python 函式呼叫都顯著加速。我們以 pyperformance 測得了 3-7% 的加速。

（由 Mark Shannon 於 bpo-44590 [https://bugs.python.org/issue?@action=redirect&bpo=44590] 中所貢獻。）

行內 Python 函式呼叫

在 Python 函式呼叫期間，Python 將呼叫一個正在求值的 C 函式來直譯該函式的程式碼，這有效地將純 Python 遞迴限制在對 C 堆疊的安全範圍內。

在 3.11 中，當 CPython 檢測到 Python 程式碼呼叫另一個 Python 函式時，它會設立一個新框架 (frame)，並「跳轉」到新框架內的新程式碼，這避免了呼叫整個 C 直譯函式。

現在大多數 Python 函式的呼叫因為不會佔用 C 堆疊空間而被加速。在斐波那契 (fibonacci) 或階乘等簡單遞迴函式中，觀察到 1.7 倍的加速。這也意味著遞迴函式可以遞迴得更深（如果使用者有增加遞迴限制）。我們在 pyperformance 測得 1-3% 的改進。

（由 Pablo Galindo 與 Mark Shannon 於 bpo-45256 [https://bugs.python.org/issue?@action=redirect&bpo=45256] 中所貢獻。）

PEP 659：特化的適應性直譯器

PEP 659 [https://peps.python.org/pep-0659/] 是加速 CPython 專案的關鍵部分之一。一般的想法是，雖然 Python 是一種動態語言，但大多數程式碼都有物件和型別很少去更改的區域。這個概念被稱為型別穩定 (type stability)。

在執行環境，Python 將嘗試在執行中的程式碼內尋找常用模式和型別穩定，然後 Python 將用更特化的操作替換目前操作。這種特化操作運用了僅適用於那些用例/型別的快速路徑，這通常優於它們的泛用對應 (generic counterparts)。這也引入了另一個稱為行內快取 (inline caching)的概念，其中 Python 將繁重操作的結果直接快取在位元組碼中。

特化程式 (specializer) 還將某些常用指示 (common instruction) 組合成一個超級指示 (superinstruction)，這減少了執行期間的開銷。

Python 只會在看到「熱」（被多次執行的）程式碼時特化，這可以防止 Python 將時間浪費在只運行一次的程式碼上。當程式碼過於動態或用途發生變化時，Python 也可以去特化 (de-specialize)。特化會定期被嘗試執行，而嘗試的成本也不會太高，這讓特化得以適應新的環境。

（PEP 由 Mark Shannon 撰寫、概念啟發自 Stefan Brunthaler。詳情請見 PEP 659 [https://peps.python.org/pep-0659/]。由 Mark Shannon 和 Brandt Bucher 實作，Irit Katriel 和 Dennis Sweeney 亦提供了額外的幫助。）

操作

形式

特化

操作加速程度（上限）

貢獻者

二元操作

x + x

x - x

x * x

常見型別如 int、float 與 str 的二元加法、乘法與減法，為底層型別採取了特製的快速路徑。

10%

Mark Shannon, Donghee Na, Brandt Bucher, Dennis Sweeney

下標

a[i]

下標容器型別如 list、tuple 和 dict 直接索引底層的資料結構。

下標自訂 __getitem__() 也是行內的，類似於 行內 Python 函式呼叫。

10-25%

Irit Katriel, Mark Shannon

儲存下標

a[i] = z

類似於上面的下標特化。

10-25%

Dennis Sweeney

呼叫

f(arg)

C(arg)

常見內建 (C) 函式和型別的呼叫，例如 len() 和 str，會直接呼叫它們的 C 版本底層，這避免了透過內部呼叫的慣例。

20%

Mark Shannon, Ken Jin

載入全域變數

print

len

全域/內建之命名空間內的物件索引被快取起來。載入全域與內建變數不需要任何命名空間的查找。

[1]

Mark Shannon

載入屬性

o.attr

和載入全域變數類似，類別/物件之命名空間內的屬性索引被快取起來。在大部分情況中，載入屬性不需要任何命名空間的查找。

[2]

Mark Shannon

載入要呼叫的方法

o.meth()

方法的真實記憶體地址被快取 (cache) 起來，方法的載入現在不需要命名空間的查找 -- 即便有很長繼承鏈結的類別也是。

10-20%

Ken Jin, Mark Shannon

儲存屬性

o.attr = z

和載入屬性的最佳化相似。

2% 於 pyperformance 中

Mark Shannon

拆解 (unpack) 序列

*seq

為像是 list 和 tuple 的常見容器所特化，避免了內部呼叫慣例。

8%

Brandt Bucher

[1]

類似的最佳化自從 Python 3.8 就存在。3.11 特別處理了更多形式並減少效能開銷 (overhead)。

[2]

類似的最佳化自從 Python 3.10 就存在。3.11 特別處理了更多形式。此外，所有屬性載入也被 bpo-45947 [https://bugs.python.org/issue?@action=redirect&bpo=45947] 所加速。

雜項

物件現在因為使用了惰性建立的物件命名空間所以需要更少的記憶體。它們的命名空間字典現在也更自由地共享鍵。（由 Mark Shannon 於 bpo-45340 [https://bugs.python.org/issue?@action=redirect&bpo=45340] 和 bpo-40116 [https://bugs.python.org/issue?@action=redirect&bpo=40116] 貢獻。 ）

實作了「無代價 (Zero-cost)」的例外，消除了在沒有例外被引發時的 try 陳述式開銷。（由 Mark Shannon 於 bpo-40222 [https://bugs.python.org/issue?@action=redirect&bpo=40222] 貢獻。）

在直譯器內使用更簡潔的例外表示法將捕獲一個例外所需的時間減少了大約 10%。 由 Irit Katriel 在 bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711] 中貢獻。）

re 的正規表示式比對引擎部分被重構，且現在會有支援的平台上使用 computed gotos（或者「執行緒程式碼 (threaded code)」），因此 Python 3.11 在執行 pyperformance 正規表示式基準量測 [https://pyperformance.readthedocs.io/benchmarks.html#regex-dna]的表現上比起 Python 3.10 快了 10%。（由 Brandt Bucher 於 gh-91404 [https://github.com/python/cpython/issues/91404] 中貢獻。）

FAQ

我該如何在程式碼中取得這些加速？

撰寫符合 Python 風格 (Pythonic) 且依循常見最佳實踐的程式碼就好，你不需要改變你的程式碼。CPython 加速計畫中，我們為所觀察到的常見程式編寫模式來做最佳化。

Python 3.11 會不會使用更多記憶體？

也許不會。我們預期不會有超出 3.10 20% 的記憶體使用量。這數字會和上述禎物件與物件字典的記憶體最佳化而有所偏差。

我在我的程式當中沒感覺到任何加速，為什麼？

某些程式中不會有顯著的好處。如果你的程式花了大部分的時間在 I/O 操作上，或已經將大部分計算用像是 numpy 的 C 擴充函式庫處理，那就不會有明顯的加速。這個計畫是對純 Python 的工作負荷最有幫助。

此外，pyperformance 數值為一個幾何平均數 (geometric mean)。即便在 pyperformance 基準量測中，某些測試稍微慢了一些，但其他加快了將近兩倍！

有用到 JIT 編譯器嗎？

沒有，我們還在探索其他最佳化方式。

關於

CPython 加速計畫探索了各種 CPython 最佳化的可能性。主要團隊由微軟 (microsoft) 所資助以全職發展該計畫，Pablo Galindo Salgado 亦由彭博有限合夥企業 (Bloomberg LP) 資助來兼職開發，更有許許多多來自社群的自發性貢獻者。

CPython 位元組碼變更

位元組碼現在包含行內快取條目，它們採用新添加的 CACHE 指示的形式。許多操作碼預期後面要有確切數量的快取，並指示直譯器在執行環境跳過它們。傳遞的 (populated) 快取看起來像任意指示，因此在讀取或修改包含加速資料的原始且適應 (adaptive) 位元組碼時應格外小心。

新增 opcode

ASYNC_GEN_WRAP、RETURN_GENERATOR 和 SEND 被用於產生器與協程。

COPY_FREE_VARS，避免了為閉包 (closure) 而生的特殊呼叫方 (caller-side) 程式碼的需求。

JUMP_BACKWARD_NO_INTERRUPT，用於某些不需要處理中斷的循環。

MAKE_CELL 被用於建立 Cell 物件。

CHECK_EG_MATCH 和 PREP_RERAISE_STAR，處理 PEP 654 [https://peps.python.org/pep-0654/] 所加入的新增例外群組和 except*。

PUSH_EXC_INFO 被用於例外處理函式。

RESUME，為無操作 (no-po)，用於內部追查、除錯和最佳化檢查。

被取代的操作碼 (opcode)

被取代的操作碼

新的操作碼

註記

BINARY_*

INPLACE_*

BINARY_OP

以單一一個操作碼來取代所有數值的、二進位/原位 (in-place) 操作碼

CALL_FUNCTION

CALL_FUNCTION_KW

CALL_METHOD

CALL

KW_NAMES

PRECALL

PUSH_NULL

將方法的引數搬移 (argument shifting) 與關鍵字引數的處理分離開來；允許更好的呼叫特化

DUP_TOP

DUP_TOP_TWO

ROT_TWO

ROT_THREE

ROT_FOUR

ROT_N

COPY

SWAP

堆疊操作指示

JUMP_IF_NOT_EXC_MATCH

CHECK_EXC_MATCH

現在執行檢查但不跳位 (jump)

JUMP_ABSOLUTE

POP_JUMP_IF_FALSE

POP_JUMP_IF_TRUE

JUMP_BACKWARD

POP_JUMP_BACKWARD_IF_*

POP_JUMP_FORWARD_IF_*

參見 [3]；每個方向的 TRUE、FALSE、NONE 和 NOT_NONE 變體

SETUP_WITH

SETUP_ASYNC_WITH

BEFORE_WITH

with 區塊設置

[3]

所有跳位操作碼 (jump opcode) 現在都是相對的，包括現有的 JUMP_IF_TRUE_OR_POP 和 JUMP_IF_FALSE_OR_POP。該引數現在是目前指示 (instruction) 的偏移量而不是絕對位置。

有更動/被移除的 opcode

更改了 MATCH_CLASS 和 MATCH_KEYS ，不再推送一個額外的布林值來表示成功/失敗。取而代之的是會在失敗時推送 None，而非一個包含提取值的元組。

更改了運作於例外的操作碼以反映它們現在在堆疊中的表示為一項而不是三項（請參閱 gh-89874 [https://github.com/python/cpython/issues/89874]）。

刪除 COPY_DICT_WITHOUT_KEYS、GEN_START、POP_BLOCK、SETUP_FINALLY 和 YIELD_FROM。

已棄用

這個部分列出了在 Python 3.11 中棄用的 Python API。

被棄用的 C API 被獨立列出。

語言/內建

鏈接 classmethod 描述器（在 bpo-19072 [https://bugs.python.org/issue?@action=redirect&bpo=19072] 中引入）現已棄用。它不能再用於包裝其他描述器，例如 property。此功能的核心設計存在缺陷，並導致了許多下游問題。要「傳遞通過 (pass-through)」classmethod，請考慮使用 Python 3.10 中添加的 __wrapped__ 屬性。（由 Raymond Hettinger 在 gh-89519 [https://github.com/python/cpython/issues/89519] 中貢獻。）

值大於 0o377（十進位為 255）的字串和位元組文本值 (bytes literal) 中的八進位跳脫 (octal escape) 現在會產生 DeprecationWarning。在未來的 Python 版本中，他們將引發一個 SyntaxWarning 並最終引發一個 SyntaxError。（由 Serhiy Storchaka 在 gh-81548 [https://github.com/python/cpython/issues/81548] 中貢獻。）

int() 到 __trunc__() 的授權 (delegation) 現已棄用。當 type(a) 有實作 __trunc__() 但沒有 __int__() 或 __index__()，呼叫 int(a) 現在會引發一個 DeprecationWarning。（由 Zackery Spytz 在 bpo-44977 [https://bugs.python.org/issue?@action=redirect&bpo=44977] 中貢獻。）

模組

PEP 594 [https://peps.python.org/pep-0594/] 引領下列模組的棄用，並排訂於 Python 3.13 移除：

aifc

chunk

msilib

pipes

telnetlib

audioop

crypt

nis

sndhdr

uu

cgi

imghdr

nntplib

spwd

xdrlib

cgitb

mailcap

ossaudiodev

sunau

（由 Brett Cannon 和 Victor Stinner 分別於 bpo-47061 [https://bugs.python.org/issue?@action=redirect&bpo=47061] 與 gh-68966 [https://github.com/python/cpython/issues/68966] 中所貢獻。）

asynchat、asyncore 和 smtpd 至少在 Python 3.6 以前就被棄用，它們的文件與棄用警告現在已被更新為會提示它們即將於 Python 3.12 中移除。（由 Hugo van Kemenade 於 bpo-47022 [https://bugs.python.org/issue?@action=redirect&bpo=47022] 中貢獻。）

:mod:!lib2to3` 套件和 2to3 工具現已棄用，可能無法剖析 Python 3.10 或更新版本。有關詳細資訊請參閱 PEP 617 [https://peps.python.org/pep-0617/]，它引入了新的 PEG 剖析器。（由 Victor Stinner 在 bpo-40360 [https://bugs.python.org/issue?@action=redirect&bpo=40360] 中貢獻。）

未被記錄於文件中的 sre_compile、sre_constants 和 sre_parse 模組現在已被棄用。（由 Serhiy Storchaka 在 bpo-47152 [https://bugs.python.org/issue?@action=redirect&bpo=47152] 中貢獻。）

標準函式庫

以下 configparser 相關項目已在 Python 3.2 中棄用，它們的棄用警告現在會提示它們即將於 Python 3.12 中移除：

configparser.SafeConfigParser 類別

configparser.ParsingError.filename 屬性

configparser.RawConfigParser.readfp() 方法

（由 Hugo van Kemenade 於 bpo-45173 [https://bugs.python.org/issue?@action=redirect&bpo=45173] 中所貢獻。）

configparser.LegacyInterpolation 自 Python 3.2 起已在文件字串中棄用，並且未在 configparser 文件中列出。它現在會發出一個 DeprecationWarning 並將在 Python 3.13 中刪除。請改用 configparser.BasicInterpolation 或 configparser.ExtendedInterpolation。（由 Hugo van Kemenade 在 bpo-46607 [https://bugs.python.org/issue?@action=redirect&bpo=46607] 中貢獻。）

舊的 importlib.resources 函式集因為不支援定位套件子目錄中的資源而被棄用、並將在未來的 Python 版本中刪除，取而代之的是在 Python 3.9 中添加的替代方案：

importlib.resources.contents()

importlib.resources.is_resource()

importlib.resources.open_binary()

importlib.resources.open_text()

importlib.resources.read_binary()

importlib.resources.read_text()

importlib.resources.path()

locale.getdefaultlocale() 函式已被棄用且將於 Python 3.15 中移除。請改用 locale.setlocale()、locale.getpreferredencoding(False) 和 locale.getlocale()。（Victor Stinner 於 gh-90817 [https://github.com/python/cpython/issues/90817] 中所貢獻。）

locale.resetlocale() 函式已棄用並將於 Python 3.13 中移除，請改用 locale.setlocale(locale.LC_ALL, "")。（由 Victor Stinner 於 gh-90817 [https://github.com/python/cpython/issues/90817] 中所貢獻。）

現在將對正規表示式中的數值群組參照 (numerical group references) 和群組名稱套用更嚴格的規則。現在只接受 ASCII 數字序列作為數值參照，並且 bytes 模式 (pattern) 的群組名稱和替換字串中只能包含 ASCII 字母、數字和底線。目前，會針對違反這些規則的語法發出棄用警告。（由 Serhiy Storchaka 在 gh-91760 [https://github.com/python/cpython/issues/91760] 中貢獻。）

在 re 模組中，re.template() 函式和相應的 re.TEMPLATE 和 re.T 旗標被棄用，因為它們沒被記錄於文件中並且缺乏明顯的目的。它們將在 Python 3.13 中被刪除。（由 Serhiy Storchaka 和 Miro Hrončok 在 gh-92728 [https://github.com/python/cpython/issues/92728] 中貢獻。）

turtle.settiltangle() 自 Python 3.1 以來已被棄用；它現在會發出棄用警告，並將在 Python 3.13 中刪除。請改用 turtle.tiltangle()（它之前被錯誤地標記為已棄用，其文件字串現在已更正）。（由 Hugo van Kemenade 在 bpo-45837 [https://bugs.python.org/issue?@action=redirect&bpo=45837] 中貢獻。）

僅用於支援 Python 2 和 Python 3 程式碼間相容性的 typing.Text 現已棄用。目前未計劃刪除它，但鼓勵用戶盡可能使用 str 代替。（由 Alex Waygood 在 gh-92332 [https://github.com/python/cpython/issues/92332] 中貢獻。）

用於建構 typing.TypedDict 型別的關鍵字引數語法現已棄用。將在 Python 3.13 中停止支援。（由 Jingchen Ye 在 gh-90224 [https://github.com/python/cpython/issues/90224] 中貢獻。）

webbrowser.MacOSX 已被棄用且將於 Python 3.13 中移除。它並沒有被測試過、沒紀錄於文件、也沒有被 webbrowser 本身使用。（由 Donghee Na 於 bpo-42255 [https://bugs.python.org/issue?@action=redirect&bpo=42255]。）

回傳從 TestCase 和 IsolatedAsyncioTestCase 測試方法（預設的 None 值除外）給定值的行為現已棄用。

棄用以下並沒有正式紀錄於文件中的 unittest 函式，並預計於 Python 3.13 中移除：

unittest.findTestCases()

unittest.makeSuite()

unittest.getTestCaseNames()

改用 TestLoader 方法：

unittest.TestLoader.loadTestsFromModule()

unittest.TestLoader.loadTestsFromTestCase()

unittest.TestLoader.getTestCaseNames()

（由 Erlend E. Aasland 於 bpo-5846 [https://bugs.python.org/issue?@action=redirect&bpo=5846] 中所貢獻。）

unittest.TestProgram.usageExit() 被標記為已棄用，即將在 3.13 中移除（由 Carlos Damázio 在 gh-67048 [https://github.com/python/cpython/issues/67048] 中貢獻。）

Python 3.12 中待決議的移除項目

下列 API 已在先前的 Python 發布版本中棄用，並將於 Python 3.12 中移除。

待定的 C API 移除項目為獨立列出的。

asynchat 模組

asyncore 模組

整個 distutils 套件

imp 模組

typing.io 命名空間

typing.re 命名空間

cgi.log()

importlib.find_loader()

importlib.abc.Loader.module_repr()

importlib.abc.MetaPathFinder.find_module()

importlib.abc.PathEntryFinder.find_loader()

importlib.abc.PathEntryFinder.find_module()

importlib.machinery.BuiltinImporter.find_module()

importlib.machinery.BuiltinLoader.module_repr()

importlib.machinery.FileFinder.find_loader()

importlib.machinery.FileFinder.find_module()

importlib.machinery.FrozenImporter.find_module()

importlib.machinery.FrozenLoader.module_repr()

importlib.machinery.PathFinder.find_module()

importlib.machinery.WindowsRegistryFinder.find_module()

importlib.util.module_for_loader()

importlib.util.set_loader_wrapper()

importlib.util.set_package_wrapper()

pkgutil.ImpImporter

pkgutil.ImpLoader

pathlib.Path.link_to()

sqlite3.enable_shared_cache()

sqlite3.OptimizedUnicode()

PYTHONTHREADDEBUG 環境變數

unittest 中被棄用的別名：

已棄用的別名

方法名稱

棄用於

failUnless

assertTrue()

3.1

failIf

assertFalse()

3.1

failUnlessEqual

assertEqual()

3.1

failIfEqual

assertNotEqual()

3.1

failUnlessAlmostEqual

assertAlmostEqual()

3.1

failIfAlmostEqual

assertNotAlmostEqual()

3.1

failUnlessRaises

assertRaises()

3.1

assert_

assertTrue()

3.2

assertEquals

assertEqual()

3.2

assertNotEquals

assertNotEqual()

3.2

assertAlmostEquals

assertAlmostEqual()

3.2

assertNotAlmostEquals

assertNotAlmostEqual()

3.2

assertRegexpMatches

assertRegex()

3.2

assertRaisesRegexp

assertRaisesRegex()

3.2

assertNotRegexpMatches

assertNotRegex()

3.5

已移除

此部分列出 Python 3.11 中移除的 Python API。

被移除的 C API 被獨立列出。

刪除了 @asyncio.coroutine() decorator 使遺留的基於生成器的協程 (generator-based coroutine) 與 async / await 程式碼相容。該函式自 Python 3.8 起已被棄用，計劃於 Python 3.10 刪除。請改用 async def。（由 Illia Volochii 在 bpo-43216 [https://bugs.python.org/issue?@action=redirect&bpo=43216] 中貢獻。）

移除除錯模式中用於包裝遺留基於產生器之協程物件的 asyncio.coroutines.CoroWrapper。（由 Illia Volochii 於 bpo-43216 [https://bugs.python.org/issue?@action=redirect&bpo=43216] 中貢獻。）

因為有重大的安全性考量，Python 3.9 中停用的 asyncio.loop.create_datagram_endpoint() 之 reuse_address 參數目前已經移除。這是因為 UDP socket 選項 SO_REUSEADDR 的行為所致。（由 Hugo van Kemenade 於 bpo-45129 [https://bugs.python.org/issue?@action=redirect&bpo=45129] 中貢獻。）

移除 Python 3.9 中棄用的 binhex 模組，與其相關且相似的 binascii 函式也一併被移除：

binascii.a2b_hqx()

binascii.b2a_hqx()

binascii.rlecode_hqx()

binascii.rldecode_hqx()

binascii.crc_hqx() 維持可用。

（由 Victor Stinner 於 bpo-45085 [https://bugs.python.org/issue?@action=redirect&bpo=45085] 中所貢獻。）

移除 Python 3.9 中棄用的 distutils bdist_msi 命令。請改用 bdist_wheel（wheel 套件）。（由 Hugo van Kemenade 於 bpo-45124 [https://bugs.python.org/issue?@action=redirect&bpo=45124] 中貢獻。）

將 xml.dom.pulldom.DOMEventStream、wsgiref.util.FileWrapper 和 fileinput.FileInput 自 Python 3.9 中棄用的 __getitem__() 方法移除。(由 Hugo van Kemenade 在 bpo-45132 [https://bugs.python.org/issue?@action=redirect&bpo=45132] 中貢獻。)

刪除了已棄用的 gettext 函式 lgettext()、ldgettext()、lngettext() 和 ldngettext()，也刪除了 bind_textdomain_codeset() 函式、NullTranslations.output_charset() 和 NullTranslations.set_output_charset() 方法，以及 translation() 和 install() 的 codeset 參數，因為它們僅被用於 l*gettext() 函式。（由 Donghee Na 和 Serhiy Storchaka 在 bpo-44235 [https://bugs.python.org/issue?@action=redirect&bpo=44235] 中貢獻。）

於 inspect 模組中移除：

Python 3.0 中棄用的 getargspec()；改用 inspect.signature() 或 inspect.getfullargspec()。

Python 3.5 中棄用的 formatargspec() 函式；請直接用 inspect.signature() 函式或 inspect.Signature 物件。

Python 3.5 中停用且沒有被紀錄於文件上的 Signature.from_builtin() 和 Signature.from_function() 方法；改用 Signature.from_callable() 方法。

（由 Hugo van Kemenade 於 bpo-45320 [https://bugs.python.org/issue?@action=redirect&bpo=45320] 中所貢獻。）

自 pathlib.PurePath 中移除 __class_getitem__() 方法，因為它是前一版本中誤加且沒被使用。（由 Nikita Sobolev 於 bpo-46483 [https://bugs.python.org/issue?@action=redirect&bpo=46483] 中所貢獻。）

移除 smtpd 模組中的 MailmanProxy 類別，因為它無法獨立於外部套件 mailman 使用。（由 Donghee Na 於 bpo-35800 [https://bugs.python.org/issue?@action=redirect&bpo=35800] 貢獻。）

移除 _tkinter.TkappType 已被棄用的 split() 方法。（由 Erlend E. Aasland 於 bpo-38371 [https://bugs.python.org/issue?@action=redirect&bpo=38371] 貢獻。）

從 unittest 中刪除了命名空間套件支援。它在 Python 3.4 中引入，但自 Python 3.7 以來已無法運作。（由 Inada Naoki 在 bpo-23882 [https://bugs.python.org/issue?@action=redirect&bpo=23882] 中貢獻。）

將未被記錄於文件中的私有方法 float.__set_format__() 移除，它過去是 Python 3.7 中的 float.__setformat__()。它的文件字串 (docstring) 說到：「你大概不會想要使用這個函式，它只為了讓 Python 測試系列套件 (suite) 使用而存在。」（由 Victor Stinner 於 bpo-46852 [https://bugs.python.org/issue?@action=redirect&bpo=46852] 中貢獻。）

移除 --experimental-isolated-subinterpreters 配置旗標（與對應的 EXPERIMENTAL_ISOLATED_SUBINTERPRETERS 巨集）。

Pynche [https://pypi.org/project/Pynche/] --- Python 風格的自然色彩與色調編輯器 --- 已被移出 Tools/scripts，獨立開發 [https://gitlab.com/warsaw/pynche/-/tree/main]於 Python 原始碼之外。

移植至 Python 3.11

本部分列出了之前描述的 Python API 中可能需要你去更改 Python 程式碼的變更和其他錯誤修復。

C API 的移植被獨立列出。

open()、io.open()、codecs.open() 和 fileinput.FileInput 不再接受 'U'（"universal newline"，通用換行符）文件模式。在 Python 3 中，每當以文本模式 (text mode) 打開檔案時，預設情況下會使用「通用換行符」模式，並且自 Python 3.3 以來就不推薦使用 'U' 旗標。這些函式的 newline 參數控制了通用換行符的作用方式。（由 Victor Stinner 在 bpo-37330 [https://bugs.python.org/issue?@action=redirect&bpo=37330] 中貢獻。）

ast.AST 節點位置現在會在提供給 compile() 和其他相關函式時被驗證。如果檢測到無效位置，則會引發 ValueError。（由 Pablo Galindo 在 gh-93351 [https://github.com/python/cpython/issues/93351] 中貢獻）

在 Python 3.8 中棄用後，禁止將非 concurrent.futures.ThreadPoolExecutor 執行器傳遞給 asyncio.loop.set_default_executor()。（由 Illia Volochii 在 bpo-43234 [https://bugs.python.org/issue?@action=redirect&bpo=43234] 中貢獻。）

calendar：calendar.LocaleTextCalendar 和 calendar.LocaleHTMLCalendar 類別如果沒有指定語言環境，現在會使用 locale.getlocale() 而非 locale.getdefaultlocale()。（由 Victor Stinner 在 bpo-46659 [https://bugs.python.org/issue?@action=redirect&bpo=46659] 中貢獻。）

pdb 模組現在會讀取 'UTF-8' 編碼的 .pdbrc 配置檔案。（Srinivas Reddy Thatiparthy (శ్రీనివాస్ రెడ్డి తాటిపర్తి) 於 bpo-41137 [https://bugs.python.org/issue?@action=redirect&bpo=41137] 貢獻。）

random.sample() 的 population 參數必須是一個序列，不再支援 set 到 list 的自動轉換。此外，如果抽樣大小大於總體大小，則會引發 ValueError。（由 Raymond Hettinger 在 bpo-40465 [https://bugs.python.org/issue?@action=redirect&bpo=40465] 中貢獻。）

刪除了 random.shuffle() 的 random 可選參數。它以前是用於隨機排列 (shuffle) 的任意隨機函式；現在都會使用 random.random()（這是它以前的預設值）。

在 re 正規表示式語法 中，全域行內旗標（例如 (?i)）現在只能在正規表示式的開頭使用。自 Python 3.6 以來，在其他地方使用它們已被棄用。（由 Serhiy Storchaka 在 bpo-47066 [https://bugs.python.org/issue?@action=redirect&bpo=47066] 中貢獻。）

在 re 模組中修復了幾個長期存在的錯誤，在極少數情況下，這些錯誤可能會導致捕獲群組 (capture group) 得到錯誤的結果。因此，這可能會在這些情況下更改捕獲的輸出。（Ma Lin 在 bpo-35859 [https://bugs.python.org/issue?@action=redirect&bpo=35859] 中貢獻。）

建置變更

CPython 現在有 PEP 11 [https://peps.python.org/pep-0011/] Tier 3 支援 [https://peps.python.org/pep-0011/#tier-3] 以用於交叉編譯至 WebAssembly [https://webassembly.org/] 平台 Emscripten [https://emscripten.org/]（wasm32-unknown-emscripten，即瀏覽器中的 Python）和 WebAssembly 系統介面 (WASI) [https://wasi.dev/] (wasm32-unknown-wasi)。這個靈感來自過往的貢獻，例如 Pyodide [https://pyodide.org/]。這些平台提供了有限的 POSIX API 子集；Python 標準函式庫功能和與網路、行程、執行緒、訊號、mmap、用戶/群組相關的模組不開放使用或無法正常使用。（Emscripten 由 Christian Heimes 和 Ethan Smith 在 gh-84461 [https://github.com/python/cpython/issues/84461] 貢獻，WASI 由 Christian Heimes 在 gh-90473 [https://github.com/python/cpython/issues/90473] 貢獻；平台在 gh-95085 [https://github.com/python/cpython/issues/95085] 中推廣）

建置 CPython 現在必須要有：

C11 [https://en.cppreference.com/w/c/11] 編譯器與標準函式庫。可選的 C11 特性 [https://en.wikipedia.org/wiki/C11_(C_standard_revision)#Optional_features] 並非必要。（由 Victor Stinner 於 bpo-46656 [https://bugs.python.org/issue?@action=redirect&bpo=46656]、bpo-45440 [https://bugs.python.org/issue?@action=redirect&bpo=45440] 和 bpo-46640 [https://bugs.python.org/issue?@action=redirect&bpo=46640] 中貢獻。）

對 IEEE 754 [https://en.wikipedia.org/wiki/IEEE_754] 浮點數的支援（由 Victor Stinner 於 bpo-46917 [https://bugs.python.org/issue?@action=redirect&bpo=46917] 中所貢獻。）

Py_NO_NAN 巨集已被移除。因為 CPython 現在需要 IEEE 754 浮點數，NaN 數值皆為可得的。（由 Victor Stinner 在 bpo-46656 [https://bugs.python.org/issue?@action=redirect&bpo=46656] 中貢獻。）

tkinter 套件現在必須要有 Tcl/Tk [https://www.tcl.tk] 8.5.12 或更新的版本。（由 Serhiy Storchaka 於 bpo-46996 [https://bugs.python.org/issue?@action=redirect&bpo=46996] 中所貢獻。）

大多數 stdlib 擴充模組的依賴套件、編譯器旗標 (compiler flag) 和鏈接器旗標 (linker flags) 現在可以透過 configure 檢測出來。（當可用時）pkg-config [https://www.freedesktop.org/wiki/Software/pkg-config/] 會檢測出 libffi、libnsl、libsqlite3、zlib、bzip2、liblzma、libcrypt、Tcl/Tk 和 uuid 旗標。tkinter 現在需要一個 pkg-config 命令來檢測 Tcl/Tk [https://www.tcl.tk] 標頭檔和函式庫的開發設定。（由 Christian Heimes 和 Erlend Egeberg Aasland 在 bpo-45847 [https://bugs.python.org/issue?@action=redirect&bpo=45847]、bpo-45747 [https://bugs.python.org/issue?@action=redirect&bpo=45747] 和 bpo-45763 [https://bugs.python.org/issue?@action=redirect&bpo=45763] 中貢獻。）

libpython 不再鏈接到 libcrypt。（由 Mike Gilbert 在 bpo-45433 [https://bugs.python.org/issue?@action=redirect&bpo=45433] 中貢獻。）

CPython 現在可以透過將 thin 傳遞給 --with-lto（也就是 --with-lto=thin）來以 ThinLTO [https://clang.llvm.org/docs/ThinLTO.html] 選項建置。（由 Donghee Na 與 Brett Holman 於 bpo-44340 [https://bugs.python.org/issue?@action=redirect&bpo=44340] 中所貢獻。）

Freelists for object structs can now be disabled. A new configure option --without-freelists can be used to disable all freelists except empty tuple singleton. (Contributed by Christian Heimes in bpo-45522 [https://bugs.python.org/issue?@action=redirect&bpo=45522].)

Modules/Setup 和 Modules/makesetup 已得到改進和綁定。現在可以透過 makesetup 建置擴充模組。除了一些測試模組外，所有模組都可以靜態鏈接到主要的二進制文件或函式庫中。（由 Brett Cannon 和 Christian Heimes 在 bpo-45548 [https://bugs.python.org/issue?@action=redirect&bpo=45548]、bpo-45570 [https://bugs.python.org/issue?@action=redirect&bpo=45570]、bpo-45571 [https://bugs.python.org/issue?@action=redirect&bpo=45571] 和 bpo-43974 [https://bugs.python.org/issue?@action=redirect&bpo=43974] 中貢獻。）

備註

使用環境變數 TCLTK_CFLAGS 和 TCLTK_LIBS 以手動指定 Tcl/Tk 標頭檔和函式庫的位置。configure 選項 —with-tcltk-includes 和 —with-tcltk-libs 已被刪除。

RHEL 7 和 CentOS 7 上的開發套件並無提供 tcl.pc 和 tk.pc；要使用 TCLTK_LIBS="-ltk8.5 -ltkstub8.5 -ltcl8.5"。目錄 Misc/rhel7 包含 .pc 檔案與如何使用 RHEL 7 和 CentOS 7 的 Tcl/Tk 與 OpenSSL 建置 Python 的指示。

CPython 現在預設使用 30-bit 數字來實作 Python int。以前，在 SIZEOF_VOID_P >= 8 的平台上預設使用 30-bit 數字，否則使用 15-bit 數字，但仍能透過配置腳本的 --enable-big-digits 選項或（於 Windows）PC/pyconfig.h 中的 PYLONG_BITS_IN_DIGIT 變數來明確請求使用 15-bit 數字，但此選項可能會在將來的某個時候被刪除。（由 Mark Dickinson 在 bpo-45569 [https://bugs.python.org/issue?@action=redirect&bpo=45569] 中貢獻。）

C API 變更

新增功能

新增 PyType_GetName() 函式來取得型別的短名。（由 Hai Shi 於 bpo-42035 [https://bugs.python.org/issue?@action=redirect&bpo=42035] 中所貢獻。）

新增 PyType_GetQualName() 函式來取得型別的合格名稱 (qualified name)。（由 Hai Shi 於 bpo-42035 [https://bugs.python.org/issue?@action=redirect&bpo=42035] 中所貢獻。）

在受限 C API (limited C API) 中新增 PyThreadState_EnterTracing() 和 PyThreadState_LeaveTracing() 函式來中止和繼續追蹤 (tracing) 和性能分析 (profiling)。（由 Victor Stinner 於 bpo-43760 [https://bugs.python.org/issue?@action=redirect&bpo=43760] 中貢獻。）

添加了 Py_Version 常數，其值與 PY_VERSION_HEX 相同。（由 Gabriele N. Tornetta 在 bpo-43931 [https://bugs.python.org/issue?@action=redirect&bpo=43931] 中貢獻。）

Py_buffer 與 API 目前是受限 API 與穩定 ABI 中的一部分：

PyObject_CheckBuffer()

PyObject_GetBuffer()

PyBuffer_GetPointer()

PyBuffer_SizeFromFormat()

PyBuffer_ToContiguous()

PyBuffer_FromContiguous()

PyObject_CopyData()

PyBuffer_IsContiguous()

PyBuffer_FillContiguousStrides()

PyBuffer_FillInfo()

PyBuffer_Release()

PyMemoryView_FromBuffer()

bf_getbuffer 與 bf_releasebuffer 型別插槽 (type slot)

（由 Christian Heimes 於 bpo-45459 [https://bugs.python.org/issue?@action=redirect&bpo=45459] 中所貢獻。）

新增 PyType_GetModuleByDef() 函式，它將被用於取得定義一個方法的模組，以免這項資訊無法直接被取得（透過 PyCMethod）。（由 Petr Viktorin 於 bpo-46613 [https://bugs.python.org/issue?@action=redirect&bpo=46613] 中所貢獻。）

新增函式以打包 (pack) 和取出 (unpack) C double（序列化和反序列化）：PyFloat_Pack2()、PyFloat_Pack4()、PyFloat_Pack8()、PyFloat_Unpack2() , PyFloat_Unpack4() 和 PyFloat_Unpack8()。（由 Victor Stinner 在 bpo-46906 [https://bugs.python.org/issue?@action=redirect&bpo=46906] 中貢獻。）

新增取得幀物件屬性的函式：PyFrame_GetBuiltins()、PyFrame_GetGenerator()、PyFrame_GetGlobals()、PyFrame_GetLasti()。

添加了兩個新函式來獲得和設置仍在作用的例外實例：PyErr_GetHandledException() 和 PyErr_SetHandledException()。這些是 PyErr_SetExcInfo() 和 PyErr_GetExcInfo() 的替代品，它們與例外的遺留三元組表示法一起作用。（由 Irit Katriel 在 bpo-46343 [https://bugs.python.org/issue?@action=redirect&bpo=46343] 中貢獻。）

新增 PyConfig.safe_path 成員。（由 Victor Stinner 於 gh-57684 [https://github.com/python/cpython/issues/57684] 中所貢獻。）

移植至 Python 3.11

一些巨集已轉換為行內靜態函式以避免巨集陷阱 (macro pitfalls) [https://gcc.gnu.org/onlinedocs/cpp/Macro-Pitfalls.html]。這種變化對用戶來說應該是透明的，因為替換函式會將它們的引數轉換為預期的型別，以避免由於靜態型別檢查而產生的編譯器警告。但是，當受限 C API 設置為 >=3.11 時，這些轉換不會完成，使用者需要將引數轉換為他們期望的型別。有關更多詳細資訊，請參閱 PEP 670 [https://peps.python.org/pep-0670/]。（由 Victor Stinner 和 Erlend E. Aasland 在 gh-89653 [https://github.com/python/cpython/issues/89653] 中貢獻。）

PyErr_SetExcInfo() 不再使用 type 和 traceback 引數，直譯器現在從例外實例（value 引數）中獲得這些值。該函式仍會偷用這三個引數的參照。（由 Irit Katriel 在 bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711] 中貢獻。）

PyErr_GetExcInfo() 現在從例外實例的結果（value 欄位）中導出 type 和 traceback 欄位。（由 Irit Katriel 在 bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711] 中貢獻。）

_frozen 有一個新的 is_package 欄位來表示凍結模組是否為一個套件。以前 size 欄位中的負值是指標，現在只有非負值可用於 size。（由 Kumar Aditya 在 bpo-46608 [https://bugs.python.org/issue?@action=redirect&bpo=46608] 中貢獻。）

_PyFrameEvalFunction() 現在將 _PyInterpreterFrame* 作為其第二個參數，而不是 PyFrameObject*。有關如何使用此函式指標型別的更多詳細資訊，請參閱 PEP 523 [https://peps.python.org/pep-0523/]。

PyCode_New() 和 PyCode_NewWithPosOnlyArgs() 現在採用額外的 exception_table 引數。如果可能的話應該避免使用這些函式。要取得自訂程式碼物件，使用編譯器建立一個程式碼物件，然後使用 replace 方法來得到修改後的版本。

PyCodeObject 不再會有 co_code、co_varnames、co_cellvars 和 co_freevars 欄位。分別被改為透過 C API 的 PyCode_GetCode()、PyCode_GetVarnames()、PyCode_GetCellvars() 和 PyCode_GetFreevars() 來存取。（由 Brandt Bucher 在 bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]、Ken Jin 在 gh-92154 [https://github.com/python/cpython/issues/92154] 與 gh-94936 [https://github.com/python/cpython/issues/94936] 中貢獻。）

舊的回收筒巨集 (trashcan macro) (Py_TRASHCAN_SAFE_BEGIN/Py_TRASHCAN_SAFE_END) 現在已經被棄用，它們應被新的巨集 Py_TRASHCAN_BEGIN 和 Py_TRASHCAN_END 所取代。

一個用到老舊巨集的 tp_dealloc 函式，像是：

static void
mytype_dealloc(mytype *p)
{
    PyObject_GC_UnTrack(p);
    Py_TRASHCAN_SAFE_BEGIN(p);
    ...
    Py_TRASHCAN_SAFE_END
}

應該要搬遷到新的巨集，如下所示：

static void
mytype_dealloc(mytype *p)
{
    PyObject_GC_UnTrack(p);
    Py_TRASHCAN_BEGIN(p, mytype_dealloc)
    ...
    Py_TRASHCAN_END
}

請注意 Py_TRASHCAN_BEGIN 有第二個引數，它應該是它所在的釋放函式 (deallocation function)。

為支援舊版 Python 在同一份程式碼中，你可以定義以下巨集並在程式碼中使用它們（要歸功於 mypy 程式碼，這些是從那邊複製過來的）：

#if PY_VERSION_HEX >= 0x03080000
#  define CPy_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_BEGIN(op, dealloc)
#  define CPy_TRASHCAN_END(op) Py_TRASHCAN_END
#else
#  define CPy_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_SAFE_BEGIN(op)
#  define CPy_TRASHCAN_END(op) Py_TRASHCAN_SAFE_END(op)
#endif

如果一個型別是以 Py_TPFLAGS_HAVE_GC 旗標來定義，但卻沒有遍歷函式 (traverse function) (PyTypeObject.tp_traverse)，那 PyType_Ready() 函式現在會引發一個錯誤。（由 Victor Stinner 於 bpo-44263 [https://bugs.python.org/issue?@action=redirect&bpo=44263] 中貢獻。）

帶有 Py_TPFLAGS_IMMUTABLETYPE 旗標的堆積型別現在可以繼承 PEP 590 [https://peps.python.org/pep-0590/] 向量呼叫協定 (vectorcall protocol)。以前這僅適用於 static types。（由 Erlend E. Aasland 在 bpo-43908 [https://bugs.python.org/issue?@action=redirect&bpo=43908] 中貢獻）。

由於 Py_TYPE() 更改為行內靜態函式 (inline static function)，因此 Py_TYPE(obj) = new_type 必須替換為 Py_SET_TYPE(obj, new_type)：參見 Py_SET_TYPE() 函式（自 Python 3.9 起可用）。為了向後相容，可以使用這個巨集：

#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_TYPE)
static inline void _Py_SET_TYPE(PyObject *ob, PyTypeObject *type)
{ ob->ob_type = type; }
#define Py_SET_TYPE(ob, type) _Py_SET_TYPE((PyObject*)(ob), type)
#endif

（由 Victor Stinner 於 bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573] 中所貢獻。）

由於 Py_SIZE() 更改為行內靜態函式，因此 Py_SIZE(obj) = new_size 必須替換為 Py_SET_SIZE(obj, new_size)：參見 Py_SET_SIZE() 函式（自 Python 3.9 起可用）。為了向後相容，可以使用這個巨集：

#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_SIZE)
static inline void _Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size)
{ ob->ob_size = size; }
#define Py_SET_SIZE(ob, size) _Py_SET_SIZE((PyVarObject*)(ob), size)
#endif

（由 Victor Stinner 於 bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573] 中所貢獻。）

當 Py_LIMITED_API 巨集被設定為 0x030b0000（Python 3.11）或以上，<Python.h> 不再會包含標頭檔 <stdlib.h>、<stdio.h>、<errno.h> 和 <string.h>。C 擴充程式應該要清楚的在 #include <Python.h> 之後引入標頭檔案。（由 Victor Stinner 於 bpo-45434 [https://bugs.python.org/issue?@action=redirect&bpo=45434] 中貢獻。）

非受限 API (non-limited API) 檔案 cellobject.h、classobject.h、code.h、context.h、funcobject.h、genobject. h 和 longintrepr.h 已移至 Include/cpython 目錄。此外，eval.h 標頭檔已被刪除。不能直接引入這些文件，因為它們已被包含在 Python.h 中：引入檔案。如果它們已被直接引入，請考慮改為引入 Python.h。 （由 Victor Stinner 在 bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134] 中貢獻。）

PyUnicode_CHECK_INTERNED() 巨集已從受限 C API 中移出，它從來沒辦法被使用，因為它使用了受限 C API 不提供的內部結構。（由 Victor Stinner 於 bpo-46007 [https://bugs.python.org/issue?@action=redirect&bpo=46007] 中所貢獻。）

以下用於幀 (frame) 的函式與型別現在可直接透過 #include <Python.h> 來使用，不必再加上 #include <frameobject.h>：

PyFrame_Check()

PyFrame_GetBack()

PyFrame_GetBuiltins()

PyFrame_GetGenerator()

PyFrame_GetGlobals()

PyFrame_GetLasti()

PyFrame_GetLocals()

PyFrame_Type

（由 Victor Stinner 於 gh-93937 [https://github.com/python/cpython/issues/93937] 中所貢獻。）

PyFrameObject 結構成員已經從公開的 C API 中移除。

雖然文件指出 PyFrameObject 欄位隨時可能發生變化，但它們已經穩定了很長時間，並被用於幾個流行的擴充套件中。

Python 3.11 中，幀的結構被重新編制來為性能做最佳化，有些作為舊版實作細節的欄位被整個移除。

PyFrameObject 欄位：

f_back：使用 PyFrame_GetBack()。

f_blockstack：已移除。

f_builtins：使用 PyFrame_GetBuiltins()。

f_code：使用 PyFrame_GetCode()。

f_gen：使用 PyFrame_GetGenerator()。

f_globals：使用 PyFrame_GetGlobals()。

f_iblock：已移除。

f_lasti：使用 PyFrame_GetLasti()。程式碼中 f_lasti 有與 PyCode_Addr2Line() 同時使用的部分應該改用 PyFrame_GetLineNumber()；它可能會更快。

f_lineno：使用 PyFrame_GetLineNumber()

f_locals：使用 PyFrame_GetLocals()。

f_stackdepth：已移除。

f_state：無公開 API（重新命名為 f_frame.f_state）。

f_trace：無公開 API。

f_trace_lines：使用 PyObject_GetAttrString((PyObject*)frame, "f_trace_lines")。

f_trace_opcodes：使用 PyObject_GetAttrString((PyObject*)frame, "f_trace_opcodes")。

f_localsplus：無公開 API（重新命名為 f_frame.localsplus）。

f_valuestack：已移除。

Python 幀物件的建立現為惰性的 (lazily)，一個副作用是 f_back 成員不能被直接存取，因為其職的計算也是惰性的，要改呼叫 PyFrame_GetBack()。

直接存取 f_locals 的除錯器必須改為呼叫 PyFrame_GetLocals()。他們不再需要呼叫 PyFrame_FastToLocalsWithError() 或 PyFrame_LocalsToFast()，事實上他們不應該呼叫這些函式。框架的必要更新現在由虛擬機管理。

PyFrame_GetCode() 在 Python 3.8 以前的程式定義：

#if PY_VERSION_HEX < 0x030900B1
static inline PyCodeObject* PyFrame_GetCode(PyFrameObject *frame)
{
    Py_INCREF(frame->f_code);
    return frame->f_code;
}
#endif

PyFrame_GetBack() 在 Python 3.8 以前的程式定義：

#if PY_VERSION_HEX < 0x030900B1
static inline PyFrameObject* PyFrame_GetBack(PyFrameObject *frame)
{
    Py_XINCREF(frame->f_back);
    return frame->f_back;
}
#endif

或是使用 pythoncap_compat 計畫 [https://github.com/python/pythoncapi-compat]來在舊版 Python 函式中取得這兩個函式。

PyThreadState 結構成員的改動：

frame：已移除，改用 PyThreadState_GetFrame()（bpo-40429 [https://bugs.python.org/issue?@action=redirect&bpo=40429] 於 Python 3.9 新增的函式）。警告：會回傳 strong reference 的函式必須呼叫 Py_XDECREF()。

tracing：已變更，改用 PyThreadState_EnterTracing() 和 PyThreadState_LeaveTracing()（bpo-43760 [https://bugs.python.org/issue?@action=redirect&bpo=43760] 於 Python 3.11 中新增的函式）。

recursion_depth：已移除，請改用 (tstate->recursion_limit - tstate->recursion_remaining)。

stackcheck_counter：已移除。

PyThreadState_GetFrame() 在 Python 3.8 以前的程式定義：

#if PY_VERSION_HEX < 0x030900B1
static inline PyFrameObject* PyThreadState_GetFrame(PyThreadState *tstate)
{
    Py_XINCREF(tstate->frame);
    return tstate->frame;
}
#endif

PyThreadState_EnterTracing() 與 PyThreadState_LeaveTracing() 在 Python 3.10 以前的程式定義：

#if PY_VERSION_HEX < 0x030B00A2
static inline void PyThreadState_EnterTracing(PyThreadState *tstate)
{
    tstate->tracing++;
#if PY_VERSION_HEX >= 0x030A00A1
    tstate->cframe->use_tracing = 0;
#else
    tstate->use_tracing = 0;
#endif
}

static inline void PyThreadState_LeaveTracing(PyThreadState *tstate)
{
    int use_tracing = (tstate->c_tracefunc != NULL || tstate->c_profilefunc != NULL);
    tstate->tracing--;
#if PY_VERSION_HEX >= 0x030A00A1
    tstate->cframe->use_tracing = use_tracing;
#else
    tstate->use_tracing = use_tracing;
#endif
}
#endif

或是使用 pythoncap-compat 專案 [https://github.com/python/pythoncapi-compat]來在舊版 Python 函式中取得它們。

鼓勵發布者們使用最佳化過的 Blake2 函式庫 libb2 [https://www.blake2.net/] 來建置 Python。

初始化中若是要用 PyConfig.module_search_paths 來初始化 sys.path，則現在 PyConfig.module_search_paths_set 必須被設為 1。否則，初始化會重新計算路徑並取代所有被加到 module_search_paths 的值。

PyConfig_Read() 不再計算初始搜尋路徑，並且不會將任何值填充到 PyConfig.module_search_paths 中。若要計算預設路徑然後修改它們，完成初始化並使用 PySys_GetObject() 以取得 sys.path 作為 Python 列表物件並直接修改它。

已棄用

棄用以下用來配置 Python 初始化的函式：

PySys_AddWarnOptionUnicode()

PySys_AddWarnOption()

PySys_AddXOption()

PySys_HasWarnOptions()

PySys_SetArgvEx()

PySys_SetArgv()

PySys_SetPath()

Py_SetPath()

Py_SetProgramName()

Py_SetPythonHome()

Py_SetStandardStreamEncoding()

_Py_SetProgramFullPath()

請改用 Python 初始化配置中新的 PyConfig API。（由 Victor Stinner 於 gh-88279 [https://github.com/python/cpython/issues/88279] 中所貢獻。）

棄用 PyBytesObject 中的 ob_shash 成員。請改用 PyObject_Hash()。（由 Inada Naoki 於 bpo-46864 [https://bugs.python.org/issue?@action=redirect&bpo=46864] 中所貢獻。）

Python 3.12 中待決議的移除項目

以下 C API 已於先前 Python 發布版本中棄用，並將於 Python 3.12 中移除。

PyUnicode_AS_DATA()

PyUnicode_AS_UNICODE()

PyUnicode_AsUnicodeAndSize()

PyUnicode_AsUnicode()

PyUnicode_FromUnicode()

PyUnicode_GET_DATA_SIZE()

PyUnicode_GET_SIZE()

PyUnicode_GetSize()

PyUnicode_IS_COMPACT()

PyUnicode_IS_READY()

PyUnicode_READY()

PyUnicode_WSTR_LENGTH()

_PyUnicode_AsUnicode()

PyUnicode_WCHAR_KIND

PyUnicodeObject

PyUnicode_InternImmortal()

已移除

PyFrame_BlockSetup() and PyFrame_BlockPop() have been removed. (Contributed by Mark Shannon in bpo-40222 [https://bugs.python.org/issue?@action=redirect&bpo=40222].)

移除以下使用到 errno 變數的數學巨集：

Py_ADJUST_ERANGE1()

Py_ADJUST_ERANGE2()

Py_OVERFLOWED()

Py_SET_ERANGE_IF_OVERFLOW()

Py_SET_ERRNO_ON_MATH_ERROR()

（由 Victor Stinner 於 bpo-45412 [https://bugs.python.org/issue?@action=redirect&bpo=45412] 中所貢獻。）

移除在 Python 3.3 中棄用的 Py_UNICODE_COPY() 和 Py_UNICODE_FILL()。請改用 PyUnicode_CopyCharacters() 或 memcpy()（wchar_t* 字串）和 PyUnicode_Fill() 函式。（由 Victor Stinner 於 bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123] 中所貢獻。）

移除 pystrhex.h 標頭檔案。它只有包含私有函式。C 的擴充應該只要引入主要的 <Python.h> 標頭檔案。（由 Victor Stinner 於 bpo-45434 [https://bugs.python.org/issue?@action=redirect&bpo=45434] 中所貢獻。）

移除 Py_FORCE_DOUBLE() 巨集。它先前被用於 Py_IS_INFINITY() 巨集。（由 Victor Stinner 於 bpo-45440 [https://bugs.python.org/issue?@action=redirect&bpo=45440] 中所貢獻。）

當 Py_LIMITED_API 有被定義時，以下項目將無法被取得：

PyMarshal_WriteLongToFile()

PyMarshal_WriteObjectToFile()

PyMarshal_ReadObjectFromString()

PyMarshal_WriteObjectToString()

Py_MARSHAL_VERSION 巨集

These are not part of the limited API.

（由 Victor Stinner 於 bpo-45474 [https://bugs.python.org/issue?@action=redirect&bpo=45474] 中所貢獻。）

將 PyWeakref_GET_OBJECT() 排除於受限 C API 之外，它因為 PyWeakReference 結構在受限 C API 中過於晦澀而從未運作。（由 Victor Stinner 於 bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134] 中所貢獻。）

移除 PyHeapType_GET_MEMBERS() 巨集，它是不小心才被放到公開的 C API 中，應該只能被 Python 內部所使用。請改用 PyTypeObject.tp_members。（由 Victor Stinner 於 bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170] 中所貢獻。）

移除 HAVE_PY_SET_53BIT_PRECISION 巨集（移動至內部 C API）。（由 Victor Stinner 於 bpo-45412 [https://bugs.python.org/issue?@action=redirect&bpo=45412] 中所貢獻。）

移除 Py_UNICODE 編碼器 API，它們自從 Python 3.3 就被棄用，非常少用且和推薦的替代方案已無太大關聯。

被移除的函式為：

PyUnicode_Encode()

PyUnicode_EncodeASCII()

PyUnicode_EncodeLatin1()

PyUnicode_EncodeUTF7()

PyUnicode_EncodeUTF8()

PyUnicode_EncodeUTF16()

PyUnicode_EncodeUTF32()

PyUnicode_EncodeUnicodeEscape()

PyUnicode_EncodeRawUnicodeEscape()

PyUnicode_EncodeCharmap()

PyUnicode_TranslateCharmap()

PyUnicode_EncodeDecimal()

PyUnicode_TransformDecimalToASCII()

詳情請見 PEP 624 [https://peps.python.org/pep-0624/] 與搬遷指南 [https://peps.python.org/pep-0624/#alternative-apis]。（由 Inada Naoki 於 bpo-44029 [https://bugs.python.org/issue?@action=redirect&bpo=44029] 中所貢獻。）

Python 3.11.4 中顯著的變更

tarfile

The extraction methods in tarfile, and shutil.unpack_archive(), have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See 解壓縮篩選器 for details. In Python 3.12, use without the filter argument will show a DeprecationWarning. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in PEP 706 [https://peps.python.org/pep-0706/].)

Python 3.11.5 中顯著的變更

OpenSSL

Windows builds and macOS installers from python.org now use OpenSSL 3.0.

Python 3.10 有什麼新功能

編輯者:

Pablo Galindo Salgado

本文介紹了 Python 3.10 與 3.9 相比多了哪些新功能。Python 3.10 已於 2021 年 10 月 4 日發布。有關完整詳細資訊，請參閱 changelog。

發布重點摘要

新增語法特性：

PEP 634 [https://peps.python.org/pep-0634/]，結構模式匹配 (Structural Pattern Matching)：規範

PEP 635 [https://peps.python.org/pep-0635/]，結構模式匹配：動機和基本原理

PEP 636 [https://peps.python.org/pep-0636/]，結構模式匹配：教學

bpo-12782 [https://bugs.python.org/issue?@action=redirect&bpo=12782]，現在正式允許帶括號的情境管理器 (context manager)。

標準函式庫中的新功能：

PEP 618 [https://peps.python.org/pep-0618/]，新增可選的長度檢查到 zip。

直譯器改進：

PEP 626 [https://peps.python.org/pep-0626/]，用於除錯和其他工具的精確列號。

新的 typing 功能：

PEP 604 [https://peps.python.org/pep-0604/]，允許將聯集型別 (union types) 寫為 X | Y

PEP 612 [https://peps.python.org/pep-0612/]，參數規範變數 (Parameter Specification Variables)

PEP 613 [https://peps.python.org/pep-0613/]，顯式型別別名 (Explicit Type Aliases)

PEP 647 [https://peps.python.org/pep-0647/]，使用者定義的型別防護 (User-Defined Type Guards)

重要的棄用、刪除或限制：

PEP 644 [https://peps.python.org/pep-0644/]，需要 OpenSSL 1.1.1 或更高版本

PEP 632 [https://peps.python.org/pep-0632/]，棄用 distutils 模組。

PEP 623 [https://peps.python.org/pep-0623/]，棄用並準備刪除 PyUnicodeObject 中的 wstr 成員。

PEP 624 [https://peps.python.org/pep-0624/]，刪除 Py_UNICODE 編碼器 API

PEP 597 [https://peps.python.org/pep-0597/]，新增可選的 EncodingWarning

新增功能

帶括號的情境管理器

現在支援使用成對的括號來將多個情境管理器以數行表示。這允許了與過去的引入陳述式 (import statement) 類似的方法來格式化一組多行的情境管理器集合。例如，以下範例現在都是有效的：

with (CtxManager() as example):
    ...

with (
    CtxManager1(),
    CtxManager2()
):
    ...

with (CtxManager1() as example,
      CtxManager2()):
    ...

with (CtxManager1(),
      CtxManager2() as example):
    ...

with (
    CtxManager1() as example1,
    CtxManager2() as example2
):
    ...

也可以在封閉群組的末尾使用逗號：

with (
    CtxManager1() as example1,
    CtxManager2() as example2,
    CtxManager3() as example3,
):
    ...

此新語法使用新剖析器的非 LL(1) 功能。檢查 PEP 617 [https://peps.python.org/pep-0617/] 了解更多詳細資訊。

（由 Guido van Rossum、Pablo Galindo 和 Lysandros Nikolaou 在 bpo-12782 [https://bugs.python.org/issue?@action=redirect&bpo=12782] 和 bpo-40334 [https://bugs.python.org/issue?@action=redirect&bpo=40334] 中貢獻。）

更好的錯誤訊息

SyntaxErrors

當剖析包含未成對括號或方括號的程式碼時，直譯器現在會包含未成對括號的位置，而不是顯示 SyntaxError: unexpected EOF while parsing 或指向某些不正確的位置。例如，以下程式碼（注意未閉合的 { ）：

expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
            38: 4, 39: 4, 45: 5, 46: 5, 47: 5, 48: 5, 49: 5, 54: 6,
some_other_code = foo()

以前版本的直譯器會在奇怪的地方顯示有語法錯誤：

File "example.py", line 3
    some_other_code = foo()
                    ^
SyntaxError: invalid syntax

但在 Python 3.10 中，會發出一個資訊更豐富的錯誤：

File "example.py", line 1
    expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
               ^
SyntaxError: '{' was never closed

同樣地，涉及未成對字串字面值（單引號和三引號）的錯誤現在會指向字串的開頭，而不是報告 EOF/EOL。

這些改進是受到 PyPy 直譯器的啟發。

（由 Pablo Galindo 在 bpo-42864 [https://bugs.python.org/issue?@action=redirect&bpo=42864] 和 Batuhan Taskaya 在 bpo-40176 [https://bugs.python.org/issue?@action=redirect&bpo=40176] 中貢獻。）

直譯器引發的 SyntaxError 例外現在會突顯 (highlight) 構成語法錯誤之運算式的完整錯誤範圍，而不僅是檢測到問題的位置。如此一來，過去（像 Python 3.10 之前）的：

>>> foo(x, z for z in range(10), t, w)
  File "<stdin>", line 1
    foo(x, z for z in range(10), t, w)
           ^
SyntaxError: Generator expression must be parenthesized

現在 Python 3.10 則會將例外顯示為：

>>> foo(x, z for z in range(10), t, w)
  File "<stdin>", line 1
    foo(x, z for z in range(10), t, w)
           ^^^^^^^^^^^^^^^^^^^^
SyntaxError: Generator expression must be parenthesized

此改進由 Pablo Galindo 在 bpo-43914 [https://bugs.python.org/issue?@action=redirect&bpo=43914] 中貢獻。

已合併了大量針對 SyntaxError 例外的新專用訊息。一些最值得注意的如下：

在區塊之前缺少 ::

>>> if rocket.position > event_horizon
  File "<stdin>", line 1
    if rocket.position > event_horizon
                                      ^
SyntaxError: expected ':'

（由 Pablo Galindo 在 bpo-42997 [https://bugs.python.org/issue?@action=redirect&bpo=42997] 中貢獻。）

綜合運算目標中未加括號的元組：

>>> {x,y for x,y in zip('abcd', '1234')}
  File "<stdin>", line 1
    {x,y for x,y in zip('abcd', '1234')}
     ^
SyntaxError: did you forget parentheses around the comprehension target?

（由 Pablo Galindo 在 bpo-43017 [https://bugs.python.org/issue?@action=redirect&bpo=43017] 中貢獻。）

容器字面值 (collection literals) 中和運算式之間缺少逗號：

>>> items = {
... x: 1,
... y: 2
... z: 3,
  File "<stdin>", line 3
    y: 2
       ^
SyntaxError: invalid syntax. Perhaps you forgot a comma?

（由 Pablo Galindo 在 bpo-43822 [https://bugs.python.org/issue?@action=redirect&bpo=43822] 中貢獻。）

不帶括號的多個例外型別：

>>> try:
...     build_dyson_sphere()
... except NotEnoughScienceError, NotEnoughResourcesError:
  File "<stdin>", line 3
    except NotEnoughScienceError, NotEnoughResourcesError:
           ^
SyntaxError: multiple exception types must be parenthesized

（由 Pablo Galindo 在 bpo-43149 [https://bugs.python.org/issue?@action=redirect&bpo=43149] 中貢獻。）

字典字面值中缺少 : 和值：

>>> values = {
... x: 1,
... y: 2,
... z:
... }
  File "<stdin>", line 4
    z:
     ^
SyntaxError: expression expected after dictionary key and ':'

>>> values = {x:1, y:2, z w:3}
  File "<stdin>", line 1
    values = {x:1, y:2, z w:3}
                        ^
SyntaxError: ':' expected after dictionary key

（由 Pablo Galindo 在 bpo-43823 [https://bugs.python.org/issue?@action=redirect&bpo=43823] 中貢獻。）

沒有 except 或 finally 區塊的 try 區塊：

>>> try:
...     x = 2
... something = 3
  File "<stdin>", line 3
    something  = 3
    ^^^^^^^^^
SyntaxError: expected 'except' or 'finally' block

（由 Pablo Galindo 在 bpo-44305 [https://bugs.python.org/issue?@action=redirect&bpo=44305] 中貢獻。）

於比較中使用 = 而非 ==：

>>> if rocket.position = event_horizon:
  File "<stdin>", line 1
    if rocket.position = event_horizon:
                       ^
SyntaxError: cannot assign to attribute here. Maybe you meant '==' instead of '='?

（由 Pablo Galindo 在 bpo-43797 [https://bugs.python.org/issue?@action=redirect&bpo=43797] 中貢獻。）

f 字串中使用 *：

>>> f"Black holes {*all_black_holes} and revelations"
  File "<stdin>", line 1
    (*all_black_holes)
     ^
SyntaxError: f-string: cannot use starred expression here

（由 Pablo Galindo 在 bpo-41064 [https://bugs.python.org/issue?@action=redirect&bpo=41064] 中貢獻。）

IndentationErrors

許多 IndentationError 例外現在支援更多關於哪種區塊需要縮進的情境，包括陳述式的位置：

>>> def foo():
...    if lel:
...    x = 2
  File "<stdin>", line 3
    x = 2
    ^
IndentationError: expected an indented block after 'if' statement in line 2

AttributeErrors

當印出 AttributeError 時，PyErr_Display() 將提供引發例外的物件中類似屬性名稱的建議：

>>> collections.namedtoplo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'collections' has no attribute 'namedtoplo'. Did you mean: namedtuple?

（由 Pablo Galindo 在 bpo-38530 [https://bugs.python.org/issue?@action=redirect&bpo=38530] 中貢獻。）

警告

請注意，如果未呼叫 PyErr_Display() 來顯示錯誤（可能為了要使用其他自定義錯誤顯示函式），則此操作將不起作用。這是 IPython 等某些 REPL 中的常見狀況。

NameErrors

當印出直譯器引發的 NameError 時，PyErr_Display() 將在引發例外的函式中提供類似變數名稱的建議：

>>> schwarzschild_black_hole = None
>>> schwarschild_black_hole
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'schwarschild_black_hole' is not defined. Did you mean: schwarzschild_black_hole?

（由 Pablo Galindo 在 bpo-38530 [https://bugs.python.org/issue?@action=redirect&bpo=38530] 中貢獻。）

警告

請注意，如果未呼叫 PyErr_Display() 來顯示錯誤，則此操作將不起作用，如果使用其他自訂錯誤顯示函式，則可能會發生這種情況。這是 IPython 等某些 REPL 中的常見場景。

PEP 626：用於除錯和其他工具的精確列號

PEP 626 為除錯、分析 (profiling) 和覆蓋 (coverage) 工具帶來了更精確、更可靠的列號 (line numbers)。為所有已執行的程式碼列且僅針對已執行的程式碼行產生具有正確列號的追蹤事件。

影格 (frame) 物件的 f_lineno 屬性總會包含預期的列號。

程式碼物件的 co_lnotab 屬性已棄用，並將在 3.12 中刪除。需要從偏移量轉換為列號的程式碼應使用新的 co_lines() 方法。

PEP 634：結構模式匹配

已新增結構模式匹配 (structural pattern matching)，其形式為具有關聯操作之模式的 match 陳述式 和 case 陳述式。模式由序列、對映、原始資料型別 (primitive data types) 以及類別實例組成。模式匹配使程式能夠從複雜的資料型別中提取資訊，在資料結構上進行分支，並根據不同形式的資料應用特定的操作。

語法和操作

模式匹配的通用語法是：

match subject:
    case <pattern_1>:
        <action_1>
    case <pattern_2>:
        <action_2>
    case <pattern_3>:
        <action_3>
    case _:
        <action_wildcard>

match 陳述式採用一個運算式，並將其值與作為一個或多個 case 區塊給出的連續模式進行比較。具體來說，模式匹配是透過以下方式進行操作：

使用具有型別 (type) 和特徵 (shape) 的資料 (主語 subject)

match 陳述式中 subject 的求值 (evaluating)

從上到下將主語與 case 陳述式中的每個模式進行比較，直到確認匹配。

執行與已確認匹配模式對應的操作

如果未確認完全匹配，則最後一種情況，即萬用字元 _ （如果有提供）將作為匹配到的情況。如未有任何匹配且不存在萬用字元的 case，則整個 match 區塊會是個無操作 (no-op)。

宣告式方法 (Declarative approach)

讀者可能會透過使用 C、Java 或 JavaScript（以及許多其他語言）中的 switch 陳述式將主語（資料物件）與字面值 (literal)（模式）進行匹配的簡單範例來了解模式匹配。 switch 語句通常用於將物件/運算式與包含字面值的 case 陳述式進行比較。

更強大的模式匹配範例可以在 Scala 和 Elixir 等語言中找到。對於結構模式匹配，該方法是「宣告式的 (declarative)」，並且明確地說明了資料匹配的條件（模式）。

雖然使用巢狀 "if" 陳述式的「命令式 (imperative)」指令系列可用於完成類似於結構模式匹配的操作，但它不如「宣告式 (declarative)」方法清晰。相反地，「聲明式」方法規定了匹配所需滿足的條件，並且因其明確表達模式而更具可讀性。雖然結構模式匹配可以用其最簡單的形式達成，將變數與 case 陳述式中的字面值進行比較，但它對 Python 的真正價值在於它對主語的型別和特徵的處理。

簡單模式：與字面值匹配

讓我們將此範例視為最簡單形式的模式匹配：一個值（主語）與多個文字（模式）匹配。在下面的範例中，status 是匹配陳述式的主語。這些模式是每個 case 陳述式，其中文字表示請求狀態程式碼。與案例相關的操作在匹配後執行：

def http_error(status):
    match status:
        case 400:
            return "Bad request"
        case 404:
            return "Not found"
        case 418:
            return "I'm a teapot"
        case _:
            return "Something's wrong with the internet"

如果上面的函式傳遞了 418 status，則回傳 "I'm a teapot"。如果上面的函式傳遞了 500 status，則帶有 _ 的 case 語句將作為萬用字元進行匹配，並回傳 "Something's wrong with the internet"。請注意最後一個區塊：變數名稱 _ 充當 萬用字元 並確保主語始終匹配。_ 的使用是可選的。

你可以使用 | ("or") 將多個字面值組合在一個模式中：

case 401 | 403 | 404:
    return "Not allowed"

沒有萬用字元 (wildcard) 的行為

如果我們透過刪除最後一個 case 區塊來修改上面的範例，則範例將變為：

def http_error(status):
    match status:
        case 400:
            return "Bad request"
        case 404:
            return "Not found"
        case 418:
            return "I'm a teapot"

如果在 case 陳述式中不使用 _，則可能不存在匹配項目。如果不存在匹配項目，則該行為是無操作 (no-op)。例如，如果 status 為 500，則不會有任何操作。

具有字面值和變數的模式

模式看起來就像解包賦值 (unpacking assignment)，並且模式可用於繫結 (bind) 變數。在此範例中，可以將資料點解包為其 x 坐標和 y 坐標：

# point 是一個 (x, y) 元組
match point:
    case (0, 0):
        print("Origin")
    case (0, y):
        print(f"Y={y}")
    case (x, 0):
        print(f"X={x}")
    case (x, y):
        print(f"X={x}, Y={y}")
    case _:
        raise ValueError("Not a point")

第一個模式有兩個字面值 (0, 0)，並且可以被認為是上面顯示的字面值模式的擴充。接下來的兩個模式組合了一個字面值和一個變數，並且變數繫結來自主語（point）的值。第四個模式捕獲兩個值，這使得它在概念上類似於解包賦值 (x, y) = point。

模式和類別

如果你使用類別來建構資料，則可以用類別名稱與後面的引數列表組合成的建構函式作為模式。該模式能夠將實例屬性捕獲到變數中：

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

def location(point):
    match point:
        case Point(x=0, y=0):
            print("Origin is the point's location.")
        case Point(x=0, y=y):
            print(f"Y={y} and the point is on the y-axis.")
        case Point(x=x, y=0):
            print(f"X={x} and the point is on the x-axis.")
        case Point():
            print("The point is located somewhere else on the plane.")
        case _:
            print("Not a point")

具有位置參數的模式

你可以將位置參數與一些會為其屬性排序的內建類別（例如 dataclasses）一起使用。你還可以透過在類別中設定 __match_args__ 特殊屬性來定義模式中屬性的特定位置。如果它被設定為 ("x", "y")，則以下模式都是等效的（且都將 y 屬性繫結到 var 變數）：

Point(1, var)
Point(1, y=var)
Point(x=1, y=var)
Point(y=var, x=1)

巢狀模式

模式可以任意巢套。例如，如果我們的資料是一個簡短的座標點列表，則可以這樣匹配：

match points:
    case []:
        print("No points in the list.")
    case [Point(0, 0)]:
        print("The origin is the only point in the list.")
    case [Point(x, y)]:
        print(f"A single point {x}, {y} is in the list.")
    case [Point(0, y1), Point(0, y2)]:
        print(f"Two points on the Y axis at {y1}, {y2} are in the list.")
    case _:
        print("Something else is found in the list.")

複雜模式和萬用字元

到目前為止，範例在最後一個 case 陳述式中單獨使用了 _。萬用字元可以用在更複雜的模式中，像是 ('error', code, _)。例如：

match test_variable:
    case ('warning', code, 40):
        print("A warning has been received.")
    case ('error', code, _):
        print(f"An error {code} occurred.")

在上述情況下，值像是 ('error', code, 100) 和 ('error', code, 800) 的 test_variable 將會成功匹配。

Guard

我們可以在模式中新增一個 if 子句，稱為 "guard"。如果 guard 為 false，則 match 會繼續嘗試下一個 case 區塊。請注意，值的捕獲發生在 guard 的求值 (evaluate) 之前：

match point:
    case Point(x, y) if x == y:
        print(f"The point is located on the diagonal Y=X at {x}.")
    case Point(x, y):
        print(f"Point is not on the diagonal.")

其他主要功能

其他幾個主要功能：

與賦值的解包一樣，tuple 和 list 模式具有完全相同的含義，並且實際上匹配任意序列。從技術上來說，主語必須是一個序列。因此，一個重要的例外是模式不會去匹配疊代器。另外，為了防止常常出錯，序列模式也不會去匹配字串。

序列模式支援萬用字元：[x, y, *rest] 和 (x, y, *rest) 與解包賦值中的萬用字元類似。 * 後面的名稱也可能是 _，因此 (x, y, *_) 會匹配至少兩個項目的序列，且不繫結其餘項目。

對映模式： {"bandwidth": b, "latency": l} 從字典中捕獲 "bandwidth" 和 "latency" 值。與序列模式不同，額外的鍵將被忽略。也支援萬用字元 **rest。（但是 **_ 是多餘的，所以是不允許的。）

可以使用 as 關鍵字捕獲子模式：

case (Point(x1, y1), Point(x2, y2) as p2): ...

這將繫結 x1、y1、x2、y2，如同沒有 as 子句的情況下所預期的，並將 p2 繫結到主語的整個第二項目。

大多數字面值都是透過相等進行比較的。然而，單例 True、False 和 None 是按標識值 (identity) 來進行比較的。

附名常數 (named constant) 可以在模式中使用。這些附名常數必須有帶有點的名稱 (dotted name)，以防止常數被直譯為捕獲的變數：

from enum import Enum
class Color(Enum):
    RED = 0
    GREEN = 1
    BLUE = 2

color = Color.GREEN
match color:
    case Color.RED:
        print("I see red!")
    case Color.GREEN:
        print("Grass is green")
    case Color.BLUE:
        print("I'm feeling the blues :(")

有關完整規範，請參閱 PEP 634 [https://peps.python.org/pep-0634/]。動機和基本原理位於 PEP 635 [https://peps.python.org/pep-0635/] 中，較完整的教學位於 PEP 636 [https://peps.python.org/pep-0636/] 中。

可選的 EncodingWarning 和 encoding="locale" 選項

TextIOWrapper 和 open() 的預設編碼取決於平台和區域設定。由於大多數 Unix 平台都使用 UTF-8，因此在打開 UTF-8 檔案（例如 JSON、YAML、TOML、Markdown）時省略 encoding 選項是個常見的 bug，例如：

# BUG: "rb" mode or encoding="utf-8" should be used.
with open("data.json") as f:
    data = json.load(f)

為了發現這種錯誤，新增了一個可選的 EncodingWarning。當 sys.flags.warn_default_encoding 為 true 且使用特定於語言環境的預設編碼時，會發出該信號。

新增 -X warn_default_encoding 選項和 PYTHONWARNDEFAULTENCODING 來啟用警告。

更多資訊請見 文字編碼。

與型別提示相關的新功能

本節介紹影響 PEP 484 [https://peps.python.org/pep-0484/] 型別提示和 typing 模組的主要更改。

PEP 604：新型聯集運算子

引入了一種新的聯集運算子，該運算子啟用像是 X | Y 的語法。這提供了一種在型別提示中更清晰的方式來表達「型別 X 或型別 Y」，來取代使用 typing.Union。

在以前版本的 Python 中，要使用接受多種型別之引數的型別提示的函式，要使用 typing.Union：

def square(number: Union[int, float]) -> Union[int, float]:
    return number ** 2

現在可以用更簡潔的方式編寫型別提示：

def square(number: int | float) -> int | float:
    return number ** 2

這種新語法也接受作為 isinstance() 和 issubclass() 的第二個引數：

>>> isinstance(1, int | str)
True

更多資訊請見 聯合型別 (Union Type) 與 PEP 604 [https://peps.python.org/pep-0604/]。

（由 Maggie Moss 和 Philippe Prados 在 bpo-41428 [https://bugs.python.org/issue?@action=redirect&bpo=41428] 中貢獻，由 Yurii Karabas 和 Serhiy Storchaka 在 bpo-44490 [https://bugs.python.org/issue?@action=redirect&bpo=44490] 中補充。）

PEP 612：參數規範變數

typing 模組中新增了兩個新選項，用於改進為 PEP 484 [https://peps.python.org/pep-0484/] Callable 的靜態型別檢查器 (static type checker) 所提供的資訊。

第一個是參數規範變數 (parameter specification variable)。它們用於將一個可呼叫物件的參數型別轉發到另一個可呼叫物件 -- 這是高階函式和裝飾器中常見的模式。使用範例可以在 typing.ParamSpec 中找到。在過去是沒有簡單的方法可以如此精確地來為參數型別的依賴關係做型別註釋。

第二個選項是新的 Concatenate 運算子。它與參數規範變數結合使用，來對一個高階、會新增或刪除另一個可呼叫物件參數的可呼叫物件進行型別註釋。使用範例可以在 typing.Concatenate 中找到。

請參閱 typing.Callable、typing.ParamSpec、typing.Concatenate、typing.ParamSpecArgs、typing.ParamSpecKwargs 和 PEP 612 [https://peps.python.org/pep-0612/] 以了解更多詳情。

（由 Ken Jin 在 bpo-41559 [https://bugs.python.org/issue?@action=redirect&bpo=41559] 中貢獻、Jelle Zijlstra 在 bpo-43783 [https://bugs.python.org/issue?@action=redirect&bpo=43783] 中進行了小幅改進。PEP 由 Mark Mendoza 編寫。）

PEP 613：型別別名 (TypeAlias)

PEP 484 [https://peps.python.org/pep-0484/] 引入了型別別名 (type aliases) 的概念，只要求它們是最高階、未註釋的賦值 (top-level unannotated assignments)。這種簡單性有時使型別檢查器難以區分型別別名和普通賦值，尤其是在涉及傳遞參照 (reference) 或無效型別時。比較如下：

StrCache = 'Cache[str]'  # a type alias
LOG_PREFIX = 'LOG[DEBUG]'  # a module constant

現在 typing 模組有一個特殊值 TypeAlias，它可以讓你更明確地宣告型別別名：

StrCache: TypeAlias = 'Cache[str]'  # a type alias
LOG_PREFIX = 'LOG[DEBUG]'  # a module constant

更多資訊請見 PEP 613 [https://peps.python.org/pep-0613/]。

（由 Mikhail Golubev 在 bpo-41923 [https://bugs.python.org/issue?@action=redirect&bpo=41923] 中貢獻。）

PEP 647：使用者定義的型別防護

TypeGuard（型別防護）已新增到 typing 模組中，用以註釋型別防護函式並改進在型別窄縮 (type narrowing) 期間提供給靜態型別檢查器的資訊。有關更多資訊，請參閱 TypeGuard 的文件和 PEP 647 [https://peps.python.org/pep-0647/]。

（由 Ken Jin 和 Guido van Rossum 在 bpo-43766 [https://bugs.python.org/issue?@action=redirect&bpo=43766] 中貢獻。PEP 由 Eric Traut 編寫。）

其他語言更動

int 型別有一個新方法 int.bit_count()，回傳給定整數的二進位展開式中 1 的數量，也稱為總體計數 (population count)。（由 Niklas Fiekas 在 bpo-29882 [https://bugs.python.org/issue?@action=redirect&bpo=29882] 中貢獻。）

dict.keys()、dict.values() 和 dict.items() 回傳的視圖 (view) 現在都有一個 mapping 屬性，該屬性提供 types.MappingProxyType 包裝原始的字典物件。（由 Dennis Sweeney 在 bpo-40890 [https://bugs.python.org/issue?@action=redirect&bpo=40890] 中貢獻。）

PEP 618 [https://peps.python.org/pep-0618/]：zip() 函式現在有一個可選的 strict 旗標，用於要求所有可疊代物件具有相同的長度。

採用整數引數的內建函式和擴充函式不再接受 Decimal、Fraction 以及其他只能在有損失的情況下轉換為整數的物件（例如有 __int__() 方法，但沒有 __index__() 方法）。（由 Serhiy Storchaka 在 bpo-37999 [https://bugs.python.org/issue?@action=redirect&bpo=37999] 中貢獻。）

如果 object.__ipow__() 回傳 NotImplemented，則該運算子將按預期正確回退到 object.__pow__() 和 object.__rpow__() 。（由 Alex Shkop 在 bpo-38302 [https://bugs.python.org/issue?@action=redirect&bpo=38302] 中貢獻。）

現在可以在集合字面值 (set literals) 和集合綜合運算 (set comprehensions) 以及序列索引（但不能是切片）中使用不帶括號的賦值運算式 (assignment expressions)。

函式有一個新的 __builtins__ 屬性，用於在執行函式時查找內建符號，而不是查找 __globals__['__builtins__'] 。如果 __globals__["__builtins__"] 存在，則屬性會以此做初始化，否則從目前內建物件 (builtins) 初始化。（由 Mark Shannon 在 bpo-42990 [https://bugs.python.org/issue?@action=redirect&bpo=42990] 中貢獻。）

新增兩個內建函式 -- aiter() 和 anext()，分別為 iter() 和 next() 提供非同步的對應函式。（由 Joshua Bronson、Daniel Pope 和 Justin Wang 在 bpo-31861 [https://bugs.python.org/issue?@action=redirect&bpo=31861] 中貢獻。）

靜態方法 (@staticmethod) 和類別方法 (@classmethod) 現在繼承方法屬性 (__module__, __name__, __qualname__, __doc__, __annotations__) 並有一個新的 __wrapped__ 屬性。此外，靜態方法現在可以像是常規函式般呼叫。（由 Victor Stinner 在 bpo-43682 [https://bugs.python.org/issue?@action=redirect&bpo=43682] 中貢獻。）

複雜目標（除 PEP 526 [https://peps.python.org/pep-0526/] 定義的 simple name 目標之外的所有內容）的註釋不再使用 from __future__ import comments 造成任何執行環境 (runtime) 影響。（由 Batuhan Taskaya 在 bpo-42737 [https://bugs.python.org/issue?@action=redirect&bpo=42737] 中貢獻。）

類別和模組物件現在會根據需求來延遲建立 (lazy-create) 空的註釋字典 (annotations dicts)。註釋字典儲存在物件的 __dict__ 中以達成向後相容性。這改進了 __annotations__ 使用方式的最佳實踐方法；有關更多資訊，請參閱 註釋 (annotation) 最佳實踐。（由 Larry Hastings 在 bpo-43901 [https://bugs.python.org/issue?@action=redirect&bpo=43901] 中貢獻。）

附名運算式或由 yield、yield from、await 組成的註釋現在在 from __future__ import comments 下被禁止，因為它們有些不預期的行為。（由 Batuhan Taskaya 在 bpo-42725 [https://bugs.python.org/issue?@action=redirect&bpo=42725] 中貢獻。）

未繫結變數 (unbound variable)、super() 和其他可能會改變處理註釋之符號表 (symbol table) 的運算式，現在在 from __future__ import comments 下變得無效。（由 Batuhan Taskaya 在 bpo-42725 [https://bugs.python.org/issue?@action=redirect&bpo=42725] 中貢獻。）

float 型別和 decimal.Decimal 型別的 NaN 值的雜湊值現在取決於物件的標識值 (identity)。以前即使 NaN 值彼此不相等，它們也總是被雜湊為 0。由於在建立包含多個 NaN 的字典和集合時出現過多的雜湊衝突 (hash collision)，可能導致潛在的二次方執行環境行為 (quadratic runtime behavior)。（由 Raymond Hettinger 在 bpo-43475 [https://bugs.python.org/issue?@action=redirect&bpo=43475] 中貢獻。）

刪除 __debug__ 常數時將引發 SyntaxError （而不是 NameError）。（由 Donghee Na 在 bpo-45000 [https://bugs.python.org/issue?@action=redirect&bpo=45000] 中貢獻。）

SyntaxError 例外現在具有 end_lineno 和 end_offset 屬性。如果未被決定，它們將會是 None。（由 Pablo Galindo 在 bpo-43914 [https://bugs.python.org/issue?@action=redirect&bpo=43914] 中貢獻。）

新模組

無。

改進的模組

asyncio

新增缺少的 connect_accepted_socket() 方法。（由 Alex Grönholm 在 bpo-41332 [https://bugs.python.org/issue?@action=redirect&bpo=41332] 中貢獻。）

argparse

argparse 幫助中的誤導性用詞「可選引數 (optional arguments)」已被替換為「選項 (options)」。某些依賴於精確輸出匹配的測試可能需要進行調整。（由 Raymond Hettinger 在 bpo-9694 [https://bugs.python.org/issue?@action=redirect&bpo=9694] 中貢獻。）

array

array.array 的 index() 方法現在具有可選的 start 和 stop 參數。（由 Anders Lorentsen 和 Zackery Spytz 在 bpo-31956 [https://bugs.python.org/issue?@action=redirect&bpo=31956] 中貢獻。）

asynchat, asyncore, smtpd

自 Python 3.6 起，這些模組在其文件中被標記為已棄用。引入時的 DeprecationWarning 現已新增到這三個模組中。

base64

新增 base64.b32hexencode() 和 base64.b32hexdecode() 以支援擴充十六進位字母的 Base32 編碼 (Base32 Encoding with Extended Hex Alphabet)。

bdb

新增 clearBreakpoints() 來重置所有設定的斷點。（由 Irit Katriel 在 bpo-24160 [https://bugs.python.org/issue?@action=redirect&bpo=24160] 中貢獻。）

bisect

新增向 bisect 模組 API 提供 key 函式的可能性。（由 Raymond Hettinger 在 bpo-4356 [https://bugs.python.org/issue?@action=redirect&bpo=4356] 中貢獻。）

codecs

新增 codecs.unregister() 函式來取消註冊 (unregister) 一個編解碼器的搜尋功能。（Hai Shi 在 bpo-41842 [https://bugs.python.org/issue?@action=redirect&bpo=41842] 中貢獻。）

collections.abc

collections.abc.Callable 的參數化泛型 (parameterized generic) 的 __args__ 現在與 typing.Callable 一致。collections.abc.Callable 泛型現在會將型別參數攤平，類似於 typing.Callable 目前的做法。這意味著 collections.abc.Callable[[int, str], str] 將具有 (int, str, str) 的 __args__；在以前這是 ([int, str], str)。為了允許此更改，現在可以對 types.GenericAlias 進行子類別化，並且在下標 (subscript) collections.abc.Callable 型別時將回傳子類別。請注意，對於無效形式的 collections.abc.Callable 參數化可能會引發 TypeError，而在 Python 3.9 中該參數可能會無引發例外地傳遞。（由 Ken Jin 在 bpo-42195 [https://bugs.python.org/issue?@action=redirect&bpo=42195] 中貢獻。）

contextlib

新增 contextlib.aclosing() 情境管理器以安全地關閉非同步產生器和表示非同步釋放資源的物件。（由 Joongi Kim 和 John Belmonte 在 bpo-41229 [https://bugs.python.org/issue?@action=redirect&bpo=41229] 中貢獻。）

向 contextlib.nullcontext() 新增非同步情境管理器支援。（由 Tom Gringauz 在 bpo-41543 [https://bugs.python.org/issue?@action=redirect&bpo=41543] 中貢獻。）

新增 AsyncContextDecorator，用於支援將非同步情境管理器作為裝飾器使用。

curses

ncurses 6.1 中新增的擴充顏色函式將由 curses.color_content()、curses.init_color()、curses.init_pair() 和 curses.pair_content() 透明地使用。新函式 curses.has_extended_color_support() 表示了底層的 ncurses 函式庫是否支援擴充顏色。（由 Jeffrey Kintscher 和 Hans Petter Jansson 在 bpo-36982 [https://bugs.python.org/issue?@action=redirect&bpo=36982] 中貢獻。）

如果 BUTTON5_* 常數是由底層 curses 函式庫提供的，那麼它們現在會在 curses 模組中公開。（由 Zackery Spytz 在 bpo-39273 [https://bugs.python.org/issue?@action=redirect&bpo=39273] 中貢獻。）

dataclasses

__slots__

在 dataclasses.dataclass() 裝飾器中新增了 slots 參數。（由 Yurii Karabas 在 bpo-42269 [https://bugs.python.org/issue?@action=redirect&bpo=42269] 中貢獻）

僅限關鍵字欄位 (Keyword-only fields)

dataclasses 現在支援在產生的 __init__ 方法中包含僅限關鍵字的欄位。有多種方法可以指定僅限關鍵字欄位。

你可以說每個欄位都是關鍵字：

from dataclasses import dataclass

@dataclass(kw_only=True)
class Birthday:
    name: str
    birthday: datetime.date

name 和 birthday 都是產生的 __init__ 方法的僅限關鍵字參數。

你可以在每個欄位的基礎上指定僅限關鍵字：

from dataclasses import dataclass, field

@dataclass
class Birthday:
    name: str
    birthday: datetime.date = field(kw_only=True)

這裡只有 birthday 是僅限關鍵字。如果你在各個欄位上設定 kw_only，請注意，由於僅限關鍵字欄位需要遵循非僅限關鍵字欄位，因此會有欄位重新排序的相關規則。詳細資訊請參閱完整的 dataclasses 文件。

你還可以指定 KW_ONLY 標記後面的所有欄位均為僅限關鍵字欄位。這可能是最常見的用法：

from dataclasses import dataclass, KW_ONLY

@dataclass
class Point:
    x: float
    y: float
    _: KW_ONLY
    z: float = 0.0
    t: float = 0.0

這裡的 z 和 t 是僅限關鍵字參數，而 x 和 y 則不是。（由 Eric V. Smith 在 bpo-43532 [https://bugs.python.org/issue?@action=redirect&bpo=43532] 中貢獻。）

distutils

整個 distutils 套件已被棄用，將在 Python 3.12 中刪除。它指定套件建置的功能已經完全被第三方套件 setuptools 和 packaging 所取代，並且大多數其他常用的 API 都可以在標準函式庫的其他地方被找到（例如 platform 、shutil、subprocess 或 sysconfig）。目前沒有將 distutils 遷移任何其他地方的計畫，且使用其他功能的應用程式應該開始規劃如何取得程式碼的私有副本。請參閱 PEP 632 [https://peps.python.org/pep-0632/] 的討論。

Python 3.8 中不推薦使用的 bdist_wininst 命令已被刪除。現在建議使用 bdist_wheel 命令來在 Windows 上發布二進位套件。（由 Victor Stinner 在 bpo-42802 [https://bugs.python.org/issue?@action=redirect&bpo=42802] 中貢獻。）

doctest

當模組未定義 __loader__ 時，回退到 __spec__.loader 。（由 Brett Cannon 在 bpo-42133 [https://bugs.python.org/issue?@action=redirect&bpo=42133] 中貢獻。）

encodings

encodings.normalize_encoding() 現在會忽略非 ASCII 字元。（Hai Shi 在 bpo-39337 [https://bugs.python.org/issue?@action=redirect&bpo=39337] 中貢獻。）

enum

Enum __repr__() 現在會回傳 enum_name.member_name 、__str__() 現在會回傳 member_name 。可用作模組常數的標準函式庫列舉會有 module_name.member_name 的 repr()。（由 Ethan Furman 在 bpo-40066 [https://bugs.python.org/issue?@action=redirect&bpo=40066] 中貢獻。）

新增 enum.StrEnum，為所有成員都是字串的列舉。（由 Ethan Furman 在 bpo-41816 [https://bugs.python.org/issue?@action=redirect&bpo=41816] 中貢獻。）

fileinput

在 fileinput.input() 和 fileinput.FileInput 中新增 encoding 和 errors 參數。（由 Inada Naoki 在 bpo-43712 [https://bugs.python.org/issue?@action=redirect&bpo=43712] 中貢獻。）

當 mode 為 "r" 並且檔案有被壓縮時，fileinput.hook_compressed() 現在會回傳 TextIOWrapper 物件（和未壓縮檔案一樣）。（由 Inada Naoki 在 bpo-5758 [https://bugs.python.org/issue?@action=redirect&bpo=5758] 中貢獻。）

faulthandler

faulthandler 模組現在可以檢測垃圾收集器 (garbage collector) 在收集期間是否發生嚴重錯誤。（由 Victor Stinner 在 bpo-44466 [https://bugs.python.org/issue?@action=redirect&bpo=44466] 中貢獻。）

gc

為 gc.get_objects()、gc.get_referrers() 和 gc.get_referents() 新增稽核掛鉤 (audit hooks)。（由 Pablo Galindo 在 bpo-43439 [https://bugs.python.org/issue?@action=redirect&bpo=43439] 中貢獻。）

glob

在 glob() 和 iglob() 中新增 root_dir 和 dir_fd 參數，允許指定搜尋的根目錄。（由 Serhiy Storchaka 在 bpo-38144 [https://bugs.python.org/issue?@action=redirect&bpo=38144] 中貢獻。）

hashlib

hashlib 模組需要 OpenSSL 1.1.1 或更高版本。（由 Christian Heimes 在 PEP 644 [https://peps.python.org/pep-0644/] 和 bpo-43669 [https://bugs.python.org/issue?@action=redirect&bpo=43669] 中貢獻。）

hashlib 模組初步支援 OpenSSL 3.0.0。（由 Christian Heimes 在 bpo-38820 [https://bugs.python.org/issue?@action=redirect&bpo=38820] 和其他問題中貢獻。）

純 Python 的 pbkdf2_hmac() 後備 (fallback) 已被棄用。將來只有在有 OpenSSL 支援的建置 Python 中才能夠使用 PBKDF2-HMAC。（由 Christian Heimes 在 bpo-43880 [https://bugs.python.org/issue?@action=redirect&bpo=43880] 中貢獻。）

hmac

hmac 模組現在在內部使用 OpenSSL 的 HMAC 實作。（由 Christian Heimes 在 bpo-40645 [https://bugs.python.org/issue?@action=redirect&bpo=40645] 中貢獻。）

IDLE 和 idlelib

讓 IDLE 叫用 sys.excepthook() （在沒有 -n 的情況下啟動時）。使用者掛鉤 (user hooks) 在以前是被忽略的。（由 Ken Hilton 在 bpo-43008 [https://bugs.python.org/issue?@action=redirect&bpo=43008] 中貢獻。）

重新排列設定對話框。將 General 分頁拆分為 Windows 和 Shell/Ed 分頁。將擴充 Help 選單的幫助來源移至 Extensions 分頁。為新選項騰出空間並縮短對話框，而後者使對話框更好地適應較小的螢幕。（由 Terry Jan Reedy 在 bpo-40468 [https://bugs.python.org/issue?@action=redirect&bpo=40468] 中貢獻。）將縮排空間設定從 Font 分頁移至新的 Windows 分頁。（由 Mark Roseman 和 Terry Jan Reedy 在 bpo-33962 [https://bugs.python.org/issue?@action=redirect&bpo=33962] 中貢獻。）

上述更改已向後移植到 3.9 維護版本。

新增 Shell 側邊欄。將主要提示字元 (>>>) 移至側邊欄。將輔助提示字元（...）新增到側邊欄。點擊左鍵再拖動能夠選擇一行或多行文字，和編輯器列號側邊欄操作一樣。選擇文字列後點擊右鍵會顯示帶有「一併複製提示字元 (copy with prompts)」的情境選單，這會將側邊欄中提示字元與所選文字並排，此選項也會出現在文字的情境選單上。（由 Tal Einat 在 bpo-37903 [https://bugs.python.org/issue?@action=redirect&bpo=37903] 中貢獻。）

使用空格而不是製表符號 (tab) 來縮進交互式程式碼。這能夠使交互式程式碼條目「看起來正確」。新增 shell 側邊欄的主要動機是實現這一點。（由 Terry Jan Reedy 在 bpo-37892 [https://bugs.python.org/issue?@action=redirect&bpo=37892] 中貢獻。）

突顯 (highlight) 模式匹配陳述式中的新軟關鍵字 (soft keywords) match、case 和 _。然而這種突顯並不完美，並且在某些罕見的情況下會出錯，包括 case 模式中的一些 _。（由 Tal Einat 在 bpo-44010 [https://bugs.python.org/issue?@action=redirect&bpo=44010] 中貢獻。）

3.10 維護版本中的新增功能。

將語法突顯 (syntax highlighting) 應用於 .pyi 檔案。（由 Alex Waygood 和 Terry Jan Reedy 在 bpo-45447 [https://bugs.python.org/issue?@action=redirect&bpo=45447] 中貢獻。）

保存帶有輸入和輸出的 Shell 時，會包含提示字元。（由 Terry Jan Reedy 在 gh-95191 [https://github.com/python/cpython/issues/95191] 中貢獻。）

importlib.metadata

與 importlib_metadata 4.6 功能相同（歷史 [https://importlib-metadata.readthedocs.io/en/latest/history.html]）。

importlib.metadata 入口點現在透過新的 importlib.metadata.EntryPoints 類別提供了以群組和名稱選擇入口點的更好體驗。有關棄用與用法的更多資訊，請參閱文件中的相容性說明。

新增了 importlib.metadata.packages_distributions() 用於將頂階 Python 模組和套件解析出 importlib.metadata.Distribution。

inspect

當模組未定義 __loader__ 時，回退到 __spec__.loader 。（由 Brett Cannon 在 bpo-42133 [https://bugs.python.org/issue?@action=redirect&bpo=42133] 中貢獻。）

新增 inspect.get_annotations()，它可以安全地計算物件上定義的註釋。它是存取各種型別物件註釋的怪作法 (quirks) 的變通解法 (work around)，並且對其檢查的物件做出很少的假設。 inspect.get_annotations() 也可以正確地取消字串化註釋 (stringized annotations)。 inspect.get_annotations() 現在被認為是存取任何 Python 物件上定義的註釋字典的最佳實踐；有關使用註釋的最佳實踐的更多資訊，請參閱 註釋 (annotation) 最佳實踐。相關地，inspect.signature()、inspect.Signature.from_callable() 和 inspect.Signature.from_function() 現在呼叫 inspect.get_annotations() 來檢索註釋。這意味著 inspect.signature() 和 inspect.Signature.from_callable() 現在也可以取消字串化註釋。（由 Larry Hastings 在 bpo-43817 [https://bugs.python.org/issue?@action=redirect&bpo=43817] 中貢獻。）

itertools

新增 itertools.pairwise()。（由 Raymond Hettinger 在 bpo-38200 [https://bugs.python.org/issue?@action=redirect&bpo=38200] 中貢獻。）

linecache

當模組未定義 __loader__ 時，回退到 __spec__.loader 。（由 Brett Cannon 在 bpo-42133 [https://bugs.python.org/issue?@action=redirect&bpo=42133] 中貢獻。）

os

為 VxWorks RTOS 新增 os.cpu_count() 支援。（由 Peixing Xin 在 bpo-41440 [https://bugs.python.org/issue?@action=redirect&bpo=41440] 中貢獻。）

新增函式 os.eventfd() 和相關幫助程式來包裝 Linux 上的 eventfd2 系統呼叫。（由 Christian Heimes 在 bpo-41001 [https://bugs.python.org/issue?@action=redirect&bpo=41001] 中貢獻。）

新增 os.splice() 以允許在兩個檔案描述器 (file descriptor) 之間移動資料，而無需在核心地址空間 (kernel address space) 和使用者地址空間 (user address space) 之間進行複製，其中檔案描述器之一必須是個 pipe。（由 Pablo Galindo 在 bpo-41625 [https://bugs.python.org/issue?@action=redirect&bpo=41625] 中貢獻。）

為 macOS 新增 O_EVTONLY、O_FSYNC、O_SYMLINK 和 O_NOFOLLOW_ANY。（由 Donghee Na 在 bpo-43106 [https://bugs.python.org/issue?@action=redirect&bpo=43106] 中貢獻。）

os.path

os.path.realpath() 現在接受一個 strict 僅限關鍵字引數。當設定為 True 時，如果路徑不存在或遇到符號鏈接循環 (symlink loop)，則會引發 OSError。（由 Barney Gale 在 bpo-43757 [https://bugs.python.org/issue?@action=redirect&bpo=43757] 中貢獻。）

pathlib

新增 PurePath.parents 對於切片的支援。 （由 Joshua Cannon 在 bpo-35498 [https://bugs.python.org/issue?@action=redirect&bpo=35498] 中貢獻。）

向 PurePath.parents 新增負索引支援。（由 Yaroslav Pankovych 在 bpo-21041 [https://bugs.python.org/issue?@action=redirect&bpo=21041] 中貢獻。）

新增替代 link_to() 的 Path.hardlink_to 方法。新方法與 symlink_to() 具有相同的引數順序。（由 Barney Gale 在 bpo-39950 [https://bugs.python.org/issue?@action=redirect&bpo=39950] 中貢獻。）

pathlib.Path.stat() 和 chmod() 現在接受 follow_symlinks 僅限關鍵字引數，以與 os 模組中的相應函式保持一致。（由 Barney Gale 在 bpo-39906 [https://bugs.python.org/issue?@action=redirect&bpo=39906] 中貢獻。）

platform

新增 platform.freedesktop_os_release() 以從 freedesktop.org os-release [https://www.freedesktop.org/software/systemd/man/os-release.html] 標準檔案中檢索出作業系統識別。（由 Christian Heimes 在 bpo-28468 [https://bugs.python.org/issue?@action=redirect&bpo=28468] 中貢獻。）

pprint

pprint.pprint() 現在接受新的 underscore_numbers 關鍵字引數。（由 sblondon 在 bpo-42914 [https://bugs.python.org/issue?@action=redirect&bpo=42914] 中貢獻。）

pprint 現在可以漂亮地印出 dataclasses.dataclass 實例。（由 Lewis Gaul 在 bpo-43080 [https://bugs.python.org/issue?@action=redirect&bpo=43080] 中貢獻。）

py_compile

將 --quiet 選項新增到 py_compile 的命令列介面。（由 Gregory Schevchenko 在 bpo-38731 [https://bugs.python.org/issue?@action=redirect&bpo=38731] 中貢獻。）

pyclbr

將 end_lineno 屬性新增到 pyclbr.readmodule() 和 pyclbr.readmodule_ex() 回傳的樹中的 Function 和 Class 物件。它與現有的（開始） lineno 匹配。（由 Aviral Srivastava 在 bpo-38307 [https://bugs.python.org/issue?@action=redirect&bpo=38307] 中貢獻。）

shelve

現在，shelve 模組在建立 shelve 時預設使用 pickle.DEFAULT_PROTOCOL，而不是 pickle 的協定 3。（由 Zackery Spytz 在 bpo-34204 [https://bugs.python.org/issue?@action=redirect&bpo=34204] 中貢獻。）

statistics

新增 covariance()、Pearson correlation() 和簡單 linear_regression() 函式。（由 Tymoteusz Wołodźko 在 bpo-38490 [https://bugs.python.org/issue?@action=redirect&bpo=38490] 中貢獻。）

site

當模組未定義 __loader__ 時，回退到 __spec__.loader 。（由 Brett Cannon 在 bpo-42133 [https://bugs.python.org/issue?@action=redirect&bpo=42133] 中貢獻。）

socket

socket.timeout 例外現在是 TimeoutError 的別名。（由 Christian Heimes 在 bpo-42413 [https://bugs.python.org/issue?@action=redirect&bpo=42413] 中貢獻。）

新增使用 IPPROTO_MPTCP 建立 MPTCP socket 的選項（由 Rui Cunha 在 bpo-43571 [https://bugs.python.org/issue?@action=redirect&bpo=43571] 中貢獻。）

新增 IP_RECVTOS 選項以接收服務型別 (type of service, ToS) 或 DSCP/ECN 欄位（由 Georg Sauthoff 在 44077 中貢獻。）

ssl

ssl 模組需要 OpenSSL 1.1.1 或更高版本。（由 Christian Heimes 在 PEP 644 [https://peps.python.org/pep-0644/] 和 bpo-43669 [https://bugs.python.org/issue?@action=redirect&bpo=43669] 中貢獻。）

ssl 模組初步支援 OpenSSL 3.0.0 和新選項 OP_IGNORE_UNEXPECTED_EOF。（由 Christian Heimes 於 bpo-38820 [https://bugs.python.org/issue?@action=redirect&bpo=38820]、bpo-43794 [https://bugs.python.org/issue?@action=redirect&bpo=43794]、bpo-43788 [https://bugs.python.org/issue?@action=redirect&bpo=43788]、bpo-43791 [https://bugs.python.org/issue?@action=redirect&bpo=43791]、bpo-43799 [https://bugs.python.org/issue?@action=redirect&bpo=43799]、bpo-43920 [https://bugs.python.org/issue?@action=redirect&bpo=43920]、bpo-43789 [https://bugs.python.org/issue?@action=redirect&bpo=43789] 和 bpo-43811 [https://bugs.python.org/issue?@action=redirect&bpo=43811] 貢獻。)

已棄用函式和使用已棄用常數現在會導致 DeprecationWarning。 ssl.SSLContext.options 預設設定有 OP_NO_SSLv2 和 OP_NO_SSLv3，因此無法再次發出設定該旗標的警告。棄用部分包含已棄用功能的列表。（由 Christian Heimes 在 bpo-43880 [https://bugs.python.org/issue?@action=redirect&bpo=43880] 中貢獻。）

ssl 模組現在具有更安全的預設設定。預設情況下禁用沒有前向保密或 SHA-1 MAC 的密碼。安全級別 2 禁止安全性低於 112 位元的弱 RSA、DH 和 ECC 密鑰。 SSLContext 預設為最低協定版本 TLS 1.2。設定基於 Hynek Schlawack 的研究。（由 Christian Heimes 在 bpo-43998 [https://bugs.python.org/issue?@action=redirect&bpo=43998] 中貢獻。）

不再正式支援已棄用的協定 SSL 3.0、TLS 1.0 和 TLS 1.1。 Python 不會主動阻止它們。然而，OpenSSL 建置選項、發行版配置、發行商補丁和密碼套件可能會阻止交握的成功。

向 ssl.get_server_certificate() 函式新增 timeout 參數。（由 Zackery Spytz 在 bpo-31870 [https://bugs.python.org/issue?@action=redirect&bpo=31870] 中貢獻。）

ssl 模組使用堆疊類型 (heap-types) 和多階段初始化 (multi-phase initialization)。（由 Christian Heimes 在 bpo-42333 [https://bugs.python.org/issue?@action=redirect&bpo=42333] 中貢獻。）

新增驗證旗標 VERIFY_X509_PARTIAL_CHAIN。（由 l0x 在 bpo-40849 [https://bugs.python.org/issue?@action=redirect&bpo=40849] 中貢獻。）

sqlite3

新增 connect()、enable_load_extension() 和 load_extension() 的稽核事件。（由 Erlend E. Aasland 在 bpo-43762 [https://bugs.python.org/issue?@action=redirect&bpo=43762] 中貢獻。）

sys

新增 sys.orig_argv 屬性：傳遞給 Python 可執行檔案的原始命令列引數列表。（由 Victor Stinner 在 bpo-23427 [https://bugs.python.org/issue?@action=redirect&bpo=23427] 中貢獻。）

新增 sys.stdlib_module_names，其中包含標準函式庫模組的名稱列表。 （由 Victor Stinner 在 bpo-42955 [https://bugs.python.org/issue?@action=redirect&bpo=42955] 中貢獻。）

_thread

_thread.interrupt_main() 現在需要一個可選的信號編號來進行模擬（預設值仍然是 signal.SIGINT）。（由 Antoine Pitrou 在 bpo-43356 [https://bugs.python.org/issue?@action=redirect&bpo=43356] 中貢獻。）

threading

新增 threading.gettrace() 和 threading.getprofile() 分別取得 threading.settrace() 和 threading.setprofile() 設定的函式。（由 Mario Corchero 在 bpo-42251 [https://bugs.python.org/issue?@action=redirect&bpo=42251] 中貢獻。）

新增 threading.__excepthook__ 以允許取得 threading.excepthook() 的原始值，以防它被設定為損壞或不同的值。（由 Mario Corchero 在 bpo-42308 [https://bugs.python.org/issue?@action=redirect&bpo=42308] 中貢獻。）

traceback

format_exception()、format_exception_only() 和 print_exception() 函式現在可以將例外物件作為僅限位置引數。（由 Zackery Spytz 和 Matthias Bussonnier 在 bpo-26389 [https://bugs.python.org/issue?@action=redirect&bpo=26389] 中貢獻。）

types

重新引入 types.EllipsisType、types.NoneType 和 types.NotImplementedType 類別，提供一組易於型別檢查器直譯的新型別。（由 Bas van Beek 在 bpo-41810 [https://bugs.python.org/issue?@action=redirect&bpo=41810] 中貢獻。）

typing

有關重大更改，請參閱與型別提示相關的新功能。

typing.Literal 的行為已更改為符合 PEP 586 [https://peps.python.org/pep-0586/] 並匹配 PEP 中指定的靜態型別檢查器的行為。

Literal 現在可以刪除重複參數。

Literal 物件之間的相等性比較現在與順序無關。

現在型別的比較會優先於 Literal 的比較。例如，Literal[0] == Literal[False] 先前之求值為 True，但現在它是 False。為了支援此更改，內部使用的型別快取現在支援了型別的辨認。

如果 Literal 物件的任一參數不是可雜湊的，那麼它們現在將在相等性比較期間引發 TypeError 例外。請注意，使用不可雜湊的參數宣告 Literal 不會引發錯誤：

>>> from typing import Literal
>>> Literal[{0}]
>>> Literal[{0}] == Literal[{False}]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'set'

（由 Yurii Karabas 在 bpo-42345 [https://bugs.python.org/issue?@action=redirect&bpo=42345] 中貢獻。）

新增函式 typing.is_typeddict() 來自我審查 (introspect) 註釋是否為 typing.TypedDict。（由 Patrick Reader 在 bpo-41792 [https://bugs.python.org/issue?@action=redirect&bpo=41792] 中貢獻。）

僅宣告了資料變數的 typing.Protocol 子類別現在在使用 isinstance 檢查時會引發 TypeError ，除非它們用 runtime_checkable() 裝飾。此前，這些檢查都是悄無聲息地通過的。如果使用者需要執行環境協定 (runtime protocol)，則應該使用 runtime_checkable() 裝飾器來裝飾其子類別。（由 Yurii Karabas 在 bpo-38908 [https://bugs.python.org/issue?@action=redirect&bpo=38908] 中貢獻。）

從 typing.io 和 typing.re 子模組引入現在將發出 DeprecationWarning。這些子模組自 Python 3.8 起已被棄用，並將在未來版本的 Python 中刪除。屬於這些子模組的任何內容都應該直接從 typing 引入。 （由 Sebastian Rittau 在 bpo-38291 [https://bugs.python.org/issue?@action=redirect&bpo=38291] 中貢獻。）

unittest

新增方法 assertNoLogs() 以補足現有的 assertLogs()。（由 Kit Yan Choi 在 bpo-39385 [https://bugs.python.org/issue?@action=redirect&bpo=39385] 中貢獻。）

urllib.parse

Python 3.10 之前的 Python 版本允許在 urllib.parse.parse_qs() 和 urllib.parse.parse_qsl() 中使用 ; 和 & 作為查詢參數 (query parameter) 的分隔符號。出於安全考慮，並且為了符合更新的 W3C 建議，已將其更改為僅允許單個分隔符號鍵，預設為 &。此更改還會影響 cgi.parse() 和 cgi.parse_multipart()，因為它們在內部使用受影響的函式。有關更多詳細資訊，請參閱各自的文件。（由 Adam Goldschmidt、Senthil Kumaran 和 Ken Jin 在 bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967] 中貢獻。）

The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html], ASCII newline \n, \r and tab \t characters are stripped from the URL by the parser in urllib.parse preventing such attacks. The removal characters are controlled by a new module level variable urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (See gh-88048 [https://github.com/python/cpython/issues/88048])

xml

新增 LexicalHandler 類別到 xml.sax.handler 模組。（由 Jonathan Gossage 和 Zackery Spytz 在 bpo-35018 [https://bugs.python.org/issue?@action=redirect&bpo=35018] 中貢獻。）

zipimport

新增與 PEP 451 [https://peps.python.org/pep-0451/] 相關的方法：find_spec()、zipimport.zipimporter.create_module() 和 zipimport.zipimporter.exec_module()。（由 Brett Cannon 在 bpo-42131 [https://bugs.python.org/issue?@action=redirect&bpo=42131] 中貢獻。）

新增 invalidate_caches() 方法。（由 Desmond Cheong 在 bpo-14678 [https://bugs.python.org/issue?@action=redirect&bpo=14678] 中貢獻。）

最佳化

建構函式 str()、bytes() 和 bytearray() 現在更快了（對於小型物件大約快了 30--40%）。（由 Serhiy Storchaka 在 bpo-41334 [https://bugs.python.org/issue?@action=redirect&bpo=41334] 中貢獻。）

runpy 模組現在引入更少的模組。python3 -m module-name 指令啟動時間平均快了 1.4 倍。在 Linux 上，python3 -I -m module-name 在 Python 3.9 上引入 69 個模組，而在 Python 3.10 上僅引入 51 個模組 (-18)。（由 Victor Stinner 在 bpo-41006 [https://bugs.python.org/issue?@action=redirect&bpo=41006] 和 bpo-41718 [https://bugs.python.org/issue?@action=redirect&bpo=41718] 中貢獻。）

LOAD_ATTR 指令現在使用新的「操作碼快取 (per opcode cache)」機制。現在一般屬性的速度提高了約 36%，槽位 (slot) 的速度提高了 44%。（由 Pablo Galindo 和 Yury Selivanov 在 bpo-42093 [https://bugs.python.org/issue?@action=redirect&bpo=42093] 中以及 Guido van Rossum 在 bpo-42927 [https://bugs.python.org/issue?@action=redirect&bpo=42927] 中貢獻，基於最初在 PyPy 和 MicroPython 中實作的想法。）

當使用 --enable-optimizations 建置 Python 時，現在 -fno-semantic-interposition 被新增到編譯和鏈接列 (link line) 中。這使得使用 --enable-shared 和 gcc 建立的 Python 直譯器的建置速度提高了 30%。請參閱本文 [https://developers.redhat.com/blog/2020/06/25/red-hat-enterprise-linux-8-2-brings-faster-python-3-8-run-speeds/] 以了解詳情。（由 Victor Stinner 和 Pablo Galindo 在 bpo-38980 [https://bugs.python.org/issue?@action=redirect&bpo=38980] 中貢獻。）

對 bz2 / lzma / zlib 模組使用新的輸出緩衝區管理程式碼，並將 .readall() 函式新增到 _compression.DecompressReader 類別。 bz2 解壓縮速度提高了 1.09x ~ 1.17x，lzma 解壓縮速度提高了 1.20x ~ 1.32x，GzipFile.read(-1) 速度提高了 1.11x ~ 1.18x。（由 Ma Lin 於 bpo-41486 [https://bugs.python.org/issue?@action=redirect&bpo=41486] 貢獻、由 Gregory P. Smith 審閱）

使用字串化註釋時，建立函式時不再建立函式的註釋字典。取而代之的是它們被儲存為字串元組，且函式物件會根據需求才將其延遲轉換 (lazily convert) 為註釋字典。此最佳化將定義帶有註釋的函式所需的 CPU 時間減少了一半。（由 Yurii Karabas 和 Inada Naoki 在 bpo-42202 [https://bugs.python.org/issue?@action=redirect&bpo=42202] 中貢獻。）

像是 str1 in str2 和 str2.find(str1) 之類的子字串搜尋函式現在有時會使用 Crochemore & Perrin 的「雙向」字串搜尋演算法來避免作用於長字串上時發生二次方行為 (quadratic behavior)。（由 Dennis Sweeney 在 bpo-41972 [https://bugs.python.org/issue?@action=redirect&bpo=41972] 中貢獻）

向 _PyType_Lookup() 新增微最佳化以提高快取命中的常見情況下的型別屬性快取查找性能。這使得直譯器平均速度提高了 1.04 倍。（由 Dino Viehland 在 bpo-43452 [https://bugs.python.org/issue?@action=redirect&bpo=43452] 中貢獻。）

以下內建函式現在支援更快的 PEP 590 [https://peps.python.org/pep-0590/] vectorcall 呼叫慣例：map()、filter()、reversed()、bool() 和 float()。（由 Donghee Na 和 Jeroen Demeyer 在 bpo-43575 [https://bugs.python.org/issue?@action=redirect&bpo=43575]、bpo-43287 [https://bugs.python.org/issue?@action=redirect&bpo=43287]、bpo-41922 [https://bugs.python.org/issue?@action=redirect&bpo=41922]、bpo-41873 [https://bugs.python.org/issue?@action=redirect&bpo=41873] 和 bpo-41870 [https://bugs.python.org/issue?@action=redirect&bpo=41870] 中貢獻。）

透過刪除內部 RLock，BZ2File 的性能得到了改進。這使得 BZ2File 在面對多個同時的讀取器或寫入器時執行緒不安全，就像 gzip 和 lzma 中的等效類別一樣。（由 Inada Naoki 在 bpo-43785 [https://bugs.python.org/issue?@action=redirect&bpo=43785] 中貢獻。）

已棄用

目前 Python 接受緊跟關鍵字的數字字面值 (numeric literals)，例如 0in x、1or x、0if 1else 2。它允許了令人困惑和不明確的運算式，例如 [0x1for x in y] （可以直譯為 [0x1 for x in y] 或 [0x1f or x in y] ）。從此版本開始，如果數字字面值後緊跟關鍵字 and、else、for、if、in、is 與 or 其中之一，則會引發棄用警告。在未來的版本中，它將被變更為語法警告，最後成為為語法錯誤。（由 Serhiy Storchaka 在 bpo-43833 [https://bugs.python.org/issue?@action=redirect&bpo=43833] 中貢獻。）

從這個版本開始，我們將齊心協力開始清理為相容 Python 2.7 而保留的舊引入語義。具體來說， find_loader()/find_module() （被 find_spec() 取代）、load_module() （被 exec_module() 取代）、 module_repr() （引入系統負責處理你）、__package__ 屬性（由 __spec__.parent 取代）、 __loader__ 屬性（由 __spec__.loader 取代）和 __cached__ 屬性（由 __spec__.cached 取代）將慢慢被刪除（以及 importlib 中的其他類別和方法）。將酌情引發 ImportWarning 和/或 DeprecationWarning 以幫助識別在此轉換期間需要更新的程式碼。

整個 distutils 命名空間已棄用，將在 Python 3.12 中刪除。請參閱模組更改 以取得更多資訊。

random.randrange() 的非整數引數已棄用。ValueError 已被棄用，取而代之的是 TypeError。（由 Serhiy Storchaka 和 Raymond Hettinger 在 bpo-37319 [https://bugs.python.org/issue?@action=redirect&bpo=37319] 中貢獻。）

importlib 的各種 load_module() 方法自 Python 3.6 起已被記錄為已棄用，但現在也會觸發 DeprecationWarning。請改用 exec_module()。（由 Brett Cannon 在 bpo-26131 [https://bugs.python.org/issue?@action=redirect&bpo=26131] 中貢獻。）

zimport.zipimporter.load_module() 已被棄用，請用 exec_module()。（由 Brett Cannon 在 bpo-26131 [https://bugs.python.org/issue?@action=redirect&bpo=26131] 中貢獻。）

引入系統使用 load_module() 現在會觸發 ImportWarning，因為 exec_module() 是目前首選。（由 Brett Cannon 在 bpo-26131 [https://bugs.python.org/issue?@action=redirect&bpo=26131] 中貢獻。）

引入系統使用 importlib.abc.MetaPathFinder.find_module() 和 importlib.abc.PathEntryFinder.find_module() 現在會觸發 ImportWarning，因為 importlib.abc.MetaPathFinder.find_spec() 和 importlib.abc.PathEntryFinder.find_spec() 分別是替代方案的首選。你可以使用 importlib.util.spec_from_loader() 來幫助移植。（由 Brett Cannon 在 bpo-42134 [https://bugs.python.org/issue?@action=redirect&bpo=42134] 中貢獻。）

引入系統使用 importlib.abc.PathEntryFinder.find_loader() 現在會觸發 ImportWarning，因為 importlib.abc.PathEntryFinder.find_spec() 是首選。你可以使用 importlib.util.spec_from_loader() 來幫助移植。（由 Brett Cannon 在 bpo-43672 [https://bugs.python.org/issue?@action=redirect&bpo=43672] 中貢獻。）

importlib.abc.MetaPathFinder.find_module() 的各種實作（importlib.machinery.BuiltinImporter.find_module()、importlib.machinery.FrozenImporter.find_module()、importlib.machinery.WindowsRegistryFinder.find_module()、importlib.machinery.PathFinder.find_module()、importlib.abc.MetaPathFinder.find_module() )、importlib.abc.PathEntryFinder.find_module() (importlib.machinery.FileFinder.find_module() ) 和 importlib.abc.PathEntryFinder.find_loader() (importlib.machinery.FileFinder.find_loader() ) 現在引發 DeprecationWarning 並計劃在 Python 3.12 中刪除（之前它們已在 Python 3.4 中被記錄為已棄用）。（由 Brett Cannon 在 bpo-42135 [https://bugs.python.org/issue?@action=redirect&bpo=42135] 中貢獻。）

importlib.abc.Finder 已被棄用（包括其唯一方法 find_module()）。importlib.abc.MetaPathFinder 和 importlib.abc.PathEntryFinder 都不再從該類別繼承。使用者應該根據需求來選擇其一以繼承。（由 Brett Cannon 在 bpo-42135 [https://bugs.python.org/issue?@action=redirect&bpo=42135] 中貢獻。）

棄用 imp、importlib.find_loader()、importlib.util.set_package_wrapper()、importlib.util.set_loader_wrapper()、importlib.util.module_for_loader()、pkgutil.ImpImporter 和 pkgutil.ImpLoader 均已更新，將於 Python 3.12 列為預定的刪除版本（它們開始在過去版本的 Python 中引發 DeprecationWarning） 。（由 Brett Cannon 在 bpo-43720 [https://bugs.python.org/issue?@action=redirect&bpo=43720] 中貢獻。）

引入系統現在在模組上使用 __spec__ 屬性，然後才會回退使用 module_repr() 作為模組的 __repr__() 方法。計劃在 Python 3.12 中刪除 module_repr() 的使用。（由 Brett Cannon 在 bpo-42137 [https://bugs.python.org/issue?@action=redirect&bpo=42137] 中貢獻。）

importlib.abc.Loader.module_repr()、importlib.machinery.FrozenLoader.module_repr() 和 importlib.machinery.BuiltinLoader.module_repr() 已棄用並計劃在 Python 3.12 中刪除。（由 Brett Cannon 在 bpo-42136 [https://bugs.python.org/issue?@action=redirect&bpo=42136] 中貢獻。）

自 Python 3.3 起，sqlite3.OptimizedUnicode 就沒有文件記錄並且已過時，當時它被用作 str 的別名。它現已被棄用，並計劃在 Python 3.12 中刪除。（由 Erlend E. Aasland 在 bpo-42264 [https://bugs.python.org/issue?@action=redirect&bpo=42264] 中貢獻。）

未記錄於說明文件的內建函式 sqlite3.enable_shared_cache 現已棄用，計劃在 Python 3.12 中刪除。SQLite3 文件強烈建議不去使用它。有關更多詳細資訊，請參閱 SQLite3 文件 [https://sqlite.org/c3ref/enable_shared_cache.html]。如果必須使用共享快取，請使用 cache=shared 查詢參數以 URI 模式打開資料庫。（由 Erlend E. Aasland 在 bpo-24464 [https://bugs.python.org/issue?@action=redirect&bpo=24464] 中貢獻。）

以下 threading 方法現已棄用：

threading.currentThread => threading.current_thread()

threading.activeCount => threading.active_count()

threading.Condition.notifyAll => threading.Condition.notify_all()

threading.Event.isSet => threading.Event.is_set()

threading.Thread.setName => threading.Thread.name

threading.thread.getName => threading.Thread.name

threading.Thread.isDaemon => threading.Thread.daemon

threading.Thread.setDaemon => threading.Thread.daemon

（由 Jelle Zijlstra 在 gh-87889 [https://github.com/python/cpython/issues/87889] 中貢獻。）

pathlib.Path.link_to() 已棄用並計劃在 Python 3.12 中刪除。請改用 pathlib.Path.hardlink_to()。（由 Barney Gale 在 bpo-39950 [https://bugs.python.org/issue?@action=redirect&bpo=39950] 中貢獻。）

cgi.log() 已棄用並計劃在 Python 3.12 中刪除。（由 Inada Naoki 在 bpo-41139 [https://bugs.python.org/issue?@action=redirect&bpo=41139] 中貢獻。）

自 Python 3.6、Python 3.7 或 OpenSSL 1.1.0 起，以下 ssl 功能已被棄用，並將在 3.11 中刪除：

OP_NO_SSLv2、OP_NO_SSLv3、OP_NO_TLSv1、OP_NO_TLSv1_1、OP_NO_TLSv1_2、和 OP_NO_TLSv1_3 已被替換為 minimum_version 和 maximum_version。

PROTOCOL_SSLv2、PROTOCOL_SSLv3、PROTOCOL_SSLv23、PROTOCOL_TLSv1、PROTOCOL_TLSv1_1、PROTOCOL_TLSv1_2 和 PROTOCOL_TLS 已棄用，取而代之的是 PROTOCOL_TLS_CLIENT 和 PROTOCOL_TLS_SERVER

wrap_socket() 被替換為 ssl.SSLContext.wrap_socket()

match_hostname()

RAND_pseudo_bytes(), RAND_egd()

NPN 功能如 ssl.SSLSocket.selected_npn_protocol() 和 ssl.SSLContext.set_npn_protocols() 已被 ALPN 取代。

執行緒除錯（PYTHONTHREADDEBUG 環境變數）在 Python 3.10 中已棄用，並將在 Python 3.12 中刪除。此功能需要一個 Python 的除錯用建置版本。（由 Victor Stinner 在 bpo-44584 [https://bugs.python.org/issue?@action=redirect&bpo=44584] 中貢獻。）

從 typing.io 和 typing.re 子模組引入現在將發出 DeprecationWarning。這些子模組將在 Python 的未來版本中刪除。屬於這些子模組的任何內容都應該直接從 typing 引入。（由 Sebastian Rittau 在 bpo-38291 [https://bugs.python.org/issue?@action=redirect&bpo=38291] 中貢獻。）

已刪除

刪除了 complex 類別的特殊方法 __int__、__float__、__floordiv__、__mod__、__divmod__、__rfloordiv__、__rmod__ 和 __rdivmod__ 。它們都會引發 TypeError。（由 Serhiy Storchaka 在 bpo-41974 [https://bugs.python.org/issue?@action=redirect&bpo=41974] 中貢獻。）

_markupbase 模組中私有、未於文件記錄的 ParserBase.error() 方法已被刪除。html.parser.HTMLParser 是 ParserBase 的唯一子類別，它的 error() 實作已在 Python 3.5 中刪除。（由 Berker Peksag 在 bpo-31844 [https://bugs.python.org/issue?@action=redirect&bpo=31844] 中貢獻。）

刪除了 unicodedata.ucnhash_CAPI 屬性，該屬性是內部 PyCapsule 物件。相關的私有 _PyUnicode_Name_CAPI 結構已移至內部 C API。（由 Victor Stinner 在 bpo-42157 [https://bugs.python.org/issue?@action=redirect&bpo=42157] 中貢獻。）

刪除了由於切換到新的 PEG 剖析器而在 3.9 中被棄用的 parser 模組。僅由舊剖析器使用的所有 C 原始碼和標頭檔也已被刪除，包括 node.h、parser.h、graminit.h 和 grammar.h。

刪除了公開 C API 函式 PyParser_SimpleParseStringFlags、PyParser_SimpleParseStringFlagsFilename、PyParser_SimpleParseFileFlags 和 PyNode_Compile，這些函式由於切換到新的 PEG 剖析器而在 3.9 中被棄用。

刪除了 formatter 模組，該模組在 Python 3.4 中已棄用。它有些過時、很少被使用，也沒有經過測試。它最初計劃在 Python 3.6 中刪除，但此類別的刪除被推遲到 Python 2.7 EOL 之後。現有使用者應該將他們使用的任何類別複製到他們的程式碼中。（由 Donghee Na 和 Terry J. Reedy 在 bpo-42299 [https://bugs.python.org/issue?@action=redirect&bpo=42299] 中貢獻。）

刪除了 PyModule_GetWarningsModule() 函式，該函式現在無用，因為 _warnings 模組在 2.6 中已轉換為內建模組。（由 Hai Shi 在 bpo-42599 [https://bugs.python.org/issue?@action=redirect&bpo=42599] 中貢獻。）

從 collections 模組中刪除已棄用的、對 Collections Abstract Base Classes 的別名。（由 Victor Stinner 在 bpo-37324 [https://bugs.python.org/issue?@action=redirect&bpo=37324] 中貢獻。）

在 Python 3.8 中棄用後，loop 參數已從大多數 asyncio 的高階 API 中刪除。這一變化的背後動機是多方面的：

這簡化了高階 API。

自 Python 3.7 以來，高階 API 中的函式一直隱式取得目前執行緒正在運行的事件循環。在大多數正常用例中，不需要將事件循環傳遞給 API。

事件循環的傳遞很容易出錯，尤其是在處理在不同執行緒中運行的循環時。

請注意，低階 API 仍會接受 loop。有關如何替換現有程式碼的範例，請參閱 Python API 的變更。

（由 Yurii Karabas、Andrew Svetlov、Yury Selivanov 和 Kyle Stanley 在 bpo-42392 [https://bugs.python.org/issue?@action=redirect&bpo=42392] 中貢獻。）

移植到 Python 3.10

本節列出了前面描述的更改以及可能需要更改程式碼的其他錯誤修復。

Python 語法的變化

如果數字字面值後面緊跟關鍵字（如 0in x），在以前是有效的語法，但現在在編譯時會發出棄用警告。在未來的版本中，它將更改為語法警告，最後更改為語法錯誤。要消除警告並使程式碼與未來版本相容，只需在數字字面值和以下關鍵字之間新增一個空格即可。（由 Serhiy Storchaka 在 bpo-43833 [https://bugs.python.org/issue?@action=redirect&bpo=43833] 中貢獻。）

Python API 的變更

format_exception()、format_exception_only() 和 traceback 模組中的 print_exception() 函式的 etype 參數已重命名為 exc。（由 Zackery Spytz 和 Matthias Bussonnier 在 bpo-26389 [https://bugs.python.org/issue?@action=redirect&bpo=26389] 中貢獻。）

atexit：在 Python 退出時，如果一個使用 atexit.register() 註冊的回呼 (callback) 失敗，該例外現在會被記錄下來。在以前只記錄一些例外，並且最後一個例外總是被默默地忽略。（由 Victor Stinner 在 bpo-42639 [https://bugs.python.org/issue?@action=redirect&bpo=42639] 中貢獻。）

collections.abc.Callable 泛型現在會攤平型別參數，類似於 typing.Callable 目前的做法。這意味著 collections.abc.Callable[[int, str], str] 將具有 (int, str, str) 的 __args__；以前這是 ([int, str], str)。透過 typing.get_args() 或 __args__ 存取參數的程式碼需要考慮此變更。此外，對於無效形式的參數化 collections.abc.Callable，可能會引發 TypeError，而在 Python 3.9 中，該參數可能已被默默地傳遞。（由 Ken Jin 在 bpo-42195 [https://bugs.python.org/issue?@action=redirect&bpo=42195] 中貢獻。）

如果給定參數不適合 16 位元無符號整數 (16-bit unsigned integer)，socket.htons() 和 socket.ntohs() 現在會引發 OverflowError 而不是 DeprecationWarning。（由 Erlend E. Aasland 在 bpo-42393 [https://bugs.python.org/issue?@action=redirect&bpo=42393] 中貢獻。）

在 Python 3.8 中棄用後，loop 參數已從大多數 asyncio 的高階 API 中刪除。

目前如下所示的協程：

async def foo(loop):
    await asyncio.sleep(1, loop=loop)

應替換為：

async def foo():
    await asyncio.sleep(1)

如果 foo() 被專門設計為 不 在目前執行緒的事件循環中運行（例如在另一個執行緒的事件循環中運行），請考慮改用 asyncio.run_coroutine_threadsafe()。

（由 Yurii Karabas、Andrew Svetlov、Yury Selivanov 和 Kyle Stanley 在 bpo-42392 [https://bugs.python.org/issue?@action=redirect&bpo=42392] 中貢獻。）

如果 globals 字典沒有 "__builtins__" 鍵，則 types.FunctionType 建構函式現在會繼承目前的內建物件，而不是使用 {"None": None}：相同行為如 eval() 和 exec() 函式。在 Python 中使用 def function(...): ... 定義函式不受影響，全域變數不能用此語法覆蓋：它也繼承目前的內建物件。（由 Victor Stinner 在 bpo-42990 [https://bugs.python.org/issue?@action=redirect&bpo=42990] 中貢獻。）

C API 中的改動

由於切換到新的 PEG 剖析器，C API 函式 PyParser_SimpleParseStringFlags、PyParser_SimpleParseStringFlagsFilename、PyParser_SimpleParseFileFlags、PyNode_Compile 和被這些函式使用的型別 struct _node 被刪除。

現在應該將源程式碼直接（例如透過 Py_CompileString()）編譯為程式碼物件。然後可以（例如透過 PyEval_EvalCode()）為產生的程式碼物件求值 (evaluated)。

具體來說：

後跟有 PyNode_Compile 呼叫的 PyParser_SimpleParseStringFlags 呼叫，可以替換為呼叫 Py_CompileString()。

沒有 PyParser_SimpleParseFileFlags 的直接替代品。要從 FILE * 引數編譯程式碼，你需要用 C 讀取檔案並將結果緩衝區傳遞給 Py_CompileString()。

要編譯給定 char * 檔案名稱的檔案，請顯式打開該檔案，讀取它並編譯結果。一種方法是使用 io 模組和 PyImport_ImportModule()、PyObject_CallMethod()、PyBytes_AsString() 和 Py_CompileString()，如下所示。（宣告和錯誤處理在此被省略。）：

io_module = Import_ImportModule("io");
fileobject = PyObject_CallMethod(io_module, "open", "ss", filename, "rb");
source_bytes_object = PyObject_CallMethod(fileobject, "read", "");
result = PyObject_CallMethod(fileobject, "close", "");
source_buf = PyBytes_AsString(source_bytes_object);
code = Py_CompileString(source_buf, filename, Py_file_input);

對於 FrameObject 物件，f_lasti 成員現在表示了字碼偏移量 (wordcode offset)，而不是位元組碼字串的簡單偏移量。這意味著這個數字需要乘以 2 才能與需要位元組偏移量的 API 一起使用（例如 PyCode_Addr2Line()）。還要注意，FrameObject 物件的 f_lasti 成員不被認為是穩定的：請改用 PyFrame_GetLineNumber()。

CPython 位元組碼變更

MAKE_FUNCTION 指令現在接受字典或字串元組作為函式的註釋。（由 Yurii Karabas 和 Inada Naoki 在 bpo-42202 [https://bugs.python.org/issue?@action=redirect&bpo=42202] 中貢獻。）

建置變更

PEP 644 [https://peps.python.org/pep-0644/]：Python 現在需要 OpenSSL 1.1.1 或更高版本。不再支援 OpenSSL 1.0.2。（由 Christian Heimes 在 bpo-43669 [https://bugs.python.org/issue?@action=redirect&bpo=43669] 中貢獻。）

現在需要 C99 函式 snprintf() 和 vsnprintf() 來建置 Python。 （由 Victor Stinner 在 bpo-36020 [https://bugs.python.org/issue?@action=redirect&bpo=36020] 中貢獻。）

sqlite3 需要 SQLite 3.7.15 或更新版本。（由 Sergey Fedoseev 和 Erlend E. Aasland 在 bpo-40744 [https://bugs.python.org/issue?@action=redirect&bpo=40744] 和 bpo-40810 [https://bugs.python.org/issue?@action=redirect&bpo=40810] 中貢獻。）

atexit 模組現在必須都被建置為內建模組。（由 Victor Stinner 在 bpo-42639 [https://bugs.python.org/issue?@action=redirect&bpo=42639] 中貢獻。）

將 --disable-test-modules 選項新增到 configure 腳本中：不建置也不安裝測試模組。（由 Xavier de Gaye、Thomas Petazzoni 和 Peixing Xin 在 bpo-27640 [https://bugs.python.org/issue?@action=redirect&bpo=27640] 中貢獻。）

將 --with-wheel-pkg-dir=PATH 選項 新增到 ./configure 腳本中。如果有指定，ensurepip 模組會在此目錄中查找 setuptools 和 pip wheel 套件：如果兩者都存在，則使用這些 wheel 套件而不是 ensurepip 捆綁的 wheel 套件。

一些 Linux 發行版的打包策略建議不要一併包入依賴項目。例如，Fedora 在 /usr/share/python-wheels/ 目錄中安裝 wheel 套件，並且不安裝 ensurepip._bundled 套件。

（由 Victor Stinner 在 bpo-42856 [https://bugs.python.org/issue?@action=redirect&bpo=42856] 中貢獻。）

新增 configure --without-static-libpython 選項 以不建置 libpythonMAJOR.MINOR.a 靜態函式庫且不安裝 python.o 目標檔案。

（由 Victor Stinner 在 bpo-43103 [https://bugs.python.org/issue?@action=redirect&bpo=43103] 中貢獻。）

如果可用，configure 腳本現在使用 pkg-config 工具程式 (utility) 來檢測 Tcl/Tk 標頭檔和函式庫的位置。和以前一樣，可以使用 --with-tcltk-includes 和 --with-tcltk-libs 配置選項顯式指定這些位置。（由 Manolis Stamatogiannakis 在 bpo-42603 [https://bugs.python.org/issue?@action=redirect&bpo=42603] 中貢獻。）

將 --with-openssl-rpath 選項新增到 configure 腳本中。該選項簡化了使用自訂 OpenSSL 安裝建置 Python 的過程，例如 ./configure --with-openssl=/path/to/openssl --with-openssl-rpath=auto。（由 Christian Heimes 在 bpo-43466 [https://bugs.python.org/issue?@action=redirect&bpo=43466] 中貢獻。）

C API 變更

PEP 652：維護穩定 ABI

用於擴充模組或嵌入 Python 的穩定 ABI（應用程式二進位介面）現已明確定義。 C API 穩定性 描述了 C API 和 ABI 穩定性保證以及使用穩定 ABI 的最佳實踐。

（由 Petr Viktorin 在 PEP 652 [https://peps.python.org/pep-0652/] 和 bpo-43795 [https://bugs.python.org/issue?@action=redirect&bpo=43795] 中貢獻。）

新增功能

PyNumber_Index() 的結果現在都具有精確的 int 型別。在以前，結果可能是 int 子類別的實例。（由 Serhiy Storchaka 在 bpo-40792 [https://bugs.python.org/issue?@action=redirect&bpo=40792] 中貢獻。）

將新的 orig_argv 成員新增到 PyConfig 結構：傳遞給 Python 可執行檔案的原始命令列參數列表。（由 Victor Stinner 在 bpo-23427 [https://bugs.python.org/issue?@action=redirect&bpo=23427] 中貢獻。）

新增了 PyDateTime_DATE_GET_TZINFO() 和 PyDateTime_TIME_GET_TZINFO() 巨集，用於存取 datetime.datetime 和 datetime.time 物件的 tzinfo 屬性。（由 Zackery Spytz 在 bpo-30155 [https://bugs.python.org/issue?@action=redirect&bpo=30155] 中貢獻。）

新增 PyCodec_Unregister() 函式來取消註冊編解碼器搜尋函式。（由 Hai Shi 在 bpo-41842 [https://bugs.python.org/issue?@action=redirect&bpo=41842] 中貢獻。）

新增了 PyIter_Send() 函式，以允許將值發送到疊代器中，而不會引發 StopIteration 例外。（由 Vladimir Matveev 在 bpo-41756 [https://bugs.python.org/issue?@action=redirect&bpo=41756] 中貢獻。）

將 PyUnicode_AsUTF8AndSize() 新增到受限 C API (limited C API) 中。（由 Alex Gaynor 在 bpo-41784 [https://bugs.python.org/issue?@action=redirect&bpo=41784] 中貢獻。）

新增 PyModule_AddObjectRef() 函式：類似於 PyModule_AddObject() 但成功時不竊取對值的參照。（由 Victor Stinner 在 bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741] 中貢獻。）

新增 Py_NewRef() 和 Py_XNewRef() 函式來增加物件的參照計數並回傳物件。（由 Victor Stinner 在 bpo-42262 [https://bugs.python.org/issue?@action=redirect&bpo=42262] 中貢獻。）

PyType_FromSpecWithBases() 和 PyType_FromModuleAndSpec() 函式現在接受單個類別作為 bases 引數。（由 Serhiy Storchaka 在 bpo-42423 [https://bugs.python.org/issue?@action=redirect&bpo=42423] 中貢獻。）

PyType_FromModuleAndSpec() 函式現在接受 NULL tp_doc 槽位。（由 Hai Shi 在 bpo-41832 [https://bugs.python.org/issue?@action=redirect&bpo=41832] 中貢獻。）

PyType_GetSlot() 函式可以接受靜態型別 (static type)。（由 Hai Shi 和 Petr Viktorin 在 bpo-41073 [https://bugs.python.org/issue?@action=redirect&bpo=41073] 中貢獻。）

向 C-API 新增 PySet_CheckExact() 函式，以檢查物件是否是 set 的實例而不是子型別的實例。（由 Pablo Galindo 在 bpo-43277 [https://bugs.python.org/issue?@action=redirect&bpo=43277] 中貢獻。）

新增 PyErr_SetInterruptEx()，它允許傳遞信號編號來進行模擬。（由 Antoine Pitrou 在 bpo-43356 [https://bugs.python.org/issue?@action=redirect&bpo=43356] 中貢獻。）

如 Python 是在除錯模式 (debug mode) 下建置的（如果有定義 Py_DEBUG 巨集），現在會支援受限 C API。在受限 C API 中，如果 Python 是在除錯模式下建置的，並且 Py_LIMITED_API 巨集的目標是 Python 3.10 或更新版本，Py_INCREF() 和 Py_DECREF() 函式現在的實作是不透明函式呼叫，而不是直接存取 PyObject.ob_refcnt 成員。在除錯模式下支援受限 C API 成為可能，因為自 Python 3.8 以來，PyObject 結構在發布和除錯模式下是相同的（請參閱:issue:36465）。

--with-trace-refs 特殊建置（Py_TRACE_REFS 巨集）仍不支援受限 C API。（由 Victor Stinner 在 bpo-43688 [https://bugs.python.org/issue?@action=redirect&bpo=43688] 中貢獻。）

新增 Py_Is(x, y) 函式來測試 x 物件是否為 y 物件，與 Python 中的 x is y 相同。還新增 Py_IsNone()、Py_IsTrue()、Py_IsFalse() 函式來分別測試物件是否為 None 單例、 True 單例或 False 單例。（由 Victor Stinner 在 bpo-43753 [https://bugs.python.org/issue?@action=redirect&bpo=43753] 中貢獻。）

新增函式以從 C 程式碼控制垃圾收集器：PyGC_Enable()、PyGC_Disable()、PyGC_IsEnabled()。這些函式使得能夠從 C 程式碼啟用、停用和查詢垃圾收集器的狀態，而無需引入 gc 模組。

新增 Py_TPFLAGS_DISALLOW_INSTANTIATION 型別旗標以禁止建立型別實例。（由 Victor Stinner 在 bpo-43916 [https://bugs.python.org/issue?@action=redirect&bpo=43916] 中貢獻。）

新增 Py_TPFLAGS_IMMUTABLETYPE 型別旗標用於建立不可變型別物件：無法設定或刪除型別屬性。（由 Victor Stinner 和 Erlend E. Aasland 在 bpo-43908 [https://bugs.python.org/issue?@action=redirect&bpo=43908] 中貢獻。）

移植到 Python 3.10

現在必須定義 PY_SSIZE_T_CLEAN 巨集以使用 PyArg_ParseTuple() 和 Py_BuildValue() 格式，這些格式使用 #: es#, et#、s#、u#、y#、z#、U# 和 Z#。請參閱 剖析引數與建置數值 和 PEP 353 [https://peps.python.org/pep-0353/]。（由 Victor Stinner 在 bpo-40943 [https://bugs.python.org/issue?@action=redirect&bpo=40943] 中貢獻。）

由於 Py_REFCNT() 更改為行內靜態函式 (inline static function)，因此 Py_REFCNT(obj) = new_refcnt 必須替換為 Py_SET_REFCNT(obj, new_refcnt) ：參見 Py_SET_REFCNT() （自 Python 3.9 起可用）。為了向後相容，可以使用該巨集：

#if PY_VERSION_HEX < 0x030900A4
#  define Py_SET_REFCNT(obj, refcnt) ((Py_REFCNT(obj) = (refcnt)), (void)0)
#endif

（由 Victor Stinner 在 bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573] 中貢獻。）

由於過去的種種原因，過去在不持有 GIL 的情況下呼叫 PyDict_GetItem() 是被允許的。目前已被禁止。（由 Victor Stinner 在 bpo-40839 [https://bugs.python.org/issue?@action=redirect&bpo=40839] 中貢獻。）

PyUnicode_FromUnicode(NULL, size) 和 PyUnicode_FromStringAndSize(NULL, size) 現在會引發 DeprecationWarning。請改用 PyUnicode_New() 來分配沒有初始資料的 Unicode 物件。（由 Inada Naoki 在 bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346] 中貢獻。）

PyCapsule API unicodedata.ucnhash_CAPI 的私有 _PyUnicode_Name_CAPI 結構已移至內部 C API。（由 Victor Stinner 在 bpo-42157 [https://bugs.python.org/issue?@action=redirect&bpo=42157] 中貢獻。）

如果在 Py_Initialize() 之前（Python 初始化之前）被呼叫，Py_GetPath()、Py_GetPrefix()、Py_GetExecPrefix()、Py_GetProgramFullPath()、Py_GetPythonHome() 和 Py_GetProgramName() 現在會回傳 NULL。使用新的 Python 初始化設定 API 來取得 Python 路徑配置。（由 Victor Stinner 在 bpo-42260 [https://bugs.python.org/issue?@action=redirect&bpo=42260] 中貢獻。）

PyList_SET_ITEM()、PyTuple_SET_ITEM() 和 PyCell_SET() 巨集不能再用作左值 (l-value) 或右值 (r-value)。例如，x = PyList_SET_ITEM(a, b, c) 和 PyList_SET_ITEM(a, b, c) = x 現在會失敗並出現編譯器錯誤。它可以防止如 if (PyList_SET_ITEM (a, b, c) < 0) ... 測試之類的錯誤。（由 Zackery Spytz 和 Victor Stinner 在 bpo-30459 [https://bugs.python.org/issue?@action=redirect&bpo=30459] 中貢獻。）

非受限 API 檔案 odictobject.h、parser_interface.h、picklebufobject.h、pyarena.h、pyctype.h、pydebug.h、pyfpe.h 和 pytime.h 已移至 Include/cpython 目錄。這些檔案不得直接被引入，因為它們已於 Python.h 中引入；請參閱 引入檔案 (include files)。如果直接引入它們，請考慮改為引入 Python.h。（由 Nicholas Sim 在 bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134] 中貢獻。）

使用 Py_TPFLAGS_IMMUTABLETYPE 型別旗標來建立不可變型別物件。不要依賴 Py_TPFLAGS_HEAPTYPE 來決定型別物件是否可變；應改為檢查是否設定了 Py_TPFLAGS_IMMUTABLETYPE。（由 Victor Stinner 和 Erlend E. Aasland 在 bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134] 中貢獻。）

未以說明文件記錄的函式 Py_FrozenMain 已從受限 API 中刪除。該函式主要用於 Python 的自訂建置。（由 Petr Viktorin 在 bpo-26241 [https://bugs.python.org/issue?@action=redirect&bpo=26241] 中貢獻。）

已棄用

PyUnicode_InternImmortal() 函式現已棄用，並將在 Python 3.12 中刪除：請改用 PyUnicode_InternInPlace()。（由 Victor Stinner 在 bpo-41692 [https://bugs.python.org/issue?@action=redirect&bpo=41692] 中貢獻。）

已刪除

刪除了操作 Py_UNICODE* 字串的 Py_UNICODE_str* 函式。（由 Inada Naoki 在 bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123] 中貢獻。）

Py_UNICODE_strlen：使用 PyUnicode_GetLength() 或 PyUnicode_GET_LENGTH

Py_UNICODE_strcat：使用 PyUnicode_CopyCharacters() 或 PyUnicode_FromFormat()

Py_UNICODE_strcpy、Py_UNICODE_strncpy：使用 PyUnicode_CopyCharacters() 或 PyUnicode_Substring()

Py_UNICODE_strcmp：使用 PyUnicode_Compare()

Py_UNICODE_strncmp：使用 PyUnicode_Tailmatch()

Py_UNICODE_strchr、Py_UNICODE_strrchr：使用 PyUnicode_FindChar()

刪除了 PyUnicode_GetMax()。請改用新的 (PEP 393 [https://peps.python.org/pep-0393/]) API。（由 Inada Naoki 在 bpo-41103 [https://bugs.python.org/issue?@action=redirect&bpo=41103] 中貢獻。）

刪除了 PyLong_FromUnicode()。請改用 PyLong_FromUnicodeObject()。（由 Inada Naoki 在 bpo-41103 [https://bugs.python.org/issue?@action=redirect&bpo=41103] 中貢獻。）

刪除了 PyUnicode_AsUnicodeCopy()。請改用 PyUnicode_AsUCS4Copy() 或 PyUnicode_AsWideCharString() （由 Inada Naoki 在 bpo-41103 [https://bugs.python.org/issue?@action=redirect&bpo=41103] 中貢獻。）

刪除了 _Py_CheckRecursionLimit 變數：它已被 PyInterpreterState 結構的 ceval.recursion_limit 取代。（由 Victor Stinner 在 bpo-41834 [https://bugs.python.org/issue?@action=redirect&bpo=41834] 中貢獻。）

刪除了未被說明文件記錄的巨集 Py_ALLOW_RECURSION 和 Py_END_ALLOW_RECURSION 以及 PyInterpreterState 結構的 recursion_ritic 欄位。（由 Serhiy Storchaka 在 bpo-41936 [https://bugs.python.org/issue?@action=redirect&bpo=41936] 中貢獻。）

刪除了未被說明文件記錄的 PyOS_InitInterrupts() 函式。初始化 Python 已經隱式安裝信號處理程式：請參閱 PyConfig.install_signal_handlers。（由 Victor Stinner 在 bpo-41713 [https://bugs.python.org/issue?@action=redirect&bpo=41713] 中貢獻。）

刪除 PyAST_Validate() 函式。不再可能使用公開 C API 來建置 AST 物件（mod_ty 類型）。該函式已被排除在受限 C API 之外 (PEP 384 [https://peps.python.org/pep-0384/])。（由 Victor Stinner 在 bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244] 中貢獻。）

刪除 symtable.h 標頭檔和未被說明文件記錄的函式：

PyST_GetScope()

PySymtable_Build()

PySymtable_BuildObject()

PySymtable_Free()

Py_SymtableString()

Py_SymtableStringObject()

Py_SymtableString() 函式錯誤地成為穩定 ABI 的一部分，但它因為 symtable.h 標頭檔被排除在受限 C API 之外而無法使用。

請改用 Python symtable 模組。（由 Victor Stinner 在 bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244] 中貢獻。）

從受限 C API 標頭和 python3.dll （在 Windows 上提供穩定 ABI 的函式庫）中刪除 PyOS_ReadlineFunctionPointer()。由於該函式採用 FILE* 引數，因此無法保證其 ABI 穩定性。（由 Petr Viktorin 在 bpo-43868 [https://bugs.python.org/issue?@action=redirect&bpo=43868] 中貢獻。）

刪除 ast.h、asdl.h 和 Python-ast.h 標頭檔。這些函式沒有文件記錄，並且被排除在受限 C API 之外。這些標頭檔定義的大多數名稱都沒有前綴 Py，因此可能會產生名稱衝突。例如，Python-ast.h 定義了一個 Yield 巨集，它與 Windows <winbase.h> 標頭使用的 Yield 有名稱衝突。請改用 Python ast 模組。（由 Victor Stinner 在 bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244] 中貢獻。）

刪除編譯器和使用 struct _mod 的剖析器函式，因為公開 AST C API 已被刪除：

PyAST_Compile()

PyAST_CompileEx()

PyAST_CompileObject()

PyFuture_FromAST()

PyFuture_FromASTObject()

PyParser_ASTFromFile()

PyParser_ASTFromFileObject()

PyParser_ASTFromFilename()

PyParser_ASTFromString()

PyParser_ASTFromStringObject()

這些函式沒有文件記錄，並且被排除在受限 C API 之外。（由 Victor Stinner 在 bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244] 中貢獻。）

刪除包含以下函式的 pyarena.h 標頭檔：

PyArena_New()

PyArena_Free()

PyArena_Malloc()

PyArena_AddPyObject()

這些函式沒有文件記錄、被排除在受限 C API 之外，並僅被編譯器於內部使用。（由 Victor Stinner 在 bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244] 中貢獻。）

為了 Python 最佳化，已刪除 PyThreadState.use_tracing 成員。（由 Mark Shannon 在 bpo-43760 [https://bugs.python.org/issue?@action=redirect&bpo=43760] 中貢獻。）

Python 3.10.7 中顯著的安全性功能

Converting between int and str in bases other than 2 (binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity. This is a mitigation for CVE 2020-10735 [https://www.cve.org/CVERecord?id=CVE-2020-10735]. This limit can be configured or disabled by environment variable, command line flag, or sys APIs. See the integer string conversion length limitation documentation. The default limit is 4300 digits in string form.

Python 3.10.8 中顯著的安全性功能

The deprecated mailcap module now refuses to inject unsafe text (filenames, MIME types, parameters) into shell commands. Instead of using such text, it will warn and act as if a match was not found (or for test commands, as if the test failed). (Contributed by Petr Viktorin in gh-98966 [https://github.com/python/cpython/issues/98966].)

Python 3.10.12 中顯著的變更

tarfile

The extraction methods in tarfile, and shutil.unpack_archive(), have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See 解壓縮篩選器 for details. In Python 3.12, use without the filter argument will show a DeprecationWarning. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in PEP 706 [https://peps.python.org/pep-0706/].)

Python 3.9 有什麼新功能

編輯者:

Łukasz Langa

本文介紹了 Python 3.9 與 3.8 相比多了哪些新功能。Python 3.9 已於 2020 年 10 月 5 日發布。有關完整詳細資訊，請參閱 changelog。

也參考

PEP 596 [https://peps.python.org/pep-0596/] - Python 3.9 發佈時程

發布重點摘要

新增語法特性：

PEP 584 [https://peps.python.org/pep-0584/], union operators added to dict;

PEP 585 [https://peps.python.org/pep-0585/], type hinting generics in standard collections;

PEP 614 [https://peps.python.org/pep-0614/], relaxed grammar restrictions on decorators.

新的內建功能：

PEP 616 [https://peps.python.org/pep-0616/], string methods to remove prefixes and suffixes.

New features in the standard library:

PEP 593 [https://peps.python.org/pep-0593/], flexible function and variable annotations;

os.pidfd_open() added that allows process management without races and signals.

直譯器的改進：

PEP 573 [https://peps.python.org/pep-0573/], fast access to module state from methods of C extension types;

PEP 617 [https://peps.python.org/pep-0617/], CPython now uses a new parser based on PEG;

a number of Python builtins (range, tuple, set, frozenset, list, dict) are now sped up using PEP 590 [https://peps.python.org/pep-0590/] vectorcall;

garbage collection does not block on resurrected objects;

a number of Python modules (_abc, audioop, _bz2, _codecs, _contextvars, _crypt, _functools, _json, _locale, math, operator, resource, time, _weakref) now use multiphase initialization as defined by PEP 489;

a number of standard library modules (audioop, ast, grp, _hashlib, pwd, _posixsubprocess, random, select, struct, termios, zlib) are now using the stable ABI defined by PEP 384.

新的函式庫模組：

PEP 615 [https://peps.python.org/pep-0615/], the IANA Time Zone Database is now present in the standard library in the zoneinfo module;

an implementation of a topological sort of a graph is now provided in the new graphlib module.

Release process changes:

PEP 602 [https://peps.python.org/pep-0602/], CPython adopts an annual release cycle.

You should check for DeprecationWarning in your code

When Python 2.7 was still supported, a lot of functionality in Python 3 was kept for backward compatibility with Python 2.7. With the end of Python 2 support, these backward compatibility layers have been removed, or will be removed soon. Most of them emitted a DeprecationWarning warning for several years. For example, using collections.Mapping instead of collections.abc.Mapping emits a DeprecationWarning since Python 3.3, released in 2012.

Test your application with the -W default command-line option to see DeprecationWarning and PendingDeprecationWarning, or even with -W error to treat them as errors. Warnings Filter can be used to ignore warnings from third-party code.

Python 3.9 is the last version providing those Python 2 backward compatibility layers, to give more time to Python projects maintainers to organize the removal of the Python 2 support and add support for Python 3.9.

Aliases to Abstract Base Classes in the collections module, like collections.Mapping alias to collections.abc.Mapping, are kept for one last release for backward compatibility. They will be removed from Python 3.10.

More generally, try to run your tests in the Python Development Mode which helps to prepare your code to make it compatible with the next Python version.

Note: a number of pre-existing deprecations were removed in this version of Python as well. Consult the 已移除 section.

新增功能

Dictionary Merge & Update Operators

Merge (|) and update (|=) operators have been added to the built-in dict class. Those complement the existing dict.update and {**d1, **d2} methods of merging dictionaries.

範例：

>>> x = {"key1": "value1 from x", "key2": "value2 from x"}
>>> y = {"key2": "value2 from y", "key3": "value3 from y"}
>>> x | y
{'key1': 'value1 from x', 'key2': 'value2 from y', 'key3': 'value3 from y'}
>>> y | x
{'key2': 'value2 from x', 'key3': 'value3 from y', 'key1': 'value1 from x'}

See PEP 584 [https://peps.python.org/pep-0584/] for a full description. (Contributed by Brandt Bucher in bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144].)

New String Methods to Remove Prefixes and Suffixes

str.removeprefix(prefix) and str.removesuffix(suffix) have been added to easily remove an unneeded prefix or a suffix from a string. Corresponding bytes, bytearray, and collections.UserString methods have also been added. See PEP 616 [https://peps.python.org/pep-0616/] for a full description. (Contributed by Dennis Sweeney in bpo-39939 [https://bugs.python.org/issue?@action=redirect&bpo=39939].)

Type Hinting Generics in Standard Collections

In type annotations you can now use built-in collection types such as list and dict as generic types instead of importing the corresponding capitalized types (e.g. List or Dict) from typing. Some other types in the standard library are also now generic, for example queue.Queue.

範例：

def greet_all(names: list[str]) -> None:
    for name in names:
        print("Hello", name)

See PEP 585 [https://peps.python.org/pep-0585/] for more details. (Contributed by Guido van Rossum, Ethan Smith, and Batuhan Taşkaya in bpo-39481 [https://bugs.python.org/issue?@action=redirect&bpo=39481].)

新型剖析器

Python 3.9 uses a new parser, based on PEG [https://en.wikipedia.org/wiki/Parsing_expression_grammar] instead of LL(1) [https://en.wikipedia.org/wiki/LL_parser]. The new parser's performance is roughly comparable to that of the old parser, but the PEG formalism is more flexible than LL(1) when it comes to designing new language features. We'll start using this flexibility in Python 3.10 and later.

The ast module uses the new parser and produces the same AST as the old parser.

In Python 3.10, the old parser will be deleted and so will all functionality that depends on it (primarily the parser module, which has long been deprecated). In Python 3.9 only, you can switch back to the LL(1) parser using a command line switch (-X oldparser) or an environment variable (PYTHONOLDPARSER=1).

See PEP 617 [https://peps.python.org/pep-0617/] for more details. (Contributed by Guido van Rossum, Pablo Galindo and Lysandros Nikolaou in bpo-40334 [https://bugs.python.org/issue?@action=redirect&bpo=40334].)

其他語言更動

__import__() now raises ImportError instead of ValueError, which used to occur when a relative import went past its top-level package. (Contributed by Ngalim Siregar in bpo-37444 [https://bugs.python.org/issue?@action=redirect&bpo=37444].)

Python now gets the absolute path of the script filename specified on the command line (ex: python3 script.py): the __file__ attribute of the __main__ module became an absolute path, rather than a relative path. These paths now remain valid after the current directory is changed by os.chdir(). As a side effect, the traceback also displays the absolute path for __main__ module frames in this case. (Contributed by Victor Stinner in bpo-20443 [https://bugs.python.org/issue?@action=redirect&bpo=20443].)

In the Python Development Mode and in debug build, the encoding and errors arguments are now checked for string encoding and decoding operations. Examples: open(), str.encode() and bytes.decode().

By default, for best performance, the errors argument is only checked at the first encoding/decoding error and the encoding argument is sometimes ignored for empty strings. (Contributed by Victor Stinner in bpo-37388 [https://bugs.python.org/issue?@action=redirect&bpo=37388].)

"".replace("", s, n) now returns s instead of an empty string for all non-zero n. It is now consistent with "".replace("", s). There are similar changes for bytes and bytearray objects. (Contributed by Serhiy Storchaka in bpo-28029 [https://bugs.python.org/issue?@action=redirect&bpo=28029].)

Any valid expression can now be used as a decorator. Previously, the grammar was much more restrictive. See PEP 614 [https://peps.python.org/pep-0614/] for details. (Contributed by Brandt Bucher in bpo-39702 [https://bugs.python.org/issue?@action=redirect&bpo=39702].)

Improved help for the typing module. Docstrings are now shown for all special forms and special generic aliases (like Union and List). Using help() with generic alias like List[int] will show the help for the correspondent concrete type (list in this case). (Contributed by Serhiy Storchaka in bpo-40257 [https://bugs.python.org/issue?@action=redirect&bpo=40257].)

Parallel running of aclose() / asend() / athrow() is now prohibited, and ag_running now reflects the actual running status of the async generator. (Contributed by Yury Selivanov in bpo-30773 [https://bugs.python.org/issue?@action=redirect&bpo=30773].)

Unexpected errors in calling the __iter__ method are no longer masked by TypeError in the in operator and functions contains(), indexOf() and countOf() of the operator module. (Contributed by Serhiy Storchaka in bpo-40824 [https://bugs.python.org/issue?@action=redirect&bpo=40824].)

Unparenthesized lambda expressions can no longer be the expression part in an if clause in comprehensions and generator expressions. See bpo-41848 [https://bugs.python.org/issue?@action=redirect&bpo=41848] and bpo-43755 [https://bugs.python.org/issue?@action=redirect&bpo=43755] for details.

新模組

zoneinfo

The zoneinfo module brings support for the IANA time zone database to the standard library. It adds zoneinfo.ZoneInfo, a concrete datetime.tzinfo implementation backed by the system's time zone data.

範例：

>>> from zoneinfo import ZoneInfo
>>> from datetime import datetime, timedelta

>>> # 日光節約時間
>>> dt = datetime(2020, 10, 31, 12, tzinfo=ZoneInfo("America/Los_Angeles"))
>>> print(dt)
2020-10-31 12:00:00-07:00
>>> dt.tzname()
'PDT'

>>> # 標準時間
>>> dt += timedelta(days=7)
>>> print(dt)
2020-11-07 12:00:00-08:00
>>> print(dt.tzname())
PST

As a fall-back source of data for platforms that don't ship the IANA database, the tzdata [https://pypi.org/project/tzdata/] module was released as a first-party package -- distributed via PyPI and maintained by the CPython core team.

也參考

PEP 615 [https://peps.python.org/pep-0615/] -- Support for the IANA Time Zone Database in the Standard Library

由 Paul Ganssle 撰寫 PEP 與實作

graphlib

A new module, graphlib, was added that contains the graphlib.TopologicalSorter class to offer functionality to perform topological sorting of graphs. (Contributed by Pablo Galindo, Tim Peters and Larry Hastings in bpo-17005 [https://bugs.python.org/issue?@action=redirect&bpo=17005].)

改進的模組

ast

Added the indent option to dump() which allows it to produce a multiline indented output. (Contributed by Serhiy Storchaka in bpo-37995 [https://bugs.python.org/issue?@action=redirect&bpo=37995].)

Added ast.unparse() as a function in the ast module that can be used to unparse an ast.AST object and produce a string with code that would produce an equivalent ast.AST object when parsed. (Contributed by Pablo Galindo and Batuhan Taskaya in bpo-38870 [https://bugs.python.org/issue?@action=redirect&bpo=38870].)

Added docstrings to AST nodes that contains the ASDL signature used to construct that node. (Contributed by Batuhan Taskaya in bpo-39638 [https://bugs.python.org/issue?@action=redirect&bpo=39638].)

asyncio

Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint() is no longer supported. This is because of the behavior of the socket option SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228 [https://bugs.python.org/issue?@action=redirect&bpo=37228].)

Added a new coroutine shutdown_default_executor() that schedules a shutdown for the default executor that waits on the ThreadPoolExecutor to finish closing. Also, asyncio.run() has been updated to use the new coroutine. (Contributed by Kyle Stanley in bpo-34037 [https://bugs.python.org/issue?@action=redirect&bpo=34037].)

Added asyncio.PidfdChildWatcher, a Linux-specific child watcher implementation that polls process file descriptors. (bpo-38692 [https://bugs.python.org/issue?@action=redirect&bpo=38692])

Added a new coroutine asyncio.to_thread(). It is mainly used for running IO-bound functions in a separate thread to avoid blocking the event loop, and essentially works as a high-level version of run_in_executor() that can directly take keyword arguments. (Contributed by Kyle Stanley and Yury Selivanov in bpo-32309 [https://bugs.python.org/issue?@action=redirect&bpo=32309].)

When cancelling the task due to a timeout, asyncio.wait_for() will now wait until the cancellation is complete also in the case when timeout is <= 0, like it does with positive timeouts. (Contributed by Elvis Pranskevichus in bpo-32751 [https://bugs.python.org/issue?@action=redirect&bpo=32751].)

asyncio now raises TypeError when calling incompatible methods with an ssl.SSLSocket socket. (Contributed by Ido Michael in bpo-37404 [https://bugs.python.org/issue?@action=redirect&bpo=37404].)

compileall

Added new possibility to use hardlinks for duplicated .pyc files: hardlink_dupes parameter and --hardlink-dupes command line option. (Contributed by Lumír 'Frenzy' Balhar in bpo-40495 [https://bugs.python.org/issue?@action=redirect&bpo=40495].)

Added new options for path manipulation in resulting .pyc files: stripdir, prependdir, limit_sl_dest parameters and -s, -p, -e command line options. Added the possibility to specify the option for an optimization level multiple times. (Contributed by Lumír 'Frenzy' Balhar in bpo-38112 [https://bugs.python.org/issue?@action=redirect&bpo=38112].)

concurrent.futures

Added a new cancel_futures parameter to concurrent.futures.Executor.shutdown() that cancels all pending futures which have not started running, instead of waiting for them to complete before shutting down the executor. (Contributed by Kyle Stanley in bpo-39349 [https://bugs.python.org/issue?@action=redirect&bpo=39349].)

Removed daemon threads from ThreadPoolExecutor and ProcessPoolExecutor. This improves compatibility with subinterpreters and predictability in their shutdown processes. (Contributed by Kyle Stanley in bpo-39812 [https://bugs.python.org/issue?@action=redirect&bpo=39812].)

Workers in ProcessPoolExecutor are now spawned on demand, only when there are no available idle workers to reuse. This optimizes startup overhead and reduces the amount of lost CPU time to idle workers. (Contributed by Kyle Stanley in bpo-39207 [https://bugs.python.org/issue?@action=redirect&bpo=39207].)

curses

Added curses.get_escdelay(), curses.set_escdelay(), curses.get_tabsize(), and curses.set_tabsize() functions. (Contributed by Anthony Sottile in bpo-38312 [https://bugs.python.org/issue?@action=redirect&bpo=38312].)

datetime

The isocalendar() of datetime.date and isocalendar() of datetime.datetime methods now returns a namedtuple() instead of a tuple. (Contributed by Donghee Na in bpo-24416 [https://bugs.python.org/issue?@action=redirect&bpo=24416].)

distutils

The upload command now creates SHA2-256 and Blake2b-256 hash digests. It skips MD5 on platforms that block MD5 digest. (Contributed by Christian Heimes in bpo-40698 [https://bugs.python.org/issue?@action=redirect&bpo=40698].)

fcntl

Added constants fcntl.F_OFD_GETLK, fcntl.F_OFD_SETLK and fcntl.F_OFD_SETLKW. (Contributed by Donghee Na in bpo-38602 [https://bugs.python.org/issue?@action=redirect&bpo=38602].)

ftplib

FTP and FTP_TLS now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. (Contributed by Donghee Na in bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259].)

gc

When the garbage collector makes a collection in which some objects resurrect (they are reachable from outside the isolated cycles after the finalizers have been executed), do not block the collection of all objects that are still unreachable. (Contributed by Pablo Galindo and Tim Peters in bpo-38379 [https://bugs.python.org/issue?@action=redirect&bpo=38379].)

Added a new function gc.is_finalized() to check if an object has been finalized by the garbage collector. (Contributed by Pablo Galindo in bpo-39322 [https://bugs.python.org/issue?@action=redirect&bpo=39322].)

hashlib

The hashlib module can now use SHA3 hashes and SHAKE XOF from OpenSSL when available. (Contributed by Christian Heimes in bpo-37630 [https://bugs.python.org/issue?@action=redirect&bpo=37630].)

Builtin hash modules can now be disabled with ./configure --without-builtin-hashlib-hashes or selectively enabled with e.g. ./configure --with-builtin-hashlib-hashes=sha3,blake2 to force use of OpenSSL based implementation. (Contributed by Christian Heimes in bpo-40479 [https://bugs.python.org/issue?@action=redirect&bpo=40479])

http

HTTP status codes 103 EARLY_HINTS, 418 IM_A_TEAPOT and 425 TOO_EARLY are added to http.HTTPStatus. (Contributed by Donghee Na in bpo-39509 [https://bugs.python.org/issue?@action=redirect&bpo=39509] and Ross Rhodes in bpo-39507 [https://bugs.python.org/issue?@action=redirect&bpo=39507].)

IDLE 和 idlelib

Added option to toggle cursor blink off. (Contributed by Zackery Spytz in bpo-4603 [https://bugs.python.org/issue?@action=redirect&bpo=4603].)

Escape key now closes IDLE completion windows. (Contributed by Johnny Najera in bpo-38944 [https://bugs.python.org/issue?@action=redirect&bpo=38944].)

Added keywords to module name completion list. (Contributed by Terry J. Reedy in bpo-37765 [https://bugs.python.org/issue?@action=redirect&bpo=37765].)

New in 3.9 maintenance releases

Make IDLE invoke sys.excepthook() (when started without '-n'). User hooks were previously ignored. (Contributed by Ken Hilton in bpo-43008 [https://bugs.python.org/issue?@action=redirect&bpo=43008].)

The changes above have been backported to 3.8 maintenance releases.

Rearrange the settings dialog. Split the General tab into Windows and Shell/Ed tabs. Move help sources, which extend the Help menu, to the Extensions tab. Make space for new options and shorten the dialog. The latter makes the dialog better fit small screens. (Contributed by Terry Jan Reedy in bpo-40468 [https://bugs.python.org/issue?@action=redirect&bpo=40468].) Move the indent space setting from the Font tab to the new Windows tab. (Contributed by Mark Roseman and Terry Jan Reedy in bpo-33962 [https://bugs.python.org/issue?@action=redirect&bpo=33962].)

Apply syntax highlighting to .pyi files. (Contributed by Alex Waygood and Terry Jan Reedy in bpo-45447 [https://bugs.python.org/issue?@action=redirect&bpo=45447].)

imaplib

IMAP4 and IMAP4_SSL now have an optional timeout parameter for their constructors. Also, the open() method now has an optional timeout parameter with this change. The overridden methods of IMAP4_SSL and IMAP4_stream were applied to this change. (Contributed by Donghee Na in bpo-38615 [https://bugs.python.org/issue?@action=redirect&bpo=38615].)

imaplib.IMAP4.unselect() is added. imaplib.IMAP4.unselect() frees server's resources associated with the selected mailbox and returns the server to the authenticated state. This command performs the same actions as imaplib.IMAP4.close(), except that no messages are permanently removed from the currently selected mailbox. (Contributed by Donghee Na in bpo-40375 [https://bugs.python.org/issue?@action=redirect&bpo=40375].)

importlib

To improve consistency with import statements, importlib.util.resolve_name() now raises ImportError instead of ValueError for invalid relative import attempts. (Contributed by Ngalim Siregar in bpo-37444 [https://bugs.python.org/issue?@action=redirect&bpo=37444].)

Import loaders which publish immutable module objects can now publish immutable packages in addition to individual modules. (Contributed by Dino Viehland in bpo-39336 [https://bugs.python.org/issue?@action=redirect&bpo=39336].)

Added importlib.resources.files() function with support for subdirectories in package data, matching backport in importlib_resources version 1.5. (Contributed by Jason R. Coombs in bpo-39791 [https://bugs.python.org/issue?@action=redirect&bpo=39791].)

Refreshed importlib.metadata from importlib_metadata version 1.6.1.

inspect

inspect.BoundArguments.arguments is changed from OrderedDict to regular dict. (Contributed by Inada Naoki in bpo-36350 [https://bugs.python.org/issue?@action=redirect&bpo=36350] and bpo-39775 [https://bugs.python.org/issue?@action=redirect&bpo=39775].)

ipaddress

ipaddress now supports IPv6 Scoped Addresses (IPv6 address with suffix %<scope_id>).

Scoped IPv6 addresses can be parsed using ipaddress.IPv6Address. If present, scope zone ID is available through the scope_id attribute. (Contributed by Oleksandr Pavliuk in bpo-34788 [https://bugs.python.org/issue?@action=redirect&bpo=34788].)

Starting with Python 3.9.5 the ipaddress module no longer accepts any leading zeros in IPv4 address strings. (Contributed by Christian Heimes in bpo-36384 [https://bugs.python.org/issue?@action=redirect&bpo=36384]).

math

Expanded the math.gcd() function to handle multiple arguments. Formerly, it only supported two arguments. (Contributed by Serhiy Storchaka in bpo-39648 [https://bugs.python.org/issue?@action=redirect&bpo=39648].)

Added math.lcm(): return the least common multiple of specified arguments. (Contributed by Mark Dickinson, Ananthakrishnan and Serhiy Storchaka in bpo-39479 [https://bugs.python.org/issue?@action=redirect&bpo=39479] and bpo-39648 [https://bugs.python.org/issue?@action=redirect&bpo=39648].)

Added math.nextafter(): return the next floating-point value after x towards y. (Contributed by Victor Stinner in bpo-39288 [https://bugs.python.org/issue?@action=redirect&bpo=39288].)

Added math.ulp(): return the value of the least significant bit of a float. (Contributed by Victor Stinner in bpo-39310 [https://bugs.python.org/issue?@action=redirect&bpo=39310].)

multiprocessing

The multiprocessing.SimpleQueue class has a new close() method to explicitly close the queue. (Contributed by Victor Stinner in bpo-30966 [https://bugs.python.org/issue?@action=redirect&bpo=30966].)

nntplib

NNTP and NNTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. (Contributed by Donghee Na in bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259].)

os

Added CLD_KILLED and CLD_STOPPED for si_code. (Contributed by Donghee Na in bpo-38493 [https://bugs.python.org/issue?@action=redirect&bpo=38493].)

Exposed the Linux-specific os.pidfd_open() (bpo-38692 [https://bugs.python.org/issue?@action=redirect&bpo=38692]) and os.P_PIDFD (bpo-38713 [https://bugs.python.org/issue?@action=redirect&bpo=38713]) for process management with file descriptors.

The os.unsetenv() function is now also available on Windows. (Contributed by Victor Stinner in bpo-39413 [https://bugs.python.org/issue?@action=redirect&bpo=39413].)

The os.putenv() and os.unsetenv() functions are now always available. (Contributed by Victor Stinner in bpo-39395 [https://bugs.python.org/issue?@action=redirect&bpo=39395].)

Added os.waitstatus_to_exitcode() function: convert a wait status to an exit code. (Contributed by Victor Stinner in bpo-40094 [https://bugs.python.org/issue?@action=redirect&bpo=40094].)

pathlib

Added pathlib.Path.readlink() which acts similarly to os.readlink(). (Contributed by Girts Folkmanis in bpo-30618 [https://bugs.python.org/issue?@action=redirect&bpo=30618])

pdb

On Windows now Pdb supports ~/.pdbrc. (Contributed by Tim Hopper and Dan Lidral-Porter in bpo-20523 [https://bugs.python.org/issue?@action=redirect&bpo=20523].)

poplib

POP3 and POP3_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. (Contributed by Donghee Na in bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259].)

pprint

pprint can now pretty-print types.SimpleNamespace. (Contributed by Carl Bordum Hansen in bpo-37376 [https://bugs.python.org/issue?@action=redirect&bpo=37376].)

pydoc

The documentation string is now shown not only for class, function, method etc, but for any object that has its own __doc__ attribute. (Contributed by Serhiy Storchaka in bpo-40257 [https://bugs.python.org/issue?@action=redirect&bpo=40257].)

random

Added a new random.Random.randbytes() method: generate random bytes. (Contributed by Victor Stinner in bpo-40286 [https://bugs.python.org/issue?@action=redirect&bpo=40286].)

signal

Exposed the Linux-specific signal.pidfd_send_signal() for sending to signals to a process using a file descriptor instead of a pid. (bpo-38712 [https://bugs.python.org/issue?@action=redirect&bpo=38712])

smtplib

SMTP and SMTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. (Contributed by Donghee Na in bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259].)

LMTP constructor now has an optional timeout parameter. (Contributed by Donghee Na in bpo-39329 [https://bugs.python.org/issue?@action=redirect&bpo=39329].)

socket

The socket module now exports the CAN_RAW_JOIN_FILTERS constant on Linux 4.1 and greater. (Contributed by Stefan Tatschner and Zackery Spytz in bpo-25780 [https://bugs.python.org/issue?@action=redirect&bpo=25780].)

The socket module now supports the CAN_J1939 protocol on platforms that support it. (Contributed by Karl Ding in bpo-40291 [https://bugs.python.org/issue?@action=redirect&bpo=40291].)

The socket module now has the socket.send_fds() and socket.recv_fds() functions. (Contributed by Joannah Nanjekye, Shinya Okano and Victor Stinner in bpo-28724 [https://bugs.python.org/issue?@action=redirect&bpo=28724].)

time

On AIX, thread_time() is now implemented with thread_cputime() which has nanosecond resolution, rather than clock_gettime(CLOCK_THREAD_CPUTIME_ID) which has a resolution of 10 milliseconds. (Contributed by Batuhan Taskaya in bpo-40192 [https://bugs.python.org/issue?@action=redirect&bpo=40192])

sys

Added a new sys.platlibdir attribute: name of the platform-specific library directory. It is used to build the path of standard library and the paths of installed extension modules. It is equal to "lib" on most platforms. On Fedora and SuSE, it is equal to "lib64" on 64-bit platforms. (Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner in bpo-1294959 [https://bugs.python.org/issue?@action=redirect&bpo=1294959].)

Previously, sys.stderr was block-buffered when non-interactive. Now stderr defaults to always being line-buffered. (Contributed by Jendrik Seipp in bpo-13601 [https://bugs.python.org/issue?@action=redirect&bpo=13601].)

tracemalloc

Added tracemalloc.reset_peak() to set the peak size of traced memory blocks to the current size, to measure the peak of specific pieces of code. (Contributed by Huon Wilson in bpo-40630 [https://bugs.python.org/issue?@action=redirect&bpo=40630].)

typing

PEP 593 [https://peps.python.org/pep-0593/] introduced an typing.Annotated type to decorate existing types with context-specific metadata and new include_extras parameter to typing.get_type_hints() to access the metadata at runtime. (Contributed by Till Varoquaux and Konstantin Kashin.)

unicodedata

The Unicode database has been updated to version 13.0.0. (bpo-39926 [https://bugs.python.org/issue?@action=redirect&bpo=39926]).

venv

The activation scripts provided by venv now all specify their prompt customization consistently by always using the value specified by __VENV_PROMPT__. Previously some scripts unconditionally used __VENV_PROMPT__, others only if it happened to be set (which was the default case), and one used __VENV_NAME__ instead. (Contributed by Brett Cannon in bpo-37663 [https://bugs.python.org/issue?@action=redirect&bpo=37663].)

xml

White space characters within attributes are now preserved when serializing xml.etree.ElementTree to XML file. EOLNs are no longer normalized to "n". This is the result of discussion about how to interpret section 2.11 of XML spec. (Contributed by Mefistotelis in bpo-39011 [https://bugs.python.org/issue?@action=redirect&bpo=39011].)

最佳化

Optimized the idiom for assignment a temporary variable in comprehensions. Now for y in [expr] in comprehensions is as fast as a simple assignment y = expr. For example:

sums = [s for s in [0] for x in data for s in [s + x]]

Unlike the := operator this idiom does not leak a variable to the outer scope.

（由 Serhiy Storchaka 在 bpo-32856 [https://bugs.python.org/issue?@action=redirect&bpo=32856] 中貢獻。）

Optimized signal handling in multithreaded applications. If a thread different than the main thread gets a signal, the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending signals which cannot be handled. Only the main thread of the main interpreter can handle signals.

Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread handles signals. (Contributed by Victor Stinner in bpo-40010 [https://bugs.python.org/issue?@action=redirect&bpo=40010].)

Optimized the subprocess module on FreeBSD using closefrom(). (Contributed by Ed Maste, Conrad Meyer, Kyle Evans, Kubilay Kocak and Victor Stinner in bpo-38061 [https://bugs.python.org/issue?@action=redirect&bpo=38061].)

PyLong_FromDouble() is now up to 1.87x faster for values that fit into long. (Contributed by Sergey Fedoseev in bpo-37986 [https://bugs.python.org/issue?@action=redirect&bpo=37986].)

A number of Python builtins (range, tuple, set, frozenset, list, dict) are now sped up by using PEP 590 [https://peps.python.org/pep-0590/] vectorcall protocol. (Contributed by Donghee Na, Mark Shannon, Jeroen Demeyer and Petr Viktorin in bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207].)

Optimized set.difference_update() for the case when the other set is much larger than the base set. (Suggested by Evgeny Kapun with code contributed by Michele Orrù in bpo-8425 [https://bugs.python.org/issue?@action=redirect&bpo=8425].)

Python's small object allocator (obmalloc.c) now allows (no more than) one empty arena to remain available for immediate reuse, without returning it to the OS. This prevents thrashing in simple loops where an arena could be created and destroyed anew on each iteration. (Contributed by Tim Peters in bpo-37257 [https://bugs.python.org/issue?@action=redirect&bpo=37257].)

floor division of float operation now has a better performance. Also the message of ZeroDivisionError for this operation is updated. (Contributed by Donghee Na in bpo-39434 [https://bugs.python.org/issue?@action=redirect&bpo=39434].)

Decoding short ASCII strings with UTF-8 and ascii codecs is now about 15% faster. (Contributed by Inada Naoki in bpo-37348 [https://bugs.python.org/issue?@action=redirect&bpo=37348].)

Here's a summary of performance improvements from Python 3.4 through Python 3.9:

Python version                       3.4     3.5     3.6     3.7     3.8    3.9
--------------                       ---     ---     ---     ---     ---    ---

Variable and attribute read access:
    read_local                       7.1     7.1     5.4     5.1     3.9    3.9
    read_nonlocal                    7.1     8.1     5.8     5.4     4.4    4.5
    read_global                     15.5    19.0    14.3    13.6     7.6    7.8
    read_builtin                    21.1    21.6    18.5    19.0     7.5    7.8
    read_classvar_from_class        25.6    26.5    20.7    19.5    18.4   17.9
    read_classvar_from_instance     22.8    23.5    18.8    17.1    16.4   16.9
    read_instancevar                32.4    33.1    28.0    26.3    25.4   25.3
    read_instancevar_slots          27.8    31.3    20.8    20.8    20.2   20.5
    read_namedtuple                 73.8    57.5    45.0    46.8    18.4   18.7
    read_boundmethod                37.6    37.9    29.6    26.9    27.7   41.1

Variable and attribute write access:
    write_local                      8.7     9.3     5.5     5.3     4.3    4.3
    write_nonlocal                  10.5    11.1     5.6     5.5     4.7    4.8
    write_global                    19.7    21.2    18.0    18.0    15.8   16.7
    write_classvar                  92.9    96.0   104.6   102.1    39.2   39.8
    write_instancevar               44.6    45.8    40.0    38.9    35.5   37.4
    write_instancevar_slots         35.6    36.1    27.3    26.6    25.7   25.8

Data structure read access:
    read_list                       24.2    24.5    20.8    20.8    19.0   19.5
    read_deque                      24.7    25.5    20.2    20.6    19.8   20.2
    read_dict                       24.3    25.7    22.3    23.0    21.0   22.4
    read_strdict                    22.6    24.3    19.5    21.2    18.9   21.5

Data structure write access:
    write_list                      27.1    28.5    22.5    21.6    20.0   20.0
    write_deque                     28.7    30.1    22.7    21.8    23.5   21.7
    write_dict                      31.4    33.3    29.3    29.2    24.7   25.4
    write_strdict                   28.4    29.9    27.5    25.2    23.1   24.5

Stack (or queue) operations:
    list_append_pop                 93.4   112.7    75.4    74.2    50.8   50.6
    deque_append_pop                43.5    57.0    49.4    49.2    42.5   44.2
    deque_append_popleft            43.7    57.3    49.7    49.7    42.8   46.4

Timing loop:
    loop_overhead                    0.5     0.6     0.4     0.3     0.3    0.3

These results were generated from the variable access benchmark script at: Tools/scripts/var_access_benchmark.py. The benchmark script displays timings in nanoseconds. The benchmarks were measured on an Intel® Core™ i7-4960HQ processor [https://ark.intel.com/content/www/us/en/ark/products/76088/intel-core-i7-4960hq-processor-6m-cache-up-to-3-80-ghz.html] running the macOS 64-bit builds found at python.org [https://www.python.org/downloads/macos/].

已棄用

The distutils bdist_msi command is now deprecated, use bdist_wheel (wheel packages) instead. (Contributed by Hugo van Kemenade in bpo-39586 [https://bugs.python.org/issue?@action=redirect&bpo=39586].)

Currently math.factorial() accepts float instances with non-negative integer values (like 5.0). It raises a ValueError for non-integral and negative floats. It is now deprecated. In future Python versions it will raise a TypeError for all floats. (Contributed by Serhiy Storchaka in bpo-37315 [https://bugs.python.org/issue?@action=redirect&bpo=37315].)

The parser and symbol modules are deprecated and will be removed in future versions of Python. For the majority of use cases, users can leverage the Abstract Syntax Tree (AST) generation and compilation stage, using the ast module.

The Public C API functions PyParser_SimpleParseStringFlags(), PyParser_SimpleParseStringFlagsFilename(), PyParser_SimpleParseFileFlags() and PyNode_Compile() are deprecated and will be removed in Python 3.10 together with the old parser.

Using NotImplemented in a boolean context has been deprecated, as it is almost exclusively the result of incorrect rich comparator implementations. It will be made a TypeError in a future version of Python. (Contributed by Josh Rosenberg in bpo-35712 [https://bugs.python.org/issue?@action=redirect&bpo=35712].)

The random module currently accepts any hashable type as a possible seed value. Unfortunately, some of those types are not guaranteed to have a deterministic hash value. After Python 3.9, the module will restrict its seeds to None, int, float, str, bytes, and bytearray.

Opening the GzipFile file for writing without specifying the mode argument is deprecated. In future Python versions it will always be opened for reading by default. Specify the mode argument for opening it for writing and silencing a warning. (Contributed by Serhiy Storchaka in bpo-28286 [https://bugs.python.org/issue?@action=redirect&bpo=28286].)

Deprecated the split() method of _tkinter.TkappType in favour of the splitlist() method which has more consistent and predictable behavior. (Contributed by Serhiy Storchaka in bpo-38371 [https://bugs.python.org/issue?@action=redirect&bpo=38371].)

The explicit passing of coroutine objects to asyncio.wait() has been deprecated and will be removed in version 3.11. (Contributed by Yury Selivanov and Kyle Stanley in bpo-34790 [https://bugs.python.org/issue?@action=redirect&bpo=34790].)

binhex4 and hexbin4 standards are now deprecated. The binhex module and the following binascii functions are now deprecated:

b2a_hqx()、a2b_hqx()

rlecode_hqx()、rledecode_hqx()

（由 Victor Stinner 在 bpo-39353 [https://bugs.python.org/issue?@action=redirect&bpo=39353] 中貢獻。）

ast classes slice, Index and ExtSlice are considered deprecated and will be removed in future Python versions. value itself should be used instead of Index(value). Tuple(slices, Load()) should be used instead of ExtSlice(slices). (Contributed by Serhiy Storchaka in bpo-34822 [https://bugs.python.org/issue?@action=redirect&bpo=34822].)

ast classes Suite, Param, AugLoad and AugStore are considered deprecated and will be removed in future Python versions. They were not generated by the parser and not accepted by the code generator in Python 3. (Contributed by Batuhan Taskaya in bpo-39639 [https://bugs.python.org/issue?@action=redirect&bpo=39639] and bpo-39969 [https://bugs.python.org/issue?@action=redirect&bpo=39969] and Serhiy Storchaka in bpo-39988 [https://bugs.python.org/issue?@action=redirect&bpo=39988].)

The PyEval_InitThreads() and PyEval_ThreadsInitialized() functions are now deprecated and will be removed in Python 3.11. Calling PyEval_InitThreads() now does nothing. The GIL is initialized by Py_Initialize() since Python 3.7. (Contributed by Victor Stinner in bpo-39877 [https://bugs.python.org/issue?@action=redirect&bpo=39877].)

Passing None as the first argument to the shlex.split() function has been deprecated. (Contributed by Zackery Spytz in bpo-33262 [https://bugs.python.org/issue?@action=redirect&bpo=33262].)

smtpd.MailmanProxy() is now deprecated as it is unusable without an external module, mailman. (Contributed by Samuel Colvin in bpo-35800 [https://bugs.python.org/issue?@action=redirect&bpo=35800].)

The lib2to3 module now emits a PendingDeprecationWarning. Python 3.9 switched to a PEG parser (see PEP 617 [https://peps.python.org/pep-0617/]), and Python 3.10 may include new language syntax that is not parsable by lib2to3's LL(1) parser. The lib2to3 module may be removed from the standard library in a future Python version. Consider third-party alternatives such as LibCST [https://libcst.readthedocs.io/] or parso [https://parso.readthedocs.io/]. (Contributed by Carl Meyer in bpo-40360 [https://bugs.python.org/issue?@action=redirect&bpo=40360].)

The random parameter of random.shuffle() has been deprecated. (Contributed by Raymond Hettinger in bpo-40465 [https://bugs.python.org/issue?@action=redirect&bpo=40465])

已移除

The erroneous version at unittest.mock.__version__ has been removed.

nntplib.NNTP: xpath() and xgtitle() methods have been removed. These methods are deprecated since Python 3.3. Generally, these extensions are not supported or not enabled by NNTP server administrators. For xgtitle(), please use nntplib.NNTP.descriptions() or nntplib.NNTP.description() instead. (Contributed by Donghee Na in bpo-39366 [https://bugs.python.org/issue?@action=redirect&bpo=39366].)

array.array: tostring() and fromstring() methods have been removed. They were aliases to tobytes() and frombytes(), deprecated since Python 3.2. (Contributed by Victor Stinner in bpo-38916 [https://bugs.python.org/issue?@action=redirect&bpo=38916].)

The undocumented sys.callstats() function has been removed. Since Python 3.7, it was deprecated and always returned None. It required a special build option CALL_PROFILE which was already removed in Python 3.7. (Contributed by Victor Stinner in bpo-37414 [https://bugs.python.org/issue?@action=redirect&bpo=37414].)

The sys.getcheckinterval() and sys.setcheckinterval() functions have been removed. They were deprecated since Python 3.2. Use sys.getswitchinterval() and sys.setswitchinterval() instead. (Contributed by Victor Stinner in bpo-37392 [https://bugs.python.org/issue?@action=redirect&bpo=37392].)

The C function PyImport_Cleanup() has been removed. It was documented as: "Empty the module table. For internal use only." (Contributed by Victor Stinner in bpo-36710 [https://bugs.python.org/issue?@action=redirect&bpo=36710].)

_dummy_thread and dummy_threading modules have been removed. These modules were deprecated since Python 3.7 which requires threading support. (Contributed by Victor Stinner in bpo-37312 [https://bugs.python.org/issue?@action=redirect&bpo=37312].)

aifc.openfp() alias to aifc.open(), sunau.openfp() alias to sunau.open(), and wave.openfp() alias to wave.open() have been removed. They were deprecated since Python 3.7. (Contributed by Victor Stinner in bpo-37320 [https://bugs.python.org/issue?@action=redirect&bpo=37320].)

The isAlive() method of threading.Thread has been removed. It was deprecated since Python 3.8. Use is_alive() instead. (Contributed by Donghee Na in bpo-37804 [https://bugs.python.org/issue?@action=redirect&bpo=37804].)

Methods getchildren() and getiterator() of classes ElementTree and Element in the ElementTree module have been removed. They were deprecated in Python 3.2. Use iter(x) or list(x) instead of x.getchildren() and x.iter() or list(x.iter()) instead of x.getiterator(). (Contributed by Serhiy Storchaka in bpo-36543 [https://bugs.python.org/issue?@action=redirect&bpo=36543].)

The old plistlib API has been removed, it was deprecated since Python 3.4. Use the load(), loads(), dump(), and dumps() functions. Additionally, the use_builtin_types parameter was removed, standard bytes objects are always used instead. (Contributed by Jon Janzen in bpo-36409 [https://bugs.python.org/issue?@action=redirect&bpo=36409].)

The C function PyGen_NeedsFinalizing has been removed. It was not documented, tested, or used anywhere within CPython after the implementation of PEP 442 [https://peps.python.org/pep-0442/]. Patch by Joannah Nanjekye. (Contributed by Joannah Nanjekye in bpo-15088 [https://bugs.python.org/issue?@action=redirect&bpo=15088])

base64.encodestring() and base64.decodestring(), aliases deprecated since Python 3.1, have been removed: use base64.encodebytes() and base64.decodebytes() instead. (Contributed by Victor Stinner in bpo-39351 [https://bugs.python.org/issue?@action=redirect&bpo=39351].)

fractions.gcd() function has been removed, it was deprecated since Python 3.5 (bpo-22486 [https://bugs.python.org/issue?@action=redirect&bpo=22486]): use math.gcd() instead. (Contributed by Victor Stinner in bpo-39350 [https://bugs.python.org/issue?@action=redirect&bpo=39350].)

The buffering parameter of bz2.BZ2File has been removed. Since Python 3.0, it was ignored and using it emitted a DeprecationWarning. Pass an open file object to control how the file is opened. (Contributed by Victor Stinner in bpo-39357 [https://bugs.python.org/issue?@action=redirect&bpo=39357].)

The encoding parameter of json.loads() has been removed. As of Python 3.1, it was deprecated and ignored; using it has emitted a DeprecationWarning since Python 3.8. (Contributed by Inada Naoki in bpo-39377 [https://bugs.python.org/issue?@action=redirect&bpo=39377])

with (await asyncio.lock): and with (yield from asyncio.lock): statements are not longer supported, use async with lock instead. The same is correct for asyncio.Condition and asyncio.Semaphore. (Contributed by Andrew Svetlov in bpo-34793 [https://bugs.python.org/issue?@action=redirect&bpo=34793].)

The sys.getcounts() function, the -X showalloccount command line option and the show_alloc_count field of the C structure PyConfig have been removed. They required a special Python build by defining COUNT_ALLOCS macro. (Contributed by Victor Stinner in bpo-39489 [https://bugs.python.org/issue?@action=redirect&bpo=39489].)

The _field_types attribute of the typing.NamedTuple class has been removed. It was deprecated since Python 3.8. Use the __annotations__ attribute instead. (Contributed by Serhiy Storchaka in bpo-40182 [https://bugs.python.org/issue?@action=redirect&bpo=40182].)

The symtable.SymbolTable.has_exec() method has been removed. It was deprecated since 2006, and only returning False when it's called. (Contributed by Batuhan Taskaya in bpo-40208 [https://bugs.python.org/issue?@action=redirect&bpo=40208])

The asyncio.Task.current_task() and asyncio.Task.all_tasks() have been removed. They were deprecated since Python 3.7 and you can use asyncio.current_task() and asyncio.all_tasks() instead. (Contributed by Rémi Lapeyre in bpo-40967 [https://bugs.python.org/issue?@action=redirect&bpo=40967])

The unescape() method in the html.parser.HTMLParser class has been removed (it was deprecated since Python 3.4). html.unescape() should be used for converting character references to the corresponding unicode characters.

移植至 Python 3.9

This section lists previously described changes and other bugfixes that may require changes to your code.

Python API 的變更

__import__() and importlib.util.resolve_name() now raise ImportError where it previously raised ValueError. Callers catching the specific exception type and supporting both Python 3.9 and earlier versions will need to catch both using except (ImportError, ValueError):.

The venv activation scripts no longer special-case when __VENV_PROMPT__ is set to "".

The select.epoll.unregister() method no longer ignores the EBADF error. (Contributed by Victor Stinner in bpo-39239 [https://bugs.python.org/issue?@action=redirect&bpo=39239].)

The compresslevel parameter of bz2.BZ2File became keyword-only, since the buffering parameter has been removed. (Contributed by Victor Stinner in bpo-39357 [https://bugs.python.org/issue?@action=redirect&bpo=39357].)

Simplified AST for subscription. Simple indices will be represented by their value, extended slices will be represented as tuples. Index(value) will return a value itself, ExtSlice(slices) will return Tuple(slices, Load()). (Contributed by Serhiy Storchaka in bpo-34822 [https://bugs.python.org/issue?@action=redirect&bpo=34822].)

The importlib module now ignores the PYTHONCASEOK environment variable when the -E or -I command line options are being used.

The encoding parameter has been added to the classes ftplib.FTP and ftplib.FTP_TLS as a keyword-only parameter, and the default encoding is changed from Latin-1 to UTF-8 to follow RFC 2640 [https://datatracker.ietf.org/doc/html/rfc2640.html].

asyncio.loop.shutdown_default_executor() has been added to AbstractEventLoop, meaning alternative event loops that inherit from it should have this method defined. (Contributed by Kyle Stanley in bpo-34037 [https://bugs.python.org/issue?@action=redirect&bpo=34037].)

The constant values of future flags in the __future__ module is updated in order to prevent collision with compiler flags. Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing with CO_FUTURE_DIVISION. (Contributed by Batuhan Taskaya in bpo-39562 [https://bugs.python.org/issue?@action=redirect&bpo=39562])

array('u') now uses wchar_t as C type instead of Py_UNICODE. This change doesn't affect to its behavior because Py_UNICODE is alias of wchar_t since Python 3.3. (Contributed by Inada Naoki in bpo-34538 [https://bugs.python.org/issue?@action=redirect&bpo=34538].)

The logging.getLogger() API now returns the root logger when passed the name 'root', whereas previously it returned a non-root logger named 'root'. This could affect cases where user code explicitly wants a non-root logger named 'root', or instantiates a logger using logging.getLogger(__name__) in some top-level module called 'root.py'. (Contributed by Vinay Sajip in bpo-37742 [https://bugs.python.org/issue?@action=redirect&bpo=37742].)

Division handling of PurePath now returns NotImplemented instead of raising a TypeError when passed something other than an instance of str or PurePath. This allows creating compatible classes that don't inherit from those mentioned types. (Contributed by Roger Aiudi in bpo-34775 [https://bugs.python.org/issue?@action=redirect&bpo=34775]).

Starting with Python 3.9.5 the ipaddress module no longer accepts any leading zeros in IPv4 address strings. Leading zeros are ambiguous and interpreted as octal notation by some libraries. For example the legacy function socket.inet_aton() treats leading zeros as octal notatation. glibc implementation of modern inet_pton() does not accept any leading zeros. (Contributed by Christian Heimes in bpo-36384 [https://bugs.python.org/issue?@action=redirect&bpo=36384]).

codecs.lookup() now normalizes the encoding name the same way as encodings.normalize_encoding(), except that codecs.lookup() also converts the name to lower case. For example, "latex+latin1" encoding name is now normalized to "latex_latin1". (Contributed by Jordon Xu in bpo-37751 [https://bugs.python.org/issue?@action=redirect&bpo=37751].)

C API 中的改動

Instances of heap-allocated types (such as those created with PyType_FromSpec() and similar APIs) hold a reference to their type object since Python 3.8. As indicated in the "Changes in the C API" of Python 3.8, for the vast majority of cases, there should be no side effect but for types that have a custom tp_traverse function, ensure that all custom tp_traverse functions of heap-allocated types visit the object's type.

範例：

int
foo_traverse(PyObject *self, visitproc visit, void *arg)
{
// Rest of the traverse function
#if PY_VERSION_HEX >= 0x03090000
    // This was not needed before Python 3.9 (Python issue 35810 and 40217)
    Py_VISIT(Py_TYPE(self));
#endif
}

If your traverse function delegates to tp_traverse of its base class (or another type), ensure that Py_TYPE(self) is visited only once. Note that only heap type are expected to visit the type in tp_traverse.

For example, if your tp_traverse function includes:

base->tp_traverse(self, visit, arg)

then add:

#if PY_VERSION_HEX >= 0x03090000
    // This was not needed before Python 3.9 (bpo-35810 and bpo-40217)
    if (base->tp_flags & Py_TPFLAGS_HEAPTYPE) {
        // a heap type's tp_traverse already visited Py_TYPE(self)
    } else {
        Py_VISIT(Py_TYPE(self));
    }
#else

（更多資訊請見 bpo-35810 [https://bugs.python.org/issue?@action=redirect&bpo=35810] 與 bpo-40217 [https://bugs.python.org/issue?@action=redirect&bpo=40217]。）

The functions PyEval_CallObject, PyEval_CallFunction, PyEval_CallMethod and PyEval_CallObjectWithKeywords are deprecated. Use PyObject_Call() and its variants instead. (See more details in bpo-29548 [https://bugs.python.org/issue?@action=redirect&bpo=29548].)

CPython 位元組碼變更

The LOAD_ASSERTION_ERROR opcode was added for handling the assert statement. Previously, the assert statement would not work correctly if the AssertionError exception was being shadowed. (Contributed by Zackery Spytz in bpo-34880 [https://bugs.python.org/issue?@action=redirect&bpo=34880].)

The COMPARE_OP opcode was split into four distinct instructions:

COMPARE_OP for rich comparisons

IS_OP for 'is' and 'is not' tests

CONTAINS_OP for 'in' and 'not in' tests

JUMP_IF_NOT_EXC_MATCH for checking exceptions in 'try-except' statements.

（由 Mark Shannon 在 bpo-39156 [https://bugs.python.org/issue?@action=redirect&bpo=39156] 中貢獻。）

建置變更

Added --with-platlibdir option to the configure script: name of the platform-specific library directory, stored in the new sys.platlibdir attribute. See sys.platlibdir attribute for more information. (Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner in bpo-1294959 [https://bugs.python.org/issue?@action=redirect&bpo=1294959].)

The COUNT_ALLOCS special build macro has been removed. (Contributed by Victor Stinner in bpo-39489 [https://bugs.python.org/issue?@action=redirect&bpo=39489].)

On non-Windows platforms, the setenv() and unsetenv() functions are now required to build Python. (Contributed by Victor Stinner in bpo-39395 [https://bugs.python.org/issue?@action=redirect&bpo=39395].)

On non-Windows platforms, creating bdist_wininst installers is now officially unsupported. (See bpo-10945 [https://bugs.python.org/issue?@action=redirect&bpo=10945] for more details.)

When building Python on macOS from source, _tkinter now links with non-system Tcl and Tk frameworks if they are installed in /Library/Frameworks, as had been the case on older releases of macOS. If a macOS SDK is explicitly configured, by using --enable-universalsdk or -isysroot, only the SDK itself is searched. The default behavior can still be overridden with --with-tcltk-includes and --with-tcltk-libs. (Contributed by Ned Deily in bpo-34956 [https://bugs.python.org/issue?@action=redirect&bpo=34956].)

Python can now be built for Windows 10 ARM64. (Contributed by Steve Dower in bpo-33125 [https://bugs.python.org/issue?@action=redirect&bpo=33125].)

Some individual tests are now skipped when --pgo is used. The tests in question increased the PGO task time significantly and likely didn't help improve optimization of the final executable. This speeds up the task by a factor of about 15x. Running the full unit test suite is slow. This change may result in a slightly less optimized build since not as many code branches will be executed. If you are willing to wait for the much slower build, the old behavior can be restored using ./configure [..] PROFILE_TASK="-m test --pgo-extended". We make no guarantees as to which PGO task set produces a faster build. Users who care should run their own relevant benchmarks as results can depend on the environment, workload, and compiler tool chain. (See bpo-36044 [https://bugs.python.org/issue?@action=redirect&bpo=36044] and bpo-37707 [https://bugs.python.org/issue?@action=redirect&bpo=37707] for more details.)

C API 變更

新增功能

PEP 573 [https://peps.python.org/pep-0573/]: Added PyType_FromModuleAndSpec() to associate a module with a class; PyType_GetModule() and PyType_GetModuleState() to retrieve the module and its state; and PyCMethod and METH_METHOD to allow a method to access the class it was defined in. (Contributed by Marcel Plch and Petr Viktorin in bpo-38787 [https://bugs.python.org/issue?@action=redirect&bpo=38787].)

Added PyFrame_GetCode() function: get a frame code. Added PyFrame_GetBack() function: get the frame next outer frame. (Contributed by Victor Stinner in bpo-40421 [https://bugs.python.org/issue?@action=redirect&bpo=40421].)

Added PyFrame_GetLineNumber() to the limited C API. (Contributed by Victor Stinner in bpo-40421 [https://bugs.python.org/issue?@action=redirect&bpo=40421].)

Added PyThreadState_GetInterpreter() and PyInterpreterState_Get() functions to get the interpreter. Added PyThreadState_GetFrame() function to get the current frame of a Python thread state. Added PyThreadState_GetID() function: get the unique identifier of a Python thread state. (Contributed by Victor Stinner in bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947].)

Added a new public PyObject_CallNoArgs() function to the C API, which calls a callable Python object without any arguments. It is the most efficient way to call a callable Python object without any argument. (Contributed by Victor Stinner in bpo-37194 [https://bugs.python.org/issue?@action=redirect&bpo=37194].)

Changes in the limited C API (if Py_LIMITED_API macro is defined):

Provide Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() as regular functions for the limited API. Previously, there were defined as macros, but these macros didn't compile with the limited C API which cannot access PyThreadState.recursion_depth field (the structure is opaque in the limited C API).

PyObject_INIT() and PyObject_INIT_VAR() become regular "opaque" function to hide implementation details.

（由 Victor Stinner 在 38644 和 39542 中貢獻。）

The PyModule_AddType() function is added to help adding a type to a module. (Contributed by Donghee Na in bpo-40024 [https://bugs.python.org/issue?@action=redirect&bpo=40024].)

Added the functions PyObject_GC_IsTracked() and PyObject_GC_IsFinalized() to the public API to allow to query if Python objects are being currently tracked or have been already finalized by the garbage collector respectively. (Contributed by Pablo Galindo Salgado in bpo-40241 [https://bugs.python.org/issue?@action=redirect&bpo=40241].)

Added _PyObject_FunctionStr() to get a user-friendly string representation of a function-like object. (Patch by Jeroen Demeyer in bpo-37645 [https://bugs.python.org/issue?@action=redirect&bpo=37645].)

Added PyObject_CallOneArg() for calling an object with one positional argument (Patch by Jeroen Demeyer in bpo-37483 [https://bugs.python.org/issue?@action=redirect&bpo=37483].)

移植至 Python 3.9

PyInterpreterState.eval_frame (PEP 523 [https://peps.python.org/pep-0523/]) now requires a new mandatory tstate parameter (PyThreadState*). (Contributed by Victor Stinner in bpo-38500 [https://bugs.python.org/issue?@action=redirect&bpo=38500].)

Extension modules: m_traverse, m_clear and m_free functions of PyModuleDef are no longer called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, these functions are not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

Extension modules without module state (m_size <= 0) are not affected.

If Py_AddPendingCall() is called in a subinterpreter, the function is now scheduled to be called from the subinterpreter, rather than being called from the main interpreter. Each subinterpreter now has its own list of scheduled calls. (Contributed by Victor Stinner in bpo-39984 [https://bugs.python.org/issue?@action=redirect&bpo=39984].)

The Windows registry is no longer used to initialize sys.path when the -E option is used (if PyConfig.use_environment is set to 0). This is significant when embedding Python on Windows. (Contributed by Zackery Spytz in bpo-8901 [https://bugs.python.org/issue?@action=redirect&bpo=8901].)

The global variable PyStructSequence_UnnamedField is now a constant and refers to a constant string. (Contributed by Serhiy Storchaka in bpo-38650 [https://bugs.python.org/issue?@action=redirect&bpo=38650].)

The PyGC_Head structure is now opaque. It is only defined in the internal C API (pycore_gc.h). (Contributed by Victor Stinner in bpo-40241 [https://bugs.python.org/issue?@action=redirect&bpo=40241].)

The Py_UNICODE_COPY, Py_UNICODE_FILL, PyUnicode_WSTR_LENGTH, PyUnicode_FromUnicode(), PyUnicode_AsUnicode(), _PyUnicode_AsUnicode, and PyUnicode_AsUnicodeAndSize() are marked as deprecated in C. They have been deprecated by PEP 393 [https://peps.python.org/pep-0393/] since Python 3.3. (Contributed by Inada Naoki in bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346].)

The Py_FatalError() function is replaced with a macro which logs automatically the name of the current function, unless the Py_LIMITED_API macro is defined. (Contributed by Victor Stinner in bpo-39882 [https://bugs.python.org/issue?@action=redirect&bpo=39882].)

The vectorcall protocol now requires that the caller passes only strings as keyword names. (See bpo-37540 [https://bugs.python.org/issue?@action=redirect&bpo=37540] for more information.)

Implementation details of a number of macros and functions are now hidden:

PyObject_IS_GC() macro was converted to a function.

The PyObject_NEW() macro becomes an alias to the PyObject_New macro, and the PyObject_NEW_VAR() macro becomes an alias to the PyObject_NewVar macro. They no longer access directly the PyTypeObject.tp_basicsize member.

PyObject_GET_WEAKREFS_LISTPTR() macro was converted to a function: the macro accessed directly the PyTypeObject.tp_weaklistoffset member.

PyObject_CheckBuffer() macro was converted to a function: the macro accessed directly the PyTypeObject.tp_as_buffer member.

PyIndex_Check() is now always declared as an opaque function to hide implementation details: removed the PyIndex_Check() macro. The macro accessed directly the PyTypeObject.tp_as_number member.

（更多資訊請見 bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]。）

已移除

Excluded PyFPE_START_PROTECT() and PyFPE_END_PROTECT() macros of pyfpe.h from the limited C API. (Contributed by Victor Stinner in bpo-38835 [https://bugs.python.org/issue?@action=redirect&bpo=38835].)

The tp_print slot of PyTypeObject has been removed. It was used for printing objects to files in Python 2.7 and before. Since Python 3.0, it has been ignored and unused. (Contributed by Jeroen Demeyer in bpo-36974 [https://bugs.python.org/issue?@action=redirect&bpo=36974].)

Changes in the limited C API (if Py_LIMITED_API macro is defined):

Excluded the following functions from the limited C API:

PyThreadState_DeleteCurrent() (Contributed by Joannah Nanjekye in bpo-37878 [https://bugs.python.org/issue?@action=redirect&bpo=37878].)

_Py_CheckRecursionLimit

_Py_NewReference()

_Py_ForgetReference()

_PyTraceMalloc_NewReference()

_Py_GetRefTotal()

The trashcan mechanism which never worked in the limited C API.

PyTrash_UNWIND_LEVEL

Py_TRASHCAN_BEGIN_CONDITION

Py_TRASHCAN_BEGIN

Py_TRASHCAN_END

Py_TRASHCAN_SAFE_BEGIN

Py_TRASHCAN_SAFE_END

Moved following functions and definitions to the internal C API:

_PyDebug_PrintTotalRefs()

_Py_PrintReferences()

_Py_PrintReferenceAddresses()

_Py_tracemalloc_config

_Py_AddToAllObjects() (specific to Py_TRACE_REFS build)

（由 Victor Stinner 在 38644 和 39542 中貢獻。）

Removed _PyRuntime.getframe hook and removed _PyThreadState_GetFrame macro which was an alias to _PyRuntime.getframe. They were only exposed by the internal C API. Removed also PyThreadFrameGetter type. (Contributed by Victor Stinner in bpo-39946 [https://bugs.python.org/issue?@action=redirect&bpo=39946].)

Removed the following functions from the C API. Call PyGC_Collect() explicitly to clear all free lists. (Contributed by Inada Naoki and Victor Stinner in bpo-37340 [https://bugs.python.org/issue?@action=redirect&bpo=37340], bpo-38896 [https://bugs.python.org/issue?@action=redirect&bpo=38896] and bpo-40428 [https://bugs.python.org/issue?@action=redirect&bpo=40428].)

PyAsyncGen_ClearFreeLists()

PyContext_ClearFreeList()

PyDict_ClearFreeList()

PyFloat_ClearFreeList()

PyFrame_ClearFreeList()

PyList_ClearFreeList()

PyMethod_ClearFreeList() and PyCFunction_ClearFreeList(): the free lists of bound method objects have been removed.

PySet_ClearFreeList(): the set free list has been removed in Python 3.4.

PyTuple_ClearFreeList()

PyUnicode_ClearFreeList(): the Unicode free list has been removed in Python 3.3.

Removed _PyUnicode_ClearStaticStrings() function. (Contributed by Victor Stinner in bpo-39465 [https://bugs.python.org/issue?@action=redirect&bpo=39465].)

Removed Py_UNICODE_MATCH. It has been deprecated by PEP 393 [https://peps.python.org/pep-0393/], and broken since Python 3.3. The PyUnicode_Tailmatch() function can be used instead. (Contributed by Inada Naoki in bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346].)

Cleaned header files of interfaces defined but with no implementation. The public API symbols being removed are: _PyBytes_InsertThousandsGroupingLocale, _PyBytes_InsertThousandsGrouping, _Py_InitializeFromArgs, _Py_InitializeFromWideArgs, _PyFloat_Repr, _PyFloat_Digits, _PyFloat_DigitsInit, PyFrame_ExtendStack, _PyAIterWrapper_Type, PyNullImporter_Type, PyCmpWrapper_Type, PySortWrapper_Type, PyNoArgsFunction. (Contributed by Pablo Galindo Salgado in bpo-39372 [https://bugs.python.org/issue?@action=redirect&bpo=39372].)

Python 3.9.1 中顯著的變更

typing

The behavior of typing.Literal was changed to conform with PEP 586 [https://peps.python.org/pep-0586/] and to match the behavior of static type checkers specified in the PEP.

Literal now de-duplicates parameters.

Equality comparisons between Literal objects are now order independent.

Literal comparisons now respect types. For example, Literal[0] == Literal[False] previously evaluated to True. It is now False. To support this change, the internally used type cache now supports differentiating types.

Literal objects will now raise a TypeError exception during equality comparisons if any of their parameters are not hashable. Note that declaring Literal with mutable parameters will not throw an error:

>>> from typing import Literal
>>> Literal[{0}]
>>> Literal[{0}] == Literal[{False}]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'set'

（由 Yurii Karabas 在 bpo-42345 [https://bugs.python.org/issue?@action=redirect&bpo=42345] 中貢獻。）

macOS 11.0 (Big Sur) and Apple Silicon Mac support

As of 3.9.1, Python now fully supports building and running on macOS 11.0 (Big Sur) and on Apple Silicon Macs (based on the ARM64 architecture). A new universal build variant, universal2, is now available to natively support both ARM64 and Intel 64 in one set of executables. Binaries can also now be built on current versions of macOS to be deployed on a range of older macOS versions (tested to 10.9) while making some newer OS functions and options conditionally available based on the operating system version in use at runtime ("weaklinking").

（由 Ronald Oussoren 和 Lawrence D'Anna 在 bpo-41100 [https://bugs.python.org/issue?@action=redirect&bpo=41100] 中貢獻。）

Python 3.9.2 中顯著的變更

collections.abc

collections.abc.Callable generic now flattens type parameters, similar to what typing.Callable currently does. This means that collections.abc.Callable[[int, str], str] will have __args__ of (int, str, str); previously this was ([int, str], str). To allow this change, types.GenericAlias can now be subclassed, and a subclass will be returned when subscripting the collections.abc.Callable type. Code which accesses the arguments via typing.get_args() or __args__ need to account for this change. A DeprecationWarning may be emitted for invalid forms of parameterizing collections.abc.Callable which may have passed silently in Python 3.9.1. This DeprecationWarning will become a TypeError in Python 3.10. (Contributed by Ken Jin in bpo-42195 [https://bugs.python.org/issue?@action=redirect&bpo=42195].)

urllib.parse

Earlier Python versions allowed using both ; and & as query parameter separators in urllib.parse.parse_qs() and urllib.parse.parse_qsl(). Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with & as the default. This change also affects cgi.parse() and cgi.parse_multipart() as they use the affected functions internally. For more details, please see their respective documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967].)

Python 3.9.3 中顯著的變更

A security fix alters the ftplib.FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel. We reuse the ftp server IP address instead. For unusual code requiring the old behavior, set a trust_server_pasv_ipv4_address attribute on your FTP instance to True. (See gh-87451 [https://github.com/python/cpython/issues/87451])

Python 3.9.5 中顯著的變更

urllib.parse

The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html], ASCII newline \n, \r and tab \t characters are stripped from the URL by the parser in urllib.parse preventing such attacks. The removal characters are controlled by a new module level variable urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (See gh-88048 [https://github.com/python/cpython/issues/88048])

Python 3.9.14 中顯著的安全性功能

Converting between int and str in bases other than 2 (binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity. This is a mitigation for CVE 2020-10735 [https://www.cve.org/CVERecord?id=CVE-2020-10735]. This limit can be configured or disabled by environment variable, command line flag, or sys APIs. See the integer string conversion length limitation documentation. The default limit is 4300 digits in string form.

Python 3.9.17 中顯著的變更

tarfile

The extraction methods in tarfile, and shutil.unpack_archive(), have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See 解壓縮篩選器 for details. In Python 3.12, use without the filter argument will show a DeprecationWarning. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in PEP 706 [https://peps.python.org/pep-0706/].)

Python 3.8 有什麼新功能

編輯者:

Raymond Hettinger

本文介紹了 Python 3.8 與 3.7 相比多了哪些新功能。Python 3.8 已於 2019 年 10 月 14 日發布。有關完整詳細資訊，請參閱 changelog。

發布重點摘要

新增功能

Assignment expressions

There is new syntax := that assigns values to variables as part of a larger expression. It is affectionately known as "the walrus operator" due to its resemblance to the eyes and tusks of a walrus [https://en.wikipedia.org/wiki/Walrus#/media/File:Pacific_Walrus_-_Bull_(8247646168).jpg].

In this example, the assignment expression helps avoid calling len() twice:

if (n := len(a)) > 10:
    print(f"List is too long ({n} elements, expected <= 10)")

A similar benefit arises during regular expression matching where match objects are needed twice, once to test whether a match occurred and another to extract a subgroup:

discount = 0.0
if (mo := re.search(r'(\d+)% discount', advertisement)):
    discount = float(mo.group(1)) / 100.0

The operator is also useful with while-loops that compute a value to test loop termination and then need that same value again in the body of the loop:

# Loop over fixed length blocks
while (block := f.read(256)) != '':
    process(block)

Another motivating use case arises in list comprehensions where a value computed in a filtering condition is also needed in the expression body:

[clean_name.title() for name in names
 if (clean_name := normalize('NFC', name)) in allowed_names]

Try to limit use of the walrus operator to clean cases that reduce complexity and improve readability.

完整敘述請見 PEP 572 [https://peps.python.org/pep-0572/]。

（由 Emily Morehouse 在 bpo-35224 [https://bugs.python.org/issue?@action=redirect&bpo=35224] 中貢獻。）

Positional-only parameters

There is a new function parameter syntax / to indicate that some function parameters must be specified positionally and cannot be used as keyword arguments. This is the same notation shown by help() for C functions annotated with Larry Hastings' Argument Clinic [https://devguide.python.org/development-tools/clinic/] tool.

In the following example, parameters a and b are positional-only, while c or d can be positional or keyword, and e or f are required to be keywords:

def f(a, b, /, c, d, *, e, f):
    print(a, b, c, d, e, f)

以下是有效的呼叫：

f(10, 20, 30, d=40, e=50, f=60)

然而以下這些呼叫是無效的：

f(10, b=20, c=30, d=40, e=50, f=60)   # b 不得為關鍵字引數
f(10, 20, 30, 40, 50, f=60)           # e 必須為關鍵字引數

One use case for this notation is that it allows pure Python functions to fully emulate behaviors of existing C coded functions. For example, the built-in divmod() function does not accept keyword arguments:

def divmod(a, b, /):
    "Emulate the built in divmod() function"
    return (a // b, a % b)

Another use case is to preclude keyword arguments when the parameter name is not helpful. For example, the builtin len() function has the signature len(obj, /). This precludes awkward calls such as:

len(obj='hello')  # The "obj" keyword argument impairs readability

A further benefit of marking a parameter as positional-only is that it allows the parameter name to be changed in the future without risk of breaking client code. For example, in the statistics module, the parameter name dist may be changed in the future. This was made possible with the following function specification:

def quantiles(dist, /, *, n=4, method='exclusive')
    ...

Since the parameters to the left of / are not exposed as possible keywords, the parameters names remain available for use in **kwargs:

>>> def f(a, b, /, **kwargs):
...     print(a, b, kwargs)
...
>>> f(10, 20, a=1, b=2, c=3)         # a 和 b 被用於兩種方式
10 20 {'a': 1, 'b': 2, 'c': 3}

This greatly simplifies the implementation of functions and methods that need to accept arbitrary keyword arguments. For example, here is an excerpt from code in the collections module:

class Counter(dict):

    def __init__(self, iterable=None, /, **kwds):
        # Note "iterable" is a possible keyword argument

完整敘述請見 PEP 570 [https://peps.python.org/pep-0570/]。

（由 Pablo Galindo 在 bpo-36540 [https://bugs.python.org/issue?@action=redirect&bpo=36540] 中貢獻。）

Parallel filesystem cache for compiled bytecode files

The new PYTHONPYCACHEPREFIX setting (also available as -X pycache_prefix) configures the implicit bytecode cache to use a separate parallel filesystem tree, rather than the default __pycache__ subdirectories within each source directory.

The location of the cache is reported in sys.pycache_prefix (None indicates the default location in __pycache__ subdirectories).

（由 Carl Meyer 在 bpo-33499 [https://bugs.python.org/issue?@action=redirect&bpo=33499] 中貢獻。）

Debug build uses the same ABI as release build

Python now uses the same ABI whether it's built in release or debug mode. On Unix, when Python is built in debug mode, it is now possible to load C extensions built in release mode and C extensions built using the stable ABI.

Release builds and debug builds are now ABI compatible: defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro, which introduces the only ABI incompatibility. The Py_TRACE_REFS macro, which adds the sys.getobjects() function and the PYTHONDUMPREFS environment variable, can be set using the new ./configure --with-trace-refs build option. (Contributed by Victor Stinner in bpo-36465 [https://bugs.python.org/issue?@action=redirect&bpo=36465].)

On Unix, C extensions are no longer linked to libpython except on Android and Cygwin. It is now possible for a statically linked Python to load a C extension built using a shared library Python. (Contributed by Victor Stinner in bpo-21536 [https://bugs.python.org/issue?@action=redirect&bpo=21536].)

On Unix, when Python is built in debug mode, import now also looks for C extensions compiled in release mode and for C extensions compiled with the stable ABI. (Contributed by Victor Stinner in bpo-36722 [https://bugs.python.org/issue?@action=redirect&bpo=36722].)

To embed Python into an application, a new --embed option must be passed to python3-config --libs --embed to get -lpython3.8 (link the application to libpython). To support both 3.8 and older, try python3-config --libs --embed first and fallback to python3-config --libs (without --embed) if the previous command fails.

Add a pkg-config python-3.8-embed module to embed Python into an application: pkg-config python-3.8-embed --libs includes -lpython3.8. To support both 3.8 and older, try pkg-config python-X.Y-embed --libs first and fallback to pkg-config python-X.Y --libs (without --embed) if the previous command fails (replace X.Y with the Python version).

On the other hand, pkg-config python3.8 --libs no longer contains -lpython3.8. C extensions must not be linked to libpython (except on Android and Cygwin, whose cases are handled by the script); this change is backward incompatible on purpose. (Contributed by Victor Stinner in bpo-36721 [https://bugs.python.org/issue?@action=redirect&bpo=36721].)

f-strings support = for self-documenting expressions and debugging

Added an = specifier to f-strings. An f-string such as f'{expr=}' will expand to the text of the expression, an equal sign, then the representation of the evaluated expression. For example:

>>> user = 'eric_idle'
>>> member_since = date(1975, 7, 31)
>>> f'{user=} {member_since=}'
"user='eric_idle' member_since=datetime.date(1975, 7, 31)"

The usual f-string format specifiers allow more control over how the result of the expression is displayed:

>>> delta = date.today() - member_since
>>> f'{user=!s}  {delta.days=:,d}'
'user=eric_idle  delta.days=16,075'

The = specifier will display the whole expression so that calculations can be shown:

>>> print(f'{theta=}  {cos(radians(theta))=:.3f}')
theta=30  cos(radians(theta))=0.866

（由 Eric V. Smith 和 Larry Hastings 在 bpo-36817 [https://bugs.python.org/issue?@action=redirect&bpo=36817] 中貢獻。）

PEP 578: Python Runtime Audit Hooks

The PEP adds an Audit Hook and Verified Open Hook. Both are available from Python and native code, allowing applications and frameworks written in pure Python code to take advantage of extra notifications, while also allowing embedders or system administrators to deploy builds of Python where auditing is always enabled.

完整細節請見 PEP 578 [https://peps.python.org/pep-0578/]。

PEP 587: Python Initialization Configuration

The PEP 587 [https://peps.python.org/pep-0587/] adds a new C API to configure the Python Initialization providing finer control on the whole configuration and better error reporting.

New structures:

PyConfig

PyPreConfig

PyStatus

PyWideStringList

New functions:

PyConfig_Clear()

PyConfig_InitIsolatedConfig()

PyConfig_InitPythonConfig()

PyConfig_Read()

PyConfig_SetArgv()

PyConfig_SetBytesArgv()

PyConfig_SetBytesString()

PyConfig_SetString()

PyPreConfig_InitIsolatedConfig()

PyPreConfig_InitPythonConfig()

PyStatus_Error()

PyStatus_Exception()

PyStatus_Exit()

PyStatus_IsError()

PyStatus_IsExit()

PyStatus_NoMemory()

PyStatus_Ok()

PyWideStringList_Append()

PyWideStringList_Insert()

Py_BytesMain()

Py_ExitStatusException()

Py_InitializeFromConfig()

Py_PreInitialize()

Py_PreInitializeFromArgs()

Py_PreInitializeFromBytesArgs()

Py_RunMain()

This PEP also adds _PyRuntimeState.preconfig (PyPreConfig type) and PyInterpreterState.config (PyConfig type) fields to these internal structures. PyInterpreterState.config becomes the new reference configuration, replacing global configuration variables and other private variables.

See Python Initialization Configuration for the documentation.

完整敘述請見 PEP 587 [https://peps.python.org/pep-0587/]。

（由 Victor Stinner 在 bpo-36763 [https://bugs.python.org/issue?@action=redirect&bpo=36763] 中貢獻。）

PEP 590: Vectorcall: a fast calling protocol for CPython

Vectorcall 協定 is added to the Python/C API. It is meant to formalize existing optimizations which were already done for various classes. Any static type implementing a callable can use this protocol.

This is currently provisional. The aim is to make it fully public in Python 3.9.

完整敘述請見 PEP 590 [https://peps.python.org/pep-0590/]。

（由 Jeroen Demeyer、Mark Shannon 和 Petr Viktorin 在 bpo-36974 [https://bugs.python.org/issue?@action=redirect&bpo=36974] 中貢獻。）

Pickle protocol 5 with out-of-band data buffers

When pickle is used to transfer large data between Python processes in order to take advantage of multi-core or multi-machine processing, it is important to optimize the transfer by reducing memory copies, and possibly by applying custom techniques such as data-dependent compression.

The pickle protocol 5 introduces support for out-of-band buffers where PEP 3118 [https://peps.python.org/pep-3118/]-compatible data can be transmitted separately from the main pickle stream, at the discretion of the communication layer.

完整敘述請見 PEP 574 [https://peps.python.org/pep-0574/]。

（由 Antoine Pitrou 在 bpo-36785 [https://bugs.python.org/issue?@action=redirect&bpo=36785] 中貢獻。）

其他語言更動

A continue statement was illegal in the finally clause due to a problem with the implementation. In Python 3.8 this restriction was lifted. (Contributed by Serhiy Storchaka in bpo-32489 [https://bugs.python.org/issue?@action=redirect&bpo=32489].)

The bool, int, and fractions.Fraction types now have an as_integer_ratio() method like that found in float and decimal.Decimal. This minor API extension makes it possible to write numerator, denominator = x.as_integer_ratio() and have it work across multiple numeric types. (Contributed by Lisa Roach in bpo-33073 [https://bugs.python.org/issue?@action=redirect&bpo=33073] and Raymond Hettinger in bpo-37819 [https://bugs.python.org/issue?@action=redirect&bpo=37819].)

Constructors of int, float and complex will now use the __index__() special method, if available and the corresponding method __int__(), __float__() or __complex__() is not available. (Contributed by Serhiy Storchaka in bpo-20092 [https://bugs.python.org/issue?@action=redirect&bpo=20092].)

Added support of \N{name} escapes in regular expressions:

>>> notice = 'Copyright © 2019'
>>> copyright_year_pattern = re.compile(r'\N{copyright sign}\s*(\d{4})')
>>> int(copyright_year_pattern.search(notice).group(1))
2019

（由 Jonathan Eunice 和 Serhiy Storchaka 在 bpo-30688 [https://bugs.python.org/issue?@action=redirect&bpo=30688] 中貢獻。）

Dict and dictviews are now iterable in reversed insertion order using reversed(). (Contributed by Rémi Lapeyre in bpo-33462 [https://bugs.python.org/issue?@action=redirect&bpo=33462].)

The syntax allowed for keyword names in function calls was further restricted. In particular, f((keyword)=arg) is no longer allowed. It was never intended to permit more than a bare name on the left-hand side of a keyword argument assignment term. (Contributed by Benjamin Peterson in bpo-34641 [https://bugs.python.org/issue?@action=redirect&bpo=34641].)

Generalized iterable unpacking in yield and return statements no longer requires enclosing parentheses. This brings the yield and return syntax into better agreement with normal assignment syntax:

>>> def parse(family):
...     lastname, *members = family.split()
...     return lastname.upper(), *members
...
>>> parse('simpsons homer marge bart lisa maggie')
('SIMPSONS', 'homer', 'marge', 'bart', 'lisa', 'maggie')

（由 David Cuthbert 和 Jordan Chapman 在 bpo-32117 [https://bugs.python.org/issue?@action=redirect&bpo=32117] 中貢獻。）

When a comma is missed in code such as [(10, 20) (30, 40)], the compiler displays a SyntaxWarning with a helpful suggestion. This improves on just having a TypeError indicating that the first tuple was not callable. (Contributed by Serhiy Storchaka in bpo-15248 [https://bugs.python.org/issue?@action=redirect&bpo=15248].)

Arithmetic operations between subclasses of datetime.date or datetime.datetime and datetime.timedelta objects now return an instance of the subclass, rather than the base class. This also affects the return type of operations whose implementation (directly or indirectly) uses datetime.timedelta arithmetic, such as astimezone(). (Contributed by Paul Ganssle in bpo-32417 [https://bugs.python.org/issue?@action=redirect&bpo=32417].)

When the Python interpreter is interrupted by Ctrl-C (SIGINT) and the resulting KeyboardInterrupt exception is not caught, the Python process now exits via a SIGINT signal or with the correct exit code such that the calling process can detect that it died due to a Ctrl-C. Shells on POSIX and Windows use this to properly terminate scripts in interactive sessions. (Contributed by Google via Gregory P. Smith in bpo-1054041 [https://bugs.python.org/issue?@action=redirect&bpo=1054041].)

Some advanced styles of programming require updating the types.CodeType object for an existing function. Since code objects are immutable, a new code object needs to be created, one that is modeled on the existing code object. With 19 parameters, this was somewhat tedious. Now, the new replace() method makes it possible to create a clone with a few altered parameters.

Here's an example that alters the statistics.mean() function to prevent the data parameter from being used as a keyword argument:

>>> from statistics import mean
>>> mean(data=[10, 20, 90])
40
>>> mean.__code__ = mean.__code__.replace(co_posonlyargcount=1)
>>> mean(data=[10, 20, 90])
Traceback (most recent call last):
  ...
TypeError: mean() got some positional-only arguments passed as keyword arguments: 'data'

（由 Victor Stinner 在 bpo-37032 [https://bugs.python.org/issue?@action=redirect&bpo=37032] 中貢獻。）

For integers, the three-argument form of the pow() function now permits the exponent to be negative in the case where the base is relatively prime to the modulus. It then computes a modular inverse to the base when the exponent is -1, and a suitable power of that inverse for other negative exponents. For example, to compute the modular multiplicative inverse [https://en.wikipedia.org/wiki/Modular_multiplicative_inverse] of 38 modulo 137, write:

>>> pow(38, -1, 137)
119
>>> 119 * 38 % 137
1

Modular inverses arise in the solution of linear Diophantine equations [https://en.wikipedia.org/wiki/Diophantine_equation]. For example, to find integer solutions for 4258𝑥 + 147𝑦 = 369, first rewrite as 4258𝑥 ≡ 369 (mod 147) then solve:

>>> x = 369 * pow(4258, -1, 147) % 147
>>> y = (4258 * x - 369) // -147
>>> 4258 * x + 147 * y
369

（由 Mark Dickinson 在 bpo-36027 [https://bugs.python.org/issue?@action=redirect&bpo=36027] 中貢獻。）

Dict comprehensions have been synced-up with dict literals so that the key is computed first and the value second:

>>> # Dict comprehension
>>> cast = {input('role? '): input('actor? ') for i in range(2)}
role? King Arthur
actor? Chapman
role? Black Knight
actor? Cleese

>>> # Dict literal
>>> cast = {input('role? '): input('actor? ')}
role? Sir Robin
actor? Eric Idle

The guaranteed execution order is helpful with assignment expressions because variables assigned in the key expression will be available in the value expression:

>>> names = ['Martin von Löwis', 'Łukasz Langa', 'Walter Dörwald']
>>> {(n := normalize('NFC', name)).casefold() : n for name in names}
{'martin von löwis': 'Martin von Löwis',
 'łukasz langa': 'Łukasz Langa',
 'walter dörwald': 'Walter Dörwald'}

（由 Jörn Heissler 在 bpo-35224 [https://bugs.python.org/issue?@action=redirect&bpo=35224] 中貢獻。）

The object.__reduce__() method can now return a tuple from two to six elements long. Formerly, five was the limit. The new, optional sixth element is a callable with a (obj, state) signature. This allows the direct control over the state-updating behavior of a specific object. If not None, this callable will have priority over the object's __setstate__() method. (Contributed by Pierre Glaser and Olivier Grisel in bpo-35900 [https://bugs.python.org/issue?@action=redirect&bpo=35900].)

新增模組

The new importlib.metadata module provides (provisional) support for reading metadata from third-party packages. For example, it can extract an installed package's version number, list of entry points, and more:

>>> # Note following example requires that the popular "requests"
>>> # package has been installed.
>>>
>>> from importlib.metadata import version, requires, files
>>> version('requests')
'2.22.0'
>>> list(requires('requests'))
['chardet (<3.1.0,>=3.0.2)']
>>> list(files('requests'))[:5]
[PackagePath('requests-2.22.0.dist-info/INSTALLER'),
 PackagePath('requests-2.22.0.dist-info/LICENSE'),
 PackagePath('requests-2.22.0.dist-info/METADATA'),
 PackagePath('requests-2.22.0.dist-info/RECORD'),
 PackagePath('requests-2.22.0.dist-info/WHEEL')]

（由 Barry Warsaw 和 Jason R. Coombs 在 bpo-34632 [https://bugs.python.org/issue?@action=redirect&bpo=34632] 中貢獻。）

改進的模組

ast

AST nodes now have end_lineno and end_col_offset attributes, which give the precise location of the end of the node. (This only applies to nodes that have lineno and col_offset attributes.)

New function ast.get_source_segment() returns the source code for a specific AST node.

（由 Ivan Levkivskyi 在 bpo-33416 [https://bugs.python.org/issue?@action=redirect&bpo=33416] 中貢獻。）

ast.parse() 函式有一些新旗標：

type_comments=True causes it to return the text of PEP 484 [https://peps.python.org/pep-0484/] and PEP 526 [https://peps.python.org/pep-0526/] type comments associated with certain AST nodes;

mode='func_type' can be used to parse PEP 484 [https://peps.python.org/pep-0484/] "signature type comments" (returned for function definition AST nodes);

feature_version=(3, N) allows specifying an earlier Python 3 version. For example, feature_version=(3, 4) will treat async and await as non-reserved words.

（由 Guido van Rossum 在 bpo-35766 [https://bugs.python.org/issue?@action=redirect&bpo=35766] 中貢獻。）

asyncio

asyncio.run() has graduated from the provisional to stable API. This function can be used to execute a coroutine and return the result while automatically managing the event loop. For example:

import asyncio

async def main():
    await asyncio.sleep(0)
    return 42

asyncio.run(main())

這大致等價於：

import asyncio

async def main():
    await asyncio.sleep(0)
    return 42

loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
try:
    loop.run_until_complete(main())
finally:
    asyncio.set_event_loop(None)
    loop.close()

The actual implementation is significantly more complex. Thus, asyncio.run() should be the preferred way of running asyncio programs.

（由 Yury Selivanov 在 bpo-32314 [https://bugs.python.org/issue?@action=redirect&bpo=32314] 中貢獻。）

Running python -m asyncio launches a natively async REPL. This allows rapid experimentation with code that has a top-level await. There is no longer a need to directly call asyncio.run() which would spawn a new event loop on every invocation:

$ python -m asyncio
asyncio REPL 3.8.0
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> await asyncio.sleep(10, result='hello')
hello

（由 Yury Selivanov 在 bpo-37028 [https://bugs.python.org/issue?@action=redirect&bpo=37028] 中貢獻。）

The exception asyncio.CancelledError now inherits from BaseException rather than Exception and no longer inherits from concurrent.futures.CancelledError. (Contributed by Yury Selivanov in bpo-32528 [https://bugs.python.org/issue?@action=redirect&bpo=32528].)

On Windows, the default event loop is now ProactorEventLoop. (Contributed by Victor Stinner in bpo-34687 [https://bugs.python.org/issue?@action=redirect&bpo=34687].)

ProactorEventLoop now also supports UDP. (Contributed by Adam Meily and Andrew Svetlov in bpo-29883 [https://bugs.python.org/issue?@action=redirect&bpo=29883].)

ProactorEventLoop can now be interrupted by KeyboardInterrupt ("CTRL+C"). (Contributed by Vladimir Matveev in bpo-23057 [https://bugs.python.org/issue?@action=redirect&bpo=23057].)

Added asyncio.Task.get_coro() for getting the wrapped coroutine within an asyncio.Task. (Contributed by Alex Grönholm in bpo-36999 [https://bugs.python.org/issue?@action=redirect&bpo=36999].)

Asyncio tasks can now be named, either by passing the name keyword argument to asyncio.create_task() or the create_task() event loop method, or by calling the set_name() method on the task object. The task name is visible in the repr() output of asyncio.Task and can also be retrieved using the get_name() method. (Contributed by Alex Grönholm in bpo-34270 [https://bugs.python.org/issue?@action=redirect&bpo=34270].)

Added support for Happy Eyeballs [https://en.wikipedia.org/wiki/Happy_Eyeballs] to asyncio.loop.create_connection(). To specify the behavior, two new parameters have been added: happy_eyeballs_delay and interleave. The Happy Eyeballs algorithm improves responsiveness in applications that support IPv4 and IPv6 by attempting to simultaneously connect using both. (Contributed by twisteroid ambassador in bpo-33530 [https://bugs.python.org/issue?@action=redirect&bpo=33530].)

builtins（內建）

The compile() built-in has been improved to accept the ast.PyCF_ALLOW_TOP_LEVEL_AWAIT flag. With this new flag passed, compile() will allow top-level await, async for and async with constructs that are usually considered invalid syntax. Asynchronous code object marked with the CO_COROUTINE flag may then be returned. (Contributed by Matthias Bussonnier in bpo-34616 [https://bugs.python.org/issue?@action=redirect&bpo=34616])

collections

The _asdict() method for collections.namedtuple() now returns a dict instead of a collections.OrderedDict. This works because regular dicts have guaranteed ordering since Python 3.7. If the extra features of OrderedDict are required, the suggested remediation is to cast the result to the desired type: OrderedDict(nt._asdict()). (Contributed by Raymond Hettinger in bpo-35864 [https://bugs.python.org/issue?@action=redirect&bpo=35864].)

cProfile

The cProfile.Profile class can now be used as a context manager. Profile a block of code by running:

import cProfile

with cProfile.Profile() as profiler:
      # code to be profiled
      ...

（由 Scott Sanderson 在 bpo-29235 [https://bugs.python.org/issue?@action=redirect&bpo=29235] 中貢獻。）

csv

The csv.DictReader now returns instances of dict instead of a collections.OrderedDict. The tool is now faster and uses less memory while still preserving the field order. (Contributed by Michael Selik in bpo-34003 [https://bugs.python.org/issue?@action=redirect&bpo=34003].)

curses

Added a new variable holding structured version information for the underlying ncurses library: ncurses_version. (Contributed by Serhiy Storchaka in bpo-31680 [https://bugs.python.org/issue?@action=redirect&bpo=31680].)

ctypes

On Windows, CDLL and subclasses now accept a winmode parameter to specify flags for the underlying LoadLibraryEx call. The default flags are set to only load DLL dependencies from trusted locations, including the path where the DLL is stored (if a full or partial path is used to load the initial DLL) and paths added by add_dll_directory(). (Contributed by Steve Dower in bpo-36085 [https://bugs.python.org/issue?@action=redirect&bpo=36085].)

datetime

Added new alternate constructors datetime.date.fromisocalendar() and datetime.datetime.fromisocalendar(), which construct date and datetime objects respectively from ISO year, week number, and weekday; these are the inverse of each class's isocalendar method. (Contributed by Paul Ganssle in bpo-36004 [https://bugs.python.org/issue?@action=redirect&bpo=36004].)

functools

functools.lru_cache() can now be used as a straight decorator rather than as a function returning a decorator. So both of these are now supported:

@lru_cache
def f(x):
    ...

@lru_cache(maxsize=256)
def f(x):
    ...

（由 Raymond Hettinger 在 bpo-36772 [https://bugs.python.org/issue?@action=redirect&bpo=36772] 中貢獻。）

Added a new functools.cached_property() decorator, for computed properties cached for the life of the instance.

import functools
import statistics

class Dataset:
   def __init__(self, sequence_of_numbers):
      self.data = sequence_of_numbers

   @functools.cached_property
   def variance(self):
      return statistics.variance(self.data)

（由 Carl Meyer 在 bpo-21145 [https://bugs.python.org/issue?@action=redirect&bpo=21145] 中貢獻）

Added a new functools.singledispatchmethod() decorator that converts methods into generic functions using single dispatch:

from functools import singledispatchmethod
from contextlib import suppress

class TaskManager:

    def __init__(self, tasks):
        self.tasks = list(tasks)

    @singledispatchmethod
    def discard(self, value):
        with suppress(ValueError):
            self.tasks.remove(value)

    @discard.register(list)
    def _(self, tasks):
        targets = set(tasks)
        self.tasks = [x for x in self.tasks if x not in targets]

（由 Ethan Smith 在 bpo-32380 [https://bugs.python.org/issue?@action=redirect&bpo=32380] 中貢獻）

gc

get_objects() can now receive an optional generation parameter indicating a generation to get objects from. (Contributed by Pablo Galindo in bpo-36016 [https://bugs.python.org/issue?@action=redirect&bpo=36016].)

gettext

Added pgettext() and its variants. (Contributed by Franz Glasner, Éric Araujo, and Cheryl Sabella in bpo-2504 [https://bugs.python.org/issue?@action=redirect&bpo=2504].)

gzip

Added the mtime parameter to gzip.compress() for reproducible output. (Contributed by Guo Ci Teo in bpo-34898 [https://bugs.python.org/issue?@action=redirect&bpo=34898].)

A BadGzipFile exception is now raised instead of OSError for certain types of invalid or corrupt gzip files. (Contributed by Filip Gruszczyński, Michele Orrù, and Zackery Spytz in bpo-6584 [https://bugs.python.org/issue?@action=redirect&bpo=6584].)

IDLE 和 idlelib

Output over N lines (50 by default) is squeezed down to a button. N can be changed in the PyShell section of the General page of the Settings dialog. Fewer, but possibly extra long, lines can be squeezed by right clicking on the output. Squeezed output can be expanded in place by double-clicking the button or into the clipboard or a separate window by right-clicking the button. (Contributed by Tal Einat in bpo-1529353 [https://bugs.python.org/issue?@action=redirect&bpo=1529353].)

Add "Run Customized" to the Run menu to run a module with customized settings. Any command line arguments entered are added to sys.argv. They also re-appear in the box for the next customized run. One can also suppress the normal Shell main module restart. (Contributed by Cheryl Sabella, Terry Jan Reedy, and others in bpo-5680 [https://bugs.python.org/issue?@action=redirect&bpo=5680] and bpo-37627 [https://bugs.python.org/issue?@action=redirect&bpo=37627].)

Added optional line numbers for IDLE editor windows. Windows open without line numbers unless set otherwise in the General tab of the configuration dialog. Line numbers for an existing window are shown and hidden in the Options menu. (Contributed by Tal Einat and Saimadhav Heblikar in bpo-17535 [https://bugs.python.org/issue?@action=redirect&bpo=17535].)

OS native encoding is now used for converting between Python strings and Tcl objects. This allows IDLE to work with emoji and other non-BMP characters. These characters can be displayed or copied and pasted to or from the clipboard. Converting strings from Tcl to Python and back now never fails. (Many people worked on this for eight years but the problem was finally solved by Serhiy Storchaka in bpo-13153 [https://bugs.python.org/issue?@action=redirect&bpo=13153].)

New in 3.8.1:

Add option to toggle cursor blink off. (Contributed by Zackery Spytz in bpo-4603 [https://bugs.python.org/issue?@action=redirect&bpo=4603].)

Escape key now closes IDLE completion windows. (Contributed by Johnny Najera in bpo-38944 [https://bugs.python.org/issue?@action=redirect&bpo=38944].)

The changes above have been backported to 3.7 maintenance releases.

Add keywords to module name completion list. (Contributed by Terry J. Reedy in bpo-37765 [https://bugs.python.org/issue?@action=redirect&bpo=37765].)

inspect

The inspect.getdoc() function can now find docstrings for __slots__ if that attribute is a dict where the values are docstrings. This provides documentation options similar to what we already have for property(), classmethod(), and staticmethod():

class AudioClip:
    __slots__ = {'bit_rate': 'expressed in kilohertz to one decimal place',
                 'duration': 'in seconds, rounded up to an integer'}
    def __init__(self, bit_rate, duration):
        self.bit_rate = round(bit_rate / 1000.0, 1)
        self.duration = ceil(duration)

（由 Raymond Hettinger 在 bpo-36326 [https://bugs.python.org/issue?@action=redirect&bpo=36326] 中貢獻。）

io

In development mode (-X env) and in debug build, the io.IOBase finalizer now logs the exception if the close() method fails. The exception is ignored silently by default in release build. (Contributed by Victor Stinner in bpo-18748 [https://bugs.python.org/issue?@action=redirect&bpo=18748].)

itertools

The itertools.accumulate() function added an option initial keyword argument to specify an initial value:

>>> from itertools import accumulate
>>> list(accumulate([10, 5, 30, 15], initial=1000))
[1000, 1010, 1015, 1045, 1060]

（由 Lisa Roach 在 bpo-34659 [https://bugs.python.org/issue?@action=redirect&bpo=34659] 中貢獻。）

json.tool

Add option --json-lines to parse every input line as a separate JSON object. (Contributed by Weipeng Hong in bpo-31553 [https://bugs.python.org/issue?@action=redirect&bpo=31553].)

logging

Added a force keyword argument to logging.basicConfig(). When set to true, any existing handlers attached to the root logger are removed and closed before carrying out the configuration specified by the other arguments.

This solves a long-standing problem. Once a logger or basicConfig() had been called, subsequent calls to basicConfig() were silently ignored. This made it difficult to update, experiment with, or teach the various logging configuration options using the interactive prompt or a Jupyter notebook.

(Suggested by Raymond Hettinger, implemented by Donghee Na, and reviewed by Vinay Sajip in bpo-33897 [https://bugs.python.org/issue?@action=redirect&bpo=33897].)

math

Added new function math.dist() for computing Euclidean distance between two points. (Contributed by Raymond Hettinger in bpo-33089 [https://bugs.python.org/issue?@action=redirect&bpo=33089].)

Expanded the math.hypot() function to handle multiple dimensions. Formerly, it only supported the 2-D case. (Contributed by Raymond Hettinger in bpo-33089 [https://bugs.python.org/issue?@action=redirect&bpo=33089].)

Added new function, math.prod(), as analogous function to sum() that returns the product of a 'start' value (default: 1) times an iterable of numbers:

>>> prior = 0.8
>>> likelihoods = [0.625, 0.84, 0.30]
>>> math.prod(likelihoods, start=prior)
0.126

（由 Pablo Galindo 在 bpo-35606 [https://bugs.python.org/issue?@action=redirect&bpo=35606] 中貢獻。）

Added two new combinatoric functions math.perm() and math.comb():

>>> math.perm(10, 3)    # Permutations of 10 things taken 3 at a time
720
>>> math.comb(10, 3)    # Combinations of 10 things taken 3 at a time
120

（由 Yash Aggarwal、Keller Fuchs、Serhiy Storchaka 和 Raymond Hettinger 在 bpo-37128 [https://bugs.python.org/issue?@action=redirect&bpo=37128]、bpo-37178 [https://bugs.python.org/issue?@action=redirect&bpo=37178] 和 bpo-35431 [https://bugs.python.org/issue?@action=redirect&bpo=35431] 中貢獻。）

Added a new function math.isqrt() for computing accurate integer square roots without conversion to floating point. The new function supports arbitrarily large integers. It is faster than floor(sqrt(n)) but slower than math.sqrt():

>>> r = 650320427
>>> s = r ** 2
>>> isqrt(s - 1)         # 正確
650320426
>>> floor(sqrt(s - 1))   # 錯誤
650320427

（由 Mark Dickinson 在 bpo-36887 [https://bugs.python.org/issue?@action=redirect&bpo=36887] 中貢獻。）

The function math.factorial() no longer accepts arguments that are not int-like. (Contributed by Pablo Galindo in bpo-33083 [https://bugs.python.org/issue?@action=redirect&bpo=33083].)

mmap

The mmap.mmap class now has an madvise() method to access the madvise() system call. (Contributed by Zackery Spytz in bpo-32941 [https://bugs.python.org/issue?@action=redirect&bpo=32941].)

multiprocessing

Added new multiprocessing.shared_memory module. (Contributed by Davin Potts in bpo-35813 [https://bugs.python.org/issue?@action=redirect&bpo=35813].)

On macOS, the spawn start method is now used by default. (Contributed by Victor Stinner in bpo-33725 [https://bugs.python.org/issue?@action=redirect&bpo=33725].)

os

Added new function add_dll_directory() on Windows for providing additional search paths for native dependencies when importing extension modules or loading DLLs using ctypes. (Contributed by Steve Dower in bpo-36085 [https://bugs.python.org/issue?@action=redirect&bpo=36085].)

A new os.memfd_create() function was added to wrap the memfd_create() syscall. (Contributed by Zackery Spytz and Christian Heimes in bpo-26836 [https://bugs.python.org/issue?@action=redirect&bpo=26836].)

On Windows, much of the manual logic for handling reparse points (including symlinks and directory junctions) has been delegated to the operating system. Specifically, os.stat() will now traverse anything supported by the operating system, while os.lstat() will only open reparse points that identify as "name surrogates" while others are opened as for os.stat(). In all cases, os.stat_result.st_mode will only have S_IFLNK set for symbolic links and not other kinds of reparse points. To identify other kinds of reparse point, check the new os.stat_result.st_reparse_tag attribute.

On Windows, os.readlink() is now able to read directory junctions. Note that islink() will return False for directory junctions, and so code that checks islink first will continue to treat junctions as directories, while code that handles errors from os.readlink() may now treat junctions as links.

（由 Steve Dower 在 bpo-37834 [https://bugs.python.org/issue?@action=redirect&bpo=37834] 中貢獻。）

os.path

os.path functions that return a boolean result like exists(), lexists(), isdir(), isfile(), islink(), and ismount() now return False instead of raising ValueError or its subclasses UnicodeEncodeError and UnicodeDecodeError for paths that contain characters or bytes unrepresentable at the OS level. (Contributed by Serhiy Storchaka in bpo-33721 [https://bugs.python.org/issue?@action=redirect&bpo=33721].)

expanduser() on Windows now prefers the USERPROFILE environment variable and does not use HOME, which is not normally set for regular user accounts. (Contributed by Anthony Sottile in bpo-36264 [https://bugs.python.org/issue?@action=redirect&bpo=36264].)

isdir() on Windows no longer returns True for a link to a non-existent directory.

realpath() on Windows now resolves reparse points, including symlinks and directory junctions.

（由 Steve Dower 在 bpo-37834 [https://bugs.python.org/issue?@action=redirect&bpo=37834] 中貢獻。）

pathlib

pathlib.Path methods that return a boolean result like exists(), is_dir(), is_file(), is_mount(), is_symlink(), is_block_device(), is_char_device(), is_fifo(), is_socket() now return False instead of raising ValueError or its subclass UnicodeEncodeError for paths that contain characters unrepresentable at the OS level. (Contributed by Serhiy Storchaka in bpo-33721 [https://bugs.python.org/issue?@action=redirect&bpo=33721].)

Added pathlib.Path.link_to() which creates a hard link pointing to a path. (Contributed by Joannah Nanjekye in bpo-26978 [https://bugs.python.org/issue?@action=redirect&bpo=26978]) Note that link_to was deprecated in 3.10 and removed in 3.12 in favor of a hardlink_to method added in 3.10 which matches the semantics of the existing symlink_to method.

pickle

pickle extensions subclassing the C-optimized Pickler can now override the pickling logic of functions and classes by defining the special reducer_override() method. (Contributed by Pierre Glaser and Olivier Grisel in bpo-35900 [https://bugs.python.org/issue?@action=redirect&bpo=35900].)

plistlib

Added new plistlib.UID and enabled support for reading and writing NSKeyedArchiver-encoded binary plists. (Contributed by Jon Janzen in bpo-26707 [https://bugs.python.org/issue?@action=redirect&bpo=26707].)

pprint

The pprint module added a sort_dicts parameter to several functions. By default, those functions continue to sort dictionaries before rendering or printing. However, if sort_dicts is set to false, the dictionaries retain the order that keys were inserted. This can be useful for comparison to JSON inputs during debugging.

In addition, there is a convenience new function, pprint.pp() that is like pprint.pprint() but with sort_dicts defaulting to False:

>>> from pprint import pprint, pp
>>> d = dict(source='input.txt', operation='filter', destination='output.txt')
>>> pp(d, width=40)                  # 原本的順序
{'source': 'input.txt',
 'operation': 'filter',
 'destination': 'output.txt'}
>>> pprint(d, width=40)              # 以字母順序排序鍵
{'destination': 'output.txt',
 'operation': 'filter',
 'source': 'input.txt'}

（由 Rémi Lapeyre 在 bpo-30670 [https://bugs.python.org/issue?@action=redirect&bpo=30670] 中貢獻。）

py_compile

py_compile.compile() now supports silent mode. (Contributed by Joannah Nanjekye in bpo-22640 [https://bugs.python.org/issue?@action=redirect&bpo=22640].)

shlex

The new shlex.join() function acts as the inverse of shlex.split(). (Contributed by Bo Bayles in bpo-32102 [https://bugs.python.org/issue?@action=redirect&bpo=32102].)

shutil

shutil.copytree() now accepts a new dirs_exist_ok keyword argument. (Contributed by Josh Bronson in bpo-20849 [https://bugs.python.org/issue?@action=redirect&bpo=20849].)

shutil.make_archive() now defaults to the modern pax (POSIX.1-2001) format for new archives to improve portability and standards conformance, inherited from the corresponding change to the tarfile module. (Contributed by C.A.M. Gerlach in bpo-30661 [https://bugs.python.org/issue?@action=redirect&bpo=30661].)

shutil.rmtree() on Windows now removes directory junctions without recursively removing their contents first. (Contributed by Steve Dower in bpo-37834 [https://bugs.python.org/issue?@action=redirect&bpo=37834].)

socket

Added create_server() and has_dualstack_ipv6() convenience functions to automate the necessary tasks usually involved when creating a server socket, including accepting both IPv4 and IPv6 connections on the same socket. (Contributed by Giampaolo Rodolà in bpo-17561 [https://bugs.python.org/issue?@action=redirect&bpo=17561].)

The socket.if_nameindex(), socket.if_nametoindex(), and socket.if_indextoname() functions have been implemented on Windows. (Contributed by Zackery Spytz in bpo-37007 [https://bugs.python.org/issue?@action=redirect&bpo=37007].)

ssl

Added post_handshake_auth to enable and verify_client_post_handshake() to initiate TLS 1.3 post-handshake authentication. (Contributed by Christian Heimes in bpo-34670 [https://bugs.python.org/issue?@action=redirect&bpo=34670].)

statistics

Added statistics.fmean() as a faster, floating-point variant of statistics.mean(). (Contributed by Raymond Hettinger and Steven D'Aprano in bpo-35904 [https://bugs.python.org/issue?@action=redirect&bpo=35904].)

新增 statistics.geometric_mean()（由 Raymond Hettinger 在 bpo-27181 [https://bugs.python.org/issue?@action=redirect&bpo=27181] 中貢獻。）

Added statistics.multimode() that returns a list of the most common values. (Contributed by Raymond Hettinger in bpo-35892 [https://bugs.python.org/issue?@action=redirect&bpo=35892].)

Added statistics.quantiles() that divides data or a distribution in to equiprobable intervals (e.g. quartiles, deciles, or percentiles). (Contributed by Raymond Hettinger in bpo-36546 [https://bugs.python.org/issue?@action=redirect&bpo=36546].)

Added statistics.NormalDist, a tool for creating and manipulating normal distributions of a random variable. (Contributed by Raymond Hettinger in bpo-36018 [https://bugs.python.org/issue?@action=redirect&bpo=36018].)

>>> temperature_feb = NormalDist.from_samples([4, 12, -3, 2, 7, 14])
>>> temperature_feb.mean
6.0
>>> temperature_feb.stdev
6.356099432828281

>>> temperature_feb.cdf(3)            # Chance of being under 3 degrees
0.3184678262814532
>>> # Relative chance of being 7 degrees versus 10 degrees
>>> temperature_feb.pdf(7) / temperature_feb.pdf(10)
1.2039930378537762

>>> el_niño = NormalDist(4, 2.5)
>>> temperature_feb += el_niño        # Add in a climate effect
>>> temperature_feb
NormalDist(mu=10.0, sigma=6.830080526611674)

>>> temperature_feb * (9/5) + 32      # Convert to Fahrenheit
NormalDist(mu=50.0, sigma=12.294144947901014)
>>> temperature_feb.samples(3)        # Generate random samples
[7.672102882379219, 12.000027119750287, 4.647488369766392]

sys

Add new sys.unraisablehook() function which can be overridden to control how "unraisable exceptions" are handled. It is called when an exception has occurred but there is no way for Python to handle it. For example, when a destructor raises an exception or during garbage collection (gc.collect()). (Contributed by Victor Stinner in bpo-36829 [https://bugs.python.org/issue?@action=redirect&bpo=36829].)

tarfile

The tarfile module now defaults to the modern pax (POSIX.1-2001) format for new archives, instead of the previous GNU-specific one. This improves cross-platform portability with a consistent encoding (UTF-8) in a standardized and extensible format, and offers several other benefits. (Contributed by C.A.M. Gerlach in bpo-36268 [https://bugs.python.org/issue?@action=redirect&bpo=36268].)

threading

Add a new threading.excepthook() function which handles uncaught threading.Thread.run() exception. It can be overridden to control how uncaught threading.Thread.run() exceptions are handled. (Contributed by Victor Stinner in bpo-1230540 [https://bugs.python.org/issue?@action=redirect&bpo=1230540].)

Add a new threading.get_native_id() function and a native_id attribute to the threading.Thread class. These return the native integral Thread ID of the current thread assigned by the kernel. This feature is only available on certain platforms, see get_native_id for more information. (Contributed by Jake Tesler in bpo-36084 [https://bugs.python.org/issue?@action=redirect&bpo=36084].)

tokenize

The tokenize module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. (Contributed by Ammar Askar in bpo-33899 [https://bugs.python.org/issue?@action=redirect&bpo=33899].)

tkinter

Added methods selection_from(), selection_present(), selection_range() and selection_to() in the tkinter.Spinbox class. (Contributed by Juliette Monsel in bpo-34829 [https://bugs.python.org/issue?@action=redirect&bpo=34829].)

Added method moveto() in the tkinter.Canvas class. (Contributed by Juliette Monsel in bpo-23831 [https://bugs.python.org/issue?@action=redirect&bpo=23831].)

The tkinter.PhotoImage class now has transparency_get() and transparency_set() methods. (Contributed by Zackery Spytz in bpo-25451 [https://bugs.python.org/issue?@action=redirect&bpo=25451].)

time

Added new clock CLOCK_UPTIME_RAW for macOS 10.12. (Contributed by Joannah Nanjekye in bpo-35702 [https://bugs.python.org/issue?@action=redirect&bpo=35702].)

typing

The typing module incorporates several new features:

A dictionary type with per-key types. See PEP 589 [https://peps.python.org/pep-0589/] and typing.TypedDict. TypedDict uses only string keys. By default, every key is required to be present. Specify "total=False" to allow keys to be optional:

class Location(TypedDict, total=False):
    lat_long: tuple
    grid_square: str
    xy_coordinate: tuple

Literal types. See PEP 586 [https://peps.python.org/pep-0586/] and typing.Literal. Literal types indicate that a parameter or return value is constrained to one or more specific literal values:

def get_status(port: int) -> Literal['connected', 'disconnected']:
    ...

"Final" variables, functions, methods and classes. See PEP 591 [https://peps.python.org/pep-0591/], typing.Final and typing.final(). The final qualifier instructs a static type checker to restrict subclassing, overriding, or reassignment:

pi: Final[float] = 3.1415926536

Protocol definitions. See PEP 544 [https://peps.python.org/pep-0544/], typing.Protocol and typing.runtime_checkable(). Simple ABCs like typing.SupportsInt are now Protocol subclasses.

新的協定類別 typing.SupportsIndex。

新的函式 typing.get_origin() 和 typing.get_args()。

unicodedata

The unicodedata module has been upgraded to use the Unicode 12.1.0 [https://blog.unicode.org/2019/05/unicode-12-1-en.html] release.

New function is_normalized() can be used to verify a string is in a specific normal form, often much faster than by actually normalizing the string. (Contributed by Max Belanger, David Euresti, and Greg Price in bpo-32285 [https://bugs.python.org/issue?@action=redirect&bpo=32285] and bpo-37966 [https://bugs.python.org/issue?@action=redirect&bpo=37966]).

unittest

Added AsyncMock to support an asynchronous version of Mock. Appropriate new assert functions for testing have been added as well. (Contributed by Lisa Roach in bpo-26467 [https://bugs.python.org/issue?@action=redirect&bpo=26467]).

Added addModuleCleanup() and addClassCleanup() to unittest to support cleanups for setUpModule() and setUpClass(). (Contributed by Lisa Roach in bpo-24412 [https://bugs.python.org/issue?@action=redirect&bpo=24412].)

Several mock assert functions now also print a list of actual calls upon failure. (Contributed by Petter Strandmark in bpo-35047 [https://bugs.python.org/issue?@action=redirect&bpo=35047].)

unittest module gained support for coroutines to be used as test cases with unittest.IsolatedAsyncioTestCase. (Contributed by Andrew Svetlov in bpo-32972 [https://bugs.python.org/issue?@action=redirect&bpo=32972].)

範例：

import unittest

class TestRequest(unittest.IsolatedAsyncioTestCase):

    async def asyncSetUp(self):
        self.connection = await AsyncConnection()

    async def test_get(self):
        response = await self.connection.get("https://example.com")
        self.assertEqual(response.status_code, 200)

    async def asyncTearDown(self):
        await self.connection.close()

if __name__ == "__main__":
    unittest.main()

venv

venv now includes an Activate.ps1 script on all platforms for activating virtual environments under PowerShell Core 6.1. (Contributed by Brett Cannon in bpo-32718 [https://bugs.python.org/issue?@action=redirect&bpo=32718].)

weakref

The proxy objects returned by weakref.proxy() now support the matrix multiplication operators @ and @= in addition to the other numeric operators. (Contributed by Mark Dickinson in bpo-36669 [https://bugs.python.org/issue?@action=redirect&bpo=36669].)

xml

As mitigation against DTD and external entity retrieval, the xml.dom.minidom and xml.sax modules no longer process external entities by default. (Contributed by Christian Heimes in bpo-17239 [https://bugs.python.org/issue?@action=redirect&bpo=17239].)

The .find*() methods in the xml.etree.ElementTree module support wildcard searches like {*}tag which ignores the namespace and {namespace}* which returns all tags in the given namespace. (Contributed by Stefan Behnel in bpo-28238 [https://bugs.python.org/issue?@action=redirect&bpo=28238].)

The xml.etree.ElementTree module provides a new function canonicalize() that implements C14N 2.0. (Contributed by Stefan Behnel in bpo-13611 [https://bugs.python.org/issue?@action=redirect&bpo=13611].)

The target object of xml.etree.ElementTree.XMLParser can receive namespace declaration events through the new callback methods start_ns() and end_ns(). Additionally, the xml.etree.ElementTree.TreeBuilder target can be configured to process events about comments and processing instructions to include them in the generated tree. (Contributed by Stefan Behnel in bpo-36676 [https://bugs.python.org/issue?@action=redirect&bpo=36676] and bpo-36673 [https://bugs.python.org/issue?@action=redirect&bpo=36673].)

xmlrpc

xmlrpc.client.ServerProxy now supports an optional headers keyword argument for a sequence of HTTP headers to be sent with each request. Among other things, this makes it possible to upgrade from default basic authentication to faster session authentication. (Contributed by Cédric Krier in bpo-35153 [https://bugs.python.org/issue?@action=redirect&bpo=35153].)

最佳化

The subprocess module can now use the os.posix_spawn() function in some cases for better performance. Currently, it is only used on macOS and Linux (using glibc 2.24 or newer) if all these conditions are met:

close_fds is false;

preexec_fn, pass_fds, cwd and start_new_session parameters are not set;

the executable path contains a directory.

（由 Joannah Nanjekye 和 Victor Stinner 在 bpo-35537 [https://bugs.python.org/issue?@action=redirect&bpo=35537] 中貢獻。）

shutil.copyfile(), shutil.copy(), shutil.copy2(), shutil.copytree() and shutil.move() use platform-specific "fast-copy" syscalls on Linux and macOS in order to copy the file more efficiently. "fast-copy" means that the copying operation occurs within the kernel, avoiding the use of userspace buffers in Python as in "outfd.write(infd.read())". On Windows shutil.copyfile() uses a bigger default buffer size (1 MiB instead of 16 KiB) and a memoryview()-based variant of shutil.copyfileobj() is used. The speedup for copying a 512 MiB file within the same partition is about +26% on Linux, +50% on macOS and +40% on Windows. Also, much less CPU cycles are consumed. See Platform-dependent efficient copy operations section. (Contributed by Giampaolo Rodolà in bpo-33671 [https://bugs.python.org/issue?@action=redirect&bpo=33671].)

shutil.copytree() uses os.scandir() function and all copy functions depending from it use cached os.stat() values. The speedup for copying a directory with 8000 files is around +9% on Linux, +20% on Windows and +30% on a Windows SMB share. Also the number of os.stat() syscalls is reduced by 38% making shutil.copytree() especially faster on network filesystems. (Contributed by Giampaolo Rodolà in bpo-33695 [https://bugs.python.org/issue?@action=redirect&bpo=33695].)

The default protocol in the pickle module is now Protocol 4, first introduced in Python 3.4. It offers better performance and smaller size compared to Protocol 3 available since Python 3.0.

Removed one Py_ssize_t member from PyGC_Head. All GC tracked objects (e.g. tuple, list, dict) size is reduced 4 or 8 bytes. (Contributed by Inada Naoki in bpo-33597 [https://bugs.python.org/issue?@action=redirect&bpo=33597].)

uuid.UUID now uses __slots__ to reduce its memory footprint. (Contributed by Wouter Bolsterlee and Tal Einat in bpo-30977 [https://bugs.python.org/issue?@action=redirect&bpo=30977])

Improved performance of operator.itemgetter() by 33%. Optimized argument handling and added a fast path for the common case of a single non-negative integer index into a tuple (which is the typical use case in the standard library). (Contributed by Raymond Hettinger in bpo-35664 [https://bugs.python.org/issue?@action=redirect&bpo=35664].)

Sped-up field lookups in collections.namedtuple(). They are now more than two times faster, making them the fastest form of instance variable lookup in Python. (Contributed by Raymond Hettinger, Pablo Galindo, and Joe Jevnik, Serhiy Storchaka in bpo-32492 [https://bugs.python.org/issue?@action=redirect&bpo=32492].)

The list constructor does not overallocate the internal item buffer if the input iterable has a known length (the input implements __len__). This makes the created list 12% smaller on average. (Contributed by Raymond Hettinger and Pablo Galindo in bpo-33234 [https://bugs.python.org/issue?@action=redirect&bpo=33234].)

Doubled the speed of class variable writes. When a non-dunder attribute was updated, there was an unnecessary call to update slots. (Contributed by Stefan Behnel, Pablo Galindo Salgado, Raymond Hettinger, Neil Schemenauer, and Serhiy Storchaka in bpo-36012 [https://bugs.python.org/issue?@action=redirect&bpo=36012].)

Reduced an overhead of converting arguments passed to many builtin functions and methods. This sped up calling some simple builtin functions and methods up to 20--50%. (Contributed by Serhiy Storchaka in bpo-23867 [https://bugs.python.org/issue?@action=redirect&bpo=23867], bpo-35582 [https://bugs.python.org/issue?@action=redirect&bpo=35582] and bpo-36127 [https://bugs.python.org/issue?@action=redirect&bpo=36127].)

LOAD_GLOBAL instruction now uses new "per opcode cache" mechanism. It is about 40% faster now. (Contributed by Yury Selivanov and Inada Naoki in bpo-26219 [https://bugs.python.org/issue?@action=redirect&bpo=26219].)

建置和 C API 變更

Default sys.abiflags became an empty string: the m flag for pymalloc became useless (builds with and without pymalloc are ABI compatible) and so has been removed. (Contributed by Victor Stinner in bpo-36707 [https://bugs.python.org/issue?@action=redirect&bpo=36707].)

Example of changes:

Only python3.8 program is installed, python3.8m program is gone.

Only python3.8-config script is installed, python3.8m-config script is gone.

The m flag has been removed from the suffix of dynamic library filenames: extension modules in the standard library as well as those produced and installed by third-party packages, like those downloaded from PyPI. On Linux, for example, the Python 3.7 suffix .cpython-37m-x86_64-linux-gnu.so became .cpython-38-x86_64-linux-gnu.so in Python 3.8.

The header files have been reorganized to better separate the different kinds of APIs:

Include/*.h should be the portable public stable C API.

Include/cpython/*.h should be the unstable C API specific to CPython; public API, with some private API prefixed by _Py or _PY.

Include/internal/*.h is the private internal C API very specific to CPython. This API comes with no backward compatibility warranty and should not be used outside CPython. It is only exposed for very specific needs like debuggers and profiles which has to access to CPython internals without calling functions. This API is now installed by make install.

（由 Victor Stinner 在 bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134] 和 bpo-35081 [https://bugs.python.org/issue?@action=redirect&bpo=35081] 中貢獻，該工作由 Eric Snow 在 Python 3.7 中發起。）

Some macros have been converted to static inline functions: parameter types and return type are well defined, they don't have issues specific to macros, variables have a local scopes. Examples:

Py_INCREF(), Py_DECREF()

Py_XINCREF(), Py_XDECREF()

PyObject_INIT, PyObject_INIT_VAR

Private functions: _PyObject_GC_TRACK(), _PyObject_GC_UNTRACK(), _Py_Dealloc()

（由 Victor Stinner 在 bpo-35059 [https://bugs.python.org/issue?@action=redirect&bpo=35059] 中貢獻。）

The PyByteArray_Init() and PyByteArray_Fini() functions have been removed. They did nothing since Python 2.7.4 and Python 3.2.0, were excluded from the limited API (stable ABI), and were not documented. (Contributed by Victor Stinner in bpo-35713 [https://bugs.python.org/issue?@action=redirect&bpo=35713].)

The result of PyExceptionClass_Name() is now of type const char * rather of char *. (Contributed by Serhiy Storchaka in bpo-33818 [https://bugs.python.org/issue?@action=redirect&bpo=33818].)

The duality of Modules/Setup.dist and Modules/Setup has been removed. Previously, when updating the CPython source tree, one had to manually copy Modules/Setup.dist (inside the source tree) to Modules/Setup (inside the build tree) in order to reflect any changes upstream. This was of a small benefit to packagers at the expense of a frequent annoyance to developers following CPython development, as forgetting to copy the file could produce build failures.

Now the build system always reads from Modules/Setup inside the source tree. People who want to customize that file are encouraged to maintain their changes in a git fork of CPython or as patch files, as they would do for any other change to the source tree.

（由 Antoine Pitrou 在 bpo-32430 [https://bugs.python.org/issue?@action=redirect&bpo=32430] 中貢獻。）

Functions that convert Python number to C integer like PyLong_AsLong() and argument parsing functions like PyArg_ParseTuple() with integer converting format units like 'i' will now use the __index__() special method instead of __int__(), if available. The deprecation warning will be emitted for objects with the __int__() method but without the __index__() method (like Decimal and Fraction). PyNumber_Check() will now return 1 for objects implementing __index__(). PyNumber_Long(), PyNumber_Float() and PyFloat_AsDouble() also now use the __index__() method if available. (Contributed by Serhiy Storchaka in bpo-36048 [https://bugs.python.org/issue?@action=redirect&bpo=36048] and bpo-20092 [https://bugs.python.org/issue?@action=redirect&bpo=20092].)

Heap-allocated type objects will now increase their reference count in PyObject_Init() (and its parallel macro PyObject_INIT) instead of in PyType_GenericAlloc(). Types that modify instance allocation or deallocation may need to be adjusted. (Contributed by Eddie Elizondo in bpo-35810 [https://bugs.python.org/issue?@action=redirect&bpo=35810].)

The new function PyCode_NewWithPosOnlyArgs() allows to create code objects like PyCode_New(), but with an extra posonlyargcount parameter for indicating the number of positional-only arguments. (Contributed by Pablo Galindo in bpo-37221 [https://bugs.python.org/issue?@action=redirect&bpo=37221].)

Py_SetPath() now sets sys.executable to the program full path (Py_GetProgramFullPath()) rather than to the program name (Py_GetProgramName()). (Contributed by Victor Stinner in bpo-38234 [https://bugs.python.org/issue?@action=redirect&bpo=38234].)

已棄用

The distutils bdist_wininst command is now deprecated, use bdist_wheel (wheel packages) instead. (Contributed by Victor Stinner in bpo-37481 [https://bugs.python.org/issue?@action=redirect&bpo=37481].)

Deprecated methods getchildren() and getiterator() in the ElementTree module now emit a DeprecationWarning instead of PendingDeprecationWarning. They will be removed in Python 3.9. (Contributed by Serhiy Storchaka in bpo-29209 [https://bugs.python.org/issue?@action=redirect&bpo=29209].)

Passing an object that is not an instance of concurrent.futures.ThreadPoolExecutor to loop.set_default_executor() is deprecated and will be prohibited in Python 3.9. (Contributed by Elvis Pranskevichus in bpo-34075 [https://bugs.python.org/issue?@action=redirect&bpo=34075].)

The __getitem__() methods of xml.dom.pulldom.DOMEventStream, wsgiref.util.FileWrapper and fileinput.FileInput have been deprecated.

Implementations of these methods have been ignoring their index parameter, and returning the next item instead. (Contributed by Berker Peksag in bpo-9372 [https://bugs.python.org/issue?@action=redirect&bpo=9372].)

The typing.NamedTuple class has deprecated the _field_types attribute in favor of the __annotations__ attribute which has the same information. (Contributed by Raymond Hettinger in bpo-36320 [https://bugs.python.org/issue?@action=redirect&bpo=36320].)

ast classes Num, Str, Bytes, NameConstant and Ellipsis are considered deprecated and will be removed in future Python versions. Constant should be used instead. (Contributed by Serhiy Storchaka in bpo-32892 [https://bugs.python.org/issue?@action=redirect&bpo=32892].)

ast.NodeVisitor methods visit_Num(), visit_Str(), visit_Bytes(), visit_NameConstant() and visit_Ellipsis() are deprecated now and will not be called in future Python versions. Add the visit_Constant() method to handle all constant nodes. (Contributed by Serhiy Storchaka in bpo-36917 [https://bugs.python.org/issue?@action=redirect&bpo=36917].)

The @asyncio.coroutine decorator is deprecated and will be removed in version 3.10. Instead of @asyncio.coroutine, use async def instead. (Contributed by Andrew Svetlov in bpo-36921 [https://bugs.python.org/issue?@action=redirect&bpo=36921].)

In asyncio, the explicit passing of a loop argument has been deprecated and will be removed in version 3.10 for the following: asyncio.sleep(), asyncio.gather(), asyncio.shield(), asyncio.wait_for(), asyncio.wait(), asyncio.as_completed(), asyncio.Task, asyncio.Lock, asyncio.Event, asyncio.Condition, asyncio.Semaphore, asyncio.BoundedSemaphore, asyncio.Queue, asyncio.create_subprocess_exec(), and asyncio.create_subprocess_shell().

The explicit passing of coroutine objects to asyncio.wait() has been deprecated and will be removed in version 3.11. (Contributed by Yury Selivanov in bpo-34790 [https://bugs.python.org/issue?@action=redirect&bpo=34790].)

The following functions and methods are deprecated in the gettext module: lgettext(), ldgettext(), lngettext() and ldngettext(). They return encoded bytes, and it's possible that you will get unexpected Unicode-related exceptions if there are encoding problems with the translated strings. It's much better to use alternatives which return Unicode strings in Python 3. These functions have been broken for a long time.

Function bind_textdomain_codeset(), methods NullTranslations.output_charset() and NullTranslations.set_output_charset(), and the codeset parameter of functions translation() and install() are also deprecated, since they are only used for the l*gettext() functions. (Contributed by Serhiy Storchaka in bpo-33710 [https://bugs.python.org/issue?@action=redirect&bpo=33710].)

The isAlive() method of threading.Thread has been deprecated. (Contributed by Donghee Na in bpo-35283 [https://bugs.python.org/issue?@action=redirect&bpo=35283].)

Many builtin and extension functions that take integer arguments will now emit a deprecation warning for Decimals, Fractions and any other objects that can be converted to integers only with a loss (e.g. that have the __int__() method but do not have the __index__() method). In future version they will be errors. (Contributed by Serhiy Storchaka in bpo-36048 [https://bugs.python.org/issue?@action=redirect&bpo=36048].)

Deprecated passing the following arguments as keyword arguments:

func in functools.partialmethod(), weakref.finalize(), profile.Profile.runcall(), cProfile.Profile.runcall(), bdb.Bdb.runcall(), trace.Trace.runfunc() and curses.wrapper().

function in unittest.TestCase.addCleanup().

fn in the submit() method of concurrent.futures.ThreadPoolExecutor and concurrent.futures.ProcessPoolExecutor.

callback in contextlib.ExitStack.callback(), contextlib.AsyncExitStack.callback() and contextlib.AsyncExitStack.push_async_callback().

c and typeid in the create() method of multiprocessing.managers.Server and multiprocessing.managers.SharedMemoryServer.

obj in weakref.finalize().

In future releases of Python, they will be positional-only. (Contributed by Serhiy Storchaka in bpo-36492 [https://bugs.python.org/issue?@action=redirect&bpo=36492].)

API 與功能的移除

The following features and APIs have been removed from Python 3.8:

Starting with Python 3.3, importing ABCs from collections was deprecated, and importing should be done from collections.abc. Being able to import from collections was marked for removal in 3.8, but has been delayed to 3.9. (See gh-81134 [https://github.com/python/cpython/issues/81134].)

The macpath module, deprecated in Python 3.7, has been removed. (Contributed by Victor Stinner in bpo-35471 [https://bugs.python.org/issue?@action=redirect&bpo=35471].)

The function platform.popen() has been removed, after having been deprecated since Python 3.3: use os.popen() instead. (Contributed by Victor Stinner in bpo-35345 [https://bugs.python.org/issue?@action=redirect&bpo=35345].)

The function time.clock() has been removed, after having been deprecated since Python 3.3: use time.perf_counter() or time.process_time() instead, depending on your requirements, to have well-defined behavior. (Contributed by Matthias Bussonnier in bpo-36895 [https://bugs.python.org/issue?@action=redirect&bpo=36895].)

The pyvenv script has been removed in favor of python3.8 -m venv to help eliminate confusion as to what Python interpreter the pyvenv script is tied to. (Contributed by Brett Cannon in bpo-25427 [https://bugs.python.org/issue?@action=redirect&bpo=25427].)

parse_qs, parse_qsl, and escape are removed from the cgi module. They are deprecated in Python 3.2 or older. They should be imported from the urllib.parse and html modules instead.

filemode function is removed from the tarfile module. It is not documented and deprecated since Python 3.3.

The XMLParser constructor no longer accepts the html argument. It never had an effect and was deprecated in Python 3.4. All other parameters are now keyword-only. (Contributed by Serhiy Storchaka in bpo-29209 [https://bugs.python.org/issue?@action=redirect&bpo=29209].)

Removed the doctype() method of XMLParser. (Contributed by Serhiy Storchaka in bpo-29209 [https://bugs.python.org/issue?@action=redirect&bpo=29209].)

"unicode_internal" codec is removed. (Contributed by Inada Naoki in bpo-36297 [https://bugs.python.org/issue?@action=redirect&bpo=36297].)

The Cache and Statement objects of the sqlite3 module are not exposed to the user. (Contributed by Aviv Palivoda in bpo-30262 [https://bugs.python.org/issue?@action=redirect&bpo=30262].)

The bufsize keyword argument of fileinput.input() and fileinput.FileInput() which was ignored and deprecated since Python 3.6 has been removed. bpo-36952 [https://bugs.python.org/issue?@action=redirect&bpo=36952] (Contributed by Matthias Bussonnier.)

The functions sys.set_coroutine_wrapper() and sys.get_coroutine_wrapper() deprecated in Python 3.7 have been removed; bpo-36933 [https://bugs.python.org/issue?@action=redirect&bpo=36933] (Contributed by Matthias Bussonnier.)

移植至 Python 3.8

This section lists previously described changes and other bugfixes that may require changes to your code.

Python 行為的改變

Yield expressions (both yield and yield from clauses) are now disallowed in comprehensions and generator expressions (aside from the iterable expression in the leftmost for clause). (Contributed by Serhiy Storchaka in bpo-10544 [https://bugs.python.org/issue?@action=redirect&bpo=10544].)

The compiler now produces a SyntaxWarning when identity checks (is and is not) are used with certain types of literals (e.g. strings, numbers). These can often work by accident in CPython, but are not guaranteed by the language spec. The warning advises users to use equality tests (== and !=) instead. (Contributed by Serhiy Storchaka in bpo-34850 [https://bugs.python.org/issue?@action=redirect&bpo=34850].)

The CPython interpreter can swallow exceptions in some circumstances. In Python 3.8 this happens in fewer cases. In particular, exceptions raised when getting the attribute from the type dictionary are no longer ignored. (Contributed by Serhiy Storchaka in bpo-35459 [https://bugs.python.org/issue?@action=redirect&bpo=35459].)

Removed __str__ implementations from builtin types bool, int, float, complex and few classes from the standard library. They now inherit __str__() from object. As result, defining the __repr__() method in the subclass of these classes will affect their string representation. (Contributed by Serhiy Storchaka in bpo-36793 [https://bugs.python.org/issue?@action=redirect&bpo=36793].)

On AIX, sys.platform doesn't contain the major version anymore. It is always 'aix', instead of 'aix3' .. 'aix7'. Since older Python versions include the version number, so it is recommended to always use sys.platform.startswith('aix'). (Contributed by M. Felt in bpo-36588 [https://bugs.python.org/issue?@action=redirect&bpo=36588].)

PyEval_AcquireLock() and PyEval_AcquireThread() now terminate the current thread if called while the interpreter is finalizing, making them consistent with PyEval_RestoreThread(), Py_END_ALLOW_THREADS(), and PyGILState_Ensure(). If this behavior is not desired, guard the call by checking _Py_IsFinalizing() or sys.is_finalizing(). (Contributed by Joannah Nanjekye in bpo-36475 [https://bugs.python.org/issue?@action=redirect&bpo=36475].)

Python API 的變更

The os.getcwdb() function now uses the UTF-8 encoding on Windows, rather than the ANSI code page: see PEP 529 [https://peps.python.org/pep-0529/] for the rationale. The function is no longer deprecated on Windows. (Contributed by Victor Stinner in bpo-37412 [https://bugs.python.org/issue?@action=redirect&bpo=37412].)

subprocess.Popen can now use os.posix_spawn() in some cases for better performance. On Windows Subsystem for Linux and QEMU User Emulation, the Popen constructor using os.posix_spawn() no longer raises an exception on errors like "missing program". Instead the child process fails with a non-zero returncode. (Contributed by Joannah Nanjekye and Victor Stinner in bpo-35537 [https://bugs.python.org/issue?@action=redirect&bpo=35537].)

The preexec_fn argument of * subprocess.Popen is no longer compatible with subinterpreters. The use of the parameter in a subinterpreter now raises RuntimeError. (Contributed by Eric Snow in bpo-34651 [https://bugs.python.org/issue?@action=redirect&bpo=34651], modified by Christian Heimes in bpo-37951 [https://bugs.python.org/issue?@action=redirect&bpo=37951].)

The imaplib.IMAP4.logout() method no longer silently ignores arbitrary exceptions. (Contributed by Victor Stinner in bpo-36348 [https://bugs.python.org/issue?@action=redirect&bpo=36348].)

The function platform.popen() has been removed, after having been deprecated since Python 3.3: use os.popen() instead. (Contributed by Victor Stinner in bpo-35345 [https://bugs.python.org/issue?@action=redirect&bpo=35345].)

The statistics.mode() function no longer raises an exception when given multimodal data. Instead, it returns the first mode encountered in the input data. (Contributed by Raymond Hettinger in bpo-35892 [https://bugs.python.org/issue?@action=redirect&bpo=35892].)

The selection() method of the tkinter.ttk.Treeview class no longer takes arguments. Using it with arguments for changing the selection was deprecated in Python 3.6. Use specialized methods like selection_set() for changing the selection. (Contributed by Serhiy Storchaka in bpo-31508 [https://bugs.python.org/issue?@action=redirect&bpo=31508].)

The writexml(), toxml() and toprettyxml() methods of xml.dom.minidom and the write() method of xml.etree.ElementTree now preserve the attribute order specified by the user. (Contributed by Diego Rojas and Raymond Hettinger in bpo-34160 [https://bugs.python.org/issue?@action=redirect&bpo=34160].)

A dbm.dumb database opened with flags 'r' is now read-only. dbm.dumb.open() with flags 'r' and 'w' no longer creates a database if it does not exist. (Contributed by Serhiy Storchaka in bpo-32749 [https://bugs.python.org/issue?@action=redirect&bpo=32749].)

The doctype() method defined in a subclass of XMLParser will no longer be called and will emit a RuntimeWarning instead of a DeprecationWarning. Define the doctype() method on a target for handling an XML doctype declaration. (Contributed by Serhiy Storchaka in bpo-29209 [https://bugs.python.org/issue?@action=redirect&bpo=29209].)

A RuntimeError is now raised when the custom metaclass doesn't provide the __classcell__ entry in the namespace passed to type.__new__. A DeprecationWarning was emitted in Python 3.6--3.7. (Contributed by Serhiy Storchaka in bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722].)

The cProfile.Profile class can now be used as a context manager. (Contributed by Scott Sanderson in bpo-29235 [https://bugs.python.org/issue?@action=redirect&bpo=29235].)

shutil.copyfile(), shutil.copy(), shutil.copy2(), shutil.copytree() and shutil.move() use platform-specific "fast-copy" syscalls (see Platform-dependent efficient copy operations section).

shutil.copyfile() default buffer size on Windows was changed from 16 KiB to 1 MiB.

The PyGC_Head struct has changed completely. All code that touched the struct member should be rewritten. (See bpo-33597 [https://bugs.python.org/issue?@action=redirect&bpo=33597].)

The PyInterpreterState struct has been moved into the "internal" header files (specifically Include/internal/pycore_pystate.h). An opaque PyInterpreterState is still available as part of the public API (and stable ABI). The docs indicate that none of the struct's fields are public, so we hope no one has been using them. However, if you do rely on one or more of those private fields and have no alternative then please open a BPO issue. We'll work on helping you adjust (possibly including adding accessor functions to the public API). (See bpo-35886 [https://bugs.python.org/issue?@action=redirect&bpo=35886].)

The mmap.flush() method now returns None on success and raises an exception on error under all platforms. Previously, its behavior was platform-dependent: a nonzero value was returned on success; zero was returned on error under Windows. A zero value was returned on success; an exception was raised on error under Unix. (Contributed by Berker Peksag in bpo-2122 [https://bugs.python.org/issue?@action=redirect&bpo=2122].)

xml.dom.minidom and xml.sax modules no longer process external entities by default. (Contributed by Christian Heimes in bpo-17239 [https://bugs.python.org/issue?@action=redirect&bpo=17239].)

Deleting a key from a read-only dbm database (dbm.dumb, dbm.gnu or dbm.ndbm) raises error (dbm.dumb.error, dbm.gnu.error or dbm.ndbm.error) instead of KeyError. (Contributed by Xiang Zhang in bpo-33106 [https://bugs.python.org/issue?@action=redirect&bpo=33106].)

Simplified AST for literals. All constants will be represented as ast.Constant instances. Instantiating old classes Num, Str, Bytes, NameConstant and Ellipsis will return an instance of Constant. (Contributed by Serhiy Storchaka in bpo-32892 [https://bugs.python.org/issue?@action=redirect&bpo=32892].)

expanduser() on Windows now prefers the USERPROFILE environment variable and does not use HOME, which is not normally set for regular user accounts. (Contributed by Anthony Sottile in bpo-36264 [https://bugs.python.org/issue?@action=redirect&bpo=36264].)

The exception asyncio.CancelledError now inherits from BaseException rather than Exception and no longer inherits from concurrent.futures.CancelledError. (Contributed by Yury Selivanov in bpo-32528 [https://bugs.python.org/issue?@action=redirect&bpo=32528].)

The function asyncio.wait_for() now correctly waits for cancellation when using an instance of asyncio.Task. Previously, upon reaching timeout, it was cancelled and immediately returned. (Contributed by Elvis Pranskevichus in bpo-32751 [https://bugs.python.org/issue?@action=redirect&bpo=32751].)

The function asyncio.BaseTransport.get_extra_info() now returns a safe to use socket object when 'socket' is passed to the name parameter. (Contributed by Yury Selivanov in bpo-37027 [https://bugs.python.org/issue?@action=redirect&bpo=37027].)

asyncio.BufferedProtocol has graduated to the stable API.

DLL dependencies for extension modules and DLLs loaded with ctypes on Windows are now resolved more securely. Only the system paths, the directory containing the DLL or PYD file, and directories added with add_dll_directory() are searched for load-time dependencies. Specifically, PATH and the current working directory are no longer used, and modifications to these will no longer have any effect on normal DLL resolution. If your application relies on these mechanisms, you should check for add_dll_directory() and if it exists, use it to add your DLLs directory while loading your library. Note that Windows 7 users will need to ensure that Windows Update KB2533623 has been installed (this is also verified by the installer). (Contributed by Steve Dower in bpo-36085 [https://bugs.python.org/issue?@action=redirect&bpo=36085].)

The header files and functions related to pgen have been removed after its replacement by a pure Python implementation. (Contributed by Pablo Galindo in bpo-36623 [https://bugs.python.org/issue?@action=redirect&bpo=36623].)

types.CodeType has a new parameter in the second position of the constructor (posonlyargcount) to support positional-only arguments defined in PEP 570 [https://peps.python.org/pep-0570/]. The first argument (argcount) now represents the total number of positional arguments (including positional-only arguments). The new replace() method of types.CodeType can be used to make the code future-proof.

The parameter digestmod for hmac.new() no longer uses the MD5 digest by default.

C API 中的改動

The PyCompilerFlags structure got a new cf_feature_version field. It should be initialized to PY_MINOR_VERSION. The field is ignored by default, and is used if and only if PyCF_ONLY_AST flag is set in cf_flags. (Contributed by Guido van Rossum in bpo-35766 [https://bugs.python.org/issue?@action=redirect&bpo=35766].)

The PyEval_ReInitThreads() function has been removed from the C API. It should not be called explicitly: use PyOS_AfterFork_Child() instead. (Contributed by Victor Stinner in bpo-36728 [https://bugs.python.org/issue?@action=redirect&bpo=36728].)

On Unix, C extensions are no longer linked to libpython except on Android and Cygwin. When Python is embedded, libpython must not be loaded with RTLD_LOCAL, but RTLD_GLOBAL instead. Previously, using RTLD_LOCAL, it was already not possible to load C extensions which were not linked to libpython, like C extensions of the standard library built by the *shared* section of Modules/Setup. (Contributed by Victor Stinner in bpo-21536 [https://bugs.python.org/issue?@action=redirect&bpo=21536].)

Use of # variants of formats in parsing or building value (e.g. PyArg_ParseTuple(), Py_BuildValue(), PyObject_CallFunction(), etc.) without PY_SSIZE_T_CLEAN defined raises DeprecationWarning now. It will be removed in 3.10 or 4.0. Read 剖析引數與建置數值 for detail. (Contributed by Inada Naoki in bpo-36381 [https://bugs.python.org/issue?@action=redirect&bpo=36381].)

Instances of heap-allocated types (such as those created with PyType_FromSpec()) hold a reference to their type object. Increasing the reference count of these type objects has been moved from PyType_GenericAlloc() to the more low-level functions, PyObject_Init() and PyObject_INIT. This makes types created through PyType_FromSpec() behave like other classes in managed code.

Statically allocated types are not affected.

For the vast majority of cases, there should be no side effect. However, types that manually increase the reference count after allocating an instance (perhaps to work around the bug) may now become immortal. To avoid this, these classes need to call Py_DECREF on the type object during instance deallocation.

To correctly port these types into 3.8, please apply the following changes:

Remove Py_INCREF on the type object after allocating an instance - if any. This may happen after calling PyObject_New, PyObject_NewVar, PyObject_GC_New(), PyObject_GC_NewVar(), or any other custom allocator that uses PyObject_Init() or PyObject_INIT.

範例：

static foo_struct *
foo_new(PyObject *type) {
    foo_struct *foo = PyObject_GC_New(foo_struct, (PyTypeObject *) type);
    if (foo == NULL)
        return NULL;
#if PY_VERSION_HEX < 0x03080000
    // Workaround for Python issue 35810; no longer necessary in Python 3.8
    PY_INCREF(type)
#endif
    return foo;
}

Ensure that all custom tp_dealloc functions of heap-allocated types decrease the type's reference count.

範例：

static void
foo_dealloc(foo_struct *instance) {
    PyObject *type = Py_TYPE(instance);
    PyObject_GC_Del(instance);
#if PY_VERSION_HEX >= 0x03080000
    // This was not needed before Python 3.8 (Python issue 35810)
    Py_DECREF(type);
#endif
}

（由 Eddie Elizondo 在 bpo-35810 [https://bugs.python.org/issue?@action=redirect&bpo=35810] 中貢獻。）

The Py_DEPRECATED() macro has been implemented for MSVC. The macro now must be placed before the symbol name.

範例：

Py_DEPRECATED(3.8) PyAPI_FUNC(int) Py_OldFunction(void);

（由 Zackery Spytz 在 bpo-33407 [https://bugs.python.org/issue?@action=redirect&bpo=33407] 中貢獻。）

The interpreter does not pretend to support binary compatibility of extension types across feature releases, anymore. A PyTypeObject exported by a third-party extension module is supposed to have all the slots expected in the current Python version, including tp_finalize (Py_TPFLAGS_HAVE_FINALIZE is not checked anymore before reading tp_finalize).

（由 Antoine Pitrou 在 bpo-32388 [https://bugs.python.org/issue?@action=redirect&bpo=32388] 中貢獻。）

The functions PyNode_AddChild() and PyParser_AddToken() now accept two additional int arguments end_lineno and end_col_offset.

The libpython38.a file to allow MinGW tools to link directly against python38.dll is no longer included in the regular Windows distribution. If you require this file, it may be generated with the gendef and dlltool tools, which are part of the MinGW binutils package:

gendef - python38.dll > tmp.def
dlltool --dllname python38.dll --def tmp.def --output-lib libpython38.a

The location of an installed pythonXY.dll will depend on the installation options and the version and language of Windows. See 在 Windows 上使用 Python for more information. The resulting library should be placed in the same directory as pythonXY.lib, which is generally the libs directory under your Python installation.

（由 Steve Dower 在 bpo-37351 [https://bugs.python.org/issue?@action=redirect&bpo=37351] 中貢獻。）

CPython 位元組碼變更

The interpreter loop has been simplified by moving the logic of unrolling the stack of blocks into the compiler. The compiler emits now explicit instructions for adjusting the stack of values and calling the cleaning-up code for break, continue and return.

Removed opcodes BREAK_LOOP, CONTINUE_LOOP, SETUP_LOOP and SETUP_EXCEPT. Added new opcodes ROT_FOUR, BEGIN_FINALLY, CALL_FINALLY and POP_FINALLY. Changed the behavior of END_FINALLY and WITH_CLEANUP_START.

（由 Mark Shannon、Antoine Pitrou 和 Serhiy Storchaka 在 bpo-17611 [https://bugs.python.org/issue?@action=redirect&bpo=17611] 中貢獻。）

Added new opcode END_ASYNC_FOR for handling exceptions raised when awaiting a next item in an async for loop. (Contributed by Serhiy Storchaka in bpo-33041 [https://bugs.python.org/issue?@action=redirect&bpo=33041].)

The MAP_ADD now expects the value as the first element in the stack and the key as the second element. This change was made so the key is always evaluated before the value in dictionary comprehensions, as proposed by PEP 572 [https://peps.python.org/pep-0572/]. (Contributed by Jörn Heissler in bpo-35224 [https://bugs.python.org/issue?@action=redirect&bpo=35224].)

Demos and Tools

Added a benchmark script for timing various ways to access variables: Tools/scripts/var_access_benchmark.py. (Contributed by Raymond Hettinger in bpo-35884 [https://bugs.python.org/issue?@action=redirect&bpo=35884].)

Here's a summary of performance improvements since Python 3.3:

Python version                       3.3     3.4     3.5     3.6     3.7     3.8
--------------                       ---     ---     ---     ---     ---     ---

Variable and attribute read access:
    read_local                       4.0     7.1     7.1     5.4     5.1     3.9
    read_nonlocal                    5.3     7.1     8.1     5.8     5.4     4.4
    read_global                     13.3    15.5    19.0    14.3    13.6     7.6
    read_builtin                    20.0    21.1    21.6    18.5    19.0     7.5
    read_classvar_from_class        20.5    25.6    26.5    20.7    19.5    18.4
    read_classvar_from_instance     18.5    22.8    23.5    18.8    17.1    16.4
    read_instancevar                26.8    32.4    33.1    28.0    26.3    25.4
    read_instancevar_slots          23.7    27.8    31.3    20.8    20.8    20.2
    read_namedtuple                 68.5    73.8    57.5    45.0    46.8    18.4
    read_boundmethod                29.8    37.6    37.9    29.6    26.9    27.7

Variable and attribute write access:
    write_local                      4.6     8.7     9.3     5.5     5.3     4.3
    write_nonlocal                   7.3    10.5    11.1     5.6     5.5     4.7
    write_global                    15.9    19.7    21.2    18.0    18.0    15.8
    write_classvar                  81.9    92.9    96.0   104.6   102.1    39.2
    write_instancevar               36.4    44.6    45.8    40.0    38.9    35.5
    write_instancevar_slots         28.7    35.6    36.1    27.3    26.6    25.7

Data structure read access:
    read_list                       19.2    24.2    24.5    20.8    20.8    19.0
    read_deque                      19.9    24.7    25.5    20.2    20.6    19.8
    read_dict                       19.7    24.3    25.7    22.3    23.0    21.0
    read_strdict                    17.9    22.6    24.3    19.5    21.2    18.9

Data structure write access:
    write_list                      21.2    27.1    28.5    22.5    21.6    20.0
    write_deque                     23.8    28.7    30.1    22.7    21.8    23.5
    write_dict                      25.9    31.4    33.3    29.3    29.2    24.7
    write_strdict                   22.9    28.4    29.9    27.5    25.2    23.1

Stack (or queue) operations:
    list_append_pop                144.2    93.4   112.7    75.4    74.2    50.8
    deque_append_pop                30.4    43.5    57.0    49.4    49.2    42.5
    deque_append_popleft            30.8    43.7    57.3    49.7    49.7    42.8

Timing loop:
    loop_overhead                    0.3     0.5     0.6     0.4     0.3     0.3

The benchmarks were measured on an Intel® Core™ i7-4960HQ processor [https://ark.intel.com/content/www/us/en/ark/products/76088/intel-core-i7-4960hq-processor-6m-cache-up-to-3-80-ghz.html] running the macOS 64-bit builds found at python.org [https://www.python.org/downloads/macos/]. The benchmark script displays timings in nanoseconds.

Python 3.8.1 中顯著的變更

Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint() is no longer supported. This is because of the behavior of the socket option SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228 [https://bugs.python.org/issue?@action=redirect&bpo=37228].)

Python 3.8.2 中顯著的變更

Fixed a regression with the ignore callback of shutil.copytree(). The argument types are now str and List[str] again. (Contributed by Manuel Barkhau and Giampaolo Rodola in gh-83571 [https://github.com/python/cpython/issues/83571].)

Python 3.8.3 中顯著的變更

The constant values of future flags in the __future__ module are updated in order to prevent collision with compiler flags. Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing with CO_FUTURE_DIVISION. (Contributed by Batuhan Taskaya in gh-83743 [https://github.com/python/cpython/issues/83743])

Python 3.8.8 中顯著的變更

Earlier Python versions allowed using both ; and & as query parameter separators in urllib.parse.parse_qs() and urllib.parse.parse_qsl(). Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with & as the default. This change also affects cgi.parse() and cgi.parse_multipart() as they use the affected functions internally. For more details, please see their respective documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967].)

Python 3.8.9 中顯著的變更

A security fix alters the ftplib.FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel. We reuse the ftp server IP address instead. For unusual code requiring the old behavior, set a trust_server_pasv_ipv4_address attribute on your FTP instance to True. (See gh-87451 [https://github.com/python/cpython/issues/87451])

Python 3.8.10 中顯著的變更

macOS 11.0 (Big Sur) and Apple Silicon Mac support

As of 3.8.10, Python now supports building and running on macOS 11 (Big Sur) and on Apple Silicon Macs (based on the ARM64 architecture). A new universal build variant, universal2, is now available to natively support both ARM64 and Intel 64 in one set of executables. Note that support for "weaklinking", building binaries targeted for newer versions of macOS that will also run correctly on older versions by testing at runtime for missing features, is not included in this backport from Python 3.9; to support a range of macOS versions, continue to target for and build on the oldest version in the range.

(Originally contributed by Ronald Oussoren and Lawrence D'Anna in gh-85272 [https://github.com/python/cpython/issues/85272], with fixes by FX Coudert and Eli Rykoff, and backported to 3.8 by Maxime Bélanger and Ned Deily)

Python 3.8.10 中顯著的變更

urllib.parse

The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html], ASCII newline \n, \r and tab \t characters are stripped from the URL by the parser in urllib.parse preventing such attacks. The removal characters are controlled by a new module level variable urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (See bpo-43882 [https://bugs.python.org/issue?@action=redirect&bpo=43882])

Python 3.8.12 中顯著的變更

Python API 的變更

Starting with Python 3.8.12 the ipaddress module no longer accepts any leading zeros in IPv4 address strings. Leading zeros are ambiguous and interpreted as octal notation by some libraries. For example the legacy function socket.inet_aton() treats leading zeros as octal notation. glibc implementation of modern inet_pton() does not accept any leading zeros.

(Originally contributed by Christian Heimes in bpo-36384 [https://bugs.python.org/issue?@action=redirect&bpo=36384], and backported to 3.8 by Achraf Merzouki.)

Python 3.8.14 中顯著的安全性功能

Converting between int and str in bases other than 2 (binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity. This is a mitigation for CVE 2020-10735 [https://www.cve.org/CVERecord?id=CVE-2020-10735]. This limit can be configured or disabled by environment variable, command line flag, or sys APIs. See the integer string conversion length limitation documentation. The default limit is 4300 digits in string form.

Python 3.8.17 中顯著的變更

tarfile

The extraction methods in tarfile, and shutil.unpack_archive(), have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See 解壓縮篩選器 for details. In Python 3.12, use without the filter argument will show a DeprecationWarning. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in PEP 706 [https://peps.python.org/pep-0706/].)

Python 3.7 有什麼新功能

編輯者:

Elvis Pranskevichus <elvis@magic.io>

本文介紹了 Python 3.7 與 3.6 相比多了哪些新功能。Python 3.7 已於 2018 年 6 月 27 日發布。有關完整詳細資訊，請參閱 changelog。

發布重點摘要

新增語法特性：

PEP 563, postponed evaluation of type annotations.

Backwards incompatible syntax changes:

async 和 await 現為保留關鍵字。

新的函式庫模組：

contextvars: PEP 567 -- Context Variables

dataclasses: PEP 557 -- Data Classes

importlib.resources

新的內建功能：

PEP 553, the new breakpoint() function.

Python 資料模型改進：

PEP 562, customization of access to module attributes.

PEP 560, core support for typing module and generic types.

the insertion-order preservation nature of dict objects has been declared [https://mail.python.org/pipermail/python-dev/2017-December/151283.html] to be an official part of the Python language spec.

標準函式庫中的顯著改進

The asyncio module has received new features, significant usability and performance improvements.

The time module gained support for functions with nanosecond resolution.

CPython 實作改進：

Avoiding the use of ASCII as a default text encoding:

PEP 538, legacy C locale coercion

PEP 540, forced UTF-8 runtime mode

PEP 552, deterministic .pycs

新版 Python 開發模式

PEP 565, improved DeprecationWarning handling

C API 改進：

PEP 539, new C API for thread-local storage

Documentation improvements:

PEP 545, Python documentation translations

New documentation translations: Japanese [https://docs.python.org/ja/], French [https://docs.python.org/fr/], and Korean [https://docs.python.org/ko/].

This release features notable performance improvements in many areas. The 最佳化 section lists them in detail.

For a list of changes that may affect compatibility with previous Python releases please refer to the 移植至 Python 3.7 section.

新增功能

PEP 563：延後評估註釋

The advent of type hints in Python uncovered two glaring usability issues with the functionality of annotations added in PEP 3107 [https://peps.python.org/pep-3107/] and refined further in PEP 526 [https://peps.python.org/pep-0526/]:

annotations could only use names which were already available in the current scope, in other words they didn't support forward references of any kind; and

annotating source code had adverse effects on startup time of Python programs.

Both of these issues are fixed by postponing the evaluation of annotations. Instead of compiling code which executes expressions in annotations at their definition time, the compiler stores the annotation in a string form equivalent to the AST of the expression in question. If needed, annotations can be resolved at runtime using typing.get_type_hints(). In the common case where this is not required, the annotations are cheaper to store (since short strings are interned by the interpreter) and make startup time faster.

Usability-wise, annotations now support forward references, making the following syntax valid:

class C:
    @classmethod
    def from_string(cls, source: str) -> C:
        ...

    def validate_b(self, obj: B) -> bool:
        ...

class B:
    ...

Since this change breaks compatibility, the new behavior needs to be enabled on a per-module basis in Python 3.7 using a __future__ import:

from __future__ import annotations

這將在 Python 3.10 中成為預設值。

也參考

PEP 563 [https://peps.python.org/pep-0563/] -- Postponed evaluation of annotations

PEP written and implemented by Łukasz Langa.

PEP 538: Legacy C Locale Coercion

An ongoing challenge within the Python 3 series has been determining a sensible default strategy for handling the "7-bit ASCII" text encoding assumption currently implied by the use of the default C or POSIX locale on non-Windows platforms.

PEP 538 [https://peps.python.org/pep-0538/] updates the default interpreter command line interface to automatically coerce that locale to an available UTF-8 based locale as described in the documentation of the new PYTHONCOERCECLOCALE environment variable. Automatically setting LC_CTYPE this way means that both the core interpreter and locale-aware C extensions (such as readline) will assume the use of UTF-8 as the default text encoding, rather than ASCII.

The platform support definition in PEP 11 [https://peps.python.org/pep-0011/] has also been updated to limit full text handling support to suitably configured non-ASCII based locales.

As part of this change, the default error handler for stdin and stdout is now surrogateescape (rather than strict) when using any of the defined coercion target locales (currently C.UTF-8, C.utf8, and UTF-8). The default error handler for stderr continues to be backslashreplace, regardless of locale.

Locale coercion is silent by default, but to assist in debugging potentially locale related integration problems, explicit warnings (emitted directly on stderr) can be requested by setting PYTHONCOERCECLOCALE=warn. This setting will also cause the Python runtime to emit a warning if the legacy C locale remains active when the core interpreter is initialized.

While PEP 538 [https://peps.python.org/pep-0538/]'s locale coercion has the benefit of also affecting extension modules (such as GNU readline), as well as child processes (including those running non-Python applications and older versions of Python), it has the downside of requiring that a suitable target locale be present on the running system. To better handle the case where no suitable target locale is available (as occurs on RHEL/CentOS 7, for example), Python 3.7 also implements PEP 540: Forced UTF-8 Runtime Mode.

也參考

PEP 538 [https://peps.python.org/pep-0538/] -- Coercing the legacy C locale to a UTF-8 based locale

由 Nick Coghlan 撰寫 PEP 與實作。

PEP 540: Forced UTF-8 Runtime Mode

The new -X utf8 command line option and PYTHONUTF8 environment variable can be used to enable the Python UTF-8 Mode.

When in UTF-8 mode, CPython ignores the locale settings, and uses the UTF-8 encoding by default. The error handlers for sys.stdin and sys.stdout streams are set to surrogateescape.

The forced UTF-8 mode can be used to change the text handling behavior in an embedded Python interpreter without changing the locale settings of an embedding application.

While PEP 540 [https://peps.python.org/pep-0540/]'s UTF-8 mode has the benefit of working regardless of which locales are available on the running system, it has the downside of having no effect on extension modules (such as GNU readline), child processes running non-Python applications, and child processes running older versions of Python. To reduce the risk of corrupting text data when communicating with such components, Python 3.7 also implements PEP 540: Forced UTF-8 Runtime Mode).

The UTF-8 mode is enabled by default when the locale is C or POSIX, and the PEP 538 [https://peps.python.org/pep-0538/] locale coercion feature fails to change it to a UTF-8 based alternative (whether that failure is due to PYTHONCOERCECLOCALE=0 being set, LC_ALL being set, or the lack of a suitable target locale).

也參考

PEP 540 [https://peps.python.org/pep-0540/] -- 新增 UTF-8 模式

由 Victor Stinner 撰寫 PEP 與實作

PEP 553：內建的 breakpoint()

Python 3.7 includes the new built-in breakpoint() function as an easy and consistent way to enter the Python debugger.

Built-in breakpoint() calls sys.breakpointhook(). By default, the latter imports pdb and then calls pdb.set_trace(), but by binding sys.breakpointhook() to the function of your choosing, breakpoint() can enter any debugger. Additionally, the environment variable PYTHONBREAKPOINT can be set to the callable of your debugger of choice. Set PYTHONBREAKPOINT=0 to completely disable built-in breakpoint().

也參考

PEP 553 [https://peps.python.org/pep-0553/] -- 內建的 breakpoint()

由 Barry Warsaw 撰寫 PEP 與實作

PEP 539: New C API for Thread-Local Storage

While Python provides a C API for thread-local storage support; the existing Thread Local Storage (TLS) API has used int to represent TLS keys across all platforms. This has not generally been a problem for officially support platforms, but that is neither POSIX-compliant, nor portable in any practical sense.

PEP 539 [https://peps.python.org/pep-0539/] changes this by providing a new Thread Specific Storage (TSS) API to CPython which supersedes use of the existing TLS API within the CPython interpreter, while deprecating the existing API. The TSS API uses a new type Py_tss_t instead of int to represent TSS keys--an opaque type the definition of which may depend on the underlying TLS implementation. Therefore, this will allow to build CPython on platforms where the native TLS key is defined in a way that cannot be safely cast to int.

Note that on platforms where the native TLS key is defined in a way that cannot be safely cast to int, all functions of the existing TLS API will be no-op and immediately return failure. This indicates clearly that the old API is not supported on platforms where it cannot be used reliably, and that no effort will be made to add such support.

也參考

PEP 539 [https://peps.python.org/pep-0539/] -- A New C-API for Thread-Local Storage in CPython

PEP 由 Erik M. Bray 撰寫；由 Masayuki Yamamoto 實作。

PEP 562: Customization of Access to Module Attributes

Python 3.7 allows defining __getattr__() on modules and will call it whenever a module attribute is otherwise not found. Defining __dir__() on modules is now also allowed.

A typical example of where this may be useful is module attribute deprecation and lazy loading.

也參考

PEP 562 [https://peps.python.org/pep-0562/] -- __getattr__ 與 __dir__ 模組

由 Ivan Levkivskyi 撰寫 PEP 與實作

PEP 564: New Time Functions With Nanosecond Resolution

The resolution of clocks in modern systems can exceed the limited precision of a floating-point number returned by the time.time() function and its variants. To avoid loss of precision, PEP 564 [https://peps.python.org/pep-0564/] adds six new "nanosecond" variants of the existing timer functions to the time module:

time.clock_gettime_ns()

time.clock_settime_ns()

time.monotonic_ns()

time.perf_counter_ns()

time.process_time_ns()

time.time_ns()

The new functions return the number of nanoseconds as an integer value.

Measurements [https://peps.python.org/pep-0564/#annex-clocks-resolution-in-python] show that on Linux and Windows the resolution of time.time_ns() is approximately 3 times better than that of time.time().

也參考

PEP 564 [https://peps.python.org/pep-0564/] -- Add new time functions with nanosecond resolution

由 Victor Stinner 撰寫 PEP 與實作

PEP 565：在 __main__ 中顯示 DeprecationWarning

The default handling of DeprecationWarning has been changed such that these warnings are once more shown by default, but only when the code triggering them is running directly in the __main__ module. As a result, developers of single file scripts and those using Python interactively should once again start seeing deprecation warnings for the APIs they use, but deprecation warnings triggered by imported application, library and framework modules will continue to be hidden by default.

As a result of this change, the standard library now allows developers to choose between three different deprecation warning behaviours:

FutureWarning: always displayed by default, recommended for warnings intended to be seen by application end users (e.g. for deprecated application configuration settings).

DeprecationWarning: displayed by default only in __main__ and when running tests, recommended for warnings intended to be seen by other Python developers where a version upgrade may result in changed behaviour or an error.

PendingDeprecationWarning: displayed by default only when running tests, intended for cases where a future version upgrade will change the warning category to DeprecationWarning or FutureWarning.

Previously both DeprecationWarning and PendingDeprecationWarning were only visible when running tests, which meant that developers primarily writing single file scripts or using Python interactively could be surprised by breaking changes in the APIs they used.

也參考

PEP 565 [https://peps.python.org/pep-0565/] -- 在 __main__ 中顯示 DeprecationWarning

由 Nick Coghlan 撰寫 PEP 與實作

PEP 560：對 typing 模組與泛用型別的核心支援

Initially PEP 484 [https://peps.python.org/pep-0484/] was designed in such way that it would not introduce any changes to the core CPython interpreter. Now type hints and the typing module are extensively used by the community, so this restriction is removed. The PEP introduces two special methods __class_getitem__() and __mro_entries__(), these methods are now used by most classes and special constructs in typing. As a result, the speed of various operations with types increased up to 7 times, the generic types can be used without metaclass conflicts, and several long standing bugs in typing module are fixed.

也參考

PEP 560 [https://peps.python.org/pep-0560/] -- 對 typing 模組與泛用型別的核心支援

由 Ivan Levkivskyi 撰寫 PEP 與實作

PEP 552：基於雜湊值的 .pyc 檔案

Python has traditionally checked the up-to-dateness of bytecode cache files (i.e., .pyc files) by comparing the source metadata (last-modified timestamp and size) with source metadata saved in the cache file header when it was generated. While effective, this invalidation method has its drawbacks. When filesystem timestamps are too coarse, Python can miss source updates, leading to user confusion. Additionally, having a timestamp in the cache file is problematic for build reproducibility [https://reproducible-builds.org/] and content-based build systems.

PEP 552 [https://peps.python.org/pep-0552/] extends the pyc format to allow the hash of the source file to be used for invalidation instead of the source timestamp. Such .pyc files are called "hash-based". By default, Python still uses timestamp-based invalidation and does not generate hash-based .pyc files at runtime. Hash-based .pyc files may be generated with py_compile or compileall.

Hash-based .pyc files come in two variants: checked and unchecked. Python validates checked hash-based .pyc files against the corresponding source files at runtime but doesn't do so for unchecked hash-based pycs. Unchecked hash-based .pyc files are a useful performance optimization for environments where a system external to Python (e.g., the build system) is responsible for keeping .pyc files up-to-date.

更多資訊請見 Cached bytecode invalidation。

也參考

PEP 552 [https://peps.python.org/pep-0552/] -- Deterministic pycs

由 Benjamin Peterson 撰寫 PEP 與實作

PEP 545：Python 文件翻譯

PEP 545 [https://peps.python.org/pep-0545/] 描述了建立與維護 Python 文件翻譯的流程。

新增了三種翻譯：

日文：https://docs.python.org/ja/

法文：https://docs.python.org/fr/

韓文：https://docs.python.org/ko/

也參考

PEP 545 [https://peps.python.org/pep-0545/] -- Python 文件翻譯

PEP 由 Julien Palard、Inada Naoki 與 Victor Stinner 撰寫。

Python 開發模式（-X dev）

The new -X dev command line option or the new PYTHONDEVMODE environment variable can be used to enable Python Development Mode. When in development mode, Python performs additional runtime checks that are too expensive to be enabled by default. See Python Development Mode documentation for the full description.

其他語言更動

An await expression and comprehensions containing an async for clause were illegal in the expressions in formatted string literals due to a problem with the implementation. In Python 3.7 this restriction was lifted.

More than 255 arguments can now be passed to a function, and a function can now have more than 255 parameters. (Contributed by Serhiy Storchaka in bpo-12844 [https://bugs.python.org/issue?@action=redirect&bpo=12844] and bpo-18896 [https://bugs.python.org/issue?@action=redirect&bpo=18896].)

bytes.fromhex() and bytearray.fromhex() now ignore all ASCII whitespace, not only spaces. (Contributed by Robert Xiao in bpo-28927 [https://bugs.python.org/issue?@action=redirect&bpo=28927].)

str, bytes, and bytearray gained support for the new isascii() method, which can be used to test if a string or bytes contain only the ASCII characters. (Contributed by INADA Naoki in bpo-32677 [https://bugs.python.org/issue?@action=redirect&bpo=32677].)

ImportError now displays module name and module __file__ path when from ... import ... fails. (Contributed by Matthias Bussonnier in bpo-29546 [https://bugs.python.org/issue?@action=redirect&bpo=29546].)

Circular imports involving absolute imports with binding a submodule to a name are now supported. (Contributed by Serhiy Storchaka in bpo-30024 [https://bugs.python.org/issue?@action=redirect&bpo=30024].)

object.__format__(x, '') is now equivalent to str(x) rather than format(str(self), ''). (Contributed by Serhiy Storchaka in bpo-28974 [https://bugs.python.org/issue?@action=redirect&bpo=28974].)

In order to better support dynamic creation of stack traces, types.TracebackType can now be instantiated from Python code, and the tb_next attribute on tracebacks is now writable. (Contributed by Nathaniel J. Smith in bpo-30579 [https://bugs.python.org/issue?@action=redirect&bpo=30579].)

When using the -m switch, sys.path[0] is now eagerly expanded to the full starting directory path, rather than being left as the empty directory (which allows imports from the current working directory at the time when an import occurs) (Contributed by Nick Coghlan in bpo-33053 [https://bugs.python.org/issue?@action=redirect&bpo=33053].)

The new -X importtime option or the PYTHONPROFILEIMPORTTIME environment variable can be used to show the timing of each module import. (Contributed by Inada Naoki in bpo-31415 [https://bugs.python.org/issue?@action=redirect&bpo=31415].)

新模組

contextvars

The new contextvars module and a set of new C APIs introduce support for context variables. Context variables are conceptually similar to thread-local variables. Unlike TLS, context variables support asynchronous code correctly.

The asyncio and decimal modules have been updated to use and support context variables out of the box. Particularly the active decimal context is now stored in a context variable, which allows decimal operations to work with the correct context in asynchronous code.

也參考

PEP 567 [https://peps.python.org/pep-0567/] -- 情境變數

由 Yury Selivanov 撰寫 PEP 與實作

dataclasses

The new dataclass() decorator provides a way to declare data classes. A data class describes its attributes using class variable annotations. Its constructor and other magic methods, such as __repr__(), __eq__(), and __hash__() are generated automatically.

範例：

@dataclass
class Point:
    x: float
    y: float
    z: float = 0.0

p = Point(1.5, 2.5)
print(p)   # produces "Point(x=1.5, y=2.5, z=0.0)"

也參考

PEP 557 [https://peps.python.org/pep-0557/] -- Data Classes

由 Eric V. Smith 撰寫 PEP 與實作

importlib.resources

The new importlib.resources module provides several new APIs and one new ABC for access to, opening, and reading resources inside packages. Resources are roughly similar to files inside packages, but they needn't be actual files on the physical file system. Module loaders can provide a get_resource_reader() function which returns a importlib.abc.ResourceReader instance to support this new API. Built-in file path loaders and zip file loaders both support this.

由 Barry Warsaw 與 Brett Cannon 在 bpo-32248 [https://bugs.python.org/issue?@action=redirect&bpo=32248] 中貢獻。

也參考

importlib_resources [https://importlib-resources.readthedocs.io/en/latest/] -- a PyPI backport for earlier Python versions.

改進的模組

argparse

The new ArgumentParser.parse_intermixed_args() method allows intermixing options and positional arguments. (Contributed by paul.j3 in bpo-14191 [https://bugs.python.org/issue?@action=redirect&bpo=14191].)

asyncio

The asyncio module has received many new features, usability and performance improvements. Notable changes include:

The new provisional asyncio.run() function can be used to run a coroutine from synchronous code by automatically creating and destroying the event loop. (Contributed by Yury Selivanov in bpo-32314 [https://bugs.python.org/issue?@action=redirect&bpo=32314].)

asyncio gained support for contextvars. loop.call_soon(), loop.call_soon_threadsafe(), loop.call_later(), loop.call_at(), and Future.add_done_callback() have a new optional keyword-only context parameter. Tasks now track their context automatically. See PEP 567 [https://peps.python.org/pep-0567/] for more details. (Contributed by Yury Selivanov in bpo-32436 [https://bugs.python.org/issue?@action=redirect&bpo=32436].)

The new asyncio.create_task() function has been added as a shortcut to asyncio.get_event_loop().create_task(). (Contributed by Andrew Svetlov in bpo-32311 [https://bugs.python.org/issue?@action=redirect&bpo=32311].)

The new loop.start_tls() method can be used to upgrade an existing connection to TLS. (Contributed by Yury Selivanov in bpo-23749 [https://bugs.python.org/issue?@action=redirect&bpo=23749].)

The new loop.sock_recv_into() method allows reading data from a socket directly into a provided buffer making it possible to reduce data copies. (Contributed by Antoine Pitrou in bpo-31819 [https://bugs.python.org/issue?@action=redirect&bpo=31819].)

The new asyncio.current_task() function returns the currently running Task instance, and the new asyncio.all_tasks() function returns a set of all existing Task instances in a given loop. The Task.current_task() and Task.all_tasks() methods have been deprecated. (Contributed by Andrew Svetlov in bpo-32250 [https://bugs.python.org/issue?@action=redirect&bpo=32250].)

The new provisional BufferedProtocol class allows implementing streaming protocols with manual control over the receive buffer. (Contributed by Yury Selivanov in bpo-32251 [https://bugs.python.org/issue?@action=redirect&bpo=32251].)

The new asyncio.get_running_loop() function returns the currently running loop, and raises a RuntimeError if no loop is running. This is in contrast with asyncio.get_event_loop(), which will create a new event loop if none is running. (Contributed by Yury Selivanov in bpo-32269 [https://bugs.python.org/issue?@action=redirect&bpo=32269].)

The new StreamWriter.wait_closed() coroutine method allows waiting until the stream writer is closed. The new StreamWriter.is_closing() method can be used to determine if the writer is closing. (Contributed by Andrew Svetlov in bpo-32391 [https://bugs.python.org/issue?@action=redirect&bpo=32391].)

The new loop.sock_sendfile() coroutine method allows sending files using os.sendfile when possible. (Contributed by Andrew Svetlov in bpo-32410 [https://bugs.python.org/issue?@action=redirect&bpo=32410].)

The new Future.get_loop() and Task.get_loop() methods return the instance of the loop on which a task or a future were created. Server.get_loop() allows doing the same for asyncio.Server objects. (Contributed by Yury Selivanov in bpo-32415 [https://bugs.python.org/issue?@action=redirect&bpo=32415] and Srinivas Reddy Thatiparthy in bpo-32418 [https://bugs.python.org/issue?@action=redirect&bpo=32418].)

It is now possible to control how instances of asyncio.Server begin serving. Previously, the server would start serving immediately when created. The new start_serving keyword argument to loop.create_server() and loop.create_unix_server(), as well as Server.start_serving(), and Server.serve_forever() can be used to decouple server instantiation and serving. The new Server.is_serving() method returns True if the server is serving. Server objects are now asynchronous context managers:

srv = await loop.create_server(...)

async with srv:
    # some code

# At this point, srv is closed and no longer accepts new connections.

（由 Yury Selivanov 在 bpo-32662 [https://bugs.python.org/issue?@action=redirect&bpo=32662] 中貢獻。）

Callback objects returned by loop.call_later() gained the new when() method which returns an absolute scheduled callback timestamp. (Contributed by Andrew Svetlov in bpo-32741 [https://bugs.python.org/issue?@action=redirect&bpo=32741].)

The loop.create_datagram_endpoint() method gained support for Unix sockets. (Contributed by Quentin Dawans in bpo-31245 [https://bugs.python.org/issue?@action=redirect&bpo=31245].)

The asyncio.open_connection(), asyncio.start_server() functions, loop.create_connection(), loop.create_server(), loop.create_accepted_socket() methods and their corresponding UNIX socket variants now accept the ssl_handshake_timeout keyword argument. (Contributed by Neil Aspinall in bpo-29970 [https://bugs.python.org/issue?@action=redirect&bpo=29970].)

The new Handle.cancelled() method returns True if the callback was cancelled. (Contributed by Marat Sharafutdinov in bpo-31943 [https://bugs.python.org/issue?@action=redirect&bpo=31943].)

The asyncio source has been converted to use the async/await syntax. (Contributed by Andrew Svetlov in bpo-32193 [https://bugs.python.org/issue?@action=redirect&bpo=32193].)

The new ReadTransport.is_reading() method can be used to determine the reading state of the transport. Additionally, calls to ReadTransport.resume_reading() and ReadTransport.pause_reading() are now idempotent. (Contributed by Yury Selivanov in bpo-32356 [https://bugs.python.org/issue?@action=redirect&bpo=32356].)

Loop methods which accept socket paths now support passing path-like objects. (Contributed by Yury Selivanov in bpo-32066 [https://bugs.python.org/issue?@action=redirect&bpo=32066].)

In asyncio TCP sockets on Linux are now created with TCP_NODELAY flag set by default. (Contributed by Yury Selivanov and Victor Stinner in bpo-27456 [https://bugs.python.org/issue?@action=redirect&bpo=27456].)

Exceptions occurring in cancelled tasks are no longer logged. (Contributed by Yury Selivanov in bpo-30508 [https://bugs.python.org/issue?@action=redirect&bpo=30508].)

New WindowsSelectorEventLoopPolicy and WindowsProactorEventLoopPolicy classes. (Contributed by Yury Selivanov in bpo-33792 [https://bugs.python.org/issue?@action=redirect&bpo=33792].)

Several asyncio APIs have been deprecated.

binascii

The b2a_uu() function now accepts an optional backtick keyword argument. When it's true, zeros are represented by '`' instead of spaces. (Contributed by Xiang Zhang in bpo-30103 [https://bugs.python.org/issue?@action=redirect&bpo=30103].)

calendar

The HTMLCalendar class has new class attributes which ease the customization of CSS classes in the produced HTML calendar. (Contributed by Oz Tiram in bpo-30095 [https://bugs.python.org/issue?@action=redirect&bpo=30095].)

collections

collections.namedtuple() now supports default values. (Contributed by Raymond Hettinger in bpo-32320 [https://bugs.python.org/issue?@action=redirect&bpo=32320].)

compileall

compileall.compile_dir() learned the new invalidation_mode parameter, which can be used to enable hash-based .pyc invalidation. The invalidation mode can also be specified on the command line using the new --invalidation-mode argument. (Contributed by Benjamin Peterson in bpo-31650 [https://bugs.python.org/issue?@action=redirect&bpo=31650].)

concurrent.futures

ProcessPoolExecutor and ThreadPoolExecutor now support the new initializer and initargs constructor arguments. (Contributed by Antoine Pitrou in bpo-21423 [https://bugs.python.org/issue?@action=redirect&bpo=21423].)

The ProcessPoolExecutor can now take the multiprocessing context via the new mp_context argument. (Contributed by Thomas Moreau in bpo-31540 [https://bugs.python.org/issue?@action=redirect&bpo=31540].)

contextlib

The new nullcontext() is a simpler and faster no-op context manager than ExitStack. (Contributed by Jesse-Bakker in bpo-10049 [https://bugs.python.org/issue?@action=redirect&bpo=10049].)

The new asynccontextmanager(), AbstractAsyncContextManager, and AsyncExitStack have been added to complement their synchronous counterparts. (Contributed by Jelle Zijlstra in bpo-29679 [https://bugs.python.org/issue?@action=redirect&bpo=29679] and bpo-30241 [https://bugs.python.org/issue?@action=redirect&bpo=30241], and by Alexander Mohr and Ilya Kulakov in bpo-29302 [https://bugs.python.org/issue?@action=redirect&bpo=29302].)

cProfile

The cProfile command line now accepts -m module_name as an alternative to script path. (Contributed by Sanyam Khurana in bpo-21862 [https://bugs.python.org/issue?@action=redirect&bpo=21862].)

crypt

The crypt module now supports the Blowfish hashing method. (Contributed by Serhiy Storchaka in bpo-31664 [https://bugs.python.org/issue?@action=redirect&bpo=31664].)

The mksalt() function now allows specifying the number of rounds for hashing. (Contributed by Serhiy Storchaka in bpo-31702 [https://bugs.python.org/issue?@action=redirect&bpo=31702].)

datetime

The new datetime.fromisoformat() method constructs a datetime object from a string in one of the formats output by datetime.isoformat(). (Contributed by Paul Ganssle in bpo-15873 [https://bugs.python.org/issue?@action=redirect&bpo=15873].)

The tzinfo class now supports sub-minute offsets. (Contributed by Alexander Belopolsky in bpo-5288 [https://bugs.python.org/issue?@action=redirect&bpo=5288].)

dbm

dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.

decimal

The decimal module now uses context variables to store the decimal context. (Contributed by Yury Selivanov in bpo-32630 [https://bugs.python.org/issue?@action=redirect&bpo=32630].)

dis

The dis() function is now able to disassemble nested code objects (the code of comprehensions, generator expressions and nested functions, and the code used for building nested classes). The maximum depth of disassembly recursion is controlled by the new depth parameter. (Contributed by Serhiy Storchaka in bpo-11822 [https://bugs.python.org/issue?@action=redirect&bpo=11822].)

distutils

README.rst is now included in the list of distutils standard READMEs and therefore included in source distributions. (Contributed by Ryan Gonzalez in bpo-11913 [https://bugs.python.org/issue?@action=redirect&bpo=11913].)

enum

The Enum learned the new _ignore_ class property, which allows listing the names of properties which should not become enum members. (Contributed by Ethan Furman in bpo-31801 [https://bugs.python.org/issue?@action=redirect&bpo=31801].)

In Python 3.8, attempting to check for non-Enum objects in Enum classes will raise a TypeError (e.g. 1 in Color); similarly, attempting to check for non-Flag objects in a Flag member will raise TypeError (e.g. 1 in Perm.RW); currently, both operations return False instead and are deprecated. (Contributed by Ethan Furman in bpo-33217 [https://bugs.python.org/issue?@action=redirect&bpo=33217].)

functools

functools.singledispatch() now supports registering implementations using type annotations. (Contributed by Łukasz Langa in bpo-32227 [https://bugs.python.org/issue?@action=redirect&bpo=32227].)

gc

The new gc.freeze() function allows freezing all objects tracked by the garbage collector and excluding them from future collections. This can be used before a POSIX fork() call to make the GC copy-on-write friendly or to speed up collection. The new gc.unfreeze() functions reverses this operation. Additionally, gc.get_freeze_count() can be used to obtain the number of frozen objects. (Contributed by Li Zekun in bpo-31558 [https://bugs.python.org/issue?@action=redirect&bpo=31558].)

hmac

The hmac module now has an optimized one-shot digest() function, which is up to three times faster than HMAC(). (Contributed by Christian Heimes in bpo-32433 [https://bugs.python.org/issue?@action=redirect&bpo=32433].)

http.client

HTTPConnection and HTTPSConnection now support the new blocksize argument for improved upload throughput. (Contributed by Nir Soffer in bpo-31945 [https://bugs.python.org/issue?@action=redirect&bpo=31945].)

http.server

SimpleHTTPRequestHandler now supports the HTTP If-Modified-Since header. The server returns the 304 response status if the target file was not modified after the time specified in the header. (Contributed by Pierre Quentel in bpo-29654 [https://bugs.python.org/issue?@action=redirect&bpo=29654].)

SimpleHTTPRequestHandler accepts the new directory argument, in addition to the new --directory command line argument. With this parameter, the server serves the specified directory, by default it uses the current working directory. (Contributed by Stéphane Wirtel and Julien Palard in bpo-28707 [https://bugs.python.org/issue?@action=redirect&bpo=28707].)

The new ThreadingHTTPServer class uses threads to handle requests using ThreadingMixIn. It is used when http.server is run with -m. (Contributed by Julien Palard in bpo-31639 [https://bugs.python.org/issue?@action=redirect&bpo=31639].)

idlelib 與 IDLE

Multiple fixes for autocompletion. (Contributed by Louie Lu in bpo-15786 [https://bugs.python.org/issue?@action=redirect&bpo=15786].)

Module Browser (on the File menu, formerly called Class Browser), now displays nested functions and classes in addition to top-level functions and classes. (Contributed by Guilherme Polo, Cheryl Sabella, and Terry Jan Reedy in bpo-1612262 [https://bugs.python.org/issue?@action=redirect&bpo=1612262].)

The Settings dialog (Options, Configure IDLE) has been partly rewritten to improve both appearance and function. (Contributed by Cheryl Sabella and Terry Jan Reedy in multiple issues.)

The font sample now includes a selection of non-Latin characters so that users can better see the effect of selecting a particular font. (Contributed by Terry Jan Reedy in bpo-13802 [https://bugs.python.org/issue?@action=redirect&bpo=13802].) The sample can be edited to include other characters. (Contributed by Serhiy Storchaka in bpo-31860 [https://bugs.python.org/issue?@action=redirect&bpo=31860].)

The IDLE features formerly implemented as extensions have been reimplemented as normal features. Their settings have been moved from the Extensions tab to other dialog tabs. (Contributed by Charles Wohlganger and Terry Jan Reedy in bpo-27099 [https://bugs.python.org/issue?@action=redirect&bpo=27099].)

Editor code context option revised. Box displays all context lines up to maxlines. Clicking on a context line jumps the editor to that line. Context colors for custom themes is added to Highlights tab of Settings dialog. (Contributed by Cheryl Sabella and Terry Jan Reedy in bpo-33642 [https://bugs.python.org/issue?@action=redirect&bpo=33642], bpo-33768 [https://bugs.python.org/issue?@action=redirect&bpo=33768], and bpo-33679 [https://bugs.python.org/issue?@action=redirect&bpo=33679].)

On Windows, a new API call tells Windows that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect. (Contributed by Terry Jan Reedy in bpo-33656 [https://bugs.python.org/issue?@action=redirect&bpo=33656].)

New in 3.7.1:

Output over N lines (50 by default) is squeezed down to a button. N can be changed in the PyShell section of the General page of the Settings dialog. Fewer, but possibly extra long, lines can be squeezed by right clicking on the output. Squeezed output can be expanded in place by double-clicking the button or into the clipboard or a separate window by right-clicking the button. (Contributed by Tal Einat in bpo-1529353 [https://bugs.python.org/issue?@action=redirect&bpo=1529353].)

The changes above have been backported to 3.6 maintenance releases.

NEW in 3.7.4:

Add "Run Customized" to the Run menu to run a module with customized settings. Any command line arguments entered are added to sys.argv. They re-appear in the box for the next customized run. One can also suppress the normal Shell main module restart. (Contributed by Cheryl Sabella, Terry Jan Reedy, and others in bpo-5680 [https://bugs.python.org/issue?@action=redirect&bpo=5680] and bpo-37627 [https://bugs.python.org/issue?@action=redirect&bpo=37627].)

New in 3.7.5:

Add optional line numbers for IDLE editor windows. Windows open without line numbers unless set otherwise in the General tab of the configuration dialog. Line numbers for an existing window are shown and hidden in the Options menu. (Contributed by Tal Einat and Saimadhav Heblikar in bpo-17535 [https://bugs.python.org/issue?@action=redirect&bpo=17535].)

importlib

The importlib.abc.ResourceReader ABC was introduced to support the loading of resources from packages. See also importlib.resources. (Contributed by Barry Warsaw, Brett Cannon in bpo-32248 [https://bugs.python.org/issue?@action=redirect&bpo=32248].)

importlib.reload() now raises ModuleNotFoundError if the module lacks a spec. (Contributed by Garvit Khatri in bpo-29851 [https://bugs.python.org/issue?@action=redirect&bpo=29851].)

importlib.util.find_spec() now raises ModuleNotFoundError instead of AttributeError if the specified parent module is not a package (i.e. lacks a __path__ attribute). (Contributed by Milan Oberkirch in bpo-30436 [https://bugs.python.org/issue?@action=redirect&bpo=30436].)

The new importlib.util.source_hash() can be used to compute the hash of the passed source. A hash-based .pyc file embeds the value returned by this function.

io

The new TextIOWrapper.reconfigure() method can be used to reconfigure the text stream with the new settings. (Contributed by Antoine Pitrou in bpo-30526 [https://bugs.python.org/issue?@action=redirect&bpo=30526] and INADA Naoki in bpo-15216 [https://bugs.python.org/issue?@action=redirect&bpo=15216].)

ipaddress

The new subnet_of() and supernet_of() methods of ipaddress.IPv6Network and ipaddress.IPv4Network can be used for network containment tests. (Contributed by Michel Albert and Cheryl Sabella in bpo-20825 [https://bugs.python.org/issue?@action=redirect&bpo=20825].)

itertools

itertools.islice() now accepts integer-like objects as start, stop, and slice arguments. (Contributed by Will Roberts in bpo-30537 [https://bugs.python.org/issue?@action=redirect&bpo=30537].)

locale

The new monetary argument to locale.format_string() can be used to make the conversion use monetary thousands separators and grouping strings. (Contributed by Garvit in bpo-10379 [https://bugs.python.org/issue?@action=redirect&bpo=10379].)

The locale.getpreferredencoding() function now always returns 'UTF-8' on Android or when in the forced UTF-8 mode.

logging

Logger instances can now be pickled. (Contributed by Vinay Sajip in bpo-30520 [https://bugs.python.org/issue?@action=redirect&bpo=30520].)

The new StreamHandler.setStream() method can be used to replace the logger stream after handler creation. (Contributed by Vinay Sajip in bpo-30522 [https://bugs.python.org/issue?@action=redirect&bpo=30522].)

It is now possible to specify keyword arguments to handler constructors in configuration passed to logging.config.fileConfig(). (Contributed by Preston Landers in bpo-31080 [https://bugs.python.org/issue?@action=redirect&bpo=31080].)

math

The new math.remainder() function implements the IEEE 754-style remainder operation. (Contributed by Mark Dickinson in bpo-29962 [https://bugs.python.org/issue?@action=redirect&bpo=29962].)

mimetypes

The MIME type of .bmp has been changed from 'image/x-ms-bmp' to 'image/bmp'. (Contributed by Nitish Chandra in bpo-22589 [https://bugs.python.org/issue?@action=redirect&bpo=22589].)

msilib

The new Database.Close() method can be used to close the MSI database. (Contributed by Berker Peksag in bpo-20486 [https://bugs.python.org/issue?@action=redirect&bpo=20486].)

multiprocessing

The new Process.close() method explicitly closes the process object and releases all resources associated with it. ValueError is raised if the underlying process is still running. (Contributed by Antoine Pitrou in bpo-30596 [https://bugs.python.org/issue?@action=redirect&bpo=30596].)

The new Process.kill() method can be used to terminate the process using the SIGKILL signal on Unix. (Contributed by Vitor Pereira in bpo-30794 [https://bugs.python.org/issue?@action=redirect&bpo=30794].)

Non-daemonic threads created by Process are now joined on process exit. (Contributed by Antoine Pitrou in bpo-18966 [https://bugs.python.org/issue?@action=redirect&bpo=18966].)

os

os.fwalk() now accepts the path argument as bytes. (Contributed by Serhiy Storchaka in bpo-28682 [https://bugs.python.org/issue?@action=redirect&bpo=28682].)

os.scandir() gained support for file descriptors. (Contributed by Serhiy Storchaka in bpo-25996 [https://bugs.python.org/issue?@action=redirect&bpo=25996].)

The new register_at_fork() function allows registering Python callbacks to be executed at process fork. (Contributed by Antoine Pitrou in bpo-16500 [https://bugs.python.org/issue?@action=redirect&bpo=16500].)

Added os.preadv() (combine the functionality of os.readv() and os.pread()) and os.pwritev() functions (combine the functionality of os.writev() and os.pwrite()). (Contributed by Pablo Galindo in bpo-31368 [https://bugs.python.org/issue?@action=redirect&bpo=31368].)

The mode argument of os.makedirs() no longer affects the file permission bits of newly created intermediate-level directories. (Contributed by Serhiy Storchaka in bpo-19930 [https://bugs.python.org/issue?@action=redirect&bpo=19930].)

os.dup2() now returns the new file descriptor. Previously, None was always returned. (Contributed by Benjamin Peterson in bpo-32441 [https://bugs.python.org/issue?@action=redirect&bpo=32441].)

The structure returned by os.stat() now contains the st_fstype attribute on Solaris and its derivatives. (Contributed by Jesús Cea Avión in bpo-32659 [https://bugs.python.org/issue?@action=redirect&bpo=32659].)

pathlib

The new Path.is_mount() method is now available on POSIX systems and can be used to determine whether a path is a mount point. (Contributed by Cooper Ry Lees in bpo-30897 [https://bugs.python.org/issue?@action=redirect&bpo=30897].)

pdb

pdb.set_trace() now takes an optional header keyword-only argument. If given, it is printed to the console just before debugging begins. (Contributed by Barry Warsaw in bpo-31389 [https://bugs.python.org/issue?@action=redirect&bpo=31389].)

pdb command line now accepts -m module_name as an alternative to script file. (Contributed by Mario Corchero in bpo-32206 [https://bugs.python.org/issue?@action=redirect&bpo=32206].)

py_compile

py_compile.compile() -- and by extension, compileall -- now respects the SOURCE_DATE_EPOCH environment variable by unconditionally creating .pyc files for hash-based validation. This allows for guaranteeing reproducible builds [https://reproducible-builds.org/] of .pyc files when they are created eagerly. (Contributed by Bernhard M. Wiedemann in bpo-29708 [https://bugs.python.org/issue?@action=redirect&bpo=29708].)

pydoc

The pydoc server can now bind to an arbitrary hostname specified by the new -n command-line argument. (Contributed by Feanil Patel in bpo-31128 [https://bugs.python.org/issue?@action=redirect&bpo=31128].)

queue

The new SimpleQueue class is an unbounded FIFO queue. (Contributed by Antoine Pitrou in bpo-14976 [https://bugs.python.org/issue?@action=redirect&bpo=14976].)

re

The flags re.ASCII, re.LOCALE and re.UNICODE can be set within the scope of a group. (Contributed by Serhiy Storchaka in bpo-31690 [https://bugs.python.org/issue?@action=redirect&bpo=31690].)

re.split() now supports splitting on a pattern like r'\b', '^$' or (?=-) that matches an empty string. (Contributed by Serhiy Storchaka in bpo-25054 [https://bugs.python.org/issue?@action=redirect&bpo=25054].)

Regular expressions compiled with the re.LOCALE flag no longer depend on the locale at compile time. Locale settings are applied only when the compiled regular expression is used. (Contributed by Serhiy Storchaka in bpo-30215 [https://bugs.python.org/issue?@action=redirect&bpo=30215].)

FutureWarning is now emitted if a regular expression contains character set constructs that will change semantically in the future, such as nested sets and set operations. (Contributed by Serhiy Storchaka in bpo-30349 [https://bugs.python.org/issue?@action=redirect&bpo=30349].)

Compiled regular expression and match objects can now be copied using copy.copy() and copy.deepcopy(). (Contributed by Serhiy Storchaka in bpo-10076 [https://bugs.python.org/issue?@action=redirect&bpo=10076].)

signal

The new warn_on_full_buffer argument to the signal.set_wakeup_fd() function makes it possible to specify whether Python prints a warning on stderr when the wakeup buffer overflows. (Contributed by Nathaniel J. Smith in bpo-30050 [https://bugs.python.org/issue?@action=redirect&bpo=30050].)

socket

The new socket.getblocking() method returns True if the socket is in blocking mode and False otherwise. (Contributed by Yury Selivanov in bpo-32373 [https://bugs.python.org/issue?@action=redirect&bpo=32373].)

The new socket.close() function closes the passed socket file descriptor. This function should be used instead of os.close() for better compatibility across platforms. (Contributed by Christian Heimes in bpo-32454 [https://bugs.python.org/issue?@action=redirect&bpo=32454].)

The socket module now exposes the socket.TCP_CONGESTION (Linux 2.6.13), socket.TCP_USER_TIMEOUT (Linux 2.6.37), and socket.TCP_NOTSENT_LOWAT (Linux 3.12) constants. (Contributed by Omar Sandoval in bpo-26273 [https://bugs.python.org/issue?@action=redirect&bpo=26273] and Nathaniel J. Smith in bpo-29728 [https://bugs.python.org/issue?@action=redirect&bpo=29728].)

Support for socket.AF_VSOCK sockets has been added to allow communication between virtual machines and their hosts. (Contributed by Cathy Avery in bpo-27584 [https://bugs.python.org/issue?@action=redirect&bpo=27584].)

Sockets now auto-detect family, type and protocol from file descriptor by default. (Contributed by Christian Heimes in bpo-28134 [https://bugs.python.org/issue?@action=redirect&bpo=28134].)

socketserver

socketserver.ThreadingMixIn.server_close now waits until all non-daemon threads complete. socketserver.ForkingMixIn.server_close now waits until all child processes complete.

Add a new socketserver.ForkingMixIn.block_on_close class attribute to socketserver.ForkingMixIn and socketserver.ThreadingMixIn classes. Set the class attribute to False to get the pre-3.7 behaviour.

sqlite3

sqlite3.Connection now exposes the backup() method when the underlying SQLite library is at version 3.6.11 or higher. (Contributed by Lele Gaifax in bpo-27645 [https://bugs.python.org/issue?@action=redirect&bpo=27645].)

The database argument of sqlite3.connect() now accepts any path-like object, instead of just a string. (Contributed by Anders Lorentsen in bpo-31843 [https://bugs.python.org/issue?@action=redirect&bpo=31843].)

ssl

The ssl module now uses OpenSSL's builtin API instead of match_hostname() to check a host name or an IP address. Values are validated during TLS handshake. Any certificate validation error including failing the host name check now raises SSLCertVerificationError and aborts the handshake with a proper TLS Alert message. The new exception contains additional information. Host name validation can be customized with SSLContext.hostname_checks_common_name. (Contributed by Christian Heimes in bpo-31399 [https://bugs.python.org/issue?@action=redirect&bpo=31399].)

備註

The improved host name check requires a libssl implementation compatible with OpenSSL 1.0.2 or 1.1. Consequently, OpenSSL 0.9.8 and 1.0.1 are no longer supported (see Platform Support Removals for more details). The ssl module is mostly compatible with LibreSSL 2.7.2 and newer.

The ssl module no longer sends IP addresses in SNI TLS extension. (Contributed by Christian Heimes in bpo-32185 [https://bugs.python.org/issue?@action=redirect&bpo=32185].)

match_hostname() no longer supports partial wildcards like www*.example.org. (Contributed by Mandeep Singh in bpo-23033 [https://bugs.python.org/issue?@action=redirect&bpo=23033] and Christian Heimes in bpo-31399 [https://bugs.python.org/issue?@action=redirect&bpo=31399].)

The default cipher suite selection of the ssl module now uses a blacklist approach rather than a hard-coded whitelist. Python no longer re-enables ciphers that have been blocked by OpenSSL security updates. Default cipher suite selection can be configured at compile time. (Contributed by Christian Heimes in bpo-31429 [https://bugs.python.org/issue?@action=redirect&bpo=31429].)

Validation of server certificates containing internationalized domain names (IDNs) is now supported. As part of this change, the SSLSocket.server_hostname attribute now stores the expected hostname in A-label form ("xn--pythn-mua.org"), rather than the U-label form ("pythön.org"). (Contributed by Nathaniel J. Smith and Christian Heimes in bpo-28414 [https://bugs.python.org/issue?@action=redirect&bpo=28414].)

The ssl module has preliminary and experimental support for TLS 1.3 and OpenSSL 1.1.1. At the time of Python 3.7.0 release, OpenSSL 1.1.1 is still under development and TLS 1.3 hasn't been finalized yet. The TLS 1.3 handshake and protocol behaves slightly differently than TLS 1.2 and earlier, see TLS 1.3. (Contributed by Christian Heimes in bpo-32947 [https://bugs.python.org/issue?@action=redirect&bpo=32947], bpo-20995 [https://bugs.python.org/issue?@action=redirect&bpo=20995], bpo-29136 [https://bugs.python.org/issue?@action=redirect&bpo=29136], bpo-30622 [https://bugs.python.org/issue?@action=redirect&bpo=30622] and bpo-33618 [https://bugs.python.org/issue?@action=redirect&bpo=33618])

SSLSocket and SSLObject no longer have a public constructor. Direct instantiation was never a documented and supported feature. Instances must be created with SSLContext methods wrap_socket() and wrap_bio(). (Contributed by Christian Heimes in bpo-32951 [https://bugs.python.org/issue?@action=redirect&bpo=32951])

OpenSSL 1.1 APIs for setting the minimum and maximum TLS protocol version are available as SSLContext.minimum_version and SSLContext.maximum_version. Supported protocols are indicated by several new flags, such as HAS_TLSv1_1. (Contributed by Christian Heimes in bpo-32609 [https://bugs.python.org/issue?@action=redirect&bpo=32609].)

Added ssl.SSLContext.post_handshake_auth to enable and ssl.SSLSocket.verify_client_post_handshake() to initiate TLS 1.3 post-handshake authentication. (Contributed by Christian Heimes in gh-78851 [https://github.com/python/cpython/issues/78851].)

string

string.Template now lets you to optionally modify the regular expression pattern for braced placeholders and non-braced placeholders separately. (Contributed by Barry Warsaw in bpo-1198569 [https://bugs.python.org/issue?@action=redirect&bpo=1198569].)

subprocess

The subprocess.run() function accepts the new capture_output keyword argument. When true, stdout and stderr will be captured. This is equivalent to passing subprocess.PIPE as stdout and stderr arguments. (Contributed by Bo Bayles in bpo-32102 [https://bugs.python.org/issue?@action=redirect&bpo=32102].)

The subprocess.run function and the subprocess.Popen constructor now accept the text keyword argument as an alias to universal_newlines. (Contributed by Andrew Clegg in bpo-31756 [https://bugs.python.org/issue?@action=redirect&bpo=31756].)

On Windows the default for close_fds was changed from False to True when redirecting the standard handles. It's now possible to set close_fds to true when redirecting the standard handles. See subprocess.Popen. This means that close_fds now defaults to True on all supported platforms. (Contributed by Segev Finer in bpo-19764 [https://bugs.python.org/issue?@action=redirect&bpo=19764].)

The subprocess module is now more graceful when handling KeyboardInterrupt during subprocess.call(), subprocess.run(), or in a Popen context manager. It now waits a short amount of time for the child to exit, before continuing the handling of the KeyboardInterrupt exception. (Contributed by Gregory P. Smith in bpo-25942 [https://bugs.python.org/issue?@action=redirect&bpo=25942].)

sys

The new sys.breakpointhook() hook function is called by the built-in breakpoint(). (Contributed by Barry Warsaw in bpo-31353 [https://bugs.python.org/issue?@action=redirect&bpo=31353].)

On Android, the new sys.getandroidapilevel() returns the build-time Android API version. (Contributed by Victor Stinner in bpo-28740 [https://bugs.python.org/issue?@action=redirect&bpo=28740].)

The new sys.get_coroutine_origin_tracking_depth() function returns the current coroutine origin tracking depth, as set by the new sys.set_coroutine_origin_tracking_depth(). asyncio has been converted to use this new API instead of the deprecated sys.set_coroutine_wrapper(). (Contributed by Nathaniel J. Smith in bpo-32591 [https://bugs.python.org/issue?@action=redirect&bpo=32591].)

time

PEP 564 [https://peps.python.org/pep-0564/] adds six new functions with nanosecond resolution to the time module:

time.clock_gettime_ns()

time.clock_settime_ns()

time.monotonic_ns()

time.perf_counter_ns()

time.process_time_ns()

time.time_ns()

New clock identifiers have been added:

time.CLOCK_BOOTTIME (Linux): Identical to time.CLOCK_MONOTONIC, except it also includes any time that the system is suspended.

time.CLOCK_PROF (FreeBSD, NetBSD and OpenBSD): High-resolution per-process CPU timer.

time.CLOCK_UPTIME (FreeBSD, OpenBSD): Time whose absolute value is the time the system has been running and not suspended, providing accurate uptime measurement.

The new time.thread_time() and time.thread_time_ns() functions can be used to get per-thread CPU time measurements. (Contributed by Antoine Pitrou in bpo-32025 [https://bugs.python.org/issue?@action=redirect&bpo=32025].)

The new time.pthread_getcpuclockid() function returns the clock ID of the thread-specific CPU-time clock.

tkinter

The new tkinter.ttk.Spinbox class is now available. (Contributed by Alan Moore in bpo-32585 [https://bugs.python.org/issue?@action=redirect&bpo=32585].)

tracemalloc

tracemalloc.Traceback behaves more like regular tracebacks, sorting the frames from oldest to most recent. Traceback.format() now accepts negative limit, truncating the result to the abs(limit) oldest frames. To get the old behaviour, use the new most_recent_first argument to Traceback.format(). (Contributed by Jesse Bakker in bpo-32121 [https://bugs.python.org/issue?@action=redirect&bpo=32121].)

types

The new WrapperDescriptorType, MethodWrapperType, MethodDescriptorType, and ClassMethodDescriptorType classes are now available. (Contributed by Manuel Krebber and Guido van Rossum in bpo-29377 [https://bugs.python.org/issue?@action=redirect&bpo=29377], and Serhiy Storchaka in bpo-32265 [https://bugs.python.org/issue?@action=redirect&bpo=32265].)

The new types.resolve_bases() function resolves MRO entries dynamically as specified by PEP 560 [https://peps.python.org/pep-0560/]. (Contributed by Ivan Levkivskyi in bpo-32717 [https://bugs.python.org/issue?@action=redirect&bpo=32717].)

unicodedata

The internal unicodedata database has been upgraded to use Unicode 11 [https://www.unicode.org/versions/Unicode11.0.0/]. (Contributed by Benjamin Peterson.)

unittest

The new -k command-line option allows filtering tests by a name substring or a Unix shell-like pattern. For example, python -m unittest -k foo runs foo_tests.SomeTest.test_something, bar_tests.SomeTest.test_foo, but not bar_tests.FooTest.test_something. (Contributed by Jonas Haag in bpo-32071 [https://bugs.python.org/issue?@action=redirect&bpo=32071].)

unittest.mock

The sentinel attributes now preserve their identity when they are copied or pickled. (Contributed by Serhiy Storchaka in bpo-20804 [https://bugs.python.org/issue?@action=redirect&bpo=20804].)

The new seal() function allows sealing Mock instances, which will disallow further creation of attribute mocks. The seal is applied recursively to all attributes that are themselves mocks. (Contributed by Mario Corchero in bpo-30541 [https://bugs.python.org/issue?@action=redirect&bpo=30541].)

urllib.parse

urllib.parse.quote() has been updated from RFC 2396 [https://datatracker.ietf.org/doc/html/rfc2396.html] to RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html], adding ~ to the set of characters that are never quoted by default. (Contributed by Christian Theune and Ratnadeep Debnath in bpo-16285 [https://bugs.python.org/issue?@action=redirect&bpo=16285].)

uu

The uu.encode() function now accepts an optional backtick keyword argument. When it's true, zeros are represented by '`' instead of spaces. (Contributed by Xiang Zhang in bpo-30103 [https://bugs.python.org/issue?@action=redirect&bpo=30103].)

uuid

The new UUID.is_safe attribute relays information from the platform about whether generated UUIDs are generated with a multiprocessing-safe method. (Contributed by Barry Warsaw in bpo-22807 [https://bugs.python.org/issue?@action=redirect&bpo=22807].)

uuid.getnode() now prefers universally administered MAC addresses over locally administered MAC addresses. This makes a better guarantee for global uniqueness of UUIDs returned from uuid.uuid1(). If only locally administered MAC addresses are available, the first such one found is returned. (Contributed by Barry Warsaw in bpo-32107 [https://bugs.python.org/issue?@action=redirect&bpo=32107].)

warnings

The initialization of the default warnings filters has changed as follows:

warnings enabled via command line options (including those for -b and the new CPython-specific -X dev option) are always passed to the warnings machinery via the sys.warnoptions attribute.

warnings filters enabled via the command line or the environment now have the following order of precedence:

the BytesWarning filter for -b (or -bb)

any filters specified with the -W option

any filters specified with the PYTHONWARNINGS environment variable

any other CPython specific filters (e.g. the default filter added for the new -X dev mode)

any implicit filters defined directly by the warnings machinery

in CPython debug builds, all warnings are now displayed by default (the implicit filter list is empty)

（由 Nick Coghlan 和 Victor Stinner 在 bpo-20361 [https://bugs.python.org/issue?@action=redirect&bpo=20361]、bpo-32043 [https://bugs.python.org/issue?@action=redirect&bpo=32043] 和 bpo-32230 [https://bugs.python.org/issue?@action=redirect&bpo=32230] 中貢獻。）

Deprecation warnings are once again shown by default in single-file scripts and at the interactive prompt. See PEP 565：在 __main__ 中顯示 DeprecationWarning for details. (Contributed by Nick Coghlan in bpo-31975 [https://bugs.python.org/issue?@action=redirect&bpo=31975].)

xml

As mitigation against DTD and external entity retrieval, the xml.dom.minidom and xml.sax modules no longer process external entities by default. (Contributed by Christian Heimes in gh-61441 [https://github.com/python/cpython/issues/61441].)

xml.etree

ElementPath predicates in the find() methods can now compare text of the current node with [. = "text"], not only text in children. Predicates also allow adding spaces for better readability. (Contributed by Stefan Behnel in bpo-31648 [https://bugs.python.org/issue?@action=redirect&bpo=31648].)

xmlrpc.server

SimpleXMLRPCDispatcher.register_function() can now be used as a decorator. (Contributed by Xiang Zhang in bpo-7769 [https://bugs.python.org/issue?@action=redirect&bpo=7769].)

zipapp

Function create_archive() now accepts an optional filter argument to allow the user to select which files should be included in the archive. (Contributed by Irmen de Jong in bpo-31072 [https://bugs.python.org/issue?@action=redirect&bpo=31072].)

Function create_archive() now accepts an optional compressed argument to generate a compressed archive. A command line option --compress has also been added to support compression. (Contributed by Zhiming Wang in bpo-31638 [https://bugs.python.org/issue?@action=redirect&bpo=31638].)

zipfile

ZipFile now accepts the new compresslevel parameter to control the compression level. (Contributed by Bo Bayles in bpo-21417 [https://bugs.python.org/issue?@action=redirect&bpo=21417].)

Subdirectories in archives created by ZipFile are now stored in alphabetical order. (Contributed by Bernhard M. Wiedemann in bpo-30693 [https://bugs.python.org/issue?@action=redirect&bpo=30693].)

C API 變更

A new API for thread-local storage has been implemented. See PEP 539: New C API for Thread-Local Storage for an overview and Thread Specific Storage (TSS) API for a complete reference. (Contributed by Masayuki Yamamoto in bpo-25658 [https://bugs.python.org/issue?@action=redirect&bpo=25658].)

The new context variables functionality exposes a number of new C APIs.

The new PyImport_GetModule() function returns the previously imported module with the given name. (Contributed by Eric Snow in bpo-28411 [https://bugs.python.org/issue?@action=redirect&bpo=28411].)

The new Py_RETURN_RICHCOMPARE macro eases writing rich comparison functions. (Contributed by Petr Victorin in bpo-23699 [https://bugs.python.org/issue?@action=redirect&bpo=23699].)

The new Py_UNREACHABLE macro can be used to mark unreachable code paths. (Contributed by Barry Warsaw in bpo-31338 [https://bugs.python.org/issue?@action=redirect&bpo=31338].)

The tracemalloc now exposes a C API through the new PyTraceMalloc_Track() and PyTraceMalloc_Untrack() functions. (Contributed by Victor Stinner in bpo-30054 [https://bugs.python.org/issue?@action=redirect&bpo=30054].)

The new import__find__load__start and import__find__load__done static markers can be used to trace module imports. (Contributed by Christian Heimes in bpo-31574 [https://bugs.python.org/issue?@action=redirect&bpo=31574].)

The fields name and doc of structures PyMemberDef, PyGetSetDef, PyStructSequence_Field, PyStructSequence_Desc, and wrapperbase are now of type const char * rather of char *. (Contributed by Serhiy Storchaka in bpo-28761 [https://bugs.python.org/issue?@action=redirect&bpo=28761].)

The result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8() is now of type const char * rather of char *. (Contributed by Serhiy Storchaka in bpo-28769 [https://bugs.python.org/issue?@action=redirect&bpo=28769].)

The result of PyMapping_Keys(), PyMapping_Values() and PyMapping_Items() is now always a list, rather than a list or a tuple. (Contributed by Oren Milman in bpo-28280 [https://bugs.python.org/issue?@action=redirect&bpo=28280].)

Added functions PySlice_Unpack() and PySlice_AdjustIndices(). (Contributed by Serhiy Storchaka in bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867].)

PyOS_AfterFork() is deprecated in favour of the new functions PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child(). (Contributed by Antoine Pitrou in bpo-16500 [https://bugs.python.org/issue?@action=redirect&bpo=16500].)

The PyExc_RecursionErrorInst singleton that was part of the public API has been removed as its members being never cleared may cause a segfault during finalization of the interpreter. Contributed by Xavier de Gaye in bpo-22898 [https://bugs.python.org/issue?@action=redirect&bpo=22898] and bpo-30697 [https://bugs.python.org/issue?@action=redirect&bpo=30697].

Added C API support for timezones with timezone constructors PyTimeZone_FromOffset() and PyTimeZone_FromOffsetAndName(), and access to the UTC singleton with PyDateTime_TimeZone_UTC. Contributed by Paul Ganssle in bpo-10381 [https://bugs.python.org/issue?@action=redirect&bpo=10381].

The type of results of PyThread_start_new_thread() and PyThread_get_thread_ident(), and the id parameter of PyThreadState_SetAsyncExc() changed from long to unsigned long. (Contributed by Serhiy Storchaka in bpo-6532 [https://bugs.python.org/issue?@action=redirect&bpo=6532].)

PyUnicode_AsWideCharString() now raises a ValueError if the second argument is NULL and the wchar_t* string contains null characters. (Contributed by Serhiy Storchaka in bpo-30708 [https://bugs.python.org/issue?@action=redirect&bpo=30708].)

Changes to the startup sequence and the management of dynamic memory allocators mean that the long documented requirement to call Py_Initialize() before calling most C API functions is now relied on more heavily, and failing to abide by it may lead to segfaults in embedding applications. See the 移植至 Python 3.7 section in this document and the Python 初始化之前 section in the C API documentation for more details.

The new PyInterpreterState_GetID() returns the unique ID for a given interpreter. (Contributed by Eric Snow in bpo-29102 [https://bugs.python.org/issue?@action=redirect&bpo=29102].)

Py_DecodeLocale(), Py_EncodeLocale() now use the UTF-8 encoding when the UTF-8 mode is enabled. (Contributed by Victor Stinner in bpo-29240 [https://bugs.python.org/issue?@action=redirect&bpo=29240].)

PyUnicode_DecodeLocaleAndSize() and PyUnicode_EncodeLocale() now use the current locale encoding for surrogateescape error handler. (Contributed by Victor Stinner in bpo-29240 [https://bugs.python.org/issue?@action=redirect&bpo=29240].)

The start and end parameters of PyUnicode_FindChar() are now adjusted to behave like string slices. (Contributed by Xiang Zhang in bpo-28822 [https://bugs.python.org/issue?@action=redirect&bpo=28822].)

建置變更

Support for building --without-threads has been removed. The threading module is now always available. (Contributed by Antoine Pitrou in bpo-31370 [https://bugs.python.org/issue?@action=redirect&bpo=31370].).

A full copy of libffi is no longer bundled for use when building the _ctypes module on non-OSX UNIX platforms. An installed copy of libffi is now required when building _ctypes on such platforms. (Contributed by Zachary Ware in bpo-27979 [https://bugs.python.org/issue?@action=redirect&bpo=27979].)

The Windows build process no longer depends on Subversion to pull in external sources, a Python script is used to download zipfiles from GitHub instead. If Python 3.6 is not found on the system (via py -3.6), NuGet is used to download a copy of 32-bit Python for this purpose. (Contributed by Zachary Ware in bpo-30450 [https://bugs.python.org/issue?@action=redirect&bpo=30450].)

The ssl module requires OpenSSL 1.0.2 or 1.1 compatible libssl. OpenSSL 1.0.1 has reached end of lifetime on 2016-12-31 and is no longer supported. LibreSSL is temporarily not supported as well. LibreSSL releases up to version 2.6.4 are missing required OpenSSL 1.0.2 APIs.

最佳化

The overhead of calling many methods of various standard library classes implemented in C has been significantly reduced by porting more code to use the METH_FASTCALL convention. (Contributed by Victor Stinner in bpo-29300 [https://bugs.python.org/issue?@action=redirect&bpo=29300], bpo-29507 [https://bugs.python.org/issue?@action=redirect&bpo=29507], bpo-29452 [https://bugs.python.org/issue?@action=redirect&bpo=29452], and bpo-29286 [https://bugs.python.org/issue?@action=redirect&bpo=29286].)

Various optimizations have reduced Python startup time by 10% on Linux and up to 30% on macOS. (Contributed by Victor Stinner, INADA Naoki in bpo-29585 [https://bugs.python.org/issue?@action=redirect&bpo=29585], and Ivan Levkivskyi in bpo-31333 [https://bugs.python.org/issue?@action=redirect&bpo=31333].)

Method calls are now up to 20% faster due to the bytecode changes which avoid creating bound method instances. (Contributed by Yury Selivanov and INADA Naoki in bpo-26110 [https://bugs.python.org/issue?@action=redirect&bpo=26110].)

The asyncio module received a number of notable optimizations for commonly used functions:

The asyncio.get_event_loop() function has been reimplemented in C to make it up to 15 times faster. (Contributed by Yury Selivanov in bpo-32296 [https://bugs.python.org/issue?@action=redirect&bpo=32296].)

asyncio.Future callback management has been optimized. (Contributed by Yury Selivanov in bpo-32348 [https://bugs.python.org/issue?@action=redirect&bpo=32348].)

asyncio.gather() is now up to 15% faster. (Contributed by Yury Selivanov in bpo-32355 [https://bugs.python.org/issue?@action=redirect&bpo=32355].)

asyncio.sleep() is now up to 2 times faster when the delay argument is zero or negative. (Contributed by Andrew Svetlov in bpo-32351 [https://bugs.python.org/issue?@action=redirect&bpo=32351].)

The performance overhead of asyncio debug mode has been reduced. (Contributed by Antoine Pitrou in bpo-31970 [https://bugs.python.org/issue?@action=redirect&bpo=31970].)

As a result of PEP 560 work, the import time of typing has been reduced by a factor of 7, and many typing operations are now faster. (Contributed by Ivan Levkivskyi in bpo-32226 [https://bugs.python.org/issue?@action=redirect&bpo=32226].)

sorted() and list.sort() have been optimized for common cases to be up to 40-75% faster. (Contributed by Elliot Gorokhovsky in bpo-28685 [https://bugs.python.org/issue?@action=redirect&bpo=28685].)

dict.copy() is now up to 5.5 times faster. (Contributed by Yury Selivanov in bpo-31179 [https://bugs.python.org/issue?@action=redirect&bpo=31179].)

hasattr() and getattr() are now about 4 times faster when name is not found and obj does not override object.__getattr__() or object.__getattribute__(). (Contributed by INADA Naoki in bpo-32544 [https://bugs.python.org/issue?@action=redirect&bpo=32544].)

Searching for certain Unicode characters (like Ukrainian capital "Є") in a string was up to 25 times slower than searching for other characters. It is now only 3 times slower in the worst case. (Contributed by Serhiy Storchaka in bpo-24821 [https://bugs.python.org/issue?@action=redirect&bpo=24821].)

The collections.namedtuple() factory has been reimplemented to make the creation of named tuples 4 to 6 times faster. (Contributed by Jelle Zijlstra with further improvements by INADA Naoki, Serhiy Storchaka, and Raymond Hettinger in bpo-28638 [https://bugs.python.org/issue?@action=redirect&bpo=28638].)

datetime.date.fromordinal() and datetime.date.fromtimestamp() are now up to 30% faster in the common case. (Contributed by Paul Ganssle in bpo-32403 [https://bugs.python.org/issue?@action=redirect&bpo=32403].)

The os.fwalk() function is now up to 2 times faster thanks to the use of os.scandir(). (Contributed by Serhiy Storchaka in bpo-25996 [https://bugs.python.org/issue?@action=redirect&bpo=25996].)

The speed of the shutil.rmtree() function has been improved by 20--40% thanks to the use of the os.scandir() function. (Contributed by Serhiy Storchaka in bpo-28564 [https://bugs.python.org/issue?@action=redirect&bpo=28564].)

Optimized case-insensitive matching and searching of regular expressions. Searching some patterns can now be up to 20 times faster. (Contributed by Serhiy Storchaka in bpo-30285 [https://bugs.python.org/issue?@action=redirect&bpo=30285].)

re.compile() now converts flags parameter to int object if it is RegexFlag. It is now as fast as Python 3.5, and faster than Python 3.6 by about 10% depending on the pattern. (Contributed by INADA Naoki in bpo-31671 [https://bugs.python.org/issue?@action=redirect&bpo=31671].)

The modify() methods of classes selectors.EpollSelector, selectors.PollSelector and selectors.DevpollSelector may be around 10% faster under heavy loads. (Contributed by Giampaolo Rodola' in bpo-30014 [https://bugs.python.org/issue?@action=redirect&bpo=30014])

Constant folding has been moved from the peephole optimizer to the new AST optimizer, which is able perform optimizations more consistently. (Contributed by Eugene Toder and INADA Naoki in bpo-29469 [https://bugs.python.org/issue?@action=redirect&bpo=29469] and bpo-11549 [https://bugs.python.org/issue?@action=redirect&bpo=11549].)

Most functions and methods in abc have been rewritten in C. This makes creation of abstract base classes, and calling isinstance() and issubclass() on them 1.5x faster. This also reduces Python start-up time by up to 10%. (Contributed by Ivan Levkivskyi and INADA Naoki in bpo-31333 [https://bugs.python.org/issue?@action=redirect&bpo=31333])

Significant speed improvements to alternate constructors for datetime.date and datetime.datetime by using fast-path constructors when not constructing subclasses. (Contributed by Paul Ganssle in bpo-32403 [https://bugs.python.org/issue?@action=redirect&bpo=32403])

The speed of comparison of array.array instances has been improved considerably in certain cases. It is now from 10x to 70x faster when comparing arrays holding values of the same integer type. (Contributed by Adrian Wielgosik in bpo-24700 [https://bugs.python.org/issue?@action=redirect&bpo=24700].)

The math.erf() and math.erfc() functions now use the (faster) C library implementation on most platforms. (Contributed by Serhiy Storchaka in bpo-26121 [https://bugs.python.org/issue?@action=redirect&bpo=26121].)

Other CPython Implementation Changes

Trace hooks may now opt out of receiving the line and opt into receiving the opcode events from the interpreter by setting the corresponding new f_trace_lines and f_trace_opcodes attributes on the frame being traced. (Contributed by Nick Coghlan in bpo-31344 [https://bugs.python.org/issue?@action=redirect&bpo=31344].)

Fixed some consistency problems with namespace package module attributes. Namespace module objects now have an __file__ that is set to None (previously unset), and their __spec__.origin is also set to None (previously the string "namespace"). See bpo-32305 [https://bugs.python.org/issue?@action=redirect&bpo=32305]. Also, the namespace module object's __spec__.loader is set to the same value as __loader__ (previously, the former was set to None). See bpo-32303 [https://bugs.python.org/issue?@action=redirect&bpo=32303].

The locals() dictionary now displays in the lexical order that variables were defined. Previously, the order was undefined. (Contributed by Raymond Hettinger in bpo-32690 [https://bugs.python.org/issue?@action=redirect&bpo=32690].)

The distutils upload command no longer tries to change CR end-of-line characters to CRLF. This fixes a corruption issue with sdists that ended with a byte equivalent to CR. (Contributed by Bo Bayles in bpo-32304 [https://bugs.python.org/issue?@action=redirect&bpo=32304].)

已棄用的 Python 行為

Yield expressions (both yield and yield from clauses) are now deprecated in comprehensions and generator expressions (aside from the iterable expression in the leftmost for clause). This ensures that comprehensions always immediately return a container of the appropriate type (rather than potentially returning a generator iterator object), while generator expressions won't attempt to interleave their implicit output with the output from any explicit yield expressions. In Python 3.7, such expressions emit DeprecationWarning when compiled, in Python 3.8 this will be a SyntaxError. (Contributed by Serhiy Storchaka in bpo-10544 [https://bugs.python.org/issue?@action=redirect&bpo=10544].)

Returning a subclass of complex from object.__complex__() is deprecated and will be an error in future Python versions. This makes __complex__() consistent with object.__int__() and object.__float__(). (Contributed by Serhiy Storchaka in bpo-28894 [https://bugs.python.org/issue?@action=redirect&bpo=28894].)

已棄用的 Python 模組、函式和方法

aifc

aifc.openfp() has been deprecated and will be removed in Python 3.9. Use aifc.open() instead. (Contributed by Brian Curtin in bpo-31985 [https://bugs.python.org/issue?@action=redirect&bpo=31985].)

asyncio

Support for directly await-ing instances of asyncio.Lock and other asyncio synchronization primitives has been deprecated. An asynchronous context manager must be used in order to acquire and release the synchronization resource. (Contributed by Andrew Svetlov in bpo-32253 [https://bugs.python.org/issue?@action=redirect&bpo=32253].)

The asyncio.Task.current_task() and asyncio.Task.all_tasks() methods have been deprecated. (Contributed by Andrew Svetlov in bpo-32250 [https://bugs.python.org/issue?@action=redirect&bpo=32250].)

collections

In Python 3.8, the abstract base classes in collections.abc will no longer be exposed in the regular collections module. This will help create a clearer distinction between the concrete classes and the abstract base classes. (Contributed by Serhiy Storchaka in bpo-25988 [https://bugs.python.org/issue?@action=redirect&bpo=25988].)

dbm

dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed. A deprecation warning is now emitted if the index file is missing and recreated in the 'r' and 'w' modes (this will be an error in future Python releases). (Contributed by Serhiy Storchaka in bpo-28847 [https://bugs.python.org/issue?@action=redirect&bpo=28847].)

enum

In Python 3.8, attempting to check for non-Enum objects in Enum classes will raise a TypeError (e.g. 1 in Color); similarly, attempting to check for non-Flag objects in a Flag member will raise TypeError (e.g. 1 in Perm.RW); currently, both operations return False instead. (Contributed by Ethan Furman in bpo-33217 [https://bugs.python.org/issue?@action=redirect&bpo=33217].)

gettext

Using non-integer value for selecting a plural form in gettext is now deprecated. It never correctly worked. (Contributed by Serhiy Storchaka in bpo-28692 [https://bugs.python.org/issue?@action=redirect&bpo=28692].)

importlib

Methods MetaPathFinder.find_module() (replaced by MetaPathFinder.find_spec()) and PathEntryFinder.find_loader() (replaced by PathEntryFinder.find_spec()) both deprecated in Python 3.4 now emit DeprecationWarning. (Contributed by Matthias Bussonnier in bpo-29576 [https://bugs.python.org/issue?@action=redirect&bpo=29576].)

The importlib.abc.ResourceLoader ABC has been deprecated in favour of importlib.abc.ResourceReader.

locale

locale.format() has been deprecated, use locale.format_string() instead. (Contributed by Garvit in bpo-10379 [https://bugs.python.org/issue?@action=redirect&bpo=10379].)

macpath

The macpath is now deprecated and will be removed in Python 3.8. (Contributed by Chi Hsuan Yen in bpo-9850 [https://bugs.python.org/issue?@action=redirect&bpo=9850].)

threading

dummy_threading and _dummy_thread have been deprecated. It is no longer possible to build Python with threading disabled. Use threading instead. (Contributed by Antoine Pitrou in bpo-31370 [https://bugs.python.org/issue?@action=redirect&bpo=31370].)

socket

The silent argument value truncation in socket.htons() and socket.ntohs() has been deprecated. In future versions of Python, if the passed argument is larger than 16 bits, an exception will be raised. (Contributed by Oren Milman in bpo-28332 [https://bugs.python.org/issue?@action=redirect&bpo=28332].)

ssl

ssl.wrap_socket() is deprecated. Use ssl.SSLContext.wrap_socket() instead. (Contributed by Christian Heimes in bpo-28124 [https://bugs.python.org/issue?@action=redirect&bpo=28124].)

sunau

sunau.openfp() has been deprecated and will be removed in Python 3.9. Use sunau.open() instead. (Contributed by Brian Curtin in bpo-31985 [https://bugs.python.org/issue?@action=redirect&bpo=31985].)

sys

Deprecated sys.set_coroutine_wrapper() and sys.get_coroutine_wrapper().

The undocumented sys.callstats() function has been deprecated and will be removed in a future Python version. (Contributed by Victor Stinner in bpo-28799 [https://bugs.python.org/issue?@action=redirect&bpo=28799].)

wave

wave.openfp() has been deprecated and will be removed in Python 3.9. Use wave.open() instead. (Contributed by Brian Curtin in bpo-31985 [https://bugs.python.org/issue?@action=redirect&bpo=31985].)

Deprecated functions and types of the C API

Function PySlice_GetIndicesEx() is deprecated and replaced with a macro if Py_LIMITED_API is not set or set to a value in the range between 0x03050400 and 0x03060000 (not inclusive), or is 0x03060100 or higher. (Contributed by Serhiy Storchaka in bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867].)

PyOS_AfterFork() has been deprecated. Use PyOS_BeforeFork(), PyOS_AfterFork_Parent() or PyOS_AfterFork_Child() instead. (Contributed by Antoine Pitrou in bpo-16500 [https://bugs.python.org/issue?@action=redirect&bpo=16500].)

Platform Support Removals

FreeBSD 9 and older are no longer officially supported.

For full Unicode support, including within extension modules, *nix platforms are now expected to provide at least one of C.UTF-8 (full locale), C.utf8 (full locale) or UTF-8 (LC_CTYPE-only locale) as an alternative to the legacy ASCII-based C locale.

OpenSSL 0.9.8 and 1.0.1 are no longer supported, which means building CPython 3.7 with SSL/TLS support on older platforms still using these versions requires custom build options that link to a more recent version of OpenSSL.

Notably, this issue affects the Debian 8 (aka "jessie") and Ubuntu 14.04 (aka "Trusty") LTS Linux distributions, as they still use OpenSSL 1.0.1 by default.

Debian 9 ("stretch") and Ubuntu 16.04 ("xenial"), as well as recent releases of other LTS Linux releases (e.g. RHEL/CentOS 7.5, SLES 12-SP3), use OpenSSL 1.0.2 or later, and remain supported in the default build configuration.

CPython's own CI configuration file [https://github.com/python/cpython/blob/v3.7.13/.travis.yml] provides an example of using the SSL compatibility testing infrastructure [https://github.com/python/cpython/tree/3.14/Tools/ssl/multissltests.py] in CPython's test suite to build and link against OpenSSL 1.1.0 rather than an outdated system provided OpenSSL.

API 與功能的移除

The following features and APIs have been removed from Python 3.7:

The os.stat_float_times() function has been removed. It was introduced in Python 2.3 for backward compatibility with Python 2.2, and was deprecated since Python 3.1.

Unknown escapes consisting of '\' and an ASCII letter in replacement templates for re.sub() were deprecated in Python 3.5, and will now cause an error.

Removed support of the exclude argument in tarfile.TarFile.add(). It was deprecated in Python 2.7 and 3.2. Use the filter argument instead.

The ntpath.splitunc() function was deprecated in Python 3.1, and has now been removed. Use splitdrive() instead.

collections.namedtuple() no longer supports the verbose parameter or _source attribute which showed the generated source code for the named tuple class. This was part of an optimization designed to speed-up class creation. (Contributed by Jelle Zijlstra with further improvements by INADA Naoki, Serhiy Storchaka, and Raymond Hettinger in bpo-28638 [https://bugs.python.org/issue?@action=redirect&bpo=28638].)

Functions bool(), float(), list() and tuple() no longer take keyword arguments. The first argument of int() can now be passed only as positional argument.

Removed previously deprecated in Python 2.4 classes Plist, Dict and _InternalDict in the plistlib module. Dict values in the result of functions readPlist() and readPlistFromBytes() are now normal dicts. You no longer can use attribute access to access items of these dictionaries.

The asyncio.windows_utils.socketpair() function has been removed. Use the socket.socketpair() function instead, it is available on all platforms since Python 3.5. asyncio.windows_utils.socketpair was just an alias to socket.socketpair on Python 3.5 and newer.

asyncio no longer exports the selectors and _overlapped modules as asyncio.selectors and asyncio._overlapped. Replace from asyncio import selectors with import selectors.

Direct instantiation of ssl.SSLSocket and ssl.SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were supposed to use ssl.wrap_socket() or ssl.SSLContext. (Contributed by Christian Heimes in bpo-32951 [https://bugs.python.org/issue?@action=redirect&bpo=32951].)

The unused distutils install_misc command has been removed. (Contributed by Eric N. Vander Weele in bpo-29218 [https://bugs.python.org/issue?@action=redirect&bpo=29218].)

Module Removals

The fpectl module has been removed. It was never enabled by default, never worked correctly on x86-64, and it changed the Python ABI in ways that caused unexpected breakage of C extensions. (Contributed by Nathaniel J. Smith in bpo-29137 [https://bugs.python.org/issue?@action=redirect&bpo=29137].)

Windows-only Changes

The python launcher, (py.exe), can accept 32 & 64 bit specifiers without having to specify a minor version as well. So py -3-32 and py -3-64 become valid as well as py -3.7-32, also the -m-64 and -m.n-64 forms are now accepted to force 64 bit python even if 32 bit would have otherwise been used. If the specified version is not available py.exe will error exit. (Contributed by Steve Barnes in bpo-30291 [https://bugs.python.org/issue?@action=redirect&bpo=30291].)

The launcher can be run as py -0 to produce a list of the installed pythons, with default marked with an asterisk. Running py -0p will include the paths. If py is run with a version specifier that cannot be matched it will also print the short form list of available specifiers. (Contributed by Steve Barnes in bpo-30362 [https://bugs.python.org/issue?@action=redirect&bpo=30362].)

移植至 Python 3.7

This section lists previously described changes and other bugfixes that may require changes to your code.

Python 行為的改變

async and await names are now reserved keywords. Code using these names as identifiers will now raise a SyntaxError. (Contributed by Jelle Zijlstra in bpo-30406 [https://bugs.python.org/issue?@action=redirect&bpo=30406].)

PEP 479 [https://peps.python.org/pep-0479/] is enabled for all code in Python 3.7, meaning that StopIteration exceptions raised directly or indirectly in coroutines and generators are transformed into RuntimeError exceptions. (Contributed by Yury Selivanov in bpo-32670 [https://bugs.python.org/issue?@action=redirect&bpo=32670].)

object.__aiter__() methods can no longer be declared as asynchronous. (Contributed by Yury Selivanov in bpo-31709 [https://bugs.python.org/issue?@action=redirect&bpo=31709].)

Due to an oversight, earlier Python versions erroneously accepted the following syntax:

f(1 for x in [1],)

class C(1 for x in [1]):
    pass

Python 3.7 now correctly raises a SyntaxError, as a generator expression always needs to be directly inside a set of parentheses and cannot have a comma on either side, and the duplication of the parentheses can be omitted only on calls. (Contributed by Serhiy Storchaka in bpo-32012 [https://bugs.python.org/issue?@action=redirect&bpo=32012] and bpo-32023 [https://bugs.python.org/issue?@action=redirect&bpo=32023].)

When using the -m switch, the initial working directory is now added to sys.path, rather than an empty string (which dynamically denoted the current working directory at the time of each import). Any programs that are checking for the empty string, or otherwise relying on the previous behaviour, will need to be updated accordingly (e.g. by also checking for os.getcwd() or os.path.dirname(__main__.__file__), depending on why the code was checking for the empty string in the first place).

Python API 的變更

socketserver.ThreadingMixIn.server_close now waits until all non-daemon threads complete. Set the new socketserver.ThreadingMixIn.block_on_close class attribute to False to get the pre-3.7 behaviour. (Contributed by Victor Stinner in bpo-31233 [https://bugs.python.org/issue?@action=redirect&bpo=31233] and bpo-33540 [https://bugs.python.org/issue?@action=redirect&bpo=33540].)

socketserver.ForkingMixIn.server_close now waits until all child processes complete. Set the new socketserver.ForkingMixIn.block_on_close class attribute to False to get the pre-3.7 behaviour. (Contributed by Victor Stinner in bpo-31151 [https://bugs.python.org/issue?@action=redirect&bpo=31151] and bpo-33540 [https://bugs.python.org/issue?@action=redirect&bpo=33540].)

The locale.localeconv() function now temporarily sets the LC_CTYPE locale to the value of LC_NUMERIC in some cases. (Contributed by Victor Stinner in bpo-31900 [https://bugs.python.org/issue?@action=redirect&bpo=31900].)

pkgutil.walk_packages() now raises a ValueError if path is a string. Previously an empty list was returned. (Contributed by Sanyam Khurana in bpo-24744 [https://bugs.python.org/issue?@action=redirect&bpo=24744].)

A format string argument for string.Formatter.format() is now positional-only. Passing it as a keyword argument was deprecated in Python 3.5. (Contributed by Serhiy Storchaka in bpo-29193 [https://bugs.python.org/issue?@action=redirect&bpo=29193].)

Attributes key, value and coded_value of class http.cookies.Morsel are now read-only. Assigning to them was deprecated in Python 3.5. Use the set() method for setting them. (Contributed by Serhiy Storchaka in bpo-29192 [https://bugs.python.org/issue?@action=redirect&bpo=29192].)

The mode argument of os.makedirs() no longer affects the file permission bits of newly created intermediate-level directories. To set their file permission bits you can set the umask before invoking makedirs(). (Contributed by Serhiy Storchaka in bpo-19930 [https://bugs.python.org/issue?@action=redirect&bpo=19930].)

The struct.Struct.format type is now str instead of bytes. (Contributed by Victor Stinner in bpo-21071 [https://bugs.python.org/issue?@action=redirect&bpo=21071].)

cgi.parse_multipart() now accepts the encoding and errors arguments and returns the same results as FieldStorage: for non-file fields, the value associated to a key is a list of strings, not bytes. (Contributed by Pierre Quentel in bpo-29979 [https://bugs.python.org/issue?@action=redirect&bpo=29979].)

Due to internal changes in socket, calling socket.fromshare() on a socket created by socket.share in older Python versions is not supported.

repr for BaseException has changed to not include the trailing comma. Most exceptions are affected by this change. (Contributed by Serhiy Storchaka in bpo-30399 [https://bugs.python.org/issue?@action=redirect&bpo=30399].)

repr for datetime.timedelta has changed to include the keyword arguments in the output. (Contributed by Utkarsh Upadhyay in bpo-30302 [https://bugs.python.org/issue?@action=redirect&bpo=30302].)

Because shutil.rmtree() is now implemented using the os.scandir() function, the user specified handler onerror is now called with the first argument os.scandir instead of os.listdir when listing the directory is failed.

Support for nested sets and set operations in regular expressions as in Unicode Technical Standard #18 [https://unicode.org/reports/tr18/] might be added in the future. This would change the syntax. To facilitate this future change a FutureWarning will be raised in ambiguous cases for the time being. That include sets starting with a literal '[' or containing literal character sequences '--', '&&', '~~', and '||'. To avoid a warning, escape them with a backslash. (Contributed by Serhiy Storchaka in bpo-30349 [https://bugs.python.org/issue?@action=redirect&bpo=30349].)

The result of splitting a string on a regular expression that could match an empty string has been changed. For example splitting on r'\s*' will now split not only on whitespaces as it did previously, but also on empty strings before all non-whitespace characters and just before the end of the string. The previous behavior can be restored by changing the pattern to r'\s+'. A FutureWarning was emitted for such patterns since Python 3.5.

For patterns that match both empty and non-empty strings, the result of searching for all matches may also be changed in other cases. For example in the string 'a\n\n', the pattern r'(?m)^\s*?$' will not only match empty strings at positions 2 and 3, but also the string '\n' at positions 2--3. To match only blank lines, the pattern should be rewritten as r'(?m)^[^\S\n]*$'.

re.sub() now replaces empty matches adjacent to a previous non-empty match. For example re.sub('x*', '-', 'abxd') returns now '-a-b--d-' instead of '-a-b-d-' (the first minus between 'b' and 'd' replaces 'x', and the second minus replaces an empty string between 'x' and 'd').

（由 Serhiy Storchaka 在 bpo-25054 [https://bugs.python.org/issue?@action=redirect&bpo=25054] 和 bpo-32308 [https://bugs.python.org/issue?@action=redirect&bpo=32308] 中貢獻。）

Change re.escape() to only escape regex special characters instead of escaping all characters other than ASCII letters, numbers, and '_'. (Contributed by Serhiy Storchaka in bpo-29995 [https://bugs.python.org/issue?@action=redirect&bpo=29995].)

tracemalloc.Traceback frames are now sorted from oldest to most recent to be more consistent with traceback. (Contributed by Jesse Bakker in bpo-32121 [https://bugs.python.org/issue?@action=redirect&bpo=32121].)

On OSes that support socket.SOCK_NONBLOCK or socket.SOCK_CLOEXEC bit flags, the socket.type no longer has them applied. Therefore, checks like if sock.type == socket.SOCK_STREAM work as expected on all platforms. (Contributed by Yury Selivanov in bpo-32331 [https://bugs.python.org/issue?@action=redirect&bpo=32331].)

On Windows the default for the close_fds argument of subprocess.Popen was changed from False to True when redirecting the standard handles. If you previously depended on handles being inherited when using subprocess.Popen with standard io redirection, you will have to pass close_fds=False to preserve the previous behaviour, or use STARTUPINFO.lpAttributeList.

importlib.machinery.PathFinder.invalidate_caches() -- which implicitly affects importlib.invalidate_caches() -- now deletes entries in sys.path_importer_cache which are set to None. (Contributed by Brett Cannon in bpo-33169 [https://bugs.python.org/issue?@action=redirect&bpo=33169].)

In asyncio, loop.sock_recv(), loop.sock_sendall(), loop.sock_accept(), loop.getaddrinfo(), loop.getnameinfo() have been changed to be proper coroutine methods to match their documentation. Previously, these methods returned asyncio.Future instances. (Contributed by Yury Selivanov in bpo-32327 [https://bugs.python.org/issue?@action=redirect&bpo=32327].)

asyncio.Server.sockets now returns a copy of the internal list of server sockets, instead of returning it directly. (Contributed by Yury Selivanov in bpo-32662 [https://bugs.python.org/issue?@action=redirect&bpo=32662].)

Struct.format is now a str instance instead of a bytes instance. (Contributed by Victor Stinner in bpo-21071 [https://bugs.python.org/issue?@action=redirect&bpo=21071].)

argparse subparsers can now be made mandatory by passing required=True to ArgumentParser.add_subparsers(). (Contributed by Anthony Sottile in bpo-26510 [https://bugs.python.org/issue?@action=redirect&bpo=26510].)

ast.literal_eval() is now stricter. Addition and subtraction of arbitrary numbers are no longer allowed. (Contributed by Serhiy Storchaka in bpo-31778 [https://bugs.python.org/issue?@action=redirect&bpo=31778].)

Calendar.itermonthdates will now consistently raise an exception when a date falls outside of the 0001-01-01 through 9999-12-31 range. To support applications that cannot tolerate such exceptions, the new Calendar.itermonthdays3 and Calendar.itermonthdays4 can be used. The new methods return tuples and are not restricted by the range supported by datetime.date. (Contributed by Alexander Belopolsky in bpo-28292 [https://bugs.python.org/issue?@action=redirect&bpo=28292].)

collections.ChainMap now preserves the order of the underlying mappings. (Contributed by Raymond Hettinger in bpo-32792 [https://bugs.python.org/issue?@action=redirect&bpo=32792].)

The submit() method of concurrent.futures.ThreadPoolExecutor and concurrent.futures.ProcessPoolExecutor now raises a RuntimeError if called during interpreter shutdown. (Contributed by Mark Nemec in bpo-33097 [https://bugs.python.org/issue?@action=redirect&bpo=33097].)

The configparser.ConfigParser constructor now uses read_dict() to process the default values, making its behavior consistent with the rest of the parser. Non-string keys and values in the defaults dictionary are now being implicitly converted to strings. (Contributed by James Tocknell in bpo-23835 [https://bugs.python.org/issue?@action=redirect&bpo=23835].)

Several undocumented internal imports were removed. One example is that os.errno is no longer available; use import errno directly instead. Note that such undocumented internal imports may be removed any time without notice, even in micro version releases.

C API 中的改動

The function PySlice_GetIndicesEx() is considered unsafe for resizable sequences. If the slice indices are not instances of int, but objects that implement the __index__() method, the sequence can be resized after passing its length to PySlice_GetIndicesEx(). This can lead to returning indices out of the length of the sequence. For avoiding possible problems use new functions PySlice_Unpack() and PySlice_AdjustIndices(). (Contributed by Serhiy Storchaka in bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867].)

CPython 位元組碼變更

There are two new opcodes: LOAD_METHOD and CALL_METHOD. (Contributed by Yury Selivanov and INADA Naoki in bpo-26110 [https://bugs.python.org/issue?@action=redirect&bpo=26110].)

The STORE_ANNOTATION opcode has been removed. (Contributed by Mark Shannon in bpo-32550 [https://bugs.python.org/issue?@action=redirect&bpo=32550].)

Windows-only Changes

The file used to override sys.path is now called <python-executable>._pth instead of 'sys.path'. See 找尋模組 for more information. (Contributed by Steve Dower in bpo-28137 [https://bugs.python.org/issue?@action=redirect&bpo=28137].)

Other CPython implementation changes

In preparation for potential future changes to the public CPython runtime initialization API (see PEP 432 [https://peps.python.org/pep-0432/] for an initial, but somewhat outdated, draft), CPython's internal startup and configuration management logic has been significantly refactored. While these updates are intended to be entirely transparent to both embedding applications and users of the regular CPython CLI, they're being mentioned here as the refactoring changes the internal order of various operations during interpreter startup, and hence may uncover previously latent defects, either in embedding applications, or in CPython itself. (Initially contributed by Nick Coghlan and Eric Snow as part of bpo-22257 [https://bugs.python.org/issue?@action=redirect&bpo=22257], and further updated by Nick, Eric, and Victor Stinner in a number of other issues). Some known details affected:

PySys_AddWarnOptionUnicode() is not currently usable by embedding applications due to the requirement to create a Unicode object prior to calling Py_Initialize. Use PySys_AddWarnOption() instead.

warnings filters added by an embedding application with PySys_AddWarnOption() should now more consistently take precedence over the default filters set by the interpreter

Due to changes in the way the default warnings filters are configured, setting Py_BytesWarningFlag to a value greater than one is no longer sufficient to both emit BytesWarning messages and have them converted to exceptions. Instead, the flag must be set (to cause the warnings to be emitted in the first place), and an explicit error::BytesWarning warnings filter added to convert them to exceptions.

Due to a change in the way docstrings are handled by the compiler, the implicit return None in a function body consisting solely of a docstring is now marked as occurring on the same line as the docstring, not on the function's header line.

The current exception state has been moved from the frame object to the co-routine. This simplified the interpreter and fixed a couple of obscure bugs caused by having swap exception state when entering or exiting a generator. (Contributed by Mark Shannon in bpo-25612 [https://bugs.python.org/issue?@action=redirect&bpo=25612].)

Python 3.7.1 中顯著的變更

Starting in 3.7.1, Py_Initialize() now consistently reads and respects all of the same environment settings as Py_Main() (in earlier Python versions, it respected an ill-defined subset of those environment variables, while in Python 3.7.0 it didn't read any of them due to bpo-34247 [https://bugs.python.org/issue?@action=redirect&bpo=34247]). If this behavior is unwanted, set Py_IgnoreEnvironmentFlag to 1 before calling Py_Initialize().

In 3.7.1 the C API for Context Variables was updated to use PyObject pointers. See also bpo-34762 [https://bugs.python.org/issue?@action=redirect&bpo=34762].

In 3.7.1 the tokenize module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. (Contributed by Ammar Askar in bpo-33899 [https://bugs.python.org/issue?@action=redirect&bpo=33899].)

Python 3.7.2 中顯著的變更

In 3.7.2, venv on Windows no longer copies the original binaries, but creates redirector scripts named python.exe and pythonw.exe instead. This resolves a long standing issue where all virtual environments would have to be upgraded or recreated with each Python update. However, note that this release will still require recreation of virtual environments in order to get the new scripts.

Python 3.7.6 中顯著的變更

Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint() is no longer supported. This is because of the behavior of the socket option SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228 [https://bugs.python.org/issue?@action=redirect&bpo=37228].)

Python 3.7.10 中顯著的變更

Earlier Python versions allowed using both ; and & as query parameter separators in urllib.parse.parse_qs() and urllib.parse.parse_qsl(). Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with & as the default. This change also affects cgi.parse() and cgi.parse_multipart() as they use the affected functions internally. For more details, please see their respective documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967].)

Python 3.7.11 中顯著的變更

A security fix alters the ftplib.FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel. We reuse the ftp server IP address instead. For unusual code requiring the old behavior, set a trust_server_pasv_ipv4_address attribute on your FTP instance to True. (See gh-87451 [https://github.com/python/cpython/issues/87451])

The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986, ASCII newline \n, \r and tab \t characters are stripped from the URL by the parser urllib.parse() preventing such attacks. The removal characters are controlled by a new module level variable urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (See gh-88048 [https://github.com/python/cpython/issues/88048])

Python 3.7.14 中顯著的安全性功能

Converting between int and str in bases other than 2 (binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity. This is a mitigation for CVE 2020-10735 [https://www.cve.org/CVERecord?id=CVE-2020-10735]. This limit can be configured or disabled by environment variable, command line flag, or sys APIs. See the integer string conversion length limitation documentation. The default limit is 4300 digits in string form.

Python 3.6 有什麼新功能

編輯者:

Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <yury@magic.io>

本文介紹了 Python 3.6 與 3.5 相比多了哪些新功能。Python 3.6 已於 2016 年 12 月 23 日發布。完整詳情請見 changelog [https://docs.python.org/3.6/whatsnew/changelog.html]。

也參考

PEP 494 [https://peps.python.org/pep-0494/] - Python 3.6 發佈時程

發布重點摘要

新增語法特性：

PEP 498, formatted string literals.

PEP 515, underscores in numeric literals.

PEP 526, syntax for variable annotations.

PEP 525, asynchronous generators.

PEP 530: asynchronous comprehensions.

新的函式庫模組：

secrets: PEP 506 -- Adding A Secrets Module To The Standard Library.

CPython 實作改進：

The dict type has been reimplemented to use a more compact representation based on a proposal by Raymond Hettinger [https://mail.python.org/pipermail/python-dev/2012-December/123028.html] and similar to the PyPy dict implementation [https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html]. This resulted in dictionaries using 20% to 25% less memory when compared to Python 3.5.

Customization of class creation has been simplified with the new protocol.

The class attribute definition order is now preserved.

The order of elements in **kwargs now corresponds to the order in which keyword arguments were passed to the function.

DTrace and SystemTap probing support has been added.

The new PYTHONMALLOC environment variable can now be used to debug the interpreter memory allocation and access errors.

標準函式庫中的顯著改進

The asyncio module has received new features, significant usability and performance improvements, and a fair amount of bug fixes. Starting with Python 3.6 the asyncio module is no longer provisional and its API is considered stable.

A new file system path protocol has been implemented to support path-like objects. All standard library functions operating on paths have been updated to work with the new protocol.

The datetime module has gained support for Local Time Disambiguation.

The typing module received a number of improvements.

The tracemalloc module has been significantly reworked and is now used to provide better output for ResourceWarning as well as provide better diagnostics for memory allocation errors. See the PYTHONMALLOC section for more information.

安全性改進：

The new secrets module has been added to simplify the generation of cryptographically strong pseudo-random numbers suitable for managing secrets such as account authentication, tokens, and similar.

On Linux, os.urandom() now blocks until the system urandom entropy pool is initialized to increase the security. See the PEP 524 [https://peps.python.org/pep-0524/] for the rationale.

hashlib 與 ssl 模組現在支援 OpenSSL 1.1.0。

The default settings and feature set of the ssl module have been improved.

The hashlib module received support for the BLAKE2, SHA-3 and SHAKE hash algorithms and the scrypt() key derivation function.

Windows 改進：

PEP 528 and PEP 529, Windows filesystem and console encoding changed to UTF-8.

The py.exe launcher, when used interactively, no longer prefers Python 2 over Python 3 when the user doesn't specify a version (via command line arguments or a config file). Handling of shebang lines remains unchanged - "python" refers to Python 2 in that case.

python.exe and pythonw.exe have been marked as long-path aware, which means that the 260 character path limit may no longer apply. See removing the MAX_PATH limitation for details.

A ._pth file can be added to force isolated mode and fully specify all search paths to avoid registry and environment lookup. See the documentation for more information.

A python36.zip file now works as a landmark to infer PYTHONHOME. See the documentation for more information.

新增功能

PEP 498: Formatted string literals

PEP 498 [https://peps.python.org/pep-0498/] introduces a new kind of string literals: f-strings, or formatted string literals.

Formatted string literals are prefixed with 'f' and are similar to the format strings accepted by str.format(). They contain replacement fields surrounded by curly braces. The replacement fields are expressions, which are evaluated at run time, and then formatted using the format() protocol:

>>> name = "Fred"
>>> f"He said his name is {name}."
'He said his name is Fred.'
>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal("12.34567")
>>> f"result: {value:{width}.{precision}}"  # 巢狀欄位
'result:      12.35'

也參考

PEP 498 [https://peps.python.org/pep-0498/] -- Literal String Interpolation.

由 Eric V. Smith 撰寫 PEP 與實作。

Feature documentation.

PEP 526: Syntax for variable annotations

PEP 484 [https://peps.python.org/pep-0484/] introduced the standard for type annotations of function parameters, a.k.a. type hints. This PEP adds syntax to Python for annotating the types of variables including class variables and instance variables:

primes: List[int] = []

captain: str  # Note: no initial value!

class Starship:
    stats: Dict[str, int] = {}

Just as for function annotations, the Python interpreter does not attach any particular meaning to variable annotations and only stores them in the __annotations__ attribute of a class or module.

In contrast to variable declarations in statically typed languages, the goal of annotation syntax is to provide an easy way to specify structured type metadata for third party tools and libraries via the abstract syntax tree and the __annotations__ attribute.

也參考

PEP 526 [https://peps.python.org/pep-0526/] -- Syntax for variable annotations.

PEP written by Ryan Gonzalez, Philip House, Ivan Levkivskyi, Lisa Roach, and Guido van Rossum. Implemented by Ivan Levkivskyi.

Tools that use or will use the new syntax: mypy [https://www.mypy-lang.org/], pytype [https://github.com/google/pytype], PyCharm, etc.

PEP 515: Underscores in Numeric Literals

PEP 515 [https://peps.python.org/pep-0515/] adds the ability to use underscores in numeric literals for improved readability. For example:

>>> 1_000_000_000_000_000
1000000000000000
>>> 0x_FF_FF_FF_FF
4294967295

Single underscores are allowed between digits and after any base specifier. Leading, trailing, or multiple underscores in a row are not allowed.

The string formatting language also now has support for the '_' option to signal the use of an underscore for a thousands separator for floating-point presentation types and for integer presentation type 'd'. For integer presentation types 'b', 'o', 'x', and 'X', underscores will be inserted every 4 digits:

>>> '{:_}'.format(1000000)
'1_000_000'
>>> '{:_x}'.format(0xFFFFFFFF)
'ffff_ffff'

也參考

PEP 515 [https://peps.python.org/pep-0515/] -- Underscores in Numeric Literals

由 Georg Brandl 與 Serhiy Storchaka 撰寫 PEP。

PEP 525: Asynchronous Generators

PEP 492 [https://peps.python.org/pep-0492/] introduced support for native coroutines and async / await syntax to Python 3.5. A notable limitation of the Python 3.5 implementation is that it was not possible to use await and yield in the same function body. In Python 3.6 this restriction has been lifted, making it possible to define asynchronous generators:

async def ticker(delay, to):
    """Yield numbers from 0 to *to* every *delay* seconds."""
    for i in range(to):
        yield i
        await asyncio.sleep(delay)

The new syntax allows for faster and more concise code.

也參考

PEP 525 [https://peps.python.org/pep-0525/] -- Asynchronous Generators

由 Yury Selivanov 撰寫 PEP 與實作。

PEP 530: Asynchronous Comprehensions

PEP 530 [https://peps.python.org/pep-0530/] adds support for using async for in list, set, dict comprehensions and generator expressions:

result = [i async for i in aiter() if i % 2]

Additionally, await expressions are supported in all kinds of comprehensions:

result = [await fun() for fun in funcs if await condition()]

也參考

PEP 530 [https://peps.python.org/pep-0530/] -- Asynchronous Comprehensions

由 Yury Selivanov 撰寫 PEP 與實作。

PEP 487: Simpler customization of class creation

It is now possible to customize subclass creation without using a metaclass. The new __init_subclass__ classmethod will be called on the base class whenever a new subclass is created:

class PluginBase:
    subclasses = []

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.subclasses.append(cls)

class Plugin1(PluginBase):
    pass

class Plugin2(PluginBase):
    pass

In order to allow zero-argument super() calls to work correctly from __init_subclass__() implementations, custom metaclasses must ensure that the new __classcell__ namespace entry is propagated to type.__new__ (as described in Creating the class object).

也參考

PEP 487 [https://peps.python.org/pep-0487/] -- Simpler customization of class creation

由 Martin Teichmann 撰寫 PEP 與實作。

Feature documentation

PEP 487: Descriptor Protocol Enhancements

PEP 487 [https://peps.python.org/pep-0487/] extends the descriptor protocol to include the new optional __set_name__() method. Whenever a new class is defined, the new method will be called on all descriptors included in the definition, providing them with a reference to the class being defined and the name given to the descriptor within the class namespace. In other words, instances of descriptors can now know the attribute name of the descriptor in the owner class:

class IntField:
    def __get__(self, instance, owner):
        return instance.__dict__[self.name]

    def __set__(self, instance, value):
        if not isinstance(value, int):
            raise ValueError(f'expecting integer in {self.name}')
        instance.__dict__[self.name] = value

    # this is the new initializer:
    def __set_name__(self, owner, name):
        self.name = name

class Model:
    int_field = IntField()

也參考

PEP 487 [https://peps.python.org/pep-0487/] -- Simpler customization of class creation

由 Martin Teichmann 撰寫 PEP 與實作。

Feature documentation

PEP 519: Adding a file system path protocol

File system paths have historically been represented as str or bytes objects. This has led to people who write code which operate on file system paths to assume that such objects are only one of those two types (an int representing a file descriptor does not count as that is not a file path). Unfortunately that assumption prevents alternative object representations of file system paths like pathlib from working with pre-existing code, including Python's standard library.

To fix this situation, a new interface represented by os.PathLike has been defined. By implementing the __fspath__() method, an object signals that it represents a path. An object can then provide a low-level representation of a file system path as a str or bytes object. This means an object is considered path-like if it implements os.PathLike or is a str or bytes object which represents a file system path. Code can use os.fspath(), os.fsdecode(), or os.fsencode() to explicitly get a str and/or bytes representation of a path-like object.

The built-in open() function has been updated to accept os.PathLike objects, as have all relevant functions in the os and os.path modules, and most other functions and classes in the standard library. The os.DirEntry class and relevant classes in pathlib have also been updated to implement os.PathLike.

The hope is that updating the fundamental functions for operating on file system paths will lead to third-party code to implicitly support all path-like objects without any code changes, or at least very minimal ones (e.g. calling os.fspath() at the beginning of code before operating on a path-like object).

Here are some examples of how the new interface allows for pathlib.Path to be used more easily and transparently with pre-existing code:

>>> import pathlib
>>> with open(pathlib.Path("README")) as f:
...     contents = f.read()
...
>>> import os.path
>>> os.path.splitext(pathlib.Path("some_file.txt"))
('some_file', '.txt')
>>> os.path.join("/a/b", pathlib.Path("c"))
'/a/b/c'
>>> import os
>>> os.fspath(pathlib.Path("some_file.txt"))
'some_file.txt'

(Implemented by Brett Cannon, Ethan Furman, Dusty Phillips, and Jelle Zijlstra.)

也參考

PEP 519 [https://peps.python.org/pep-0519/] -- Adding a file system path protocol

由 Brett Cannon 與 Koos Zevenhoven 撰寫 PEP。

PEP 495: Local Time Disambiguation

In most world locations, there have been and will be times when local clocks are moved back. In those times, intervals are introduced in which local clocks show the same time twice in the same day. In these situations, the information displayed on a local clock (or stored in a Python datetime instance) is insufficient to identify a particular moment in time.

PEP 495 [https://peps.python.org/pep-0495/] adds the new fold attribute to instances of datetime.datetime and datetime.time classes to differentiate between two moments in time for which local times are the same:

>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0

The values of the fold attribute have the value 0 for all instances except those that represent the second (chronologically) moment in time in an ambiguous case.

也參考

PEP 495 [https://peps.python.org/pep-0495/] -- Local Time Disambiguation

PEP written by Alexander Belopolsky and Tim Peters, implementation by Alexander Belopolsky.

PEP 529: Change Windows filesystem encoding to UTF-8

Representing filesystem paths is best performed with str (Unicode) rather than bytes. However, there are some situations where using bytes is sufficient and correct.

Prior to Python 3.6, data loss could result when using bytes paths on Windows. With this change, using bytes to represent paths is now supported on Windows, provided those bytes are encoded with the encoding returned by sys.getfilesystemencoding(), which now defaults to 'utf-8'.

Applications that do not use str to represent paths should use os.fsencode() and os.fsdecode() to ensure their bytes are correctly encoded. To revert to the previous behaviour, set PYTHONLEGACYWINDOWSFSENCODING or call sys._enablelegacywindowsfsencoding().

See PEP 529 [https://peps.python.org/pep-0529/] for more information and discussion of code modifications that may be required.

PEP 528: Change Windows console encoding to UTF-8

The default console on Windows will now accept all Unicode characters and provide correctly read str objects to Python code. sys.stdin, sys.stdout and sys.stderr now default to utf-8 encoding.

This change only applies when using an interactive console, and not when redirecting files or pipes. To revert to the previous behaviour for interactive console use, set PYTHONLEGACYWINDOWSSTDIO.

也參考

PEP 528 [https://peps.python.org/pep-0528/] -- Change Windows console encoding to UTF-8

由 Steve Dower 撰寫 PEP 與實作。

PEP 520: Preserving Class Attribute Definition Order

Attributes in a class definition body have a natural ordering: the same order in which the names appear in the source. This order is now preserved in the new class's __dict__ attribute.

Also, the effective default class execution namespace (returned from type.__prepare__()) is now an insertion-order-preserving mapping.

也參考

PEP 520 [https://peps.python.org/pep-0520/] -- Preserving Class Attribute Definition Order

由 Eric Snow 撰寫 PEP 與實作。

PEP 468: Preserving Keyword Argument Order

**kwargs in a function signature is now guaranteed to be an insertion-order-preserving mapping.

也參考

PEP 468 [https://peps.python.org/pep-0468/] -- Preserving Keyword Argument Order

由 Eric Snow 撰寫 PEP 與實作。

New dict implementation

The dict type now uses a "compact" representation based on a proposal by Raymond Hettinger [https://mail.python.org/pipermail/python-dev/2012-December/123028.html] which was first implemented by PyPy [https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html]. The memory usage of the new dict() is between 20% and 25% smaller compared to Python 3.5.

The order-preserving aspect of this new implementation is considered an implementation detail and should not be relied upon (this may change in the future, but it is desired to have this new dict implementation in the language for a few releases before changing the language spec to mandate order-preserving semantics for all current and future Python implementations; this also helps preserve backwards-compatibility with older versions of the language where random iteration order is still in effect, e.g. Python 3.5).

(Contributed by INADA Naoki in bpo-27350 [https://bugs.python.org/issue?@action=redirect&bpo=27350]. Idea originally suggested by Raymond Hettinger [https://mail.python.org/pipermail/python-dev/2012-December/123028.html].)

PEP 523: Adding a frame evaluation API to CPython

While Python provides extensive support to customize how code executes, one place it has not done so is in the evaluation of frame objects. If you wanted some way to intercept frame evaluation in Python there really wasn't any way without directly manipulating function pointers for defined functions.

PEP 523 [https://peps.python.org/pep-0523/] changes this by providing an API to make frame evaluation pluggable at the C level. This will allow for tools such as debuggers and JITs to intercept frame evaluation before the execution of Python code begins. This enables the use of alternative evaluation implementations for Python code, tracking frame evaluation, etc.

This API is not part of the limited C API and is marked as private to signal that usage of this API is expected to be limited and only applicable to very select, low-level use-cases. Semantics of the API will change with Python as necessary.

也參考

PEP 523 [https://peps.python.org/pep-0523/] -- Adding a frame evaluation API to CPython

由 Brett Cannon 與 Dino Viehland 撰寫 PEP。

PYTHONMALLOC environment variable

The new PYTHONMALLOC environment variable allows setting the Python memory allocators and installing debug hooks.

It is now possible to install debug hooks on Python memory allocators on Python compiled in release mode using PYTHONMALLOC=debug. Effects of debug hooks:

Newly allocated memory is filled with the byte 0xCB

Freed memory is filled with the byte 0xDB

Detect violations of the Python memory allocator API. For example, PyObject_Free() called on a memory block allocated by PyMem_Malloc().

Detect writes before the start of a buffer (buffer underflows)

Detect writes after the end of a buffer (buffer overflows)

Check that the GIL is held when allocator functions of PYMEM_DOMAIN_OBJ (ex: PyObject_Malloc()) and PYMEM_DOMAIN_MEM (ex: PyMem_Malloc()) domains are called.

Checking if the GIL is held is also a new feature of Python 3.6.

See the PyMem_SetupDebugHooks() function for debug hooks on Python memory allocators.

It is now also possible to force the usage of the malloc() allocator of the C library for all Python memory allocations using PYTHONMALLOC=malloc. This is helpful when using external memory debuggers like Valgrind on a Python compiled in release mode.

On error, the debug hooks on Python memory allocators now use the tracemalloc module to get the traceback where a memory block was allocated.

Example of fatal error on buffer overflow using python3.6 -X tracemalloc=5 (store 5 frames in traces):

Debug memory block at address p=0x7fbcd41666f8: API 'o'
    4 bytes originally requested
    The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
    The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb):
        at tail+0: 0x02 *** OUCH
        at tail+1: 0xfb
        at tail+2: 0xfb
        at tail+3: 0xfb
        at tail+4: 0xfb
        at tail+5: 0xfb
        at tail+6: 0xfb
        at tail+7: 0xfb
    The block was made by call #1233329 to debug malloc/realloc.
    Data at p: 1a 2b 30 00

Memory block allocated at (most recent call first):
  File "test/test_bytes.py", line 323
  File "unittest/case.py", line 600
  File "unittest/case.py", line 648
  File "unittest/suite.py", line 122
  File "unittest/suite.py", line 84

Fatal Python error: bad trailing pad byte

Current thread 0x00007fbcdbd32700 (most recent call first):
  File "test/test_bytes.py", line 323 in test_hex
  File "unittest/case.py", line 600 in run
  File "unittest/case.py", line 648 in __call__
  File "unittest/suite.py", line 122 in run
  File "unittest/suite.py", line 84 in __call__
  File "unittest/suite.py", line 122 in run
  File "unittest/suite.py", line 84 in __call__
  ...

（由 Victor Stinner 於 bpo-26516 [https://bugs.python.org/issue?@action=redirect&bpo=26516] 和 bpo-26564 [https://bugs.python.org/issue?@action=redirect&bpo=26564] 中貢獻。）

DTrace and SystemTap probing support

Python can now be built --with-dtrace which enables static markers for the following events in the interpreter:

function call/return

garbage collection started/finished

line of code executed.

This can be used to instrument running interpreters in production, without the need to recompile specific debug builds or providing application-specific profiling/debugging code.

More details in 使用 DTrace 和 SystemTap 檢測 CPython.

The current implementation is tested on Linux and macOS. Additional markers may be added in the future.

(Contributed by Łukasz Langa in bpo-21590 [https://bugs.python.org/issue?@action=redirect&bpo=21590], based on patches by Jesús Cea Avión, David Malcolm, and Nikhil Benesch.)

其他語言更動

Some smaller changes made to the core Python language are:

A global or nonlocal statement must now textually appear before the first use of the affected name in the same scope. Previously this was a SyntaxWarning.

It is now possible to set a special method to None to indicate that the corresponding operation is not available. For example, if a class sets __iter__() to None, the class is not iterable. (Contributed by Andrew Barnert and Ivan Levkivskyi in bpo-25958 [https://bugs.python.org/issue?@action=redirect&bpo=25958].)

Long sequences of repeated traceback lines are now abbreviated as "[Previous line repeated {count} more times]" (see traceback for an example). (Contributed by Emanuel Barry in bpo-26823 [https://bugs.python.org/issue?@action=redirect&bpo=26823].)

Import now raises the new exception ModuleNotFoundError (subclass of ImportError) when it cannot find a module. Code that currently checks for ImportError (in try-except) will still work. (Contributed by Eric Snow in bpo-15767 [https://bugs.python.org/issue?@action=redirect&bpo=15767].)

Class methods relying on zero-argument super() will now work correctly when called from metaclass methods during class creation. (Contributed by Martin Teichmann in bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722].)

新模組

secrets

The main purpose of the new secrets module is to provide an obvious way to reliably generate cryptographically strong pseudo-random values suitable for managing secrets, such as account authentication, tokens, and similar.

警告

Note that the pseudo-random generators in the random module should NOT be used for security purposes. Use secrets on Python 3.6+ and os.urandom() on Python 3.5 and earlier.

也參考

PEP 506 [https://peps.python.org/pep-0506/] -- Adding A Secrets Module To The Standard Library

由 Steven D'Aprano 撰寫 PEP 與實作。

改進的模組

array

Exhausted iterators of array.array will now stay exhausted even if the iterated array is extended. This is consistent with the behavior of other mutable sequences.

由 Serhiy Storchaka 於 bpo-26492 [https://bugs.python.org/issue?@action=redirect&bpo=26492] 中貢獻。

ast

The new ast.Constant AST node has been added. It can be used by external AST optimizers for the purposes of constant folding.

由 Victor Stinner 於 bpo-26146 [https://bugs.python.org/issue?@action=redirect&bpo=26146] 中貢獻。

asyncio

Starting with Python 3.6 the asyncio module is no longer provisional and its API is considered stable.

Notable changes in the asyncio module since Python 3.5.0 (all backported to 3.5.x due to the provisional status):

The get_event_loop() function has been changed to always return the currently running loop when called from coroutines and callbacks. (Contributed by Yury Selivanov in bpo-28613 [https://bugs.python.org/issue?@action=redirect&bpo=28613].)

The ensure_future() function and all functions that use it, such as loop.run_until_complete(), now accept all kinds of awaitable objects. (Contributed by Yury Selivanov.)

New run_coroutine_threadsafe() function to submit coroutines to event loops from other threads. (Contributed by Vincent Michel.)

New Transport.is_closing() method to check if the transport is closing or closed. (Contributed by Yury Selivanov.)

The loop.create_server() method can now accept a list of hosts. (Contributed by Yann Sionneau.)

New loop.create_future() method to create Future objects. This allows alternative event loop implementations, such as uvloop [https://github.com/MagicStack/uvloop], to provide a faster asyncio.Future implementation. (Contributed by Yury Selivanov in bpo-27041 [https://bugs.python.org/issue?@action=redirect&bpo=27041].)

New loop.get_exception_handler() method to get the current exception handler. (Contributed by Yury Selivanov in bpo-27040 [https://bugs.python.org/issue?@action=redirect&bpo=27040].)

New StreamReader.readuntil() method to read data from the stream until a separator bytes sequence appears. (Contributed by Mark Korenberg.)

The performance of StreamReader.readexactly() has been improved. (Contributed by Mark Korenberg in bpo-28370 [https://bugs.python.org/issue?@action=redirect&bpo=28370].)

The loop.getaddrinfo() method is optimized to avoid calling the system getaddrinfo function if the address is already resolved. (Contributed by A. Jesse Jiryu Davis.)

The loop.stop() method has been changed to stop the loop immediately after the current iteration. Any new callbacks scheduled as a result of the last iteration will be discarded. (Contributed by Guido van Rossum in bpo-25593 [https://bugs.python.org/issue?@action=redirect&bpo=25593].)

Future.set_exception will now raise TypeError when passed an instance of the StopIteration exception. (Contributed by Chris Angelico in bpo-26221 [https://bugs.python.org/issue?@action=redirect&bpo=26221].)

New loop.connect_accepted_socket() method to be used by servers that accept connections outside of asyncio, but that use asyncio to handle them. (Contributed by Jim Fulton in bpo-27392 [https://bugs.python.org/issue?@action=redirect&bpo=27392].)

TCP_NODELAY flag is now set for all TCP transports by default. (Contributed by Yury Selivanov in bpo-27456 [https://bugs.python.org/issue?@action=redirect&bpo=27456].)

New loop.shutdown_asyncgens() to properly close pending asynchronous generators before closing the loop. (Contributed by Yury Selivanov in bpo-28003 [https://bugs.python.org/issue?@action=redirect&bpo=28003].)

Future and Task classes now have an optimized C implementation which makes asyncio code up to 30% faster. (Contributed by Yury Selivanov and INADA Naoki in bpo-26081 [https://bugs.python.org/issue?@action=redirect&bpo=26081] and bpo-28544 [https://bugs.python.org/issue?@action=redirect&bpo=28544].)

binascii

The b2a_base64() function now accepts an optional newline keyword argument to control whether the newline character is appended to the return value. (Contributed by Victor Stinner in bpo-25357 [https://bugs.python.org/issue?@action=redirect&bpo=25357].)

cmath

The new cmath.tau (τ) constant has been added. (Contributed by Lisa Roach in bpo-12345 [https://bugs.python.org/issue?@action=redirect&bpo=12345], see PEP 628 [https://peps.python.org/pep-0628/] for details.)

New constants: cmath.inf and cmath.nan to match math.inf and math.nan, and also cmath.infj and cmath.nanj to match the format used by complex repr. (Contributed by Mark Dickinson in bpo-23229 [https://bugs.python.org/issue?@action=redirect&bpo=23229].)

collections

The new Collection abstract base class has been added to represent sized iterable container classes. (Contributed by Ivan Levkivskyi, docs by Neil Girdhar in bpo-27598 [https://bugs.python.org/issue?@action=redirect&bpo=27598].)

The new Reversible abstract base class represents iterable classes that also provide the __reversed__() method. (Contributed by Ivan Levkivskyi in bpo-25987 [https://bugs.python.org/issue?@action=redirect&bpo=25987].)

The new AsyncGenerator abstract base class represents asynchronous generators. (Contributed by Yury Selivanov in bpo-28720 [https://bugs.python.org/issue?@action=redirect&bpo=28720].)

The namedtuple() function now accepts an optional keyword argument module, which, when specified, is used for the __module__ attribute of the returned named tuple class. (Contributed by Raymond Hettinger in bpo-17941 [https://bugs.python.org/issue?@action=redirect&bpo=17941].)

The verbose and rename arguments for namedtuple() are now keyword-only. (Contributed by Raymond Hettinger in bpo-25628 [https://bugs.python.org/issue?@action=redirect&bpo=25628].)

Recursive collections.deque instances can now be pickled. (Contributed by Serhiy Storchaka in bpo-26482 [https://bugs.python.org/issue?@action=redirect&bpo=26482].)

concurrent.futures

The ThreadPoolExecutor class constructor now accepts an optional thread_name_prefix argument to make it possible to customize the names of the threads created by the pool. (Contributed by Gregory P. Smith in bpo-27664 [https://bugs.python.org/issue?@action=redirect&bpo=27664].)

contextlib

The contextlib.AbstractContextManager class has been added to provide an abstract base class for context managers. It provides a sensible default implementation for __enter__() which returns self and leaves __exit__() an abstract method. A matching class has been added to the typing module as typing.ContextManager. (Contributed by Brett Cannon in bpo-25609 [https://bugs.python.org/issue?@action=redirect&bpo=25609].)

datetime

The datetime and time classes have the new fold attribute used to disambiguate local time when necessary. Many functions in the datetime have been updated to support local time disambiguation. See Local Time Disambiguation section for more information. (Contributed by Alexander Belopolsky in bpo-24773 [https://bugs.python.org/issue?@action=redirect&bpo=24773].)

The datetime.strftime() and date.strftime() methods now support ISO 8601 date directives %G, %u and %V. (Contributed by Ashley Anderson in bpo-12006 [https://bugs.python.org/issue?@action=redirect&bpo=12006].)

The datetime.isoformat() function now accepts an optional timespec argument that specifies the number of additional components of the time value to include. (Contributed by Alessandro Cucci and Alexander Belopolsky in bpo-19475 [https://bugs.python.org/issue?@action=redirect&bpo=19475].)

The datetime.combine() now accepts an optional tzinfo argument. (Contributed by Alexander Belopolsky in bpo-27661 [https://bugs.python.org/issue?@action=redirect&bpo=27661].)

decimal

New Decimal.as_integer_ratio() method that returns a pair (n, d) of integers that represent the given Decimal instance as a fraction, in lowest terms and with a positive denominator:

>>> Decimal('-3.14').as_integer_ratio()
(-157, 50)

（由 Stefan Krah 和 Mark Dickinson 於 bpo-25928 [https://bugs.python.org/issue?@action=redirect&bpo=25928] 中貢獻。）

distutils

The default_format attribute has been removed from distutils.command.sdist.sdist and the formats attribute defaults to ['gztar']. Although not anticipated, any code relying on the presence of default_format may need to be adapted. See bpo-27819 [https://bugs.python.org/issue?@action=redirect&bpo=27819] for more details.

email

The new email API, enabled via the policy keyword to various constructors, is no longer provisional. The email documentation has been reorganized and rewritten to focus on the new API, while retaining the old documentation for the legacy API. (Contributed by R. David Murray in bpo-24277 [https://bugs.python.org/issue?@action=redirect&bpo=24277].)

The email.mime classes now all accept an optional policy keyword. (Contributed by Berker Peksag in bpo-27331 [https://bugs.python.org/issue?@action=redirect&bpo=27331].)

The DecodedGenerator now supports the policy keyword.

There is a new policy attribute, message_factory, that controls what class is used by default when the parser creates new message objects. For the email.policy.compat32 policy this is Message, for the new policies it is EmailMessage. (Contributed by R. David Murray in bpo-20476 [https://bugs.python.org/issue?@action=redirect&bpo=20476].)

encodings

On Windows, added the 'oem' encoding to use CP_OEMCP, and the 'ansi' alias for the existing 'mbcs' encoding, which uses the CP_ACP code page. (Contributed by Steve Dower in bpo-27959 [https://bugs.python.org/issue?@action=redirect&bpo=27959].)

enum

Two new enumeration base classes have been added to the enum module: Flag and IntFlag. Both are used to define constants that can be combined using the bitwise operators. (Contributed by Ethan Furman in bpo-23591 [https://bugs.python.org/issue?@action=redirect&bpo=23591].)

Many standard library modules have been updated to use the IntFlag class for their constants.

The new enum.auto value can be used to assign values to enum members automatically:

>>> from enum import Enum, auto
>>> class Color(Enum):
...     red = auto()
...     blue = auto()
...     green = auto()
...
>>> list(Color)
[<Color.red: 1>, <Color.blue: 2>, <Color.green: 3>]

faulthandler

On Windows, the faulthandler module now installs a handler for Windows exceptions: see faulthandler.enable(). (Contributed by Victor Stinner in bpo-23848 [https://bugs.python.org/issue?@action=redirect&bpo=23848].)

fileinput

hook_encoded() now supports the errors argument. (Contributed by Joseph Hackman in bpo-25788 [https://bugs.python.org/issue?@action=redirect&bpo=25788].)

hashlib

hashlib supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2. (Contributed by Christian Heimes in bpo-26470 [https://bugs.python.org/issue?@action=redirect&bpo=26470].)

BLAKE2 hash functions were added to the module. blake2b() and blake2s() are always available and support the full feature set of BLAKE2. (Contributed by Christian Heimes in bpo-26798 [https://bugs.python.org/issue?@action=redirect&bpo=26798] based on code by Dmitry Chestnykh and Samuel Neves. Documentation written by Dmitry Chestnykh.)

The SHA-3 hash functions sha3_224(), sha3_256(), sha3_384(), sha3_512(), and SHAKE hash functions shake_128() and shake_256() were added. (Contributed by Christian Heimes in bpo-16113 [https://bugs.python.org/issue?@action=redirect&bpo=16113]. Keccak Code Package by Guido Bertoni, Joan Daemen, Michaël Peeters, Gilles Van Assche, and Ronny Van Keer.)

The password-based key derivation function scrypt() is now available with OpenSSL 1.1.0 and newer. (Contributed by Christian Heimes in bpo-27928 [https://bugs.python.org/issue?@action=redirect&bpo=27928].)

http.client

HTTPConnection.request() and endheaders() both now support chunked encoding request bodies. (Contributed by Demian Brecht and Rolf Krahl in bpo-12319 [https://bugs.python.org/issue?@action=redirect&bpo=12319].)

idlelib 與 IDLE

The idlelib package is being modernized and refactored to make IDLE look and work better and to make the code easier to understand, test, and improve. Part of making IDLE look better, especially on Linux and Mac, is using ttk widgets, mostly in the dialogs. As a result, IDLE no longer runs with tcl/tk 8.4. It now requires tcl/tk 8.5 or 8.6. We recommend running the latest release of either.

'Modernizing' includes renaming and consolidation of idlelib modules. The renaming of files with partial uppercase names is similar to the renaming of, for instance, Tkinter and TkFont to tkinter and tkinter.font in 3.0. As a result, imports of idlelib files that worked in 3.5 will usually not work in 3.6. At least a module name change will be needed (see idlelib/README.txt), sometimes more. (Name changes contributed by Al Swiegart and Terry Reedy in bpo-24225 [https://bugs.python.org/issue?@action=redirect&bpo=24225]. Most idlelib patches since have been and will be part of the process.)

In compensation, the eventual result with be that some idlelib classes will be easier to use, with better APIs and docstrings explaining them. Additional useful information will be added to idlelib when available.

New in 3.6.2:

Multiple fixes for autocompletion. (Contributed by Louie Lu in bpo-15786 [https://bugs.python.org/issue?@action=redirect&bpo=15786].)

New in 3.6.3:

Module Browser (on the File menu, formerly called Class Browser), now displays nested functions and classes in addition to top-level functions and classes. (Contributed by Guilherme Polo, Cheryl Sabella, and Terry Jan Reedy in bpo-1612262 [https://bugs.python.org/issue?@action=redirect&bpo=1612262].)

The IDLE features formerly implemented as extensions have been reimplemented as normal features. Their settings have been moved from the Extensions tab to other dialog tabs. (Contributed by Charles Wohlganger and Terry Jan Reedy in bpo-27099 [https://bugs.python.org/issue?@action=redirect&bpo=27099].)

The Settings dialog (Options, Configure IDLE) has been partly rewritten to improve both appearance and function. (Contributed by Cheryl Sabella and Terry Jan Reedy in multiple issues.)

New in 3.6.4:

The font sample now includes a selection of non-Latin characters so that users can better see the effect of selecting a particular font. (Contributed by Terry Jan Reedy in bpo-13802 [https://bugs.python.org/issue?@action=redirect&bpo=13802].) The sample can be edited to include other characters. (Contributed by Serhiy Storchaka in bpo-31860 [https://bugs.python.org/issue?@action=redirect&bpo=31860].)

New in 3.6.6:

Editor code context option revised. Box displays all context lines up to maxlines. Clicking on a context line jumps the editor to that line. Context colors for custom themes is added to Highlights tab of Settings dialog. (Contributed by Cheryl Sabella and Terry Jan Reedy in bpo-33642 [https://bugs.python.org/issue?@action=redirect&bpo=33642], bpo-33768 [https://bugs.python.org/issue?@action=redirect&bpo=33768], and bpo-33679 [https://bugs.python.org/issue?@action=redirect&bpo=33679].)

On Windows, a new API call tells Windows that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect. (Contributed by Terry Jan Reedy in bpo-33656 [https://bugs.python.org/issue?@action=redirect&bpo=33656].)

New in 3.6.7:

Output over N lines (50 by default) is squeezed down to a button. N can be changed in the PyShell section of the General page of the Settings dialog. Fewer, but possibly extra long, lines can be squeezed by right clicking on the output. Squeezed output can be expanded in place by double-clicking the button or into the clipboard or a separate window by right-clicking the button. (Contributed by Tal Einat in bpo-1529353 [https://bugs.python.org/issue?@action=redirect&bpo=1529353].)

importlib

Import now raises the new exception ModuleNotFoundError (subclass of ImportError) when it cannot find a module. Code that current checks for ImportError (in try-except) will still work. (Contributed by Eric Snow in bpo-15767 [https://bugs.python.org/issue?@action=redirect&bpo=15767].)

importlib.util.LazyLoader now calls create_module() on the wrapped loader, removing the restriction that importlib.machinery.BuiltinImporter and importlib.machinery.ExtensionFileLoader couldn't be used with importlib.util.LazyLoader.

importlib.util.cache_from_source(), importlib.util.source_from_cache(), and importlib.util.spec_from_file_location() now accept a path-like object.

inspect

The inspect.signature() function now reports the implicit .0 parameters generated by the compiler for comprehension and generator expression scopes as if they were positional-only parameters called implicit0. (Contributed by Jelle Zijlstra in bpo-19611 [https://bugs.python.org/issue?@action=redirect&bpo=19611].)

To reduce code churn when upgrading from Python 2.7 and the legacy inspect.getargspec() API, the previously documented deprecation of inspect.getfullargspec() has been reversed. While this function is convenient for single/source Python 2/3 code bases, the richer inspect.signature() interface remains the recommended approach for new code. (Contributed by Nick Coghlan in bpo-27172 [https://bugs.python.org/issue?@action=redirect&bpo=27172])

json

json.load() and json.loads() now support binary input. Encoded JSON should be represented using either UTF-8, UTF-16, or UTF-32. (Contributed by Serhiy Storchaka in bpo-17909 [https://bugs.python.org/issue?@action=redirect&bpo=17909].)

logging

The new WatchedFileHandler.reopenIfNeeded() method has been added to add the ability to check if the log file needs to be reopened. (Contributed by Marian Horban in bpo-24884 [https://bugs.python.org/issue?@action=redirect&bpo=24884].)

math

The tau (τ) constant has been added to the math and cmath modules. (Contributed by Lisa Roach in bpo-12345 [https://bugs.python.org/issue?@action=redirect&bpo=12345], see PEP 628 [https://peps.python.org/pep-0628/] for details.)

multiprocessing

Proxy Objects returned by multiprocessing.Manager() can now be nested. (Contributed by Davin Potts in bpo-6766 [https://bugs.python.org/issue?@action=redirect&bpo=6766].)

os

See the summary of PEP 519 for details on how the os and os.path modules now support path-like objects.

scandir() now supports bytes paths on Windows.

A new close() method allows explicitly closing a scandir() iterator. The scandir() iterator now supports the context manager protocol. If a scandir() iterator is neither exhausted nor explicitly closed a ResourceWarning will be emitted in its destructor. (Contributed by Serhiy Storchaka in bpo-25994 [https://bugs.python.org/issue?@action=redirect&bpo=25994].)

On Linux, os.urandom() now blocks until the system urandom entropy pool is initialized to increase the security. See the PEP 524 [https://peps.python.org/pep-0524/] for the rationale.

The Linux getrandom() syscall (get random bytes) is now exposed as the new os.getrandom() function. (Contributed by Victor Stinner, part of the PEP 524 [https://peps.python.org/pep-0524/])

pathlib

pathlib now supports path-like objects. (Contributed by Brett Cannon in bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186].)

細節請見 PEP 519 中的摘要。

pdb

The Pdb class constructor has a new optional readrc argument to control whether .pdbrc files should be read.

pickle

Objects that need __new__ called with keyword arguments can now be pickled using pickle protocols older than protocol version 4. Protocol version 4 already supports this case. (Contributed by Serhiy Storchaka in bpo-24164 [https://bugs.python.org/issue?@action=redirect&bpo=24164].)

pickletools

pickletools.dis() now outputs the implicit memo index for the MEMOIZE opcode. (Contributed by Serhiy Storchaka in bpo-25382 [https://bugs.python.org/issue?@action=redirect&bpo=25382].)

pydoc

The pydoc module has learned to respect the MANPAGER environment variable. (Contributed by Matthias Klose in bpo-8637 [https://bugs.python.org/issue?@action=redirect&bpo=8637].)

help() and pydoc can now list named tuple fields in the order they were defined rather than alphabetically. (Contributed by Raymond Hettinger in bpo-24879 [https://bugs.python.org/issue?@action=redirect&bpo=24879].)

random

The new choices() function returns a list of elements of specified size from the given population with optional weights. (Contributed by Raymond Hettinger in bpo-18844 [https://bugs.python.org/issue?@action=redirect&bpo=18844].)

re

Added support of modifier spans in regular expressions. Examples: '(?i:p)ython' matches 'python' and 'Python', but not 'PYTHON'; '(?i)g(?-i:v)r' matches 'GvR' and 'gvr', but not 'GVR'. (Contributed by Serhiy Storchaka in bpo-433028 [https://bugs.python.org/issue?@action=redirect&bpo=433028].)

Match object groups can be accessed by __getitem__, which is equivalent to group(). So mo['name'] is now equivalent to mo.group('name'). (Contributed by Eric Smith in bpo-24454 [https://bugs.python.org/issue?@action=redirect&bpo=24454].)

Match objects now support index-like objects as group indices. (Contributed by Jeroen Demeyer and Xiang Zhang in bpo-27177 [https://bugs.python.org/issue?@action=redirect&bpo=27177].)

readline

Added set_auto_history() to enable or disable automatic addition of input to the history list. (Contributed by Tyler Crompton in bpo-26870 [https://bugs.python.org/issue?@action=redirect&bpo=26870].)

rlcompleter

Private and special attribute names now are omitted unless the prefix starts with underscores. A space or a colon is added after some completed keywords. (Contributed by Serhiy Storchaka in bpo-25011 [https://bugs.python.org/issue?@action=redirect&bpo=25011] and bpo-25209 [https://bugs.python.org/issue?@action=redirect&bpo=25209].)

shlex

The shlex has much improved shell compatibility through the new punctuation_chars argument to control which characters are treated as punctuation. (Contributed by Vinay Sajip in bpo-1521950 [https://bugs.python.org/issue?@action=redirect&bpo=1521950].)

site

When specifying paths to add to sys.path in a .pth file, you may now specify file paths on top of directories (e.g. zip files). (Contributed by Wolfgang Langner in bpo-26587 [https://bugs.python.org/issue?@action=redirect&bpo=26587]).

sqlite3

sqlite3.Cursor.lastrowid now supports the REPLACE statement. (Contributed by Alex LordThorsen in bpo-16864 [https://bugs.python.org/issue?@action=redirect&bpo=16864].)

socket

The ioctl() function now supports the SIO_LOOPBACK_FAST_PATH control code. (Contributed by Daniel Stokes in bpo-26536 [https://bugs.python.org/issue?@action=redirect&bpo=26536].)

The getsockopt() constants SO_DOMAIN, SO_PROTOCOL, SO_PEERSEC, and SO_PASSSEC are now supported. (Contributed by Christian Heimes in bpo-26907 [https://bugs.python.org/issue?@action=redirect&bpo=26907].)

The setsockopt() now supports the setsockopt(level, optname, None, optlen: int) form. (Contributed by Christian Heimes in bpo-27744 [https://bugs.python.org/issue?@action=redirect&bpo=27744].)

The socket module now supports the address family AF_ALG to interface with Linux Kernel crypto API. ALG_*, SOL_ALG and sendmsg_afalg() were added. (Contributed by Christian Heimes in bpo-27744 [https://bugs.python.org/issue?@action=redirect&bpo=27744] with support from Victor Stinner.)

New Linux constants TCP_USER_TIMEOUT and TCP_CONGESTION were added. (Contributed by Omar Sandoval, bpo-26273 [https://bugs.python.org/issue?@action=redirect&bpo=26273]).

socketserver

Servers based on the socketserver module, including those defined in http.server, xmlrpc.server and wsgiref.simple_server, now support the context manager protocol. (Contributed by Aviv Palivoda in bpo-26404 [https://bugs.python.org/issue?@action=redirect&bpo=26404].)

The wfile attribute of StreamRequestHandler classes now implements the io.BufferedIOBase writable interface. In particular, calling write() is now guaranteed to send the data in full. (Contributed by Martin Panter in bpo-26721 [https://bugs.python.org/issue?@action=redirect&bpo=26721].)

ssl

ssl supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2. (Contributed by Christian Heimes in bpo-26470 [https://bugs.python.org/issue?@action=redirect&bpo=26470].)

3DES has been removed from the default cipher suites and ChaCha20 Poly1305 cipher suites have been added. (Contributed by Christian Heimes in bpo-27850 [https://bugs.python.org/issue?@action=redirect&bpo=27850] and bpo-27766 [https://bugs.python.org/issue?@action=redirect&bpo=27766].)

SSLContext has better default configuration for options and ciphers. (Contributed by Christian Heimes in bpo-28043 [https://bugs.python.org/issue?@action=redirect&bpo=28043].)

SSL session can be copied from one client-side connection to another with the new SSLSession class. TLS session resumption can speed up the initial handshake, reduce latency and improve performance (Contributed by Christian Heimes in bpo-19500 [https://bugs.python.org/issue?@action=redirect&bpo=19500] based on a draft by Alex Warhawk.)

The new get_ciphers() method can be used to get a list of enabled ciphers in order of cipher priority.

All constants and flags have been converted to IntEnum and IntFlag. (Contributed by Christian Heimes in bpo-28025 [https://bugs.python.org/issue?@action=redirect&bpo=28025].)

Server and client-side specific TLS protocols for SSLContext were added. (Contributed by Christian Heimes in bpo-28085 [https://bugs.python.org/issue?@action=redirect&bpo=28085].)

Added ssl.SSLContext.post_handshake_auth to enable and ssl.SSLSocket.verify_client_post_handshake() to initiate TLS 1.3 post-handshake authentication. (Contributed by Christian Heimes in gh-78851 [https://github.com/python/cpython/issues/78851].)

statistics

A new harmonic_mean() function has been added. (Contributed by Steven D'Aprano in bpo-27181 [https://bugs.python.org/issue?@action=redirect&bpo=27181].)

struct

struct now supports IEEE 754 half-precision floats via the 'e' format specifier. (Contributed by Eli Stevens, Mark Dickinson in bpo-11734 [https://bugs.python.org/issue?@action=redirect&bpo=11734].)

subprocess

subprocess.Popen destructor now emits a ResourceWarning warning if the child process is still running. Use the context manager protocol (with proc: ...) or explicitly call the wait() method to read the exit status of the child process. (Contributed by Victor Stinner in bpo-26741 [https://bugs.python.org/issue?@action=redirect&bpo=26741].)

The subprocess.Popen constructor and all functions that pass arguments through to it now accept encoding and errors arguments. Specifying either of these will enable text mode for the stdin, stdout and stderr streams. (Contributed by Steve Dower in bpo-6135 [https://bugs.python.org/issue?@action=redirect&bpo=6135].)

sys

The new getfilesystemencodeerrors() function returns the name of the error mode used to convert between Unicode filenames and bytes filenames. (Contributed by Steve Dower in bpo-27781 [https://bugs.python.org/issue?@action=redirect&bpo=27781].)

On Windows the return value of the getwindowsversion() function now includes the platform_version field which contains the accurate major version, minor version and build number of the current operating system, rather than the version that is being emulated for the process (Contributed by Steve Dower in bpo-27932 [https://bugs.python.org/issue?@action=redirect&bpo=27932].)

telnetlib

telnetlib.Telnet is now a context manager (contributed by Stéphane Wirtel in bpo-25485 [https://bugs.python.org/issue?@action=redirect&bpo=25485]).

time

The struct_time attributes tm_gmtoff and tm_zone are now available on all platforms.

timeit

The new Timer.autorange() convenience method has been added to call Timer.timeit() repeatedly so that the total run time is greater or equal to 200 milliseconds. (Contributed by Steven D'Aprano in bpo-6422 [https://bugs.python.org/issue?@action=redirect&bpo=6422].)

timeit now warns when there is substantial (4x) variance between best and worst times. (Contributed by Serhiy Storchaka in bpo-23552 [https://bugs.python.org/issue?@action=redirect&bpo=23552].)

tkinter

Added methods Variable.trace_add(), Variable.trace_remove() and trace_info() in the tkinter.Variable class. They replace old methods trace_variable(), trace(), trace_vdelete() and trace_vinfo() that use obsolete Tcl commands and might not work in future versions of Tcl. (Contributed by Serhiy Storchaka in bpo-22115 [https://bugs.python.org/issue?@action=redirect&bpo=22115]).

traceback

Both the traceback module and the interpreter's builtin exception display now abbreviate long sequences of repeated lines in tracebacks as shown in the following example:

>>> def f(): f()
...
>>> f()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in f
  File "<stdin>", line 1, in f
  File "<stdin>", line 1, in f
  [Previous line repeated 995 more times]
RecursionError: maximum recursion depth exceeded

（由 Emanuel Barry 於 bpo-26823 [https://bugs.python.org/issue?@action=redirect&bpo=26823] 中貢獻。）

tracemalloc

The tracemalloc module now supports tracing memory allocations in multiple different address spaces.

The new DomainFilter filter class has been added to filter block traces by their address space (domain).

（由 Victor Stinner 於 bpo-26588 [https://bugs.python.org/issue?@action=redirect&bpo=26588] 中貢獻。）

typing

Since the typing module is provisional, all changes introduced in Python 3.6 have also been backported to Python 3.5.x.

The typing module has a much improved support for generic type aliases. For example Dict[str, Tuple[S, T]] is now a valid type annotation. (Contributed by Guido van Rossum in Github #195 [https://github.com/python/typing/pull/195].)

The typing.ContextManager class has been added for representing contextlib.AbstractContextManager. (Contributed by Brett Cannon in bpo-25609 [https://bugs.python.org/issue?@action=redirect&bpo=25609].)

The typing.Collection class has been added for representing collections.abc.Collection. (Contributed by Ivan Levkivskyi in bpo-27598 [https://bugs.python.org/issue?@action=redirect&bpo=27598].)

The typing.ClassVar type construct has been added to mark class variables. As introduced in PEP 526 [https://peps.python.org/pep-0526/], a variable annotation wrapped in ClassVar indicates that a given attribute is intended to be used as a class variable and should not be set on instances of that class. (Contributed by Ivan Levkivskyi in Github #280 [https://github.com/python/typing/pull/280].)

A new TYPE_CHECKING constant that is assumed to be True by the static type checkers, but is False at runtime. (Contributed by Guido van Rossum in Github #230 [https://github.com/python/typing/issues/230].)

A new NewType() helper function has been added to create lightweight distinct types for annotations:

from typing import NewType

UserId = NewType('UserId', int)
some_id = UserId(524313)

The static type checker will treat the new type as if it were a subclass of the original type. (Contributed by Ivan Levkivskyi in Github #189 [https://github.com/python/typing/issues/189].)

unicodedata

The unicodedata module now uses data from Unicode 9.0.0 [https://unicode.org/versions/Unicode9.0.0/]. (Contributed by Benjamin Peterson.)

unittest.mock

Mock 類別有以下改進：

Two new methods, Mock.assert_called() and Mock.assert_called_once() to check if the mock object was called. (Contributed by Amit Saha in bpo-26323 [https://bugs.python.org/issue?@action=redirect&bpo=26323].)

The Mock.reset_mock() method now has two optional keyword only arguments: return_value and side_effect. (Contributed by Kushal Das in bpo-21271 [https://bugs.python.org/issue?@action=redirect&bpo=21271].)

urllib.request

If a HTTP request has a file or iterable body (other than a bytes object) but no Content-Length header, rather than throwing an error, AbstractHTTPHandler now falls back to use chunked transfer encoding. (Contributed by Demian Brecht and Rolf Krahl in bpo-12319 [https://bugs.python.org/issue?@action=redirect&bpo=12319].)

urllib.robotparser

RobotFileParser now supports the Crawl-delay and Request-rate extensions. (Contributed by Nikolay Bogoychev in bpo-16099 [https://bugs.python.org/issue?@action=redirect&bpo=16099].)

venv

venv accepts a new parameter --prompt. This parameter provides an alternative prefix for the virtual environment. (Proposed by Łukasz Balcerzak and ported to 3.6 by Stéphane Wirtel in bpo-22829 [https://bugs.python.org/issue?@action=redirect&bpo=22829].)

warnings

A new optional source parameter has been added to the warnings.warn_explicit() function: the destroyed object which emitted a ResourceWarning. A source attribute has also been added to warnings.WarningMessage (contributed by Victor Stinner in bpo-26568 [https://bugs.python.org/issue?@action=redirect&bpo=26568] and bpo-26567 [https://bugs.python.org/issue?@action=redirect&bpo=26567]).

When a ResourceWarning warning is logged, the tracemalloc module is now used to try to retrieve the traceback where the destroyed object was allocated.

Example with the script example.py:

import warnings

def func():
    return open(__file__)

f = func()
f = None

Output of the command python3.6 -Wd -X tracemalloc=5 example.py:

example.py:7: ResourceWarning: unclosed file <_io.TextIOWrapper name='example.py' mode='r' encoding='UTF-8'>
  f = None
Object allocated at (most recent call first):
  File "example.py", lineno 4
    return open(__file__)
  File "example.py", lineno 6
    f = func()

The "Object allocated at" traceback is new and is only displayed if tracemalloc is tracing Python memory allocations and if the warnings module was already imported.

winreg

Added the 64-bit integer type REG_QWORD. (Contributed by Clement Rouault in bpo-23026 [https://bugs.python.org/issue?@action=redirect&bpo=23026].)

winsound

Allowed keyword arguments to be passed to Beep, MessageBeep, and PlaySound (bpo-27982 [https://bugs.python.org/issue?@action=redirect&bpo=27982]).

xmlrpc.client

The xmlrpc.client module now supports unmarshalling additional data types used by the Apache XML-RPC implementation for numerics and None. (Contributed by Serhiy Storchaka in bpo-26885 [https://bugs.python.org/issue?@action=redirect&bpo=26885].)

zipfile

A new ZipInfo.from_file() class method allows making a ZipInfo instance from a filesystem file. A new ZipInfo.is_dir() method can be used to check if the ZipInfo instance represents a directory. (Contributed by Thomas Kluyver in bpo-26039 [https://bugs.python.org/issue?@action=redirect&bpo=26039].)

The ZipFile.open() method can now be used to write data into a ZIP file, as well as for extracting data. (Contributed by Thomas Kluyver in bpo-26039 [https://bugs.python.org/issue?@action=redirect&bpo=26039].)

zlib

The compress() and decompress() functions now accept keyword arguments. (Contributed by Aviv Palivoda in bpo-26243 [https://bugs.python.org/issue?@action=redirect&bpo=26243] and Xiang Zhang in bpo-16764 [https://bugs.python.org/issue?@action=redirect&bpo=16764] respectively.)

最佳化

The Python interpreter now uses a 16-bit wordcode instead of bytecode which made a number of opcode optimizations possible. (Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in bpo-26647 [https://bugs.python.org/issue?@action=redirect&bpo=26647] and bpo-28050 [https://bugs.python.org/issue?@action=redirect&bpo=28050].)

The asyncio.Future class now has an optimized C implementation. (Contributed by Yury Selivanov and INADA Naoki in bpo-26081 [https://bugs.python.org/issue?@action=redirect&bpo=26081].)

The asyncio.Task class now has an optimized C implementation. (Contributed by Yury Selivanov in bpo-28544 [https://bugs.python.org/issue?@action=redirect&bpo=28544].)

Various implementation improvements in the typing module (such as caching of generic types) allow up to 30 times performance improvements and reduced memory footprint.

The ASCII decoder is now up to 60 times as fast for error handlers surrogateescape, ignore and replace (Contributed by Victor Stinner in bpo-24870 [https://bugs.python.org/issue?@action=redirect&bpo=24870]).

The ASCII and the Latin1 encoders are now up to 3 times as fast for the error handler surrogateescape (Contributed by Victor Stinner in bpo-25227 [https://bugs.python.org/issue?@action=redirect&bpo=25227]).

The UTF-8 encoder is now up to 75 times as fast for error handlers ignore, replace, surrogateescape, surrogatepass (Contributed by Victor Stinner in bpo-25267 [https://bugs.python.org/issue?@action=redirect&bpo=25267]).

The UTF-8 decoder is now up to 15 times as fast for error handlers ignore, replace and surrogateescape (Contributed by Victor Stinner in bpo-25301 [https://bugs.python.org/issue?@action=redirect&bpo=25301]).

bytes % args is now up to 2 times faster. (Contributed by Victor Stinner in bpo-25349 [https://bugs.python.org/issue?@action=redirect&bpo=25349]).

bytearray % args is now between 2.5 and 5 times faster. (Contributed by Victor Stinner in bpo-25399 [https://bugs.python.org/issue?@action=redirect&bpo=25399]).

Optimize bytes.fromhex() and bytearray.fromhex(): they are now between 2x and 3.5x faster. (Contributed by Victor Stinner in bpo-25401 [https://bugs.python.org/issue?@action=redirect&bpo=25401]).

Optimize bytes.replace(b'', b'.') and bytearray.replace(b'', b'.'): up to 80% faster. (Contributed by Josh Snider in bpo-26574 [https://bugs.python.org/issue?@action=redirect&bpo=26574]).

Allocator functions of the PyMem_Malloc() domain (PYMEM_DOMAIN_MEM) now use the pymalloc memory allocator instead of malloc() function of the C library. The pymalloc allocator is optimized for objects smaller or equal to 512 bytes with a short lifetime, and use malloc() for larger memory blocks. (Contributed by Victor Stinner in bpo-26249 [https://bugs.python.org/issue?@action=redirect&bpo=26249]).

pickle.load() and pickle.loads() are now up to 10% faster when deserializing many small objects (Contributed by Victor Stinner in bpo-27056 [https://bugs.python.org/issue?@action=redirect&bpo=27056]).

Passing keyword arguments to a function has an overhead in comparison with passing positional arguments. Now in extension functions implemented with using Argument Clinic this overhead is significantly decreased. (Contributed by Serhiy Storchaka in bpo-27574 [https://bugs.python.org/issue?@action=redirect&bpo=27574]).

Optimized glob() and iglob() functions in the glob module; they are now about 3--6 times faster. (Contributed by Serhiy Storchaka in bpo-25596 [https://bugs.python.org/issue?@action=redirect&bpo=25596]).

Optimized globbing in pathlib by using os.scandir(); it is now about 1.5--4 times faster. (Contributed by Serhiy Storchaka in bpo-26032 [https://bugs.python.org/issue?@action=redirect&bpo=26032]).

xml.etree.ElementTree parsing, iteration and deepcopy performance has been significantly improved. (Contributed by Serhiy Storchaka in bpo-25638 [https://bugs.python.org/issue?@action=redirect&bpo=25638], bpo-25873 [https://bugs.python.org/issue?@action=redirect&bpo=25873], and bpo-25869 [https://bugs.python.org/issue?@action=redirect&bpo=25869].)

Creation of fractions.Fraction instances from floats and decimals is now 2 to 3 times faster. (Contributed by Serhiy Storchaka in bpo-25971 [https://bugs.python.org/issue?@action=redirect&bpo=25971].)

建置和 C API 變更

Python now requires some C99 support in the toolchain to build. Most notably, Python now uses standard integer types and macros in place of custom macros like PY_LONG_LONG. For more information, see PEP 7 [https://peps.python.org/pep-0007/] and bpo-17884 [https://bugs.python.org/issue?@action=redirect&bpo=17884].

Cross-compiling CPython with the Android NDK and the Android API level set to 21 (Android 5.0 Lollipop) or greater runs successfully. While Android is not yet a supported platform, the Python test suite runs on the Android emulator with only about 16 tests failures. See the Android meta-issue bpo-26865 [https://bugs.python.org/issue?@action=redirect&bpo=26865].

The --enable-optimizations configure flag has been added. Turning it on will activate expensive optimizations like PGO. (Original patch by Alecsandru Patrascu of Intel in bpo-26359 [https://bugs.python.org/issue?@action=redirect&bpo=26359].)

The GIL must now be held when allocator functions of PYMEM_DOMAIN_OBJ (ex: PyObject_Malloc()) and PYMEM_DOMAIN_MEM (ex: PyMem_Malloc()) domains are called.

New Py_FinalizeEx() API which indicates if flushing buffered data failed. (Contributed by Martin Panter in bpo-5319 [https://bugs.python.org/issue?@action=redirect&bpo=5319].)

PyArg_ParseTupleAndKeywords() now supports positional-only parameters. Positional-only parameters are defined by empty names. (Contributed by Serhiy Storchaka in bpo-26282 [https://bugs.python.org/issue?@action=redirect&bpo=26282]).

PyTraceback_Print method now abbreviates long sequences of repeated lines as "[Previous line repeated {count} more times]". (Contributed by Emanuel Barry in bpo-26823 [https://bugs.python.org/issue?@action=redirect&bpo=26823].)

The new PyErr_SetImportErrorSubclass() function allows for specifying a subclass of ImportError to raise. (Contributed by Eric Snow in bpo-15767 [https://bugs.python.org/issue?@action=redirect&bpo=15767].)

The new PyErr_ResourceWarning() function can be used to generate a ResourceWarning providing the source of the resource allocation. (Contributed by Victor Stinner in bpo-26567 [https://bugs.python.org/issue?@action=redirect&bpo=26567].)

The new PyOS_FSPath() function returns the file system representation of a path-like object. (Contributed by Brett Cannon in bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186].)

The PyUnicode_FSConverter() and PyUnicode_FSDecoder() functions will now accept path-like objects.

其他改進

When --version (short form: -V) is supplied twice, Python prints sys.version for detailed information.

$ ./python -VV
Python 3.6.0b4+ (3.6:223967b49e49+, Nov 21 2016, 20:55:04)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)]

已棄用

新關鍵字

async and await are not recommended to be used as variable, class, function or module names. Introduced by PEP 492 [https://peps.python.org/pep-0492/] in Python 3.5, they will become proper keywords in Python 3.7. Starting in Python 3.6, the use of async or await as names will generate a DeprecationWarning.

已棄用的 Python 行為

Raising the StopIteration exception inside a generator will now generate a DeprecationWarning, and will trigger a RuntimeError in Python 3.7. See PEP 479: Change StopIteration handling inside generators for details.

The __aiter__() method is now expected to return an asynchronous iterator directly instead of returning an awaitable as previously. Doing the former will trigger a DeprecationWarning. Backward compatibility will be removed in Python 3.7. (Contributed by Yury Selivanov in bpo-27243 [https://bugs.python.org/issue?@action=redirect&bpo=27243].)

A backslash-character pair that is not a valid escape sequence now generates a DeprecationWarning. Although this will eventually become a SyntaxError, that will not be for several Python releases. (Contributed by Emanuel Barry in bpo-27364 [https://bugs.python.org/issue?@action=redirect&bpo=27364].)

When performing a relative import, falling back on __name__ and __path__ from the calling module when __spec__ or __package__ are not defined now raises an ImportWarning. (Contributed by Rose Ames in bpo-25791 [https://bugs.python.org/issue?@action=redirect&bpo=25791].)

已棄用的 Python 模組、函式和方法

asynchat

The asynchat has been deprecated in favor of asyncio. (Contributed by Mariatta in bpo-25002 [https://bugs.python.org/issue?@action=redirect&bpo=25002].)

asyncore

The asyncore has been deprecated in favor of asyncio. (Contributed by Mariatta in bpo-25002 [https://bugs.python.org/issue?@action=redirect&bpo=25002].)

dbm

Unlike other dbm implementations, the dbm.dumb module creates databases with the 'rw' mode and allows modifying the database opened with the 'r' mode. This behavior is now deprecated and will be removed in 3.8. (Contributed by Serhiy Storchaka in bpo-21708 [https://bugs.python.org/issue?@action=redirect&bpo=21708].)

distutils

The undocumented extra_path argument to the distutils.Distribution constructor is now considered deprecated and will raise a warning if set. Support for this parameter will be removed in a future Python release. See bpo-27919 [https://bugs.python.org/issue?@action=redirect&bpo=27919] for details.

grp

The support of non-integer arguments in getgrgid() has been deprecated. (Contributed by Serhiy Storchaka in bpo-26129 [https://bugs.python.org/issue?@action=redirect&bpo=26129].)

importlib

The importlib.machinery.SourceFileLoader.load_module() and importlib.machinery.SourcelessFileLoader.load_module() methods are now deprecated. They were the only remaining implementations of importlib.abc.Loader.load_module() in importlib that had not been deprecated in previous versions of Python in favour of importlib.abc.Loader.exec_module().

The importlib.machinery.WindowsRegistryFinder class is now deprecated. As of 3.6.0, it is still added to sys.meta_path by default (on Windows), but this may change in future releases.

os

Undocumented support of general bytes-like objects as paths in os functions, compile() and similar functions is now deprecated. (Contributed by Serhiy Storchaka in bpo-25791 [https://bugs.python.org/issue?@action=redirect&bpo=25791] and bpo-26754 [https://bugs.python.org/issue?@action=redirect&bpo=26754].)

re

Support for inline flags (?letters) in the middle of the regular expression has been deprecated and will be removed in a future Python version. Flags at the start of a regular expression are still allowed. (Contributed by Serhiy Storchaka in bpo-22493 [https://bugs.python.org/issue?@action=redirect&bpo=22493].)

ssl

OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported. In the future the ssl module will require at least OpenSSL 1.0.2 or 1.1.0.

SSL-related arguments like certfile, keyfile and check_hostname in ftplib, http.client, imaplib, poplib, and smtplib have been deprecated in favor of context. (Contributed by Christian Heimes in bpo-28022 [https://bugs.python.org/issue?@action=redirect&bpo=28022].)

A couple of protocols and functions of the ssl module are now deprecated. Some features will no longer be available in future versions of OpenSSL. Other features are deprecated in favor of a different API. (Contributed by Christian Heimes in bpo-28022 [https://bugs.python.org/issue?@action=redirect&bpo=28022] and bpo-26470 [https://bugs.python.org/issue?@action=redirect&bpo=26470].)

tkinter

The tkinter.tix module is now deprecated. tkinter users should use tkinter.ttk instead.

venv

The pyvenv script has been deprecated in favour of python3 -m venv. This prevents confusion as to what Python interpreter pyvenv is connected to and thus what Python interpreter will be used by the virtual environment. (Contributed by Brett Cannon in bpo-25154 [https://bugs.python.org/issue?@action=redirect&bpo=25154].)

xml

As mitigation against DTD and external entity retrieval, the xml.dom.minidom and xml.sax modules no longer process external entities by default. (Contributed by Christian Heimes in gh-61441 [https://github.com/python/cpython/issues/61441].)

C API 的已棄用函式和型別

Undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsEncodedUnicode() and PyUnicode_AsDecodedUnicode() are deprecated now. Use the generic codec based API instead.

已棄用的建置選項

The --with-system-ffi configure flag is now on by default on non-macOS UNIX platforms. It may be disabled by using --without-system-ffi, but using the flag is deprecated and will not be accepted in Python 3.7. macOS is unaffected by this change. Note that many OS distributors already use the --with-system-ffi flag when building their system Python.

已移除

API 與功能的移除

Unknown escapes consisting of '\' and an ASCII letter in regular expressions will now cause an error. In replacement templates for re.sub() they are still allowed, but deprecated. The re.LOCALE flag can now only be used with binary patterns.

inspect.getmoduleinfo() was removed (was deprecated since CPython 3.3). inspect.getmodulename() should be used for obtaining the module name for a given path. (Contributed by Yury Selivanov in bpo-13248 [https://bugs.python.org/issue?@action=redirect&bpo=13248].)

traceback 模組中的 traceback.Ignore 類別和 traceback.usage、traceback.modname、traceback.fullmodname、traceback.find_lines_from_code、traceback.find_lines、traceback.find_strings 和 traceback.find_executable_lines 方法已被移除。它們是自 Python 3.2 以來已棄用的未記錄方法，等效的功能現在可從私有方法獲得。

The tk_menuBar() and tk_bindForTraversal() dummy methods in tkinter widget classes were removed (corresponding Tk commands were obsolete since Tk 4.0).

The open() method of the zipfile.ZipFile class no longer supports the 'U' mode (was deprecated since Python 3.4). Use io.TextIOWrapper for reading compressed text files in universal newlines mode.

The undocumented IN, CDROM, DLFCN, TYPES, CDIO, and STROPTS modules have been removed. They had been available in the platform specific Lib/plat-*/ directories, but were chronically out of date, inconsistently available across platforms, and unmaintained. The script that created these modules is still available in the source distribution at Tools/scripts/h2py.py [https://github.com/python/cpython/blob/v3.6.15/Tools/scripts/h2py.py].

已棄用的 asynchat.fifo 類別已移除。

移植至 Python 3.6

This section lists previously described changes and other bugfixes that may require changes to your code.

'python' 命令的行為變更

The output of a special Python build with defined COUNT_ALLOCS, SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default. It can be re-enabled using the -X showalloccount option. It now outputs to stderr instead of stdout. (Contributed by Serhiy Storchaka in bpo-23034 [https://bugs.python.org/issue?@action=redirect&bpo=23034].)

Python API 的變更

open() will no longer allow combining the 'U' mode flag with '+'. (Contributed by Jeff Balogh and John O'Connor in bpo-2091 [https://bugs.python.org/issue?@action=redirect&bpo=2091].)

sqlite3 no longer implicitly commits an open transaction before DDL statements.

On Linux, os.urandom() now blocks until the system urandom entropy pool is initialized to increase the security.

When importlib.abc.Loader.exec_module() is defined, importlib.abc.Loader.create_module() must also be defined.

PyErr_SetImportError() now sets TypeError when its msg argument is not set. Previously only NULL was returned.

The format of the co_lnotab attribute of code objects changed to support a negative line number delta. By default, Python does not emit bytecode with a negative line number delta. Functions using frame.f_lineno, PyFrame_GetLineNumber() or PyCode_Addr2Line() are not affected. Functions directly decoding co_lnotab should be updated to use a signed 8-bit integer type for the line number delta, but this is only required to support applications using a negative line number delta. See Objects/lnotab_notes.txt for the co_lnotab format and how to decode it, and see the PEP 511 [https://peps.python.org/pep-0511/] for the rationale.

The functions in the compileall module now return booleans instead of 1 or 0 to represent success or failure, respectively. Thanks to booleans being a subclass of integers, this should only be an issue if you were doing identity checks for 1 or 0. See bpo-25768 [https://bugs.python.org/issue?@action=redirect&bpo=25768].

Reading the port attribute of urllib.parse.urlsplit() and urlparse() results now raises ValueError for out-of-range values, rather than returning None. See bpo-20059 [https://bugs.python.org/issue?@action=redirect&bpo=20059].

The imp module now raises a DeprecationWarning instead of PendingDeprecationWarning.

The following modules have had missing APIs added to their __all__ attributes to match the documented APIs: calendar, cgi, csv, ElementTree, enum, fileinput, ftplib, logging, mailbox, mimetypes, optparse, plistlib, smtpd, subprocess, tarfile, threading and wave. This means they will export new symbols when import * is used. (Contributed by Joel Taddei and Jacek Kołodziej in bpo-23883 [https://bugs.python.org/issue?@action=redirect&bpo=23883].)

When performing a relative import, if __package__ does not compare equal to __spec__.parent then ImportWarning is raised. (Contributed by Brett Cannon in bpo-25791 [https://bugs.python.org/issue?@action=redirect&bpo=25791].)

When a relative import is performed and no parent package is known, then ImportError will be raised. Previously, SystemError could be raised. (Contributed by Brett Cannon in bpo-18018 [https://bugs.python.org/issue?@action=redirect&bpo=18018].)

Servers based on the socketserver module, including those defined in http.server, xmlrpc.server and wsgiref.simple_server, now only catch exceptions derived from Exception. Therefore if a request handler raises an exception like SystemExit or KeyboardInterrupt, handle_error() is no longer called, and the exception will stop a single-threaded server. (Contributed by Martin Panter in bpo-23430 [https://bugs.python.org/issue?@action=redirect&bpo=23430].)

spwd.getspnam() now raises a PermissionError instead of KeyError if the user doesn't have privileges.

The socket.socket.close() method now raises an exception if an error (e.g. EBADF) was reported by the underlying system call. (Contributed by Martin Panter in bpo-26685 [https://bugs.python.org/issue?@action=redirect&bpo=26685].)

The decode_data argument for the smtpd.SMTPChannel and smtpd.SMTPServer constructors is now False by default. This means that the argument passed to process_message() is now a bytes object by default, and process_message() will be passed keyword arguments. Code that has already been updated in accordance with the deprecation warning generated by 3.5 will not be affected.

在 json 模組中，dump()、dumps()、load() 和 loads() 函式以及 JSONEncoder 和 JSONDecoder 類別建構函式的所有可選引數現在都是僅限關鍵字引數。（由 Serhiy Storchaka 在 bpo-18726 [https://bugs.python.org/issue?@action=redirect&bpo=18726] 中貢獻。）

Subclasses of type which don't override type.__new__ may no longer use the one-argument form to get the type of an object.

As part of PEP 487 [https://peps.python.org/pep-0487/], the handling of keyword arguments passed to type (other than the metaclass hint, metaclass) is now consistently delegated to object.__init_subclass__(). This means that type.__new__ and type.__init__ both now accept arbitrary keyword arguments, but object.__init_subclass__() (which is called from type.__new__) will reject them by default. Custom metaclasses accepting additional keyword arguments will need to adjust their calls to type.__new__ (whether direct or via super) accordingly.

In distutils.command.sdist.sdist, the default_format attribute has been removed and is no longer honored. Instead, the gzipped tarfile format is the default on all platforms and no platform-specific selection is made. In environments where distributions are built on Windows and zip distributions are required, configure the project with a setup.cfg file containing the following:

[sdist]
formats=zip

This behavior has also been backported to earlier Python versions by Setuptools 26.0.0.

In the urllib.request module and the http.client.HTTPConnection.request() method, if no Content-Length header field has been specified and the request body is a file object, it is now sent with HTTP 1.1 chunked encoding. If a file object has to be sent to a HTTP 1.0 server, the Content-Length value now has to be specified by the caller. (Contributed by Demian Brecht and Rolf Krahl with tweaks from Martin Panter in bpo-12319 [https://bugs.python.org/issue?@action=redirect&bpo=12319].)

The DictReader now returns rows of type OrderedDict. (Contributed by Steve Holden in bpo-27842 [https://bugs.python.org/issue?@action=redirect&bpo=27842].)

The crypt.METHOD_CRYPT will no longer be added to crypt.methods if unsupported by the platform. (Contributed by Victor Stinner in bpo-25287 [https://bugs.python.org/issue?@action=redirect&bpo=25287].)

The verbose and rename arguments for namedtuple() are now keyword-only. (Contributed by Raymond Hettinger in bpo-25628 [https://bugs.python.org/issue?@action=redirect&bpo=25628].)

On Linux, ctypes.util.find_library() now looks in LD_LIBRARY_PATH for shared libraries. (Contributed by Vinay Sajip in bpo-9998 [https://bugs.python.org/issue?@action=redirect&bpo=9998].)

The imaplib.IMAP4 class now handles flags containing the ']' character in messages sent from the server to improve real-world compatibility. (Contributed by Lita Cho in bpo-21815 [https://bugs.python.org/issue?@action=redirect&bpo=21815].)

The mmap.mmap.write() function now returns the number of bytes written like other write methods. (Contributed by Jakub Stasiak in bpo-26335 [https://bugs.python.org/issue?@action=redirect&bpo=26335].)

The pkgutil.iter_modules() and pkgutil.walk_packages() functions now return ModuleInfo named tuples. (Contributed by Ramchandra Apte in bpo-17211 [https://bugs.python.org/issue?@action=redirect&bpo=17211].)

re.sub() now raises an error for invalid numerical group references in replacement templates even if the pattern is not found in the string. The error message for invalid group references now includes the group index and the position of the reference. (Contributed by SilentGhost, Serhiy Storchaka in bpo-25953 [https://bugs.python.org/issue?@action=redirect&bpo=25953].)

zipfile.ZipFile will now raise NotImplementedError for unrecognized compression values. Previously a plain RuntimeError was raised. Additionally, calling ZipFile methods on a closed ZipFile or calling the write() method on a ZipFile created with mode 'r' will raise a ValueError. Previously, a RuntimeError was raised in those scenarios.

when custom metaclasses are combined with zero-argument super() or direct references from methods to the implicit __class__ closure variable, the implicit __classcell__ namespace entry must now be passed up to type.__new__ for initialisation. Failing to do so will result in a DeprecationWarning in Python 3.6 and a RuntimeError in Python 3.8.

With the introduction of ModuleNotFoundError, import system consumers may start expecting import system replacements to raise that more specific exception when appropriate, rather than the less-specific ImportError. To provide future compatibility with such consumers, implementers of alternative import systems that completely replace __import__() will need to update their implementations to raise the new subclass when a module can't be found at all. Implementers of compliant plugins to the default import system shouldn't need to make any changes, as the default import system will raise the new subclass when appropriate.

C API 中的改動

The PyMem_Malloc() allocator family now uses the pymalloc allocator rather than the system malloc(). Applications calling PyMem_Malloc() without holding the GIL can now crash. Set the PYTHONMALLOC environment variable to debug to validate the usage of memory allocators in your application. See bpo-26249 [https://bugs.python.org/issue?@action=redirect&bpo=26249].

Py_Exit() (and the main interpreter) now override the exit status with 120 if flushing buffered data failed. See bpo-5319 [https://bugs.python.org/issue?@action=redirect&bpo=5319].

CPython 位元組碼變更

There have been several major changes to the bytecode in Python 3.6.

The Python interpreter now uses a 16-bit wordcode instead of bytecode. (Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in bpo-26647 [https://bugs.python.org/issue?@action=redirect&bpo=26647] and bpo-28050 [https://bugs.python.org/issue?@action=redirect&bpo=28050].)

The new FORMAT_VALUE and BUILD_STRING opcodes as part of the formatted string literal implementation. (Contributed by Eric Smith in bpo-25483 [https://bugs.python.org/issue?@action=redirect&bpo=25483] and Serhiy Storchaka in bpo-27078 [https://bugs.python.org/issue?@action=redirect&bpo=27078].)

The new BUILD_CONST_KEY_MAP opcode to optimize the creation of dictionaries with constant keys. (Contributed by Serhiy Storchaka in bpo-27140 [https://bugs.python.org/issue?@action=redirect&bpo=27140].)

The function call opcodes have been heavily reworked for better performance and simpler implementation. The MAKE_FUNCTION, CALL_FUNCTION, CALL_FUNCTION_KW and BUILD_MAP_UNPACK_WITH_CALL opcodes have been modified, the new CALL_FUNCTION_EX and BUILD_TUPLE_UNPACK_WITH_CALL have been added, and CALL_FUNCTION_VAR, CALL_FUNCTION_VAR_KW and MAKE_CLOSURE opcodes have been removed. (Contributed by Demur Rumed in bpo-27095 [https://bugs.python.org/issue?@action=redirect&bpo=27095], and Serhiy Storchaka in bpo-27213 [https://bugs.python.org/issue?@action=redirect&bpo=27213], bpo-28257 [https://bugs.python.org/issue?@action=redirect&bpo=28257].)

The new SETUP_ANNOTATIONS and STORE_ANNOTATION opcodes have been added to support the new variable annotation syntax. (Contributed by Ivan Levkivskyi in bpo-27985 [https://bugs.python.org/issue?@action=redirect&bpo=27985].)

Python 3.6.2 中顯著的變更

新增 make regen-all 建置目標

To simplify cross-compilation, and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available, the autotools-based build system no longer attempts to implicitly recompile generated files based on file modification times.

Instead, a new make regen-all command has been added to force regeneration of these files when desired (e.g. after an initial version of Python has already been built based on the pregenerated versions).

More selective regeneration targets are also defined - see Makefile.pre.in [https://github.com/python/cpython/tree/3.14/Makefile.pre.in] for details.

（由 Victor Stinner 於 bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404] 中貢獻。）

在 3.6.2 版被加入.

移除 make touch 建置目標

The make touch build target previously used to request implicit regeneration of generated files by updating their modification times has been removed.

它已被新的 make regen-all 目標取代。

（由 Victor Stinner 於 bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404] 中貢獻。）

在 3.6.2 版的變更.

Python 3.6.4 中顯著的變更

The PyExc_RecursionErrorInst singleton that was part of the public API has been removed as its members being never cleared may cause a segfault during finalization of the interpreter. (Contributed by Xavier de Gaye in bpo-22898 [https://bugs.python.org/issue?@action=redirect&bpo=22898] and bpo-30697 [https://bugs.python.org/issue?@action=redirect&bpo=30697].)

Python 3.6.5 中顯著的變更

The locale.localeconv() function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale in some cases. (Contributed by Victor Stinner in bpo-31900 [https://bugs.python.org/issue?@action=redirect&bpo=31900].)

Python 3.6.7 中顯著的變更

xml.dom.minidom and xml.sax modules no longer process external entities by default. See also gh-61441 [https://github.com/python/cpython/issues/61441].

In 3.6.7 the tokenize module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. (Contributed by Ammar Askar in bpo-33899 [https://bugs.python.org/issue?@action=redirect&bpo=33899].)

Python 3.6.10 中顯著的變更

Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint() is no longer supported. This is because of the behavior of the socket option SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228 [https://bugs.python.org/issue?@action=redirect&bpo=37228].)

Python 3.6.13 中顯著的變更

Earlier Python versions allowed using both ; and & as query parameter separators in urllib.parse.parse_qs() and urllib.parse.parse_qsl(). Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with & as the default. This change also affects cgi.parse() and cgi.parse_multipart() as they use the affected functions internally. For more details, please see their respective documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967].)

Python 3.6.14 中顯著的變更

A security fix alters the ftplib.FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel. We reuse the ftp server IP address instead. For unusual code requiring the old behavior, set a trust_server_pasv_ipv4_address attribute on your FTP instance to True. (See gh-87451 [https://github.com/python/cpython/issues/87451])

The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986, ASCII newline \n, \r and tab \t characters are stripped from the URL by the parser urllib.parse() preventing such attacks. The removal characters are controlled by a new module level variable urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (See gh-88048 [https://github.com/python/cpython/issues/88048])

Python 3.5 有什麼新功能

編輯者:

Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <yury@magic.io>

本文介紹了 Python 3.5 與 3.4 相比多了哪些新功能。Python 3.1 已於 2015 年 9 月 13 日發布。完整詳情請見 changelog [https://docs.python.org/3.5/whatsnew/changelog.html]。

也參考

PEP 478 [https://peps.python.org/pep-0478/] - Python 3.5 發佈時程

發布重點摘要

新增語法特性：

PEP 492，使用 async 和 await 語法的協程

PEP 465, a new matrix multiplication operator: a @ b.

PEP 448, additional unpacking generalizations.

新的函式庫模組：

typing：PEP 484 -- 型別提示。

zipapp：PEP 441 改進 Python ZIP 應用程式支援。

新的內建功能

bytes % args, bytearray % args: PEP 461 -- Adding % formatting to bytes and bytearray.

New bytes.hex(), bytearray.hex() and memoryview.hex() methods. (Contributed by Arnon Yaari in bpo-9951 [https://bugs.python.org/issue?@action=redirect&bpo=9951].)

memoryview now supports tuple indexing (including multi-dimensional). (Contributed by Antoine Pitrou in bpo-23632 [https://bugs.python.org/issue?@action=redirect&bpo=23632].)

Generators have a new gi_yieldfrom attribute, which returns the object being iterated by yield from expressions. (Contributed by Benno Leslie and Yury Selivanov in bpo-24450 [https://bugs.python.org/issue?@action=redirect&bpo=24450].)

A new RecursionError exception is now raised when maximum recursion depth is reached. (Contributed by Georg Brandl in bpo-19235 [https://bugs.python.org/issue?@action=redirect&bpo=19235].)

CPython 實作改進：

When the LC_TYPE locale is the POSIX locale (C locale), sys.stdin and sys.stdout now use the surrogateescape error handler, instead of the strict error handler. (Contributed by Victor Stinner in bpo-19977 [https://bugs.python.org/issue?@action=redirect&bpo=19977].)

.pyo files are no longer used and have been replaced by a more flexible scheme that includes the optimization level explicitly in .pyc name. (See PEP 488 overview.)

Builtin and extension modules are now initialized in a multi-phase process, which is similar to how Python modules are loaded. (See PEP 489 overview.)

標準函式庫中的顯著改進

collections.OrderedDict is now implemented in C, which makes it 4 to 100 times faster.

The ssl module gained support for Memory BIO, which decouples SSL protocol handling from network IO.

The new os.scandir() function provides a better and significantly faster way of directory traversal.

functools.lru_cache() has been mostly reimplemented in C, yielding much better performance.

The new subprocess.run() function provides a streamlined way to run subprocesses.

The traceback module has been significantly enhanced for improved performance and developer convenience.

安全性改進：

SSLv3 is now disabled throughout the standard library. It can still be enabled by instantiating a ssl.SSLContext manually. (See bpo-22638 [https://bugs.python.org/issue?@action=redirect&bpo=22638] for more details; this change was backported to CPython 3.4 and 2.7.)

HTTP cookie parsing is now stricter, in order to protect against potential injection attacks. (Contributed by Antoine Pitrou in bpo-22796 [https://bugs.python.org/issue?@action=redirect&bpo=22796].)

Windows 改進：

Windows 的新安裝程式取代了舊的 MSI。詳情請參見 在 Windows 上使用 Python。

Windows builds now use Microsoft Visual C++ 14.0, and extension modules should use the same.

Please read on for a comprehensive list of user-facing changes, including many other smaller improvements, CPython optimizations, deprecations, and potential porting issues.

新增功能

PEP 492 - 使用 async 和 await 語法的協程

PEP 492 [https://peps.python.org/pep-0492/] greatly improves support for asynchronous programming in Python by adding awaitable objects, coroutine functions, asynchronous iteration, and asynchronous context managers.

Coroutine functions are declared using the new async def syntax:

>>> async def coro():
...     return 'spam'

Inside a coroutine function, the new await expression can be used to suspend coroutine execution until the result is available. Any object can be awaited, as long as it implements the awaitable protocol by defining the __await__() method.

PEP 492 also adds async for statement for convenient iteration over asynchronous iterables.

An example of a rudimentary HTTP client written using the new syntax:

import asyncio

async def http_get(domain):
    reader, writer = await asyncio.open_connection(domain, 80)

    writer.write(b'\r\n'.join([
        b'GET / HTTP/1.1',
        b'Host: %b' % domain.encode('latin-1'),
        b'Connection: close',
        b'', b''
    ]))

    async for line in reader:
        print('>>>', line)

    writer.close()

loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(http_get('example.com'))
finally:
    loop.close()

Similarly to asynchronous iteration, there is a new syntax for asynchronous context managers. The following script:

import asyncio

async def coro(name, lock):
    print('coro {}: waiting for lock'.format(name))
    async with lock:
        print('coro {}: holding the lock'.format(name))
        await asyncio.sleep(1)
        print('coro {}: releasing the lock'.format(name))

loop = asyncio.get_event_loop()
lock = asyncio.Lock()
coros = asyncio.gather(coro(1, lock), coro(2, lock))
try:
    loop.run_until_complete(coros)
finally:
    loop.close()

將輸出：

coro 2: waiting for lock
coro 2: holding the lock
coro 1: waiting for lock
coro 2: releasing the lock
coro 1: holding the lock
coro 1: releasing the lock

Note that both async for and async with can only be used inside a coroutine function declared with async def.

Coroutine functions are intended to be run inside a compatible event loop, such as the asyncio loop.

備註

在 3.5.2 版的變更: Starting with CPython 3.5.2, __aiter__ can directly return asynchronous iterators. Returning an awaitable object will result in a PendingDeprecationWarning.

更多細節請見 Asynchronous Iterators 文件部分。

也參考

PEP 492 [https://peps.python.org/pep-0492/] -- 使用 async 和 await 語法的協程

由 Yury Selivanov 撰寫 PEP 與實作。

PEP 465 - A dedicated infix operator for matrix multiplication

PEP 465 [https://peps.python.org/pep-0465/] adds the @ infix operator for matrix multiplication. Currently, no builtin Python types implement the new operator, however, it can be implemented by defining __matmul__(), __rmatmul__(), and __imatmul__() for regular, reflected, and in-place matrix multiplication. The semantics of these methods is similar to that of methods defining other infix arithmetic operators.

Matrix multiplication is a notably common operation in many fields of mathematics, science, engineering, and the addition of @ allows writing cleaner code:

S = (H @ beta - r).T @ inv(H @ V @ H.T) @ (H @ beta - r)

instead of:

S = dot((dot(H, beta) - r).T,
        dot(inv(dot(dot(H, V), H.T)), dot(H, beta) - r))

NumPy 1.10 has support for the new operator:

>>> import numpy

>>> x = numpy.ones(3)
>>> x
array([ 1., 1., 1.])

>>> m = numpy.eye(3)
>>> m
array([[ 1., 0., 0.],
       [ 0., 1., 0.],
       [ 0., 0., 1.]])

>>> x @ m
array([ 1., 1., 1.])

也參考

PEP 465 [https://peps.python.org/pep-0465/] -- A dedicated infix operator for matrix multiplication

由 Nathaniel J. Smith 撰寫 PEP；由 Benjamin Peterson 實作。

PEP 448 - Additional Unpacking Generalizations

PEP 448 [https://peps.python.org/pep-0448/] extends the allowed uses of the * iterable unpacking operator and ** dictionary unpacking operator. It is now possible to use an arbitrary number of unpackings in function calls:

>>> print(*[1], *[2], 3, *[4, 5])
1 2 3 4 5

>>> def fn(a, b, c, d):
...     print(a, b, c, d)
...

>>> fn(**{'a': 1, 'c': 3}, **{'b': 2, 'd': 4})
1 2 3 4

Similarly, tuple, list, set, and dictionary displays allow multiple unpackings (see Expression lists and Dictionary displays):

>>> *range(4), 4
(0, 1, 2, 3, 4)

>>> [*range(4), 4]
[0, 1, 2, 3, 4]

>>> {*range(4), 4, *(5, 6, 7)}
{0, 1, 2, 3, 4, 5, 6, 7}

>>> {'x': 1, **{'y': 2}}
{'x': 1, 'y': 2}

也參考

PEP 448 [https://peps.python.org/pep-0448/] -- Additional Unpacking Generalizations

PEP written by Joshua Landau; implemented by Neil Girdhar, Thomas Wouters, and Joshua Landau.

PEP 461 - percent formatting support for bytes and bytearray

PEP 461 [https://peps.python.org/pep-0461/] adds support for the % interpolation operator to bytes and bytearray.

While interpolation is usually thought of as a string operation, there are cases where interpolation on bytes or bytearrays makes sense, and the work needed to make up for this missing functionality detracts from the overall readability of the code. This issue is particularly important when dealing with wire format protocols, which are often a mixture of binary and ASCII compatible text.

範例：

>>> b'Hello %b!' % b'World'
b'Hello World!'

>>> b'x=%i y=%f' % (1, 2.5)
b'x=1 y=2.500000'

Unicode is not allowed for %b, but it is accepted by %a (equivalent of repr(obj).encode('ascii', 'backslashreplace')):

>>> b'Hello %b!' % 'World'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: %b requires bytes, or an object that implements __bytes__, not 'str'

>>> b'price: %a' % '10€'
b"price: '10\\u20ac'"

Note that %s and %r conversion types, although supported, should only be used in codebases that need compatibility with Python 2.

也參考

PEP 461 [https://peps.python.org/pep-0461/] -- Adding % formatting to bytes and bytearray

PEP written by Ethan Furman; implemented by Neil Schemenauer and Ethan Furman.

PEP 484 - 型別提示

Function annotation syntax has been a Python feature since version 3.0 (PEP 3107 [https://peps.python.org/pep-3107/]), however the semantics of annotations has been left undefined.

Experience has shown that the majority of function annotation uses were to provide type hints to function parameters and return values. It became evident that it would be beneficial for Python users, if the standard library included the base definitions and tools for type annotations.

PEP 484 [https://peps.python.org/pep-0484/] introduces a provisional module to provide these standard definitions and tools, along with some conventions for situations where annotations are not available.

For example, here is a simple function whose argument and return type are declared in the annotations:

def greeting(name: str) -> str:
    return 'Hello ' + name

While these annotations are available at runtime through the usual __annotations__ attribute, no automatic type checking happens at runtime. Instead, it is assumed that a separate off-line type checker (e.g. mypy [https://mypy-lang.org]) will be used for on-demand source code analysis.

The type system supports unions, generic types, and a special type named Any which is consistent with (i.e. assignable to and from) all types.

也參考

typing 模組文件

PEP 484 [https://peps.python.org/pep-0484/] -- 型別提示

PEP written by Guido van Rossum, Jukka Lehtosalo, and Łukasz Langa; implemented by Guido van Rossum.

PEP 483 [https://peps.python.org/pep-0483/] -- 型別提示理論

由 Guido van Rossum 撰寫 PEP

PEP 471 - os.scandir() function -- a better and faster directory iterator

PEP 471 [https://peps.python.org/pep-0471/] adds a new directory iteration function, os.scandir(), to the standard library. Additionally, os.walk() is now implemented using scandir, which makes it 3 to 5 times faster on POSIX systems and 7 to 20 times faster on Windows systems. This is largely achieved by greatly reducing the number of calls to os.stat() required to walk a directory tree.

Additionally, scandir returns an iterator, as opposed to returning a list of file names, which improves memory efficiency when iterating over very large directories.

The following example shows a simple use of os.scandir() to display all the files (excluding directories) in the given path that don't start with '.'. The entry.is_file() call will generally not make an additional system call:

for entry in os.scandir(path):
    if not entry.name.startswith('.') and entry.is_file():
        print(entry.name)

也參考

PEP 471 [https://peps.python.org/pep-0471/] -- os.scandir() function -- a better and faster directory iterator

在 Victor Stinner 協助下由 Ben Hoyt 撰寫 PEP 與實作。

PEP 475: Retry system calls failing with EINTR

An errno.EINTR error code is returned whenever a system call, that is waiting for I/O, is interrupted by a signal. Previously, Python would raise InterruptedError in such cases. This meant that, when writing a Python application, the developer had two choices:

Ignore the InterruptedError.

Handle the InterruptedError and attempt to restart the interrupted system call at every call site.

The first option makes an application fail intermittently. The second option adds a large amount of boilerplate that makes the code nearly unreadable. Compare:

print("Hello World")

和：

while True:
    try:
        print("Hello World")
        break
    except InterruptedError:
        continue

PEP 475 [https://peps.python.org/pep-0475/] implements automatic retry of system calls on EINTR. This removes the burden of dealing with EINTR or InterruptedError in user code in most situations and makes Python programs, including the standard library, more robust. Note that the system call is only retried if the signal handler does not raise an exception.

Below is a list of functions which are now retried when interrupted by a signal:

open() 和 io.open()；

faulthandler 模組的函式；

os functions: fchdir(), fchmod(), fchown(), fdatasync(), fstat(), fstatvfs(), fsync(), ftruncate(), mkfifo(), mknod(), open(), posix_fadvise(), posix_fallocate(), pread(), pwrite(), read(), readv(), sendfile(), wait3(), wait4(), wait(), waitid(), waitpid(), write(), writev();

special cases: os.close() and os.dup2() now ignore EINTR errors; the syscall is not retried (see the PEP for the rationale);

select functions: devpoll.poll(), epoll.poll(), kqueue.control(), poll.poll(), select();

methods of the socket class: accept(), connect() (except for non-blocking sockets), recv(), recvfrom(), recvmsg(), send(), sendall(), sendmsg(), sendto();

signal.sigtimedwait() 和 signal.sigwaitinfo()；

time.sleep()。

也參考

PEP 475 [https://peps.python.org/pep-0475/] -- Retry system calls failing with EINTR

PEP and implementation written by Charles-François Natali and Victor Stinner, with the help of Antoine Pitrou (the French connection).

PEP 479: Change StopIteration handling inside generators

The interaction of generators and StopIteration in Python 3.4 and earlier was sometimes surprising, and could conceal obscure bugs. Previously, StopIteration raised accidentally inside a generator function was interpreted as the end of the iteration by the loop construct driving the generator.

PEP 479 [https://peps.python.org/pep-0479/] changes the behavior of generators: when a StopIteration exception is raised inside a generator, it is replaced with a RuntimeError before it exits the generator frame. The main goal of this change is to ease debugging in the situation where an unguarded next() call raises StopIteration and causes the iteration controlled by the generator to terminate silently. This is particularly pernicious in combination with the yield from construct.

This is a backwards incompatible change, so to enable the new behavior, a __future__ import is necessary:

>>> from __future__ import generator_stop

>>> def gen():
...     next(iter([]))
...     yield
...
>>> next(gen())
Traceback (most recent call last):
  File "<stdin>", line 2, in gen
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: generator raised StopIteration

Without a __future__ import, a PendingDeprecationWarning will be raised whenever a StopIteration exception is raised inside a generator.

也參考

PEP 479 [https://peps.python.org/pep-0479/] -- Change StopIteration handling inside generators

PEP written by Chris Angelico and Guido van Rossum. Implemented by Chris Angelico, Yury Selivanov and Nick Coghlan.

PEP 485: A function for testing approximate equality

PEP 485 [https://peps.python.org/pep-0485/] adds the math.isclose() and cmath.isclose() functions which tell whether two values are approximately equal or "close" to each other. Whether or not two values are considered close is determined according to given absolute and relative tolerances. Relative tolerance is the maximum allowed difference between isclose arguments, relative to the larger absolute value:

>>> import math
>>> a = 5.0
>>> b = 4.99998
>>> math.isclose(a, b, rel_tol=1e-5)
True
>>> math.isclose(a, b, rel_tol=1e-6)
False

It is also possible to compare two values using absolute tolerance, which must be a non-negative value:

>>> import math
>>> a = 5.0
>>> b = 4.99998
>>> math.isclose(a, b, abs_tol=0.00003)
True
>>> math.isclose(a, b, abs_tol=0.00001)
False

也參考

PEP 485 [https://peps.python.org/pep-0485/] -- A function for testing approximate equality

PEP written by Christopher Barker; implemented by Chris Barker and Tal Einat.

PEP 486: Make the Python Launcher aware of virtual environments

PEP 486 [https://peps.python.org/pep-0486/] makes the Windows launcher (see PEP 397 [https://peps.python.org/pep-0397/]) aware of an active virtual environment. When the default interpreter would be used and the VIRTUAL_ENV environment variable is set, the interpreter in the virtual environment will be used.

也參考

PEP 486 [https://peps.python.org/pep-0486/] -- Make the Python Launcher aware of virtual environments

由 Paul Moore 撰寫 PEP 與實作。

PEP 488: Elimination of PYO files

PEP 488 [https://peps.python.org/pep-0488/] does away with the concept of .pyo files. This means that .pyc files represent both unoptimized and optimized bytecode. To prevent the need to constantly regenerate bytecode files, .pyc files now have an optional opt- tag in their name when the bytecode is optimized. This has the side-effect of no more bytecode file name clashes when running under either -O or -OO. Consequently, bytecode files generated from -O, and -OO may now exist simultaneously. importlib.util.cache_from_source() has an updated API to help with this change.

也參考

PEP 488 [https://peps.python.org/pep-0488/] -- 消除 PYO 檔案

由 Brett Cannon 撰寫 PEP 與實作。

PEP 489: Multi-phase extension module initialization

PEP 489 [https://peps.python.org/pep-0489/] updates extension module initialization to take advantage of the two step module loading mechanism introduced by PEP 451 [https://peps.python.org/pep-0451/] in Python 3.4.

This change brings the import semantics of extension modules that opt-in to using the new mechanism much closer to those of Python source and bytecode modules, including the ability to use any valid identifier as a module name, rather than being restricted to ASCII.

也參考

PEP 489 [https://peps.python.org/pep-0489/] -- 多階段擴充模組初始化

PEP written by Petr Viktorin, Stefan Behnel, and Nick Coghlan; implemented by Petr Viktorin.

其他語言更動

Some smaller changes made to the core Python language are:

Added the "namereplace" error handlers. The "backslashreplace" error handlers now work with decoding and translating. (Contributed by Serhiy Storchaka in bpo-19676 [https://bugs.python.org/issue?@action=redirect&bpo=19676] and bpo-22286 [https://bugs.python.org/issue?@action=redirect&bpo=22286].)

The -b option now affects comparisons of bytes with int. (Contributed by Serhiy Storchaka in bpo-23681 [https://bugs.python.org/issue?@action=redirect&bpo=23681].)

New Kazakh kz1048 and Tajik koi8_t codecs. (Contributed by Serhiy Storchaka in bpo-22682 [https://bugs.python.org/issue?@action=redirect&bpo=22682] and bpo-22681 [https://bugs.python.org/issue?@action=redirect&bpo=22681].)

Property docstrings are now writable. This is especially useful for collections.namedtuple() docstrings. (Contributed by Berker Peksag in bpo-24064 [https://bugs.python.org/issue?@action=redirect&bpo=24064].)

Circular imports involving relative imports are now supported. (Contributed by Brett Cannon and Antoine Pitrou in bpo-17636 [https://bugs.python.org/issue?@action=redirect&bpo=17636].)

新增模組

typing

The new typing provisional module provides standard definitions and tools for function type annotations. See Type Hints for more information.

zipapp

The new zipapp module (specified in PEP 441 [https://peps.python.org/pep-0441/]) provides an API and command line tool for creating executable Python Zip Applications, which were introduced in Python 2.6 in bpo-1739468 [https://bugs.python.org/issue?@action=redirect&bpo=1739468], but which were not well publicized, either at the time or since.

With the new module, bundling your application is as simple as putting all the files, including a __main__.py file, into a directory myapp and running:

$ python -m zipapp myapp
$ python myapp.pyz

模組實作由 Paul Moore 在 bpo-23491 [https://bugs.python.org/issue?@action=redirect&bpo=23491] 貢獻。

也參考

PEP 441 [https://peps.python.org/pep-0441/] -- 改進 Python ZIP 應用程式支援

改進的模組

argparse

The ArgumentParser class now allows disabling abbreviated usage of long options by setting allow_abbrev to False. (Contributed by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson in bpo-14910 [https://bugs.python.org/issue?@action=redirect&bpo=14910].)

asyncio

Since the asyncio module is provisional, all changes introduced in Python 3.5 have also been backported to Python 3.4.x.

Python 3.4.0 以來 asyncio 模組的顯著變更：

New debugging APIs: loop.set_debug() and loop.get_debug() methods. (Contributed by Victor Stinner.)

The proactor event loop now supports SSL. (Contributed by Antoine Pitrou and Victor Stinner in bpo-22560 [https://bugs.python.org/issue?@action=redirect&bpo=22560].)

A new loop.is_closed() method to check if the event loop is closed. (Contributed by Victor Stinner in bpo-21326 [https://bugs.python.org/issue?@action=redirect&bpo=21326].)

A new loop.create_task() to conveniently create and schedule a new Task for a coroutine. The create_task method is also used by all asyncio functions that wrap coroutines into tasks, such as asyncio.wait(), asyncio.gather(), etc. (Contributed by Victor Stinner.)

A new transport.get_write_buffer_limits() method to inquire for high- and low- water limits of the flow control. (Contributed by Victor Stinner.)

The async() function is deprecated in favor of ensure_future(). (Contributed by Yury Selivanov.)

New loop.set_task_factory() and loop.get_task_factory() methods to customize the task factory that loop.create_task() method uses. (Contributed by Yury Selivanov.)

New Queue.join() and Queue.task_done() queue methods. (Contributed by Victor Stinner.)

The JoinableQueue class was removed, in favor of the asyncio.Queue class. (Contributed by Victor Stinner.)

3.5.1 的更新：

The ensure_future() function and all functions that use it, such as loop.run_until_complete(), now accept all kinds of awaitable objects. (Contributed by Yury Selivanov.)

New run_coroutine_threadsafe() function to submit coroutines to event loops from other threads. (Contributed by Vincent Michel.)

New Transport.is_closing() method to check if the transport is closing or closed. (Contributed by Yury Selivanov.)

The loop.create_server() method can now accept a list of hosts. (Contributed by Yann Sionneau.)

3.5.2 的更新：

New loop.create_future() method to create Future objects. This allows alternative event loop implementations, such as uvloop [https://github.com/MagicStack/uvloop], to provide a faster asyncio.Future implementation. (Contributed by Yury Selivanov.)

New loop.get_exception_handler() method to get the current exception handler. (Contributed by Yury Selivanov.)

New StreamReader.readuntil() method to read data from the stream until a separator bytes sequence appears. (Contributed by Mark Korenberg.)

The loop.create_connection() and loop.create_server() methods are optimized to avoid calling the system getaddrinfo function if the address is already resolved. (Contributed by A. Jesse Jiryu Davis.)

The loop.sock_connect(sock, address) no longer requires the address to be resolved prior to the call. (Contributed by A. Jesse Jiryu Davis.)

bz2

The BZ2Decompressor.decompress method now accepts an optional max_length argument to limit the maximum size of decompressed data. (Contributed by Nikolaus Rath in bpo-15955 [https://bugs.python.org/issue?@action=redirect&bpo=15955].)

cgi

The FieldStorage class now supports the context manager protocol. (Contributed by Berker Peksag in bpo-20289 [https://bugs.python.org/issue?@action=redirect&bpo=20289].)

cmath

A new function isclose() provides a way to test for approximate equality. (Contributed by Chris Barker and Tal Einat in bpo-24270 [https://bugs.python.org/issue?@action=redirect&bpo=24270].)

code

The InteractiveInterpreter.showtraceback() method now prints the full chained traceback, just like the interactive interpreter. (Contributed by Claudiu Popa in bpo-17442 [https://bugs.python.org/issue?@action=redirect&bpo=17442].)

collections

The OrderedDict class is now implemented in C, which makes it 4 to 100 times faster. (Contributed by Eric Snow in bpo-16991 [https://bugs.python.org/issue?@action=redirect&bpo=16991].)

OrderedDict.items(), OrderedDict.keys(), and OrderedDict.values() views now support reversed() iteration. (Contributed by Serhiy Storchaka in bpo-19505 [https://bugs.python.org/issue?@action=redirect&bpo=19505].)

The deque class now defines index(), insert(), and copy(), and supports the + and * operators. This allows deques to be recognized as a MutableSequence and improves their substitutability for lists. (Contributed by Raymond Hettinger in bpo-23704 [https://bugs.python.org/issue?@action=redirect&bpo=23704].)

Docstrings produced by namedtuple() can now be updated:

Point = namedtuple('Point', ['x', 'y'])
Point.__doc__ += ': Cartesian coordinate'
Point.x.__doc__ = 'abscissa'
Point.y.__doc__ = 'ordinate'

（由 Berker Peksag 在 bpo-24064 [https://bugs.python.org/issue?@action=redirect&bpo=24064] 中貢獻。）

The UserString class now implements the __getnewargs__(), __rmod__(), casefold(), format_map(), isprintable(), and maketrans() methods to match the corresponding methods of str. (Contributed by Joe Jevnik in bpo-22189 [https://bugs.python.org/issue?@action=redirect&bpo=22189].)

collections.abc

The Sequence.index() method now accepts start and stop arguments to match the corresponding methods of tuple, list, etc. (Contributed by Devin Jeanpierre in bpo-23086 [https://bugs.python.org/issue?@action=redirect&bpo=23086].)

A new Generator abstract base class. (Contributed by Stefan Behnel in bpo-24018 [https://bugs.python.org/issue?@action=redirect&bpo=24018].)

New Awaitable, Coroutine, AsyncIterator, and AsyncIterable abstract base classes. (Contributed by Yury Selivanov in bpo-24184 [https://bugs.python.org/issue?@action=redirect&bpo=24184].)

For earlier Python versions, a backport of the new ABCs is available in an external PyPI package [https://pypi.org/project/backports_abc/].

compileall

A new compileall option, -j N, allows running N workers simultaneously to perform parallel bytecode compilation. The compile_dir() function has a corresponding workers parameter. (Contributed by Claudiu Popa in bpo-16104 [https://bugs.python.org/issue?@action=redirect&bpo=16104].)

Another new option, -r, allows controlling the maximum recursion level for subdirectories. (Contributed by Claudiu Popa in bpo-19628 [https://bugs.python.org/issue?@action=redirect&bpo=19628].)

The -q command line option can now be specified more than once, in which case all output, including errors, will be suppressed. The corresponding quiet parameter in compile_dir(), compile_file(), and compile_path() can now accept an integer value indicating the level of output suppression. (Contributed by Thomas Kluyver in bpo-21338 [https://bugs.python.org/issue?@action=redirect&bpo=21338].)

concurrent.futures

The Executor.map() method now accepts a chunksize argument to allow batching of tasks to improve performance when ProcessPoolExecutor() is used. (Contributed by Dan O'Reilly in bpo-11271 [https://bugs.python.org/issue?@action=redirect&bpo=11271].)

The number of workers in the ThreadPoolExecutor constructor is optional now. The default value is 5 times the number of CPUs. (Contributed by Claudiu Popa in bpo-21527 [https://bugs.python.org/issue?@action=redirect&bpo=21527].)

configparser

configparser now provides a way to customize the conversion of values by specifying a dictionary of converters in the ConfigParser constructor, or by defining them as methods in ConfigParser subclasses. Converters defined in a parser instance are inherited by its section proxies.

範例：

>>> import configparser
>>> conv = {}
>>> conv['list'] = lambda v: [e.strip() for e in v.split() if e.strip()]
>>> cfg = configparser.ConfigParser(converters=conv)
>>> cfg.read_string("""
... [s]
... list = a b c d e f g
... """)
>>> cfg.get('s', 'list')
'a b c d e f g'
>>> cfg.getlist('s', 'list')
['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> section = cfg['s']
>>> section.getlist('list')
['a', 'b', 'c', 'd', 'e', 'f', 'g']

（由 Łukasz Langa 在 bpo-18159 [https://bugs.python.org/issue?@action=redirect&bpo=18159] 中貢獻。）

contextlib

The new redirect_stderr() context manager (similar to redirect_stdout()) makes it easier for utility scripts to handle inflexible APIs that write their output to sys.stderr and don't provide any options to redirect it:

>>> import contextlib, io, logging
>>> f = io.StringIO()
>>> with contextlib.redirect_stderr(f):
...     logging.warning('warning')
...
>>> f.getvalue()
'WARNING:root:warning\n'

（由 Berker Peksag 在 bpo-22389 [https://bugs.python.org/issue?@action=redirect&bpo=22389] 中貢獻。）

csv

writerow() 方法現在支援任意可疊代物件，而不僅限於序列。（由 Serhiy Storchaka 在 bpo-23171 [https://bugs.python.org/issue?@action=redirect&bpo=23171] 中貢獻。）

curses

The new update_lines_cols() function updates the LINES and COLS module variables. This is useful for detecting manual screen resizing. (Contributed by Arnon Yaari in bpo-4254 [https://bugs.python.org/issue?@action=redirect&bpo=4254].)

dbm

dumb.open always creates a new database when the flag has the value "n". (Contributed by Claudiu Popa in bpo-18039 [https://bugs.python.org/issue?@action=redirect&bpo=18039].)

difflib

The charset of HTML documents generated by HtmlDiff.make_file() can now be customized by using a new charset keyword-only argument. The default charset of HTML document changed from "ISO-8859-1" to "utf-8". (Contributed by Berker Peksag in bpo-2052 [https://bugs.python.org/issue?@action=redirect&bpo=2052].)

The diff_bytes() function can now compare lists of byte strings. This fixes a regression from Python 2. (Contributed by Terry J. Reedy and Greg Ward in bpo-17445 [https://bugs.python.org/issue?@action=redirect&bpo=17445].)

distutils

Both the build and build_ext commands now accept a -j option to enable parallel building of extension modules. (Contributed by Antoine Pitrou in bpo-5309 [https://bugs.python.org/issue?@action=redirect&bpo=5309].)

The distutils module now supports xz compression, and can be enabled by passing xztar as an argument to bdist --format. (Contributed by Serhiy Storchaka in bpo-16314 [https://bugs.python.org/issue?@action=redirect&bpo=16314].)

doctest

The DocTestSuite() function returns an empty unittest.TestSuite if module contains no docstrings, instead of raising ValueError. (Contributed by Glenn Jones in bpo-15916 [https://bugs.python.org/issue?@action=redirect&bpo=15916].)

email

A new policy option Policy.mangle_from_ controls whether or not lines that start with "From " in email bodies are prefixed with a ">" character by generators. The default is True for compat32 and False for all other policies. (Contributed by Milan Oberkirch in bpo-20098 [https://bugs.python.org/issue?@action=redirect&bpo=20098].)

A new Message.get_content_disposition() method provides easy access to a canonical value for the Content-Disposition header. (Contributed by Abhilash Raj in bpo-21083 [https://bugs.python.org/issue?@action=redirect&bpo=21083].)

A new policy option EmailPolicy.utf8 can be set to True to encode email headers using the UTF-8 charset instead of using encoded words. This allows Messages to be formatted according to RFC 6532 [https://datatracker.ietf.org/doc/html/rfc6532.html] and used with an SMTP server that supports the RFC 6531 [https://datatracker.ietf.org/doc/html/rfc6531.html] SMTPUTF8 extension. (Contributed by R. David Murray in bpo-24211 [https://bugs.python.org/issue?@action=redirect&bpo=24211].)

The mime.text.MIMEText constructor now accepts a charset.Charset instance. (Contributed by Claude Paroz and Berker Peksag in bpo-16324 [https://bugs.python.org/issue?@action=redirect&bpo=16324].)

enum

The Enum callable has a new parameter start to specify the initial number of enum values if only names are provided:

>>> Animal = enum.Enum('Animal', 'cat dog', start=10)
>>> Animal.cat
<Animal.cat: 10>
>>> Animal.dog
<Animal.dog: 11>

（由 Ethan Furman 在 bpo-21706 [https://bugs.python.org/issue?@action=redirect&bpo=21706] 中貢獻。）

faulthandler

The enable(), register(), dump_traceback() and dump_traceback_later() functions now accept file descriptors in addition to file-like objects. (Contributed by Wei Wu in bpo-23566 [https://bugs.python.org/issue?@action=redirect&bpo=23566].)

functools

Most of the lru_cache() machinery is now implemented in C, making it significantly faster. (Contributed by Matt Joiner, Alexey Kachayev, and Serhiy Storchaka in bpo-14373 [https://bugs.python.org/issue?@action=redirect&bpo=14373].)

glob

The iglob() and glob() functions now support recursive search in subdirectories, using the "**" pattern. (Contributed by Serhiy Storchaka in bpo-13968 [https://bugs.python.org/issue?@action=redirect&bpo=13968].)

gzip

The mode argument of the GzipFile constructor now accepts "x" to request exclusive creation. (Contributed by Tim Heaney in bpo-19222 [https://bugs.python.org/issue?@action=redirect&bpo=19222].)

heapq

Element comparison in merge() can now be customized by passing a key function in a new optional key keyword argument, and a new optional reverse keyword argument can be used to reverse element comparison:

>>> import heapq
>>> a = ['9', '777', '55555']
>>> b = ['88', '6666']
>>> list(heapq.merge(a, b, key=len))
['9', '88', '777', '6666', '55555']
>>> list(heapq.merge(reversed(a), reversed(b), key=len, reverse=True))
['55555', '6666', '777', '88', '9']

（由 Raymond Hettinger 在 bpo-13742 [https://bugs.python.org/issue?@action=redirect&bpo=13742] 中貢獻。）

http

A new HTTPStatus enum that defines a set of HTTP status codes, reason phrases and long descriptions written in English. (Contributed by Demian Brecht in bpo-21793 [https://bugs.python.org/issue?@action=redirect&bpo=21793].)

http.client

HTTPConnection.getresponse() now raises a RemoteDisconnected exception when a remote server connection is closed unexpectedly. Additionally, if a ConnectionError (of which RemoteDisconnected is a subclass) is raised, the client socket is now closed automatically, and will reconnect on the next request:

import http.client
conn = http.client.HTTPConnection('www.python.org')
for retries in range(3):
    try:
        conn.request('GET', '/')
        resp = conn.getresponse()
    except http.client.RemoteDisconnected:
        pass

（由 Martin Panter 在 bpo-3566 [https://bugs.python.org/issue?@action=redirect&bpo=3566] 中貢獻。）

idlelib 與 IDLE

Since idlelib implements the IDLE shell and editor and is not intended for import by other programs, it gets improvements with every release. See Lib/idlelib/NEWS.txt for a cumulative list of changes since 3.4.0, as well as changes made in future 3.5.x releases. This file is also available from the IDLE Help ‣ About IDLE dialog.

imaplib

The IMAP4 class now supports the context manager protocol. When used in a with statement, the IMAP4 LOGOUT command will be called automatically at the end of the block. (Contributed by Tarek Ziadé and Serhiy Storchaka in bpo-4972 [https://bugs.python.org/issue?@action=redirect&bpo=4972].)

The imaplib module now supports RFC 5161 [https://datatracker.ietf.org/doc/html/rfc5161.html] (ENABLE Extension) and RFC 6855 [https://datatracker.ietf.org/doc/html/rfc6855.html] (UTF-8 Support) via the IMAP4.enable() method. A new IMAP4.utf8_enabled attribute tracks whether or not RFC 6855 [https://datatracker.ietf.org/doc/html/rfc6855.html] support is enabled. (Contributed by Milan Oberkirch, R. David Murray, and Maciej Szulik in bpo-21800 [https://bugs.python.org/issue?@action=redirect&bpo=21800].)

The imaplib module now automatically encodes non-ASCII string usernames and passwords using UTF-8, as recommended by the RFCs. (Contributed by Milan Oberkirch in bpo-21800 [https://bugs.python.org/issue?@action=redirect&bpo=21800].)

imghdr

The what() function now recognizes the OpenEXR [https://www.openexr.com] format (contributed by Martin Vignali and Claudiu Popa in bpo-20295 [https://bugs.python.org/issue?@action=redirect&bpo=20295]), and the WebP [https://en.wikipedia.org/wiki/WebP] format (contributed by Fabrice Aneche and Claudiu Popa in bpo-20197 [https://bugs.python.org/issue?@action=redirect&bpo=20197].)

importlib

The util.LazyLoader class allows for lazy loading of modules in applications where startup time is important. (Contributed by Brett Cannon in bpo-17621 [https://bugs.python.org/issue?@action=redirect&bpo=17621].)

The abc.InspectLoader.source_to_code() method is now a static method. This makes it easier to initialize a module object with code compiled from a string by running exec(code, module.__dict__). (Contributed by Brett Cannon in bpo-21156 [https://bugs.python.org/issue?@action=redirect&bpo=21156].)

The new util.module_from_spec() function is now the preferred way to create a new module. As opposed to creating a types.ModuleType instance directly, this new function will set the various import-controlled attributes based on the passed-in spec object. (Contributed by Brett Cannon in bpo-20383 [https://bugs.python.org/issue?@action=redirect&bpo=20383].)

inspect

Both the Signature and Parameter classes are now picklable and hashable. (Contributed by Yury Selivanov in bpo-20726 [https://bugs.python.org/issue?@action=redirect&bpo=20726] and bpo-20334 [https://bugs.python.org/issue?@action=redirect&bpo=20334].)

A new BoundArguments.apply_defaults() method provides a way to set default values for missing arguments:

>>> def foo(a, b='ham', *args): pass
>>> ba = inspect.signature(foo).bind('spam')
>>> ba.apply_defaults()
>>> ba.arguments
OrderedDict([('a', 'spam'), ('b', 'ham'), ('args', ())])

（由 Yury Selivanov 在 bpo-24190 [https://bugs.python.org/issue?@action=redirect&bpo=24190] 中貢獻。）

A new class method Signature.from_callable() makes subclassing of Signature easier. (Contributed by Yury Selivanov and Eric Snow in bpo-17373 [https://bugs.python.org/issue?@action=redirect&bpo=17373].)

The signature() function now accepts a follow_wrapped optional keyword argument, which, when set to False, disables automatic following of __wrapped__ links. (Contributed by Yury Selivanov in bpo-20691 [https://bugs.python.org/issue?@action=redirect&bpo=20691].)

A set of new functions to inspect coroutine functions and coroutine objects has been added: iscoroutine(), iscoroutinefunction(), isawaitable(), getcoroutinelocals(), and getcoroutinestate(). (Contributed by Yury Selivanov in bpo-24017 [https://bugs.python.org/issue?@action=redirect&bpo=24017] and bpo-24400 [https://bugs.python.org/issue?@action=redirect&bpo=24400].)

The stack(), trace(), getouterframes(), and getinnerframes() functions now return a list of named tuples. (Contributed by Daniel Shahaf in bpo-16808 [https://bugs.python.org/issue?@action=redirect&bpo=16808].)

io

A new BufferedIOBase.readinto1() method, that uses at most one call to the underlying raw stream's RawIOBase.read() or RawIOBase.readinto() methods. (Contributed by Nikolaus Rath in bpo-20578 [https://bugs.python.org/issue?@action=redirect&bpo=20578].)

ipaddress

Both the IPv4Network and IPv6Network classes now accept an (address, netmask) tuple argument, so as to easily construct network objects from existing addresses:

>>> import ipaddress
>>> ipaddress.IPv4Network(('127.0.0.0', 8))
IPv4Network('127.0.0.0/8')
>>> ipaddress.IPv4Network(('127.0.0.0', '255.0.0.0'))
IPv4Network('127.0.0.0/8')

（由 Peter Moody 和 Antoine Pitrou 在 bpo-16531 [https://bugs.python.org/issue?@action=redirect&bpo=16531] 中貢獻。）

A new reverse_pointer attribute for the IPv4Address and IPv6Address classes returns the name of the reverse DNS PTR record:

>>> import ipaddress
>>> addr = ipaddress.IPv4Address('127.0.0.1')
>>> addr.reverse_pointer
'1.0.0.127.in-addr.arpa'
>>> addr6 = ipaddress.IPv6Address('::1')
>>> addr6.reverse_pointer
'1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa'

（由 Leon Weber 在 bpo-20480 [https://bugs.python.org/issue?@action=redirect&bpo=20480] 中貢獻。）

json

The json.tool command line interface now preserves the order of keys in JSON objects passed in input. The new --sort-keys option can be used to sort the keys alphabetically. (Contributed by Berker Peksag in bpo-21650 [https://bugs.python.org/issue?@action=redirect&bpo=21650].)

JSON decoder now raises JSONDecodeError instead of ValueError to provide better context information about the error. (Contributed by Serhiy Storchaka in bpo-19361 [https://bugs.python.org/issue?@action=redirect&bpo=19361].)

linecache

A new lazycache() function can be used to capture information about a non-file-based module to permit getting its lines later via getline(). This avoids doing I/O until a line is actually needed, without having to carry the module globals around indefinitely. (Contributed by Robert Collins in bpo-17911 [https://bugs.python.org/issue?@action=redirect&bpo=17911].)

locale

A new delocalize() function can be used to convert a string into a normalized number string, taking the LC_NUMERIC settings into account:

>>> import locale
>>> locale.setlocale(locale.LC_NUMERIC, 'de_DE.UTF-8')
'de_DE.UTF-8'
>>> locale.delocalize('1.234,56')
'1234.56'
>>> locale.setlocale(locale.LC_NUMERIC, 'en_US.UTF-8')
'en_US.UTF-8'
>>> locale.delocalize('1,234.56')
'1234.56'

（由 Cédric Krier 在 bpo-13918 [https://bugs.python.org/issue?@action=redirect&bpo=13918] 中貢獻。）

logging

All logging methods (Logger log(), exception(), critical(), debug(), etc.), now accept exception instances as an exc_info argument, in addition to boolean values and exception tuples:

>>> import logging
>>> try:
...     1/0
... except ZeroDivisionError as ex:
...     logging.error('exception', exc_info=ex)
ERROR:root:exception

（由 Yury Selivanov 在 bpo-20537 [https://bugs.python.org/issue?@action=redirect&bpo=20537] 中貢獻。）

The handlers.HTTPHandler class now accepts an optional ssl.SSLContext instance to configure SSL settings used in an HTTP connection. (Contributed by Alex Gaynor in bpo-22788 [https://bugs.python.org/issue?@action=redirect&bpo=22788].)

The handlers.QueueListener class now takes a respect_handler_level keyword argument which, if set to True, will pass messages to handlers taking handler levels into account. (Contributed by Vinay Sajip.)

lzma

The LZMADecompressor.decompress() method now accepts an optional max_length argument to limit the maximum size of decompressed data. (Contributed by Martin Panter in bpo-15955 [https://bugs.python.org/issue?@action=redirect&bpo=15955].)

math

Two new constants have been added to the math module: inf and nan. (Contributed by Mark Dickinson in bpo-23185 [https://bugs.python.org/issue?@action=redirect&bpo=23185].)

一個新函式 isclose() 提供了測試近似相等性的方式。（由 Chris Barker 和 Tal Einat 在 bpo-24270 [https://bugs.python.org/issue?@action=redirect&bpo=24270] 中貢獻。）

A new gcd() function has been added. The fractions.gcd() function is now deprecated. (Contributed by Mark Dickinson and Serhiy Storchaka in bpo-22486 [https://bugs.python.org/issue?@action=redirect&bpo=22486].)

multiprocessing

sharedctypes.synchronized() objects now support the context manager protocol. (Contributed by Charles-François Natali in bpo-21565 [https://bugs.python.org/issue?@action=redirect&bpo=21565].)

operator

attrgetter(), itemgetter(), and methodcaller() objects now support pickling. (Contributed by Josh Rosenberg and Serhiy Storchaka in bpo-22955 [https://bugs.python.org/issue?@action=redirect&bpo=22955].)

New matmul() and imatmul() functions to perform matrix multiplication. (Contributed by Benjamin Peterson in bpo-21176 [https://bugs.python.org/issue?@action=redirect&bpo=21176].)

os

The new scandir() function returning an iterator of DirEntry objects has been added. If possible, scandir() extracts file attributes while scanning a directory, removing the need to perform subsequent system calls to determine file type or attributes, which may significantly improve performance. (Contributed by Ben Hoyt with the help of Victor Stinner in bpo-22524 [https://bugs.python.org/issue?@action=redirect&bpo=22524].)

On Windows, a new stat_result.st_file_attributes attribute is now available. It corresponds to the dwFileAttributes member of the BY_HANDLE_FILE_INFORMATION structure returned by GetFileInformationByHandle(). (Contributed by Ben Hoyt in bpo-21719 [https://bugs.python.org/issue?@action=redirect&bpo=21719].)

The urandom() function now uses the getrandom() syscall on Linux 3.17 or newer, and getentropy() on OpenBSD 5.6 and newer, removing the need to use /dev/urandom and avoiding failures due to potential file descriptor exhaustion. (Contributed by Victor Stinner in bpo-22181 [https://bugs.python.org/issue?@action=redirect&bpo=22181].)

New get_blocking() and set_blocking() functions allow getting and setting a file descriptor's blocking mode (O_NONBLOCK.) (Contributed by Victor Stinner in bpo-22054 [https://bugs.python.org/issue?@action=redirect&bpo=22054].)

Windows 現在支援 truncate() 和 ftruncate() 函式。（由 Steve Dower 在 bpo-23668 [https://bugs.python.org/issue?@action=redirect&bpo=23668] 中貢獻。）

There is a new os.path.commonpath() function returning the longest common sub-path of each passed pathname. Unlike the os.path.commonprefix() function, it always returns a valid path:

>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
'/usr/l'

>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
'/usr'

（由 Rafik Draoui 和 Serhiy Storchaka 在 bpo-10395 [https://bugs.python.org/issue?@action=redirect&bpo=10395] 中貢獻。）

pathlib

The new Path.samefile() method can be used to check whether the path points to the same file as another path, which can be either another Path object, or a string:

>>> import pathlib
>>> p1 = pathlib.Path('/etc/hosts')
>>> p2 = pathlib.Path('/etc/../etc/hosts')
>>> p1.samefile(p2)
True

（由 Vajrasky Kok 和 Antoine Pitrou 在 bpo-19775 [https://bugs.python.org/issue?@action=redirect&bpo=19775] 中貢獻。）

The Path.mkdir() method now accepts a new optional exist_ok argument to match mkdir -p and os.makedirs() functionality. (Contributed by Berker Peksag in bpo-21539 [https://bugs.python.org/issue?@action=redirect&bpo=21539].)

There is a new Path.expanduser() method to expand ~ and ~user prefixes. (Contributed by Serhiy Storchaka and Claudiu Popa in bpo-19776 [https://bugs.python.org/issue?@action=redirect&bpo=19776].)

A new Path.home() class method can be used to get a Path instance representing the user’s home directory. (Contributed by Victor Salgado and Mayank Tripathi in bpo-19777 [https://bugs.python.org/issue?@action=redirect&bpo=19777].)

New Path.write_text(), Path.read_text(), Path.write_bytes(), Path.read_bytes() methods to simplify read/write operations on files.

以下程式碼片段將會建立或重寫已存在的檔案 ~/spam42：

>>> import pathlib
>>> p = pathlib.Path('~/spam42')
>>> p.expanduser().write_text('ham')
3

（由 Christopher Welborn 在 bpo-20218 [https://bugs.python.org/issue?@action=redirect&bpo=20218] 中貢獻。）

pickle

Nested objects, such as unbound methods or nested classes, can now be pickled using pickle protocols older than protocol version 4. Protocol version 4 already supports these cases. (Contributed by Serhiy Storchaka in bpo-23611 [https://bugs.python.org/issue?@action=redirect&bpo=23611].)

poplib

A new POP3.utf8() command enables RFC 6856 [https://datatracker.ietf.org/doc/html/rfc6856.html] (Internationalized Email) support, if a POP server supports it. (Contributed by Milan OberKirch in bpo-21804 [https://bugs.python.org/issue?@action=redirect&bpo=21804].)

re

References and conditional references to groups with fixed length are now allowed in lookbehind assertions:

>>> import re
>>> pat = re.compile(r'(a|b).(?<=\1)c')
>>> pat.match('aac')
<_sre.SRE_Match object; span=(0, 3), match='aac'>
>>> pat.match('bbc')
<_sre.SRE_Match object; span=(0, 3), match='bbc'>

（由 Serhiy Storchaka 在 bpo-9179 [https://bugs.python.org/issue?@action=redirect&bpo=9179] 中貢獻。）

The number of capturing groups in regular expressions is no longer limited to 100. (Contributed by Serhiy Storchaka in bpo-22437 [https://bugs.python.org/issue?@action=redirect&bpo=22437].)

The sub() and subn() functions now replace unmatched groups with empty strings instead of raising an exception. (Contributed by Serhiy Storchaka in bpo-1519638 [https://bugs.python.org/issue?@action=redirect&bpo=1519638].)

The re.error exceptions have new attributes, msg, pattern, pos, lineno, and colno, that provide better context information about the error:

>>> re.compile("""
...     (?x)
...     .++
... """)
Traceback (most recent call last):
   ...
sre_constants.error: multiple repeat at position 16 (line 3, column 7)

（由 Serhiy Storchaka 在 bpo-22578 [https://bugs.python.org/issue?@action=redirect&bpo=22578] 中貢獻。）

readline

A new append_history_file() function can be used to append the specified number of trailing elements in history to the given file. (Contributed by Bruno Cauet in bpo-22940 [https://bugs.python.org/issue?@action=redirect&bpo=22940].)

selectors

The new DevpollSelector supports efficient /dev/poll polling on Solaris. (Contributed by Giampaolo Rodola' in bpo-18931 [https://bugs.python.org/issue?@action=redirect&bpo=18931].)

shutil

The move() function now accepts a copy_function argument, allowing, for example, the copy() function to be used instead of the default copy2() if there is a need to ignore file metadata when moving. (Contributed by Claudiu Popa in bpo-19840 [https://bugs.python.org/issue?@action=redirect&bpo=19840].)

make_archive() 函式現在支援 xztar 格式。（由 Serhiy Storchaka 在 bpo-5411 [https://bugs.python.org/issue?@action=redirect&bpo=5411] 中貢獻。）

signal

On Windows, the set_wakeup_fd() function now also supports socket handles. (Contributed by Victor Stinner in bpo-22018 [https://bugs.python.org/issue?@action=redirect&bpo=22018].)

Various SIG* constants in the signal module have been converted into Enums. This allows meaningful names to be printed during debugging, instead of integer "magic numbers". (Contributed by Giampaolo Rodola' in bpo-21076 [https://bugs.python.org/issue?@action=redirect&bpo=21076].)

smtpd

Both the SMTPServer and SMTPChannel classes now accept a decode_data keyword argument to determine if the DATA portion of the SMTP transaction is decoded using the "utf-8" codec or is instead provided to the SMTPServer.process_message() method as a byte string. The default is True for backward compatibility reasons, but will change to False in Python 3.6. If decode_data is set to False, the process_message method must be prepared to accept keyword arguments. (Contributed by Maciej Szulik in bpo-19662 [https://bugs.python.org/issue?@action=redirect&bpo=19662].)

The SMTPServer class now advertises the 8BITMIME extension (RFC 6152 [https://datatracker.ietf.org/doc/html/rfc6152.html]) if decode_data has been set True. If the client specifies BODY=8BITMIME on the MAIL command, it is passed to SMTPServer.process_message() via the mail_options keyword. (Contributed by Milan Oberkirch and R. David Murray in bpo-21795 [https://bugs.python.org/issue?@action=redirect&bpo=21795].)

The SMTPServer class now also supports the SMTPUTF8 extension (RFC 6531 [https://datatracker.ietf.org/doc/html/rfc6531.html]: Internationalized Email). If the client specified SMTPUTF8 BODY=8BITMIME on the MAIL command, they are passed to SMTPServer.process_message() via the mail_options keyword. It is the responsibility of the process_message method to correctly handle the SMTPUTF8 data. (Contributed by Milan Oberkirch in bpo-21725 [https://bugs.python.org/issue?@action=redirect&bpo=21725].)

It is now possible to provide, directly or via name resolution, IPv6 addresses in the SMTPServer constructor, and have it successfully connect. (Contributed by Milan Oberkirch in bpo-14758 [https://bugs.python.org/issue?@action=redirect&bpo=14758].)

smtplib

A new SMTP.auth() method provides a convenient way to implement custom authentication mechanisms. (Contributed by Milan Oberkirch in bpo-15014 [https://bugs.python.org/issue?@action=redirect&bpo=15014].)

The SMTP.set_debuglevel() method now accepts an additional debuglevel (2), which enables timestamps in debug messages. (Contributed by Gavin Chappell and Maciej Szulik in bpo-16914 [https://bugs.python.org/issue?@action=redirect&bpo=16914].)

Both the SMTP.sendmail() and SMTP.send_message() methods now support RFC 6531 [https://datatracker.ietf.org/doc/html/rfc6531.html] (SMTPUTF8). (Contributed by Milan Oberkirch and R. David Murray in bpo-22027 [https://bugs.python.org/issue?@action=redirect&bpo=22027].)

sndhdr

The what() and whathdr() functions now return a namedtuple(). (Contributed by Claudiu Popa in bpo-18615 [https://bugs.python.org/issue?@action=redirect&bpo=18615].)

socket

Functions with timeouts now use a monotonic clock, instead of a system clock. (Contributed by Victor Stinner in bpo-22043 [https://bugs.python.org/issue?@action=redirect&bpo=22043].)

A new socket.sendfile() method allows sending a file over a socket by using the high-performance os.sendfile() function on UNIX, resulting in uploads being from 2 to 3 times faster than when using plain socket.send(). (Contributed by Giampaolo Rodola' in bpo-17552 [https://bugs.python.org/issue?@action=redirect&bpo=17552].)

The socket.sendall() method no longer resets the socket timeout every time bytes are received or sent. The socket timeout is now the maximum total duration to send all data. (Contributed by Victor Stinner in bpo-23853 [https://bugs.python.org/issue?@action=redirect&bpo=23853].)

The backlog argument of the socket.listen() method is now optional. By default it is set to SOMAXCONN or to 128, whichever is less. (Contributed by Charles-François Natali in bpo-21455 [https://bugs.python.org/issue?@action=redirect&bpo=21455].)

ssl

記憶體 BIO 支援

（由 Geert Jansen 在 bpo-21965 [https://bugs.python.org/issue?@action=redirect&bpo=21965] 中貢獻。）

The new SSLObject class has been added to provide SSL protocol support for cases when the network I/O capabilities of SSLSocket are not necessary or are suboptimal. SSLObject represents an SSL protocol instance, but does not implement any network I/O methods, and instead provides a memory buffer interface. The new MemoryBIO class can be used to pass data between Python and an SSL protocol instance.

The memory BIO SSL support is primarily intended to be used in frameworks implementing asynchronous I/O for which SSLSocket's readiness model ("select/poll") is inefficient.

A new SSLContext.wrap_bio() method can be used to create a new SSLObject instance.

Application-Layer Protocol Negotiation Support

（由 Benjamin Peterson 在 bpo-20188 [https://bugs.python.org/issue?@action=redirect&bpo=20188] 中貢獻。）

Where OpenSSL support is present, the ssl module now implements the Application-Layer Protocol Negotiation TLS extension as described in RFC 7301 [https://datatracker.ietf.org/doc/html/rfc7301.html].

The new SSLContext.set_alpn_protocols() can be used to specify which protocols a socket should advertise during the TLS handshake.

The new SSLSocket.selected_alpn_protocol() returns the protocol that was selected during the TLS handshake. The HAS_ALPN flag indicates whether ALPN support is present.

其他變更

There is a new SSLSocket.version() method to query the actual protocol version in use. (Contributed by Antoine Pitrou in bpo-20421 [https://bugs.python.org/issue?@action=redirect&bpo=20421].)

The SSLSocket class now implements a SSLSocket.sendfile() method. (Contributed by Giampaolo Rodola' in bpo-17552 [https://bugs.python.org/issue?@action=redirect&bpo=17552].)

The SSLSocket.send() method now raises either the ssl.SSLWantReadError or ssl.SSLWantWriteError exception on a non-blocking socket if the operation would block. Previously, it would return 0. (Contributed by Nikolaus Rath in bpo-20951 [https://bugs.python.org/issue?@action=redirect&bpo=20951].)

The cert_time_to_seconds() function now interprets the input time as UTC and not as local time, per RFC 5280 [https://datatracker.ietf.org/doc/html/rfc5280.html]. Additionally, the return value is always an int. (Contributed by Akira Li in bpo-19940 [https://bugs.python.org/issue?@action=redirect&bpo=19940].)

New SSLObject.shared_ciphers() and SSLSocket.shared_ciphers() methods return the list of ciphers sent by the client during the handshake. (Contributed by Benjamin Peterson in bpo-23186 [https://bugs.python.org/issue?@action=redirect&bpo=23186].)

The SSLSocket.do_handshake(), SSLSocket.read(), SSLSocket.shutdown(), and SSLSocket.write() methods of the SSLSocket class no longer reset the socket timeout every time bytes are received or sent. The socket timeout is now the maximum total duration of the method. (Contributed by Victor Stinner in bpo-23853 [https://bugs.python.org/issue?@action=redirect&bpo=23853].)

match_hostname() 函式現在支援 IP 位址的比對。（由 Antoine Pitrou 在 bpo-23239 [https://bugs.python.org/issue?@action=redirect&bpo=23239] 中貢獻。）

sqlite3

The Row class now fully supports the sequence protocol, in particular reversed() iteration and slice indexing. (Contributed by Claudiu Popa in bpo-10203 [https://bugs.python.org/issue?@action=redirect&bpo=10203]; by Lucas Sinclair, Jessica McKellar, and Serhiy Storchaka in bpo-13583 [https://bugs.python.org/issue?@action=redirect&bpo=13583].)

subprocess

新增 run() 函式。它運行指定的命令並回傳一個 CompletedProcess 物件，該物件描述了一個已完成的行程。新的 API 更加一致，並且是以較為推薦方法來叫用子行程，適用於不需要與早期 Python 版本保持相容性的 Python 程式碼。（由 Thomas Kluyver 在 bpo-23342 [https://bugs.python.org/issue?@action=redirect&bpo=23342] 中貢獻。）

範例：

>>> subprocess.run(["ls", "-l"])  # 沒有捕捉到輸出
CompletedProcess(args=['ls', '-l'], returncode=0)

>>> subprocess.run("exit 1", shell=True, check=True)
Traceback (most recent call last):
  ...
subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1

>>> subprocess.run(["ls", "-l", "/dev/null"], stdout=subprocess.PIPE)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n')

sys

A new set_coroutine_wrapper() function allows setting a global hook that will be called whenever a coroutine object is created by an async def function. A corresponding get_coroutine_wrapper() can be used to obtain a currently set wrapper. Both functions are provisional, and are intended for debugging purposes only. (Contributed by Yury Selivanov in bpo-24017 [https://bugs.python.org/issue?@action=redirect&bpo=24017].)

A new is_finalizing() function can be used to check if the Python interpreter is shutting down. (Contributed by Antoine Pitrou in bpo-22696 [https://bugs.python.org/issue?@action=redirect&bpo=22696].)

sysconfig

The name of the user scripts directory on Windows now includes the first two components of the Python version. (Contributed by Paul Moore in bpo-23437 [https://bugs.python.org/issue?@action=redirect&bpo=23437].)

tarfile

The mode argument of the open() function now accepts "x" to request exclusive creation. (Contributed by Berker Peksag in bpo-21717 [https://bugs.python.org/issue?@action=redirect&bpo=21717].)

The TarFile.extractall() and TarFile.extract() methods now take a keyword argument numeric_owner. If set to True, the extracted files and directories will be owned by the numeric uid and gid from the tarfile. If set to False (the default, and the behavior in versions prior to 3.5), they will be owned by the named user and group in the tarfile. (Contributed by Michael Vogt and Eric Smith in bpo-23193 [https://bugs.python.org/issue?@action=redirect&bpo=23193].)

The TarFile.list() now accepts an optional members keyword argument that can be set to a subset of the list returned by TarFile.getmembers(). (Contributed by Serhiy Storchaka in bpo-21549 [https://bugs.python.org/issue?@action=redirect&bpo=21549].)

threading

Both the Lock.acquire() and RLock.acquire() methods now use a monotonic clock for timeout management. (Contributed by Victor Stinner in bpo-22043 [https://bugs.python.org/issue?@action=redirect&bpo=22043].)

time

monotonic() 函式現在總是可用的。（由 Victor Stinner 在 bpo-22043 [https://bugs.python.org/issue?@action=redirect&bpo=22043] 中貢獻。）

timeit

A new command line option -u or --unit=U can be used to specify the time unit for the timer output. Supported options are usec, msec, or sec. (Contributed by Julian Gindi in bpo-18983 [https://bugs.python.org/issue?@action=redirect&bpo=18983].)

The timeit() function has a new globals parameter for specifying the namespace in which the code will be running. (Contributed by Ben Roberts in bpo-2527 [https://bugs.python.org/issue?@action=redirect&bpo=2527].)

tkinter

The tkinter._fix module used for setting up the Tcl/Tk environment on Windows has been replaced by a private function in the _tkinter module which makes no permanent changes to environment variables. (Contributed by Zachary Ware in bpo-20035 [https://bugs.python.org/issue?@action=redirect&bpo=20035].)

traceback

New walk_stack() and walk_tb() functions to conveniently traverse frame and traceback objects. (Contributed by Robert Collins in bpo-17911 [https://bugs.python.org/issue?@action=redirect&bpo=17911].)

New lightweight classes: TracebackException, StackSummary, and FrameSummary. (Contributed by Robert Collins in bpo-17911 [https://bugs.python.org/issue?@action=redirect&bpo=17911].)

Both the print_tb() and print_stack() functions now support negative values for the limit argument. (Contributed by Dmitry Kazakov in bpo-22619 [https://bugs.python.org/issue?@action=redirect&bpo=22619].)

types

A new coroutine() function to transform generator and generator-like objects into awaitables. (Contributed by Yury Selivanov in bpo-24017 [https://bugs.python.org/issue?@action=redirect&bpo=24017].)

A new type called CoroutineType, which is used for coroutine objects created by async def functions. (Contributed by Yury Selivanov in bpo-24400 [https://bugs.python.org/issue?@action=redirect&bpo=24400].)

unicodedata

unicodedata 模組現在使用來自 Unicode 8.0.0 [https://unicode.org/versions/Unicode8.0.0/] 的資料。

unittest

The TestLoader.loadTestsFromModule() method now accepts a keyword-only argument pattern which is passed to load_tests as the third argument. Found packages are now checked for load_tests regardless of whether their path matches pattern, because it is impossible for a package name to match the default pattern. (Contributed by Robert Collins and Barry A. Warsaw in bpo-16662 [https://bugs.python.org/issue?@action=redirect&bpo=16662].)

Unittest discovery errors now are exposed in the TestLoader.errors attribute of the TestLoader instance. (Contributed by Robert Collins in bpo-19746 [https://bugs.python.org/issue?@action=redirect&bpo=19746].)

A new command line option --locals to show local variables in tracebacks. (Contributed by Robert Collins in bpo-22936 [https://bugs.python.org/issue?@action=redirect&bpo=22936].)

unittest.mock

Mock 類別有以下改進：

The class constructor has a new unsafe parameter, which causes mock objects to raise AttributeError on attribute names starting with "assert". (Contributed by Kushal Das in bpo-21238 [https://bugs.python.org/issue?@action=redirect&bpo=21238].)

A new Mock.assert_not_called() method to check if the mock object was called. (Contributed by Kushal Das in bpo-21262 [https://bugs.python.org/issue?@action=redirect&bpo=21262].)

The MagicMock class now supports __truediv__(), __divmod__() and __matmul__() operators. (Contributed by Johannes Baiter in bpo-20968 [https://bugs.python.org/issue?@action=redirect&bpo=20968], and Håkan Lövdahl in bpo-23581 [https://bugs.python.org/issue?@action=redirect&bpo=23581] and bpo-23568 [https://bugs.python.org/issue?@action=redirect&bpo=23568].)

It is no longer necessary to explicitly pass create=True to the patch() function when patching builtin names. (Contributed by Kushal Das in bpo-17660 [https://bugs.python.org/issue?@action=redirect&bpo=17660].)

urllib

A new request.HTTPPasswordMgrWithPriorAuth class allows HTTP Basic Authentication credentials to be managed so as to eliminate unnecessary 401 response handling, or to unconditionally send credentials on the first request in order to communicate with servers that return a 404 response instead of a 401 if the Authorization header is not sent. (Contributed by Matej Cepl in bpo-19494 [https://bugs.python.org/issue?@action=redirect&bpo=19494] and Akshit Khurana in bpo-7159 [https://bugs.python.org/issue?@action=redirect&bpo=7159].)

A new quote_via argument for the parse.urlencode() function provides a way to control the encoding of query parts if needed. (Contributed by Samwyse and Arnon Yaari in bpo-13866 [https://bugs.python.org/issue?@action=redirect&bpo=13866].)

The request.urlopen() function accepts an ssl.SSLContext object as a context argument, which will be used for the HTTPS connection. (Contributed by Alex Gaynor in bpo-22366 [https://bugs.python.org/issue?@action=redirect&bpo=22366].)

The parse.urljoin() was updated to use the RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html] semantics for the resolution of relative URLs, rather than RFC 1808 [https://datatracker.ietf.org/doc/html/rfc1808.html] and RFC 2396 [https://datatracker.ietf.org/doc/html/rfc2396.html]. (Contributed by Demian Brecht and Senthil Kumaran in bpo-22118 [https://bugs.python.org/issue?@action=redirect&bpo=22118].)

wsgiref

The headers argument of the headers.Headers class constructor is now optional. (Contributed by Pablo Torres Navarrete and SilentGhost in bpo-5800 [https://bugs.python.org/issue?@action=redirect&bpo=5800].)

xmlrpc

The client.ServerProxy class now supports the context manager protocol. (Contributed by Claudiu Popa in bpo-20627 [https://bugs.python.org/issue?@action=redirect&bpo=20627].)

The client.ServerProxy constructor now accepts an optional ssl.SSLContext instance. (Contributed by Alex Gaynor in bpo-22960 [https://bugs.python.org/issue?@action=redirect&bpo=22960].)

xml.sax

SAX parsers now support a character stream of the xmlreader.InputSource object. (Contributed by Serhiy Storchaka in bpo-2175 [https://bugs.python.org/issue?@action=redirect&bpo=2175].)

parseString() 現在接受一個 str 實例。（由 Serhiy Storchaka 在 bpo-10590 [https://bugs.python.org/issue?@action=redirect&bpo=10590] 中貢獻。）

zipfile

ZIP output can now be written to unseekable streams. (Contributed by Serhiy Storchaka in bpo-23252 [https://bugs.python.org/issue?@action=redirect&bpo=23252].)

The mode argument of ZipFile.open() method now accepts "x" to request exclusive creation. (Contributed by Serhiy Storchaka in bpo-21717 [https://bugs.python.org/issue?@action=redirect&bpo=21717].)

其他模組層級的變更

Many functions in the mmap, ossaudiodev, socket, ssl, and codecs modules now accept writable bytes-like objects. (Contributed by Serhiy Storchaka in bpo-23001 [https://bugs.python.org/issue?@action=redirect&bpo=23001].)

最佳化

The os.walk() function has been sped up by 3 to 5 times on POSIX systems, and by 7 to 20 times on Windows. This was done using the new os.scandir() function, which exposes file information from the underlying readdir or FindFirstFile/FindNextFile system calls. (Contributed by Ben Hoyt with help from Victor Stinner in bpo-23605 [https://bugs.python.org/issue?@action=redirect&bpo=23605].)

Construction of bytes(int) (filled by zero bytes) is faster and uses less memory for large objects. calloc() is used instead of malloc() to allocate memory for these objects. (Contributed by Victor Stinner in bpo-21233 [https://bugs.python.org/issue?@action=redirect&bpo=21233].)

Some operations on ipaddress IPv4Network and IPv6Network have been massively sped up, such as subnets(), supernet(), summarize_address_range(), collapse_addresses(). The speed up can range from 3 to 15 times. (Contributed by Antoine Pitrou, Michel Albert, and Markus in bpo-21486 [https://bugs.python.org/issue?@action=redirect&bpo=21486], bpo-21487 [https://bugs.python.org/issue?@action=redirect&bpo=21487], bpo-20826 [https://bugs.python.org/issue?@action=redirect&bpo=20826], bpo-23266 [https://bugs.python.org/issue?@action=redirect&bpo=23266].)

Pickling of ipaddress objects was optimized to produce significantly smaller output. (Contributed by Serhiy Storchaka in bpo-23133 [https://bugs.python.org/issue?@action=redirect&bpo=23133].)

Many operations on io.BytesIO are now 50% to 100% faster. (Contributed by Serhiy Storchaka in bpo-15381 [https://bugs.python.org/issue?@action=redirect&bpo=15381] and David Wilson in bpo-22003 [https://bugs.python.org/issue?@action=redirect&bpo=22003].)

The marshal.dumps() function is now faster: 65--85% with versions 3 and 4, 20--25% with versions 0 to 2 on typical data, and up to 5 times in best cases. (Contributed by Serhiy Storchaka in bpo-20416 [https://bugs.python.org/issue?@action=redirect&bpo=20416] and bpo-23344 [https://bugs.python.org/issue?@action=redirect&bpo=23344].)

The UTF-32 encoder is now 3 to 7 times faster. (Contributed by Serhiy Storchaka in bpo-15027 [https://bugs.python.org/issue?@action=redirect&bpo=15027].)

Regular expressions are now parsed up to 10% faster. (Contributed by Serhiy Storchaka in bpo-19380 [https://bugs.python.org/issue?@action=redirect&bpo=19380].)

The json.dumps() function was optimized to run with ensure_ascii=False as fast as with ensure_ascii=True. (Contributed by Naoki Inada in bpo-23206 [https://bugs.python.org/issue?@action=redirect&bpo=23206].)

The PyObject_IsInstance() and PyObject_IsSubclass() functions have been sped up in the common case that the second argument has type as its metaclass. (Contributed Georg Brandl by in bpo-22540 [https://bugs.python.org/issue?@action=redirect&bpo=22540].)

Method caching was slightly improved, yielding up to 5% performance improvement in some benchmarks. (Contributed by Antoine Pitrou in bpo-22847 [https://bugs.python.org/issue?@action=redirect&bpo=22847].)

Objects from the random module now use 50% less memory on 64-bit builds. (Contributed by Serhiy Storchaka in bpo-23488 [https://bugs.python.org/issue?@action=redirect&bpo=23488].)

The property() getter calls are up to 25% faster. (Contributed by Joe Jevnik in bpo-23910 [https://bugs.python.org/issue?@action=redirect&bpo=23910].)

fractions.Fraction 的實例化現在快了 30%。（由 Stefan Behnel 在 bpo-22464 [https://bugs.python.org/issue?@action=redirect&bpo=22464] 中貢獻。）

String methods find(), rfind(), split(), partition() and the in string operator are now significantly faster for searching 1-character substrings. (Contributed by Serhiy Storchaka in bpo-23573 [https://bugs.python.org/issue?@action=redirect&bpo=23573].)

建置和 C API 變更

新增了 calloc 函式：

PyMem_RawCalloc(),

PyMem_Calloc(),

PyObject_Calloc().

（由 Victor Stinner 在 bpo-21233 [https://bugs.python.org/issue?@action=redirect&bpo=21233] 中貢獻。）

New encoding/decoding helper functions:

Py_DecodeLocale()（取代 _Py_char2wchar()），

Py_EncodeLocale()（取代 _Py_wchar2char()）。

（由 Victor Stinner 在 bpo-18395 [https://bugs.python.org/issue?@action=redirect&bpo=18395] 中貢獻。）

A new PyCodec_NameReplaceErrors() function to replace the unicode encode error with \N{...} escapes. (Contributed by Serhiy Storchaka in bpo-19676 [https://bugs.python.org/issue?@action=redirect&bpo=19676].)

A new PyErr_FormatV() function similar to PyErr_Format(), but accepts a va_list argument. (Contributed by Antoine Pitrou in bpo-18711 [https://bugs.python.org/issue?@action=redirect&bpo=18711].)

新增 PyExc_RecursionError 例外。（由 Georg Brandl 在 bpo-19235 [https://bugs.python.org/issue?@action=redirect&bpo=19235] 中貢獻。）

New PyModule_FromDefAndSpec(), PyModule_FromDefAndSpec2(), and PyModule_ExecDef() functions introduced by PEP 489 [https://peps.python.org/pep-0489/] -- multi-phase extension module initialization. (Contributed by Petr Viktorin in bpo-24268 [https://bugs.python.org/issue?@action=redirect&bpo=24268].)

New PyNumber_MatrixMultiply() and PyNumber_InPlaceMatrixMultiply() functions to perform matrix multiplication. (Contributed by Benjamin Peterson in bpo-21176 [https://bugs.python.org/issue?@action=redirect&bpo=21176]. See also PEP 465 [https://peps.python.org/pep-0465/] for details.)

PyTypeObject.tp_finalize 插槽現在是穩定 ABI 的一部分。

Windows builds now require Microsoft Visual C++ 14.0, which is available as part of Visual Studio 2015 [https://visualstudio.microsoft.com/en/vs/older-downloads/#visual-studio-2015-and-other-products].

Extension modules now include a platform information tag in their filename on some platforms (the tag is optional, and CPython will import extensions without it, although if the tag is present and mismatched, the extension won't be loaded):

On Linux, extension module filenames end with .cpython-<major><minor>m-<architecture>-<os>.pyd:

<major> 是 Python 版本的主要號碼；對於 Python 3.5 來說這是 3。

<minor> 是 Python 版本的次要號碼；對於 Python 3.5 來說這是 5。

<architecture> is the hardware architecture the extension module was built to run on. It's most commonly either i386 for 32-bit Intel platforms or x86_64 for 64-bit Intel (and AMD) platforms.

<os> is always linux-gnu, except for extensions built to talk to the 32-bit ABI on 64-bit platforms, in which case it is linux-gnu32 (and <architecture> will be x86_64).

On Windows, extension module filenames end with <debug>.cp<major><minor>-<platform>.pyd:

<major> 是 Python 版本的主要號碼；對於 Python 3.5 來說這是 3。

<minor> 是 Python 版本的次要號碼；對於 Python 3.5 來說這是 5。

<platform> is the platform the extension module was built for, either win32 for Win32, win_amd64 for Win64, win_ia64 for Windows Itanium 64, and win_arm for Windows on ARM.

If built in debug mode, <debug> will be _d, otherwise it will be blank.

On OS X platforms, extension module filenames now end with -darwin.so.

On all other platforms, extension module filenames are the same as they were with Python 3.4.

已棄用

新關鍵字

async and await are not recommended to be used as variable, class, function or module names. Introduced by PEP 492 [https://peps.python.org/pep-0492/] in Python 3.5, they will become proper keywords in Python 3.7.

已棄用的 Python 行為

Raising the StopIteration exception inside a generator will now generate a silent PendingDeprecationWarning, which will become a non-silent deprecation warning in Python 3.6 and will trigger a RuntimeError in Python 3.7. See PEP 479: Change StopIteration handling inside generators for details.

不支援的作業系統

Windows XP is no longer supported by Microsoft, thus, per PEP 11 [https://peps.python.org/pep-0011/], CPython 3.5 is no longer officially supported on this OS.

已棄用的 Python 模組、函式和方法

The formatter module has now graduated to full deprecation and is still slated for removal in Python 3.6.

The asyncio.async() function is deprecated in favor of ensure_future().

The smtpd module has in the past always decoded the DATA portion of email messages using the utf-8 codec. This can now be controlled by the new decode_data keyword to SMTPServer. The default value is True, but this default is deprecated. Specify the decode_data keyword with an appropriate value to avoid the deprecation warning.

Directly assigning values to the key, value and coded_value of http.cookies.Morsel objects is deprecated. Use the set() method instead. In addition, the undocumented LegalChars parameter of set() is deprecated, and is now ignored.

Passing a format string as keyword argument format_string to the format() method of the string.Formatter class has been deprecated. (Contributed by Serhiy Storchaka in bpo-23671 [https://bugs.python.org/issue?@action=redirect&bpo=23671].)

The platform.dist() and platform.linux_distribution() functions are now deprecated. Linux distributions use too many different ways of describing themselves, so the functionality is left to a package. (Contributed by Vajrasky Kok and Berker Peksag in bpo-1322 [https://bugs.python.org/issue?@action=redirect&bpo=1322].)

The previously undocumented from_function and from_builtin methods of inspect.Signature are deprecated. Use the new Signature.from_callable() method instead. (Contributed by Yury Selivanov in bpo-24248 [https://bugs.python.org/issue?@action=redirect&bpo=24248].)

The inspect.getargspec() function is deprecated and scheduled to be removed in Python 3.6. (See bpo-20438 [https://bugs.python.org/issue?@action=redirect&bpo=20438] for details.)

The inspect getfullargspec(), getcallargs(), and formatargspec() functions are deprecated in favor of the inspect.signature() API. (Contributed by Yury Selivanov in bpo-20438 [https://bugs.python.org/issue?@action=redirect&bpo=20438].)

getargvalues() and formatargvalues() functions were inadvertently marked as deprecated with the release of Python 3.5.0.

Use of re.LOCALE flag with str patterns or re.ASCII is now deprecated. (Contributed by Serhiy Storchaka in bpo-22407 [https://bugs.python.org/issue?@action=redirect&bpo=22407].)

Use of unrecognized special sequences consisting of '\' and an ASCII letter in regular expression patterns and replacement patterns now raises a deprecation warning and will be forbidden in Python 3.6. (Contributed by Serhiy Storchaka in bpo-23622 [https://bugs.python.org/issue?@action=redirect&bpo=23622].)

The undocumented and unofficial use_load_tests default argument of the unittest.TestLoader.loadTestsFromModule() method now is deprecated and ignored. (Contributed by Robert Collins and Barry A. Warsaw in bpo-16662 [https://bugs.python.org/issue?@action=redirect&bpo=16662].)

已移除

API 與功能的移除

The following obsolete and previously deprecated APIs and features have been removed:

The __version__ attribute has been dropped from the email package. The email code hasn't been shipped separately from the stdlib for a long time, and the __version__ string was not updated in the last few releases.

The internal Netrc class in the ftplib module was deprecated in 3.4, and has now been removed. (Contributed by Matt Chaput in bpo-6623 [https://bugs.python.org/issue?@action=redirect&bpo=6623].)

已移除 .pyo 檔案的概念。

The JoinableQueue class in the provisional asyncio module was deprecated in 3.4.4 and is now removed. (Contributed by A. Jesse Jiryu Davis in bpo-23464 [https://bugs.python.org/issue?@action=redirect&bpo=23464].)

移植至 Python 3.5

This section lists previously described changes and other bugfixes that may require changes to your code.

Python 行為的改變

Due to an oversight, earlier Python versions erroneously accepted the following syntax:

f(1 for x in [1], *args)
f(1 for x in [1], **kwargs)

Python 3.5 now correctly raises a SyntaxError, as generator expressions must be put in parentheses if not a sole argument to a function.

Python API 的變更

PEP 475 [https://peps.python.org/pep-0475/]: System calls are now retried when interrupted by a signal instead of raising InterruptedError if the Python signal handler does not raise an exception.

Before Python 3.5, a datetime.time object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See bpo-13936 [https://bugs.python.org/issue?@action=redirect&bpo=13936] for full details.

The ssl.SSLSocket.send() method now raises either ssl.SSLWantReadError or ssl.SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0. (Contributed by Nikolaus Rath in bpo-20951 [https://bugs.python.org/issue?@action=redirect&bpo=20951].)

The __name__ attribute of generators is now set from the function name, instead of being set from the code name. Use gen.gi_code.co_name to retrieve the code name. Generators also have a new __qualname__ attribute, the qualified name, which is now used for the representation of a generator (repr(gen)). (Contributed by Victor Stinner in bpo-21205 [https://bugs.python.org/issue?@action=redirect&bpo=21205].)

The deprecated "strict" mode and argument of HTMLParser, HTMLParser.error(), and the HTMLParserError exception have been removed. (Contributed by Ezio Melotti in bpo-15114 [https://bugs.python.org/issue?@action=redirect&bpo=15114].) The convert_charrefs argument of HTMLParser is now True by default. (Contributed by Berker Peksag in bpo-21047 [https://bugs.python.org/issue?@action=redirect&bpo=21047].)

Although it is not formally part of the API, it is worth noting for porting purposes (ie: fixing tests) that error messages that were previously of the form "'sometype' does not support the buffer protocol" are now of the form "a bytes-like object is required, not 'sometype'". (Contributed by Ezio Melotti in bpo-16518 [https://bugs.python.org/issue?@action=redirect&bpo=16518].)

If the current directory is set to a directory that no longer exists then FileNotFoundError will no longer be raised and instead find_spec() will return None without caching None in sys.path_importer_cache, which is different than the typical case (bpo-22834 [https://bugs.python.org/issue?@action=redirect&bpo=22834]).

HTTP status code and messages from http.client and http.server were refactored into a common HTTPStatus enum. The values in http.client and http.server remain available for backwards compatibility. (Contributed by Demian Brecht in bpo-21793 [https://bugs.python.org/issue?@action=redirect&bpo=21793].)

When an import loader defines exec_module() it is now expected to also define create_module() (raises a DeprecationWarning now, will be an error in Python 3.6). If the loader inherits from importlib.abc.Loader then there is nothing to do, else simply define create_module() to return None. (Contributed by Brett Cannon in bpo-23014 [https://bugs.python.org/issue?@action=redirect&bpo=23014].)

The re.split() function always ignored empty pattern matches, so the "x*" pattern worked the same as "x+", and the "\b" pattern never worked. Now re.split() raises a warning if the pattern could match an empty string. For compatibility, use patterns that never match an empty string (e.g. "x+" instead of "x*"). Patterns that could only match an empty string (such as "\b") now raise an error. (Contributed by Serhiy Storchaka in bpo-22818 [https://bugs.python.org/issue?@action=redirect&bpo=22818].)

The http.cookies.Morsel dict-like interface has been made self consistent: morsel comparison now takes the key and value into account, copy() now results in a Morsel instance rather than a dict, and update() will now raise an exception if any of the keys in the update dictionary are invalid. In addition, the undocumented LegalChars parameter of set() is deprecated and is now ignored. (Contributed by Demian Brecht in bpo-2211 [https://bugs.python.org/issue?@action=redirect&bpo=2211].)

PEP 488 [https://peps.python.org/pep-0488/] has removed .pyo files from Python and introduced the optional opt- tag in .pyc file names. The importlib.util.cache_from_source() has gained an optimization parameter to help control the opt- tag. Because of this, the debug_override parameter of the function is now deprecated. .pyo files are also no longer supported as a file argument to the Python interpreter and thus serve no purpose when distributed on their own (i.e. sourceless code distribution). Due to the fact that the magic number for bytecode has changed in Python 3.5, all old .pyo files from previous versions of Python are invalid regardless of this PEP.

The socket module now exports the CAN_RAW_FD_FRAMES constant on linux 3.6 and greater.

The ssl.cert_time_to_seconds() function now interprets the input time as UTC and not as local time, per RFC 5280 [https://datatracker.ietf.org/doc/html/rfc5280.html]. Additionally, the return value is always an int. (Contributed by Akira Li in bpo-19940 [https://bugs.python.org/issue?@action=redirect&bpo=19940].)

The pygettext.py Tool now uses the standard +NNNN format for timezones in the POT-Creation-Date header.

The smtplib module now uses sys.stderr instead of the previous module-level stderr variable for debug output. If your (test) program depends on patching the module-level variable to capture the debug output, you will need to update it to capture sys.stderr instead.

The str.startswith() and str.endswith() methods no longer return True when finding the empty string and the indexes are completely out of range. (Contributed by Serhiy Storchaka in bpo-24284 [https://bugs.python.org/issue?@action=redirect&bpo=24284].)

The inspect.getdoc() function now returns documentation strings inherited from base classes. Documentation strings no longer need to be duplicated if the inherited documentation is appropriate. To suppress an inherited string, an empty string must be specified (or the documentation may be filled in). This change affects the output of the pydoc module and the help() function. (Contributed by Serhiy Storchaka in bpo-15582 [https://bugs.python.org/issue?@action=redirect&bpo=15582].)

Nested functools.partial() calls are now flattened. If you were relying on the previous behavior, you can now either add an attribute to a functools.partial() object or you can create a subclass of functools.partial(). (Contributed by Alexander Belopolsky in bpo-7830 [https://bugs.python.org/issue?@action=redirect&bpo=7830].)

C API 中的改動

The undocumented format member of the (non-public) PyMemoryViewObject structure has been removed. All extensions relying on the relevant parts in memoryobject.h must be rebuilt.

PyMemAllocator 結構已重命名為 PyMemAllocatorEx，並新增了 calloc 欄位。

Removed non-documented macro PyObject_REPR() which leaked references. Use format character %R in PyUnicode_FromFormat()-like functions to format the repr() of the object. (Contributed by Serhiy Storchaka in bpo-22453 [https://bugs.python.org/issue?@action=redirect&bpo=22453].)

Because the lack of the __module__ attribute breaks pickling and introspection, a deprecation warning is now raised for builtin types without the __module__ attribute. This will be an AttributeError in the future. (Contributed by Serhiy Storchaka in bpo-20204 [https://bugs.python.org/issue?@action=redirect&bpo=20204].)

As part of the PEP 492 [https://peps.python.org/pep-0492/] implementation, the tp_reserved slot of PyTypeObject was replaced with a tp_as_async slot. Refer to Coroutine（協程）物件 for new types, structures and functions.

Python 3.5.4 中顯著的變更

新增 make regen-all 建置目標

To simplify cross-compilation, and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available, the autotools-based build system no longer attempts to implicitly recompile generated files based on file modification times.

Instead, a new make regen-all command has been added to force regeneration of these files when desired (e.g. after an initial version of Python has already been built based on the pregenerated versions).

More selective regeneration targets are also defined - see Makefile.pre.in [https://github.com/python/cpython/tree/3.14/Makefile.pre.in] for details.

（由 Victor Stinner 在 bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404] 中貢獻。）

在 3.5.4 版被加入.

移除 make touch 建置目標

The make touch build target previously used to request implicit regeneration of generated files by updating their modification times has been removed.

它已被新的 make regen-all 目標取代。

（由 Victor Stinner 在 bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404] 中貢獻。）

在 3.5.4 版的變更.

Python 3.4 有什麼新功能

作者:

R. David Murray <rdmurray@bitdance.com> （編輯者）

本文介紹了 Python 3.4 與 3.3 相比多了哪些新功能。Python 3.1 已於 2014 年 3 月 16 日發布。完整詳情請見 changelog [https://docs.python.org/3.4/whatsnew/changelog.html]。

也參考

PEP 429 [https://peps.python.org/pep-0429/] - Python 3.4 發佈時程

發布重點摘要

新增語法特性：

Python 3.4 沒有新增任何新的語法特性。

其他新特性：

pip should always be available (PEP 453 [https://peps.python.org/pep-0453/]).

Newly created file descriptors are non-inheritable (PEP 446 [https://peps.python.org/pep-0446/]).

command line option for isolated mode (bpo-16499 [https://bugs.python.org/issue?@action=redirect&bpo=16499]).

improvements in the handling of codecs that are not text encodings (multiple issues).

A ModuleSpec Type for the Import System (PEP 451 [https://peps.python.org/pep-0451/]). (Affects importer authors.)

The marshal format has been made more compact and efficient (bpo-16475 [https://bugs.python.org/issue?@action=redirect&bpo=16475]).

新的函式庫模組：

asyncio: 新的用於非同步 IO 的臨時 API (PEP 3156 [https://peps.python.org/pep-3156/])。

ensurepip: 初始建置 pip 安裝程式 (PEP 453 [https://peps.python.org/pep-0453/])。

enum: 支援列舉型別 (PEP 435 [https://peps.python.org/pep-0435/])。

pathlib: 物件導向檔案系統路徑 (PEP 428 [https://peps.python.org/pep-0428/])。

selectors: High-level and efficient I/O multiplexing, built upon the select module primitives (part of PEP 3156 [https://peps.python.org/pep-3156/]).

statistics: A basic numerically stable statistics library (PEP 450 [https://peps.python.org/pep-0450/]).

tracemalloc: 追蹤 Python 記憶體配置 (PEP 454 [https://peps.python.org/pep-0454/])。

顯著改進的函式庫模組：

Single-dispatch generic functions in functools (PEP 443 [https://peps.python.org/pep-0443/]).

新的 pickle 協定 4 (PEP 3154 [https://peps.python.org/pep-3154/])。

multiprocessing 現在有一個選項可以避免在 Unix 上使用 os.fork (bpo-8713 [https://bugs.python.org/issue?@action=redirect&bpo=8713])。

email has a new submodule, contentmanager, and a new Message subclass (EmailMessage) that simplify MIME handling (bpo-18891 [https://bugs.python.org/issue?@action=redirect&bpo=18891]).

The inspect and pydoc modules are now capable of correct introspection of a much wider variety of callable objects, which improves the output of the Python help() system.

ipaddress 模組 API 已宣告為穩定版本

安全性改進：

Secure and interchangeable hash algorithm (PEP 456 [https://peps.python.org/pep-0456/]).

Make newly created file descriptors non-inheritable (PEP 446 [https://peps.python.org/pep-0446/]) to avoid leaking file descriptors to child processes.

用於隔離模式的新命令列選項 (bpo-16499 [https://bugs.python.org/issue?@action=redirect&bpo=16499])。

multiprocessing now has an option to avoid using os.fork on Unix. spawn and forkserver are more secure because they avoid sharing data with child processes.

multiprocessing child processes on Windows no longer inherit all of the parent's inheritable handles, only the necessary ones.

新的 hashlib.pbkdf2_hmac() 函式提供了基於密碼的 PKCS#5 密鑰生成函式 2 [https://en.wikipedia.org/wiki/PBKDF2]。

ssl 對 TLSv1.1 和 TLSv1.2 的支援。

Retrieving certificates from the Windows system cert store support for ssl.

Server-side SNI (Server Name Indication) support for ssl.

The ssl.SSLContext class has a lot of improvements.

All modules in the standard library that support SSL now support server certificate verification, including hostname matching (ssl.match_hostname()) and CRLs (Certificate Revocation lists, see ssl.SSLContext.load_verify_locations()).

CPython 實作改進：

Safe object finalization (PEP 442 [https://peps.python.org/pep-0442/]).

Leveraging PEP 442 [https://peps.python.org/pep-0442/], in most cases module globals are no longer set to None during finalization (bpo-18214 [https://bugs.python.org/issue?@action=redirect&bpo=18214]).

Configurable memory allocators (PEP 445 [https://peps.python.org/pep-0445/]).

Argument Clinic (PEP 436 [https://peps.python.org/pep-0436/]).

Please read on for a comprehensive list of user-facing changes, including many other smaller improvements, CPython optimizations, deprecations, and potential porting issues.

新增功能

PEP 453: Explicit Bootstrapping of PIP in Python Installations

Bootstrapping pip By Default

The new ensurepip module (defined in PEP 453 [https://peps.python.org/pep-0453/]) provides a standard cross-platform mechanism to bootstrap the pip installer into Python installations and virtual environments. The version of pip included with Python 3.4.0 is pip 1.5.4, and future 3.4.x maintenance releases will update the bundled version to the latest version of pip that is available at the time of creating the release candidate.

By default, the commands pipX and pipX.Y will be installed on all platforms (where X.Y stands for the version of the Python installation), along with the pip Python package and its dependencies. On Windows and in virtual environments on all platforms, the unversioned pip command will also be installed. On other platforms, the system wide unversioned pip command typically refers to the separately installed Python 2 version.

The pyvenv command line utility and the venv module make use of the ensurepip module to make pip readily available in virtual environments. When using the command line utility, pip is installed by default, while when using the venv module API installation of pip must be requested explicitly.

For CPython source builds on POSIX systems, the make install and make altinstall commands bootstrap pip by default. This behaviour can be controlled through configure options, and overridden through Makefile options.

On Windows and Mac OS X, the CPython installers now default to installing pip along with CPython itself (users may opt out of installing it during the installation process). Window users will need to opt in to the automatic PATH modifications to have pip available from the command line by default, otherwise it can still be accessed through the Python launcher for Windows as py -m pip.

As discussed in the PEP [https://peps.python.org/pep-0453/#recommendations-for-downstream-distributors] platform packagers may choose not to install these commands by default, as long as, when invoked, they provide clear and simple directions on how to install them on that platform (usually using the system package manager).

備註

To avoid conflicts between parallel Python 2 and Python 3 installations, only the versioned pip3 and pip3.4 commands are bootstrapped by default when ensurepip is invoked directly - the --default-pip option is needed to also request the unversioned pip command. pyvenv and the Windows installer ensure that the unqualified pip command is made available in those environments, and pip can always be invoked via the -m switch rather than directly to avoid ambiguity on systems with multiple Python installations.

文件更動

As part of this change, the 安裝 Python 模組 and 發布 Python 模組 sections of the documentation have been completely redesigned as short getting started and FAQ documents. Most packaging documentation has now been moved out to the Python Packaging Authority maintained Python Packaging User Guide [https://packaging.python.org] and the documentation of the individual projects.

However, as this migration is currently still incomplete, the legacy versions of those guides remaining available as 用 setuptools 建置 C 與 C++ 擴充套件 and 用 setuptools 建置 C 與 C++ 擴充套件.

也參考

PEP 453 [https://peps.python.org/pep-0453/] -- Explicit bootstrapping of pip in Python installations

PEP written by Donald Stufft and Nick Coghlan, implemented by Donald Stufft, Nick Coghlan, Martin von Löwis and Ned Deily.

PEP 446: Newly Created File Descriptors Are Non-Inheritable

PEP 446 [https://peps.python.org/pep-0446/] makes newly created file descriptors non-inheritable. In general, this is the behavior an application will want: when launching a new process, having currently open files also open in the new process can lead to all sorts of hard to find bugs, and potentially to security issues.

However, there are occasions when inheritance is desired. To support these cases, the following new functions and methods are available:

os.get_inheritable()、os.set_inheritable()

os.get_handle_inheritable()、os.set_handle_inheritable()

socket.socket.get_inheritable()、socket.socket.set_inheritable()

也參考

PEP 446 [https://peps.python.org/pep-0446/] - 使新建立的檔案描述器不可繼承

由 Victor Stinner 撰寫 PEP 與實作。

編解碼器處理的改進

Since it was first introduced, the codecs module has always been intended to operate as a type-neutral dynamic encoding and decoding system. However, its close coupling with the Python text model, especially the type restricted convenience methods on the builtin str, bytes and bytearray types, has historically obscured that fact.

As a key step in clarifying the situation, the codecs.encode() and codecs.decode() convenience functions are now properly documented in Python 2.7, 3.3 and 3.4. These functions have existed in the codecs module (and have been covered by the regression test suite) since Python 2.4, but were previously only discoverable through runtime introspection.

Unlike the convenience methods on str, bytes and bytearray, the codecs convenience functions support arbitrary codecs in both Python 2 and Python 3, rather than being limited to Unicode text encodings (in Python 3) or basestring <-> basestring conversions (in Python 2).

In Python 3.4, the interpreter is able to identify the known non-text encodings provided in the standard library and direct users towards these general purpose convenience functions when appropriate:

>>> b"abcdef".decode("hex")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: 'hex' is not a text encoding; use codecs.decode() to handle arbitrary codecs

>>> "hello".encode("rot13")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: 'rot13' is not a text encoding; use codecs.encode() to handle arbitrary codecs

>>> open("foo.txt", encoding="hex")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: 'hex' is not a text encoding; use codecs.open() to handle arbitrary codecs

In a related change, whenever it is feasible without breaking backwards compatibility, exceptions raised during encoding and decoding operations are wrapped in a chained exception of the same type that mentions the name of the codec responsible for producing the error:

>>> import codecs

>>> codecs.decode(b"abcdefgh", "hex")
Traceback (most recent call last):
  File "/usr/lib/python3.4/encodings/hex_codec.py", line 20, in hex_decode
    return (binascii.a2b_hex(input), len(input))
binascii.Error: Non-hexadecimal digit found

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
binascii.Error: decoding with 'hex' codec failed (Error: Non-hexadecimal digit found)

>>> codecs.encode("hello", "bz2")
Traceback (most recent call last):
  File "/usr/lib/python3.4/encodings/bz2_codec.py", line 17, in bz2_encode
    return (bz2.compress(input), len(input))
  File "/usr/lib/python3.4/bz2.py", line 498, in compress
    return comp.compress(data) + comp.flush()
TypeError: 'str' does not support the buffer interface

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: encoding with 'bz2' codec failed (TypeError: 'str' does not support the buffer interface)

Finally, as the examples above show, these improvements have permitted the restoration of the convenience aliases for the non-Unicode codecs that were themselves restored in Python 3.2. This means that encoding binary data to and from its hexadecimal representation (for example) can now be written as:

>>> from codecs import encode, decode
>>> encode(b"hello", "hex")
b'68656c6c6f'
>>> decode(b"68656c6c6f", "hex")
b'hello'

The binary and text transforms provided in the standard library are detailed in Binary Transforms and Text Transforms.

（由 Nick Coghlan 在 bpo-7475 [https://bugs.python.org/issue?@action=redirect&bpo=7475]、bpo-17827 [https://bugs.python.org/issue?@action=redirect&bpo=17827]、bpo-17828 [https://bugs.python.org/issue?@action=redirect&bpo=17828] 和 bpo-19619 [https://bugs.python.org/issue?@action=redirect&bpo=19619] 中貢獻。）

PEP 451：用於引入系統的 ModuleSpec 型別

PEP 451 [https://peps.python.org/pep-0451/] provides an encapsulation of the information about a module that the import machinery will use to load it (that is, a module specification). This helps simplify both the import implementation and several import-related APIs. The change is also a stepping stone for several future import-related improvements [https://mail.python.org/pipermail/python-dev/2013-November/130111.html].

The public-facing changes from the PEP are entirely backward-compatible. Furthermore, they should be transparent to everyone but importer authors. Key finder and loader methods have been deprecated, but they will continue working. New importers should use the new methods described in the PEP. Existing importers should be updated to implement the new methods. See the 已棄用 section for a list of methods that should be replaced and their replacements.

其他語言更動

Some smaller changes made to the core Python language are:

Unicode database updated to UCD version 6.3.

min() and max() now accept a default keyword-only argument that can be used to specify the value they return if the iterable they are evaluating has no elements. (Contributed by Julian Berman in bpo-18111 [https://bugs.python.org/issue?@action=redirect&bpo=18111].)

Module objects are now weakly referenceable.

Module __file__ attributes (and related values) should now always contain absolute paths by default, with the sole exception of __main__.__file__ when a script has been executed directly using a relative path. (Contributed by Brett Cannon in bpo-18416 [https://bugs.python.org/issue?@action=redirect&bpo=18416].)

All the UTF-* codecs (except UTF-7) now reject surrogates during both encoding and decoding unless the surrogatepass error handler is used, with the exception of the UTF-16 decoder (which accepts valid surrogate pairs) and the UTF-16 encoder (which produces them while encoding non-BMP characters). (Contributed by Victor Stinner, Kang-Hao (Kenny) Lu and Serhiy Storchaka in bpo-12892 [https://bugs.python.org/issue?@action=redirect&bpo=12892].)

New German EBCDIC codec cp273. (Contributed by Michael Bierenfeld and Andrew Kuchling in bpo-1097797 [https://bugs.python.org/issue?@action=redirect&bpo=1097797].)

New Ukrainian codec cp1125. (Contributed by Serhiy Storchaka in bpo-19668 [https://bugs.python.org/issue?@action=redirect&bpo=19668].)

bytes.join() and bytearray.join() now accept arbitrary buffer objects as arguments. (Contributed by Antoine Pitrou in bpo-15958 [https://bugs.python.org/issue?@action=redirect&bpo=15958].)

The int constructor now accepts any object that has an __index__ method for its base argument. (Contributed by Mark Dickinson in bpo-16772 [https://bugs.python.org/issue?@action=redirect&bpo=16772].)

Frame objects now have a clear() method that clears all references to local variables from the frame. (Contributed by Antoine Pitrou in bpo-17934 [https://bugs.python.org/issue?@action=redirect&bpo=17934].)

memoryview is now registered as a Sequence, and supports the reversed() builtin. (Contributed by Nick Coghlan and Claudiu Popa in bpo-18690 [https://bugs.python.org/issue?@action=redirect&bpo=18690] and bpo-19078 [https://bugs.python.org/issue?@action=redirect&bpo=19078].)

Signatures reported by help() have been modified and improved in several cases as a result of the introduction of Argument Clinic and other changes to the inspect and pydoc modules.

__length_hint__() is now part of the formal language specification (see PEP 424 [https://peps.python.org/pep-0424/]). (Contributed by Armin Ronacher in bpo-16148 [https://bugs.python.org/issue?@action=redirect&bpo=16148].)

新模組

asyncio

The new asyncio module (defined in PEP 3156 [https://peps.python.org/pep-3156/]) provides a standard pluggable event loop model for Python, providing solid asynchronous IO support in the standard library, and making it easier for other event loop implementations to interoperate with the standard library and each other.

For Python 3.4, this module is considered a provisional API.

也參考

PEP 3156 [https://peps.python.org/pep-3156/] -- Asynchronous IO Support Rebooted: the "asyncio" Module

由 Guido van Rossum 撰寫 PEP 與帶領實作。

ensurepip

The new ensurepip module is the primary infrastructure for the PEP 453 [https://peps.python.org/pep-0453/] implementation. In the normal course of events end users will not need to interact with this module, but it can be used to manually bootstrap pip if the automated bootstrapping into an installation or virtual environment was declined.

ensurepip includes a bundled copy of pip, up-to-date as of the first release candidate of the release of CPython with which it ships (this applies to both maintenance releases and feature releases). ensurepip does not access the internet. If the installation has internet access, after ensurepip is run the bundled pip can be used to upgrade pip to a more recent release than the bundled one. (Note that such an upgraded version of pip is considered to be a separately installed package and will not be removed if Python is uninstalled.)

The module is named ensurepip because if called when pip is already installed, it does nothing. It also has an --upgrade option that will cause it to install the bundled copy of pip if the existing installed version of pip is older than the bundled copy.

enum

The new enum module (defined in PEP 435 [https://peps.python.org/pep-0435/]) provides a standard implementation of enumeration types, allowing other modules (such as socket) to provide more informative error messages and better debugging support by replacing opaque integer constants with backwards compatible enumeration values.

也參考

PEP 435 [https://peps.python.org/pep-0435/] -- Adding an Enum type to the Python standard library

PEP written by Barry Warsaw, Eli Bendersky and Ethan Furman, implemented by Ethan Furman.

pathlib

The new pathlib module offers classes representing filesystem paths with semantics appropriate for different operating systems. Path classes are divided between pure paths, which provide purely computational operations without I/O, and concrete paths, which inherit from pure paths but also provide I/O operations.

For Python 3.4, this module is considered a provisional API.

也參考

PEP 428 [https://peps.python.org/pep-0428/] -- The pathlib module -- object-oriented filesystem paths

由 Antoine Pitrou 撰寫 PEP 與實作。

selectors

The new selectors module (created as part of implementing PEP 3156 [https://peps.python.org/pep-3156/]) allows high-level and efficient I/O multiplexing, built upon the select module primitives.

statistics

The new statistics module (defined in PEP 450 [https://peps.python.org/pep-0450/]) offers some core statistics functionality directly in the standard library. This module supports calculation of the mean, median, mode, variance and standard deviation of a data series.

也參考

PEP 450 [https://peps.python.org/pep-0450/] -- Adding A Statistics Module To The Standard Library

由 Steven D'Aprano 撰寫 PEP 與實作

tracemalloc

The new tracemalloc module (defined in PEP 454 [https://peps.python.org/pep-0454/]) is a debug tool to trace memory blocks allocated by Python. It provides the following information:

Trace where an object was allocated

Statistics on allocated memory blocks per filename and per line number: total size, number and average size of allocated memory blocks

Compute the differences between two snapshots to detect memory leaks

也參考

PEP 454 [https://peps.python.org/pep-0454/] -- Add a new tracemalloc module to trace Python memory allocations

由 Victor Stinner 撰寫 PEP 與實作

改進的模組

abc

New function abc.get_cache_token() can be used to know when to invalidate caches that are affected by changes in the object graph. (Contributed by Łukasz Langa in bpo-16832 [https://bugs.python.org/issue?@action=redirect&bpo=16832].)

New class ABC has ABCMeta as its meta class. Using ABC as a base class has essentially the same effect as specifying metaclass=abc.ABCMeta, but is simpler to type and easier to read. (Contributed by Bruno Dupuis in bpo-16049 [https://bugs.python.org/issue?@action=redirect&bpo=16049].)

aifc

The getparams() method now returns a namedtuple rather than a plain tuple. (Contributed by Claudiu Popa in bpo-17818 [https://bugs.python.org/issue?@action=redirect&bpo=17818].)

aifc.open() now supports the context management protocol: when used in a with block, the close() method of the returned object will be called automatically at the end of the block. (Contributed by Serhiy Storchacha in bpo-16486 [https://bugs.python.org/issue?@action=redirect&bpo=16486].)

The writeframesraw() and writeframes() methods now accept any bytes-like object. (Contributed by Serhiy Storchaka in bpo-8311 [https://bugs.python.org/issue?@action=redirect&bpo=8311].)

argparse

The FileType class now accepts encoding and errors arguments, which are passed through to open(). (Contributed by Lucas Maystre in bpo-11175 [https://bugs.python.org/issue?@action=redirect&bpo=11175].)

audioop

audioop now supports 24-bit samples. (Contributed by Serhiy Storchaka in bpo-12866 [https://bugs.python.org/issue?@action=redirect&bpo=12866].)

New byteswap() function converts big-endian samples to little-endian and vice versa. (Contributed by Serhiy Storchaka in bpo-19641 [https://bugs.python.org/issue?@action=redirect&bpo=19641].)

All audioop functions now accept any bytes-like object. Strings are not accepted: they didn't work before, now they raise an error right away. (Contributed by Serhiy Storchaka in bpo-16685 [https://bugs.python.org/issue?@action=redirect&bpo=16685].)

base64

The encoding and decoding functions in base64 now accept any bytes-like object in cases where it previously required a bytes or bytearray instance. (Contributed by Nick Coghlan in bpo-17839 [https://bugs.python.org/issue?@action=redirect&bpo=17839].)

New functions a85encode(), a85decode(), b85encode(), and b85decode() provide the ability to encode and decode binary data from and to Ascii85 and the git/mercurial Base85 formats, respectively. The a85 functions have options that can be used to make them compatible with the variants of the Ascii85 encoding, including the Adobe variant. (Contributed by Martin Morrison, the Mercurial project, Serhiy Storchaka, and Antoine Pitrou in bpo-17618 [https://bugs.python.org/issue?@action=redirect&bpo=17618].)

collections

The ChainMap.new_child() method now accepts an m argument specifying the child map to add to the chain. This allows an existing mapping and/or a custom mapping type to be used for the child. (Contributed by Vinay Sajip in bpo-16613 [https://bugs.python.org/issue?@action=redirect&bpo=16613].)

colorsys

The number of digits in the coefficients for the RGB --- YIQ conversions have been expanded so that they match the FCC NTSC versions. The change in results should be less than 1% and may better match results found elsewhere. (Contributed by Brian Landers and Serhiy Storchaka in bpo-14323 [https://bugs.python.org/issue?@action=redirect&bpo=14323].)

contextlib

The new contextlib.suppress context manager helps to clarify the intent of code that deliberately suppresses exceptions from a single statement. (Contributed by Raymond Hettinger in bpo-15806 [https://bugs.python.org/issue?@action=redirect&bpo=15806] and Zero Piraeus in bpo-19266 [https://bugs.python.org/issue?@action=redirect&bpo=19266].)

The new contextlib.redirect_stdout() context manager makes it easier for utility scripts to handle inflexible APIs that write their output to sys.stdout and don't provide any options to redirect it. Using the context manager, the sys.stdout output can be redirected to any other stream or, in conjunction with io.StringIO, to a string. The latter can be especially useful, for example, to capture output from a function that was written to implement a command line interface. It is recommended only for utility scripts because it affects the global state of sys.stdout. (Contributed by Raymond Hettinger in bpo-15805 [https://bugs.python.org/issue?@action=redirect&bpo=15805].)

The contextlib documentation has also been updated to include a discussion of the differences between single use, reusable and reentrant context managers.

dbm

dbm.open() objects now support the context management protocol. When used in a with statement, the close method of the database object will be called automatically at the end of the block. (Contributed by Claudiu Popa and Nick Coghlan in bpo-19282 [https://bugs.python.org/issue?@action=redirect&bpo=19282].)

dis

Functions show_code(), dis(), distb(), and disassemble() now accept a keyword-only file argument that controls where they write their output.

The dis module is now built around an Instruction class that provides object oriented access to the details of each individual bytecode operation.

A new method, get_instructions(), provides an iterator that emits the Instruction stream for a given piece of Python code. Thus it is now possible to write a program that inspects and manipulates a bytecode object in ways different from those provided by the dis module itself. For example:

>>> import dis
>>> for instr in dis.get_instructions(lambda x: x + 1):
...     print(instr.opname)
LOAD_FAST
LOAD_CONST
BINARY_ADD
RETURN_VALUE

The various display tools in the dis module have been rewritten to use these new components.

In addition, a new application-friendly class Bytecode provides an object-oriented API for inspecting bytecode in both in human-readable form and for iterating over instructions. The Bytecode constructor takes the same arguments that get_instructions() does (plus an optional current_offset), and the resulting object can be iterated to produce Instruction objects. But it also has a dis method, equivalent to calling dis on the constructor argument, but returned as a multi-line string:

>>> bytecode = dis.Bytecode(lambda x: x + 1, current_offset=3)
>>> for instr in bytecode:
...     print('{} ({})'.format(instr.opname, instr.opcode))
LOAD_FAST (124)
LOAD_CONST (100)
BINARY_ADD (23)
RETURN_VALUE (83)
>>> bytecode.dis().splitlines()
['  1           0 LOAD_FAST                0 (x)',
 '      -->     3 LOAD_CONST               1 (1)',
 '              6 BINARY_ADD',
 '              7 RETURN_VALUE']

Bytecode also has a class method, from_traceback(), that provides the ability to manipulate a traceback (that is, print(Bytecode.from_traceback(tb).dis()) is equivalent to distb(tb)).

（由 Nick Coghlan、Ryan Kelly 和 Thomas Kluyver 在 bpo-11816 [https://bugs.python.org/issue?@action=redirect&bpo=11816] 中以及 Claudiu Popa 在 bpo-17916 [https://bugs.python.org/issue?@action=redirect&bpo=17916] 中貢獻。）

New function stack_effect() computes the effect on the Python stack of a given opcode and argument, information that is not otherwise available. (Contributed by Larry Hastings in bpo-19722 [https://bugs.python.org/issue?@action=redirect&bpo=19722].)

doctest

A new option flag, FAIL_FAST, halts test running as soon as the first failure is detected. (Contributed by R. David Murray and Daniel Urban in bpo-16522 [https://bugs.python.org/issue?@action=redirect&bpo=16522].)

The doctest command line interface now uses argparse, and has two new options, -o and -f. -o allows doctest options to be specified on the command line, and -f is a shorthand for -o FAIL_FAST (to parallel the similar option supported by the unittest CLI). (Contributed by R. David Murray in bpo-11390 [https://bugs.python.org/issue?@action=redirect&bpo=11390].)

doctest will now find doctests in extension module __doc__ strings. (Contributed by Zachary Ware in bpo-3158 [https://bugs.python.org/issue?@action=redirect&bpo=3158].)

email

as_string() now accepts a policy argument to override the default policy of the message when generating a string representation of it. This means that as_string can now be used in more circumstances, instead of having to create and use a generator in order to pass formatting parameters to its flatten method. (Contributed by R. David Murray in bpo-18600 [https://bugs.python.org/issue?@action=redirect&bpo=18600].)

New method as_bytes() added to produce a bytes representation of the message in a fashion similar to how as_string produces a string representation. It does not accept the maxheaderlen argument, but does accept the unixfrom and policy arguments. The Message __bytes__() method calls it, meaning that bytes(mymsg) will now produce the intuitive result: a bytes object containing the fully formatted message. (Contributed by R. David Murray in bpo-18600 [https://bugs.python.org/issue?@action=redirect&bpo=18600].)

The Message.set_param() message now accepts a replace keyword argument. When specified, the associated header will be updated without changing its location in the list of headers. For backward compatibility, the default is False. (Contributed by R. David Murray in bpo-18891 [https://bugs.python.org/issue?@action=redirect&bpo=18891].)

A pair of new subclasses of Message have been added (EmailMessage and MIMEPart), along with a new sub-module, contentmanager and a new policy attribute content_manager. All documentation is currently in the new module, which is being added as part of email's new provisional API. These classes provide a number of new methods that make extracting content from and inserting content into email messages much easier. For details, see the contentmanager documentation and the email：範例. These API additions complete the bulk of the work that was planned as part of the email6 project. The currently provisional API is scheduled to become final in Python 3.5 (possibly with a few minor additions in the area of error handling). (Contributed by R. David Murray in bpo-18891 [https://bugs.python.org/issue?@action=redirect&bpo=18891].)

filecmp

A new clear_cache() function provides the ability to clear the filecmp comparison cache, which uses os.stat() information to determine if the file has changed since the last compare. This can be used, for example, if the file might have been changed and re-checked in less time than the resolution of a particular filesystem's file modification time field. (Contributed by Mark Levitt in bpo-18149 [https://bugs.python.org/issue?@action=redirect&bpo=18149].)

New module attribute DEFAULT_IGNORES provides the list of directories that are used as the default value for the ignore parameter of the dircmp() function. (Contributed by Eli Bendersky in bpo-15442 [https://bugs.python.org/issue?@action=redirect&bpo=15442].)

functools

The new partialmethod() descriptor brings partial argument application to descriptors, just as partial() provides for normal callables. The new descriptor also makes it easier to get arbitrary callables (including partial() instances) to behave like normal instance methods when included in a class definition. (Contributed by Alon Horev and Nick Coghlan in bpo-4331 [https://bugs.python.org/issue?@action=redirect&bpo=4331].)

The new singledispatch() decorator brings support for single-dispatch generic functions to the Python standard library. Where object oriented programming focuses on grouping multiple operations on a common set of data into a class, a generic function focuses on grouping multiple implementations of an operation that allows it to work with different kinds of data.

也參考

PEP 443 [https://peps.python.org/pep-0443/] -- Single-dispatch generic functions

由 Łukasz Langa 撰寫 PEP 與實作。

total_ordering() now supports a return value of NotImplemented from the underlying comparison function. (Contributed by Katie Miller in bpo-10042 [https://bugs.python.org/issue?@action=redirect&bpo=10042].)

A pure-python version of the partial() function is now in the stdlib; in CPython it is overridden by the C accelerated version, but it is available for other implementations to use. (Contributed by Brian Thorne in bpo-12428 [https://bugs.python.org/issue?@action=redirect&bpo=12428].)

gc

New function get_stats() returns a list of three per-generation dictionaries containing the collections statistics since interpreter startup. (Contributed by Antoine Pitrou in bpo-16351 [https://bugs.python.org/issue?@action=redirect&bpo=16351].)

glob

A new function escape() provides a way to escape special characters in a filename so that they do not become part of the globbing expansion but are instead matched literally. (Contributed by Serhiy Storchaka in bpo-8402 [https://bugs.python.org/issue?@action=redirect&bpo=8402].)

hashlib

新的 hashlib.pbkdf2_hmac() 函式提供了基於密碼的 PKCS#5 密鑰生成函式 2 [https://en.wikipedia.org/wiki/PBKDF2]。（由 Christian Heimes 在 bpo-18582 [https://bugs.python.org/issue?@action=redirect&bpo=18582] 中貢獻。）

The name attribute of hashlib hash objects is now a formally supported interface. It has always existed in CPython's hashlib (although it did not return lower case names for all supported hashes), but it was not a public interface and so some other Python implementations have not previously supported it. (Contributed by Jason R. Coombs in bpo-18532 [https://bugs.python.org/issue?@action=redirect&bpo=18532].)

hmac

hmac now accepts bytearray as well as bytes for the key argument to the new() function, and the msg parameter to both the new() function and the update() method now accepts any type supported by the hashlib module. (Contributed by Jonas Borgström in bpo-18240 [https://bugs.python.org/issue?@action=redirect&bpo=18240].)

The digestmod argument to the hmac.new() function may now be any hash digest name recognized by hashlib. In addition, the current behavior in which the value of digestmod defaults to MD5 is deprecated: in a future version of Python there will be no default value. (Contributed by Christian Heimes in bpo-17276 [https://bugs.python.org/issue?@action=redirect&bpo=17276].)

With the addition of block_size and name attributes (and the formal documentation of the digest_size attribute), the hmac module now conforms fully to the PEP 247 [https://peps.python.org/pep-0247/] API. (Contributed by Christian Heimes in bpo-18775 [https://bugs.python.org/issue?@action=redirect&bpo=18775].)

html

New function unescape() function converts HTML5 character references to the corresponding Unicode characters. (Contributed by Ezio Melotti in bpo-2927 [https://bugs.python.org/issue?@action=redirect&bpo=2927].)

HTMLParser accepts a new keyword argument convert_charrefs that, when True, automatically converts all character references. For backward-compatibility, its value defaults to False, but it will change to True in a future version of Python, so you are invited to set it explicitly and update your code to use this new feature. (Contributed by Ezio Melotti in bpo-13633 [https://bugs.python.org/issue?@action=redirect&bpo=13633].)

The strict argument of HTMLParser is now deprecated. (Contributed by Ezio Melotti in bpo-15114 [https://bugs.python.org/issue?@action=redirect&bpo=15114].)

http

send_error() now accepts an optional additional explain parameter which can be used to provide an extended error description, overriding the hardcoded default if there is one. This extended error description will be formatted using the error_message_format attribute and sent as the body of the error response. (Contributed by Karl Cow in bpo-12921 [https://bugs.python.org/issue?@action=redirect&bpo=12921].)

The http.server command line interface now has a -b/--bind option that causes the server to listen on a specific address. (Contributed by Malte Swart in bpo-17764 [https://bugs.python.org/issue?@action=redirect&bpo=17764].)

idlelib 與 IDLE

Since idlelib implements the IDLE shell and editor and is not intended for import by other programs, it gets improvements with every release. See Lib/idlelib/NEWS.txt for a cumulative list of changes since 3.3.0, as well as changes made in future 3.4.x releases. This file is also available from the IDLE Help ‣ About IDLE dialog.

importlib

The InspectLoader ABC defines a new method, source_to_code() that accepts source data and a path and returns a code object. The default implementation is equivalent to compile(data, path, 'exec', dont_inherit=True). (Contributed by Eric Snow and Brett Cannon in bpo-15627 [https://bugs.python.org/issue?@action=redirect&bpo=15627].)

InspectLoader also now has a default implementation for the get_code() method. However, it will normally be desirable to override the default implementation for performance reasons. (Contributed by Brett Cannon in bpo-18072 [https://bugs.python.org/issue?@action=redirect&bpo=18072].)

The reload() function has been moved from imp to importlib as part of the imp module deprecation. (Contributed by Berker Peksag in bpo-18193 [https://bugs.python.org/issue?@action=redirect&bpo=18193].)

importlib.util now has a MAGIC_NUMBER attribute providing access to the bytecode version number. This replaces the get_magic() function in the deprecated imp module. (Contributed by Brett Cannon in bpo-18192 [https://bugs.python.org/issue?@action=redirect&bpo=18192].)

New importlib.util functions cache_from_source() and source_from_cache() replace the same-named functions in the deprecated imp module. (Contributed by Brett Cannon in bpo-18194 [https://bugs.python.org/issue?@action=redirect&bpo=18194].)

The importlib bootstrap NamespaceLoader now conforms to the InspectLoader ABC, which means that runpy and python -m can now be used with namespace packages. (Contributed by Brett Cannon in bpo-18058 [https://bugs.python.org/issue?@action=redirect&bpo=18058].)

importlib.util has a new function decode_source() that decodes source from bytes using universal newline processing. This is useful for implementing InspectLoader.get_source() methods.

importlib.machinery.ExtensionFileLoader now has a get_filename() method. This was inadvertently omitted in the original implementation. (Contributed by Eric Snow in bpo-19152 [https://bugs.python.org/issue?@action=redirect&bpo=19152].)

inspect

The inspect module now offers a basic command line interface to quickly display source code and other information for modules, classes and functions. (Contributed by Claudiu Popa and Nick Coghlan in bpo-18626 [https://bugs.python.org/issue?@action=redirect&bpo=18626].)

unwrap() makes it easy to unravel wrapper function chains created by functools.wraps() (and any other API that sets the __wrapped__ attribute on a wrapper function). (Contributed by Daniel Urban, Aaron Iles and Nick Coghlan in bpo-13266 [https://bugs.python.org/issue?@action=redirect&bpo=13266].)

As part of the implementation of the new enum module, the inspect module now has substantially better support for custom __dir__ methods and dynamic class attributes provided through metaclasses. (Contributed by Ethan Furman in bpo-18929 [https://bugs.python.org/issue?@action=redirect&bpo=18929] and bpo-19030 [https://bugs.python.org/issue?@action=redirect&bpo=19030].)

getfullargspec() and getargspec() now use the signature() API. This allows them to support a much broader range of callables, including those with __signature__ attributes, those with metadata provided by argument clinic, functools.partial() objects and more. Note that, unlike signature(), these functions still ignore __wrapped__ attributes, and report the already bound first argument for bound methods, so it is still necessary to update your code to use signature() directly if those features are desired. (Contributed by Yury Selivanov in bpo-17481 [https://bugs.python.org/issue?@action=redirect&bpo=17481].)

signature() now supports duck types of CPython functions, which adds support for functions compiled with Cython. (Contributed by Stefan Behnel and Yury Selivanov in bpo-17159 [https://bugs.python.org/issue?@action=redirect&bpo=17159].)

ipaddress

ipaddress was added to the standard library in Python 3.3 as a provisional API. With the release of Python 3.4, this qualification has been removed: ipaddress is now considered a stable API, covered by the normal standard library requirements to maintain backwards compatibility.

A new is_global property is True if an address is globally routeable. (Contributed by Peter Moody in bpo-17400 [https://bugs.python.org/issue?@action=redirect&bpo=17400].)

logging

The TimedRotatingFileHandler has a new atTime parameter that can be used to specify the time of day when rollover should happen. (Contributed by Ronald Oussoren in bpo-9556 [https://bugs.python.org/issue?@action=redirect&bpo=9556].)

SocketHandler and DatagramHandler now support Unix domain sockets (by setting port to None). (Contributed by Vinay Sajip in commit ce46195b56a9.)

fileConfig() now accepts a configparser.RawConfigParser subclass instance for the fname parameter. This facilitates using a configuration file when logging configuration is just a part of the overall application configuration, or where the application modifies the configuration before passing it to fileConfig(). (Contributed by Vinay Sajip in bpo-16110 [https://bugs.python.org/issue?@action=redirect&bpo=16110].)

Logging configuration data received from a socket via the logging.config.listen() function can now be validated before being processed by supplying a verification function as the argument to the new verify keyword argument. (Contributed by Vinay Sajip in bpo-15452 [https://bugs.python.org/issue?@action=redirect&bpo=15452].)

marshal

The default marshal version has been bumped to 3. The code implementing the new version restores the Python2 behavior of recording only one copy of interned strings and preserving the interning on deserialization, and extends this "one copy" ability to any object type (including handling recursive references). This reduces both the size of .pyc files and the amount of memory a module occupies in memory when it is loaded from a .pyc (or .pyo) file. (Contributed by Kristján Valur Jónsson in bpo-16475 [https://bugs.python.org/issue?@action=redirect&bpo=16475], with additional speedups by Antoine Pitrou in bpo-19219 [https://bugs.python.org/issue?@action=redirect&bpo=19219].)

mmap

mmap objects are now weakly referenceable. (Contributed by Valerie Lambert in bpo-4885 [https://bugs.python.org/issue?@action=redirect&bpo=4885].)

multiprocessing

On Unix two new start methods, spawn and forkserver, have been added for starting processes using multiprocessing. These make the mixing of processes with threads more robust, and the spawn method matches the semantics that multiprocessing has always used on Windows. New function get_all_start_methods() reports all start methods available on the platform, get_start_method() reports the current start method, and set_start_method() sets the start method. (Contributed by Richard Oudkerk in bpo-8713 [https://bugs.python.org/issue?@action=redirect&bpo=8713].)

multiprocessing also now has the concept of a context, which determines how child processes are created. New function get_context() returns a context that uses a specified start method. It has the same API as the multiprocessing module itself, so you can use it to create Pools and other objects that will operate within that context. This allows a framework and an application or different parts of the same application to use multiprocessing without interfering with each other. (Contributed by Richard Oudkerk in bpo-18999 [https://bugs.python.org/issue?@action=redirect&bpo=18999].)

Except when using the old fork start method, child processes no longer inherit unneeded handles/file descriptors from their parents (part of bpo-8713 [https://bugs.python.org/issue?@action=redirect&bpo=8713]).

multiprocessing now relies on runpy (which implements the -m switch) to initialise __main__ appropriately in child processes when using the spawn or forkserver start methods. This resolves some edge cases where combining multiprocessing, the -m command line switch, and explicit relative imports could cause obscure failures in child processes. (Contributed by Nick Coghlan in bpo-19946 [https://bugs.python.org/issue?@action=redirect&bpo=19946].)

operator

New function length_hint() provides an implementation of the specification for how the __length_hint__() special method should be used, as part of the PEP 424 [https://peps.python.org/pep-0424/] formal specification of this language feature. (Contributed by Armin Ronacher in bpo-16148 [https://bugs.python.org/issue?@action=redirect&bpo=16148].)

There is now a pure-python version of the operator module available for reference and for use by alternate implementations of Python. (Contributed by Zachary Ware in bpo-16694 [https://bugs.python.org/issue?@action=redirect&bpo=16694].)

os

There are new functions to get and set the inheritable flag of a file descriptor (os.get_inheritable(), os.set_inheritable()) or a Windows handle (os.get_handle_inheritable(), os.set_handle_inheritable()).

New function cpu_count() reports the number of CPUs available on the platform on which Python is running (or None if the count can't be determined). The multiprocessing.cpu_count() function is now implemented in terms of this function). (Contributed by Trent Nelson, Yogesh Chaudhari, Victor Stinner, and Charles-François Natali in bpo-17914 [https://bugs.python.org/issue?@action=redirect&bpo=17914].)

os.path.samestat() is now available on the Windows platform (and the os.path.samefile() implementation is now shared between Unix and Windows). (Contributed by Brian Curtin in bpo-11939 [https://bugs.python.org/issue?@action=redirect&bpo=11939].)

os.path.ismount() now recognizes volumes mounted below a drive root on Windows. (Contributed by Tim Golden in bpo-9035 [https://bugs.python.org/issue?@action=redirect&bpo=9035].)

os.open() supports two new flags on platforms that provide them, O_PATH (un-opened file descriptor), and O_TMPFILE (unnamed temporary file; as of 3.4.0 release available only on Linux systems with a kernel version of 3.11 or newer that have uapi headers). (Contributed by Christian Heimes in bpo-18673 [https://bugs.python.org/issue?@action=redirect&bpo=18673] and Benjamin Peterson, respectively.)

pdb

pdb has been enhanced to handle generators, yield, and yield from in a more useful fashion. This is especially helpful when debugging asyncio based programs. (Contributed by Andrew Svetlov and Xavier de Gaye in bpo-16596 [https://bugs.python.org/issue?@action=redirect&bpo=16596].)

The print command has been removed from pdb, restoring access to the Python print() function from the pdb command line. Python2's pdb did not have a print command; instead, entering print executed the print statement. In Python3 print was mistakenly made an alias for the pdb p command. p, however, prints the repr of its argument, not the str like the Python2 print command did. Worse, the Python3 pdb print command shadowed the Python3 print function, making it inaccessible at the pdb prompt. (Contributed by Connor Osborn in bpo-18764 [https://bugs.python.org/issue?@action=redirect&bpo=18764].)

pickle

pickle now supports (but does not use by default) a new pickle protocol, protocol 4. This new protocol addresses a number of issues that were present in previous protocols, such as the serialization of nested classes, very large strings and containers, and classes whose __new__() method takes keyword-only arguments. It also provides some efficiency improvements.

也參考

PEP 3154 [https://peps.python.org/pep-3154/] -- Pickle 協定 4

由 Antoine Pitrou 撰寫 PEP、Alexandre Vassalotti 實作。

plistlib

plistlib now has an API that is similar to the standard pattern for stdlib serialization protocols, with new load(), dump(), loads(), and dumps() functions. (The older API is now deprecated.) In addition to the already supported XML plist format (FMT_XML), it also now supports the binary plist format (FMT_BINARY). (Contributed by Ronald Oussoren and others in bpo-14455 [https://bugs.python.org/issue?@action=redirect&bpo=14455].)

poplib

Two new methods have been added to poplib: capa(), which returns the list of capabilities advertised by the POP server, and stls(), which switches a clear-text POP3 session into an encrypted POP3 session if the POP server supports it. (Contributed by Lorenzo Catucci in bpo-4473 [https://bugs.python.org/issue?@action=redirect&bpo=4473].)

pprint

The pprint module's PrettyPrinter class and its pformat(), and pprint() functions have a new option, compact, that controls how the output is formatted. Currently setting compact to True means that sequences will be printed with as many sequence elements as will fit within width on each (indented) line. (Contributed by Serhiy Storchaka in bpo-19132 [https://bugs.python.org/issue?@action=redirect&bpo=19132].)

Long strings are now wrapped using Python's normal line continuation syntax. (Contributed by Antoine Pitrou in bpo-17150 [https://bugs.python.org/issue?@action=redirect&bpo=17150].)

pty

pty.spawn() now returns the status value from os.waitpid() on the child process, instead of None. (Contributed by Gregory P. Smith.)

pydoc

The pydoc module is now based directly on the inspect.signature() introspection API, allowing it to provide signature information for a wider variety of callable objects. This change also means that __wrapped__ attributes are now taken into account when displaying help information. (Contributed by Larry Hastings in bpo-19674 [https://bugs.python.org/issue?@action=redirect&bpo=19674].)

The pydoc module no longer displays the self parameter for already bound methods. Instead, it aims to always display the exact current signature of the supplied callable. (Contributed by Larry Hastings in bpo-20710 [https://bugs.python.org/issue?@action=redirect&bpo=20710].)

In addition to the changes that have been made to pydoc directly, its handling of custom __dir__ methods and various descriptor behaviours has also been improved substantially by the underlying changes in the inspect module.

As the help() builtin is based on pydoc, the above changes also affect the behaviour of help().

re

New fullmatch() function and Pattern.fullmatch() method anchor the pattern at both ends of the string to match. This provides a way to be explicit about the goal of the match, which avoids a class of subtle bugs where $ characters get lost during code changes or the addition of alternatives to an existing regular expression. (Contributed by Matthew Barnett in bpo-16203 [https://bugs.python.org/issue?@action=redirect&bpo=16203].)

The repr of regex objects now includes the pattern and the flags; the repr of match objects now includes the start, end, and the part of the string that matched. (Contributed by Hugo Lopes Tavares and Serhiy Storchaka in bpo-13592 [https://bugs.python.org/issue?@action=redirect&bpo=13592] and bpo-17087 [https://bugs.python.org/issue?@action=redirect&bpo=17087].)

resource

New prlimit() function, available on Linux platforms with a kernel version of 2.6.36 or later and glibc of 2.13 or later, provides the ability to query or set the resource limits for processes other than the one making the call. (Contributed by Christian Heimes in bpo-16595 [https://bugs.python.org/issue?@action=redirect&bpo=16595].)

On Linux kernel version 2.6.36 or later, there are also some new Linux specific constants: RLIMIT_MSGQUEUE, RLIMIT_NICE, RLIMIT_RTPRIO, RLIMIT_RTTIME, and RLIMIT_SIGPENDING. (Contributed by Christian Heimes in bpo-19324 [https://bugs.python.org/issue?@action=redirect&bpo=19324].)

On FreeBSD version 9 and later, there some new FreeBSD specific constants: RLIMIT_SBSIZE, RLIMIT_SWAP, and RLIMIT_NPTS. (Contributed by Claudiu Popa in bpo-19343 [https://bugs.python.org/issue?@action=redirect&bpo=19343].)

select

epoll objects now support the context management protocol. When used in a with statement, the close() method will be called automatically at the end of the block. (Contributed by Serhiy Storchaka in bpo-16488 [https://bugs.python.org/issue?@action=redirect&bpo=16488].)

devpoll objects now have fileno() and close() methods, as well as a new attribute closed. (Contributed by Victor Stinner in bpo-18794 [https://bugs.python.org/issue?@action=redirect&bpo=18794].)

shelve

Shelf instances may now be used in with statements, and will be automatically closed at the end of the with block. (Contributed by Filip Gruszczyński in bpo-13896 [https://bugs.python.org/issue?@action=redirect&bpo=13896].)

shutil

copyfile() now raises a specific Error subclass, SameFileError, when the source and destination are the same file, which allows an application to take appropriate action on this specific error. (Contributed by Atsuo Ishimoto and Hynek Schlawack in bpo-1492704 [https://bugs.python.org/issue?@action=redirect&bpo=1492704].)

smtpd

The SMTPServer and SMTPChannel classes now accept a map keyword argument which, if specified, is passed in to asynchat.async_chat as its map argument. This allows an application to avoid affecting the global socket map. (Contributed by Vinay Sajip in bpo-11959 [https://bugs.python.org/issue?@action=redirect&bpo=11959].)

smtplib

SMTPException is now a subclass of OSError, which allows both socket level errors and SMTP protocol level errors to be caught in one try/except statement by code that only cares whether or not an error occurred. (Contributed by Ned Jackson Lovely in bpo-2118 [https://bugs.python.org/issue?@action=redirect&bpo=2118].)

socket

The socket module now supports the CAN_BCM protocol on platforms that support it. (Contributed by Brian Thorne in bpo-15359 [https://bugs.python.org/issue?@action=redirect&bpo=15359].)

Socket objects have new methods to get or set their inheritable flag, get_inheritable() and set_inheritable().

The socket.AF_* and socket.SOCK_* constants are now enumeration values using the new enum module. This allows meaningful names to be printed during debugging, instead of integer "magic numbers".

The AF_LINK constant is now available on BSD and OSX.

inet_pton() and inet_ntop() are now supported on Windows. (Contributed by Atsuo Ishimoto in bpo-7171 [https://bugs.python.org/issue?@action=redirect&bpo=7171].)

sqlite3

A new boolean parameter to the connect() function, uri, can be used to indicate that the database parameter is a uri (see the SQLite URI documentation [https://www.sqlite.org/uri.html]). (Contributed by poq in bpo-13773 [https://bugs.python.org/issue?@action=redirect&bpo=13773].)

ssl

PROTOCOL_TLSv1_1 and PROTOCOL_TLSv1_2 (TLSv1.1 and TLSv1.2 support) have been added; support for these protocols is only available if Python is linked with OpenSSL 1.0.1 or later. (Contributed by Michele Orrù and Antoine Pitrou in bpo-16692 [https://bugs.python.org/issue?@action=redirect&bpo=16692].)

New function create_default_context() provides a standard way to obtain an SSLContext whose settings are intended to be a reasonable balance between compatibility and security. These settings are more stringent than the defaults provided by the SSLContext constructor, and may be adjusted in the future, without prior deprecation, if best-practice security requirements change. The new recommended best practice for using stdlib libraries that support SSL is to use create_default_context() to obtain an SSLContext object, modify it if needed, and then pass it as the context argument of the appropriate stdlib API. (Contributed by Christian Heimes in bpo-19689 [https://bugs.python.org/issue?@action=redirect&bpo=19689].)

SSLContext method load_verify_locations() accepts a new optional argument cadata, which can be used to provide PEM or DER encoded certificates directly via strings or bytes, respectively. (Contributed by Christian Heimes in bpo-18138 [https://bugs.python.org/issue?@action=redirect&bpo=18138].)

New function get_default_verify_paths() returns a named tuple of the paths and environment variables that the set_default_verify_paths() method uses to set OpenSSL's default cafile and capath. This can be an aid in debugging default verification issues. (Contributed by Christian Heimes in bpo-18143 [https://bugs.python.org/issue?@action=redirect&bpo=18143].)

SSLContext has a new method, cert_store_stats(), that reports the number of loaded X.509 certs, X.509 CA certs, and certificate revocation lists (crls), as well as a get_ca_certs() method that returns a list of the loaded CA certificates. (Contributed by Christian Heimes in bpo-18147 [https://bugs.python.org/issue?@action=redirect&bpo=18147].)

If OpenSSL 0.9.8 or later is available, SSLContext has a new attribute verify_flags that can be used to control the certificate verification process by setting it to some combination of the new constants VERIFY_DEFAULT, VERIFY_CRL_CHECK_LEAF, VERIFY_CRL_CHECK_CHAIN, or VERIFY_X509_STRICT. OpenSSL does not do any CRL verification by default. (Contributed by Christien Heimes in bpo-8813 [https://bugs.python.org/issue?@action=redirect&bpo=8813].)

New SSLContext method load_default_certs() loads a set of default "certificate authority" (CA) certificates from default locations, which vary according to the platform. It can be used to load both TLS web server authentication certificates (purpose=SERVER_AUTH) for a client to use to verify a server, and certificates for a server to use in verifying client certificates (purpose=CLIENT_AUTH). (Contributed by Christian Heimes in bpo-19292 [https://bugs.python.org/issue?@action=redirect&bpo=19292].)

Two new windows-only functions, enum_certificates() and enum_crls() provide the ability to retrieve certificates, certificate information, and CRLs from the Windows cert store. (Contributed by Christian Heimes in bpo-17134 [https://bugs.python.org/issue?@action=redirect&bpo=17134].)

Support for server-side SNI (Server Name Indication) using the new ssl.SSLContext.set_servername_callback() method. (Contributed by Daniel Black in bpo-8109 [https://bugs.python.org/issue?@action=redirect&bpo=8109].)

The dictionary returned by SSLSocket.getpeercert() contains additional X509v3 extension items: crlDistributionPoints, calIssuers, and OCSP URIs. (Contributed by Christian Heimes in bpo-18379 [https://bugs.python.org/issue?@action=redirect&bpo=18379].)

stat

The stat module is now backed by a C implementation in _stat. A C implementation is required as most of the values aren't standardized and are platform-dependent. (Contributed by Christian Heimes in bpo-11016 [https://bugs.python.org/issue?@action=redirect&bpo=11016].)

The module supports new ST_MODE flags, S_IFDOOR, S_IFPORT, and S_IFWHT. (Contributed by Christian Hiemes in bpo-11016 [https://bugs.python.org/issue?@action=redirect&bpo=11016].)

struct

New function iter_unpack and a new struct.Struct.iter_unpack() method on compiled formats provide streamed unpacking of a buffer containing repeated instances of a given format of data. (Contributed by Antoine Pitrou in bpo-17804 [https://bugs.python.org/issue?@action=redirect&bpo=17804].)

subprocess

check_output() now accepts an input argument that can be used to provide the contents of stdin for the command that is run. (Contributed by Zack Weinberg in bpo-16624 [https://bugs.python.org/issue?@action=redirect&bpo=16624].)

getoutput() and getstatusoutput() now work on Windows. This change was actually inadvertently made in 3.3.4. (Contributed by Tim Golden in bpo-10197 [https://bugs.python.org/issue?@action=redirect&bpo=10197].)

sunau

The getparams() method now returns a namedtuple rather than a plain tuple. (Contributed by Claudiu Popa in bpo-18901 [https://bugs.python.org/issue?@action=redirect&bpo=18901].)

sunau.open() now supports the context management protocol: when used in a with block, the close method of the returned object will be called automatically at the end of the block. (Contributed by Serhiy Storchaka in bpo-18878 [https://bugs.python.org/issue?@action=redirect&bpo=18878].)

AU_write.setsampwidth() now supports 24 bit samples, thus adding support for writing 24 sample using the module. (Contributed by Serhiy Storchaka in bpo-19261 [https://bugs.python.org/issue?@action=redirect&bpo=19261].)

The writeframesraw() and writeframes() methods now accept any bytes-like object. (Contributed by Serhiy Storchaka in bpo-8311 [https://bugs.python.org/issue?@action=redirect&bpo=8311].)

sys

New function sys.getallocatedblocks() returns the current number of blocks allocated by the interpreter. (In CPython with the default --with-pymalloc setting, this is allocations made through the PyObject_Malloc() API.) This can be useful for tracking memory leaks, especially if automated via a test suite. (Contributed by Antoine Pitrou in bpo-13390 [https://bugs.python.org/issue?@action=redirect&bpo=13390].)

When the Python interpreter starts in interactive mode, it checks for an __interactivehook__ attribute on the sys module. If the attribute exists, its value is called with no arguments just before interactive mode is started. The check is made after the PYTHONSTARTUP file is read, so it can be set there. The site module sets it to a function that enables tab completion and history saving (in ~/.python-history) if the platform supports readline. If you do not want this (new) behavior, you can override it in PYTHONSTARTUP, sitecustomize, or usercustomize by deleting this attribute from sys (or setting it to some other callable). (Contributed by Éric Araujo and Antoine Pitrou in bpo-5845 [https://bugs.python.org/issue?@action=redirect&bpo=5845].)

tarfile

The tarfile module now supports a simple 命令列介面 when called as a script directly or via -m. This can be used to create and extract tarfile archives. (Contributed by Berker Peksag in bpo-13477 [https://bugs.python.org/issue?@action=redirect&bpo=13477].)

textwrap

The TextWrapper class has two new attributes/constructor arguments: max_lines, which limits the number of lines in the output, and placeholder, which is a string that will appear at the end of the output if it has been truncated because of max_lines. Building on these capabilities, a new convenience function shorten() collapses all of the whitespace in the input to single spaces and produces a single line of a given width that ends with the placeholder (by default, [...]). (Contributed by Antoine Pitrou and Serhiy Storchaka in bpo-18585 [https://bugs.python.org/issue?@action=redirect&bpo=18585] and bpo-18725 [https://bugs.python.org/issue?@action=redirect&bpo=18725].)

threading

The Thread object representing the main thread can be obtained from the new main_thread() function. In normal conditions this will be the thread from which the Python interpreter was started. (Contributed by Andrew Svetlov in bpo-18882 [https://bugs.python.org/issue?@action=redirect&bpo=18882].)

traceback

A new traceback.clear_frames() function takes a traceback object and clears the local variables in all of the frames it references, reducing the amount of memory consumed. (Contributed by Andrew Kuchling in bpo-1565525 [https://bugs.python.org/issue?@action=redirect&bpo=1565525].)

types

A new DynamicClassAttribute() descriptor provides a way to define an attribute that acts normally when looked up through an instance object, but which is routed to the class __getattr__ when looked up through the class. This allows one to have properties active on a class, and have virtual attributes on the class with the same name (see enum for an example). (Contributed by Ethan Furman in bpo-19030 [https://bugs.python.org/issue?@action=redirect&bpo=19030].)

urllib

urllib.request now supports data: URLs via the DataHandler class. (Contributed by Mathias Panzenböck in bpo-16423 [https://bugs.python.org/issue?@action=redirect&bpo=16423].)

The http method that will be used by a Request class can now be specified by setting a method class attribute on the subclass. (Contributed by Jason R Coombs in bpo-18978 [https://bugs.python.org/issue?@action=redirect&bpo=18978].)

Request objects are now reusable: if the full_url or data attributes are modified, all relevant internal properties are updated. This means, for example, that it is now possible to use the same Request object in more than one OpenerDirector.open() call with different data arguments, or to modify a Request's url rather than recomputing it from scratch. There is also a new remove_header() method that can be used to remove headers from a Request. (Contributed by Alexey Kachayev in bpo-16464 [https://bugs.python.org/issue?@action=redirect&bpo=16464], Daniel Wozniak in bpo-17485 [https://bugs.python.org/issue?@action=redirect&bpo=17485], and Damien Brecht and Senthil Kumaran in bpo-17272 [https://bugs.python.org/issue?@action=redirect&bpo=17272].)

HTTPError objects now have a headers attribute that provides access to the HTTP response headers associated with the error. (Contributed by Berker Peksag in bpo-15701 [https://bugs.python.org/issue?@action=redirect&bpo=15701].)

unittest

The TestCase class has a new method, subTest(), that produces a context manager whose with block becomes a "sub-test". This context manager allows a test method to dynamically generate subtests by, say, calling the subTest context manager inside a loop. A single test method can thereby produce an indefinite number of separately identified and separately counted tests, all of which will run even if one or more of them fail. For example:

class NumbersTest(unittest.TestCase):
    def test_even(self):
        for i in range(6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)

will result in six subtests, each identified in the unittest verbose output with a label consisting of the variable name i and a particular value for that variable (i=0, i=1, etc). See Distinguishing test iterations using subtests for the full version of this example. (Contributed by Antoine Pitrou in bpo-16997 [https://bugs.python.org/issue?@action=redirect&bpo=16997].)

unittest.main() now accepts an iterable of test names for defaultTest, where previously it only accepted a single test name as a string. (Contributed by Jyrki Pulliainen in bpo-15132 [https://bugs.python.org/issue?@action=redirect&bpo=15132].)

If SkipTest is raised during test discovery (that is, at the module level in the test file), it is now reported as a skip instead of an error. (Contributed by Zach Ware in bpo-16935 [https://bugs.python.org/issue?@action=redirect&bpo=16935].)

discover() now sorts the discovered files to provide consistent test ordering. (Contributed by Martin Melin and Jeff Ramnani in bpo-16709 [https://bugs.python.org/issue?@action=redirect&bpo=16709].)

TestSuite now drops references to tests as soon as the test has been run, if the test is successful. On Python interpreters that do garbage collection, this allows the tests to be garbage collected if nothing else is holding a reference to the test. It is possible to override this behavior by creating a TestSuite subclass that defines a custom _removeTestAtIndex method. (Contributed by Tom Wardill, Matt McClure, and Andrew Svetlov in bpo-11798 [https://bugs.python.org/issue?@action=redirect&bpo=11798].)

A new test assertion context-manager, assertLogs(), will ensure that a given block of code emits a log message using the logging module. By default the message can come from any logger and have a priority of INFO or higher, but both the logger name and an alternative minimum logging level may be specified. The object returned by the context manager can be queried for the LogRecords and/or formatted messages that were logged. (Contributed by Antoine Pitrou in bpo-18937 [https://bugs.python.org/issue?@action=redirect&bpo=18937].)

Test discovery now works with namespace packages (Contributed by Claudiu Popa in bpo-17457 [https://bugs.python.org/issue?@action=redirect&bpo=17457].)

unittest.mock objects now inspect their specification signatures when matching calls, which means an argument can now be matched by either position or name, instead of only by position. (Contributed by Antoine Pitrou in bpo-17015 [https://bugs.python.org/issue?@action=redirect&bpo=17015].)

mock_open() objects now have readline and readlines methods. (Contributed by Toshio Kuratomi in bpo-17467 [https://bugs.python.org/issue?@action=redirect&bpo=17467].)

venv

venv now includes activation scripts for the csh and fish shells. (Contributed by Andrew Svetlov in bpo-15417 [https://bugs.python.org/issue?@action=redirect&bpo=15417].)

EnvBuilder and the create() convenience function take a new keyword argument with_pip, which defaults to False, that controls whether or not EnvBuilder ensures that pip is installed in the virtual environment. (Contributed by Nick Coghlan in bpo-19552 [https://bugs.python.org/issue?@action=redirect&bpo=19552] as part of the PEP 453 [https://peps.python.org/pep-0453/] implementation.)

wave

The getparams() method now returns a namedtuple rather than a plain tuple. (Contributed by Claudiu Popa in bpo-17487 [https://bugs.python.org/issue?@action=redirect&bpo=17487].)

wave.open() now supports the context management protocol. (Contributed by Claudiu Popa in bpo-17616 [https://bugs.python.org/issue?@action=redirect&bpo=17616].)

wave can now write output to unseekable files. (Contributed by David Jones, Guilherme Polo, and Serhiy Storchaka in bpo-5202 [https://bugs.python.org/issue?@action=redirect&bpo=5202].)

The writeframesraw() and writeframes() methods now accept any bytes-like object. (Contributed by Serhiy Storchaka in bpo-8311 [https://bugs.python.org/issue?@action=redirect&bpo=8311].)

weakref

New WeakMethod class simulates weak references to bound methods. (Contributed by Antoine Pitrou in bpo-14631 [https://bugs.python.org/issue?@action=redirect&bpo=14631].)

New finalize class makes it possible to register a callback to be invoked when an object is garbage collected, without needing to carefully manage the lifecycle of the weak reference itself. (Contributed by Richard Oudkerk in bpo-15528 [https://bugs.python.org/issue?@action=redirect&bpo=15528].)

The callback, if any, associated with a ref is now exposed via the __callback__ attribute. (Contributed by Mark Dickinson in bpo-17643 [https://bugs.python.org/issue?@action=redirect&bpo=17643].)

xml.etree

A new parser, XMLPullParser, allows a non-blocking applications to parse XML documents. An example can be seen at Pull API for non-blocking parsing. (Contributed by Antoine Pitrou in bpo-17741 [https://bugs.python.org/issue?@action=redirect&bpo=17741].)

The xml.etree.ElementTree tostring() and tostringlist() functions, and the ElementTree write() method, now have a short_empty_elements keyword-only parameter providing control over whether elements with no content are written in abbreviated (<tag />) or expanded (<tag></tag>) form. (Contributed by Ariel Poliak and Serhiy Storchaka in bpo-14377 [https://bugs.python.org/issue?@action=redirect&bpo=14377].)

zipfile

The writepy() method of the PyZipFile class has a new filterfunc option that can be used to control which directories and files are added to the archive. For example, this could be used to exclude test files from the archive. (Contributed by Christian Tismer in bpo-19274 [https://bugs.python.org/issue?@action=redirect&bpo=19274].)

The allowZip64 parameter to ZipFile and PyZipFile is now True by default. (Contributed by William Mallard in bpo-17201 [https://bugs.python.org/issue?@action=redirect&bpo=17201].)

CPython 實作變更

PEP 445: Customization of CPython Memory Allocators

PEP 445 [https://peps.python.org/pep-0445/] adds new C level interfaces to customize memory allocation in the CPython interpreter.

也參考

PEP 445 [https://peps.python.org/pep-0445/] -- Add new APIs to customize Python memory allocators

由 Victor Stinner 撰寫 PEP 與實作。

PEP 442: Safe Object Finalization

PEP 442 [https://peps.python.org/pep-0442/] removes the current limitations and quirks of object finalization in CPython. With it, objects with __del__() methods, as well as generators with finally clauses, can be finalized when they are part of a reference cycle.

As part of this change, module globals are no longer forcibly set to None during interpreter shutdown in most cases, instead relying on the normal operation of the cyclic garbage collector. This avoids a whole class of interpreter-shutdown-time errors, usually involving __del__ methods, that have plagued Python since the cyclic GC was first introduced.

也參考

PEP 442 [https://peps.python.org/pep-0442/] -- 安全的物件最終化

由 Antoine Pitrou 撰寫 PEP 與實作。

PEP 456: Secure and Interchangeable Hash Algorithm

PEP 456 [https://peps.python.org/pep-0456/] follows up on earlier security fix work done on Python's hash algorithm to address certain DOS attacks to which public facing APIs backed by dictionary lookups may be subject. (See bpo-14621 [https://bugs.python.org/issue?@action=redirect&bpo=14621] for the start of the current round of improvements.) The PEP unifies CPython's hash code to make it easier for a packager to substitute a different hash algorithm, and switches Python's default implementation to a SipHash implementation on platforms that have a 64 bit data type. Any performance differences in comparison with the older FNV algorithm are trivial.

The PEP adds additional fields to the sys.hash_info named tuple to describe the hash algorithm in use by the currently executing binary. Otherwise, the PEP does not alter any existing CPython APIs.

PEP 436: Argument Clinic

"Argument Clinic" (PEP 436 [https://peps.python.org/pep-0436/]) is now part of the CPython build process and can be used to simplify the process of defining and maintaining accurate signatures for builtins and standard library extension modules implemented in C.

Some standard library extension modules have been converted to use Argument Clinic in Python 3.4, and pydoc and inspect have been updated accordingly.

It is expected that signature metadata for programmatic introspection will be added to additional callables implemented in C as part of Python 3.4 maintenance releases.

備註

The Argument Clinic PEP is not fully up to date with the state of the implementation. This has been deemed acceptable by the release manager and core development team in this case, as Argument Clinic will not be made available as a public API for third party use in Python 3.4.

也參考

PEP 436 [https://peps.python.org/pep-0436/] -- The Argument Clinic DSL

由 Larry Hastings 撰寫 PEP 與實作。

其他建置和 C API 變更

The new PyType_GetSlot() function has been added to the stable ABI, allowing retrieval of function pointers from named type slots when using the limited API. (Contributed by Martin von Löwis in bpo-17162 [https://bugs.python.org/issue?@action=redirect&bpo=17162].)

The new Py_SetStandardStreamEncoding() pre-initialization API allows applications embedding the CPython interpreter to reliably force a particular encoding and error handler for the standard streams. (Contributed by Bastien Montagne and Nick Coghlan in bpo-16129 [https://bugs.python.org/issue?@action=redirect&bpo=16129].)

Most Python C APIs that don't mutate string arguments are now correctly marked as accepting const char * rather than char *. (Contributed by Serhiy Storchaka in bpo-1772673 [https://bugs.python.org/issue?@action=redirect&bpo=1772673].)

A new shell version of python-config can be used even when a python interpreter is not available (for example, in cross compilation scenarios).

PyUnicode_FromFormat() now supports width and precision specifications for %s, %A, %U, %V, %S, and %R. (Contributed by Ysj Ray and Victor Stinner in bpo-7330 [https://bugs.python.org/issue?@action=redirect&bpo=7330].)

New function PyStructSequence_InitType2() supplements the existing PyStructSequence_InitType() function. The difference is that it returns 0 on success and -1 on failure.

The CPython source can now be compiled using the address sanity checking features of recent versions of GCC and clang: the false alarms in the small object allocator have been silenced. (Contributed by Dhiru Kholia in bpo-18596 [https://bugs.python.org/issue?@action=redirect&bpo=18596].)

The Windows build now uses Address Space Layout Randomization [https://en.wikipedia.org/wiki/Address_space_layout_randomization] and Data Execution Prevention [https://en.wikipedia.org/wiki/Data_Execution_Prevention]. (Contributed by Christian Heimes in bpo-16632 [https://bugs.python.org/issue?@action=redirect&bpo=16632].)

New function PyObject_LengthHint() is the C API equivalent of operator.length_hint(). (Contributed by Armin Ronacher in bpo-16148 [https://bugs.python.org/issue?@action=redirect&bpo=16148].)

其他改進

The python command has a new option, -I, which causes it to run in "isolated mode", which means that sys.path contains neither the script's directory nor the user's site-packages directory, and all PYTHON* environment variables are ignored (it implies both -s and -E). Other restrictions may also be applied in the future, with the goal being to isolate the execution of a script from the user's environment. This is appropriate, for example, when Python is used to run a system script. On most POSIX systems it can and should be used in the #! line of system scripts. (Contributed by Christian Heimes in bpo-16499 [https://bugs.python.org/issue?@action=redirect&bpo=16499].)

Tab-completion is now enabled by default in the interactive interpreter on systems that support readline. History is also enabled by default, and is written to (and read from) the file ~/.python-history. (Contributed by Antoine Pitrou and Éric Araujo in bpo-5845 [https://bugs.python.org/issue?@action=redirect&bpo=5845].)

Invoking the Python interpreter with --version now outputs the version to standard output instead of standard error (bpo-18338 [https://bugs.python.org/issue?@action=redirect&bpo=18338]). Similar changes were made to argparse (bpo-18920 [https://bugs.python.org/issue?@action=redirect&bpo=18920]) and other modules that have script-like invocation capabilities (bpo-18922 [https://bugs.python.org/issue?@action=redirect&bpo=18922]).

The CPython Windows installer now adds .py to the PATHEXT variable when extensions are registered, allowing users to run a python script at the windows command prompt by just typing its name without the .py extension. (Contributed by Paul Moore in bpo-18569 [https://bugs.python.org/issue?@action=redirect&bpo=18569].)

A new make target coverage-report [https://devguide.python.org/coverage/#measuring-coverage-of-c-code-with-gcov-and-lcov] will build python, run the test suite, and generate an HTML coverage report for the C codebase using gcov and lcov [https://github.com/linux-test-project/lcov].

python 迴歸測試套裝 的 -R 選項現在也可以透過使用 sys.getallocatedblocks() 來檢查記憶體配置洩漏。（由 Antoine Pitrou 在 bpo-13390 [https://bugs.python.org/issue?@action=redirect&bpo=13390] 貢獻。）

python -m 現在可以使用於命名空間套件。

The stat module is now implemented in C, which means it gets the values for its constants from the C header files, instead of having the values hard-coded in the python module as was previously the case.

Loading multiple python modules from a single OS module (.so, .dll) now works correctly (previously it silently returned the first python module in the file). (Contributed by Václav Šmilauer in bpo-16421 [https://bugs.python.org/issue?@action=redirect&bpo=16421].)

A new opcode, LOAD_CLASSDEREF, has been added to fix a bug in the loading of free variables in class bodies that could be triggered by certain uses of __prepare__. (Contributed by Benjamin Peterson in bpo-17853 [https://bugs.python.org/issue?@action=redirect&bpo=17853].)

A number of MemoryError-related crashes were identified and fixed by Victor Stinner using his PEP 445 [https://peps.python.org/pep-0445/]-based pyfailmalloc tool (bpo-18408 [https://bugs.python.org/issue?@action=redirect&bpo=18408], bpo-18520 [https://bugs.python.org/issue?@action=redirect&bpo=18520]).

The pyvenv command now accepts a --copies option to use copies rather than symlinks even on systems where symlinks are the default. (Contributed by Vinay Sajip in bpo-18807 [https://bugs.python.org/issue?@action=redirect&bpo=18807].)

The pyvenv command also accepts a --without-pip option to suppress the otherwise-automatic bootstrapping of pip into the virtual environment. (Contributed by Nick Coghlan in bpo-19552 [https://bugs.python.org/issue?@action=redirect&bpo=19552] as part of the PEP 453 [https://peps.python.org/pep-0453/] implementation.)

The encoding name is now optional in the value set for the PYTHONIOENCODING environment variable. This makes it possible to set just the error handler, without changing the default encoding. (Contributed by Serhiy Storchaka in bpo-18818 [https://bugs.python.org/issue?@action=redirect&bpo=18818].)

The bz2, lzma, and gzip module open functions now support x (exclusive creation) mode. (Contributed by Tim Heaney and Vajrasky Kok in bpo-19201 [https://bugs.python.org/issue?@action=redirect&bpo=19201], bpo-19222 [https://bugs.python.org/issue?@action=redirect&bpo=19222], and bpo-19223 [https://bugs.python.org/issue?@action=redirect&bpo=19223].)

顯著最佳化

The UTF-32 decoder is now 3x to 4x faster. (Contributed by Serhiy Storchaka in bpo-14625 [https://bugs.python.org/issue?@action=redirect&bpo=14625].)

The cost of hash collisions for sets is now reduced. Each hash table probe now checks a series of consecutive, adjacent key/hash pairs before continuing to make random probes through the hash table. This exploits cache locality to make collision resolution less expensive. The collision resolution scheme can be described as a hybrid of linear probing and open addressing. The number of additional linear probes defaults to nine. This can be changed at compile-time by defining LINEAR_PROBES to be any value. Set LINEAR_PROBES=0 to turn-off linear probing entirely. (Contributed by Raymond Hettinger in bpo-18771 [https://bugs.python.org/issue?@action=redirect&bpo=18771].)

The interpreter starts about 30% faster. A couple of measures lead to the speedup. The interpreter loads fewer modules on startup, e.g. the re, collections and locale modules and their dependencies are no longer imported by default. The marshal module has been improved to load compiled Python code faster. (Contributed by Antoine Pitrou, Christian Heimes and Victor Stinner in bpo-19219 [https://bugs.python.org/issue?@action=redirect&bpo=19219], bpo-19218 [https://bugs.python.org/issue?@action=redirect&bpo=19218], bpo-19209 [https://bugs.python.org/issue?@action=redirect&bpo=19209], bpo-19205 [https://bugs.python.org/issue?@action=redirect&bpo=19205] and bpo-9548 [https://bugs.python.org/issue?@action=redirect&bpo=9548].)

bz2.BZ2File is now as fast or faster than the Python2 version for most cases. lzma.LZMAFile has also been optimized. (Contributed by Serhiy Storchaka and Nadeem Vawda in bpo-16034 [https://bugs.python.org/issue?@action=redirect&bpo=16034].)

random.getrandbits() is 20%-40% faster for small integers (the most common use case). (Contributed by Serhiy Storchaka in bpo-16674 [https://bugs.python.org/issue?@action=redirect&bpo=16674].)

By taking advantage of the new storage format for strings, pickling of strings is now significantly faster. (Contributed by Victor Stinner and Antoine Pitrou in bpo-15596 [https://bugs.python.org/issue?@action=redirect&bpo=15596].)

A performance issue in io.FileIO.readall() has been solved. This particularly affects Windows, and significantly speeds up the case of piping significant amounts of data through subprocess. (Contributed by Richard Oudkerk in bpo-15758 [https://bugs.python.org/issue?@action=redirect&bpo=15758].)

html.escape() is now 10x faster. (Contributed by Matt Bryant in bpo-18020 [https://bugs.python.org/issue?@action=redirect&bpo=18020].)

On Windows, the native VirtualAlloc is now used instead of the CRT malloc in obmalloc. Artificial benchmarks show about a 3% memory savings.

os.urandom() now uses a lazily opened persistent file descriptor so as to avoid using many file descriptors when run in parallel from multiple threads. (Contributed by Antoine Pitrou in bpo-18756 [https://bugs.python.org/issue?@action=redirect&bpo=18756].)

已棄用

This section covers various APIs and other features that have been deprecated in Python 3.4, and will be removed in Python 3.5 or later. In most (but not all) cases, using the deprecated APIs will produce a DeprecationWarning when the interpreter is run with deprecation warnings enabled (for example, by using -Wd).

已棄用的 Python API

As mentioned in PEP 451：用於引入系統的 ModuleSpec 型別, a number of importlib methods and functions are deprecated: importlib.find_loader() is replaced by importlib.util.find_spec(); importlib.machinery.PathFinder.find_module() is replaced by importlib.machinery.PathFinder.find_spec(); importlib.abc.MetaPathFinder.find_module() is replaced by importlib.abc.MetaPathFinder.find_spec(); importlib.abc.PathEntryFinder.find_loader() and find_module() are replaced by importlib.abc.PathEntryFinder.find_spec(); all of the xxxLoader ABC load_module methods (importlib.abc.Loader.load_module(), importlib.abc.InspectLoader.load_module(), importlib.abc.FileLoader.load_module(), importlib.abc.SourceLoader.load_module()) should no longer be implemented, instead loaders should implement an exec_module method (importlib.abc.Loader.exec_module(), importlib.abc.InspectLoader.exec_module() importlib.abc.SourceLoader.exec_module()) and let the import system take care of the rest; and importlib.abc.Loader.module_repr(), importlib.util.module_for_loader(), importlib.util.set_loader(), and importlib.util.set_package() are no longer needed because their functions are now handled automatically by the import system.

The imp module is pending deprecation. To keep compatibility with Python 2/3 code bases, the module's removal is currently not scheduled.

The formatter module is pending deprecation and is slated for removal in Python 3.6.

MD5 as the default digestmod for the hmac.new() function is deprecated. Python 3.6 will require an explicit digest name or constructor as digestmod argument.

The internal Netrc class in the ftplib module has been documented as deprecated in its docstring for quite some time. It now emits a DeprecationWarning and will be removed completely in Python 3.5.

The undocumented endtime argument to subprocess.Popen.wait() should not have been exposed and is hopefully not in use; it is deprecated and will mostly likely be removed in Python 3.5.

The strict argument of HTMLParser is deprecated.

The plistlib readPlist(), writePlist(), readPlistFromBytes(), and writePlistToBytes() functions are deprecated in favor of the corresponding new functions load(), dump(), loads(), and dumps(). Data() is deprecated in favor of just using the bytes constructor.

The sysconfig key SO is deprecated, it has been replaced by EXT_SUFFIX.

The U mode accepted by various open functions is deprecated. In Python3 it does not do anything useful, and should be replaced by appropriate uses of io.TextIOWrapper (if needed) and its newline argument.

The parser argument of xml.etree.ElementTree.iterparse() has been deprecated, as has the html argument of XMLParser(). To prepare for the removal of the latter, all arguments to XMLParser should be passed by keyword.

已棄用功能

Running IDLE --- Python 編輯器與 shell with the -n flag (no subprocess) is deprecated. However, the feature will not be removed until bpo-18823 [https://bugs.python.org/issue?@action=redirect&bpo=18823] is resolved.

The site module adding a "site-python" directory to sys.path, if it exists, is deprecated (bpo-19375 [https://bugs.python.org/issue?@action=redirect&bpo=19375]).

已移除

不再支援的作業系統

Support for the following operating systems has been removed from the source and build tools:

OS/2 (bpo-16135 [https://bugs.python.org/issue?@action=redirect&bpo=16135])。

Windows 2000 (changeset e52df05b496a).

Windows systems where COMSPEC points to command.com (bpo-14470 [https://bugs.python.org/issue?@action=redirect&bpo=14470]).

VMS (bpo-16136 [https://bugs.python.org/issue?@action=redirect&bpo=16136])。

API 與功能的移除

The following obsolete and previously deprecated APIs and features have been removed:

The unmaintained Misc/TextMate and Misc/vim directories have been removed (see the devguide [https://devguide.python.org] for suggestions on what to use instead).

The SO makefile macro is removed (it was replaced by the SHLIB_SUFFIX and EXT_SUFFIX macros) (bpo-16754 [https://bugs.python.org/issue?@action=redirect&bpo=16754]).

The PyThreadState.tick_counter field has been removed; its value has been meaningless since Python 3.2, when the "new GIL" was introduced (bpo-19199 [https://bugs.python.org/issue?@action=redirect&bpo=19199]).

PyLoader and PyPycLoader have been removed from importlib. (Contributed by Taras Lyapun in bpo-15641 [https://bugs.python.org/issue?@action=redirect&bpo=15641].)

The strict argument to HTTPConnection and HTTPSConnection has been removed. HTTP 0.9-style "Simple Responses" are no longer supported.

The deprecated urllib.request.Request getter and setter methods add_data, has_data, get_data, get_type, get_host, get_selector, set_proxy, get_origin_req_host, and is_unverifiable have been removed (use direct attribute access instead).

Support for loading the deprecated TYPE_INT64 has been removed from marshal. (Contributed by Dan Riti in bpo-15480 [https://bugs.python.org/issue?@action=redirect&bpo=15480].)

inspect.Signature: positional-only parameters are now required to have a valid name.

object.__format__() no longer accepts non-empty format strings, it now raises a TypeError instead. Using a non-empty string has been deprecated since Python 3.2. This change has been made to prevent a situation where previously working (but incorrect) code would start failing if an object gained a __format__ method, which means that your code may now raise a TypeError if you are using an 's' format code with objects that do not have a __format__ method that handles it. See bpo-7994 [https://bugs.python.org/issue?@action=redirect&bpo=7994] for background.

difflib.SequenceMatcher.isbjunk() and difflib.SequenceMatcher.isbpopular() were deprecated in 3.2, and have now been removed: use x in sm.bjunk and x in sm.bpopular, where sm is a SequenceMatcher object (bpo-13248 [https://bugs.python.org/issue?@action=redirect&bpo=13248]).

程式碼的清除

The unused and undocumented internal Scanner class has been removed from the pydoc module.

The private and effectively unused _gestalt module has been removed, along with the private platform functions _mac_ver_lookup, _mac_ver_gstalt, and _bcd2str, which would only have ever been called on badly broken OSX systems (see bpo-18393 [https://bugs.python.org/issue?@action=redirect&bpo=18393]).

The hardcoded copies of certain stat constants that were included in the tarfile module namespace have been removed.

移植至 Python 3.4

This section lists previously described changes and other bugfixes that may require changes to your code.

Changes in 'python' Command Behavior

In a posix shell, setting the PATH environment variable to an empty value is equivalent to not setting it at all. However, setting PYTHONPATH to an empty value was not equivalent to not setting it at all: setting PYTHONPATH to an empty value was equivalent to setting it to ., which leads to confusion when reasoning by analogy to how PATH works. The behavior now conforms to the posix convention for PATH.

The [X refs, Y blocks] output of a debug (--with-pydebug) build of the CPython interpreter is now off by default. It can be re-enabled using the -X showrefcount option. (Contributed by Ezio Melotti in bpo-17323 [https://bugs.python.org/issue?@action=redirect&bpo=17323].)

The python command and most stdlib scripts (as well as argparse) now output --version information to stdout instead of stderr (for issue list see 其他改進 above).

Python API 的變更

The ABCs defined in importlib.abc now either raise the appropriate exception or return a default value instead of raising NotImplementedError blindly. This will only affect code calling super() and falling through all the way to the ABCs. For compatibility, catch both NotImplementedError or the appropriate exception as needed.

The module type now initializes the __package__ and __loader__ attributes to None by default. To determine if these attributes were set in a backwards-compatible fashion, use e.g. getattr(module, '__loader__', None) is not None. (bpo-17115 [https://bugs.python.org/issue?@action=redirect&bpo=17115].)

importlib.util.module_for_loader() now sets __loader__ and __package__ unconditionally to properly support reloading. If this is not desired then you will need to set these attributes manually. You can use importlib.util.module_to_load() for module management.

Import now resets relevant attributes (e.g. __name__, __loader__, __package__, __file__, __cached__) unconditionally when reloading. Note that this restores a pre-3.3 behavior in that it means a module is re-found when re-loaded (bpo-19413 [https://bugs.python.org/issue?@action=redirect&bpo=19413]).

Frozen packages no longer set __path__ to a list containing the package name, they now set it to an empty list. The previous behavior could cause the import system to do the wrong thing on submodule imports if there was also a directory with the same name as the frozen package. The correct way to determine if a module is a package or not is to use hasattr(module, '__path__') (bpo-18065 [https://bugs.python.org/issue?@action=redirect&bpo=18065]).

Frozen modules no longer define a __file__ attribute. It's semantically incorrect for frozen modules to set the attribute as they are not loaded from any explicit location. If you must know that a module comes from frozen code then you can see if the module's __spec__.location is set to 'frozen', check if the loader is a subclass of importlib.machinery.FrozenImporter, or if Python 2 compatibility is necessary you can use imp.is_frozen().

py_compile.compile() now raises FileExistsError if the file path it would write to is a symlink or a non-regular file. This is to act as a warning that import will overwrite those files with a regular file regardless of what type of file path they were originally.

importlib.abc.SourceLoader.get_source() no longer raises ImportError when the source code being loaded triggers a SyntaxError or UnicodeDecodeError. As ImportError is meant to be raised only when source code cannot be found but it should, it was felt to be over-reaching/overloading of that meaning when the source code is found but improperly structured. If you were catching ImportError before and wish to continue to ignore syntax or decoding issues, catch all three exceptions now.

functools.update_wrapper() and functools.wraps() now correctly set the __wrapped__ attribute to the function being wrapped, even if that function also had its __wrapped__ attribute set. This means __wrapped__ attributes now correctly link a stack of decorated functions rather than every __wrapped__ attribute in the chain referring to the innermost function. Introspection libraries that assumed the previous behaviour was intentional can use inspect.unwrap() to access the first function in the chain that has no __wrapped__ attribute.

inspect.getfullargspec() has been reimplemented on top of inspect.signature() and hence handles a much wider variety of callable objects than it did in the past. It is expected that additional builtin and extension module callables will gain signature metadata over the course of the Python 3.4 series. Code that assumes that inspect.getfullargspec() will fail on non-Python callables may need to be adjusted accordingly.

importlib.machinery.PathFinder now passes on the current working directory to objects in sys.path_hooks for the empty string. This results in sys.path_importer_cache never containing '', thus iterating through sys.path_importer_cache based on sys.path will not find all keys. A module's __file__ when imported in the current working directory will also now have an absolute path, including when using -m with the interpreter (except for __main__.__file__ when a script has been executed directly using a relative path) (Contributed by Brett Cannon in bpo-18416 [https://bugs.python.org/issue?@action=redirect&bpo=18416]). is specified on the command-line) (bpo-18416 [https://bugs.python.org/issue?@action=redirect&bpo=18416]).

The removal of the strict argument to HTTPConnection and HTTPSConnection changes the meaning of the remaining arguments if you are specifying them positionally rather than by keyword. If you've been paying attention to deprecation warnings your code should already be specifying any additional arguments via keywords.

Strings between from __future__ import ... statements now always raise a SyntaxError. Previously if there was no leading docstring, an interstitial string would sometimes be ignored. This brings CPython into compliance with the language spec; Jython and PyPy already were. (bpo-17434 [https://bugs.python.org/issue?@action=redirect&bpo=17434]).

ssl.SSLSocket.getpeercert() and ssl.SSLSocket.do_handshake() now raise an OSError with ENOTCONN when the SSLSocket is not connected, instead of the previous behavior of raising an AttributeError. In addition, getpeercert() will raise a ValueError if the handshake has not yet been done.

base64.b32decode() now raises a binascii.Error when the input string contains non-b32-alphabet characters, instead of a TypeError. This particular TypeError was missed when the other TypeErrors were converted. (Contributed by Serhiy Storchaka in bpo-18011 [https://bugs.python.org/issue?@action=redirect&bpo=18011].) Note: this change was also inadvertently applied in Python 3.3.3.

The file attribute is now automatically closed when the creating cgi.FieldStorage instance is garbage collected. If you were pulling the file object out separately from the cgi.FieldStorage instance and not keeping the instance alive, then you should either store the entire cgi.FieldStorage instance or read the contents of the file before the cgi.FieldStorage instance is garbage collected.

Calling read or write on a closed SSL socket now raises an informative ValueError rather than the previous more mysterious AttributeError (bpo-9177 [https://bugs.python.org/issue?@action=redirect&bpo=9177]).

slice.indices() no longer produces an OverflowError for huge values. As a consequence of this fix, slice.indices() now raises a ValueError if given a negative length; previously it returned nonsense values (bpo-14794 [https://bugs.python.org/issue?@action=redirect&bpo=14794]).

The complex constructor, unlike the cmath functions, was incorrectly accepting float values if an object's __complex__ special method returned one. This now raises a TypeError. (bpo-16290 [https://bugs.python.org/issue?@action=redirect&bpo=16290].)

The int constructor in 3.2 and 3.3 erroneously accepts float values for the base parameter. It is unlikely anyone was doing this, but if so, it will now raise a TypeError (bpo-16772 [https://bugs.python.org/issue?@action=redirect&bpo=16772]).

Defaults for keyword-only arguments are now evaluated after defaults for regular keyword arguments, instead of before. Hopefully no one wrote any code that depends on the previous buggy behavior (bpo-16967 [https://bugs.python.org/issue?@action=redirect&bpo=16967]).

Stale thread states are now cleared after fork(). This may cause some system resources to be released that previously were incorrectly kept perpetually alive (for example, database connections kept in thread-local storage). (bpo-17094 [https://bugs.python.org/issue?@action=redirect&bpo=17094].)

Parameter names in __annotations__ dicts are now mangled properly, similarly to __kwdefaults__. (Contributed by Yury Selivanov in bpo-20625 [https://bugs.python.org/issue?@action=redirect&bpo=20625].)

hashlib.hash.name now always returns the identifier in lower case. Previously some builtin hashes had uppercase names, but now that it is a formal public interface the naming has been made consistent (bpo-18532 [https://bugs.python.org/issue?@action=redirect&bpo=18532]).

Because unittest.TestSuite now drops references to tests after they are run, test harnesses that reuse a TestSuite to re-run a set of tests may fail. Test suites should not be re-used in this fashion since it means state is retained between test runs, breaking the test isolation that unittest is designed to provide. However, if the lack of isolation is considered acceptable, the old behavior can be restored by creating a TestSuite subclass that defines a _removeTestAtIndex method that does nothing (see TestSuite.__iter__()) (bpo-11798 [https://bugs.python.org/issue?@action=redirect&bpo=11798]).

unittest now uses argparse for command line parsing. There are certain invalid command forms that used to work that are no longer allowed; in theory this should not cause backward compatibility issues since the disallowed command forms didn't make any sense and are unlikely to be in use.

The re.split(), re.findall(), and re.sub() functions, and the group() and groups() methods of match objects now always return a bytes object when the string to be matched is a bytes-like object. Previously the return type matched the input type, so if your code was depending on the return value being, say, a bytearray, you will need to change your code.

audioop functions now raise an error immediately if passed string input, instead of failing randomly later on (bpo-16685 [https://bugs.python.org/issue?@action=redirect&bpo=16685]).

The new convert_charrefs argument to HTMLParser currently defaults to False for backward compatibility, but will eventually be changed to default to True. It is recommended that you add this keyword, with the appropriate value, to any HTMLParser calls in your code (bpo-13633 [https://bugs.python.org/issue?@action=redirect&bpo=13633]).

Since the digestmod argument to the hmac.new() function will in the future have no default, all calls to hmac.new() should be changed to explicitly specify a digestmod (bpo-17276 [https://bugs.python.org/issue?@action=redirect&bpo=17276]).

Calling sysconfig.get_config_var() with the SO key, or looking SO up in the results of a call to sysconfig.get_config_vars() is deprecated. This key should be replaced by EXT_SUFFIX or SHLIB_SUFFIX, depending on the context (bpo-19555 [https://bugs.python.org/issue?@action=redirect&bpo=19555]).

Any calls to open functions that specify U should be modified. U is ineffective in Python3 and will eventually raise an error if used. Depending on the function, the equivalent of its old Python2 behavior can be achieved using either a newline argument, or if necessary by wrapping the stream in TextIOWrapper to use its newline argument (bpo-15204 [https://bugs.python.org/issue?@action=redirect&bpo=15204]).

If you use pyvenv in a script and desire that pip not be installed, you must add --without-pip to your command invocation.

The default behavior of json.dump() and json.dumps() when an indent is specified has changed: it no longer produces trailing spaces after the item separating commas at the ends of lines. This will matter only if you have tests that are doing white-space-sensitive comparisons of such output (bpo-16333 [https://bugs.python.org/issue?@action=redirect&bpo=16333]).

doctest now looks for doctests in extension module __doc__ strings, so if your doctest test discovery includes extension modules that have things that look like doctests in them you may see test failures you've never seen before when running your tests (bpo-3158 [https://bugs.python.org/issue?@action=redirect&bpo=3158]).

The collections.abc module has been slightly refactored as part of the Python startup improvements. As a consequence of this, it is no longer the case that importing collections automatically imports collections.abc. If your program depended on the (undocumented) implicit import, you will need to add an explicit import collections.abc (bpo-20784 [https://bugs.python.org/issue?@action=redirect&bpo=20784]).

C API 中的改動

PyEval_EvalFrameEx(), PyObject_Repr(), and PyObject_Str(), along with some other internal C APIs, now include a debugging assertion that ensures they are not used in situations where they may silently discard a currently active exception. In cases where discarding the active exception is expected and desired (for example, because it has already been saved locally with PyErr_Fetch() or is being deliberately replaced with a different exception), an explicit PyErr_Clear() call will be needed to avoid triggering the assertion when invoking these operations (directly or indirectly) and running against a version of Python that is compiled with assertions enabled.

PyErr_SetImportError() now sets TypeError when its msg argument is not set. Previously only NULL was returned with no exception set.

The result of the PyOS_ReadlineFunctionPointer callback must now be a string allocated by PyMem_RawMalloc() or PyMem_RawRealloc(), or NULL if an error occurred, instead of a string allocated by PyMem_Malloc() or PyMem_Realloc() (bpo-16742 [https://bugs.python.org/issue?@action=redirect&bpo=16742])

PyThread_set_key_value() now always set the value. In Python 3.3, the function did nothing if the key already exists (if the current value is a non-NULL pointer).

The f_tstate (thread state) field of the PyFrameObject structure has been removed to fix a bug: see bpo-14432 [https://bugs.python.org/issue?@action=redirect&bpo=14432] for the rationale.

3.4.3 中的變更

PEP 476: Enabling certificate verification by default for stdlib http clients

http.client and modules which use it, such as urllib.request and xmlrpc.client, will now verify that the server presents a certificate which is signed by a CA in the platform trust store and whose hostname matches the hostname being requested by default, significantly improving security for many applications.

For applications which require the old previous behavior, they can pass an alternate context:

import urllib.request
import ssl

# This disables all verification
context = ssl._create_unverified_context()

# This allows using a specific certificate for the host, which doesn't need
# to be in the trust store
context = ssl.create_default_context(cafile="/path/to/file.crt")

urllib.request.urlopen("https://invalid-cert", context=context)

Python 3.3 有什麼新功能

本文介紹了 Python 3.3 與 3.2 相比多了哪些新功能。Python 3.1 已於 2012 年 9 月 29 日發布。完整詳情請見 changelog [https://docs.python.org/3.3/whatsnew/changelog.html]。

也參考

PEP 398 [https://peps.python.org/pep-0398/] - Python 3.3 發佈時程

發布重點摘要

新增語法特性：

New yield from expression for generator delegation.

str 物件再次接受 u'unicode' 語法。

新的函式庫模組：

faulthandler (helps debugging low-level crashes)

ipaddress (high-level objects representing IP addresses and masks)

lzma (compress data using the XZ / LZMA algorithm)

unittest.mock (replace parts of your system under test with mock objects)

venv (Python virtual environments, as in the popular virtualenv package)

新的內建功能：

重新設計 I/O 例外層次結構。

實作改進：

Rewritten import machinery based on importlib.

More compact unicode strings.

More compact attribute dictionaries.

顯著改進的函式庫模組：

C Accelerator for the decimal module.

Better unicode handling in the email module (provisional).

安全性改進：

預設情況下，雜湊隨機化處於打開狀態。

Please read on for a comprehensive list of user-facing changes.

PEP 405：虛擬環境

Virtual environments help create separate Python setups while sharing a system-wide base install, for ease of maintenance. Virtual environments have their own set of private site packages (i.e. locally installed libraries), and are optionally segregated from the system-wide site packages. Their concept and implementation are inspired by the popular virtualenv third-party package, but benefit from tighter integration with the interpreter core.

This PEP adds the venv module for programmatic access, and the pyvenv script for command-line access and administration. The Python interpreter checks for a pyvenv.cfg, file whose existence signals the base of a virtual environment's directory tree.

也參考

PEP 405 [https://peps.python.org/pep-0405/] - Python 虛擬環境

由 Carl Meyer 撰寫 PEP；由 Carl Meyer 與 Vinay Sajip 實作

PEP 420: Implicit Namespace Packages

Native support for package directories that don't require __init__.py marker files and can automatically span multiple path segments (inspired by various third party approaches to namespace packages, as described in PEP 420 [https://peps.python.org/pep-0420/])

也參考

PEP 420 [https://peps.python.org/pep-0420/] - Implicit Namespace Packages

由 Eric V. Smith 撰寫 PEP；由 Eric V. Smith 和 Barry Warsaw 實施

PEP 3118: New memoryview implementation and buffer protocol documentation

The implementation of PEP 3118 [https://peps.python.org/pep-3118/] has been significantly improved.

The new memoryview implementation comprehensively fixes all ownership and lifetime issues of dynamically allocated fields in the Py_buffer struct that led to multiple crash reports. Additionally, several functions that crashed or returned incorrect results for non-contiguous or multi-dimensional input have been fixed.

The memoryview object now has a PEP-3118 compliant getbufferproc() that checks the consumer's request type. Many new features have been added, most of them work in full generality for non-contiguous arrays and arrays with suboffsets.

The documentation has been updated, clearly spelling out responsibilities for both exporters and consumers. Buffer request flags are grouped into basic and compound flags. The memory layout of non-contiguous and multi-dimensional NumPy-style arrays is explained.

功能

All native single character format specifiers in struct module syntax (optionally prefixed with '@') are now supported.

With some restrictions, the cast() method allows changing of format and shape of C-contiguous arrays.

Multi-dimensional list representations are supported for any array type.

Multi-dimensional comparisons are supported for any array type.

One-dimensional memoryviews of hashable (read-only) types with formats B, b or c are now hashable. (Contributed by Antoine Pitrou in bpo-13411 [https://bugs.python.org/issue?@action=redirect&bpo=13411].)

Arbitrary slicing of any 1-D arrays type is supported. For example, it is now possible to reverse a memoryview in O(1) by using a negative step.

API 變更

The maximum number of dimensions is officially limited to 64.

The representation of empty shape, strides and suboffsets is now an empty tuple instead of None.

Accessing a memoryview element with format 'B' (unsigned bytes) now returns an integer (in accordance with the struct module syntax). For returning a bytes object the view must be cast to 'c' first.

memoryview comparisons now use the logical structure of the operands and compare all array elements by value. All format strings in struct module syntax are supported. Views with unrecognised format strings are still permitted, but will always compare as unequal, regardless of view contents.

For further changes see Build and C API Changes and Porting C code.

（由 Stefan Krah 在 bpo-10181 [https://bugs.python.org/issue?@action=redirect&bpo=10181] 中貢獻。）

也參考

PEP 3118 [https://peps.python.org/pep-3118/] - 修訂緩衝協定

PEP 393: Flexible String Representation

The Unicode string type is changed to support multiple internal representations, depending on the character with the largest Unicode ordinal (1, 2, or 4 bytes) in the represented string. This allows a space-efficient representation in common cases, but gives access to full UCS-4 on all systems. For compatibility with existing APIs, several representations may exist in parallel; over time, this compatibility should be phased out.

On the Python side, there should be no downside to this change.

On the C API side, PEP 393 [https://peps.python.org/pep-0393/] is fully backward compatible. The legacy API should remain available at least five years. Applications using the legacy API will not fully benefit of the memory reduction, or - worse - may use a bit more memory, because Python may have to maintain two versions of each string (in the legacy format and in the new efficient storage).

功能性

PEP 393 [https://peps.python.org/pep-0393/] 引入的更改如下：

Python now always supports the full range of Unicode code points, including non-BMP ones (i.e. from U+0000 to U+10FFFF). The distinction between narrow and wide builds no longer exists and Python now behaves like a wide build, even under Windows.

With the death of narrow builds, the problems specific to narrow builds have also been fixed, for example:

len() now always returns 1 for non-BMP characters, so len('\U0010FFFF') == 1;

surrogate pairs are not recombined in string literals, so '\uDBFF\uDFFF' != '\U0010FFFF';

indexing or slicing non-BMP characters returns the expected value, so '\U0010FFFF'[0] now returns '\U0010FFFF' and not '\uDBFF';

all other functions in the standard library now correctly handle non-BMP code points.

The value of sys.maxunicode is now always 1114111 (0x10FFFF in hexadecimal). The PyUnicode_GetMax() function still returns either 0xFFFF or 0x10FFFF for backward compatibility, and it should not be used with the new Unicode API (see bpo-13054 [https://bugs.python.org/issue?@action=redirect&bpo=13054]).

./configure 旗標 --with-wide-unicode 已被刪除。

性能和資源使用情況

The storage of Unicode strings now depends on the highest code point in the string:

pure ASCII and Latin1 strings (U+0000-U+00FF) use 1 byte per code point;

BMP strings (U+0000-U+FFFF) use 2 bytes per code point;

non-BMP strings (U+10000-U+10FFFF) use 4 bytes per code point.

The net effect is that for most applications, memory usage of string storage should decrease significantly - especially compared to former wide unicode builds - as, in many cases, strings will be pure ASCII even in international contexts (because many strings store non-human language data, such as XML fragments, HTTP headers, JSON-encoded data, etc.). We also hope that it will, for the same reasons, increase CPU cache efficiency on non-trivial applications. The memory usage of Python 3.3 is two to three times smaller than Python 3.2, and a little bit better than Python 2.7, on a Django benchmark (see the PEP for details).

也參考

PEP 393 [https://peps.python.org/pep-0393/] - Flexible String Representation

PEP 由 Martin von Löwis 撰寫；由 Torsten Becker 和 Martin von Löwis 實作。

PEP 397：適用於 Windows 的 Python 啟動器

The Python 3.3 Windows installer now includes a py launcher application that can be used to launch Python applications in a version independent fashion.

This launcher is invoked implicitly when double-clicking *.py files. If only a single Python version is installed on the system, that version will be used to run the file. If multiple versions are installed, the most recent version is used by default, but this can be overridden by including a Unix-style "shebang line" in the Python script.

The launcher can also be used explicitly from the command line as the py application. Running py follows the same version selection rules as implicitly launching scripts, but a more specific version can be selected by passing appropriate arguments (such as -3 to request Python 3 when Python 2 is also installed, or -2.6 to specifically request an earlier Python version when a more recent version is installed).

In addition to the launcher, the Windows installer now includes an option to add the newly installed Python to the system PATH. (Contributed by Brian Curtin in bpo-3561 [https://bugs.python.org/issue?@action=redirect&bpo=3561].)

也參考

PEP 397 [https://peps.python.org/pep-0397/] - 適用於 Windows 的 Python 啟動器

由 Mark Hammond 和 Martin v. Löwis 撰寫 PEP；由 Vinay Sajip 實作。

啟動器文件：Python 安裝管理員

Installer PATH modification: Python 安裝管理員

PEP 3151: Reworking the OS and IO exception hierarchy

The hierarchy of exceptions raised by operating system errors is now both simplified and finer-grained.

You don't have to worry anymore about choosing the appropriate exception type between OSError, IOError, EnvironmentError, WindowsError, mmap.error, socket.error or select.error. All these exception types are now only one: OSError. The other names are kept as aliases for compatibility reasons.

Also, it is now easier to catch a specific error condition. Instead of inspecting the errno attribute (or args[0]) for a particular constant from the errno module, you can catch the adequate OSError subclass. The available subclasses are the following:

BlockingIOError

ChildProcessError

ConnectionError

FileExistsError

FileNotFoundError

InterruptedError

IsADirectoryError

NotADirectoryError

PermissionError

ProcessLookupError

TimeoutError

And the ConnectionError itself has finer-grained subclasses:

BrokenPipeError

ConnectionAbortedError

ConnectionRefusedError

ConnectionResetError

Thanks to the new exceptions, common usages of the errno can now be avoided. For example, the following code written for Python 3.2:

from errno import ENOENT, EACCES, EPERM

try:
    with open("document.txt") as f:
        content = f.read()
except IOError as err:
    if err.errno == ENOENT:
        print("document.txt file is missing")
    elif err.errno in (EACCES, EPERM):
        print("You are not allowed to read document.txt")
    else:
        raise

can now be written without the errno import and without manual inspection of exception attributes:

try:
    with open("document.txt") as f:
        content = f.read()
except FileNotFoundError:
    print("document.txt file is missing")
except PermissionError:
    print("You are not allowed to read document.txt")

也參考

PEP 3151 [https://peps.python.org/pep-3151/] - Reworking the OS and IO Exception Hierarchy

由 Antoine Pitrou 撰寫 PEP 與實作

PEP 380: Syntax for Delegating to a Subgenerator

PEP 380 adds the yield from expression, allowing a generator to delegate part of its operations to another generator. This allows a section of code containing yield to be factored out and placed in another generator. Additionally, the subgenerator is allowed to return with a value, and the value is made available to the delegating generator.

While designed primarily for use in delegating to a subgenerator, the yield from expression actually allows delegation to arbitrary subiterators.

For simple iterators, yield from iterable is essentially just a shortened form of for item in iterable: yield item:

>>> def g(x):
...     yield from range(x, 0, -1)
...     yield from range(x)
...
>>> list(g(5))
[5, 4, 3, 2, 1, 0, 1, 2, 3, 4]

However, unlike an ordinary loop, yield from allows subgenerators to receive sent and thrown values directly from the calling scope, and return a final value to the outer generator:

>>> def accumulate():
...     tally = 0
...     while 1:
...         next = yield
...         if next is None:
...             return tally
...         tally += next
...
>>> def gather_tallies(tallies):
...     while 1:
...         tally = yield from accumulate()
...         tallies.append(tally)
...
>>> tallies = []
>>> acc = gather_tallies(tallies)
>>> next(acc)  # Ensure the accumulator is ready to accept values
>>> for i in range(4):
...     acc.send(i)
...
>>> acc.send(None)  # Finish the first tally
>>> for i in range(5):
...     acc.send(i)
...
>>> acc.send(None)  # Finish the second tally
>>> tallies
[6, 10]

The main principle driving this change is to allow even generators that are designed to be used with the send and throw methods to be split into multiple subgenerators as easily as a single large function can be split into multiple subfunctions.

也參考

PEP 380 [https://peps.python.org/pep-0380/] - Syntax for Delegating to a Subgenerator

PEP written by Greg Ewing; implementation by Greg Ewing, integrated into 3.3 by Renaud Blanch, Ryan Kelly and Nick Coghlan; documentation by Zbigniew Jędrzejewski-Szmek and Nick Coghlan

PEP 409: Suppressing exception context

PEP 409 introduces new syntax that allows the display of the chained exception context to be disabled. This allows cleaner error messages in applications that convert between exception types:

>>> class D:
...     def __init__(self, extra):
...         self._extra_attributes = extra
...     def __getattr__(self, attr):
...         try:
...             return self._extra_attributes[attr]
...         except KeyError:
...             raise AttributeError(attr) from None
...
>>> D({}).x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 8, in __getattr__
AttributeError: x

Without the from None suffix to suppress the cause, the original exception would be displayed by default:

>>> class C:
...     def __init__(self, extra):
...         self._extra_attributes = extra
...     def __getattr__(self, attr):
...         try:
...             return self._extra_attributes[attr]
...         except KeyError:
...             raise AttributeError(attr)
...
>>> C({}).x
Traceback (most recent call last):
  File "<stdin>", line 6, in __getattr__
KeyError: 'x'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 8, in __getattr__
AttributeError: x

No debugging capability is lost, as the original exception context remains available if needed (for example, if an intervening library has incorrectly suppressed valuable underlying details):

>>> try:
...     D({}).x
... except AttributeError as exc:
...     print(repr(exc.__context__))
...
KeyError('x',)

也參考

PEP 409 [https://peps.python.org/pep-0409/] - Suppressing exception context

PEP written by Ethan Furman; implemented by Ethan Furman and Nick Coghlan.

PEP 414: Explicit Unicode literals

To ease the transition from Python 2 for Unicode aware Python applications that make heavy use of Unicode literals, Python 3.3 once again supports the "u" prefix for string literals. This prefix has no semantic significance in Python 3, it is provided solely to reduce the number of purely mechanical changes in migrating to Python 3, making it easier for developers to focus on the more significant semantic changes (such as the stricter default separation of binary and text data).

也參考

PEP 414 [https://peps.python.org/pep-0414/] - Explicit Unicode literals

由 Armin Ronacher 撰寫 PEP。

PEP 3155: Qualified name for classes and functions

Functions and class objects have a new __qualname__ attribute representing the "path" from the module top-level to their definition. For global functions and classes, this is the same as __name__. For other functions and classes, it provides better information about where they were actually defined, and how they might be accessible from the global scope.

Example with (non-bound) methods:

>>> class C:
...     def meth(self):
...         pass
...
>>> C.meth.__name__
'meth'
>>> C.meth.__qualname__
'C.meth'

巢狀類別範例：

>>> class C:
...     class D:
...         def meth(self):
...             pass
...
>>> C.D.__name__
'D'
>>> C.D.__qualname__
'C.D'
>>> C.D.meth.__name__
'meth'
>>> C.D.meth.__qualname__
'C.D.meth'

巢狀函式範例：

>>> def outer():
...     def inner():
...         pass
...     return inner
...
>>> outer().__name__
'inner'
>>> outer().__qualname__
'outer.<locals>.inner'

The string representation of those objects is also changed to include the new, more precise information:

>>> str(C.D)
"<class '__main__.C.D'>"
>>> str(C.D.meth)
'<function C.D.meth at 0x7f46b9fe31e0>'

也參考

PEP 3155 [https://peps.python.org/pep-3155/] - Qualified name for classes and functions

由 Antoine Pitrou 撰寫 PEP 與實作。

PEP 412: Key-Sharing Dictionary

Dictionaries used for the storage of objects' attributes are now able to share part of their internal storage between each other (namely, the part which stores the keys and their respective hashes). This reduces the memory consumption of programs creating many instances of non-builtin types.

也參考

PEP 412 [https://peps.python.org/pep-0412/] - 密鑰共享字典

由 Mark Shannon 撰寫 PEP 與實作。

PEP 362：函式簽名物件

A new function inspect.signature() makes introspection of python callables easy and straightforward. A broad range of callables is supported: python functions, decorated or not, classes, and functools.partial() objects. New classes inspect.Signature, inspect.Parameter and inspect.BoundArguments hold information about the call signatures, such as, annotations, default values, parameters kinds, and bound arguments, which considerably simplifies writing decorators and any code that validates or amends calling signatures or arguments.

也參考

PEP 362 [https://peps.python.org/pep-0362/]: - 函式簽名物件

PEP 由 Brett Cannon、Yury Selivanov、Larry Hastings、Jiwon Seo 撰寫；由 Yury Selivanov 實作。

PEP 421：新增 sys.implementation

A new attribute on the sys module exposes details specific to the implementation of the currently running interpreter. The initial set of attributes on sys.implementation are name, version, hexversion, and cache_tag.

The intention of sys.implementation is to consolidate into one namespace the implementation-specific data used by the standard library. This allows different Python implementations to share a single standard library code base much more easily. In its initial state, sys.implementation holds only a small portion of the implementation-specific data. Over time that ratio will shift in order to make the standard library more portable.

One example of improved standard library portability is cache_tag. As of Python 3.3, sys.implementation.cache_tag is used by importlib to support PEP 3147 [https://peps.python.org/pep-3147/] compliance. Any Python implementation that uses importlib for its built-in import system may use cache_tag to control the caching behavior for modules.

SimpleNamespace

The implementation of sys.implementation also introduces a new type to Python: types.SimpleNamespace. In contrast to a mapping-based namespace, like dict, SimpleNamespace is attribute-based, like object. However, unlike object, SimpleNamespace instances are writable. This means that you can add, remove, and modify the namespace through normal attribute access.

也參考

PEP 421 [https://peps.python.org/pep-0421/] - 新增 sys.implementation

由 Eric Snow 撰寫 PEP 與實作。

使用 importlib 作為 import 的實作

bpo-2377 [https://bugs.python.org/issue?@action=redirect&bpo=2377] - Replace __import__ w/ importlib.__import__ bpo-13959 [https://bugs.python.org/issue?@action=redirect&bpo=13959] - Re-implement parts of imp in pure Python bpo-14605 [https://bugs.python.org/issue?@action=redirect&bpo=14605] - Make import machinery explicit bpo-14646 [https://bugs.python.org/issue?@action=redirect&bpo=14646] - Require loaders set __loader__ and __package__

The __import__() function is now powered by importlib.__import__(). This work leads to the completion of "phase 2" of PEP 302 [https://peps.python.org/pep-0302/]. There are multiple benefits to this change. First, it has allowed for more of the machinery powering import to be exposed instead of being implicit and hidden within the C code. It also provides a single implementation for all Python VMs supporting Python 3.3 to use, helping to end any VM-specific deviations in import semantics. And finally it eases the maintenance of import, allowing for future growth to occur.

For the common user, there should be no visible change in semantics. For those whose code currently manipulates import or calls import programmatically, the code changes that might possibly be required are covered in the Porting Python code section of this document.

新 API

One of the large benefits of this work is the exposure of what goes into making the import statement work. That means the various importers that were once implicit are now fully exposed as part of the importlib package.

The abstract base classes defined in importlib.abc have been expanded to properly delineate between meta path finders and path entry finders by introducing importlib.abc.MetaPathFinder and importlib.abc.PathEntryFinder, respectively. The old ABC of importlib.abc.Finder is now only provided for backwards-compatibility and does not enforce any method requirements.

In terms of finders, importlib.machinery.FileFinder exposes the mechanism used to search for source and bytecode files of a module. Previously this class was an implicit member of sys.path_hooks.

For loaders, the new abstract base class importlib.abc.FileLoader helps write a loader that uses the file system as the storage mechanism for a module's code. The loader for source files (importlib.machinery.SourceFileLoader), sourceless bytecode files (importlib.machinery.SourcelessFileLoader), and extension modules (importlib.machinery.ExtensionFileLoader) are now available for direct use.

ImportError now has name and path attributes which are set when there is relevant data to provide. The message for failed imports will also provide the full name of the module now instead of just the tail end of the module's name.

The importlib.invalidate_caches() function will now call the method with the same name on all finders cached in sys.path_importer_cache to help clean up any stored state as necessary.

明顯的變更

For potential required changes to code, see the Porting Python code section.

Beyond the expanse of what importlib now exposes, there are other visible changes to import. The biggest is that sys.meta_path and sys.path_hooks now store all of the meta path finders and path entry hooks used by import. Previously the finders were implicit and hidden within the C code of import instead of being directly exposed. This means that one can now easily remove or change the order of the various finders to fit one's needs.

Another change is that all modules have a __loader__ attribute, storing the loader used to create the module. PEP 302 [https://peps.python.org/pep-0302/] has been updated to make this attribute mandatory for loaders to implement, so in the future once 3rd-party loaders have been updated people will be able to rely on the existence of the attribute. Until such time, though, import is setting the module post-load.

Loaders are also now expected to set the __package__ attribute from PEP 366 [https://peps.python.org/pep-0366/]. Once again, import itself is already setting this on all loaders from importlib and import itself is setting the attribute post-load.

None is now inserted into sys.path_importer_cache when no finder can be found on sys.path_hooks. Since imp.NullImporter is not directly exposed on sys.path_hooks it could no longer be relied upon to always be available to use as a value representing no finder found.

All other changes relate to semantic changes which should be taken into consideration when updating code for Python 3.3, and thus should be read about in the Porting Python code section of this document.

（由 Brett Cannon 實作）

其他語言更動

對核心 Python 語言所做的一些較小的更改包括：

Added support for Unicode name aliases and named sequences. Both unicodedata.lookup() and '\N{...}' now resolve name aliases, and unicodedata.lookup() resolves named sequences too.

（由 Ezio Melotti 在 bpo-12753 [https://bugs.python.org/issue?@action=redirect&bpo=12753] 中貢獻。）

Unicode 資料庫更新至 UCD 版本 6.1.0

Equality comparisons on range() objects now return a result reflecting the equality of the underlying sequences generated by those range objects. (bpo-13201 [https://bugs.python.org/issue?@action=redirect&bpo=13201])

The count(), find(), rfind(), index() and rindex() methods of bytes and bytearray objects now accept an integer between 0 and 255 as their first argument.

（由 Petri Lehtinen 在 bpo-12170 [https://bugs.python.org/issue?@action=redirect&bpo=12170] 中貢獻。）

The rjust(), ljust(), and center() methods of bytes and bytearray now accept a bytearray for the fill argument. (Contributed by Petri Lehtinen in bpo-12380 [https://bugs.python.org/issue?@action=redirect&bpo=12380].)

New methods have been added to list and bytearray: copy() and clear() (bpo-10516 [https://bugs.python.org/issue?@action=redirect&bpo=10516]). Consequently, MutableSequence now also defines a clear() method (bpo-11388 [https://bugs.python.org/issue?@action=redirect&bpo=11388]).

Raw bytes literals can now be written rb"..." as well as br"...".

（由 Antoine Pitrou 在 bpo-13748 [https://bugs.python.org/issue?@action=redirect&bpo=13748] 中貢獻。）

dict.setdefault() now does only one lookup for the given key, making it atomic when used with built-in types.

（由 Filip Gruszczyński 在 bpo-13521 [https://bugs.python.org/issue?@action=redirect&bpo=13521] 中貢獻。）

The error messages produced when a function call does not match the function signature have been significantly improved.

（由 Benjamin Peterson 貢獻。）

A Finer-Grained Import Lock

Previous versions of CPython have always relied on a global import lock. This led to unexpected annoyances, such as deadlocks when importing a module would trigger code execution in a different thread as a side-effect. Clumsy workarounds were sometimes employed, such as the PyImport_ImportModuleNoBlock() C API function.

In Python 3.3, importing a module takes a per-module lock. This correctly serializes importation of a given module from multiple threads (preventing the exposure of incompletely initialized modules), while eliminating the aforementioned annoyances.

（由 Antoine Pitrou 在 bpo-9260 [https://bugs.python.org/issue?@action=redirect&bpo=9260] 中貢獻。）

內建函式和型別

open() gets a new opener parameter: the underlying file descriptor for the file object is then obtained by calling opener with (file, flags). It can be used to use custom flags like os.O_CLOEXEC for example. The 'x' mode was added: open for exclusive creation, failing if the file already exists.

print(): added the flush keyword argument. If the flush keyword argument is true, the stream is forcibly flushed.

hash(): hash randomization is enabled by default, see object.__hash__() and PYTHONHASHSEED.

The str type gets a new casefold() method: return a casefolded copy of the string, casefolded strings may be used for caseless matching. For example, 'ß'.casefold() returns 'ss'.

The sequence documentation has been substantially rewritten to better explain the binary/text sequence distinction and to provide specific documentation sections for the individual builtin sequence types (bpo-4966 [https://bugs.python.org/issue?@action=redirect&bpo=4966]).

新模組

faulthandler

This new debug module faulthandler contains functions to dump Python tracebacks explicitly, on a fault (a crash like a segmentation fault), after a timeout, or on a user signal. Call faulthandler.enable() to install fault handlers for the SIGSEGV, SIGFPE, SIGABRT, SIGBUS, and SIGILL signals. You can also enable them at startup by setting the PYTHONFAULTHANDLER environment variable or by using -X faulthandler command line option.

Example of a segmentation fault on Linux:

$ python -q -X faulthandler
>>> import ctypes
>>> ctypes.string_at(0)
Fatal Python error: Segmentation fault

Current thread 0x00007fb899f39700:
  File "/home/python/cpython/Lib/ctypes/__init__.py", line 486 in string_at
  File "<stdin>", line 1 in <module>
Segmentation fault

ipaddress

The new ipaddress module provides tools for creating and manipulating objects representing IPv4 and IPv6 addresses, networks and interfaces (i.e. an IP address associated with a specific IP subnet).

（由 Google 和 Peter Moody 在 PEP 3144 [https://peps.python.org/pep-3144/] 中貢獻。）

lzma

The newly added lzma module provides data compression and decompression using the LZMA algorithm, including support for the .xz and .lzma file formats.

（由 Nadeem Vawda 和 Per Øyvind Karlsen 在 bpo-6715 [https://bugs.python.org/issue?@action=redirect&bpo=6715] 中貢獻。）

改進的模組

abc

Improved support for abstract base classes containing descriptors composed with abstract methods. The recommended approach to declaring abstract descriptors is now to provide __isabstractmethod__ as a dynamically updated property. The built-in descriptors have been updated accordingly.

abc.abstractproperty 已被棄用，請改 property 和 abc.abstractmethod()。

abc.abstractclassmethod 已被棄用，請改用 classmethod 和 abc.abstractmethod()。

abc.abstractstaticmethod 已被棄用，請改用 staticmethod 和 abc.abstractmethod()。

（由 Darren Dale 在 bpo-11610 [https://bugs.python.org/issue?@action=redirect&bpo=11610] 中貢獻。）

abc.ABCMeta.register() now returns the registered subclass, which means it can now be used as a class decorator (bpo-10868 [https://bugs.python.org/issue?@action=redirect&bpo=10868]).

array

The array module supports the long long type using q and Q type codes.

（由 Oren Tirosh 和 Hirokazu Yamamoto 在 bpo-1172711 [https://bugs.python.org/issue?@action=redirect&bpo=1172711] 中貢獻。）

base64

ASCII-only Unicode strings are now accepted by the decoding functions of the base64 modern interface. For example, base64.b64decode('YWJj') returns b'abc'. (Contributed by Catalin Iacob in bpo-13641 [https://bugs.python.org/issue?@action=redirect&bpo=13641].)

binascii

In addition to the binary objects they normally accept, the a2b_ functions now all also accept ASCII-only strings as input. (Contributed by Antoine Pitrou in bpo-13637 [https://bugs.python.org/issue?@action=redirect&bpo=13637].)

bz2

The bz2 module has been rewritten from scratch. In the process, several new features have been added:

New bz2.open() function: open a bzip2-compressed file in binary or text mode.

bz2.BZ2File can now read from and write to arbitrary file-like objects, by means of its constructor's fileobj argument.

（由 Nadeem Vawda 在 bpo-5863 [https://bugs.python.org/issue?@action=redirect&bpo=5863] 中貢獻。）

bz2.BZ2File and bz2.decompress() can now decompress multi-stream inputs (such as those produced by the pbzip2 tool). bz2.BZ2File can now also be used to create this type of file, using the 'a' (append) mode.

（由 Nir Aides 在 bpo-1625 [https://bugs.python.org/issue?@action=redirect&bpo=1625] 中貢獻。）

bz2.BZ2File now implements all of the io.BufferedIOBase API, except for the detach() and truncate() methods.

codecs

The mbcs codec has been rewritten to handle correctly replace and ignore error handlers on all Windows versions. The mbcs codec now supports all error handlers, instead of only replace to encode and ignore to decode.

A new Windows-only codec has been added: cp65001 (bpo-13216 [https://bugs.python.org/issue?@action=redirect&bpo=13216]). It is the Windows code page 65001 (Windows UTF-8, CP_UTF8). For example, it is used by sys.stdout if the console output code page is set to cp65001 (e.g., using chcp 65001 command).

Multibyte CJK decoders now resynchronize faster. They only ignore the first byte of an invalid byte sequence. For example, b'\xff\n'.decode('gb2312', 'replace') now returns a \n after the replacement character.

(bpo-12016 [https://bugs.python.org/issue?@action=redirect&bpo=12016])

Incremental CJK codec encoders are no longer reset at each call to their encode() methods. For example:

>>> import codecs
>>> encoder = codecs.getincrementalencoder('hz')('strict')
>>> b''.join(encoder.encode(x) for x in '\u52ff\u65bd\u65bc\u4eba\u3002 Bye.')
b'~{NpJ)l6HK!#~} Bye.'

This example gives b'~{Np~}~{J)~}~{l6~}~{HK~}~{!#~} Bye.' with older Python versions.

(bpo-12100 [https://bugs.python.org/issue?@action=redirect&bpo=12100])

unicode_internal 編解碼器已被棄用。

collections

Addition of a new ChainMap class to allow treating a number of mappings as a single unit. (Written by Raymond Hettinger for bpo-11089 [https://bugs.python.org/issue?@action=redirect&bpo=11089], made public in bpo-11297 [https://bugs.python.org/issue?@action=redirect&bpo=11297].)

The abstract base classes have been moved in a new collections.abc module, to better differentiate between the abstract and the concrete collections classes. Aliases for ABCs are still present in the collections module to preserve existing imports. (bpo-11085 [https://bugs.python.org/issue?@action=redirect&bpo=11085])

The Counter class now supports the unary + and - operators, as well as the in-place operators +=, -=, |=, and &=. (Contributed by Raymond Hettinger in bpo-13121 [https://bugs.python.org/issue?@action=redirect&bpo=13121].)

contextlib

ExitStack now provides a solid foundation for programmatic manipulation of context managers and similar cleanup functionality. Unlike the previous contextlib.nested API (which was deprecated and removed), the new API is designed to work correctly regardless of whether context managers acquire their resources in their __init__ method (for example, file objects) or in their __enter__ method (for example, synchronisation objects from the threading module).

(bpo-13585 [https://bugs.python.org/issue?@action=redirect&bpo=13585])

crypt

Addition of salt and modular crypt format (hashing method) and the mksalt() function to the crypt module.

(bpo-10924 [https://bugs.python.org/issue?@action=redirect&bpo=10924])

curses

If the curses module is linked to the ncursesw library, use Unicode functions when Unicode strings or characters are passed (e.g. waddwstr()), and bytes functions otherwise (e.g. waddstr()).

Use the locale encoding instead of utf-8 to encode Unicode strings.

curses.window 有一個新的 curses.window.encoding 屬性。

curses.window 類別有一個新的 get_wch() 方法來獲取寬字元

The curses module has a new unget_wch() function to push a wide character so the next get_wch() will return it

（由 Iñigo Serna 在 bpo-6755 [https://bugs.python.org/issue?@action=redirect&bpo=6755] 中貢獻。）

datetime

Equality comparisons between naive and aware datetime instances now return False instead of raising TypeError (bpo-15006 [https://bugs.python.org/issue?@action=redirect&bpo=15006]).

New datetime.datetime.timestamp() method: Return POSIX timestamp corresponding to the datetime instance.

The datetime.datetime.strftime() method supports formatting years older than 1000.

The datetime.datetime.astimezone() method can now be called without arguments to convert datetime instance to the system timezone.

decimal

bpo-7652 [https://bugs.python.org/issue?@action=redirect&bpo=7652] - integrate fast native decimal arithmetic.

由 Stefan Krah 編寫的 C 模組和 libmpdec。

The new C version of the decimal module integrates the high speed libmpdec library for arbitrary precision correctly rounded decimal floating-point arithmetic. libmpdec conforms to IBM's General Decimal Arithmetic Specification.

Performance gains range from 10x for database applications to 100x for numerically intensive applications. These numbers are expected gains for standard precisions used in decimal floating-point arithmetic. Since the precision is user configurable, the exact figures may vary. For example, in integer bignum arithmetic the differences can be significantly higher.

The following table is meant as an illustration. Benchmarks are available at https://www.bytereef.org/mpdecimal/quickstart.html.

decimal.py

_decimal

speedup

pi

42.02s

0.345s

120x

telco

172.19s

5.68s

30x

psycopg

3.57s

0.29s

12x

功能

The FloatOperation signal optionally enables stricter semantics for mixing floats and Decimals.

If Python is compiled without threads, the C version automatically disables the expensive thread local context machinery. In this case, the variable HAVE_THREADS is set to False.

API 變更

The C module has the following context limits, depending on the machine architecture:

32 位元

64 位元

MAX_PREC

425000000

999999999999999999

MAX_EMAX

425000000

999999999999999999

MIN_EMIN

-425000000

-999999999999999999

In the context templates (DefaultContext, BasicContext and ExtendedContext) the magnitude of Emax and Emin has changed to 999999.

The Decimal constructor in decimal.py does not observe the context limits and converts values with arbitrary exponents or precision exactly. Since the C version has internal limits, the following scheme is used: If possible, values are converted exactly, otherwise InvalidOperation is raised and the result is NaN. In the latter case it is always possible to use create_decimal() in order to obtain a rounded or inexact value.

The power function in decimal.py is always correctly rounded. In the C version, it is defined in terms of the correctly rounded exp() and ln() functions, but the final result is only "almost always correctly rounded".

In the C version, the context dictionary containing the signals is a MutableMapping. For speed reasons, flags and traps always refer to the same MutableMapping that the context was initialized with. If a new signal dictionary is assigned, flags and traps are updated with the new values, but they do not reference the RHS dictionary.

Pickling a Context produces a different output in order to have a common interchange format for the Python and C versions.

The order of arguments in the Context constructor has been changed to match the order displayed by repr().

quantize() 方法中的 watchexp 參數已棄用。

email

Policy Framework

The email package now has a policy framework. A Policy is an object with several methods and properties that control how the email package behaves. The primary policy for Python 3.3 is the Compat32 policy, which provides backward compatibility with the email package in Python 3.2. A policy can be specified when an email message is parsed by a parser, or when a Message object is created, or when an email is serialized using a generator. Unless overridden, a policy passed to a parser is inherited by all the Message object and sub-objects created by the parser. By default a generator will use the policy of the Message object it is serializing. The default policy is compat32.

The minimum set of controls implemented by all policy objects are:

max_line_length

The maximum length, excluding the linesep character(s), individual lines may have when a Message is serialized. Defaults to 78.

linesep

The character used to separate individual lines when a Message is serialized. Defaults to \n.

cte_type

7bit or 8bit. 8bit applies only to a Bytes generator, and means that non-ASCII may be used where allowed by the protocol (or where it exists in the original input).

raise_on_defect

Causes a parser to raise error when defects are encountered instead of adding them to the Message object's defects list.

A new policy instance, with new settings, is created using the clone() method of policy objects. clone takes any of the above controls as keyword arguments. Any control not specified in the call retains its default value. Thus you can create a policy that uses \r\n linesep characters like this:

mypolicy = compat32.clone(linesep='\r\n')

Policies can be used to make the generation of messages in the format needed by your application simpler. Instead of having to remember to specify linesep='\r\n' in all the places you call a generator, you can specify it once, when you set the policy used by the parser or the Message, whichever your program uses to create Message objects. On the other hand, if you need to generate messages in multiple forms, you can still specify the parameters in the appropriate generator call. Or you can have custom policy instances for your different cases, and pass those in when you create the generator.

Provisional Policy with New Header API

While the policy framework is worthwhile all by itself, the main motivation for introducing it is to allow the creation of new policies that implement new features for the email package in a way that maintains backward compatibility for those who do not use the new policies. Because the new policies introduce a new API, we are releasing them in Python 3.3 as a provisional policy. Backwards incompatible changes (up to and including removal of the code) may occur if deemed necessary by the core developers.

The new policies are instances of EmailPolicy, and add the following additional controls:

refold_source

Controls whether or not headers parsed by a parser are refolded by the generator. It can be none, long, or all. The default is long, which means that source headers with a line longer than max_line_length get refolded. none means no line get refolded, and all means that all lines get refolded.

header_factory

A callable that take a name and value and produces a custom header object.

The header_factory is the key to the new features provided by the new policies. When one of the new policies is used, any header retrieved from a Message object is an object produced by the header_factory, and any time you set a header on a Message it becomes an object produced by header_factory. All such header objects have a name attribute equal to the header name. Address and Date headers have additional attributes that give you access to the parsed data of the header. This means you can now do things like this:

>>> m = Message(policy=SMTP)
>>> m['To'] = 'Éric <foo@example.com>'
>>> m['to']
'Éric <foo@example.com>'
>>> m['to'].addresses
(Address(display_name='Éric', username='foo', domain='example.com'),)
>>> m['to'].addresses[0].username
'foo'
>>> m['to'].addresses[0].display_name
'Éric'
>>> m['Date'] = email.utils.localtime()
>>> m['Date'].datetime
datetime.datetime(2012, 5, 25, 21, 39, 24, 465484, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000), 'EDT'))
>>> m['Date']
'Fri, 25 May 2012 21:44:27 -0400'
>>> print(m)
To: =?utf-8?q?=C3=89ric?= <foo@example.com>
Date: Fri, 25 May 2012 21:44:27 -0400

You will note that the unicode display name is automatically encoded as utf-8 when the message is serialized, but that when the header is accessed directly, you get the unicode version. This eliminates any need to deal with the email.header decode_header() or make_header() functions.

You can also create addresses from parts:

>>> m['cc'] = [Group('pals', [Address('Bob', 'bob', 'example.com'),
...                           Address('Sally', 'sally', 'example.com')]),
...            Address('Bonzo', addr_spec='bonz@laugh.com')]
>>> print(m)
To: =?utf-8?q?=C3=89ric?= <foo@example.com>
Date: Fri, 25 May 2012 21:44:27 -0400
cc: pals: Bob <bob@example.com>, Sally <sally@example.com>;, Bonzo <bonz@laugh.com>

解碼為 unicode 是自動完成的：

>>> m2 = message_from_string(str(m))
>>> m2['to']
'Éric <foo@example.com>'

When you parse a message, you can use the addresses and groups attributes of the header objects to access the groups and individual addresses:

>>> m2['cc'].addresses
(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com'), Address(display_name='Bonzo', username='bonz', domain='laugh.com'))
>>> m2['cc'].groups
(Group(display_name='pals', addresses=(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com')), Group(display_name=None, addresses=(Address(display_name='Bonzo', username='bonz', domain='laugh.com'),))

In summary, if you use one of the new policies, header manipulation works the way it ought to: your application works with unicode strings, and the email package transparently encodes and decodes the unicode to and from the RFC standard Content Transfer Encodings.

其他 API 變更

New BytesHeaderParser, added to the parser module to complement HeaderParser and complete the Bytes API.

新工具函式：

format_datetime(): given a datetime, produce a string formatted for use in an email header.

parsedate_to_datetime(): given a date string from an email header, convert it into an aware datetime, or a naive datetime if the offset is -0000.

localtime(): With no argument, returns the current local time as an aware datetime using the local timezone. Given an aware datetime, converts it into an aware datetime using the local timezone.

ftplib

ftplib.FTP now accepts a source_address keyword argument to specify the (host, port) to use as the source address in the bind call when creating the outgoing socket. (Contributed by Giampaolo Rodolà in bpo-8594 [https://bugs.python.org/issue?@action=redirect&bpo=8594].)

The FTP_TLS class now provides a new ccc() function to revert control channel back to plaintext. This can be useful to take advantage of firewalls that know how to handle NAT with non-secure FTP without opening fixed ports. (Contributed by Giampaolo Rodolà in bpo-12139 [https://bugs.python.org/issue?@action=redirect&bpo=12139].)

Added ftplib.FTP.mlsd() method which provides a parsable directory listing format and deprecates ftplib.FTP.nlst() and ftplib.FTP.dir(). (Contributed by Giampaolo Rodolà in bpo-11072 [https://bugs.python.org/issue?@action=redirect&bpo=11072].)

functools

The functools.lru_cache() decorator now accepts a typed keyword argument (that defaults to False to ensure that it caches values of different types that compare equal in separate cache slots. (Contributed by Raymond Hettinger in bpo-13227 [https://bugs.python.org/issue?@action=redirect&bpo=13227].)

gc

It is now possible to register callbacks invoked by the garbage collector before and after collection using the new callbacks list.

hmac

A new compare_digest() function has been added to prevent side channel attacks on digests through timing analysis. (Contributed by Nick Coghlan and Christian Heimes in bpo-15061 [https://bugs.python.org/issue?@action=redirect&bpo=15061].)

http

http.server.BaseHTTPRequestHandler now buffers the headers and writes them all at once when end_headers() is called. A new method flush_headers() can be used to directly manage when the accumulated headers are sent. (Contributed by Andrew Schaaf in bpo-3709 [https://bugs.python.org/issue?@action=redirect&bpo=3709].)

http.server now produces valid HTML 4.01 strict output. (Contributed by Ezio Melotti in bpo-13295 [https://bugs.python.org/issue?@action=redirect&bpo=13295].)

http.client.HTTPResponse now has a readinto() method, which means it can be used as an io.RawIOBase class. (Contributed by John Kuhn in bpo-13464 [https://bugs.python.org/issue?@action=redirect&bpo=13464].)

html

html.parser.HTMLParser is now able to parse broken markup without raising errors, therefore the strict argument of the constructor and the HTMLParseError exception are now deprecated. The ability to parse broken markup is the result of a number of bug fixes that are also available on the latest bug fix releases of Python 2.7/3.2. (Contributed by Ezio Melotti in bpo-15114 [https://bugs.python.org/issue?@action=redirect&bpo=15114], and bpo-14538 [https://bugs.python.org/issue?@action=redirect&bpo=14538], bpo-13993 [https://bugs.python.org/issue?@action=redirect&bpo=13993], bpo-13960 [https://bugs.python.org/issue?@action=redirect&bpo=13960], bpo-13358 [https://bugs.python.org/issue?@action=redirect&bpo=13358], bpo-1745761 [https://bugs.python.org/issue?@action=redirect&bpo=1745761], bpo-755670 [https://bugs.python.org/issue?@action=redirect&bpo=755670], bpo-13357 [https://bugs.python.org/issue?@action=redirect&bpo=13357], bpo-12629 [https://bugs.python.org/issue?@action=redirect&bpo=12629], bpo-1200313 [https://bugs.python.org/issue?@action=redirect&bpo=1200313], bpo-670664 [https://bugs.python.org/issue?@action=redirect&bpo=670664], bpo-13273 [https://bugs.python.org/issue?@action=redirect&bpo=13273], bpo-12888 [https://bugs.python.org/issue?@action=redirect&bpo=12888], bpo-7311 [https://bugs.python.org/issue?@action=redirect&bpo=7311].)

A new html5 dictionary that maps HTML5 named character references to the equivalent Unicode character(s) (e.g. html5['gt;'] == '>') has been added to the html.entities module. The dictionary is now also used by HTMLParser. (Contributed by Ezio Melotti in bpo-11113 [https://bugs.python.org/issue?@action=redirect&bpo=11113] and bpo-15156 [https://bugs.python.org/issue?@action=redirect&bpo=15156].)

imaplib

The IMAP4_SSL constructor now accepts an SSLContext parameter to control parameters of the secure channel.

（由 Sijin Joseph 在 bpo-8808 [https://bugs.python.org/issue?@action=redirect&bpo=8808] 中貢獻。）

inspect

A new getclosurevars() function has been added. This function reports the current binding of all names referenced from the function body and where those names were resolved, making it easier to verify correct internal state when testing code that relies on stateful closures.

（由 Meador Inge 與 Nick Coghlan 在 bpo-13062 [https://bugs.python.org/issue?@action=redirect&bpo=13062] 中貢獻。）

A new getgeneratorlocals() function has been added. This function reports the current binding of local variables in the generator's stack frame, making it easier to verify correct internal state when testing generators.

（由 Meador Inge 於 bpo-15153 [https://bugs.python.org/issue?@action=redirect&bpo=15153] 中貢獻。）

io

The open() function has a new 'x' mode that can be used to exclusively create a new file, and raise a FileExistsError if the file already exists. It is based on the C11 'x' mode to fopen().

（由 David Townshend 於 bpo-12760 [https://bugs.python.org/issue?@action=redirect&bpo=12760] 中貢獻。）

The constructor of the TextIOWrapper class has a new write_through optional argument. If write_through is True, calls to write() are guaranteed not to be buffered: any data written on the TextIOWrapper object is immediately handled to its underlying binary buffer.

itertools

accumulate() now takes an optional func argument for providing a user-supplied binary function.

logging

The basicConfig() function now supports an optional handlers argument taking an iterable of handlers to be added to the root logger.

A class level attribute append_nul has been added to SysLogHandler to allow control of the appending of the NUL (\000) byte to syslog records, since for some daemons it is required while for others it is passed through to the log.

math

The math module has a new function, log2(), which returns the base-2 logarithm of x.

（由 Mark Dickinson 於 bpo-11888 [https://bugs.python.org/issue?@action=redirect&bpo=11888] 中撰寫）

mmap

The read() method is now more compatible with other file-like objects: if the argument is omitted or specified as None, it returns the bytes from the current file position to the end of the mapping. (Contributed by Petri Lehtinen in bpo-12021 [https://bugs.python.org/issue?@action=redirect&bpo=12021].)

multiprocessing

The new multiprocessing.connection.wait() function allows polling multiple objects (such as connections, sockets and pipes) with a timeout. (Contributed by Richard Oudkerk in bpo-12328 [https://bugs.python.org/issue?@action=redirect&bpo=12328].)

multiprocessing.connection.Connection objects can now be transferred over multiprocessing connections. (Contributed by Richard Oudkerk in bpo-4892 [https://bugs.python.org/issue?@action=redirect&bpo=4892].)

multiprocessing.Process now accepts a daemon keyword argument to override the default behavior of inheriting the daemon flag from the parent process (bpo-6064 [https://bugs.python.org/issue?@action=redirect&bpo=6064]).

New attribute multiprocessing.Process.sentinel allows a program to wait on multiple Process objects at one time using the appropriate OS primitives (for example, select on posix systems).

New methods multiprocessing.pool.Pool.starmap() and starmap_async() provide itertools.starmap() equivalents to the existing multiprocessing.pool.Pool.map() and map_async() functions. (Contributed by Hynek Schlawack in bpo-12708 [https://bugs.python.org/issue?@action=redirect&bpo=12708].)

nntplib

The nntplib.NNTP class now supports the context management protocol to unconditionally consume socket.error exceptions and to close the NNTP connection when done:

>>> from nntplib import NNTP
>>> with NNTP('news.gmane.org') as n:
...     n.group('gmane.comp.python.committers')
...
('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, 'gmane.comp.python.committers')
>>>

（由 Giampaolo Rodolà 於 bpo-9795 [https://bugs.python.org/issue?@action=redirect&bpo=9795] 中貢獻。）

os

The os module has a new pipe2() function that makes it possible to create a pipe with O_CLOEXEC or O_NONBLOCK flags set atomically. This is especially useful to avoid race conditions in multi-threaded programs.

The os module has a new sendfile() function which provides an efficient "zero-copy" way for copying data from one file (or socket) descriptor to another. The phrase "zero-copy" refers to the fact that all of the copying of data between the two descriptors is done entirely by the kernel, with no copying of data into userspace buffers. sendfile() can be used to efficiently copy data from a file on disk to a network socket, e.g. for downloading a file.

（由 Ross Lagerwall 和 Giampaolo Rodolà 於 bpo-10882 [https://bugs.python.org/issue?@action=redirect&bpo=10882] 提交補丁。）

To avoid race conditions like symlink attacks and issues with temporary files and directories, it is more reliable (and also faster) to manipulate file descriptors instead of file names. Python 3.3 enhances existing functions and introduces new functions to work on file descriptors (bpo-4761 [https://bugs.python.org/issue?@action=redirect&bpo=4761], bpo-10755 [https://bugs.python.org/issue?@action=redirect&bpo=10755] and bpo-14626 [https://bugs.python.org/issue?@action=redirect&bpo=14626]).

The os module has a new fwalk() function similar to walk() except that it also yields file descriptors referring to the directories visited. This is especially useful to avoid symlink races.

The following functions get new optional dir_fd (paths relative to directory descriptors) and/or follow_symlinks (not following symlinks): access(), chflags(), chmod(), chown(), link(), lstat(), mkdir(), mkfifo(), mknod(), open(), readlink(), remove(), rename(), replace(), rmdir(), stat(), symlink(), unlink(), utime(). Platform support for using these parameters can be checked via the sets os.supports_dir_fd and os.supports_follow_symlinks.

The following functions now support a file descriptor for their path argument: chdir(), chmod(), chown(), execve(), listdir(), pathconf(), exists(), stat(), statvfs(), utime(). Platform support for this can be checked via the os.supports_fd set.

access() accepts an effective_ids keyword argument to turn on using the effective uid/gid rather than the real uid/gid in the access check. Platform support for this can be checked via the supports_effective_ids set.

The os module has two new functions: getpriority() and setpriority(). They can be used to get or set process niceness/priority in a fashion similar to os.nice() but extended to all processes instead of just the current one.

（由 Giampaolo Rodolà 於 bpo-10784 [https://bugs.python.org/issue?@action=redirect&bpo=10784] 提交補丁。）

The new os.replace() function allows cross-platform renaming of a file with overwriting the destination. With os.rename(), an existing destination file is overwritten under POSIX, but raises an error under Windows. (Contributed by Antoine Pitrou in bpo-8828 [https://bugs.python.org/issue?@action=redirect&bpo=8828].)

The stat family of functions (stat(), fstat(), and lstat()) now support reading a file's timestamps with nanosecond precision. Symmetrically, utime() can now write file timestamps with nanosecond precision. (Contributed by Larry Hastings in bpo-14127 [https://bugs.python.org/issue?@action=redirect&bpo=14127].)

The new os.get_terminal_size() function queries the size of the terminal attached to a file descriptor. See also shutil.get_terminal_size(). (Contributed by Zbigniew Jędrzejewski-Szmek in bpo-13609 [https://bugs.python.org/issue?@action=redirect&bpo=13609].)

New functions to support Linux extended attributes (bpo-12720 [https://bugs.python.org/issue?@action=redirect&bpo=12720]): getxattr(), listxattr(), removexattr(), setxattr().

New interface to the scheduler. These functions control how a process is allocated CPU time by the operating system. New functions: sched_get_priority_max(), sched_get_priority_min(), sched_getaffinity(), sched_getparam(), sched_getscheduler(), sched_rr_get_interval(), sched_setaffinity(), sched_setparam(), sched_setscheduler(), sched_yield(),

New functions to control the file system:

posix_fadvise(): Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations.

posix_fallocate(): Ensures that enough disk space is allocated for a file.

sync(): Force write of everything to disk.

其他新的 posix 函式：

lockf(): Apply, test or remove a POSIX lock on an open file descriptor.

pread(): Read from a file descriptor at an offset, the file offset remains unchanged.

pwrite(): Write to a file descriptor from an offset, leaving the file offset unchanged.

readv(): Read from a file descriptor into a number of writable buffers.

truncate(): Truncate the file corresponding to path, so that it is at most length bytes in size.

waitid(): Wait for the completion of one or more child processes.

writev(): Write the contents of buffers to a file descriptor, where buffers is an arbitrary sequence of buffers.

getgrouplist() (bpo-9344 [https://bugs.python.org/issue?@action=redirect&bpo=9344]): Return list of group ids that specified user belongs to.

times() and uname(): Return type changed from a tuple to a tuple-like object with named attributes.

Some platforms now support additional constants for the lseek() function, such as os.SEEK_HOLE and os.SEEK_DATA.

New constants RTLD_LAZY, RTLD_NOW, RTLD_GLOBAL, RTLD_LOCAL, RTLD_NODELETE, RTLD_NOLOAD, and RTLD_DEEPBIND are available on platforms that support them. These are for use with the sys.setdlopenflags() function, and supersede the similar constants defined in ctypes and DLFCN. (Contributed by Victor Stinner in bpo-13226 [https://bugs.python.org/issue?@action=redirect&bpo=13226].)

os.symlink() now accepts (and ignores) the target_is_directory keyword argument on non-Windows platforms, to ease cross-platform support.

pdb

Tab-completion is now available not only for command names, but also their arguments. For example, for the break command, function and file names are completed.

（由 Georg Brandl 在 bpo-14210 [https://bugs.python.org/issue?@action=redirect&bpo=14210] 中貢獻）

pickle

pickle.Pickler objects now have an optional dispatch_table attribute allowing per-pickler reduction functions to be set.

（由 Richard Oudkerk 在 bpo-14166 [https://bugs.python.org/issue?@action=redirect&bpo=14166] 中貢獻。）

pydoc

The Tk GUI and the serve() function have been removed from the pydoc module: pydoc -g and serve() have been deprecated in Python 3.2.

re

str regular expressions now support \u and \U escapes.

（由 Serhiy Storchaka 在 bpo-3665 [https://bugs.python.org/issue?@action=redirect&bpo=3665] 中貢獻。）

sched

run() now accepts a blocking parameter which when set to false makes the method execute the scheduled events due to expire soonest (if any) and then return immediately. This is useful in case you want to use the scheduler in non-blocking applications. (Contributed by Giampaolo Rodolà in bpo-13449 [https://bugs.python.org/issue?@action=redirect&bpo=13449].)

scheduler class can now be safely used in multi-threaded environments. (Contributed by Josiah Carlson and Giampaolo Rodolà in bpo-8684 [https://bugs.python.org/issue?@action=redirect&bpo=8684].)

timefunc and delayfunct parameters of scheduler class constructor are now optional and defaults to time.time() and time.sleep() respectively. (Contributed by Chris Clark in bpo-13245 [https://bugs.python.org/issue?@action=redirect&bpo=13245].)

enter() 和 enterabs() argument 參數現在是可選的。（由 Chris Clark 在 bpo-13245 [https://bugs.python.org/issue?@action=redirect&bpo=13245] 中貢獻。）

enter() 和 enterabs() 現在接受 kwargs 參數。（由 Chris Clark 在 bpo-13245 [https://bugs.python.org/issue?@action=redirect&bpo=13245] 中貢獻。）

select

Solaris and derivative platforms have a new class select.devpoll for high performance asynchronous sockets via /dev/poll. (Contributed by Jesús Cea Avión in bpo-6397 [https://bugs.python.org/issue?@action=redirect&bpo=6397].)

shlex

The previously undocumented helper function quote from the pipes modules has been moved to the shlex module and documented. quote() properly escapes all characters in a string that might be otherwise given special meaning by the shell.

shutil

新功能：

disk_usage(): provides total, used and free disk space statistics. (Contributed by Giampaolo Rodolà in bpo-12442 [https://bugs.python.org/issue?@action=redirect&bpo=12442].)

chown(): allows one to change user and/or group of the given path also specifying the user/group names and not only their numeric ids. (Contributed by Sandro Tosi in bpo-12191 [https://bugs.python.org/issue?@action=redirect&bpo=12191].)

shutil.get_terminal_size(): returns the size of the terminal window to which the interpreter is attached. (Contributed by Zbigniew Jędrzejewski-Szmek in bpo-13609 [https://bugs.python.org/issue?@action=redirect&bpo=13609].)

copy2() and copystat() now preserve file timestamps with nanosecond precision on platforms that support it. They also preserve file "extended attributes" on Linux. (Contributed by Larry Hastings in bpo-14127 [https://bugs.python.org/issue?@action=redirect&bpo=14127] and bpo-15238 [https://bugs.python.org/issue?@action=redirect&bpo=15238].)

Several functions now take an optional symlinks argument: when that parameter is true, symlinks aren't dereferenced and the operation instead acts on the symlink itself (or creates one, if relevant). (Contributed by Hynek Schlawack in bpo-12715 [https://bugs.python.org/issue?@action=redirect&bpo=12715].)

When copying files to a different file system, move() now handles symlinks the way the posix mv command does, recreating the symlink rather than copying the target file contents. (Contributed by Jonathan Niehof in bpo-9993 [https://bugs.python.org/issue?@action=redirect&bpo=9993].) move() now also returns the dst argument as its result.

rmtree() is now resistant to symlink attacks on platforms which support the new dir_fd parameter in os.open() and os.unlink(). (Contributed by Martin von Löwis and Hynek Schlawack in bpo-4489 [https://bugs.python.org/issue?@action=redirect&bpo=4489].)

signal

signal 模組有了新的函式：

pthread_sigmask(): fetch and/or change the signal mask of the calling thread (Contributed by Jean-Paul Calderone in bpo-8407 [https://bugs.python.org/issue?@action=redirect&bpo=8407]);

pthread_kill()：向執行緒發送訊號；

sigpending()：檢查未定的函式；

sigwait()：等待訊號；

sigwaitinfo()：等待訊號，回傳有關該訊號的詳細資訊；

sigtimedwait()：類似於 sigwaitinfo() 但有超時。

The signal handler writes the signal number as a single byte instead of a nul byte into the wakeup file descriptor. So it is possible to wait more than one signal and know which signals were raised.

signal.signal() 和 signal.siginterrupt() 會引發 OSError，而不是 RuntimeError：OSError 有一個 errno 屬性。

smtpd

The smtpd module now supports RFC 5321 [https://datatracker.ietf.org/doc/html/rfc5321.html] (extended SMTP) and RFC 1870 [https://datatracker.ietf.org/doc/html/rfc1870.html] (size extension). Per the standard, these extensions are enabled if and only if the client initiates the session with an EHLO command.

(Initial ELHO support by Alberto Trevino. Size extension by Juhana Jauhiainen. Substantial additional work on the patch contributed by Michele Orrù and Dan Boswell. bpo-8739 [https://bugs.python.org/issue?@action=redirect&bpo=8739])

smtplib

The SMTP, SMTP_SSL, and LMTP classes now accept a source_address keyword argument to specify the (host, port) to use as the source address in the bind call when creating the outgoing socket. (Contributed by Paulo Scardine in bpo-11281 [https://bugs.python.org/issue?@action=redirect&bpo=11281].)

SMTP 現在支援情境管理協定，允許在 with 陳述式中使用 SMTP 實例。（由 Giampaolo Rodolà 在 bpo-11289 [https://bugs.python.org/issue?@action=redirect&bpo=11289] 中貢獻。）

SMTP_SSL 構造函式和 starttls() 方法現在接受 SSLContext 參數來控制安全通道的參數。（由 Kasun Herath 在 bpo-8809 [https://bugs.python.org/issue?@action=redirect&bpo=8809] 中貢獻。）

socket

當底層平台支援時，socket 類現在公開了額外的方法來處理輔助資料：

sendmsg()

recvmsg()

recvmsg_into()

（由 David Watson 在 bpo-6560 [https://bugs.python.org/issue?@action=redirect&bpo=6560] 中貢獻，其基於 Heiko Wundram 的早期補丁）

socket 類別現在支援 Linux (https://lwn.net/Articles/253425) 上的 PF_CAN 協定系列 (https://en.wikipedia.org/wiki/Socketcan)。

（在 bpo-10141 [https://bugs.python.org/issue?@action=redirect&bpo=10141] 中由 Matthias Fuchs 貢獻、並由 Tiago Gonçalves 更新。）

socket 類別現在支援 PF_RDS 協定系列（https://en.wikipedia.org/wiki/Reliable_Datagram_Sockets 和 https://oss.oracle.com/projects/rds [https://web.archive.org/web/20130115155505/https://oss.oracle.com/projects/rds/]）。

socket 類別現在支援 OS X 上的 PF_SYSTEM 協定系列。（由 Michael Goderbauer 在 bpo-13777 [https://bugs.python.org/issue?@action=redirect&bpo=13777] 中貢獻。）

New function sethostname() allows the hostname to be set on Unix systems if the calling process has sufficient privileges. (Contributed by Ross Lagerwall in bpo-10866 [https://bugs.python.org/issue?@action=redirect&bpo=10866].)

socketserver

BaseServer now has an overridable method service_actions() that is called by the serve_forever() method in the service loop. ForkingMixIn now uses this to clean up zombie child processes. (Contributed by Justin Warkentin in bpo-11109 [https://bugs.python.org/issue?@action=redirect&bpo=11109].)

sqlite3

New sqlite3.Connection method set_trace_callback() can be used to capture a trace of all sql commands processed by sqlite. (Contributed by Torsten Landschoff in bpo-11688 [https://bugs.python.org/issue?@action=redirect&bpo=11688].)

ssl

ssl 模組有兩個新的隨機生成函式：

RAND_bytes()：生成加密的強偽隨機位元組。

RAND_pseudo_bytes()：生成偽隨機位元組。

（由 Victor Stinner 在 bpo-12049 [https://bugs.python.org/issue?@action=redirect&bpo=12049] 中貢獻。）

The ssl module now exposes a finer-grained exception hierarchy in order to make it easier to inspect the various kinds of errors. (Contributed by Antoine Pitrou in bpo-11183 [https://bugs.python.org/issue?@action=redirect&bpo=11183].)

load_cert_chain() now accepts a password argument to be used if the private key is encrypted. (Contributed by Adam Simpkins in bpo-12803 [https://bugs.python.org/issue?@action=redirect&bpo=12803].)

Diffie-Hellman key exchange, both regular and Elliptic Curve-based, is now supported through the load_dh_params() and set_ecdh_curve() methods. (Contributed by Antoine Pitrou in bpo-13626 [https://bugs.python.org/issue?@action=redirect&bpo=13626] and bpo-13627 [https://bugs.python.org/issue?@action=redirect&bpo=13627].)

SSL sockets have a new get_channel_binding() method allowing the implementation of certain authentication mechanisms such as SCRAM-SHA-1-PLUS. (Contributed by Jacek Konieczny in bpo-12551 [https://bugs.python.org/issue?@action=redirect&bpo=12551].)

You can query the SSL compression algorithm used by an SSL socket, thanks to its new compression() method. The new attribute OP_NO_COMPRESSION can be used to disable compression. (Contributed by Antoine Pitrou in bpo-13634 [https://bugs.python.org/issue?@action=redirect&bpo=13634].)

Support has been added for the Next Protocol Negotiation extension using the ssl.SSLContext.set_npn_protocols() method. (Contributed by Colin Marc in bpo-14204 [https://bugs.python.org/issue?@action=redirect&bpo=14204].)

SSL errors can now be introspected more easily thanks to library and reason attributes. (Contributed by Antoine Pitrou in bpo-14837 [https://bugs.python.org/issue?@action=redirect&bpo=14837].)

The get_server_certificate() function now supports IPv6. (Contributed by Charles-François Natali in bpo-11811 [https://bugs.python.org/issue?@action=redirect&bpo=11811].)

New attribute OP_CIPHER_SERVER_PREFERENCE allows setting SSLv3 server sockets to use the server's cipher ordering preference rather than the client's (bpo-13635 [https://bugs.python.org/issue?@action=redirect&bpo=13635]).

stat

The undocumented tarfile.filemode function has been moved to stat.filemode(). It can be used to convert a file's mode to a string of the form '-rwxrwxrwx'.

（由 Giampaolo Rodolà 在 bpo-14807 [https://bugs.python.org/issue?@action=redirect&bpo=14807] 中貢獻。）

struct

The struct module now supports ssize_t and size_t via the new codes n and N, respectively. (Contributed by Antoine Pitrou in bpo-3163 [https://bugs.python.org/issue?@action=redirect&bpo=3163].)

subprocess

Command strings can now be bytes objects on posix platforms. (Contributed by Victor Stinner in bpo-8513 [https://bugs.python.org/issue?@action=redirect&bpo=8513].)

A new constant DEVNULL allows suppressing output in a platform-independent fashion. (Contributed by Ross Lagerwall in bpo-5870 [https://bugs.python.org/issue?@action=redirect&bpo=5870].)

sys

The sys module has a new thread_info named tuple holding information about the thread implementation (bpo-11223 [https://bugs.python.org/issue?@action=redirect&bpo=11223]).

tarfile

tarfile 現在透過 lzma 模組支援 lzma 編碼。（由 Lars Gustäbel 在 bpo-5689 [https://bugs.python.org/issue?@action=redirect&bpo=5689] 中貢獻。）

tempfile

tempfile.SpooledTemporaryFile's truncate() method now accepts a size parameter. (Contributed by Ryan Kelly in bpo-9957 [https://bugs.python.org/issue?@action=redirect&bpo=9957].)

textwrap

The textwrap module has a new indent() that makes it straightforward to add a common prefix to selected lines in a block of text (bpo-13857 [https://bugs.python.org/issue?@action=redirect&bpo=13857]).

threading

threading.Condition, threading.Semaphore, threading.BoundedSemaphore, threading.Event, and threading.Timer, all of which used to be factory functions returning a class instance, are now classes and may be subclassed. (Contributed by Éric Araujo in bpo-10968 [https://bugs.python.org/issue?@action=redirect&bpo=10968].)

The threading.Thread constructor now accepts a daemon keyword argument to override the default behavior of inheriting the daemon flag value from the parent thread (bpo-6064 [https://bugs.python.org/issue?@action=redirect&bpo=6064]).

The formerly private function _thread.get_ident is now available as the public function threading.get_ident(). This eliminates several cases of direct access to the _thread module in the stdlib. Third party code that used _thread.get_ident should likewise be changed to use the new public interface.

time

PEP 418 [https://peps.python.org/pep-0418/] 向 time 模組新增了新功能：

get_clock_info()：取得時鐘資訊。

monotonic()：單調時鐘（不能倒退），不受系統時鐘更新的影響。

perf_counter(): Performance counter with the highest available resolution to measure a short duration.

process_time()：目前行程的系統和使用者 CPU 時間總和。

其他新功能：

clock_getres()、clock_gettime() 和 clock_settime() 函式帶有 CLOCK_xxx 常數。（由 Victor Stinner 在 bpo-10278 [https://bugs.python.org/issue?@action=redirect&bpo=10278] 中貢獻。）

To improve cross platform consistency, sleep() now raises a ValueError when passed a negative sleep value. Previously this was an error on posix, but produced an infinite sleep on Windows.

types

Add a new types.MappingProxyType class: Read-only proxy of a mapping. (bpo-14386 [https://bugs.python.org/issue?@action=redirect&bpo=14386])

The new functions types.new_class() and types.prepare_class() provide support for PEP 3115 [https://peps.python.org/pep-3115/] compliant dynamic type creation. (bpo-14588 [https://bugs.python.org/issue?@action=redirect&bpo=14588])

unittest

assertRaises(), assertRaisesRegex(), assertWarns(), and assertWarnsRegex() now accept a keyword argument msg when used as context managers. (Contributed by Ezio Melotti and Winston Ewert in bpo-10775 [https://bugs.python.org/issue?@action=redirect&bpo=10775].)

unittest.TestCase.run() 現在回傳 TestResult 物件。

urllib

The Request class, now accepts a method argument used by get_method() to determine what HTTP method should be used. For example, this will send a 'HEAD' request:

>>> urlopen(Request('https://www.python.org', method='HEAD'))

(bpo-1673007 [https://bugs.python.org/issue?@action=redirect&bpo=1673007])

webbrowser

The webbrowser module supports more "browsers": Google Chrome (named chrome, chromium, chrome-browser or chromium-browser depending on the version and operating system), and the generic launchers xdg-open, from the FreeDesktop.org project, and gvfs-open, which is the default URI handler for GNOME 3. (The former contributed by Arnaud Calmettes in bpo-13620 [https://bugs.python.org/issue?@action=redirect&bpo=13620], the latter by Matthias Klose in bpo-14493 [https://bugs.python.org/issue?@action=redirect&bpo=14493].)

xml.etree.ElementTree

The xml.etree.ElementTree module now imports its C accelerator by default; there is no longer a need to explicitly import xml.etree.cElementTree (this module stays for backwards compatibility, but is now deprecated). In addition, the iter family of methods of Element has been optimized (rewritten in C). The module's documentation has also been greatly improved with added examples and a more detailed reference.

zlib

New attribute zlib.Decompress.eof makes it possible to distinguish between a properly formed compressed stream and an incomplete or truncated one. (Contributed by Nadeem Vawda in bpo-12646 [https://bugs.python.org/issue?@action=redirect&bpo=12646].)

New attribute zlib.ZLIB_RUNTIME_VERSION reports the version string of the underlying zlib library that is loaded at runtime. (Contributed by Torsten Landschoff in bpo-12306 [https://bugs.python.org/issue?@action=redirect&bpo=12306].)

最佳化

Major performance enhancements have been added:

Thanks to PEP 393 [https://peps.python.org/pep-0393/], some operations on Unicode strings have been optimized:

the memory footprint is divided by 2 to 4 depending on the text

encode an ASCII string to UTF-8 doesn't need to encode characters anymore, the UTF-8 representation is shared with the ASCII representation

the UTF-8 encoder has been optimized

repeating a single ASCII letter and getting a substring of an ASCII string is 4 times faster

UTF-8 is now 2x to 4x faster. UTF-16 encoding is now up to 10x faster.

（由 Serhiy Storchaka 於 bpo-14624 [https://bugs.python.org/issue?@action=redirect&bpo=14624]、bpo-14738 [https://bugs.python.org/issue?@action=redirect&bpo=14738] 和 bpo-15026 [https://bugs.python.org/issue?@action=redirect&bpo=15026] 貢獻。）

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

新的 PEP 3118 [https://peps.python.org/pep-3118/] 相關功能：

PyMemoryView_FromMemory()

PEP 393 [https://peps.python.org/pep-0393/] added new Unicode types, macros and functions:

高階 API：

PyUnicode_CopyCharacters()

PyUnicode_FindChar()

PyUnicode_GetLength(), PyUnicode_GET_LENGTH

PyUnicode_New()

PyUnicode_Substring()

PyUnicode_ReadChar(), PyUnicode_WriteChar()

低階 API：

Py_UCS1、Py_UCS2、Py_UCS4 型別

PyASCIIObject 和 PyCompactUnicodeObject 結構

PyUnicode_READY

PyUnicode_FromKindAndData()

PyUnicode_AsUCS4(), PyUnicode_AsUCS4Copy()

PyUnicode_DATA, PyUnicode_1BYTE_DATA, PyUnicode_2BYTE_DATA, PyUnicode_4BYTE_DATA

PyUnicode_KIND with PyUnicode_Kind enum: PyUnicode_WCHAR_KIND, PyUnicode_1BYTE_KIND, PyUnicode_2BYTE_KIND, PyUnicode_4BYTE_KIND

PyUnicode_READ, PyUnicode_READ_CHAR, PyUnicode_WRITE

PyUnicode_MAX_CHAR_VALUE

PyArg_ParseTuple 現在接受 bytearray 為 c 格式 (bpo-12380 [https://bugs.python.org/issue?@action=redirect&bpo=12380])。

已棄用

不支援的作業系統

由於缺乏維護者，OS/2 和 VMS 不再受支援。

Windows 2000 and Windows platforms which set COMSPEC to command.com are no longer supported due to maintenance burden.

OSF 支援在 3.2 中已棄用，現已完全刪除。

已棄用的 Python 模組、函式和方法

Passing a non-empty string to object.__format__() is deprecated, and will produce a TypeError in Python 3.4 (bpo-9856 [https://bugs.python.org/issue?@action=redirect&bpo=9856]).

The unicode_internal codec has been deprecated because of the PEP 393 [https://peps.python.org/pep-0393/], use UTF-8, UTF-16 (utf-16-le or utf-16-be), or UTF-32 (utf-32-le or utf-32-be)

ftplib.FTP.nlst() 和 ftplib.FTP.dir()：使用 ftplib.FTP.mlsd()

platform.popen()：使用 subprocess 模組。請特別檢查 Replacing Older Functions with the subprocess Module 部分 (bpo-11377 [https://bugs.python.org/issue?@action=redirect&bpo=11377])。

bpo-13374 [https://bugs.python.org/issue?@action=redirect&bpo=13374]: The Windows bytes API has been deprecated in the os module. Use Unicode filenames, instead of bytes filenames, to not depend on the ANSI code page anymore and to support any filename.

bpo-13988 [https://bugs.python.org/issue?@action=redirect&bpo=13988]: The xml.etree.cElementTree module is deprecated. The accelerator is used automatically whenever available.

The behaviour of time.clock() depends on the platform: use the new time.perf_counter() or time.process_time() function instead, depending on your requirements, to have a well defined behaviour.

os.stat_float_times() 函式已棄用。

abc 模組：

abc.abstractproperty 已被棄用，請改 property 和 abc.abstractmethod()。

abc.abstractclassmethod 已被棄用，請改用 classmethod 和 abc.abstractmethod()。

abc.abstractstaticmethod 已被棄用，請改用 staticmethod 和 abc.abstractmethod()。

importlib 套件：

importlib.abc.SourceLoader.path_mtime() is now deprecated in favour of importlib.abc.SourceLoader.path_stats() as bytecode files now store both the modification time and size of the source file the bytecode file was compiled from.

C API 中已棄用的函式和型別

Py_UNICODE 已被 PEP 393 [https://peps.python.org/pep-0393/] 棄用，並將在 Python 4 中刪除。所有使用此型別的函式均已棄用：

Unicode functions and methods using Py_UNICODE and Py_UNICODE* types:

PyUnicode_FromUnicode：使用 PyUnicode_FromWideChar() 或 PyUnicode_FromKindAndData()

PyUnicode_AS_UNICODE、PyUnicode_AsUnicode()、PyUnicode_AsUnicodeAndSize()：使用 PyUnicode_AsWideCharString()

PyUnicode_AS_DATA：將 PyUnicode_DATA 與 PyUnicode_READ 和 PyUnicode_WRITE 一起使用

PyUnicode_GET_SIZE、PyUnicode_GetSize()：使用 PyUnicode_GET_LENGTH 或 PyUnicode_GetLength()

PyUnicode_GET_DATA_SIZE：使用 PyUnicode_GET_LENGTH(str) * PyUnicode_KIND(str)（僅適用於準備好的字串）

PyUnicode_AsUnicodeCopy()：使用 PyUnicode_AsUCS4Copy() 或 PyUnicode_AsWideCharString()

PyUnicode_GetMax()

操作 Py_UNICODE* 字串的函式和巨集：

Py_UNICODE_strlen()：使用 PyUnicode_GetLength() 或 PyUnicode_GET_LENGTH

Py_UNICODE_strcat()：使用 PyUnicode_CopyCharacters() 或 PyUnicode_FromFormat()

Py_UNICODE_strcpy()、Py_UNICODE_strncpy()、Py_UNICODE_COPY()：使用 PyUnicode_CopyCharacters() 或 PyUnicode_Substring()

Py_UNICODE_strcmp()：使用 PyUnicode_Compare()

Py_UNICODE_strncmp(): 使用 PyUnicode_Tailmatch()

Py_UNICODE_strchr(), Py_UNICODE_strrchr(): 使用 PyUnicode_FindChar()

Py_UNICODE_FILL(): 使用 PyUnicode_Fill()

Py_UNICODE_MATCH

編碼器：

PyUnicode_Encode()：使用 PyUnicode_AsEncodedObject()

PyUnicode_EncodeUTF7()

PyUnicode_EncodeUTF8()：使用 PyUnicode_AsUTF8() 或 PyUnicode_AsUTF8String()

PyUnicode_EncodeUTF32()

PyUnicode_EncodeUTF16()

PyUnicode_EncodeUnicodeEscape() 使用 PyUnicode_AsUnicodeEscapeString()

PyUnicode_EncodeRawUnicodeEscape() 使用 PyUnicode_AsRawUnicodeEscapeString()

PyUnicode_EncodeLatin1(): 使用 PyUnicode_AsLatin1String()

PyUnicode_EncodeASCII()：使用 PyUnicode_AsASCIIString()

PyUnicode_EncodeCharmap()

PyUnicode_TranslateCharmap()

PyUnicode_EncodeMBCS()：使用 PyUnicode_AsMBCSString() 或 PyUnicode_EncodeCodePage() （帶有 CP_ACP code_page）

PyUnicode_EncodeDecimal()、PyUnicode_TransformDecimalToASCII()

已棄用的功能

The array module's 'u' format code is now deprecated and will be removed in Python 4 together with the rest of the (Py_UNICODE) API.

移植到 Python 3.3

本節列出了前面描述的更改以及可能需要你更改程式碼的其他錯誤修復。

移植 Python 程式碼

Hash randomization is enabled by default. Set the PYTHONHASHSEED environment variable to 0 to disable hash randomization. See also the object.__hash__() method.

bpo-12326 [https://bugs.python.org/issue?@action=redirect&bpo=12326]: On Linux, sys.platform doesn't contain the major version anymore. It is now always 'linux', instead of 'linux2' or 'linux3' depending on the Linux version used to build Python. Replace sys.platform == 'linux2' with sys.platform.startswith('linux'), or directly sys.platform == 'linux' if you don't need to support older Python versions.

bpo-13847 [https://bugs.python.org/issue?@action=redirect&bpo=13847], bpo-14180 [https://bugs.python.org/issue?@action=redirect&bpo=14180]: time and datetime: OverflowError is now raised instead of ValueError if a timestamp is out of range. OSError is now raised if C functions gmtime() or localtime() failed.

The default finders used by import now utilize a cache of what is contained within a specific directory. If you create a Python source file or sourceless bytecode file, make sure to call importlib.invalidate_caches() to clear out the cache for the finders to notice the new file.

ImportError now uses the full name of the module that was attempted to be imported. Doctests that check ImportErrors' message will need to be updated to use the full name of the module instead of just the tail of the name.

The index argument to __import__() now defaults to 0 instead of -1 and no longer support negative values. It was an oversight when PEP 328 [https://peps.python.org/pep-0328/] was implemented that the default value remained -1. If you need to continue to perform a relative import followed by an absolute import, then perform the relative import using an index of 1, followed by another import using an index of 0. It is preferred, though, that you use importlib.import_module() rather than call __import__() directly.

__import__() no longer allows one to use an index value other than 0 for top-level modules. E.g. __import__('sys', level=1) is now an error.

Because sys.meta_path and sys.path_hooks now have finders on them by default, you will most likely want to use list.insert() instead of list.append() to add to those lists.

Because None is now inserted into sys.path_importer_cache, if you are clearing out entries in the dictionary of paths that do not have a finder, you will need to remove keys paired with values of None and imp.NullImporter to be backwards-compatible. This will lead to extra overhead on older versions of Python that re-insert None into sys.path_importer_cache where it represents the use of implicit finders, but semantically it should not change anything.

importlib.abc.Finder no longer specifies a find_module() abstract method that must be implemented. If you were relying on subclasses to implement that method, make sure to check for the method's existence first. You will probably want to check for find_loader() first, though, in the case of working with path entry finders.

pkgutil has been converted to use importlib internally. This eliminates many edge cases where the old behaviour of the PEP 302 [https://peps.python.org/pep-0302/] import emulation failed to match the behaviour of the real import system. The import emulation itself is still present, but is now deprecated. The pkgutil.iter_importers() and pkgutil.walk_packages() functions special case the standard import hooks so they are still supported even though they do not provide the non-standard iter_modules() method.

A longstanding RFC-compliance bug (bpo-1079 [https://bugs.python.org/issue?@action=redirect&bpo=1079]) in the parsing done by email.header.decode_header() has been fixed. Code that uses the standard idiom to convert encoded headers into unicode (str(make_header(decode_header(h))) will see no change, but code that looks at the individual tuples returned by decode_header will see that whitespace that precedes or follows ASCII sections is now included in the ASCII section. Code that builds headers using make_header should also continue to work without change, since make_header continues to add whitespace between ASCII and non-ASCII sections if it is not already present in the input strings.

email.utils.formataddr() now does the correct content transfer encoding when passed non-ASCII display names. Any code that depended on the previous buggy behavior that preserved the non-ASCII unicode in the formatted output string will need to be changed (bpo-1690608 [https://bugs.python.org/issue?@action=redirect&bpo=1690608]).

poplib.POP3.quit() may now raise protocol errors like all other poplib methods. Code that assumes quit does not raise poplib.error_proto errors may need to be changed if errors on quit are encountered by a particular application (bpo-11291 [https://bugs.python.org/issue?@action=redirect&bpo=11291]).

自 Python 2.4 以來已棄用的 email.parser.Parser 的 strict 引數終於被刪除了。

已棄用的方法 unittest.TestCase.assertSameElements 已被刪除。

已棄用的變數 time.accept2dyear 已被刪除。

The deprecated Context._clamp attribute has been removed from the decimal module. It was previously replaced by the public attribute clamp. (See bpo-8540 [https://bugs.python.org/issue?@action=redirect&bpo=8540].)

The undocumented internal helper class SSLFakeFile has been removed from smtplib, since its functionality has long been provided directly by socket.socket.makefile().

Passing a negative value to time.sleep() on Windows now raises an error instead of sleeping forever. It has always raised an error on posix.

The ast.__version__ constant has been removed. If you need to make decisions affected by the AST version, use sys.version_info to make the decision.

Code that used to work around the fact that the threading module used factory functions by subclassing the private classes will need to change to subclass the now-public classes.

The undocumented debugging machinery in the threading module has been removed, simplifying the code. This should have no effect on production code, but is mentioned here in case any application debug frameworks were interacting with it (bpo-13550 [https://bugs.python.org/issue?@action=redirect&bpo=13550]).

Porting C code

In the course of changes to the buffer API the undocumented smalltable member of the Py_buffer structure has been removed and the layout of the PyMemoryViewObject has changed.

All extensions relying on the relevant parts in memoryobject.h or object.h must be rebuilt.

Due to PEP 393, the Py_UNICODE type and all functions using this type are deprecated (but will stay available for at least five years). If you were using low-level Unicode APIs to construct and access unicode objects and you want to benefit of the memory footprint reduction provided by PEP 393 [https://peps.python.org/pep-0393/], you have to convert your code to the new Unicode API.

However, if you only have been using high-level functions such as PyUnicode_Concat(), PyUnicode_Join() or PyUnicode_FromFormat(), your code will automatically take advantage of the new unicode representations.

PyImport_GetMagicNumber() 現在在失敗時回傳 -1。

As a negative value for the level argument to __import__() is no longer valid, the same now holds for PyImport_ImportModuleLevel(). This also means that the value of level used by PyImport_ImportModuleEx() is now 0 instead of -1.

Building C extensions

The range of possible file names for C extensions has been narrowed. Very rarely used spellings have been suppressed: under POSIX, files named xxxmodule.so, xxxmodule.abi3.so and xxxmodule.cpython-*.so are no longer recognized as implementing the xxx module. If you had been generating such files, you have to switch to the other spellings (i.e., remove the module string from the file names).

（於 bpo-14040 [https://bugs.python.org/issue?@action=redirect&bpo=14040] 中實作。）

命令列開關更改

The -Q command-line flag and related artifacts have been removed. Code checking sys.flags.division_warning will need updating.

（由 Éric Araujo 於 bpo-10998 [https://bugs.python.org/issue?@action=redirect&bpo=10998] 中實作。）

When python is started with -S, import site will no longer add site-specific paths to the module search paths. In previous versions, it did.

（bpo-11591 [https://bugs.python.org/issue?@action=redirect&bpo=11591]，由 Carl Meyer 貢獻並由 Éric Araujo 修訂。）

Python 3.2 有什麼新功能

作者:

Raymond Hettinger

This article explains the new features in Python 3.2 as compared to 3.1. Python 3.2 was released on February 20, 2011. It focuses on a few highlights and gives a few examples. For full details, see the Misc/NEWS [https://github.com/python/cpython/blob/076ca6c3c8df3030307e548d9be792ce3c1c6eea/Misc/NEWS] file.

也參考

PEP 392 [https://peps.python.org/pep-0392/] - Python 3.2 發佈時程

PEP 384: Defining a Stable ABI

In the past, extension modules built for one Python version were often not usable with other Python versions. Particularly on Windows, every feature release of Python required rebuilding all extension modules that one wanted to use. This requirement was the result of the free access to Python interpreter internals that extension modules could use.

With Python 3.2, an alternative approach becomes available: extension modules which restrict themselves to a limited API (by defining Py_LIMITED_API) cannot use many of the internals, but are constrained to a set of API functions that are promised to be stable for several releases. As a consequence, extension modules built for 3.2 in that mode will also work with 3.3, 3.4, and so on. Extension modules that make use of details of memory structures can still be built, but will need to be recompiled for every feature release.

也參考

PEP 384 [https://peps.python.org/pep-0384/] - 定義一個穩定 ABI

由 Martin von Löwis 撰寫 PEP。

PEP 389: Argparse 命令列剖析模組

A new module for command line parsing, argparse, was introduced to overcome the limitations of optparse which did not provide support for positional arguments (not just options), subcommands, required options and other common patterns of specifying and validating options.

This module has already had widespread success in the community as a third-party module. Being more fully featured than its predecessor, the argparse module is now the preferred module for command-line processing. The older module is still being kept available because of the substantial amount of legacy code that depends on it.

Here's an annotated example parser showing features like limiting results to a set of choices, specifying a metavar in the help screen, validating that one or more positional arguments is present, and making a required option:

import argparse
parser = argparse.ArgumentParser(
            description = 'Manage servers',         # main description for help
            epilog = 'Tested on Solaris and Linux') # displayed after help
parser.add_argument('action',                       # argument name
            choices = ['deploy', 'start', 'stop'],  # three allowed values
            help = 'action on each target')         # help msg
parser.add_argument('targets',
            metavar = 'HOSTNAME',                   # var name used in help msg
            nargs = '+',                            # require one or more targets
            help = 'url for target machines')       # help msg explanation
parser.add_argument('-u', '--user',                 # -u or --user option
            required = True,                        # make it a required argument
            help = 'login as user')

Example of calling the parser on a command string:

>>> cmd = 'deploy sneezy.example.com sleepy.example.com -u skycaptain'
>>> result = parser.parse_args(cmd.split())
>>> result.action
'deploy'
>>> result.targets
['sneezy.example.com', 'sleepy.example.com']
>>> result.user
'skycaptain'

Example of the parser's automatically generated help:

>>> parser.parse_args('-h'.split())

usage: manage_cloud.py [-h] -u USER
                       {deploy,start,stop} HOSTNAME [HOSTNAME ...]

Manage servers

positional arguments:
  {deploy,start,stop}   action on each target
  HOSTNAME              url for target machines

optional arguments:
  -h, --help            show this help message and exit
  -u USER, --user USER  login as user

Tested on Solaris and Linux

An especially nice argparse feature is the ability to define subparsers, each with their own argument patterns and help displays:

import argparse
parser = argparse.ArgumentParser(prog='HELM')
subparsers = parser.add_subparsers()

parser_l = subparsers.add_parser('launch', help='Launch Control')   # first subgroup
parser_l.add_argument('-m', '--missiles', action='store_true')
parser_l.add_argument('-t', '--torpedos', action='store_true')

parser_m = subparsers.add_parser('move', help='Move Vessel',        # second subgroup
                                 aliases=('steer', 'turn'))         # equivalent names
parser_m.add_argument('-c', '--course', type=int, required=True)
parser_m.add_argument('-s', '--speed', type=int, default=0)

$ ./helm.py --help                         # top level help (launch and move)
$ ./helm.py launch --help                  # help for launch options
$ ./helm.py launch --missiles              # set missiles=True and torpedos=False
$ ./helm.py steer --course 180 --speed 5   # set movement parameters

也參考

PEP 389 [https://peps.python.org/pep-0389/] - 新命令列剖析模組

由 Steven Bethard 撰寫 PEP。

將 optparse 程式碼遷移到 argparse for details on the differences from optparse.

PEP 391: Dictionary Based Configuration for Logging

The logging module provided two kinds of configuration, one style with function calls for each option or another style driven by an external file saved in a configparser format. Those options did not provide the flexibility to create configurations from JSON or YAML files, nor did they support incremental configuration, which is needed for specifying logger options from a command line.

To support a more flexible style, the module now offers logging.config.dictConfig() for specifying logging configuration with plain Python dictionaries. The configuration options include formatters, handlers, filters, and loggers. Here's a working example of a configuration dictionary:

{"version": 1,
 "formatters": {"brief": {"format": "%(levelname)-8s: %(name)-15s: %(message)s"},
                "full": {"format": "%(asctime)s %(name)-15s %(levelname)-8s %(message)s"}
                },
 "handlers": {"console": {
                   "class": "logging.StreamHandler",
                   "formatter": "brief",
                   "level": "INFO",
                   "stream": "ext://sys.stdout"},
              "console_priority": {
                   "class": "logging.StreamHandler",
                   "formatter": "full",
                   "level": "ERROR",
                   "stream": "ext://sys.stderr"}
              },
 "root": {"level": "DEBUG", "handlers": ["console", "console_priority"]}}

If that dictionary is stored in a file called conf.json, it can be loaded and called with code like this:

>>> import json, logging.config
>>> with open('conf.json') as f:
...     conf = json.load(f)
...
>>> logging.config.dictConfig(conf)
>>> logging.info("Transaction completed normally")
INFO    : root           : Transaction completed normally
>>> logging.critical("Abnormal termination")
2011-02-17 11:14:36,694 root            CRITICAL Abnormal termination

也參考

PEP 391 [https://peps.python.org/pep-0391/] - Dictionary Based Configuration for Logging

由 Vinay Sajip 撰寫 PEP。

PEP 3148：concurrent.futures 模組

Code for creating and managing concurrency is being collected in a new top-level namespace, concurrent. Its first member is a futures package which provides a uniform high-level interface for managing threads and processes.

The design for concurrent.futures was inspired by the java.util.concurrent package. In that model, a running call and its result are represented by a Future object that abstracts features common to threads, processes, and remote procedure calls. That object supports status checks (running or done), timeouts, cancellations, adding callbacks, and access to results or exceptions.

The primary offering of the new module is a pair of executor classes for launching and managing calls. The goal of the executors is to make it easier to use existing tools for making parallel calls. They save the effort needed to setup a pool of resources, launch the calls, create a results queue, add time-out handling, and limit the total number of threads, processes, or remote procedure calls.

Ideally, each application should share a single executor across multiple components so that process and thread limits can be centrally managed. This solves the design challenge that arises when each component has its own competing strategy for resource management.

Both classes share a common interface with three methods: submit() for scheduling a callable and returning a Future object; map() for scheduling many asynchronous calls at a time, and shutdown() for freeing resources. The class is a context manager and can be used in a with statement to assure that resources are automatically released when currently pending futures are done executing.

A simple of example of ThreadPoolExecutor is a launch of four parallel threads for copying files:

import concurrent.futures, shutil
with concurrent.futures.ThreadPoolExecutor(max_workers=4) as e:
    e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
    e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
    e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
    e.submit(shutil.copy, 'src3.txt', 'dest4.txt')

也參考

PEP 3148 [https://peps.python.org/pep-3148/] - Futures -- Execute Computations Asynchronously

由 Brian Quinlan 撰寫 PEP。

Code for Threaded Parallel URL reads, an example using threads to fetch multiple web pages in parallel.

Code for computing prime numbers in parallel, an example demonstrating ProcessPoolExecutor.

PEP 3147: PYC Repository Directories

Python's scheme for caching bytecode in .pyc files did not work well in environments with multiple Python interpreters. If one interpreter encountered a cached file created by another interpreter, it would recompile the source and overwrite the cached file, thus losing the benefits of caching.

The issue of "pyc fights" has become more pronounced as it has become commonplace for Linux distributions to ship with multiple versions of Python. These conflicts also arise with CPython alternatives such as Unladen Swallow.

To solve this problem, Python's import machinery has been extended to use distinct filenames for each interpreter. Instead of Python 3.2 and Python 3.3 and Unladen Swallow each competing for a file called "mymodule.pyc", they will now look for "mymodule.cpython-32.pyc", "mymodule.cpython-33.pyc", and "mymodule.unladen10.pyc". And to prevent all of these new files from cluttering source directories, the pyc files are now collected in a "__pycache__" directory stored under the package directory.

Aside from the filenames and target directories, the new scheme has a few aspects that are visible to the programmer:

Imported modules now have a __cached__ attribute which stores the name of the actual file that was imported:

>>> import collections
>>> collections.__cached__
'c:/py32/lib/__pycache__/collections.cpython-32.pyc'

The tag that is unique to each interpreter is accessible from the imp module:

>>> import imp
>>> imp.get_tag()
'cpython-32'

Scripts that try to deduce source filename from the imported file now need to be smarter. It is no longer sufficient to simply strip the "c" from a ".pyc" filename. Instead, use the new functions in the imp module:

>>> imp.source_from_cache('c:/py32/lib/__pycache__/collections.cpython-32.pyc')
'c:/py32/lib/collections.py'
>>> imp.cache_from_source('c:/py32/lib/collections.py')
'c:/py32/lib/__pycache__/collections.cpython-32.pyc'

The py_compile and compileall modules have been updated to reflect the new naming convention and target directory. The command-line invocation of compileall has new options: -i for specifying a list of files and directories to compile and -b which causes bytecode files to be written to their legacy location rather than __pycache__.

The importlib.abc module has been updated with new abstract base classes for loading bytecode files. The obsolete ABCs, PyLoader and PyPycLoader, have been deprecated (instructions on how to stay Python 3.1 compatible are included with the documentation).

也參考

PEP 3147 [https://peps.python.org/pep-3147/] - PYC Repository Directories

由 Barry Warsaw 撰寫 PEP。

PEP 3149: ABI Version Tagged .so Files

The PYC repository directory allows multiple bytecode cache files to be co-located. This PEP implements a similar mechanism for shared object files by giving them a common directory and distinct names for each version.

The common directory is "pyshared" and the file names are made distinct by identifying the Python implementation (such as CPython, PyPy, Jython, etc.), the major and minor version numbers, and optional build flags (such as "d" for debug, "m" for pymalloc, "u" for wide-unicode). For an arbitrary package "foo", you may see these files when the distribution package is installed:

/usr/share/pyshared/foo.cpython-32m.so
/usr/share/pyshared/foo.cpython-33md.so

In Python itself, the tags are accessible from functions in the sysconfig module:

>>> import sysconfig
>>> sysconfig.get_config_var('SOABI')       # find the version tag
'cpython-32mu'
>>> sysconfig.get_config_var('EXT_SUFFIX')  # find the full filename extension
'.cpython-32mu.so'

也參考

PEP 3149 [https://peps.python.org/pep-3149/] - ABI Version Tagged .so Files

由 Barry Warsaw 撰寫 PEP。

PEP 3333: Python Web Server Gateway Interface v1.0.1

This informational PEP clarifies how bytes/text issues are to be handled by the WSGI protocol. The challenge is that string handling in Python 3 is most conveniently handled with the str type even though the HTTP protocol is itself bytes oriented.

The PEP differentiates so-called native strings that are used for request/response headers and metadata versus byte strings which are used for the bodies of requests and responses.

The native strings are always of type str but are restricted to code points between U+0000 through U+00FF which are translatable to bytes using Latin-1 encoding. These strings are used for the keys and values in the environment dictionary and for response headers and statuses in the start_response() function. They must follow RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html] with respect to encoding. That is, they must either be ISO-8859-1 characters or use RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] MIME encoding.

For developers porting WSGI applications from Python 2, here are the salient points:

If the app already used strings for headers in Python 2, no change is needed.

If instead, the app encoded output headers or decoded input headers, then the headers will need to be re-encoded to Latin-1. For example, an output header encoded in utf-8 was using h.encode('utf-8') now needs to convert from bytes to native strings using h.encode('utf-8').decode('latin-1').

Values yielded by an application or sent using the write() method must be byte strings. The start_response() function and environ must use native strings. The two cannot be mixed.

For server implementers writing CGI-to-WSGI pathways or other CGI-style protocols, the users must to be able access the environment using native strings even though the underlying platform may have a different convention. To bridge this gap, the wsgiref module has a new function, wsgiref.handlers.read_environ() for transcoding CGI variables from os.environ into native strings and returning a new dictionary.

也參考

PEP 3333 [https://peps.python.org/pep-3333/] - Python Web Server Gateway Interface v1.0.1

由 Phillip Eby 撰寫 PEP。

其他語言更動

Some smaller changes made to the core Python language are:

String formatting for format() and str.format() gained new capabilities for the format character #. Previously, for integers in binary, octal, or hexadecimal, it caused the output to be prefixed with '0b', '0o', or '0x' respectively. Now it can also handle floats, complex, and Decimal, causing the output to always have a decimal point even when no digits follow it.

>>> format(20, '#o')
'0o24'
>>> format(12.34, '#5.0f')
'  12.'

(Suggested by Mark Dickinson and implemented by Eric Smith in bpo-7094 [https://bugs.python.org/issue?@action=redirect&bpo=7094].)

There is also a new str.format_map() method that extends the capabilities of the existing str.format() method by accepting arbitrary mapping objects. This new method makes it possible to use string formatting with any of Python's many dictionary-like objects such as defaultdict, Shelf, ConfigParser, or dbm. It is also useful with custom dict subclasses that normalize keys before look-up or that supply a __missing__() method for unknown keys:

>>> import shelve
>>> d = shelve.open('tmp.shl')
>>> 'The {project_name} status is {status} as of {date}'.format_map(d)
'The testing project status is green as of February 15, 2011'

>>> class LowerCasedDict(dict):
...     def __getitem__(self, key):
...         return dict.__getitem__(self, key.lower())
...
>>> lcd = LowerCasedDict(part='widgets', quantity=10)
>>> 'There are {QUANTITY} {Part} in stock'.format_map(lcd)
'There are 10 widgets in stock'

>>> class PlaceholderDict(dict):
...     def __missing__(self, key):
...         return '<{}>'.format(key)
...
>>> 'Hello {name}, welcome to {location}'.format_map(PlaceholderDict())
'Hello <name>, welcome to <location>'

(Suggested by Raymond Hettinger and implemented by Eric Smith in bpo-6081 [https://bugs.python.org/issue?@action=redirect&bpo=6081].)

The interpreter can now be started with a quiet option, -q, to prevent the copyright and version information from being displayed in the interactive mode. The option can be introspected using the sys.flags attribute:

$ python -q
>>> sys.flags
sys.flags(debug=0, division_warning=0, inspect=0, interactive=0,
optimize=0, dont_write_bytecode=0, no_user_site=0, no_site=0,
ignore_environment=0, verbose=0, bytes_warning=0, quiet=1)

（由 Marcin Wojdyr 在 bpo-1772833 [https://bugs.python.org/issue?@action=redirect&bpo=1772833] 中貢獻）。

The hasattr() function works by calling getattr() and detecting whether an exception is raised. This technique allows it to detect methods created dynamically by __getattr__() or __getattribute__() which would otherwise be absent from the class dictionary. Formerly, hasattr would catch any exception, possibly masking genuine errors. Now, hasattr has been tightened to only catch AttributeError and let other exceptions pass through:

>>> class A:
...     @property
...     def f(self):
...         return 1 // 0
...
>>> a = A()
>>> hasattr(a, 'f')
Traceback (most recent call last):
  ...
ZeroDivisionError: integer division or modulo by zero

(Discovered by Yury Selivanov and fixed by Benjamin Peterson; bpo-9666 [https://bugs.python.org/issue?@action=redirect&bpo=9666].)

The str() of a float or complex number is now the same as its repr(). Previously, the str() form was shorter but that just caused confusion and is no longer needed now that the shortest possible repr() is displayed by default:

>>> import math
>>> repr(math.pi)
'3.141592653589793'
>>> str(math.pi)
'3.141592653589793'

(Proposed and implemented by Mark Dickinson; bpo-9337 [https://bugs.python.org/issue?@action=redirect&bpo=9337].)

memoryview objects now have a release() method and they also now support the context management protocol. This allows timely release of any resources that were acquired when requesting a buffer from the original object.

>>> with memoryview(b'abcdefgh') as v:
...     print(v.tolist())
[97, 98, 99, 100, 101, 102, 103, 104]

(Added by Antoine Pitrou; bpo-9757 [https://bugs.python.org/issue?@action=redirect&bpo=9757].)

Previously it was illegal to delete a name from the local namespace if it occurs as a free variable in a nested block:

def outer(x):
    def inner():
        return x
    inner()
    del x

This is now allowed. Remember that the target of an except clause is cleared, so this code which used to work with Python 2.6, raised a SyntaxError with Python 3.1 and now works again:

def f():
    def print_error():
        print(e)
    try:
        something
    except Exception as e:
        print_error()
        # implicit "del e" here

（請見 bpo-4617 [https://bugs.python.org/issue?@action=redirect&bpo=4617]。）

Struct sequence types are now subclasses of tuple. This means that C structures like those returned by os.stat(), time.gmtime(), and sys.version_info now work like a named tuple and now work with functions and methods that expect a tuple as an argument. This is a big step forward in making the C structures as flexible as their pure Python counterparts:

>>> import sys
>>> isinstance(sys.version_info, tuple)
True
>>> 'Version %d.%d.%d %s(%d)' % sys.version_info
'Version 3.2.0 final(0)'

(Suggested by Arfrever Frehtes Taifersar Arahesis and implemented by Benjamin Peterson in bpo-8413 [https://bugs.python.org/issue?@action=redirect&bpo=8413].)

Warnings are now easier to control using the PYTHONWARNINGS environment variable as an alternative to using -W at the command line:

$ export PYTHONWARNINGS='ignore::RuntimeWarning::,once::UnicodeWarning::'

(Suggested by Barry Warsaw and implemented by Philip Jenvey in bpo-7301 [https://bugs.python.org/issue?@action=redirect&bpo=7301].)

A new warning category, ResourceWarning, has been added. It is emitted when potential issues with resource consumption or cleanup are detected. It is silenced by default in normal release builds but can be enabled through the means provided by the warnings module, or on the command line.

A ResourceWarning is issued at interpreter shutdown if the gc.garbage list isn't empty, and if gc.DEBUG_UNCOLLECTABLE is set, all uncollectable objects are printed. This is meant to make the programmer aware that their code contains object finalization issues.

A ResourceWarning is also issued when a file object is destroyed without having been explicitly closed. While the deallocator for such object ensures it closes the underlying operating system resource (usually, a file descriptor), the delay in deallocating the object could produce various issues, especially under Windows. Here is an example of enabling the warning from the command line:

$ python -q -Wdefault
>>> f = open("foo", "wb")
>>> del f
__main__:1: ResourceWarning: unclosed file <_io.BufferedWriter name='foo'>

(Added by Antoine Pitrou and Georg Brandl in bpo-10093 [https://bugs.python.org/issue?@action=redirect&bpo=10093] and bpo-477863 [https://bugs.python.org/issue?@action=redirect&bpo=477863].)

range objects now support index and count methods. This is part of an effort to make more objects fully implement the collections.Sequence abstract base class. As a result, the language will have a more uniform API. In addition, range objects now support slicing and negative indices, even with values larger than sys.maxsize. This makes range more interoperable with lists:

>>> range(0, 100, 2).count(10)
1
>>> range(0, 100, 2).index(10)
5
>>> range(0, 100, 2)[5]
10
>>> range(0, 100, 2)[0:5]
range(0, 10, 2)

（由 Daniel Stutzbach 在 bpo-9213 [https://bugs.python.org/issue?@action=redirect&bpo=9213]、Alexander Belopolsky 在 bpo-2690 [https://bugs.python.org/issue?@action=redirect&bpo=2690]、Nick Coghlan 在 bpo-10889 [https://bugs.python.org/issue?@action=redirect&bpo=10889] 中貢獻。）

The callable() builtin function from Py2.x was resurrected. It provides a concise, readable alternative to using an abstract base class in an expression like isinstance(x, collections.Callable):

>>> callable(max)
True
>>> callable(20)
False

（請見 bpo-10518 [https://bugs.python.org/issue?@action=redirect&bpo=10518]。）

Python's import mechanism can now load modules installed in directories with non-ASCII characters in the path name. This solved an aggravating problem with home directories for users with non-ASCII characters in their usernames.

(Required extensive work by Victor Stinner in bpo-9425 [https://bugs.python.org/issue?@action=redirect&bpo=9425].)

New, Improved, and Deprecated Modules

Python's standard library has undergone significant maintenance efforts and quality improvements.

The biggest news for Python 3.2 is that the email package, mailbox module, and nntplib modules now work correctly with the bytes/text model in Python 3. For the first time, there is correct handling of messages with mixed encodings.

Throughout the standard library, there has been more careful attention to encodings and text versus bytes issues. In particular, interactions with the operating system are now better able to exchange non-ASCII data using the Windows MBCS encoding, locale-aware encodings, or UTF-8.

Another significant win is the addition of substantially better support for SSL connections and security certificates.

In addition, more classes now implement a context manager to support convenient and reliable resource clean-up using a with statement.

email

The usability of the email package in Python 3 has been mostly fixed by the extensive efforts of R. David Murray. The problem was that emails are typically read and stored in the form of bytes rather than str text, and they may contain multiple encodings within a single email. So, the email package had to be extended to parse and generate email messages in bytes format.

New functions message_from_bytes() and message_from_binary_file(), and new classes BytesFeedParser and BytesParser allow binary message data to be parsed into model objects.

Given bytes input to the model, get_payload() will by default decode a message body that has a Content-Transfer-Encoding of 8bit using the charset specified in the MIME headers and return the resulting string.

Given bytes input to the model, Generator will convert message bodies that have a Content-Transfer-Encoding of 8bit to instead have a 7bit Content-Transfer-Encoding.

Headers with unencoded non-ASCII bytes are deemed to be RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html]-encoded using the unknown-8bit character set.

A new class BytesGenerator produces bytes as output, preserving any unchanged non-ASCII data that was present in the input used to build the model, including message bodies with a Content-Transfer-Encoding of 8bit.

The smtplib SMTP class now accepts a byte string for the msg argument to the sendmail() method, and a new method, send_message() accepts a Message object and can optionally obtain the from_addr and to_addrs addresses directly from the object.

(Proposed and implemented by R. David Murray, bpo-4661 [https://bugs.python.org/issue?@action=redirect&bpo=4661] and bpo-10321 [https://bugs.python.org/issue?@action=redirect&bpo=10321].)

elementtree

The xml.etree.ElementTree package and its xml.etree.cElementTree counterpart have been updated to version 1.3.

Several new and useful functions and methods have been added:

xml.etree.ElementTree.fromstringlist() which builds an XML document from a sequence of fragments

xml.etree.ElementTree.register_namespace() for registering a global namespace prefix

xml.etree.ElementTree.tostringlist() for string representation including all sublists

xml.etree.ElementTree.Element.extend() for appending a sequence of zero or more elements

xml.etree.ElementTree.Element.iterfind() searches an element and subelements

xml.etree.ElementTree.Element.itertext() creates a text iterator over an element and its subelements

xml.etree.ElementTree.TreeBuilder.end() closes the current element

xml.etree.ElementTree.TreeBuilder.doctype() handles a doctype declaration

有兩個方法已被棄用：

xml.etree.ElementTree.getchildren() use list(elem) instead.

xml.etree.ElementTree.getiterator() use Element.iter instead.

For details of the update, see Introducing ElementTree [https://web.archive.org/web/20200703234532/http://effbot.org/zone/elementtree-13-intro.htm] on Fredrik Lundh's website.

（由 Florent Xicluna 和 Fredrik Lundh 貢獻，bpo-6472 [https://bugs.python.org/issue?@action=redirect&bpo=6472]。）

functools

The functools module includes a new decorator for caching function calls. functools.lru_cache() can save repeated queries to an external resource whenever the results are expected to be the same.

For example, adding a caching decorator to a database query function can save database accesses for popular searches:

>>> import functools
>>> @functools.lru_cache(maxsize=300)
... def get_phone_number(name):
...     c = conn.cursor()
...     c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,))
...     return c.fetchone()[0]

>>> for name in user_requests:
...     get_phone_number(name)        # cached lookup

To help with choosing an effective cache size, the wrapped function is instrumented for tracking cache statistics:

>>> get_phone_number.cache_info()
CacheInfo(hits=4805, misses=980, maxsize=300, currsize=300)

If the phonelist table gets updated, the outdated contents of the cache can be cleared with:

>>> get_phone_number.cache_clear()

(Contributed by Raymond Hettinger and incorporating design ideas from Jim Baker, Miki Tebeka, and Nick Coghlan; see recipe 498245 [https://code.activestate.com/recipes/498245-lru-and-lfu-cache-decorators/], recipe 577479 [https://code.activestate.com/recipes/577479-simple-caching-decorator/], bpo-10586 [https://bugs.python.org/issue?@action=redirect&bpo=10586], and bpo-10593 [https://bugs.python.org/issue?@action=redirect&bpo=10593].)

The functools.wraps() decorator now adds a __wrapped__ attribute pointing to the original callable function. This allows wrapped functions to be introspected. It also copies __annotations__ if defined. And now it also gracefully skips over missing attributes such as __doc__ which might not be defined for the wrapped callable.

In the above example, the cache can be removed by recovering the original function:

>>> get_phone_number = get_phone_number.__wrapped__    # uncached function

(By Nick Coghlan and Terrence Cole; bpo-9567 [https://bugs.python.org/issue?@action=redirect&bpo=9567], bpo-3445 [https://bugs.python.org/issue?@action=redirect&bpo=3445], and bpo-8814 [https://bugs.python.org/issue?@action=redirect&bpo=8814].)

To help write classes with rich comparison methods, a new decorator functools.total_ordering() will use existing equality and inequality methods to fill in the remaining methods.

For example, supplying __eq__ and __lt__ will enable total_ordering() to fill-in __le__, __gt__ and __ge__:

@total_ordering
class Student:
    def __eq__(self, other):
        return ((self.lastname.lower(), self.firstname.lower()) ==
                (other.lastname.lower(), other.firstname.lower()))

    def __lt__(self, other):
        return ((self.lastname.lower(), self.firstname.lower()) <
                (other.lastname.lower(), other.firstname.lower()))

With the total_ordering decorator, the remaining comparison methods are filled in automatically.

（由 Raymond Hettinger 貢獻。）

To aid in porting programs from Python 2, the functools.cmp_to_key() function converts an old-style comparison function to modern key function:

>>> # locale-aware sort order
>>> sorted(iterable, key=cmp_to_key(locale.strcoll))

For sorting examples and a brief sorting tutorial, see the Sorting HowTo [https://wiki.python.org/moin/HowTo/Sorting/] tutorial.

（由 Raymond Hettinger 貢獻。）

itertools

The itertools module has a new accumulate() function modeled on APL's scan operator and Numpy's accumulate function:

>>> from itertools import accumulate
>>> list(accumulate([8, 2, 50]))
[8, 10, 60]

>>> prob_dist = [0.1, 0.4, 0.2, 0.3]
>>> list(accumulate(prob_dist))      # cumulative probability distribution
[0.1, 0.5, 0.7, 1.0]

For an example using accumulate(), see the examples for the random module.

（由 Raymond Hettinger 貢獻，並結合了 Mark Dickinson 的設計建議。）

collections

The collections.Counter class now has two forms of in-place subtraction, the existing -= operator for saturating subtraction [https://en.wikipedia.org/wiki/Saturation_arithmetic] and the new subtract() method for regular subtraction. The former is suitable for multisets [https://en.wikipedia.org/wiki/Multiset] which only have positive counts, and the latter is more suitable for use cases that allow negative counts:

>>> from collections import Counter
>>> tally = Counter(dogs=5, cats=3)
>>> tally -= Counter(dogs=2, cats=8)    # saturating subtraction
>>> tally
Counter({'dogs': 3})

>>> tally = Counter(dogs=5, cats=3)
>>> tally.subtract(dogs=2, cats=8)      # regular subtraction
>>> tally
Counter({'dogs': 3, 'cats': -5})

（由 Raymond Hettinger 貢獻。）

The collections.OrderedDict class has a new method move_to_end() which takes an existing key and moves it to either the first or last position in the ordered sequence.

The default is to move an item to the last position. This is equivalent of renewing an entry with od[k] = od.pop(k).

A fast move-to-end operation is useful for resequencing entries. For example, an ordered dictionary can be used to track order of access by aging entries from the oldest to the most recently accessed.

>>> from collections import OrderedDict
>>> d = OrderedDict.fromkeys(['a', 'b', 'X', 'd', 'e'])
>>> list(d)
['a', 'b', 'X', 'd', 'e']
>>> d.move_to_end('X')
>>> list(d)
['a', 'b', 'd', 'e', 'X']

（由 Raymond Hettinger 貢獻。）

The collections.deque class grew two new methods count() and reverse() that make them more substitutable for list objects:

>>> from collections import deque
>>> d = deque('simsalabim')
>>> d.count('s')
2
>>> d.reverse()
>>> d
deque(['m', 'i', 'b', 'a', 'l', 'a', 's', 'm', 'i', 's'])

（由 Raymond Hettinger 貢獻。）

threading

The threading module has a new Barrier synchronization class for making multiple threads wait until all of them have reached a common barrier point. Barriers are useful for making sure that a task with multiple preconditions does not run until all of the predecessor tasks are complete.

Barriers can work with an arbitrary number of threads. This is a generalization of a Rendezvous [https://en.wikipedia.org/wiki/Synchronous_rendezvous] which is defined for only two threads.

Implemented as a two-phase cyclic barrier, Barrier objects are suitable for use in loops. The separate filling and draining phases assure that all threads get released (drained) before any one of them can loop back and re-enter the barrier. The barrier fully resets after each cycle.

Example of using barriers:

from threading import Barrier, Thread

def get_votes(site):
    ballots = conduct_election(site)
    all_polls_closed.wait()        # do not count until all polls are closed
    totals = summarize(ballots)
    publish(site, totals)

all_polls_closed = Barrier(len(sites))
for site in sites:
    Thread(target=get_votes, args=(site,)).start()

In this example, the barrier enforces a rule that votes cannot be counted at any polling site until all polls are closed. Notice how a solution with a barrier is similar to one with threading.Thread.join(), but the threads stay alive and continue to do work (summarizing ballots) after the barrier point is crossed.

If any of the predecessor tasks can hang or be delayed, a barrier can be created with an optional timeout parameter. Then if the timeout period elapses before all the predecessor tasks reach the barrier point, all waiting threads are released and a BrokenBarrierError exception is raised:

def get_votes(site):
    ballots = conduct_election(site)
    try:
        all_polls_closed.wait(timeout=midnight - time.now())
    except BrokenBarrierError:
        lockbox = seal_ballots(ballots)
        queue.put(lockbox)
    else:
        totals = summarize(ballots)
        publish(site, totals)

In this example, the barrier enforces a more robust rule. If some election sites do not finish before midnight, the barrier times-out and the ballots are sealed and deposited in a queue for later handling.

See Barrier Synchronization Patterns [https://osl.cs.illinois.edu/media/papers/karmani-2009-barrier_synchronization_pattern.pdf] for more examples of how barriers can be used in parallel computing. Also, there is a simple but thorough explanation of barriers in The Little Book of Semaphores [https://greenteapress.com/semaphores/LittleBookOfSemaphores.pdf], section 3.6.

（在 bpo-8777 [https://bugs.python.org/issue?@action=redirect&bpo=8777] 中由 Kristján Valur Jónsson 貢獻、Jeffrey Yasskin 進行 API 審查。）

datetime 和 time

The datetime module has a new type timezone that implements the tzinfo interface by returning a fixed UTC offset and timezone name. This makes it easier to create timezone-aware datetime objects:

>>> from datetime import datetime, timezone

>>> datetime.now(timezone.utc)
datetime.datetime(2010, 12, 8, 21, 4, 2, 923754, tzinfo=datetime.timezone.utc)

>>> datetime.strptime("01/01/2000 12:00 +0000", "%m/%d/%Y %H:%M %z")
datetime.datetime(2000, 1, 1, 12, 0, tzinfo=datetime.timezone.utc)

Also, timedelta objects can now be multiplied by float and divided by float and int objects. And timedelta objects can now divide one another.

The datetime.date.strftime() method is no longer restricted to years after 1900. The new supported year range is from 1000 to 9999 inclusive.

Whenever a two-digit year is used in a time tuple, the interpretation has been governed by time.accept2dyear. The default is True which means that for a two-digit year, the century is guessed according to the POSIX rules governing the %y strptime format.

Starting with Py3.2, use of the century guessing heuristic will emit a DeprecationWarning. Instead, it is recommended that time.accept2dyear be set to False so that large date ranges can be used without guesswork:

>>> import time, warnings
>>> warnings.resetwarnings()      # remove the default warning filters

>>> time.accept2dyear = True      # guess whether 11 means 11 or 2011
>>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0))
Warning (from warnings module):
  ...
DeprecationWarning: Century info guessed for a 2-digit year.
'Fri Jan  1 12:34:56 2011'

>>> time.accept2dyear = False     # use the full range of allowable dates
>>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0))
'Fri Jan  1 12:34:56 11'

Several functions now have significantly expanded date ranges. When time.accept2dyear is false, the time.asctime() function will accept any year that fits in a C int, while the time.mktime() and time.strftime() functions will accept the full range supported by the corresponding operating system functions.

（由 Alexander Belopolsky 和 Victor Stinner 在 bpo-1289118 [https://bugs.python.org/issue?@action=redirect&bpo=1289118]、bpo-5094 [https://bugs.python.org/issue?@action=redirect&bpo=5094]、bpo-6641 [https://bugs.python.org/issue?@action=redirect&bpo=6641]、bpo-2706 [https://bugs.python.org/issue?@action=redirect&bpo=2706]、bpo-1777412 [https://bugs.python.org/issue?@action=redirect&bpo=1777412]、bpo-8013 [https://bugs.python.org/issue?@action=redirect&bpo=8013] 和 bpo-10827 [https://bugs.python.org/issue?@action=redirect&bpo=10827] 中貢獻。）

math

The math module has been updated with six new functions inspired by the C99 standard.

The isfinite() function provides a reliable and fast way to detect special values. It returns True for regular numbers and False for Nan or Infinity:

>>> from math import isfinite
>>> [isfinite(x) for x in (123, 4.56, float('Nan'), float('Inf'))]
[True, True, False, False]

The expm1() function computes e**x-1 for small values of x without incurring the loss of precision that usually accompanies the subtraction of nearly equal quantities:

>>> from math import expm1
>>> expm1(0.013671875)   # more accurate way to compute e**x-1 for a small x
0.013765762467652909

The erf() function computes a probability integral or Gaussian error function [https://en.wikipedia.org/wiki/Error_function]. The complementary error function, erfc(), is 1 - erf(x):

>>> from math import erf, erfc, sqrt
>>> erf(1.0/sqrt(2.0))   # portion of normal distribution within 1 standard deviation
0.682689492137086
>>> erfc(1.0/sqrt(2.0))  # portion of normal distribution outside 1 standard deviation
0.31731050786291404
>>> erf(1.0/sqrt(2.0)) + erfc(1.0/sqrt(2.0))
1.0

The gamma() function is a continuous extension of the factorial function. See https://en.wikipedia.org/wiki/Gamma_function for details. Because the function is related to factorials, it grows large even for small values of x, so there is also a lgamma() function for computing the natural logarithm of the gamma function:

>>> from math import gamma, lgamma
>>> gamma(7.0)           # six factorial
720.0
>>> lgamma(801.0)        # log(800 factorial)
4551.950730698041

（由 Mark Dickinson 貢獻。）

abc

The abc module now supports abstractclassmethod() and abstractstaticmethod().

These tools make it possible to define an abstract base class that requires a particular classmethod() or staticmethod() to be implemented:

class Temperature(metaclass=abc.ABCMeta):
    @abc.abstractclassmethod
    def from_fahrenheit(cls, t):
        ...
    @abc.abstractclassmethod
    def from_celsius(cls, t):
        ...

(Patch submitted by Daniel Urban; bpo-5867 [https://bugs.python.org/issue?@action=redirect&bpo=5867].)

io

The io.BytesIO has a new method, getbuffer(), which provides functionality similar to memoryview(). It creates an editable view of the data without making a copy. The buffer's random access and support for slice notation are well-suited to in-place editing:

>>> REC_LEN, LOC_START, LOC_LEN = 34, 7, 11

>>> def change_location(buffer, record_number, location):
...     start = record_number * REC_LEN + LOC_START
...     buffer[start: start+LOC_LEN] = location

>>> import io

>>> byte_stream = io.BytesIO(
...     b'G3805  storeroom  Main chassis    '
...     b'X7899  shipping   Reserve cog     '
...     b'L6988  receiving  Primary sprocket'
... )
>>> buffer = byte_stream.getbuffer()
>>> change_location(buffer, 1, b'warehouse  ')
>>> change_location(buffer, 0, b'showroom   ')
>>> print(byte_stream.getvalue())
b'G3805  showroom   Main chassis    '
b'X7899  warehouse  Reserve cog     '
b'L6988  receiving  Primary sprocket'

（由 Antoine Pitrou 在 bpo-5506 [https://bugs.python.org/issue?@action=redirect&bpo=5506] 中貢獻。）

reprlib

When writing a __repr__() method for a custom container, it is easy to forget to handle the case where a member refers back to the container itself. Python's builtin objects such as list and set handle self-reference by displaying "..." in the recursive part of the representation string.

To help write such __repr__() methods, the reprlib module has a new decorator, recursive_repr(), for detecting recursive calls to __repr__() and substituting a placeholder string instead:

>>> class MyList(list):
...     @recursive_repr()
...     def __repr__(self):
...         return '<' + '|'.join(map(repr, self)) + '>'
...
>>> m = MyList('abc')
>>> m.append(m)
>>> m.append('x')
>>> print(m)
<'a'|'b'|'c'|...|'x'>

（由 Raymond Hettinger 在 bpo-9826 [https://bugs.python.org/issue?@action=redirect&bpo=9826] 和 bpo-9840 [https://bugs.python.org/issue?@action=redirect&bpo=9840] 中貢獻。）

logging

In addition to dictionary-based configuration described above, the logging package has many other improvements.

The logging documentation has been augmented by a basic tutorial, an advanced tutorial, and a cookbook of logging recipes. These documents are the fastest way to learn about logging.

The logging.basicConfig() set-up function gained a style argument to support three different types of string formatting. It defaults to "%" for traditional %-formatting, can be set to "{" for the new str.format() style, or can be set to "$" for the shell-style formatting provided by string.Template. The following three configurations are equivalent:

>>> from logging import basicConfig
>>> basicConfig(style='%', format="%(name)s -> %(levelname)s: %(message)s")
>>> basicConfig(style='{', format="{name} -> {levelname} {message}")
>>> basicConfig(style='$', format="$name -> $levelname: $message")

If no configuration is set-up before a logging event occurs, there is now a default configuration using a StreamHandler directed to sys.stderr for events of WARNING level or higher. Formerly, an event occurring before a configuration was set-up would either raise an exception or silently drop the event depending on the value of logging.raiseExceptions. The new default handler is stored in logging.lastResort.

The use of filters has been simplified. Instead of creating a Filter object, the predicate can be any Python callable that returns True or False.

There were a number of other improvements that add flexibility and simplify configuration. See the module documentation for a full listing of changes in Python 3.2.

csv

The csv module now supports a new dialect, unix_dialect, which applies quoting for all fields and a traditional Unix style with '\n' as the line terminator. The registered dialect name is unix.

The csv.DictWriter has a new method, writeheader() for writing-out an initial row to document the field names:

>>> import csv, sys
>>> w = csv.DictWriter(sys.stdout, ['name', 'dept'], dialect='unix')
>>> w.writeheader()
"name","dept"
>>> w.writerows([
...     {'name': 'tom', 'dept': 'accounting'},
...     {'name': 'susan', 'dept': 'Salesl'}])
"tom","accounting"
"susan","sales"

(New dialect suggested by Jay Talbot in bpo-5975 [https://bugs.python.org/issue?@action=redirect&bpo=5975], and the new method suggested by Ed Abraham in bpo-1537721 [https://bugs.python.org/issue?@action=redirect&bpo=1537721].)

contextlib

There is a new and slightly mind-blowing tool ContextDecorator that is helpful for creating a context manager that does double duty as a function decorator.

As a convenience, this new functionality is used by contextmanager() so that no extra effort is needed to support both roles.

The basic idea is that both context managers and function decorators can be used for pre-action and post-action wrappers. Context managers wrap a group of statements using a with statement, and function decorators wrap a group of statements enclosed in a function. So, occasionally there is a need to write a pre-action or post-action wrapper that can be used in either role.

For example, it is sometimes useful to wrap functions or groups of statements with a logger that can track the time of entry and time of exit. Rather than writing both a function decorator and a context manager for the task, the contextmanager() provides both capabilities in a single definition:

from contextlib import contextmanager
import logging

logging.basicConfig(level=logging.INFO)

@contextmanager
def track_entry_and_exit(name):
    logging.info('Entering: %s', name)
    yield
    logging.info('Exiting: %s', name)

Formerly, this would have only been usable as a context manager:

with track_entry_and_exit('widget loader'):
    print('Some time consuming activity goes here')
    load_widget()

Now, it can be used as a decorator as well:

@track_entry_and_exit('widget loader')
def activity():
    print('Some time consuming activity goes here')
    load_widget()

Trying to fulfill two roles at once places some limitations on the technique. Context managers normally have the flexibility to return an argument usable by a with statement, but there is no parallel for function decorators.

In the above example, there is not a clean way for the track_entry_and_exit context manager to return a logging instance for use in the body of enclosed statements.

（由 Michael Foord 在 bpo-9110 [https://bugs.python.org/issue?@action=redirect&bpo=9110] 中貢獻。）

decimal and fractions

Mark Dickinson crafted an elegant and efficient scheme for assuring that different numeric datatypes will have the same hash value whenever their actual values are equal (bpo-8188 [https://bugs.python.org/issue?@action=redirect&bpo=8188]):

assert hash(Fraction(3, 2)) == hash(1.5) == \
       hash(Decimal("1.5")) == hash(complex(1.5, 0))

Some of the hashing details are exposed through a new attribute, sys.hash_info, which describes the bit width of the hash value, the prime modulus, the hash values for infinity and nan, and the multiplier used for the imaginary part of a number:

>>> sys.hash_info
sys.hash_info(width=64, modulus=2305843009213693951, inf=314159, nan=0, imag=1000003)

An early decision to limit the interoperability of various numeric types has been relaxed. It is still unsupported (and ill-advised) to have implicit mixing in arithmetic expressions such as Decimal('1.1') + float('1.1') because the latter loses information in the process of constructing the binary float. However, since existing floating-point value can be converted losslessly to either a decimal or rational representation, it makes sense to add them to the constructor and to support mixed-type comparisons.

The decimal.Decimal constructor now accepts float objects directly so there in no longer a need to use the from_float() method (bpo-8257 [https://bugs.python.org/issue?@action=redirect&bpo=8257]).

Mixed type comparisons are now fully supported so that Decimal objects can be directly compared with float and fractions.Fraction (bpo-2531 [https://bugs.python.org/issue?@action=redirect&bpo=2531] and bpo-8188 [https://bugs.python.org/issue?@action=redirect&bpo=8188]).

Similar changes were made to fractions.Fraction so that the from_float() and from_decimal() methods are no longer needed (bpo-8294 [https://bugs.python.org/issue?@action=redirect&bpo=8294]):

>>> from decimal import Decimal
>>> from fractions import Fraction
>>> Decimal(1.1)
Decimal('1.100000000000000088817841970012523233890533447265625')
>>> Fraction(1.1)
Fraction(2476979795053773, 2251799813685248)

Another useful change for the decimal module is that the Context.clamp attribute is now public. This is useful in creating contexts that correspond to the decimal interchange formats specified in IEEE 754 (see bpo-8540 [https://bugs.python.org/issue?@action=redirect&bpo=8540]).

（由 Mark Dickinson 和 Raymond Hettinger 貢獻。）

ftp

The ftplib.FTP class now supports the context management protocol to unconditionally consume socket.error exceptions and to close the FTP connection when done:

>>> from ftplib import FTP
>>> with FTP("ftp1.at.proftpd.org") as ftp:
        ftp.login()
        ftp.dir()

'230 Anonymous login ok, restrictions apply.'
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 .
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 ..
dr-xr-xr-x   5 ftp      ftp          4096 May  6 10:43 CentOS
dr-xr-xr-x   3 ftp      ftp            18 Jul 10  2008 Fedora

Other file-like objects such as mmap.mmap and fileinput.input() also grew auto-closing context managers:

with fileinput.input(files=('log1.txt', 'log2.txt')) as f:
    for line in f:
        process(line)

（由 Tarek Ziadé 和 Giampaolo Rodolà 在 bpo-4972 [https://bugs.python.org/issue?@action=redirect&bpo=4972] 中貢獻，由 Georg Brandl 在 bpo-8046 [https://bugs.python.org/issue?@action=redirect&bpo=8046] 和 bpo-1286 [https://bugs.python.org/issue?@action=redirect&bpo=1286] 中貢獻。）

The FTP_TLS class now accepts a context parameter, which is a ssl.SSLContext object allowing bundling SSL configuration options, certificates and private keys into a single (potentially long-lived) structure.

（由 Giampaolo Rodolà 貢獻；bpo-8806 [https://bugs.python.org/issue?@action=redirect&bpo=8806]。）

popen

The os.popen() and subprocess.Popen() functions now support with statements for auto-closing of the file descriptors.

（由 Antoine Pitrou 和 Brian Curtin 在 bpo-7461 [https://bugs.python.org/issue?@action=redirect&bpo=7461] 和 bpo-10554 [https://bugs.python.org/issue?@action=redirect&bpo=10554] 中貢獻。）

select

The select module now exposes a new, constant attribute, PIPE_BUF, which gives the minimum number of bytes which are guaranteed not to block when select.select() says a pipe is ready for writing.

>>> import select
>>> select.PIPE_BUF
512

(Available on Unix systems. Patch by Sébastien Sablé in bpo-9862 [https://bugs.python.org/issue?@action=redirect&bpo=9862])

gzip 和 zipfile

gzip.GzipFile now implements the io.BufferedIOBase abstract base class (except for truncate()). It also has a peek() method and supports unseekable as well as zero-padded file objects.

The gzip module also gains the compress() and decompress() functions for easier in-memory compression and decompression. Keep in mind that text needs to be encoded as bytes before compressing and decompressing:

>>> import gzip
>>> s = 'Three shall be the number thou shalt count, '
>>> s += 'and the number of the counting shall be three'
>>> b = s.encode()                        # convert to utf-8
>>> len(b)
89
>>> c = gzip.compress(b)
>>> len(c)
77
>>> gzip.decompress(c).decode()[:42]      # decompress and convert to text
'Three shall be the number thou shalt count'

（由 Anand B. Pillai 在 bpo-3488 [https://bugs.python.org/issue?@action=redirect&bpo=3488] 中貢獻；由 Antoine Pitrou、Nir Aides 和 Brian Curtin 在 bpo-9962 [https://bugs.python.org/issue?@action=redirect&bpo=9962]、bpo-1675951 [https://bugs.python.org/issue?@action=redirect&bpo=1675951]、bpo-7471 [https://bugs.python.org/issue?@action=redirect&bpo=7471] 和 bpo-2846 [https://bugs.python.org/issue?@action=redirect&bpo=2846] 中貢獻。）

Also, the zipfile.ZipExtFile class was reworked internally to represent files stored inside an archive. The new implementation is significantly faster and can be wrapped in an io.BufferedReader object for more speedups. It also solves an issue where interleaved calls to read and readline gave the wrong results.

(Patch submitted by Nir Aides in bpo-7610 [https://bugs.python.org/issue?@action=redirect&bpo=7610].)

tarfile

The TarFile class can now be used as a context manager. In addition, its add() method has a new option, filter, that controls which files are added to the archive and allows the file metadata to be edited.

The new filter option replaces the older, less flexible exclude parameter which is now deprecated. If specified, the optional filter parameter needs to be a keyword argument. The user-supplied filter function accepts a TarInfo object and returns an updated TarInfo object, or if it wants the file to be excluded, the function can return None:

>>> import tarfile, glob

>>> def myfilter(tarinfo):
...     if tarinfo.isfile():             # only save real files
...         tarinfo.uname = 'monty'      # redact the user name
...         return tarinfo

>>> with tarfile.open(name='myarchive.tar.gz', mode='w:gz') as tf:
...     for filename in glob.glob('*.txt'):
...         tf.add(filename, filter=myfilter)
...     tf.list()
-rw-r--r-- monty/501        902 2011-01-26 17:59:11 annotations.txt
-rw-r--r-- monty/501        123 2011-01-26 17:59:11 general_questions.txt
-rw-r--r-- monty/501       3514 2011-01-26 17:59:11 prion.txt
-rw-r--r-- monty/501        124 2011-01-26 17:59:11 py_todo.txt
-rw-r--r-- monty/501       1399 2011-01-26 17:59:11 semaphore_notes.txt

（由 Tarek Ziadé 提議並由 Lars Gustäbel 實作於 bpo-6856 [https://bugs.python.org/issue?@action=redirect&bpo=6856]。）

hashlib

The hashlib module has two new constant attributes listing the hashing algorithms guaranteed to be present in all implementations and those available on the current implementation:

>>> import hashlib

>>> hashlib.algorithms_guaranteed
{'sha1', 'sha224', 'sha384', 'sha256', 'sha512', 'md5'}

>>> hashlib.algorithms_available
{'md2', 'SHA256', 'SHA512', 'dsaWithSHA', 'mdc2', 'SHA224', 'MD4', 'sha256',
'sha512', 'ripemd160', 'SHA1', 'MDC2', 'SHA', 'SHA384', 'MD2',
'ecdsa-with-SHA1','md4', 'md5', 'sha1', 'DSA-SHA', 'sha224',
'dsaEncryption', 'DSA', 'RIPEMD160', 'sha', 'MD5', 'sha384'}

（由 Carl Chenet 在 bpo-7418 [https://bugs.python.org/issue?@action=redirect&bpo=7418] 中提議。）

ast

The ast module has a wonderful a general-purpose tool for safely evaluating expression strings using the Python literal syntax. The ast.literal_eval() function serves as a secure alternative to the builtin eval() function which is easily abused. Python 3.2 adds bytes and set literals to the list of supported types: strings, bytes, numbers, tuples, lists, dicts, sets, booleans, and None.

>>> from ast import literal_eval

>>> request = "{'req': 3, 'func': 'pow', 'args': (2, 0.5)}"
>>> literal_eval(request)
{'args': (2, 0.5), 'req': 3, 'func': 'pow'}

>>> request = "os.system('do something harmful')"
>>> literal_eval(request)
Traceback (most recent call last):
  ...
ValueError: malformed node or string: <_ast.Call object at 0x101739a10>

（由 Benjamin Peterson 和 Georg Brandl 實作。）

os

Different operating systems use various encodings for filenames and environment variables. The os module provides two new functions, fsencode() and fsdecode(), for encoding and decoding filenames:

>>> import os
>>> filename = 'Sehenswürdigkeiten'
>>> os.fsencode(filename)
b'Sehensw\xc3\xbcrdigkeiten'

Some operating systems allow direct access to encoded bytes in the environment. If so, the os.supports_bytes_environ constant will be true.

For direct access to encoded environment variables (if available), use the new os.getenvb() function or use os.environb which is a bytes version of os.environ.

（由 Victor Stinner 貢獻。）

shutil

The shutil.copytree() function has two new options:

ignore_dangling_symlinks: when symlinks=False so that the function copies a file pointed to by a symlink, not the symlink itself. This option will silence the error raised if the file doesn't exist.

copy_function: is a callable that will be used to copy files. shutil.copy2() is used by default.

（由 Tarek Ziadé 貢獻。）

In addition, the shutil module now supports archiving operations for zipfiles, uncompressed tarfiles, gzipped tarfiles, and bzipped tarfiles. And there are functions for registering additional archiving file formats (such as xz compressed tarfiles or custom formats).

The principal functions are make_archive() and unpack_archive(). By default, both operate on the current directory (which can be set by os.chdir()) and on any sub-directories. The archive filename needs to be specified with a full pathname. The archiving step is non-destructive (the original files are left unchanged).

>>> import shutil, pprint

>>> os.chdir('mydata')  # change to the source directory
>>> f = shutil.make_archive('/var/backup/mydata',
...                         'zip')      # archive the current directory
>>> f                                   # show the name of archive
'/var/backup/mydata.zip'
>>> os.chdir('tmp')                     # change to an unpacking
>>> shutil.unpack_archive('/var/backup/mydata.zip')  # recover the data

>>> pprint.pprint(shutil.get_archive_formats())  # display known formats
[('bztar', "bzip2'ed tar-file"),
 ('gztar', "gzip'ed tar-file"),
 ('tar', 'uncompressed tar file'),
 ('zip', 'ZIP file')]

>>> shutil.register_archive_format(     # register a new archive format
...     name='xz',
...     function=xz.compress,           # callable archiving function
...     extra_args=[('level', 8)],      # arguments to the function
...     description='xz compression'
... )

（由 Tarek Ziadé 貢獻。）

sqlite3

The sqlite3 module was updated to pysqlite version 2.6.0. It has two new capabilities.

The sqlite3.Connection.in_transit attribute is true if there is an active transaction for uncommitted changes.

The sqlite3.Connection.enable_load_extension() and sqlite3.Connection.load_extension() methods allows you to load SQLite extensions from ".so" files. One well-known extension is the fulltext-search extension distributed with SQLite.

（由 R. David Murray 和 Shashwat Anand 貢獻；bpo-8845 [https://bugs.python.org/issue?@action=redirect&bpo=8845]。）

html

A new html module was introduced with only a single function, escape(), which is used for escaping reserved characters from HTML markup:

>>> import html
>>> html.escape('x > 2 && x < 7')
'x &gt; 2 &amp;&amp; x &lt; 7'

socket

The socket module has two new improvements.

Socket objects now have a detach() method which puts the socket into closed state without actually closing the underlying file descriptor. The latter can then be reused for other purposes. (Added by Antoine Pitrou; bpo-8524 [https://bugs.python.org/issue?@action=redirect&bpo=8524].)

socket.create_connection() now supports the context management protocol to unconditionally consume socket.error exceptions and to close the socket when done. (Contributed by Giampaolo Rodolà; bpo-9794 [https://bugs.python.org/issue?@action=redirect&bpo=9794].)

ssl

The ssl module added a number of features to satisfy common requirements for secure (encrypted, authenticated) internet connections:

A new class, SSLContext, serves as a container for persistent SSL data, such as protocol settings, certificates, private keys, and various other options. It includes a wrap_socket() for creating an SSL socket from an SSL context.

A new function, ssl.match_hostname(), supports server identity verification for higher-level protocols by implementing the rules of HTTPS (from RFC 2818 [https://datatracker.ietf.org/doc/html/rfc2818.html]) which are also suitable for other protocols.

The ssl.wrap_socket() constructor function now takes a ciphers argument. The ciphers string lists the allowed encryption algorithms using the format described in the OpenSSL documentation [https://docs.openssl.org/1.0.2/man1/ciphers/#cipher-list-format].

When linked against recent versions of OpenSSL, the ssl module now supports the Server Name Indication extension to the TLS protocol, allowing multiple "virtual hosts" using different certificates on a single IP port. This extension is only supported in client mode, and is activated by passing the server_hostname argument to ssl.SSLContext.wrap_socket().

Various options have been added to the ssl module, such as OP_NO_SSLv2 which disables the insecure and obsolete SSLv2 protocol.

The extension now loads all the OpenSSL ciphers and digest algorithms. If some SSL certificates cannot be verified, they are reported as an "unknown algorithm" error.

The version of OpenSSL being used is now accessible using the module attributes ssl.OPENSSL_VERSION (a string), ssl.OPENSSL_VERSION_INFO (a 5-tuple), and ssl.OPENSSL_VERSION_NUMBER (an integer).

（由 Antoine Pitrou 在 bpo-8850 [https://bugs.python.org/issue?@action=redirect&bpo=8850]、bpo-1589 [https://bugs.python.org/issue?@action=redirect&bpo=1589]、bpo-8322 [https://bugs.python.org/issue?@action=redirect&bpo=8322]、bpo-5639 [https://bugs.python.org/issue?@action=redirect&bpo=5639]、bpo-4870 [https://bugs.python.org/issue?@action=redirect&bpo=4870]、bpo-8484 [https://bugs.python.org/issue?@action=redirect&bpo=8484] 和 bpo-8321 [https://bugs.python.org/issue?@action=redirect&bpo=8321] 中貢獻。）

nntp

The nntplib module has a revamped implementation with better bytes and text semantics as well as more practical APIs. These improvements break compatibility with the nntplib version in Python 3.1, which was partly dysfunctional in itself.

Support for secure connections through both implicit (using nntplib.NNTP_SSL) and explicit (using nntplib.NNTP.starttls()) TLS has also been added.

（由 Antoine Pitrou 在 bpo-9360 [https://bugs.python.org/issue?@action=redirect&bpo=9360] 中和 Andrew Vant 在 bpo-1926 [https://bugs.python.org/issue?@action=redirect&bpo=1926] 中貢獻。）

certificates

http.client.HTTPSConnection, urllib.request.HTTPSHandler and urllib.request.urlopen() now take optional arguments to allow for server certificate checking against a set of Certificate Authorities, as recommended in public uses of HTTPS.

(Added by Antoine Pitrou, bpo-9003 [https://bugs.python.org/issue?@action=redirect&bpo=9003].)

imaplib

Support for explicit TLS on standard IMAP4 connections has been added through the new imaplib.IMAP4.starttls method.

（由 Lorenzo M. Catucci 和 Antoine Pitrou 於 bpo-4471 [https://bugs.python.org/issue?@action=redirect&bpo=4471] 貢獻。）

http.client

There were a number of small API improvements in the http.client module. The old-style HTTP 0.9 simple responses are no longer supported and the strict parameter is deprecated in all classes.

The HTTPConnection and HTTPSConnection classes now have a source_address parameter for a (host, port) tuple indicating where the HTTP connection is made from.

Support for certificate checking and HTTPS virtual hosts were added to HTTPSConnection.

The request() method on connection objects allowed an optional body argument so that a file object could be used to supply the content of the request. Conveniently, the body argument now also accepts an iterable object so long as it includes an explicit Content-Length header. This extended interface is much more flexible than before.

To establish an HTTPS connection through a proxy server, there is a new set_tunnel() method that sets the host and port for HTTP Connect tunneling.

To match the behavior of http.server, the HTTP client library now also encodes headers with ISO-8859-1 (Latin-1) encoding. It was already doing that for incoming headers, so now the behavior is consistent for both incoming and outgoing traffic. (See work by Armin Ronacher in bpo-10980 [https://bugs.python.org/issue?@action=redirect&bpo=10980].)

unittest

The unittest module has a number of improvements supporting test discovery for packages, easier experimentation at the interactive prompt, new testcase methods, improved diagnostic messages for test failures, and better method names.

The command-line call python -m unittest can now accept file paths instead of module names for running specific tests (bpo-10620 [https://bugs.python.org/issue?@action=redirect&bpo=10620]). The new test discovery can find tests within packages, locating any test importable from the top-level directory. The top-level directory can be specified with the -t option, a pattern for matching files with -p, and a directory to start discovery with -s:

$ python -m unittest discover -s my_proj_dir -p _test.py

（由 Michael Foord 貢獻。）

Experimentation at the interactive prompt is now easier because the unittest.TestCase class can now be instantiated without arguments:

>>> from unittest import TestCase
>>> TestCase().assertEqual(pow(2, 3), 8)

（由 Michael Foord 貢獻。）

The unittest module has two new methods, assertWarns() and assertWarnsRegex() to verify that a given warning type is triggered by the code under test:

with self.assertWarns(DeprecationWarning):
    legacy_function('XYZ')

（由 Antoine Pitrou 於 bpo-9754 [https://bugs.python.org/issue?@action=redirect&bpo=9754] 貢獻。）

Another new method, assertCountEqual() is used to compare two iterables to determine if their element counts are equal (whether the same elements are present with the same number of occurrences regardless of order):

def test_anagram(self):
    self.assertCountEqual('algorithm', 'logarithm')

（由 Raymond Hettinger 貢獻。）

A principal feature of the unittest module is an effort to produce meaningful diagnostics when a test fails. When possible, the failure is recorded along with a diff of the output. This is especially helpful for analyzing log files of failed test runs. However, since diffs can sometime be voluminous, there is a new maxDiff attribute that sets maximum length of diffs displayed.

In addition, the method names in the module have undergone a number of clean-ups.

For example, assertRegex() is the new name for assertRegexpMatches() which was misnamed because the test uses re.search(), not re.match(). Other methods using regular expressions are now named using short form "Regex" in preference to "Regexp" -- this matches the names used in other unittest implementations, matches Python's old name for the re module, and it has unambiguous camel-casing.

（由 Raymond Hettinger 貢獻，由 Ezio Melotti 實作。）

To improve consistency, some long-standing method aliases are being deprecated in favor of the preferred names:

舊名稱

Preferred Name

assert_()

assertTrue()

assertEquals()

assertEqual()

assertNotEquals()

assertNotEqual()

assertAlmostEquals()

assertAlmostEqual()

assertNotAlmostEquals()

assertNotAlmostEqual()

Likewise, the TestCase.fail* methods deprecated in Python 3.1 are expected to be removed in Python 3.3.

（由 Ezio Melotti 貢獻；bpo-9424 [https://bugs.python.org/issue?@action=redirect&bpo=9424]。）

The assertDictContainsSubset() method was deprecated because it was misimplemented with the arguments in the wrong order. This created hard-to-debug optical illusions where tests like TestCase().assertDictContainsSubset({'a':1, 'b':2}, {'a':1}) would fail.

（由 Raymond Hettinger 貢獻。）

random

The integer methods in the random module now do a better job of producing uniform distributions. Previously, they computed selections with int(n*random()) which had a slight bias whenever n was not a power of two. Now, multiple selections are made from a range up to the next power of two and a selection is kept only when it falls within the range 0 <= x < n. The functions and methods affected are randrange(), randint(), choice(), shuffle() and sample().

（由 Raymond Hettinger 貢獻；bpo-9025 [https://bugs.python.org/issue?@action=redirect&bpo=9025]。）

poplib

POP3_SSL class now accepts a context parameter, which is a ssl.SSLContext object allowing bundling SSL configuration options, certificates and private keys into a single (potentially long-lived) structure.

（由 Giampaolo Rodolà 貢獻；bpo-8807 [https://bugs.python.org/issue?@action=redirect&bpo=8807]。）

asyncore

asyncore.dispatcher now provides a handle_accepted() method returning a (sock, addr) pair which is called when a connection has actually been established with a new remote endpoint. This is supposed to be used as a replacement for old handle_accept() and avoids the user to call accept() directly.

（由 Giampaolo Rodolà 貢獻；bpo-6706 [https://bugs.python.org/issue?@action=redirect&bpo=6706]。）

tempfile

The tempfile module has a new context manager, TemporaryDirectory which provides easy deterministic cleanup of temporary directories:

with tempfile.TemporaryDirectory() as tmpdirname:
    print('created temporary dir:', tmpdirname)

（由 Neil Schedulenauer 和 Nick Coghlan 貢獻；bpo-5178 [https://bugs.python.org/issue?@action=redirect&bpo=5178]。）

inspect

The inspect module has a new function getgeneratorstate() to easily identify the current state of a generator-iterator:

>>> from inspect import getgeneratorstate
>>> def gen():
...     yield 'demo'
...
>>> g = gen()
>>> getgeneratorstate(g)
'GEN_CREATED'
>>> next(g)
'demo'
>>> getgeneratorstate(g)
'GEN_SUSPENDED'
>>> next(g, None)
>>> getgeneratorstate(g)
'GEN_CLOSED'

（由 Rodolfo Eckhardt 和 Nick Coghlan 於 bpo-10220 [https://bugs.python.org/issue?@action=redirect&bpo=10220] 貢獻。）

To support lookups without the possibility of activating a dynamic attribute, the inspect module has a new function, getattr_static(). Unlike hasattr(), this is a true read-only search, guaranteed not to change state while it is searching:

>>> class A:
...     @property
...     def f(self):
...         print('Running')
...         return 10
...
>>> a = A()
>>> getattr(a, 'f')
Running
10
>>> inspect.getattr_static(a, 'f')
<property object at 0x1022bd788>

（由 Michael Foord 貢獻。）

pydoc

The pydoc module now provides a much-improved web server interface, as well as a new command-line option -b to automatically open a browser window to display that server:

$ pydoc3.2 -b

（由 Ron Adam 貢獻；bpo-2001 [https://bugs.python.org/issue?@action=redirect&bpo=2001]。）

dis

The dis module gained two new functions for inspecting code, code_info() and show_code(). Both provide detailed code object information for the supplied function, method, source code string or code object. The former returns a string and the latter prints it:

>>> import dis, random
>>> dis.show_code(random.choice)
Name:              choice
Filename:          /Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/random.py
Argument count:    2
Kw-only arguments: 0
Number of locals:  3
Stack size:        11
Flags:             OPTIMIZED, NEWLOCALS, NOFREE
Constants:
   0: 'Choose a random element from a non-empty sequence.'
   1: 'Cannot choose from an empty sequence'
Names:
   0: _randbelow
   1: len
   2: ValueError
   3: IndexError
Variable names:
   0: self
   1: seq
   2: i

In addition, the dis() function now accepts string arguments so that the common idiom dis(compile(s, '', 'eval')) can be shortened to dis(s):

>>> dis('3*x+1 if x%2==1 else x//2')
  1           0 LOAD_NAME                0 (x)
              3 LOAD_CONST               0 (2)
              6 BINARY_MODULO
              7 LOAD_CONST               1 (1)
             10 COMPARE_OP               2 (==)
             13 POP_JUMP_IF_FALSE       28
             16 LOAD_CONST               2 (3)
             19 LOAD_NAME                0 (x)
             22 BINARY_MULTIPLY
             23 LOAD_CONST               1 (1)
             26 BINARY_ADD
             27 RETURN_VALUE
        >>   28 LOAD_NAME                0 (x)
             31 LOAD_CONST               0 (2)
             34 BINARY_FLOOR_DIVIDE
             35 RETURN_VALUE

Taken together, these improvements make it easier to explore how CPython is implemented and to see for yourself what the language syntax does under-the-hood.

（由 Nick Coghlan 在 bpo-9147 [https://bugs.python.org/issue?@action=redirect&bpo=9147] 中貢獻。）

dbm

All database modules now support the get() and setdefault() methods.

（由 Ray Allen 在 bpo-9523 [https://bugs.python.org/issue?@action=redirect&bpo=9523] 中建議。）

ctypes

A new type, ctypes.c_ssize_t represents the C ssize_t datatype.

site

The site module has three new functions useful for reporting on the details of a given Python installation.

getsitepackages() lists all global site-packages directories.

getuserbase() reports on the user's base directory where data can be stored.

getusersitepackages() reveals the user-specific site-packages directory path.

>>> import site
>>> site.getsitepackages()
['/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/site-packages',
 '/Library/Frameworks/Python.framework/Versions/3.2/lib/site-python',
 '/Library/Python/3.2/site-packages']
>>> site.getuserbase()
'/Users/raymondhettinger/Library/Python/3.2'
>>> site.getusersitepackages()
'/Users/raymondhettinger/Library/Python/3.2/lib/python/site-packages'

Conveniently, some of site's functionality is accessible directly from the command-line:

$ python -m site --user-base
/Users/raymondhettinger/.local
$ python -m site --user-site
/Users/raymondhettinger/.local/lib/python3.2/site-packages

（由 Tarek Ziadé 在 bpo-6693 [https://bugs.python.org/issue?@action=redirect&bpo=6693] 中貢獻。）

sysconfig

The new sysconfig module makes it straightforward to discover installation paths and configuration variables that vary across platforms and installations.

The module offers access simple access functions for platform and version information:

get_platform() returning values like linux-i586 or macosx-10.6-ppc.

get_python_version() returns a Python version string such as "3.2".

It also provides access to the paths and variables corresponding to one of seven named schemes used by distutils. Those include posix_prefix, posix_home, posix_user, nt, nt_user, os2, os2_home:

get_paths() makes a dictionary containing installation paths for the current installation scheme.

get_config_vars() returns a dictionary of platform specific variables.

There is also a convenient command-line interface:

C:\Python32>python -m sysconfig
Platform: "win32"
Python version: "3.2"
Current installation scheme: "nt"

Paths:
        data = "C:\Python32"
        include = "C:\Python32\Include"
        platinclude = "C:\Python32\Include"
        platlib = "C:\Python32\Lib\site-packages"
        platstdlib = "C:\Python32\Lib"
        purelib = "C:\Python32\Lib\site-packages"
        scripts = "C:\Python32\Scripts"
        stdlib = "C:\Python32\Lib"

Variables:
        BINDIR = "C:\Python32"
        BINLIBDEST = "C:\Python32\Lib"
        EXE = ".exe"
        INCLUDEPY = "C:\Python32\Include"
        LIBDEST = "C:\Python32\Lib"
        SO = ".pyd"
        VERSION = "32"
        abiflags = ""
        base = "C:\Python32"
        exec_prefix = "C:\Python32"
        platbase = "C:\Python32"
        prefix = "C:\Python32"
        projectbase = "C:\Python32"
        py_version = "3.2"
        py_version_nodot = "32"
        py_version_short = "3.2"
        srcdir = "C:\Python32"
        userbase = "C:\Documents and Settings\Raymond\Application Data\Python"

(Moved out of Distutils by Tarek Ziadé.)

pdb

The pdb debugger module gained a number of usability improvements:

pdb.py now has a -c option that executes commands as given in a .pdbrc script file.

A .pdbrc script file can contain continue and next commands that continue debugging.

現在 Pdb 類別建構函式接受 nosigint 引數。

New commands: l(list), ll(long list) and source for listing source code.

New commands: display and undisplay for showing or hiding the value of an expression if it has changed.

New command: interact for starting an interactive interpreter containing the global and local names found in the current scope.

Breakpoints can be cleared by breakpoint number.

（由 Georg Brandl、Antonio Cuni 和 Ilya Sandler 貢獻。）

configparser

The configparser module was modified to improve usability and predictability of the default parser and its supported INI syntax. The old ConfigParser class was removed in favor of SafeConfigParser which has in turn been renamed to ConfigParser. Support for inline comments is now turned off by default and section or option duplicates are not allowed in a single configuration source.

Config parsers gained a new API based on the mapping protocol:

>>> parser = ConfigParser()
>>> parser.read_string("""
... [DEFAULT]
... location = upper left
... visible = yes
... editable = no
... color = blue
...
... [main]
... title = Main Menu
... color = green
...
... [options]
... title = Options
... """)
>>> parser['main']['color']
'green'
>>> parser['main']['editable']
'no'
>>> section = parser['options']
>>> section['title']
'Options'
>>> section['title'] = 'Options (editable: %(editable)s)'
>>> section['title']
'Options (editable: no)'

The new API is implemented on top of the classical API, so custom parser subclasses should be able to use it without modifications.

The INI file structure accepted by config parsers can now be customized. Users can specify alternative option/value delimiters and comment prefixes, change the name of the DEFAULT section or switch the interpolation syntax.

There is support for pluggable interpolation including an additional interpolation handler ExtendedInterpolation:

>>> parser = ConfigParser(interpolation=ExtendedInterpolation())
>>> parser.read_dict({'buildout': {'directory': '/home/ambv/zope9'},
...                   'custom': {'prefix': '/usr/local'}})
>>> parser.read_string("""
... [buildout]
... parts =
...   zope9
...   instance
... find-links =
...   ${buildout:directory}/downloads/dist
...
... [zope9]
... recipe = plone.recipe.zope9install
... location = /opt/zope
...
... [instance]
... recipe = plone.recipe.zope9instance
... zope9-location = ${zope9:location}
... zope-conf = ${custom:prefix}/etc/zope.conf
... """)
>>> parser['buildout']['find-links']
'\n/home/ambv/zope9/downloads/dist'
>>> parser['instance']['zope-conf']
'/usr/local/etc/zope.conf'
>>> instance = parser['instance']
>>> instance['zope-conf']
'/usr/local/etc/zope.conf'
>>> instance['zope9-location']
'/opt/zope'

A number of smaller features were also introduced, like support for specifying encoding in read operations, specifying fallback values for get-functions, or reading directly from dictionaries and strings.

(All changes contributed by Łukasz Langa.)

urllib.parse

A number of usability improvements were made for the urllib.parse module.

The urlparse() function now supports IPv6 [https://en.wikipedia.org/wiki/IPv6] addresses as described in RFC 2732 [https://datatracker.ietf.org/doc/html/rfc2732.html]:

>>> import urllib.parse
>>> urllib.parse.urlparse('http://[dead:beef:cafe:5417:affe:8FA3:deaf:feed]/foo/')
ParseResult(scheme='http',
            netloc='[dead:beef:cafe:5417:affe:8FA3:deaf:feed]',
            path='/foo/',
            params='',
            query='',
            fragment='')

The urldefrag() function now returns a named tuple:

>>> r = urllib.parse.urldefrag('http://python.org/about/#target')
>>> r
DefragResult(url='http://python.org/about/', fragment='target')
>>> r[0]
'http://python.org/about/'
>>> r.fragment
'target'

And, the urlencode() function is now much more flexible, accepting either a string or bytes type for the query argument. If it is a string, then the safe, encoding, and error parameters are sent to quote_plus() for encoding:

>>> urllib.parse.urlencode([
...      ('type', 'telenovela'),
...      ('name', '¿Dónde Está Elisa?')],
...      encoding='latin-1')
'type=telenovela&name=%BFD%F3nde+Est%E1+Elisa%3F'

As detailed in Parsing ASCII Encoded Bytes, all the urllib.parse functions now accept ASCII-encoded byte strings as input, so long as they are not mixed with regular strings. If ASCII-encoded byte strings are given as parameters, the return types will also be an ASCII-encoded byte strings:

>>> urllib.parse.urlparse(b'http://www.python.org:80/about/')
ParseResultBytes(scheme=b'http', netloc=b'www.python.org:80',
                 path=b'/about/', params=b'', query=b'', fragment=b'')

(Work by Nick Coghlan, Dan Mahn, and Senthil Kumaran in bpo-2987 [https://bugs.python.org/issue?@action=redirect&bpo=2987], bpo-5468 [https://bugs.python.org/issue?@action=redirect&bpo=5468], and bpo-9873 [https://bugs.python.org/issue?@action=redirect&bpo=9873].)

mailbox

Thanks to a concerted effort by R. David Murray, the mailbox module has been fixed for Python 3.2. The challenge was that mailbox had been originally designed with a text interface, but email messages are best represented with bytes because various parts of a message may have different encodings.

The solution harnessed the email package's binary support for parsing arbitrary email messages. In addition, the solution required a number of API changes.

As expected, the add() method for mailbox.Mailbox objects now accepts binary input.

StringIO and text file input are deprecated. Also, string input will fail early if non-ASCII characters are used. Previously it would fail when the email was processed in a later step.

There is also support for binary output. The get_file() method now returns a file in the binary mode (where it used to incorrectly set the file to text-mode). There is also a new get_bytes() method that returns a bytes representation of a message corresponding to a given key.

It is still possible to get non-binary output using the old API's get_string() method, but that approach is not very useful. Instead, it is best to extract messages from a Message object or to load them from binary input.

(Contributed by R. David Murray, with efforts from Steffen Daode Nurpmeso and an initial patch by Victor Stinner in bpo-9124 [https://bugs.python.org/issue?@action=redirect&bpo=9124].)

turtledemo

The demonstration code for the turtle module was moved from the Demo directory to main library. It includes over a dozen sample scripts with lively displays. Being on sys.path, it can now be run directly from the command-line:

$ python -m turtledemo

(Moved from the Demo directory by Alexander Belopolsky in bpo-10199 [https://bugs.python.org/issue?@action=redirect&bpo=10199].)

Multi-threading

The mechanism for serializing execution of concurrently running Python threads (generally known as the GIL or Global Interpreter Lock) has been rewritten. Among the objectives were more predictable switching intervals and reduced overhead due to lock contention and the number of ensuing system calls. The notion of a "check interval" to allow thread switches has been abandoned and replaced by an absolute duration expressed in seconds. This parameter is tunable through sys.setswitchinterval(). It currently defaults to 5 milliseconds.

Additional details about the implementation can be read from a python-dev mailing-list message [https://mail.python.org/pipermail/python-dev/2009-October/093321.html] (however, "priority requests" as exposed in this message have not been kept for inclusion).

（由 Antoine Pitrou 貢獻。）

Regular and recursive locks now accept an optional timeout argument to their acquire() method. (Contributed by Antoine Pitrou; bpo-7316 [https://bugs.python.org/issue?@action=redirect&bpo=7316].)

Similarly, threading.Semaphore.acquire() also gained a timeout argument. (Contributed by Torsten Landschoff; bpo-850728 [https://bugs.python.org/issue?@action=redirect&bpo=850728].)

Regular and recursive lock acquisitions can now be interrupted by signals on platforms using Pthreads. This means that Python programs that deadlock while acquiring locks can be successfully killed by repeatedly sending SIGINT to the process (by pressing Ctrl+C in most shells). (Contributed by Reid Kleckner; bpo-8844 [https://bugs.python.org/issue?@action=redirect&bpo=8844].)

最佳化

A number of small performance enhancements have been added:

Python's peephole optimizer now recognizes patterns such x in {1, 2, 3} as being a test for membership in a set of constants. The optimizer recasts the set as a frozenset and stores the pre-built constant.

Now that the speed penalty is gone, it is practical to start writing membership tests using set-notation. This style is both semantically clear and operationally fast:

extension = name.rpartition('.')[2]
if extension in {'xml', 'html', 'xhtml', 'css'}:
    handle(name)

(Patch and additional tests contributed by Dave Malcolm; bpo-6690 [https://bugs.python.org/issue?@action=redirect&bpo=6690]).

Serializing and unserializing data using the pickle module is now several times faster.

（由 Alexandre Vassalotti、Antoine Pitrou 和 Unladen Swallow 團隊在 bpo-9410 [https://bugs.python.org/issue?@action=redirect&bpo=9410] 和 bpo-3873 [https://bugs.python.org/issue?@action=redirect&bpo=3873] 中貢獻。）

The Timsort algorithm [https://en.wikipedia.org/wiki/Timsort] used in list.sort() and sorted() now runs faster and uses less memory when called with a key function. Previously, every element of a list was wrapped with a temporary object that remembered the key value associated with each element. Now, two arrays of keys and values are sorted in parallel. This saves the memory consumed by the sort wrappers, and it saves time lost to delegating comparisons.

(Patch by Daniel Stutzbach in bpo-9915 [https://bugs.python.org/issue?@action=redirect&bpo=9915].)

JSON decoding performance is improved and memory consumption is reduced whenever the same string is repeated for multiple keys. Also, JSON encoding now uses the C speedups when the sort_keys argument is true.

（由 Antoine Pitrou 在 bpo-7451 [https://bugs.python.org/issue?@action=redirect&bpo=7451] 中貢獻、由 Raymond Hettinger 和 Antoine Pitrou 在 bpo-10314 [https://bugs.python.org/issue?@action=redirect&bpo=10314] 中貢獻。）

Recursive locks (created with the threading.RLock() API) now benefit from a C implementation which makes them as fast as regular locks, and between 10x and 15x faster than their previous pure Python implementation.

（由 Antoine Pitrou 貢獻；bpo-3001 [https://bugs.python.org/issue?@action=redirect&bpo=3001]。）

The fast-search algorithm in stringlib is now used by the split(), rsplit(), splitlines() and replace() methods on bytes, bytearray and str objects. Likewise, the algorithm is also used by rfind(), rindex(), rsplit() and rpartition().

(Patch by Florent Xicluna in bpo-7622 [https://bugs.python.org/issue?@action=redirect&bpo=7622] and bpo-7462 [https://bugs.python.org/issue?@action=redirect&bpo=7462].)

Integer to string conversions now work two "digits" at a time, reducing the number of division and modulo operations.

(bpo-6713 [https://bugs.python.org/issue?@action=redirect&bpo=6713] by Gawain Bolton, Mark Dickinson, and Victor Stinner.)

There were several other minor optimizations. Set differencing now runs faster when one operand is much larger than the other (patch by Andress Bennetts in bpo-8685 [https://bugs.python.org/issue?@action=redirect&bpo=8685]). The array.repeat() method has a faster implementation (bpo-1569291 [https://bugs.python.org/issue?@action=redirect&bpo=1569291] by Alexander Belopolsky). The BaseHTTPRequestHandler has more efficient buffering (bpo-3709 [https://bugs.python.org/issue?@action=redirect&bpo=3709] by Andrew Schaaf). The operator.attrgetter() function has been sped-up (bpo-10160 [https://bugs.python.org/issue?@action=redirect&bpo=10160] by Christos Georgiou). And ConfigParser loads multi-line arguments a bit faster (bpo-7113 [https://bugs.python.org/issue?@action=redirect&bpo=7113] by Łukasz Langa).

Unicode

Python has been updated to Unicode 6.0.0 [https://unicode.org/versions/Unicode6.0.0/]. The update to the standard adds over 2,000 new characters including emoji [https://en.wikipedia.org/wiki/Emoji] symbols which are important for mobile phones.

In addition, the updated standard has altered the character properties for two Kannada characters (U+0CF1, U+0CF2) and one New Tai Lue numeric character (U+19DA), making the former eligible for use in identifiers while disqualifying the latter. For more information, see Unicode Character Database Changes [https://www.unicode.org/versions/Unicode6.0.0/#Database_Changes].

編解碼器

Support was added for cp720 Arabic DOS encoding (bpo-1616979 [https://bugs.python.org/issue?@action=redirect&bpo=1616979]).

MBCS encoding no longer ignores the error handler argument. In the default strict mode, it raises an UnicodeDecodeError when it encounters an undecodable byte sequence and an UnicodeEncodeError for an unencodable character.

The MBCS codec supports 'strict' and 'ignore' error handlers for decoding, and 'strict' and 'replace' for encoding.

To emulate Python3.1 MBCS encoding, select the 'ignore' handler for decoding and the 'replace' handler for encoding.

On Mac OS X, Python decodes command line arguments with 'utf-8' rather than the locale encoding.

By default, tarfile uses 'utf-8' encoding on Windows (instead of 'mbcs') and the 'surrogateescape' error handler on all operating systems.

文件

The documentation continues to be improved.

A table of quick links has been added to the top of lengthy sections such as 內建函式. In the case of itertools, the links are accompanied by tables of cheatsheet-style summaries to provide an overview and memory jog without having to read all of the docs.

In some cases, the pure Python source code can be a helpful adjunct to the documentation, so now many modules now feature quick links to the latest version of the source code. For example, the functools module documentation has a quick link at the top labeled:

Source code Lib/functools.py [https://github.com/python/cpython/tree/3.14/Lib/functools.py].

(Contributed by Raymond Hettinger; see rationale [https://rhettinger.wordpress.com/2011/01/28/open-your-source-more/].)

The docs now contain more examples and recipes. In particular, re module has an extensive section, Regular Expression Examples. Likewise, the itertools module continues to be updated with new Itertools 應用技巧.

The datetime module now has an auxiliary implementation in pure Python. No functionality was changed. This just provides an easier-to-read alternate implementation.

（由 Alexander Belopolsky 在 bpo-9528 [https://bugs.python.org/issue?@action=redirect&bpo=9528] 中貢獻。）

The unmaintained Demo directory has been removed. Some demos were integrated into the documentation, some were moved to the Tools/demo directory, and others were removed altogether.

（由 Georg Brandl 在 bpo-7962 [https://bugs.python.org/issue?@action=redirect&bpo=7962] 中貢獻。）

IDLE

The format menu now has an option to clean source files by stripping trailing whitespace.

（由 Raymond Hettinger 貢獻；bpo-5150 [https://bugs.python.org/issue?@action=redirect&bpo=5150]。）

IDLE on Mac OS X now works with both Carbon AquaTk and Cocoa AquaTk.

（由 Kevin Walzer、Ned Deily 和 Ronald Oussoren 貢獻；bpo-6075 [https://bugs.python.org/issue?@action=redirect&bpo=6075]。）

Code Repository

In addition to the existing Subversion code repository at https://svn.python.org there is now a Mercurial [https://www.mercurial-scm.org/] repository at https://hg.python.org/.

After the 3.2 release, there are plans to switch to Mercurial as the primary repository. This distributed version control system should make it easier for members of the community to create and share external changesets. See PEP 385 [https://peps.python.org/pep-0385/] for details.

To learn to use the new version control system, see the Quick Start [https://www.mercurial-scm.org/wiki/QuickStart] or the Guide to Mercurial Workflows [https://www.mercurial-scm.org/guide].

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

The idle, pydoc and 2to3 scripts are now installed with a version-specific suffix on make altinstall (bpo-10679 [https://bugs.python.org/issue?@action=redirect&bpo=10679]).

The C functions that access the Unicode Database now accept and return characters from the full Unicode range, even on narrow unicode builds (Py_UNICODE_TOLOWER, Py_UNICODE_ISDECIMAL, and others). A visible difference in Python is that unicodedata.numeric() now returns the correct value for large code points, and repr() may consider more characters as printable.

(Reported by Bupjoe Lee and fixed by Amaury Forgeot D'Arc; bpo-5127 [https://bugs.python.org/issue?@action=redirect&bpo=5127].)

Computed gotos are now enabled by default on supported compilers (which are detected by the configure script). They can still be disabled selectively by specifying --without-computed-gotos.

（由 Antoine Pitrou 貢獻；bpo-9203 [https://bugs.python.org/issue?@action=redirect&bpo=9203]。）

The option --with-wctype-functions was removed. The built-in unicode database is now used for all functions.

（由 Amaury Forgeot D'Arc 貢獻；bpo-9210 [https://bugs.python.org/issue?@action=redirect&bpo=9210]。）

Hash values are now values of a new type, Py_hash_t, which is defined to be the same size as a pointer. Previously they were of type long, which on some 64-bit operating systems is still only 32 bits long. As a result of this fix, set and dict can now hold more than 2**32 entries on builds with 64-bit pointers (previously, they could grow to that size but their performance degraded catastrophically).

（由 Raymond Hettinger 建議並由 Benjamin Peterson 實作；bpo-9778 [https://bugs.python.org/issue?@action=redirect&bpo=9778]。）

A new macro Py_VA_COPY copies the state of the variable argument list. It is equivalent to C99 va_copy but available on all Python platforms (bpo-2443 [https://bugs.python.org/issue?@action=redirect&bpo=2443]).

A new C API function PySys_SetArgvEx() allows an embedded interpreter to set sys.argv without also modifying sys.path (bpo-5753 [https://bugs.python.org/issue?@action=redirect&bpo=5753]).

PyEval_CallObject() is now only available in macro form. The function declaration, which was kept for backwards compatibility reasons, is now removed -- the macro was introduced in 1997 (bpo-8276 [https://bugs.python.org/issue?@action=redirect&bpo=8276]).

There is a new function PyLong_AsLongLongAndOverflow() which is analogous to PyLong_AsLongAndOverflow(). They both serve to convert Python int into a native fixed-width type while providing detection of cases where the conversion won't fit (bpo-7767 [https://bugs.python.org/issue?@action=redirect&bpo=7767]).

The PyUnicode_CompareWithASCIIString() function now returns not equal if the Python string is NUL terminated.

There is a new function PyErr_NewExceptionWithDoc() that is like PyErr_NewException() but allows a docstring to be specified. This lets C exceptions have the same self-documenting capabilities as their pure Python counterparts (bpo-7033 [https://bugs.python.org/issue?@action=redirect&bpo=7033]).

When compiled with the --with-valgrind option, the pymalloc allocator will be automatically disabled when running under Valgrind. This gives improved memory leak detection when running under Valgrind, while taking advantage of pymalloc at other times (bpo-2422 [https://bugs.python.org/issue?@action=redirect&bpo=2422]).

Removed the O? format from the PyArg_Parse functions. The format is no longer used and it had never been documented (bpo-8837 [https://bugs.python.org/issue?@action=redirect&bpo=8837]).

There were a number of other small changes to the C-API. See the Misc/NEWS [https://github.com/python/cpython/blob/v3.2.6/Misc/NEWS] file for a complete list.

Also, there were a number of updates to the Mac OS X build, see Mac/BuildScript/README.txt [https://github.com/python/cpython/blob/v3.2.6/Mac/BuildScript/README.txt] for details. For users running a 32/64-bit build, there is a known problem with the default Tcl/Tk on Mac OS X 10.6. Accordingly, we recommend installing an updated alternative such as ActiveState Tcl/Tk 8.5.9 [https://web.archive.org/web/20101208191259/https://www.activestate.com/activetcl/downloads]. See https://www.python.org/download/mac/tcltk/ for additional details.

移植至 Python 3.2

This section lists previously described changes and other bugfixes that may require changes to your code:

The configparser module has a number of clean-ups. The major change is to replace the old ConfigParser class with long-standing preferred alternative SafeConfigParser. In addition there are a number of smaller incompatibilities:

The interpolation syntax is now validated on get() and set() operations. In the default interpolation scheme, only two tokens with percent signs are valid: %(name)s and %%, the latter being an escaped percent sign.

The set() and add_section() methods now verify that values are actual strings. Formerly, unsupported types could be introduced unintentionally.

Duplicate sections or options from a single source now raise either DuplicateSectionError or DuplicateOptionError. Formerly, duplicates would silently overwrite a previous entry.

Inline comments are now disabled by default so now the ; character can be safely used in values.

Comments now can be indented. Consequently, for ; or # to appear at the start of a line in multiline values, it has to be interpolated. This keeps comment prefix characters in values from being mistaken as comments.

"" is now a valid value and is no longer automatically converted to an empty string. For empty strings, use "option =" in a line.

The nntplib module was reworked extensively, meaning that its APIs are often incompatible with the 3.1 APIs.

bytearray objects can no longer be used as filenames; instead, they should be converted to bytes.

The array.tostring() and array.fromstring() have been renamed to array.tobytes() and array.frombytes() for clarity. The old names have been deprecated. (See bpo-8990 [https://bugs.python.org/issue?@action=redirect&bpo=8990].)

PyArg_Parse*() 函式：

"t#" 格式已被移除：請改用 "s#" 或 "s*"

"w" 和 "w#" 格式已被移除：請改用 "w*"

The PyCObject type, deprecated in 3.1, has been removed. To wrap opaque C pointers in Python objects, the PyCapsule API should be used instead; the new type has a well-defined interface for passing typing safety information and a less complicated signature for calling a destructor.

The sys.setfilesystemencoding() function was removed because it had a flawed design.

The random.seed() function and method now salt string seeds with an sha512 hash function. To access the previous version of seed in order to reproduce Python 3.1 sequences, set the version argument to 1, random.seed(s, version=1).

The previously deprecated string.maketrans() function has been removed in favor of the static methods bytes.maketrans() and bytearray.maketrans(). This change solves the confusion around which types were supported by the string module. Now, str, bytes, and bytearray each have their own maketrans and translate methods with intermediate translation tables of the appropriate type.

（由 Georg Brandl 貢獻；bpo-5675 [https://bugs.python.org/issue?@action=redirect&bpo=5675]。）

The previously deprecated contextlib.nested() function has been removed in favor of a plain with statement which can accept multiple context managers. The latter technique is faster (because it is built-in), and it does a better job finalizing multiple context managers when one of them raises an exception:

with open('mylog.txt') as infile, open('a.out', 'w') as outfile:
    for line in infile:
        if '<critical>' in line:
            outfile.write(line)

（由 Georg Brandl 和 Mattias Brändström 貢獻；appspot 問題 53094 [https://codereview.appspot.com/53094]。）

struct.pack() now only allows bytes for the s string pack code. Formerly, it would accept text arguments and implicitly encode them to bytes using UTF-8. This was problematic because it made assumptions about the correct encoding and because a variable-length encoding can fail when writing to fixed length segment of a structure.

Code such as struct.pack('<6sHHBBB', 'GIF87a', x, y) should be rewritten with to use bytes instead of text, struct.pack('<6sHHBBB', b'GIF87a', x, y).

(Discovered by David Beazley and fixed by Victor Stinner; bpo-10783 [https://bugs.python.org/issue?@action=redirect&bpo=10783].)

The xml.etree.ElementTree class now raises an xml.etree.ElementTree.ParseError when a parse fails. Previously it raised an xml.parsers.expat.ExpatError.

The new, longer str() value on floats may break doctests which rely on the old output format.

In subprocess.Popen, the default value for close_fds is now True under Unix; under Windows, it is True if the three standard streams are set to None, False otherwise. Previously, close_fds was always False by default, which produced difficult to solve bugs or race conditions when open file descriptors would leak into the child process.

Support for legacy HTTP 0.9 has been removed from urllib.request and http.client. Such support is still present on the server side (in http.server).

（由 Antoine Pitrou 於 bpo-10711 [https://bugs.python.org/issue?@action=redirect&bpo=10711] 貢獻。）

SSL sockets in timeout mode now raise socket.timeout when a timeout occurs, rather than a generic SSLError.

（由 Antoine Pitrou 於 bpo-10272 [https://bugs.python.org/issue?@action=redirect&bpo=10272] 貢獻。）

The misleading functions PyEval_AcquireLock() and PyEval_ReleaseLock() have been officially deprecated. The thread-state aware APIs (such as PyEval_SaveThread() and PyEval_RestoreThread()) should be used instead.

Due to security risks, asyncore.handle_accept() has been deprecated, and a new function, asyncore.handle_accepted(), was added to replace it.

（由 Giampaolo Rodola 在 bpo-6706 [https://bugs.python.org/issue?@action=redirect&bpo=6706] 中貢獻。）

Due to the new GIL implementation, PyEval_InitThreads() cannot be called before Py_Initialize() anymore.

Python 3.1 有什麼新功能

作者:

Raymond Hettinger

本文介紹了 Python 3.1 與 3.0 相比的新功能。Python 3.1 已於 2009 年 6 月 27 日發布。

PEP 372 [https://peps.python.org/pep-0372/]：有序字典

Regular Python dictionaries iterate over key/value pairs in arbitrary order. Over the years, a number of authors have written alternative implementations that remember the order that the keys were originally inserted. Based on the experiences from those implementations, a new collections.OrderedDict class has been introduced.

The OrderedDict API is substantially the same as regular dictionaries but will iterate over keys and values in a guaranteed order depending on when a key was first inserted. If a new entry overwrites an existing entry, the original insertion position is left unchanged. Deleting an entry and reinserting it will move it to the end.

The standard library now supports use of ordered dictionaries in several modules. The configparser module uses them by default. This lets configuration files be read, modified, and then written back in their original order. The _asdict() method for collections.namedtuple() now returns an ordered dictionary with the values appearing in the same order as the underlying tuple indices. The json module is being built-out with an object_pairs_hook to allow OrderedDicts to be built by the decoder. Support was also added for third-party tools like PyYAML [https://pyyaml.org/].

也參考

PEP 372 [https://peps.python.org/pep-0372/] - 有序字典

PEP written by Armin Ronacher and Raymond Hettinger. Implementation written by Raymond Hettinger.

Since an ordered dictionary remembers its insertion order, it can be used in conjunction with sorting to make a sorted dictionary:

>>> # regular unsorted dictionary
>>> d = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2}

>>> # dictionary sorted by key
>>> OrderedDict(sorted(d.items(), key=lambda t: t[0]))
OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])

>>> # dictionary sorted by value
>>> OrderedDict(sorted(d.items(), key=lambda t: t[1]))
OrderedDict([('pear', 1), ('orange', 2), ('banana', 3), ('apple', 4)])

>>> # dictionary sorted by length of the key string
>>> OrderedDict(sorted(d.items(), key=lambda t: len(t[0])))
OrderedDict([('pear', 1), ('apple', 4), ('orange', 2), ('banana', 3)])

The new sorted dictionaries maintain their sort order when entries are deleted. But when new keys are added, the keys are appended to the end and the sort is not maintained.

PEP 378: Format Specifier for Thousands Separator

The built-in format() function and the str.format() method use a mini-language that now includes a simple, non-locale aware way to format a number with a thousands separator. That provides a way to humanize a program's output, improving its professional appearance and readability:

>>> format(1234567, ',d')
'1,234,567'
>>> format(1234567.89, ',.2f')
'1,234,567.89'
>>> format(12345.6 + 8901234.12j, ',f')
'12,345.600000+8,901,234.120000j'
>>> format(Decimal('1234567.89'), ',f')
'1,234,567.89'

The supported types are int, float, complex and decimal.Decimal.

Discussions are underway about how to specify alternative separators like dots, spaces, apostrophes, or underscores. Locale-aware applications should use the existing n format specifier which already has some support for thousands separators.

也參考

PEP 378 [https://peps.python.org/pep-0378/] - Format Specifier for Thousands Separator

PEP written by Raymond Hettinger and implemented by Eric Smith and Mark Dickinson.

其他語言更動

Some smaller changes made to the core Python language are:

Directories and zip archives containing a __main__.py file can now be executed directly by passing their name to the interpreter. The directory/zipfile is automatically inserted as the first entry in sys.path. (Suggestion and initial patch by Andy Chu; revised patch by Phillip J. Eby and Nick Coghlan; bpo-1739468 [https://bugs.python.org/issue?@action=redirect&bpo=1739468].)

The int() type gained a bit_length method that returns the number of bits necessary to represent its argument in binary:

>>> n = 37
>>> bin(37)
'0b100101'
>>> n.bit_length()
6
>>> n = 2**123-1
>>> n.bit_length()
123
>>> (n+1).bit_length()
124

（由 Fredrik Johansson、Victor Stinner、Raymond Hettinger 和 Mark Dickinson 貢獻；bpo-3439 [https://bugs.python.org/issue?@action=redirect&bpo=3439]。）

The fields in format() strings can now be automatically numbered:

>>> 'Sir {} of {}'.format('Gallahad', 'Camelot')
'Sir Gallahad of Camelot'

Formerly, the string would have required numbered fields such as: 'Sir {0} of {1}'.

（由 Eric Smith 貢獻；bpo-5237 [https://bugs.python.org/issue?@action=redirect&bpo=5237]。）

The string.maketrans() function is deprecated and is replaced by new static methods, bytes.maketrans() and bytearray.maketrans(). This change solves the confusion around which types were supported by the string module. Now, str, bytes, and bytearray each have their own maketrans and translate methods with intermediate translation tables of the appropriate type.

（由 Georg Brandl 貢獻；bpo-5675 [https://bugs.python.org/issue?@action=redirect&bpo=5675]。）

The syntax of the with statement now allows multiple context managers in a single statement:

>>> with open('mylog.txt') as infile, open('a.out', 'w') as outfile:
...     for line in infile:
...         if '<critical>' in line:
...             outfile.write(line)

With the new syntax, the contextlib.nested() function is no longer needed and is now deprecated.

（由 Georg Brandl 和 Mattias Brändström 貢獻；appspot 問題 53094 [https://codereview.appspot.com/53094]。）

round(x, n) now returns an integer if x is an integer. Previously it returned a float:

>>> round(1123, -2)
1100

（由 Mark Dickinson 貢獻；bpo-4707 [https://bugs.python.org/issue?@action=redirect&bpo=4707]。）

Python now uses David Gay's algorithm for finding the shortest floating-point representation that doesn't change its value. This should help mitigate some of the confusion surrounding binary floating-point numbers.

The significance is easily seen with a number like 1.1 which does not have an exact equivalent in binary floating point. Since there is no exact equivalent, an expression like float('1.1') evaluates to the nearest representable value which is 0x1.199999999999ap+0 in hex or 1.100000000000000088817841970012523233890533447265625 in decimal. That nearest value was and still is used in subsequent floating-point calculations.

What is new is how the number gets displayed. Formerly, Python used a simple approach. The value of repr(1.1) was computed as format(1.1, '.17g') which evaluated to '1.1000000000000001'. The advantage of using 17 digits was that it relied on IEEE-754 guarantees to assure that eval(repr(1.1)) would round-trip exactly to its original value. The disadvantage is that many people found the output to be confusing (mistaking intrinsic limitations of binary floating-point representation as being a problem with Python itself).

The new algorithm for repr(1.1) is smarter and returns '1.1'. Effectively, it searches all equivalent string representations (ones that get stored with the same underlying float value) and returns the shortest representation.

The new algorithm tends to emit cleaner representations when possible, but it does not change the underlying values. So, it is still the case that 1.1 + 2.2 != 3.3 even though the representations may suggest otherwise.

The new algorithm depends on certain features in the underlying floating-point implementation. If the required features are not found, the old algorithm will continue to be used. Also, the text pickle protocols assure cross-platform portability by using the old algorithm.

（由 Eric Smith 和 Mark Dickinson 貢獻；bpo-1580 [https://bugs.python.org/issue?@action=redirect&bpo=1580]）

新增、改進和棄用的模組

Added a collections.Counter class to support convenient counting of unique items in a sequence or iterable:

>>> Counter(['red', 'blue', 'red', 'green', 'blue', 'blue'])
Counter({'blue': 3, 'red': 2, 'green': 1})

（由 Raymond Hettinger 貢獻；bpo-1696199 [https://bugs.python.org/issue?@action=redirect&bpo=1696199]。）

Added a new module, tkinter.ttk for access to the Tk themed widget set. The basic idea of ttk is to separate, to the extent possible, the code implementing a widget's behavior from the code implementing its appearance.

（由 Guilherme Polo 貢獻；bpo-2983 [https://bugs.python.org/issue?@action=redirect&bpo=2983]。）

The gzip.GzipFile and bz2.BZ2File classes now support the context management protocol:

>>> # 在寫入後自動關閉檔案
>>> with gzip.GzipFile(filename, "wb") as f:
...     f.write(b"xxx")

（由 Antoine Pitrou 貢獻。）

The decimal module now supports methods for creating a decimal object from a binary float. The conversion is exact but can sometimes be surprising:

>>> Decimal.from_float(1.1)
Decimal('1.100000000000000088817841970012523233890533447265625')

The long decimal result shows the actual binary fraction being stored for 1.1. The fraction has many digits because 1.1 cannot be exactly represented in binary.

（由 Raymond Hettinger 和 Mark Dickinso 貢獻。）

The itertools module grew two new functions. The itertools.combinations_with_replacement() function is one of four for generating combinatorics including permutations and Cartesian products. The itertools.compress() function mimics its namesake from APL. Also, the existing itertools.count() function now has an optional step argument and can accept any type of counting sequence including fractions.Fraction and decimal.Decimal:

>>> [p+q for p,q in combinations_with_replacement('LOVE', 2)]
['LL', 'LO', 'LV', 'LE', 'OO', 'OV', 'OE', 'VV', 'VE', 'EE']

>>> list(compress(data=range(10), selectors=[0,0,1,1,0,1,0,1,0,0]))
[2, 3, 5, 7]

>>> c = count(start=Fraction(1,2), step=Fraction(1,6))
>>> [next(c), next(c), next(c), next(c)]
[Fraction(1, 2), Fraction(2, 3), Fraction(5, 6), Fraction(1, 1)]

（由 Raymond Hettinger 貢獻。）

collections.namedtuple() now supports a keyword argument rename which lets invalid fieldnames be automatically converted to positional names in the form _0, _1, etc. This is useful when the field names are being created by an external source such as a CSV header, SQL field list, or user input:

>>> query = input()
SELECT region, dept, count(*) FROM main GROUPBY region, dept

>>> cursor.execute(query)
>>> query_fields = [desc[0] for desc in cursor.description]
>>> UserQuery = namedtuple('UserQuery', query_fields, rename=True)
>>> pprint.pprint([UserQuery(*row) for row in cursor])
[UserQuery(region='South', dept='Shipping', _2=185),
 UserQuery(region='North', dept='Accounting', _2=37),
 UserQuery(region='West', dept='Sales', _2=419)]

（由 Raymond Hettinger 貢獻；bpo-1818 [https://bugs.python.org/issue?@action=redirect&bpo=1818]。）

The re.sub()、re.subn() 和 re.split() 函式現在接受一個 flags 參數。

（由 Gregory Smith 貢獻。）

The logging module now implements a simple logging.NullHandler class for applications that are not using logging but are calling library code that does. Setting-up a null handler will suppress spurious warnings such as "No handlers could be found for logger foo":

>>> h = logging.NullHandler()
>>> logging.getLogger("foo").addHandler(h)

（由 Vinay Sajip 貢獻；bpo-4384 [https://bugs.python.org/issue?@action=redirect&bpo=4384]）。

The runpy module which supports the -m command line switch now supports the execution of packages by looking for and executing a __main__ submodule when a package name is supplied.

（由 Andi Vajda 貢獻；bpo-4195 [https://bugs.python.org/issue?@action=redirect&bpo=4195]。）

The pdb module can now access and display source code loaded via zipimport (or any other conformant PEP 302 [https://peps.python.org/pep-0302/] loader).

（由 Alexander Belopolsky 貢獻；bpo-4201 [https://bugs.python.org/issue?@action=redirect&bpo=4201]。）

functools.partial objects can now be pickled.

（由 Antoine Pitrou 和 Jesse Noller 建議。由 Jack Diederich 實作；bpo-5228 [https://bugs.python.org/issue?@action=redirect&bpo=5228]。）

Add pydoc help topics for symbols so that help('@') works as expected in the interactive environment.

（由 David Laban 貢獻；bpo-4739 [https://bugs.python.org/issue?@action=redirect&bpo=4739]。）

The unittest module now supports skipping individual tests or classes of tests. And it supports marking a test as an expected failure, a test that is known to be broken, but shouldn't be counted as a failure on a TestResult:

class TestGizmo(unittest.TestCase):

    @unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
    def test_gizmo_on_windows(self):
        ...

    @unittest.expectedFailure
    def test_gimzo_without_required_library(self):
        ...

Also, tests for exceptions have been builtout to work with context managers using the with statement:

def test_division_by_zero(self):
    with self.assertRaises(ZeroDivisionError):
        x / 0

In addition, several new assertion methods were added including assertSetEqual(), assertDictEqual(), assertDictContainsSubset(), assertListEqual(), assertTupleEqual(), assertSequenceEqual(), assertRaisesRegexp(), assertIsNone(), and assertIsNotNone().

（由 Benjamin Peterson 和 Antoine Pitrou 貢獻。）

The io 模組為 seek() 方法新增了三個常數：SEEK_SET、SEEK_CUR 和 SEEK_END。

The sys.version_info tuple is now a named tuple:

>>> sys.version_info
sys.version_info(major=3, minor=1, micro=0, releaselevel='alpha', serial=2)

（由 Ross Light 貢獻；bpo-4285 [https://bugs.python.org/issue?@action=redirect&bpo=4285]。）

The nntplib and imaplib modules now support IPv6.

（由 Derek Morr 貢獻；bpo-1655 [https://bugs.python.org/issue?@action=redirect&bpo=1655] 和 bpo-1664 [https://bugs.python.org/issue?@action=redirect&bpo=1664]。）

The pickle module has been adapted for better interoperability with Python 2.x when used with protocol 2 or lower. The reorganization of the standard library changed the formal reference for many objects. For example, __builtin__.set in Python 2 is called builtins.set in Python 3. This change confounded efforts to share data between different versions of Python. But now when protocol 2 or lower is selected, the pickler will automatically use the old Python 2 names for both loading and dumping. This remapping is turned-on by default but can be disabled with the fix_imports option:

>>> s = {1, 2, 3}
>>> pickle.dumps(s, protocol=0)
b'c__builtin__\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.'
>>> pickle.dumps(s, protocol=0, fix_imports=False)
b'cbuiltins\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.'

An unfortunate but unavoidable side-effect of this change is that protocol 2 pickles produced by Python 3.1 won't be readable with Python 3.0. The latest pickle protocol, protocol 3, should be used when migrating data between Python 3.x implementations, as it doesn't attempt to remain compatible with Python 2.x.

（由 Alexandre Vassalotti 和 Antoine Pitrou 貢獻，bpo-6137 [https://bugs.python.org/issue?@action=redirect&bpo=6137]。）

A new module, importlib was added. It provides a complete, portable, pure Python reference implementation of the import statement and its counterpart, the __import__() function. It represents a substantial step forward in documenting and defining the actions that take place during imports.

（由 Brett Cannon 貢獻。）

最佳化

Major performance enhancements have been added:

The new I/O library (as defined in PEP 3116 [https://peps.python.org/pep-3116/]) was mostly written in Python and quickly proved to be a problematic bottleneck in Python 3.0. In Python 3.1, the I/O library has been entirely rewritten in C and is 2 to 20 times faster depending on the task at hand. The pure Python version is still available for experimentation purposes through the _pyio module.

（由 Amaury Forgeot d'Arc 和 Antoine Pitrou 貢獻。）

Added a heuristic so that tuples and dicts containing only untrackable objects are not tracked by the garbage collector. This can reduce the size of collections and therefore the garbage collection overhead on long-running programs, depending on their particular use of datatypes.

（由 Antoine Pitrou 貢獻，bpo-4688 [https://bugs.python.org/issue?@action=redirect&bpo=4688]。）

Enabling a configure option named --with-computed-gotos on compilers that support it (notably: gcc, SunPro, icc), the bytecode evaluation loop is compiled with a new dispatch mechanism which gives speedups of up to 20%, depending on the system, the compiler, and the benchmark.

（由 Antoine Pitrou 和其他一些參與者共同貢獻，bpo-4753 [https://bugs.python.org/issue?@action=redirect&bpo=4753]）。

The decoding of UTF-8, UTF-16 and LATIN-1 is now two to four times faster.

（由 Antoine Pitrou 和 Amaury Forgeot d'Arc 貢獻，bpo-4868 [https://bugs.python.org/issue?@action=redirect&bpo=4868]。）

The json module now has a C extension to substantially improve its performance. In addition, the API was modified so that json works only with str, not with bytes. That change makes the module closely match the JSON specification [https://json.org/] which is defined in terms of Unicode.

（由 Bob Ippolito 貢獻，由 Antoine Pitrou 和 Benjamin Peterson 轉換為 Py3.1；bpo-4136 [https://bugs.python.org/issue?@action=redirect&bpo=4136]。）

Unpickling now interns the attribute names of pickled objects. This saves memory and allows pickles to be smaller.

（由 Jake McGuire 和 Antoine Pitrou 貢獻；bpo-5084 [https://bugs.python.org/issue?@action=redirect&bpo=5084]。）

IDLE

IDLE's format menu now provides an option to strip trailing whitespace from a source file.

（由 Roger D. Serwy 貢獻；bpo-5150 [https://bugs.python.org/issue?@action=redirect&bpo=5150]。）

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

Integers are now stored internally either in base 2**15 or in base 2**30, the base being determined at build time. Previously, they were always stored in base 2**15. Using base 2**30 gives significant performance improvements on 64-bit machines, but benchmark results on 32-bit machines have been mixed. Therefore, the default is to use base 2**30 on 64-bit machines and base 2**15 on 32-bit machines; on Unix, there's a new configure option --enable-big-digits that can be used to override this default.

Apart from the performance improvements this change should be invisible to end users, with one exception: for testing and debugging purposes there's a new sys.int_info that provides information about the internal format, giving the number of bits per digit and the size in bytes of the C type used to store each digit:

>>> import sys
>>> sys.int_info
sys.int_info(bits_per_digit=30, sizeof_digit=4)

（由 Mark Dickinson 貢獻；bpo-4258 [https://bugs.python.org/issue?@action=redirect&bpo=4258]。）

The PyLong_AsUnsignedLongLong() function now handles a negative pylong by raising OverflowError instead of TypeError.

（由 Mark Dickinson 和 Lisandro Dalcrin 貢獻；bpo-5175 [https://bugs.python.org/issue?@action=redirect&bpo=5175]。）

已棄用 PyNumber_Int()。請改用 PyNumber_Long()。

（由 Mark Dickinson 貢獻；bpo-4910 [https://bugs.python.org/issue?@action=redirect&bpo=4910]。）

Added a new PyOS_string_to_double() function to replace the deprecated functions PyOS_ascii_strtod() and PyOS_ascii_atof().

（由 Mark Dickinson 貢獻；bpo-5914 [https://bugs.python.org/issue?@action=redirect&bpo=5914]。）

Added PyCapsule as a replacement for the PyCObject API. The principal difference is that the new type has a well defined interface for passing typing safety information and a less complicated signature for calling a destructor. The old type had a problematic API and is now deprecated.

（由 Larry Hastings 貢獻；bpo-5630 [https://bugs.python.org/issue?@action=redirect&bpo=5630]。）

移植至 Python 3.1

This section lists previously described changes and other bugfixes that may require changes to your code:

The new floating-point string representations can break existing doctests. For example:

def e():
    '''計算自然對數的底。

    >>> e()
    2.7182818284590451

    '''
    return sum(1/math.factorial(x) for x in reversed(range(30)))

doctest.testmod()

**********************************************************************
Failed example:
    e()
Expected:
    2.7182818284590451
Got:
    2.718281828459045
**********************************************************************

The automatic name remapping in the pickle module for protocol 2 or lower can make Python 3.1 pickles unreadable in Python 3.0. One solution is to use protocol 3. Another solution is to set the fix_imports option to False. See the discussion above for more details.

Python 3.0 有什麼新功能

作者:

Guido van Rossum

This article explains the new features in Python 3.0, compared to 2.6. Python 3.0, also known as "Python 3000" or "Py3K", is the first ever intentionally backwards incompatible Python release. Python 3.0 was released on December 3, 2008. There are more changes than in a typical release, and more that are important for all Python users. Nevertheless, after digesting the changes, you'll find that Python really hasn't changed all that much -- by and large, we're mostly fixing well-known annoyances and warts, and removing a lot of old cruft.

This article doesn't attempt to provide a complete specification of all new features, but instead tries to give a convenient overview. For full details, you should refer to the documentation for Python 3.0, and/or the many PEPs referenced in the text. If you want to understand the complete implementation and design rationale for a particular feature, PEPs usually have more details than the regular documentation; but note that PEPs usually are not kept up-to-date once a feature has been fully implemented.

Due to time constraints this document is not as complete as it should have been. As always for a new release, the Misc/NEWS file in the source distribution contains a wealth of detailed information about every small thing that was changed.

Common Stumbling Blocks

This section lists those few changes that are most likely to trip you up if you're used to Python 2.5.

Print 是一個函式

print 陳述式已經被 print() 函式所取代，且舊 print 陳述式的大部分特殊語法也被關鍵字引數所取代 (PEP 3105 [https://peps.python.org/pep-3105/])。範例如下：

Old: print "The answer is", 2*2
New: print("The answer is", 2*2)

Old: print x,           # Trailing comma suppresses newline
New: print(x, end=" ")  # Appends a space instead of a newline

Old: print              # Prints a newline
New: print()            # You must call the function!

Old: print >>sys.stderr, "fatal error"
New: print("fatal error", file=sys.stderr)

Old: print (x, y)       # prints repr((x, y))
New: print((x, y))      # Not the same as print(x, y)!

You can also customize the separator between items, e.g.:

print("There are <", 2**32, "> possibilities!", sep="")

which produces:

There are <4294967296> possibilities!

Note:

The print() function doesn't support the "softspace" feature of the old print statement. For example, in Python 2.x, print "A\n", "B" would write "A\nB\n"; but in Python 3.0, print("A\n", "B") writes "A\n B\n".

Initially, you'll be finding yourself typing the old print x a lot in interactive mode. Time to retrain your fingers to type print(x) instead!

When using the 2to3 source-to-source conversion tool, all print statements are automatically converted to print() function calls, so this is mostly a non-issue for larger projects.

Views And Iterators Instead Of Lists

一些眾所周知的 API 不再回傳串列：

dict methods dict.keys(), dict.items() and dict.values() return "views" instead of lists. For example, this no longer works: k = d.keys(); k.sort(). Use k = sorted(d) instead (this works in Python 2.5 too and is just as efficient).

Also, the dict.iterkeys(), dict.iteritems() and dict.itervalues() methods are no longer supported.

map() and filter() return iterators. If you really need a list and the input sequences are all of equal length, a quick fix is to wrap map() in list(), e.g. list(map(...)), but a better fix is often to use a list comprehension (especially when the original code uses lambda), or rewriting the code so it doesn't need a list at all. Particularly tricky is map() invoked for the side effects of the function; the correct transformation is to use a regular for loop (since creating a list would just be wasteful).

If the input sequences are not of equal length, map() will stop at the termination of the shortest of the sequences. For full compatibility with map() from Python 2.x, also wrap the sequences in itertools.zip_longest(), e.g. map(func, *sequences) becomes list(map(func, itertools.zip_longest(*sequences))).

range() now behaves like xrange() used to behave, except it works with values of arbitrary size. The latter no longer exists.

zip() 現在會回傳一個疊代器。

Ordering Comparisons

Python 3.0 has simplified the rules for ordering comparisons:

The ordering comparison operators (<, <=, >=, >) raise a TypeError exception when the operands don't have a meaningful natural ordering. Thus, expressions like 1 < '', 0 > None or len <= len are no longer valid, and e.g. None < None raises TypeError instead of returning False. A corollary is that sorting a heterogeneous list no longer makes sense -- all the elements must be comparable to each other. Note that this does not apply to the == and != operators: objects of different incomparable types always compare unequal to each other.

sorted() and list.sort() no longer accept the cmp argument providing a comparison function. Use the key argument instead. N.B. the key and reverse arguments are now "keyword-only".

The cmp() function should be treated as gone, and the __cmp__() special method is no longer supported. Use __lt__() for sorting, __eq__() with __hash__(), and other rich comparisons as needed. (If you really need the cmp() functionality, you could use the expression (a > b) - (a < b) as the equivalent for cmp(a, b).)

整數

PEP 237 [https://peps.python.org/pep-0237/]: Essentially, long renamed to int. That is, there is only one built-in integral type, named int; but it behaves mostly like the old long type.

PEP 238 [https://peps.python.org/pep-0238/]: An expression like 1/2 returns a float. Use 1//2 to get the truncating behavior. (The latter syntax has existed for years, at least since Python 2.2.)

The sys.maxint constant was removed, since there is no longer a limit to the value of integers. However, sys.maxsize can be used as an integer larger than any practical list or string index. It conforms to the implementation's "natural" integer size and is typically the same as sys.maxint in previous releases on the same platform (assuming the same build options).

The repr() of a long integer doesn't include the trailing L anymore, so code that unconditionally strips that character will chop off the last digit instead. (Use str() instead.)

Octal literals are no longer of the form 0720; use 0o720 instead.

Text Vs. Data Instead Of Unicode Vs. 8-bit

Everything you thought you knew about binary data and Unicode has changed.

Python 3.0 uses the concepts of text and (binary) data instead of Unicode strings and 8-bit strings. All text is Unicode; however encoded Unicode is represented as binary data. The type used to hold text is str, the type used to hold data is bytes. The biggest difference with the 2.x situation is that any attempt to mix text and data in Python 3.0 raises TypeError, whereas if you were to mix Unicode and 8-bit strings in Python 2.x, it would work if the 8-bit string happened to contain only 7-bit (ASCII) bytes, but you would get UnicodeDecodeError if it contained non-ASCII values. This value-specific behavior has caused numerous sad faces over the years.

As a consequence of this change in philosophy, pretty much all code that uses Unicode, encodings or binary data most likely has to change. The change is for the better, as in the 2.x world there were numerous bugs having to do with mixing encoded and unencoded text. To be prepared in Python 2.x, start using unicode for all unencoded text, and str for binary or encoded data only. Then the 2to3 tool will do most of the work for you.

You can no longer use u"..." literals for Unicode text. However, you must use b"..." literals for binary data.

As the str and bytes types cannot be mixed, you must always explicitly convert between them. Use str.encode() to go from str to bytes, and bytes.decode() to go from bytes to str. You can also use bytes(s, encoding=...) and str(b, encoding=...), respectively.

Like str, the bytes type is immutable. There is a separate mutable type to hold buffered binary data, bytearray. Nearly all APIs that accept bytes also accept bytearray. The mutable API is based on collections.MutableSequence.

All backslashes in raw string literals are interpreted literally. This means that '\U' and '\u' escapes in raw strings are not treated specially. For example, r'\u20ac' is a string of 6 characters in Python 3.0, whereas in 2.6, ur'\u20ac' was the single "euro" character. (Of course, this change only affects raw string literals; the euro character is '\u20ac' in Python 3.0.)

The built-in basestring abstract type was removed. Use str instead. The str and bytes types don't have functionality enough in common to warrant a shared base class. The 2to3 tool (see below) replaces every occurrence of basestring with str.

Files opened as text files (still the default mode for open()) always use an encoding to map between strings (in memory) and bytes (on disk). Binary files (opened with a b in the mode argument) always use bytes in memory. This means that if a file is opened using an incorrect mode or encoding, I/O will likely fail loudly, instead of silently producing incorrect data. It also means that even Unix users will have to specify the correct mode (text or binary) when opening a file. There is a platform-dependent default encoding, which on Unixy platforms can be set with the LANG environment variable (and sometimes also with some other platform-specific locale-related environment variables). In many cases, but not all, the system default is UTF-8; you should never count on this default. Any application reading or writing more than pure ASCII text should probably have a way to override the encoding. There is no longer any need for using the encoding-aware streams in the codecs module.

The initial values of sys.stdin, sys.stdout and sys.stderr are now unicode-only text files (i.e., they are instances of io.TextIOBase). To read and write bytes data with these streams, you need to use their io.TextIOBase.buffer attribute.

Filenames are passed to and returned from APIs as (Unicode) strings. This can present platform-specific problems because on some platforms filenames are arbitrary byte strings. (On the other hand, on Windows filenames are natively stored as Unicode.) As a work-around, most APIs (e.g. open() and many functions in the os module) that take filenames accept bytes objects as well as strings, and a few APIs have a way to ask for a bytes return value. Thus, os.listdir() returns a list of bytes instances if the argument is a bytes instance, and os.getcwdb() returns the current working directory as a bytes instance. Note that when os.listdir() returns a list of strings, filenames that cannot be decoded properly are omitted rather than raising UnicodeError.

Some system APIs like os.environ and sys.argv can also present problems when the bytes made available by the system is not interpretable using the default encoding. Setting the LANG variable and rerunning the program is probably the best approach.

PEP 3138 [https://peps.python.org/pep-3138/]: The repr() of a string no longer escapes non-ASCII characters. It still escapes control characters and code points with non-printable status in the Unicode standard, however.

PEP 3120 [https://peps.python.org/pep-3120/]: The default source encoding is now UTF-8.

PEP 3131 [https://peps.python.org/pep-3131/]: Non-ASCII letters are now allowed in identifiers. (However, the standard library remains ASCII-only with the exception of contributor names in comments.)

The StringIO and cStringIO modules are gone. Instead, import the io module and use io.StringIO or io.BytesIO for text and data respectively.

也請見為了 Python 3.0 所更新的 Unicode HOWTO。

語法變更概要

This section gives a brief overview of every syntactic change in Python 3.0.

新增語法

PEP 3107 [https://peps.python.org/pep-3107/]: Function argument and return value annotations. This provides a standardized way of annotating a function's parameters and return value. There are no semantics attached to such annotations except that they can be introspected at runtime using the __annotations__ attribute. The intent is to encourage experimentation through metaclasses, decorators or frameworks.

PEP 3102 [https://peps.python.org/pep-3102/]: Keyword-only arguments. Named parameters occurring after *args in the parameter list must be specified using keyword syntax in the call. You can also use a bare * in the parameter list to indicate that you don't accept a variable-length argument list, but you do have keyword-only arguments.

Keyword arguments are allowed after the list of base classes in a class definition. This is used by the new convention for specifying a metaclass (see next section), but can be used for other purposes as well, as long as the metaclass supports it.

PEP 3104 [https://peps.python.org/pep-3104/]: nonlocal statement. Using nonlocal x you can now assign directly to a variable in an outer (but non-global) scope. nonlocal is a new reserved word.

PEP 3132 [https://peps.python.org/pep-3132/]: Extended Iterable Unpacking. You can now write things like a, b, *rest = some_sequence. And even *rest, a = stuff. The rest object is always a (possibly empty) list; the right-hand side may be any iterable. Example:

(a, *rest, b) = range(5)

這會將 a 設為 0、將 b 設為 4，並將 rest 設為 [1, 2, 3]。

Dictionary comprehensions: {k: v for k, v in stuff} means the same thing as dict(stuff) but is more flexible. (This is PEP 274 [https://peps.python.org/pep-0274/] vindicated. :-)

Set literals, e.g. {1, 2}. Note that {} is an empty dictionary; use set() for an empty set. Set comprehensions are also supported; e.g., {x for x in stuff} means the same thing as set(stuff) but is more flexible.

New octal literals, e.g. 0o720 (already in 2.6). The old octal literals (0720) are gone.

New binary literals, e.g. 0b1010 (already in 2.6), and there is a new corresponding built-in function, bin().

Bytes literals are introduced with a leading b or B, and there is a new corresponding built-in function, bytes().

語法變更

PEP 3109 [https://peps.python.org/pep-3109/] and PEP 3134 [https://peps.python.org/pep-3134/]: new raise statement syntax: raise [expr [from expr]]. See below.

as and with are now reserved words. (Since 2.6, actually.)

True, False, and None are reserved words. (2.6 partially enforced the restrictions on None already.)

Change from except exc, var to except exc as var. See PEP 3110 [https://peps.python.org/pep-3110/].

PEP 3115 [https://peps.python.org/pep-3115/]: New Metaclass Syntax. Instead of:

class C:
    __metaclass__ = M
    ...

現在必須使用：

class C(metaclass=M):
    ...

The module-global __metaclass__ variable is no longer supported. (It was a crutch to make it easier to default to new-style classes without deriving every class from object.)

List comprehensions no longer support the syntactic form [... for var in item1, item2, ...]. Use [... for var in (item1, item2, ...)] instead. Also note that list comprehensions have different semantics: they are closer to syntactic sugar for a generator expression inside a list() constructor, and in particular the loop control variables are no longer leaked into the surrounding scope.

The ellipsis (...) can be used as an atomic expression anywhere. (Previously it was only allowed in slices.) Also, it must now be spelled as .... (Previously it could also be spelled as . . ., by a mere accident of the grammar.)

已被移除的語法

PEP 3113 [https://peps.python.org/pep-3113/]: Tuple parameter unpacking removed. You can no longer write def foo(a, (b, c)): .... Use def foo(a, b_c): b, c = b_c instead.

移除反引號（請改用 repr()）。

移除 <>（請改用 !=）。

Removed keyword: exec() is no longer a keyword; it remains as a function. (Fortunately the function syntax was also accepted in 2.x.) Also note that exec() no longer takes a stream argument; instead of exec(f) you can use exec(f.read()).

Integer literals no longer support a trailing l or L.

String literals no longer support a leading u or U.

The from module import * syntax is only allowed at the module level, no longer inside functions.

The only acceptable syntax for relative imports is from .[module] import name. All import forms not starting with . are interpreted as absolute imports. (PEP 328 [https://peps.python.org/pep-0328/])

Classic classes are gone.

Changes Already Present In Python 2.6

Since many users presumably make the jump straight from Python 2.5 to Python 3.0, this section reminds the reader of new features that were originally designed for Python 3.0 but that were back-ported to Python 2.6. The corresponding sections in Python 2.6 有什麼新功能 should be consulted for longer descriptions.

PEP 343：'with' 陳述式. The with statement is now a standard feature and no longer needs to be imported from the __future__. Also check out Writing Context Managers and contextlib 模組.

PEP 366: Explicit Relative Imports From a Main Module. This enhances the usefulness of the -m option when the referenced module lives in a package.

PEP 370: Per-user site-packages Directory。

PEP 371: The multiprocessing Package。

PEP 3101: Advanced String Formatting. Note: the 2.6 description mentions the format() method for both 8-bit and Unicode strings. In 3.0, only the str type (text strings with Unicode support) supports this method; the bytes type does not. The plan is to eventually make this the only API for string formatting, and to start deprecating the % operator in Python 3.1.

PEP 3105: print As a Function. This is now a standard feature and no longer needs to be imported from __future__. More details were given above.

PEP 3110: Exception-Handling Changes. The except exc as var syntax is now standard and except exc, var is no longer supported. (Of course, the as var part is still optional.)

PEP 3112: Byte Literals. The b"..." string literal notation (and its variants like b'...', b"""...""", and br"...") now produces a literal of type bytes.

PEP 3116：新 I/O 函式庫. The io module is now the standard way of doing file I/O. The built-in open() function is now an alias for io.open() and has additional keyword arguments encoding, errors, newline and closefd. Also note that an invalid mode argument now raises ValueError, not IOError. The binary file object underlying a text file object can be accessed as f.buffer (but beware that the text object maintains a buffer of itself in order to speed up the encoding and decoding operations).

PEP 3118：修訂緩衝協定. The old builtin buffer() is now really gone; the new builtin memoryview() provides (mostly) similar functionality.

PEP 3119: Abstract Base Classes. The abc module and the ABCs defined in the collections module plays a somewhat more prominent role in the language now, and built-in collection types like dict and list conform to the collections.MutableMapping and collections.MutableSequence ABCs, respectively.

PEP 3127: Integer Literal Support and Syntax. As mentioned above, the new octal literal notation is the only one supported, and binary literals have been added.

PEP 3129: Class Decorators。

PEP 3141: A Type Hierarchy for Numbers. The numbers module is another new use of ABCs, defining Python's "numeric tower". Also note the new fractions module which implements numbers.Rational.

函式庫變更

Due to time constraints, this document does not exhaustively cover the very extensive changes to the standard library. PEP 3108 [https://peps.python.org/pep-3108/] is the reference for the major changes to the library. Here's a capsule review:

Many old modules were removed. Some, like gopherlib (no longer used) and md5 (replaced by hashlib), were already deprecated by PEP 4 [https://peps.python.org/pep-0004/]. Others were removed as a result of the removal of support for various platforms such as Irix, BeOS and Mac OS 9 (see PEP 11 [https://peps.python.org/pep-0011/]). Some modules were also selected for removal in Python 3.0 due to lack of use or because a better replacement exists. See PEP 3108 [https://peps.python.org/pep-3108/] for an exhaustive list.

The bsddb3 package was removed because its presence in the core standard library has proved over time to be a particular burden for the core developers due to testing instability and Berkeley DB's release schedule. However, the package is alive and well, externally maintained at https://www.jcea.es/programacion/pybsddb.htm.

一些模組因為舊名稱違反了 PEP 8 [https://peps.python.org/pep-0008/] 或其他原因而被重新命名。以下為變更清單：

舊名

新名

_winreg

winreg

ConfigParser

configparser

copy_reg

copyreg

Queue

queue

SocketServer

socketserver

markupbase

_markupbase

repr

reprlib

test.test_support

test.support

A common pattern in Python 2.x is to have one version of a module implemented in pure Python, with an optional accelerated version implemented as a C extension; for example, pickle and cPickle. This places the burden of importing the accelerated version and falling back on the pure Python version on each user of these modules. In Python 3.0, the accelerated versions are considered implementation details of the pure Python versions. Users should always import the standard version, which attempts to import the accelerated version and falls back to the pure Python version. The pickle / cPickle pair received this treatment. The profile module is on the list for 3.1. The StringIO module has been turned into a class in the io module.

Some related modules have been grouped into packages, and usually the submodule names have been simplified. The resulting new packages are:

dbm（anydbm、dbhash、dbm、dumbdbm、gdbm、whichdb）。

html（HTMLParser、htmlentitydefs）。

http（httplib、BaseHTTPServer、CGIHTTPServer、SimpleHTTPServer、Cookie、cookielib）。

tkinter (all Tkinter-related modules except turtle). The target audience of turtle doesn't really care about tkinter. Also note that as of Python 2.6, the functionality of turtle has been greatly enhanced.

urllib（urllib、urllib2、urlparse、robotparse）。

xmlrpc（xmlrpclib、DocXMLRPCServer、SimpleXMLRPCServer）。

Some other changes to standard library modules, not covered by PEP 3108 [https://peps.python.org/pep-3108/]:

移除 sets。請使用內建的 set() 類別。

Cleanup of the sys module: removed sys.exitfunc(), sys.exc_clear(), sys.exc_type, sys.exc_value, sys.exc_traceback. (Note that sys.last_type etc. remain.)

Cleanup of the array.array type: the read() and write() methods are gone; use fromfile() and tofile() instead. Also, the 'c' typecode for array is gone -- use either 'b' for bytes or 'u' for Unicode characters.

清理 operator 模組：移除 sequenceIncludes() 和 isCallable()。

Cleanup of the thread module: acquire_lock() and release_lock() are gone; use acquire() and release() instead.

清理 random 模組：移除 jumpahead() API。

移除 new 模組。

The functions os.tmpnam(), os.tempnam() and os.tmpfile() have been removed in favor of the tempfile module.

The tokenize module has been changed to work with bytes. The main entry point is now tokenize.tokenize(), instead of generate_tokens.

string.letters and its friends (string.lowercase and string.uppercase) are gone. Use string.ascii_letters etc. instead. (The reason for the removal is that string.letters and friends had locale-specific behavior, which is a bad idea for such attractively named global "constants".)

Renamed module __builtin__ to builtins (removing the underscores, adding an 's'). The __builtins__ variable found in most global namespaces is unchanged. To modify a builtin, you should use builtins, not __builtins__!

PEP 3101 [https://peps.python.org/pep-3101/]: A New Approach To String Formatting

A new system for built-in string formatting operations replaces the % string formatting operator. (However, the % operator is still supported; it will be deprecated in Python 3.1 and removed from the language at some later time.) Read PEP 3101 [https://peps.python.org/pep-3101/] for the full scoop.

Changes To Exceptions

The APIs for raising and catching exception have been cleaned up and new powerful features added:

PEP 352 [https://peps.python.org/pep-0352/]: All exceptions must be derived (directly or indirectly) from BaseException. This is the root of the exception hierarchy. This is not new as a recommendation, but the requirement to inherit from BaseException is new. (Python 2.6 still allowed classic classes to be raised, and placed no restriction on what you can catch.) As a consequence, string exceptions are finally truly and utterly dead.

Almost all exceptions should actually derive from Exception; BaseException should only be used as a base class for exceptions that should only be handled at the top level, such as SystemExit or KeyboardInterrupt. The recommended idiom for handling all exceptions except for this latter category is to use except Exception.

StandardError 已被移除。

Exceptions no longer behave as sequences. Use the args attribute instead.

PEP 3109 [https://peps.python.org/pep-3109/]: Raising exceptions. You must now use raise Exception(args) instead of raise Exception, args. Additionally, you can no longer explicitly specify a traceback; instead, if you have to do this, you can assign directly to the __traceback__ attribute (see below).

PEP 3110 [https://peps.python.org/pep-3110/]: Catching exceptions. You must now use except SomeException as variable instead of except SomeException, variable. Moreover, the variable is explicitly deleted when the except block is left.

PEP 3134 [https://peps.python.org/pep-3134/]: Exception chaining. There are two cases: implicit chaining and explicit chaining. Implicit chaining happens when an exception is raised in an except or finally handler block. This usually happens due to a bug in the handler block; we call this a secondary exception. In this case, the original exception (that was being handled) is saved as the __context__ attribute of the secondary exception. Explicit chaining is invoked with this syntax:

raise SecondaryException() from primary_exception

(where primary_exception is any expression that produces an exception object, probably an exception that was previously caught). In this case, the primary exception is stored on the __cause__ attribute of the secondary exception. The traceback printed when an unhandled exception occurs walks the chain of __cause__ and __context__ attributes and prints a separate traceback for each component of the chain, with the primary exception at the top. (Java users may recognize this behavior.)

PEP 3134 [https://peps.python.org/pep-3134/]: Exception objects now store their traceback as the __traceback__ attribute. This means that an exception object now contains all the information pertaining to an exception, and there are fewer reasons to use sys.exc_info() (though the latter is not removed).

A few exception messages are improved when Windows fails to load an extension module. For example, error code 193 is now %1 is not a valid Win32 application. Strings now deal with non-English locales.

Miscellaneous Other Changes

Operators And Special Methods

!= now returns the opposite of ==, unless == returns NotImplemented.

The concept of "unbound methods" has been removed from the language. When referencing a method as a class attribute, you now get a plain function object.

__getslice__(), __setslice__() and __delslice__() were killed. The syntax a[i:j] now translates to a.__getitem__(slice(i, j)) (or __setitem__() or __delitem__(), when used as an assignment or deletion target, respectively).

PEP 3114 [https://peps.python.org/pep-3114/]: the standard next() method has been renamed to __next__().

The __oct__() and __hex__() special methods are removed -- oct() and hex() use __index__() now to convert the argument to an integer.

移除對 __members__ 和 __methods__ 的支援。

The function attributes named func_X have been renamed to use the __X__ form, freeing up these names in the function attribute namespace for user-defined attributes. To wit, func_closure, func_code, func_defaults, func_dict, func_doc, func_globals, func_name were renamed to __closure__, __code__, __defaults__, __dict__, __doc__, __globals__, __name__, respectively.

__nonzero__() 現在為 __bool__()。

Builtins

PEP 3135 [https://peps.python.org/pep-3135/]: New super(). You can now invoke super() without arguments and (assuming this is in a regular instance method defined inside a class statement) the right class and instance will automatically be chosen. With arguments, the behavior of super() is unchanged.

PEP 3111 [https://peps.python.org/pep-3111/]: raw_input() was renamed to input(). That is, the new input() function reads a line from sys.stdin and returns it with the trailing newline stripped. It raises EOFError if the input is terminated prematurely. To get the old behavior of input(), use eval(input()).

A new built-in function next() was added to call the __next__() method on an object.

The round() function rounding strategy and return type have changed. Exact halfway cases are now rounded to the nearest even result instead of away from zero. (For example, round(2.5) now returns 2 rather than 3.) round(x[, n]) now delegates to x.__round__([n]) instead of always returning a float. It generally returns an integer when called with a single argument and a value of the same type as x when called with two arguments.

Moved intern() to sys.intern().

移除 apply()。請使用 f(*args) 來替換 apply(f, args)。

Removed callable(). Instead of callable(f) you can use isinstance(f, collections.Callable). The operator.isCallable() function is also gone.

Removed coerce(). This function no longer serves a purpose now that classic classes are gone.

移除 execfile()。請使用 exec(open(fn).read()) 來替換 execfile(fn)。

Removed the file type. Use open(). There are now several different kinds of streams that open can return in the io module.

Removed reduce(). Use functools.reduce() if you really need it; however, 99 percent of the time an explicit for loop is more readable.

移除 reload()。請使用 imp.reload()。

Removed. dict.has_key() -- use the in operator instead.

建置和 C API 變更

Due to time constraints, here is a very incomplete list of changes to the C API.

Support for several platforms was dropped, including but not limited to Mac OS 9, BeOS, RISCOS, Irix, and Tru64.

PEP 3118 [https://peps.python.org/pep-3118/]：新的緩衝 API。

PEP 3121 [https://peps.python.org/pep-3121/]: Extension Module Initialization & Finalization.

PEP 3123 [https://peps.python.org/pep-3123/]: Making PyObject_HEAD conform to standard C.

No more C API support for restricted execution.

PyNumber_Coerce(), PyNumber_CoerceEx(), PyMember_Get(), and PyMember_Set() C APIs are removed.

New C API PyImport_ImportModuleNoBlock(), works like PyImport_ImportModule() but won't block on the import lock (returning an error instead).

Renamed the boolean conversion C-level slot and method: nb_nonzero is now nb_bool.

移除 C API 中的 METH_OLDARGS 和 WITH_CYCLE_GC。

效能

The net result of the 3.0 generalizations is that Python 3.0 runs the pystone benchmark around 10% slower than Python 2.5. Most likely the biggest cause is the removal of special-casing for small integers. There's room for improvement, but it will happen after 3.0 is released!

Porting To Python 3.0

For porting existing Python 2.5 or 2.6 source code to Python 3.0, the best strategy is the following:

(Prerequisite:) Start with excellent test coverage.

Port to Python 2.6. This should be no more work than the average port from Python 2.x to Python 2.(x+1). Make sure all your tests pass.

(Still using 2.6:) Turn on the -3 command line switch. This enables warnings about features that will be removed (or change) in 3.0. Run your test suite again, and fix code that you get warnings about until there are no warnings left, and all your tests still pass.

Run the 2to3 source-to-source translator over your source code tree. Run the result of the translation under Python 3.0. Manually fix up any remaining issues, fixing problems until all tests pass again.

It is not recommended to try to write source code that runs unchanged under both Python 2.6 and 3.0; you'd have to use a very contorted coding style, e.g. avoiding print statements, metaclasses, and much more. If you are maintaining a library that needs to support both Python 2.6 and Python 3.0, the best approach is to modify step 3 above by editing the 2.6 version of the source code and running the 2to3 translator again, rather than editing the 3.0 version of the source code.

For porting C extensions to Python 3.0, please see 遷移延伸模組到 Python 3.

Python 2.7 有什麼新功能

作者:

A.M. Kuchling (amk at amk.ca)

This article explains the new features in Python 2.7. Python 2.7 was released on July 3, 2010.

Numeric handling has been improved in many ways, for both floating-point numbers and for the Decimal class. There are some useful additions to the standard library, such as a greatly enhanced unittest module, the argparse module for parsing command-line options, convenient OrderedDict and Counter classes in the collections module, and many other improvements.

Python 2.7 is planned to be the last of the 2.x releases, so we worked on making it a good release for the long term. To help with porting to Python 3, several new features from the Python 3.x series have been included in 2.7.

This article doesn't attempt to provide a complete specification of the new features, but instead provides a convenient overview. For full details, you should refer to the documentation for Python 2.7 at https://docs.python.org. If you want to understand the rationale for the design and implementation, refer to the PEP for a particular new feature or the issue on https://bugs.python.org in which a change was discussed. Whenever possible, "What's New in Python" links to the bug/patch item for each change.

Python 2.x 的未來

Python 2.7 is the last major release in the 2.x series, as the Python maintainers have shifted the focus of their new feature development efforts to the Python 3.x series. This means that while Python 2 continues to receive bug fixes, and to be updated to build correctly on new hardware and versions of supported operated systems, there will be no new full feature releases for the language or standard library.

However, while there is a large common subset between Python 2.7 and Python 3, and many of the changes involved in migrating to that common subset, or directly to Python 3, can be safely automated, some other changes (notably those associated with Unicode handling) may require careful consideration, and preferably robust automated regression test suites, to migrate effectively.

This means that Python 2.7 will remain in place for a long time, providing a stable and supported base platform for production systems that have not yet been ported to Python 3. The full expected lifecycle of the Python 2.7 series is detailed in PEP 373 [https://peps.python.org/pep-0373/].

Some key consequences of the long-term significance of 2.7 are:

As noted above, the 2.7 release has a much longer period of maintenance when compared to earlier 2.x versions. Python 2.7 is currently expected to remain supported by the core development team (receiving security updates and other bug fixes) until at least 2020 (10 years after its initial release, compared to the more typical support period of 18--24 months).

As the Python 2.7 standard library ages, making effective use of the Python Package Index (either directly or via a redistributor) becomes more important for Python 2 users. In addition to a wide variety of third party packages for various tasks, the available packages include backports of new modules and features from the Python 3 standard library that are compatible with Python 2, as well as various tools and libraries that can make it easier to migrate to Python 3. The Python Packaging User Guide [https://packaging.python.org] provides guidance on downloading and installing software from the Python Package Index.

While the preferred approach to enhancing Python 2 is now the publication of new packages on the Python Package Index, this approach doesn't necessarily work in all cases, especially those related to network security. In exceptional cases that cannot be handled adequately by publishing new or updated packages on PyPI, the Python Enhancement Proposal process may be used to make the case for adding new features directly to the Python 2 standard library. Any such additions, and the maintenance releases where they were added, will be noted in the New Features Added to Python 2.7 Maintenance Releases section below.

For projects wishing to migrate from Python 2 to Python 3, or for library and framework developers wishing to support users on both Python 2 and Python 3, there are a variety of tools and guides available to help decide on a suitable approach and manage some of the technical details involved. The recommended starting point is the 如何將 Python 2 的程式碼移植到 Python 3 HOWTO guide.

Changes to the Handling of Deprecation Warnings

For Python 2.7, a policy decision was made to silence warnings only of interest to developers by default. DeprecationWarning and its descendants are now ignored unless otherwise requested, preventing users from seeing warnings triggered by an application. This change was also made in the branch that became Python 3.2. (Discussed on stdlib-sig and carried out in bpo-7319 [https://bugs.python.org/issue?@action=redirect&bpo=7319].)

In previous releases, DeprecationWarning messages were enabled by default, providing Python developers with a clear indication of where their code may break in a future major version of Python.

However, there are increasingly many users of Python-based applications who are not directly involved in the development of those applications. DeprecationWarning messages are irrelevant to such users, making them worry about an application that's actually working correctly and burdening application developers with responding to these concerns.

You can re-enable display of DeprecationWarning messages by running Python with the -Wdefault (short form: -Wd) switch, or by setting the PYTHONWARNINGS environment variable to "default" (or "d") before running Python. Python code can also re-enable them by calling warnings.simplefilter('default').

The unittest module also automatically reenables deprecation warnings when running tests.

Python 3.1 Features

Much as Python 2.6 incorporated features from Python 3.0, version 2.7 incorporates some of the new features in Python 3.1. The 2.x series continues to provide tools for migrating to the 3.x series.

A partial list of 3.1 features that were backported to 2.7:

The syntax for set literals ({1,2,3} is a mutable set).

Dictionary and set comprehensions ({i: i*2 for i in range(3)}).

Multiple context managers in a single with statement.

A new version of the io library, rewritten in C for performance.

The ordered-dictionary type described in PEP 372: Adding an Ordered Dictionary to collections.

The new "," format specifier described in PEP 378: Format Specifier for Thousands Separator.

memoryview 物件。

A small subset of the importlib module, described below.

The repr() of a float x is shorter in many cases: it's now based on the shortest decimal string that's guaranteed to round back to x. As in previous versions of Python, it's guaranteed that float(repr(x)) recovers x.

Float-to-string and string-to-float conversions are correctly rounded. The round() function is also now correctly rounded.

The PyCapsule type, used to provide a C API for extension modules.

PyLong_AsLongAndOverflow() C API 函式。

Other new Python3-mode warnings include:

operator.isCallable() and operator.sequenceIncludes(), which are not supported in 3.x, now trigger warnings.

The -3 switch now automatically enables the -Qwarn switch that causes warnings about using classic division with integers and long integers.

PEP 372: Adding an Ordered Dictionary to collections

Regular Python dictionaries iterate over key/value pairs in arbitrary order. Over the years, a number of authors have written alternative implementations that remember the order that the keys were originally inserted. Based on the experiences from those implementations, 2.7 introduces a new OrderedDict class in the collections module.

The OrderedDict API provides the same interface as regular dictionaries but iterates over keys and values in a guaranteed order depending on when a key was first inserted:

>>> from collections import OrderedDict
>>> d = OrderedDict([('first', 1),
...                  ('second', 2),
...                  ('third', 3)])
>>> d.items()
[('first', 1), ('second', 2), ('third', 3)]

If a new entry overwrites an existing entry, the original insertion position is left unchanged:

>>> d['second'] = 4
>>> d.items()
[('first', 1), ('second', 4), ('third', 3)]

Deleting an entry and reinserting it will move it to the end:

>>> del d['second']
>>> d['second'] = 5
>>> d.items()
[('first', 1), ('third', 3), ('second', 5)]

The popitem() method has an optional last argument that defaults to True. If last is true, the most recently added key is returned and removed; if it's false, the oldest key is selected:

>>> od = OrderedDict([(x,0) for x in range(20)])
>>> od.popitem()
(19, 0)
>>> od.popitem()
(18, 0)
>>> od.popitem(last=False)
(0, 0)
>>> od.popitem(last=False)
(1, 0)

Comparing two ordered dictionaries checks both the keys and values, and requires that the insertion order was the same:

>>> od1 = OrderedDict([('first', 1),
...                    ('second', 2),
...                    ('third', 3)])
>>> od2 = OrderedDict([('third', 3),
...                    ('first', 1),
...                    ('second', 2)])
>>> od1 == od2
False
>>> # Move 'third' key to the end
>>> del od2['third']; od2['third'] = 3
>>> od1 == od2
True

Comparing an OrderedDict with a regular dictionary ignores the insertion order and just compares the keys and values.

How does the OrderedDict work? It maintains a doubly linked list of keys, appending new keys to the list as they're inserted. A secondary dictionary maps keys to their corresponding list node, so deletion doesn't have to traverse the entire linked list and therefore remains O(1).

The standard library now supports use of ordered dictionaries in several modules.

The ConfigParser module uses them by default, meaning that configuration files can now be read, modified, and then written back in their original order.

The _asdict() method for collections.namedtuple() now returns an ordered dictionary with the values appearing in the same order as the underlying tuple indices.

The json module's JSONDecoder class constructor was extended with an object_pairs_hook parameter to allow OrderedDict instances to be built by the decoder. Support was also added for third-party tools like PyYAML [https://pyyaml.org/].

也參考

PEP 372 [https://peps.python.org/pep-0372/] - 在 collections 中新增有序字典

PEP written by Armin Ronacher and Raymond Hettinger; implemented by Raymond Hettinger.

PEP 378: Format Specifier for Thousands Separator

To make program output more readable, it can be useful to add separators to large numbers, rendering them as 18,446,744,073,709,551,616 instead of 18446744073709551616.

The fully general solution for doing this is the locale module, which can use different separators ("," in North America, "." in Europe) and different grouping sizes, but locale is complicated to use and unsuitable for multi-threaded applications where different threads are producing output for different locales.

Therefore, a simple comma-grouping mechanism has been added to the mini-language used by the str.format() method. When formatting a floating-point number, simply include a comma between the width and the precision:

>>> '{:20,.2f}'.format(18446744073709551616.0)
'18,446,744,073,709,551,616.00'

When formatting an integer, include the comma after the width:

>>> '{:20,d}'.format(18446744073709551616)
'18,446,744,073,709,551,616'

This mechanism is not adaptable at all; commas are always used as the separator and the grouping is always into three-digit groups. The comma-formatting mechanism isn't as general as the locale module, but it's easier to use.

也參考

PEP 378 [https://peps.python.org/pep-0378/] - Format Specifier for Thousands Separator

由 Raymond Hettinger 撰寫 PEP；由 Eric Smith 實作。

PEP 389: The argparse Module for Parsing Command Lines

The argparse module for parsing command-line arguments was added as a more powerful replacement for the optparse module.

This means Python now supports three different modules for parsing command-line arguments: getopt, optparse, and argparse. The getopt module closely resembles the C library's getopt() function, so it remains useful if you're writing a Python prototype that will eventually be rewritten in C. optparse becomes redundant, but there are no plans to remove it because there are many scripts still using it, and there's no automated way to update these scripts. (Making the argparse API consistent with optparse's interface was discussed but rejected as too messy and difficult.)

In short, if you're writing a new script and don't need to worry about compatibility with earlier versions of Python, use argparse instead of optparse.

以下是個範例：

import argparse

parser = argparse.ArgumentParser(description='Command-line example.')

# Add optional switches
parser.add_argument('-v', action='store_true', dest='is_verbose',
                    help='produce verbose output')
parser.add_argument('-o', action='store', dest='output',
                    metavar='FILE',
                    help='direct output to FILE instead of stdout')
parser.add_argument('-C', action='store', type=int, dest='context',
                    metavar='NUM', default=0,
                    help='display NUM lines of added context')

# Allow any number of additional arguments.
parser.add_argument(nargs='*', action='store', dest='inputs',
                    help='input filenames (default is stdin)')

args = parser.parse_args()
print args.__dict__

Unless you override it, -h and --help switches are automatically added, and produce neatly formatted output:

-> ./python.exe argparse-example.py --help
usage: argparse-example.py [-h] [-v] [-o FILE] [-C NUM] [inputs [inputs ...]]

Command-line example.

positional arguments:
  inputs      input filenames (default is stdin)

optional arguments:
  -h, --help  show this help message and exit
  -v          produce verbose output
  -o FILE     direct output to FILE instead of stdout
  -C NUM      display NUM lines of added context

As with optparse, the command-line switches and arguments are returned as an object with attributes named by the dest parameters:

-> ./python.exe argparse-example.py -v
{'output': None,
 'is_verbose': True,
 'context': 0,
 'inputs': []}

-> ./python.exe argparse-example.py -v -o /tmp/output -C 4 file1 file2
{'output': '/tmp/output',
 'is_verbose': True,
 'context': 4,
 'inputs': ['file1', 'file2']}

argparse has much fancier validation than optparse; you can specify an exact number of arguments as an integer, 0 or more arguments by passing '*', 1 or more by passing '+', or an optional argument with '?'. A top-level parser can contain sub-parsers to define subcommands that have different sets of switches, as in svn commit, svn checkout, etc. You can specify an argument's type as FileType, which will automatically open files for you and understands that '-' means standard input or output.

也參考

argparse 文件

argparse 模組的文件頁面。

將 optparse 程式碼遷移到 argparse

Part of the Python documentation, describing how to convert code that uses optparse.

PEP 389 [https://peps.python.org/pep-0389/] - argparse - New Command Line Parsing Module

由 Steven Bethard 撰寫 PEP 與實作。

PEP 391: Dictionary-Based Configuration For Logging

The logging module is very flexible; applications can define a tree of logging subsystems, and each logger in this tree can filter out certain messages, format them differently, and direct messages to a varying number of handlers.

All this flexibility can require a lot of configuration. You can write Python statements to create objects and set their properties, but a complex set-up requires verbose but boring code. logging also supports a fileConfig() function that parses a file, but the file format doesn't support configuring filters, and it's messier to generate programmatically.

Python 2.7 adds a dictConfig() function that uses a dictionary to configure logging. There are many ways to produce a dictionary from different sources: construct one with code; parse a file containing JSON; or use a YAML parsing library if one is installed. For more information see Configuration functions.

The following example configures two loggers, the root logger and a logger named "network". Messages sent to the root logger will be sent to the system log using the syslog protocol, and messages to the "network" logger will be written to a network.log file that will be rotated once the log reaches 1MB.

import logging
import logging.config

configdict = {
 'version': 1,    # Configuration schema in use; must be 1 for now
 'formatters': {
     'standard': {
         'format': ('%(asctime)s %(name)-15s '
                    '%(levelname)-8s %(message)s')}},

 'handlers': {'netlog': {'backupCount': 10,
                     'class': 'logging.handlers.RotatingFileHandler',
                     'filename': '/logs/network.log',
                     'formatter': 'standard',
                     'level': 'INFO',
                     'maxBytes': 1000000},
              'syslog': {'class': 'logging.handlers.SysLogHandler',
                         'formatter': 'standard',
                         'level': 'ERROR'}},

 # Specify all the subordinate loggers
 'loggers': {
             'network': {
                         'handlers': ['netlog']
             }
 },
 # Specify properties of the root logger
 'root': {
          'handlers': ['syslog']
 },
}

# Set up configuration
logging.config.dictConfig(configdict)

# As an example, log two error messages
logger = logging.getLogger('/')
logger.error('Database not found')

netlogger = logging.getLogger('network')
netlogger.error('Connection failed')

Three smaller enhancements to the logging module, all implemented by Vinay Sajip, are:

The SysLogHandler class now supports syslogging over TCP. The constructor has a socktype parameter giving the type of socket to use, either socket.SOCK_DGRAM for UDP or socket.SOCK_STREAM for TCP. The default protocol remains UDP.

Logger instances gained a getChild() method that retrieves a descendant logger using a relative path. For example, once you retrieve a logger by doing log = getLogger('app'), calling log.getChild('network.listen') is equivalent to getLogger('app.network.listen').

The LoggerAdapter class gained an isEnabledFor() method that takes a level and returns whether the underlying logger would process a message of that level of importance.

也參考

PEP 391 [https://peps.python.org/pep-0391/] - Dictionary-Based Configuration For Logging

由 Vinay Sajip 撰寫 PEP 與實作。

PEP 3106: Dictionary Views

The dictionary methods keys(), values(), and items() are different in Python 3.x. They return an object called a view instead of a fully materialized list.

It's not possible to change the return values of keys(), values(), and items() in Python 2.7 because too much code would break. Instead the 3.x versions were added under the new names viewkeys(), viewvalues(), and viewitems().

>>> d = dict((i*10, chr(65+i)) for i in range(26))
>>> d
{0: 'A', 130: 'N', 10: 'B', 140: 'O', 20: ..., 250: 'Z'}
>>> d.viewkeys()
dict_keys([0, 130, 10, 140, 20, 150, 30, ..., 250])

Views can be iterated over, but the key and item views also behave like sets. The & operator performs intersection, and | performs a union:

>>> d1 = dict((i*10, chr(65+i)) for i in range(26))
>>> d2 = dict((i**.5, i) for i in range(1000))
>>> d1.viewkeys() & d2.viewkeys()
set([0.0, 10.0, 20.0, 30.0])
>>> d1.viewkeys() | range(0, 30)
set([0, 1, 130, 3, 4, 5, 6, ..., 120, 250])

The view keeps track of the dictionary and its contents change as the dictionary is modified:

>>> vk = d.viewkeys()
>>> vk
dict_keys([0, 130, 10, ..., 250])
>>> d[260] = '&'
>>> vk
dict_keys([0, 130, 260, 10, ..., 250])

However, note that you can't add or remove keys while you're iterating over the view:

>>> for k in vk:
...     d[k*2] = k
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: dictionary changed size during iteration

You can use the view methods in Python 2.x code, and the 2to3 converter will change them to the standard keys(), values(), and items() methods.

也參考

PEP 3106 [https://peps.python.org/pep-3106/] - Revamping dict.keys(), .values() and .items()

PEP written by Guido van Rossum. Backported to 2.7 by Alexandre Vassalotti; bpo-1967 [https://bugs.python.org/issue?@action=redirect&bpo=1967].

PEP 3137: The memoryview Object

The memoryview object provides a view of another object's memory content that matches the bytes type's interface.

>>> import string
>>> m = memoryview(string.letters)
>>> m
<memory at 0x37f850>
>>> len(m)           # Returns length of underlying object
52
>>> m[0], m[25], m[26]   # Indexing returns one byte
('a', 'z', 'A')
>>> m2 = m[0:26]         # Slicing returns another memoryview
>>> m2
<memory at 0x37f080>

The content of the view can be converted to a string of bytes or a list of integers:

>>> m2.tobytes()
'abcdefghijklmnopqrstuvwxyz'
>>> m2.tolist()
[97, 98, 99, 100, 101, 102, 103, ... 121, 122]
>>>

memoryview objects allow modifying the underlying object if it's a mutable object.

>>> m2[0] = 75
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot modify read-only memory
>>> b = bytearray(string.letters)  # Creating a mutable object
>>> b
bytearray(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
>>> mb = memoryview(b)
>>> mb[0] = '*'         # Assign to view, changing the bytearray.
>>> b[0:5]              # The bytearray has been changed.
bytearray(b'*bcde')
>>>

也參考

PEP 3137 [https://peps.python.org/pep-3137/] - Immutable Bytes and Mutable Buffer

PEP written by Guido van Rossum. Implemented by Travis Oliphant, Antoine Pitrou and others. Backported to 2.7 by Antoine Pitrou; bpo-2396 [https://bugs.python.org/issue?@action=redirect&bpo=2396].

其他語言更動

Some smaller changes made to the core Python language are:

The syntax for set literals has been backported from Python 3.x. Curly brackets are used to surround the contents of the resulting mutable set; set literals are distinguished from dictionaries by not containing colons and values. {} continues to represent an empty dictionary; use set() for an empty set.

>>> {1, 2, 3, 4, 5}
set([1, 2, 3, 4, 5])
>>> set() # 空集合
set([])
>>> {}    # 空字典
{}

Backported by Alexandre Vassalotti; bpo-2335 [https://bugs.python.org/issue?@action=redirect&bpo=2335].

Dictionary and set comprehensions are another feature backported from 3.x, generalizing list/generator comprehensions to use the literal syntax for sets and dictionaries.

>>> {x: x*x for x in range(6)}
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
>>> {('a'*x) for x in range(6)}
set(['', 'a', 'aa', 'aaa', 'aaaa', 'aaaaa'])

Backported by Alexandre Vassalotti; bpo-2333 [https://bugs.python.org/issue?@action=redirect&bpo=2333].

The with statement can now use multiple context managers in one statement. Context managers are processed from left to right and each one is treated as beginning a new with statement. This means that:

with A() as a, B() as b:
    ... suite of statements ...

等價於：

with A() as a:
    with B() as b:
        ... suite of statements ...

The contextlib.nested() function provides a very similar function, so it's no longer necessary and has been deprecated.

（於 https://codereview.appspot.com/53094 提出；由 Georg Brandl 實作。）

Conversions between floating-point numbers and strings are now correctly rounded on most platforms. These conversions occur in many different places: str() on floats and complex numbers; the float and complex constructors; numeric formatting; serializing and deserializing floats and complex numbers using the marshal, pickle and json modules; parsing of float and imaginary literals in Python code; and Decimal-to-float conversion.

Related to this, the repr() of a floating-point number x now returns a result based on the shortest decimal string that's guaranteed to round back to x under correct rounding (with round-half-to-even rounding mode). Previously it gave a string based on rounding x to 17 decimal digits.

The rounding library responsible for this improvement works on Windows and on Unix platforms using the gcc, icc, or suncc compilers. There may be a small number of platforms where correct operation of this code cannot be guaranteed, so the code is not used on such systems. You can find out which code is being used by checking sys.float_repr_style, which will be short if the new code is in use and legacy if it isn't.

Implemented by Eric Smith and Mark Dickinson, using David Gay's dtoa.c library; bpo-7117 [https://bugs.python.org/issue?@action=redirect&bpo=7117].

Conversions from long integers and regular integers to floating point now round differently, returning the floating-point number closest to the number. This doesn't matter for small integers that can be converted exactly, but for large numbers that will unavoidably lose precision, Python 2.7 now approximates more closely. For example, Python 2.6 computed the following:

>>> n = 295147905179352891391
>>> float(n)
2.9514790517935283e+20
>>> n - long(float(n))
65535L

Python 2.7's floating-point result is larger, but much closer to the true value:

>>> n = 295147905179352891391
>>> float(n)
2.9514790517935289e+20
>>> n - long(float(n))
-1L

（由 Mark Dickinson 實作；bpo-3166 [https://bugs.python.org/issue?@action=redirect&bpo=3166]。）

Integer division is also more accurate in its rounding behaviours. (Also implemented by Mark Dickinson; bpo-1811 [https://bugs.python.org/issue?@action=redirect&bpo=1811].)

Implicit coercion for complex numbers has been removed; the interpreter will no longer ever attempt to call a __coerce__() method on complex objects. (Removed by Meador Inge and Mark Dickinson; bpo-5211 [https://bugs.python.org/issue?@action=redirect&bpo=5211].)

The str.format() method now supports automatic numbering of the replacement fields. This makes using str.format() more closely resemble using %s formatting:

>>> '{}:{}:{}'.format(2009, 04, 'Sunday')
'2009:4:Sunday'
>>> '{}:{}:{day}'.format(2009, 4, day='Sunday')
'2009:4:Sunday'

The auto-numbering takes the fields from left to right, so the first {...} specifier will use the first argument to str.format(), the next specifier will use the next argument, and so on. You can't mix auto-numbering and explicit numbering -- either number all of your specifier fields or none of them -- but you can mix auto-numbering and named fields, as in the second example above. (Contributed by Eric Smith; bpo-5237 [https://bugs.python.org/issue?@action=redirect&bpo=5237].)

Complex numbers now correctly support usage with format(), and default to being right-aligned. Specifying a precision or comma-separation applies to both the real and imaginary parts of the number, but a specified field width and alignment is applied to the whole of the resulting 1.5+3j output. (Contributed by Eric Smith; bpo-1588 [https://bugs.python.org/issue?@action=redirect&bpo=1588] and bpo-7988 [https://bugs.python.org/issue?@action=redirect&bpo=7988].)

The 'F' format code now always formats its output using uppercase characters, so it will now produce 'INF' and 'NAN'. (Contributed by Eric Smith; bpo-3382 [https://bugs.python.org/issue?@action=redirect&bpo=3382].)

A low-level change: the object.__format__() method now triggers a PendingDeprecationWarning if it's passed a format string, because the __format__() method for object converts the object to a string representation and formats that. Previously the method silently applied the format string to the string representation, but that could hide mistakes in Python code. If you're supplying formatting information such as an alignment or precision, presumably you're expecting the formatting to be applied in some object-specific way. (Fixed by Eric Smith; bpo-7994 [https://bugs.python.org/issue?@action=redirect&bpo=7994].)

The int() and long() types gained a bit_length method that returns the number of bits necessary to represent its argument in binary:

>>> n = 37
>>> bin(n)
'0b100101'
>>> n.bit_length()
6
>>> n = 2**123-1
>>> n.bit_length()
123
>>> (n+1).bit_length()
124

（由 Fredrik Johansson 和 Victor Stinner 貢獻；bpo-3439 [https://bugs.python.org/issue?@action=redirect&bpo=3439]。）

The import statement will no longer try an absolute import if a relative import (e.g. from .os import sep) fails. This fixes a bug, but could possibly break certain import statements that were only working by accident. (Fixed by Meador Inge; bpo-7902 [https://bugs.python.org/issue?@action=redirect&bpo=7902].)

It's now possible for a subclass of the built-in unicode type to override the __unicode__() method. (Implemented by Victor Stinner; bpo-1583863 [https://bugs.python.org/issue?@action=redirect&bpo=1583863].)

The bytearray type's translate() method now accepts None as its first argument. (Fixed by Georg Brandl; bpo-4759 [https://bugs.python.org/issue?@action=redirect&bpo=4759].)

When using @classmethod and @staticmethod to wrap methods as class or static methods, the wrapper object now exposes the wrapped function as their __func__ attribute. (Contributed by Amaury Forgeot d'Arc, after a suggestion by George Sakkis; bpo-5982 [https://bugs.python.org/issue?@action=redirect&bpo=5982].)

When a restricted set of attributes were set using __slots__, deleting an unset attribute would not raise AttributeError as you would expect. Fixed by Benjamin Peterson; bpo-7604 [https://bugs.python.org/issue?@action=redirect&bpo=7604].)

Two new encodings are now supported: "cp720", used primarily for Arabic text; and "cp858", a variant of CP 850 that adds the euro symbol. (CP720 contributed by Alexander Belchenko and Amaury Forgeot d'Arc in bpo-1616979 [https://bugs.python.org/issue?@action=redirect&bpo=1616979]; CP858 contributed by Tim Hatch in bpo-8016 [https://bugs.python.org/issue?@action=redirect&bpo=8016].)

The file object will now set the filename attribute on the IOError exception when trying to open a directory on POSIX platforms (noted by Jan Kaliszewski; bpo-4764 [https://bugs.python.org/issue?@action=redirect&bpo=4764]), and now explicitly checks for and forbids writing to read-only file objects instead of trusting the C library to catch and report the error (fixed by Stefan Krah; bpo-5677 [https://bugs.python.org/issue?@action=redirect&bpo=5677]).

The Python tokenizer now translates line endings itself, so the compile() built-in function now accepts code using any line-ending convention. Additionally, it no longer requires that the code end in a newline.

Extra parentheses in function definitions are illegal in Python 3.x, meaning that you get a syntax error from def f((x)): pass. In Python3-warning mode, Python 2.7 will now warn about this odd usage. (Noted by James Lingard; bpo-7362 [https://bugs.python.org/issue?@action=redirect&bpo=7362].)

It's now possible to create weak references to old-style class objects. New-style classes were always weak-referenceable. (Fixed by Antoine Pitrou; bpo-8268 [https://bugs.python.org/issue?@action=redirect&bpo=8268].)

When a module object is garbage-collected, the module's dictionary is now only cleared if no one else is holding a reference to the dictionary (bpo-7140 [https://bugs.python.org/issue?@action=redirect&bpo=7140]).

Interpreter Changes

A new environment variable, PYTHONWARNINGS, allows controlling warnings. It should be set to a string containing warning settings, equivalent to those used with the -W switch, separated by commas. (Contributed by Brian Curtin; bpo-7301 [https://bugs.python.org/issue?@action=redirect&bpo=7301].)

For example, the following setting will print warnings every time they occur, but turn warnings from the Cookie module into an error. (The exact syntax for setting an environment variable varies across operating systems and shells.)

export PYTHONWARNINGS=all,error:::Cookie:0

最佳化

Several performance enhancements have been added:

A new opcode was added to perform the initial setup for with statements, looking up the __enter__() and __exit__() methods. (Contributed by Benjamin Peterson.)

The garbage collector now performs better for one common usage pattern: when many objects are being allocated without deallocating any of them. This would previously take quadratic time for garbage collection, but now the number of full garbage collections is reduced as the number of objects on the heap grows. The new logic only performs a full garbage collection pass when the middle generation has been collected 10 times and when the number of survivor objects from the middle generation exceeds 10% of the number of objects in the oldest generation. (Suggested by Martin von Löwis and implemented by Antoine Pitrou; bpo-4074 [https://bugs.python.org/issue?@action=redirect&bpo=4074].)

The garbage collector tries to avoid tracking simple containers which can't be part of a cycle. In Python 2.7, this is now true for tuples and dicts containing atomic types (such as ints, strings, etc.). Transitively, a dict containing tuples of atomic types won't be tracked either. This helps reduce the cost of each garbage collection by decreasing the number of objects to be considered and traversed by the collector. (Contributed by Antoine Pitrou; bpo-4688 [https://bugs.python.org/issue?@action=redirect&bpo=4688].)

Long integers are now stored internally either in base 2**15 or in base 2**30, the base being determined at build time. Previously, they were always stored in base 2**15. Using base 2**30 gives significant performance improvements on 64-bit machines, but benchmark results on 32-bit machines have been mixed. Therefore, the default is to use base 2**30 on 64-bit machines and base 2**15 on 32-bit machines; on Unix, there's a new configure option --enable-big-digits that can be used to override this default.

Apart from the performance improvements this change should be invisible to end users, with one exception: for testing and debugging purposes there's a new structseq sys.long_info that provides information about the internal format, giving the number of bits per digit and the size in bytes of the C type used to store each digit:

>>> import sys
>>> sys.long_info
sys.long_info(bits_per_digit=30, sizeof_digit=4)

（由 Mark Dickinson 貢獻；bpo-4258 [https://bugs.python.org/issue?@action=redirect&bpo=4258]。）

Another set of changes made long objects a few bytes smaller: 2 bytes smaller on 32-bit systems and 6 bytes on 64-bit. (Contributed by Mark Dickinson; bpo-5260 [https://bugs.python.org/issue?@action=redirect&bpo=5260].)

The division algorithm for long integers has been made faster by tightening the inner loop, doing shifts instead of multiplications, and fixing an unnecessary extra iteration. Various benchmarks show speedups of between 50% and 150% for long integer divisions and modulo operations. (Contributed by Mark Dickinson; bpo-5512 [https://bugs.python.org/issue?@action=redirect&bpo=5512].) Bitwise operations are also significantly faster (initial patch by Gregory Smith; bpo-1087418 [https://bugs.python.org/issue?@action=redirect&bpo=1087418]).

The implementation of % checks for the left-side operand being a Python string and special-cases it; this results in a 1--3% performance increase for applications that frequently use % with strings, such as templating libraries. (Implemented by Collin Winter; bpo-5176 [https://bugs.python.org/issue?@action=redirect&bpo=5176].)

List comprehensions with an if condition are compiled into faster bytecode. (Patch by Antoine Pitrou, back-ported to 2.7 by Jeffrey Yasskin; bpo-4715 [https://bugs.python.org/issue?@action=redirect&bpo=4715].)

Converting an integer or long integer to a decimal string was made faster by special-casing base 10 instead of using a generalized conversion function that supports arbitrary bases. (Patch by Gawain Bolton; bpo-6713 [https://bugs.python.org/issue?@action=redirect&bpo=6713].)

The split(), replace(), rindex(), rpartition(), and rsplit() methods of string-like types (strings, Unicode strings, and bytearray objects) now use a fast reverse-search algorithm instead of a character-by-character scan. This is sometimes faster by a factor of 10. (Added by Florent Xicluna; bpo-7462 [https://bugs.python.org/issue?@action=redirect&bpo=7462] and bpo-7622 [https://bugs.python.org/issue?@action=redirect&bpo=7622].)

The pickle and cPickle modules now automatically intern the strings used for attribute names, reducing memory usage of the objects resulting from unpickling. (Contributed by Jake McGuire; bpo-5084 [https://bugs.python.org/issue?@action=redirect&bpo=5084].)

The cPickle module now special-cases dictionaries, nearly halving the time required to pickle them. (Contributed by Collin Winter; bpo-5670 [https://bugs.python.org/issue?@action=redirect&bpo=5670].)

New and Improved Modules

As in every release, Python's standard library received a number of enhancements and bug fixes. Here's a partial list of the most notable changes, sorted alphabetically by module name. Consult the Misc/NEWS file in the source tree for a more complete list of changes, or look through the Subversion logs for all the details.

The bdb module's base debugging class Bdb gained a feature for skipping modules. The constructor now takes an iterable containing glob-style patterns such as django.*; the debugger will not step into stack frames from a module that matches one of these patterns. (Contributed by Maru Newby after a suggestion by Senthil Kumaran; bpo-5142 [https://bugs.python.org/issue?@action=redirect&bpo=5142].)

The binascii module now supports the buffer API, so it can be used with memoryview instances and other similar buffer objects. (Backported from 3.x by Florent Xicluna; bpo-7703 [https://bugs.python.org/issue?@action=redirect&bpo=7703].)

Updated module: the bsddb module has been updated from 4.7.2devel9 to version 4.8.4 of the pybsddb package [https://www.jcea.es/programacion/pybsddb.htm]. The new version features better Python 3.x compatibility, various bug fixes, and adds several new BerkeleyDB flags and methods. (Updated by Jesús Cea Avión; bpo-8156 [https://bugs.python.org/issue?@action=redirect&bpo=8156]. The pybsddb changelog can be read at https://hg.jcea.es/pybsddb/file/tip/ChangeLog.)

The bz2 module's BZ2File now supports the context management protocol, so you can write with bz2.BZ2File(...) as f:. (Contributed by Hagen Fürstenau; bpo-3860 [https://bugs.python.org/issue?@action=redirect&bpo=3860].)

New class: the Counter class in the collections module is useful for tallying data. Counter instances behave mostly like dictionaries but return zero for missing keys instead of raising a KeyError:

>>> from collections import Counter
>>> c = Counter()
>>> for letter in 'here is a sample of english text':
...   c[letter] += 1
...
>>> c
Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,
'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,
'p': 1, 'r': 1, 'x': 1})
>>> c['e']
5
>>> c['z']
0

There are three additional Counter methods. most_common() returns the N most common elements and their counts. elements() returns an iterator over the contained elements, repeating each element as many times as its count. subtract() takes an iterable and subtracts one for each element instead of adding; if the argument is a dictionary or another Counter, the counts are subtracted.

>>> c.most_common(5)
[(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]
>>> c.elements() ->
   'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',
   'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',
   'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',
   's', 's', 'r', 't', 't', 'x'
>>> c['e']
5
>>> c.subtract('very heavy on the letter e')
>>> c['e']    # Count is now lower
-1

由 Raymond Hettinger 貢獻；bpo-1696199 [https://bugs.python.org/issue?@action=redirect&bpo=1696199]。

New class: OrderedDict is described in the earlier section PEP 372: Adding an Ordered Dictionary to collections.

New method: The deque data type now has a count() method that returns the number of contained elements equal to the supplied argument x, and a reverse() method that reverses the elements of the deque in-place. deque also exposes its maximum length as the read-only maxlen attribute. (Both features added by Raymond Hettinger.)

The namedtuple class now has an optional rename parameter. If rename is true, field names that are invalid because they've been repeated or aren't legal Python identifiers will be renamed to legal names that are derived from the field's position within the list of fields:

>>> from collections import namedtuple
>>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True)
>>> T._fields
('field1', '_1', '_2', 'field2')

(Added by Raymond Hettinger; bpo-1818 [https://bugs.python.org/issue?@action=redirect&bpo=1818].)

Finally, the Mapping abstract base class now returns NotImplemented if a mapping is compared to another type that isn't a Mapping. (Fixed by Daniel Stutzbach; bpo-8729 [https://bugs.python.org/issue?@action=redirect&bpo=8729].)

Constructors for the parsing classes in the ConfigParser module now take an allow_no_value parameter, defaulting to false; if true, options without values will be allowed. For example:

>>> import ConfigParser, StringIO
>>> sample_config = """
... [mysqld]
... user = mysql
... pid-file = /var/run/mysqld/mysqld.pid
... skip-bdb
... """
>>> config = ConfigParser.RawConfigParser(allow_no_value=True)
>>> config.readfp(StringIO.StringIO(sample_config))
>>> config.get('mysqld', 'user')
'mysql'
>>> print config.get('mysqld', 'skip-bdb')
None
>>> print config.get('mysqld', 'unknown')
Traceback (most recent call last):
  ...
NoOptionError: No option 'unknown' in section: 'mysqld'

（由 Mats Kindahl 貢獻；bpo-7005 [https://bugs.python.org/issue?@action=redirect&bpo=7005]。）

Deprecated function: contextlib.nested(), which allows handling more than one context manager with a single with statement, has been deprecated, because the with statement now supports multiple context managers.

The cookielib module now ignores cookies that have an invalid version field, one that doesn't contain an integer value. (Fixed by John J. Lee; bpo-3924 [https://bugs.python.org/issue?@action=redirect&bpo=3924].)

The copy module's deepcopy() function will now correctly copy bound instance methods. (Implemented by Robert Collins; bpo-1515 [https://bugs.python.org/issue?@action=redirect&bpo=1515].)

The ctypes module now always converts None to a C NULL pointer for arguments declared as pointers. (Changed by Thomas Heller; bpo-4606 [https://bugs.python.org/issue?@action=redirect&bpo=4606].) The underlying libffi library [https://sourceware.org/libffi/] has been updated to version 3.0.9, containing various fixes for different platforms. (Updated by Matthias Klose; bpo-8142 [https://bugs.python.org/issue?@action=redirect&bpo=8142].)

New method: the datetime module's timedelta class gained a total_seconds() method that returns the number of seconds in the duration. (Contributed by Brian Quinlan; bpo-5788 [https://bugs.python.org/issue?@action=redirect&bpo=5788].)

New method: the Decimal class gained a from_float() class method that performs an exact conversion of a floating-point number to a Decimal. This exact conversion strives for the closest decimal approximation to the floating-point representation's value; the resulting decimal value will therefore still include the inaccuracy, if any. For example, Decimal.from_float(0.1) returns Decimal('0.1000000000000000055511151231257827021181583404541015625'). (Implemented by Raymond Hettinger; bpo-4796 [https://bugs.python.org/issue?@action=redirect&bpo=4796].)

Comparing instances of Decimal with floating-point numbers now produces sensible results based on the numeric values of the operands. Previously such comparisons would fall back to Python's default rules for comparing objects, which produced arbitrary results based on their type. Note that you still cannot combine Decimal and floating point in other operations such as addition, since you should be explicitly choosing how to convert between float and Decimal. (Fixed by Mark Dickinson; bpo-2531 [https://bugs.python.org/issue?@action=redirect&bpo=2531].)

The constructor for Decimal now accepts floating-point numbers (added by Raymond Hettinger; bpo-8257 [https://bugs.python.org/issue?@action=redirect&bpo=8257]) and non-European Unicode characters such as Arabic-Indic digits (contributed by Mark Dickinson; bpo-6595 [https://bugs.python.org/issue?@action=redirect&bpo=6595]).

Most of the methods of the Context class now accept integers as well as Decimal instances; the only exceptions are the canonical() and is_canonical() methods. (Patch by Juan José Conti; bpo-7633 [https://bugs.python.org/issue?@action=redirect&bpo=7633].)

When using Decimal instances with a string's format() method, the default alignment was previously left-alignment. This has been changed to right-alignment, which is more sensible for numeric types. (Changed by Mark Dickinson; bpo-6857 [https://bugs.python.org/issue?@action=redirect&bpo=6857].)

Comparisons involving a signaling NaN value (or sNAN) now signal InvalidOperation instead of silently returning a true or false value depending on the comparison operator. Quiet NaN values (or NaN) are now hashable. (Fixed by Mark Dickinson; bpo-7279 [https://bugs.python.org/issue?@action=redirect&bpo=7279].)

The difflib module now produces output that is more compatible with modern diff/patch tools through one small change, using a tab character instead of spaces as a separator in the header giving the filename. (Fixed by Anatoly Techtonik; bpo-7585 [https://bugs.python.org/issue?@action=redirect&bpo=7585].)

The Distutils sdist command now always regenerates the MANIFEST file, since even if the MANIFEST.in or setup.py files haven't been modified, the user might have created some new files that should be included. (Fixed by Tarek Ziadé; bpo-8688 [https://bugs.python.org/issue?@action=redirect&bpo=8688].)

The doctest module's IGNORE_EXCEPTION_DETAIL flag will now ignore the name of the module containing the exception being tested. (Patch by Lennart Regebro; bpo-7490 [https://bugs.python.org/issue?@action=redirect&bpo=7490].)

The email module's Message class will now accept a Unicode-valued payload, automatically converting the payload to the encoding specified by output_charset. (Added by R. David Murray; bpo-1368247 [https://bugs.python.org/issue?@action=redirect&bpo=1368247].)

The Fraction class now accepts a single float or Decimal instance, or two rational numbers, as arguments to its constructor. (Implemented by Mark Dickinson; rationals added in bpo-5812 [https://bugs.python.org/issue?@action=redirect&bpo=5812], and float/decimal in bpo-8294 [https://bugs.python.org/issue?@action=redirect&bpo=8294].)

Ordering comparisons (<, <=, >, >=) between fractions and complex numbers now raise a TypeError. This fixes an oversight, making the Fraction match the other numeric types.

New class: FTP_TLS in the ftplib module provides secure FTP connections using TLS encapsulation of authentication as well as subsequent control and data transfers. (Contributed by Giampaolo Rodola; bpo-2054 [https://bugs.python.org/issue?@action=redirect&bpo=2054].)

The storbinary() method for binary uploads can now restart uploads thanks to an added rest parameter (patch by Pablo Mouzo; bpo-6845 [https://bugs.python.org/issue?@action=redirect&bpo=6845].)

New class decorator: total_ordering() in the functools module takes a class that defines an __eq__() method and one of __lt__(), __le__(), __gt__(), or __ge__(), and generates the missing comparison methods. Since the __cmp__() method is being deprecated in Python 3.x, this decorator makes it easier to define ordered classes. (Added by Raymond Hettinger; bpo-5479 [https://bugs.python.org/issue?@action=redirect&bpo=5479].)

New function: cmp_to_key() will take an old-style comparison function that expects two arguments and return a new callable that can be used as the key parameter to functions such as sorted(), min() and max(), etc. The primary intended use is to help with making code compatible with Python 3.x. (Added by Raymond Hettinger.)

New function: the gc module's is_tracked() returns true if a given instance is tracked by the garbage collector, false otherwise. (Contributed by Antoine Pitrou; bpo-4688 [https://bugs.python.org/issue?@action=redirect&bpo=4688].)

The gzip module's GzipFile now supports the context management protocol, so you can write with gzip.GzipFile(...) as f: (contributed by Hagen Fürstenau; bpo-3860 [https://bugs.python.org/issue?@action=redirect&bpo=3860]), and it now implements the io.BufferedIOBase ABC, so you can wrap it with io.BufferedReader for faster processing (contributed by Nir Aides; bpo-7471 [https://bugs.python.org/issue?@action=redirect&bpo=7471]). It's also now possible to override the modification time recorded in a gzipped file by providing an optional timestamp to the constructor. (Contributed by Jacques Frechet; bpo-4272 [https://bugs.python.org/issue?@action=redirect&bpo=4272].)

Files in gzip format can be padded with trailing zero bytes; the gzip module will now consume these trailing bytes. (Fixed by Tadek Pietraszek and Brian Curtin; bpo-2846 [https://bugs.python.org/issue?@action=redirect&bpo=2846].)

New attribute: the hashlib module now has an algorithms attribute containing a tuple naming the supported algorithms. In Python 2.7, hashlib.algorithms contains ('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512'). (Contributed by Carl Chenet; bpo-7418 [https://bugs.python.org/issue?@action=redirect&bpo=7418].)

The default HTTPResponse class used by the httplib module now supports buffering, resulting in much faster reading of HTTP responses. (Contributed by Kristján Valur Jónsson; bpo-4879 [https://bugs.python.org/issue?@action=redirect&bpo=4879].)

The HTTPConnection and HTTPSConnection classes now support a source_address parameter, a (host, port) 2-tuple giving the source address that will be used for the connection. (Contributed by Eldon Ziegler; bpo-3972 [https://bugs.python.org/issue?@action=redirect&bpo=3972].)

The ihooks module now supports relative imports. Note that ihooks is an older module for customizing imports, superseded by the imputil module added in Python 2.0. (Relative import support added by Neil Schemenauer.)

The imaplib module now supports IPv6 addresses. (Contributed by Derek Morr; bpo-1655 [https://bugs.python.org/issue?@action=redirect&bpo=1655].)

New function: the inspect module's getcallargs() takes a callable and its positional and keyword arguments, and figures out which of the callable's parameters will receive each argument, returning a dictionary mapping argument names to their values. For example:

>>> from inspect import getcallargs
>>> def f(a, b=1, *pos, **named):
...     pass
...
>>> getcallargs(f, 1, 2, 3)
{'a': 1, 'b': 2, 'pos': (3,), 'named': {}}
>>> getcallargs(f, a=2, x=4)
{'a': 2, 'b': 1, 'pos': (), 'named': {'x': 4}}
>>> getcallargs(f)
Traceback (most recent call last):
...
TypeError: f() takes at least 1 argument (0 given)

由 George Sakkis 貢獻；bpo-3135 [https://bugs.python.org/issue?@action=redirect&bpo=3135]。

Updated module: The io library has been upgraded to the version shipped with Python 3.1. For 3.1, the I/O library was entirely rewritten in C and is 2 to 20 times faster depending on the task being performed. The original Python version was renamed to the _pyio module.

One minor resulting change: the io.TextIOBase class now has an errors attribute giving the error setting used for encoding and decoding errors (one of 'strict', 'replace', 'ignore').

The io.FileIO class now raises an OSError when passed an invalid file descriptor. (Implemented by Benjamin Peterson; bpo-4991 [https://bugs.python.org/issue?@action=redirect&bpo=4991].) The truncate() method now preserves the file position; previously it would change the file position to the end of the new file. (Fixed by Pascal Chambon; bpo-6939 [https://bugs.python.org/issue?@action=redirect&bpo=6939].)

New function: itertools.compress(data, selectors) takes two iterators. Elements of data are returned if the corresponding value in selectors is true:

itertools.compress('ABCDEF', [1,0,1,0,1,1]) =>
  A, C, E, F

New function: itertools.combinations_with_replacement(iter, r) returns all the possible r-length combinations of elements from the iterable iter. Unlike combinations(), individual elements can be repeated in the generated combinations:

itertools.combinations_with_replacement('abc', 2) =>
  ('a', 'a'), ('a', 'b'), ('a', 'c'),
  ('b', 'b'), ('b', 'c'), ('c', 'c')

Note that elements are treated as unique depending on their position in the input, not their actual values.

The itertools.count() function now has a step argument that allows incrementing by values other than 1. count() also now allows keyword arguments, and using non-integer values such as floats or Decimal instances. (Implemented by Raymond Hettinger; bpo-5032 [https://bugs.python.org/issue?@action=redirect&bpo=5032].)

itertools.combinations() and itertools.product() previously raised ValueError for values of r larger than the input iterable. This was deemed a specification error, so they now return an empty iterator. (Fixed by Raymond Hettinger; bpo-4816 [https://bugs.python.org/issue?@action=redirect&bpo=4816].)

Updated module: The json module was upgraded to version 2.0.9 of the simplejson package, which includes a C extension that makes encoding and decoding faster. (Contributed by Bob Ippolito; bpo-4136 [https://bugs.python.org/issue?@action=redirect&bpo=4136].)

To support the new collections.OrderedDict type, json.load() now has an optional object_pairs_hook parameter that will be called with any object literal that decodes to a list of pairs. (Contributed by Raymond Hettinger; bpo-5381 [https://bugs.python.org/issue?@action=redirect&bpo=5381].)

The mailbox module's Maildir class now records the timestamp on the directories it reads, and only re-reads them if the modification time has subsequently changed. This improves performance by avoiding unneeded directory scans. (Fixed by A.M. Kuchling and Antoine Pitrou; bpo-1607951 [https://bugs.python.org/issue?@action=redirect&bpo=1607951], bpo-6896 [https://bugs.python.org/issue?@action=redirect&bpo=6896].)

New functions: the math module gained erf() and erfc() for the error function and the complementary error function, expm1() which computes e**x - 1 with more precision than using exp() and subtracting 1, gamma() for the Gamma function, and lgamma() for the natural log of the Gamma function. (Contributed by Mark Dickinson and nirinA raseliarison; bpo-3366 [https://bugs.python.org/issue?@action=redirect&bpo=3366].)

The multiprocessing module's Manager* classes can now be passed a callable that will be called whenever a subprocess is started, along with a set of arguments that will be passed to the callable. (Contributed by lekma; bpo-5585 [https://bugs.python.org/issue?@action=redirect&bpo=5585].)

The Pool class, which controls a pool of worker processes, now has an optional maxtasksperchild parameter. Worker processes will perform the specified number of tasks and then exit, causing the Pool to start a new worker. This is useful if tasks may leak memory or other resources, or if some tasks will cause the worker to become very large. (Contributed by Charles Cazabon; bpo-6963 [https://bugs.python.org/issue?@action=redirect&bpo=6963].)

The nntplib module now supports IPv6 addresses. (Contributed by Derek Morr; bpo-1664 [https://bugs.python.org/issue?@action=redirect&bpo=1664].)

New functions: the os module wraps the following POSIX system calls: getresgid() and getresuid(), which return the real, effective, and saved GIDs and UIDs; setresgid() and setresuid(), which set real, effective, and saved GIDs and UIDs to new values; initgroups(), which initialize the group access list for the current process. (GID/UID functions contributed by Travis H.; bpo-6508 [https://bugs.python.org/issue?@action=redirect&bpo=6508]. Support for initgroups added by Jean-Paul Calderone; bpo-7333 [https://bugs.python.org/issue?@action=redirect&bpo=7333].)

The os.fork() function now re-initializes the import lock in the child process; this fixes problems on Solaris when fork() is called from a thread. (Fixed by Zsolt Cserna; bpo-7242 [https://bugs.python.org/issue?@action=redirect&bpo=7242].)

In the os.path module, the normpath() and abspath() functions now preserve Unicode; if their input path is a Unicode string, the return value is also a Unicode string. (normpath() fixed by Matt Giuca in bpo-5827 [https://bugs.python.org/issue?@action=redirect&bpo=5827]; abspath() fixed by Ezio Melotti in bpo-3426 [https://bugs.python.org/issue?@action=redirect&bpo=3426].)

The pydoc module now has help for the various symbols that Python uses. You can now do help('<<') or help('@'), for example. (Contributed by David Laban; bpo-4739 [https://bugs.python.org/issue?@action=redirect&bpo=4739].)

The re module's split(), sub(), and subn() now accept an optional flags argument, for consistency with the other functions in the module. (Added by Gregory P. Smith.)

New function: run_path() in the runpy module will execute the code at a provided path argument. path can be the path of a Python source file (example.py), a compiled bytecode file (example.pyc), a directory (./package/), or a zip archive (example.zip). If a directory or zip path is provided, it will be added to the front of sys.path and the module __main__ will be imported. It's expected that the directory or zip contains a __main__.py; if it doesn't, some other __main__.py might be imported from a location later in sys.path. This makes more of the machinery of runpy available to scripts that want to mimic the way Python's command line processes an explicit path name. (Added by Nick Coghlan; bpo-6816 [https://bugs.python.org/issue?@action=redirect&bpo=6816].)

New function: in the shutil module, make_archive() takes a filename, archive type (zip or tar-format), and a directory path, and creates an archive containing the directory's contents. (Added by Tarek Ziadé.)

shutil's copyfile() and copytree() functions now raise a SpecialFileError exception when asked to copy a named pipe. Previously the code would treat named pipes like a regular file by opening them for reading, and this would block indefinitely. (Fixed by Antoine Pitrou; bpo-3002 [https://bugs.python.org/issue?@action=redirect&bpo=3002].)

The signal module no longer re-installs the signal handler unless this is truly necessary, which fixes a bug that could make it impossible to catch the EINTR signal robustly. (Fixed by Charles-Francois Natali; bpo-8354 [https://bugs.python.org/issue?@action=redirect&bpo=8354].)

New functions: in the site module, three new functions return various site- and user-specific paths. getsitepackages() returns a list containing all global site-packages directories, getusersitepackages() returns the path of the user's site-packages directory, and getuserbase() returns the value of the USER_BASE environment variable, giving the path to a directory that can be used to store data. (Contributed by Tarek Ziadé; bpo-6693 [https://bugs.python.org/issue?@action=redirect&bpo=6693].)

The site module now reports exceptions occurring when the sitecustomize module is imported, and will no longer catch and swallow the KeyboardInterrupt exception. (Fixed by Victor Stinner; bpo-3137 [https://bugs.python.org/issue?@action=redirect&bpo=3137].)

The create_connection() function gained a source_address parameter, a (host, port) 2-tuple giving the source address that will be used for the connection. (Contributed by Eldon Ziegler; bpo-3972 [https://bugs.python.org/issue?@action=redirect&bpo=3972].)

The recv_into() and recvfrom_into() methods will now write into objects that support the buffer API, most usefully the bytearray and memoryview objects. (Implemented by Antoine Pitrou; bpo-8104 [https://bugs.python.org/issue?@action=redirect&bpo=8104].)

The SocketServer module's TCPServer class now supports socket timeouts and disabling the Nagle algorithm. The disable_nagle_algorithm class attribute defaults to False; if overridden to be true, new request connections will have the TCP_NODELAY option set to prevent buffering many small sends into a single TCP packet. The timeout class attribute can hold a timeout in seconds that will be applied to the request socket; if no request is received within that time, handle_timeout() will be called and handle_request() will return. (Contributed by Kristján Valur Jónsson; bpo-6192 [https://bugs.python.org/issue?@action=redirect&bpo=6192] and bpo-6267 [https://bugs.python.org/issue?@action=redirect&bpo=6267].)

Updated module: the sqlite3 module has been updated to version 2.6.0 of the pysqlite package [https://github.com/ghaering/pysqlite]. Version 2.6.0 includes a number of bugfixes, and adds the ability to load SQLite extensions from shared libraries. Call the enable_load_extension(True) method to enable extensions, and then call load_extension() to load a particular shared library. (Updated by Gerhard Häring.)

The ssl module's SSLSocket objects now support the buffer API, which fixed a test suite failure (fix by Antoine Pitrou; bpo-7133 [https://bugs.python.org/issue?@action=redirect&bpo=7133]) and automatically set OpenSSL's SSL_MODE_AUTO_RETRY, which will prevent an error code being returned from recv() operations that trigger an SSL renegotiation (fix by Antoine Pitrou; bpo-8222 [https://bugs.python.org/issue?@action=redirect&bpo=8222]).

The wrap_socket() constructor function now takes a ciphers argument that's a string listing the encryption algorithms to be allowed; the format of the string is described in the OpenSSL documentation [https://docs.openssl.org/1.0.2/man1/ciphers/]. (Added by Antoine Pitrou; bpo-8322 [https://bugs.python.org/issue?@action=redirect&bpo=8322].)

Another change makes the extension load all of OpenSSL's ciphers and digest algorithms so that they're all available. Some SSL certificates couldn't be verified, reporting an "unknown algorithm" error. (Reported by Beda Kosata, and fixed by Antoine Pitrou; bpo-8484 [https://bugs.python.org/issue?@action=redirect&bpo=8484].)

The version of OpenSSL being used is now available as the module attributes ssl.OPENSSL_VERSION (a string), ssl.OPENSSL_VERSION_INFO (a 5-tuple), and ssl.OPENSSL_VERSION_NUMBER (an integer). (Added by Antoine Pitrou; bpo-8321 [https://bugs.python.org/issue?@action=redirect&bpo=8321].)

The struct module will no longer silently ignore overflow errors when a value is too large for a particular integer format code (one of bBhHiIlLqQ); it now always raises a struct.error exception. (Changed by Mark Dickinson; bpo-1523 [https://bugs.python.org/issue?@action=redirect&bpo=1523].) The pack() function will also attempt to use __index__() to convert and pack non-integers before trying the __int__() method or reporting an error. (Changed by Mark Dickinson; bpo-8300 [https://bugs.python.org/issue?@action=redirect&bpo=8300].)

New function: the subprocess module's check_output() runs a command with a specified set of arguments and returns the command's output as a string when the command runs without error, or raises a CalledProcessError exception otherwise.

>>> subprocess.check_output(['df', '-h', '.'])
'Filesystem     Size   Used  Avail Capacity  Mounted on\n
/dev/disk0s2    52G    49G   3.0G    94%    /\n'

>>> subprocess.check_output(['df', '-h', '/bogus'])
  ...
subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1

（由 Gregory P. Smith 所貢獻。）

The subprocess module will now retry its internal system calls on receiving an EINTR signal. (Reported by several people; final patch by Gregory P. Smith in bpo-1068268 [https://bugs.python.org/issue?@action=redirect&bpo=1068268].)

New function: is_declared_global() in the symtable module returns true for variables that are explicitly declared to be global, false for ones that are implicitly global. (Contributed by Jeremy Hylton.)

The syslog module will now use the value of sys.argv[0] as the identifier instead of the previous default value of 'python'. (Changed by Sean Reifschneider; bpo-8451 [https://bugs.python.org/issue?@action=redirect&bpo=8451].)

The sys.version_info value is now a named tuple, with attributes named major, minor, micro, releaselevel, and serial. (Contributed by Ross Light; bpo-4285 [https://bugs.python.org/issue?@action=redirect&bpo=4285].)

sys.getwindowsversion() also returns a named tuple, with attributes named major, minor, build, platform, service_pack, service_pack_major, service_pack_minor, suite_mask, and product_type. (Contributed by Brian Curtin; bpo-7766 [https://bugs.python.org/issue?@action=redirect&bpo=7766].)

The tarfile module's default error handling has changed, to no longer suppress fatal errors. The default error level was previously 0, which meant that errors would only result in a message being written to the debug log, but because the debug log is not activated by default, these errors go unnoticed. The default error level is now 1, which raises an exception if there's an error. (Changed by Lars Gustäbel; bpo-7357 [https://bugs.python.org/issue?@action=redirect&bpo=7357].)

tarfile now supports filtering the TarInfo objects being added to a tar file. When you call add(), you may supply an optional filter argument that's a callable. The filter callable will be passed the TarInfo for every file being added, and can modify and return it. If the callable returns None, the file will be excluded from the resulting archive. This is more powerful than the existing exclude argument, which has therefore been deprecated. (Added by Lars Gustäbel; bpo-6856 [https://bugs.python.org/issue?@action=redirect&bpo=6856].) The TarFile class also now supports the context management protocol. (Added by Lars Gustäbel; bpo-7232 [https://bugs.python.org/issue?@action=redirect&bpo=7232].)

The wait() method of the threading.Event class now returns the internal flag on exit. This means the method will usually return true because wait() is supposed to block until the internal flag becomes true. The return value will only be false if a timeout was provided and the operation timed out. (Contributed by Tim Lesher; bpo-1674032 [https://bugs.python.org/issue?@action=redirect&bpo=1674032].)

The Unicode database provided by the unicodedata module is now used internally to determine which characters are numeric, whitespace, or represent line breaks. The database also includes information from the Unihan.txt data file (patch by Anders Chrigström and Amaury Forgeot d'Arc; bpo-1571184 [https://bugs.python.org/issue?@action=redirect&bpo=1571184]) and has been updated to version 5.2.0 (updated by Florent Xicluna; bpo-8024 [https://bugs.python.org/issue?@action=redirect&bpo=8024]).

The urlparse module's urlsplit() now handles unknown URL schemes in a fashion compliant with RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html]: if the URL is of the form "<something>://...", the text before the :// is treated as the scheme, even if it's a made-up scheme that the module doesn't know about. This change may break code that worked around the old behaviour. For example, Python 2.6.4 or 2.5 will return the following:

>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', '', '//host/filename?query', '', '')

Python 2.7 (and Python 2.6.5) will return:

>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', 'host', '/filename?query', '', '')

(Python 2.7 actually produces slightly different output, since it returns a named tuple instead of a standard tuple.)

The urlparse module also supports IPv6 literal addresses as defined by RFC 2732 [https://datatracker.ietf.org/doc/html/rfc2732.html] (contributed by Senthil Kumaran; bpo-2987 [https://bugs.python.org/issue?@action=redirect&bpo=2987]).

>>> urlparse.urlparse('http://[1080::8:800:200C:417A]/foo')
ParseResult(scheme='http', netloc='[1080::8:800:200C:417A]',
            path='/foo', params='', query='', fragment='')

New class: the WeakSet class in the weakref module is a set that only holds weak references to its elements; elements will be removed once there are no references pointing to them. (Originally implemented in Python 3.x by Raymond Hettinger, and backported to 2.7 by Michael Foord.)

The xml.etree.ElementTree library, no longer escapes ampersands and angle brackets when outputting an XML processing instruction (which looks like <?xml-stylesheet href="#style1"?>) or comment (which looks like <!-- comment -->). (Patch by Neil Muller; bpo-2746 [https://bugs.python.org/issue?@action=redirect&bpo=2746].)

The XML-RPC client and server, provided by the xmlrpclib and SimpleXMLRPCServer modules, have improved performance by supporting HTTP/1.1 keep-alive and by optionally using gzip encoding to compress the XML being exchanged. The gzip compression is controlled by the encode_threshold attribute of SimpleXMLRPCRequestHandler, which contains a size in bytes; responses larger than this will be compressed. (Contributed by Kristján Valur Jónsson; bpo-6267 [https://bugs.python.org/issue?@action=redirect&bpo=6267].)

The zipfile module's ZipFile now supports the context management protocol, so you can write with zipfile.ZipFile(...) as f:. (Contributed by Brian Curtin; bpo-5511 [https://bugs.python.org/issue?@action=redirect&bpo=5511].)

zipfile now also supports archiving empty directories and extracts them correctly. (Fixed by Kuba Wieczorek; bpo-4710 [https://bugs.python.org/issue?@action=redirect&bpo=4710].) Reading files out of an archive is faster, and interleaving read() and readline() now works correctly. (Contributed by Nir Aides; bpo-7610 [https://bugs.python.org/issue?@action=redirect&bpo=7610].)

The is_zipfile() function now accepts a file object, in addition to the path names accepted in earlier versions. (Contributed by Gabriel Genellina; bpo-4756 [https://bugs.python.org/issue?@action=redirect&bpo=4756].)

The writestr() method now has an optional compress_type parameter that lets you override the default compression method specified in the ZipFile constructor. (Contributed by Ronald Oussoren; bpo-6003 [https://bugs.python.org/issue?@action=redirect&bpo=6003].)

新模組：importlib

Python 3.1 includes the importlib package, a re-implementation of the logic underlying Python's import statement. importlib is useful for implementers of Python interpreters and to users who wish to write new importers that can participate in the import process. Python 2.7 doesn't contain the complete importlib package, but instead has a tiny subset that contains a single function, import_module().

import_module(name, package=None) imports a module. name is a string containing the module or package's name. It's possible to do relative imports by providing a string that begins with a . character, such as ..utils.errors. For relative imports, the package argument must be provided and is the name of the package that will be used as the anchor for the relative import. import_module() both inserts the imported module into sys.modules and returns the module object.

以下是一些範例：

>>> from importlib import import_module
>>> anydbm = import_module('anydbm')  # Standard absolute import
>>> anydbm
<module 'anydbm' from '/p/python/Lib/anydbm.py'>
>>> # Relative import
>>> file_util = import_module('..file_util', 'distutils.command')
>>> file_util
<module 'distutils.file_util' from '/python/Lib/distutils/file_util.pyc'>

importlib was implemented by Brett Cannon and introduced in Python 3.1.

新模組：sysconfig

The sysconfig module has been pulled out of the Distutils package, becoming a new top-level module in its own right. sysconfig provides functions for getting information about Python's build process: compiler switches, installation paths, the platform name, and whether Python is running from its source directory.

Some of the functions in the module are:

get_config_var() returns variables from Python's Makefile and the pyconfig.h file.

get_config_vars() returns a dictionary containing all of the configuration variables.

get_path() returns the configured path for a particular type of module: the standard library, site-specific modules, platform-specific modules, etc.

is_python_build() returns true if you're running a binary from a Python source tree, and false otherwise.

Consult the sysconfig documentation for more details and for a complete list of functions.

The Distutils package and sysconfig are now maintained by Tarek Ziadé, who has also started a Distutils2 package (source repository at https://hg.python.org/distutils2/) for developing a next-generation version of Distutils.

ttk: Themed Widgets for Tk

Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk widgets but have a more customizable appearance and can therefore more closely resemble the native platform's widgets. This widget set was originally called Tile, but was renamed to Ttk (for "themed Tk") on being added to Tcl/Tck release 8.5.

To learn more, read the ttk module documentation. You may also wish to read the Tcl/Tk manual page describing the Ttk theme engine, available at https://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.html. Some screenshots of the Python/Ttk code in use are at https://code.google.com/archive/p/python-ttk/wikis/Screenshots.wiki.

The tkinter.ttk module was written by Guilherme Polo and added in bpo-2983 [https://bugs.python.org/issue?@action=redirect&bpo=2983]. An alternate version called Tile.py, written by Martin Franklin and maintained by Kevin Walzer, was proposed for inclusion in bpo-2618 [https://bugs.python.org/issue?@action=redirect&bpo=2618], but the authors argued that Guilherme Polo's work was more comprehensive.

改進模組：unittest

The unittest module was greatly enhanced; many new features were added. Most of these features were implemented by Michael Foord, unless otherwise noted. The enhanced version of the module is downloadable separately for use with Python versions 2.4 to 2.6, packaged as the unittest2 package, from unittest2 [https://pypi.org/project/unittest2/].

When used from the command line, the module can automatically discover tests. It's not as fancy as py.test [https://pytest.org] or nose [https://nose.readthedocs.io/], but provides a simple way to run tests kept within a set of package directories. For example, the following command will search the test/ subdirectory for any importable test files named test*.py:

python -m unittest discover -s test

Consult the unittest module documentation for more details. (Developed in bpo-6001 [https://bugs.python.org/issue?@action=redirect&bpo=6001].)

The main() function supports some other new options:

-b or --buffer will buffer the standard output and standard error streams during each test. If the test passes, any resulting output will be discarded; on failure, the buffered output will be displayed.

-c or --catch will cause the control-C interrupt to be handled more gracefully. Instead of interrupting the test process immediately, the currently running test will be completed and then the partial results up to the interruption will be reported. If you're impatient, a second press of control-C will cause an immediate interruption.

This control-C handler tries to avoid causing problems when the code being tested or the tests being run have defined a signal handler of their own, by noticing that a signal handler was already set and calling it. If this doesn't work for you, there's a removeHandler() decorator that can be used to mark tests that should have the control-C handling disabled.

-f or --failfast makes test execution stop immediately when a test fails instead of continuing to execute further tests. (Suggested by Cliff Dyer and implemented by Michael Foord; bpo-8074 [https://bugs.python.org/issue?@action=redirect&bpo=8074].)

The progress messages now show 'x' for expected failures and 'u' for unexpected successes when run in verbose mode. (Contributed by Benjamin Peterson.)

Test cases can raise the SkipTest exception to skip a test (bpo-1034053 [https://bugs.python.org/issue?@action=redirect&bpo=1034053]).

The error messages for assertEqual(), assertTrue(), and assertFalse() failures now provide more information. If you set the longMessage attribute of your TestCase classes to true, both the standard error message and any additional message you provide will be printed for failures. (Added by Michael Foord; bpo-5663 [https://bugs.python.org/issue?@action=redirect&bpo=5663].)

The assertRaises() method now returns a context handler when called without providing a callable object to run. For example, you can write this:

with self.assertRaises(KeyError):
    {}['foo']

（由 Antoine Pitrou 實作；bpo-4444 [https://bugs.python.org/issue?@action=redirect&bpo=4444]。）

Module- and class-level setup and teardown fixtures are now supported. Modules can contain setUpModule() and tearDownModule() functions. Classes can have setUpClass() and tearDownClass() methods that must be defined as class methods (using @classmethod or equivalent). These functions and methods are invoked when the test runner switches to a test case in a different module or class.

The methods addCleanup() and doCleanups() were added. addCleanup() lets you add cleanup functions that will be called unconditionally (after setUp() if setUp() fails, otherwise after tearDown()). This allows for much simpler resource allocation and deallocation during tests (bpo-5679 [https://bugs.python.org/issue?@action=redirect&bpo=5679]).

A number of new methods were added that provide more specialized tests. Many of these methods were written by Google engineers for use in their test suites; Gregory P. Smith, Michael Foord, and GvR worked on merging them into Python's version of unittest.

assertIsNone() and assertIsNotNone() take one expression and verify that the result is or is not None.

assertIs() and assertIsNot() take two values and check whether the two values evaluate to the same object or not. (Added by Michael Foord; bpo-2578 [https://bugs.python.org/issue?@action=redirect&bpo=2578].)

assertIsInstance() and assertNotIsInstance() check whether the resulting object is an instance of a particular class, or of one of a tuple of classes. (Added by Georg Brandl; bpo-7031 [https://bugs.python.org/issue?@action=redirect&bpo=7031].)

assertGreater(), assertGreaterEqual(), assertLess(), and assertLessEqual() compare two quantities.

assertMultiLineEqual() compares two strings, and if they're not equal, displays a helpful comparison that highlights the differences in the two strings. This comparison is now used by default when Unicode strings are compared with assertEqual().

assertRegexpMatches() and assertNotRegexpMatches() checks whether the first argument is a string matching or not matching the regular expression provided as the second argument (bpo-8038 [https://bugs.python.org/issue?@action=redirect&bpo=8038]).

assertRaisesRegexp() checks whether a particular exception is raised, and then also checks that the string representation of the exception matches the provided regular expression.

assertIn() and assertNotIn() tests whether first is or is not in second.

assertItemsEqual() tests whether two provided sequences contain the same elements.

assertSetEqual() compares whether two sets are equal, and only reports the differences between the sets in case of error.

Similarly, assertListEqual() and assertTupleEqual() compare the specified types and explain any differences without necessarily printing their full values; these methods are now used by default when comparing lists and tuples using assertEqual(). More generally, assertSequenceEqual() compares two sequences and can optionally check whether both sequences are of a particular type.

assertDictEqual() compares two dictionaries and reports the differences; it's now used by default when you compare two dictionaries using assertEqual(). assertDictContainsSubset() checks whether all of the key/value pairs in first are found in second.

assertAlmostEqual() and assertNotAlmostEqual() test whether first and second are approximately equal. This method can either round their difference to an optionally specified number of places (the default is 7) and compare it to zero, or require the difference to be smaller than a supplied delta value.

loadTestsFromName() properly honors the suiteClass attribute of the TestLoader. (Fixed by Mark Roddy; bpo-6866 [https://bugs.python.org/issue?@action=redirect&bpo=6866].)

A new hook lets you extend the assertEqual() method to handle new data types. The addTypeEqualityFunc() method takes a type object and a function. The function will be used when both of the objects being compared are of the specified type. This function should compare the two objects and raise an exception if they don't match; it's a good idea for the function to provide additional information about why the two objects aren't matching, much as the new sequence comparison methods do.

unittest.main() now takes an optional exit argument. If false, main() doesn't call sys.exit(), allowing main() to be used from the interactive interpreter. (Contributed by J. Pablo Fernández; bpo-3379 [https://bugs.python.org/issue?@action=redirect&bpo=3379].)

TestResult has new startTestRun() and stopTestRun() methods that are called immediately before and after a test run. (Contributed by Robert Collins; bpo-5728 [https://bugs.python.org/issue?@action=redirect&bpo=5728].)

With all these changes, the unittest.py was becoming awkwardly large, so the module was turned into a package and the code split into several files (by Benjamin Peterson). This doesn't affect how the module is imported or used.

也參考

https://web.archive.org/web/20210619163128/http://www.voidspace.org.uk/python/articles/unittest2.shtml

Describes the new features, how to use them, and the rationale for various design decisions. (By Michael Foord.)

改進模組：ElementTree 1.3

The version of the ElementTree library included with Python was updated to version 1.3. Some of the new features are:

The various parsing functions now take a parser keyword argument giving an XMLParser instance that will be used. This makes it possible to override the file's internal encoding:

p = ET.XMLParser(encoding='utf-8')
t = ET.XML("""<root/>""", parser=p)

Errors in parsing XML now raise a ParseError exception, whose instances have a position attribute containing a (line, column) tuple giving the location of the problem.

ElementTree's code for converting trees to a string has been significantly reworked, making it roughly twice as fast in many cases. The ElementTree.write() and Element.write() methods now have a method parameter that can be "xml" (the default), "html", or "text". HTML mode will output empty elements as <empty></empty> instead of <empty/>, and text mode will skip over elements and only output the text chunks. If you set the tag attribute of an element to None but leave its children in place, the element will be omitted when the tree is written out, so you don't need to do more extensive rearrangement to remove a single element.

Namespace handling has also been improved. All xmlns:<whatever> declarations are now output on the root element, not scattered throughout the resulting XML. You can set the default namespace for a tree by setting the default_namespace attribute and can register new prefixes with register_namespace(). In XML mode, you can use the true/false xml_declaration parameter to suppress the XML declaration.

New Element method: extend() appends the items from a sequence to the element's children. Elements themselves behave like sequences, so it's easy to move children from one element to another:

from xml.etree import ElementTree as ET

t = ET.XML("""<list>
  <item>1</item> <item>2</item>  <item>3</item>
</list>""")
new = ET.XML('<root/>')
new.extend(t)

# 輸出 <root><item>1</item>...</root>
print ET.tostring(new)

New Element method: iter() yields the children of the element as a generator. It's also possible to write for child in elem: to loop over an element's children. The existing method getiterator() is now deprecated, as is getchildren() which constructs and returns a list of children.

New Element method: itertext() yields all chunks of text that are descendants of the element. For example:

t = ET.XML("""<list>
  <item>1</item> <item>2</item>  <item>3</item>
</list>""")

# 輸出 ['\n  ', '1', ' ', '2', '  ', '3', '\n']
print list(t.itertext())

Deprecated: using an element as a Boolean (i.e., if elem:) would return true if the element had any children, or false if there were no children. This behaviour is confusing -- None is false, but so is a childless element? -- so it will now trigger a FutureWarning. In your code, you should be explicit: write len(elem) != 0 if you're interested in the number of children, or elem is not None.

Fredrik Lundh develops ElementTree and produced the 1.3 version; you can read his article describing 1.3 at https://web.archive.org/web/20200703234532/http://effbot.org/zone/elementtree-13-intro.htm. Florent Xicluna updated the version included with Python, after discussions on python-dev and in bpo-6472 [https://bugs.python.org/issue?@action=redirect&bpo=6472].)

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

The latest release of the GNU Debugger, GDB 7, can be scripted using Python [https://web.archive.org/web/20110715084810/http://sourceware.org/gdb/current/onlinedocs/gdb/Python.html]. When you begin debugging an executable program P, GDB will look for a file named P-gdb.py and automatically read it. Dave Malcolm contributed a python-gdb.py that adds a number of commands useful when debugging Python itself. For example, py-up and py-down go up or down one Python stack frame, which usually corresponds to several C stack frames. py-print prints the value of a Python variable, and py-bt prints the Python stack trace. (Added as a result of bpo-8032 [https://bugs.python.org/issue?@action=redirect&bpo=8032].)

If you use the .gdbinit file provided with Python, the "pyo" macro in the 2.7 version now works correctly when the thread being debugged doesn't hold the GIL; the macro now acquires it before printing. (Contributed by Victor Stinner; bpo-3632 [https://bugs.python.org/issue?@action=redirect&bpo=3632].)

Py_AddPendingCall() is now thread-safe, letting any worker thread submit notifications to the main Python thread. This is particularly useful for asynchronous IO operations. (Contributed by Kristján Valur Jónsson; bpo-4293 [https://bugs.python.org/issue?@action=redirect&bpo=4293].)

New function: PyCode_NewEmpty() creates an empty code object; only the filename, function name, and first line number are required. This is useful for extension modules that are attempting to construct a more useful traceback stack. Previously such extensions needed to call PyCode_New(), which had many more arguments. (Added by Jeffrey Yasskin.)

New function: PyErr_NewExceptionWithDoc() creates a new exception class, just as the existing PyErr_NewException() does, but takes an extra char * argument containing the docstring for the new exception class. (Added by 'lekma' on the Python bug tracker; bpo-7033 [https://bugs.python.org/issue?@action=redirect&bpo=7033].)

New function: PyFrame_GetLineNumber() takes a frame object and returns the line number that the frame is currently executing. Previously code would need to get the index of the bytecode instruction currently executing, and then look up the line number corresponding to that address. (Added by Jeffrey Yasskin.)

New functions: PyLong_AsLongAndOverflow() and PyLong_AsLongLongAndOverflow() approximates a Python long integer as a C long or long long. If the number is too large to fit into the output type, an overflow flag is set and returned to the caller. (Contributed by Case Van Horsen; bpo-7528 [https://bugs.python.org/issue?@action=redirect&bpo=7528] and bpo-7767 [https://bugs.python.org/issue?@action=redirect&bpo=7767].)

New function: stemming from the rewrite of string-to-float conversion, a new PyOS_string_to_double() function was added. The old PyOS_ascii_strtod() and PyOS_ascii_atof() functions are now deprecated.

New function: PySys_SetArgvEx() sets the value of sys.argv and can optionally update sys.path to include the directory containing the script named by sys.argv[0] depending on the value of an updatepath parameter.

This function was added to close a security hole for applications that embed Python. The old function, PySys_SetArgv(), would always update sys.path, and sometimes it would add the current directory. This meant that, if you ran an application embedding Python in a directory controlled by someone else, attackers could put a Trojan-horse module in the directory (say, a file named os.py) that your application would then import and run.

If you maintain a C/C++ application that embeds Python, check whether you're calling PySys_SetArgv() and carefully consider whether the application should be using PySys_SetArgvEx() with updatepath set to false.

Security issue reported as CVE 2008-5983 [https://www.cve.org/CVERecord?id=CVE-2008-5983]; discussed in bpo-5753 [https://bugs.python.org/issue?@action=redirect&bpo=5753], and fixed by Antoine Pitrou.

New macros: the Python header files now define the following macros: Py_ISALNUM, Py_ISALPHA, Py_ISDIGIT, Py_ISLOWER, Py_ISSPACE, Py_ISUPPER, Py_ISXDIGIT, Py_TOLOWER, and Py_TOUPPER. All of these functions are analogous to the C standard macros for classifying characters, but ignore the current locale setting, because in several places Python needs to analyze characters in a locale-independent way. (Added by Eric Smith; bpo-5793 [https://bugs.python.org/issue?@action=redirect&bpo=5793].)

Removed function: PyEval_CallObject() is now only available as a macro. A function version was being kept around to preserve ABI linking compatibility, but that was in 1997; it can certainly be deleted by now. (Removed by Antoine Pitrou; bpo-8276 [https://bugs.python.org/issue?@action=redirect&bpo=8276].)

New format codes: the PyString_FromFormat(), PyString_FromFormatV(), and PyErr_Format() functions now accept %lld and %llu format codes for displaying C's long long types. (Contributed by Mark Dickinson; bpo-7228 [https://bugs.python.org/issue?@action=redirect&bpo=7228].)

The complicated interaction between threads and process forking has been changed. Previously, the child process created by os.fork() might fail because the child is created with only a single thread running, the thread performing the os.fork(). If other threads were holding a lock, such as Python's import lock, when the fork was performed, the lock would still be marked as "held" in the new process. But in the child process nothing would ever release the lock, since the other threads weren't replicated, and the child process would no longer be able to perform imports.

Python 2.7 acquires the import lock before performing an os.fork(), and will also clean up any locks created using the threading module. C extension modules that have internal locks, or that call fork() themselves, will not benefit from this clean-up.

(Fixed by Thomas Wouters; bpo-1590864 [https://bugs.python.org/issue?@action=redirect&bpo=1590864].)

The Py_Finalize() function now calls the internal threading._shutdown() function; this prevents some exceptions from being raised when an interpreter shuts down. (Patch by Adam Olsen; bpo-1722344 [https://bugs.python.org/issue?@action=redirect&bpo=1722344].)

When using the PyMemberDef structure to define attributes of a type, Python will no longer let you try to delete or set a T_STRING_INPLACE attribute.

Global symbols defined by the ctypes module are now prefixed with Py, or with _ctypes. (Implemented by Thomas Heller; bpo-3102 [https://bugs.python.org/issue?@action=redirect&bpo=3102].)

New configure option: the --with-system-expat switch allows building the pyexpat module to use the system Expat library. (Contributed by Arfrever Frehtes Taifersar Arahesis; bpo-7609 [https://bugs.python.org/issue?@action=redirect&bpo=7609].)

New configure option: the --with-valgrind option will now disable the pymalloc allocator, which is difficult for the Valgrind memory-error detector to analyze correctly. Valgrind will therefore be better at detecting memory leaks and overruns. (Contributed by James Henstridge; bpo-2422 [https://bugs.python.org/issue?@action=redirect&bpo=2422].)

New configure option: you can now supply an empty string to --with-dbmliborder= in order to disable all of the various DBM modules. (Added by Arfrever Frehtes Taifersar Arahesis; bpo-6491 [https://bugs.python.org/issue?@action=redirect&bpo=6491].)

The configure script now checks for floating-point rounding bugs on certain 32-bit Intel chips and defines a X87_DOUBLE_ROUNDING preprocessor definition. No code currently uses this definition, but it's available if anyone wishes to use it. (Added by Mark Dickinson; bpo-2937 [https://bugs.python.org/issue?@action=redirect&bpo=2937].)

configure also now sets a LDCXXSHARED Makefile variable for supporting C++ linking. (Contributed by Arfrever Frehtes Taifersar Arahesis; bpo-1222585 [https://bugs.python.org/issue?@action=redirect&bpo=1222585].)

The build process now creates the necessary files for pkg-config support. (Contributed by Clinton Roy; bpo-3585 [https://bugs.python.org/issue?@action=redirect&bpo=3585].)

The build process now supports Subversion 1.7. (Contributed by Arfrever Frehtes Taifersar Arahesis; bpo-6094 [https://bugs.python.org/issue?@action=redirect&bpo=6094].)

Capsules

Python 3.1 adds a new C datatype, PyCapsule, for providing a C API to an extension module. A capsule is essentially the holder of a C void * pointer, and is made available as a module attribute; for example, the socket module's API is exposed as socket.CAPI, and unicodedata exposes ucnhash_CAPI. Other extensions can import the module, access its dictionary to get the capsule object, and then get the void * pointer, which will usually point to an array of pointers to the module's various API functions.

There is an existing data type already used for this, PyCObject, but it doesn't provide type safety. Evil code written in pure Python could cause a segmentation fault by taking a PyCObject from module A and somehow substituting it for the PyCObject in module B. Capsules know their own name, and getting the pointer requires providing the name:

void *vtable;

if (!PyCapsule_IsValid(capsule, "mymodule.CAPI") {
        PyErr_SetString(PyExc_ValueError, "argument type invalid");
        return NULL;
}

vtable = PyCapsule_GetPointer(capsule, "mymodule.CAPI");

You are assured that vtable points to whatever you're expecting. If a different capsule was passed in, PyCapsule_IsValid() would detect the mismatched name and return false. Refer to Providing a C API for an Extension Module for more information on using these objects.

Python 2.7 now uses capsules internally to provide various extension-module APIs, but the PyCObject_AsVoidPtr() was modified to handle capsules, preserving compile-time compatibility with the PyCObject interface. Use of PyCObject_AsVoidPtr() will signal a PendingDeprecationWarning, which is silent by default.

Implemented in Python 3.1 and backported to 2.7 by Larry Hastings; discussed in bpo-5630 [https://bugs.python.org/issue?@action=redirect&bpo=5630].

Port-Specific Changes: Windows

The msvcrt module now contains some constants from the crtassem.h header file: CRT_ASSEMBLY_VERSION, VC_ASSEMBLY_PUBLICKEYTOKEN, and LIBRARIES_ASSEMBLY_NAME_PREFIX. (Contributed by David Cournapeau; bpo-4365 [https://bugs.python.org/issue?@action=redirect&bpo=4365].)

The _winreg module for accessing the registry now implements the CreateKeyEx() and DeleteKeyEx() functions, extended versions of previously supported functions that take several extra arguments. The DisableReflectionKey(), EnableReflectionKey(), and QueryReflectionKey() were also tested and documented. (Implemented by Brian Curtin: bpo-7347 [https://bugs.python.org/issue?@action=redirect&bpo=7347].)

The new _beginthreadex() API is used to start threads, and the native thread-local storage functions are now used. (Contributed by Kristján Valur Jónsson; bpo-3582 [https://bugs.python.org/issue?@action=redirect&bpo=3582].)

The os.kill() function now works on Windows. The signal value can be the constants CTRL_C_EVENT, CTRL_BREAK_EVENT, or any integer. The first two constants will send Control-C and Control-Break keystroke events to subprocesses; any other value will use the TerminateProcess() API. (Contributed by Miki Tebeka; bpo-1220212 [https://bugs.python.org/issue?@action=redirect&bpo=1220212].)

The os.listdir() function now correctly fails for an empty path. (Fixed by Hirokazu Yamamoto; bpo-5913 [https://bugs.python.org/issue?@action=redirect&bpo=5913].)

The mimetypes module will now read the MIME database from the Windows registry when initializing. (Patch by Gabriel Genellina; bpo-4969 [https://bugs.python.org/issue?@action=redirect&bpo=4969].)

Port-Specific Changes: Mac OS X

The path /Library/Python/2.7/site-packages is now appended to sys.path, in order to share added packages between the system installation and a user-installed copy of the same version. (Changed by Ronald Oussoren; bpo-4865 [https://bugs.python.org/issue?@action=redirect&bpo=4865].)

在 2.7.13 版的變更: As of 2.7.13, this change was removed. /Library/Python/2.7/site-packages, the site-packages directory used by the Apple-supplied system Python 2.7 is no longer appended to sys.path for user-installed Pythons such as from the python.org installers. As of macOS 10.12, Apple changed how the system site-packages directory is configured, which could cause installation of pip components, like setuptools, to fail. Packages installed for the system Python will no longer be shared with user-installed Pythons. (bpo-28440 [https://bugs.python.org/issue?@action=redirect&bpo=28440])

Port-Specific Changes: FreeBSD

FreeBSD 7.1's SO_SETFIB constant, used with the socket() methods getsockopt()/setsockopt() to select an alternate routing table, is now available in the socket module. (Added by Kyle VanderBeek; bpo-8235 [https://bugs.python.org/issue?@action=redirect&bpo=8235].)

Other Changes and Fixes

Two benchmark scripts, iobench and ccbench, were added to the Tools directory. iobench measures the speed of the built-in file I/O objects returned by open() while performing various operations, and ccbench is a concurrency benchmark that tries to measure computing throughput, thread switching latency, and IO processing bandwidth when performing several tasks using a varying number of threads.

The Tools/i18n/msgfmt.py script now understands plural forms in .po files. (Fixed by Martin von Löwis; bpo-5464 [https://bugs.python.org/issue?@action=redirect&bpo=5464].)

When importing a module from a .pyc or .pyo file with an existing .py counterpart, the co_filename attributes of the resulting code objects are overwritten when the original filename is obsolete. This can happen if the file has been renamed, moved, or is accessed through different paths. (Patch by Ziga Seilnacht and Jean-Paul Calderone; bpo-1180193 [https://bugs.python.org/issue?@action=redirect&bpo=1180193].)

The regrtest.py script now takes a --randseed= switch that takes an integer that will be used as the random seed for the -r option that executes tests in random order. The -r option also reports the seed that was used (Added by Collin Winter.)

Another regrtest.py switch is -j, which takes an integer specifying how many tests run in parallel. This allows reducing the total runtime on multi-core machines. This option is compatible with several other options, including the -R switch which is known to produce long runtimes. (Added by Antoine Pitrou, bpo-6152 [https://bugs.python.org/issue?@action=redirect&bpo=6152].) This can also be used with a new -F switch that runs selected tests in a loop until they fail. (Added by Antoine Pitrou; bpo-7312 [https://bugs.python.org/issue?@action=redirect&bpo=7312].)

When executed as a script, the py_compile.py module now accepts '-' as an argument, which will read standard input for the list of filenames to be compiled. (Contributed by Piotr Ożarowski; bpo-8233 [https://bugs.python.org/issue?@action=redirect&bpo=8233].)

移植至 Python 2.7

This section lists previously described changes and other bugfixes that may require changes to your code:

The range() function processes its arguments more consistently; it will now call __int__() on non-float, non-integer arguments that are supplied to it. (Fixed by Alexander Belopolsky; bpo-1533 [https://bugs.python.org/issue?@action=redirect&bpo=1533].)

The string format() method changed the default precision used for floating-point and complex numbers from 6 decimal places to 12, which matches the precision used by str(). (Changed by Eric Smith; bpo-5920 [https://bugs.python.org/issue?@action=redirect&bpo=5920].)

Because of an optimization for the with statement, the special methods __enter__() and __exit__() must belong to the object's type, and cannot be directly attached to the object's instance. This affects new-style classes (derived from object) and C extension types. (bpo-6101 [https://bugs.python.org/issue?@action=redirect&bpo=6101].)

Due to a bug in Python 2.6, the exc_value parameter to __exit__() methods was often the string representation of the exception, not an instance. This was fixed in 2.7, so exc_value will be an instance as expected. (Fixed by Florent Xicluna; bpo-7853 [https://bugs.python.org/issue?@action=redirect&bpo=7853].)

When a restricted set of attributes were set using __slots__, deleting an unset attribute would not raise AttributeError as you would expect. Fixed by Benjamin Peterson; bpo-7604 [https://bugs.python.org/issue?@action=redirect&bpo=7604].)

標準函式庫中：

Operations with datetime instances that resulted in a year falling outside the supported range didn't always raise OverflowError. Such errors are now checked more carefully and will now raise the exception. (Reported by Mark Leander, patch by Anand B. Pillai and Alexander Belopolsky; bpo-7150 [https://bugs.python.org/issue?@action=redirect&bpo=7150].)

When using Decimal instances with a string's format() method, the default alignment was previously left-alignment. This has been changed to right-alignment, which might change the output of your programs. (Changed by Mark Dickinson; bpo-6857 [https://bugs.python.org/issue?@action=redirect&bpo=6857].)

Comparisons involving a signaling NaN value (or sNAN) now signal InvalidOperation instead of silently returning a true or false value depending on the comparison operator. Quiet NaN values (or NaN) are now hashable. (Fixed by Mark Dickinson; bpo-7279 [https://bugs.python.org/issue?@action=redirect&bpo=7279].)

The xml.etree.ElementTree library no longer escapes ampersands and angle brackets when outputting an XML processing instruction (which looks like <?xml-stylesheet href="#style1"?>) or comment (which looks like <!-- comment -->). (Patch by Neil Muller; bpo-2746 [https://bugs.python.org/issue?@action=redirect&bpo=2746].)

The readline() method of StringIO objects now does nothing when a negative length is requested, as other file-like objects do. (bpo-7348 [https://bugs.python.org/issue?@action=redirect&bpo=7348]).

The syslog module will now use the value of sys.argv[0] as the identifier instead of the previous default value of 'python'. (Changed by Sean Reifschneider; bpo-8451 [https://bugs.python.org/issue?@action=redirect&bpo=8451].)

The tarfile module's default error handling has changed, to no longer suppress fatal errors. The default error level was previously 0, which meant that errors would only result in a message being written to the debug log, but because the debug log is not activated by default, these errors go unnoticed. The default error level is now 1, which raises an exception if there's an error. (Changed by Lars Gustäbel; bpo-7357 [https://bugs.python.org/issue?@action=redirect&bpo=7357].)

The urlparse module's urlsplit() now handles unknown URL schemes in a fashion compliant with RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html]: if the URL is of the form "<something>://...", the text before the :// is treated as the scheme, even if it's a made-up scheme that the module doesn't know about. This change may break code that worked around the old behaviour. For example, Python 2.6.4 or 2.5 will return the following:

>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', '', '//host/filename?query', '', '')

Python 2.7 (and Python 2.6.5) will return:

>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', 'host', '/filename?query', '', '')

(Python 2.7 actually produces slightly different output, since it returns a named tuple instead of a standard tuple.)

For C extensions:

C extensions that use integer format codes with the PyArg_Parse* family of functions will now raise a TypeError exception instead of triggering a DeprecationWarning (bpo-5080 [https://bugs.python.org/issue?@action=redirect&bpo=5080]).

Use the new PyOS_string_to_double() function instead of the old PyOS_ascii_strtod() and PyOS_ascii_atof() functions, which are now deprecated.

For applications that embed Python:

The PySys_SetArgvEx() function was added, letting applications close a security hole when the existing PySys_SetArgv() function was used. Check whether you're calling PySys_SetArgv() and carefully consider whether the application should be using PySys_SetArgvEx() with updatepath set to false.

New Features Added to Python 2.7 Maintenance Releases

New features may be added to Python 2.7 maintenance releases when the situation genuinely calls for it. Any such additions must go through the Python Enhancement Proposal process, and make a compelling case for why they can't be adequately addressed by either adding the new feature solely to Python 3, or else by publishing it on the Python Package Index.

In addition to the specific proposals listed below, there is a general exemption allowing new -3 warnings to be added in any Python 2.7 maintenance release.

偵錯模式下的兩個新環境變數

In debug mode, the [xxx refs] statistic is not written by default, the PYTHONSHOWREFCOUNT environment variable now must also be set. (Contributed by Victor Stinner; bpo-31733 [https://bugs.python.org/issue?@action=redirect&bpo=31733].)

When Python is compiled with COUNT_ALLOC defined, allocation counts are no longer dumped by default anymore: the PYTHONSHOWALLOCCOUNT environment variable must now also be set. Moreover, allocation counts are now dumped into stderr, rather than stdout. (Contributed by Victor Stinner; bpo-31692 [https://bugs.python.org/issue?@action=redirect&bpo=31692].)

在 2.7.15 版被加入.

PEP 434: IDLE Enhancement Exception for All Branches

PEP 434 [https://peps.python.org/pep-0434/] describes a general exemption for changes made to the IDLE development environment shipped along with Python. This exemption makes it possible for the IDLE developers to provide a more consistent user experience across all supported versions of Python 2 and 3.

For details of any IDLE changes, refer to the NEWS file for the specific release.

PEP 466: Network Security Enhancements for Python 2.7

PEP 466 [https://peps.python.org/pep-0466/] describes a number of network security enhancement proposals that have been approved for inclusion in Python 2.7 maintenance releases, with the first of those changes appearing in the Python 2.7.7 release.

Python 2.7.7 中新增的 PEP 466 [https://peps.python.org/pep-0466/] 相關功能：

hmac.compare_digest() was backported from Python 3 to make a timing attack resistant comparison operation available to Python 2 applications. (Contributed by Alex Gaynor; bpo-21306 [https://bugs.python.org/issue?@action=redirect&bpo=21306].)

OpenSSL 1.0.1g was upgraded in the official Windows installers published on python.org. (Contributed by Zachary Ware; bpo-21462 [https://bugs.python.org/issue?@action=redirect&bpo=21462].)

Python 2.7.8 中新增的 PEP 466 [https://peps.python.org/pep-0466/] 相關功能：

hashlib.pbkdf2_hmac() was backported from Python 3 to make a hashing algorithm suitable for secure password storage broadly available to Python 2 applications. (Contributed by Alex Gaynor; bpo-21304 [https://bugs.python.org/issue?@action=redirect&bpo=21304].)

OpenSSL 1.0.1h was upgraded for the official Windows installers published on python.org. (Contributed by Zachary Ware in bpo-21671 [https://bugs.python.org/issue?@action=redirect&bpo=21671] for CVE 2014-0224 [https://www.cve.org/CVERecord?id=CVE-2014-0224].)

Python 2.7.9 中新增的 PEP 466 [https://peps.python.org/pep-0466/] 相關功能：

Most of Python 3.4's ssl module was backported. This means ssl now supports Server Name Indication, TLS1.x settings, access to the platform certificate store, the SSLContext class, and other features. (Contributed by Alex Gaynor and David Reid; bpo-21308 [https://bugs.python.org/issue?@action=redirect&bpo=21308].)

Refer to the "Version added: 2.7.9" notes in the module documentation for specific details.

os.urandom() was changed to cache a file descriptor to /dev/urandom instead of reopening /dev/urandom on every call. (Contributed by Alex Gaynor; bpo-21305 [https://bugs.python.org/issue?@action=redirect&bpo=21305].)

hashlib.algorithms_guaranteed and hashlib.algorithms_available were backported from Python 3 to make it easier for Python 2 applications to select the strongest available hash algorithm. (Contributed by Alex Gaynor in bpo-21307 [https://bugs.python.org/issue?@action=redirect&bpo=21307])

PEP 477: Backport ensurepip (PEP 453) to Python 2.7

PEP 477 [https://peps.python.org/pep-0477/] approves the inclusion of the PEP 453 [https://peps.python.org/pep-0453/] ensurepip module and the improved documentation that was enabled by it in the Python 2.7 maintenance releases, appearing first in the Python 2.7.9 release.

Bootstrapping pip By Default

The new ensurepip module (defined in PEP 453 [https://peps.python.org/pep-0453/]) provides a standard cross-platform mechanism to bootstrap the pip installer into Python installations. The version of pip included with Python 2.7.9 is pip 1.5.6, and future 2.7.x maintenance releases will update the bundled version to the latest version of pip that is available at the time of creating the release candidate.

By default, the commands pip, pipX and pipX.Y will be installed on all platforms (where X.Y stands for the version of the Python installation), along with the pip Python package and its dependencies.

For CPython source builds on POSIX systems, the make install and make altinstall commands do not bootstrap pip by default. This behaviour can be controlled through configure options, and overridden through Makefile options.

On Windows and Mac OS X, the CPython installers now default to installing pip along with CPython itself (users may opt out of installing it during the installation process). Window users will need to opt in to the automatic PATH modifications to have pip available from the command line by default, otherwise it can still be accessed through the Python launcher for Windows as py -m pip.

As discussed in the PEP [https://peps.python.org/pep-0477/#disabling-ensurepip-by-downstream-distributors], platform packagers may choose not to install these commands by default, as long as, when invoked, they provide clear and simple directions on how to install them on that platform (usually using the system package manager).

文件更動

As part of this change, the 安裝 Python 模組 and 發布 Python 模組 sections of the documentation have been completely redesigned as short getting started and FAQ documents. Most packaging documentation has now been moved out to the Python Packaging Authority maintained Python Packaging User Guide [https://packaging.python.org] and the documentation of the individual projects.

However, as this migration is currently still incomplete, the legacy versions of those guides remaining available as 用 setuptools 建置 C 與 C++ 擴充套件 and 用 setuptools 建置 C 與 C++ 擴充套件.

也參考

PEP 453 [https://peps.python.org/pep-0453/] -- Explicit bootstrapping of pip in Python installations

PEP written by Donald Stufft and Nick Coghlan, implemented by Donald Stufft, Nick Coghlan, Martin von Löwis and Ned Deily.

PEP 476: Enabling certificate verification by default for stdlib http clients

PEP 476 [https://peps.python.org/pep-0476/] updated httplib and modules which use it, such as urllib2 and xmlrpclib, to now verify that the server presents a certificate which is signed by a Certificate Authority in the platform trust store and whose hostname matches the hostname being requested by default, significantly improving security for many applications. This change was made in the Python 2.7.9 release.

For applications which require the old previous behavior, they can pass an alternate context:

import urllib2
import ssl

# This disables all verification
context = ssl._create_unverified_context()

# This allows using a specific certificate for the host, which doesn't need
# to be in the trust store
context = ssl.create_default_context(cafile="/path/to/file.crt")

urllib2.urlopen("https://invalid-cert", context=context)

PEP 493: HTTPS verification migration tools for Python 2.7

PEP 493 [https://peps.python.org/pep-0493/] provides additional migration tools to support a more incremental infrastructure upgrade process for environments containing applications and services relying on the historically permissive processing of server certificates when establishing client HTTPS connections. These additions were made in the Python 2.7.12 release.

These tools are intended for use in cases where affected applications and services can't be modified to explicitly pass a more permissive SSL context when establishing the connection.

For applications and services which can't be modified at all, the new PYTHONHTTPSVERIFY environment variable may be set to 0 to revert an entire Python process back to the default permissive behaviour of Python 2.7.8 and earlier.

For cases where the connection establishment code can't be modified, but the overall application can be, the new ssl._https_verify_certificates() function can be used to adjust the default behaviour at runtime.

新增 make regen-all 建置目標

To simplify cross-compilation, and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available, the autotools-based build system no longer attempts to implicitly recompile generated files based on file modification times.

Instead, a new make regen-all command has been added to force regeneration of these files when desired (e.g. after an initial version of Python has already been built based on the pregenerated versions).

More selective regeneration targets are also defined - see Makefile.pre.in [https://github.com/python/cpython/tree/3.14/Makefile.pre.in] for details.

（由 Victor Stinner 於 bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404] 中貢獻。）

在 2.7.14 版被加入.

移除 make touch 建置目標

The make touch build target previously used to request implicit regeneration of generated files by updating their modification times has been removed.

已被新的 make regen-all 目標取代。

（由 Victor Stinner 於 bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404] 中貢獻。）

在 2.7.14 版的變更.

致謝

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Nick Coghlan, Philip Jenvey, Ryan Lovett, R. David Murray, Hugh Secker-Walker.

Python 2.6 有什麼新功能

作者:

A.M. Kuchling (amk at amk.ca)

本文介紹了已於 2008 年 10 月 1 日發布的 Python 2.6 有哪些新功能。發布時間表請見 PEP 361 [https://peps.python.org/pep-0361/]。

The major theme of Python 2.6 is preparing the migration path to Python 3.0, a major redesign of the language. Whenever possible, Python 2.6 incorporates new features and syntax from 3.0 while remaining compatible with existing code by not removing older features or syntax. When it's not possible to do that, Python 2.6 tries to do what it can, adding compatibility functions in a future_builtins module and a -3 switch to warn about usages that will become unsupported in 3.0.

Some significant new packages have been added to the standard library, such as the multiprocessing and json modules, but there aren't many new features that aren't related to Python 3.0 in some way.

Python 2.6 also sees a number of improvements and bugfixes throughout the source. A search through the change logs finds there were 259 patches applied and 612 bugs fixed between Python 2.5 and 2.6. Both figures are likely to be underestimates.

This article doesn't attempt to provide a complete specification of the new features, but instead provides a convenient overview. For full details, you should refer to the documentation for Python 2.6. If you want to understand the rationale for the design and implementation, refer to the PEP for a particular new feature. Whenever possible, "What's New in Python" links to the bug/patch item for each change.

Python 3.0

The development cycle for Python versions 2.6 and 3.0 was synchronized, with the alpha and beta releases for both versions being made on the same days. The development of 3.0 has influenced many features in 2.6.

Python 3.0 is a far-ranging redesign of Python that breaks compatibility with the 2.x series. This means that existing Python code will need some conversion in order to run on Python 3.0. However, not all the changes in 3.0 necessarily break compatibility. In cases where new features won't cause existing code to break, they've been backported to 2.6 and are described in this document in the appropriate place. Some of the 3.0-derived features are:

A __complex__() method for converting objects to a complex number.

Alternate syntax for catching exceptions: except TypeError as exc.

The addition of functools.reduce() as a synonym for the built-in reduce() function.

Python 3.0 adds several new built-in functions and changes the semantics of some existing builtins. Functions that are new in 3.0 such as bin() have simply been added to Python 2.6, but existing builtins haven't been changed; instead, the future_builtins module has versions with the new 3.0 semantics. Code written to be compatible with 3.0 can do from future_builtins import hex, map as necessary.

A new command-line switch, -3, enables warnings about features that will be removed in Python 3.0. You can run code with this switch to see how much work will be necessary to port code to 3.0. The value of this switch is available to Python code as the boolean variable sys.py3kwarning, and to C extension code as Py_Py3kWarningFlag.

也參考

The 3xxx series of PEPs, which contains proposals for Python 3.0. PEP 3000 [https://peps.python.org/pep-3000/] describes the development process for Python 3.0. Start with PEP 3100 [https://peps.python.org/pep-3100/] that describes the general goals for Python 3.0, and then explore the higher-numbered PEPs that propose specific features.

Changes to the Development Process

While 2.6 was being developed, the Python development process underwent two significant changes: we switched from SourceForge's issue tracker to a customized Roundup installation, and the documentation was converted from LaTeX to reStructuredText.

New Issue Tracker: Roundup

For a long time, the Python developers had been growing increasingly annoyed by SourceForge's bug tracker. SourceForge's hosted solution doesn't permit much customization; for example, it wasn't possible to customize the life cycle of issues.

The infrastructure committee of the Python Software Foundation therefore posted a call for issue trackers, asking volunteers to set up different products and import some of the bugs and patches from SourceForge. Four different trackers were examined: Jira [https://www.atlassian.com/software/jira/], Launchpad [https://launchpad.net/], Roundup [https://roundup.sourceforge.io/], and Trac [https://trac.edgewall.org/]. The committee eventually settled on Jira and Roundup as the two candidates. Jira is a commercial product that offers no-cost hosted instances to free-software projects; Roundup is an open-source project that requires volunteers to administer it and a server to host it.

After posting a call for volunteers, a new Roundup installation was set up at https://bugs.python.org. One installation of Roundup can host multiple trackers, and this server now also hosts issue trackers for Jython and for the Python web site. It will surely find other uses in the future. Where possible, this edition of "What's New in Python" links to the bug/patch item for each change.

Hosting of the Python bug tracker is kindly provided by Upfront Systems [https://upfrontsoftware.co.za] of Stellenbosch, South Africa. Martin von Löwis put a lot of effort into importing existing bugs and patches from SourceForge; his scripts for this import operation are at https://svn.python.org/view/tracker/importer/ and may be useful to other projects wishing to move from SourceForge to Roundup.

也參考

https://bugs.python.org

Python 問題追蹤系統。

https://bugs.jython.org:

Jython 問題追蹤系統。

https://roundup.sourceforge.io/

Roundup downloads and documentation.

https://svn.python.org/view/tracker/importer/

Martin von Löwis 的轉換腳本。

新文件格式：使用 Sphinx 的 reStructuredText

The Python documentation was written using LaTeX since the project started around 1989. In the 1980s and early 1990s, most documentation was printed out for later study, not viewed online. LaTeX was widely used because it provided attractive printed output while remaining straightforward to write once the basic rules of the markup were learned.

Today LaTeX is still used for writing publications destined for printing, but the landscape for programming tools has shifted. We no longer print out reams of documentation; instead, we browse through it online and HTML has become the most important format to support. Unfortunately, converting LaTeX to HTML is fairly complicated and Fred L. Drake Jr., the long-time Python documentation editor, spent a lot of time maintaining the conversion process. Occasionally people would suggest converting the documentation into SGML and later XML, but performing a good conversion is a major task and no one ever committed the time required to finish the job.

During the 2.6 development cycle, Georg Brandl put a lot of effort into building a new toolchain for processing the documentation. The resulting package is called Sphinx, and is available from https://www.sphinx-doc.org/.

Sphinx concentrates on HTML output, producing attractively styled and modern HTML; printed output is still supported through conversion to LaTeX. The input format is reStructuredText, a markup syntax supporting custom extensions and directives that is commonly used in the Python community.

Sphinx is a standalone package that can be used for writing, and almost two dozen other projects (listed on the Sphinx web site [https://www.sphinx-doc.org/en/master/examples.html]) have adopted Sphinx as their documentation tool.

也參考

Python 文件撰寫 [https://devguide.python.org/documenting/]

說明如何為 Python 撰寫文件。

Sphinx [https://www.sphinx-doc.org/]

Sphinx 工具鏈的文件和程式碼。

Docutils [https://docutils.sourceforge.io]

底層 reStructuredText 剖析器和工具集。

PEP 343：'with' 陳述式

The previous version, Python 2.5, added the 'with' statement as an optional feature, to be enabled by a from __future__ import with_statement directive. In 2.6 the statement no longer needs to be specially enabled; this means that with is now always a keyword. The rest of this section is a copy of the corresponding section from the "What's New in Python 2.5" document; if you're familiar with the 'with' statement from Python 2.5, you can skip this section.

The 'with' statement clarifies code that previously would use try...finally blocks to ensure that clean-up code is executed. In this section, I'll discuss the statement as it will commonly be used. In the next section, I'll examine the implementation details and show how to write objects for use with this statement.

The 'with' statement is a control-flow structure whose basic structure is:

with expression [as variable]:
    with-block

The expression is evaluated, and it should result in an object that supports the context management protocol (that is, has __enter__() and __exit__() methods).

The object's __enter__() is called before with-block is executed and therefore can run set-up code. It also may return a value that is bound to the name variable, if given. (Note carefully that variable is not assigned the result of expression.)

After execution of the with-block is finished, the object's __exit__() method is called, even if the block raised an exception, and can therefore run clean-up code.

Some standard Python objects now support the context management protocol and can be used with the 'with' statement. File objects are one example:

with open('/etc/passwd', 'r') as f:
    for line in f:
        print line
        ... 更多處理程式碼 ...

After this statement has executed, the file object in f will have been automatically closed, even if the for loop raised an exception part-way through the block.

備註

In this case, f is the same object created by open(), because __enter__() returns self.

The threading module's locks and condition variables also support the 'with' statement:

lock = threading.Lock()
with lock:
    # Critical section of code
    ...

The lock is acquired before the block is executed and always released once the block is complete.

The localcontext() function in the decimal module makes it easy to save and restore the current decimal context, which encapsulates the desired precision and rounding characteristics for computations:

from decimal import Decimal, Context, localcontext

# Displays with default precision of 28 digits
v = Decimal('578')
print v.sqrt()

with localcontext(Context(prec=16)):
    # All code in this block uses a precision of 16 digits.
    # The original context is restored on exiting the block.
    print v.sqrt()

Writing Context Managers

Under the hood, the 'with' statement is fairly complicated. Most people will only use 'with' in company with existing objects and don't need to know these details, so you can skip the rest of this section if you like. Authors of new objects will need to understand the details of the underlying implementation and should keep reading.

A high-level explanation of the context management protocol is:

The expression is evaluated and should result in an object called a "context manager". The context manager must have __enter__() and __exit__() methods.

The context manager's __enter__() method is called. The value returned is assigned to VAR. If no as VAR clause is present, the value is simply discarded.

BLOCK 中的程式碼會被執行。

If BLOCK raises an exception, the context manager's __exit__() method is called with three arguments, the exception details (type, value, traceback, the same values returned by sys.exc_info(), which can also be None if no exception occurred). The method's return value controls whether an exception is re-raised: any false value re-raises the exception, and True will result in suppressing it. You'll only rarely want to suppress the exception, because if you do the author of the code containing the 'with' statement will never realize anything went wrong.

If BLOCK didn't raise an exception, the __exit__() method is still called, but type, value, and traceback are all None.

Let's think through an example. I won't present detailed code but will only sketch the methods necessary for a database that supports transactions.

(For people unfamiliar with database terminology: a set of changes to the database are grouped into a transaction. Transactions can be either committed, meaning that all the changes are written into the database, or rolled back, meaning that the changes are all discarded and the database is unchanged. See any database textbook for more information.)

Let's assume there's an object representing a database connection. Our goal will be to let the user write code like this:

db_connection = DatabaseConnection()
with db_connection as cursor:
    cursor.execute('insert into ...')
    cursor.execute('delete from ...')
    # ... 更多操作 ...

The transaction should be committed if the code in the block runs flawlessly or rolled back if there's an exception. Here's the basic interface for DatabaseConnection that I'll assume:

class DatabaseConnection:
    # Database interface
    def cursor(self):
        "Returns a cursor object and starts a new transaction"
    def commit(self):
        "Commits current transaction"
    def rollback(self):
        "Rolls back current transaction"

The __enter__() method is pretty easy, having only to start a new transaction. For this application the resulting cursor object would be a useful result, so the method will return it. The user can then add as cursor to their 'with' statement to bind the cursor to a variable name.

class DatabaseConnection:
    ...
    def __enter__(self):
        # Code to start a new transaction
        cursor = self.cursor()
        return cursor

The __exit__() method is the most complicated because it's where most of the work has to be done. The method has to check if an exception occurred. If there was no exception, the transaction is committed. The transaction is rolled back if there was an exception.

In the code below, execution will just fall off the end of the function, returning the default value of None. None is false, so the exception will be re-raised automatically. If you wished, you could be more explicit and add a return statement at the marked location.

class DatabaseConnection:
    ...
    def __exit__(self, type, value, tb):
        if tb is None:
            # No exception, so commit
            self.commit()
        else:
            # Exception occurred, so rollback.
            self.rollback()
            # return False

contextlib 模組

The contextlib module provides some functions and a decorator that are useful when writing objects for use with the 'with' statement.

The decorator is called contextmanager(), and lets you write a single generator function instead of defining a new class. The generator should yield exactly one value. The code up to the yield will be executed as the __enter__() method, and the value yielded will be the method's return value that will get bound to the variable in the 'with' statement's as clause, if any. The code after the yield will be executed in the __exit__() method. Any exception raised in the block will be raised by the yield statement.

Using this decorator, our database example from the previous section could be written as:

from contextlib import contextmanager

@contextmanager
def db_transaction(connection):
    cursor = connection.cursor()
    try:
        yield cursor
    except:
        connection.rollback()
        raise
    else:
        connection.commit()

db = DatabaseConnection()
with db_transaction(db) as cursor:
    ...

The contextlib module also has a nested(mgr1, mgr2, ...) function that combines a number of context managers so you don't need to write nested 'with' statements. In this example, the single 'with' statement both starts a database transaction and acquires a thread lock:

lock = threading.Lock()
with nested (db_transaction(db), lock) as (cursor, locked):
    ...

Finally, the closing() function returns its argument so that it can be bound to a variable, and calls the argument's .close() method at the end of the block.

import urllib, sys
from contextlib import closing

with closing(urllib.urlopen('http://www.yahoo.com')) as f:
    for line in f:
        sys.stdout.write(line)

也參考

PEP 343 [https://peps.python.org/pep-0343/] - "with" 陳述式

PEP written by Guido van Rossum and Nick Coghlan; implemented by Mike Bland, Guido van Rossum, and Neal Norwitz. The PEP shows the code generated for a 'with' statement, which can be helpful in learning how the statement works.

contextlib 模組的文件。

PEP 366: Explicit Relative Imports From a Main Module

Python's -m switch allows running a module as a script. When you ran a module that was located inside a package, relative imports didn't work correctly.

The fix for Python 2.6 adds a module.__package__ attribute. When this attribute is present, relative imports will be relative to the value of this attribute instead of the __name__ attribute.

PEP 302-style importers can then set __package__ as necessary. The runpy module that implements the -m switch now does this, so relative imports will now work correctly in scripts running from inside a package.

PEP 370: Per-user site-packages Directory

When you run Python, the module search path sys.path usually includes a directory whose path ends in "site-packages". This directory is intended to hold locally installed packages available to all users using a machine or a particular site installation.

Python 2.6 introduces a convention for user-specific site directories. The directory varies depending on the platform:

Unix 和 Mac OS X：~/.local/

Windows：%APPDATA%/Python

Within this directory, there will be version-specific subdirectories, such as lib/python2.6/site-packages on Unix/Mac OS and Python26/site-packages on Windows.

If you don't like the default directory, it can be overridden by an environment variable. PYTHONUSERBASE sets the root directory used for all Python versions supporting this feature. On Windows, the directory for application-specific data can be changed by setting the APPDATA environment variable. You can also modify the site.py file for your Python installation.

The feature can be disabled entirely by running Python with the -s option or setting the PYTHONNOUSERSITE environment variable.

也參考

PEP 370 [https://peps.python.org/pep-0370/] - Per-user site-packages Directory

由 Christian Heimes 撰寫 PEP 與實作。

PEP 371: The multiprocessing Package

The new multiprocessing package lets Python programs create new processes that will perform a computation and return a result to the parent. The parent and child processes can communicate using queues and pipes, synchronize their operations using locks and semaphores, and can share simple arrays of data.

The multiprocessing module started out as an exact emulation of the threading module using processes instead of threads. That goal was discarded along the path to Python 2.6, but the general approach of the module is still similar. The fundamental class is the Process, which is passed a callable object and a collection of arguments. The start() method sets the callable running in a subprocess, after which you can call the is_alive() method to check whether the subprocess is still running and the join() method to wait for the process to exit.

Here's a simple example where the subprocess will calculate a factorial. The function doing the calculation is written strangely so that it takes significantly longer when the input argument is a multiple of 4.

import time
from multiprocessing import Process, Queue

def factorial(queue, N):
    "計算階乘。"
    # 如果 N 是 4 的倍數，則此函式將花費更多時間。
    if (N % 4) == 0:
        time.sleep(.05 * N/4)

    # 計算結果
    fact = 1L
    for i in range(1, N+1):
        fact = fact * i

    # 將結果放進佇列裡
    queue.put(fact)

if __name__ == '__main__':
    queue = Queue()

    N = 5

    p = Process(target=factorial, args=(queue, N))
    p.start()
    p.join()

    result = queue.get()
    print 'Factorial', N, '=', result

A Queue is used to communicate the result of the factorial. The Queue object is stored in a global variable. The child process will use the value of the variable when the child was created; because it's a Queue, parent and child can use the object to communicate. (If the parent were to change the value of the global variable, the child's value would be unaffected, and vice versa.)

Two other classes, Pool and Manager, provide higher-level interfaces. Pool will create a fixed number of worker processes, and requests can then be distributed to the workers by calling apply() or apply_async() to add a single request, and map() or map_async() to add a number of requests. The following code uses a Pool to spread requests across 5 worker processes and retrieve a list of results:

from multiprocessing import Pool

def factorial(N, dictionary):
    "計算階乘。"
    ...
p = Pool(5)
result = p.map(factorial, range(1, 1000, 10))
for v in result:
    print v

This produces the following output:

1
39916800
51090942171709440000
8222838654177922817725562880000000
33452526613163807108170062053440751665152000000000
...

The other high-level interface, the Manager class, creates a separate server process that can hold master copies of Python data structures. Other processes can then access and modify these data structures using proxy objects. The following example creates a shared dictionary by calling the dict() method; the worker processes then insert values into the dictionary. (Locking is not done for you automatically, which doesn't matter in this example. Manager's methods also include Lock(), RLock(), and Semaphore() to create shared locks.)

import time
from multiprocessing import Pool, Manager

def factorial(N, dictionary):
    "Compute a factorial."
    # Calculate the result
    fact = 1L
    for i in range(1, N+1):
        fact = fact * i

    # Store result in dictionary
    dictionary[N] = fact

if __name__ == '__main__':
    p = Pool(5)
    mgr = Manager()
    d = mgr.dict()         # Create shared dictionary

    # Run tasks using the pool
    for N in range(1, 1000, 10):
        p.apply_async(factorial, (N, d))

    # Mark pool as closed -- no more tasks can be added.
    p.close()

    # Wait for tasks to exit
    p.join()

    # Output results
    for k, v in sorted(d.items()):
        print k, v

This will produce the output:

1 1
11 39916800
21 51090942171709440000
31 8222838654177922817725562880000000
41 33452526613163807108170062053440751665152000000000
51 15511187532873822802242430164693032110632597200169861120000...

也參考

multiprocessing 模組的文件。

PEP 371 [https://peps.python.org/pep-0371/] - Addition of the multiprocessing package

PEP written by Jesse Noller and Richard Oudkerk; implemented by Richard Oudkerk and Jesse Noller.

PEP 3101: Advanced String Formatting

In Python 3.0, the % operator is supplemented by a more powerful string formatting method, format(). Support for the str.format() method has been backported to Python 2.6.

In 2.6, both 8-bit and Unicode strings have a .format() method that treats the string as a template and takes the arguments to be formatted. The formatting template uses curly brackets ({, }) as special characters:

>>> # Substitute positional argument 0 into the string.
>>> "User ID: {0}".format("root")
'User ID: root'
>>> # Use the named keyword arguments
>>> "User ID: {uid}   Last seen: {last_login}".format(
...    uid="root",
...    last_login = "5 Mar 2008 07:20")
'User ID: root   Last seen: 5 Mar 2008 07:20'

Curly brackets can be escaped by doubling them:

>>> "Empty dict: {{}}".format()
"Empty dict: {}"

Field names can be integers indicating positional arguments, such as {0}, {1}, etc. or names of keyword arguments. You can also supply compound field names that read attributes or access dictionary keys:

>>> import sys
>>> print 'Platform: {0.platform}\nPython version: {0.version}'.format(sys)
Platform: darwin
Python version: 2.6a1+ (trunk:61261M, Mar  5 2008, 20:29:41)
[GCC 4.0.1 (Apple Computer, Inc. build 5367)]'

>>> import mimetypes
>>> 'Content-type: {0[.mp4]}'.format(mimetypes.types_map)
'Content-type: video/mp4'

Note that when using dictionary-style notation such as [.mp4], you don't need to put any quotation marks around the string; it will look up the value using .mp4 as the key. Strings beginning with a number will be converted to an integer. You can't write more complicated expressions inside a format string.

So far we've shown how to specify which field to substitute into the resulting string. The precise formatting used is also controllable by adding a colon followed by a format specifier. For example:

>>> # Field 0: left justify, pad to 15 characters
>>> # Field 1: right justify, pad to 6 characters
>>> fmt = '{0:15} ${1:>6}'
>>> fmt.format('Registration', 35)
'Registration    $    35'
>>> fmt.format('Tutorial', 50)
'Tutorial        $    50'
>>> fmt.format('Banquet', 125)
'Banquet         $   125'

Format specifiers can reference other fields through nesting:

>>> fmt = '{0:{1}}'
>>> width = 15
>>> fmt.format('Invoice #1234', width)
'Invoice #1234  '
>>> width = 35
>>> fmt.format('Invoice #1234', width)
'Invoice #1234                      '

The alignment of a field within the desired width can be specified:

字元

效果

< (default)

Left-align

>

Right-align

^

Center

=

(For numeric types only) Pad after the sign.

Format specifiers can also include a presentation type, which controls how the value is formatted. For example, floating-point numbers can be formatted as a general number or in exponential notation:

>>> '{0:g}'.format(3.75)
'3.75'
>>> '{0:e}'.format(3.75)
'3.750000e+00'

A variety of presentation types are available. Consult the 2.6 documentation for a complete list; here's a sample:

b

Binary. Outputs the number in base 2.

c

Character. Converts the integer to the corresponding Unicode character before printing.

d

Decimal Integer. Outputs the number in base 10.

o

Octal format. Outputs the number in base 8.

x

Hex format. Outputs the number in base 16, using lower-case letters for the digits above 9.

e

Exponent notation. Prints the number in scientific notation using the letter 'e' to indicate the exponent.

g

General format. This prints the number as a fixed-point number, unless the number is too large, in which case it switches to 'e' exponent notation.

n

Number. This is the same as 'g' (for floats) or 'd' (for integers), except that it uses the current locale setting to insert the appropriate number separator characters.

%

Percentage. Multiplies the number by 100 and displays in fixed ('f') format, followed by a percent sign.

Classes and types can define a __format__() method to control how they're formatted. It receives a single argument, the format specifier:

def __format__(self, format_spec):
    if isinstance(format_spec, unicode):
        return unicode(str(self))
    else:
        return str(self)

There's also a format() builtin that will format a single value. It calls the type's __format__() method with the provided specifier:

>>> format(75.6564, '.2f')
'75.66'

也參考

格式化文字語法

The reference documentation for format fields.

PEP 3101 [https://peps.python.org/pep-3101/] - Advanced String Formatting

由 Talin 撰寫 PEP、由 Eric Smith 實作。

PEP 3105: print As a Function

The print statement becomes the print() function in Python 3.0. Making print() a function makes it possible to replace the function by doing def print(...) or importing a new function from somewhere else.

Python 2.6 has a __future__ import that removes print as language syntax, letting you use the functional form instead. For example:

>>> from __future__ import print_function
>>> print('# of entries', len(dictionary), file=sys.stderr)

The signature of the new function is:

def print(*args, sep=' ', end='\n', file=None)

The parameters are:

args: positional arguments whose values will be printed out.

sep: the separator, which will be printed between arguments.

end: the ending text, which will be printed after all of the arguments have been output.

file: the file object to which the output will be sent.

也參考

PEP 3105 [https://peps.python.org/pep-3105/] - 將 print 變成函式

由 Georg Brandl 撰寫 PEP。

PEP 3110: Exception-Handling Changes

One error that Python programmers occasionally make is writing the following code:

try:
    ...
except TypeError, ValueError:  # 錯誤！
    ...

The author is probably trying to catch both TypeError and ValueError exceptions, but this code actually does something different: it will catch TypeError and bind the resulting exception object to the local name "ValueError". The ValueError exception will not be caught at all. The correct code specifies a tuple of exceptions:

try:
    ...
except (TypeError, ValueError):
    ...

This error happens because the use of the comma here is ambiguous: does it indicate two different nodes in the parse tree, or a single node that's a tuple?

Python 3.0 makes this unambiguous by replacing the comma with the word "as". To catch an exception and store the exception object in the variable exc, you must write:

try:
    ...
except TypeError as exc:
    ...

Python 3.0 will only support the use of "as", and therefore interprets the first example as catching two different exceptions. Python 2.6 supports both the comma and "as", so existing code will continue to work. We therefore suggest using "as" when writing new Python code that will only be executed with 2.6.

也參考

PEP 3110 [https://peps.python.org/pep-3110/] - Catching Exceptions in Python 3000

由 Collin Winter 撰寫 PEP 與實作。

PEP 3112: Byte Literals

Python 3.0 adopts Unicode as the language's fundamental string type and denotes 8-bit literals differently, either as b'string' or using a bytes constructor. For future compatibility, Python 2.6 adds bytes as a synonym for the str type, and it also supports the b'' notation.

The 2.6 str differs from 3.0's bytes type in various ways; most notably, the constructor is completely different. In 3.0, bytes([65, 66, 67]) is 3 elements long, containing the bytes representing ABC; in 2.6, bytes([65, 66, 67]) returns the 12-byte string representing the str() of the list.

The primary use of bytes in 2.6 will be to write tests of object type such as isinstance(x, bytes). This will help the 2to3 converter, which can't tell whether 2.x code intends strings to contain either characters or 8-bit bytes; you can now use either bytes or str to represent your intention exactly, and the resulting code will also be correct in Python 3.0.

There's also a __future__ import that causes all string literals to become Unicode strings. This means that \u escape sequences can be used to include Unicode characters:

from __future__ import unicode_literals

s = ('\u751f\u3080\u304e\u3000\u751f\u3054'
     '\u3081\u3000\u751f\u305f\u307e\u3054')

print len(s)               # 12 個 Unicode 字元

At the C level, Python 3.0 will rename the existing 8-bit string type, called PyStringObject in Python 2.x, to PyBytesObject. Python 2.6 uses #define to support using the names PyBytesObject(), PyBytes_Check(), PyBytes_FromStringAndSize(), and all the other functions and macros used with strings.

Instances of the bytes type are immutable just as strings are. A new bytearray type stores a mutable sequence of bytes:

>>> bytearray([65, 66, 67])
bytearray(b'ABC')
>>> b = bytearray(u'\u21ef\u3244', 'utf-8')
>>> b
bytearray(b'\xe2\x87\xaf\xe3\x89\x84')
>>> b[0] = '\xe3'
>>> b
bytearray(b'\xe3\x87\xaf\xe3\x89\x84')
>>> unicode(str(b), 'utf-8')
u'\u31ef \u3244'

Byte arrays support most of the methods of string types, such as startswith()/endswith(), find()/rfind(), and some of the methods of lists, such as append(), pop(), and reverse().

>>> b = bytearray('ABC')
>>> b.append('d')
>>> b.append(ord('e'))
>>> b
bytearray(b'ABCde')

There's also a corresponding C API, with PyByteArray_FromObject(), PyByteArray_FromStringAndSize(), and various other functions.

也參考

PEP 3112 [https://peps.python.org/pep-3112/] - Bytes literals in Python 3000

PEP written by Jason Orendorff; backported to 2.6 by Christian Heimes.

PEP 3116：新 I/O 函式庫

Python's built-in file objects support a number of methods, but file-like objects don't necessarily support all of them. Objects that imitate files usually support read() and write(), but they may not support readline(), for example. Python 3.0 introduces a layered I/O library in the io module that separates buffering and text-handling features from the fundamental read and write operations.

There are three levels of abstract base classes provided by the io module:

RawIOBase defines raw I/O operations: read(), readinto(), write(), seek(), tell(), truncate(), and close(). Most of the methods of this class will often map to a single system call. There are also readable(), writable(), and seekable() methods for determining what operations a given object will allow.

Python 3.0 has concrete implementations of this class for files and sockets, but Python 2.6 hasn't restructured its file and socket objects in this way.

BufferedIOBase is an abstract base class that buffers data in memory to reduce the number of system calls used, making I/O processing more efficient. It supports all of the methods of RawIOBase, and adds a raw attribute holding the underlying raw object.

There are five concrete classes implementing this ABC. BufferedWriter and BufferedReader are for objects that support write-only or read-only usage that have a seek() method for random access. BufferedRandom objects support read and write access upon the same underlying stream, and BufferedRWPair is for objects such as TTYs that have both read and write operations acting upon unconnected streams of data. The BytesIO class supports reading, writing, and seeking over an in-memory buffer.

TextIOBase: Provides functions for reading and writing strings (remember, strings will be Unicode in Python 3.0), and supporting universal newlines. TextIOBase defines the readline() method and supports iteration upon objects.

There are two concrete implementations. TextIOWrapper wraps a buffered I/O object, supporting all of the methods for text I/O and adding a buffer attribute for access to the underlying object. StringIO simply buffers everything in memory without ever writing anything to disk.

(In Python 2.6, io.StringIO is implemented in pure Python, so it's pretty slow. You should therefore stick with the existing StringIO module or cStringIO for now. At some point Python 3.0's io module will be rewritten into C for speed, and perhaps the C implementation will be backported to the 2.x releases.)

In Python 2.6, the underlying implementations haven't been restructured to build on top of the io module's classes. The module is being provided to make it easier to write code that's forward-compatible with 3.0, and to save developers the effort of writing their own implementations of buffering and text I/O.

也參考

PEP 3116 [https://peps.python.org/pep-3116/] - New I/O

PEP written by Daniel Stutzbach, Mike Verdone, and Guido van Rossum. Code by Guido van Rossum, Georg Brandl, Walter Doerwald, Jeremy Hylton, Martin von Löwis, Tony Lownds, and others.

PEP 3118：修訂緩衝協定

The buffer protocol is a C-level API that lets Python types exchange pointers into their internal representations. A memory-mapped file can be viewed as a buffer of characters, for example, and this lets another module such as re treat memory-mapped files as a string of characters to be searched.

The primary users of the buffer protocol are numeric-processing packages such as NumPy, which expose the internal representation of arrays so that callers can write data directly into an array instead of going through a slower API. This PEP updates the buffer protocol in light of experience from NumPy development, adding a number of new features such as indicating the shape of an array or locking a memory region.

The most important new C API function is PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags), which takes an object and a set of flags, and fills in the Py_buffer structure with information about the object's memory representation. Objects can use this operation to lock memory in place while an external caller could be modifying the contents, so there's a corresponding PyBuffer_Release(Py_buffer *view) to indicate that the external caller is done.

The flags argument to PyObject_GetBuffer() specifies constraints upon the memory returned. Some examples are:

PyBUF_WRITABLE indicates that the memory must be writable.

PyBUF_LOCK requests a read-only or exclusive lock on the memory.

PyBUF_C_CONTIGUOUS and PyBUF_F_CONTIGUOUS requests a C-contiguous (last dimension varies the fastest) or Fortran-contiguous (first dimension varies the fastest) array layout.

Two new argument codes for PyArg_ParseTuple(), s* and z*, return locked buffer objects for a parameter.

也參考

PEP 3118 [https://peps.python.org/pep-3118/] - Revising the buffer protocol

PEP written by Travis Oliphant and Carl Banks; implemented by Travis Oliphant.

PEP 3119: Abstract Base Classes

Some object-oriented languages such as Java support interfaces, declaring that a class has a given set of methods or supports a given access protocol. Abstract Base Classes (or ABCs) are an equivalent feature for Python. The ABC support consists of an abc module containing a metaclass called ABCMeta, special handling of this metaclass by the isinstance() and issubclass() builtins, and a collection of basic ABCs that the Python developers think will be widely useful. Future versions of Python will probably add more ABCs.

Let's say you have a particular class and wish to know whether it supports dictionary-style access. The phrase "dictionary-style" is vague, however. It probably means that accessing items with obj[1] works. Does it imply that setting items with obj[2] = value works? Or that the object will have keys(), values(), and items() methods? What about the iterative variants such as iterkeys()? copy`and :meth:()!update`? Iterating over the object with iter()?

The Python 2.6 collections module includes a number of different ABCs that represent these distinctions. Iterable indicates that a class defines __iter__(), and Container means the class defines a __contains__() method and therefore supports x in y expressions. The basic dictionary interface of getting items, setting items, and keys(), values(), and items(), is defined by the MutableMapping ABC.

You can derive your own classes from a particular ABC to indicate they support that ABC's interface:

import collections

class Storage(collections.MutableMapping):
    ...

Alternatively, you could write the class without deriving from the desired ABC and instead register the class by calling the ABC's register() method:

import collections

class Storage:
    ...

collections.MutableMapping.register(Storage)

For classes that you write, deriving from the ABC is probably clearer. The register() method is useful when you've written a new ABC that can describe an existing type or class, or if you want to declare that some third-party class implements an ABC. For example, if you defined a PrintableType ABC, it's legal to do:

# 註冊 Python 的型別
PrintableType.register(int)
PrintableType.register(float)
PrintableType.register(str)

Classes should obey the semantics specified by an ABC, but Python can't check this; it's up to the class author to understand the ABC's requirements and to implement the code accordingly.

To check whether an object supports a particular interface, you can now write:

def func(d):
    if not isinstance(d, collections.MutableMapping):
        raise ValueError("Mapping object expected, not %r" % d)

Don't feel that you must now begin writing lots of checks as in the above example. Python has a strong tradition of duck-typing, where explicit type-checking is never done and code simply calls methods on an object, trusting that those methods will be there and raising an exception if they aren't. Be judicious in checking for ABCs and only do it where it's absolutely necessary.

You can write your own ABCs by using abc.ABCMeta as the metaclass in a class definition:

from abc import ABCMeta, abstractmethod

class Drawable():
    __metaclass__ = ABCMeta

    @abstractmethod
    def draw(self, x, y, scale=1.0):
        pass

    def draw_doubled(self, x, y):
        self.draw(x, y, scale=2.0)

class Square(Drawable):
    def draw(self, x, y, scale):
        ...

In the Drawable ABC above, the draw_doubled() method renders the object at twice its size and can be implemented in terms of other methods described in Drawable. Classes implementing this ABC therefore don't need to provide their own implementation of draw_doubled(), though they can do so. An implementation of draw() is necessary, though; the ABC can't provide a useful generic implementation.

You can apply the @~abc.abstractmethod decorator to methods such as draw() that must be implemented; Python will then raise an exception for classes that don't define the method. Note that the exception is only raised when you actually try to create an instance of a subclass lacking the method:

>>> class Circle(Drawable):
...     pass
...
>>> c = Circle()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class Circle with abstract methods draw
>>>

Abstract data attributes can be declared using the @abstractproperty decorator:

from abc import abstractproperty
...

@abstractproperty
def readonly(self):
   return self._x

Subclasses must then define a readonly property.

也參考

PEP 3119 [https://peps.python.org/pep-3119/] - Introducing Abstract Base Classes

PEP written by Guido van Rossum and Talin. Implemented by Guido van Rossum. Backported to 2.6 by Benjamin Aranguren, with Alex Martelli.

PEP 3127: Integer Literal Support and Syntax

Python 3.0 changes the syntax for octal (base-8) integer literals, prefixing them with "0o" or "0O" instead of a leading zero, and adds support for binary (base-2) integer literals, signalled by a "0b" or "0B" prefix.

Python 2.6 doesn't drop support for a leading 0 signalling an octal number, but it does add support for "0o" and "0b":

>>> 0o21, 2*8 + 1
(17, 17)
>>> 0b101111
47

The oct() builtin still returns numbers prefixed with a leading zero, and a new bin() builtin returns the binary representation for a number:

>>> oct(42)
'052'
>>> future_builtins.oct(42)
'0o52'
>>> bin(173)
'0b10101101'

The int() and long() builtins will now accept the "0o" and "0b" prefixes when base-8 or base-2 are requested, or when the base argument is zero (signalling that the base used should be determined from the string):

>>> int ('0o52', 0)
42
>>> int('1101', 2)
13
>>> int('0b1101', 2)
13
>>> int('0b1101', 0)
13

也參考

PEP 3127 [https://peps.python.org/pep-3127/] - Integer Literal Support and Syntax

PEP written by Patrick Maupin; backported to 2.6 by Eric Smith.

PEP 3129: Class Decorators

Decorators have been extended from functions to classes. It's now legal to write:

@foo
@bar
class A:
  pass

這等價於：

class A:
  pass

A = foo(bar(A))

也參考

PEP 3129 [https://peps.python.org/pep-3129/] - 類別裝飾器

由 Collin Winter 撰寫 PEP。

PEP 3141: A Type Hierarchy for Numbers

Python 3.0 adds several abstract base classes for numeric types inspired by Scheme's numeric tower. These classes were backported to 2.6 as the numbers module.

The most general ABC is Number. It defines no operations at all, and only exists to allow checking if an object is a number by doing isinstance(obj, Number).

Complex is a subclass of Number. Complex numbers can undergo the basic operations of addition, subtraction, multiplication, division, and exponentiation, and you can retrieve the real and imaginary parts and obtain a number's conjugate. Python's built-in complex type is an implementation of Complex.

Real further derives from Complex, and adds operations that only work on real numbers: floor(), trunc(), rounding, taking the remainder mod N, floor division, and comparisons.

Rational numbers derive from Real, have numerator and denominator properties, and can be converted to floats. Python 2.6 adds a simple rational-number class, Fraction, in the fractions module. (It's called Fraction instead of Rational to avoid a name clash with numbers.Rational.)

Integral numbers derive from Rational, and can be shifted left and right with << and >>, combined using bitwise operations such as & and |, and can be used as array indexes and slice boundaries.

In Python 3.0, the PEP slightly redefines the existing builtins round(), math.floor(), math.ceil(), and adds a new one, math.trunc(), that's been backported to Python 2.6. math.trunc() rounds toward zero, returning the closest Integral that's between the function's argument and zero.

也參考

PEP 3141 [https://peps.python.org/pep-3141/] - A Type Hierarchy for Numbers

由 Jeffrey Yasskin 撰寫 PEP。

Scheme's numerical tower [https://www.gnu.org/software/guile/manual/html_node/Numerical-Tower.html#Numerical-Tower], from the Guile manual.

Scheme's number datatypes [https://conservatory.scheme.org/schemers/Documents/Standards/R5RS/HTML/r5rs-Z-H-9.html#%_sec_6.2] from the R5RS Scheme specification.

The fractions Module

To fill out the hierarchy of numeric types, the fractions module provides a rational-number class. Rational numbers store their values as a numerator and denominator forming a fraction, and can exactly represent numbers such as 2/3 that floating-point numbers can only approximate.

The Fraction constructor takes two Integral values that will be the numerator and denominator of the resulting fraction.

>>> from fractions import Fraction
>>> a = Fraction(2, 3)
>>> b = Fraction(2, 5)
>>> float(a), float(b)
(0.66666666666666663, 0.40000000000000002)
>>> a+b
Fraction(16, 15)
>>> a/b
Fraction(5, 3)

For converting floating-point numbers to rationals, the float type now has an as_integer_ratio() method that returns the numerator and denominator for a fraction that evaluates to the same floating-point value:

>>> (2.5) .as_integer_ratio()
(5, 2)
>>> (3.1415) .as_integer_ratio()
(7074029114692207L, 2251799813685248L)
>>> (1./3) .as_integer_ratio()
(6004799503160661L, 18014398509481984L)

Note that values that can only be approximated by floating-point numbers, such as 1./3, are not simplified to the number being approximated; the fraction attempts to match the floating-point value exactly.

The fractions module is based upon an implementation by Sjoerd Mullender that was in Python's Demo/classes/ directory for a long time. This implementation was significantly updated by Jeffrey Yasskin.

其他語言更動

Some smaller changes made to the core Python language are:

Directories and zip archives containing a __main__.py file can now be executed directly by passing their name to the interpreter. The directory or zip archive is automatically inserted as the first entry in sys.path. (Suggestion and initial patch by Andy Chu, subsequently revised by Phillip J. Eby and Nick Coghlan; bpo-1739468 [https://bugs.python.org/issue?@action=redirect&bpo=1739468].)

The hasattr() function was catching and ignoring all errors, under the assumption that they meant a __getattr__() method was failing somehow and the return value of hasattr() would therefore be False. This logic shouldn't be applied to KeyboardInterrupt and SystemExit, however; Python 2.6 will no longer discard such exceptions when hasattr() encounters them. (Fixed by Benjamin Peterson; bpo-2196 [https://bugs.python.org/issue?@action=redirect&bpo=2196].)

When calling a function using the ** syntax to provide keyword arguments, you are no longer required to use a Python dictionary; any mapping will now work:

>>> def f(**kw):
...    print sorted(kw)
...
>>> ud=UserDict.UserDict()
>>> ud['a'] = 1
>>> ud['b'] = 'string'
>>> f(**ud)
['a', 'b']

（由 Alexander Belopolsky 所貢獻；bpo-1686487 [https://bugs.python.org/issue?@action=redirect&bpo=1686487]。）

It's also become legal to provide keyword arguments after a *args argument to a function call.

>>> def f(*args, **kw):
...     print args, kw
...
>>> f(1,2,3, *(4,5,6), keyword=13)
(1, 2, 3, 4, 5, 6) {'keyword': 13}

Previously this would have been a syntax error. (Contributed by Amaury Forgeot d'Arc; bpo-3473 [https://bugs.python.org/issue?@action=redirect&bpo=3473].)

A new builtin, next(iterator, [default]) returns the next item from the specified iterator. If the default argument is supplied, it will be returned if iterator has been exhausted; otherwise, the StopIteration exception will be raised. (Backported in bpo-2719 [https://bugs.python.org/issue?@action=redirect&bpo=2719].)

Tuples now have index() and count() methods matching the list type's index() and count() methods:

>>> t = (0,1,2,3,4,0,1,2)
>>> t.index(3)
3
>>> t.count(0)
2

（由 Raymond Hettinger 所貢獻。）

The built-in types now have improved support for extended slicing syntax, accepting various combinations of (start, stop, step). Previously, the support was partial and certain corner cases wouldn't work. (Implemented by Thomas Wouters.)

Properties now have three attributes, getter, setter and deleter, that are decorators providing useful shortcuts for adding a getter, setter or deleter function to an existing property. You would use them like this:

class C(object):
    @property
    def x(self):
        return self._x

    @x.setter
    def x(self, value):
        self._x = value

    @x.deleter
    def x(self):
        del self._x

class D(C):
    @C.x.getter
    def x(self):
        return self._x * 2

    @x.setter
    def x(self, value):
        self._x = value / 2

Several methods of the built-in set types now accept multiple iterables: intersection(), intersection_update(), union(), update(), difference() and difference_update().

>>> s=set('1234567890')
>>> s.intersection('abc123', 'cdf246')  # 所有輸入的交集
set(['2'])
>>> s.difference('246', '789')
set(['1', '0', '3', '5'])

（由 Raymond Hettinger 所貢獻。）

Many floating-point features were added. The float() function will now turn the string nan into an IEEE 754 Not A Number value, and +inf and -inf into positive or negative infinity. This works on any platform with IEEE 754 semantics. (Contributed by Christian Heimes; bpo-1635 [https://bugs.python.org/issue?@action=redirect&bpo=1635].)

Other functions in the math module, isinf() and isnan(), return true if their floating-point argument is infinite or Not A Number. (bpo-1640 [https://bugs.python.org/issue?@action=redirect&bpo=1640])

Conversion functions were added to convert floating-point numbers into hexadecimal strings (bpo-3008 [https://bugs.python.org/issue?@action=redirect&bpo=3008]). These functions convert floats to and from a string representation without introducing rounding errors from the conversion between decimal and binary. Floats have a hex() method that returns a string representation, and the float.fromhex() method converts a string back into a number:

>>> a = 3.75
>>> a.hex()
'0x1.e000000000000p+1'
>>> float.fromhex('0x1.e000000000000p+1')
3.75
>>> b=1./3
>>> b.hex()
'0x1.5555555555555p-2'

A numerical nicety: when creating a complex number from two floats on systems that support signed zeros (-0 and +0), the complex() constructor will now preserve the sign of the zero. (Fixed by Mark T. Dickinson; bpo-1507 [https://bugs.python.org/issue?@action=redirect&bpo=1507].)

Classes that inherit a __hash__() method from a parent class can set __hash__ = None to indicate that the class isn't hashable. This will make hash(obj) raise a TypeError and the class will not be indicated as implementing the Hashable ABC.

You should do this when you've defined a __cmp__() or __eq__() method that compares objects by their value rather than by identity. All objects have a default hash method that uses id(obj) as the hash value. There's no tidy way to remove the __hash__() method inherited from a parent class, so assigning None was implemented as an override. At the C level, extensions can set tp_hash to PyObject_HashNotImplemented(). (Fixed by Nick Coghlan and Amaury Forgeot d'Arc; bpo-2235 [https://bugs.python.org/issue?@action=redirect&bpo=2235].)

The GeneratorExit exception now subclasses BaseException instead of Exception. This means that an exception handler that does except Exception: will not inadvertently catch GeneratorExit. (Contributed by Chad Austin; bpo-1537 [https://bugs.python.org/issue?@action=redirect&bpo=1537].)

Generator objects now have a gi_code attribute that refers to the original code object backing the generator. (Contributed by Collin Winter; bpo-1473257 [https://bugs.python.org/issue?@action=redirect&bpo=1473257].)

The compile() built-in function now accepts keyword arguments as well as positional parameters. (Contributed by Thomas Wouters; bpo-1444529 [https://bugs.python.org/issue?@action=redirect&bpo=1444529].)

The complex() constructor now accepts strings containing parenthesized complex numbers, meaning that complex(repr(cplx)) will now round-trip values. For example, complex('(3+4j)') now returns the value (3+4j). (bpo-1491866 [https://bugs.python.org/issue?@action=redirect&bpo=1491866])

The string translate() method now accepts None as the translation table parameter, which is treated as the identity transformation. This makes it easier to carry out operations that only delete characters. (Contributed by Bengt Richter and implemented by Raymond Hettinger; bpo-1193128 [https://bugs.python.org/issue?@action=redirect&bpo=1193128].)

The built-in dir() function now checks for a __dir__() method on the objects it receives. This method must return a list of strings containing the names of valid attributes for the object, and lets the object control the value that dir() produces. Objects that have __getattr__() or __getattribute__() methods can use this to advertise pseudo-attributes they will honor. (bpo-1591665 [https://bugs.python.org/issue?@action=redirect&bpo=1591665])

Instance method objects have new attributes for the object and function comprising the method; the new synonym for im_self is __self__, and im_func is also available as __func__. The old names are still supported in Python 2.6, but are gone in 3.0.

An obscure change: when you use the locals() function inside a class statement, the resulting dictionary no longer returns free variables. (Free variables, in this case, are variables referenced in the class statement that aren't attributes of the class.)

最佳化

The warnings module has been rewritten in C. This makes it possible to invoke warnings from the parser, and may also make the interpreter's startup faster. (Contributed by Neal Norwitz and Brett Cannon; bpo-1631171 [https://bugs.python.org/issue?@action=redirect&bpo=1631171].)

Type objects now have a cache of methods that can reduce the work required to find the correct method implementation for a particular class; once cached, the interpreter doesn't need to traverse base classes to figure out the right method to call. The cache is cleared if a base class or the class itself is modified, so the cache should remain correct even in the face of Python's dynamic nature. (Original optimization implemented by Armin Rigo, updated for Python 2.6 by Kevin Jacobs; bpo-1700288 [https://bugs.python.org/issue?@action=redirect&bpo=1700288].)

By default, this change is only applied to types that are included with the Python core. Extension modules may not necessarily be compatible with this cache, so they must explicitly add Py_TPFLAGS_HAVE_VERSION_TAG to the module's tp_flags field to enable the method cache. (To be compatible with the method cache, the extension module's code must not directly access and modify the tp_dict member of any of the types it implements. Most modules don't do this, but it's impossible for the Python interpreter to determine that. See bpo-1878 [https://bugs.python.org/issue?@action=redirect&bpo=1878] for some discussion.)

Function calls that use keyword arguments are significantly faster by doing a quick pointer comparison, usually saving the time of a full string comparison. (Contributed by Raymond Hettinger, after an initial implementation by Antoine Pitrou; bpo-1819 [https://bugs.python.org/issue?@action=redirect&bpo=1819].)

All of the functions in the struct module have been rewritten in C, thanks to work at the Need For Speed sprint. (Contributed by Raymond Hettinger.)

Some of the standard built-in types now set a bit in their type objects. This speeds up checking whether an object is a subclass of one of these types. (Contributed by Neal Norwitz.)

Unicode strings now use faster code for detecting whitespace and line breaks; this speeds up the split() method by about 25% and splitlines() by 35%. (Contributed by Antoine Pitrou.) Memory usage is reduced by using pymalloc for the Unicode string's data.

The with statement now stores the __exit__() method on the stack, producing a small speedup. (Implemented by Jeffrey Yasskin.)

To reduce memory usage, the garbage collector will now clear internal free lists when garbage-collecting the highest generation of objects. This may return memory to the operating system sooner.

Interpreter Changes

Two command-line options have been reserved for use by other Python implementations. The -J switch has been reserved for use by Jython for Jython-specific options, such as switches that are passed to the underlying JVM. -X has been reserved for options specific to a particular implementation of Python such as CPython, Jython, or IronPython. If either option is used with Python 2.6, the interpreter will report that the option isn't currently used.

Python can now be prevented from writing .pyc or .pyo files by supplying the -B switch to the Python interpreter, or by setting the PYTHONDONTWRITEBYTECODE environment variable before running the interpreter. This setting is available to Python programs as the sys.dont_write_bytecode variable, and Python code can change the value to modify the interpreter's behaviour. (Contributed by Neal Norwitz and Georg Brandl.)

The encoding used for standard input, output, and standard error can be specified by setting the PYTHONIOENCODING environment variable before running the interpreter. The value should be a string in the form <encoding> or <encoding>:<errorhandler>. The encoding part specifies the encoding's name, e.g. utf-8 or latin-1; the optional errorhandler part specifies what to do with characters that can't be handled by the encoding, and should be one of "error", "ignore", or "replace". (Contributed by Martin von Löwis.)

New and Improved Modules

As in every release, Python's standard library received a number of enhancements and bug fixes. Here's a partial list of the most notable changes, sorted alphabetically by module name. Consult the Misc/NEWS file in the source tree for a more complete list of changes, or look through the Subversion logs for all the details.

The asyncore and asynchat modules are being actively maintained again, and a number of patches and bugfixes were applied. (Maintained by Josiah Carlson; see bpo-1736190 [https://bugs.python.org/issue?@action=redirect&bpo=1736190] for one patch.)

The bsddb module also has a new maintainer, Jesús Cea Avión, and the package is now available as a standalone package. The web page for the package is www.jcea.es/programacion/pybsddb.htm [https://www.jcea.es/programacion/pybsddb.htm]. The plan is to remove the package from the standard library in Python 3.0, because its pace of releases is much more frequent than Python's.

The bsddb.dbshelve module now uses the highest pickling protocol available, instead of restricting itself to protocol 1. (Contributed by W. Barnes.)

The cgi module will now read variables from the query string of an HTTP POST request. This makes it possible to use form actions with URLs that include query strings such as "/cgi-bin/add.py?category=1". (Contributed by Alexandre Fiori and Nubis; bpo-1817 [https://bugs.python.org/issue?@action=redirect&bpo=1817].)

The parse_qs() and parse_qsl() functions have been relocated from the cgi module to the urlparse module. The versions still available in the cgi module will trigger PendingDeprecationWarning messages in 2.6 (bpo-600362 [https://bugs.python.org/issue?@action=redirect&bpo=600362]).

The cmath module underwent extensive revision, contributed by Mark Dickinson and Christian Heimes. Five new functions were added:

polar() converts a complex number to polar form, returning the modulus and argument of the complex number.

rect() does the opposite, turning a modulus, argument pair back into the corresponding complex number.

phase() returns the argument (also called the angle) of a complex number.

isnan() returns True if either the real or imaginary part of its argument is a NaN.

isinf() returns True if either the real or imaginary part of its argument is infinite.

The revisions also improved the numerical soundness of the cmath module. For all functions, the real and imaginary parts of the results are accurate to within a few units of least precision (ulps) whenever possible. See bpo-1381 [https://bugs.python.org/issue?@action=redirect&bpo=1381] for the details. The branch cuts for asinh(), atanh(): and atan() have also been corrected.

The tests for the module have been greatly expanded; nearly 2000 new test cases exercise the algebraic functions.

On IEEE 754 platforms, the cmath module now handles IEEE 754 special values and floating-point exceptions in a manner consistent with Annex 'G' of the C99 standard.

A new data type in the collections module: namedtuple(typename, fieldnames) is a factory function that creates subclasses of the standard tuple whose fields are accessible by name as well as index. For example:

>>> var_type = collections.namedtuple('variable',
...             'id name type size')
>>> # Names are separated by spaces or commas.
>>> # 'id, name, type, size' would also work.
>>> var_type._fields
('id', 'name', 'type', 'size')

>>> var = var_type(1, 'frequency', 'int', 4)
>>> print var[0], var.id    # Equivalent
1 1
>>> print var[2], var.type  # Equivalent
int int
>>> var._asdict()
{'size': 4, 'type': 'int', 'id': 1, 'name': 'frequency'}
>>> v2 = var._replace(name='amplitude')
>>> v2
variable(id=1, name='amplitude', type='int', size=4)

Several places in the standard library that returned tuples have been modified to return namedtuple() instances. For example, the Decimal.as_tuple() method now returns a named tuple with sign, digits, and exponent fields.

（由 Raymond Hettinger 所貢獻。）

Another change to the collections module is that the deque type now supports an optional maxlen parameter; if supplied, the deque's size will be restricted to no more than maxlen items. Adding more items to a full deque causes old items to be discarded.

>>> from collections import deque
>>> dq=deque(maxlen=3)
>>> dq
deque([], maxlen=3)
>>> dq.append(1); dq.append(2); dq.append(3)
>>> dq
deque([1, 2, 3], maxlen=3)
>>> dq.append(4)
>>> dq
deque([2, 3, 4], maxlen=3)

（由 Raymond Hettinger 所貢獻。）

The Cookie module's Morsel objects now support an httponly attribute. In some browsers. cookies with this attribute set cannot be accessed or manipulated by JavaScript code. (Contributed by Arvin Schnell; bpo-1638033 [https://bugs.python.org/issue?@action=redirect&bpo=1638033].)

A new window method in the curses module, chgat(), changes the display attributes for a certain number of characters on a single line. (Contributed by Fabian Kreutz.)

# Boldface text starting at y=0,x=21
# and affecting the rest of the line.
stdscr.chgat(0, 21, curses.A_BOLD)

The Textbox class in the curses.textpad module now supports editing in insert mode as well as overwrite mode. Insert mode is enabled by supplying a true value for the insert_mode parameter when creating the Textbox instance.

The datetime module's strftime() methods now support a %f format code that expands to the number of microseconds in the object, zero-padded on the left to six places. (Contributed by Skip Montanaro; bpo-1158 [https://bugs.python.org/issue?@action=redirect&bpo=1158].)

The decimal module was updated to version 1.66 of the General Decimal Specification [https://speleotrove.com/decimal/decarith.html]. New features include some methods for some basic mathematical functions such as exp() and log10():

>>> Decimal(1).exp()
Decimal("2.718281828459045235360287471")
>>> Decimal("2.7182818").ln()
Decimal("0.9999999895305022877376682436")
>>> Decimal(1000).log10()
Decimal("3")

The as_tuple() method of Decimal objects now returns a named tuple with sign, digits, and exponent fields.

(Implemented by Facundo Batista and Mark Dickinson. Named tuple support added by Raymond Hettinger.)

The difflib module's SequenceMatcher class now returns named tuples representing matches, with a, b, and size attributes. (Contributed by Raymond Hettinger.)

An optional timeout parameter, specifying a timeout measured in seconds, was added to the ftplib.FTP class constructor as well as the connect() method. (Added by Facundo Batista.) Also, the FTP class's storbinary() and storlines() now take an optional callback parameter that will be called with each block of data after the data has been sent. (Contributed by Phil Schwartz; bpo-1221598 [https://bugs.python.org/issue?@action=redirect&bpo=1221598].)

The reduce() built-in function is also available in the functools module. In Python 3.0, the builtin has been dropped and reduce() is only available from functools; currently there are no plans to drop the builtin in the 2.x series. (Patched by Christian Heimes; bpo-1739906 [https://bugs.python.org/issue?@action=redirect&bpo=1739906].)

When possible, the getpass module will now use /dev/tty to print a prompt message and read the password, falling back to standard error and standard input. If the password may be echoed to the terminal, a warning is printed before the prompt is displayed. (Contributed by Gregory P. Smith.)

The glob.glob() function can now return Unicode filenames if a Unicode path was used and Unicode filenames are matched within the directory. (bpo-1001604 [https://bugs.python.org/issue?@action=redirect&bpo=1001604])

A new function in the heapq module, merge(iter1, iter2, ...), takes any number of iterables returning data in sorted order, and returns a new generator that returns the contents of all the iterators, also in sorted order. For example:

>>> list(heapq.merge([1, 3, 5, 9], [2, 8, 16]))
[1, 2, 3, 5, 8, 9, 16]

Another new function, heappushpop(heap, item), pushes item onto heap, then pops off and returns the smallest item. This is more efficient than making a call to heappush() and then heappop().

heapq is now implemented to only use less-than comparison, instead of the less-than-or-equal comparison it previously used. This makes heapq's usage of a type match the list.sort() method. (Contributed by Raymond Hettinger.)

An optional timeout parameter, specifying a timeout measured in seconds, was added to the httplib.HTTPConnection and HTTPSConnection class constructors. (Added by Facundo Batista.)

Most of the inspect module's functions, such as getmoduleinfo() and getargs(), now return named tuples. In addition to behaving like tuples, the elements of the return value can also be accessed as attributes. (Contributed by Raymond Hettinger.)

Some new functions in the module include isgenerator(), isgeneratorfunction(), and isabstract().

The itertools module gained several new functions.

izip_longest(iter1, iter2, ...[, fillvalue]) makes tuples from each of the elements; if some of the iterables are shorter than others, the missing values are set to fillvalue. For example:

>>> tuple(itertools.izip_longest([1,2,3], [1,2,3,4,5]))
((1, 1), (2, 2), (3, 3), (None, 4), (None, 5))

product(iter1, iter2, ..., [repeat=N]) returns the Cartesian product of the supplied iterables, a set of tuples containing every possible combination of the elements returned from each iterable.

>>> list(itertools.product([1,2,3], [4,5,6]))
[(1, 4), (1, 5), (1, 6),
 (2, 4), (2, 5), (2, 6),
 (3, 4), (3, 5), (3, 6)]

The optional repeat keyword argument is used for taking the product of an iterable or a set of iterables with themselves, repeated N times. With a single iterable argument, N-tuples are returned:

>>> list(itertools.product([1,2], repeat=3))
[(1, 1, 1), (1, 1, 2), (1, 2, 1), (1, 2, 2),
 (2, 1, 1), (2, 1, 2), (2, 2, 1), (2, 2, 2)]

With two iterables, 2N-tuples are returned.

>>> list(itertools.product([1,2], [3,4], repeat=2))
[(1, 3, 1, 3), (1, 3, 1, 4), (1, 3, 2, 3), (1, 3, 2, 4),
 (1, 4, 1, 3), (1, 4, 1, 4), (1, 4, 2, 3), (1, 4, 2, 4),
 (2, 3, 1, 3), (2, 3, 1, 4), (2, 3, 2, 3), (2, 3, 2, 4),
 (2, 4, 1, 3), (2, 4, 1, 4), (2, 4, 2, 3), (2, 4, 2, 4)]

combinations(iterable, r) returns sub-sequences of length r from the elements of iterable.

>>> list(itertools.combinations('123', 2))
[('1', '2'), ('1', '3'), ('2', '3')]
>>> list(itertools.combinations('123', 3))
[('1', '2', '3')]
>>> list(itertools.combinations('1234', 3))
[('1', '2', '3'), ('1', '2', '4'),
 ('1', '3', '4'), ('2', '3', '4')]

permutations(iter[, r]) returns all the permutations of length r of the iterable's elements. If r is not specified, it will default to the number of elements produced by the iterable.

>>> list(itertools.permutations([1,2,3,4], 2))
[(1, 2), (1, 3), (1, 4),
 (2, 1), (2, 3), (2, 4),
 (3, 1), (3, 2), (3, 4),
 (4, 1), (4, 2), (4, 3)]

itertools.chain(*iterables) is an existing function in itertools that gained a new constructor in Python 2.6. itertools.chain.from_iterable(iterable) takes a single iterable that should return other iterables. chain() will then return all the elements of the first iterable, then all the elements of the second, and so on.

>>> list(itertools.chain.from_iterable([[1,2,3], [4,5,6]]))
[1, 2, 3, 4, 5, 6]

（均由 Raymond Hettinger 所貢獻。）

The logging module's FileHandler class and its subclasses WatchedFileHandler, RotatingFileHandler, and TimedRotatingFileHandler now have an optional delay parameter to their constructors. If delay is true, opening of the log file is deferred until the first emit() call is made. (Contributed by Vinay Sajip.)

TimedRotatingFileHandler also has a utc constructor parameter. If the argument is true, UTC time will be used in determining when midnight occurs and in generating filenames; otherwise local time will be used.

Several new functions were added to the math module:

isinf() and isnan() determine whether a given float is a (positive or negative) infinity or a NaN (Not a Number), respectively.

copysign() copies the sign bit of an IEEE 754 number, returning the absolute value of x combined with the sign bit of y. For example, math.copysign(1, -0.0) returns -1.0. (Contributed by Christian Heimes.)

factorial() computes the factorial of a number. (Contributed by Raymond Hettinger; bpo-2138 [https://bugs.python.org/issue?@action=redirect&bpo=2138].)

fsum() adds up the stream of numbers from an iterable, and is careful to avoid loss of precision through using partial sums. (Contributed by Jean Brouwers, Raymond Hettinger, and Mark Dickinson; bpo-2819 [https://bugs.python.org/issue?@action=redirect&bpo=2819].)

acosh(), asinh() and atanh() compute the inverse hyperbolic functions.

log1p() returns the natural logarithm of 1+x (base e).

trunc() rounds a number toward zero, returning the closest Integral that's between the function's argument and zero. Added as part of the backport of PEP 3141's type hierarchy for numbers.

The math module has been improved to give more consistent behaviour across platforms, especially with respect to handling of floating-point exceptions and IEEE 754 special values.

Whenever possible, the module follows the recommendations of the C99 standard about 754's special values. For example, sqrt(-1.) should now give a ValueError across almost all platforms, while sqrt(float('NaN')) should return a NaN on all IEEE 754 platforms. Where Annex 'F' of the C99 standard recommends signaling 'divide-by-zero' or 'invalid', Python will raise ValueError. Where Annex 'F' of the C99 standard recommends signaling 'overflow', Python will raise OverflowError. (See bpo-711019 [https://bugs.python.org/issue?@action=redirect&bpo=711019] and bpo-1640 [https://bugs.python.org/issue?@action=redirect&bpo=1640].)

（由 Christian Heimes 和 Mark Dickinson 所貢獻。）

mmap objects now have a rfind() method that searches for a substring beginning at the end of the string and searching backwards. The find() method also gained an end parameter giving an index at which to stop searching. (Contributed by John Lenton.)

The operator module gained a methodcaller() function that takes a name and an optional set of arguments, returning a callable that will call the named function on any arguments passed to it. For example:

>>> # 等價於 lambda s: s.replace('old', 'new')
>>> replacer = operator.methodcaller('replace', 'old', 'new')
>>> replacer('old wine in old bottles')
'new wine in new bottles'

（經 Gregory Petrosyan 建議後由 Georg Brandl 所貢獻。）

The attrgetter() function now accepts dotted names and performs the corresponding attribute lookups:

>>> inst_name = operator.attrgetter(
...        '__class__.__name__')
>>> inst_name('')
'str'
>>> inst_name(help)
'_Helper'

（經 Barry Warsaw 建議後由 Georg Brandl 所貢獻。）

The os module now wraps several new system calls. fchmod(fd, mode) and fchown(fd, uid, gid) change the mode and ownership of an opened file, and lchmod(path, mode) changes the mode of a symlink. (Contributed by Georg Brandl and Christian Heimes.)

chflags() and lchflags() are wrappers for the corresponding system calls (where they're available), changing the flags set on a file. Constants for the flag values are defined in the stat module; some possible values include UF_IMMUTABLE to signal the file may not be changed and UF_APPEND to indicate that data can only be appended to the file. (Contributed by M. Levinson.)

os.closerange(low, high) efficiently closes all file descriptors from low to high, ignoring any errors and not including high itself. This function is now used by the subprocess module to make starting processes faster. (Contributed by Georg Brandl; bpo-1663329 [https://bugs.python.org/issue?@action=redirect&bpo=1663329].)

The os.environ object's clear() method will now unset the environment variables using os.unsetenv() in addition to clearing the object's keys. (Contributed by Martin Horcicka; bpo-1181 [https://bugs.python.org/issue?@action=redirect&bpo=1181].)

The os.walk() function now has a followlinks parameter. If set to True, it will follow symlinks pointing to directories and visit the directory's contents. For backward compatibility, the parameter's default value is false. Note that the function can fall into an infinite recursion if there's a symlink that points to a parent directory. (bpo-1273829 [https://bugs.python.org/issue?@action=redirect&bpo=1273829])

In the os.path module, the splitext() function has been changed to not split on leading period characters. This produces better results when operating on Unix's dot-files. For example, os.path.splitext('.ipython') now returns ('.ipython', '') instead of ('', '.ipython'). (bpo-1115886 [https://bugs.python.org/issue?@action=redirect&bpo=1115886])

A new function, os.path.relpath(path, start='.'), returns a relative path from the start path, if it's supplied, or from the current working directory to the destination path. (Contributed by Richard Barran; bpo-1339796 [https://bugs.python.org/issue?@action=redirect&bpo=1339796].)

On Windows, os.path.expandvars() will now expand environment variables given in the form "%var%", and "~user" will be expanded into the user's home directory path. (Contributed by Josiah Carlson; bpo-957650 [https://bugs.python.org/issue?@action=redirect&bpo=957650].)

The Python debugger provided by the pdb module gained a new command: "run" restarts the Python program being debugged and can optionally take new command-line arguments for the program. (Contributed by Rocky Bernstein; bpo-1393667 [https://bugs.python.org/issue?@action=redirect&bpo=1393667].)

The pdb.post_mortem() function, used to begin debugging a traceback, will now use the traceback returned by sys.exc_info() if no traceback is supplied. (Contributed by Facundo Batista; bpo-1106316 [https://bugs.python.org/issue?@action=redirect&bpo=1106316].)

The pickletools module now has an optimize() function that takes a string containing a pickle and removes some unused opcodes, returning a shorter pickle that contains the same data structure. (Contributed by Raymond Hettinger.)

A get_data() function was added to the pkgutil module that returns the contents of resource files included with an installed Python package. For example:

>>> import pkgutil
>>> print pkgutil.get_data('test', 'exception_hierarchy.txt')
BaseException
 +-- SystemExit
 +-- KeyboardInterrupt
 +-- GeneratorExit
 +-- Exception
      +-- StopIteration
      +-- StandardError
 ...

（由 Paul Moore 貢獻；bpo-2439 [https://bugs.python.org/issue?@action=redirect&bpo=2439]。）

The pyexpat module's Parser objects now allow setting their buffer_size attribute to change the size of the buffer used to hold character data. (Contributed by Achim Gaedke; bpo-1137 [https://bugs.python.org/issue?@action=redirect&bpo=1137].)

The Queue module now provides queue variants that retrieve entries in different orders. The PriorityQueue class stores queued items in a heap and retrieves them in priority order, and LifoQueue retrieves the most recently added entries first, meaning that it behaves like a stack. (Contributed by Raymond Hettinger.)

The random module's Random objects can now be pickled on a 32-bit system and unpickled on a 64-bit system, and vice versa. Unfortunately, this change also means that Python 2.6's Random objects can't be unpickled correctly on earlier versions of Python. (Contributed by Shawn Ligocki; bpo-1727780 [https://bugs.python.org/issue?@action=redirect&bpo=1727780].)

The new triangular(low, high, mode) function returns random numbers following a triangular distribution. The returned values are between low and high, not including high itself, and with mode as the most frequently occurring value in the distribution. (Contributed by Wladmir van der Laan and Raymond Hettinger; bpo-1681432 [https://bugs.python.org/issue?@action=redirect&bpo=1681432].)

Long regular expression searches carried out by the re module will check for signals being delivered, so time-consuming searches can now be interrupted. (Contributed by Josh Hoyt and Ralf Schmitt; bpo-846388 [https://bugs.python.org/issue?@action=redirect&bpo=846388].)

The regular expression module is implemented by compiling bytecodes for a tiny regex-specific virtual machine. Untrusted code could create malicious strings of bytecode directly and cause crashes, so Python 2.6 includes a verifier for the regex bytecode. (Contributed by Guido van Rossum from work for Google App Engine; bpo-3487 [https://bugs.python.org/issue?@action=redirect&bpo=3487].)

The rlcompleter module's Completer.complete() method will now ignore exceptions triggered while evaluating a name. (Fixed by Lorenz Quack; bpo-2250 [https://bugs.python.org/issue?@action=redirect&bpo=2250].)

The sched module's scheduler instances now have a read-only queue attribute that returns the contents of the scheduler's queue, represented as a list of named tuples with the fields (time, priority, action, argument). (Contributed by Raymond Hettinger; bpo-1861 [https://bugs.python.org/issue?@action=redirect&bpo=1861].)

The select module now has wrapper functions for the Linux epoll() and BSD kqueue() system calls. modify() method was added to the existing poll objects; pollobj.modify(fd, eventmask) takes a file descriptor or file object and an event mask, modifying the recorded event mask for that file. (Contributed by Christian Heimes; bpo-1657 [https://bugs.python.org/issue?@action=redirect&bpo=1657].)

The shutil.copytree() function now has an optional ignore argument that takes a callable object. This callable will receive each directory path and a list of the directory's contents, and returns a list of names that will be ignored, not copied.

The shutil module also provides an ignore_patterns() function for use with this new parameter. ignore_patterns() takes an arbitrary number of glob-style patterns and returns a callable that will ignore any files and directories that match any of these patterns. The following example copies a directory tree, but skips both .svn directories and Emacs backup files, which have names ending with '~':

shutil.copytree('Doc/library', '/tmp/library',
                ignore=shutil.ignore_patterns('*~', '.svn'))

（由 Tarek Ziadé 貢獻；bpo-2663 [https://bugs.python.org/issue?@action=redirect&bpo=2663]。）

Integrating signal handling with GUI handling event loops like those used by Tkinter or GTk+ has long been a problem; most software ends up polling, waking up every fraction of a second to check if any GUI events have occurred. The signal module can now make this more efficient. Calling signal.set_wakeup_fd(fd) sets a file descriptor to be used; when a signal is received, a byte is written to that file descriptor. There's also a C-level function, PySignal_SetWakeupFd(), for setting the descriptor.

Event loops will use this by opening a pipe to create two descriptors, one for reading and one for writing. The writable descriptor will be passed to set_wakeup_fd(), and the readable descriptor will be added to the list of descriptors monitored by the event loop via select() or poll(). On receiving a signal, a byte will be written and the main event loop will be woken up, avoiding the need to poll.

（由 Adam Olsen 貢獻；bpo-1583 [https://bugs.python.org/issue?@action=redirect&bpo=1583]。）

The siginterrupt() function is now available from Python code, and allows changing whether signals can interrupt system calls or not. (Contributed by Ralf Schmitt.)

The setitimer() and getitimer() functions have also been added (where they're available). setitimer() allows setting interval timers that will cause a signal to be delivered to the process after a specified time, measured in wall-clock time, consumed process time, or combined process+system time. (Contributed by Guilherme Polo; bpo-2240 [https://bugs.python.org/issue?@action=redirect&bpo=2240].)

The smtplib module now supports SMTP over SSL thanks to the addition of the SMTP_SSL class. This class supports an interface identical to the existing SMTP class. (Contributed by Monty Taylor.) Both class constructors also have an optional timeout parameter that specifies a timeout for the initial connection attempt, measured in seconds. (Contributed by Facundo Batista.)

An implementation of the LMTP protocol (RFC 2033 [https://datatracker.ietf.org/doc/html/rfc2033.html]) was also added to the module. LMTP is used in place of SMTP when transferring e-mail between agents that don't manage a mail queue. (LMTP implemented by Leif Hedstrom; bpo-957003 [https://bugs.python.org/issue?@action=redirect&bpo=957003].)

SMTP.starttls() now complies with RFC 3207 [https://datatracker.ietf.org/doc/html/rfc3207.html] and forgets any knowledge obtained from the server not obtained from the TLS negotiation itself. (Patch contributed by Bill Fenner; bpo-829951 [https://bugs.python.org/issue?@action=redirect&bpo=829951].)

The socket module now supports TIPC (https://tipc.sourceforge.net/), a high-performance non-IP-based protocol designed for use in clustered environments. TIPC addresses are 4- or 5-tuples. (Contributed by Alberto Bertogli; bpo-1646 [https://bugs.python.org/issue?@action=redirect&bpo=1646].)

A new function, create_connection(), takes an address and connects to it using an optional timeout value, returning the connected socket object. This function also looks up the address's type and connects to it using IPv4 or IPv6 as appropriate. Changing your code to use create_connection() instead of socket(socket.AF_INET, ...) may be all that's required to make your code work with IPv6.

The base classes in the SocketServer module now support calling a handle_timeout() method after a span of inactivity specified by the server's timeout attribute. (Contributed by Michael Pomraning.) The serve_forever() method now takes an optional poll interval measured in seconds, controlling how often the server will check for a shutdown request. (Contributed by Pedro Werneck and Jeffrey Yasskin; bpo-742598 [https://bugs.python.org/issue?@action=redirect&bpo=742598], bpo-1193577 [https://bugs.python.org/issue?@action=redirect&bpo=1193577].)

The sqlite3 module, maintained by Gerhard Häring, has been updated from version 2.3.2 in Python 2.5 to version 2.4.1.

The struct module now supports the C99 _Bool type, using the format character '?'. (Contributed by David Remahl.)

The Popen objects provided by the subprocess module now have terminate(), kill(), and send_signal() methods. On Windows, send_signal() only supports the SIGTERM signal, and all these methods are aliases for the Win32 API function TerminateProcess(). (Contributed by Christian Heimes.)

A new variable in the sys module, float_info, is an object containing information derived from the float.h file about the platform's floating-point support. Attributes of this object include mant_dig (number of digits in the mantissa), epsilon (smallest difference between 1.0 and the next largest value representable), and several others. (Contributed by Christian Heimes; bpo-1534 [https://bugs.python.org/issue?@action=redirect&bpo=1534].)

Another new variable, dont_write_bytecode, controls whether Python writes any .pyc or .pyo files on importing a module. If this variable is true, the compiled files are not written. The variable is initially set on start-up by supplying the -B switch to the Python interpreter, or by setting the PYTHONDONTWRITEBYTECODE environment variable before running the interpreter. Python code can subsequently change the value of this variable to control whether bytecode files are written or not. (Contributed by Neal Norwitz and Georg Brandl.)

Information about the command-line arguments supplied to the Python interpreter is available by reading attributes of a named tuple available as sys.flags. For example, the verbose attribute is true if Python was executed in verbose mode, debug is true in debugging mode, etc. These attributes are all read-only. (Contributed by Christian Heimes.)

A new function, getsizeof(), takes a Python object and returns the amount of memory used by the object, measured in bytes. Built-in objects return correct results; third-party extensions may not, but can define a __sizeof__() method to return the object's size. (Contributed by Robert Schuppenies; bpo-2898 [https://bugs.python.org/issue?@action=redirect&bpo=2898].)

It's now possible to determine the current profiler and tracer functions by calling sys.getprofile() and sys.gettrace(). (Contributed by Georg Brandl; bpo-1648 [https://bugs.python.org/issue?@action=redirect&bpo=1648].)

The tarfile module now supports POSIX.1-2001 (pax) tarfiles in addition to the POSIX.1-1988 (ustar) and GNU tar formats that were already supported. The default format is GNU tar; specify the format parameter to open a file using a different format:

tar = tarfile.open("output.tar", "w",
                   format=tarfile.PAX_FORMAT)

The new encoding and errors parameters specify an encoding and an error handling scheme for character conversions. 'strict', 'ignore', and 'replace' are the three standard ways Python can handle errors,; 'utf-8' is a special value that replaces bad characters with their UTF-8 representation. (Character conversions occur because the PAX format supports Unicode filenames, defaulting to UTF-8 encoding.)

The TarFile.add() method now accepts an exclude argument that's a function that can be used to exclude certain filenames from an archive. The function must take a filename and return true if the file should be excluded or false if it should be archived. The function is applied to both the name initially passed to add() and to the names of files in recursively added directories.

（所有更改均由 Lars Gustäbel 貢獻。）

An optional timeout parameter was added to the telnetlib.Telnet class constructor, specifying a timeout measured in seconds. (Added by Facundo Batista.)

The tempfile.NamedTemporaryFile class usually deletes the temporary file it created when the file is closed. This behaviour can now be changed by passing delete=False to the constructor. (Contributed by Damien Miller; bpo-1537850 [https://bugs.python.org/issue?@action=redirect&bpo=1537850].)

A new class, SpooledTemporaryFile, behaves like a temporary file but stores its data in memory until a maximum size is exceeded. On reaching that limit, the contents will be written to an on-disk temporary file. (Contributed by Dustin J. Mitchell.)

The NamedTemporaryFile and SpooledTemporaryFile classes both work as context managers, so you can write with tempfile.NamedTemporaryFile() as tmp: .... (Contributed by Alexander Belopolsky; bpo-2021 [https://bugs.python.org/issue?@action=redirect&bpo=2021].)

The test.test_support module gained a number of context managers useful for writing tests. EnvironmentVarGuard() is a context manager that temporarily changes environment variables and automatically restores them to their old values.

Another context manager, TransientResource, can surround calls to resources that may or may not be available; it will catch and ignore a specified list of exceptions. For example, a network test may ignore certain failures when connecting to an external web site:

with test_support.TransientResource(IOError,
                                errno=errno.ETIMEDOUT):
    f = urllib.urlopen('https://sf.net')
    ...

Finally, check_warnings() resets the warning module's warning filters and returns an object that will record all warning messages triggered (bpo-3781 [https://bugs.python.org/issue?@action=redirect&bpo=3781]):

with test_support.check_warnings() as wrec:
    warnings.simplefilter("always")
    # ... 觸發警告的程式碼 ...
    assert str(wrec.message) == "function is outdated"
    assert len(wrec.warnings) == 1, "Multiple warnings raised"

（由 Brett Cannon 貢獻。）

The textwrap module can now preserve existing whitespace at the beginnings and ends of the newly created lines by specifying drop_whitespace=False as an argument:

>>> S = """This  sentence  has a bunch   of
...   extra   whitespace."""
>>> print textwrap.fill(S, width=15)
This  sentence
has a bunch
of    extra
whitespace.
>>> print textwrap.fill(S, drop_whitespace=False, width=15)
This  sentence
  has a bunch
   of    extra
   whitespace.
>>>

（由 Dwayne Bailey 貢獻；bpo-1581073 [https://bugs.python.org/issue?@action=redirect&bpo=1581073]。）

The threading module API is being changed to use properties such as daemon instead of setDaemon() and isDaemon() methods, and some methods have been renamed to use underscores instead of camel-case; for example, the activeCount() method is renamed to active_count(). Both the 2.6 and 3.0 versions of the module support the same properties and renamed methods, but don't remove the old methods. No date has been set for the deprecation of the old APIs in Python 3.x; the old APIs won't be removed in any 2.x version. (Carried out by several people, most notably Benjamin Peterson.)

The threading module's Thread objects gained an ident property that returns the thread's identifier, a nonzero integer. (Contributed by Gregory P. Smith; bpo-2871 [https://bugs.python.org/issue?@action=redirect&bpo=2871].)

The timeit module now accepts callables as well as strings for the statement being timed and for the setup code. Two convenience functions were added for creating Timer instances: repeat(stmt, setup, time, repeat, number) and timeit(stmt, setup, time, number) create an instance and call the corresponding method. (Contributed by Erik Demaine; bpo-1533909 [https://bugs.python.org/issue?@action=redirect&bpo=1533909].)

The Tkinter module now accepts lists and tuples for options, separating the elements by spaces before passing the resulting value to Tcl/Tk. (Contributed by Guilherme Polo; bpo-2906 [https://bugs.python.org/issue?@action=redirect&bpo=2906].)

The turtle module for turtle graphics was greatly enhanced by Gregor Lingl. New features in the module include:

更好的海龜移動和旋轉動畫。

Control over turtle movement using the new delay(), tracer(), and speed() methods.

The ability to set new shapes for the turtle, and to define a new coordinate system.

Turtles now have an undo() method that can roll back actions.

Simple support for reacting to input events such as mouse and keyboard activity, making it possible to write simple games.

A turtle.cfg file can be used to customize the starting appearance of the turtle's screen.

The module's docstrings can be replaced by new docstrings that have been translated into another language.

(bpo-1513695 [https://bugs.python.org/issue?@action=redirect&bpo=1513695])

An optional timeout parameter was added to the urllib.urlopen function and the urllib.ftpwrapper class constructor, as well as the urllib2.urlopen function. The parameter specifies a timeout measured in seconds. For example:

>>> u = urllib2.urlopen("http://slow.example.com",
                        timeout=3)
Traceback (most recent call last):
  ...
urllib2.URLError: <urlopen error timed out>
>>>

（由 Facundo Batista 新增。）

The Unicode database provided by the unicodedata module has been updated to version 5.1.0. (Updated by Martin von Löwis; bpo-3811 [https://bugs.python.org/issue?@action=redirect&bpo=3811].)

The warnings module's formatwarning() and showwarning() gained an optional line argument that can be used to supply the line of source code. (Added as part of bpo-1631171 [https://bugs.python.org/issue?@action=redirect&bpo=1631171], which re-implemented part of the warnings module in C code.)

A new function, catch_warnings(), is a context manager intended for testing purposes that lets you temporarily modify the warning filters and then restore their original values (bpo-3781 [https://bugs.python.org/issue?@action=redirect&bpo=3781]).

The XML-RPC SimpleXMLRPCServer and DocXMLRPCServer classes can now be prevented from immediately opening and binding to their socket by passing False as the bind_and_activate constructor parameter. This can be used to modify the instance's allow_reuse_address attribute before calling the server_bind() and server_activate() methods to open the socket and begin listening for connections. (Contributed by Peter Parente; bpo-1599845 [https://bugs.python.org/issue?@action=redirect&bpo=1599845].)

SimpleXMLRPCServer also has a _send_traceback_header attribute; if true, the exception and formatted traceback are returned as HTTP headers "X-Exception" and "X-Traceback". This feature is for debugging purposes only and should not be used on production servers because the tracebacks might reveal passwords or other sensitive information. (Contributed by Alan McIntyre as part of his project for Google's Summer of Code 2007.)

The xmlrpclib module no longer automatically converts datetime.date and datetime.time to the xmlrpclib.DateTime type; the conversion semantics were not necessarily correct for all applications. Code using xmlrpclib should convert date and time instances. (bpo-1330538 [https://bugs.python.org/issue?@action=redirect&bpo=1330538]) The code can also handle dates before 1900 (contributed by Ralf Schmitt; bpo-2014 [https://bugs.python.org/issue?@action=redirect&bpo=2014]) and 64-bit integers represented by using <i8> in XML-RPC responses (contributed by Riku Lindblad; bpo-2985 [https://bugs.python.org/issue?@action=redirect&bpo=2985]).

The zipfile module's ZipFile class now has extract() and extractall() methods that will unpack a single file or all the files in the archive to the current directory, or to a specified directory:

z = zipfile.ZipFile('python-251.zip')

# Unpack a single file, writing it relative
# to the /tmp directory.
z.extract('Python/sysmodule.c', '/tmp')

# Unpack all the files in the archive.
z.extractall()

（由 Alan McIntyre 貢獻；bpo-467924 [https://bugs.python.org/issue?@action=redirect&bpo=467924]。）

The open(), read() and extract() methods can now take either a filename or a ZipInfo object. This is useful when an archive accidentally contains a duplicated filename. (Contributed by Graham Horler; bpo-1775025 [https://bugs.python.org/issue?@action=redirect&bpo=1775025].)

Finally, zipfile now supports using Unicode filenames for archived files. (Contributed by Alexey Borzenkov; bpo-1734346 [https://bugs.python.org/issue?@action=redirect&bpo=1734346].)

ast 模組

The ast module provides an Abstract Syntax Tree representation of Python code, and Armin Ronacher contributed a set of helper functions that perform a variety of common tasks. These will be useful for HTML templating packages, code analyzers, and similar tools that process Python code.

The parse() function takes an expression and returns an AST. The dump() function outputs a representation of a tree, suitable for debugging:

import ast

t = ast.parse("""
d = {}
for i in 'abcdefghijklm':
    d[i + i] = ord(i) - ord('a') + 1
print d
""")
print ast.dump(t)

This outputs a deeply nested tree:

Module(body=[
  Assign(targets=[
    Name(id='d', ctx=Store())
   ], value=Dict(keys=[], values=[]))
  For(target=Name(id='i', ctx=Store()),
      iter=Str(s='abcdefghijklm'), body=[
    Assign(targets=[
      Subscript(value=
        Name(id='d', ctx=Load()),
          slice=
          Index(value=
            BinOp(left=Name(id='i', ctx=Load()), op=Add(),
             right=Name(id='i', ctx=Load()))), ctx=Store())
     ], value=
     BinOp(left=
      BinOp(left=
       Call(func=
        Name(id='ord', ctx=Load()), args=[
          Name(id='i', ctx=Load())
         ], keywords=[], starargs=None, kwargs=None),
       op=Sub(), right=Call(func=
        Name(id='ord', ctx=Load()), args=[
          Str(s='a')
         ], keywords=[], starargs=None, kwargs=None)),
       op=Add(), right=Num(n=1)))
    ], orelse=[])
   Print(dest=None, values=[
     Name(id='d', ctx=Load())
   ], nl=True)
 ])

The literal_eval() method takes a string or an AST representing a literal expression, parses and evaluates it, and returns the resulting value. A literal expression is a Python expression containing only strings, numbers, dictionaries, etc. but no statements or function calls. If you need to evaluate an expression but cannot accept the security risk of using an eval() call, literal_eval() will handle it safely:

>>> literal = '("a", "b", {2:4, 3:8, 1:2})'
>>> print ast.literal_eval(literal)
('a', 'b', {1: 2, 2: 4, 3: 8})
>>> print ast.literal_eval('"a" + "b"')
Traceback (most recent call last):
  ...
ValueError: malformed string

The module also includes NodeVisitor and NodeTransformer classes for traversing and modifying an AST, and functions for common transformations such as changing line numbers.

future_builtins 模組

Python 3.0 makes many changes to the repertoire of built-in functions, and most of the changes can't be introduced in the Python 2.x series because they would break compatibility. The future_builtins module provides versions of these built-in functions that can be imported when writing 3.0-compatible code.

此模組中的函式目前包括：

ascii(obj): equivalent to repr(). In Python 3.0, repr() will return a Unicode string, while ascii() will return a pure ASCII bytestring.

filter(predicate, iterable), map(func, iterable1, ...): the 3.0 versions return iterators, unlike the 2.x builtins which return lists.

hex(value), oct(value): instead of calling the __hex__() or __oct__() methods, these versions will call the __index__() method and convert the result to hexadecimal or octal. oct() will use the new 0o notation for its result.

The json module: JavaScript Object Notation

The new json module supports the encoding and decoding of Python types in JSON (Javascript Object Notation). JSON is a lightweight interchange format often used in web applications. For more information about JSON, see http://www.json.org.

json comes with support for decoding and encoding most built-in Python types. The following example encodes and decodes a dictionary:

>>> import json
>>> data = {"spam": "foo", "parrot": 42}
>>> in_json = json.dumps(data) # 為資料編碼
>>> in_json
'{"parrot": 42, "spam": "foo"}'
>>> json.loads(in_json) # 解碼為 Python 物件
{"spam": "foo", "parrot": 42}

It's also possible to write your own decoders and encoders to support more types. Pretty-printing of the JSON strings is also supported.

json (originally called simplejson) was written by Bob Ippolito.

The plistlib module: A Property-List Parser

The .plist format is commonly used on Mac OS X to store basic data types (numbers, strings, lists, and dictionaries) by serializing them into an XML-based format. It resembles the XML-RPC serialization of data types.

Despite being primarily used on Mac OS X, the format has nothing Mac-specific about it and the Python implementation works on any platform that Python supports, so the plistlib module has been promoted to the standard library.

Using the module is simple:

import sys
import plistlib
import datetime

# Create data structure
data_struct = dict(lastAccessed=datetime.datetime.now(),
                   version=1,
                   categories=('Personal','Shared','Private'))

# Create string containing XML.
plist_str = plistlib.writePlistToString(data_struct)
new_struct = plistlib.readPlistFromString(plist_str)
print data_struct
print new_struct

# Write data structure to a file and read it back.
plistlib.writePlist(data_struct, '/tmp/customizations.plist')
new_struct = plistlib.readPlist('/tmp/customizations.plist')

# read/writePlist accepts file-like objects as well as paths.
plistlib.writePlist(data_struct, sys.stdout)

ctypes Enhancements

Thomas Heller continued to maintain and enhance the ctypes module.

ctypes now supports a c_bool datatype that represents the C99 bool type. (Contributed by David Remahl; bpo-1649190 [https://bugs.python.org/issue?@action=redirect&bpo=1649190].)

The ctypes string, buffer and array types have improved support for extended slicing syntax, where various combinations of (start, stop, step) are supplied. (Implemented by Thomas Wouters.)

All ctypes data types now support from_buffer() and from_buffer_copy() methods that create a ctypes instance based on a provided buffer object. from_buffer_copy() copies the contents of the object, while from_buffer() will share the same memory area.

A new calling convention tells ctypes to clear the errno or Win32 LastError variables at the outset of each wrapped call. (Implemented by Thomas Heller; bpo-1798 [https://bugs.python.org/issue?@action=redirect&bpo=1798].)

You can now retrieve the Unix errno variable after a function call. When creating a wrapped function, you can supply use_errno=True as a keyword parameter to the DLL() function and then call the module-level methods set_errno() and get_errno() to set and retrieve the error value.

The Win32 LastError variable is similarly supported by the DLL(), OleDLL(), and WinDLL() functions. You supply use_last_error=True as a keyword parameter and then call the module-level methods set_last_error() and get_last_error().

The byref() function, used to retrieve a pointer to a ctypes instance, now has an optional offset parameter that is a byte count that will be added to the returned pointer.

Improved SSL Support

Bill Janssen made extensive improvements to Python 2.6's support for the Secure Sockets Layer by adding a new module, ssl, that's built atop the OpenSSL [https://www.openssl.org/] library. This new module provides more control over the protocol negotiated, the X.509 certificates used, and has better support for writing SSL servers (as opposed to clients) in Python. The existing SSL support in the socket module hasn't been removed and continues to work, though it will be removed in Python 3.0.

To use the new module, you must first create a TCP connection in the usual way and then pass it to the ssl.wrap_socket() function. It's possible to specify whether a certificate is required, and to obtain certificate info by calling the getpeercert() method.

也參考

The documentation for the ssl module.

Deprecations and Removals

String exceptions have been removed. Attempting to use them raises a TypeError.

Changes to the Exception interface as dictated by PEP 352 [https://peps.python.org/pep-0352/] continue to be made. For 2.6, the message attribute is being deprecated in favor of the args attribute.

(3.0-warning mode) Python 3.0 will feature a reorganized standard library that will drop many outdated modules and rename others. Python 2.6 running in 3.0-warning mode will warn about these modules when they are imported.

The list of deprecated modules is: audiodev, bgenlocations, buildtools, bundlebuilder, Canvas, compiler, dircache, dl, fpformat, gensuitemodule, ihooks, imageop, imgfile, linuxaudiodev, mhlib, mimetools, multifile, new, pure, statvfs, sunaudiodev, test.testall, and toaiff.

The gopherlib module has been removed.

The MimeWriter module and mimify module have been deprecated; use the email package instead.

The md5 module has been deprecated; use the hashlib module instead.

The posixfile module has been deprecated; fcntl.lockf() provides better locking.

The popen2 module has been deprecated; use the subprocess module.

The rgbimg module has been removed.

The sets module has been deprecated; it's better to use the built-in set and frozenset types.

The sha module has been deprecated; use the hashlib module instead.

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

Python now must be compiled with C89 compilers (after 19 years!). This means that the Python source tree has dropped its own implementations of memmove() and strerror(), which are in the C89 standard library.

Python 2.6 can be built with Microsoft Visual Studio 2008 (version 9.0), and this is the new default compiler. See the PCbuild directory for the build files. (Implemented by Christian Heimes.)

On Mac OS X, Python 2.6 can be compiled as a 4-way universal build. The configure script can take a --with-universal-archs=[32-bit|64-bit|all] switch, controlling whether the binaries are built for 32-bit architectures (x86, PowerPC), 64-bit (x86-64 and PPC-64), or both. (Contributed by Ronald Oussoren.)

A new function added in Python 2.6.6, PySys_SetArgvEx(), sets the value of sys.argv and can optionally update sys.path to include the directory containing the script named by sys.argv[0] depending on the value of an updatepath parameter.

This function was added to close a security hole for applications that embed Python. The old function, PySys_SetArgv(), would always update sys.path, and sometimes it would add the current directory. This meant that, if you ran an application embedding Python in a directory controlled by someone else, attackers could put a Trojan-horse module in the directory (say, a file named os.py) that your application would then import and run.

If you maintain a C/C++ application that embeds Python, check whether you're calling PySys_SetArgv() and carefully consider whether the application should be using PySys_SetArgvEx() with updatepath set to false. Note that using this function will break compatibility with Python versions 2.6.5 and earlier; if you have to continue working with earlier versions, you can leave the call to PySys_SetArgv() alone and call PyRun_SimpleString("sys.path.pop(0)\n") afterwards to discard the first sys.path component.

Security issue reported as CVE 2008-5983 [https://www.cve.org/CVERecord?id=CVE-2008-5983]; discussed in gh-50003 [https://github.com/python/cpython/issues/50003], and fixed by Antoine Pitrou.

The BerkeleyDB module now has a C API object, available as bsddb.db.api. This object can be used by other C extensions that wish to use the bsddb module for their own purposes. (Contributed by Duncan Grisby.)

The new buffer interface, previously described in the PEP 3118 section, adds PyObject_GetBuffer() and PyBuffer_Release(), as well as a few other functions.

Python's use of the C stdio library is now thread-safe, or at least as thread-safe as the underlying library is. A long-standing potential bug occurred if one thread closed a file object while another thread was reading from or writing to the object. In 2.6 file objects have a reference count, manipulated by the PyFile_IncUseCount() and PyFile_DecUseCount() functions. File objects can't be closed unless the reference count is zero. PyFile_IncUseCount() should be called while the GIL is still held, before carrying out an I/O operation using the FILE * pointer, and PyFile_DecUseCount() should be called immediately after the GIL is re-acquired. (Contributed by Antoine Pitrou and Gregory P. Smith.)

Importing modules simultaneously in two different threads no longer deadlocks; it will now raise an ImportError. A new API function, PyImport_ImportModuleNoBlock(), will look for a module in sys.modules first, then try to import it after acquiring an import lock. If the import lock is held by another thread, an ImportError is raised. (Contributed by Christian Heimes.)

Several functions return information about the platform's floating-point support. PyFloat_GetMax() returns the maximum representable floating-point value, and PyFloat_GetMin() returns the minimum positive value. PyFloat_GetInfo() returns an object containing more information from the float.h file, such as "mant_dig" (number of digits in the mantissa), "epsilon" (smallest difference between 1.0 and the next largest value representable), and several others. (Contributed by Christian Heimes; bpo-1534 [https://bugs.python.org/issue?@action=redirect&bpo=1534].)

C functions and methods that use PyComplex_AsCComplex() will now accept arguments that have a __complex__() method. In particular, the functions in the cmath module will now accept objects with this method. This is a backport of a Python 3.0 change. (Contributed by Mark Dickinson; bpo-1675423 [https://bugs.python.org/issue?@action=redirect&bpo=1675423].)

Python's C API now includes two functions for case-insensitive string comparisons, PyOS_stricmp(char*, char*) and PyOS_strnicmp(char*, char*, Py_ssize_t). (Contributed by Christian Heimes; bpo-1635 [https://bugs.python.org/issue?@action=redirect&bpo=1635].)

Many C extensions define their own little macro for adding integers and strings to the module's dictionary in the init* function. Python 2.6 finally defines standard macros for adding values to a module, PyModule_AddStringMacro and PyModule_AddIntMacro(). (Contributed by Christian Heimes.)

Some macros were renamed in both 3.0 and 2.6 to make it clearer that they are macros, not functions. Py_Size() became Py_SIZE(), Py_Type() became Py_TYPE(), and Py_Refcnt() became Py_REFCNT(). The mixed-case macros are still available in Python 2.6 for backward compatibility. (bpo-1629 [https://bugs.python.org/issue?@action=redirect&bpo=1629])

Distutils now places C extensions it builds in a different directory when running on a debug version of Python. (Contributed by Collin Winter; bpo-1530959 [https://bugs.python.org/issue?@action=redirect&bpo=1530959].)

Several basic data types, such as integers and strings, maintain internal free lists of objects that can be re-used. The data structures for these free lists now follow a naming convention: the variable is always named free_list, the counter is always named numfree, and a macro Py<typename>_MAXFREELIST is always defined.

A new Makefile target, "make patchcheck", prepares the Python source tree for making a patch: it fixes trailing whitespace in all modified .py files, checks whether the documentation has been changed, and reports whether the Misc/ACKS and Misc/NEWS files have been updated. (Contributed by Brett Cannon.)

Another new target, "make profile-opt", compiles a Python binary using GCC's profile-guided optimization. It compiles Python with profiling enabled, runs the test suite to obtain a set of profiling results, and then compiles using these results for optimization. (Contributed by Gregory P. Smith.)

Port-Specific Changes: Windows

The support for Windows 95, 98, ME and NT4 has been dropped. Python 2.6 requires at least Windows 2000 SP4.

The new default compiler on Windows is Visual Studio 2008 (version 9.0). The build directories for Visual Studio 2003 (version 7.1) and 2005 (version 8.0) were moved into the PC/ directory. The new PCbuild directory supports cross compilation for X64, debug builds and Profile Guided Optimization (PGO). PGO builds are roughly 10% faster than normal builds. (Contributed by Christian Heimes with help from Amaury Forgeot d'Arc and Martin von Löwis.)

The msvcrt module now supports both the normal and wide char variants of the console I/O API. The getwch() function reads a keypress and returns a Unicode value, as does the getwche() function. The putwch() function takes a Unicode character and writes it to the console. (Contributed by Christian Heimes.)

os.path.expandvars() will now expand environment variables in the form "%var%", and "~user" will be expanded into the user's home directory path. (Contributed by Josiah Carlson; bpo-957650 [https://bugs.python.org/issue?@action=redirect&bpo=957650].)

The socket module's socket objects now have an ioctl() method that provides a limited interface to the WSAIoctl() system interface.

The _winreg module now has a function, ExpandEnvironmentStrings(), that expands environment variable references such as %NAME% in an input string. The handle objects provided by this module now support the context protocol, so they can be used in with statements. (Contributed by Christian Heimes.)

_winreg also has better support for x64 systems, exposing the DisableReflectionKey(), EnableReflectionKey(), and QueryReflectionKey() functions, which enable and disable registry reflection for 32-bit processes running on 64-bit systems. (bpo-1753245 [https://bugs.python.org/issue?@action=redirect&bpo=1753245])

The msilib module's Record object gained GetInteger() and GetString() methods that return field values as an integer or a string. (Contributed by Floris Bruynooghe; bpo-2125 [https://bugs.python.org/issue?@action=redirect&bpo=2125].)

Port-Specific Changes: Mac OS X

When compiling a framework build of Python, you can now specify the framework name to be used by providing the --with-framework-name= option to the configure script.

The macfs module has been removed. This in turn required the macostools.touched() function to be removed because it depended on the macfs module. (bpo-1490190 [https://bugs.python.org/issue?@action=redirect&bpo=1490190])

Many other Mac OS modules have been deprecated and will be removed in Python 3.0: _builtinSuites, aepack, aetools, aetypes, applesingle, appletrawmain, appletrunner, argvemulator, Audio_mac, autoGIL, Carbon, cfmfile, CodeWarrior, ColorPicker, EasyDialogs, Explorer, Finder, FrameWork, findertools, ic, icglue, icopen, macerrors, MacOS, macfs, macostools, macresource, MiniAEFrame, Nav, Netscape, OSATerminology, pimp, PixMapWrapper, StdSuites, SystemEvents, Terminal, and terminalcommand.

Port-Specific Changes: IRIX

A number of old IRIX-specific modules were deprecated and will be removed in Python 3.0: al and AL, cd, cddb, cdplayer, CL and cl, DEVICE, ERRNO, FILE, FL and fl, flp, fm, GET, GLWS, GL and gl, IN, IOCTL, jpeg, panelparser, readcd, SV and sv, torgb, videoreader, and WAIT.

Porting to Python 2.6

This section lists previously described changes and other bugfixes that may require changes to your code:

Classes that aren't supposed to be hashable should set __hash__ = None in their definitions to indicate the fact.

String exceptions have been removed. Attempting to use them raises a TypeError.

The __init__() method of collections.deque now clears any existing contents of the deque before adding elements from the iterable. This change makes the behavior match list.__init__().

object.__init__() previously accepted arbitrary arguments and keyword arguments, ignoring them. In Python 2.6, this is no longer allowed and will result in a TypeError. This will affect __init__() methods that end up calling the corresponding method on object (perhaps through using super()). See bpo-1683368 [https://bugs.python.org/issue?@action=redirect&bpo=1683368] for discussion.

The Decimal constructor now accepts leading and trailing whitespace when passed a string. Previously it would raise an InvalidOperation exception. On the other hand, the create_decimal() method of Context objects now explicitly disallows extra whitespace, raising a ConversionSyntax exception.

Due to an implementation accident, if you passed a file path to the built-in __import__() function, it would actually import the specified file. This was never intended to work, however, and the implementation now explicitly checks for this case and raises an ImportError.

C API: the PyImport_Import() and PyImport_ImportModule() functions now default to absolute imports, not relative imports. This will affect C extensions that import other modules.

C API: extension data types that shouldn't be hashable should define their tp_hash slot to PyObject_HashNotImplemented().

The socket module exception socket.error now inherits from IOError. Previously it wasn't a subclass of StandardError but now it is, through IOError. (Implemented by Gregory P. Smith; bpo-1706815 [https://bugs.python.org/issue?@action=redirect&bpo=1706815].)

The xmlrpclib module no longer automatically converts datetime.date and datetime.time to the xmlrpclib.DateTime type; the conversion semantics were not necessarily correct for all applications. Code using xmlrpclib should convert date and time instances. (bpo-1330538 [https://bugs.python.org/issue?@action=redirect&bpo=1330538])

(3.0-warning mode) The Exception class now warns when accessed using slicing or index access; having Exception behave like a tuple is being phased out.

(3.0-warning mode) inequality comparisons between two dictionaries or two objects that don't implement comparison methods are reported as warnings. dict1 == dict2 still works, but dict1 < dict2 is being phased out.

Comparisons between cells, which are an implementation detail of Python's scoping rules, also cause warnings because such comparisons are forbidden entirely in 3.0.

For applications that embed Python:

The PySys_SetArgvEx() function was added in Python 2.6.6, letting applications close a security hole when the existing PySys_SetArgv() function was used. Check whether you're calling PySys_SetArgv() and carefully consider whether the application should be using PySys_SetArgvEx() with updatepath set to false.

致謝

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Georg Brandl, Steve Brown, Nick Coghlan, Ralph Corderoy, Jim Jewett, Kent Johnson, Chris Lambacher, Martin Michlmayr, Antoine Pitrou, Brian Warner.

Python 2.5 有什麼新功能

作者:

A.M. Kuchling

This article explains the new features in Python 2.5. The final release of Python 2.5 is scheduled for August 2006; PEP 356 [https://peps.python.org/pep-0356/] describes the planned release schedule. Python 2.5 was released on September 19, 2006.

The changes in Python 2.5 are an interesting mix of language and library improvements. The library enhancements will be more important to Python's user community, I think, because several widely useful packages were added. New modules include ElementTree for XML processing (xml.etree), the SQLite database module (sqlite), and the ctypes module for calling C functions.

The language changes are of middling significance. Some pleasant new features were added, but most of them aren't features that you'll use every day. Conditional expressions were finally added to the language using a novel syntax; see section PEP 308: Conditional Expressions. The new 'with' statement will make writing cleanup code easier (section PEP 343：'with' 陳述式). Values can now be passed into generators (section PEP 342: New Generator Features). Imports are now visible as either absolute or relative (section PEP 328: Absolute and Relative Imports). Some corner cases of exception handling are handled better (section PEP 341: Unified try/except/finally). All these improvements are worthwhile, but they're improvements to one specific language feature or another; none of them are broad modifications to Python's semantics.

As well as the language and library additions, other improvements and bugfixes were made throughout the source tree. A search through the SVN change logs finds there were 353 patches applied and 458 bugs fixed between Python 2.4 and 2.5. (Both figures are likely to be underestimates.)

This article doesn't try to be a complete specification of the new features; instead changes are briefly introduced using helpful examples. For full details, you should always refer to the documentation for Python 2.5 at https://docs.python.org. If you want to understand the complete implementation and design rationale, refer to the PEP for a particular new feature.

Comments, suggestions, and error reports for this document are welcome; please e-mail them to the author or open a bug in the Python bug tracker.

PEP 308: Conditional Expressions

For a long time, people have been requesting a way to write conditional expressions, which are expressions that return value A or value B depending on whether a Boolean value is true or false. A conditional expression lets you write a single assignment statement that has the same effect as the following:

if condition:
    x = true_value
else:
    x = false_value

There have been endless tedious discussions of syntax on both python-dev and comp.lang.python. A vote was even held that found the majority of voters wanted conditional expressions in some form, but there was no syntax that was preferred by a clear majority. Candidates included C's cond ? true_v : false_v, if cond then true_v else false_v, and 16 other variations.

Guido van Rossum eventually chose a surprising syntax:

x = true_value if condition else false_value

Evaluation is still lazy as in existing Boolean expressions, so the order of evaluation jumps around a bit. The condition expression in the middle is evaluated first, and the true_value expression is evaluated only if the condition was true. Similarly, the false_value expression is only evaluated when the condition is false.

This syntax may seem strange and backwards; why does the condition go in the middle of the expression, and not in the front as in C's c ? x : y? The decision was checked by applying the new syntax to the modules in the standard library and seeing how the resulting code read. In many cases where a conditional expression is used, one value seems to be the 'common case' and one value is an 'exceptional case', used only on rarer occasions when the condition isn't met. The conditional syntax makes this pattern a bit more obvious:

contents = ((doc + '\n') if doc else '')

I read the above statement as meaning "here contents is usually assigned a value of doc+'\n'; sometimes doc is empty, in which special case an empty string is returned." I doubt I will use conditional expressions very often where there isn't a clear common and uncommon case.

There was some discussion of whether the language should require surrounding conditional expressions with parentheses. The decision was made to not require parentheses in the Python language's grammar, but as a matter of style I think you should always use them. Consider these two statements:

# First version -- no parens
level = 1 if logging else 0

# Second version -- with parens
level = (1 if logging else 0)

In the first version, I think a reader's eye might group the statement into 'level = 1', 'if logging', 'else 0', and think that the condition decides whether the assignment to level is performed. The second version reads better, in my opinion, because it makes it clear that the assignment is always performed and the choice is being made between two values.

Another reason for including the brackets: a few odd combinations of list comprehensions and lambdas could look like incorrect conditional expressions. See PEP 308 [https://peps.python.org/pep-0308/] for some examples. If you put parentheses around your conditional expressions, you won't run into this case.

也參考

PEP 308 [https://peps.python.org/pep-0308/] - Conditional Expressions

PEP written by Guido van Rossum and Raymond D. Hettinger; implemented by Thomas Wouters.

PEP 309: Partial Function Application

The functools module is intended to contain tools for functional-style programming.

One useful tool in this module is the partial() function. For programs written in a functional style, you'll sometimes want to construct variants of existing functions that have some of the parameters filled in. Consider a Python function f(a, b, c); you could create a new function g(b, c) that was equivalent to f(1, b, c). This is called "partial function application".

partial() takes the arguments (function, arg1, arg2, ... kwarg1=value1, kwarg2=value2). The resulting object is callable, so you can just call it to invoke function with the filled-in arguments.

Here's a small but realistic example:

import functools

def log (message, subsystem):
    "Write the contents of 'message' to the specified subsystem."
    print '%s: %s' % (subsystem, message)
    ...

server_log = functools.partial(log, subsystem='server')
server_log('Unable to open socket')

Here's another example, from a program that uses PyGTK. Here a context-sensitive pop-up menu is being constructed dynamically. The callback provided for the menu option is a partially applied version of the open_item() method, where the first argument has been provided.

...
class Application:
    def open_item(self, path):
       ...
    def init (self):
        open_func = functools.partial(self.open_item, item_path)
        popup_menu.append( ("Open", open_func, 1) )

Another function in the functools module is the update_wrapper(wrapper, wrapped) function that helps you write well-behaved decorators. update_wrapper() copies the name, module, and docstring attribute to a wrapper function so that tracebacks inside the wrapped function are easier to understand. For example, you might write:

def my_decorator(f):
    def wrapper(*args, **kwds):
        print 'Calling decorated function'
        return f(*args, **kwds)
    functools.update_wrapper(wrapper, f)
    return wrapper

wraps() is a decorator that can be used inside your own decorators to copy the wrapped function's information. An alternate version of the previous example would be:

def my_decorator(f):
    @functools.wraps(f)
    def wrapper(*args, **kwds):
        print 'Calling decorated function'
        return f(*args, **kwds)
    return wrapper

也參考

PEP 309 [https://peps.python.org/pep-0309/] - Partial Function Application

PEP proposed and written by Peter Harris; implemented by Hye-Shik Chang and Nick Coghlan, with adaptations by Raymond Hettinger.

PEP 314: Metadata for Python Software Packages v1.1

Some simple dependency support was added to Distutils. The setup() function now has requires, provides, and obsoletes keyword parameters. When you build a source distribution using the sdist command, the dependency information will be recorded in the PKG-INFO file.

Another new keyword parameter is download_url, which should be set to a URL for the package's source code. This means it's now possible to look up an entry in the package index, determine the dependencies for a package, and download the required packages.

VERSION = '1.0'
setup(name='PyPackage',
      version=VERSION,
      requires=['numarray', 'zlib (>=1.1.4)'],
      obsoletes=['OldPackage']
      download_url=('http://www.example.com/pypackage/dist/pkg-%s.tar.gz'
                    % VERSION),
     )

Another new enhancement to the Python package index at https://pypi.org is storing source and binary archives for a package. The new upload Distutils command will upload a package to the repository.

Before a package can be uploaded, you must be able to build a distribution using the sdist Distutils command. Once that works, you can run python setup.py upload to add your package to the PyPI archive. Optionally you can GPG-sign the package by supplying the --sign and --identity options.

Package uploading was implemented by Martin von Löwis and Richard Jones.

也參考

PEP 314 [https://peps.python.org/pep-0314/] - Metadata for Python Software Packages v1.1

PEP proposed and written by A.M. Kuchling, Richard Jones, and Fred Drake; implemented by Richard Jones and Fred Drake.

PEP 328: Absolute and Relative Imports

The simpler part of PEP 328 [https://peps.python.org/pep-0328/] was implemented in Python 2.4: parentheses could now be used to enclose the names imported from a module using the from ... import ... statement, making it easier to import many different names.

The more complicated part has been implemented in Python 2.5: importing a module can be specified to use absolute or package-relative imports. The plan is to move toward making absolute imports the default in future versions of Python.

Let's say you have a package directory like this:

pkg/
pkg/__init__.py
pkg/main.py
pkg/string.py

This defines a package named pkg containing the pkg.main and pkg.string submodules.

Consider the code in the main.py module. What happens if it executes the statement import string? In Python 2.4 and earlier, it will first look in the package's directory to perform a relative import, finds pkg/string.py, imports the contents of that file as the pkg.string module, and that module is bound to the name string in the pkg.main module's namespace.

That's fine if pkg.string was what you wanted. But what if you wanted Python's standard string module? There's no clean way to ignore pkg.string and look for the standard module; generally you had to look at the contents of sys.modules, which is slightly unclean. Holger Krekel's py.std package provides a tidier way to perform imports from the standard library, import py; py.std.string.join(), but that package isn't available on all Python installations.

Reading code which relies on relative imports is also less clear, because a reader may be confused about which module, string or pkg.string, is intended to be used. Python users soon learned not to duplicate the names of standard library modules in the names of their packages' submodules, but you can't protect against having your submodule's name being used for a new module added in a future version of Python.

In Python 2.5, you can switch import's behaviour to absolute imports using a from __future__ import absolute_import directive. This absolute-import behaviour will become the default in a future version (probably Python 2.7). Once absolute imports are the default, import string will always find the standard library's version. It's suggested that users should begin using absolute imports as much as possible, so it's preferable to begin writing from pkg import string in your code.

Relative imports are still possible by adding a leading period to the module name when using the from ... import form:

# Import names from pkg.string
from .string import name1, name2
# Import pkg.string
from . import string

This imports the string module relative to the current package, so in pkg.main this will import name1 and name2 from pkg.string. Additional leading periods perform the relative import starting from the parent of the current package. For example, code in the A.B.C module can do:

from . import D                 # 引入 A.B.D
from .. import E                # 引入 A.E
from ..F import G               # 引入 A.F.G

Leading periods cannot be used with the import modname form of the import statement, only the from ... import form.

也參考

PEP 328 [https://peps.python.org/pep-0328/] - Imports: Multi-Line and Absolute/Relative

由 Aahz 撰寫 PEP；由 Thomas Wouters 實作。

https://pylib.readthedocs.io/

The py library by Holger Krekel, which contains the py.std package.

PEP 338: Executing Modules as Scripts

The -m switch added in Python 2.4 to execute a module as a script gained a few more abilities. Instead of being implemented in C code inside the Python interpreter, the switch now uses an implementation in a new module, runpy.

The runpy module implements a more sophisticated import mechanism so that it's now possible to run modules in a package such as pychecker.checker. The module also supports alternative import mechanisms such as the zipimport module. This means you can add a .zip archive's path to sys.path and then use the -m switch to execute code from the archive.

也參考

PEP 338 [https://peps.python.org/pep-0338/] - Executing modules as scripts

由 Nick Coghlan 撰寫 PEP 與實作。

PEP 341: Unified try/except/finally

Until Python 2.5, the try statement came in two flavours. You could use a finally block to ensure that code is always executed, or one or more except blocks to catch specific exceptions. You couldn't combine both except blocks and a finally block, because generating the right bytecode for the combined version was complicated and it wasn't clear what the semantics of the combined statement should be.

Guido van Rossum spent some time working with Java, which does support the equivalent of combining except blocks and a finally block, and this clarified what the statement should mean. In Python 2.5, you can now write:

try:
    block-1 ...
except Exception1:
    handler-1 ...
except Exception2:
    handler-2 ...
else:
    else-block
finally:
    final-block

The code in block-1 is executed. If the code raises an exception, the various except blocks are tested: if the exception is of class Exception1, handler-1 is executed; otherwise if it's of class Exception2, handler-2 is executed, and so forth. If no exception is raised, the else-block is executed.

No matter what happened previously, the final-block is executed once the code block is complete and any raised exceptions handled. Even if there's an error in an exception handler or the else-block and a new exception is raised, the code in the final-block is still run.

也參考

PEP 341 [https://peps.python.org/pep-0341/] - Unifying try-except and try-finally

由 Georg Brandl 撰寫 PEP；由 Thomas Lee 實作。

PEP 342: New Generator Features

Python 2.5 adds a simple way to pass values into a generator. As introduced in Python 2.3, generators only produce output; once a generator's code was invoked to create an iterator, there was no way to pass any new information into the function when its execution is resumed. Sometimes the ability to pass in some information would be useful. Hackish solutions to this include making the generator's code look at a global variable and then changing the global variable's value, or passing in some mutable object that callers then modify.

To refresh your memory of basic generators, here's a simple example:

def counter (maximum):
    i = 0
    while i < maximum:
        yield i
        i += 1

When you call counter(10), the result is an iterator that returns the values from 0 up to 9. On encountering the yield statement, the iterator returns the provided value and suspends the function's execution, preserving the local variables. Execution resumes on the following call to the iterator's next() method, picking up after the yield statement.

In Python 2.3, yield was a statement; it didn't return any value. In 2.5, yield is now an expression, returning a value that can be assigned to a variable or otherwise operated on:

val = (yield i)

I recommend that you always put parentheses around a yield expression when you're doing something with the returned value, as in the above example. The parentheses aren't always necessary, but it's easier to always add them instead of having to remember when they're needed.

(PEP 342 [https://peps.python.org/pep-0342/] explains the exact rules, which are that a yield-expression must always be parenthesized except when it occurs at the top-level expression on the right-hand side of an assignment. This means you can write val = yield i but have to use parentheses when there's an operation, as in val = (yield i) + 12.)

Values are sent into a generator by calling its send(value) method. The generator's code is then resumed and the yield expression returns the specified value. If the regular next() method is called, the yield returns None.

Here's the previous example, modified to allow changing the value of the internal counter.

def counter (maximum):
    i = 0
    while i < maximum:
        val = (yield i)
        # 如果有提供值，則改變計數器
        if val is not None:
            i = val
        else:
            i += 1

這是個改變計數器的範例：

>>> it = counter(10)
>>> print it.next()
0
>>> print it.next()
1
>>> print it.send(8)
8
>>> print it.next()
9
>>> print it.next()
Traceback (most recent call last):
  File "t.py", line 15, in ?
    print it.next()
StopIteration

yield will usually return None, so you should always check for this case. Don't just use its value in expressions unless you're sure that the send() method will be the only method used to resume your generator function.

In addition to send(), there are two other new methods on generators:

throw(type, value=None, traceback=None) is used to raise an exception inside the generator; the exception is raised by the yield expression where the generator's execution is paused.

close() raises a new GeneratorExit exception inside the generator to terminate the iteration. On receiving this exception, the generator's code must either raise GeneratorExit or StopIteration. Catching the GeneratorExit exception and returning a value is illegal and will trigger a RuntimeError; if the function raises some other exception, that exception is propagated to the caller. close() will also be called by Python's garbage collector when the generator is garbage-collected.

If you need to run cleanup code when a GeneratorExit occurs, I suggest using a try: ... finally: suite instead of catching GeneratorExit.

The cumulative effect of these changes is to turn generators from one-way producers of information into both producers and consumers.

Generators also become coroutines, a more generalized form of subroutines. Subroutines are entered at one point and exited at another point (the top of the function, and a return statement), but coroutines can be entered, exited, and resumed at many different points (the yield statements). We'll have to figure out patterns for using coroutines effectively in Python.

The addition of the close() method has one side effect that isn't obvious. close() is called when a generator is garbage-collected, so this means the generator's code gets one last chance to run before the generator is destroyed. This last chance means that try...finally statements in generators can now be guaranteed to work; the finally clause will now always get a chance to run. The syntactic restriction that you couldn't mix yield statements with a try...finally suite has therefore been removed. This seems like a minor bit of language trivia, but using generators and try...finally is actually necessary in order to implement the with statement described by PEP 343 [https://peps.python.org/pep-0343/]. I'll look at this new statement in the following section.

Another even more esoteric effect of this change: previously, the gi_frame attribute of a generator was always a frame object. It's now possible for gi_frame to be None once the generator has been exhausted.

也參考

PEP 342 [https://peps.python.org/pep-0342/] - Coroutines via Enhanced Generators

PEP written by Guido van Rossum and Phillip J. Eby; implemented by Phillip J. Eby. Includes examples of some fancier uses of generators as coroutines.

Earlier versions of these features were proposed in PEP 288 [https://peps.python.org/pep-0288/] by Raymond Hettinger and PEP 325 [https://peps.python.org/pep-0325/] by Samuele Pedroni.

https://en.wikipedia.org/wiki/Coroutine

The Wikipedia entry for coroutines.

https://web.archive.org/web/20160321211320/http://www.sidhe.org/~dan/blog/archives/000178.html

An explanation of coroutines from a Perl point of view, written by Dan Sugalski.

PEP 343：'with' 陳述式

The 'with' statement clarifies code that previously would use try...finally blocks to ensure that clean-up code is executed. In this section, I'll discuss the statement as it will commonly be used. In the next section, I'll examine the implementation details and show how to write objects for use with this statement.

The 'with' statement is a new control-flow structure whose basic structure is:

with expression [as variable]:
    with-block

The expression is evaluated, and it should result in an object that supports the context management protocol (that is, has __enter__() and __exit__() methods.

The object's __enter__() is called before with-block is executed and therefore can run set-up code. It also may return a value that is bound to the name variable, if given. (Note carefully that variable is not assigned the result of expression.)

After execution of the with-block is finished, the object's __exit__() method is called, even if the block raised an exception, and can therefore run clean-up code.

To enable the statement in Python 2.5, you need to add the following directive to your module:

from __future__ import with_statement

The statement will always be enabled in Python 2.6.

Some standard Python objects now support the context management protocol and can be used with the 'with' statement. File objects are one example:

with open('/etc/passwd', 'r') as f:
    for line in f:
        print line
        ... more processing code ...

After this statement has executed, the file object in f will have been automatically closed, even if the for loop raised an exception part-way through the block.

備註

In this case, f is the same object created by open(), because __enter__() returns self.

The threading module's locks and condition variables also support the 'with' statement:

lock = threading.Lock()
with lock:
    # Critical section of code
    ...

The lock is acquired before the block is executed and always released once the block is complete.

The new localcontext() function in the decimal module makes it easy to save and restore the current decimal context, which encapsulates the desired precision and rounding characteristics for computations:

from decimal import Decimal, Context, localcontext

# Displays with default precision of 28 digits
v = Decimal('578')
print v.sqrt()

with localcontext(Context(prec=16)):
    # All code in this block uses a precision of 16 digits.
    # The original context is restored on exiting the block.
    print v.sqrt()

Writing Context Managers

Under the hood, the 'with' statement is fairly complicated. Most people will only use 'with' in company with existing objects and don't need to know these details, so you can skip the rest of this section if you like. Authors of new objects will need to understand the details of the underlying implementation and should keep reading.

A high-level explanation of the context management protocol is:

The expression is evaluated and should result in an object called a "context manager". The context manager must have __enter__() and __exit__() methods.

The context manager's __enter__() method is called. The value returned is assigned to VAR. If no 'as VAR' clause is present, the value is simply discarded.

The code in BLOCK is executed.

If BLOCK raises an exception, the __exit__(type, value, traceback) is called with the exception details, the same values returned by sys.exc_info(). The method's return value controls whether the exception is re-raised: any false value re-raises the exception, and True will result in suppressing it. You'll only rarely want to suppress the exception, because if you do the author of the code containing the 'with' statement will never realize anything went wrong.

If BLOCK didn't raise an exception, the __exit__() method is still called, but type, value, and traceback are all None.

Let's think through an example. I won't present detailed code but will only sketch the methods necessary for a database that supports transactions.

(For people unfamiliar with database terminology: a set of changes to the database are grouped into a transaction. Transactions can be either committed, meaning that all the changes are written into the database, or rolled back, meaning that the changes are all discarded and the database is unchanged. See any database textbook for more information.)

Let's assume there's an object representing a database connection. Our goal will be to let the user write code like this:

db_connection = DatabaseConnection()
with db_connection as cursor:
    cursor.execute('insert into ...')
    cursor.execute('delete from ...')
    # ... more operations ...

The transaction should be committed if the code in the block runs flawlessly or rolled back if there's an exception. Here's the basic interface for DatabaseConnection that I'll assume:

class DatabaseConnection:
    # Database interface
    def cursor (self):
        "Returns a cursor object and starts a new transaction"
    def commit (self):
        "Commits current transaction"
    def rollback (self):
        "Rolls back current transaction"

The __enter__() method is pretty easy, having only to start a new transaction. For this application the resulting cursor object would be a useful result, so the method will return it. The user can then add as cursor to their 'with' statement to bind the cursor to a variable name.

class DatabaseConnection:
    ...
    def __enter__ (self):
        # Code to start a new transaction
        cursor = self.cursor()
        return cursor

The __exit__() method is the most complicated because it's where most of the work has to be done. The method has to check if an exception occurred. If there was no exception, the transaction is committed. The transaction is rolled back if there was an exception.

In the code below, execution will just fall off the end of the function, returning the default value of None. None is false, so the exception will be re-raised automatically. If you wished, you could be more explicit and add a return statement at the marked location.

class DatabaseConnection:
    ...
    def __exit__ (self, type, value, tb):
        if tb is None:
            # No exception, so commit
            self.commit()
        else:
            # Exception occurred, so rollback.
            self.rollback()
            # return False

contextlib 模組

The new contextlib module provides some functions and a decorator that are useful for writing objects for use with the 'with' statement.

The decorator is called contextmanager(), and lets you write a single generator function instead of defining a new class. The generator should yield exactly one value. The code up to the yield will be executed as the __enter__() method, and the value yielded will be the method's return value that will get bound to the variable in the 'with' statement's as clause, if any. The code after the yield will be executed in the __exit__() method. Any exception raised in the block will be raised by the yield statement.

Our database example from the previous section could be written using this decorator as:

from contextlib import contextmanager

@contextmanager
def db_transaction (connection):
    cursor = connection.cursor()
    try:
        yield cursor
    except:
        connection.rollback()
        raise
    else:
        connection.commit()

db = DatabaseConnection()
with db_transaction(db) as cursor:
    ...

The contextlib module also has a nested(mgr1, mgr2, ...) function that combines a number of context managers so you don't need to write nested 'with' statements. In this example, the single 'with' statement both starts a database transaction and acquires a thread lock:

lock = threading.Lock()
with nested (db_transaction(db), lock) as (cursor, locked):
    ...

Finally, the closing(object) function returns object so that it can be bound to a variable, and calls object.close at the end of the block.

import urllib, sys
from contextlib import closing

with closing(urllib.urlopen('http://www.yahoo.com')) as f:
    for line in f:
        sys.stdout.write(line)

也參考

PEP 343 [https://peps.python.org/pep-0343/] - "with" 陳述式

PEP written by Guido van Rossum and Nick Coghlan; implemented by Mike Bland, Guido van Rossum, and Neal Norwitz. The PEP shows the code generated for a 'with' statement, which can be helpful in learning how the statement works.

contextlib 模組的文件。

PEP 352: Exceptions as New-Style Classes

Exception classes can now be new-style classes, not just classic classes, and the built-in Exception class and all the standard built-in exceptions (NameError, ValueError, etc.) are now new-style classes.

The inheritance hierarchy for exceptions has been rearranged a bit. In 2.5, the inheritance relationships are:

BaseException       # New in Python 2.5
|- KeyboardInterrupt
|- SystemExit
|- Exception
   |- (all other current built-in exceptions)

This rearrangement was done because people often want to catch all exceptions that indicate program errors. KeyboardInterrupt and SystemExit aren't errors, though, and usually represent an explicit action such as the user hitting Control-C or code calling sys.exit(). A bare except: will catch all exceptions, so you commonly need to list KeyboardInterrupt and SystemExit in order to re-raise them. The usual pattern is:

try:
    ...
except (KeyboardInterrupt, SystemExit):
    raise
except:
    # Log error...
    # Continue running program...

In Python 2.5, you can now write except Exception to achieve the same result, catching all the exceptions that usually indicate errors but leaving KeyboardInterrupt and SystemExit alone. As in previous versions, a bare except: still catches all exceptions.

The goal for Python 3.0 is to require any class raised as an exception to derive from BaseException or some descendant of BaseException, and future releases in the Python 2.x series may begin to enforce this constraint. Therefore, I suggest you begin making all your exception classes derive from Exception now. It's been suggested that the bare except: form should be removed in Python 3.0, but Guido van Rossum hasn't decided whether to do this or not.

Raising of strings as exceptions, as in the statement raise "Error occurred", is deprecated in Python 2.5 and will trigger a warning. The aim is to be able to remove the string-exception feature in a few releases.

也參考

PEP 352 [https://peps.python.org/pep-0352/] - Required Superclass for Exceptions

PEP written by Brett Cannon and Guido van Rossum; implemented by Brett Cannon.

PEP 353: Using ssize_t as the index type

A wide-ranging change to Python's C API, using a new Py_ssize_t type definition instead of int, will permit the interpreter to handle more data on 64-bit platforms. This change doesn't affect Python's capacity on 32-bit platforms.

Various pieces of the Python interpreter used C's int type to store sizes or counts; for example, the number of items in a list or tuple were stored in an int. The C compilers for most 64-bit platforms still define int as a 32-bit type, so that meant that lists could only hold up to 2**31 - 1 = 2147483647 items. (There are actually a few different programming models that 64-bit C compilers can use -- see https://unix.org/version2/whatsnew/lp64_wp.html for a discussion -- but the most commonly available model leaves int as 32 bits.)

A limit of 2147483647 items doesn't really matter on a 32-bit platform because you'll run out of memory before hitting the length limit. Each list item requires space for a pointer, which is 4 bytes, plus space for a PyObject representing the item. 2147483647*4 is already more bytes than a 32-bit address space can contain.

It's possible to address that much memory on a 64-bit platform, however. The pointers for a list that size would only require 16 GiB of space, so it's not unreasonable that Python programmers might construct lists that large. Therefore, the Python interpreter had to be changed to use some type other than int, and this will be a 64-bit type on 64-bit platforms. The change will cause incompatibilities on 64-bit machines, so it was deemed worth making the transition now, while the number of 64-bit users is still relatively small. (In 5 or 10 years, we may all be on 64-bit machines, and the transition would be more painful then.)

This change most strongly affects authors of C extension modules. Python strings and container types such as lists and tuples now use Py_ssize_t to store their size. Functions such as PyList_Size() now return Py_ssize_t. Code in extension modules may therefore need to have some variables changed to Py_ssize_t.

The PyArg_ParseTuple() and Py_BuildValue() functions have a new conversion code, n, for Py_ssize_t. PyArg_ParseTuple()'s s# and t# still output int by default, but you can define the macro PY_SSIZE_T_CLEAN before including Python.h to make them return Py_ssize_t.

PEP 353 [https://peps.python.org/pep-0353/] has a section on conversion guidelines that extension authors should read to learn about supporting 64-bit platforms.

也參考

PEP 353 [https://peps.python.org/pep-0353/] - Using ssize_t as the index type

由 Martin von Löwis 撰寫 PEP 與實作。

PEP 357: The '__index__' method

The NumPy developers had a problem that could only be solved by adding a new special method, __index__(). When using slice notation, as in [start:stop:step], the values of the start, stop, and step indexes must all be either integers or long integers. NumPy defines a variety of specialized integer types corresponding to unsigned and signed integers of 8, 16, 32, and 64 bits, but there was no way to signal that these types could be used as slice indexes.

Slicing can't just use the existing __int__() method because that method is also used to implement coercion to integers. If slicing used __int__(), floating-point numbers would also become legal slice indexes and that's clearly an undesirable behaviour.

Instead, a new special method called __index__() was added. It takes no arguments and returns an integer giving the slice index to use. For example:

class C:
    def __index__ (self):
        return self.value

The return value must be either a Python integer or long integer. The interpreter will check that the type returned is correct, and raises a TypeError if this requirement isn't met.

A corresponding nb_index slot was added to the C-level PyNumberMethods structure to let C extensions implement this protocol. PyNumber_Index(obj) can be used in extension code to call the __index__() function and retrieve its result.

也參考

PEP 357 [https://peps.python.org/pep-0357/] - Allowing Any Object to be Used for Slicing

由 Travis Oliphant 撰寫 PEP 與實作。

其他語言更動

Here are all of the changes that Python 2.5 makes to the core Python language.

The dict type has a new hook for letting subclasses provide a default value when a key isn't contained in the dictionary. When a key isn't found, the dictionary's __missing__(key) method will be called. This hook is used to implement the new defaultdict class in the collections module. The following example defines a dictionary that returns zero for any missing key:

class zerodict (dict):
    def __missing__ (self, key):
        return 0

d = zerodict({1:1, 2:2})
print d[1], d[2]   # 印出 1, 2
print d[3], d[4]   # 印出 0, 0

Both 8-bit and Unicode strings have new partition(sep) and rpartition(sep) methods that simplify a common use case.

The find(S) method is often used to get an index which is then used to slice the string and obtain the pieces that are before and after the separator. partition(sep) condenses this pattern into a single method call that returns a 3-tuple containing the substring before the separator, the separator itself, and the substring after the separator. If the separator isn't found, the first element of the tuple is the entire string and the other two elements are empty. rpartition(sep) also returns a 3-tuple but starts searching from the end of the string; the r stands for 'reverse'.

一些範例：

>>> ('http://www.python.org').partition('://')
('http', '://', 'www.python.org')
>>> ('file:/usr/share/doc/index.html').partition('://')
('file:/usr/share/doc/index.html', '', '')
>>> (u'Subject: a quick question').partition(':')
(u'Subject', u':', u' a quick question')
>>> 'www.python.org'.rpartition('.')
('www.python', '.', 'org')
>>> 'www.python.org'.rpartition(':')
('', '', 'www.python.org')

(Implemented by Fredrik Lundh following a suggestion by Raymond Hettinger.)

The startswith() and endswith() methods of string types now accept tuples of strings to check for.

def is_image_file (filename):
    return filename.endswith(('.gif', '.jpg', '.tiff'))

（由 Georg Brandl 實作、後有 Tom Lynn 提出建議。）

The min() and max() built-in functions gained a key keyword parameter analogous to the key argument for sort(). This parameter supplies a function that takes a single argument and is called for every value in the list; min()/max() will return the element with the smallest/largest return value from this function. For example, to find the longest string in a list, you can do:

L = ['medium', 'longest', 'short']
# Prints 'longest'
print max(L, key=len)
# Prints 'short', because lexicographically 'short' has the largest value
print max(L)

（由 Steven Bethard 和 Raymond Hettinger 所貢獻。）

Two new built-in functions, any() and all(), evaluate whether an iterator contains any true or false values. any() returns True if any value returned by the iterator is true; otherwise it will return False. all() returns True only if all of the values returned by the iterator evaluate as true. (Suggested by Guido van Rossum, and implemented by Raymond Hettinger.)

The result of a class's __hash__() method can now be either a long integer or a regular integer. If a long integer is returned, the hash of that value is taken. In earlier versions the hash value was required to be a regular integer, but in 2.5 the id() built-in was changed to always return non-negative numbers, and users often seem to use id(self) in __hash__() methods (though this is discouraged).

ASCII is now the default encoding for modules. It's now a syntax error if a module contains string literals with 8-bit characters but doesn't have an encoding declaration. In Python 2.4 this triggered a warning, not a syntax error. See PEP 263 [https://peps.python.org/pep-0263/] for how to declare a module's encoding; for example, you might add a line like this near the top of the source file:

# -*- coding: latin1 -*-

A new warning, UnicodeWarning, is triggered when you attempt to compare a Unicode string and an 8-bit string that can't be converted to Unicode using the default ASCII encoding. The result of the comparison is false:

>>> chr(128) == unichr(128)   # 無法將 chr(128) 轉換為 Unicode
__main__:1: UnicodeWarning: Unicode equal comparison failed
  to convert both arguments to Unicode - interpreting them
  as being unequal
False
>>> chr(127) == unichr(127)   # chr(127) 可以被轉換
True

Previously this would raise a UnicodeDecodeError exception, but in 2.5 this could result in puzzling problems when accessing a dictionary. If you looked up unichr(128) and chr(128) was being used as a key, you'd get a UnicodeDecodeError exception. Other changes in 2.5 resulted in this exception being raised instead of suppressed by the code in dictobject.c that implements dictionaries.

Raising an exception for such a comparison is strictly correct, but the change might have broken code, so instead UnicodeWarning was introduced.

（由 Marc-André Lemburg 實作。）

One error that Python programmers sometimes make is forgetting to include an __init__.py module in a package directory. Debugging this mistake can be confusing, and usually requires running Python with the -v switch to log all the paths searched. In Python 2.5, a new ImportWarning warning is triggered when an import would have picked up a directory as a package but no __init__.py was found. This warning is silently ignored by default; provide the -Wd option when running the Python executable to display the warning message. (Implemented by Thomas Wouters.)

The list of base classes in a class definition can now be empty. As an example, this is now legal:

class C():
    pass

（由 Brett Cannon 實作。）

Interactive Interpreter Changes

In the interactive interpreter, quit and exit have long been strings so that new users get a somewhat helpful message when they try to quit:

>>> quit
'Use Ctrl-D (i.e. EOF) to exit.'

In Python 2.5, quit and exit are now objects that still produce string representations of themselves, but are also callable. Newbies who try quit() or exit() will now exit the interpreter as they expect. (Implemented by Georg Brandl.)

The Python executable now accepts the standard long options --help and --version; on Windows, it also accepts the /? option for displaying a help message. (Implemented by Georg Brandl.)

最佳化

Several of the optimizations were developed at the NeedForSpeed sprint, an event held in Reykjavik, Iceland, from May 21--28 2006. The sprint focused on speed enhancements to the CPython implementation and was funded by EWT LLC with local support from CCP Games. Those optimizations added at this sprint are specially marked in the following list.

When they were introduced in Python 2.4, the built-in set and frozenset types were built on top of Python's dictionary type. In 2.5 the internal data structure has been customized for implementing sets, and as a result sets will use a third less memory and are somewhat faster. (Implemented by Raymond Hettinger.)

The speed of some Unicode operations, such as finding substrings, string splitting, and character map encoding and decoding, has been improved. (Substring search and splitting improvements were added by Fredrik Lundh and Andrew Dalke at the NeedForSpeed sprint. Character maps were improved by Walter Dörwald and Martin von Löwis.)

The long(str, base) function is now faster on long digit strings because fewer intermediate results are calculated. The peak is for strings of around 800--1000 digits where the function is 6 times faster. (Contributed by Alan McIntyre and committed at the NeedForSpeed sprint.)

It's now illegal to mix iterating over a file with for line in file and calling the file object's read()/readline()/readlines() methods. Iteration uses an internal buffer and the read*() methods don't use that buffer. Instead they would return the data following the buffer, causing the data to appear out of order. Mixing iteration and these methods will now trigger a ValueError from the read*() method. (Implemented by Thomas Wouters.)

The struct module now compiles structure format strings into an internal representation and caches this representation, yielding a 20% speedup. (Contributed by Bob Ippolito at the NeedForSpeed sprint.)

The re module got a 1 or 2% speedup by switching to Python's allocator functions instead of the system's malloc() and free(). (Contributed by Jack Diederich at the NeedForSpeed sprint.)

The code generator's peephole optimizer now performs simple constant folding in expressions. If you write something like a = 2+3, the code generator will do the arithmetic and produce code corresponding to a = 5. (Proposed and implemented by Raymond Hettinger.)

Function calls are now faster because code objects now keep the most recently finished frame (a "zombie frame") in an internal field of the code object, reusing it the next time the code object is invoked. (Original patch by Michael Hudson, modified by Armin Rigo and Richard Jones; committed at the NeedForSpeed sprint.) Frame objects are also slightly smaller, which may improve cache locality and reduce memory usage a bit. (Contributed by Neal Norwitz.)

Python's built-in exceptions are now new-style classes, a change that speeds up instantiation considerably. Exception handling in Python 2.5 is therefore about 30% faster than in 2.4. (Contributed by Richard Jones, Georg Brandl and Sean Reifschneider at the NeedForSpeed sprint.)

Importing now caches the paths tried, recording whether they exist or not so that the interpreter makes fewer open() and stat() calls on startup. (Contributed by Martin von Löwis and Georg Brandl.)

New, Improved, and Removed Modules

The standard library received many enhancements and bug fixes in Python 2.5. Here's a partial list of the most notable changes, sorted alphabetically by module name. Consult the Misc/NEWS file in the source tree for a more complete list of changes, or look through the SVN logs for all the details.

The audioop module now supports the a-LAW encoding, and the code for u-LAW encoding has been improved. (Contributed by Lars Immisch.)

The codecs module gained support for incremental codecs. The codec.lookup() function now returns a CodecInfo instance instead of a tuple. CodecInfo instances behave like a 4-tuple to preserve backward compatibility but also have the attributes encode, decode, incrementalencoder, incrementaldecoder, streamwriter, and streamreader. Incremental codecs can receive input and produce output in multiple chunks; the output is the same as if the entire input was fed to the non-incremental codec. See the codecs module documentation for details. (Designed and implemented by Walter Dörwald.)

The collections module gained a new type, defaultdict, that subclasses the standard dict type. The new type mostly behaves like a dictionary but constructs a default value when a key isn't present, automatically adding it to the dictionary for the requested key value.

The first argument to defaultdict's constructor is a factory function that gets called whenever a key is requested but not found. This factory function receives no arguments, so you can use built-in type constructors such as list() or int(). For example, you can make an index of words based on their initial letter like this:

words = """Nel mezzo del cammin di nostra vita
mi ritrovai per una selva oscura
che la diritta via era smarrita""".lower().split()

index = defaultdict(list)

for w in words:
    init_letter = w[0]
    index[init_letter].append(w)

Printing index results in the following output:

defaultdict(<type 'list'>, {'c': ['cammin', 'che'], 'e': ['era'],
        'd': ['del', 'di', 'diritta'], 'm': ['mezzo', 'mi'],
        'l': ['la'], 'o': ['oscura'], 'n': ['nel', 'nostra'],
        'p': ['per'], 's': ['selva', 'smarrita'],
        'r': ['ritrovai'], 'u': ['una'], 'v': ['vita', 'via']}

（由 Guido van Rossum 所貢獻。）

The deque double-ended queue type supplied by the collections module now has a remove(value) method that removes the first occurrence of value in the queue, raising ValueError if the value isn't found. (Contributed by Raymond Hettinger.)

New module: The contextlib module contains helper functions for use with the new 'with' statement. See section contextlib 模組 for more about this module.

New module: The cProfile module is a C implementation of the existing profile module that has much lower overhead. The module's interface is the same as profile: you run cProfile.run('main()') to profile a function, can save profile data to a file, etc. It's not yet known if the Hotshot profiler, which is also written in C but doesn't match the profile module's interface, will continue to be maintained in future versions of Python. (Contributed by Armin Rigo.)

Also, the pstats module for analyzing the data measured by the profiler now supports directing the output to any file object by supplying a stream argument to the Stats constructor. (Contributed by Skip Montanaro.)

The csv module, which parses files in comma-separated value format, received several enhancements and a number of bugfixes. You can now set the maximum size in bytes of a field by calling the csv.field_size_limit(new_limit) function; omitting the new_limit argument will return the currently set limit. The reader class now has a line_num attribute that counts the number of physical lines read from the source; records can span multiple physical lines, so line_num is not the same as the number of records read.

The CSV parser is now stricter about multi-line quoted fields. Previously, if a line ended within a quoted field without a terminating newline character, a newline would be inserted into the returned field. This behavior caused problems when reading files that contained carriage return characters within fields, so the code was changed to return the field without inserting newlines. As a consequence, if newlines embedded within fields are important, the input should be split into lines in a manner that preserves the newline characters.

（由 Skip Montanaro 和 Andrew McNamara 所貢獻。）

The datetime class in the datetime module now has a strptime(string, format) method for parsing date strings, contributed by Josh Spoerri. It uses the same format characters as time.strptime() and time.strftime():

from datetime import datetime

ts = datetime.strptime('10:13:15 2006-03-07',
                       '%H:%M:%S %Y-%m-%d')

The SequenceMatcher.get_matching_blocks() method in the difflib module now guarantees to return a minimal list of blocks describing matching subsequences. Previously, the algorithm would occasionally break a block of matching elements into two list entries. (Enhancement by Tim Peters.)

The doctest module gained a SKIP option that keeps an example from being executed at all. This is intended for code snippets that are usage examples intended for the reader and aren't actually test cases.

An encoding parameter was added to the testfile() function and the DocFileSuite class to specify the file's encoding. This makes it easier to use non-ASCII characters in tests contained within a docstring. (Contributed by Bjorn Tillenius.)

The email package has been updated to version 4.0. (Contributed by Barry Warsaw.)

The fileinput module was made more flexible. Unicode filenames are now supported, and a mode parameter that defaults to "r" was added to the input() function to allow opening files in binary or universal newlines mode. Another new parameter, openhook, lets you use a function other than open() to open the input files. Once you're iterating over the set of files, the FileInput object's new fileno() returns the file descriptor for the currently opened file. (Contributed by Georg Brandl.)

In the gc module, the new get_count() function returns a 3-tuple containing the current collection counts for the three GC generations. This is accounting information for the garbage collector; when these counts reach a specified threshold, a garbage collection sweep will be made. The existing gc.collect() function now takes an optional generation argument of 0, 1, or 2 to specify which generation to collect. (Contributed by Barry Warsaw.)

The nsmallest() and nlargest() functions in the heapq module now support a key keyword parameter similar to the one provided by the min()/max() functions and the sort() methods. For example:

>>> import heapq
>>> L = ["short", 'medium', 'longest', 'longer still']
>>> heapq.nsmallest(2, L)  # Return two lowest elements, lexicographically
['longer still', 'longest']
>>> heapq.nsmallest(2, L, key=len)   # Return two shortest elements
['short', 'medium']

（由 Raymond Hettinger 所貢獻。）

The itertools.islice() function now accepts None for the start and step arguments. This makes it more compatible with the attributes of slice objects, so that you can now write the following:

s = slice(5)     # Create slice object
itertools.islice(iterable, s.start, s.stop, s.step)

（由 Raymond Hettinger 所貢獻。）

The format() function in the locale module has been modified and two new functions were added, format_string() and currency().

The format() function's val parameter could previously be a string as long as no more than one %char specifier appeared; now the parameter must be exactly one %char specifier with no surrounding text. An optional monetary parameter was also added which, if True, will use the locale's rules for formatting currency in placing a separator between groups of three digits.

To format strings with multiple %char specifiers, use the new format_string() function that works like format() but also supports mixing %char specifiers with arbitrary text.

A new currency() function was also added that formats a number according to the current locale's settings.

（由 Georg Brandl 所貢獻。）

The mailbox module underwent a massive rewrite to add the capability to modify mailboxes in addition to reading them. A new set of classes that include mbox, MH, and Maildir are used to read mailboxes, and have an add(message) method to add messages, remove(key) to remove messages, and lock()/unlock() to lock/unlock the mailbox. The following example converts a maildir-format mailbox into an mbox-format one:

import mailbox

# 'factory=None' uses email.Message.Message as the class representing
# individual messages.
src = mailbox.Maildir('maildir', factory=None)
dest = mailbox.mbox('/tmp/mbox')

for msg in src:
    dest.add(msg)

(Contributed by Gregory K. Johnson. Funding was provided by Google's 2005 Summer of Code.)

New module: the msilib module allows creating Microsoft Installer .msi files and CAB files. Some support for reading the .msi database is also included. (Contributed by Martin von Löwis.)

The nis module now supports accessing domains other than the system default domain by supplying a domain argument to the nis.match() and nis.maps() functions. (Contributed by Ben Bell.)

The operator module's itemgetter() and attrgetter() functions now support multiple fields. A call such as operator.attrgetter('a', 'b') will return a function that retrieves the a and b attributes. Combining this new feature with the sort() method's key parameter lets you easily sort lists using multiple fields. (Contributed by Raymond Hettinger.)

The optparse module was updated to version 1.5.1 of the Optik library. The OptionParser class gained an epilog attribute, a string that will be printed after the help message, and a destroy() method to break reference cycles created by the object. (Contributed by Greg Ward.)

The os module underwent several changes. The stat_float_times variable now defaults to true, meaning that os.stat() will now return time values as floats. (This doesn't necessarily mean that os.stat() will return times that are precise to fractions of a second; not all systems support such precision.)

Constants named os.SEEK_SET, os.SEEK_CUR, and os.SEEK_END have been added; these are the parameters to the os.lseek() function. Two new constants for locking are os.O_SHLOCK and os.O_EXLOCK.

Two new functions, wait3() and wait4(), were added. They're similar the waitpid() function which waits for a child process to exit and returns a tuple of the process ID and its exit status, but wait3() and wait4() return additional information. wait3() doesn't take a process ID as input, so it waits for any child process to exit and returns a 3-tuple of process-id, exit-status, resource-usage as returned from the resource.getrusage() function. wait4(pid) does take a process ID. (Contributed by Chad J. Schroeder.)

On FreeBSD, the os.stat() function now returns times with nanosecond resolution, and the returned object now has st_gen and st_birthtime. The st_flags attribute is also available, if the platform supports it. (Contributed by Antti Louko and Diego Pettenò.)

The Python debugger provided by the pdb module can now store lists of commands to execute when a breakpoint is reached and execution stops. Once breakpoint #1 has been created, enter commands 1 and enter a series of commands to be executed, finishing the list with end. The command list can include commands that resume execution, such as continue or next. (Contributed by Grégoire Dooms.)

The pickle and cPickle modules no longer accept a return value of None from the __reduce__() method; the method must return a tuple of arguments instead. The ability to return None was deprecated in Python 2.4, so this completes the removal of the feature.

The pkgutil module, containing various utility functions for finding packages, was enhanced to support PEP 302 [https://peps.python.org/pep-0302/]'s import hooks and now also works for packages stored in ZIP-format archives. (Contributed by Phillip J. Eby.)

The pybench benchmark suite by Marc-André Lemburg is now included in the Tools/pybench directory. The pybench suite is an improvement on the commonly used pystone.py program because pybench provides a more detailed measurement of the interpreter's speed. It times particular operations such as function calls, tuple slicing, method lookups, and numeric operations, instead of performing many different operations and reducing the result to a single number as pystone.py does.

The pyexpat module now uses version 2.0 of the Expat parser. (Contributed by Trent Mick.)

The Queue class provided by the Queue module gained two new methods. join() blocks until all items in the queue have been retrieved and all processing work on the items have been completed. Worker threads call the other new method, task_done(), to signal that processing for an item has been completed. (Contributed by Raymond Hettinger.)

The old regex and regsub modules, which have been deprecated ever since Python 2.0, have finally been deleted. Other deleted modules: statcache, tzparse, whrandom.

Also deleted: the lib-old directory, which includes ancient modules such as dircmp and ni, was removed. lib-old wasn't on the default sys.path, so unless your programs explicitly added the directory to sys.path, this removal shouldn't affect your code.

The rlcompleter module is no longer dependent on importing the readline module and therefore now works on non-Unix platforms. (Patch from Robert Kiendl.)

The SimpleXMLRPCServer and DocXMLRPCServer classes now have a rpc_paths attribute that constrains XML-RPC operations to a limited set of URL paths; the default is to allow only '/' and '/RPC2'. Setting rpc_paths to None or an empty tuple disables this path checking.

The socket module now supports AF_NETLINK sockets on Linux, thanks to a patch from Philippe Biondi. Netlink sockets are a Linux-specific mechanism for communications between a user-space process and kernel code; an introductory article about them is at https://www.linuxjournal.com/article/7356. In Python code, netlink addresses are represented as a tuple of 2 integers, (pid, group_mask).

Two new methods on socket objects, recv_into(buffer) and recvfrom_into(buffer), store the received data in an object that supports the buffer protocol instead of returning the data as a string. This means you can put the data directly into an array or a memory-mapped file.

Socket objects also gained getfamily(), gettype(), and getproto() accessor methods to retrieve the family, type, and protocol values for the socket.

New module: the spwd module provides functions for accessing the shadow password database on systems that support shadow passwords.

The struct is now faster because it compiles format strings into Struct objects with pack() and unpack() methods. This is similar to how the re module lets you create compiled regular expression objects. You can still use the module-level pack() and unpack() functions; they'll create Struct objects and cache them. Or you can use Struct instances directly:

s = struct.Struct('ih3s')

data = s.pack(1972, 187, 'abc')
year, number, name = s.unpack(data)

You can also pack and unpack data to and from buffer objects directly using the pack_into(buffer, offset, v1, v2, ...) and unpack_from(buffer, offset) methods. This lets you store data directly into an array or a memory-mapped file.

(Struct objects were implemented by Bob Ippolito at the NeedForSpeed sprint. Support for buffer objects was added by Martin Blais, also at the NeedForSpeed sprint.)

The Python developers switched from CVS to Subversion during the 2.5 development process. Information about the exact build version is available as the sys.subversion variable, a 3-tuple of (interpreter-name, branch-name, revision-range). For example, at the time of writing my copy of 2.5 was reporting ('CPython', 'trunk', '45313:45315').

This information is also available to C extensions via the Py_GetBuildInfo() function that returns a string of build information like this: "trunk:45355:45356M, Apr 13 2006, 07:42:19". (Contributed by Barry Warsaw.)

Another new function, sys._current_frames(), returns the current stack frames for all running threads as a dictionary mapping thread identifiers to the topmost stack frame currently active in that thread at the time the function is called. (Contributed by Tim Peters.)

The TarFile class in the tarfile module now has an extractall() method that extracts all members from the archive into the current working directory. It's also possible to set a different directory as the extraction target, and to unpack only a subset of the archive's members.

The compression used for a tarfile opened in stream mode can now be autodetected using the mode 'r|*'. (Contributed by Lars Gustäbel.)

The threading module now lets you set the stack size used when new threads are created. The stack_size([*size*]) function returns the currently configured stack size, and supplying the optional size parameter sets a new value. Not all platforms support changing the stack size, but Windows, POSIX threading, and OS/2 all do. (Contributed by Andrew MacIntyre.)

The unicodedata module has been updated to use version 4.1.0 of the Unicode character database. Version 3.2.0 is required by some specifications, so it's still available as unicodedata.ucd_3_2_0.

New module: the uuid module generates universally unique identifiers (UUIDs) according to RFC 4122 [https://datatracker.ietf.org/doc/html/rfc4122.html]. The RFC defines several different UUID versions that are generated from a starting string, from system properties, or purely randomly. This module contains a UUID class and functions named uuid1(), uuid3(), uuid4(), and uuid5() to generate different versions of UUID. (Version 2 UUIDs are not specified in RFC 4122 [https://datatracker.ietf.org/doc/html/rfc4122.html] and are not supported by this module.)

>>> import uuid
>>> # make a UUID based on the host ID and current time
>>> uuid.uuid1()
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

>>> # make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

>>> # make a random UUID
>>> uuid.uuid4()
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

>>> # make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

（由 Ka-Ping Yee 所貢獻。）

The weakref module's WeakKeyDictionary and WeakValueDictionary types gained new methods for iterating over the weak references contained in the dictionary. iterkeyrefs() and keyrefs() methods were added to WeakKeyDictionary, and itervaluerefs() and valuerefs() were added to WeakValueDictionary. (Contributed by Fred L. Drake, Jr.)

The webbrowser module received a number of enhancements. It's now usable as a script with python -m webbrowser, taking a URL as the argument; there are a number of switches to control the behaviour (-n for a new browser window, -t for a new tab). New module-level functions, open_new() and open_new_tab(), were added to support this. The module's open() function supports an additional feature, an autoraise parameter that signals whether to raise the open window when possible. A number of additional browsers were added to the supported list such as Firefox, Opera, Konqueror, and elinks. (Contributed by Oleg Broytmann and Georg Brandl.)

The xmlrpclib module now supports returning datetime objects for the XML-RPC date type. Supply use_datetime=True to the loads() function or the Unmarshaller class to enable this feature. (Contributed by Skip Montanaro.)

The zipfile module now supports the ZIP64 version of the format, meaning that a .zip archive can now be larger than 4 GiB and can contain individual files larger than 4 GiB. (Contributed by Ronald Oussoren.)

The zlib module's Compress and Decompress objects now support a copy() method that makes a copy of the object's internal state and returns a new Compress or Decompress object. (Contributed by Chris AtLee.)

ctypes 套件

The ctypes package, written by Thomas Heller, has been added to the standard library. ctypes lets you call arbitrary functions in shared libraries or DLLs. Long-time users may remember the dl module, which provides functions for loading shared libraries and calling functions in them. The ctypes package is much fancier.

To load a shared library or DLL, you must create an instance of the CDLL class and provide the name or path of the shared library or DLL. Once that's done, you can call arbitrary functions by accessing them as attributes of the CDLL object.

import ctypes

libc = ctypes.CDLL('libc.so.6')
result = libc.printf("Line of output\n")

Type constructors for the various C types are provided: c_int(), c_float(), c_double(), c_char_p() (equivalent to char*), and so forth. Unlike Python's types, the C versions are all mutable; you can assign to their value attribute to change the wrapped value. Python integers and strings will be automatically converted to the corresponding C types, but for other types you must call the correct type constructor. (And I mean must; getting it wrong will often result in the interpreter crashing with a segmentation fault.)

You shouldn't use c_char_p() with a Python string when the C function will be modifying the memory area, because Python strings are supposed to be immutable; breaking this rule will cause puzzling bugs. When you need a modifiable memory area, use create_string_buffer():

s = "this is a string"
buf = ctypes.create_string_buffer(s)
libc.strfry(buf)

C functions are assumed to return integers, but you can set the restype attribute of the function object to change this:

>>> libc.atof('2.71828')
-1783957616
>>> libc.atof.restype = ctypes.c_double
>>> libc.atof('2.71828')
2.71828

ctypes also provides a wrapper for Python's C API as the ctypes.pythonapi object. This object does not release the global interpreter lock before calling a function, because the lock must be held when calling into the interpreter's code. There's a py_object type constructor that will create a PyObject* pointer. A simple usage:

import ctypes

d = {}
ctypes.pythonapi.PyObject_SetItem(ctypes.py_object(d),
          ctypes.py_object("abc"),  ctypes.py_object(1))
# d 現在為 {'abc', 1}.

Don't forget to use py_object(); if it's omitted you end up with a segmentation fault.

ctypes has been around for a while, but people still write and distribution hand-coded extension modules because you can't rely on ctypes being present. Perhaps developers will begin to write Python wrappers atop a library accessed through ctypes instead of extension modules, now that ctypes is included with core Python.

也參考

https://web.archive.org/web/20180410025338/http://starship.python.net/crew/theller/ctypes/

The pre-stdlib ctypes web page, with a tutorial, reference, and FAQ.

ctypes 模組的文件。

ElementTree 套件

A subset of Fredrik Lundh's ElementTree library for processing XML has been added to the standard library as xml.etree. The available modules are ElementTree, ElementPath, and ElementInclude from ElementTree 1.2.6. The cElementTree accelerator module is also included.

The rest of this section will provide a brief overview of using ElementTree. Full documentation for ElementTree is available at https://web.archive.org/web/20201124024954/http://effbot.org/zone/element-index.htm.

ElementTree represents an XML document as a tree of element nodes. The text content of the document is stored as the text and tail attributes of (This is one of the major differences between ElementTree and the Document Object Model; in the DOM there are many different types of node, including TextNode.)

The most commonly used parsing function is parse(), that takes either a string (assumed to contain a filename) or a file-like object and returns an ElementTree instance:

from xml.etree import ElementTree as ET

tree = ET.parse('ex-1.xml')

feed = urllib.urlopen(
          'http://planet.python.org/rss10.xml')
tree = ET.parse(feed)

Once you have an ElementTree instance, you can call its getroot() method to get the root Element node.

There's also an XML() function that takes a string literal and returns an Element node (not an ElementTree). This function provides a tidy way to incorporate XML fragments, approaching the convenience of an XML literal:

svg = ET.XML("""<svg width="10px" version="1.0">
             </svg>""")
svg.set('height', '320px')
svg.append(elem1)

Each XML element supports some dictionary-like and some list-like access methods. Dictionary-like operations are used to access attribute values, and list-like operations are used to access child nodes.

操作

結果

elem[n]

Returns n'th child element.

elem[m:n]

Returns list of m'th through n'th child elements.

len(elem)

Returns number of child elements.

list(elem)

Returns list of child elements.

elem.append(elem2)

Adds elem2 as a child.

elem.insert(index, elem2)

Inserts elem2 at the specified location.

del elem[n]

Deletes n'th child element.

elem.keys()

Returns list of attribute names.

elem.get(name)

Returns value of attribute name.

elem.set(name, value)

Sets new value for attribute name.

elem.attrib

Retrieves the dictionary containing attributes.

del elem.attrib[name]

Deletes attribute name.

Comments and processing instructions are also represented as Element nodes. To check if a node is a comment or processing instructions:

if elem.tag is ET.Comment:
    ...
elif elem.tag is ET.ProcessingInstruction:
    ...

To generate XML output, you should call the ElementTree.write() method. Like parse(), it can take either a string or a file-like object:

# 編碼為 US-ASCII
tree.write('output.xml')

# 編碼為 UTF-8
f = open('output.xml', 'w')
tree.write(f, encoding='utf-8')

(Caution: the default encoding used for output is ASCII. For general XML work, where an element's name may contain arbitrary Unicode characters, ASCII isn't a very useful encoding because it will raise an exception if an element's name contains any characters with values greater than 127. Therefore, it's best to specify a different encoding such as UTF-8 that can handle any Unicode character.)

This section is only a partial description of the ElementTree interfaces. Please read the package's official documentation for more details.

也參考

https://web.archive.org/web/20201124024954/http://effbot.org/zone/element-index.htm

ElementTree 的官方文件。

hashlib 套件

A new hashlib module, written by Gregory P. Smith, has been added to replace the md5 and sha modules. hashlib adds support for additional secure hashes (SHA-224, SHA-256, SHA-384, and SHA-512). When available, the module uses OpenSSL for fast platform optimized implementations of algorithms.

The old md5 and sha modules still exist as wrappers around hashlib to preserve backwards compatibility. The new module's interface is very close to that of the old modules, but not identical. The most significant difference is that the constructor functions for creating new hashing objects are named differently.

# Old versions
h = md5.md5()
h = md5.new()

# New version
h = hashlib.md5()

# Old versions
h = sha.sha()
h = sha.new()

# New version
h = hashlib.sha1()

# Hash that weren't previously available
h = hashlib.sha224()
h = hashlib.sha256()
h = hashlib.sha384()
h = hashlib.sha512()

# Alternative form
h = hashlib.new('md5')          # Provide algorithm as a string

Once a hash object has been created, its methods are the same as before: update(string) hashes the specified string into the current digest state, digest() and hexdigest() return the digest value as a binary string or a string of hex digits, and copy() returns a new hashing object with the same digest state.

也參考

hashlib 模組的文件。

sqlite3 套件

The pysqlite module (https://www.pysqlite.org), a wrapper for the SQLite embedded database, has been added to the standard library under the package name sqlite3.

SQLite is a C library that provides a lightweight disk-based database that doesn't require a separate server process and allows accessing the database using a nonstandard variant of the SQL query language. Some applications can use SQLite for internal data storage. It's also possible to prototype an application using SQLite and then port the code to a larger database such as PostgreSQL or Oracle.

pysqlite was written by Gerhard Häring and provides a SQL interface compliant with the DB-API 2.0 specification described by PEP 249 [https://peps.python.org/pep-0249/].

If you're compiling the Python source yourself, note that the source tree doesn't include the SQLite code, only the wrapper module. You'll need to have the SQLite libraries and headers installed before compiling Python, and the build process will compile the module when the necessary headers are available.

To use the module, you must first create a Connection object that represents the database. Here the data will be stored in the /tmp/example file:

conn = sqlite3.connect('/tmp/example')

You can also supply the special name :memory: to create a database in RAM.

Once you have a Connection, you can create a Cursor object and call its execute() method to perform SQL commands:

c = conn.cursor()

# Create table
c.execute('''create table stocks
(date text, trans text, symbol text,
 qty real, price real)''')

# Insert a row of data
c.execute("""insert into stocks
          values ('2006-01-05','BUY','RHAT',100,35.14)""")

Usually your SQL operations will need to use values from Python variables. You shouldn't assemble your query using Python's string operations because doing so is insecure; it makes your program vulnerable to an SQL injection attack.

Instead, use the DB-API's parameter substitution. Put ? as a placeholder wherever you want to use a value, and then provide a tuple of values as the second argument to the cursor's execute() method. (Other database modules may use a different placeholder, such as %s or :1.) For example:

# Never do this -- insecure!
symbol = 'IBM'
c.execute("... where symbol = '%s'" % symbol)

# Do this instead
t = (symbol,)
c.execute('select * from stocks where symbol=?', t)

# Larger example
for t in (('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
          ('2006-04-05', 'BUY', 'MSOFT', 1000, 72.00),
          ('2006-04-06', 'SELL', 'IBM', 500, 53.00),
         ):
    c.execute('insert into stocks values (?,?,?,?,?)', t)

To retrieve data after executing a SELECT statement, you can either treat the cursor as an iterator, call the cursor's fetchone() method to retrieve a single matching row, or call fetchall() to get a list of the matching rows.

This example uses the iterator form:

>>> c = conn.cursor()
>>> c.execute('select * from stocks order by price')
>>> for row in c:
...    print row
...
(u'2006-01-05', u'BUY', u'RHAT', 100, 35.140000000000001)
(u'2006-03-28', u'BUY', u'IBM', 1000, 45.0)
(u'2006-04-06', u'SELL', u'IBM', 500, 53.0)
(u'2006-04-05', u'BUY', u'MSOFT', 1000, 72.0)
>>>

For more information about the SQL dialect supported by SQLite, see https://www.sqlite.org.

也參考

https://www.pysqlite.org

pysqlite 網頁。

https://www.sqlite.org

The SQLite web page; the documentation describes the syntax and the available data types for the supported SQL dialect.

sqlite3 模組的文件。

PEP 249 [https://peps.python.org/pep-0249/] - 資料庫 API 規範 2.0

由 Marc-André Lemburg 撰寫 PEP。

wsgiref 套件

The Web Server Gateway Interface (WSGI) v1.0 defines a standard interface between web servers and Python web applications and is described in PEP 333 [https://peps.python.org/pep-0333/]. The wsgiref package is a reference implementation of the WSGI specification.

The package includes a basic HTTP server that will run a WSGI application; this server is useful for debugging but isn't intended for production use. Setting up a server takes only a few lines of code:

from wsgiref import simple_server

wsgi_app = ...

host = ''
port = 8000
httpd = simple_server.make_server(host, port, wsgi_app)
httpd.serve_forever()

也參考

https://web.archive.org/web/20160331090247/http://wsgi.readthedocs.org/en/latest/

A central web site for WSGI-related resources.

PEP 333 [https://peps.python.org/pep-0333/] - Python 網頁伺服器閘道介面 v1.0

由 Phillip J. Eby 撰寫 PEP。

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

The Python source tree was converted from CVS to Subversion, in a complex migration procedure that was supervised and flawlessly carried out by Martin von Löwis. The procedure was developed as PEP 347 [https://peps.python.org/pep-0347/].

Coverity, a company that markets a source code analysis tool called Prevent, provided the results of their examination of the Python source code. The analysis found about 60 bugs that were quickly fixed. Many of the bugs were refcounting problems, often occurring in error-handling code. See https://scan.coverity.com for the statistics.

The largest change to the C API came from PEP 353 [https://peps.python.org/pep-0353/], which modifies the interpreter to use a Py_ssize_t type definition instead of int. See the earlier section PEP 353: Using ssize_t as the index type for a discussion of this change.

The design of the bytecode compiler has changed a great deal, no longer generating bytecode by traversing the parse tree. Instead the parse tree is converted to an abstract syntax tree (or AST), and it is the abstract syntax tree that's traversed to produce the bytecode.

It's possible for Python code to obtain AST objects by using the compile() built-in and specifying _ast.PyCF_ONLY_AST as the value of the flags parameter:

from _ast import PyCF_ONLY_AST
ast = compile("""a=0
for i in range(10):
    a += i
""", "<string>", 'exec', PyCF_ONLY_AST)

assignment = ast.body[0]
for_loop = ast.body[1]

No official documentation has been written for the AST code yet, but PEP 339 [https://peps.python.org/pep-0339/] discusses the design. To start learning about the code, read the definition of the various AST nodes in Parser/Python.asdl. A Python script reads this file and generates a set of C structure definitions in Include/Python-ast.h. The PyParser_ASTFromString() and PyParser_ASTFromFile(), defined in Include/pythonrun.h, take Python source as input and return the root of an AST representing the contents. This AST can then be turned into a code object by PyAST_Compile(). For more information, read the source code, and then ask questions on python-dev.

The AST code was developed under Jeremy Hylton's management, and implemented by (in alphabetical order) Brett Cannon, Nick Coghlan, Grant Edwards, John Ehresman, Kurt Kaiser, Neal Norwitz, Tim Peters, Armin Rigo, and Neil Schemenauer, plus the participants in a number of AST sprints at conferences such as PyCon.

Evan Jones's patch to obmalloc, first described in a talk at PyCon DC 2005, was applied. Python 2.4 allocated small objects in 256K-sized arenas, but never freed arenas. With this patch, Python will free arenas when they're empty. The net effect is that on some platforms, when you allocate many objects, Python's memory usage may actually drop when you delete them and the memory may be returned to the operating system. (Implemented by Evan Jones, and reworked by Tim Peters.)

Note that this change means extension modules must be more careful when allocating memory. Python's API has many different functions for allocating memory that are grouped into families. For example, PyMem_Malloc(), PyMem_Realloc(), and PyMem_Free() are one family that allocates raw memory, while PyObject_Malloc(), PyObject_Realloc(), and PyObject_Free() are another family that's supposed to be used for creating Python objects.

Previously these different families all reduced to the platform's malloc() and free() functions. This meant it didn't matter if you got things wrong and allocated memory with the PyMem function but freed it with the PyObject function. With 2.5's changes to obmalloc, these families now do different things and mismatches will probably result in a segfault. You should carefully test your C extension modules with Python 2.5.

The built-in set types now have an official C API. Call PySet_New() and PyFrozenSet_New() to create a new set, PySet_Add() and PySet_Discard() to add and remove elements, and PySet_Contains() and PySet_Size() to examine the set's state. (Contributed by Raymond Hettinger.)

C code can now obtain information about the exact revision of the Python interpreter by calling the Py_GetBuildInfo() function that returns a string of build information like this: "trunk:45355:45356M, Apr 13 2006, 07:42:19". (Contributed by Barry Warsaw.)

Two new macros can be used to indicate C functions that are local to the current file so that a faster calling convention can be used. Py_LOCAL declares the function as returning a value of the specified type and uses a fast-calling qualifier. Py_LOCAL_INLINE does the same thing and also requests the function be inlined. If macro PY_LOCAL_AGGRESSIVE is defined before python.h is included, a set of more aggressive optimizations are enabled for the module; you should benchmark the results to find out if these optimizations actually make the code faster. (Contributed by Fredrik Lundh at the NeedForSpeed sprint.)

PyErr_NewException(name, base, dict) can now accept a tuple of base classes as its base argument. (Contributed by Georg Brandl.)

The PyErr_Warn() function for issuing warnings is now deprecated in favour of PyErr_WarnEx(category, message, stacklevel) which lets you specify the number of stack frames separating this function and the caller. A stacklevel of 1 is the function calling PyErr_WarnEx(), 2 is the function above that, and so forth. (Added by Neal Norwitz.)

The CPython interpreter is still written in C, but the code can now be compiled with a C++ compiler without errors. (Implemented by Anthony Baxter, Martin von Löwis, Skip Montanaro.)

The PyRange_New() function was removed. It was never documented, never used in the core code, and had dangerously lax error checking. In the unlikely case that your extensions were using it, you can replace it by something like the following:

range = PyObject_CallFunction((PyObject*) &PyRange_Type, "lll",
                              start, stop, step);

Port-Specific Changes

MacOS X (10.3 and higher): dynamic loading of modules now uses the dlopen() function instead of MacOS-specific functions.

MacOS X: an --enable-universalsdk switch was added to the configure script that compiles the interpreter as a universal binary able to run on both PowerPC and Intel processors. (Contributed by Ronald Oussoren; bpo-2573 [https://bugs.python.org/issue?@action=redirect&bpo=2573].)

Windows: .dll is no longer supported as a filename extension for extension modules. .pyd is now the only filename extension that will be searched for.

Porting to Python 2.5

This section lists previously described changes that may require changes to your code:

ASCII is now the default encoding for modules. It's now a syntax error if a module contains string literals with 8-bit characters but doesn't have an encoding declaration. In Python 2.4 this triggered a warning, not a syntax error.

Previously, the gi_frame attribute of a generator was always a frame object. Because of the PEP 342 [https://peps.python.org/pep-0342/] changes described in section PEP 342: New Generator Features, it's now possible for gi_frame to be None.

A new warning, UnicodeWarning, is triggered when you attempt to compare a Unicode string and an 8-bit string that can't be converted to Unicode using the default ASCII encoding. Previously such comparisons would raise a UnicodeDecodeError exception.

Library: the csv module is now stricter about multi-line quoted fields. If your files contain newlines embedded within fields, the input should be split into lines in a manner which preserves the newline characters.

Library: the locale module's format() function's would previously accept any string as long as no more than one %char specifier appeared. In Python 2.5, the argument must be exactly one %char specifier with no surrounding text.

Library: The pickle and cPickle modules no longer accept a return value of None from the __reduce__() method; the method must return a tuple of arguments instead. The modules also no longer accept the deprecated bin keyword parameter.

Library: The SimpleXMLRPCServer and DocXMLRPCServer classes now have a rpc_paths attribute that constrains XML-RPC operations to a limited set of URL paths; the default is to allow only '/' and '/RPC2'. Setting rpc_paths to None or an empty tuple disables this path checking.

C API: Many functions now use Py_ssize_t instead of int to allow processing more data on 64-bit machines. Extension code may need to make the same change to avoid warnings and to support 64-bit machines. See the earlier section PEP 353: Using ssize_t as the index type for a discussion of this change.

C API: The obmalloc changes mean that you must be careful to not mix usage of the PyMem_* and PyObject_* families of functions. Memory allocated with one family's *_Malloc must be freed with the corresponding family's *_Free function.

致謝

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Georg Brandl, Nick Coghlan, Phillip J. Eby, Lars Gustäbel, Raymond Hettinger, Ralf W. Grosse-Kunstleve, Kent Johnson, Iain Lowe, Martin von Löwis, Fredrik Lundh, Andrew McNamara, Skip Montanaro, Gustavo Niemeyer, Paul Prescod, James Pryor, Mike Rovner, Scott Weikart, Barry Warsaw, Thomas Wouters.

Python 2.4 有什麼新功能

作者:

A.M. Kuchling

This article explains the new features in Python 2.4.1, released on March 30, 2005.

Python 2.4 is a medium-sized release. It doesn't introduce as many changes as the radical Python 2.2, but introduces more features than the conservative 2.3 release. The most significant new language features are function decorators and generator expressions; most other changes are to the standard library.

According to the CVS change logs, there were 481 patches applied and 502 bugs fixed between Python 2.3 and 2.4. Both figures are likely to be underestimates.

This article doesn't attempt to provide a complete specification of every single new feature, but instead provides a brief introduction to each feature. For full details, you should refer to the documentation for Python 2.4, such as the Python Library Reference and the Python Reference Manual. Often you will be referred to the PEP for a particular new feature for explanations of the implementation and design rationale.

PEP 218: Built-In Set Objects

Python 2.3 introduced the sets module. C implementations of set data types have now been added to the Python core as two new built-in types, set(iterable) and frozenset(iterable). They provide high speed operations for membership testing, for eliminating duplicates from sequences, and for mathematical operations like unions, intersections, differences, and symmetric differences.

>>> a = set('abracadabra')              # form a set from a string
>>> 'z' in a                            # fast membership testing
False
>>> a                                   # unique letters in a
set(['a', 'r', 'b', 'c', 'd'])
>>> ''.join(a)                          # convert back into a string
'arbcd'

>>> b = set('alacazam')                 # form a second set
>>> a - b                               # letters in a but not in b
set(['r', 'd', 'b'])
>>> a | b                               # letters in either a or b
set(['a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'])
>>> a & b                               # letters in both a and b
set(['a', 'c'])
>>> a ^ b                               # letters in a or b but not both
set(['r', 'd', 'b', 'm', 'z', 'l'])

>>> a.add('z')                          # add a new element
>>> a.update('wxy')                     # add multiple new elements
>>> a
set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'x', 'z'])
>>> a.remove('x')                       # take one element out
>>> a
set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'z'])

The frozenset() type is an immutable version of set(). Since it is immutable and hashable, it may be used as a dictionary key or as a member of another set.

The sets module remains in the standard library, and may be useful if you wish to subclass the Set or ImmutableSet classes. There are currently no plans to deprecate the module.

也參考

PEP 218 [https://peps.python.org/pep-0218/] - Adding a Built-In Set Object Type

最初由 Greg Wilson 提出，最終由 Raymond Hettinger 實作。

PEP 237: Unifying Long Integers and Integers

The lengthy transition process for this PEP, begun in Python 2.2, takes another step forward in Python 2.4. In 2.3, certain integer operations that would behave differently after int/long unification triggered FutureWarning warnings and returned values limited to 32 or 64 bits (depending on your platform). In 2.4, these expressions no longer produce a warning and instead produce a different result that's usually a long integer.

The problematic expressions are primarily left shifts and lengthy hexadecimal and octal constants. For example, 2 << 32 results in a warning in 2.3, evaluating to 0 on 32-bit platforms. In Python 2.4, this expression now returns the correct answer, 8589934592.

也參考

PEP 237 [https://peps.python.org/pep-0237/] - Unifying Long Integers and Integers

原始的 PEP 由 Moshe Zadka 和 GvR 撰寫。2.4 的變更由 Kalle Svensson 實作。

PEP 289：產生器運算式

The iterator feature introduced in Python 2.2 and the itertools module make it easier to write programs that loop through large data sets without having the entire data set in memory at one time. List comprehensions don't fit into this picture very well because they produce a Python list object containing all of the items. This unavoidably pulls all of the objects into memory, which can be a problem if your data set is very large. When trying to write a functionally styled program, it would be natural to write something like:

links = [link for link in get_all_links() if not link.followed]
for link in links:
    ...

instead of

for link in get_all_links():
    if link.followed:
        continue
    ...

The first form is more concise and perhaps more readable, but if you're dealing with a large number of link objects you'd have to write the second form to avoid having all link objects in memory at the same time.

Generator expressions work similarly to list comprehensions but don't materialize the entire list; instead they create a generator that will return elements one by one. The above example could be written as:

links = (link for link in get_all_links() if not link.followed)
for link in links:
    ...

Generator expressions always have to be written inside parentheses, as in the above example. The parentheses signalling a function call also count, so if you want to create an iterator that will be immediately passed to a function you could write:

print sum(obj.count for obj in list_all_objects())

Generator expressions differ from list comprehensions in various small ways. Most notably, the loop variable (obj in the above example) is not accessible outside of the generator expression. List comprehensions leave the variable assigned to its last value; future versions of Python will change this, making list comprehensions match generator expressions in this respect.

也參考

PEP 289 [https://peps.python.org/pep-0289/] - 產生器運算式

由 Raymond Hettinger 提出，Jiwon Seo 實作，早期工作由 Hye-Shik Chang 指導。

PEP 292: Simpler String Substitutions

Some new classes in the standard library provide an alternative mechanism for substituting variables into strings; this style of substitution may be better for applications where untrained users need to edit templates.

The usual way of substituting variables by name is the % operator:

>>> '%(page)i: %(title)s' % {'page':2, 'title': 'The Best of Times'}
'2: The Best of Times'

When writing the template string, it can be easy to forget the i or s after the closing parenthesis. This isn't a big problem if the template is in a Python module, because you run the code, get an "Unsupported format character" ValueError, and fix the problem. However, consider an application such as Mailman where template strings or translations are being edited by users who aren't aware of the Python language. The format string's syntax is complicated to explain to such users, and if they make a mistake, it's difficult to provide helpful feedback to them.

PEP 292 adds a Template class to the string module that uses $ to indicate a substitution:

>>> import string
>>> t = string.Template('$page: $title')
>>> t.substitute({'page':2, 'title': 'The Best of Times'})
'2: The Best of Times'

If a key is missing from the dictionary, the substitute() method will raise a KeyError. There's also a safe_substitute() method that ignores missing keys:

>>> t = string.Template('$page: $title')
>>> t.safe_substitute({'page':3})
'3: $title'

也參考

PEP 292 [https://peps.python.org/pep-0292/] - Simpler String Substitutions

由 Barry Warsaw 撰寫與實作。

PEP 318: Decorators for Functions and Methods

Python 2.2 extended Python's object model by adding static methods and class methods, but it didn't extend Python's syntax to provide any new way of defining static or class methods. Instead, you had to write a def statement in the usual way, and pass the resulting method to a staticmethod() or classmethod() function that would wrap up the function as a method of the new type. Your code would look like this:

class C:
   def meth (cls):
       ...

   meth = classmethod(meth)   # Rebind name to wrapped-up class method

If the method was very long, it would be easy to miss or forget the classmethod() invocation after the function body.

The intention was always to add some syntax to make such definitions more readable, but at the time of 2.2's release a good syntax was not obvious. Today a good syntax still isn't obvious but users are asking for easier access to the feature; a new syntactic feature has been added to meet this need.

The new feature is called "function decorators". The name comes from the idea that classmethod(), staticmethod(), and friends are storing additional information on a function object; they're decorating functions with more details.

The notation borrows from Java and uses the '@' character as an indicator. Using the new syntax, the example above would be written:

class C:

   @classmethod
   def meth (cls):
       ...

The @classmethod is shorthand for the meth=classmethod(meth) assignment. More generally, if you have the following:

@A
@B
@C
def f ():
    ...

It's equivalent to the following pre-decorator code:

def f(): ...
f = A(B(C(f)))

Decorators must come on the line before a function definition, one decorator per line, and can't be on the same line as the def statement, meaning that @A def f(): ... is illegal. You can only decorate function definitions, either at the module level or inside a class; you can't decorate class definitions.

A decorator is just a function that takes the function to be decorated as an argument and returns either the same function or some new object. The return value of the decorator need not be callable (though it typically is), unless further decorators will be applied to the result. It's easy to write your own decorators. The following simple example just sets an attribute on the function object:

>>> def deco(func):
...    func.attr = 'decorated'
...    return func
...
>>> @deco
... def f(): pass
...
>>> f
<function f at 0x402ef0d4>
>>> f.attr
'decorated'
>>>

As a slightly more realistic example, the following decorator checks that the supplied argument is an integer:

def require_int (func):
    def wrapper (arg):
        assert isinstance(arg, int)
        return func(arg)

    return wrapper

@require_int
def p1 (arg):
    print arg

@require_int
def p2(arg):
    print arg*2

An example in PEP 318 [https://peps.python.org/pep-0318/] contains a fancier version of this idea that lets you both specify the required type and check the returned type.

Decorator functions can take arguments. If arguments are supplied, your decorator function is called with only those arguments and must return a new decorator function; this function must take a single function and return a function, as previously described. In other words, @A @B @C(args) becomes:

def f(): ...
_deco = C(args)
f = A(B(_deco(f)))

Getting this right can be slightly brain-bending, but it's not too difficult.

A small related change makes the func_name attribute of functions writable. This attribute is used to display function names in tracebacks, so decorators should change the name of any new function that's constructed and returned.

也參考

PEP 318 [https://peps.python.org/pep-0318/] - Decorators for Functions, Methods and Classes

Written by Kevin D. Smith, Jim Jewett, and Skip Montanaro. Several people wrote patches implementing function decorators, but the one that was actually checked in was patch #979728, written by Mark Russell.

https://wiki.python.org/moin/PythonDecoratorLibrary

This Wiki page contains several examples of decorators.

PEP 322: Reverse Iteration

A new built-in function, reversed(seq), takes a sequence and returns an iterator that loops over the elements of the sequence in reverse order.

>>> for i in reversed(xrange(1,4)):
...    print i
...
3
2
1

Compared to extended slicing, such as range(1,4)[::-1], reversed() is easier to read, runs faster, and uses substantially less memory.

Note that reversed() only accepts sequences, not arbitrary iterators. If you want to reverse an iterator, first convert it to a list with list().

>>> input = open('/etc/passwd', 'r')
>>> for line in reversed(list(input)):
...   print line
...
root:*:0:0:System Administrator:/var/root:/bin/tcsh
  ...

也參考

PEP 322 [https://peps.python.org/pep-0322/] - Reverse Iteration

由 Raymond Hettinger 撰寫與實作。

PEP 324: New subprocess Module

The standard library provides a number of ways to execute a subprocess, offering different features and different levels of complexity. os.system(command) is easy to use, but slow (it runs a shell process which executes the command) and dangerous (you have to be careful about escaping the shell's metacharacters). The popen2 module offers classes that can capture standard output and standard error from the subprocess, but the naming is confusing. The subprocess module cleans this up, providing a unified interface that offers all the features you might need.

Instead of popen2's collection of classes, subprocess contains a single class called subprocess.Popen whose constructor supports a number of different keyword arguments.

class Popen(args, bufsize=0, executable=None,
            stdin=None, stdout=None, stderr=None,
            preexec_fn=None, close_fds=False, shell=False,
            cwd=None, env=None, universal_newlines=False,
            startupinfo=None, creationflags=0):

args is commonly a sequence of strings that will be the arguments to the program executed as the subprocess. (If the shell argument is true, args can be a string which will then be passed on to the shell for interpretation, just as os.system() does.)

stdin, stdout, and stderr specify what the subprocess's input, output, and error streams will be. You can provide a file object or a file descriptor, or you can use the constant subprocess.PIPE to create a pipe between the subprocess and the parent.

The constructor has a number of handy options:

close_fds requests that all file descriptors be closed before running the subprocess.

cwd specifies the working directory in which the subprocess will be executed (defaulting to whatever the parent's working directory is).

env is a dictionary specifying environment variables.

preexec_fn is a function that gets called before the child is started.

universal_newlines opens the child's input and output using Python's universal newlines feature.

Once you've created the Popen instance, you can call its wait() method to pause until the subprocess has exited, poll() to check if it's exited without pausing, or communicate(data) to send the string data to the subprocess's standard input. communicate(data) then reads any data that the subprocess has sent to its standard output or standard error, returning a tuple (stdout_data, stderr_data).

call() is a shortcut that passes its arguments along to the Popen constructor, waits for the command to complete, and returns the status code of the subprocess. It can serve as a safer analog to os.system():

sts = subprocess.call(['dpkg', '-i', '/tmp/new-package.deb'])
if sts == 0:
    # 成功
    ...
else:
    # dpkg 回傳一個錯誤
    ...

The command is invoked without use of the shell. If you really do want to use the shell, you can add shell=True as a keyword argument and provide a string instead of a sequence:

sts = subprocess.call('dpkg -i /tmp/new-package.deb', shell=True)

The PEP takes various examples of shell and Python code and shows how they'd be translated into Python code that uses subprocess. Reading this section of the PEP is highly recommended.

也參考

PEP 324 [https://peps.python.org/pep-0324/] - subprocess - 新的行程模組

由 Peter Åstrand 撰寫與實作，並由 Fredrik Lundh 和其他人協助。

PEP 327：Decimal 資料型別

Python has always supported floating-point (FP) numbers, based on the underlying C double type, as a data type. However, while most programming languages provide a floating-point type, many people (even programmers) are unaware that floating-point numbers don't represent certain decimal fractions accurately. The new Decimal type can represent these fractions accurately, up to a user-specified precision limit.

為什麼需要 Decimal？

The limitations arise from the representation used for floating-point numbers. FP numbers are made up of three components:

The sign, which is positive or negative.

The mantissa, which is a single-digit binary number followed by a fractional part. For example, 1.01 in base-2 notation is 1 + 0/2 + 1/4, or 1.25 in decimal notation.

The exponent, which tells where the decimal point is located in the number represented.

For example, the number 1.25 has positive sign, a mantissa value of 1.01 (in binary), and an exponent of 0 (the decimal point doesn't need to be shifted). The number 5 has the same sign and mantissa, but the exponent is 2 because the mantissa is multiplied by 4 (2 to the power of the exponent 2); 1.25 * 4 equals 5.

Modern systems usually provide floating-point support that conforms to a standard called IEEE 754. C's double type is usually implemented as a 64-bit IEEE 754 number, which uses 52 bits of space for the mantissa. This means that numbers can only be specified to 52 bits of precision. If you're trying to represent numbers whose expansion repeats endlessly, the expansion is cut off after 52 bits. Unfortunately, most software needs to produce output in base 10, and common fractions in base 10 are often repeating decimals in binary. For example, 1.1 decimal is binary 1.0001100110011 ...; .1 = 1/16 + 1/32 + 1/256 plus an infinite number of additional terms. IEEE 754 has to chop off that infinitely repeated decimal after 52 digits, so the representation is slightly inaccurate.

Sometimes you can see this inaccuracy when the number is printed:

>>> 1.1
1.1000000000000001

The inaccuracy isn't always visible when you print the number because the FP-to-decimal-string conversion is provided by the C library, and most C libraries try to produce sensible output. Even if it's not displayed, however, the inaccuracy is still there and subsequent operations can magnify the error.

For many applications this doesn't matter. If I'm plotting points and displaying them on my monitor, the difference between 1.1 and 1.1000000000000001 is too small to be visible. Reports often limit output to a certain number of decimal places, and if you round the number to two or three or even eight decimal places, the error is never apparent. However, for applications where it does matter, it's a lot of work to implement your own custom arithmetic routines.

Hence, the Decimal type was created.

Decimal 型別

A new module, decimal, was added to Python's standard library. It contains two classes, Decimal and Context. Decimal instances represent numbers, and Context instances are used to wrap up various settings such as the precision and default rounding mode.

Decimal instances are immutable, like regular Python integers and FP numbers; once it's been created, you can't change the value an instance represents. Decimal instances can be created from integers or strings:

>>> import decimal
>>> decimal.Decimal(1972)
Decimal("1972")
>>> decimal.Decimal("1.1")
Decimal("1.1")

You can also provide tuples containing the sign, the mantissa represented as a tuple of decimal digits, and the exponent:

>>> decimal.Decimal((1, (1, 4, 7, 5), -2))
Decimal("-14.75")

Cautionary note: the sign bit is a Boolean value, so 0 is positive and 1 is negative.

Converting from floating-point numbers poses a bit of a problem: should the FP number representing 1.1 turn into the decimal number for exactly 1.1, or for 1.1 plus whatever inaccuracies are introduced? The decision was to dodge the issue and leave such a conversion out of the API. Instead, you should convert the floating-point number into a string using the desired precision and pass the string to the Decimal constructor:

>>> f = 1.1
>>> decimal.Decimal(str(f))
Decimal("1.1")
>>> decimal.Decimal('%.12f' % f)
Decimal("1.100000000000")

Once you have Decimal instances, you can perform the usual mathematical operations on them. One limitation: exponentiation requires an integer exponent:

>>> a = decimal.Decimal('35.72')
>>> b = decimal.Decimal('1.73')
>>> a+b
Decimal("37.45")
>>> a-b
Decimal("33.99")
>>> a*b
Decimal("61.7956")
>>> a/b
Decimal("20.64739884393063583815028902")
>>> a ** 2
Decimal("1275.9184")
>>> a**b
Traceback (most recent call last):
  ...
decimal.InvalidOperation: x ** (non-integer)

You can combine Decimal instances with integers, but not with floating-point numbers:

>>> a + 4
Decimal("39.72")
>>> a + 4.5
Traceback (most recent call last):
  ...
TypeError: You can interact Decimal only with int, long or Decimal data types.
>>>

Decimal numbers can be used with the math and cmath modules, but note that they'll be immediately converted to floating-point numbers before the operation is performed, resulting in a possible loss of precision and accuracy. You'll also get back a regular floating-point number and not a Decimal.

>>> import math, cmath
>>> d = decimal.Decimal('123456789012.345')
>>> math.sqrt(d)
351364.18288201344
>>> cmath.sqrt(-d)
351364.18288201344j

Decimal instances have a sqrt() method that returns a Decimal, but if you need other things such as trigonometric functions you'll have to implement them.

>>> d.sqrt()
Decimal("351364.1828820134592177245001")

Context 型別

Instances of the Context class encapsulate several settings for decimal operations:

prec is the precision, the number of decimal places.

rounding specifies the rounding mode. The decimal module has constants for the various possibilities: ROUND_DOWN, ROUND_CEILING, ROUND_HALF_EVEN, and various others.

traps is a dictionary specifying what happens on encountering certain error conditions: either an exception is raised or a value is returned. Some examples of error conditions are division by zero, loss of precision, and overflow.

There's a thread-local default context available by calling getcontext(); you can change the properties of this context to alter the default precision, rounding, or trap handling. The following example shows the effect of changing the precision of the default context:

>>> decimal.getcontext().prec
28
>>> decimal.Decimal(1) / decimal.Decimal(7)
Decimal("0.1428571428571428571428571429")
>>> decimal.getcontext().prec = 9
>>> decimal.Decimal(1) / decimal.Decimal(7)
Decimal("0.142857143")

The default action for error conditions is selectable; the module can either return a special value such as infinity or not-a-number, or exceptions can be raised:

>>> decimal.Decimal(1) / decimal.Decimal(0)
Traceback (most recent call last):
  ...
decimal.DivisionByZero: x / 0
>>> decimal.getcontext().traps[decimal.DivisionByZero] = False
>>> decimal.Decimal(1) / decimal.Decimal(0)
Decimal("Infinity")
>>>

The Context instance also has various methods for formatting numbers such as to_eng_string() and to_sci_string().

For more information, see the documentation for the decimal module, which includes a quick-start tutorial and a reference.

也參考

PEP 327 [https://peps.python.org/pep-0327/] - Decimal Data Type

由 Facundo Batista 撰寫，並由 Facundo Batista、Eric Price、Raymond Hettinger、Aahz 和 Tim Peters 實作。

http://www.lahey.com/float.htm [https://web.archive.org/web/20230604072523/http://www.lahey.com/float.htm]

The article uses Fortran code to illustrate many of the problems that floating-point inaccuracy can cause.

https://speleotrove.com/decimal/

A description of a decimal-based representation. This representation is being proposed as a standard, and underlies the new Python decimal type. Much of this material was written by Mike Cowlishaw, designer of the Rexx language.

PEP 328: Multi-line Imports

One language change is a small syntactic tweak aimed at making it easier to import many names from a module. In a from module import names statement, names is a sequence of names separated by commas. If the sequence is very long, you can either write multiple imports from the same module, or you can use backslashes to escape the line endings like this:

from SimpleXMLRPCServer import SimpleXMLRPCServer,\
            SimpleXMLRPCRequestHandler,\
            CGIXMLRPCRequestHandler,\
            resolve_dotted_attribute

The syntactic change in Python 2.4 simply allows putting the names within parentheses. Python ignores newlines within a parenthesized expression, so the backslashes are no longer needed:

from SimpleXMLRPCServer import (SimpleXMLRPCServer,
                                SimpleXMLRPCRequestHandler,
                                CGIXMLRPCRequestHandler,
                                resolve_dotted_attribute)

The PEP also proposes that all import statements be absolute imports, with a leading . character to indicate a relative import. This part of the PEP was not implemented for Python 2.4, but was completed for Python 2.5.

也參考

PEP 328 [https://peps.python.org/pep-0328/] - Imports: Multi-Line and Absolute/Relative

由 Aahz 撰寫。多行引入由 Dima Dorfman 實作。

PEP 331: Locale-Independent Float/String Conversions

The locale modules lets Python software select various conversions and display conventions that are localized to a particular country or language. However, the module was careful to not change the numeric locale because various functions in Python's implementation required that the numeric locale remain set to the 'C' locale. Often this was because the code was using the C library's atof() function.

Not setting the numeric locale caused trouble for extensions that used third-party C libraries, however, because they wouldn't have the correct locale set. The motivating example was GTK+, whose user interface widgets weren't displaying numbers in the current locale.

The solution described in the PEP is to add three new functions to the Python API that perform ASCII-only conversions, ignoring the locale setting:

PyOS_ascii_strtod(str, ptr) and PyOS_ascii_atof(str, ptr) both convert a string to a C double.

PyOS_ascii_formatd(buffer, buf_len, format, d) converts a double to an ASCII string.

The code for these functions came from the GLib library (https://developer-old.gnome.org/glib/2.26/ [http://web.archive.org/web/20210306104320/https://developer.gnome.org/glib/2.26/]), whose developers kindly relicensed the relevant functions and donated them to the Python Software Foundation. The locale module can now change the numeric locale, letting extensions such as GTK+ produce the correct results.

也參考

PEP 331 [https://peps.python.org/pep-0331/] - Locale-Independent Float/String Conversions

由 Christian R. Reis 撰寫，並由 Gustavo Carneiro 實作。

其他語言更動

Here are all of the changes that Python 2.4 makes to the core Python language.

Decorators for functions and methods were added (PEP 318 [https://peps.python.org/pep-0318/]).

Built-in set() and frozenset() types were added (PEP 218 [https://peps.python.org/pep-0218/]). Other new built-ins include the reversed(seq) function (PEP 322 [https://peps.python.org/pep-0322/]).

Generator expressions were added (PEP 289 [https://peps.python.org/pep-0289/]).

Certain numeric expressions no longer return values restricted to 32 or 64 bits (PEP 237 [https://peps.python.org/pep-0237/]).

You can now put parentheses around the list of names in a from module import names statement (PEP 328 [https://peps.python.org/pep-0328/]).

The dict.update() method now accepts the same argument forms as the dict constructor. This includes any mapping, any iterable of key/value pairs, and keyword arguments. (Contributed by Raymond Hettinger.)

The string methods ljust(), rjust(), and center() now take an optional argument for specifying a fill character other than a space. (Contributed by Raymond Hettinger.)

Strings also gained an rsplit() method that works like the split() method but splits from the end of the string. (Contributed by Sean Reifschneider.)

>>> 'www.python.org'.split('.', 1)
['www', 'python.org']
'www.python.org'.rsplit('.', 1)
['www.python', 'org']

Three keyword parameters, cmp, key, and reverse, were added to the sort() method of lists. These parameters make some common usages of sort() simpler. All of these parameters are optional.

For the cmp parameter, the value should be a comparison function that takes two parameters and returns -1, 0, or +1 depending on how the parameters compare. This function will then be used to sort the list. Previously this was the only parameter that could be provided to sort().

key should be a single-parameter function that takes a list element and returns a comparison key for the element. The list is then sorted using the comparison keys. The following example sorts a list case-insensitively:

>>> L = ['A', 'b', 'c', 'D']
>>> L.sort()                 # Case-sensitive sort
>>> L
['A', 'D', 'b', 'c']
>>> # Using 'key' parameter to sort list
>>> L.sort(key=lambda x: x.lower())
>>> L
['A', 'b', 'c', 'D']
>>> # Old-fashioned way
>>> L.sort(cmp=lambda x,y: cmp(x.lower(), y.lower()))
>>> L
['A', 'b', 'c', 'D']

The last example, which uses the cmp parameter, is the old way to perform a case-insensitive sort. It works but is slower than using a key parameter. Using key calls lower() method once for each element in the list while using cmp will call it twice for each comparison, so using key saves on invocations of the lower() method.

For simple key functions and comparison functions, it is often possible to avoid a lambda expression by using an unbound method instead. For example, the above case-insensitive sort is best written as:

>>> L.sort(key=str.lower)
>>> L
['A', 'b', 'c', 'D']

Finally, the reverse parameter takes a Boolean value. If the value is true, the list will be sorted into reverse order. Instead of L.sort(); L.reverse(), you can now write L.sort(reverse=True).

The results of sorting are now guaranteed to be stable. This means that two entries with equal keys will be returned in the same order as they were input. For example, you can sort a list of people by name, and then sort the list by age, resulting in a list sorted by age where people with the same age are in name-sorted order.

(All changes to sort() contributed by Raymond Hettinger.)

There is a new built-in function sorted(iterable) that works like the in-place list.sort() method but can be used in expressions. The differences are:

the input may be any iterable;

a newly formed copy is sorted, leaving the original intact; and

the expression returns the new sorted copy

>>> L = [9,7,8,3,2,4,1,6,5]
>>> [10+i for i in sorted(L)]       # usable in a list comprehension
[11, 12, 13, 14, 15, 16, 17, 18, 19]
>>> L                               # original is left unchanged
[9,7,8,3,2,4,1,6,5]
>>> sorted('Monty Python')          # any iterable may be an input
[' ', 'M', 'P', 'h', 'n', 'n', 'o', 'o', 't', 't', 'y', 'y']

>>> # List the contents of a dict sorted by key values
>>> colormap = dict(red=1, blue=2, green=3, black=4, yellow=5)
>>> for k, v in sorted(colormap.iteritems()):
...     print k, v
...
black 4
blue 2
green 3
red 1
yellow 5

（由 Raymond Hettinger 所貢獻。）

Integer operations will no longer trigger an OverflowWarning. The OverflowWarning warning will disappear in Python 2.5.

The interpreter gained a new switch, -m, that takes a name, searches for the corresponding module on sys.path, and runs the module as a script. For example, you can now run the Python profiler with python -m profile. (Contributed by Nick Coghlan.)

The eval(expr, globals, locals) and execfile(filename, globals, locals) functions and the exec statement now accept any mapping type for the locals parameter. Previously this had to be a regular Python dictionary. (Contributed by Raymond Hettinger.)

The zip() built-in function and itertools.izip() now return an empty list if called with no arguments. Previously they raised a TypeError exception. This makes them more suitable for use with variable length argument lists:

>>> def transpose(array):
...    return zip(*array)
...
>>> transpose([(1,2,3), (4,5,6)])
[(1, 4), (2, 5), (3, 6)]
>>> transpose([])
[]

（由 Raymond Hettinger 所貢獻。）

Encountering a failure while importing a module no longer leaves a partially initialized module object in sys.modules. The incomplete module object left behind would fool further imports of the same module into succeeding, leading to confusing errors. (Fixed by Tim Peters.)

None is now a constant; code that binds a new value to the name None is now a syntax error. (Contributed by Raymond Hettinger.)

最佳化

The inner loops for list and tuple slicing were optimized and now run about one-third faster. The inner loops for dictionaries were also optimized, resulting in performance boosts for keys(), values(), items(), iterkeys(), itervalues(), and iteritems(). (Contributed by Raymond Hettinger.)

The machinery for growing and shrinking lists was optimized for speed and for space efficiency. Appending and popping from lists now runs faster due to more efficient code paths and less frequent use of the underlying system realloc(). List comprehensions also benefit. list.extend() was also optimized and no longer converts its argument into a temporary list before extending the base list. (Contributed by Raymond Hettinger.)

list(), tuple(), map(), filter(), and zip() now run several times faster with non-sequence arguments that supply a __len__() method. (Contributed by Raymond Hettinger.)

The methods list.__getitem__(), dict.__getitem__(), and dict.__contains__() are now implemented as method_descriptor objects rather than wrapper_descriptor objects. This form of access doubles their performance and makes them more suitable for use as arguments to functionals: map(mydict.__getitem__, keylist). (Contributed by Raymond Hettinger.)

Added a new opcode, LIST_APPEND, that simplifies the generated bytecode for list comprehensions and speeds them up by about a third. (Contributed by Raymond Hettinger.)

The peephole bytecode optimizer has been improved to produce shorter, faster bytecode; remarkably, the resulting bytecode is more readable. (Enhanced by Raymond Hettinger.)

String concatenations in statements of the form s = s + "abc" and s += "abc" are now performed more efficiently in certain circumstances. This optimization won't be present in other Python implementations such as Jython, so you shouldn't rely on it; using the join() method of strings is still recommended when you want to efficiently glue a large number of strings together. (Contributed by Armin Rigo.)

The net result of the 2.4 optimizations is that Python 2.4 runs the pystone benchmark around 5% faster than Python 2.3 and 35% faster than Python 2.2. (pystone is not a particularly good benchmark, but it's the most commonly used measurement of Python's performance. Your own applications may show greater or smaller benefits from Python 2.4.)

New, Improved, and Deprecated Modules

As usual, Python's standard library received a number of enhancements and bug fixes. Here's a partial list of the most notable changes, sorted alphabetically by module name. Consult the Misc/NEWS file in the source tree for a more complete list of changes, or look through the CVS logs for all the details.

The asyncore module's loop() function now has a count parameter that lets you perform a limited number of passes through the polling loop. The default is still to loop forever.

The base64 module now has more complete RFC 3548 [https://datatracker.ietf.org/doc/html/rfc3548.html] support for Base64, Base32, and Base16 encoding and decoding, including optional case folding and optional alternative alphabets. (Contributed by Barry Warsaw.)

The bisect module now has an underlying C implementation for improved performance. (Contributed by Dmitry Vasiliev.)

The CJKCodecs collections of East Asian codecs, maintained by Hye-Shik Chang, was integrated into 2.4. The new encodings are:

Chinese (PRC): gb2312, gbk, gb18030, big5hkscs, hz

Chinese (ROC): big5, cp950

Japanese: cp932, euc-jis-2004, euc-jp, euc-jisx0213, iso-2022-jp,

iso-2022-jp-1, iso-2022-jp-2, iso-2022-jp-3, iso-2022-jp-ext, iso-2022-jp-2004, shift-jis, shift-jisx0213, shift-jis-2004

Korean: cp949, euc-kr, johab, iso-2022-kr

Some other new encodings were added: HP Roman8, ISO_8859-11, ISO_8859-16, PCTP-154, and TIS-620.

The UTF-8 and UTF-16 codecs now cope better with receiving partial input. Previously the StreamReader class would try to read more data, making it impossible to resume decoding from the stream. The read() method will now return as much data as it can and future calls will resume decoding where previous ones left off. (Implemented by Walter Dörwald.)

There is a new collections module for various specialized collection datatypes. Currently it contains just one type, deque, a double-ended queue that supports efficiently adding and removing elements from either end:

>>> from collections import deque
>>> d = deque('ghi')        # make a new deque with three items
>>> d.append('j')           # add a new entry to the right side
>>> d.appendleft('f')       # add a new entry to the left side
>>> d                       # show the representation of the deque
deque(['f', 'g', 'h', 'i', 'j'])
>>> d.pop()                 # return and remove the rightmost item
'j'
>>> d.popleft()             # return and remove the leftmost item
'f'
>>> list(d)                 # list the contents of the deque
['g', 'h', 'i']
>>> 'h' in d                # search the deque
True

Several modules, such as the Queue and threading modules, now take advantage of collections.deque for improved performance. (Contributed by Raymond Hettinger.)

The ConfigParser classes have been enhanced slightly. The read() method now returns a list of the files that were successfully parsed, and the set() method raises TypeError if passed a value argument that isn't a string. (Contributed by John Belmonte and David Goodger.)

The curses module now supports the ncurses extension use_default_colors(). On platforms where the terminal supports transparency, this makes it possible to use a transparent background. (Contributed by Jörg Lehmann.)

The difflib module now includes an HtmlDiff class that creates an HTML table showing a side by side comparison of two versions of a text. (Contributed by Dan Gass.)

The email package was updated to version 3.0, which dropped various deprecated APIs and removes support for Python versions earlier than 2.3. The 3.0 version of the package uses a new incremental parser for MIME messages, available in the email.FeedParser module. The new parser doesn't require reading the entire message into memory, and doesn't raise exceptions if a message is malformed; instead it records any problems in the defect attribute of the message. (Developed by Anthony Baxter, Barry Warsaw, Thomas Wouters, and others.)

The heapq module has been converted to C. The resulting tenfold improvement in speed makes the module suitable for handling high volumes of data. In addition, the module has two new functions nlargest() and nsmallest() that use heaps to find the N largest or smallest values in a dataset without the expense of a full sort. (Contributed by Raymond Hettinger.)

The httplib module now contains constants for HTTP status codes defined in various HTTP-related RFC documents. Constants have names such as OK, CREATED, CONTINUE, and MOVED_PERMANENTLY; use pydoc to get a full list. (Contributed by Andrew Eland.)

The imaplib module now supports IMAP's THREAD command (contributed by Yves Dionne) and new deleteacl() and myrights() methods (contributed by Arnaud Mazin).

The itertools module gained a groupby(iterable[, *func*]) function. iterable is something that can be iterated over to return a stream of elements, and the optional func parameter is a function that takes an element and returns a key value; if omitted, the key is simply the element itself. groupby() then groups the elements into subsequences which have matching values of the key, and returns a series of 2-tuples containing the key value and an iterator over the subsequence.

Here's an example to make this clearer. The key function simply returns whether a number is even or odd, so the result of groupby() is to return consecutive runs of odd or even numbers.

>>> import itertools
>>> L = [2, 4, 6, 7, 8, 9, 11, 12, 14]
>>> for key_val, it in itertools.groupby(L, lambda x: x % 2):
...    print key_val, list(it)
...
0 [2, 4, 6]
1 [7]
0 [8]
1 [9, 11]
0 [12, 14]
>>>

groupby() is typically used with sorted input. The logic for groupby() is similar to the Unix uniq filter which makes it handy for eliminating, counting, or identifying duplicate elements:

>>> word = 'abracadabra'
>>> letters = sorted(word)   # Turn string into a sorted list of letters
>>> letters
['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r']
>>> for k, g in itertools.groupby(letters):
...    print k, list(g)
...
a ['a', 'a', 'a', 'a', 'a']
b ['b', 'b']
c ['c']
d ['d']
r ['r', 'r']
>>> # List unique letters
>>> [k for k, g in groupby(letters)]
['a', 'b', 'c', 'd', 'r']
>>> # Count letter occurrences
>>> [(k, len(list(g))) for k, g in groupby(letters)]
[('a', 5), ('b', 2), ('c', 1), ('d', 1), ('r', 2)]

（由 Hye-Shik Chang 所貢獻。）

itertools also gained a function named tee(iterator, N) that returns N independent iterators that replicate iterator. If N is omitted, the default is 2.

>>> L = [1,2,3]
>>> i1, i2 = itertools.tee(L)
>>> i1,i2
(<itertools.tee object at 0x402c2080>, <itertools.tee object at 0x402c2090>)
>>> list(i1)               # Run the first iterator to exhaustion
[1, 2, 3]
>>> list(i2)               # Run the second iterator to exhaustion
[1, 2, 3]

Note that tee() has to keep copies of the values returned by the iterator; in the worst case, it may need to keep all of them. This should therefore be used carefully if the leading iterator can run far ahead of the trailing iterator in a long stream of inputs. If the separation is large, then you might as well use list() instead. When the iterators track closely with one another, tee() is ideal. Possible applications include bookmarking, windowing, or lookahead iterators. (Contributed by Raymond Hettinger.)

A number of functions were added to the locale module, such as bind_textdomain_codeset() to specify a particular encoding and a family of l*gettext() functions that return messages in the chosen encoding. (Contributed by Gustavo Niemeyer.)

Some keyword arguments were added to the logging package's basicConfig() function to simplify log configuration. The default behavior is to log messages to standard error, but various keyword arguments can be specified to log to a particular file, change the logging format, or set the logging level. For example:

import logging
logging.basicConfig(filename='/var/log/application.log',
    level=0,  # Log all messages
    format='%(levelname):%(process):%(thread):%(message)')

Other additions to the logging package include a log(level, msg) convenience method, as well as a TimedRotatingFileHandler class that rotates its log files at a timed interval. The module already had RotatingFileHandler, which rotated logs once the file exceeded a certain size. Both classes derive from a new BaseRotatingHandler class that can be used to implement other rotating handlers.

（由 Vinay Sajip 所實作。）

The marshal module now shares interned strings on unpacking a data structure. This may shrink the size of certain pickle strings, but the primary effect is to make .pyc files significantly smaller. (Contributed by Martin von Löwis.)

The nntplib module's NNTP class gained description() and descriptions() methods to retrieve newsgroup descriptions for a single group or for a range of groups. (Contributed by Jürgen A. Erhard.)

Two new functions were added to the operator module, attrgetter(attr) and itemgetter(index). Both functions return callables that take a single argument and return the corresponding attribute or item; these callables make excellent data extractors when used with map() or sorted(). For example:

>>> L = [('c', 2), ('d', 1), ('a', 4), ('b', 3)]
>>> map(operator.itemgetter(0), L)
['c', 'd', 'a', 'b']
>>> map(operator.itemgetter(1), L)
[2, 1, 4, 3]
>>> sorted(L, key=operator.itemgetter(1)) # 以第二個元組項目來排序串列
[('d', 1), ('c', 2), ('b', 3), ('a', 4)]

（由 Raymond Hettinger 所貢獻。）

The optparse module was updated in various ways. The module now passes its messages through gettext.gettext(), making it possible to internationalize Optik's help and error messages. Help messages for options can now include the string '%default', which will be replaced by the option's default value. (Contributed by Greg Ward.)

The long-term plan is to deprecate the rfc822 module in some future Python release in favor of the email package. To this end, the email.Utils.formatdate function has been changed to make it usable as a replacement for rfc822.formatdate(). You may want to write new e-mail processing code with this in mind. (Change implemented by Anthony Baxter.)

A new urandom(n) function was added to the os module, returning a string containing n bytes of random data. This function provides access to platform-specific sources of randomness such as /dev/urandom on Linux or the Windows CryptoAPI. (Contributed by Trevor Perrin.)

Another new function: os.path.lexists(path) returns true if the file specified by path exists, whether or not it's a symbolic link. This differs from the existing os.path.exists(path) function, which returns false if path is a symlink that points to a destination that doesn't exist. (Contributed by Beni Cherniavsky.)

A new getsid() function was added to the posix module that underlies the os module. (Contributed by J. Raynor.)

The poplib module now supports POP over SSL. (Contributed by Hector Urtubia.)

The profile module can now profile C extension functions. (Contributed by Nick Bastin.)

The random module has a new method called getrandbits(N) that returns a long integer N bits in length. The existing randrange() method now uses getrandbits() where appropriate, making generation of arbitrarily large random numbers more efficient. (Contributed by Raymond Hettinger.)

The regular expression language accepted by the re module was extended with simple conditional expressions, written as (?(group)A|B). group is either a numeric group ID or a group name defined with (?P<group>...) earlier in the expression. If the specified group matched, the regular expression pattern A will be tested against the string; if the group didn't match, the pattern B will be used instead. (Contributed by Gustavo Niemeyer.)

The re module is also no longer recursive, thanks to a massive amount of work by Gustavo Niemeyer. In a recursive regular expression engine, certain patterns result in a large amount of C stack space being consumed, and it was possible to overflow the stack. For example, if you matched a 30000-byte string of a characters against the expression (a|b)+, one stack frame was consumed per character. Python 2.3 tried to check for stack overflow and raise a RuntimeError exception, but certain patterns could sidestep the checking and if you were unlucky Python could segfault. Python 2.4's regular expression engine can match this pattern without problems.

The signal module now performs tighter error-checking on the parameters to the signal.signal() function. For example, you can't set a handler on the SIGKILL signal; previous versions of Python would quietly accept this, but 2.4 will raise a RuntimeError exception.

Two new functions were added to the socket module. socketpair() returns a pair of connected sockets and getservbyport(port) looks up the service name for a given port number. (Contributed by Dave Cole and Barry Warsaw.)

The sys.exitfunc() function has been deprecated. Code should be using the existing atexit module, which correctly handles calling multiple exit functions. Eventually sys.exitfunc() will become a purely internal interface, accessed only by atexit.

The tarfile module now generates GNU-format tar files by default. (Contributed by Lars Gustäbel.)

The threading module now has an elegantly simple way to support thread-local data. The module contains a local class whose attribute values are local to different threads.

import threading

data = threading.local()
data.number = 42
data.url = ('www.python.org', 80)

Other threads can assign and retrieve their own values for the number and url attributes. You can subclass local to initialize attributes or to add methods. (Contributed by Jim Fulton.)

The timeit module now automatically disables periodic garbage collection during the timing loop. This change makes consecutive timings more comparable. (Contributed by Raymond Hettinger.)

The weakref module now supports a wider variety of objects including Python functions, class instances, sets, frozensets, deques, arrays, files, sockets, and regular expression pattern objects. (Contributed by Raymond Hettinger.)

The xmlrpclib module now supports a multi-call extension for transmitting multiple XML-RPC calls in a single HTTP operation. (Contributed by Brian Quinlan.)

The mpz, rotor, and xreadlines modules have been removed.

cookielib

The cookielib library supports client-side handling for HTTP cookies, mirroring the Cookie module's server-side cookie support. Cookies are stored in cookie jars; the library transparently stores cookies offered by the web server in the cookie jar, and fetches the cookie from the jar when connecting to the server. As in web browsers, policy objects control whether cookies are accepted or not.

In order to store cookies across sessions, two implementations of cookie jars are provided: one that stores cookies in the Netscape format so applications can use the Mozilla or Lynx cookie files, and one that stores cookies in the same format as the Perl libwww library.

urllib2 has been changed to interact with cookielib: HTTPCookieProcessor manages a cookie jar that is used when accessing URLs.

This module was contributed by John J. Lee.

doctest

The doctest module underwent considerable refactoring thanks to Edward Loper and Tim Peters. Testing can still be as simple as running doctest.testmod(), but the refactorings allow customizing the module's operation in various ways

The new DocTestFinder class extracts the tests from a given object's docstrings:

def f (x, y):
    """>>> f(2,2)
4
>>> f(3,2)
6
    """
    return x*y

finder = doctest.DocTestFinder()

# 取得 DocTest 實例的串列
tests = finder.find(f)

The new DocTestRunner class then runs individual tests and can produce a summary of the results:

runner = doctest.DocTestRunner()
for t in tests:
    tried, failed = runner.run(t)

runner.summarize(verbose=1)

The above example produces the following output:

1 items passed all tests:
   2 tests in f
2 tests in 1 items.
2 passed and 0 failed.
Test passed.

DocTestRunner uses an instance of the OutputChecker class to compare the expected output with the actual output. This class takes a number of different flags that customize its behaviour; ambitious users can also write a completely new subclass of OutputChecker.

The default output checker provides a number of handy features. For example, with the doctest.ELLIPSIS option flag, an ellipsis (...) in the expected output matches any substring, making it easier to accommodate outputs that vary in minor ways:

def o (n):
    """>>> o(1)
<__main__.C instance at 0x...>
>>>
"""

Another special string, <BLANKLINE>, matches a blank line:

def p (n):
    """>>> p(1)
<BLANKLINE>
>>>
"""

Another new capability is producing a diff-style display of the output by specifying the doctest.REPORT_UDIFF (unified diffs), doctest.REPORT_CDIFF (context diffs), or doctest.REPORT_NDIFF (delta-style) option flags. For example:

def g (n):
    """>>> g(4)
here
is
a
lengthy
>>>"""
    L = 'here is a rather lengthy list of words'.split()
    for word in L[:n]:
        print word

Running the above function's tests with doctest.REPORT_UDIFF specified, you get the following output:

**********************************************************************
File "t.py", line 15, in g
Failed example:
    g(4)
Differences (unified diff with -expected +actual):
    @@ -2,3 +2,3 @@
     is
     a
    -lengthy
    +rather
**********************************************************************

建置和 C API 變更

Some of the changes to Python's build process and to the C API are:

Three new convenience macros were added for common return values from extension functions: Py_RETURN_NONE, Py_RETURN_TRUE, and Py_RETURN_FALSE. (Contributed by Brett Cannon.)

Another new macro, Py_CLEAR, decreases the reference count of obj and sets obj to the null pointer. (Contributed by Jim Fulton.)

A new function, PyTuple_Pack(N, obj1, obj2, ..., objN), constructs tuples from a variable length argument list of Python objects. (Contributed by Raymond Hettinger.)

A new function, PyDict_Contains(d, k), implements fast dictionary lookups without masking exceptions raised during the look-up process. (Contributed by Raymond Hettinger.)

The Py_IS_NAN(X) macro returns 1 if its float or double argument X is a NaN. (Contributed by Tim Peters.)

C code can avoid unnecessary locking by using the new PyEval_ThreadsInitialized() function to tell if any thread operations have been performed. If this function returns false, no lock operations are needed. (Contributed by Nick Coghlan.)

A new function, PyArg_VaParseTupleAndKeywords(), is the same as PyArg_ParseTupleAndKeywords() but takes a va_list instead of a number of arguments. (Contributed by Greg Chapman.)

A new method flag, METH_COEXIST, allows a function defined in slots to co-exist with a PyCFunction having the same name. This can halve the access time for a method such as set.__contains__(). (Contributed by Raymond Hettinger.)

Python can now be built with additional profiling for the interpreter itself, intended as an aid to people developing the Python core. Providing --enable-profiling to the configure script will let you profile the interpreter with gprof, and providing the --with-tsc switch enables profiling using the Pentium's Time-Stamp-Counter register. Note that the --with-tsc switch is slightly misnamed, because the profiling feature also works on the PowerPC platform, though that processor architecture doesn't call that register "the TSC register". (Contributed by Jeremy Hylton.)

The tracebackobject type has been renamed to PyTracebackObject.

Port-Specific Changes

The Windows port now builds under MSVC++ 7.1 as well as version 6. (Contributed by Martin von Löwis.)

Porting to Python 2.4

This section lists previously described changes that may require changes to your code:

Left shifts and hexadecimal/octal constants that are too large no longer trigger a FutureWarning and return a value limited to 32 or 64 bits; instead they return a long integer.

Integer operations will no longer trigger an OverflowWarning. The OverflowWarning warning will disappear in Python 2.5.

The zip() built-in function and itertools.izip() now return an empty list instead of raising a TypeError exception if called with no arguments.

You can no longer compare the date and datetime instances provided by the datetime module. Two instances of different classes will now always be unequal, and relative comparisons (<, >) will raise a TypeError.

dircache.listdir() now passes exceptions to the caller instead of returning empty lists.

LexicalHandler.startDTD() used to receive the public and system IDs in the wrong order. This has been corrected; applications relying on the wrong order need to be fixed.

fcntl.ioctl() now warns if the mutate argument is omitted and relevant.

The tarfile module now generates GNU-format tar files by default.

Encountering a failure while importing a module no longer leaves a partially initialized module object in sys.modules.

None is now a constant; code that binds a new value to the name None is now a syntax error.

The signals.signal() function now raises a RuntimeError exception for certain illegal values; previously these errors would pass silently. For example, you can no longer set a handler on the SIGKILL signal.

致謝

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Koray Can, Hye-Shik Chang, Michael Dyck, Raymond Hettinger, Brian Hurt, Hamish Lawson, Fredrik Lundh, Sean Reifschneider, Sadruddin Rejeb.

Python 2.3 有什麼新功能

作者:

A.M. Kuchling

This article explains the new features in Python 2.3. Python 2.3 was released on July 29, 2003.

The main themes for Python 2.3 are polishing some of the features added in 2.2, adding various small but useful enhancements to the core language, and expanding the standard library. The new object model introduced in the previous version has benefited from 18 months of bugfixes and from optimization efforts that have improved the performance of new-style classes. A few new built-in functions have been added such as sum() and enumerate(). The in operator can now be used for substring searches (e.g. "ab" in "abc" returns True).

Some of the many new library features include Boolean, set, heap, and date/time data types, the ability to import modules from ZIP-format archives, metadata support for the long-awaited Python catalog, an updated version of IDLE, and modules for logging messages, wrapping text, parsing CSV files, processing command-line options, using BerkeleyDB databases... the list of new and enhanced modules is lengthy.

This article doesn't attempt to provide a complete specification of the new features, but instead provides a convenient overview. For full details, you should refer to the documentation for Python 2.3, such as the Python Library Reference and the Python Reference Manual. If you want to understand the complete implementation and design rationale, refer to the PEP for a particular new feature.

PEP 218: A Standard Set Datatype

The new sets module contains an implementation of a set datatype. The Set class is for mutable sets, sets that can have members added and removed. The ImmutableSet class is for sets that can't be modified, and instances of ImmutableSet can therefore be used as dictionary keys. Sets are built on top of dictionaries, so the elements within a set must be hashable.

以下是個簡單範例：

>>> import sets
>>> S = sets.Set([1,2,3])
>>> S
Set([1, 2, 3])
>>> 1 in S
True
>>> 0 in S
False
>>> S.add(5)
>>> S.remove(3)
>>> S
Set([1, 2, 5])
>>>

The union and intersection of sets can be computed with the union() and intersection() methods; an alternative notation uses the bitwise operators & and |. Mutable sets also have in-place versions of these methods, union_update() and intersection_update().

>>> S1 = sets.Set([1,2,3])
>>> S2 = sets.Set([4,5,6])
>>> S1.union(S2)
Set([1, 2, 3, 4, 5, 6])
>>> S1 | S2                  # 另一種標記法
Set([1, 2, 3, 4, 5, 6])
>>> S1.intersection(S2)
Set([])
>>> S1 & S2                  # 另一種標記法
Set([])
>>> S1.union_update(S2)
>>> S1
Set([1, 2, 3, 4, 5, 6])
>>>

It's also possible to take the symmetric difference of two sets. This is the set of all elements in the union that aren't in the intersection. Another way of putting it is that the symmetric difference contains all elements that are in exactly one set. Again, there's an alternative notation (^), and an in-place version with the ungainly name symmetric_difference_update().

>>> S1 = sets.Set([1,2,3,4])
>>> S2 = sets.Set([3,4,5,6])
>>> S1.symmetric_difference(S2)
Set([1, 2, 5, 6])
>>> S1 ^ S2
Set([1, 2, 5, 6])
>>>

There are also issubset() and issuperset() methods for checking whether one set is a subset or superset of another:

>>> S1 = sets.Set([1,2,3])
>>> S2 = sets.Set([2,3])
>>> S2.issubset(S1)
True
>>> S1.issubset(S2)
False
>>> S1.issuperset(S2)
True
>>>

也參考

PEP 218 [https://peps.python.org/pep-0218/] - Adding a Built-In Set Object Type

PEP written by Greg V. Wilson. Implemented by Greg V. Wilson, Alex Martelli, and GvR.

PEP 255：簡單產生器

In Python 2.2, generators were added as an optional feature, to be enabled by a from __future__ import generators directive. In 2.3 generators no longer need to be specially enabled, and are now always present; this means that yield is now always a keyword. The rest of this section is a copy of the description of generators from the "What's New in Python 2.2" document; if you read it back when Python 2.2 came out, you can skip the rest of this section.

You're doubtless familiar with how function calls work in Python or C. When you call a function, it gets a private namespace where its local variables are created. When the function reaches a return statement, the local variables are destroyed and the resulting value is returned to the caller. A later call to the same function will get a fresh new set of local variables. But, what if the local variables weren't thrown away on exiting a function? What if you could later resume the function where it left off? This is what generators provide; they can be thought of as resumable functions.

以下是產生器函式最簡單的範例：

def generate_ints(N):
    for i in range(N):
        yield i

A new keyword, yield, was introduced for generators. Any function containing a yield statement is a generator function; this is detected by Python's bytecode compiler which compiles the function specially as a result.

When you call a generator function, it doesn't return a single value; instead it returns a generator object that supports the iterator protocol. On executing the yield statement, the generator outputs the value of i, similar to a return statement. The big difference between yield and a return statement is that on reaching a yield the generator's state of execution is suspended and local variables are preserved. On the next call to the generator's .next() method, the function will resume executing immediately after the yield statement. (For complicated reasons, the yield statement isn't allowed inside the try block of a try...finally statement; read PEP 255 [https://peps.python.org/pep-0255/] for a full explanation of the interaction between yield and exceptions.)

Here's a sample usage of the generate_ints() generator:

>>> gen = generate_ints(3)
>>> gen
<generator object at 0x8117f90>
>>> gen.next()
0
>>> gen.next()
1
>>> gen.next()
2
>>> gen.next()
Traceback (most recent call last):
  File "stdin", line 1, in ?
  File "stdin", line 2, in generate_ints
StopIteration

You could equally write for i in generate_ints(5), or a,b,c = generate_ints(3).

Inside a generator function, the return statement can only be used without a value, and signals the end of the procession of values; afterwards the generator cannot return any further values. return with a value, such as return 5, is a syntax error inside a generator function. The end of the generator's results can also be indicated by raising StopIteration manually, or by just letting the flow of execution fall off the bottom of the function.

You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables. For example, returning a list of integers could be done by setting self.count to 0, and having the next() method increment self.count and return it. However, for a moderately complicated generator, writing a corresponding class would be much messier. Lib/test/test_generators.py contains a number of more interesting examples. The simplest one implements an in-order traversal of a tree using generators recursively.

# A recursive generator that generates Tree leaves in in-order.
def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x
        yield t.label
        for x in inorder(t.right):
            yield x

Two other examples in Lib/test/test_generators.py produce solutions for the N-Queens problem (placing $N$ queens on an $NxN$ chess board so that no queen threatens another) and the Knight's Tour (a route that takes a knight to every square of an $NxN$ chessboard without visiting any square twice).

The idea of generators comes from other programming languages, especially Icon (https://www2.cs.arizona.edu/icon/), where the idea of generators is central. In Icon, every expression and function call behaves like a generator. One example from "An Overview of the Icon Programming Language" at https://www2.cs.arizona.edu/icon/docs/ipd266.htm gives an idea of what this looks like:

sentence := "Store it in the neighboring harbor"
if (i := find("or", sentence)) > 5 then write(i)

In Icon the find() function returns the indexes at which the substring "or" is found: 3, 23, 33. In the if statement, i is first assigned a value of 3, but 3 is less than 5, so the comparison fails, and Icon retries it with the second value of 23. 23 is greater than 5, so the comparison now succeeds, and the code prints the value 23 to the screen.

Python doesn't go nearly as far as Icon in adopting generators as a central concept. Generators are considered part of the core Python language, but learning or using them isn't compulsory; if they don't solve any problems that you have, feel free to ignore them. One novel feature of Python's interface as compared to Icon's is that a generator's state is represented as a concrete object (the iterator) that can be passed around to other functions or stored in a data structure.

也參考

PEP 255 [https://peps.python.org/pep-0255/] - 簡單產生器

Written by Neil Schemenauer, Tim Peters, Magnus Lie Hetland. Implemented mostly by Neil Schemenauer and Tim Peters, with other fixes from the Python Labs crew.

PEP 263: Source Code Encodings

Python source files can now be declared as being in different character set encodings. Encodings are declared by including a specially formatted comment in the first or second line of the source file. For example, a UTF-8 file can be declared with:

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

Without such an encoding declaration, the default encoding used is 7-bit ASCII. Executing or importing modules that contain string literals with 8-bit characters and have no encoding declaration will result in a DeprecationWarning being signalled by Python 2.3; in 2.4 this will be a syntax error.

The encoding declaration only affects Unicode string literals, which will be converted to Unicode using the specified encoding. Note that Python identifiers are still restricted to ASCII characters, so you can't have variable names that use characters outside of the usual alphanumerics.

也參考

PEP 263 [https://peps.python.org/pep-0263/] - Defining Python Source Code Encodings

Written by Marc-André Lemburg and Martin von Löwis; implemented by Suzuki Hisao and Martin von Löwis.

PEP 273: Importing Modules from ZIP Archives

The new zipimport module adds support for importing modules from a ZIP-format archive. You don't need to import the module explicitly; it will be automatically imported if a ZIP archive's filename is added to sys.path. For example:

amk@nyman:~/src/python$ unzip -l /tmp/example.zip
Archive:  /tmp/example.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
     8467  11-26-02 22:30   jwzthreading.py
 --------                   -------
     8467                   1 file
amk@nyman:~/src/python$ ./python
Python 2.3 (#1, Aug 1 2003, 19:54:32)
>>> import sys
>>> sys.path.insert(0, '/tmp/example.zip')  # Add .zip file to front of path
>>> import jwzthreading
>>> jwzthreading.__file__
'/tmp/example.zip/jwzthreading.py'
>>>

An entry in sys.path can now be the filename of a ZIP archive. The ZIP archive can contain any kind of files, but only files named *.py, *.pyc, or *.pyo can be imported. If an archive only contains *.py files, Python will not attempt to modify the archive by adding the corresponding *.pyc file, meaning that if a ZIP archive doesn't contain *.pyc files, importing may be rather slow.

A path within the archive can also be specified to only import from a subdirectory; for example, the path /tmp/example.zip/lib/ would only import from the lib/ subdirectory within the archive.

也參考

PEP 273 [https://peps.python.org/pep-0273/] - Import Modules from Zip Archives

Written by James C. Ahlstrom, who also provided an implementation. Python 2.3 follows the specification in PEP 273 [https://peps.python.org/pep-0273/], but uses an implementation written by Just van Rossum that uses the import hooks described in PEP 302 [https://peps.python.org/pep-0302/]. See section PEP 302: New Import Hooks for a description of the new import hooks.

PEP 277: Unicode file name support for Windows NT

On Windows NT, 2000, and XP, the system stores file names as Unicode strings. Traditionally, Python has represented file names as byte strings, which is inadequate because it renders some file names inaccessible.

Python now allows using arbitrary Unicode strings (within the limitations of the file system) for all functions that expect file names, most notably the open() built-in function. If a Unicode string is passed to os.listdir(), Python now returns a list of Unicode strings. A new function, os.getcwdu(), returns the current directory as a Unicode string.

Byte strings still work as file names, and on Windows Python will transparently convert them to Unicode using the mbcs encoding.

Other systems also allow Unicode strings as file names but convert them to byte strings before passing them to the system, which can cause a UnicodeError to be raised. Applications can test whether arbitrary Unicode strings are supported as file names by checking os.path.supports_unicode_filenames, a Boolean value.

Under MacOS, os.listdir() may now return Unicode filenames.

也參考

PEP 277 [https://peps.python.org/pep-0277/] - Unicode file name support for Windows NT

Written by Neil Hodgson; implemented by Neil Hodgson, Martin von Löwis, and Mark Hammond.

PEP 278: Universal Newline Support

The three major operating systems used today are Microsoft Windows, Apple's Macintosh OS, and the various Unix derivatives. A minor irritation of cross-platform work is that these three platforms all use different characters to mark the ends of lines in text files. Unix uses the linefeed (ASCII character 10), MacOS uses the carriage return (ASCII character 13), and Windows uses a two-character sequence of a carriage return plus a newline.

Python's file objects can now support end of line conventions other than the one followed by the platform on which Python is running. Opening a file with the mode 'U' or 'rU' will open a file for reading in universal newlines mode. All three line ending conventions will be translated to a '\n' in the strings returned by the various file methods such as read() and readline().

Universal newline support is also used when importing modules and when executing a file with the execfile() function. This means that Python modules can be shared between all three operating systems without needing to convert the line-endings.

This feature can be disabled when compiling Python by specifying the --without-universal-newlines switch when running Python's configure script.

也參考

PEP 278 [https://peps.python.org/pep-0278/] - Universal Newline Support

由 Jack Jansen 撰寫並實作。

PEP 279：enumerate()

A new built-in function, enumerate(), will make certain loops a bit clearer. enumerate(thing), where thing is either an iterator or a sequence, returns an iterator that will return (0, thing[0]), (1, thing[1]), (2, thing[2]), and so forth.

A common idiom to change every element of a list looks like this:

for i in range(len(L)):
    item = L[i]
    # ... compute some result based on item ...
    L[i] = result

This can be rewritten using enumerate() as:

for i, item in enumerate(L):
    # ... compute some result based on item ...
    L[i] = result

也參考

PEP 279 [https://peps.python.org/pep-0279/] - The enumerate() built-in function

由 Raymond D. Hettinger 撰寫並實作。

PEP 282: The logging Package

A standard package for writing logs, logging, has been added to Python 2.3. It provides a powerful and flexible mechanism for generating logging output which can then be filtered and processed in various ways. A configuration file written in a standard format can be used to control the logging behavior of a program. Python includes handlers that will write log records to standard error or to a file or socket, send them to the system log, or even e-mail them to a particular address; of course, it's also possible to write your own handler classes.

The Logger class is the primary class. Most application code will deal with one or more Logger objects, each one used by a particular subsystem of the application. Each Logger is identified by a name, and names are organized into a hierarchy using . as the component separator. For example, you might have Logger instances named server, server.auth and server.network. The latter two instances are below server in the hierarchy. This means that if you turn up the verbosity for server or direct server messages to a different handler, the changes will also apply to records logged to server.auth and server.network. There's also a root Logger that's the parent of all other loggers.

For simple uses, the logging package contains some convenience functions that always use the root log:

import logging

logging.debug('Debugging information')
logging.info('Informational message')
logging.warning('Warning:config file %s not found', 'server.conf')
logging.error('Error occurred')
logging.critical('Critical error -- shutting down')

This produces the following output:

WARNING:root:Warning:config file server.conf not found
ERROR:root:Error occurred
CRITICAL:root:Critical error -- shutting down

In the default configuration, informational and debugging messages are suppressed and the output is sent to standard error. You can enable the display of informational and debugging messages by calling the setLevel() method on the root logger.

Notice the warning() call's use of string formatting operators; all of the functions for logging messages take the arguments (msg, arg1, arg2, ...) and log the string resulting from msg % (arg1, arg2, ...).

There's also an exception() function that records the most recent traceback. Any of the other functions will also record the traceback if you specify a true value for the keyword argument exc_info.

def f():
    try:    1/0
    except: logging.exception('Problem recorded')

f()

This produces the following output:

ERROR:root:Problem recorded
Traceback (most recent call last):
  File "t.py", line 6, in f
    1/0
ZeroDivisionError: integer division or modulo by zero

Slightly more advanced programs will use a logger other than the root logger. The getLogger(name) function is used to get a particular log, creating it if it doesn't exist yet. getLogger(None) returns the root logger.

log = logging.getLogger('server')
 ...
log.info('Listening on port %i', port)
 ...
log.critical('Disk full')
 ...

Log records are usually propagated up the hierarchy, so a message logged to server.auth is also seen by server and root, but a Logger can prevent this by setting its propagate attribute to False.

There are more classes provided by the logging package that can be customized. When a Logger instance is told to log a message, it creates a LogRecord instance that is sent to any number of different Handler instances. Loggers and handlers can also have an attached list of filters, and each filter can cause the LogRecord to be ignored or can modify the record before passing it along. When they're finally output, LogRecord instances are converted to text by a Formatter class. All of these classes can be replaced by your own specially written classes.

With all of these features the logging package should provide enough flexibility for even the most complicated applications. This is only an incomplete overview of its features, so please see the package's reference documentation for all of the details. Reading PEP 282 [https://peps.python.org/pep-0282/] will also be helpful.

也參考

PEP 282 [https://peps.python.org/pep-0282/] - 日誌記錄系統

Written by Vinay Sajip and Trent Mick; implemented by Vinay Sajip.

PEP 285：布林型別

A Boolean type was added to Python 2.3. Two new constants were added to the __builtin__ module, True and False. (True and False constants were added to the built-ins in Python 2.2.1, but the 2.2.1 versions are simply set to integer values of 1 and 0 and aren't a different type.)

The type object for this new type is named bool; the constructor for it takes any Python value and converts it to True or False.

>>> bool(1)
True
>>> bool(0)
False
>>> bool([])
False
>>> bool( (1,) )
True

Most of the standard library modules and built-in functions have been changed to return Booleans.

>>> obj = []
>>> hasattr(obj, 'append')
True
>>> isinstance(obj, list)
True
>>> isinstance(obj, tuple)
False

Python's Booleans were added with the primary goal of making code clearer. For example, if you're reading a function and encounter the statement return 1, you might wonder whether the 1 represents a Boolean truth value, an index, or a coefficient that multiplies some other quantity. If the statement is return True, however, the meaning of the return value is quite clear.

Python's Booleans were not added for the sake of strict type-checking. A very strict language such as Pascal would also prevent you performing arithmetic with Booleans, and would require that the expression in an if statement always evaluate to a Boolean result. Python is not this strict and never will be, as PEP 285 [https://peps.python.org/pep-0285/] explicitly says. This means you can still use any expression in an if statement, even ones that evaluate to a list or tuple or some random object. The Boolean type is a subclass of the int class so that arithmetic using a Boolean still works.

>>> True + 1
2
>>> False + 1
1
>>> False * 75
0
>>> True * 75
75

To sum up True and False in a sentence: they're alternative ways to spell the integer values 1 and 0, with the single difference that str() and repr() return the strings 'True' and 'False' instead of '1' and '0'.

也參考

PEP 285 [https://peps.python.org/pep-0285/] - Adding a bool type

由 GvR 撰寫並實作。

PEP 293: Codec Error Handling Callbacks

When encoding a Unicode string into a byte string, unencodable characters may be encountered. So far, Python has allowed specifying the error processing as either "strict" (raising UnicodeError), "ignore" (skipping the character), or "replace" (using a question mark in the output string), with "strict" being the default behavior. It may be desirable to specify alternative processing of such errors, such as inserting an XML character reference or HTML entity reference into the converted string.

Python now has a flexible framework to add different processing strategies. New error handlers can be added with codecs.register_error(), and codecs then can access the error handler with codecs.lookup_error(). An equivalent C API has been added for codecs written in C. The error handler gets the necessary state information such as the string being converted, the position in the string where the error was detected, and the target encoding. The handler can then either raise an exception or return a replacement string.

Two additional error handlers have been implemented using this framework: "backslashreplace" uses Python backslash quoting to represent unencodable characters and "xmlcharrefreplace" emits XML character references.

也參考

PEP 293 [https://peps.python.org/pep-0293/] - Codec Error Handling Callbacks

由 Walter Dörwald 撰寫並實作。

PEP 301: Package Index and Metadata for Distutils

Support for the long-requested Python catalog makes its first appearance in 2.3.

The heart of the catalog is the new Distutils register command. Running python setup.py register will collect the metadata describing a package, such as its name, version, maintainer, description, &c., and send it to a central catalog server. The resulting catalog is available from https://pypi.org.

To make the catalog a bit more useful, a new optional classifiers keyword argument has been added to the Distutils setup() function. A list of Trove [http://catb.org/~esr/trove/]-style strings can be supplied to help classify the software.

Here's an example setup.py with classifiers, written to be compatible with older versions of the Distutils:

from distutils import core
kw = {'name': "Quixote",
      'version': "0.5.1",
      'description': "A highly Pythonic Web application framework",
      # ...
      }

if (hasattr(core, 'setup_keywords') and
    'classifiers' in core.setup_keywords):
    kw['classifiers'] = \
        ['Topic :: Internet :: WWW/HTTP :: Dynamic Content',
         'Environment :: No Input/Output (Daemon)',
         'Intended Audience :: Developers'],

core.setup(**kw)

The full list of classifiers can be obtained by running python setup.py register --list-classifiers.

也參考

PEP 301 [https://peps.python.org/pep-0301/] - Package Index and Metadata for Distutils

由 Richard Jones 撰寫並實作。

PEP 302: New Import Hooks

While it's been possible to write custom import hooks ever since the ihooks module was introduced in Python 1.3, no one has ever been really happy with it because writing new import hooks is difficult and messy. There have been various proposed alternatives such as the imputil and iu modules, but none of them has ever gained much acceptance, and none of them were easily usable from C code.

PEP 302 [https://peps.python.org/pep-0302/] borrows ideas from its predecessors, especially from Gordon McMillan's iu module. Three new items are added to the sys module:

sys.path_hooks is a list of callable objects; most often they'll be classes. Each callable takes a string containing a path and either returns an importer object that will handle imports from this path or raises an ImportError exception if it can't handle this path.

sys.path_importer_cache caches importer objects for each path, so sys.path_hooks will only need to be traversed once for each path.

sys.meta_path is a list of importer objects that will be traversed before sys.path is checked. This list is initially empty, but user code can add objects to it. Additional built-in and frozen modules can be imported by an object added to this list.

Importer objects must have a single method, find_module(fullname, path=None). fullname will be a module or package name, e.g. string or distutils.core. find_module() must return a loader object that has a single method, load_module(fullname), that creates and returns the corresponding module object.

Pseudo-code for Python's new import logic, therefore, looks something like this (simplified a bit; see PEP 302 [https://peps.python.org/pep-0302/] for the full details):

for mp in sys.meta_path:
    loader = mp(fullname)
    if loader is not None:
        <module> = loader.load_module(fullname)

for path in sys.path:
    for hook in sys.path_hooks:
        try:
            importer = hook(path)
        except ImportError:
            # ImportError, so try the other path hooks
            pass
        else:
            loader = importer.find_module(fullname)
            <module> = loader.load_module(fullname)

# Not found!
raise ImportError

也參考

PEP 302 [https://peps.python.org/pep-0302/] - New Import Hooks

Written by Just van Rossum and Paul Moore. Implemented by Just van Rossum.

PEP 305: Comma-separated Files

Comma-separated files are a format frequently used for exporting data from databases and spreadsheets. Python 2.3 adds a parser for comma-separated files.

Comma-separated format is deceptively simple at first glance:

Costs,150,200,3.95

Read a line and call line.split(','): what could be simpler? But toss in string data that can contain commas, and things get more complicated:

"Costs",150,200,3.95,"Includes taxes, shipping, and sundry items"

A big ugly regular expression can parse this, but using the new csv package is much simpler:

import csv

input = open('datafile', 'rb')
reader = csv.reader(input)
for line in reader:
    print line

The reader() function takes a number of different options. The field separator isn't limited to the comma and can be changed to any character, and so can the quoting and line-ending characters.

Different dialects of comma-separated files can be defined and registered; currently there are two dialects, both used by Microsoft Excel. A separate csv.writer class will generate comma-separated files from a succession of tuples or lists, quoting strings that contain the delimiter.

也參考

PEP 305 [https://peps.python.org/pep-0305/] - CSV 檔案 API

Written and implemented by Kevin Altis, Dave Cole, Andrew McNamara, Skip Montanaro, Cliff Wells.

PEP 307: Pickle Enhancements

The pickle and cPickle modules received some attention during the 2.3 development cycle. In 2.2, new-style classes could be pickled without difficulty, but they weren't pickled very compactly; PEP 307 [https://peps.python.org/pep-0307/] quotes a trivial example where a new-style class results in a pickled string three times longer than that for a classic class.

The solution was to invent a new pickle protocol. The pickle.dumps() function has supported a text-or-binary flag for a long time. In 2.3, this flag is redefined from a Boolean to an integer: 0 is the old text-mode pickle format, 1 is the old binary format, and now 2 is a new 2.3-specific format. A new constant, pickle.HIGHEST_PROTOCOL, can be used to select the fanciest protocol available.

Unpickling is no longer considered a safe operation. 2.2's pickle provided hooks for trying to prevent unsafe classes from being unpickled (specifically, a __safe_for_unpickling__ attribute), but none of this code was ever audited and therefore it's all been ripped out in 2.3. You should not unpickle untrusted data in any version of Python.

To reduce the pickling overhead for new-style classes, a new interface for customizing pickling was added using three special methods: __getstate__(), __setstate__(), and __getnewargs__(). Consult PEP 307 [https://peps.python.org/pep-0307/] for the full semantics of these methods.

As a way to compress pickles yet further, it's now possible to use integer codes instead of long strings to identify pickled classes. The Python Software Foundation will maintain a list of standardized codes; there's also a range of codes for private use. Currently no codes have been specified.

也參考

PEP 307 [https://peps.python.org/pep-0307/] - Extensions to the pickle protocol

由 Guido van Rossum 和 Tim Peters 撰寫並實作。

Extended Slices

Ever since Python 1.4, the slicing syntax has supported an optional third "step" or "stride" argument. For example, these are all legal Python syntax: L[1:10:2], L[:-1:1], L[::-1]. This was added to Python at the request of the developers of Numerical Python, which uses the third argument extensively. However, Python's built-in list, tuple, and string sequence types have never supported this feature, raising a TypeError if you tried it. Michael Hudson contributed a patch to fix this shortcoming.

For example, you can now easily extract the elements of a list that have even indexes:

>>> L = range(10)
>>> L[::2]
[0, 2, 4, 6, 8]

Negative values also work to make a copy of the same list in reverse order:

>>> L[::-1]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

This also works for tuples, arrays, and strings:

>>> s='abcd'
>>> s[::2]
'ac'
>>> s[::-1]
'dcba'

If you have a mutable sequence such as a list or an array you can assign to or delete an extended slice, but there are some differences between assignment to extended and regular slices. Assignment to a regular slice can be used to change the length of the sequence:

>>> a = range(3)
>>> a
[0, 1, 2]
>>> a[1:3] = [4, 5, 6]
>>> a
[0, 4, 5, 6]

Extended slices aren't this flexible. When assigning to an extended slice, the list on the right hand side of the statement must contain the same number of items as the slice it is replacing:

>>> a = range(4)
>>> a
[0, 1, 2, 3]
>>> a[::2]
[0, 2]
>>> a[::2] = [0, -1]
>>> a
[0, 1, -1, 3]
>>> a[::2] = [0,1,2]
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ValueError: attempt to assign sequence of size 3 to extended slice of size 2

Deletion is more straightforward:

>>> a = range(4)
>>> a
[0, 1, 2, 3]
>>> a[::2]
[0, 2]
>>> del a[::2]
>>> a
[1, 3]

One can also now pass slice objects to the __getitem__() methods of the built-in sequences:

>>> range(10).__getitem__(slice(0, 5, 2))
[0, 2, 4]

Or use slice objects directly in subscripts:

>>> range(10)[slice(0, 5, 2)]
[0, 2, 4]

To simplify implementing sequences that support extended slicing, slice objects now have a method indices(length) which, given the length of a sequence, returns a (start, stop, step) tuple that can be passed directly to range(). indices() handles omitted and out-of-bounds indices in a manner consistent with regular slices (and this innocuous phrase hides a welter of confusing details!). The method is intended to be used like this:

class FakeSeq:
    ...
    def calc_item(self, i):
        ...
    def __getitem__(self, item):
        if isinstance(item, slice):
            indices = item.indices(len(self))
            return FakeSeq([self.calc_item(i) for i in range(*indices)])
        else:
            return self.calc_item(i)

From this example you can also see that the built-in slice object is now the type object for the slice type, and is no longer a function. This is consistent with Python 2.2, where int, str, etc., underwent the same change.

其他語言更動

Here are all of the changes that Python 2.3 makes to the core Python language.

The yield statement is now always a keyword, as described in section PEP 255：簡單產生器 of this document.

A new built-in function enumerate() was added, as described in section PEP 279：enumerate() of this document.

Two new constants, True and False were added along with the built-in bool type, as described in section PEP 285：布林型別 of this document.

The int() type constructor will now return a long integer instead of raising an OverflowError when a string or floating-point number is too large to fit into an integer. This can lead to the paradoxical result that isinstance(int(expression), int) is false, but that seems unlikely to cause problems in practice.

Built-in types now support the extended slicing syntax, as described in section Extended Slices of this document.

A new built-in function, sum(iterable, start=0), adds up the numeric items in the iterable object and returns their sum. sum() only accepts numbers, meaning that you can't use it to concatenate a bunch of strings. (Contributed by Alex Martelli.)

list.insert(pos, value) used to insert value at the front of the list when pos was negative. The behaviour has now been changed to be consistent with slice indexing, so when pos is -1 the value will be inserted before the last element, and so forth.

list.index(value), which searches for value within the list and returns its index, now takes optional start and stop arguments to limit the search to only part of the list.

Dictionaries have a new method, pop(key[, *default*]), that returns the value corresponding to key and removes that key/value pair from the dictionary. If the requested key isn't present in the dictionary, default is returned if it's specified and KeyError raised if it isn't.

>>> d = {1:2}
>>> d
{1: 2}
>>> d.pop(4)
Traceback (most recent call last):
  File "stdin", line 1, in ?
KeyError: 4
>>> d.pop(1)
2
>>> d.pop(1)
Traceback (most recent call last):
  File "stdin", line 1, in ?
KeyError: 'pop(): dictionary is empty'
>>> d
{}
>>>

There's also a new class method, dict.fromkeys(iterable, value), that creates a dictionary with keys taken from the supplied iterator iterable and all values set to value, defaulting to None.

(Patches contributed by Raymond Hettinger.)

Also, the dict() constructor now accepts keyword arguments to simplify creating small dictionaries:

>>> dict(red=1, blue=2, green=3, black=4)
{'blue': 2, 'black': 4, 'green': 3, 'red': 1}

（由 Just van Rossum 所貢獻。）

The assert statement no longer checks the __debug__ flag, so you can no longer disable assertions by assigning to __debug__. Running Python with the -O switch will still generate code that doesn't execute any assertions.

Most type objects are now callable, so you can use them to create new objects such as functions, classes, and modules. (This means that the new module can be deprecated in a future Python version, because you can now use the type objects available in the types module.) For example, you can create a new module object with the following code:

>>> import types
>>> m = types.ModuleType('abc','docstring')
>>> m
<module 'abc' (built-in)>
>>> m.__doc__
'docstring'

A new warning, PendingDeprecationWarning was added to indicate features which are in the process of being deprecated. The warning will not be printed by default. To check for use of features that will be deprecated in the future, supply -Walways::PendingDeprecationWarning:: on the command line or use warnings.filterwarnings().

The process of deprecating string-based exceptions, as in raise "Error occurred", has begun. Raising a string will now trigger PendingDeprecationWarning.

Using None as a variable name will now result in a SyntaxWarning warning. In a future version of Python, None may finally become a keyword.

The xreadlines() method of file objects, introduced in Python 2.1, is no longer necessary because files now behave as their own iterator. xreadlines() was originally introduced as a faster way to loop over all the lines in a file, but now you can simply write for line in file_obj. File objects also have a new read-only encoding attribute that gives the encoding used by the file; Unicode strings written to the file will be automatically converted to bytes using the given encoding.

The method resolution order used by new-style classes has changed, though you'll only notice the difference if you have a really complicated inheritance hierarchy. Classic classes are unaffected by this change. Python 2.2 originally used a topological sort of a class's ancestors, but 2.3 now uses the C3 algorithm as described in the paper "A Monotonic Superclass Linearization for Dylan" [https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.19.3910]. To understand the motivation for this change, read Michele Simionato's article Python 2.3 方法解析順序, or read the thread on python-dev starting with the message at https://mail.python.org/pipermail/python-dev/2002-October/029035.html. Samuele Pedroni first pointed out the problem and also implemented the fix by coding the C3 algorithm.

Python runs multithreaded programs by switching between threads after executing N bytecodes. The default value for N has been increased from 10 to 100 bytecodes, speeding up single-threaded applications by reducing the switching overhead. Some multithreaded applications may suffer slower response time, but that's easily fixed by setting the limit back to a lower number using sys.setcheckinterval(N). The limit can be retrieved with the new sys.getcheckinterval() function.

One minor but far-reaching change is that the names of extension types defined by the modules included with Python now contain the module and a '.' in front of the type name. For example, in Python 2.2, if you created a socket and printed its __class__, you'd get this output:

>>> s = socket.socket()
>>> s.__class__
<type 'socket'>

在 2.3 中你會得到這個：

>>> s.__class__
<type '_socket.socket'>

One of the noted incompatibilities between old- and new-style classes has been removed: you can now assign to the __name__ and __bases__ attributes of new-style classes. There are some restrictions on what can be assigned to __bases__ along the lines of those relating to assigning to an instance's __class__ attribute.

String Changes

The in operator now works differently for strings. Previously, when evaluating X in Y where X and Y are strings, X could only be a single character. That's now changed; X can be a string of any length, and X in Y will return True if X is a substring of Y. If X is the empty string, the result is always True.

>>> 'ab' in 'abcd'
True
>>> 'ad' in 'abcd'
False
>>> '' in 'abcd'
True

Note that this doesn't tell you where the substring starts; if you need that information, use the find() string method.

The strip(), lstrip(), and rstrip() string methods now have an optional argument for specifying the characters to strip. The default is still to remove all whitespace characters:

>>> '   abc '.strip()
'abc'
>>> '><><abc<><><>'.strip('<>')
'abc'
>>> '><><abc<><><>\n'.strip('<>')
'abc<><><>\n'
>>> u'\u4000\u4001abc\u4000'.strip(u'\u4000')
u'\u4001abc'
>>>

(Suggested by Simon Brunning and implemented by Walter Dörwald.)

The startswith() and endswith() string methods now accept negative numbers for the start and end parameters.

Another new string method is zfill(), originally a function in the string module. zfill() pads a numeric string with zeros on the left until it's the specified width. Note that the % operator is still more flexible and powerful than zfill().

>>> '45'.zfill(4)
'0045'
>>> '12345'.zfill(4)
'12345'
>>> 'goofy'.zfill(6)
'0goofy'

（由 Walter Dörwald 所貢獻。）

A new type object, basestring, has been added. Both 8-bit strings and Unicode strings inherit from this type, so isinstance(obj, basestring) will return True for either kind of string. It's a completely abstract type, so you can't create basestring instances.

Interned strings are no longer immortal and will now be garbage-collected in the usual way when the only reference to them is from the internal dictionary of interned strings. (Implemented by Oren Tirosh.)

最佳化

The creation of new-style class instances has been made much faster; they're now faster than classic classes!

The sort() method of list objects has been extensively rewritten by Tim Peters, and the implementation is significantly faster.

Multiplication of large long integers is now much faster thanks to an implementation of Karatsuba multiplication, an algorithm that scales better than the O(n²) required for the grade-school multiplication algorithm. (Original patch by Christopher A. Craig, and significantly reworked by Tim Peters.)

The SET_LINENO opcode is now gone. This may provide a small speed increase, depending on your compiler's idiosyncrasies. See section Other Changes and Fixes for a longer explanation. (Removed by Michael Hudson.)

xrange() objects now have their own iterator, making for i in xrange(n) slightly faster than for i in range(n). (Patch by Raymond Hettinger.)

A number of small rearrangements have been made in various hotspots to improve performance, such as inlining a function or removing some code. (Implemented mostly by GvR, but lots of people have contributed single changes.)

The net result of the 2.3 optimizations is that Python 2.3 runs the pystone benchmark around 25% faster than Python 2.2.

New, Improved, and Deprecated Modules

As usual, Python's standard library received a number of enhancements and bug fixes. Here's a partial list of the most notable changes, sorted alphabetically by module name. Consult the Misc/NEWS file in the source tree for a more complete list of changes, or look through the CVS logs for all the details.

The array module now supports arrays of Unicode characters using the 'u' format character. Arrays also now support using the += assignment operator to add another array's contents, and the *= assignment operator to repeat an array. (Contributed by Jason Orendorff.)

The bsddb module has been replaced by version 4.1.6 of the PyBSDDB [https://pybsddb.sourceforge.net] package, providing a more complete interface to the transactional features of the BerkeleyDB library.

The old version of the module has been renamed to bsddb185 and is no longer built automatically; you'll have to edit Modules/Setup to enable it. Note that the new bsddb package is intended to be compatible with the old module, so be sure to file bugs if you discover any incompatibilities. When upgrading to Python 2.3, if the new interpreter is compiled with a new version of the underlying BerkeleyDB library, you will almost certainly have to convert your database files to the new version. You can do this fairly easily with the new scripts db2pickle.py and pickle2db.py which you will find in the distribution's Tools/scripts directory. If you've already been using the PyBSDDB package and importing it as bsddb3, you will have to change your import statements to import it as bsddb.

The new bz2 module is an interface to the bz2 data compression library. bz2-compressed data is usually smaller than corresponding zlib-compressed data. (Contributed by Gustavo Niemeyer.)

A set of standard date/time types has been added in the new datetime module. See the following section for more details.

The Distutils Extension class now supports an extra constructor argument named depends for listing additional source files that an extension depends on. This lets Distutils recompile the module if any of the dependency files are modified. For example, if sampmodule.c includes the header file sample.h, you would create the Extension object like this:

ext = Extension("samp",
                sources=["sampmodule.c"],
                depends=["sample.h"])

Modifying sample.h would then cause the module to be recompiled. (Contributed by Jeremy Hylton.)

Other minor changes to Distutils: it now checks for the CC, CFLAGS, CPP, LDFLAGS, and CPPFLAGS environment variables, using them to override the settings in Python's configuration (contributed by Robert Weber).

Previously the doctest module would only search the docstrings of public methods and functions for test cases, but it now also examines private ones as well. The DocTestSuite() function creates a unittest.TestSuite object from a set of doctest tests.

The new gc.get_referents(object) function returns a list of all the objects referenced by object.

The getopt module gained a new function, gnu_getopt(), that supports the same arguments as the existing getopt() function but uses GNU-style scanning mode. The existing getopt() stops processing options as soon as a non-option argument is encountered, but in GNU-style mode processing continues, meaning that options and arguments can be mixed. For example:

>>> getopt.getopt(['-f', 'filename', 'output', '-v'], 'f:v')
([('-f', 'filename')], ['output', '-v'])
>>> getopt.gnu_getopt(['-f', 'filename', 'output', '-v'], 'f:v')
([('-f', 'filename'), ('-v', '')], ['output'])

（由 Peter Åstrand 所貢獻。）

The grp, pwd, and resource modules now return enhanced tuples:

>>> import grp
>>> g = grp.getgrnam('amk')
>>> g.gr_name, g.gr_gid
('amk', 500)

The gzip module can now handle files exceeding 2 GiB.

The new heapq module contains an implementation of a heap queue algorithm. A heap is an array-like data structure that keeps items in a partially sorted order such that, for every index k, heap[k] <= heap[2*k+1] and heap[k] <= heap[2*k+2]. This makes it quick to remove the smallest item, and inserting a new item while maintaining the heap property is O(log n). (See https://xlinux.nist.gov/dads//HTML/priorityque.html for more information about the priority queue data structure.)

The heapq module provides heappush() and heappop() functions for adding and removing items while maintaining the heap property on top of some other mutable Python sequence type. Here's an example that uses a Python list:

>>> import heapq
>>> heap = []
>>> for item in [3, 7, 5, 11, 1]:
...    heapq.heappush(heap, item)
...
>>> heap
[1, 3, 5, 11, 7]
>>> heapq.heappop(heap)
1
>>> heapq.heappop(heap)
3
>>> heap
[5, 7, 11]

（由 Kevin O'Connor 所貢獻。）

The IDLE integrated development environment has been updated using the code from the IDLEfork project (https://idlefork.sourceforge.net). The most notable feature is that the code being developed is now executed in a subprocess, meaning that there's no longer any need for manual reload() operations. IDLE's core code has been incorporated into the standard library as the idlelib package.

The imaplib module now supports IMAP over SSL. (Contributed by Piers Lauder and Tino Lange.)

The itertools contains a number of useful functions for use with iterators, inspired by various functions provided by the ML and Haskell languages. For example, itertools.ifilter(predicate, iterator) returns all elements in the iterator for which the function predicate() returns True, and itertools.repeat(obj, N) returns obj N times. There are a number of other functions in the module; see the package's reference documentation for details. (Contributed by Raymond Hettinger.)

Two new functions in the math module, degrees(rads) and radians(degs), convert between radians and degrees. Other functions in the math module such as math.sin() and math.cos() have always required input values measured in radians. Also, an optional base argument was added to math.log() to make it easier to compute logarithms for bases other than e and 10. (Contributed by Raymond Hettinger.)

Several new POSIX functions (getpgid(), killpg(), lchown(), loadavg(), major(), makedev(), minor(), and mknod()) were added to the posix module that underlies the os module. (Contributed by Gustavo Niemeyer, Geert Jansen, and Denis S. Otkidach.)

In the os module, the *stat() family of functions can now report fractions of a second in a timestamp. Such time stamps are represented as floats, similar to the value returned by time.time().

During testing, it was found that some applications will break if time stamps are floats. For compatibility, when using the tuple interface of the stat_result time stamps will be represented as integers. When using named fields (a feature first introduced in Python 2.2), time stamps are still represented as integers, unless os.stat_float_times() is invoked to enable float return values:

>>> os.stat("/tmp").st_mtime
1034791200
>>> os.stat_float_times(True)
>>> os.stat("/tmp").st_mtime
1034791200.6335014

In Python 2.4, the default will change to always returning floats.

Application developers should enable this feature only if all their libraries work properly when confronted with floating-point time stamps, or if they use the tuple API. If used, the feature should be activated on an application level instead of trying to enable it on a per-use basis.

The optparse module contains a new parser for command-line arguments that can convert option values to a particular Python type and will automatically generate a usage message. See the following section for more details.

The old and never-documented linuxaudiodev module has been deprecated, and a new version named ossaudiodev has been added. The module was renamed because the OSS sound drivers can be used on platforms other than Linux, and the interface has also been tidied and brought up to date in various ways. (Contributed by Greg Ward and Nicholas FitzRoy-Dale.)

The new platform module contains a number of functions that try to determine various properties of the platform you're running on. There are functions for getting the architecture, CPU type, the Windows OS version, and even the Linux distribution version. (Contributed by Marc-André Lemburg.)

The parser objects provided by the pyexpat module can now optionally buffer character data, resulting in fewer calls to your character data handler and therefore faster performance. Setting the parser object's buffer_text attribute to True will enable buffering.

The sample(population, k) function was added to the random module. population is a sequence or xrange object containing the elements of a population, and sample() chooses k elements from the population without replacing chosen elements. k can be any value up to len(population). For example:

>>> days = ['Mo', 'Tu', 'We', 'Th', 'Fr', 'St', 'Sn']
>>> random.sample(days, 3)      # Choose 3 elements
['St', 'Sn', 'Th']
>>> random.sample(days, 7)      # Choose 7 elements
['Tu', 'Th', 'Mo', 'We', 'St', 'Fr', 'Sn']
>>> random.sample(days, 7)      # Choose 7 again
['We', 'Mo', 'Sn', 'Fr', 'Tu', 'St', 'Th']
>>> random.sample(days, 8)      # Can't choose eight
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "random.py", line 414, in sample
      raise ValueError, "sample larger than population"
ValueError: sample larger than population
>>> random.sample(xrange(1,10000,2), 10)   # Choose ten odd nos. under 10000
[3407, 3805, 1505, 7023, 2401, 2267, 9733, 3151, 8083, 9195]

The random module now uses a new algorithm, the Mersenne Twister, implemented in C. It's faster and more extensively studied than the previous algorithm.

(All changes contributed by Raymond Hettinger.)

The readline module also gained a number of new functions: get_history_item(), get_current_history_length(), and redisplay().

The rexec and Bastion modules have been declared dead, and attempts to import them will fail with a RuntimeError. New-style classes provide new ways to break out of the restricted execution environment provided by rexec, and no one has interest in fixing them or time to do so. If you have applications using rexec, rewrite them to use something else.

(Sticking with Python 2.2 or 2.1 will not make your applications any safer because there are known bugs in the rexec module in those versions. To repeat: if you're using rexec, stop using it immediately.)

The rotor module has been deprecated because the algorithm it uses for encryption is not believed to be secure. If you need encryption, use one of the several AES Python modules that are available separately.

The shutil module gained a move(src, dest) function that recursively moves a file or directory to a new location.

Support for more advanced POSIX signal handling was added to the signal but then removed again as it proved impossible to make it work reliably across platforms.

The socket module now supports timeouts. You can call the settimeout(t) method on a socket object to set a timeout of t seconds. Subsequent socket operations that take longer than t seconds to complete will abort and raise a socket.timeout exception.

The original timeout implementation was by Tim O'Malley. Michael Gilfix integrated it into the Python socket module and shepherded it through a lengthy review. After the code was checked in, Guido van Rossum rewrote parts of it. (This is a good example of a collaborative development process in action.)

On Windows, the socket module now ships with Secure Sockets Layer (SSL) support.

The value of the C PYTHON_API_VERSION macro is now exposed at the Python level as sys.api_version. The current exception can be cleared by calling the new sys.exc_clear() function.

The new tarfile module allows reading from and writing to tar-format archive files. (Contributed by Lars Gustäbel.)

The new textwrap module contains functions for wrapping strings containing paragraphs of text. The wrap(text, width) function takes a string and returns a list containing the text split into lines of no more than the chosen width. The fill(text, width) function returns a single string, reformatted to fit into lines no longer than the chosen width. (As you can guess, fill() is built on top of wrap(). For example:

>>> import textwrap
>>> paragraph = "Not a whit, we defy augury: ... more text ..."
>>> textwrap.wrap(paragraph, 60)
["Not a whit, we defy augury: there's a special providence in",
 "the fall of a sparrow. If it be now, 'tis not to come; if it",
 ...]
>>> print textwrap.fill(paragraph, 35)
Not a whit, we defy augury: there's
a special providence in the fall of
a sparrow. If it be now, 'tis not
to come; if it be not to come, it
will be now; if it be not now, yet
it will come: the readiness is all.
>>>

The module also contains a TextWrapper class that actually implements the text wrapping strategy. Both the TextWrapper class and the wrap() and fill() functions support a number of additional keyword arguments for fine-tuning the formatting; consult the module's documentation for details. (Contributed by Greg Ward.)

The thread and threading modules now have companion modules, dummy_thread and dummy_threading, that provide a do-nothing implementation of the thread module's interface for platforms where threads are not supported. The intention is to simplify thread-aware modules (ones that don't rely on threads to run) by putting the following code at the top:

try:
    import threading as _threading
except ImportError:
    import dummy_threading as _threading

In this example, _threading is used as the module name to make it clear that the module being used is not necessarily the actual threading module. Code can call functions and use classes in _threading whether or not threads are supported, avoiding an if statement and making the code slightly clearer. This module will not magically make multithreaded code run without threads; code that waits for another thread to return or to do something will simply hang forever.

The time module's strptime() function has long been an annoyance because it uses the platform C library's strptime() implementation, and different platforms sometimes have odd bugs. Brett Cannon contributed a portable implementation that's written in pure Python and should behave identically on all platforms.

The new timeit module helps measure how long snippets of Python code take to execute. The timeit.py file can be run directly from the command line, or the module's Timer class can be imported and used directly. Here's a short example that figures out whether it's faster to convert an 8-bit string to Unicode by appending an empty Unicode string to it or by using the unicode() function:

import timeit

timer1 = timeit.Timer('unicode("abc")')
timer2 = timeit.Timer('"abc" + u""')

# Run three trials
print timer1.repeat(repeat=3, number=100000)
print timer2.repeat(repeat=3, number=100000)

# On my laptop this outputs:
# [0.36831796169281006, 0.37441694736480713, 0.35304892063140869]
# [0.17574405670166016, 0.18193507194519043, 0.17565798759460449]

The Tix module has received various bug fixes and updates for the current version of the Tix package.

The Tkinter module now works with a thread-enabled version of Tcl. Tcl's threading model requires that widgets only be accessed from the thread in which they're created; accesses from another thread can cause Tcl to panic. For certain Tcl interfaces, Tkinter will now automatically avoid this when a widget is accessed from a different thread by marshalling a command, passing it to the correct thread, and waiting for the results. Other interfaces can't be handled automatically but Tkinter will now raise an exception on such an access so that you can at least find out about the problem. See https://mail.python.org/pipermail/python-dev/2002-December/031107.html for a more detailed explanation of this change. (Implemented by Martin von Löwis.)

Calling Tcl methods through _tkinter no longer returns only strings. Instead, if Tcl returns other objects those objects are converted to their Python equivalent, if one exists, or wrapped with a _tkinter.Tcl_Obj object if no Python equivalent exists. This behavior can be controlled through the wantobjects() method of tkapp objects.

When using _tkinter through the Tkinter module (as most Tkinter applications will), this feature is always activated. It should not cause compatibility problems, since Tkinter would always convert string results to Python types where possible.

If any incompatibilities are found, the old behavior can be restored by setting the wantobjects variable in the Tkinter module to false before creating the first tkapp object.

import Tkinter
Tkinter.wantobjects = 0

Any breakage caused by this change should be reported as a bug.

The UserDict module has a new DictMixin class which defines all dictionary methods for classes that already have a minimum mapping interface. This greatly simplifies writing classes that need to be substitutable for dictionaries, such as the classes in the shelve module.

Adding the mix-in as a superclass provides the full dictionary interface whenever the class defines __getitem__(), __setitem__(), __delitem__(), and keys(). For example:

>>> import UserDict
>>> class SeqDict(UserDict.DictMixin):
...     """Dictionary lookalike implemented with lists."""
...     def __init__(self):
...         self.keylist = []
...         self.valuelist = []
...     def __getitem__(self, key):
...         try:
...             i = self.keylist.index(key)
...         except ValueError:
...             raise KeyError
...         return self.valuelist[i]
...     def __setitem__(self, key, value):
...         try:
...             i = self.keylist.index(key)
...             self.valuelist[i] = value
...         except ValueError:
...             self.keylist.append(key)
...             self.valuelist.append(value)
...     def __delitem__(self, key):
...         try:
...             i = self.keylist.index(key)
...         except ValueError:
...             raise KeyError
...         self.keylist.pop(i)
...         self.valuelist.pop(i)
...     def keys(self):
...         return list(self.keylist)
...
>>> s = SeqDict()
>>> dir(s)      # See that other dictionary methods are implemented
['__cmp__', '__contains__', '__delitem__', '__doc__', '__getitem__',
 '__init__', '__iter__', '__len__', '__module__', '__repr__',
 '__setitem__', 'clear', 'get', 'has_key', 'items', 'iteritems',
 'iterkeys', 'itervalues', 'keylist', 'keys', 'pop', 'popitem',
 'setdefault', 'update', 'valuelist', 'values']

（由 Raymond Hettinger 所貢獻。）

The DOM implementation in xml.dom.minidom can now generate XML output in a particular encoding by providing an optional encoding argument to the toxml() and toprettyxml() methods of DOM nodes.

The xmlrpclib module now supports an XML-RPC extension for handling nil data values such as Python's None. Nil values are always supported on unmarshalling an XML-RPC response. To generate requests containing None, you must supply a true value for the allow_none parameter when creating a Marshaller instance.

The new DocXMLRPCServer module allows writing self-documenting XML-RPC servers. Run it in demo mode (as a program) to see it in action. Pointing the web browser to the RPC server produces pydoc-style documentation; pointing xmlrpclib to the server allows invoking the actual methods. (Contributed by Brian Quinlan.)

Support for internationalized domain names (RFCs 3454, 3490, 3491, and 3492) has been added. The "idna" encoding can be used to convert between a Unicode domain name and the ASCII-compatible encoding (ACE) of that name.

>{}>{}> u"www.Alliancefrançaise.nu".encode("idna")
'www.xn--alliancefranaise-npb.nu'

The socket module has also been extended to transparently convert Unicode hostnames to the ACE version before passing them to the C library. Modules that deal with hostnames such as httplib and ftplib) also support Unicode host names; httplib also sends HTTP Host headers using the ACE version of the domain name. urllib supports Unicode URLs with non-ASCII host names as long as the path part of the URL is ASCII only.

To implement this change, the stringprep module, the mkstringprep tool and the punycode encoding have been added.

Date/Time Type

Date and time types suitable for expressing timestamps were added as the datetime module. The types don't support different calendars or many fancy features, and just stick to the basics of representing time.

The three primary types are: date, representing a day, month, and year; time, consisting of hour, minute, and second; and datetime, which contains all the attributes of both date and time. There's also a timedelta class representing differences between two points in time, and time zone logic is implemented by classes inheriting from the abstract tzinfo class.

You can create instances of date and time by either supplying keyword arguments to the appropriate constructor, e.g. datetime.date(year=1972, month=10, day=15), or by using one of a number of class methods. For example, the today() class method returns the current local date.

Once created, instances of the date/time classes are all immutable. There are a number of methods for producing formatted strings from objects:

>>> import datetime
>>> now = datetime.datetime.now()
>>> now.isoformat()
'2002-12-30T21:27:03.994956'
>>> now.ctime()  # Only available on date, datetime
'Mon Dec 30 21:27:03 2002'
>>> now.strftime('%Y %d %b')
'2002 30 Dec'

The replace() method allows modifying one or more fields of a date or datetime instance, returning a new instance:

>>> d = datetime.datetime.now()
>>> d
datetime.datetime(2002, 12, 30, 22, 15, 38, 827738)
>>> d.replace(year=2001, hour = 12)
datetime.datetime(2001, 12, 30, 12, 15, 38, 827738)
>>>

Instances can be compared, hashed, and converted to strings (the result is the same as that of isoformat()). date and datetime instances can be subtracted from each other, and added to timedelta instances. The largest missing feature is that there's no standard library support for parsing strings and getting back a date or datetime.

For more information, refer to the module's reference documentation. (Contributed by Tim Peters.)

The optparse Module

The getopt module provides simple parsing of command-line arguments. The new optparse module (originally named Optik) provides more elaborate command-line parsing that follows the Unix conventions, automatically creates the output for --help, and can perform different actions for different options.

You start by creating an instance of OptionParser and telling it what your program's options are.

import sys
from optparse import OptionParser

op = OptionParser()
op.add_option('-i', '--input',
              action='store', type='string', dest='input',
              help='set input filename')
op.add_option('-l', '--length',
              action='store', type='int', dest='length',
              help='set maximum length of output')

Parsing a command line is then done by calling the parse_args() method.

options, args = op.parse_args(sys.argv[1:])
print options
print args

This returns an object containing all of the option values, and a list of strings containing the remaining arguments.

Invoking the script with the various arguments now works as you'd expect it to. Note that the length argument is automatically converted to an integer.

$ ./python opt.py -i data arg1
<Values at 0x400cad4c: {'input': 'data', 'length': None}>
['arg1']
$ ./python opt.py --input=data --length=4
<Values at 0x400cad2c: {'input': 'data', 'length': 4}>
[]
$

The help message is automatically generated for you:

$ ./python opt.py --help
usage: opt.py [options]

options:
  -h, --help            show this help message and exit
  -iINPUT, --input=INPUT
                        set input filename
  -lLENGTH, --length=LENGTH
                        set maximum length of output
$

更多細節請見 module 文件。

Optik was written by Greg Ward, with suggestions from the readers of the Getopt SIG.

Pymalloc: A Specialized Object Allocator

Pymalloc, a specialized object allocator written by Vladimir Marangozov, was a feature added to Python 2.1. Pymalloc is intended to be faster than the system malloc() and to have less memory overhead for allocation patterns typical of Python programs. The allocator uses C's malloc() function to get large pools of memory and then fulfills smaller memory requests from these pools.

In 2.1 and 2.2, pymalloc was an experimental feature and wasn't enabled by default; you had to explicitly enable it when compiling Python by providing the --with-pymalloc option to the configure script. In 2.3, pymalloc has had further enhancements and is now enabled by default; you'll have to supply --without-pymalloc to disable it.

This change is transparent to code written in Python; however, pymalloc may expose bugs in C extensions. Authors of C extension modules should test their code with pymalloc enabled, because some incorrect code may cause core dumps at runtime.

There's one particularly common error that causes problems. There are a number of memory allocation functions in Python's C API that have previously just been aliases for the C library's malloc() and free(), meaning that if you accidentally called mismatched functions the error wouldn't be noticeable. When the object allocator is enabled, these functions aren't aliases of malloc() and free() any more, and calling the wrong function to free memory may get you a core dump. For example, if memory was allocated using PyObject_Malloc(), it has to be freed using PyObject_Free(), not free(). A few modules included with Python fell afoul of this and had to be fixed; doubtless there are more third-party modules that will have the same problem.

As part of this change, the confusing multiple interfaces for allocating memory have been consolidated down into two API families. Memory allocated with one family must not be manipulated with functions from the other family. There is one family for allocating chunks of memory and another family of functions specifically for allocating Python objects.

To allocate and free an undistinguished chunk of memory use the "raw memory" family: PyMem_Malloc(), PyMem_Realloc(), and PyMem_Free().

The "object memory" family is the interface to the pymalloc facility described above and is biased towards a large number of "small" allocations: PyObject_Malloc(), PyObject_Realloc(), and PyObject_Free().

To allocate and free Python objects, use the "object" family PyObject_New, PyObject_NewVar, and PyObject_Del().

Thanks to lots of work by Tim Peters, pymalloc in 2.3 also provides debugging features to catch memory overwrites and doubled frees in both extension modules and in the interpreter itself. To enable this support, compile a debugging version of the Python interpreter by running configure with --with-pydebug.

To aid extension writers, a header file Misc/pymemcompat.h is distributed with the source to Python 2.3 that allows Python extensions to use the 2.3 interfaces to memory allocation while compiling against any version of Python since 1.5.2. You would copy the file from Python's source distribution and bundle it with the source of your extension.

也參考

https://hg.python.org/cpython/file/default/Objects/obmalloc.c

For the full details of the pymalloc implementation, see the comments at the top of the file Objects/obmalloc.c in the Python source code. The above link points to the file within the python.org SVN browser.

建置和 C API 變更

Python 建置程序和 C API 的變更包括：

The cycle detection implementation used by the garbage collection has proven to be stable, so it's now been made mandatory. You can no longer compile Python without it, and the --with-cycle-gc switch to configure has been removed.

Python can now optionally be built as a shared library (libpython2.3.so) by supplying --enable-shared when running Python's configure script. (Contributed by Ondrej Palkovsky.)

The DL_EXPORT and DL_IMPORT macros are now deprecated. Initialization functions for Python extension modules should now be declared using the new macro PyMODINIT_FUNC, while the Python core will generally use the PyAPI_FUNC and PyAPI_DATA macros.

The interpreter can be compiled without any docstrings for the built-in functions and modules by supplying --without-doc-strings to the configure script. This makes the Python executable about 10% smaller, but will also mean that you can't get help for Python's built-ins. (Contributed by Gustavo Niemeyer.)

The PyArg_NoArgs() macro is now deprecated, and code that uses it should be changed. For Python 2.2 and later, the method definition table can specify the METH_NOARGS flag, signalling that there are no arguments, and the argument checking can then be removed. If compatibility with pre-2.2 versions of Python is important, the code could use PyArg_ParseTuple(args, "") instead, but this will be slower than using METH_NOARGS.

PyArg_ParseTuple() accepts new format characters for various sizes of unsigned integers: B for unsigned char, H for unsigned short int, I for unsigned int, and K for unsigned long long.

A new function, PyObject_DelItemString(mapping, char *key) was added as shorthand for PyObject_DelItem(mapping, PyString_New(key)).

File objects now manage their internal string buffer differently, increasing it exponentially when needed. This results in the benchmark tests in Lib/test/test_bufio.py speeding up considerably (from 57 seconds to 1.7 seconds, according to one measurement).

It's now possible to define class and static methods for a C extension type by setting either the METH_CLASS or METH_STATIC flags in a method's PyMethodDef structure.

Python now includes a copy of the Expat XML parser's source code, removing any dependence on a system version or local installation of Expat.

If you dynamically allocate type objects in your extension, you should be aware of a change in the rules relating to the __module__ and __name__ attributes. In summary, you will want to ensure the type's dictionary contains a '__module__' key; making the module name the part of the type name leading up to the final period will no longer have the desired effect. For more detail, read the API reference documentation or the source.

Port-Specific Changes

Support for a port to IBM's OS/2 using the EMX runtime environment was merged into the main Python source tree. EMX is a POSIX emulation layer over the OS/2 system APIs. The Python port for EMX tries to support all the POSIX-like capability exposed by the EMX runtime, and mostly succeeds; fork() and fcntl() are restricted by the limitations of the underlying emulation layer. The standard OS/2 port, which uses IBM's Visual Age compiler, also gained support for case-sensitive import semantics as part of the integration of the EMX port into CVS. (Contributed by Andrew MacIntyre.)

On MacOS, most toolbox modules have been weaklinked to improve backward compatibility. This means that modules will no longer fail to load if a single routine is missing on the current OS version. Instead calling the missing routine will raise an exception. (Contributed by Jack Jansen.)

The RPM spec files, found in the Misc/RPM/ directory in the Python source distribution, were updated for 2.3. (Contributed by Sean Reifschneider.)

Other new platforms now supported by Python include AtheOS (http://www.atheos.cx/), GNU/Hurd, and OpenVMS.

Other Changes and Fixes

As usual, there were a bunch of other improvements and bugfixes scattered throughout the source tree. A search through the CVS change logs finds there were 523 patches applied and 514 bugs fixed between Python 2.2 and 2.3. Both figures are likely to be underestimates.

Some of the more notable changes are:

If the PYTHONINSPECT environment variable is set, the Python interpreter will enter the interactive prompt after running a Python program, as if Python had been invoked with the -i option. The environment variable can be set before running the Python interpreter, or it can be set by the Python program as part of its execution.

The regrtest.py script now provides a way to allow "all resources except foo." A resource name passed to the -u option can now be prefixed with a hyphen ('-') to mean "remove this resource." For example, the option '-uall,-bsddb' could be used to enable the use of all resources except bsddb.

The tools used to build the documentation now work under Cygwin as well as Unix.

The SET_LINENO opcode has been removed. Back in the mists of time, this opcode was needed to produce line numbers in tracebacks and support trace functions (for, e.g., pdb). Since Python 1.5, the line numbers in tracebacks have been computed using a different mechanism that works with "python -O". For Python 2.3 Michael Hudson implemented a similar scheme to determine when to call the trace function, removing the need for SET_LINENO entirely.

It would be difficult to detect any resulting difference from Python code, apart from a slight speed up when Python is run without -O.

C extensions that access the f_lineno field of frame objects should instead call PyCode_Addr2Line(f->f_code, f->f_lasti). This will have the added effect of making the code work as desired under "python -O" in earlier versions of Python.

A nifty new feature is that trace functions can now assign to the f_lineno attribute of frame objects, changing the line that will be executed next. A jump command has been added to the pdb debugger taking advantage of this new feature. (Implemented by Richie Hindle.)

Porting to Python 2.3

This section lists previously described changes that may require changes to your code:

yield is now always a keyword; if it's used as a variable name in your code, a different name must be chosen.

For strings X and Y, X in Y now works if X is more than one character long.

The int() type constructor will now return a long integer instead of raising an OverflowError when a string or floating-point number is too large to fit into an integer.

If you have Unicode strings that contain 8-bit characters, you must declare the file's encoding (UTF-8, Latin-1, or whatever) by adding a comment to the top of the file. See section PEP 263: Source Code Encodings for more information.

Calling Tcl methods through _tkinter no longer returns only strings. Instead, if Tcl returns other objects those objects are converted to their Python equivalent, if one exists, or wrapped with a _tkinter.Tcl_Obj object if no Python equivalent exists.

Large octal and hex literals such as 0xffffffff now trigger a FutureWarning. Currently they're stored as 32-bit numbers and result in a negative value, but in Python 2.4 they'll become positive long integers.

There are a few ways to fix this warning. If you really need a positive number, just add an L to the end of the literal. If you're trying to get a 32-bit integer with low bits set and have previously used an expression such as ~(1 << 31), it's probably clearest to start with all bits set and clear the desired upper bits. For example, to clear just the top bit (bit 31), you could write 0xffffffffL &~(1L<<31).

You can no longer disable assertions by assigning to __debug__.

The Distutils setup() function has gained various new keyword arguments such as depends. Old versions of the Distutils will abort if passed unknown keywords. A solution is to check for the presence of the new get_distutil_options() function in your setup.py and only uses the new keywords with a version of the Distutils that supports them:

from distutils import core

kw = {'sources': 'foo.c', ...}
if hasattr(core, 'get_distutil_options'):
    kw['depends'] = ['foo.h']
ext = Extension(**kw)

Using None as a variable name will now result in a SyntaxWarning warning.

Names of extension types defined by the modules included with Python now contain the module and a '.' in front of the type name.

致謝

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Jeff Bauer, Simon Brunning, Brett Cannon, Michael Chermside, Andrew Dalke, Scott David Daniels, Fred L. Drake, Jr., David Fraser, Kelly Gerber, Raymond Hettinger, Michael Hudson, Chris Lambert, Detlef Lannert, Martin von Löwis, Andrew MacIntyre, Lalo Martins, Chad Netzer, Gustavo Niemeyer, Neal Norwitz, Hans Nowak, Chris Reedy, Francesco Ricciardi, Vinay Sajip, Neil Schemenauer, Roman Suzi, Jason Tishler, Just van Rossum.

Python 2.2 有什麼新功能

作者:

A.M. Kuchling

簡介

This article explains the new features in Python 2.2.2, released on October 14, 2002. Python 2.2.2 is a bugfix release of Python 2.2, originally released on December 21, 2001.

Python 2.2 can be thought of as the "cleanup release". There are some features such as generators and iterators that are completely new, but most of the changes, significant and far-reaching though they may be, are aimed at cleaning up irregularities and dark corners of the language design.

This article doesn't attempt to provide a complete specification of the new features, but instead provides a convenient overview. For full details, you should refer to the documentation for Python 2.2, such as the Python Library Reference [https://docs.python.org/2.2/lib/lib.html] and the Python Reference Manual [https://docs.python.org/2.2/ref/ref.html]. If you want to understand the complete implementation and design rationale for a change, refer to the PEP for a particular new feature.

PEPs 252 and 253: Type and Class Changes

The largest and most far-reaching changes in Python 2.2 are to Python's model of objects and classes. The changes should be backward compatible, so it's likely that your code will continue to run unchanged, but the changes provide some amazing new capabilities. Before beginning this, the longest and most complicated section of this article, I'll provide an overview of the changes and offer some comments.

A long time ago I wrote a web page listing flaws in Python's design. One of the most significant flaws was that it's impossible to subclass Python types implemented in C. In particular, it's not possible to subclass built-in types, so you can't just subclass, say, lists in order to add a single useful method to them. The UserList module provides a class that supports all of the methods of lists and that can be subclassed further, but there's lots of C code that expects a regular Python list and won't accept a UserList instance.

Python 2.2 fixes this, and in the process adds some exciting new capabilities. A brief summary:

You can subclass built-in types such as lists and even integers, and your subclasses should work in every place that requires the original type.

It's now possible to define static and class methods, in addition to the instance methods available in previous versions of Python.

It's also possible to automatically call methods on accessing or setting an instance attribute by using a new mechanism called properties. Many uses of __getattr__() can be rewritten to use properties instead, making the resulting code simpler and faster. As a small side benefit, attributes can now have docstrings, too.

The list of legal attributes for an instance can be limited to a particular set using slots, making it possible to safeguard against typos and perhaps make more optimizations possible in future versions of Python.

Some users have voiced concern about all these changes. Sure, they say, the new features are neat and lend themselves to all sorts of tricks that weren't possible in previous versions of Python, but they also make the language more complicated. Some people have said that they've always recommended Python for its simplicity, and feel that its simplicity is being lost.

Personally, I think there's no need to worry. Many of the new features are quite esoteric, and you can write a lot of Python code without ever needed to be aware of them. Writing a simple class is no more difficult than it ever was, so you don't need to bother learning or teaching them unless they're actually needed. Some very complicated tasks that were previously only possible from C will now be possible in pure Python, and to my mind that's all for the better.

I'm not going to attempt to cover every single corner case and small change that were required to make the new features work. Instead this section will paint only the broad strokes. See section 相關連結, "Related Links", for further sources of information about Python 2.2's new object model.

舊的和新的類別

First, you should know that Python 2.2 really has two kinds of classes: classic or old-style classes, and new-style classes. The old-style class model is exactly the same as the class model in earlier versions of Python. All the new features described in this section apply only to new-style classes. This divergence isn't intended to last forever; eventually old-style classes will be dropped, possibly in Python 3.0.

So how do you define a new-style class? You do it by subclassing an existing new-style class. Most of Python's built-in types, such as integers, lists, dictionaries, and even files, are new-style classes now. A new-style class named object, the base class for all built-in types, has also been added so if no built-in type is suitable, you can just subclass object:

class C(object):
    def __init__ (self):
        ...
    ...

This means that class statements that don't have any base classes are always classic classes in Python 2.2. (Actually you can also change this by setting a module-level variable named __metaclass__ --- see PEP 253 [https://peps.python.org/pep-0253/] for the details --- but it's easier to just subclass object.)

The type objects for the built-in types are available as built-ins, named using a clever trick. Python has always had built-in functions named int(), float(), and str(). In 2.2, they aren't functions any more, but type objects that behave as factories when called.

>>> int
<type 'int'>
>>> int('123')
123

To make the set of types complete, new type objects such as dict() and file() have been added. Here's a more interesting example, adding a lock() method to file objects:

class LockableFile(file):
    def lock (self, operation, length=0, start=0, whence=0):
        import fcntl
        return fcntl.lockf(self.fileno(), operation,
                           length, start, whence)

The now-obsolete posixfile module contained a class that emulated all of a file object's methods and also added a lock() method, but this class couldn't be passed to internal functions that expected a built-in file, something which is possible with our new LockableFile.

描述器

In previous versions of Python, there was no consistent way to discover what attributes and methods were supported by an object. There were some informal conventions, such as defining __members__ and __methods__ attributes that were lists of names, but often the author of an extension type or a class wouldn't bother to define them. You could fall back on inspecting the __dict__ of an object, but when class inheritance or an arbitrary __getattr__() hook were in use this could still be inaccurate.

The one big idea underlying the new class model is that an API for describing the attributes of an object using descriptors has been formalized. Descriptors specify the value of an attribute, stating whether it's a method or a field. With the descriptor API, static methods and class methods become possible, as well as more exotic constructs.

Attribute descriptors are objects that live inside class objects, and have a few attributes of their own:

__name__ 是屬性的名稱。

__doc__ 是屬性的文件字串 (docstring)。

__get__(object) is a method that retrieves the attribute value from object.

__set__(object, value) sets the attribute on object to value.

__delete__(object, value) deletes the value attribute of object.

For example, when you write obj.x, the steps that Python actually performs are:

descriptor = obj.__class__.x
descriptor.__get__(obj)

For methods, descriptor.__get__ returns a temporary object that's callable, and wraps up the instance and the method to be called on it. This is also why static methods and class methods are now possible; they have descriptors that wrap up just the method, or the method and the class. As a brief explanation of these new kinds of methods, static methods aren't passed the instance, and therefore resemble regular functions. Class methods are passed the class of the object, but not the object itself. Static and class methods are defined like this:

class C(object):
    def f(arg1, arg2):
        ...
    f = staticmethod(f)

    def g(cls, arg1, arg2):
        ...
    g = classmethod(g)

The staticmethod() function takes the function f(), and returns it wrapped up in a descriptor so it can be stored in the class object. You might expect there to be special syntax for creating such methods (def static f, defstatic f(), or something like that) but no such syntax has been defined yet; that's been left for future versions of Python.

More new features, such as slots and properties, are also implemented as new kinds of descriptors, and it's not difficult to write a descriptor class that does something novel. For example, it would be possible to write a descriptor class that made it possible to write Eiffel-style preconditions and postconditions for a method. A class that used this feature might be defined like this:

from eiffel import eiffelmethod

class C(object):
    def f(self, arg1, arg2):
        # The actual function
        ...
    def pre_f(self):
        # Check preconditions
        ...
    def post_f(self):
        # Check postconditions
        ...

    f = eiffelmethod(f, pre_f, post_f)

Note that a person using the new eiffelmethod() doesn't have to understand anything about descriptors. This is why I think the new features don't increase the basic complexity of the language. There will be a few wizards who need to know about it in order to write eiffelmethod() or the ZODB or whatever, but most users will just write code on top of the resulting libraries and ignore the implementation details.

Multiple Inheritance: The Diamond Rule

Multiple inheritance has also been made more useful through changing the rules under which names are resolved. Consider this set of classes (diagram taken from PEP 253 [https://peps.python.org/pep-0253/] by Guido van Rossum):

      class A:
        ^ ^  def save(self): ...
       /   \
      /     \
     /       \
    /         \
class B     class C:
    ^         ^  def save(self): ...
     \       /
      \     /
       \   /
        \ /
      class D

The lookup rule for classic classes is simple but not very smart; the base classes are searched depth-first, going from left to right. A reference to D.save() will search the classes D, B, and then A, where save() would be found and returned. C.save() would never be found at all. This is bad, because if C's save() method is saving some internal state specific to C, not calling it will result in that state never getting saved.

New-style classes follow a different algorithm that's a bit more complicated to explain, but does the right thing in this situation. (Note that Python 2.3 changes this algorithm to one that produces the same results in most cases, but produces more useful results for really complicated inheritance graphs.)

List all the base classes, following the classic lookup rule and include a class multiple times if it's visited repeatedly. In the above example, the list of visited classes is [D, B, A, C, A].

Scan the list for duplicated classes. If any are found, remove all but one occurrence, leaving the last one in the list. In the above example, the list becomes [D, B, C, A] after dropping duplicates.

Following this rule, referring to D.save() will return C.save(), which is the behaviour we're after. This lookup rule is the same as the one followed by Common Lisp. A new built-in function, super(), provides a way to get at a class's superclasses without having to reimplement Python's algorithm. The most commonly used form will be super(class, obj), which returns a bound superclass object (not the actual class object). This form will be used in methods to call a method in the superclass; for example, D's save() method would look like this:

class D (B,C):
    def save (self):
        # Call superclass .save()
        super(D, self).save()
        # Save D's private information here
        ...

super() can also return unbound superclass objects when called as super(class) or super(class1, class2), but this probably won't often be useful.

Attribute Access

A fair number of sophisticated Python classes define hooks for attribute access using __getattr__(); most commonly this is done for convenience, to make code more readable by automatically mapping an attribute access such as obj.parent into a method call such as obj.get_parent. Python 2.2 adds some new ways of controlling attribute access.

First, __getattr__(attr_name) is still supported by new-style classes, and nothing about it has changed. As before, it will be called when an attempt is made to access obj.foo and no attribute named foo is found in the instance's dictionary.

New-style classes also support a new method, __getattribute__(attr_name). The difference between the two methods is that __getattribute__() is always called whenever any attribute is accessed, while the old __getattr__() is only called if foo isn't found in the instance's dictionary.

However, Python 2.2's support for properties will often be a simpler way to trap attribute references. Writing a __getattr__() method is complicated because to avoid recursion you can't use regular attribute accesses inside them, and instead have to mess around with the contents of __dict__. __getattr__() methods also end up being called by Python when it checks for other methods such as __repr__() or __coerce__(), and so have to be written with this in mind. Finally, calling a function on every attribute access results in a sizable performance loss.

property is a new built-in type that packages up three functions that get, set, or delete an attribute, and a docstring. For example, if you want to define a size attribute that's computed, but also settable, you could write:

class C(object):
    def get_size (self):
        result = ... computation ...
        return result
    def set_size (self, size):
        ... compute something based on the size
        and set internal state appropriately ...

    # Define a property.  The 'delete this attribute'
    # method is defined as None, so the attribute
    # can't be deleted.
    size = property(get_size, set_size,
                    None,
                    "Storage size of this instance")

That is certainly clearer and easier to write than a pair of __getattr__()/__setattr__() methods that check for the size attribute and handle it specially while retrieving all other attributes from the instance's __dict__. Accesses to size are also the only ones which have to perform the work of calling a function, so references to other attributes run at their usual speed.

Finally, it's possible to constrain the list of attributes that can be referenced on an object using the new __slots__ class attribute. Python objects are usually very dynamic; at any time it's possible to define a new attribute on an instance by just doing obj.new_attr=1. A new-style class can define a class attribute named __slots__ to limit the legal attributes to a particular set of names. An example will make this clear:

>>> class C(object):
...     __slots__ = ('template', 'name')
...
>>> obj = C()
>>> print obj.template
None
>>> obj.template = 'Test'
>>> print obj.template
Test
>>> obj.newattr = None
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'C' object has no attribute 'newattr'

Note how you get an AttributeError on the attempt to assign to an attribute not listed in __slots__.

相關連結

This section has just been a quick overview of the new features, giving enough of an explanation to start you programming, but many details have been simplified or ignored. Where should you go to get a more complete picture?

The 描述器 (Descriptor) 指南 is a lengthy tutorial introduction to the descriptor features, written by Guido van Rossum. If my description has whetted your appetite, go read this tutorial next, because it goes into much more detail about the new features while still remaining quite easy to read.

Next, there are two relevant PEPs, PEP 252 [https://peps.python.org/pep-0252/] and PEP 253 [https://peps.python.org/pep-0253/]. PEP 252 [https://peps.python.org/pep-0252/] is titled "Making Types Look More Like Classes", and covers the descriptor API. PEP 253 [https://peps.python.org/pep-0253/] is titled "Subtyping Built-in Types", and describes the changes to type objects that make it possible to subtype built-in objects. PEP 253 [https://peps.python.org/pep-0253/] is the more complicated PEP of the two, and at a few points the necessary explanations of types and meta-types may cause your head to explode. Both PEPs were written and implemented by Guido van Rossum, with substantial assistance from the rest of the Zope Corp. team.

Finally, there's the ultimate authority: the source code. Most of the machinery for the type handling is in Objects/typeobject.c, but you should only resort to it after all other avenues have been exhausted, including posting a question to python-list or python-dev.

PEP 234：疊代器

Another significant addition to 2.2 is an iteration interface at both the C and Python levels. Objects can define how they can be looped over by callers.

In Python versions up to 2.1, the usual way to make for item in obj work is to define a __getitem__() method that looks something like this:

def __getitem__(self, index):
    return <next item>

__getitem__() is more properly used to define an indexing operation on an object so that you can write obj[5] to retrieve the sixth element. It's a bit misleading when you're using this only to support for loops. Consider some file-like object that wants to be looped over; the index parameter is essentially meaningless, as the class probably assumes that a series of __getitem__() calls will be made with index incrementing by one each time. In other words, the presence of the __getitem__() method doesn't mean that using file[5] to randomly access the sixth element will work, though it really should.

In Python 2.2, iteration can be implemented separately, and __getitem__() methods can be limited to classes that really do support random access. The basic idea of iterators is simple. A new built-in function, iter(obj) or iter(C, sentinel), is used to get an iterator. iter(obj) returns an iterator for the object obj, while iter(C, sentinel) returns an iterator that will invoke the callable object C until it returns sentinel to signal that the iterator is done.

Python classes can define an __iter__() method, which should create and return a new iterator for the object; if the object is its own iterator, this method can just return self. In particular, iterators will usually be their own iterators. Extension types implemented in C can implement a tp_iter function in order to return an iterator, and extension types that want to behave as iterators can define a tp_iternext function.

So, after all this, what do iterators actually do? They have one required method, next(), which takes no arguments and returns the next value. When there are no more values to be returned, calling next() should raise the StopIteration exception.

>>> L = [1,2,3]
>>> i = iter(L)
>>> print i
<iterator object at 0x8116870>
>>> i.next()
1
>>> i.next()
2
>>> i.next()
3
>>> i.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
StopIteration
>>>

In 2.2, Python's for statement no longer expects a sequence; it expects something for which iter() will return an iterator. For backward compatibility and convenience, an iterator is automatically constructed for sequences that don't implement __iter__() or a tp_iter slot, so for i in [1,2,3] will still work. Wherever the Python interpreter loops over a sequence, it's been changed to use the iterator protocol. This means you can do things like this:

>>> L = [1,2,3]
>>> i = iter(L)
>>> a,b,c = i
>>> a,b,c
(1, 2, 3)

Iterator support has been added to some of Python's basic types. Calling iter() on a dictionary will return an iterator which loops over its keys:

>>> m = {'Jan': 1, 'Feb': 2, 'Mar': 3, 'Apr': 4, 'May': 5, 'Jun': 6,
...      'Jul': 7, 'Aug': 8, 'Sep': 9, 'Oct': 10, 'Nov': 11, 'Dec': 12}
>>> for key in m: print key, m[key]
...
Mar 3
Feb 2
Aug 8
Sep 9
May 5
Jun 6
Jul 7
Jan 1
Apr 4
Nov 11
Dec 12
Oct 10

That's just the default behaviour. If you want to iterate over keys, values, or key/value pairs, you can explicitly call the iterkeys(), itervalues(), or iteritems() methods to get an appropriate iterator. In a minor related change, the in operator now works on dictionaries, so key in dict is now equivalent to dict.has_key(key).

Files also provide an iterator, which calls the readline() method until there are no more lines in the file. This means you can now read each line of a file using code like this:

for line in file:
    # do something for each line
    ...

Note that you can only go forward in an iterator; there's no way to get the previous element, reset the iterator, or make a copy of it. An iterator object could provide such additional capabilities, but the iterator protocol only requires a next() method.

也參考

PEP 234 [https://peps.python.org/pep-0234/] - 疊代器

由 Ka-Ping Yee 和 GvR 撰寫；由 Python Labs 團隊實作，主要為 GvR 和 Tim Peters 所貢獻。

PEP 255：簡單產生器

Generators are another new feature, one that interacts with the introduction of iterators.

You're doubtless familiar with how function calls work in Python or C. When you call a function, it gets a private namespace where its local variables are created. When the function reaches a return statement, the local variables are destroyed and the resulting value is returned to the caller. A later call to the same function will get a fresh new set of local variables. But, what if the local variables weren't thrown away on exiting a function? What if you could later resume the function where it left off? This is what generators provide; they can be thought of as resumable functions.

Here's the simplest example of a generator function:

def generate_ints(N):
    for i in range(N):
        yield i

A new keyword, yield, was introduced for generators. Any function containing a yield statement is a generator function; this is detected by Python's bytecode compiler which compiles the function specially as a result. Because a new keyword was introduced, generators must be explicitly enabled in a module by including a from __future__ import generators statement near the top of the module's source code. In Python 2.3 this statement will become unnecessary.

When you call a generator function, it doesn't return a single value; instead it returns a generator object that supports the iterator protocol. On executing the yield statement, the generator outputs the value of i, similar to a return statement. The big difference between yield and a return statement is that on reaching a yield the generator's state of execution is suspended and local variables are preserved. On the next call to the generator's next() method, the function will resume executing immediately after the yield statement. (For complicated reasons, the yield statement isn't allowed inside the try block of a try...finally statement; read PEP 255 [https://peps.python.org/pep-0255/] for a full explanation of the interaction between yield and exceptions.)

Here's a sample usage of the generate_ints() generator:

>>> gen = generate_ints(3)
>>> gen
<generator object at 0x8117f90>
>>> gen.next()
0
>>> gen.next()
1
>>> gen.next()
2
>>> gen.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 2, in generate_ints
StopIteration

You could equally write for i in generate_ints(5), or a,b,c = generate_ints(3).

Inside a generator function, the return statement can only be used without a value, and signals the end of the procession of values; afterwards the generator cannot return any further values. return with a value, such as return 5, is a syntax error inside a generator function. The end of the generator's results can also be indicated by raising StopIteration manually, or by just letting the flow of execution fall off the bottom of the function.

You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables. For example, returning a list of integers could be done by setting self.count to 0, and having the next() method increment self.count and return it. However, for a moderately complicated generator, writing a corresponding class would be much messier. Lib/test/test_generators.py contains a number of more interesting examples. The simplest one implements an in-order traversal of a tree using generators recursively.

# A recursive generator that generates Tree leaves in in-order.
def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x
        yield t.label
        for x in inorder(t.right):
            yield x

Two other examples in Lib/test/test_generators.py produce solutions for the N-Queens problem (placing $N$ queens on an $NxN$ chess board so that no queen threatens another) and the Knight's Tour (a route that takes a knight to every square of an $NxN$ chessboard without visiting any square twice).

The idea of generators comes from other programming languages, especially Icon (https://www2.cs.arizona.edu/icon/), where the idea of generators is central. In Icon, every expression and function call behaves like a generator. One example from "An Overview of the Icon Programming Language" at https://www2.cs.arizona.edu/icon/docs/ipd266.htm gives an idea of what this looks like:

sentence := "Store it in the neighboring harbor"
if (i := find("or", sentence)) > 5 then write(i)

In Icon the find() function returns the indexes at which the substring "or" is found: 3, 23, 33. In the if statement, i is first assigned a value of 3, but 3 is less than 5, so the comparison fails, and Icon retries it with the second value of 23. 23 is greater than 5, so the comparison now succeeds, and the code prints the value 23 to the screen.

Python doesn't go nearly as far as Icon in adopting generators as a central concept. Generators are considered a new part of the core Python language, but learning or using them isn't compulsory; if they don't solve any problems that you have, feel free to ignore them. One novel feature of Python's interface as compared to Icon's is that a generator's state is represented as a concrete object (the iterator) that can be passed around to other functions or stored in a data structure.

也參考

PEP 255 [https://peps.python.org/pep-0255/] - 簡單產生器

Written by Neil Schemenauer, Tim Peters, Magnus Lie Hetland. Implemented mostly by Neil Schemenauer and Tim Peters, with other fixes from the Python Labs crew.

PEP 237: Unifying Long Integers and Integers

In recent versions, the distinction between regular integers, which are 32-bit values on most machines, and long integers, which can be of arbitrary size, was becoming an annoyance. For example, on platforms that support files larger than 2**32 bytes, the tell() method of file objects has to return a long integer. However, there were various bits of Python that expected plain integers and would raise an error if a long integer was provided instead. For example, in Python 1.5, only regular integers could be used as a slice index, and 'abc'[1L:] would raise a TypeError exception with the message 'slice index must be int'.

Python 2.2 will shift values from short to long integers as required. The 'L' suffix is no longer needed to indicate a long integer literal, as now the compiler will choose the appropriate type. (Using the 'L' suffix will be discouraged in future 2.x versions of Python, triggering a warning in Python 2.4, and probably dropped in Python 3.0.) Many operations that used to raise an OverflowError will now return a long integer as their result. For example:

>>> 1234567890123
1234567890123L
>>> 2 ** 64
18446744073709551616L

In most cases, integers and long integers will now be treated identically. You can still distinguish them with the type() built-in function, but that's rarely needed.

也參考

PEP 237 [https://peps.python.org/pep-0237/] - Unifying Long Integers and Integers

Written by Moshe Zadka and Guido van Rossum. Implemented mostly by Guido van Rossum.

PEP 238: Changing the Division Operator

The most controversial change in Python 2.2 heralds the start of an effort to fix an old design flaw that's been in Python from the beginning. Currently Python's division operator, /, behaves like C's division operator when presented with two integer arguments: it returns an integer result that's truncated down when there would be a fractional part. For example, 3/2 is 1, not 1.5, and (-1)/2 is -1, not -0.5. This means that the results of division can vary unexpectedly depending on the type of the two operands and because Python is dynamically typed, it can be difficult to determine the possible types of the operands.

(The controversy is over whether this is really a design flaw, and whether it's worth breaking existing code to fix this. It's caused endless discussions on python-dev, and in July 2001 erupted into a storm of acidly sarcastic postings on comp.lang.python. I won't argue for either side here and will stick to describing what's implemented in 2.2. Read PEP 238 [https://peps.python.org/pep-0238/] for a summary of arguments and counter-arguments.)

Because this change might break code, it's being introduced very gradually. Python 2.2 begins the transition, but the switch won't be complete until Python 3.0.

First, I'll borrow some terminology from PEP 238 [https://peps.python.org/pep-0238/]. "True division" is the division that most non-programmers are familiar with: 3/2 is 1.5, 1/4 is 0.25, and so forth. "Floor division" is what Python's / operator currently does when given integer operands; the result is the floor of the value returned by true division. "Classic division" is the current mixed behaviour of /; it returns the result of floor division when the operands are integers, and returns the result of true division when one of the operands is a floating-point number.

Here are the changes 2.2 introduces:

A new operator, //, is the floor division operator. (Yes, we know it looks like C++'s comment symbol.) // always performs floor division no matter what the types of its operands are, so 1 // 2 is 0 and 1.0 // 2.0 is also 0.0.

// is always available in Python 2.2; you don't need to enable it using a __future__ statement.

By including a from __future__ import division in a module, the / operator will be changed to return the result of true division, so 1/2 is 0.5. Without the __future__ statement, / still means classic division. The default meaning of / will not change until Python 3.0.

Classes can define methods called __truediv__() and __floordiv__() to overload the two division operators. At the C level, there are also slots in the PyNumberMethods structure so extension types can define the two operators.

Python 2.2 supports some command-line arguments for testing whether code will work with the changed division semantics. Running python with -Q warn will cause a warning to be issued whenever division is applied to two integers. You can use this to find code that's affected by the change and fix it. By default, Python 2.2 will simply perform classic division without a warning; the warning will be turned on by default in Python 2.3.

也參考

PEP 238 [https://peps.python.org/pep-0238/] - Changing the Division Operator

Written by Moshe Zadka and Guido van Rossum. Implemented by Guido van Rossum..

Unicode 變更

Python's Unicode support has been enhanced a bit in 2.2. Unicode strings are usually stored as UCS-2, as 16-bit unsigned integers. Python 2.2 can also be compiled to use UCS-4, 32-bit unsigned integers, as its internal encoding by supplying --enable-unicode=ucs4 to the configure script. (It's also possible to specify --disable-unicode to completely disable Unicode support.)

When built to use UCS-4 (a "wide Python"), the interpreter can natively handle Unicode characters from U+000000 to U+110000, so the range of legal values for the unichr() function is expanded accordingly. Using an interpreter compiled to use UCS-2 (a "narrow Python"), values greater than 65535 will still cause unichr() to raise a ValueError exception. This is all described in PEP 261 [https://peps.python.org/pep-0261/], "Support for 'wide' Unicode characters"; consult it for further details.

Another change is simpler to explain. Since their introduction, Unicode strings have supported an encode() method to convert the string to a selected encoding such as UTF-8 or Latin-1. A symmetric decode([*encoding*]) method has been added to 8-bit strings (though not to Unicode strings) in 2.2. decode() assumes that the string is in the specified encoding and decodes it, returning whatever is returned by the codec.

Using this new feature, codecs have been added for tasks not directly related to Unicode. For example, codecs have been added for uu-encoding, MIME's base64 encoding, and compression with the zlib module:

>>> s = """Here is a lengthy piece of redundant, overly verbose,
... and repetitive text.
... """
>>> data = s.encode('zlib')
>>> data
'x\x9c\r\xc9\xc1\r\x80 \x10\x04\xc0?Ul...'
>>> data.decode('zlib')
'Here is a lengthy piece of redundant, overly verbose,\nand repetitive text.\n'
>>> print s.encode('uu')
begin 666 <data>
M2&5R92!I<R!A(&QE;F=T:'D@<&EE8V4@;V8@<F5D=6YD86YT+"!O=F5R;'D@
>=F5R8F]S92P*86YD(')E<&5T:71I=F4@=&5X="X*

end
>>> "sheesh".encode('rot-13')
'furrfu'

To convert a class instance to Unicode, a __unicode__() method can be defined by a class, analogous to __str__().

encode(), decode(), and __unicode__() were implemented by Marc-André Lemburg. The changes to support using UCS-4 internally were implemented by Fredrik Lundh and Martin von Löwis.

也參考

PEP 261 [https://peps.python.org/pep-0261/] - 支援 'wide' Unicode 字元

由 Paul Prescod 撰寫。

PEP 227: Nested Scopes

In Python 2.1, statically nested scopes were added as an optional feature, to be enabled by a from __future__ import nested_scopes directive. In 2.2 nested scopes no longer need to be specially enabled, and are now always present. The rest of this section is a copy of the description of nested scopes from my "What's New in Python 2.1" document; if you read it when 2.1 came out, you can skip the rest of this section.

The largest change introduced in Python 2.1, and made complete in 2.2, is to Python's scoping rules. In Python 2.0, at any given time there are at most three namespaces used to look up variable names: local, module-level, and the built-in namespace. This often surprised people because it didn't match their intuitive expectations. For example, a nested recursive function definition doesn't work:

def f():
    ...
    def g(value):
        ...
        return g(value-1) + 1
    ...

The function g() will always raise a NameError exception, because the binding of the name g isn't in either its local namespace or in the module-level namespace. This isn't much of a problem in practice (how often do you recursively define interior functions like this?), but this also made using the lambda expression clumsier, and this was a problem in practice. In code which uses lambda you can often find local variables being copied by passing them as the default values of arguments.

def find(self, name):
    "回傳串列中任何等於 'name' 的項目"
    L = filter(lambda x, name=name: x == name,
               self.list_attribute)
    return L

The readability of Python code written in a strongly functional style suffers greatly as a result.

The most significant change to Python 2.2 is that static scoping has been added to the language to fix this problem. As a first effect, the name=name default argument is now unnecessary in the above example. Put simply, when a given variable name is not assigned a value within a function (by an assignment, or the def, class, or import statements), references to the variable will be looked up in the local namespace of the enclosing scope. A more detailed explanation of the rules, and a dissection of the implementation, can be found in the PEP.

This change may cause some compatibility problems for code where the same variable name is used both at the module level and as a local variable within a function that contains further function definitions. This seems rather unlikely though, since such code would have been pretty confusing to read in the first place.

One side effect of the change is that the from module import * and exec statements have been made illegal inside a function scope under certain conditions. The Python reference manual has said all along that from module import * is only legal at the top level of a module, but the CPython interpreter has never enforced this before. As part of the implementation of nested scopes, the compiler which turns Python source into bytecodes has to generate different code to access variables in a containing scope. from module import * and exec make it impossible for the compiler to figure this out, because they add names to the local namespace that are unknowable at compile time. Therefore, if a function contains function definitions or lambda expressions with free variables, the compiler will flag this by raising a SyntaxError exception.

To make the preceding explanation a bit clearer, here's an example:

x = 1
def f():
    # 下一行為語法錯誤
    exec 'x=2'
    def g():
        return x

Line 4 containing the exec statement is a syntax error, since exec would define a new local variable named x whose value should be accessed by g().

This shouldn't be much of a limitation, since exec is rarely used in most Python code (and when it is used, it's often a sign of a poor design anyway).

也參考

PEP 227 [https://peps.python.org/pep-0227/] - Statically Nested Scopes

由 Jeremy Hylton 撰寫並實作。

New and Improved Modules

The xmlrpclib module was contributed to the standard library by Fredrik Lundh, providing support for writing XML-RPC clients. XML-RPC is a simple remote procedure call protocol built on top of HTTP and XML. For example, the following snippet retrieves a list of RSS channels from the O'Reilly Network, and then lists the recent headlines for one channel:

import xmlrpclib
s = xmlrpclib.Server(
      'http://www.oreillynet.com/meerkat/xml-rpc/server.php')
channels = s.meerkat.getChannels()
# channels is a list of dictionaries, like this:
# [{'id': 4, 'title': 'Freshmeat Daily News'}
#  {'id': 190, 'title': '32Bits Online'},
#  {'id': 4549, 'title': '3DGamers'}, ... ]

# Get the items for one channel
items = s.meerkat.getItems( {'channel': 4} )

# 'items' is another list of dictionaries, like this:
# [{'link': 'http://freshmeat.net/releases/52719/',
#   'description': 'A utility which converts HTML to XSL FO.',
#   'title': 'html2fo 0.3 (Default)'}, ... ]

The SimpleXMLRPCServer module makes it easy to create straightforward XML-RPC servers. See http://xmlrpc.scripting.com/ for more information about XML-RPC.

The new hmac module implements the HMAC algorithm described by RFC 2104 [https://datatracker.ietf.org/doc/html/rfc2104.html]. (Contributed by Gerhard Häring.)

Several functions that originally returned lengthy tuples now return pseudo-sequences that still behave like tuples but also have mnemonic attributes such as memberst_mtime or tm_year. The enhanced functions include stat(), fstat(), statvfs(), and fstatvfs() in the os module, and localtime(), gmtime(), and strptime() in the time module.

For example, to obtain a file's size using the old tuples, you'd end up writing something like file_size = os.stat(filename)[stat.ST_SIZE], but now this can be written more clearly as file_size = os.stat(filename).st_size.

The original patch for this feature was contributed by Nick Mathewson.

The Python profiler has been extensively reworked and various errors in its output have been corrected. (Contributed by Fred L. Drake, Jr. and Tim Peters.)

The socket module can be compiled to support IPv6; specify the --enable-ipv6 option to Python's configure script. (Contributed by Jun-ichiro "itojun" Hagino.)

Two new format characters were added to the struct module for 64-bit integers on platforms that support the C long long type. q is for a signed 64-bit integer, and Q is for an unsigned one. The value is returned in Python's long integer type. (Contributed by Tim Peters.)

In the interpreter's interactive mode, there's a new built-in function help() that uses the pydoc module introduced in Python 2.1 to provide interactive help. help(object) displays any available help text about object. help() with no argument puts you in an online help utility, where you can enter the names of functions, classes, or modules to read their help text. (Contributed by Guido van Rossum, using Ka-Ping Yee's pydoc module.)

Various bugfixes and performance improvements have been made to the SRE engine underlying the re module. For example, the re.sub() and re.split() functions have been rewritten in C. Another contributed patch speeds up certain Unicode character ranges by a factor of two, and a new finditer() method that returns an iterator over all the non-overlapping matches in a given string. (SRE is maintained by Fredrik Lundh. The BIGCHARSET patch was contributed by Martin von Löwis.)

The smtplib module now supports RFC 2487 [https://datatracker.ietf.org/doc/html/rfc2487.html], "Secure SMTP over TLS", so it's now possible to encrypt the SMTP traffic between a Python program and the mail transport agent being handed a message. smtplib also supports SMTP authentication. (Contributed by Gerhard Häring.)

The imaplib module, maintained by Piers Lauder, has support for several new extensions: the NAMESPACE extension defined in RFC 2342 [https://datatracker.ietf.org/doc/html/rfc2342.html], SORT, GETACL and SETACL. (Contributed by Anthony Baxter and Michel Pelletier.)

The rfc822 module's parsing of email addresses is now compliant with RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html], an update to RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html]. (The module's name is not going to be changed to rfc2822.) A new package, email, has also been added for parsing and generating e-mail messages. (Contributed by Barry Warsaw, and arising out of his work on Mailman.)

The difflib module now contains a new Differ class for producing human-readable lists of changes (a "delta") between two sequences of lines of text. There are also two generator functions, ndiff() and restore(), which respectively return a delta from two sequences, or one of the original sequences from a delta. (Grunt work contributed by David Goodger, from ndiff.py code by Tim Peters who then did the generatorization.)

New constants ascii_letters, ascii_lowercase, and ascii_uppercase were added to the string module. There were several modules in the standard library that used string.letters to mean the ranges A-Za-z, but that assumption is incorrect when locales are in use, because string.letters varies depending on the set of legal characters defined by the current locale. The buggy modules have all been fixed to use ascii_letters instead. (Reported by an unknown person; fixed by Fred L. Drake, Jr.)

The mimetypes module now makes it easier to use alternative MIME-type databases by the addition of a MimeTypes class, which takes a list of filenames to be parsed. (Contributed by Fred L. Drake, Jr.)

A Timer class was added to the threading module that allows scheduling an activity to happen at some future time. (Contributed by Itamar Shtull-Trauring.)

直譯器的變更與修正

Some of the changes only affect people who deal with the Python interpreter at the C level because they're writing Python extension modules, embedding the interpreter, or just hacking on the interpreter itself. If you only write Python code, none of the changes described here will affect you very much.

Profiling and tracing functions can now be implemented in C, which can operate at much higher speeds than Python-based functions and should reduce the overhead of profiling and tracing. This will be of interest to authors of development environments for Python. Two new C functions were added to Python's API, PyEval_SetProfile() and PyEval_SetTrace(). The existing sys.setprofile() and sys.settrace() functions still exist, and have simply been changed to use the new C-level interface. (Contributed by Fred L. Drake, Jr.)

Another low-level API, primarily of interest to implementers of Python debuggers and development tools, was added. PyInterpreterState_Head() and PyInterpreterState_Next() let a caller walk through all the existing interpreter objects; PyInterpreterState_ThreadHead() and PyThreadState_Next() allow looping over all the thread states for a given interpreter. (Contributed by David Beazley.)

The C-level interface to the garbage collector has been changed to make it easier to write extension types that support garbage collection and to debug misuses of the functions. Various functions have slightly different semantics, so a bunch of functions had to be renamed. Extensions that use the old API will still compile but will not participate in garbage collection, so updating them for 2.2 should be considered fairly high priority.

To upgrade an extension module to the new API, perform the following steps:

將 Py_TPFLAGS_GC 重新命名為 Py_TPFLAGS_HAVE_GC。

Use PyObject_GC_New() or PyObject_GC_NewVar() to allocate

objects, and PyObject_GC_Del() to deallocate them.

Rename PyObject_GC_Init() to PyObject_GC_Track() and PyObject_GC_Fini() to PyObject_GC_UnTrack().

Remove PyGC_HEAD_SIZE from object size calculations.

Remove calls to PyObject_AS_GC() and PyObject_FROM_GC().

A new et format sequence was added to PyArg_ParseTuple(); et takes both a parameter and an encoding name, and converts the parameter to the given encoding if the parameter turns out to be a Unicode string, or leaves it alone if it's an 8-bit string, assuming it to already be in the desired encoding. This differs from the es format character, which assumes that 8-bit strings are in Python's default ASCII encoding and converts them to the specified new encoding. (Contributed by M.-A. Lemburg, and used for the MBCS support on Windows described in the following section.)

A different argument parsing function, PyArg_UnpackTuple(), has been added that's simpler and presumably faster. Instead of specifying a format string, the caller simply gives the minimum and maximum number of arguments expected, and a set of pointers to PyObject* variables that will be filled in with argument values.

Two new flags METH_NOARGS and METH_O are available in method definition tables to simplify implementation of methods with no arguments or a single untyped argument. Calling such methods is more efficient than calling a corresponding method that uses METH_VARARGS. Also, the old METH_OLDARGS style of writing C methods is now officially deprecated.

Two new wrapper functions, PyOS_snprintf() and PyOS_vsnprintf() were added to provide cross-platform implementations for the relatively new snprintf() and vsnprintf() C lib APIs. In contrast to the standard sprintf() and vsprintf() functions, the Python versions check the bounds of the buffer used to protect against buffer overruns. (Contributed by M.-A. Lemburg.)

The _PyTuple_Resize() function has lost an unused parameter, so now it takes 2 parameters instead of 3. The third argument was never used, and can simply be discarded when porting code from earlier versions to Python 2.2.

其他改動與修正

As usual there were a bunch of other improvements and bugfixes scattered throughout the source tree. A search through the CVS change logs finds there were 527 patches applied and 683 bugs fixed between Python 2.1 and 2.2; 2.2.1 applied 139 patches and fixed 143 bugs; 2.2.2 applied 106 patches and fixed 82 bugs. These figures are likely to be underestimates.

一些較顯著的變更為：

The code for the MacOS port for Python, maintained by Jack Jansen, is now kept in the main Python CVS tree, and many changes have been made to support MacOS X.

The most significant change is the ability to build Python as a framework, enabled by supplying the --enable-framework option to the configure script when compiling Python. According to Jack Jansen, "This installs a self-contained Python installation plus the OS X framework "glue" into /Library/Frameworks/Python.framework (or another location of choice). For now there is little immediate added benefit to this (actually, there is the disadvantage that you have to change your PATH to be able to find Python), but it is the basis for creating a full-blown Python application, porting the MacPython IDE, possibly using Python as a standard OSA scripting language and much more."

Most of the MacPython toolbox modules, which interface to MacOS APIs such as windowing, QuickTime, scripting, etc. have been ported to OS X, but they've been left commented out in setup.py. People who want to experiment with these modules can uncomment them manually.

Keyword arguments passed to built-in functions that don't take them now cause a TypeError exception to be raised, with the message "function takes no keyword arguments".

Weak references, added in Python 2.1 as an extension module, are now part of the core because they're used in the implementation of new-style classes. The ReferenceError exception has therefore moved from the weakref module to become a built-in exception.

A new script, Tools/scripts/cleanfuture.py by Tim Peters, automatically removes obsolete __future__ statements from Python source code.

An additional flags argument has been added to the built-in function compile(), so the behaviour of __future__ statements can now be correctly observed in simulated shells, such as those presented by IDLE and other development environments. This is described in PEP 264 [https://peps.python.org/pep-0264/]. (Contributed by Michael Hudson.)

The new license introduced with Python 1.6 wasn't GPL-compatible. This is fixed by some minor textual changes to the 2.2 license, so it's now legal to embed Python inside a GPLed program again. Note that Python itself is not GPLed, but instead is under a license that's essentially equivalent to the BSD license, same as it always was. The license changes were also applied to the Python 2.0.1 and 2.1.1 releases.

When presented with a Unicode filename on Windows, Python will now convert it to an MBCS encoded string, as used by the Microsoft file APIs. As MBCS is explicitly used by the file APIs, Python's choice of ASCII as the default encoding turns out to be an annoyance. On Unix, the locale's character set is used if locale.nl_langinfo(CODESET) is available. (Windows support was contributed by Mark Hammond with assistance from Marc-André Lemburg. Unix support was added by Martin von Löwis.)

Large file support is now enabled on Windows. (Contributed by Tim Peters.)

The Tools/scripts/ftpmirror.py script now parses a .netrc file, if you have one. (Contributed by Mike Romberg.)

Some features of the object returned by the xrange() function are now deprecated, and trigger warnings when they're accessed; they'll disappear in Python 2.3. xrange objects tried to pretend they were full sequence types by supporting slicing, sequence multiplication, and the in operator, but these features were rarely used and therefore buggy. The tolist() method and the start, stop, and step attributes are also being deprecated. At the C level, the fourth argument to the PyRange_New() function, repeat, has also been deprecated.

There were a bunch of patches to the dictionary implementation, mostly to fix potential core dumps if a dictionary contains objects that sneakily changed their hash value, or mutated the dictionary they were contained in. For a while python-dev fell into a gentle rhythm of Michael Hudson finding a case that dumped core, Tim Peters fixing the bug, Michael finding another case, and round and round it went.

On Windows, Python can now be compiled with Borland C thanks to a number of patches contributed by Stephen Hansen, though the result isn't fully functional yet. (But this is progress...)

Another Windows enhancement: Wise Solutions generously offered PythonLabs use of their InstallerMaster 8.1 system. Earlier PythonLabs Windows installers used Wise 5.0a, which was beginning to show its age. (Packaged up by Tim Peters.)

Files ending in .pyw can now be imported on Windows. .pyw is a Windows-only thing, used to indicate that a script needs to be run using PYTHONW.EXE instead of PYTHON.EXE in order to prevent a DOS console from popping up to display the output. This patch makes it possible to import such scripts, in case they're also usable as modules. (Implemented by David Bolen.)

On platforms where Python uses the C dlopen() function to load extension modules, it's now possible to set the flags used by dlopen() using the sys.getdlopenflags() and sys.setdlopenflags() functions. (Contributed by Bram Stolk.)

The pow() built-in function no longer supports 3 arguments when floating-point numbers are supplied. pow(x, y, z) returns (x**y) % z, but this is never useful for floating-point numbers, and the final result varies unpredictably depending on the platform. A call such as pow(2.0, 8.0, 7.0) will now raise a TypeError exception.

致謝

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Fred Bremmer, Keith Briggs, Andrew Dalke, Fred L. Drake, Jr., Carel Fellinger, David Goodger, Mark Hammond, Stephen Hansen, Michael Hudson, Jack Jansen, Marc-André Lemburg, Martin von Löwis, Fredrik Lundh, Michael McLay, Nick Mathewson, Paul Moore, Gustavo Niemeyer, Don O'Donnell, Joonas Paalasma, Tim Peters, Jens Quade, Tom Reinhardt, Neil Schemenauer, Guido van Rossum, Greg Ward, Edward Welbourne.

Python 2.1 有什麼新功能

作者:

A.M. Kuchling

簡介

This article explains the new features in Python 2.1. While there aren't as many changes in 2.1 as there were in Python 2.0, there are still some pleasant surprises in store. 2.1 is the first release to be steered through the use of Python Enhancement Proposals, or PEPs, so most of the sizable changes have accompanying PEPs that provide more complete documentation and a design rationale for the change. This article doesn't attempt to document the new features completely, but simply provides an overview of the new features for Python programmers. Refer to the Python 2.1 documentation, or to the specific PEP, for more details about any new feature that particularly interests you.

One recent goal of the Python development team has been to accelerate the pace of new releases, with a new release coming every 6 to 9 months. 2.1 is the first release to come out at this faster pace, with the first alpha appearing in January, 3 months after the final version of 2.0 was released.

The final release of Python 2.1 was made on April 17, 2001.

PEP 227: Nested Scopes

The largest change in Python 2.1 is to Python's scoping rules. In Python 2.0, at any given time there are at most three namespaces used to look up variable names: local, module-level, and the built-in namespace. This often surprised people because it didn't match their intuitive expectations. For example, a nested recursive function definition doesn't work:

def f():
    ...
    def g(value):
        ...
        return g(value-1) + 1
    ...

The function g() will always raise a NameError exception, because the binding of the name g isn't in either its local namespace or in the module-level namespace. This isn't much of a problem in practice (how often do you recursively define interior functions like this?), but this also made using the lambda expression clumsier, and this was a problem in practice. In code which uses lambda you can often find local variables being copied by passing them as the default values of arguments.

def find(self, name):
    "回傳串列中任何等於 'name' 的項目"
    L = filter(lambda x, name=name: x == name,
               self.list_attribute)
    return L

The readability of Python code written in a strongly functional style suffers greatly as a result.

The most significant change to Python 2.1 is that static scoping has been added to the language to fix this problem. As a first effect, the name=name default argument is now unnecessary in the above example. Put simply, when a given variable name is not assigned a value within a function (by an assignment, or the def, class, or import statements), references to the variable will be looked up in the local namespace of the enclosing scope. A more detailed explanation of the rules, and a dissection of the implementation, can be found in the PEP.

This change may cause some compatibility problems for code where the same variable name is used both at the module level and as a local variable within a function that contains further function definitions. This seems rather unlikely though, since such code would have been pretty confusing to read in the first place.

One side effect of the change is that the from module import * and exec statements have been made illegal inside a function scope under certain conditions. The Python reference manual has said all along that from module import * is only legal at the top level of a module, but the CPython interpreter has never enforced this before. As part of the implementation of nested scopes, the compiler which turns Python source into bytecodes has to generate different code to access variables in a containing scope. from module import * and exec make it impossible for the compiler to figure this out, because they add names to the local namespace that are unknowable at compile time. Therefore, if a function contains function definitions or lambda expressions with free variables, the compiler will flag this by raising a SyntaxError exception.

To make the preceding explanation a bit clearer, here's an example:

x = 1
def f():
    # The next line is a syntax error
    exec 'x=2'
    def g():
        return x

Line 4 containing the exec statement is a syntax error, since exec would define a new local variable named x whose value should be accessed by g().

This shouldn't be much of a limitation, since exec is rarely used in most Python code (and when it is used, it's often a sign of a poor design anyway).

Compatibility concerns have led to nested scopes being introduced gradually; in Python 2.1, they aren't enabled by default, but can be turned on within a module by using a future statement as described in PEP 236 [https://peps.python.org/pep-0236/]. (See the following section for further discussion of PEP 236 [https://peps.python.org/pep-0236/].) In Python 2.2, nested scopes will become the default and there will be no way to turn them off, but users will have had all of 2.1's lifetime to fix any breakage resulting from their introduction.

也參考

PEP 227 [https://peps.python.org/pep-0227/] - 靜態巢狀作用域

由 Jeremy Hylton 撰寫與實作。

PEP 236: __future__ Directives

The reaction to nested scopes was widespread concern about the dangers of breaking code with the 2.1 release, and it was strong enough to make the Pythoneers take a more conservative approach. This approach consists of introducing a convention for enabling optional functionality in release N that will become compulsory in release N+1.

The syntax uses a from...import statement using the reserved module name __future__. Nested scopes can be enabled by the following statement:

from __future__ import nested_scopes

While it looks like a normal import statement, it's not; there are strict rules on where such a future statement can be put. They can only be at the top of a module, and must precede any Python code or regular import statements. This is because such statements can affect how the Python bytecode compiler parses code and generates bytecode, so they must precede any statement that will result in bytecodes being produced.

也參考

PEP 236 [https://peps.python.org/pep-0236/] - Back to the __future__

由 Tim Peters 撰寫，主要由 Jeremy Hylton 實作。

PEP 207: Rich Comparisons

In earlier versions, Python's support for implementing comparisons on user-defined classes and extension types was quite simple. Classes could implement a __cmp__() method that was given two instances of a class, and could only return 0 if they were equal or +1 or -1 if they weren't; the method couldn't raise an exception or return anything other than a Boolean value. Users of Numeric Python often found this model too weak and restrictive, because in the number-crunching programs that numeric Python is used for, it would be more useful to be able to perform elementwise comparisons of two matrices, returning a matrix containing the results of a given comparison for each element. If the two matrices are of different sizes, then the compare has to be able to raise an exception to signal the error.

In Python 2.1, rich comparisons were added in order to support this need. Python classes can now individually overload each of the <, <=, >, >=, ==, and != operations. The new magic method names are:

操作

方法名稱

<

__lt__()

<=

__le__()

>

__gt__()

>=

__ge__()

==

__eq__()

!=

__ne__()

(The magic methods are named after the corresponding Fortran operators .LT.. .LE., &c. Numeric programmers are almost certainly quite familiar with these names and will find them easy to remember.)

Each of these magic methods is of the form method(self, other), where self will be the object on the left-hand side of the operator, while other will be the object on the right-hand side. For example, the expression A < B will cause A.__lt__(B) to be called.

Each of these magic methods can return anything at all: a Boolean, a matrix, a list, or any other Python object. Alternatively they can raise an exception if the comparison is impossible, inconsistent, or otherwise meaningless.

The built-in cmp(A,B) function can use the rich comparison machinery, and now accepts an optional argument specifying which comparison operation to use; this is given as one of the strings "<", "<=", ">", ">=", "==", or "!=". If called without the optional third argument, cmp() will only return -1, 0, or +1 as in previous versions of Python; otherwise it will call the appropriate method and can return any Python object.

There are also corresponding changes of interest to C programmers; there's a new slot tp_richcmp in type objects and an API for performing a given rich comparison. I won't cover the C API here, but will refer you to PEP 207 [https://peps.python.org/pep-0207/], or to 2.1's C API documentation, for the full list of related functions.

也參考

PEP 207 [https://peps.python.org/pep-0207/] - Rich Comparisons

由 Guido van Rossum 撰寫，並大量採用 David Ascher 的早期工作，由 Guido van Rossum 實作。

PEP 230：警告框架

Over its 10 years of existence, Python has accumulated a certain number of obsolete modules and features along the way. It's difficult to know when a feature is safe to remove, since there's no way of knowing how much code uses it --- perhaps no programs depend on the feature, or perhaps many do. To enable removing old features in a more structured way, a warning framework was added. When the Python developers want to get rid of a feature, it will first trigger a warning in the next version of Python. The following Python version can then drop the feature, and users will have had a full release cycle to remove uses of the old feature.

Python 2.1 adds the warning framework to be used in this scheme. It adds a warnings module that provide functions to issue warnings, and to filter out warnings that you don't want to be displayed. Third-party modules can also use this framework to deprecate old features that they no longer wish to support.

For example, in Python 2.1 the regex module is deprecated, so importing it causes a warning to be printed:

>>> import regex
__main__:1: DeprecationWarning: the regex module
         is deprecated; please use the re module
>>>

Warnings can be issued by calling the warnings.warn() function:

warnings.warn("feature X no longer supported")

The first parameter is the warning message; an additional optional parameters can be used to specify a particular warning category.

Filters can be added to disable certain warnings; a regular expression pattern can be applied to the message or to the module name in order to suppress a warning. For example, you may have a program that uses the regex module and not want to spare the time to convert it to use the re module right now. The warning can be suppressed by calling

import warnings
warnings.filterwarnings(action = 'ignore',
                        message='.*regex module is deprecated',
                        category=DeprecationWarning,
                        module = '__main__')

This adds a filter that will apply only to warnings of the class DeprecationWarning triggered in the __main__ module, and applies a regular expression to only match the message about the regex module being deprecated, and will cause such warnings to be ignored. Warnings can also be printed only once, printed every time the offending code is executed, or turned into exceptions that will cause the program to stop (unless the exceptions are caught in the usual way, of course).

Functions were also added to Python's C API for issuing warnings; refer to PEP 230 or to Python's API documentation for the details.

也參考

PEP 5 [https://peps.python.org/pep-0005/] - Guidelines for Language Evolution

Written by Paul Prescod, to specify procedures to be followed when removing old features from Python. The policy described in this PEP hasn't been officially adopted, but the eventual policy probably won't be too different from Prescod's proposal.

PEP 230 [https://peps.python.org/pep-0230/] - Warning Framework

由 Guido van Rossum 撰寫與實作。

PEP 229: New Build System

When compiling Python, the user had to go in and edit the Modules/Setup file in order to enable various additional modules; the default set is relatively small and limited to modules that compile on most Unix platforms. This means that on Unix platforms with many more features, most notably Linux, Python installations often don't contain all useful modules they could.

Python 2.0 added the Distutils, a set of modules for distributing and installing extensions. In Python 2.1, the Distutils are used to compile much of the standard library of extension modules, autodetecting which ones are supported on the current machine. It's hoped that this will make Python installations easier and more featureful.

Instead of having to edit the Modules/Setup file in order to enable modules, a setup.py script in the top directory of the Python source distribution is run at build time, and attempts to discover which modules can be enabled by examining the modules and header files on the system. If a module is configured in Modules/Setup, the setup.py script won't attempt to compile that module and will defer to the Modules/Setup file's contents. This provides a way to specific any strange command-line flags or libraries that are required for a specific platform.

In another far-reaching change to the build mechanism, Neil Schemenauer restructured things so Python now uses a single makefile that isn't recursive, instead of makefiles in the top directory and in each of the Python/, Parser/, Objects/, and Modules/ subdirectories. This makes building Python faster and also makes hacking the Makefiles clearer and simpler.

也參考

PEP 229 [https://peps.python.org/pep-0229/] - Using Distutils to Build Python

由 A.M. Kuchling 撰寫與實作。

PEP 205: Weak References

Weak references, available through the weakref module, are a minor but useful new data type in the Python programmer's toolbox.

Storing a reference to an object (say, in a dictionary or a list) has the side effect of keeping that object alive forever. There are a few specific cases where this behaviour is undesirable, object caches being the most common one, and another being circular references in data structures such as trees.

For example, consider a memoizing function that caches the results of another function f(x) by storing the function's argument and its result in a dictionary:

_cache = {}
def memoize(x):
    if _cache.has_key(x):
        return _cache[x]

    retval = f(x)

    # 快取回傳物件
    _cache[x] = retval

    return retval

This version works for simple things such as integers, but it has a side effect; the _cache dictionary holds a reference to the return values, so they'll never be deallocated until the Python process exits and cleans up. This isn't very noticeable for integers, but if f() returns an object, or a data structure that takes up a lot of memory, this can be a problem.

Weak references provide a way to implement a cache that won't keep objects alive beyond their time. If an object is only accessible through weak references, the object will be deallocated and the weak references will now indicate that the object it referred to no longer exists. A weak reference to an object obj is created by calling wr = weakref.ref(obj). The object being referred to is returned by calling the weak reference as if it were a function: wr(). It will return the referenced object, or None if the object no longer exists.

This makes it possible to write a memoize() function whose cache doesn't keep objects alive, by storing weak references in the cache.

_cache = {}
def memoize(x):
    if _cache.has_key(x):
        obj = _cache[x]()
        # If weak reference object still exists,
        # return it
        if obj is not None: return obj

    retval = f(x)

    # Cache a weak reference
    _cache[x] = weakref.ref(retval)

    return retval

The weakref module also allows creating proxy objects which behave like weak references --- an object referenced only by proxy objects is deallocated -- but instead of requiring an explicit call to retrieve the object, the proxy transparently forwards all operations to the object as long as the object still exists. If the object is deallocated, attempting to use a proxy will cause a weakref.ReferenceError exception to be raised.

proxy = weakref.proxy(obj)
proxy.attr   # Equivalent to obj.attr
proxy.meth() # Equivalent to obj.meth()
del obj
proxy.attr   # raises weakref.ReferenceError

也參考

PEP 205 [https://peps.python.org/pep-0205/] - Weak References

由 Fred L. Drake, Jr. 撰寫與實作。

PEP 232：函式屬性

In Python 2.1, functions can now have arbitrary information attached to them. People were often using docstrings to hold information about functions and methods, because the __doc__ attribute was the only way of attaching any information to a function. For example, in the Zope web application server, functions are marked as safe for public access by having a docstring, and in John Aycock's SPARK parsing framework, docstrings hold parts of the BNF grammar to be parsed. This overloading is unfortunate, since docstrings are really intended to hold a function's documentation; for example, it means you can't properly document functions intended for private use in Zope.

Arbitrary attributes can now be set and retrieved on functions using the regular Python syntax:

def f(): pass

f.publish = 1
f.secure = 1
f.grammar = "A ::= B (C D)*"

The dictionary containing attributes can be accessed as the function's __dict__. Unlike the __dict__ attribute of class instances, in functions you can actually assign a new dictionary to __dict__, though the new value is restricted to a regular Python dictionary; you can't be tricky and set it to a UserDict instance, or any other random object that behaves like a mapping.

也參考

PEP 232 [https://peps.python.org/pep-0232/] - 函式屬性

由 Barry Warsaw 撰寫與實作。

PEP 235: Importing Modules on Case-Insensitive Platforms

Some operating systems have filesystems that are case-insensitive, MacOS and Windows being the primary examples; on these systems, it's impossible to distinguish the filenames FILE.PY and file.py, even though they do store the file's name in its original case (they're case-preserving, too).

In Python 2.1, the import statement will work to simulate case-sensitivity on case-insensitive platforms. Python will now search for the first case-sensitive match by default, raising an ImportError if no such file is found, so import file will not import a module named FILE.PY. Case-insensitive matching can be requested by setting the PYTHONCASEOK environment variable before starting the Python interpreter.

PEP 217: Interactive Display Hook

When using the Python interpreter interactively, the output of commands is displayed using the built-in repr() function. In Python 2.1, the variable sys.displayhook() can be set to a callable object which will be called instead of repr(). For example, you can set it to a special pretty-printing function:

>>> # 建立一個遞迴的資料結構
... L = [1,2,3]
>>> L.append(L)
>>> L # 顯示 Python 的預設輸出
[1, 2, 3, [...]]
>>> # 使用 pprint.pprint() 作為顯示函式
... import sys, pprint
>>> sys.displayhook = pprint.pprint
>>> L
[1, 2, 3,  <Recursion on list with id=135143996>]
>>>

也參考

PEP 217 [https://peps.python.org/pep-0217/] - Display Hook for Interactive Use

由 Moshe Zadka 撰寫與實作。

PEP 208: New Coercion Model

How numeric coercion is done at the C level was significantly modified. This will only affect the authors of C extensions to Python, allowing them more flexibility in writing extension types that support numeric operations.

Extension types can now set the type flag Py_TPFLAGS_CHECKTYPES in their PyTypeObject structure to indicate that they support the new coercion model. In such extension types, the numeric slot functions can no longer assume that they'll be passed two arguments of the same type; instead they may be passed two arguments of differing types, and can then perform their own internal coercion. If the slot function is passed a type it can't handle, it can indicate the failure by returning a reference to the Py_NotImplemented singleton value. The numeric functions of the other type will then be tried, and perhaps they can handle the operation; if the other type also returns Py_NotImplemented, then a TypeError will be raised. Numeric methods written in Python can also return Py_NotImplemented, causing the interpreter to act as if the method did not exist (perhaps raising a TypeError, perhaps trying another object's numeric methods).

也參考

PEP 208 [https://peps.python.org/pep-0208/] - Reworking the Coercion Model

Written and implemented by Neil Schemenauer, heavily based upon earlier work by Marc-André Lemburg. Read this to understand the fine points of how numeric operations will now be processed at the C level.

PEP 241: Metadata in Python Packages

A common complaint from Python users is that there's no single catalog of all the Python modules in existence. T. Middleton's Vaults of Parnassus at www.vex.net/parnassus/ (retired in February 2009, available in the Internet Archive Wayback Machine [https://web.archive.org/web/20090130140102/http://www.vex.net/parnassus/]) was the largest catalog of Python modules, but registering software at the Vaults is optional, and many people did not bother.

As a first small step toward fixing the problem, Python software packaged using the Distutils sdist command will include a file named PKG-INFO containing information about the package such as its name, version, and author (metadata, in cataloguing terminology). PEP 241 [https://peps.python.org/pep-0241/] contains the full list of fields that can be present in the PKG-INFO file. As people began to package their software using Python 2.1, more and more packages will include metadata, making it possible to build automated cataloguing systems and experiment with them. With the result experience, perhaps it'll be possible to design a really good catalog and then build support for it into Python 2.2. For example, the Distutils sdist and bdist_* commands could support an upload option that would automatically upload your package to a catalog server.

You can start creating packages containing PKG-INFO even if you're not using Python 2.1, since a new release of the Distutils will be made for users of earlier Python versions. Version 1.0.2 of the Distutils includes the changes described in PEP 241 [https://peps.python.org/pep-0241/], as well as various bugfixes and enhancements. It will be available from the Distutils SIG at https://www.python.org/community/sigs/current/distutils-sig/.

也參考

PEP 241 [https://peps.python.org/pep-0241/] - Metadata for Python Software Packages

由 A.M. Kuchling 撰寫與實作。

PEP 243 [https://peps.python.org/pep-0243/] - Module Repository Upload Mechanism

Written by Sean Reifschneider, this draft PEP describes a proposed mechanism for uploading Python packages to a central server.

New and Improved Modules

Ka-Ping Yee contributed two new modules: inspect.py, a module for getting information about live Python code, and pydoc.py, a module for interactively converting docstrings to HTML or text. As a bonus, Tools/scripts/pydoc, which is now automatically installed, uses pydoc.py to display documentation given a Python module, package, or class name. For example, pydoc xml.dom displays the following:

Python Library Documentation: package xml.dom in xml

NAME
    xml.dom - W3C Document Object Model implementation for Python.

FILE
    /usr/local/lib/python2.1/xml/dom/__init__.pyc

DESCRIPTION
    The Python mapping of the Document Object Model is documented in the
    Python Library Reference in the section on the xml.dom package.

    This package contains the following modules:
      ...

pydoc also includes a Tk-based interactive help browser. pydoc quickly becomes addictive; try it out!

Two different modules for unit testing were added to the standard library. The doctest module, contributed by Tim Peters, provides a testing framework based on running embedded examples in docstrings and comparing the results against the expected output. PyUnit, contributed by Steve Purcell, is a unit testing framework inspired by JUnit, which was in turn an adaptation of Kent Beck's Smalltalk testing framework. See https://pyunit.sourceforge.net/ for more information about PyUnit.

The difflib module contains a class, SequenceMatcher, which compares two sequences and computes the changes required to transform one sequence into the other. For example, this module can be used to write a tool similar to the Unix diff program, and in fact the sample program Tools/scripts/ndiff.py demonstrates how to write such a script.

curses.panel, a wrapper for the panel library, part of ncurses and of SYSV curses, was contributed by Thomas Gellekum. The panel library provides windows with the additional feature of depth. Windows can be moved higher or lower in the depth ordering, and the panel library figures out where panels overlap and which sections are visible.

The PyXML package has gone through a few releases since Python 2.0, and Python 2.1 includes an updated version of the xml package. Some of the noteworthy changes include support for Expat 1.2 and later versions, the ability for Expat parsers to handle files in any encoding supported by Python, and various bugfixes for SAX, DOM, and the minidom module.

Ping also contributed another hook for handling uncaught exceptions. sys.excepthook() can be set to a callable object. When an exception isn't caught by any try...except blocks, the exception will be passed to sys.excepthook(), which can then do whatever it likes. At the Ninth Python Conference, Ping demonstrated an application for this hook: printing an extended traceback that not only lists the stack frames, but also lists the function arguments and the local variables for each frame.

Various functions in the time module, such as asctime() and localtime(), require a floating-point argument containing the time in seconds since the epoch. The most common use of these functions is to work with the current time, so the floating-point argument has been made optional; when a value isn't provided, the current time will be used. For example, log file entries usually need a string containing the current time; in Python 2.1, time.asctime() can be used, instead of the lengthier time.asctime(time.localtime(time.time())) that was previously required.

此變更由 Thomas Wouters 提出並實作。

The ftplib module now defaults to retrieving files in passive mode, because passive mode is more likely to work from behind a firewall. This request came from the Debian bug tracking system, since other Debian packages use ftplib to retrieve files and then don't work from behind a firewall. It's deemed unlikely that this will cause problems for anyone, because Netscape defaults to passive mode and few people complain, but if passive mode is unsuitable for your application or network setup, call set_pasv(0) on FTP objects to disable passive mode.

Support for raw socket access has been added to the socket module, contributed by Grant Edwards.

The pstats module now contains a simple interactive statistics browser for displaying timing profiles for Python programs, invoked when the module is run as a script. Contributed by Eric S. Raymond.

A new implementation-dependent function, sys._getframe([depth]), has been added to return a given frame object from the current call stack. sys._getframe() returns the frame at the top of the call stack; if the optional integer argument depth is supplied, the function returns the frame that is depth calls below the top of the stack. For example, sys._getframe(1) returns the caller's frame object.

This function is only present in CPython, not in Jython or the .NET implementation. Use it for debugging, and resist the temptation to put it into production code.

其他變更與修正

There were relatively few smaller changes made in Python 2.1 due to the shorter release cycle. A search through the CVS change logs turns up 117 patches applied, and 136 bugs fixed; both figures are likely to be underestimates. Some of the more notable changes are:

A specialized object allocator is now optionally available, that should be faster than the system malloc() and have less memory overhead. The allocator uses C's malloc() function to get large pools of memory, and then fulfills smaller memory requests from these pools. It can be enabled by providing the --with-pymalloc option to the configure script; see Objects/obmalloc.c for the implementation details.

Authors of C extension modules should test their code with the object allocator enabled, because some incorrect code may break, causing core dumps at runtime. There are a bunch of memory allocation functions in Python's C API that have previously been just aliases for the C library's malloc() and free(), meaning that if you accidentally called mismatched functions, the error wouldn't be noticeable. When the object allocator is enabled, these functions aren't aliases of malloc() and free() any more, and calling the wrong function to free memory will get you a core dump. For example, if memory was allocated using PyMem_New, it has to be freed using PyMem_Del(), not free(). A few modules included with Python fell afoul of this and had to be fixed; doubtless there are more third-party modules that will have the same problem.

The object allocator was contributed by Vladimir Marangozov.

The speed of line-oriented file I/O has been improved because people often complain about its lack of speed, and because it's often been used as a naïve benchmark. The readline() method of file objects has therefore been rewritten to be much faster. The exact amount of the speedup will vary from platform to platform depending on how slow the C library's getc() was, but is around 66%, and potentially much faster on some particular operating systems. Tim Peters did much of the benchmarking and coding for this change, motivated by a discussion in comp.lang.python.

A new module and method for file objects was also added, contributed by Jeff Epler. The new method, xreadlines(), is similar to the existing xrange() built-in. xreadlines() returns an opaque sequence object that only supports being iterated over, reading a line on every iteration but not reading the entire file into memory as the existing readlines() method does. You'd use it like this:

for line in sys.stdin.xreadlines():
    # ... do something for each line ...
    ...

For a fuller discussion of the line I/O changes, see the python-dev summary for January 1--15, 2001 at https://mail.python.org/pipermail/python-dev/2001-January/.

A new method, popitem(), was added to dictionaries to enable destructively iterating through the contents of a dictionary; this can be faster for large dictionaries because there's no need to construct a list containing all the keys or values. D.popitem() removes a random (key, value) pair from the dictionary D and returns it as a 2-tuple. This was implemented mostly by Tim Peters and Guido van Rossum, after a suggestion and preliminary patch by Moshe Zadka.

Modules can now control which names are imported when from module import * is used, by defining an __all__ attribute containing a list of names that will be imported. One common complaint is that if the module imports other modules such as sys or string, from module import * will add them to the importing module's namespace. To fix this, simply list the public names in __all__:

# List public names
__all__ = ['Database', 'open']

A stricter version of this patch was first suggested and implemented by Ben Wolfson, but after some python-dev discussion, a weaker final version was checked in.

Applying repr() to strings previously used octal escapes for non-printable characters; for example, a newline was '\012'. This was a vestigial trace of Python's C ancestry, but today octal is of very little practical use. Ka-Ping Yee suggested using hex escapes instead of octal ones, and using the \n, \t, \r escapes for the appropriate characters, and implemented this new formatting.

Syntax errors detected at compile-time can now raise exceptions containing the filename and line number of the error, a pleasant side effect of the compiler reorganization done by Jeremy Hylton.

C extensions which import other modules have been changed to use PyImport_ImportModule(), which means that they will use any import hooks that have been installed. This is also encouraged for third-party extensions that need to import some other module from C code.

The size of the Unicode character database was shrunk by another 340K thanks to Fredrik Lundh.

Some new ports were contributed: MacOS X (by Steven Majewski), Cygwin (by Jason Tishler); RISCOS (by Dietmar Schwertberger); Unixware 7 (by Billy G. Allie).

And there's the usual list of minor bugfixes, minor memory leaks, docstring edits, and other tweaks, too lengthy to be worth itemizing; see the CVS logs for the full details if you want them.

致謝

The author would like to thank the following people for offering suggestions on various drafts of this article: Graeme Cross, David Goodger, Jay Graves, Michael Hudson, Marc-André Lemburg, Fredrik Lundh, Neil Schemenauer, Thomas Wouters.

Python 2.0 有什麼新功能

作者:

A.M. Kuchling 和 Moshe Zadka

簡介

Python 的新版本 2.0 於 2000 年 10 月 16 日發布。本文介紹 2.0 中令人興奮的新功能、重點說明一些其他有用的變更，並指出一些可能需要重寫程式碼的不相容變更。

Python 的開發在各版本之間從未完全停止，錯誤修正和改進總是源源不斷地被提交。大量的小修正、一些最佳化、額外的說明字串和更好的錯誤訊息都納入了 2.0；要全部列出是不可能的，但它們確實很重要。如果你想看完整的清單，請查閱公開的 CVS 日誌。這些進展歸功於在 PythonLabs 工作的五位開發者現在有薪酬來專職修復錯誤，也歸功於遷移到 SourceForge 後改善的溝通。

Python 1.6 呢？

Python 1.6 可以被視為履行合約義務的 Python 版本。在核心開發團隊於 2000 年 5 月離開 CNRI 後，CNRI 要求建立一個 1.6 版本，包含所有在 CNRI 完成的 Python 工作。因此 Python 1.6 代表了 2000 年 5 月時 CVS 樹的狀態，最重要的新功能是 Unicode 支援。當然，開發在五月之後仍持續進行，所以 1.6 分支收到了一些修正以確保它與 Python 2.0 向前相容。因此 1.6 是 Python 演進的一部分，而非旁支。

那麼，你應該對 Python 1.6 很感興趣嗎？大概不需要。1.6 final 和 2.0 beta1 是在同一天（2000 年 9 月 5 日）釋出的，計畫是在大約一個月內完成 Python 2.0。如果你有應用程式需要維護，遷移到 1.6 導致程式出問題、修復它們、然後一個月內又因遷移到 2.0 而再次出問題，這似乎沒什麼意義；你最好直接升級到 2.0。本文描述的大多數真正有趣的功能只存在於 2.0，因為五月到九月之間完成了大量工作。

新的開發流程

Python 2.0 最重要的變更可能根本不在程式碼，而是 Python 的開發方式：2000 年 5 月，Python 開發者開始使用 SourceForge 提供的工具來儲存原始碼、追蹤錯誤報告和管理補丁提交佇列。要回報錯誤或為 Python 2.0 提交補丁，請使用 Python 專案頁面（位於 https://sourceforge.net/projects/python/）上的錯誤追蹤和補丁管理工具。

目前託管在 SourceForge 上最重要的服務是 Python CVS 樹，這是包含 Python 原始碼的版本控制儲存庫。以前大約只有 7 個人左右擁有 CVS 樹的寫入權限，所有補丁都必須由這份短名單上的人檢查並提交。這顯然不太具有擴展性。將 CVS 樹移至 SourceForge 後，可以授予更多人寫入權限；截至 2000 年 9 月，有 27 人能夠提交變更，增加了四倍。這讓我們有機會進行大規模變更，如果這些變更必須經過少數核心開發者過濾，就不會有人嘗試。例如有一天 Peter Schneider-Kamp 突發奇想，決定放棄 K&R C 相容性並將 Python 的 C 原始碼轉換為 ANSI C。在 python-dev 郵件列表上獲得批准後，他開始了持續約一週的密集提交，其他開發者也加入幫忙，工作就完成了。如果只有 5 個人有寫入權限，這項任務可能會被視為「不錯，但不值得花費所需的時間和精力」，永遠不會完成。

轉向使用 SourceForge 的服務使開發速度顯著提升。補丁現在會被提交、評論、由原作者以外的人修改，並在人們之間來回傳遞，直到補丁被認為值得簽入。程式錯誤 (bugs) 在一個集中的位置被追蹤，可以指派給特定的人修復，我們可以計算未解決的錯誤數量來衡量進度。這並非沒有代價：開發者現在有更多電子郵件要處理、更多郵件列表要關注，還必須為新環境編寫特殊工具。例如 SourceForge 發送的預設補丁和錯誤通知電子郵件完全沒有幫助，所以 Ka-Ping Yee 寫了一個 HTML 爬蟲來發送更有用的訊息。

新增程式碼的便利性造成了一些初期的成長陣痛，例如程式碼在還沒準備好或者還沒有得到開發者群組的明確同意之前就被簽入。已經形成的審批流程與 Apache 組織使用的流程有些類似。開發者可以對補丁投票 +1、+0、-0 或 -1；+1 和 -1 表示接受或拒絕，而 +0 和 -0 表示開發者對該變更基本上持中立態度，但略微傾向正面或負面。與 Apache 模式最顯著的不同是，投票本質上只是諮詢性質的，讓擁有「終身仁慈獨裁者」地位的 Guido van Rossum 了解一般意見。即使社群不同意他的意見，他仍然可以忽略投票結果來批准或拒絕一個變更。

製作實際的補丁是新增功能的最後一步，與早期提出好設計的任務相比通常比較容易。關於新功能的討論往往會爆發成冗長的郵件列表討論串，使討論難以追蹤，而且沒有人能讀完 python-dev 上的每一篇文章。因此，我們以網際網路 RFC 流程為藍本建立了一個相對正式的流程來撰寫 Python 增強提案（PEP）。PEP 是描述提議新功能的草案文件，並持續修改直到社群達成共識以接受或拒絕該提案。引用 PEP 1 [https://peps.python.org/pep-0001/]「PEP 目的與準則」的介紹：

PEP 代表 Python Enhancement Proposal（Python 增強提案）。PEP 是一份設計文件，向 Python 社群提供資訊，或描述 Python 的新功能。PEP 應該提供該功能的簡潔技術規格和該功能的基本原理。

我們打算讓 PEP 成為提議新功能、收集社群對議題意見、以及記錄 Python 設計決策的主要機制。PEP 作者負責在社群內建立共識並記錄不同意見。

閱讀 PEP 1 [https://peps.python.org/pep-0001/] 的其餘部分以了解 PEP 編輯流程、風格和格式的詳細資訊。PEP 保存在 SourceForge 上的 Python CVS 樹中，雖然它們不是 Python 2.0 發布板的一部分，但也可以從 https://peps.python.org/ 取得 HTML 格式。截至 2000 年 9 月，共有 25 個 PEP，從 PEP 201 [https://peps.python.org/pep-0201/] "Lockstep Iteration" 到 PEP 225 "Elementwise/Objectwise Operators"。

Unicode

Python 2.0 中最大的新功能是一個新的基本資料型別：Unicode 字串。Unicode 使用 16 位元數字來表示字元，而不是 ASCII 使用的 8 位元數字，這意味著可以支援 65,536 個不同的字元。

Unicode 支援的最終介面是經過 python-dev 郵件列表上無數次激烈討論後確定的，主要由 Marc-André Lemburg 實作，基於 Fredrik Lundh 的 Unicode 字串型別實作。介面的詳細說明寫在 PEP 100 [https://peps.python.org/pep-0100/] "Python Unicode Integration" 中。本文僅介紹 Unicode 介面最重要的幾點。

在 Python 原始碼中，Unicode 字串寫成 u"string"。可以使用新的跳脫序列 \uHHHH 來寫入任意 Unicode 字元，其中 HHHH 是從 0000 到 FFFF 的 4 位十六進位數字。也可以使用現有的 \xHH 跳脫序列，而八進位跳脫可用於 U+01FF 以下的字元，以 \777 表示。

Unicode 字串就像一般字串是不可變的序列型別。它們可以被索引和切片，但不能原地 (in place) 修改。Unicode 字串有一個 encode( [encoding] ) 方法，會回傳所需編碼的 8 位元字串。編碼以字串命名，如 'ascii'、'utf-8'、'iso-8859-1' 等。有定義了一個編解碼器 API 來實作和註冊新的編碼，然後就可在整個 Python 程式中使用。如果未指定編碼，預設編碼通常是 7 位元 ASCII，不過可以透過在自訂版本的 site.py 中呼叫 sys.setdefaultencoding(encoding) 函式來為你的 Python 安裝改變它。

結合 8 位元字串和 Unicode 字串時，總是會使用預設的 ASCII 編碼強制轉換為 Unicode；'a' + u'bc' 的結果是 u'abc'。

新增了內建函式，並修改了現有的內建函式以支援 Unicode：

unichr(ch) 會回傳一個長度為 1 的 Unicode 字串，其包含字元 ch。

ord(u)，其中 u 是長度為 1 的一般字串或 Unicode 字串，以整數回傳該字元的數值。

unicode(string [, encoding]  [, errors] ) 從 8 位元字串建立 Unicode 字串。encoding 是指定要使用的編碼的字串。errors 參數指定如何處理目前編碼的無效字元；傳入 'strict' 作為值會在任何編碼錯誤時引發例外，而 'ignore' 會默默地忽略錯誤，'replace' 則在出現任何問題時使用 U+FFFD（官方替換字元）。

exec 陳述式以及各種內建函式如 eval()、getattr() 和 setattr() 現在也接受 Unicode 字串和一般字串。（在修復過程中可能遺漏了一些內建函式；如果你發現某個接受字串的內建函式完全不接受 Unicode 字串，請當作程式錯誤回報。）

新模組 unicodedata 提供了 Unicode 字元屬性的介面。例如，unicodedata.category(u'A') 回傳 2 字元的字串 'Lu'，'L' 表示它是字母，'u' 表示它是大寫。unicodedata.bidirectional(u'\u0660') 回傳 'AN'，表示 U+0660 是阿拉伯數字。

codecs 模組包含查找現有編碼和註冊新編碼的函式。除非你想實作新的編碼，否則最常使用的是 codecs.lookup(encoding) 函式，它回傳一個 4 元素的元組：(encode_func, decode_func, stream_reader, stream_writer)。

encode_func 是一個接受 Unicode 字串並回傳 2 元組 (string, length) 的函式。string 是一個 8 位元字串，包含轉換為給定編碼的 Unicode 字串的一部分（可能是全部），length 告訴你有多少 Unicode 字串被轉換了。

decode_func 是 encode_func 的相反操作，接受一個 8 位元字串並回傳一個 2 元組 (ustring, length)，包含結果 Unicode 字串 ustring 和整數 length，告訴你消耗了多少 8 位元字串。

stream_reader 是一個支援從串流解碼輸入的類別。stream_reader(file_obj) 回傳一個支援 read()、readline() 和 readlines() 方法的物件。這些方法都會從給定的編碼進行轉換並回傳 Unicode 字串。

stream_writer 同樣是一個支援將輸出編碼到串流的類別。stream_writer(file_obj) 回傳一個支援 write() 和 writelines() 方法的物件。這些方法預期接收 Unicode 字串，並在輸出時將其轉換為給定的編碼。

例如，以下程式碼會將 Unicode 字串寫入檔案並編碼為 UTF-8：

import codecs

unistr = u'\u0660\u2000ab ...'

(UTF8_encode, UTF8_decode,
 UTF8_streamreader, UTF8_streamwriter) = codecs.lookup('UTF-8')

output = UTF8_streamwriter( open( '/tmp/output', 'wb') )
output.write( unistr )
output.close()

以下程式碼接著從檔案讀取 UTF-8 輸入：

input = UTF8_streamreader( open( '/tmp/output', 'rb') )
print repr(input.read())
input.close()

支援 Unicode 的正規表示式可透過 re 模組使用，該模組有一個新的底層實作，稱為 SRE，由 Secret Labs AB 的 Fredrik Lundh 編寫。

新增了 -U 命令列選項，使 Python 編譯器將所有字串字面值解釋為 Unicode 字串字面值。這是用於測試和讓你的 Python 程式碼面向未來，因為 Python 的某個未來版本可能會放棄對 8 位元字串的支援，只提供 Unicode 字串。

串列綜合運算（List Comprehension）

串列是 Python 中的主力資料型別，許多程式在某個時候都會操作串列。對串列的兩個常見操作是對它們進行迴圈，然後選出符合特定條件的元素，或對每個元素套用某個函式。例如，給定一個字串串列，你可能想要取出所有包含特定子字串的字串，或去除每行末尾的空白。

現有的 map() 和 filter() 函式可以用於此目的，但它們需要一個函式作為引數之一。如果有一個現成的內建函式可以直接傳遞就沒問題，但如果沒有的話你必須建立一個小函式來完成所需的工作，而且如果這個小函式需要額外的資訊，Python 的作用域規則會讓結果變得醜陋。以前一段的第一個例子為例，找出串列中所有包含給定子字串的字串。你可以這樣寫來完成它：

# 給定串列 L，建立一個包含子字串 S 的
# 所有字串的串列。
sublist = filter( lambda s, substring=S:
                     string.find(s, substring) != -1,
                  L)

由於 Python 的作用域規則，預設引數會被使用，以便 lambda 運算式建立的匿名函式知道要搜尋的是什麼子字串。串列綜合運算使這更簡潔：

sublist = [ s for s in L if string.find(s, S) != -1 ]

串列綜合運算的形式如下：

[ expression for expr in sequence1
             for expr2 in sequence2 ...
             for exprN in sequenceN
             if condition ]

for...in 子句包含要疊代的序列。這些序列不必具有相同的長度，因為它們不是並行疊代的，而是從左到右；這在以下段落中會更清楚地解釋。產生的串列的元素將是 expression 的連續值。最後的 if 子句是可選的；如果存在，只有當 condition 為真時，expression 才會被計算並加入結果。

為了讓語義非常清楚，串列綜合運算等價於以下 Python 程式碼：

for expr1 in sequence1:
    for expr2 in sequence2:
    ...
        for exprN in sequenceN:
             if (condition):
                  # 將運算式的值
                  # 附加到結果串列。

這意味著當有多個 for...in 子句時，結果串列的長度將等於所有序列長度的乘積。如果你有兩個長度為 3 的串列，輸出串列將有 9 個元素：

seq1 = 'abc'
seq2 = (1,2,3)
>>> [ (x,y) for x in seq1 for y in seq2]
[('a', 1), ('a', 2), ('a', 3), ('b', 1), ('b', 2), ('b', 3), ('c', 1),
('c', 2), ('c', 3)]

為了避免在 Python 的文法中引入歧義，如果 expression 是建立一個元組，它必須用括號包圍。下面第一個串列綜合運算是語法錯誤，而第二個是正確的：

# 語法錯誤
[ x,y for x in seq1 for y in seq2]
# 正確
[ (x,y) for x in seq1 for y in seq2]

串列綜合運算的概念最初來自函式程式設計語言 Haskell (https://www.haskell.org)。Greg Ewing 最有效地主張將它們加入 Python，並撰寫了最初的串列綜合運算補丁，然後在 python-dev 郵件列表上討論了好久好久，後來由 Skip Montanaro 持續更新。

擴增賦值（Augmented Assignment）

擴增賦值運算子是另一個長期被要求的功能，已加入 Python 2.0。擴增賦值運算子包括 +=、-=、*= 等等。例如陳述式 a += 2 將變數 a 的值增加 2，等同於稍長的 a = a + 2。

支援的賦值運算子完整清單是 +=、-=、*=、/=、%=、**=、&=、|=、^=、>>= 和 <<=。Python 類別可以透過定義名為 __iadd__()、__isub__() 等方法來覆寫擴增賦值運算子。例如，以下的 Number 類別儲存一個數字，並支援使用 += 來建立一個具有增加值的新實例。

class Number:
    def __init__(self, value):
        self.value = value
    def __iadd__(self, increment):
        return Number( self.value + increment)

n = Number(5)
n += 3
print n.value

__iadd__() 特殊方法會以增量值被呼叫，並應回傳一個具有適當修改值的新實例；這個回傳值會被繫結為左側變數的新值。

擴增賦值運算子最初是在 C 程式語言中引入的，大多數源自 C 的語言，如 awk、C++、Java、Perl 和 PHP 也支援它們。擴增指定的補丁由 Thomas Wouters 實作。

字串方法

到目前為止，字串操作功能都在 string 模組中，它通常是用 C 編寫的 strop 模組的前端。Unicode 的加入給 strop 模組帶來了困難，因為所有函式都需要為了接受 8 位元或 Unicode 字串而重寫。對於像 string.replace() 這樣接受 3 個字串引數的函式，這代表要處理八種可能的排列組合以及相應複雜的程式碼。

不過 Python 2.0 將問題推給字串型別，使字串操作功能可透過 8 位元字串和 Unicode 字串的方法使用。

>>> 'andrew'.capitalize()
'Andrew'
>>> 'hostname'.replace('os', 'linux')
'hlinuxtname'
>>> 'moshe'.find('sh')
2

有一件事沒有改變，儘管有一個值得注意的愚人節玩笑，那就是 Python 字串是不可變的。因此，字串方法會回傳新字串，而不會修改它們所操作的字串。

舊的 string 模組為了向後相容仍然保留，但它主要充當新字串方法的前端。

有兩個方法在 2.0 之前的版本中沒有對應功能：startswith() 和 endswith()，不過它們在 JPython 中已經存在了一段時間。s.startswith(t) 等同於 s[:len(t)] == t，而 s.endswith(t) 等同於 s[-len(t):] == t。

另一個值得特別提及的方法是 join()。字串的 join() 方法接收一個參數，即字串序列，等同於舊 string 模組中的 string.join() 函式，但引數順序相反。換句話說，s.join(seq) 等同於舊的 string.join(seq, s)。

循環的垃圾回收

Python 的 C 實作使用參照計數來實作垃圾回收。每個 Python 物件都維護一個指向自身的參照數量計數，並在建立或銷毀參照時調整該計數。一旦參照計數達到零，該物件就不再可存取，因為你需要有物件的參照才能存取它，如果計數為零，就表示不再有任何參照存在。

參照計數有一些不錯的特性：它易於理解和實作，而且產生的實作具有可攜性、相當快速，並且能與其他有實作自己的記憶體處理方案的函式庫良好配合。參照計數的主要問題是它有時無法意識到物件已不再可存取，導致記憶體洩漏。這種情況發生在存在參照循環時。

考慮最簡單的循環情況，一個類別實例具有對自身的參照：

instance = SomeClass()
instance.myself = instance

執行上述兩行程式碼後，instance 的參照計數為 2；一個參照來自名為 'instance' 的變數，另一個來自實例的 myself 屬性。

如果下一行程式碼是 del instance，會發生什麼事？instance 的參照計數減少 1，所以它的參照計數變成 1；myself 屬性中的參照仍然存在。然而該實例已經無法透過 Python 程式碼存取，它可以被刪除。如果多個物件互相參照，它們就可以形成循環，導致所有這些物件都被洩漏。

Python 2.0 透過定期執行循環偵測演算法來修復這個問題，該演算法會尋找不可存取的循環並刪除涉及的物件。新的 gc 模組提供了執行垃圾回收、取得偵錯統計資訊和調整回收器參數的函式。

執行循環偵測演算法需要一些時間，因此會產生一些額外的開銷。希望在使用 2.0 得到循環回收的經驗後，Python 2.1 將能夠仔細調整以最小化這些開銷。目前因為基準測試很棘手所以還不清楚會損失多少效能，而且關鍵取決於程式建立和銷毀物件的頻率。如果即便是微小的速度損失你也都無法承受，或者懷疑循環回收機制有誤，可以在編譯 Python 時停用循環偵測，方式為執行 configure 腳本時指定 --without-cycle-gc 開關。

多人處理了這個問題並為解決方案做出了貢獻。循環偵測方法的早期實作由 Toby Kelsey 編寫。目前的演算法是 Eric Tiedemann 在訪問 CNRI 時建議的，Guido van Rossum 和 Neil Schemenauer 編寫了兩個不同的實作，後來由 Neil 整合起來。也有許多人在過程中提供了建議；python-dev 郵件列表的 2000 年 3 月存檔包含了大部分相關討論，特別是標題為 "Reference cycle collection for Python" 和 "Finalization again" 的討論串。

其他核心變更

對 Python 的語法和內建函式進行了各種小幅變更。這些變更的影響不大，但它們是便利的功能。

次要語言變更

新的語法使得使用引數元組和/或關鍵字引數字典呼叫給定函式更加方便。在 Python 1.5 及更早版本中，你會使用 apply() 內建函式：apply(f, args, kw) 使用引數元組 args 和字典 kw 中的關鍵字引數來呼叫函式 f()。apply() 在 2.0 中仍然相同，但多虧了 Greg Ewing 的補丁，f(*args, **kw) 是達成相同效果的更簡短、更清晰的方式。此語法與定義函式的語法對稱：

def f(*args, **kw):
    # args 是位置引數的元組，
    # kw 是關鍵字引數的字典
    ...

現在可以透過在 print 後面加上 >> file 來將 print 陳述式的輸出導向至類檔案物件，類似於 Unix shell 中的重新導向運算子。以前你必須使用類檔案物件的 write() 方法，這缺乏 print 的便利性和簡潔性，或者你可以為 sys.stdout 指定新值然後恢復舊值。對於將輸出發送到標準錯誤，這樣寫簡單多了：

print >> sys.stderr, "Warning: action field not supplied"

現在可以在引入模組時重新命名它們，使用語法 import module as name 或 from module import name as othername。該補丁由 Thomas Wouters 提交。

使用 % 運算子時新增了一個新的格式樣式；'%r' 將插入其引數的 repr()。這也是出於對稱性考量而新增的，這次是與現有的 '%s' 格式樣式對稱，後者會插入其引數的 str()。例如，'%r %s' % ('abc', 'abc') 回傳一個包含 'abc' abc 的字串。

以前沒有辦法實作一個覆寫 Python 內建 in 運算子並實作自訂版本的類別。如果 obj 存在於序列 seq 中，obj in seq 回傳 true；Python 透過簡單地嘗試序列的每個索引來計算這個，直到找到 obj 或遇到 IndexError。Moshe Zadka 貢獻了一個補丁，新增了一個 __contains__() 魔術方法，用於提供 in 的自訂實作。此外，用 C 編寫的新內建物件可以透過序列協定中的新插槽來定義 in 對它們的意義。

早期版本的 Python 使用遞迴演算法來刪除物件。深度巢狀的資料結構可能會導致直譯器填滿 C 堆疊並當機；Christian Tismer 重寫了刪除邏輯來修復這個問題。比較遞迴物件會造成無限遞迴並導致崩潰 (crash)；Jeremy Hylton 重寫了程式碼使其不再崩潰，而是產生有用的結果。例如在這段程式碼之後：

a = []
b = []
a.append(a)
b.append(b)

a==b 的比較會回傳 true，因為這兩個遞迴資料結構是同構的 (isomorphic)。請參閱 python-dev 郵件列表 2000 年 4 月存檔中的 "trashcan and PR#7" 討論串，以了解最後決定此實作的討論和一些有用的相關連結。請注意，比較現在也可以引發例外。在早期版本的 Python 中，像 cmp(a,b) 這樣的比較操作總是會產生答案，即使使用者定義的 __cmp__() 方法遇到錯誤，因為產生的例外會被默默地吞掉。

已經完成了將 Python 移植到 Itanium 處理器上的 64 位元 Windows 的工作，主要由 ActiveState 的 Trent Mick 完成。（令人困惑的是，sys.platform 在 Win64 上仍然是 'win32'，因為似乎為了方便移植，MS Visual C++ 在 Itanium 上將程式碼視為 32 位元。）PythonWin 也支援 Windows CE；詳見 https://pythonce.sourceforge.net/ 上的 Python CE 頁面以取得更多資訊。

另一個新平台是 Darwin/MacOS X；Python 2.0 中包含了對它的初步支援。如果你指定 "configure --with-dyld --with-suffix=.x"，動態載入就可以運作。請參閱 Python 原始碼發布板中的 README 以取得更多指示。

程式碼中的區域變數在被指定值前就被參照的話，經常引發令人困惑的 NameError 例外，這個 Python 的缺陷有被嘗試改善。拿以下程式碼為例，它於 1.5.2 和 2.0 中都會在 print 陳述式上引發例外；在 1.5.2 中會引發 NameError 例外，而 2.0 會引發新的 UnboundLocalError 例外。UnboundLocalError 是 NameError 的子類別，所以任何預期會引發 NameError 的現有程式碼應該仍然可以運作。

def f():
    print "i=",i
    i = i + 1
f()

引入了兩個新例外，TabError 和 IndentationError。它們都是 SyntaxError 的子類別，當發現 Python 程式碼縮排不正確時就會被引發。

內建函式的變更

新增了一個內建函式 zip(seq1, seq2, ...)。zip() 回傳一個元組串列，其中每個元組包含來自每個引數序列的第 i 個元素。zip() 和 map(None, seq1, seq2) 之間的區別是，如果序列的長度不同，map() 會用 None 填充序列，而 zip() 會將回傳的串列截斷為最短引數序列的長度。

當第一個引數是字串時，int() 和 long() 函式現在接受可選的 "base" 參數。int('123', 10) 回傳 123，而 int('123', 16) 回傳 291。int(123, 16) 會引發 TypeError 例外，訊息為 "can't convert non-string with explicit base"。

在 sys 模組中新增了一個包含更詳細版本資訊的新變數。sys.version_info 是一個元組 (major, minor, micro, level, serial)。例如，在假設的 2.0.1beta1 中，sys.version_info 會是 (2, 0, 1, 'beta', 1)。level 是一個字串，如 "alpha"、"beta" 或最終版本的 "final"。

字典有一個奇特的新方法 setdefault(key, default)，其行為類似於現有的 get() 方法。然而如果鍵不存在，setdefault() 既會像 get() 一樣回傳 default 的值，也會將其作為 key 的值插入字典。因此，以下幾行程式碼：

if dict.has_key( key ): return dict[key]
else:
    dict[key] = []
    return dict[key]

可以簡化為單一的 return dict.setdefault(key, []) 陳述式。

直譯器會設定最大遞迴深度，以便在填滿 C 堆疊並導致核心傾印 (core dump) 或 GPF 之前捕獲失控的遞迴。以前這個限制在編譯 Python 時就固定了，但在 2.0 中最大遞迴深度可以使用 sys.getrecursionlimit() 和 sys.setrecursionlimit() 來讀取和修改。預設值是 1000，可以透過執行新的腳本 Misc/find_recursionlimit.py 來找到給定平台約略的最大值。

移植到 2.0

新的 Python 版本努力與先前的版本相容，而且過去記錄維持很好。然而有些變更被認為只是足夠有用而已，通常是因為它們修正了後來證明是完全錯誤的初始設計決策，因此並不總是能避免破壞向後相容性。本節列出了 Python 2.0 中可能導致舊 Python 程式碼出問題的變更。

可能會破壞最多程式碼的變更是收緊某些方法接受的引數。某些方法會接受多個引數並將它們視為元組，特別是各種串列方法如 append() 和 insert()。在早期版本的 Python 中，如果 L 是一個串列，L.append( 1,2 ) 會將元組 (1,2) 附加到串列中。在 Python 2.0 中，這會導致引發 TypeError 例外，訊息為：'append requires exactly 1 argument; 2 given'。修正方法單純是加一組額外的括號來將兩個值作為元組傳遞：L.append( (1,2) )。

這些方法的早期版本更寬容，因為它們使用 Python C 介面中的舊函式來剖析引數；2.0 將它們現代化為使用 PyArg_ParseTuple()，即目前的引數剖析函式，它提供更有幫助的錯誤訊息並將多引數呼叫視為錯誤。如果你必須使用 2.0 但無法修正你的程式碼，你可以編輯 Objects/listobject.c 並定義前處理器 (preprocessor) 符號 NO_STRICT_LIST_APPEND 來保留舊行為；但不建議這樣做。

socket 模組中的某些函式在這方面仍然很寬容。例如 socket.connect( ('hostname', 25) ) 仍是傳遞一個代表 IP 位址的元組的正確形式，但 socket.connect('hostname', 25) 也可以運作。socket.connect_ex 和 socket.bind 同樣寬鬆。2.0alpha1 收緊了這些函式，但因為文件實際上使用了錯誤的多引數形式，許多人寫的程式碼會因更嚴格的檢查而出問題。GvR 考慮公眾反應而撤回了變更，所以 socket 模組文件因此被修正了，多引數形式只是被標記為已棄用；它將會在未來的 Python 版本中再次被收緊。

字串字面值中的 \x 跳脫現在正好取 2 個十六進位數字。以前它會消耗 'x' 後面的所有十六進位數字並取結果的最低 8 位元，所以 \x123456 等同於 \x56。

AttributeError 和 NameError 例外有了更友善的錯誤訊息，其文字會類似於 'Spam' instance has no attribute 'eggs' 或 name 'eggs' is not defined。以前錯誤訊息只是缺少的屬性名稱 eggs，利用這一事實編寫的程式碼在 2.0 中會出問題。

已經完成了一些使整數和長整數更具互換性的工作。在 1.5.2 中，為 Solaris 新增了大型檔案支援，允許讀取大於 2 GiB 的檔案；這使得檔案物件的 tell() 方法改為回傳長整數而不是一般整數。某些程式碼會將兩個檔案偏移量相減並嘗試使用結果來乘以序列或切片字串，但這會引發 TypeError。在 2.0 中，長整數可以用於乘以或切片序列，它會按你直覺預期的方式運作；3L * 'abc' 會產生 'abcabcabc'、(0,1,2,3)[2L:4L] 會產生 (2,3)。長整數也可以用於以前只接受整數的各種情況，例如檔案物件的 seek() 方法，以及 % 運算子支援的格式（%d、%i、%x 等）。例如 "%d" % 2L**64 會產生字串 18446744073709551616。

所有長整數變更中最微妙的是長整數的 str() 不再有尾隨的 'L' 字元，儘管 repr() 仍然包含它。'L' 讓許多想要印出看起來像普通整數的長整數的人感到惱火，因為他們必須特意去掉這個字元。在 2.0 中這不再是問題，但執行 str(longval)[:-1] 並假設 'L' 存在的程式碼現在會丟失最後一個數字。

取浮點數的 repr() 現在使用與 str() 不同的格式化精度。repr() 對 C 的 sprintf() 使用 %.17g 格式字串，而 str() 像以前一樣使用 %.12g。效果是對於某些數字，repr() 可能偶爾會顯示比 str() 更多的小數位。例如數字 8.1 無法用二進位精確表示，所以 repr(8.1) 是 '8.0999999999999996'，而 str(8.1) 是 '8.1'。

-X 命令列選項已被移除，該選項會將所有標準例外轉換為字串而不是類別；現在標準例外將始終是類別。包含標準例外的 exceptions 模組已從 Python 翻譯為內建的 C 模組，這由 Barry Warsaw 和 Fredrik Lundh 編寫。

擴充/嵌入變更

有些變更是在底層，只有編寫 C 擴充模組或將 Python 直譯器嵌入到較大應用程式中的人才會注意到。如果你不處理 Python 的 C API，可以安全地跳過本節。

Python C API 的版本號已增加，因此為 1.5.2 編譯的 C 擴充必須重新編譯才能與 2.0 一起使用。在 Windows 上由於 Windows DLL 的運作方式，Python 2.0 無法引入為 Python 1.5.x 建立的第三方擴充，因此 Python 會引發例外且引入會失敗。

Jim Fulton 的 ExtensionClass 模組使用者會高興地發現掛鉤已被添加，使 ExtensionClass 現在有被 isinstance() 和 issubclass() 支援。這意味著你不再需要記得編寫像 if type(obj) == myExtensionClass 這樣的程式碼，而是可以使用更自然的 if isinstance(obj, myExtensionClass)。

Python/importdl.c 檔案以前是一堆 #ifdef 來支援許多不同平台上的動態載入，這已被 Greg Stein 清理和重組。importdl.c 現在相當小，平台特定的程式碼已移至一系列 Python/dynload_*.c 檔案中。有另一個清理工作：Include/ 目錄中的許多 my*.h 檔案包含各種為改善可攜性的 hack；它們已被合併到單一檔案 Include/pyport.h。

Vladimir Marangozov 完成了備受期待的 malloc 重構，使 Python 直譯器可以輕鬆使用自訂記憶體分配器而不是 C 的標準 malloc()。相關文件請閱讀 Include/pymem.h 和 Include/objimpl.h 中的註解。敲定介面的冗長討論，請參閱 python.org 上 'patches' 和 'python-dev' 列表的網路存檔。

MacOS 的 GUSI 開發環境的近期版本支援了 POSIX 執行緒。因此，Python 的 POSIX 執行緒支援現在可以在 Macintosh 上運作。也貢獻了有用到使用者空間 GNU pth 函式庫的執行緒支援。

Windows 上的執行緒支援也得到了改進。Windows 支援僅在爭用情況 (contention) 下使用核心 (kernel) 物件的執行緒鎖定；在沒有爭用的常見情況下，它們使用更簡單的函式，速度快一個數量級。NT 上 Python 1.5.2 的執行緒版本比非執行緒版本慢兩倍；經過 2.0 的變更，差異只有 10%。這些改進由 Yakov Markovitch 貢獻。

Python 2.0 的原始碼現在只使用 ANSI C 原型，因此編譯 Python 現在需要 ANSI C 編譯器，不能再使用只支援 K&R C 的編譯器。

以前 Python 虛擬機在其位元組碼中使用 16 位元數字，限制了原始檔的大小。特別是這影響了 Python 原始碼中字面串列和字典的最大大小；偶爾生成 Python 程式碼的人會遇到這個限制。Charles G. Waldman 的補丁將限制從 2**16 提高到 2**32。

新增了三個便利函式，以用於在模組初始化時將常數加入模組的字典：PyModule_AddObject()、PyModule_AddIntConstant() 和 PyModule_AddStringConstant()。這些函式分別接受一個模組物件、一個包含要新增名稱的以 null 結尾的 C 字串，以及一個用於指定給該名稱的值的第三個引數。這第三個引數分別是 Python 物件、C long 或 C 字串。

為 Unix 風格的訊號處理程式新增了一個包裝器 API。PyOS_getsig() 會取得訊號處理程式，PyOS_setsig() 會設定新的處理程式。

Distutils：讓模組安裝變簡單

在 Python 2.0 之前，安裝模組是一件繁瑣的事情 —— 沒有辦法自動找出 Python 安裝在哪裡，或者擴充模組應該使用什麼編譯器選項。軟體作者必須經歷編輯 Makefile 和設定檔的艱苦過程，而這些只真正適用於 Unix，使得 Windows 和 MacOS 不受支援。不同擴充套件會有迥異的安裝方式，使得 Python 使用者們需要面對歧異度過高的各種安裝指南，使得管理 Python 安裝成為一件苦差事。

由 Greg Ward 領導的發布工具 SIG 建立了 Distutils，一個讓套件安裝更容易的系統。它們構成了 distutils 套件，是 Python 標準函式庫新的部分。在最佳情況下，從原始碼安裝 Python 模組只需要相同的步驟：首先你只需解壓縮 tarball 或 zip 檔案，然後執行 "python setup.py install"，這就會自動偵測平台、識別編譯器、編譯 C 擴充模組，並將發布板安裝到適當的目錄。可選的命令列引數提供對安裝過程的更多控制，distutils 套件提供了許多能夠覆寫預設值的地方 —— 將建置與安裝分開、在非預設目錄中建置或安裝等等。

為了使用 Distutils，你需要編寫一個 setup.py 腳本。對於簡單的情況，當軟體只包含 .py 檔案時，一個最小的 setup.py 可能只有幾行：

from distutils.core import setup
setup (name = "foo", version = "1.0",
       py_modules = ["module1", "module2"])

如果軟體由數個套件組成的話，setup.py 檔案也不會複雜太多：

from distutils.core import setup
setup (name = "foo", version = "1.0",
       packages = ["package", "package.subpackage"])

C 擴充可能是最複雜的情況；這是一個取自 PyXML 套件的範例：

from distutils.core import setup, Extension

expat_extension = Extension('xml.parsers.pyexpat',
     define_macros = [('XML_NS', None)],
     include_dirs = [ 'extensions/expat/xmltok',
                      'extensions/expat/xmlparse' ],
     sources = [ 'extensions/pyexpat.c',
                 'extensions/expat/xmltok/xmltok.c',
                 'extensions/expat/xmltok/xmlrole.c', ]
       )
setup (name = "PyXML", version = "0.5.4",
       ext_modules =[ expat_extension ] )

Distutils 也可以建立原始碼和二進位發布板。透過 "python setup.py sdist" 執行的 "sdist" 命令會建立原始碼發布板，如 foo-1.0.tar.gz。新增命令並不困難，"bdist_rpm" 和 "bdist_wininst" 命令已被貢獻，分別用於建立軟體的 RPM 發布板和 Windows 安裝程式。建立其他發行格式（如 Debian 套件和 Solaris .pkg 檔案）的命令正處於不同的開發階段。

所有這些都記錄在新的手冊 Distributing Python Modules 中，該手冊加入了 Python 的基本文件集。

XML 模組

Python 1.5.2 包含了一個以 xmllib 模組形式提供的簡單 XML 剖析器，其由 Sjoerd Mullender 所貢獻。自 1.5.2 發布以來，兩種不同的 XML 處理介面變得常見：SAX2（Simple API for XML 的第二版）提供了一個事件驅動的介面，它與 xmllib 有些相似，而 DOM（Document Object Model，文件物件模型）提供了一個基於樹狀結構的介面，將 XML 文件轉換為可以遍歷和修改的節點樹。Python 2.0 包含了 SAX2 介面和精簡的 DOM 介面，作為 xml 套件的一部分。這裡我們將簡要概述這些新介面；請查閱 Python 文件或原始碼以取得完整詳情。Python XML SIG 也正在改進文件。

SAX2 支援

SAX 定義了一個用於剖析 XML 的事件驅動介面。要使用 SAX，你必須編寫一個 SAX 處理程式類別。處理程式類別繼承自 SAX 提供的各種類別，並覆寫各種方法，然後這些方法會被 XML 剖析器呼叫。例如，startElement() 和 endElement() 方法會在剖析器遇到每個開始標籤和結束標籤時被呼叫，characters() 方法會在每個字元資料區塊時被呼叫，依此類推。

事件驅動方法的優點是整個文件不必在任何時候都駐留在記憶體中，如果你正在處理非常龐大的文件，這一點會很重要。然而如果你試圖以某種複雜的方式修改文件結構，編寫 SAX 處理程式類別可能會變得非常複雜。

例如這個定義了一個處理程式的小範例程式，它會為每個開始標籤和結束標籤印出訊息，然後使用它來剖析檔案 hamlet.xml：

from xml import sax

class SimpleHandler(sax.ContentHandler):
    def startElement(self, name, attrs):
        print 'Start of element:', name, attrs.keys()

    def endElement(self, name):
        print 'End of element:', name

# 建立剖析器物件
parser = sax.make_parser()

# 告訴它使用哪個處理程式
handler = SimpleHandler()
parser.setContentHandler( handler )

# 剖析檔案！
parser.parse( 'hamlet.xml' )

如需更多資訊，請查閱 Python 文件，或位於 https://pyxml.sourceforge.net/topics/howto/xml-howto.html 的 XML HOWTO。

DOM 支援

文件物件模型是 XML 文件的樹狀表示法。頂層 Document 實例是樹的根，有一個子節點是頂層 Element 實例。這個 Element 有子節點代表字元資料和任何子元素，這些子元素可能又有自己的子節點，依此類推。使用 DOM 你可以用任何你喜歡的方式遍歷結果樹、存取元素和屬性值、插入和刪除節點，並將樹轉換回 XML。

DOM 對於修改 XML 文件很有用，因為你可以建立 DOM 樹、透過新增節點或重新排列子樹來修改它，然後產生新的 XML 文件作為輸出。你也可以手動建構 DOM 樹並將其轉換為 XML，這可能比簡單地將 <tag1>...</tag1> 寫入檔案更靈活地產生 XML 輸出。

Python 附帶的 DOM 實作位於 xml.dom.minidom 模組中。它是 Level 1 DOM 的輕量級實作，支援 XML 命名空間。它提供了 parse() 和 parseString() 便利函式來產生 DOM 樹：

from xml.dom import minidom
doc = minidom.parse('hamlet.xml')

doc 是一個 Document 實例。Document 與所有其他 DOM 類別（如 Element 和 Text）一樣，是 Node 基礎類別的子類別。因此 DOM 樹中的所有節點都支援某些共同方法，例如 toxml() 會回傳一個包含節點及其子節點的 XML 表示的字串。每個類別也有自己的特殊方法；例如 Element 和 Document 實例有一個方法可以找到所有具有給定標籤名稱的子元素。從前面的 2 行範例繼續：

perslist = doc.getElementsByTagName( 'PERSONA' )
print perslist[0].toxml()
print perslist[1].toxml()

對於 Hamlet XML 檔案，以上幾行會輸出：

<PERSONA>CLAUDIUS, king of Denmark. </PERSONA>
<PERSONA>HAMLET, son to the late, and nephew to the present king.</PERSONA>

文件的根元素可透過 doc.documentElement 取得，其子節點可以透過刪除、新增或移除節點輕鬆修改：

root = doc.documentElement

# 移除第一個子節點
root.removeChild( root.childNodes[0] )

# 將新的第一個子節點移到末尾
root.appendChild( root.childNodes[0] )

# 將新的第一個子節點（原本是第三個子節點）
# 插入到第 20 個子節點之前。
root.insertBefore( root.childNodes[0], root.childNodes[20] )

我會再次將你引導至相對應的 Python 文件以取得不同 Node 類別及其各種方法的完整列表。

與 PyXML 的關係

XML 專項興趣小組 (Special Interest Group) 這段時間以來一直在開發與 XML 相關的 Python 程式碼。它的程式碼發布版稱為 PyXML，可從 SIG 的網頁 https://www.python.org/community/sigs/current/xml-sig 取得。PyXML 發布版也使用 xml 作為套件名稱。如果你編寫過使用 PyXML 的程式，你可能想知道它與 2.0 xml 套件的相容性。

答案是 Python 2.0 的 xml 套件與 PyXML 不相容，但可以透過安裝最新版本的 PyXML 來使其相容。許多應用程式可以使用 Python 2.0 附帶的 XML 支援，但更複雜的應用程式需要安裝完整的 PyXML 套件。安裝後，PyXML 0.6.0 或更高版本將取代 Python 附帶的 xml 套件，成為標準套件的嚴格超集，並新增一系列額外功能。PyXML 中的一些額外功能包括：

4DOM，來自 FourThought, Inc. 的完整 DOM 實作。

xmlproc 驗證剖析器，由 Lars Marius Garshol 編寫。

sgmlop 剖析器加速模組，由 Fredrik Lundh 編寫。

模組變更

對 Python 龐大的標準函式庫進行了大量改進和錯誤修正；一些受影響的模組包括 readline、ConfigParser、cgi、calendar、posix、readline、xmllib、aifc、chunk、wave、random、shelve 和 nntplib。請查閱 CVS 日誌以取得補丁的確切詳情。

Brian Gallew 為 socket 模組貢獻了 OpenSSL 支援。OpenSSL 是 Secure Socket Layer 的實作，它會加密透過 socket 發送的資料。編譯 Python 時，你可以編輯 Modules/Setup 來包含 SSL 支援，這會在 socket 模組中新增一個額外的函式：socket.ssl(socket, keyfile, certfile)，它接受一個 socket 物件並回傳一個 SSL socket。httplib 和 urllib 模組也被修改以支援 https:// URL，儘管還沒有人實作基於 SSL 的 FTP 或 SMTP。

httplib 模組已由 Greg Stein 重寫以支援 HTTP/1.1。

提供了與 1.5 版本 httplib 的向後相容性，但使用 HTTP/1.1 功能（如管線化 (pipelining)）將需要重寫程式碼以使用不同的介面集。

Tkinter 模組現在支援 Tcl/Tk 版本 8.1、8.2 或 8.3，並且已放棄對舊版 7.x 的支援。Tkinter 模組現在支援在 Tk widget 中顯示 Unicode 字串。此外，Fredrik Lundh 貢獻了一項最佳化，使像 create_line 和 create_polygon 這樣的操作變快許多，特別是在使用大量座標時。

curses 模組已大幅擴展，從 Oliver Andrich 的改進版本開始，提供了許多來自 ncurses 和 SYSV curses 的額外函式，如顏色、替代字元集支援、pad 和滑鼠支援。這意味著該模組不再與只有 BSD curses 的作業系統相容，但似乎沒有任何目前仍在維護的作業系統屬於這個類別。

如同先前關於 2.0 Unicode 支援的討論中提到的，re 模組提供的正規表示式底層實作已經改變。SRE 是一個由 Fredrik Lundh 編寫並由 Hewlett Packard 部分資助的新正規表示式引擎，支援對 8 位元字串和 Unicode 字串進行匹配。

新增模組

新增了一些模組。我們僅在此列出簡要描述；請參閱 2.0 說明文件以了解特定模組的詳細資訊。

atexit：用於註冊在 Python 直譯器退出前要呼叫的函式。目前直接設定 sys.exitfunc 的程式碼應改為使用 atexit 模組，引入 atexit 並使用要在退出時呼叫的函式呼叫 atexit.register()。（由 Skip Montanaro 貢獻。）

codecs、encodings、unicodedata：作為新 Unicode 支援的一部分而新增。

filecmp：取代舊的 cmp、cmpcache 和 dircmp 模組，這些模組現已被棄用。（由 Gordon MacMillan 和 Moshe Zadka 貢獻。）

gettext：此模組透過提供 GNU gettext 訊息目錄函式庫的介面，為 Python 程式提供國際化 (I18N) 和本地化 (L10N) 支援。（由 Barry Warsaw 整合，來自 Martin von Löwis、Peter Funk 和 James Henstridge 的個別貢獻。）

linuxaudiodev：支援 Linux 上的 /dev/audio 裝置，是現有 sunaudiodev 模組的孿生模組。（由 Peter Bosch 貢獻、Jeremy Hylton 修正。）

mmap：Windows 和 Unix 上記憶體對映檔案的介面。檔案的內容可以直接對映到記憶體中，此時它的行為就像一個可變字串，因此可以讀取和修改其內容。它們甚至可以傳遞給預期要接受普通字串的函式，例如 re 模組。（由 Sam Rushing 貢獻，A.M. Kuchling 進行了一些擴展。）

pyexpat：Expat XML 剖析器的介面。（由 Paul Prescod 貢獻。）

robotparser：剖析 robots.txt 檔案，用於編寫能禮貌地避開網站某些區域的網路爬蟲。剖析器接受 robots.txt 檔案的內容，並從中建立一組規則，然後可以回答關於給定 URL 是否可抓取的問題。（由 Skip Montanaro 貢獻。）

tabnanny：一個用於檢查 Python 原始碼中不明確縮排的模組/腳本。（由 Tim Peters 貢獻。）

UserString：一個用於衍生行為類似字串的物件的基礎類別。

webbrowser：一個不相依於平台、能以特定 URL 啟動網頁瀏覽器的模組。對於各個平台，會依特定順序嘗試各種瀏覽器。使用者可以透過設定 BROWSER 環境變數來更改啟動哪個瀏覽器。（最初受到 Eric S. Raymond 對 urllib 的補丁啟發，該補丁新增了類似功能，但最終模組來自 Fred Drake 最初實作的 Tools/idle/BrowserControl.py 程式碼，並由 Fred 改編為標準函式庫。）

_winreg：Windows 登錄檔的介面。_winreg 是自 1995 年以來一直是 PythonWin 一部分函式的改編版本，但現在已被加入核心發布板，並被改進以支援 Unicode。_winreg 由 Bill Tutt 和 Mark Hammond 編寫。

zipfile：一個用於讀取和寫入 ZIP 格式封存檔案的模組。這些是由 DOS/Windows 上的 PKZIP 或 Unix 上的 zip 產生的封存檔案，不要與 gzip格式的檔案（由 gzip 模組支援）混淆。（由 James C. Ahlstrom 貢獻。）

imputil：一個與現有的 ihooks 模組相比，提供更簡單方式來編寫自訂引入掛鉤的模組。（由 Greg Stein 實作，過程中在 python-dev 上有許多討論。）

IDLE 改進

IDLE 是官方的 Python 跨平台 IDE，使用 Tkinter 編寫。Python 2.0 包含 IDLE 0.6，新增了許多新功能和改進。部分列表如下：

UI 改進和最佳化，特別是在語法突顯 (syntax highlighting) 和自動縮排 (auto-indentation) 方面。

類別瀏覽器現在顯示更多資訊，例如模組中的頂層函式。

Tab 寬度現在是使用者可設定的選項。開啟現有的 Python 檔案時，IDLE 會自動偵測縮排慣例並調整。

現在支援在各種平台上呼叫瀏覽器，用於在瀏覽器中開啟 Python 說明文件。

IDLE 現在有一個命令列，與原版 Python 直譯器大致相似。

在許多地方新增了呼叫提示。

IDLE 現在可以作為套件安裝。

在編輯器視窗中，底部現在有一個行/列狀態列。

三個新的按鍵命令：檢查模組（Alt-F5）、引入模組（F5）和執行腳本（Ctrl-F5）。

已刪除和已棄用的模組

一些模組因為已過時或因為現在有更好的方法來完成相同的事情而被移除。stdwin 模組已被移除；它是用於一個不再開發的與平台無關的視窗工具組。

許多模組已被移至 lib-old 子目錄：cmp、cmpcache、dircmp、dump、find、grep、packmail、poly、util、whatsound、zmod。如果你的程式碼依賴於已被移至 lib-old 的模組，你可以簡單地將該目錄加入 sys.path 來取回它們，但建議你更新任何使用這些模組的程式碼。

致謝

作者想感謝以下對本文各版本草稿提供建議的協力者：David Bolen、Mark Hammond、Gregg Hauser、Jeremy Hylton、Fredrik Lundh、Detlef Lannert、Aahz Maruch、Skip Montanaro、Vladimir Marangozov、Tobias Polzin、Guido van Rossum、Neil Schemenauer 和 Russ Schmidt。

Changelog（更動日誌）

Python next

Release date: XXXX-XX-XX

Windows

gh-128067 [https://github.com/python/cpython/issues/128067]: Fix a bug in PyREPL on Windows where output without a trailing newline was overwritten by the next prompt.

Tools/Demos

gh-142095 [https://github.com/python/cpython/issues/142095]: Make gdb 'py-bt' command use frame from thread local state when available. Patch by Sam Gross and Victor Stinner.

Tests

gh-143460 [https://github.com/python/cpython/issues/143460]: Skip tests relying on infinite recusion if stack size is unlimited.

gh-65784 [https://github.com/python/cpython/issues/65784]: Add support for parametrized resource wantobjects in regrtests, which allows to run Tkinter tests with the specified value of tkinter.wantobjects, for example -u wantobjects=0.

gh-143553 [https://github.com/python/cpython/issues/143553]: Add support for parametrized resources, such as -u xpickle=2.7.

gh-142836 [https://github.com/python/cpython/issues/142836]: Accommodated Solaris in test_pdb.test_script_target_anonymous_pipe.

bpo-31391 [https://bugs.python.org/issue?@action=redirect&bpo=31391]: Forward-port test_xpickle from Python 2 to Python 3 and add the resource back to test's command line.

Security

gh-144125 [https://github.com/python/cpython/issues/144125]: BytesGenerator will now refuse to serialize (write) headers that are unsafely folded or delimited; see verify_generated_headers. (Contributed by Bas Bloemsaat and Petr Viktorin in gh-121650 [https://github.com/python/cpython/issues/121650]).

gh-143935 [https://github.com/python/cpython/issues/143935]: Fixed a bug in the folding of comments when flattening an email message using a modern email policy. Comments consisting of a very long sequence of non-foldable characters could trigger a forced line wrap that omitted the required leading space on the continuation line, causing the remainder of the comment to be interpreted as a new header field. This enabled header injection with carefully crafted inputs.

gh-143925 [https://github.com/python/cpython/issues/143925]: Reject control characters in data: URL media types.

gh-143919 [https://github.com/python/cpython/issues/143919]: Reject control characters in http.cookies.Morsel fields and values.

gh-143916 [https://github.com/python/cpython/issues/143916]: Reject C0 control characters within wsgiref.headers.Headers fields, values, and parameters.

Library

gh-144169 [https://github.com/python/cpython/issues/144169]: Fix three crashes when non-string keyword arguments are supplied to objects in the ast module.

gh-144100 [https://github.com/python/cpython/issues/144100]: Fixed a crash in ctypes when using a deprecated POINTER(str) type in argtypes. Instead of aborting, ctypes now raises a proper Python exception when the pointer target type is unresolved.

gh-144050 [https://github.com/python/cpython/issues/144050]: Fix stat.filemode() in the pure-Python implementation to avoid misclassifying invalid mode values as block devices.

gh-144023 [https://github.com/python/cpython/issues/144023]: Fixed validation of file descriptor 0 in posix functions when used with follow_symlinks parameter.

gh-143999 [https://github.com/python/cpython/issues/143999]: Fix an issue where inspect.getgeneratorstate() and inspect.getcoroutinestate() could fail for generators wrapped by types.coroutine() in the suspended state.

gh-143831 [https://github.com/python/cpython/issues/143831]: annotationlib.ForwardRef objects are now hashable when created from annotation scopes with closures. Previously, hashing such objects would throw an exception. Patch by Bartosz Sławecki.

gh-143874 [https://github.com/python/cpython/issues/143874]: Fixed a bug in pdb where expression results were not sent back to remote client.

gh-143880 [https://github.com/python/cpython/issues/143880]: Fix data race in functools.partial() in the free threading build.

gh-143706 [https://github.com/python/cpython/issues/143706]: Fix multiprocessing forkserver so that sys.argv is correctly set before __main__ is preloaded. Previously, sys.argv was empty during main module import in forkserver child processes. This fixes a regression introduced in 3.13.8 and 3.14.1. Root caused by Aaron Wieczorek, test provided by Thomas Watson, thanks!

gh-143638 [https://github.com/python/cpython/issues/143638]: Forbid reentrant calls of the pickle.Pickler and pickle.Unpickler methods for the C implementation. Previously, this could cause crash or data corruption, now concurrent calls of methods of the same object raise RuntimeError.

gh-78724 [https://github.com/python/cpython/issues/78724]: Raise RuntimeError's when user attempts to call methods on half-initialized Struct objects, For example, created by Struct.__new__(Struct). Patch by Sergey B Kirpichev.

gh-143196 [https://github.com/python/cpython/issues/143196]: Fix crash when the internal encoder object returned by undocumented function json.encoder.c_make_encoder() was called with non-zero second (_current_indent_level) argument.

gh-143191 [https://github.com/python/cpython/issues/143191]: _thread.stack_size() now raises ValueError if the stack size is too small. Patch by Victor Stinner.

gh-143602 [https://github.com/python/cpython/issues/143602]: Fix a inconsistency issue in write() that leads to unexpected buffer overwrite by deduplicating the buffer exports.

gh-143547 [https://github.com/python/cpython/issues/143547]: Fix sys.unraisablehook() when the hook raises an exception and changes sys.unraisablehook(): hold a strong reference to the old hook. Patch by Victor Stinner.

gh-143517 [https://github.com/python/cpython/issues/143517]: annotationlib.get_annotations() no longer raises a SyntaxError when evaluating a stringified starred annotation that starts with one or more whitespace characters followed by a *. Patch by Bartosz Sławecki.

gh-143378 [https://github.com/python/cpython/issues/143378]: Fix use-after-free crashes when a BytesIO object is concurrently mutated during write() or writelines().

gh-143346 [https://github.com/python/cpython/issues/143346]: Fix incorrect wrapping of the Base64 data in plistlib._PlistWriter when the indent contains a mix of tabs and spaces.

gh-143310 [https://github.com/python/cpython/issues/143310]: tkinter: fix a crash when a Python list is mutated during the conversion to a Tcl object (e.g., when setting a Tcl variable). Patch by Bénédikt Tran.

gh-143309 [https://github.com/python/cpython/issues/143309]: Fix a crash in os.execve() on non-Windows platforms when given a custom environment mapping which is then mutated during parsing. Patch by Bénédikt Tran.

gh-143308 [https://github.com/python/cpython/issues/143308]: pickle: fix use-after-free crashes when a PickleBuffer is concurrently mutated by a custom buffer callback during pickling. Patch by Bénédikt Tran and Aaron Wieczorek.

gh-143237 [https://github.com/python/cpython/issues/143237]: Fix support of named pipes in the rotating logging handlers.

gh-143249 [https://github.com/python/cpython/issues/143249]: Fix possible buffer leaks in Windows overlapped I/O on error handling.

gh-143241 [https://github.com/python/cpython/issues/143241]: zoneinfo: fix infinite loop in ZoneInfo.from_file when parsing a malformed TZif file. Patch by Fatih Celik.

gh-142830 [https://github.com/python/cpython/issues/142830]: sqlite3: fix use-after-free crashes when the connection's callbacks are mutated during a callback execution. Patch by Bénédikt Tran.

gh-143200 [https://github.com/python/cpython/issues/143200]: xml.etree.ElementTree: fix use-after-free crashes in __getitem__() and __setitem__() methods of Element when the element is concurrently mutated. Patch by Bénédikt Tran.

gh-142195 [https://github.com/python/cpython/issues/142195]: Updated timeout evaluation logic in subprocess to be compatible with deterministic environments like Shadow where time moves exactly as requested.

gh-142164 [https://github.com/python/cpython/issues/142164]: Fix the ctypes bitfield overflow error message to report the correct offset and size calculation.

gh-143145 [https://github.com/python/cpython/issues/143145]: Fixed a possible reference leak in ctypes when constructing results with multiple output parameters on error.

gh-122431 [https://github.com/python/cpython/issues/122431]: Corrected the error message in readline.append_history_file() to state that nelements must be non-negative instead of positive.

gh-143004 [https://github.com/python/cpython/issues/143004]: Fix a potential use-after-free in collections.Counter.update() when user code mutates the Counter during an update.

gh-143046 [https://github.com/python/cpython/issues/143046]: The asyncio REPL no longer prints copyright and version messages in the quiet mode (-q). Patch by Bartosz Sławecki.

gh-140648 [https://github.com/python/cpython/issues/140648]: The asyncio REPL now respects the -I flag (isolated mode). Previously, it would load and execute PYTHONSTARTUP even if the flag was set. Contributed by Bartosz Sławecki.

gh-142991 [https://github.com/python/cpython/issues/142991]: Fixed socket operations such as recvfrom() and sendto() for FreeBSD divert(4) socket.

gh-143010 [https://github.com/python/cpython/issues/143010]: Fixed a bug in mailbox where the precise timing of an external event could result in the library opening an existing file instead of a file it expected to create.

gh-142881 [https://github.com/python/cpython/issues/142881]: Fix concurrent and reentrant call of atexit.unregister().

gh-112127 [https://github.com/python/cpython/issues/112127]: Fix possible use-after-free in atexit.unregister() when the callback is unregistered during comparison.

gh-142783 [https://github.com/python/cpython/issues/142783]: Fix zoneinfo use-after-free with descriptor _weak_cache. a descriptor as _weak_cache could cause crashes during object creation. The fix ensures proper reference counting for descriptor-provided objects.

gh-142754 [https://github.com/python/cpython/issues/142754]: Add the ownerDocument attribute to xml.dom.minidom elements and attributes created by directly instantiating the Element or Attr class. Note that this way of creating nodes is not supported; creator functions like xml.dom.Document.documentElement() should be used instead.

gh-142784 [https://github.com/python/cpython/issues/142784]: The asyncio REPL now properly closes the loop upon the end of interactive session. Previously, it could cause surprising warnings. Contributed by Bartosz Sławecki.

gh-142594 [https://github.com/python/cpython/issues/142594]: Fix crash in TextIOWrapper.close() when the underlying buffer's closed property calls detach().

gh-142451 [https://github.com/python/cpython/issues/142451]: hmac: Ensure that the HMAC.block_size attribute is correctly copied by HMAC.copy. Patch by Bénédikt Tran.

gh-142495 [https://github.com/python/cpython/issues/142495]: collections.defaultdict now prioritizes __setitem__() when inserting default values from default_factory. This prevents race conditions where a default value would overwrite a value set before default_factory returns.

gh-142651 [https://github.com/python/cpython/issues/142651]: unittest.mock: fix a thread safety issue where Mock.call_count may return inaccurate values when the mock is called concurrently from multiple threads.

gh-142595 [https://github.com/python/cpython/issues/142595]: Added type check during initialization of the decimal module to prevent a crash in case of broken stdlib. Patch by Sergey B Kirpichev.

gh-142556 [https://github.com/python/cpython/issues/142556]: Fix crash when a task gets re-registered during finalization in asyncio. Patch by Kumar Aditya.

gh-123241 [https://github.com/python/cpython/issues/123241]: Avoid reference count operations in garbage collection of ctypes objects.

gh-142517 [https://github.com/python/cpython/issues/142517]: The non-compat32 email policies now correctly handle refolding encoded words that contain bytes that can not be decoded in their specified character set. Previously this resulted in an encoding exception during folding.

gh-112527 [https://github.com/python/cpython/issues/112527]: The help text for required options in argparse no longer extended with " (default: None)".

gh-142346 [https://github.com/python/cpython/issues/142346]: Fix usage formatting for mutually exclusive groups in argparse when they are preceded by positional arguments or followed or intermixed with other optional arguments.

gh-142315 [https://github.com/python/cpython/issues/142315]: Pdb can now run scripts from anonymous pipes used in process substitution. Patch by Bartosz Sławecki.

gh-142332 [https://github.com/python/cpython/issues/142332]: Fix usage formatting for positional arguments in mutually exclusive groups in argparse. in argparse.

gh-142282 [https://github.com/python/cpython/issues/142282]: Fix winreg.QueryValueEx() to not accidentally read garbage buffer under race condition.

gh-75949 [https://github.com/python/cpython/issues/75949]: Fix argparse to preserve | separators in mutually exclusive groups when the usage line wraps due to length.

gh-142267 [https://github.com/python/cpython/issues/142267]: Improve argparse performance by caching the formatter used for argument validation.

gh-68552 [https://github.com/python/cpython/issues/68552]: MisplacedEnvelopeHeaderDefect and Missing header name defects are now correctly passed to the handle_defect method of policy in FeedParser.

gh-142006 [https://github.com/python/cpython/issues/142006]: Fix a bug in the email.policy.default folding algorithm which incorrectly resulted in a doubled newline when a line ending at exactly max_line_length was followed by an unfoldable token.

gh-105836 [https://github.com/python/cpython/issues/105836]: Fix asyncio.run_coroutine_threadsafe() leaving underlying cancelled asyncio task running.

gh-139971 [https://github.com/python/cpython/issues/139971]: pydoc: Ensure that the link to the online documentation of a stdlib module is correct.

gh-139262 [https://github.com/python/cpython/issues/139262]: Some keystrokes can be swallowed in the new PyREPL on Windows, especially when used together with the ALT key. Fix by Chris Eibl.

gh-138897 [https://github.com/python/cpython/issues/138897]: Improved license/copyright/credits display in the REPL: now uses a pager.

gh-79986 [https://github.com/python/cpython/issues/79986]: Add parsing for References and In-Reply-To headers to the email library that parses the header content as lists of message id tokens. This prevents them from being folded incorrectly.

gh-136282 [https://github.com/python/cpython/issues/136282]: Add support for UNNAMED_SECTION when creating a section via the mapping protocol access

gh-109263 [https://github.com/python/cpython/issues/109263]: Starting a process from spawn context in multiprocessing no longer sets the start method globally.

gh-133253 [https://github.com/python/cpython/issues/133253]: Fix thread-safety issues in linecache.

gh-132715 [https://github.com/python/cpython/issues/132715]: Skip writing objects during marshalling once a failure has occurred.

IDLE

gh-143774 [https://github.com/python/cpython/issues/143774]: Better explain the operation of Format / Format Paragraph.

Documentation

gh-140806 [https://github.com/python/cpython/issues/140806]: Add documentation for enum.bin().

Core and Builtins

gh-144307 [https://github.com/python/cpython/issues/144307]: Prevent a reference leak in module teardown at interpreter finalization.

gh-144194 [https://github.com/python/cpython/issues/144194]: Fix error handling in perf jitdump initialization on memory allocation failure.

gh-144012 [https://github.com/python/cpython/issues/144012]: Check if the result is NULL in BINARY_OP_EXTENT opcode.

gh-141805 [https://github.com/python/cpython/issues/141805]: Fix crash in set when objects with the same hash are concurrently added to the set after removing an element with the same hash while the set still contains elements with the same hash.

gh-143670 [https://github.com/python/cpython/issues/143670]: Fixes a crash in ga_repr_items_list function.

gh-143377 [https://github.com/python/cpython/issues/143377]: Fix a crash in _interpreters.capture_exception() when the exception is incorrectly formatted. Patch by Bénédikt Tran.

gh-136924 [https://github.com/python/cpython/issues/136924]: The interactive help mode in the REPL no longer incorrectly syntax highlights text input as Python code. Contributed by Olga Matoula.

gh-143189 [https://github.com/python/cpython/issues/143189]: Fix crash when inserting a non-str key into a split table dictionary when the key matches an existing key in the split table but has no corresponding value in the dict.

gh-143228 [https://github.com/python/cpython/issues/143228]: Fix use-after-free in perf trampoline when toggling profiling while threads are running or during interpreter finalization with daemon threads active. The fix uses reference counting to ensure trampolines are not freed while any code object could still reference them. Pach by Pablo Galindo

gh-142664 [https://github.com/python/cpython/issues/142664]: Fix a use-after-free crash in memoryview.__hash__ when the __hash__ method of the referenced object mutates that object or the view. Patch by Bénédikt Tran.

gh-142557 [https://github.com/python/cpython/issues/142557]: Fix a use-after-free crash in bytearray.__mod__ when the bytearray is mutated while formatting the %-style arguments. Patch by Bénédikt Tran.

gh-143195 [https://github.com/python/cpython/issues/143195]: Fix use-after-free crashes in bytearray.hex() and memoryview.hex() when the separator's __len__() mutates the original object. Patch by Bénédikt Tran.

gh-142975 [https://github.com/python/cpython/issues/142975]: Fix crash after unfreezing all objects tracked by the garbage collector on the free threaded build.

gh-143135 [https://github.com/python/cpython/issues/143135]: Set sys.flags.inspect to 1 when PYTHONINSPECT is 0. Previously, it was set to 0 in this case.

gh-143003 [https://github.com/python/cpython/issues/143003]: Fix an overflow of the shared empty buffer in bytearray.extend() when __length_hint__() returns 0 for non-empty iterator.

gh-143006 [https://github.com/python/cpython/issues/143006]: Fix a possible assertion error when comparing negative non-integer float and int with the same number of bits in the integer part.

gh-143057 [https://github.com/python/cpython/issues/143057]: Avoid locking in PyTraceMalloc_Track() and PyTraceMalloc_Untrack() when tracemalloc is not enabled.

gh-142776 [https://github.com/python/cpython/issues/142776]: Fix a file descriptor leak in import.c

gh-142829 [https://github.com/python/cpython/issues/142829]: Fix a use-after-free crash in contextvars.Context comparison when a custom __eq__ method modifies the context via set().

gh-142766 [https://github.com/python/cpython/issues/142766]: Clear the frame of a generator when generator.close() is called.

gh-142737 [https://github.com/python/cpython/issues/142737]: Tracebacks will be displayed in fallback mode even if io.open() is lost. Previously, this would crash the interpreter. Patch by Bartosz Sławecki.

gh-142554 [https://github.com/python/cpython/issues/142554]: Fix a crash in divmod() when _pylong.int_divmod() does not return a tuple of length two exactly. Patch by Bénédikt Tran.

gh-142560 [https://github.com/python/cpython/issues/142560]: Fix use-after-free in bytearray search-like methods (find(), count(), index(), rindex(), and rfind()) by marking the storage as exported which causes reallocation attempts to raise BufferError. For contains(), split(), and rsplit() the buffer protocol is used for this.

gh-142531 [https://github.com/python/cpython/issues/142531]: Fix a free-threaded GC performance regression. If there are many untracked tuples, the GC will run too often, resulting in poor performance. The fix is to include untracked tuples in the "long lived" object count. The number of frozen objects is also now included since the free-threaded GC must scan those too.

gh-142402 [https://github.com/python/cpython/issues/142402]: Fix reference counting when adjacent literal parts are merged while constructing string.templatelib.Template, preventing the displaced string object from leaking.

gh-133932 [https://github.com/python/cpython/issues/133932]: Fix crash in the free threading build when clearing frames that hold tagged integers.

gh-142343 [https://github.com/python/cpython/issues/142343]: Fix SIGILL crash on m68k due to incorrect assembly constraint.

gh-100964 [https://github.com/python/cpython/issues/100964]: Fix reference cycle in exhausted generator frames. Patch by Savannah Ostrowski.

gh-69605 [https://github.com/python/cpython/issues/69605]: Fix edge-cases around already imported modules in the REPL auto-completion of imports.

gh-138568 [https://github.com/python/cpython/issues/138568]: Adjusted the built-in help() function so that empty inputs are ignored in interactive mode.

gh-137007 [https://github.com/python/cpython/issues/137007]: Fix a bug during JIT compilation failure which caused garbage collection debug assertions to fail.

C API

gh-142589 [https://github.com/python/cpython/issues/142589]: Fix PyUnstable_Object_IsUniqueReferencedTemporary() handling of tagged ints on the interpreter stack.

gh-142571 [https://github.com/python/cpython/issues/142571]: PyUnstable_CopyPerfMapFile() now checks that opening the file succeeded before flushing.

Build

gh-142454 [https://github.com/python/cpython/issues/142454]: When calculating the digest of the JIT stencils input, sort the hashed files by filenames before adding their content to the hasher. This ensures deterministic hash input and hence deterministic hash, independent on filesystem order.

gh-141808 [https://github.com/python/cpython/issues/141808]: When running make clean-retain-profile, keep the generated JIT stencils. That way, the stencils are not generated twice when Profile-guided optimization (PGO) is used. It also allows distributors to supply their own pre-built JIT stencils.

gh-138061 [https://github.com/python/cpython/issues/138061]: Ensure reproducible builds by making JIT stencil header generation deterministic.

Python 3.14.2 final

Release date: 2025-12-05

Security

gh-142145 [https://github.com/python/cpython/issues/142145]: Remove quadratic behavior in xml.minidom node ID cache clearing.

gh-119452 [https://github.com/python/cpython/issues/119452]: Fix a potential memory denial of service in the http.server module. When a malicious user is connected to the CGI server on Windows, it could cause an arbitrary amount of memory to be allocated. This could have led to symptoms including a MemoryError, swapping, out of memory (OOM) killed processes or containers, or even system crashes.

Library

gh-140797 [https://github.com/python/cpython/issues/140797]: Revert changes to the undocumented re.Scanner class. Capturing groups are still allowed for backward compatibility, although using them can lead to incorrect result. They will be forbidden in future Python versions.

gh-142206 [https://github.com/python/cpython/issues/142206]: The resource tracker in the multiprocessing module now uses the original communication protocol, as in Python 3.14.0 and below, by default. This avoids issues with upgrading Python while it is running. (Note that such 'in-place' upgrades are not tested.) The tracker remains compatible with subprocesses that use new protocol (that is, subprocesses using Python 3.13.10, 3.14.1 and 3.15).

gh-142214 [https://github.com/python/cpython/issues/142214]: Fix two regressions in dataclasses in Python 3.14.1 related to annotations.

An exception is no longer raised if slots=True is used and the __init__ method does not have an __annotate__ attribute (likely because init=False was used).

An exception is no longer raised if annotations are requested on the __init__ method and one of the fields is not present in the class annotations. This can occur in certain dynamic scenarios.

Patch by Jelle Zijlstra.

Core and Builtins

gh-142218 [https://github.com/python/cpython/issues/142218]: Fix crash when inserting into a split table dictionary with a non str key that matches an existing key.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Fix cmath data race when initializing trigonometric tables with subinterpreters.

Python 3.14.1 final

Release date: 2025-12-02

Windows

gh-139810 [https://github.com/python/cpython/issues/139810]: Installing with py install 3[.x]-dev will now select final versions as well as prereleases.

Tools/Demos

gh-141692 [https://github.com/python/cpython/issues/141692]: Each slice of an iOS XCframework now contains a lib folder that contains a symlink to the libpython dylib. This allows binary modules to be compiled for iOS using dynamic libreary linking, rather than Framework linking.

gh-141442 [https://github.com/python/cpython/issues/141442]: The iOS testbed now correctly handles test arguments that contain spaces.

gh-140702 [https://github.com/python/cpython/issues/140702]: The iOS testbed app will now expose the GITHUB_ACTIONS environment variable to iOS apps being tested.

gh-137484 [https://github.com/python/cpython/issues/137484]: Have Tools/wasm/wasi put the build Python into a directory named after the build triple instead of "build".

gh-137248 [https://github.com/python/cpython/issues/137248]: Add a --logdir option to Tools/wasm/wasi for specifying where to write log files.

gh-137243 [https://github.com/python/cpython/issues/137243]: Have Tools/wasm/wasi detect a WASI SDK install in /opt when it was directly extracted from a release tarball.

Tests

gh-140482 [https://github.com/python/cpython/issues/140482]: Preserve and restore the state of stty echo as part of the test environment.

gh-140082 [https://github.com/python/cpython/issues/140082]: Update python -m test to set FORCE_COLOR=1 when being run with color enabled so that unittest which is run by it with redirected output will output in color.

gh-139208 [https://github.com/python/cpython/issues/139208]: Fix regrtest --fast-ci --verbose: don't ignore the --verbose option anymore. Patch by Victor Stinner.

gh-136442 [https://github.com/python/cpython/issues/136442]: Use exitcode 1 instead of 5 if unittest.TestCase.setUpClass() raises an exception

Security

gh-139700 [https://github.com/python/cpython/issues/139700]: Check consistency of the zip64 end of central directory record. Support records with "zip64 extensible data" if there are no bytes prepended to the ZIP file.

gh-139283 [https://github.com/python/cpython/issues/139283]: sqlite3: correctly handle maximum number of rows to fetch in Cursor.fetchmany and reject negative values for Cursor.arraysize. Patch by Bénédikt Tran.

gh-137836 [https://github.com/python/cpython/issues/137836]: Add support of the "plaintext" element, RAWTEXT elements "xmp", "iframe", "noembed" and "noframes", and optionally RAWTEXT element "noscript" in html.parser.HTMLParser.

gh-136063 [https://github.com/python/cpython/issues/136063]: email.message: ensure linear complexity for legacy HTTP parameters parsing. Patch by Bénédikt Tran.

gh-136065 [https://github.com/python/cpython/issues/136065]: Fix quadratic complexity in os.path.expandvars().

gh-119451 [https://github.com/python/cpython/issues/119451]: Fix a potential memory denial of service in the http.client module. When connecting to a malicious server, it could cause an arbitrary amount of memory to be allocated. This could have led to symptoms including a MemoryError, swapping, out of memory (OOM) killed processes or containers, or even system crashes.

gh-119342 [https://github.com/python/cpython/issues/119342]: Fix a potential memory denial of service in the plistlib module. When reading a Plist file received from untrusted source, it could cause an arbitrary amount of memory to be allocated. This could have led to symptoms including a MemoryError, swapping, out of memory (OOM) killed processes or containers, or even system crashes.

Library

gh-74389 [https://github.com/python/cpython/issues/74389]: When the stdin being used by a subprocess.Popen instance is closed, this is now ignored in subprocess.Popen.communicate() instead of leaving the class in an inconsistent state.

gh-87512 [https://github.com/python/cpython/issues/87512]: Fix subprocess.Popen.communicate() timeout handling on Windows when writing large input. Previously, the timeout was ignored during stdin writing, causing the method to block indefinitely if the child process did not consume input quickly. The stdin write is now performed in a background thread, allowing the timeout to be properly enforced.

gh-141473 [https://github.com/python/cpython/issues/141473]: When subprocess.Popen.communicate() was called with input and a timeout and is called for a second time after a TimeoutExpired exception before the process has died, it should no longer hang.

gh-59000 [https://github.com/python/cpython/issues/59000]: Fix pdb breakpoint resolution for class methods when the module defining the class is not imported.

gh-141570 [https://github.com/python/cpython/issues/141570]: Support file-like object raising OSError from fileno() in color detection (_colorize.can_colorize()). This can occur when sys.stdout is redirected.

gh-141659 [https://github.com/python/cpython/issues/141659]: Fix bad file descriptor errors from _posixsubprocess on AIX.

gh-141600 [https://github.com/python/cpython/issues/141600]: Fix musl version detection on Void Linux.

gh-141497 [https://github.com/python/cpython/issues/141497]: ipaddress: ensure that the methods IPv4Network.hosts() and IPv6Network.hosts() always return an iterator.

gh-140938 [https://github.com/python/cpython/issues/140938]: The statistics.stdev() and statistics.pstdev() functions now raise a ValueError when the input contains an infinity or a NaN.

gh-124111 [https://github.com/python/cpython/issues/124111]: Updated Tcl threading configuration in _tkinter to assume that threads are always available in Tcl 9 and later.

gh-137109 [https://github.com/python/cpython/issues/137109]: The os.fork and related forking APIs will no longer warn in the common case where Linux or macOS platform APIs return the number of threads in a process and find the answer to be 1 even when a os.register_at_fork() after_in_parent= callback (re)starts a thread.

gh-141314 [https://github.com/python/cpython/issues/141314]: Fix assertion failure in io.TextIOWrapper.tell() when reading files with standalone carriage return (\r) line endings.

gh-141311 [https://github.com/python/cpython/issues/141311]: Fix assertion failure in io.BytesIO.readinto() and undefined behavior arising when read position is above capcity in io.BytesIO.

gh-141141 [https://github.com/python/cpython/issues/141141]: Fix a thread safety issue with base64.b85decode(). Contributed by Benel Tayar.

gh-137969 [https://github.com/python/cpython/issues/137969]: Fix annotationlib.ForwardRef.evaluate() returning ForwardRef objects which don't update with new globals.

gh-140911 [https://github.com/python/cpython/issues/140911]: collections: Ensure that the methods UserString.rindex() and UserString.index() accept collections.UserString instances as the sub argument.

gh-140797 [https://github.com/python/cpython/issues/140797]: The undocumented re.Scanner class now forbids regular expressions containing capturing groups in its lexicon patterns. Patterns using capturing groups could previously lead to crashes with segmentation fault. Use non-capturing groups (?:...) instead.

gh-125115 [https://github.com/python/cpython/issues/125115]: Refactor the pdb parsing issue so positional arguments can pass through intuitively.

gh-140815 [https://github.com/python/cpython/issues/140815]: faulthandler now detects if a frame or a code object is invalid or freed. Patch by Victor Stinner.

gh-100218 [https://github.com/python/cpython/issues/100218]: Correctly set errno when socket.if_nametoindex() or socket.if_indextoname() raise an OSError. Patch by Bénédikt Tran.

gh-140875 [https://github.com/python/cpython/issues/140875]: Fix handling of unclosed character references (named and numerical) followed by the end of file in html.parser.HTMLParser with convert_charrefs=False.

gh-140734 [https://github.com/python/cpython/issues/140734]: multiprocessing: fix off-by-one error when checking the length of a temporary socket file path. Patch by Bénédikt Tran.

gh-140874 [https://github.com/python/cpython/issues/140874]: Bump the version of pip bundled in ensurepip to version 25.3

gh-140691 [https://github.com/python/cpython/issues/140691]: In urllib.request, when opening a FTP URL fails because a data connection cannot be made, the control connection's socket is now closed to avoid a ResourceWarning.

gh-103847 [https://github.com/python/cpython/issues/103847]: Fix hang when cancelling process created by asyncio.create_subprocess_exec() or asyncio.create_subprocess_shell(). Patch by Kumar Aditya.

gh-120057 [https://github.com/python/cpython/issues/120057]: Add os.reload_environ() to os.__all__.

gh-140228 [https://github.com/python/cpython/issues/140228]: Avoid making unnecessary filesystem calls for frozen modules in linecache when the global module cache is not present.

gh-140590 [https://github.com/python/cpython/issues/140590]: Fix arguments checking for the functools.partial.__setstate__() that may lead to internal state corruption and crash. Patch by Sergey Miryanov.

gh-125434 [https://github.com/python/cpython/issues/125434]: Display thread name in faulthandler on Windows. Patch by Victor Stinner.

gh-140634 [https://github.com/python/cpython/issues/140634]: Fix a reference counting bug in os.sched_param.__reduce__().

gh-140633 [https://github.com/python/cpython/issues/140633]: Ignore AttributeError when setting a module's __file__ attribute when loading an extension module packaged as Apple Framework.

gh-140593 [https://github.com/python/cpython/issues/140593]: xml.parsers.expat: Fix a memory leak that could affect users with ElementDeclHandler() set to a custom element declaration handler. Patch by Sebastian Pipping.

gh-140607 [https://github.com/python/cpython/issues/140607]: Inside io.RawIOBase.read(), validate that the count of bytes returned by io.RawIOBase.readinto() is valid (inside the provided buffer).

gh-138162 [https://github.com/python/cpython/issues/138162]: Fix logging.LoggerAdapter with merge_extra=True and without the extra argument.

gh-138774 [https://github.com/python/cpython/issues/138774]: ast.unparse() now generates full source code when handling ast.Interpolation nodes that do not have a specified source.

gh-140474 [https://github.com/python/cpython/issues/140474]: Fix memory leak in array.array when creating arrays from an empty str and the u type code.

gh-137530 [https://github.com/python/cpython/issues/137530]: dataclasses Fix annotations for generated __init__ methods by replacing the annotations that were in-line in the generated source code with __annotate__ functions attached to the methods.

gh-140348 [https://github.com/python/cpython/issues/140348]: Fix regression in Python 3.14.0 where using the | operator on a typing.Union object combined with an object that is not a type would raise an error.

gh-140272 [https://github.com/python/cpython/issues/140272]: Fix memory leak in the clear() method of the dbm.gnu database.

gh-140041 [https://github.com/python/cpython/issues/140041]: Fix import of ctypes on Android and Cygwin when ABI flags are present.

gh-140120 [https://github.com/python/cpython/issues/140120]: Fixed a memory leak in hmac when it was using the hacl-star backend. Discovered by @ashm-dev using AddressSanitizer.

gh-139905 [https://github.com/python/cpython/issues/139905]: Add suggestion to error message for typing.Generic subclasses when cls.__parameters__ is missing due to a parent class failing to call super().__init_subclass__() in its __init_subclass__.

gh-139894 [https://github.com/python/cpython/issues/139894]: Fix incorrect sharing of current task with the child process while forking in asyncio. Patch by Kumar Aditya.

gh-139845 [https://github.com/python/cpython/issues/139845]: Fix to not print KeyboardInterrupt twice in default asyncio REPL.

gh-139783 [https://github.com/python/cpython/issues/139783]: Fix inspect.getsourcelines() for the case when a decorator is followed by a comment or an empty line.

gh-139809 [https://github.com/python/cpython/issues/139809]: Prevent premature colorization of subparser prog in argparse.ArgumentParser.add_subparsers() to respect color environment variable changes after parser creation.

gh-139736 [https://github.com/python/cpython/issues/139736]: Fix excessive indentation in the default argparse HelpFormatter. Patch by Alexander Edland.

gh-70765 [https://github.com/python/cpython/issues/70765]: http.server: fix default handling of HTTP/0.9 requests in BaseHTTPRequestHandler. Previously, BaseHTTPRequestHandler.parse_request() incorrectly waited for headers in the request although those are not supported in HTTP/0.9. Patch by Bénédikt Tran.

gh-63161 [https://github.com/python/cpython/issues/63161]: Fix tokenize.detect_encoding(). Support non-UTF-8 shebang and comments if non-UTF-8 encoding is specified. Detect decoding error for non-UTF-8 encoding. Detect null bytes in source code.

gh-139391 [https://github.com/python/cpython/issues/139391]: Fix an issue when, on non-Windows platforms, it was not possible to gracefully exit a python -m asyncio process suspended by Ctrl+Z and later resumed by fg [https://manpages.debian.org/fg] other than with kill [https://manpages.debian.org/kill].

gh-101828 [https://github.com/python/cpython/issues/101828]: Fix 'shift_jisx0213', 'shift_jis_2004', 'euc_jisx0213' and 'euc_jis_2004' codecs truncating null chars as they were treated as part of multi-character sequences.

gh-139289 [https://github.com/python/cpython/issues/139289]: Do a real lazy-import on rlcompleter in pdb and restore the existing completer after importing rlcompleter.

gh-139246 [https://github.com/python/cpython/issues/139246]: fix: paste zero-width in default repl width is wrong.

gh-90949 [https://github.com/python/cpython/issues/90949]: Add SetAllocTrackerActivationThreshold() and SetAllocTrackerMaximumAmplification() to xmlparser objects to prevent use of disproportional amounts of dynamic memory from within an Expat parser. Patch by Bénédikt Tran.

gh-139210 [https://github.com/python/cpython/issues/139210]: Fix use-after-free when reporting unknown event in xml.etree.ElementTree.iterparse(). Patch by Ken Jin.

gh-138860 [https://github.com/python/cpython/issues/138860]: Lazy import rlcompleter in pdb to avoid deadlock in subprocess.

gh-112729 [https://github.com/python/cpython/issues/112729]: Fix crash when calling concurrent.interpreters.create() when the process is out of memory.

gh-135729 [https://github.com/python/cpython/issues/135729]: Fix unraisable exception during finalization when using concurrent.interpreters in the REPL.

gh-139076 [https://github.com/python/cpython/issues/139076]: Fix a bug in the pydoc module that was hiding functions in a Python module if they were implemented in an extension module and the module did not have __all__.

gh-139065 [https://github.com/python/cpython/issues/139065]: Fix trailing space before a wrapped long word if the line length is exactly width in textwrap.

gh-139001 [https://github.com/python/cpython/issues/139001]: Fix race condition in pathlib.Path on the internal _raw_paths field.

gh-138813 [https://github.com/python/cpython/issues/138813]: multiprocessing.BaseProcess defaults kwargs to None instead of a shared dictionary.

gh-138993 [https://github.com/python/cpython/issues/138993]: Dedent credits text.

gh-138891 [https://github.com/python/cpython/issues/138891]: Fix SyntaxError when inspect.get_annotations(f, eval_str=True) is called on a function annotated with a PEP 646 [https://peps.python.org/pep-0646/] star_expression

gh-130567 [https://github.com/python/cpython/issues/130567]: Fix possible crash in locale.strxfrm() due to a platform bug on macOS.

gh-138859 [https://github.com/python/cpython/issues/138859]: Fix generic type parameterization raising a TypeError when omitting a ParamSpec that has a default which is not a list of types.

gh-138764 [https://github.com/python/cpython/issues/138764]: Prevent annotationlib.call_annotate_function() from calling __annotate__ functions that don't support VALUE_WITH_FAKE_GLOBALS in a fake globals namespace with empty globals.

Make FORWARDREF and STRING annotations fall back to using VALUE annotations in the case that neither their own format, nor VALUE_WITH_FAKE_GLOBALS are supported.

gh-138775 [https://github.com/python/cpython/issues/138775]: Use of python -m with base64 has been fixed to detect input from a terminal so that it properly notices EOF.

gh-138779 [https://github.com/python/cpython/issues/138779]: Support device numbers larger than 2**63-1 for the st_rdev field of the os.stat_result structure.

gh-137706 [https://github.com/python/cpython/issues/137706]: Fix the partial evaluation of annotations that use typing.Annotated[T, x] where T is a forward reference.

gh-88375 [https://github.com/python/cpython/issues/88375]: Fix normalization of the robots.txt rules and URLs in the urllib.robotparser module. No longer ignore trailing ?. Distinguish raw special characters ?, = and & from the percent-encoded ones.

gh-111788 [https://github.com/python/cpython/issues/111788]: Fix parsing errors in the urllib.robotparser module. Don't fail trying to parse weird paths. Don't fail trying to decode non-UTF-8 robots.txt files.

gh-98896 [https://github.com/python/cpython/issues/98896]: Fix a failure in multiprocessing resource_tracker when SharedMemory names contain colons. Patch by Rani Pinchuk.

gh-138425 [https://github.com/python/cpython/issues/138425]: Fix partial evaluation of annotationlib.ForwardRef objects which rely on names defined as globals.

gh-138432 [https://github.com/python/cpython/issues/138432]: zoneinfo.reset_tzpath() will now convert any os.PathLike objects it receives into strings before adding them to TZPATH. It will raise TypeError if anything other than a string is found after this conversion. If given an os.PathLike object that represents a relative path, it will now raise ValueError instead of TypeError, and present a more informative error message.

gh-138008 [https://github.com/python/cpython/issues/138008]: Fix segmentation faults in the ctypes module due to invalid argtypes. Patch by Dung Nguyen.

gh-60462 [https://github.com/python/cpython/issues/60462]: Fix locale.strxfrm() on Solaris (and possibly other platforms).

gh-138239 [https://github.com/python/cpython/issues/138239]: The REPL now highlights type as a soft keyword in type statements.

gh-138204 [https://github.com/python/cpython/issues/138204]: Forbid expansion of shared anonymous memory maps on Linux, which caused a bus error.

gh-138010 [https://github.com/python/cpython/issues/138010]: Fix an issue where defining a class with an @warnings.deprecated-decorated base class may not invoke the correct __init_subclass__() method in cases involving multiple inheritance. Patch by Brian Schubert.

gh-138151 [https://github.com/python/cpython/issues/138151]: In annotationlib, improve evaluation of forward references to nonlocal variables that are not yet defined when the annotations are initially evaluated.

gh-137317 [https://github.com/python/cpython/issues/137317]: inspect.signature() now correctly handles classes that use a descriptor on a wrapped __init__() or __new__() method. Contributed by Yongyu Yan.

gh-137754 [https://github.com/python/cpython/issues/137754]: Fix import of the zoneinfo module if the C implementation of the datetime module is not available.

gh-137490 [https://github.com/python/cpython/issues/137490]: Handle ECANCELED in the same way as EINTR in signal.sigwaitinfo() on NetBSD.

gh-137477 [https://github.com/python/cpython/issues/137477]: Fix inspect.getblock(), inspect.getsourcelines() and inspect.getsource() for generator expressions.

gh-137044 [https://github.com/python/cpython/issues/137044]: Return large limit values as positive integers instead of negative integers in resource.getrlimit(). Accept large values and reject negative values (except RLIM_INFINITY) for limits in resource.setrlimit().

gh-75989 [https://github.com/python/cpython/issues/75989]: tarfile.TarFile.extractall() and tarfile.TarFile.extract() now overwrite symlinks when extracting hardlinks. (Contributed by Alexander Enrique Urieles Nieto in gh-75989 [https://github.com/python/cpython/issues/75989].)

gh-137017 [https://github.com/python/cpython/issues/137017]: Fix threading.Thread.is_alive to remain True until the underlying OS thread is fully cleaned up. This avoids false negatives in edge cases involving thread monitoring or premature threading.Thread.is_alive calls.

gh-137273 [https://github.com/python/cpython/issues/137273]: Fix debug assertion failure in locale.setlocale() on Windows.

gh-137239 [https://github.com/python/cpython/issues/137239]: heapq: Update heapq.__all__ with *_max functions.

gh-81325 [https://github.com/python/cpython/issues/81325]: tarfile.TarFile now accepts a path-like when working on a tar archive. (Contributed by Alexander Enrique Urieles Nieto in gh-81325 [https://github.com/python/cpython/issues/81325].)

gh-137185 [https://github.com/python/cpython/issues/137185]: Fix a potential async-signal-safety issue in faulthandler when printing C stack traces.

gh-136914 [https://github.com/python/cpython/issues/136914]: Fix retrieval of doctest.DocTest.lineno for objects decorated with functools.cache() or functools.cached_property.

gh-136912 [https://github.com/python/cpython/issues/136912]: hmac.digest() now properly handles large keys and messages by falling back to the pure Python implementation when necessary. Patch by Bénédikt Tran.

gh-83424 [https://github.com/python/cpython/issues/83424]: Allows creating a ctypes.CDLL without name when passing a handle as an argument.

gh-136234 [https://github.com/python/cpython/issues/136234]: Fix asyncio.WriteTransport.writelines() to be robust to connection failure, by using the same behavior as write().

gh-136507 [https://github.com/python/cpython/issues/136507]: Fix mimetypes CLI to handle multiple file parameters.

gh-136057 [https://github.com/python/cpython/issues/136057]: Fixed the bug in pdb and bdb where next and step can't go over the line if a loop exists in the line.

gh-135386 [https://github.com/python/cpython/issues/135386]: Fix opening a dbm.sqlite3 database for reading from read-only file or directory.

gh-135444 [https://github.com/python/cpython/issues/135444]: Fix asyncio.DatagramTransport.sendto() to account for datagram header size when data cannot be sent.

gh-126631 [https://github.com/python/cpython/issues/126631]: Fix multiprocessing forkserver bug which prevented __main__ from being preloaded.

gh-135307 [https://github.com/python/cpython/issues/135307]: email: Fix exception in set_content() when encoding text and max_line_length is set to 0 or None (unlimited).

gh-134453 [https://github.com/python/cpython/issues/134453]: Fixed subprocess.Popen.communicate() input= handling of memoryview instances that were non-byte shaped on POSIX platforms. Those are now properly cast to a byte shaped view instead of truncating the input. Windows platforms did not have this bug.

gh-134698 [https://github.com/python/cpython/issues/134698]: Fix a crash when calling methods of ssl.SSLContext or ssl.SSLSocket across multiple threads.

gh-125996 [https://github.com/python/cpython/issues/125996]: Fix thread safety of collections.OrderedDict. Patch by Kumar Aditya.

gh-133789 [https://github.com/python/cpython/issues/133789]: Fix unpickling of pathlib objects that were pickled in Python 3.13.

gh-127081 [https://github.com/python/cpython/issues/127081]: Fix libc thread safety issues with dbm by performing stateful operations in critical sections.

gh-132551 [https://github.com/python/cpython/issues/132551]: Make io.BytesIO safe in free-threaded build.

gh-131788 [https://github.com/python/cpython/issues/131788]: Make ResourceTracker.send from multiprocessing re-entrant safe

gh-118981 [https://github.com/python/cpython/issues/118981]: Fix potential hang in multiprocessing.popen_spawn_posix that can happen when the child proc dies early by closing the child fds right away.

gh-102431 [https://github.com/python/cpython/issues/102431]: Clarify constraints for "logical" arguments in methods of decimal.Context.

gh-78319 [https://github.com/python/cpython/issues/78319]: UTF8 support for the IMAP APPEND command has been made RFC compliant.

bpo-38735 [https://bugs.python.org/issue?@action=redirect&bpo=38735]: Fix failure when importing a module from the root directory on unix-like platforms with sys.pycache_prefix set.

bpo-41839 [https://bugs.python.org/issue?@action=redirect&bpo=41839]: Allow negative priority values from os.sched_get_priority_min() and os.sched_get_priority_max() functions.

IDLE

gh-96491 [https://github.com/python/cpython/issues/96491]: Deduplicate version number in IDLE shell title bar after saving to a file.

gh-139742 [https://github.com/python/cpython/issues/139742]: Colorize t-string prefixes for template strings in IDLE, as done for f-string prefixes.

Documentation

gh-141994 [https://github.com/python/cpython/issues/141994]: xml.sax.handler: Make Documentation of xml.sax.handler.feature_external_ges warn of opening up to external entity attacks [https://en.wikipedia.org/wiki/XML_external_entity_attack]. Patch by Sebastian Pipping.

gh-140578 [https://github.com/python/cpython/issues/140578]: Remove outdated sencence in the documentation for multiprocessing, that implied that concurrent.futures.ThreadPoolExecutor did not exist.

Core and Builtins

gh-142048 [https://github.com/python/cpython/issues/142048]: Fix quadratically increasing garbage collection delays in free-threaded build.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Fix thread safety issue with re scanner objects in free-threaded builds.

Core and Builtins

gh-141930 [https://github.com/python/cpython/issues/141930]: When importing a module, use Python's regular file object to ensure that writes to .pyc files are complete or an appropriate error is raised.

gh-120158 [https://github.com/python/cpython/issues/120158]: Fix inconsistent state when enabling or disabling monitoring events too many times.

gh-139653 [https://github.com/python/cpython/issues/139653]: Only raise a RecursionError or trigger a fatal error if the stack pointer is both below the limit pointer and above the stack base. If outside of these bounds assume that it is OK. This prevents false positives when user-space threads swap stacks.

gh-139103 [https://github.com/python/cpython/issues/139103]: Improve multithreaded scaling of dataclasses on the free-threaded build.

gh-141579 [https://github.com/python/cpython/issues/141579]: Fix sys.activate_stack_trampoline() to properly support the perf_jit backend. Patch by Pablo Galindo.

gh-114203 [https://github.com/python/cpython/issues/114203]: Skip locking if object is already locked by two-mutex critical section.

gh-141528 [https://github.com/python/cpython/issues/141528]: Suggest using concurrent.interpreters.Interpreter.close() instead of the private _interpreters.destroy function when warning about remaining subinterpreters. Patch by Sergey Miryanov.

gh-141312 [https://github.com/python/cpython/issues/141312]: Fix the assertion failure in the __setstate__ method of the range iterator when a non-integer argument is passed. Patch by Sergey Miryanov.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Make csv module thread-safe on the free threaded build.

Core and Builtins

gh-140939 [https://github.com/python/cpython/issues/140939]: Fix memory leak when bytearray or bytes is formated with the %*b format with a large width that results in a MemoryError.

Library

gh-140260 [https://github.com/python/cpython/issues/140260]: Fix struct data race in endian table initialization with subinterpreters. Patch by Shamil Abdulaev.

Core and Builtins

gh-140530 [https://github.com/python/cpython/issues/140530]: Fix a reference leak when raise exc from cause fails. Patch by Bénédikt Tran.

gh-140373 [https://github.com/python/cpython/issues/140373]: Correctly emit PY_UNWIND event when generator object is closed. Patch by Mikhail Efimov.

gh-140576 [https://github.com/python/cpython/issues/140576]: Fixed crash in tokenize.generate_tokens() in case of specific incorrect input. Patch by Mikhail Efimov.

gh-140551 [https://github.com/python/cpython/issues/140551]: Fixed crash in dict if dict.clear() is called at the lookup stage. Patch by Mikhail Efimov and Inada Naoki.

gh-140517 [https://github.com/python/cpython/issues/140517]: Fixed a reference leak when iterating over the result of map() with strict=True when the input iterables have different lengths. Patch by Mikhail Efimov.

gh-140471 [https://github.com/python/cpython/issues/140471]: Fix potential buffer overflow in ast.AST node initialization when encountering malformed _fields containing non-str.

gh-140431 [https://github.com/python/cpython/issues/140431]: Fix a crash in Python's garbage collector due to partially initialized coroutine objects when coroutine origin tracking depth is enabled (sys.set_coroutine_origin_tracking_depth()).

Library

gh-140398 [https://github.com/python/cpython/issues/140398]: Fix memory leaks in readline functions read_init_file(), read_history_file(), write_history_file(), and append_history_file() when PySys_Audit() fails.

Core and Builtins

gh-140406 [https://github.com/python/cpython/issues/140406]: Fix memory leak when an object's __hash__() method returns an object that isn't an int.

gh-140358 [https://github.com/python/cpython/issues/140358]: Restore elapsed time and unreachable object count in GC debug output. These were inadvertently removed during a refactor of gc.c. The debug log now again reports elapsed collection time and the number of unreachable objects. Contributed by Pål Grønås Drange.

gh-140306 [https://github.com/python/cpython/issues/140306]: Fix memory leaks in cross-interpreter channel operations and shared namespace handling.

gh-140301 [https://github.com/python/cpython/issues/140301]: Fix memory leak of PyConfig in subinterpreters.

gh-140257 [https://github.com/python/cpython/issues/140257]: Fix data race between interpreter_clear() and take_gil() on eval_breaker during finalization with daemon threads.

gh-139951 [https://github.com/python/cpython/issues/139951]: Fixes a regression in GC performance for a growing heap composed mostly of small tuples.

Counts number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead.

Does not track most untrackable tuples during creation. This prevents large numbers of small tuples causing excessive GCs.

gh-140104 [https://github.com/python/cpython/issues/140104]: Fix a bug with exception handling in the JIT. Patch by Ken Jin. Bug reported by Daniel Diniz.

gh-140061 [https://github.com/python/cpython/issues/140061]: Fixing the checking of whether an object is uniquely referenced to ensure free-threaded compatibility. Patch by Sergey Miryanov.

gh-140067 [https://github.com/python/cpython/issues/140067]: Fix memory leak in sub-interpreter creation.

gh-140000 [https://github.com/python/cpython/issues/140000]: Fix potential memory leak when a reference cycle exists between an instance of typing.TypeAliasType, typing.TypeVar, typing.ParamSpec, or typing.TypeVarTuple and its __name__ attribute. Patch by Mikhail Efimov.

gh-139914 [https://github.com/python/cpython/issues/139914]: Restore support for HP PA-RISC, which has an upwards-growing stack.

gh-139988 [https://github.com/python/cpython/issues/139988]: Fix a memory leak when failing to create a Union type. Patch by Bénédikt Tran.

gh-139748 [https://github.com/python/cpython/issues/139748]: Fix reference leaks in error branches of functions accepting path strings or bytes such as compile() and os.system(). Patch by Bénédikt Tran.

gh-139516 [https://github.com/python/cpython/issues/139516]: Fix lambda colon erroneously start format spec in f-string in tokenizer.

gh-139640 [https://github.com/python/cpython/issues/139640]: ast.parse() no longer emits syntax warnings for return/break/continue in finally (see PEP 765 [https://peps.python.org/pep-0765/]) -- they are only emitted during compilation.

gh-139640 [https://github.com/python/cpython/issues/139640]: Fix swallowing some syntax warnings in different modules if they accidentally have the same message and are emitted from the same line. Fix duplicated warnings in the finally block.

gh-63161 [https://github.com/python/cpython/issues/63161]: Support non-UTF-8 shebang and comments in Python source files if non-UTF-8 encoding is specified. Detect decoding error in comments for default (UTF-8) encoding. Show the line and position of decoding error for default encoding in a traceback. Show the line containing the coding cookie when it conflicts with the BOM in a traceback.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Make mmap thread-safe on the free threaded build.

Core and Builtins

gh-138558 [https://github.com/python/cpython/issues/138558]: Fix handling of unusual t-string annotations in annotationlib. Patch by Dave Peck.

gh-134466 [https://github.com/python/cpython/issues/134466]: Don't run PyREPL in a degraded environment where setting termios attributes is not allowed.

gh-138944 [https://github.com/python/cpython/issues/138944]: Fix SyntaxError message when invalid syntax appears on the same line as a valid import ... as ... or from ... import ... as ... statement. Patch by Brian Schubert.

gh-105487 [https://github.com/python/cpython/issues/105487]: Remove non-existent __copy__(), __deepcopy__(), and __bases__ from the __dir__() entries of types.GenericAlias.

gh-69605 [https://github.com/python/cpython/issues/69605]: Fix some standard library submodules missing from the REPL auto-completion of imports.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Make cProfile thread-safe on the free threaded build.

gh-138004 [https://github.com/python/cpython/issues/138004]: On Solaris/Illumos platforms, thread names are now encoded as ASCII to avoid errors on systems (e.g. OpenIndiana) that don't support non-ASCII names.

Core and Builtins

gh-137433 [https://github.com/python/cpython/issues/137433]: Fix a potential deadlock in the free threading build when daemon threads enable or disable profiling or tracing while the main thread is shutting down the interpreter.

gh-137400 [https://github.com/python/cpython/issues/137400]: Fix a crash in the free threading build when disabling profiling or tracing across all threads with PyEval_SetProfileAllThreads() or PyEval_SetTraceAllThreads() or their Python equivalents threading.settrace_all_threads() and threading.setprofile_all_threads().

gh-58124 [https://github.com/python/cpython/issues/58124]: Fix name of the Python encoding in Unicode errors of the code page codec: use "cp65000" and "cp65001" instead of "CP_UTF7" and "CP_UTF8" which are not valid Python code names. Patch by Victor Stinner.

gh-132657 [https://github.com/python/cpython/issues/132657]: Improve performance of frozenset by removing locks in the free-threading build.

gh-133400 [https://github.com/python/cpython/issues/133400]: Fixed Ctrl+D (^D) behavior in _pyrepl module to match old pre-3.13 REPL behavior.

gh-128640 [https://github.com/python/cpython/issues/128640]: Fix a crash when using threads inside of a subinterpreter.

C API

gh-137422 [https://github.com/python/cpython/issues/137422]: Fix free threading race condition in PyImport_AddModuleRef(). It was previously possible for two calls to the function return two different objects, only one of which was stored in sys.modules.

gh-140042 [https://github.com/python/cpython/issues/140042]: Removed the sqlite3_shutdown call that could cause closing connections for sqlite when used with multiple sub interpreters.

gh-141042 [https://github.com/python/cpython/issues/141042]: Make qNaN in PyFloat_Pack2() and PyFloat_Pack4(), if while conversion to a narrower precision floating-point format --- the remaining after truncation payload will be zero. Patch by Sergey B Kirpichev.

gh-140487 [https://github.com/python/cpython/issues/140487]: Fix Py_RETURN_NOTIMPLEMENTED in limited C API 3.11 and older: don't treat Py_NotImplemented as immortal. Patch by Victor Stinner.

gh-140153 [https://github.com/python/cpython/issues/140153]: Fix Py_REFCNT() definition on limited C API 3.11-3.13. Patch by Victor Stinner.

gh-139653 [https://github.com/python/cpython/issues/139653]: Add PyUnstable_ThreadState_SetStackProtection() and PyUnstable_ThreadState_ResetStackProtection() functions to set the stack protection base address and stack protection size of a Python thread state. Patch by Victor Stinner.

Build

gh-141808 [https://github.com/python/cpython/issues/141808]: Do not generate the jit stencils twice in case of PGO builds on Windows.

gh-141784 [https://github.com/python/cpython/issues/141784]: Fix _remote_debugging_module.c compilation on 32-bit Linux. Include Python.h before system headers to make sure that _remote_debugging_module.c uses the same types (ABI) than Python. Patch by Victor Stinner.

gh-140768 [https://github.com/python/cpython/issues/140768]: Warn when the WASI SDK version doesn't match what's supported.

gh-140513 [https://github.com/python/cpython/issues/140513]: Generate a clear compilation error when _Py_TAIL_CALL_INTERP is enabled but either preserve_none or musttail is not supported.

gh-140189 [https://github.com/python/cpython/issues/140189]: iOS builds were added to CI.

gh-138489 [https://github.com/python/cpython/issues/138489]: When cross-compiling for WASI by build_wasm or build_emscripten, the build-details.json step is now included in the build process, just like with native builds.

This fixes the libinstall task which requires the build-details.json file during the process.

gh-137618 [https://github.com/python/cpython/issues/137618]: PYTHON_FOR_REGEN now requires Python 3.10 to Python 3.15. Patch by Adam Turner.

gh-123681 [https://github.com/python/cpython/issues/123681]: Check the strftime() behavior at runtime instead of at the compile time to support cross-compiling. Remove the internal macro _Py_NORMALIZE_CENTURY.

Python 3.14.0 final

Release date: 2025-10-07

macOS

gh-124111 [https://github.com/python/cpython/issues/124111]: Update macOS installer to use Tcl/Tk 8.6.17.

gh-139573 [https://github.com/python/cpython/issues/139573]: Updated bundled version of OpenSSL to 3.0.18.

Windows

gh-139573 [https://github.com/python/cpython/issues/139573]: Updated bundled version of OpenSSL to 3.0.18.

Tools/Demos

gh-139330 [https://github.com/python/cpython/issues/139330]: SBOM generation tool didn't cross-check the version and checksum values against the Modules/expat/refresh.sh script, leading to the values becoming out-of-date during routine updates.

gh-132006 [https://github.com/python/cpython/issues/132006]: XCframeworks now include privacy manifests to satisfy Apple App Store submission requirements.

gh-138171 [https://github.com/python/cpython/issues/138171]: A script for building an iOS XCframework was added. As part of this change, the top level iOS folder has been moved to be a subdirectory of the Apple folder.

Security

gh-139400 [https://github.com/python/cpython/issues/139400]: xml.parsers.expat: Make sure that parent Expat parsers are only garbage-collected once they are no longer referenced by subparsers created by ExternalEntityParserCreate(). Patch by Sebastian Pipping.

Library

gh-139312 [https://github.com/python/cpython/issues/139312]: Upgrade bundled libexpat to 2.7.3

Python 3.14.0 release candidate 3

Release date: 2025-09-18

Windows

gh-138896 [https://github.com/python/cpython/issues/138896]: Fix error installing C runtime on non-updated Windows machines

Tools/Demos

gh-137873 [https://github.com/python/cpython/issues/137873]: The iOS test runner has been simplified, resolving some issues that have been observed using the runner in GitHub Actions and Azure Pipelines test environments.

Security

gh-135661 [https://github.com/python/cpython/issues/135661]: Fix CDATA section parsing in html.parser.HTMLParser according to the HTML5 standard: ] ]> and ]] > no longer end the CDATA section. Add private method _set_support_cdata() which can be used to specify how to parse <[CDATA[ --- as a CDATA section in foreign content (SVG or MathML) or as a bogus comment in the HTML namespace.

Library

gh-138998 [https://github.com/python/cpython/issues/138998]: Update bundled libexpat to 2.7.2

gh-118803 [https://github.com/python/cpython/issues/118803]: Add back collections.abc.ByteString and typing.ByteString. Both had been removed in prior alpha, beta and release candidates for Python 3.14, but their removal has now been postponed to Python 3.17.

gh-137226 [https://github.com/python/cpython/issues/137226]: Fix typing.get_type_hints() calls on generic typing.TypedDict classes defined with string annotations.

gh-138804 [https://github.com/python/cpython/issues/138804]: Raise TypeError instead of AttributeError when an argument of incorrect type is passed to shlex.quote(). This restores the behavior of the function prior to 3.14.

gh-128636 [https://github.com/python/cpython/issues/128636]: Fix crash in PyREPL when os.environ is overwritten with an invalid value for mac

gh-138514 [https://github.com/python/cpython/issues/138514]: Raise ValueError when a multi-character string is passed to the echo_char parameter of getpass.getpass(). Patch by Benjamin Johnson.

gh-138515 [https://github.com/python/cpython/issues/138515]: email is added to Emscripten build.

gh-99948 [https://github.com/python/cpython/issues/99948]: ctypes.util.find_library() now works in Emscripten build.

gh-138253 [https://github.com/python/cpython/issues/138253]: Add the block parameter in the put() and get() methods of the concurrent.interpreters queues for compatibility with the queue.Queue interface.

gh-138133 [https://github.com/python/cpython/issues/138133]: Prevent infinite traceback loop when sending CTRL^C to Python through strace.

gh-134869 [https://github.com/python/cpython/issues/134869]: Fix an issue where pressing Ctrl+C during tab completion in the REPL would leave the autocompletion menu in a corrupted state.

gh-90548 [https://github.com/python/cpython/issues/90548]: Fix musl detection for platform.libc_ver() on Alpine Linux if compiled with --strip-all.

gh-136134 [https://github.com/python/cpython/issues/136134]: SMTP.auth_cram_md5() now raises an SMTPException instead of a ValueError if Python has been built without MD5 support. In particular, SMTP clients will not attempt to use this method even if the remote server is assumed to support it. Patch by Bénédikt Tran.

gh-136134 [https://github.com/python/cpython/issues/136134]: IMAP4.login_cram_md5 now raises an IMAP4.error if CRAM-MD5 authentication is not supported. Patch by Bénédikt Tran.

gh-134953 [https://github.com/python/cpython/issues/134953]: Expand _colorize theme with keyword_constant and implement in repl.

Core and Builtins

gh-71810 [https://github.com/python/cpython/issues/71810]: Raise OverflowError for (-1).to_bytes() for signed conversions when bytes count is zero. Patch by Sergey B Kirpichev.

gh-138192 [https://github.com/python/cpython/issues/138192]: Fix contextvars initialization so that all subinterpreters are assigned the MISSING value.

gh-138479 [https://github.com/python/cpython/issues/138479]: Fix a crash when a generic object's __typing_subst__ returns an object that isn't a tuple.

gh-138372 [https://github.com/python/cpython/issues/138372]: Fix SyntaxWarning emitted for erroneous subscript expressions involving template string literals. Patch by Brian Schubert.

gh-138318 [https://github.com/python/cpython/issues/138318]: The default REPL now avoids highlighting built-in names (for instance set or format()) when they are used as attribute names (for instance in value.set or text.format).

gh-138349 [https://github.com/python/cpython/issues/138349]: Fix crash in certain cases where a module contains both a module-level annotation and a comprehension.

gh-137384 [https://github.com/python/cpython/issues/137384]: Fix a crash when using the warnings module in a finalizer at shutdown. Patch by Kumar Aditya.

gh-137883 [https://github.com/python/cpython/issues/137883]: Fix runaway recursion when calling a function with keyword arguments.

gh-137079 [https://github.com/python/cpython/issues/137079]: Fix keyword typo recognition when parsing files. Patch by Pablo Galindo.

gh-137728 [https://github.com/python/cpython/issues/137728]: Fix the JIT's handling of many local variables. This previously caused a segfault.

gh-137576 [https://github.com/python/cpython/issues/137576]: Fix for incorrect source code being shown in tracebacks from the Basic REPL when PYTHONSTARTUP is given. Patch by Adam Hartz.

Python 3.14.0 release candidate 2

Release date: 2025-08-14

macOS

gh-137450 [https://github.com/python/cpython/issues/137450]: macOS installer shell path management improvements: separate the installer Shell profile updater postinstall script from the Update Shell Profile.command to enable more robust error handling.

gh-137134 [https://github.com/python/cpython/issues/137134]: Update macOS installer to ship with SQLite version 3.50.4.

Windows

gh-137134 [https://github.com/python/cpython/issues/137134]: Update Windows installer to ship with SQLite 3.50.4.

Library

gh-137426 [https://github.com/python/cpython/issues/137426]: Remove the code deprecation of importlib.abc.ResourceLoader. It is documented as deprecated, but left for backwards compatibility with other classes in importlib.abc.

gh-137282 [https://github.com/python/cpython/issues/137282]: Fix tab completion and dir() on concurrent.futures.

gh-137257 [https://github.com/python/cpython/issues/137257]: Bump the version of pip bundled in ensurepip to version 25.2

gh-137226 [https://github.com/python/cpython/issues/137226]: Fix behavior of annotationlib.ForwardRef.evaluate() when the type_params parameter is passed and the name of a type param is also present in an enclosing scope.

gh-130522 [https://github.com/python/cpython/issues/130522]: Fix unraisable TypeError raised during interpreter shutdown in the threading module.

gh-137059 [https://github.com/python/cpython/issues/137059]: Fix handling of file URLs with a Windows drive letter in the URL authority by urllib.request.url2pathname(). This fixes a regression in earlier pre-releases of Python 3.14.

gh-130577 [https://github.com/python/cpython/issues/130577]: tarfile now validates archives to ensure member offsets are non-negative. (Contributed by Alexander Enrique Urieles Nieto in gh-130577 [https://github.com/python/cpython/issues/130577].)

gh-135228 [https://github.com/python/cpython/issues/135228]: When dataclasses replaces a class with a slotted dataclass, the original class can now be garbage collected again. Earlier changes in Python 3.14 caused this class to always remain in existence together with the replacement class synthesized by dataclasses.

Documentation

gh-136155 [https://github.com/python/cpython/issues/136155]: We are now checking for fatal errors in EPUB builds in CI.

Core and Builtins

gh-137400 [https://github.com/python/cpython/issues/137400]: Fix a crash in the free threading build when disabling profiling or tracing across all threads with PyEval_SetProfileAllThreads() or PyEval_SetTraceAllThreads() or their Python equivalents threading.settrace_all_threads() and threading.setprofile_all_threads().

gh-137314 [https://github.com/python/cpython/issues/137314]: Fixed a regression where raw f-strings incorrectly interpreted escape sequences in format specifications. Raw f-strings now properly preserve literal backslashes in format specs, matching the behavior from Python 3.11. For example, rf"{obj:\xFF}" now correctly produces '\\xFF' instead of 'ÿ'. Patch by Pablo Galindo.

gh-137308 [https://github.com/python/cpython/issues/137308]: A standalone docstring in a node body is optimized as a pass statement to ensure that the node's body is never empty. There was a ValueError in compile() otherwise.

gh-137288 [https://github.com/python/cpython/issues/137288]: Fix bug where some bytecode instructions of a boolean expression are not associated with the correct exception handler.

gh-134291 [https://github.com/python/cpython/issues/134291]: Remove some newer macOS API usage from the JIT compiler in order to restore compatibility with older OSX 10.15 deployment targets.

gh-131338 [https://github.com/python/cpython/issues/131338]: Disable computed stack limit checks on non-glibc linux platforms to fix crashes on deep recursion.

gh-136870 [https://github.com/python/cpython/issues/136870]: Fix data races while de-instrumenting bytecode of code objects running concurrently in threads.

C API

gh-137573 [https://github.com/python/cpython/issues/137573]: Mark _PyOptimizer_Optimize as Py_NO_INLINE to prevent stack overflow crashes on macOS.

Build

gh-132339 [https://github.com/python/cpython/issues/132339]: Add support for OpenSSL 3.5.

Python 3.14.0 release candidate 1

Release date: 2025-07-22

Tools/Demos

gh-136251 [https://github.com/python/cpython/issues/136251]: Fixes and usability improvements for Tools/wasm/emscripten/web_example

Security

gh-135661 [https://github.com/python/cpython/issues/135661]: Fix parsing attributes with whitespaces around the = separator in html.parser.HTMLParser according to the HTML5 standard.

gh-118350 [https://github.com/python/cpython/issues/118350]: Fix support of escapable raw text mode (elements "textarea" and "title") in html.parser.HTMLParser.

Library

gh-136170 [https://github.com/python/cpython/issues/136170]: Removed the unreleased zipfile.ZipFile.data_offset property added in 3.14.0a7 as it wasn't fully clear which behavior it should have in some situations so the result was not always what a user might expect.

gh-124621 [https://github.com/python/cpython/issues/124621]: pyrepl now works in Emscripten.

gh-136874 [https://github.com/python/cpython/issues/136874]: Discard URL query and fragment in urllib.request.url2pathname().

gh-130645 [https://github.com/python/cpython/issues/130645]: Enable color help by default in argparse.

gh-136549 [https://github.com/python/cpython/issues/136549]: Fix signature of threading.excepthook().

gh-136523 [https://github.com/python/cpython/issues/136523]: Fix wave.Wave_write emitting an unraisable when open raises.

gh-52876 [https://github.com/python/cpython/issues/52876]: Add missing keepends (default True) parameter to codecs.StreamReaderWriter.readline() and codecs.StreamReaderWriter.readlines().

gh-136470 [https://github.com/python/cpython/issues/136470]: Correct concurrent.futures.InterpreterPoolExecutor's default thread name.

gh-136476 [https://github.com/python/cpython/issues/136476]: Fix a bug that was causing the get_async_stack_trace function to miss some frames in the stack trace.

gh-136434 [https://github.com/python/cpython/issues/136434]: Fix docs generation of UnboundItem in concurrent.interpreters when running with -OO.

gh-136380 [https://github.com/python/cpython/issues/136380]: Raises AttributeError when accessing concurrent.futures.InterpreterPoolExecutor and subinterpreters are not available.

gh-134759 [https://github.com/python/cpython/issues/134759]: Fix UnboundLocalError in email.message.Message.get_payload() when the payload to decode is a bytes object. Patch by Kliment Lamonov.

gh-134657 [https://github.com/python/cpython/issues/134657]: asyncio: Remove some private names from asyncio.__all__.

Core and Builtins

gh-136801 [https://github.com/python/cpython/issues/136801]: Fix PyREPL syntax highlighting on match cases after multi-line case. Contributed by Olga Matoula.

Library

gh-136421 [https://github.com/python/cpython/issues/136421]: Fix crash when initializing datetime concurrently.

Core and Builtins

gh-136541 [https://github.com/python/cpython/issues/136541]: Fix some issues with the perf trampolines on x86-64 and aarch64. The trampolines were not being generated correctly for some cases, which could lead to the perf integration not working correctly. Patch by Pablo Galindo.

gh-136517 [https://github.com/python/cpython/issues/136517]: Fixed a typo that prevented printing of uncollectable objects when the gc.DEBUG_UNCOLLECTABLE mode was set.

gh-136525 [https://github.com/python/cpython/issues/136525]: Fix issue where per-thread bytecode was not instrumented for newly created threads.

gh-132661 [https://github.com/python/cpython/issues/132661]: Interpolation.expression now has a default, the empty string.

gh-132661 [https://github.com/python/cpython/issues/132661]: Reflect recent PEP 750 [https://peps.python.org/pep-0750/] change.

Disallow concatenation of string.templatelib.Template and str. Also, disallow implicit concatenation of t-string literals with string or f-string literals.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Make functions in grp thread-safe on the free threaded build.

Core and Builtins

gh-135148 [https://github.com/python/cpython/issues/135148]: Fixed a bug where f-string debug expressions (using =) would incorrectly strip out parts of strings containing escaped quotes and # characters. Patch by Pablo Galindo.

gh-133136 [https://github.com/python/cpython/issues/133136]: Limit excess memory usage in the free threading build when a large dictionary or list is resized and accessed by multiple threads.

gh-91153 [https://github.com/python/cpython/issues/91153]: Fix a crash when a bytearray is concurrently mutated during item assignment.

gh-127971 [https://github.com/python/cpython/issues/127971]: Fix off-by-one read beyond the end of a string in string search.

C API

gh-112068 [https://github.com/python/cpython/issues/112068]: Revert support of nullable arguments in PyArg_Parse().

gh-133296 [https://github.com/python/cpython/issues/133296]: New variants for the critical section API that accept one or two PyMutex pointers rather than PyObject instances are now public in the non-limited C API.

gh-134009 [https://github.com/python/cpython/issues/134009]: Expose PyMutex_IsLocked() as part of the public C API.

Build

gh-135621 [https://github.com/python/cpython/issues/135621]: PyREPL no longer depends on the curses standard library. Contributed by Łukasz Langa.

Python 3.14.0 beta 4

Release date: 2025-07-08

Tools/Demos

gh-135968 [https://github.com/python/cpython/issues/135968]: Stubs for strip are now provided as part of an iOS install.

gh-133600 [https://github.com/python/cpython/issues/133600]: Backport file reorganization for Tools/wasm/wasi.

This should make backporting future code changes easier. It also simplifies instructions around how to do WASI builds in the devguide.

Tests

gh-135966 [https://github.com/python/cpython/issues/135966]: The iOS testbed now handles the app_packages folder as a site directory.

gh-135494 [https://github.com/python/cpython/issues/135494]: Fix regrtest to support excluding tests from --pgo tests. Patch by Victor Stinner.

Security

gh-136053 [https://github.com/python/cpython/issues/136053]: marshal: fix a possible crash when deserializing slice objects.

gh-135661 [https://github.com/python/cpython/issues/135661]: Fix parsing start and end tags in html.parser.HTMLParser according to the HTML5 standard.

Whitespaces no longer accepted between </ and the tag name. E.g. </ script> does not end the script section.

Vertical tabulation (\v) and non-ASCII whitespaces no longer recognized as whitespaces. The only whitespaces are \t\n\r\f and space.

Null character (U+0000) no longer ends the tag name.

Attributes and slashes after the tag name in end tags are now ignored, instead of terminating after the first > in quoted attribute value. E.g. </script/foo=">"/>.

Multiple slashes and whitespaces between the last attribute and closing > are now ignored in both start and end tags. E.g. <a foo=bar/ //>.

Multiple = between attribute name and value are no longer collapsed. E.g. <a foo==bar> produces attribute "foo" with value "=bar".

[Reverted in gh-136927 [https://github.com/python/cpython/issues/136927]] Whitespaces between the = separator and attribute name or value are no longer ignored. E.g. <a foo =bar> produces two attributes "foo" and "=bar", both with value None; <a foo= bar> produces two attributes: "foo" with value "" and "bar" with value None.

gh-102555 [https://github.com/python/cpython/issues/102555]: Fix comment parsing in html.parser.HTMLParser according to the HTML5 standard. --!> now ends the comment. -- > no longer ends the comment. Support abnormally ended empty comments <--> and <--->.

Library

gh-136286 [https://github.com/python/cpython/issues/136286]: Fix pickling failures for protocols 0 and 1 for many objects realted to subinterpreters.

gh-136316 [https://github.com/python/cpython/issues/136316]: Improve support for evaluating nested forward references in typing.evaluate_forward_ref().

gh-85702 [https://github.com/python/cpython/issues/85702]: If zoneinfo._common.load_tzdata is given a package without a resource a zoneinfo.ZoneInfoNotFoundError is raised rather than a PermissionError. Patch by Victor Stinner.

gh-136028 [https://github.com/python/cpython/issues/136028]: Fix parsing month names containing "İ" (U+0130, LATIN CAPITAL LETTER I WITH DOT ABOVE) in time.strptime(). This affects locales az_AZ, ber_DZ, ber_MA and crh_UA.

gh-135995 [https://github.com/python/cpython/issues/135995]: In the palmos encoding, make byte 0x9b decode to › (U+203A - SINGLE RIGHT-POINTING ANGLE QUOTATION MARK).

gh-53203 [https://github.com/python/cpython/issues/53203]: Fix time.strptime() for %c and %x formats on locales byn_ER, wal_ET and lzh_TW, and for %X format on locales ar_SA, bg_BG and lzh_TW.

gh-91555 [https://github.com/python/cpython/issues/91555]: An earlier change, which was introduced in 3.14.0b2, has been reverted. It disabled logging for a logger during handling of log messages for that logger. Since the reversion, the behaviour should be as it was before 3.14.0b2.

gh-135878 [https://github.com/python/cpython/issues/135878]: Fixes a crash of types.SimpleNamespace on free threading builds, when several threads were calling its __repr__() method at the same time.

gh-135836 [https://github.com/python/cpython/issues/135836]: Fix IndexError in asyncio.loop.create_connection() that could occur when non-OSError exception is raised during connection and socket's close() raises OSError.

gh-135836 [https://github.com/python/cpython/issues/135836]: Fix IndexError in asyncio.loop.create_connection() that could occur when the Happy Eyeballs algorithm resulted in an empty exceptions list during connection attempts.

gh-135855 [https://github.com/python/cpython/issues/135855]: Raise TypeError instead of SystemError when _interpreters.set___main___attrs() is passed a non-dict object. Patch by Brian Schubert.

gh-135815 [https://github.com/python/cpython/issues/135815]: netrc: skip security checks if os.getuid() is missing. Patch by Bénédikt Tran.

gh-135640 [https://github.com/python/cpython/issues/135640]: Address bug where it was possible to call xml.etree.ElementTree.ElementTree.write() on an ElementTree object with an invalid root element. This behavior blanked the file passed to write if it already existed.

gh-135645 [https://github.com/python/cpython/issues/135645]: Added supports_isolated_interpreters field to sys.implementation.

gh-135646 [https://github.com/python/cpython/issues/135646]: Raise consistent NameError exceptions in annotationlib.ForwardRef.evaluate()

gh-135557 [https://github.com/python/cpython/issues/135557]: Fix races on heapq updates and list reads on the free threaded build.

gh-119180 [https://github.com/python/cpython/issues/119180]: Only fetch globals and locals if necessary in annotationlib.get_annotations()

gh-135561 [https://github.com/python/cpython/issues/135561]: Fix a crash on DEBUG builds when an HACL* HMAC routine fails. Patch by Bénédikt Tran.

gh-135487 [https://github.com/python/cpython/issues/135487]: Fix reprlib.Repr.repr_int() when given integers with more than sys.get_int_max_str_digits() digits. Patch by Bénédikt Tran.

gh-135335 [https://github.com/python/cpython/issues/135335]: multiprocessing: Flush stdout and stderr after preloading modules in the forkserver.

gh-135069 [https://github.com/python/cpython/issues/135069]: Fix the "Invalid error handling" exception in encodings.idna.IncrementalDecoder to correctly replace the 'errors' parameter.

gh-130662 [https://github.com/python/cpython/issues/130662]: +Accept leading zeros in precision and width fields for +:class:Decimal formatting, for example format(Decimal(1.25), '.016f').

gh-130662 [https://github.com/python/cpython/issues/130662]: Accept leading zeros in precision and width fields for Fraction formatting, for example format(Fraction(1, 3), '.016f').

gh-87790 [https://github.com/python/cpython/issues/87790]: Support underscore and comma as thousands separators in the fractional part for Fraction's formatting. Patch by Sergey B Kirpichev.

gh-87790 [https://github.com/python/cpython/issues/87790]: Support underscore and comma as thousands separators in the fractional part for Decimal's formatting. Patch by Sergey B Kirpichev.

gh-130664 [https://github.com/python/cpython/issues/130664]: Handle corner-case for Fraction's formatting: treat zero-padding (preceding the width field by a zero ('0') character) as an equivalent to a fill character of '0' with an alignment type of '=', just as in case of float's.

Documentation

gh-136155 [https://github.com/python/cpython/issues/136155]: EPUB builds are fixed by excluding non-XHTML-compatible tags.

Core and Builtins

gh-109700 [https://github.com/python/cpython/issues/109700]: Fix memory error handling in PyDict_SetDefault().

gh-78465 [https://github.com/python/cpython/issues/78465]: Fix error message for cls.__new__(cls, ...) where cls is not instantiable builtin or extension type (with tp_new set to NULL).

gh-129958 [https://github.com/python/cpython/issues/129958]: Differentiate between t-strings and f-strings in syntax error for newlines in format specifiers of single-quoted interpolated strings.

gh-135871 [https://github.com/python/cpython/issues/135871]: Non-blocking mutex lock attempts now return immediately when the lock is busy instead of briefly spinning in the free threading build.

gh-135106 [https://github.com/python/cpython/issues/135106]: Restrict the trashcan mechanism to GC'ed objects and untrack them while in the trashcan to prevent the GC and trashcan mechanisms conflicting.

gh-135607 [https://github.com/python/cpython/issues/135607]: Fix potential weakref races in an object's destructor on the free threaded build.

gh-135608 [https://github.com/python/cpython/issues/135608]: Fix a crash in the JIT involving attributes of modules.

gh-135543 [https://github.com/python/cpython/issues/135543]: Emit sys.remote_exec audit event when sys.remote_exec() is called and migrate remote_debugger_script to cpython.remote_debugger_script.

gh-134280 [https://github.com/python/cpython/issues/134280]: Disable constant folding for ~ with a boolean argument. This moves the deprecation warning from compile time to runtime.

C API

gh-135906 [https://github.com/python/cpython/issues/135906]: Fix compilation errors when compiling the internal headers with a C++ compiler.

Build

gh-134273 [https://github.com/python/cpython/issues/134273]: Add support for configuring compiler flags for the JIT with CFLAGS_JIT

Python 3.14.0 beta 3

Release date: 2025-06-17

Windows

gh-135099 [https://github.com/python/cpython/issues/135099]: Fix a crash that could occur on Windows when a background thread waits on a PyMutex while the main thread is shutting down the interpreter.

Tests

gh-132815 [https://github.com/python/cpython/issues/132815]: Fix test__opcode: add JUMP_BACKWARD to specialization stats.

gh-135489 [https://github.com/python/cpython/issues/135489]: Show verbose output for failing tests during PGO profiling step with --enable-optimizations.

gh-135120 [https://github.com/python/cpython/issues/135120]: Add test.support.subTests().

Security

gh-135462 [https://github.com/python/cpython/issues/135462]: Fix quadratic complexity in processing specially crafted input in html.parser.HTMLParser. End-of-file errors are now handled according to the HTML5 specs -- comments and declarations are automatically closed, tags are ignored.

gh-135034 [https://github.com/python/cpython/issues/135034]: Fixes multiple issues that allowed tarfile extraction filters (filter="data" and filter="tar") to be bypassed using crafted symlinks and hard links.

Addresses CVE 2024-12718 [https://www.cve.org/CVERecord?id=CVE-2024-12718], CVE 2025-4138 [https://www.cve.org/CVERecord?id=CVE-2025-4138], CVE 2025-4330 [https://www.cve.org/CVERecord?id=CVE-2025-4330], and CVE 2025-4517 [https://www.cve.org/CVERecord?id=CVE-2025-4517].

Library

gh-65697 [https://github.com/python/cpython/issues/65697]: configparser's error message when attempting to write an invalid key is now more helpful.

gh-135497 [https://github.com/python/cpython/issues/135497]: Fix os.getlogin() failing for longer usernames on BSD-based platforms.

gh-135429 [https://github.com/python/cpython/issues/135429]: Fix the argument mismatch in _lsprof for PY_THROW event.

gh-135368 [https://github.com/python/cpython/issues/135368]: Fix unittest.mock.Mock generation on dataclasses.dataclass() objects. Now all special attributes are set as it was before gh-124429 [https://github.com/python/cpython/issues/124429].

gh-133967 [https://github.com/python/cpython/issues/133967]: Do not normalize locale name 'C.UTF-8' to 'en_US.UTF-8'.

gh-135321 [https://github.com/python/cpython/issues/135321]: Raise a correct exception for values greater than 0x7fffffff for the BINSTRING opcode in the C implementation of pickle.

gh-135276 [https://github.com/python/cpython/issues/135276]: Backported bugfixes in zipfile.Path from zipp 3.23. Fixed .name, .stem and other basename-based properties on Windows when working with a zipfile on disk.

gh-135244 [https://github.com/python/cpython/issues/135244]: uuid: when the MAC address cannot be determined, the 48-bit node ID is now generated with a cryptographically-secure pseudo-random number generator (CSPRNG) as per RFC 9562, §6.10.3 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-6.10-3]. This affects uuid1() and uuid6().

gh-134970 [https://github.com/python/cpython/issues/134970]: Fix the "unknown action" exception in argparse.ArgumentParser.add_argument_group() to correctly replace the action class.

gh-134718 [https://github.com/python/cpython/issues/134718]: ast.dump() now only omits None and [] values if they are default values.

gh-134939 [https://github.com/python/cpython/issues/134939]: Add the concurrent.interpreters module. See PEP 734 [https://peps.python.org/pep-0734/].

gh-134885 [https://github.com/python/cpython/issues/134885]: Fix possible crash in the compression.zstd module related to setting parameter types. Patch by Jelle Zijlstra.

gh-134857 [https://github.com/python/cpython/issues/134857]: Improve error report for doctests run with unittest. Remove doctest module frames from tracebacks and redundant newline character from a failure message.

gh-128840 [https://github.com/python/cpython/issues/128840]: Fix parsing long IPv6 addresses with embedded IPv4 address.

gh-134637 [https://github.com/python/cpython/issues/134637]: Fix performance regression in calling a ctypes function pointer in free threading.

gh-134696 [https://github.com/python/cpython/issues/134696]: Built-in HACL* and OpenSSL implementations of hash function constructors now correctly accept the same documented named arguments. For instance, md5() could be previously invoked as md5(data=data) or md5(string=string) depending on the underlying implementation but these calls were not compatible. Patch by Bénédikt Tran.

gh-134151 [https://github.com/python/cpython/issues/134151]: email: Fix TypeError in email.utils.decode_params() when sorting RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] continuations that contain an unnumbered section.

gh-134210 [https://github.com/python/cpython/issues/134210]: curses.window.getch() now correctly handles signals. Patch by Bénédikt Tran.

gh-134152 [https://github.com/python/cpython/issues/134152]: email: Fix parsing of email message ID with invalid domain.

gh-133489 [https://github.com/python/cpython/issues/133489]: random.getrandbits() can now generate more that 2³¹ bits. random.randbytes() can now generate more that 256 MiB.

gh-132813 [https://github.com/python/cpython/issues/132813]: Improve error messages for incorrect types and values of csv.Dialect attributes.

gh-132969 [https://github.com/python/cpython/issues/132969]: Prevent the ProcessPoolExecutor executor thread, which remains running when shutdown(wait=False), from attempting to adjust the pool's worker processes after the object state has already been reset during shutdown. A combination of conditions, including a worker process having terminated abormally, resulted in an exception and a potential hang when the still-running executor thread attempted to replace dead workers within the pool.

gh-127081 [https://github.com/python/cpython/issues/127081]: Fix libc thread safety issues with os by replacing getlogin with getlogin_r re-entrant version.

gh-131884 [https://github.com/python/cpython/issues/131884]: Fix formatting issues in json.dump() when both indent and skipkeys are used.

gh-130999 [https://github.com/python/cpython/issues/130999]: Avoid exiting the new REPL and offer suggestions even if there are non-string candidates when errors occur.

Documentation

gh-135171 [https://github.com/python/cpython/issues/135171]: Document that the iterator for the leftmost for clause in the generator expression is created immediately.

bpo-45210 [https://bugs.python.org/issue?@action=redirect&bpo=45210]: Document that error indicator may be set in tp_dealloc, and how to avoid clobbering it.

Core and Builtins

gh-135496 [https://github.com/python/cpython/issues/135496]: Fix typo in the f-string conversion type error ("exclamanation" -> "exclamation").

gh-135371 [https://github.com/python/cpython/issues/135371]: Fixed asyncio debugging tools to properly display internal coroutine call stacks alongside external task dependencies. The python -m asyncio ps and python -m asyncio pstree commands now show complete execution context. Patch by Pablo Galindo.

Library

gh-127319 [https://github.com/python/cpython/issues/127319]: Set the allow_reuse_port class variable to False on the XMLRPC, logging, and HTTP servers. This matches the behavior in prior Python releases, which is to not allow port reuse.

Core and Builtins

gh-135171 [https://github.com/python/cpython/issues/135171]: Reverts the behavior of async generator expressions when created with object w/o __aiter__ method to the pre-3.13 behavior of raising a TypeError.

gh-130077 [https://github.com/python/cpython/issues/130077]: Properly raise custom syntax errors when incorrect syntax containing names that are prefixes of soft keywords is encountered. Patch by Pablo Galindo.

gh-135171 [https://github.com/python/cpython/issues/135171]: Reverts the behavior of generator expressions when created with a non-iterable to the pre-3.13 behavior of raising a TypeError. It is no longer possible to cause a crash in the debugger by altering the generator expression's local variables. This is achieved by moving the GET_ITER instruction back to the creation of the generator expression and adding an additional check to FOR_ITER.

Library

gh-116738 [https://github.com/python/cpython/issues/116738]: Make methods in heapq thread-safe on the free threaded build.

Core and Builtins

gh-134876 [https://github.com/python/cpython/issues/134876]: Add support to PEP 768 [https://peps.python.org/pep-0768/] remote debugging for Linux kernels which don't have CONFIG_CROSS_MEMORY_ATTACH configured.

gh-134889 [https://github.com/python/cpython/issues/134889]: Fix handling of a few opcodes that leave operands on the stack when optimizing LOAD_FAST.

Library

gh-134908 [https://github.com/python/cpython/issues/134908]: Fix crash when iterating over lines in a text file on the free threaded build.

Core and Builtins

gh-132617 [https://github.com/python/cpython/issues/132617]: Fix dict.update() modification check that could incorrectly raise a "dict mutated during update" error when a different dictionary was modified that happens to share the same underlying keys object.

gh-134679 [https://github.com/python/cpython/issues/134679]: Fix crash in the free threading build's QSBR code that could occur when changing an object's __dict__ attribute.

gh-127682 [https://github.com/python/cpython/issues/127682]: No longer call __iter__ twice in list comprehensions. This brings the behavior of list comprehensions in line with other forms of iteration

gh-133912 [https://github.com/python/cpython/issues/133912]: Fix the C API function PyObject_GenericSetDict to handle extension classes with inline values.

C API

gh-134989 [https://github.com/python/cpython/issues/134989]: Fix Py_RETURN_NONE, Py_RETURN_TRUE and Py_RETURN_FALSE macros in the limited C API 3.11 and older: don't treat Py_None, Py_True and Py_False as immortal. Patch by Victor Stinner.

gh-134989 [https://github.com/python/cpython/issues/134989]: Implement PyObject_DelAttr() and PyObject_DelAttrString() as macros in the limited C API 3.12 and older. Patch by Victor Stinner.

gh-133968 [https://github.com/python/cpython/issues/133968]: Add PyUnicodeWriter_WriteASCII() function to write an ASCII string into a PyUnicodeWriter. The function is faster than PyUnicodeWriter_WriteUTF8(), but has an undefined behavior if the input string contains non-ASCII characters. Patch by Victor Stinner.

Build

gh-119132 [https://github.com/python/cpython/issues/119132]: Remove "experimental" tag from the CPython free-threading build.

gh-135497 [https://github.com/python/cpython/issues/135497]: Fix the detection of MAXLOGNAME in the configure.ac script.

gh-134923 [https://github.com/python/cpython/issues/134923]: Windows builds with profile-guided optimization enabled now use /GENPROFILE and /USEPROFILE instead of deprecated /LTCG: options.

gh-134774 [https://github.com/python/cpython/issues/134774]: Fix Py_DEBUG macro redefinition warnings on Windows debug builds. Patch by Chris Eibl.

gh-134632 [https://github.com/python/cpython/issues/134632]: Fixed build-details.json generation to use INCLUDEPY, in order to reference the pythonX.Y subdirectory of the include directory, as required in PEP 739 [https://peps.python.org/pep-0739/], instead of the top-level include directory.

Python 3.14.0 beta 2

Release date: 2025-05-26

Windows

gh-130727 [https://github.com/python/cpython/issues/130727]: Fix a race in internal calls into WMI that can result in an "invalid handle" exception under high load. Patch by Chris Eibl.

gh-76023 [https://github.com/python/cpython/issues/76023]: Make os.path.realpath() ignore Windows error 1005 when in non-strict mode.

gh-133779 [https://github.com/python/cpython/issues/133779]: Reverts the change to generate different pyconfig.h files based on compiler settings, as it was frequently causing extension builds to break. In particular, the Py_GIL_DISABLED preprocessor variable must now always be defined explicitly when compiling for the experimental free-threaded runtime. The sysconfig.get_config_var() function can be used to determine whether the current runtime was compiled with that flag or not.

gh-133626 [https://github.com/python/cpython/issues/133626]: Ensures packages are not accidentally bundled into the traditional installer.

Tools/Demos

gh-134215 [https://github.com/python/cpython/issues/134215]: REPL import autocomplete only suggests private modules when explicitly specified.

Tests

gh-133744 [https://github.com/python/cpython/issues/133744]: Fix multiprocessing interrupt test. Add an event to synchronize the parent process with the child process: wait until the child process starts sleeping. Patch by Victor Stinner.

gh-133682 [https://github.com/python/cpython/issues/133682]: Fixed test case test.test_annotationlib.TestStringFormat.test_displays which ensures proper handling of complex data structures (lists, sets, dictionaries, and tuples) in string annotations.

gh-133639 [https://github.com/python/cpython/issues/133639]: Fix TestPyReplAutoindent.test_auto_indent_default() doesn't run input_code.

Security

gh-133767 [https://github.com/python/cpython/issues/133767]: Fix use-after-free in the "unicode-escape" decoder with a non-"strict" error handler.

gh-128840 [https://github.com/python/cpython/issues/128840]: Short-circuit the processing of long IPv6 addresses early in ipaddress to prevent excessive memory consumption and a minor denial-of-service.

Library

gh-132710 [https://github.com/python/cpython/issues/132710]: If possible, ensure that uuid.getnode() returns the same result even across different processes. Previously, the result was constant only within the same process. Patch by Bénédikt Tran.

gh-80334 [https://github.com/python/cpython/issues/80334]: multiprocessing.freeze_support() now checks for work on any "spawn" start method platform rather than only on Windows.

gh-134582 [https://github.com/python/cpython/issues/134582]: Fix tokenize.untokenize() round-trip errors related to t-strings braces escaping

gh-134546 [https://github.com/python/cpython/issues/134546]: Ensure pdb remote debugging script is readable by remote Python process.

gh-134451 [https://github.com/python/cpython/issues/134451]: Converted asyncio.tools.CycleFoundException from dataclass to a regular exception type.

gh-114177 [https://github.com/python/cpython/issues/114177]: Fix asyncio to not close subprocess pipes which would otherwise error out when the event loop is already closed.

gh-90871 [https://github.com/python/cpython/issues/90871]: Fixed an off by one error concerning the backlog parameter in create_unix_server(). Contributed by Christian Harries.

gh-134323 [https://github.com/python/cpython/issues/134323]: Fix the threading.RLock.locked() method.

gh-86802 [https://github.com/python/cpython/issues/86802]: Fixed asyncio memory leak in cancelled shield tasks. For shielded tasks where the shield was cancelled, log potential exceptions through the exception handler. Contributed by Christian Harries.

gh-134209 [https://github.com/python/cpython/issues/134209]: curses: The curses.window.instr() and curses.window.getstr() methods now allocate their internal buffer on the heap instead of the stack; in addition, the max buffer size is increased from 1023 to 2047.

gh-134235 [https://github.com/python/cpython/issues/134235]: Updated tab completion on REPL to include builtin modules. Contributed by Tom Wang, Hunter Young

gh-134152 [https://github.com/python/cpython/issues/134152]: Fixed UnboundLocalError that could occur during email header parsing if an expected trailing delimiter is missing in some contexts.

gh-134168 [https://github.com/python/cpython/issues/134168]: http.server: Fix IPv6 address binding and --directory handling when using HTTPS.

gh-62184 [https://github.com/python/cpython/issues/62184]: Remove import of C implementation of io.FileIO from Python implementation which has its own implementation

gh-133982 [https://github.com/python/cpython/issues/133982]: Emit RuntimeWarning in the Python implementation of io when the file-like object is not closed explicitly in the presence of multiple I/O layers.

gh-133890 [https://github.com/python/cpython/issues/133890]: The tarfile module now handles UnicodeEncodeError in the same way as OSError when cannot extract a member.

gh-134097 [https://github.com/python/cpython/issues/134097]: Fix interaction of the new REPL and -X showrefcount command line option.

gh-133889 [https://github.com/python/cpython/issues/133889]: The generated directory listing page in http.server.SimpleHTTPRequestHandler now only shows the decoded path component of the requested URL, and not the query and fragment.

gh-134098 [https://github.com/python/cpython/issues/134098]: Fix handling paths that end with a percent-encoded slash (%2f or %2F) in http.server.SimpleHTTPRequestHandler.

gh-132124 [https://github.com/python/cpython/issues/132124]: On POSIX-compliant systems, multiprocessing.util.get_temp_dir() now ignores TMPDIR (and similar environment variables) if the path length of AF_UNIX socket files exceeds the platform-specific maximum length when using the forkserver start method. Patch by Bénédikt Tran.

gh-134062 [https://github.com/python/cpython/issues/134062]: ipaddress: fix collisions in __hash__() for IPv4Network and IPv6Network objects.

gh-133970 [https://github.com/python/cpython/issues/133970]: Make string.templatelib.Template and string.templatelib.Interpolation generic.

gh-71253 [https://github.com/python/cpython/issues/71253]: Raise ValueError in open() if opener returns a negative file-descriptor in the Python implementation of io to match the C implementation.

gh-133960 [https://github.com/python/cpython/issues/133960]: Simplify and improve typing.evaluate_forward_ref(). It now no longer raises errors on certain invalid types. In several situations, it is now able to evaluate forward references that were previously unsupported.

gh-133925 [https://github.com/python/cpython/issues/133925]: Make the private class typing._UnionGenericAlias hashable.

gh-133653 [https://github.com/python/cpython/issues/133653]: Fix argparse.ArgumentParser with the formatter_class argument. Fix TypeError when formatter_class is a custom subclass of HelpFormatter. Fix TypeError when formatter_class is not a subclass of HelpFormatter and non-standard prefix_char is used. Fix support of colorizing when formatter_class is not a subclass of HelpFormatter.

gh-132641 [https://github.com/python/cpython/issues/132641]: Fixed a race in functools.lru_cache() under free-threading.

gh-133783 [https://github.com/python/cpython/issues/133783]: Fix bug with applying copy.replace() to ast objects. Attributes that default to None were incorrectly treated as required for manually created AST nodes.

gh-133684 [https://github.com/python/cpython/issues/133684]: Fix bug where annotationlib.get_annotations() would return the wrong result for certain classes that are part of a class hierarchy where from __future__ import annotations is used.

gh-77057 [https://github.com/python/cpython/issues/77057]: Fix handling of invalid markup declarations in html.parser.HTMLParser.

gh-130328 [https://github.com/python/cpython/issues/130328]: Speedup pasting in PyREPL on Windows in a legacy console. Patch by Chris Eibl.

gh-133701 [https://github.com/python/cpython/issues/133701]: Fix bug where typing.TypedDict classes defined under from __future__ import annotations and inheriting from another TypedDict had an incorrect __annotations__ attribute.

gh-133581 [https://github.com/python/cpython/issues/133581]: Improve unparsing of t-strings in ast.unparse() and from __future__ import annotations. Empty t-strings now round-trip correctly and formatting in interpolations is preserved. Patch by Jelle Zijlstra.

gh-133551 [https://github.com/python/cpython/issues/133551]: Support t-strings (PEP 750 [https://peps.python.org/pep-0750/]) in annotationlib. Patch by Jelle Zijlstra.

gh-133439 [https://github.com/python/cpython/issues/133439]: Fix dot commands with trailing spaces are mistaken for multi-line SQL statements in the sqlite3 command-line interface.

gh-132493 [https://github.com/python/cpython/issues/132493]: Avoid accessing __annotations__ unnecessarily in inspect.signature().

gh-132876 [https://github.com/python/cpython/issues/132876]: ldexp() on Windows doesn't round subnormal results before Windows 11, but should. Python's math.ldexp() wrapper now does round them, so results may change slightly, in rare cases of very small results, on Windows versions before 11.

gh-133009 [https://github.com/python/cpython/issues/133009]: xml.etree.ElementTree: Fix a crash in Element.__deepcopy__ when the element is concurrently mutated. Patch by Bénédikt Tran.

gh-91555 [https://github.com/python/cpython/issues/91555]: Ignore log messages generated during handling of log messages, to avoid deadlock or infinite recursion. [NOTE: This change has since been reverted.]

gh-125028 [https://github.com/python/cpython/issues/125028]: functools.Placeholder cannot be passed to functools.partial() as a keyword argument.

gh-62824 [https://github.com/python/cpython/issues/62824]: Fix aliases for iso8859_8 encoding. Patch by Dave Goncalves.

gh-86155 [https://github.com/python/cpython/issues/86155]: html.parser.HTMLParser.close() no longer loses data when the <script> tag is not closed. Patch by Waylan Limberg.

gh-69426 [https://github.com/python/cpython/issues/69426]: Fix html.parser.HTMLParser to not unescape character entities in attribute values if they are followed by an ASCII alphanumeric or an equals sign.

bpo-28494 [https://bugs.python.org/issue?@action=redirect&bpo=28494]: Improve Zip file validation false positive rate in zipfile.is_zipfile().

gh-134381 [https://github.com/python/cpython/issues/134381]: Fix RuntimeError when using a not-started threading.Thread after calling os.fork()

Core and Builtins

gh-127960 [https://github.com/python/cpython/issues/127960]: PyREPL interactive shell no longer starts with __package__ and __file__ global names set to _pyrepl package internals. Contributed by Yuichiro Tachibana.

gh-130397 [https://github.com/python/cpython/issues/130397]: Remove special-casing for C stack depth limits for WASI. Due to WebAssembly's built-in stack protection this does not pose a security concern.

gh-128066 [https://github.com/python/cpython/issues/128066]: Fixes an edge case where PyREPL improperly threw an error when Python is invoked on a read only filesystem while trying to write history file entries.

gh-69605 [https://github.com/python/cpython/issues/69605]: When auto-completing an import in the REPL, finding no candidates now issues no suggestion, rather than suggestions from the current namespace.

gh-134158 [https://github.com/python/cpython/issues/134158]: Fix coloring of double braces in f-strings and t-strings in the REPL.

gh-134119 [https://github.com/python/cpython/issues/134119]: Fix crash when calling next() on an exhausted template string iterator. Patch by Jelle Zijlstra.

gh-134100 [https://github.com/python/cpython/issues/134100]: Fix a use-after-free bug that occurs when an imported module isn't in sys.modules after its initial import. Patch by Nico-Posada.

gh-133999 [https://github.com/python/cpython/issues/133999]: Fix SyntaxError regression in except parsing after gh-123440 [https://github.com/python/cpython/issues/123440].

gh-133886 [https://github.com/python/cpython/issues/133886]: Fix sys.remote_exec() for non-ASCII paths in non-UTF-8 locales and non-UTF-8 paths in UTF-8 locales.

gh-133703 [https://github.com/python/cpython/issues/133703]: Fix hashtable in dict can be bigger than intended in some situations.

gh-133778 [https://github.com/python/cpython/issues/133778]: Fix bug where assigning to the __annotations__ attributes of classes defined under from __future__ import annotations had no effect.

gh-132762 [https://github.com/python/cpython/issues/132762]: fromkeys() no longer loops forever when adding a small set of keys to a large base dict. Patch by Angela Liss.

gh-133541 [https://github.com/python/cpython/issues/133541]: Inconsistent indentation in user input crashed the new REPL when syntax highlighting was active. This is now fixed.

gh-133516 [https://github.com/python/cpython/issues/133516]: Raise ValueError when constants True, False or None are used as an identifier after NFKC normalization.

gh-132542 [https://github.com/python/cpython/issues/132542]: Update Thread.native_id after fork(2) [https://manpages.debian.org/fork(2)] to ensure accuracy. Patch by Noam Cohen.

C API

gh-134144 [https://github.com/python/cpython/issues/134144]: Fix crash when calling Py_EndInterpreter() with a thread state that isn't the initial thread for the interpreter.

Build

gh-134455 [https://github.com/python/cpython/issues/134455]: Fixed build-details.json generation to use the correct c_api.headers as defined in PEP 739 [https://peps.python.org/pep-0739/], instead of c_api.include.

gh-131769 [https://github.com/python/cpython/issues/131769]: Fix detecting when the build Python in a cross-build is a pydebug build.

gh-117088 [https://github.com/python/cpython/issues/117088]: AIX linker don't support -h option, so avoid it through platform check

Python 3.14.0 beta 1

Release date: 2025-05-06

Windows

gh-132930 [https://github.com/python/cpython/issues/132930]: Marks the installer for Windows as deprecated and updates documentation to cover the new Python install manager.

gh-127405 [https://github.com/python/cpython/issues/127405]: Add ABIFLAGS to sysconfig.get_config_vars() on Windows. Patch by Xuehai Pan.

Tools/Demos

gh-130453 [https://github.com/python/cpython/issues/130453]: Allow passing multiple keyword arguments with the same function name in pygettext.

gh-130195 [https://github.com/python/cpython/issues/130195]: Add warning messages when pygettext unimplemented -a/--extract-all option is called.

Tests

gh-133131 [https://github.com/python/cpython/issues/133131]: The iOS testbed will now select the most recently released "SE-class" device for testing if a device isn't explicitly specified.

gh-91048 [https://github.com/python/cpython/issues/91048]: Add ability to externally inspect all pending asyncio tasks, even if no task is currently entered on the event loop.

gh-109981 [https://github.com/python/cpython/issues/109981]: The test helper that counts the list of open file descriptors now uses the optimised /dev/fd approach on all Apple platforms, not just macOS. This avoids crashes caused by guarded file descriptors.

gh-132678 [https://github.com/python/cpython/issues/132678]: Add --prioritize to -m test. This option allows the user to specify which selected tests should execute first, even if the order is otherwise randomized. This is particularly useful for tests that run the longest.

gh-131290 [https://github.com/python/cpython/issues/131290]: Tests in Lib/test can now be correctly executed as standalone scripts.

Security

gh-115322 [https://github.com/python/cpython/issues/115322]: The underlying extension modules behind readline:, subprocess, and ctypes now raise audit events on previously uncovered code paths that could lead to file system access related to C function calling and external binary execution. The ctypes.call_function audit hook has also been fixed to use an unsigned value for its function pointer.

Library

gh-133490 [https://github.com/python/cpython/issues/133490]: Add color support to PDB in remote mode.

gh-132493 [https://github.com/python/cpython/issues/132493]: Avoid eagerly evaluating annotations in functions decorated with reprlib.recursive_repr().

gh-130645 [https://github.com/python/cpython/issues/130645]: Add color to stdlib argparse CLIs. Patch by Hugo van Kemenade.

gh-119180 [https://github.com/python/cpython/issues/119180]: Make annotationlib.get_annotations() succeed with the FORWARDREF format if evaluating the annotations throws an exception other than NameError or AttributeError.

gh-133351 [https://github.com/python/cpython/issues/133351]: Fix remote PDB to correctly request tab completions for Python expressions from the server when completing a continuation line of a multi-line Python block.

gh-133367 [https://github.com/python/cpython/issues/133367]: Add the --feature-version, --optimize, and --show-empty options to the ast command-line interface. Patch by Semyon Moroz.

gh-133363 [https://github.com/python/cpython/issues/133363]: The cmd.Cmd class has been fixed to reliably call the completedefault method whenever the do_shell method is not defined and tab completion is requested for a line beginning with !.

gh-113081 [https://github.com/python/cpython/issues/113081]: Highlight syntax on source code in pdb.

gh-133349 [https://github.com/python/cpython/issues/133349]: Introduced auto-indent in pdb multi-line input.

gh-133306 [https://github.com/python/cpython/issues/133306]: Use \z instead of \Z in fnmatch.translate() and glob.translate().

gh-133306 [https://github.com/python/cpython/issues/133306]: Support \z as a synonym for \Z in regular expressions.

gh-133300 [https://github.com/python/cpython/issues/133300]: Make argparse.ArgumentParser's suggest_on_error a keyword-only parameter. Patch by Hugo van Kemenade.

gh-133290 [https://github.com/python/cpython/issues/133290]: Fix attribute caching issue when setting ctypes._Pointer._type_ in the undocumented and deprecated ctypes.SetPointerType() function and the undocumented set_type() method.

gh-133223 [https://github.com/python/cpython/issues/133223]: When PDB is attached to a remote process, do a better job of intercepting Ctrl+C and forwarding it to the remote process.

gh-133153 [https://github.com/python/cpython/issues/133153]: Do not complete pdb commands in interact mode of pdb.

gh-133139 [https://github.com/python/cpython/issues/133139]: Add the curses.assume_default_colors() function, a refinement of the curses.use_default_colors() function which allows to change the color pair 0.

gh-133089 [https://github.com/python/cpython/issues/133089]: Use original timeout value for subprocess.TimeoutExpired when the func subprocess.run() is called with a timeout instead of sometimes a confusing partial remaining time out value used internally on the final wait().

gh-133036 [https://github.com/python/cpython/issues/133036]: codecs.open() is now deprecated. Use open() instead. Contributed by Inada Naoki.

gh-132987 [https://github.com/python/cpython/issues/132987]: Many builtin and extension functions which accept an unsigned integer argument, now use __index__() if available.

gh-124703 [https://github.com/python/cpython/issues/124703]: Set return code to 1 when aborting process from pdb.

gh-133005 [https://github.com/python/cpython/issues/133005]: Support passing preset option to tarfile.open() when using 'w|xz' mode.

gh-115032 [https://github.com/python/cpython/issues/115032]: Support for custom logging handlers with the strm argument is deprecated and scheduled for removal in Python 3.16. Define handlers with the stream argument instead. Patch by Mariusz Felisiak.

gh-132991 [https://github.com/python/cpython/issues/132991]: Add socket.IP_FREEBIND constant on Linux 2.4 and later.

gh-132995 [https://github.com/python/cpython/issues/132995]: Bump the version of pip bundled in ensurepip to version 25.1.1

gh-132933 [https://github.com/python/cpython/issues/132933]: The zipapp module now applies the filter when creating the list of files to add, rather than waiting until the file is being added to the archive.

gh-121249 [https://github.com/python/cpython/issues/121249]: Always support the float complex and double complex C types in the struct module. Patch by Sergey B Kirpichev.

gh-132915 [https://github.com/python/cpython/issues/132915]: fcntl.fcntl() and fcntl.ioctl() can now detect a buffer overflow and raise SystemError. The stack and memory can be corrupted in such case, so treat this error as fatal.

gh-132017 [https://github.com/python/cpython/issues/132017]: Fix error when pyrepl is suspended, then resumed and terminated.

gh-132893 [https://github.com/python/cpython/issues/132893]: Improved statistics.NormalDist.cdf() accuracy for inputs smaller than the mean.

gh-130328 [https://github.com/python/cpython/issues/130328]: Speedup pasting in PyREPL on Windows. Fix by Chris Eibl.

gh-132882 [https://github.com/python/cpython/issues/132882]: Fix copying of typing.Union objects containing objects that do not support the | operator.

gh-93696 [https://github.com/python/cpython/issues/93696]: Fixed the breakpoint display error for frozen modules in pdb.

gh-129965 [https://github.com/python/cpython/issues/129965]: Add MIME types for .7z, .apk, .deb, .glb, .gltf, .gz, .m4v, .php, .rar, .rpm, .stl and .wmv. Patch by Hugo van Kemenade.

gh-132742 [https://github.com/python/cpython/issues/132742]: fcntl.fcntl() now supports arbitrary bytes-like objects, not only bytes. fcntl.ioctl() now automatically retries system calls failing with EINTR and releases the GIL during a system call even for large bytes-like object.

gh-132451 [https://github.com/python/cpython/issues/132451]: The CLI for the PDB debugger now accepts a -p PID argument to allow attaching to a running process. The process must be running the same version of Python as the one running PDB.

gh-125618 [https://github.com/python/cpython/issues/125618]: Add a format parameter to annotationlib.ForwardRef.evaluate(). Evaluating annotations in the FORWARDREF format now succeeds in more cases that would previously have raised an exception.

gh-132805 [https://github.com/python/cpython/issues/132805]: Fix incorrect handling of nested non-constant values in the FORWARDREF format in annotationlib.

gh-132734 [https://github.com/python/cpython/issues/132734]: Add new constants for Bluetooth sockets.

gh-132673 [https://github.com/python/cpython/issues/132673]: Fix AssertionError raised on ctypes.Structure with _align_ = 0 and _fields_ = [].

gh-132578 [https://github.com/python/cpython/issues/132578]: Rename the threading.Thread._handle field to avoid shadowing methods defined on subclasses of threading.Thread.

gh-132561 [https://github.com/python/cpython/issues/132561]: Fix the public locked method of multiprocessing.SemLock class. Also adding 2 tests for the derivated multiprocessing.Lock and multiprocessing.RLock classes.

gh-121468 [https://github.com/python/cpython/issues/121468]: Add pdb.set_trace_async() function to support await statements in pdb.

gh-132493 [https://github.com/python/cpython/issues/132493]: typing.Protocol now uses annotationlib.get_annotations() when checking whether or not an instance implements the protocol with isinstance(). This enables support for isinstance checks against classes with deferred annotations.

gh-132536 [https://github.com/python/cpython/issues/132536]: Do not disable PY_THROW event in bdb because it can't be disabled.

gh-132527 [https://github.com/python/cpython/issues/132527]: Include the valid typecode 'w' in the error message when an invalid typecode is passed to array.array.

gh-132099 [https://github.com/python/cpython/issues/132099]: The Bluetooth socket with the BTPROTO_HCI protocol on Linux now accepts an address in the format of an integer device_id, not only a tuple (device_id,).

gh-81793 [https://github.com/python/cpython/issues/81793]: Fix os.link() on platforms (like Linux) where the system link() function does not follow symlinks. On Linux, it now follows symlinks by default or if follow_symlinks=True is specified. On Windows, it now raises an error if follow_symlinks=True is passed. On macOS, it now raises an error if follow_symlinks=False is passed and the system linkat() function is not available at runtime.

gh-132493 [https://github.com/python/cpython/issues/132493]: Support creation of typing.Protocol classes with annotations that cannot be resolved at class creation time.

gh-132491 [https://github.com/python/cpython/issues/132491]: Rename annotationlib.value_to_string to annotationlib.type_repr() and provide better handling for function objects.

gh-132426 [https://github.com/python/cpython/issues/132426]: Add annotationlib.get_annotate_from_class_namespace() as a helper for accessing annotations in metaclasses, and remove annotationlib.get_annotate_function.

gh-70145 [https://github.com/python/cpython/issues/70145]: Add support for channels in Bluetooth HCI protocol (BTPROTO_HCI).

gh-131913 [https://github.com/python/cpython/issues/131913]: Add a shortcut function multiprocessing.Process.interrupt() alongside the existing multiprocessing.Process.terminate() and multiprocessing.Process.kill() for an improved control over child process termination.

gh-132439 [https://github.com/python/cpython/issues/132439]: Fix PyREPL on Windows: characters entered via AltGr are swallowed. Patch by Chris Eibl.

gh-132429 [https://github.com/python/cpython/issues/132429]: Fix support of Bluetooth sockets on NetBSD and DragonFly BSD. Add support for cid and bdaddr_type in the BTPROTO_L2CAP address on FreeBSD. Return cid in getsockname() for BTPROTO_L2CAP if it is not zero.

gh-132106 [https://github.com/python/cpython/issues/132106]: QueueListener.start now raises a RuntimeError if the listener is already started.

gh-132417 [https://github.com/python/cpython/issues/132417]: Fix a NULL pointer dereference when a C function called using ctypes with restype py_object returns NULL.

gh-132385 [https://github.com/python/cpython/issues/132385]: Fix instance error suggestions trigger potential exceptions in object.__getattr__() in traceback.

gh-125866 [https://github.com/python/cpython/issues/125866]: Add optional add_scheme argument to urllib.request.pathname2url(); when set to true, a complete URL is returned. Likewise add optional require_scheme argument to url2pathname(); when set to true, a complete URL is accepted.

gh-132308 [https://github.com/python/cpython/issues/132308]: A traceback.TracebackException now correctly renders the __context__ and __cause__ attributes from falsey Exception, and the exceptions attribute from falsey ExceptionGroup.

gh-130645 [https://github.com/python/cpython/issues/130645]: Add colour to argparse help output. Patch by Hugo van Kemenade.

gh-127495 [https://github.com/python/cpython/issues/127495]: In PyREPL, append a new entry to the PYTHON_HISTORY file after every statement. This should preserve command-line history after interpreter is terminated. Patch by Sergey B Kirpichev.

gh-129463 [https://github.com/python/cpython/issues/129463]: Comparison of annotationlib.ForwardRef objects no longer uses the internal __code__ and __ast_node__ attributes, which are used as caches.

gh-132250 [https://github.com/python/cpython/issues/132250]: Fixed the SystemError in cProfile when locating the actual C function of a method raises an exception.

gh-132064 [https://github.com/python/cpython/issues/132064]: annotationlib.get_annotations() now uses the __annotate__ attribute if it is present, even if __annotations__ is not present. Additionally, the function now raises a TypeError if it is passed an object that does not have any annotatins.

gh-130664 [https://github.com/python/cpython/issues/130664]: Support the '_' digit separator in formatting of the integral part of Decimal's. Patch by Sergey B Kirpichev.

gh-131952 [https://github.com/python/cpython/issues/131952]: Add color output to the json CLI. Patch by Tomas Roun.

gh-132063 [https://github.com/python/cpython/issues/132063]: Prevent exceptions that evaluate as falsey (namely, when their __bool__ method returns False or their __len__ method returns 0) from being ignored by concurrent.futures.ProcessPoolExecutor and concurrent.futures.ThreadPoolExecutor.

gh-132106 [https://github.com/python/cpython/issues/132106]: logging.handlers.QueueListener now implements the context manager protocol, allowing it to be used in a with statement.

gh-132054 [https://github.com/python/cpython/issues/132054]: The application/yaml mime type (RFC 9512 [https://datatracker.ietf.org/doc/html/rfc9512.html]) is now supported by mimetypes. Patch by Sasha "Nelie" Chernykh and Hugo van Kemenade.

gh-119605 [https://github.com/python/cpython/issues/119605]: Respect follow_wrapped for __init__() and __new__() methods when getting the class signature for a class with inspect.signature(). Preserve class signature after wrapping with warnings.deprecated(). Patch by Xuehai Pan.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import times by up to 33x for the shlex module, and improve the performance of shlex.quote() by up to 12x. Patch by Adam Turner.

gh-85302 [https://github.com/python/cpython/issues/85302]: Add support for BTPROTO_SCO in sockets on FreeBSD.

gh-131757 [https://github.com/python/cpython/issues/131757]: Make functools.lru_cache() call the cached function unlocked to allow concurrency.

gh-131423 [https://github.com/python/cpython/issues/131423]: ssl can show descriptions for errors added in OpenSSL 3.4.1. Patch by Bénédikt Tran.

gh-131434 [https://github.com/python/cpython/issues/131434]: Improve error reporting for incorrect format in time.strptime().

gh-131524 [https://github.com/python/cpython/issues/131524]: Add help message to platform command-line interface. Contributed by Harry Lees.

gh-100926 [https://github.com/python/cpython/issues/100926]: Move ctypes.POINTER() types cache from a global internal cache (_pointer_type_cache) to the ctypes._CData.__pointer_type__ attribute of the corresponding ctypes types. This will stop the cache from growing without limits in some situations.

gh-85702 [https://github.com/python/cpython/issues/85702]: If zoneinfo._common.load_tzdata is given a package without a resource a ZoneInfoNotFoundError is raised rather than a IsADirectoryError.

gh-123471 [https://github.com/python/cpython/issues/123471]: Make concurrent iterations over itertools.repeat safe under free-threading.

gh-131127 [https://github.com/python/cpython/issues/131127]: Systems using LibreSSL now successfully build.

gh-89157 [https://github.com/python/cpython/issues/89157]: Make the pure Python implementation of datetime.date.fromisoformat(), only accept ASCII strings for consistency with the C implementation.

gh-130941 [https://github.com/python/cpython/issues/130941]: Fix configparser.ConfigParser parsing empty interpolation with allow_no_value set to True.

gh-110067 [https://github.com/python/cpython/issues/110067]: Make heapq max-heap functions heapq.heapify_max(), heapq.heappush_max(), heapq.heappop_max(), and heapq.heapreplace_max() public. Previous underscored naming is kept for backwards compatibility. Additionally, the missing function heapq.heappushpop_max() has been added to both the C and Python implementations.

gh-129098 [https://github.com/python/cpython/issues/129098]: Fix REPL traceback reporting when using compile() with an inexisting file. Patch by Bénédikt Tran.

gh-130631 [https://github.com/python/cpython/issues/130631]: http.cookiejar.join_header_words() is now more similar to the original Perl version. It now quotes the same set of characters and always quote values that end with "\n".

gh-130482 [https://github.com/python/cpython/issues/130482]: Add ability to specify name for tkinter.OptionMenu and tkinter.ttk.OptionMenu.

gh-77065 [https://github.com/python/cpython/issues/77065]: Add keyword-only optional argument echo_char for getpass.getpass() for optional visual keyboard feedback support. Patch by Semyon Moroz.

gh-130317 [https://github.com/python/cpython/issues/130317]: Fix PyFloat_Pack2() and PyFloat_Unpack2() for NaN's with payload. This corrects round-trip for struct.unpack() and struct.pack() in case of the IEEE 754 binary16 "half precision" type. Patch by Sergey B Kirpichev.

gh-130402 [https://github.com/python/cpython/issues/130402]: Joining running daemon threads during interpreter shutdown now raises PythonFinalizationError.

gh-130167 [https://github.com/python/cpython/issues/130167]: Improve speed of difflib.IS_LINE_JUNK(). Patch by Semyon Moroz.

gh-101410 [https://github.com/python/cpython/issues/101410]: Added more detailed messages for domain errors in the math module.

gh-128384 [https://github.com/python/cpython/issues/128384]: Make warnings.catch_warnings use a context variable for holding the warning filtering state if the sys.flags.context_aware_warnings flag is set to true. This makes using the context manager thread-safe in multi-threaded programs. The flag is true by default in free-threaded builds and is otherwise false. The value of the flag can be overridden by the the -X context_aware_warnings command-line option or by the PYTHON_CONTEXT_AWARE_WARNINGS environment variable.

gh-129719 [https://github.com/python/cpython/issues/129719]: Fix missing socket.CAN_RAW_ERR_FILTER constant in the socket module on Linux systems. It was missing since Python 3.11.

gh-129027 [https://github.com/python/cpython/issues/129027]: Raise DeprecationWarning for sys._clear_type_cache(). This function was deprecated in Python 3.13 but it didn't raise a runtime warning.

gh-128307 [https://github.com/python/cpython/issues/128307]: Add eager_start keyword argument to asyncio.loop.create_task()

gh-127604 [https://github.com/python/cpython/issues/127604]: Add support for printing the C stack trace on systems that support it via faulthandler.dump_c_stack() or via the c_stack argument in faulthandler.enable().

gh-127385 [https://github.com/python/cpython/issues/127385]: Add the F_DUPFD_QUERY constant to the fcntl module.

gh-126838 [https://github.com/python/cpython/issues/126838]: Add resolve_host keyword-only parameter to urllib.request.url2pathname(), and fix handling of file URLs with authorities.

gh-82129 [https://github.com/python/cpython/issues/82129]: Fix NameError when calling typing.get_type_hints() on a dataclasses.dataclass() created by dataclasses.make_dataclass() with un-annotated fields.

gh-122559 [https://github.com/python/cpython/issues/122559]: Remove __reduce__() and __reduce_ex__() methods that always raise TypeError in the C implementation of io.FileIO, io.BufferedReader, io.BufferedWriter and io.BufferedRandom and replace them with default __getstate__() methods that raise TypeError. This restores fine details of behavior of Python 3.11 and older versions.

gh-122179 [https://github.com/python/cpython/issues/122179]: hashlib.file_digest() now raises BlockingIOError when no data is available during non-blocking I/O. Before, it added spurious null bytes to the digest.

gh-53032 [https://github.com/python/cpython/issues/53032]: Expose decimal.IEEEContext() to support creation of contexts corresponding to the IEEE 754 (2008) decimal interchange formats. Patch by Sergey B Kirpichev.

gh-120220 [https://github.com/python/cpython/issues/120220]: Deprecate the tkinter.Variable methods trace_variable(), trace_vdelete() and trace_vinfo(). Methods trace_add(), trace_remove() and trace_info() can be used instead.

gh-113539 [https://github.com/python/cpython/issues/113539]: webbrowser: Names in the BROWSER environment variable can now refer to already registered web browsers, instead of always generating a new browser command.

This makes it possible to set BROWSER to the value of one of the supported browsers on macOS.

bpo-44172 [https://bugs.python.org/issue?@action=redirect&bpo=44172]: Keep a reference to original curses windows in subwindows so that the original window does not get deleted before subwindows.

gh-75223 [https://github.com/python/cpython/issues/75223]: Deprecate undotted extensions in mimetypes.MimeTypes.add_type(). Patch by Hugo van Kemenade.

IDLE

gh-112936 [https://github.com/python/cpython/issues/112936]: fix IDLE: no Shell menu item in single-process mode.

Documentation

gh-107006 [https://github.com/python/cpython/issues/107006]: Move documentation and example code for threading.local from its docstring to the official docs.

gh-125142 [https://github.com/python/cpython/issues/125142]: As part of the builtin help intro text, show the keyboard shortcuts for the new, non-basic REPL (F1, F2, and F3).

Core and Builtins

gh-133336 [https://github.com/python/cpython/issues/133336]: -J is no longer reserved for use by Jython. Patch by Adam Turner.

gh-133261 [https://github.com/python/cpython/issues/133261]: Fix bug where the cycle GC could untrack objects in the trashcan because they looked like they were immortal. When objects are added to the trashcan, we take care to ensure they keep a mortal reference count.

gh-133346 [https://github.com/python/cpython/issues/133346]: Added experimental color theming support to the _colorize module.

gh-132917 [https://github.com/python/cpython/issues/132917]: For the free-threaded build, check the process memory usage increase before triggering a full automatic garbage collection. If the memory used has not increased 10% since the last collection then defer it.

gh-91048 [https://github.com/python/cpython/issues/91048]: Add a new python -m asyncio ps PID command-line interface to inspect asyncio tasks in a running Python process. Displays a flat table of await relationships. A variant showing a tree view is also available as python -m asyncio pstree PID. Both are useful for debugging async code. Patch by Pablo Galindo, Łukasz Langa, Yury Selivanov, and Marta Gomez Macias.

gh-133304 [https://github.com/python/cpython/issues/133304]: Workaround NaN's "canonicalization" in PyFloat_Pack4() and PyFloat_Unpack4() on RISC-V.

gh-133197 [https://github.com/python/cpython/issues/133197]: Improve SyntaxError error messages for incompatible string / bytes prefixes.

gh-133231 [https://github.com/python/cpython/issues/133231]: Add new utilities of observing JIT compilation: sys._jit.is_available(), sys._jit.is_enabled(), and sys._jit.is_active().

Library

gh-133194 [https://github.com/python/cpython/issues/133194]: ast.parse() will no longer parse new PEP 758 [https://peps.python.org/pep-0758/] syntax with older feature_version passed.

Core and Builtins

gh-131798 [https://github.com/python/cpython/issues/131798]: Split CALL_LEN into several uops allowing the JIT to remove them when optimizing. Patch by Diego Russo.

gh-131798 [https://github.com/python/cpython/issues/131798]: Use sym_new_type instead of sym_new_not_null for _BUILD_STRING, _BUILD_SET

gh-132942 [https://github.com/python/cpython/issues/132942]: Fix two races in the type lookup cache. This affected the free-threaded build and could cause crashes (apparently quite difficult to trigger).

gh-131798 [https://github.com/python/cpython/issues/131798]: Propagate the return type of _BINARY_OP_SUBSCR_TUPLE_INT in JIT. Patch by Tomas Roun

gh-132952 [https://github.com/python/cpython/issues/132952]: Speed up startup with the -S argument by importing the private _io module instead of io. This fixes a performance regression introduced earlier in Python 3.14 development and restores performance to the level of Python 3.13.

gh-131798 [https://github.com/python/cpython/issues/131798]: Allow the JIT to remove int guards after _CALL_LEN by setting the return type to int. Patch by Diego Russo

gh-131798 [https://github.com/python/cpython/issues/131798]: Split CALL_TUPLE_1 into several uops allowing the JIT to remove some of them. Patch by Tomas Roun

gh-131798 [https://github.com/python/cpython/issues/131798]: Split CALL_STR_1 into several uops allowing the JIT to remove some of them. Patch by Tomas Roun

gh-132825 [https://github.com/python/cpython/issues/132825]: Enhance unhashable key/element error messages for dict and set. Patch by Victor Stinner.

gh-131591 [https://github.com/python/cpython/issues/131591]: Reset any PEP 768 [https://peps.python.org/pep-0768/] remote debugging pending call in children after os.fork() calls.

gh-132713 [https://github.com/python/cpython/issues/132713]: Fix repr(list) race condition: hold a strong reference to the item while calling repr(item). Patch by Victor Stinner.

gh-132661 [https://github.com/python/cpython/issues/132661]: Implement PEP 750 [https://peps.python.org/pep-0750/] (Template Strings). Add new syntax for t-strings and implement new internal string.templatelib.Template and string.templatelib.Interpolation types.

gh-132479 [https://github.com/python/cpython/issues/132479]: Fix compiler crash in certain circumstances where multiple module-level annotations include comprehensions and other nested scopes.

gh-132747 [https://github.com/python/cpython/issues/132747]: Fix a crash when calling __get__() of a method with a None second argument.

gh-132744 [https://github.com/python/cpython/issues/132744]: Certain calls now check for runaway recursion and respect the system recursion limit.

gh-132449 [https://github.com/python/cpython/issues/132449]: Syntax errors that look like misspellings of Python keywords now provide a helpful fix suggestion for the typo. Contributed by Pablo Galindo Salgado.

Library

gh-132737 [https://github.com/python/cpython/issues/132737]: Support profiling code that requires __main__, such as pickle.

Core and Builtins

gh-132639 [https://github.com/python/cpython/issues/132639]: Added PyLong_AsNativeBytes(), PyLong_FromNativeBytes() and PyLong_FromUnsignedNativeBytes() to the limited C API.

gh-100239 [https://github.com/python/cpython/issues/100239]: Add specialisation for BINARY_OP/SUBSCR on list and slice.

gh-132508 [https://github.com/python/cpython/issues/132508]: Uses tagged integers on the evaluation stack to represent the instruction offsets when reraising an exception. This avoids the need to box the integer which could fail in low memory conditions.

gh-124476 [https://github.com/python/cpython/issues/124476]: Fix decoding from the locale encoding in the C.UTF-8 locale.

gh-131927 [https://github.com/python/cpython/issues/131927]: Compiler warnings originating from the same module and line number are now only emitted once, matching the behaviour of warnings emitted from user code. This can also be configured with warnings filters.

gh-132457 [https://github.com/python/cpython/issues/132457]: Make staticmethod() and classmethod() generic.

gh-131798 [https://github.com/python/cpython/issues/131798]: Use sym_new_type instead of sym_new_not_null for _BUILD_LIST, _BUILD_SET, _BUILD_MAP

gh-131798 [https://github.com/python/cpython/issues/131798]: Split CALL_TYPE_1 into several uops allowing the JIT to remove some of them.

gh-132386 [https://github.com/python/cpython/issues/132386]: Fix crash when passing a dict subclass as the globals parameter to exec().

gh-127682 [https://github.com/python/cpython/issues/127682]: No longer call __iter__ twice when creating and executing a generator expression. Creating a generator expression from a non-interable will raise only when the generator expression is executed. This brings the behavior of generator expressions in line with other generators.

gh-132261 [https://github.com/python/cpython/issues/132261]: The internal storage for annotations and annotate functions on classes now uses different keys in the class dictionary. This eliminates various edge cases where access to the __annotate__ and __annotations__ attributes would behave unpredictably.

gh-132284 [https://github.com/python/cpython/issues/132284]: Don't wrap base PyCFunction slots on class creation if not overridden.

gh-130415 [https://github.com/python/cpython/issues/130415]: Improve the JIT's ability to remove unused constant and local variable loads, and fix an issue where deallocating unused values could cause JIT code to crash or behave incorrectly.

gh-126703 [https://github.com/python/cpython/issues/126703]: Fix possible use after free in cases where a method's definition has the same lifetime as its self.

gh-132286 [https://github.com/python/cpython/issues/132286]: Fix that type.__annotate__ was not deleted, when type.__annotations__ was deleted.

gh-131798 [https://github.com/python/cpython/issues/131798]: Allow the JIT to remove an extra _TO_BOOL_BOOL instruction after _CONTAINS_OP_DICT by setting the return type to bool.

gh-124715 [https://github.com/python/cpython/issues/124715]: Prevents against stack overflows when calling Py_DECREF(). Third-party extension objects no longer need to use the "trashcan" mechanism, as protection is now built into the Py_DECREF() macro.

gh-131798 [https://github.com/python/cpython/issues/131798]: Allow the JIT compiler to remove some type checks for operations on lists, tuples, dictionaries, and sets.

gh-128398 [https://github.com/python/cpython/issues/128398]: Improve error message when an object supporting the synchronous (resp. asynchronous) context manager protocol is entered using async with (resp. with) instead of with (resp. async with). Patch by Bénédikt Tran.

gh-131798 [https://github.com/python/cpython/issues/131798]: Allow the JIT to remove unicode guards after _BINARY_OP_SUBSCR_STR_INT by setting the return type to string.

gh-131878 [https://github.com/python/cpython/issues/131878]: Handle uncaught exceptions in the main input loop for the new REPL.

gh-131878 [https://github.com/python/cpython/issues/131878]: Fix support of unicode characters with two or more codepoints on Windows in the new REPL.

gh-126835 [https://github.com/python/cpython/issues/126835]: Move constant folding to the peephole optimizer. Rename AST optimization related files (Python/ast_opt.c -> Python/ast_preprocess.c), structs (_PyASTOptimizeState -> _PyASTPreprocessState) and functions (_PyAST_Optimize -> _PyAST_Preprocess, _PyCompile_AstOptimize -> _PyCompile_AstPreprocess).

gh-114809 [https://github.com/python/cpython/issues/114809]: Add support for macOS multi-arch builds with the JIT enabled

gh-131507 [https://github.com/python/cpython/issues/131507]: PyREPL now supports syntax highlighting. Contributed by Łukasz Langa.

gh-130907 [https://github.com/python/cpython/issues/130907]: If the __annotations__ of a module object are accessed while the module is executing, return the annotations that have been defined so far, without caching them.

gh-130104 [https://github.com/python/cpython/issues/130104]: Three-argument pow() now try calling __rpow__() if necessary. Previously it was only called in two-argument pow() and the binary power operator.

gh-130070 [https://github.com/python/cpython/issues/130070]: Fixed an assertion error for exec() passed a string source and a non-None closure. Patch by Bartosz Sławecki.

gh-129958 [https://github.com/python/cpython/issues/129958]: Fix a bug that was allowing newlines inconsistently in format specifiers for single-quoted f-strings. Patch by Pablo Galindo.

gh-129858 [https://github.com/python/cpython/issues/129858]: elif statements that follow an else block now have a specific error message.

gh-69605 [https://github.com/python/cpython/issues/69605]: Add module autocomplete to PyREPL.

gh-128555 [https://github.com/python/cpython/issues/128555]: Add the sys.flags.thread_inherit_context flag.

This flag is set to true by default on the free-threaded build and false otherwise. If the flag is true, starting a new thread using threading.Thread will, by default, use a copy of the contextvars.Context from the caller of threading.Thread.start() rather than using an empty context.

Add the -X thread_inherit_context command-line option and PYTHON_THREAD_INHERIT_CONTEXT environment variable, which set the thread_inherit_context flag.

Add the context keyword parameter to Thread. It can be used to explicitly pass a context value to be used by a new thread.

Make the _contextvars module built-in.

gh-123539 [https://github.com/python/cpython/issues/123539]: Improve SyntaxError message for using import ... as and from ... import ... as with not a name.

gh-102567 [https://github.com/python/cpython/issues/102567]: -X importtime now accepts value 2, which indicates that an importtime entry should also be printed if an imported module has already been loaded. Patch by Noah Kim and Adam Turner.

gh-116436 [https://github.com/python/cpython/issues/116436]: Improve error message when TypeError occurs during dict.update()

gh-103997 [https://github.com/python/cpython/issues/103997]: String arguments passed to "-c" are now automatically dedented as if by textwrap.dedent(). This allows "python -c" invocations to be indented in shell scripts without causing indentation errors. (Patch by Jon Crall and Steven Sun)

Library

gh-89562 [https://github.com/python/cpython/issues/89562]: Remove hostflags member from PySSLContext struct.

C API

gh-133166 [https://github.com/python/cpython/issues/133166]: Fix regression where PyType_GetModuleByDef() returns NULL without setting TypeError when a static type is passed.

gh-133164 [https://github.com/python/cpython/issues/133164]: Add PyUnstable_Object_IsUniqueReferencedTemporary() function for determining if an object exists as a unique temporary variable on the interpreter's stack. This is a replacement for some cases where checking that Py_REFCNT() is one is no longer sufficient to determine if it's safe to modify a Python object in-place with no visible side effects.

gh-133140 [https://github.com/python/cpython/issues/133140]: Add PyUnstable_Object_IsUniquelyReferenced() as a replacement for Py_REFNCT(op) == 1 on free threaded builds of Python.

gh-131747 [https://github.com/python/cpython/issues/131747]: On non-Windows platforms, deprecate using ctypes.Structure._pack_ to use a Windows-compatible layout on non-Windows platforms. The layout should be specified explicitly by setting ctypes.Structure._layout_ to 'ms'.

gh-128972 [https://github.com/python/cpython/issues/128972]: For non-free-threaded builds, the memory layout of PyASCIIObject is reverted to match Python 3.13. (Note that the structure is not part of stable ABI and so its memory layout is guaranteed to remain stable.)

gh-133079 [https://github.com/python/cpython/issues/133079]: The undocumented APIs Py_C_RECURSION_LIMIT and PyThreadState.c_recursion_remaining, added in 3.13, are removed without a deprecation period.

gh-132987 [https://github.com/python/cpython/issues/132987]: The k and K formats in PyArg_Parse() now support the __index__() special method, like all other integer formats.

gh-132909 [https://github.com/python/cpython/issues/132909]: Fix an overflow when handling the K format in Py_BuildValue(). Patch by Bénédikt Tran.

gh-132798 [https://github.com/python/cpython/issues/132798]: Deprecated and undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsEncodedUnicode() and PyUnicode_AsDecodedUnicode() are scheduled for removal in 3.15.

gh-132470 [https://github.com/python/cpython/issues/132470]: Creating a ctypes.CField with a byte_size that does not match the actual type size now raises a ValueError instead of crashing the interpreter.

gh-112068 [https://github.com/python/cpython/issues/112068]: [Reverted in gh-136991 [https://github.com/python/cpython/issues/136991]] Add support of nullable arguments in PyArg_Parse() and similar functions. Adding ? after any format unit makes None be accepted as a value.

gh-50333 [https://github.com/python/cpython/issues/50333]: Non-tuple sequences are deprecated as argument for the (items) format unit in PyArg_ParseTuple() and other argument parsing functions if items contains format units which store a borrowed buffer or a borrowed reference.

Build

gh-113464 [https://github.com/python/cpython/issues/113464]: Use the cpython-bin-deps "externals" repository for Windows LLVM dependency management. Installing LLVM manually is no longer necessary for Windows JIT builds.

gh-133183 [https://github.com/python/cpython/issues/133183]: iOS compiler shims now include IPHONEOS_DEPLOYMENT_TARGET in target triples, ensuring that SDK version minimums are honored.

gh-133167 [https://github.com/python/cpython/issues/133167]: Fix compilation process with --enable-optimizations and --without-docstrings.

gh-133171 [https://github.com/python/cpython/issues/133171]: Since free-threaded builds do not support the experimental JIT compiler, prevent these configurations from being combined.

gh-132758 [https://github.com/python/cpython/issues/132758]: Fix building with tail call interpreter and pystats.

gh-132649 [https://github.com/python/cpython/issues/132649]: The PClayout script now allows passing --include-tcltk on Windows ARM64.

gh-132257 [https://github.com/python/cpython/issues/132257]: Change the default LTO flags on GCC to not pass -flto-partition=none, and allow parallelization of LTO. For newer GNU makes and GCC, this has a multiple factor speedup for LTO build times, with no noticeable loss in performance.

gh-132026 [https://github.com/python/cpython/issues/132026]: Fix use of undefined identifiers in platform triplet detection on MIPS Linux platforms.

Python 3.14.0 alpha 7

Release date: 2025-04-08

macOS

gh-124111 [https://github.com/python/cpython/issues/124111]: Update macOS installer to use Tcl/Tk 8.6.16.

gh-131423 [https://github.com/python/cpython/issues/131423]: Update macOS installer to use OpenSSL 3.0.16. Patch by Bénédikt Tran.

gh-131025 [https://github.com/python/cpython/issues/131025]: Update macOS installer to ship with SQLite 3.49.1.

Windows

gh-131423 [https://github.com/python/cpython/issues/131423]: Update bundled version of OpenSSL to 3.0.16. The new build also disables uplink support, which may be relevant to embedders but has no impact on normal use.

gh-131453 [https://github.com/python/cpython/issues/131453]: Some SND_* and MB_* constants are added to winsound.

gh-91349 [https://github.com/python/cpython/issues/91349]: Replaces our copy of zlib with zlib-ng, for performance improvements in zlib.

gh-131025 [https://github.com/python/cpython/issues/131025]: Update Windows installer to ship with SQLite 3.49.1.

Tools/Demos

gh-132121 [https://github.com/python/cpython/issues/132121]: Always escape non-printable Unicode characters in pygettext.

gh-131852 [https://github.com/python/cpython/issues/131852]: msgfmt no longer adds the POT-Creation-Date to generated .mo files for consistency with GNU msgfmt.

Tests

gh-131277 [https://github.com/python/cpython/issues/131277]: Allow to unset one or more environment variables at once via EnvironmentVarGuard.unset(). Patch by Bénédikt Tran.

gh-131050 [https://github.com/python/cpython/issues/131050]: test_ssl.test_dh_params is skipped if the underlying TLS library does not support finite-field ephemeral Diffie-Hellman.

Security

gh-131809 [https://github.com/python/cpython/issues/131809]: Update bundled libexpat to 2.7.1

gh-131261 [https://github.com/python/cpython/issues/131261]: Upgrade to libexpat 2.7.0

gh-121284 [https://github.com/python/cpython/issues/121284]: Fix bug in the folding of rfc2047 encoded-words when flattening an email message using a modern email policy. Previously when an encoded-word was too long for a line, it would be decoded, split across lines, and re-encoded. But commas and other special characters in the original text could be left unencoded and unquoted. This could theoretically be used to spoof header lines using a carefully constructed encoded-word if the resulting rendered email was transmitted or re-parsed.

Library

gh-132174 [https://github.com/python/cpython/issues/132174]: Fix function name in error message of _interpreters.run_string.

gh-132171 [https://github.com/python/cpython/issues/132171]: Fix crash of _interpreters.run_string on string subclasses.

gh-129204 [https://github.com/python/cpython/issues/129204]: Introduce new _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment variable knob in subprocess to control the use of os.posix_spawn().

gh-132159 [https://github.com/python/cpython/issues/132159]: Do not shadow user arguments in generated __new__() by decorator warnings.deprecated. Patch by Xuehai Pan.

gh-132168 [https://github.com/python/cpython/issues/132168]: The ctypes.py_object type now supports subscription, making it a generic type.

gh-84481 [https://github.com/python/cpython/issues/84481]: Add the zipfile.ZipFile.data_offset attribute, which stores the offset to the beginning of ZIP data in a file when available. When the zipfile.ZipFile is opened in either mode 'w' or 'x' and the underlying file does not support tell(), the value will be None instead.

gh-132075 [https://github.com/python/cpython/issues/132075]: Fix possible use of socket address structures with uninitialized members. Now all structure members are initialized with zeroes by default.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import times by up to 27x for the string module. Patch by Adam Turner.

gh-125434 [https://github.com/python/cpython/issues/125434]: Display thread name in faulthandler. Patch by Victor Stinner.

gh-132002 [https://github.com/python/cpython/issues/132002]: Fix crash when deallocating contextvars.ContextVar with weird unahashable string names.

gh-131938 [https://github.com/python/cpython/issues/131938]: xml.etree.ElementTree: update the error message when an element to remove via Element.remove is not found. Patch by Bénédikt Tran.

gh-115942 [https://github.com/python/cpython/issues/115942]: Add threading.RLock.locked(), multiprocessing.Lock.locked(), multiprocessing.RLock.locked(), and allow multiprocessing.managers.SyncManager.Lock() and multiprocessing.managers.SyncManager.RLock() to proxy locked() call.

gh-131974 [https://github.com/python/cpython/issues/131974]: Fix several thread-safety issues in ctypes on the free threaded build.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve the import time of the ast module by extracting the unparse() function to a helper module.

gh-107369 [https://github.com/python/cpython/issues/107369]: Improved performance of textwrap.indent() by an average of ~1.3x. Patch by Adam Turner.

gh-131792 [https://github.com/python/cpython/issues/131792]: Improved performance of textwrap.dedent() by an average of ~2.4x, (with improvements of up to 4x for large inputs), and fixed a bug where blank lines with whitespace characters other than space or horizontal tab were not normalised to the newline. Patch by Adam Turner, Marius Juston, and Pieter Eendebak.

gh-131668 [https://github.com/python/cpython/issues/131668]: socket: Fix code parsing AF_BLUETOOTH socket addresses.

gh-60115 [https://github.com/python/cpython/issues/60115]: Support frozen modules for linecache.getline().

gh-131492 [https://github.com/python/cpython/issues/131492]: Fix a resource leak when constructing a gzip.GzipFile with a filename fails, for example when passing an invalid compresslevel.

gh-131435 [https://github.com/python/cpython/issues/131435]: 10-20% performance improvement of random.randint().

gh-131461 [https://github.com/python/cpython/issues/131461]: Fix ResourceWarning when constructing a gzip.GzipFile in write mode with a broken file object.

gh-125866 [https://github.com/python/cpython/issues/125866]: Deprecate the nturl2path module. Call urllib.request.url2pathname() and pathname2url() instead.

gh-126367 [https://github.com/python/cpython/issues/126367]: Fix issue where urllib.request.url2pathname() raised OSError when given a Windows URI containing a colon character not following a drive letter, such as before an NTFS alternate data stream.

gh-120144 [https://github.com/python/cpython/issues/120144]: Disable CALL event in bdb in monitoring backend when we don't need any new events on the code object to get a better performance.

gh-131358 [https://github.com/python/cpython/issues/131358]: Register cseuckr as an encoding alias for euc_kr.

gh-131325 [https://github.com/python/cpython/issues/131325]: Fix sendfile fallback implementation to drain data after writing to transport in asyncio.

gh-90548 [https://github.com/python/cpython/issues/90548]: platform.libc_ver() can now detect and report the version of musl on Alpine Linux.

gh-129843 [https://github.com/python/cpython/issues/129843]: Fix incorrect argument passing in warnings.warn_explicit().

gh-70647 [https://github.com/python/cpython/issues/70647]: When creating a datetime object with an out of range date a more informative error is raised.

gh-130914 [https://github.com/python/cpython/issues/130914]: Allow graphlib.TopologicalSorter.prepare() to be called more than once as long as sorting has not started. Patch by Daniel Pope.

gh-131236 [https://github.com/python/cpython/issues/131236]: Allow to generate multiple UUIDs at once via python -m uuid --count.

gh-126895 [https://github.com/python/cpython/issues/126895]: Fix readline in free-threaded build.

gh-121468 [https://github.com/python/cpython/issues/121468]: $_asynctask is added as a pdb convenience variable to access the current asyncio task if applicable.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of locale using lazy import re. Patch by Semyon Moroz.

gh-129598 [https://github.com/python/cpython/issues/129598]: Fix ast.unparse() when ast.Interactive contains multiple statements.

gh-85162 [https://github.com/python/cpython/issues/85162]: The http.server module now includes built-in support for HTTPS servers exposed by http.server.HTTPSServer. This functionality is exposed by the command-line interface (python -m http.server) through the --tls-cert, --tls-key and --tls-password-file options. Patch by Semyon Moroz.

gh-129463 [https://github.com/python/cpython/issues/129463]: The implementations of equality and hashing for annotationlib.ForwardRef now use all attributes on the object. Two ForwardRef objects are equal only if all attributes are equal.

gh-128593 [https://github.com/python/cpython/issues/128593]: annotationlib.ForwardRef objects no longer cache their value when they are successfully evaluated. Successive calls to annotationlib.ForwardRef.evaluate() may return different values.

gh-117779 [https://github.com/python/cpython/issues/117779]: Fix reading duplicated entries in zipfile by name. Reading duplicated entries (except the last one) by ZipInfo now emits a warning instead of raising an exception.

gh-128715 [https://github.com/python/cpython/issues/128715]: The class of Structure/Union field descriptors is now available as CField, and has new attributes to aid debugging and introspection.

gh-128055 [https://github.com/python/cpython/issues/128055]: Fix test.test_sysconfig.test_sysconfigdata_json when running outside the build directory (eg. after installing).

gh-126037 [https://github.com/python/cpython/issues/126037]: xml.etree.ElementTree: Fix a crash in Element.find, Element.findtext and Element.findall when the tag to find implements an __eq__() method mutating the element being queried. Patch by Bénédikt Tran.

gh-127794 [https://github.com/python/cpython/issues/127794]: When headers are added to email.message.Message objects, either through email.message.Message.__setitem__() or email.message.Message.add_header(), the field name is now validated according to RFC 5322, Section 2.2 [https://datatracker.ietf.org/doc/html/rfc5322.html#section-2.2] and a ValueError is raised if the field name contains any invalid characters.

gh-123599 [https://github.com/python/cpython/issues/123599]: Deprecate pathlib.PurePath.as_uri(); use pathlib.Path.as_uri() instead.

gh-126033 [https://github.com/python/cpython/issues/126033]: xml.etree.ElementTree: Fix a crash in Element.remove when the element is concurrently mutated. Patch by Bénédikt Tran.

gh-120144 [https://github.com/python/cpython/issues/120144]: Add the optional backend of sys.monitoring to bdb and use it for pdb.

gh-74598 [https://github.com/python/cpython/issues/74598]: Add fnmatch.filterfalse() for excluding names matching a pattern. Patch by Bénédikt Tran.

gh-114917 [https://github.com/python/cpython/issues/114917]: Add support for AI_NUMERICSERV in getaddrinfo emulation

bpo-17254 [https://bugs.python.org/issue?@action=redirect&bpo=17254]: Added aliases for Thai Language using Microsoft Code Pages.

Documentation

gh-131417 [https://github.com/python/cpython/issues/131417]: Mention asyncio.Future and asyncio.Task in generic classes list.

Core and Builtins

gh-131798 [https://github.com/python/cpython/issues/131798]: Allow the JIT to remove an extra _TO_BOOL_BOOL instruction after _CONTAINS_OP_SET by setting the return type to bool.

gh-132011 [https://github.com/python/cpython/issues/132011]: Fix crash when calling list.append() as an unbound method.

gh-131998 [https://github.com/python/cpython/issues/131998]: Fix a crash when using an unbound method descriptor object in a function where a bound method descriptor was used.

gh-131591 [https://github.com/python/cpython/issues/131591]: Implement PEP 768 [https://peps.python.org/pep-0768/] (Safe external debugger interface for CPython). Add a new sys.remote_exec() function to the sys module. This function schedules the execution of a Python file in a separate process. Patch by Pablo Galindo, Matt Wozniski and Ivona Stojanovic.

gh-131798 [https://github.com/python/cpython/issues/131798]: Allow JIT to omit str guard in truthiness test when str type is known.

gh-131833 [https://github.com/python/cpython/issues/131833]: Add support for optionally dropping grouping parentheses when using multiple exception types as per PEP 758 [https://peps.python.org/pep-0758/]. Patch by Pablo Galindo

gh-130924 [https://github.com/python/cpython/issues/130924]: Usage of a name in a function-scope annotation no longer triggers creation of a cell for that variable. This fixes a regression in earlier alphas of Python 3.14.

gh-131800 [https://github.com/python/cpython/issues/131800]: Improve the experimental JIT's ability to remove type checks for certain subscripting operations.

gh-131738 [https://github.com/python/cpython/issues/131738]: Compiler emits optimized code for builtin any/all/tuple calls over a generator expression.

gh-131719 [https://github.com/python/cpython/issues/131719]: Fix missing NULL check in _PyMem_FreeDelayed in free-threaded build.

gh-131670 [https://github.com/python/cpython/issues/131670]: Fix anext() failing on sync __anext__() raising an exception.

gh-131666 [https://github.com/python/cpython/issues/131666]: Fix signature of anext_awaitable.close objects. Patch by Bénédikt Tran.

gh-130415 [https://github.com/python/cpython/issues/130415]: Optimize comparison of two constants in JIT builds

gh-129149 [https://github.com/python/cpython/issues/129149]: Add fast path for small and medium-size integers in PyLong_FromInt32(), PyLong_FromUInt32(), PyLong_FromInt64() and PyLong_FromUInt64(). Patch by Chris Eibl.

gh-130887 [https://github.com/python/cpython/issues/130887]: Optimize the AArch64 code generation for the JIT. Patch by Diego Russo

gh-130956 [https://github.com/python/cpython/issues/130956]: Optimize the AArch64 code generation for the JIT. Patch by Diego Russo

gh-130928 [https://github.com/python/cpython/issues/130928]: Fix error message when formatting bytes using the 'i' flag. Patch by Maxim Ageev.

gh-130935 [https://github.com/python/cpython/issues/130935]: Annotations at the class and module level that are conditionally defined are now only reflected in __annotations__ if the block they are in is executed. Patch by Jelle Zijlstra.

gh-130775 [https://github.com/python/cpython/issues/130775]: Do not crash on negative column and end_column in ast locations.

gh-130704 [https://github.com/python/cpython/issues/130704]: Optimize LOAD_FAST and its superinstruction form to reduce reference counting overhead. These instructions are replaced with faster variants that load borrowed references onto the operand stack when we can prove that the reference in the frame outlives the reference loaded onto the stack.

gh-88887 [https://github.com/python/cpython/issues/88887]: Fixing multiprocessing Resource Tracker process leaking, usually observed when running Python as PID 1.

gh-130115 [https://github.com/python/cpython/issues/130115]: Fix an issue with thread identifiers being sign-extended on some platforms.

Library

gh-99108 [https://github.com/python/cpython/issues/99108]: Add support for built-in implementation of HMAC (RFC 2104 [https://datatracker.ietf.org/doc/html/rfc2104.html]) based on HACL*. Patch by Bénédikt Tran.

Core and Builtins

gh-130080 [https://github.com/python/cpython/issues/130080]: Implement PEP 765: Disallow return/break/continue that exit a finally block.

gh-129900 [https://github.com/python/cpython/issues/129900]: Fix return codes inside SystemExit not getting returned by the REPL.

gh-128632 [https://github.com/python/cpython/issues/128632]: Disallow __classdict__ as the name of a type parameter. Using this name would previously crash the interpreter in some circumstances.

gh-126703 [https://github.com/python/cpython/issues/126703]: Improve performance of builtin methods by using a freelist.

gh-126703 [https://github.com/python/cpython/issues/126703]: Improve performance of range by using a freelist.

C API

gh-131740 [https://github.com/python/cpython/issues/131740]: Update PyUnstable_GC_VisitObjects to traverse perm gen.

gh-131525 [https://github.com/python/cpython/issues/131525]: The PyTupleObject now caches the computed hash value in the new field ob_hash.

Build

gh-131865 [https://github.com/python/cpython/issues/131865]: The DTrace build now properly passes the CC and CFLAGS variables to the dtrace command when utilizing SystemTap on Linux.

gh-131675 [https://github.com/python/cpython/issues/131675]: Fix mimalloc library builds for 32-bit ARM targets.

gh-131691 [https://github.com/python/cpython/issues/131691]: clang-cl on Windows needs option /EHa to support SEH (structured exception handling) correctly. Fix by Chris Eibl.

gh-131278 [https://github.com/python/cpython/issues/131278]: Add optimizing flag WITH_COMPUTED_GOTOS to Windows builds for when using a compiler that supports it (currently clang-cl). Patch by Chris Eibl.

gh-130213 [https://github.com/python/cpython/issues/130213]: Update the vendored HACL* library to fix build issues with older clang compilers.

gh-130673 [https://github.com/python/cpython/issues/130673]: Fix potential KeyError when handling object sections during JIT building process.

Python 3.14.0 alpha 6

Release date: 2025-03-14

macOS

gh-128540 [https://github.com/python/cpython/issues/128540]: Ensure web browser is launched by webbrowser.open() on macOS, even for file:// URLs.

Windows

gh-131020 [https://github.com/python/cpython/issues/131020]: pylauncher [https://github.com/python/cpython/tree/3.14/PC/launcher2.c] correctly detects a BOM when searching for the shebang. Fix by Chris Eibl.

Tools/Demos

gh-130453 [https://github.com/python/cpython/issues/130453]: Make it possible to override default keywords in pygettext.

gh-85012 [https://github.com/python/cpython/issues/85012]: Correctly reset msgctxt when compiling messages in msgfmt.

gh-130453 [https://github.com/python/cpython/issues/130453]: Extend support for specifying custom keywords in pygettext.

gh-130195 [https://github.com/python/cpython/issues/130195]: Add warning messages when pygettext unimplemented -a/--extract-all option is called.

gh-130057 [https://github.com/python/cpython/issues/130057]: Add support for translator comments in pygettext.py.

gh-130025 [https://github.com/python/cpython/issues/130025]: The iOS testbed now correctly handles symlinks used as Python framework references.

gh-129911 [https://github.com/python/cpython/issues/129911]: Fix the keyword entry in the help output of pygettext.

Tests

gh-129200 [https://github.com/python/cpython/issues/129200]: Multiple iOS testbed runners can now be started at the same time without introducing an ambiguity over simulator ownership.

gh-130292 [https://github.com/python/cpython/issues/130292]: The iOS testbed will now run successfully on a machine that has not previously run Xcode tests (such as CI configurations).

gh-130293 [https://github.com/python/cpython/issues/130293]: The tests of terminal colorization are no longer sensitive to the value of the TERM variable in the testing environment.

gh-129401 [https://github.com/python/cpython/issues/129401]: Fix a flaky test in test_repr_rlock that checks the representation of multiprocessing.RLock.

gh-126332 [https://github.com/python/cpython/issues/126332]: Add unit tests for pyrepl.

Security

gh-127371 [https://github.com/python/cpython/issues/127371]: Avoid unbounded buffering for tempfile.SpooledTemporaryFile.writelines(). Previously, disk spillover was only checked after the lines iterator had been exhausted. This is now done after each line is written.

Library

gh-131204 [https://github.com/python/cpython/issues/131204]: Use monospace font from System Font Stack for cross-platform support in difflib.HtmlDiff.

gh-131196 [https://github.com/python/cpython/issues/131196]: Improve performance of uuid.UUID.hex and uuid.UUID.__str__.

gh-130940 [https://github.com/python/cpython/issues/130940]: The behavior of PyConfig.use_system_logger was modified to be enabled by default on iOS. It remains disabled by default on macOS.

gh-131123 [https://github.com/python/cpython/issues/131123]: Supported completions for attributes of convenience variables in pdb.

gh-93096 [https://github.com/python/cpython/issues/93096]: Removed undocumented CLI python -m difflib. Use python -m doctest Lib/difflib.py -v instead. Patch by Semyon Moroz.

gh-93096 [https://github.com/python/cpython/issues/93096]: Removed undocumented -t and -v arguments of python -m pickle. Use python -m doctest Lib/pickle.py -v instead. Patch by Semyon Moroz.

gh-81267 [https://github.com/python/cpython/issues/81267]: Correct time.sleep() error message when an object that cannot be interpreted as an integer or float is provided.

gh-93096 [https://github.com/python/cpython/issues/93096]: Removed undocumented -t and -v arguments of python -m pickletools. Use python -m doctest Lib/pickletools.py -v instead. Patch by Semyon Moroz.

gh-131045 [https://github.com/python/cpython/issues/131045]: Fix issue with __contains__, values, and pseudo-members for enum.Flag.

gh-130959 [https://github.com/python/cpython/issues/130959]: Fix pure-Python implementation of datetime.time.fromisoformat() to reject times with spaces in fractional part (for example, 12:34:56.400 +02:00), matching the C implementation. Patch by Michał Gorny.

gh-130806 [https://github.com/python/cpython/issues/130806]: Deleting gzip.GzipFile before it is closed now emits a ResourceWarning.

gh-130637 [https://github.com/python/cpython/issues/130637]: Add validation for numeric response data in poplib.POP3.stat() method

gh-130665 [https://github.com/python/cpython/issues/130665]: Only apply locale to calendar CLI when set via --locale and not via LANG environment variable.

gh-130660 [https://github.com/python/cpython/issues/130660]: sys.ps1 and sys.ps2 are now restored after code.interact() call.

gh-130608 [https://github.com/python/cpython/issues/130608]: Remove dirs_exist_ok argument from pathlib.Path.copy() and copy_into(). These methods are new in Python 3.14.

gh-130461 [https://github.com/python/cpython/issues/130461]: Remove .. index:: directives from the uuid module documentation. These directives previously created entries in the general index for getnode() as well as the uuid1(), uuid3(), uuid4(), uuid5(), and uuid8() constructor functions.

gh-130379 [https://github.com/python/cpython/issues/130379]: The zipapp module now calculates the list of files to be added to the archive before creating the archive. This avoids accidentally including the target when it is being created in the source directory.

gh-82987 [https://github.com/python/cpython/issues/82987]: Inline breakpoints like breakpoint() or pdb.set_trace() will always stop the program at calling frame, ignoring the skip pattern (if any).

gh-125377 [https://github.com/python/cpython/issues/125377]: <tab> at the beginning of the line in pdb multi-line input will fill in a 4-space indentation now, instead of inserting a \t character.

gh-125413 [https://github.com/python/cpython/issues/125413]: Ensure the path returned from pathlib.Path.copy() or move() has fresh info.

gh-65697 [https://github.com/python/cpython/issues/65697]: stdlib configparser will now attempt to validate that keys it writes will not result in file corruption (creating a file unable to be accurately parsed by a future read() call from the same parser). Attempting a corrupting write() will raise an InvalidWriteError.

gh-125413 [https://github.com/python/cpython/issues/125413]: Speed up Path.copy by making better use of info internally.

gh-130285 [https://github.com/python/cpython/issues/130285]: Fix corner case for random.sample() allowing the counts parameter to specify an empty population. So now, sample([], 0, counts=[]) and sample('abc', k=0, counts=[0, 0, 0]) both give the same result as sample([], 0).

gh-124703 [https://github.com/python/cpython/issues/124703]: Executing quit command in pdb will raise bdb.BdbQuit when pdb is started from an interactive console using breakpoint() or pdb.set_trace().

gh-107773 [https://github.com/python/cpython/issues/107773]: Make datetime subclass __repr__() consistent both implementations. Patch by Semyon Moroz.

gh-130250 [https://github.com/python/cpython/issues/130250]: Fix regression in traceback.print_last().

gh-123471 [https://github.com/python/cpython/issues/123471]: Make concurrent iterations over itertools.batched safe under free-threading.

gh-57537 [https://github.com/python/cpython/issues/57537]: Support breakpoints for zipimport modules on pdb

gh-130230 [https://github.com/python/cpython/issues/130230]: Fix crash in pow() with only Decimal third argument.

gh-126944 [https://github.com/python/cpython/issues/126944]: Show explicit errors when required arguments of pdb commands are missing

gh-127750 [https://github.com/python/cpython/issues/127750]: Improve repr of functools.singledispatchmethod methods and descriptors.

gh-128520 [https://github.com/python/cpython/issues/128520]: Apply type conversion consistently in pathlib.PurePath and Path methods can accept a path object as an argument, such as match() and rename(). The argument is now converted to path object if it lacks a with_segments() attribute, and not otherwise.

gh-118761 [https://github.com/python/cpython/issues/118761]: Reverts a change in the previous release attempting to make some stdlib imports used within the subprocess module lazy as this was causing errors during __del__ finalizers calling methods such as terminate, or kill, or send_signal.

gh-130164 [https://github.com/python/cpython/issues/130164]: Fixed failure to raise TypeError in inspect.Signature.bind() for positional-only arguments provided by keyword when a variadic keyword argument (e.g. **kwargs) is present.

gh-130151 [https://github.com/python/cpython/issues/130151]: Fix reference leaks in _hashlib.hmac_new() and _hashlib.hmac_digest(). Patch by Bénédikt Tran.

gh-130145 [https://github.com/python/cpython/issues/130145]: Fix asyncio.AbstractEventloop.run_forever() when another loop is already running.

gh-130139 [https://github.com/python/cpython/issues/130139]: Fix bug where ast.parse() did not error on AST input which is not of the correct type, when called with optimize=False.

gh-127260 [https://github.com/python/cpython/issues/127260]: Forbid the use of colon (":") as a fractional component separator and other improvements to the consistency of error raising between the C and Python implementations of datetime.time.fromisoformat() and datetime.datetime.fromisoformat(). Patch by Semyon Moroz.

gh-85795 [https://github.com/python/cpython/issues/85795]: Using super() and __class__ closure variable in user-defined methods of typing.NamedTuple subclasses is now explicitly prohibited at runtime. Contributed by Bartosz Sławecki in gh-130082 [https://github.com/python/cpython/issues/130082].

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of cmd by lazy importing inspect and removing string. Patch by Semyon Moroz.

gh-129726 [https://github.com/python/cpython/issues/129726]: Fix gzip.GzipFile raising an unraisable exception during garbage collection when referring to a temporary object by breaking the reference loop with weakref.

gh-127750 [https://github.com/python/cpython/issues/127750]: Remove broken functools.singledispatchmethod() caching introduced in gh-85160 [https://github.com/python/cpython/issues/85160]. Achieve the same performance using different optimization.

gh-129948 [https://github.com/python/cpython/issues/129948]: Add support for shared set to multiprocessing.managers.SyncManager via SyncManager.set().

gh-129965 [https://github.com/python/cpython/issues/129965]: Update MIME types for .avi and .wav. Add MIME types for .docx, .pptx, .xlsx, .epub, .flac, .m4a, .odg, .odp, .ods, .odt, .oga, .ogg, .ogx and .weba. Patch by Hugo van Kemenade.

gh-129889 [https://github.com/python/cpython/issues/129889]: Support context manager protocol by contextvars.Token. Patch by Andrew Svetlov.

gh-97850 [https://github.com/python/cpython/issues/97850]: Update the deprecation warning of importlib.abc.Loader.load_module().

gh-129678 [https://github.com/python/cpython/issues/129678]: configparser.ConfigParser: do not write an empty unnamed section

gh-128641 [https://github.com/python/cpython/issues/128641]: Restore configparser.ConfigParser.read() performance.

gh-129569 [https://github.com/python/cpython/issues/129569]: Fix unicodedata.normalize() to always return a built-in str object when given an input of a str subclass, regardless of whether the string is already normalized.

gh-128231 [https://github.com/python/cpython/issues/128231]: Execution of multiple statements in the new REPL now stops immediately upon the first exception encountered. Patch by Bartosz Sławecki.

gh-96092 [https://github.com/python/cpython/issues/96092]: Fix bug in traceback.walk_stack() called with None where it was skipping more frames than in prior versions. This bug fix also changes walk_stack to walk the stack in the frame where it was called rather than where it first gets used.

gh-129288 [https://github.com/python/cpython/issues/129288]: Add optional l2_cid and l2_bdaddr_type fields to socket BTPROTO_L2CAP sockaddr tuple.

gh-128703 [https://github.com/python/cpython/issues/128703]: Fix mimetypes.guess_type() to use default mapping for empty Content-Type in registry.

gh-128647 [https://github.com/python/cpython/issues/128647]: Eagerly write to buffers passed to gzip.GzipFile's readinto() and readinto1() implementations, avoiding unnecessary allocations. Patch by Chris Markiewicz.

gh-128184 [https://github.com/python/cpython/issues/128184]: Improve display of annotationlib.ForwardRef object within inspect.Signature representations. This also fixes a NameError that was raised when using dataclasses.dataclass() on classes with unresolvable forward references.

gh-128041 [https://github.com/python/cpython/issues/128041]: Add concurrent.futures.ProcessPoolExecutor.terminate_workers() and concurrent.futures.ProcessPoolExecutor.kill_workers() as ways to terminate or kill all living worker processes in the given pool. (Contributed by Charles Machalow in gh-130849 [https://github.com/python/cpython/issues/130849].)

gh-127647 [https://github.com/python/cpython/issues/127647]: Add protocols io.Reader and io.Writer as alternatives to typing.IO, typing.TextIO, and typing.BinaryIO.

gh-109798 [https://github.com/python/cpython/issues/109798]: Added additional information into error messages in datetime, and made the messages more consistent between the C and Python implementations. Patch by Semyon Moroz.

gh-125746 [https://github.com/python/cpython/issues/125746]: Delay deprecated zipimport.zipimporter.load_module() removal time to 3.15. Use zipimport.zipimporter.exec_module() instead.

gh-74028 [https://github.com/python/cpython/issues/74028]: Add the optional buffersize parameter to concurrent.futures.Executor.map() to limit the number of submitted tasks whose results have not yet been yielded. If the buffer is full, iteration over the iterables pauses until a result is yielded from the buffer.

gh-124927 [https://github.com/python/cpython/issues/124927]: Non-printing characters are now properly handled in the new REPL.

gh-124096 [https://github.com/python/cpython/issues/124096]: Turn on virtual terminal mode and enable bracketed paste in REPL on Windows console. (If the terminal does not support bracketed paste, enabling it does nothing.)

gh-89083 [https://github.com/python/cpython/issues/89083]: Add uuid.uuid7() for generating UUIDv7 objects as specified in RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html]. Patch by Bénédikt Tran.

gh-89083 [https://github.com/python/cpython/issues/89083]: Add uuid.uuid6() for generating UUIDv6 objects as specified in RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html]. Patch by Bénédikt Tran.

gh-117151 [https://github.com/python/cpython/issues/117151]: Increase io.DEFAULT_BUFFER_SIZE from 8k to 128k and adjust open() on platforms where os.fstat() provides a st_blksize field (such as Linux) to use max(min(blocksize, 8 MiB), io.DEFAULT_BUFFER_SIZE) rather than always using the device block size. This should improve I/O performance. Patch by Romain Morotti.

gh-105499 [https://github.com/python/cpython/issues/105499]: Make types.UnionType an alias for typing.Union. Both int | str and Union[int, str] now create instances of the same type. Patch by Jelle Zijlstra.

gh-93096 [https://github.com/python/cpython/issues/93096]: Document the command-line for mimetypes. It now exits with 1 on failure instead of 0 and 2 on incorrect command-line parameters instead of 1. Also, errors are printed to stderr instead of stdout and their text is made tighter. Patch by Oleg Iarygin and Hugo van Kemenade.

Documentation

gh-125722 [https://github.com/python/cpython/issues/125722]: Require Sphinx 8.2.0 or later to build the Python documentation. Patch by Adam Turner.

gh-129712 [https://github.com/python/cpython/issues/129712]: The wheel tags supported by each macOS universal SDK option are now documented.

gh-46236 [https://github.com/python/cpython/issues/46236]: C API: Document PyUnicode_RSplit(), PyUnicode_Partition() and PyUnicode_RPartition().

Core and Builtins

gh-131141 [https://github.com/python/cpython/issues/131141]: Fix data race in sys.monitoring instrumentation while registering callback.

gh-130804 [https://github.com/python/cpython/issues/130804]: Fix support of unicode characters on Windows in the new REPL.

gh-130932 [https://github.com/python/cpython/issues/130932]: Fix incorrect exception handling in _PyModule_IsPossiblyShadowing

gh-122029 [https://github.com/python/cpython/issues/122029]: sys.setprofile() and sys.settrace() will not generate a c_call event for INSTRUMENTED_CALL_FUNCTION_EX if the callable is a method with a C function wrapped, because we do not generate c_return event in such case.

gh-129964 [https://github.com/python/cpython/issues/129964]: Fix JIT crash on Windows on Arm. Patch by Diego Russo and Brandt Bucher.

gh-130851 [https://github.com/python/cpython/issues/130851]: Fix a crash in the free threading build when constructing a code object with co_consts that contains instances of types that are not otherwise generated by the bytecode compiler.

gh-128534 [https://github.com/python/cpython/issues/128534]: Ensure that both left and right branches have the same source for async for loops. Add these branches to the co_branches() iterator.

gh-130794 [https://github.com/python/cpython/issues/130794]: Fix memory leak in the free threaded build when resizing a shared list or dictionary from multiple short-lived threads.

gh-130415 [https://github.com/python/cpython/issues/130415]: Improve JIT understanding of integers in boolean context.

gh-130382 [https://github.com/python/cpython/issues/130382]: Fix PyRefTracer_DESTROY not being sent from Python/ceval.c Py_DECREF().

gh-130574 [https://github.com/python/cpython/issues/130574]: Renumber RESUME from 149 to 128.

gh-124878 [https://github.com/python/cpython/issues/124878]: Fix race conditions during runtime finalization that could lead to accessing freed memory.

gh-130415 [https://github.com/python/cpython/issues/130415]: Improve the experimental JIT's ability to narrow boolean values based on the results of truthiness tests.

gh-130618 [https://github.com/python/cpython/issues/130618]: Fix a bug that was causing UnicodeDecodeError or SystemError to be raised when using f-strings with lambda expressions with non-ASCII characters. Patch by Pablo Galindo

gh-123044 [https://github.com/python/cpython/issues/123044]: Make sure that the location of branch targets in match cases is in the body, not the pattern.

gh-128534 [https://github.com/python/cpython/issues/128534]: Add branch monitoring (BRANCH_LEFT and BRANCH_RIGHT events) for async for loops.

gh-130163 [https://github.com/python/cpython/issues/130163]: Fix possible crashes related to concurrent change and use of the sys module attributes.

gh-122029 [https://github.com/python/cpython/issues/122029]: INSTRUMENTED_CALL_KW will expand the method before monitoring to reflect the actual behavior more accurately.

gh-130415 [https://github.com/python/cpython/issues/130415]: Improve JIT's ability to optimize strings in boolean contexts.

gh-130396 [https://github.com/python/cpython/issues/130396]: Use actual stack limits (from pthread_getattr_np(3) [https://manpages.debian.org/pthread_getattr_np(3)]) for linux, and other systems with _GNU_SOURCE defined, when determining limits for C stack protection.

gh-128396 [https://github.com/python/cpython/issues/128396]: Fix a crash that occurs when calling locals() inside an inline comprehension that uses the same local variable as the outer frame scope where the variable is a free or cell var.

gh-129107 [https://github.com/python/cpython/issues/129107]: Fix two more bytearray functions for free threading.

gh-127705 [https://github.com/python/cpython/issues/127705]: Use tagged references (_PyStackRef) for the default build as well as for the free-threading build. This has a small negative performance impact short-term but will enable larger speedups in the future and significantly reduce maintenance costs by allowing a single implementation of tagged references in the future.

gh-130094 [https://github.com/python/cpython/issues/130094]: Fix two race conditions involving concurrent imports that could lead to spurious failures with ModuleNotFoundError.

gh-129107 [https://github.com/python/cpython/issues/129107]: Make bytearray iterator safe under free threading.

gh-115802 [https://github.com/python/cpython/issues/115802]: Use the more efficient "medium" code model for JIT-compiled code on supported platforms.

gh-107956 [https://github.com/python/cpython/issues/107956]: A build-details.json file is now install in the platform-independent standard library directory (PEP 739 [https://peps.python.org/pep-0739/] implementation).

gh-116042 [https://github.com/python/cpython/issues/116042]: Fix location for SyntaxErrors of invalid escapes in the tokenizer. Patch by Pablo Galindo

gh-91079 [https://github.com/python/cpython/issues/91079]: Change C stack overflow protection to consider the amount of stack consumed, rather than a counter. This allows deeper recursion in many cases, but remains safe.

gh-129715 [https://github.com/python/cpython/issues/129715]: Improve the experimental JIT's handling of returns to unknown callers.

Library

gh-129983 [https://github.com/python/cpython/issues/129983]: Fix data race in compile_template in sre.c.

Core and Builtins

gh-129967 [https://github.com/python/cpython/issues/129967]: Fix a race condition in the free threading build when repr(set) is called concurrently with set.clear().

gh-129953 [https://github.com/python/cpython/issues/129953]: The internal (evaluation) stack is now spilled to memory whenever execution escapes from the interpreter or JIT compiled code. This should have no observable effect in either Python or builtin extensions, but will allow various important optimizations in the future.

gh-129515 [https://github.com/python/cpython/issues/129515]: Clarify syntax error messages for conditional expressions when a statement is specified before an if or after an else keyword.

gh-129349 [https://github.com/python/cpython/issues/129349]: bytes.fromhex() and bytearray.fromhex() now accepts ASCII bytes and bytes-like objects.

gh-129149 [https://github.com/python/cpython/issues/129149]: Add fast path for medium-size integers in PyLong_FromSsize_t(). Patch by Chris Eibl.

gh-129107 [https://github.com/python/cpython/issues/129107]: Make the bytearray safe under free threading.

gh-128974 [https://github.com/python/cpython/issues/128974]: Fix a crash in UnicodeError.__str__ when custom attributes implement __str__() with side-effects. Patch by Bénédikt Tran.

gh-126085 [https://github.com/python/cpython/issues/126085]: typing.TypeAliasType now supports star unpacking.

gh-125331 [https://github.com/python/cpython/issues/125331]: from __future__ import barry_as_FLUFL now works in more contexts, including when it is used in files, with the -c flag, and in the REPL when there are multiple statements on the same line. Previously, it worked only on subsequent lines in the REPL, and when the appropriate flags were passed directly to compile(). Patch by Pablo Galindo.

gh-121464 [https://github.com/python/cpython/issues/121464]: Make concurrent iterations over the same enumerate() iterator safe under free-threading. See Strategy for Iterators in Free Threading [https://github.com/python/cpython/issues/124397].

gh-87790 [https://github.com/python/cpython/issues/87790]: Support underscore and comma as thousands separators in the fractional part for floating-point presentation types of the new-style string formatting (with format() or f-string（f 字串）). Patch by Sergey B Kirpichev.

gh-124445 [https://github.com/python/cpython/issues/124445]: Fix specialization of generic aliases that are generic over a typing.ParamSpec and have been specialized with a nested type variable.

gh-120608 [https://github.com/python/cpython/issues/120608]: Adapt reversed() for use in the free-threading build. The reversed() is still not thread-safe in the sense that concurrent iterations may see the same object, but they will not corrupt the interpreter state.

Library

gh-100388 [https://github.com/python/cpython/issues/100388]: Fix the platform._sys_version() method when __DATE__ is undefined at buildtime by changing default buildtime datetime string to the UNIX epoch.

Core and Builtins

bpo-44369 [https://bugs.python.org/issue?@action=redirect&bpo=44369]: Improve syntax errors for incorrectly closed strings. Patch by Pablo Galindo

C API

gh-111178 [https://github.com/python/cpython/issues/111178]: Fix PyCMethod API: replace size_t nargs with Py_ssize_t nargs in PyCMethod. Patch by Victor Stinner.

gh-130947 [https://github.com/python/cpython/issues/130947]: Add again PySequence_Fast() to the limited C API. Patch by Victor Stinner.

gh-128863 [https://github.com/python/cpython/issues/128863]: The following private functions are deprecated and planned for removal in Python 3.18:

_PyUnicodeWriter_Init(): replace _PyUnicodeWriter_Init(&writer) with writer = PyUnicodeWriter_Create(0).

_PyUnicodeWriter_Finish(): replace _PyUnicodeWriter_Finish(&writer) with PyUnicodeWriter_Finish(writer).

_PyUnicodeWriter_Dealloc(): replace _PyUnicodeWriter_Dealloc(&writer) with PyUnicodeWriter_Discard(writer).

_PyUnicodeWriter_WriteChar(): replace _PyUnicodeWriter_WriteChar(&writer, ch) with PyUnicodeWriter_WriteChar(writer, ch).

_PyUnicodeWriter_WriteStr(): replace _PyUnicodeWriter_WriteStr(&writer, str) with PyUnicodeWriter_WriteStr(writer, str).

_PyUnicodeWriter_WriteSubstring(): replace _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) with PyUnicodeWriter_WriteSubstring(writer, str, start, end).

_PyUnicodeWriter_WriteASCIIString(): replace _PyUnicodeWriter_WriteASCIIString(&writer, str) with PyUnicodeWriter_WriteUTF8(writer, str).

_PyUnicodeWriter_WriteLatin1String(): replace _PyUnicodeWriter_WriteLatin1String(&writer, str) with PyUnicodeWriter_WriteUTF8(writer, str).

_PyUnicodeWriter_Prepare(): (no replacement).

_PyUnicodeWriter_PrepareKind(): (no replacement).

The pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] can be used to get these new public functions on Python 3.13 and older.

Patch by Victor Stinner.

gh-45325 [https://github.com/python/cpython/issues/45325]: Add a new p format parameter to Py_BuildValue() that allows to take a C integer and produce a Python bool object. Patch by Pablo Galindo.

Build

gh-131035 [https://github.com/python/cpython/issues/131035]: Use -flto=thin for faster build times using clang-cl on Windows. Patch by Chris Eibl.

gh-130740 [https://github.com/python/cpython/issues/130740]: Ensure that Python.h is included before stdbool.h unless pyconfig.h is included before or in some platform-specific contexts.

gh-130090 [https://github.com/python/cpython/issues/130090]: Building with PlatformToolset=ClangCL on Windows now supports PGO (profile guided optimization). Patch by Chris Eibl with invaluable support from Steve Dover.

gh-129819 [https://github.com/python/cpython/issues/129819]: Allow building the JIT with the tailcall interpreter.

gh-129989 [https://github.com/python/cpython/issues/129989]: Fix a bug where the tailcall interpreter was enabled when --without-tail-call-interp was provided to the configure script.

gh-129838 [https://github.com/python/cpython/issues/129838]: Don't redefine _Py_NO_SANITIZE_UNDEFINED when compiling with a recent GCC version and undefined sanitizer enabled.

gh-82909 [https://github.com/python/cpython/issues/82909]: #pragma-based linking with python3*.lib can now be switched off with Py_NO_LINK_LIB. Patch by Jean-Christophe Fillion-Robin.

Python 3.14.0 alpha 5

Release date: 2025-02-11

macOS

gh-91132 [https://github.com/python/cpython/issues/91132]: Update macOS installer to use ncurses 6.5.

Tools/Demos

gh-129248 [https://github.com/python/cpython/issues/129248]: The iOS test runner now strips the log prefix from each line output by the test suite.

gh-104400 [https://github.com/python/cpython/issues/104400]: Fix several bugs in extraction by switching to an AST parser in pygettext.

Tests

gh-129386 [https://github.com/python/cpython/issues/129386]: Add test.support.reset_code, which can be used to reset various bytecode-level optimizations and local instrumentation for a function.

gh-128474 [https://github.com/python/cpython/issues/128474]: Disable test_embed test cases that segfault on BOLT instrument binaries. The tests are only disabled when BOLT is enabled.

gh-128003 [https://github.com/python/cpython/issues/128003]: Add an option --parallel-threads=N to the regression test runner that runs individual tests in multiple threads in parallel in order to find concurrency bugs. Note that most of the test suite is not yet reviewed for thread-safety or annotated with @thread_unsafe when necessary.

Security

gh-105704 [https://github.com/python/cpython/issues/105704]: When using urllib.parse.urlsplit() and urllib.parse.urlparse() host parsing would not reject domain names containing square brackets ([ and ]). Square brackets are only valid for IPv6 and IPvFuture hosts according to RFC 3986 Section 3.2.2 [https://www.rfc-editor.org/rfc/rfc3986#section-3.2.2].

gh-126108 [https://github.com/python/cpython/issues/126108]: Fix a possible NULL pointer dereference in PySys_AddWarnOptionUnicode().

gh-80222 [https://github.com/python/cpython/issues/80222]: Fix bug in the folding of quoted strings when flattening an email message using a modern email policy. Previously when a quoted string was folded so that it spanned more than one line, the surrounding quotes and internal escapes would be omitted. This could theoretically be used to spoof header lines using a carefully constructed quoted string if the resulting rendered email was transmitted or re-parsed.

gh-119511 [https://github.com/python/cpython/issues/119511]: Fix a potential denial of service in the imaplib module. When connecting to a malicious server, it could cause an arbitrary amount of memory to be allocated. On many systems this is harmless as unused virtual memory is only a mapping, but if this hit a virtual address size limit it could lead to a MemoryError or other process crash. On unusual systems or builds where all allocated memory is touched and backed by actual ram or storage it could've consumed resources doing so until similarly crashing.

Library

gh-129939 [https://github.com/python/cpython/issues/129939]: Comparison pages with highlighted changes generated by the difflib.HtmlDiff class now support dark mode.

gh-129928 [https://github.com/python/cpython/issues/129928]: Raise sqlite3.ProgrammingError if a user-defined SQL function with invalid number of parameters is created. Patch by Erlend Aasland.

gh-129583 [https://github.com/python/cpython/issues/129583]: Update bundled pip to 25.0.1

gh-129766 [https://github.com/python/cpython/issues/129766]: Fix crash in warnings, when calling _release_lock() with no existing lock.

gh-129005 [https://github.com/python/cpython/issues/129005]: _pyio.FileIO.readall() now allocates, resizes, and fills a data buffer using the same algorithm _io.FileIO.readall() uses.

gh-129646 [https://github.com/python/cpython/issues/129646]: Update the locale alias mapping in the locale module to match the latest X Org locale alias mapping and support new locales in Glibc 2.41.

gh-128317 [https://github.com/python/cpython/issues/128317]: Put CLI calendar highlighting in private class, removing highlight_day from public calendar.TextCalendar API. Patch by Hugo van Kemenade.

gh-129603 [https://github.com/python/cpython/issues/129603]: Fix bugs where sqlite3.Row objects could segfault if their inherited description was set to None. Patch by Erlend Aasland.

gh-129559 [https://github.com/python/cpython/issues/129559]: Add bytearray.resize() method so bytearray can be efficiently resized in place.

gh-129502 [https://github.com/python/cpython/issues/129502]: Unlikely errors in preparing arguments for ctypes callback are now handled in the same way as errors raised in the callback of in converting the result of the callback -- using sys.unraisablehook() instead of sys.excepthook() and not setting sys.last_exc and other variables.

gh-129403 [https://github.com/python/cpython/issues/129403]: Corrected ValueError message for asyncio.Barrier and threading.Barrier.

gh-129409 [https://github.com/python/cpython/issues/129409]: Fix an integer overflow in the csv module when writing a data field larger than 2GB.

gh-126400 [https://github.com/python/cpython/issues/126400]: Add a socket timeout keyword argument to logging.handlers.SysLogHandler.

gh-118761 [https://github.com/python/cpython/issues/118761]: Always lazy import warnings in threading. Patch by Taneli Hukkinen.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of subprocess by lazy importing locale and signal. Patch by Taneli Hukkinen.

gh-129346 [https://github.com/python/cpython/issues/129346]: In sqlite3, handle out-of-memory when creating user-defined SQL functions.

gh-129005 [https://github.com/python/cpython/issues/129005]: Optimize _pyio.FileIO.readinto by avoiding unnecessary objects and copies using os.readinto().

gh-129195 [https://github.com/python/cpython/issues/129195]: Support reporting call graph information from asyncio.staggered.staggered_race().

gh-129205 [https://github.com/python/cpython/issues/129205]: Add os.readinto() to read into a buffer object from a file descriptor.

gh-128772 [https://github.com/python/cpython/issues/128772]: Fix pydoc for methods with the __module__ attribute equal to None.

gh-129061 [https://github.com/python/cpython/issues/129061]: Fix FORCE_COLOR and NO_COLOR when empty strings. Patch by Hugo van Kemenade.

gh-92897 [https://github.com/python/cpython/issues/92897]: Scheduled the deprecation of the check_home argument of sysconfig.is_python_build() to Python 3.15.

gh-129064 [https://github.com/python/cpython/issues/129064]: Deprecate sysconfig.expand_makefile_vars(), in favor of using sysconfig.get_paths() with the vars argument.

gh-128550 [https://github.com/python/cpython/issues/128550]: Removed an incorrect optimization relating to eager tasks in asyncio.TaskGroup that resulted in cancellations being missed.

gh-128991 [https://github.com/python/cpython/issues/128991]: Release the enter frame reference within bdb callback

gh-118761 [https://github.com/python/cpython/issues/118761]: Reduce import time of pstats and zipfile by up to 20%, by removing unnecessary imports to typing. Patch by Bénédikt Tran.

gh-128978 [https://github.com/python/cpython/issues/128978]: Fix a NameError in sysconfig.expand_makefile_vars(). Patch by Bénédikt Tran.

gh-128961 [https://github.com/python/cpython/issues/128961]: Fix a crash when setting state on an exhausted array.array iterator.

gh-128894 [https://github.com/python/cpython/issues/128894]: Fix traceback.TracebackException._format_syntax_error not to fail on exceptions with custom metadata.

gh-128916 [https://github.com/python/cpython/issues/128916]: Do not attempt to set SO_REUSEPORT on sockets of address families other than AF_INET and AF_INET6, as it is meaningless with these address families, and the call with fail with Linux kernel 6.12.9 and newer.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of tomllib by removing typing, string, and tomllib._types imports. Patch by Taneli Hukkinen.

gh-128679 [https://github.com/python/cpython/issues/128679]: tracemalloc: Fix race conditions when tracemalloc.stop() is called by a thread, while other threads are tracing memory allocations. Patch by Victor Stinner.

gh-128891 [https://github.com/python/cpython/issues/128891]: Add specialized opcodes to opcode.opname.

gh-118761 [https://github.com/python/cpython/issues/118761]: Reduce import time of gettext by up to ten times, by importing re on demand. In particular, re is no longer implicitly exposed as gettext.re. Patch by Eli Schwartz.

gh-118761 [https://github.com/python/cpython/issues/118761]: Reduce the import time of optparse when no help text is printed. Patch by Eli Schwartz.

gh-128657 [https://github.com/python/cpython/issues/128657]: Fix possible extra reference when using objects returned by hashlib.sha256() under free threading.

gh-118761 [https://github.com/python/cpython/issues/118761]: Reduce the import time of csv by up to five times, by importing re on demand. In particular, re is no more implicitly exposed as csv.re. Patch by Bénédikt Tran.

gh-128308 [https://github.com/python/cpython/issues/128308]: Support the name keyword argument for eager tasks in asyncio.loop.create_task(), asyncio.create_task() and asyncio.TaskGroup.create_task(), by passing on all kwargs to the task factory set by asyncio.loop.set_task_factory().

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve the performance of base64.b16decode() by up to ten times by more efficiently checking the byte-string for hexadecimal digits. Reduce the import time of base64 by up to six times, by no longer importing re. Patch by Bénédikt Tran, Chris Markiewicz, and Adam Turner.

gh-128156 [https://github.com/python/cpython/issues/128156]: When using macOS system libffi, support for complex types in ctypes is now checked at runtime (macOS 10.15 or newer). The types must also be available at build time.

gh-128636 [https://github.com/python/cpython/issues/128636]: Fix PyREPL failure when os.environ is overwritten with an invalid value.

gh-128498 [https://github.com/python/cpython/issues/128498]: Default to stdout isatty for color detection instead of stderr. Patch by Hugo van Kemenade.

gh-128384 [https://github.com/python/cpython/issues/128384]: Add locking to warnings to avoid some data races when free-threading is used. Change _warnings_runtime_state.mutex to be a recursive mutex and expose it to warnings, via the _acquire_lock() and _release_lock() functions. The lock is held when filters and _filters_version are updated.

gh-128509 [https://github.com/python/cpython/issues/128509]: Add sys._is_immortal() for identifying immortal objects at runtime.

gh-128479 [https://github.com/python/cpython/issues/128479]: Fix asyncio.staggered.staggered_race() leaking tasks and issuing an unhandled exception.

gh-128427 [https://github.com/python/cpython/issues/128427]: uuid.NIL and uuid.MAX are now available to represent the Nil and Max UUID formats as defined by RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html].

gh-91279 [https://github.com/python/cpython/issues/91279]: zipfile.ZipFile.writestr() now respect SOURCE_DATE_EPOCH that distributions can set centrally and have build tools consume this in order to produce reproducible output.

gh-112064 [https://github.com/python/cpython/issues/112064]: Fix incorrect handling of negative read sizes in HTTPResponse.read. Patch by Yury Manushkin.

gh-58956 [https://github.com/python/cpython/issues/58956]: Fixed a frame reference leak in bdb.

gh-128131 [https://github.com/python/cpython/issues/128131]: Completely support random access of uncompressed unencrypted read-only zip files obtained by ZipFile.open.

gh-127975 [https://github.com/python/cpython/issues/127975]: Avoid reusing quote types in ast.unparse() if not needed.

gh-115514 [https://github.com/python/cpython/issues/115514]: Fix exceptions and incomplete writes after asyncio._SelectorTransport is closed before writes are completed.

gh-121604 [https://github.com/python/cpython/issues/121604]: Add missing Deprecation warnings for importlib.machinery.DEBUG_BYTECODE_SUFFIXES, importlib.machinery.OPTIMIZED_BYTECODE_SUFFIXES, importlib.machinery.WindowsRegistryFinder, importlib.abc.ResourceLoader, importlib.abc.SourceLoader.path_mtime().

gh-127873 [https://github.com/python/cpython/issues/127873]: When -E is set, only ignore PYTHON_COLORS and not FORCE_COLOR/NO_COLOR/TERM when colourising output. Patch by Hugo van Kemenade.

gh-125413 [https://github.com/python/cpython/issues/125413]: Add pathlib.Path.info attribute, which stores an object implementing the pathlib.types.PathInfo protocol (also new). The object supports querying the file type and internally caching stat() results. Path objects generated by iterdir() are initialized with file type information gleaned from scanning the parent directory.

gh-127712 [https://github.com/python/cpython/issues/127712]: Fix handling of the secure argument of logging.handlers.SMTPHandler.

gh-127096 [https://github.com/python/cpython/issues/127096]: Do not recreate unnamed section on every read in configparser.ConfigParser. Patch by Andrey Efremov.

gh-124369 [https://github.com/python/cpython/issues/124369]: Deprecate pdb.Pdb.curframe_locals

gh-126332 [https://github.com/python/cpython/issues/126332]: Fix _pyrepl crash when entering a double CTRL-Z on an overflowing line.

gh-125553 [https://github.com/python/cpython/issues/125553]: Fix round-trip invariance for backslash continuations in tokenize.untokenize().

gh-91048 [https://github.com/python/cpython/issues/91048]: Add asyncio.capture_call_graph() and asyncio.print_call_graph() functions.

gh-124703 [https://github.com/python/cpython/issues/124703]: Quitting pdb in inline mode will emit a confirmation prompt and exit gracefully now, instead of printing an exception traceback.

gh-123987 [https://github.com/python/cpython/issues/123987]: Fixed issue in NamespaceReader where a non-path item in a namespace path, such as a sentinel added by an editable installer, would break resource loading.

gh-119349 [https://github.com/python/cpython/issues/119349]: Add the ctypes.util.dllist() function to list the loaded shared libraries for the current process.

gh-55454 [https://github.com/python/cpython/issues/55454]: Add IMAP4 IDLE support to the imaplib module. Patch by Forest.

gh-119257 [https://github.com/python/cpython/issues/119257]: Show tab completions menu below the current line, which results in less janky behaviour, and fixes a cursor movement bug. Patch by Daniel Hollas

gh-101410 [https://github.com/python/cpython/issues/101410]: Support custom messages for domain errors in the math module (math.sqrt(), math.log() and math.atanh() were modified as examples). Patch by Charlie Zhao and Sergey B Kirpichev.

gh-81340 [https://github.com/python/cpython/issues/81340]: Use os.copy_file_range() in shutil.copy(), shutil.copy2(), and shutil.copyfile() functions by default. An underlying Linux system call gives filesystems an opportunity to implement the use of copy-on-write (in case of btrfs and XFS) or server-side copy (in the case of NFS.) Patch by Illia Volochii.

bpo-27307 [https://bugs.python.org/issue?@action=redirect&bpo=27307]: Add attribute and item access support to string.Formatter in auto-numbering mode, which allows format strings like '{.name}' and '{[1]}'.

IDLE

gh-129873 [https://github.com/python/cpython/issues/129873]: Simplify displaying the IDLE doc by only copying the text section of idle.html to idlelib/help.html. Patch by Stan Ulbrych.

Documentation

gh-125722 [https://github.com/python/cpython/issues/125722]: Require Sphinx 8.1.3 or later to build the Python documentation. Patch by Adam Turner.

gh-67206 [https://github.com/python/cpython/issues/67206]: Document that string.printable is not printable in the POSIX sense. In particular, string.printable.isprintable() returns False. Patch by Bénédikt Tran.

Core and Builtins

gh-100239 [https://github.com/python/cpython/issues/100239]: Replace the opcode BINARY_SUBSCR and its family by BINARY_OP with oparg NB_SUBSCR.

gh-129732 [https://github.com/python/cpython/issues/129732]: Fixed a race in _Py_qsbr_reserve in the free threading build.

gh-129763 [https://github.com/python/cpython/issues/129763]: Remove the internal LLTRACE macro (use Py_DEBUG instead).

gh-129715 [https://github.com/python/cpython/issues/129715]: Improve JIT performance for generators.

gh-129643 [https://github.com/python/cpython/issues/129643]: Fix thread safety of PyList_Insert() in free-threading builds.

gh-129668 [https://github.com/python/cpython/issues/129668]: Fix race condition when raising MemoryError in the free threaded build.

gh-129643 [https://github.com/python/cpython/issues/129643]: Fix thread safety of PyList_SetItem() in free-threading builds. Patch by Kumar Aditya.

gh-128563 [https://github.com/python/cpython/issues/128563]: Fix an issue where the "lltrace" debug feature could have been incorrectly enabled for some frames.

gh-129393 [https://github.com/python/cpython/issues/129393]: On FreeBSD, sys.platform doesn't contain the major version anymore. It is always 'freebsd', instead of 'freebsd13' or 'freebsd14'.

Library

gh-129345 [https://github.com/python/cpython/issues/129345]: Fix null pointer dereference in syslog.openlog() when an audit hook raises an exception.

Core and Builtins

gh-129231 [https://github.com/python/cpython/issues/129231]: Improve memory layout of JIT traces. Patch by Diego Russo

gh-129149 [https://github.com/python/cpython/issues/129149]: Add fast path for medium-size integers in PyLong_FromUnsignedLong(), PyLong_FromUnsignedLongLong() and PyLong_FromSize_t().

gh-129201 [https://github.com/python/cpython/issues/129201]: The free-threaded version of the cyclic garbage collector has been optimized to conditionally use CPU prefetch instructions during the collection. This can reduce collection times by making it more likely that data is in the CPU cache when it is needed. The prefetch instructions are enabled if the number of long-lived objects (objects surviving a full collection) exceeds a threshold.

gh-129093 [https://github.com/python/cpython/issues/129093]: Fix f-strings such as f'{expr=}' sometimes not displaying the full expression when the expression contains !=.

gh-124363 [https://github.com/python/cpython/issues/124363]: Treat debug expressions in f-string as raw strings. Patch by Pablo Galindo

gh-128714 [https://github.com/python/cpython/issues/128714]: Fix the potential races in get/set dunder methods __annotations__, __annotate__ and __type_params__ for function object, and add related tests.

gh-128799 [https://github.com/python/cpython/issues/128799]: Add frame of except* to traceback when it wraps a naked exception.

gh-128842 [https://github.com/python/cpython/issues/128842]: Collect JIT memory stats using pystats. Patch by Diego Russo.

gh-100239 [https://github.com/python/cpython/issues/100239]: Specialize BINARY_OP for bitwise logical operations on compact ints.

gh-128910 [https://github.com/python/cpython/issues/128910]: Undocumented and unused private C-API functions _PyTrash_begin and _PyTrash_end are removed.

gh-128807 [https://github.com/python/cpython/issues/128807]: Add a marking phase to the free-threaded GC. This is similar to what was done in gh-126491 [https://github.com/python/cpython/issues/126491]. Since the free-threaded GC does not have generations and is not incremental, the marking phase looks for all objects reachable from known roots. The roots are objects known to not be garbage, like the module dictionary for sys. For most programs, this marking phase should make the GC a bit faster since typically less work is done per object.

gh-100239 [https://github.com/python/cpython/issues/100239]: Add opcode BINARY_OP_EXTEND which executes a pair of functions (guard and specialization functions) accessed from the inline cache.

gh-128563 [https://github.com/python/cpython/issues/128563]: A new type of interpreter has been added to CPython. This interpreter uses tail calls for its instruction handlers. Preliminary benchmark results suggest 7-11% geometric mean faster on pyperformance (depending on platform), and up to 30% faster on Python-intensive workloads. This interpreter currently only works on newer compilers, such as clang-19. Other compilers will continue using the old interpreter. Patch by Ken Jin, with ideas on how to implement this in CPython by Mark Shannon, Garret Gu, Haoran Xu, and Josh Haberman.

gh-126703 [https://github.com/python/cpython/issues/126703]: Improve performance of iterating over lists and tuples by using a freelist for the iterator objects.

gh-127953 [https://github.com/python/cpython/issues/127953]: The time to handle a LINE event in sys.monitoring (and sys.settrace) is now independent of the number of lines in the code object.

gh-128330 [https://github.com/python/cpython/issues/128330]: Restore terminal control characters on REPL exit.

gh-128016 [https://github.com/python/cpython/issues/128016]: Improved the SyntaxWarning message for invalid escape sequences to clarify that such sequences will raise a SyntaxError in future Python releases. The new message also suggests a potential fix, i.e., Did you mean "\\e"?.

gh-126004 [https://github.com/python/cpython/issues/126004]: Fix handling of UnicodeError.start and UnicodeError.end values in the codecs.replace_errors() error handler. Patch by Bénédikt Tran.

gh-126004 [https://github.com/python/cpython/issues/126004]: Fix handling of UnicodeError.start and UnicodeError.end values in the codecs.backslashreplace_errors() error handler. Patch by Bénédikt Tran.

gh-126004 [https://github.com/python/cpython/issues/126004]: Fix handling of UnicodeError.start and UnicodeError.end values in the codecs.xmlcharrefreplace_errors() error handler. Patch by Bénédikt Tran.

gh-127119 [https://github.com/python/cpython/issues/127119]: Slightly optimize the int deallocator.

gh-127349 [https://github.com/python/cpython/issues/127349]: Fixed the error when resizing terminal in Python REPL. Patch by Semyon Moroz.

gh-125723 [https://github.com/python/cpython/issues/125723]: Fix crash with gi_frame.f_locals when generator frames outlive their generator. Patch by Mikhail Efimov.

Library

gh-126349 [https://github.com/python/cpython/issues/126349]: Add turtle.fill(), turtle.poly() and turtle.no_animation() context managers. Patch by Marie Roald and Yngve Mardal Moe.

Core and Builtins

gh-115911 [https://github.com/python/cpython/issues/115911]: If the current working directory cannot be determined due to permissions, then import will no longer raise PermissionError. Patch by Alex Willmer.

Library

gh-112713 [https://github.com/python/cpython/issues/112713]: Added support for the Partitioned cookie flag in http.cookies.

C API

gh-129533 [https://github.com/python/cpython/issues/129533]: Update PyGC_Enable(), PyGC_Disable(), PyGC_IsEnabled() to use atomic operation for thread-safety at free-threading build. Patch by Donghee Na.

gh-89188 [https://github.com/python/cpython/issues/89188]: Implement PyUnicode_KIND() and PyUnicode_DATA() as function, in addition to the macros with the same names. The macros rely on C bit fields which have compiler-specific layout. Patch by Victor Stinner.

gh-91417 [https://github.com/python/cpython/issues/91417]: Remove PySequence_Fast() from the limited C API, since this function has to be used with PySequence_Fast_GET_ITEM which never worked in the limited C API. Patch by Victor Stinner.

gh-128509 [https://github.com/python/cpython/issues/128509]: Add PyUnstable_IsImmortal() for determining whether an object is immortal.

gh-129033 [https://github.com/python/cpython/issues/129033]: Remove _PyInterpreterState_GetConfigCopy() and _PyInterpreterState_SetConfig() private functions. Use instead PyConfig_Get() and PyConfig_Set(), public C API added by PEP 741 [https://peps.python.org/pep-0741/] "Python Configuration C API". Patch by Victor Stinner.

gh-129033 [https://github.com/python/cpython/issues/129033]: Remove the private _Py_InitializeMain() function. It was a provisional API added to Python 3.8 by PEP 587 [https://peps.python.org/pep-0587/]. Patch by Victor Stinner.

gh-128844 [https://github.com/python/cpython/issues/128844]: Add PyUnstable_TryIncRef() and PyUnstable_EnableTryIncRef() unstable APIs. These are helpers for dealing with unowned references in a thread-safe way, particularly in the free threading build.

gh-128911 [https://github.com/python/cpython/issues/128911]: Add PyImport_ImportModuleAttr() and PyImport_ImportModuleAttrString() helper functions to import a module and get an attribute of the module. Patch by Victor Stinner.

gh-128863 [https://github.com/python/cpython/issues/128863]: The following private functions are deprecated and planned for removal in Python 3.18:

_PyBytes_Join(): use PyBytes_Join().

_PyDict_GetItemStringWithError(): use PyDict_GetItemStringRef().

_PyDict_Pop(): use PyDict_Pop().

_PyLong_Sign(): use PyLong_GetSign().

_PyLong_FromDigits() and _PyLong_New(): use PyLongWriter_Create().

_PyThreadState_UncheckedGet(): use PyThreadState_GetUnchecked().

_PyUnicode_AsString(): use PyUnicode_AsUTF8().

_Py_HashPointer(): use Py_HashPointer().

_Py_fopen_obj(): use Py_fopen().

The pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] can be used to get these new public functions on Python 3.13 and older.

Patch by Victor Stinner.

gh-126599 [https://github.com/python/cpython/issues/126599]: Remove some internal test APIs for the experimental JIT compiler.

gh-127925 [https://github.com/python/cpython/issues/127925]: Convert the decimal module to use PEP 757 [https://peps.python.org/pep-0757/] C API (export-import integers), offering some speed-up if the integer part of the Decimal instance is small. Patch by Sergey B Kirpichev.

Build

gh-129660 [https://github.com/python/cpython/issues/129660]: Drop test_embed from PGO training, whose contribution in recent versions is considered to be ignorable.

gh-128902 [https://github.com/python/cpython/issues/128902]: Fix compile errors with Clang 9 and older due to lack of __attribute__((fallthrough)) support.

Python 3.14.0 alpha 4

Release date: 2025-01-14

macOS

gh-127592 [https://github.com/python/cpython/issues/127592]: Usage of the unified Apple System Log APIs was disabled when the minimum macOS version is earlier than 10.12.

Tools/Demos

gh-128152 [https://github.com/python/cpython/issues/128152]: Fix a bug where Argument Clinic's C pre-processor parser tried to parse pre-processor directives inside C comments. Patch by Erlend Aasland.

Tests

gh-128690 [https://github.com/python/cpython/issues/128690]: Temporarily do not use test_embed in PGO profile builds until the problem with test_init_pyvenv_cfg failing in some configurations is resolved.

Library

gh-128731 [https://github.com/python/cpython/issues/128731]: Fix ResourceWarning in urllib.robotparser.RobotFileParser.read().

gh-71339 [https://github.com/python/cpython/issues/71339]: Add new assertion methods for unittest: assertHasAttr(), assertNotHasAttr(), assertIsSubclass(), assertNotIsSubclass() assertStartsWith(), assertNotStartsWith(), assertEndsWith() and assertNotEndsWith().

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of pickle by 25% by removing an unnecessary regular expression. As such, re is no more implicitly available as pickle.re. Patch by Bénédikt Tran.

gh-128661 [https://github.com/python/cpython/issues/128661]: Fixes typing.evaluate_forward_ref() not showing deprecation when type_params arg is not passed.

gh-128562 [https://github.com/python/cpython/issues/128562]: Fix possible conflicts in generated tkinter widget names if the widget class name ends with a digit.

gh-128559 [https://github.com/python/cpython/issues/128559]: Improved import time of asyncio.

gh-128552 [https://github.com/python/cpython/issues/128552]: Fix cyclic garbage introduced by asyncio.loop.create_task() and asyncio.TaskGroup.create_task() holding a reference to the created task if it is eager.

gh-128340 [https://github.com/python/cpython/issues/128340]: Add internal thread safe handle to be used in asyncio.loop.call_soon_threadsafe() for thread safe cancellation.

gh-128182 [https://github.com/python/cpython/issues/128182]: Fix crash when using ctypes pointers concurrently on the free threaded build.

gh-128400 [https://github.com/python/cpython/issues/128400]: Only show the current thread in faulthandler on the free threaded build to prevent races.

gh-128400 [https://github.com/python/cpython/issues/128400]: Fix crash when using faulthandler.dump_traceback() while other threads are active on the free threaded build.

gh-128388 [https://github.com/python/cpython/issues/128388]: Fix PyREPL on Windows to support more keybindings, like the Control-← and Control-→ word-skipping keybindings and those with meta (i.e. Alt), e.g. Alt-d to kill-word or Alt-Backspace backward-kill-word.

gh-88834 [https://github.com/python/cpython/issues/88834]: Unify the instance check for typing.Union and types.UnionType: Union now uses the instance checks against its parameters instead of the subclass checks.

gh-128302 [https://github.com/python/cpython/issues/128302]: Fix xml.dom.xmlbuilder.DOMEntityResolver.resolveEntity(), which was broken by the Python 3.0 transition.

gh-128317 [https://github.com/python/cpython/issues/128317]: Highlight today in colour in calendar's CLI output. Patch by Hugo van Kemenade.

gh-128302 [https://github.com/python/cpython/issues/128302]: Allow xml.dom.xmlbuilder.DOMParser.parse() to correctly handle xml.dom.xmlbuilder.DOMInputSource instances that only have a systemId attribute set.

gh-128151 [https://github.com/python/cpython/issues/128151]: Improve generation of UUID objects version 3, 4, 5, and 8 via their dedicated functions by 30%. Patch by Bénédikt Tran.

gh-128118 [https://github.com/python/cpython/issues/128118]: Improve performance of copy.copy() by 30% via a fast path for atomic types and container types.

gh-127946 [https://github.com/python/cpython/issues/127946]: Fix crash when modifying ctypes._CFuncPtr objects concurrently on the free threaded build.

gh-128062 [https://github.com/python/cpython/issues/128062]: Revert the font of turtledemo's menu bar to its default value and display the shortcut keys in the correct position.

gh-128014 [https://github.com/python/cpython/issues/128014]: Fix resetting the default window icon by passing default='' to the tkinter method wm_iconbitmap().

gh-41872 [https://github.com/python/cpython/issues/41872]: Fix quick extraction of module docstrings from a file in pydoc. It now supports docstrings with single quotes, escape sequences, raw string literals, and other Python syntax.

gh-127060 [https://github.com/python/cpython/issues/127060]: Set TERM environment variable to "dumb" to disable traceback colors in IDLE, since IDLE doesn't understand ANSI escape sequences. Patch by Victor Stinner.

gh-126742 [https://github.com/python/cpython/issues/126742]: Fix support of localized error messages reported by dlerror(3) [https://manpages.debian.org/dlerror(3)] and gdbm_strerror [https://manpages.debian.org/gdbm(3)] in ctypes and dbm.gnu functions respectively. Patch by Bénédikt Tran.

gh-122548 [https://github.com/python/cpython/issues/122548]: Adds two new local events to sys.monitoring, BRANCH_LEFT and BRANCH_RIGHT. This allows the two arms of the branch to be disabled independently, which should hugely improve performance of branch-level coverage tools. The old branch event, BRANCH is now deprecated.

gh-127847 [https://github.com/python/cpython/issues/127847]: Fix the position when doing interleaved seeks and reads in uncompressed, unencrypted zip files returned by zipfile.ZipFile.open().

gh-127688 [https://github.com/python/cpython/issues/127688]: Add the SCHED_DEADLINE and SCHED_NORMAL constants to the os module.

gh-83662 [https://github.com/python/cpython/issues/83662]: Add missing __class_getitem__ method to the Python implementation of functools.partial(), to make it compatible with the C version. This is mainly relevant for alternative Python implementations like PyPy and GraalPy, because CPython will usually use the C-implementation of that function.

gh-127586 [https://github.com/python/cpython/issues/127586]: multiprocessing.pool.Pool now properly restores blocked signal handlers of the parent thread when creating processes via either spawn or forkserver.

gh-98188 [https://github.com/python/cpython/issues/98188]: Fix an issue in email.message.Message.get_payload() where data cannot be decoded if the Content Transfer Encoding mechanism contains trailing whitespaces or additional junk text. Patch by Hui Liu.

gh-127529 [https://github.com/python/cpython/issues/127529]: Correct behavior of asyncio.selector_events.BaseSelectorEventLoop._accept_connection() in handling ConnectionAbortedError in a loop. This improves performance on OpenBSD.

gh-127360 [https://github.com/python/cpython/issues/127360]: When a descriptive error message cannot be provided for an ssl.SSLError, the "unknown error" message now shows the internal error code (as retrieved by ERR_get_error and similar OpenSSL functions).

gh-127196 [https://github.com/python/cpython/issues/127196]: Fix crash when dict with keys in invalid encoding were passed to several functions in _interpreters module.

gh-124130 [https://github.com/python/cpython/issues/124130]: Fix a bug in matching regular expression \B in empty input string. Now it is always the opposite of \b. To get an old behavior, use (?!\A\Z)\B. To get a new behavior in old Python versions, use (?!\b).

gh-126639 [https://github.com/python/cpython/issues/126639]: tempfile.NamedTemporaryFile will now issue a ResourceWarning when it is finalized by the garbage collector without being explicitly closed.

gh-126624 [https://github.com/python/cpython/issues/126624]: Expose error code XML_ERROR_NOT_STARTED of Expat >=2.6.4 in xml.parsers.expat.errors.

gh-126225 [https://github.com/python/cpython/issues/126225]: getopt and optparse are no longer marked as deprecated. There are legitimate reasons to use one of these modules in preference to argparse, and none of these modules are at risk of being removed from the standard library. Of the three, argparse remains the recommended default choice, unless one of the concerns noted at the top of the optparse module documentation applies.

gh-124761 [https://github.com/python/cpython/issues/124761]: Add SO_REUSEPORT_LB constant to socket for FreeBSD.

gh-121720 [https://github.com/python/cpython/issues/121720]: enum.EnumDict can now be used without resorting to private API.

gh-123424 [https://github.com/python/cpython/issues/123424]: Add zipfile.ZipInfo._for_archive() setting default properties on ZipInfo objects. Patch by Bénédikt Tran and Jason R. Coombs.

gh-121676 [https://github.com/python/cpython/issues/121676]: Deprecate calling the Python implementation of functools.reduce() with a function or sequence as a keyword argument. This will be forbidden in Python 3.16 in order to match the C implementation.

gh-112015 [https://github.com/python/cpython/issues/112015]: ctypes.memoryview_at() now exists to create a memoryview object that refers to the supplied pointer and length. This works like ctypes.string_at() except it avoids a buffer copy, and is typically useful when implementing pure Python callback functions that are passed dynamically-sized buffers.

gh-95371 [https://github.com/python/cpython/issues/95371]: Added support for other image formats (PNG, PGM, and PPM) to the turtle module. Patch by Shin-myoung-serp.

Core and Builtins

gh-128078 [https://github.com/python/cpython/issues/128078]: Fix a SystemError when using anext() with a default tuple value. Patch by Bénédikt Tran.

gh-128717 [https://github.com/python/cpython/issues/128717]: Fix a crash when setting the recursion limit while other threads are active on the free threaded build.

gh-124483 [https://github.com/python/cpython/issues/124483]: Treat Py_DECREF and variants as escaping when generating opcode and uop metadata. This prevents the possibility of a __del__ method causing the JIT to behave incorrectly.

gh-126703 [https://github.com/python/cpython/issues/126703]: Improve performance of class methods by using a freelist.

gh-128137 [https://github.com/python/cpython/issues/128137]: Update PyASCIIObject layout to handle interned field with the atomic operation. Patch by Donghee Na.

Library

gh-128192 [https://github.com/python/cpython/issues/128192]: Upgrade HTTP digest authentication algorithm for urllib.request by supporting SHA-256 digest authentication as specified in RFC 7616 [https://datatracker.ietf.org/doc/html/rfc7616.html].

Core and Builtins

gh-126868 [https://github.com/python/cpython/issues/126868]: Increase usage of freelist for int allocation.

gh-114203 [https://github.com/python/cpython/issues/114203]: Optimize Py_BEGIN_CRITICAL_SECTION for simple recursive calls.

gh-127705 [https://github.com/python/cpython/issues/127705]: Adds stackref debugging when Py_STACKREF_DEBUG is set. Finds all double-closes and leaks, logging the origin and last borrow.

Inspired by HPy's debug mode. https://docs.hpyproject.org/en/latest/debug-mode.html

gh-128079 [https://github.com/python/cpython/issues/128079]: Fix a bug where except* does not properly check the return value of an ExceptionGroup's split() function, leading to a crash in some cases. Now when split() returns an invalid object, except* raises a TypeError with the original raised ExceptionGroup object chained to it.

gh-128030 [https://github.com/python/cpython/issues/128030]: Avoid error from calling PyModule_GetFilenameObject on a non-module object when importing a non-existent symbol from a non-module object.

Library

gh-128035 [https://github.com/python/cpython/issues/128035]: Indicate through ssl.HAS_PHA whether the ssl module supports TLSv1.3 post-handshake client authentication (PHA). Patch by Will Childs-Klein.

Core and Builtins

gh-127274 [https://github.com/python/cpython/issues/127274]: Add a new flag, CO_METHOD, to co_flags that indicates whether the code object belongs to a function defined in class scope.

gh-66409 [https://github.com/python/cpython/issues/66409]: During the path initialization, we now check if base_exec_prefix is the same as base_prefix before falling back to searching the Python interpreter directory.

gh-127970 [https://github.com/python/cpython/issues/127970]: We now use the location of the libpython runtime library used in the current process to determine sys.base_prefix on all platforms implementing the dladdr [https://pubs.opengroup.org/onlinepubs/9799919799/functions/dladdr.html] function defined by the UNIX standard — this includes Linux, Android, macOS, iOS, FreeBSD, etc. This was already the case on Windows and macOS Framework builds.

gh-127773 [https://github.com/python/cpython/issues/127773]: Do not use the type attribute cache for types with incompatible MRO.

gh-127903 [https://github.com/python/cpython/issues/127903]: Objects/unicodeobject.c: fix a crash on DEBUG builds in _copy_characters when there is nothing to copy.

gh-127809 [https://github.com/python/cpython/issues/127809]: Fix an issue where the experimental JIT may infer an incorrect result type for exponentiation (** and **=), leading to bugs or crashes.

gh-126862 [https://github.com/python/cpython/issues/126862]: Fix a possible overflow when a class inherits from an absurd number of super-classes. Reported by Valery Fedorenko. Patch by Bénédikt Tran.

C API

gh-128400 [https://github.com/python/cpython/issues/128400]: Py_FatalError() no longer shows all threads on the free threaded build to prevent crashes.

gh-128629 [https://github.com/python/cpython/issues/128629]: Add macros Py_PACK_VERSION() and Py_PACK_FULL_VERSION() for bit-packing Python version numbers.

gh-128008 [https://github.com/python/cpython/issues/128008]: Add PyWeakref_IsDead() function, which tests if a weak reference is dead.

gh-127350 [https://github.com/python/cpython/issues/127350]: Add Py_fopen() function to open a file. Similar to the fopen() function, but the path parameter is a Python object and an exception is set on error. Add also Py_fclose() function to close a file, function needed for Windows support. Patch by Victor Stinner.

Build

gh-128627 [https://github.com/python/cpython/issues/128627]: For Emscripten builds the function pointer cast call trampoline now uses the wasm-gc ref.test instruction if it's available instead of Wasm JS type reflection.

gh-128472 [https://github.com/python/cpython/issues/128472]: Skip BOLT optimization of functions using computed gotos, fixing errors on build with LLVM 19.

gh-115765 [https://github.com/python/cpython/issues/115765]: GNU Autoconf 2.72 is now required to generate configure. Patch by Erlend Aasland.

gh-123925 [https://github.com/python/cpython/issues/123925]: Fix building the curses module on platforms with libncurses but without libncursesw.

gh-90905 [https://github.com/python/cpython/issues/90905]: Add support for cross-compiling to x86_64 on aarch64/arm64 macOS.

gh-128321 [https://github.com/python/cpython/issues/128321]: Set LIBS instead of LDFLAGS when checking if sqlite3 library functions are available. This fixes the ordering of linked libraries during checks, which was incorrect when using a statically linked libsqlite3.

gh-100384 [https://github.com/python/cpython/issues/100384]: Error on unguarded-availability in macOS builds, preventing invalid use of symbols that are not available in older versions of the OS.

gh-128104 [https://github.com/python/cpython/issues/128104]: Remove Py_STRFTIME_C99_SUPPORT conditions in favor of requiring C99 strftime(3) [https://manpages.debian.org/strftime(3)] specifier support at build time. When cross-compiling, there is no build time check and support is assumed.

gh-127951 [https://github.com/python/cpython/issues/127951]: Add option --pystats to the Windows build to enable performance statistics collection.

Python 3.14.0 alpha 3

Release date: 2024-12-17

Windows

gh-127353 [https://github.com/python/cpython/issues/127353]: Allow to force color output on Windows using environment variables. Patch by Andrey Efremov.

gh-125729 [https://github.com/python/cpython/issues/125729]: Makes the presence of the turtle module dependent on the Tcl/Tk installer option. Previously, the module was always installed but would be unusable without Tcl/Tk.

Tools/Demos

gh-126700 [https://github.com/python/cpython/issues/126700]: Add support for multi-argument gettext functions in pygettext.py.

Tests

gh-127906 [https://github.com/python/cpython/issues/127906]: Test the limited C API in test_cppext. Patch by Victor Stinner.

gh-127637 [https://github.com/python/cpython/issues/127637]: Add tests for the dis command-line interface. Patch by Bénédikt Tran.

gh-126925 [https://github.com/python/cpython/issues/126925]: iOS test results are now streamed during test execution, and the deprecated xcresulttool is no longer used.

gh-127076 [https://github.com/python/cpython/issues/127076]: Disable strace based system call tests when LD_PRELOAD is set.

gh-127076 [https://github.com/python/cpython/issues/127076]: Filter out memory-related mmap, munmap, and mprotect calls from file-related ones when testing io behavior using strace.

Security

gh-127655 [https://github.com/python/cpython/issues/127655]: Fixed the asyncio.selector_events._SelectorSocketTransport transport not pausing writes for the protocol when the buffer reaches the high water mark when using asyncio.WriteTransport.writelines().

Library

gh-126907 [https://github.com/python/cpython/issues/126907]: Fix crash when using atexit concurrently on the free-threaded build.

gh-127870 [https://github.com/python/cpython/issues/127870]: Detect recursive calls in ctypes _as_parameter_ handling. Patch by Victor Stinner.

gh-127732 [https://github.com/python/cpython/issues/127732]: The platform module now correctly detects Windows Server 2025.

gh-126789 [https://github.com/python/cpython/issues/126789]: Fixed sysconfig.get_config_vars(), sysconfig.get_paths(), and siblings, returning outdated cached data if the value of sys.prefix or sys.exec_prefix changes. Overwriting sys.prefix or sys.exec_prefix still is discouraged, as that might break other parts of the code.

gh-127718 [https://github.com/python/cpython/issues/127718]: Add colour to test.regrtest output. Patch by Hugo van Kemenade.

gh-127610 [https://github.com/python/cpython/issues/127610]: Added validation for more than one var-positional or var-keyword parameters in inspect.Signature. Patch by Maxim Ageev.

gh-127627 [https://github.com/python/cpython/issues/127627]: Added posix._emscripten_debugger() to help with debugging the test suite on the Emscripten target.

gh-126821 [https://github.com/python/cpython/issues/126821]: macOS and iOS apps can now choose to redirect stdout and stderr to the system log during interpreter configuration.

gh-93312 [https://github.com/python/cpython/issues/93312]: Include <sys/pidfd.h> to get os.PIDFD_NONBLOCK constant. Patch by Victor Stinner.

gh-127481 [https://github.com/python/cpython/issues/127481]: Add the EPOLLWAKEUP constant to the select module.

gh-127065 [https://github.com/python/cpython/issues/127065]: Make operator.methodcaller() thread-safe and re-entrant safe.

gh-127321 [https://github.com/python/cpython/issues/127321]: pdb.set_trace() will not stop at an opcode that does not have an associated line number anymore.

gh-127429 [https://github.com/python/cpython/issues/127429]: Fixed bug where, on cross-builds, the sysconfig POSIX data was being generated with the host Python's Makefile. The data is now generated from current build's Makefile.

gh-127413 [https://github.com/python/cpython/issues/127413]: Add the dis --specialized command-line option to show specialized bytecode. Patch by Bénédikt Tran.

gh-125413 [https://github.com/python/cpython/issues/125413]: Revert addition of pathlib.Path.scandir(). This method was added in 3.14.0a2. The optimizations remain for file system paths, but other subclasses should only have to implement pathlib.Path.iterdir().

gh-127257 [https://github.com/python/cpython/issues/127257]: In ssl, system call failures that OpenSSL reports using ERR_LIB_SYS are now raised as OSError.

gh-59705 [https://github.com/python/cpython/issues/59705]: On Linux, threading.Thread now sets the thread name to the operating system. Patch by Victor Stinner.

gh-127303 [https://github.com/python/cpython/issues/127303]: Publicly expose EXACT_TOKEN_TYPES in token.__all__.

gh-127331 [https://github.com/python/cpython/issues/127331]: ssl can show descriptions for errors added in OpenSSL 3.4.

gh-123967 [https://github.com/python/cpython/issues/123967]: Fix faulthandler for trampoline frames. If the top-most frame is a trampoline frame, skip it. Patch by Victor Stinner.

gh-127178 [https://github.com/python/cpython/issues/127178]: A _sysconfig_vars_(...).json file is now shipped in the standard library directory. It contains the output of sysconfig.get_config_vars() on the default environment encoded as JSON data. This is an implementation detail, and may change at any time.

gh-127072 [https://github.com/python/cpython/issues/127072]: Remove outdated socket.NETLINK_* constants not present in Linux kernels beyond 2.6.17.

gh-127255 [https://github.com/python/cpython/issues/127255]: The CopyComPointer() function is now public. Previously, this was private and only available in _ctypes.

gh-127182 [https://github.com/python/cpython/issues/127182]: Fix io.StringIO.__setstate__() crash, when None was passed as the first value.

gh-127217 [https://github.com/python/cpython/issues/127217]: Fix urllib.request.pathname2url() for paths starting with multiple slashes on Posix.

gh-125866 [https://github.com/python/cpython/issues/125866]: urllib.request.pathname2url() now adds an empty authority when generating a URL for a path that begins with exactly one slash. For example, the path /etc/hosts is converted to the scheme-less URL ///etc/hosts. As a result of this change, URLs without authorities are only generated for relative paths.

gh-127221 [https://github.com/python/cpython/issues/127221]: Add colour to unittest output. Patch by Hugo van Kemenade.

gh-127035 [https://github.com/python/cpython/issues/127035]: Fix shutil.which on Windows. Now it looks at direct match if and only if the command ends with a PATHEXT extension or X_OK is not in mode. Support extensionless files if "." is in PATHEXT. Support PATHEXT extensions that end with a dot.

gh-122273 [https://github.com/python/cpython/issues/122273]: Support PyREPL history on Windows. Patch by devdanzin and Victor Stinner.

gh-125866 [https://github.com/python/cpython/issues/125866]: urllib.request.pathname2url() and url2pathname() no longer convert Windows drive letters to uppercase.

gh-127078 [https://github.com/python/cpython/issues/127078]: Fix issue where urllib.request.url2pathname() failed to discard an extra slash before a UNC drive in the URL path on Windows.

gh-126766 [https://github.com/python/cpython/issues/126766]: Fix issue where urllib.request.url2pathname() failed to discard any 'localhost' authority present in the URL.

gh-127065 [https://github.com/python/cpython/issues/127065]: Fix crash when calling a operator.methodcaller() instance from multiple threads in the free threading build.

gh-127090 [https://github.com/python/cpython/issues/127090]: Fix value of urllib.response.addinfourl.url for file: URLs that express relative paths and absolute Windows paths. The canonical URL generated by urllib.request.pathname2url() is now used.

gh-126992 [https://github.com/python/cpython/issues/126992]: Fix LONG and INT opcodes to only use base 10 for string to integer conversion in pickle.

gh-126997 [https://github.com/python/cpython/issues/126997]: Fix support of STRING and GLOBAL opcodes with non-ASCII arguments in pickletools. pickletools.dis() now outputs non-ASCII bytes in STRING, BINSTRING and SHORT_BINSTRING arguments as escaped (\xXX).

gh-126316 [https://github.com/python/cpython/issues/126316]: grp: Make grp.getgrall() thread-safe by adding a mutex. Patch by Victor Stinner.

gh-126618 [https://github.com/python/cpython/issues/126618]: Fix the representation of itertools.count objects when the count value is sys.maxsize.

gh-126615 [https://github.com/python/cpython/issues/126615]: The COMError exception is now public. Previously, this was private and only available in _ctypes.

gh-126985 [https://github.com/python/cpython/issues/126985]: When running under a virtual environment with the site disabled (see -S), sys.prefix and sys.base_prefix will now point to the virtual environment, instead of the base installation.

gh-112192 [https://github.com/python/cpython/issues/112192]: In the trace module, increase the coverage precision (cov%) to one decimal.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of mimetypes by around 11-16 times. Patch by Hugo van Kemenade.

gh-126947 [https://github.com/python/cpython/issues/126947]: Raise TypeError in _pydatetime.timedelta.__new__() if the passed arguments are not int or float, so that the Python implementation is in line with the C implementation.

gh-126946 [https://github.com/python/cpython/issues/126946]: Improve the GetoptError error message when a long option prefix matches multiple accepted options in getopt.getopt() and getopt.gnu_getopt().

gh-126899 [https://github.com/python/cpython/issues/126899]: Make tkinter widget methods after() and after_idle() accept arguments passed by keyword.

gh-85168 [https://github.com/python/cpython/issues/85168]: Fix issue where urllib.request.url2pathname() and pathname2url() always used UTF-8 when quoting and unquoting file URIs. They now use the filesystem encoding and error handler.

gh-126780 [https://github.com/python/cpython/issues/126780]: Fix os.path.normpath() for drive-relative paths on Windows.

gh-126775 [https://github.com/python/cpython/issues/126775]: Make linecache.checkcache() thread safe and GC re-entrancy safe.

gh-126601 [https://github.com/python/cpython/issues/126601]: Fix issue where urllib.request.pathname2url() raised OSError when given a Windows path containing a colon character not following a drive letter, such as before an NTFS alternate data stream.

gh-126727 [https://github.com/python/cpython/issues/126727]: locale.nl_langinfo(locale.ERA) now returns multiple era description segments separated by semicolons. Previously it only returned the first segment on platforms with Glibc.

gh-85046 [https://github.com/python/cpython/issues/85046]: Add EHWPOISON error code to errno.

gh-118201 [https://github.com/python/cpython/issues/118201]: Fixed intermittent failures of os.confstr, os.pathconf and os.sysconf on iOS and Android.

gh-86463 [https://github.com/python/cpython/issues/86463]: The usage parameter of argparse.ArgumentParser no longer affects the default value of the prog parameter in subparsers.

gh-124008 [https://github.com/python/cpython/issues/124008]: Fix possible crash (in debug build), incorrect output or returning incorrect value from raw binary write() when writing to console on Windows.

gh-123401 [https://github.com/python/cpython/issues/123401]: The http.cookies module now supports parsing obsolete RFC 850 [https://datatracker.ietf.org/doc/html/rfc850.html] date formats, in accordance with RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html] requirements. Patch by Nano Zheng.

gh-122431 [https://github.com/python/cpython/issues/122431]: readline.append_history_file() now raises a ValueError when given a negative value.

gh-122356 [https://github.com/python/cpython/issues/122356]: Guarantee that the position of a file-like object passed to zipfile.is_zipfile() is left untouched after the call. Patch by Bénédikt Tran.

gh-122288 [https://github.com/python/cpython/issues/122288]: Improve the performances of fnmatch.translate() by a factor 1.7. Patch by Bénédikt Tran.

gh-88110 [https://github.com/python/cpython/issues/88110]: Fixed multiprocessing.Process reporting a .exitcode of 1 even on success when using the "fork" start method while using a concurrent.futures.ThreadPoolExecutor.

gh-97514 [https://github.com/python/cpython/issues/97514]: Authentication was added to the multiprocessing forkserver start method control socket so that only processes with the authentication key generated by the process that spawned the forkserver can control it. This is an enhancement over the other gh-97514 [https://github.com/python/cpython/issues/97514] fixes so that access is no longer limited only by filesystem permissions.

The file descriptor exchange of control pipes with the forked worker process now requires an explicit acknowledgement byte to be sent over the socket after the exchange on all forkserver supporting platforms. That makes testing the above much easier.

Documentation

gh-127347 [https://github.com/python/cpython/issues/127347]: Publicly expose traceback.print_list() in traceback.__all__.

Core and Builtins

gh-127740 [https://github.com/python/cpython/issues/127740]: Fix error message in bytes.fromhex() when given an odd number of digits to properly indicate that an even number of hexadecimal digits is required.

gh-127058 [https://github.com/python/cpython/issues/127058]: PySequence_Tuple now creates the resulting tuple atomically, preventing partially created tuples being visible to the garbage collector or through gc.get_referrers()

gh-127599 [https://github.com/python/cpython/issues/127599]: Fix statistics for increments of object reference counts (in particular, when a reference count was increased by more than 1 in a single operation).

gh-127651 [https://github.com/python/cpython/issues/127651]: When raising ImportError for missing symbols in from imports, use __file__ in the error message if __spec__.origin is not a location

gh-127582 [https://github.com/python/cpython/issues/127582]: Fix non-thread-safe object resurrection when calling finalizers and watcher callbacks in the free threading build.

gh-127434 [https://github.com/python/cpython/issues/127434]: The iOS compiler shims can now accept arguments with spaces.

gh-127536 [https://github.com/python/cpython/issues/127536]: Add missing locks around some list assignment operations in the free threading build.

gh-127085 [https://github.com/python/cpython/issues/127085]: Fix race when exporting a buffer from a memoryview object on the free-threaded build.

gh-127238 [https://github.com/python/cpython/issues/127238]: Correct error message for sys.set_int_max_str_digits().

gh-113841 [https://github.com/python/cpython/issues/113841]: Fix possible undefined behavior division by zero in complex's _Py_c_pow().

Library

gh-127133 [https://github.com/python/cpython/issues/127133]: Calling argparse.ArgumentParser.add_argument_group() on an argument group, and calling argparse.ArgumentParser.add_argument_group() or argparse.ArgumentParser.add_mutually_exclusive_group() on a mutually exclusive group now raise exceptions. This nesting was never supported, often failed to work correctly, and was unintentionally exposed through inheritance. This functionality has been deprecated since Python 3.11.

Core and Builtins

gh-126491 [https://github.com/python/cpython/issues/126491]: Add a marking phase to the GC. All objects that can be transitively reached from builtin modules or the stacks are marked as reachable before cycle detection. This reduces the amount of work done by the GC by approximately half.

gh-127020 [https://github.com/python/cpython/issues/127020]: Fix a crash in the free threading build when PyCode_GetCode(), PyCode_GetVarnames(), PyCode_GetCellvars(), or PyCode_GetFreevars() were called from multiple threads at the same time.

gh-127010 [https://github.com/python/cpython/issues/127010]: Simplify GC tracking of dictionaries. All dictionaries are tracked when created, rather than being lazily tracked when a trackable object was added to them. This simplifies the code considerably and results in a slight speedup.

gh-126980 [https://github.com/python/cpython/issues/126980]: Fix __buffer__() of bytearray crashing when READ or WRITE are passed as flags.

gh-126937 [https://github.com/python/cpython/issues/126937]: Fix TypeError when a ctypes.Structure has a field size that doesn't fit into an unsigned 16-bit integer. Instead, the maximum number of bits is sys.maxsize.

gh-126868 [https://github.com/python/cpython/issues/126868]: Increase performance of int by adding a freelist for compact ints.

gh-126881 [https://github.com/python/cpython/issues/126881]: Fix crash in finalization of dtoa state. Patch by Kumar Aditya.

gh-126892 [https://github.com/python/cpython/issues/126892]: Require cold or invalidated code to "warm up" before being JIT compiled again.

gh-126091 [https://github.com/python/cpython/issues/126091]: Ensure stack traces are complete when throwing into a generator chain that ends in a custom generator.

gh-126024 [https://github.com/python/cpython/issues/126024]: Optimize decoding of short UTF-8 sequences containing non-ASCII characters by approximately 15%.

gh-125420 [https://github.com/python/cpython/issues/125420]: Add memoryview.index() to memoryview objects. Patch by Bénédikt Tran.

gh-125420 [https://github.com/python/cpython/issues/125420]: Add memoryview.count() to memoryview objects. Patch by Bénédikt Tran.

gh-124470 [https://github.com/python/cpython/issues/124470]: Fix crash in free-threaded builds when replacing object dictionary while reading attribute on another thread

gh-69639 [https://github.com/python/cpython/issues/69639]: Implement mixed-mode arithmetic rules combining real and complex numbers as specified by C standards since C99. Patch by Sergey B Kirpichev.

gh-120010 [https://github.com/python/cpython/issues/120010]: Correct invalid corner cases which resulted in (nan+nanj) output in complex multiplication, e.g., (1e300+1j)*(nan+infj). Patch by Sergey B Kirpichev.

gh-109746 [https://github.com/python/cpython/issues/109746]: If _thread.start_new_thread() fails to start a new thread, it deletes its state from interpreter and thus avoids its repeated cleanup on finalization.

C API

gh-127896 [https://github.com/python/cpython/issues/127896]: The previously undocumented function PySequence_In() is soft deprecated. Use PySequence_Contains() instead.

gh-127791 [https://github.com/python/cpython/issues/127791]: Fix loss of callbacks after more than one call to PyUnstable_AtExit().

gh-127691 [https://github.com/python/cpython/issues/127691]: The Unicode Exception Objects C API now raises a TypeError if its exception argument is not a UnicodeError object. Patch by Bénédikt Tran.

gh-123378 [https://github.com/python/cpython/issues/123378]: Ensure that the value of UnicodeEncodeError.end retrieved by PyUnicodeEncodeError_GetEnd() lies in [min(1, objlen), max(min(1, objlen), objlen)] where objlen is the length of UnicodeEncodeError.object. Similar arguments apply to UnicodeDecodeError and UnicodeTranslateError and their corresponding C interface. Patch by Bénédikt Tran.

gh-127314 [https://github.com/python/cpython/issues/127314]: Improve error message when calling the C API without an active thread state on the free-threaded build.

gh-123378 [https://github.com/python/cpython/issues/123378]: Ensure that the value of UnicodeEncodeError.start retrieved by PyUnicodeEncodeError_GetStart() lies in [0, max(0, objlen - 1)] where objlen is the length of UnicodeEncodeError.object. Similar arguments apply to UnicodeDecodeError and UnicodeTranslateError and their corresponding C interface. Patch by Bénédikt Tran.

gh-109523 [https://github.com/python/cpython/issues/109523]: Reading text from a non-blocking stream with read may now raise a BlockingIOError if the operation cannot immediately return bytes.

gh-102471 [https://github.com/python/cpython/issues/102471]: Add a new import and export API for Python int objects (PEP 757 [https://peps.python.org/pep-0757/]):

PyLong_GetNativeLayout();

PyLong_Export();

PyLong_FreeExport();

PyLongWriter_Create();

PyLongWriter_Finish();

PyLongWriter_Discard().

Patch by Victor Stinner.

gh-121058 [https://github.com/python/cpython/issues/121058]: PyThreadState_Clear() now warns (and calls sys.excepthook) if the thread state still has an active exception.

Build

gh-127865 [https://github.com/python/cpython/issues/127865]: Fix build failure on systems without thread-locals support.

gh-127629 [https://github.com/python/cpython/issues/127629]: Emscripten builds now include ctypes support.

gh-127111 [https://github.com/python/cpython/issues/127111]: Updated the Emscripten web example to use ES6 modules and be built into a distinct web_example subfolder.

gh-115869 [https://github.com/python/cpython/issues/115869]: Make jit_stencils.h (which is produced during JIT builds) reproducible.

gh-126898 [https://github.com/python/cpython/issues/126898]: The Emscripten build of Python is now based on ES6 modules.

Python 3.14.0 alpha 2

Release date: 2024-11-19

Windows

gh-126911 [https://github.com/python/cpython/issues/126911]: Update credits command output.

gh-118973 [https://github.com/python/cpython/issues/118973]: Ensures the experimental free-threaded install includes the _tkinter module. The optional Tcl/Tk component must also be installed in order for the module to work.

gh-126497 [https://github.com/python/cpython/issues/126497]: Fixes venv failure due to missing redirector executables in experimental free-threaded installs.

gh-126074 [https://github.com/python/cpython/issues/126074]: Removed unnecessary DLLs from Windows embeddable package

gh-125315 [https://github.com/python/cpython/issues/125315]: Avoid crashing in platform due to slow WMI calls on some Windows machines.

gh-126084 [https://github.com/python/cpython/issues/126084]: Fix venvwlauncher to launch pythonw instead of python so no extra console window is created.

gh-125842 [https://github.com/python/cpython/issues/125842]: Fix a SystemError when sys.exit() is called with 0xffffffff on Windows.

gh-125550 [https://github.com/python/cpython/issues/125550]: Enable the Python 安裝管理員 to detect Python 3.14 installs from the Windows Store.

gh-123803 [https://github.com/python/cpython/issues/123803]: All Windows code pages are now supported as "cpXXX" codecs on Windows.

Tools/Demos

gh-126807 [https://github.com/python/cpython/issues/126807]: Fix extraction warnings in pygettext.py caused by mistaking function definitions for function calls.

gh-126167 [https://github.com/python/cpython/issues/126167]: The iOS testbed was modified so that it can be used by third-party projects for testing purposes.

Tests

gh-126909 [https://github.com/python/cpython/issues/126909]: Fix test_os extended attribute tests to work on filesystems with 1 KiB xattr size limit.

gh-125730 [https://github.com/python/cpython/issues/125730]: Change make test to not run GUI tests by default. Use make ci to run tests with GUI tests instead.

gh-124295 [https://github.com/python/cpython/issues/124295]: Add translation tests to the argparse module.

Security

gh-126623 [https://github.com/python/cpython/issues/126623]: Upgrade libexpat to 2.6.4

Library

gh-85957 [https://github.com/python/cpython/issues/85957]: Add missing MIME types for images with RFCs: emf, fits, g3fax, jp2, jpm, jpx, t38, tiff-fx and wmf. Patch by Hugo van Kemenade.

gh-126920 [https://github.com/python/cpython/issues/126920]: Fix the prefix and exec_prefix keys from sysconfig.get_config_vars() incorrectly having the same value as sys.base_prefix and sys.base_exec_prefix, respectively, inside virtual environments. They now accurately reflect sys.prefix and sys.exec_prefix.

gh-67877 [https://github.com/python/cpython/issues/67877]: Fix memory leaks when regular expression matching terminates abruptly, either because of a signal or because memory allocation fails.

gh-125063 [https://github.com/python/cpython/issues/125063]: marshal now supports slice objects. The marshal format version was increased to 5.

gh-126789 [https://github.com/python/cpython/issues/126789]: Fixed the values of sysconfig.get_config_vars(), sysconfig.get_paths(), and their siblings when the site initialization happens after sysconfig has built a cache for sysconfig.get_config_vars().

gh-126188 [https://github.com/python/cpython/issues/126188]: Update bundled pip to 24.3.1

gh-126766 [https://github.com/python/cpython/issues/126766]: Fix issue where urllib.request.url2pathname() failed to discard two leading slashes introducing an empty authority section.

gh-126705 [https://github.com/python/cpython/issues/126705]: Allow os.PathLike to be a base for Protocols.

gh-126699 [https://github.com/python/cpython/issues/126699]: Allow collections.abc.AsyncIterator to be a base for Protocols.

gh-126654 [https://github.com/python/cpython/issues/126654]: Fix crash when non-dict was passed to several functions in _interpreters module.

gh-104745 [https://github.com/python/cpython/issues/104745]: Limit starting a patcher (from unittest.mock.patch() or unittest.mock.patch.object()) more than once without stopping it

gh-126595 [https://github.com/python/cpython/issues/126595]: Fix a crash when instantiating itertools.count with an initial count of sys.maxsize on debug builds. Patch by Bénédikt Tran.

gh-120423 [https://github.com/python/cpython/issues/120423]: Fix issue where urllib.request.pathname2url() mishandled Windows paths with embedded forward slashes.

gh-126565 [https://github.com/python/cpython/issues/126565]: Improve performances of zipfile.Path.open() for non-reading modes.

gh-126505 [https://github.com/python/cpython/issues/126505]: Fix bugs in compiling case-insensitive regular expressions with character classes containing non-BMP characters: upper-case non-BMP character did was ignored and the ASCII flag was ignored when matching a character range whose upper bound is beyond the BMP region.

gh-117378 [https://github.com/python/cpython/issues/117378]: Fixed the multiprocessing "forkserver" start method forkserver process to correctly inherit the parent's sys.path during the importing of multiprocessing.set_forkserver_preload() modules in the same manner as sys.path is configured in workers before executing work items.

This bug caused some forkserver module preloading to silently fail to preload. This manifested as a performance degradation in child processes when the sys.path was required due to additional repeated work in every worker.

It could also have a side effect of "" remaining in sys.path during forkserver preload imports instead of the absolute path from os.getcwd() at multiprocessing import time used in the worker sys.path.

The sys.path differences between phases in the child process could potentially have caused preload to import incorrect things from the wrong location. We are unaware of that actually having happened in practice.

gh-125679 [https://github.com/python/cpython/issues/125679]: The multiprocessing.Lock and multiprocessing.RLock repr values no longer say "unknown" on macOS.

gh-126476 [https://github.com/python/cpython/issues/126476]: Raise calendar.IllegalMonthError (now a subclass of IndexError) for calendar.month() when the input month is not correct.

gh-126489 [https://github.com/python/cpython/issues/126489]: The Python implementation of pickle no longer calls pickle.Pickler.persistent_id() for the result of persistent_id().

gh-126451 [https://github.com/python/cpython/issues/126451]: Register the contextvars.Context type to collections.abc.Mapping.

gh-126175 [https://github.com/python/cpython/issues/126175]: Add msg, doc, pos, lineno and colno attributes to tomllib.TOMLDecodeError. Deprecate instantiating with free-form arguments.

gh-89416 [https://github.com/python/cpython/issues/89416]: Add RFC 9559 [https://datatracker.ietf.org/doc/html/rfc9559.html] MIME types for Matroska audiovisual container formats. Patch by Hugo van Kemenade.

gh-126417 [https://github.com/python/cpython/issues/126417]: Register the multiprocessing.managers.DictProxy and multiprocessing.managers.ListProxy types in multiprocessing.managers to collections.abc.MutableMapping and collections.abc.MutableSequence, respectively.

gh-126390 [https://github.com/python/cpython/issues/126390]: Add support for returning intermixed options and non-option arguments in order in getopt.gnu_getopt().

gh-126374 [https://github.com/python/cpython/issues/126374]: Add support for options with optional arguments in the getopt module.

gh-126363 [https://github.com/python/cpython/issues/126363]: Speed up pattern parsing in pathlib.Path.glob() by skipping creation of a pathlib.Path object for the pattern.

gh-126353 [https://github.com/python/cpython/issues/126353]: asyncio.get_event_loop() now does not implicitly creates an event loop. It now raises a RuntimeError if there is no set event loop. Patch by Kumar Aditya.

gh-126313 [https://github.com/python/cpython/issues/126313]: Fix an issue in curses.napms() when curses.initscr() has not yet been called. Patch by Bénédikt Tran.

gh-126303 [https://github.com/python/cpython/issues/126303]: Fix pickling and copying of os.sched_param objects.

gh-126138 [https://github.com/python/cpython/issues/126138]: Fix a use-after-free crash on asyncio.Task objects whose underlying coroutine yields an object that implements an evil __getattribute__(). Patch by Nico Posada.

gh-120057 [https://github.com/python/cpython/issues/120057]: Replace the os.environ.refresh() method with a new os.reload_environ() function. Patch by Victor Stinner.

gh-126220 [https://github.com/python/cpython/issues/126220]: Fix crash in cProfile.Profile and _lsprof.Profiler when their callbacks were directly called with 0 arguments.

gh-126212 [https://github.com/python/cpython/issues/126212]: Fix issue where urllib.request.pathname2url() and url2pathname() removed slashes from Windows DOS drive paths and URLs.

gh-126223 [https://github.com/python/cpython/issues/126223]: Raise a UnicodeEncodeError instead of a SystemError upon calling _interpreters.create() with an invalid Unicode character.

gh-126205 [https://github.com/python/cpython/issues/126205]: Fix issue where urllib.request.pathname2url() generated URLs beginning with four slashes (rather than two) when given a Windows UNC path.

gh-126156 [https://github.com/python/cpython/issues/126156]: Improved performances of creating Morsel objects by a factor of 3.8x.

gh-126105 [https://github.com/python/cpython/issues/126105]: Fix a crash in ast when the ast.AST._fields attribute is deleted.

gh-126106 [https://github.com/python/cpython/issues/126106]: Fixes a possible NULL pointer dereference in ssl.

gh-126080 [https://github.com/python/cpython/issues/126080]: Fix a use-after-free crash on asyncio.Task objects for which the underlying event loop implements an evil __getattribute__(). Reported by Nico-Posada. Patch by Bénédikt Tran.

gh-125322 [https://github.com/python/cpython/issues/125322]: Correct detection of complex numbers support in libffi.

gh-126083 [https://github.com/python/cpython/issues/126083]: Fixed a reference leak in asyncio.Task objects when reinitializing the same object with a non-None context. Patch by Nico Posada.

gh-126068 [https://github.com/python/cpython/issues/126068]: Fix exceptions in the argparse module so that only error messages for ArgumentError and ArgumentTypeError are now translated. ArgumentError is now only used for command line errors, not for logical errors in the program. TypeError is now raised instead of ValueError for some logical errors.

gh-125413 [https://github.com/python/cpython/issues/125413]: Add pathlib.Path.scandir() method to efficiently fetch directory children and their file attributes. This is a trivial wrapper of os.scandir().

gh-125984 [https://github.com/python/cpython/issues/125984]: Fix use-after-free crashes on asyncio.Future objects for which the underlying event loop implements an evil __getattribute__(). Reported by Nico-Posada. Patch by Bénédikt Tran.

gh-125926 [https://github.com/python/cpython/issues/125926]: Fix urllib.parse.urljoin() for base URI with undefined authority. Although RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html] only specify reference resolution for absolute base URI, urljoin() should continue to return sensible result for relative base URI.

gh-125969 [https://github.com/python/cpython/issues/125969]: Fix an out-of-bounds crash when an evil asyncio.loop.call_soon() mutates the length of the internal callbacks list. Patch by Bénédikt Tran.

gh-125966 [https://github.com/python/cpython/issues/125966]: Fix a use-after-free crash in asyncio.Future.remove_done_callback(). Patch by Bénédikt Tran.

gh-125789 [https://github.com/python/cpython/issues/125789]: Fix possible crash when mutating list of callbacks returned by asyncio.Future._callbacks. It now always returns a new copy in C implementation _asyncio. Patch by Kumar Aditya.

gh-126916 [https://github.com/python/cpython/issues/126916]: Allow the initial parameter of functools.reduce() to be passed as a keyword argument. Patch by Sayandip Dutta.

gh-124452 [https://github.com/python/cpython/issues/124452]: Fix an issue in email.policy.EmailPolicy.header_source_parse() and email.policy.Compat32.header_source_parse() that introduced spurious leading whitespaces into header values when the header includes a newline character after the header name delimiter (:) and before the value.

gh-117941 [https://github.com/python/cpython/issues/117941]: argparse.BooleanOptionalAction now rejects option names starting with --no-.

gh-125884 [https://github.com/python/cpython/issues/125884]: Fixed the bug for pdb where it can't set breakpoints on functions with certain annotations.

gh-125355 [https://github.com/python/cpython/issues/125355]: Fix several bugs in argparse.ArgumentParser.parse_intermixed_args().

The parser no longer changes temporarily during parsing.

Default values are not processed twice.

Required mutually exclusive groups containing positional arguments are now supported.

The missing arguments report now includes the names of all required optional and positional arguments.

Unknown options can be intermixed with positional arguments in parse_known_intermixed_args().

gh-125767 [https://github.com/python/cpython/issues/125767]: super objects are now pickleable and copyable.

gh-124969 [https://github.com/python/cpython/issues/124969]: locale.nl_langinfo(locale.ALT_DIGITS) now returns a string again. The returned value consists of up to 100 semicolon-separated symbols.

gh-84850 [https://github.com/python/cpython/issues/84850]: Remove URLopener and FancyURLopener classes from urllib.request. They had previously raised DeprecationWarning since Python 3.3.

gh-125666 [https://github.com/python/cpython/issues/125666]: Avoid the exiting the interpreter if a null byte is given as input in the new REPL.

gh-125710 [https://github.com/python/cpython/issues/125710]: [Enum] fix hashable<->nonhashable comparisons for member values

gh-125631 [https://github.com/python/cpython/issues/125631]: Restore ability to set persistent_id and persistent_load attributes of instances of the Pickler and Unpickler classes in the pickle module.

gh-125378 [https://github.com/python/cpython/issues/125378]: Fixed the bug in pdb where after a multi-line command, an empty line repeats the first line of the multi-line command, instead of the full command.

gh-125682 [https://github.com/python/cpython/issues/125682]: Reject non-ASCII digits in the Python implementation of json.loads() conforming to the JSON specification.

gh-125660 [https://github.com/python/cpython/issues/125660]: Reject invalid unicode escapes for Python implementation of json.loads().

gh-52551 [https://github.com/python/cpython/issues/52551]: Use wcsftime() to implement time.strftime() on Windows.

gh-125259 [https://github.com/python/cpython/issues/125259]: Fix the notes removal logic for errors thrown in enum initialization.

gh-125633 [https://github.com/python/cpython/issues/125633]: Add function inspect.ispackage() to determine whether an object is a package or not.

gh-125614 [https://github.com/python/cpython/issues/125614]: In the FORWARDREF format of annotationlib, fix bug where nested expressions were not returned as annotationlib.ForwardRef format.

gh-125590 [https://github.com/python/cpython/issues/125590]: Allow FrameLocalsProxy to delete and pop if the key is not a fast variable.

gh-125600 [https://github.com/python/cpython/issues/125600]: Only show stale code warning in pdb when we display source code.

gh-125542 [https://github.com/python/cpython/issues/125542]: Deprecate passing keyword-only prefix_chars argument to argparse.ArgumentParser.add_argument_group().

gh-125541 [https://github.com/python/cpython/issues/125541]: Pressing Ctrl-C while blocked in threading.Lock.acquire(), threading.RLock.acquire(), and threading.Thread.join() now interrupts the function call and raises a KeyboardInterrupt exception on Windows, similar to how those functions behave on macOS and Linux.

gh-125519 [https://github.com/python/cpython/issues/125519]: Improve traceback if importlib.reload() is called with an object that is not a module. Patch by Alex Waygood.

gh-125451 [https://github.com/python/cpython/issues/125451]: Fix deadlock when concurrent.futures.ProcessPoolExecutor shuts down concurrently with an error when feeding a job to a worker process.

gh-125115 [https://github.com/python/cpython/issues/125115]: Fixed a bug in pdb where arguments starting with - can't be passed to the debugged script.

gh-125398 [https://github.com/python/cpython/issues/125398]: Fix the conversion of the VIRTUAL_ENV path in the activate script in venv when running in Git Bash for Windows.

gh-125245 [https://github.com/python/cpython/issues/125245]: Fix race condition when importing collections.abc, which could incorrectly return an empty module.

gh-52551 [https://github.com/python/cpython/issues/52551]: Fix encoding issues in time.strftime(), the strftime() method of the datetime classes datetime, date and time and formatting of these classes. Characters not encodable in the current locale are now acceptable in the format string. Surrogate pairs and sequence of surrogatescape-encoded bytes are no longer recombinated. Embedded null character no longer terminates the format string.

gh-124984 [https://github.com/python/cpython/issues/124984]: Fixed thread safety in ssl in the free-threaded build. OpenSSL operations are now protected by a per-object lock.

gh-124651 [https://github.com/python/cpython/issues/124651]: Properly quote template strings in venv activation scripts.

gh-124694 [https://github.com/python/cpython/issues/124694]: We've added concurrent.futures.InterpreterPoolExecutor, which allows you to run code in multiple isolated interpreters. This allows you to circumvent the limitations of CPU-bound threads (due to the GIL). Patch by Eric Snow.

This addition is unrelated to PEP 734 [https://peps.python.org/pep-0734/].

gh-58032 [https://github.com/python/cpython/issues/58032]: Deprecate the argparse.FileType type converter.

gh-99749 [https://github.com/python/cpython/issues/99749]: Adds a feature to optionally enable suggestions for argument choices and subparser names if mistyped by the user.

gh-58956 [https://github.com/python/cpython/issues/58956]: Fixed a bug in pdb where sometimes the breakpoint won't trigger if it was set on a function which is already in the call stack.

gh-124111 [https://github.com/python/cpython/issues/124111]: The tkinter module can now be built to use either the new version 9.0.0 of Tcl/Tk or the latest release 8.6.15 of Tcl/Tk 8. Tcl/Tk 9 includes many improvements, both to the Tcl language and to the appearance and utility of the graphical user interface provided by Tk.

gh-80958 [https://github.com/python/cpython/issues/80958]: unittest discovery supports PEP 420 namespace packages as start directory again.

gh-123370 [https://github.com/python/cpython/issues/123370]: Fix the canvas not clearing after running turtledemo clock.

gh-89083 [https://github.com/python/cpython/issues/89083]: Add uuid.uuid8() for generating UUIDv8 objects as specified in RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html]. Patch by Bénédikt Tran

gh-122549 [https://github.com/python/cpython/issues/122549]: Add platform.invalidate_caches() to invalidate cached results.

gh-120754 [https://github.com/python/cpython/issues/120754]: Update unbounded read calls in zipfile to specify an explicit size putting a limit on how much data they may read. This also updates handling around ZIP max comment size to match the standard instead of reading comments that are one byte too long.

gh-121267 [https://github.com/python/cpython/issues/121267]: Improve the performance of tarfile when writing files, by caching user names and group names.

gh-70764 [https://github.com/python/cpython/issues/70764]: Fixed an issue where inspect.getclosurevars() would incorrectly classify an attribute name as a global variable when the name exists both as an attribute name and a global variable.

gh-118289 [https://github.com/python/cpython/issues/118289]: posixpath.realpath() now raises NotADirectoryError when strict mode is enabled and a non-directory path with a trailing slash is supplied.

gh-119826 [https://github.com/python/cpython/issues/119826]: Always return an absolute path for os.path.abspath() on Windows.

gh-97850 [https://github.com/python/cpython/issues/97850]: Remove deprecated pkgutil.get_loader() and pkgutil.find_loader().

gh-118986 [https://github.com/python/cpython/issues/118986]: Add socket.IPV6_RECVERR constant (available since Linux 2.2).

gh-116897 [https://github.com/python/cpython/issues/116897]: Accepting objects with false values (like 0 and []) except empty strings, byte-like objects and None in urllib.parse functions parse_qsl() and parse_qs() is now deprecated.

gh-101955 [https://github.com/python/cpython/issues/101955]: Fix SystemError when match regular expression pattern containing some combination of possessive quantifier, alternative and capture group.

gh-71936 [https://github.com/python/cpython/issues/71936]: Fix a race condition in multiprocessing.pool.Pool.

bpo-46128 [https://bugs.python.org/issue?@action=redirect&bpo=46128]: Strip unittest.IsolatedAsyncioTestCase stack frames from reported stacktraces.

gh-84852 [https://github.com/python/cpython/issues/84852]: Add MIME types for MS Embedded OpenType, OpenType Layout, TrueType, WOFF 1.0 and 2.0 fonts. Patch by Sahil Prajapati and Hugo van Kemenade.

Documentation

gh-126622 [https://github.com/python/cpython/issues/126622]: Added stub pages for removed modules explaining their removal, where to find replacements, and linking to the last Python version that supported them. Contributed by Ned Batchelder.

gh-125277 [https://github.com/python/cpython/issues/125277]: Require Sphinx 7.2.6 or later to build the Python documentation. Patch by Adam Turner.

gh-60712 [https://github.com/python/cpython/issues/60712]: Include the object type in the lists of documented types. Change by Furkan Onder and Martin Panter.

Core and Builtins

gh-126795 [https://github.com/python/cpython/issues/126795]: Increase the threshold for JIT code warmup. Depending on platform and workload, this can result in performance gains of 1-9% and memory savings of 3-5%.

gh-126341 [https://github.com/python/cpython/issues/126341]: Now ValueError is raised instead of SystemError when trying to iterate over a released memoryview object.

gh-126688 [https://github.com/python/cpython/issues/126688]: Fix a crash when calling os.fork() on some operating systems, including SerenityOS.

Library

gh-126066 [https://github.com/python/cpython/issues/126066]: Fix importlib to not write an incomplete .pyc files when a ulimit or some other operating system mechanism is preventing the write to go through fully.

Core and Builtins

gh-126222 [https://github.com/python/cpython/issues/126222]: Do not include count of "peek" items in _PyUop_num_popped. This ensures that the correct number of items are popped from the stack when a micro-op exits with an error.

gh-126366 [https://github.com/python/cpython/issues/126366]: Fix crash when using yield from on an object that raises an exception in its __iter__.

Library

gh-126209 [https://github.com/python/cpython/issues/126209]: Fix an issue with skip_file_prefixes parameter which resulted in an inconsistent behaviour between the C and Python implementations of warnings.warn(). Patch by Daehee Kim.

Core and Builtins

gh-126312 [https://github.com/python/cpython/issues/126312]: Fix crash during garbage collection on an object frozen by gc.freeze() on the free-threaded build.

gh-103951 [https://github.com/python/cpython/issues/103951]: Relax optimization requirements to allow fast attribute access to module subclasses.

gh-126072 [https://github.com/python/cpython/issues/126072]: Following gh-126101 [https://github.com/python/cpython/issues/126101], for 程式碼物件 like lambda, annotation and type alias, we no longer add None to its co_consts.

gh-126195 [https://github.com/python/cpython/issues/126195]: Improve JIT performance by 1.4% on macOS Apple Silicon by using platform-specific memory protection APIs. Patch by Diego Russo.

gh-126139 [https://github.com/python/cpython/issues/126139]: Provide better error location when attempting to use a future statement with an unknown future feature.

gh-126072 [https://github.com/python/cpython/issues/126072]: Add a new attribute in co_flags to indicate whether the first item in co_consts is the docstring. If a code object has no docstring, None will NOT be inserted.

gh-126076 [https://github.com/python/cpython/issues/126076]: Relocated objects such as tuple, bytes and str objects are properly tracked by tracemalloc and its associated hooks. Patch by Pablo Galindo.

gh-90370 [https://github.com/python/cpython/issues/90370]: Avoid temporary tuple creation for vararg in argument passing with Argument Clinic generated code (if arguments either vararg or positional-only).

gh-126018 [https://github.com/python/cpython/issues/126018]: Fix a crash in sys.audit() when passing a non-string as first argument and Python was compiled in debug mode.

gh-126012 [https://github.com/python/cpython/issues/126012]: The memoryview type now supports subscription, making it a generic type.

gh-125837 [https://github.com/python/cpython/issues/125837]: Adds LOAD_SMALL_INT and LOAD_CONST_IMMORTAL instructions. LOAD_SMALL_INT pushes a small integer equal to the oparg to the stack. LOAD_CONST_IMMORTAL does the same as LOAD_CONST but is more efficient for immortal objects. Removes RETURN_CONST instruction.

gh-125942 [https://github.com/python/cpython/issues/125942]: On Android, the errors setting of sys.stdout was changed from surrogateescape to backslashreplace.

gh-125859 [https://github.com/python/cpython/issues/125859]: Fix a crash in the free threading build when gc.get_objects() or gc.get_referrers() is called during an in-progress garbage collection.

gh-125868 [https://github.com/python/cpython/issues/125868]: It was possible in 3.14.0a1 only for attribute lookup to give the wrong value. This was due to an incorrect specialization in very specific circumstances. This is fixed in 3.14.0a2.

gh-125498 [https://github.com/python/cpython/issues/125498]: The JIT has been updated to leverage Clang 19’s new preserve_none attribute, which supports more platforms and is more useful than LLVM's existing ghccc calling convention. This also removes the need to manually patch the calling convention in LLVM IR, simplifying the JIT compilation process.

gh-125703 [https://github.com/python/cpython/issues/125703]: Correctly honour tracemalloc hooks in specialized Py_DECREF paths. Patch by Pablo Galindo

gh-125593 [https://github.com/python/cpython/issues/125593]: Use color to highlight error locations in traceback from exception group

gh-125017 [https://github.com/python/cpython/issues/125017]: Fix crash on certain accesses to the __annotations__ of staticmethod and classmethod objects.

gh-125588 [https://github.com/python/cpython/issues/125588]: The Python PEG generator can now use f-strings in the grammar actions. Patch by Pablo Galindo

gh-125444 [https://github.com/python/cpython/issues/125444]: Fix illegal instruction for older Arm architectures. Patch by Diego Russo, testing by Ross Burton.

gh-118423 [https://github.com/python/cpython/issues/118423]: Add a new INSTRUCTION_SIZE macro to the cases generator which returns the current instruction size.

gh-125038 [https://github.com/python/cpython/issues/125038]: Fix crash when iterating over a generator expression after direct changes on gi_frame.f_locals. Patch by Mikhail Efimov.

gh-124855 [https://github.com/python/cpython/issues/124855]: Don't allow the JIT and perf support to be active at the same time. Patch by Pablo Galindo

gh-123714 [https://github.com/python/cpython/issues/123714]: Update JIT compilation to use LLVM 19

gh-123930 [https://github.com/python/cpython/issues/123930]: Improve the error message when a script shadowing a module from the standard library causes ImportError to be raised during a "from" import. Similarly, improve the error message when a script shadowing a third party module attempts to "from" import an attribute from that third party module while still initialising.

gh-119793 [https://github.com/python/cpython/issues/119793]: The map() built-in now has an optional keyword-only strict flag like zip() to check that all the iterables are of equal length. Patch by Wannes Boeykens.

Library

gh-118950 [https://github.com/python/cpython/issues/118950]: Fix bug where SSLProtocol.connection_lost wasn't getting called when OSError was thrown on writing to socket.

gh-113570 [https://github.com/python/cpython/issues/113570]: Fixed a bug in reprlib.repr where it incorrectly called the repr method on shadowed Python built-in types.

C API

gh-126554 [https://github.com/python/cpython/issues/126554]: Fix error handling in ctypes.CDLL objects which could result in a crash in rare situations.

gh-126061 [https://github.com/python/cpython/issues/126061]: Add PyLong_IsPositive(), PyLong_IsNegative() and PyLong_IsZero() for checking if a PyLongObject is positive, negative, or zero, respectively.

gh-125608 [https://github.com/python/cpython/issues/125608]: Fix a bug where dictionary watchers (e.g., PyDict_Watch()) on an object's attribute dictionary (__dict__) were not triggered when the object's attributes were modified.

gh-123619 [https://github.com/python/cpython/issues/123619]: Added the PyUnstable_Object_EnableDeferredRefcount() function for enabling PEP 703 [https://peps.python.org/pep-0703/] deferred reference counting.

gh-121654 [https://github.com/python/cpython/issues/121654]: Add PyType_Freeze() function to make a type immutable. Patch by Victor Stinner.

gh-120026 [https://github.com/python/cpython/issues/120026]: The Py_HUGE_VAL macro is soft deprecated.

Build

gh-126691 [https://github.com/python/cpython/issues/126691]: Removed the --with-emscripten-target configure flag. We unified the node and browser options and the same build can now be used, independent of target runtime.

gh-123877 [https://github.com/python/cpython/issues/123877]: Use wasm32-wasip1 as the target triple for WASI instead of wasm32-wasi. The latter will eventually be reclaimed for WASI 1.0 while CPython currently only supports WASI preview1.

gh-126458 [https://github.com/python/cpython/issues/126458]: Disable SIMD support for HACL under WASI.

gh-89640 [https://github.com/python/cpython/issues/89640]: Hard-code float word ordering as little endian on WASM.

gh-126206 [https://github.com/python/cpython/issues/126206]: make clinic now runs Argument Clinic using the --force option, thus forcefully regenerating generated code.

gh-126187 [https://github.com/python/cpython/issues/126187]: Introduced Tools/wasm/emscripten.py to simplify doing Emscripten builds.

gh-124932 [https://github.com/python/cpython/issues/124932]: For cross builds, there is now support for having a different install prefix than the host_prefix used by getpath.py. This is set to / by default for Emscripten, on other platforms the default behavior is the same as before.

gh-125946 [https://github.com/python/cpython/issues/125946]: The minimum supported Android version is now 7.0 (API level 24).

gh-125940 [https://github.com/python/cpython/issues/125940]: The Android build now supports 16 KB page sizes [https://developer.android.com/guide/practices/page-sizes].

gh-89640 [https://github.com/python/cpython/issues/89640]: Improve detection of float word ordering on Linux when link-time optimizations are enabled.

gh-124928 [https://github.com/python/cpython/issues/124928]: Emscripten builds now require node >= 18.

gh-115382 [https://github.com/python/cpython/issues/115382]: Fix cross compile failures when the host and target SOABIs match.

Python 3.14.0 alpha 1

Release date: 2024-10-15

macOS

gh-124448 [https://github.com/python/cpython/issues/124448]: Update bundled Tcl/Tk in macOS installer to 8.6.15.

gh-123797 [https://github.com/python/cpython/issues/123797]: Check for runtime availability of ptsname_r function on macos.

gh-123418 [https://github.com/python/cpython/issues/123418]: Updated macOS installer build to use OpenSSL 3.0.15.

Windows

gh-124487 [https://github.com/python/cpython/issues/124487]: Increases Windows required OS and API level to Windows 10.

gh-124609 [https://github.com/python/cpython/issues/124609]: Fix _Py_ThreadId for Windows builds using MinGW. Patch by Tony Roberts.

gh-124448 [https://github.com/python/cpython/issues/124448]: Updated bundled Tcl/Tk to 8.6.15.

gh-124254 [https://github.com/python/cpython/issues/124254]: Ensures experimental free-threaded binaries remain installed when updating.

gh-123915 [https://github.com/python/cpython/issues/123915]: Ensure that Tools\msi\buildrelease.bat uses different directories for AMD64 and ARM64 builds.

gh-123418 [https://github.com/python/cpython/issues/123418]: Updated Windows build to use OpenSSL 3.0.15.

gh-123476 [https://github.com/python/cpython/issues/123476]: Add support for socket.TCP_QUICKACK on Windows platforms.

gh-122573 [https://github.com/python/cpython/issues/122573]: The Windows build of CPython now requires 3.10 or newer.

gh-100256 [https://github.com/python/cpython/issues/100256]: mimetypes no longer fails when it encounters an inaccessible registry key.

gh-119679 [https://github.com/python/cpython/issues/119679]: Ensures correct import libraries are included in Windows installs.

gh-119690 [https://github.com/python/cpython/issues/119690]: Adds Unicode support and fixes audit events for _winapi.CreateNamedPipe.

gh-111201 [https://github.com/python/cpython/issues/111201]: Add support for new pyrepl on Windows

gh-119070 [https://github.com/python/cpython/issues/119070]: Fixes py.exe handling of shebangs like /usr/bin/env python3.12, which were previously interpreted as python3.exe instead of python3.12.exe.

gh-117505 [https://github.com/python/cpython/issues/117505]: Fixes an issue with the Windows installer not running ensurepip in a fully isolated environment. This could cause unexpected interactions with the user site-packages.

gh-118209 [https://github.com/python/cpython/issues/118209]: Avoid crashing in mmap on Windows when the mapped memory is inaccessible due to file system errors or access violations.

gh-79846 [https://github.com/python/cpython/issues/79846]: Makes ssl.create_default_context() ignore invalid certificates in the Windows certificate store

Tools/Demos

gh-123418 [https://github.com/python/cpython/issues/123418]: Update GitHub CI workflows to use OpenSSL 3.0.15 and multissltests to use 3.0.15, 3.1.7, and 3.2.3.

Tests

gh-125041 [https://github.com/python/cpython/issues/125041]: Re-enable skipped tests for zlib on the s390x architecture: only skip checks of the compressed bytes, which can be different between zlib's software implementation and the hardware-accelerated implementation.

gh-124378 [https://github.com/python/cpython/issues/124378]: Updated test_ttk to pass with Tcl/Tk 8.6.15.

gh-124213 [https://github.com/python/cpython/issues/124213]: Detect whether the test suite is running inside a systemd-nspawn container with --suppress-sync=true option, and skip the test_os and test_mmap tests that are failing in this scenario.

gh-124190 [https://github.com/python/cpython/issues/124190]: Add capability to ignore entire files or directories in check warning CI tool

gh-121921 [https://github.com/python/cpython/issues/121921]: Update Lib/test/crashers/bogus_code_obj.py so that it crashes properly again.

gh-112301 [https://github.com/python/cpython/issues/112301]: Add tooling to check for changes in compiler warnings. Patch by Nate Ohlson.

gh-59022 [https://github.com/python/cpython/issues/59022]: Add tests for pkgutil.extend_path(). Patch by Andreas Stocker.

gh-99242 [https://github.com/python/cpython/issues/99242]: os.getloadavg() may throw OSError when running regression tests under certain conditions (e.g. chroot). This error is now caught and ignored, since reporting load average is optional.

gh-121084 [https://github.com/python/cpython/issues/121084]: Fix test_typing random leaks. Clear typing ABC caches when running tests for refleaks (-R option): call _abc_caches_clear() on typing abstract classes and their subclasses. Patch by Victor Stinner.

gh-121160 [https://github.com/python/cpython/issues/121160]: Add a test for readline.set_history_length(). Note that this test may fail on readline libraries.

gh-121200 [https://github.com/python/cpython/issues/121200]: Fix test_expanduser_pwd2() of test_posixpath. Call getpwnam() to get pw_dir, since it can be different than getpwall() pw_dir. Patch by Victor Stinner.

gh-121188 [https://github.com/python/cpython/issues/121188]: When creating the JUnit XML file, regrtest now escapes characters which are invalid in XML, such as the chr(27) control character used in ANSI escape sequences. Patch by Victor Stinner.

gh-120801 [https://github.com/python/cpython/issues/120801]: Cleaned up fixtures for importlib.metadata tests and consolidated behavior with 'test.support.os_helper'.

gh-119727 [https://github.com/python/cpython/issues/119727]: Add --single-process command line option to Python test runner (regrtest). Patch by Victor Stinner.

gh-119273 [https://github.com/python/cpython/issues/119273]: Python test runner no longer runs tests using TTY (ex: test_ioctl) in a process group (using setsid()). Previously, tests using TTY were skipped. Patch by Victor Stinner.

gh-119050 [https://github.com/python/cpython/issues/119050]: regrtest test runner: Add XML support to the refleak checker (-R option). Patch by Victor Stinner.

gh-101525 [https://github.com/python/cpython/issues/101525]: Skip test_gdb if the binary is relocated by BOLT. Patch by Donghee Na.

gh-107562 [https://github.com/python/cpython/issues/107562]: Test certificates have been updated to expire far in the future. This allows testing Y2038 with system time set to after that, so that actual Y2038 issues can be exposed, and not masked by expired certificate errors.

Security

gh-125140 [https://github.com/python/cpython/issues/125140]: Remove the current directory from sys.path when using PyREPL.

gh-123678 [https://github.com/python/cpython/issues/123678]: Upgrade libexpat to 2.6.3

gh-112301 [https://github.com/python/cpython/issues/112301]: Enable compiler options that warn of potential security vulnerabilities.

gh-122792 [https://github.com/python/cpython/issues/122792]: Changed IPv4-mapped ipaddress.IPv6Address to consistently use the mapped IPv4 address value for deciding properties. Properties which have their behavior fixed are is_multicast, is_reserved, is_link_local, is_global, and is_unspecified.

gh-112301 [https://github.com/python/cpython/issues/112301]: Add ability to ignore warnings per file with warning count in warning checking tooling. Patch by Nate Ohlson.

gh-112301 [https://github.com/python/cpython/issues/112301]: Add macOS warning tracking to warning check tooling. Patch by Nate Ohlson.

gh-122133 [https://github.com/python/cpython/issues/122133]: Authenticate the socket connection for the socket.socketpair() fallback on platforms where AF_UNIX is not available like Windows.

Patch by Gregory P. Smith <greg@krypto.org> and Seth Larson <seth@python.org>. Reported by Ellie <el@horse64.org>

gh-121957 [https://github.com/python/cpython/issues/121957]: Fixed missing audit events around interactive use of Python, now also properly firing for python -i, as well as for python -m asyncio. The events in question are cpython.run_stdin and cpython.run_startup.

gh-112301 [https://github.com/python/cpython/issues/112301]: Enable runtime protections for glibc to abort execution when unsafe behavior is encountered, for all platforms except Windows.

gh-121285 [https://github.com/python/cpython/issues/121285]: Remove backtracking from tarfile header parsing for hdrcharset, PAX, and GNU sparse headers.

gh-112301 [https://github.com/python/cpython/issues/112301]: Add default compiler options to improve security. Enable -Wimplicit-fallthrough, -fstack-protector-strong, -Wtrampolines.

gh-118773 [https://github.com/python/cpython/issues/118773]: Fixes creation of ACLs in os.mkdir() on Windows to work correctly on non-English machines.

gh-118486 [https://github.com/python/cpython/issues/118486]: os.mkdir() on Windows now accepts mode of 0o700 to restrict the new directory to the current user. This fixes CVE 2024-4030 [https://www.cve.org/CVERecord?id=CVE-2024-4030] affecting tempfile.mkdtemp() in scenarios where the base temporary directory is more permissive than the default.

Library

gh-125422 [https://github.com/python/cpython/issues/125422]: Fixed the bug where pdb and bdb can step into the bottom caller frame.

gh-100141 [https://github.com/python/cpython/issues/100141]: Fixed the bug where pdb will be stuck in an infinite loop when debugging an empty file.

gh-53203 [https://github.com/python/cpython/issues/53203]: Fix time.strptime() for %c, %x and %X formats in many locales that use non-ASCII digits, like Persian, Burmese, Odia and Shan.

gh-125206 [https://github.com/python/cpython/issues/125206]: Workaround for old libffi versions is added. Module ctypes supports double complex only with libffi >= 3.3.0. Patch by Mikhail Efimov.

gh-89967 [https://github.com/python/cpython/issues/89967]: Make WeakKeyDictionary and WeakValueDictionary safe against concurrent mutations from other threads. Patch by Kumar Aditya.

gh-125260 [https://github.com/python/cpython/issues/125260]: The gzip.compress() mtime parameter now defaults to 0 for reproducible output. Patch by Bernhard M. Wiedemann and Adam Turner.

gh-125243 [https://github.com/python/cpython/issues/125243]: Fix data race when creating zoneinfo.ZoneInfo objects in the free threading build.

gh-125254 [https://github.com/python/cpython/issues/125254]: Fix a bug where ArgumentError includes the incorrect ambiguous option in argparse.

gh-125235 [https://github.com/python/cpython/issues/125235]: Keep tkinter TCL paths in venv pointing to base installation on Windows.

gh-61011 [https://github.com/python/cpython/issues/61011]: Fix inheritance of nested mutually exclusive groups from parent parser in argparse.ArgumentParser. Previously, all nested mutually exclusive groups lost their connection to the group containing them and were displayed as belonging directly to the parser.

gh-125118 [https://github.com/python/cpython/issues/125118]: Don't copy arbitrary values to _Bool in the struct module.

gh-125069 [https://github.com/python/cpython/issues/125069]: Fix an issue where providing a pathlib.PurePath object as an initializer argument to a second PurePath object with a different parser resulted in arguments to the former object's initializer being joined by the latter object's parser.

gh-125096 [https://github.com/python/cpython/issues/125096]: If the PYTHON_BASIC_REPL environment variable is set, the site module no longer imports the _pyrepl module. Moreover, the site module now respects -E and -I command line options: ignore PYTHON_BASIC_REPL in this case. Patch by Victor Stinner.

gh-124969 [https://github.com/python/cpython/issues/124969]: Fix locale.nl_langinfo(locale.ALT_DIGITS). Now it returns a tuple of up to 100 strings (an empty tuple on most locales). Previously it returned the first item of that tuple or an empty string.

gh-124960 [https://github.com/python/cpython/issues/124960]: Fix support for the barry_as_FLUFL future flag in the new REPL.

gh-69998 [https://github.com/python/cpython/issues/69998]: Fix locale.nl_langinfo() in case when different categories have different locales. The function now sets temporarily the LC_CTYPE locale in some cases. This temporary change affects other threads.

gh-124958 [https://github.com/python/cpython/issues/124958]: Fix refcycles in exceptions raised from asyncio.TaskGroup and the python implementation of asyncio.Future

gh-53203 [https://github.com/python/cpython/issues/53203]: Fix time.strptime() for %c and %x formats in many locales: Arabic, Bislama, Breton, Bodo, Kashubian, Chuvash, Estonian, French, Irish, Ge'ez, Gurajati, Manx Gaelic, Hebrew, Hindi, Chhattisgarhi, Haitian Kreyol, Japanese, Kannada, Korean, Marathi, Malay, Norwegian, Nynorsk, Punjabi, Rajasthani, Tok Pisin, Yoruba, Yue Chinese, Yau/Nungon and Chinese.

gh-123961 [https://github.com/python/cpython/issues/123961]: Convert curses to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]), thereby fixing reference leaks at interpreter shutdown. Patch by Bénédikt Tran.

gh-124944 [https://github.com/python/cpython/issues/124944]: Add SO_ORIGINAL_DST to the socket module.

gh-117151 [https://github.com/python/cpython/issues/117151]: The default buffer size used by shutil.copyfileobj() has been increased from 64k to 256k on non-Windows platforms. It was already larger on Windows.

gh-90102 [https://github.com/python/cpython/issues/90102]: Skip the isatty system call during open() when the file is known to not be a character device. This provides a slight performance improvement when reading whole files.

gh-124917 [https://github.com/python/cpython/issues/124917]: Allow calling os.path.exists() and os.path.lexists() with keyword arguments on Windows. Fixes a regression in 3.13.0.

gh-65865 [https://github.com/python/cpython/issues/65865]: argparse now raises early error for invalid help arguments to add_argument(), add_subparsers() and add_parser().

gh-124653 [https://github.com/python/cpython/issues/124653]: Fix detection of the minimal Queue API needed by the logging module. Patch by Bénédikt Tran.

gh-91818 [https://github.com/python/cpython/issues/91818]: The CLI of many modules (ast, ensurepip, json, pdb, sqlite3, tokenize, venv) now uses the actual executable name instead of simply "python" to display in the usage message.

gh-124858 [https://github.com/python/cpython/issues/124858]: Fix reference cycles left in tracebacks in asyncio.open_connection() when used with happy_eyeballs_delay

gh-124390 [https://github.com/python/cpython/issues/124390]: Fixed AssertionError when using asyncio.staggered.staggered_race() with asyncio.eager_task_factory.

gh-85935 [https://github.com/python/cpython/issues/85935]: argparse.ArgumentParser.add_argument() now raises an exception if an action that does not consume arguments (like 'store_const' or 'store_true') or explicit nargs=0 are specified for positional arguments.

gh-124835 [https://github.com/python/cpython/issues/124835]: Make tomllib.loads() raise TypeError not AttributeError on bad input types that do not have the replace attribute. Improve error message when bytes is received.

gh-124693 [https://github.com/python/cpython/issues/124693]: Fix a bug where argparse doesn't recognize negative complex numbers or negative numbers using scientific notation.

gh-124787 [https://github.com/python/cpython/issues/124787]: Fix typing.TypeAliasType with incorrect type_params argument. Now it raises a TypeError when a type parameter without a default follows one with a default, and when an entry in the type_params tuple is not a type parameter object.

gh-66436 [https://github.com/python/cpython/issues/66436]: Improved prog default value for argparse.ArgumentParser. It will now include the name of the Python executable along with the module or package name, or the path to a directory, ZIP file, or directory within a ZIP file if the code was run that way.

gh-116850 [https://github.com/python/cpython/issues/116850]: Fix argparse for namespaces with not directly writable dict (e.g. classes).

gh-101552 [https://github.com/python/cpython/issues/101552]: Add an annoation_format parameter to inspect.signature(). Add an quote_annotation_strings parameter to inspect.Signature.format(). Use the new functionality to improve the display of annotations in signatures in pydoc. Patch by Jelle Zijlstra.

gh-58573 [https://github.com/python/cpython/issues/58573]: Fix conflicts between abbreviated long options in the parent parser and subparsers in argparse.

gh-124594 [https://github.com/python/cpython/issues/124594]: All asyncio REPL prompts run in the same context. Contributed by Bartosz Sławecki.

gh-61181 [https://github.com/python/cpython/issues/61181]: Fix support of choices with string value in argparse. Substrings of the specified string no longer considered valid values.

gh-116750 [https://github.com/python/cpython/issues/116750]: Provide sys.monitoring.clear_tool_id() to unregister all events and callbacks set by the tool.

gh-124552 [https://github.com/python/cpython/issues/124552]: Improve the accuracy of bdb's check for the possibility of breakpoint in a frame. This makes it possible to disable unnecessary events in functions.

gh-124538 [https://github.com/python/cpython/issues/124538]: Fixed crash when using gc.get_referents() on a capsule object.

gh-80259 [https://github.com/python/cpython/issues/80259]: Fix argparse support of positional arguments with nargs='?', default=argparse.SUPPRESS and specified type.

gh-120378 [https://github.com/python/cpython/issues/120378]: Fix a crash related to an integer overflow in curses.resizeterm() and curses.resize_term().

gh-124498 [https://github.com/python/cpython/issues/124498]: Fix typing.TypeAliasType not to be generic, when type_params is an empty tuple.

gh-53834 [https://github.com/python/cpython/issues/53834]: Fix support of arguments with choices in argparse. Positional arguments with nargs equal to '?' or '*' no longer check default against choices. Optional arguments with nargs equal to '?' no longer check const against choices.

gh-123884 [https://github.com/python/cpython/issues/123884]: Fixed bug in itertools.tee() handling of other tee inputs (a tee in a tee). The output now has the promised n independent new iterators. Formerly, the first iterator was identical (not independent) to the input iterator. This would sometimes give surprising results.

gh-123017 [https://github.com/python/cpython/issues/123017]: Due to unreliable results on some devices, time.strftime() no longer accepts negative years on Android.

gh-123014 [https://github.com/python/cpython/issues/123014]: os.pidfd_open() and signal.pidfd_send_signal() are now unavailable when building against Android API levels older than 31, since the underlying system calls may cause a crash.

gh-124176 [https://github.com/python/cpython/issues/124176]: Add support for dataclasses.dataclass() in unittest.mock.create_autospec(). Now create_autospec will check for potential dataclasses and use dataclasses.fields() function to retrieve the spec information.

gh-124345 [https://github.com/python/cpython/issues/124345]: argparse supports abbreviated single-dash long options separated by = from its value.

gh-124400 [https://github.com/python/cpython/issues/124400]: Fixed a pdb bug where until has no effect when it appears in a commands sequence. Also avoid printing the frame information at a breakpoint that has a command list containing a command that resumes execution.

gh-90562 [https://github.com/python/cpython/issues/90562]: Modify dataclasses to support zero-argument super() when slots=True is specified. This works by modifying all references to __class__ to point to the newly created class.

gh-104860 [https://github.com/python/cpython/issues/104860]: Fix disallowing abbreviation of single-dash long options in argparse with allow_abbrev=False.

gh-63143 [https://github.com/python/cpython/issues/63143]: Fix parsing mutually exclusive arguments in argparse. Arguments with the value identical to the default value (e.g. booleans, small integers, empty or 1-character strings) are no longer considered "not present".

gh-72795 [https://github.com/python/cpython/issues/72795]: Positional arguments with nargs equal to '*' or argparse.REMAINDER are no longer required. This allows to use positional argument with nargs='*' and without default in mutually exclusive group and improves error message about required arguments.

gh-59317 [https://github.com/python/cpython/issues/59317]: Fix parsing positional argument with nargs equal to '?' or '*' if it is preceded by an option and another positional argument.

gh-100980 [https://github.com/python/cpython/issues/100980]: The _fields_ attribute of ctypes.Structure and Union is no longer set if the setattr operation raises an error.

gh-53780 [https://github.com/python/cpython/issues/53780]: argparse now ignores the first "--" (double dash) between an option and command.

gh-124217 [https://github.com/python/cpython/issues/124217]: Add RFC 9637 reserved IPv6 block 3fff::/20 in ipaddress module.

gh-111513 [https://github.com/python/cpython/issues/111513]: Improve the error message that may be raised by datetime.date.fromtimestamp().

gh-124248 [https://github.com/python/cpython/issues/124248]: Fixed potential crash when using struct to process zero-width 'Pascal string' fields (0p).

gh-81691 [https://github.com/python/cpython/issues/81691]: Fix handling of multiple "--" (double dashes) in argparse. Only the first one has now been removed, all subsequent ones are now taken literally.

gh-87041 [https://github.com/python/cpython/issues/87041]: Fix a bug in argparse where lengthy subparser argument help is incorrectly indented.

gh-84559 [https://github.com/python/cpython/issues/84559]: The default multiprocessing start method on Linux and other POSIX systems has been changed away from often unsafe "fork" to "forkserver" (when the platform supports sending file handles over pipes as most do) or "spawn". Mac and Windows are unchanged as they already default to "spawn".

gh-124212 [https://github.com/python/cpython/issues/124212]: Fix invalid variable in venv handling of failed symlink on Windows

gh-124171 [https://github.com/python/cpython/issues/124171]: Add workaround for broken fmod() implementations on Windows, that loose zero sign (e.g. fmod(-10, 1) returns 0.0). Patch by Sergey B Kirpichev.

gh-123978 [https://github.com/python/cpython/issues/123978]: Remove broken time.thread_time() and time.thread_time_ns() on NetBSD.

gh-123934 [https://github.com/python/cpython/issues/123934]: Fix unittest.mock.MagicMock resetting magic methods return values after .reset_mock(return_value=True) was called.

gh-124016 [https://github.com/python/cpython/issues/124016]: Update unicodedata database to Unicode 16.0.0.

gh-123968 [https://github.com/python/cpython/issues/123968]: Fix the command-line interface for the random module to select floats between 0 and N, not 1 and N.

gh-123945 [https://github.com/python/cpython/issues/123945]: Fix a bug where argparse doesn't recognize negative numbers with underscores

gh-123935 [https://github.com/python/cpython/issues/123935]: Fix parent slots detection for dataclasses that inherit from classes with __dictoffset__.

gh-123892 [https://github.com/python/cpython/issues/123892]: Add "_wmi" to sys.stdlib_module_names. Patch by Victor Stinner.

gh-84808 [https://github.com/python/cpython/issues/84808]: Fix error handling in socket method connect_ex() on platforms where errno can be negative.

gh-123756 [https://github.com/python/cpython/issues/123756]: Added a new argument mode to pdb.Pdb. Only allow pdb from command line to use restart command.

gh-122765 [https://github.com/python/cpython/issues/122765]: Fix unbalanced quote errors occurring when activate.csh in venv was sourced with a custom prompt containing unpaired quotes or newlines.

gh-123657 [https://github.com/python/cpython/issues/123657]: Fix crash and memory leak in decimal.getcontext(). It crashed when using a thread-local context by --with-decimal-contextvar=no.

gh-123339 [https://github.com/python/cpython/issues/123339]: Fix inspect.getsource() for classes in collections.abc and decimal (for pure Python implementation) modules. inspect.getcomments() now raises OSError instead of IndexError if the __firstlineno__ value for a class is out of bound.

gh-123374 [https://github.com/python/cpython/issues/123374]: Remove check for redefined memo entry in pickletools.dis().

gh-123504 [https://github.com/python/cpython/issues/123504]: Fixed reference leak in the finalization of tkinter.

gh-123430 [https://github.com/python/cpython/issues/123430]: Pages generated by the http.server module allow the browser to apply its default dark mode.

gh-123446 [https://github.com/python/cpython/issues/123446]: Fix empty function name in TypeError when csv.reader(), csv.writer(), or csv.register_dialect() are used without the required args.

gh-123448 [https://github.com/python/cpython/issues/123448]: Fixed memory leak of typing.NoDefault by moving it to the static types array.

gh-123409 [https://github.com/python/cpython/issues/123409]: Fix ipaddress.IPv6Address.reverse_pointer output according to RFC 3596, §2.5 [https://datatracker.ietf.org/doc/html/rfc3596.html#section-2.5]. Patch by Bénédikt Tran.

gh-123089 [https://github.com/python/cpython/issues/123089]: Make weakref.WeakSet safe against concurrent mutations while it is being iterated. Patch by Kumar Aditya.

gh-123363 [https://github.com/python/cpython/issues/123363]: Show string value of CONTAINS_OP oparg in dis output. Patch by Alexandr153.

gh-123341 [https://github.com/python/cpython/issues/123341]: Add __class_getitem__() to tkinter.Event for type subscript support at runtime. Patch by Adonis Rakateli.

gh-123340 [https://github.com/python/cpython/issues/123340]: Show string value of IS_OP oparg in dis output.

gh-119518 [https://github.com/python/cpython/issues/119518]: Speed up normalization of pathlib.PurePath and Path objects by not interning string parts.

gh-123270 [https://github.com/python/cpython/issues/123270]: Applied a more surgical fix for malformed payloads in zipfile.Path causing infinite loops (gh-122905 [https://github.com/python/cpython/issues/122905]) without breaking contents using legitimate characters.

gh-73991 [https://github.com/python/cpython/issues/73991]: Add pathlib.Path.copy_into() and move_into(), which copy and move files and directories into existing directories.

gh-123228 [https://github.com/python/cpython/issues/123228]: Fix return type for _pyrepl.readline._ReadlineWrapper.get_line_buffer() to be str(). Patch by Sergey B Kirpichev.

gh-123240 [https://github.com/python/cpython/issues/123240]: Raise audit events for the input() in the new REPL.

gh-76960 [https://github.com/python/cpython/issues/76960]: Fix urllib.parse.urljoin() and urllib.parse.urldefrag() for URIs containing empty components. For example, urljoin() with relative reference "?" now sets empty query and removes fragment. Preserve empty components (authority, params, query, fragment) in urljoin(). Preserve empty components (authority, params, query) in urldefrag().

gh-116810 [https://github.com/python/cpython/issues/116810]: Resolve a memory leak introduced in CPython 3.10's ssl when the ssl.SSLSocket.session property was accessed. Speeds up read and write access to said property by no longer unnecessarily cloning session objects via serialization.

gh-123243 [https://github.com/python/cpython/issues/123243]: Fix memory leak in _decimal.

gh-122546 [https://github.com/python/cpython/issues/122546]: Consistently use same file name for different exceptions in the new repl. Patch by Sergey B Kirpichev.

gh-123213 [https://github.com/python/cpython/issues/123213]: xml.etree.ElementTree.Element.extend() and Element assignment no longer hide the internal exception if an erroneous generator is passed. Patch by Bar Harel.

gh-85110 [https://github.com/python/cpython/issues/85110]: Preserve relative path in URL without netloc in urllib.parse.urlunsplit() and urllib.parse.urlunparse().

gh-123165 [https://github.com/python/cpython/issues/123165]: Add support for rendering Positions in dis.

gh-122909 [https://github.com/python/cpython/issues/122909]: In urllib.request when URLError is raised opening an ftp URL, the exception argument is now consistently a string. Earlier versions passed either a string or an ftplib exception instance as the argument to URLError.

gh-123084 [https://github.com/python/cpython/issues/123084]: Deprecate shutil.ExecError, which hasn't been raised by any shutil function since Python 3.4. It's now an alias for RuntimeError.

gh-123085 [https://github.com/python/cpython/issues/123085]: In a bare call to importlib.resources.files(), ensure the caller's frame is properly detected when importlib.resources is itself available as a compiled module only (no source).

gh-123067 [https://github.com/python/cpython/issues/123067]: Fix quadratic complexity in parsing "-quoted cookie values with backslashes by http.cookies.

gh-123049 [https://github.com/python/cpython/issues/123049]: Add support for UNNAMED_SECTION in configparser.ConfigParser.add_section().

gh-121735 [https://github.com/python/cpython/issues/121735]: When working with zip archives, importlib.resources now properly honors module-adjacent references (e.g. files(pkg.mod) and not just files(pkg)).

gh-122981 [https://github.com/python/cpython/issues/122981]: Fix inspect.getsource() for generated classes with Python base classes (e.g. enums).

gh-122903 [https://github.com/python/cpython/issues/122903]: zipfile.Path.glob now correctly matches directories instead of silently omitting them.

gh-122905 [https://github.com/python/cpython/issues/122905]: zipfile.Path objects now sanitize names from the zipfile.

gh-122873 [https://github.com/python/cpython/issues/122873]: Enable json module to work as a script using the -m switch: python -m json. See the JSON command-line interface documentation. Patch by Trey Hunner.

gh-122858 [https://github.com/python/cpython/issues/122858]: Deprecate asyncio.iscoroutinefunction() in favor of inspect.iscoroutinefunction().

gh-116263 [https://github.com/python/cpython/issues/116263]: logging.handlers.RotatingFileHandler no longer rolls over empty log files.

gh-105376 [https://github.com/python/cpython/issues/105376]: Restore the deprecated logging warn() method. It was removed in Python 3.13 alpha 1. Keep the deprecated warn() method in Python 3.13. Patch by Victor Stinner.

gh-122311 [https://github.com/python/cpython/issues/122311]: Improve errors in the pickle module. PicklingError is now raised more often instead of UnicodeEncodeError, ValueError and AttributeError, and the original exception is chained to it. Improve and unify error messages in Python and C implementations.

gh-122744 [https://github.com/python/cpython/issues/122744]: Bump the version of pip bundled in ensurepip to version 24.2.

gh-118761 [https://github.com/python/cpython/issues/118761]: Improve import time of pprint by around seven times. Patch by Hugo van Kemenade.

gh-118974 [https://github.com/python/cpython/issues/118974]: Add decorator parameter to dataclasses.make_dataclass() to customize the functional creation of dataclasses.

gh-118814 [https://github.com/python/cpython/issues/118814]: Fix the typing.TypeVar constructor when name is passed by keyword.

gh-122637 [https://github.com/python/cpython/issues/122637]: Adjust cmath.tanh(nanj) and cmath.tanh(infj) for recent C standards.

gh-122478 [https://github.com/python/cpython/issues/122478]: Remove internal frames from tracebacks shown in code.InteractiveInterpreter with non-default sys.excepthook(). Save correct tracebacks in sys.last_traceback and update __traceback__ attribute of sys.last_value and sys.last_exc.

gh-116622 [https://github.com/python/cpython/issues/116622]: On Android, the FICLONE and FICLONERANGE constants are no longer exposed by fcntl, as these ioctls are blocked by SELinux.

gh-82378 [https://github.com/python/cpython/issues/82378]: Make sure that the new REPL interprets sys.tracebacklimit in the same way that the classic REPL did.

gh-122334 [https://github.com/python/cpython/issues/122334]: Fix crash when importing ssl after the main interpreter restarts.

gh-122459 [https://github.com/python/cpython/issues/122459]: Optimize pickling by name objects without the __module__ attribute.

gh-87320 [https://github.com/python/cpython/issues/87320]: In code.InteractiveInterpreter, handle exceptions caused by calling a non-default sys.excepthook(). Before, the exception bubbled up to the caller, ending the REPL.

gh-122272 [https://github.com/python/cpython/issues/122272]: On some platforms such as Linux, year with century was not 0-padded when formatted by strftime() with C99-specific specifiers '%C' or '%F'. The 0-padding behavior is now guaranteed when the format specifiers '%C' and '%F' are supported by the C library. Patch by Ben Hsing

gh-122400 [https://github.com/python/cpython/issues/122400]: Handle ValueErrors raised by os.stat() in filecmp.dircmp and filecmp.cmpfiles(). Patch by Bénédikt Tran.

gh-122311 [https://github.com/python/cpython/issues/122311]: Fix some error messages in pickle.

gh-121650 [https://github.com/python/cpython/issues/121650]: email headers with embedded newlines are now quoted on output. The generator will now refuse to serialize (write) headers that are unsafely folded or delimited; see verify_generated_headers. (Contributed by Bas Bloemsaat and Petr Viktorin in gh-121650 [https://github.com/python/cpython/issues/121650].)

gh-122332 [https://github.com/python/cpython/issues/122332]: Fixed segfault with asyncio.Task.get_coro() when using an eager task factory.

gh-105733 [https://github.com/python/cpython/issues/105733]: ctypes.ARRAY() is now soft deprecated: it no longer emits deprecation warnings and is not scheduled for removal.

gh-122213 [https://github.com/python/cpython/issues/122213]: Add notes for pickle serialization errors that allow to identify the source of the error.

gh-119180 [https://github.com/python/cpython/issues/119180]: As part of PEP 749 [https://peps.python.org/pep-0749/], add the following attributes for customizing evaluation of annotation scopes:

evaluate_value on typing.TypeAliasType

evaluate_bound, evaluate_constraints, and evaluate_default on typing.TypeVar

evaluate_default on typing.ParamSpec

evaluate_default on typing.TypeVarTuple

gh-119180 [https://github.com/python/cpython/issues/119180]: Fix handling of classes with custom metaclasses in annotationlib.get_annotations.

gh-122170 [https://github.com/python/cpython/issues/122170]: Handle ValueErrors raised by os.stat() in linecache. Patch by Bénédikt Tran.

gh-122163 [https://github.com/python/cpython/issues/122163]: Add notes for JSON serialization errors that allow to identify the source of the error.

gh-122129 [https://github.com/python/cpython/issues/122129]: Improve support of method descriptors and wrappers in the help title.

gh-122145 [https://github.com/python/cpython/issues/122145]: Fix an issue when reporting tracebacks corresponding to Python code emitting an empty AST body. Patch by Nikita Sobolev and Bénédikt Tran.

gh-121723 [https://github.com/python/cpython/issues/121723]: Make logging.config.dictConfig() accept any object implementing the Queue public API. See the queue configuration section for details. Patch by Bénédikt Tran.

gh-82951 [https://github.com/python/cpython/issues/82951]: Serializing objects with complex __qualname__ (such as unbound methods and nested classes) by name no longer involves serializing parent objects by value in pickle protocols < 4.

gh-120754 [https://github.com/python/cpython/issues/120754]: Pathlib.read_bytes no longer opens the file in Python's buffered I/O mode. This reduces overheads as the code reads a file in whole leading to a modest speedup.

gh-113785 [https://github.com/python/cpython/issues/113785]: csv now correctly parses numeric fields (when used with csv.QUOTE_NONNUMERIC or csv.QUOTE_STRINGS) which start with an escape character.

gh-122088 [https://github.com/python/cpython/issues/122088]: @warnings.deprecated now copies the coroutine status of functions and methods so that inspect.iscoroutinefunction() returns the correct result.

gh-122081 [https://github.com/python/cpython/issues/122081]: Fix a crash in the decimal.IEEEContext() optional function available via the EXTRA_FUNCTIONALITY configuration flag.

gh-73991 [https://github.com/python/cpython/issues/73991]: Add pathlib.Path.move(), which moves a file or directory tree.

gh-121268 [https://github.com/python/cpython/issues/121268]: Remove workarounds for non-IEEE 754 systems in cmath.

gh-119698 [https://github.com/python/cpython/issues/119698]: Due to the lack of interest for symtable.Class.get_methods(), the method is marked as deprecated and will be removed in Python 3.16. Patch by Bénédikt Tran.

gh-121889 [https://github.com/python/cpython/issues/121889]: Adjusts cmath.acosh(complex('0+nanj')) for recent C standards.

gh-121804 [https://github.com/python/cpython/issues/121804]: Correctly show error locations, when SyntaxError raised in new repl. Patch by Sergey B Kirpichev.

gh-121797 [https://github.com/python/cpython/issues/121797]: Add alternative Fraction constructor Fraction.from_number().

gh-121798 [https://github.com/python/cpython/issues/121798]: Add alternative Decimal constructor Decimal.from_number().

gh-120930 [https://github.com/python/cpython/issues/120930]: Fixed a bug introduced by gh-92081 [https://github.com/python/cpython/issues/92081] that added an incorrect extra blank to encoded words occurring in wrapped headers.

gh-57141 [https://github.com/python/cpython/issues/57141]: The shallow argument to filecmp.dircmp (new in Python 3.13) is now keyword-only.

gh-121245 [https://github.com/python/cpython/issues/121245]: Simplify handling of the history file in site.register_readline() helper. The CAN_USE_PYREPL variable now will be initialized, when imported. Patch by Sergey B Kirpichev.

gh-121249 [https://github.com/python/cpython/issues/121249]: Support the float complex and double complex C types in the struct module if the compiler has C11 complex arithmetic. Patch by Sergey B Kirpichev.

gh-121486 [https://github.com/python/cpython/issues/121486]: math functions isqrt(), log(), log2() and log10() now support integers larger than 2**2**32 on 32-bit platforms.

gh-121474 [https://github.com/python/cpython/issues/121474]: Fix missing sanity check for parties arg in threading.Barrier constructor. Patch by Clinton Christian (pygeek).

gh-121450 [https://github.com/python/cpython/issues/121450]: Hard-coded breakpoints (breakpoint() and pdb.set_trace()) now reuse the most recent Pdb instance that calls Pdb.set_trace(), instead of creating a new one each time. As a result, all the instance specific data like display and commands are preserved across Hard-coded breakpoints.

gh-119169 [https://github.com/python/cpython/issues/119169]: Slightly speed up os.walk() by simplifying exception handling.

gh-121423 [https://github.com/python/cpython/issues/121423]: Improve import time of socket by lazy importing modules and writing socket.errorTab as a constant.

gh-59110 [https://github.com/python/cpython/issues/59110]: zipimport supports now namespace packages when no directory entry exists.

gh-119004 [https://github.com/python/cpython/issues/119004]: Fix a crash in OrderedDict.__eq__ when operands are mutated during the check. Patch by Bénédikt Tran.

gh-121313 [https://github.com/python/cpython/issues/121313]: Limit the reading size in the multiprocessing.connection.Connection class to 64 KiB to prevent memory overallocation and unnecessary memory management system calls.

gh-121332 [https://github.com/python/cpython/issues/121332]: Fix constructor of ast nodes with custom _attributes. Previously, passing custom attributes would raise a DeprecationWarning. Passing arguments to the constructor that are not in _fields or _attributes remains deprecated. Patch by Jelle Zijlstra.

gh-121245 [https://github.com/python/cpython/issues/121245]: Fix a bug in the handling of the command history of the new REPL that caused the history file to be wiped at REPL exit.

gh-121210 [https://github.com/python/cpython/issues/121210]: Handle AST nodes with missing runtime fields or attributes in ast.compare(). Patch by Bénédikt Tran.

gh-121163 [https://github.com/python/cpython/issues/121163]: Add support for all as an valid action for warnings.simplefilter() and warnings.filterwarnings().

gh-121151 [https://github.com/python/cpython/issues/121151]: Fix wrapping of long usage text of arguments inside a mutually exclusive group in argparse.

gh-121141 [https://github.com/python/cpython/issues/121141]: Add support for copy.replace() to AST nodes. Patch by Bénédikt Tran.

gh-87744 [https://github.com/python/cpython/issues/87744]: Fix waitpid race while calling send_signal() in asyncio. Patch by Kumar Aditya.

gh-121027 [https://github.com/python/cpython/issues/121027]: Add a future warning in functools.partial.__get__(). In future Python versions functools.partial will be a method descriptor.

gh-121027 [https://github.com/python/cpython/issues/121027]: Make the functools.partial object a method descriptor.

gh-117784 [https://github.com/python/cpython/issues/117784]: CPython now detects whether its linked TLS library supports TLSv1.3 post-handshake authentication and disables that feature if support is lacking.

gh-121025 [https://github.com/python/cpython/issues/121025]: Improve the __repr__() of functools.partialmethod. Patch by Bénédikt Tran.

gh-121018 [https://github.com/python/cpython/issues/121018]: Fixed issues where argparse.ArgumentParser.parse_args() did not honor exit_on_error=False. Based on patch by Ben Hsing.

gh-119614 [https://github.com/python/cpython/issues/119614]: Fix truncation of strings with embedded null characters in some internal operations in tkinter.

gh-120910 [https://github.com/python/cpython/issues/120910]: When reading installed files from an egg, use relative_to(walk_up=True) to honor files installed outside of the installation root.

gh-61103 [https://github.com/python/cpython/issues/61103]: Support float complex, double complex and long double complex C types in ctypes as c_float_complex, c_double_complex and c_longdouble_complex if the compiler has C11 complex arithmetic. Patch by Sergey B Kirpichev.

gh-120888 [https://github.com/python/cpython/issues/120888]: Upgrade pip wheel bundled with ensurepip (pip 24.1.1)

gh-101830 [https://github.com/python/cpython/issues/101830]: Accessing the tkinter object's string representation no longer converts the underlying Tcl object to a string on Windows.

gh-120678 [https://github.com/python/cpython/issues/120678]: Fix regression in the new REPL that meant that globals from files passed using the -i argument would not be included in the REPL's global namespace. Patch by Alex Waygood.

gh-120811 [https://github.com/python/cpython/issues/120811]: Fix possible memory leak in contextvars.Context.run().

gh-120782 [https://github.com/python/cpython/issues/120782]: Fix wrong references of the datetime types after reloading the module.

gh-120713 [https://github.com/python/cpython/issues/120713]: datetime.datetime.strftime() now 0-pads years with less than four digits for the format specifiers %Y and %G on Linux. Patch by Ben Hsing

gh-120769 [https://github.com/python/cpython/issues/120769]: Make empty line in pdb repeats the last command even when the command is from cmdqueue.

gh-120780 [https://github.com/python/cpython/issues/120780]: Show string value of LOAD_SPECIAL oparg in dis output.

gh-41431 [https://github.com/python/cpython/issues/41431]: Add datetime.time.strptime() and datetime.date.strptime(). Contributed by Wannes Boeykens.

gh-120743 [https://github.com/python/cpython/issues/120743]: Soft deprecate os.popen() and os.spawn* functions. They should no longer be used to write new code. The subprocess module is recommended instead. Patch by Victor Stinner.

gh-120732 [https://github.com/python/cpython/issues/120732]: Fix name passing to unittest.mock.Mock object when using unittest.mock.create_autospec().

gh-111259 [https://github.com/python/cpython/issues/111259]: re now handles patterns like "[\s\S]" or "\s|\S" which match any character as effectively as a dot with the DOTALL modifier ("(?s:.)").

gh-120683 [https://github.com/python/cpython/issues/120683]: Fix an error in logging.LogRecord, when the integer part of the timestamp is rounded up, while the millisecond calculation truncates, causing the log timestamp to be wrong by up to 999 ms (affected roughly 1 in 8 million timestamps).

gh-118710 [https://github.com/python/cpython/issues/118710]: ipaddress.IPv4Address and ipaddress.IPv6Address attributes version and max_prefixlen are now available on the class.

gh-120633 [https://github.com/python/cpython/issues/120633]: Move scrollbar and remove tear-off menus in turtledemo.

gh-120606 [https://github.com/python/cpython/issues/120606]: Allow users to use EOF to exit commands definition in pdb

gh-120284 [https://github.com/python/cpython/issues/120284]: Allow asyncio.Runner.run() to accept awaitable objects instead of simply coroutines.

gh-120541 [https://github.com/python/cpython/issues/120541]: Improve the prompt in the "less" pager when help() is called with non-string argument.

gh-120495 [https://github.com/python/cpython/issues/120495]: Fix incorrect exception handling in Tab Nanny. Patch by Wulian233.

gh-120388 [https://github.com/python/cpython/issues/120388]: Improve a warning message when a test method in unittest returns something other than None. Now we show the returned object type and optional asyncio-related tip.

gh-120381 [https://github.com/python/cpython/issues/120381]: Correct inspect.ismethoddescriptor() to check also for the lack of __delete__(). Patch by Jan Kaliszewski.

gh-90425 [https://github.com/python/cpython/issues/90425]: The OS byte in gzip headers is now always set to 255 when using gzip.compress().

gh-120343 [https://github.com/python/cpython/issues/120343]: Fix column offset reporting for tokens that come after multiline f-strings in the tokenize module.

gh-119180 [https://github.com/python/cpython/issues/119180]: As part of implementing PEP 649 [https://peps.python.org/pep-0649/] and PEP 749 [https://peps.python.org/pep-0749/], add a new module annotationlib. Add support for unresolved forward references in annotations to dataclasses, typing.TypedDict, and typing.NamedTuple.

gh-119600 [https://github.com/python/cpython/issues/119600]: Fix unittest.mock.patch() to not read attributes of the target when new_callable is set. Patch by Robert Collins.

gh-120289 [https://github.com/python/cpython/issues/120289]: Fixed the use-after-free issue in cProfile by disallowing disable() and clear() in external timers.

gh-82017 [https://github.com/python/cpython/issues/82017]: Added support for converting any objects that have the as_integer_ratio() method to a Fraction.

gh-114053 [https://github.com/python/cpython/issues/114053]: Fix edge-case bug where typing.get_type_hints() would produce incorrect results if type parameters in a class scope were overridden by assignments in a class scope and from __future__ import annotations semantics were enabled. Patch by Alex Waygood.

gh-114053 [https://github.com/python/cpython/issues/114053]: Fix erroneous NameError when calling inspect.get_annotations() with eval_str=True` on a class that made use of PEP 695 [https://peps.python.org/pep-0695/] type parameters in a module that had from __future__ import annotations at the top of the file. Patch by Alex Waygood.

gh-120268 [https://github.com/python/cpython/issues/120268]: Prohibit passing None to pure-Python datetime.date.fromtimestamp() to achieve consistency with C-extension implementation.

gh-120244 [https://github.com/python/cpython/issues/120244]: Fix memory leak in re.sub() when the replacement string contains backreferences.

gh-120254 [https://github.com/python/cpython/issues/120254]: Added commands argument to pdb.set_trace() which allows users to send debugger commands from the source file.

gh-120211 [https://github.com/python/cpython/issues/120211]: Fix tkinter.ttk with Tcl/Tk 9.0.

gh-71587 [https://github.com/python/cpython/issues/71587]: Fix crash in C version of datetime.datetime.strptime() when called again on the restarted interpreter.

gh-117983 [https://github.com/python/cpython/issues/117983]: Defer the threading import in importlib.util until lazy loading is used.

gh-120157 [https://github.com/python/cpython/issues/120157]: Remove unused constant concurrent.futures._base._FUTURE_STATES in concurrent.futures. Patch by Clinton Christian (pygeek).

gh-120161 [https://github.com/python/cpython/issues/120161]: datetime no longer crashes in certain complex reference cycle situations.

gh-119698 [https://github.com/python/cpython/issues/119698]: Fix symtable.Class.get_methods() and document its behaviour. Patch by Bénédikt Tran.

gh-120121 [https://github.com/python/cpython/issues/120121]: Add concurrent.futures.InvalidStateError to module's __all__.

gh-119933 [https://github.com/python/cpython/issues/119933]: Add the symtable.SymbolTableType enumeration to represent the possible outputs of the symtable.SymbolTable.get_type method. Patch by Bénédikt Tran.

gh-120029 [https://github.com/python/cpython/issues/120029]: Expose symtable.Symbol methods is_free_class(), is_comp_iter() and is_comp_cell(). Patch by Bénédikt Tran.

gh-120108 [https://github.com/python/cpython/issues/120108]: Fix calling copy.deepcopy() on ast trees that have been modified to have references to parent nodes. Patch by Jelle Zijlstra.

gh-120056 [https://github.com/python/cpython/issues/120056]: Add socket.IP_RECVERR and socket.IP_RECVTTL constants (both available since Linux 2.2). And socket.IP_RECVORIGDSTADDR constant (available since Linux 2.6.29).

gh-112672 [https://github.com/python/cpython/issues/112672]: Support building tkinter with Tcl 9.0.

gh-120057 [https://github.com/python/cpython/issues/120057]: Added the os.environ.refresh() method to update os.environ with changes to the environment made by os.putenv(), by os.unsetenv(), or made outside Python in the same process. Patch by Victor Stinner.

gh-120029 [https://github.com/python/cpython/issues/120029]: Expose symtable.Symbol.is_type_parameter() in the symtable module. Patch by Bénédikt Tran.

gh-119819 [https://github.com/python/cpython/issues/119819]: Fix regression to allow logging configuration with multiprocessing queue types.

gh-65454 [https://github.com/python/cpython/issues/65454]: unittest.mock.Mock.attach_mock() no longer triggers a call to a PropertyMock being attached.

gh-117142 [https://github.com/python/cpython/issues/117142]: The ctypes module may now be imported in all subinterpreters, including those that have their own GIL.

gh-118835 [https://github.com/python/cpython/issues/118835]: Fix _pyrepl crash when using custom prompt with ANSI escape codes.

gh-81936 [https://github.com/python/cpython/issues/81936]: help() and showtopic() methods now respect a configured output argument to pydoc.Helper and not use the pager in such cases. Patch by Enrico Tröger.

gh-117398 [https://github.com/python/cpython/issues/117398]: The _datetime module (C implementation for datetime) now supports being imported in multiple interpreters.

gh-119824 [https://github.com/python/cpython/issues/119824]: Print stack entry in pdb when and only when user input is needed.

gh-119838 [https://github.com/python/cpython/issues/119838]: In mixed arithmetic operations with Fraction and complex, the fraction is now converted to float instead of complex.

gh-119770 [https://github.com/python/cpython/issues/119770]: Make termios ioctl() constants positive. Patch by Victor Stinner.

gh-89727 [https://github.com/python/cpython/issues/89727]: Fix issue with shutil.rmtree() where a RecursionError is raised on deep directory trees.

gh-119577 [https://github.com/python/cpython/issues/119577]: The DeprecationWarning emitted when testing the truth value of an xml.etree.ElementTree.Element now describes unconditionally returning True in a future version rather than raising an exception in Python 3.14.

gh-89727 [https://github.com/python/cpython/issues/89727]: Partially fix issue with shutil.rmtree() where a RecursionError is raised on deep directory trees. A recursion error is no longer raised when rmtree.avoids_symlink_attacks is false.

gh-93963 [https://github.com/python/cpython/issues/93963]: Remove deprecated names from importlib.abc as found in importlib.resources.abc.

gh-119118 [https://github.com/python/cpython/issues/119118]: Fix performance regression in the tokenize module by caching the line token attribute and calculating the column offset more efficiently.

gh-89727 [https://github.com/python/cpython/issues/89727]: Fix issue with os.fwalk() where a RecursionError was raised on deep directory trees by adjusting the implementation to be iterative instead of recursive.

gh-119594 [https://github.com/python/cpython/issues/119594]: If one calls pow(fractions.Fraction, x, module) with modulo not None, the error message now says that the types are incompatible rather than saying pow only takes 2 arguments. Patch by Wim Jeantine-Glenn and Mark Dickinson.

gh-119588 [https://github.com/python/cpython/issues/119588]: zipfile.Path.is_symlink now assesses if the given path is a symlink.

gh-119562 [https://github.com/python/cpython/issues/119562]: Remove ast.Num, ast.Str, ast.Bytes, ast.NameConstant and ast.Ellipsis. They had all emitted deprecation warnings since Python 3.12. Patch by Alex Waygood.

gh-119555 [https://github.com/python/cpython/issues/119555]: Catch SyntaxError from compile() in the runsource() method of the InteractiveColoredConsole. Patch by Sergey B Kirpichev.

gh-118908 [https://github.com/python/cpython/issues/118908]: Limit exposed globals from internal imports and definitions on new REPL startup. Patch by Eugene Triguba and Pablo Galindo.

gh-117865 [https://github.com/python/cpython/issues/117865]: Improve the import time of the ast module by deferring the import of re. Patch by Jelle Zijlstra.

gh-119127 [https://github.com/python/cpython/issues/119127]: Positional arguments of functools.partial() objects now support placeholders via functools.Placeholder.

gh-113892 [https://github.com/python/cpython/issues/113892]: Now, the method sock_connect of asyncio.ProactorEventLoop raises a ValueError if given socket is not in non-blocking mode, as well as in other loop implementations.

gh-119506 [https://github.com/python/cpython/issues/119506]: Fix io.TextIOWrapper.write() method breaks internal buffer when the method is called again during flushing internal buffer.

gh-69214 [https://github.com/python/cpython/issues/69214]: Fix fcntl.ioctl() request parameter: use an unsigned long instead of an unsigned int for the request parameter of fcntl.ioctl() to support requests larger than UINT_MAX. Patch by Victor Stinner.

gh-119105 [https://github.com/python/cpython/issues/119105]: difflib's DIffer.compare() (and so also ndiff) can no longer be provoked into cubic-time behavior, or into unbounded recursion, and should generally be faster in ordinary cases too. Results may change in some cases, although that should be rare. Correctness of diffs is not affected. Some similar lines far apart may be reported as deleting one and adding the other, where before they were displayed on adjacent output lines with markup showing the intraline differences.

gh-119443 [https://github.com/python/cpython/issues/119443]: The interactive REPL no longer runs with from __future__ import annotations enabled. Patch by Jelle Zijlstra.

gh-119461 [https://github.com/python/cpython/issues/119461]: Add socket.VMADDR_CID_LOCAL constant. Patch by Victor Stinner.

gh-117398 [https://github.com/python/cpython/issues/117398]: Objects in the datetime C-API are now all statically allocated, which means better memory safety, especially when the module is reloaded. This should be transparent to users.

gh-118894 [https://github.com/python/cpython/issues/118894]: asyncio REPL now has the same capabilities as PyREPL.

gh-118830 [https://github.com/python/cpython/issues/118830]: Bump pickle default protocol to 5.

gh-118911 [https://github.com/python/cpython/issues/118911]: In PyREPL, updated maybe-accept's logic so that if the user hits Enter twice, they are able to terminate the block even if there's trailing whitespace. Also, now when the user hits arrow up, the cursor is on the last functional line. This matches IPython's behavior. Patch by Aya Elsayed.

gh-115225 [https://github.com/python/cpython/issues/115225]: Raise error on certain technically valid but pathological ISO 8601 strings passed to datetime.time.fromisoformat() that were previously parsed incorrectly.

gh-111201 [https://github.com/python/cpython/issues/111201]: Remove dependency to readline from the new Python REPL.

gh-119189 [https://github.com/python/cpython/issues/119189]: When using the ** operator or pow() with Fraction as the base and an exponent that is not rational, a float, or a complex, the fraction is no longer converted to a float.

gh-119174 [https://github.com/python/cpython/issues/119174]: Fix high DPI causes turtledemo(turtle-graphics examples) windows blurry Patch by Wulian233 and Terry Jan Reedy

gh-119121 [https://github.com/python/cpython/issues/119121]: Fix a NameError happening in asyncio.staggered.staggered_race. This function is now tested.

gh-119105 [https://github.com/python/cpython/issues/119105]: difflib.Differ is much faster for some cases of diffs where many pairs of lines are equally similar.

gh-119113 [https://github.com/python/cpython/issues/119113]: Fix issue where pathlib.PurePath.with_suffix() didn't raise TypeError when given None as a suffix.

gh-118643 [https://github.com/python/cpython/issues/118643]: Fix an AttributeError in the email module when re-fold a long address list. Also fix more cases of incorrect encoding of the address separator in the address list.

gh-73991 [https://github.com/python/cpython/issues/73991]: Add pathlib.Path.copy(), which copies a file or directory to another.

gh-58933 [https://github.com/python/cpython/issues/58933]: Make pdb return to caller frame correctly when f_trace of the caller frame is not set

gh-82805 [https://github.com/python/cpython/issues/82805]: Support single-dot file extensions in pathlib.PurePath.suffix and related attributes and methods. For example, the suffixes of PurePath('foo.bar.') are now ['.bar', '.'] rather than []. This brings file extension splitting in line with os.path.splitext().

gh-118924 [https://github.com/python/cpython/issues/118924]: Remove version and version_info from sqlite3. Patch by Hugo van Kemenade.

gh-118928 [https://github.com/python/cpython/issues/118928]: Disallow using a sequence of parameters with named placeholders in sqlite3 queries. Patch by Erlend E. Aasland.

gh-118895 [https://github.com/python/cpython/issues/118895]: Setting attributes on typing.NoDefault now raises AttributeError instead of TypeError.

gh-118868 [https://github.com/python/cpython/issues/118868]: Fixed issue where kwargs were no longer passed to the logging handler QueueHandler

gh-118827 [https://github.com/python/cpython/issues/118827]: Remove deprecated Quoter class from urllib.parse. It had previously raised a DeprecationWarning since Python 3.11. Patch by Nikita Sobolev.

gh-118824 [https://github.com/python/cpython/issues/118824]: Remove deprecated pty.master_open() and pty.slave_open(). Use pty.openpty() instead. Patch by Nikita Sobolev.

gh-118851 [https://github.com/python/cpython/issues/118851]: ctx arguments to the constructors of ast node classes now default to ast.Load(). Patch by Jelle Zijlstra.

gh-101588 [https://github.com/python/cpython/issues/101588]: Remove copy, deepcopy, and pickle from itertools. These had previously raised a DeprecationWarning since Python 3.12.

gh-118805 [https://github.com/python/cpython/issues/118805]: Remove type, choices, and metavar parameters of argparse.BooleanOptionalAction. They were deprecated since Python 3.12.

gh-118803 [https://github.com/python/cpython/issues/118803]: typing.ByteString and collections.abc.ByteString are removed. They had previously raised a DeprecationWarning since Python 3.12.

gh-118798 [https://github.com/python/cpython/issues/118798]: The isdst parameter has been removed from email.utils.localtime(). Patch by Hugo van Kemenade.

gh-118760 [https://github.com/python/cpython/issues/118760]: Restore the default value of tkiter.wantobjects to 1.

gh-118760 [https://github.com/python/cpython/issues/118760]: Fix errors in calling Tkinter bindings on Windows.

gh-74033 [https://github.com/python/cpython/issues/74033]: Drop support for passing keyword arguments to pathlib.Path.

gh-101357 [https://github.com/python/cpython/issues/101357]: Suppress all OSError exceptions from pathlib.Path.exists() and is_*() methods, rather than a selection of more common errors. The new behaviour is consistent with os.path.exists(), os.path.isdir(), etc. Use pathlib.Path.stat() to retrieve the file status without suppressing exceptions.

gh-78707 [https://github.com/python/cpython/issues/78707]: Drop support for passing additional positional arguments to pathlib.PurePath.relative_to() and is_relative_to().

gh-118507 [https://github.com/python/cpython/issues/118507]: Fix os.path.isfile() on Windows for pipes. Speedup os.path.isjunction() and os.path.lexists() on Windows with a native implementation.

gh-118772 [https://github.com/python/cpython/issues/118772]: Allow typing.TypeVar instances without a default to follow instances without a default in some cases. Patch by Jelle Zijlstra.

gh-118714 [https://github.com/python/cpython/issues/118714]: Allow restart in post-mortem debugging of pdb. Removed restart message when the user quits pdb from post-mortem mode.

gh-118673 [https://github.com/python/cpython/issues/118673]: Removed executable bits and shebang from stdlib modules.

gh-110863 [https://github.com/python/cpython/issues/110863]: os.path.realpath() now suppresses any OSError from os.readlink() when strict mode is disabled (the default).

gh-118263 [https://github.com/python/cpython/issues/118263]: Speed up os.path.splitroot() & os.path.normpath() with a direct C call.

gh-110190 [https://github.com/python/cpython/issues/110190]: Fix ctypes structs with array on SPARC by setting MAX_STRUCT_SIZE to 32 in stgdict. Patch by Jakub Kulik

gh-118033 [https://github.com/python/cpython/issues/118033]: Fix dataclasses.dataclass() not creating a __weakref__ slot when subclassing typing.Generic.

gh-117766 [https://github.com/python/cpython/issues/117766]: Always use str() to print choices in argparse.

gh-106531 [https://github.com/python/cpython/issues/106531]: In importlib.resources, sync with importlib_resources 6.3.2 [https://importlib-resources.readthedocs.io/en/latest/history.html#v6-3-2], including: MultiplexedPath now expects Traversable paths, deprecating string arguments to MultiplexedPath; Enabled support for resources in namespace packages in zip files; Fixed NotADirectoryError when calling files on a subdirectory of a namespace package.

gh-115937 [https://github.com/python/cpython/issues/115937]: Removed extra preprocessing for the __signature__ attribute: the code just check if it's a inspect.Signature instance. Patch by Sergey B Kirpichev.

gh-115808 [https://github.com/python/cpython/issues/115808]: Add operator.is_none() and operator.is_not_none() functions.

gh-114264 [https://github.com/python/cpython/issues/114264]: Improve performance of copy.deepcopy() by adding a fast path for atomic types.

gh-113878 [https://github.com/python/cpython/issues/113878]: Add doc parameter to dataclasses.field(), so it can be stored and shown as a documentation / metadata. If @dataclass(slots=True) is used, then the supplied string is available in the __slots__ dict. Otherwise, the supplied string is only available in the corresponding dataclasses.Field object.

In order to support this feature we are changing the __slots__ format in dataclasses from tuple to dict when documentation / metadata is present.

gh-113978 [https://github.com/python/cpython/issues/113978]: Ignore warnings on text completion inside REPL.

gh-113008 [https://github.com/python/cpython/issues/113008]: Correct argparse usage output for required, mutually exclusive groups containing a positional argument

gh-108172 [https://github.com/python/cpython/issues/108172]: webbrowser honors OS preferred browser on Linux when its desktop entry name contains the text of a known browser name.

gh-109109 [https://github.com/python/cpython/issues/109109]: You can now get the raw TLS certificate chains from TLS connections via ssl.SSLSocket.get_verified_chain() and ssl.SSLSocket.get_unverified_chain() methods.

Contributed by Mateusz Nowak.

gh-105623 [https://github.com/python/cpython/issues/105623]: Fix performance degradation in logging.handlers.RotatingFileHandler. Patch by Craig Robson.

gh-102450 [https://github.com/python/cpython/issues/102450]: Add missing ISO-8601 24:00 alternative to midnight of next day to datetime.datetime.fromisoformat() and datetime.time.fromisoformat(). Patch by Izan "TizzySaurus" Robinson (tizzysaurus@gmail.com)

gh-103956 [https://github.com/python/cpython/issues/103956]: Fix lack of newline characters in trace module output when line tracing is enabled but source code line for current frame is not available.

gh-92081 [https://github.com/python/cpython/issues/92081]: Fix missing spaces in email headers when the spaces are mixed with encoded 8-bit characters.

gh-103194 [https://github.com/python/cpython/issues/103194]: Prepare Tkinter for C API changes in Tcl 8.7/9.0 to avoid _tkinter.Tcl_Obj being unexpectedly returned instead of bool, str, bytearray, or int.

gh-87106 [https://github.com/python/cpython/issues/87106]: Fixed handling in inspect.Signature.bind() of keyword arguments having the same name as positional-only arguments when a variadic keyword argument (e.g. **kwargs) is present.

gh-103134 [https://github.com/python/cpython/issues/103134]: Add additional methods to proxy objects in the multiprocessing module:

clear() and copy() for proxies of list

fromkeys(), reversed(d), d | {}, {} | d, d |= {'b': 2} for proxies of dict

bpo-45767 [https://bugs.python.org/issue?@action=redirect&bpo=45767]: Fix integer conversion in os.major(), os.minor(), and os.makedev(). Support device numbers larger than 2**63-1. Support non-existent device number (NODEV).

bpo-44864 [https://bugs.python.org/issue?@action=redirect&bpo=44864]: Do not translate user-provided strings in argparse.ArgumentParser.

bpo-41843 [https://bugs.python.org/issue?@action=redirect&bpo=41843]: Solaris now uses os.sendfile() fast-copy syscall for more efficient shutil file copy related functions.

bpo-15987 [https://bugs.python.org/issue?@action=redirect&bpo=15987]: Implemented ast.compare() for comparing two ASTs. Patch by Batuhan Taskaya with some help from Jeremy Hylton.

gh-67693 [https://github.com/python/cpython/issues/67693]: Fix urllib.parse.urlunparse() and urllib.parse.urlunsplit() for URIs with path starting with multiple slashes and no authority. Based on patch by Ashwin Ramaswami.

bpo-14074 [https://bugs.python.org/issue?@action=redirect&bpo=14074]: Fix argparse metavar processing to allow positional arguments to have a tuple metavar.

IDLE

gh-122392 [https://github.com/python/cpython/issues/122392]: Increase currently inadequate vertical spacing for the IDLE browsers (path, module, and stack) on high-resolution monitors.

gh-112938 [https://github.com/python/cpython/issues/112938]: Fix uninteruptable hang when Shell gets rapid continuous output.

gh-122482 [https://github.com/python/cpython/issues/122482]: Change About IDLE to direct users to discuss.python.org instead of the now unused idle-dev email and mailing list.

gh-78889 [https://github.com/python/cpython/issues/78889]: Stop Shell freezes by blocking user access to non-method sys.stdout.shell attributes, which are all private.

gh-120083 [https://github.com/python/cpython/issues/120083]: Add explicit black IDLE Hovertip foreground color needed for recent macOS. Fixes Sonoma showing unreadable white on pale yellow. Patch by John Riggles.

gh-120104 [https://github.com/python/cpython/issues/120104]: Fix padding in config and search dialog windows in IDLE.

Documentation

gh-124872 [https://github.com/python/cpython/issues/124872]: Added definitions for context, current context, and context management protocol, updated related definitions to be consistent, and expanded the documentation for contextvars.Context.

gh-125018 [https://github.com/python/cpython/issues/125018]: The importlib.metadata documentation now includes semantic cross-reference targets for the significant documented APIs. This means intersphinx references like importlib.metadata.version() will now work as expected.

gh-124720 [https://github.com/python/cpython/issues/124720]: Update "Using Python on a Mac" section of the "Python Setup and Usage" document and include information on installing free-threading support.

gh-124457 [https://github.com/python/cpython/issues/124457]: Remove coverity scan from the CPython repo. It has not been used since 2020 and is currently unmaintained.

gh-116622 [https://github.com/python/cpython/issues/116622]: Add an Android platform guide, and flag modules not available on Android.

gh-123976 [https://github.com/python/cpython/issues/123976]: Refresh docs around custom providers.

gh-70870 [https://github.com/python/cpython/issues/70870]: Clarified the dual usage of the term "free variable" (both the formal meaning of any reference to names defined outside the local scope, and the narrower pragmatic meaning of nonlocal variables named in co_freevars).

gh-121277 [https://github.com/python/cpython/issues/121277]: Writers of CPython's documentation can now use next as the version for the versionchanged, versionadded, deprecated directives.

gh-117765 [https://github.com/python/cpython/issues/117765]: Improved documentation for unittest.mock.patch.dict()

gh-121749 [https://github.com/python/cpython/issues/121749]: Fix documentation for PyModule_AddObjectRef().

gh-120012 [https://github.com/python/cpython/issues/120012]: Clarify the behaviours of multiprocessing.Queue.empty() and multiprocessing.SimpleQueue.empty() on closed queues. Patch by Bénédikt Tran.

gh-119574 [https://github.com/python/cpython/issues/119574]: Added some missing environment variables to the output of --help-env.

bpo-34008 [https://bugs.python.org/issue?@action=redirect&bpo=34008]: The Py_Main() documentation moved from the "Very High Level API" section to the "Initialization and Finalization" section.

Also make it explicit that we expect Py_Main to typically be called instead of Py_Initialize rather than after it (since Py_Main makes its own call to Py_Initialize). Document that calling both is supported but is version dependent on which settings will be applied correctly.

Core and Builtins

gh-124375 [https://github.com/python/cpython/issues/124375]: Fix a crash in the free threading build when the GC runs concurrently with a new thread starting.

gh-125221 [https://github.com/python/cpython/issues/125221]: Fix possible race condition when calling __reduce_ex__() for the first time in the free threading build.

gh-125174 [https://github.com/python/cpython/issues/125174]: Make the handling of reference counts of immortal objects more robust. Immortal objects with reference counts that deviate from their original reference count by up to a billion (half a billion on 32 bit builds) are still counted as immortal.

gh-125039 [https://github.com/python/cpython/issues/125039]: Make this_instr and prev_instr const in cases generator.

Library

gh-125008 [https://github.com/python/cpython/issues/125008]: Fix tokenize.untokenize() producing invalid syntax for double braces preceded by certain escape characters.

Core and Builtins

gh-124871 [https://github.com/python/cpython/issues/124871]: Fix compiler bug (in some versions of 3.13) where an assertion fails during reachability analysis.

gh-123378 [https://github.com/python/cpython/issues/123378]: Fix a crash in the __str__() method of UnicodeError objects when the UnicodeError.start and UnicodeError.end values are invalid or out-of-range. Patch by Bénédikt Tran.

gh-118093 [https://github.com/python/cpython/issues/118093]: Improve the experimental JIT compiler's ability to stay "on trace" when encountering highly-biased branches.

gh-124642 [https://github.com/python/cpython/issues/124642]: Fixed scalability issue in free-threaded builds for lock-free reads from dictionaries in multi-threaded scenarios

gh-116510 [https://github.com/python/cpython/issues/116510]: Fix a crash caused by immortal interned strings being shared between sub-interpreters that use basic single-phase init. In that case, the string can be used by an interpreter that outlives the interpreter that created and interned it. For interpreters that share obmalloc state, also share the interned dict with the main interpreter.

gh-116510 [https://github.com/python/cpython/issues/116510]: Fix a bug that can cause a crash when sub-interpreters use "basic" single-phase extension modules. Shared objects could refer to PyGC_Head nodes that had been freed as part of interpreter cleanup.

gh-119180 [https://github.com/python/cpython/issues/119180]: The __main__ module no longer always contains an __annotations__ dictionary in its global namespace.

gh-124547 [https://github.com/python/cpython/issues/124547]: When deallocating an object with inline values whose __dict__ is still live: if memory allocation for the inline values fails, clear the dictionary. Prevents an interpreter crash.

gh-124513 [https://github.com/python/cpython/issues/124513]: Fix a crash in FrameLocalsProxy constructor: check the number of arguments. Patch by Victor Stinner.

gh-124442 [https://github.com/python/cpython/issues/124442]: Fix nondeterminism in compilation by sorting the value of __static_attributes__. Patch by kp2pml30.

gh-124285 [https://github.com/python/cpython/issues/124285]: Fix bug where bool(a) can be invoked more than once during the evaluation of a compound boolean expression.

gh-123856 [https://github.com/python/cpython/issues/123856]: Fix PyREPL failure when a keyboard interrupt is triggered after using a history search

gh-65961 [https://github.com/python/cpython/issues/65961]: Deprecate the setting and using __package__ and __cached__.

gh-119726 [https://github.com/python/cpython/issues/119726]: The JIT now generates more efficient code for calls to C functions resulting in up to 0.8% memory savings and 1.5% speed improvement on AArch64. Patch by Diego Russo.

gh-122878 [https://github.com/python/cpython/issues/122878]: Use the pager binary, if available (e.g. on Debian and derivatives), to display REPL help().

gh-124188 [https://github.com/python/cpython/issues/124188]: Fix reading and decoding a line from the source file with non-UTF-8 encoding for syntax errors raised in the compiler.

gh-124027 [https://github.com/python/cpython/issues/124027]: Support <page up>, <page down>, and <delete> keys in the Python REPL when $TERM is set to vt100.

gh-124022 [https://github.com/python/cpython/issues/124022]: Fix bug where docstring is removed from classes in interactive mode.

gh-123958 [https://github.com/python/cpython/issues/123958]: docstrings are now removed from the optimized AST in optimization level 2.

gh-123923 [https://github.com/python/cpython/issues/123923]: The f_executable field in the internal _PyInterpreterFrame struct now uses a tagged pointer. Profilers and debuggers that uses this field should clear the least significant bit to recover the PyObject* pointer.

gh-77894 [https://github.com/python/cpython/issues/77894]: Fix possible crash in the garbage collector when it tries to break a reference loop containing a memoryview object. Now a memoryview object can only be cleared if there are no buffers that refer it.

gh-120221 [https://github.com/python/cpython/issues/120221]: asyncio REPL is now again properly recognizing KeyboardInterrupts. Display of exceptions raised in secondary threads is fixed.

gh-119310 [https://github.com/python/cpython/issues/119310]: Allow the new interactive shell to read history files written with the editline library that use unicode-escaped entries. Patch by aorcajo and Łukasz Langa.

gh-123572 [https://github.com/python/cpython/issues/123572]: Fix key mappings for various F-keys in Windows for the new REPL. Patch by devdanzin

Library

gh-123614 [https://github.com/python/cpython/issues/123614]: Add turtle.save() to easily save Turtle drawings as PostScript files. Patch by Marie Roald and Yngve Mardal Moe.

Core and Builtins

gh-123339 [https://github.com/python/cpython/issues/123339]: Setting the __module__ attribute for a class now removes the __firstlineno__ item from the type's dict, so they will no longer be inconsistent.

gh-119034 [https://github.com/python/cpython/issues/119034]: Change <page up> and <page down> keys of the Python REPL to history search forward/backward. Patch by Victor Stinner.

gh-123562 [https://github.com/python/cpython/issues/123562]: Improve SyntaxError message for using case ... as ... with not a name.

gh-123545 [https://github.com/python/cpython/issues/123545]: Fix a double decref in rare cases on experimental JIT builds.

gh-123484 [https://github.com/python/cpython/issues/123484]: Fix _Py_DebugOffsets for long objects to be relative to the start of the object rather than the start of a subobject.

gh-123446 [https://github.com/python/cpython/issues/123446]: Fix empty function name in TypeError when builtin magic methods are used without the required args.

gh-123440 [https://github.com/python/cpython/issues/123440]: Improve SyntaxError message for using except as with not a name.

gh-116017 [https://github.com/python/cpython/issues/116017]: Improved JIT memory consumption by periodically freeing memory used by infrequently-executed code. This change is especially likely to improve the memory footprint of long-running programs.

gh-123344 [https://github.com/python/cpython/issues/123344]: Add AST optimizations for type parameter defaults.

gh-123321 [https://github.com/python/cpython/issues/123321]: Prevent Parser/myreadline race condition from segfaulting on multi-threaded use. Patch by Bar Harel and Amit Wienner.

gh-123177 [https://github.com/python/cpython/issues/123177]: Fix a bug causing stray prompts to appear in the middle of wrapped lines in the new REPL.

gh-122982 [https://github.com/python/cpython/issues/122982]: Extend the deprecation period for bool inversion (~) by two years.

gh-123271 [https://github.com/python/cpython/issues/123271]: Make concurrent iterations over the same zip() iterator safe under free-threading.

gh-123275 [https://github.com/python/cpython/issues/123275]: Support -X gil=1 and PYTHON_GIL=1 on non-free-threaded builds.

gh-123177 [https://github.com/python/cpython/issues/123177]: Deactivate line wrap in the Apple Terminal via a ANSI escape code. Patch by Pablo Galindo

gh-123229 [https://github.com/python/cpython/issues/123229]: Fix valgrind warning by initializing the f-string buffers to 0 in the tokenizer. Patch by Pablo Galindo

gh-122298 [https://github.com/python/cpython/issues/122298]: Restore printout of GC stats when gc.set_debug(gc.DEBUG_STATS) is called. This feature was accidentally removed when implementing incremental GC.

gh-121804 [https://github.com/python/cpython/issues/121804]: Correctly show error locations when a SyntaxError is raised in the basic REPL. Patch by Sergey B Kirpichev.

gh-115776 [https://github.com/python/cpython/issues/115776]: Enables inline values (Python's equivalent of hidden classes) on any class who's instances are of a fixed size.

gh-123142 [https://github.com/python/cpython/issues/123142]: Fix too-wide source location in exception tracebacks coming from broken iterables in comprehensions.

gh-123048 [https://github.com/python/cpython/issues/123048]: Fix a bug where pattern matching code could emit a JUMP_FORWARD with no source location.

gh-118093 [https://github.com/python/cpython/issues/118093]: Break up CALL_ALLOC_AND_ENTER_INIT into micro-ops and relax requirement for exact args, in order to increase the amount of code supported by tier 2.

gh-123123 [https://github.com/python/cpython/issues/123123]: Fix displaying SyntaxError exceptions covering multiple lines. Patch by Pablo Galindo

gh-123083 [https://github.com/python/cpython/issues/123083]: Fix a potential use-after-free in STORE_ATTR_WITH_HINT.

gh-123022 [https://github.com/python/cpython/issues/123022]: Fix crash in free-threaded build when calling Py_Initialize() from a non-main thread.

gh-118093 [https://github.com/python/cpython/issues/118093]: Add three specializations for CALL_KW:

CALL_KW_PY for calls to Python functions

CALL_KW_BOUND_METHOD for calls to bound methods

CALL_KW_NON_PY for all other calls

gh-122821 [https://github.com/python/cpython/issues/122821]: Make sure that branches in while statements have consistent offsets for sys.monitoring. while statements are now compiled with a simple jump at the end of the body, instead of duplicating the test.

gh-122907 [https://github.com/python/cpython/issues/122907]: Building with HAVE_DYNAMIC_LOADING now works as well as it did in 3.12. Existing deficiences will be addressed separately. (See https://github.com/python/cpython/issues/122950.)

gh-122888 [https://github.com/python/cpython/issues/122888]: Fix crash on certain calls to str() with positional arguments of the wrong type. Patch by Jelle Zijlstra.

gh-118093 [https://github.com/python/cpython/issues/118093]: Improve the experimental JIT's handling of polymorphic code.

gh-122697 [https://github.com/python/cpython/issues/122697]: Fixed memory leaks at interpreter shutdown in the free-threaded build, and also reporting of leaked memory blocks via -X showrefcount.

gh-116622 [https://github.com/python/cpython/issues/116622]: Fix Android stdout and stderr messages being truncated or lost.

gh-122527 [https://github.com/python/cpython/issues/122527]: Fix a crash that occurred when a PyStructSequence was deallocated after its type's dictionary was cleared by the GC. The type's tp_basicsize now accounts for non-sequence fields that aren't included in the Py_SIZE of the sequence.

gh-122445 [https://github.com/python/cpython/issues/122445]: Add only fields which are modified via self.* to __static_attributes__.

gh-122417 [https://github.com/python/cpython/issues/122417]: In the free-threaded build, the reference counts for heap type objects are now partially stored in a distributed manner in per-thread arrays. This reduces contention on the heap type's reference count fields when creating or destroying instances of the same type from multiple threads concurrently.

gh-116090 [https://github.com/python/cpython/issues/116090]: Fix an issue in JIT builds that prevented some for loops from correctly firing RAISE monitoring events.

gh-122300 [https://github.com/python/cpython/issues/122300]: Preserve AST nodes for f-string with single-element format specifiers. Patch by Pablo Galindo

gh-120906 [https://github.com/python/cpython/issues/120906]: frame.f_locals now supports arbitrary hashable objects as keys.

gh-122239 [https://github.com/python/cpython/issues/122239]: When a list, tuple or dict with too many elements is unpacked, show the actual length in the error message.

gh-122245 [https://github.com/python/cpython/issues/122245]: Detection of writes to __debug__ is moved from the compiler's codegen stage to the symtable. This means that these errors are now detected even in code that is optimized away before codegen (such as assertions with the -O command line option).

gh-122234 [https://github.com/python/cpython/issues/122234]: Specializations for sums with float and complex inputs in sum() now always use compensated summation. Also, for integer items in above specializations: PyLong_AsDouble() is used, instead of PyLong_AsLongAndOverflow(). Patch by Sergey B Kirpichev.

gh-122208 [https://github.com/python/cpython/issues/122208]: Dictionary watchers now only deliver the PyDict_EVENT_ADDED event when the insertion is in a known good state to succeed.

gh-122160 [https://github.com/python/cpython/issues/122160]: Remove the BUILD_CONST_KEY_MAP opcode. Use BUILD_MAP instead.

gh-122029 [https://github.com/python/cpython/issues/122029]: Emit c_call events in sys.setprofile() when a PyMethodObject pointing to a PyCFunction is called.

gh-122026 [https://github.com/python/cpython/issues/122026]: Fix a bug that caused the tokenizer to not correctly identify mismatched parentheses inside f-strings in some situations. Patch by Pablo Galindo

gh-99108 [https://github.com/python/cpython/issues/99108]: Python's hashlib now unconditionally uses the vendored HACL* library for Blake2. Python no longer accepts libb2 as an optional dependency for Blake2.

We refreshed HACL* to the latest version, and now vendor HACL*'s 128-bit and 256-bit wide vector implementations for Blake2, which are used on x86/x64 toolchains when the required CPU features are available at runtime.

HACL*'s 128-bit wide vector implementation of Blake2 can also run on ARM NEON and Power8, but lacking evidence of a performance gain, these are not enabled (yet).

Library

gh-121999 [https://github.com/python/cpython/issues/121999]: The default extraction filter for the tarfile module is now set to 'data'.

Core and Builtins

gh-121860 [https://github.com/python/cpython/issues/121860]: Fix crash when rematerializing a managed dictionary after it was deleted.

gh-121795 [https://github.com/python/cpython/issues/121795]: Improve performance of set membership testing, set.remove() and set.discard() when the argument is a set.

gh-121814 [https://github.com/python/cpython/issues/121814]: Fixed the SegFault when PyEval_SetTrace() is used with no Python frame on stack.

gh-121295 [https://github.com/python/cpython/issues/121295]: Fix PyREPL console getting into a blocked state after interrupting a long paste

gh-121794 [https://github.com/python/cpython/issues/121794]: Fix bug in free-threaded Python where a resurrected object could lead to a negative ref count assertion failure.

gh-121657 [https://github.com/python/cpython/issues/121657]: Improve the SyntaxError message if the user tries to use yield from outside a function.

gh-121609 [https://github.com/python/cpython/issues/121609]: Fix pasting of characters containing unicode character joiners in the new REPL. Patch by Marta Gomez Macias

gh-121297 [https://github.com/python/cpython/issues/121297]: Previously, incorrect usage of await or asynchronous comprehensions in code removed by the -O option was not flagged by the Python compiler. Now, such code raises SyntaxError. Patch by Jelle Zijlstra.

gh-117482 [https://github.com/python/cpython/issues/117482]: Unexpected slot wrappers are no longer created for builtin static types in subinterpreters.

gh-121562 [https://github.com/python/cpython/issues/121562]: Optimized performance of hex_from_char by replacing switch-case with a lookup table

gh-121499 [https://github.com/python/cpython/issues/121499]: Fix a bug affecting how multi-line history was being rendered in the new REPL after interacting with the new screen cache. Patch by Pablo Galindo

gh-121497 [https://github.com/python/cpython/issues/121497]: Fix a bug that was preventing the REPL to correctly respect the history when an input hook was set. Patch by Pablo Galindo

gh-121012 [https://github.com/python/cpython/issues/121012]: Tier 2 execution now ensures that list iterators remain exhausted, once they become exhausted.

gh-121439 [https://github.com/python/cpython/issues/121439]: Allow tuples of length 20 in the freelist to be reused.

gh-121288 [https://github.com/python/cpython/issues/121288]: ValueError messages for list.index(), range.index(), deque.index(), deque.remove() and ShareableList.index() no longer contain the repr of the searched value (which can be arbitrary large) and are consistent with error messages for other index() and remove() methods.

gh-121368 [https://github.com/python/cpython/issues/121368]: Fix race condition in _PyType_Lookup in the free-threaded build due to a missing memory fence. This could lead to _PyType_Lookup returning incorrect results on arm64.

gh-121149 [https://github.com/python/cpython/issues/121149]: Added specialization for summation of complexes, this also improves accuracy of builtin sum() for such inputs. Patch by Sergey B Kirpichev.

gh-121130 [https://github.com/python/cpython/issues/121130]: Fix f-strings with debug expressions in format specifiers. Patch by Pablo Galindo

Library

gh-121381 [https://github.com/python/cpython/issues/121381]: Remove subprocess._USE_VFORK escape hatch code and documentation. It was added just in case, and doesn't have any known cases that require it.

Core and Builtins

gh-119726 [https://github.com/python/cpython/issues/119726]: Optimize code layout for calls to C functions from the JIT on AArch64. Patch by Diego Russo.

gh-121115 [https://github.com/python/cpython/issues/121115]: PyLong_AsNativeBytes() no longer uses __index__() methods by default. The Py_ASNATIVEBYTES_ALLOW_INDEX flag has been added to allow it.

gh-120838 [https://github.com/python/cpython/issues/120838]: Py_Finalize() and Py_FinalizeEx() now always run with the main interpreter active.

gh-113433 [https://github.com/python/cpython/issues/113433]: Subinterpreters now get cleaned up automatically during runtime finalization.

gh-119726 [https://github.com/python/cpython/issues/119726]: Improve the speed and memory use of C function calls from JIT code on AArch64. Patch by Diego Russo

gh-116017 [https://github.com/python/cpython/issues/116017]: Simplify the warmup mechanism used for "side exits" in JIT code, resulting in slightly better performance and slightly lower memory usage for most platforms.

gh-98442 [https://github.com/python/cpython/issues/98442]: Fix too wide source locations of the cleanup instructions of a with statement.

gh-120754 [https://github.com/python/cpython/issues/120754]: Reduce the number of system calls invoked when reading a whole file (ex. open('a.txt').read()). For a sample program that reads the contents of the 400+ .rst files in the cpython repository Doc folder, there is an over 10% reduction in system call count.

gh-119462 [https://github.com/python/cpython/issues/119462]: Make sure that invariants of type versioning are maintained: * Superclasses always have their version number assigned before subclasses * The version tag is always zero if the tag is not valid. * The version tag is always non-if the tag is valid.

gh-120437 [https://github.com/python/cpython/issues/120437]: Fix _CHECK_STACK_SPACE optimization problems introduced in gh-118322 [https://github.com/python/cpython/issues/118322].

gh-120722 [https://github.com/python/cpython/issues/120722]: Correctly set the bytecode position on return instructions within lambdas. Patch by Jelle Zijlstra.

gh-120367 [https://github.com/python/cpython/issues/120367]: Fix bug where compiler creates a redundant jump during pseudo-op replacement. Can only happen with a synthetic AST that has a try on the same line as the instruction following the exception handler.

gh-120507 [https://github.com/python/cpython/issues/120507]: Remove the BEFORE_WITH and BEFORE_ASYNC_WITH instructions. Add the new LOAD_SPECIAL instruction. Generate code for with and async with statements using the new instruction.

gh-113993 [https://github.com/python/cpython/issues/113993]: Strings interned with sys.intern() are again garbage-collected when no longer used, as per the documentation. Strings interned with the C function PyUnicode_InternInPlace() are still immortal. Internals of the string interning mechanism have been changed. This may affect performance and identities of str objects.

Library

gh-120485 [https://github.com/python/cpython/issues/120485]: Add an override of allow_reuse_port on classes subclassing socketserver.TCPServer where allow_reuse_address is also overridden.

Core and Builtins

gh-120384 [https://github.com/python/cpython/issues/120384]: Fix an array out of bounds crash in list_ass_subscript, which could be invoked via some specifically tailored input: including concurrent modification of a list object, where one thread assigns a slice and another clears it.

gh-120367 [https://github.com/python/cpython/issues/120367]: Fix crash in compiler on code with redundant NOPs and JUMPs which show up after exception handlers are moved to the end of the code.

Library

gh-120380 [https://github.com/python/cpython/issues/120380]: Fix Python implementation of pickle.Pickler for bytes and bytearray objects when using protocol version 5. Patch by Bénédikt Tran.

Core and Builtins

gh-120397 [https://github.com/python/cpython/issues/120397]: Improve the throughput by up to two times for the str.count(), bytes.count() and bytearray.count() methods for counting single characters.

gh-120221 [https://github.com/python/cpython/issues/120221]: Deliver real signals on Ctrl-C and Ctrl-Z in the new REPL. Patch by Pablo Galindo

gh-120346 [https://github.com/python/cpython/issues/120346]: Respect PYTHON_BASIC_REPL when running in interactive inspect mode (python -i). Patch by Pablo Galindo

gh-93691 [https://github.com/python/cpython/issues/93691]: Fix source locations of instructions generated for the iterator of a for statement.

gh-120198 [https://github.com/python/cpython/issues/120198]: Fix a crash when multiple threads read and write to the same __class__ of an object concurrently.

gh-120298 [https://github.com/python/cpython/issues/120298]: Fix use-after free in list_richcompare_impl which can be invoked via some specifically tailored evil input.

gh-119666 [https://github.com/python/cpython/issues/119666]: Fix a compiler crash in the case where two comprehensions in class scope both reference __class__.

gh-119726 [https://github.com/python/cpython/issues/119726]: JIT: Re-use trampolines on AArch64 when creating stencils. Patch by Diego Russo

gh-120225 [https://github.com/python/cpython/issues/120225]: Fix crash in compiler on empty block at end of exception handler.

gh-93691 [https://github.com/python/cpython/issues/93691]: Fix source locations of instructions generated for with statements.

gh-120097 [https://github.com/python/cpython/issues/120097]: FrameLocalsProxy now subclasses collections.abc.Mapping and can be matched as a mapping in match statements

gh-120080 [https://github.com/python/cpython/issues/120080]: Direct call to the int.__round__() now accepts None as a valid argument.

gh-119933 [https://github.com/python/cpython/issues/119933]: Improve SyntaxError messages for invalid expressions in a type parameters bound, a type parameter constraint tuple or a default type parameter. Patch by Bénédikt Tran.

gh-119724 [https://github.com/python/cpython/issues/119724]: Reverted improvements to error messages for elif/else statements not matching any valid statements, which made in hard to locate the syntax errors inside those elif/else blocks.

gh-119879 [https://github.com/python/cpython/issues/119879]: String search is now slightly faster for certain cases. It now utilizes last character gap (good suffix rule) for two-way periodic needles.

gh-119842 [https://github.com/python/cpython/issues/119842]: Honor PyOS_InputHook() in the new REPL. Patch by Pablo Galindo

gh-119180 [https://github.com/python/cpython/issues/119180]: classmethod() and staticmethod() now wrap the __annotations__ and __annotate__ attributes of their underlying callable lazily. See PEP 649 [https://peps.python.org/pep-0649/]. Patch by Jelle Zijlstra.

gh-119821 [https://github.com/python/cpython/issues/119821]: Fix execution of annotation scopes within classes when globals is set to a non-dict. Patch by Jelle Zijlstra.

gh-118934 [https://github.com/python/cpython/issues/118934]: Make PyEval_GetLocals return borrowed reference

gh-119740 [https://github.com/python/cpython/issues/119740]: Remove the previously-deprecated delegation of int() to __trunc__().

gh-119689 [https://github.com/python/cpython/issues/119689]: Generate stack effect metadata for pseudo instructions from bytecodes.c.

gh-109218 [https://github.com/python/cpython/issues/109218]: complex() accepts now a string only as a positional argument. Passing a complex number as the "real" or "imag" argument is deprecated; it should only be passed as a single positional argument.

gh-119548 [https://github.com/python/cpython/issues/119548]: Add a clear command to the REPL. Patch by Pablo Galindo

gh-111999 [https://github.com/python/cpython/issues/111999]: Fix the signature of str.format_map().

gh-119560 [https://github.com/python/cpython/issues/119560]: An invalid assert in beta 1 has been removed. The assert would fail if PyState_FindModule() was used in an extension module's init function before the module def had been initialized.

gh-119369 [https://github.com/python/cpython/issues/119369]: Fix deadlock during thread deletion in free-threaded build, which could occur when the GIL was enabled at runtime.

gh-119525 [https://github.com/python/cpython/issues/119525]: Fix deadlock involving _PyType_Lookup() cache in the free-threaded build when the GIL is dynamically enabled at runtime.

gh-119258 [https://github.com/python/cpython/issues/119258]: Eliminate type version guards in the tier two interpreter.

Note that setting the tp_version_tag manually (which has never been supported) may result in crashes.

gh-119311 [https://github.com/python/cpython/issues/119311]: Fix bug where names are unexpectedly mangled in the bases of generic classes.

gh-119395 [https://github.com/python/cpython/issues/119395]: Fix bug where names appearing after a generic class are mangled as if they are in the generic class.

gh-119372 [https://github.com/python/cpython/issues/119372]: Correct invalid corner cases in complex division (resulted in (nan+nanj) output), e.g. 1/complex('(inf+infj)'). Patch by Sergey B Kirpichev.

gh-119180 [https://github.com/python/cpython/issues/119180]: Evaluation of annotations is now deferred. See PEP 649 [https://peps.python.org/pep-0649/] for details.

gh-119180 [https://github.com/python/cpython/issues/119180]: Replace LOAD_ASSERTION_ERROR opcode with LOAD_COMMON_CONSTANT and add support for NotImplementedError.

gh-119213 [https://github.com/python/cpython/issues/119213]: Non-builtin modules built with argument clinic were crashing if used in a subinterpreter before the main interpreter. The objects that were causing the problem by leaking between interpreters carelessly have been fixed.

gh-119011 [https://github.com/python/cpython/issues/119011]: Fixes type.__type_params__ to return an empty tuple instead of a descriptor.

gh-118692 [https://github.com/python/cpython/issues/118692]: Avoid creating unnecessary StopIteration instances for monitoring.

gh-119180 [https://github.com/python/cpython/issues/119180]: Add an __annotate__ attribute to functions, classes, and modules as part of PEP 649 [https://peps.python.org/pep-0649/]. Patch by Jelle Zijlstra.

gh-119049 [https://github.com/python/cpython/issues/119049]: Fix displaying the source line for warnings created by the C API if the warnings module had not yet been imported.

gh-119057 [https://github.com/python/cpython/issues/119057]: Improve ZeroDivisionError error message. Now, all error messages are harmonized: all /, //, and % operations just use "division by zero" message. And 0 ** -1 operation uses "zero to a negative power".

gh-118844 [https://github.com/python/cpython/issues/118844]: Fix build failures when configuring with both --disable-gil and --enable-experimental-jit.

gh-118921 [https://github.com/python/cpython/issues/118921]: Add copy() method for FrameLocalsProxy which returns a snapshot dict for local variables.

gh-117657 [https://github.com/python/cpython/issues/117657]: Fix data races on the field that stores a pointer to the interpreter's main thread that occur in free-threaded builds.

gh-118750 [https://github.com/python/cpython/issues/118750]: If the C version of the decimal module is available, int(str) now uses it to supply an asymptotically much faster conversion. However, this only applies if the string contains over about 2 million digits.

gh-118767 [https://github.com/python/cpython/issues/118767]: Using NotImplemented in a boolean context now raises TypeError. Contributed by Jelle Zijlstra.

gh-118561 [https://github.com/python/cpython/issues/118561]: Fix race condition in free-threaded build where list.extend() could expose uninitialised memory to concurrent readers.

gh-117139 [https://github.com/python/cpython/issues/117139]: Convert the Python evaluation stack to use internal stack references. The purpose is to support tagged pointers. In PEP 703 [https://peps.python.org/pep-0703/], this will allow for its form of deferred reference counting. For both the default and free-threaded builds, this sets up the infrastructure for unboxed integers in the future.

Library

gh-115801 [https://github.com/python/cpython/issues/115801]: Raise TypeError when passing a string to difflib.unified_diff() and difflib.context_diff().

Core and Builtins

gh-117558 [https://github.com/python/cpython/issues/117558]: Improve error messages when a string, bytes or bytearray object of length 1 is expected.

gh-117195 [https://github.com/python/cpython/issues/117195]: Avoid assertion failure for debug builds when calling object.__sizeof__(1)

gh-116022 [https://github.com/python/cpython/issues/116022]: Improve the __repr__() output of AST nodes.

gh-114091 [https://github.com/python/cpython/issues/114091]: Changed the error message for awaiting something that can't be awaited from "object <type> can't be used in an await expression" to "'<type>' object can't be awaited".

gh-113190 [https://github.com/python/cpython/issues/113190]: Py_Finalize() now deletes all interned strings.

gh-84978 [https://github.com/python/cpython/issues/84978]: Add class methods float.from_number() and complex.from_number().

gh-95144 [https://github.com/python/cpython/issues/95144]: Improve the error message from a in b when b is not a container to mention the term "container".

bpo-24766 [https://bugs.python.org/issue?@action=redirect&bpo=24766]: Fix handling of doc argument to subclasses of property.

C API

gh-123961 [https://github.com/python/cpython/issues/123961]: Convert the curses.window static type exposed by the PyCursesWindow_Type macro in Include/py_curses.h to a heap type. Patch by Bénédikt Tran.

gh-124502 [https://github.com/python/cpython/issues/124502]: Add PyUnicode_Equal() function to the limited C API: test if two strings are equal. Patch by Victor Stinner.

gh-124296 [https://github.com/python/cpython/issues/124296]: PyDictObject no longer maintains a private version tag field ma_version_tag per PEP 699 [https://peps.python.org/pep-0699/]. This field was originally added in Python 3.6 (PEP 509 [https://peps.python.org/pep-0509/]) and deprecated in Python 3.12.

gh-124160 [https://github.com/python/cpython/issues/124160]: Fix crash when importing modules containing state and single-phase initialization in a subinterpreter.

gh-124153 [https://github.com/python/cpython/issues/124153]: Add PyType_GetBaseByToken() and Py_tp_token slot for easier type checking, related to PEP 489 [https://peps.python.org/pep-0489/] and PEP 630 [https://peps.python.org/pep-0630/].

gh-124127 [https://github.com/python/cpython/issues/124127]: In the limited C API 3.14 and newer, Py_REFCNT() is now implemented as an opaque function call to hide implementation details. Patch by Victor Stinner.

gh-123880 [https://github.com/python/cpython/issues/123880]: Fixed a bug that prevented circular imports of extension modules that use single-phase initialization.

gh-123909 [https://github.com/python/cpython/issues/123909]: PyType_FromSpec(), PyType_FromSpecWithBases() and PyType_FromModuleAndSpec() will now fail if the metaclass of the new type has custom tp_new.

gh-107954 [https://github.com/python/cpython/issues/107954]: Add functions to configure the Python initialization (PEP 741 [https://peps.python.org/pep-0741/]):

PyInitConfig_Create()

PyInitConfig_Free()

PyInitConfig_GetError()

PyInitConfig_GetExitCode()

PyInitConfig_HasOption()

PyInitConfig_GetInt()

PyInitConfig_GetStr()

PyInitConfig_GetStrList()

PyInitConfig_FreeStrList()

PyInitConfig_SetInt()

PyInitConfig_SetStr()

PyInitConfig_SetStrList()

PyInitConfig_AddModule()

Py_InitializeFromInitConfig()

Patch by Victor Stinner.

gh-107954 [https://github.com/python/cpython/issues/107954]: Add functions to get and set the current runtime Python configuration:

PyConfig_Get()

PyConfig_GetInt()

PyConfig_Set()

PyConfig_Names()

Patch by Victor Stinner.

gh-123465 [https://github.com/python/cpython/issues/123465]: Py_RELATIVE_OFFSET is now allowed in PyMemberDef for the special offset member "__vectorcalloffset__", as well as the discouraged special offset members "__dictoffset__" and "__weaklistoffset__"

gh-100554 [https://github.com/python/cpython/issues/100554]: Added a slot Py_tp_vectorcall to set tp_vectorcall via the PyType_FromSpec() function family. Limited API extensions can use this feature to provide more efficient vector call-based implementation of __new__ and __init__.

gh-122854 [https://github.com/python/cpython/issues/122854]: Add Py_HashBuffer() to compute and return the hash value of a buffer. Patch by Antoine Pitrou and Victor Stinner.

gh-122728 [https://github.com/python/cpython/issues/122728]: Fix PyEval_GetLocals() to avoid SystemError ("bad argument to internal function"). Patch by Victor Stinner.

gh-116622 [https://github.com/python/cpython/issues/116622]: Make PyObject_Print work around a bug in Android and OpenBSD which prevented it from throwing an exception when trying to write to a read-only stream.

gh-105201 [https://github.com/python/cpython/issues/105201]: Add PyIter_NextItem() to replace PyIter_Next(), which has an ambiguous return value. Patch by Irit Katriel and Erlend Aasland.

gh-121489 [https://github.com/python/cpython/issues/121489]: Export private _PyBytes_Join() again.

gh-121645 [https://github.com/python/cpython/issues/121645]: Add PyBytes_Join(sep, iterable) function, similar to sep.join(iterable) in Python. Patch by Victor Stinner.

gh-89364 [https://github.com/python/cpython/issues/89364]: Export the PySignal_SetWakeupFd() function. Previously, the function was documented but it couldn't be used in 3rd party code. Patch by Victor Stinner.

gh-113993 [https://github.com/python/cpython/issues/113993]: PyUnicode_InternInPlace() no longer prevents its argument from being garbage collected.

Several functions that take char * are now documented as possibly preventing string objects from being garbage collected; refer to their documentation for details: PyUnicode_InternFromString(), PyDict_SetItemString(), PyObject_SetAttrString(), PyObject_DelAttrString(), PyUnicode_InternFromString(), and PyModule_Add* convenience functions.

gh-113601 [https://github.com/python/cpython/issues/113601]: Removed debug build assertions related to interning strings, which were falsely triggered by stable ABI extensions.

gh-112136 [https://github.com/python/cpython/issues/112136]: Restore the private _PyArg_Parser structure and the private _PyArg_ParseTupleAndKeywordsFast() function, previously removed in Python 3.13 alpha 1. Patch by Victor Stinner.

gh-120642 [https://github.com/python/cpython/issues/120642]: Remove the private _Py_CODEUNIT type from the public C API. The internal pycore_code.h header should now be used to get this internal type. Patch by Victor Stinner.

gh-120858 [https://github.com/python/cpython/issues/120858]: PyDict_Next() no longer locks the dictionary in the free-threaded build. The locking needs to be done by the caller around the entire iteration loop.

gh-120642 [https://github.com/python/cpython/issues/120642]: Remove the following unstable functions:

PyUnstable_Replace_Executor()

PyUnstable_SetOptimizer()

PyUnstable_GetOptimizer()

PyUnstable_GetExecutor()

PyUnstable_Optimizer_NewCounter()

PyUnstable_Optimizer_NewUOpOptimizer()

Patch by Victor Stinner.

gh-120389 [https://github.com/python/cpython/issues/120389]: Add new functions to convert C <stdint.h> numbers from/to Python int:

PyLong_FromInt32()

PyLong_FromUInt32()

PyLong_FromInt64()

PyLong_FromUInt64()

PyLong_AsInt32()

PyLong_AsUInt32()

PyLong_AsInt64()

PyLong_AsUInt64()

Patch by Victor Stinner.

gh-120600 [https://github.com/python/cpython/issues/120600]: In the limited C API 3.14 and newer, Py_TYPE() is now implemented as an opaque function call to hide implementation details. Patch by Victor Stinner.

gh-70278 [https://github.com/python/cpython/issues/70278]: PyUnicode_FromFormat() no longer produces the ending \ufffd character for truncated C string when use precision with %s and %V. It now truncates the string before the start of truncated multibyte sequences.

gh-119771 [https://github.com/python/cpython/issues/119771]: Set errno in _Py_c_pow() on overflows. Patch by Sergey B Kirpichev.

gh-119182 [https://github.com/python/cpython/issues/119182]: Add a new PyUnicodeWriter API to create a Python str object:

PyUnicodeWriter_Create().

PyUnicodeWriter_Discard().

PyUnicodeWriter_Finish().

PyUnicodeWriter_WriteChar().

PyUnicodeWriter_WriteUTF8().

PyUnicodeWriter_WriteUCS4().

PyUnicodeWriter_WriteWideChar().

PyUnicodeWriter_WriteStr().

PyUnicodeWriter_WriteRepr().

PyUnicodeWriter_WriteSubstring().

PyUnicodeWriter_Format().

PyUnicodeWriter_DecodeUTF8Stateful().

Patch by Victor Stinner.

gh-119613 [https://github.com/python/cpython/issues/119613]: Soft deprecate the Py_MEMCPY macro: use directly memcpy() instead. Patch by Victor Stinner.

gh-119775 [https://github.com/python/cpython/issues/119775]: Creating immutable types with mutable bases was deprecated since 3.12 and now raises a TypeError.

gh-119585 [https://github.com/python/cpython/issues/119585]: Fix crash when a thread state that was created by PyGILState_Ensure() calls a destructor that during PyThreadState_Clear() that calls back into PyGILState_Ensure() and PyGILState_Release(). This might occur when in the free-threaded build or when using thread-local variables whose destructors call PyGILState_Ensure().

gh-119613 [https://github.com/python/cpython/issues/119613]: Macros Py_IS_NAN, Py_IS_INFINITY and Py_IS_FINITE are soft deprecated.

gh-119336 [https://github.com/python/cpython/issues/119336]: Restore the removed _PyLong_NumBits() function. It is used by the pywin32 project. Patch by Ethan Smith

gh-119344 [https://github.com/python/cpython/issues/119344]: The critical section API is now public as part of the non-limited C API.

gh-119333 [https://github.com/python/cpython/issues/119333]: Add PyContext_AddWatcher() and PyContext_ClearWatcher() APIs to register callbacks to receive notification on enter and exit of context objects.

gh-119247 [https://github.com/python/cpython/issues/119247]: Added Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST and Py_END_CRITICAL_SECTION_SEQUENCE_FAST macros to make it possible to use PySequence_Fast APIs safely when free-threaded, and update str.join to work without the GIL using them.

gh-111389 [https://github.com/python/cpython/issues/111389]: Add PyHASH_MULTIPLIER constant: prime multiplier used in string and various other hashes. Patch by Victor Stinner.

gh-118771 [https://github.com/python/cpython/issues/118771]: Several C declarations with names that didn't start with the Py or _Py prefixes, which were added by mistake in 3.13 alpha and beta releases, were moved to internal headers.

gh-116984 [https://github.com/python/cpython/issues/116984]: Make mimalloc includes relative to the current file to avoid embedders or extensions needing to include Internal/mimalloc if they are already including internal CPython headers.

gh-118789 [https://github.com/python/cpython/issues/118789]: Add PyUnstable_Object_ClearWeakRefsNoCallbacks(), which clears weakrefs without calling their callbacks.

gh-118789 [https://github.com/python/cpython/issues/118789]: Restore _PyWeakref_ClearRef that was previously removed in Python 3.13 alpha 1.

gh-117511 [https://github.com/python/cpython/issues/117511]: Make the PyMutex public in the non-limited C API.

gh-116560 [https://github.com/python/cpython/issues/116560]: Add PyLong_GetSign() function. Patch by Sergey B Kirpichev.

gh-97588 [https://github.com/python/cpython/issues/97588]: Fix creating bitfields in ctypes structures and unions. Fields no longer overlap.

gh-87135 [https://github.com/python/cpython/issues/87135]: Attempting to acquire the GIL after runtime finalization has begun in a different thread now causes the thread to hang rather than terminate, which avoids potential crashes or memory corruption caused by attempting to terminate a thread that is running code not specifically designed to support termination. In most cases this hanging is harmless since the process will soon exit anyway.

The PyThread_exit_thread function is now deprecated. Its behavior is inconsistent across platforms, and it can only be used safely in the unlikely case that every function in the entire call stack has been designed to support the platform-dependent termination mechanism. It is recommended that users of this function change their design to not require thread termination. In the unlikely case that thread termination is needed and can be done safely, users may migrate to calling platform-specific APIs such as pthread_exit (POSIX) or _endthreadex (Windows) directly.

bpo-34008 [https://bugs.python.org/issue?@action=redirect&bpo=34008]: Added Py_IsInitialized to the list of APIs that are safe to call before the interpreter is initialized, and updated the embedding tests to cover it.

Build

gh-125269 [https://github.com/python/cpython/issues/125269]: Fix detection of whether -latomic is needed when cross-compiling CPython using the configure script.

gh-123990 [https://github.com/python/cpython/issues/123990]: Remove WITH_FREELISTS macro and --without-freelists build configuration

gh-124102 [https://github.com/python/cpython/issues/124102]: Update internal documentation under PCbuild, so it now correctly states that Windows requires VS2017 or later and Python 3.10 or later

gh-124043 [https://github.com/python/cpython/issues/124043]: Building using --with-trace-refs is (temporarily) disallowed when the GIL is disabled.

gh-123418 [https://github.com/python/cpython/issues/123418]: Updated Android build to use OpenSSL 3.0.15.

gh-123297 [https://github.com/python/cpython/issues/123297]: Propagate the value of LDFLAGS to LDCXXSHARED in sysconfig. Patch by Pablo Galindo

gh-121634 [https://github.com/python/cpython/issues/121634]: Allow for specifying the target compile triple for WASI.

gh-122578 [https://github.com/python/cpython/issues/122578]: Use WASI SDK 24 for testing.

gh-116622 [https://github.com/python/cpython/issues/116622]: Rename build variable MODULE_LDFLAGS back to LIBPYTHON, as it's used by package build systems (e.g. Meson).

gh-118943 [https://github.com/python/cpython/issues/118943]: Fix an issue where the experimental JIT could be built several times by the make regen-all target, leading to possible race conditions on heavily parallelized builds.

gh-121996 [https://github.com/python/cpython/issues/121996]: Introduce ./configure --disable-safety and --enable-slower-safety options. Patch by Donghee Na.

gh-120522 [https://github.com/python/cpython/issues/120522]: Added a --with-app-store-compliance option to patch out known issues with macOS/iOS App Store review processes.

gh-120371 [https://github.com/python/cpython/issues/120371]: Support WASI SDK 22 by explicitly skipping functions that are just stubs in wasi-libc.

gh-121731 [https://github.com/python/cpython/issues/121731]: Fix mimalloc compile error on GNU/Hurd

gh-121487 [https://github.com/python/cpython/issues/121487]: Fix deprecation warning for ATOMIC_VAR_INIT in mimalloc.

gh-121467 [https://github.com/python/cpython/issues/121467]: Fix a Makefile bug that prevented mimalloc header files from being installed.

gh-121103 [https://github.com/python/cpython/issues/121103]: On POSIX systems, excluding macOS framework installs, the lib directory for the free-threaded build now includes a "t" suffix to avoid conflicts with a co-located default build installation.

gh-120831 [https://github.com/python/cpython/issues/120831]: The default minimum iOS version was increased to 13.0.

gh-121082 [https://github.com/python/cpython/issues/121082]: Fix build failure when the developer use --enable-pystats arguments in configuration command after #118450.

gh-120671 [https://github.com/python/cpython/issues/120671]: Fix failing configure tests due to a missing space when appending to CFLAGS.

gh-120602 [https://github.com/python/cpython/issues/120602]: Correctly handle LLVM installs with LLVM_VERSION_SUFFIX when building with --enable-experimental-jit.

gh-120688 [https://github.com/python/cpython/issues/120688]: On WASI in debug mode, Python is now built with compiler flag -O3 instead of -Og, to support more recursive calls. Patch by Victor Stinner.

gh-118943 [https://github.com/python/cpython/issues/118943]: Fix a possible race condition affecting parallel builds configured with --enable-experimental-jit, in which FileNotFoundError could be caused by another process already moving jit_stencils.h.new to jit_stencils.h.

gh-120326 [https://github.com/python/cpython/issues/120326]: On Windows, fix build error when --disable-gil and --experimental-jit options are combined.

gh-120291 [https://github.com/python/cpython/issues/120291]: Make the python-config shell script compatible with non-bash shells.

gh-113565 [https://github.com/python/cpython/issues/113565]: Improve curses and curses.panel dependency checks in configure.

gh-119729 [https://github.com/python/cpython/issues/119729]: On POSIX systems, the pkg-config (.pc) filenames now include the ABI flags, which may include debug ("d") and free-threaded ("t"). For example: * python-3.14.pc (default, non-debug build) * python-3.14d.pc (default, debug build) * python-3.14t.pc (free-threaded build)

gh-119400 [https://github.com/python/cpython/issues/119400]: make_ssl_certs, the script that prepares certificate data for the test suite, now allows specifying expiration dates.

gh-115119 [https://github.com/python/cpython/issues/115119]: Fall back to the bundled libmpdec if a system version cannot be found.

gh-119132 [https://github.com/python/cpython/issues/119132]: Update sys.version to identify whether the build is default build or free-threading build. Patch By Donghee Na.

gh-118836 [https://github.com/python/cpython/issues/118836]: Fix an AssertionError when building with --enable-experimental-jit and the compiler emits a SHT_NOTE section.

gh-118943 [https://github.com/python/cpython/issues/118943]: Fix a possible race condition affecting parallel builds configured with --enable-experimental-jit, in which compilation errors could be caused by an incompletely-generated header file.

Python 3.13.0 beta 1

Release date: 2024-05-08

Security

gh-116741 [https://github.com/python/cpython/issues/116741]: Update bundled libexpat to 2.6.2

gh-117233 [https://github.com/python/cpython/issues/117233]: Detect BLAKE2, SHA3, Shake, & truncated SHA512 support in the OpenSSL-ish libcrypto library at build time. This allows hashlib to be used with libraries that do not to support every algorithm that upstream OpenSSL does.

Core and Builtins

gh-118414 [https://github.com/python/cpython/issues/118414]: Add instrumented opcodes to YIELD_VALUE assertion for tracing cases.

gh-117953 [https://github.com/python/cpython/issues/117953]: When a builtin or extension module is imported for the first time, while a subinterpreter is active, the module's init function is now run by the main interpreter first before import continues in the subinterpreter. Consequently, single-phase init modules now fail in an isolated subinterpreter without the init function running under that interpreter, whereas before it would run under the subinterpreter before failing, potentially leaving behind global state and callbacks and otherwise leaving the module in an inconsistent state.

gh-117549 [https://github.com/python/cpython/issues/117549]: Don't use designated initializer syntax in inline functions in internal headers. They cause problems for C++ or MSVC users who aren't yet using the latest C++ standard (C++20). While internal, pycore_backoff.h, is included (indirectly, via pycore_code.h) by some key 3rd party software that does so for speed.

Library

gh-95382 [https://github.com/python/cpython/issues/95382]: Improve performance of json.dumps() and json.dump() when using the argument indent. Depending on the data the encoding using json.dumps() with indent can be up to 2 to 3 times faster.

Core and Builtins

gh-116322 [https://github.com/python/cpython/issues/116322]: In --disable-gil builds, the GIL will be enabled while loading C extension modules. If the module indicates that it supports running without the GIL, the GIL will be disabled once loading is complete. Otherwise, the GIL will remain enabled for the remainder of the interpreter's lifetime. This behavior does not apply if the GIL has been explicitly enabled or disabled with PYTHON_GIL or -Xgil.

gh-118513 [https://github.com/python/cpython/issues/118513]: Fix incorrect UnboundLocalError when two comprehensions in the same function both reference the same name, and in one comprehension the name is bound while in the other it's an implicit global.

gh-118518 [https://github.com/python/cpython/issues/118518]: Allow the Linux perf support to work without frame pointers using perf's advanced JIT support. The feature is activated when using the PYTHON_PERF_JIT_SUPPORT environment variable or when running Python with -Xperf_jit. Patch by Pablo Galindo.

gh-117514 [https://github.com/python/cpython/issues/117514]: Add sys._is_gil_enabled() function that returns whether the GIL is currently enabled. In the default build it always returns True because the GIL is always enabled. In the free-threaded build, it may return True or False.

gh-118164 [https://github.com/python/cpython/issues/118164]: Break a loop between the Python implementation of the decimal module and the Python code for integer to string conversion. Also optimize integer to string conversion for values in the range from 9_000 to 135_000 decimal digits.

gh-118473 [https://github.com/python/cpython/issues/118473]: Fix sys.set_asyncgen_hooks() not to be partially set when raising TypeError.

gh-118465 [https://github.com/python/cpython/issues/118465]: Compiler populates the new __firstlineno__ field on a class with the line number of the first line of the class definition.

gh-118492 [https://github.com/python/cpython/issues/118492]: Fix an issue where the type cache can expose a previously accessed attribute when a finalizer is run.

gh-117714 [https://github.com/python/cpython/issues/117714]: update async_generator.athrow().close() and async_generator.asend().close() to close their section of the underlying async generator

gh-111201 [https://github.com/python/cpython/issues/111201]: The interactive interpreter is now implemented in Python, which allows for a number of new features like colors, multiline input, history viewing, and paste mode. Contributed by Pablo Galindo, Łukasz Langa and Lysandros Nikolaou based on code from the PyPy project.

gh-74929 [https://github.com/python/cpython/issues/74929]: Implement PEP 667: converted FrameType.f_locals and PyFrame_GetLocals() to return a write-through proxy object when the frame refers to a function or comprehension.

gh-116767 [https://github.com/python/cpython/issues/116767]: Fix crash in compiler on 'async with' that has many context managers.

gh-118335 [https://github.com/python/cpython/issues/118335]: Change how to use the tier 2 interpreter. Instead of running Python with -X uops or setting the environment variable PYTHON_UOPS=1, this choice is now made at build time by configuring with --enable-experimental-jit=interpreter.

Beware! This changes the environment variable to enable or disable micro-ops to PYTHON_JIT. The old PYTHON_UOPS is no longer used.

gh-118306 [https://github.com/python/cpython/issues/118306]: Update JIT compilation to use LLVM 18

gh-118160 [https://github.com/python/cpython/issues/118160]: Annotation scopes within classes can now contain comprehensions. However, such comprehensions are not inlined into their parent scope at runtime. Patch by Jelle Zijlstra.

gh-118272 [https://github.com/python/cpython/issues/118272]: Fix bug where generator.close does not free the generator frame's locals.

gh-118216 [https://github.com/python/cpython/issues/118216]: Don't consider __future__ imports with dots before the module name.

gh-118074 [https://github.com/python/cpython/issues/118074]: Make sure that the Executor objects in the COLD_EXITS array aren't assumed to be GC-able (which would access bytes outside the object).

gh-107674 [https://github.com/python/cpython/issues/107674]: Lazy load frame line number to improve performance of tracing

gh-118082 [https://github.com/python/cpython/issues/118082]: Improve SyntaxError message for imports without names, like in from x import and import cases. It now points out to users that import expects at least one name after it.

gh-118090 [https://github.com/python/cpython/issues/118090]: Improve SyntaxError message for empty type param brackets.

gh-117958 [https://github.com/python/cpython/issues/117958]: Added a get_jit_code() method to access JIT compiled machine code from the UOp Executor when the experimental JIT is enabled. Patch by Anthony Shaw.

gh-117901 [https://github.com/python/cpython/issues/117901]: Add option for compiler's codegen to save nested instruction sequences for introspection.

gh-116622 [https://github.com/python/cpython/issues/116622]: Redirect stdout and stderr to system log when embedded in an Android app.

gh-109118 [https://github.com/python/cpython/issues/109118]: annotation scope within class scopes can now contain lambdas.

gh-117894 [https://github.com/python/cpython/issues/117894]: Prevent agen.aclose() objects being re-used after .throw().

gh-117881 [https://github.com/python/cpython/issues/117881]: prevent concurrent access to an async generator via athrow().throw() or asend().throw()

gh-117536 [https://github.com/python/cpython/issues/117536]: Fix a RuntimeWarning when calling agen.aclose().throw(Exception).

gh-117755 [https://github.com/python/cpython/issues/117755]: Fix mimalloc allocator for huge memory allocation (around 8,589,934,592 GiB) on s390x. Patch by Victor Stinner.

gh-117750 [https://github.com/python/cpython/issues/117750]: Fix issue where an object's dict would get out of sync with the object's internal values when being cleared. obj.__dict__.clear() now clears the internal values, but leaves the dict attached to the object.

gh-117431 [https://github.com/python/cpython/issues/117431]: Improve the performance of the following bytes and bytearray methods by adapting them to the METH_FASTCALL calling convention:

count()

find()

index()

rfind()

rindex()

gh-117709 [https://github.com/python/cpython/issues/117709]: Speed up calls to str() with positional-only argument, by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Erlend Aasland.

gh-117680 [https://github.com/python/cpython/issues/117680]: Give _PyInstructionSequence a Python interface and use it in tests.

gh-115776 [https://github.com/python/cpython/issues/115776]: Statically allocated objects are, by definition, immortal so must be marked as such regardless of whether they are in extension modules or not.

gh-117385 [https://github.com/python/cpython/issues/117385]: Remove unhandled PY_MONITORING_EVENT_BRANCH and PY_MONITORING_EVENT_EXCEPTION_HANDLED events from sys.settrace().

gh-116322 [https://github.com/python/cpython/issues/116322]: Extension modules may indicate to the runtime that they can run without the GIL. Multi-phase init modules do so by calling providing Py_MOD_GIL_NOT_USED for the Py_mod_gil slot, while single-phase init modules call PyUnstable_Module_SetGIL(mod, Py_MOD_GIL_NOT_USED) from their init function.

gh-116129 [https://github.com/python/cpython/issues/116129]: Implement PEP 696 [https://peps.python.org/pep-0696/], adding support for defaults on type parameters. Patch by Jelle Zijlstra.

gh-93502 [https://github.com/python/cpython/issues/93502]: Add two new functions to the C-API, PyRefTracer_SetTracer() and PyRefTracer_GetTracer(), that allows to track object creation and destruction the same way the tracemalloc module does. Patch by Pablo Galindo

gh-107674 [https://github.com/python/cpython/issues/107674]: Improved the performance of sys.settrace() significantly

gh-95754 [https://github.com/python/cpython/issues/95754]: Improve the error message when a script shadowing a module from the standard library causes AttributeError to be raised. Similarly, improve the error message when a script shadowing a third party module attempts to access an attribute from that third party module while still initialising.

gh-99180 [https://github.com/python/cpython/issues/99180]: Elide uninformative traceback indicators in return and simple assignment statements. Patch by Pablo Galindo.

gh-105879 [https://github.com/python/cpython/issues/105879]: Allow the globals and locals arguments to exec() and eval() to be passed as keywords.

Library

gh-118418 [https://github.com/python/cpython/issues/118418]: A DeprecationWarning is now emitted if you fail to pass a value to the new type_params parameter of typing._eval_type() or typing.ForwardRef._evaluate(). (Using either of these private and undocumented functions is discouraged to begin with, but failing to pass a value to the type_params parameter may lead to incorrect behaviour on Python 3.12 or newer.)

gh-118660 [https://github.com/python/cpython/issues/118660]: Add an optional second type parameter to typing.ContextManager and typing.AsyncContextManager, representing the return types of __exit__() and __aexit__() respectively. This parameter defaults to bool | None.

gh-118650 [https://github.com/python/cpython/issues/118650]: The enum module allows method named _repr_* to be defined on Enum types.

gh-118648 [https://github.com/python/cpython/issues/118648]: Add type parameter defaults to typing.Generator and typing.AsyncGenerator.

gh-101137 [https://github.com/python/cpython/issues/101137]: Mime type text/x-rst is now supported by mimetypes.

gh-118164 [https://github.com/python/cpython/issues/118164]: The Python implementation of the decimal module could appear to hang in relatively small power cases (like 2**117) if context precision was set to a very high value. A different method to check for exactly representable results is used now that doesn't rely on computing 10**precision (which could be effectively too large to compute).

gh-111744 [https://github.com/python/cpython/issues/111744]: breakpoint() and pdb.set_trace() now enter the debugger immediately after the call rather than before the next line is executed.

gh-118500 [https://github.com/python/cpython/issues/118500]: Add pdb support for zipapps

gh-118406 [https://github.com/python/cpython/issues/118406]: Add signature for sqlite3.Connection objects.

gh-101732 [https://github.com/python/cpython/issues/101732]: Use a Y2038 compatible openssl time function when available.

gh-118404 [https://github.com/python/cpython/issues/118404]: Fix inspect.signature() for non-comparable callables.

gh-118402 [https://github.com/python/cpython/issues/118402]: Fix inspect.signature() for the result of the functools.cmp_to_key() call.

gh-116622 [https://github.com/python/cpython/issues/116622]: On Android, sysconfig.get_platform now returns the format specified by PEP 738 [https://peps.python.org/pep-0738/].

gh-118285 [https://github.com/python/cpython/issues/118285]: Allow to specify the signature of custom callable instances of extension type by the __text_signature__ attribute. Specify signatures of operator.attrgetter, operator.itemgetter, and operator.methodcaller instances.

gh-118314 [https://github.com/python/cpython/issues/118314]: Fix an edge case in binascii.a2b_base64() strict mode, where excessive padding is not detected when no padding is necessary.

gh-118271 [https://github.com/python/cpython/issues/118271]: Add the PhotoImage methods read() to read an image from a file and data() to get the image data. Add background and grayscale parameters to PhotoImage method write().

gh-118225 [https://github.com/python/cpython/issues/118225]: Add the PhotoImage method copy_replace() to copy a region from one image to other image, possibly with pixel zooming and/or subsampling. Add from_coords parameter to PhotoImage methods copy(), zoom() and subsample(). Add zoom and subsample parameters to PhotoImage method copy().

gh-118221 [https://github.com/python/cpython/issues/118221]: Fix a bug where sqlite3.Connection.iterdump() could fail if a custom row factory was used. Patch by Erlend Aasland.

gh-118013 [https://github.com/python/cpython/issues/118013]: Fix regression introduced in gh-103193 [https://github.com/python/cpython/issues/103193] that meant that calling inspect.getattr_static() on an instance would cause a strong reference to that instance's class to persist in an internal cache in the inspect module. This caused unexpected memory consumption if the class was dynamically created, the class held strong references to other objects which took up a significant amount of memory, and the cache contained the sole strong reference to the class. The fix for the regression leads to a slowdown in getattr_static(), but the function should still be significantly faster than it was in Python 3.11. Patch by Alex Waygood.

gh-118218 [https://github.com/python/cpython/issues/118218]: Speed up itertools.pairwise() in the common case by up to 1.8x.

gh-117486 [https://github.com/python/cpython/issues/117486]: Improve the behavior of user-defined subclasses of ast.AST. Such classes will now require no changes in the usual case to conform with the behavior changes of the ast module in Python 3.13. Patch by Jelle Zijlstra.

gh-90848 [https://github.com/python/cpython/issues/90848]: Fixed unittest.mock.create_autospec() to configure parent mock with keyword arguments.

gh-118168 [https://github.com/python/cpython/issues/118168]: Fix incorrect argument substitution when typing.Unpack is used with the builtin tuple. typing.Unpack now raises TypeError when used with certain invalid types. Patch by Jelle Zijlstra.

gh-118131 [https://github.com/python/cpython/issues/118131]: Add command-line interface for the random module. Patch by Hugo van Kemenade.

gh-118107 [https://github.com/python/cpython/issues/118107]: Fix zipimport reading of ZIP64 files with file entries that are too big or offset too far.

gh-102511 [https://github.com/python/cpython/issues/102511]: Fix os.path.normpath() for UNC paths on Windows. Speed up os.path.splitroot() with a native implementation.

gh-117535 [https://github.com/python/cpython/issues/117535]: Change the unknown filename of warnings from sys to <sys> to clarify that it's not a real filename.

gh-114053 [https://github.com/python/cpython/issues/114053]: Fix erroneous NameError when calling typing.get_type_hints() on a class that made use of PEP 695 [https://peps.python.org/pep-0695/] type parameters in a module that had from __future__ import annotations at the top of the file. Patch by Alex Waygood.

gh-116931 [https://github.com/python/cpython/issues/116931]: Add parameter fileobj check for tarfile.TarFile.addfile()

gh-117995 [https://github.com/python/cpython/issues/117995]: Don't raise DeprecationWarning when a sequence of parameters is used to bind indexed, nameless placeholders. See also gh-100668 [https://github.com/python/cpython/issues/100668].

gh-80361 [https://github.com/python/cpython/issues/80361]: Fix TypeError in email.message.Message.get_payload() when the charset is RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] encoded.

gh-86650 [https://github.com/python/cpython/issues/86650]: Fix IndexError when parse some emails with invalid Message-ID (including one-off addresses generated by Microsoft Outlook).

gh-117691 [https://github.com/python/cpython/issues/117691]: Improve the error messages emitted by tarfile deprecation warnings relating to PEP 706. If a filter argument is not provided to extract() or extractall, the deprecation warning now points to the line in the user's code where the relevant function was called. Patch by Alex Waygood.

gh-115874 [https://github.com/python/cpython/issues/115874]: Fixed a possible segfault during garbage collection of _asyncio.FutureIter objects. Patch by Savannah Ostrowski.

gh-115060 [https://github.com/python/cpython/issues/115060]: Speed up pathlib.Path.glob() by omitting an initial is_dir() call. As a result of this change, glob() can no longer raise OSError.

gh-77102 [https://github.com/python/cpython/issues/77102]: site module now parses .pth file with UTF-8 first, and locale encoding if UnicodeDecodeError happened. It supported only locale encoding before.

gh-76785 [https://github.com/python/cpython/issues/76785]: We've exposed the low-level _interpreters module for the sake of the PyPI implementation of PEP 734 [https://peps.python.org/pep-0734/]. It was sometimes available as the _xxsubinterpreters module and was formerly used only for testing. For the most part, it should be considered an internal module, like _thread and _imp. See https://discuss.python.org/t/pep-734-multiple-interpreters-in-the-stdlib/41147/26.

gh-115060 [https://github.com/python/cpython/issues/115060]: Speed up pathlib.Path.glob() by not scanning directories for non-wildcard pattern segments.

gh-117727 [https://github.com/python/cpython/issues/117727]: Speed up pathlib.Path.iterdir() by using os.scandir() internally.

gh-117586 [https://github.com/python/cpython/issues/117586]: Speed up pathlib.Path.walk() by working with strings internally.

gh-117722 [https://github.com/python/cpython/issues/117722]: Change the new multi-separator support in asyncio.StreamReader.readuntil() to only accept tuples of separators rather than arbitrary iterables.

gh-117692 [https://github.com/python/cpython/issues/117692]: Fixes a bug when doctest.DocTestFinder was failing on wrapped builtin_function_or_method.

gh-117348 [https://github.com/python/cpython/issues/117348]: Largely restored import time performance of configparser by avoiding dataclasses.

gh-117641 [https://github.com/python/cpython/issues/117641]: Speedup os.path.commonpath() on Unix.

gh-117663 [https://github.com/python/cpython/issues/117663]: Fix _simple_enum to detect aliases when multiple arguments are present but only one is the member value.

gh-117636 [https://github.com/python/cpython/issues/117636]: Speedup os.path.join().

gh-117618 [https://github.com/python/cpython/issues/117618]: Support package.module as filename for break command of pdb

gh-102247 [https://github.com/python/cpython/issues/102247]: the status codes enum with constants in http.HTTPStatus are updated to include the names from RFC9110. This RFC includes some HTTP statuses previously only used for WEBDAV and assigns more generic names to them.

The old constants are preserved for backwards compatibility.

gh-117607 [https://github.com/python/cpython/issues/117607]: Speedup os.path.relpath().

gh-117586 [https://github.com/python/cpython/issues/117586]: Speed up pathlib.Path.glob() by working with strings internally.

gh-117225 [https://github.com/python/cpython/issues/117225]: Add colour to doctest output. Patch by Hugo van Kemenade.

gh-117566 [https://github.com/python/cpython/issues/117566]: ipaddress.IPv6Address.is_loopback() will now return True for IPv4-mapped loopback addresses, i.e. addresses in the ::ffff:127.0.0.0/104 address space.

gh-117546 [https://github.com/python/cpython/issues/117546]: Fix issue where os.path.realpath() stopped resolving symlinks after encountering a symlink loop on POSIX.

gh-116720 [https://github.com/python/cpython/issues/116720]: Improved behavior of asyncio.TaskGroup when an external cancellation collides with an internal cancellation. For example, when two task groups are nested and both experience an exception in a child task simultaneously, it was possible that the outer task group would misbehave, because its internal cancellation was swallowed by the inner task group.

In the case where a task group is cancelled externally and also must raise an ExceptionGroup, it will now call the parent task's cancel() method. This ensures that a asyncio.CancelledError will be raised at the next await, so the cancellation is not lost.

An added benefit of these changes is that task groups now preserve the cancellation count (asyncio.Task.cancelling()).

In order to handle some corner cases, asyncio.Task.uncancel() may now reset the undocumented _must_cancel flag when the cancellation count reaches zero.

gh-117516 [https://github.com/python/cpython/issues/117516]: Add typing.TypeIs, implementing PEP 742 [https://peps.python.org/pep-0742/]. Patch by Jelle Zijlstra.

gh-117503 [https://github.com/python/cpython/issues/117503]: Fix support of non-ASCII user names in bytes paths in os.path.expanduser() on Posix.

gh-117394 [https://github.com/python/cpython/issues/117394]: os.path.ismount() is now 2-3 times faster if the user has permissions.

gh-117313 [https://github.com/python/cpython/issues/117313]: Only treat '\n', '\r' and '\r\n' as line separators in re-folding the email messages. Preserve control characters '\v', '\f', '\x1c', '\x1d' and '\x1e' and Unicode line separators '\x85', '\u2028' and '\u2029' as is.

gh-117142 [https://github.com/python/cpython/issues/117142]: Convert _ctypes to multi-phase initialisation (PEP 489 [https://peps.python.org/pep-0489/]).

gh-66543 [https://github.com/python/cpython/issues/66543]: Add the mimetypes.guess_file_type() function which works with file path. Passing file path instead of URL in guess_type() is soft deprecated.

gh-68583 [https://github.com/python/cpython/issues/68583]: webbrowser CLI: replace getopt with argparse, add long options. Patch by Hugo van Kemenade.

gh-116871 [https://github.com/python/cpython/issues/116871]: Name suggestions for AttributeError and ImportError now only include underscored names if the original name was underscored.

gh-116023 [https://github.com/python/cpython/issues/116023]: Don't show empty fields (value None or []) in ast.dump() by default. Add show_empty=False parameter to optionally show them.

gh-115961 [https://github.com/python/cpython/issues/115961]: Added name and mode attributes for compressed and archived file-like objects in modules bz2, lzma, tarfile and zipfile. The value of the mode attribute of gzip.GzipFile was changed from integer (1 or 2) to string ('rb' or 'wb'). The value of the mode attribute of the readable file-like object returned by zipfile.ZipFile.open() was changed from 'r' to 'rb'.

gh-82062 [https://github.com/python/cpython/issues/82062]: Fix inspect.signature() to correctly handle parameter defaults on methods in extension modules that use names defined in the module namespace.

gh-83856 [https://github.com/python/cpython/issues/83856]: Honor atexit for all multiprocessing start methods

gh-113081 [https://github.com/python/cpython/issues/113081]: Print colorized exception just like built-in traceback in pdb

gh-112855 [https://github.com/python/cpython/issues/112855]: Speed up pickling of pathlib.PurePath objects. Patch by Barney Gale.

gh-111744 [https://github.com/python/cpython/issues/111744]: Support opcode events in bdb

gh-109617 [https://github.com/python/cpython/issues/109617]: ncurses: fixed a crash that could occur on macOS 13 or earlier when Python was built with Apple Xcode 15's SDK.

gh-83151 [https://github.com/python/cpython/issues/83151]: Enabled arbitrary statements and evaluations in pdb shell to access the local variables of the current frame, which made it possible for multi-scope code like generators or nested function to work.

gh-110209 [https://github.com/python/cpython/issues/110209]: Add __class_getitem__() to types.GeneratorType and types.CoroutineType for type hinting purposes. Patch by James Hilton-Balfe.

gh-108191 [https://github.com/python/cpython/issues/108191]: The types.SimpleNamespace now accepts an optional positional argument which specifies initial values of attributes as a dict or an iterable of key-value pairs.

gh-62090 [https://github.com/python/cpython/issues/62090]: Fix assertion errors caused by whitespace in metavars or SUPPRESS-ed groups in argparse by simplifying usage formatting. Patch by Ali Hamdan.

gh-102402 [https://github.com/python/cpython/issues/102402]: Adjust logging.LogRecord to use time.time_ns() and fix minor bug related to floating-point math.

gh-100242 [https://github.com/python/cpython/issues/100242]: Bring pure Python implementation functools.partial.__new__ more in line with the C-implementation by not just always checking for the presence of the attribute 'func' on the first argument of partial. Instead, both the Python version and the C version perform an isinstance(func, partial) check on the first argument of partial.

gh-99730 [https://github.com/python/cpython/issues/99730]: HEAD requests are no longer upgraded to GET request during redirects in urllib.

gh-66410 [https://github.com/python/cpython/issues/66410]: Setting the tkinter module global wantobjects to 2 before creating the Tk object or call the wantobjects() method of the Tk object with argument 2 makes now arguments to callbacks registered in the tkinter module to be passed as various Python objects (int, float, bytes, tuple), depending on their internal representation in Tcl, instead of always str. tkinter.wantobjects is now set to 2 by default.

bpo-40943 [https://bugs.python.org/issue?@action=redirect&bpo=40943]: Fix several IndexError when parse emails with truncated Message-ID, address, routes, etc, e.g. example@.

bpo-39324 [https://bugs.python.org/issue?@action=redirect&bpo=39324]: Add mime type mapping for .md <-> text/markdown

bpo-18108 [https://bugs.python.org/issue?@action=redirect&bpo=18108]: shutil.chown() now supports dir_fd and follow_symlinks keyword arguments.

bpo-30988 [https://bugs.python.org/issue?@action=redirect&bpo=30988]: Fix parsing of emails with invalid address headers having a leading or trailing dot. Patch by tsufeki.

bpo-32839 [https://bugs.python.org/issue?@action=redirect&bpo=32839]: Add the after_info() method for Tkinter widgets.

Documentation

gh-117928 [https://github.com/python/cpython/issues/117928]: The minimum Sphinx version required for the documentation is now 6.2.1.

Build

gh-118734 [https://github.com/python/cpython/issues/118734]: Fixes Windows build when invoked directly (not through the build.bat script) without specifying a value for UseTIER2.

gh-115119 [https://github.com/python/cpython/issues/115119]: The configure option --with-system-libmpdec now defaults to yes. The bundled copy of libmpdecimal will be removed in Python 3.15.

gh-117845 [https://github.com/python/cpython/issues/117845]: Fix building against recent libedit versions by detecting readline hook signatures in configure.

gh-116622 [https://github.com/python/cpython/issues/116622]: A testbed project was added to run the test suite on Android.

gh-117645 [https://github.com/python/cpython/issues/117645]: Increase WASI stack size from 512 KiB to 8 MiB and the initial memory from 10 MiB to 20 MiB. Patch by Victor Stinner.

gh-115119 [https://github.com/python/cpython/issues/115119]: configure now uses pkg-config to detect decimal dependencies if the --with-system-libmpdec option is given.

Windows

gh-115119 [https://github.com/python/cpython/issues/115119]: Update Windows installer to use libmpdecimal 4.0.0.

gh-118486 [https://github.com/python/cpython/issues/118486]: os.mkdir() now accepts mode of 0o700 to restrict the new directory to the current user.

gh-118347 [https://github.com/python/cpython/issues/118347]: Fixes launcher updates not being installed.

gh-118293 [https://github.com/python/cpython/issues/118293]: The multiprocessing module now passes the STARTF_FORCEOFFFEEDBACK flag when spawning processes to tell Windows not to change the mouse cursor.

gh-115009 [https://github.com/python/cpython/issues/115009]: Update Windows installer to use SQLite 3.45.3.

gh-90329 [https://github.com/python/cpython/issues/90329]: Suppress the warning displayed on virtual environment creation when the requested and created paths differ only by a short (8.3 style) name. Warnings will continue to be shown if a junction or symlink in the path caused the venv to be created in a different location than originally requested.

gh-117786 [https://github.com/python/cpython/issues/117786]: Fixes virtual environments not correctly launching when created from a Store install.

macOS

gh-115119 [https://github.com/python/cpython/issues/115119]: Update macOS installer to use libmpdecimal 4.0.0.

gh-114099 [https://github.com/python/cpython/issues/114099]: iOS preprocessor symbol usage was made compatible with older macOS SDKs.

gh-115009 [https://github.com/python/cpython/issues/115009]: Update macOS installer to use SQLite 3.45.3.

gh-91629 [https://github.com/python/cpython/issues/91629]: Use ~/.config/fish/conf.d configs and fish_add_path to set PATH when installing for the Fish shell.

IDLE

bpo-34774 [https://bugs.python.org/issue?@action=redirect&bpo=34774]: Use user-selected color theme for Help => IDLE Doc.

C API

gh-118124 [https://github.com/python/cpython/issues/118124]: Fix Py_BUILD_ASSERT and Py_BUILD_ASSERT_EXPR for non-constant expressions: use static_assert() on C11 and newer. Patch by Victor Stinner.

gh-110850 [https://github.com/python/cpython/issues/110850]: Add "Raw" variant of PyTime functions

PyTime_MonotonicRaw()

PyTime_PerfCounterRaw()

PyTime_TimeRaw()

Patch by Victor Stinner.

gh-117987 [https://github.com/python/cpython/issues/117987]: Restore functions removed in Python 3.13 alpha 1:

Py_SetPythonHome()

Py_SetProgramName()

PySys_SetArgvEx()

PySys_SetArgv()

Patch by Victor Stinner.

gh-117929 [https://github.com/python/cpython/issues/117929]: Restore removed PyEval_InitThreads() function. Patch by Victor Stinner.

gh-117534 [https://github.com/python/cpython/issues/117534]: Improve validation logic in the C implementation of datetime.datetime.fromisoformat() to better handle invalid years. Patch by Vlad Efanov.

gh-68114 [https://github.com/python/cpython/issues/68114]: Fixed skipitem()'s handling of the old 'w' and 'w#' formatters. These are no longer supported and now raise an exception if used.

gh-111997 [https://github.com/python/cpython/issues/111997]: Add a C-API for firing monitoring events.

Python 3.13.0 alpha 6

Release date: 2024-04-09

Core and Builtins

gh-117494 [https://github.com/python/cpython/issues/117494]: Refactored the instruction sequence data structure out of compile.c into instruction_sequence.c.

gh-116968 [https://github.com/python/cpython/issues/116968]: Introduce a unified 16-bit backoff counter type (_Py_BackoffCounter), shared between the Tier 1 adaptive specializer and the Tier 2 optimizer. The API used for adaptive specialization counters is changed but the behavior is (supposed to be) identical.

The behavior of the Tier 2 counters is changed:

There are no longer dynamic thresholds (we never varied these).

All counters now use the same exponential backoff.

The counter for JUMP_BACKWARD starts counting down from 16.

The temperature in side exits starts counting down from 64.

gh-117431 [https://github.com/python/cpython/issues/117431]: Improve the performance of the following bytes and bytearray methods by adapting them to the METH_FASTCALL calling convention:

endswith()

startswith()

gh-117431 [https://github.com/python/cpython/issues/117431]: Improve the performance of the following str methods by adapting them to the METH_FASTCALL calling convention:

count()

endswith()

find()

index()

rfind()

rindex()

startswith()

gh-117411 [https://github.com/python/cpython/issues/117411]: Move PyFutureFeatures to an internal header and make it private.

gh-109120 [https://github.com/python/cpython/issues/109120]: Added handle of incorrect star expressions, e.g f(3, *). Patch by Grigoryev Semyon

gh-117266 [https://github.com/python/cpython/issues/117266]: Fix crashes for certain user-created subclasses of ast.AST. Such classes are now expected to set the _field_types attribute.

gh-99108 [https://github.com/python/cpython/issues/99108]: Updated the hashlib built-in HACL* project [https://github.com/hacl-star/hacl-star] C code from upstream that we use for many implementations when they are not present via OpenSSL in a given build. This also avoids the rare potential for a C symbol name one definition rule linking issue.

gh-117108 [https://github.com/python/cpython/issues/117108]: Change the old space bit of objects in the young generation from 0 to gcstate->visited, so that any objects created during GC will have the old bit set correctly if they get moved into the old generation.

gh-117108 [https://github.com/python/cpython/issues/117108]: The cycle GC now chooses the size of increments based on the total heap size, instead of the rate of object creation. This ensures that it can keep up with growing heaps.

gh-116735 [https://github.com/python/cpython/issues/116735]: For INSTRUMENTED_CALL_FUNCTION_EX, set arg0 to sys.monitoring.MISSING instead of None for CALL event.

gh-113964 [https://github.com/python/cpython/issues/113964]: Starting new threads and process creation through os.fork() are now only prevented once all non-daemon threads exit.

gh-116626 [https://github.com/python/cpython/issues/116626]: Ensure INSTRUMENTED_CALL_FUNCTION_EX always emits CALL

gh-116554 [https://github.com/python/cpython/issues/116554]: list.sort() now exploits more cases of partial ordering, particularly those with long descending runs with sub-runs of equal values. Those are recognized as single runs now (previously, each block of repeated values caused a new run to be created).

gh-114099 [https://github.com/python/cpython/issues/114099]: Added a Loader that can discover extension modules in an iOS-style Frameworks folder.

gh-115775 [https://github.com/python/cpython/issues/115775]: Compiler populates the new __static_attributes__ field on a class with the names of attributes of this class which are accessed through self.X from any function in its body.

gh-115776 [https://github.com/python/cpython/issues/115776]: The array of values, the PyDictValues struct is now embedded in the object during allocation. This provides better performance in the common case, and does not degrade as much when the object's __dict__ is materialized.

gh-108362 [https://github.com/python/cpython/issues/108362]: Implement an incremental cyclic garbage collector. By collecting the old generation in increments, there is no need for a full heap scan. This can hugely reduce maximum pause time for programs with large heaps.

Reduce the number of generations from three to two. The old generation is split into two spaces, "visited" and "pending".

Collection happens in two steps:: * An increment is formed from the young generation and a small part of the pending space. * This increment is scanned and the survivors moved to the end of the visited space.

When the collecting space becomes empty, the two spaces are swapped.

Library

gh-109870 [https://github.com/python/cpython/issues/109870]: Dataclasses now calls exec() once per dataclass, instead of once per method being added. This can speed up dataclass creation by up to 20%.

gh-97901 [https://github.com/python/cpython/issues/97901]: Mime type text/rtf is now supported by mimetypes.

Core and Builtins

bpo-24612 [https://bugs.python.org/issue?@action=redirect&bpo=24612]: Improve the SyntaxError that happens when 'not' appears after an operator. Patch by Pablo Galindo

Library

gh-117648 [https://github.com/python/cpython/issues/117648]: Improve performance of os.path.join() and os.path.expanduser().

gh-117584 [https://github.com/python/cpython/issues/117584]: Raise TypeError for non-paths in posixpath.relpath.

gh-117467 [https://github.com/python/cpython/issues/117467]: Preserve mailbox ownership when rewriting in mailbox.mbox.flush. Patch by Tony Mountifield.

gh-114848 [https://github.com/python/cpython/issues/114848]: Raise FileNotFoundError when getcwd() returns '(unreachable)', which can happen on Linux >= 2.6.36 with glibc < 2.27.

gh-117459 [https://github.com/python/cpython/issues/117459]: asyncio.asyncio.run_coroutine_threadsafe() now keeps the traceback of CancelledError, TimeoutError and InvalidStateError which are raised in the coroutine.

gh-117381 [https://github.com/python/cpython/issues/117381]: Fix error message for ntpath.commonpath().

gh-117337 [https://github.com/python/cpython/issues/117337]: Deprecate undocumented glob.glob0() and glob.glob1() functions. Use glob.glob() and pass a directory to its root_dir argument instead.

gh-117349 [https://github.com/python/cpython/issues/117349]: Optimise several functions in os.path.

gh-117348 [https://github.com/python/cpython/issues/117348]: Refactored configparser.RawConfigParser._read() to reduce cyclometric complexity and improve comprehensibility.

gh-117335 [https://github.com/python/cpython/issues/117335]: Raise TypeError for non-sequences for ntpath.commonpath().

gh-66449 [https://github.com/python/cpython/issues/66449]: configparser.ConfigParser now accepts unnamed sections before named ones, if configured to do so.

gh-88014 [https://github.com/python/cpython/issues/88014]: In documentation of gzip.GzipFile in module gzip, explain data type of optional constructor argument mtime, and recommend mtime = 0 for generating deterministic streams.

gh-117310 [https://github.com/python/cpython/issues/117310]: Fixed an unlikely early & extra Py_DECREF triggered crash in ssl when creating a new _ssl._SSLContext if CPython was built implausibly such that the default cipher list is empty or the SSL library it was linked against reports a failure from its C SSL_CTX_set_cipher_list() API.

gh-117294 [https://github.com/python/cpython/issues/117294]: A DocTestCase now reports as skipped if all examples in the doctest are skipped.

gh-98966 [https://github.com/python/cpython/issues/98966]: In subprocess, raise a more informative message when stdout=STDOUT.

gh-117225 [https://github.com/python/cpython/issues/117225]: doctest: only print "and X failed" when non-zero, don't pluralise "1 items". Patch by Hugo van Kemenade.

gh-117205 [https://github.com/python/cpython/issues/117205]: Speed up compileall.compile_dir() by 20% when using multiprocessing by increasing chunksize.

gh-117178 [https://github.com/python/cpython/issues/117178]: Fix regression in lazy loading of self-referential modules, introduced in gh-114781 [https://github.com/python/cpython/issues/114781].

gh-112383 [https://github.com/python/cpython/issues/112383]: Fix dis module's handling of ENTER_EXECUTOR instructions.

gh-117182 [https://github.com/python/cpython/issues/117182]: Lazy-loading of modules that modify their own __class__ no longer reverts the __class__ to types.ModuleType.

gh-117084 [https://github.com/python/cpython/issues/117084]: Fix zipfile extraction for directory entries with the name containing backslashes on Windows.

gh-117114 [https://github.com/python/cpython/issues/117114]: Make os.path.isdevdrive() available on all platforms. For those that do not offer Dev Drives, it will always return False.

gh-117110 [https://github.com/python/cpython/issues/117110]: Fix a bug that prevents subclasses of typing.Any to be instantiated with arguments. Patch by Chris Fu.

gh-109653 [https://github.com/python/cpython/issues/109653]: Deferred select imports in importlib.metadata and importlib.resources for a 14% speedup.

gh-70647 [https://github.com/python/cpython/issues/70647]: Start the deprecation period for the current behavior of datetime.datetime.strptime() and time.strptime() which always fails to parse a date string with a ValueError involving a day of month such as strptime("02-29", "%m-%d") when a year is not specified and the date happen to be February 29th. This should help avoid users finding new bugs every four years due to a natural mistaken assumption about the API when parsing partial date values.

gh-116987 [https://github.com/python/cpython/issues/116987]: Fixed inspect.findsource() for class code objects.

gh-114099 [https://github.com/python/cpython/issues/114099]: Modify standard library to allow for iOS platform differences.

gh-90872 [https://github.com/python/cpython/issues/90872]: On Windows, subprocess.Popen.wait() no longer calls WaitForSingleObject() with a negative timeout: pass 0 ms if the timeout is negative. Patch by Victor Stinner.

gh-116957 [https://github.com/python/cpython/issues/116957]: configparser: Don't leave ConfigParser values in an invalid state (stored as a list instead of a str) after an earlier read raised DuplicateSectionError or DuplicateOptionError.

gh-115538 [https://github.com/python/cpython/issues/115538]: _io.WindowsConsoleIO now emit a warning if a boolean value is passed as a filedescriptor argument.

gh-90095 [https://github.com/python/cpython/issues/90095]: Ignore empty lines and comments in .pdbrc

gh-106531 [https://github.com/python/cpython/issues/106531]: Refreshed zipfile._path from zipp 3.18 [https://zipp.readthedocs.io/en/latest/history.html#v3-18-0], providing better compatibility for PyPy, better glob performance for deeply nested zipfiles, and providing internal access to CompleteDirs.inject for use in other tests (like importlib.resources).

gh-63207 [https://github.com/python/cpython/issues/63207]: On Windows, time.time() now uses the GetSystemTimePreciseAsFileTime() clock to have a resolution better than 1 us, instead of the GetSystemTimeAsFileTime() clock which has a resolution of 15.6 ms. Patch by Victor Stinner.

gh-116764 [https://github.com/python/cpython/issues/116764]: Restore support of None and other false values in urllib.parse functions parse_qs() and parse_qsl(). Also, they now raise a TypeError for non-zero integers and non-empty sequences.

gh-116811 [https://github.com/python/cpython/issues/116811]: In PathFinder.invalidate_caches, delegate to MetadataPathFinder.invalidate_caches.

gh-116647 [https://github.com/python/cpython/issues/116647]: Fix recursive child in dataclasses

gh-113171 [https://github.com/python/cpython/issues/113171]: Fixed various false positives and false negatives in

ipaddress.IPv4Address.is_private (see these docs for details)

ipaddress.IPv4Address.is_global

ipaddress.IPv6Address.is_private

ipaddress.IPv6Address.is_global

Also in the corresponding ipaddress.IPv4Network and ipaddress.IPv6Network attributes.

gh-63283 [https://github.com/python/cpython/issues/63283]: In encodings.idna, any capitalization of the ACE prefix (xn--) is now acceptable. Patch by Pepijn de Vos and Zackery Spytz.

gh-71042 [https://github.com/python/cpython/issues/71042]: Add platform.android_ver(), which provides device and OS information on Android.

gh-73468 [https://github.com/python/cpython/issues/73468]: Added new math.fma() function, wrapping C99's fma() operation: fused multiply-add function. Patch by Mark Dickinson and Victor Stinner.

gh-116608 [https://github.com/python/cpython/issues/116608]: The importlib.resources functions is_resource(), open_binary(), open_text(), path(), read_binary(), and read_text() are un-deprecated, and support subdirectories via multiple positional arguments. The contents() function also allows subdirectories, but remains deprecated.

gh-116484 [https://github.com/python/cpython/issues/116484]: Change automatically generated tkinter.Checkbutton widget names to avoid collisions with automatically generated tkinter.ttk.Checkbutton widget names within the same parent widget.

gh-114314 [https://github.com/python/cpython/issues/114314]: In ctypes, ctype data is now stored in type objects directly rather than in a dict subclass. This is an internal change that should not affect usage.

gh-116401 [https://github.com/python/cpython/issues/116401]: Fix blocking os.fwalk() and shutil.rmtree() on opening named pipe.

gh-71052 [https://github.com/python/cpython/issues/71052]: Implement ctypes.util.find_library() on Android.

gh-90535 [https://github.com/python/cpython/issues/90535]: Fix support of interval values > 1 in logging.TimedRotatingFileHandler for when='MIDNIGHT' and when='Wx'.

gh-113308 [https://github.com/python/cpython/issues/113308]: Remove some internal protected parts from uuid: _has_uuid_generate_time_safe, _netbios_getnode, _ipconfig_getnode, and _load_system_functions. They were unused.

gh-115627 [https://github.com/python/cpython/issues/115627]: Fix the ssl module error handling of connection terminate by peer. It now throws an OSError with the appropriate error code instead of an EOFError.

gh-114847 [https://github.com/python/cpython/issues/114847]: Speed up os.path.realpath() on non-Windows platforms.

gh-114271 [https://github.com/python/cpython/issues/114271]: Fix a race in threading.Thread.join().

threading._MainThread now always represents the main thread of the main interpreter.

PyThreadState.on_delete and PyThreadState.on_delete_data have been removed.

gh-113538 [https://github.com/python/cpython/issues/113538]: Add asyncio.Server.close_clients() and asyncio.Server.abort_clients() methods which allow to more forcefully close an asyncio server.

gh-85287 [https://github.com/python/cpython/issues/85287]: Changes Unicode codecs to return UnicodeEncodeError or UnicodeDecodeError, rather than just UnicodeError.

gh-113548 [https://github.com/python/cpython/issues/113548]: pdb now allows CLI arguments to pdb -m.

gh-112948 [https://github.com/python/cpython/issues/112948]: Make completion of pdb similar to Python REPL

gh-105866 [https://github.com/python/cpython/issues/105866]: Fixed _get_slots bug which caused error when defining dataclasses with slots and a weakref_slot.

gh-96471 [https://github.com/python/cpython/issues/96471]: Add asyncio.Queue termination with shutdown() method.

gh-89739 [https://github.com/python/cpython/issues/89739]: The zipimport module can now read ZIP64 files.

bpo-33533 [https://bugs.python.org/issue?@action=redirect&bpo=33533]: asyncio.as_completed() now returns an object that is both an asynchronous iterator and plain iterator. The new asynchronous iteration pattern allows for easier correlation between prior tasks and their completed results. This is a closer match to concurrent.futures.as_completed()'s iteration pattern. Patch by Justin Arthur.

bpo-27578 [https://bugs.python.org/issue?@action=redirect&bpo=27578]: inspect.getsource() (and related functions) work with empty module files, returning '\n' (or reasonable equivalent) instead of raising OSError. Patch by Kernc.

bpo-37141 [https://bugs.python.org/issue?@action=redirect&bpo=37141]: Accept an iterable of separators in asyncio.StreamReader.readuntil(), stopping when one of them is encountered.

gh-66543 [https://github.com/python/cpython/issues/66543]: Make mimetypes.guess_type() properly parsing of URLs with only a host name, URLs containing fragment or query, and filenames with only a UNC sharepoint on Windows. Based on patch by Dong-hee Na.

bpo-15010 [https://bugs.python.org/issue?@action=redirect&bpo=15010]: unittest.TestLoader.discover() now saves the original value of unittest.TestLoader._top_level_dir and restores it at the end of the call.

Documentation

gh-115977 [https://github.com/python/cpython/issues/115977]: Remove compatibility references to Emscripten.

gh-114099 [https://github.com/python/cpython/issues/114099]: Add an iOS platform guide, and flag modules not available on iOS.

gh-91565 [https://github.com/python/cpython/issues/91565]: Changes to documentation files and config outputs to reflect the new location for reporting bugs - i.e. GitHub rather than bugs.python.org.

Tests

gh-83434 [https://github.com/python/cpython/issues/83434]: Disable JUnit XML output (--junit-xml=FILE command line option) in regrtest when hunting for reference leaks (-R option). Patch by Victor Stinner.

gh-117187 [https://github.com/python/cpython/issues/117187]: Fix XML tests for vanilla Expat <2.6.0.

gh-116333 [https://github.com/python/cpython/issues/116333]: Tests of TLS related things (error codes, etc) were updated to be more lenient about specific error message strings and behaviors as seen in the BoringSSL and AWS-LC forks of OpenSSL.

gh-117089 [https://github.com/python/cpython/issues/117089]: Consolidated tests for importlib.metadata in their own metadata package.

gh-115979 [https://github.com/python/cpython/issues/115979]: Update test_importlib so that it passes under WASI SDK 21.

gh-112536 [https://github.com/python/cpython/issues/112536]: Add --tsan to test.regrtest for running TSAN tests in reasonable execution times. Patch by Donghee Na.

gh-116307 [https://github.com/python/cpython/issues/116307]: Added import helper isolated_modules as CleanImport does not remove modules imported during the context. Use it in importlib.resources tests to avoid leaving mod around to impede importlib.metadata tests.

Build

gh-114736 [https://github.com/python/cpython/issues/114736]: Have WASI builds use WASI SDK 21.

gh-115983 [https://github.com/python/cpython/issues/115983]: Skip building test modules that must be built as shared under WASI.

gh-71052 [https://github.com/python/cpython/issues/71052]: Add Android build script and instructions.

Windows

gh-117267 [https://github.com/python/cpython/issues/117267]: Ensure DirEntry.stat().st_ctime behaves consistently with os.stat() during the deprecation period of st_ctime by containing the same value as st_birthtime. After the deprecation period, st_ctime will be the metadata change time (or unavailable through DirEntry), and only st_birthtime will contain the creation time.

gh-116195 [https://github.com/python/cpython/issues/116195]: Improves performance of os.getppid() by using an alternate system API when available. Contributed by vxiiduu.

gh-88494 [https://github.com/python/cpython/issues/88494]: On Windows, time.monotonic() now uses the QueryPerformanceCounter() clock to have a resolution better than 1 us, instead of the GetTickCount64() clock which has a resolution of 15.6 ms. Patch by Victor Stinner.

gh-116773 [https://github.com/python/cpython/issues/116773]: Fix instances of <_overlapped.Overlapped object at 0xXXX> still has pending operation at deallocation, the process may crash.

gh-91227 [https://github.com/python/cpython/issues/91227]: Fix the asyncio ProactorEventLoop implementation so that sending a datagram to an address that is not listening does not prevent receiving any more datagrams.

gh-115119 [https://github.com/python/cpython/issues/115119]: Switched from vendored libmpdecimal code to a separately-hosted external package in the cpython-source-deps repository when building the _decimal module.

C API

gh-117642 [https://github.com/python/cpython/issues/117642]: Fix PEP 737 [https://peps.python.org/pep-0737/] implementation for %#T and %#N.

gh-87193 [https://github.com/python/cpython/issues/87193]: _PyBytes_Resize() can now be called for bytes objects with reference count > 1, including 1-byte bytes objects. It creates a new bytes object and destroys the old one if it has reference count > 1.

gh-117021 [https://github.com/python/cpython/issues/117021]: Fix integer overflow in PyLong_AsPid() on non-Windows 64-bit platforms.

gh-115756 [https://github.com/python/cpython/issues/115756]: PyCode_GetFirstFree() is an ustable API now and has been renamed to PyUnstable_Code_GetFirstFree(). (Contributed by Bogdan Romanyuk in gh-115781 [https://github.com/python/cpython/issues/115781])

gh-116869 [https://github.com/python/cpython/issues/116869]: Add test_cext test: build a C extension to check if the Python C API emits C compiler warnings. Patch by Victor Stinner.

gh-116869 [https://github.com/python/cpython/issues/116869]: Make the C API compatible with -Werror=declaration-after-statement compiler flag again. Patch by Victor Stinner.

gh-116936 [https://github.com/python/cpython/issues/116936]: Add PyType_GetModuleByDef() to the limited C API. Patch by Victor Stinner.

gh-116809 [https://github.com/python/cpython/issues/116809]: Restore removed private _PyErr_ChainExceptions1() function. Patch by Victor Stinner.

gh-115754 [https://github.com/python/cpython/issues/115754]: In the limited C API version 3.13, getting Py_None, Py_False, Py_True, Py_Ellipsis and Py_NotImplemented singletons is now implemented as function calls at the stable ABI level to hide implementation details. Getting these constants still return borrowed references. Patch by Victor Stinner.

gh-115754 [https://github.com/python/cpython/issues/115754]: Add Py_GetConstant() and Py_GetConstantBorrowed() functions to get constants. For example, Py_GetConstant(Py_CONSTANT_ZERO) returns a strong reference to the constant zero. Patch by Victor Stinner.

gh-111696 [https://github.com/python/cpython/issues/111696]: Add support for %T, %T#, %N and %N# formats to PyUnicode_FromFormat(): format the fully qualified name of an object type and of a type: call PyType_GetModuleName(). See PEP 737 [https://peps.python.org/pep-0737/] for more information. Patch by Victor Stinner.

gh-111696 [https://github.com/python/cpython/issues/111696]: Add PyType_GetModuleName() function to get the type's module name. Equivalent to getting the type.__module__ attribute. Patch by Eric Snow and Victor Stinner.

gh-111696 [https://github.com/python/cpython/issues/111696]: Add PyType_GetFullyQualifiedName() function to get the type's fully qualified name. Equivalent to f"{type.__module__}.{type.__qualname__}", or type.__qualname__ if type.__module__ is not a string or is equal to "builtins". Patch by Victor Stinner.

gh-85283 [https://github.com/python/cpython/issues/85283]: The fcntl, grp, pwd, termios, _statistics and _testconsole C extensions are now built with the limited C API. Patch by Victor Stinner.

gh-111140 [https://github.com/python/cpython/issues/111140]: Add additional flags to PyLong_AsNativeBytes() and PyLong_FromNativeBytes() to allow the caller to determine how to handle edge cases around values that fill the entire buffer.

gh-113024 [https://github.com/python/cpython/issues/113024]: Add PyObject_GenericHash() function.

Python 3.13.0 alpha 5

Release date: 2024-03-12

Security

gh-115398 [https://github.com/python/cpython/issues/115398]: Allow controlling Expat >=2.6.0 reparse deferral (CVE 2023-52425 [https://www.cve.org/CVERecord?id=CVE-2023-52425]) by adding five new methods:

xml.etree.ElementTree.XMLParser.flush()

xml.etree.ElementTree.XMLPullParser.flush()

xml.parsers.expat.xmlparser.GetReparseDeferralEnabled()

xml.parsers.expat.xmlparser.SetReparseDeferralEnabled()

xml.sax.expatreader.ExpatParser.flush()

gh-114572 [https://github.com/python/cpython/issues/114572]: ssl.SSLContext.cert_store_stats() and ssl.SSLContext.get_ca_certs() now correctly lock access to the certificate store, when the ssl.SSLContext is shared across multiple threads.

Core and Builtins

gh-116604 [https://github.com/python/cpython/issues/116604]: Respect the status of the garbage collector when indirect calls are made via PyErr_CheckSignals() and the evaluation breaker. Patch by Pablo Galindo

gh-112087 [https://github.com/python/cpython/issues/112087]: list is now compatible with the implementation of PEP 703 [https://peps.python.org/pep-0703/].

gh-116381 [https://github.com/python/cpython/issues/116381]: Add specialization for CONTAINS_OP.

gh-116296 [https://github.com/python/cpython/issues/116296]: Fix possible refleak in object.__reduce__() internal error handling.

gh-115823 [https://github.com/python/cpython/issues/115823]: Properly calculate error ranges in the parser when raising SyntaxError exceptions caused by invalid byte sequences. Patch by Pablo Galindo

gh-115778 [https://github.com/python/cpython/issues/115778]: Add tierN annotation for instruction definition in interpreter DSL.

gh-115733 [https://github.com/python/cpython/issues/115733]: Fix crash when calling next() on exhausted list iterators.

gh-115700 [https://github.com/python/cpython/issues/115700]: The regen-cases build stage now works on Windows.

gh-115347 [https://github.com/python/cpython/issues/115347]: Fix bug where docstring was replaced by a redundant NOP when Python is run with -OO.

gh-115323 [https://github.com/python/cpython/issues/115323]: Make error message more meaningful for when bytearray.extend() is called with a str object.

gh-112175 [https://github.com/python/cpython/issues/112175]: Every PyThreadState now has its own eval_breaker, allowing specific threads to be interrupted.

Library

gh-115154 [https://github.com/python/cpython/issues/115154]: Fix a bug that was causing the tokenize.untokenize() function to handle unicode named literals incorrectly. Patch by Pablo Galindo

Core and Builtins

gh-112433 [https://github.com/python/cpython/issues/112433]: Add ability to force alignment of ctypes.Structure by way of the new _align_ attribute on the class.

Library

gh-104090 [https://github.com/python/cpython/issues/104090]: The multiprocessing resource tracker now exits with non-zero status code if a resource leak was detected. It still exits with status code 0 otherwise.

Core and Builtins

gh-105858 [https://github.com/python/cpython/issues/105858]: Improve the constructors for ast nodes. Arguments of list types now default to an empty list if omitted, and optional fields default to None. AST nodes now have an __annotations__ attribute with the expected types of their attributes. Passing unrecognized extra arguments to AST nodes is deprecated and will become an error in Python 3.15. Omitting a required argument to an AST node is deprecated and will become an error in Python 3.15. Patch by Jelle Zijlstra.

gh-101860 [https://github.com/python/cpython/issues/101860]: Expose __name__ attribute on property.

gh-96497 [https://github.com/python/cpython/issues/96497]: Fix incorrect resolution of mangled class variables used in assignment expressions in comprehensions.

Library

gh-116600 [https://github.com/python/cpython/issues/116600]: Fix repr() for global Flag members.

gh-116349 [https://github.com/python/cpython/issues/116349]: platform.java_ver() is deprecated and will be removed in 3.15. It was largely untested, had a confusing API, and was only useful for Jython support.

gh-116143 [https://github.com/python/cpython/issues/116143]: Fix a race in pydoc _start_server, eliminating a window in which _start_server can return a thread that is "serving" but without a docserver set.

gh-116127 [https://github.com/python/cpython/issues/116127]: typing: implement PEP 705 [https://peps.python.org/pep-0705/] which adds typing.ReadOnly support to typing.TypedDict.

gh-116325 [https://github.com/python/cpython/issues/116325]: typing: raise SyntaxError instead of AttributeError on forward references as empty strings.

gh-115957 [https://github.com/python/cpython/issues/115957]: When asyncio.TaskGroup.create_task is called on an inactive asyncio.TaskGroup, the given coroutine will be closed (which prevents a RuntimeWarning).

gh-115978 [https://github.com/python/cpython/issues/115978]: Disable preadv(), readv(), pwritev(), and writev() on WASI.

Under wasmtime for WASI 0.2, these functions don't pass test_posix (https://github.com/bytecodealliance/wasmtime/issues/7830).

gh-88352 [https://github.com/python/cpython/issues/88352]: Fix the computation of the next rollover time in the logging.TimedRotatingFileHandler handler. computeRollover() now always returns a timestamp larger than the specified time and works correctly during the DST change. doRollover() no longer overwrite the already rolled over file, saving from data loss when run at midnight or during repeated time at the DST change.

gh-87115 [https://github.com/python/cpython/issues/87115]: Set __main__.__spec__ to None when running a script with pdb

gh-76511 [https://github.com/python/cpython/issues/76511]: Fix UnicodeEncodeError in email.Message.as_string() that results when a message that claims to be in the ascii character set actually has non-ascii characters. Non-ascii characters are now replaced with the U+FFFD replacement character, like in the replace error handler.

gh-89547 [https://github.com/python/cpython/issues/89547]: Add support for nested typing special forms like Final[ClassVar[int]].

gh-65824 [https://github.com/python/cpython/issues/65824]: Improve the less prompt in pydoc.

gh-116040 [https://github.com/python/cpython/issues/116040]: [Enum] fix by-value calls when second value is falsey; e.g. Cardinal(1, 0)

gh-115821 [https://github.com/python/cpython/issues/115821]: [Enum] Improve error message when calling super().__new__() in custom __new__.

gh-85644 [https://github.com/python/cpython/issues/85644]: Use the XDG_CURRENT_DESKTOP environment variable in webbrowser to check desktop. Prefer it to the deprecated GNOME_DESKTOP_SESSION_ID for GNOME detection.

gh-75988 [https://github.com/python/cpython/issues/75988]: Fixed unittest.mock.create_autospec() to pass the call through to the wrapped object to return the real result.

gh-115881 [https://github.com/python/cpython/issues/115881]: Fix issue where ast.parse() would incorrectly flag conditional context managers (such as with (x() if y else z()): ...) as invalid syntax if feature_version=(3, 8) was passed. This reverts changes to the grammar made as part of gh-94949 [https://github.com/python/cpython/issues/94949].

gh-115886 [https://github.com/python/cpython/issues/115886]: Fix silent truncation of the name with an embedded null character in multiprocessing.shared_memory.SharedMemory.

gh-115532 [https://github.com/python/cpython/issues/115532]: Add kernel density estimation to the statistics module.

gh-115714 [https://github.com/python/cpython/issues/115714]: On WASI, the time module no longer get process time using times() or CLOCK_PROCESS_CPUTIME_ID, system API is that is unreliable and is likely to be removed from WASI. The affected clock functions fall back to calling clock().

gh-115809 [https://github.com/python/cpython/issues/115809]: Improve algorithm for computing which rolled-over log files to delete in logging.TimedRotatingFileHandler. It is now reliable for handlers without namer and with arbitrary deterministic namer that leaves the datetime part in the file name unmodified.

gh-74668 [https://github.com/python/cpython/issues/74668]: urllib.parse functions parse_qs() and parse_qsl() now support bytes arguments containing raw and percent-encoded non-ASCII data.

gh-67044 [https://github.com/python/cpython/issues/67044]: csv.writer() now always quotes or escapes '\r' and '\n', regardless of lineterminator value.

gh-115712 [https://github.com/python/cpython/issues/115712]: Restore support of space delimiter with skipinitialspace=True in csv. csv.writer() now quotes empty fields if delimiter is a space and skipinitialspace is true and raises exception if quoting is not possible.

gh-112364 [https://github.com/python/cpython/issues/112364]: Fixed ast.unparse() to handle format_spec with ", ' or \\. Patched by Frank Hoffmann.

gh-112997 [https://github.com/python/cpython/issues/112997]: Stop logging potentially sensitive callback arguments in asyncio unless debug mode is active.

gh-114914 [https://github.com/python/cpython/issues/114914]: Fix an issue where an abandoned StreamWriter would not be garbage collected.

gh-111358 [https://github.com/python/cpython/issues/111358]: Fix a bug in asyncio.BaseEventLoop.shutdown_default_executor() to ensure the timeout passed to the coroutine behaves as expected.

gh-115618 [https://github.com/python/cpython/issues/115618]: Fix improper decreasing the reference count for None argument in property methods getter(), setter() and deleter().

gh-112720 [https://github.com/python/cpython/issues/112720]: Refactor dis.ArgResolver to make it possible to subclass and change the way jump args are interpreted.

gh-112006 [https://github.com/python/cpython/issues/112006]: Fix inspect.unwrap() for types with the __wrapper__ data descriptor. Fix inspect.Signature.from_callable() for builtins classmethod() and staticmethod().

gh-101293 [https://github.com/python/cpython/issues/101293]: Support callables with the __call__() method and types with __new__() and __init__() methods set to class methods, static methods, bound methods, partial functions, and other types of methods and descriptors in inspect.Signature.from_callable().

gh-103092 [https://github.com/python/cpython/issues/103092]: Isolate _lsprof (apply PEP 687 [https://peps.python.org/pep-0687/]).

gh-113942 [https://github.com/python/cpython/issues/113942]: pydoc no longer skips global functions implemented as builtin methods, such as MethodDescriptorType and WrapperDescriptorType.

gh-115256 [https://github.com/python/cpython/issues/115256]: Added DeprecationWarning when accessing the tarfile attribute of TarInfo objects. The attribute is never used internally and is only attached to TarInfos when the tarfile is opened in write-mode, not read-mode. The attribute creates an unnecessary reference cycle which may cause corruption when not closing the handle after writing a tarfile.

gh-115197 [https://github.com/python/cpython/issues/115197]: urllib.request no longer resolves the hostname before checking it against the system's proxy bypass list on macOS and Windows.

gh-113812 [https://github.com/python/cpython/issues/113812]: DatagramTransport.sendto() will now send zero-length datagrams if called with an empty bytes object. The transport flow control also now accounts for the datagram header when calculating the buffer size.

gh-114763 [https://github.com/python/cpython/issues/114763]: Protect modules loaded with importlib.util.LazyLoader from race conditions when multiple threads try to access attributes before the loading is complete.

gh-114709 [https://github.com/python/cpython/issues/114709]: posixpath.commonpath() now raises a ValueError exception when passed an empty iterable. Previously, IndexError was raised.

posixpath.commonpath() now raises a TypeError exception when passed None. Previously, ValueError was raised.

gh-114610 [https://github.com/python/cpython/issues/114610]: Fix bug where pathlib.PurePath.with_stem() converted a non-empty path suffix to a stem when given an empty stem argument. It now raises ValueError, just like pathlib.PurePath.with_suffix() does when called on a path with an empty stem, given a non-empty suffix argument.

gh-107361 [https://github.com/python/cpython/issues/107361]: Add ssl.VERIFY_X509_PARTIAL_CHAIN and VERIFY_X509_STRICT to the default SSL context created with ssl.create_default_context().

gh-112281 [https://github.com/python/cpython/issues/112281]: Allow creating union of types for typing.Annotated with unhashable metadata.

gh-111775 [https://github.com/python/cpython/issues/111775]: Fix importlib.resources.simple.ResourceHandle.open() for text mode, added missed stream argument.

gh-90095 [https://github.com/python/cpython/issues/90095]: Make .pdbrc and -c work with any valid pdb commands.

gh-107625 [https://github.com/python/cpython/issues/107625]: Raise configparser.ParsingError from read() and read_file() methods of configparser.ConfigParser if a key without a corresponding value is continued (that is, followed by an indented line).

gh-107155 [https://github.com/python/cpython/issues/107155]: Fix incorrect output of help(x) where x is a lambda function, which has an __annotations__ dictionary attribute with a "return" key.

gh-57141 [https://github.com/python/cpython/issues/57141]: Add option for non-shallow comparisons to filecmp.dircmp like filecmp.cmp(). Original patch by Steven Ward. Enhanced by Tobias Rautenkranz

gh-69990 [https://github.com/python/cpython/issues/69990]: Profile.print_stats() has been improved to accept multiple sort arguments. Patched by Chiu-Hsiang Hsu and Furkan Onder.

gh-104061 [https://github.com/python/cpython/issues/104061]: Add socket.SO_BINDTOIFINDEX constant.

gh-60346 [https://github.com/python/cpython/issues/60346]: Fix ArgumentParser inconsistent with parse_known_args.

gh-102389 [https://github.com/python/cpython/issues/102389]: Add windows_31j to aliases for cp932 codec

gh-72249 [https://github.com/python/cpython/issues/72249]: Always include the module name in the repr() of functools.partial() objects. Patch by Furkan Onder and Anilyka Barry.

gh-100985 [https://github.com/python/cpython/issues/100985]: Update HTTPSConnection to consistently wrap IPv6 Addresses when using a proxy.

gh-100884 [https://github.com/python/cpython/issues/100884]: email: fix misfolding of comma in address-lists over multiple lines in combination with unicode encoding.

gh-95782 [https://github.com/python/cpython/issues/95782]: Fix io.BufferedReader.tell(), io.BufferedReader.seek(), _pyio.BufferedReader.tell(), io.BufferedRandom.tell(), io.BufferedRandom.seek() and _pyio.BufferedRandom.tell() being able to return negative offsets.

gh-96310 [https://github.com/python/cpython/issues/96310]: Fix a traceback in argparse when all options in a mutually exclusive group are suppressed.

gh-93205 [https://github.com/python/cpython/issues/93205]: Fixed a bug in logging.handlers.TimedRotatingFileHandler where multiple rotating handler instances pointing to files with the same name but different extensions would conflict and not delete the correct files.

bpo-31116 [https://bugs.python.org/issue?@action=redirect&bpo=31116]: Add Z85 encoding to base64.

bpo-44865 [https://bugs.python.org/issue?@action=redirect&bpo=44865]: Add missing call to localization function in argparse.

bpo-43952 [https://bugs.python.org/issue?@action=redirect&bpo=43952]: Fix multiprocessing.connection.Listener.accept() to accept empty bytes as authkey. Not accepting empty bytes as key causes it to hang indefinitely.

bpo-42125 [https://bugs.python.org/issue?@action=redirect&bpo=42125]: linecache: get module name from __spec__ if available. This allows getting source code for the __main__ module when a custom loader is used.

bpo-41122 [https://bugs.python.org/issue?@action=redirect&bpo=41122]: Failing to pass arguments properly to functools.singledispatchmethod() now throws a TypeError instead of hitting an index out of bounds internally.

bpo-40818 [https://bugs.python.org/issue?@action=redirect&bpo=40818]: The asyncio REPL now runs sys.__interactivehook__ on startup. The default implementation of sys.__interactivehook__ provides auto-completion to the asyncio REPL. Patch contributed by Rémi Lapeyre.

bpo-33775 [https://bugs.python.org/issue?@action=redirect&bpo=33775]: Add 'default' and 'version' help text for localization in argparse.

Documentation

gh-115399 [https://github.com/python/cpython/issues/115399]: Document CVE 2023-52425 [https://www.cve.org/CVERecord?id=CVE-2023-52425] of Expat <2.6.0 under "XML vulnerabilities".

gh-109653 [https://github.com/python/cpython/issues/109653]: Improve import time of uuid on Linux.

Tests

gh-71052 [https://github.com/python/cpython/issues/71052]: Add test exclusions to support running the test suite on Android.

gh-71052 [https://github.com/python/cpython/issues/71052]: Enable test_concurrent_futures on platforms that support threading but not multiprocessing.

gh-115796 [https://github.com/python/cpython/issues/115796]: Make '_testinternalcapi.assemble_code_object' construct the exception table for the code object.

gh-115720 [https://github.com/python/cpython/issues/115720]: Leak tests (-R, --huntrleaks) now show a summary of the number of leaks found in each iteration.

gh-115122 [https://github.com/python/cpython/issues/115122]: Add --bisect option to regrtest test runner: run failed tests with test.bisect_cmd to identify failing tests. Patch by Victor Stinner.

gh-115596 [https://github.com/python/cpython/issues/115596]: Fix ProgramPriorityTests in test_os permanently changing the process priority.

gh-115556 [https://github.com/python/cpython/issues/115556]: On Windows, commas passed in arguments to Tools\buildbot\test.bat and PCbuild\\rt.bat are now properly handled.

gh-115420 [https://github.com/python/cpython/issues/115420]: Fix translation of exception handler targets by _testinternalcapi.optimize_cfg.

gh-115376 [https://github.com/python/cpython/issues/115376]: Fix segfault in _testinternalcapi.compiler_codegen on bad input.

Build

gh-116313 [https://github.com/python/cpython/issues/116313]: Get WASI builds to work under wasmtime 18 w/ WASI 0.2/preview2 primitives.

gh-71052 [https://github.com/python/cpython/issues/71052]: Change Android's sys.platform from "linux" to "android".

gh-116117 [https://github.com/python/cpython/issues/116117]: Backport libb2's PR #42 to fix compiling CPython on 32-bit Windows with clang-cl.

gh-71052 [https://github.com/python/cpython/issues/71052]: Fix several Android build issues

gh-114099 [https://github.com/python/cpython/issues/114099]: A testbed project was added to run the test suite on iOS.

gh-115350 [https://github.com/python/cpython/issues/115350]: Fix building ctypes module with -DWIN32_LEAN_AND_MEAN defined

gh-111225 [https://github.com/python/cpython/issues/111225]: Link extension modules against libpython on Android.

gh-115737 [https://github.com/python/cpython/issues/115737]: The install name for libPython is now correctly set for non-framework macOS builds.

gh-114099 [https://github.com/python/cpython/issues/114099]: Makefile targets were added to support compiling an iOS-compatible framework build.

Windows

gh-116012 [https://github.com/python/cpython/issues/116012]: Ensure the value of GetLastError() is preserved across GIL operations.

gh-115582 [https://github.com/python/cpython/issues/115582]: Building extensions intended for free-threaded builds of CPython now require compiling with /DPy_GIL_DISABLED manually when using a regular install. This is expected to change in future releases.

gh-115554 [https://github.com/python/cpython/issues/115554]: The installer now has more strict rules about updating the Python 安裝管理員. In general, most users only have a single launcher installed and will see no difference. When multiple launchers have been installed, the option to install the launcher is disabled until all but one have been removed. Downgrading the launcher (which was never allowed) is now more obviously blocked.

gh-115543 [https://github.com/python/cpython/issues/115543]: Python 安裝管理員 can now detect Python 3.13 when installed from the Microsoft Store, and will install Python 3.12 by default when PYLAUNCHER_ALLOW_INSTALL is set.

macOS

gh-116145 [https://github.com/python/cpython/issues/116145]: Update macOS installer to Tcl/Tk 8.6.14.

IDLE

gh-88516 [https://github.com/python/cpython/issues/88516]: On macOS show a proxy icon in the title bar of editor windows to match platform behaviour.

Tools/Demos

gh-100176 [https://github.com/python/cpython/issues/100176]: Remove outdated Tools/{io,cc,string}bench

bpo-45101 [https://bugs.python.org/issue?@action=redirect&bpo=45101]: Add consistency in usage message IO between 2 versions of python-config.

C API

gh-114626 [https://github.com/python/cpython/issues/114626]: Add again _PyCFunctionFastWithKeywords name, removed in Python 3.13 alpha 4 by mistake. Keep the old private _PyCFunctionFastWithKeywords name (Python 3.7) as an alias to the new public name PyCFunctionFastWithKeywords (Python 3.13a4). Patch by Victor Stinner.

gh-111418 [https://github.com/python/cpython/issues/111418]: Add PyHASH_MODULUS, PyHASH_BITS, PyHASH_INF and PyHASH_IMAG C macros. Patch by Sergey B Kirpichev.

Python 3.13.0 alpha 4

Release date: 2024-02-15

Security

gh-115399 [https://github.com/python/cpython/issues/115399]: Update bundled libexpat to 2.6.0

gh-115243 [https://github.com/python/cpython/issues/115243]: Fix possible crashes in collections.deque.index() when the deque is concurrently modified.

Core and Builtins

gh-112087 [https://github.com/python/cpython/issues/112087]: For an empty reverse iterator for list will be reduced to reversed(). Patch by Donghee Na

gh-114570 [https://github.com/python/cpython/issues/114570]: Add PythonFinalizationError exception. This exception derived from RuntimeError is raised when an operation is blocked during the Python finalization. Patch by Victor Stinner.

gh-114695 [https://github.com/python/cpython/issues/114695]: Add sys._clear_internal_caches(), which clears all internal performance-related caches (and deprecate the less-general sys._clear_type_cache() function).

gh-114828 [https://github.com/python/cpython/issues/114828]: Fix compilation crashes in uncommon code examples using super() inside a comprehension in a class body.

gh-112069 [https://github.com/python/cpython/issues/112069]: Adapt set and frozenset methods to Argument Clinic.

gh-115011 [https://github.com/python/cpython/issues/115011]: Setters for members with an unsigned integer type now support the same range of valid values for objects that has a __index__() method as for int.

gh-114887 [https://github.com/python/cpython/issues/114887]: Changed socket type validation in create_datagram_endpoint() to accept all non-stream sockets. This fixes a regression in compatibility with raw sockets.

gh-114944 [https://github.com/python/cpython/issues/114944]: Fixes a race between PyParkingLot_Park and _PyParkingLot_UnparkAll.

gh-113462 [https://github.com/python/cpython/issues/113462]: Limit the number of versions that a single class can use. Prevents a few wayward classes using up all the version numbers.

gh-76763 [https://github.com/python/cpython/issues/76763]: The chr() builtin function now always raises ValueError for values outside the valid range. Previously it raised OverflowError for very large or small values.

gh-114806 [https://github.com/python/cpython/issues/114806]: No longer specialize calls to classes, if those classes have metaclasses. Fixes bug where the __call__ method of the metaclass was not being called.

gh-107944 [https://github.com/python/cpython/issues/107944]: Improve error message for function calls with bad keyword arguments via getargs

gh-112529 [https://github.com/python/cpython/issues/112529]: The free-threaded build no longer allocates space for the PyGC_Head structure in objects that support cyclic garbage collection. A number of other fields and data structures are used as replacements, including ob_gc_bits, ob_tid, and mimalloc internal data structures.

gh-114456 [https://github.com/python/cpython/issues/114456]: Lower the recursion limit under a debug build of WASI.

gh-114083 [https://github.com/python/cpython/issues/114083]: Compiler applies folding of LOAD_CONST with following instruction in a separate pass before other optimisations. This enables jump threading in certain circumstances.

gh-114388 [https://github.com/python/cpython/issues/114388]: Fix a RuntimeWarning emitted when assign an integer-like value that is not an instance of int to an attribute that corresponds to a C struct member of type T_UINT and T_ULONG. Fix a double RuntimeWarning emitted when assign a negative integer value to an attribute that corresponds to a C struct member of type T_UINT.

gh-114265 [https://github.com/python/cpython/issues/114265]: Compiler propagates line numbers before optimization, leading to more optimization opportunities and removing the need for the guarantee_lineno_for_exits hack.

gh-112529 [https://github.com/python/cpython/issues/112529]: The free-threaded build now has its own thread-safe GC implementation that uses mimalloc to find GC tracked objects. It is non-generational, unlike the existing GC implementation.

gh-114050 [https://github.com/python/cpython/issues/114050]: Fix segmentation fault caused by an incorrect format string in TypeError exception when more than two arguments are passed to int.

gh-112354 [https://github.com/python/cpython/issues/112354]: The END_FOR instruction now pops only one value. This is to better support side exits in loops.

gh-113884 [https://github.com/python/cpython/issues/113884]: Make queue.SimpleQueue thread safe when the GIL is disabled.

gh-114058 [https://github.com/python/cpython/issues/114058]: Implement the foundations of the Tier 2 redundancy eliminator.

gh-113939 [https://github.com/python/cpython/issues/113939]: frame.clear(): Clear frame.f_locals as well, and not only the fast locals. This is relevant once frame.f_locals was accessed, which would contain also references to all the locals.

gh-112050 [https://github.com/python/cpython/issues/112050]: Convert collections.deque to use Argument Clinic.

gh-112050 [https://github.com/python/cpython/issues/112050]: Make methods on collections.deque thread-safe when the GIL is disabled.

gh-113464 [https://github.com/python/cpython/issues/113464]: Add an option (--enable-experimental-jit for configure-based builds or --experimental-jit for PCbuild-based ones) to build an experimental just-in-time compiler, based on copy-and-patch [https://fredrikbk.com/publications/copy-and-patch.pdf]

gh-113055 [https://github.com/python/cpython/issues/113055]: Make interp->obmalloc a pointer. For interpreters that share state with the main interpreter, this points to the same static memory structure. For interpreters with their own obmalloc state, it is heap allocated. Add free_obmalloc_arenas() which will free the obmalloc arenas and radix tree structures for interpreters with their own obmalloc state.

gh-55664 [https://github.com/python/cpython/issues/55664]: Add warning when creating type using a namespace dictionary with non-string keys. Patched by Daniel Urban and Furkan Onder.

gh-104530 [https://github.com/python/cpython/issues/104530]: Use native Win32 condition variables.

Library

gh-115392 [https://github.com/python/cpython/issues/115392]: Fix a bug in doctest where incorrect line numbers would be reported for decorated functions.

gh-114563 [https://github.com/python/cpython/issues/114563]: Fix several format() bugs when using the C implementation of Decimal: * memory leak in some rare cases when using the z format option (coerce negative 0) * incorrect output when applying the z format option to type F (fixed-point with capital NAN / INF) * incorrect output when applying the # format option (alternate form)

gh-102840 [https://github.com/python/cpython/issues/102840]: Fix confused traceback when floordiv, mod, or divmod operations happens between instances of fractions.Fraction and complex.

gh-115165 [https://github.com/python/cpython/issues/115165]: Most exceptions are now ignored when attempting to set the __orig_class__ attribute on objects returned when calling typing generic aliases (including generic aliases created using typing.Annotated). Previously only AttributeError was ignored. Patch by Dave Shawley.

gh-112903 [https://github.com/python/cpython/issues/112903]: Fix "issubclass() arg 1 must be a class" errors in certain cases of multiple inheritance with generic aliases (regression in early 3.13 alpha releases).

gh-115133 [https://github.com/python/cpython/issues/115133]: Fix tests for XMLPullParser with Expat 2.6.0.

gh-115059 [https://github.com/python/cpython/issues/115059]: io.BufferedRandom.read1() now flushes the underlying write buffer.

gh-79382 [https://github.com/python/cpython/issues/79382]: Trailing ** no longer allows to match files and non-existing paths in recursive glob().

gh-67837 [https://github.com/python/cpython/issues/67837]: Avoid race conditions in the creation of directories during concurrent extraction in tarfile and zipfile.

gh-115060 [https://github.com/python/cpython/issues/115060]: Speed up pathlib.Path.glob() by removing redundant regex matching.

gh-97928 [https://github.com/python/cpython/issues/97928]: Partially revert the behavior of tkinter.Text.count(). By default it preserves the behavior of older Python versions, except that setting wantobjects to 0 no longer has effect. Add a new parameter return_ints: specifying return_ints=True makes Text.count() always returning the single count as an integer instead of a 1-tuple or None.

gh-114628 [https://github.com/python/cpython/issues/114628]: When csv.Error is raised when handling TypeError, do not print the TypeError traceback.

gh-85984 [https://github.com/python/cpython/issues/85984]: Added _POSIX_VDISABLE from C's <unistd.h> to termios.

gh-114965 [https://github.com/python/cpython/issues/114965]: Update bundled pip to 24.0

gh-114959 [https://github.com/python/cpython/issues/114959]: tarfile no longer ignores errors when trying to extract a directory on top of a file.

gh-114894 [https://github.com/python/cpython/issues/114894]: Add array.array.clear().

gh-114071 [https://github.com/python/cpython/issues/114071]: Support tuple subclasses using auto() for enum member value.

gh-109475 [https://github.com/python/cpython/issues/109475]: Fix support of explicit option value "--" in argparse (e.g. --option=--).

gh-49766 [https://github.com/python/cpython/issues/49766]: Fix date-datetime comparison. Now the special comparison methods like __eq__ and __lt__ return NotImplemented if one of comparands is date and other is datetime instead of ignoring the time part and the time zone or forcefully return "not equal" or raise TypeError. It makes comparison of date and datetime subclasses more symmetric and allows to change the default behavior by overriding the special comparison methods in subclasses.

gh-110190 [https://github.com/python/cpython/issues/110190]: Fix ctypes structs with array on Windows ARM64 platform by setting MAX_STRUCT_SIZE to 32 in stgdict. Patch by Diego Russo

gh-114678 [https://github.com/python/cpython/issues/114678]: Ensure that deprecation warning for 'N' specifier in Decimal format is not raised for cases where 'N' appears in other places in the format specifier. Based on patch by Stefan Krah.

gh-70303 [https://github.com/python/cpython/issues/70303]: Return both files and directories from pathlib.Path.glob() if a pattern ends with "**". Previously only directories were returned.

gh-109653 [https://github.com/python/cpython/issues/109653]: Improve import time of importlib.metadata and email.utils.

gh-113280 [https://github.com/python/cpython/issues/113280]: Fix a leak of open socket in rare cases when error occurred in ssl.SSLSocket creation.

gh-77749 [https://github.com/python/cpython/issues/77749]: email.policy.EmailPolicy.fold() now always encodes non-ASCII characters in headers if utf8 is false.

gh-83383 [https://github.com/python/cpython/issues/83383]: Synchronization of the dbm.dumb database is now no-op if there was no modification since opening or last synchronization. The directory file for a newly created empty dbm.dumb database is now created immediately after opening instead of deferring this until synchronizing or closing.

gh-91602 [https://github.com/python/cpython/issues/91602]: Add filter keyword-only parameter to sqlite3.Connection.iterdump() for filtering database objects to dump. Patch by Mariusz Felisiak.

gh-112451 [https://github.com/python/cpython/issues/112451]: Prohibit subclassing pure-Python datetime.timezone. This is consistent with C-extension implementation. Patch by Mariusz Felisiak.

gh-69893 [https://github.com/python/cpython/issues/69893]: Add the close() method for the iterator returned by xml.etree.ElementTree.iterparse().

gh-109653 [https://github.com/python/cpython/issues/109653]: Reduce the import time of threading module by ~50%. Patch by Daniel Hollas.

gh-114492 [https://github.com/python/cpython/issues/114492]: Make the result of termios.tcgetattr() reproducible on Alpine Linux. Previously it could leave a random garbage in some fields.

gh-114315 [https://github.com/python/cpython/issues/114315]: Make threading.Lock a real class, not a factory function. Add __new__ to _thread.lock type.

gh-100414 [https://github.com/python/cpython/issues/100414]: Add dbm.sqlite3 as a backend to dbm, and make it the new default dbm backend. Patch by Raymond Hettinger and Erlend E. Aasland.

gh-113267 [https://github.com/python/cpython/issues/113267]: Revert changes in gh-106584 [https://github.com/python/cpython/issues/106584] which made calls of TestResult methods startTest() and stopTest() unbalanced.

gh-75128 [https://github.com/python/cpython/issues/75128]: Ignore an OSError in asyncio.BaseEventLoop.create_server() when IPv6 is available but the interface cannot actually support it.

gh-114423 [https://github.com/python/cpython/issues/114423]: _DummyThread entries in threading._active are now automatically removed when the related thread dies.

gh-114257 [https://github.com/python/cpython/issues/114257]: Dismiss the FileNotFound error in ctypes.util.find_library() and just return None on Linux.

gh-114321 [https://github.com/python/cpython/issues/114321]: Expose more platform specific constants in the fcntl module on Linux, macOS, FreeBSD and NetBSD.

gh-114328 [https://github.com/python/cpython/issues/114328]: The tty.setcbreak() and new tty.cfmakecbreak() no longer clears the terminal input ICRLF flag. This fixes a regression introduced in 3.12 that no longer matched how OSes define cbreak mode in their stty(1) manual pages.

gh-114281 [https://github.com/python/cpython/issues/114281]: Remove type hints from Lib/asyncio/staggered.py. The annotations in the typeshed [https://github.com/python/typeshed] project should be used instead.

gh-101438 [https://github.com/python/cpython/issues/101438]: Avoid reference cycle in ElementTree.iterparse. The iterator returned by ElementTree.iterparse may hold on to a file descriptor. The reference cycle prevented prompt clean-up of the file descriptor if the returned iterator was not exhausted.

gh-114198 [https://github.com/python/cpython/issues/114198]: The signature for the __replace__ method on dataclasses now has the first argument named self, rather than obj.

gh-104522 [https://github.com/python/cpython/issues/104522]: OSError raised when run a subprocess now only has filename attribute set to cwd if the error was caused by a failed attempt to change the current directory.

gh-114149 [https://github.com/python/cpython/issues/114149]: Enum: correctly handle tuple subclasses in custom __new__.

gh-83648 [https://github.com/python/cpython/issues/83648]: Support deprecation of options, positional arguments and subcommands in argparse.

gh-114087 [https://github.com/python/cpython/issues/114087]: Speed up dataclasses.asdict up to 1.35x.

gh-109534 [https://github.com/python/cpython/issues/109534]: Fix a reference leak in asyncio.selector_events.BaseSelectorEventLoop when SSL handshakes fail. Patch contributed by Jamie Phan.

gh-79634 [https://github.com/python/cpython/issues/79634]: Accept path-like objects as patterns in pathlib.Path.glob() and rglob().

gh-112202 [https://github.com/python/cpython/issues/112202]: Ensure that a asyncio.Condition.notify() call does not get lost if the awakened Task is simultaneously cancelled or encounters any other error.

gh-113951 [https://github.com/python/cpython/issues/113951]: Fix the behavior of tag_unbind() methods of tkinter.Text and tkinter.Canvas classes with three arguments. Previously, widget.tag_unbind(tag, sequence, funcid) destroyed the current binding for sequence, leaving sequence unbound, and deleted the funcid command. Now it removes only funcid from the binding for sequence, keeping other commands, and deletes the funcid command. It leaves sequence unbound only if funcid was the last bound command.

gh-97959 [https://github.com/python/cpython/issues/97959]: Fix rendering class methods, bound methods, method and function aliases in pydoc. Class methods no longer have "method of builtins.type instance" note. Corresponding notes are now added for class and unbound methods. Method and function aliases now have references to the module or the class where the origin was defined if it differs from the current. Bound methods are now listed in the static methods section. Methods of builtin classes are now supported as well as methods of Python classes.

gh-113796 [https://github.com/python/cpython/issues/113796]: Add more validation checks in the csv.Dialect constructor. ValueError is now raised if the same character is used in different roles.

gh-113732 [https://github.com/python/cpython/issues/113732]: Fix support of QUOTE_NOTNULL and QUOTE_STRINGS in csv.reader().

gh-113225 [https://github.com/python/cpython/issues/113225]: Speed up pathlib.Path.walk() by using os.DirEntry.path where possible.

gh-89039 [https://github.com/python/cpython/issues/89039]: When replace() method is called on a subclass of datetime, date or time, properly call derived constructor. Previously, only the base class's constructor was called.

Also, make sure to pass non-zero fold values when creating subclasses in various methods. Previously, fold was silently ignored.

gh-112919 [https://github.com/python/cpython/issues/112919]: Speed-up datetime.datetime.replace(), datetime.date.replace() and datetime.time.replace().

gh-59013 [https://github.com/python/cpython/issues/59013]: Set breakpoint on the first executable line of the function, instead of the line of function definition when the user do break func using pdb

gh-112343 [https://github.com/python/cpython/issues/112343]: Improve handling of pdb convenience variables to avoid replacing string contents.

gh-112240 [https://github.com/python/cpython/issues/112240]: Add option to calendar module CLI to specify the weekday to start each week. Patch by Steven Ward.

gh-111741 [https://github.com/python/cpython/issues/111741]: Recognise image/webp as a standard format in the mimetypes module.

gh-43457 [https://github.com/python/cpython/issues/43457]: Fix the tkinter widget method wm_attributes(). It now accepts the attribute name without the minus prefix to get window attributes and allows to specify attributes and values to set as keyword arguments. Add new optional keyword argument return_python_dict: calling w.wm_attributes(return_python_dict=True) returns the attributes as a dict instead of a tuple. Calling w.wm_attributes() now returns a tuple instead of string if wantobjects was set to 0.

gh-82626 [https://github.com/python/cpython/issues/82626]: Many functions now emit a warning if a boolean value is passed as a file descriptor argument.

gh-111051 [https://github.com/python/cpython/issues/111051]: Added check for file modification during debugging with pdb

gh-110345 [https://github.com/python/cpython/issues/110345]: Show the Tcl/Tk patchlevel (rather than version) in tkinter._test().

gh-38807 [https://github.com/python/cpython/issues/38807]: Fix race condition in trace. Instead of checking if a directory exists and creating it, directly call os.makedirs() with the kwarg exist_ok=True.

gh-75705 [https://github.com/python/cpython/issues/75705]: Set unixfrom envelope in mailbox.mbox and mailbox.MMDF.

gh-106233 [https://github.com/python/cpython/issues/106233]: Fix stacklevel in InvalidTZPathWarning during zoneinfo module import.

gh-105102 [https://github.com/python/cpython/issues/105102]: Allow ctypes.Union to be nested in ctypes.Structure when the system endianness is the opposite of the classes.

gh-104282 [https://github.com/python/cpython/issues/104282]: Fix null pointer dereference in lzma._decode_filter_properties() due to improper handling of BCJ filters with properties of zero length. Patch by Radislav Chugunov.

gh-96471 [https://github.com/python/cpython/issues/96471]: Add queue.Queue termination with shutdown().

gh-101599 [https://github.com/python/cpython/issues/101599]: Changed argparse flag options formatting to remove redundancy.

gh-85984 [https://github.com/python/cpython/issues/85984]: Add POSIX pseudo-terminal functions os.posix_openpt(), os.grantpt(), os.unlockpt(), and os.ptsname().

gh-102512 [https://github.com/python/cpython/issues/102512]: When os.fork() is called from a foreign thread (aka _DummyThread), the type of the thread in a child process is changed to _MainThread. Also changed its name and daemonic status, it can be now joined.

gh-88569 [https://github.com/python/cpython/issues/88569]: Add os.path.isreserved(), which identifies reserved pathnames such as "NUL", "AUX" and "CON". This function is only available on Windows.

Deprecate pathlib.PurePath.is_reserved().

bpo-38364 [https://bugs.python.org/issue?@action=redirect&bpo=38364]: The inspect functions isgeneratorfunction, iscoroutinefunction, isasyncgenfunction now support functools.partialmethod wrapped functions the same way they support functools.partial.

Documentation

gh-115233 [https://github.com/python/cpython/issues/115233]: Fix an example for LoggerAdapter in the Logging Cookbook.

gh-114123 [https://github.com/python/cpython/issues/114123]: Move the csv module docstring to the csv module instead of reexporting it from the internal _csv module, and remove __doc__ from csv.__all__.

Move csv.__version__ to the csv module instead of reexporting it from the internal _csv module, and remove __version__ from csv.__all__.

Tests

gh-114099 [https://github.com/python/cpython/issues/114099]: Added test exclusions required to run the test suite on iOS.

gh-105089 [https://github.com/python/cpython/issues/105089]: Fix test.test_zipfile.test_core.TestWithDirectory.test_create_directory_with_write test in AIX by doing a bitwise AND of 0xFFFF on mode , so that it will be in sync with zinfo.external_attr

Build

gh-115167 [https://github.com/python/cpython/issues/115167]: Avoid vendoring vcruntime140_threads.dll when building with Visual Studio 2022 version 17.8.

gh-113632 [https://github.com/python/cpython/issues/113632]: Promote WASI to a tier 2 platform and drop Emscripten from tier 3 in configure.ac.

gh-114099 [https://github.com/python/cpython/issues/114099]: configure and Makefile were refactored to accommodate framework builds on Apple platforms other than macOS.

gh-114875 [https://github.com/python/cpython/issues/114875]: Add getgrent() as a prerequisite for building the grp module.

Windows

gh-115049 [https://github.com/python/cpython/issues/115049]: Fixes py.exe launcher failing when run as users without user profiles.

gh-115009 [https://github.com/python/cpython/issues/115009]: Update Windows installer to use SQLite 3.45.1.

gh-109991 [https://github.com/python/cpython/issues/109991]: Update Windows build to use OpenSSL 3.0.13.

gh-111239 [https://github.com/python/cpython/issues/111239]: Update Windows builds to use zlib v1.3.1.

gh-100107 [https://github.com/python/cpython/issues/100107]: The py.exe launcher will no longer attempt to run the Microsoft Store redirector when launching a script containing a /usr/bin/env shebang

gh-112984 [https://github.com/python/cpython/issues/112984]: Adds free-threaded binaries to Windows installer as an optional component.

gh-89240 [https://github.com/python/cpython/issues/89240]: Allows multiprocessing to create pools of greater than 62 processes.

macOS

gh-115009 [https://github.com/python/cpython/issues/115009]: Update macOS installer to use SQLite 3.45.1.

gh-109991 [https://github.com/python/cpython/issues/109991]: Update macOS installer to use OpenSSL 3.0.13.

gh-114490 [https://github.com/python/cpython/issues/114490]: Add Mach-O linkage support for platform.architecture().

gh-87804 [https://github.com/python/cpython/issues/87804]: On macOS the result of os.statvfs and os.fstatvfs now correctly report the size of very large disks, in previous versions the reported number of blocks was wrong for disks with at least 2**32 blocks.

IDLE

gh-96905 [https://github.com/python/cpython/issues/96905]: In idlelib code, stop redefining built-ins 'dict' and 'object'.

gh-103820 [https://github.com/python/cpython/issues/103820]: Revise IDLE bindings so that events from mouse button 4/5 on non-X11 windowing systems (i.e. Win32 and Aqua) are not mistaken for scrolling.

Tools/Demos

gh-113516 [https://github.com/python/cpython/issues/113516]: Don't set LDSHARED when building for WASI.

gh-109991 [https://github.com/python/cpython/issues/109991]: Update GitHub CI workflows to use OpenSSL 3.0.13 and multissltests to use 1.1.1w, 3.0.13, 3.1.5, and 3.2.1.

gh-115015 [https://github.com/python/cpython/issues/115015]: Fix a bug in Argument Clinic that generated incorrect code for methods with no parameters that use the METH_METHOD | METH_FASTCALL | METH_KEYWORDS calling convention. Only the positional parameter count was checked; any keyword argument passed would be silently accepted.

C API

gh-111140 [https://github.com/python/cpython/issues/111140]: Adds PyLong_AsNativeBytes(), PyLong_FromNativeBytes() and PyLong_FromUnsignedNativeBytes() functions.

gh-114685 [https://github.com/python/cpython/issues/114685]: PyBuffer_FillInfo() now raises a SystemError if called with PyBUF_READ or PyBUF_WRITE as flags. These flags should only be used with the PyMemoryView_* C API.

gh-114685 [https://github.com/python/cpython/issues/114685]: PyObject_GetBuffer() now raises a SystemError if called with PyBUF_READ or PyBUF_WRITE as flags. These flags should only be used with the PyMemoryView_* C API.

gh-114626 [https://github.com/python/cpython/issues/114626]: Add PyCFunctionFast and PyCFunctionFastWithKeywords typedefs (identical to the existing _PyCFunctionFast and _PyCFunctionFastWithKeywords typedefs, just without a leading _ prefix).

gh-114329 [https://github.com/python/cpython/issues/114329]: Add PyList_GetItemRef(), which is similar to PyList_GetItem() but returns a strong reference instead of a borrowed reference.

gh-110850 [https://github.com/python/cpython/issues/110850]: Add PyTime C API:

PyTime_t type.

PyTime_MIN and PyTime_MAX constants.

PyTime_AsSecondsDouble(), PyTime_Monotonic(), PyTime_PerfCounter(), and PyTime_Time() functions.

Patch by Victor Stinner.

gh-112066 [https://github.com/python/cpython/issues/112066]: Add PyDict_SetDefaultRef(): insert a key and value into a dictionary if the key is not already present. This is similar to dict.setdefault(), but returns an integer value indicating if the key was already present. It is also similar to PyDict_SetDefault(), but returns a strong reference instead of a borrowed reference.

Python 3.13.0 alpha 3

Release date: 2024-01-17

Security

gh-113659 [https://github.com/python/cpython/issues/113659]: Skip .pth files with names starting with a dot or hidden file attribute.

gh-112302 [https://github.com/python/cpython/issues/112302]: Created a Software Bill-of-Materials document and tooling for tracking dependencies.

Core and Builtins

gh-107901 [https://github.com/python/cpython/issues/107901]: Compiler duplicates basic blocks that have an eval breaker check, no line number, and multiple predecessors.

gh-107901 [https://github.com/python/cpython/issues/107901]: A jump leaving an exception handler back to normal code no longer checks the eval breaker.

gh-113655 [https://github.com/python/cpython/issues/113655]: Set the C recursion limit to 4000 on Windows, and 10000 on Linux/OSX. This seems to be near the sweet spot to maintain safety, but not compromise backwards compatibility.

gh-113710 [https://github.com/python/cpython/issues/113710]: Add typed stack effects to the interpreter DSL, along with various instruction annotations.

gh-77046 [https://github.com/python/cpython/issues/77046]: On Windows, file descriptors wrapping Windows handles are now created non inheritable by default (PEP 446 [https://peps.python.org/pep-0446/]). Patch by Zackery Spytz and Victor Stinner.

gh-113853 [https://github.com/python/cpython/issues/113853]: Guarantee that all executors make progress. This then guarantees that tier 2 execution always makes progress.

gh-113753 [https://github.com/python/cpython/issues/113753]: Fix an issue where the finalizer of PyAsyncGenASend objects might not be called if they were allocated from a free list.

gh-107901 [https://github.com/python/cpython/issues/107901]: Compiler changed so that synthetic jumps which are not at loop end no longer check the eval breaker.

gh-113703 [https://github.com/python/cpython/issues/113703]: Fix a regression in the codeop module that was causing it to incorrectly identify incomplete f-strings. Patch by Pablo Galindo

gh-89811 [https://github.com/python/cpython/issues/89811]: Check for a valid tp_version_tag before performing bytecode specializations that rely on this value being usable.

gh-111488 [https://github.com/python/cpython/issues/111488]: Changed error message in case of no 'in' keyword after 'for' in list comprehensions

gh-113657 [https://github.com/python/cpython/issues/113657]: Fix an issue that caused important instruction pointer updates to be optimized out of tier two traces.

gh-113603 [https://github.com/python/cpython/issues/113603]: Fixed bug where a redundant NOP is not removed, causing an assertion to fail in the compiler in debug mode.

gh-113602 [https://github.com/python/cpython/issues/113602]: Fix an error that was causing the parser to try to overwrite existing errors and crashing in the process. Patch by Pablo Galindo

gh-113486 [https://github.com/python/cpython/issues/113486]: No longer issue spurious PY_UNWIND events for optimized calls to classes.

gh-113297 [https://github.com/python/cpython/issues/113297]: Fix segfault in the compiler on with statement with 19 context managers.

gh-113212 [https://github.com/python/cpython/issues/113212]: Improve super error messages.

gh-111375 [https://github.com/python/cpython/issues/111375]: Only use NULL in the exception stack to indicate an exception was handled. Patch by Carey Metcalfe.

gh-112215 [https://github.com/python/cpython/issues/112215]: Increase the C recursion limit by a factor of 3 for non-debug builds, except for webassembly and s390 platforms which are unchanged. This mitigates some regressions in 3.12 with deep recursion mixing builtin (C) and Python code.

gh-113054 [https://github.com/python/cpython/issues/113054]: Fixed bug where a redundant NOP is not removed, causing an assertion to fail in the compiler in debug mode.

gh-106905 [https://github.com/python/cpython/issues/106905]: Use per AST-parser state rather than global state to track recursion depth within the AST parser to prevent potential race condition due to simultaneous parsing.

The issue primarily showed up in 3.11 by multithreaded users of ast.parse(). In 3.12 a change to when garbage collection can be triggered prevented the race condition from occurring.

gh-108866 [https://github.com/python/cpython/issues/108866]: Change the API and contract of _PyExecutorObject to return the next_instr pointer, instead of the frame, and to always execute at least one instruction.

gh-90350 [https://github.com/python/cpython/issues/90350]: Optimize builtin functions min() and max().

gh-112943 [https://github.com/python/cpython/issues/112943]: Correctly compute end column offsets for multiline tokens in the tokenize module. Patch by Pablo Galindo

gh-112125 [https://github.com/python/cpython/issues/112125]: Fix None.__ne__(None) returning NotImplemented instead of False.

gh-74616 [https://github.com/python/cpython/issues/74616]: input() now raises a ValueError when output on the terminal if the prompt contains embedded null characters instead of silently truncating it.

gh-112716 [https://github.com/python/cpython/issues/112716]: Fix SystemError in the import statement and in __reduce__() methods of builtin types when __builtins__ is not a dict.

gh-112730 [https://github.com/python/cpython/issues/112730]: Use color to highlight error locations in tracebacks. Patch by Pablo Galindo

gh-112625 [https://github.com/python/cpython/issues/112625]: Fixes a bug where a bytearray object could be cleared while iterating over an argument in the bytearray.join() method that could result in reading memory after it was freed.

gh-112660 [https://github.com/python/cpython/issues/112660]: Do not clear unexpected errors during formatting error messages for ImportError and AttributeError for modules.

gh-105967 [https://github.com/python/cpython/issues/105967]: Workaround a bug in Apple's macOS platform zlib library where zlib.crc32() and binascii.crc32() could produce incorrect results on multi-gigabyte inputs. Including when using zipfile on zips containing large data.

gh-95754 [https://github.com/python/cpython/issues/95754]: Provide a better error message when accessing invalid attributes on partially initialized modules. The origin of the module being accessed is now included in the message to help with the common issue of shadowing other modules.

gh-112217 [https://github.com/python/cpython/issues/112217]: Add check for the type of __cause__ returned from calling the type T in raise from T.

gh-111058 [https://github.com/python/cpython/issues/111058]: Change coro.cr_frame/gen.gi_frame to return None after the coroutine/generator has been closed. This fixes a bug where getcoroutinestate() and getgeneratorstate() return the wrong state for a closed coroutine/generator.

gh-112388 [https://github.com/python/cpython/issues/112388]: Fix an error that was causing the parser to try to overwrite tokenizer errors. Patch by pablo Galindo

gh-112387 [https://github.com/python/cpython/issues/112387]: Fix error positions for decoded strings with backwards tokenize errors. Patch by Pablo Galindo

gh-99606 [https://github.com/python/cpython/issues/99606]: Make code generated for an empty f-string identical to the code of an empty normal string.

gh-112367 [https://github.com/python/cpython/issues/112367]: Avoid undefined behaviour when using the perf trampolines by not freeing the code arenas until shutdown. Patch by Pablo Galindo

gh-112320 [https://github.com/python/cpython/issues/112320]: The Tier 2 translator now tracks the confidence level for staying "on trace" (i.e. not exiting back to the Tier 1 interpreter) for branch instructions based on the number of bits set in the branch "counter". Trace translation ends when the confidence drops below 1/3rd.

gh-109598 [https://github.com/python/cpython/issues/109598]: PyComplex_RealAsDouble()/PyComplex_ImagAsDouble() now tries to convert an object to a complex instance using its __complex__() method before falling back to the __float__() method. Patch by Sergey B Kirpichev.

gh-94606 [https://github.com/python/cpython/issues/94606]: Fix UnicodeEncodeError when email.message.get_payload() reads a message with a Unicode surrogate character and the message content is not well-formed for surrogateescape encoding. Patch by Sidney Markowitz.

bpo-21861 [https://bugs.python.org/issue?@action=redirect&bpo=21861]: Use the object's actual class name in _io.FileIO.__repr__(), _io._WindowsConsoleIO() and _io.TextIOWrapper.__repr__(), to make these methods subclass friendly.

bpo-45369 [https://bugs.python.org/issue?@action=redirect&bpo=45369]: Remove LibreSSL workarounds as per PEP 644 [https://peps.python.org/pep-0644/].

bpo-34392 [https://bugs.python.org/issue?@action=redirect&bpo=34392]: Added sys._is_interned().

Library

gh-114077 [https://github.com/python/cpython/issues/114077]: Fix possible OverflowError in socket.socket.sendfile() when pass count larger than 2 GiB on 32-bit platform.

gh-111803 [https://github.com/python/cpython/issues/111803]: plistlib now supports loading more deeply nested lists in binary format.

gh-114014 [https://github.com/python/cpython/issues/114014]: Fixed a bug in fractions.Fraction where an invalid string using d in the decimals part creates a different error compared to other invalid letters/characters. Patch by Jeremiah Gabriel Pascual.

gh-108364 [https://github.com/python/cpython/issues/108364]: sqlite3.Connection.iterdump() now ensures that foreign key support is disabled before dumping the database schema, if there is any foreign key violation. Patch by Erlend E. Aasland and Mariusz Felisiak.

gh-113971 [https://github.com/python/cpython/issues/113971]: The zipfile.ZipInfo previously protected ._compresslevel attribute has been made public as .compress_level with the old _compresslevel name remaining available as a property to retain compatibility.

gh-113877 [https://github.com/python/cpython/issues/113877]: Fix tkinter method winfo_pathname() on 64-bit Windows.

gh-113868 [https://github.com/python/cpython/issues/113868]: Added mmap.MAP_NORESERVE, mmap.MAP_NOEXTEND, mmap.MAP_HASSEMAPHORE, mmap.MAP_NOCACHE, mmap.MAP_JIT, mmap.MAP_RESILIENT_CODESIGN, mmap.MAP_RESILIENT_MEDIA, mmap.MAP_32BIT, mmap.MAP_TRANSLATED_ALLOW_EXECUTE, mmap.MAP_UNIX03 and mmap.MAP_TPRO. All of them are mmap(2) flags on macOS.

gh-113848 [https://github.com/python/cpython/issues/113848]: asyncio.TaskGroup() and asyncio.timeout() context managers now handle CancelledError subclasses as well as exact CancelledError.

gh-113661 [https://github.com/python/cpython/issues/113661]: unittest runner: Don't exit 5 if tests were skipped. The intention of exiting 5 was to detect issues where the test suite wasn't discovered at all. If we skipped tests, it was correctly discovered.

gh-96037 [https://github.com/python/cpython/issues/96037]: Insert TimeoutError in the context of the exception that was raised during exiting an expired asyncio.timeout() block.

gh-113781 [https://github.com/python/cpython/issues/113781]: Silence unraisable AttributeError when warnings are emitted during Python finalization.

gh-113238 [https://github.com/python/cpython/issues/113238]: Add Anchor to importlib.resources (in order for the code to comply with the documentation)

gh-111693 [https://github.com/python/cpython/issues/111693]: asyncio.Condition.wait() now re-raises the same CancelledError instance that may have caused it to be interrupted. Fixed race condition in asyncio.Semaphore.acquire() when interrupted with a CancelledError.

gh-113791 [https://github.com/python/cpython/issues/113791]: Add CLOCK_MONOTONIC_RAW_APPROX and CLOCK_UPTIME_RAW_APPROX to time on macOS. These are clocks available on macOS 10.12 or later.

gh-112932 [https://github.com/python/cpython/issues/112932]: Restore the ability for zipfile to extractall from zip files with a "/" directory entry in them as is commonly added to zips by some wiki or bug tracker data exporters.

gh-113568 [https://github.com/python/cpython/issues/113568]: Raise deprecation warnings from pathlib.PurePath and not its private base class PurePathBase.

gh-113594 [https://github.com/python/cpython/issues/113594]: Fix UnicodeEncodeError in email when re-fold lines that contain unknown-8bit encoded part followed by non-unknown-8bit encoded part.

gh-113538 [https://github.com/python/cpython/issues/113538]: In asyncio.StreamReaderProtocol.connection_made(), there is callback that logs an error if the task wrapping the "connected callback" fails. This callback would itself fail if the task was cancelled. Prevent this by checking whether the task was cancelled first. If so, close the transport but don't log an error.

gh-113626 [https://github.com/python/cpython/issues/113626]: Add support for the allow_code argument in the marshal module. Passing allow_code=False prevents serialization and de-serialization of code objects which is incompatible between Python versions.

gh-85567 [https://github.com/python/cpython/issues/85567]: Fix resource warnings for unclosed files in pickle and pickletools command line interfaces.

gh-113537 [https://github.com/python/cpython/issues/113537]: Support loads str in plistlib.loads().

gh-89850 [https://github.com/python/cpython/issues/89850]: Add default implementations of pickle.Pickler.persistent_id() and pickle.Unpickler.persistent_load() methods in the C implementation. Calling super().persistent_id() and super().persistent_load() in subclasses of the C implementation of pickle.Pickler and pickle.Unpickler classes no longer causes infinite recursion.

gh-113569 [https://github.com/python/cpython/issues/113569]: Indicate if there were no actual calls in unittest assert_has_calls() failure.

gh-101225 [https://github.com/python/cpython/issues/101225]: Increase the backlog for multiprocessing.connection.Listener objects created by multiprocessing.manager and multiprocessing.resource_sharer to significantly reduce the risk of getting a connection refused error when creating a multiprocessing.connection.Connection to them.

gh-113568 [https://github.com/python/cpython/issues/113568]: Raise audit events from pathlib.Path and not its private base class PathBase.

gh-113543 [https://github.com/python/cpython/issues/113543]: Make sure that webbrowser.MacOSXOSAScript sends webbrowser.open audit event.

gh-113028 [https://github.com/python/cpython/issues/113028]: When a second reference to a string appears in the input to pickle, and the Python implementation is in use, we are guaranteed that a single copy gets pickled and a single object is shared when reloaded. Previously, in protocol 0, when a string contained certain characters (e.g. newline) it resulted in duplicate objects.

gh-113421 [https://github.com/python/cpython/issues/113421]: Fix multiprocessing logger for %(filename)s.

gh-111784 [https://github.com/python/cpython/issues/111784]: Fix segfaults in the _elementtree module. Fix first segfault during deallocation of _elementtree.XMLParser instances by keeping strong reference to pyexpat module in module state for capsule lifetime. Fix second segfault which happens in the same deallocation process by keeping strong reference to _elementtree module in XMLParser structure for _elementtree module lifetime.

gh-113407 [https://github.com/python/cpython/issues/113407]: Fix import of unittest.mock when CPython is built without docstrings.

gh-113320 [https://github.com/python/cpython/issues/113320]: Fix regression in Python 3.12 where Protocol classes that were not marked as runtime-checkable would be unnecessarily introspected, potentially causing exceptions to be raised if the protocol had problematic members. Patch by Alex Waygood.

gh-53502 [https://github.com/python/cpython/issues/53502]: Add a new option aware_datetime in plistlib to loads or dumps aware datetime.

gh-113358 [https://github.com/python/cpython/issues/113358]: Fix rendering tracebacks with exceptions with a broken __getattr__

gh-113214 [https://github.com/python/cpython/issues/113214]: Fix an AttributeError during asyncio SSL protocol aborts in SSL-over-SSL scenarios.

gh-113246 [https://github.com/python/cpython/issues/113246]: Update bundled pip to 23.3.2.

gh-87264 [https://github.com/python/cpython/issues/87264]: Fixed tarfile list() method to show file type.

gh-112182 [https://github.com/python/cpython/issues/112182]: asyncio.futures.Future.set_exception() now transforms StopIteration into RuntimeError instead of hanging or other misbehavior. Patch contributed by Jamie Phan.

gh-113225 [https://github.com/python/cpython/issues/113225]: Speed up pathlib.Path.glob() by using os.DirEntry.path where possible.

gh-113149 [https://github.com/python/cpython/issues/113149]: Improve error message when a JSON array or object contains a trailing comma. Patch by Carson Radtke.

gh-113117 [https://github.com/python/cpython/issues/113117]: The subprocess module can now use the os.posix_spawn() function with close_fds=True on platforms where posix_spawn_file_actions_addclosefrom_np is available. Patch by Jakub Kulik.

gh-113199 [https://github.com/python/cpython/issues/113199]: Make http.client.HTTPResponse.read1 and http.client.HTTPResponse.readline close IO after reading all data when content length is known. Patch by Illia Volochii.

gh-113191 [https://github.com/python/cpython/issues/113191]: Add support of os.fchmod() and a file descriptor in os.chmod() on Windows.

gh-113188 [https://github.com/python/cpython/issues/113188]: Fix shutil.copymode() and shutil.copystat() on Windows. Previously they worked differently if dst is a symbolic link: they modified the permission bits of dst itself rather than the file it points to if follow_symlinks is true or src is not a symbolic link, and did not modify the permission bits if follow_symlinks is false and src is a symbolic link.

gh-113119 [https://github.com/python/cpython/issues/113119]: os.posix_spawn() now accepts env=None, which makes the newly spawned process use the current process environment. Patch by Jakub Kulik.

gh-113202 [https://github.com/python/cpython/issues/113202]: Add a strict option to batched() in the itertools module.

gh-61648 [https://github.com/python/cpython/issues/61648]: Detect line numbers of properties in doctests.

gh-113175 [https://github.com/python/cpython/issues/113175]: Sync with importlib_metadata 7.0, including improved type annotations, fixed issue with symlinked packages in package_distributions, added EntryPoints.__repr__, introduced the diagnose script, added Distribution.origin property, and removed deprecated EntryPoint access by numeric index (tuple behavior).

gh-59616 [https://github.com/python/cpython/issues/59616]: Add support of os.lchmod() and the follow_symlinks argument in os.chmod() on Windows. Note that the default value of follow_symlinks in os.lchmod() is False on Windows.

gh-112559 [https://github.com/python/cpython/issues/112559]: signal.signal() and signal.getsignal() no longer call repr on callable handlers. asyncio.run() and asyncio.Runner.run() no longer call repr on the task results. Patch by Yilei Yang.

gh-112962 [https://github.com/python/cpython/issues/112962]: dis module functions add cache information to the Instruction instance rather than creating fake Instruction instances to represent the cache entries.

gh-112989 [https://github.com/python/cpython/issues/112989]: Reduce overhead to connect sockets with asyncio SelectorEventLoop.

gh-112970 [https://github.com/python/cpython/issues/112970]: Use closefrom() on Linux where available (e.g. glibc-2.34), rather than only FreeBSD.

gh-110190 [https://github.com/python/cpython/issues/110190]: Fix ctypes structs with array on PPC64LE platform by setting MAX_STRUCT_SIZE to 64 in stgdict. Patch by Diego Russo.

gh-112540 [https://github.com/python/cpython/issues/112540]: The statistics.geometric_mean() function now returns zero for datasets containing a zero. Formerly, it would raise an exception.

gh-87286 [https://github.com/python/cpython/issues/87286]: Added LOG_FTP, LOG_NETINFO, LOG_REMOTEAUTH, LOG_INSTALL, LOG_RAS, and LOG_LAUNCHD tot the syslog module, all of them constants on used on macOS.

gh-112800 [https://github.com/python/cpython/issues/112800]: Fix asyncio SubprocessTransport.close() not to throw PermissionError when used with setuid executables.

gh-51944 [https://github.com/python/cpython/issues/51944]: Add the following constants to the termios module. These values are present in macOS system headers: ALTWERASE, B14400, B28800, B7200, B76800, CCAR_OFLOW, CCTS_OFLOW, CDSR_OFLOW, CDTR_IFLOW, CIGNORE, CRTS_IFLOW, EXTPROC, IUTF8, MDMBUF, NL2, NL3, NOKERNINFO, ONOEOT, OXTABS, VDSUSP, VSTATUS.

gh-79325 [https://github.com/python/cpython/issues/79325]: Fix an infinite recursion error in tempfile.TemporaryDirectory() cleanup on Windows.

gh-94692 [https://github.com/python/cpython/issues/94692]: shutil.rmtree() now only catches OSError exceptions. Previously a symlink attack resistant version of shutil.rmtree() could ignore or pass to the error handler arbitrary exception when invalid arguments were provided.

gh-112736 [https://github.com/python/cpython/issues/112736]: The use of del-safe symbols in subprocess was refactored to allow for use in cross-platform build environments.

gh-112727 [https://github.com/python/cpython/issues/112727]: Speed up pathlib.Path.absolute(). Patch by Barney Gale.

gh-74690 [https://github.com/python/cpython/issues/74690]: Speedup issubclass() checks against simple runtime-checkable protocols by around 6%. Patch by Alex Waygood.

gh-74690 [https://github.com/python/cpython/issues/74690]: Speedup isinstance() checks by roughly 20% for runtime-checkable protocols that only have one callable member. Speedup issubclass() checks for these protocols by roughly 10%. Patch by Alex Waygood.

gh-112645 [https://github.com/python/cpython/issues/112645]: Remove deprecation error on passing onerror to shutil.rmtree().

gh-112640 [https://github.com/python/cpython/issues/112640]: Add kwdefaults parameter to types.FunctionType to set default keyword argument values.

gh-112622 [https://github.com/python/cpython/issues/112622]: Ensure name parameter is passed to event loop in asyncio.create_task().

gh-112618 [https://github.com/python/cpython/issues/112618]: Fix a caching bug relating to typing.Annotated. Annotated[str, True] is no longer identical to Annotated[str, 1].

gh-112334 [https://github.com/python/cpython/issues/112334]: Fixed a performance regression in 3.12's subprocess on Linux where it would no longer use the fast-path vfork() system call when it could have due to a logic bug, instead falling back to the safe but slower fork().

Also fixed a second 3.12.0 potential security bug. If a value of extra_groups=[] was passed to subprocess.Popen or related APIs, the underlying setgroups(0, NULL) system call to clear the groups list would not be made in the child process prior to exec().

This was identified via code inspection in the process of fixing the first bug.

gh-110190 [https://github.com/python/cpython/issues/110190]: Fix ctypes structs with array on Arm platform by setting MAX_STRUCT_SIZE to 32 in stgdict. Patch by Diego Russo.

gh-81194 [https://github.com/python/cpython/issues/81194]: Fix a crash in socket.if_indextoname() with specific value (UINT_MAX). Fix an integer overflow in socket.if_indextoname() on 64-bit non-Windows platforms.

gh-112578 [https://github.com/python/cpython/issues/112578]: Fix a spurious RuntimeWarning when executing the zipfile module.

gh-112516 [https://github.com/python/cpython/issues/112516]: Update the bundled copy of pip to version 23.3.1.

gh-112510 [https://github.com/python/cpython/issues/112510]: Add readline.backend for the backend readline uses (editline or readline)

gh-112328 [https://github.com/python/cpython/issues/112328]: [Enum] Make EnumDict, EnumDict.member_names, EnumType._add_alias_ and EnumType._add_value_alias_ public.

gh-112509 [https://github.com/python/cpython/issues/112509]: Fix edge cases that could cause a key to be present in both the __required_keys__ and __optional_keys__ attributes of a typing.TypedDict. Patch by Jelle Zijlstra.

gh-101336 [https://github.com/python/cpython/issues/101336]: Add keep_alive keyword parameter for AbstractEventLoop.create_server() and BaseEventLoop.create_server().

gh-63284 [https://github.com/python/cpython/issues/63284]: Added support for TLS-PSK (pre-shared key) mode to the ssl module.

gh-112414 [https://github.com/python/cpython/issues/112414]: Fix regression in Python 3.12 where calling repr() on a module that had been imported using a custom loader could fail with AttributeError. Patch by Alex Waygood.

gh-112358 [https://github.com/python/cpython/issues/112358]: Revert change to struct.Struct initialization that broke some cases of subclassing.

gh-112405 [https://github.com/python/cpython/issues/112405]: Optimize pathlib.PurePath.relative_to(). Patch by Alex Waygood.

gh-94722 [https://github.com/python/cpython/issues/94722]: Fix bug where comparison between instances of DocTest fails if one of them has None as its lineno.

gh-112361 [https://github.com/python/cpython/issues/112361]: Speed up a small handful of pathlib methods by removing some temporary objects.

gh-112345 [https://github.com/python/cpython/issues/112345]: Improve error message when trying to call issubclass() against a typing.Protocol that has non-method members. Patch by Randolf Scholz.

gh-112137 [https://github.com/python/cpython/issues/112137]: Change dis output to display no-lineno as "--" instead of "None".

gh-112332 [https://github.com/python/cpython/issues/112332]: Deprecate the exc_type field of traceback.TracebackException. Add exc_type_str to replace it.

gh-81620 [https://github.com/python/cpython/issues/81620]: Add extra tests for random.binomialvariate()

gh-112292 [https://github.com/python/cpython/issues/112292]: Fix a crash in readline when imported from a sub interpreter. Patch by Anthony Shaw

gh-77621 [https://github.com/python/cpython/issues/77621]: Slightly improve the import time of the pathlib module by deferring some imports. Patch by Barney Gale.

gh-112137 [https://github.com/python/cpython/issues/112137]: Change dis output to display logical labels for jump targets instead of offsets.

gh-112139 [https://github.com/python/cpython/issues/112139]: Add Signature.format() to format signatures to string with extra options. And use it in pydoc to render more readable signatures that have new lines between parameters.

gh-112105 [https://github.com/python/cpython/issues/112105]: Make readline.set_completer_delims() work with libedit

gh-106922 [https://github.com/python/cpython/issues/106922]: Display multiple lines with traceback when errors span multiple lines.

gh-111874 [https://github.com/python/cpython/issues/111874]: When creating a typing.NamedTuple class, ensure __set_name__() is called on all objects that define __set_name__ and exist in the values of the NamedTuple class's class dictionary. Patch by Alex Waygood.

gh-68166 [https://github.com/python/cpython/issues/68166]: Add support of the "vsapi" element type in tkinter.ttk.Style.element_create().

gh-110275 [https://github.com/python/cpython/issues/110275]: Named tuple's methods _replace() and __replace__() now raise TypeError instead of ValueError for invalid keyword arguments.

gh-99367 [https://github.com/python/cpython/issues/99367]: Do not mangle sys.path[0] in pdb if safe_path is set

gh-111615 [https://github.com/python/cpython/issues/111615]: Fix a regression caused by a fix to gh-93162 [https://github.com/python/cpython/issues/93162] whereby you couldn't configure a QueueHandler without specifying handlers.

gh-75666 [https://github.com/python/cpython/issues/75666]: Fix the behavior of tkinter widget's unbind() method with two arguments. Previously, widget.unbind(sequence, funcid) destroyed the current binding for sequence, leaving sequence unbound, and deleted the funcid command. Now it removes only funcid from the binding for sequence, keeping other commands, and deletes the funcid command. It leaves sequence unbound only if funcid was the last bound command.

gh-67790 [https://github.com/python/cpython/issues/67790]: Implement basic formatting support (minimum width, alignment, fill) for fractions.Fraction.

gh-111049 [https://github.com/python/cpython/issues/111049]: Fix crash during garbage collection of the io.BytesIO buffer object.

gh-102980 [https://github.com/python/cpython/issues/102980]: Redirect the output of interact command of pdb to the same channel as the debugger. Add tests and improve docs.

gh-102988 [https://github.com/python/cpython/issues/102988]: email.utils.getaddresses() and email.utils.parseaddr() now return ('', '') 2-tuples in more situations where invalid email addresses are encountered instead of potentially inaccurate values. Add optional strict parameter to these two functions: use strict=False to get the old behavior, accept malformed inputs. getattr(email.utils, 'supports_strict_parsing', False) can be use to check if the strict parameter is available. Patch by Thomas Dwyer and Victor Stinner to improve the CVE 2023-27043 [https://www.cve.org/CVERecord?id=CVE-2023-27043] fix.

gh-52161 [https://github.com/python/cpython/issues/52161]: cmd.Cmd.do_help() now cleans docstrings with inspect.cleandoc() before writing them. Patch by Filip Łapkiewicz.

gh-82300 [https://github.com/python/cpython/issues/82300]: Add track parameter to multiprocessing.shared_memory.SharedMemory that allows using shared memory blocks without having to register with the POSIX resource tracker that automatically releases them upon process exit.

gh-110109 [https://github.com/python/cpython/issues/110109]: Add private pathlib._PurePathBase class: a base class for pathlib.PurePath that omits certain magic methods. It may be made public (along with _PathBase) in future.

gh-109858 [https://github.com/python/cpython/issues/109858]: Protect zipfile from "quoted-overlap" zipbomb. It now raises BadZipFile when try to read an entry that overlaps with other entry or central directory.

gh-109786 [https://github.com/python/cpython/issues/109786]: Fix possible reference leaks and crash when re-enter the __next__() method of itertools.pairwise.

gh-91539 [https://github.com/python/cpython/issues/91539]: Small (10 - 20%) and trivial performance improvement of urllib.request.getproxies_environment(), typically useful when there are many environment variables to go over.

gh-103363 [https://github.com/python/cpython/issues/103363]: Add follow_symlinks keyword-only argument to pathlib.Path.owner() and group(), defaulting to True.

gh-102130 [https://github.com/python/cpython/issues/102130]: Support tab completion in cmd for editline.

gh-99437 [https://github.com/python/cpython/issues/99437]: runpy.run_path() now decodes path-like objects, making sure __file__ and sys.argv[0] of the module being run are always strings.

gh-104003 [https://github.com/python/cpython/issues/104003]: Add warnings.deprecated(), a decorator to mark deprecated functions to static type checkers and to warn on usage of deprecated classes and functions. See PEP 702 [https://peps.python.org/pep-0702/]. Patch by Jelle Zijlstra.

gh-103708 [https://github.com/python/cpython/issues/103708]: Make hardcoded python name, a configurable parameter so that different implementations of python can override it instead of making huge diffs in sysconfig.py

gh-66515 [https://github.com/python/cpython/issues/66515]: mailbox.MH now supports folders that do not contain a .mh_sequences file (e.g. Claws Mail IMAP-cache folders). Patch by Serhiy Storchaka.

gh-83162 [https://github.com/python/cpython/issues/83162]: Renamed re.error to PatternError for clarity, and kept re.error for backward compatibility. Patch by Matthias Bussonnier and Adam Chhina.

gh-91133 [https://github.com/python/cpython/issues/91133]: Fix a bug in tempfile.TemporaryDirectory cleanup, which now no longer dereferences symlinks when working around file system permission errors.

bpo-43153 [https://bugs.python.org/issue?@action=redirect&bpo=43153]: On Windows, tempfile.TemporaryDirectory previously masked a PermissionError with NotADirectoryError during directory cleanup. It now correctly raises PermissionError if errors are not ignored. Patch by Andrei Kulakov and Ken Jin.

bpo-32731 [https://bugs.python.org/issue?@action=redirect&bpo=32731]: getpass.getuser() now raises OSError for all failures rather than ImportError on systems lacking the pwd module or KeyError if the password database is empty.

bpo-34321 [https://bugs.python.org/issue?@action=redirect&bpo=34321]: mmap.mmap now has a trackfd parameter on Unix; if it is False, the file descriptor specified by fileno will not be duplicated.

bpo-35332 [https://bugs.python.org/issue?@action=redirect&bpo=35332]: The shutil.rmtree() function now ignores errors when calling os.close() when ignore_errors is True, and os.close() no longer retried after error.

bpo-35928 [https://bugs.python.org/issue?@action=redirect&bpo=35928]: io.TextIOWrapper now correctly handles the decoding buffer after read() and write().

bpo-26791 [https://bugs.python.org/issue?@action=redirect&bpo=26791]: shutil.move() now moves a symlink into a directory when that directory is the target of the symlink. This provides the same behavior as the mv shell command. The previous behavior raised an exception. Patch by Jeffrey Kintscher.

bpo-41422 [https://bugs.python.org/issue?@action=redirect&bpo=41422]: Fixed memory leaks of pickle.Pickler and pickle.Unpickler involving cyclic references via the internal memo mapping.

bpo-19821 [https://bugs.python.org/issue?@action=redirect&bpo=19821]: The pydoc.ispackage() function has been deprecated.

bpo-40262 [https://bugs.python.org/issue?@action=redirect&bpo=40262]: The ssl.SSLSocket.recv_into() method no longer requires the buffer argument to implement __len__ and supports buffers with arbitrary item size.

bpo-39912 [https://bugs.python.org/issue?@action=redirect&bpo=39912]: warnings.filterwarnings() and warnings.simplefilter() now raise appropriate exceptions instead of AssertionError. Patch contributed by Rémi Lapeyre.

bpo-37260 [https://bugs.python.org/issue?@action=redirect&bpo=37260]: Fixed a race condition in shutil.rmtree() in which directory entries removed by another process or thread while shutil.rmtree() is running can cause it to raise FileNotFoundError. Patch by Jeffrey Kintscher.

bpo-36959 [https://bugs.python.org/issue?@action=redirect&bpo=36959]: Fix some error messages for invalid ISO format string combinations in strptime() that referred to directives not contained in the format string. Patch by Gordon P. Hemsley.

bpo-18060 [https://bugs.python.org/issue?@action=redirect&bpo=18060]: Fixed a class inheritance issue that can cause segfaults when deriving two or more levels of subclasses from a base class of Structure or Union.

bpo-29779 [https://bugs.python.org/issue?@action=redirect&bpo=29779]: Add a new PYTHON_HISTORY environment variable to set the location of a .python_history file.

bpo-21360 [https://bugs.python.org/issue?@action=redirect&bpo=21360]: mailbox.Maildir now ignores files with a leading dot.

Documentation

gh-111699 [https://github.com/python/cpython/issues/111699]: Relocate smtpd deprecation notice to its own section rather than under locale in What's New in Python 3.12 document

gh-110746 [https://github.com/python/cpython/issues/110746]: Improved markup for valid options/values for methods ttk.treeview.column and ttk.treeview.heading, and for Layouts.

gh-95649 [https://github.com/python/cpython/issues/95649]: Document that the asyncio module contains code taken from v0.16.0 of the uvloop project [https://github.com/MagicStack/uvloop/tree/v0.16.0], as well as the required MIT licensing information.

Tests

gh-111798 [https://github.com/python/cpython/issues/111798]: Disable test_super_deep() from test_call under pydebug builds on WASI; the stack depth is too small to make the test useful.

gh-111801 [https://github.com/python/cpython/issues/111801]: Lower the recursion limit in test_isinstance for test_infinitely_many_bases(). This prevents a stack overflow on a pydebug build of WASI.

gh-111802 [https://github.com/python/cpython/issues/111802]: Specify a low recursion depth for test_bad_getattr() in test.pickletester to avoid exhausting the stack under a pydebug build for WASI.

gh-44626 [https://github.com/python/cpython/issues/44626]: Fix os.path.isabs() incorrectly returning True when given a path that starts with exactly one (back)slash on Windows.

Fix pathlib.PureWindowsPath.is_absolute() incorrectly returning False for some paths beginning with two (back)slashes.

gh-113633 [https://github.com/python/cpython/issues/113633]: Use module state for the _testcapi extension module.

gh-109980 [https://github.com/python/cpython/issues/109980]: Fix test_tarfile_vs_tar in test_shutil for macOS, where system tar can include more information in the archive than shutil.make_archive.

gh-112769 [https://github.com/python/cpython/issues/112769]: The tests now correctly compare zlib version when zlib.ZLIB_RUNTIME_VERSION contains non-integer suffixes. For example zlib-ng defines the version as 1.3.0.zlib-ng.

gh-112334 [https://github.com/python/cpython/issues/112334]: Adds a regression test to verify that vfork() is used when expected by subprocess on vfork enabled POSIX systems (Linux).

gh-108927 [https://github.com/python/cpython/issues/108927]: Fixed order dependence in running tests in the same process when a test that has submodules (e.g. test_importlib) follows a test that imports its submodule (e.g. test_importlib.util) and precedes a test (e.g. test_unittest or test_compileall) that uses that submodule.

bpo-40648 [https://bugs.python.org/issue?@action=redirect&bpo=40648]: Test modes that file can get with chmod() on Windows.

Build

gh-114013 [https://github.com/python/cpython/issues/114013]: Fix Tools/wasm/wasi.py to not include the path to python.wasm as part of HOSTRUNNER. The environment variable is meant to specify how to run the WASI host only, having python.wasm and relevant flags appended to the HOSTRUNNER. This fixes make test work.

gh-113258 [https://github.com/python/cpython/issues/113258]: Changed the Windows build to write out generated frozen modules into the build tree instead of the source tree.

gh-112305 [https://github.com/python/cpython/issues/112305]: Fixed the check-clean-src step performed on out of tree builds to detect errant $(srcdir)/Python/frozen_modules/*.h files and recommend appropriate source tree cleanup steps to get a working build again.

gh-112536 [https://github.com/python/cpython/issues/112536]: Add support for thread sanitizer (TSAN)

gh-112867 [https://github.com/python/cpython/issues/112867]: Fix the build for the case that WITH_PYMALLOC_RADIX_TREE=0 set.

gh-103065 [https://github.com/python/cpython/issues/103065]: Introduce Tools/wasm/wasi.py to simplify doing a WASI build.

bpo-11102 [https://bugs.python.org/issue?@action=redirect&bpo=11102]: The os.major(), os.makedev(), and os.minor() functions are now available on HP-UX v3.

bpo-36351 [https://bugs.python.org/issue?@action=redirect&bpo=36351]: Do not set ipv6type when cross-compiling.

Windows

gh-114096 [https://github.com/python/cpython/issues/114096]: Process privileges that are activated for creating directory junctions are now restored afterwards, avoiding behaviour changes in other parts of the program.

gh-111877 [https://github.com/python/cpython/issues/111877]: os.stat() calls were returning incorrect time values for files that could not be accessed directly.

gh-111973 [https://github.com/python/cpython/issues/111973]: Update Windows installer to use SQLite 3.44.2.

gh-113009 [https://github.com/python/cpython/issues/113009]: multiprocessing: On Windows, fix a race condition in Process.terminate(): no longer set the returncode attribute to always call WaitForSingleObject() in Process.wait(). Previously, sometimes the process was still running after TerminateProcess() even if GetExitCodeProcess() is not STILL_ACTIVE. Patch by Victor Stinner.

gh-86179 [https://github.com/python/cpython/issues/86179]: Fixes path calculations when launching Python on Windows through a symlink.

gh-71383 [https://github.com/python/cpython/issues/71383]: Update Tcl/Tk in Windows installer to 8.6.13 with a patch to suppress incorrect ThemeChanged warnings.

gh-111650 [https://github.com/python/cpython/issues/111650]: Ensures the Py_GIL_DISABLED preprocessor variable is defined in pyconfig.h so that extension modules written in C are able to use it.

gh-112278 [https://github.com/python/cpython/issues/112278]: Reduce the time cost for some functions in platform on Windows if current user has no permission to the WMI.

gh-73427 [https://github.com/python/cpython/issues/73427]: Deprecate sys._enablelegacywindowsfsencoding(). Use PYTHONLEGACYWINDOWSFSENCODING instead. Patch by Inada Naoki.

gh-87868 [https://github.com/python/cpython/issues/87868]: Correctly sort and remove duplicate environment variables in _winapi.CreateProcess().

bpo-37308 [https://bugs.python.org/issue?@action=redirect&bpo=37308]: Fix mojibake in mmap.mmap when using a non-ASCII tagname argument on Windows.

macOS

gh-113666 [https://github.com/python/cpython/issues/113666]: Add the following constants to module stat: UF_SETTABLE, UF_TRACKED, UF_DATAVAULT, SF_SUPPORTED, SF_SETTABLE, SF_SYNTHETIC, SF_RESTRICTED, SF_FIRMLINK and SF_DATALESS. The values UF_SETTABLE, SF_SUPPORTED, SF_SETTABLE and SF_SYNTHETIC are only available on macOS.

gh-113536 [https://github.com/python/cpython/issues/113536]: os.waitid() is now available on macOS

gh-110459 [https://github.com/python/cpython/issues/110459]: Running configure ... --with-openssl-rpath=X/Y/Z no longer fails to detect OpenSSL on macOS.

gh-74573 [https://github.com/python/cpython/issues/74573]: Document that dbm.ndbm can silently corrupt DBM files on updates when exceeding undocumented platform limits, and can crash (segmentation fault) when reading such a corrupted file. (FB8919203)

gh-65701 [https://github.com/python/cpython/issues/65701]: The freeze tool doesn't work with framework builds of Python. Document this and bail out early when running the tool with such a build.

gh-87277 [https://github.com/python/cpython/issues/87277]: webbrowser: Don't look for X11 browsers on macOS. Those are generally not used and probing for them can result in starting XQuartz even if it isn't used otherwise.

gh-111973 [https://github.com/python/cpython/issues/111973]: Update macOS installer to use SQLite 3.44.2.

gh-108269 [https://github.com/python/cpython/issues/108269]: Set CFBundleAllowMixedLocalizations to true in the Info.plist for the framework, embedded Python.app and IDLE.app with framework installs on macOS. This allows applications to pick up the user's preferred locale when that's different from english.

gh-102362 [https://github.com/python/cpython/issues/102362]: Make sure the result of sysconfig.get_plaform() includes at least a major and minor versions, even if MACOSX_DEPLOYMENT_TARGET is set to only a major version during build to match the format expected by pip.

gh-110017 [https://github.com/python/cpython/issues/110017]: Disable a signal handling stress test on macOS due to a bug in macOS (FB13453490).

gh-110820 [https://github.com/python/cpython/issues/110820]: Make sure the preprocessor definitions for ALIGNOF_MAX_ALIGN_T, SIZEOF_LONG_DOUBLE and HAVE_GCC_ASM_FOR_X64 are correct for Universal 2 builds on macOS.

gh-109981 [https://github.com/python/cpython/issues/109981]: Use /dev/fd on macOS to determine the number of open files in test.support.os_helper.fd_count to avoid a crash with "guarded" file descriptors when probing for open files.

IDLE

gh-72284 [https://github.com/python/cpython/issues/72284]: Improve the lists of features, editor key bindings, and shell key bingings in the IDLE doc.

gh-113903 [https://github.com/python/cpython/issues/113903]: Fix rare failure of test.test_idle, in test_configdialog.

gh-113729 [https://github.com/python/cpython/issues/113729]: Fix the "Help -> IDLE Doc" menu bug in 3.11.7 and 3.12.1.

gh-113269 [https://github.com/python/cpython/issues/113269]: Fix test_editor hang on macOS Catalina.

gh-112898 [https://github.com/python/cpython/issues/112898]: Fix processing unsaved files when quitting IDLE on macOS.

bpo-13586 [https://bugs.python.org/issue?@action=redirect&bpo=13586]: Enter the selected text when opening the "Replace" dialog.

C API

gh-106560 [https://github.com/python/cpython/issues/106560]: Fix redundant declarations in the public C API. Declare PyBool_Type, PyLong_Type and PySys_Audit() only once. Patch by Victor Stinner.

gh-112438 [https://github.com/python/cpython/issues/112438]: Fix support of format units "es", "et", "es#", and "et#" in nested tuples in PyArg_ParseTuple()-like functions.

gh-111545 [https://github.com/python/cpython/issues/111545]: Add Py_HashPointer() function to hash a pointer. Patch by Victor Stinner.

gh-65210 [https://github.com/python/cpython/issues/65210]: Change the declaration of the keywords parameter of PyArg_ParseTupleAndKeywords() and PyArg_VaParseTupleAndKeywords() for better compatibility with C++.

Python 3.13.0 alpha 2

Release date: 2023-11-22

Core and Builtins

gh-112243 [https://github.com/python/cpython/issues/112243]: Don't include comments in f-string debug expressions. Patch by Pablo Galindo

gh-112287 [https://github.com/python/cpython/issues/112287]: Slightly optimize the Tier 2 (uop) interpreter by only loading oparg and operand when needed. Also double the trace size limit again, to 512 this time.

gh-112266 [https://github.com/python/cpython/issues/112266]: Change docstrings of __dict__ and __weakref__.

gh-111807 [https://github.com/python/cpython/issues/111807]: Lower the max parser stack depth to 1000 under WASI debug builds.

gh-111798 [https://github.com/python/cpython/issues/111798]: When Python is built in debug mode, set the C recursion limit to 500 instead of 1500. A debug build is likely built with low optimization level which implies higher stack memory usage than a release build. Patch by Victor Stinner.

gh-106529 [https://github.com/python/cpython/issues/106529]: Enable translating unspecialized FOR_ITER to Tier 2.

gh-111916 [https://github.com/python/cpython/issues/111916]: Make hashlib related modules thread-safe without the GIL

gh-81137 [https://github.com/python/cpython/issues/81137]: Deprecate assignment to a function's __code__ field when the new code object is of a mismatched type (e.g., from a generator to a plain function).

gh-79932 [https://github.com/python/cpython/issues/79932]: Raise exception if frame.clear() is called on a suspended frame.

gh-81925 [https://github.com/python/cpython/issues/81925]: Implement native thread ids for GNU KFreeBSD.

gh-111843 [https://github.com/python/cpython/issues/111843]: Use exponential backoff to reduce the number of failed tier 2 optimization attempts by over 99%.

gh-110829 [https://github.com/python/cpython/issues/110829]: Joining a thread now ensures the underlying OS thread has exited. This is required for safer fork() in multi-threaded processes.

gh-109369 [https://github.com/python/cpython/issues/109369]: Make sure that tier 2 traces are de-optimized if the code is instrumented

gh-111772 [https://github.com/python/cpython/issues/111772]: Specialize slot loads and stores for _Py_T_OBJECT as well as Py_T_OBJECT_EX

gh-111666 [https://github.com/python/cpython/issues/111666]: Speed up BaseExceptionGroup.derive(), BaseExceptionGroup.subgroup(), and BaseExceptionGroup.split() by changing how they parse passed arguments.

gh-111654 [https://github.com/python/cpython/issues/111654]: Fix runtime crash when some error happens in opcode LOAD_FROM_DICT_OR_DEREF.

gh-111623 [https://github.com/python/cpython/issues/111623]: Add support for sharing tuples between interpreters using the cross-interpreter API. Patch by Anthony Shaw.

gh-111354 [https://github.com/python/cpython/issues/111354]: The oparg of YIELD_VALUE is now 1 if the instruction is part of a yield-from or await, and 0 otherwise.

The SUSPENDED frame state is now split into SUSPENDED and SUSPENDED_YIELD_FROM. This simplifies the code in _PyGen_yf.

gh-111520 [https://github.com/python/cpython/issues/111520]: Merge the Tier 1 (bytecode) and Tier 2 (micro-ops) interpreters together, moving the Tier 2 interpreter loop and switch into _PyEval_EvalFrameDefault() in Python/ceval.c. The Python/executor.c file is gone. Also the TIER_ONE and TIER_TWO macros are now handled by the code generator.

Beware! This changes the environment variables to enable micro-ops and their debugging to PYTHON_UOPS and PYTHON_LLTRACE.

gh-109181 [https://github.com/python/cpython/issues/109181]: Speed up Traceback object creation by lazily compute the line number. Patch by Pablo Galindo

gh-111420 [https://github.com/python/cpython/issues/111420]: Allow type comments in parenthesized with statements

gh-111438 [https://github.com/python/cpython/issues/111438]: Add support for sharing floats between interpreters using the cross-interpreter API. Patch by Anthony Shaw.

gh-111435 [https://github.com/python/cpython/issues/111435]: Add support for sharing of True and False between interpreters using the cross-interpreter API. Patch by Anthony Shaw.

gh-102388 [https://github.com/python/cpython/issues/102388]: Fix a bug where iso2022_jp_3 and iso2022_jp_2004 codecs read out of bounds

gh-111366 [https://github.com/python/cpython/issues/111366]: Fix an issue in the codeop that was causing SyntaxError exceptions raised in the presence of invalid syntax to not contain precise error messages. Patch by Pablo Galindo

gh-111380 [https://github.com/python/cpython/issues/111380]: Fix a bug that was causing SyntaxWarning to appear twice when parsing if invalid syntax is encountered later. Patch by Pablo galindo

gh-111374 [https://github.com/python/cpython/issues/111374]: Added a new environment variable PYTHON_FROZEN_MODULES. It determines whether or not frozen modules are ignored by the import machinery, equivalent of the -X frozen_modules command-line option.

gh-111354 [https://github.com/python/cpython/issues/111354]: Remove oparg from YIELD_VALUE. Change oparg of RESUME to include information about the except-depth. These changes make it possible to simplify the code in generator close.

gh-94438 [https://github.com/python/cpython/issues/94438]: Fix a regression that prevented jumping across is None and is not None when debugging. Patch by Savannah Ostrowski.

gh-67224 [https://github.com/python/cpython/issues/67224]: Show source lines in tracebacks when using the -c option when running Python. Patch by Pablo Galindo

gh-111123 [https://github.com/python/cpython/issues/111123]: Fix a bug where a global declaration in an except block is rejected when the global is used in the else block.

gh-110938 [https://github.com/python/cpython/issues/110938]: Fix error messages for indented blocks with functions and classes with generic type parameters. Patch by Pablo Galindo

gh-109214 [https://github.com/python/cpython/issues/109214]: Remove unnecessary instruction pointer updates before returning from frames.

gh-110912 [https://github.com/python/cpython/issues/110912]: Correctly display the traceback for MemoryError exceptions using the traceback module. Patch by Pablo Galindo

gh-109894 [https://github.com/python/cpython/issues/109894]: Fixed crash due to improperly initialized static MemoryError in subinterpreter.

gh-110892 [https://github.com/python/cpython/issues/110892]: Return NULL for PyTrace_RETURN events caused by an exception

gh-110864 [https://github.com/python/cpython/issues/110864]: Fix argument parsing by _PyArg_UnpackKeywordsWithVararg for functions defining pos-or-keyword, vararg, and kw-only parameters.

gh-109094 [https://github.com/python/cpython/issues/109094]: Replace prev_instr on the interpreter frame by instr_ptr which points to the beginning of the instruction that is currently executing (or will execute once the frame resumes).

gh-110805 [https://github.com/python/cpython/issues/110805]: Allow the repl to show source code and complete tracebacks. Patch by Pablo Galindo

gh-110722 [https://github.com/python/cpython/issues/110722]: Add PYTHON_PRESITE=package.module to import a module early in the interpreter lifecycle before site.py is executed. Python needs to be built in debug mode for this option to exist.

gh-110481 [https://github.com/python/cpython/issues/110481]: Implement biased reference counting in --disable-gil builds.

gh-110543 [https://github.com/python/cpython/issues/110543]: Fix regression in Python 3.12 where types.CodeType.replace() would produce a broken code object if called on a module or class code object that contains a comprehension. Patch by Jelle Zijlstra.

gh-89519 [https://github.com/python/cpython/issues/89519]: Removed chained classmethod descriptors (introduced in bpo-19072 [https://bugs.python.org/issue?@action=redirect&bpo=19072]). This can no longer be used to wrap other descriptors such as property. The core design of this feature was flawed and caused a number of downstream problems. To "pass-through" a classmethod, consider using the __wrapped__ attribute that was added in Python 3.10.

gh-103615 [https://github.com/python/cpython/issues/103615]: Use local events for opcode tracing

bpo-46657 [https://bugs.python.org/issue?@action=redirect&bpo=46657]: Add mimalloc memory allocator support.

gh-106718 [https://github.com/python/cpython/issues/106718]: When PyConfig.stdlib_dir is explicitly set, it's now respected and won't be overridden by PyConfig.home.

gh-106905 [https://github.com/python/cpython/issues/106905]: Fix incorrect SystemError about AST constructor recursion depth mismatch.

gh-100445 [https://github.com/python/cpython/issues/100445]: Improve error message for unterminated strings with escapes.

bpo-45759 [https://bugs.python.org/issue?@action=redirect&bpo=45759]: Improved error messages for elif/else statements not matching any valid statements. Patch by Jeremiah Vivian.

Library

gh-111942 [https://github.com/python/cpython/issues/111942]: Fix SystemError in the TextIOWrapper constructor with non-encodable "errors" argument in non-debug mode.

gh-111995 [https://github.com/python/cpython/issues/111995]: Added the NI_IDN constant to the socket module when present in C at build time for use with socket.getnameinfo().

gh-109538 [https://github.com/python/cpython/issues/109538]: Issue warning message instead of having RuntimeError be displayed when event loop has already been closed at StreamWriter.__del__().

gh-111942 [https://github.com/python/cpython/issues/111942]: Fix crashes in io.TextIOWrapper.reconfigure() when pass invalid arguments, e.g. non-string encoding.

gh-111460 [https://github.com/python/cpython/issues/111460]: curses: restore wide character support (including curses.unget_wch() and get_wch()) on macOS, which was unavailable due to a regression in Python 3.12.

gh-103791 [https://github.com/python/cpython/issues/103791]: contextlib.suppress now supports suppressing exceptions raised as part of a BaseExceptionGroup, in addition to the recent support for ExceptionGroup.

gh-111835 [https://github.com/python/cpython/issues/111835]: The mmap.mmap class now has an seekable() method that can be used when a seekable file-like object is required. The seek() method now returns the new absolute position. Patch by Donghee Na.

gh-111804 [https://github.com/python/cpython/issues/111804]: Remove posix.fallocate() under WASI as the underlying posix_fallocate() is not available in WASI preview2.

gh-111841 [https://github.com/python/cpython/issues/111841]: Fix truncating arguments on an embedded null character in os.putenv() and os.unsetenv() on Windows.

gh-111768 [https://github.com/python/cpython/issues/111768]: wsgiref.util.is_hop_by_hop() is now exposed correctly in __all__.

gh-80731 [https://github.com/python/cpython/issues/80731]: Avoid executing the default function in cmd.Cmd in an except block

gh-111541 [https://github.com/python/cpython/issues/111541]: Fix doctest for SyntaxError not-builtin subclasses.

gh-111719 [https://github.com/python/cpython/issues/111719]: Add extra argument validation for alias command in pdb

gh-111482 [https://github.com/python/cpython/issues/111482]: time: Make time.clock_gettime() and time.clock_gettime_ns() functions up to 2x faster by faster calling convention. Patch by Victor Stinner.

gh-110894 [https://github.com/python/cpython/issues/110894]: Call loop exception handler for exceptions in client_connected_cb of asyncio.start_server() so that applications can handle it. Patch by Kumar Aditya.

gh-111531 [https://github.com/python/cpython/issues/111531]: Fix reference leaks in bind_class() and bind_all() methods of tkinter widgets.

gh-111246 [https://github.com/python/cpython/issues/111246]: asyncio.loop.create_unix_server() will now automatically remove the Unix socket when the server is closed.

gh-111356 [https://github.com/python/cpython/issues/111356]: Added io.text_encoding(), io.DEFAULT_BUFFER_SIZE, and io.IncrementalNewlineDecoder to io.__all__.

gh-66425 [https://github.com/python/cpython/issues/66425]: Remove the code to set the REMOTE_HOST header from wsgiref module, as it is unreachable. This header is used for performance reasons, which is not necessary in the wsgiref module.

gh-111429 [https://github.com/python/cpython/issues/111429]: Speed up pathlib.PurePath.relative_to() and is_relative_to().

gh-111342 [https://github.com/python/cpython/issues/111342]: Fixed typo in math.sumprod().

gh-68166 [https://github.com/python/cpython/issues/68166]: Remove mention of not supported "vsapi" element type in tkinter.ttk.Style.element_create(). Add tests for element_create() and other ttk.Style methods. Add examples for element_create() in the documentation.

gh-111388 [https://github.com/python/cpython/issues/111388]: Add show_group parameter to traceback.format_exception_only(), which allows to format ExceptionGroup instances.

gh-79033 [https://github.com/python/cpython/issues/79033]: Another attempt at fixing asyncio.Server.wait_closed(). It now blocks until both conditions are true: the server is closed, and there are no more active connections. (This means that in some cases where in 3.12.0 this function would incorrectly have returned immediately, it will now block; in particular, when there are no active connections but the server hasn't been closed yet.)

gh-111259 [https://github.com/python/cpython/issues/111259]: Optimize recursive wildcards in pathlib.

gh-111295 [https://github.com/python/cpython/issues/111295]: Fix time not checking for errors when initializing.

gh-111253 [https://github.com/python/cpython/issues/111253]: Add error checking during _socket module init.

gh-111251 [https://github.com/python/cpython/issues/111251]: Fix _blake2 not checking for errors when initializing.

gh-111233 [https://github.com/python/cpython/issues/111233]: Fix select not checking for errors when initializing.

gh-111230 [https://github.com/python/cpython/issues/111230]: Fix ssl not checking for errors when initializing.

gh-111174 [https://github.com/python/cpython/issues/111174]: Fix crash in io.BytesIO.getbuffer() called repeatedly for empty BytesIO.

gh-111187 [https://github.com/python/cpython/issues/111187]: Postpone removal version for locale.getdefaultlocale() to Python 3.15.

gh-111159 [https://github.com/python/cpython/issues/111159]: Fix doctest output comparison for exceptions with notes.

gh-110910 [https://github.com/python/cpython/issues/110910]: Fix invalid state handling in asyncio.TaskGroup and asyncio.Timeout. They now raise proper RuntimeError if they are improperly used and are left in consistent state after this.

gh-111092 [https://github.com/python/cpython/issues/111092]: Make turtledemo run without default root enabled.

gh-110944 [https://github.com/python/cpython/issues/110944]: Support alias and convenience vars for pdb completion

gh-110745 [https://github.com/python/cpython/issues/110745]: Added newline parameter to pathlib.Path.read_text(). Patch by Junya Okabe.

gh-84583 [https://github.com/python/cpython/issues/84583]: Make pdb enter post-mortem mode even for SyntaxError

gh-80675 [https://github.com/python/cpython/issues/80675]: Set f_trace_lines = True on all frames upon pdb.set_trace()

gh-110771 [https://github.com/python/cpython/issues/110771]: Expose the setup and cleanup portions of asyncio.run_forever() as the standalone methods asyncio.run_forever_setup() and asyncio.run_forever_cleanup(). This allows for tighter integration with GUI event loops.

gh-110774 [https://github.com/python/cpython/issues/110774]: Support setting the asyncio.Runner loop_factory kwarg in unittest.IsolatedAsyncioTestCase

gh-110392 [https://github.com/python/cpython/issues/110392]: Fix tty.setraw() and tty.setcbreak(): previously they returned partially modified list of the original tty attributes. tty.cfmakeraw() and tty.cfmakecbreak() now make a copy of the list of special characters before modifying it.

gh-59013 [https://github.com/python/cpython/issues/59013]: Make line number of function breakpoint more precise in pdb

gh-88434 [https://github.com/python/cpython/issues/88434]: Emit deprecation warning for non-integer numbers in gettext functions and methods that consider plural forms even if the translation was not found.

gh-110395 [https://github.com/python/cpython/issues/110395]: Ensure that select.kqueue() objects correctly appear as closed in forked children, to prevent operations on an invalid file descriptor.

gh-110196 [https://github.com/python/cpython/issues/110196]: Add __reduce__ method to IPv6Address in order to keep scope_id

gh-109747 [https://github.com/python/cpython/issues/109747]: Improve errors for unsupported look-behind patterns. Now re.error is raised instead of OverflowError or RuntimeError for too large width of look-behind pattern.

gh-109466 [https://github.com/python/cpython/issues/109466]: Add the ipaddress.IPv4Address.ipv6_mapped property, which returns the IPv4-mapped IPv6 address.

gh-85098 [https://github.com/python/cpython/issues/85098]: Implement the CLI of the symtable module and improve the repr of Symbol.

gh-108791 [https://github.com/python/cpython/issues/108791]: Improved error handling in pdb command line interface, making it produce more concise error messages.

gh-105931 [https://github.com/python/cpython/issues/105931]: Change compileall to only strip the stripdir prefix from the full path recorded in the compiled .pyc file, when the prefix matches the start of the full path in its entirety. When the prefix does not match, no stripping is performed and a warning to this effect is displayed.

Previously all path components of the stripdir prefix that matched the full path were removed, while those that did not match were left alone (including ones interspersed between matching components).

gh-107431 [https://github.com/python/cpython/issues/107431]: Make the DictProxy and ListProxy types in multiprocessing.managers Generic Alias Types for [] use in typing contexts.

gh-72904 [https://github.com/python/cpython/issues/72904]: Add glob.translate(). This function converts a pathname with shell-style wildcards to a regular expression.

gh-90026 [https://github.com/python/cpython/issues/90026]: Define USE_XATTRS on Cygwin so that XATTR-related functions in the os module become available.

gh-90890 [https://github.com/python/cpython/issues/90890]: New methods mailbox.Maildir.get_info(), mailbox.Maildir.set_info(), mailbox.Maildir.get_flags(), mailbox.Maildir.set_flags(), mailbox.Maildir.add_flag(), mailbox.Maildir.remove_flag(). These methods speed up accessing a message's info and/or flags and are useful when it is not necessary to access the message's contents, as when iterating over a Maildir to find messages with specific flags.

gh-102956 [https://github.com/python/cpython/issues/102956]: Fix returning of empty byte strings after seek in zipfile module

gh-102895 [https://github.com/python/cpython/issues/102895]: Added a parameter local_exit for code.interact() to prevent exit() and quit from closing sys.stdin and raise SystemExit.

gh-97928 [https://github.com/python/cpython/issues/97928]: Change the behavior of tkinter.Text.count(). It now always returns an integer if one or less counting options are specified. Previously it could return a single count as a 1-tuple, an integer (only if option "update" was specified) or None if no items found. The result is now the same if wantobjects is set to 0.

gh-96954 [https://github.com/python/cpython/issues/96954]: Switch the storage of the unicode codepoint names to use a different data-structure, a directed acyclic word graph [https://en.wikipedia.org/wiki/Deterministic_acyclic_finite_state_automaton]. This makes the unicodedata shared library about 440 KiB smaller. Contributed by Carl Friedrich Bolz-Tereick using code from the PyPy project.

gh-73561 [https://github.com/python/cpython/issues/73561]: Omit the interface scope from an IPv6 address when used as Host header by http.client.

gh-86826 [https://github.com/python/cpython/issues/86826]: zipinfo now supports the full range of values in the TZ string determined by RFC 8536 and detects all invalid formats. Both Python and C implementations now raise exceptions of the same type on invalid data.

Tests

gh-111808 [https://github.com/python/cpython/issues/111808]: Make the default value of test.support.infinite_recursion() to be conditional based on whether optimizations were used when compiling the interpreter. This helps with platforms like WASI whose stack size is greatly restricted in debug builds.

gh-110722 [https://github.com/python/cpython/issues/110722]: Gathering line coverage of standard libraries within the regression test suite is now precise, as well as much faster. Patch by Łukasz Langa.

gh-110367 [https://github.com/python/cpython/issues/110367]: Make regrtest --verbose3 option compatible with --huntrleaks -jN options. The ./python -m test -j1 -R 3:3 --verbose3 command now works as expected. Patch by Victor Stinner.

gh-111165 [https://github.com/python/cpython/issues/111165]: Remove no longer used functions run_unittest() and run_doctest() from the test.support module.

gh-110932 [https://github.com/python/cpython/issues/110932]: Fix regrtest if the SOURCE_DATE_EPOCH environment variable is defined: use the variable value as the random seed. Patch by Victor Stinner.

gh-110995 [https://github.com/python/cpython/issues/110995]: test_gdb: Fix detection of gdb built without Python scripting support. Patch by Victor Stinner.

gh-110918 [https://github.com/python/cpython/issues/110918]: Test case matching patterns specified by options --match, --ignore, --matchfile and --ignorefile are now tested in the order of specification, and the last match determines whether the test case be run or ignored.

gh-108747 [https://github.com/python/cpython/issues/108747]: Add unit test for usercustomize and sitecustomize hooks from site.

Build

gh-96954 [https://github.com/python/cpython/issues/96954]: Make make regen-unicodedata work for out-of-tree builds of CPython.

gh-112088 [https://github.com/python/cpython/issues/112088]: Add Tools/build/regen-configure.sh script to regenerate the configure with an Ubuntu container image. The quay.io/tiran/cpython_autoconf:271 container image (tiran/cpython_autoconf [https://github.com/tiran/cpython_autoconf]) is no longer used. Patch by Victor Stinner.

gh-111046 [https://github.com/python/cpython/issues/111046]: For wasi-threads, memory is now exported to fix compatibility issues with some wasm runtimes.

gh-110828 [https://github.com/python/cpython/issues/110828]: AIX 32bit needs -latomic to build the _testcapi extension module.

gh-85283 [https://github.com/python/cpython/issues/85283]: The errno, md5, resource, winsound, _ctypes_test, _multiprocessing.posixshmem, _scproxy, _stat, _testimportmultiple and _uuid C extensions are now built with the limited C API. Patch by Victor Stinner.

Windows

gh-111856 [https://github.com/python/cpython/issues/111856]: Fixes fstat() on file systems that do not support file ID requests. This includes FAT32 and exFAT.

gh-111293 [https://github.com/python/cpython/issues/111293]: Fix os.DirEntry.inode dropping higher 64 bits of a file id on some filesystems on Windows.

gh-110913 [https://github.com/python/cpython/issues/110913]: WindowsConsoleIO now correctly chunks large buffers without splitting up UTF-8 sequences.

macOS

gh-59703 [https://github.com/python/cpython/issues/59703]: For macOS framework builds, in getpath.c use the system dladdr function to find the path to the shared library rather than depending on deprecated macOS APIs.

gh-110950 [https://github.com/python/cpython/issues/110950]: Update macOS installer to include an upstream Tcl/Tk fix for the Secure coding is not enabled for restorable state! warning encountered in Tkinter on macOS 14 Sonoma.

gh-111015 [https://github.com/python/cpython/issues/111015]: Ensure that IDLE.app and Python Launcher.app are installed with appropriate permissions on macOS builds.

gh-71383 [https://github.com/python/cpython/issues/71383]: Update macOS installer to include an upstream Tcl/Tk fix for the ttk::ThemeChanged error encountered in Tkinter.

gh-92603 [https://github.com/python/cpython/issues/92603]: Update macOS installer to include a fix accepted by upstream Tcl/Tk for a crash encountered after the first tkinter.Tk() instance is destroyed.

IDLE

bpo-35668 [https://bugs.python.org/issue?@action=redirect&bpo=35668]: Add docstrings to the IDLE debugger module. Fix two bugs: initialize Idb.botframe (should be in Bdb); in Idb.in_rpc_code, check whether prev_frame is None before trying to use it. Greatly expand test_debugger.

Tools/Demos

gh-111903 [https://github.com/python/cpython/issues/111903]: Argument Clinic now supports the @critical_section directive that instructs Argument Clinic to generate a critical section around the function call, which locks the self object in --disable-gil builds. Patch by Sam Gross.

C API

gh-112026 [https://github.com/python/cpython/issues/112026]: Add again the private _PyThreadState_UncheckedGet() function as an alias to the new public PyThreadState_GetUnchecked() function. Patch by Victor Stinner.

gh-112026 [https://github.com/python/cpython/issues/112026]: Restore the removed _PyDict_GetItemStringWithError() function. It is used by numpy. Patch by Victor Stinner.

gh-112026 [https://github.com/python/cpython/issues/112026]: Restore removed private C API functions, macros and structures which have no simple replacement for now:

_PyDict_GetItem_KnownHash()

_PyDict_NewPresized()

_PyHASH_BITS

_PyHASH_IMAG

_PyHASH_INF

_PyHASH_MODULUS

_PyHASH_MULTIPLIER

_PyLong_Copy()

_PyLong_FromDigits()

_PyLong_New()

_PyLong_Sign()

_PyObject_CallMethodId()

_PyObject_CallMethodNoArgs()

_PyObject_CallMethodOneArg()

_PyObject_CallOneArg()

_PyObject_EXTRA_INIT

_PyObject_FastCallDict()

_PyObject_GetAttrId()

_PyObject_Vectorcall()

_PyObject_VectorcallMethod()

_PyStack_AsDict()

_PyThread_CurrentFrames()

_PyUnicodeWriter structure

_PyUnicodeWriter_Dealloc()

_PyUnicodeWriter_Finish()

_PyUnicodeWriter_Init()

_PyUnicodeWriter_Prepare()

_PyUnicodeWriter_PrepareKind()

_PyUnicodeWriter_WriteASCIIString()

_PyUnicodeWriter_WriteChar()

_PyUnicodeWriter_WriteLatin1String()

_PyUnicodeWriter_WriteStr()

_PyUnicodeWriter_WriteSubstring()

_PyUnicode_AsString()

_PyUnicode_FromId()

_PyVectorcall_Function()

_Py_IDENTIFIER()

_Py_c_abs()

_Py_c_diff()

_Py_c_neg()

_Py_c_pow()

_Py_c_prod()

_Py_c_quot()

_Py_c_sum()

_Py_static_string()

_Py_static_string_init()

Patch by Victor Stinner.

gh-112026 [https://github.com/python/cpython/issues/112026]: Add again <ctype.h> and <unistd.h> includes in Python.h, but don't include them in the limited C API version 3.13 and newer. Patch by Victor Stinner.

gh-111956 [https://github.com/python/cpython/issues/111956]: Add internal-only one-time initialization API: _PyOnceFlag and _PyOnceFlag_CallOnce.

gh-111262 [https://github.com/python/cpython/issues/111262]: Add PyDict_Pop() and PyDict_PopString() functions: remove a key from a dictionary and optionally return the removed value. This is similar to dict.pop(), but without the default value and not raising KeyError if the key missing. Patch by Stefan Behnel and Victor Stinner.

gh-111863 [https://github.com/python/cpython/issues/111863]: Rename Py_NOGIL to Py_GIL_DISABLED. Patch by Hugo van Kemenade.

gh-111138 [https://github.com/python/cpython/issues/111138]: Add PyList_Extend() and PyList_Clear() functions: similar to Python list.extend() and list.clear() methods. Patch by Victor Stinner.

gh-108765 [https://github.com/python/cpython/issues/108765]: On Windows, Python.h no longer includes the <stddef.h> standard header file. If needed, it should now be included explicitly. Patch by Victor Stinner.

gh-111569 [https://github.com/python/cpython/issues/111569]: Implement "Python Critical Sections" from PEP 703 [https://peps.python.org/pep-0703/]. These are macros to help replace the GIL with per-object locks in the --disable-gil build of CPython. The macros are no-ops in the default build.

gh-111506 [https://github.com/python/cpython/issues/111506]: In the limited C API version 3.13, Py_SET_REFCNT() function is now implemented as an opaque function call. Patch by Victor Stinner.

gh-108082 [https://github.com/python/cpython/issues/108082]: Add PyErr_FormatUnraisable() function.

gh-110964 [https://github.com/python/cpython/issues/110964]: Move the undocumented private _PyArg functions and _PyArg_Parser structure to internal C API (pycore_modsupport.h). Patch by Victor Stinner.

gh-110815 [https://github.com/python/cpython/issues/110815]: Support non-ASCII keyword names in PyArg_ParseTupleAndKeywords().

gh-109587 [https://github.com/python/cpython/issues/109587]: Introduced PyUnstable_PerfTrampoline_CompileCode(), PyUnstable_PerfTrampoline_SetPersistAfterFork() and PyUnstable_CopyPerfMapFile(). These functions allow extension modules to initialize trampolines eagerly, after the application is "warmed up". This makes it possible to have perf-trampolines running in an always-enabled fashion.

gh-85283 [https://github.com/python/cpython/issues/85283]: Add the PySys_Audit() function to the limited C API. Patch by Victor Stinner.

gh-85283 [https://github.com/python/cpython/issues/85283]: Add PyMem_RawMalloc(), PyMem_RawCalloc(), PyMem_RawRealloc() and PyMem_RawFree() to the limited C API. Patch by Victor Stinner.

gh-106672 [https://github.com/python/cpython/issues/106672]: Functions PyDict_GetItem(), PyDict_GetItemString(), PyMapping_HasKey(), PyMapping_HasKeyString(), PyObject_HasAttr(), PyObject_HasAttrString(), and PySys_GetObject(), which clear all errors occurred during calling the function, report now them using sys.unraisablehook().

gh-67565 [https://github.com/python/cpython/issues/67565]: Remove redundant C-contiguity check in getargs.c, binascii, ssl and Argument Clinic. Patched by Stefan Krah and Furkan Onder

Python 3.13.0 alpha 1

Release date: 2023-10-13

Security

gh-108310 [https://github.com/python/cpython/issues/108310]: Fixed an issue where instances of ssl.SSLSocket were vulnerable to a bypass of the TLS handshake and included protections (like certificate verification) and treating sent unencrypted data as if it were post-handshake TLS encrypted data. Security issue reported as CVE 2023-40217 [https://www.cve.org/CVERecord?id=CVE-2023-40217] by Aapo Oksman. Patch by Gregory P. Smith.

gh-107774 [https://github.com/python/cpython/issues/107774]: PEP 669 specifies that sys.monitoring.register_callback will generate an audit event. Pre-releases of Python 3.12 did not generate the audit event. This is now fixed.

gh-102988 [https://github.com/python/cpython/issues/102988]: Reverted the email.utils security improvement change released in 3.12beta4 that unintentionally caused email.utils.getaddresses to fail to parse email addresses with a comma in the quoted name field. See gh-106669 [https://github.com/python/cpython/issues/106669].

gh-99108 [https://github.com/python/cpython/issues/99108]: Refresh our new HACL* built-in hashlib code from upstream. Built-in SHA2 should be faster and an issue with SHA3 on 32-bit platforms is fixed.

gh-102509 [https://github.com/python/cpython/issues/102509]: Start initializing ob_digit during creation of PyLongObject objects. Patch by Illia Volochii.

Core and Builtins

gh-110782 [https://github.com/python/cpython/issues/110782]: Fix crash when typing.TypeVar is constructed with a keyword argument. Patch by Jelle Zijlstra.

gh-110752 [https://github.com/python/cpython/issues/110752]: Reset ceval.eval_breaker in interpreter_clear()

gh-110721 [https://github.com/python/cpython/issues/110721]: Use the traceback implementation for the default PyErr_Display() functionality. Patch by Pablo Galindo

gh-110696 [https://github.com/python/cpython/issues/110696]: Fix incorrect error message for invalid argument unpacking. Patch by Pablo Galindo

gh-104169 [https://github.com/python/cpython/issues/104169]: Split the tokenizer into two separate directories: - One part includes the actual lexeme producing logic and lives in Parser/lexer. - The second part wraps the lexer according to the different tokenization modes we have (string, utf-8, file, interactive, readline) and lives in Parser/tokenizer.

gh-110688 [https://github.com/python/cpython/issues/110688]: Remove undocumented test_c_api method from set, which was only defined for testing purposes under Py_DEBUG. Now we have proper CAPI tests.

gh-104584 [https://github.com/python/cpython/issues/104584]: Fix a reference leak when running with PYTHONUOPS or -X uops enabled.

gh-110514 [https://github.com/python/cpython/issues/110514]: Add PY_THROW to sys.setprofile() events

gh-110489 [https://github.com/python/cpython/issues/110489]: Optimise math.ceil() when the input is exactly a float, resulting in about a 10% improvement.

gh-110455 [https://github.com/python/cpython/issues/110455]: Guard assert(tstate->thread_id > 0) with #ifndef HAVE_PTHREAD_STUBS. This allows for for pydebug builds to work under WASI which (currently) lacks thread support.

gh-110309 [https://github.com/python/cpython/issues/110309]: Remove unnecessary empty constant nodes in the ast of f-string specs.

gh-110259 [https://github.com/python/cpython/issues/110259]: Correctly identify the format spec in f-strings (with single or triple quotes) that have multiple lines in the expression part and include a formatting spec. Patch by Pablo Galindo

gh-110237 [https://github.com/python/cpython/issues/110237]: Fix missing error checks for calls to PyList_Append in _PyEval_MatchClass.

gh-110164 [https://github.com/python/cpython/issues/110164]: regrtest: If the SOURCE_DATE_EPOCH environment variable is defined, regrtest now disables tests randomization. Patch by Victor Stinner.

gh-109889 [https://github.com/python/cpython/issues/109889]: Fix the compiler's redundant NOP detection algorithm to skip over NOPs with no line number when looking for the next instruction's lineno.

gh-109853 [https://github.com/python/cpython/issues/109853]: sys.path[0] is now set correctly for subinterpreters.

gh-109923 [https://github.com/python/cpython/issues/109923]: Set line number on the POP_TOP that follows a RETURN_GENERATOR.

gh-105716 [https://github.com/python/cpython/issues/105716]: Subinterpreters now correctly handle the case where they have threads running in the background. Before, such threads would interfere with cleaning up and destroying them, as well as prevent running another script.

gh-109369 [https://github.com/python/cpython/issues/109369]: The internal eval_breaker and supporting flags, plus the monitoring version have been merged into a single atomic integer to speed up checks.

gh-109823 [https://github.com/python/cpython/issues/109823]: Fix bug where compiler does not adjust labels when removing an empty basic block which is a jump target.

gh-109793 [https://github.com/python/cpython/issues/109793]: The main thread no longer exits prematurely when a subinterpreter is cleaned up during runtime finalization. The bug was a problem particularly because, when triggered, the Python process would always return with a 0 exitcode, even if it failed.

gh-109719 [https://github.com/python/cpython/issues/109719]: Fix missing jump target labels when compiler reorders cold/warm blocks.

gh-109595 [https://github.com/python/cpython/issues/109595]: Add -X cpu_count command line option to override return results of os.cpu_count() and os.process_cpu_count(). This option is useful for users who need to limit CPU resources of a container system without having to modify the container (application code). Patch by Donghee Na.

gh-109627 [https://github.com/python/cpython/issues/109627]: Fix bug where the compiler does not assign a new jump target label to a duplicated small exit block.

gh-109596 [https://github.com/python/cpython/issues/109596]: Fix some tokens in the grammar that were incorrectly marked as soft keywords. Also fix some repeated rule names and ensure that repeated rules are not allowed. Patch by Pablo Galindo

gh-109496 [https://github.com/python/cpython/issues/109496]: On a Python built in debug mode, Py_DECREF() now calls _Py_NegativeRefcount() if the object is a dangling pointer to deallocated memory: memory filled with 0xDD "dead byte" by the debug hook on memory allocators. The fix is to check the reference count before checking for _Py_IsImmortal(). Patch by Victor Stinner.

gh-107265 [https://github.com/python/cpython/issues/107265]: Deopt opcodes hidden by the executor when base opcode is needed

gh-109371 [https://github.com/python/cpython/issues/109371]: Deopted instructions correctly for tool initialization and modified the incorrect assertion in instrumentation, when a previous tool already sets INSTRUCTION events

gh-105658 [https://github.com/python/cpython/issues/105658]: Fix bug where the line trace of an except block ending with a conditional includes an excess event with the line of the conditional expression.

gh-109219 [https://github.com/python/cpython/issues/109219]: Fix compiling type param scopes that use a name which is also free in an inner scope.

gh-109351 [https://github.com/python/cpython/issues/109351]: Fix crash when compiling an invalid AST involving a named (walrus) expression.

gh-109341 [https://github.com/python/cpython/issues/109341]: Fix crash when compiling an invalid AST involving a ast.TypeAlias.

gh-109195 [https://github.com/python/cpython/issues/109195]: Fix source location for the LOAD_* instruction preceding a LOAD_SUPER_ATTR to load the super global (or shadowing variable) so that it encompasses only the name super and not the following parentheses.

gh-109256 [https://github.com/python/cpython/issues/109256]: Opcode IDs for specialized opcodes are allocated in their own range to improve stability of the IDs for the 'real' opcodes.

gh-109216 [https://github.com/python/cpython/issues/109216]: Fix possible memory leak in BUILD_MAP.

gh-109207 [https://github.com/python/cpython/issues/109207]: Fix a SystemError in __repr__ of symtable entry object.

gh-109179 [https://github.com/python/cpython/issues/109179]: Fix bug where the C traceback display drops notes from SyntaxError.

gh-109118 [https://github.com/python/cpython/issues/109118]: Disallow nested scopes (lambdas, generator expressions, and comprehensions) within PEP 695 annotation scopes that are nested within classes.

gh-109156 [https://github.com/python/cpython/issues/109156]: Add tests for de-instrumenting instructions while keeping the instrumentation for lines

gh-109114 [https://github.com/python/cpython/issues/109114]: Relax the detection of the error message for invalid lambdas inside f-strings to not search for arbitrary replacement fields to avoid false positives. Patch by Pablo Galindo

gh-105848 [https://github.com/python/cpython/issues/105848]: Add a new CALL_KW opcode, used for calls containing keyword arguments. Also, fix a possible crash when jumping over method calls in a debugger.

gh-109052 [https://github.com/python/cpython/issues/109052]: Use the base opcode when comparing code objects to avoid interference from instrumentation

gh-109118 [https://github.com/python/cpython/issues/109118]: Fix interpreter crash when a NameError is raised inside the type parameters of a generic class.

gh-88943 [https://github.com/python/cpython/issues/88943]: Improve syntax error for non-ASCII character that follows a numerical literal. It now points on the invalid non-ASCII character, not on the valid numerical literal.

gh-108976 [https://github.com/python/cpython/issues/108976]: Fix crash that occurs after de-instrumenting a code object in a monitoring callback.

gh-108732 [https://github.com/python/cpython/issues/108732]: Make iteration variables of module- and class-scoped comprehensions visible to pdb and other tools that use frame.f_locals again.

gh-108959 [https://github.com/python/cpython/issues/108959]: Fix caret placement for error locations for subscript and binary operations that involve non-semantic parentheses and spaces. Patch by Pablo Galindo

gh-104584 [https://github.com/python/cpython/issues/104584]: Fix a crash when running with PYTHONUOPS or -X uops enabled and an error occurs during optimization.

gh-108727 [https://github.com/python/cpython/issues/108727]: Define tp_dealloc for CounterOptimizer_Type. This fixes a segfault on deallocation.

gh-108520 [https://github.com/python/cpython/issues/108520]: Fix multiprocessing.synchronize.SemLock.__setstate__() to properly initialize multiprocessing.synchronize.SemLock._is_fork_ctx. This fixes a regression when passing a SemLock across nested processes.

Rename multiprocessing.synchronize.SemLock.is_fork_ctx to multiprocessing.synchronize.SemLock._is_fork_ctx to avoid exposing it as public API.

gh-108654 [https://github.com/python/cpython/issues/108654]: Restore locals shadowed by an inlined comprehension if the comprehension raises an exception.

gh-108488 [https://github.com/python/cpython/issues/108488]: Change the initialization of inline cache entries so that the cache entry for JUMP_BACKWARD is initialized to zero, instead of the adaptive_counter_warmup() value used for all other instructions. This counter, unique among instructions, counts up from zero.

gh-108716 [https://github.com/python/cpython/issues/108716]: Turn off deep-freezing of code objects. Modules are still frozen, so that a file system search is not needed for common modules.

gh-108614 [https://github.com/python/cpython/issues/108614]: Add RESUME_CHECK instruction, to avoid having to handle instrumentation, signals, and contexts switches in the tier 2 execution engine.

gh-108487 [https://github.com/python/cpython/issues/108487]: Move an assert that would cause a spurious crash in a devious case that should only trigger deoptimization.

gh-106176 [https://github.com/python/cpython/issues/106176]: Use a WeakValueDictionary to track the lists containing the modules each thread is currently importing. This helps avoid a reference leak from keeping the list around longer than necessary. Weakrefs are used as GC can't interrupt the cleanup.

gh-105481 [https://github.com/python/cpython/issues/105481]: The regen-opcode build stage was removed and its work is now done in regen-cases.

gh-107901 [https://github.com/python/cpython/issues/107901]: Fix missing line number on JUMP_BACKWARD at the end of a for loop.

gh-108113 [https://github.com/python/cpython/issues/108113]: The compile() built-in can now accept a new flag, ast.PyCF_OPTIMIZED_AST, which is similar to ast.PyCF_ONLY_AST except that the returned AST is optimized according to the value of the optimize argument.

ast.parse() now accepts an optional argument optimize which is passed on to the compile() built-in. This makes it possible to obtain an optimized AST.

gh-107971 [https://github.com/python/cpython/issues/107971]: Opcode IDs are generated from bytecodes.c instead of being hard coded in opcode.py.

gh-107944 [https://github.com/python/cpython/issues/107944]: Improve error message for function calls with bad keyword arguments. Patch by Pablo Galindo

gh-108390 [https://github.com/python/cpython/issues/108390]: Raise an exception when setting a non-local event (RAISE, EXCEPTION_HANDLED, etc.) in sys.monitoring.set_local_events.

Fixes crash when tracing in recursive calls to Python classes.

gh-108035 [https://github.com/python/cpython/issues/108035]: Remove the _PyCFrame struct, moving the pointer to the current interpreter frame back to the threadstate, as it was for 3.10 and earlier. The _PyCFrame existed as a performance optimization for tracing. Since PEP 669 has been implemented, this optimization no longer applies.

gh-91051 [https://github.com/python/cpython/issues/91051]: Fix abort / segfault when using all eight type watcher slots, on platforms where char is signed by default.

gh-106581 [https://github.com/python/cpython/issues/106581]: Fix possible assertion failures and missing instrumentation events when PYTHONUOPS or -X uops is enabled.

gh-107526 [https://github.com/python/cpython/issues/107526]: Revert converting vars, dir, next, getattr, and iter to argument clinic.

gh-84805 [https://github.com/python/cpython/issues/84805]: Autogenerate signature for METH_NOARGS and METH_O extension functions.

gh-107758 [https://github.com/python/cpython/issues/107758]: Make the dump_stack() routine used by the lltrace feature (low-level interpreter debugging) robust against recursion by ensuring that it never calls a __repr__ method implemented in Python. Also make the similar output for Tier-2 uops appear on stdout (instead of stderr), to match the lltrace code in ceval.c.

gh-107659 [https://github.com/python/cpython/issues/107659]: Add docstrings for ctypes.pointer() and ctypes.POINTER().

gh-105848 [https://github.com/python/cpython/issues/105848]: Modify the bytecode so that the actual callable for a CALL is at a consistent position on the stack (regardless of whether or not bound-method-calling optimizations are active).

gh-107674 [https://github.com/python/cpython/issues/107674]: Fixed performance regression in sys.settrace.

gh-107724 [https://github.com/python/cpython/issues/107724]: In pre-release versions of 3.12, up to rc1, the sys.monitoring callback function for the PY_THROW event was missing the third, exception argument. That is now fixed.

gh-84436 [https://github.com/python/cpython/issues/84436]: Skip reference count modifications for many known immortal objects.

gh-107596 [https://github.com/python/cpython/issues/107596]: Specialize subscripting str objects by int indexes.

gh-107080 [https://github.com/python/cpython/issues/107080]: Trace refs builds (--with-trace-refs) were crashing when used with isolated subinterpreters. The problematic global state has been isolated to each interpreter. Other fixing the crashes, this change does not affect users.

gh-107557 [https://github.com/python/cpython/issues/107557]: Generate the cases needed for the barebones tier 2 abstract interpreter for optimization passes in CPython.

gh-106608 [https://github.com/python/cpython/issues/106608]: Make _PyUOpExecutorObject variable length.

gh-100964 [https://github.com/python/cpython/issues/100964]: Clear generators' exception state after return to break reference cycles.

gh-107455 [https://github.com/python/cpython/issues/107455]: Improve error messages when converting an incompatible type to ctypes.c_char_p, ctypes.c_wchar_p and ctypes.c_void_p.

gh-107263 [https://github.com/python/cpython/issues/107263]: Increase C recursion limit for functions other than the main interpreter from 800 to 1500. This should allow functions like list.__repr__ and json.dumps to handle all the inputs that they could prior to 3.12

gh-104584 [https://github.com/python/cpython/issues/104584]: Fix an issue which caused incorrect inline caches to be read when running with PYTHONUOPS or -X uops enabled.

gh-104432 [https://github.com/python/cpython/issues/104432]: Fix potential unaligned memory access on C APIs involving returned sequences of char * pointers within the grp and socket modules. These were revealed using a -fsaniziter=alignment build on ARM macOS. Patch by Christopher Chavez.

gh-106078 [https://github.com/python/cpython/issues/106078]: Isolate _decimal (apply PEP 687 [https://peps.python.org/pep-0687/]). Patch by Charlie Zhao.

gh-106898 [https://github.com/python/cpython/issues/106898]: Add the exception as the third argument to PY_UNIND callbacks in sys.monitoring. This makes the PY_UNWIND callback consistent with the other exception handling callbacks.

gh-106895 [https://github.com/python/cpython/issues/106895]: Raise a ValueError when a monitoring callback function returns DISABLE for events that cannot be disabled locally.

gh-106897 [https://github.com/python/cpython/issues/106897]: Add a RERAISE event to sys.monitoring, which occurs when an exception is reraise, either explicitly by a plain raise statement, or implicitly in an except or finally block.

gh-77377 [https://github.com/python/cpython/issues/77377]: Ensure that multiprocessing synchronization objects created in a fork context are not sent to a different process created in a spawn context. This changes a segfault into an actionable RuntimeError in the parent process.

gh-106931 [https://github.com/python/cpython/issues/106931]: Statically allocated string objects are now interned globally instead of per-interpreter. This fixes a situation where such a string would only be interned in a single interpreter. Normal string objects are unaffected.

gh-104621 [https://github.com/python/cpython/issues/104621]: Unsupported modules now always fail to be imported.

gh-107122 [https://github.com/python/cpython/issues/107122]: Add dbm.ndbm.ndbm.clear() to dbm.ndbm. Patch By Donghee Na.

gh-107122 [https://github.com/python/cpython/issues/107122]: Add dbm.gnu.gdbm.clear() to dbm.gnu. Patch By Donghee Na.

gh-107015 [https://github.com/python/cpython/issues/107015]: The ASYNC and AWAIT tokens are removed from the Grammar, which removes the possibility of making async and await soft keywords when using feature_version<7 in ast.parse().

gh-106917 [https://github.com/python/cpython/issues/106917]: Fix classmethod-style super() method calls (i.e., where the second argument to super(), or the implied second argument drawn from self/cls in the case of zero-arg super, is a type) when the target of the call is not a classmethod.

gh-105699 [https://github.com/python/cpython/issues/105699]: Python no longer crashes due an infrequent race when initializing per-interpreter interned strings. The crash would manifest when the interpreter was finalized.

gh-105699 [https://github.com/python/cpython/issues/105699]: Python no longer crashes due to an infrequent race in setting Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors (both deprecated), when simultaneously initializing two isolated subinterpreters. Now they are only set during runtime initialization.

gh-106908 [https://github.com/python/cpython/issues/106908]: Fix various hangs, reference leaks, test failures, and tracing/introspection bugs when running with PYTHONUOPS or -X uops enabled.

gh-106092 [https://github.com/python/cpython/issues/106092]: Fix a segmentation fault caused by a use-after-free bug in frame_dealloc when the trashcan delays the deallocation of a PyFrameObject.

gh-106485 [https://github.com/python/cpython/issues/106485]: Reduce the number of materialized instances dictionaries by dematerializing them when possible.

gh-106719 [https://github.com/python/cpython/issues/106719]: No longer suppress arbitrary errors in the __annotations__ getter and setter in the type and module types.

gh-106723 [https://github.com/python/cpython/issues/106723]: Propagate frozen_modules to multiprocessing spawned process interpreters.

gh-104909 [https://github.com/python/cpython/issues/104909]: Split LOAD_ATTR_INSTANCE_VALUE into micro-ops.

gh-104909 [https://github.com/python/cpython/issues/104909]: Split LOAD_GLOBAL specializations into micro-ops.

gh-106597 [https://github.com/python/cpython/issues/106597]: A new debug structure of offsets has been added to the _PyRuntimeState that will help out-of-process debuggers and profilers to obtain the offsets to relevant interpreter structures in a way that is agnostic of how Python was compiled and that doesn't require copying the headers. Patch by Pablo Galindo

gh-106487 [https://github.com/python/cpython/issues/106487]: Allow the count argument of str.replace() to be a keyword. Patch by Hugo van Kemenade.

gh-96844 [https://github.com/python/cpython/issues/96844]: Improve error message of list.remove(). Patch by Donghee Na.

gh-81283 [https://github.com/python/cpython/issues/81283]: Compiler now strips indents from docstrings. It reduces pyc file size 5% when the module is heavily documented. This change affects to __doc__ so tools like doctest will be affected.

gh-106396 [https://github.com/python/cpython/issues/106396]: When the format specification of an f-string expression is empty, the parser now generates an empty ast.JoinedStr node for it instead of an one-element ast.JoinedStr with an empty string ast.Constant.

gh-100288 [https://github.com/python/cpython/issues/100288]: Specialize LOAD_ATTR for non-descriptors on the class. Adds LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES and LOAD_ATTR_NONDESCRIPTOR_NO_DICT.

gh-106008 [https://github.com/python/cpython/issues/106008]: Fix possible reference leaks when failing to optimize comparisons with None in the bytecode compiler.

gh-106145 [https://github.com/python/cpython/issues/106145]: Make end_lineno and end_col_offset required on type_param ast nodes.

gh-106213 [https://github.com/python/cpython/issues/106213]: Changed the way that Emscripten call trampolines work for compatibility with Wasm/JS Promise integration.

gh-106182 [https://github.com/python/cpython/issues/106182]: sys.getfilesystemencoding() and sys.getfilesystemencodeerrors now return interned Unicode object.

gh-106210 [https://github.com/python/cpython/issues/106210]: Removed Emscripten import trampoline as it was no longer necessary for Pyodide.

gh-104584 [https://github.com/python/cpython/issues/104584]: Added a new, experimental, tracing optimizer and interpreter (a.k.a. "tier 2"). This currently pessimizes, so don't use yet -- this is infrastructure so we can experiment with optimizing passes. To enable it, pass -Xuops or set PYTHONUOPS=1. To get debug output, set PYTHONUOPSDEBUG=N where N is a debug level (0-4, where 0 is no debug output and 4 is excessively verbose).

gh-105775 [https://github.com/python/cpython/issues/105775]: LOAD_CLOSURE is now a pseudo-op.

gh-105730 [https://github.com/python/cpython/issues/105730]: Allow any callable other than type objects as the condition predicate in BaseExceptionGroup.split() and BaseExceptionGroup.subgroup().

gh-105979 [https://github.com/python/cpython/issues/105979]: Fix crash in _imp.get_frozen_object() due to improper exception handling.

gh-106003 [https://github.com/python/cpython/issues/106003]: Add a new TO_BOOL instruction, which performs boolean conversions for POP_JUMP_IF_TRUE, POP_JUMP_IF_FALSE, and UNARY_NOT (which all expect exact bool values now). Also, modify the oparg of COMPARE_OP to include an optional "boolean conversion" flag.

gh-98931 [https://github.com/python/cpython/issues/98931]: Ensure custom SyntaxError error messages are raised for invalid imports with multiple targets. Patch by Pablo Galindo

gh-105724 [https://github.com/python/cpython/issues/105724]: Improve assert error messages by providing exact error range.

gh-105908 [https://github.com/python/cpython/issues/105908]: Fixed bug where gh-99111 [https://github.com/python/cpython/issues/99111] breaks future import barry_as_FLUFL in the Python REPL.

gh-105840 [https://github.com/python/cpython/issues/105840]: Fix possible crashes when specializing function calls with too many __defaults__.

gh-105831 [https://github.com/python/cpython/issues/105831]: Fix an f-string bug, where using a debug expression (the = sign) that appears in the last line of a file results to the debug buffer that holds the expression text being one character too small.

gh-105800 [https://github.com/python/cpython/issues/105800]: Correctly issue SyntaxWarning in f-strings if invalid sequences are used. Patch by Pablo Galindo

gh-105340 [https://github.com/python/cpython/issues/105340]: Include the comprehension iteration variable in locals() inside a module- or class-scope comprehension.

gh-105331 [https://github.com/python/cpython/issues/105331]: Raise ValueError if the delay argument to asyncio.sleep() is a NaN (matching time.sleep()).

gh-105587 [https://github.com/python/cpython/issues/105587]: The runtime can't guarantee that immortal objects will not be mutated by Extensions. Thus, this modifies _PyStaticObject_CheckRefcnt to warn instead of asserting.

gh-105564 [https://github.com/python/cpython/issues/105564]: Don't include artificil newlines in the line attribute of tokens in the APIs of the tokenize module. Patch by Pablo Galindo

gh-105549 [https://github.com/python/cpython/issues/105549]: Tokenize separately NUMBER and NAME tokens that are not ambiguous. Patch by Pablo Galindo.

gh-105588 [https://github.com/python/cpython/issues/105588]: Fix an issue that could result in crashes when compiling malformed ast nodes.

gh-100987 [https://github.com/python/cpython/issues/100987]: Allow objects other than code objects as the "executable" in internal frames. In the long term, this can help tools like Cython and PySpy interact more efficiently. In the shorter term, it allows us to perform some optimizations more simply.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in the builtins module where exceptions could end up being overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bug in the compiler where an exception could end up being overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Improve error handling in PyUnicode_BuildEncodingMap() where an exception could end up being overwritten.

gh-105486 [https://github.com/python/cpython/issues/105486]: Change the repr of ParamSpec list of args in types.GenericAlias.

gh-105678 [https://github.com/python/cpython/issues/105678]: Break the MAKE_FUNCTION instruction into two parts, MAKE_FUNCTION which makes the function and SET_FUNCTION_ATTRIBUTE which sets the attributes on the function. This makes the stack effect of MAKE_FUNCTION regular to ease optimization and code generation.

gh-105435 [https://github.com/python/cpython/issues/105435]: Fix spurious newline character if file ends on a comment without a newline. Patch by Pablo Galindo

gh-105390 [https://github.com/python/cpython/issues/105390]: Correctly raise tokenize.TokenError exceptions instead of SyntaxError for tokenize errors such as incomplete input. Patch by Pablo Galindo

gh-105259 [https://github.com/python/cpython/issues/105259]: Don't include newline character for trailing NEWLINE tokens emitted in the tokenize module. Patch by Pablo Galindo

gh-104635 [https://github.com/python/cpython/issues/104635]: Eliminate redundant STORE_FAST instructions in the compiler. Patch by Donghee Na and Carl Meyer.

gh-105324 [https://github.com/python/cpython/issues/105324]: Fix the main function of the tokenize module when reading from sys.stdin. Patch by Pablo Galindo

gh-33092 [https://github.com/python/cpython/issues/33092]: Simplify and speed up interpreter for f-strings. Removes FORMAT_VALUE opcode. Add CONVERT_VALUE, FORMAT_SIMPLE and FORMAT_WITH_SPEC opcode. Compiler emits more efficient sequence for each format expression.

gh-105229 [https://github.com/python/cpython/issues/105229]: Remove remaining two-codeunit superinstructions. All remaining superinstructions only take a single codeunit, simplifying instrumentation and quickening.

gh-105235 [https://github.com/python/cpython/issues/105235]: Prevent out-of-bounds memory access during mmap.find() calls.

gh-98963 [https://github.com/python/cpython/issues/98963]: Restore the ability for a subclass of property to define __slots__ or otherwise be dict-less by ignoring failures to set a docstring on such a class. This behavior had regressed in 3.12beta1. An AttributeError where there had not previously been one was disruptive to existing code.

gh-104812 [https://github.com/python/cpython/issues/104812]: The "pending call" machinery now works for all interpreters, not just the main interpreter, and runs in all threads, not just the main thread. Some calls are still only done in the main thread, ergo in the main interpreter. This change does not affect signal handling nor the existing public C-API (Py_AddPendingCall()), which both still only target the main thread. The new functionality is meant strictly for internal use for now, since consequences of its use are not well understood yet outside some very restricted cases. This change brings the capability in line with the intention when the state was made per-interpreter several years ago.

gh-105194 [https://github.com/python/cpython/issues/105194]: Do not escape with backslashes f-string format specifiers. Patch by Pablo Galindo

gh-105229 [https://github.com/python/cpython/issues/105229]: Replace some dynamic superinstructions with single instruction equivalents.

gh-105162 [https://github.com/python/cpython/issues/105162]: Fixed bug in generator.close()/throw() where an inner iterator would be ignored when the outer iterator was instrumented.

gh-105164 [https://github.com/python/cpython/issues/105164]: Ensure annotations are set up correctly if the only annotation in a block is within a match block. Patch by Jelle Zijlstra.

gh-105148 [https://github.com/python/cpython/issues/105148]: Make _PyASTOptimizeState internal to ast_opt.c. Make _PyAST_Optimize take two integers instead of a pointer to this struct. This avoids the need to include pycore_compile.h in ast_opt.c.

gh-104799 [https://github.com/python/cpython/issues/104799]: Attributes of ast nodes that are lists now default to the empty list if omitted. This means that some code that previously raised TypeError when the AST node was used will now proceed with the empty list instead. Patch by Jelle Zijlstra.

gh-105111 [https://github.com/python/cpython/issues/105111]: Remove the old trashcan macros Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END. They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END.

gh-105035 [https://github.com/python/cpython/issues/105035]: Fix super() calls on types with custom tp_getattro implementation (e.g. meta-types.)

gh-105017 [https://github.com/python/cpython/issues/105017]: Show CRLF lines in the tokenize string attribute in both NL and NEWLINE tokens. Patch by Marta Gómez.

gh-105013 [https://github.com/python/cpython/issues/105013]: Fix handling of multiline parenthesized lambdas in inspect.getsource(). Patch by Pablo Galindo

gh-105017 [https://github.com/python/cpython/issues/105017]: Do not include an additional final NL token when parsing files having CRLF lines. Patch by Marta Gómez.

gh-104976 [https://github.com/python/cpython/issues/104976]: Ensure that trailing DEDENT tokenize.TokenInfo objects emitted by the tokenize module are reported as in Python 3.11. Patch by Pablo Galindo

gh-104972 [https://github.com/python/cpython/issues/104972]: Ensure that the line attribute in tokenize.TokenInfo objects in the tokenize module are always correct. Patch by Pablo Galindo

gh-104955 [https://github.com/python/cpython/issues/104955]: Fix signature for the new __release_buffer__() slot. Patch by Jelle Zijlstra.

gh-104690 [https://github.com/python/cpython/issues/104690]: Starting new threads and process creation through os.fork() during interpreter shutdown (such as from atexit handlers) is no longer supported. It can lead to race condition between the main Python runtime thread freeing thread states while internal threading routines are trying to allocate and use the state of just created threads. Or forked children trying to use the mid-shutdown runtime and thread state in the child process.

gh-104879 [https://github.com/python/cpython/issues/104879]: Fix crash when accessing the __module__ attribute of type aliases defined outside a module. Patch by Jelle Zijlstra.

gh-104825 [https://github.com/python/cpython/issues/104825]: Tokens emitted by the tokenize module do not include an implicit \n character in the line attribute anymore. Patch by Pablo Galindo

gh-104770 [https://github.com/python/cpython/issues/104770]: If a generator returns a value upon being closed, the value is now returned by generator.close().

gh-89091 [https://github.com/python/cpython/issues/89091]: Raise RuntimeWarning for unawaited async generator methods like asend(), athrow() and aclose(). Patch by Kumar Aditya.

gh-96663 [https://github.com/python/cpython/issues/96663]: Add a better, more introspect-able error message when setting attributes on classes without a __dict__ and no slot member for the attribute.

gh-93627 [https://github.com/python/cpython/issues/93627]: Update the Python pickle module implementation to match the C implementation of the pickle module. For objects setting reduction methods like __reduce_ex__() or __reduce__() to None, pickling will result in a TypeError.

gh-101006 [https://github.com/python/cpython/issues/101006]: Improve error handling when read marshal data.

gh-91095 [https://github.com/python/cpython/issues/91095]: Specializes calls to most Python classes. Specifically, any class that inherits from object, or another Python class, and does not override __new__.

The specialized instruction does the following:

Creates the object (by calling object.__new__)

Pushes a shim frame to the frame stack (to cleanup after __init__)

Pushes the frame for __init__ to the frame stack

Speeds up the instantiation of most Python classes.

Library

gh-110786 [https://github.com/python/cpython/issues/110786]: sysconfig's CLI now ignores BrokenPipeError, making it exit normally if its output is being piped and the pipe closes.

gh-103480 [https://github.com/python/cpython/issues/103480]: The sysconfig module is now a package, instead of a single-file module.

gh-110733 [https://github.com/python/cpython/issues/110733]: Micro-optimization: Avoid calling min(), max() in BaseEventLoop._run_once().

gh-94597 [https://github.com/python/cpython/issues/94597]: Added asyncio.EventLoop for use with the asyncio.run() loop_factory kwarg to avoid calling the asyncio policy system.

gh-110682 [https://github.com/python/cpython/issues/110682]: runtime-checkable protocols used to consider __match_args__ a protocol member in __instancecheck__ if it was present on the protocol. Now, this attribute is ignored if it is present.

gh-110488 [https://github.com/python/cpython/issues/110488]: Fix a couple of issues in pathlib.PurePath.with_name(): a single dot was incorrectly considered a valid name, and in PureWindowsPath, a name with an NTFS alternate data stream, like a:b, was incorrectly considered invalid.

gh-110590 [https://github.com/python/cpython/issues/110590]: Fix a bug in _sre.compile() where TypeError would be overwritten by OverflowError when the code argument was a list of non-ints.

gh-65052 [https://github.com/python/cpython/issues/65052]: Prevent pdb from crashing when trying to display undisplayable objects

gh-110519 [https://github.com/python/cpython/issues/110519]: Deprecation warning about non-integer number in gettext now always refers to the line in the user code where gettext function or method is used. Previously it could refer to a line in gettext code.

gh-89902 [https://github.com/python/cpython/issues/89902]: Deprecate non-standard format specifier "N" for decimal.Decimal. It was not documented and only supported in the C implementation.

gh-110378 [https://github.com/python/cpython/issues/110378]: contextmanager() and asynccontextmanager() context managers now close an invalid underlying generator object that yields more then one value.

gh-106670 [https://github.com/python/cpython/issues/106670]: In pdb, set convenience variable $_exception for post mortem debugging.

gh-110365 [https://github.com/python/cpython/issues/110365]: Fix termios.tcsetattr() bug that was overwriting existing errors during parsing integers from term list.

gh-109653 [https://github.com/python/cpython/issues/109653]: Slightly improve the import time of several standard-library modules by deferring imports of warnings within those modules. Patch by Alex Waygood.

gh-110273 [https://github.com/python/cpython/issues/110273]: dataclasses.replace() now raises TypeError instead of ValueError if specify keyword argument for a field declared with init=False or miss keyword argument for required InitVar field.

gh-110249 [https://github.com/python/cpython/issues/110249]: Add --inline-caches flag to dis command line.

gh-109653 [https://github.com/python/cpython/issues/109653]: Fix a Python 3.12 regression in the import time of random. Patch by Alex Waygood.

gh-110222 [https://github.com/python/cpython/issues/110222]: Add support of struct sequence objects in copy.replace(). Patched by Xuehai Pan.

gh-109649 [https://github.com/python/cpython/issues/109649]: multiprocessing, concurrent.futures, compileall: Replace os.cpu_count() with os.process_cpu_count() to select the default number of worker threads and processes. Get the CPU affinity if supported. Patch by Victor Stinner.

gh-110150 [https://github.com/python/cpython/issues/110150]: Fix base case handling in statistics.quantiles. Now allows a single data point.

gh-110036 [https://github.com/python/cpython/issues/110036]: On Windows, multiprocessing Popen.terminate() now catches PermissionError and get the process exit code. If the process is still running, raise again the PermissionError. Otherwise, the process terminated as expected: store its exit code. Patch by Victor Stinner.

gh-110038 [https://github.com/python/cpython/issues/110038]: Fixed an issue that caused KqueueSelector.select() to not return all the ready events in some cases when a file descriptor is registered for both read and write.

gh-110045 [https://github.com/python/cpython/issues/110045]: Update the symtable module to support the new scopes introduced by PEP 695 [https://peps.python.org/pep-0695/].

gh-88402 [https://github.com/python/cpython/issues/88402]: Add new variables to sysconfig.get_config_vars() on Windows: LIBRARY, LDLIBRARY, LIBDIR, SOABI, and Py_NOGIL.

gh-109631 [https://github.com/python/cpython/issues/109631]: re functions such as re.findall(), re.split(), re.search() and re.sub() which perform short repeated matches can now be interrupted by user.

gh-109653 [https://github.com/python/cpython/issues/109653]: Reduce the import time of email.utils by around 43%. This results in the import time of email.message falling by around 18%, which in turn reduces the import time of importlib.metadata by around 6%. Patch by Alex Waygood.

gh-109818 [https://github.com/python/cpython/issues/109818]: Fix reprlib.recursive_repr() not copying __type_params__ from decorated function.

gh-109047 [https://github.com/python/cpython/issues/109047]: concurrent.futures: The executor manager thread now catches exceptions when adding an item to the call queue. During Python finalization, creating a new thread can now raise RuntimeError. Catch the exception and call terminate_broken() in this case. Patch by Victor Stinner.

gh-109782 [https://github.com/python/cpython/issues/109782]: Ensure the signature of os.path.isdir() is identical on all platforms. Patch by Amin Alaee.

gh-109653 [https://github.com/python/cpython/issues/109653]: Improve import time of functools by around 13%. Patch by Alex Waygood.

gh-109590 [https://github.com/python/cpython/issues/109590]: shutil.which() will prefer files with an extension in PATHEXT if the given mode includes os.X_OK on win32. If no PATHEXT match is found, a file without an extension in PATHEXT can be returned. This change will have shutil.which() act more similarly to previous behavior in Python 3.11.

gh-109653 [https://github.com/python/cpython/issues/109653]: Reduce the import time of enum by over 50%. Patch by Alex Waygood.

gh-109593 [https://github.com/python/cpython/issues/109593]: Avoid deadlocking on a reentrant call to the multiprocessing resource tracker. Such a reentrant call, though unlikely, can happen if a GC pass invokes the finalizer for a multiprocessing object such as SemLock.

gh-109653 [https://github.com/python/cpython/issues/109653]: Reduce the import time of typing by around a third. Patch by Alex Waygood.

gh-109649 [https://github.com/python/cpython/issues/109649]: Add os.process_cpu_count() function to get the number of logical CPUs usable by the calling thread of the current process. Patch by Victor Stinner.

gh-74481 [https://github.com/python/cpython/issues/74481]: Add set_error_mode related constants in msvcrt module in Python debug build.

gh-109613 [https://github.com/python/cpython/issues/109613]: Fix os.stat() and os.DirEntry.stat(): check for exceptions. Previously, on Python built in debug mode, these functions could trigger a fatal Python error (and abort the process) when a function succeeded with an exception set. Patch by Victor Stinner.

gh-109599 [https://github.com/python/cpython/issues/109599]: Expose the type of PyCapsule objects as types.CapsuleType.

gh-109109 [https://github.com/python/cpython/issues/109109]: You can now get the raw TLS certificate chains from TLS connections via ssl.SSLSocket.get_verified_chain() and ssl.SSLSocket.get_unverified_chain() methods.

Contributed by Mateusz Nowak.

gh-109559 [https://github.com/python/cpython/issues/109559]: Update unicodedata database to Unicode 15.1.0.

gh-109543 [https://github.com/python/cpython/issues/109543]: Remove unnecessary hasattr() check during typing.TypedDict creation.

gh-109495 [https://github.com/python/cpython/issues/109495]: Remove unnecessary extra __slots__ in datetime's pure python implementation to reduce memory size, as they are defined in the superclass. Patch by James Hilton-Balfe

gh-109461 [https://github.com/python/cpython/issues/109461]: logging: Use a context manager for lock acquisition.

gh-109096 [https://github.com/python/cpython/issues/109096]: http.server.CGIHTTPRequestHandler has been deprecated for removal in 3.15. Its design is old and the web world has long since moved beyond CGI.

gh-109409 [https://github.com/python/cpython/issues/109409]: Fix error when it was possible to inherit a frozen dataclass from multiple parents some of which were possibly not frozen.

gh-109375 [https://github.com/python/cpython/issues/109375]: The pdb alias command now prevents registering aliases without arguments.

gh-109319 [https://github.com/python/cpython/issues/109319]: Deprecate the dis.HAVE_ARGUMENT field in favour of dis.hasarg.

gh-107219 [https://github.com/python/cpython/issues/107219]: Fix a race condition in concurrent.futures. When a process in the process pool was terminated abruptly (while the future was running or pending), close the connection write end. If the call queue is blocked on sending bytes to a worker process, closing the connection write end interrupts the send, so the queue can be closed. Patch by Victor Stinner.

gh-66143 [https://github.com/python/cpython/issues/66143]: The codecs.CodecInfo object has been made copyable and pickleable. Patched by Robert Lehmann and Furkan Onder.

gh-109187 [https://github.com/python/cpython/issues/109187]: pathlib.Path.resolve() now treats symlink loops like other errors: in strict mode, OSError is raised, and in non-strict mode, no exception is raised.

gh-50644 [https://github.com/python/cpython/issues/50644]: Attempts to pickle or create a shallow or deep copy of codecs streams now raise a TypeError. Previously, copying failed with a RecursionError, while pickling produced wrong results that eventually caused unpickling to fail with a RecursionError.

gh-109174 [https://github.com/python/cpython/issues/109174]: Add support of types.SimpleNamespace in copy.replace().

gh-109164 [https://github.com/python/cpython/issues/109164]: pdb: Replace getopt with argparse for parsing command line arguments.

gh-109151 [https://github.com/python/cpython/issues/109151]: Enable readline editing features in the sqlite3 command-line interface (python -m sqlite3).

gh-108987 [https://github.com/python/cpython/issues/108987]: Fix _thread.start_new_thread() race condition. If a thread is created during Python finalization, the newly spawned thread now exits immediately instead of trying to access freed memory and lead to a crash. Patch by Victor Stinner.

gh-108682 [https://github.com/python/cpython/issues/108682]: Enum: require names=() or type=... to create an empty enum using the functional syntax.

gh-109033 [https://github.com/python/cpython/issues/109033]: Exceptions raised by os.utime builtin function now include the related filename

gh-108843 [https://github.com/python/cpython/issues/108843]: Fix an issue in ast.unparse() when unparsing f-strings containing many quote types.

gh-108469 [https://github.com/python/cpython/issues/108469]: ast.unparse() now supports new f-string syntax introduced in Python 3.12. Note that the f-string quotes are reselected for simplicity under the new syntax. (Patch by Steven Sun)

gh-108751 [https://github.com/python/cpython/issues/108751]: Add copy.replace() function which allows to create a modified copy of an object. It supports named tuples, dataclasses, and many other objects.

gh-108682 [https://github.com/python/cpython/issues/108682]: Enum: raise TypeError if super().__new__() is called from a custom __new__.

gh-108278 [https://github.com/python/cpython/issues/108278]: Deprecate passing the callback callable by keyword for the following sqlite3.Connection APIs:

set_authorizer()

set_progress_handler()

set_trace_callback()

The affected parameters will become positional-only in Python 3.15.

Patch by Erlend E. Aasland.

gh-105829 [https://github.com/python/cpython/issues/105829]: Fix concurrent.futures.ProcessPoolExecutor deadlock

gh-108295 [https://github.com/python/cpython/issues/108295]: Fix crashes related to use of weakrefs on typing.TypeVar.

gh-108463 [https://github.com/python/cpython/issues/108463]: Make expressions/statements work as expected in pdb

gh-108277 [https://github.com/python/cpython/issues/108277]: Add os.timerfd_create(), os.timerfd_settime(), os.timerfd_gettime(), os.timerfd_settime_ns(), and os.timerfd_gettime_ns() to provide a low level interface for Linux's timer notification file descriptor.

gh-107811 [https://github.com/python/cpython/issues/107811]: tarfile: extraction of members with overly large UID or GID (e.g. on an OS with 32-bit id_t) now fails in the same way as failing to set the ID.

gh-64662 [https://github.com/python/cpython/issues/64662]: Fix support for virtual tables in sqlite3.Connection.iterdump(). Patch by Aviv Palivoda.

gh-108111 [https://github.com/python/cpython/issues/108111]: Fix a regression introduced in gh-101251 [https://github.com/python/cpython/issues/101251] for 3.12, resulting in an incorrect offset calculation in gzip.GzipFile.seek().

gh-108294 [https://github.com/python/cpython/issues/108294]: time.sleep() now raises an auditing event.

gh-108278 [https://github.com/python/cpython/issues/108278]: Deprecate passing name, number of arguments, and the callable as keyword arguments, for the following sqlite3.Connection APIs:

create_function()

create_aggregate()

The affected parameters will become positional-only in Python 3.15.

Patch by Erlend E. Aasland.

gh-108322 [https://github.com/python/cpython/issues/108322]: Speed-up NormalDist.samples() by using the inverse CDF method instead of calling random.gauss().

gh-83417 [https://github.com/python/cpython/issues/83417]: Add the ability for venv to create a .gitignore file which causes the created environment to be ignored by Git. It is on by default when venv is called via its CLI.

gh-105736 [https://github.com/python/cpython/issues/105736]: Harmonized the pure Python version of OrderedDict with the C version. Now, both versions set up their internal state in __new__. Formerly, the pure Python version did the set up in __init__.

gh-108083 [https://github.com/python/cpython/issues/108083]: Fix bugs in the constructor of sqlite3.Connection and sqlite3.Connection.close() where exceptions could be leaked. Patch by Erlend E. Aasland.

gh-107932 [https://github.com/python/cpython/issues/107932]: Fix dis module to properly report and display bytecode that do not have source lines.

gh-105539 [https://github.com/python/cpython/issues/105539]: sqlite3 now emits an ResourceWarning if a sqlite3.Connection object is not closed explicitly. Patch by Erlend E. Aasland.

gh-107995 [https://github.com/python/cpython/issues/107995]: The __module__ attribute on instances of functools.cached_property is now set to the name of the module in which the cached_property is defined, rather than "functools". This means that doctests in cached_property docstrings are now properly collected by the doctest module. Patch by Tyler Smart.

gh-107963 [https://github.com/python/cpython/issues/107963]: Fix multiprocessing.set_forkserver_preload() to check the given list of modules names. Patch by Donghee Na.

gh-106242 [https://github.com/python/cpython/issues/106242]: Fixes os.path.normpath() to handle embedded null characters without truncating the path.

gh-81555 [https://github.com/python/cpython/issues/81555]: xml.dom.minidom now only quotes " in attributes.

gh-50002 [https://github.com/python/cpython/issues/50002]: xml.dom.minidom now preserves whitespaces in attributes.

gh-93057 [https://github.com/python/cpython/issues/93057]: Passing more than one positional argument to sqlite3.connect() and the sqlite3.Connection constructor is deprecated. The remaining parameters will become keyword-only in Python 3.15. Patch by Erlend E. Aasland.

gh-76913 [https://github.com/python/cpython/issues/76913]: Add merge_extra parameter/feature to logging.LoggerAdapter

gh-107913 [https://github.com/python/cpython/issues/107913]: Fix possible losses of errno and winerror values in OSError exceptions if they were cleared or modified by the cleanup code before creating the exception object.

gh-107845 [https://github.com/python/cpython/issues/107845]: tarfile.data_filter() now takes the location of symlinks into account when determining their target, so it will no longer reject some valid tarballs with LinkOutsideDestinationError.

gh-107812 [https://github.com/python/cpython/issues/107812]: Extend socket's netlink support to the FreeBSD platform.

gh-107805 [https://github.com/python/cpython/issues/107805]: Fix signatures of module-level generated functions in turtle.

gh-107782 [https://github.com/python/cpython/issues/107782]: pydoc is now able to show signatures which are not representable in Python, e.g. for getattr and dict.pop.

gh-56166 [https://github.com/python/cpython/issues/56166]: Deprecate passing optional arguments maxsplit, count and flags in module-level functions re.split(), re.sub() and re.subn() as positional. They should only be passed by keyword.

gh-107710 [https://github.com/python/cpython/issues/107710]: Speed up logging.getHandlerNames().

gh-107715 [https://github.com/python/cpython/issues/107715]: Fix doctest.DocTestFinder.find() in presence of class names with special characters. Patch by Gertjan van Zwieten.

gh-100814 [https://github.com/python/cpython/issues/100814]: Passing a callable object as an option value to a Tkinter image now raises the expected TclError instead of an AttributeError.

gh-72684 [https://github.com/python/cpython/issues/72684]: Add tkinter widget methods: tk_busy_hold(), tk_busy_configure(), tk_busy_cget(), tk_busy_forget(), tk_busy_current(), and tk_busy_status().

gh-106684 [https://github.com/python/cpython/issues/106684]: Raise ResourceWarning when asyncio.StreamWriter is not closed leading to memory leaks. Patch by Kumar Aditya.

gh-107465 [https://github.com/python/cpython/issues/107465]: Add pathlib.Path.from_uri() classmethod.

gh-107077 [https://github.com/python/cpython/issues/107077]: Seems that in some conditions, OpenSSL will return SSL_ERROR_SYSCALL instead of SSL_ERROR_SSL when a certification verification has failed, but the error parameters will still contain ERR_LIB_SSL and SSL_R_CERTIFICATE_VERIFY_FAILED. We are now detecting this situation and raising the appropriate ssl.SSLCertVerificationError. Patch by Pablo Galindo

gh-107576 [https://github.com/python/cpython/issues/107576]: Fix types.get_original_bases() to only return __orig_bases__ if it is present on cls directly. Patch by James Hilton-Balfe.

gh-105481 [https://github.com/python/cpython/issues/105481]: Remove opcode.is_pseudo, opcode.MIN_PSEUDO_OPCODE and opcode.MAX_PSEUDO_OPCODE, which were added in 3.12, were never documented and were not intended to be used externally.

gh-105481 [https://github.com/python/cpython/issues/105481]: opcode.ENABLE_SPECIALIZATION (which was added in 3.12 but never documented or intended for external usage) is moved to _opcode.ENABLE_SPECIALIZATION where tests can access it.

gh-107396 [https://github.com/python/cpython/issues/107396]: tarfiles; Fixed use before assignment of self.exception for gzip decompression

gh-107409 [https://github.com/python/cpython/issues/107409]: Set __wrapped__ attribute in reprlib.recursive_repr().

gh-107406 [https://github.com/python/cpython/issues/107406]: Implement new __repr__() method for struct.Struct. Now it returns Struct(<format repr>).

gh-107369 [https://github.com/python/cpython/issues/107369]: Optimize textwrap.indent(). It is ~30% faster for large input. Patch by Inada Naoki.

gh-78722 [https://github.com/python/cpython/issues/78722]: Fix issue where pathlib.Path.iterdir() did not raise OSError until iterated.

gh-105578 [https://github.com/python/cpython/issues/105578]: Deprecate typing.AnyStr in favor of the new Type Parameter syntax. See PEP 695.

gh-62519 [https://github.com/python/cpython/issues/62519]: Make gettext.pgettext() search plural definitions when translation is not found.

gh-107089 [https://github.com/python/cpython/issues/107089]: Shelves opened with shelve.open() have a much faster clear() method. Patch by James Cave.

gh-82500 [https://github.com/python/cpython/issues/82500]: Fix overflow on 32-bit systems with asyncio os.sendfile() implementation.

gh-83006 [https://github.com/python/cpython/issues/83006]: Document behavior of shutil.disk_usage() for non-mounted filesystems on Unix.

gh-65495 [https://github.com/python/cpython/issues/65495]: Use lowercase mail from and rcpt to in smptlib.SMTP.

gh-106186 [https://github.com/python/cpython/issues/106186]: Do not report MultipartInvariantViolationDefect defect when the email.parser.Parser class is used to parse emails with headersonly=True.

gh-105002 [https://github.com/python/cpython/issues/105002]: Fix invalid result from PurePath.relative_to() method when attempting to walk a ".." segment in other with walk_up enabled. A ValueError exception is now raised in this case.

gh-106739 [https://github.com/python/cpython/issues/106739]: Add the rtype_cache to the warning message (as an addition to the type of leaked objects and the number of leaked objects already included in the message) to make debugging leaked objects easier when the multiprocessing resource tracker process finds leaked objects at shutdown. This helps more quickly identify what was leaked and/or why the leaked object was not properly cleaned up.

gh-106751 [https://github.com/python/cpython/issues/106751]: Optimize SelectSelector.select() for many iteration case. Patch By Donghee Na.

gh-106751 [https://github.com/python/cpython/issues/106751]: Optimize _PollLikeSelector.select() for many iteration case.

gh-106751 [https://github.com/python/cpython/issues/106751]: Optimize KqueueSelector.select() for many iteration case. Patch By Donghee Na.

gh-106831 [https://github.com/python/cpython/issues/106831]: Fix potential missing NULL check of d2i_SSL_SESSION result in _ssl.c.

gh-105481 [https://github.com/python/cpython/issues/105481]: The various opcode lists in the dis module are now generated from bytecodes.c instead of explicitly constructed in opcode.py.

gh-106727 [https://github.com/python/cpython/issues/106727]: Make inspect.getsource() smarter for class for same name definitions

gh-106789 [https://github.com/python/cpython/issues/106789]: Remove import of pprint from sysconfig.

gh-105726 [https://github.com/python/cpython/issues/105726]: Added __slots__ to contextlib.AbstractContextManager and contextlib.AbstractAsyncContextManager so that child classes can use __slots__.

gh-106774 [https://github.com/python/cpython/issues/106774]: Update the bundled copy of pip to version 23.2.1.

gh-106751 [https://github.com/python/cpython/issues/106751]: selectors: Optimize EpollSelector.select() code by moving some code outside of the loop.

gh-106752 [https://github.com/python/cpython/issues/106752]: Fixed several bugs in zipfile.Path, including: in zipfile.Path.match(), Windows separators are no longer honored (and never were meant to be); Fixed name/suffix/suffixes/stem operations when no filename is present and the Path is not at the root of the zipfile; Reworked glob for performance and more correct matching behavior.

gh-105293 [https://github.com/python/cpython/issues/105293]: Remove call to SSL_CTX_set_session_id_context during client side context creation in the ssl module.

gh-106734 [https://github.com/python/cpython/issues/106734]: Disable tab completion in multiline mode of pdb

gh-105481 [https://github.com/python/cpython/issues/105481]: Expose opcode metadata through _opcode.

gh-106670 [https://github.com/python/cpython/issues/106670]: Add the new exceptions command to the Pdb debugger. It makes it possible to move between chained exceptions when using post mortem debugging.

gh-106602 [https://github.com/python/cpython/issues/106602]: Add __copy__ and __deepcopy__ in enum

gh-106664 [https://github.com/python/cpython/issues/106664]: selectors: Add _SelectorMapping.get() method and optimize _SelectorMapping.__getitem__().

gh-106628 [https://github.com/python/cpython/issues/106628]: Speed up parsing of emails by about 20% by not compiling a new regular expression for every single email.

gh-89427 [https://github.com/python/cpython/issues/89427]: Set the environment variable VIRTUAL_ENV_PROMPT at venv activation, even when VIRTUAL_ENV_DISABLE_PROMPT is set.

gh-106530 [https://github.com/python/cpython/issues/106530]: Revert a change to colorsys.rgb_to_hls() that caused division by zero for certain almost-white inputs. Patch by Terry Jan Reedy.

gh-106584 [https://github.com/python/cpython/issues/106584]: Fix exit code for unittest if all tests are skipped. Patch by Egor Eliseev.

gh-106566 [https://github.com/python/cpython/issues/106566]: Optimize (?!) (pattern which always fails) in regular expressions.

gh-106554 [https://github.com/python/cpython/issues/106554]: selectors: Reduce Selector overhead by using a dict.get() to lookup file descriptors.

gh-106558 [https://github.com/python/cpython/issues/106558]: Remove ref cycle in callers of convert_to_error() by deleting result from scope in a finally block.

gh-100502 [https://github.com/python/cpython/issues/100502]: Add pathlib.PurePath.pathmod class attribute that stores the implementation of os.path used for low-level path operations: either posixpath or ntpath.

gh-106527 [https://github.com/python/cpython/issues/106527]: Reduce overhead to add and remove asyncio readers and writers.

gh-106524 [https://github.com/python/cpython/issues/106524]: Fix crash in _sre.template() with templates containing invalid group indices.

gh-106531 [https://github.com/python/cpython/issues/106531]: Removed _legacy and the names it provided from importlib.resources: Resource, contents, is_resource, open_binary, open_text, path, read_binary, and read_text.

gh-106052 [https://github.com/python/cpython/issues/106052]: re module: fix the matching of possessive quantifiers in the case of a subpattern containing backtracking.

gh-106510 [https://github.com/python/cpython/issues/106510]: Improve debug output for atomic groups in regular expressions.

gh-106503 [https://github.com/python/cpython/issues/106503]: Fix ref cycle in asyncio._SelectorSocketTransport by removing _write_ready in close.

gh-105497 [https://github.com/python/cpython/issues/105497]: Fix flag mask inversion when unnamed flags exist.

gh-90876 [https://github.com/python/cpython/issues/90876]: Prevent multiprocessing.spawn from failing to import in environments where sys.executable is None. This regressed in 3.11 with the addition of support for path-like objects in multiprocessing.

gh-106403 [https://github.com/python/cpython/issues/106403]: Instances of typing.TypeVar, typing.ParamSpec, typing.ParamSpecArgs, typing.ParamSpecKwargs, and typing.TypeVarTuple once again support weak references, fixing a regression introduced in Python 3.12.0 beta 1. Patch by Jelle Zijlstra.

gh-89812 [https://github.com/python/cpython/issues/89812]: Add private pathlib._PathBase class, which provides experimental support for virtual filesystems, and may be made public in a future version of Python.

gh-106292 [https://github.com/python/cpython/issues/106292]: Check for an instance-dict cached value in the __get__() method of functools.cached_property(). This better matches the pre-3.12 behavior and improves compatibility for users subclassing functools.cached_property() and adding a __set__() method.

gh-106350 [https://github.com/python/cpython/issues/106350]: Detect possible memory allocation failure in the libtommath function mp_init() used by the _tkinter module.

gh-106330 [https://github.com/python/cpython/issues/106330]: Fix incorrect matching of empty paths in pathlib.PurePath.match(). This bug was introduced in Python 3.12.0 beta 1.

gh-106309 [https://github.com/python/cpython/issues/106309]: Deprecate typing.no_type_check_decorator(). No major type checker ever added support for this decorator. Patch by Alex Waygood.

gh-102541 [https://github.com/python/cpython/issues/102541]: Make pydoc.doc() catch bad module ImportError when output stream is not None.

gh-106263 [https://github.com/python/cpython/issues/106263]: Fix crash when calling repr with a manually constructed SignalDict object. Patch by Charlie Zhao.

gh-106236 [https://github.com/python/cpython/issues/106236]: Replace assert statements with raise RuntimeError in threading, so that _DummyThread cannot be joined even with -OO.

gh-106238 [https://github.com/python/cpython/issues/106238]: Fix rare concurrency bug in lock acquisition by the logging package.

gh-106152 [https://github.com/python/cpython/issues/106152]: Added PY_THROW event hook for cProfile for generators

gh-106075 [https://github.com/python/cpython/issues/106075]: Added asyncio.taskgroups.__all__ to asyncio.__all__ for export in star imports.

gh-104527 [https://github.com/python/cpython/issues/104527]: Zipapp will now skip over appending an archive to itself.

gh-106046 [https://github.com/python/cpython/issues/106046]: Improve the error message from os.fspath() if called on an object where __fspath__ is set to None. Patch by Alex Waygood.

gh-105987 [https://github.com/python/cpython/issues/105987]: Fix crash due to improper reference counting in asyncio eager task factory internal routines.

gh-105974 [https://github.com/python/cpython/issues/105974]: Fix bug where a typing.Protocol class that had one or more non-callable members would raise TypeError when issubclass() was called against it, even if it defined a custom __subclasshook__ method. The behaviour in Python 3.11 and lower -- which has now been restored -- was not to raise TypeError in these situations if a custom __subclasshook__ method was defined. Patch by Alex Waygood.

gh-96145 [https://github.com/python/cpython/issues/96145]: Reverted addition of json.AttrDict.

gh-89812 [https://github.com/python/cpython/issues/89812]: Add pathlib.UnsupportedOperation, which is raised instead of NotImplementedError when a path operation isn't supported.

gh-105808 [https://github.com/python/cpython/issues/105808]: Fix a regression introduced in gh-101251 [https://github.com/python/cpython/issues/101251] for 3.12, causing gzip.GzipFile.flush() to not flush the compressor (nor pass along the zip_mode argument).

gh-105481 [https://github.com/python/cpython/issues/105481]: stack_effect() no longer raises an exception if an oparg is provided for an opcode that doesn't use its arg, or when it is not provided for an opcode that does use it. In the latter case, the stack effect is returned for oparg=0.

gh-104799 [https://github.com/python/cpython/issues/104799]: Enable ast.unparse() to unparse function and class definitions created without the new type_params field from PEP 695 [https://peps.python.org/pep-0695/]. Patch by Jelle Zijlstra.

gh-105793 [https://github.com/python/cpython/issues/105793]: Add follow_symlinks keyword-only argument to pathlib.Path.is_dir() and is_file(), defaulting to True.

gh-105570 [https://github.com/python/cpython/issues/105570]: Deprecate two methods of creating typing.TypedDict classes with 0 fields using the functional syntax: TD = TypedDict("TD") and TD = TypedDict("TD", None). Both will be disallowed in Python 3.15. To create a TypedDict class with 0 fields, either use class TD(TypedDict): pass or TD = TypedDict("TD", {}).

gh-105745 [https://github.com/python/cpython/issues/105745]: Fix webbrowser.Konqueror.open method.

gh-105733 [https://github.com/python/cpython/issues/105733]: ctypes: Deprecate undocumented ctypes.SetPointerType() and ctypes.ARRAY() functions. Patch by Victor Stinner.

gh-105687 [https://github.com/python/cpython/issues/105687]: Remove deprecated re.template, re.T, re.TEMPLATE, sre_constans.SRE_FLAG_TEMPLATE.

gh-105684 [https://github.com/python/cpython/issues/105684]: Supporting asyncio.Task.set_name() is now mandatory for third party task implementations. The undocumented _set_task_name() function (deprecated since 3.8) has been removed. Patch by Kumar Aditya.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix a bug in _Unpickler_SetInputStream() where an exception could end up being overwritten in case of failure.

gh-105626 [https://github.com/python/cpython/issues/105626]: Change the default return value of http.client.HTTPConnection.get_proxy_response_headers() to be None and not {}.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in sys where exceptions could end up being overwritten because of deferred error handling.

gh-105605 [https://github.com/python/cpython/issues/105605]: Harden pyexpat error handling during module initialisation to prevent exceptions from possibly being overwritten, and objects from being dereferenced twice.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bug in decimal where an exception could end up being overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in _datetime where exceptions could be overwritten in case of module initialisation failure.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in _ssl initialisation which could lead to leaked references and overwritten exceptions.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix a bug in array.array where an exception could end up being overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in _ctypes where exceptions could end up being overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix a bug in the posix module where an exception could be overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in _elementtree where exceptions could be overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in zoneinfo where exceptions could be overwritten.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in errno where exceptions could be overwritten.

gh-105566 [https://github.com/python/cpython/issues/105566]: Deprecate creating a typing.NamedTuple class using keyword arguments to denote the fields (NT = NamedTuple("NT", x=int, y=str)). This will be disallowed in Python 3.15. Use the class-based syntax or the functional syntax instead.

Two methods of creating NamedTuple classes with 0 fields using the functional syntax are also deprecated, and will be disallowed in Python 3.15: NT = NamedTuple("NT") and NT = NamedTuple("NT", None). To create a NamedTuple class with 0 fields, either use class NT(NamedTuple): pass or NT = NamedTuple("NT", []).

gh-105545 [https://github.com/python/cpython/issues/105545]: Remove deprecated in 3.11 webbrowser.MacOSXOSAScript._name attribute.

gh-105497 [https://github.com/python/cpython/issues/105497]: Fix flag inversion when alias/mask members exist.

gh-105509 [https://github.com/python/cpython/issues/105509]: typing.Annotated is now implemented as an instance of typing._SpecialForm rather than a class. This should have no user-facing impact for users of the typing module public API.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix bugs in pickle where exceptions could be overwritten.

gh-70303 [https://github.com/python/cpython/issues/70303]: Emit FutureWarning from pathlib.Path.glob() and rglob() if the given pattern ends with "**". In a future Python release, patterns with this ending will match both files and directories. Add a trailing slash to only match directories.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix a bug in sqlite3 where an exception could be overwritten in the collation callback.

gh-105382 [https://github.com/python/cpython/issues/105382]: Remove cafile, capath and cadefault parameters of the urllib.request.urlopen() function, deprecated in Python 3.6. Patch by Victor Stinner.

gh-105376 [https://github.com/python/cpython/issues/105376]: logging: Remove undocumented and untested Logger.warn() and LoggerAdapter.warn() methods and logging.warn() function. Deprecated since Python 3.3, they were aliases to the logging.Logger.warning() method, logging.LoggerAdapter.warning() method and logging.warning() function. Patch by Victor Stinner.

gh-105332 [https://github.com/python/cpython/issues/105332]: Revert pickling method from by-name back to by-value.

gh-104554 [https://github.com/python/cpython/issues/104554]: Add RTSPS scheme support in urllib.parse

gh-105292 [https://github.com/python/cpython/issues/105292]: Add option to traceback.format_exception_only() to recurse into the nested exception of a BaseExceptionGroup.

gh-105280 [https://github.com/python/cpython/issues/105280]: Fix bug where isinstance([], collections.abc.Mapping) could evaluate to True if garbage collection happened at the wrong time. The bug was caused by changes to the implementation of typing.Protocol in Python 3.12.

gh-80480 [https://github.com/python/cpython/issues/80480]: array: Add 'w' typecode that represents Py_UCS4.

gh-105239 [https://github.com/python/cpython/issues/105239]: Fix longstanding bug where issubclass(object, typing.Protocol) would evaluate to True in some edge cases. Patch by Alex Waygood.

gh-104310 [https://github.com/python/cpython/issues/104310]: In the beta 1 release we added a utility function for extension module authors, to use when testing their module for support in multiple interpreters or under a per-interpreter GIL. The name of that function has changed from allowing_all_extensions to _incompatible_extension_module_restrictions. The default for the "disable_check" argument has change from True to False, to better match the new function name.

gh-105080 [https://github.com/python/cpython/issues/105080]: Fixed inconsistent signature on derived classes for inspect.signature()

gh-105144 [https://github.com/python/cpython/issues/105144]: Fix a recent regression in the typing module. The regression meant that doing class Foo(X, typing.Protocol), where X was a class that had abc.ABCMeta as its metaclass, would then cause subsequent isinstance(1, X) calls to erroneously raise TypeError. Patch by Alex Waygood.

gh-62948 [https://github.com/python/cpython/issues/62948]: The io.IOBase finalizer now logs the close() method errors with sys.unraisablehook. Previously, errors were ignored silently by default, and only logged in Python Development Mode or on Python built on debug mode. Patch by Victor Stinner.

gh-105096 [https://github.com/python/cpython/issues/105096]: wave: Deprecate the getmark(), setmark() and getmarkers() methods of the wave.Wave_read and wave.Wave_write classes. They will be removed in Python 3.15. Patch by Victor Stinner.

gh-104992 [https://github.com/python/cpython/issues/104992]: Remove the untested and undocumented unittest.TestProgram.usageExit() method, deprecated in Python 3.11. Patch by Hugo van Kemenade.

gh-104996 [https://github.com/python/cpython/issues/104996]: Improve performance of pathlib.PurePath initialisation by deferring joining of paths when multiple arguments are given.

gh-101588 [https://github.com/python/cpython/issues/101588]: Deprecate undocumented copy/deepcopy/pickle support for itertools.

gh-103631 [https://github.com/python/cpython/issues/103631]: Fix pathlib.PurePosixPath(pathlib.PureWindowsPath(...)) not converting path separators to restore 3.11 compatible behavior.

gh-104947 [https://github.com/python/cpython/issues/104947]: Make comparisons between pathlib.PureWindowsPath objects consistent across Windows and Posix to match 3.11 behavior.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the audioop module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the aifc module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the uu module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104935 [https://github.com/python/cpython/issues/104935]: Fix bugs with the interaction between typing.runtime_checkable() and typing.Generic that were introduced by the PEP 695 [https://peps.python.org/pep-0695/] implementation. Patch by Jelle Zijlstra.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the crypt module and its private _crypt extension, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the nis module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104898 [https://github.com/python/cpython/issues/104898]: Add missing __slots__ to os.PathLike.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the xdrlib module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the nntplib module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104886 [https://github.com/python/cpython/issues/104886]: Remove the undocumented configparser.LegacyInterpolation class, deprecated in the docstring since Python 3.2, and with a deprecation warning since Python 3.11. Patch by Hugo van Kemenade.

gh-104786 [https://github.com/python/cpython/issues/104786]: Remove kwargs-based typing.TypedDict creation

gh-104876 [https://github.com/python/cpython/issues/104876]: Remove the turtle.RawTurtle.settiltangle() method, deprecated in docs since Python 3.1 and with a deprecation warning since Python 3.11. Patch by Hugo van Kemenade.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Removed the msilib package, deprecated in Python 3.11.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the spwd module, deprecated in Python 3.11: the python-pam [https://pypi.org/project/python-pam/] project can be used instead. Patch by Victor Stinner.

gh-75552 [https://github.com/python/cpython/issues/75552]: Removed the tkinter.tix module, deprecated since Python 3.6.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the chunk module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the mailcap module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the sunau module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104780 [https://github.com/python/cpython/issues/104780]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the ossaudiodev module, deprecated in Python 3.11. Patch Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the pipes module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104873 [https://github.com/python/cpython/issues/104873]: Add typing.get_protocol_members() to return the set of members defining a typing.Protocol. Add typing.is_protocol() to check whether a class is a typing.Protocol. Patch by Jelle Zijlstra.

gh-104874 [https://github.com/python/cpython/issues/104874]: Document the __name__ and __supertype__ attributes of typing.NewType. Patch by Jelle Zijlstra.

gh-104835 [https://github.com/python/cpython/issues/104835]: Removed the following unittest functions, deprecated in Python 3.11:

unittest.findTestCases()

unittest.makeSuite()

unittest.getTestCaseNames()

Use TestLoader methods instead:

unittest.TestLoader.loadTestsFromModule()

unittest.TestLoader.loadTestsFromTestCase()

unittest.TestLoader.getTestCaseNames()

Patch by Hugo van Kemenade.

gh-104804 [https://github.com/python/cpython/issues/104804]: Remove the untested and undocumented webbrowser MacOSX class, deprecated in Python 3.11. Patch by Hugo van Kemenade.

gh-83863 [https://github.com/python/cpython/issues/83863]: Support for using pathlib.Path objects as context managers has been removed. Before Python 3.9, exiting the context manager marked a path as "closed", which caused some (but not all!) methods to raise when called. Since Python 3.9, using a path as a context manager does nothing.

gh-104799 [https://github.com/python/cpython/issues/104799]: Adjust the location of the (see PEP 695 [https://peps.python.org/pep-0695/]) type_params field on ast.ClassDef, ast.AsyncFunctionDef, and ast.FunctionDef to better preserve backward compatibility. Patch by Jelle Zijlstra

gh-104797 [https://github.com/python/cpython/issues/104797]: Allow typing.Protocol classes to inherit from collections.abc.Buffer. Patch by Jelle Zijlstra.

gh-104783 [https://github.com/python/cpython/issues/104783]: Remove locale.resetlocale() function deprecated in Python 3.11. Patch by Victor Stinner.

gh-104780 [https://github.com/python/cpython/issues/104780]: Remove the 2to3 program and the lib2to3 module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the telnetlib module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the imghdr module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the cgi and cgitb modules, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104773 [https://github.com/python/cpython/issues/104773]: PEP 594 [https://peps.python.org/pep-0594/]: Remove the sndhdr module, deprecated in Python 3.11. Patch by Victor Stinner.

gh-104372 [https://github.com/python/cpython/issues/104372]: On Linux where subprocess can use the vfork() syscall for faster spawning, prevent the parent process from blocking other threads by dropping the GIL while it waits for the vfork'ed child process exec() outcome. This prevents spawning a binary from a slow filesystem from blocking the rest of the application.

gh-99108 [https://github.com/python/cpython/issues/99108]: We now release the GIL around built-in hashlib computations of reasonable size for the SHA families and MD5 hash functions, matching what our OpenSSL backed hash computations already does.

gh-102613 [https://github.com/python/cpython/issues/102613]: Improve performance of pathlib.Path.glob() when expanding a pattern with a non-terminal "**" component by filtering walked paths through a regular expression, rather than calling os.scandir() more than once on each directory.

gh-104399 [https://github.com/python/cpython/issues/104399]: Prepare the _tkinter module for building with Tcl 9.0 and future libtommath by replacing usage of deprecated functions mp_to_unsigned_bin_n() and mp_unsigned_bin_size() when necessary.

gh-102676 [https://github.com/python/cpython/issues/102676]: Add fields start_offset, cache_offset, end_offset, baseopname, baseopcode, jump_target and oparg to dis.Instruction.

gh-103558 [https://github.com/python/cpython/issues/103558]: Fixed parent argument validation mechanism of argparse. Improved test coverage.

gh-103464 [https://github.com/python/cpython/issues/103464]: Provide helpful usage messages when parsing incorrect pdb commands.

gh-103384 [https://github.com/python/cpython/issues/103384]: Generalize the regex pattern BaseConfigurator.INDEX_PATTERN to allow spaces and non-alphanumeric characters in keys.

gh-103124 [https://github.com/python/cpython/issues/103124]: Added multiline statement support for pdb

gh-101162 [https://github.com/python/cpython/issues/101162]: Forbid using builtins.issubclass() with types.GenericAlias as the first argument.

gh-103200 [https://github.com/python/cpython/issues/103200]: Fix cache repopulation semantics of zipimport.invalidate_caches(). The cache is now repopulated upon retrieving files with an invalid cache, not when the cache is invalidated.

gh-100061 [https://github.com/python/cpython/issues/100061]: Fix a bug that causes wrong matches for regular expressions with possessive qualifier.

gh-77609 [https://github.com/python/cpython/issues/77609]: Add follow_symlinks argument to pathlib.Path.glob() and rglob(), defaulting to false.

gh-102541 [https://github.com/python/cpython/issues/102541]: Hide traceback in help() prompt, when import failed.

gh-102120 [https://github.com/python/cpython/issues/102120]: Added a stream mode to tarfile that allows for reading archives without caching info about the inner files.

gh-102029 [https://github.com/python/cpython/issues/102029]: Deprecate passing any arguments to threading.RLock().

gh-88233 [https://github.com/python/cpython/issues/88233]: Refactored zipfile._strip_extra to use higher level abstractions for extras instead of a heavy-state loop.

gh-102024 [https://github.com/python/cpython/issues/102024]: Reduce calls of _idle_semaphore.release() in concurrent.futures.thread._worker().

gh-73435 [https://github.com/python/cpython/issues/73435]: Add support for recursive wildcards in pathlib.PurePath.match().

gh-84867 [https://github.com/python/cpython/issues/84867]: unittest.TestLoader no longer loads test cases from exact unittest.TestCase and unittest.FunctionTestCase classes.

gh-99203 [https://github.com/python/cpython/issues/99203]: Restore following CPython <= 3.10.5 behavior of shutil.make_archive(): do not create an empty archive if root_dir is not a directory, and, in that case, raise FileNotFoundError or NotADirectoryError regardless of format choice. Beyond the brought-back behavior, the function may now also raise these exceptions in dry_run mode.

gh-80480 [https://github.com/python/cpython/issues/80480]: Emit DeprecationWarning for array's 'u' type code, deprecated in docs since Python 3.3.

gh-94924 [https://github.com/python/cpython/issues/94924]: unittest.mock.create_autospec() now properly returns coroutine functions compatible with inspect.iscoroutinefunction()

gh-94777 [https://github.com/python/cpython/issues/94777]: Fix hanging multiprocessing ProcessPoolExecutor when a child process crashes while data is being written in the call queue.

gh-92871 [https://github.com/python/cpython/issues/92871]: Remove the typing.io and typing.re namespaces, deprecated since Python 3.8. All items are still available from the main typing module.

bpo-43633 [https://bugs.python.org/issue?@action=redirect&bpo=43633]: Improve the textual representation of IPv4-mapped IPv6 addresses (RFC 4291 [https://datatracker.ietf.org/doc/html/rfc4291.html] Sections 2.2, 2.5.5.2) in ipaddress. Patch by Oleksandr Pavliuk.

bpo-44850 [https://bugs.python.org/issue?@action=redirect&bpo=44850]: Improve performance of operator.methodcaller() using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall convention. Patch by Anthony Lee and Pieter Eendebak.

bpo-44185 [https://bugs.python.org/issue?@action=redirect&bpo=44185]: unittest.mock.mock_open() will call the close() method of the file handle mock when it is exiting from the context manager. Patch by Samet Yaslan.

bpo-40988 [https://bugs.python.org/issue?@action=redirect&bpo=40988]: Improve performance of functools.singledispatchmethod by caching the generated dispatch wrapper. Optimization suggested by frederico. Patch by @mental32, Alex Waygood and Pieter Eendebak.

bpo-41768 [https://bugs.python.org/issue?@action=redirect&bpo=41768]: unittest.mock speccing no longer calls class properties. Patch by Melanie Witt.

bpo-18319 [https://bugs.python.org/issue?@action=redirect&bpo=18319]: Ensure gettext(msg) retrieve translations even if a plural form exists. In other words: gettext(msg) == ngettext(msg, '', 1).

bpo-17013 [https://bugs.python.org/issue?@action=redirect&bpo=17013]: Add ThreadingMock to unittest.mock that can be used to create Mock objects that can wait until they are called. Patch by Karthikeyan Singaravelan and Mario Corchero.

Documentation

gh-109209 [https://github.com/python/cpython/issues/109209]: The minimum Sphinx version required for the documentation is now 4.2.

gh-108826 [https://github.com/python/cpython/issues/108826]: dis module command-line interface is now mentioned in documentation.

gh-107305 [https://github.com/python/cpython/issues/107305]: Add documentation for PyInterpreterConfig and Py_NewInterpreterFromConfig(). Also clarify some of the nearby docs relative to per-interpreter GIL.

gh-107008 [https://github.com/python/cpython/issues/107008]: Document the curses module variables LINES and COLS.

gh-106948 [https://github.com/python/cpython/issues/106948]: Add a number of standard external names to nitpick_ignore.

gh-106232 [https://github.com/python/cpython/issues/106232]: Make timeit doc command lines compatible with Windows by using double quotes for arguments. This works on linux and macOS also.

gh-105172 [https://github.com/python/cpython/issues/105172]: Fixed functools.lru_cache() docstring accounting for typed argument's different handling of str and int. Patch by Bar Harel.

gh-105052 [https://github.com/python/cpython/issues/105052]: Update timeit doc to specify that time in seconds is just the default.

gh-89455 [https://github.com/python/cpython/issues/89455]: Add missing documentation for the max_group_depth and max_group_width parameters and the exceptions attribute of the traceback.TracebackException class.

gh-89412 [https://github.com/python/cpython/issues/89412]: Add missing documentation for the end_lineno and end_offset attributes of the traceback.TracebackException class.

gh-104943 [https://github.com/python/cpython/issues/104943]: Remove mentions of old Python versions in typing.NamedTuple.

gh-54738 [https://github.com/python/cpython/issues/54738]: Add documentation on how to localize the argparse module.

gh-102823 [https://github.com/python/cpython/issues/102823]: Document the return type of x // y when x and y have type float.

gh-102759 [https://github.com/python/cpython/issues/102759]: Align function signature for functools.reduce in documentation and docstring with the C implementation.

Tests

gh-110647 [https://github.com/python/cpython/issues/110647]: Fix test_stress_modifying_handlers() of test_signal. Patch by Victor Stinner.

gh-103053 [https://github.com/python/cpython/issues/103053]: Fix test_tools.test_freeze on FreeBSD: run "make distclean" instead of "make clean" in the copied source directory to remove also the "python" program. Patch by Victor Stinner.

gh-110167 [https://github.com/python/cpython/issues/110167]: Fix a deadlock in test_socket when server fails with a timeout but the client is still running in its thread. Don't hold a lock to call cleanup functions in doCleanups(). One of the cleanup function waits until the client completes, whereas the client could deadlock if it called addCleanup() in such situation. Patch by Victor Stinner.

gh-110388 [https://github.com/python/cpython/issues/110388]: Add tests for tty.

gh-81002 [https://github.com/python/cpython/issues/81002]: Add tests for termios.

gh-110367 [https://github.com/python/cpython/issues/110367]: regrtest: When using worker processes (-jN) with --verbose3 option, regrtest can now display the worker output even if a worker process does crash. Previously, sys.stdout and sys.stderr were replaced and so the worker output was lost on a crash. Patch by Victor Stinner.

gh-110267 [https://github.com/python/cpython/issues/110267]: Add tests for pickling and copying PyStructSequence objects. Patched by Xuehai Pan.

gh-110171 [https://github.com/python/cpython/issues/110171]: libregrtest now always sets and shows random.seed, so tests are more reproducible. Use --randseed flag to pass the explicit random seed for tests.

gh-110152 [https://github.com/python/cpython/issues/110152]: Remove Tools/scripts/run_tests.py and make hostrunnertest. Just run ./python -m test --slow-ci, make buildbottest or make test instead. Python test runner (regrtest) now handles cross-compilation and HOSTRUNNER. It also adds options to Python such fast -u -E -W default -bb when --fast-ci or --slow-ci option is used. Patch by Victor Stinner.

gh-110031 [https://github.com/python/cpython/issues/110031]: Skip test_threading tests using thread+fork if Python is built with Address Sanitizer (ASAN). Patch by Victor Stinner.

gh-110088 [https://github.com/python/cpython/issues/110088]: Fix test_asyncio timeouts: don't measure the maximum duration, a test should not measure a CI performance. Only measure the minimum duration when a task has a timeout or delay. Add CLOCK_RES to test_asyncio.utils. Patch by Victor Stinner.

gh-109974 [https://github.com/python/cpython/issues/109974]: Fix race conditions in test_threading lock tests. Wait until a condition is met rather than using time.sleep() with a hardcoded number of seconds. Patch by Victor Stinner.

gh-110033 [https://github.com/python/cpython/issues/110033]: Fix test_interprocess_signal() of test_signal. Make sure that the subprocess.Popen object is deleted before the test raising an exception in a signal handler. Otherwise, Popen.__del__() can get the exception which is logged as Exception ignored in: ... and the test fails. Patch by Victor Stinner.

gh-109594 [https://github.com/python/cpython/issues/109594]: Fix test_timeout() of test_concurrent_futures.test_wait. Remove the future which may or may not complete depending if it takes longer than the timeout or not. Keep the second future which does not complete before wait() timeout. Patch by Victor Stinner.

gh-109972 [https://github.com/python/cpython/issues/109972]: Split test_gdb.py file into a test_gdb package made of multiple tests, so tests can now be run in parallel. Patch by Victor Stinner.

gh-109566 [https://github.com/python/cpython/issues/109566]: regrtest: When --fast-ci or --slow-ci option is used, regrtest now replaces the current process with a new process to add -u -W default -bb -E options to Python. Patch by Victor Stinner.

gh-109748 [https://github.com/python/cpython/issues/109748]: Fix test_zippath_from_non_installed_posix() of test_venv: don't copy __pycache__/ sub-directories, because they can be modified by other Python tests running in parallel. Patch by Victor Stinner.

gh-109739 [https://github.com/python/cpython/issues/109739]: regrtest: Fix reference leak check on Windows. Disable the load tracker on Windows in the reference leak check mode (-R option). Patch by Victor Stinner.

gh-109276 [https://github.com/python/cpython/issues/109276]: regrtest: When a test fails with "env changed" and the --rerun option is used, the test is now re-run in verbose mode in a fresh process. Patch by Victor Stinner.

gh-103053 [https://github.com/python/cpython/issues/103053]: Skip test_freeze_simple_script() of test_tools.test_freeze if Python is built with ./configure --enable-optimizations, which means with Profile Guided Optimization (PGO): it just makes the test too slow. The freeze tool is tested by many other CIs with other (faster) compiler flags. Patch by Victor Stinner.

gh-109580 [https://github.com/python/cpython/issues/109580]: Skip test_perf_profiler if Python is built with ASAN, MSAN or UBSAN sanitizer. Python does crash randomly in this test on such build. Patch by Victor Stinner.

gh-109566 [https://github.com/python/cpython/issues/109566]: regrtest: Add --fast-ci and --slow-ci options. --fast-ci uses a default timeout of 10 minutes and -u all,-cpu (skip slowest tests). --slow-ci uses a default timeout of 20 minutes and -u all (run all tests). Patch by Victor Stinner.

gh-109425 [https://github.com/python/cpython/issues/109425]: libregrtest now decodes stdout of test worker processes with the "backslashreplace" error handler to log corrupted stdout, instead of failing with an error and not logging the stdout. Patch by Victor Stinner.

gh-109396 [https://github.com/python/cpython/issues/109396]: Fix test_socket.test_hmac_sha1() in FIPS mode. Use a longer key: FIPS mode requires at least of at least 112 bits. The previous key was only 32 bits. Patch by Victor Stinner.

gh-104736 [https://github.com/python/cpython/issues/104736]: Fix test_gdb on Python built with LLVM clang 16 on Linux ppc64le (ex: Fedora 38). Search patterns in gdb "bt" command output to detect when gdb fails to retrieve the traceback. For example, skip a test if Backtrace stopped: frame did not save the PC is found. Patch by Victor Stinner.

gh-109276 [https://github.com/python/cpython/issues/109276]: libregrtest now calls random.seed() before running each test file when -r/--randomize command line option is used. Moreover, it's also called in worker processes. It should help to make tests more deterministic. Previously, it was only called once in the main process before running all test files and it was not called in worker processes. Patch by Victor Stinner.

gh-109276 [https://github.com/python/cpython/issues/109276]: libregrtest now uses a separated file descriptor to write test result as JSON. Previously, if a test wrote debug messages late around the JSON, the main test process failed to parse JSON. Patch by Victor Stinner.

gh-108996 [https://github.com/python/cpython/issues/108996]: Fix and enable test_msvcrt.

gh-109237 [https://github.com/python/cpython/issues/109237]: Fix test_site.test_underpth_basic() when the working directory contains at least one non-ASCII character: encode the ._pth file to UTF-8 and enable the UTF-8 Mode to use UTF-8 for the child process stdout. Patch by Victor Stinner.

gh-109230 [https://github.com/python/cpython/issues/109230]: Fix test_pyexpat.test_exception(): it can now be run from a directory different than Python source code directory. Before, the test failed in this case. Skip the test if Modules/pyexpat.c source is not available. Skip also the test on Python implementations other than CPython. Patch by Victor Stinner.

gh-108996 [https://github.com/python/cpython/issues/108996]: Add tests for msvcrt.

gh-109015 [https://github.com/python/cpython/issues/109015]: Fix test_asyncio, test_imaplib and test_socket tests on FreeBSD if the TCP blackhole is enabled (sysctl net.inet.tcp.blackhole). Skip the few tests which failed with ETIMEDOUT which such non standard configuration. Currently, the FreeBSD GCP image enables TCP and UDP blackhole [https://reviews.freebsd.org/D41751] (sysctl net.inet.tcp.blackhole=2 and sysctl net.inet.udp.blackhole=1). Patch by Victor Stinner.

gh-91960 [https://github.com/python/cpython/issues/91960]: Skip test_gdb if gdb is unable to retrieve Python frame objects: if a frame is <optimized out>. When Python is built with "clang -Og", gdb can fail to retrieve the frame parameter of _PyEval_EvalFrameDefault(). In this case, tests like py_bt() are likely to fail. Without getting access to Python frames, python-gdb.py is mostly clueless on retrieving the Python traceback. Moreover, test_gdb is no longer skipped on macOS if Python is built with Clang. Patch by Victor Stinner.

gh-108962 [https://github.com/python/cpython/issues/108962]: Skip test_tempfile.test_flags() if chflags() fails with "OSError: [Errno 45] Operation not supported" (ex: on FreeBSD 13). Patch by Victor Stinner.

gh-91960 [https://github.com/python/cpython/issues/91960]: FreeBSD 13.2 CI coverage for pull requests is now provided by Cirrus-CI (a hosted CI service that supports Linux, macOS, Windows, and FreeBSD).

gh-89392 [https://github.com/python/cpython/issues/89392]: Removed support of test_main() function in tests. They now always use normal unittest test runner.

gh-108851 [https://github.com/python/cpython/issues/108851]: Fix test_tomllib recursion tests for WASI buildbots: reduce the recursion limit and compute the maximum nested array/dict depending on the current available recursion limit. Patch by Victor Stinner.

gh-108851 [https://github.com/python/cpython/issues/108851]: Add get_recursion_available() and get_recursion_depth() functions to the test.support module. Patch by Victor Stinner.

gh-108834 [https://github.com/python/cpython/issues/108834]: Add --fail-rerun option option to regrtest: if a test failed when then passed when rerun in verbose mode, exit the process with exit code 2 (error), instead of exit code 0 (success). Patch by Victor Stinner.

gh-108834 [https://github.com/python/cpython/issues/108834]: Rename regrtest --verbose2 option (-w) to --rerun. Keep --verbose2 as a deprecated alias. Patch by Victor Stinner.

gh-108834 [https://github.com/python/cpython/issues/108834]: When regrtest reruns failed tests in verbose mode (./python -m test --rerun), tests are now rerun in fresh worker processes rather than being executed in the main process. If a test does crash or is killed by a timeout, the main process can detect and handle the killed worker process. Tests are rerun in parallel if the -jN option is used to run tests in parallel. Patch by Victor Stinner.

gh-108822 [https://github.com/python/cpython/issues/108822]: regrtest now computes statistics on all tests: successes, failures and skipped. test_netrc, test_pep646_syntax and test_xml_etree now return results in their test_main() function. Patch by Victor Stinner and Alex Waygood.

gh-108794 [https://github.com/python/cpython/issues/108794]: The doctest.DocTestRunner.run() method now counts the number of skipped tests. Add doctest.DocTestRunner.skips and doctest.TestResults.skipped attributes. Patch by Victor Stinner.

gh-108388 [https://github.com/python/cpython/issues/108388]: Convert test_concurrent_futures to a package of 7 sub-tests. Patch by Victor Stinner.

gh-108388 [https://github.com/python/cpython/issues/108388]: Split test_multiprocessing_fork, test_multiprocessing_forkserver and test_multiprocessing_spawn into test packages. Each package is made of 4 sub-tests: processes, threads, manager and misc. It allows running more tests in parallel and so reduce the total test duration. Patch by Victor Stinner.

gh-105776 [https://github.com/python/cpython/issues/105776]: Fix test_cppext when the C compiler command -std=c11 option: remove -std= options from the compiler command. Patch by Victor Stinner.

gh-107652 [https://github.com/python/cpython/issues/107652]: Set up CIFuzz to run fuzz targets in GitHub Actions. Patch by Illia Volochii.

gh-107237 [https://github.com/python/cpython/issues/107237]: test_logging: Fix test_udp_reconnection() by increasing the timeout from 100 ms to 5 minutes (LONG_TIMEOUT). Patch by Victor Stinner.

gh-107178 [https://github.com/python/cpython/issues/107178]: Add the C API test for functions in the Mapping Protocol, the Sequence Protocol and some functions in the Object Protocol.

gh-106714 [https://github.com/python/cpython/issues/106714]: test_capi: Fix test_no_FatalError_infinite_loop() to no longer write a coredump, by using test.support.SuppressCrashReport. Patch by Victor Stinner.

gh-104090 [https://github.com/python/cpython/issues/104090]: Avoid creating a reference to the test object in collectedDurations().

gh-106752 [https://github.com/python/cpython/issues/106752]: Moved tests for zipfile.Path into Lib/test/test_zipfile/_path. Made zipfile._path a package.

gh-106690 [https://github.com/python/cpython/issues/106690]: Add .coveragerc to cpython repository for use with coverage package.

gh-101634 [https://github.com/python/cpython/issues/101634]: When running the Python test suite with -jN option, if a worker stdout cannot be decoded from the locale encoding report a failed testn so the exitcode is non-zero. Patch by Victor Stinner.

gh-105084 [https://github.com/python/cpython/issues/105084]: When the Python build is configured --with-wheel-pkg-dir, tests requiring the setuptools and wheel wheels will search for the wheels in WHEEL_PKG_DIR.

gh-81005 [https://github.com/python/cpython/issues/81005]: String tests are modified to reflect that str and unicode are merged in Python 3. Patch by Daniel Fortunov.

gh-103186 [https://github.com/python/cpython/issues/103186]: Suppress and assert expected RuntimeWarnings in test_sys_settrace.py

gh-69714 [https://github.com/python/cpython/issues/69714]: Add additional tests to calendar to achieve full test coverage.

Build

gh-103053 [https://github.com/python/cpython/issues/103053]: "make check-clean-src" now also checks if the "python" program is found in the source directory: fail with an error if it does exist. Patch by Victor Stinner.

gh-109191 [https://github.com/python/cpython/issues/109191]: Fix compile error when building with recent versions of libedit.

gh-110276 [https://github.com/python/cpython/issues/110276]: No longer ignore PROFILE_TASK failure silently: command used by Profile Guided Optimization (PGO). Patch by Victor Stinner.

gh-109566 [https://github.com/python/cpython/issues/109566]: Remove make testall target: use make buildbottest instead. Patch by Victor Stinner.

gh-109740 [https://github.com/python/cpython/issues/109740]: The experimental --disable-gil configure flag now includes "t" (for "threaded") in extension ABI tags.

gh-109054 [https://github.com/python/cpython/issues/109054]: Fix building the _testcapi extension on Linux AArch64 which requires linking to libatomic when <cpython/pyatomic.h> is used: the _Py_atomic_or_uint64() function requires libatomic __atomic_fetch_or_8() on this platform. The configure script now checks if linking to libatomic is needed and generates a new LIBATOMIC variable used to build the _testcapi extension. Patch by Victor Stinner.

gh-63760 [https://github.com/python/cpython/issues/63760]: Fix Solaris build: no longer redefine the gethostname() function. Solaris defines the function since 2005. Patch by Victor Stinner, original patch by Jakub Kulík.

gh-108740 [https://github.com/python/cpython/issues/108740]: Fix a race condition in make regen-all. The deepfreeze.c source and files generated by Argument Clinic are now generated or updated before generating "global objects". Previously, some identifiers may miss depending on the order in which these files were generated. Patch by Victor Stinner.

gh-108634 [https://github.com/python/cpython/issues/108634]: Python built with configure --with-trace-refs (tracing references) is now ABI compatible with Python release build and debug build. Patch by Victor Stinner.

gh-85283 [https://github.com/python/cpython/issues/85283]: The _stat C extension is now built with the limited C API. Patch by Victor Stinner.

gh-108447 [https://github.com/python/cpython/issues/108447]: Fix x86_64 GNU/Hurd build

gh-107814 [https://github.com/python/cpython/issues/107814]: When calling find_python.bat with -q it did not properly silence the output of nuget. That is now fixed.

gh-105481 [https://github.com/python/cpython/issues/105481]: Remove the make target regen-opcode-targets, merge its work into regen-opcode which repeats most of the calculation. This simplifies the code for the build and reduces code duplication.

gh-106881 [https://github.com/python/cpython/issues/106881]: Check for linux/limits.h before including it in Modules/posixmodule.c.

gh-95855 [https://github.com/python/cpython/issues/95855]: Refactor platform triplet detection code and add detection for MIPS soft float and musl libc.

gh-106962 [https://github.com/python/cpython/issues/106962]: Detect MPI compilers in configure.

gh-106118 [https://github.com/python/cpython/issues/106118]: Fix compilation for platforms without O_CLOEXEC. The issue was introduced with Python 3.12b1 in gh-103295 [https://github.com/python/cpython/issues/103295]. Patch by Erlend Aasland.

gh-105875 [https://github.com/python/cpython/issues/105875]: SQLite 3.15.2 or newer is required to build the sqlite3 extension module. Patch by Erlend Aasland.

gh-90005 [https://github.com/python/cpython/issues/90005]: Fix a regression in configure where we could end up unintentionally linking with libbsd.

gh-102404 [https://github.com/python/cpython/issues/102404]: Document how to perform a WASI build on Linux. Also add Tools/wasm/build_wasi.sh as a reference implementation of the docs.

gh-89886 [https://github.com/python/cpython/issues/89886]: Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate configure.

gh-104692 [https://github.com/python/cpython/issues/104692]: Include commoninstall as a prerequisite for bininstall

This ensures that commoninstall is completed before bininstall is started when parallel builds are used (make -j install), and so the python3 symlink is only installed after all standard library modules are installed.

gh-101538 [https://github.com/python/cpython/issues/101538]: Add experimental wasi-threads support. Patch by Takashi Yamamoto.

Windows

gh-110437 [https://github.com/python/cpython/issues/110437]: Allows overriding the source of VC redistributables so that releases can be guaranteed to never downgrade between updates.

gh-109286 [https://github.com/python/cpython/issues/109286]: Update Windows installer to use SQLite 3.43.1.

gh-82367 [https://github.com/python/cpython/issues/82367]: os.path.realpath() now resolves MS-DOS style file names even if the file is not accessible. Patch by Moonsik Park.

gh-109991 [https://github.com/python/cpython/issues/109991]: Update Windows build to use OpenSSL 3.0.11.

gh-106242 [https://github.com/python/cpython/issues/106242]: Fixes realpath() to behave consistently when passed a path containing an embedded null character on Windows. In strict mode, it now raises OSError instead of the unexpected ValueError, and in non-strict mode will make the path absolute.

gh-83180 [https://github.com/python/cpython/issues/83180]: Changes the Python 安裝管理員 to prefer an active virtual environment when the launched script has a shebang line using a Unix-like virtual command, even if the command requests a specific version of Python.

gh-106844 [https://github.com/python/cpython/issues/106844]: Fix integer overflow and truncating by the null character in _winapi.LCMapStringEx() which affects ntpath.normcase().

gh-105436 [https://github.com/python/cpython/issues/105436]: Ensure that an empty environment block is terminated by two null characters, as is required by Windows.

gh-105146 [https://github.com/python/cpython/issues/105146]: Updated the links at the end of the installer to point to Discourse rather than the mailing lists.

gh-103646 [https://github.com/python/cpython/issues/103646]: When installed from the Microsoft Store, pip no longer defaults to per-user installs. However, as the install directory is unwritable, it should automatically decide to do a per-user install anyway. This should resolve issues when pip is passed an option that conflicts with --user.

gh-88745 [https://github.com/python/cpython/issues/88745]: Improve performance of shutil.copy2() by using the operating system's CopyFile2 function. This may result in subtle changes to metadata copied along with some files, bringing them in line with normal OS behavior.

gh-104820 [https://github.com/python/cpython/issues/104820]: Fixes stat() and related functions on file systems that do not support file ID requests. This includes FAT32 and exFAT.

gh-104803 [https://github.com/python/cpython/issues/104803]: Add os.path.isdevdrive() to detect whether a path is on a Windows Dev Drive. Returns False on platforms that do not support Dev Drive, and is absent on non-Windows platforms.

macOS

gh-109286 [https://github.com/python/cpython/issues/109286]: Update macOS installer to use SQLite 3.43.1.

gh-109991 [https://github.com/python/cpython/issues/109991]: Update macOS installer to use OpenSSL 3.0.11.

gh-99079 [https://github.com/python/cpython/issues/99079]: Update macOS installer to use OpenSSL 3.0.9.

IDLE

gh-104719 [https://github.com/python/cpython/issues/104719]: Remove IDLE's modification of tokenize.tabsize and test other uses of tokenize data and methods.

Tools/Demos

gh-109991 [https://github.com/python/cpython/issues/109991]: Update GitHub CI workflows to use OpenSSL 3.0.11 and multissltests to use 1.1.1w, 3.0.11, and 3.1.3.

gh-108494 [https://github.com/python/cpython/issues/108494]: Argument Clinic [https://devguide.python.org/development-tools/clinic/] now has a partial support of the Limited API: see documentation in the Python Developer's Guide [https://devguide.python.org/development-tools/clinic/#clinic-howto-limited-capi] Patch by Victor Stinner.

gh-107704 [https://github.com/python/cpython/issues/107704]: It is now possible to deprecate passing keyword arguments for keyword-or-positional parameters with Argument Clinic, using the new / [from X.Y] syntax. (To be read as "positional-only from Python version X.Y".) See documentation in the Python Developer's Guide [https://devguide.python.org/development-tools/clinic/#clinic-howto-deprecate-keyword] for more information.

gh-107880 [https://github.com/python/cpython/issues/107880]: Argument Clinic can now clone __init__() and __new__() methods.

gh-104683 [https://github.com/python/cpython/issues/104683]: Add --exclude option to Argument Clinic CLI.

gh-95065 [https://github.com/python/cpython/issues/95065]: Argument Clinic now supports overriding automatically generated signature by using directive @text_signature. See documentation in the Python Developer's Guide [https://devguide.python.org/development-tools/clinic/#clinic-howto-override-signature]

gh-107609 [https://github.com/python/cpython/issues/107609]: Fix duplicate module check in Argument Clinic. Previously, a duplicate definition would incorrectly be silently accepted. Patch by Erlend E. Aasland.

gh-107467 [https://github.com/python/cpython/issues/107467]: The Argument Clinic command-line tool now prints to stderr instead of stdout on failure.

gh-106970 [https://github.com/python/cpython/issues/106970]: Fix bugs in the Argument Clinic destination <name> clear command; the destination buffers would never be cleared, and the destination directive parser would simply continue to the fault handler after processing the command. Patch by Erlend E. Aasland.

gh-106706 [https://github.com/python/cpython/issues/106706]: Change bytecode syntax for families to remove redundant name matching pseudo syntax.

gh-106359 [https://github.com/python/cpython/issues/106359]: Argument Clinic now explicitly forbids "kwarg splats" in function calls used as annotations.

gh-103186 [https://github.com/python/cpython/issues/103186]: freeze now fetches CONFIG_ARGS from the original CPython instance the Makefile uses to call utility scripts. Patch by Ijtaba Hussain.

gh-95065 [https://github.com/python/cpython/issues/95065]: It is now possible to deprecate passing parameters positionally with Argument Clinic, using the new * [from X.Y] syntax. (To be read as "keyword-only from Python version X.Y".) See documentation in the Python Developer's Guide [https://devguide.python.org/development-tools/clinic/#clinic-howto-deprecate-positional] for more information. Patch by Erlend E. Aasland with help from Alex Waygood, Nikita Sobolev, and Serhiy Storchaka.

C API

gh-85283 [https://github.com/python/cpython/issues/85283]: If the Py_LIMITED_API macro is defined, Py_BUILD_CORE, Py_BUILD_CORE_BUILTIN and Py_BUILD_CORE_MODULE macros are now undefined by <Python.h>. Patch by Victor Stinner.

gh-110289 [https://github.com/python/cpython/issues/110289]: Add PyUnicode_EqualToUTF8AndSize() and PyUnicode_EqualToUTF8() functions.

gh-110235 [https://github.com/python/cpython/issues/110235]: Raise TypeError for duplicate/unknown fields in PyStructSequence constructor. Patched by Xuehai Pan.

gh-110014 [https://github.com/python/cpython/issues/110014]: Remove undocumented PY_TIMEOUT_MAX constant from the limited C API. Patch by Victor Stinner.

gh-109521 [https://github.com/python/cpython/issues/109521]: PyImport_GetImporter() now sets RuntimeError if it fails to get sys.path_hooks or sys.path_importer_cache or they are not list and dict correspondingly. Previously it could return NULL without setting error in obscure cases, crash or raise SystemError if these attributes have wrong type.

gh-108724 [https://github.com/python/cpython/issues/108724]: Add PyMutex internal-only lightweight locking API.

gh-85283 [https://github.com/python/cpython/issues/85283]: Add PySys_AuditTuple() function: similar to PySys_Audit(), but pass event arguments as a Python tuple object. Patch by Victor Stinner.

gh-108867 [https://github.com/python/cpython/issues/108867]: Add PyThreadState_GetUnchecked() function: similar to PyThreadState_Get(), but don't kill the process with a fatal error if it is NULL. The caller is responsible to check if the result is NULL. Previously, the function was private and known as _PyThreadState_UncheckedGet(). Patch by Victor Stinner.

gh-108765 [https://github.com/python/cpython/issues/108765]: Python.h no longer includes the <ctype.h> standard header file. If needed, it should now be included explicitly. For example, it provides isalpha() and tolower() functions which are locale dependent. Python provides locale independent functions, like Py_ISALPHA() and Py_TOLOWER(). Patch by Victor Stinner.

gh-108765 [https://github.com/python/cpython/issues/108765]: Python.h no longer includes the <unistd.h> standard header file. If needed, it should now be included explicitly. For example, it provides the functions: close(), getpagesize(), getpid() and sysconf(). Patch by Victor Stinner.

gh-108765 [https://github.com/python/cpython/issues/108765]: Python.h no longer includes the <ieeefp.h> standard header. It was included for the finite() function which is now provided by the <math.h> header. It should now be included explicitly if needed. Remove also the HAVE_IEEEFP_H macro. Patch by Victor Stinner.

gh-108765 [https://github.com/python/cpython/issues/108765]: Python.h no longer includes these standard header files: <time.h>, <sys/select.h> and <sys/time.h>. If needed, they should now be included explicitly. For example, <time.h> provides the clock() and gmtime() functions, <sys/select.h> provides the select() function, and <sys/time.h> provides the futimes(), gettimeofday() and setitimer() functions. Patch by Victor Stinner.

gh-108511 [https://github.com/python/cpython/issues/108511]: Add functions PyObject_HasAttrWithError(), PyObject_HasAttrStringWithError(), PyMapping_HasKeyWithError() and PyMapping_HasKeyStringWithError().

gh-107073 [https://github.com/python/cpython/issues/107073]: Add PyObject_VisitManagedDict() and PyObject_ClearManagedDict() functions which must be called by the traverse and clear functions of a type using Py_TPFLAGS_MANAGED_DICT flag. Patch by Victor Stinner.

gh-108634 [https://github.com/python/cpython/issues/108634]: Python built with configure --with-trace-refs (tracing references) now supports the Limited API. Patch by Victor Stinner.

gh-108014 [https://github.com/python/cpython/issues/108014]: Add PyLong_AsInt() function: similar to PyLong_AsLong(), but store the result in a C int instead of a C long. Previously, it was known as the private function _PyLong_AsInt() (with an underscore prefix). Patch by Victor Stinner.

gh-108314 [https://github.com/python/cpython/issues/108314]: Add PyDict_ContainsString() function: same as PyDict_Contains(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*. Patch by Victor Stinner.

gh-108337 [https://github.com/python/cpython/issues/108337]: Add atomic operations on additional data types in pyatomic.h.

gh-108014 [https://github.com/python/cpython/issues/108014]: Add Py_IsFinalizing() function: check if the main Python interpreter is shutting down. Patch by Victor Stinner.

gh-107916 [https://github.com/python/cpython/issues/107916]: C API functions PyErr_SetFromErrnoWithFilename(), PyErr_SetExcFromWindowsErrWithFilename() and PyErr_SetFromWindowsErrWithFilename() save now the error code before calling PyUnicode_DecodeFSDefault().

gh-107915 [https://github.com/python/cpython/issues/107915]: Such C API functions as PyErr_SetString(), PyErr_Format(), PyErr_SetFromErrnoWithFilename() and many others no longer crash or ignore errors if it failed to format the error message or decode the filename. Instead, they keep a corresponding error.

gh-107810 [https://github.com/python/cpython/issues/107810]: Improve DeprecationWarning for uses of PyType_Spec with metaclasses that have custom tp_new.

gh-107249 [https://github.com/python/cpython/issues/107249]: Implement the Py_UNUSED macro for Windows MSVC compiler. Patch by Victor Stinner.

gh-107226 [https://github.com/python/cpython/issues/107226]: PyModule_AddObjectRef() is now only available in the limited API version 3.10 or later.

gh-106320 [https://github.com/python/cpython/issues/106320]: Remove private _PyUnicode_AsString() alias to PyUnicode_AsUTF8(). It was kept for backward compatibility with Python 3.0 - 3.2. The PyUnicode_AsUTF8() is available since Python 3.3. The PyUnicode_AsUTF8String() function can be used to keep compatibility with Python 3.2 and older. Patch by Victor Stinner.

gh-106572 [https://github.com/python/cpython/issues/106572]: Convert PyObject_DelAttr() and PyObject_DelAttrString() macros to functions. Patch by Victor Stinner.

gh-106307 [https://github.com/python/cpython/issues/106307]: Add PyMapping_GetOptionalItem() function.

gh-106521 [https://github.com/python/cpython/issues/106521]: Add PyObject_GetOptionalAttr() and PyObject_GetOptionalAttrString() functions.

gh-106320 [https://github.com/python/cpython/issues/106320]: Remove _PyInterpreterState_Get() alias to PyInterpreterState_Get() which was kept for backward compatibility with Python 3.8. Patch by Victor Stinner.

gh-106316 [https://github.com/python/cpython/issues/106316]: Remove cpython/pytime.h header file: it only contained private functions. Patch by Victor Stinner.

gh-106023 [https://github.com/python/cpython/issues/106023]: Remove private _PyObject_FastCall() function: use PyObject_Vectorcall() which is available since Python 3.8 (PEP 590 [https://peps.python.org/pep-0590/]). Patch by Victor Stinner.

gh-106168 [https://github.com/python/cpython/issues/106168]: If Python is built in debug mode or with assertions, PyTuple_SET_ITEM() and PyList_SET_ITEM() now check the index argument with an assertion. If the assertion fails, make sure that the size is set before. Patch by Victor Stinner.

gh-106084 [https://github.com/python/cpython/issues/106084]: Remove the old aliases to functions calling functions which were kept for backward compatibility with Python 3.8 provisional API:

_PyObject_CallMethodNoArgs(): use PyObject_CallMethodNoArgs()

_PyObject_CallMethodOneArg(): use PyObject_CallMethodOneArg()

_PyObject_CallOneArg(): use PyObject_CallOneArg()

_PyObject_FastCallDict(): use PyObject_VectorcallDict()

_PyObject_Vectorcall(): use PyObject_Vectorcall()

_PyObject_VectorcallMethod(): use PyObject_VectorcallMethod()

_PyVectorcall_Function(): use PyVectorcall_Function()

Just remove the underscore prefix to update your code. Patch by Victor Stinner.

gh-106004 [https://github.com/python/cpython/issues/106004]: Adds PyDict_GetItemRef() and PyDict_GetItemStringRef() functions: similar to PyDict_GetItemWithError() but returning a strong reference instead of a borrowed reference. Patch by Victor Stinner.

gh-105927 [https://github.com/python/cpython/issues/105927]: Deprecate the PyWeakref_GetObject() and PyWeakref_GET_OBJECT() functions: use the new PyWeakref_GetRef() function instead. Patch by Victor Stinner.

gh-105927 [https://github.com/python/cpython/issues/105927]: Add PyWeakref_GetRef() function: similar to PyWeakref_GetObject() but returns a strong reference, or NULL if the referent is no longer live. Patch by Victor Stinner.

gh-105922 [https://github.com/python/cpython/issues/105922]: Add PyImport_AddModuleRef(): similar to PyImport_AddModule(), but return a strong reference instead of a borrowed reference. Patch by Victor Stinner.

gh-105227 [https://github.com/python/cpython/issues/105227]: The new PyType_GetDict() provides the dictionary for the given type object that is normally exposed by cls.__dict__. Normally it's sufficient to use tp_dict, but for the static builtin types tp_dict is now always NULL. PyType_GetDict() provides the correct dict object instead.

gh-105375 [https://github.com/python/cpython/issues/105375]: Fix a bug in PyErr_WarnExplicit() where an exception could end up being overwritten if the API failed internally.

gh-105603 [https://github.com/python/cpython/issues/105603]: We've renamed the new (in 3.12) PyInterpreterConfig.own_gil to PyInterpreterConfig.gil and changed the meaning of the value from "bool" to an integer with supported values of PyInterpreterConfig_DEFAULT_GIL, PyInterpreterConfig_SHARED_GIL, and PyInterpreterConfig_OWN_GIL. The default is "shared".

gh-105387 [https://github.com/python/cpython/issues/105387]: In the limited C API version 3.12, Py_INCREF() and Py_DECREF() functions are now implemented as opaque function calls to hide implementation details. Patch by Victor Stinner.

gh-105396 [https://github.com/python/cpython/issues/105396]: Deprecate the PyImport_ImportModuleNoBlock() function which is just an alias to PyImport_ImportModule() since Python 3.3. Patch by Victor Stinner.

gh-103968 [https://github.com/python/cpython/issues/103968]: PyType_FromMetaclass() now allows metaclasses with tp_new set to NULL.

gh-105268 [https://github.com/python/cpython/issues/105268]: Remove the old private, undocumented and untested _PyGC_FINALIZED() macro which was kept for backward compatibility with Python 3.8 and older. Patch by Victor Stinner.

gh-105182 [https://github.com/python/cpython/issues/105182]: Remove PyEval_AcquireLock() and PyEval_ReleaseLock() functions, deprecated in Python 3.2. Patch by Victor Stinner.

gh-105182 [https://github.com/python/cpython/issues/105182]: Remove PyEval_InitThreads() and PyEval_ThreadsInitialized() functions, deprecated in Python 3.9. Patch by Victor Stinner.

gh-105145 [https://github.com/python/cpython/issues/105145]: Deprecate old Python initialization functions:

PySys_ResetWarnOptions()

Py_GetExecPrefix()

Py_GetPath()

Py_GetPrefix()

Py_GetProgramFullPath()

Py_GetProgramName()

Py_GetPythonHome()

Patch by Victor Stinner.

gh-85275 [https://github.com/python/cpython/issues/85275]: PyObject_AsCharBuffer(), PyObject_AsReadBuffer(), PyObject_CheckReadBuffer(), and PyObject_AsWriteBuffer() are removed. Please migrate to new buffer protocol; PyObject_GetBuffer() and PyBuffer_Release().

gh-105156 [https://github.com/python/cpython/issues/105156]: Deprecate the old Py_UNICODE and PY_UNICODE_TYPE types: use directly the wchar_t type instead. Since Python 3.3, Py_UNICODE and PY_UNICODE_TYPE are just aliases to wchar_t. Patch by Victor Stinner.

gh-105145 [https://github.com/python/cpython/issues/105145]: Remove the following old functions to configure the Python initialization, deprecated in Python 3.11:

PySys_AddWarnOptionUnicode()

PySys_AddWarnOption()

PySys_AddXOption()

PySys_HasWarnOptions()

PySys_SetArgvEx()

PySys_SetArgv()

PySys_SetPath()

Py_SetPath()

Py_SetProgramName()

Py_SetPythonHome()

Py_SetStandardStreamEncoding()

_Py_SetProgramFullPath()

Patch by Victor Stinner.

gh-105107 [https://github.com/python/cpython/issues/105107]: Remove functions deprecated in Python 3.9.

PyEval_CallObject(), PyEval_CallObjectWithKeywords(): use PyObject_CallNoArgs() and PyObject_Call() (positional arguments must not be NULL) instead.

PyEval_CallFunction(): use PyObject_CallFunction() instead.

PyEval_CallMethod(): use PyObject_CallMethod() instead.

PyCFunction_Call(): use PyObject_Call() instead.

Patch by Victor Stinner.

gh-105115 [https://github.com/python/cpython/issues/105115]: PyTypeObject.tp_bases (and tp_mro) for builtin static types are now shared by all interpreters, whereas in 3.12-beta1 they were stored on PyInterpreterState. Also note that now the tuples are immortal objects.

gh-105071 [https://github.com/python/cpython/issues/105071]: Add PyUnstable_Exc_PrepReraiseStar to the unstable C api to expose the implementation of except*.

gh-104922 [https://github.com/python/cpython/issues/104922]: PY_SSIZE_T_CLEAN is no longer required to use '#' formats in APIs like PyArg_ParseTuple() and Py_BuildValue(). They uses Py_ssize_t for '#' regardless PY_SSIZE_T_CLEAN.

gh-104584 [https://github.com/python/cpython/issues/104584]: Add an unstable C API for hooking in an optimizer. This is mainly internal, but marked "unstable" to allow third-party experimentation.

gh-104668 [https://github.com/python/cpython/issues/104668]: Don't call PyOS_InputHook or PyOS_ReadlineFunctionPointer in subinterpreters, since it's generally difficult to avoid using global state in their registered callbacks. This also avoids situations where extensions may find themselves running in a subinterpreter they don't support (or haven't yet been loaded in).

bpo-42327 [https://bugs.python.org/issue?@action=redirect&bpo=42327]: Add PyModule_Add() function: similar to PyModule_AddObjectRef() and PyModule_AddObject(), but always steals a reference to the value.

bpo-40309 [https://bugs.python.org/issue?@action=redirect&bpo=40309]: Properly handle trailing spaces before closing parenthesis in Py_BuildValue() format strings.

Python 3.12.0 beta 1

Release date: 2023-05-22

Security

gh-99889 [https://github.com/python/cpython/issues/99889]: Fixed a security in flaw in uu.decode() that could allow for directory traversal based on the input if no out_file was specified.

gh-104049 [https://github.com/python/cpython/issues/104049]: Do not expose the local on-disk location in directory indexes produced by http.client.SimpleHTTPRequestHandler.

gh-99108 [https://github.com/python/cpython/issues/99108]: Upgrade built-in hashlib SHA3 implementation to a verified implementation from the HACL* project. Used when OpenSSL is not present or lacks SHA3.

gh-102153 [https://github.com/python/cpython/issues/102153]: urllib.parse.urlsplit() now strips leading C0 control and space characters following the specification for URLs defined by WHATWG in response to CVE 2023-24329 [https://www.cve.org/CVERecord?id=CVE-2023-24329]. Patch by Illia Volochii.

Library

gh-102856 [https://github.com/python/cpython/issues/102856]: Implement PEP 701 changes in the tokenize module. Patch by Marta Gómez Macías and Pablo Galindo Salgado

Core and Builtins

gh-104615 [https://github.com/python/cpython/issues/104615]: Fix wrong ordering of assignments in code like a, a = x, y. Contributed by Carl Meyer.

gh-104572 [https://github.com/python/cpython/issues/104572]: Improve syntax error message for invalid constructs in PEP 695 [https://peps.python.org/pep-0695/] contexts and in annotations when from __future__ import annotations is active.

gh-104482 [https://github.com/python/cpython/issues/104482]: Fix three error handling bugs in ast.c's validation of pattern matching statements.

gh-102818 [https://github.com/python/cpython/issues/102818]: Do not add a frame to the traceback in the sys.setprofile and sys.settrace trampoline functions. This ensures that frames are not duplicated if an exception is raised in the callback function, and ensures that frames are not omitted if a C callback is used and that does not add the frame.

gh-104405 [https://github.com/python/cpython/issues/104405]: Fix an issue where some bytecode instructions could ignore PEP 523 [https://peps.python.org/pep-0523/] when "inlining" calls.

gh-103082 [https://github.com/python/cpython/issues/103082]: Change behavior of sys.monitoring.events.LINE events in sys.monitoring: Line events now occur when a new line is reached dynamically, instead of using a static approximation, as before. This makes the behavior very similar to that of "line" events in sys.settrace. This should ease porting of tools from 3.11 to 3.12.

gh-104263 [https://github.com/python/cpython/issues/104263]: Fix float("nan") to produce a quiet NaN on platforms (like MIPS) where the meaning of the signalling / quiet bit is inverted from its usual meaning. Also introduce a new macro Py_INFINITY matching C99's INFINITY, and refactor internals to rely on C99's NAN and INFINITY macros instead of hard-coding bit patterns for infinities and NaNs. Thanks Sebastian Berg.

gh-99113 [https://github.com/python/cpython/issues/99113]: Multi-phase init extension modules may now indicate that they support running in subinterpreters that have their own GIL. This is done by using Py_MOD_PER_INTERPRETER_GIL_SUPPORTED as the value for the Py_mod_multiple_interpreters module def slot. Otherwise the module, by default, cannot be imported in such subinterpreters. (This does not affect the main interpreter or subinterpreters that do not have their own GIL.) In addition to the isolation that multi-phase init already normally requires, support for per-interpreter GIL involves one additional constraint: thread-safety. If the module has external (linked) dependencies and those libraries have any state that isn't thread-safe then the module must do the additional work to add thread-safety. This should be an uncommon case.

gh-99113 [https://github.com/python/cpython/issues/99113]: The GIL is now (optionally) per-interpreter. This is the fundamental change for PEP 684. This is all made possible by virtue of the isolated state of each interpreter in the process. The behavior of the main interpreter remains unchanged. Likewise, interpreters created using Py_NewInterpreter() are not affected. To get an interpreter with its own GIL, call Py_NewInterpreterFromConfig().

gh-104108 [https://github.com/python/cpython/issues/104108]: Multi-phase init extension modules may now indicate whether or not they actually support multiple interpreters. By default such modules are expected to support use in multiple interpreters. In the uncommon case that one does not, it may use the new Py_mod_multiple_interpreters module def slot. A value of 0 means the module does not support them. 1 means it does. The default is 1.

gh-104142 [https://github.com/python/cpython/issues/104142]: Fix an issue where list or tuple repetition could fail to respect PEP 683 [https://peps.python.org/pep-0683/].

gh-104078 [https://github.com/python/cpython/issues/104078]: Improve the performance of PyObject_HasAttrString()

gh-104066 [https://github.com/python/cpython/issues/104066]: Improve the performance of hasattr() for module objects with a missing attribute.

gh-104028 [https://github.com/python/cpython/issues/104028]: Reduce object creation while calling callback function from gc. Patch by Donghee Na.

gh-104018 [https://github.com/python/cpython/issues/104018]: Disallow the "z" format specifier in %-format of bytes objects.

gh-102213 [https://github.com/python/cpython/issues/102213]: Fix performance loss when accessing an object's attributes with __getattr__ defined.

gh-103895 [https://github.com/python/cpython/issues/103895]: Improve handling of edge cases in showing Exception.__notes__. Ensures that the messages always end with a newline and that string/bytes are not exploded over multiple lines. Patch by Carey Metcalfe.

gh-103907 [https://github.com/python/cpython/issues/103907]: Don't modify the refcounts of known immortal objects (True, False, and None) in the main interpreter loop.

gh-103899 [https://github.com/python/cpython/issues/103899]: Provide a helpful hint in the TypeError message when accidentally calling a module object that has a callable attribute of the same name (such as dis.dis() or datetime.datetime).

gh-103845 [https://github.com/python/cpython/issues/103845]: Remove both line and instruction instrumentation before adding new ones for monitoring, to avoid newly added instrumentation being removed immediately.

gh-103763 [https://github.com/python/cpython/issues/103763]: Implement PEP 695 [https://peps.python.org/pep-0695/], adding syntactic support for generic classes, generic functions, and type aliases.

A new type X = ... syntax is added for type aliases, which resolves at runtime to an instance of the new class typing.TypeAliasType. The value is lazily evaluated and is accessible through the .__value__ attribute. This is implemented as a new AST node ast.TypeAlias.

New syntax (class X[T]: ..., def func[T](): ...) is added for defining generic functions and classes. This is implemented as a new type_params attribute on the AST nodes for classes and functions. This node holds instances of the new AST classes ast.TypeVar, ast.ParamSpec, and ast.TypeVarTuple.

typing.TypeVar, typing.ParamSpec, typing.ParamSpecArgs, typing.ParamSpecKwargs, typing.TypeVarTuple, and typing.Generic are now implemented in C rather than Python.

There are new bytecode instructions LOAD_LOCALS, LOAD_CLASSDICT_OR_GLOBAL, and LOAD_CLASSDICT_OR_DEREF to support correct resolution of names in class namespaces.

Patch by Eric Traut, Larry Hastings, and Jelle Zijlstra.

Library

gh-103801 [https://github.com/python/cpython/issues/103801]: Adds three minor linting fixes to the wasm module caught that were caught by ruff.

gh-103793 [https://github.com/python/cpython/issues/103793]: Optimized asyncio Task creation by deferring expensive string formatting (task name generation) from Task creation to the first time get_name is called. This makes asyncio benchmarks up to 5% faster.

Core and Builtins

gh-102310 [https://github.com/python/cpython/issues/102310]: Change the error range for invalid bytes literals.

gh-103590 [https://github.com/python/cpython/issues/103590]: Do not wrap a single exception raised from a try-except* construct in an ExceptionGroup.

gh-103650 [https://github.com/python/cpython/issues/103650]: Change the perf map format to remove the '0x' prefix from the addresses

gh-102856 [https://github.com/python/cpython/issues/102856]: Implement the required C tokenizer changes for PEP 701. Patch by Pablo Galindo Salgado, Lysandros Nikolaou, Batuhan Taskaya, Marta Gómez Macías and sunmy2019.

gh-100530 [https://github.com/python/cpython/issues/100530]: Clarify the error message raised when the called part of a class pattern isn't actually a class.

gh-101517 [https://github.com/python/cpython/issues/101517]: Fix bug in line numbers of instructions emitted for except*.

gh-103492 [https://github.com/python/cpython/issues/103492]: Clarify SyntaxWarning with literal is comparison by specifying which literal is problematic, since comparisons using is with e.g. None and bool literals are idiomatic.

gh-87729 [https://github.com/python/cpython/issues/87729]: Add LOAD_SUPER_ATTR (and a specialization for super().method()) to speed up super().method() and super().attr. This makes super().method() roughly 2.3x faster and brings it within 20% of the performance of a simple method call. Patch by Vladimir Matveev and Carl Meyer.

gh-103488 [https://github.com/python/cpython/issues/103488]: Change the internal offset distinguishing yield and return target addresses, so that the instruction pointer is correct for exception handling and other stack unwinding.

gh-82012 [https://github.com/python/cpython/issues/82012]: The bitwise inversion operator (~) on bool is deprecated. It returns the bitwise inversion of the underlying int representation such that bool(~True) == True, which can be confusing. Use not for logical negation of bools. In the rare case that you really need the bitwise inversion of the underlying int, convert to int explicitly ~int(x).

gh-77757 [https://github.com/python/cpython/issues/77757]: Exceptions raised in a typeobject's __set_name__ method are no longer wrapped by a RuntimeError. Context information is added to the exception as a PEP 678 [https://peps.python.org/pep-0678/] note.

gh-103333 [https://github.com/python/cpython/issues/103333]: AttributeError now retains the name attribute when pickled and unpickled.

gh-103242 [https://github.com/python/cpython/issues/103242]: Migrate set_ecdh_curve() method not to use deprecated OpenSSL APIs. Patch by Donghee Na.

gh-103323 [https://github.com/python/cpython/issues/103323]: We've replaced our use of _PyRuntime.tstate_current with a thread-local variable. This is a fairly low-level implementation detail, and there should be no change in behavior.

gh-84436 [https://github.com/python/cpython/issues/84436]: The implementation of PEP-683 which adds Immortal Objects by using a fixed reference count that skips reference counting to make objects truly immutable.

gh-102700 [https://github.com/python/cpython/issues/102700]: Allow built-in modules to be submodules. This allows submodules to be statically linked into a CPython binary.

gh-103082 [https://github.com/python/cpython/issues/103082]: Implement PEP 669 [https://peps.python.org/pep-0669/] Low Impact Monitoring for CPython.

gh-88691 [https://github.com/python/cpython/issues/88691]: Reduce the number of inline CACHE entries for CALL.

gh-102500 [https://github.com/python/cpython/issues/102500]: Make the buffer protocol accessible in Python code using the new __buffer__ and __release_buffer__ magic methods. See PEP 688 [https://peps.python.org/pep-0688/] for details. Patch by Jelle Zijlstra.

gh-97933 [https://github.com/python/cpython/issues/97933]: PEP 709 [https://peps.python.org/pep-0709/]: inline list, dict and set comprehensions to improve performance and reduce bytecode size.

gh-99184 [https://github.com/python/cpython/issues/99184]: Bypass instance attribute access of __name__ in repr of weakref.ref.

gh-98003 [https://github.com/python/cpython/issues/98003]: Complex function calls are now faster and consume no C stack space.

bpo-39610 [https://bugs.python.org/issue?@action=redirect&bpo=39610]: len() for 0-dimensional memoryview objects (such as memoryview(ctypes.c_uint8(42))) now raises a TypeError. Previously this returned 1, which was not consistent with mem_0d[0] raising an IndexError.

Library

bpo-31821 [https://bugs.python.org/issue?@action=redirect&bpo=31821]: Fix pause_reading() to work when called from connection_made() in asyncio.

gh-104600 [https://github.com/python/cpython/issues/104600]: functools.update_wrapper() now sets the __type_params__ attribute (added by PEP 695 [https://peps.python.org/pep-0695/]).

gh-104340 [https://github.com/python/cpython/issues/104340]: When an asyncio pipe protocol loses its connection due to an error, and the caller doesn't await wait_closed() on the corresponding StreamWriter, don't log a warning about an exception that was never retrieved. After all, according to the StreamWriter.close() docs, the wait_closed() call is optional ("not mandatory").

gh-104555 [https://github.com/python/cpython/issues/104555]: Fix issue where an issubclass() check comparing a class X against a runtime-checkable protocol Y with non-callable members would not cause TypeError to be raised if an isinstance() call had previously been made comparing an instance of X to Y. This issue was present in edge cases on Python 3.11, but became more prominent in 3.12 due to some unrelated changes that were made to runtime-checkable protocols. Patch by Alex Waygood.

gh-104372 [https://github.com/python/cpython/issues/104372]: Refactored the _posixsubprocess internals to avoid Python C API usage between fork and exec when marking pass_fds= file descriptors inheritable.

gh-104484 [https://github.com/python/cpython/issues/104484]: Added case_sensitive argument to pathlib.PurePath.match()

gh-75367 [https://github.com/python/cpython/issues/75367]: Fix data descriptor detection in inspect.getattr_static().

gh-104536 [https://github.com/python/cpython/issues/104536]: Fix a race condition in the internal multiprocessing.process cleanup logic that could manifest as an unintended AttributeError when calling process.close().

gh-103857 [https://github.com/python/cpython/issues/103857]: Update datetime deprecations' stracktrace to point to the calling line

gh-101520 [https://github.com/python/cpython/issues/101520]: Move the core functionality of the tracemalloc module in the Python/ folder, leaving just the module wrapper in Modules/.

gh-104392 [https://github.com/python/cpython/issues/104392]: Remove undocumented and unused _paramspec_tvars attribute from some classes in typing.

gh-102613 [https://github.com/python/cpython/issues/102613]: Fix issue where pathlib.Path.glob() raised RecursionError when walking deep directory trees.

gh-103000 [https://github.com/python/cpython/issues/103000]: Improve performance of dataclasses.asdict() for the common case where dict_factory is dict. Patch by David C Ellis.

gh-104301 [https://github.com/python/cpython/issues/104301]: Allow leading whitespace in disambiguated statements in pdb.

gh-104139 [https://github.com/python/cpython/issues/104139]: Teach urllib.parse.unsplit() to retain the "//" when assembling itms-services://?action=generate-bugs style Apple Platform Deployment [https://support.apple.com/en-gb/guide/deployment/depce7cefc4d/web] URLs.

gh-104307 [https://github.com/python/cpython/issues/104307]: socket.getnameinfo() now releases the GIL while contacting the DNS server

gh-104310 [https://github.com/python/cpython/issues/104310]: Users may now use importlib.util.allowing_all_extensions() (a context manager) to temporarily disable the strict compatibility checks for importing extension modules in subinterpreters.

gh-87695 [https://github.com/python/cpython/issues/87695]: Fix issue where pathlib.Path.glob() raised OSError when it encountered a symlink to an overly long path.

gh-104265 [https://github.com/python/cpython/issues/104265]: Prevent possible crash by disallowing instantiation of the _csv.Reader and _csv.Writer types. The regression was introduced in 3.10.0a4 with PR 23224 (bpo-14935 [https://bugs.python.org/issue?@action=redirect&bpo=14935]). Patch by Radislav Chugunov.

gh-102613 [https://github.com/python/cpython/issues/102613]: Improve performance of pathlib.Path.glob() when expanding recursive wildcards ("**") by merging adjacent wildcards and de-duplicating results only when necessary.

gh-65772 [https://github.com/python/cpython/issues/65772]: Remove unneeded comments and code in turtle.py.

gh-90208 [https://github.com/python/cpython/issues/90208]: Fixed issue where pathlib.Path.glob() returned incomplete results when it encountered a PermissionError. This method now suppresses all OSError exceptions, except those raised from calling is_dir() on the top-level path.

gh-104144 [https://github.com/python/cpython/issues/104144]: Optimize asyncio.TaskGroup when using asyncio.eager_task_factory(). Skip scheduling a done callback if a TaskGroup task completes eagerly.

gh-104144 [https://github.com/python/cpython/issues/104144]: Optimize asyncio.gather() when using asyncio.eager_task_factory() to complete eagerly if all fututres completed eagerly. Avoid scheduling done callbacks for futures that complete eagerly.

gh-104114 [https://github.com/python/cpython/issues/104114]: Fix issue where pathlib.Path.glob() returns paths using the case of non-wildcard segments for corresponding path segments, rather than the real filesystem case.

gh-104104 [https://github.com/python/cpython/issues/104104]: Improve performance of pathlib.Path.glob() by using re.IGNORECASE to implement case-insensitive matching.

gh-104102 [https://github.com/python/cpython/issues/104102]: Improve performance of pathlib.Path.glob() when evaluating patterns that contain '../' segments.

gh-103822 [https://github.com/python/cpython/issues/103822]: Update the return type of weekday to the newly added Day attribute

gh-103629 [https://github.com/python/cpython/issues/103629]: Update the repr of typing.Unpack according to PEP 692 [https://peps.python.org/pep-0692/].

gh-103963 [https://github.com/python/cpython/issues/103963]: Make dis display the names of the args for CALL_INTRINSIC_*.

gh-104035 [https://github.com/python/cpython/issues/104035]: Do not ignore user-defined __getstate__ and __setstate__ methods for slotted frozen dataclasses.

gh-103987 [https://github.com/python/cpython/issues/103987]: In mmap, fix several bugs that could lead to access to memory-mapped files after they have been invalidated.

gh-103977 [https://github.com/python/cpython/issues/103977]: Improve import time of platform module.

gh-88773 [https://github.com/python/cpython/issues/88773]: Added turtle.teleport() to the turtle module to move a turtle to a new point without tracing a line, visible or invisible. Patch by Liam Gersten.

gh-103935 [https://github.com/python/cpython/issues/103935]: Use io.open_code() for files to be executed instead of raw open()

gh-68968 [https://github.com/python/cpython/issues/68968]: Fixed garbled output of assertEqual() when an input lacks final newline.

gh-100370 [https://github.com/python/cpython/issues/100370]: Fix potential OverflowError in sqlite3.Connection.blobopen() for 32-bit builds. Patch by Erlend E. Aasland.

gh-102628 [https://github.com/python/cpython/issues/102628]: Substitute CTRL-D with CTRL-Z in sqlite3 CLI banner when running on Windows.

gh-103636 [https://github.com/python/cpython/issues/103636]: Module-level attributes January and February are deprecated from calendar.

gh-103583 [https://github.com/python/cpython/issues/103583]: Isolate _multibytecodec and codecs extension modules. Patches by Erlend E. Aasland.

gh-103848 [https://github.com/python/cpython/issues/103848]: Add checks to ensure that [ bracketed ] hosts found by urllib.parse.urlsplit() are of IPv6 or IPvFuture format.

gh-103872 [https://github.com/python/cpython/issues/103872]: Update the bundled copy of pip to version 23.1.2.

gh-99944 [https://github.com/python/cpython/issues/99944]: Make dis display the value of oparg of KW_NAMES.

gh-74940 [https://github.com/python/cpython/issues/74940]: The C.UTF-8 locale is no longer converted to en_US.UTF-8, enabling the use of UTF-8 encoding on systems which have no locales installed.

gh-103861 [https://github.com/python/cpython/issues/103861]: Fix zipfile.Zipfile creating invalid zip files when force_zip64 was used to add files to them. Patch by Carey Metcalfe.

gh-103857 [https://github.com/python/cpython/issues/103857]: Deprecated datetime.datetime.utcnow() and datetime.datetime.utcfromtimestamp(). (Patch by Paul Ganssle)

gh-103839 [https://github.com/python/cpython/issues/103839]: Avoid compilation error due to tommath.h not being found when building Tkinter against Tcl 8.7 built with bundled libtommath.

gh-103791 [https://github.com/python/cpython/issues/103791]: contextlib.suppress now supports suppressing exceptions raised as part of an ExceptionGroup. If other exceptions exist on the group, they are re-raised in a group that does not contain the suppressed exceptions.

gh-90750 [https://github.com/python/cpython/issues/90750]: Use datetime.datetime.fromisocalendar() in the implementation of datetime.datetime.strptime(), which should now accept only valid ISO dates. (Patch by Paul Ganssle)

gh-103685 [https://github.com/python/cpython/issues/103685]: Prepare tkinter.Menu.index() for Tk 8.7 so that it does not raise TclError: expected integer but got "" when it should return None.

gh-81403 [https://github.com/python/cpython/issues/81403]: urllib.request.CacheFTPHandler no longer raises URLError if a cached FTP instance is reused. ftplib's endtransfer method calls voidresp to drain the connection to handle FTP instance reuse properly.

gh-103699 [https://github.com/python/cpython/issues/103699]: Add __orig_bases__ to non-generic TypedDicts, call-based TypedDicts, and call-based NamedTuples. Other TypedDicts and NamedTuples already had the attribute.

gh-103693 [https://github.com/python/cpython/issues/103693]: Add convenience variable feature to pdb

gh-92248 [https://github.com/python/cpython/issues/92248]: Deprecate type, choices, and metavar parameters of argparse.BooleanOptionalAction.

gh-89415 [https://github.com/python/cpython/issues/89415]: Add socket constants for source-specific multicast. Patch by Reese Hyde.

gh-103673 [https://github.com/python/cpython/issues/103673]: socketserver gains ForkingUnixStreamServer and ForkingUnixDatagramServer classes. Patch by Jay Berry.

gh-103636 [https://github.com/python/cpython/issues/103636]: Added Enum for months and days in the calendar module.

gh-84976 [https://github.com/python/cpython/issues/84976]: Create a new Lib/_pydatetime.py file that defines the Python version of the datetime module, and make datetime import the contents of the new library only if the C implementation is missing. Currently, the full Python implementation is defined and then deleted if the C implementation is not available, slowing down import datetime unnecessarily.

gh-103596 [https://github.com/python/cpython/issues/103596]: Attributes/methods are no longer shadowed by same-named enum members, although they may be shadowed by enum.property's.

gh-103584 [https://github.com/python/cpython/issues/103584]: Updated importlib.metadata with changes from importlib_metadata 5.2 through 6.5.0, including: Support installed-files.txt for Distribution.files when present. PackageMetadata now stipulates an additional get method allowing for easy querying of metadata keys that may not be present. packages_distributions now honors packages and modules with Python modules that not .py sources (e.g. .pyc, .so). Expand protocol for PackageMetadata.get_all to match the upstream implementation of email.message.Message.get_all in python/typeshed#9620. Deprecated use of Distribution without defining abstract methods. Deprecated expectation that PackageMetadata.__getitem__ will return None for missing keys. In the future, it will raise a KeyError.

gh-103578 [https://github.com/python/cpython/issues/103578]: Fixed a bug where pdb crashes when reading source file with different encoding by replacing io.open() with io.open_code(). The new method would also call into the hook set by PyFile_SetOpenCodeHook().

gh-103556 [https://github.com/python/cpython/issues/103556]: Now creating inspect.Signature objects with positional-only parameter with a default followed by a positional-or-keyword parameter without one is impossible.

gh-103559 [https://github.com/python/cpython/issues/103559]: Update the bundled copy of pip to version 23.1.1.

gh-103548 [https://github.com/python/cpython/issues/103548]: Improve performance of pathlib.Path.absolute() and cwd() by joining paths only when necessary. Also improve performance of pathlib.PurePath.is_absolute() on Posix by skipping path parsing and normalization.

gh-103538 [https://github.com/python/cpython/issues/103538]: Remove _tkinter module code guarded by definition of the TK_AQUA macro which was only needed for Tk 8.4.7 or earlier and was never actually defined by any build system or documented for manual use.

gh-103533 [https://github.com/python/cpython/issues/103533]: Update cProfile to use PEP 669 API

gh-103525 [https://github.com/python/cpython/issues/103525]: Fix misleading exception message when mixed str and bytes arguments are supplied to pathlib.PurePath and Path.

gh-103489 [https://github.com/python/cpython/issues/103489]: Add getconfig() and setconfig() to Connection to make configuration changes to a database connection. Patch by Erlend E. Aasland.

gh-103365 [https://github.com/python/cpython/issues/103365]: Set default Flag boundary to STRICT and fix bitwise operations.

gh-103472 [https://github.com/python/cpython/issues/103472]: Avoid a potential ResourceWarning in http.client.HTTPConnection by closing the proxy / tunnel's CONNECT response explicitly.

gh-103462 [https://github.com/python/cpython/issues/103462]: Fixed an issue with using writelines() in asyncio to send very large payloads that exceed the amount of data that can be written in one call to socket.socket.send() or socket.socket.sendmsg(), resulting in the remaining buffer being left unwritten.

gh-103449 [https://github.com/python/cpython/issues/103449]: Fix a bug in doc string generation in dataclasses.dataclass().

gh-103092 [https://github.com/python/cpython/issues/103092]: Isolate _collections (apply PEP 687 [https://peps.python.org/pep-0687/]). Patch by Erlend E. Aasland.

gh-103357 [https://github.com/python/cpython/issues/103357]: Added support for logging.Formatter defaults parameter to logging.config.dictConfig() and logging.config.fileConfig(). Patch by Bar Harel.

gh-103092 [https://github.com/python/cpython/issues/103092]: Adapt the winreg extension module to PEP 687 [https://peps.python.org/pep-0687/].

gh-74690 [https://github.com/python/cpython/issues/74690]: The performance of isinstance() checks against runtime-checkable protocols has been considerably improved for protocols that only have a few members. To achieve this improvement, several internal implementation details of the typing module have been refactored, including typing._ProtocolMeta.__instancecheck__, typing._is_callable_members_only, and typing._get_protocol_attrs. Patches by Alex Waygood.

gh-74690 [https://github.com/python/cpython/issues/74690]: The members of a runtime-checkable protocol are now considered "frozen" at runtime as soon as the class has been created. See "What's new in Python 3.12" for more details.

gh-103256 [https://github.com/python/cpython/issues/103256]: Fixed a bug that caused hmac to raise an exception when the requested hash algorithm was not available in OpenSSL despite being available separately as part of hashlib itself. It now falls back properly to the built-in. This could happen when, for example, your OpenSSL does not include SHA3 support and you want to compute hmac.digest(b'K', b'M', 'sha3_256').

gh-102778 [https://github.com/python/cpython/issues/102778]: Support sys.last_exc in idlelib.

gh-103285 [https://github.com/python/cpython/issues/103285]: Improve performance of ast.get_source_segment().

gh-103225 [https://github.com/python/cpython/issues/103225]: Fix a bug in pdb when displaying line numbers of module-level source code.

gh-103092 [https://github.com/python/cpython/issues/103092]: Adapt the msvcrt extension module to PEP 687 [https://peps.python.org/pep-0687/].

gh-103092 [https://github.com/python/cpython/issues/103092]: Adapt the winsound extension module to PEP 687 [https://peps.python.org/pep-0687/].

gh-93910 [https://github.com/python/cpython/issues/93910]: Remove deprecation of enum member.member access.

gh-102978 [https://github.com/python/cpython/issues/102978]: Fixes unittest.mock.patch() not enforcing function signatures for methods decorated with @classmethod or @staticmethod when patch is called with autospec=True.

gh-103092 [https://github.com/python/cpython/issues/103092]: Isolate _socket (apply PEP 687 [https://peps.python.org/pep-0687/]). Patch by Erlend E. Aasland.

gh-100479 [https://github.com/python/cpython/issues/100479]: Add pathlib.PurePath.with_segments(), which creates a path object from arguments. This method is called whenever a derivative path is created, such as from pathlib.PurePath.parent. Subclasses may override this method to share information between path objects.

gh-103220 [https://github.com/python/cpython/issues/103220]: Fix issue where os.path.join() added a slash when joining onto an incomplete UNC drive with a trailing slash on Windows.

gh-103204 [https://github.com/python/cpython/issues/103204]: Fixes http.server accepting HTTP requests with HTTP version numbers preceded by '+', or '-', or with digit-separating '_' characters. The length of the version numbers is also constrained.

gh-75586 [https://github.com/python/cpython/issues/75586]: Fix various Windows-specific issues with shutil.which.

gh-103193 [https://github.com/python/cpython/issues/103193]: Improve performance of inspect.getattr_static(). Patch by Alex Waygood.

gh-103176 [https://github.com/python/cpython/issues/103176]: sys._current_exceptions() now returns a mapping from thread-id to an exception instance, rather than to a (typ, exc, tb) tuple.

gh-103143 [https://github.com/python/cpython/issues/103143]: Polish the help messages and docstrings of pdb.

gh-103015 [https://github.com/python/cpython/issues/103015]: Add entrypoint keyword-only parameter to sqlite3.Connection.load_extension(), for overriding the SQLite extension entry point. Patch by Erlend E. Aasland.

gh-103000 [https://github.com/python/cpython/issues/103000]: Improve performance of dataclasses.astuple() and dataclasses.asdict() in cases where the contents are common Python types.

gh-102953 [https://github.com/python/cpython/issues/102953]: The extraction methods in tarfile, and shutil.unpack_archive(), have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See 解壓縮篩選器 for details.

gh-97696 [https://github.com/python/cpython/issues/97696]: Implemented an eager task factory in asyncio. When used as a task factory on an event loop, it performs eager execution of coroutines. Coroutines that are able to complete synchronously (e.g. return or raise without blocking) are returned immediately as a finished task, and the task is never scheduled to the event loop. If the coroutine blocks, the (pending) task is scheduled and returned.

gh-81079 [https://github.com/python/cpython/issues/81079]: Add case_sensitive keyword-only argument to pathlib.Path.glob() and rglob().

gh-101819 [https://github.com/python/cpython/issues/101819]: Isolate the io extension module by applying PEP 687 [https://peps.python.org/pep-0687/]. Patch by Kumar Aditya, Victor Stinner, and Erlend E. Aasland.

gh-91896 [https://github.com/python/cpython/issues/91896]: Deprecate collections.abc.ByteString

gh-101362 [https://github.com/python/cpython/issues/101362]: Speed up pathlib.Path construction by omitting the path anchor from the internal list of path parts.

gh-102114 [https://github.com/python/cpython/issues/102114]: Functions in the dis module that accept a source code string as argument now print a more concise traceback when the string contains a syntax or indentation error.

gh-62432 [https://github.com/python/cpython/issues/62432]: The unittest runner will now exit with status code 5 if no tests were run. It is common for test runner misconfiguration to fail to find any tests, this should be an error.

gh-78079 [https://github.com/python/cpython/issues/78079]: Fix incorrect normalization of UNC device path roots, and partial UNC share path roots, in pathlib.PurePath. Pathlib no longer appends a trailing slash to such paths.

gh-85984 [https://github.com/python/cpython/issues/85984]: Add tty.cfmakeraw() and tty.cfmakecbreak() to tty and modernize, the behavior of tty.setraw() and tty.setcbreak() to use POSIX.1-2017 Chapter 11 "General Terminal Interface" flag masks by default.

gh-101688 [https://github.com/python/cpython/issues/101688]: Implement types.get_original_bases() to provide further introspection for types.

gh-101640 [https://github.com/python/cpython/issues/101640]: argparse.ArgumentParser now catches errors when writing messages, such as when sys.stderr is None. Patch by Oleg Iarygin.

gh-83861 [https://github.com/python/cpython/issues/83861]: Fix datetime.astimezone method return value when invoked on a naive datetime instance that represents local time falling in a timezone transition gap. PEP 495 requires that instances with fold=1 produce earlier times than those with fold=0 in this case.

gh-89550 [https://github.com/python/cpython/issues/89550]: Decrease execution time of some gzip file writes by 15% by adding more appropriate buffering.

gh-95299 [https://github.com/python/cpython/issues/95299]: Remove the bundled setuptools wheel from ensurepip, and stop installing setuptools in environments created by venv.

gh-99353 [https://github.com/python/cpython/issues/99353]: Respect the http.client.HTTPConnection .debuglevel flag in urllib.request.AbstractHTTPHandler when its constructor parameter debuglevel is not set. And do the same for *HTTPS*.

gh-98040 [https://github.com/python/cpython/issues/98040]: Remove the long-deprecated imp module.

gh-97850 [https://github.com/python/cpython/issues/97850]: Deprecate pkgutil.find_loader() and pkgutil.get_loader() in favor of importlib.util.find_spec().

gh-94473 [https://github.com/python/cpython/issues/94473]: Flatten arguments in tkinter.Canvas.coords(). It now accepts not only x1, y1, x2, y2, ... and [x1, y1, x2, y2, ...], but also (x1, y1), (x2, y2), ... and [(x1, y1), (x2, y2), ...].

gh-98040 [https://github.com/python/cpython/issues/98040]: Remove more deprecated importlib APIs: find_loader(), find_module(), importlib.abc.Finder, pkgutil.ImpImporter, pkgutil.ImpLoader.

gh-96522 [https://github.com/python/cpython/issues/96522]: Fix potential deadlock in pty.spawn()

gh-96534 [https://github.com/python/cpython/issues/96534]: Support divert(4) added in FreeBSD 14.

gh-87474 [https://github.com/python/cpython/issues/87474]: Fix potential file descriptor leaks in subprocess.Popen.

gh-94906 [https://github.com/python/cpython/issues/94906]: Support multiple steps in math.nextafter(). Patch by Shantanu Jain and Matthias Gorgens.

gh-51574 [https://github.com/python/cpython/issues/51574]: Make tempfile.mkdtemp() return absolute paths when its dir parameter is relative.

gh-94518 [https://github.com/python/cpython/issues/94518]: Convert private _posixsubprocess.fork_exec() to use Argument Clinic.

gh-92184 [https://github.com/python/cpython/issues/92184]: When creating zip files using zipfile, os.altsep, if not None, will always be treated as a path separator even when it is not /. Patch by Carey Metcalfe.

bpo-46797 [https://bugs.python.org/issue?@action=redirect&bpo=46797]: Deprecation warnings are now emitted for ast.Num, ast.Bytes, ast.Str, ast.NameConstant and ast.Ellipsis. These have been documented as deprecated since Python 3.8, and will be removed in Python 3.14.

bpo-44844 [https://bugs.python.org/issue?@action=redirect&bpo=44844]: Enables webbrowser to detect and launch Microsoft Edge browser.

bpo-45606 [https://bugs.python.org/issue?@action=redirect&bpo=45606]: Fixed the bug in pathlib.Path.glob() -- previously a dangling symlink would not be found by this method when the pattern is an exact match, but would be found when the pattern contains a wildcard or the recursive wildcard (**). With this change, a dangling symlink will be found in both cases.

bpo-23041 [https://bugs.python.org/issue?@action=redirect&bpo=23041]: Add QUOTE_STRINGS and QUOTE_NOTNULL to the suite of csv module quoting styles.

bpo-24964 [https://bugs.python.org/issue?@action=redirect&bpo=24964]: Added http.client.HTTPConnection.get_proxy_response_headers() that provides access to the HTTP headers on a proxy server response to the CONNECT request.

bpo-17258 [https://bugs.python.org/issue?@action=redirect&bpo=17258]: multiprocessing now supports stronger HMAC algorithms for inter-process connection authentication rather than only HMAC-MD5.

bpo-39744 [https://bugs.python.org/issue?@action=redirect&bpo=39744]: Make asyncio.subprocess.Process.communicate() close the subprocess's stdin even when called with input=None.

bpo-22708 [https://bugs.python.org/issue?@action=redirect&bpo=22708]: http.client CONNECT method tunnel improvements: Use HTTP 1.1 protocol; send a matching Host: header with CONNECT, if one is not provided; convert IDN domain names to Punycode. Patch by Michael Handler.

Documentation

gh-67056 [https://github.com/python/cpython/issues/67056]: Document that the effect of registering or unregistering an atexit cleanup function from within a registered cleanup function is undefined.

gh-103629 [https://github.com/python/cpython/issues/103629]: Mention the new way of typing **kwargs with Unpack and TypedDict introduced in PEP 692 [https://peps.python.org/pep-0692/].

gh-48241 [https://github.com/python/cpython/issues/48241]: Clarifying documentation about the url parameter to urllib.request.urlopen and urllib.request.Request needing to be encoded properly.

gh-86094 [https://github.com/python/cpython/issues/86094]: Add support for Unicode Path Extra Field in ZipFile. Patch by Yeojin Kim and Andrea Giudiceandrea

gh-99202 [https://github.com/python/cpython/issues/99202]: Fix extension type from documentation for compiling in C++20 mode

Tests

gh-104494 [https://github.com/python/cpython/issues/104494]: Update test_pack_configure_in and test_place_configure_in for changes to error message formatting in Tk 8.7.

gh-104461 [https://github.com/python/cpython/issues/104461]: Run test_configure_screen on X11 only, since the DISPLAY environment variable and -screen option for toplevels are not useful on Tk for Win32 or Aqua.

gh-86275 [https://github.com/python/cpython/issues/86275]: Added property-based tests to the zoneinfo tests, along with stubs for the hypothesis interface. (Patch by Paul Ganssle)

gh-103329 [https://github.com/python/cpython/issues/103329]: Regression tests for the behaviour of unittest.mock.PropertyMock were added.

gh-102795 [https://github.com/python/cpython/issues/102795]: fix use of poll in test_epoll's test_control_and_wait

gh-75729 [https://github.com/python/cpython/issues/75729]: Fix the os.spawn* tests failing on Windows when the working directory or interpreter path contains spaces.

Build

gh-101282 [https://github.com/python/cpython/issues/101282]: BOLT optimization is now applied to the libpython shared library if building a shared library. BOLT instrumentation and application settings can now be influenced via the BOLT_INSTRUMENT_FLAGS and BOLT_APPLY_FLAGS configure variables.

gh-99017 [https://github.com/python/cpython/issues/99017]: PYTHON_FOR_REGEN now require Python 3.10 or newer.

gh-104490 [https://github.com/python/cpython/issues/104490]: Define .PHONY / virtual make targets consistently and properly.

gh-104106 [https://github.com/python/cpython/issues/104106]: Add gcc fallback of mkfifoat/mknodat for macOS. Patch by Donghee Na.

gh-103532 [https://github.com/python/cpython/issues/103532]: The TKINTER_PROTECT_LOADTK macro is no longer defined or used in the _tkinter module. It was previously only defined when building against Tk 8.4.13 and older, but Tk older than 8.5.12 has been unsupported since gh-91152 [https://github.com/python/cpython/issues/91152].

gh-99069 [https://github.com/python/cpython/issues/99069]: Extended workaround defining static_assert when missing from the libc headers to all clang and gcc builds. In particular, this fixes building on macOS <= 10.10.

gh-100220 [https://github.com/python/cpython/issues/100220]: Changed the default value of the SHELL Makefile variable from /bin/sh to /bin/sh -e to ensure that complex recipes correctly fail after an error. Previously, make install could fail to install some files and yet return a successful result.

gh-90656 [https://github.com/python/cpython/issues/90656]: Add platform triplets for 64-bit LoongArch:

loongarch64-linux-gnusf

loongarch64-linux-gnuf32

loongarch64-linux-gnu

Patch by Zhang Na.

Windows

gh-104623 [https://github.com/python/cpython/issues/104623]: Update Windows installer to use SQLite 3.42.0.

gh-82814 [https://github.com/python/cpython/issues/82814]: Fix a potential [Errno 13] Permission denied when using shutil.copystat() within Windows Subsystem for Linux (WSL) on a mounted filesystem by adding errno.EACCES to the list of ignored errors within the internal implementation.

gh-103088 [https://github.com/python/cpython/issues/103088]: Fix virtual environment activate script having incorrect line endings for Cygwin.

gh-103088 [https://github.com/python/cpython/issues/103088]: Fixes venvs not working in bash on Windows across different disks

gh-102997 [https://github.com/python/cpython/issues/102997]: Update Windows installer to use SQLite 3.41.2.

gh-88013 [https://github.com/python/cpython/issues/88013]: Fixed a bug where TypeError was raised when calling ntpath.realpath() with a bytes parameter in some cases.

macOS

gh-99834 [https://github.com/python/cpython/issues/99834]: Update macOS installer to Tcl/Tk 8.6.13.

gh-104623 [https://github.com/python/cpython/issues/104623]: Update macOS installer to SQLite 3.42.0.

gh-103545 [https://github.com/python/cpython/issues/103545]: Add os.PRIO_DARWIN_THREAD, os.PRIO_DARWIN_PROCESS, os.PRIO_DARWIN_BG and os.PRIO_DARWIN_NONUI. These can be used with os.setpriority to run the process at a lower priority and make use of the efficiency cores on Apple Silicon systems.

gh-104180 [https://github.com/python/cpython/issues/104180]: Support reading SOCKS proxy configuration from macOS System Configuration. Patch by Sam Schott.

gh-60436 [https://github.com/python/cpython/issues/60436]: update curses textbox to additionally handle backspace using the curses.ascii.DEL key press.

gh-102997 [https://github.com/python/cpython/issues/102997]: Update macOS installer to SQLite 3.41.2.

IDLE

gh-104499 [https://github.com/python/cpython/issues/104499]: Fix completions for Tk Aqua 8.7 (currently blank).

gh-104496 [https://github.com/python/cpython/issues/104496]: About prints both tcl and tk versions if different (expected someday).

gh-88496 [https://github.com/python/cpython/issues/88496]: Fix IDLE test hang on macOS.

Tools/Demos

gh-104389 [https://github.com/python/cpython/issues/104389]: Argument Clinic C converters now accept the unused keyword, for wrapping a parameter with Py_UNUSED. Patch by Erlend E. Aasland.

C API

gh-101291 [https://github.com/python/cpython/issues/101291]: Added unstable C API for extracting the value of "compact" integers: PyUnstable_Long_IsCompact() and PyUnstable_Long_CompactValue().

gh-104109 [https://github.com/python/cpython/issues/104109]: We've added Py_NewInterpreterFromConfig() and PyInterpreterConfig to the public C-API (but not the stable ABI; not yet at least). The new function may be used to create a new interpreter with various features configured. The function was added to support PEP 684 (per-interpreter GIL).

gh-103968 [https://github.com/python/cpython/issues/103968]: PyType_FromSpec() and its variants now allow creating classes whose metaclass overrides tp_new. The tp_new is ignored. This behavior is deprecated and will be disallowed in 3.14+. The new PyType_FromMetaclass() already disallows it.

gh-103743 [https://github.com/python/cpython/issues/103743]: Add PyUnstable_Object_GC_NewWithExtraData() function that can be used to allocate additional memory after an object for data not managed by Python.

gh-103295 [https://github.com/python/cpython/issues/103295]: Introduced PyUnstable_WritePerfMapEntry(), PyUnstable_PerfMapState_Init() and PyUnstable_PerfMapState_Fini(). These allow extension modules (JIT compilers in particular) to write to perf-map files in a thread safe manner. The Python 對 Linux perf 分析器的支援 also uses these APIs to write entries in the perf-map file.

gh-103509 [https://github.com/python/cpython/issues/103509]: Added C API for extending types whose instance memory layout is opaque: PyType_Spec.basicsize can now be zero or negative, PyObject_GetTypeData() can be used to get subclass-specific data, and Py_TPFLAGS_ITEMS_AT_END can be used to safely extend variable-size objects. See PEP 697 [https://peps.python.org/pep-0697/] for details.

gh-103091 [https://github.com/python/cpython/issues/103091]: Add a new C-API function to eagerly assign a version tag to a PyTypeObject: PyUnstable_Type_AssignVersionTag().

gh-101408 [https://github.com/python/cpython/issues/101408]: PyObject_GC_Resize should calculate preheader size if needed. Patch by Donghee Na.

gh-98836 [https://github.com/python/cpython/issues/98836]: Add support of more formatting options (left aligning, octals, uppercase hexadecimals, intmax_t, ptrdiff_t, wchar_t C strings, variable width and precision) in PyUnicode_FromFormat() and PyUnicode_FromFormatV().

gh-96803 [https://github.com/python/cpython/issues/96803]: Add unstable C-API functions to get the code object, lasti and line number from the internal _PyInterpreterFrame in the limited API. The functions are:

PyCodeObject * PyUnstable_InterpreterFrame_GetCode(struct _PyInterpreterFrame *frame)

int PyUnstable_InterpreterFrame_GetLasti(struct _PyInterpreterFrame *frame)

int PyUnstable_InterpreterFrame_GetLine(struct _PyInterpreterFrame *frame)

Python 3.12.0 alpha 7

Release date: 2023-04-04

Core and Builtins

gh-102192 [https://github.com/python/cpython/issues/102192]: Deprecated _PyErr_ChainExceptions in favour of _PyErr_ChainExceptions1.

gh-89987 [https://github.com/python/cpython/issues/89987]: Reduce the number of inline CACHE entries for BINARY_SUBSCR.

gh-102859 [https://github.com/python/cpython/issues/102859]: Removed JUMP_IF_FALSE_OR_POP and JUMP_IF_TRUE_OR_POP instructions.

gh-101975 [https://github.com/python/cpython/issues/101975]: Fixed stacktop value on tracing entries to avoid corruption on garbage collection.

gh-102778 [https://github.com/python/cpython/issues/102778]: Add sys.last_exc and deprecate sys.last_type, sys.last_value and sys.last_traceback, which hold the same information in its legacy form.

gh-100982 [https://github.com/python/cpython/issues/100982]: Replace all occurrences of COMPARE_AND_BRANCH with COMPARE_OP.

gh-102701 [https://github.com/python/cpython/issues/102701]: Fix overflow when creating very large dict.

gh-102755 [https://github.com/python/cpython/issues/102755]: Add PyErr_DisplayException() which takes just an exception instance, to replace the legacy PyErr_Display() which takes the (typ, exc, tb) triplet.

gh-102594 [https://github.com/python/cpython/issues/102594]: Add note to exception raised in PyErr_SetObject when normalization fails.

gh-90997 [https://github.com/python/cpython/issues/90997]: Shrink the number of inline CACHE entries used by LOAD_GLOBAL.

Library

gh-102491 [https://github.com/python/cpython/issues/102491]: Improve import time of platform by removing IronPython version parsing. The IronPython version parsing was not functional (see https://github.com/IronLanguages/ironpython3/issues/1667).

Core and Builtins

gh-101291 [https://github.com/python/cpython/issues/101291]: Rearrage bits in first field (after header) of PyLongObject. * Bits 0 and 1: 1 - sign. I.e. 0 for positive numbers, 1 for zero and 2 for negative numbers. * Bit 2 reserved (probably for the immortal bit) * Bits 3+ the unsigned size.

This makes a few operations slightly more efficient, and will enable a more compact and faster 2s-complement representation of most ints in future.

gh-102397 [https://github.com/python/cpython/issues/102397]: Fix segfault from race condition in signal handling during garbage collection. Patch by Kumar Aditya.

gh-102406 [https://github.com/python/cpython/issues/102406]: codecs encoding/decoding errors now get the context information (which operation and which codecs) attached as PEP 678 [https://peps.python.org/pep-0678/] notes instead of through chaining a new instance of the exception.

gh-102281 [https://github.com/python/cpython/issues/102281]: Fix potential nullptr dereference and use of uninitialized memory in fileutils. Patch by Max Bachmann.

gh-102300 [https://github.com/python/cpython/issues/102300]: Reuse operands with refcount of 1 in float specializations of BINARY_OP.

gh-102213 [https://github.com/python/cpython/issues/102213]: Fix performance loss when accessing an object's attributes with __getattr__ defined.

gh-102255 [https://github.com/python/cpython/issues/102255]: Improve build support for the Xbox. Patch by Max Bachmann.

Build

gh-102027 [https://github.com/python/cpython/issues/102027]: Fix SSE2 and SSE3 detection in _blake2 internal module. Patch by Max Bachmann.

Core and Builtins

gh-101865 [https://github.com/python/cpython/issues/101865]: Deprecate co_lnotab in code objects, schedule it for removal in Python 3.14

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Adapt _pickle to PEP 687 [https://peps.python.org/pep-0687/]. Patch by Mohamed Koubaa and Erlend Aasland.

gh-103085 [https://github.com/python/cpython/issues/103085]: Pure python locale.getencoding() will not warn deprecation.

gh-103068 [https://github.com/python/cpython/issues/103068]: It's no longer possible to register conditional breakpoints in Pdb that raise SyntaxError. Patch by Tian Gao.

gh-102549 [https://github.com/python/cpython/issues/102549]: Don't ignore exceptions in member type creation.

gh-103056 [https://github.com/python/cpython/issues/103056]: Ensure final _generate_next_value_ is a staticmethod.

gh-103046 [https://github.com/python/cpython/issues/103046]: Display current line label correctly in dis when show_caches is False and lasti points to a CACHE entry.

gh-102433 [https://github.com/python/cpython/issues/102433]: isinstance() checks against runtime-checkable protocols now use inspect.getattr_static() rather than hasattr() to lookup whether attributes exist. This means that descriptors and __getattr__() methods are no longer unexpectedly evaluated during isinstance() checks against runtime-checkable protocols. However, it may also mean that some objects which used to be considered instances of a runtime-checkable protocol may no longer be considered instances of that protocol on Python 3.12+, and vice versa. Most users are unlikely to be affected by this change. Patch by Alex Waygood.

gh-103023 [https://github.com/python/cpython/issues/103023]: It's no longer possible to register expressions to display in Pdb that raise SyntaxError. Patch by Tian Gao.

gh-102947 [https://github.com/python/cpython/issues/102947]: Improve traceback when dataclasses.fields() is called on a non-dataclass. Patch by Alex Waygood

gh-102780 [https://github.com/python/cpython/issues/102780]: The asyncio.Timeout context manager now works reliably even when performing cleanup due to task cancellation. Previously it could raise a CancelledError instead of an TimeoutError in such cases.

gh-102871 [https://github.com/python/cpython/issues/102871]: Remove support for obsolete browsers from webbrowser. Removed browsers include Grail, Mosaic, Netscape, Galeon, Skipstone, Iceape, Firebird, and Firefox versions 35 and below.

gh-102839 [https://github.com/python/cpython/issues/102839]: Improve performance of math.log() arguments handling by removing the argument clinic.

gh-102828 [https://github.com/python/cpython/issues/102828]: Add the onexc arg to shutil.rmtree(), which is like onerror but expects an exception instance rather than an exc_info tuple. Deprecate onerror.

gh-88965 [https://github.com/python/cpython/issues/88965]: typing: Fix a bug relating to substitution in custom classes generic over a ParamSpec. Previously, if the ParamSpec was substituted with a parameters list that itself contained a TypeVar, the TypeVar in the parameters list could not be subsequently substituted. This is now fixed.

Patch by Nikita Sobolev.

gh-76846 [https://github.com/python/cpython/issues/76846]: Fix issue where __new__() and __init__() methods of pathlib.PurePath and Path subclasses were not called in some circumstances.

gh-78530 [https://github.com/python/cpython/issues/78530]: asyncio.wait() now accepts generators yielding tasks. Patch by Kumar Aditya.

gh-102748 [https://github.com/python/cpython/issues/102748]: asyncio.iscoroutine() now returns False for generators as asyncio does not support legacy generator-based coroutines. Patch by Kumar Aditya.

gh-102670 [https://github.com/python/cpython/issues/102670]: Optimized fmean(), correlation(), covariance(), and linear_regression() using the new math.sumprod() function.

gh-102615 [https://github.com/python/cpython/issues/102615]: Typing: Improve the repr of generic aliases for classes generic over a ParamSpec. (Use square brackets to represent a parameter list.)

gh-100112 [https://github.com/python/cpython/issues/100112]: asyncio.Task.get_coro() now always returns a coroutine when wrapping an awaitable object. Patch by Kumar Aditya.

gh-102578 [https://github.com/python/cpython/issues/102578]: Speed up setting or deleting mutable attributes on non-dataclass subclasses of frozen dataclasses. Due to the implementation of __setattr__ and __delattr__ for frozen dataclasses, this previously had a time complexity of O(n). It now has a time complexity of O(1).

gh-102519 [https://github.com/python/cpython/issues/102519]: Add os.listdrives(), os.listvolumes() and os.listmounts() functions on Windows for enumerating drives, volumes and mount points

gh-74468 [https://github.com/python/cpython/issues/74468]: Attribute name of the extracted tarfile file object now holds filename of itself rather than of the archive it is contained in. Patch by Oleg Iarygin.

gh-102378 [https://github.com/python/cpython/issues/102378]: Private helper method inspect._signature_strip_non_python_syntax will no longer strip / from the input string.

gh-79940 [https://github.com/python/cpython/issues/79940]: Add inspect.getasyncgenstate() and inspect.getasyncgenlocals(). Patch by Thomas Krennwallner.

gh-102103 [https://github.com/python/cpython/issues/102103]: Add module argument to dataclasses.make_dataclass() and make classes produced by it pickleable.

gh-102069 [https://github.com/python/cpython/issues/102069]: Fix __weakref__ descriptor generation for custom dataclasses.

gh-102038 [https://github.com/python/cpython/issues/102038]: Skip a stat in site if we have already found a pyvenv.cfg

gh-98886 [https://github.com/python/cpython/issues/98886]: Fix issues when defining dataclasses that have fields with specific underscore names that aren't clearly reserved by dataclasses.

gh-101673 [https://github.com/python/cpython/issues/101673]: Fix a pdb bug where ll clears the changes to local variables.

gh-101313 [https://github.com/python/cpython/issues/101313]: Added -h and --help arguments to the webbrowser CLI

gh-100372 [https://github.com/python/cpython/issues/100372]: ssl.SSLContext.load_verify_locations() no longer incorrectly accepts some cases of trailing data when parsing DER.

gh-89727 [https://github.com/python/cpython/issues/89727]: Fix pathlib.Path.walk RecursionError on deep directory trees by rewriting it using iteration instead of recursion.

gh-100131 [https://github.com/python/cpython/issues/100131]: Added an optional delete keyword argument to tempfile.TemporaryDirectory.

gh-48330 [https://github.com/python/cpython/issues/48330]: Added --durations command line option, showing the N slowest test cases. unittest.TextTestRunner and unittest.TextTestResult constructors accept a new durations keyword argument. Subclasses should take this into account or accept **kwargs. Added unittest.TestResult.addDuration() method and unittest.TestResult.collectedDurations attribute.

(Contributed by Giampaolo Rodola)

gh-98169 [https://github.com/python/cpython/issues/98169]: Fix dataclasses.astuple() crash when collections.defaultdict is present in the attributes.

gh-96931 [https://github.com/python/cpython/issues/96931]: Fix incorrect results from ssl.SSLSocket.shared_ciphers()

gh-95495 [https://github.com/python/cpython/issues/95495]: When built against OpenSSL 3.0, the ssl module had a bug where it reported unauthenticated EOFs (i.e. without close_notify) as a clean TLS-level EOF. It now raises SSLEOFError, matching the behavior in previous versions of OpenSSL. The options attribute on SSLContext also no longer includes OP_IGNORE_UNEXPECTED_EOF by default. This option may be set to specify the previous OpenSSL 3.0 behavior.

gh-94684 [https://github.com/python/cpython/issues/94684]: Now uuid.uuid3() and uuid.uuid5() functions support bytes objects as their name argument.

gh-94440 [https://github.com/python/cpython/issues/94440]: Fix a concurrent.futures.process bug where ProcessPoolExecutor shutdown could hang after a future has been quickly submitted and canceled.

gh-72346 [https://github.com/python/cpython/issues/72346]: Added deprecation warning to isdst parameter of email.utils.localtime().

bpo-36305 [https://bugs.python.org/issue?@action=redirect&bpo=36305]: Fix handling of Windows filenames that resemble drives, such as ./a:b, in pathlib.

Documentation

gh-103112 [https://github.com/python/cpython/issues/103112]: Add docstring to http.client.HTTPResponse.read() to fix pydoc output.

Tests

gh-102980 [https://github.com/python/cpython/issues/102980]: Improve test coverage on pdb.

gh-102537 [https://github.com/python/cpython/issues/102537]: Adjust the error handling strategy in test_zoneinfo.TzPathTest.python_tzpath_context. Patch by Paul Ganssle.

gh-101377 [https://github.com/python/cpython/issues/101377]: Improved test_locale_calendar_formatweekday of calendar.

Build

gh-102973 [https://github.com/python/cpython/issues/102973]: Add a dev container (along with accompanying Dockerfile) for development purposes.

gh-102711 [https://github.com/python/cpython/issues/102711]: Fix -Wstrict-prototypes compiler warnings.

Windows

gh-102690 [https://github.com/python/cpython/issues/102690]: Update webbrowser to fall back to Microsoft Edge instead of Internet Explorer.

gh-99726 [https://github.com/python/cpython/issues/99726]: Improves correctness of stat results for Windows, and uses faster API when available

Tools/Demos

gh-102809 [https://github.com/python/cpython/issues/102809]: Misc/gdbinit was removed.

C API

gh-102013 [https://github.com/python/cpython/issues/102013]: Add a new (unstable) C-API function for iterating over GC'able objects using a callback: PyUnstable_VisitObjects.

Python 3.12.0 alpha 6

Release date: 2023-03-07

Security

gh-99108 [https://github.com/python/cpython/issues/99108]: Replace builtin hashlib implementations of MD5 and SHA1 with verified ones from the HACL* project.

gh-101727 [https://github.com/python/cpython/issues/101727]: Updated the OpenSSL version used in Windows and macOS binary release builds to 1.1.1t to address CVE 2023-0286 [https://www.cve.org/CVERecord?id=CVE-2023-0286], CVE 2022-4303 [https://www.cve.org/CVERecord?id=CVE-2022-4303], and CVE 2022-4303 [https://www.cve.org/CVERecord?id=CVE-2022-4303] per the OpenSSL 2023-02-07 security advisory [https://openssl-library.org/news/secadv/20230207.txt].

gh-99108 [https://github.com/python/cpython/issues/99108]: Replace the builtin hashlib implementations of SHA2-384 and SHA2-512 originally from LibTomCrypt with formally verified, side-channel resistant code from the HACL* [https://github.com/hacl-star/hacl-star/] project. The builtins remain a fallback only used when OpenSSL does not provide them.

gh-101283 [https://github.com/python/cpython/issues/101283]: subprocess.Popen now uses a safer approach to find cmd.exe when launching with shell=True. Patch by Eryk Sun, based on a patch by Oleg Iarygin.

Core and Builtins

gh-102493 [https://github.com/python/cpython/issues/102493]: Fix regression in semantics of normalisation in PyErr_SetObject.

gh-102416 [https://github.com/python/cpython/issues/102416]: Do not memoize incorrectly automatically generated loop rules in the parser. Patch by Pablo Galindo.

gh-102356 [https://github.com/python/cpython/issues/102356]: Fix a bug that caused a crash when deallocating deeply nested filter objects. Patch by Marta Gómez Macías.

gh-102336 [https://github.com/python/cpython/issues/102336]: Cleanup Windows 7 specific special handling. Patch by Max Bachmann.

gh-102250 [https://github.com/python/cpython/issues/102250]: Fixed a segfault occurring when the interpreter calls a __bool__ method that raises.

gh-102126 [https://github.com/python/cpython/issues/102126]: Fix deadlock at shutdown when clearing thread states if any finalizer tries to acquire the runtime head lock. Patch by Kumar Aditya.

gh-102027 [https://github.com/python/cpython/issues/102027]: Use GetCurrentProcessId on Windows when getpid is unavailable. Patch by Max Bachmann.

gh-102056 [https://github.com/python/cpython/issues/102056]: Fix error handling bugs in interpreter's exception printing code, which could cause a crash on infinite recursion.

gh-100982 [https://github.com/python/cpython/issues/100982]: Restrict the scope of the FOR_ITER_RANGE instruction to the scope of the original FOR_ITER instruction, to allow instrumentation.

gh-101967 [https://github.com/python/cpython/issues/101967]: Fix possible segfault in positional_only_passed_as_keyword function, when new list created.

gh-101952 [https://github.com/python/cpython/issues/101952]: Fix possible segfault in BUILD_SET opcode, when new set created.

gh-74895 [https://github.com/python/cpython/issues/74895]: socket.getaddrinfo no longer raises OverflowError for int port values outside of the C long range. Out of range values are left up to the underlying string based C library API to report. A socket.gaierror SAI_SERVICE may occur instead, or no error at all as not all platform C libraries generate an error.

gh-101799 [https://github.com/python/cpython/issues/101799]: Add CALL_INTRINSIC_2 and use it instead of PREP_RERAISE_STAR.

gh-101857 [https://github.com/python/cpython/issues/101857]: Fix xattr support detection on Linux systems by widening the check to linux, not just glibc. This fixes support for musl.

gh-84783 [https://github.com/python/cpython/issues/84783]: Make the slice object hashable. Patch by Will Bradshaw and Furkan Onder.

gh-87849 [https://github.com/python/cpython/issues/87849]: Change the SEND instruction to leave the receiver on the stack. This allows the specialized form of SEND to skip the chain of C calls and jump directly to the RESUME in the generator or coroutine.

gh-101765 [https://github.com/python/cpython/issues/101765]: Fix SystemError / segmentation fault in iter __reduce__ when internal access of builtins.__dict__ keys mutates the iter object.

gh-101430 [https://github.com/python/cpython/issues/101430]: Update tracemalloc to handle presize of object properly. Patch by Donghee Na.

gh-101696 [https://github.com/python/cpython/issues/101696]: Invalidate type version tag in _PyStaticType_Dealloc for static types, avoiding bug where a false cache hit could crash the interpreter. Patch by Kumar Aditya.

gh-101632 [https://github.com/python/cpython/issues/101632]: Adds a new RETURN_CONST instruction.

gh-100719 [https://github.com/python/cpython/issues/100719]: Remove gi_code field from generator (and coroutine and async generator) objects as it is redundant. The frame already includes a reference to the code object.

gh-98627 [https://github.com/python/cpython/issues/98627]: When an interpreter is configured to check (and only then), importing an extension module will now fail when the extension does not support multiple interpreters (i.e. doesn't implement PEP 489 multi-phase init). This does not apply to the main interpreter, nor to subinterpreters created with Py_NewInterpreter().

Library

gh-102302 [https://github.com/python/cpython/issues/102302]: Micro-optimise hashing of inspect.Parameter, reducing the time it takes to hash an instance by around 40%.

gh-101979 [https://github.com/python/cpython/issues/101979]: Fix a bug where parentheses in the metavar argument to argparse.ArgumentParser.add_argument() were dropped. Patch by Yeojin Kim.

gh-91038 [https://github.com/python/cpython/issues/91038]: platform.platform() now has boolean default arguments.

gh-81652 [https://github.com/python/cpython/issues/81652]: Add mmap.MAP_ALIGNED_SUPER FreeBSD and mmap.MAP_CONCEAL OpenBSD constants to mmap. Patch by Yeojin Kim.

gh-102179 [https://github.com/python/cpython/issues/102179]: Fix os.dup2() error message for negative fds.

gh-101961 [https://github.com/python/cpython/issues/101961]: For the binary mode, fileinput.hookcompressed() doesn't set the encoding value even if the value is None. Patch by Gihwan Kim.

gh-101936 [https://github.com/python/cpython/issues/101936]: The default value of fp becomes io.BytesIO if HTTPError is initialized without a designated fp parameter. Patch by Long Vo.

gh-101566 [https://github.com/python/cpython/issues/101566]: In zipfile, sync Path with zipp 3.14 [https://zipp.readthedocs.io/en/latest/history.html#v3-14-0], including fix for extractall on the underlying zipfile after being wrapped in Path.

gh-97930 [https://github.com/python/cpython/issues/97930]: Apply changes from importlib_resources 5.12 [https://importlib-resources.readthedocs.io/en/latest/history.html#v5-12-0], including fix for MultiplexedPath to support directories in multiple namespaces (python/importlib_resources#265).

gh-101997 [https://github.com/python/cpython/issues/101997]: Upgrade pip wheel bundled with ensurepip (pip 23.0.1)

gh-99108 [https://github.com/python/cpython/issues/99108]: The built-in extension modules for hashlib SHA2 algorithms, used when OpenSSL does not provide them, now live in a single internal _sha2 module instead of separate _sha256 and _sha512 modules.

gh-101892 [https://github.com/python/cpython/issues/101892]: Callable iterators no longer raise SystemError when the callable object exhausts the iterator but forgets to either return a sentinel value or raise StopIteration.

gh-87634 [https://github.com/python/cpython/issues/87634]: Remove locking behavior from functools.cached_property().

gh-97786 [https://github.com/python/cpython/issues/97786]: Fix potential undefined behaviour in corner cases of floating-point-to-time conversions.

gh-101517 [https://github.com/python/cpython/issues/101517]: Fixed bug where bdb looks up the source line with linecache with a lineno=None, which causes it to fail with an unhandled exception.

gh-101773 [https://github.com/python/cpython/issues/101773]: Optimize fractions.Fraction for small components. The private argument _normalize of the fractions.Fraction constructor has been removed.

gh-101693 [https://github.com/python/cpython/issues/101693]: In sqlite3.Cursor.execute(), DeprecationWarning is now emitted when named placeholders are used together with parameters supplied as a sequence instead of as a dict. Starting from Python 3.14, using named placeholders with parameters supplied as a sequence will raise a ProgrammingError. Patch by Erlend E. Aasland.

gh-101446 [https://github.com/python/cpython/issues/101446]: Change repr of collections.OrderedDict to use regular dictionary formatting instead of pairs of keys and values.

gh-101362 [https://github.com/python/cpython/issues/101362]: Speed up pathlib.PurePath construction by handling arguments more uniformly. When a pathlib.Path argument is supplied, we use its string representation rather than joining its parts with os.path.join().

gh-101362 [https://github.com/python/cpython/issues/101362]: Speed up pathlib.PurePath construction by calling os.path.join() only when two or more arguments are given.

gh-101362 [https://github.com/python/cpython/issues/101362]: Speed up pathlib.Path construction by running the path flavour compatibility check only when pathlib is imported.

gh-85984 [https://github.com/python/cpython/issues/85984]: Refactored the implementation of pty.fork() to use os.login_tty().

A DeprecationWarning is now raised by pty.master_open() and pty.slave_open(). They were undocumented and deprecated long long ago in the docstring in favor of pty.openpty().

gh-101561 [https://github.com/python/cpython/issues/101561]: Add a new decorator typing.override(). See PEP 698 [https://peps.python.org/pep-0698/] for details. Patch by Steven Troxler.

gh-63301 [https://github.com/python/cpython/issues/63301]: Set exit code when tabnanny CLI exits on error.

gh-101360 [https://github.com/python/cpython/issues/101360]: Fix anchor matching in pathlib.PureWindowsPath.match(). Path and pattern anchors are now matched with fnmatch, just like other path parts. This allows patterns such as "*:/Users/*" to be matched.

gh-101277 [https://github.com/python/cpython/issues/101277]: Remove global state from itertools module (PEP 687 [https://peps.python.org/pep-0687/]). Patches by Erlend E. Aasland.

gh-100809 [https://github.com/python/cpython/issues/100809]: Fix handling of drive-relative paths (like 'C:' and 'C:foo') in pathlib.Path.absolute(). This method now uses the OS API to retrieve the correct current working directory for the drive.

gh-99138 [https://github.com/python/cpython/issues/99138]: Apply PEP 687 [https://peps.python.org/pep-0687/] to zoneinfo. Patch by Erlend E. Aasland.

gh-96764 [https://github.com/python/cpython/issues/96764]: asyncio.wait_for() now uses asyncio.timeout() as its underlying implementation. Patch by Kumar Aditya.

gh-88233 [https://github.com/python/cpython/issues/88233]: Correctly preserve "extra" fields in zipfile regardless of their ordering relative to a zip64 "extra."

bpo-23224 [https://bugs.python.org/issue?@action=redirect&bpo=23224]: Fix segfaults when creating lzma.LZMADecompressor and bz2.BZ2Decompressor objects without calling __init__(), and fix leakage of locks and internal buffers when calling the __init__() methods of lzma.LZMADecompressor, lzma.LZMACompressor, bz2.BZ2Compressor, and bz2.BZ2Decompressor objects multiple times.

Documentation

gh-85417 [https://github.com/python/cpython/issues/85417]: Update cmath documentation to clarify behaviour on branch cuts.

gh-97725 [https://github.com/python/cpython/issues/97725]: Fix asyncio.Task.print_stack() description for file=None. Patch by Oleg Iarygin.

Tests

gh-102019 [https://github.com/python/cpython/issues/102019]: Fix deadlock on shutdown if test_current_{exception,frames} fails. Patch by Jacob Bower.

gh-85984 [https://github.com/python/cpython/issues/85984]: Utilize new "winsize" functions from termios in pty tests.

gh-89792 [https://github.com/python/cpython/issues/89792]: test_tools now copies up to 10x less source data to a temporary directory during the freeze test by ignoring git metadata and other artifacts. It also limits its python build parallelism based on os.cpu_count instead of hard coding it as 8 cores.

Build

gh-99942 [https://github.com/python/cpython/issues/99942]: On Android, in a static build, python-config in embed mode no longer incorrectly reports a library to link to.

gh-99942 [https://github.com/python/cpython/issues/99942]: On Android, python.pc now correctly reports the library to link to, the same as python-config.sh.

gh-100221 [https://github.com/python/cpython/issues/100221]: Fix creating install directories in make sharedinstall if they exist outside DESTDIR already.

gh-96821 [https://github.com/python/cpython/issues/96821]: Explicitly mark C extension modules that need defined signed integer overflow, and add a configure option --with-strict-overflow. Patch by Matthias Görgens and Shantanu Jain.

Windows

gh-102344 [https://github.com/python/cpython/issues/102344]: Implement winreg.QueryValue using QueryValueEx and winreg.SetValue using SetValueEx. Patch by Max Bachmann.

gh-101881 [https://github.com/python/cpython/issues/101881]: Handle read and write operations on non-blocking pipes properly on Windows.

gh-101881 [https://github.com/python/cpython/issues/101881]: Add support for the os.get_blocking() and os.set_blocking() functions on Windows.

gh-101849 [https://github.com/python/cpython/issues/101849]: Ensures installer will correctly upgrade existing py.exe launcher installs.

gh-101763 [https://github.com/python/cpython/issues/101763]: Updates copy of libffi bundled with Windows installs to 3.4.4.

gh-101759 [https://github.com/python/cpython/issues/101759]: Update Windows installer to SQLite 3.40.1.

gh-101614 [https://github.com/python/cpython/issues/101614]: Correctly handle extensions built against debug binaries that reference python3_d.dll.

gh-101196 [https://github.com/python/cpython/issues/101196]: The functions os.path.isdir, os.path.isfile, os.path.islink and os.path.exists are now 13% to 28% faster on Windows, by making fewer Win32 API calls.

macOS

gh-101759 [https://github.com/python/cpython/issues/101759]: Update macOS installer to SQLite 3.40.1.

C API

gh-101907 [https://github.com/python/cpython/issues/101907]: Removes use of non-standard C++ extension in public header files.

gh-99293 [https://github.com/python/cpython/issues/99293]: Document that the Py_TPFLAGS_VALID_VERSION_TAG is an internal feature, should not be used, and will be removed.

gh-101578 [https://github.com/python/cpython/issues/101578]: Add PyErr_GetRaisedException() and PyErr_SetRaisedException() for saving and restoring the current exception. These functions return and accept a single exception object, rather than the triple arguments of the now-deprecated PyErr_Fetch() and PyErr_Restore(). This is less error prone and a bit more efficient.

Add PyException_GetArgs() and PyException_SetArgs() as convenience functions for retrieving and modifying the args passed to the exception's constructor.

gh-91744 [https://github.com/python/cpython/issues/91744]: Introduced the Unstable C API tier, marking APi that is allowed to change in minor releases without a deprecation period. See PEP 689 [https://peps.python.org/pep-0689/] for details.

Python 3.12.0 alpha 5

Release date: 2023-02-07

Security

gh-99108 [https://github.com/python/cpython/issues/99108]: Replace the builtin hashlib implementations of SHA2-224 and SHA2-256 originally from LibTomCrypt with formally verified, side-channel resistant code from the HACL* [https://github.com/hacl-star/hacl-star/] project. The builtins remain a fallback only used when OpenSSL does not provide them.

Core and Builtins

gh-92173 [https://github.com/python/cpython/issues/92173]: Fix the defs and kwdefs arguments to PyEval_EvalCodeEx() and a reference leak in that function.

gh-59956 [https://github.com/python/cpython/issues/59956]: The GILState API is now partially compatible with subinterpreters. Previously, PyThreadState_GET() and PyGILState_GetThisThreadState() would get out of sync, causing inconsistent behavior and crashes.

gh-101400 [https://github.com/python/cpython/issues/101400]: Fix wrong lineno in exception message on continue or break which are not in a loop. Patch by Donghee Na.

gh-101372 [https://github.com/python/cpython/issues/101372]: Fix is_normalized() to properly handle the UCD 3.2.0 cases. Patch by Donghee Na.

gh-101266 [https://github.com/python/cpython/issues/101266]: Fix sys.getsizeof() reporting for int subclasses.

gh-101291 [https://github.com/python/cpython/issues/101291]: Refactor the PyLongObject struct into a normal Python object header and a PyLongValue struct.

gh-101046 [https://github.com/python/cpython/issues/101046]: Fix a possible memory leak in the parser when raising MemoryError. Patch by Pablo Galindo

gh-101037 [https://github.com/python/cpython/issues/101037]: Fix potential memory underallocation issue for instances of int subclasses with value zero.

gh-100762 [https://github.com/python/cpython/issues/100762]: Record the (virtual) exception block depth in the oparg of YIELD_VALUE. Use this to avoid the expensive throw() when closing generators (and coroutines) that can be closed trivially.

gh-100982 [https://github.com/python/cpython/issues/100982]: Adds a new COMPARE_AND_BRANCH instruction. This is a bit more efficient when performing a comparison immediately followed by a branch, and restores the design intent of PEP 659 that specializations are local to a single instruction.

gh-100942 [https://github.com/python/cpython/issues/100942]: Fixed segfault in property.getter/setter/deleter that occurred when a property subclass overrode the __new__ method to return a non-property instance.

gh-100923 [https://github.com/python/cpython/issues/100923]: Remove the mask cache entry for the COMPARE_OP instruction and embed the mask into the oparg.

gh-100892 [https://github.com/python/cpython/issues/100892]: Fix race while iterating over thread states in clearing threading.local. Patch by Kumar Aditya.

gh-91351 [https://github.com/python/cpython/issues/91351]: Fix a case where re-entrant imports could corrupt the import deadlock detection code and cause a KeyError to be raised out of importlib/_bootstrap. In addition to the straightforward cases, this could also happen when garbage collection leads to a warning being emitted -- as happens when it collects an open socket or file)

gh-100726 [https://github.com/python/cpython/issues/100726]: Optimize construction of range object for medium size integers.

gh-100712 [https://github.com/python/cpython/issues/100712]: Added option to build cpython with specialization disabled, by setting ENABLE_SPECIALIZATION=False in opcode, followed by make regen-all.

Library

bpo-32780 [https://bugs.python.org/issue?@action=redirect&bpo=32780]: Inter-field padding is now inserted into the PEP3118 format strings obtained from ctypes.Structure objects, reflecting their true representation in memory.

gh-101541 [https://github.com/python/cpython/issues/101541]: [Enum] - fix psuedo-flag creation

gh-101570 [https://github.com/python/cpython/issues/101570]: Upgrade pip wheel bundled with ensurepip (pip 23.0)

gh-101323 [https://github.com/python/cpython/issues/101323]: Fix a bug where errors where not thrown by zlib._ZlibDecompressor if encountered during decompressing.

gh-101317 [https://github.com/python/cpython/issues/101317]: Add ssl_shutdown_timeout parameter for asyncio.StreamWriter.start_tls().

gh-101326 [https://github.com/python/cpython/issues/101326]: Fix regression when passing None as second or third argument to FutureIter.throw.

gh-92123 [https://github.com/python/cpython/issues/92123]: Adapt the _elementtree extension module to multi-phase init (PEP 489 [https://peps.python.org/pep-0489/]). Patches by Erlend E. Aasland.

gh-100795 [https://github.com/python/cpython/issues/100795]: Avoid potential unexpected freeaddrinfo call (double free) in socket when when a libc getaddrinfo() implementation leaves garbage in an output pointer when returning an error. Original patch by Sergey G. Brester.

gh-101143 [https://github.com/python/cpython/issues/101143]: Remove unused references to TimerHandle in asyncio.base_events.BaseEventLoop._add_callback.

gh-101144 [https://github.com/python/cpython/issues/101144]: Make zipfile.Path.open() and zipfile.Path.read_text() also accept encoding as a positional argument. This was the behavior in Python 3.9 and earlier. 3.10 introduced a regression where supplying it as a positional argument would lead to a TypeError.

gh-94518 [https://github.com/python/cpython/issues/94518]: Group-related variables of _posixsubprocess module are renamed to stress that supplementary group affinity is added to a fork, not replace the inherited ones. Patch by Oleg Iarygin.

gh-101015 [https://github.com/python/cpython/issues/101015]: Fix typing.get_type_hints() on '*tuple[...]' and *tuple[...]. It must not drop the Unpack part.

gh-101000 [https://github.com/python/cpython/issues/101000]: Add os.path.splitroot(), which splits a path into a 3-item tuple (drive, root, tail). This new function is used by pathlib to improve the performance of path construction by up to a third.

gh-100573 [https://github.com/python/cpython/issues/100573]: Fix a Windows asyncio bug with named pipes where a client doing os.stat() on the pipe would cause an error in the server that disabled serving future requests.

gh-39615 [https://github.com/python/cpython/issues/39615]: warnings.warn() now has the ability to skip stack frames based on code filename prefix rather than only a numeric stacklevel via the new skip_file_prefixes keyword argument.

gh-100750 [https://github.com/python/cpython/issues/100750]: pass encoding kwarg to subprocess in platform

gh-100160 [https://github.com/python/cpython/issues/100160]: Emit a deprecation warning in asyncio.DefaultEventLoopPolicy.get_event_loop() if there is no current event loop set and it decides to create one.

gh-96290 [https://github.com/python/cpython/issues/96290]: Fix handling of partial and invalid UNC drives in ntpath.splitdrive(), and in ntpath.normpath() on non-Windows systems. Paths such as '\server' and '\' are now considered by splitdrive() to contain only a drive, and consequently are not modified by normpath() on non-Windows systems. The behaviour of normpath() on Windows systems is unaffected, as native OS APIs are used. Patch by Eryk Sun, with contributions by Barney Gale.

gh-99952 [https://github.com/python/cpython/issues/99952]: Fix a reference undercounting issue in ctypes.Structure with from_param() results larger than a C pointer.

gh-67790 [https://github.com/python/cpython/issues/67790]: Add float-style formatting support for fractions.Fraction instances.

gh-99266 [https://github.com/python/cpython/issues/99266]: Preserve more detailed error messages in ctypes.

gh-86682 [https://github.com/python/cpython/issues/86682]: Ensure runtime-created collections have the correct module name using the newly added (internal) sys._getframemodulename().

gh-88597 [https://github.com/python/cpython/issues/88597]: uuid now has a command line interface. Try python -m uuid -h.

gh-60580 [https://github.com/python/cpython/issues/60580]: ctypes.wintypes.BYTE definition changed from c_byte to c_ubyte to match Windows SDK. Patch by Anatoly Techtonik and Oleg Iarygin.

gh-94518 [https://github.com/python/cpython/issues/94518]: _posixsubprocess now initializes all UID and GID variables using a reserved -1 value instead of a separate flag. Patch by Oleg Iarygin.

bpo-38941 [https://bugs.python.org/issue?@action=redirect&bpo=38941]: The xml.etree.ElementTree module now emits DeprecationWarning when testing the truth value of an xml.etree.ElementTree.Element. Before, the Python implementation emitted FutureWarning, and the C implementation emitted nothing.

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert elementtree types to heap types. Patch by Erlend E. Aasland.

bpo-29847 [https://bugs.python.org/issue?@action=redirect&bpo=29847]: Fix a bug where pathlib.Path accepted and ignored keyword arguments. Patch provided by Yurii Karabas.

gh-77772 [https://github.com/python/cpython/issues/77772]: ctypes.CDLL, ctypes.OleDLL, ctypes.WinDLL, and ctypes.PyDLL now accept path-like objects as their name argument. Patch by Robert Hoelzl.

Documentation

gh-88324 [https://github.com/python/cpython/issues/88324]: Reword subprocess to emphasize default behavior of stdin, stdout, and stderr arguments. Remove inaccurate statement about child file handle inheritance.

Tests

gh-101334 [https://github.com/python/cpython/issues/101334]: test_tarfile has been updated to pass when run as a high UID.

Build

gh-101282 [https://github.com/python/cpython/issues/101282]: Update BOLT configuration not to use deprecated usage of --split functions. Patch by Donghee Na.

gh-101522 [https://github.com/python/cpython/issues/101522]: Allow overriding Windows dependencies versions and paths using MSBuild properties.

gh-77532 [https://github.com/python/cpython/issues/77532]: Minor fixes to allow building with PlatformToolset=ClangCL on Windows.

gh-101152 [https://github.com/python/cpython/issues/101152]: In accordance with PEP 699 [https://peps.python.org/pep-0699/], the ma_version_tag field in PyDictObject is deprecated for extension modules. Accessing this field will generate a compiler warning at compile time. This field will be removed in Python 3.14.

gh-100340 [https://github.com/python/cpython/issues/100340]: Allows -Wno-int-conversion for wasm-sdk 17 and onwards, thus enables building WASI builds once against the latest sdk.

gh-101060 [https://github.com/python/cpython/issues/101060]: Conditionally add -fno-reorder-blocks-and-partition in configure. Effectively fixes --enable-bolt when using Clang, as this appears to be a GCC-only flag.

gh-98705 [https://github.com/python/cpython/issues/98705]: __bool__ is defined in AIX system header files which breaks the build in AIX, so undefine it.

gh-98636 [https://github.com/python/cpython/issues/98636]: Fix a regression in detecting gdbm_compat library for the _gdbm module build.

gh-96305 [https://github.com/python/cpython/issues/96305]: _aix_support now uses a simple code to get platform details rather than the now non-existent _bootsubprocess during bootstrap.

Windows

gh-101543 [https://github.com/python/cpython/issues/101543]: Ensure the install path in the registry is only used when the standard library hasn't been located in any other way.

gh-101467 [https://github.com/python/cpython/issues/101467]: The py.exe launcher now correctly filters when only a single runtime is installed. It also correctly handles prefix matches on tags so that -3.1 does not match 3.11, but would still match 3.1-32.

gh-99834 [https://github.com/python/cpython/issues/99834]: Updates bundled copy of Tcl/Tk to 8.6.13.0

gh-101135 [https://github.com/python/cpython/issues/101135]: Restore ability to launch older 32-bit versions from the py.exe launcher when both 32-bit and 64-bit installs of the same version are available.

gh-82052 [https://github.com/python/cpython/issues/82052]: Fixed an issue where writing more than 32K of Unicode output to the console screen in one go can result in mojibake.

gh-100320 [https://github.com/python/cpython/issues/100320]: Ensures the PythonPath registry key from an install is used when launching from a different copy of Python that relies on an existing install to provide a copy of its modules and standard library.

gh-100247 [https://github.com/python/cpython/issues/100247]: Restores support for the py.exe launcher finding shebang commands in its configuration file using the full command name.

Python 3.12.0 alpha 4

Release date: 2023-01-10

Core and Builtins

gh-100776 [https://github.com/python/cpython/issues/100776]: Fix misleading default value in input()'s __text_signature__.

gh-99005 [https://github.com/python/cpython/issues/99005]: Remove UNARY_POSITIVE, ASYNC_GEN_WRAP and LIST_TO_TUPLE, replacing them with intrinsics.

gh-99005 [https://github.com/python/cpython/issues/99005]: Add new CALL_INTRINSIC_1 instruction. Remove IMPORT_STAR, PRINT_EXPR and STOPITERATION_ERROR, replacing them with the CALL_INTRINSIC_1 instruction.

gh-100288 [https://github.com/python/cpython/issues/100288]: Remove the LOAD_ATTR_METHOD_WITH_DICT specialized instruction. Stats show it is not useful.

gh-100720 [https://github.com/python/cpython/issues/100720]: Added _PyFrame_NumSlotsForCodeObject, which returns the number of slots needed in a frame for a given code object.

gh-100719 [https://github.com/python/cpython/issues/100719]: Removed the co_nplaincellvars field from the code object, as it is redundant.

gh-100637 [https://github.com/python/cpython/issues/100637]: Fix int.__sizeof__() calculation to include the 1-element ob_digit array for 0 and False.

gh-100649 [https://github.com/python/cpython/issues/100649]: Update the native_thread_id field of PyThreadState after fork.

gh-100126 [https://github.com/python/cpython/issues/100126]: Fix an issue where "incomplete" frames could be briefly visible to C code while other frames are being torn down, possibly resulting in corruption or hard crashes of the interpreter while running finalizers.

gh-87447 [https://github.com/python/cpython/issues/87447]: Fix SyntaxError on comprehension rebind checking with names that are not actually redefined.

Now reassigning b in [(b := 1) for a, b.prop in some_iter] is allowed. Reassigning a is still disallowed as per PEP 572 [https://peps.python.org/pep-0572/].

gh-100268 [https://github.com/python/cpython/issues/100268]: Add int.is_integer() to improve duck type compatibility between int and float.

gh-100425 [https://github.com/python/cpython/issues/100425]: Improve the accuracy of sum() with compensated summation.

Library

gh-100374 [https://github.com/python/cpython/issues/100374]: Fix incorrect result and delay in socket.getfqdn(). Patch by Dominic Socular.

Core and Builtins

gh-100357 [https://github.com/python/cpython/issues/100357]: Convert vars, dir, next, getattr, and iter to argument clinic.

gh-100117 [https://github.com/python/cpython/issues/100117]: Improve the output of codeobject.co_lines() by emitting only one entry for each line range.

gh-90043 [https://github.com/python/cpython/issues/90043]: Handle NaNs when specializing COMPARE_OP for float values.

gh-100222 [https://github.com/python/cpython/issues/100222]: Redefine the _Py_CODEUNIT typedef as a union to describe its layout to the C compiler, avoiding type punning and improving clarity.

gh-99955 [https://github.com/python/cpython/issues/99955]: Internal compiler functions (in compile.c) now consistently return -1 on error and 0 on success.

gh-100188 [https://github.com/python/cpython/issues/100188]: The BINARY_SUBSCR_LIST_INT and BINARY_SUBSCR_TUPLE_INT instructions are no longer used for negative integers because those instructions always miss when encountering negative integers.

gh-99110 [https://github.com/python/cpython/issues/99110]: Initialize frame->previous in frameobject.c to fix a segmentation fault when accessing frames created by PyFrame_New().

gh-94155 [https://github.com/python/cpython/issues/94155]: Improved the hashing algorithm for code objects, mitigating some hash collisions.

gh-99540 [https://github.com/python/cpython/issues/99540]: None now hashes to a constant value. This is not a requirements change.

gh-100143 [https://github.com/python/cpython/issues/100143]: When built with --enable-pystats, stats collection is now off by default. To enable it early at startup, pass the -Xpystats flag. Stats are now always dumped, even if switched off.

gh-100146 [https://github.com/python/cpython/issues/100146]: Improve BUILD_LIST opcode so that it works similarly to the BUILD_TUPLE opcode, by stealing references from the stack rather than repeatedly using stack operations to set list elements. Implementation details are in a new private API _PyList_FromArraySteal().

gh-100110 [https://github.com/python/cpython/issues/100110]: Specialize FOR_ITER for tuples.

gh-100050 [https://github.com/python/cpython/issues/100050]: Honor existing errors obtained when searching for mismatching parentheses in the tokenizer. Patch by Pablo Galindo

gh-92216 [https://github.com/python/cpython/issues/92216]: Improve the performance of hasattr() for type objects with a missing attribute.

gh-99582 [https://github.com/python/cpython/issues/99582]: Freeze zipimport module into _bootstrap_python.

gh-99554 [https://github.com/python/cpython/issues/99554]: Pack debugging location tables more efficiently during bytecode compilation.

gh-98522 [https://github.com/python/cpython/issues/98522]: Add an internal version number to code objects, to give better versioning of inner functions and comprehensions, and thus better specialization of those functions. This change is invisible to both Python and C extensions.

gh-94603 [https://github.com/python/cpython/issues/94603]: Improve performance of list.pop for small lists.

Library

gh-89051 [https://github.com/python/cpython/issues/89051]: Add ssl.OP_LEGACY_SERVER_CONNECT

Core and Builtins

bpo-32782 [https://bugs.python.org/issue?@action=redirect&bpo=32782]: ctypes arrays of length 0 now report a correct itemsize when a memoryview is constructed from them, rather than always giving a value of 0.

Library

gh-100833 [https://github.com/python/cpython/issues/100833]: Speed up math.fsum() by removing defensive volatile qualifiers.

gh-100805 [https://github.com/python/cpython/issues/100805]: Modify random.choice() implementation to once again work with NumPy arrays.

gh-100813 [https://github.com/python/cpython/issues/100813]: Add socket.IP_PKTINFO constant.

gh-100792 [https://github.com/python/cpython/issues/100792]: Make email.message.Message.__contains__() twice as fast.

gh-91851 [https://github.com/python/cpython/issues/91851]: Microoptimizations for fractions.Fraction.__round__(), fractions.Fraction.__ceil__() and fractions.Fraction.__floor__().

gh-90104 [https://github.com/python/cpython/issues/90104]: Avoid RecursionError on repr if a dataclass field definition has a cyclic reference.

gh-100689 [https://github.com/python/cpython/issues/100689]: Fix crash in pyexpat by statically allocating PyExpat_CAPI capsule.

gh-100740 [https://github.com/python/cpython/issues/100740]: Fix unittest.mock.Mock not respecting the spec for attribute names prefixed with assert.

gh-91219 [https://github.com/python/cpython/issues/91219]: Change SimpleHTTPRequestHandler to support subclassing to provide a different set of index file names instead of using __init__ parameters.

gh-100690 [https://github.com/python/cpython/issues/100690]: Mock objects which are not unsafe will now raise an AttributeError when accessing an attribute that matches the name of an assertion but without the prefix assert_, e.g. accessing called_once instead of assert_called_once. This is in addition to this already happening for accessing attributes with prefixes assert, assret, asert, aseert, and assrt.

gh-89727 [https://github.com/python/cpython/issues/89727]: Simplify and optimize os.walk() by using isinstance() checks to check the top of the stack.

gh-100485 [https://github.com/python/cpython/issues/100485]: Add math.sumprod() to compute the sum of products.

gh-86508 [https://github.com/python/cpython/issues/86508]: Fix asyncio.open_connection() to skip binding to local addresses of different family. Patch by Kumar Aditya.

gh-97930 [https://github.com/python/cpython/issues/97930]: importlib.resources.files now accepts a module as an anchor instead of only accepting packages. If a module is passed, resources are resolved adjacent to that module (in the same package or at the package root). The parameter was renamed from package to anchor with a compatibility shim for those passing by keyword. Additionally, the new anchor parameter is now optional and will default to the caller's module.

gh-100585 [https://github.com/python/cpython/issues/100585]: Fixed a bug where importlib.resources.as_file was leaving file pointers open

gh-100562 [https://github.com/python/cpython/issues/100562]: Improve performance of pathlib.Path.absolute() by nearly 2x. This comes at the cost of a performance regression in pathlib.Path.cwd(), which is generally used less frequently in user code.

gh-100519 [https://github.com/python/cpython/issues/100519]: Small simplification of http.cookiejar.eff_request_host() that improves readability and better matches the RFC wording.

gh-100287 [https://github.com/python/cpython/issues/100287]: Fix the interaction of unittest.mock.seal() with unittest.mock.AsyncMock.

gh-100488 [https://github.com/python/cpython/issues/100488]: Add Fraction.is_integer() to check whether a fractions.Fraction is an integer. This improves duck type compatibility with float and int.

gh-100474 [https://github.com/python/cpython/issues/100474]: http.server now checks that an index page is actually a regular file before trying to serve it. This avoids issues with directories named index.html.

gh-100363 [https://github.com/python/cpython/issues/100363]: Speed up asyncio.get_running_loop() by removing redundant getpid checks. Patch by Kumar Aditya.

gh-78878 [https://github.com/python/cpython/issues/78878]: Fix crash when creating an instance of _ctypes.CField.

gh-100348 [https://github.com/python/cpython/issues/100348]: Fix ref cycle in asyncio._SelectorSocketTransport by removing _read_ready_cb in close.

gh-100344 [https://github.com/python/cpython/issues/100344]: Provide C implementation for asyncio.current_task() for a 4x-6x speedup.

gh-100272 [https://github.com/python/cpython/issues/100272]: Fix JSON serialization of OrderedDict. It now preserves the order of keys.

gh-83076 [https://github.com/python/cpython/issues/83076]: Instantiation of Mock() and AsyncMock() is now 3.8x faster.

gh-100234 [https://github.com/python/cpython/issues/100234]: Set a default value of 1.0 for the lambd parameter in random.expovariate().

gh-100228 [https://github.com/python/cpython/issues/100228]: A DeprecationWarning may be raised when os.fork() or os.forkpty() is called from multi-threaded processes. Forking with threads is unsafe and can cause deadlocks, crashes and subtle problems. Lack of a warning does not indicate that the fork call was actually safe, as Python may not be aware of all threads.

gh-100039 [https://github.com/python/cpython/issues/100039]: Improve signatures for enums and flags.

gh-100133 [https://github.com/python/cpython/issues/100133]: Fix regression in asyncio where a subprocess would sometimes lose data received from pipe.

bpo-44592 [https://bugs.python.org/issue?@action=redirect&bpo=44592]: Fixes inconsistent handling of case sensitivity of extrasaction arg in csv.DictWriter.

gh-100098 [https://github.com/python/cpython/issues/100098]: Fix tuple subclasses being cast to tuple when used as enum values.

gh-85432 [https://github.com/python/cpython/issues/85432]: Rename the fmt parameter of the pure-Python implementation of datetime.time.strftime() to format. Rename the t parameter of datetime.datetime.fromtimestamp() to timestamp. These changes mean the parameter names in the pure-Python implementation now match the parameter names in the C implementation. Patch by Alex Waygood.

gh-98778 [https://github.com/python/cpython/issues/98778]: Update HTTPError to be initialized properly, even if the fp is None. Patch by Donghee Na.

gh-99925 [https://github.com/python/cpython/issues/99925]: Unify error messages in JSON serialization between json.dumps(float('nan'), allow_nan=False) and json.dumps(float('nan'), allow_nan=False, indent=<SOMETHING>). Now both include the representation of the value that could not be serialized.

gh-89727 [https://github.com/python/cpython/issues/89727]: Fix issue with os.walk() where a RecursionError would occur on deep directory structures by adjusting the implementation of os.walk() to be iterative instead of recursive.

gh-94943 [https://github.com/python/cpython/issues/94943]: Add Dataclass support to the Enum __repr__(). When inheriting from a dataclass, only show the field names in the value section of the member repr(), and not the dataclass' class name.

gh-83035 [https://github.com/python/cpython/issues/83035]: Fix inspect.getsource() handling of decorator calls with nested parentheses.

gh-99576 [https://github.com/python/cpython/issues/99576]: Fix .save() method for LWPCookieJar and MozillaCookieJar: saved file was not truncated on repeated save.

gh-94912 [https://github.com/python/cpython/issues/94912]: Add inspect.markcoroutinefunction() decorator which manually marks a function as a coroutine for the benefit of iscoroutinefunction().

gh-99509 [https://github.com/python/cpython/issues/99509]: Add PEP 585 [https://peps.python.org/pep-0585/] support for multiprocessing.queues.Queue.

gh-99482 [https://github.com/python/cpython/issues/99482]: Remove Jython partial compatibility code from several stdlib modules.

gh-99433 [https://github.com/python/cpython/issues/99433]: Fix doctest failure on types.MethodWrapperType in modules.

gh-85267 [https://github.com/python/cpython/issues/85267]: Several improvements to inspect.signature()'s handling of __text_signature. - Fixes a case where inspect.signature() dropped parameters - Fixes a case where inspect.signature() raised tokenize.TokenError - Allows inspect.signature() to understand defaults involving binary operations of constants - inspect.signature() is documented as only raising TypeError or ValueError, but sometimes raised RuntimeError. These cases now raise ValueError - Removed a dead code path

gh-91166 [https://github.com/python/cpython/issues/91166]: asyncio is optimized to avoid excessive copying when writing to socket and use sendmsg() if the platform supports it. Patch by Kumar Aditya.

gh-98030 [https://github.com/python/cpython/issues/98030]: Add missing TCP socket options from Linux: TCP_MD5SIG, TCP_THIN_LINEAR_TIMEOUTS, TCP_THIN_DUPACK, TCP_REPAIR, TCP_REPAIR_QUEUE, TCP_QUEUE_SEQ, TCP_REPAIR_OPTIONS, TCP_TIMESTAMP, TCP_CC_INFO, TCP_SAVE_SYN, TCP_SAVED_SYN, TCP_REPAIR_WINDOW, TCP_FASTOPEN_CONNECT, TCP_ULP, TCP_MD5SIG_EXT, TCP_FASTOPEN_KEY, TCP_FASTOPEN_NO_COOKIE, TCP_ZEROCOPY_RECEIVE, TCP_INQ, TCP_TX_DELAY.

gh-88500 [https://github.com/python/cpython/issues/88500]: Reduced the memory usage of urllib.parse.unquote() and urllib.parse.unquote_to_bytes() on large values.

gh-96127 [https://github.com/python/cpython/issues/96127]: inspect.signature was raising TypeError on call with mock objects. Now it correctly returns (*args, **kwargs) as inferred signature.

gh-95882 [https://github.com/python/cpython/issues/95882]: Fix a 3.11 regression in asynccontextmanager(), which caused it to propagate exceptions with incorrect tracebacks and fix a 3.11 regression in contextmanager(), which caused it to propagate exceptions with incorrect tracebacks for StopIteration.

gh-78707 [https://github.com/python/cpython/issues/78707]: Deprecate passing more than one positional argument to pathlib.PurePath.relative_to() and is_relative_to().

gh-92122 [https://github.com/python/cpython/issues/92122]: Fix reStructuredText syntax errors in docstrings in the enum module.

gh-91851 [https://github.com/python/cpython/issues/91851]: Optimize the Fraction arithmetics for small components.

bpo-24132 [https://bugs.python.org/issue?@action=redirect&bpo=24132]: Make pathlib.PurePath and Path subclassable (private to start). Previously, attempting to instantiate a subclass resulted in an AttributeError being raised. Patch by Barney Gale.

bpo-40447 [https://bugs.python.org/issue?@action=redirect&bpo=40447]: Accept os.PathLike (such as pathlib.Path) in the stripdir arguments of compileall.compile_file() and compileall.compile_dir().

bpo-36880 [https://bugs.python.org/issue?@action=redirect&bpo=36880]: Fix a reference counting issue when a ctypes callback with return type py_object returns None, which could cause crashes.

Documentation

gh-100616 [https://github.com/python/cpython/issues/100616]: Document existing attr parameter to curses.window.vline() function in curses.

gh-100472 [https://github.com/python/cpython/issues/100472]: Remove claim in documentation that the stripdir, prependdir and limit_sl_dest parameters of compileall.compile_dir() and compileall.compile_file() could be bytes.

bpo-25377 [https://bugs.python.org/issue?@action=redirect&bpo=25377]: Clarify use of octal format of mode argument in help(os.chmod) as well as help(os.fchmod)

Tests

gh-100454 [https://github.com/python/cpython/issues/100454]: Start running SSL tests with OpenSSL 3.1.0-beta1.

gh-100086 [https://github.com/python/cpython/issues/100086]: The Python test runner (libregrtest) now logs Python build information like "debug" vs "release" build, or LTO and PGO optimizations. Patch by Victor Stinner.

gh-93018 [https://github.com/python/cpython/issues/93018]: Make two tests forgiving towards host system libexpat with backported security fixes applied.

Build

gh-100540 [https://github.com/python/cpython/issues/100540]: Removed the --with-system-ffi configure option; libffi must now always be supplied by the system on all non-Windows platforms. The option has had no effect on non-Darwin platforms for several releases, and in 3.11 only had the non-obvious effect of invoking pkg-config to find libffi and never setting -DUSING_APPLE_OS_LIBFFI. Now on Darwin platforms configure will first check for the OS libffi and then fall back to the same processing as other platforms if it is not found.

gh-88267 [https://github.com/python/cpython/issues/88267]: Avoid exporting Python symbols in linked Windows applications when the core is built as static.

bpo-41916 [https://bugs.python.org/issue?@action=redirect&bpo=41916]: Allow override of ac_cv_cxx_thread so that cross compiled python can set -pthread for CXX.

Windows

gh-100180 [https://github.com/python/cpython/issues/100180]: Update Windows installer to OpenSSL 1.1.1s

gh-99191 [https://github.com/python/cpython/issues/99191]: Use _MSVC_LANG >= 202002L instead of less-precise _MSC_VER >=1929 to more accurately test for C++20 support in PC/_wmimodule.cpp.

gh-79218 [https://github.com/python/cpython/issues/79218]: Define MS_WIN64 for Mingw-w64 64bit, fix cython compilation failure.

gh-99941 [https://github.com/python/cpython/issues/99941]: Ensure that asyncio.Protocol.data_received() receives an immutable bytes object (as documented), instead of bytearray.

bpo-43984 [https://bugs.python.org/issue?@action=redirect&bpo=43984]: winreg.SetValueEx() now leaves the target value untouched in the case of conversion errors. Previously, -1 would be written in case of such errors.

bpo-34816 [https://bugs.python.org/issue?@action=redirect&bpo=34816]: hasattr(ctypes.windll, 'nonexistant') now returns False instead of raising OSError.

macOS

gh-100180 [https://github.com/python/cpython/issues/100180]: Update macOS installer to OpenSSL 1.1.1s

gh-100540 [https://github.com/python/cpython/issues/100540]: Removed obsolete dlfcn.h shim from the _ctypes extension module, which has not been necessary since Mac OS X 10.2.

Tools/Demos

bpo-45256 [https://bugs.python.org/issue?@action=redirect&bpo=45256]: Fix a bug that caused an AttributeError to be raised in python-gdb.py when py-locals is used without a frame.

gh-100342 [https://github.com/python/cpython/issues/100342]: Add missing NULL check for possible allocation failure in *args parsing in Argument Clinic.

C API

gh-99947 [https://github.com/python/cpython/issues/99947]: Raising SystemError on import will now have its cause be set to the original unexpected exception.

gh-99240 [https://github.com/python/cpython/issues/99240]: In argument parsing, after deallocating newly allocated memory, reset its pointer to NULL.

gh-98724 [https://github.com/python/cpython/issues/98724]: The Py_CLEAR, Py_SETREF and Py_XSETREF macros now only evaluate their arguments once. If an argument has side effects, these side effects are no longer duplicated. Patch by Victor Stinner.

Python 3.12.0 alpha 3

Release date: 2022-12-06

Security

gh-100001 [https://github.com/python/cpython/issues/100001]: python -m http.server no longer allows terminal control characters sent within a garbage request to be printed to the stderr server log.

This is done by changing the http.server BaseHTTPRequestHandler .log_message method to replace control characters with a \xHH hex escape before printing.

gh-87604 [https://github.com/python/cpython/issues/87604]: Avoid publishing list of active per-interpreter audit hooks via the gc module

Core and Builtins

gh-99891 [https://github.com/python/cpython/issues/99891]: Fix a bug in the tokenizer that could cause infinite recursion when showing syntax warnings that happen in the first line of the source. Patch by Pablo Galindo

gh-91054 [https://github.com/python/cpython/issues/91054]: Add PyCode_AddWatcher() and PyCode_ClearWatcher() APIs to register callbacks to receive notification on creation and destruction of code objects.

gh-99729 [https://github.com/python/cpython/issues/99729]: Fix an issue that could cause frames to be visible to Python code as they are being torn down, possibly leading to memory corruption or hard crashes of the interpreter.

gh-99708 [https://github.com/python/cpython/issues/99708]: Fix bug where compiler crashes on an if expression with an empty body block.

gh-99578 [https://github.com/python/cpython/issues/99578]: Fix a reference bug in _imp.create_builtin() after the creation of the first sub-interpreter for modules builtins and sys. Patch by Victor Stinner.

gh-99581 [https://github.com/python/cpython/issues/99581]: Fixed a bug that was causing a buffer overflow if the tokenizer copies a line missing the newline character from a file that is as long as the available tokenizer buffer. Patch by Pablo galindo

gh-99553 [https://github.com/python/cpython/issues/99553]: Fix bug where an ExceptionGroup subclass can wrap a BaseException.

Library

gh-99547 [https://github.com/python/cpython/issues/99547]: Add a function to os.path to check if a path is a junction: isjunction. Add similar functionality to pathlib.Path as is_junction.

gh-99370 [https://github.com/python/cpython/issues/99370]: Fix zip path for venv created from a non-installed python on POSIX platforms.

Core and Builtins

gh-99377 [https://github.com/python/cpython/issues/99377]: Add audit events for thread creation and clear operations.

gh-98686 [https://github.com/python/cpython/issues/98686]: Remove the BINARY_OP_GENERIC and COMPARE_OP_GENERIC "specializations".

gh-99298 [https://github.com/python/cpython/issues/99298]: Remove the remaining error paths for attribute specializations, and refuse to specialize attribute accesses on types that haven't had PyType_Ready() called on them yet.

gh-99127 [https://github.com/python/cpython/issues/99127]: Allow some features of syslog to the main interpreter only. Patch by Donghee Na.

gh-91053 [https://github.com/python/cpython/issues/91053]: Optimizing interpreters and JIT compilers may need to invalidate internal metadata when functions are modified. This change adds the ability to provide a callback that will be invoked each time a function is created, modified, or destroyed.

gh-90994 [https://github.com/python/cpython/issues/90994]: Improve error messages when there's a syntax error with call arguments. The following three cases are covered: - No value is assigned to a named argument, eg foo(a=). - A value is assigned to a star argument, eg foo(*args=[0]). - A value is assigned to a double-star keyword argument, eg foo(**kwarg={'a': 0}).

bpo-45026 [https://bugs.python.org/issue?@action=redirect&bpo=45026]: Optimize the range object iterator. It is now smaller, faster iteration of ranges containing large numbers. Smaller pickles, faster unpickling.

bpo-31718 [https://bugs.python.org/issue?@action=redirect&bpo=31718]: Raise ValueError instead of SystemError when methods of uninitialized io.IncrementalNewlineDecoder objects are called. Patch by Oren Milman.

bpo-38031 [https://bugs.python.org/issue?@action=redirect&bpo=38031]: Fix a possible assertion failure in io.FileIO when the opener returns an invalid file descriptor.

Library

gh-100001 [https://github.com/python/cpython/issues/100001]: Also escape s in the http.server BaseHTTPRequestHandler.log_message so that it is technically possible to parse the line and reconstruct what the original data was. Without this a xHH is ambiguous as to if it is a hex replacement we put in or the characters r"x" came through in the original request line.

gh-99957 [https://github.com/python/cpython/issues/99957]: Add frozen_default parameter to typing.dataclass_transform().

gh-79033 [https://github.com/python/cpython/issues/79033]: Fix asyncio.Server.wait_closed() to actually do what the docs promise -- wait for all existing connections to complete, after closing the server.

gh-51524 [https://github.com/python/cpython/issues/51524]: Fix bug when calling trace.CoverageResults with valid infile.

gh-99645 [https://github.com/python/cpython/issues/99645]: Fix a bug in handling class cleanups in unittest.TestCase. Now addClassCleanup() uses separate lists for different TestCase subclasses, and doClassCleanups() only cleans up the particular class.

gh-99508 [https://github.com/python/cpython/issues/99508]: Fix TypeError in Lib/importlib/_bootstrap_external.py while calling _imp.source_hash().

gh-66285 [https://github.com/python/cpython/issues/66285]: Fix asyncio to not share event loop and signal wakeupfd in forked processes. Patch by Kumar Aditya.

gh-97001 [https://github.com/python/cpython/issues/97001]: Release the GIL when calling termios APIs to avoid blocking threads.

gh-92647 [https://github.com/python/cpython/issues/92647]: Use final status of an enum to determine lookup or creation branch of functional API.

gh-99388 [https://github.com/python/cpython/issues/99388]: Add loop_factory parameter to asyncio.run() to allow specifying a custom event loop factory. Patch by Kumar Aditya.

gh-99341 [https://github.com/python/cpython/issues/99341]: Fix ast.increment_lineno() to also cover ast.TypeIgnore when changing line numbers.

gh-99382 [https://github.com/python/cpython/issues/99382]: Check the number of arguments in substitution in user generics containing a TypeVarTuple and one or more TypeVar.

gh-99379 [https://github.com/python/cpython/issues/99379]: Fix substitution of ParamSpec followed by TypeVarTuple in generic aliases.

gh-99344 [https://github.com/python/cpython/issues/99344]: Fix substitution of TypeVarTuple and ParamSpec together in user generics.

gh-99284 [https://github.com/python/cpython/issues/99284]: Remove _use_broken_old_ctypes_structure_semantics_ old untested and undocumented hack from ctypes.

gh-99201 [https://github.com/python/cpython/issues/99201]: Fix IndexError when initializing the config variables on Windows if HAVE_DYNAMIC_LOADING is not set.

gh-99240 [https://github.com/python/cpython/issues/99240]: Fix double-free bug in Argument Clinic str_converter by extracting memory clean up to a new post_parsing section.

gh-64490 [https://github.com/python/cpython/issues/64490]: Fix refcount error when arguments are packed to tuple in Argument Clinic.

gh-99029 [https://github.com/python/cpython/issues/99029]: pathlib.PurePath.relative_to() now treats naked Windows drive paths as relative. This brings its behaviour in line with other parts of pathlib.

gh-98253 [https://github.com/python/cpython/issues/98253]: The implementation of the typing module is now more resilient to reference leaks in binary extension modules.

Previously, a reference leak in a typed C API-based extension module could leak internals of the typing module, which could in turn introduce leaks in essentially any other package with typed function signatures. Although the typing package is not the original source of the problem, such non-local dependences exacerbate debugging of large-scale projects, and the implementation was therefore changed to reduce harm by providing better isolation.

gh-98458 [https://github.com/python/cpython/issues/98458]: Fix infinite loop in unittest when a self-referencing chained exception is raised

gh-93453 [https://github.com/python/cpython/issues/93453]: asyncio.get_event_loop() and many other asyncio functions like asyncio.ensure_future(), asyncio.shield() or asyncio.gather(), and also the get_event_loop() method of asyncio.BaseDefaultEventLoopPolicy now raise a RuntimeError if called when there is no running event loop and the current event loop was not set. Previously they implicitly created and set a new current event loop. DeprecationWarning is no longer emitted if there is no running event loop but the current event loop was set.

gh-97966 [https://github.com/python/cpython/issues/97966]: On uname_result, restored expectation that _fields and _asdict would include all six properties including processor.

gh-98248 [https://github.com/python/cpython/issues/98248]: Provide informative error messages in struct.pack() when its integral arguments are not in range.

gh-98108 [https://github.com/python/cpython/issues/98108]: zipfile.Path is now pickleable if its initialization parameters were pickleable (e.g. for file system paths).

gh-98098 [https://github.com/python/cpython/issues/98098]: Created packages from zipfile and test_zipfile modules, separating zipfile.Path functionality.

gh-82836 [https://github.com/python/cpython/issues/82836]: Fix is_private properties in the ipaddress module. Previously non-private networks (0.0.0.0/0) would return True from this method; now they correctly return False.

gh-96828 [https://github.com/python/cpython/issues/96828]: Add an OP_ENABLE_KTLS option for enabling the use of the kernel TLS (kTLS). Patch by Illia Volochii.

gh-88863 [https://github.com/python/cpython/issues/88863]: To avoid apparent memory leaks when asyncio.open_connection() raises, break reference cycles generated by local exception and future instances (which has exception instance as its member var). Patch by Dong Uk, Kang.

gh-91078 [https://github.com/python/cpython/issues/91078]: TarFile.next() now returns None when called on an empty tarfile.

bpo-47220 [https://bugs.python.org/issue?@action=redirect&bpo=47220]: Document the optional callback parameter of WeakMethod. Patch by Géry Ogam.

bpo-44817 [https://bugs.python.org/issue?@action=redirect&bpo=44817]: Ignore WinError 53 (ERROR_BAD_NETPATH), 65 (ERROR_NETWORK_ACCESS_DENIED) and 161 (ERROR_BAD_PATHNAME) when using ntpath.realpath().

bpo-41260 [https://bugs.python.org/issue?@action=redirect&bpo=41260]: Rename the fmt parameter of the pure Python implementation of datetime.date.strftime() to format.

bpo-15999 [https://bugs.python.org/issue?@action=redirect&bpo=15999]: All built-in functions now accept arguments of any type instead of just bool and int for boolean parameters.

Documentation

gh-99931 [https://github.com/python/cpython/issues/99931]: Use sphinxext-opengraph [https://sphinxext-opengraph.readthedocs.io/] to generate OpenGraph metadata [https://ogp.me/].

gh-89682 [https://github.com/python/cpython/issues/89682]: Reworded docstring of the default __contains__ to clarify that it returns a bool.

gh-88330 [https://github.com/python/cpython/issues/88330]: Improved the description of what a resource is in importlib.resources docs.

gh-92892 [https://github.com/python/cpython/issues/92892]: Document that calling variadic functions with ctypes requires special care on macOS/arm64 (and possibly other platforms).

bpo-41825 [https://bugs.python.org/issue?@action=redirect&bpo=41825]: Restructured the documentation for the os.wait* family of functions, and improved the docs for os.waitid() with more explanation of the possible argument constants.

Tests

gh-99892 [https://github.com/python/cpython/issues/99892]: Skip test_normalization() of test_unicodedata if it fails to download NormalizationTest.txt file from pythontest.net. Patch by Victor Stinner.

gh-99934 [https://github.com/python/cpython/issues/99934]: Correct test_marsh on (32 bit) x86: test_deterministic sets was failing.

gh-99741 [https://github.com/python/cpython/issues/99741]: We've implemented multi-phase init (PEP 489/630/687) for the internal (for testing) _xxsubinterpreters module.

gh-99659 [https://github.com/python/cpython/issues/99659]: Optional big memory tests in test_sqlite3 now catch the correct sqlite.DataError exception type in case of too large strings and/or blobs passed.

gh-99593 [https://github.com/python/cpython/issues/99593]: Cover the Unicode C API with tests.

gh-96002 [https://github.com/python/cpython/issues/96002]: Add functional test for Argument Clinic.

Build

gh-99086 [https://github.com/python/cpython/issues/99086]: Fix -Wimplicit-int, -Wstrict-prototypes, and -Wimplicit-function-declaration compiler warnings in configure checks.

gh-99337 [https://github.com/python/cpython/issues/99337]: Fix a compilation issue with GCC 12 on macOS.

gh-99289 [https://github.com/python/cpython/issues/99289]: Add a COMPILEALL_OPTS variable in Makefile to override compileall options (default: -j0) in make install. Also merged the compileall commands into a single command building .pyc files for the all optimization levels (0, 1, 2) at once. Patch by Victor Stinner.

gh-98872 [https://github.com/python/cpython/issues/98872]: Fix a possible fd leak in Programs/_freeze_module.c introduced in Python 3.11.

gh-88226 [https://github.com/python/cpython/issues/88226]: Always define TARGET_* labels in Python/ceval.c, even if USE_COMPUTED_GOTOS is disabled. This allows breakpoints to be set at those labels in (for instance) gdb.

Windows

gh-99345 [https://github.com/python/cpython/issues/99345]: Use faster initialization functions to detect install location for Windows Store package

gh-98629 [https://github.com/python/cpython/issues/98629]: Fix initialization of sys.version and sys._git on Windows

gh-99442 [https://github.com/python/cpython/issues/99442]: Fix handling in Python 安裝管理員 when argv[0] does not include a file extension.

bpo-40882 [https://bugs.python.org/issue?@action=redirect&bpo=40882]: Fix a memory leak in multiprocessing.shared_memory.SharedMemory on Windows.

macOS

gh-87235 [https://github.com/python/cpython/issues/87235]: On macOS python3 /dev/fd/9 9</path/to/script.py failed for any script longer than a couple of bytes.

gh-98940 [https://github.com/python/cpython/issues/98940]: Fix Mac/Extras.install.py file filter bug.

Tools/Demos

gh-64490 [https://github.com/python/cpython/issues/64490]: Argument Clinic varargs bugfixes

Fix out-of-bounds error in _PyArg_UnpackKeywordsWithVararg().

Fix incorrect check which allowed more than one varargs in clinic.py.

Fix miscalculation of noptargs in generated code.

Do not generate noptargs when there is a vararg argument and no optional argument.

C API

gh-98680 [https://github.com/python/cpython/issues/98680]: PyBUF_* constants were marked as part of Limited API of Python 3.11+. These were available in 3.11.0 with Py_LIMITED_API defined for 3.11, and are necessary to use the buffer API.

gh-99612 [https://github.com/python/cpython/issues/99612]: Fix PyUnicode_DecodeUTF8Stateful() for ASCII-only data: *consumed was not set.

gh-47146 [https://github.com/python/cpython/issues/47146]: The structmember.h header is deprecated. Its non-deprecated contents are now available just by including Python.h, with a Py_ prefix added if it was missing. (Deprecated contents are T_OBJECT, T_NONE, and no-op flags.) Patch by Petr Viktorin, based on earlier work by Alexander Belopolsky and Matthias Braun.

Python 3.12.0 alpha 2

Release date: 2022-11-14

Security

gh-98433 [https://github.com/python/cpython/issues/98433]: The IDNA codec decoder used on DNS hostnames by socket or asyncio related name resolution functions no longer involves a quadratic algorithm. This prevents a potential CPU denial of service if an out-of-spec excessive length hostname involving bidirectional characters were decoded. Some protocols such as urllib http 3xx redirects potentially allow for an attacker to supply such a name.

Individual labels within an IDNA encoded DNS name will now raise an error early during IDNA decoding if they are longer than 1024 unicode characters given that each decoded DNS label must be 63 or fewer characters and the entire decoded DNS name is limited to 255. Only an application presenting a hostname or label consisting primarily of RFC 3454 [https://datatracker.ietf.org/doc/html/rfc3454.html] section 3.1 "Nothing" characters to be removed would run into of this new limit. See also RFC 5894 [https://datatracker.ietf.org/doc/html/rfc5894.html] section 6 and RFC 3491 [https://datatracker.ietf.org/doc/html/rfc3491.html].

gh-98739 [https://github.com/python/cpython/issues/98739]: Update bundled libexpat to 2.5.0

Core and Builtins

gh-81057 [https://github.com/python/cpython/issues/81057]: The docs clearly say that PyImport_Inittab, PyImport_AppendInittab(), and PyImport_ExtendInittab() should not be used after Py_Initialize() has been called. We now enforce this for the two functions. Additionally, the runtime now uses an internal copy of PyImport_Inittab, to guard against modification.

gh-99298 [https://github.com/python/cpython/issues/99298]: Fix an issue that could potentially cause incorrect error handling for some bytecode instructions.

gh-99254 [https://github.com/python/cpython/issues/99254]: The compiler now removes all unused constants from code objects (except the first one, which may be a docstring).

gh-99205 [https://github.com/python/cpython/issues/99205]: Fix an issue that prevented PyThreadState and PyInterpreterState memory from being freed properly.

gh-81057 [https://github.com/python/cpython/issues/81057]: The 18 global C variables holding the state of the allocators have been moved to _PyRuntimeState. This is a strictly internal change with no change in behavior.

gh-99181 [https://github.com/python/cpython/issues/99181]: Fix failure in except* with unhashable exceptions.

gh-99204 [https://github.com/python/cpython/issues/99204]: Fix calculation of sys._base_executable when inside a POSIX virtual environment using copies of the python binary when the base installation does not provide the executable name used by the venv. Calculation will fall back to alternative names ("python<MAJOR>", "python<MAJOR>.<MINOR>").

gh-96055 [https://github.com/python/cpython/issues/96055]: Update faulthandler to emit an error message with the proper unexpected signal number. Patch by Donghee Na.

gh-99153 [https://github.com/python/cpython/issues/99153]: Fix location of SyntaxError for a try block with both except and except*.

gh-98686 [https://github.com/python/cpython/issues/98686]: Merge the adaptive opcode logic into each instruction's unquickened variant, and merge the logic in EXTENDED_ARG_QUICK into EXTENDED_ARG. With these changes, the quickening that happens at code object creation is now only responsible for initializing warmup counters and inserting superinstructions.

gh-99103 [https://github.com/python/cpython/issues/99103]: Fix the error reporting positions of specialized traceback anchors when the source line contains Unicode characters.

gh-99139 [https://github.com/python/cpython/issues/99139]: Improve the error suggestion for NameError exceptions for instances. Now if a NameError is raised in a method and the instance has an attribute that's exactly equal to the name in the exception, the suggestion will include self.<NAME> instead of the closest match in the method scope. Patch by Pablo Galindo

gh-98401 [https://github.com/python/cpython/issues/98401]: Octal escapes with value larger than 0o377 (ex: "\477"), deprecated in Python 3.11, now produce a SyntaxWarning, instead of DeprecationWarning. In a future Python version they will be eventually a SyntaxError. Patch by Victor Stinner.

gh-98401 [https://github.com/python/cpython/issues/98401]: A backslash-character pair that is not a valid escape sequence now generates a SyntaxWarning, instead of DeprecationWarning. For example, re.compile("\d+\.\d+") now emits a SyntaxWarning ("\d" is an invalid escape sequence), use raw strings for regular expression: re.compile(r"\d+\.\d+"). In a future Python version, SyntaxError will eventually be raised, instead of SyntaxWarning. Patch by Victor Stinner.

gh-96793 [https://github.com/python/cpython/issues/96793]: Handle StopIteration and StopAsyncIteration raised in generator or coroutines in the bytecode, rather than in wrapping C code.

gh-98931 [https://github.com/python/cpython/issues/98931]: Improve the SyntaxError error message when the user types import x from y instead of from y import x. Patch by Pablo Galindo

gh-98852 [https://github.com/python/cpython/issues/98852]: Fix subscription of type aliases containing bare generic types or types like TypeVar: for example tuple[A, T][int] and tuple[TypeVar, T][int], where A is a generic type, and T is a type variable.

gh-98925 [https://github.com/python/cpython/issues/98925]: Lower the recursion depth for marshal on WASI to support (in-development) wasmtime 2.0.

gh-98783 [https://github.com/python/cpython/issues/98783]: Fix multiple crashes in debug mode when str subclasses are used instead of str itself.

gh-98811 [https://github.com/python/cpython/issues/98811]: Use complete source locations to simplify detection of __future__ imports which are not at the beginning of the file. Also corrects the offset in the exception raised in one case, which was off by one and impeded highlighting.

gh-96793 [https://github.com/python/cpython/issues/96793]: Add specialization of FOR_ITER for generators. Saves multiple layers of dispatch and checking to get from the FOR_ITER instruction in the caller to the RESUME in the generator.

gh-98762 [https://github.com/python/cpython/issues/98762]: Fix source locations of match sub-patterns.

gh-98586 [https://github.com/python/cpython/issues/98586]: Added the methods PyObject_Vectorcall() and PyObject_VectorcallMethod() to the Limited API along with the auxiliary macro constant PY_VECTORCALL_ARGUMENTS_OFFSET.

The availability of these functions enables more efficient PEP 590 [https://peps.python.org/pep-0590/] vector calls from binary extension modules that avoid argument boxing/unboxing overheads.

gh-99257 [https://github.com/python/cpython/issues/99257]: Fix an issue where member descriptors (such as those for __slots__) could behave incorrectly or crash instead of raising a TypeError when accessed via an instance of an invalid type.

gh-93143 [https://github.com/python/cpython/issues/93143]: Rather than changing co_code, the interpreter will now display a RuntimeWarning and assign None to any fast locals that are left unbound after jumps or del statements executed while tracing.

gh-96421 [https://github.com/python/cpython/issues/96421]: When calling into Python code from C code, through PyEval_EvalFrameEx() or a related C-API function, a shim frame in inserted into the call stack. This occurs in the _PyEval_EvalFrameDefault() function. The extra frame should be invisible to all Python and most C extensions, but out-of-process profilers and debuggers need to be aware of it. These shim frames can be detected by checking frame->owner == FRAME_OWNED_BY_CSTACK.

Extensions implementing their own interpreters using PEP 523 need to be aware of this shim frame and the changes to the semantics of RETURN_VALUE, YIELD_VALUE, and RETURN_GENERATOR, which now clear the frame.

Build

gh-98415 [https://github.com/python/cpython/issues/98415]: Fix detection of MAC addresses for uuid on certain OSs. Patch by Chaim Sanders

Core and Builtins

gh-98686 [https://github.com/python/cpython/issues/98686]: Quicken all code objects, and specialize adaptive bytecode instructions more aggressively.

gh-92119 [https://github.com/python/cpython/issues/92119]: Print exception class name instead of its string representation when raising errors from ctypes calls.

gh-91058 [https://github.com/python/cpython/issues/91058]: ImportError raised from failed from <module> import <name> now include suggestions for the value of <name> based on the available names in <module>. Patch by Pablo Galindo

gh-96793 [https://github.com/python/cpython/issues/96793]: The FOR_ITER now leaves the iterator on the stack on termination of the loop. This is to assist specialization of loops for generators.

gh-90716 [https://github.com/python/cpython/issues/90716]: Add _pylong.py module. It includes asymptotically faster algorithms that can be used for operations on integers with many digits. It is used by longobject.c to speed up some operations.

gh-95389 [https://github.com/python/cpython/issues/95389]: Expose ETH_P_ALL and some of the ETHERTYPE_* constants in socket. Patch by Noam Cohen.

Library

gh-93696 [https://github.com/python/cpython/issues/93696]: Allow pdb to locate source for frozen modules in the standard library.

gh-99418 [https://github.com/python/cpython/issues/99418]: Fix bug in urllib.parse.urlparse() that causes URL schemes that begin with a digit, a plus sign, or a minus sign to be parsed incorrectly.

gh-94597 [https://github.com/python/cpython/issues/94597]: Deprecate asyncio.AbstractChildWatcher to be removed in Python 3.14. Patch by Kumar Aditya.

gh-99305 [https://github.com/python/cpython/issues/99305]: Improve performance of secrets.token_hex().

gh-74044 [https://github.com/python/cpython/issues/74044]: Fixed bug where inspect.signature() reported incorrect arguments for decorated methods.

gh-99275 [https://github.com/python/cpython/issues/99275]: Fix SystemError in ctypes when exception was not set during __initsubclass__.

gh-99277 [https://github.com/python/cpython/issues/99277]: Remove older version of _SSLProtocolTransport.get_write_buffer_limits in asyncio.sslproto

gh-99248 [https://github.com/python/cpython/issues/99248]: fix negative numbers failing in verify()

gh-99155 [https://github.com/python/cpython/issues/99155]: Fix statistics.NormalDist pickle with 0 and 1 protocols.

gh-93464 [https://github.com/python/cpython/issues/93464]: enum.auto() is now correctly activated when combined with other assignment values. E.g. ONE = auto(), 'some text' will now evaluate as (1, 'some text').

gh-99134 [https://github.com/python/cpython/issues/99134]: Update the bundled copy of pip to version 22.3.1.

gh-92584 [https://github.com/python/cpython/issues/92584]: Remove the distutils package. It was deprecated in Python 3.10 by PEP 632 [https://peps.python.org/pep-0632/] "Deprecate distutils module". For projects still using distutils and cannot be updated to something else, the setuptools project can be installed: it still provides distutils. Patch by Victor Stinner.

gh-98999 [https://github.com/python/cpython/issues/98999]: Now _pyio is consistent with _io in raising ValueError when executing methods over closed buffers.

gh-83004 [https://github.com/python/cpython/issues/83004]: Clean up refleak on failed module initialisation in _zoneinfo

gh-83004 [https://github.com/python/cpython/issues/83004]: Clean up refleaks on failed module initialisation in _pickle

gh-83004 [https://github.com/python/cpython/issues/83004]: Clean up refleak on failed module initialisation in _io.

gh-98897 [https://github.com/python/cpython/issues/98897]: Fix memory leak in math.dist() when both points don't have the same dimension. Patch by Kumar Aditya.

gh-98878 [https://github.com/python/cpython/issues/98878]: Use the frame bound builtins when offering a name suggestion in traceback to prevent crashing when __builtins__ is not a dict.

gh-98139 [https://github.com/python/cpython/issues/98139]: In importlib._bootstrap, enhance namespace package repr to <module 'x' (namespace) from ['path']>.

gh-90352 [https://github.com/python/cpython/issues/90352]: Fix _SelectorDatagramTransport to inherit from DatagramTransport in asyncio. Patch by Kumar Aditya.

gh-98793 [https://github.com/python/cpython/issues/98793]: Fix argument typechecks in _overlapped.WSAConnect() and _overlapped.Overlapped.WSASendTo() functions.

gh-98744 [https://github.com/python/cpython/issues/98744]: Prevent crashing in traceback when retrieving the byte-offset for some source files that contain certain unicode characters.

gh-98740 [https://github.com/python/cpython/issues/98740]: Fix internal error in the re module which in very rare circumstances prevented compilation of a regular expression containing a conditional expression without the "else" branch.

gh-98703 [https://github.com/python/cpython/issues/98703]: Fix asyncio.StreamWriter.drain() to call protocol.connection_lost callback only once on Windows.

gh-98624 [https://github.com/python/cpython/issues/98624]: Add a mutex to unittest.mock.NonCallableMock to protect concurrent access to mock attributes.

gh-98658 [https://github.com/python/cpython/issues/98658]: The array.array class now supports subscripting, making it a generic type.

gh-98284 [https://github.com/python/cpython/issues/98284]: Improved TypeError message for undefined abstract methods of a abc.ABC instance. The names of the missing methods are surrounded by single-quotes to highlight them.

gh-96151 [https://github.com/python/cpython/issues/96151]: Allow BUILTINS to be a valid field name for frozen dataclasses.

gh-98086 [https://github.com/python/cpython/issues/98086]: Make sure patch.dict() can be applied on async functions.

gh-72719 [https://github.com/python/cpython/issues/72719]: Remove modules asyncore and asynchat, which were deprecated by PEP 594 [https://peps.python.org/pep-0594/].

gh-96192 [https://github.com/python/cpython/issues/96192]: Fix handling of bytes path-like objects in os.ismount().

gh-94172 [https://github.com/python/cpython/issues/94172]: ftplib: Remove the FTP_TLS.ssl_version class attribute: use the context parameter instead. Patch by Victor Stinner

gh-94172 [https://github.com/python/cpython/issues/94172]: Remove the keyfile and certfile parameters from the ftplib, imaplib, poplib and smtplib modules, and the key_file, cert_file and check_hostname parameters from the http.client module, all deprecated since Python 3.6. Use the context parameter (ssl_context in imaplib) instead. Patch by Victor Stinner.

gh-83638 [https://github.com/python/cpython/issues/83638]: Add the autocommit attribute to sqlite3.Connection and the autocommit parameter to sqlite3.connect() to control PEP 249 [https://peps.python.org/pep-0249/]-compliant transaction handling. Patch by Erlend E. Aasland.

gh-92452 [https://github.com/python/cpython/issues/92452]: Fixed a race condition that could cause sysconfig.get_config_var() to incorrectly return None in multi-threaded programs.

gh-91803 [https://github.com/python/cpython/issues/91803]: Fix an error when using a method of objects mocked with unittest.mock.create_autospec() after it was sealed with unittest.mock.seal() function.

bpo-38523 [https://bugs.python.org/issue?@action=redirect&bpo=38523]: shutil.copytree() now applies the ignore_dangling_symlinks argument recursively.

bpo-40358 [https://bugs.python.org/issue?@action=redirect&bpo=40358]: Add walk_up argument in pathlib.PurePath.relative_to().

bpo-36267 [https://bugs.python.org/issue?@action=redirect&bpo=36267]: Fix IndexError in argparse.ArgumentParser when a store_true action is given an explicit argument.

Documentation

gh-98832 [https://github.com/python/cpython/issues/98832]: Changes wording of docstring for pathlib.Path.iterdir().

gh-97966 [https://github.com/python/cpython/issues/97966]: Update uname docs to clarify the special nature of the platform attribute and to indicate when it became late-bound.

Tests

gh-98903 [https://github.com/python/cpython/issues/98903]: The Python test suite now fails with exit code 4 if no tests ran. It should help detecting typos in test names and test methods.

gh-98713 [https://github.com/python/cpython/issues/98713]: Fix a bug in the typing tests where a test relying on CPython-specific implementation details was not decorated with @cpython_only and was not skipped on other implementations.

gh-87390 [https://github.com/python/cpython/issues/87390]: Add tests for star-unpacking with PEP 646, and some other miscellaneous PEP 646 tests.

gh-96853 [https://github.com/python/cpython/issues/96853]: Added explicit coverage of Py_Initialize (and hence Py_InitializeEx) back to the embedding tests (all other embedding tests migrated to Py_InitializeFromConfig in Python 3.11)

bpo-34272 [https://bugs.python.org/issue?@action=redirect&bpo=34272]: Some C API tests were moved into the new Lib/test/test_capi/ directory.

Build

gh-99086 [https://github.com/python/cpython/issues/99086]: Fix -Wimplicit-int compiler warning in configure check for PTHREAD_SCOPE_SYSTEM.

gh-99016 [https://github.com/python/cpython/issues/99016]: Fix build with PYTHON_FOR_REGEN=python3.8.

gh-97731 [https://github.com/python/cpython/issues/97731]: Specify the full path to the source location for make docclean (needed for cross-builds).

gh-98949 [https://github.com/python/cpython/issues/98949]: Drop unused build dependency on readelf.

gh-98989 [https://github.com/python/cpython/issues/98989]: Use python3.11, if available, for regeneration and freezing.

gh-98831 [https://github.com/python/cpython/issues/98831]: Add new tooling, in Tools/cases_generator, to generate the interpreter switch statement from a list of opcode definitions. This only affects adding, modifying or removing instruction definitions. The instruction definitions now live in Python/bytecodes.c, in the form of a custom DSL (under development) [https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md]. The tooling reads this file and writes Python/generated_cases.c.h, which is then included by Python/ceval.c to provide most of the cases of the main interpreter switch.

gh-98817 [https://github.com/python/cpython/issues/98817]: Remove PCbuild/lib.pyproj: it's not used for anything, is only a minor convenience for Visual Studio users (who probably mostly don't even know about it), and it takes a lot of maintenance effort to keep updated.

gh-98776 [https://github.com/python/cpython/issues/98776]: Fix make regen-test-levenshtein for out-of-tree builds.

gh-98707 [https://github.com/python/cpython/issues/98707]: Don't use vendored libmpdec headers if --with-system-libmpdec is passed to configure. Don't use vendored libexpat headers if --with-system-expat is passed to configure.

Windows

gh-98689 [https://github.com/python/cpython/issues/98689]: Update Windows builds to zlib v1.2.13. v1.2.12 has CVE 2022-37434 [https://www.cve.org/CVERecord?id=CVE-2022-37434], but the vulnerable inflateGetHeader API is not used by Python.

gh-98790 [https://github.com/python/cpython/issues/98790]: Assumes that a missing DLLs directory means that standard extension modules are in the executable's directory.

gh-98745 [https://github.com/python/cpython/issues/98745]: Update py.exe launcher to install 3.11 by default and 3.12 on request.

gh-98692 [https://github.com/python/cpython/issues/98692]: Fix the Python 安裝管理員 ignoring unrecognized shebang lines instead of treating them as local paths

gh-94328 [https://github.com/python/cpython/issues/94328]: Update Windows installer to use SQLite 3.39.4.

macOS

gh-94328 [https://github.com/python/cpython/issues/94328]: Update macOS installer to SQLite 3.39.4.

C API

gh-98724 [https://github.com/python/cpython/issues/98724]: The Py_CLEAR, Py_SETREF and Py_XSETREF macros now only evaluate their argument once. If the argument has side effects, these side effects are no longer duplicated. Patch by Victor Stinner.

gh-98978 [https://github.com/python/cpython/issues/98978]: Fix use-after-free in Py_SetPythonHome(NULL), Py_SetProgramName(NULL) and _Py_SetProgramFullPath(NULL) function calls. Issue reported by Benedikt Reinartz. Patch by Victor Stinner.

gh-98410 [https://github.com/python/cpython/issues/98410]: Add getbufferproc and releasebufferproc to the stable API.

gh-98610 [https://github.com/python/cpython/issues/98610]: Some configurable capabilities of sub-interpreters have changed. They always allow subprocesses (subprocess) now, whereas before subprocesses could be optionally disallowed for a sub-interpreter. Instead os.exec() can now be disallowed. Disallowing daemon threads is now supported. Disallowing all threads is still allowed, but is never done by default. Note that the optional restrictions are only available through _Py_NewInterpreterFromConfig(), which isn't a public API. They do not affect the main interpreter, nor Py_NewInterpreter().

gh-98608 [https://github.com/python/cpython/issues/98608]: A _PyInterpreterConfig has been added and _Py_NewInterpreter() has been renamed to _Py_NewInterpreterFromConfig(). The "isolated_subinterpreters" argument is now a granular config that captures the previous behavior. Note that this is all "private" API.

gh-96853 [https://github.com/python/cpython/issues/96853]: Py_InitializeEx now correctly calls PyConfig_Clear after initializing the interpreter (the omission didn't cause a memory leak only because none of the dynamically allocated config fields are populated by the wrapper function)

gh-91248 [https://github.com/python/cpython/issues/91248]: Add PyFrame_GetVar() and PyFrame_GetVarString() functions to get a frame variable by its name. Patch by Victor Stinner.

Python 3.12.0 alpha 1

Release date: 2022-10-25

Security

gh-97616 [https://github.com/python/cpython/issues/97616]: Fix multiplying a list by an integer (list *= int): detect the integer overflow when the new allocated length is close to the maximum size. Issue reported by Jordan Limor. Patch by Victor Stinner.

gh-97514 [https://github.com/python/cpython/issues/97514]: On Linux the multiprocessing module returns to using filesystem backed unix domain sockets for communication with the forkserver process instead of the Linux abstract socket namespace. Only code that chooses to use the "forkserver" start method is affected.

Abstract sockets have no permissions and could allow any user on the system in the same network namespace [https://man7.org/linux/man-pages/man7/network_namespaces.7.html] (often the whole system) to inject code into the multiprocessing forkserver process. This was a potential privilege escalation. Filesystem based socket permissions restrict this to the forkserver process user as was the default in Python 3.8 and earlier.

This prevents Linux CVE 2022-42919 [https://www.cve.org/CVERecord?id=CVE-2022-42919].

gh-87389 [https://github.com/python/cpython/issues/87389]: http.server: Fix an open redirection vulnerability in the HTTP server when an URI path starts with //. Vulnerability discovered, and initial fix proposed, by Hamza Avvan.

gh-79096 [https://github.com/python/cpython/issues/79096]: LWPCookieJar and MozillaCookieJar create files with file mode 600 instead of 644 (Microsoft Windows is not affected)

gh-92888 [https://github.com/python/cpython/issues/92888]: Fix memoryview use after free when accessing the backing buffer in certain cases.

gh-68966 [https://github.com/python/cpython/issues/68966]: The deprecated mailcap module now refuses to inject unsafe text (filenames, MIME types, parameters) into shell commands. Instead of using such text, it will warn and act as if a match was not found (or for test commands, as if the test failed).

Core and Builtins

gh-98374 [https://github.com/python/cpython/issues/98374]: Suppress ImportError for invalid query for help() command. Patch by Donghee Na.

gh-98461 [https://github.com/python/cpython/issues/98461]: Fix source location in bytecode for list, set and dict comprehensions as well as generator expressions.

gh-98354 [https://github.com/python/cpython/issues/98354]: Added unicode check for name attribute of spec argument passed in _imp.create_builtin() function.

gh-98398 [https://github.com/python/cpython/issues/98398]: Fix source location of 'assert' bytecodes.

gh-98390 [https://github.com/python/cpython/issues/98390]: Fix location of sub-expressions of boolean expressions, by reducing their scope to that of the sub-expression.

gh-98254 [https://github.com/python/cpython/issues/98254]: Modules from the standard library are now potentially suggested as part of the error messages displayed by the interpreter when an NameError is raised to the top level. Patch by Pablo Galindo

gh-97997 [https://github.com/python/cpython/issues/97997]: Add running column offset to the tokenizer state to avoid calculating AST column information with pointer arithmetic.

gh-97973 [https://github.com/python/cpython/issues/97973]: Modify the tokenizer to return all necessary information the parser needs to set location information in the AST nodes, so that the parser does not have to calculate those doing pointer arithmetic.

Library

gh-96078 [https://github.com/python/cpython/issues/96078]: os.sched_yield() now release the GIL while calling sched_yield(2). Patch by Donghee Na.

gh-97955 [https://github.com/python/cpython/issues/97955]: Migrate zoneinfo to Argument Clinic.

Core and Builtins

gh-97912 [https://github.com/python/cpython/issues/97912]: The compiler now avoids quadratic behavior when finding which instructions should use the LOAD_FAST_CHECK opcode.

gh-97002 [https://github.com/python/cpython/issues/97002]: Fix an issue where several frame objects could be backed by the same interpreter frame, possibly leading to corrupted memory and hard crashes of the interpreter.

gh-97943 [https://github.com/python/cpython/issues/97943]: Bugfix: PyFunction_GetAnnotations() should return a borrowed reference. It was returning a new reference.

gh-97922 [https://github.com/python/cpython/issues/97922]: The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead on object allocations. The GC can also run when PyErr_CheckSignals() is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically.

gh-65961 [https://github.com/python/cpython/issues/65961]: When __package__ is different than __spec__.parent, raise a DeprecationWarning instead of ImportWarning.

Also remove importlib.util.set_package() which was scheduled for removal.

gh-97850 [https://github.com/python/cpython/issues/97850]: Long deprecated, module_repr() should now be completely eradicated.

gh-86298 [https://github.com/python/cpython/issues/86298]: In cases where warnings.warn_explicit() consults the module's loader, an DeprecationWarning is issued when m.__loader__ differs from m.__spec__.loader.

gh-97779 [https://github.com/python/cpython/issues/97779]: Ensure that all Python frame objects are backed by "complete" frames.

gh-91052 [https://github.com/python/cpython/issues/91052]: Add API for subscribing to modification events on selected dictionaries.

gh-97752 [https://github.com/python/cpython/issues/97752]: Fix possible data corruption or crashes when accessing the f_back member of newly-created generator or coroutine frames.

gh-97591 [https://github.com/python/cpython/issues/97591]: Fixed a missing incref/decref pair in Exception.__setstate__(). Patch by Ofey Chan.

gh-97670 [https://github.com/python/cpython/issues/97670]: Remove the sys.getdxp() function and the Tools/scripts/analyze_dxp.py script. DXP stands for "dynamic execution pairs". They were related to DYNAMIC_EXECUTION_PROFILE and DXPAIRS macros which have been removed in Python 3.11. Python can now be built with ./configure --enable-pystats to gather statistics on Python opcodes. Patch by Victor Stinner.

gh-94526 [https://github.com/python/cpython/issues/94526]: Fix the Python path configuration used to initialized sys.path at Python startup. Paths are no longer encoded to UTF-8/strict to avoid encoding errors if it contains surrogate characters (bytes paths are decoded with the surrogateescape error handler). Patch by Victor Stinner.

gh-96670 [https://github.com/python/cpython/issues/96670]: The parser now raises SyntaxError when parsing source code containing null bytes. Patch by Pablo Galindo

gh-96975 [https://github.com/python/cpython/issues/96975]: Fix a crash occurring when PyEval_GetFrame() is called while the topmost Python frame is in a partially-initialized state.

gh-96848 [https://github.com/python/cpython/issues/96848]: Fix command line parsing: reject -X int_max_str_digits option with no value (invalid) when the PYTHONINTMAXSTRDIGITS environment variable is set to a valid limit. Patch by Victor Stinner.

gh-95921 [https://github.com/python/cpython/issues/95921]: Fix overly-broad source position information for chained comparisons used as branching conditions.

Library

gh-96821 [https://github.com/python/cpython/issues/96821]: Fix undefined behaviour in audioop.c.

Core and Builtins

gh-96821 [https://github.com/python/cpython/issues/96821]: Fix undefined behaviour in _testcapimodule.c.

gh-95778 [https://github.com/python/cpython/issues/95778]: When ValueError is raised if an integer is larger than the limit, mention the sys.set_int_max_str_digits() function in the error message. Patch by Victor Stinner.

gh-96387 [https://github.com/python/cpython/issues/96387]: At Python exit, sometimes a thread holding the GIL can wait forever for a thread (usually a daemon thread) which requested to drop the GIL, whereas the thread already exited. To fix the race condition, the thread which requested the GIL drop now resets its request before exiting. Issue discovered and analyzed by Mingliang ZHAO. Patch by Victor Stinner.

gh-96864 [https://github.com/python/cpython/issues/96864]: Fix a possible assertion failure, fatal error, or SystemError if a line tracing event raises an exception while opcode tracing is enabled.

gh-95778 [https://github.com/python/cpython/issues/95778]: The PyLong_FromString function was refactored to make it more maintainable and extensible.

gh-96678 [https://github.com/python/cpython/issues/96678]: Fix undefined behaviour in C code of null pointer arithmetic.

gh-96754 [https://github.com/python/cpython/issues/96754]: Make sure that all frame objects created are created from valid interpreter frames. Prevents the possibility of invalid frames in backtraces and signal handlers.

gh-90997 [https://github.com/python/cpython/issues/90997]: Improve the performance of reading and writing inline bytecode caches on some platforms.

gh-96751 [https://github.com/python/cpython/issues/96751]: Remove dead code from CALL_FUNCTION_EX opcode.

gh-90751 [https://github.com/python/cpython/issues/90751]: memoryview now supports half-floats. Patch by Donghee Na and Antoine Pitrou.

gh-96678 [https://github.com/python/cpython/issues/96678]: Fix case of undefined behavior in ceval.c

Library

gh-64373 [https://github.com/python/cpython/issues/64373]: Convert _functools to argument clinic.

gh-96641 [https://github.com/python/cpython/issues/96641]: Do not expose KeyWrapper in _functools.

Core and Builtins

gh-96636 [https://github.com/python/cpython/issues/96636]: Ensure that tracing, sys.setrace(), is turned on immediately. In pre-release versions of 3.11, some tracing events might have been lost when turning on tracing in a __del__ method or interrupt.

gh-96572 [https://github.com/python/cpython/issues/96572]: Fix use after free in trace refs build mode. Patch by Kumar Aditya.

gh-96611 [https://github.com/python/cpython/issues/96611]: When loading a file with invalid UTF-8 inside a multi-line string, a correct SyntaxError is emitted.

gh-96612 [https://github.com/python/cpython/issues/96612]: Make sure that incomplete frames do not show up in tracemalloc traces.

gh-90230 [https://github.com/python/cpython/issues/90230]: Fix compiler warnings and test failures when building with --enable-pystats.

gh-96587 [https://github.com/python/cpython/issues/96587]: Correctly raise SyntaxError on exception groups (PEP 654 [https://peps.python.org/pep-0654/]) on python versions prior to 3.11

gh-96569 [https://github.com/python/cpython/issues/96569]: Remove two cases of undefined behavior, by adding NULL checks.

gh-96582 [https://github.com/python/cpython/issues/96582]: Fix possible NULL pointer dereference in _PyThread_CurrentFrames. Patch by Kumar Aditya.

gh-91079 [https://github.com/python/cpython/issues/91079]: Separate Python recursion checking from C recursion checking which reduces the chance of C stack overflow and allows the recursion limit to be increased safely.

gh-93911 [https://github.com/python/cpython/issues/93911]: Fix an issue that could prevent LOAD_ATTR from specializing properly when accessing properties.

gh-96348 [https://github.com/python/cpython/issues/96348]: Emit a DeprecationWarning when throw(), throw() or athrow() are called with more than one argument.

gh-95196 [https://github.com/python/cpython/issues/95196]: Disable incorrect pickling of the C implemented classmethod descriptors.

gh-96364 [https://github.com/python/cpython/issues/96364]: Fix text signatures of list.__getitem__ and dict.__getitem__.

gh-96352 [https://github.com/python/cpython/issues/96352]: Fix AttributeError missing name and obj attributes in object.__getattribute__(). Patch by Philip Georgi.

gh-93554 [https://github.com/python/cpython/issues/93554]: Change the jump opcodes so that all conditional jumps are forward jumps. Backward jumps are converted by the assembler into a conditional forward jump whose target is the fallthrough block (and with a reversed condition), followed by an unconditional backward jump. For example:

POP_JUMP_IF_TRUE BACKWARD_TARGET becomes POP_JUMP_IF_FALSE NEXT_BLOCK; JUMP BACKWARD_TARGET.

All the directed conditional jump opcodes were removed: POP_JUMP_FORWARD_IF_TRUE, POP_JUMP_BACKWARD_IF_TRUE, POP_JUMP_FORWARD_IF_FALSE, POP_JUMP_BACKWARD_IF_FALSE, POP_JUMP_FORWARD_IF_NONE, POP_JUMP_BACKWARD_IF_NONE, POP_JUMP_FORWARD_IF_NOT_NONE, POP_JUMP_BACKWARD_IF_NOT_NONE.

The corresponding opcodes without direction are no longer pseudo-instructions, and they implement the forward conditional jumps.

gh-96268 [https://github.com/python/cpython/issues/96268]: Loading a file with invalid UTF-8 will now report the broken character at the correct location.

gh-96237 [https://github.com/python/cpython/issues/96237]: The internal field _PyInterpreterFrame.f_func is renamed to _PyInterpreterFrame.f_funcobj and may be any object. The f_globals and f_builtin fields may hold junk values.

It is safest to treat the _PyInterpreterFrame struct as opaque.

gh-96187 [https://github.com/python/cpython/issues/96187]: Fixed a bug that caused _PyCode_GetExtra to return garbage for negative indexes. Patch by Pablo Galindo

gh-96143 [https://github.com/python/cpython/issues/96143]: Add a new -X perf Python command line option as well as sys.activate_stack_trampoline() and sys.deactivate_stack_trampoline() function in the sys module that allows to set/unset the interpreter in a way that the Linux perf profiler can detect Python calls. The new sys.is_stack_trampoline_active() function allows to query the state of the perf trampoline. Design by Pablo Galindo. Patch by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon.

gh-96071 [https://github.com/python/cpython/issues/96071]: Fix a deadlock in PyGILState_Ensure() when allocating new thread state. Patch by Kumar Aditya.

gh-96046 [https://github.com/python/cpython/issues/96046]: PyType_Ready() now initializes ht_cached_keys and performs additional checks to ensure that type objects are properly configured. This avoids crashes in 3rd party packages that don't use regular API to create new types.

gh-96005 [https://github.com/python/cpython/issues/96005]: On WASI ENOTCAPABLE is now mapped to PermissionError. The errno modules exposes the new error number. getpath.py now ignores PermissionError when it cannot open landmark files pybuilddir.txt and pyenv.cfg.

gh-93678 [https://github.com/python/cpython/issues/93678]: Added test a harness for direct unit tests of the compiler's optimization stage. The _testinternalcapi.optimize_cfg() function runs the optimiser on a sequence of instructions. The CfgOptimizationTestCase class in test.support has utilities for invoking the optimizer and checking the output.

gh-95245 [https://github.com/python/cpython/issues/95245]: Reduces the size of a "simple" Python object from 8 to 6 words by moving the weakreflist pointer into the pre-header directly before the object's dict/values pointer.

gh-90997 [https://github.com/python/cpython/issues/90997]: Compile virtual try/except blocks to handle exceptions raised during close() or throw() calls through a suspended frame.

gh-95977 [https://github.com/python/cpython/issues/95977]: Optimized calling __get__() with vectorcall. Patch by Kumar Aditya.

gh-91210 [https://github.com/python/cpython/issues/91210]: Improve error message when a parameter without a default value follows one with a default value, and show the same message, even when the non-default/default sequence is preceded by positional-only parameters.

gh-95922 [https://github.com/python/cpython/issues/95922]: Fixed bug where the compiler's eliminate_empty_basic_blocks function ignores the last block of the code unit.

gh-95818 [https://github.com/python/cpython/issues/95818]: Skip over incomplete frames in PyThreadState_GetFrame().

gh-95876 [https://github.com/python/cpython/issues/95876]: Fix format string in _PyPegen_raise_error_known_location that can lead to memory corruption on some 64bit systems. The function was building a tuple with i (int) instead of n (Py_ssize_t) for Py_ssize_t arguments.

gh-95605 [https://github.com/python/cpython/issues/95605]: Fix misleading contents of error message when converting an all-whitespace string to float.

gh-95150 [https://github.com/python/cpython/issues/95150]: Update code object hashing and equality to consider all debugging and exception handling tables. This fixes an issue where certain non-identical code objects could be "deduplicated" during compilation.

gh-91146 [https://github.com/python/cpython/issues/91146]: Reduce allocation size of list from str.split() and str.rsplit(). Patch by Donghee Na and Inada Naoki.

gh-87092 [https://github.com/python/cpython/issues/87092]: Create a 'jump target label' abstraction in the compiler so that the compiler's codegen stage does not work directly with basic blocks. This prepares the code for changes to the underlying CFG generation mechanism.

gh-95355 [https://github.com/python/cpython/issues/95355]: _PyPegen_Parser_New now properly detects token memory allocation errors. Patch by Honglin Zhu.

gh-90081 [https://github.com/python/cpython/issues/90081]: Run Python code in tracer/profiler function at full speed. Fixes slowdown in earlier versions of 3.11.

gh-95324 [https://github.com/python/cpython/issues/95324]: Emit a warning in debug mode if an object does not call PyObject_GC_UnTrack() before deallocation. Patch by Pablo Galindo.

gh-95245 [https://github.com/python/cpython/issues/95245]: Merge managed dict and values pointer into a single tagged pointer to save one word in the pre-header.

gh-93678 [https://github.com/python/cpython/issues/93678]: Add cfg_builder struct and refactor the relevant code so that a cfg can be constructed without an instance of the compiler struct.

gh-95185 [https://github.com/python/cpython/issues/95185]: Prevented crashes in the AST constructor when compiling some absurdly long expressions like "+0"*1000000. RecursionError is now raised instead. Patch by Pablo Galindo

gh-93351 [https://github.com/python/cpython/issues/93351]: ast.AST node positions are now validated when provided to compile() and other related functions. If invalid positions are detected, a ValueError will be raised.

gh-94438 [https://github.com/python/cpython/issues/94438]: Fix an issue that caused extended opcode arguments and some conditional pops to be ignored when calculating valid jump targets for assignments to the f_lineno attribute of frame objects. In some cases, this could cause inconsistent internal state, resulting in a hard crash of the interpreter.

gh-95060 [https://github.com/python/cpython/issues/95060]: Undocumented PyCode_Addr2Location function now properly returns when addrq argument is less than zero.

gh-95113 [https://github.com/python/cpython/issues/95113]: Replace all EXTENDED_ARG_QUICK instructions with basic EXTENDED_ARG instructions in unquickened code. Consumers of non-adaptive bytecode should be able to handle extended arguments the same way they were handled in CPython 3.10 and older.

gh-91409 [https://github.com/python/cpython/issues/91409]: Fix incorrect source location info caused by certain optimizations in the bytecode compiler.

Library

gh-95023 [https://github.com/python/cpython/issues/95023]: Implement os.setns() and os.unshare() for Linux. Patch by Noam Cohen.

Core and Builtins

gh-94036 [https://github.com/python/cpython/issues/94036]: Fix incorrect source location info for some multi-line attribute accesses and method calls.

gh-94938 [https://github.com/python/cpython/issues/94938]: Fix error detection in some builtin functions when keyword argument name is an instance of a str subclass with overloaded __eq__ and __hash__. Previously it could cause SystemError or other undesired behavior.

Library

gh-94996 [https://github.com/python/cpython/issues/94996]: ast.parse() will no longer parse function definitions with positional-only params when passed feature_version less than (3, 8). Patch by Shantanu Jain.

Core and Builtins

gh-94739 [https://github.com/python/cpython/issues/94739]: Allow jumping within, out of, and across exception handlers in the debugger.

Library

gh-94949 [https://github.com/python/cpython/issues/94949]: ast.parse() will no longer parse parenthesized context managers when passed feature_version less than (3, 9). Patch by Shantanu Jain.

gh-94947 [https://github.com/python/cpython/issues/94947]: ast.parse() will no longer parse assignment expressions when passed feature_version less than (3, 8). Patch by Shantanu Jain.

Core and Builtins

gh-91256 [https://github.com/python/cpython/issues/91256]: Ensures the program name is known for help text during interpreter startup.

gh-94869 [https://github.com/python/cpython/issues/94869]: Fix the column offsets for some expressions in multi-line f-strings ast nodes. Patch by Pablo Galindo.

gh-94893 [https://github.com/python/cpython/issues/94893]: Fix an issue where frame object manipulations could corrupt inline bytecode caches.

gh-94822 [https://github.com/python/cpython/issues/94822]: Fix an issue where lookups of metaclass descriptors may be ignored when an identically-named attribute also exists on the class itself.

gh-91153 [https://github.com/python/cpython/issues/91153]: Fix an issue where a bytearray item assignment could crash if it's resized by the new value's __index__() method.

gh-90699 [https://github.com/python/cpython/issues/90699]: Fix reference counting bug in bool.__repr__(). Patch by Kumar Aditya.

gh-94694 [https://github.com/python/cpython/issues/94694]: Fix an issue that could cause code with multi-line method lookups to have misleading or incorrect column offset information. In some cases (when compiling a hand-built AST) this could have resulted in a hard crash of the interpreter.

gh-93252 [https://github.com/python/cpython/issues/93252]: Fix an issue that caused internal frames to outlive failed Python function calls, possibly resulting in memory leaks or hard interpreter crashes.

gh-94215 [https://github.com/python/cpython/issues/94215]: Fix an issue where exceptions raised by line-tracing events would cause frames to be left in an invalid state, possibly resulting in a hard crash of the interpreter.

gh-92228 [https://github.com/python/cpython/issues/92228]: Disable the compiler's inline-small-exit-blocks optimization for exit blocks that are associated with source code lines. This fixes a bug where the debugger cannot tell where an exception handler ends and the following code block begins.

gh-94485 [https://github.com/python/cpython/issues/94485]: Line number of a module's RESUME instruction is set to 0 as specified in PEP 626 [https://peps.python.org/pep-0626/].

gh-94438 [https://github.com/python/cpython/issues/94438]: Account for instructions that can push NULL to the stack when setting line number in a frame. Prevents some (unlikely) crashes.

gh-91719 [https://github.com/python/cpython/issues/91719]: Reload opcode when raising unknown opcode error in the interpreter main loop, for C compilers to generate dispatching code independently.

gh-94329 [https://github.com/python/cpython/issues/94329]: Compile and run code with unpacking of extremely large sequences (1000s of elements). Such code failed to compile. It now compiles and runs correctly.

gh-94360 [https://github.com/python/cpython/issues/94360]: Fixed a tokenizer crash when reading encoded files with syntax errors from stdin with non utf-8 encoded text. Patch by Pablo Galindo

gh-88116 [https://github.com/python/cpython/issues/88116]: Fix an issue when reading line numbers from code objects if the encoded line numbers are close to INT_MIN. Patch by Pablo Galindo

gh-94262 [https://github.com/python/cpython/issues/94262]: Don't create frame objects for incomplete frames. Prevents the creation of generators and closures from being observable to Python and C extensions, restoring the behavior of 3.10 and earlier.

gh-94192 [https://github.com/python/cpython/issues/94192]: Fix error for dictionary literals with invalid expression as value.

gh-87995 [https://github.com/python/cpython/issues/87995]: types.MappingProxyType instances are now hashable if the underlying mapping is hashable.

gh-93883 [https://github.com/python/cpython/issues/93883]: Revise the display strategy of traceback enhanced error locations. The indicators are only shown when the location doesn't span the whole line.

gh-94163 [https://github.com/python/cpython/issues/94163]: Add BINARY_SLICE and STORE_SLICE instructions for more efficient handling and better specialization of slicing operations, where the slice is explicit in the source code.

gh-94021 [https://github.com/python/cpython/issues/94021]: Fix unreachable code warning in Python/specialize.c.

gh-93911 [https://github.com/python/cpython/issues/93911]: Specialize LOAD_ATTR for objects with custom __getattribute__.

gh-93955 [https://github.com/python/cpython/issues/93955]: Improve performance of attribute lookups on objects with custom __getattribute__ and __getattr__. Patch by Ken Jin.

gh-93911 [https://github.com/python/cpython/issues/93911]: Specialize LOAD_ATTR for property() attributes.

gh-93678 [https://github.com/python/cpython/issues/93678]: Refactor compiler optimisation code so that it no longer needs the struct assembler and struct compiler passed around. Instead, each function takes the CFG and other data that it actually needs. This will make it possible to test this code directly.

gh-93841 [https://github.com/python/cpython/issues/93841]: When built with -enable-pystats, sys._stats_on(), sys._stats_off(), sys._stats_clear() and sys._stats_dump() functions have been added to enable gathering stats for parts of programs.

gh-93516 [https://github.com/python/cpython/issues/93516]: Store offset of first traceable instruction in code object to avoid having to recompute it for each instruction when tracing.

gh-93516 [https://github.com/python/cpython/issues/93516]: Lazily create a table mapping bytecode offsets to line numbers to speed up calculation of line numbers when tracing.

gh-89828 [https://github.com/python/cpython/issues/89828]: types.GenericAlias no longer relays the __class__ attribute. For example, isinstance(list[int], type) no longer returns True.

gh-93678 [https://github.com/python/cpython/issues/93678]: Refactor the compiler to reduce boilerplate and repetition.

gh-93671 [https://github.com/python/cpython/issues/93671]: Fix some exponential backtrace case happening with deeply nested sequence patterns in match statements. Patch by Pablo Galindo

gh-93662 [https://github.com/python/cpython/issues/93662]: Make sure that the end column offsets are correct in multi-line method calls. Previously, the end column could precede the column offset.

Library

gh-93461 [https://github.com/python/cpython/issues/93461]: importlib.invalidate_caches() now drops entries from sys.path_importer_cache with a relative path as name. This solves a caching issue when a process changes its current working directory.

FileFinder no longer inserts a dot in the path, e.g. /egg/./spam is now /egg/spam.

Core and Builtins

gh-93621 [https://github.com/python/cpython/issues/93621]: Change order of bytecode instructions emitted for with and async with to reduce the number of entries in the exception table.

gh-93533 [https://github.com/python/cpython/issues/93533]: Reduce the size of the inline cache for LOAD_METHOD by 2 bytes.

gh-93444 [https://github.com/python/cpython/issues/93444]: Removed redundant fields from the compiler's basicblock struct: b_nofallthrough, b_exit, b_return. They can be easily calculated from the opcode of the last instruction of the block.

gh-93429 [https://github.com/python/cpython/issues/93429]: LOAD_METHOD instruction has been removed. It was merged back into LOAD_ATTR.

gh-93418 [https://github.com/python/cpython/issues/93418]: Fixed an assert where an f-string has an equal sign '=' following an expression, but there's no trailing brace. For example, f"{i=".

gh-93382 [https://github.com/python/cpython/issues/93382]: Cache the result of PyCode_GetCode() function to restore the O(1) lookup of the co_code attribute.

gh-93359 [https://github.com/python/cpython/issues/93359]: Ensure that custom ast nodes without explicit end positions can be compiled. Patch by Pablo Galindo.

gh-93356 [https://github.com/python/cpython/issues/93356]: Code for exception handlers is emitted at the end of the code unit's bytecode. This avoids one jump when no exception is raised.

gh-93354 [https://github.com/python/cpython/issues/93354]: Use exponential backoff for specialization counters in the interpreter. Can reduce the number of failed specializations significantly and avoid slowdown for those parts of a program that are not suitable for specialization.

gh-93283 [https://github.com/python/cpython/issues/93283]: Improve error message for invalid syntax of conversion character in f-string expressions.

gh-93345 [https://github.com/python/cpython/issues/93345]: Fix a crash in substitution of a TypeVar in nested generic alias after TypeVarTuple.

gh-93223 [https://github.com/python/cpython/issues/93223]: When a bytecode instruction jumps to an unconditional jump instruction, the first instruction can often be optimized to target the unconditional jump's target directly. For tracing reasons, this would previously only occur if both instructions have the same line number. This also now occurs if the unconditional jump is artificial, i.e., if it has no associated line number.

gh-84694 [https://github.com/python/cpython/issues/84694]: The --experimental-isolated-subinterpreters configure option and EXPERIMENTAL_ISOLATED_SUBINTERPRETERS macro have been removed.

gh-91924 [https://github.com/python/cpython/issues/91924]: Fix __lltrace__ debug feature if the stdout encoding is not UTF-8. Patch by Victor Stinner.

gh-93040 [https://github.com/python/cpython/issues/93040]: Wraps unused parameters in Objects/obmalloc.c with Py_UNUSED.

gh-93143 [https://github.com/python/cpython/issues/93143]: Avoid NULL checks for uninitialized local variables by determining at compile time which variables must be initialized.

gh-93061 [https://github.com/python/cpython/issues/93061]: Backward jumps after async for loops are no longer given dubious line numbers.

gh-93065 [https://github.com/python/cpython/issues/93065]: Fix contextvars HAMT implementation to handle iteration over deep trees.

The bug was discovered and fixed by Eli Libman. See MagicStack/immutables#84 [https://github.com/MagicStack/immutables/issues/84] for more details.

gh-93012 [https://github.com/python/cpython/issues/93012]: Added the new function PyType_FromMetaclass(), which generalizes the existing PyType_FromModuleAndSpec() using an additional metaclass argument. This is useful for language binding tools, where it can be used to intercept type-related operations like subclassing or static attribute access by specifying a metaclass with custom slots.

Importantly, PyType_FromMetaclass() is available in the Limited API, which provides a path towards migrating more binding tools onto the Stable ABI.

gh-93021 [https://github.com/python/cpython/issues/93021]: Fix the __text_signature__ for __get__() methods implemented in C. Patch by Jelle Zijlstra.

gh-89914 [https://github.com/python/cpython/issues/89914]: The operand of the YIELD_VALUE instruction is set to the stack depth. This is done to help frame handling on yield and may assist debuggers.

gh-92955 [https://github.com/python/cpython/issues/92955]: Fix memory leak in code object's lines and positions iterators as they were not finalized at exit. Patch by Kumar Aditya.

gh-92930 [https://github.com/python/cpython/issues/92930]: Fixed a crash in _pickle.c from mutating collections during __reduce__ or persistent_id.

gh-90690 [https://github.com/python/cpython/issues/90690]: The PRECALL instruction has been removed. It offered only a small advantage for specialization and is not needed in the vast majority of cases.

gh-92914 [https://github.com/python/cpython/issues/92914]: Always round the allocated size for lists up to the nearest even number.

gh-92858 [https://github.com/python/cpython/issues/92858]: Improve error message for some suites with syntax error before ':'

gh-90473 [https://github.com/python/cpython/issues/90473]: Decrease default recursion limit on WASI to address limited call stack size.

gh-92804 [https://github.com/python/cpython/issues/92804]: Fix memory leak in memoryview iterator as it was not finalized at exit. Patch by Kumar Aditya.

gh-92777 [https://github.com/python/cpython/issues/92777]: Specialize LOAD_METHOD for objects with lazy dictionaries. Patch by Ken Jin.

gh-92658 [https://github.com/python/cpython/issues/92658]: Add support for connecting and binding to Hyper-V sockets on Windows Hyper-V hosts and guests.

gh-92236 [https://github.com/python/cpython/issues/92236]: Remove spurious "LINE" event when starting a generator or coroutine, visible tracing functions implemented in C.

Library

gh-91102 [https://github.com/python/cpython/issues/91102]: _warnings.warn_explicit() is ported to Argument Clinic.

Core and Builtins

gh-92619 [https://github.com/python/cpython/issues/92619]: Make the compiler duplicate an exit block only if none of its instructions have a lineno (previously only the first instruction in the block was checked, leading to unnecessarily duplicated blocks).

gh-88750 [https://github.com/python/cpython/issues/88750]: The deprecated debug build only PYTHONTHREADDEBUG environment variable no longer does anything.

Library

gh-92261 [https://github.com/python/cpython/issues/92261]: Fix hang when trying to iterate over a typing.Union.

Core and Builtins

gh-91432 [https://github.com/python/cpython/issues/91432]: Specialized the FOR_ITER opcode using the PEP 659 machinery

gh-91399 [https://github.com/python/cpython/issues/91399]: Removed duplicate '{0, 0, 0, 0, 0, 0}' entry in 'Objects/unicodetype_db.h'.

gh-91578 [https://github.com/python/cpython/issues/91578]: Updates the error message for abstract class.

bpo-47091 [https://bugs.python.org/issue?@action=redirect&bpo=47091]: Improve performance of repetition of list and tuple by using memcpy to copy data and performing the reference increments in one step.

bpo-46142 [https://bugs.python.org/issue?@action=redirect&bpo=46142]: Make --help output shorter by moving some info to the new --help-env and --help-xoptions command-line options. Also add --help-all option to print complete usage.

bpo-42316 [https://bugs.python.org/issue?@action=redirect&bpo=42316]: Document some places where an assignment expression needs parentheses.

Library

gh-89237 [https://github.com/python/cpython/issues/89237]: Fix hang on Windows in subprocess.wait_closed() in asyncio with ProactorEventLoop. Patch by Kumar Aditya.

gh-97928 [https://github.com/python/cpython/issues/97928]: tkinter.Text.count() raises now an exception for options starting with "-" instead of silently ignoring them.

gh-98393 [https://github.com/python/cpython/issues/98393]: The os module no longer accepts bytes-like paths, like bytearray and memoryview types: only the exact bytes type is accepted for bytes strings. Patch by Victor Stinner.

gh-98363 [https://github.com/python/cpython/issues/98363]: Added itertools.batched() to batch data into lists of a given length with the last list possibly being shorter than the others.

gh-98331 [https://github.com/python/cpython/issues/98331]: Update the bundled copies of pip and setuptools to versions 22.3 and 65.5.0 respectively.

gh-98307 [https://github.com/python/cpython/issues/98307]: A createSocket() method was added to SysLogHandler.

gh-96035 [https://github.com/python/cpython/issues/96035]: Fix bug in urllib.parse.urlparse() that causes certain port numbers containing whitespace, underscores, plus and minus signs, or non-ASCII digits to be incorrectly accepted.

gh-98257 [https://github.com/python/cpython/issues/98257]: Make sys.setprofile() and sys.settrace() functions reentrant. They can no long fail with: RuntimeError("Cannot install a trace function while another trace function is being installed"). Patch by Victor Stinner.

gh-98251 [https://github.com/python/cpython/issues/98251]: Allow venv to pass along PYTHON* variables to ensurepip and pip when they do not impact path resolution

gh-94597 [https://github.com/python/cpython/issues/94597]: Deprecated asyncio.AbstractEventLoopPolicy.get_child_watcher() and asyncio.AbstractEventLoopPolicy.set_child_watcher() methods to be removed in Python 3.14. Patch by Kumar Aditya.

gh-98178 [https://github.com/python/cpython/issues/98178]: On macOS, fix a crash in syslog.syslog() in multi-threaded applications. On macOS, the libc syslog() function is not thread-safe, so syslog.syslog() no longer releases the GIL to call it. Patch by Victor Stinner.

gh-44098 [https://github.com/python/cpython/issues/44098]: Release the GIL when creating mmap.mmap objects on Unix.

gh-87730 [https://github.com/python/cpython/issues/87730]: Wrap network errors consistently in urllib FTP support, so the test suite doesn't fail when a network is available but the public internet is not reachable.

gh-94597 [https://github.com/python/cpython/issues/94597]: The child watcher classes MultiLoopChildWatcher, FastChildWatcher and SafeChildWatcher are deprecated and will be removed in Python 3.14. Patch by Kumar Aditya.

gh-98023 [https://github.com/python/cpython/issues/98023]: Change default child watcher to PidfdChildWatcher on Linux systems which supports it. Patch by Kumar Aditya.

gh-90985 [https://github.com/python/cpython/issues/90985]: Earlier in 3.11 we deprecated asyncio.Task.cancel("message"). We realized we were too harsh, and have undeprecated it.

gh-65961 [https://github.com/python/cpython/issues/65961]: Do not rely solely on __cached__ on modules; code will also support __spec__.cached.

gh-97646 [https://github.com/python/cpython/issues/97646]: Replace deprecated application/javascript with text/javascript in mimetypes. See RFC 9239 [https://datatracker.ietf.org/doc/html/rfc9239.html]. Patch by Noam Cohen.

gh-97930 [https://github.com/python/cpython/issues/97930]: Apply changes from importlib_resources 5.8 and 5.9: Traversable.joinpath provides a concrete implementation. as_file now supports directories of resources.

gh-97850 [https://github.com/python/cpython/issues/97850]: Remove deprecated importlib.util.set_loader() and importlib.util.module_for_loader() from importlib.util.

gh-97837 [https://github.com/python/cpython/issues/97837]: Change deprecate warning message in unittest from

It is deprecated to return a value!=None

to

It is deprecated to return a value that is not None from a test case

gh-97825 [https://github.com/python/cpython/issues/97825]: Fixes AttributeError when subprocess.check_output() is used with argument input=None and either of the arguments encoding or errors are used.

gh-97008 [https://github.com/python/cpython/issues/97008]: NameError and AttributeError spelling suggestions provided since gh-82711 [https://github.com/python/cpython/issues/82711] are now also emitted by the pure Python traceback module. Tests for those suggestions now exercise both implementations to ensure they are equivalent. Patch by Carl Friedrich Bolz-Tereick and Łukasz Langa.

gh-97799 [https://github.com/python/cpython/issues/97799]: dataclass now uses inspect.get_annotations() to examine the annotations on class objects.

gh-97781 [https://github.com/python/cpython/issues/97781]: Removed deprecated interfaces in importlib.metadata (entry points accessed as dictionary, implicit dictionary construction of sequence of EntryPoint objects, mutablility of EntryPoints result, access of entry point by index). entry_points now has a simpler, more straightforward API (returning EntryPoints).

gh-96827 [https://github.com/python/cpython/issues/96827]: Avoid spurious tracebacks from asyncio when default executor cleanup is delayed until after the event loop is closed (e.g. as the result of a keyboard interrupt).

gh-95534 [https://github.com/python/cpython/issues/95534]: gzip.GzipFile.read() reads 10% faster.

gh-97592 [https://github.com/python/cpython/issues/97592]: Avoid a crash in the C version of asyncio.Future.remove_done_callback() when an evil argument is passed.

gh-97639 [https://github.com/python/cpython/issues/97639]: Remove tokenize.NL check from tabnanny.

gh-97545 [https://github.com/python/cpython/issues/97545]: Make Semaphore run faster.

gh-73588 [https://github.com/python/cpython/issues/73588]: Fix generation of the default name of tkinter.Checkbutton. Previously, checkbuttons in different parent widgets could have the same short name and share the same state if arguments "name" and "variable" are not specified. Now they are globally unique.

gh-96865 [https://github.com/python/cpython/issues/96865]: fix Flag to use boundary CONFORM

This restores previous Flag behavior of allowing flags with non-sequential values to be combined; e.g.

class Skip(Flag): TWO = 2 EIGHT = 8

Skip.TWO | Skip.EIGHT -> <Skip.TWO|EIGHT: 10>

gh-97005 [https://github.com/python/cpython/issues/97005]: Update bundled libexpat to 2.4.9

gh-85760 [https://github.com/python/cpython/issues/85760]: Fix race condition in asyncio where process_exited() called before the pipe_data_received() leading to inconsistent output. Patch by Kumar Aditya.

gh-96704 [https://github.com/python/cpython/issues/96704]: Pass the correct contextvars.Context when a asyncio exception handler is called on behalf of a task or callback handle. This adds a new Task method, get_context, and also a new Handle method with the same name. If this method is not found on a task object (perhaps because it is a third-party library that does not yet provide this method), the context prevailing at the time the exception handler is called is used.

gh-96819 [https://github.com/python/cpython/issues/96819]: Fixed check in multiprocessing.resource_tracker that guarantees that the length of a write to a pipe is not greater than PIPE_BUF.

gh-95865 [https://github.com/python/cpython/issues/95865]: Reduce urllib.parse.quote_from_bytes() memory use on large values.

Contributed by Dennis Sweeney.

gh-96741 [https://github.com/python/cpython/issues/96741]: Corrected type annotation for dataclass attribute pstats.FunctionProfile.ncalls to be str.

gh-96734 [https://github.com/python/cpython/issues/96734]: Update unicodedata database to Unicode 15.0.0.

gh-96735 [https://github.com/python/cpython/issues/96735]: Fix undefined behaviour in struct.unpack().

gh-46412 [https://github.com/python/cpython/issues/46412]: Improve performance of bool(db) for large ndb/gdb databases. Previously this would call len(db) which would iterate over all keys -- the answer (empty or not) is known after the first key.

gh-96652 [https://github.com/python/cpython/issues/96652]: Fix the faulthandler implementation of faulthandler.register(signal, chain=True) if the sigaction() function is not available: don't call the previous signal handler if it's NULL. Patch by Victor Stinner.

gh-68163 [https://github.com/python/cpython/issues/68163]: Correct conversion of numbers.Rational's to float.

gh-96538 [https://github.com/python/cpython/issues/96538]: Speed up bisect.bisect() functions by taking advantage of type-stability.

gh-96465 [https://github.com/python/cpython/issues/96465]: Fraction hashes are now cached.

gh-96079 [https://github.com/python/cpython/issues/96079]: In typing, fix missing field name and incorrect __module__ in _AnnotatedAlias.

gh-96415 [https://github.com/python/cpython/issues/96415]: Remove types._cell_factory from module namespace.

gh-95987 [https://github.com/python/cpython/issues/95987]: Fix repr of Any subclasses.

gh-96388 [https://github.com/python/cpython/issues/96388]: Work around missing socket functions in socket's __repr__.

gh-96385 [https://github.com/python/cpython/issues/96385]: Fix TypeVarTuple.__typing_prepare_subst__. TypeError was not raised when using more than one TypeVarTuple, like [*T, *V] in type alias substitutions.

gh-96142 [https://github.com/python/cpython/issues/96142]: Add match_args, kw_only, slots, and weakref_slot to _DataclassParams.

gh-96073 [https://github.com/python/cpython/issues/96073]: In inspect, fix overeager replacement of "typing." in formatting annotations.

gh-89258 [https://github.com/python/cpython/issues/89258]: Added a getChildren() method to logging.Logger, to get the immediate child loggers of a logger.

gh-96346 [https://github.com/python/cpython/issues/96346]: Use double caching for compiled RE patterns.

gh-96349 [https://github.com/python/cpython/issues/96349]: Fixed a minor performance regression in threading.Event.__init__()

gh-90467 [https://github.com/python/cpython/issues/90467]: Fix asyncio.streams.StreamReaderProtocol to keep a strong reference to the created task, so that it's not garbage collected

gh-96172 [https://github.com/python/cpython/issues/96172]: Fix a bug in unicodedata: east_asian_width used to return the wrong value for unassigned characters; and for yet unassigned, but reserved characters.

gh-96159 [https://github.com/python/cpython/issues/96159]: Fix a performance regression in logging TimedRotatingFileHandler. Only check for special files when the rollover time has passed.

gh-96175 [https://github.com/python/cpython/issues/96175]: Fix unused localName parameter in the Attr class in xml.dom.minidom.

gh-96145 [https://github.com/python/cpython/issues/96145]: Add AttrDict to JSON module for use with object_hook.

gh-96052 [https://github.com/python/cpython/issues/96052]: Fix handling compiler warnings (SyntaxWarning and DeprecationWarning) in codeop.compile_command() when checking for incomplete input. Previously it emitted warnings and raised a SyntaxError. Now it always returns None for incomplete input without emitting any warnings.

gh-96125 [https://github.com/python/cpython/issues/96125]: Fix incorrect condition that causes sys.thread_info.name to be wrong on pthread platforms.

gh-96019 [https://github.com/python/cpython/issues/96019]: Fix a bug in the makeunicodedata.py script leading to about 13 KiB of space saving in the unicodedata module, specifically the character decomposition data.

gh-95463 [https://github.com/python/cpython/issues/95463]: Remove an incompatible change from bpo-28080 [https://bugs.python.org/issue?@action=redirect&bpo=28080] that caused a regression that ignored the utf8 in ZipInfo.flag_bits. Patch by Pablo Galindo.

gh-69142 [https://github.com/python/cpython/issues/69142]: Add %:z strftime format code (generates tzoffset with colons as separator), see strftime() 與 strptime() 的行為.

gh-95899 [https://github.com/python/cpython/issues/95899]: Fix asyncio.Runner to call asyncio.set_event_loop() only once to avoid calling attach_loop() multiple times on child watchers. Patch by Kumar Aditya.

gh-95736 [https://github.com/python/cpython/issues/95736]: Fix unittest.IsolatedAsyncioTestCase to set event loop before calling setup functions. Patch by Kumar Aditya.

gh-95865 [https://github.com/python/cpython/issues/95865]: Speed up urllib.parse.quote_from_bytes() by replacing a list comprehension with map().

gh-95861 [https://github.com/python/cpython/issues/95861]: Add support for computing Spearman's correlation coefficient to the existing statistics.correlation() function.

gh-95804 [https://github.com/python/cpython/issues/95804]: Fix logging shutdown handler so it respects MemoryHandler.flushOnClose.

gh-95704 [https://github.com/python/cpython/issues/95704]: When a task catches asyncio.CancelledError and raises some other error, the other error should generally not silently be suppressed.

gh-95149 [https://github.com/python/cpython/issues/95149]: The HTTPStatus enum offers a couple of properties to indicate the HTTP status category e.g. HTTPStatus.OK.is_success.

gh-95609 [https://github.com/python/cpython/issues/95609]: Update bundled pip to 22.2.2.

gh-95289 [https://github.com/python/cpython/issues/95289]: Fix asyncio.TaskGroup to propagate exception when asyncio.CancelledError was replaced with another exception by a context manager. Patch by Kumar Aditya and Guido van Rossum.

gh-94909 [https://github.com/python/cpython/issues/94909]: Fix incorrect joining of relative Windows paths with drives in pathlib.PurePath initializer.

gh-95385 [https://github.com/python/cpython/issues/95385]: Faster json.dumps() when sorting of keys is not requested (default).

gh-83901 [https://github.com/python/cpython/issues/83901]: Improve Signature.bind error message for missing keyword-only arguments.

gh-95339 [https://github.com/python/cpython/issues/95339]: Update bundled pip to 22.2.1.

gh-95045 [https://github.com/python/cpython/issues/95045]: Fix GC crash when deallocating _lsprof.Profiler by untracking it before calling any callbacks. Patch by Kumar Aditya.

gh-95231 [https://github.com/python/cpython/issues/95231]: Fail gracefully if EPERM or ENOSYS is raised when loading crypt methods. This may happen when trying to load MD5 on a Linux kernel with FIPS enabled.

gh-95097 [https://github.com/python/cpython/issues/95097]: Fix asyncio.run() for asyncio.Task implementations without uncancel() method. Patch by Kumar Aditya.

gh-95087 [https://github.com/python/cpython/issues/95087]: Fix IndexError in parsing invalid date in the email module.

gh-95199 [https://github.com/python/cpython/issues/95199]: Upgrade bundled setuptools to 63.2.0.

gh-95194 [https://github.com/python/cpython/issues/95194]: Upgrade bundled pip to 22.2.

gh-93899 [https://github.com/python/cpython/issues/93899]: Fix check for existence of os.EFD_CLOEXEC, os.EFD_NONBLOCK and os.EFD_SEMAPHORE flags on older kernel versions where these flags are not present. Patch by Kumar Aditya.

gh-95166 [https://github.com/python/cpython/issues/95166]: Fix concurrent.futures.Executor.map() to cancel the currently waiting on future on an error - e.g. TimeoutError or KeyboardInterrupt.

gh-95132 [https://github.com/python/cpython/issues/95132]: Fix a sqlite3 regression where *args and **kwds were incorrectly relayed from connect() to the Connection factory. The regression was introduced in 3.11a1 with PR 24421 (gh-85128 [https://github.com/python/cpython/issues/85128]). Patch by Erlend E. Aasland.

gh-93157 [https://github.com/python/cpython/issues/93157]: Fix fileinput module didn't support errors option when inplace is true.

gh-91212 [https://github.com/python/cpython/issues/91212]: Fixed flickering of the turtle window when the tracer is turned off. Patch by Shin-myoung-serp.

gh-95077 [https://github.com/python/cpython/issues/95077]: Add deprecation warning for enum member.member access (e.g. Color.RED.BLUE). Remove EnumMeta.__getattr__.

gh-95109 [https://github.com/python/cpython/issues/95109]: Ensure that timeouts scheduled with asyncio.Timeout that have already expired are delivered promptly.

gh-95105 [https://github.com/python/cpython/issues/95105]: wsgiref.types.InputStream.__iter__() should return Iterator[bytes], not Iterable[bytes]. Patch by Shantanu Jain.

gh-95066 [https://github.com/python/cpython/issues/95066]: Replaced assert with exception in ast.parse(), when feature_version has an invalid major version. Patch by Shantanu Jain.

gh-77617 [https://github.com/python/cpython/issues/77617]: Add sqlite3 command-line interface. Patch by Erlend Aasland.

gh-95005 [https://github.com/python/cpython/issues/95005]: Replace _PyAccu with _PyUnicodeWriter in JSON encoder and StringIO and remove the _PyAccu implementation.

gh-90085 [https://github.com/python/cpython/issues/90085]: Remove -c/--clock and -t/--time CLI options of timeit. The options had been deprecated since Python 3.3 and the functionality was removed in Python 3.7. Patch by Shantanu Jain.

gh-94857 [https://github.com/python/cpython/issues/94857]: Fix refleak in _io.TextIOWrapper.reconfigure. Patch by Kumar Aditya.

gh-94821 [https://github.com/python/cpython/issues/94821]: Fix binding of unix socket to empty address on Linux to use an available address from the abstract namespace, instead of "0".

gh-94736 [https://github.com/python/cpython/issues/94736]: Fix crash when deallocating an instance of a subclass of _multiprocessing.SemLock. Patch by Kumar Aditya.

gh-81620 [https://github.com/python/cpython/issues/81620]: Add random.binomialvariate().

gh-74116 [https://github.com/python/cpython/issues/74116]: Allow asyncio.StreamWriter.drain() to be awaited concurrently by multiple tasks. Patch by Kumar Aditya.

gh-87822 [https://github.com/python/cpython/issues/87822]: When called with capture_locals=True, the traceback module functions swallow exceptions raised from calls to repr() on local variables of frames. This is in order to prioritize the original exception over rendering errors. An indication of the failure is printed in place of the missing value. (Patch by Simon-Martin Schroeder).

gh-88050 [https://github.com/python/cpython/issues/88050]: Fix asyncio subprocess transport to kill process cleanly when process is blocked and avoid RuntimeError when loop is closed. Patch by Kumar Aditya.

gh-94637 [https://github.com/python/cpython/issues/94637]: SSLContext.set_default_verify_paths() now releases the GIL around SSL_CTX_set_default_verify_paths call. The function call performs I/O and CPU intensive work.

gh-94309 [https://github.com/python/cpython/issues/94309]: Deprecate aliases typing.Hashable and typing.Sized

gh-92546 [https://github.com/python/cpython/issues/92546]: An undocumented python -m pprint benchmark is moved into pprint suite of pyperformance. Patch by Oleg Iarygin.

gh-94607 [https://github.com/python/cpython/issues/94607]: Fix subclassing complex generics with type variables in typing. Previously an error message saying Some type variables ... are not listed in Generic[...] was shown. typing no longer populates __parameters__ with the __parameters__ of a Python class.

gh-94619 [https://github.com/python/cpython/issues/94619]: Remove the long-deprecated module_repr() from importlib.

gh-93910 [https://github.com/python/cpython/issues/93910]: The ability to access the other values of an enum on an enum (e.g. Color.RED.BLUE) has been restored in order to fix a performance regression.

gh-93896 [https://github.com/python/cpython/issues/93896]: Fix asyncio.run() and unittest.IsolatedAsyncioTestCase to always the set event loop as it was done in Python 3.10 and earlier. Patch by Kumar Aditya.

gh-94343 [https://github.com/python/cpython/issues/94343]: Allow setting the attributes of reprlib.Repr during object initialization

gh-94382 [https://github.com/python/cpython/issues/94382]: Port static types of _multiprocessing module to heap types. Patch by Kumar Aditya.

gh-78724 [https://github.com/python/cpython/issues/78724]: Fix crash in struct.Struct when it was not completely initialized by initializing it in __new__(). Patch by Kumar Aditya.

gh-94510 [https://github.com/python/cpython/issues/94510]: Re-entrant calls to sys.setprofile() and sys.settrace() now raise RuntimeError. Patch by Pablo Galindo.

gh-92336 [https://github.com/python/cpython/issues/92336]: Fix bug where linecache.getline() fails on bad files with UnicodeDecodeError or SyntaxError. It now returns an empty string as per the documentation.

gh-94398 [https://github.com/python/cpython/issues/94398]: Once a asyncio.TaskGroup has started shutting down (i.e., at least one task has failed and the task group has started cancelling the remaining tasks), it should not be possible to add new tasks to the task group.

gh-94383 [https://github.com/python/cpython/issues/94383]: xml.etree: Remove the ElementTree.Element.copy() method of the pure Python implementation, deprecated in Python 3.10, use the copy.copy() function instead. The C implementation of xml.etree has no copy() method, only a __copy__() method. Patch by Victor Stinner.

gh-94379 [https://github.com/python/cpython/issues/94379]: zipimport: Remove find_loader() and find_module() methods, deprecated in Python 3.10: use the find_spec() method instead. See PEP 451 [https://peps.python.org/pep-0451/] for the rationale. Patch by Victor Stinner.

gh-94352 [https://github.com/python/cpython/issues/94352]: shlex.split(): Passing None for s argument now raises an exception, rather than reading sys.stdin. The feature was deprecated in Python 3.9. Patch by Victor Stinner.

gh-94318 [https://github.com/python/cpython/issues/94318]: Strip trailing spaces in pydoc text output.

gh-89988 [https://github.com/python/cpython/issues/89988]: Fix memory leak in pickle.Pickler when looking up dispatch_table. Patch by Kumar Aditya.

gh-90016 [https://github.com/python/cpython/issues/90016]: Deprecate sqlite3 default adapters and converters. Patch by Erlend E. Aasland.

gh-94254 [https://github.com/python/cpython/issues/94254]: Fixed types of struct module to be immutable. Patch by Kumar Aditya.

gh-93259 [https://github.com/python/cpython/issues/93259]: Now raise ValueError when None or an empty string are passed to Distribution.from_name (and other callers).

gh-74696 [https://github.com/python/cpython/issues/74696]: shutil.make_archive() now passes the root_dir argument to custom archivers which support it.

gh-94216 [https://github.com/python/cpython/issues/94216]: The dis module now has the opcodes for pseudo instructions (those which are used by the compiler during code generation but then removed or replaced by real opcodes before the final bytecode is emitted).

gh-93096 [https://github.com/python/cpython/issues/93096]: Removed undocumented python -m codecs. Use python -m unittest test.test_codecs.EncodedFileTest instead.

gh-94207 [https://github.com/python/cpython/issues/94207]: Made _struct.Struct GC-tracked in order to fix a reference leak in the _struct module.

gh-93096 [https://github.com/python/cpython/issues/93096]: Removed undocumented -t argument of python -m base64. Use python -m unittest test.test_base64.LegacyBase64TestCase.test_encodebytes instead.

gh-94226 [https://github.com/python/cpython/issues/94226]: Remove the locale.format() function, deprecated in Python 3.7: use locale.format_string() instead. Patch by Victor Stinner.

gh-94199 [https://github.com/python/cpython/issues/94199]: Remove the ssl.match_hostname() function. The ssl.match_hostname() was deprecated in Python 3.7. OpenSSL performs hostname matching since Python 3.7, Python no longer uses the ssl.match_hostname() function. Patch by Victor Stinner.

gh-94214 [https://github.com/python/cpython/issues/94214]: Document the context object used in the venv.EnvBuilder class, and add the new environment's library path to it.

gh-94199 [https://github.com/python/cpython/issues/94199]: Remove the ssl.wrap_socket() function, deprecated in Python 3.7: instead, create a ssl.SSLContext object and call its ssl.SSLContext.wrap_socket method. Any package that still uses ssl.wrap_socket() is broken and insecure. The function neither sends a SNI TLS extension nor validates server hostname. Code is subject to CWE 295 [https://cwe.mitre.org/data/definitions/295.html] Improper Certificate Validation. Patch by Victor Stinner.

gh-94199 [https://github.com/python/cpython/issues/94199]: Remove the ssl.RAND_pseudo_bytes() function, deprecated in Python 3.6: use os.urandom() or ssl.RAND_bytes() instead. Patch by Victor Stinner.

gh-94199 [https://github.com/python/cpython/issues/94199]: hashlib: Remove the pure Python implementation of hashlib.pbkdf2_hmac(), deprecated in Python 3.10. Python 3.10 and newer requires OpenSSL 1.1.1 (PEP 644 [https://peps.python.org/pep-0644/]): this OpenSSL version provides a C implementation of pbkdf2_hmac() which is faster. Patch by Victor Stinner.

gh-94196 [https://github.com/python/cpython/issues/94196]: gzip: Remove the filename attribute of gzip.GzipFile, deprecated since Python 2.6, use the name attribute instead. In write mode, the filename attribute added '.gz' file extension if it was not present. Patch by Victor Stinner.

gh-94182 [https://github.com/python/cpython/issues/94182]: run the asyncio.PidfdChildWatcher on the running loop, this allows event loops to run subprocesses when there is no default event loop running on the main thread

gh-94169 [https://github.com/python/cpython/issues/94169]: Remove io.OpenWrapper and _pyio.OpenWrapper, deprecated in Python 3.10: just use open() instead. The open() (io.open()) function is a built-in function. Since Python 3.10, _pyio.open() is also a static method. Patch by Victor Stinner.

gh-91742 [https://github.com/python/cpython/issues/91742]: Fix pdb crash after jump caused by a null pointer dereference. Patch by Kumar Aditya.

gh-94101 [https://github.com/python/cpython/issues/94101]: Manual instantiation of ssl.SSLSession objects is no longer allowed as it lead to misconfigured instances that crashed the interpreter when attributes where accessed on them.

gh-84753 [https://github.com/python/cpython/issues/84753]: inspect.iscoroutinefunction(), inspect.isgeneratorfunction(), and inspect.isasyncgenfunction() now properly return True for duck-typed function-like objects like instances of unittest.mock.AsyncMock.

This makes inspect.iscoroutinefunction() consistent with the behavior of asyncio.iscoroutinefunction(). Patch by Mehdi ABAAKOUK.

gh-94028 [https://github.com/python/cpython/issues/94028]: Fix a regression in the sqlite3 where statement objects were not properly cleared and reset after use in cursor iters. The regression was introduced by PR 27884 in Python 3.11a1. Patch by Erlend E. Aasland.

gh-93973 [https://github.com/python/cpython/issues/93973]: Add keyword argument all_errors to asyncio.create_connection so that multiple connection errors can be raised as an ExceptionGroup.

gh-93963 [https://github.com/python/cpython/issues/93963]: Officially deprecate from importlib.abc classes moved to importlib.resources.abc.

gh-93858 [https://github.com/python/cpython/issues/93858]: Prevent error when activating venv in nested fish instances.

gh-93820 [https://github.com/python/cpython/issues/93820]: Pickle enum.Flag by name.

gh-93847 [https://github.com/python/cpython/issues/93847]: Fix repr of enum of generic aliases.

gh-91404 [https://github.com/python/cpython/issues/91404]: Revert the re memory leak when a match is terminated by a signal or memory allocation failure as the implemented fix caused a major performance regression.

gh-83499 [https://github.com/python/cpython/issues/83499]: Fix double closing of file description in tempfile.

gh-93820 [https://github.com/python/cpython/issues/93820]: Fixed a regression when copy.copy()-ing enum.Flag with multiple flag members.

gh-79512 [https://github.com/python/cpython/issues/79512]: Fixed names and __module__ value of weakref classes ReferenceType, ProxyType, CallableProxyType. It makes them pickleable.

gh-91389 [https://github.com/python/cpython/issues/91389]: Fix an issue where dis utilities could report missing or incorrect position information in the presence of CACHE entries.

gh-93626 [https://github.com/python/cpython/issues/93626]: Set __future__.annotations to have a None mandatoryRelease to indicate that it is currently 'TBD'.

gh-90473 [https://github.com/python/cpython/issues/90473]: Emscripten and WASI have no home directory and cannot provide PEP 370 [https://peps.python.org/pep-0370/] user site directory.

gh-90494 [https://github.com/python/cpython/issues/90494]: copy.copy() and copy.deepcopy() now always raise a TypeError if __reduce__() returns a tuple with length 6 instead of silently ignore the 6th item or produce incorrect result.

gh-90549 [https://github.com/python/cpython/issues/90549]: Fix a multiprocessing bug where a global named resource (such as a semaphore) could leak when a child process is spawned (as opposed to forked).

gh-93521 [https://github.com/python/cpython/issues/93521]: Fixed a case where dataclasses would try to add __weakref__ into the __slots__ for a dataclass that specified weakref_slot=True when it was already defined in one of its bases. This resulted in a TypeError upon the new class being created.

gh-79579 [https://github.com/python/cpython/issues/79579]: sqlite3 now correctly detects DML queries with leading comments. Patch by Erlend E. Aasland.

gh-93421 [https://github.com/python/cpython/issues/93421]: Update sqlite3.Cursor.rowcount when a DML statement has run to completion. This fixes the row count for SQL queries like UPDATE ... RETURNING. Patch by Erlend E. Aasland.

gh-93475 [https://github.com/python/cpython/issues/93475]: Expose FICLONE and FICLONERANGE constants in fcntl. Patch by Illia Volochii.

gh-93370 [https://github.com/python/cpython/issues/93370]: Deprecate version and version_info.

gh-91810 [https://github.com/python/cpython/issues/91810]: Suppress writing an XML declaration in open files in ElementTree.write() with encoding='unicode' and xml_declaration=None.

gh-91162 [https://github.com/python/cpython/issues/91162]: Support splitting of unpacked arbitrary-length tuple over TypeVar and TypeVarTuple parameters. For example:

A[T, *Ts][*tuple[int, ...]] -> A[int, *tuple[int, ...]]

A[*Ts, T][*tuple[int, ...]] -> A[*tuple[int, ...], int]

gh-93353 [https://github.com/python/cpython/issues/93353]: Fix the importlib.resources.as_file() context manager to remove the temporary file if destroyed late during Python finalization: keep a local reference to the os.remove() function. Patch by Victor Stinner.

gh-83658 [https://github.com/python/cpython/issues/83658]: Make multiprocessing.Pool raise an exception if maxtasksperchild is not None or a positive int.

gh-93312 [https://github.com/python/cpython/issues/93312]: Add os.PIDFD_NONBLOCK flag to open a file descriptor for a process with os.pidfd_open() in non-blocking mode. Patch by Kumar Aditya.

gh-88123 [https://github.com/python/cpython/issues/88123]: Implement Enum.__contains__ that returns True or False to replace the deprecated behaviour that would sometimes raise a TypeError.

gh-93297 [https://github.com/python/cpython/issues/93297]: Make asyncio task groups prevent child tasks from being GCed

gh-85308 [https://github.com/python/cpython/issues/85308]: Changed argparse.ArgumentParser to use filesystem encoding and error handler instead of default text encoding to read arguments from file (e.g. fromfile_prefix_chars option). This change affects Windows; argument file should be encoded with UTF-8 instead of ANSI Codepage.

gh-93156 [https://github.com/python/cpython/issues/93156]: Accessing the pathlib.PurePath.parents sequence of an absolute path using negative index values produced incorrect results.

gh-93162 [https://github.com/python/cpython/issues/93162]: Add the ability for logging.config.dictConfig() to usefully configure QueueHandler and QueueListener as a pair, and add logging.getHandlerByName() and logging.getHandlerNames() APIs to allow access to handlers by name.

gh-93243 [https://github.com/python/cpython/issues/93243]: The smtpd module was removed per the schedule in PEP 594 [https://peps.python.org/pep-0594/].

gh-92886 [https://github.com/python/cpython/issues/92886]: Replace assert statements with raise AssertionError() in BaseHandler so that the tested behaviour is maintained running with optimizations (-O).

gh-90155 [https://github.com/python/cpython/issues/90155]: Fix broken asyncio.Semaphore when acquire is cancelled.

gh-90817 [https://github.com/python/cpython/issues/90817]: The locale.resetlocale() function is deprecated and will be removed in Python 3.13. Use locale.setlocale(locale.LC_ALL, "") instead. Patch by Victor Stinner.

gh-91513 [https://github.com/python/cpython/issues/91513]: Added taskName attribute to logging module for use with asyncio tasks.

gh-74696 [https://github.com/python/cpython/issues/74696]: shutil.make_archive() no longer temporarily changes the current working directory during creation of standard .zip or tar archives.

gh-92728 [https://github.com/python/cpython/issues/92728]: The re.template() function and the corresponding re.TEMPLATE and re.T flags are restored after they were removed in 3.11.0b1, but they are now deprecated, so they might be removed from Python 3.13.

gh-93033 [https://github.com/python/cpython/issues/93033]: Search in some strings (platform dependent i.e [U+0xFFFF, U+0x0100] on Windows or [U+0xFFFFFFFF, U+0x00010000] on Linux 64-bit) are now up to 10 times faster.

gh-89973 [https://github.com/python/cpython/issues/89973]: Fix re.error raised in fnmatch if the pattern contains a character range with upper bound lower than lower bound (e.g. [c-a]). Now such ranges are interpreted as empty ranges.

gh-93044 [https://github.com/python/cpython/issues/93044]: No longer convert the database argument of sqlite3.connect() to bytes before passing it to the factory.

gh-93010 [https://github.com/python/cpython/issues/93010]: In a very special case, the email package tried to append the nonexistent InvalidHeaderError to the defect list. It should have been InvalidHeaderDefect.

gh-92986 [https://github.com/python/cpython/issues/92986]: Fix ast.unparse() when ImportFrom.level is None

gh-92932 [https://github.com/python/cpython/issues/92932]: Now dis() and get_instructions() handle operand values for instructions prefixed by EXTENDED_ARG_QUICK. Patch by Sam Gross and Donghee Na.

gh-92675 [https://github.com/python/cpython/issues/92675]: Fix venv.ensure_directories() to accept pathlib.Path arguments in addition to str paths. Patch by David Foster.

gh-87901 [https://github.com/python/cpython/issues/87901]: Removed the encoding argument from os.popen() that was added in 3.11b1.

gh-91922 [https://github.com/python/cpython/issues/91922]: Fix function sqlite.connect() and the sqlite.Connection constructor on non-UTF-8 locales. Also, they now support bytes paths non-decodable with the current FS encoding.

gh-92869 [https://github.com/python/cpython/issues/92869]: Added c_time_t to ctypes, which has the same size as the time_t type in C.

gh-92839 [https://github.com/python/cpython/issues/92839]: Fixed crash resulting from calling bisect.insort() or bisect.insort_left() with the key argument not equal to None.

gh-90473 [https://github.com/python/cpython/issues/90473]: subprocess now fails early on Emscripten and WASI platforms to work around missing os.pipe() on WASI.

gh-89325 [https://github.com/python/cpython/issues/89325]: Removed many old deprecated unittest features: TestCase method aliases, undocumented and broken TestCase method assertDictContainsSubset, undocumented TestLoader.loadTestsFromModule parameter use_load_tests, and an underscored alias of the TextTestResult class.

gh-92734 [https://github.com/python/cpython/issues/92734]: Allow multi-element reprs emitted by reprlib to be pretty-printed using configurable indentation.

gh-92671 [https://github.com/python/cpython/issues/92671]: Fixed ast.unparse() for empty tuples in the assignment target context.

gh-91581 [https://github.com/python/cpython/issues/91581]: utcfromtimestamp() no longer attempts to resolve fold in the pure Python implementation, since the fold is never 1 in UTC. In addition to being slightly faster in the common case, this also prevents some errors when the timestamp is close to datetime.min. Patch by Paul Ganssle.

gh-86388 [https://github.com/python/cpython/issues/86388]: Removed randrange() functionality deprecated since Python 3.10. Formerly, randrange(10.0) losslessly converted to randrange(10). Now, it raises a TypeError. Also, the exception raised for non-integral values such as randrange(10.5) or randrange('10') has been changed from ValueError to TypeError.

gh-90385 [https://github.com/python/cpython/issues/90385]: Add pathlib.Path.walk() as an alternative to os.walk().

gh-92550 [https://github.com/python/cpython/issues/92550]: Fix pathlib.Path.rglob() for empty pattern.

gh-92591 [https://github.com/python/cpython/issues/92591]: Allow logging filters to return a logging.LogRecord instance so that filters attached to logging.Handlers can enrich records without side effects on other handlers.

gh-92445 [https://github.com/python/cpython/issues/92445]: Fix a bug in argparse where nargs="*" would raise an error instead of returning an empty list when 0 arguments were supplied if choice was also defined in parser.add_argument.

gh-92547 [https://github.com/python/cpython/issues/92547]: Remove undocumented sqlite3 features deprecated in Python 3.10:

sqlite3.enable_shared_cache()

sqlite3.OptimizedUnicode

Patch by Erlend E. Aasland.

gh-92530 [https://github.com/python/cpython/issues/92530]: Fix an issue that occurred after interrupting threading.Condition.notify().

gh-92531 [https://github.com/python/cpython/issues/92531]: The statistics.median_grouped() function now always return a float. Formerly, it did not convert the input type when for sequences of length one.

gh-84131 [https://github.com/python/cpython/issues/84131]: The pathlib.Path deprecated method link_to has been removed. Use 3.10's hardlink_to() method instead as its semantics are consistent with that of symlink_to().

gh-89336 [https://github.com/python/cpython/issues/89336]: Removed configparser module APIs: the SafeConfigParser class alias, the ParsingError.filename property and parameter, and the ConfigParser.readfp method, all of which were deprecated since Python 3.2.

gh-92391 [https://github.com/python/cpython/issues/92391]: Add __class_getitem__() to csv.DictReader and csv.DictWriter, allowing them to be parameterized at runtime. Patch by Marc Mueller.

gh-91968 [https://github.com/python/cpython/issues/91968]: Add SO_RTABLE and SO_USER_COOKIE constants to socket.

gh-91810 [https://github.com/python/cpython/issues/91810]: ElementTree method write() and function tostring() now use the text file's encoding ("UTF-8" if not available) instead of locale encoding in XML declaration when encoding="unicode" is specified.

gh-81790 [https://github.com/python/cpython/issues/81790]: os.path.splitdrive() now understands DOS device paths with UNC links (beginning \\?\UNC\). Contributed by Barney Gale.

gh-91760 [https://github.com/python/cpython/issues/91760]: Apply more strict rules for numerical group references and group names in regular expressions. Only sequence of ASCII digits is now accepted as a numerical reference. The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore.

gh-90622 [https://github.com/python/cpython/issues/90622]: Worker processes for concurrent.futures.ProcessPoolExecutor are no longer spawned on demand (a feature added in 3.9) when the multiprocessing context start method is "fork" as that can lead to deadlocks in the child processes due to a fork happening while threads are running.

gh-91577 [https://github.com/python/cpython/issues/91577]: Move imports in SharedMemory methods to module level so that they can be executed late in python finalization.

gh-91581 [https://github.com/python/cpython/issues/91581]: Remove an unhandled error case in the C implementation of calls to datetime.fromtimestamp with no time zone (i.e. getting a local time from an epoch timestamp). This should have no user-facing effect other than giving a possibly more accurate error message when called with timestamps that fall on 10000-01-01 in the local time. Patch by Paul Ganssle.

gh-91539 [https://github.com/python/cpython/issues/91539]: Improve performance of urllib.request.getproxies_environment when there are many environment variables

gh-91524 [https://github.com/python/cpython/issues/91524]: Speed up the regular expression substitution (functions re.sub() and re.subn() and corresponding re.Pattern methods) for replacement strings containing group references by 2--3 times.

gh-91447 [https://github.com/python/cpython/issues/91447]: Fix findtext in the xml module to only give an empty string when the text attribute is set to None.

gh-91456 [https://github.com/python/cpython/issues/91456]: Deprecate current default auto() behavior: In 3.13 the default will be for for auto() to always return the largest member value incremented by 1, and to raise if incompatible value types are used.

bpo-47231 [https://bugs.python.org/issue?@action=redirect&bpo=47231]: Fixed an issue with inconsistent trailing slashes in tarfile longname directories.

bpo-39064 [https://bugs.python.org/issue?@action=redirect&bpo=39064]: zipfile.ZipFile now raises zipfile.BadZipFile instead of ValueError when reading a corrupt zip file in which the central directory offset is negative.

bpo-41287 [https://bugs.python.org/issue?@action=redirect&bpo=41287]: Fix handling of the doc argument in subclasses of property().

gh-90005 [https://github.com/python/cpython/issues/90005]: ctypes dependency libffi is now detected with pkg-config.

bpo-32547 [https://bugs.python.org/issue?@action=redirect&bpo=32547]: The constructors for DictWriter and DictReader now coerce the fieldnames argument to a list if it is an iterator.

bpo-35540 [https://bugs.python.org/issue?@action=redirect&bpo=35540]: Fix dataclasses.asdict() crash when collections.defaultdict is present in the attributes.

bpo-47063 [https://bugs.python.org/issue?@action=redirect&bpo=47063]: Add an index_pages parameter to support using non-default index page names.

bpo-47025 [https://bugs.python.org/issue?@action=redirect&bpo=47025]: Drop support for bytes on sys.path.

bpo-46951 [https://bugs.python.org/issue?@action=redirect&bpo=46951]: Order the contents of zipapp archives, to make builds more reproducible.

bpo-42777 [https://bugs.python.org/issue?@action=redirect&bpo=42777]: Implement pathlib.Path.is_mount() for Windows paths.

bpo-46755 [https://bugs.python.org/issue?@action=redirect&bpo=46755]: In QueueHandler, clear stack_info from LogRecord to prevent stack trace from being written twice.

bpo-45393 [https://bugs.python.org/issue?@action=redirect&bpo=45393]: Fix the formatting for await x and not x in the operator precedence table when using the help() system.

bpo-46642 [https://bugs.python.org/issue?@action=redirect&bpo=46642]: Improve error message when trying to subclass an instance of typing.TypeVar, typing.ParamSpec, typing.TypeVarTuple, etc. Based on patch by Gregory Beauregard.

bpo-46364 [https://bugs.python.org/issue?@action=redirect&bpo=46364]: Restrict use of sockets instead of pipes for stdin of subprocesses created by asyncio to AIX platform only.

bpo-28249 [https://bugs.python.org/issue?@action=redirect&bpo=28249]: Set doctest.DocTest.lineno to None when an object does not have __doc__.

bpo-46197 [https://bugs.python.org/issue?@action=redirect&bpo=46197]: Fix ensurepip environment isolation for subprocess running pip.

bpo-45924 [https://bugs.python.org/issue?@action=redirect&bpo=45924]: Fix asyncio incorrect traceback when future's exception is raised multiple times. Patch by Kumar Aditya.

bpo-45046 [https://bugs.python.org/issue?@action=redirect&bpo=45046]: Add support of context managers in unittest: methods enterContext() and enterClassContext() of class TestCase, method enterAsyncContext() of class IsolatedAsyncioTestCase and function unittest.enterModuleContext().

bpo-44173 [https://bugs.python.org/issue?@action=redirect&bpo=44173]: Enable fast seeking of uncompressed unencrypted zipfile.ZipExtFile

bpo-42627 [https://bugs.python.org/issue?@action=redirect&bpo=42627]: Fix incorrect parsing of Windows registry proxy settings

bpo-42047 [https://bugs.python.org/issue?@action=redirect&bpo=42047]: Add threading.get_native_id() support for DragonFly BSD. Patch by David Carlier.

bpo-14243 [https://bugs.python.org/issue?@action=redirect&bpo=14243]: The tempfile.NamedTemporaryFile function has a new optional parameter delete_on_close

bpo-41246 [https://bugs.python.org/issue?@action=redirect&bpo=41246]: Give the same callback function for when the overlapped operation is done to the functions recv, recv_into, recvfrom, sendto, send and sendfile inside IocpProactor.

bpo-39264 [https://bugs.python.org/issue?@action=redirect&bpo=39264]: Fixed collections.UserDict.get() to not call __missing__() when a value is not found. This matches the behavior of dict. Patch by Bar Harel.

bpo-38693 [https://bugs.python.org/issue?@action=redirect&bpo=38693]: importlib now uses f-strings internally instead of str.format.

bpo-38267 [https://bugs.python.org/issue?@action=redirect&bpo=38267]: Add timeout parameter to asyncio.loop.shutdown_default_executor(). The default value is None, which means the executor will be given an unlimited amount of time. When called from asyncio.Runner or asyncio.run(), the default timeout is 5 minutes.

bpo-34828 [https://bugs.python.org/issue?@action=redirect&bpo=34828]: sqlite3.Connection.iterdump() now handles databases that use AUTOINCREMENT in one or more tables.

bpo-32990 [https://bugs.python.org/issue?@action=redirect&bpo=32990]: Support reading wave files with the WAVE_FORMAT_EXTENSIBLE format in the wave module.

bpo-26253 [https://bugs.python.org/issue?@action=redirect&bpo=26253]: Allow adjustable compression level for tarfile streams in tarfile.open().

Documentation

gh-85525 [https://github.com/python/cpython/issues/85525]: Remove extra row

gh-86404 [https://github.com/python/cpython/issues/86404]: Deprecated tools make suspicious and rstlint.py are now removed. They have been replaced by sphinx-lint [https://pypi.org/project/sphinx-lint/].

gh-97741 [https://github.com/python/cpython/issues/97741]: Fix ! in c domain ref target syntax via a conf.py patch, so it works as intended to disable ref target resolution.

gh-96432 [https://github.com/python/cpython/issues/96432]: Fraction literals now support whitespace around the forward slash, Fraction('2 / 3').

gh-96098 [https://github.com/python/cpython/issues/96098]: Improve discoverability of the higher level concurrent.futures module by providing clearer links from the lower level threading and multiprocessing modules.

gh-95957 [https://github.com/python/cpython/issues/95957]: What's New 3.11 now has instructions for how to provide compiler and linker flags for Tcl/Tk and OpenSSL on RHEL 7 and CentOS 7.

gh-95588 [https://github.com/python/cpython/issues/95588]: Clarified the conflicting advice given in the ast documentation about ast.literal_eval() being "safe" for use on untrusted input while at the same time warning that it can crash the process. The latter statement is true and is deemed unfixable without a large amount of work unsuitable for a bugfix. So we keep the warning and no longer claim that literal_eval is safe.

gh-91207 [https://github.com/python/cpython/issues/91207]: Fix stylesheet not working in Windows CHM htmlhelp docs and add warning that they are deprecated. Contributed by C.A.M. Gerlach.

gh-95454 [https://github.com/python/cpython/issues/95454]: Replaced incorrectly written true/false values in documentation. Patch by Robert O'Shea

gh-95451 [https://github.com/python/cpython/issues/95451]: Update library documentation with availability information on WebAssembly platforms wasm32-emscripten and wasm32-wasi.

gh-95415 [https://github.com/python/cpython/issues/95415]: Use consistent syntax for platform availability. The directive now supports a content body and emits a warning when it encounters an unknown platform.

gh-94321 [https://github.com/python/cpython/issues/94321]: Document the PEP 246 [https://peps.python.org/pep-0246/] style protocol type sqlite3.PrepareProtocol.

gh-86128 [https://github.com/python/cpython/issues/86128]: Document a limitation in ThreadPoolExecutor where its exit handler is executed before any handlers in atexit.

gh-61162 [https://github.com/python/cpython/issues/61162]: Clarify sqlite3 behavior when How to use the connection context manager.

gh-87260 [https://github.com/python/cpython/issues/87260]: Align sqlite3 argument specs with the actual implementation.

gh-86986 [https://github.com/python/cpython/issues/86986]: The minimum Sphinx version required to build the documentation is now 3.2.

gh-88831 [https://github.com/python/cpython/issues/88831]: Augmented documentation of asyncio.create_task(). Clarified the need to keep strong references to tasks and added a code snippet detailing how to do this.

gh-86438 [https://github.com/python/cpython/issues/86438]: Clarify that -W and PYTHONWARNINGS are matched literally and case-insensitively, rather than as regular expressions, in warnings.

gh-93031 [https://github.com/python/cpython/issues/93031]: Update tutorial introduction output to use 3.10+ SyntaxError invalid range.

gh-92240 [https://github.com/python/cpython/issues/92240]: Added release dates for "What's New in Python 3.X" for 3.0, 3.1, 3.2, 3.8 and 3.10

bpo-47161 [https://bugs.python.org/issue?@action=redirect&bpo=47161]: Document that pathlib.PurePath does not collapse initial double slashes because they denote UNC paths.

bpo-40838 [https://bugs.python.org/issue?@action=redirect&bpo=40838]: Document that inspect.getdoc(), inspect.getmodule(), and inspect.getsourcefile() might return None.

bpo-43689 [https://bugs.python.org/issue?@action=redirect&bpo=43689]: The Differ documentation now also mentions other whitespace characters, which make it harder to understand the diff output.

bpo-38056 [https://bugs.python.org/issue?@action=redirect&bpo=38056]: Overhaul the Error Handlers documentation in codecs.

bpo-13553 [https://bugs.python.org/issue?@action=redirect&bpo=13553]: Document tkinter.Tk args.

Tests

gh-95027 [https://github.com/python/cpython/issues/95027]: On Windows, when the Python test suite is run with the -jN option, the ANSI code page is now used as the encoding for the stdout temporary file, rather than using UTF-8 which can lead to decoding errors. Patch by Victor Stinner.

gh-96624 [https://github.com/python/cpython/issues/96624]: Fixed the failure of repeated runs of test.test_unittest caused by side effects in test_dotted_but_module_not_loaded.

gh-95243 [https://github.com/python/cpython/issues/95243]: Mitigate the inherent race condition from using find_unused_port() in testSockName() by trying to find an unused port a few times before failing. Patch by Ross Burton.

gh-95573 [https://github.com/python/cpython/issues/95573]: Lib/test/test_asyncio/test_ssl.py [https://github.com/python/cpython/tree/3.14/Lib/test/test_asyncio/test_ssl.py] exposed a bug in the macOS kernel where intense concurrent load on non-blocking sockets occasionally causes errno.ENOBUFS ("No buffer space available") to be emitted. FB11063974 filed with Apple, in the mean time as a workaround buffer size used in tests on macOS is decreased to avoid intermittent failures. Patch by Fantix King.

gh-95280 [https://github.com/python/cpython/issues/95280]: Fix problem with test_ssl test_get_ciphers on systems that require perfect forward secrecy (PFS) ciphers.

gh-95212 [https://github.com/python/cpython/issues/95212]: Make multiprocessing test case test_shared_memory_recreate parallel-safe.

gh-95218 [https://github.com/python/cpython/issues/95218]: Move tests for importlib.resources into test_importlib.resources.

gh-93963 [https://github.com/python/cpython/issues/93963]: Updated tests to use preferred location for importlib.resources ABCs.

gh-94675 [https://github.com/python/cpython/issues/94675]: Add a regression test for re exponentional slowdown when using rjsmin.

gh-91330 [https://github.com/python/cpython/issues/91330]: Added more tests for dataclasses to cover behavior with data descriptor-based fields.

gh-94208 [https://github.com/python/cpython/issues/94208]: test_ssl is now checking for supported TLS version and protocols in more tests.

gh-94315 [https://github.com/python/cpython/issues/94315]: Tests now check for DAC override capability instead of relying on os.geteuid().

gh-54781 [https://github.com/python/cpython/issues/54781]: Rename test_tk to test_tkinter, and rename test_ttk_guionly to test_ttk. Patch by Victor Stinner.

gh-93839 [https://github.com/python/cpython/issues/93839]: Move Lib/ctypes/test/ to Lib/test/test_ctypes/. Patch by Victor Stinner.

gh-93951 [https://github.com/python/cpython/issues/93951]: In test_bdb.StateTestCase.test_skip, avoid including auxiliary importers.

gh-93957 [https://github.com/python/cpython/issues/93957]: Provide nicer error reporting from subprocesses in test_venv.EnsurePipTest.test_with_pip.

gh-93884 [https://github.com/python/cpython/issues/93884]: Add test cases for PyNumber_ToBase() that take a large number or a non-int object as parameter.

gh-93852 [https://github.com/python/cpython/issues/93852]: test_asyncio, test_logging, test_socket and test_socketserver now create AF_UNIX domains in the current directory to no longer fail with OSError("AF_UNIX path too long") if the temporary directory (the TMPDIR environment variable) is too long. Patch by Victor Stinner.

gh-93353 [https://github.com/python/cpython/issues/93353]: regrtest now checks if a test leaks temporary files or directories if run with -jN option. Patch by Victor Stinner.

gh-84461 [https://github.com/python/cpython/issues/84461]: run_tests.py now handles cross compiling env vars correctly and pass HOSTRUNNER to regression tests.

gh-93616 [https://github.com/python/cpython/issues/93616]: test_modulefinder now creates a temporary directory in ModuleFinderTest.setUp() instead of module scope.

gh-93575 [https://github.com/python/cpython/issues/93575]: Fix issue with test_unicode test_raiseMemError. The test case now use test.support.calcobjsize to calculate size of PyUnicode structs. sys.getsizeof() may return different size when string has UTF-8 memory.

gh-90473 [https://github.com/python/cpython/issues/90473]: WASI does not have a chmod(2) syscall. os.chmod() is now a dummy function on WASI. Skip all tests that depend on working os.chmod().

gh-90473 [https://github.com/python/cpython/issues/90473]: Skip tests on WASI that require symlinks with absolute paths.

gh-57539 [https://github.com/python/cpython/issues/57539]: Increase calendar test coverage for calendar.LocaleTextCalendar.formatweekday().

gh-90473 [https://github.com/python/cpython/issues/90473]: Skip symlink tests on WASI. wasmtime uses openat2(2) with RESOLVE_BENEATH flag, which prevents symlinks with absolute paths.

gh-89858 [https://github.com/python/cpython/issues/89858]: Fix test_embed for out-of-tree builds. Patch by Kumar Aditya.

gh-92886 [https://github.com/python/cpython/issues/92886]: Fixing tests that fail when running with optimizations (-O) in test_imaplib.py.

gh-92886 [https://github.com/python/cpython/issues/92886]: Fixing tests that fail when running with optimizations (-O) in test_zipimport.py

gh-92886 [https://github.com/python/cpython/issues/92886]: Fixing tests that fail when running with optimizations (-O) in test_py_compile.py

gh-92886 [https://github.com/python/cpython/issues/92886]: Fixing tests that fail when running with optimizations (-O) in test_sys_settrace.py.

gh-92886 [https://github.com/python/cpython/issues/92886]: Fixing tests that fail when running with optimizations (-O) in _test_multiprocessing.py

gh-92670 [https://github.com/python/cpython/issues/92670]: Skip test_shutil.TestCopy.test_copyfile_nonexistent_dir test on AIX as the test uses a trailing slash to force the OS consider the path as a directory, but on AIX the trailing slash has no effect and is considered as a file.

gh-92514 [https://github.com/python/cpython/issues/92514]: Remove unused test.support.BasicTestRunner. Patch by Jelle Zijlstra.

bpo-47016 [https://bugs.python.org/issue?@action=redirect&bpo=47016]: Create a GitHub Actions workflow for verifying bundled pip and setuptools. Patch by Illia Volochii and Adam Turner.

Build

gh-96761 [https://github.com/python/cpython/issues/96761]: Fix the build process of clang compiler for _bootstrap_python if LTO optimization is applied. Patch by Matthias Görgens and Donghee Na.

gh-96883 [https://github.com/python/cpython/issues/96883]: wasm32-emscripten builds for browsers now include concurrent.futures for asyncio and unittest.mock.

gh-85936 [https://github.com/python/cpython/issues/85936]: CPython now uses the ThinLTO option as the default policy if the Clang compiler accepts the flag. Patch by Donghee Na.

gh-96729 [https://github.com/python/cpython/issues/96729]: Ensure that Windows releases built with Tools\msi\buildrelease.bat are upgradable to and from official Python releases.

gh-96269 [https://github.com/python/cpython/issues/96269]: Shared module targets now depend on new MODULE_DEPS variable, which includes EXPORTSYMS. This fixes a build order issue on unsupported AIX platform.

gh-84461 [https://github.com/python/cpython/issues/84461]: wasm32-emscripten platform no longer builds resource module, getresuid(), getresgid(), and their setters. The APIs are stubs and not functional.

gh-95973 [https://github.com/python/cpython/issues/95973]: Add a new --with-dsymutil configure option to link debug information in macOS. Patch by Pablo Galindo.

gh-90536 [https://github.com/python/cpython/issues/90536]: Use the BOLT post-link optimizer to improve performance, particularly on medium-to-large applications.

gh-93744 [https://github.com/python/cpython/issues/93744]: Remove the configure --with-cxx-main build option: it didn't work for many years. Remove the MAINCC variable from configure and Makefile. Patch by Victor Stinner.

gh-94801 [https://github.com/python/cpython/issues/94801]: Fix a regression in configure script that caused some header checks to ignore custom CPPFLAGS. The regression was introduced in gh-94802 [https://github.com/python/cpython/issues/94802].

gh-95145 [https://github.com/python/cpython/issues/95145]: wasm32-wasi builds no longer depend on WASIX's pthread stubs. Python now has its own stubbed pthread API.

gh-95174 [https://github.com/python/cpython/issues/95174]: Python now detects missing dup function in WASI and works around some missing errno, select, and socket constants.

gh-95174 [https://github.com/python/cpython/issues/95174]: Python now skips missing socket functions and methods on WASI. WASI can only create sockets from existing fd / accept and has no netdb.

gh-95085 [https://github.com/python/cpython/issues/95085]: Platforms wasm32-unknown-emscripten and wasm32-unknown-wasi have been promoted to PEP 11 [https://peps.python.org/pep-0011/] tier 3 platform support.

gh-94847 [https://github.com/python/cpython/issues/94847]: Fixed _decimal module build issue on GCC when compiling with LTO and pydebug. Debug builds no longer force inlining of functions.

gh-94841 [https://github.com/python/cpython/issues/94841]: Fix the possible performance regression of PyObject_Free() compiled with MSVC version 1932.

gh-94801 [https://github.com/python/cpython/issues/94801]: configure now uses custom flags like ZLIB_CFLAGS and ZLIB_LIBS when searching for headers and libraries.

gh-94773 [https://github.com/python/cpython/issues/94773]: deepfreeze.py now supports code object with frozensets that contain incompatible, unsortable types.

gh-94682 [https://github.com/python/cpython/issues/94682]: Build and test with OpenSSL 1.1.1q

gh-90005 [https://github.com/python/cpython/issues/90005]: Dependencies of readline and curses module are now detected in configure script with pkg-config. Only ncurses / ncursesw are detected automatically. The old curses library is not configured automatically. Workaround for missing termcap or tinfo library has been removed.

gh-90005 [https://github.com/python/cpython/issues/90005]: Fix building _ctypes extension without pkg-config.

gh-90005 [https://github.com/python/cpython/issues/90005]: _dbm module dependencies are now detected by configure.

gh-94404 [https://github.com/python/cpython/issues/94404]: makesetup now works around an issue with sed on macOS and uses correct CFLAGS for object files that end up in a shared extension. Module CFLAGS are used before PY_STDMODULE_CFLAGS to avoid clashes with system headers.

gh-93939 [https://github.com/python/cpython/issues/93939]: C extension modules are now built by configure and make instead of distutils and setup.py.

gh-93939 [https://github.com/python/cpython/issues/93939]: The 2to3, idle, and pydoc scripts are now generated and installed by Makefile instead of setup.py.

gh-94280 [https://github.com/python/cpython/issues/94280]: Updated pegen regeneration script on Windows to find and use Python 3.9 or higher. Prior to this, pegen regeneration already required 3.9 or higher, but the script may have used lower versions of Python.

gh-93584 [https://github.com/python/cpython/issues/93584]: Address race condition in Makefile when installing a PGO build. All test and install targets now depend on all target.

gh-93491 [https://github.com/python/cpython/issues/93491]: configure now detects and reports PEP 11 [https://peps.python.org/pep-0011/] support tiers.

gh-69093 [https://github.com/python/cpython/issues/69093]: Fix Modules/Setup.stdlib.in rule for _sqlite3 extension.

gh-93207 [https://github.com/python/cpython/issues/93207]: va_start() with two parameters, like va_start(args, format), is now required to build Python. va_start() is no longer called with a single parameter. Patch by Kumar Aditya.

gh-93202 [https://github.com/python/cpython/issues/93202]: Python now always use the %zu and %zd printf formats to format a size_t or Py_ssize_t number. Building Python 3.12 requires a C11 compiler, so these printf formats are now always supported. Patch by Victor Stinner.

gh-90473 [https://github.com/python/cpython/issues/90473]: Disable pymalloc and increase stack size on wasm32-wasi.

bpo-34449 [https://bugs.python.org/issue?@action=redirect&bpo=34449]: Drop invalid compiler switch -fPIC for HP aCC on HP-UX. Patch by Michael Osipov.

Windows

gh-98360 [https://github.com/python/cpython/issues/98360]: Fixes multiprocessing spawning child processes on Windows from a virtual environment to ensure that child processes that also use multiprocessing to spawn more children will recognize that they are in a virtual environment.

gh-98414 [https://github.com/python/cpython/issues/98414]: Fix py.exe launcher handling of -V:<company>/ option when default preferences have been set in environment variables or configuration files.

gh-97728 [https://github.com/python/cpython/issues/97728]: Fix possible crashes caused by the use of uninitialized variables when pass invalid arguments in os.system() on Windows and in Windows-specific modules (like winreg).

gh-90989 [https://github.com/python/cpython/issues/90989]: Made Python 安裝管理員 install per-user by default (unless an all users install already exists), and clarify some text in the installer.

gh-97649 [https://github.com/python/cpython/issues/97649]: The Tools directory is no longer installed on Windows

gh-96965 [https://github.com/python/cpython/issues/96965]: Update libffi to 3.4.3

gh-96577 [https://github.com/python/cpython/issues/96577]: Fixes a potential buffer overrun in msilib.

gh-96559 [https://github.com/python/cpython/issues/96559]: Fixes the Windows launcher not using the compatible interpretation of default tags found in configuration files when no tag was passed to the command.

gh-94781 [https://github.com/python/cpython/issues/94781]: Fix pcbuild.proj to clean previous instances of output files in Python\deepfreeze and Python\frozen_modules directories on Windows. Patch by Charlie Zhao.

gh-89545 [https://github.com/python/cpython/issues/89545]: Updates platform code getting the Windows version to use native Windows Management Instrumentation (WMI) queries to determine OS version, type, and architecture.

gh-95733 [https://github.com/python/cpython/issues/95733]: Make certain requirements of the Windows Store package optional to allow installing on earlier updates of Windows.

gh-95656 [https://github.com/python/cpython/issues/95656]: Enable the enable_load_extension() sqlite3 API.

gh-95587 [https://github.com/python/cpython/issues/95587]: Fixes some issues where the Windows installer would incorrectly detect certain features of an existing install when upgrading.

gh-94399 [https://github.com/python/cpython/issues/94399]: Restores the behaviour of Python 安裝管理員 for /usr/bin/env shebang lines, which will now search PATH for an executable matching the given command. If none is found, the usual search process is used.

gh-95445 [https://github.com/python/cpython/issues/95445]: Fixes the unsuccessful removal of the HTML document directory when uninstalling with Windows msi.

gh-95359 [https://github.com/python/cpython/issues/95359]: Fix Python 安裝管理員 handling of py.ini commands (it was incorrectly expecting a py_ prefix on keys) and crashes when reading per-user configuration file.

gh-95285 [https://github.com/python/cpython/issues/95285]: Fix Python 安裝管理員 handling of command lines where it is only passed a short executable name.

gh-90844 [https://github.com/python/cpython/issues/90844]: Allow virtual environments to correctly launch when they have spaces in the path.

gh-94772 [https://github.com/python/cpython/issues/94772]: Fix incorrect handling of shebang lines in py.exe launcher

gh-94018 [https://github.com/python/cpython/issues/94018]: zipfile will now remove trailing spaces from path components when extracting files on Windows.

gh-93824 [https://github.com/python/cpython/issues/93824]: Drag and drop of files onto Python files in Windows Explorer has been enabled for Windows ARM64.

gh-43414 [https://github.com/python/cpython/issues/43414]: os.get_terminal_size() now attempts to read the size from any provided handle, rather than only supporting file descriptors 0, 1 and 2.

gh-92817 [https://github.com/python/cpython/issues/92817]: Ensures that py.exe will prefer an active virtual environment over default tags specified with environment variables or through a py.ini file.

gh-92984 [https://github.com/python/cpython/issues/92984]: Explicitly disable incremental linking for non-Debug builds

gh-92841 [https://github.com/python/cpython/issues/92841]: asyncio no longer throws RuntimeError: Event loop is closed on interpreter exit after asynchronous socket activity. Patch by Oleg Iarygin.

bpo-46907 [https://bugs.python.org/issue?@action=redirect&bpo=46907]: Update Windows installer to use SQLite 3.38.4.

gh-91061 [https://github.com/python/cpython/issues/91061]: Accept os.PathLike for the argument to winsound.PlaySound

bpo-42658 [https://bugs.python.org/issue?@action=redirect&bpo=42658]: Support native Windows case-insensitive path comparisons by using LCMapStringEx instead of str.lower() in ntpath.normcase(). Add LCMapStringEx to the _winapi module.

bpo-38704 [https://bugs.python.org/issue?@action=redirect&bpo=38704]: Prevent installation on unsupported Windows versions.

macOS

gh-97897 [https://github.com/python/cpython/issues/97897]: The macOS 13 SDK includes support for the mkfifoat and mknodat system calls. Using the dir_fd option with either os.mkfifo() or os.mknod() could result in a segfault if cpython is built with the macOS 13 SDK but run on an earlier version of macOS. Prevent this by adding runtime support for detection of these system calls ("weaklinking") as is done for other newer syscalls on macOS.

IDLE

gh-97527 [https://github.com/python/cpython/issues/97527]: Fix a bug in the previous bugfix that caused IDLE to not start when run with 3.10.8, 3.12.0a1, and at least Microsoft Python 3.10.2288.0 installed without the Lib/test package. 3.11.0 was never affected.

gh-65802 [https://github.com/python/cpython/issues/65802]: Document handling of extensions in Save As dialogs.

gh-95191 [https://github.com/python/cpython/issues/95191]: Include prompts when saving Shell (interactive input and output).

gh-95511 [https://github.com/python/cpython/issues/95511]: Fix the Shell context menu copy-with-prompts bug of copying an extra line when one selects whole lines.

gh-95471 [https://github.com/python/cpython/issues/95471]: In the Edit menu, move Select All and add a new separator.

gh-95411 [https://github.com/python/cpython/issues/95411]: Enable using IDLE's module browser with .pyw files.

gh-89610 [https://github.com/python/cpython/issues/89610]: Add .pyi as a recognized extension for IDLE on macOS. This allows opening stub files by double clicking on them in the Finder.

Tools/Demos

gh-68686 [https://github.com/python/cpython/issues/68686]: Remove ptags and eptags scripts.

gh-97681 [https://github.com/python/cpython/issues/97681]: Remove the Tools/demo/ directory which contained old demo scripts. A copy can be found in the old-demos project [https://github.com/gvanrossum/old-demos]. Patch by Victor Stinner.

gh-97669 [https://github.com/python/cpython/issues/97669]: Remove outdated example scripts of the Tools/scripts/ directory. A copy can be found in the old-demos project [https://github.com/gvanrossum/old-demos]. Patch by Victor Stinner.

gh-95853 [https://github.com/python/cpython/issues/95853]: The wasm_build.py script now pre-builds Emscripten ports, checks for broken EMSDK versions, and warns about pkg-config env vars.

gh-95853 [https://github.com/python/cpython/issues/95853]: The new tool Tools/wasm/wasm_builder.py automates configure, compile, and test steps for building CPython on WebAssembly platforms.

gh-95731 [https://github.com/python/cpython/issues/95731]: Fix handling of module docstrings in Tools/i18n/pygettext.py.

gh-93939 [https://github.com/python/cpython/issues/93939]: Add script Tools/scripts/check_modules.py to check and validate builtin and shared extension modules. The script also handles Modules/Setup and will eventually replace setup.py.

gh-94538 [https://github.com/python/cpython/issues/94538]: Fix Argument Clinic output to custom file destinations. Patch by Erlend E. Aasland.

gh-94430 [https://github.com/python/cpython/issues/94430]: Allow parameters named module and self with custom C names in Argument Clinic. Patch by Erlend E. Aasland

gh-86087 [https://github.com/python/cpython/issues/86087]: The Tools/scripts/parseentities.py script used to parse HTML4 entities has been removed.

C API

gh-98393 [https://github.com/python/cpython/issues/98393]: The PyUnicode_FSDecoder() function no longer accepts bytes-like paths, like bytearray and memoryview types: only the exact bytes type is accepted for bytes strings. Patch by Victor Stinner.

gh-91051 [https://github.com/python/cpython/issues/91051]: Add PyType_Watch() and related APIs to allow callbacks on PyType_Modified().

gh-95756 [https://github.com/python/cpython/issues/95756]: Lazily create and cache co_ attributes for better performance for code getters.

gh-96512 [https://github.com/python/cpython/issues/96512]: Configuration for the integer string conversion length limitation now lives in the PyConfig C API struct.

gh-95589 [https://github.com/python/cpython/issues/95589]: Extensions classes that set tp_dictoffset and tp_weaklistoffset lose the support for multiple inheritance, but are now safe. Extension classes should use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead.

gh-95781 [https://github.com/python/cpython/issues/95781]: An unrecognized format character in PyUnicode_FromFormat() and PyUnicode_FromFormatV() now sets a SystemError. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded.

gh-92678 [https://github.com/python/cpython/issues/92678]: Restore the 3.10 behavior for multiple inheritance of C extension classes that store their dictionary at the end of the struct.

gh-92678 [https://github.com/python/cpython/issues/92678]: Support C extensions using managed dictionaries by setting the Py_TPFLAGS_MANAGED_DICT flag.

gh-93274 [https://github.com/python/cpython/issues/93274]: API for implementing vectorcall (Py_TPFLAGS_HAVE_VECTORCALL, PyVectorcall_NARGS() and PyVectorcall_Call()) was added to the limited API and stable ABI.

gh-95504 [https://github.com/python/cpython/issues/95504]: Fix sign placement when specifying width or precision in PyUnicode_FromFormat() and PyUnicode_FromFormatV(). Patch by Philip Georgi.

gh-93012 [https://github.com/python/cpython/issues/93012]: The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class's __call__() method is reassigned. This makes vectorcall safe to use with mutable types (i.e. heap types without the immutable flag). Mutable types that do not override tp_call now inherit the Py_TPFLAGS_HAVE_VECTORCALL flag.

gh-95388 [https://github.com/python/cpython/issues/95388]: Creating immutable types with mutable bases is deprecated and is planned to be disabled in Python 3.14.

gh-92678 [https://github.com/python/cpython/issues/92678]: Adds unstable C-API functions _PyObject_VisitManagedDict and _PyObject_ClearManagedDict to allow C extensions to allow the VM to manage their object's dictionaries.

gh-94936 [https://github.com/python/cpython/issues/94936]: Added PyCode_GetVarnames(), PyCode_GetCellvars() and PyCode_GetFreevars() for accessing co_varnames, co_cellvars and co_freevars respectively via the C API.

gh-94930 [https://github.com/python/cpython/issues/94930]: Fix SystemError raised when PyArg_ParseTupleAndKeywords() is used with # in (...) but without PY_SSIZE_T_CLEAN defined.

gh-94731 [https://github.com/python/cpython/issues/94731]: Python again uses C-style casts for most casting operations when compiled with C++. This may trigger compiler warnings, if they are enabled with e.g. -Wold-style-cast or -Wzero-as-null-pointer-constant options for g++.

gh-93937 [https://github.com/python/cpython/issues/93937]: The following frame functions and type are now directly available with #include <Python.h>, it's no longer needed to add #include <frameobject.h>:

PyFrame_Check()

PyFrame_GetBack()

PyFrame_GetBuiltins()

PyFrame_GetGenerator()

PyFrame_GetGlobals()

PyFrame_GetLasti()

PyFrame_GetLocals()

PyFrame_Type

Patch by Victor Stinner.

gh-91321 [https://github.com/python/cpython/issues/91321]: Fix the compatibility of the Python C API with C++ older than C++11. Patch by Victor Stinner.

gh-91731 [https://github.com/python/cpython/issues/91731]: Avoid defining the static_assert when compiling with C++ 11, where this is a keyword and redefining it can lead to undefined behavior. Patch by Pablo Galindo

gh-89546 [https://github.com/python/cpython/issues/89546]: PyType_FromMetaclass() (and other PyType_From* functions) now check that offsets and the base class's tp_basicsize fit in the new class's tp_basicsize.

gh-93503 [https://github.com/python/cpython/issues/93503]: Add two new public functions to the public C-API, PyEval_SetProfileAllThreads() and PyEval_SetTraceAllThreads(), that allow to set tracing and profiling functions in all running threads in addition to the calling one. Also, two analogous functions to the threading module (threading.setprofile_all_threads() and threading.settrace_all_threads()) that allow to do the same from Python. Patch by Pablo Galindo

gh-93442 [https://github.com/python/cpython/issues/93442]: Add C++ overloads for _Py_CAST_impl() to handle 0/NULL. This will allow C++ extensions that pass 0 or NULL to macros using _Py_CAST() to continue to compile.

gh-93466 [https://github.com/python/cpython/issues/93466]: Slot IDs in PyType_Spec may not be repeated. The documentation was updated to mention this. For some cases of repeated slots, PyType_FromSpec and related functions will now raise an exception.

gh-92898 [https://github.com/python/cpython/issues/92898]: Fix C++ compiler warnings when casting function arguments to PyObject*. Patch by Serge Guelton.

gh-93103 [https://github.com/python/cpython/issues/93103]: Deprecate global configuration variables, like Py_IgnoreEnvironmentFlag, in the documentation: the Py_InitializeFromConfig() API should be instead. Patch by Victor Stinner.

gh-77782 [https://github.com/python/cpython/issues/77782]: Deprecate global configuration variable like Py_IgnoreEnvironmentFlag: the Py_InitializeFromConfig() API should be instead. Patch by Victor Stinner.

gh-92913 [https://github.com/python/cpython/issues/92913]: Ensures changes to PyConfig.module_search_paths are ignored unless PyConfig.module_search_paths_set is set

gh-92781 [https://github.com/python/cpython/issues/92781]: Avoid mixing declarations and code in the C API to fix the compiler warning: "ISO C90 forbids mixed declarations and code" [-Werror=declaration-after-statement]. Patch by Victor Stinner.

gh-92651 [https://github.com/python/cpython/issues/92651]: Remove the token.h header file. There was never any public tokenizer C API. The token.h header file was only designed to be used by Python internals. Patch by Victor Stinner.

gh-92536 [https://github.com/python/cpython/issues/92536]: Remove legacy Unicode APIs based on Py_UNICODE*.

gh-85858 [https://github.com/python/cpython/issues/85858]: Remove the PyUnicode_InternImmortal() function and the SSTATE_INTERNED_IMMORTAL macro. Patch by Victor Stinner.

gh-92193 [https://github.com/python/cpython/issues/92193]: Add new function PyFunction_SetVectorcall() to the C API which sets the vectorcall field of a given PyFunctionObject.

Warning: extensions using this API must preserve the behavior of the unaltered function!

gh-59121 [https://github.com/python/cpython/issues/59121]: Fixed an assert that prevented PyRun_InteractiveOne from providing tracebacks when parsing from the provided FD.

bpo-45383 [https://bugs.python.org/issue?@action=redirect&bpo=45383]: The PyType_FromSpec() API will now find and use a metaclass based on the provided bases. An error will be raised if there is a metaclass conflict.

Python 3.11.0 beta 1

Release date: 2022-05-06

Security

gh-57684 [https://github.com/python/cpython/issues/57684]: Add the -P command line option and the PYTHONSAFEPATH environment variable to not prepend a potentially unsafe path to sys.path. Patch by Victor Stinner.

Core and Builtins

gh-89519 [https://github.com/python/cpython/issues/89519]: Chaining classmethod descriptors (introduced in bpo-19072 [https://bugs.python.org/issue?@action=redirect&bpo=19072]) is deprecated. It can no longer be used to wrap other descriptors such as property(). The core design of this feature was flawed, and it caused a number of downstream problems.

gh-92345 [https://github.com/python/cpython/issues/92345]: pymain_run_python() now imports readline and rlcompleter before sys.path is extended to include the current working directory of an interactive interpreter. Non-interactive interpreters are not affected.

bpo-43857 [https://bugs.python.org/issue?@action=redirect&bpo=43857]: Improve the AttributeError message when deleting a missing attribute. Patch by Géry Ogam.

gh-92245 [https://github.com/python/cpython/issues/92245]: Make sure that PEP 523 is respected in all cases. In 3.11a7, specialization may have prevented Python-to-Python calls respecting PEP 523.

gh-92203 [https://github.com/python/cpython/issues/92203]: Add a closure keyword-only parameter to exec(). It can only be specified when exec-ing a code object that uses free variables. When specified, it must be a tuple, with exactly the number of cell variables referenced by the code object. closure has a default value of None, and it must be None if the code object doesn't refer to any free variables.

gh-91173 [https://github.com/python/cpython/issues/91173]: Disable frozen modules in debug builds. Patch by Kumar Aditya.

gh-92114 [https://github.com/python/cpython/issues/92114]: Improve error message when subscript a type with __class_getitem__ set to None.

gh-92112 [https://github.com/python/cpython/issues/92112]: Fix crash triggered by an evil custom mro() on a metaclass.

gh-92063 [https://github.com/python/cpython/issues/92063]: The PRECALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS instruction now ensures methods are called only on objects of the correct type.

gh-92031 [https://github.com/python/cpython/issues/92031]: Deoptimize statically allocated code objects during Py_FINALIZE() so that future _PyCode_Quicken calls always start with unquickened code.

gh-92036 [https://github.com/python/cpython/issues/92036]: Fix a crash in subinterpreters related to the garbage collector. When a subinterpreter is deleted, untrack all objects tracked by its GC. To prevent a crash in deallocator functions expecting objects to be tracked by the GC, leak a strong reference to these objects on purpose, so they are never deleted and their deallocator functions are not called. Patch by Victor Stinner.

gh-92032 [https://github.com/python/cpython/issues/92032]: The interpreter can now autocomplete soft keywords, as of now match, case, and _ (wildcard pattern) from PEP 634 [https://peps.python.org/pep-0634/].

gh-87999 [https://github.com/python/cpython/issues/87999]: The warning emitted by the Python parser for a numeric literal immediately followed by keyword has been changed from deprecation warning to syntax warning.

gh-91869 [https://github.com/python/cpython/issues/91869]: Fix an issue where specialized opcodes with extended arguments could produce incorrect tracing output or lead to assertion failures.

gh-91603 [https://github.com/python/cpython/issues/91603]: Speed up types.UnionType instantiation. Based on patch provided by Yurii Karabas.

gh-89373 [https://github.com/python/cpython/issues/89373]: If Python is built in debug mode, Python now ensures that deallocator functions leave the current exception unchanged. Patch by Victor Stinner.

gh-91632 [https://github.com/python/cpython/issues/91632]: Fix a minor memory leak at exit: release the memory of the generic_alias_iterator type. Patch by Donghee Na.

gh-81548 [https://github.com/python/cpython/issues/81548]: Octal escapes with value larger than 0o377 now produce a DeprecationWarning. In a future Python version they will be a SyntaxWarning and eventually a SyntaxError.

bpo-43950 [https://bugs.python.org/issue?@action=redirect&bpo=43950]: Use a single compact table for line starts, ends and column offsets. Reduces memory consumption for location info by half

gh-91102 [https://github.com/python/cpython/issues/91102]: Use Argument Clinic for EncodingMap. Patch by Oleg Iarygin.

gh-91636 [https://github.com/python/cpython/issues/91636]: Fixed a crash in a garbage-collection edge-case, in which a PyFunction_Type.tp_clear function could leave a python function object in an inconsistent state.

gh-91603 [https://github.com/python/cpython/issues/91603]: Speed up isinstance() and issubclass() checks for types.UnionType. Patch by Yurii Karabas.

gh-91625 [https://github.com/python/cpython/issues/91625]: Fixed a bug in which adaptive opcodes ignored any preceding EXTENDED_ARGs on specialization failure.

gh-78607 [https://github.com/python/cpython/issues/78607]: The LLTRACE special build now looks for the name __lltrace__ defined in module globals, rather than the name __ltrace__, which had been introduced as a typo.

gh-91576 [https://github.com/python/cpython/issues/91576]: Speed up iteration of ascii strings by 50%. Patch by Kumar Aditya.

gh-89279 [https://github.com/python/cpython/issues/89279]: Improve interpreter performance on Windows by inlining a few specific macros.

gh-91502 [https://github.com/python/cpython/issues/91502]: Add a new _PyFrame_IsEntryFrame() API function, to check if a PyFrameObject is an entry frame. Patch by Pablo Galindo.

gh-91266 [https://github.com/python/cpython/issues/91266]: Refactor the bytearray strip methods strip, lstrip and rstrip to use a common implementation.

gh-91479 [https://github.com/python/cpython/issues/91479]: Replaced the __note__ field of BaseException (added in an earlier version of 3.11) with the final design of PEP 678 [https://peps.python.org/pep-0678/]. Namely, BaseException gets an add_note() method, and its __notes__ field is created when necessary.

gh-46055 [https://github.com/python/cpython/issues/46055]: Speed up right shift of negative integers, by removing unnecessary creation of temporaries. Original patch by Xinhang Xu, reworked by Mark Dickinson.

gh-91462 [https://github.com/python/cpython/issues/91462]: Make the interpreter's low-level tracing (lltrace) feature output more readable by displaying opcode names (rather than just numbers), and by displaying stack contents before each opcode.

gh-89455 [https://github.com/python/cpython/issues/89455]: Fixed an uninitialized bool value in the traceback printing code path that was introduced by the initial bpo-45292 [https://bugs.python.org/issue?@action=redirect&bpo=45292] exception groups work.

gh-91421 [https://github.com/python/cpython/issues/91421]: Fix a potential integer overflow in _Py_DecodeUTF8Ex.

gh-91428 [https://github.com/python/cpython/issues/91428]: Add static const char *const _PyOpcode_OpName[256] = {...}; to opcode.h for debug builds to assist in debugging the Python interpreter. It is now more convenient to make various forms of debugging output more human-readable by including opcode names rather than just the corresponding decimal digits.

bpo-47120 [https://bugs.python.org/issue?@action=redirect&bpo=47120]: Make POP_JUMP_IF_TRUE, POP_JUMP_IF_FALSE, POP_JUMP_IF_NONE and POP_JUMP_IF_NOT_NONE virtual, mapping to new relative jump opcodes.

bpo-45317 [https://bugs.python.org/issue?@action=redirect&bpo=45317]: Add internal documentation explaining design of new (for 3.11) frame stack.

Library

bpo-47197 [https://bugs.python.org/issue?@action=redirect&bpo=47197]: ctypes used to mishandle void return types, so that for instance a function declared like ctypes.CFUNCTYPE(None, ctypes.c_int) would be called with signature int f(int) instead of void f(int). Wasm targets require function pointers to be called with the correct signatures so this led to crashes. The problem is now fixed.

Core and Builtins

bpo-47120 [https://bugs.python.org/issue?@action=redirect&bpo=47120]: Make opcodes JUMP_IF_TRUE_OR_POP and JUMP_IF_FALSE_OR_POP relative rather than absolute.

bpo-47177 [https://bugs.python.org/issue?@action=redirect&bpo=47177]: Replace the f_lasti member of the internal _PyInterpreterFrame structure with a prev_instr pointer, which reduces overhead in the main interpreter loop. The f_lasti attribute of Python-layer frame objects is preserved for backward-compatibility.

bpo-46961 [https://bugs.python.org/issue?@action=redirect&bpo=46961]: Integer mod/remainder operations, including the three-argument form of pow(), now consistently return ints from the global small integer cache when applicable.

bpo-46962 [https://bugs.python.org/issue?@action=redirect&bpo=46962]: Classes and functions that unconditionally declared their docstrings ignoring the --without-doc-strings compilation flag no longer do so.

The classes affected are ctypes.UnionType, pickle.PickleBuffer, testcapi.RecursingInfinitelyError, and types.GenericAlias.

The functions affected are 24 methods in ctypes.

Patch by Oleg Iarygin.

bpo-46942 [https://bugs.python.org/issue?@action=redirect&bpo=46942]: Use Argument Clinic for the types.MethodType constructor. Patch by Oleg Iarygin.

bpo-46764 [https://bugs.python.org/issue?@action=redirect&bpo=46764]: Fix wrapping bound methods with @classmethod

bpo-43464 [https://bugs.python.org/issue?@action=redirect&bpo=43464]: Optimize set.intersection() for non-set arguments.

bpo-46721 [https://bugs.python.org/issue?@action=redirect&bpo=46721]: Optimize set.issuperset() for non-set argument.

bpo-46509 [https://bugs.python.org/issue?@action=redirect&bpo=46509]: Add type-specialized versions of the Py_DECREF(), and use them for float, int, str, bool, and None to avoid pointer-chasing at runtime where types are known at C compile time.

Build

bpo-46045 [https://bugs.python.org/issue?@action=redirect&bpo=46045]: Do not use POSIX semaphores on NetBSD

Core and Builtins

bpo-36819 [https://bugs.python.org/issue?@action=redirect&bpo=36819]: Fix crashes in built-in encoders with error handlers that return position less or equal than the starting position of non-encodable characters.

bpo-34093 [https://bugs.python.org/issue?@action=redirect&bpo=34093]: marshal.dumps() uses FLAG_REF for all interned strings. This makes output more deterministic and helps reproducible build.

bpo-26579 [https://bugs.python.org/issue?@action=redirect&bpo=26579]: Added object.__getstate__ which provides the default implementation of the __getstate__() method.

Copying and pickling instances of subclasses of builtin types bytearray, set, frozenset, collections.OrderedDict, collections.deque, weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes implemented as slots.

Library

gh-87901 [https://github.com/python/cpython/issues/87901]: Add the encoding parameter to os.popen().

gh-90997 [https://github.com/python/cpython/issues/90997]: Fix an issue where dis utilities may interpret populated inline cache entries as valid instructions.

gh-92332 [https://github.com/python/cpython/issues/92332]: Deprecate typing.Text (removal of the class is currently not planned). Patch by Alex Waygood.

gh-78157 [https://github.com/python/cpython/issues/78157]: Deprecate nested classes in enum definitions becoming members -- in 3.13 they will be normal classes; add member and nonmember functions to allow control over results now.

gh-92356 [https://github.com/python/cpython/issues/92356]: Fixed a performance regression in ctypes function calls.

gh-90997 [https://github.com/python/cpython/issues/90997]: Show the actual named values stored in inline caches when show_caches=True is passed to dis utilities.

gh-92301 [https://github.com/python/cpython/issues/92301]: Prefer close_range() to iterating over procfs for file descriptor closing in subprocess for better performance.

gh-67248 [https://github.com/python/cpython/issues/67248]: Sort the miscellaneous topics in Cmd.do_help()

gh-92210 [https://github.com/python/cpython/issues/92210]: Port socket.__init__ to Argument Clinic. Patch by Cinder.

gh-80010 [https://github.com/python/cpython/issues/80010]: Add support for generalized ISO 8601 parsing to datetime.datetime.fromisoformat(), datetime.date.fromisoformat() and datetime.time.fromisoformat(). Patch by Paul Ganssle.

gh-92118 [https://github.com/python/cpython/issues/92118]: Fix a 3.11 regression in contextmanager(), which caused it to propagate exceptions with incorrect tracebacks.

gh-90887 [https://github.com/python/cpython/issues/90887]: Adding COPYFILE_STAT, COPYFILE_ACL and COPYFILE_XATTR constants for os.fcopyfile() available in macOs.

gh-91215 [https://github.com/python/cpython/issues/91215]: For @~dataclasses.dataclass, add weakref_slot. The new parameter defaults to False. If true, and if slots=True, add a slot named "__weakref__", which will allow instances to be weakref'd. Contributed by Eric V. Smith

gh-85984 [https://github.com/python/cpython/issues/85984]: New function os.login_tty() for Unix.

gh-92128 [https://github.com/python/cpython/issues/92128]: Add __class_getitem__() to logging.LoggerAdapter and logging.StreamHandler, allowing them to be parameterized at runtime. Patch by Alex Waygood.

gh-92049 [https://github.com/python/cpython/issues/92049]: Forbid pickling constants re._constants.SUCCESS etc. Previously, pickling did not fail, but the result could not be unpickled.

gh-92062 [https://github.com/python/cpython/issues/92062]: inspect.Parameter now raises ValueError if name is a keyword, in addition to the existing check that it is an identifier.

gh-87390 [https://github.com/python/cpython/issues/87390]: Add an __unpacked__ attribute to types.GenericAlias. Patch by Jelle Zijlstra.

gh-88089 [https://github.com/python/cpython/issues/88089]: Add support for generic typing.NamedTuple.

gh-91996 [https://github.com/python/cpython/issues/91996]: New http.HTTPMethod enum to represent all the available HTTP request methods in a convenient way

gh-91984 [https://github.com/python/cpython/issues/91984]: Modified test strings in test_argparse.py to not contain trailing spaces before end of line.

gh-91952 [https://github.com/python/cpython/issues/91952]: Add encoding="locale" support to TextIOWrapper.reconfigure().

gh-91954 [https://github.com/python/cpython/issues/91954]: Add encoding and errors arguments to subprocess.getoutput() and subprocess.getstatusoutput().

bpo-47029 [https://bugs.python.org/issue?@action=redirect&bpo=47029]: Always close the read end of the pipe used by multiprocessing.Queue after the last write of buffered data to the write end of the pipe to avoid BrokenPipeError at garbage collection and at multiprocessing.Queue.close() calls. Patch by Géry Ogam.

gh-91928 [https://github.com/python/cpython/issues/91928]: Add datetime.UTC alias for datetime.timezone.utc.

Patch by Kabir Kwatra.

gh-68966 [https://github.com/python/cpython/issues/68966]: The mailcap module is now deprecated and will be removed in Python 3.13. See PEP 594 [https://peps.python.org/pep-0594/] for the rationale and the mimetypes module for an alternative. Patch by Victor Stinner.

gh-91401 [https://github.com/python/cpython/issues/91401]: Provide a way to disable subprocess use of vfork() just in case it is ever needed and document the existing mechanism for posix_spawn().

gh-64783 [https://github.com/python/cpython/issues/64783]: Fix signal.NSIG value on FreeBSD to accept signal numbers greater than 32, like signal.SIGRTMIN and signal.SIGRTMAX. Patch by Victor Stinner.

gh-91910 [https://github.com/python/cpython/issues/91910]: Add missing f prefix to f-strings in error messages from the multiprocessing and asyncio modules.

gh-91860 [https://github.com/python/cpython/issues/91860]: Add typing.dataclass_transform(), implementing PEP 681 [https://peps.python.org/pep-0681/]. Patch by Jelle Zijlstra.

gh-91832 [https://github.com/python/cpython/issues/91832]: Add required attribute to argparse.Action repr output.

gh-91827 [https://github.com/python/cpython/issues/91827]: In the tkinter module add method info_patchlevel() which returns the exact version of the Tcl library as a named tuple similar to sys.version_info.

gh-84461 [https://github.com/python/cpython/issues/84461]: Add --enable-wasm-pthreads to enable pthreads support for WASM builds. Emscripten/node no longer has threading enabled by default. Include additional file systems.

gh-91821 [https://github.com/python/cpython/issues/91821]: Fix unstable test_from_tuple test in test_decimal.py.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the xdrlib module.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the uu module.

gh-91760 [https://github.com/python/cpython/issues/91760]: More strict rules will be applied for numerical group references and group names in regular expressions. For now, a deprecation warning is emitted for group references and group names which will be errors in future Python versions.

gh-84461 [https://github.com/python/cpython/issues/84461]: Add provisional sys._emscripten_info named tuple with build-time and run-time information about Emscripten platform.

gh-90623 [https://github.com/python/cpython/issues/90623]: signal.raise_signal() and os.kill() now check immediately for pending signals. Patch by Victor Stinner.

gh-91734 [https://github.com/python/cpython/issues/91734]: Fix OSS audio support on Solaris.

gh-90633 [https://github.com/python/cpython/issues/90633]: Include the passed value in the exception thrown by typing.assert_never(). Patch by Jelle Zijlstra.

gh-91700 [https://github.com/python/cpython/issues/91700]: Compilation of regular expression containing a conditional expression (?(group)...) now raises an appropriate re.error if the group number refers to not defined group. Previously an internal RuntimeError was raised.

gh-91231 [https://github.com/python/cpython/issues/91231]: Add an optional keyword shutdown_timeout parameter to the multiprocessing.BaseManager constructor. Kill the process if terminate() takes longer than the timeout. Patch by Victor Stinner.

gh-91621 [https://github.com/python/cpython/issues/91621]: Fix typing.get_type_hints() for collections.abc.Callable. Patch by Shantanu Jain.

gh-90568 [https://github.com/python/cpython/issues/90568]: Parsing \N escapes of Unicode Named Character Sequences in a regular expression raises now re.error instead of TypeError.

gh-91670 [https://github.com/python/cpython/issues/91670]: Remove deprecated SO config variable in sysconfig.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the telnetlib module.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the sunau module.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the spwd module.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the sndhdr module, as well as inline needed functionality for email.mime.MIMEAudio.

gh-91616 [https://github.com/python/cpython/issues/91616]: re module, fix fullmatch() mismatch when using Atomic Grouping or Possessive Quantifiers.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the 'pipes' module.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the ossaudiodev module.

bpo-47256 [https://bugs.python.org/issue?@action=redirect&bpo=47256]: re module, limit the maximum capturing group to 1,073,741,823 in 64-bit build, this increases the depth of backtracking.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the nis module.

gh-91595 [https://github.com/python/cpython/issues/91595]: Fix the comparison of character and integer inside Tools.gdb.libpython.write_repr(). Patch by Yu Liu.

gh-74166 [https://github.com/python/cpython/issues/74166]: Add option to raise all errors from create_connection() in an ExceptionGroup when it fails to create a connection. The default remains to raise only the last error that had occurred when multiple addresses were tried.

gh-91487 [https://github.com/python/cpython/issues/91487]: Optimize asyncio UDP speed, over 100 times faster when transferring a large file.

gh-91575 [https://github.com/python/cpython/issues/91575]: Update case-insensitive matching in the re module to the latest Unicode version.

gh-90622 [https://github.com/python/cpython/issues/90622]: In concurrent.futures.process.ProcessPoolExecutor disallow the "fork" multiprocessing start method when the new max_tasks_per_child feature is used as the mix of threads+fork can hang the child processes. Default to using the safe "spawn" start method in that circumstance if no mp_context was supplied.

gh-89022 [https://github.com/python/cpython/issues/89022]: In sqlite3, SQLITE_MISUSE result codes are now mapped to InterfaceError instead of ProgrammingError. Also, more accurate exceptions are raised when binding parameters fail. Patch by Erlend E. Aasland.

gh-91526 [https://github.com/python/cpython/issues/91526]: Stop calling os.device_encoding(file.fileno()) in TextIOWrapper. It was complex, never documented, and didn't work for most cases. (Patch by Inada Naoki.)

gh-88116 [https://github.com/python/cpython/issues/88116]: Change the frame-related functions in the inspect module to return a regular object (that is backwards compatible with the old tuple-like interface) that include the extended PEP 657 [https://peps.python.org/pep-0657/] position information (end line number, column and end column). The affected functions are: inspect.getframeinfo(), inspect.getouterframes(), inspect.getinnerframes(), inspect.stack() and inspect.trace(). Patch by Pablo Galindo.

gh-69093 [https://github.com/python/cpython/issues/69093]: Add indexing and slicing support to sqlite3.Blob. Patch by Aviv Palivoda and Erlend E. Aasland.

gh-69093 [https://github.com/python/cpython/issues/69093]: Add context manager support to sqlite3.Blob. Patch by Aviv Palivoda and Erlend E. Aasland.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate nntplib.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate msilib.

gh-91404 [https://github.com/python/cpython/issues/91404]: Improve the performance of re matching by using computed gotos (or "threaded code") on supported platforms and removing expensive pointer indirections.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the imghdr module.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the crypt module.

gh-91276 [https://github.com/python/cpython/issues/91276]: Make space for longer opcodes in dis output.

bpo-47000 [https://bugs.python.org/issue?@action=redirect&bpo=47000]: Make TextIOWrapper uses locale encoding when encoding="locale" is specified even in UTF-8 mode.

gh-91230 [https://github.com/python/cpython/issues/91230]: warnings.catch_warnings() now accepts arguments for warnings.simplefilter(), providing a more concise way to locally ignore warnings or convert them to errors.

gh-91217 [https://github.com/python/cpython/issues/91217]: Deprecate the chunk module.

gh-91498 [https://github.com/python/cpython/issues/91498]: Add the TCP_CONNECTION_INFO option (available on macOS) to socket.

bpo-47260 [https://bugs.python.org/issue?@action=redirect&bpo=47260]: Fix os.closerange() potentially being a no-op in a Linux seccomp sandbox.

bpo-47087 [https://bugs.python.org/issue?@action=redirect&bpo=47087]: Implement typing.Required and typing.NotRequired (PEP 655 [https://peps.python.org/pep-0655/]). Patch by David Foster and Jelle Zijlstra.

bpo-47061 [https://bugs.python.org/issue?@action=redirect&bpo=47061]: Deprecate cgi and cgitb.

bpo-47061 [https://bugs.python.org/issue?@action=redirect&bpo=47061]: Deprecate audioop.

bpo-47000 [https://bugs.python.org/issue?@action=redirect&bpo=47000]: Add locale.getencoding() to get the current locale encoding. It is similar to locale.getpreferredencoding(False) but ignores the Python UTF-8 Mode.

bpo-42012 [https://bugs.python.org/issue?@action=redirect&bpo=42012]: Add wsgiref.types, containing WSGI-specific types for static type checking.

bpo-47227 [https://bugs.python.org/issue?@action=redirect&bpo=47227]: Suppress expression chaining for more re parsing errors.

bpo-47211 [https://bugs.python.org/issue?@action=redirect&bpo=47211]: Remove undocumented and never working function re.template() and flag re.TEMPLATE. This was later reverted in 3.11.0b2 and deprecated instead.

bpo-47135 [https://bugs.python.org/issue?@action=redirect&bpo=47135]: decimal.localcontext() now accepts context attributes via keyword arguments

bpo-43323 [https://bugs.python.org/issue?@action=redirect&bpo=43323]: Fix errors in the email module if the charset itself contains undecodable/unencodable characters.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Disassembly of quickened code.

bpo-46681 [https://bugs.python.org/issue?@action=redirect&bpo=46681]: Forward gzip.compress() compresslevel to zlib.

bpo-45100 [https://bugs.python.org/issue?@action=redirect&bpo=45100]: Add typing.get_overloads() and typing.clear_overloads(). Patch by Jelle Zijlstra.

bpo-44807 [https://bugs.python.org/issue?@action=redirect&bpo=44807]: typing.Protocol no longer silently replaces __init__() methods defined on subclasses. Patch by Adrian Garcia Badaracco.

bpo-46787 [https://bugs.python.org/issue?@action=redirect&bpo=46787]: Fix concurrent.futures.ProcessPoolExecutor exception memory leak

bpo-46720 [https://bugs.python.org/issue?@action=redirect&bpo=46720]: Add support for path-like objects to multiprocessing.set_executable() for Windows to be on a par with Unix-like systems. Patch by Géry Ogam.

bpo-46696 [https://bugs.python.org/issue?@action=redirect&bpo=46696]: Add SO_INCOMING_CPU constant to socket.

bpo-46053 [https://bugs.python.org/issue?@action=redirect&bpo=46053]: Fix OSS audio support on NetBSD.

bpo-45639 [https://bugs.python.org/issue?@action=redirect&bpo=45639]: image/avif and image/webp were added to mimetypes.

bpo-46285 [https://bugs.python.org/issue?@action=redirect&bpo=46285]: Add command-line option -p/--protocol to module http.server which specifies the HTTP version to which the server is conformant (HTTP/1.1 conformant servers can now be run from the command-line interface of module http.server). Patch by Géry Ogam.

bpo-44791 [https://bugs.python.org/issue?@action=redirect&bpo=44791]: Accept ellipsis as the last argument of typing.Concatenate.

bpo-46547 [https://bugs.python.org/issue?@action=redirect&bpo=46547]: Remove variables leaking into pydoc.Helper class namespace.

bpo-46415 [https://bugs.python.org/issue?@action=redirect&bpo=46415]: Fix ipaddress.ip_{address,interface,network} raising TypeError instead of ValueError if given invalid tuple as address parameter.

bpo-46075 [https://bugs.python.org/issue?@action=redirect&bpo=46075]: CookieJar with DefaultCookiePolicy now can process cookies from localhost with domain=localhost explicitly specified in Set-Cookie header.

bpo-45995 [https://bugs.python.org/issue?@action=redirect&bpo=45995]: Add a "z" option to the string formatting specification that coerces negative zero floating-point values to positive zero after rounding to the format precision. Contributed by John Belmonte.

bpo-26175 [https://bugs.python.org/issue?@action=redirect&bpo=26175]: Fully implement the io.BufferedIOBase or io.TextIOBase interface for tempfile.SpooledTemporaryFile objects. This lets them work correctly with higher-level layers (like compression modules). Patch by Carey Metcalfe.

bpo-45138 [https://bugs.python.org/issue?@action=redirect&bpo=45138]: Fix a regression in the sqlite3 trace callback where bound parameters were not expanded in the passed statement string. The regression was introduced in Python 3.10 by bpo-40318 [https://bugs.python.org/issue?@action=redirect&bpo=40318]. Patch by Erlend E. Aasland.

bpo-44863 [https://bugs.python.org/issue?@action=redirect&bpo=44863]: Allow TypedDict subclasses to also include Generic as a base class in class based syntax. Thereby allowing the user to define a generic TypedDict, just like a user-defined generic but with TypedDict semantics.

bpo-44587 [https://bugs.python.org/issue?@action=redirect&bpo=44587]: Fix BooleanOptionalAction to not automatically add a default string. If a default string is desired, use a formatter to add it.

bpo-43827 [https://bugs.python.org/issue?@action=redirect&bpo=43827]: All positional-or-keyword parameters to ABCMeta.__new__ are now positional-only to avoid conflicts with keyword arguments to be passed to __init_subclass__().

bpo-43218 [https://bugs.python.org/issue?@action=redirect&bpo=43218]: Prevent creation of a venv whose path contains the PATH separator. This could affect the usage of the activate script. Patch by Dustin Rodrigues.

bpo-38435 [https://bugs.python.org/issue?@action=redirect&bpo=38435]: Add a process_group parameter to subprocess.Popen to help move more things off of the unsafe preexec_fn parameter.

bpo-42066 [https://bugs.python.org/issue?@action=redirect&bpo=42066]: Fix cookies getting sorted in CookieJar.__iter__() which is an extra behavior and not mentioned in RFC 2965 or Netscape cookie protocol. Now the cookies in CookieJar follows the order of the Set-Cookie header. Patch by Iman Kermani.

bpo-40617 [https://bugs.python.org/issue?@action=redirect&bpo=40617]: Add create_window_function() to sqlite3.Connection for creating aggregate window functions. Patch by Erlend E. Aasland.

bpo-40676 [https://bugs.python.org/issue?@action=redirect&bpo=40676]: Convert csv to use Argument Clinic for csv.field_size_limit(), csv.get_dialect(), csv.unregister_dialect() and csv.list_dialects().

bpo-39716 [https://bugs.python.org/issue?@action=redirect&bpo=39716]: Raise an ArgumentError when the same subparser name is added twice to an argparse.ArgumentParser. This is consistent with the (default) behavior when the same option string is added twice to an ArgumentParser.

bpo-36073 [https://bugs.python.org/issue?@action=redirect&bpo=36073]: Raise ProgrammingError instead of segfaulting on recursive usage of cursors in sqlite3 converters. Patch by Sergey Fedoseev.

bpo-34975 [https://bugs.python.org/issue?@action=redirect&bpo=34975]: Adds a start_tls() method to StreamWriter, which upgrades the connection with TLS using the given SSLContext.

bpo-22276 [https://bugs.python.org/issue?@action=redirect&bpo=22276]: Path methods glob() and rglob() return only directories if pattern ends with a pathname components separator (/ or sep). Patch by Eisuke Kawashima.

bpo-24905 [https://bugs.python.org/issue?@action=redirect&bpo=24905]: Add blobopen() to sqlite3.Connection. sqlite3.Blob allows incremental I/O operations on blobs. Patch by Aviv Palivoda and Erlend E. Aasland.

Documentation

gh-91888 [https://github.com/python/cpython/issues/91888]: Add a new gh role to the documentation to link to GitHub issues.

gh-91783 [https://github.com/python/cpython/issues/91783]: Document security issues concerning the use of the function shutil.unpack_archive()

gh-91547 [https://github.com/python/cpython/issues/91547]: Remove "Undocumented modules" page.

gh-91298 [https://github.com/python/cpython/issues/91298]: In importlib.resources.abc, refined the documentation of the Traversable Protocol, applying changes from importlib_resources 5.7.1.

bpo-44347 [https://bugs.python.org/issue?@action=redirect&bpo=44347]: Clarify the meaning of dirs_exist_ok, a kwarg of shutil.copytree().

bpo-36329 [https://bugs.python.org/issue?@action=redirect&bpo=36329]: Remove 'make -C Doc serve' in favour of 'make -C Doc htmlview'

bpo-47189 [https://bugs.python.org/issue?@action=redirect&bpo=47189]: Add a What's New in Python 3.11 entry for the Faster CPython project. Documentation by Ken Jin and Kumar Aditya.

bpo-38668 [https://bugs.python.org/issue?@action=redirect&bpo=38668]: Update the introduction to documentation for os.path to remove warnings that became irrelevant after the implementations of PEP 383 [https://peps.python.org/pep-0383/] and PEP 529 [https://peps.python.org/pep-0529/].

bpo-47115 [https://bugs.python.org/issue?@action=redirect&bpo=47115]: The documentation now lists which members of C structs are part of the Limited API/Stable ABI.

bpo-46962 [https://bugs.python.org/issue?@action=redirect&bpo=46962]: All docstrings in code snippets are now wrapped into PyDoc_STR to follow the guideline of PEP 7's Documentation Strings paragraph [https://peps.python.org/pep-0007/#documentation-strings]. Patch by Oleg Iarygin.

bpo-26792 [https://bugs.python.org/issue?@action=redirect&bpo=26792]: Improve the docstrings of runpy.run_module() and runpy.run_path(). Original patch by Andrew Brezovsky.

Tests

gh-92169 [https://github.com/python/cpython/issues/92169]: Use warnings_helper.import_deprecated() to import deprecated modules uniformly in tests. Patch by Hugo van Kemenade.

gh-84461 [https://github.com/python/cpython/issues/84461]: When multiprocessing is enabled, libregrtest can now use a Python executable other than sys.executable via the --python flag.

gh-91904 [https://github.com/python/cpython/issues/91904]: Fix initialization of PYTHONREGRTEST_UNICODE_GUARD which prevented running regression tests on non-UTF-8 locale.

gh-91752 [https://github.com/python/cpython/issues/91752]: Added @requires_zlib to test.test_tools.test_freeze.TestFreeze.

gh-91607 [https://github.com/python/cpython/issues/91607]: Fix test_concurrent_futures to test the correct multiprocessing start method context in several cases where the test logic mixed this up.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Threading tests are now skipped on WASM targets without pthread support.

bpo-47109 [https://bugs.python.org/issue?@action=redirect&bpo=47109]: Test for ctypes.macholib.dyld, ctypes.macholib.dylib, and ctypes.macholib.framework are brought from manual pre-unittest times to ctypes.test location and structure. Patch by Oleg Iarygin.

bpo-29890 [https://bugs.python.org/issue?@action=redirect&bpo=29890]: Add tests for ipaddress.IPv4Interface and ipaddress.IPv6Interface construction with tuple arguments. Original patch and tests by louisom.

Build

gh-89452 [https://github.com/python/cpython/issues/89452]: gdbm-compat is now preferred over ndbm if both are available on the system. This allows avoiding the problematic ndbm.h on macOS.

gh-91731 [https://github.com/python/cpython/issues/91731]: Python is now built with -std=c11 compiler option, rather than -std=c99. Patch by Victor Stinner.

bpo-47152 [https://bugs.python.org/issue?@action=redirect&bpo=47152]: Add script and make target for generating sre_constants.h.

bpo-47103 [https://bugs.python.org/issue?@action=redirect&bpo=47103]: Windows PGInstrument builds now copy a required DLL into the output directory, making it easier to run the profile stage of a PGO build.

Windows

bpo-46907 [https://bugs.python.org/issue?@action=redirect&bpo=46907]: Update Windows installer to use SQLite 3.38.3.

bpo-47239 [https://bugs.python.org/issue?@action=redirect&bpo=47239]: Fixed --list and --list-paths output for Python 安裝管理員 when used in an active virtual environment.

bpo-46907 [https://bugs.python.org/issue?@action=redirect&bpo=46907]: Update Windows installer to use SQLite 3.38.2.

bpo-46785 [https://bugs.python.org/issue?@action=redirect&bpo=46785]: Fix race condition between os.stat() and unlinking a file on Windows, by using errors codes returned by FindFirstFileW() when appropriate in win32_xstat_impl.

bpo-40859 [https://bugs.python.org/issue?@action=redirect&bpo=40859]: Update Windows build to use xz-5.2.5

macOS

bpo-46907 [https://bugs.python.org/issue?@action=redirect&bpo=46907]: Update macOS installer to SQLite 3.38.4.

Tools/Demos

gh-91583 [https://github.com/python/cpython/issues/91583]: Fix regression in the code generated by Argument Clinic for functions with the defining_class parameter.

gh-91575 [https://github.com/python/cpython/issues/91575]: Add script Tools/scripts/generate_re_casefix.py and the make target regen-re for generating additional data for case-insensitive matching according to the current Unicode version.

gh-91551 [https://github.com/python/cpython/issues/91551]: Remove the ancient Pynche color editor. It has moved to https://gitlab.com/warsaw/pynche

C API

gh-88279 [https://github.com/python/cpython/issues/88279]: Deprecate the C functions: PySys_SetArgv(), PySys_SetArgvEx(), PySys_SetPath(). Patch by Victor Stinner.

gh-92154 [https://github.com/python/cpython/issues/92154]: Added the PyCode_GetCode() function. This function does the equivalent of the Python code getattr(code_object, 'co_code').

gh-92173 [https://github.com/python/cpython/issues/92173]: Fix the closure argument to PyEval_EvalCodeEx().

gh-91320 [https://github.com/python/cpython/issues/91320]: Fix C++ compiler warnings about "old-style cast" (g++ -Wold-style-cast) in the Python C API. Use C++ reinterpret_cast<> and static_cast<> casts when the Python C API is used in C++. Patch by Victor Stinner.

gh-80527 [https://github.com/python/cpython/issues/80527]: Mark functions as deprecated by PEP 623 [https://peps.python.org/pep-0623/]: PyUnicode_AS_DATA(), PyUnicode_AS_UNICODE(), PyUnicode_GET_DATA_SIZE(), PyUnicode_GET_SIZE(). Patch by Victor Stinner.

gh-91768 [https://github.com/python/cpython/issues/91768]: Py_REFCNT(), Py_TYPE(), Py_SIZE() and Py_IS_TYPE() functions argument type is now PyObject*, rather than const PyObject*. Patch by Victor Stinner.

gh-91020 [https://github.com/python/cpython/issues/91020]: Add PyBytes_Type.tp_alloc to initialize PyBytesObject.ob_shash for bytes subclasses.

bpo-40421 [https://bugs.python.org/issue?@action=redirect&bpo=40421]: Add PyFrame_GetLasti C-API function to access frame object's f_lasti attribute safely from C code.

bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134]: Remove the Include/code.h header file. C extensions should only include the main <Python.h> header file. Patch by Victor Stinner.

bpo-47169 [https://bugs.python.org/issue?@action=redirect&bpo=47169]: PyOS_CheckStack() is now exported in the Stable ABI on Windows.

bpo-47169 [https://bugs.python.org/issue?@action=redirect&bpo=47169]: PyThread_get_thread_native_id() is excluded from the stable ABI on platforms where it doesn't exist (like Solaris).

bpo-46343 [https://bugs.python.org/issue?@action=redirect&bpo=46343]: Added PyErr_GetHandledException() and PyErr_SetHandledException() as simpler alternatives to PyErr_GetExcInfo() and PyErr_SetExcInfo().

They are included in the stable ABI.

Python 3.11.0 alpha 7

Release date: 2022-04-05

Core and Builtins

bpo-47212 [https://bugs.python.org/issue?@action=redirect&bpo=47212]: Raise IndentationError instead of SyntaxError for a bare except with no following indent. Improve SyntaxError locations for an un-parenthesized generator used as arguments. Patch by Matthieu Dartiailh.

bpo-47186 [https://bugs.python.org/issue?@action=redirect&bpo=47186]: Replace JUMP_IF_NOT_EG_MATCH by CHECK_EG_MATCH + jump.

bpo-47176 [https://bugs.python.org/issue?@action=redirect&bpo=47176]: Emscripten builds cannot handle signals in the usual way due to platform limitations. Python can now handle signals. To use, set Module.Py_EmscriptenSignalBuffer to be a single byte SharedArrayBuffer and set Py_EMSCRIPTEN_SIGNAL_HANDLING to 1. Writing a number into the SharedArrayBuffer will cause the corresponding signal to be raised into the Python thread.

bpo-47186 [https://bugs.python.org/issue?@action=redirect&bpo=47186]: Replace JUMP_IF_NOT_EXC_MATCH by CHECK_EXC_MATCH + jump.

bpo-47120 [https://bugs.python.org/issue?@action=redirect&bpo=47120]: Replace the absolute jump opcode JUMP_NO_INTERRUPT by the relative JUMP_BACKWARD_NO_INTERRUPT.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Avoid unnecessary allocations when comparing code objects.

bpo-47182 [https://bugs.python.org/issue?@action=redirect&bpo=47182]: Fix a crash when using a named unicode character like "\N{digit nine}" after the main interpreter has been initialized a second time.

bpo-47162 [https://bugs.python.org/issue?@action=redirect&bpo=47162]: WebAssembly cannot deal with bad function pointer casts (different count or types of arguments). Python can now use call trampolines to mitigate the problem. Define PY_CALL_TRAMPOLINE to enable call trampolines.

bpo-46775 [https://bugs.python.org/issue?@action=redirect&bpo=46775]: Some Windows system error codes(>= 10000) are now mapped into the correct errno and may now raise a subclass of OSError. Patch by Donghee Na.

bpo-47129 [https://bugs.python.org/issue?@action=redirect&bpo=47129]: Improve error messages in f-string syntax errors concerning empty expressions.

bpo-47117 [https://bugs.python.org/issue?@action=redirect&bpo=47117]: Fix a crash if we fail to decode characters in interactive mode if the tokenizer buffers are uninitialized. Patch by Pablo Galindo.

bpo-47127 [https://bugs.python.org/issue?@action=redirect&bpo=47127]: Speed up calls to c functions with keyword arguments by 25% with specialization. Patch by Kumar Aditya.

bpo-47120 [https://bugs.python.org/issue?@action=redirect&bpo=47120]: Replaced JUMP_ABSOLUTE by the relative jump JUMP_BACKWARD.

bpo-42197 [https://bugs.python.org/issue?@action=redirect&bpo=42197]: PyFrame_FastToLocalsWithError() and PyFrame_LocalsToFast() are no longer called during profiling nor tracing. C code can access the f_locals attribute of PyFrameObject by calling PyFrame_GetLocals().

bpo-47070 [https://bugs.python.org/issue?@action=redirect&bpo=47070]: Improve performance of array_inplace_repeat by reducing the number of invocations of memcpy. Refactor the repeat and inplace repeat methods of array, bytes, bytearray and unicodeobject to use the common _PyBytes_Repeat.

bpo-47053 [https://bugs.python.org/issue?@action=redirect&bpo=47053]: Reduce de-optimization in the specialized BINARY_OP_INPLACE_ADD_UNICODE opcode.

bpo-47045 [https://bugs.python.org/issue?@action=redirect&bpo=47045]: Remove the f_state field from the _PyInterpreterFrame struct. Add the owner field to the _PyInterpreterFrame struct to make ownership explicit to simplify clearing and deallocing frames and generators.

Library

bpo-46968 [https://bugs.python.org/issue?@action=redirect&bpo=46968]: Check for the existence of the "sys/auxv.h" header in faulthandler to avoid compilation problems in systems where this header doesn't exist. Patch by Pablo Galindo

Core and Builtins

bpo-46329 [https://bugs.python.org/issue?@action=redirect&bpo=46329]: Use low bit of LOAD_GLOBAL to indicate whether to push a NULL before the global. Helps streamline the call sequence a bit.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Quicken bytecode in-place by storing it as part of the corresponding PyCodeObject.

bpo-47012 [https://bugs.python.org/issue?@action=redirect&bpo=47012]: Speed up iteration of bytes and bytearray by 30%. Patch by Kumar Aditya.

bpo-47009 [https://bugs.python.org/issue?@action=redirect&bpo=47009]: Improved the performance of list.append() and list comprehensions by optimizing for the common case, where no resize is needed. Patch by Dennis Sweeney.

bpo-47005 [https://bugs.python.org/issue?@action=redirect&bpo=47005]: Improve performance of bytearray_repeat and bytearray_irepeat by reducing the number of invocations of memcpy.

Library

bpo-46829 [https://bugs.python.org/issue?@action=redirect&bpo=46829]: Deprecate passing a message into asyncio.Future.cancel() and asyncio.Task.cancel()

Core and Builtins

bpo-46993 [https://bugs.python.org/issue?@action=redirect&bpo=46993]: Speed up bytearray creation from list and tuple by 40%. Patch by Kumar Aditya.

bpo-39829 [https://bugs.python.org/issue?@action=redirect&bpo=39829]: Removed the __len__() call when initializing a list and moved initializing to list_extend. Patch by Jeremiah Pascual.

bpo-46944 [https://bugs.python.org/issue?@action=redirect&bpo=46944]: Speed up throwing exception in generator with METH_FASTCALL calling convention. Patch by Kumar Aditya.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Modify STORE_SUBSCR to use an inline cache entry (rather than its oparg) as an adaptive counter.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use inline caching for PRECALL and CALL, and remove the internal machinery for managing the (now unused) non-inline caches.

bpo-46881 [https://bugs.python.org/issue?@action=redirect&bpo=46881]: Statically allocate and initialize the latin1 characters.

bpo-46838 [https://bugs.python.org/issue?@action=redirect&bpo=46838]: Improve syntax errors for incorrect function definitions. Patch by Pablo Galindo

bpo-43721 [https://bugs.python.org/issue?@action=redirect&bpo=43721]: Fix docstrings of getter, setter, and deleter to clarify that they create a new copy of the property.

bpo-43224 [https://bugs.python.org/issue?@action=redirect&bpo=43224]: Make grammar changes required for PEP 646.

Library

bpo-47208 [https://bugs.python.org/issue?@action=redirect&bpo=47208]: Allow vendors to override CTYPES_MAX_ARGCOUNT.

bpo-23689 [https://bugs.python.org/issue?@action=redirect&bpo=23689]: re module: fix memory leak when a match is terminated by a signal or memory allocation failure. Patch by Ma Lin.

bpo-47167 [https://bugs.python.org/issue?@action=redirect&bpo=47167]: Allow overriding a future compliance check in asyncio.Task.

bpo-47151 [https://bugs.python.org/issue?@action=redirect&bpo=47151]: When subprocess tries to use vfork, it now falls back to fork if vfork returns an error. This allows use in situations where vfork isn't allowed by the OS kernel.

bpo-47152 [https://bugs.python.org/issue?@action=redirect&bpo=47152]: Convert the re module into a package. Deprecate modules sre_compile, sre_constants and sre_parse.

bpo-4833 [https://bugs.python.org/issue?@action=redirect&bpo=4833]: Add ZipFile.mkdir()

bpo-27929 [https://bugs.python.org/issue?@action=redirect&bpo=27929]: Fix asyncio.loop.sock_connect() to only resolve names for socket.AF_INET or socket.AF_INET6 families. Resolution may not make sense for other families, like socket.AF_BLUETOOTH and socket.AF_UNIX.

bpo-14265 [https://bugs.python.org/issue?@action=redirect&bpo=14265]: Adds the fully qualified test name to unittest output

bpo-47061 [https://bugs.python.org/issue?@action=redirect&bpo=47061]: Deprecate the aifc module.

bpo-39622 [https://bugs.python.org/issue?@action=redirect&bpo=39622]: Handle Ctrl+C in asyncio programs to interrupt the main task.

bpo-47101 [https://bugs.python.org/issue?@action=redirect&bpo=47101]: hashlib.algorithms_available now lists only algorithms that are provided by activated crypto providers on OpenSSL 3.0. Legacy algorithms are not listed unless the legacy provider has been loaded into the default OSSL context.

bpo-47099 [https://bugs.python.org/issue?@action=redirect&bpo=47099]: All URLError exception messages raised in urllib.request.URLopener now contain a colon between ftp error and the rest of the message. Previously, open_ftp() missed the colon. Patch by Oleg Iarygin.

bpo-47099 [https://bugs.python.org/issue?@action=redirect&bpo=47099]: Exception chaining is changed from Exception.with_traceback()/sys.exc_info() to PEP 3134 [https://peps.python.org/pep-3134/]. Patch by Oleg Iarygin.

bpo-47095 [https://bugs.python.org/issue?@action=redirect&bpo=47095]: hashlib's internal _blake2 module now prefers libb2 from https://www.blake2.net/ over Python's vendored copy of blake2.

bpo-47098 [https://bugs.python.org/issue?@action=redirect&bpo=47098]: The Keccak Code Package for hashlib's internal _sha3 module has been replaced with tiny_sha3. The module is used as fallback when Python is built without OpenSSL.

bpo-47088 [https://bugs.python.org/issue?@action=redirect&bpo=47088]: Implement typing.LiteralString, part of PEP 675 [https://peps.python.org/pep-0675/]. Patch by Jelle Zijlstra.

bpo-42885 [https://bugs.python.org/issue?@action=redirect&bpo=42885]: Optimize re.search(), re.split(), re.findall(), re.finditer() and re.sub() for regular expressions starting with \A or ^.

bpo-23691 [https://bugs.python.org/issue?@action=redirect&bpo=23691]: Protect the re.finditer() iterator from re-entering.

bpo-47067 [https://bugs.python.org/issue?@action=redirect&bpo=47067]: Optimize calling GenericAlias objects by using PEP 590 [https://peps.python.org/pep-0590/] vectorcall and by replacing PyObject_SetAttrString with PyObject_SetAttr.

bpo-28080 [https://bugs.python.org/issue?@action=redirect&bpo=28080]: Add the metadata_encoding parameter in the zipfile.ZipFile constructor and the --metadata-encoding option in the zipfile CLI to allow reading zipfiles using non-standard codecs to encode the filenames within the archive.

bpo-47000 [https://bugs.python.org/issue?@action=redirect&bpo=47000]: Make io.text_encoding() returns "utf-8" when UTF-8 mode is enabled.

bpo-42369 [https://bugs.python.org/issue?@action=redirect&bpo=42369]: Fix thread safety of zipfile._SharedFile.tell() to avoid a "zipfile.BadZipFile: Bad CRC-32 for file" exception when reading a ZipFile from multiple threads.

bpo-38256 [https://bugs.python.org/issue?@action=redirect&bpo=38256]: Fix binascii.crc32() when it is compiled to use zlib'c crc32 to work properly on inputs 4+GiB in length instead of returning the wrong result. The workaround prior to this was to always feed the function data in increments smaller than 4GiB or to just call the zlib module function.

We also have binascii.crc32() release the GIL when computing on larger inputs as zlib.crc32() and hashlib do.

This also boosts performance on Windows as it now uses the zlib crc32 implementation for binascii.crc32() for a 2-3x speedup.

That the stdlib has a crc32 API in two modules is a known historical oddity. This moves us closer to a single implementation behind them.

bpo-47066 [https://bugs.python.org/issue?@action=redirect&bpo=47066]: Global inline flags (e.g. (?i)) can now only be used at the start of the regular expressions. Using them not at the start of expression was deprecated since Python 3.6.

bpo-39394 [https://bugs.python.org/issue?@action=redirect&bpo=39394]: A warning about inline flags not at the start of the regular expression now contains the position of the flag.

bpo-433030 [https://bugs.python.org/issue?@action=redirect&bpo=433030]: Add support of atomic grouping ((?>...)) and possessive quantifiers (*+, ++, ?+, {m,n}+) in regular expressions.

bpo-47062 [https://bugs.python.org/issue?@action=redirect&bpo=47062]: Implement asyncio.Runner context manager.

bpo-46382 [https://bugs.python.org/issue?@action=redirect&bpo=46382]: dataclass() slots=True now correctly omits slots already defined in base classes. Patch by Arie Bovenberg.

bpo-47057 [https://bugs.python.org/issue?@action=redirect&bpo=47057]: Use FASTCALL convention for FutureIter.throw()

bpo-47061 [https://bugs.python.org/issue?@action=redirect&bpo=47061]: Deprecate the various modules listed by PEP 594 [https://peps.python.org/pep-0594/]:

aifc, asynchat, asyncore, audioop, cgi, cgitb, chunk, crypt, imghdr, msilib, nntplib, nis, ossaudiodev, pipes, smtpd, sndhdr, spwd, sunau, telnetlib, uu, xdrlib

bpo-34790 [https://bugs.python.org/issue?@action=redirect&bpo=34790]: Remove passing coroutine objects to asyncio.wait().

bpo-47039 [https://bugs.python.org/issue?@action=redirect&bpo=47039]: Normalize repr() of asyncio future and task objects.

bpo-2604 [https://bugs.python.org/issue?@action=redirect&bpo=2604]: Fix bug where doctests using globals would fail when run multiple times.

bpo-45150 [https://bugs.python.org/issue?@action=redirect&bpo=45150]: Add hashlib.file_digest() helper for efficient hashing of file object.

bpo-34861 [https://bugs.python.org/issue?@action=redirect&bpo=34861]: Made cumtime the default sorting key for cProfile

bpo-45997 [https://bugs.python.org/issue?@action=redirect&bpo=45997]: Fix asyncio.Semaphore re-aquiring FIFO order.

bpo-47022 [https://bugs.python.org/issue?@action=redirect&bpo=47022]: The asynchat, asyncore and smtpd modules have been deprecated since at least Python 3.6. Their documentation and deprecation warnings and have now been updated to note they will removed in Python 3.12 (PEP 594 [https://peps.python.org/pep-0594/]).

bpo-43253 [https://bugs.python.org/issue?@action=redirect&bpo=43253]: Fix a crash when closing transports where the underlying socket handle is already invalid on the Proactor event loop.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: select.select() now passes NULL to select for each empty fdset.

bpo-47004 [https://bugs.python.org/issue?@action=redirect&bpo=47004]: Apply bugfixes from importlib_metadata 4.11.3, including bugfix for EntryPoint.extras, which was returning match objects and not the extras strings.

bpo-46998 [https://bugs.python.org/issue?@action=redirect&bpo=46998]: Allow subclassing of typing.Any. Patch by Shantanu Jain.

bpo-46995 [https://bugs.python.org/issue?@action=redirect&bpo=46995]: Deprecate missing asyncio.Task.set_name() for third-party task implementations, schedule making it mandatory in Python 3.13.

bpo-46994 [https://bugs.python.org/issue?@action=redirect&bpo=46994]: Accept explicit contextvars.Context in asyncio.create_task() and asyncio.loop.create_task().

bpo-46981 [https://bugs.python.org/issue?@action=redirect&bpo=46981]: typing.get_args(typing.Tuple[()]) now returns () instead of ((),).

bpo-46968 [https://bugs.python.org/issue?@action=redirect&bpo=46968]: Add os.sysconf_names['SC_MINSIGSTKSZ'].

bpo-46985 [https://bugs.python.org/issue?@action=redirect&bpo=46985]: Upgrade pip wheel bundled with ensurepip (pip 22.0.4)

bpo-46968 [https://bugs.python.org/issue?@action=redirect&bpo=46968]: faulthandler: On Linux 5.14 and newer, dynamically determine size of signal handler stack size CPython allocates using getauxval(AT_MINSIGSTKSZ). This changes allows for Python extension's request to Linux kernel to use AMX_TILE instruction set on Sapphire Rapids Xeon processor to succeed, unblocking use of the ISA in frameworks.

bpo-46917 [https://bugs.python.org/issue?@action=redirect&bpo=46917]: The math.nan value is now always available. Patch by Victor Stinner.

bpo-46955 [https://bugs.python.org/issue?@action=redirect&bpo=46955]: Expose asyncio.base_events.Server as asyncio.Server. Patch by Stefan Zabka.

bpo-23325 [https://bugs.python.org/issue?@action=redirect&bpo=23325]: The signal module no longer assumes that SIG_IGN and SIG_DFL are small int singletons.

bpo-46932 [https://bugs.python.org/issue?@action=redirect&bpo=46932]: Update bundled libexpat to 2.4.7

bpo-46933 [https://bugs.python.org/issue?@action=redirect&bpo=46933]: The pwd module is now optional. os.path.expanduser() returns the path when the pwd module is not available.

bpo-40059 [https://bugs.python.org/issue?@action=redirect&bpo=40059]: PEP 680 [https://peps.python.org/pep-0680/], the tomllib module. Adds support for parsing TOML.

bpo-464471 [https://bugs.python.org/issue?@action=redirect&bpo=464471]: asyncio.timeout() and asyncio.timeout_at() context managers added. Patch by Tin Tvrtković and Andrew Svetlov.

bpo-46805 [https://bugs.python.org/issue?@action=redirect&bpo=46805]: Added raw datagram socket functions for asyncio: sock_sendto(), sock_recvfrom() and sock_recvfrom_into().

bpo-46644 [https://bugs.python.org/issue?@action=redirect&bpo=46644]: No longer require valid typeforms to be callable. This allows typing.Annotated to wrap typing.ParamSpecArgs and dataclasses.InitVar. Patch by Gregory Beauregard.

bpo-46581 [https://bugs.python.org/issue?@action=redirect&bpo=46581]: Brings ParamSpec propagation for GenericAlias in line with Concatenate (and others).

bpo-45413 [https://bugs.python.org/issue?@action=redirect&bpo=45413]: Define posix_venv and nt_venv sysconfig installation schemes to be used for bootstrapping new virtual environments. Add venv sysconfig installation scheme to get the appropriate one of the above. The schemes are identical to the pre-existing posix_prefix and nt install schemes. The venv module now uses the venv scheme to create new virtual environments instead of hardcoding the paths depending only on the platform. Downstream Python distributors customizing the posix_prefix or nt install scheme in a way that is not compatible with the install scheme used in virtual environments are encouraged not to customize the venv schemes. When Python itself runs in a virtual environment, sysconfig.get_default_scheme() and sysconfig.get_preferred_scheme() with key="prefix" returns venv.

bpo-43224 [https://bugs.python.org/issue?@action=redirect&bpo=43224]: Implement support for PEP 646 in typing.py.

bpo-43224 [https://bugs.python.org/issue?@action=redirect&bpo=43224]: Allow unpacking types.GenericAlias objects, e.g. *tuple[int, str].

bpo-46557 [https://bugs.python.org/issue?@action=redirect&bpo=46557]: Warnings captured by the logging module are now logged without a format string to prevent systems that group logs by the msg argument from grouping captured warnings together.

bpo-41370 [https://bugs.python.org/issue?@action=redirect&bpo=41370]: typing.get_type_hints() now supports evaluating strings as forward references in PEP 585 generic aliases.

bpo-46607 [https://bugs.python.org/issue?@action=redirect&bpo=46607]: Add DeprecationWarning to LegacyInterpolation, deprecated in the docstring since Python 3.2. Will be removed in Python 3.13. Use BasicInterpolation or ExtendedInterpolation instead.

bpo-26120 [https://bugs.python.org/issue?@action=redirect&bpo=26120]: pydoc now excludes __future__ imports from the module's data items.

bpo-46480 [https://bugs.python.org/issue?@action=redirect&bpo=46480]: Add typing.assert_type(). Patch by Jelle Zijlstra.

bpo-46421 [https://bugs.python.org/issue?@action=redirect&bpo=46421]: Fix a unittest issue where if the command was invoked as python -m unittest and the filename(s) began with a dot (.), a ValueError is returned.

bpo-46245 [https://bugs.python.org/issue?@action=redirect&bpo=46245]: Add optional parameter dir_fd in shutil.rmtree().

bpo-22859 [https://bugs.python.org/issue?@action=redirect&bpo=22859]: unittest.TestProgram.usageExit() is marked as deprecated, to be removed in Python 3.13.

bpo-46170 [https://bugs.python.org/issue?@action=redirect&bpo=46170]: Improve the error message when you try to subclass an instance of typing.NewType.

bpo-40296 [https://bugs.python.org/issue?@action=redirect&bpo=40296]: Fix supporting generic aliases in pydoc.

bpo-20392 [https://bugs.python.org/issue?@action=redirect&bpo=20392]: Fix inconsistency with uppercase file extensions in MimeTypes.guess_type(). Patch by Kumar Aditya.

bpo-46030 [https://bugs.python.org/issue?@action=redirect&bpo=46030]: Add LOCAL_CREDS, LOCAL_CREDS_PERSISTENT and SCM_CREDS2 FreeBSD constants to the socket module.

bpo-44439 [https://bugs.python.org/issue?@action=redirect&bpo=44439]: Fix .write() method of a member file in ZipFile, when the input data is an object that supports the buffer protocol, the file length may be wrong.

bpo-45171 [https://bugs.python.org/issue?@action=redirect&bpo=45171]: Fix handling of the stacklevel argument to logging functions in the logging module so that it is consistent across all logging functions and, as advertised, similar to the stacklevel argument used in warn().

bpo-24959 [https://bugs.python.org/issue?@action=redirect&bpo=24959]: Fix bug where unittest sometimes drops frames from tracebacks of exceptions raised in tests.

bpo-44859 [https://bugs.python.org/issue?@action=redirect&bpo=44859]: Raise more accurate and PEP 249 [https://peps.python.org/pep-0249/] compatible exceptions in sqlite3.

Raise InterfaceError instead of ProgrammingError for SQLITE_MISUSE errors.

Don't overwrite BufferError with ValueError when conversion to BLOB fails.

Raise ProgrammingError instead of Warning if user tries to execute() more than one SQL statement.

Raise ProgrammingError instead of ValueError if an SQL query contains null characters.

bpo-44493 [https://bugs.python.org/issue?@action=redirect&bpo=44493]: Add missing terminated NUL in sockaddr_un's length

This was potentially observable when using non-abstract AF_UNIX datagram sockets to processes written in another programming language.

bpo-41930 [https://bugs.python.org/issue?@action=redirect&bpo=41930]: Add serialize() and deserialize() support to sqlite3. Patch by Erlend E. Aasland.

bpo-33178 [https://bugs.python.org/issue?@action=redirect&bpo=33178]: Added ctypes.BigEndianUnion and ctypes.LittleEndianUnion classes, as originally documented in the library docs but not yet implemented.

bpo-43352 [https://bugs.python.org/issue?@action=redirect&bpo=43352]: Add an Barrier object in synchronization primitives of asyncio Lib in order to be consistent with Barrier from threading and multiprocessing libs*

bpo-35859 [https://bugs.python.org/issue?@action=redirect&bpo=35859]: re module, fix a few bugs about capturing group. In rare cases, capturing group gets an incorrect string. Patch by Ma Lin.

Documentation

bpo-45099 [https://bugs.python.org/issue?@action=redirect&bpo=45099]: Document internal asyncio API.

bpo-47126 [https://bugs.python.org/issue?@action=redirect&bpo=47126]: Update PEP URLs to PEP 676 [https://peps.python.org/pep-0676/]'s new canonical form.

bpo-47040 [https://bugs.python.org/issue?@action=redirect&bpo=47040]: Clarified the old Python versions compatibility note of binascii.crc32() / zlib.adler32() / zlib.crc32() functions.

bpo-46033 [https://bugs.python.org/issue?@action=redirect&bpo=46033]: Clarify for statement execution in its doc.

bpo-45790 [https://bugs.python.org/issue?@action=redirect&bpo=45790]: Adjust inaccurate phrasing in 擴充型別定義教學 about the ob_base field and the macros used to access its contents.

bpo-42340 [https://bugs.python.org/issue?@action=redirect&bpo=42340]: Document that in some circumstances KeyboardInterrupt may cause the code to enter an inconsistent state. Provided a sample workaround to avoid it if needed.

bpo-41233 [https://bugs.python.org/issue?@action=redirect&bpo=41233]: Link the errnos referenced in Doc/library/exceptions.rst to their respective section in Doc/library/errno.rst, and vice versa. Previously this was only done for EINTR and InterruptedError. Patch by Yan "yyyyyyyan" Orestes.

Tests

bpo-47205 [https://bugs.python.org/issue?@action=redirect&bpo=47205]: Skip test for sched_getaffinity() and sched_setaffinity() error case on FreeBSD.

bpo-46126 [https://bugs.python.org/issue?@action=redirect&bpo=46126]: Restore 'descriptions' when running tests internally.

bpo-47104 [https://bugs.python.org/issue?@action=redirect&bpo=47104]: Rewrite asyncio.to_thread() tests to use unittest.IsolatedAsyncioTestCase.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: The test suite is now passing on the Emscripten platform. All fork, socket, and subprocess-based tests are skipped.

bpo-47037 [https://bugs.python.org/issue?@action=redirect&bpo=47037]: Skip strftime("%4Y") feature test on Windows. It can cause an assertion error in debug builds.

bpo-46587 [https://bugs.python.org/issue?@action=redirect&bpo=46587]: Skip tests if platform's strftime does not support non-portable glibc extensions.

bpo-47015 [https://bugs.python.org/issue?@action=redirect&bpo=47015]: A test case for os.sendfile() is converted from deprecated asyncore (see PEP 594 [https://peps.python.org/pep-0594/]) to asyncio. Patch by Oleg Iarygin.

Build

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Add configure option --enable-wasm-dynamic-linking to enable dlopen and MAIN_MODULE / SIDE_MODULE on wasm32-emscripten.

bpo-46023 [https://bugs.python.org/issue?@action=redirect&bpo=46023]: makesetup now detects and skips all duplicated module definitions. The first entry wins.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Add SOABI wasm32-emscripten for Emscripten and wasm32-wasi for WASI on 32bit WASM as well as wasm64 counter parts.

bpo-47032 [https://bugs.python.org/issue?@action=redirect&bpo=47032]: Ensure Windows install builds fail correctly with a non-zero exit code when part of the build fails.

bpo-47024 [https://bugs.python.org/issue?@action=redirect&bpo=47024]: Update OpenSSL to 1.1.1n for macOS installers and all Windows builds.

bpo-46996 [https://bugs.python.org/issue?@action=redirect&bpo=46996]: The tkinter package now requires Tcl/Tk version 8.5.12 or newer.

bpo-46973 [https://bugs.python.org/issue?@action=redirect&bpo=46973]: Add regen-configure make target to regenerate configure script with Christian's container image quay.io/tiran/cpython_autoconf:269.

bpo-46917 [https://bugs.python.org/issue?@action=redirect&bpo=46917]: Building Python now requires support of IEEE 754 floating-point numbers. Patch by Victor Stinner.

bpo-45774 [https://bugs.python.org/issue?@action=redirect&bpo=45774]: configure now verifies that all SQLite C APIs needed for the sqlite3 extension module are found.

Windows

bpo-47194 [https://bugs.python.org/issue?@action=redirect&bpo=47194]: Update zlib to v1.2.12 to resolve CVE 2018-25032 [https://www.cve.org/CVERecord?id=CVE-2018-25032].

bpo-47171 [https://bugs.python.org/issue?@action=redirect&bpo=47171]: Enables installing the py.exe launcher on Windows ARM64.

bpo-46566 [https://bugs.python.org/issue?@action=redirect&bpo=46566]: Upgraded Python 安裝管理員 to support a new -V:company/tag argument for full PEP 514 [https://peps.python.org/pep-0514/] support and to detect ARM64 installs. The -64 suffix on arguments is deprecated, but still selects any non-32-bit install. Setting PYLAUNCHER_ALLOW_INSTALL and specifying a version that is not installed will attempt to install the requested version from the Microsoft Store.

bpo-47086 [https://bugs.python.org/issue?@action=redirect&bpo=47086]: The installer for Windows now includes documentation as loose HTML files rather than a single compiled .chm file.

bpo-46907 [https://bugs.python.org/issue?@action=redirect&bpo=46907]: Update Windows installer to use SQLite 3.38.1.

bpo-44549 [https://bugs.python.org/issue?@action=redirect&bpo=44549]: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE 2016-3189 [https://www.cve.org/CVERecord?id=CVE-2016-3189] and CVE 2019-12900 [https://www.cve.org/CVERecord?id=CVE-2019-12900].

bpo-46948 [https://bugs.python.org/issue?@action=redirect&bpo=46948]: Prevent CVE 2022-26488 [https://www.cve.org/CVERecord?id=CVE-2022-26488] by ensuring the Add to PATH option in the Windows installer uses the correct path when being repaired.

macOS

bpo-46890 [https://bugs.python.org/issue?@action=redirect&bpo=46890]: Fix a regression in the setting of sys._base_executable in framework builds, and thereby fix a regression in venv virtual environments with such builds.

bpo-46907 [https://bugs.python.org/issue?@action=redirect&bpo=46907]: Update macOS installer to SQLite 3.38.1.

Tools/Demos

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Replace Emscripten's limited shell with Katie Bell's browser-ui REPL from python-wasm project.

C API

bpo-40421 [https://bugs.python.org/issue?@action=redirect&bpo=40421]: Add PyFrame_GetBuiltins, PyFrame_GetGenerator and PyFrame_GetGlobals C-API functions to access frame object attributes safely from C code.

bpo-46850 [https://bugs.python.org/issue?@action=redirect&bpo=46850]: Move the private _PyFrameEvalFunction type, and private _PyInterpreterState_GetEvalFrameFunc() and _PyInterpreterState_SetEvalFrameFunc() functions to the internal C API. The _PyFrameEvalFunction callback function type now uses the _PyInterpreterFrame type which is part of the internal C API. Patch by Victor Stinner.

bpo-46850 [https://bugs.python.org/issue?@action=redirect&bpo=46850]: Move the private undocumented _PyEval_EvalFrameDefault() function to the internal C API. The function now uses the _PyInterpreterFrame type which is part of the internal C API. Patch by Victor Stinner.

bpo-46850 [https://bugs.python.org/issue?@action=redirect&bpo=46850]: Remove the private undocumented function _PyEval_CallTracing() from the C API. Call the public sys.call_tracing() function instead. Patch by Victor Stinner.

bpo-46850 [https://bugs.python.org/issue?@action=redirect&bpo=46850]: Remove the private undocumented function _PyEval_GetCoroutineOriginTrackingDepth() from the C API. Call the public sys.get_coroutine_origin_tracking_depth() function instead. Patch by Victor Stinner.

bpo-46850 [https://bugs.python.org/issue?@action=redirect&bpo=46850]: Remove the following private undocumented functions from the C API:

_PyEval_GetAsyncGenFirstiter()

_PyEval_GetAsyncGenFinalizer()

_PyEval_SetAsyncGenFirstiter()

_PyEval_SetAsyncGenFinalizer()

Call the public sys.get_asyncgen_hooks() and sys.set_asyncgen_hooks() functions instead. Patch by Victor Stinner.

bpo-46987 [https://bugs.python.org/issue?@action=redirect&bpo=46987]: Remove private functions _PySys_GetObjectId() and _PySys_SetObjectId(). Patch by Donghee Na.

bpo-46906 [https://bugs.python.org/issue?@action=redirect&bpo=46906]: Add new functions to pack and unpack C double (serialize and deserialize): PyFloat_Pack2(), PyFloat_Pack4(), PyFloat_Pack8(), PyFloat_Unpack2(), PyFloat_Unpack4() and PyFloat_Unpack8(). Patch by Victor Stinner.

Python 3.11.0 alpha 6

Release date: 2022-03-07

Core and Builtins

bpo-46940 [https://bugs.python.org/issue?@action=redirect&bpo=46940]: Avoid overriding AttributeError metadata information for nested attribute access calls. Patch by Pablo Galindo.

bpo-46927 [https://bugs.python.org/issue?@action=redirect&bpo=46927]: Include the type's name in the error message for subscripting non-generic types.

bpo-46921 [https://bugs.python.org/issue?@action=redirect&bpo=46921]: Support vectorcall for super(). Patch by Ken Jin.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Fix incorrect handling of inline cache entries when specializing BINARY_OP.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use an oparg to simplify the construction of helpful error messages in GET_AWAITABLE.

bpo-46903 [https://bugs.python.org/issue?@action=redirect&bpo=46903]: Make sure that str subclasses can be used as attribute names for instances with virtual dictionaries. Fixes regression in 3.11alpha

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Add more detailed specialization failure stats for COMPARE_OP followed by EXTENDED_ARG.

bpo-46891 [https://bugs.python.org/issue?@action=redirect&bpo=46891]: Fix bug introduced during 3.11alpha where subclasses of types.ModuleType with __slots__ were not initialized correctly, resulting in an interpreter crash.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use inline caching for LOAD_ATTR, LOAD_METHOD, and STORE_ATTR.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use inline cache for BINARY_SUBSCR.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use inline caching for COMPARE_OP.

bpo-46864 [https://bugs.python.org/issue?@action=redirect&bpo=46864]: Deprecate PyBytesObject.ob_shash. It will be removed in Python 3.13.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use inline caching for UNPACK_SEQUENCE.

bpo-46845 [https://bugs.python.org/issue?@action=redirect&bpo=46845]: Reduces dict size by removing hash value from hash table when all inserted keys are Unicode. For example, sys.getsizeof(dict.fromkeys("abcdefg")) becomes 272 bytes from 352 bytes on 64bit platform.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Use inline cache for LOAD_GLOBAL.

bpo-46852 [https://bugs.python.org/issue?@action=redirect&bpo=46852]: Rename the private undocumented float.__set_format__() method to float.__setformat__() to fix a typo introduced in Python 3.7. The method is only used by test_float. Patch by Victor Stinner.

bpo-46852 [https://bugs.python.org/issue?@action=redirect&bpo=46852]: Remove the undocumented private float.__set_format__() method, previously known as float.__setformat__() in Python 3.7. Its docstring said: "You probably don't want to use this function. It exists mainly to be used in Python's test suite." Patch by Victor Stinner.

bpo-40116 [https://bugs.python.org/issue?@action=redirect&bpo=40116]: Fix regression that dict.update(other) may don't respect iterate order of other when other is key sharing dict.

bpo-46712 [https://bugs.python.org/issue?@action=redirect&bpo=46712]: Share global string identifiers in deep-frozen modules.

bpo-46430 [https://bugs.python.org/issue?@action=redirect&bpo=46430]: Fix memory leak in interned strings of deep-frozen modules.

bpo-46841 [https://bugs.python.org/issue?@action=redirect&bpo=46841]: Store BINARY_OP caches inline using a new CACHE instruction.

bpo-45107 [https://bugs.python.org/issue?@action=redirect&bpo=45107]: Specialize LOAD_METHOD for instances with a dict.

bpo-44337 [https://bugs.python.org/issue?@action=redirect&bpo=44337]: Reduce the memory usage of specialized LOAD_ATTR and STORE_ATTR instructions.

bpo-46729 [https://bugs.python.org/issue?@action=redirect&bpo=46729]: Add number of sub-exceptions to BaseException.__str__().

bpo-45885 [https://bugs.python.org/issue?@action=redirect&bpo=45885]: Don't un-adapt COMPARE_OP when collecting specialization stats.

bpo-46329 [https://bugs.python.org/issue?@action=redirect&bpo=46329]: Fix specialization stats gathering for PRECALL instructions.

Library

bpo-46794 [https://bugs.python.org/issue?@action=redirect&bpo=46794]: Bump up the libexpat version into 2.4.6

Core and Builtins

bpo-46823 [https://bugs.python.org/issue?@action=redirect&bpo=46823]: Implement a specialized combined opcode LOAD_FAST__LOAD_ATTR_INSTANCE_VALUE. Patch by Dennis Sweeney.

bpo-46820 [https://bugs.python.org/issue?@action=redirect&bpo=46820]: Fix parsing a numeric literal immediately (without spaces) followed by "not in" keywords, like in 1not in x. Now the parser only emits a warning, not a syntax error.

bpo-46329 [https://bugs.python.org/issue?@action=redirect&bpo=46329]: Move KW_NAMES before PRECALL instruction in call sequence. Change operand of CALL to match PRECALL for easier specialization.

bpo-46808 [https://bugs.python.org/issue?@action=redirect&bpo=46808]: Remove the NEXT_BLOCK macro from compile.c, and make the compiler automatically generate implicit blocks when they are needed.

bpo-46329 [https://bugs.python.org/issue?@action=redirect&bpo=46329]: Add PUSH_NULL instruction. This is used as a prefix when evaluating a callable, so that the stack has the same shape for methods and other calls. PRECALL_FUNCTION and PRECALL_METHOD are merged into a single PRECALL instruction.

There is no change in semantics.

bpo-46762 [https://bugs.python.org/issue?@action=redirect&bpo=46762]: Fix an assert failure in debug builds when a '<', '>', or '=' is the last character in an f-string that's missing a closing right brace.

bpo-46730 [https://bugs.python.org/issue?@action=redirect&bpo=46730]: Message of AttributeError caused by getting, setting or deleting a property without the corresponding function now mentions that the attribute is in fact a property and also specifies type of the class that it belongs to.

bpo-46724 [https://bugs.python.org/issue?@action=redirect&bpo=46724]: Make sure that all backwards jumps use the JUMP_ABSOLUTE instruction, rather than JUMP_FORWARD with an argument of (2**32)+offset.

bpo-46732 [https://bugs.python.org/issue?@action=redirect&bpo=46732]: Correct the docstring for the __bool__() method. Patch by Jelle Zijlstra.

bpo-46072 [https://bugs.python.org/issue?@action=redirect&bpo=46072]: Add more detailed specialization failure statistics for BINARY_OP.

bpo-46707 [https://bugs.python.org/issue?@action=redirect&bpo=46707]: Avoid potential exponential backtracking when producing some syntax errors involving lots of brackets. Patch by Pablo Galindo.

Library

bpo-46323 [https://bugs.python.org/issue?@action=redirect&bpo=46323]: ctypes now allocates memory on the stack instead of on the heap to pass arguments while calling a Python callback function. Patch by Donghee Na.

Core and Builtins

bpo-45923 [https://bugs.python.org/issue?@action=redirect&bpo=45923]: Add a quickened form of RESUME that skips quickening checks.

bpo-46702 [https://bugs.python.org/issue?@action=redirect&bpo=46702]: Specialize UNPACK_SEQUENCE for tuple and list unpackings.

bpo-46072 [https://bugs.python.org/issue?@action=redirect&bpo=46072]: Opcode pair stats are now gathered with --enable-pystats. Defining DYNAMIC_EXECUTION_PROFILE or DXPAIRS no longer has any effect.

bpo-46675 [https://bugs.python.org/issue?@action=redirect&bpo=46675]: Allow more than 16 items in a split dict before it is combined. The limit is now 254.

Library

bpo-40479 [https://bugs.python.org/issue?@action=redirect&bpo=40479]: Add a missing call to va_end() in Modules/_hashopenssl.c.

bpo-46323 [https://bugs.python.org/issue?@action=redirect&bpo=46323]: Use PyObject_Vectorcall() while calling ctypes callback function. Patch by Donghee Na.

Core and Builtins

bpo-46615 [https://bugs.python.org/issue?@action=redirect&bpo=46615]: When iterating over sets internally in setobject.c, acquire strong references to the resulting items from the set. This prevents crashes in corner-cases of various set operations where the set gets mutated.

bpo-45828 [https://bugs.python.org/issue?@action=redirect&bpo=45828]: The bytecode compiler now attempts to apply runtime stack manipulations at compile-time (whenever it is feasible to do so).

bpo-30496 [https://bugs.python.org/issue?@action=redirect&bpo=30496]: Fixed a minor portability issue in the implementation of PyLong_FromLong(), and added a fast path for single-digit integers to PyLong_FromLongLong().

Library

bpo-25707 [https://bugs.python.org/issue?@action=redirect&bpo=25707]: Fixed a file leak in xml.etree.ElementTree.iterparse() when the iterator is not exhausted. Patch by Jacob Walls.

bpo-46877 [https://bugs.python.org/issue?@action=redirect&bpo=46877]: Export unittest.doModuleCleanups() in unittest. Patch by Kumar Aditya.

bpo-46848 [https://bugs.python.org/issue?@action=redirect&bpo=46848]: For performance, use the optimized string-searching implementations from find() and rfind() for find() and rfind().

bpo-46736 [https://bugs.python.org/issue?@action=redirect&bpo=46736]: SimpleHTTPRequestHandler now uses HTML5 grammar. Patch by Donghee Na.

bpo-44886 [https://bugs.python.org/issue?@action=redirect&bpo=44886]: Inherit asyncio proactor datagram transport from asyncio.DatagramTransport.

bpo-46827 [https://bugs.python.org/issue?@action=redirect&bpo=46827]: Support UDP sockets in asyncio.loop.sock_connect() for selector-based event loops. Patch by Thomas Grainger.

bpo-46811 [https://bugs.python.org/issue?@action=redirect&bpo=46811]: Make test suite support Expat >=2.4.5

bpo-46252 [https://bugs.python.org/issue?@action=redirect&bpo=46252]: Raise TypeError if ssl.SSLSocket is passed to transport-based APIs.

bpo-46784 [https://bugs.python.org/issue?@action=redirect&bpo=46784]: Fix libexpat symbols collisions with user dynamically loaded or statically linked libexpat in embedded Python.

bpo-46786 [https://bugs.python.org/issue?@action=redirect&bpo=46786]: The HTML serialisation in xml.etree.ElementTree now writes embed, source, track and wbr as empty tags, as defined in HTML 5.

bpo-39327 [https://bugs.python.org/issue?@action=redirect&bpo=39327]: shutil.rmtree() can now work with VirtualBox shared folders when running from the guest operating-system.

bpo-45390 [https://bugs.python.org/issue?@action=redirect&bpo=45390]: Propagate asyncio.CancelledError message from inner task to outer awaiter.

bpo-46756 [https://bugs.python.org/issue?@action=redirect&bpo=46756]: Fix a bug in urllib.request.HTTPPasswordMgr.find_user_password() and urllib.request.HTTPPasswordMgrWithPriorAuth.is_authenticated() which allowed to bypass authorization. For example, access to URI example.org/foobar was allowed if the user was authorized for URI example.org/foo.

bpo-46737 [https://bugs.python.org/issue?@action=redirect&bpo=46737]: random.gauss() and random.normalvariate() now have default arguments.

bpo-46752 [https://bugs.python.org/issue?@action=redirect&bpo=46752]: Add task groups to asyncio (structured concurrency, inspired by Trio's nurseries). This also introduces a change to task cancellation, where a cancelled task can't be cancelled again until it calls .uncancel().

bpo-46724 [https://bugs.python.org/issue?@action=redirect&bpo=46724]: Fix dis behavior on negative jump offsets.

bpo-46333 [https://bugs.python.org/issue?@action=redirect&bpo=46333]: The __repr__() method of typing.ForwardRef now includes the module parameter of typing.ForwardRef when it is set.

bpo-46643 [https://bugs.python.org/issue?@action=redirect&bpo=46643]: In typing.get_type_hints(), support evaluating stringified ParamSpecArgs and ParamSpecKwargs annotations. Patch by Gregory Beauregard.

bpo-45863 [https://bugs.python.org/issue?@action=redirect&bpo=45863]: When the tarfile module creates a pax format archive, it will put an integer representation of timestamps in the ustar header (if possible) for the benefit of older unarchivers, in addition to the existing full-precision timestamps in the pax extended header.

bpo-46066 [https://bugs.python.org/issue?@action=redirect&bpo=46066]: Deprecate kwargs-based syntax for typing.TypedDict definitions. It had confusing semantics when specifying totality, and was largely unused. Patch by Jingchen Ye.

bpo-46676 [https://bugs.python.org/issue?@action=redirect&bpo=46676]: Make typing.ParamSpec args and kwargs equal to themselves. Patch by Gregory Beauregard.

bpo-46323 [https://bugs.python.org/issue?@action=redirect&bpo=46323]: ctypes.CFUNCTYPE() and ctypes.WINFUNCTYPE() now fail to create the type if its _argtypes_ member contains too many arguments. Previously, the error was only raised when calling a function. Patch by Victor Stinner.

bpo-46672 [https://bugs.python.org/issue?@action=redirect&bpo=46672]: Fix NameError in asyncio.gather() when initial type check fails.

bpo-46659 [https://bugs.python.org/issue?@action=redirect&bpo=46659]: The calendar.LocaleTextCalendar and calendar.LocaleHTMLCalendar classes now use locale.getlocale(), instead of using locale.getdefaultlocale(), if no locale is specified. Patch by Victor Stinner.

bpo-46659 [https://bugs.python.org/issue?@action=redirect&bpo=46659]: The locale.getdefaultlocale() function is deprecated and will be removed in Python 3.13. Use locale.setlocale(), locale.getpreferredencoding(False) and locale.getlocale() functions instead. Patch by Victor Stinner.

bpo-46655 [https://bugs.python.org/issue?@action=redirect&bpo=46655]: In typing.get_type_hints(), support evaluating bare stringified TypeAlias annotations. Patch by Gregory Beauregard.

bpo-45948 [https://bugs.python.org/issue?@action=redirect&bpo=45948]: Fixed a discrepancy in the C implementation of the xml.etree.ElementTree module. Now, instantiating an xml.etree.ElementTree.XMLParser with a target=None keyword provides a default xml.etree.ElementTree.TreeBuilder target as the Python implementation does.

bpo-46626 [https://bugs.python.org/issue?@action=redirect&bpo=46626]: Expose Linux's IP_BIND_ADDRESS_NO_PORT option in socket.

bpo-46521 [https://bugs.python.org/issue?@action=redirect&bpo=46521]: Fix a bug in the codeop module that was incorrectly identifying invalid code involving string quotes as valid code.

bpo-46571 [https://bugs.python.org/issue?@action=redirect&bpo=46571]: Improve typing.no_type_check().

Now it does not modify external classes and functions. We also now correctly mark classmethods as not to be type checked.

bpo-46400 [https://bugs.python.org/issue?@action=redirect&bpo=46400]: expat: Update libexpat from 2.4.1 to 2.4.4

bpo-46556 [https://bugs.python.org/issue?@action=redirect&bpo=46556]: Deprecate undocumented support for using a pathlib.Path object as a context manager.

bpo-46534 [https://bugs.python.org/issue?@action=redirect&bpo=46534]: Implement PEP 673 [https://peps.python.org/pep-0673/] typing.Self. Patch by James Hilton-Balfe.

bpo-46522 [https://bugs.python.org/issue?@action=redirect&bpo=46522]: Make various module __getattr__ AttributeErrors more closely match a typical AttributeError

bpo-46475 [https://bugs.python.org/issue?@action=redirect&bpo=46475]: Add typing.Never and typing.assert_never(). Patch by Jelle Zijlstra.

bpo-46333 [https://bugs.python.org/issue?@action=redirect&bpo=46333]: The __eq__() and __hash__() methods of typing.ForwardRef now honor the module parameter of typing.ForwardRef. Forward references from different modules are now differentiated.

bpo-46246 [https://bugs.python.org/issue?@action=redirect&bpo=46246]: Add missing __slots__ to importlib.metadata.DeprecatedList. Patch by Arie Bovenberg.

bpo-46232 [https://bugs.python.org/issue?@action=redirect&bpo=46232]: The ssl module now handles certificates with bit strings in DN correctly.

bpo-46195 [https://bugs.python.org/issue?@action=redirect&bpo=46195]: typing.get_type_hints() no longer adds Optional to parameters with None as a default. This aligns to changes to PEP 484 in https://github.com/python/peps/pull/689

bpo-31369 [https://bugs.python.org/issue?@action=redirect&bpo=31369]: Add RegexFlag to re.__all__ and documented it. Add NOFLAG to indicate no flags being set.

bpo-45898 [https://bugs.python.org/issue?@action=redirect&bpo=45898]: ctypes no longer defines ffi_type_* symbols in cfield.c. The symbols have been provided by libffi for over a decade.

bpo-44953 [https://bugs.python.org/issue?@action=redirect&bpo=44953]: Calling operator.itemgetter objects and operator.attrgetter objects is now faster due to use of the vectorcall calling convention.

bpo-44289 [https://bugs.python.org/issue?@action=redirect&bpo=44289]: Fix an issue with is_tarfile() method when using fileobj argument: position in the fileobj was advanced forward which made it unreadable with tarfile.TarFile.open().

bpo-44011 [https://bugs.python.org/issue?@action=redirect&bpo=44011]: Reimplement SSL/TLS support in asyncio, borrow the implementation from uvloop library.

bpo-41086 [https://bugs.python.org/issue?@action=redirect&bpo=41086]: Make the configparser.ConfigParser constructor raise TypeError if the interpolation parameter is not of type configparser.Interpolation

bpo-29418 [https://bugs.python.org/issue?@action=redirect&bpo=29418]: Implement inspect.ismethodwrapper() and fix inspect.isroutine() for cases where methodwrapper is given. Patch by Hakan Çelik.

bpo-14156 [https://bugs.python.org/issue?@action=redirect&bpo=14156]: argparse.FileType now supports an argument of '-' in binary mode, returning the .buffer attribute of sys.stdin/sys.stdout as appropriate. Modes including 'x' and 'a' are treated equivalently to 'w' when argument is '-'. Patch contributed by Josh Rosenberg

Documentation

bpo-42238 [https://bugs.python.org/issue?@action=redirect&bpo=42238]: Doc/tools/rstlint.py has moved to its own repository and is now packaged on PyPI as sphinx-lint.

Tests

bpo-46913 [https://bugs.python.org/issue?@action=redirect&bpo=46913]: Fix test_faulthandler.test_sigfpe() if Python is built with undefined behavior sanitizer (UBSAN): disable UBSAN on the faulthandler_sigfpe() function. Patch by Victor Stinner.

bpo-46760 [https://bugs.python.org/issue?@action=redirect&bpo=46760]: Remove bytecode offsets from expected values in test.test_dis module. Reduces the obstacles to modifying the VM or compiler.

bpo-46708 [https://bugs.python.org/issue?@action=redirect&bpo=46708]: Prevent default asyncio event loop policy modification warning after test_asyncio execution.

bpo-46678 [https://bugs.python.org/issue?@action=redirect&bpo=46678]: The function make_legacy_pyc in Lib/test/support/import_helper.py no longer fails when PYTHONPYCACHEPREFIX is set to a directory on a different device from where tempfiles are stored.

bpo-46623 [https://bugs.python.org/issue?@action=redirect&bpo=46623]: Skip test_pair() and test_speech128() of test_zlib on s390x since they fail if zlib uses the s390x hardware accelerator. Patch by Victor Stinner.

Build

bpo-46860 [https://bugs.python.org/issue?@action=redirect&bpo=46860]: Respect --with-suffix when building on case-insensitive file systems.

bpo-46656 [https://bugs.python.org/issue?@action=redirect&bpo=46656]: Building Python now requires a C11 compiler. Optional C11 features are not required. Patch by Victor Stinner.

bpo-46656 [https://bugs.python.org/issue?@action=redirect&bpo=46656]: Building Python now requires support for floating-point Not-a-Number (NaN): remove the Py_NO_NAN macro. Patch by Victor Stinner.

bpo-46640 [https://bugs.python.org/issue?@action=redirect&bpo=46640]: Building Python now requires a C99 <math.h> header file providing a NAN constant, or the __builtin_nan() built-in function. Patch by Victor Stinner.

bpo-46608 [https://bugs.python.org/issue?@action=redirect&bpo=46608]: Exclude marshalled-frozen data if deep-freezing to save 300 KB disk space. This includes adding a new is_package field to _frozen. Patch by Kumar Aditya.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Fix wasm32-emscripten test failures and platform issues. - Disable syscalls that are not supported or don't work, e.g. wait, getrusage, prlimit, mkfifo, mknod, setres[gu]id, setgroups. - Use fd_count to count open fds. - Add more checks for subprocess and fork. - Add workarounds for missing _multiprocessing and failing socket.accept(). - Enable bzip2. - Disable large file support. - Disable signal.alarm.

bpo-46430 [https://bugs.python.org/issue?@action=redirect&bpo=46430]: Intern strings in deep-frozen modules. Patch by Kumar Aditya.

Windows

bpo-46744 [https://bugs.python.org/issue?@action=redirect&bpo=46744]: The default all users install directory for ARM64 is now under the native Program Files folder, rather than Program Files (Arm) which is intended for ARM (32-bit) files.

bpo-46567 [https://bugs.python.org/issue?@action=redirect&bpo=46567]: Adds Tcl and Tk support for Windows ARM64. This also adds IDLE to the installation.

bpo-46638 [https://bugs.python.org/issue?@action=redirect&bpo=46638]: Ensures registry virtualization is consistently disabled. For 3.10 and earlier, it remains enabled (some registry writes are protected), while for 3.11 and later it is disabled (registry modifications affect all applications).

IDLE

bpo-46630 [https://bugs.python.org/issue?@action=redirect&bpo=46630]: Make query dialogs on Windows start with a cursor in the entry box.

bpo-45447 [https://bugs.python.org/issue?@action=redirect&bpo=45447]: Apply IDLE syntax highlighting to .pyi files. Patch by Alex Waygood and Terry Jan Reedy.

C API

bpo-46748 [https://bugs.python.org/issue?@action=redirect&bpo=46748]: Python's public headers no longer import <stdbool.h>, leaving code that embeds/extends Python free to define bool, true and false.

bpo-46836 [https://bugs.python.org/issue?@action=redirect&bpo=46836]: Move the PyFrameObject type definition (struct _frame) to the internal C API pycore_frame.h header file. Patch by Victor Stinner.

bpo-45459 [https://bugs.python.org/issue?@action=redirect&bpo=45459]: Rename Include/buffer.h header file to Include/pybuffer.h to avoid conflicts with projects having an existing buffer.h header file. Patch by Victor Stinner.

bpo-45412 [https://bugs.python.org/issue?@action=redirect&bpo=45412]: Remove the HAVE_PY_SET_53BIT_PRECISION macro (moved to the internal C API). Patch by Victor Stinner.

bpo-46613 [https://bugs.python.org/issue?@action=redirect&bpo=46613]: Added function PyType_GetModuleByDef(), which allows access to module state when a method's defining class is not available.

Python 3.11.0 alpha 5

Release date: 2022-02-03

Core and Builtins

bpo-45773 [https://bugs.python.org/issue?@action=redirect&bpo=45773]: Remove two invalid "peephole" optimizations from the bytecode compiler.

bpo-46564 [https://bugs.python.org/issue?@action=redirect&bpo=46564]: Do not create frame objects when creating super object. Patch by Kumar Aditya.

bpo-45885 [https://bugs.python.org/issue?@action=redirect&bpo=45885]: Added more fined-grained specialization failure stats regarding the COMPARE_OP bytecode.

bpo-44977 [https://bugs.python.org/issue?@action=redirect&bpo=44977]: The delegation of int() to __trunc__() is now deprecated. Calling int(a) when type(a) implements __trunc__() but not __int__() or __index__() now raises a DeprecationWarning.

bpo-46458 [https://bugs.python.org/issue?@action=redirect&bpo=46458]: Reorder code emitted by the compiler for a try-except block so that the else block's code immediately follows the try body (without a jump). This is more optimal for the happy path.

bpo-46527 [https://bugs.python.org/issue?@action=redirect&bpo=46527]: Allow passing iterable as a keyword argument to enumerate() again. Patch by Jelle Zijlstra.

bpo-46528 [https://bugs.python.org/issue?@action=redirect&bpo=46528]: Replace several stack manipulation instructions (DUP_TOP, DUP_TOP_TWO, ROT_TWO, ROT_THREE, ROT_FOUR, and ROT_N) with new COPY and SWAP instructions.

bpo-46329 [https://bugs.python.org/issue?@action=redirect&bpo=46329]: Use two or three bytecodes to implement most calls.

Calls without named arguments are implemented as a sequence of two instructions: PRECALL; CALL. Calls with named arguments are implemented as a sequence of three instructions: PRECALL; KW_NAMES; CALL. There are two different PRECALL instructions: PRECALL_FUNTION and PRECALL_METHOD. The latter pairs with LOAD_METHOD.

This partition into pre-call and call allows better specialization, and thus better performance ultimately.

There is no change in semantics.

bpo-46503 [https://bugs.python.org/issue?@action=redirect&bpo=46503]: Fix an assert when parsing some invalid N escape sequences in f-strings.

bpo-46431 [https://bugs.python.org/issue?@action=redirect&bpo=46431]: Improve error message on invalid calls to BaseExceptionGroup.__new__().

bpo-46476 [https://bugs.python.org/issue?@action=redirect&bpo=46476]: Fix memory leak in code objects generated by deepfreeze. Patch by Kumar Aditya.

bpo-46481 [https://bugs.python.org/issue?@action=redirect&bpo=46481]: Speed up calls to weakref.ref.__call__() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-46417 [https://bugs.python.org/issue?@action=redirect&bpo=46417]: Fix a race condition on setting a type __bases__ attribute: the internal function add_subclass() now gets the PyTypeObject.tp_subclasses member after calling PyWeakref_NewRef() which can trigger a garbage collection which can indirectly modify PyTypeObject.tp_subclasses. Patch by Victor Stinner.

bpo-46417 [https://bugs.python.org/issue?@action=redirect&bpo=46417]: python -X showrefcount now shows the total reference count after clearing and destroyed the main Python interpreter. Previously, it was shown before. Patch by Victor Stinner.

bpo-43683 [https://bugs.python.org/issue?@action=redirect&bpo=43683]: Add ASYNC_GEN_WRAP opcode to wrap the value to be yielded in async generators. Removes the need to special case async generators in the YIELD_VALUE instruction.

bpo-46407 [https://bugs.python.org/issue?@action=redirect&bpo=46407]: Optimize some modulo operations in Objects/longobject.c. Patch by Jeremiah Vivian.

bpo-46409 [https://bugs.python.org/issue?@action=redirect&bpo=46409]: Add new RETURN_GENERATOR bytecode to make generators. Simplifies calling Python functions in the VM, as they no longer any need to special case generator functions.

Also add JUMP_NO_INTERRUPT bytecode that acts like JUMP_ABSOLUTE, but does not check for interrupts.

bpo-46406 [https://bugs.python.org/issue?@action=redirect&bpo=46406]: The integer division // implementation has been optimized to better let the compiler understand its constraints. It can be 20% faster on the amd64 platform when dividing an int by a value smaller than 2**30.

Library

bpo-46383 [https://bugs.python.org/issue?@action=redirect&bpo=46383]: Fix invalid signature of _zoneinfo's module_free function to resolve a crash on wasm32-emscripten platform.

Core and Builtins

bpo-46361 [https://bugs.python.org/issue?@action=redirect&bpo=46361]: Ensure that "small" integers created by int.from_bytes() and decimal.Decimal are properly cached.

bpo-46161 [https://bugs.python.org/issue?@action=redirect&bpo=46161]: Fix the class building error when the arguments are constants and CALL_FUNCTION_EX is used.

bpo-46028 [https://bugs.python.org/issue?@action=redirect&bpo=46028]: Fixes calculation of sys._base_executable when inside a virtual environment that uses symlinks with different binary names than the base environment provides.

bpo-46091 [https://bugs.python.org/issue?@action=redirect&bpo=46091]: Correctly calculate indentation levels for lines with whitespace character that are ended by line continuation characters. Patch by Pablo Galindo

Library

bpo-30512 [https://bugs.python.org/issue?@action=redirect&bpo=30512]: Add CAN Socket support for NetBSD.

Build

bpo-46045 [https://bugs.python.org/issue?@action=redirect&bpo=46045]: Do not use POSIX semaphores on NetBSD

Core and Builtins

bpo-44024 [https://bugs.python.org/issue?@action=redirect&bpo=44024]: Improve the TypeError message for non-string second arguments passed to the built-in functions getattr() and hasattr(). Patch by Géry Ogam.

Library

bpo-46624 [https://bugs.python.org/issue?@action=redirect&bpo=46624]: Restore support for non-integer arguments of random.randrange() and random.randint().

bpo-46591 [https://bugs.python.org/issue?@action=redirect&bpo=46591]: Make the IDLE doc URL on the About IDLE dialog clickable.

bpo-46565 [https://bugs.python.org/issue?@action=redirect&bpo=46565]: Remove loop variables that are leaking into modules' namespaces.

bpo-46553 [https://bugs.python.org/issue?@action=redirect&bpo=46553]: In typing.get_type_hints(), support evaluating bare stringified ClassVar annotations. Patch by Gregory Beauregard.

bpo-46544 [https://bugs.python.org/issue?@action=redirect&bpo=46544]: Don't leak x & uspace intermediate vars in textwrap.TextWrapper.

bpo-46487 [https://bugs.python.org/issue?@action=redirect&bpo=46487]: Add the get_write_buffer_limits method to asyncio.transports.WriteTransport and to the SSL transport.

bpo-45173 [https://bugs.python.org/issue?@action=redirect&bpo=45173]: Note the configparser deprecations will be removed in Python 3.12.

bpo-45162 [https://bugs.python.org/issue?@action=redirect&bpo=45162]: The deprecated unittest APIs removed in 3.11a1 have been temporarily restored to be removed in 3.12 while cleanups in external projects go in.

bpo-46539 [https://bugs.python.org/issue?@action=redirect&bpo=46539]: In typing.get_type_hints(), support evaluating stringified ClassVar and Final annotations inside Annotated. Patch by Gregory Beauregard.

bpo-46510 [https://bugs.python.org/issue?@action=redirect&bpo=46510]: Add missing test for types.TracebackType and types.FrameType. Calculate them directly from the caught exception without calling sys.exc_info().

bpo-46491 [https://bugs.python.org/issue?@action=redirect&bpo=46491]: Allow typing.Annotated to wrap typing.Final and typing.ClassVar. Patch by Gregory Beauregard.

bpo-46483 [https://bugs.python.org/issue?@action=redirect&bpo=46483]: Remove __class_getitem__() from pathlib.PurePath as this class was not supposed to be generic.

bpo-46436 [https://bugs.python.org/issue?@action=redirect&bpo=46436]: Fix command-line option -d/--directory in module http.server which is ignored when combined with command-line option --cgi. Patch by Géry Ogam.

bpo-41403 [https://bugs.python.org/issue?@action=redirect&bpo=41403]: Make mock.patch() raise a TypeError with a relevant error message on invalid arg. Previously it allowed a cryptic AttributeError to escape.

bpo-46474 [https://bugs.python.org/issue?@action=redirect&bpo=46474]: In importlib.metadata.EntryPoint.pattern, avoid potential REDoS by limiting ambiguity in consecutive whitespace.

bpo-46474 [https://bugs.python.org/issue?@action=redirect&bpo=46474]: Removed private method from importlib.metadata.Path. Sync with importlib_metadata 4.10.0.

bpo-46470 [https://bugs.python.org/issue?@action=redirect&bpo=46470]: Remove unused branch from typing._remove_dups_flatten

bpo-46469 [https://bugs.python.org/issue?@action=redirect&bpo=46469]: asyncio generic classes now return types.GenericAlias in __class_getitem__ instead of the same class.

bpo-41906 [https://bugs.python.org/issue?@action=redirect&bpo=41906]: Support passing filter instances in the filters values of handlers and loggers in the dictionary passed to logging.config.dictConfig().

bpo-46422 [https://bugs.python.org/issue?@action=redirect&bpo=46422]: Use dis.Positions in dis.Instruction instead of a regular tuple.

bpo-46434 [https://bugs.python.org/issue?@action=redirect&bpo=46434]: pdb now gracefully handles help when __doc__ is missing, for example when run with pregenerated optimized .pyc files.

bpo-43869 [https://bugs.python.org/issue?@action=redirect&bpo=43869]: Python uses the same time Epoch on all platforms. Add an explicit unit test to ensure that it's the case. Patch by Victor Stinner.

bpo-46414 [https://bugs.python.org/issue?@action=redirect&bpo=46414]: Add typing.reveal_type(). Patch by Jelle Zijlstra.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: subprocess now imports Windows-specific imports when msvcrt module is available, and POSIX-specific imports on all other platforms. This gives a clean exception when _posixsubprocess is not available (e.g. Emscripten browser target).

bpo-40066 [https://bugs.python.org/issue?@action=redirect&bpo=40066]: IntEnum, IntFlag, and StrEnum use the mixed-in type for their str() and format() output.

bpo-46316 [https://bugs.python.org/issue?@action=redirect&bpo=46316]: Optimize pathlib.Path.iterdir() by removing an unnecessary check for special entries.

bpo-29688 [https://bugs.python.org/issue?@action=redirect&bpo=29688]: Document pathlib.Path.absolute() (which has always existed).

bpo-43012 [https://bugs.python.org/issue?@action=redirect&bpo=43012]: The pathlib module's obsolete and internal _Accessor class has been removed to prepare the terrain for upcoming enhancements to the module.

bpo-46258 [https://bugs.python.org/issue?@action=redirect&bpo=46258]: Speed up math.isqrt() for small positive integers by replacing two division steps with a lookup table.

bpo-46242 [https://bugs.python.org/issue?@action=redirect&bpo=46242]: Improve error message when creating a new enum.Enum type subclassing an existing Enum with _member_names_ using enum.Enum.__call__().

bpo-43118 [https://bugs.python.org/issue?@action=redirect&bpo=43118]: Fix a bug in inspect.signature() that was causing it to fail on some subclasses of classes with a __text_signature__ referencing module globals. Patch by Weipeng Hong.

bpo-26552 [https://bugs.python.org/issue?@action=redirect&bpo=26552]: Fixed case where failing asyncio.ensure_future() did not close the coroutine. Patch by Kumar Aditya.

bpo-21987 [https://bugs.python.org/issue?@action=redirect&bpo=21987]: Fix an issue with tarfile.TarFile.getmember() getting a directory name with a trailing slash.

bpo-46124 [https://bugs.python.org/issue?@action=redirect&bpo=46124]: Update zoneinfo to rely on importlib.resources traversable API.

bpo-46103 [https://bugs.python.org/issue?@action=redirect&bpo=46103]: Now inspect.getmembers() only gets __bases__ attribute from class type. Patch by Weipeng Hong.

bpo-46080 [https://bugs.python.org/issue?@action=redirect&bpo=46080]: Fix exception in argparse help text generation if a argparse.BooleanOptionalAction argument's default is argparse.SUPPRESS and it has help specified. Patch by Felix Fontein.

bpo-44791 [https://bugs.python.org/issue?@action=redirect&bpo=44791]: Fix substitution of ParamSpec in Concatenate with different parameter expressions. Substitution with a list of types returns now a tuple of types. Substitution with Concatenate returns now a Concatenate with concatenated lists of arguments.

Documentation

bpo-46463 [https://bugs.python.org/issue?@action=redirect&bpo=46463]: Fixes escape4chm.py script used when building the CHM documentation file

Tests

bpo-43478 [https://bugs.python.org/issue?@action=redirect&bpo=43478]: Mocks can no longer be provided as the specs for other Mocks. As a result, an already-mocked object cannot be passed to mock.Mock(). This can uncover bugs in tests since these Mock-derived Mocks will always pass certain tests (e.g. isinstance) and builtin assert functions (e.g. assert_called_once_with) will unconditionally pass.

bpo-46616 [https://bugs.python.org/issue?@action=redirect&bpo=46616]: Ensures test_importlib.test_windows cleans up registry keys after completion.

bpo-44359 [https://bugs.python.org/issue?@action=redirect&bpo=44359]: test_ftplib now silently ignores socket errors to prevent logging unhandled threading exceptions. Patch by Victor Stinner.

bpo-46600 [https://bugs.python.org/issue?@action=redirect&bpo=46600]: Fix test_gdb.test_pycfunction() for Python built with clang -Og. Tolerate inlined functions in the gdb traceback. Patch by Victor Stinner.

bpo-46542 [https://bugs.python.org/issue?@action=redirect&bpo=46542]: Fix a Python crash in test_lib2to3 when using Python built in debug mode: limit the recursion limit. Patch by Victor Stinner.

bpo-46576 [https://bugs.python.org/issue?@action=redirect&bpo=46576]: test_peg_generator now disables compiler optimization when testing compilation of its own C extensions to significantly speed up the testing on non-debug builds of CPython.

bpo-46542 [https://bugs.python.org/issue?@action=redirect&bpo=46542]: Fix test_json tests checking for RecursionError: modify these tests to use support.infinite_recursion(). Patch by Victor Stinner.

bpo-13886 [https://bugs.python.org/issue?@action=redirect&bpo=13886]: Skip test_builtin PTY tests on non-ASCII characters if the readline module is loaded. The readline module changes input() behavior, but test_builtin is not intended to test the readline module. Patch by Victor Stinner.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Add test.support.requires_fork() decorators to mark tests that require a working os.fork().

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Add test.support.requires_subprocess() decorator to mark tests which require working subprocess module or os.spawn*. The wasm32-emscripten platform has no support for processes.

bpo-46126 [https://bugs.python.org/issue?@action=redirect&bpo=46126]: Disable 'descriptions' when running tests internally.

Build

bpo-46602 [https://bugs.python.org/issue?@action=redirect&bpo=46602]: Tidied up configure.ac so that conftest.c is truncated rather than appended. This assists in the case where the 'rm' of conftest.c fails to happen between tests. Downstream issues such as a clobbered SOABI can result.

bpo-46600 [https://bugs.python.org/issue?@action=redirect&bpo=46600]: Fix the test checking if the C compiler supports -Og option in the ./configure script to also use -Og on clang which supports it. Patch by Victor Stinner.

bpo-38472 [https://bugs.python.org/issue?@action=redirect&bpo=38472]: Fix GCC detection in setup.py when cross-compiling. The C compiler is now run with LC_ALL=C. Previously, the detection failed with a German locale.

bpo-46513 [https://bugs.python.org/issue?@action=redirect&bpo=46513]: configure no longer uses AC_C_CHAR_UNSIGNED macro and pyconfig.h no longer defines reserved symbol __CHAR_UNSIGNED__.

bpo-46471 [https://bugs.python.org/issue?@action=redirect&bpo=46471]: Use global singletons for single byte bytes objects in deepfreeze.

bpo-46443 [https://bugs.python.org/issue?@action=redirect&bpo=46443]: Deepfreeze now uses cached small integers as it saves some space for common small integers.

bpo-46429 [https://bugs.python.org/issue?@action=redirect&bpo=46429]: Merge all deep-frozen files into one for space savings. Patch by Kumar Aditya.

bpo-45569 [https://bugs.python.org/issue?@action=redirect&bpo=45569]: The build now defaults to using 30-bit digits for Python integers. Previously either 15-bit or 30-bit digits would be selected, depending on the platform. 15-bit digits may still be selected using the --enable-big-digits=15 option to the configure script, or by defining PYLONG_BITS_IN_DIGIT in pyconfig.h.

bpo-45925 [https://bugs.python.org/issue?@action=redirect&bpo=45925]: Update Windows installer to use SQLite 3.37.2.

bpo-43112 [https://bugs.python.org/issue?@action=redirect&bpo=43112]: Detect musl libc as a separate SOABI (tagged as linux-musl).

Windows

bpo-33125 [https://bugs.python.org/issue?@action=redirect&bpo=33125]: The traditional EXE/MSI based installer for Windows is now available for ARM64

bpo-46362 [https://bugs.python.org/issue?@action=redirect&bpo=46362]: os.path.abspath("C:CON") is now fixed to return "\.CON", not the same path. The regression was true of all legacy DOS devices such as COM1, LPT1, or NUL.

bpo-44934 [https://bugs.python.org/issue?@action=redirect&bpo=44934]: The installer now offers a command-line only option to add the installation directory to the end of PATH instead of at the start.

macOS

bpo-45925 [https://bugs.python.org/issue?@action=redirect&bpo=45925]: Update macOS installer to SQLite 3.37.2.

IDLE

bpo-45296 [https://bugs.python.org/issue?@action=redirect&bpo=45296]: Clarify close, quit, and exit in IDLE. In the File menu, 'Close' and 'Exit' are now 'Close Window' (the current one) and 'Exit' is now 'Exit IDLE' (by closing all windows). In Shell, 'quit()' and 'exit()' mean 'close Shell'. If there are no other windows, this also exits IDLE.

C API

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Remove the PyHeapType_GET_MEMBERS() macro. It was exposed in the public C API by mistake, it must only be used by Python internally. Use the PyTypeObject.tp_members member instead. Patch by Victor Stinner.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Move _Py_GetAllocatedBlocks() and _PyObject_DebugMallocStats() private functions to the internal C API. Patch by Victor Stinner.

bpo-46433 [https://bugs.python.org/issue?@action=redirect&bpo=46433]: The internal function _PyType_GetModuleByDef now correctly handles inheritance patterns involving static types.

bpo-45459 [https://bugs.python.org/issue?@action=redirect&bpo=45459]: Py_buffer and various Py_buffer related functions are now part of the limited API and stable ABI.

bpo-14916 [https://bugs.python.org/issue?@action=redirect&bpo=14916]: Fixed bug in the tokenizer that prevented PyRun_InteractiveOne from parsing from the provided FD.

Python 3.11.0 alpha 4

Release date: 2022-01-13

Core and Builtins

bpo-46070 [https://bugs.python.org/issue?@action=redirect&bpo=46070]: Py_EndInterpreter() now explicitly untracks all objects currently tracked by the GC. Previously, if an object was used later by another interpreter, calling PyObject_GC_UnTrack() on the object crashed if the previous or the next object of the PyGC_Head structure became a dangling pointer. Patch by Victor Stinner.

bpo-46347 [https://bugs.python.org/issue?@action=redirect&bpo=46347]: Fix memory leak in PyEval_EvalCodeEx.

bpo-46339 [https://bugs.python.org/issue?@action=redirect&bpo=46339]: Fix a crash in the parser when retrieving the error text for multi-line f-strings expressions that do not start in the first line of the string. Patch by Pablo Galindo

bpo-46331 [https://bugs.python.org/issue?@action=redirect&bpo=46331]: Do not set line number of instruction storing doc-string. Fixes regression introduced in 3.11 alpha.

bpo-46314 [https://bugs.python.org/issue?@action=redirect&bpo=46314]: Remove spurious "call" event when creating a lambda function that was accidentally introduced in 3.11a4.

bpo-46289 [https://bugs.python.org/issue?@action=redirect&bpo=46289]: ASDL declaration of FormattedValue has changed to reflect conversion field is not optional.

bpo-46297 [https://bugs.python.org/issue?@action=redirect&bpo=46297]: Fixed an interpreter crash on bootup with multiple PythonPaths set in the Windows registry. Patch by Derzsi Dániel.

bpo-46237 [https://bugs.python.org/issue?@action=redirect&bpo=46237]: Fix the line number of tokenizer errors inside f-strings. Patch by Pablo Galindo.

bpo-46263 [https://bugs.python.org/issue?@action=redirect&bpo=46263]: We always expect the "use_frozen_modules" config to be set, now that getpath.c was rewritten in pure Python and the logic improved.

bpo-46006 [https://bugs.python.org/issue?@action=redirect&bpo=46006]: Fix a regression when a type method like __init__() is modified in a subinterpreter. Fix a regression in _PyUnicode_EqualToASCIIId() and type update_slot(). Revert the change which made the Unicode dictionary of interned strings compatible with subinterpreters: the internal interned dictionary is shared again by all interpreters. Patch by Victor Stinner.

bpo-45923 [https://bugs.python.org/issue?@action=redirect&bpo=45923]: Add RESUME opcode. This is a logical no-op. It is emitted by the compiler anywhere a Python function can be entered. It is used by the interpreter to perform tracing and optimizer checks.

Library

bpo-46208 [https://bugs.python.org/issue?@action=redirect&bpo=46208]: Fix the regression of os.path.normpath("A/../../B") not returning expected "../B" but "B".

Core and Builtins

bpo-46240 [https://bugs.python.org/issue?@action=redirect&bpo=46240]: Correct the error message for unclosed parentheses when the tokenizer doesn't reach the end of the source when the error is reported. Patch by Pablo Galindo

bpo-46009 [https://bugs.python.org/issue?@action=redirect&bpo=46009]: Remove the GEN_START opcode.

bpo-46235 [https://bugs.python.org/issue?@action=redirect&bpo=46235]: Certain sequence multiplication operations like [0] * 1_000 are now faster due to reference-counting optimizations. Patch by Dennis Sweeney.

bpo-46221 [https://bugs.python.org/issue?@action=redirect&bpo=46221]: PREP_RERAISE_STAR no longer pushes lasti to the stack.

bpo-46202 [https://bugs.python.org/issue?@action=redirect&bpo=46202]: Remove POP_EXCEPT_AND_RERAISE and replace it by an equivalent sequence of other opcodes.

Library

bpo-46085 [https://bugs.python.org/issue?@action=redirect&bpo=46085]: Fix iterator cache mechanism of OrderedDict.

Core and Builtins

bpo-46055 [https://bugs.python.org/issue?@action=redirect&bpo=46055]: Speed up shifting operation involving integers less than PyLong_BASE. Patch by Xinhang Xu.

bpo-46110 [https://bugs.python.org/issue?@action=redirect&bpo=46110]: Add a maximum recursion check to the PEG parser to avoid stack overflow. Patch by Pablo Galindo

bpo-46107 [https://bugs.python.org/issue?@action=redirect&bpo=46107]: Fix bug where ExceptionGroup.split() and ExceptionGroup.subgroup() did not copy the exception group's __note__ field to the parts.

bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711]: The interpreter state's representation of handled exceptions (a.k.a exc_info, or _PyErr_StackItem) now has only the exc_value field, exc_type and exc_traceback have been removed as their values can be derived from exc_value.

bpo-44525 [https://bugs.python.org/issue?@action=redirect&bpo=44525]: Replace the four call bytecode instructions which one pre-call instruction and two call instructions.

Removes CALL_FUNCTION, CALL_FUNCTION_KW, CALL_METHOD and CALL_METHOD_KW.

Adds CALL_NO_KW and CALL_KW call instructions, and PRECALL_METHOD prefix for pairing with LOAD_METHOD.

bpo-46039 [https://bugs.python.org/issue?@action=redirect&bpo=46039]: Remove the YIELD_FROM instruction and replace it with the SEND instruction which performs the same operation, but without the loop.

bpo-45635 [https://bugs.python.org/issue?@action=redirect&bpo=45635]: The code called from _PyErr_Display() was refactored to improve error handling. It now exits immediately upon an unrecoverable error.

bpo-46054 [https://bugs.python.org/issue?@action=redirect&bpo=46054]: Fix parser error when parsing non-utf8 characters in source files. Patch by Pablo Galindo.

bpo-46042 [https://bugs.python.org/issue?@action=redirect&bpo=46042]: Improve the location of the caret in SyntaxError exceptions emitted by the symbol table. Patch by Pablo Galindo.

bpo-46049 [https://bugs.python.org/issue?@action=redirect&bpo=46049]: Ensure ._pth files work as intended on platforms other than Windows.

bpo-46048 [https://bugs.python.org/issue?@action=redirect&bpo=46048]: Fixes parsing of ._pth files on startup so that single-character paths are correctly read.

bpo-37971 [https://bugs.python.org/issue?@action=redirect&bpo=37971]: Fix a bug where the line numbers given in a traceback when a decorator application raised an exception were wrong.

bpo-46031 [https://bugs.python.org/issue?@action=redirect&bpo=46031]: Add POP_JUMP_IF_NOT_NONE and POP_JUMP_IF_NONE opcodes to speed up conditional jumps.

bpo-45654 [https://bugs.python.org/issue?@action=redirect&bpo=45654]: Deepfreeze runpy, patch by Kumar Aditya.

bpo-46025 [https://bugs.python.org/issue?@action=redirect&bpo=46025]: Fix a crash in the atexit module involving functions that unregister themselves before raising exceptions. Patch by Pablo Galindo.

Library

bpo-46000 [https://bugs.python.org/issue?@action=redirect&bpo=46000]: Improve compatibility of the curses module with NetBSD curses.

Core and Builtins

bpo-44525 [https://bugs.python.org/issue?@action=redirect&bpo=44525]: Specialize the CALL_FUNCTION instruction for calls to builtin types with a single argument. Speeds up range(x), list(x), and specifically type(obj).

bpo-42918 [https://bugs.python.org/issue?@action=redirect&bpo=42918]: Fix bug where the built-in compile() function did not always raise a SyntaxError when passed multiple statements in 'single' mode. Patch by Weipeng Hong.

bpo-45953 [https://bugs.python.org/issue?@action=redirect&bpo=45953]: The main interpreter in _PyRuntimeState.interpreters is now statically allocated (as part of _PyRuntime). Likewise for the initial thread state of each interpreter. This means less allocation during runtime init, as well as better memory locality for these key state objects.

bpo-45292 [https://bugs.python.org/issue?@action=redirect&bpo=45292]: Complete the PEP 654 [https://peps.python.org/pep-0654/] implementation: add except*.

bpo-43413 [https://bugs.python.org/issue?@action=redirect&bpo=43413]: Revert changes in set.__init__. Subclass of set needs to define a __init__() method if it defines a __new__() method with additional keyword parameters.

bpo-43931 [https://bugs.python.org/issue?@action=redirect&bpo=43931]: Added the Py_Version constant which bears the same value as PY_VERSION_HEX. Patch by Gabriele N. Tornetta.

Library

bpo-46342 [https://bugs.python.org/issue?@action=redirect&bpo=46342]: The @typing.final decorator now sets the __final__ attribute on the decorated object to allow runtime introspection. Patch by Jelle Zijlstra.

bpo-46328 [https://bugs.python.org/issue?@action=redirect&bpo=46328]: Added the sys.exception() method which returns the active exception instance.

bpo-46307 [https://bugs.python.org/issue?@action=redirect&bpo=46307]: Add string.Template.is_valid() and string.Template.get_identifiers() methods.

bpo-46306 [https://bugs.python.org/issue?@action=redirect&bpo=46306]: Assume that types.CodeType always has types.CodeType.co_firstlineno in doctest.

bpo-40479 [https://bugs.python.org/issue?@action=redirect&bpo=40479]: Fix hashlib usedforsecurity option to work correctly with OpenSSL 3.0.0 in FIPS mode.

bpo-46070 [https://bugs.python.org/issue?@action=redirect&bpo=46070]: Fix possible segfault when importing the asyncio module from different sub-interpreters in parallel. Patch by Erlend E. Aasland.

bpo-46244 [https://bugs.python.org/issue?@action=redirect&bpo=46244]: Removed __slots__ from typing.ParamSpec and typing.TypeVar. They served no purpose. Patch by Arie Bovenberg.

bpo-46278 [https://bugs.python.org/issue?@action=redirect&bpo=46278]: Reflect context argument in AbstractEventLoop.call_*() methods. Loop implementations already support it.

bpo-46269 [https://bugs.python.org/issue?@action=redirect&bpo=46269]: Remove special-casing of __new__ in enum.Enum.__dir__().

bpo-46266 [https://bugs.python.org/issue?@action=redirect&bpo=46266]: Improve day constants in calendar.

Now all constants (MONDAY ... SUNDAY) are documented, tested, and added to __all__.

bpo-46257 [https://bugs.python.org/issue?@action=redirect&bpo=46257]: Optimized the mean, variance, and stdev functions in the statistics module. If the input is an iterator, it is consumed in a single pass rather than eating memory by conversion to a list. The single pass algorithm is about twice as fast as the previous two pass code.

bpo-41011 [https://bugs.python.org/issue?@action=redirect&bpo=41011]: Added two new variables to pyvenv.cfg which is generated by venv module: executable for the executable and command for the command line used to create the environment.

bpo-46239 [https://bugs.python.org/issue?@action=redirect&bpo=46239]: Improve error message when importing asyncio.windows_events on non-Windows.

bpo-46238 [https://bugs.python.org/issue?@action=redirect&bpo=46238]: Reuse _winapi constants in asyncio.windows_events.

bpo-46222 [https://bugs.python.org/issue?@action=redirect&bpo=46222]: Adding SF_NOCACHE sendfile constant for FreeBSD for the posixmodule.

bpo-37295 [https://bugs.python.org/issue?@action=redirect&bpo=37295]: Add fast path for 0 <= k <= n <= 67 for math.comb().

bpo-46176 [https://bugs.python.org/issue?@action=redirect&bpo=46176]: Adding the MAP_STACK constant for the mmap module.

bpo-43424 [https://bugs.python.org/issue?@action=redirect&bpo=43424]: Deprecate webbrowser.MacOSXOSAScript._name and use name instead.

bpo-45321 [https://bugs.python.org/issue?@action=redirect&bpo=45321]: Added missing error codes to module xml.parsers.expat.errors.

bpo-46125 [https://bugs.python.org/issue?@action=redirect&bpo=46125]: Refactor tests to test traversable API directly. Includes changes from importlib 5.4.0.

bpo-46118 [https://bugs.python.org/issue?@action=redirect&bpo=46118]: Moved importlib.resources and its related functionality to a package.

bpo-37578 [https://bugs.python.org/issue?@action=redirect&bpo=37578]: Add include_hidden parameter to glob() and iglob() to match hidden files and directories when using special characters like *, **, ? and [].

bpo-20369 [https://bugs.python.org/issue?@action=redirect&bpo=20369]: concurrent.futures.wait() no longer blocks forever when given duplicate Futures. Patch by Kumar Aditya.

bpo-46105 [https://bugs.python.org/issue?@action=redirect&bpo=46105]: Honor spec when generating requirement specs with urls and extras (importlib_metadata 4.8.3).

bpo-44893 [https://bugs.python.org/issue?@action=redirect&bpo=44893]: EntryPoint objects are no longer tuples. Recommended means to access is by attribute ('.name', '.group') or accessor ('.load()'). Access by index is deprecated and will raise deprecation warning.

bpo-22815 [https://bugs.python.org/issue?@action=redirect&bpo=22815]: Print unexpected successes together with failures and errors in summary in unittest.TextTestResult.

bpo-22047 [https://bugs.python.org/issue?@action=redirect&bpo=22047]: Calling add_argument_group() on an argument group is deprecated. Calling add_argument_group() or add_mutually_exclusive_group() on a mutually exclusive group is deprecated.

These features were never supported and do not always work correctly. The functions exist on the API by accident through inheritance and will be removed in the future.

bpo-26952 [https://bugs.python.org/issue?@action=redirect&bpo=26952]: argparse raises ValueError with clear message when trying to render usage for an empty mutually exclusive group. Previously it raised a cryptic IndexError.

bpo-45615 [https://bugs.python.org/issue?@action=redirect&bpo=45615]: Functions in the traceback module raise TypeError rather than AttributeError when an exception argument is not of type BaseException.

bpo-16594 [https://bugs.python.org/issue?@action=redirect&bpo=16594]: Add allow allow_reuse_port flag in socketserver.

bpo-27718 [https://bugs.python.org/issue?@action=redirect&bpo=27718]: Fix help for the signal module. Some functions (e.g. signal() and getsignal()) were omitted.

bpo-46032 [https://bugs.python.org/issue?@action=redirect&bpo=46032]: The registry() method of functools.singledispatch() functions checks now the first argument or the first parameter annotation and raises a TypeError if it is not supported. Previously unsupported "types" were ignored (e.g. typing.List[int]) or caused an error at calling time (e.g. list[int]).

bpo-46014 [https://bugs.python.org/issue?@action=redirect&bpo=46014]: Add ability to use typing.Union and types.UnionType as dispatch argument to functools.singledispatch. Patch provided by Yurii Karabas.

bpo-27062 [https://bugs.python.org/issue?@action=redirect&bpo=27062]: Add __all__ to inspect, patch by Kumar Aditya.

bpo-46018 [https://bugs.python.org/issue?@action=redirect&bpo=46018]: Ensure that math.expm1() does not raise on underflow.

bpo-46016 [https://bugs.python.org/issue?@action=redirect&bpo=46016]: Adding F_DUP2FD and F_DUP2FD_CLOEXEC constants from FreeBSD into the fcntl module.

bpo-45755 [https://bugs.python.org/issue?@action=redirect&bpo=45755]: typing generic aliases now reveal the class attributes of the original generic class when passed to dir(). This was the behavior up to Python 3.6, but was changed in 3.7-3.9.

bpo-45874 [https://bugs.python.org/issue?@action=redirect&bpo=45874]: The empty query string, consisting of no query arguments, is now handled correctly in urllib.parse.parse_qsl. This caused problems before when strict parsing was enabled.

bpo-44674 [https://bugs.python.org/issue?@action=redirect&bpo=44674]: Change how dataclasses disallows mutable default values. It used to use a list of known types (list, dict, set). Now it disallows unhashable objects to be defaults. It's using unhashability as a proxy for mutability. Patch by Eric V. Smith, idea by Raymond Hettinger.

bpo-23882 [https://bugs.python.org/issue?@action=redirect&bpo=23882]: Remove namespace package (PEP 420) support from unittest discovery. It was introduced in Python 3.4 but has been broken since Python 3.7.

bpo-25066 [https://bugs.python.org/issue?@action=redirect&bpo=25066]: Added a __repr__() method to multiprocessing.Event objects, patch by Kumar Aditya.

bpo-45643 [https://bugs.python.org/issue?@action=redirect&bpo=45643]: Added signal.SIGSTKFLT on platforms where this signal is defined.

bpo-44092 [https://bugs.python.org/issue?@action=redirect&bpo=44092]: Fetch across rollback no longer raises InterfaceError. Instead we leave it to the SQLite library to handle these cases. Patch by Erlend E. Aasland.

bpo-42413 [https://bugs.python.org/issue?@action=redirect&bpo=42413]: Replace concurrent.futures.TimeoutError and asyncio.TimeoutError with builtin TimeoutError, keep these names as deprecated aliases.

Documentation

bpo-46196 [https://bugs.python.org/issue?@action=redirect&bpo=46196]: Document method cmd.Cmd.columnize().

bpo-46120 [https://bugs.python.org/issue?@action=redirect&bpo=46120]: State that | is preferred for readability over Union in the typing docs.

bpo-46109 [https://bugs.python.org/issue?@action=redirect&bpo=46109]: Extracted importlib.resources and importlib.resources.abc documentation into separate files.

bpo-19737 [https://bugs.python.org/issue?@action=redirect&bpo=19737]: Update the documentation for the globals() function.

Tests

bpo-46296 [https://bugs.python.org/issue?@action=redirect&bpo=46296]: Add a test case for enum with _use_args_ == True and _member_type_ == object.

bpo-46205 [https://bugs.python.org/issue?@action=redirect&bpo=46205]: Fix hang in runtest_mp due to race condition

bpo-46263 [https://bugs.python.org/issue?@action=redirect&bpo=46263]: Fix test_capi on FreeBSD 14-dev: instruct jemalloc to not fill freed memory with junk byte.

bpo-46262 [https://bugs.python.org/issue?@action=redirect&bpo=46262]: Cover ValueError path in tests for enum.Flag._missing_().

bpo-46150 [https://bugs.python.org/issue?@action=redirect&bpo=46150]: Now fakename in test_pathlib.PosixPathTest.test_expanduser is checked to be non-existent.

bpo-46129 [https://bugs.python.org/issue?@action=redirect&bpo=46129]: Rewrite asyncio.locks tests with unittest.IsolatedAsyncioTestCase usage.

bpo-23819 [https://bugs.python.org/issue?@action=redirect&bpo=23819]: Fixed asyncio tests in python optimized mode. Patch by Kumar Aditya.

bpo-46114 [https://bugs.python.org/issue?@action=redirect&bpo=46114]: Fix test case for OpenSSL 3.0.1 version. OpenSSL 3.0 uses 0xMNN00PP0L.

Build

bpo-44133 [https://bugs.python.org/issue?@action=redirect&bpo=44133]: When Python is configured with --without-static-libpython, the Python static library (libpython.a) is no longer built. Patch by Victor Stinner.

bpo-44133 [https://bugs.python.org/issue?@action=redirect&bpo=44133]: When Python is built without --enable-shared, the python program is now linked to object files, rather than being linked to the Python static library (libpython.a), to make sure that all symbols are exported. Previously, the linker omitted some symbols like the Py_FrozenMain() function. Patch by Victor Stinner.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: The configure script has a new option --with-emscripten-target to select browser or node as Emscripten build target.

bpo-46315 [https://bugs.python.org/issue?@action=redirect&bpo=46315]: Added and fixed #ifdef HAVE_FEATURE checks for functionality that is not available on WASI platform.

bpo-45723 [https://bugs.python.org/issue?@action=redirect&bpo=45723]: Fixed a regression in configure check for select.epoll().

bpo-46263 [https://bugs.python.org/issue?@action=redirect&bpo=46263]: configure no longer sets MULTIARCH on FreeBSD platforms.

bpo-46106 [https://bugs.python.org/issue?@action=redirect&bpo=46106]: Updated OpenSSL to 1.1.1m in Windows builds, macOS installer builds, and CI. Patch by Kumar Aditya.

bpo-46088 [https://bugs.python.org/issue?@action=redirect&bpo=46088]: Automatically detect or install bootstrap Python runtime when building from Visual Studio.

bpo-46072 [https://bugs.python.org/issue?@action=redirect&bpo=46072]: Add a --with-pystats configure option to turn on internal statistics gathering.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: A new directory Tools/wasm contains WebAssembly-related helpers like config.site override for wasm32-emscripten, wasm assets generator to bundle the stdlib, and a README.

bpo-46023 [https://bugs.python.org/issue?@action=redirect&bpo=46023]: makesetup no longer builds extensions that have been marked as disabled. This allows users to disable modules in Modules/Setup.local.

bpo-45949 [https://bugs.python.org/issue?@action=redirect&bpo=45949]: Use pure Python freeze_module for all but importlib bootstrap files. --with-freeze-module configure option is no longer needed for cross builds.

Windows

bpo-46217 [https://bugs.python.org/issue?@action=redirect&bpo=46217]: Removed parameter that is unsupported on Windows 8.1 and early Windows 10 and may have caused build or runtime failures.

macOS

bpo-40477 [https://bugs.python.org/issue?@action=redirect&bpo=40477]: The Python Launcher app for macOS now properly launches scripts and, if necessary, the Terminal app when running on recent macOS releases.

C API

bpo-46236 [https://bugs.python.org/issue?@action=redirect&bpo=46236]: Fix a bug in PyFunction_GetAnnotations() that caused it to return a tuple instead of a dict.

bpo-46140 [https://bugs.python.org/issue?@action=redirect&bpo=46140]: PyBuffer_GetPointer(), PyBuffer_FromContiguous(), PyBuffer_ToContiguous() and PyMemoryView_FromBuffer() now take buffer info by const Py_buffer * instead of Py_buffer *, as they do not need mutability. PyBuffer_FromContiguous() also now takes the source buffer as const void *, and similarly PyBuffer_GetPointer() takes the strides as const Py_ssize_t *.

bpo-45855 [https://bugs.python.org/issue?@action=redirect&bpo=45855]: Document that the no_block argument to PyCapsule_Import() is a no-op now.

bpo-45855 [https://bugs.python.org/issue?@action=redirect&bpo=45855]: Replaced deprecated usage of PyImport_ImportModuleNoBlock() with PyImport_ImportModule() in stdlib modules. Patch by Kumar Aditya.

bpo-46007 [https://bugs.python.org/issue?@action=redirect&bpo=46007]: The PyUnicode_CHECK_INTERNED() macro has been excluded from the limited C API. It was never usable there, because it used internal structures which are not available in the limited C API. Patch by Victor Stinner.

Python 3.11.0 alpha 3

Release date: 2021-12-08

Core and Builtins

bpo-46009 [https://bugs.python.org/issue?@action=redirect&bpo=46009]: Restore behavior from 3.9 and earlier when sending non-None to newly started generator. In 3.9 this did not affect the state of the generator. In 3.10.0 and 3.10.1 gen_func().send(0) is equivalent to gen_func().throw(TypeError(...) which exhausts the generator. In 3.10.2 onward, the behavior has been reverted to that of 3.9.

bpo-46004 [https://bugs.python.org/issue?@action=redirect&bpo=46004]: Fix the SyntaxError location for errors involving for loops with invalid targets. Patch by Pablo Galindo

bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711]: _PyErr_ChainStackItem() no longer normalizes exc_info (including setting the traceback on the exception instance) because exc_info is always normalized.

bpo-45607 [https://bugs.python.org/issue?@action=redirect&bpo=45607]: The __note__ field was added to BaseException. It is None by default but can be set to a string which is added to the exception's traceback.

bpo-45947 [https://bugs.python.org/issue?@action=redirect&bpo=45947]: Place pointers to dict and values immediately before GC header. This reduces number of dependent memory loads to access either dict or values from 3 to 1.

bpo-45915 [https://bugs.python.org/issue?@action=redirect&bpo=45915]: is_valid_fd now uses faster fcntl(fd, F_GETFD) on Linux, macOS, and Windows.

bpo-44530 [https://bugs.python.org/issue?@action=redirect&bpo=44530]: Reverts a change to the code.__new__ audit event from an earlier prerelease.

bpo-42268 [https://bugs.python.org/issue?@action=redirect&bpo=42268]: Fail the configure step if the selected compiler doesn't support memory sanitizer. Patch by Pablo Galindo

bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711]: The three values of exc_info are now always consistent with each other. In particular, the type and traceback fields are now derived from the exception instance. This impacts the return values of sys.exc_info() and PyErr_GetExcInfo() if the exception instance is modified while the exception is handled, as well as PyErr_SetExcInfo(), which now ignores the type and traceback arguments provided to it.

bpo-45727 [https://bugs.python.org/issue?@action=redirect&bpo=45727]: Refine the custom syntax error that suggests that a comma may be missing to trigger only when the expressions are detected between parentheses or brackets. Patch by Pablo Galindo

bpo-45885 [https://bugs.python.org/issue?@action=redirect&bpo=45885]: Specialized the COMPARE_OP opcode using the PEP 659 machinery.

bpo-45786 [https://bugs.python.org/issue?@action=redirect&bpo=45786]: Allocate space for the interpreter frame in the frame object, to avoid an additional allocation when the frame object outlives the frame activation.

Library

bpo-45614 [https://bugs.python.org/issue?@action=redirect&bpo=45614]: Fix traceback display for exceptions with invalid module name.

Core and Builtins

bpo-45813 [https://bugs.python.org/issue?@action=redirect&bpo=45813]: Fix crash when calling coro.cr_frame.clear() after coroutine has been freed.

bpo-45811 [https://bugs.python.org/issue?@action=redirect&bpo=45811]: Improve the tokenizer errors when encountering invisible control characters in the parser. Patch by Pablo Galindo

bpo-45848 [https://bugs.python.org/issue?@action=redirect&bpo=45848]: Allow the parser to obtain error lines directly from encoded files. Patch by Pablo Galindo

bpo-45709 [https://bugs.python.org/issue?@action=redirect&bpo=45709]: Restore behavior from 3.10 when tracing an exception raised within a with statement.

bpo-44525 [https://bugs.python.org/issue?@action=redirect&bpo=44525]: Adds new COPY_FREE_VARS opcode, to make copying of free variables from function to frame explicit. Helps optimization of calls to Python function.

bpo-45829 [https://bugs.python.org/issue?@action=redirect&bpo=45829]: Specialize BINARY_SUBSCR for classes with a __getitem__ method implemented in Python

bpo-45826 [https://bugs.python.org/issue?@action=redirect&bpo=45826]: Fixed a crash when calling .with_traceback(None) on NameError. This occurs internally in unittest.TestCase.assertRaises().

bpo-45822 [https://bugs.python.org/issue?@action=redirect&bpo=45822]: Fixed a bug in the parser that was causing it to not respect PEP 263 [https://peps.python.org/pep-0263/] coding cookies when no flags are provided. Patch by Pablo Galindo

bpo-45820 [https://bugs.python.org/issue?@action=redirect&bpo=45820]: Fix a segfault when the parser fails without reading any input. Patch by Pablo Galindo

bpo-45636 [https://bugs.python.org/issue?@action=redirect&bpo=45636]: Simplify the implementation of BINARY_OP by indexing into an array of function pointers (rather than switching on the oparg).

bpo-42540 [https://bugs.python.org/issue?@action=redirect&bpo=42540]: Fix crash when os.fork() is called with an active non-default memory allocator.

bpo-45738 [https://bugs.python.org/issue?@action=redirect&bpo=45738]: Fix computation of error location for invalid continuation characters in the parser. Patch by Pablo Galindo.

bpo-45636 [https://bugs.python.org/issue?@action=redirect&bpo=45636]: Remove an existing "fast path" for old-style string formatting, since it no longer appears to have any measurable impact.

bpo-45753 [https://bugs.python.org/issue?@action=redirect&bpo=45753]: Make recursion checks a bit more efficient by tracking amount of calls left before overflow.

bpo-45773 [https://bugs.python.org/issue?@action=redirect&bpo=45773]: Fix a compiler hang when attempting to optimize certain jump patterns.

bpo-45764 [https://bugs.python.org/issue?@action=redirect&bpo=45764]: The parser now gives a better error message when leaving out the opening parenthesis ( after a def-statement:

>>> def f:
  File "<stdin>", line 1
    def f:
         ^
SyntaxError: expected '('

bpo-45609 [https://bugs.python.org/issue?@action=redirect&bpo=45609]: Specialized the STORE_SUBSCR opcode using the PEP 659 machinery.

bpo-45636 [https://bugs.python.org/issue?@action=redirect&bpo=45636]: Replace all numeric BINARY_* and INPLACE_* instructions with a single BINARY_OP implementation.

bpo-45582 [https://bugs.python.org/issue?@action=redirect&bpo=45582]: Path calculation (known as getpath) has been reimplemented as a frozen Python module. This should have no visible impact, but may affect calculation of all paths referenced in sys and sysconfig.

bpo-45450 [https://bugs.python.org/issue?@action=redirect&bpo=45450]: Improve the syntax error message for parenthesized arguments. Patch by Pablo Galindo.

Library

bpo-27946 [https://bugs.python.org/issue?@action=redirect&bpo=27946]: Fix possible crash when getting an attribute of xml.etree.ElementTree.Element simultaneously with replacing the attrib dict.

bpo-45711 [https://bugs.python.org/issue?@action=redirect&bpo=45711]: Make asyncio normalize exceptions as soon as they are captured with PyErr_Fetch(), and before they are stored as an exc_info triplet. This brings asyncio in line with the rest of the codebase, where an exc_info triplet is always normalized.

bpo-23819 [https://bugs.python.org/issue?@action=redirect&bpo=23819]: Replaced asserts with exceptions in asyncio, patch by Kumar Aditya.

bpo-13236 [https://bugs.python.org/issue?@action=redirect&bpo=13236]: unittest.TextTestResult and unittest.TextTestRunner flush now the output stream more often.

bpo-45917 [https://bugs.python.org/issue?@action=redirect&bpo=45917]: Added math.exp2():, which returns 2 raised to the power of x.

bpo-37658 [https://bugs.python.org/issue?@action=redirect&bpo=37658]: Fix issue when on certain conditions asyncio.wait_for() may allow a coroutine to complete successfully, but fail to return the result, potentially causing memory leaks or other issues.

bpo-45876 [https://bugs.python.org/issue?@action=redirect&bpo=45876]: Improve the accuracy of stdev() and pstdev() in the statistics module. When the inputs are floats or fractions, the output is a correctly rounded float

bpo-44649 [https://bugs.python.org/issue?@action=redirect&bpo=44649]: Handle dataclass(slots=True) with a field that has default a default value, but for which init=False.

bpo-45803 [https://bugs.python.org/issue?@action=redirect&bpo=45803]: Added missing kw_only parameter to dataclasses.make_dataclass().

bpo-45837 [https://bugs.python.org/issue?@action=redirect&bpo=45837]: The turtle.RawTurtle.settiltangle() is deprecated since Python 3.1, it now emits a deprecation warning and will be removed in Python 3.13.

Use turtle.RawTurtle.tiltangle() instead.

turtle.RawTurtle.tiltangle() was earlier incorrectly marked as deprecated, its docstring has been corrected.

Patch by Hugo van Kemenade.

bpo-45831 [https://bugs.python.org/issue?@action=redirect&bpo=45831]: faulthandler can now write ASCII-only strings (like filenames and function names) with a single write() syscall when dumping a traceback. It reduces the risk of getting an unreadable dump when two threads or two processes dump a traceback to the same file (like stderr) at the same time. Patch by Victor Stinner.

bpo-45828 [https://bugs.python.org/issue?@action=redirect&bpo=45828]: sqlite C callbacks now use unraisable exceptions if callback tracebacks are enabled. Patch by Erlend E. Aasland.

bpo-41735 [https://bugs.python.org/issue?@action=redirect&bpo=41735]: Fix thread lock in zlib.Decompress.flush() method before PyObject_GetBuffer.

bpo-45235 [https://bugs.python.org/issue?@action=redirect&bpo=45235]: Reverted an argparse bugfix that caused regression in the handling of default arguments for subparsers. This prevented leaf level arguments from taking precedence over root level arguments.

bpo-45754 [https://bugs.python.org/issue?@action=redirect&bpo=45754]: Fix a regression in Python 3.11a1 and 3.11a2 where sqlite3 incorrectly would use SQLITE_LIMIT_LENGTH when checking SQL statement lengths. Now, SQLITE_LIMIT_SQL_LENGTH is used. Patch by Erlend E. Aasland.

bpo-45766 [https://bugs.python.org/issue?@action=redirect&bpo=45766]: Added proportional option to statistics.linear_regression().

bpo-45765 [https://bugs.python.org/issue?@action=redirect&bpo=45765]: In importlib.metadata, fix distribution discovery for an empty path.

bpo-45757 [https://bugs.python.org/issue?@action=redirect&bpo=45757]: Fix bug where dis produced an incorrect oparg when EXTENDED_ARG is followed by an opcode that does not use its argument.

bpo-45644 [https://bugs.python.org/issue?@action=redirect&bpo=45644]: In-place JSON file formatting using python3 -m json.tool infile infile now works correctly, previously it left the file empty. Patch by Chris Wesseling.

bpo-45703 [https://bugs.python.org/issue?@action=redirect&bpo=45703]: When a namespace package is imported before another module from the same namespace is created/installed in a different sys.path location while the program is running, calling the importlib.invalidate_caches() function will now also guarantee the new module is noticed.

bpo-45535 [https://bugs.python.org/issue?@action=redirect&bpo=45535]: Improve output of dir() with Enums.

bpo-45664 [https://bugs.python.org/issue?@action=redirect&bpo=45664]: Fix types.resolve_bases() and types.new_class() for types.GenericAlias instance as a base.

bpo-45663 [https://bugs.python.org/issue?@action=redirect&bpo=45663]: Fix dataclasses.is_dataclass() for dataclasses which are subclasses of types.GenericAlias.

bpo-45662 [https://bugs.python.org/issue?@action=redirect&bpo=45662]: Fix the repr of dataclasses.InitVar with a type alias to the built-in class, e.g. InitVar[list[int]].

bpo-43137 [https://bugs.python.org/issue?@action=redirect&bpo=43137]: Launch GNOME web browsers via gio tool instead of obsolete gvfs-open

bpo-45429 [https://bugs.python.org/issue?@action=redirect&bpo=45429]: On Windows, time.sleep() now uses a waitable timer which supports high-resolution timers. Patch by Donghee Na and Eryk Sun.

bpo-37295 [https://bugs.python.org/issue?@action=redirect&bpo=37295]: Optimize math.comb() and math.perm().

bpo-45514 [https://bugs.python.org/issue?@action=redirect&bpo=45514]: Deprecated legacy functions in importlib.resources.

bpo-45507 [https://bugs.python.org/issue?@action=redirect&bpo=45507]: Add tests for truncated/missing trailers in gzip.decompress implementation.

bpo-45359 [https://bugs.python.org/issue?@action=redirect&bpo=45359]: Implement PEP 585 [https://peps.python.org/pep-0585/] for graphlib.TopologicalSorter.

bpo-44733 [https://bugs.python.org/issue?@action=redirect&bpo=44733]: Add max_tasks_per_child to concurrent.futures.ProcessPoolExecutor. This allows users to specify the maximum number of tasks a single process should execute before the process needs to be restarted.

bpo-28806 [https://bugs.python.org/issue?@action=redirect&bpo=28806]: Improve netrc library. netrc file no longer needs to contain all tokens. And if the login name is anonymous, security check is no longer need.

bpo-43498 [https://bugs.python.org/issue?@action=redirect&bpo=43498]: Avoid a possible "RuntimeError: dictionary changed size during iteration" when adjusting the process count of ProcessPoolExecutor.

bpo-42158 [https://bugs.python.org/issue?@action=redirect&bpo=42158]: Add MIME types for N-quads, N-triples, Notation3 and TriG to mimetypes.

bpo-30533 [https://bugs.python.org/issue?@action=redirect&bpo=30533]: Add inspect.getmembers_static() , it return all members without triggering dynamic lookup via the descriptor protocol. Patch by Weipeng Hong.

Documentation

bpo-42238 [https://bugs.python.org/issue?@action=redirect&bpo=42238]: make -C Doc suspicious will be removed soon in favor of make -C Doc check, mark it as deprecated.

bpo-45840 [https://bugs.python.org/issue?@action=redirect&bpo=45840]: Improve cross-references in the documentation for the data model.

bpo-45640 [https://bugs.python.org/issue?@action=redirect&bpo=45640]: Properly marked-up grammar tokens in the documentation are now clickable and take you to the definition of a given piece of grammar. Patch by Arthur Milchior.

bpo-45788 [https://bugs.python.org/issue?@action=redirect&bpo=45788]: Link doc for sys.prefix to sysconfig doc on installation paths.

bpo-45772 [https://bugs.python.org/issue?@action=redirect&bpo=45772]: socket.socket documentation is corrected to a class from a function.

bpo-45392 [https://bugs.python.org/issue?@action=redirect&bpo=45392]: Update the docstring of the type built-in to remove a redundant line and to mention keyword arguments for the constructor.

bpo-45250 [https://bugs.python.org/issue?@action=redirect&bpo=45250]: Update the documentation to note that CPython does not consistently require iterators to define __iter__.

bpo-25381 [https://bugs.python.org/issue?@action=redirect&bpo=25381]: In the extending chapter of the extending doc, update a paragraph about the global variables containing exception information.

bpo-43905 [https://bugs.python.org/issue?@action=redirect&bpo=43905]: Expanded astuple() and asdict() docs, warning about deepcopy being applied and providing a workaround.

Tests

bpo-45695 [https://bugs.python.org/issue?@action=redirect&bpo=45695]: Out-of-tree builds with a read-only source directory are now tested by CI.

bpo-19460 [https://bugs.python.org/issue?@action=redirect&bpo=19460]: Add new Test for Lib/email/mime/nonmultipart.py::MIMENonMultipart.

bpo-45835 [https://bugs.python.org/issue?@action=redirect&bpo=45835]: Fix race condition in test_queue tests with multiple "feeder" threads.

bpo-45783 [https://bugs.python.org/issue?@action=redirect&bpo=45783]: The test for the freeze tool now handles file moves and deletions.

bpo-45745 [https://bugs.python.org/issue?@action=redirect&bpo=45745]: Remove the --findleaks command line option of regrtest: use the --fail-env-changed option instead. Since Python 3.7, it was a deprecated alias to the --fail-env-changed option.

bpo-45701 [https://bugs.python.org/issue?@action=redirect&bpo=45701]: Add tests with tuple type with functools.lru_cache() to test_functools.

Build

bpo-44035 [https://bugs.python.org/issue?@action=redirect&bpo=44035]: CI now verifies that autoconf files have been regenerated with a current and unpatched autoconf package.

bpo-45950 [https://bugs.python.org/issue?@action=redirect&bpo=45950]: The build system now uses a _bootstrap_python interpreter for freezing and deepfreezing again. To speed up build process the build tools _bootstrap_python and _freeze_module are no longer build with LTO.

bpo-45881 [https://bugs.python.org/issue?@action=redirect&bpo=45881]: The configure script now accepts --with-build-python and --with-freeze-module options to make cross compiling easier.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Emscripten platform now uses .wasm suffix by default.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: Disable unusable core extension modules on WASM/Emscripten targets.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: configure now checks for socket shutdown function. The check makes it possible to disable SYS_shutdown with ac_cv_func_shutdown=no in CONFIG_SITE.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: configure now checks for functions fork1, getegid, geteuid, getgid, getppid, getuid, opendir, pipe, system, wait, ttyname.

bpo-33393 [https://bugs.python.org/issue?@action=redirect&bpo=33393]: Update config.guess to 2021-06-03 and config.sub to 2021-08-14. Makefile now has an update-config target to make updating more convenient.

bpo-45866 [https://bugs.python.org/issue?@action=redirect&bpo=45866]: make regen-all now produces the same output when run from a directory other than the source tree: when building Python out of the source tree. pegen now strips directory of the "generated by pygen from <FILENAME>" header Patch by Victor Stinner.

bpo-40280 [https://bugs.python.org/issue?@action=redirect&bpo=40280]: configure now accepts machine wasm32 or wasm64 and OS wasi or emscripten for cross building, e.g. wasm32-unknown-emscripten, wasm32-wasi, or wasm32-unknown-wasi.

bpo-41498 [https://bugs.python.org/issue?@action=redirect&bpo=41498]: Python now compiles on platforms without sigset_t. Several functions in signal are not available when sigset_t is missing.

Based on patch by Roman Yurchak for pyodide.

bpo-45881 [https://bugs.python.org/issue?@action=redirect&bpo=45881]: setup.py now uses CC from environment first to discover multiarch and cross compile paths.

bpo-45886 [https://bugs.python.org/issue?@action=redirect&bpo=45886]: The _freeze_module program path can now be overridden on the command line, e.g. make FREEZE_MODULE=../x86_64/Program/_freeze_module.

bpo-45873 [https://bugs.python.org/issue?@action=redirect&bpo=45873]: Get rid of the _bootstrap_python build step. The deepfreeze.py script is now run using $(PYTHON_FOR_REGEN) which can be Python 3.7 or newer (on Windows, 3.8 or newer).

bpo-45847 [https://bugs.python.org/issue?@action=redirect&bpo=45847]: Port builtin hashlib extensions to PY_STDLIB_MOD macro and addext().

bpo-45723 [https://bugs.python.org/issue?@action=redirect&bpo=45723]: Add autoconf helpers for saving and restoring environment variables:

SAVE_ENV: Save $CFLAGS, $LDFLAGS, $LIBS, and $CPPFLAGS.

RESTORE_ENV: Restore $CFLAGS, $LDFLAGS, $LIBS, and $CPPFLAGS.

WITH_SAVE_ENV([SCRIPT]): Run SCRIPT wrapped with SAVE_ENV and RESTORE_ENV.

Patch by Erlend E. Aasland.

bpo-45573 [https://bugs.python.org/issue?@action=redirect&bpo=45573]: Mandatory core modules, that are required to bootstrap Python, are now in Modules/Setup.bootstrap.

bpo-45573 [https://bugs.python.org/issue?@action=redirect&bpo=45573]: configure now creates Modules/Setup.stdlib with conditionally enabled/disabled extension module lines. The file is not used, yet.

bpo-45573 [https://bugs.python.org/issue?@action=redirect&bpo=45573]: configure now uses a unified format to set state, compiler flags, and linker flags in Makefile. The new macro PY_STDLIB_MOD sets three variables that are consumed by Modules/Setup and setup.py.

bpo-45816 [https://bugs.python.org/issue?@action=redirect&bpo=45816]: Python now supports building with Visual Studio 2022 (MSVC v143, VS Version 17.0). Patch by Jeremiah Vivian.

bpo-45800 [https://bugs.python.org/issue?@action=redirect&bpo=45800]: Settings for pyexpat C extension are now detected by configure. The bundled expat library is built in Makefile.

bpo-45798 [https://bugs.python.org/issue?@action=redirect&bpo=45798]: Settings for decimal internal C extension are now detected by configure. The bundled libmpdec library is built in Makefile.

bpo-45723 [https://bugs.python.org/issue?@action=redirect&bpo=45723]: configure has a new option --with-pkg-config to disable or require pkg-config.

bpo-45774 [https://bugs.python.org/issue?@action=redirect&bpo=45774]: The build dependencies for sqlite3 are now detected by configure and pkg-config. Patch by Erlend E. Aasland.

bpo-45763 [https://bugs.python.org/issue?@action=redirect&bpo=45763]: The build dependencies for zlib, bz2, and lzma are now detected by configure.

bpo-45747 [https://bugs.python.org/issue?@action=redirect&bpo=45747]: gdbm and dbm build dependencies are now detected by configure.

bpo-45743 [https://bugs.python.org/issue?@action=redirect&bpo=45743]: On macOS, the build system no longer passes search_paths_first to the linker. The flag has been the default since Xcode 4 / macOS 10.6.

bpo-45723 [https://bugs.python.org/issue?@action=redirect&bpo=45723]: configure.ac is now compatible with autoconf 2.71. Deprecated checks STDC_HEADERS and AC_HEADER_TIME have been removed.

bpo-45723 [https://bugs.python.org/issue?@action=redirect&bpo=45723]: configure now prints a warning when pkg-config is missing.

bpo-45731 [https://bugs.python.org/issue?@action=redirect&bpo=45731]: configure --enable-loadable-sqlite-extensions is now handled by new PY_SQLITE_ENABLE_LOAD_EXTENSION macro instead of logic in setup.py.

bpo-45723 [https://bugs.python.org/issue?@action=redirect&bpo=45723]: configure.ac now uses custom helper macros and AC_CACHE_CHECK to simplify and speed up configure runs.

bpo-45696 [https://bugs.python.org/issue?@action=redirect&bpo=45696]: Skip the marshal step for frozen modules by generating C code that produces a set of ready-to-use code objects. This speeds up startup time by another 10% or more.

bpo-45561 [https://bugs.python.org/issue?@action=redirect&bpo=45561]: Run smelly.py tool from $(srcdir).

Windows

bpo-46105 [https://bugs.python.org/issue?@action=redirect&bpo=46105]: Fixed calculation of sys.path in a venv on Windows.

bpo-45901 [https://bugs.python.org/issue?@action=redirect&bpo=45901]: When installed through the Microsoft Store and set as the default app for *.py files, command line arguments will now be passed to Python when invoking a script without explicitly launching Python (that is, script.py args rather than python script.py args).

bpo-45616 [https://bugs.python.org/issue?@action=redirect&bpo=45616]: Fix Python Launcher's ability to distinguish between versions 3.1 and 3.10 when either one is explicitly requested. Previously, 3.1 would be used if 3.10 was requested but not installed, and 3.10 would be used if 3.1 was requested but 3.10 was installed.

bpo-45850 [https://bugs.python.org/issue?@action=redirect&bpo=45850]: Implement changes to build with deep-frozen modules on Windows. Note that we now require Python 3.10 as the "bootstrap" or "host" Python.

bpo-45732 [https://bugs.python.org/issue?@action=redirect&bpo=45732]: Updates bundled Tcl/Tk to 8.6.12.

bpo-45720 [https://bugs.python.org/issue?@action=redirect&bpo=45720]: Internal reference to shlwapi.dll was dropped to help improve startup time. This DLL will no longer be loaded at the start of every Python process.

macOS

bpo-45732 [https://bugs.python.org/issue?@action=redirect&bpo=45732]: Update python.org macOS installer to use Tcl/Tk 8.6.12.

C API

bpo-39026 [https://bugs.python.org/issue?@action=redirect&bpo=39026]: Fix Python.h to build C extensions with Xcode: remove a relative include from Include/cpython/pystate.h.

Python 3.11.0 alpha 2

Release date: 2021-11-05

Core and Builtins

bpo-45716 [https://bugs.python.org/issue?@action=redirect&bpo=45716]: Improve the SyntaxError message when using True, None or False as keywords in a function call. Patch by Pablo Galindo.

bpo-45688 [https://bugs.python.org/issue?@action=redirect&bpo=45688]: sys.stdlib_module_names now contains the macOS-specific module _scproxy.

bpo-45379 [https://bugs.python.org/issue?@action=redirect&bpo=45379]: Clarify ImportError message when we try to explicitly import a frozen module but frozen modules are disabled.

bpo-44525 [https://bugs.python.org/issue?@action=redirect&bpo=44525]: Specialize simple calls to Python functions (no starargs, keyword dict, or closure)

bpo-45530 [https://bugs.python.org/issue?@action=redirect&bpo=45530]: Cases of sorting using tuples as keys may now be significantly faster in some cases. Patch by Tim Peters.

The order of the result may differ from earlier releases if the tuple elements don't define a total ordering (see Value comparisons for information on total ordering). It's generally true that the result of sorting simply isn't well-defined in the absence of a total ordering on list elements.

bpo-45526 [https://bugs.python.org/issue?@action=redirect&bpo=45526]: In obmalloc, set ADDRESS_BITS to not ignore any bits (ignored 16 before). That is safer in the case that the kernel gives user-space virtual addresses that span a range greater than 48 bits.

bpo-30570 [https://bugs.python.org/issue?@action=redirect&bpo=30570]: Fixed a crash in issubclass() from infinite recursion when searching pathological __bases__ tuples.

bpo-45521 [https://bugs.python.org/issue?@action=redirect&bpo=45521]: Fix a bug in the obmalloc radix tree code. On 64-bit machines, the bug causes the tree to hold 46-bits of virtual addresses, rather than the intended 48-bits.

bpo-45494 [https://bugs.python.org/issue?@action=redirect&bpo=45494]: Fix parser crash when reporting errors involving invalid continuation characters. Patch by Pablo Galindo.

bpo-45445 [https://bugs.python.org/issue?@action=redirect&bpo=45445]: Python now fails to initialize if it finds an invalid -X option in the command line. Patch by Pablo Galindo.

bpo-45340 [https://bugs.python.org/issue?@action=redirect&bpo=45340]: Object attributes are held in an array instead of a dictionary. An object's dictionary are created lazily, only when needed. Reduces the memory consumption of a typical Python object by about 30%. Patch by Mark Shannon.

bpo-45408 [https://bugs.python.org/issue?@action=redirect&bpo=45408]: Fix a crash in the parser when reporting tokenizer errors that occur at the same time unclosed parentheses are detected. Patch by Pablo Galindo.

bpo-29410 [https://bugs.python.org/issue?@action=redirect&bpo=29410]: Add SipHash13 for string hash algorithm and use it by default.

bpo-45385 [https://bugs.python.org/issue?@action=redirect&bpo=45385]: Fix reference leak from descr_check. Patch by Donghee Na.

bpo-45367 [https://bugs.python.org/issue?@action=redirect&bpo=45367]: Specialized the BINARY_MULTIPLY opcode to BINARY_MULTIPLY_INT and BINARY_MULTIPLY_FLOAT using the PEP 659 machinery.

bpo-21736 [https://bugs.python.org/issue?@action=redirect&bpo=21736]: Frozen stdlib modules now have __file__ to the .py file they would otherwise be loaded from, if possible. For packages, __path__ now has the correct entry instead of being an empty list, which allows unfrozen submodules to be imported. These are set only if the stdlib directory is known when the runtime is initialized. Note that the file at __file__ is not guaranteed to exist. None of this affects non-stdlib frozen modules nor, for now, frozen modules imported using PyImport_ImportFrozenModule(). Also, at the moment co_filename is not updated for the module.

bpo-45020 [https://bugs.python.org/issue?@action=redirect&bpo=45020]: For frozen stdlib modules, record the original module name as module.__spec__.loader_state.origname. If the value is different than module.__spec__.name then the module was defined as an alias in Tools/scripts/freeze_modules.py. If it is None then the module comes from a source file outside the stdlib.

bpo-45324 [https://bugs.python.org/issue?@action=redirect&bpo=45324]: In FrozenImporter.find_spec(), we now preserve the information needed in exec_module() to load the module. This change mostly impacts internal details, rather than changing the importer's behavior.

bpo-45292 [https://bugs.python.org/issue?@action=redirect&bpo=45292]: Implement PEP 654 [https://peps.python.org/pep-0654/]. Add ExceptionGroup and BaseExceptionGroup. Update traceback display code.

bpo-40116 [https://bugs.python.org/issue?@action=redirect&bpo=40116]: Change to the implementation of split dictionaries. Classes where the instances differ either in the exact set of attributes, or in the order in which those attributes are set, can still share keys. This should have no observable effect on users of Python or the C-API. Patch by Mark Shannon.

bpo-44050 [https://bugs.python.org/issue?@action=redirect&bpo=44050]: Extensions that indicate they use global state (by setting m_size to -1) can again be used in multiple interpreters. This reverts to behavior of Python 3.8.

bpo-44525 [https://bugs.python.org/issue?@action=redirect&bpo=44525]: Setup initial specialization infrastructure for the CALL_FUNCTION opcode. Implemented initial specializations for C function calls:

CALL_FUNCTION_BUILTIN_O for METH_O flag.

CALL_FUNCTION_BUILTIN_FAST for METH_FASTCALL flag without keywords.

CALL_FUNCTION_LEN for len(o).

CALL_FUNCTION_ISINSTANCE for isinstance(o, t).

bpo-44511 [https://bugs.python.org/issue?@action=redirect&bpo=44511]: Improve the generated bytecode for class and mapping patterns.

bpo-43706 [https://bugs.python.org/issue?@action=redirect&bpo=43706]: Speed up calls to enumerate() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

Library

bpo-45679 [https://bugs.python.org/issue?@action=redirect&bpo=45679]: Fix caching of multi-value typing.Literal. Literal[True, 2] is no longer equal to Literal[1, 2].

bpo-42064 [https://bugs.python.org/issue?@action=redirect&bpo=42064]: Convert sqlite3 to multi-phase initialisation (PEP 489). Patches by Erlend E. Aasland.

bpo-45438 [https://bugs.python.org/issue?@action=redirect&bpo=45438]: Fix typing.Signature string representation for generic builtin types.

bpo-45613 [https://bugs.python.org/issue?@action=redirect&bpo=45613]: sqlite3 now sets sqlite3.threadsafety based on the default threading mode the underlying SQLite library has been compiled with. Patch by Erlend E. Aasland.

bpo-45574 [https://bugs.python.org/issue?@action=redirect&bpo=45574]: Fix warning about print_escape being unused.

bpo-45581 [https://bugs.python.org/issue?@action=redirect&bpo=45581]: sqlite3.connect() now correctly raises MemoryError if the underlying SQLite API signals memory error. Patch by Erlend E. Aasland.

bpo-45557 [https://bugs.python.org/issue?@action=redirect&bpo=45557]: pprint.pprint() now handles underscore_numbers correctly. Previously it was always setting it to False.

bpo-44019 [https://bugs.python.org/issue?@action=redirect&bpo=44019]: Add operator.call() to operator.__all__. Patch by Kreusada.

bpo-42174 [https://bugs.python.org/issue?@action=redirect&bpo=42174]: shutil.get_terminal_size() now falls back to sane values if the column or line count are 0.

bpo-35673 [https://bugs.python.org/issue?@action=redirect&bpo=35673]: Improve the introspectability of the __loader__ attribute for namespace packages. importlib.machinery.NamespaceLoader is now public, and implements the importlib.abc.InspectLoader interface. _NamespaceLoader is kept for backward compatibility.

bpo-45515 [https://bugs.python.org/issue?@action=redirect&bpo=45515]: Add references to zoneinfo in the datetime documentation, mostly replacing outdated references to dateutil.tz. Change by Paul Ganssle.

bpo-45475 [https://bugs.python.org/issue?@action=redirect&bpo=45475]: Reverted optimization of iterating gzip.GzipFile, bz2.BZ2File, and lzma.LZMAFile (see bpo-43787 [https://bugs.python.org/issue?@action=redirect&bpo=43787]) because it caused regression when user iterate them without having reference of them. Patch by Inada Naoki.

bpo-45489 [https://bugs.python.org/issue?@action=redirect&bpo=45489]: Update ForwardRef to support | operator. Patch by Donghee Na.

bpo-42222 [https://bugs.python.org/issue?@action=redirect&bpo=42222]: Removed deprecated support for float arguments in randrange().

bpo-45428 [https://bugs.python.org/issue?@action=redirect&bpo=45428]: Fix a regression in py_compile when reading filenames from standard input.

bpo-45467 [https://bugs.python.org/issue?@action=redirect&bpo=45467]: Fix incremental decoder and stream reader in the "raw-unicode-escape" codec. Previously they failed if the escape sequence was split.

bpo-45461 [https://bugs.python.org/issue?@action=redirect&bpo=45461]: Fix incremental decoder and stream reader in the "unicode-escape" codec. Previously they failed if the escape sequence was split.

bpo-45239 [https://bugs.python.org/issue?@action=redirect&bpo=45239]: Fixed email.utils.parsedate_tz() crashing with UnboundLocalError on certain invalid input instead of returning None. Patch by Ben Hoyt.

bpo-45417 [https://bugs.python.org/issue?@action=redirect&bpo=45417]: Fix quadratic behaviour in the enum module: Creation of enum classes with a lot of entries was quadratic.

bpo-45249 [https://bugs.python.org/issue?@action=redirect&bpo=45249]: Fix the behaviour of traceback.print_exc() when displaying the caret when the end_offset in the exception is set to 0. Patch by Pablo Galindo

bpo-45416 [https://bugs.python.org/issue?@action=redirect&bpo=45416]: Fix use of asyncio.Condition with explicit asyncio.Lock objects, which was a regression due to removal of explicit loop arguments. Patch by Joongi Kim.

bpo-20028 [https://bugs.python.org/issue?@action=redirect&bpo=20028]: Empty escapechar/quotechar is not allowed when initializing csv.Dialect. Patch by Vajrasky Kok and Donghee Na.

bpo-44904 [https://bugs.python.org/issue?@action=redirect&bpo=44904]: Fix bug in the doctest module that caused it to fail if a docstring included an example with a classmethod property. Patch by Alex Waygood.

bpo-45406 [https://bugs.python.org/issue?@action=redirect&bpo=45406]: Make inspect.getmodule() catch FileNotFoundError raised by inspect.getabsfile(), and return None to indicate that the module could not be determined.

bpo-45411 [https://bugs.python.org/issue?@action=redirect&bpo=45411]: Add extensions for files containing subtitles - .srt & .vtt - to the mimetypes.py module.

bpo-10716 [https://bugs.python.org/issue?@action=redirect&bpo=10716]: Migrated pydoc to HTML5 (without changing the look of it). Side effect is to update xmlrpc's ServerHTMLDoc which now uses the CSS too. cgitb now relies less on pydoc (as it can't use the CSS file).

bpo-27580 [https://bugs.python.org/issue?@action=redirect&bpo=27580]: Add support of null characters in csv.

bpo-45262 [https://bugs.python.org/issue?@action=redirect&bpo=45262]: Prevent use-after-free in asyncio. Make sure the cached running loop holder gets cleared on dealloc to prevent use-after-free in get_running_loop

bpo-45386 [https://bugs.python.org/issue?@action=redirect&bpo=45386]: Make xmlrpc.client more robust to C runtimes where the underlying C strftime function results in a ValueError when testing for year formatting options.

bpo-20028 [https://bugs.python.org/issue?@action=redirect&bpo=20028]: Improve error message of csv.Dialect when initializing. Patch by Vajrasky Kok and Donghee Na.

bpo-45343 [https://bugs.python.org/issue?@action=redirect&bpo=45343]: Update bundled pip to 21.2.4 and setuptools to 58.1.0

bpo-45328 [https://bugs.python.org/issue?@action=redirect&bpo=45328]: Fixed http.client.HTTPConnection to work properly in OSs that don't support the TCP_NODELAY socket option.

bpo-45243 [https://bugs.python.org/issue?@action=redirect&bpo=45243]: Add setlimit() and getlimit() to sqlite3.Connection for setting and getting SQLite limits by connection basis. Patch by Erlend E. Aasland.

bpo-45320 [https://bugs.python.org/issue?@action=redirect&bpo=45320]: Removed from the inspect module:

the getargspec function, deprecated since Python 3.0;

use inspect.signature() or inspect.getfullargspec() instead.

the formatargspec function, deprecated since Python 3.5; use the inspect.signature() function and Signature object directly.

the undocumented Signature.from_builtin and Signature.from_function functions, deprecated since Python 3.5; use the Signature.from_callable() method instead.

Patch by Hugo van Kemenade.

bpo-45192 [https://bugs.python.org/issue?@action=redirect&bpo=45192]: Fix the tempfile._infer_return_type function so that the dir argument of the tempfile functions accepts an object implementing the os.PathLike protocol.

Patch by Kyungmin Lee.

bpo-45160 [https://bugs.python.org/issue?@action=redirect&bpo=45160]: When tracing a tkinter variable used by a ttk OptionMenu, callbacks are no longer made twice.

bpo-25625 [https://bugs.python.org/issue?@action=redirect&bpo=25625]: Added non parallel-safe chdir() context manager to change the current working directory and then restore it on exit. Simple wrapper around chdir().

bpo-24139 [https://bugs.python.org/issue?@action=redirect&bpo=24139]: Add support for SQLite extended result codes in sqlite3.Error. Patch by Erlend E. Aasland.

bpo-24444 [https://bugs.python.org/issue?@action=redirect&bpo=24444]: Fixed an error raised in argparse help display when help for an option is set to 1+ blank spaces or when choices arg is an empty container.

bpo-44547 [https://bugs.python.org/issue?@action=redirect&bpo=44547]: Implement Fraction.__int__, so that a fractions.Fraction instance f passes an isinstance(f, typing.SupportsInt) check.

bpo-40321 [https://bugs.python.org/issue?@action=redirect&bpo=40321]: Adds support for HTTP 308 redirects to urllib. See RFC 7538 [https://datatracker.ietf.org/doc/html/rfc7538.html] for details. Patch by Jochem Schulenklopper.

bpo-41374 [https://bugs.python.org/issue?@action=redirect&bpo=41374]: Ensure that socket.TCP_* constants are exposed on Cygwin 3.1.6 and greater.

bpo-35970 [https://bugs.python.org/issue?@action=redirect&bpo=35970]: Add help flag to the base64 module's command line interface. Patch contributed by Robert Kuska.

Documentation

bpo-45726 [https://bugs.python.org/issue?@action=redirect&bpo=45726]: Improve documentation for functools.singledispatch() and functools.singledispatchmethod.

bpo-45680 [https://bugs.python.org/issue?@action=redirect&bpo=45680]: Amend the docs on GenericAlias objects to clarify that non-container classes can also implement __class_getitem__. Patch contributed by Alex Waygood.

bpo-45618 [https://bugs.python.org/issue?@action=redirect&bpo=45618]: Update Sphinx version used to build the documentation to 4.2.0. Patch by Maciej Olko.

bpo-45655 [https://bugs.python.org/issue?@action=redirect&bpo=45655]: Add a new "relevant PEPs" section to the top of the documentation for the typing module. Patch by Alex Waygood.

bpo-45604 [https://bugs.python.org/issue?@action=redirect&bpo=45604]: Add level argument to multiprocessing.log_to_stderr function docs.

bpo-45516 [https://bugs.python.org/issue?@action=redirect&bpo=45516]: Add protocol description to the importlib.abc.TraversableResources documentation.

bpo-45464 [https://bugs.python.org/issue?@action=redirect&bpo=45464]: Mention in the documentation of Built-in Exceptions that inheriting from multiple exception types in a single subclass is not recommended due to possible memory layout incompatibility.

bpo-45449 [https://bugs.python.org/issue?@action=redirect&bpo=45449]: Add note about PEP 585 [https://peps.python.org/pep-0585/] in collections.abc.

bpo-45516 [https://bugs.python.org/issue?@action=redirect&bpo=45516]: Add protocol description to the importlib.abc.Traversable documentation.

bpo-20692 [https://bugs.python.org/issue?@action=redirect&bpo=20692]: Add Programming FAQ entry explaining that int literal attribute access requires either a space after or parentheses around the literal.

Tests

bpo-45678 [https://bugs.python.org/issue?@action=redirect&bpo=45678]: Add tests for scenarios in which functools.singledispatchmethod is stacked on top of a method that has already been wrapped by two other decorators. Patch by Alex Waygood.

bpo-45578 [https://bugs.python.org/issue?@action=redirect&bpo=45578]: Add tests for dis.distb()

bpo-45678 [https://bugs.python.org/issue?@action=redirect&bpo=45678]: Add tests to ensure that functools.singledispatchmethod correctly wraps the attributes of the target function.

bpo-45668 [https://bugs.python.org/issue?@action=redirect&bpo=45668]: PGO tests now pass when Python is built without test extension modules.

bpo-45577 [https://bugs.python.org/issue?@action=redirect&bpo=45577]: Add subtests for all pickle protocols in test_zoneinfo.

bpo-45566 [https://bugs.python.org/issue?@action=redirect&bpo=45566]: Fix test_frozen_pickle in test_dataclasses to check all pickle versions.

bpo-43592 [https://bugs.python.org/issue?@action=redirect&bpo=43592]: test.libregrtest now raises the soft resource limit for the maximum number of file descriptors when the default is too low for our test suite as was often the case on macOS.

bpo-39679 [https://bugs.python.org/issue?@action=redirect&bpo=39679]: Add more test cases for @functools.singledispatchmethod when combined with @classmethod or @staticmethod.

bpo-45410 [https://bugs.python.org/issue?@action=redirect&bpo=45410]: When libregrtest spawns a worker process, stderr is now written into stdout to keep messages order. Use a single pipe for stdout and stderr, rather than two pipes. Previously, messages were out of order which made analysis of buildbot logs harder Patch by Victor Stinner.

bpo-45402 [https://bugs.python.org/issue?@action=redirect&bpo=45402]: Fix test_tools.test_sundry() when Python is built out of tree: fix how the freeze_modules.py tool locates the _freeze_module program. Patch by Victor Stinner.

bpo-45403 [https://bugs.python.org/issue?@action=redirect&bpo=45403]: Fix test_sys.test_stdlib_dir() when Python is built outside the source tree: compare normalized paths. Patch by Victor Stinner.

bpo-45400 [https://bugs.python.org/issue?@action=redirect&bpo=45400]: Fix test_name_error_suggestions_do_not_trigger_for_too_many_locals() of test_exceptions if a directory name contains "a1" (like "Python-3.11.0a1"): use a stricter regular expression. Patch by Victor Stinner.

bpo-10572 [https://bugs.python.org/issue?@action=redirect&bpo=10572]: Rename sqlite3 tests from test_sqlite to test_sqlite3, and relocate them to Lib/test/test_sqlite3. Patch by Erlend E. Aasland.

Build

bpo-43158 [https://bugs.python.org/issue?@action=redirect&bpo=43158]: setup.py now uses values from configure script to build the _uuid extension module. Configure now detects util-linux's libuuid, too.

bpo-45666 [https://bugs.python.org/issue?@action=redirect&bpo=45666]: Fix warning of swprintf and %s usage in _testembed.c

bpo-45548 [https://bugs.python.org/issue?@action=redirect&bpo=45548]: Modules/Setup and Modules/makesetup have been improved. The Setup file now contains working rules for all extensions. Outdated comments have been removed. Rules defined by makesetup track dependencies correctly.

bpo-45548 [https://bugs.python.org/issue?@action=redirect&bpo=45548]: The math and cmath implementation now require a C99 compatible libm and no longer ship with workarounds for missing acosh, asinh, atanh, expm1, and log1p functions.

bpo-45595 [https://bugs.python.org/issue?@action=redirect&bpo=45595]: setup.py and makesetup now track build dependencies on all Python header files and module specific header files.

bpo-45571 [https://bugs.python.org/issue?@action=redirect&bpo=45571]: Modules/Setup now use PY_CFLAGS_NODIST instead of PY_CFLAGS to compile shared modules.

bpo-45570 [https://bugs.python.org/issue?@action=redirect&bpo=45570]: pyexpat and _elementtree no longer define obsolete macros HAVE_EXPAT_CONFIG_H and USE_PYEXPAT_CAPI. XML_POOR_ENTROPY is now defined in expat_config.h.

bpo-43974 [https://bugs.python.org/issue?@action=redirect&bpo=43974]: setup.py no longer defines Py_BUILD_CORE_MODULE. Instead every module, that uses the internal API, defines the macro.

bpo-45548 [https://bugs.python.org/issue?@action=redirect&bpo=45548]: Fill in missing entries in Modules/Setup.

bpo-45532 [https://bugs.python.org/issue?@action=redirect&bpo=45532]: Update sys.version to use main as fallback information. Patch by Jeong YunWon.

bpo-45536 [https://bugs.python.org/issue?@action=redirect&bpo=45536]: The configure script now checks whether OpenSSL headers and libraries provide required APIs. Most common APIs are verified. The check detects outdated or missing OpenSSL. Failures do not stop configure.

bpo-45221 [https://bugs.python.org/issue?@action=redirect&bpo=45221]: Fixed regression in handling of LDFLAGS and CPPFLAGS options where argparse.parse_known_args() could interpret an option as one of the built-in command line argument, for example -h for help.

bpo-45440 [https://bugs.python.org/issue?@action=redirect&bpo=45440]: Building Python now requires a C99 <math.h> header file providing the following functions: copysign(), hypot(), isfinite(), isinf(), isnan(), round(). Patch by Victor Stinner.

bpo-45405 [https://bugs.python.org/issue?@action=redirect&bpo=45405]: Prevent internal configure error when running configure with recent versions of non-Apple clang. Patch by David Bohman.

bpo-45433 [https://bugs.python.org/issue?@action=redirect&bpo=45433]: Avoid linking libpython with libcrypt.

Windows

bpo-43652 [https://bugs.python.org/issue?@action=redirect&bpo=43652]: Update Tcl/Tk to 8.6.11, actually this time. The previous update incorrectly included 8.6.10.

bpo-45337 [https://bugs.python.org/issue?@action=redirect&bpo=45337]: venv now warns when the created environment may need to be accessed at a different path, due to redirections, links or junctions. It also now correctly installs or upgrades components when the alternate path is required.

bpo-43851 [https://bugs.python.org/issue?@action=redirect&bpo=43851]: Build SQLite SQLITE_OMIT_AUTOINIT on Windows. Patch by Erlend E. Aasland.

macOS

bpo-44828 [https://bugs.python.org/issue?@action=redirect&bpo=44828]: Avoid tkinter file dialog failure on macOS 12 Monterey when using the Tk 8.6.11 provided by python.org macOS installers. Patch by Marc Culler of the Tk project.

IDLE

bpo-45495 [https://bugs.python.org/issue?@action=redirect&bpo=45495]: Add context keywords 'case' and 'match' to completions list.

C API

bpo-29103 [https://bugs.python.org/issue?@action=redirect&bpo=29103]: PyType_FromSpec* now copies the class name from the spec to a buffer owned by the class, so the original can be safely deallocated. Patch by Petr Viktorin.

bpo-45522 [https://bugs.python.org/issue?@action=redirect&bpo=45522]: The internal freelists for frame, float, list, dict, async generators, and context objects can now be disabled.

bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134]: Exclude PyWeakref_GET_OBJECT() from the limited C API. It never worked since the PyWeakReference structure is opaque in the limited C API.

bpo-35081 [https://bugs.python.org/issue?@action=redirect&bpo=35081]: Move the interpreteridobject.h header file from Include/ to Include/internal/. It only provides private functions. Patch by Victor Stinner.

bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134]: The non-limited API files cellobject.h, classobject.h, context.h, funcobject.h, genobject.h and longintrepr.h have been moved to the Include/cpython directory. Moreover, the eval.h header file was removed. These files must not be included directly, as they are already included in Python.h: Include Files. If they have been included directly, consider including Python.h instead. Patch by Victor Stinner.

bpo-45474 [https://bugs.python.org/issue?@action=redirect&bpo=45474]: The following items are no longer available when Py_LIMITED_API is defined:

PyMarshal_WriteLongToFile()

PyMarshal_WriteObjectToFile()

PyMarshal_ReadObjectFromString()

PyMarshal_WriteObjectToString()

the Py_MARSHAL_VERSION macro

These are not part of the limited API.

Patch by Victor Stinner.

bpo-45434 [https://bugs.python.org/issue?@action=redirect&bpo=45434]: Remove the pystrhex.h header file. It only contains private functions. C extensions should only include the main <Python.h> header file. Patch by Victor Stinner.

bpo-45440 [https://bugs.python.org/issue?@action=redirect&bpo=45440]: Remove the Py_FORCE_DOUBLE() macro. It was used by the Py_IS_INFINITY() macro. Patch by Victor Stinner.

bpo-45434 [https://bugs.python.org/issue?@action=redirect&bpo=45434]: <Python.h> no longer includes the header files <stdlib.h>, <stdio.h>, <errno.h> and <string.h> when the Py_LIMITED_API macro is set to 0x030b0000 (Python 3.11) or higher. C extensions should explicitly include the header files after #include <Python.h>. Patch by Victor Stinner.

bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123]: Remove Py_UNICODE_COPY() and Py_UNICODE_FILL() macros, deprecated since Python 3.3. Use PyUnicode_CopyCharacters() or memcpy() (wchar_t* string), and PyUnicode_Fill() functions instead. Patch by Victor Stinner.

bpo-45412 [https://bugs.python.org/issue?@action=redirect&bpo=45412]: Remove the following math macros using the errno variable:

Py_ADJUST_ERANGE1()

Py_ADJUST_ERANGE2()

Py_OVERFLOWED()

Py_SET_ERANGE_IF_OVERFLOW()

Py_SET_ERRNO_ON_MATH_ERROR()

Patch by Victor Stinner.

bpo-45395 [https://bugs.python.org/issue?@action=redirect&bpo=45395]: Custom frozen modules (the array set to PyImport_FrozenModules) are now treated as additions, rather than replacing all the default frozen modules. Frozen stdlib modules can still be disabled by setting the "code" field of the custom array entry to NULL.

bpo-43760 [https://bugs.python.org/issue?@action=redirect&bpo=43760]: Add new PyThreadState_EnterTracing(), and PyThreadState_LeaveTracing() functions to the limited C API to suspend and resume tracing and profiling. Patch by Victor Stinner.

bpo-44220 [https://bugs.python.org/issue?@action=redirect&bpo=44220]: PyStructSequence_UnnamedField is added to the Stable ABI.

Python 3.11.0 alpha 1

Release date: 2021-10-05

Security

bpo-42278 [https://bugs.python.org/issue?@action=redirect&bpo=42278]: Replaced usage of tempfile.mktemp() with TemporaryDirectory to avoid a potential race condition.

bpo-44600 [https://bugs.python.org/issue?@action=redirect&bpo=44600]: Fix incorrect line numbers while tracing some failed patterns in match statements. Patch by Charles Burkland.

bpo-41180 [https://bugs.python.org/issue?@action=redirect&bpo=41180]: Add auditing events to the marshal module, and stop raising code.__init__ events for every unmarshalled code object. Directly instantiated code objects will continue to raise an event, and audit event handlers should inspect or collect the raw marshal data. This reduces a significant performance overhead when loading from .pyc files.

bpo-44394 [https://bugs.python.org/issue?@action=redirect&bpo=44394]: Update the vendored copy of libexpat to 2.4.1 (from 2.2.8) to get the fix for the CVE 2013-0340 [https://www.cve.org/CVERecord?id=CVE-2013-0340] "Billion Laughs" vulnerability. This copy is most used on Windows and macOS.

bpo-43124 [https://bugs.python.org/issue?@action=redirect&bpo=43124]: Made the internal putcmd function in smtplib sanitize input for presence of \r and \n characters to avoid (unlikely) command injection.

bpo-44022 [https://bugs.python.org/issue?@action=redirect&bpo=44022]: http.client now avoids infinitely reading potential HTTP headers after a 100 Continue status response from the server.

Core and Builtins

bpo-43760 [https://bugs.python.org/issue?@action=redirect&bpo=43760]: The number of hardware branches per instruction dispatch is reduced from two to one by adding a special instruction for tracing. Patch by Mark Shannon.

bpo-45061 [https://bugs.python.org/issue?@action=redirect&bpo=45061]: Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF(Py_True) or Py_DECREF(Py_False) by mistake. Detect also refcount bugs when the empty tuple singleton or the Unicode empty string singleton is destroyed by mistake. Patch by Victor Stinner.

bpo-24076 [https://bugs.python.org/issue?@action=redirect&bpo=24076]: sum() was further optimised for summing up single digit integers.

bpo-45190 [https://bugs.python.org/issue?@action=redirect&bpo=45190]: Update Unicode databases to Unicode 14.0.0.

bpo-45167 [https://bugs.python.org/issue?@action=redirect&bpo=45167]: Fix deepcopying of types.GenericAlias objects.

bpo-45155 [https://bugs.python.org/issue?@action=redirect&bpo=45155]: int.to_bytes() and int.from_bytes() now take a default value of "big" for the byteorder argument. int.to_bytes() also takes a default value of 1 for the length argument.

Library

bpo-44219 [https://bugs.python.org/issue?@action=redirect&bpo=44219]: Release the GIL while performing isatty system calls on arbitrary file descriptors. In particular, this affects os.isatty(), os.device_encoding() and io.TextIOWrapper. By extension, io.open() in text mode is also affected. This change solves a deadlock in os.isatty(). Patch by Vincent Michel in bpo-44219 [https://bugs.python.org/issue?@action=redirect&bpo=44219].

Core and Builtins

bpo-44959 [https://bugs.python.org/issue?@action=redirect&bpo=44959]: Added fallback to extension modules with '.sl' suffix on HP-UX

Library

bpo-45121 [https://bugs.python.org/issue?@action=redirect&bpo=45121]: Fix issue where Protocol.__init__ raises RecursionError when it's called directly or via super(). Patch provided by Yurii Karabas.

Core and Builtins

bpo-44348 [https://bugs.python.org/issue?@action=redirect&bpo=44348]: The deallocator function of the BaseException type now uses the trashcan mechanism to prevent stack overflow. For example, when a RecursionError instance is raised, it can be linked to another RecursionError through the __context__ attribute or the __traceback__ attribute, and then a chain of exceptions is created. When the chain is destroyed, nested deallocator function calls can crash with a stack overflow if the chain is too long compared to the available stack memory. Patch by Victor Stinner.

bpo-45123 [https://bugs.python.org/issue?@action=redirect&bpo=45123]: Fix PyAiter_Check to only check for the __anext__ presence (not for __aiter__). Rename PyAiter_Check to PyAIter_Check, PyObject_GetAiter -> PyObject_GetAIter.

bpo-1514420 [https://bugs.python.org/issue?@action=redirect&bpo=1514420]: Interpreter no longer attempts to open files with names in angle brackets (like "<string>" or "<stdin>") when formatting an exception.

bpo-41031 [https://bugs.python.org/issue?@action=redirect&bpo=41031]: Match C and Python code formatting of unprintable exceptions and exceptions in the __main__ module.

bpo-37330 [https://bugs.python.org/issue?@action=redirect&bpo=37330]: open(), io.open(), codecs.open() and fileinput.FileInput no longer accept 'U' ("universal newline") in the file mode. This flag was deprecated since Python 3.3. Patch by Victor Stinner.

bpo-45083 [https://bugs.python.org/issue?@action=redirect&bpo=45083]: When the interpreter renders an exception, its name now has a complete qualname. Previously only the class name was concatenated to the module name, which sometimes resulted in an incorrect full name being displayed.

(This issue impacted only the C code exception rendering, the traceback module was using qualname already).

bpo-34561 [https://bugs.python.org/issue?@action=redirect&bpo=34561]: List sorting now uses the merge-ordering strategy from Munro and Wild's powersort(). Unlike the former strategy, this is provably near-optimal in the entropy of the distribution of run lengths. Most uses of list.sort() probably won't see a significant time difference, but may see significant improvements in cases where the former strategy was exceptionally poor. However, as these are all fast linear-time approximations to a problem that's inherently at best quadratic-time to solve truly optimally, it's also possible to contrive cases where the former strategy did better.

bpo-45056 [https://bugs.python.org/issue?@action=redirect&bpo=45056]: Compiler now removes trailing unused constants from co_consts.

bpo-45020 [https://bugs.python.org/issue?@action=redirect&bpo=45020]: Add a new command line option, "-X frozen_modules=[on|off]" to opt out of (or into) using optional frozen modules. This defaults to "on" (or "off" if it's running out of the source tree).

Library

bpo-45012 [https://bugs.python.org/issue?@action=redirect&bpo=45012]: In posix, release GIL during stat(), lstat(), and fstatat() syscalls made by os.DirEntry.stat(). Patch by Stanisław Skonieczny.

Core and Builtins

bpo-45018 [https://bugs.python.org/issue?@action=redirect&bpo=45018]: Fixed pickling of range iterators that iterated for over 2**32 times.

bpo-45000 [https://bugs.python.org/issue?@action=redirect&bpo=45000]: A SyntaxError is now raised when trying to delete __debug__. Patch by Donghee Na.

bpo-44963 [https://bugs.python.org/issue?@action=redirect&bpo=44963]: Implement send() and throw() methods for anext_awaitable objects. Patch by Pablo Galindo.

Library

bpo-44962 [https://bugs.python.org/issue?@action=redirect&bpo=44962]: Fix a race in WeakKeyDictionary, WeakValueDictionary and WeakSet when two threads attempt to commit the last pending removal. This fixes asyncio.create_task and fixes a data loss in asyncio.run where shutdown_asyncgens is not run

Core and Builtins

bpo-24234 [https://bugs.python.org/issue?@action=redirect&bpo=24234]: Implement the __bytes__() special method on the bytes type, so a bytes object b passes an isinstance(b, typing.SupportsBytes) check.

bpo-24234 [https://bugs.python.org/issue?@action=redirect&bpo=24234]: Implement the __complex__() special method on the complex type, so a complex number z passes an isinstance(z, typing.SupportsComplex) check.

bpo-44954 [https://bugs.python.org/issue?@action=redirect&bpo=44954]: Fixed a corner case bug where the result of float.fromhex('0x.8p-1074') was rounded the wrong way.

bpo-44947 [https://bugs.python.org/issue?@action=redirect&bpo=44947]: Refine the syntax error for trailing commas in import statements. Patch by Pablo Galindo.

bpo-44945 [https://bugs.python.org/issue?@action=redirect&bpo=44945]: Specialize the BINARY_ADD instruction using the PEP 659 machinery. Adds five new instructions:

BINARY_ADD_ADAPTIVE

BINARY_ADD_FLOAT

BINARY_ADD_INT

BINARY_ADD_UNICODE

BINARY_ADD_UNICODE_INPLACE_FAST

Library

bpo-44929 [https://bugs.python.org/issue?@action=redirect&bpo=44929]: Fix some edge cases of enum.Flag string representation in the REPL. Patch by Pablo Galindo.

Core and Builtins

bpo-44914 [https://bugs.python.org/issue?@action=redirect&bpo=44914]: Class version tags are no longer recycled.

This means that a version tag serves as a unique identifier for the state of a class. We rely on this for effective specialization of the LOAD_ATTR and other instructions.

bpo-44698 [https://bugs.python.org/issue?@action=redirect&bpo=44698]: Restore behaviour of complex exponentiation with integer-valued exponent of type float or complex.

bpo-44895 [https://bugs.python.org/issue?@action=redirect&bpo=44895]: A debug variable PYTHONDUMPREFSFILE is added for creating a dump file which is generated by --with-trace-refs. Patch by Donghee Na.

bpo-44900 [https://bugs.python.org/issue?@action=redirect&bpo=44900]: Add five superinstructions for PEP 659 quickening:

LOAD_FAST LOAD_FAST

STORE_FAST LOAD_FAST

LOAD_FAST LOAD_CONST

LOAD_CONST LOAD_FAST

STORE_FAST STORE_FAST

bpo-44889 [https://bugs.python.org/issue?@action=redirect&bpo=44889]: Initial implementation of adaptive specialization of LOAD_METHOD. The following specialized forms were added:

LOAD_METHOD_CACHED

LOAD_METHOD_MODULE

LOAD_METHOD_CLASS

bpo-44890 [https://bugs.python.org/issue?@action=redirect&bpo=44890]: Specialization stats are always collected in debug builds.

bpo-44885 [https://bugs.python.org/issue?@action=redirect&bpo=44885]: Correct the ast locations of f-strings with format specs and repeated expressions. Patch by Pablo Galindo

bpo-44878 [https://bugs.python.org/issue?@action=redirect&bpo=44878]: Remove the loop from the bytecode interpreter. All instructions end with a DISPATCH macro, so the loop is now redundant.

bpo-44878 [https://bugs.python.org/issue?@action=redirect&bpo=44878]: Remove switch statement for interpreter loop when using computed gotos. This makes sure that we only have one dispatch table in the interpreter.

bpo-44874 [https://bugs.python.org/issue?@action=redirect&bpo=44874]: Deprecate the old trashcan macros (Py_TRASHCAN_SAFE_BEGIN/Py_TRASHCAN_SAFE_END). They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END.

bpo-44872 [https://bugs.python.org/issue?@action=redirect&bpo=44872]: Use new trashcan macros (Py_TRASHCAN_BEGIN/END) in frameobject.c instead of the old ones (Py_TRASHCAN_SAFE_BEGIN/END).

bpo-33930 [https://bugs.python.org/issue?@action=redirect&bpo=33930]: Fix segmentation fault with deep recursion when cleaning method objects. Patch by Augusto Goulart and Pablo Galindo.

bpo-25782 [https://bugs.python.org/issue?@action=redirect&bpo=25782]: Fix bug where PyErr_SetObject hangs when the current exception has a cycle in its context chain.

bpo-44856 [https://bugs.python.org/issue?@action=redirect&bpo=44856]: Fix reference leaks in the error paths of update_bases() and __build_class__. Patch by Pablo Galindo.

bpo-44826 [https://bugs.python.org/issue?@action=redirect&bpo=44826]: Initial implementation of adaptive specialization of STORE_ATTR

Three specialized forms of STORE_ATTR are added:

STORE_ATTR_SLOT

STORE_ATTR_SPLIT_KEYS

STORE_ATTR_WITH_HINT

bpo-44838 [https://bugs.python.org/issue?@action=redirect&bpo=44838]: Fixed a bug that was causing the parser to raise an incorrect custom SyntaxError for invalid 'if' expressions. Patch by Pablo Galindo.

bpo-44821 [https://bugs.python.org/issue?@action=redirect&bpo=44821]: Create instance dictionaries (__dict__) eagerly, to improve regularity of object layout and assist specialization.

bpo-44792 [https://bugs.python.org/issue?@action=redirect&bpo=44792]: Improve syntax errors for if expressions. Patch by Miguel Brito

bpo-34013 [https://bugs.python.org/issue?@action=redirect&bpo=34013]: Generalize the invalid legacy statement custom error message (like the one generated when "print" is called without parentheses) to include more generic expressions. Patch by Pablo Galindo

bpo-44732 [https://bugs.python.org/issue?@action=redirect&bpo=44732]: Rename types.Union to types.UnionType.

bpo-44725 [https://bugs.python.org/issue?@action=redirect&bpo=44725]: Expose specialization stats in python via _opcode.get_specialization_stats().

bpo-44717 [https://bugs.python.org/issue?@action=redirect&bpo=44717]: Improve AttributeError on circular imports of submodules.

bpo-44698 [https://bugs.python.org/issue?@action=redirect&bpo=44698]: Fix undefined behaviour in complex object exponentiation.

bpo-44653 [https://bugs.python.org/issue?@action=redirect&bpo=44653]: Support typing types in parameter substitution in the union type.

bpo-44676 [https://bugs.python.org/issue?@action=redirect&bpo=44676]: Add ability to serialise types.Union objects. Patch provided by Yurii Karabas.

bpo-44633 [https://bugs.python.org/issue?@action=redirect&bpo=44633]: Parameter substitution of the union type with wrong types now raises TypeError instead of returning NotImplemented.

bpo-44661 [https://bugs.python.org/issue?@action=redirect&bpo=44661]: Update property_descr_set to use vectorcall if possible. Patch by Donghee Na.

bpo-44662 [https://bugs.python.org/issue?@action=redirect&bpo=44662]: Add __module__ to types.Union. This also fixes types.Union issues with typing.Annotated. Patch provided by Yurii Karabas.

bpo-44655 [https://bugs.python.org/issue?@action=redirect&bpo=44655]: Include the name of the type in unset __slots__ attribute errors. Patch by Pablo Galindo

bpo-44655 [https://bugs.python.org/issue?@action=redirect&bpo=44655]: Don't include a missing attribute with the same name as the failing one when offering suggestions for missing attributes. Patch by Pablo Galindo

bpo-44646 [https://bugs.python.org/issue?@action=redirect&bpo=44646]: Fix the hash of the union type: it no longer depends on the order of arguments.

bpo-44636 [https://bugs.python.org/issue?@action=redirect&bpo=44636]: Collapse union of equal types. E.g. the result of int | int is now int. Fix comparison of the union type with non-hashable objects. E.g. int | str == {} no longer raises a TypeError.

Library

bpo-44611 [https://bugs.python.org/issue?@action=redirect&bpo=44611]: On Windows, os.urandom(): uses BCryptGenRandom API instead of CryptGenRandom API which is deprecated from Microsoft Windows API. Patch by Donghee Na.

Core and Builtins

bpo-44635 [https://bugs.python.org/issue?@action=redirect&bpo=44635]: Convert None to type(None) in the union type constructor.

bpo-26280 [https://bugs.python.org/issue?@action=redirect&bpo=26280]: Implement adaptive specialization for BINARY_SUBSCR

Three specialized forms of BINARY_SUBSCR are added:

BINARY_SUBSCR_LIST_INT

BINARY_SUBSCR_TUPLE_INT

BINARY_SUBSCR_DICT

bpo-44589 [https://bugs.python.org/issue?@action=redirect&bpo=44589]: Mapping patterns in match statements with two or more equal literal keys will now raise a SyntaxError at compile-time.

bpo-44606 [https://bugs.python.org/issue?@action=redirect&bpo=44606]: Fix __instancecheck__ and __subclasscheck__ for the union type.

bpo-42073 [https://bugs.python.org/issue?@action=redirect&bpo=42073]: The @classmethod decorator can now wrap other classmethod-like descriptors.

bpo-41972 [https://bugs.python.org/issue?@action=redirect&bpo=41972]: Tuned the string-searching algorithm of fastsearch.h to have a shorter inner loop for most cases.

bpo-44590 [https://bugs.python.org/issue?@action=redirect&bpo=44590]: All necessary data for executing a Python function (local variables, stack, etc) is now kept in a per-thread stack. Frame objects are lazily allocated on demand. This increases performance by about 7% on the standard benchmark suite. Introspection and debugging are unaffected as frame objects are always available when needed. Patch by Mark Shannon.

bpo-44584 [https://bugs.python.org/issue?@action=redirect&bpo=44584]: The threading debug (PYTHONTHREADDEBUG environment variable) is deprecated in Python 3.10 and will be removed in Python 3.12. This feature requires a debug build of Python. Patch by Victor Stinner.

bpo-43895 [https://bugs.python.org/issue?@action=redirect&bpo=43895]: An obsolete internal cache of shared object file handles added in 1995 that attempted, but did not guarantee, that a .so would not be dlopen'ed twice to work around flaws in mid-1990s posix-ish operating systems has been removed from dynload_shlib.c.

Library

bpo-44490 [https://bugs.python.org/issue?@action=redirect&bpo=44490]: typing now searches for type parameters in types.Union objects. get_type_hints will also properly resolve annotations with nested types.Union objects. Patch provided by Yurii Karabas.

Core and Builtins

bpo-43950 [https://bugs.python.org/issue?@action=redirect&bpo=43950]: Code objects can now provide the column information for instructions when available. This is levaraged during traceback printing to show the expressions responsible for errors.

Contributed by Pablo Galindo, Batuhan Taskaya and Ammar Askar as part of PEP 657 [https://peps.python.org/pep-0657/].

bpo-44562 [https://bugs.python.org/issue?@action=redirect&bpo=44562]: Remove uses of PyObject_GC_Del() in error path when initializing types.GenericAlias.

Library

bpo-41486 [https://bugs.python.org/issue?@action=redirect&bpo=41486]: Fix a memory consumption and copying performance regression in earlier 3.10 beta releases if someone used an output buffer larger than 4GiB with zlib.decompress on input data that expands that large.

Core and Builtins

bpo-43908 [https://bugs.python.org/issue?@action=redirect&bpo=43908]: Heap types with the Py_TPFLAGS_IMMUTABLETYPE flag can now inherit the PEP 590 [https://peps.python.org/pep-0590/] vectorcall protocol. Previously, this was only possible for static types. Patch by Erlend E. Aasland.

bpo-44553 [https://bugs.python.org/issue?@action=redirect&bpo=44553]: Implement GC methods for types.Union to break reference cycles and prevent memory leaks.

bpo-44490 [https://bugs.python.org/issue?@action=redirect&bpo=44490]: Add __parameters__ attribute and __getitem__ operator to types.Union. Patch provided by Yurii Karabas.

bpo-44523 [https://bugs.python.org/issue?@action=redirect&bpo=44523]: Remove the pass-through for hash() of weakref.proxy objects to prevent unintended consequences when the original referred object dies while the proxy is part of a hashable object. Patch by Pablo Galindo.

bpo-44483 [https://bugs.python.org/issue?@action=redirect&bpo=44483]: Fix a crash in types.Union objects when creating a union of an object with bad __module__ field.

bpo-44486 [https://bugs.python.org/issue?@action=redirect&bpo=44486]: Modules will always have a dictionary, even when created by types.ModuleType.__new__()

bpo-44472 [https://bugs.python.org/issue?@action=redirect&bpo=44472]: Fix ltrace functionality when exceptions are raised. Patch by Pablo Galindo

bpo-12022 [https://bugs.python.org/issue?@action=redirect&bpo=12022]: A TypeError is now raised instead of an AttributeError in with and async with statements for objects which do not support the context manager or asynchronous context manager protocols correspondingly.

bpo-44297 [https://bugs.python.org/issue?@action=redirect&bpo=44297]: Make sure that the line number is set when entering a comprehension scope. This ensures that backtraces including generator expressions show the correct line number.

bpo-44456 [https://bugs.python.org/issue?@action=redirect&bpo=44456]: Improve the syntax error when mixing positional and keyword patterns. Patch by Pablo Galindo.

bpo-44409 [https://bugs.python.org/issue?@action=redirect&bpo=44409]: Fix error location information for tokenizer errors raised on initialization of the tokenizer. Patch by Pablo Galindo.

bpo-44396 [https://bugs.python.org/issue?@action=redirect&bpo=44396]: Fix a possible crash in the tokenizer when raising syntax errors for unclosed strings. Patch by Pablo Galindo.

bpo-44376 [https://bugs.python.org/issue?@action=redirect&bpo=44376]: Exact integer exponentiation (like i**2 or pow(i, 2)) with a small exponent is much faster, due to reducing overhead in such cases.

bpo-44313 [https://bugs.python.org/issue?@action=redirect&bpo=44313]: Directly imported objects and modules (through import and from import statements) don't generate LOAD_METHOD/CALL_METHOD for directly accessed objects on their namespace. They now use the regular LOAD_ATTR/CALL_FUNCTION.

bpo-44338 [https://bugs.python.org/issue?@action=redirect&bpo=44338]: Implement adaptive specialization for LOAD_GLOBAL

Two specialized forms of LOAD_GLOBAL are added:

LOAD_GLOBAL_MODULE

LOAD_GLOBAL_BUILTIN

bpo-44368 [https://bugs.python.org/issue?@action=redirect&bpo=44368]: Improve syntax errors for invalid "as" targets. Patch by Pablo Galindo

bpo-44349 [https://bugs.python.org/issue?@action=redirect&bpo=44349]: Fix an edge case when displaying text from files with encoding in syntax errors. Patch by Pablo Galindo.

bpo-44337 [https://bugs.python.org/issue?@action=redirect&bpo=44337]: Initial implementation of adaptive specialization of LOAD_ATTR

Four specialized forms of LOAD_ATTR are added:

LOAD_ATTR_SLOT

LOAD_ATTR_SPLIT_KEYS

LOAD_ATTR_WITH_HINT

LOAD_ATTR_MODULE

bpo-44335 [https://bugs.python.org/issue?@action=redirect&bpo=44335]: Fix a regression when identifying incorrect characters in syntax errors. Patch by Pablo Galindo

bpo-43693 [https://bugs.python.org/issue?@action=redirect&bpo=43693]: Computation of the offsets of cell variables is done in the compiler instead of at runtime. This reduces the overhead of handling cell and free variables, especially in the case where a variable is both an argument and cell variable.

bpo-44317 [https://bugs.python.org/issue?@action=redirect&bpo=44317]: Improve tokenizer error with improved locations. Patch by Pablo Galindo.

Library

bpo-44304 [https://bugs.python.org/issue?@action=redirect&bpo=44304]: Fix a crash in the sqlite3 module that happened when the garbage collector clears sqlite.Statement objects. Patch by Pablo Galindo

Core and Builtins

bpo-44305 [https://bugs.python.org/issue?@action=redirect&bpo=44305]: Improve error message for try blocks without except or finally blocks. Patch by Pablo Galindo.

bpo-43413 [https://bugs.python.org/issue?@action=redirect&bpo=43413]: Constructors of subclasses of some builtin classes (e.g. tuple, list, frozenset) no longer accept arbitrary keyword arguments. [reverted in 3.11a4] Subclass of set can now define a __new__() method with additional keyword parameters without overriding also __init__().

bpo-43667 [https://bugs.python.org/issue?@action=redirect&bpo=43667]: Improve Unicode support in non-UTF locales on Oracle Solaris. This issue does not affect other Solaris systems.

bpo-43693 [https://bugs.python.org/issue?@action=redirect&bpo=43693]: A new opcode MAKE_CELL has been added that effectively moves some of the work done on function entry into the compiler and into the eval loop. In addition to creating the required cell objects, the new opcode converts relevant arguments (and other locals) to cell variables on function entry.

bpo-44232 [https://bugs.python.org/issue?@action=redirect&bpo=44232]: Fix a regression in type() when a metaclass raises an exception. The C function type_new() must properly report the exception when a metaclass constructor raises an exception and the winner class is not the metaclass. Patch by Victor Stinner.

bpo-44201 [https://bugs.python.org/issue?@action=redirect&bpo=44201]: Avoid side effects of checking for specialized syntax errors in the REPL that was causing it to ask for extra tokens after a syntax error had been detected. Patch by Pablo Galindo

bpo-43693 [https://bugs.python.org/issue?@action=redirect&bpo=43693]: PyCodeObject gained co_fastlocalnames and co_fastlocalkinds as the authoritative source of fast locals info. Marshaled code objects have changed accordingly.

bpo-44184 [https://bugs.python.org/issue?@action=redirect&bpo=44184]: Fix a crash at Python exit when a deallocator function removes the last strong reference to a heap type. Patch by Victor Stinner.

bpo-44187 [https://bugs.python.org/issue?@action=redirect&bpo=44187]: Implement quickening in the interpreter. This offers no advantages as yet, but is an enabler of future optimizations. See PEP 659 for full explanation.

bpo-44180 [https://bugs.python.org/issue?@action=redirect&bpo=44180]: The parser doesn't report generic syntax errors that happen in a position further away that the one it reached in the first pass. Patch by Pablo Galindo

bpo-44168 [https://bugs.python.org/issue?@action=redirect&bpo=44168]: Fix error message in the parser involving keyword arguments with invalid expressions. Patch by Pablo Galindo

bpo-44156 [https://bugs.python.org/issue?@action=redirect&bpo=44156]: String caches in compile.c are now subinterpreter compatible.

bpo-44143 [https://bugs.python.org/issue?@action=redirect&bpo=44143]: Fixed a crash in the parser that manifest when raising tokenizer errors when an existing exception was present. Patch by Pablo Galindo.

bpo-44032 [https://bugs.python.org/issue?@action=redirect&bpo=44032]: Move 'fast' locals and other variables from the frame object to a per-thread datastack.

bpo-44114 [https://bugs.python.org/issue?@action=redirect&bpo=44114]: Fix incorrect dictkeys_reversed and dictitems_reversed function signatures in C code, which broke webassembly builds.

bpo-44110 [https://bugs.python.org/issue?@action=redirect&bpo=44110]: Improve str.__getitem__() error message

bpo-26110 [https://bugs.python.org/issue?@action=redirect&bpo=26110]: Add CALL_METHOD_KW opcode to speed up method calls with keyword arguments. Idea originated from PyPy. A side effect is executing CALL_METHOD is now branchless in the evaluation loop.

bpo-28307 [https://bugs.python.org/issue?@action=redirect&bpo=28307]: Compiler now optimizes simple C-style formatting with literal format containing only format codes %s, %r and %a by converting them to f-string expressions.

bpo-43149 [https://bugs.python.org/issue?@action=redirect&bpo=43149]: Correct the syntax error message regarding multiple exception types to not refer to "exception groups". Patch by Pablo Galindo

bpo-43822 [https://bugs.python.org/issue?@action=redirect&bpo=43822]: The parser will prioritize tokenizer errors over custom syntax errors when raising exceptions. Patch by Pablo Galindo.

bpo-40222 [https://bugs.python.org/issue?@action=redirect&bpo=40222]: "Zero cost" exception handling.

Uses a lookup table to determine how to handle exceptions.

Removes SETUP_FINALLY and POP_TOP block instructions, eliminating the runtime overhead of try statements.

Reduces the size of the frame object by about 60%.

Patch by Mark Shannon

bpo-43918 [https://bugs.python.org/issue?@action=redirect&bpo=43918]: Document the signature and default argument in the docstring of the new anext builtin.

bpo-43833 [https://bugs.python.org/issue?@action=redirect&bpo=43833]: Emit a deprecation warning if the numeric literal is immediately followed by one of keywords: and, else, for, if, in, is, or. Raise a syntax error with more informative message if it is immediately followed by other keyword or identifier.

bpo-43879 [https://bugs.python.org/issue?@action=redirect&bpo=43879]: Add native_thread_id to PyThreadState. Patch by Gabriele N. Tornetta.

bpo-43693 [https://bugs.python.org/issue?@action=redirect&bpo=43693]: Compute cell offsets relative to locals in compiler. Allows the interpreter to treats locals and cells a single array, which is slightly more efficient. Also make the LOAD_CLOSURE opcode an alias for LOAD_FAST. Preserving LOAD_CLOSURE helps keep bytecode a bit more readable.

bpo-17792 [https://bugs.python.org/issue?@action=redirect&bpo=17792]: More accurate error messages for access of unbound locals or free vars.

bpo-28146 [https://bugs.python.org/issue?@action=redirect&bpo=28146]: Fix a confusing error message in str.format().

bpo-11105 [https://bugs.python.org/issue?@action=redirect&bpo=11105]: When compiling ast.AST objects with recursive references through compile(), the interpreter doesn't crash anymore instead it raises a RecursionError.

bpo-39091 [https://bugs.python.org/issue?@action=redirect&bpo=39091]: Fix crash when using passing a non-exception to a generator's throw() method. Patch by Noah Oxer

bpo-33346 [https://bugs.python.org/issue?@action=redirect&bpo=33346]: Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions. Outer comprehensions implicitly become asynchronous.

Library

bpo-45371 [https://bugs.python.org/issue?@action=redirect&bpo=45371]: Fix clang rpath issue in distutils. The UnixCCompiler now uses correct clang option to add a runtime library directory (rpath) to a shared library.

bpo-45329 [https://bugs.python.org/issue?@action=redirect&bpo=45329]: Fix freed memory access in pyexpat.xmlparser when building it with an installed expat library <= 2.2.0.

bpo-41710 [https://bugs.python.org/issue?@action=redirect&bpo=41710]: On Unix, if the sem_clockwait() function is available in the C library (glibc 2.30 and newer), the threading.Lock.acquire() method now uses the monotonic clock (time.CLOCK_MONOTONIC) for the timeout, rather than using the system clock (time.CLOCK_REALTIME), to not be affected by system clock changes. Patch by Victor Stinner.

bpo-1596321 [https://bugs.python.org/issue?@action=redirect&bpo=1596321]: Fix the threading._shutdown() function when the threading module was imported first from a thread different than the main thread: no longer log an error at Python exit.

bpo-45274 [https://bugs.python.org/issue?@action=redirect&bpo=45274]: Fix a race condition in the Thread.join() method of the threading module. If the function is interrupted by a signal and the signal handler raises an exception, make sure that the thread remains in a consistent state to prevent a deadlock. Patch by Victor Stinner.

bpo-21302 [https://bugs.python.org/issue?@action=redirect&bpo=21302]: In Unix operating systems, time.sleep() now uses the nanosleep() function, if clock_nanosleep() is not available but nanosleep() is available. nanosleep() allows to sleep with nanosecond precision.

bpo-21302 [https://bugs.python.org/issue?@action=redirect&bpo=21302]: On Windows, time.sleep() now uses a waitable timer which has a resolution of 100 nanoseconds (10⁻⁷ seconds). Previously, it had a resolution of 1 millisecond (10⁻³ seconds). Patch by Benjamin Szőke and Victor Stinner.

bpo-45238 [https://bugs.python.org/issue?@action=redirect&bpo=45238]: Fix unittest.IsolatedAsyncioTestCase.debug(): it runs now asynchronous methods and callbacks.

bpo-36674 [https://bugs.python.org/issue?@action=redirect&bpo=36674]: unittest.TestCase.debug() raises now a unittest.SkipTest if the class or the test method are decorated with the skipping decorator.

bpo-45235 [https://bugs.python.org/issue?@action=redirect&bpo=45235]: Fix an issue where argparse would not preserve values in a provided namespace when using a subparser with defaults.

bpo-45183 [https://bugs.python.org/issue?@action=redirect&bpo=45183]: Have zipimport.zipimporter.find_spec() not raise an exception when the underlying zip file has been deleted and the internal cache has been reset via invalidate_cache().

bpo-45234 [https://bugs.python.org/issue?@action=redirect&bpo=45234]: Fixed a regression in copyfile(), copy(), copy2() raising FileNotFoundError when source is a directory, which should raise IsADirectoryError

bpo-45228 [https://bugs.python.org/issue?@action=redirect&bpo=45228]: Fix stack buffer overflow in parsing J1939 network address.

bpo-45225 [https://bugs.python.org/issue?@action=redirect&bpo=45225]: use map function instead of genexpr in capwords.

bpo-42135 [https://bugs.python.org/issue?@action=redirect&bpo=42135]: Fix typo: importlib.find_loader is really slated for removal in Python 3.12 not 3.10, like the others in PR 25169.

Patch by Hugo van Kemenade.

bpo-20524 [https://bugs.python.org/issue?@action=redirect&bpo=20524]: Improves error messages on .format() operation for str, float, int, and complex. New format now shows the problematic pattern and the object type.

bpo-45168 [https://bugs.python.org/issue?@action=redirect&bpo=45168]: Change dis.dis() output to omit op arg values that cannot be resolved due to co_consts, co_names etc not being provided. Previously the oparg itself was repeated in the value field, which is not useful and can be confusing.

bpo-21302 [https://bugs.python.org/issue?@action=redirect&bpo=21302]: In Unix operating systems, time.sleep() now uses the clock_nanosleep() function, if available, which allows to sleep for an interval specified with nanosecond precision.

bpo-45173 [https://bugs.python.org/issue?@action=redirect&bpo=45173]: Remove from the configparser module: the SafeConfigParser class, the filename property of the ParsingError class, the readfp() method of the ConfigParser class, deprecated since Python 3.2.

Patch by Hugo van Kemenade.

bpo-44987 [https://bugs.python.org/issue?@action=redirect&bpo=44987]: Pure ASCII strings are now normalized in constant time by unicodedata.normalize(). Patch by Donghee Na.

bpo-35474 [https://bugs.python.org/issue?@action=redirect&bpo=35474]: Calling mimetypes.guess_all_extensions() with strict=False no longer affects the result of the following call with strict=True. Also, mutating the returned list no longer affects the global state.

bpo-45166 [https://bugs.python.org/issue?@action=redirect&bpo=45166]: typing.get_type_hints() now works with Final wrapped in ForwardRef.

bpo-45162 [https://bugs.python.org/issue?@action=redirect&bpo=45162]: Remove many old deprecated unittest features:

"fail*" and "assert*" aliases of TestCase methods.

Broken from start TestCase method assertDictContainsSubset().

Ignored <unittest.TestLoader.loadTestsFromModule> TestLoader.loadTestsFromModule() parameter use_load_tests.

Old alias _TextTestResult of TextTestResult.

bpo-38371 [https://bugs.python.org/issue?@action=redirect&bpo=38371]: Remove the deprecated split() method of _tkinter.TkappType. Patch by Erlend E. Aasland.

bpo-20499 [https://bugs.python.org/issue?@action=redirect&bpo=20499]: Improve the speed and accuracy of statistics.pvariance().

bpo-45132 [https://bugs.python.org/issue?@action=redirect&bpo=45132]: Remove __getitem__() methods of xml.dom.pulldom.DOMEventStream, wsgiref.util.FileWrapper and fileinput.FileInput, deprecated since Python 3.9.

Patch by Hugo van Kemenade.

bpo-45129 [https://bugs.python.org/issue?@action=redirect&bpo=45129]: Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint(), disabled in Python 3.9, is now entirely removed. This is because of the behavior of the socket option SO_REUSEADDR in UDP.

Patch by Hugo van Kemenade.

bpo-45124 [https://bugs.python.org/issue?@action=redirect&bpo=45124]: The bdist_msi command, deprecated in Python 3.9, is now removed.

Use bdist_wheel (wheel packages) instead.

Patch by Hugo van Kemenade.

bpo-30856 [https://bugs.python.org/issue?@action=redirect&bpo=30856]: unittest.TestResult methods addFailure(), addError(), addSkip() and addSubTest() are now called immediately after raising an exception in test or finishing a subtest. Previously they were called only after finishing the test clean up.

bpo-45034 [https://bugs.python.org/issue?@action=redirect&bpo=45034]: Changes how error is formatted for struct.pack with 'H' and 'h' modes and too large / small numbers. Now it shows the actual numeric limits, while previously it was showing arithmetic expressions.

bpo-25894 [https://bugs.python.org/issue?@action=redirect&bpo=25894]: unittest now always reports skipped and failed subtests separately: separate characters in default mode and separate lines in verbose mode. Also the test description is now output for errors in test method, class and module cleanups.

bpo-45081 [https://bugs.python.org/issue?@action=redirect&bpo=45081]: Fix issue when dataclasses that inherit from typing.Protocol subclasses have wrong __init__. Patch provided by Yurii Karabas.

bpo-45085 [https://bugs.python.org/issue?@action=redirect&bpo=45085]: The binhex module, deprecated in Python 3.9, is now removed. The following binascii functions, deprecated in Python 3.9, are now also removed:

a2b_hqx(), b2a_hqx();

rlecode_hqx(), rledecode_hqx().

The binascii.crc_hqx() function remains available.

Patch by Victor Stinner.

bpo-40360 [https://bugs.python.org/issue?@action=redirect&bpo=40360]: The lib2to3 package is now deprecated and may not be able to parse Python 3.10 or newer. See the PEP 617 [https://peps.python.org/pep-0617/] (New PEG parser for CPython). Patch by Victor Stinner.

bpo-45075 [https://bugs.python.org/issue?@action=redirect&bpo=45075]: Rename traceback.StackSummary.format_frame() to traceback.StackSummary.format_frame_summary(). This method was added for 3.11 so it was not released yet.

Updated code and docs to better distinguish frame and FrameSummary.

bpo-31299 [https://bugs.python.org/issue?@action=redirect&bpo=31299]: Add option to completely drop frames from a traceback by returning None from a format_frame() override.

bpo-41620 [https://bugs.python.org/issue?@action=redirect&bpo=41620]: run() now always return a TestResult instance. Previously it returned None if the test class or method was decorated with a skipping decorator.

bpo-45021 [https://bugs.python.org/issue?@action=redirect&bpo=45021]: Fix a potential deadlock at shutdown of forked children when using concurrent.futures module

bpo-43913 [https://bugs.python.org/issue?@action=redirect&bpo=43913]: Fix bugs in cleaning up classes and modules in unittest:

Functions registered with addModuleCleanup() were not called unless the user defines tearDownModule() in their test module.

Functions registered with addClassCleanup() were not called if tearDownClass is set to None.

Buffering in TestResult did not work with functions registered with addClassCleanup() and addModuleCleanup().

Errors in functions registered with addClassCleanup() and addModuleCleanup() were not handled correctly in buffered and debug modes.

Errors in setUpModule() and functions registered with addModuleCleanup() were reported in wrong order.

And several lesser bugs.

bpo-45030 [https://bugs.python.org/issue?@action=redirect&bpo=45030]: Fix integer overflow in pickling and copying the range iterator.

bpo-45001 [https://bugs.python.org/issue?@action=redirect&bpo=45001]: Made email date parsing more robust against malformed input, namely a whitespace-only Date: header. Patch by Wouter Bolsterlee.

bpo-45010 [https://bugs.python.org/issue?@action=redirect&bpo=45010]: Remove support of special method __div__ in unittest.mock. It is not used in Python 3.

bpo-39218 [https://bugs.python.org/issue?@action=redirect&bpo=39218]: Improve accuracy of variance calculations by using x*x instead of x**2.

bpo-43613 [https://bugs.python.org/issue?@action=redirect&bpo=43613]: Improve the speed of gzip.compress() and gzip.decompress() by compressing and decompressing at once in memory instead of in a streamed fashion.

bpo-37596 [https://bugs.python.org/issue?@action=redirect&bpo=37596]: Ensure that set and frozenset objects are always marshalled reproducibly.

bpo-44019 [https://bugs.python.org/issue?@action=redirect&bpo=44019]: A new function operator.call has been added, such that operator.call(obj, *args, **kwargs) == obj(*args, **kwargs).

bpo-42255 [https://bugs.python.org/issue?@action=redirect&bpo=42255]: webbrowser.MacOSX is deprecated and will be removed in Python 3.13. It is untested and undocumented and also not used by webbrowser itself. Patch by Donghee Na.

bpo-44955 [https://bugs.python.org/issue?@action=redirect&bpo=44955]: Method stopTestRun() is now always called in pair with method startTestRun() for TestResult objects implicitly created in run(). Previously it was not called for test methods and classes decorated with a skipping decorator.

bpo-39039 [https://bugs.python.org/issue?@action=redirect&bpo=39039]: tarfile.open raises ReadError when a zlib error occurs during file extraction.

bpo-44935 [https://bugs.python.org/issue?@action=redirect&bpo=44935]: subprocess on Solaris now also uses os.posix_spawn() for better performance.

bpo-44911 [https://bugs.python.org/issue?@action=redirect&bpo=44911]: IsolatedAsyncioTestCase will no longer throw an exception while cancelling leaked tasks. Patch by Bar Harel.

bpo-41322 [https://bugs.python.org/issue?@action=redirect&bpo=41322]: Added DeprecationWarning for tests and async tests that return a value!=None (as this may indicate an improperly written test, for example a test written as a generator function).

bpo-44524 [https://bugs.python.org/issue?@action=redirect&bpo=44524]: Make exception message more useful when subclass from typing special form alias. Patch provided by Yurii Karabas.

bpo-38956 [https://bugs.python.org/issue?@action=redirect&bpo=38956]: argparse.BooleanOptionalAction's default value is no longer printed twice when used with argparse.ArgumentDefaultsHelpFormatter.

bpo-44860 [https://bugs.python.org/issue?@action=redirect&bpo=44860]: Fix the posix_user scheme in sysconfig to not depend on sys.platlibdir.

bpo-44859 [https://bugs.python.org/issue?@action=redirect&bpo=44859]: Improve error handling in sqlite3 and raise more accurate exceptions.

MemoryError is now raised instead of sqlite3.Warning when memory is not enough for encoding a statement to UTF-8 in Connection.__call__() and Cursor.execute().

UnicodEncodeError is now raised instead of sqlite3.Warning when the statement contains surrogate characters in Connection.__call__() and Cursor.execute().

TypeError is now raised instead of ValueError for non-string script argument in Cursor.executescript().

ValueError is now raised for script containing the null character instead of truncating it in Cursor.executescript().

Correctly handle exceptions raised when getting boolean value of the result of the progress handler.

Add many tests covering different corner cases.

bpo-44581 [https://bugs.python.org/issue?@action=redirect&bpo=44581]: Upgrade bundled pip to 21.2.3 and setuptools to 57.4.0

bpo-44849 [https://bugs.python.org/issue?@action=redirect&bpo=44849]: Fix the os.set_inheritable() function on FreeBSD 14 for file descriptor opened with the O_PATH flag: ignore the EBADF error on ioctl(), fallback on the fcntl() implementation. Patch by Victor Stinner.

bpo-44605 [https://bugs.python.org/issue?@action=redirect&bpo=44605]: The @functools.total_ordering() decorator now works with metaclasses.

bpo-44524 [https://bugs.python.org/issue?@action=redirect&bpo=44524]: Fixed an issue wherein the __name__ and __qualname__ attributes of subscribed specialforms could be None.

bpo-44839 [https://bugs.python.org/issue?@action=redirect&bpo=44839]: MemoryError raised in user-defined functions will now produce a MemoryError in sqlite3. OverflowError will now be converted to DataError. Previously OperationalError was produced in these cases.

bpo-44822 [https://bugs.python.org/issue?@action=redirect&bpo=44822]: sqlite3 user-defined functions and aggregators returning strings with embedded NUL characters are no longer truncated. Patch by Erlend E. Aasland.

bpo-44801 [https://bugs.python.org/issue?@action=redirect&bpo=44801]: Ensure that the ParamSpec variable in Callable can only be substituted with a parameters expression (a list of types, an ellipsis, ParamSpec or Concatenate).

bpo-44806 [https://bugs.python.org/issue?@action=redirect&bpo=44806]: Non-protocol subclasses of typing.Protocol ignore now the __init__ method inherited from protocol base classes.

bpo-27275 [https://bugs.python.org/issue?@action=redirect&bpo=27275]: collections.OrderedDict.popitem() and collections.OrderedDict.pop() no longer call __getitem__ and __delitem__ methods of the OrderedDict subclasses.

bpo-44793 [https://bugs.python.org/issue?@action=redirect&bpo=44793]: Fix checking the number of arguments when subscribe a generic type with ParamSpec parameter.

bpo-44784 [https://bugs.python.org/issue?@action=redirect&bpo=44784]: In importlib.metadata tests, override warnings behavior under expected DeprecationWarnings (importlib_metadata 4.6.3).

bpo-44667 [https://bugs.python.org/issue?@action=redirect&bpo=44667]: The tokenize.tokenize() doesn't incorrectly generate a NEWLINE token if the source doesn't end with a new line character but the last line is a comment, as the function is already generating a NL token. Patch by Pablo Galindo

bpo-44771 [https://bugs.python.org/issue?@action=redirect&bpo=44771]: Added importlib.simple module implementing adapters from a low-level resources reader interface to a TraversableResources interface. Legacy API (path, contents, ...) is now supported entirely by the .files() API with a compatibility shim supplied for resource loaders without that functionality. Feature parity with importlib_resources 5.2.

bpo-44752 [https://bugs.python.org/issue?@action=redirect&bpo=44752]: rcompleter does not call getattr() on property objects to avoid the side-effect of evaluating the corresponding method.

bpo-44747 [https://bugs.python.org/issue?@action=redirect&bpo=44747]: Refactor usage of sys._getframe in typing module. Patch provided by Yurii Karabas.

bpo-42378 [https://bugs.python.org/issue?@action=redirect&bpo=42378]: Fixes the issue with log file being overwritten when logging.FileHandler is used in atexit with filemode set to 'w'. Note this will cause the message in atexit not being logged if the log stream is already closed due to shutdown of logging.

bpo-44720 [https://bugs.python.org/issue?@action=redirect&bpo=44720]: weakref.proxy objects referencing non-iterators now raise TypeError rather than dereferencing the null tp_iternext slot and crashing.

bpo-44704 [https://bugs.python.org/issue?@action=redirect&bpo=44704]: The implementation of collections.abc.Set._hash() now matches that of frozenset.__hash__().

bpo-44666 [https://bugs.python.org/issue?@action=redirect&bpo=44666]: Fixed issue in compileall.compile_file() when sys.stdout is redirected. Patch by Stefan Hölzl.

bpo-44688 [https://bugs.python.org/issue?@action=redirect&bpo=44688]: sqlite3.Connection.create_collation() now accepts non-ASCII collation names. Patch by Erlend E. Aasland.

bpo-44690 [https://bugs.python.org/issue?@action=redirect&bpo=44690]: Adopt binacii.a2b_base64's strict mode in base64.b64decode.

bpo-42854 [https://bugs.python.org/issue?@action=redirect&bpo=42854]: Fixed a bug in the _ssl module that was throwing OverflowError when using _ssl._SSLSocket.write() and _ssl._SSLSocket.read() for a big value of the len parameter. Patch by Pablo Galindo.

bpo-44686 [https://bugs.python.org/issue?@action=redirect&bpo=44686]: Replace unittest.mock._importer with pkgutil.resolve_name.

bpo-44353 [https://bugs.python.org/issue?@action=redirect&bpo=44353]: Make NewType.__call__ faster by implementing it in C. Patch provided by Yurii Karabas.

bpo-44682 [https://bugs.python.org/issue?@action=redirect&bpo=44682]: Change the pdb commands directive to disallow setting commands for an invalid breakpoint and to display an appropriate error.

bpo-44353 [https://bugs.python.org/issue?@action=redirect&bpo=44353]: Refactor typing.NewType from function into callable class. Patch provided by Yurii Karabas.

bpo-44678 [https://bugs.python.org/issue?@action=redirect&bpo=44678]: Added a separate error message for discontinuous padding in binascii.a2b_base64 strict mode.

bpo-44524 [https://bugs.python.org/issue?@action=redirect&bpo=44524]: Add missing __name__ and __qualname__ attributes to typing module classes. Patch provided by Yurii Karabas.

bpo-40897 [https://bugs.python.org/issue?@action=redirect&bpo=40897]: Give priority to using the current class constructor in inspect.signature(). Patch by Weipeng Hong.

bpo-44638 [https://bugs.python.org/issue?@action=redirect&bpo=44638]: Add a reference to the zipp project and hint as to how to use it.

bpo-44648 [https://bugs.python.org/issue?@action=redirect&bpo=44648]: Fixed wrong error being thrown by inspect.getsource() when examining a class in the interactive session. Instead of TypeError, it should be OSError with appropriate error message.

bpo-44608 [https://bugs.python.org/issue?@action=redirect&bpo=44608]: Fix memory leak in _tkinter._flatten() if it is called with a sequence or set, but not list or tuple.

bpo-44594 [https://bugs.python.org/issue?@action=redirect&bpo=44594]: Fix an edge case of ExitStack and AsyncExitStack exception chaining. They will now match with block behavior when __context__ is explicitly set to None when the exception is in flight.

bpo-42799 [https://bugs.python.org/issue?@action=redirect&bpo=42799]: In fnmatch, the cache size for compiled regex patterns (functools.lru_cache()) was bumped up from 256 to 32768, affecting functions: fnmatch.fnmatch(), fnmatch.fnmatchcase(), fnmatch.filter().

bpo-41928 [https://bugs.python.org/issue?@action=redirect&bpo=41928]: Update shutil.copyfile() to raise FileNotFoundError instead of confusing IsADirectoryError when a path ending with a os.path.sep does not exist; shutil.copy() and shutil.copy2() are also affected.

bpo-44569 [https://bugs.python.org/issue?@action=redirect&bpo=44569]: Added the StackSummary.format_frame() function in traceback. This allows users to customize the way individual lines are formatted in tracebacks without re-implementing logic to handle recursive tracebacks.

bpo-44566 [https://bugs.python.org/issue?@action=redirect&bpo=44566]: handle StopIteration subclass raised from @contextlib.contextmanager generator

bpo-44558 [https://bugs.python.org/issue?@action=redirect&bpo=44558]: Make the implementation consistency of indexOf() between C and Python versions. Patch by Donghee Na.

bpo-41249 [https://bugs.python.org/issue?@action=redirect&bpo=41249]: Fixes TypedDict to work with typing.get_type_hints() and postponed evaluation of annotations across modules.

bpo-44554 [https://bugs.python.org/issue?@action=redirect&bpo=44554]: Refactor argument processing in pdb.main() to simplify detection of errors in input loading and clarify behavior around module or script invocation.

bpo-34798 [https://bugs.python.org/issue?@action=redirect&bpo=34798]: Break up paragraph about pprint.PrettyPrinter construction parameters to make it easier to read.

bpo-44539 [https://bugs.python.org/issue?@action=redirect&bpo=44539]: Added support for recognizing JPEG files without JFIF or Exif markers.

bpo-44461 [https://bugs.python.org/issue?@action=redirect&bpo=44461]: Fix bug with pdb's handling of import error due to a package which does not have a __main__ module

bpo-43625 [https://bugs.python.org/issue?@action=redirect&bpo=43625]: Fix a bug in the detection of CSV file headers by csv.Sniffer.has_header() and improve documentation of same.

bpo-44516 [https://bugs.python.org/issue?@action=redirect&bpo=44516]: Update vendored pip to 21.1.3

bpo-42892 [https://bugs.python.org/issue?@action=redirect&bpo=42892]: Fixed an exception thrown while parsing a malformed multipart email by email.message.EmailMessage.

bpo-44468 [https://bugs.python.org/issue?@action=redirect&bpo=44468]: typing.get_type_hints() now finds annotations in classes and base classes with unexpected __module__. Previously, it skipped those MRO elements.

bpo-44491 [https://bugs.python.org/issue?@action=redirect&bpo=44491]: Allow clearing the sqlite3 authorizer callback by passing None to set_authorizer(). Patch by Erlend E. Aasland.

bpo-43977 [https://bugs.python.org/issue?@action=redirect&bpo=43977]: Set the proper Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE flags for subclasses created before a parent has been registered as a collections.abc.Mapping or collections.abc.Sequence.

bpo-44482 [https://bugs.python.org/issue?@action=redirect&bpo=44482]: Fix very unlikely resource leak in glob in alternate Python implementations.

bpo-44466 [https://bugs.python.org/issue?@action=redirect&bpo=44466]: The faulthandler module now detects if a fatal error occurs during a garbage collector collection. Patch by Victor Stinner.

bpo-44471 [https://bugs.python.org/issue?@action=redirect&bpo=44471]: A TypeError is now raised instead of an AttributeError in contextlib.ExitStack.enter_context() and contextlib.AsyncExitStack.enter_async_context() for objects which do not support the context manager or asynchronous context manager protocols correspondingly.

bpo-44404 [https://bugs.python.org/issue?@action=redirect&bpo=44404]: tkinter's after() method now supports callables without the __name__ attribute.

bpo-41546 [https://bugs.python.org/issue?@action=redirect&bpo=41546]: Make pprint (like the builtin print) not attempt to write to stdout when it is None.

bpo-44458 [https://bugs.python.org/issue?@action=redirect&bpo=44458]: BUFFER_BLOCK_SIZE is now declared static, to avoid linking collisions when bz2, lmza or zlib are statically linked.

bpo-44464 [https://bugs.python.org/issue?@action=redirect&bpo=44464]: Remove exception for flake8 in deprecated importlib.metadata interfaces. Sync with importlib_metadata 4.6.

bpo-44446 [https://bugs.python.org/issue?@action=redirect&bpo=44446]: Take into account that lineno might be None in traceback.FrameSummary.

bpo-44439 [https://bugs.python.org/issue?@action=redirect&bpo=44439]: Fix in bz2.BZ2File.write() / lzma.LZMAFile.write() methods, when the input data is an object that supports the buffer protocol, the file length may be wrong.

bpo-44434 [https://bugs.python.org/issue?@action=redirect&bpo=44434]: _thread.start_new_thread() no longer calls PyThread_exit_thread() explicitly at the thread exit, the call was redundant. On Linux with the glibc, pthread_exit() aborts the whole process if dlopen() fails to open libgcc_s.so file (ex: EMFILE error). Patch by Victor Stinner.

bpo-42972 [https://bugs.python.org/issue?@action=redirect&bpo=42972]: The _thread.RLock type now fully implement the GC protocol: add a traverse function and the Py_TPFLAGS_HAVE_GC flag. Patch by Victor Stinner.

bpo-44422 [https://bugs.python.org/issue?@action=redirect&bpo=44422]: The threading.enumerate() function now uses a reentrant lock to prevent a hang on reentrant call. Patch by Victor Stinner.

bpo-38291 [https://bugs.python.org/issue?@action=redirect&bpo=38291]: Importing typing.io or typing.re now prints a DeprecationWarning.

bpo-37880 [https://bugs.python.org/issue?@action=redirect&bpo=37880]: argparse actions store_const and append_const each receive a default value of None when the const kwarg is not provided. Previously, this raised a TypeError.

bpo-44389 [https://bugs.python.org/issue?@action=redirect&bpo=44389]: Fix deprecation of ssl.OP_NO_TLSv1_3

bpo-27827 [https://bugs.python.org/issue?@action=redirect&bpo=27827]: pathlib.PureWindowsPath.is_reserved() now identifies a greater range of reserved filenames, including those with trailing spaces or colons.

bpo-44395 [https://bugs.python.org/issue?@action=redirect&bpo=44395]: Fix as_string() to pass unixfrom properly. Patch by Donghee Na.

bpo-34266 [https://bugs.python.org/issue?@action=redirect&bpo=34266]: Handle exceptions from parsing the arg of pdb's run/restart command.

bpo-44362 [https://bugs.python.org/issue?@action=redirect&bpo=44362]: Improve ssl module's deprecation messages, error reporting, and documentation for deprecations.

bpo-44342 [https://bugs.python.org/issue?@action=redirect&bpo=44342]: [Enum] Change pickling from by-value to by-name.

bpo-44356 [https://bugs.python.org/issue?@action=redirect&bpo=44356]: [Enum] Allow multiple data-type mixins if they are all the same.

bpo-44351 [https://bugs.python.org/issue?@action=redirect&bpo=44351]: Restore back parse_makefile() in distutils.sysconfig because it behaves differently than the similar implementation in sysconfig.

bpo-35800 [https://bugs.python.org/issue?@action=redirect&bpo=35800]: smtpd.MailmanProxy is now removed as it is unusable without an external module, mailman. Patch by Donghee Na.

bpo-44357 [https://bugs.python.org/issue?@action=redirect&bpo=44357]: Added a function that returns cube root of the given number math.cbrt()

bpo-44339 [https://bugs.python.org/issue?@action=redirect&bpo=44339]: Change math.pow(±0.0, -math.inf) to return inf instead of raising ValueError. This brings the special-case handling of math.pow into compliance with the IEEE 754 standard.

bpo-44242 [https://bugs.python.org/issue?@action=redirect&bpo=44242]: Remove missing flag check from Enum creation and move into a verify decorator.

bpo-44246 [https://bugs.python.org/issue?@action=redirect&bpo=44246]: In importlib.metadata, restore compatibility in the result from Distribution.entry_points (EntryPoints) to honor expectations in older implementations and issuing deprecation warnings for these cases: A. EntryPoints objects are once again mutable, allowing for sort() and other list-based mutation operations. Avoid deprecation warnings by casting to a mutable sequence (e.g. list(dist.entry_points).sort()). B. EntryPoints results once again allow for access by index. To avoid deprecation warnings, cast the result to a Sequence first (e.g. tuple(dist.entry_points)[0]).

bpo-44246 [https://bugs.python.org/issue?@action=redirect&bpo=44246]: In importlib.metadata.entry_points, de-duplication of distributions no longer requires loading the full metadata for PathDistribution objects, improving entry point loading performance by ~10x.

bpo-43858 [https://bugs.python.org/issue?@action=redirect&bpo=43858]: Added a function that returns a copy of a dict of logging levels: logging.getLevelNamesMapping()

bpo-44260 [https://bugs.python.org/issue?@action=redirect&bpo=44260]: The random.Random constructor no longer reads system entropy without need.

bpo-44254 [https://bugs.python.org/issue?@action=redirect&bpo=44254]: On Mac, give turtledemo button text a color that works on both light or dark background. Programmers cannot control the latter.

bpo-44258 [https://bugs.python.org/issue?@action=redirect&bpo=44258]: Support PEP 515 for Fraction's initialization from string.

bpo-44235 [https://bugs.python.org/issue?@action=redirect&bpo=44235]: Remove deprecated functions in the gettext. Patch by Donghee Na.

bpo-38693 [https://bugs.python.org/issue?@action=redirect&bpo=38693]: Prefer f-strings to .format in importlib.resources.

bpo-33693 [https://bugs.python.org/issue?@action=redirect&bpo=33693]: Importlib.metadata now prefers f-strings to .format.

bpo-44241 [https://bugs.python.org/issue?@action=redirect&bpo=44241]: Incorporate minor tweaks from importlib_metadata 4.1: SimplePath protocol, support for Metadata 2.2.

bpo-43216 [https://bugs.python.org/issue?@action=redirect&bpo=43216]: Remove the @asyncio.coroutine decorator enabling legacy generator-based coroutines to be compatible with async/await code; remove asyncio.coroutines.CoroWrapper used for wrapping legacy coroutine objects in the debug mode. The decorator has been deprecated since Python 3.8 and the removal was initially scheduled for Python 3.10. Patch by Illia Volochii.

bpo-44210 [https://bugs.python.org/issue?@action=redirect&bpo=44210]: Make importlib.metadata._meta.PackageMetadata public.

bpo-43643 [https://bugs.python.org/issue?@action=redirect&bpo=43643]: Declare readers.MultiplexedPath.name as a property per the spec.

bpo-27334 [https://bugs.python.org/issue?@action=redirect&bpo=27334]: The sqlite3 context manager now performs a rollback (thus releasing the database lock) if commit failed. Patch by Luca Citi and Erlend E. Aasland.

bpo-4928 [https://bugs.python.org/issue?@action=redirect&bpo=4928]: Documented existing behavior on POSIX: NamedTemporaryFiles are not deleted when creating process is killed with SIGKILL

bpo-44154 [https://bugs.python.org/issue?@action=redirect&bpo=44154]: Optimize fractions.Fraction pickling for large components.

bpo-33433 [https://bugs.python.org/issue?@action=redirect&bpo=33433]: For IPv4 mapped IPv6 addresses (RFC 4291 [https://datatracker.ietf.org/doc/html/rfc4291.html] Section 2.5.5.2), the ipaddress.IPv6Address.is_private check is deferred to the mapped IPv4 address. This solves a bug where public mapped IPv4 addresses were considered private by the IPv6 check.

bpo-44150 [https://bugs.python.org/issue?@action=redirect&bpo=44150]: Add optional weights argument to statistics.fmean().

bpo-44142 [https://bugs.python.org/issue?@action=redirect&bpo=44142]: ast.unparse() will now drop the redundant parentheses when tuples used as assignment targets (e.g in for loops).

bpo-44145 [https://bugs.python.org/issue?@action=redirect&bpo=44145]: hmac computations were not releasing the GIL while calling the OpenSSL HMAC_Update C API (a new feature in 3.9). This unintentionally prevented parallel computation as other hashlib algorithms support.

bpo-44095 [https://bugs.python.org/issue?@action=redirect&bpo=44095]: zipfile.Path now supports zipfile.Path.stem, zipfile.Path.suffixes, and zipfile.Path.suffix attributes.

bpo-44077 [https://bugs.python.org/issue?@action=redirect&bpo=44077]: It's now possible to receive the type of service (ToS), a.k.a. differentiated services (DS), a.k.a. differentiated services code point (DSCP) and explicit congestion notification (ECN) IP header fields with socket.IP_RECVTOS.

bpo-37788 [https://bugs.python.org/issue?@action=redirect&bpo=37788]: Fix a reference leak when a Thread object is never joined.

bpo-38908 [https://bugs.python.org/issue?@action=redirect&bpo=38908]: Subclasses of typing.Protocol which only have data variables declared will now raise a TypeError when checked with isinstance unless they are decorated with runtime_checkable(). Previously, these checks passed silently. Patch provided by Yurii Karabas.

bpo-44098 [https://bugs.python.org/issue?@action=redirect&bpo=44098]: typing.ParamSpec will no longer be found in the __parameters__ of most typing generics except in valid use locations specified by PEP 612 [https://peps.python.org/pep-0612/]. This prevents incorrect usage like typing.List[P][int]. This change means incorrect usage which may have passed silently in 3.10 beta 1 and earlier will now error.

bpo-44089 [https://bugs.python.org/issue?@action=redirect&bpo=44089]: Allow subclassing csv.Error in 3.10 (it was allowed in 3.9 and earlier but was disallowed in early versions of 3.10).

bpo-44081 [https://bugs.python.org/issue?@action=redirect&bpo=44081]: ast.unparse() now doesn't use redundant spaces to separate lambda and the : if there are no parameters.

bpo-44061 [https://bugs.python.org/issue?@action=redirect&bpo=44061]: Fix regression in previous release when calling pkgutil.iter_modules() with a list of pathlib.Path objects

bpo-44059 [https://bugs.python.org/issue?@action=redirect&bpo=44059]: Register the SerenityOS Browser in the webbrowser module.

bpo-36515 [https://bugs.python.org/issue?@action=redirect&bpo=36515]: The hashlib module no longer does unaligned memory accesses when compiled for ARM platforms.

bpo-40465 [https://bugs.python.org/issue?@action=redirect&bpo=40465]: Remove random module features deprecated in Python 3.9.

bpo-44018 [https://bugs.python.org/issue?@action=redirect&bpo=44018]: random.seed() no longer mutates bytearray inputs.

bpo-38352 [https://bugs.python.org/issue?@action=redirect&bpo=38352]: Add IO, BinaryIO, TextIO, Match, and Pattern to typing.__all__. Patch by Jelle Zijlstra.

bpo-44002 [https://bugs.python.org/issue?@action=redirect&bpo=44002]: urllib.parse now uses functool.lru_cache() for its internal URL splitting and quoting caches instead of rolling its own like its the '90s.

The undocumented internal urllib.parse Quoted class API is now deprecated, for removal in 3.14.

bpo-43972 [https://bugs.python.org/issue?@action=redirect&bpo=43972]: When http.server.SimpleHTTPRequestHandler sends a 301 (Moved Permanently) for a directory path not ending with /, add a Content-Length: 0 header. This improves the behavior for certain clients.

bpo-28528 [https://bugs.python.org/issue?@action=redirect&bpo=28528]: Fix a bug in pdb where checkline() raises AttributeError if it is called after reset().

bpo-43853 [https://bugs.python.org/issue?@action=redirect&bpo=43853]: Improved string handling for sqlite3 user-defined functions and aggregates:

It is now possible to pass strings with embedded null characters to UDFs

Conversion failures now correctly raise MemoryError

Patch by Erlend E. Aasland.

bpo-43666 [https://bugs.python.org/issue?@action=redirect&bpo=43666]: AIX: Lib/_aix_support.get_platform() may fail in an AIX WPAR. The fileset bos.rte appears to have a builddate in both LPAR and WPAR so this fileset is queried rather than bos.mp64. To prevent a similar situation (no builddate in ODM) a value (9988) sufficient for completing a build is provided. Patch by M Felt.

bpo-43650 [https://bugs.python.org/issue?@action=redirect&bpo=43650]: Fix MemoryError in shutil.unpack_archive() which fails inside shutil._unpack_zipfile() on large files. Patch by Igor Bolshakov.

bpo-43612 [https://bugs.python.org/issue?@action=redirect&bpo=43612]: zlib.compress() now accepts a wbits parameter which allows users to compress data as a raw deflate block without zlib headers and trailers in one go. Previously this required instantiating a zlib.compressobj. It also provides a faster alternative to gzip.compress when wbits=31 is used.

bpo-43392 [https://bugs.python.org/issue?@action=redirect&bpo=43392]: importlib._bootstrap._find_and_load() now implements a two-step check to avoid locking when modules have been already imported and are ready. This improves performance of repeated calls to importlib.import_module() and importlib.__import__().

bpo-43318 [https://bugs.python.org/issue?@action=redirect&bpo=43318]: Fix a bug where pdb does not always echo cleared breakpoints.

bpo-43234 [https://bugs.python.org/issue?@action=redirect&bpo=43234]: Prohibit passing non-concurrent.futures.ThreadPoolExecutor executors to loop.set_default_executor() following a deprecation in Python 3.8. Patch by Illia Volochii.

bpo-43232 [https://bugs.python.org/issue?@action=redirect&bpo=43232]: Prohibit previously deprecated potentially disruptive operations on asyncio.trsock.TransportSocket. Patch by Illia Volochii.

bpo-30077 [https://bugs.python.org/issue?@action=redirect&bpo=30077]: Added support for Apple's aifc/sowt pseudo-compression

bpo-42971 [https://bugs.python.org/issue?@action=redirect&bpo=42971]: Add definition of errno.EQFULL for platforms that define this constant (such as macOS).

bpo-43086 [https://bugs.python.org/issue?@action=redirect&bpo=43086]: Added a new optional strict_mode parameter to binascii.a2b_base64. When scrict_mode is set to True, the a2b_base64 function will accept only valid base64 content. More details about what "valid base64 content" is, can be found in the function's documentation.

bpo-43024 [https://bugs.python.org/issue?@action=redirect&bpo=43024]: Improve the help signature of traceback.print_exception(), traceback.format_exception() and traceback.format_exception_only().

bpo-33809 [https://bugs.python.org/issue?@action=redirect&bpo=33809]: Add the traceback.TracebackException.print() method which prints the formatted exception information.

bpo-42862 [https://bugs.python.org/issue?@action=redirect&bpo=42862]: sqlite3 now utilizes functools.lru_cache() to implement the connection statement cache. As a small optimisation, the default statement cache size has been increased from 100 to 128. Patch by Erlend E. Aasland.

bpo-41818 [https://bugs.python.org/issue?@action=redirect&bpo=41818]: Soumendra Ganguly: add termios.tcgetwinsize(), termios.tcsetwinsize().

bpo-40497 [https://bugs.python.org/issue?@action=redirect&bpo=40497]: subprocess.check_output() now raises ValueError when the invalid keyword argument check is passed by user code. Previously such use would fail later with a TypeError. Patch by Rémi Lapeyre.

bpo-37449 [https://bugs.python.org/issue?@action=redirect&bpo=37449]: ensurepip now uses importlib.resources.files() traversable APIs

bpo-40956 [https://bugs.python.org/issue?@action=redirect&bpo=40956]: Use Argument Clinic in sqlite3. Patches by Erlend E. Aasland.

bpo-41730 [https://bugs.python.org/issue?@action=redirect&bpo=41730]: DeprecationWarning is now raised when importing tkinter.tix, which has been deprecated in documentation since Python 3.6.

bpo-20684 [https://bugs.python.org/issue?@action=redirect&bpo=20684]: Remove unused _signature_get_bound_param function from inspect - by Anthony Sottile.

bpo-41402 [https://bugs.python.org/issue?@action=redirect&bpo=41402]: Fix email.message.EmailMessage.set_content() when called with binary data and 7bit content transfer encoding.

bpo-32695 [https://bugs.python.org/issue?@action=redirect&bpo=32695]: The compresslevel and preset keyword arguments of tarfile.open() are now both documented and tested.

bpo-41137 [https://bugs.python.org/issue?@action=redirect&bpo=41137]: Use utf-8 encoding while reading .pdbrc files. Patch by Srinivas Reddy Thatiparthy

bpo-24391 [https://bugs.python.org/issue?@action=redirect&bpo=24391]: Improved reprs of threading synchronization objects: Semaphore, BoundedSemaphore, Event and Barrier.

bpo-5846 [https://bugs.python.org/issue?@action=redirect&bpo=5846]: Deprecated the following unittest functions, scheduled for removal in Python 3.13:

findTestCases()

makeSuite()

getTestCaseNames()

Use TestLoader methods instead:

unittest.TestLoader.loadTestsFromModule()

unittest.TestLoader.loadTestsFromTestCase()

unittest.TestLoader.getTestCaseNames()

Patch by Erlend E. Aasland.

bpo-40563 [https://bugs.python.org/issue?@action=redirect&bpo=40563]: Support pathlike objects on dbm/shelve. Patch by Hakan Çelik and Henry-Joseph Audéoud.

bpo-34990 [https://bugs.python.org/issue?@action=redirect&bpo=34990]: Fixed a Y2k38 bug in the compileall module where it would fail to compile files with a modification time after the year 2038.

bpo-39549 [https://bugs.python.org/issue?@action=redirect&bpo=39549]: Whereas the code for reprlib.Repr had previously used a hardcoded string value of '...', this PR updates it to use of a “fillvalue” attribute, whose value defaults to '...' and can be reset in either individual reprlib.Repr instances or in subclasses thereof.

bpo-37022 [https://bugs.python.org/issue?@action=redirect&bpo=37022]: pdb now displays exceptions from repr() with its p and pp commands.

bpo-38840 [https://bugs.python.org/issue?@action=redirect&bpo=38840]: Fix test___all__ on platforms lacking a shared memory implementation.

bpo-39359 [https://bugs.python.org/issue?@action=redirect&bpo=39359]: Add one missing check that the password is a bytes object for an encrypted zipfile.

bpo-38741 [https://bugs.python.org/issue?@action=redirect&bpo=38741]: configparser: using ']' inside a section header will no longer cut the section name short at the ']'

bpo-38415 [https://bugs.python.org/issue?@action=redirect&bpo=38415]: Added missing behavior to contextlib.asynccontextmanager() to match contextlib.contextmanager() so decorated functions can themselves be decorators.

bpo-30256 [https://bugs.python.org/issue?@action=redirect&bpo=30256]: Pass multiprocessing BaseProxy argument manager_owned through AutoProxy.

bpo-27513 [https://bugs.python.org/issue?@action=redirect&bpo=27513]: email.utils.getaddresses() now accepts email.header.Header objects along with string values. Patch by Zackery Spytz.

bpo-16379 [https://bugs.python.org/issue?@action=redirect&bpo=16379]: Add SQLite error code and name to sqlite3 exceptions. Patch by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland.

bpo-26228 [https://bugs.python.org/issue?@action=redirect&bpo=26228]: pty.spawn no longer hangs on FreeBSD, macOS, and Solaris.

bpo-33349 [https://bugs.python.org/issue?@action=redirect&bpo=33349]: lib2to3 now recognizes async generators everywhere.

bpo-29298 [https://bugs.python.org/issue?@action=redirect&bpo=29298]: Fix TypeError when required subparsers without dest do not receive arguments. Patch by Anthony Sottile.

Documentation

bpo-45216 [https://bugs.python.org/issue?@action=redirect&bpo=45216]: Remove extra documentation listing methods in difflib. It was rendering twice in pydoc and was outdated in some places.

bpo-45024 [https://bugs.python.org/issue?@action=redirect&bpo=45024]: collections.abc documentation has been expanded to explicitly cover how instance and subclass checks work, with additional doctest examples and an exhaustive list of ABCs which test membership purely by presence of the right special methods. Patch by Raymond Hettinger.

bpo-44957 [https://bugs.python.org/issue?@action=redirect&bpo=44957]: Promote PEP 604 union syntax by using it where possible. Also, mention X | Y more prominently in section about Union and mention X | None at all in section about Optional.

bpo-16580 [https://bugs.python.org/issue?@action=redirect&bpo=16580]: Added code equivalents for the int.to_bytes() and int.from_bytes() methods, as well as tests ensuring that these code equivalents are valid.

bpo-44903 [https://bugs.python.org/issue?@action=redirect&bpo=44903]: Removed the othergui.rst file, any references to it, and the list of GUI frameworks in the FAQ. In their place I've added links to the Python Wiki page on GUI frameworks [https://wiki.python.org/moin/GuiProgramming].

bpo-33479 [https://bugs.python.org/issue?@action=redirect&bpo=33479]: Tkinter documentation has been greatly expanded with new "Architecture" and "Threading model" sections.

bpo-36700 [https://bugs.python.org/issue?@action=redirect&bpo=36700]: base64 RFC references were updated to point to RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html]; a section was added to point users to the new "security considerations" section of the RFC.

bpo-44740 [https://bugs.python.org/issue?@action=redirect&bpo=44740]: Replaced occurrences of uppercase "Web" and "Internet" with lowercase versions per the 2016 revised Associated Press Style Book.

bpo-44693 [https://bugs.python.org/issue?@action=redirect&bpo=44693]: Update the definition of __future__ in the glossary by replacing the confusing word "pseudo-module" with a more accurate description.

bpo-35183 [https://bugs.python.org/issue?@action=redirect&bpo=35183]: Add typical examples to os.path.splitext docs

bpo-30511 [https://bugs.python.org/issue?@action=redirect&bpo=30511]: Clarify that shutil.make_archive() is not thread-safe due to reliance on changing the current working directory.

bpo-44561 [https://bugs.python.org/issue?@action=redirect&bpo=44561]: Update of three expired hyperlinks in Doc/distributing/index.rst: "Project structure", "Building and packaging the project", and "Uploading the project to the Python Packaging Index".

bpo-44651 [https://bugs.python.org/issue?@action=redirect&bpo=44651]: Delete entry "coercion" in Doc/glossary.rst for its outdated definition.

bpo-42958 [https://bugs.python.org/issue?@action=redirect&bpo=42958]: Updated the docstring and docs of filecmp.cmp() to be more accurate and less confusing especially in respect to shallow arg.

bpo-44631 [https://bugs.python.org/issue?@action=redirect&bpo=44631]: Refactored the repr() code of the _Environ (os module).

bpo-44613 [https://bugs.python.org/issue?@action=redirect&bpo=44613]: importlib.metadata is no longer provisional.

bpo-44558 [https://bugs.python.org/issue?@action=redirect&bpo=44558]: Match the docstring and python implementation of countOf() to the behavior of its c implementation.

bpo-44544 [https://bugs.python.org/issue?@action=redirect&bpo=44544]: List all kwargs for textwrap.wrap(), textwrap.fill(), and textwrap.shorten(). Now, there are nav links to attributes of TextWrap, which makes navigation much easier while minimizing duplication in the documentation.

bpo-38062 [https://bugs.python.org/issue?@action=redirect&bpo=38062]: Clarify that atexit uses equality comparisons internally.

bpo-40620 [https://bugs.python.org/issue?@action=redirect&bpo=40620]: Convert examples in tutorial controlflow.rst section 4.3 to be interpreter-demo style.

bpo-43066 [https://bugs.python.org/issue?@action=redirect&bpo=43066]: Added a warning to zipfile docs: filename arg with a leading slash may cause archive to be un-openable on Windows systems.

bpo-39452 [https://bugs.python.org/issue?@action=redirect&bpo=39452]: Rewrote Doc/library/__main__.rst. Broadened scope of the document to explicitly discuss and differentiate between __main__.py in packages versus the __name__ == '__main__' expression (and the idioms that surround it).

bpo-13814 [https://bugs.python.org/issue?@action=redirect&bpo=13814]: In the Design FAQ, answer "Why don't generators support the with statement?"

bpo-27752 [https://bugs.python.org/issue?@action=redirect&bpo=27752]: Documentation of csv.Dialect is more descriptive.

bpo-44453 [https://bugs.python.org/issue?@action=redirect&bpo=44453]: Fix documentation for the return type of sysconfig.get_path().

bpo-44392 [https://bugs.python.org/issue?@action=redirect&bpo=44392]: Added a new section in the C API documentation for types used in type hinting. Documented Py_GenericAlias and Py_GenericAliasType.

bpo-38291 [https://bugs.python.org/issue?@action=redirect&bpo=38291]: Mark typing.io and typing.re as deprecated since Python 3.8 in the documentation. They were never properly supported by type checkers.

bpo-44322 [https://bugs.python.org/issue?@action=redirect&bpo=44322]: Document that SyntaxError args have a details tuple and that details are adjusted for errors in f-string field replacement expressions.

bpo-42392 [https://bugs.python.org/issue?@action=redirect&bpo=42392]: Document the deprecation and removal of the loop parameter for many functions and classes in asyncio.

bpo-44195 [https://bugs.python.org/issue?@action=redirect&bpo=44195]: Corrected references to TraversableResources in docs. There is no TraversableReader.

bpo-41963 [https://bugs.python.org/issue?@action=redirect&bpo=41963]: Document that ConfigParser strips off comments when reading configuration files.

bpo-44072 [https://bugs.python.org/issue?@action=redirect&bpo=44072]: Correct where in the numeric ABC hierarchy ** support is added, i.e., in numbers.Complex, not numbers.Integral.

bpo-43558 [https://bugs.python.org/issue?@action=redirect&bpo=43558]: Add the remark to dataclasses documentation that the __init__() of any base class has to be called in __post_init__(), along with a code example.

bpo-44025 [https://bugs.python.org/issue?@action=redirect&bpo=44025]: Clarify when '_' in match statements is a keyword, and when not.

bpo-41706 [https://bugs.python.org/issue?@action=redirect&bpo=41706]: Fix docs about how methods like __add__ are invoked when evaluating operator expressions.

bpo-41621 [https://bugs.python.org/issue?@action=redirect&bpo=41621]: Document that collections.defaultdict parameter default_factory defaults to None and is positional-only.

bpo-41576 [https://bugs.python.org/issue?@action=redirect&bpo=41576]: document BaseException in favor of bare except

bpo-21760 [https://bugs.python.org/issue?@action=redirect&bpo=21760]: The description for __file__ fixed. Patch by Furkan Onder

bpo-39498 [https://bugs.python.org/issue?@action=redirect&bpo=39498]: Add a "Security Considerations" index which links to standard library modules that have explicitly documented security considerations.

bpo-33479 [https://bugs.python.org/issue?@action=redirect&bpo=33479]: Remove the unqualified claim that tkinter is threadsafe. It has not been true for several years and likely never was. An explanation of what is true may be added later, after more discussion, and possibly after patching _tkinter.c,

Tests

bpo-40173 [https://bugs.python.org/issue?@action=redirect&bpo=40173]: Fix test.support.import_helper.import_fresh_module().

bpo-45280 [https://bugs.python.org/issue?@action=redirect&bpo=45280]: Add a test case for empty typing.NamedTuple.

bpo-45269 [https://bugs.python.org/issue?@action=redirect&bpo=45269]: Cover case when invalid markers type is supplied to c_make_encoder.

bpo-45128 [https://bugs.python.org/issue?@action=redirect&bpo=45128]: Fix test_multiprocessing_fork failure due to test_logging and sys.modules manipulation.

bpo-45209 [https://bugs.python.org/issue?@action=redirect&bpo=45209]: Fix UserWarning: resource_tracker warning in _test_multiprocessing._TestSharedMemory.test_shared_memory_cleaned_after_process_termination

bpo-45185 [https://bugs.python.org/issue?@action=redirect&bpo=45185]: Enables TestEnumerations test cases in test_ssl suite.

bpo-45195 [https://bugs.python.org/issue?@action=redirect&bpo=45195]: Fix test_readline.test_nonascii(): sometimes, the newline character is not written at the end, so don't expect it in the output. Patch by Victor Stinner.

bpo-45156 [https://bugs.python.org/issue?@action=redirect&bpo=45156]: Fixes infinite loop on unittest.mock.seal() of mocks created by create_autospec().

bpo-45125 [https://bugs.python.org/issue?@action=redirect&bpo=45125]: Improves pickling tests and docs of SharedMemory and SharableList objects.

bpo-44860 [https://bugs.python.org/issue?@action=redirect&bpo=44860]: Update test_sysconfig.test_user_similar() for the posix_user scheme: platlib doesn't use sys.platlibdir. Patch by Victor Stinner.

bpo-45052 [https://bugs.python.org/issue?@action=redirect&bpo=45052]: WithProcessesTestSharedMemory.test_shared_memory_basics test was ignored, because self.assertEqual(sms.size, sms2.size) line was failing. It is now removed and test is unskipped.

The main motivation for this line to be removed from the test is that the size of SharedMemory is not ever guaranteed to be the same. It is decided by the platform.

bpo-44895 [https://bugs.python.org/issue?@action=redirect&bpo=44895]: libregrtest now clears the type cache later to reduce the risk of false alarm when checking for reference leaks. Previously, the type cache was cleared too early and libregrtest raised a false alarm about reference leaks under very specific conditions. Patch by Irit Katriel and Victor Stinner.

bpo-45042 [https://bugs.python.org/issue?@action=redirect&bpo=45042]: Fixes that test classes decorated with @hashlib_helper.requires_hashdigest were skipped all the time.

bpo-25130 [https://bugs.python.org/issue?@action=redirect&bpo=25130]: Add calls of gc.collect() in tests to support PyPy.

bpo-45011 [https://bugs.python.org/issue?@action=redirect&bpo=45011]: Made tests relying on the _asyncio C extension module optional to allow running on alternative Python implementations. Patch by Serhiy Storchaka.

bpo-44949 [https://bugs.python.org/issue?@action=redirect&bpo=44949]: Fix auto history tests of test_readline: sometimes, the newline character is not written at the end, so don't expect it in the output.

bpo-44891 [https://bugs.python.org/issue?@action=redirect&bpo=44891]: Tests were added to clarify id() is preserved when obj * 1 is used on str and bytes objects. Patch by Nikita Sobolev.

bpo-44852 [https://bugs.python.org/issue?@action=redirect&bpo=44852]: Add ability to wholesale silence DeprecationWarnings while running the regression test suite.

bpo-40928 [https://bugs.python.org/issue?@action=redirect&bpo=40928]: Notify users running test_decimal regression tests on macOS of potential harmless "malloc can't allocate region" messages spewed by test_decimal.

bpo-44734 [https://bugs.python.org/issue?@action=redirect&bpo=44734]: Fixed floating-point precision issue in turtle tests.

bpo-44708 [https://bugs.python.org/issue?@action=redirect&bpo=44708]: Regression tests, when run with -w, are now re-running only the affected test methods instead of re-running the entire test file.

bpo-42095 [https://bugs.python.org/issue?@action=redirect&bpo=42095]: Added interop tests for Apple plists: generate plist files with Python plistlib and parse with Apple plutil; and the other way round.

bpo-44647 [https://bugs.python.org/issue?@action=redirect&bpo=44647]: Added a permanent Unicode-valued environment variable to regression tests to ensure they handle this use case in the future. If your test environment breaks because of that, report a bug to us, and temporarily set PYTHONREGRTEST_UNICODE_GUARD=0 in your test environment.

bpo-44515 [https://bugs.python.org/issue?@action=redirect&bpo=44515]: Adjust recently added contextlib tests to avoid assuming the use of a refcounted GC

bpo-44287 [https://bugs.python.org/issue?@action=redirect&bpo=44287]: Fix asyncio test_popen() of test_windows_utils by using a longer timeout. Use military grade battle-tested test.support.SHORT_TIMEOUT timeout rather than a hardcoded timeout of 10 seconds: it's 30 seconds by default, but it is made longer on slow buildbots. Patch by Victor Stinner.

bpo-44451 [https://bugs.python.org/issue?@action=redirect&bpo=44451]: Reset DeprecationWarning filters in test.test_importlib.test_metadata_api.APITests.test_entry_points_by_index to avoid StopIteration error if DeprecationWarnings are ignored.

bpo-44363 [https://bugs.python.org/issue?@action=redirect&bpo=44363]: Account for address sanitizer in test_capi. test_capi now passes when run GCC address sanitizer.

bpo-44364 [https://bugs.python.org/issue?@action=redirect&bpo=44364]: Add non integral tests for math.sqrt() function.

bpo-43921 [https://bugs.python.org/issue?@action=redirect&bpo=43921]: Fix test_ssl.test_wrong_cert_tls13(): use suppress_ragged_eofs=False, since read() can raise ssl.SSLEOFError on Windows. Patch by Victor Stinner.

bpo-43921 [https://bugs.python.org/issue?@action=redirect&bpo=43921]: Fix test_pha_required_nocert() of test_ssl: catch two more EOF cases (when the recv() method returns an empty string). Patch by Victor Stinner.

bpo-44131 [https://bugs.python.org/issue?@action=redirect&bpo=44131]: Add test_frozenmain to test_embed to test the Py_FrozenMain() C function. Patch by Victor Stinner.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Ignore error string case in test_file_not_exists().

bpo-42083 [https://bugs.python.org/issue?@action=redirect&bpo=42083]: Add test to check that PyStructSequence_NewType accepts a PyStructSequence_Desc with doc field set to NULL.

bpo-35753 [https://bugs.python.org/issue?@action=redirect&bpo=35753]: Fix crash in doctest when doctest parses modules that include unwrappable functions by skipping those functions.

bpo-30256 [https://bugs.python.org/issue?@action=redirect&bpo=30256]: Add test for nested queues when using multiprocessing shared objects AutoProxy[Queue] inside ListProxy and DictProxy

Build

bpo-45220 [https://bugs.python.org/issue?@action=redirect&bpo=45220]: Avoid building with the Windows 11 SDK previews automatically. This may be overridden by setting the DefaultWindowsSDKVersion environment variable before building.

bpo-45020 [https://bugs.python.org/issue?@action=redirect&bpo=45020]: Freeze stdlib modules that are imported during startup. This provides significant performance improvements to startup. If necessary, use the previously added "-X frozen_modules=off" commandline option to force importing the source modules.

bpo-45188 [https://bugs.python.org/issue?@action=redirect&bpo=45188]: Windows builds now regenerate frozen modules as the first part of the build. Previously the regeneration was later in the build, which would require it to be restarted if any modules had changed.

bpo-45163 [https://bugs.python.org/issue?@action=redirect&bpo=45163]: Fixes Haiku platform build.

bpo-45067 [https://bugs.python.org/issue?@action=redirect&bpo=45067]: The ncurses function extended_color_content was introduced in 2017

(https://invisible-island.net/ncurses/NEWS.html#index-t20170401). The

ncurses-devel package in CentOS 7 had a older version ncurses resulted in compilation error. For compiling ncurses with extended color support, we verify the version of the ncurses library >= 20170401.

bpo-45019 [https://bugs.python.org/issue?@action=redirect&bpo=45019]: Generate lines in relevant files for frozen modules. Up until now each of the files had to be edited manually. This change makes it easier to add to and modify the frozen modules.

bpo-44340 [https://bugs.python.org/issue?@action=redirect&bpo=44340]: Add support for building with clang thin lto via --with-lto=thin/full. Patch by Donghee Na and Brett Holman.

bpo-44535 [https://bugs.python.org/issue?@action=redirect&bpo=44535]: Enable building using a Visual Studio 2022 install on Windows.

bpo-43298 [https://bugs.python.org/issue?@action=redirect&bpo=43298]: Improved error message when building without a Windows SDK installed.

bpo-44381 [https://bugs.python.org/issue?@action=redirect&bpo=44381]: The Windows build now accepts EnableControlFlowGuard set to guard to enable CFG.

bpo-41282 [https://bugs.python.org/issue?@action=redirect&bpo=41282]: Fix broken make install that caused standard library extension modules to be unnecessarily and incorrectly rebuilt during the install phase of cpython.

Windows

bpo-45375 [https://bugs.python.org/issue?@action=redirect&bpo=45375]: Fixes an assertion failure due to searching for the standard library in unnormalised paths.

bpo-45022 [https://bugs.python.org/issue?@action=redirect&bpo=45022]: Update Windows release to include libffi 3.4.2

bpo-45007 [https://bugs.python.org/issue?@action=redirect&bpo=45007]: Update to OpenSSL 1.1.1l in Windows build

bpo-44848 [https://bugs.python.org/issue?@action=redirect&bpo=44848]: Upgrade Windows installer to use SQLite 3.36.0.

bpo-44572 [https://bugs.python.org/issue?@action=redirect&bpo=44572]: Avoid consuming standard input in the platform module

bpo-44582 [https://bugs.python.org/issue?@action=redirect&bpo=44582]: Accelerate speed of mimetypes initialization using a native implementation of the registry scan.

bpo-41299 [https://bugs.python.org/issue?@action=redirect&bpo=41299]: Fix 16 milliseconds jitter when using timeouts in threading, such as with threading.Lock.acquire() or threading.Condition.wait().

bpo-42686 [https://bugs.python.org/issue?@action=redirect&bpo=42686]: Build sqlite3 with math functions enabled. Patch by Erlend E. Aasland.

bpo-40263 [https://bugs.python.org/issue?@action=redirect&bpo=40263]: This is a follow-on bug from https://bugs.python.org/issue26903. Once that is applied we run into an off-by-one assertion problem. The assert was not correct.

macOS

bpo-45007 [https://bugs.python.org/issue?@action=redirect&bpo=45007]: Update macOS installer builds to use OpenSSL 1.1.1l.

bpo-34602 [https://bugs.python.org/issue?@action=redirect&bpo=34602]: When building CPython on macOS with ./configure --with-undefined-behavior-sanitizer --with-pydebug, the stack size is now quadrupled to allow for the entire test suite to pass.

bpo-44848 [https://bugs.python.org/issue?@action=redirect&bpo=44848]: Update macOS installer to use SQLite 3.36.0.

bpo-44689 [https://bugs.python.org/issue?@action=redirect&bpo=44689]: ctypes.util.find_library() now works correctly on macOS 11 Big Sur even if Python is built on an older version of macOS. Previously, when built on older macOS systems, find_library was not able to find macOS system libraries when running on Big Sur due to changes in how system libraries are stored.

bpo-41972 [https://bugs.python.org/issue?@action=redirect&bpo=41972]: The framework build's user header path in sysconfig is changed to add a 'pythonX.Y' component to match distutils's behavior.

bpo-43109 [https://bugs.python.org/issue?@action=redirect&bpo=43109]: Allow --with-lto configure option to work with Apple-supplied Xcode or Command Line Tools.

bpo-34932 [https://bugs.python.org/issue?@action=redirect&bpo=34932]: Add socket.TCP_KEEPALIVE support for macOS. Patch by Shane Harvey.

IDLE

bpo-45296 [https://bugs.python.org/issue?@action=redirect&bpo=45296]: On Windows, change exit/quit message to suggest Ctrl-D, which works, instead of <Ctrl-Z Return>, which does not work in IDLE.

bpo-45193 [https://bugs.python.org/issue?@action=redirect&bpo=45193]: Make completion boxes appear on Ubuntu again.

bpo-40128 [https://bugs.python.org/issue?@action=redirect&bpo=40128]: Mostly fix completions on macOS when not using tcl/tk 8.6.11 (as with 3.9). The added update_idletask call should be harmless and possibly helpful otherwise.

bpo-33962 [https://bugs.python.org/issue?@action=redirect&bpo=33962]: Move the indent space setting from the Font tab to the new Windows tab. Patch by Mark Roseman and Terry Jan Reedy.

bpo-40468 [https://bugs.python.org/issue?@action=redirect&bpo=40468]: Split the settings dialog General tab into Windows and Shell/ED tabs. Move help sources, which extend the Help menu, to the Extensions tab. Make space for new options and shorten the dialog. The latter makes the dialog better fit small screens.

bpo-41611 [https://bugs.python.org/issue?@action=redirect&bpo=41611]: Avoid uncaught exceptions in AutoCompleteWindow.winconfig_event().

bpo-41611 [https://bugs.python.org/issue?@action=redirect&bpo=41611]: Fix IDLE sometimes freezing upon tab-completion on macOS.

bpo-44010 [https://bugs.python.org/issue?@action=redirect&bpo=44010]: Highlight the new match statement's soft keywords: match, case, and _. However, this highlighting is not perfect and will be incorrect in some rare cases, including some _-s in case patterns.

bpo-44026 [https://bugs.python.org/issue?@action=redirect&bpo=44026]: Include interpreter's typo fix suggestions in message line for NameErrors and AttributeErrors. Patch by E. Paine.

Tools/Demos

bpo-44786 [https://bugs.python.org/issue?@action=redirect&bpo=44786]: Fix a warning in regular expression in the c-analyzer script.

bpo-44967 [https://bugs.python.org/issue?@action=redirect&bpo=44967]: pydoc now returns a non-zero status code when a module cannot be found.

bpo-44978 [https://bugs.python.org/issue?@action=redirect&bpo=44978]: Allow the Argument Clinic tool to handle __complex__ special methods.

bpo-43425 [https://bugs.python.org/issue?@action=redirect&bpo=43425]: Removed the 'test2to3' demo project that demonstrated using lib2to3 to support Python 2.x and Python 3.x from a single source in a distutils package. Patch by Donghee Na

bpo-44074 [https://bugs.python.org/issue?@action=redirect&bpo=44074]: Make patchcheck automatically detect the correct base branch name (previously it was hardcoded to 'master')

bpo-20291 [https://bugs.python.org/issue?@action=redirect&bpo=20291]: Added support for variadic positional parameters in Argument Clinic.

C API

bpo-41710 [https://bugs.python.org/issue?@action=redirect&bpo=41710]: The PyThread_acquire_lock_timed() function now clamps the timeout if it is too large, rather than aborting the process. Patch by Victor Stinner.

bpo-44687 [https://bugs.python.org/issue?@action=redirect&bpo=44687]: BufferedReader.peek() no longer raises ValueError when the entire file has already been buffered.

bpo-45116 [https://bugs.python.org/issue?@action=redirect&bpo=45116]: Add the Py_ALWAYS_INLINE macro to ask the compiler to always inline a static inline function. The compiler can ignore it and decides to not inline the function. Patch by Victor Stinner.

bpo-45094 [https://bugs.python.org/issue?@action=redirect&bpo=45094]: Add the Py_NO_INLINE macro to disable inlining on a function. Patch by Victor Stinner.

bpo-45061 [https://bugs.python.org/issue?@action=redirect&bpo=45061]: Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF(Py_True); or Py_DECREF(Py_False); by mistake. Patch by Victor Stinner.

bpo-42035 [https://bugs.python.org/issue?@action=redirect&bpo=42035]: Add a new PyType_GetQualName() function to get type's qualified name.

bpo-41103 [https://bugs.python.org/issue?@action=redirect&bpo=41103]: Reverts removal of the old buffer protocol because they are part of stable ABI.

bpo-44751 [https://bugs.python.org/issue?@action=redirect&bpo=44751]: Remove crypt.h include from the public Python.h header.

bpo-42747 [https://bugs.python.org/issue?@action=redirect&bpo=42747]: The Py_TPFLAGS_HAVE_VERSION_TAG type flag now does nothing. The Py_TPFLAGS_HAVE_AM_SEND flag (which was added in 3.10) is removed. Both were unnecessary because it is not possible to have type objects with the relevant fields missing.

bpo-44530 [https://bugs.python.org/issue?@action=redirect&bpo=44530]: Added the co_qualname to the PyCodeObject structure to propagate the qualified name from the compiler to code objects.

Patch by Gabriele N. Tornetta

bpo-44441 [https://bugs.python.org/issue?@action=redirect&bpo=44441]: Py_RunMain() now resets PyImport_Inittab to its initial value at exit. It must be possible to call PyImport_AppendInittab() or PyImport_ExtendInittab() at each Python initialization. Patch by Victor Stinner.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Remove 4 private trashcan C API functions which were only kept for the backward compatibility of the stable ABI with Python 3.8 and older, since the trashcan API was not usable with the limited C API on Python 3.8 and older. The trashcan API was excluded from the limited C API in Python 3.9.

Removed functions:

_PyTrash_deposit_object()

_PyTrash_destroy_chain()

_PyTrash_thread_deposit_object()

_PyTrash_thread_destroy_chain()

The trashcan C API was never usable with the limited C API, since old trashcan macros accessed directly PyThreadState members like _tstate->trash_delete_nesting, whereas the PyThreadState structure is opaque in the limited C API.

Exclude also the PyTrash_UNWIND_LEVEL constant from the C API.

Patch by Victor Stinner.

bpo-40939 [https://bugs.python.org/issue?@action=redirect&bpo=40939]: Removed documentation for the removed PyParser_* C API.

bpo-43795 [https://bugs.python.org/issue?@action=redirect&bpo=43795]: The list in 受限 API 的內容 now shows the public name PyFrameObject rather than _frame. The non-existing entry _node no longer appears in the list.

bpo-44378 [https://bugs.python.org/issue?@action=redirect&bpo=44378]: Py_IS_TYPE() no longer uses Py_TYPE() to avoid a compiler warning: no longer cast const PyObject* to PyObject*. Patch by Victor Stinner.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Convert the Py_TYPE() and Py_SIZE() macros to static inline functions. The Py_SET_TYPE() and Py_SET_SIZE() functions must now be used to set an object type and size. Patch by Victor Stinner.

bpo-44263 [https://bugs.python.org/issue?@action=redirect&bpo=44263]: The PyType_Ready() function now raises an error if a type is defined with the Py_TPFLAGS_HAVE_GC flag set but has no traverse function (PyTypeObject.tp_traverse). Patch by Victor Stinner.

bpo-43795 [https://bugs.python.org/issue?@action=redirect&bpo=43795]: The undocumented function Py_FrozenMain() is removed from the Limited API.

bpo-44113 [https://bugs.python.org/issue?@action=redirect&bpo=44113]: Deprecate the following functions to configure the Python initialization:

PySys_AddWarnOptionUnicode()

PySys_AddWarnOption()

PySys_AddXOption()

PySys_HasWarnOptions()

Py_SetPath()

Py_SetProgramName()

Py_SetPythonHome()

Py_SetStandardStreamEncoding()

_Py_SetProgramFullPath()

Use the new PyConfig API of the Python Initialization Configuration instead (PEP 587 [https://peps.python.org/pep-0587/]).

bpo-44094 [https://bugs.python.org/issue?@action=redirect&bpo=44094]: Remove PyErr_SetFromErrnoWithUnicodeFilename(), PyErr_SetFromWindowsErrWithUnicodeFilename(), and PyErr_SetExcFromWindowsErrWithUnicodeFilename(). They are not documented and have been deprecated since Python 3.3.

bpo-43795 [https://bugs.python.org/issue?@action=redirect&bpo=43795]: PyCodec_Unregister() is now properly exported as a function in the Windows Stable ABI DLL.

bpo-44029 [https://bugs.python.org/issue?@action=redirect&bpo=44029]: Remove deprecated Py_UNICODE APIs: PyUnicode_Encode, PyUnicode_EncodeUTF7, PyUnicode_EncodeUTF8, PyUnicode_EncodeUTF16, PyUnicode_EncodeUTF32, PyUnicode_EncodeLatin1, PyUnicode_EncodeMBCS, PyUnicode_EncodeDecimal, PyUnicode_EncodeRawUnicodeEscape, PyUnicode_EncodeCharmap, PyUnicode_EncodeUnicodeEscape, PyUnicode_TransformDecimalToASCII, PyUnicode_TranslateCharmap, PyUnicodeEncodeError_Create, PyUnicodeTranslateError_Create. See PEP 393 [https://peps.python.org/pep-0393/] and PEP 624 [https://peps.python.org/pep-0624/] for reference.

bpo-42035 [https://bugs.python.org/issue?@action=redirect&bpo=42035]: Add a new PyType_GetName() function to get type's short name.

Python 3.10.0 beta 1

Release date: 2021-05-03

Security

bpo-43434 [https://bugs.python.org/issue?@action=redirect&bpo=43434]: Creating sqlite3.Connection objects now also produces sqlite3.connect and sqlite3.connect/handle auditing events. Previously these events were only produced by sqlite3.connect() calls. Patch by Erlend E. Aasland.

bpo-43998 [https://bugs.python.org/issue?@action=redirect&bpo=43998]: The ssl module sets more secure cipher suites defaults. Ciphers without forward secrecy and with SHA-1 MAC are disabled by default. Security level 2 prohibits weak RSA, DH, and ECC keys with less than 112 bits of security. SSLContext defaults to minimum protocol version TLS 1.2. Settings are based on Hynek Schlawack's research.

bpo-43882 [https://bugs.python.org/issue?@action=redirect&bpo=43882]: The presence of newline or tab characters in parts of a URL could allow some forms of attacks.

Following the controlling specification for URLs defined by WHATWG urllib.parse() now removes ASCII newlines and tabs from URLs, preventing such attacks.

bpo-43472 [https://bugs.python.org/issue?@action=redirect&bpo=43472]: Ensures interpreter-level audit hooks receive the cpython.PyInterpreterState_New event when called through the _xxsubinterpreters module.

bpo-43362 [https://bugs.python.org/issue?@action=redirect&bpo=43362]: Fix invalid free in _sha3 module. The issue was introduced in 3.10.0a1. Python 3.9 and earlier are not affected.

bpo-43762 [https://bugs.python.org/issue?@action=redirect&bpo=43762]: Add audit events for sqlite3.connect/handle(), sqlite3.Connection.enable_load_extension(), and sqlite3.Connection.load_extension(). Patch by Erlend E. Aasland.

bpo-43756 [https://bugs.python.org/issue?@action=redirect&bpo=43756]: Add new audit event glob.glob/2 to incorporate the new root_dir and dir_fd arguments added to glob.glob() and glob.iglob().

bpo-36384 [https://bugs.python.org/issue?@action=redirect&bpo=36384]: ipaddress module no longer accepts any leading zeros in IPv4 address strings. Leading zeros are ambiguous and interpreted as octal notation by some libraries. For example the legacy function socket.inet_aton() treats leading zeros as octal notation. glibc implementation of modern inet_pton() does not accept any leading zeros. For a while the ipaddress module used to accept ambiguous leading zeros.

bpo-43075 [https://bugs.python.org/issue?@action=redirect&bpo=43075]: Fix Regular Expression Denial of Service (ReDoS) vulnerability in urllib.request.AbstractBasicAuthHandler. The ReDoS-vulnerable regex has quadratic worst-case complexity and it allows cause a denial of service when identifying crafted invalid RFCs. This ReDoS issue is on the client side and needs remote attackers to control the HTTP server.

bpo-42800 [https://bugs.python.org/issue?@action=redirect&bpo=42800]: Audit hooks are now fired for frame.f_code, traceback.tb_frame, and generator code/frame attribute access.

bpo-37363 [https://bugs.python.org/issue?@action=redirect&bpo=37363]: Add audit events to the http.client module.

Core and Builtins

bpo-43977 [https://bugs.python.org/issue?@action=redirect&bpo=43977]: Prevent classes being both a sequence and a mapping when pattern matching.

bpo-43977 [https://bugs.python.org/issue?@action=redirect&bpo=43977]: Use tp_flags on the class object to determine if the subject is a sequence or mapping when pattern matching. Avoids the need to import collections.abc when pattern matching.

bpo-43892 [https://bugs.python.org/issue?@action=redirect&bpo=43892]: Restore proper validation of complex literal value patterns when parsing match blocks.

bpo-43933 [https://bugs.python.org/issue?@action=redirect&bpo=43933]: Set frame.f_lineno to the line number of the 'with' kweyword when executing the call to __exit__.

bpo-43933 [https://bugs.python.org/issue?@action=redirect&bpo=43933]: If the current position in a frame has no line number then set the f_lineno attribute to None, instead of -1, to conform to PEP 626. This should not normally be possible, but might occur in some unusual circumstances.

bpo-43963 [https://bugs.python.org/issue?@action=redirect&bpo=43963]: Importing the _signal module in a subinterpreter has no longer side effects.

bpo-42739 [https://bugs.python.org/issue?@action=redirect&bpo=42739]: The internal representation of line number tables is changed to not use sentinels, and an explicit length parameter is added to the out of process API function PyLineTable_InitAddressRange. This makes the handling of line number tables more robust in some circumstances.

Library

bpo-43908 [https://bugs.python.org/issue?@action=redirect&bpo=43908]: Make re types immutable. Patch by Erlend E. Aasland.

bpo-43908 [https://bugs.python.org/issue?@action=redirect&bpo=43908]: Make the array.array type immutable. Patch by Erlend E. Aasland.

Core and Builtins

bpo-43901 [https://bugs.python.org/issue?@action=redirect&bpo=43901]: Change class and module objects to lazy-create empty annotations dicts on demand. The annotations dicts are stored in the object's __dict__ for backwards compatibility.

bpo-43892 [https://bugs.python.org/issue?@action=redirect&bpo=43892]: Match patterns now use new dedicated AST nodes (MatchValue, MatchSingleton, MatchSequence, MatchStar, MatchMapping, MatchClass) rather than reusing expression AST nodes. MatchAs and MatchOr are now defined as pattern nodes rather than as expression nodes. Patch by Nick Coghlan.

bpo-42725 [https://bugs.python.org/issue?@action=redirect&bpo=42725]: Usage of await/yield/yield from and named expressions within an annotation is now forbidden when PEP 563 is activated.

bpo-43754 [https://bugs.python.org/issue?@action=redirect&bpo=43754]: When performing structural pattern matching (PEP 634 [https://peps.python.org/pep-0634/]), captured names are now left unbound until the entire pattern has matched successfully.

bpo-42737 [https://bugs.python.org/issue?@action=redirect&bpo=42737]: Annotations for complex targets (everything beside simple names) no longer cause any runtime effects with from __future__ import annotations.

bpo-43914 [https://bugs.python.org/issue?@action=redirect&bpo=43914]: SyntaxError exceptions raised by the interpreter will highlight the full error range of the expression that constitutes the syntax error itself, instead of just where the problem is detected. Patch by Pablo Galindo.

bpo-38605 [https://bugs.python.org/issue?@action=redirect&bpo=38605]: Revert making from __future__ import annotations the default. This follows the Steering Council decision to postpone PEP 563 changes to at least Python 3.11. See the original email for more information regarding the decision: https://mail.python.org/archives/list/python-dev@python.org/thread/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/. Patch by Pablo Galindo.

bpo-43475 [https://bugs.python.org/issue?@action=redirect&bpo=43475]: Hashes of NaN values now depend on object identity. Formerly, they always hashed to 0 even though NaN values are not equal to one another. Having the same hash for unequal values caused pile-ups in hash tables.

bpo-43859 [https://bugs.python.org/issue?@action=redirect&bpo=43859]: Improve the error message for IndentationError exceptions. Patch by Pablo Galindo

bpo-41323 [https://bugs.python.org/issue?@action=redirect&bpo=41323]: Constant tuple folding in bytecode optimizer now reuses tuple in constant table.

bpo-43846 [https://bugs.python.org/issue?@action=redirect&bpo=43846]: Data stack usage is much reduced for large literal and call expressions.

bpo-38530 [https://bugs.python.org/issue?@action=redirect&bpo=38530]: When printing NameError raised by the interpreter, PyErr_Display() will offer suggestions of similar variable names in the function that the exception was raised from. Patch by Pablo Galindo

bpo-43823 [https://bugs.python.org/issue?@action=redirect&bpo=43823]: Improve syntax errors for invalid dictionary literals. Patch by Pablo Galindo.

bpo-43822 [https://bugs.python.org/issue?@action=redirect&bpo=43822]: Improve syntax errors in the parser for missing commas between expressions. Patch by Pablo Galindo.

bpo-43798 [https://bugs.python.org/issue?@action=redirect&bpo=43798]: ast.alias nodes now include source location metadata attributes e.g. lineno, col_offset.

bpo-43797 [https://bugs.python.org/issue?@action=redirect&bpo=43797]: Improve SyntaxError error messages for invalid comparisons. Patch by Pablo Galindo.

bpo-43760 [https://bugs.python.org/issue?@action=redirect&bpo=43760]: Move the flag for checking whether tracing is enabled to the C stack, from the heap. Should speed up dispatch in the interpreter.

bpo-43682 [https://bugs.python.org/issue?@action=redirect&bpo=43682]: Static methods (@staticmethod) and class methods (@classmethod) now inherit the method attributes (__module__, __name__, __qualname__, __doc__, __annotations__) and have a new __wrapped__ attribute. Patch by Victor Stinner.

bpo-43751 [https://bugs.python.org/issue?@action=redirect&bpo=43751]: Fixed a bug where anext(ait, default) would erroneously return None.

bpo-42128 [https://bugs.python.org/issue?@action=redirect&bpo=42128]: __match_args__ is no longer allowed to be a list.

bpo-43683 [https://bugs.python.org/issue?@action=redirect&bpo=43683]: Add GEN_START opcode. Marks start of generator, including async, or coroutine and handles sending values to a newly created generator or coroutine.

Library

bpo-43105 [https://bugs.python.org/issue?@action=redirect&bpo=43105]: Importlib now resolves relative paths when creating module spec objects from file locations.

Core and Builtins

bpo-43682 [https://bugs.python.org/issue?@action=redirect&bpo=43682]: Static methods (@staticmethod) are now callable as regular functions. Patch by Victor Stinner.

bpo-42609 [https://bugs.python.org/issue?@action=redirect&bpo=42609]: Prevented crashes in the AST validator and optimizer when compiling some absurdly long expressions like "+0"*1000000. RecursionError is now raised instead.

bpo-38530 [https://bugs.python.org/issue?@action=redirect&bpo=38530]: When printing AttributeError, PyErr_Display() will offer suggestions of similar attribute names in the object that the exception was raised from. Patch by Pablo Galindo

Library

bpo-44015 [https://bugs.python.org/issue?@action=redirect&bpo=44015]: In @dataclass(), raise a TypeError if KW_ONLY is specified more than once.

bpo-25478 [https://bugs.python.org/issue?@action=redirect&bpo=25478]: Added a total() method to collections.Counter() to compute the sum of the counts.

bpo-43733 [https://bugs.python.org/issue?@action=redirect&bpo=43733]: Change netrc.netrc to use UTF-8 encoding before using locale encoding.

bpo-43979 [https://bugs.python.org/issue?@action=redirect&bpo=43979]: Removed an unnecessary list comprehension before looping from urllib.parse.parse_qsl(). Patch by Christoph Zwerschke and Donghee Na.

bpo-43993 [https://bugs.python.org/issue?@action=redirect&bpo=43993]: Update bundled pip to 21.1.1.

bpo-43957 [https://bugs.python.org/issue?@action=redirect&bpo=43957]: [Enum] Deprecate TypeError when non-member is used in a containment check; In 3.12 True or False will be returned instead, and containment will return True if the value is either a member of that enum or one of its members' value.

bpo-42904 [https://bugs.python.org/issue?@action=redirect&bpo=42904]: For backwards compatibility with previous minor versions of Python, if typing.get_type_hints() receives no namespace dictionary arguments, typing.get_type_hints() will search through the global then local namespaces during evaluation of stringized type annotations (string forward references) inside a class.

bpo-43945 [https://bugs.python.org/issue?@action=redirect&bpo=43945]: [Enum] Deprecate non-standard mixin format() behavior: in 3.12 the enum member, not the member's value, will be used for format() calls.

bpo-41139 [https://bugs.python.org/issue?@action=redirect&bpo=41139]: Deprecate undocumented cgi.log() API.

bpo-43937 [https://bugs.python.org/issue?@action=redirect&bpo=43937]: Fixed the turtle module working with non-default root window.

bpo-43930 [https://bugs.python.org/issue?@action=redirect&bpo=43930]: Update bundled pip to 21.1 and setuptools to 56.0.0

bpo-43907 [https://bugs.python.org/issue?@action=redirect&bpo=43907]: Fix a bug in the pure-Python pickle implementation when using protocol 5, where bytearray instances that occur several time in the pickled object graph would incorrectly unpickle into repeated copies of the bytearray object.

bpo-43926 [https://bugs.python.org/issue?@action=redirect&bpo=43926]: In importlib.metadata, provide a uniform interface to Description, allow for any field to be encoded with multiline values, remove continuation lines from multiline values, and add a .json property for easy access to the PEP 566 JSON-compatible form. Sync with importlib_metadata 4.0.

bpo-43920 [https://bugs.python.org/issue?@action=redirect&bpo=43920]: OpenSSL 3.0.0: load_verify_locations() now returns a consistent error message when cadata contains no valid certificate.

bpo-43607 [https://bugs.python.org/issue?@action=redirect&bpo=43607]: urllib can now convert Windows paths with \\?\ prefixes into URL paths.

bpo-43817 [https://bugs.python.org/issue?@action=redirect&bpo=43817]: Add inspect.get_annotations(), which safely computes the annotations defined on an object. It works around the quirks of accessing the annotations from various types of objects, and makes very few assumptions about the object passed in. inspect.get_annotations() can also correctly un-stringize stringized annotations.

inspect.signature(), inspect.from_callable(), and inspect.from_function() now call inspect.get_annotations() to retrieve annotations. This means inspect.signature() and inspect.from_callable() can now un-stringize stringized annotations, too.

bpo-43284 [https://bugs.python.org/issue?@action=redirect&bpo=43284]: platform.win32_ver derives the windows version from sys.getwindowsversion().platform_version which in turn derives the version from kernel32.dll (which can be of a different version than Windows itself). Therefore change the platform.win32_ver to determine the version using the platform module's _syscmd_ver private function to return an accurate version.

bpo-42854 [https://bugs.python.org/issue?@action=redirect&bpo=42854]: The ssl module now uses SSL_read_ex and SSL_write_ex internally. The functions support reading and writing of data larger than 2 GB. Writing zero-length data no longer fails with a protocol violation error.

bpo-42333 [https://bugs.python.org/issue?@action=redirect&bpo=42333]: Port _ssl extension module to multiphase initialization.

bpo-43880 [https://bugs.python.org/issue?@action=redirect&bpo=43880]: ssl now raises DeprecationWarning for OP_NO_SSL/TLS* options, old TLS versions, old protocols, and other features that have been deprecated since Python 3.6, 3.7, or OpenSSL 1.1.0.

bpo-41559 [https://bugs.python.org/issue?@action=redirect&bpo=41559]: PEP 612 [https://peps.python.org/pep-0612/] is now implemented purely in Python; builtin types.GenericAlias objects no longer include typing.ParamSpec in __parameters__ (with the exception of collections.abc.Callable's GenericAlias). This means previously invalid uses of ParamSpec (such as list[P]) which worked in earlier versions of Python 3.10 alpha, will now raise TypeError during substitution.

bpo-43867 [https://bugs.python.org/issue?@action=redirect&bpo=43867]: The multiprocessing Server class now explicitly catches SystemExit and closes the client connection in this case. It happens when the Server.serve_client() method reaches the end of file (EOF).

bpo-40443 [https://bugs.python.org/issue?@action=redirect&bpo=40443]: Remove unused imports: pyclbr no longer uses copy, and typing no longer uses ast. Patch by Victor Stinner.

bpo-43820 [https://bugs.python.org/issue?@action=redirect&bpo=43820]: Remove an unneeded copy of the namespace passed to dataclasses.make_dataclass().

bpo-43787 [https://bugs.python.org/issue?@action=redirect&bpo=43787]: Add __iter__() method to bz2.BZ2File, gzip.GzipFile, and lzma.LZMAFile. It makes iterating them about 2x faster. Patch by Inada Naoki.

bpo-43680 [https://bugs.python.org/issue?@action=redirect&bpo=43680]: Deprecate io.OpenWrapper and _pyio.OpenWrapper: use io.open and _pyio.open instead. Until Python 3.9, _pyio.open was not a static method and builtins.open was set to OpenWrapper to not become a bound method when set to a class variable. _io.open is a built-in function whereas _pyio.open is a Python function. In Python 3.10, _pyio.open() is now a static method, and builtins.open() is now io.open().

bpo-43680 [https://bugs.python.org/issue?@action=redirect&bpo=43680]: The Python _pyio.open() function becomes a static method to behave as io.open() built-in function: don't become a bound method when stored as a class variable. It becomes possible since static methods are now callable in Python 3.10. Moreover, _pyio.OpenWrapper() becomes a simple alias to _pyio.open(). Patch by Victor Stinner.

bpo-41515 [https://bugs.python.org/issue?@action=redirect&bpo=41515]: Fix KeyError raised in typing.get_type_hints() due to synthetic modules that don't appear in sys.modules.

bpo-43776 [https://bugs.python.org/issue?@action=redirect&bpo=43776]: When subprocess.Popen args are provided as a string or as pathlib.Path, the Popen instance repr now shows the right thing.

bpo-42248 [https://bugs.python.org/issue?@action=redirect&bpo=42248]: [Enum] ensure exceptions raised in _missing__ are released

bpo-43744 [https://bugs.python.org/issue?@action=redirect&bpo=43744]: fix issue with enum member name matching the start of a private variable name

bpo-43772 [https://bugs.python.org/issue?@action=redirect&bpo=43772]: Fixed the return value of TypeVar.__ror__. Patch by Jelle Zijlstra.

bpo-43764 [https://bugs.python.org/issue?@action=redirect&bpo=43764]: Add match_args parameter to @dataclass decorator to allow suppression of __match_args__ generation.

bpo-43799 [https://bugs.python.org/issue?@action=redirect&bpo=43799]: OpenSSL 3.0.0: define OPENSSL_API_COMPAT 1.1.1 to suppress deprecation warnings. Python requires OpenSSL 1.1.1 APIs.

bpo-43478 [https://bugs.python.org/issue?@action=redirect&bpo=43478]: Mocks can no longer be used as the specs for other Mocks. As a result, an already-mocked object cannot have an attribute mocked using autospec=True or be the subject of a create_autospec(...) call. This can uncover bugs in tests since these Mock-derived Mocks will always pass certain tests (e.g. isinstance()) and builtin assert functions (e.g. assert_called_once_with) will unconditionally pass.

bpo-43794 [https://bugs.python.org/issue?@action=redirect&bpo=43794]: Add ssl.OP_IGNORE_UNEXPECTED_EOF constants (OpenSSL 3.0.0)

bpo-43785 [https://bugs.python.org/issue?@action=redirect&bpo=43785]: Improve bz2.BZ2File performance by removing the RLock from BZ2File. This makes BZ2File thread unsafe in the face of multiple simultaneous readers or writers, just like its equivalent classes in gzip and lzma have always been. Patch by Inada Naoki.

bpo-43789 [https://bugs.python.org/issue?@action=redirect&bpo=43789]: OpenSSL 3.0.0: Don't call the password callback function a second time when first call has signaled an error condition.

bpo-43788 [https://bugs.python.org/issue?@action=redirect&bpo=43788]: The header files for ssl error codes are now OpenSSL version-specific. Exceptions will now show correct reason and library codes. The make_ssl_data.py script has been rewritten to use OpenSSL's text file with error codes.

bpo-43766 [https://bugs.python.org/issue?@action=redirect&bpo=43766]: Implement PEP 647 [https://peps.python.org/pep-0647/] in the typing module by adding TypeGuard.

bpo-25264 [https://bugs.python.org/issue?@action=redirect&bpo=25264]: os.path.realpath() now accepts a strict keyword-only argument. When set to True, OSError is raised if a path doesn't exist or a symlink loop is encountered.

bpo-43780 [https://bugs.python.org/issue?@action=redirect&bpo=43780]: In importlib.metadata, incorporate changes from importlib_metadata 3.10: Add mtime-based caching during distribution discovery. Flagged use of dict result from entry_points() as deprecated.

gh-47383 [https://github.com/python/cpython/issues/47383]: The P.args and P.kwargs attributes of typing.ParamSpec are now instances of the new classes typing.ParamSpecArgs and typing.ParamSpecKwargs, which enables a more useful repr(). Patch by Jelle Zijlstra.

bpo-43731 [https://bugs.python.org/issue?@action=redirect&bpo=43731]: Add an encoding parameter logging.fileConfig().

bpo-43712 [https://bugs.python.org/issue?@action=redirect&bpo=43712]: Add encoding and errors parameters to fileinput.input() and fileinput.FileInput.

bpo-38659 [https://bugs.python.org/issue?@action=redirect&bpo=38659]: A simple_enum decorator is added to the enum module to convert a normal class into an Enum. test_simple_enum added to test simple enums against a corresponding normal Enum. Standard library modules updated to use simple_enum.

bpo-43764 [https://bugs.python.org/issue?@action=redirect&bpo=43764]: Fix an issue where __match_args__ generation could fail for some dataclasses.

bpo-43752 [https://bugs.python.org/issue?@action=redirect&bpo=43752]: Fix sqlite3 regression for zero-sized blobs with converters, where b"" was returned instead of None. The regression was introduced by PR 24723. Patch by Erlend E. Aasland.

bpo-43655 [https://bugs.python.org/issue?@action=redirect&bpo=43655]: tkinter dialog windows are now recognized as dialogs by window managers on macOS and X Window.

bpo-43723 [https://bugs.python.org/issue?@action=redirect&bpo=43723]: The following threading methods are now deprecated and should be replaced:

currentThread => threading.current_thread()

activeCount => threading.active_count()

Condition.notifyAll => threading.Condition.notify_all()

Event.isSet => threading.Event.is_set()

Thread.setName => threading.Thread.name

thread.getName => threading.Thread.name

Thread.isDaemon => threading.Thread.daemon

Thread.setDaemon => threading.Thread.daemon

Patch by Jelle Zijlstra.

bpo-2135 [https://bugs.python.org/issue?@action=redirect&bpo=2135]: Deprecate find_module() and find_loader() implementations in importlib and zipimport.

bpo-43534 [https://bugs.python.org/issue?@action=redirect&bpo=43534]: turtle.textinput() and turtle.numinput() create now a transient window working on behalf of the canvas window.

bpo-43532 [https://bugs.python.org/issue?@action=redirect&bpo=43532]: Add the ability to specify keyword-only fields to dataclasses. These fields will become keyword-only arguments to the generated __init__.

bpo-43522 [https://bugs.python.org/issue?@action=redirect&bpo=43522]: Fix problem with hostname_checks_common_name. OpenSSL does not copy hostflags from struct SSL_CTX to struct SSL.

bpo-8978 [https://bugs.python.org/issue?@action=redirect&bpo=8978]: Improve error message for tarfile.open() when lzma / bz2 are unavailable. Patch by Anthony Sottile.

bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967]: Allow bytes separator argument in urllib.parse.parse_qs and urllib.parse.parse_qsl when parsing str query strings. Previously, this raised a TypeError.

bpo-43296 [https://bugs.python.org/issue?@action=redirect&bpo=43296]: Improve sqlite3 error handling: sqlite3_value_blob() errors that set SQLITE_NOMEM now raise MemoryError. Patch by Erlend E. Aasland.

bpo-43312 [https://bugs.python.org/issue?@action=redirect&bpo=43312]: New functions sysconfig.get_preferred_scheme() and sysconfig.get_default_scheme() are added to query a platform for its preferred "user", "home", and "prefix" (default) scheme names.

bpo-43265 [https://bugs.python.org/issue?@action=redirect&bpo=43265]: Improve sqlite3.Connection.backup() error handling. The error message for non-existent target database names is now unknown database <database name> instead of SQL logic error. Patch by Erlend E. Aasland.

bpo-41282 [https://bugs.python.org/issue?@action=redirect&bpo=41282]: Install schemes in distutils.command.install are now loaded from sysconfig.

bpo-41282 [https://bugs.python.org/issue?@action=redirect&bpo=41282]: distutils.sysconfig has been merged to sysconfig.

bpo-43176 [https://bugs.python.org/issue?@action=redirect&bpo=43176]: Fixed processing of a dataclass that inherits from a frozen dataclass with no fields. It is now correctly detected as an error.

bpo-43080 [https://bugs.python.org/issue?@action=redirect&bpo=43080]: pprint now has support for dataclasses.dataclass. Patch by Lewis Gaul.

bpo-39950 [https://bugs.python.org/issue?@action=redirect&bpo=39950]: Add pathlib.Path.hardlink_to() method that supersedes link_to(). The new method has the same argument order as symlink_to().

bpo-42904 [https://bugs.python.org/issue?@action=redirect&bpo=42904]: typing.get_type_hints() now checks the local namespace of a class when evaluating PEP 563 [https://peps.python.org/pep-0563/] annotations inside said class.

bpo-42269 [https://bugs.python.org/issue?@action=redirect&bpo=42269]: Add slots parameter to dataclasses.dataclass decorator to automatically generate __slots__ for class. Patch provided by Yurii Karabas.

bpo-39529 [https://bugs.python.org/issue?@action=redirect&bpo=39529]: Deprecated use of asyncio.get_event_loop() without running event loop. Emit deprecation warning for asyncio functions which implicitly create a Future or Task objects if there is no running event loop and no explicit loop argument is passed: ensure_future(), wrap_future(), gather(), shield(), as_completed() and constructors of Future, Task, StreamReader, StreamReaderProtocol.

bpo-18369 [https://bugs.python.org/issue?@action=redirect&bpo=18369]: Certificate and PrivateKey classes were added to the ssl module. Certificates and keys can now be loaded from memory buffer, too.

bpo-41486 [https://bugs.python.org/issue?@action=redirect&bpo=41486]: Use a new output buffer management code for bz2 / lzma / zlib modules, and add .readall() function to _compression.DecompressReader class. These bring some performance improvements. Patch by Ma Lin.

bpo-31870 [https://bugs.python.org/issue?@action=redirect&bpo=31870]: The ssl.get_server_certificate() function now has a timeout parameter.

bpo-41735 [https://bugs.python.org/issue?@action=redirect&bpo=41735]: Fix thread locks in zlib module may go wrong in rare case. Patch by Ma Lin.

bpo-36470 [https://bugs.python.org/issue?@action=redirect&bpo=36470]: Fix dataclasses with InitVars and replace(). Patch by Claudiu Popa.

bpo-40849 [https://bugs.python.org/issue?@action=redirect&bpo=40849]: Expose X509_V_FLAG_PARTIAL_CHAIN ssl flag

bpo-35114 [https://bugs.python.org/issue?@action=redirect&bpo=35114]: ssl.RAND_status() now returns a boolean value (as documented) instead of 1 or 0.

bpo-39906 [https://bugs.python.org/issue?@action=redirect&bpo=39906]: pathlib.Path.stat() and chmod() now accept a follow_symlinks keyword-only argument for consistency with corresponding functions in the os module.

bpo-39899 [https://bugs.python.org/issue?@action=redirect&bpo=39899]: os.path.expanduser() now refuses to guess Windows home directories if the basename of current user's home directory does not match their username.

pathlib.Path.expanduser() and home() now consistently raise RuntimeError exception when a home directory cannot be resolved. Previously a KeyError exception could be raised on Windows when the "USERNAME" environment variable was unset.

bpo-36076 [https://bugs.python.org/issue?@action=redirect&bpo=36076]: Added SNI support to ssl.get_server_certificate().

bpo-38490 [https://bugs.python.org/issue?@action=redirect&bpo=38490]: Covariance, Pearson's correlation, and simple linear regression functionality was added to statistics module. Patch by Tymoteusz Wołodźko.

bpo-33731 [https://bugs.python.org/issue?@action=redirect&bpo=33731]: Provide a locale.localize() function, which converts a normalized number string into a locale format.

bpo-32745 [https://bugs.python.org/issue?@action=redirect&bpo=32745]: Fix a regression in the handling of ctypes' ctypes.c_wchar_p type: embedded null characters would cause a ValueError to be raised. Patch by Zackery Spytz.

Documentation

bpo-43987 [https://bugs.python.org/issue?@action=redirect&bpo=43987]: Add "Annotations Best Practices" document as a new HOWTO.

bpo-43977 [https://bugs.python.org/issue?@action=redirect&bpo=43977]: Document the new Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE type flags.

bpo-43959 [https://bugs.python.org/issue?@action=redirect&bpo=43959]: The documentation on the PyContextVar C-API was clarified.

bpo-43938 [https://bugs.python.org/issue?@action=redirect&bpo=43938]: Update dataclasses documentation to express that FrozenInstanceError is derived from AttributeError.

bpo-43778 [https://bugs.python.org/issue?@action=redirect&bpo=43778]: Fix the Sphinx glossary_search extension: create the _static/ sub-directory if it doesn't exist.

bpo-43755 [https://bugs.python.org/issue?@action=redirect&bpo=43755]: Update documentation to reflect that unparenthesized lambda expressions can no longer be the expression part in an if clause in comprehensions and generator expressions since Python 3.9.

bpo-43739 [https://bugs.python.org/issue?@action=redirect&bpo=43739]: Fixing the example code in Doc/extending/extending.rst to declare and initialize the pmodule variable to be of the right type.

Tests

bpo-43961 [https://bugs.python.org/issue?@action=redirect&bpo=43961]: Fix test_logging.test_namer_rotator_inheritance() on Windows: use os.replace() rather than os.rename(). Patch by Victor Stinner.

bpo-43842 [https://bugs.python.org/issue?@action=redirect&bpo=43842]: Fix a race condition in the SMTP test of test_logging. Don't close a file descriptor (socket) from a different thread while asyncore.loop() is polling the file descriptor. Patch by Victor Stinner.

bpo-43843 [https://bugs.python.org/issue?@action=redirect&bpo=43843]: test.libregrtest now marks a test as ENV_CHANGED (altered the execution environment) if a thread raises an exception but does not catch it. It sets a hook on threading.excepthook(). Use --fail-env-changed option to mark the test as failed. Patch by Victor Stinner.

bpo-43811 [https://bugs.python.org/issue?@action=redirect&bpo=43811]: Tests multiple OpenSSL versions on GitHub Actions. Use ccache to speed up testing.

bpo-43791 [https://bugs.python.org/issue?@action=redirect&bpo=43791]: OpenSSL 3.0.0: Disable testing of legacy protocols TLS 1.0 and 1.1. Tests are failing with TLSV1_ALERT_INTERNAL_ERROR.

Build

bpo-43567 [https://bugs.python.org/issue?@action=redirect&bpo=43567]: Improved generated code refresh (AST/tokens/opcodes/keywords) on Windows.

bpo-43669 [https://bugs.python.org/issue?@action=redirect&bpo=43669]: Implement PEP 644 [https://peps.python.org/pep-0644/]. Python now requires OpenSSL 1.1.1 or newer.

Windows

bpo-35306 [https://bugs.python.org/issue?@action=redirect&bpo=35306]: Adds additional arguments to os.startfile() function.

bpo-43538 [https://bugs.python.org/issue?@action=redirect&bpo=43538]: Avoid raising errors from pathlib.Path.exists() when passed an invalid filename.

bpo-38822 [https://bugs.python.org/issue?@action=redirect&bpo=38822]: Fixed os.stat() failing on inaccessible directories with a trailing slash, rather than falling back to the parent directory's metadata. This implicitly affected os.path.exists() and os.path.isdir().

bpo-26227 [https://bugs.python.org/issue?@action=redirect&bpo=26227]: Fixed decoding of host names in socket.gethostbyaddr() and socket.gethostbyname_ex().

bpo-40432 [https://bugs.python.org/issue?@action=redirect&bpo=40432]: Updated pegen regeneration script on Windows to find and use Python 3.8 or higher. Prior to this, pegen regeneration already required 3.8 or higher, but the script may have used lower versions of Python.

bpo-43745 [https://bugs.python.org/issue?@action=redirect&bpo=43745]: Actually updates Windows release to OpenSSL 1.1.1k. Earlier releases were mislabelled and actually included 1.1.1i again.

bpo-43652 [https://bugs.python.org/issue?@action=redirect&bpo=43652]: Update Tcl and Tk to 8.6.11 in Windows installer.

bpo-43492 [https://bugs.python.org/issue?@action=redirect&bpo=43492]: Upgrade Windows installer to use SQLite 3.35.5.

bpo-30555 [https://bugs.python.org/issue?@action=redirect&bpo=30555]: Fix WindowsConsoleIO errors in the presence of fd redirection. Patch by Segev Finer.

macOS

bpo-42119 [https://bugs.python.org/issue?@action=redirect&bpo=42119]: Fix check for macOS SDK paths when building Python. Narrow search to match contents of SDKs, namely only files in /System/Library, /System/IOSSupport, and /usr other than /usr/local. Previously, anything under /System was assumed to be in an SDK which causes problems with the new file system layout in 10.15+ where user file systems may appear to be mounted under /System. Paths in /Library were also incorrectly treated as SDK locations.

bpo-43568 [https://bugs.python.org/issue?@action=redirect&bpo=43568]: Drop support for MACOSX_DEPLOYMENT_TARGET < 10.3

bpo-44009 [https://bugs.python.org/issue?@action=redirect&bpo=44009]: Provide "python3.x-intel64" executable to allow reliably forcing macOS universal2 framework builds to run under Rosetta 2 Intel-64 emulation on Apple Silicon Macs. This can be useful for testing or when universal2 wheels are not yet available.

bpo-43851 [https://bugs.python.org/issue?@action=redirect&bpo=43851]: Build SQLite with SQLITE_OMIT_AUTOINIT on macOS. Patch by Erlend E. Aasland.

bpo-43492 [https://bugs.python.org/issue?@action=redirect&bpo=43492]: Update macOS installer to use SQLite 3.35.4.

bpo-42235 [https://bugs.python.org/issue?@action=redirect&bpo=42235]: Mac/BuildScript/build-installer.py will now use "--enable-optimizations" and --with-lto when building on macOS 10.15 or later.

IDLE

bpo-37903 [https://bugs.python.org/issue?@action=redirect&bpo=37903]: Add mouse actions to the shell sidebar. Left click and optional drag selects one or more lines, as with the editor line number sidebar. Right click after selecting raises a context menu with 'copy with prompts'. This zips together prompts from the sidebar with lines from the selected text.

bpo-43981 [https://bugs.python.org/issue?@action=redirect&bpo=43981]: Fix reference leak in test_sidebar and test_squeezer. Patches by Terry Jan Reedy and Pablo Galindo

bpo-37892 [https://bugs.python.org/issue?@action=redirect&bpo=37892]: Indent IDLE Shell input with spaces instead of tabs

bpo-43655 [https://bugs.python.org/issue?@action=redirect&bpo=43655]: IDLE dialog windows are now recognized as dialogs by window managers on macOS and X Window.

bpo-37903 [https://bugs.python.org/issue?@action=redirect&bpo=37903]: IDLE's shell now shows prompts in a separate side-bar.

C API

bpo-43916 [https://bugs.python.org/issue?@action=redirect&bpo=43916]: Add a new Py_TPFLAGS_DISALLOW_INSTANTIATION type flag to disallow creating type instances. Patch by Victor Stinner.

bpo-43774 [https://bugs.python.org/issue?@action=redirect&bpo=43774]: Remove the now unused PYMALLOC_DEBUG macro. Debug hooks on memory allocators are now installed by default if Python is built in debug mode (if Py_DEBUG macro is defined). Moreover, they can now be used on Python build in release mode (ex: using PYTHONMALLOC=debug environment variable).

bpo-43962 [https://bugs.python.org/issue?@action=redirect&bpo=43962]: _PyInterpreterState_IDIncref() now calls _PyInterpreterState_IDInitref() and always increments id_refcount. Previously, calling _xxsubinterpreters.get_current() could create an id_refcount inconsistency when a _xxsubinterpreters.InterpreterID object was deallocated. Patch by Victor Stinner.

bpo-28254 [https://bugs.python.org/issue?@action=redirect&bpo=28254]: Add new C-API functions to control the state of the garbage collector: PyGC_Enable(), PyGC_Disable(), PyGC_IsEnabled(), corresponding to the functions in the gc module.

bpo-43908 [https://bugs.python.org/issue?@action=redirect&bpo=43908]: Introduce Py_TPFLAGS_IMMUTABLETYPE flag for immutable type objects, and modify PyType_Ready() to set it for static types. Patch by Erlend E. Aasland.

bpo-43795 [https://bugs.python.org/issue?@action=redirect&bpo=43795]: PyMem_Calloc() is now available in the limited C API (Py_LIMITED_API).

bpo-43868 [https://bugs.python.org/issue?@action=redirect&bpo=43868]: PyOS_ReadlineFunctionPointer() is no longer exported by limited C API headers and by python3.dll on Windows. Like any function that takes FILE*, it is not part of the stable ABI.

bpo-43795 [https://bugs.python.org/issue?@action=redirect&bpo=43795]: Stable ABI and limited API definitions are generated from a central manifest (PEP 652 [https://peps.python.org/pep-0652/]).

bpo-43753 [https://bugs.python.org/issue?@action=redirect&bpo=43753]: Add the Py_Is(x, y) function to test if the x object is the y object, the same as x is y in Python. Add also the Py_IsNone(), Py_IsTrue(), Py_IsFalse() functions to test if an object is, respectively, the None singleton, the True singleton or the False singleton. Patch by Victor Stinner.

Python 3.10.0 alpha 7

Release date: 2021-04-05

Security

bpo-42988 [https://bugs.python.org/issue?@action=redirect&bpo=42988]: CVE 2021-3426 [https://www.cve.org/CVERecord?id=CVE-2021-3426]: Remove the getfile feature of the pydoc module which could be abused to read arbitrary files on the disk (directory traversal vulnerability). Moreover, even source code of Python modules can contain sensitive data like passwords. Vulnerability reported by David Schwörer.

bpo-43285 [https://bugs.python.org/issue?@action=redirect&bpo=43285]: ftplib no longer trusts the IP address value returned from the server in response to the PASV command by default. This prevents a malicious FTP server from using the response to probe IPv4 address and port combinations on the client network.

Code that requires the former vulnerable behavior may set a trust_server_pasv_ipv4_address attribute on their ftplib.FTP instances to True to re-enable it.

bpo-43439 [https://bugs.python.org/issue?@action=redirect&bpo=43439]: Add audit hooks for gc.get_objects(), gc.get_referrers() and gc.get_referents(). Patch by Pablo Galindo.

Core and Builtins

bpo-27129 [https://bugs.python.org/issue?@action=redirect&bpo=27129]: Update CPython bytecode magic number.

bpo-43672 [https://bugs.python.org/issue?@action=redirect&bpo=43672]: Raise ImportWarning when calling find_loader().

bpo-43660 [https://bugs.python.org/issue?@action=redirect&bpo=43660]: Fix crash that happens when replacing sys.stderr with a callable that can remove the object while an exception is being printed. Patch by Pablo Galindo.

bpo-27129 [https://bugs.python.org/issue?@action=redirect&bpo=27129]: The bytecode interpreter uses instruction, rather byte, offsets internally. This reduces the number of EXTENDED_ARG instructions needed and streamlines instruction dispatch a bit.

Library

bpo-40645 [https://bugs.python.org/issue?@action=redirect&bpo=40645]: Fix reference leak in the _hashopenssl extension. Patch by Pablo Galindo.

Core and Builtins

bpo-42134 [https://bugs.python.org/issue?@action=redirect&bpo=42134]: Calls to find_module() by the import system now raise ImportWarning.

bpo-41064 [https://bugs.python.org/issue?@action=redirect&bpo=41064]: Improve the syntax error for invalid usage of double starred elements ('**') in f-strings. Patch by Pablo Galindo.

bpo-43575 [https://bugs.python.org/issue?@action=redirect&bpo=43575]: Speed up calls to map() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-42137 [https://bugs.python.org/issue?@action=redirect&bpo=42137]: The import system now prefers using __spec__ for ModuleType.__repr__ over module_repr().

bpo-43452 [https://bugs.python.org/issue?@action=redirect&bpo=43452]: Added micro-optimizations to _PyType_Lookup() to improve cache lookup performance in the common case of cache hits.

bpo-43555 [https://bugs.python.org/issue?@action=redirect&bpo=43555]: Report the column offset for SyntaxError for invalid line continuation characters. Patch by Pablo Galindo.

bpo-43517 [https://bugs.python.org/issue?@action=redirect&bpo=43517]: Fix misdetection of circular imports when using from pkg.mod import attr, which caused false positives in non-trivial multi-threaded code.

bpo-43497 [https://bugs.python.org/issue?@action=redirect&bpo=43497]: Emit SyntaxWarnings for assertions with tuple constants, this is a regression introduced in python3.7

bpo-39316 [https://bugs.python.org/issue?@action=redirect&bpo=39316]: Tracing now has correct line numbers for attribute accesses when the attribute is on a different line from the object. Improves debugging and profiling for multi-line method chains.

bpo-35883 [https://bugs.python.org/issue?@action=redirect&bpo=35883]: Python no longer fails at startup with a fatal error if a command line argument contains an invalid Unicode character. The Py_DecodeLocale() function now escapes byte sequences which would be decoded as Unicode characters outside the [U+0000; U+10ffff] range.

bpo-43410 [https://bugs.python.org/issue?@action=redirect&bpo=43410]: Fix a bug that was causing the parser to crash when emitting syntax errors when reading input from stdin. Patch by Pablo Galindo

bpo-43406 [https://bugs.python.org/issue?@action=redirect&bpo=43406]: Fix a possible race condition where PyErr_CheckSignals tries to execute a non-Python signal handler.

bpo-42128 [https://bugs.python.org/issue?@action=redirect&bpo=42128]: Add __match_args__ to struct sequence objects. Patch by Pablo Galindo.

bpo-43390 [https://bugs.python.org/issue?@action=redirect&bpo=43390]: CPython now sets the SA_ONSTACK flag in PyOS_setsig for the VM's default signal handlers. This is friendlier to other in-process code that an extension module or embedding use could pull in (such as Golang's cgo) where tiny thread stacks are the norm and sigaltstack() has been used to provide for signal handlers. This is a no-op change for the vast majority of processes that don't use sigaltstack.

bpo-43287 [https://bugs.python.org/issue?@action=redirect&bpo=43287]: Speed up calls to filter() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-37448 [https://bugs.python.org/issue?@action=redirect&bpo=37448]: Add a radix tree based memory map to track in-use obmalloc arenas. Use to replace the old implementation of address_in_range(). The radix tree approach makes it easy to increase pool sizes beyond the OS page size. Boosting the pool and arena size allows obmalloc to handle a significantly higher percentage of requests from its ultra-fast paths.

It also has the advantage of eliminating the memory unsanitary behavior of the previous address_in_range(). The old address_in_range() was marked with the annotations _Py_NO_SANITIZE_ADDRESS, _Py_NO_SANITIZE_THREAD, and _Py_NO_SANITIZE_MEMORY. Those annotations are no longer needed.

To disable the radix tree map, set a preprocessor flag as follows: -DWITH_PYMALLOC_RADIX_TREE=0.

Co-authored-by: Tim Peters <tim.peters@gmail.com>

bpo-29988 [https://bugs.python.org/issue?@action=redirect&bpo=29988]: Only handle asynchronous exceptions and requests to drop the GIL when returning from a call or on the back edges of loops. Makes sure that __exit__() is always called in with statements, even for interrupts.

Library

bpo-43720 [https://bugs.python.org/issue?@action=redirect&bpo=43720]: Document various stdlib deprecations in imp, pkgutil, and importlib.util for removal in Python 3.12.

bpo-43433 [https://bugs.python.org/issue?@action=redirect&bpo=43433]: xmlrpc.client.ServerProxy no longer ignores query and fragment in the URL of the server.

bpo-31956 [https://bugs.python.org/issue?@action=redirect&bpo=31956]: The index() method of array.array now has optional start and stop parameters.

bpo-40066 [https://bugs.python.org/issue?@action=redirect&bpo=40066]: Enum: adjust repr() to show only enum and member name (not value, nor angle brackets) and str() to show only member name. Update and improve documentation to match.

bpo-42136 [https://bugs.python.org/issue?@action=redirect&bpo=42136]: Deprecate all module_repr() methods found in importlib as their use is being phased out by Python 3.12.

bpo-35930 [https://bugs.python.org/issue?@action=redirect&bpo=35930]: Raising an exception raised in a "future" instance will create reference cycles.

bpo-41369 [https://bugs.python.org/issue?@action=redirect&bpo=41369]: Finish updating the vendored libmpdec to version 2.5.1. Patch by Stefan Krah.

bpo-43422 [https://bugs.python.org/issue?@action=redirect&bpo=43422]: Revert the _decimal C API which was added in bpo-41324 [https://bugs.python.org/issue?@action=redirect&bpo=41324].

bpo-43577 [https://bugs.python.org/issue?@action=redirect&bpo=43577]: Fix deadlock when using ssl.SSLContext debug callback with ssl.SSLContext.sni_callback().

bpo-43571 [https://bugs.python.org/issue?@action=redirect&bpo=43571]: It's now possible to create MPTCP sockets with IPPROTO_MPTCP

bpo-43542 [https://bugs.python.org/issue?@action=redirect&bpo=43542]: image/heic and image/heif were added to mimetypes.

bpo-40645 [https://bugs.python.org/issue?@action=redirect&bpo=40645]: The hmac module now uses OpenSSL's HMAC implementation when digestmod argument is a hash name or builtin hash function.

bpo-43510 [https://bugs.python.org/issue?@action=redirect&bpo=43510]: Implement PEP 597 [https://peps.python.org/pep-0597/]: Add EncodingWarning warning, -X warn_default_encoding option, PYTHONWARNDEFAULTENCODING environment variable and encoding="locale" argument value.

bpo-43521 [https://bugs.python.org/issue?@action=redirect&bpo=43521]: ast.unparse can now render NaNs and empty sets.

bpo-42914 [https://bugs.python.org/issue?@action=redirect&bpo=42914]: pprint.pprint() gains a new boolean underscore_numbers optional argument to emit integers with thousands separated by an underscore character for improved readability (for example 1_000_000 instead of 1000000).

bpo-41361 [https://bugs.python.org/issue?@action=redirect&bpo=41361]: rotate() calls are now slightly faster due to faster argument parsing.

bpo-43423 [https://bugs.python.org/issue?@action=redirect&bpo=43423]: subprocess.communicate() no longer raises an IndexError when there is an empty stdout or stderr IO buffer during a timeout on Windows.

bpo-27820 [https://bugs.python.org/issue?@action=redirect&bpo=27820]: Fixed long-standing bug of smtplib.SMTP where doing AUTH LOGIN with initial_response_ok=False will fail.

The cause is that SMTP.auth_login _always_ returns a password if provided with a challenge string, thus non-compliant with the standard for AUTH LOGIN.

Also fixes bug with the test for smtpd.

bpo-43445 [https://bugs.python.org/issue?@action=redirect&bpo=43445]: Add frozen modules to sys.stdlib_module_names. For example, add "_frozen_importlib" and "_frozen_importlib_external" names.

bpo-43245 [https://bugs.python.org/issue?@action=redirect&bpo=43245]: Add keyword arguments support to ChainMap.new_child().

bpo-29982 [https://bugs.python.org/issue?@action=redirect&bpo=29982]: Add optional parameter ignore_cleanup_errors to tempfile.TemporaryDirectory() and allow multiple cleanup() attempts. Contributed by C.A.M. Gerlach.

bpo-43428 [https://bugs.python.org/issue?@action=redirect&bpo=43428]: Include changes from importlib_metadata 3.7 [https://importlib-metadata.readthedocs.io/en/latest/history.html#v3-7-0]:

Performance enhancements to distribution discovery.

entry_points only returns unique distributions.

Introduces new EntryPoints object for containing a set of entry points with convenience methods for selecting entry points by group or name. entry_points now returns this object if selection parameters are supplied but continues to return a dict object for compatibility. Users are encouraged to rely on the selection interface. The dict object result is likely to be deprecated in the future.

Added packages_distributions function to return a mapping of packages to the distributions that provide them.

bpo-43332 [https://bugs.python.org/issue?@action=redirect&bpo=43332]: Improves the networking efficiency of http.client when using a proxy via set_tunnel(). Fewer small send calls are made during connection setup.

bpo-43420 [https://bugs.python.org/issue?@action=redirect&bpo=43420]: Improve performance of fractions.Fraction arithmetics for large components. Contributed by Sergey B. Kirpichev.

bpo-43356 [https://bugs.python.org/issue?@action=redirect&bpo=43356]: Allow passing a signal number to _thread.interrupt_main().

bpo-43399 [https://bugs.python.org/issue?@action=redirect&bpo=43399]: Fix ElementTree.extend not working on iterators when using the Python implementation

bpo-43369 [https://bugs.python.org/issue?@action=redirect&bpo=43369]: Improve sqlite3 error handling: If sqlite3_column_text() and sqlite3_column_blob() set SQLITE_NOMEM, MemoryError is now raised. Patch by Erlend E. Aasland.

bpo-43368 [https://bugs.python.org/issue?@action=redirect&bpo=43368]: Fix a regression introduced in PR 24562, where an empty bytestring was fetched as None instead of b'' in sqlite3. Patch by Mariusz Felisiak.

bpo-41282 [https://bugs.python.org/issue?@action=redirect&bpo=41282]: Fixed stacklevel of DeprecationWarning emitted from import distutils.

bpo-42129 [https://bugs.python.org/issue?@action=redirect&bpo=42129]: importlib.resources now honors namespace packages, merging resources from each location in the namespace as introduced in importlib_resources 3.2 and including incidental changes through 5.0.3.

bpo-43295 [https://bugs.python.org/issue?@action=redirect&bpo=43295]: datetime.datetime.strptime() now raises ValueError instead of IndexError when matching 'z' with the %z format specifier.

bpo-43125 [https://bugs.python.org/issue?@action=redirect&bpo=43125]: Return empty string if base64mime.body_encode receive empty bytes

bpo-43084 [https://bugs.python.org/issue?@action=redirect&bpo=43084]: curses.window.enclose() returns now True or False (as was documented) instead of 1 or 0.

bpo-42994 [https://bugs.python.org/issue?@action=redirect&bpo=42994]: Add MIME types for opus, AAC, 3gpp and 3gpp2

bpo-14678 [https://bugs.python.org/issue?@action=redirect&bpo=14678]: Add an invalidate_caches() method to the zipimport.zipimporter class to support importlib.invalidate_caches(). Patch by Desmond Cheong.

bpo-42782 [https://bugs.python.org/issue?@action=redirect&bpo=42782]: Fail fast in shutil.move() to avoid creating destination directories on failure.

bpo-40066 [https://bugs.python.org/issue?@action=redirect&bpo=40066]: Enum's repr() and str() have changed: repr() is now EnumClass.MemberName and str() is MemberName. Additionally, stdlib Enum's whose contents are available as module attributes, such as RegexFlag.IGNORECASE, have their repr() as module.name, e.g. re.IGNORECASE.

bpo-26053 [https://bugs.python.org/issue?@action=redirect&bpo=26053]: Fixed bug where the pdb interactive run command echoed the args from the shell command line, even if those have been overridden at the pdb prompt.

bpo-24160 [https://bugs.python.org/issue?@action=redirect&bpo=24160]: Fixed bug where breakpoints did not persist across multiple debugger sessions in pdb's interactive mode.

bpo-40701 [https://bugs.python.org/issue?@action=redirect&bpo=40701]: When the tempfile.tempdir global variable is set to a value of type bytes, it is now handled consistently. Previously exceptions could be raised from some tempfile APIs when the directory did not already exist in this situation. Also ensures that the tempfile.gettempdir() and tempfile.gettempdirb() functions always return str and bytes respectively.

bpo-39342 [https://bugs.python.org/issue?@action=redirect&bpo=39342]: Expose X509_V_FLAG_ALLOW_PROXY_CERTS as VERIFY_ALLOW_PROXY_CERTS to allow proxy certificate validation as explained in https://docs.openssl.org/1.1.1/man7/proxy-certificates/.

bpo-31861 [https://bugs.python.org/issue?@action=redirect&bpo=31861]: Add builtins.aiter and builtins.anext. Patch by Joshua Bronson (@jab), Daniel Pope (@lordmauve), and Justin Wang (@justin39).

Documentation

bpo-43199 [https://bugs.python.org/issue?@action=redirect&bpo=43199]: Answer "Why is there no goto?" in the Design and History FAQ.

bpo-43407 [https://bugs.python.org/issue?@action=redirect&bpo=43407]: Clarified that a result from time.monotonic(), time.perf_counter(), time.process_time(), or time.thread_time() can be compared with the result from any following call to the same function - not just the next immediate call.

bpo-43354 [https://bugs.python.org/issue?@action=redirect&bpo=43354]: Fix type documentation for Fault.faultCode; the type has to be int instead of str.

bpo-41933 [https://bugs.python.org/issue?@action=redirect&bpo=41933]: Clarified wording of s * n in the Common Sequence Operations

Tests

bpo-37945 [https://bugs.python.org/issue?@action=redirect&bpo=37945]: Fix test_getsetlocale_issue1813() of test_locale: skip the test if setlocale() fails. Patch by Victor Stinner.

bpo-41561 [https://bugs.python.org/issue?@action=redirect&bpo=41561]: Add workaround for Ubuntu's custom OpenSSL security level policy.

Build

bpo-43179 [https://bugs.python.org/issue?@action=redirect&bpo=43179]: Introduce and correctly use ALIGNOF_X in place of SIZEOF_X for alignment-related code in optimized string routines. Patch by Jessica Clarke.

bpo-43631 [https://bugs.python.org/issue?@action=redirect&bpo=43631]: Update macOS, Windows, and CI to OpenSSL 1.1.1k.

bpo-43617 [https://bugs.python.org/issue?@action=redirect&bpo=43617]: Improve configure.ac: Check for presence of autoconf-archive package and remove our copies of M4 macros.

bpo-43466 [https://bugs.python.org/issue?@action=redirect&bpo=43466]: The configure script now supports --with-openssl-rpath option.

bpo-43372 [https://bugs.python.org/issue?@action=redirect&bpo=43372]: Use _freeze_importlib to generate code for the __hello__ module. This approach ensures the code matches the interpreter version. Previously, PYTHON_FOR_REGEN was used to generate the code, which might be wrong. The marshal format for code objects has changed with bpo-42246 [https://bugs.python.org/issue?@action=redirect&bpo=42246], commit 877df851. Update the code and the expected code sizes in ctypes test_frozentable.

Windows

bpo-43440 [https://bugs.python.org/issue?@action=redirect&bpo=43440]: Build sqlite3 with the R*Tree module enabled. Patch by Erlend E. Aasland.

IDLE

bpo-42225 [https://bugs.python.org/issue?@action=redirect&bpo=42225]: Document that IDLE can fail on Unix either from misconfigured IP masquerade rules or failure displaying complex colored (non-ascii) characters.

C API

bpo-43688 [https://bugs.python.org/issue?@action=redirect&bpo=43688]: The limited C API is now supported if Python is built in debug mode (if the Py_DEBUG macro is defined). In the limited C API, the Py_INCREF() and Py_DECREF() functions are now implemented as opaque function calls, rather than accessing directly the PyObject.ob_refcnt member, if Python is built in debug mode and the Py_LIMITED_API macro targets Python 3.10 or newer. It became possible to support the limited C API in debug mode because the PyObject structure is the same in release and debug mode since Python 3.8 (see bpo-36465 [https://bugs.python.org/issue?@action=redirect&bpo=36465]).

The limited C API is still not supported in the --with-trace-refs special build (Py_TRACE_REFS macro).

Patch by Victor Stinner.

bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244]: Remove the pyarena.h header file with functions:

PyArena_New()

PyArena_Free()

PyArena_Malloc()

PyArena_AddPyObject()

These functions were undocumented, excluded from the limited C API, and were only used internally by the compiler. Patch by Victor Stinner.

bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244]: Remove the compiler and parser functions using struct _mod type, because the public AST C API was removed:

PyAST_Compile()

PyAST_CompileEx()

PyAST_CompileObject()

PyFuture_FromAST()

PyFuture_FromASTObject()

PyParser_ASTFromFile()

PyParser_ASTFromFileObject()

PyParser_ASTFromFilename()

PyParser_ASTFromString()

PyParser_ASTFromStringObject()

These functions were undocumented and excluded from the limited C API. Patch by Victor Stinner.

bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244]: Remove ast.h, asdl.h, and Python-ast.h header files. These functions were undocumented and excluded from the limited C API. Most names defined by these header files were not prefixed by Py and so could create names conflicts. For example, Python-ast.h defined a Yield macro which was conflict with the Yield name used by the Windows <winbase.h> header. Use the Python ast module instead. Patch by Victor Stinner.

bpo-43541 [https://bugs.python.org/issue?@action=redirect&bpo=43541]: Fix a PyEval_EvalCodeEx() regression: fix reference counting on builtins. Patch by Victor Stinner.

bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244]: Remove the symtable.h header file and the undocumented functions:

PyST_GetScope()

PySymtable_Build()

PySymtable_BuildObject()

PySymtable_Free()

Py_SymtableString()

Py_SymtableStringObject()

The Py_SymtableString() function was part the stable ABI by mistake but it could not be used, because the symtable.h header file was excluded from the limited C API.

The Python symtable module remains available and is unchanged.

Patch by Victor Stinner.

bpo-43244 [https://bugs.python.org/issue?@action=redirect&bpo=43244]: Remove the PyAST_Validate() function. It is no longer possible to build a AST object (mod_ty type) with the public C API. The function was already excluded from the limited C API (PEP 384 [https://peps.python.org/pep-0384/]). Patch by Victor Stinner.

Python 3.10.0 alpha 6

Release date: 2021-03-01

Security

bpo-42967 [https://bugs.python.org/issue?@action=redirect&bpo=42967]: Fix web cache poisoning vulnerability by defaulting the query args separator to &, and allowing the user to choose a custom separator.

Core and Builtins

bpo-43321 [https://bugs.python.org/issue?@action=redirect&bpo=43321]: Fix SystemError raised when PyArg_Parse*() is used with # but without PY_SSIZE_T_CLEAN defined.

bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346]: PyArg_Parse*() functions now emits DeprecationWarning when u or Z format is used. See PEP 623 [https://peps.python.org/pep-0623/] for detail.

bpo-43277 [https://bugs.python.org/issue?@action=redirect&bpo=43277]: Add a new PySet_CheckExact() function to the C-API to check if an object is an instance of set but not an instance of a subtype. Patch by Pablo Galindo.

bpo-42990 [https://bugs.python.org/issue?@action=redirect&bpo=42990]: The types.FunctionType constructor now inherits the current builtins if the globals dictionary has no "__builtins__" key, rather than using {"None": None} as builtins: same behavior as eval() and exec() functions. Defining a function with def function(...): ... in Python is not affected, globals cannot be overridden with this syntax: it also inherits the current builtins. Patch by Victor Stinner.

bpo-42990 [https://bugs.python.org/issue?@action=redirect&bpo=42990]: Functions have a new __builtins__ attribute which is used to look for builtin symbols when a function is executed, instead of looking into __globals__['__builtins__']. Patch by Mark Shannon and Victor Stinner.

bpo-43149 [https://bugs.python.org/issue?@action=redirect&bpo=43149]: Improve the error message in the parser for exception groups without parentheses. Patch by Pablo Galindo.

bpo-43121 [https://bugs.python.org/issue?@action=redirect&bpo=43121]: Fixed an incorrect SyntaxError message for missing comma in literals. Patch by Pablo Galindo.

Library

bpo-42819 [https://bugs.python.org/issue?@action=redirect&bpo=42819]: readline: Explicitly disable bracketed paste in the interactive interpreter, even if it's set in the inputrc, is enabled by default (eg GNU Readline 8.1), or a user calls readline.read_init_file(). The Python REPL has not implemented bracketed paste support. Also, bracketed mode writes the "\x1b[?2004h" escape sequence into stdout which causes test failures in applications that don't support it. It can still be explicitly enabled by calling readline.parse_and_bind("set enable-bracketed-paste on"). Patch by Dustin Rodrigues.

Core and Builtins

bpo-42808 [https://bugs.python.org/issue?@action=redirect&bpo=42808]: Simple calls to type(object) are now faster due to the vectorcall calling convention. Patch by Dennis Sweeney.

bpo-42217 [https://bugs.python.org/issue?@action=redirect&bpo=42217]: Make the compiler merges same co_code and co_linetable objects in a module like already did for co_consts.

bpo-41972 [https://bugs.python.org/issue?@action=redirect&bpo=41972]: Substring search functions such as str1 in str2 and str2.find(str1) now sometimes use the "Two-Way" string comparison algorithm to avoid quadratic behavior on long strings.

bpo-42128 [https://bugs.python.org/issue?@action=redirect&bpo=42128]: Implement PEP 634 [https://peps.python.org/pep-0634/] (structural pattern matching). Patch by Brandt Bucher.

Library

bpo-40692 [https://bugs.python.org/issue?@action=redirect&bpo=40692]: In the concurrent.futures.ProcessPoolExecutor, validate that multiprocess.synchronize() is available on a given platform and rely on that check in the concurrent.futures test suite so we can run tests that are unrelated to ProcessPoolExecutor on those platforms.

Core and Builtins

bpo-38302 [https://bugs.python.org/issue?@action=redirect&bpo=38302]: If object.__ipow__() returns NotImplemented, the operator will correctly fall back to object.__pow__() and object.__rpow__() as expected.

Library

bpo-43316 [https://bugs.python.org/issue?@action=redirect&bpo=43316]: The python -m gzip command line application now properly fails when detecting an unsupported extension. It exits with a non-zero exit code and prints an error message to stderr.

bpo-43317 [https://bugs.python.org/issue?@action=redirect&bpo=43317]: Set the chunk size for the gzip module main function to io.DEFAULT_BUFFER_SIZE. This is slightly faster than the 1024 bytes constant that was used previously.

bpo-43146 [https://bugs.python.org/issue?@action=redirect&bpo=43146]: Handle None in single-arg versions of print_exception() and format_exception().

bpo-43260 [https://bugs.python.org/issue?@action=redirect&bpo=43260]: Fix TextIOWrapper can not flush internal buffer forever after very large text is written.

bpo-43258 [https://bugs.python.org/issue?@action=redirect&bpo=43258]: Prevent needless allocation of sqlite3 aggregate function context when no rows match an aggregate query. Patch by Erlend E. Aasland.

bpo-43251 [https://bugs.python.org/issue?@action=redirect&bpo=43251]: Improve sqlite3 error handling: sqlite3_column_name() failures now result in MemoryError. Patch by Erlend E. Aasland.

bpo-40956 [https://bugs.python.org/issue?@action=redirect&bpo=40956]: Fix segfault in sqlite3.Connection.backup() if no argument was provided. The regression was introduced by PR 23838. Patch by Erlend E. Aasland.

bpo-43172 [https://bugs.python.org/issue?@action=redirect&bpo=43172]: The readline module now passes its tests when built directly against libedit. Existing irreconcilable API differences remain in readline.get_begidx() and readline.get_endidx() behavior based on libreadline vs libedit use.

bpo-43163 [https://bugs.python.org/issue?@action=redirect&bpo=43163]: Fix a bug in codeop that was causing it to not ask for more input when multi-line snippets have unclosed parentheses. Patch by Pablo Galindo

bpo-43162 [https://bugs.python.org/issue?@action=redirect&bpo=43162]: deprecate unsupported ability to access enum members as attributes of other enum members

bpo-43146 [https://bugs.python.org/issue?@action=redirect&bpo=43146]: Fix recent regression in None argument handling in traceback module functions.

bpo-43102 [https://bugs.python.org/issue?@action=redirect&bpo=43102]: The namedtuple __new__ method had its __builtins__ set to None instead of an actual dictionary. This created problems for introspection tools.

bpo-43106 [https://bugs.python.org/issue?@action=redirect&bpo=43106]: Added O_EVTONLY, O_FSYNC, O_SYMLINK and O_NOFOLLOW_ANY for macOS. Patch by Donghee Na.

bpo-42960 [https://bugs.python.org/issue?@action=redirect&bpo=42960]: Adds resource.RLIMIT_KQUEUES constant from FreeBSD to the resource module.

bpo-42151 [https://bugs.python.org/issue?@action=redirect&bpo=42151]: Make the pure Python implementation of xml.etree.ElementTree behave the same as the C implementation (_elementree) regarding default attribute values (by not setting specified_attributes=1).

bpo-29753 [https://bugs.python.org/issue?@action=redirect&bpo=29753]: In ctypes, now packed bitfields are calculated properly and the first item of packed bitfields is now shrank correctly.

Documentation

bpo-27646 [https://bugs.python.org/issue?@action=redirect&bpo=27646]: Clarify that 'yield from <expr>' works with any iterable, not just iterators.

bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346]: Update some deprecated unicode APIs which are documented as "will be removed in 4.0" to "3.12". See PEP 623 [https://peps.python.org/pep-0623/] for detail.

Tests

bpo-43288 [https://bugs.python.org/issue?@action=redirect&bpo=43288]: Fix test_importlib to correctly skip Unicode file tests if the filesystem does not support them.

Build

bpo-43174 [https://bugs.python.org/issue?@action=redirect&bpo=43174]: Windows build now uses /utf-8 compiler option.

bpo-43103 [https://bugs.python.org/issue?@action=redirect&bpo=43103]: Add a new configure --without-static-libpython option to not build the libpythonMAJOR.MINOR.a static library and not install the python.o object file.

bpo-13501 [https://bugs.python.org/issue?@action=redirect&bpo=13501]: The configure script can now use libedit instead of readline with the command line option --with-readline=editline.

bpo-42603 [https://bugs.python.org/issue?@action=redirect&bpo=42603]: Make configure script use pkg-config to detect the location of Tcl/Tk headers and libraries, used to build tkinter.

On macOS, a Tcl/Tk configuration provided by pkg-config will be preferred over Tcl/Tk frameworks installed in /{System/,}Library/Frameworks. If both exist and the latter is preferred, the appropriate --with-tcltk-* configuration options need to be explicitly set.

bpo-39448 [https://bugs.python.org/issue?@action=redirect&bpo=39448]: Add the "regen-frozen" makefile target that regenerates the code for the frozen __hello__ module.

Windows

bpo-43155 [https://bugs.python.org/issue?@action=redirect&bpo=43155]: PyCMethod_New() is now present in python3.lib.

macOS

bpo-41837 [https://bugs.python.org/issue?@action=redirect&bpo=41837]: Update macOS installer build to use OpenSSL 1.1.1j.

IDLE

bpo-43283 [https://bugs.python.org/issue?@action=redirect&bpo=43283]: Document why printing to IDLE's Shell is often slower than printing to a system terminal and that it can be made faster by pre-formatting a single string before printing.

C API

bpo-43278 [https://bugs.python.org/issue?@action=redirect&bpo=43278]: Always put compiler and system information on the first line of the REPL welcome message.

bpo-43270 [https://bugs.python.org/issue?@action=redirect&bpo=43270]: Remove the private _PyErr_OCCURRED() macro: use the public PyErr_Occurred() function instead.

bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134]: Move odictobject.h, parser_interface.h, picklebufobject.h, pydebug.h, and pyfpe.h into the cpython/ directory. They must not be included directly, as they are already included by Python.h: Include Files.

bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134]: Move pyarena.h, pyctype.h, and pytime.h into the cpython/ directory. They must not be included directly, as they are already included by Python.h: Include Files.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: PyExceptionClass_Name() is now always declared as a function, in order to hide implementation details. The macro accessed PyTypeObject.tp_name directly. Patch by Erlend E. Aasland.

bpo-43239 [https://bugs.python.org/issue?@action=redirect&bpo=43239]: The PyCFunction_New() function is now exported in the ABI when compiled with -fvisibility=hidden.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: PyIter_Check() is now always declared as a function, in order to hide implementation details. The macro accessed PyTypeObject.tp_iternext directly. Patch by Erlend E. Aasland.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Convert PyDescr_IsData() macro to a function to hide implementation details: The macro accessed PyTypeObject.tp_descr_set directly. Patch by Erlend E. Aasland.

bpo-43181 [https://bugs.python.org/issue?@action=redirect&bpo=43181]: Convert PyObject_TypeCheck() macro to a static inline function. Patch by Erlend E. Aasland.

Python 3.10.0 alpha 5

Release date: 2021-02-02

Security

bpo-42938 [https://bugs.python.org/issue?@action=redirect&bpo=42938]: Avoid static buffers when computing the repr of ctypes.c_double and ctypes.c_longdouble values.

Core and Builtins

bpo-42990 [https://bugs.python.org/issue?@action=redirect&bpo=42990]: Refactor the PyEval_ family of functions.

An new function _PyEval_Vector is added to simplify calls to Python from C.

_PyEval_EvalCodeWithName is removed

PyEval_EvalCodeEx is retained as part of the API, but is not used internally

bpo-38631 [https://bugs.python.org/issue?@action=redirect&bpo=38631]: Replace Py_FatalError() calls in the compiler with regular SystemError exceptions. Patch by Victor Stinner.

bpo-42997 [https://bugs.python.org/issue?@action=redirect&bpo=42997]: Improve error message for missing ":" before blocks. Patch by Pablo Galindo.

bpo-43017 [https://bugs.python.org/issue?@action=redirect&bpo=43017]: Improve error message in the parser when using un-parenthesised tuples in comprehensions. Patch by Pablo Galindo.

bpo-42986 [https://bugs.python.org/issue?@action=redirect&bpo=42986]: Fix parser crash when reporting syntax errors in f-string with newlines. Patch by Pablo Galindo.

bpo-40176 [https://bugs.python.org/issue?@action=redirect&bpo=40176]: Syntax errors for unterminated string literals now point to the start of the string instead of reporting EOF/EOL.

bpo-42927 [https://bugs.python.org/issue?@action=redirect&bpo=42927]: The inline cache for LOAD_ATTR now also optimizes access to attributes defined by __slots__. This makes reading such attribute up to 30% faster.

bpo-42864 [https://bugs.python.org/issue?@action=redirect&bpo=42864]: Improve error messages in the parser when parentheses are not closed. Patch by Pablo Galindo.

bpo-42924 [https://bugs.python.org/issue?@action=redirect&bpo=42924]: Fix bytearray repetition incorrectly copying data from the start of the buffer, even if the data is offset within the buffer (e.g. after reassigning a slice at the start of the bytearray to a shorter byte string).

bpo-42882 [https://bugs.python.org/issue?@action=redirect&bpo=42882]: Fix the _PyUnicode_FromId() function (_Py_IDENTIFIER(var) API) when Py_Initialize() / Py_Finalize() is called multiple times: preserve _PyRuntime.unicode_ids.next_index value.

bpo-42827 [https://bugs.python.org/issue?@action=redirect&bpo=42827]: Fix a crash when working out the error line of a SyntaxError in some multi-line expressions.

bpo-42823 [https://bugs.python.org/issue?@action=redirect&bpo=42823]: frame.f_lineno is correct even if frame.f_trace is set to True

Library

bpo-37324 [https://bugs.python.org/issue?@action=redirect&bpo=37324]: Remove deprecated aliases to Collections Abstract Base Classes from the collections module.

Core and Builtins

bpo-41994 [https://bugs.python.org/issue?@action=redirect&bpo=41994]: Fixed possible leak in import when sys.modules is not a dict.

bpo-27772 [https://bugs.python.org/issue?@action=redirect&bpo=27772]: In string formatting, preceding the width field by '0' no longer affects the default alignment for strings.

Library

bpo-43108 [https://bugs.python.org/issue?@action=redirect&bpo=43108]: Fixed a reference leak in the curses module. Patch by Pablo Galindo

bpo-43077 [https://bugs.python.org/issue?@action=redirect&bpo=43077]: Update the bundled pip to 21.0.1 and setuptools to 52.0.0.

bpo-41282 [https://bugs.python.org/issue?@action=redirect&bpo=41282]: Deprecate distutils in documentation and add warning on import.

bpo-43014 [https://bugs.python.org/issue?@action=redirect&bpo=43014]: Improve performance of tokenize by 20-30%. Patch by Anthony Sottile.

bpo-42323 [https://bugs.python.org/issue?@action=redirect&bpo=42323]: Fix math.nextafter() for NaN on AIX.

bpo-42955 [https://bugs.python.org/issue?@action=redirect&bpo=42955]: Add sys.stdlib_module_names, containing the list of the standard library module names. Patch by Victor Stinner.

bpo-42944 [https://bugs.python.org/issue?@action=redirect&bpo=42944]: Fix random.Random.sample when counts argument is not None.

bpo-42934 [https://bugs.python.org/issue?@action=redirect&bpo=42934]: Use TracebackException's new compact param in TestResult to reduce time and memory consumed by traceback formatting.

bpo-42931 [https://bugs.python.org/issue?@action=redirect&bpo=42931]: Add randbytes() to random.__all__.

bpo-38250 [https://bugs.python.org/issue?@action=redirect&bpo=38250]: [Enum] Flags consisting of a single bit are now considered canonical, and will be the only flags returned from listing and iterating over a Flag class or a Flag member. Multi-bit flags are considered aliases; they will be returned from lookups and operations that result in their value. Iteration for both Flag and Flag members is in definition order.

bpo-42877 [https://bugs.python.org/issue?@action=redirect&bpo=42877]: Added the compact parameter to the constructor of traceback.TracebackException to reduce time and memory for use cases that only need to call TracebackException.format() and TracebackException.format_exception_only().

bpo-42923 [https://bugs.python.org/issue?@action=redirect&bpo=42923]: The Py_FatalError() function and the faulthandler module now dump the list of extension modules on a fatal error.

bpo-42848 [https://bugs.python.org/issue?@action=redirect&bpo=42848]: Removed recursion from TracebackException to allow it to handle long exception chains.

bpo-42901 [https://bugs.python.org/issue?@action=redirect&bpo=42901]: [Enum] move member creation from EnumMeta.__new__ to _proto_member.__set_name__, allowing members to be created and visible in __init_subclass__.

bpo-42780 [https://bugs.python.org/issue?@action=redirect&bpo=42780]: Fix os.set_inheritable() for O_PATH file descriptors on Linux.

bpo-42866 [https://bugs.python.org/issue?@action=redirect&bpo=42866]: Fix a reference leak in the getcodec() function of CJK codecs. Patch by Victor Stinner.

bpo-42846 [https://bugs.python.org/issue?@action=redirect&bpo=42846]: Convert the 6 CJK codec extension modules (_codecs_cn, _codecs_hk, _codecs_iso2022, _codecs_jp, _codecs_kr and _codecs_tw) to the multiphase initialization API (PEP 489 [https://peps.python.org/pep-0489/]). Patch by Victor Stinner.

bpo-42851 [https://bugs.python.org/issue?@action=redirect&bpo=42851]: remove __init_subclass__ support for Enum members

bpo-42834 [https://bugs.python.org/issue?@action=redirect&bpo=42834]: Make internal caches of the _json module compatible with subinterpreters.

bpo-41748 [https://bugs.python.org/issue?@action=redirect&bpo=41748]: Fix HTMLParser parsing rules for element attributes containing commas with spaces. Patch by Karl Dubost.

bpo-40810 [https://bugs.python.org/issue?@action=redirect&bpo=40810]: Require SQLite 3.7.15 or newer. Patch by Erlend E. Aasland.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Convert the _multibytecodec extension module (CJK codecs) to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]). Patch by Erlend E. Aasland.

bpo-42802 [https://bugs.python.org/issue?@action=redirect&bpo=42802]: The distutils bdist_wininst command deprecated in Python 3.8 has been removed. The distutils bdist_wheel command is now recommended to distribute binary packages on Windows.

bpo-24464 [https://bugs.python.org/issue?@action=redirect&bpo=24464]: The undocumented built-in function sqlite3.enable_shared_cache is now deprecated, scheduled for removal in Python 3.12. Its use is strongly discouraged by the SQLite3 documentation. Patch by Erlend E. Aasland.

bpo-42384 [https://bugs.python.org/issue?@action=redirect&bpo=42384]: Make pdb populate sys.path[0] exactly the same as regular python execution.

bpo-42383 [https://bugs.python.org/issue?@action=redirect&bpo=42383]: Fix pdb: previously pdb would fail to restart the debugging target if it was specified using a relative path and the current directory changed.

bpo-42005 [https://bugs.python.org/issue?@action=redirect&bpo=42005]: Fix CLI of cProfile and profile to catch BrokenPipeError.

bpo-41604 [https://bugs.python.org/issue?@action=redirect&bpo=41604]: Don't decrement the reference count of the previous user_ptr when set_panel_userptr fails.

bpo-41149 [https://bugs.python.org/issue?@action=redirect&bpo=41149]: Allow executing callables that have a boolean value of False when passed to Threading.thread as the target. Patch contributed by Barney Stratford.

bpo-38307 [https://bugs.python.org/issue?@action=redirect&bpo=38307]: Add an 'end_lineno' attribute to the Class and Function objects that appear in the tree returned by pyclbr functions. This and the existing 'lineno' attribute define the extent of class and def statements. Patch by Aviral Srivastava.

bpo-39273 [https://bugs.python.org/issue?@action=redirect&bpo=39273]: The BUTTON5_* constants are now exposed in the curses module if available.

bpo-33289 [https://bugs.python.org/issue?@action=redirect&bpo=33289]: Correct call to tkinter.colorchooser to return RGB triplet of ints instead of floats. Patch by Cheryl Sabella.

Documentation

bpo-40304 [https://bugs.python.org/issue?@action=redirect&bpo=40304]: Fix doc for type(name, bases, dict). Patch by Boris Verkhovskiy and Éric Araujo.

bpo-42811 [https://bugs.python.org/issue?@action=redirect&bpo=42811]: Updated importlib.util.resolve_name() doc to use __spec__.parent instead of __package__. (Thanks Yair Frid.)

Tests

bpo-40823 [https://bugs.python.org/issue?@action=redirect&bpo=40823]: Use unittest.TestLoader().loadTestsFromTestCase() instead of unittest.makeSuite() in sqlite3 tests. Patch by Erlend E. Aasland.

bpo-40810 [https://bugs.python.org/issue?@action=redirect&bpo=40810]: In sqlite3, fix CheckTraceCallbackContent for SQLite pre 3.7.15.

Build

bpo-43031 [https://bugs.python.org/issue?@action=redirect&bpo=43031]: Pass --timeout=$(TESTTIMEOUT) option to the default profile task ./python -m test --pgo command.

bpo-36143 [https://bugs.python.org/issue?@action=redirect&bpo=36143]: make regen-all now also runs regen-keyword. Patch by Victor Stinner.

bpo-42874 [https://bugs.python.org/issue?@action=redirect&bpo=42874]: Removed the grep -q and -E flags in the tzpath validation section of the configure script to better accommodate users of some platforms (specifically Solaris 10).

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Add library search path by wr-cc in add_cross_compiling_paths() for VxWorks.

bpo-42856 [https://bugs.python.org/issue?@action=redirect&bpo=42856]: Add --with-wheel-pkg-dir=PATH option to the ./configure script. If specified, the ensurepip module looks for setuptools and pip wheel packages in this directory: if both are present, these wheel packages are used instead of ensurepip bundled wheel packages.

Some Linux distribution packaging policies recommend against bundling dependencies. For example, Fedora installs wheel packages in the /usr/share/python-wheels/ directory and don't install the ensurepip._bundled package.

Windows

bpo-41837 [https://bugs.python.org/issue?@action=redirect&bpo=41837]: Updated Windows installer to include OpenSSL 1.1.1i

bpo-42584 [https://bugs.python.org/issue?@action=redirect&bpo=42584]: Upgrade Windows installer to use SQLite 3.34.0.

macOS

bpo-42504 [https://bugs.python.org/issue?@action=redirect&bpo=42504]: Ensure that the value of sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET') is always a string, even in when the value is parsable as an integer.

IDLE

bpo-43008 [https://bugs.python.org/issue?@action=redirect&bpo=43008]: Make IDLE invoke sys.excepthook() in normal, 2-process mode. Patch by Ken Hilton.

bpo-33065 [https://bugs.python.org/issue?@action=redirect&bpo=33065]: Fix problem debugging user classes with __repr__ method.

bpo-23544 [https://bugs.python.org/issue?@action=redirect&bpo=23544]: Disable Debug=>Stack Viewer when user code is running or Debugger is active, to prevent hang or crash. Patch by Zackery Spytz.

bpo-32631 [https://bugs.python.org/issue?@action=redirect&bpo=32631]: Finish zzdummy example extension module: make menu entries work; add docstrings and tests with 100% coverage.

C API

bpo-42979 [https://bugs.python.org/issue?@action=redirect&bpo=42979]: When Python is built in debug mode (with C assertions), calling a type slot like sq_length (__len__() in Python) now fails with a fatal error if the slot succeeded with an exception set, or failed with no exception set. The error message contains the slot, the type name, and the current exception (if an exception is set). Patch by Victor Stinner.

bpo-43030 [https://bugs.python.org/issue?@action=redirect&bpo=43030]: Fixed a compiler warning in Py_UNICODE_ISSPACE() on platforms with signed wchar_t.

Python 3.10.0 alpha 4

Release date: 2021-01-04

Core and Builtins

bpo-42814 [https://bugs.python.org/issue?@action=redirect&bpo=42814]: Fix undefined behavior in Objects/genericaliasobject.c.

bpo-42806 [https://bugs.python.org/issue?@action=redirect&bpo=42806]: Fix the column offsets for f-strings ast nodes surrounded by parentheses and for nodes that spawn multiple lines. Patch by Pablo Galindo.

bpo-40631 [https://bugs.python.org/issue?@action=redirect&bpo=40631]: Fix regression where a single parenthesized starred expression was a valid assignment target.

bpo-27794 [https://bugs.python.org/issue?@action=redirect&bpo=27794]: Improve the error message for failed writes/deletes to property objects. When possible, the attribute name is now shown. Patch provided by Yurii Karabas.

bpo-42745 [https://bugs.python.org/issue?@action=redirect&bpo=42745]: Make the type attribute lookup cache per-interpreter. Patch by Victor Stinner.

bpo-42246 [https://bugs.python.org/issue?@action=redirect&bpo=42246]: Jumps to jumps are not eliminated when it would break PEP 626.

bpo-42246 [https://bugs.python.org/issue?@action=redirect&bpo=42246]: Make sure that the f_lasti and f_lineno attributes of a frame are set correctly when an exception is raised or re-raised. Required for PEP 626.

bpo-32381 [https://bugs.python.org/issue?@action=redirect&bpo=32381]: The coding cookie (ex: # coding: latin1) is now ignored in the command passed to the -c command line option. Patch by Victor Stinner.

bpo-30858 [https://bugs.python.org/issue?@action=redirect&bpo=30858]: Improve error location in expressions that contain assignments. Patch by Pablo Galindo and Lysandros Nikolaou.

bpo-42615 [https://bugs.python.org/issue?@action=redirect&bpo=42615]: Remove jump commands made redundant by the deletion of unreachable bytecode blocks

Library

bpo-42639 [https://bugs.python.org/issue?@action=redirect&bpo=42639]: Make the atexit module state per-interpreter. It is now safe have more than one atexit module instance. Patch by Donghee Na and Victor Stinner.

Core and Builtins

bpo-32381 [https://bugs.python.org/issue?@action=redirect&bpo=32381]: Fix encoding name when running a .pyc file on Windows: PyRun_SimpleFileExFlags() now uses the correct encoding to decode the filename.

Library

bpo-42195 [https://bugs.python.org/issue?@action=redirect&bpo=42195]: The __args__ of the parameterized generics for typing.Callable and collections.abc.Callable are now consistent. The __args__ for collections.abc.Callable are now flattened while typing.Callable's have not changed. To allow this change, types.GenericAlias can now be subclassed and collections.abc.Callable's __class_getitem__ will now return a subclass of types.GenericAlias. Tests for typing were also updated to not subclass things like Callable[..., T] as that is not a valid base class. Finally, both Callables no longer validate their argtypes, in Callable[[argtypes], resulttype] to prepare for PEP 612 [https://peps.python.org/pep-0612/]. Patch by Ken Jin.

bpo-40137 [https://bugs.python.org/issue?@action=redirect&bpo=40137]: Convert functools module to use PyType_FromModuleAndSpec().

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert array to use heap types, and establish module state for these.

bpo-42008 [https://bugs.python.org/issue?@action=redirect&bpo=42008]: Fix _random.Random() seeding.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the pyexpat extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

Core and Builtins

bpo-40521 [https://bugs.python.org/issue?@action=redirect&bpo=40521]: Make the Unicode dictionary of interned strings compatible with subinterpreters. Patch by Victor Stinner.

bpo-39465 [https://bugs.python.org/issue?@action=redirect&bpo=39465]: Make _PyUnicode_FromId() function compatible with subinterpreters. Each interpreter now has an array of identifier objects (interned strings decoded from UTF-8). Patch by Victor Stinner.

Library

bpo-42257 [https://bugs.python.org/issue?@action=redirect&bpo=42257]: Handle empty string in variable executable in platform.libc_ver()

bpo-42772 [https://bugs.python.org/issue?@action=redirect&bpo=42772]: randrange() now raises a TypeError when step is specified without a stop argument. Formerly, it silently ignored the step argument.

bpo-42759 [https://bugs.python.org/issue?@action=redirect&bpo=42759]: Fixed equality comparison of tkinter.Variable and tkinter.font.Font. Objects which belong to different Tcl interpreters are now always different, even if they have the same name.

bpo-42756 [https://bugs.python.org/issue?@action=redirect&bpo=42756]: Configure LMTP Unix-domain socket to use socket global default timeout when a timeout is not explicitly provided.

bpo-23328 [https://bugs.python.org/issue?@action=redirect&bpo=23328]: Allow / character in username, password fields on _PROXY envars.

bpo-42740 [https://bugs.python.org/issue?@action=redirect&bpo=42740]: typing.get_args() and typing.get_origin() now support PEP 604 [https://peps.python.org/pep-0604/] union types and PEP 612 [https://peps.python.org/pep-0612/] additions to Callable.

bpo-42655 [https://bugs.python.org/issue?@action=redirect&bpo=42655]: subprocess extra_groups is now correctly passed into setgroups() system call.

bpo-42727 [https://bugs.python.org/issue?@action=redirect&bpo=42727]: EnumMeta.__prepare__ now accepts **kwds to properly support __init_subclass__

bpo-38308 [https://bugs.python.org/issue?@action=redirect&bpo=38308]: Add optional weights to statistics.harmonic_mean().

bpo-42721 [https://bugs.python.org/issue?@action=redirect&bpo=42721]: When simple query dialogs (tkinter.simpledialog), message boxes (tkinter.messagebox) or color choose dialog (tkinter.colorchooser) are created without arguments master and parent, and the default root window is not yet created, and NoDefaultRoot() was not called, a new temporal hidden root window will be created automatically. It will not be set as the default root window and will be destroyed right after closing the dialog window. It will help to use these simple dialog windows in programs which do not need other GUI.

bpo-25246 [https://bugs.python.org/issue?@action=redirect&bpo=25246]: Optimized collections.deque.remove().

bpo-35728 [https://bugs.python.org/issue?@action=redirect&bpo=35728]: Added a root parameter to tkinter.font.nametofont().

bpo-15303 [https://bugs.python.org/issue?@action=redirect&bpo=15303]: tkinter supports now widgets with boolean value False.

bpo-42681 [https://bugs.python.org/issue?@action=redirect&bpo=42681]: Fixed range checks for color and pair numbers in curses.

bpo-42685 [https://bugs.python.org/issue?@action=redirect&bpo=42685]: Improved placing of simple query windows in Tkinter (such as tkinter.simpledialog.askinteger()). They are now centered at the center of the parent window if it is specified and shown, otherwise at the center of the screen.

bpo-9694 [https://bugs.python.org/issue?@action=redirect&bpo=9694]: Argparse help no longer uses the confusing phrase, "optional arguments". It uses "options" instead.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _thread extension module to the multiphase initialization API (PEP 489 [https://peps.python.org/pep-0489/]) and convert its static types to heap types.

bpo-37961 [https://bugs.python.org/issue?@action=redirect&bpo=37961]: Fix crash in tracemalloc.Traceback.__repr__() (regressed in Python 3.9).

bpo-42630 [https://bugs.python.org/issue?@action=redirect&bpo=42630]: tkinter functions and constructors which need a default root window raise now RuntimeError with descriptive message instead of obscure AttributeError or NameError if it is not created yet or cannot be created automatically.

bpo-42639 [https://bugs.python.org/issue?@action=redirect&bpo=42639]: atexit._run_exitfuncs() now logs callback exceptions using sys.unraisablehook, rather than logging them directly into sys.stderr and raise the last exception.

bpo-42644 [https://bugs.python.org/issue?@action=redirect&bpo=42644]: logging.disable will now validate the types and value of its parameter. It also now accepts strings representing the levels (as does logging.setLevel) instead of only the numerical values.

bpo-42639 [https://bugs.python.org/issue?@action=redirect&bpo=42639]: At Python exit, if a callback registered with atexit.register() fails, its exception is now logged. Previously, only some exceptions were logged, and the last exception was always silently ignored.

bpo-36541 [https://bugs.python.org/issue?@action=redirect&bpo=36541]: Fixed lib2to3.pgen2 to be able to parse PEP-570 positional only argument syntax.

bpo-42382 [https://bugs.python.org/issue?@action=redirect&bpo=42382]: In importlib.metadata: - EntryPoint objects now expose a .dist object referencing the Distribution when constructed from a Distribution. - Add support for package discovery under package normalization rules. - The object returned by metadata() now has a formally defined protocol called PackageMetadata with declared support for the .get_all() method. - Synced with importlib_metadata 3.3.

bpo-41877 [https://bugs.python.org/issue?@action=redirect&bpo=41877]: A check is added against misspellings of autospect, auto_spec and set_spec being passed as arguments to patch, patch.object and create_autospec.

bpo-39717 [https://bugs.python.org/issue?@action=redirect&bpo=39717]: [tarfile] update nested exception raising to use from None or from e

bpo-41877 [https://bugs.python.org/issue?@action=redirect&bpo=41877]: AttributeError for suspected misspellings of assertions on mocks are now pointing out that the cause are misspelled assertions and also what to do if the misspelling is actually an intended attribute name. The unittest.mock document is also updated to reflect the current set of recognised misspellings.

bpo-41559 [https://bugs.python.org/issue?@action=redirect&bpo=41559]: Implemented PEP 612 [https://peps.python.org/pep-0612/]: added ParamSpec and Concatenate to typing. Patch by Ken Jin.

bpo-42385 [https://bugs.python.org/issue?@action=redirect&bpo=42385]: StrEnum: fix _generate_next_value_ to return a str

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Define THREAD_STACK_SIZE for VxWorks.

bpo-34750 [https://bugs.python.org/issue?@action=redirect&bpo=34750]: [Enum] _EnumDict.update() is now supported.

bpo-42517 [https://bugs.python.org/issue?@action=redirect&bpo=42517]: Enum: private names do not become members / do not generate errors -- they remain normal attributes

bpo-42678 [https://bugs.python.org/issue?@action=redirect&bpo=42678]: Enum: call __init_subclass__ after members have been added

bpo-28964 [https://bugs.python.org/issue?@action=redirect&bpo=28964]: ast.literal_eval() adds line number information (if available) in error message for malformed nodes.

bpo-42470 [https://bugs.python.org/issue?@action=redirect&bpo=42470]: random.sample() no longer warns on a sequence which is also a set.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: posixpath.expanduser() returns the input path unchanged if user home directory is None on VxWorks.

bpo-42388 [https://bugs.python.org/issue?@action=redirect&bpo=42388]: Fix subprocess.check_output(..., input=None) behavior when text=True to be consistent with that of the documentation and universal_newlines=True.

bpo-34463 [https://bugs.python.org/issue?@action=redirect&bpo=34463]: Fixed discrepancy between traceback and the interpreter in formatting of SyntaxError with lineno not set (traceback was changed to match interpreter).

bpo-42393 [https://bugs.python.org/issue?@action=redirect&bpo=42393]: Raise OverflowError instead of silent truncation in socket.ntohs() and socket.htons(). Silent truncation was deprecated in Python 3.7. Patch by Erlend E. Aasland

bpo-42222 [https://bugs.python.org/issue?@action=redirect&bpo=42222]: Harmonized random.randrange() argument handling to match range().

The integer test and conversion in randrange() now uses operator.index().

Non-integer arguments to randrange() are deprecated.

The ValueError is deprecated in favor of a TypeError.

It now runs a little faster than before.

(Contributed by Raymond Hettinger and Serhiy Storchaka.)

bpo-42163 [https://bugs.python.org/issue?@action=redirect&bpo=42163]: Restore compatibility for uname_result around deepcopy and _replace.

bpo-42090 [https://bugs.python.org/issue?@action=redirect&bpo=42090]: zipfile.Path.joinpath now accepts arbitrary arguments, same as pathlib.Path.joinpath.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _csv module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-42059 [https://bugs.python.org/issue?@action=redirect&bpo=42059]: typing.TypedDict types created using the alternative call-style syntax now correctly respect the total keyword argument when setting their __required_keys__ and __optional_keys__ class attributes.

bpo-41960 [https://bugs.python.org/issue?@action=redirect&bpo=41960]: Add globalns and localns parameters to the inspect.signature() and inspect.Signature.from_callable().

bpo-41907 [https://bugs.python.org/issue?@action=redirect&bpo=41907]: fix format() behavior for IntFlag

bpo-41891 [https://bugs.python.org/issue?@action=redirect&bpo=41891]: Ensure asyncio.wait_for waits for task completion

bpo-24792 [https://bugs.python.org/issue?@action=redirect&bpo=24792]: Fixed bug where zipimporter sometimes reports an incorrect cause of import errors.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix site and sysconfig modules for VxWorks RTOS which has no home directories.

bpo-41462 [https://bugs.python.org/issue?@action=redirect&bpo=41462]: Add os.set_blocking() support for VxWorks RTOS.

bpo-40219 [https://bugs.python.org/issue?@action=redirect&bpo=40219]: Lowered tkinter.ttk.LabeledScale dummy widget to prevent hiding part of the content label.

bpo-37193 [https://bugs.python.org/issue?@action=redirect&bpo=37193]: Fixed memory leak in socketserver.ThreadingMixIn introduced in Python 3.7.

bpo-39068 [https://bugs.python.org/issue?@action=redirect&bpo=39068]: Fix initialization race condition in a85encode() and b85encode() in base64. Patch by Brandon Stansbury.

Documentation

bpo-17140 [https://bugs.python.org/issue?@action=redirect&bpo=17140]: Add documentation for the multiprocessing.pool.ThreadPool class.

bpo-34398 [https://bugs.python.org/issue?@action=redirect&bpo=34398]: Prominently feature listings from the glossary in documentation search results. Patch by Ammar Askar.

Tests

bpo-42794 [https://bugs.python.org/issue?@action=redirect&bpo=42794]: Update test_nntplib to use official group name of news.aioe.org for testing. Patch by Donghee Na.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Skip some asyncio tests on VxWorks.

bpo-42641 [https://bugs.python.org/issue?@action=redirect&bpo=42641]: Enhance test_select.test_select(): it now takes 500 milliseconds rather than 10 seconds. Use Python rather than a shell to make the test more portable.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Skip some tests in _test_all_chown_common() on VxWorks.

bpo-42199 [https://bugs.python.org/issue?@action=redirect&bpo=42199]: Fix bytecode helper assertNotInBytecode.

bpo-41443 [https://bugs.python.org/issue?@action=redirect&bpo=41443]: Add more attribute checking in test_posix.py

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Disable os.popen and impacted tests on VxWorks

bpo-41439 [https://bugs.python.org/issue?@action=redirect&bpo=41439]: Port test_ssl and test_uuid to VxWorks RTOS.

Build

bpo-42692 [https://bugs.python.org/issue?@action=redirect&bpo=42692]: Fix __builtin_available check on older compilers. Patch by Joshua Root.

bpo-27640 [https://bugs.python.org/issue?@action=redirect&bpo=27640]: Added --disable-test-modules option to the configure script: don't build nor install test modules. Patch by Xavier de Gaye, Thomas Petazzoni and Peixing Xin.

bpo-42604 [https://bugs.python.org/issue?@action=redirect&bpo=42604]: Now all platforms use a value for the "EXT_SUFFIX" build variable derived from SOABI (for instance in freeBSD, "EXT_SUFFIX" is now ".cpython-310d.so" instead of ".so"). Previously only Linux, Mac and VxWorks were using a value for "EXT_SUFFIX" that included "SOABI".

bpo-42598 [https://bugs.python.org/issue?@action=redirect&bpo=42598]: Fix implicit function declarations in configure which could have resulted in incorrect configuration checks. Patch contributed by Joshua Root.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Enable libpython3.so for VxWorks.

bpo-29076 [https://bugs.python.org/issue?@action=redirect&bpo=29076]: Add fish shell support to macOS installer.

macOS

bpo-42361 [https://bugs.python.org/issue?@action=redirect&bpo=42361]: Update macOS installer build to use Tcl/Tk 8.6.11 (rc2, expected to be final release).

bpo-41837 [https://bugs.python.org/issue?@action=redirect&bpo=41837]: Update macOS installer build to use OpenSSL 1.1.1i.

bpo-42584 [https://bugs.python.org/issue?@action=redirect&bpo=42584]: Update macOS installer to use SQLite 3.34.0.

Tools/Demos

bpo-42726 [https://bugs.python.org/issue?@action=redirect&bpo=42726]: Fixed Python 3 compatibility issue with gdb/libpython.py handling of attribute dictionaries.

bpo-42613 [https://bugs.python.org/issue?@action=redirect&bpo=42613]: Fix freeze.py tool to use the prope config and library directories. Patch by Victor Stinner.

C API

bpo-42591 [https://bugs.python.org/issue?@action=redirect&bpo=42591]: Export the Py_FrozenMain() function: fix a Python 3.9.0 regression. Python 3.9 uses -fvisibility=hidden and the function was not exported explicitly and so not exported.

bpo-32381 [https://bugs.python.org/issue?@action=redirect&bpo=32381]: Remove the private _Py_fopen() function which is no longer needed. Use _Py_wfopen() or _Py_fopen_obj() instead. Patch by Victor Stinner.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port resource extension module to module state

bpo-42111 [https://bugs.python.org/issue?@action=redirect&bpo=42111]: Update the xxlimited module to be a better example of how to use the limited C API.

bpo-40052 [https://bugs.python.org/issue?@action=redirect&bpo=40052]: Fix an alignment build warning/error in function PyVectorcall_Function(). Patch by Andreas Schneider, Antoine Pitrou and Petr Viktorin.

Python 3.10.0 alpha 3

Release date: 2020-12-07

Security

bpo-40791 [https://bugs.python.org/issue?@action=redirect&bpo=40791]: Add volatile to the accumulator variable in hmac.compare_digest, making constant-time-defeating optimizations less likely.

Core and Builtins

bpo-42576 [https://bugs.python.org/issue?@action=redirect&bpo=42576]: types.GenericAlias will now raise a TypeError when attempting to initialize with a keyword argument. Previously, this would cause the interpreter to crash if the interpreter was compiled with debug symbols. This does not affect interpreters compiled for release. Patch by Ken Jin.

bpo-42536 [https://bugs.python.org/issue?@action=redirect&bpo=42536]: Several built-in and standard library types now ensure that their internal result tuples are always tracked by the garbage collector:

collections.OrderedDict.items()

dict.items()

enumerate()

functools.reduce()

itertools.combinations()

itertools.combinations_with_replacement()

itertools.permutations()

itertools.product()

itertools.zip_longest()

zip()

Previously, they could have become untracked by a prior garbage collection. Patch by Brandt Bucher.

bpo-42500 [https://bugs.python.org/issue?@action=redirect&bpo=42500]: Improve handling of exceptions near recursion limit. Converts a number of Fatal Errors in RecursionErrors.

bpo-42246 [https://bugs.python.org/issue?@action=redirect&bpo=42246]: PEP 626: After a return, the f_lineno attribute of a frame is always the last line executed.

bpo-42435 [https://bugs.python.org/issue?@action=redirect&bpo=42435]: Speed up comparison of bytes objects with non-bytes objects when option -b is specified. Speed up comparison of bytarray objects with non-buffer object.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _warnings extension module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]). Patch by Victor Stinner.

Core and Builtins

bpo-41686 [https://bugs.python.org/issue?@action=redirect&bpo=41686]: On Windows, the SIGINT event, _PyOS_SigintEvent(), is now created even if Python is configured to not install signal handlers (if PyConfig.install_signal_handlers equals to 0, or Py_InitializeEx(0)).

bpo-42381 [https://bugs.python.org/issue?@action=redirect&bpo=42381]: Allow assignment expressions in set literals and set comprehensions as per PEP 572. Patch by Pablo Galindo.

bpo-42202 [https://bugs.python.org/issue?@action=redirect&bpo=42202]: Change function parameters annotations internal representation to tuple of strings. Patch provided by Yurii Karabas.

bpo-42374 [https://bugs.python.org/issue?@action=redirect&bpo=42374]: Fix a regression introduced by the new parser, where an unparenthesized walrus operator was not allowed within generator expressions.

bpo-42316 [https://bugs.python.org/issue?@action=redirect&bpo=42316]: Allow an unparenthesized walrus in subscript indexes.

bpo-42349 [https://bugs.python.org/issue?@action=redirect&bpo=42349]: Make sure that the compiler front-end produces a well-formed control flow graph. Be more aggressive in the compiler back-end, as it is now safe to do so.

bpo-42296 [https://bugs.python.org/issue?@action=redirect&bpo=42296]: On Windows, fix a regression in signal handling which prevented to interrupt a program using CTRL+C. The signal handler can be run in a thread different than the Python thread, in which case the test deciding if the thread can handle signals is wrong.

bpo-42332 [https://bugs.python.org/issue?@action=redirect&bpo=42332]: types.GenericAlias objects can now be the targets of weakrefs.

bpo-42282 [https://bugs.python.org/issue?@action=redirect&bpo=42282]: Optimise constant subexpressions that appear as part of named expressions (previously the AST optimiser did not descend into named expressions). Patch by Nick Coghlan.

bpo-42266 [https://bugs.python.org/issue?@action=redirect&bpo=42266]: Fixed a bug with the LOAD_ATTR opcode cache that was not respecting monkey-patching a class-level attribute to make it a descriptor. Patch by Pablo Galindo.

Library

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert queue to use heap types.

Core and Builtins

bpo-42246 [https://bugs.python.org/issue?@action=redirect&bpo=42246]: Improved accuracy of line tracing events and f_lineno attribute of Frame objects. See PEP 626 for details.

Library

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert mmap to use heap types.

Core and Builtins

bpo-42233 [https://bugs.python.org/issue?@action=redirect&bpo=42233]: Allow GenericAlias objects to use union type expressions. This allows expressions like list[int] | dict[float, str] where previously a TypeError would have been thrown. This also fixes union type expressions not de-duplicating GenericAlias objects. (Contributed by Ken Jin in bpo-42233 [https://bugs.python.org/issue?@action=redirect&bpo=42233].)

bpo-26131 [https://bugs.python.org/issue?@action=redirect&bpo=26131]: The import system triggers a ImportWarning when it falls back to using load_module().

Library

bpo-5054 [https://bugs.python.org/issue?@action=redirect&bpo=5054]: CGIHTTPRequestHandler.run_cgi() HTTP_ACCEPT improperly parsed. Replace the special purpose getallmatchingheaders with generic get_all method and add relevant tests.

Original Patch by Martin Panter. Modified by Senthil Kumaran.

bpo-42562 [https://bugs.python.org/issue?@action=redirect&bpo=42562]: Fix issue when dis failed to parse function that has no line numbers. Patch provided by Yurii Karabas.

bpo-17735 [https://bugs.python.org/issue?@action=redirect&bpo=17735]: inspect.findsource() now raises OSError instead of IndexError when co_lineno of a code object is greater than the file length. This can happen, for example, when a file is edited after it was imported. PR by Irit Katriel.

bpo-42116 [https://bugs.python.org/issue?@action=redirect&bpo=42116]: Fix handling of trailing comments by inspect.getsource().

bpo-42532 [https://bugs.python.org/issue?@action=redirect&bpo=42532]: Remove unexpected call of __bool__ when passing a spec_arg argument to a Mock.

bpo-38200 [https://bugs.python.org/issue?@action=redirect&bpo=38200]: Added itertools.pairwise()

bpo-41818 [https://bugs.python.org/issue?@action=redirect&bpo=41818]: Fix test_master_read() so that it succeeds on all platforms that either raise OSError or return b"" upon reading from master.

bpo-42487 [https://bugs.python.org/issue?@action=redirect&bpo=42487]: ChainMap.__iter__ no longer calls __getitem__ on underlying maps

bpo-42482 [https://bugs.python.org/issue?@action=redirect&bpo=42482]: TracebackException no longer holds a reference to the exception's traceback object. Consequently, instances of TracebackException for equivalent but non-equal exceptions now compare as equal.

bpo-41818 [https://bugs.python.org/issue?@action=redirect&bpo=41818]: Make test_openpty() avoid unexpected success due to number of rows and/or number of columns being == 0.

bpo-42392 [https://bugs.python.org/issue?@action=redirect&bpo=42392]: Remove loop parameter from asyncio.subprocess and asyncio.tasks functions. Patch provided by Yurii Karabas.

bpo-42392 [https://bugs.python.org/issue?@action=redirect&bpo=42392]: Remove loop parameter from asyncio.open_connection and asyncio.start_server functions. Patch provided by Yurii Karabas.

bpo-28468 [https://bugs.python.org/issue?@action=redirect&bpo=28468]: Add platform.freedesktop_os_release() function to parse freedesktop.org os-release files.

bpo-42299 [https://bugs.python.org/issue?@action=redirect&bpo=42299]: Removed the formatter module, which was deprecated in Python 3.4. It is somewhat obsolete, little used, and not tested. It was originally scheduled to be removed in Python 3.6, but such removals were delayed until after Python 2.7 EOL. Existing users should copy whatever classes they use into their code. Patch by Donghee Na and and Terry J. Reedy.

bpo-26131 [https://bugs.python.org/issue?@action=redirect&bpo=26131]: Deprecate zipimport.zipimporter.load_module() in favour of exec_module().

bpo-41818 [https://bugs.python.org/issue?@action=redirect&bpo=41818]: Updated tests for the pty library. test_basic() has been changed to test_openpty(); this additionally checks if slave termios and slave winsize are being set properly by pty.openpty(). In order to add support for FreeBSD, NetBSD, OpenBSD, and Darwin, this also adds test_master_read(), which demonstrates that pty.spawn() should not depend on an OSError to exit from its copy loop.

bpo-42392 [https://bugs.python.org/issue?@action=redirect&bpo=42392]: Remove loop parameter from __init__ in all asyncio.locks and asyncio.Queue classes. Patch provided by Yurii Karabas.

bpo-15450 [https://bugs.python.org/issue?@action=redirect&bpo=15450]: Make filecmp.dircmp respect subclassing. Now the filecmp.dircmp.subdirs behaves as expected when subclassing dircmp.

bpo-42413 [https://bugs.python.org/issue?@action=redirect&bpo=42413]: The exception socket.timeout is now an alias of TimeoutError.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Support signal module on VxWorks.

bpo-42406 [https://bugs.python.org/issue?@action=redirect&bpo=42406]: We fixed an issue in pickle.whichmodule in which importing multiprocessing could change the how pickle identifies which module an object belongs to, potentially breaking the unpickling of those objects.

bpo-42403 [https://bugs.python.org/issue?@action=redirect&bpo=42403]: Simplify the importlib external bootstrap code: importlib._bootstrap_external now uses regular imports to import builtin modules. When it is imported, the builtin __import__() function is already fully working and so can be used to import builtin modules like sys. Patch by Victor Stinner.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Convert _sre module types to heap types (PEP 384). Patch by Erlend E. Aasland.

bpo-42375 [https://bugs.python.org/issue?@action=redirect&bpo=42375]: subprocess module update for DragonFlyBSD support.

bpo-41713 [https://bugs.python.org/issue?@action=redirect&bpo=41713]: Port the _signal extension module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]). Patch by Victor Stinner and Mohamed Koubaa.

bpo-37205 [https://bugs.python.org/issue?@action=redirect&bpo=37205]: time.time(), time.perf_counter() and time.monotonic() functions can no longer fail with a Python fatal error, instead raise a regular Python exception on failure.

bpo-42328 [https://bugs.python.org/issue?@action=redirect&bpo=42328]: Fixed tkinter.ttk.Style.map(). The function accepts now the representation of the default state as empty sequence (as returned by Style.map()). The structure of the result is now the same on all platform and does not depend on the value of wantobjects.

bpo-42345 [https://bugs.python.org/issue?@action=redirect&bpo=42345]: Fix various issues with typing.Literal parameter handling (flatten, deduplicate, use type to cache key). Patch provided by Yurii Karabas.

bpo-37205 [https://bugs.python.org/issue?@action=redirect&bpo=37205]: time.perf_counter() on Windows and time.monotonic() on macOS are now system-wide. Previously, they used an offset computed at startup to reduce the precision loss caused by the float type. Use time.perf_counter_ns() and time.monotonic_ns() added in Python 3.7 to avoid this precision loss.

bpo-42318 [https://bugs.python.org/issue?@action=redirect&bpo=42318]: Fixed support of non-BMP characters in tkinter on macOS.

bpo-42350 [https://bugs.python.org/issue?@action=redirect&bpo=42350]: Fix the threading.Thread class at fork: do nothing if the thread is already stopped (ex: fork called at Python exit). Previously, an error was logged in the child process.

bpo-42333 [https://bugs.python.org/issue?@action=redirect&bpo=42333]: Port _ssl extension module to heap types.

bpo-42014 [https://bugs.python.org/issue?@action=redirect&bpo=42014]: The onerror callback from shutil.rmtree now receives correct function when os.open fails.

bpo-42237 [https://bugs.python.org/issue?@action=redirect&bpo=42237]: Fix os.sendfile() on illumos.

bpo-42308 [https://bugs.python.org/issue?@action=redirect&bpo=42308]: Add threading.__excepthook__ to allow retrieving the original value of threading.excepthook() in case it is set to a broken or a different value. Patch by Mario Corchero.

bpo-42131 [https://bugs.python.org/issue?@action=redirect&bpo=42131]: Implement PEP 451/spec methods on zipimport.zipimporter: find_spec(), create_module(), and exec_module().

This also allows for the documented deprecation of find_loader(), find_module(), and load_module().

bpo-41877 [https://bugs.python.org/issue?@action=redirect&bpo=41877]: Mock objects which are not unsafe will now raise an AttributeError if an attribute with the prefix asert, aseert, or assrt is accessed, in addition to this already happening for the prefixes assert or assret.

bpo-42264 [https://bugs.python.org/issue?@action=redirect&bpo=42264]: sqlite3.OptimizedUnicode has been undocumented and obsolete since Python 3.3, when it was made an alias to str. It is now deprecated, scheduled for removal in Python 3.12.

bpo-42251 [https://bugs.python.org/issue?@action=redirect&bpo=42251]: Added threading.gettrace() and threading.getprofile() to retrieve the functions set by threading.settrace() and threading.setprofile() respectively. Patch by Mario Corchero.

bpo-42249 [https://bugs.python.org/issue?@action=redirect&bpo=42249]: Fixed writing binary Plist files larger than 4 GiB.

bpo-42236 [https://bugs.python.org/issue?@action=redirect&bpo=42236]: On Unix, the os.device_encoding() function now returns 'UTF-8' rather than the device encoding if the Python UTF-8 Mode is enabled.

bpo-41754 [https://bugs.python.org/issue?@action=redirect&bpo=41754]: webbrowser: Ignore NotADirectoryError when calling xdg-settings.

bpo-42183 [https://bugs.python.org/issue?@action=redirect&bpo=42183]: Fix a stack overflow error for asyncio Task or Future repr().

The overflow occurs under some circumstances when a Task or Future recursively returns itself.

bpo-42140 [https://bugs.python.org/issue?@action=redirect&bpo=42140]: Improve asyncio.wait function to create the futures set just one time.

bpo-42133 [https://bugs.python.org/issue?@action=redirect&bpo=42133]: Update various modules in the stdlib to fall back on __spec__.loader when __loader__ isn't defined on a module.

bpo-26131 [https://bugs.python.org/issue?@action=redirect&bpo=26131]: The load_module() methods found in importlib now trigger a DeprecationWarning.

bpo-39825 [https://bugs.python.org/issue?@action=redirect&bpo=39825]: Windows: Change sysconfig.get_config_var('EXT_SUFFIX') to the expected full platform_tag.extension format. Previously it was hard-coded to .pyd, now it is compatible with distutils.sysconfig and will result in something like .cp38-win_amd64.pyd. This brings windows into conformance with the other platforms.

bpo-26389 [https://bugs.python.org/issue?@action=redirect&bpo=26389]: The traceback.format_exception(), traceback.format_exception_only(), and traceback.print_exception() functions can now take an exception object as a positional-only argument.

bpo-41889 [https://bugs.python.org/issue?@action=redirect&bpo=41889]: Enum: fix regression involving inheriting a multiply inherited enum

bpo-41861 [https://bugs.python.org/issue?@action=redirect&bpo=41861]: Convert sqlite3 to use heap types (PEP 384). Patch by Erlend E. Aasland.

bpo-40624 [https://bugs.python.org/issue?@action=redirect&bpo=40624]: Added support for the XPath != operator in xml.etree

bpo-28850 [https://bugs.python.org/issue?@action=redirect&bpo=28850]: Fix pprint.PrettyPrinter.format() overrides being ignored for contents of small containers. The pprint._safe_repr() function was removed.

bpo-41625 [https://bugs.python.org/issue?@action=redirect&bpo=41625]: Expose the splice() as os.splice() in the os module. Patch by Pablo Galindo

bpo-34215 [https://bugs.python.org/issue?@action=redirect&bpo=34215]: Clarify the error message for asyncio.IncompleteReadError when expected is None.

bpo-41543 [https://bugs.python.org/issue?@action=redirect&bpo=41543]: Add async context manager support for contextlib.nullcontext.

bpo-21041 [https://bugs.python.org/issue?@action=redirect&bpo=21041]: pathlib.PurePath.parents now supports negative indexing. Patch contributed by Yaroslav Pankovych.

bpo-41332 [https://bugs.python.org/issue?@action=redirect&bpo=41332]: Added missing connect_accepted_socket() method to asyncio.AbstractEventLoop.

bpo-12800 [https://bugs.python.org/issue?@action=redirect&bpo=12800]: Extracting a symlink from a tarball should succeed and overwrite the symlink if it already exists. The fix is to remove the existing file or symlink before extraction. Based on patch by Chris AtLee, Jeffrey Kintscher, and Senthil Kumaran.

bpo-40968 [https://bugs.python.org/issue?@action=redirect&bpo=40968]: urllib.request and http.client now send http/1.1 ALPN extension during TLS handshake when no custom context is supplied.

bpo-41001 [https://bugs.python.org/issue?@action=redirect&bpo=41001]: Add os.eventfd() to provide a low level interface for Linux's event notification file descriptor.

bpo-40816 [https://bugs.python.org/issue?@action=redirect&bpo=40816]: Add AsyncContextDecorator to contextlib to support async context manager as a decorator.

bpo-40550 [https://bugs.python.org/issue?@action=redirect&bpo=40550]: Fix time-of-check/time-of-action issue in subprocess.Popen.send_signal.

bpo-39411 [https://bugs.python.org/issue?@action=redirect&bpo=39411]: Add an is_async identifier to pyclbr's Function objects. Patch by Batuhan Taskaya

bpo-35498 [https://bugs.python.org/issue?@action=redirect&bpo=35498]: Add slice support to pathlib.PurePath.parents.

Documentation

bpo-42238 [https://bugs.python.org/issue?@action=redirect&bpo=42238]: Tentative to deprecate make suspicious by first removing it from the CI and documentation builds, but keeping it around for manual uses.

bpo-42153 [https://bugs.python.org/issue?@action=redirect&bpo=42153]: Fix the URL for the IMAP protocol documents.

bpo-41028 [https://bugs.python.org/issue?@action=redirect&bpo=41028]: Language and version switchers, previously maintained in every cpython branches, are now handled by docsbuild-script.

Tests

bpo-41473 [https://bugs.python.org/issue?@action=redirect&bpo=41473]: Re-enable test_gdb on gdb 9.2 and newer: https://bugzilla.redhat.com/show_bug.cgi?id=1866884 bug is fixed in gdb 10.1.

bpo-42553 [https://bugs.python.org/issue?@action=redirect&bpo=42553]: Fix test_asyncio.test_call_later() race condition: don't measure asyncio performance in the call_later() unit test. The test failed randomly on the CI.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix test_netrc on VxWorks: create temporary directories using temp_cwd().

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: skip test_getaddrinfo_ipv6_scopeid_symbolic and test_getnameinfo_ipv6_scopeid_symbolic on VxWorks

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: skip test_test of test_mailcap on VxWorks

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: add shell requirement for test_pipes

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: skip some tests related to fifo on VxWorks

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix test_doctest.py failures for VxWorks.

bpo-40754 [https://bugs.python.org/issue?@action=redirect&bpo=40754]: Include _testinternalcapi module in Windows installer for test suite

bpo-41561 [https://bugs.python.org/issue?@action=redirect&bpo=41561]: test_ssl: skip test_min_max_version_mismatch when TLS 1.0 is not available

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix os module failures for VxWorks RTOS.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix fifo test cases for VxWorks RTOS.

Build

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: remove libnet dependency from detect_socket() for VxWorks

bpo-42398 [https://bugs.python.org/issue?@action=redirect&bpo=42398]: Fix a race condition in "make regen-all" when make -jN option is used to run jobs in parallel. The clinic.py script now only use atomic write to write files. Moveover, generated files are now left unchanged if the content does not change, to not change the file modification time.

bpo-41617 [https://bugs.python.org/issue?@action=redirect&bpo=41617]: Fix building pycore_bitutils.h internal header on old clang version without __builtin_bswap16() (ex: Xcode 4.6.3 on Mac OS X 10.7). Patch by Joshua Root and Victor Stinner.

bpo-38823 [https://bugs.python.org/issue?@action=redirect&bpo=38823]: It is no longer possible to build the _ctypes extension module without wchar_t type: remove CTYPES_UNICODE macro. Anyway, the wchar_t type is required to build Python. Patch by Victor Stinner.

bpo-42087 [https://bugs.python.org/issue?@action=redirect&bpo=42087]: Support was removed for AIX 5.3 and below. See bpo-40680 [https://bugs.python.org/issue?@action=redirect&bpo=40680].

bpo-40998 [https://bugs.python.org/issue?@action=redirect&bpo=40998]: Addressed three compiler warnings found by undefined behavior sanitizer (ubsan).

Windows

bpo-42120 [https://bugs.python.org/issue?@action=redirect&bpo=42120]: Remove macro definition of copysign (to _copysign) in headers.

bpo-38506 [https://bugs.python.org/issue?@action=redirect&bpo=38506]: The Windows launcher now properly handles Python 3.10 when listing installed Python versions.

macOS

bpo-42504 [https://bugs.python.org/issue?@action=redirect&bpo=42504]: Fix build on macOS Big Sur when MACOSX_DEPLOYMENT_TARGET=11

bpo-41116 [https://bugs.python.org/issue?@action=redirect&bpo=41116]: Ensure distutils.unixxcompiler.find_library_file can find system provided libraries on macOS 11.

bpo-41100 [https://bugs.python.org/issue?@action=redirect&bpo=41100]: Add support for macOS 11 and Apple Silicon systems.

It is now possible to build "Universal 2" binaries using "--enable-universalsdk --with-universal-archs=universal2".

Binaries build on later macOS versions can be deployed back to older versions (tested up to macOS 10.9), when using the correct deployment target. This is tested using Xcode 11 and later.

bpo-42232 [https://bugs.python.org/issue?@action=redirect&bpo=42232]: Added Darwin specific madvise options to mmap module.

bpo-38443 [https://bugs.python.org/issue?@action=redirect&bpo=38443]: The --enable-universalsdk and --with-universal-archs options for the configure script now check that the specified architectures can be used.

IDLE

bpo-42508 [https://bugs.python.org/issue?@action=redirect&bpo=42508]: Keep IDLE running on macOS. Remove obsolete workaround that prevented running files with shortcuts when using new universal2 installers built on macOS 11.

bpo-42426 [https://bugs.python.org/issue?@action=redirect&bpo=42426]: Fix reporting offset of the RE error in searchengine.

bpo-42415 [https://bugs.python.org/issue?@action=redirect&bpo=42415]: Get docstrings for IDLE calltips more often by using inspect.getdoc.

Tools/Demos

bpo-42212 [https://bugs.python.org/issue?@action=redirect&bpo=42212]: The smelly.py script now also checks the Python dynamic library and extension modules, not only the Python static library. Make also the script more verbose: explain what it does.

bpo-36310 [https://bugs.python.org/issue?@action=redirect&bpo=36310]: Allow Tools/i18n/pygettext.py to detect calls to gettext in f-strings.

C API

bpo-42423 [https://bugs.python.org/issue?@action=redirect&bpo=42423]: The PyType_FromSpecWithBases() and PyType_FromModuleAndSpec() functions now accept a single class as the bases argument.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port select extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _posixsubprocess extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _posixshmem extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _struct extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port spwd extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port gc extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _queue extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Convert Py_TYPE() and Py_SIZE() back to macros to allow using them as an l-value. Many third party C extension modules rely on the ability of using Py_TYPE() and Py_SIZE() to set an object type and size: Py_TYPE(obj) = type; and Py_SIZE(obj) = size;.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port symtable extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port grp and pwd extension modules to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _random extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _hashlib extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/])

bpo-41713 [https://bugs.python.org/issue?@action=redirect&bpo=41713]: Removed the undocumented PyOS_InitInterrupts() function. Initializing Python already implicitly installs signal handlers: see PyConfig.install_signal_handlers. Patch by Victor Stinner.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: The Py_TRASHCAN_BEGIN macro no longer accesses PyTypeObject attributes, but now can get the condition by calling the new private _PyTrash_cond() function which hides implementation details.

bpo-42260 [https://bugs.python.org/issue?@action=redirect&bpo=42260]: Py_GetPath(), Py_GetPrefix(), Py_GetExecPrefix(), Py_GetProgramFullPath(), Py_GetPythonHome() and Py_GetProgramName() functions now return NULL if called before Py_Initialize() (before Python is initialized). Use the new Python Initialization Configuration API to get the Python Path Configuration.. Patch by Victor Stinner.

bpo-42260 [https://bugs.python.org/issue?@action=redirect&bpo=42260]: The PyConfig_Read() function now only parses PyConfig.argv arguments once: PyConfig.parse_argv is set to 2 after arguments are parsed. Since Python arguments are strippped from PyConfig.argv, parsing arguments twice would parse the application options as Python options.

bpo-42262 [https://bugs.python.org/issue?@action=redirect&bpo=42262]: Added Py_NewRef() and Py_XNewRef() functions to increment the reference count of an object and return the object. Patch by Victor Stinner.

bpo-42260 [https://bugs.python.org/issue?@action=redirect&bpo=42260]: When Py_Initialize() is called twice, the second call now updates more sys attributes for the configuration, rather than only sys.argv. Patch by Victor Stinner.

bpo-41832 [https://bugs.python.org/issue?@action=redirect&bpo=41832]: The PyType_FromModuleAndSpec() function now accepts NULL tp_doc slot.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Added PyModule_AddObjectRef() function: similar to PyModule_AddObject() but don't steal a reference to the value on success. Patch by Victor Stinner.

bpo-42171 [https://bugs.python.org/issue?@action=redirect&bpo=42171]: The METH_FASTCALL calling convention is added to the limited API. The functions PyModule_AddType(), PyType_FromModuleAndSpec(), PyType_GetModule() and PyType_GetModuleState() are added to the limited API on Windows.

bpo-42085 [https://bugs.python.org/issue?@action=redirect&bpo=42085]: Add dedicated entry to PyAsyncMethods for sending values

bpo-41073 [https://bugs.python.org/issue?@action=redirect&bpo=41073]: PyType_GetSlot() can now accept static types.

bpo-30459 [https://bugs.python.org/issue?@action=redirect&bpo=30459]: PyList_SET_ITEM(), PyTuple_SET_ITEM() and PyCell_SET() macros can no longer be used as l-value or r-value. For example, x = PyList_SET_ITEM(a, b, c) and PyList_SET_ITEM(a, b, c) = x now fail with a compiler error. It prevents bugs like if (PyList_SET_ITEM (a, b, c) < 0) ... test. Patch by Zackery Spytz and Victor Stinner.

Python 3.10.0 alpha 2

Release date: 2020-11-03

Security

bpo-42103 [https://bugs.python.org/issue?@action=redirect&bpo=42103]: Prevented potential DoS attack via CPU and RAM exhaustion when processing malformed Apple Property List files in binary format.

bpo-42051 [https://bugs.python.org/issue?@action=redirect&bpo=42051]: The plistlib module no longer accepts entity declarations in XML plist files to avoid XML vulnerabilities. This should not affect users as entity declarations are not used in regular plist files.

Core and Builtins

bpo-42236 [https://bugs.python.org/issue?@action=redirect&bpo=42236]: If the nl_langinfo(CODESET) function returns an empty string, Python now uses UTF-8 as the filesystem encoding. Patch by Victor Stinner.

bpo-42218 [https://bugs.python.org/issue?@action=redirect&bpo=42218]: Fixed a bug in the PEG parser that was causing crashes in debug mode. Now errors are checked in left-recursive rules to avoid cases where such errors do not get handled in time and appear as long-distance crashes in other places.

bpo-42214 [https://bugs.python.org/issue?@action=redirect&bpo=42214]: Fixed a possible crash in the PEG parser when checking for the '!=' token in the barry_as_flufl rule. Patch by Pablo Galindo.

bpo-42206 [https://bugs.python.org/issue?@action=redirect&bpo=42206]: Propagate and raise the errors caused by PyAST_Validate() in the parser.

bpo-41796 [https://bugs.python.org/issue?@action=redirect&bpo=41796]: The ast module internal state is now per interpreter. Patch by Victor Stinner.

bpo-42143 [https://bugs.python.org/issue?@action=redirect&bpo=42143]: Fix handling of errors during creation of PyFunctionObject, which resulted in operations on uninitialized memory. Patch by Yonatan Goldschmidt.

bpo-41659 [https://bugs.python.org/issue?@action=redirect&bpo=41659]: Fix a bug in the parser, where a curly brace following a primary didn't fail immediately. This led to invalid expressions like a {b} to throw a SyntaxError with a wrong offset, or invalid expressions ending with a curly brace like a { to not fail immediately in the REPL.

bpo-42150 [https://bugs.python.org/issue?@action=redirect&bpo=42150]: Fix possible buffer overflow in the new parser when checking for continuation lines. Patch by Pablo Galindo.

bpo-42123 [https://bugs.python.org/issue?@action=redirect&bpo=42123]: Run the parser two times. On the first run, disable all the rules that only generate better error messages to gain performance. If there's a parse failure, run the parser a second time with those enabled.

bpo-42093 [https://bugs.python.org/issue?@action=redirect&bpo=42093]: The LOAD_ATTR instruction now uses new "per opcode cache" mechanism and it is about 36% faster now. Patch by Pablo Galindo and Yury Selivanov.

bpo-42030 [https://bugs.python.org/issue?@action=redirect&bpo=42030]: Support for the legacy AIX-specific shared library loading support has been removed. All versions of AIX since 4.3 have supported and defaulted to using the common Unix mechanism instead.

bpo-41984 [https://bugs.python.org/issue?@action=redirect&bpo=41984]: The garbage collector now tracks all user-defined classes. Patch by Brandt Bucher.

bpo-41993 [https://bugs.python.org/issue?@action=redirect&bpo=41993]: Fixed potential issues with removing not completely initialized module from sys.modules when import fails.

bpo-41979 [https://bugs.python.org/issue?@action=redirect&bpo=41979]: Star-unpacking is now allowed for with item's targets in the PEG parser.

bpo-41974 [https://bugs.python.org/issue?@action=redirect&bpo=41974]: Removed special methods __int__, __float__, __floordiv__, __mod__, __divmod__, __rfloordiv__, __rmod__ and __rdivmod__ of the complex class. They always raised a TypeError.

bpo-41902 [https://bugs.python.org/issue?@action=redirect&bpo=41902]: Micro optimization when compute sq_item and mp_subscript of range. Patch by Donghee Na.

bpo-41894 [https://bugs.python.org/issue?@action=redirect&bpo=41894]: When loading a native module and a load failure occurs, prevent a possible UnicodeDecodeError when not running in a UTF-8 locale by decoding the load error message using the current locale's encoding.

bpo-41902 [https://bugs.python.org/issue?@action=redirect&bpo=41902]: Micro optimization for range.index if step is 1. Patch by Donghee Na.

Library

bpo-41435 [https://bugs.python.org/issue?@action=redirect&bpo=41435]: Add sys._current_exceptions() function to retrieve a dictionary mapping each thread's identifier to the topmost exception currently active in that thread at the time the function is called.

Core and Builtins

bpo-38605 [https://bugs.python.org/issue?@action=redirect&bpo=38605]: Enable from __future__ import annotations (PEP 563 [https://peps.python.org/pep-0563/]) by default. The values found in __annotations__ dicts are now strings, for example {"x": "int"} instead of {"x": int}.

Library

bpo-35455 [https://bugs.python.org/issue?@action=redirect&bpo=35455]: On Solaris, thread_time() is now implemented with gethrvtime() because clock_gettime(CLOCK_THREAD_CPUTIME_ID) is not always available. Patch by Jakub Kulik.

bpo-42233 [https://bugs.python.org/issue?@action=redirect&bpo=42233]: The repr() of typing types containing Generic Alias Types previously did not show the parameterized types in the GenericAlias. They have now been changed to do so.

bpo-29566 [https://bugs.python.org/issue?@action=redirect&bpo=29566]: binhex.binhex() consistently writes macOS 9 line endings.

bpo-26789 [https://bugs.python.org/issue?@action=redirect&bpo=26789]: The logging.FileHandler class now keeps a reference to the builtin open() function to be able to open or reopen the file during Python finalization. Fix errors like: NameError: name 'open' is not defined. Patch by Victor Stinner.

bpo-42157 [https://bugs.python.org/issue?@action=redirect&bpo=42157]: Removed the unicodedata.ucnhash_CAPI attribute which was an internal PyCapsule object. The related private _PyUnicode_Name_CAPI structure was moved to the internal C API. Patch by Victor Stinner.

bpo-42157 [https://bugs.python.org/issue?@action=redirect&bpo=42157]: Convert the unicodedata extension module to the multiphase initialization API (PEP 489 [https://peps.python.org/pep-0489/]) and convert the unicodedata.UCD static type to a heap type. Patch by Mohamed Koubaa and Victor Stinner.

bpo-42146 [https://bugs.python.org/issue?@action=redirect&bpo=42146]: Fix memory leak in subprocess.Popen() in case an uid (gid) specified in user (group, extra_groups) overflows uid_t (gid_t).

bpo-42103 [https://bugs.python.org/issue?@action=redirect&bpo=42103]: InvalidFileException and RecursionError are now the only errors caused by loading malformed binary Plist file (previously ValueError and TypeError could be raised in some specific cases).

bpo-41490 [https://bugs.python.org/issue?@action=redirect&bpo=41490]: In importlib.resources, .path method is more aggressive about releasing handles to zipfile objects early, enabling use-cases like certifi to leave the context open but delete the underlying zip file.

bpo-41052 [https://bugs.python.org/issue?@action=redirect&bpo=41052]: Pickling heap types implemented in C with protocols 0 and 1 raises now an error instead of producing incorrect data.

bpo-42089 [https://bugs.python.org/issue?@action=redirect&bpo=42089]: In importlib.metadata.PackageNotFoundError, make reference to the package metadata being missing to improve the user experience.

bpo-41491 [https://bugs.python.org/issue?@action=redirect&bpo=41491]: plistlib: fix parsing XML plists with hexadecimal integer values

bpo-42065 [https://bugs.python.org/issue?@action=redirect&bpo=42065]: Fix an incorrectly formatted error from _codecs.charmap_decode() when called with a mapped value outside the range of valid Unicode code points. PR by Max Bernstein.

bpo-41966 [https://bugs.python.org/issue?@action=redirect&bpo=41966]: Fix pickling pure Python datetime.time subclasses. Patch by Dean Inwood.

bpo-19270 [https://bugs.python.org/issue?@action=redirect&bpo=19270]: sched.scheduler.cancel() will now cancel the correct event, if two events with same priority are scheduled for the same time. Patch by Bar Harel.

bpo-28660 [https://bugs.python.org/issue?@action=redirect&bpo=28660]: textwrap.wrap() now attempts to break long words after hyphens when break_long_words=True and break_on_hyphens=True.

bpo-35823 [https://bugs.python.org/issue?@action=redirect&bpo=35823]: Use vfork() instead of fork() for subprocess.Popen() on Linux to improve performance in cases where it is deemed safe.

bpo-42043 [https://bugs.python.org/issue?@action=redirect&bpo=42043]: Add support for zipfile.Path inheritance. zipfile.Path.is_file() now returns False for non-existent names. zipfile.Path objects now expose a .filename attribute and rely on that to resolve .name and .parent when the Path object is at the root of the zipfile.

bpo-42021 [https://bugs.python.org/issue?@action=redirect&bpo=42021]: Fix possible ref leaks in sqlite3 module init.

bpo-39101 [https://bugs.python.org/issue?@action=redirect&bpo=39101]: Fixed tests using IsolatedAsyncioTestCase from hanging on BaseExceptions.

bpo-41976 [https://bugs.python.org/issue?@action=redirect&bpo=41976]: Fixed a bug that was causing ctypes.util.find_library() to return None when triying to locate a library in an environment when gcc>=9 is available and ldconfig is not. Patch by Pablo Galindo

bpo-41943 [https://bugs.python.org/issue?@action=redirect&bpo=41943]: Fix bug where TestCase.assertLogs doesn't correctly filter messages by level.

bpo-41923 [https://bugs.python.org/issue?@action=redirect&bpo=41923]: Implement PEP 613 [https://peps.python.org/pep-0613/], introducing typing.TypeAlias annotation.

bpo-41905 [https://bugs.python.org/issue?@action=redirect&bpo=41905]: A new function in abc: update_abstractmethods to re-calculate an abstract class's abstract status. In addition, dataclass has been changed to call this function.

bpo-23706 [https://bugs.python.org/issue?@action=redirect&bpo=23706]: Added newline parameter to pathlib.Path.write_text().

bpo-41876 [https://bugs.python.org/issue?@action=redirect&bpo=41876]: Tkinter font class repr uses font name

bpo-41831 [https://bugs.python.org/issue?@action=redirect&bpo=41831]: str() for the type attribute of the tkinter.Event object always returns now the numeric code returned by Tk instead of the name of the event type.

bpo-39337 [https://bugs.python.org/issue?@action=redirect&bpo=39337]: encodings.normalize_encoding() now ignores non-ASCII characters.

bpo-41747 [https://bugs.python.org/issue?@action=redirect&bpo=41747]: Ensure all methods that generated from dataclasses.dataclass() objects now have the proper __qualname__ attribute referring to the class they belong to. Patch by Batuhan Taskaya.

bpo-30681 [https://bugs.python.org/issue?@action=redirect&bpo=30681]: Handle exceptions caused by unparsable date headers when using email "default" policy. Patch by Tim Bell, Georges Toth

bpo-41586 [https://bugs.python.org/issue?@action=redirect&bpo=41586]: Add F_SETPIPE_SZ and F_GETPIPE_SZ to fcntl module. Allow setting pipesize on subprocess.Popen.

bpo-41229 [https://bugs.python.org/issue?@action=redirect&bpo=41229]: Add contextlib.aclosing for deterministic cleanup of async generators which is analogous to contextlib.closing for non-async generators. Patch by Joongi Kim and John Belmonte.

bpo-16396 [https://bugs.python.org/issue?@action=redirect&bpo=16396]: Allow ctypes.wintypes to be imported on non-Windows systems.

bpo-4356 [https://bugs.python.org/issue?@action=redirect&bpo=4356]: Add a key function to the bisect module.

bpo-40592 [https://bugs.python.org/issue?@action=redirect&bpo=40592]: shutil.which() now ignores empty entries in PATHEXT instead of treating them as a match.

bpo-40492 [https://bugs.python.org/issue?@action=redirect&bpo=40492]: Fix --outfile for cProfile / profile not writing the output file in the original directory when the program being profiled changes the working directory. PR by Anthony Sottile.

bpo-34204 [https://bugs.python.org/issue?@action=redirect&bpo=34204]: The shelve module now uses pickle.DEFAULT_PROTOCOL by default instead of pickle protocol 3.

bpo-27321 [https://bugs.python.org/issue?@action=redirect&bpo=27321]: Fixed KeyError exception when flattening an email to a string attempts to replace a non-existent Content-Transfer-Encoding header.

bpo-38976 [https://bugs.python.org/issue?@action=redirect&bpo=38976]: The http.cookiejar module now supports the parsing of cookies in CURL-style cookiejar files through MozillaCookieJar on all platforms. Previously, such cookie entries would be silently ignored when loading a cookiejar with such entries.

Additionally, the HTTP Only attribute is persisted in the object, and will be correctly written to file if the MozillaCookieJar object is subsequently dumped.

Documentation

bpo-42061 [https://bugs.python.org/issue?@action=redirect&bpo=42061]: Document __format__ functionality for IP addresses.

bpo-41910 [https://bugs.python.org/issue?@action=redirect&bpo=41910]: Document the default implementation of object.__eq__.

bpo-42010 [https://bugs.python.org/issue?@action=redirect&bpo=42010]: Clarify that subscription expressions are also valid for certain classes and types in the standard library, and for user-defined classes and types if the classmethod __class_getitem__() is provided.

bpo-41805 [https://bugs.python.org/issue?@action=redirect&bpo=41805]: Documented generic alias type and types.GenericAlias. Also added an entry in glossary for generic types.

bpo-39693 [https://bugs.python.org/issue?@action=redirect&bpo=39693]: Fix tarfile's extractfile documentation

bpo-39416 [https://bugs.python.org/issue?@action=redirect&bpo=39416]: Document some restrictions on the default string representations of numeric classes.

Tests

bpo-41739 [https://bugs.python.org/issue?@action=redirect&bpo=41739]: Fix test_logging.test_race_between_set_target_and_flush(): the test now waits until all threads complete to avoid leaking running threads.

bpo-41970 [https://bugs.python.org/issue?@action=redirect&bpo=41970]: Avoid a test failure in test_lib2to3 if the module has already imported at the time the test executes. Patch by Pablo Galindo.

bpo-41944 [https://bugs.python.org/issue?@action=redirect&bpo=41944]: Tests for CJK codecs no longer call eval() on content received via HTTP.

bpo-41306 [https://bugs.python.org/issue?@action=redirect&bpo=41306]: Fixed a failure in test_tk.test_widgets.ScaleTest happening when executing the test with Tk 8.6.10.

Build

bpo-38980 [https://bugs.python.org/issue?@action=redirect&bpo=38980]: Add -fno-semantic-interposition to both the compile and link line when building with --enable-optimizations. Patch by Victor Stinner and Pablo Galindo.

Windows

bpo-38439 [https://bugs.python.org/issue?@action=redirect&bpo=38439]: Updates the icons for IDLE in the Windows Store package.

bpo-38252 [https://bugs.python.org/issue?@action=redirect&bpo=38252]: Use 8-byte step to detect ASCII sequence in 64-bit Windows build.

bpo-39107 [https://bugs.python.org/issue?@action=redirect&bpo=39107]: Update Tcl and Tk to 8.6.10 in Windows installer.

bpo-41557 [https://bugs.python.org/issue?@action=redirect&bpo=41557]: Update Windows installer to use SQLite 3.33.0.

bpo-38324 [https://bugs.python.org/issue?@action=redirect&bpo=38324]: Avoid Unicode errors when accessing certain locale data on Windows.

macOS

bpo-41471 [https://bugs.python.org/issue?@action=redirect&bpo=41471]: Ignore invalid prefix lengths in system proxy excludes.

IDLE

bpo-33987 [https://bugs.python.org/issue?@action=redirect&bpo=33987]: Mostly finish using ttk widgets, mainly for editor, settings, and searches. Some patches by Mark Roseman.

bpo-40511 [https://bugs.python.org/issue?@action=redirect&bpo=40511]: Typing opening and closing parentheses inside the parentheses of a function call will no longer cause unnecessary "flashing" off and on of an existing open call-tip, e.g. when typed in a string literal.

bpo-38439 [https://bugs.python.org/issue?@action=redirect&bpo=38439]: Add a 256×256 pixel IDLE icon to the Windows .ico file. Created by Andrew Clover. Remove the low-color gif variations from the .ico file.

C API

bpo-42157 [https://bugs.python.org/issue?@action=redirect&bpo=42157]: The private _PyUnicode_Name_CAPI structure of the PyCapsule API unicodedata.ucnhash_CAPI has been moved to the internal C API. Patch by Victor Stinner.

bpo-42015 [https://bugs.python.org/issue?@action=redirect&bpo=42015]: Fix potential crash in deallocating method objects when dynamically allocated PyMethodDef's lifetime is managed through the self argument of a PyCFunction.

bpo-40423 [https://bugs.python.org/issue?@action=redirect&bpo=40423]: The subprocess module and os.closerange will now use the close_range(low, high, flags) syscall when it is available for more efficient closing of ranges of descriptors.

bpo-41845 [https://bugs.python.org/issue?@action=redirect&bpo=41845]: PyObject_GenericGetDict() is available again in the limited API when targeting 3.10 or later.

bpo-40422 [https://bugs.python.org/issue?@action=redirect&bpo=40422]: Add _Py_closerange function to provide performant closing of a range of file descriptors.

bpo-41986 [https://bugs.python.org/issue?@action=redirect&bpo=41986]: Py_FileSystemDefaultEncodeErrors and Py_UTF8Mode are available again in limited API.

bpo-41756 [https://bugs.python.org/issue?@action=redirect&bpo=41756]: Add PyIter_Send function to allow sending value into generator/coroutine/iterator without raising StopIteration exception to signal return.

bpo-41784 [https://bugs.python.org/issue?@action=redirect&bpo=41784]: Added PyUnicode_AsUTF8AndSize to the limited C API.

Python 3.10.0 alpha 1

Release date: 2020-10-05

Security

bpo-41304 [https://bugs.python.org/issue?@action=redirect&bpo=41304]: Fixes python3x._pth being ignored on Windows, caused by the fix for bpo-29778 [https://bugs.python.org/issue?@action=redirect&bpo=29778] (CVE 2020-15801 [https://www.cve.org/CVERecord?id=CVE-2020-15801]).

bpo-41162 [https://bugs.python.org/issue?@action=redirect&bpo=41162]: Audit hooks are now cleared later during finalization to avoid missing events.

bpo-29778 [https://bugs.python.org/issue?@action=redirect&bpo=29778]: Ensure python3.dll is loaded from correct locations when Python is embedded (CVE 2020-15523 [https://www.cve.org/CVERecord?id=CVE-2020-15523]).

bpo-41004 [https://bugs.python.org/issue?@action=redirect&bpo=41004]: The __hash__() methods of ipaddress.IPv4Interface and ipaddress.IPv6Interface incorrectly generated constant hash values of 32 and 128 respectively. This resulted in always causing hash collisions. The fix uses hash() to generate hash values for the tuple of (address, mask length, network address).

bpo-39603 [https://bugs.python.org/issue?@action=redirect&bpo=39603]: Prevent http header injection by rejecting control characters in http.client.putrequest(...).

Core and Builtins

bpo-41909 [https://bugs.python.org/issue?@action=redirect&bpo=41909]: Fixed stack overflow in issubclass() and isinstance() when getting the __bases__ attribute leads to infinite recursion.

bpo-41922 [https://bugs.python.org/issue?@action=redirect&bpo=41922]: Speed up calls to reversed() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-41873 [https://bugs.python.org/issue?@action=redirect&bpo=41873]: Calls to float() are now faster due to the vectorcall calling convention. Patch by Dennis Sweeney.

bpo-41870 [https://bugs.python.org/issue?@action=redirect&bpo=41870]: Speed up calls to bool() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _bisect module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]).

Core and Builtins

bpo-39934 [https://bugs.python.org/issue?@action=redirect&bpo=39934]: Correctly count control blocks in 'except' in compiler. Ensures that a syntax error, rather a fatal error, occurs for deeply nested, named exception handlers.

bpo-41780 [https://bugs.python.org/issue?@action=redirect&bpo=41780]: Fix __dir__() of types.GenericAlias. Patch by Batuhan Taskaya.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _lsprof extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the cmath extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _scproxy extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the termios extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Convert the _sha256 extension module types to heap types.

Core and Builtins

bpo-41690 [https://bugs.python.org/issue?@action=redirect&bpo=41690]: Fix a possible stack overflow in the parser when parsing functions and classes with a huge amount of arguments. Patch by Pablo Galindo.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _overlapped extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _curses_panel extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _opcode extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

Core and Builtins

bpo-41681 [https://bugs.python.org/issue?@action=redirect&bpo=41681]: Fixes the wrong error description in the error raised by using 2 , in format string in f-string and str.format().

Library

bpo-41675 [https://bugs.python.org/issue?@action=redirect&bpo=41675]: The implementation of signal.siginterrupt() now uses sigaction() (if it is available in the system) instead of the deprecated siginterrupt(). Patch by Pablo Galindo.

Core and Builtins

bpo-41670 [https://bugs.python.org/issue?@action=redirect&bpo=41670]: Prevent line trace being skipped on platforms not compiled with USE_COMPUTED_GOTOS. Fixes issue where some lines nested within a try-except block were not being traced on Windows.

bpo-41654 [https://bugs.python.org/issue?@action=redirect&bpo=41654]: Fix a crash that occurred when destroying subclasses of MemoryError. Patch by Pablo Galindo.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the zlib extension module to multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

Core and Builtins

bpo-41631 [https://bugs.python.org/issue?@action=redirect&bpo=41631]: The _ast module uses again a global state. Using a module state per module instance is causing subtle practical problems. For example, the Mercurial project replaces the __import__() function to implement lazy import, whereas Python expected that import _ast always return a fully initialized _ast module.

Library

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert _operator to use PyType_FromSpec().

Core and Builtins

bpo-1653741 [https://bugs.python.org/issue?@action=redirect&bpo=1653741]: Port _sha3 to multi-phase init. Convert static types to heap types.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _blake2 extension module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]).

Core and Builtins

bpo-41533 [https://bugs.python.org/issue?@action=redirect&bpo=41533]: Free the stack allocated in va_build_stack if do_mkstack fails and the stack is not a small_stack.

bpo-41531 [https://bugs.python.org/issue?@action=redirect&bpo=41531]: Fix a bug that was dropping keys when compiling dict literals with more than 0xFFFF elements. Patch by Pablo Galindo.

bpo-41525 [https://bugs.python.org/issue?@action=redirect&bpo=41525]: The output of python --help contains now only ASCII characters.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _sha1, _sha512, and _md5 extension modules to multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]).

Core and Builtins

bpo-41431 [https://bugs.python.org/issue?@action=redirect&bpo=41431]: Optimize dict_merge() for copying dict (e.g. dict(d) and {}.update(d)).

bpo-41428 [https://bugs.python.org/issue?@action=redirect&bpo=41428]: Implement PEP 604. This supports (int | str) etc. in place of Union[str, int].

bpo-41340 [https://bugs.python.org/issue?@action=redirect&bpo=41340]: Removed fallback implementation for strdup.

bpo-38156 [https://bugs.python.org/issue?@action=redirect&bpo=38156]: Handle interrupts that come after EOF correctly in PyOS_StdioReadline.

bpo-41342 [https://bugs.python.org/issue?@action=redirect&bpo=41342]: round() with integer argument is now faster (9--60%).

bpo-41334 [https://bugs.python.org/issue?@action=redirect&bpo=41334]: Constructors str(), bytes() and bytearray() are now faster (around 30--40% for small objects).

bpo-41295 [https://bugs.python.org/issue?@action=redirect&bpo=41295]: Resolve a regression in CPython 3.8.4 where defining "__setattr__" in a multi-inheritance setup and calling up the hierarchy chain could fail if builtins/extension types were involved in the base types.

bpo-41323 [https://bugs.python.org/issue?@action=redirect&bpo=41323]: Bytecode optimizations are performed directly on the control flow graph. This will result in slightly more compact code objects in some circumstances.

bpo-41247 [https://bugs.python.org/issue?@action=redirect&bpo=41247]: Always cache the running loop holder when running asyncio.set_running_loop.

bpo-41252 [https://bugs.python.org/issue?@action=redirect&bpo=41252]: Fix incorrect refcounting in _ssl.c's _servername_callback().

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port multiprocessing to multi-phase initialization

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port winapi to multiphase initialization

Core and Builtins

bpo-41215 [https://bugs.python.org/issue?@action=redirect&bpo=41215]: Use non-NULL default values in the PEG parser keyword list to overcome a bug that was preventing Python from being properly compiled when using the XLC compiler. Patch by Pablo Galindo.

bpo-41218 [https://bugs.python.org/issue?@action=redirect&bpo=41218]: Python 3.8.3 had a regression where compiling with ast.PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension with CO_COROUTINE. Now only list comprehension making use of async/await will tagged as so.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port faulthandler to multiphase initialization.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port sha256 to multiphase initialization

Core and Builtins

bpo-41175 [https://bugs.python.org/issue?@action=redirect&bpo=41175]: Guard against a NULL pointer dereference within bytearrayobject triggered by the bytearray() + bytearray() operation.

bpo-41100 [https://bugs.python.org/issue?@action=redirect&bpo=41100]: add arm64 to the allowable Mac OS arches in mpdecimal.h

bpo-41094 [https://bugs.python.org/issue?@action=redirect&bpo=41094]: Fix decoding errors with audit when open files with non-ASCII names on non-UTF-8 locale.

bpo-39960 [https://bugs.python.org/issue?@action=redirect&bpo=39960]: The "hackcheck" that prevents sneaking around a type's __setattr__() by calling the superclass method was rewritten to allow C implemented heap types.

bpo-41084 [https://bugs.python.org/issue?@action=redirect&bpo=41084]: Prefix the error message with 'f-string: ', when parsing an f-string expression which throws a SyntaxError.

bpo-40521 [https://bugs.python.org/issue?@action=redirect&bpo=40521]: Empty frozensets are no longer singletons.

bpo-41076 [https://bugs.python.org/issue?@action=redirect&bpo=41076]: Pre-feed the parser with the location of the f-string expression, not the f-string itself, which allows us to skip the shifting of the AST node locations after the parsing is completed.

bpo-41056 [https://bugs.python.org/issue?@action=redirect&bpo=41056]: Fixes a reference to deallocated stack space during startup when constructing sys.path involving a relative symlink when code was supplied via -c. (discovered via Coverity)

bpo-41061 [https://bugs.python.org/issue?@action=redirect&bpo=41061]: Fix incorrect expressions and asserts in hashtable code and tests.

bpo-41052 [https://bugs.python.org/issue?@action=redirect&bpo=41052]: Opt out serialization/deserialization for _random.Random

bpo-40939 [https://bugs.python.org/issue?@action=redirect&bpo=40939]: Rename PyPegen* functions to PyParser*, so that we can remove the old set of PyParser* functions that were using the old parser, but keep everything backwards-compatible.

bpo-35975 [https://bugs.python.org/issue?@action=redirect&bpo=35975]: Stefan Behnel reported that cf_feature_version is used even when PyCF_ONLY_AST is not set. This is against the intention and against the documented behavior, so it's been fixed.

bpo-40939 [https://bugs.python.org/issue?@action=redirect&bpo=40939]: Remove the remaining files from the old parser and the symbol module.

Library

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert _bz2 to use PyType_FromSpec().

Core and Builtins

bpo-41006 [https://bugs.python.org/issue?@action=redirect&bpo=41006]: The encodings.latin_1 module is no longer imported at startup. Now it is only imported when it is the filesystem encoding or the stdio encoding.

bpo-40636 [https://bugs.python.org/issue?@action=redirect&bpo=40636]: zip() now supports PEP 618 [https://peps.python.org/pep-0618/]'s strict parameter, which raises a ValueError if the arguments are exhausted at different lengths. Patch by Brandt Bucher.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _gdbm to multiphase initialization.

bpo-40985 [https://bugs.python.org/issue?@action=redirect&bpo=40985]: Fix a bug that caused the SyntaxError text to be empty when a file ends with a line ending in a line continuation character (i.e. backslash). The error text should contain the text of the last line.

bpo-40958 [https://bugs.python.org/issue?@action=redirect&bpo=40958]: Fix a possible buffer overflow in the PEG parser when gathering information for emitting syntax errors. Patch by Pablo Galindo.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _dbm to multiphase initialization.

bpo-40957 [https://bugs.python.org/issue?@action=redirect&bpo=40957]: Fix refleak in _Py_fopen_obj() when PySys_Audit() fails

Library

bpo-40950 [https://bugs.python.org/issue?@action=redirect&bpo=40950]: Add a state to the nis module (PEP 3121 [https://peps.python.org/pep-3121/]) and apply the multiphase initialization. Patch by Donghee Na.

Core and Builtins

bpo-40947 [https://bugs.python.org/issue?@action=redirect&bpo=40947]: The Python Path Configuration now takes PyConfig.platlibdir in account.

bpo-40939 [https://bugs.python.org/issue?@action=redirect&bpo=40939]: Remove the old parser, the parser module and all associated support code, command-line options and environment variables. Patch by Pablo Galindo.

bpo-40847 [https://bugs.python.org/issue?@action=redirect&bpo=40847]: Fix a bug where a line with only a line continuation character is not considered a blank line at tokenizer level. In such cases, more than a single NEWLINE token was emitted. The old parser was working around the issue, but the new parser threw a SyntaxError for valid input due to this. For example, an empty line following a line continuation character was interpreted as a SyntaxError.

bpo-40890 [https://bugs.python.org/issue?@action=redirect&bpo=40890]: Each dictionary view now has a mapping attribute that provides a types.MappingProxyType wrapping the original dictionary. Patch contributed by Dennis Sweeney.

bpo-40889 [https://bugs.python.org/issue?@action=redirect&bpo=40889]: Improved the performance of symmetric difference operations on dictionary item views. Patch by Dennis Sweeney.

bpo-40904 [https://bugs.python.org/issue?@action=redirect&bpo=40904]: Fix possible segfault in the new PEG parser when parsing f-string containing yield statements with no value (f"{yield}"). Patch by Pablo Galindo

bpo-40903 [https://bugs.python.org/issue?@action=redirect&bpo=40903]: Fixed a possible segfault in the new PEG parser when producing error messages for invalid assignments of the form p=p=. Patch by Pablo Galindo

bpo-40880 [https://bugs.python.org/issue?@action=redirect&bpo=40880]: Fix invalid memory read in the new parser when checking newlines in string literals. Patch by Pablo Galindo.

bpo-40883 [https://bugs.python.org/issue?@action=redirect&bpo=40883]: Fix memory leak in when parsing f-strings in the new parser. Patch by Pablo Galindo

bpo-40870 [https://bugs.python.org/issue?@action=redirect&bpo=40870]: Raise ValueError when validating custom AST's where the constants True, False and None are used within a ast.Name node.

bpo-40854 [https://bugs.python.org/issue?@action=redirect&bpo=40854]: Allow overriding sys.platlibdir via a new PYTHONPLATLIBDIR environment variable.

bpo-40826 [https://bugs.python.org/issue?@action=redirect&bpo=40826]: Fix GIL usage in PyOS_Readline(): lock the GIL to set an exception and pass the Python thread state when checking if there is a pending signal.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port fcntl to multiphase initialization.

bpo-19468 [https://bugs.python.org/issue?@action=redirect&bpo=19468]: Delete unnecessary instance check in importlib.reload(). Patch by Furkan Önder.

bpo-40824 [https://bugs.python.org/issue?@action=redirect&bpo=40824]: Unexpected errors in calling the __iter__ method are no longer masked by TypeError in the in operator and functions contains(), indexOf() and countOf() of the operator module.

bpo-40792 [https://bugs.python.org/issue?@action=redirect&bpo=40792]: Attributes start, stop and step of the range object now always has exact type int. Previously, they could have been an instance of a subclass of int.

bpo-40780 [https://bugs.python.org/issue?@action=redirect&bpo=40780]: Fix a corner case where g-style string formatting of a float failed to remove trailing zeros.

bpo-38964 [https://bugs.python.org/issue?@action=redirect&bpo=38964]: When there's a SyntaxError in the expression part of an fstring, the filename attribute of the SyntaxError gets correctly set to the name of the file the fstring resides in.

bpo-40750 [https://bugs.python.org/issue?@action=redirect&bpo=40750]: Support the "-d" debug flag in the new PEG parser. Patch by Pablo Galindo

bpo-40217 [https://bugs.python.org/issue?@action=redirect&bpo=40217]: Instances of types created with PyType_FromSpecWithBases() will no longer automatically visit their class object when traversing references in the garbage collector. The user is expected to manually visit the object's class. Patch by Pablo Galindo.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Py_TYPE() is changed to the inline static function. Patch by Donghee Na.

bpo-40696 [https://bugs.python.org/issue?@action=redirect&bpo=40696]: Fix a hang that can arise after generator.throw() due to a cycle in the exception context chain.

bpo-40521 [https://bugs.python.org/issue?@action=redirect&bpo=40521]: Each interpreter now its has own free lists, singletons and caches:

Free lists: float, tuple, list, dict, frame, context, asynchronous generator, MemoryError.

Singletons: empty tuple, empty bytes string, empty Unicode string, single byte character, single Unicode (latin1) character.

Slice cache.

They are no longer shared by all interpreters.

bpo-40679 [https://bugs.python.org/issue?@action=redirect&bpo=40679]: Certain TypeError messages about missing or extra arguments now include the function's qualified name. Patch by Dennis Sweeney.

bpo-29590 [https://bugs.python.org/issue?@action=redirect&bpo=29590]: Make the stack trace correct after calling generator.throw() on a generator that has yielded from a yield from.

bpo-4022 [https://bugs.python.org/issue?@action=redirect&bpo=4022]: Improve performance of generators by not raising internal StopIteration.

Library

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port mmap to multiphase initialization.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _lzma to multiphase initialization.

Core and Builtins

bpo-37999 [https://bugs.python.org/issue?@action=redirect&bpo=37999]: Builtin and extension functions that take integer arguments no longer accept Decimals, Fractions and other objects that can be converted to integers only with a loss (e.g. that have the __int__() method but do not have the __index__() method).

bpo-29882 [https://bugs.python.org/issue?@action=redirect&bpo=29882]: Add int.bit_count(), counting the number of ones in the binary representation of an integer. Patch by Niklas Fiekas.

Library

bpo-36982 [https://bugs.python.org/issue?@action=redirect&bpo=36982]: Use ncurses extended color functions when available to support terminals with 256 colors, and add the new function curses.has_extended_color_support() to indicate whether extended color support is provided by the underlying ncurses library.

Core and Builtins

bpo-19569 [https://bugs.python.org/issue?@action=redirect&bpo=19569]: Add the private macros _Py_COMP_DIAG_PUSH, _Py_COMP_DIAG_IGNORE_DEPR_DECLS, and _Py_COMP_DIAG_POP.

bpo-26680 [https://bugs.python.org/issue?@action=redirect&bpo=26680]: The int type now supports the x.is_integer() method for compatibility with float.

Library

bpo-41900 [https://bugs.python.org/issue?@action=redirect&bpo=41900]: C14N 2.0 serialisation in xml.etree.ElementTree failed for unprefixed attributes when a default namespace was defined.

bpo-41887 [https://bugs.python.org/issue?@action=redirect&bpo=41887]: Strip leading spaces and tabs on ast.literal_eval(). Also document stripping of spaces and tabs for eval().

bpo-41773 [https://bugs.python.org/issue?@action=redirect&bpo=41773]: Note in documentation that random.choices() doesn't support non-finite weights, raise ValueError when given non-finite weights.

bpo-41840 [https://bugs.python.org/issue?@action=redirect&bpo=41840]: Fix a bug in the symtable module that was causing module-scope global variables to not be reported as both local and global. Patch by Pablo Galindo.

bpo-41842 [https://bugs.python.org/issue?@action=redirect&bpo=41842]: Add codecs.unregister() function to unregister a codec search function.

bpo-40564 [https://bugs.python.org/issue?@action=redirect&bpo=40564]: In zipfile.Path, mutate the passed ZipFile object type instead of making a copy. Prevents issues when both the local copy and the caller’s copy attempt to close the same file handle.

bpo-40670 [https://bugs.python.org/issue?@action=redirect&bpo=40670]: More reliable validation of statements in timeit.Timer. It now accepts "empty" statements (only whitespaces and comments) and rejects misindentent statements.

bpo-41833 [https://bugs.python.org/issue?@action=redirect&bpo=41833]: The threading.Thread constructor now uses the target name if the target argument is specified but the name argument is omitted.

bpo-41817 [https://bugs.python.org/issue?@action=redirect&bpo=41817]: fix tkinter.EventType Enum so all members are strings, and none are tuples

bpo-41810 [https://bugs.python.org/issue?@action=redirect&bpo=41810]: types.EllipsisType, types.NotImplementedType and types.NoneType have been reintroduced, providing a new set of types readily interpretable by static type checkers.

bpo-41815 [https://bugs.python.org/issue?@action=redirect&bpo=41815]: Fix SQLite3 segfault when backing up closed database. Patch contributed by Peter David McCormick.

bpo-41816 [https://bugs.python.org/issue?@action=redirect&bpo=41816]: StrEnum added: it ensures that all members are already strings or string candidates

bpo-41517 [https://bugs.python.org/issue?@action=redirect&bpo=41517]: fix bug allowing Enums to be extended via multiple inheritance

bpo-39587 [https://bugs.python.org/issue?@action=redirect&bpo=39587]: use the correct mix-in data type when constructing Enums

bpo-41792 [https://bugs.python.org/issue?@action=redirect&bpo=41792]: Add is_typeddict function to typing.py to check if a type is a TypedDict class

Previously there was no way to check that without using private API. See the relevant issue in python/typing [https://github.com/python/typing/issues/751].

bpo-41789 [https://bugs.python.org/issue?@action=redirect&bpo=41789]: Honor object overrides in Enum class creation (specifically, __str__, __repr__, __format__, and __reduce_ex__).

bpo-32218 [https://bugs.python.org/issue?@action=redirect&bpo=32218]: enum.Flag and enum.IntFlag members are now iterable.

bpo-39651 [https://bugs.python.org/issue?@action=redirect&bpo=39651]: Fix a race condition in the call_soon_threadsafe() method of asyncio.ProactorEventLoop: do nothing if the self-pipe socket has been closed.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the mashal extension module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port the _string extension module to the multi-phase initialization API (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-41732 [https://bugs.python.org/issue?@action=redirect&bpo=41732]: Added an iterator to memoryview.

bpo-41720 [https://bugs.python.org/issue?@action=redirect&bpo=41720]: Fixed turtle.Vec2D.__rmul__() for arguments which are not int or float.

bpo-41696 [https://bugs.python.org/issue?@action=redirect&bpo=41696]: Fix handling of debug mode in asyncio.run(). This allows setting PYTHONASYNCIODEBUG or -X dev to enable asyncio debug mode when using asyncio.run().

bpo-41687 [https://bugs.python.org/issue?@action=redirect&bpo=41687]: Fix implementation of sendfile to be compatible with Solaris.

bpo-41662 [https://bugs.python.org/issue?@action=redirect&bpo=41662]: No longer override exceptions raised in __len__() of a sequence of parameters in sqlite3 with ProgrammingError.

bpo-39010 [https://bugs.python.org/issue?@action=redirect&bpo=39010]: Restarting a ProactorEventLoop on Windows no longer logs spurious ConnectionResetErrors.

bpo-41638 [https://bugs.python.org/issue?@action=redirect&bpo=41638]: ProgrammingError message for absent parameter in sqlite3 contains now the name of the parameter instead of its index when parameters are supplied as a dict.

bpo-41662 [https://bugs.python.org/issue?@action=redirect&bpo=41662]: Fixed crash when mutate list of parameters during iteration in sqlite3.

bpo-41513 [https://bugs.python.org/issue?@action=redirect&bpo=41513]: Improved the accuracy of math.hypot(). Internally, each step is computed with extra precision so that the result is now almost always correctly rounded.

bpo-41609 [https://bugs.python.org/issue?@action=redirect&bpo=41609]: The pdb whatis command correctly reports instance methods as 'Method' rather than 'Function'.

bpo-39994 [https://bugs.python.org/issue?@action=redirect&bpo=39994]: Fixed pprint's handling of dict subclasses that override __repr__.

bpo-32751 [https://bugs.python.org/issue?@action=redirect&bpo=32751]: When cancelling the task due to a timeout, asyncio.wait_for() will now wait until the cancellation is complete also in the case when timeout is <= 0, like it does with positive timeouts.

bpo-37658 [https://bugs.python.org/issue?@action=redirect&bpo=37658]: asyncio.wait_for() now properly handles races between cancellation of itself and the completion of the wrapped awaitable.

bpo-40782 [https://bugs.python.org/issue?@action=redirect&bpo=40782]: Change the method asyncio.AbstractEventLoop.run_in_executor to not be a coroutine.

bpo-41520 [https://bugs.python.org/issue?@action=redirect&bpo=41520]: Fix codeop regression that prevented turning compile warnings into errors.

bpo-41528 [https://bugs.python.org/issue?@action=redirect&bpo=41528]: turtle uses math module functions to convert degrees to radians and vice versa and to calculate vector norm

bpo-41513 [https://bugs.python.org/issue?@action=redirect&bpo=41513]: Minor algorithmic improvement to math.hypot() and math.dist() giving small gains in speed and accuracy.

bpo-41503 [https://bugs.python.org/issue?@action=redirect&bpo=41503]: Fixed a race between setTarget and flush in logging.handlers.MemoryHandler.

bpo-41497 [https://bugs.python.org/issue?@action=redirect&bpo=41497]: Fix potential UnicodeDecodeError in dis module.

bpo-41467 [https://bugs.python.org/issue?@action=redirect&bpo=41467]: On Windows, fix asyncio recv_into() return value when the socket/pipe is closed (BrokenPipeError): return 0 rather than an empty byte string (b'').

bpo-41425 [https://bugs.python.org/issue?@action=redirect&bpo=41425]: Make tkinter doc example runnable.

bpo-41421 [https://bugs.python.org/issue?@action=redirect&bpo=41421]: Make an algebraic simplification to random.paretovariate(). It now is slightly less subject to round-off error and is slightly faster. Inputs that used to cause ZeroDivisionError now cause an OverflowError instead.

bpo-41440 [https://bugs.python.org/issue?@action=redirect&bpo=41440]: Add os.cpu_count() support for VxWorks RTOS.

bpo-41316 [https://bugs.python.org/issue?@action=redirect&bpo=41316]: Fix the tarfile module to write only basename of TAR file to GZIP compression header.

bpo-41384 [https://bugs.python.org/issue?@action=redirect&bpo=41384]: Raise TclError instead of TypeError when an unknown option is passed to tkinter.OptionMenu.

bpo-41317 [https://bugs.python.org/issue?@action=redirect&bpo=41317]: Use add_done_callback() in asyncio.loop.sock_accept() to unsubscribe reader early on cancellation.

bpo-41364 [https://bugs.python.org/issue?@action=redirect&bpo=41364]: Reduce import overhead of uuid.

bpo-35328 [https://bugs.python.org/issue?@action=redirect&bpo=35328]: Set the environment variable VIRTUAL_ENV_PROMPT at venv activation.

bpo-41341 [https://bugs.python.org/issue?@action=redirect&bpo=41341]: Recursive evaluation of typing.ForwardRef in get_type_hints.

bpo-41344 [https://bugs.python.org/issue?@action=redirect&bpo=41344]: Prevent creating shared_memory.SharedMemory objects with size=0.

bpo-41333 [https://bugs.python.org/issue?@action=redirect&bpo=41333]: collections.OrderedDict.pop() is now 2 times faster.

bpo-41288 [https://bugs.python.org/issue?@action=redirect&bpo=41288]: Unpickling invalid NEWOBJ_EX opcode with the C implementation raises now UnpicklingError instead of crashing.

bpo-39017 [https://bugs.python.org/issue?@action=redirect&bpo=39017]: Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE 2019-20907 [https://www.cve.org/CVERecord?id=CVE-2019-20907]).

bpo-41273 [https://bugs.python.org/issue?@action=redirect&bpo=41273]: Speed up any transport using _ProactorReadPipeTransport by calling recv_into instead of recv, thus not creating a new buffer for each recv call in the transport's read loop.

bpo-41235 [https://bugs.python.org/issue?@action=redirect&bpo=41235]: Fix the error handling in ssl.SSLContext.load_dh_params().

bpo-41207 [https://bugs.python.org/issue?@action=redirect&bpo=41207]: In distutils.spawn, restore expectation that DistutilsExecError is raised when the command is not found.

bpo-29727 [https://bugs.python.org/issue?@action=redirect&bpo=29727]: Register array.array as a MutableSequence. Patch by Pablo Galindo.

bpo-39168 [https://bugs.python.org/issue?@action=redirect&bpo=39168]: Remove the __new__ method of typing.Generic.

bpo-41194 [https://bugs.python.org/issue?@action=redirect&bpo=41194]: Fix a crash in the _ast module: it can no longer be loaded more than once. It now uses a global state rather than a module state.

bpo-41195 [https://bugs.python.org/issue?@action=redirect&bpo=41195]: Add read-only ssl.SSLContext.security_level attribute to retrieve the context's security level.

bpo-41193 [https://bugs.python.org/issue?@action=redirect&bpo=41193]: The write_history() atexit function of the readline completer now ignores any OSError to ignore error if the filesystem is read-only, instead of only ignoring FileNotFoundError and PermissionError.

bpo-41182 [https://bugs.python.org/issue?@action=redirect&bpo=41182]: selector: use DefaultSelector based upon implementation

bpo-41161 [https://bugs.python.org/issue?@action=redirect&bpo=41161]: The decimal module now requires libmpdec-2.5.0. Users of --with-system-libmpdec should update their system library.

bpo-40874 [https://bugs.python.org/issue?@action=redirect&bpo=40874]: The decimal module now requires libmpdec-2.5.0.

bpo-41138 [https://bugs.python.org/issue?@action=redirect&bpo=41138]: Fixed the trace module CLI for Python source files with non-UTF-8 encoding.

bpo-31082 [https://bugs.python.org/issue?@action=redirect&bpo=31082]: Use the term "iterable" in the docstring for functools.reduce().

bpo-40521 [https://bugs.python.org/issue?@action=redirect&bpo=40521]: Remove freelist from collections.deque().

bpo-31938 [https://bugs.python.org/issue?@action=redirect&bpo=31938]: Fix default-value signatures of several functions in the select module - by Anthony Sottile.

bpo-41068 [https://bugs.python.org/issue?@action=redirect&bpo=41068]: Fixed reading files with non-ASCII names from ZIP archive directly after writing them.

bpo-41058 [https://bugs.python.org/issue?@action=redirect&bpo=41058]: pdb.find_function() now correctly determines the source file encoding.

bpo-41056 [https://bugs.python.org/issue?@action=redirect&bpo=41056]: Invalid file descriptor values are now prevented from being passed to os.fpathconf. (discovered by Coverity)

bpo-41056 [https://bugs.python.org/issue?@action=redirect&bpo=41056]: Fix a NULL pointer dereference within the ssl module during a MemoryError in the keylog callback. (discovered by Coverity)

bpo-41056 [https://bugs.python.org/issue?@action=redirect&bpo=41056]: Fixed an instance where a MemoryError within the zoneinfo module might not be reported or not reported at its source. (found by Coverity)

bpo-41048 [https://bugs.python.org/issue?@action=redirect&bpo=41048]: mimetypes.read_mime_types() function reads the rule file using UTF-8 encoding, not the locale encoding. Patch by Srinivas Reddy Thatiparthy.

bpo-41043 [https://bugs.python.org/issue?@action=redirect&bpo=41043]: Fixed the use of glob() in the stdlib: literal part of the path is now always correctly escaped.

bpo-41025 [https://bugs.python.org/issue?@action=redirect&bpo=41025]: Fixed an issue preventing the C implementation of zoneinfo.ZoneInfo from being subclassed.

bpo-35018 [https://bugs.python.org/issue?@action=redirect&bpo=35018]: Add the xml.sax.handler.LexicalHandler class that is present in other SAX XML implementations.

bpo-41002 [https://bugs.python.org/issue?@action=redirect&bpo=41002]: Improve performance of HTTPResponse.read with a given amount. Patch by Bruce Merry.

bpo-40448 [https://bugs.python.org/issue?@action=redirect&bpo=40448]: ensurepip now disables the use of pip cache when installing the bundled versions of pip and setuptools. Patch by Krzysztof Konopko.

bpo-40967 [https://bugs.python.org/issue?@action=redirect&bpo=40967]: Removed asyncio.Task.current_task() and asyncio.Task.all_tasks(). Patch contributed by Rémi Lapeyre.

bpo-40924 [https://bugs.python.org/issue?@action=redirect&bpo=40924]: Ensure importlib.resources.path returns an extant path for the SourceFileLoader's resource reader. Avoids the regression identified in master while a long-term solution is devised.

bpo-40955 [https://bugs.python.org/issue?@action=redirect&bpo=40955]: Fix a minor memory leak in subprocess module when extra_groups was specified.

bpo-40855 [https://bugs.python.org/issue?@action=redirect&bpo=40855]: The standard deviation and variance functions in the statistics module were ignoring their mu and xbar arguments.

bpo-40939 [https://bugs.python.org/issue?@action=redirect&bpo=40939]: Use the new PEG parser when generating the stdlib keyword module.

bpo-23427 [https://bugs.python.org/issue?@action=redirect&bpo=23427]: Add sys.orig_argv attribute: the list of the original command line arguments passed to the Python executable.

bpo-33689 [https://bugs.python.org/issue?@action=redirect&bpo=33689]: Ignore empty or whitespace-only lines in .pth files. This matches the documentated behavior. Before, empty lines caused the site-packages dir to appear multiple times in sys.path. By Ido Michael, contributors Malcolm Smith and Tal Einat.

bpo-40884 [https://bugs.python.org/issue?@action=redirect&bpo=40884]: Added a defaults parameter to logging.Formatter, to allow specifying default values for custom fields. Patch by Asaf Alon and Bar Harel.

bpo-40876 [https://bugs.python.org/issue?@action=redirect&bpo=40876]: Clarify error message in the csv module.

bpo-39791 [https://bugs.python.org/issue?@action=redirect&bpo=39791]: Refresh importlib.metadata from importlib_metadata 1.6.1.

bpo-40807 [https://bugs.python.org/issue?@action=redirect&bpo=40807]: Stop codeop._maybe_compile, used by code.InteractiveInterpreter (and IDLE). from emitting each warning three times.

bpo-32604 [https://bugs.python.org/issue?@action=redirect&bpo=32604]: Fix reference leak in the select module when the module is imported in a subinterpreter.

bpo-39791 [https://bugs.python.org/issue?@action=redirect&bpo=39791]: Built-in loaders (SourceFileLoader and ZipImporter) now supply TraversableResources implementations for ResourceReader, and the fallback function has been removed.

bpo-39314 [https://bugs.python.org/issue?@action=redirect&bpo=39314]: rlcompleter.Completer and the standard Python shell now close the parenthesis for functions that take no arguments. Patch contributed by Rémi Lapeyre.

bpo-17005 [https://bugs.python.org/issue?@action=redirect&bpo=17005]: The topological sort functionality that was introduced initially in the functools module has been moved to a new graphlib module to better accommodate the new tools and keep the original scope of the functools module. Patch by Pablo Galindo

bpo-40834 [https://bugs.python.org/issue?@action=redirect&bpo=40834]: Fix truncate when sending str object with_xxsubinterpreters.channel_send.

bpo-40755 [https://bugs.python.org/issue?@action=redirect&bpo=40755]: Add rich comparisons to collections.Counter().

bpo-26407 [https://bugs.python.org/issue?@action=redirect&bpo=26407]: Unexpected errors in calling the __iter__ method are no longer masked by TypeError in csv.reader(), csv.writer.writerow() and csv.writer.writerows().

bpo-39384 [https://bugs.python.org/issue?@action=redirect&bpo=39384]: Fixed email.contentmanager to allow set_content() to set a null string.

bpo-40744 [https://bugs.python.org/issue?@action=redirect&bpo=40744]: The sqlite3 module uses SQLite API functions that require SQLite v3.7.3 or higher. This patch removes support for older SQLite versions, and explicitly requires SQLite 3.7.3 both at build, compile and runtime. Patch by Sergey Fedoseev and Erlend E. Aasland.

bpo-40777 [https://bugs.python.org/issue?@action=redirect&bpo=40777]: Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time to avoid errors on some compilers.

bpo-38488 [https://bugs.python.org/issue?@action=redirect&bpo=38488]: Update ensurepip to install pip 20.1.1 and setuptools 47.1.0.

bpo-40792 [https://bugs.python.org/issue?@action=redirect&bpo=40792]: The result of operator.index() now always has exact type int. Previously, the result could have been an instance of a subclass of int.

bpo-40767 [https://bugs.python.org/issue?@action=redirect&bpo=40767]: webbrowser now properly finds the default browser in pure Wayland systems by checking the WAYLAND_DISPLAY environment variable. Patch contributed by Jérémy Attali.

bpo-40791 [https://bugs.python.org/issue?@action=redirect&bpo=40791]: hashlib.compare_digest() uses OpenSSL's CRYPTO_memcmp() function when OpenSSL is available.

bpo-40795 [https://bugs.python.org/issue?@action=redirect&bpo=40795]: ctypes module: If ctypes fails to convert the result of a callback or if a ctypes callback function raises an exception, sys.unraisablehook is now called with an exception set. Previously, the error was logged into stderr by PyErr_Print().

bpo-16995 [https://bugs.python.org/issue?@action=redirect&bpo=16995]: Add base64.b32hexencode() and base64.b32hexdecode() to support the Base32 Encoding with Extended Hex Alphabet.

bpo-30008 [https://bugs.python.org/issue?@action=redirect&bpo=30008]: Fix ssl code to be compatible with OpenSSL 1.1.x builds that use no-deprecated and --api=1.1.0.

bpo-30064 [https://bugs.python.org/issue?@action=redirect&bpo=30064]: Fix asyncio loop.sock_* race condition issue

bpo-40759 [https://bugs.python.org/issue?@action=redirect&bpo=40759]: Deprecate the symbol module.

bpo-40756 [https://bugs.python.org/issue?@action=redirect&bpo=40756]: The second argument (extra) of LoggerAdapter.__init__ now defaults to None.

bpo-37129 [https://bugs.python.org/issue?@action=redirect&bpo=37129]: Add a new os.RWF_APPEND flag for os.pwritev().

bpo-40737 [https://bugs.python.org/issue?@action=redirect&bpo=40737]: Fix possible reference leak for sqlite3 initialization.

bpo-40726 [https://bugs.python.org/issue?@action=redirect&bpo=40726]: Handle cases where the end_lineno is None on ast.increment_lineno().

bpo-40698 [https://bugs.python.org/issue?@action=redirect&bpo=40698]: distutils upload creates SHA2-256 and Blake2b-256 digests. MD5 digests is skipped if platform blocks MD5.

bpo-40695 [https://bugs.python.org/issue?@action=redirect&bpo=40695]: hashlib no longer falls back to builtin hash implementations when OpenSSL provides a hash digest and the algorithm is blocked by security policy.

bpo-9216 [https://bugs.python.org/issue?@action=redirect&bpo=9216]: hashlib.new() passed usedforsecurity to OpenSSL EVP constructor _hashlib.new(). test_hashlib and test_smtplib handle strict security policy better.

bpo-40614 [https://bugs.python.org/issue?@action=redirect&bpo=40614]: ast.parse() will not parse self documenting expressions in f-strings when passed feature_version is less than (3, 8).

bpo-40626 [https://bugs.python.org/issue?@action=redirect&bpo=40626]: Add h5 file extension as MIME Type application/x-hdf5, as per HDF Group recommendation for HDF5 formatted data files. Patch contributed by Mark Schwab.

bpo-25920 [https://bugs.python.org/issue?@action=redirect&bpo=25920]: On macOS, when building Python for macOS 10.4 and older, which wasn't the case for python.org macOS installer, socket.getaddrinfo() no longer uses an internal lock to prevent race conditions when calling getaddrinfo() which is thread-safe since macOS 10.5. Python 3.9 requires macOS 10.6 or newer. The internal lock caused random hang on fork when another thread was calling socket.getaddrinfo(). The lock was also used on FreeBSD older than 5.3, OpenBSD older than 201311 and NetBSD older than 4.

bpo-40671 [https://bugs.python.org/issue?@action=redirect&bpo=40671]: Prepare _hashlib for PEP 489 [https://peps.python.org/pep-0489/] and use PyModule_AddType().

bpo-32309 [https://bugs.python.org/issue?@action=redirect&bpo=32309]: Added a new coroutine asyncio.to_thread(). It is mainly used for running IO-bound functions in a separate thread to avoid blocking the event loop, and essentially works as a high-level version of run_in_executor() that can directly take keyword arguments.

bpo-36543 [https://bugs.python.org/issue?@action=redirect&bpo=36543]: Restored the deprecated xml.etree.cElementTree module.

bpo-40611 [https://bugs.python.org/issue?@action=redirect&bpo=40611]: MAP_POPULATE constant has now been added to the list of exported mmap module flags.

bpo-39881 [https://bugs.python.org/issue?@action=redirect&bpo=39881]: PEP 554 for use in the test suite. (Patch By Joannah Nanjekye)

bpo-13097 [https://bugs.python.org/issue?@action=redirect&bpo=13097]: ctypes now raises an ArgumentError when a callback is invoked with more than 1024 arguments.

bpo-39385 [https://bugs.python.org/issue?@action=redirect&bpo=39385]: A new test assertion context-manager, unittest.assertNoLogs() will ensure a given block of code emits no log messages using the logging module. Contributed by Kit Yan Choi.

bpo-23082 [https://bugs.python.org/issue?@action=redirect&bpo=23082]: Updated the error message and docs of PurePath.relative_to() to better reflect the function behaviour.

bpo-40318 [https://bugs.python.org/issue?@action=redirect&bpo=40318]: Use SQLite3 trace v2 API, if it is available.

bpo-40105 [https://bugs.python.org/issue?@action=redirect&bpo=40105]: ZipFile truncates files to avoid corruption when a shorter comment is provided in append ("a") mode. Patch by Jan Mazur.

bpo-40084 [https://bugs.python.org/issue?@action=redirect&bpo=40084]: Fix Enum.__dir__: dir(Enum.member) now includes attributes as well as methods.

bpo-31122 [https://bugs.python.org/issue?@action=redirect&bpo=31122]: ssl.wrap_socket() now raises ssl.SSLEOFError rather than OSError when peer closes connection during TLS negotiation

bpo-39728 [https://bugs.python.org/issue?@action=redirect&bpo=39728]: fix default _missing_ so a duplicate ValueError is not set as the __context__ of the original ValueError.

bpo-39244 [https://bugs.python.org/issue?@action=redirect&bpo=39244]: Fixed multiprocessing.context.get_all_start_methods to properly return the default method first on macOS.

bpo-39040 [https://bugs.python.org/issue?@action=redirect&bpo=39040]: Fix parsing of invalid mime headers parameters by collapsing whitespace between encoded words in a bare-quote-string.

bpo-38731 [https://bugs.python.org/issue?@action=redirect&bpo=38731]: Add --quiet option to command-line interface of py_compile. Patch by Gregory Schevchenko.

bpo-35714 [https://bugs.python.org/issue?@action=redirect&bpo=35714]: struct.error is now raised if there is a null character in a struct format string.

bpo-38144 [https://bugs.python.org/issue?@action=redirect&bpo=38144]: Added the root_dir and dir_fd parameters in glob.glob().

bpo-26543 [https://bugs.python.org/issue?@action=redirect&bpo=26543]: Fix IMAP4.noop() when debug mode is enabled (ex: imaplib.Debug = 3).

bpo-12178 [https://bugs.python.org/issue?@action=redirect&bpo=12178]: csv.writer() now correctly escapes escapechar when input contains escapechar. Patch by Catalin Iacob, Berker Peksag, and Itay Elbirt.

bpo-36290 [https://bugs.python.org/issue?@action=redirect&bpo=36290]: AST nodes are now raising TypeError on conflicting keyword arguments. Patch contributed by Rémi Lapeyre.

bpo-33944 [https://bugs.python.org/issue?@action=redirect&bpo=33944]: Added site.py site-packages tracing in verbose mode.

bpo-35078 [https://bugs.python.org/issue?@action=redirect&bpo=35078]: Refactor formatweekday, formatmonthname methods in LocaleHTMLCalendar and LocaleTextCalendar classes in calendar module to call the base class methods.This enables customizable CSS classes for LocaleHTMLCalendar. Patch by Srinivas Reddy Thatiparthy

bpo-29620 [https://bugs.python.org/issue?@action=redirect&bpo=29620]: assertWarns() no longer raises a RuntimeException when accessing a module's __warningregistry__ causes importation of a new module, or when a new module is imported in another thread. Patch by Kernc.

bpo-31844 [https://bugs.python.org/issue?@action=redirect&bpo=31844]: Remove ParserBase.error() method from the private and undocumented _markupbase module. html.parser.HTMLParser is the only subclass of ParserBase and its error() implementation was deprecated in Python 3.4 and removed in Python 3.5.

bpo-34226 [https://bugs.python.org/issue?@action=redirect&bpo=34226]: Fix cgi.parse_multipart without content_length. Patch by Roger Duran

bpo-33660 [https://bugs.python.org/issue?@action=redirect&bpo=33660]: Fix pathlib.PosixPath to resolve a relative path located on the root directory properly.

bpo-28557 [https://bugs.python.org/issue?@action=redirect&bpo=28557]: Improve the error message for a misbehaving rawio.readinto

bpo-26680 [https://bugs.python.org/issue?@action=redirect&bpo=26680]: The d.is_integer() method is added to the Decimal type, for compatibility with other number types.

bpo-26680 [https://bugs.python.org/issue?@action=redirect&bpo=26680]: The x.is_integer() method is incorporated into the abstract types of the numeric tower, Real, Rational and Integral, with appropriate default implementations.

Documentation

bpo-41428 [https://bugs.python.org/issue?@action=redirect&bpo=41428]: Add documentation for PEP 604 [https://peps.python.org/pep-0604/] (Allow writing union types as X | Y).

bpo-41774 [https://bugs.python.org/issue?@action=redirect&bpo=41774]: In Programming FAQ "Sequences (Tuples/Lists)" section, add "How do you remove multiple items from a list".

bpo-35293 [https://bugs.python.org/issue?@action=redirect&bpo=35293]: Fix RemovedInSphinx40Warning when building the documentation. Patch by Donghee Na.

bpo-37149 [https://bugs.python.org/issue?@action=redirect&bpo=37149]: Change Shipman tkinter doc link from archive.org to TkDocs. (The doc has been removed from the NMT server.) The new link responds much faster and includes a short explanatory note.

bpo-41726 [https://bugs.python.org/issue?@action=redirect&bpo=41726]: Update the refcounts info of PyType_FromModuleAndSpec.

bpo-41624 [https://bugs.python.org/issue?@action=redirect&bpo=41624]: Fix the signature of typing.Coroutine.

bpo-40204 [https://bugs.python.org/issue?@action=redirect&bpo=40204]: Enable Sphinx 3.2 c_allow_pre_v3 option and disable c_warn_on_allowed_pre_v3 option to make the documentation compatible with Sphinx 2 and Sphinx 3.

bpo-41045 [https://bugs.python.org/issue?@action=redirect&bpo=41045]: Add documentation for debug feature of f-strings.

bpo-41314 [https://bugs.python.org/issue?@action=redirect&bpo=41314]: Changed the release when from __future__ import annotations becomes the default from 4.0 to 3.10 (following a change in PEP 563).

bpo-40979 [https://bugs.python.org/issue?@action=redirect&bpo=40979]: Refactored typing.rst, arranging more than 70 classes, functions, and decorators into new sub-sections.

bpo-40552 [https://bugs.python.org/issue?@action=redirect&bpo=40552]: Fix in tutorial section 4.2. Code snippet is now correct.

bpo-39883 [https://bugs.python.org/issue?@action=redirect&bpo=39883]: Make code, examples, and recipes in the Python documentation be licensed under the more permissive BSD0 license in addition to the existing Python 2.0 license.

bpo-37703 [https://bugs.python.org/issue?@action=redirect&bpo=37703]: Updated Documentation to comprehensively elaborate on the behaviour of gather.cancel()

Tests

bpo-41939 [https://bugs.python.org/issue?@action=redirect&bpo=41939]: Fix test_site.test_license_exists_at_url(): call urllib.request.urlcleanup() to reset the global urllib.request._opener. Patch by Victor Stinner.

bpo-41731 [https://bugs.python.org/issue?@action=redirect&bpo=41731]: Make test_cmd_line_script pass with option '-vv'.

bpo-41602 [https://bugs.python.org/issue?@action=redirect&bpo=41602]: Add tests for SIGINT handling in the runpy module.

bpo-41521 [https://bugs.python.org/issue?@action=redirect&bpo=41521]: test.support: Rename blacklist parameter of check__all__() to not_exported.

bpo-41477 [https://bugs.python.org/issue?@action=redirect&bpo=41477]: Make ctypes optional in test_genericalias.

bpo-41085 [https://bugs.python.org/issue?@action=redirect&bpo=41085]: Fix integer overflow in the array.array.index() method on 64-bit Windows for index larger than 2**31.

bpo-41069 [https://bugs.python.org/issue?@action=redirect&bpo=41069]: test.support.TESTFN and the current directory for tests when run via test.regrtest contain now non-ascii characters if possible.

bpo-38377 [https://bugs.python.org/issue?@action=redirect&bpo=38377]: On Linux, skip tests using multiprocessing if the current user cannot create a file in /dev/shm/ directory. Add the skip_if_broken_multiprocessing_synchronize() function to the test.support module.

bpo-41009 [https://bugs.python.org/issue?@action=redirect&bpo=41009]: Fix use of support.require_{linux|mac|freebsd}_version() decorators as class decorator.

bpo-41003 [https://bugs.python.org/issue?@action=redirect&bpo=41003]: Fix test_copyreg when numpy is installed: test.pickletester now saves/restores warnings filters when importing numpy, to ignore filters installed by numpy.

bpo-40964 [https://bugs.python.org/issue?@action=redirect&bpo=40964]: Disable remote imaplib tests, host cyrus.andrew.cmu.edu is blocking incoming connections.

bpo-40927 [https://bugs.python.org/issue?@action=redirect&bpo=40927]: Fix test_binhex when run twice: it now uses import_fresh_module() to ensure that it raises DeprecationWarning each time.

bpo-17258 [https://bugs.python.org/issue?@action=redirect&bpo=17258]: Skip some multiprocessing tests when MD5 hash digest is blocked.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Increase LOOPBACK_TIMEOUT to 10 for VxWorks RTOS.

bpo-38169 [https://bugs.python.org/issue?@action=redirect&bpo=38169]: Increase code coverage for SharedMemory and ShareableList

bpo-34401 [https://bugs.python.org/issue?@action=redirect&bpo=34401]: Make test_gdb properly run on HP-UX. Patch by Michael Osipov.

Build

bpo-38249 [https://bugs.python.org/issue?@action=redirect&bpo=38249]: Update Py_UNREACHABLE to use __builtin_unreachable() if only the compiler is able to use it. Patch by Donghee Na.

bpo-41617 [https://bugs.python.org/issue?@action=redirect&bpo=41617]: Fix pycore_bitutils.h header file to support old clang versions: __builtin_bswap16() is not available in LLVM clang 3.0.

bpo-40204 [https://bugs.python.org/issue?@action=redirect&bpo=40204]: Pin Sphinx version to 2.3.1 in Doc/Makefile.

bpo-36020 [https://bugs.python.org/issue?@action=redirect&bpo=36020]: The C99 functions snprintf() and vsnprintf() are now required to build Python.

bpo-40684 [https://bugs.python.org/issue?@action=redirect&bpo=40684]: make install now uses the PLATLIBDIR variable for the destination lib-dynload/ directory when ./configure --with-platlibdir is used.

bpo-40683 [https://bugs.python.org/issue?@action=redirect&bpo=40683]: Fixed an issue where the zoneinfo module and its tests were not included when Python is installed with make.

Windows

bpo-41744 [https://bugs.python.org/issue?@action=redirect&bpo=41744]: Fixes automatic import of props file when using the Nuget package.

bpo-41627 [https://bugs.python.org/issue?@action=redirect&bpo=41627]: The user site directory for 32-bit now includes a -32 suffix to distinguish it from the 64-bit interpreter's directory.

bpo-41526 [https://bugs.python.org/issue?@action=redirect&bpo=41526]: Fixed layout of final page of the installer by removing the special thanks to Mark Hammond (with his permission).

bpo-41492 [https://bugs.python.org/issue?@action=redirect&bpo=41492]: Fixes the description that appears in UAC prompts.

bpo-40948 [https://bugs.python.org/issue?@action=redirect&bpo=40948]: Improve post-install message to direct people to the "py" command.

bpo-41412 [https://bugs.python.org/issue?@action=redirect&bpo=41412]: The installer will now fail to install on Windows 7 and Windows 8. Further, the UCRT dependency is now always downloaded on demand.

bpo-40741 [https://bugs.python.org/issue?@action=redirect&bpo=40741]: Update Windows release to include SQLite 3.32.3.

bpo-41142 [https://bugs.python.org/issue?@action=redirect&bpo=41142]: msilib now supports creating CAB files with non-ASCII file path and adding files with non-ASCII file path to them.

bpo-41074 [https://bugs.python.org/issue?@action=redirect&bpo=41074]: Fixed support of non-ASCII names in functions msilib.OpenDatabase() and msilib.init_database() and non-ASCII SQL in method msilib.Database.OpenView().

bpo-41039 [https://bugs.python.org/issue?@action=redirect&bpo=41039]: Stable ABI redirection DLL (python3.dll) now uses #pragma comment(linker) for re-exporting.

bpo-40164 [https://bugs.python.org/issue?@action=redirect&bpo=40164]: Updates Windows OpenSSL to 1.1.1g

bpo-39631 [https://bugs.python.org/issue?@action=redirect&bpo=39631]: Changes the registered MIME type for .py files on Windows to text/x-python instead of text/plain.

bpo-40677 [https://bugs.python.org/issue?@action=redirect&bpo=40677]: Manually define IO_REPARSE_TAG_APPEXECLINK in case some old Windows SDK doesn't have it.

bpo-37556 [https://bugs.python.org/issue?@action=redirect&bpo=37556]: Extend py.exe help to mention overrides via venv, shebang, environmental variables & ini files.

macOS

bpo-41557 [https://bugs.python.org/issue?@action=redirect&bpo=41557]: Update macOS installer to use SQLite 3.33.0.

bpo-39580 [https://bugs.python.org/issue?@action=redirect&bpo=39580]: Avoid opening Finder window if running installer from the command line. Patch contributed by Rick Heil.

bpo-41100 [https://bugs.python.org/issue?@action=redirect&bpo=41100]: Fix configure error when building on macOS 11. Note that the current Python release was released shortly after the first developer preview of macOS 11 (Big Sur); there are other known issues with building and running on the developer preview. Big Sur is expected to be fully supported in a future bugfix release of Python 3.8.x and with 3.9.0.

bpo-40741 [https://bugs.python.org/issue?@action=redirect&bpo=40741]: Update macOS installer to use SQLite 3.32.3.

bpo-41005 [https://bugs.python.org/issue?@action=redirect&bpo=41005]: fixed an XDG settings issue not allowing macos to open browser in webbrowser.py

bpo-40741 [https://bugs.python.org/issue?@action=redirect&bpo=40741]: Update macOS installer to use SQLite 3.32.2.

IDLE

bpo-41775 [https://bugs.python.org/issue?@action=redirect&bpo=41775]: Use 'IDLE Shell' as shell title

bpo-35764 [https://bugs.python.org/issue?@action=redirect&bpo=35764]: Rewrite the Calltips doc section.

bpo-40181 [https://bugs.python.org/issue?@action=redirect&bpo=40181]: In calltips, stop reminding that '/' marks the end of positional-only arguments.

bpo-41468 [https://bugs.python.org/issue?@action=redirect&bpo=41468]: Improve IDLE run crash error message (which users should never see).

bpo-41373 [https://bugs.python.org/issue?@action=redirect&bpo=41373]: Save files loaded with no line ending, as when blank, or different line endings, by setting its line ending to the system default. Fix regression in 3.8.4 and 3.9.0b4.

bpo-41300 [https://bugs.python.org/issue?@action=redirect&bpo=41300]: Save files with non-ascii chars. Fix regression released in 3.9.0b4 and 3.8.4.

bpo-37765 [https://bugs.python.org/issue?@action=redirect&bpo=37765]: Add keywords to module name completion list. Rewrite Completions section of IDLE doc.

bpo-41152 [https://bugs.python.org/issue?@action=redirect&bpo=41152]: The encoding of stdin, stdout and stderr in IDLE is now always UTF-8.

bpo-41144 [https://bugs.python.org/issue?@action=redirect&bpo=41144]: Make Open Module open a special module such as os.path.

bpo-39885 [https://bugs.python.org/issue?@action=redirect&bpo=39885]: Make context menu Cut and Copy work again when right-clicking within a selection.

bpo-40723 [https://bugs.python.org/issue?@action=redirect&bpo=40723]: Make test_idle pass when run after import.

C API

bpo-41936 [https://bugs.python.org/issue?@action=redirect&bpo=41936]: Removed undocumented macros Py_ALLOW_RECURSION and Py_END_ALLOW_RECURSION and the recursion_critical field of the PyInterpreterState structure.

bpo-41692 [https://bugs.python.org/issue?@action=redirect&bpo=41692]: The PyUnicode_InternImmortal() function is now deprecated and will be removed in Python 3.12: use PyUnicode_InternInPlace() instead. Patch by Victor Stinner.

bpo-41842 [https://bugs.python.org/issue?@action=redirect&bpo=41842]: Add PyCodec_Unregister() function to unregister a codec search function.

bpo-41834 [https://bugs.python.org/issue?@action=redirect&bpo=41834]: Remove the _Py_CheckRecursionLimit variable: it has been replaced by ceval.recursion_limit of the PyInterpreterState structure. Patch by Victor Stinner.

bpo-41689 [https://bugs.python.org/issue?@action=redirect&bpo=41689]: Types created with PyType_FromSpec() now make any signature in their tp_doc slot accessible from __text_signature__.

bpo-41524 [https://bugs.python.org/issue?@action=redirect&bpo=41524]: Fix bug in PyOS_mystrnicmp() and PyOS_mystricmp() that incremented pointers beyond the end of a string.

bpo-41324 [https://bugs.python.org/issue?@action=redirect&bpo=41324]: Add a minimal decimal capsule API. The API supports fast conversions between Decimals up to 38 digits and their triple representation as a C struct.

bpo-30155 [https://bugs.python.org/issue?@action=redirect&bpo=30155]: Add PyDateTime_DATE_GET_TZINFO() and PyDateTime_TIME_GET_TZINFO() macros for accessing the tzinfo attributes of datetime.datetime and datetime.time objects.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Revert PyType_HasFeature() change: it reads again directly the PyTypeObject.tp_flags member when the limited C API is not used, rather than always calling PyType_GetFlags() which hides implementation details.

bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123]: Remove PyUnicode_AsUnicodeCopy.

bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123]: Removed PyLong_FromUnicode().

bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123]: Removed PyUnicode_GetMax().

bpo-41123 [https://bugs.python.org/issue?@action=redirect&bpo=41123]: Removed Py_UNICODE_str* functions manipulating Py_UNICODE* strings.

bpo-41103 [https://bugs.python.org/issue?@action=redirect&bpo=41103]: PyObject_AsCharBuffer(), PyObject_AsReadBuffer(), PyObject_CheckReadBuffer(), and PyObject_AsWriteBuffer() are removed. Please migrate to new buffer protocol; PyObject_GetBuffer() and PyBuffer_Release().

bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346]: Raises DeprecationWarning for PyUnicode_FromUnicode(NULL, size) and PyUnicode_FromStringAndSize(NULL, size) with size > 0.

bpo-36346 [https://bugs.python.org/issue?@action=redirect&bpo=36346]: Mark Py_UNICODE_COPY, Py_UNICODE_FILL, PyUnicode_WSTR_LENGTH, PyUnicode_FromUnicode, PyUnicode_AsUnicode, and PyUnicode_AsUnicodeAndSize as deprecated in C. Remove Py_UNICODE_MATCH which was deprecated and broken since Python 3.3.

bpo-40989 [https://bugs.python.org/issue?@action=redirect&bpo=40989]: The PyObject_INIT() and PyObject_INIT_VAR() macros become aliases to, respectively, PyObject_Init() and PyObject_InitVar() functions.

bpo-36020 [https://bugs.python.org/issue?@action=redirect&bpo=36020]: On Windows, #include "pyerrors.h" no longer defines snprintf and vsnprintf macros.

bpo-40943 [https://bugs.python.org/issue?@action=redirect&bpo=40943]: The PY_SSIZE_T_CLEAN macro must now be defined to use PyArg_ParseTuple() and Py_BuildValue() formats which use #: es#, et#, s#, u#, y#, z#, U# and Z#. See Parsing arguments and building values and the PEP 353 [https://peps.python.org/pep-0353/].

bpo-40910 [https://bugs.python.org/issue?@action=redirect&bpo=40910]: Export explicitly the Py_GetArgcArgv() function to the C API and document the function. Previously, it was exported implicitly which no longer works since Python is built with -fvisibility=hidden.

bpo-40724 [https://bugs.python.org/issue?@action=redirect&bpo=40724]: Allow defining buffer slots in type specs.

bpo-40679 [https://bugs.python.org/issue?@action=redirect&bpo=40679]: Fix a _PyEval_EvalCode() crash if qualname argument is NULL.

bpo-40839 [https://bugs.python.org/issue?@action=redirect&bpo=40839]: Calling PyDict_GetItem() without GIL held had been allowed for historical reason. It is no longer allowed.

bpo-40826 [https://bugs.python.org/issue?@action=redirect&bpo=40826]: PyOS_InterruptOccurred() now fails with a fatal error if it is called with the GIL released.

bpo-40792 [https://bugs.python.org/issue?@action=redirect&bpo=40792]: The result of PyNumber_Index() now always has exact type int. Previously, the result could have been an instance of a subclass of int.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Convert Py_REFCNT() and Py_SIZE() macros to static inline functions. They cannot be used as l-value anymore: use Py_SET_REFCNT() and Py_SET_SIZE() to set an object reference count and size. This change is backward incompatible on purpose, to prepare the C API for an opaque PyObject structure.

bpo-40703 [https://bugs.python.org/issue?@action=redirect&bpo=40703]: The PyType_FromSpec*() functions no longer overwrite the type's "__module__" attribute if it is set via "Py_tp_members" or "Py_tp_getset".

bpo-39583 [https://bugs.python.org/issue?@action=redirect&bpo=39583]: Remove superfluous "extern C" declarations from Include/cpython/*.h.

Python 3.9.0 beta 1

Release date: 2020-05-19

Security

bpo-40501 [https://bugs.python.org/issue?@action=redirect&bpo=40501]: uuid no longer uses ctypes to load libuuid or rpcrt4.dll at runtime.

Core and Builtins

bpo-40663 [https://bugs.python.org/issue?@action=redirect&bpo=40663]: Correctly generate annotations where parentheses are omitted but required (e.g: Type[(str, int, *other))].

bpo-40596 [https://bugs.python.org/issue?@action=redirect&bpo=40596]: Fixed str.isidentifier() for non-canonicalized strings containing non-BMP characters on Windows.

bpo-40593 [https://bugs.python.org/issue?@action=redirect&bpo=40593]: Improved syntax errors for invalid characters in source code.

bpo-40585 [https://bugs.python.org/issue?@action=redirect&bpo=40585]: Fixed a bug when using codeop.compile_command() that was causing exceptions to be swallowed with the new parser. Patch by Pablo Galindo

bpo-40566 [https://bugs.python.org/issue?@action=redirect&bpo=40566]: Apply PEP 573 [https://peps.python.org/pep-0573/] to abc.

bpo-40502 [https://bugs.python.org/issue?@action=redirect&bpo=40502]: Initialize n->n_col_offset. (Patch by Joannah Nanjekye)

bpo-40527 [https://bugs.python.org/issue?@action=redirect&bpo=40527]: Fix command line argument parsing: no longer write errors multiple times into stderr.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port errno to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-40523 [https://bugs.python.org/issue?@action=redirect&bpo=40523]: Add pass-throughs for hash() and reversed() to weakref.proxy objects. Patch by Pablo Galindo.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port syslog to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-40246 [https://bugs.python.org/issue?@action=redirect&bpo=40246]: Reporting a specialised error message for invalid string prefixes, which was introduced in bpo-40246 [https://bugs.python.org/issue?@action=redirect&bpo=40246], is being reverted due to backwards compatibility concerns for strings that immediately follow a reserved keyword without whitespace between them. Constructs like bg="#d00" if clear else"#fca" were failing to parse, which is not an acceptable breakage on such short notice.

bpo-40417 [https://bugs.python.org/issue?@action=redirect&bpo=40417]: Fix imp module deprecation warning when PyImport_ReloadModule is called. Patch by Robert Rouhani.

bpo-40408 [https://bugs.python.org/issue?@action=redirect&bpo=40408]: Fixed support of nested type variables in GenericAlias (e.g. list[list[T]]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _stat module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-29587 [https://bugs.python.org/issue?@action=redirect&bpo=29587]: Enable implicit exception chaining when calling generator.throw().

bpo-40328 [https://bugs.python.org/issue?@action=redirect&bpo=40328]: Add tools for generating mappings headers for CJKCodecs.

bpo-40228 [https://bugs.python.org/issue?@action=redirect&bpo=40228]: Setting frame.f_lineno is now robust w.r.t. changes in the source-to-bytecode compiler

bpo-38880 [https://bugs.python.org/issue?@action=redirect&bpo=38880]: Added the ability to list interpreters associated with channel ends in the internal subinterpreters module.

bpo-37986 [https://bugs.python.org/issue?@action=redirect&bpo=37986]: Improve performance of PyLong_FromDouble() for values that fit into long.

Library

bpo-40662 [https://bugs.python.org/issue?@action=redirect&bpo=40662]: Fixed ast.get_source_segment() for ast nodes that have incomplete location information. Patch by Irit Katriel.

bpo-40665 [https://bugs.python.org/issue?@action=redirect&bpo=40665]: Convert bisect to use Argument Clinic.

bpo-40536 [https://bugs.python.org/issue?@action=redirect&bpo=40536]: Added the available_timezones() function to the zoneinfo module. Patch by Paul Ganssle.

bpo-40645 [https://bugs.python.org/issue?@action=redirect&bpo=40645]: The hmac.HMAC exposes internal implementation details. The attributes digest_cons, inner, and outer are deprecated and will be removed in the future.

bpo-40645 [https://bugs.python.org/issue?@action=redirect&bpo=40645]: The internal module _hashlib wraps and exposes OpenSSL's HMAC API. The new code will be used in Python 3.10 after the internal implementation details of the pure Python HMAC module are no longer part of the public API.

bpo-40637 [https://bugs.python.org/issue?@action=redirect&bpo=40637]: Builtin hash modules can now be disabled or selectively enabled with configure --with-builtin-hashlib-hashes=sha3,blake1 or --without-builtin-hashlib-hashes.

bpo-37630 [https://bugs.python.org/issue?@action=redirect&bpo=37630]: The hashlib module can now use SHA3 hashes and SHAKE XOF from OpenSSL when available.

bpo-40479 [https://bugs.python.org/issue?@action=redirect&bpo=40479]: The hashlib now compiles with OpenSSL 3.0.0-alpha2.

bpo-40257 [https://bugs.python.org/issue?@action=redirect&bpo=40257]: Revert changes to inspect.getdoc().

bpo-40607 [https://bugs.python.org/issue?@action=redirect&bpo=40607]: When cancelling a task due to timeout, asyncio.wait_for() will now propagate the exception if an error happens during cancellation. Patch by Roman Skurikhin.

bpo-40612 [https://bugs.python.org/issue?@action=redirect&bpo=40612]: Fix edge cases in SyntaxError formatting. If the offset is <= 0, no caret is printed. If the offset is > line length, the caret is printed pointing just after the last character.

bpo-40597 [https://bugs.python.org/issue?@action=redirect&bpo=40597]: If text content lines are longer than policy.max_line_length, always use a content-encoding to make sure they are wrapped.

bpo-40571 [https://bugs.python.org/issue?@action=redirect&bpo=40571]: Added functools.cache() as a simpler, more discoverable way to access the unbounded cache variant of lru_cache(maxsize=None).

bpo-40503 [https://bugs.python.org/issue?@action=redirect&bpo=40503]: PEP 615 [https://peps.python.org/pep-0615/], the zoneinfo module. Adds support for the IANA time zone database.

bpo-40397 [https://bugs.python.org/issue?@action=redirect&bpo=40397]: Removed attributes __args__ and __parameters__ from special generic aliases like typing.List (not subscripted).

bpo-40549 [https://bugs.python.org/issue?@action=redirect&bpo=40549]: Convert posixmodule.c ("posix" or "nt" module) to the multiphase initialization (PEP 489).

bpo-31033 [https://bugs.python.org/issue?@action=redirect&bpo=31033]: Add a msg argument to Future.cancel() and Task.cancel().

bpo-40541 [https://bugs.python.org/issue?@action=redirect&bpo=40541]: Added an optional counts parameter to random.sample().

bpo-40515 [https://bugs.python.org/issue?@action=redirect&bpo=40515]: The ssl and hashlib modules now actively check that OpenSSL is build with thread support. Python 3.7.0 made thread support mandatory and no longer works safely with a no-thread builds.

bpo-31033 [https://bugs.python.org/issue?@action=redirect&bpo=31033]: When a asyncio.Task is cancelled, the exception traceback now chains all the way back to where the task was first interrupted.

bpo-40504 [https://bugs.python.org/issue?@action=redirect&bpo=40504]: functools.lru_cache() objects can now be the targets of weakrefs.

bpo-40559 [https://bugs.python.org/issue?@action=redirect&bpo=40559]: Fix possible memory leak in the C implementation of asyncio.Task.

bpo-40480 [https://bugs.python.org/issue?@action=redirect&bpo=40480]: fnmatch.fnmatch() could take exponential time in the presence of multiple * pattern characters. This was repaired by generating more elaborate regular expressions to avoid futile backtracking.

bpo-40495 [https://bugs.python.org/issue?@action=redirect&bpo=40495]: compileall is now able to use hardlinks to prevent duplicates in a case when .pyc files for different optimization levels have the same content.

bpo-40457 [https://bugs.python.org/issue?@action=redirect&bpo=40457]: The ssl module now support OpenSSL builds without TLS 1.0 and 1.1 methods.

bpo-40355 [https://bugs.python.org/issue?@action=redirect&bpo=40355]: Improve error reporting in ast.literal_eval() in the presence of malformed ast.Dict nodes instead of silently ignoring any non-conforming elements. Patch by Curtis Bucher.

bpo-40465 [https://bugs.python.org/issue?@action=redirect&bpo=40465]: Deprecated the optional random argument to random.shuffle().

bpo-40459 [https://bugs.python.org/issue?@action=redirect&bpo=40459]: platform.win32_ver() now produces correct ptype strings instead of empty strings.

bpo-39435 [https://bugs.python.org/issue?@action=redirect&bpo=39435]: The first argument of pickle.loads() is now positional-only.

bpo-39305 [https://bugs.python.org/issue?@action=redirect&bpo=39305]: Update nntplib to merge nntplib.NNTP and nntplib._NNTPBase. Patch by Donghee Na.

bpo-32494 [https://bugs.python.org/issue?@action=redirect&bpo=32494]: Update dbm.gnu to use gdbm_count if possible when calling len(). Patch by Donghee Na.

bpo-40453 [https://bugs.python.org/issue?@action=redirect&bpo=40453]: Add isolated=True keyword-only parameter to _xxsubinterpreters.create(). An isolated subinterpreter cannot spawn threads, spawn a child process or call os.fork().

bpo-40286 [https://bugs.python.org/issue?@action=redirect&bpo=40286]: Remove _random.Random.randbytes(): the C implementation of randbytes(). Implement the method in Python to ease subclassing: randbytes() now directly reuses getrandbits().

bpo-40394 [https://bugs.python.org/issue?@action=redirect&bpo=40394]: Added default arguments to difflib.SequenceMatcher.find_longest_match().

bpo-39995 [https://bugs.python.org/issue?@action=redirect&bpo=39995]: Fix a race condition in concurrent.futures._ThreadWakeup: access to _ThreadWakeup is now protected with the shutdown lock.

bpo-30966 [https://bugs.python.org/issue?@action=redirect&bpo=30966]: Process.shutdown(wait=True) of concurrent.futures now closes explicitly the result queue.

bpo-30966 [https://bugs.python.org/issue?@action=redirect&bpo=30966]: Add a new close() method to the SimpleQueue class to explicitly close the queue.

bpo-39966 [https://bugs.python.org/issue?@action=redirect&bpo=39966]: Revert bpo-25597 [https://bugs.python.org/issue?@action=redirect&bpo=25597]. unittest.mock.MagicMock with wraps' set uses default return values for magic methods.

bpo-39791 [https://bugs.python.org/issue?@action=redirect&bpo=39791]: Added files() function to importlib.resources with support for subdirectories in package data, matching backport in importlib_resources 1.5.

bpo-40375 [https://bugs.python.org/issue?@action=redirect&bpo=40375]: imaplib.IMAP4.unselect() is added. Patch by Donghee Na.

bpo-40389 [https://bugs.python.org/issue?@action=redirect&bpo=40389]: repr() now returns typing.Optional[T] when called for typing.Union of two types, one of which is NoneType.

bpo-40291 [https://bugs.python.org/issue?@action=redirect&bpo=40291]: Add support for CAN_J1939 sockets (available on Linux 5.4+)

bpo-40273 [https://bugs.python.org/issue?@action=redirect&bpo=40273]: types.MappingProxyType is now reversible.

bpo-39075 [https://bugs.python.org/issue?@action=redirect&bpo=39075]: The repr for types.SimpleNamespace is now insertion ordered rather than alphabetical.

bpo-40192 [https://bugs.python.org/issue?@action=redirect&bpo=40192]: On AIX, thread_time() is now implemented with thread_cputime() which has nanosecond resolution, rather than clock_gettime(CLOCK_THREAD_CPUTIME_ID) which has a resolution of 10 milliseconds. Patch by Batuhan Taskaya.

bpo-40025 [https://bugs.python.org/issue?@action=redirect&bpo=40025]: Raise TypeError when _generate_next_value_ is defined after members. Patch by Ethan Onstott.

bpo-39058 [https://bugs.python.org/issue?@action=redirect&bpo=39058]: In the argparse module, the repr for Namespace() and other argument holders now displayed in the order attributes were added. Formerly, it displayed in alphabetical order even though argument order is preserved the user visible parts of the module.

bpo-24416 [https://bugs.python.org/issue?@action=redirect&bpo=24416]: The isocalendar() methods of datetime.date and datetime.datetime now return a named tuple instead of a tuple.

Documentation

bpo-34790 [https://bugs.python.org/issue?@action=redirect&bpo=34790]: Add version of removal for explicit passing of coros to asyncio.wait()'s documentation

bpo-40561 [https://bugs.python.org/issue?@action=redirect&bpo=40561]: Provide docstrings for webbrowser open functions.

bpo-40499 [https://bugs.python.org/issue?@action=redirect&bpo=40499]: Mention that asyncio.wait() requires a non-empty set of awaitables.

bpo-39705 [https://bugs.python.org/issue?@action=redirect&bpo=39705]: Tutorial example for sorted() in the Loop Techniques section is given a better explanation. Also a new example is included to explain sorted()'s basic behavior.

bpo-39435 [https://bugs.python.org/issue?@action=redirect&bpo=39435]: Fix an incorrect signature for pickle.loads() in the docs

Tests

bpo-40055 [https://bugs.python.org/issue?@action=redirect&bpo=40055]: distutils.tests now saves/restores warnings filters to leave them unchanged. Importing tests imports docutils which imports pkg_resources which adds a warnings filter.

bpo-40436 [https://bugs.python.org/issue?@action=redirect&bpo=40436]: test_gdb and test.pythoninfo now check gdb command exit code.

Build

bpo-40653 [https://bugs.python.org/issue?@action=redirect&bpo=40653]: Move _dirnameW out of HAVE_SYMLINK to fix a potential compiling issue.

bpo-40514 [https://bugs.python.org/issue?@action=redirect&bpo=40514]: Add --with-experimental-isolated-subinterpreters build option to configure: better isolate subinterpreters, experimental build mode.

Windows

bpo-40650 [https://bugs.python.org/issue?@action=redirect&bpo=40650]: Include winsock2.h in pytime.c for timeval.

bpo-40458 [https://bugs.python.org/issue?@action=redirect&bpo=40458]: Increase reserved stack space to prevent overflow crash on Windows.

bpo-39148 [https://bugs.python.org/issue?@action=redirect&bpo=39148]: Add IPv6 support to asyncio datagram endpoints in ProactorEventLoop. Change the raised exception for unknown address families to ValueError as it's not coming from Windows API.

macOS

bpo-34956 [https://bugs.python.org/issue?@action=redirect&bpo=34956]: When building Python on macOS from source, _tkinter now links with non-system Tcl and Tk frameworks if they are installed in /Library/Frameworks, as had been the case on older releases of macOS. If a macOS SDK is explicitly configured, by using --enable-universalsdk= or -isysroot, only the SDK itself is searched. The default behavior can still be overridden with --with-tcltk-includes and --with-tcltk-libs.

bpo-35569 [https://bugs.python.org/issue?@action=redirect&bpo=35569]: Expose RFC 3542 IPv6 socket options.

Tools/Demos

bpo-40479 [https://bugs.python.org/issue?@action=redirect&bpo=40479]: Update multissltest helper to test with latest OpenSSL 1.0.2, 1.1.0, 1.1.1, and 3.0.0-alpha.

bpo-40431 [https://bugs.python.org/issue?@action=redirect&bpo=40431]: Fix a syntax typo in turtledemo that now raises a SyntaxError.

bpo-40163 [https://bugs.python.org/issue?@action=redirect&bpo=40163]: Fix multissltest tool. OpenSSL has changed download URL for old releases. The multissltest tool now tries to download from current and old download URLs.

C API

bpo-39465 [https://bugs.python.org/issue?@action=redirect&bpo=39465]: Remove the _PyUnicode_ClearStaticStrings() function from the C API.

bpo-38787 [https://bugs.python.org/issue?@action=redirect&bpo=38787]: Add PyCFunction_CheckExact() macro for exact type checks now that we allow subtypes of PyCFunction, as well as PyCMethod_CheckExact() and PyCMethod_Check() for the new PyCMethod subtype.

bpo-40545 [https://bugs.python.org/issue?@action=redirect&bpo=40545]: Declare _PyErr_GetTopmostException() with PyAPI_FUNC() to properly export the function in the C API. The function remains private (_Py) prefix.

bpo-40412 [https://bugs.python.org/issue?@action=redirect&bpo=40412]: Nullify inittab_copy during finalization, preventing future interpreter initializations in an embedded situation from crashing. Patch by Gregory Szorc.

bpo-40429 [https://bugs.python.org/issue?@action=redirect&bpo=40429]: The PyThreadState_GetFrame() function now returns a strong reference to the frame.

bpo-40428 [https://bugs.python.org/issue?@action=redirect&bpo=40428]: Remove the following functions from the C API. Call PyGC_Collect() explicitly to free all free lists.

PyAsyncGen_ClearFreeLists()

PyContext_ClearFreeList()

PyDict_ClearFreeList()

PyFloat_ClearFreeList()

PyFrame_ClearFreeList()

PyList_ClearFreeList()

PySet_ClearFreeList()

PyTuple_ClearFreeList()

bpo-40421 [https://bugs.python.org/issue?@action=redirect&bpo=40421]: New PyFrame_GetBack() function: get the frame next outer frame.

bpo-40421 [https://bugs.python.org/issue?@action=redirect&bpo=40421]: New PyFrame_GetCode() function: return a borrowed reference to the frame code.

bpo-40217 [https://bugs.python.org/issue?@action=redirect&bpo=40217]: Ensure that instances of types created with PyType_FromSpecWithBases() will visit its class object when traversing references in the garbage collector (implemented as an extension of the provided tp_traverse). Patch by Pablo Galindo.

bpo-38787 [https://bugs.python.org/issue?@action=redirect&bpo=38787]: Module C state is now accessible from C-defined heap type methods (PEP 573 [https://peps.python.org/pep-0573/]). Patch by Marcel Plch and Petr Viktorin.

Python 3.9.0 alpha 6

Release date: 2020-04-27

Security

bpo-40121 [https://bugs.python.org/issue?@action=redirect&bpo=40121]: Fixes audit events raised on creating a new socket.

bpo-39073 [https://bugs.python.org/issue?@action=redirect&bpo=39073]: Disallow CR or LF in email.headerregistry.Address arguments to guard against header injection attacks.

bpo-39503 [https://bugs.python.org/issue?@action=redirect&bpo=39503]: CVE 2020-8492 [https://www.cve.org/CVERecord?id=CVE-2020-8492]: The AbstractBasicAuthHandler class of the urllib.request module uses an inefficient regular expression which can be exploited by an attacker to cause a denial of service. Fix the regex to prevent the catastrophic backtracking. Vulnerability reported by Ben Caller and Matt Schwager.

Core and Builtins

bpo-40313 [https://bugs.python.org/issue?@action=redirect&bpo=40313]: Improve the performance of bytes.hex().

bpo-40334 [https://bugs.python.org/issue?@action=redirect&bpo=40334]: Switch to a new parser, based on PEG. For more details see PEP 617. To temporarily switch back to the old parser, use -X oldparser or PYTHONOLDPARSER=1. In Python 3.10 we will remove the old parser completely, including the parser module (already deprecated) and anything that depends on it.

bpo-40267 [https://bugs.python.org/issue?@action=redirect&bpo=40267]: Fix the tokenizer to display the correct error message, when there is a SyntaxError on the last input character and no newline follows. It used to be unexpected EOF while parsing, while it should be invalid syntax.

bpo-39522 [https://bugs.python.org/issue?@action=redirect&bpo=39522]: Correctly unparse explicit u prefix for strings when postponed evaluation for annotations activated. Patch by Batuhan Taskaya.

bpo-40246 [https://bugs.python.org/issue?@action=redirect&bpo=40246]: Report a specialized error message, invalid string prefix, when the tokenizer encounters a string with an invalid prefix.

bpo-40082 [https://bugs.python.org/issue?@action=redirect&bpo=40082]: Fix the signal handler: it now always uses the main interpreter, rather than trying to get the current Python thread state.

bpo-37388 [https://bugs.python.org/issue?@action=redirect&bpo=37388]: str.encode() and str.decode() no longer check the encoding and errors in development mode or in debug mode during Python finalization. The codecs machinery can no longer work on very late calls to str.encode() and str.decode().

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Fix possible refleaks in _json, memo of PyScannerObject should be traversed.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Speed up calls to dict() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention.

bpo-40141 [https://bugs.python.org/issue?@action=redirect&bpo=40141]: Add column and line information to ast.keyword nodes. Patch by Pablo Galindo.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port resource to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port math to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _uuid module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-40077 [https://bugs.python.org/issue?@action=redirect&bpo=40077]: Convert json module to use PyType_FromSpec().

bpo-40067 [https://bugs.python.org/issue?@action=redirect&bpo=40067]: Improve the error message for multiple star expressions in an assignment. Patch by Furkan Onder

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _functools module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port operator module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

bpo-20526 [https://bugs.python.org/issue?@action=redirect&bpo=20526]: Fix PyThreadState_Clear(). PyThreadState.frame is a borrowed reference, not a strong reference: PyThreadState_Clear() must not call Py_CLEAR(tstate->frame).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port time module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]). Patch by Paulo Henrique Silva.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _weakref extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-40020 [https://bugs.python.org/issue?@action=redirect&bpo=40020]: Fix a leak and subsequent crash in parsetok.c caused by realloc misuse on a rare codepath.

bpo-39939 [https://bugs.python.org/issue?@action=redirect&bpo=39939]: Added str.removeprefix and str.removesuffix methods and corresponding bytes, bytearray, and collections.UserString methods to remove affixes from a string if present. See PEP 616 [https://peps.python.org/pep-0616/] for a full description. Patch by Dennis Sweeney.

bpo-39481 [https://bugs.python.org/issue?@action=redirect&bpo=39481]: Implement PEP 585. This supports list[int], tuple[str, ...] etc.

bpo-32894 [https://bugs.python.org/issue?@action=redirect&bpo=32894]: Support unparsing of infinity numbers in postponed annotations. Patch by Batuhan Taşkaya.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Speed up calls to list() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Mark Shannon.

Library

bpo-40398 [https://bugs.python.org/issue?@action=redirect&bpo=40398]: typing.get_args() now always returns an empty tuple for special generic aliases.

bpo-40396 [https://bugs.python.org/issue?@action=redirect&bpo=40396]: Functions typing.get_origin(), typing.get_args() and typing.get_type_hints() support now generic aliases like list[int].

bpo-38061 [https://bugs.python.org/issue?@action=redirect&bpo=38061]: Optimize the subprocess module on FreeBSD using closefrom(). A single close(fd) syscall is cheap, but when sysconf(_SC_OPEN_MAX) is high, the loop calling close(fd) on each file descriptor can take several milliseconds.

The workaround on FreeBSD to improve performance was to load and mount the fdescfs kernel module, but this is not enabled by default.

Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and Kubilay Kocak (koobs): https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

bpo-38061 [https://bugs.python.org/issue?@action=redirect&bpo=38061]: On FreeBSD, os.closerange(fd_low, fd_high) now calls closefrom(fd_low) if fd_high is greater than or equal to sysconf(_SC_OPEN_MAX).

Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and Kubilay Kocak (koobs): https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

bpo-40360 [https://bugs.python.org/issue?@action=redirect&bpo=40360]: The lib2to3 module is pending deprecation due to PEP 617 [https://peps.python.org/pep-0617/].

bpo-40138 [https://bugs.python.org/issue?@action=redirect&bpo=40138]: Fix the Windows implementation of os.waitpid() for exit code larger than INT_MAX >> 8. The exit status is now interpreted as an unsigned number.

bpo-39942 [https://bugs.python.org/issue?@action=redirect&bpo=39942]: Set "__main__" as the default module name when "__name__" is missing in typing.TypeVar. Patch by Weipeng Hong.

bpo-40275 [https://bugs.python.org/issue?@action=redirect&bpo=40275]: The logging package is now imported lazily in unittest only when the assertLogs() assertion is used.

bpo-40275 [https://bugs.python.org/issue?@action=redirect&bpo=40275]: The asyncio package is now imported lazily in unittest only when the IsolatedAsyncioTestCase class is used.

bpo-40330 [https://bugs.python.org/issue?@action=redirect&bpo=40330]: In ShareableList.__setitem__(), check the size of a new string item after encoding it to utf-8, not before.

bpo-40148 [https://bugs.python.org/issue?@action=redirect&bpo=40148]: Added pathlib.Path.with_stem() to create a new Path with the stem replaced.

bpo-40325 [https://bugs.python.org/issue?@action=redirect&bpo=40325]: Deprecated support for set objects in random.sample().

bpo-40257 [https://bugs.python.org/issue?@action=redirect&bpo=40257]: Improved help for the typing module. Docstrings are now shown for all special forms and special generic aliases (like Union and List). Using help() with generic alias like List[int] will show the help for the correspondent concrete type (list in this case).

bpo-40257 [https://bugs.python.org/issue?@action=redirect&bpo=40257]: inspect.getdoc() no longer returns docstring inherited from the type of the object or from parent class if it is a class if it is not defined in the object itself. In pydoc the documentation string is now shown not only for class, function, method etc, but for any object that has its own __doc__ attribute.

bpo-40287 [https://bugs.python.org/issue?@action=redirect&bpo=40287]: Fixed SpooledTemporaryFile.seek() to return the position.

bpo-40290 [https://bugs.python.org/issue?@action=redirect&bpo=40290]: Added zscore() to statistics.NormalDist().

bpo-40282 [https://bugs.python.org/issue?@action=redirect&bpo=40282]: Allow random.getrandbits(0) to succeed and to return 0.

bpo-40286 [https://bugs.python.org/issue?@action=redirect&bpo=40286]: Add random.randbytes() function and random.Random.randbytes() method to generate random bytes.

bpo-40277 [https://bugs.python.org/issue?@action=redirect&bpo=40277]: collections.namedtuple() now provides a human-readable repr for its field accessors.

bpo-40270 [https://bugs.python.org/issue?@action=redirect&bpo=40270]: The included copy of sqlite3 on Windows is now compiled with the json extension. This allows the use of functions such as json_object.

bpo-29255 [https://bugs.python.org/issue?@action=redirect&bpo=29255]: Wait in KqueueSelector.select when no fds are registered

bpo-40260 [https://bugs.python.org/issue?@action=redirect&bpo=40260]: Ensure modulefinder uses io.open_code() and respects coding comments.

bpo-40234 [https://bugs.python.org/issue?@action=redirect&bpo=40234]: Allow again to spawn daemon threads in subinterpreters (revert change which denied them).

bpo-39207 [https://bugs.python.org/issue?@action=redirect&bpo=39207]: Workers in ProcessPoolExecutor are now spawned on demand, only when there are no available idle workers to reuse. This optimizes startup overhead and reduces the amount of lost CPU time to idle workers. Patch by Kyle Stanley.

bpo-40091 [https://bugs.python.org/issue?@action=redirect&bpo=40091]: Fix a hang at fork in the logging module: the new private _at_fork_reinit() method is now used to reinitialize locks at fork in the child process.

bpo-40149 [https://bugs.python.org/issue?@action=redirect&bpo=40149]: Implement traverse and clear slots in _abc._abc_data type.

bpo-40208 [https://bugs.python.org/issue?@action=redirect&bpo=40208]: Remove deprecated symtable.SymbolTable.has_exec().

bpo-40196 [https://bugs.python.org/issue?@action=redirect&bpo=40196]: Fix a bug in the symtable module that was causing incorrectly report global variables as local. Patch by Pablo Galindo.

bpo-40190 [https://bugs.python.org/issue?@action=redirect&bpo=40190]: Add support for _SC_AIX_REALMEM to posix.sysconf().

bpo-40182 [https://bugs.python.org/issue?@action=redirect&bpo=40182]: Removed the _field_types attribute of the typing.NamedTuple class.

bpo-36517 [https://bugs.python.org/issue?@action=redirect&bpo=36517]: Multiple inheritance with typing.NamedTuple now raises an error instead of silently ignoring other types.

bpo-40126 [https://bugs.python.org/issue?@action=redirect&bpo=40126]: Fixed reverting multiple patches in unittest.mock. Patcher's __exit__() is now never called if its __enter__() is failed. Returning true from __exit__() silences now the exception.

bpo-40094 [https://bugs.python.org/issue?@action=redirect&bpo=40094]: CGIHTTPRequestHandler of http.server now logs the CGI script exit code, rather than the CGI script exit status of os.waitpid(). For example, if the script is killed by signal 11, it now logs: "CGI script exit code -11."

bpo-40108 [https://bugs.python.org/issue?@action=redirect&bpo=40108]: Improve the error message when triying to import a module using runpy and incorrectly using the ".py" extension at the end of the module name. Patch by Pablo Galindo.

bpo-40094 [https://bugs.python.org/issue?@action=redirect&bpo=40094]: Add os.waitstatus_to_exitcode() function: convert a wait status to an exit code.

bpo-40089 [https://bugs.python.org/issue?@action=redirect&bpo=40089]: Fix threading._after_fork(): if fork was not called by a thread spawned by threading.Thread, threading._after_fork() now creates a _MainThread instance for _main_thread, instead of a _DummyThread instance.

bpo-40089 [https://bugs.python.org/issue?@action=redirect&bpo=40089]: Add a private _at_fork_reinit() method to _thread.Lock, _thread.RLock, threading.RLock and threading.Condition classes: reinitialize the lock at fork in the child process, reset the lock to the unlocked state. Rename also the private _reset_internal_locks() method of threading.Event to _at_fork_reinit().

bpo-25780 [https://bugs.python.org/issue?@action=redirect&bpo=25780]: Expose CAN_RAW_JOIN_FILTERS in the socket module.

bpo-39503 [https://bugs.python.org/issue?@action=redirect&bpo=39503]: AbstractBasicAuthHandler of urllib.request now parses all WWW-Authenticate HTTP headers and accepts multiple challenges per header: use the realm of the first Basic challenge.

bpo-39812 [https://bugs.python.org/issue?@action=redirect&bpo=39812]: Removed daemon threads from concurrent.futures by adding an internal threading._register_atexit(), which calls registered functions prior to joining all non-daemon threads. This allows for compatibility with subinterpreters, which don't support daemon threads.

bpo-40050 [https://bugs.python.org/issue?@action=redirect&bpo=40050]: Fix importlib._bootstrap_external: avoid creating a new winreg builtin module if it's already available in sys.modules, and remove redundant imports.

bpo-40014 [https://bugs.python.org/issue?@action=redirect&bpo=40014]: Fix os.getgrouplist(): if getgrouplist() function fails because the group list is too small, retry with a larger group list. On failure, the glibc implementation of getgrouplist() sets ngroups to the total number of groups. For other implementations, double the group list size.

bpo-40017 [https://bugs.python.org/issue?@action=redirect&bpo=40017]: Add time.CLOCK_TAI constant if the operating system support it.

bpo-40016 [https://bugs.python.org/issue?@action=redirect&bpo=40016]: In re docstring, clarify the relationship between inline and argument compile flags.

bpo-39953 [https://bugs.python.org/issue?@action=redirect&bpo=39953]: Update internal table of OpenSSL error codes in the ssl module.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: Added PEP 584 [https://peps.python.org/pep-0584/] operators to weakref.WeakValueDictionary.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: Added PEP 584 [https://peps.python.org/pep-0584/] operators to weakref.WeakKeyDictionary.

bpo-38891 [https://bugs.python.org/issue?@action=redirect&bpo=38891]: Fix linear runtime behaviour of the __getitem__ and __setitem__ methods in multiprocessing.shared_memory.ShareableList. This avoids quadratic performance when iterating a ShareableList. Patch by Thomas Krennwallner.

bpo-39682 [https://bugs.python.org/issue?@action=redirect&bpo=39682]: Remove undocumented support for closing a pathlib.Path object via its context manager. The context manager magic methods remain, but they are now a no-op, making Path objects immutable.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: Added PEP 584 [https://peps.python.org/pep-0584/] operators (| and |=) to collections.ChainMap.

bpo-39011 [https://bugs.python.org/issue?@action=redirect&bpo=39011]: Normalization of line endings in ElementTree attributes was removed, as line endings which were replaced by entity numbers should be preserved in original form.

bpo-38410 [https://bugs.python.org/issue?@action=redirect&bpo=38410]: Properly handle sys.audit() failures in sys.set_asyncgen_hooks().

bpo-36541 [https://bugs.python.org/issue?@action=redirect&bpo=36541]: lib2to3 now recognizes named assignment expressions (the walrus operator, :=)

bpo-35967 [https://bugs.python.org/issue?@action=redirect&bpo=35967]: In platform, delay the invocation of 'uname -p' until the processor attribute is requested.

bpo-35113 [https://bugs.python.org/issue?@action=redirect&bpo=35113]: inspect.getsource() now returns correct source code for inner class with same name as module level class. Decorators are also returned as part of source of the class. Patch by Karthikeyan Singaravelan.

bpo-33262 [https://bugs.python.org/issue?@action=redirect&bpo=33262]: Deprecate passing None as an argument for shlex.split()'s s parameter. Patch by Zackery Spytz.

bpo-31758 [https://bugs.python.org/issue?@action=redirect&bpo=31758]: Prevent crashes when using an uninitialized _elementtree.XMLParser object. Patch by Oren Milman.

Documentation

bpo-27635 [https://bugs.python.org/issue?@action=redirect&bpo=27635]: The pickle documentation incorrectly claimed that __new__ isn't called by default when unpickling.

bpo-39879 [https://bugs.python.org/issue?@action=redirect&bpo=39879]: Updated 資料模型 docs to include dict() insertion order preservation. Patch by Furkan Onder and Samy Lahfa.

bpo-38387 [https://bugs.python.org/issue?@action=redirect&bpo=38387]: Document PyDoc_STRVAR macro in the C-API reference.

bpo-13743 [https://bugs.python.org/issue?@action=redirect&bpo=13743]: Some methods within xml.dom.minidom.Element class are now better documented.

Tests

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Set expected default encoding in test_c_locale_coercion.py for VxWorks RTOS.

bpo-40162 [https://bugs.python.org/issue?@action=redirect&bpo=40162]: Update Travis CI configuration to OpenSSL 1.1.1f.

bpo-40146 [https://bugs.python.org/issue?@action=redirect&bpo=40146]: Update OpenSSL to 1.1.1f in Azure Pipelines.

bpo-40094 [https://bugs.python.org/issue?@action=redirect&bpo=40094]: Add test.support.wait_process() function.

bpo-40003 [https://bugs.python.org/issue?@action=redirect&bpo=40003]: test.bisect_cmd now copies Python command line options like -O or -W. Moreover, emit a warning if test.bisect_cmd is used with -w/--verbose2 option.

bpo-39380 [https://bugs.python.org/issue?@action=redirect&bpo=39380]: Add the encoding in ftplib.FTP and ftplib.FTP_TLS to the constructor as keyword-only and change the default from latin-1 to utf-8 to follow RFC 2640 [https://datatracker.ietf.org/doc/html/rfc2640.html].

bpo-39793 [https://bugs.python.org/issue?@action=redirect&bpo=39793]: Use the same domain when testing make_msgid. Patch by Batuhan Taskaya.

bpo-1812 [https://bugs.python.org/issue?@action=redirect&bpo=1812]: Fix newline handling in doctest.testfile when loading from a package whose loader has a get_data method. Patch by Peter Donis.

Build

bpo-38360 [https://bugs.python.org/issue?@action=redirect&bpo=38360]: Support single-argument form of macOS -isysroot flag.

bpo-40158 [https://bugs.python.org/issue?@action=redirect&bpo=40158]: Fix CPython MSBuild Properties in NuGet Package (build/native/python.props)

bpo-38527 [https://bugs.python.org/issue?@action=redirect&bpo=38527]: Fix configure check on Solaris for "float word ordering": sometimes, the correct "grep" command was not being used. Patch by Arnon Yaari.

Windows

bpo-40164 [https://bugs.python.org/issue?@action=redirect&bpo=40164]: Updates Windows to OpenSSL 1.1.1f

bpo-8901 [https://bugs.python.org/issue?@action=redirect&bpo=8901]: Ignore the Windows registry when the -E option is used.

macOS

bpo-38329 [https://bugs.python.org/issue?@action=redirect&bpo=38329]: python.org macOS installers now update the Current version symlink of /Library/Frameworks/Python.framework/Versions for 3.9 installs. Previously, Current was only updated for Python 2.x installs. This should make it easier to embed Python 3 into other macOS applications.

bpo-40164 [https://bugs.python.org/issue?@action=redirect&bpo=40164]: Update macOS installer builds to use OpenSSL 1.1.1g.

IDLE

bpo-38439 [https://bugs.python.org/issue?@action=redirect&bpo=38439]: Add a 256×256 pixel IDLE icon to support more modern environments. Created by Andrew Clover. Delete the unused macOS idle.icns icon file.

bpo-38689 [https://bugs.python.org/issue?@action=redirect&bpo=38689]: IDLE will no longer freeze when inspect.signature fails when fetching a calltip.

Tools/Demos

bpo-40385 [https://bugs.python.org/issue?@action=redirect&bpo=40385]: Removed the checkpyc.py tool. Please see compileall without force mode as a potential alternative.

bpo-40179 [https://bugs.python.org/issue?@action=redirect&bpo=40179]: Fixed translation of #elif in Argument Clinic.

bpo-40094 [https://bugs.python.org/issue?@action=redirect&bpo=40094]: Fix which.py script exit code: it now uses os.waitstatus_to_exitcode() to convert os.system() exit status into an exit code.

C API

bpo-40241 [https://bugs.python.org/issue?@action=redirect&bpo=40241]: Move the PyGC_Head structure to the internal C API.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Convert PyObject_IS_GC() macro to a function to hide implementation details.

bpo-40241 [https://bugs.python.org/issue?@action=redirect&bpo=40241]: Add the functions PyObject_GC_IsTracked() and PyObject_GC_IsFinalized() to the public API to allow to query if Python objects are being currently tracked or have been already finalized by the garbage collector respectively. Patch by Pablo Galindo.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: The PyObject_NEW() macro becomes an alias to the PyObject_New() macro, and the PyObject_NEW_VAR() macro becomes an alias to the PyObject_NewVar() macro, to hide implementation details. They no longer access directly the PyTypeObject.tp_basicsize member.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: PyType_HasFeature() now always calls PyType_GetFlags() to hide implementation details. Previously, it accessed directly the PyTypeObject.tp_flags member when the limited C API was not used.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Convert the PyObject_GET_WEAKREFS_LISTPTR() macro to a function to hide implementation details: the macro accessed directly to the PyTypeObject.tp_weaklistoffset member.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Convert PyObject_CheckBuffer() macro to a function to hide implementation details: the macro accessed directly the PyTypeObject.tp_as_buffer member.

bpo-40170 [https://bugs.python.org/issue?@action=redirect&bpo=40170]: Always declare PyIndex_Check() as an opaque function to hide implementation details: remove PyIndex_Check() macro. The macro accessed directly the PyTypeObject.tp_as_number member.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Add PyThreadState_GetID() function: get the unique identifier of a Python thread state.

Python 3.9.0 alpha 5

Release date: 2020-03-23

Security

bpo-38576 [https://bugs.python.org/issue?@action=redirect&bpo=38576]: Disallow control characters in hostnames in http.client, addressing CVE 2019-18348 [https://www.cve.org/CVERecord?id=CVE-2019-18348]. Such potentially malicious header injection URLs now cause a InvalidURL to be raised.

Core and Builtins

bpo-40010 [https://bugs.python.org/issue?@action=redirect&bpo=40010]: Optimize pending calls in multithreaded applications. If a thread different than the main thread schedules a pending call (Py_AddPendingCall()), the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending calls which cannot be executed. Only the main thread can execute pending calls.

Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread executes pending calls.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _weakref extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _collections module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-40010 [https://bugs.python.org/issue?@action=redirect&bpo=40010]: Optimize signal handling in multithreaded applications. If a thread different than the main thread gets a signal, the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending signals which cannot be handled. Only the main thread of the main interpreter can handle signals.

Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread handles signals.

bpo-39984 [https://bugs.python.org/issue?@action=redirect&bpo=39984]: If Py_AddPendingCall() is called in a subinterpreter, the function is now scheduled to be called from the subinterpreter, rather than being called from the main interpreter. Each subinterpreter now has its own list of scheduled calls.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _heapq module to multiphase initialization.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port itertools module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Speed up calls to frozenset() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-39984 [https://bugs.python.org/issue?@action=redirect&bpo=39984]: subinterpreters: Move _PyRuntimeState.ceval.tracing_possible to PyInterpreterState.ceval.tracing_possible: each interpreter now has its own variable.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Speed up calls to set() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _statistics module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-39968 [https://bugs.python.org/issue?@action=redirect&bpo=39968]: Use inline function to replace extension modules' get_module_state macros.

bpo-39965 [https://bugs.python.org/issue?@action=redirect&bpo=39965]: Correctly raise SyntaxError if await is used inside non-async functions and PyCF_ALLOW_TOP_LEVEL_AWAIT is set (like in the asyncio REPL). Patch by Pablo Galindo.

bpo-39562 [https://bugs.python.org/issue?@action=redirect&bpo=39562]: Allow executing asynchronous comprehensions on the top level when the PyCF_ALLOW_TOP_LEVEL_AWAIT flag is given. Patch by Batuhan Taskaya.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Speed up calls to tuple() by using the PEP 590 [https://peps.python.org/pep-0590/] vectorcall calling convention. Patch by Donghee Na.

bpo-38373 [https://bugs.python.org/issue?@action=redirect&bpo=38373]: Changed list overallocation strategy. It no longer overallocates if the new size is closer to overallocated size than to the old size and adds padding.

bpo-39926 [https://bugs.python.org/issue?@action=redirect&bpo=39926]: Update Unicode database to Unicode version 13.0.0.

bpo-19466 [https://bugs.python.org/issue?@action=redirect&bpo=19466]: Clear the frames of daemon threads earlier during the Python shutdown to call objects destructors. So "unclosed file" resource warnings are now emitted for daemon threads in a more reliable way.

bpo-38894 [https://bugs.python.org/issue?@action=redirect&bpo=38894]: Fix a bug that was causing incomplete results when calling pathlib.Path.glob in the presence of symlinks that point to files where the user does not have read access. Patch by Pablo Galindo and Matt Wozniski.

bpo-39877 [https://bugs.python.org/issue?@action=redirect&bpo=39877]: Fix PyEval_RestoreThread() random crash at exit with daemon threads. It now accesses the _PyRuntime variable directly instead of using tstate->interp->runtime, since tstate can be a dangling pointer after Py_Finalize() has been called. Moreover, the daemon thread now exits before trying to take the GIL.

bpo-39871 [https://bugs.python.org/issue?@action=redirect&bpo=39871]: Fix a possible SystemError in math.{atan2,copysign,remainder}() when the first argument cannot be converted to a float. Patch by Zackery Spytz.

bpo-39776 [https://bugs.python.org/issue?@action=redirect&bpo=39776]: Fix race condition where threads created by PyGILState_Ensure() could get a duplicate id.

This affects consumers of tstate->id like the contextvar caching machinery, which could return invalid cached objects under heavy thread load (observed in embedded scenarios).

bpo-39778 [https://bugs.python.org/issue?@action=redirect&bpo=39778]: Fixed a crash due to incorrect handling of weak references in collections.OrderedDict classes. Patch by Pablo Galindo.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port audioop extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-39702 [https://bugs.python.org/issue?@action=redirect&bpo=39702]: Relax decorator grammar restrictions to allow any valid expression (PEP 614 [https://peps.python.org/pep-0614/]).

bpo-38091 [https://bugs.python.org/issue?@action=redirect&bpo=38091]: Tweak import deadlock detection code to not deadlock itself.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _locale extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-39087 [https://bugs.python.org/issue?@action=redirect&bpo=39087]: Optimize PyUnicode_AsUTF8() and PyUnicode_AsUTF8AndSize() slightly when they need to create internal UTF-8 cache.

bpo-39520 [https://bugs.python.org/issue?@action=redirect&bpo=39520]: Fix unparsing of ext slices with no items (foo[:,]). Patch by Batuhan Taskaya.

bpo-39220 [https://bugs.python.org/issue?@action=redirect&bpo=39220]: Do not optimize annotations if 'from __future__ import annotations' is used. Patch by Pablo Galindo.

bpo-35712 [https://bugs.python.org/issue?@action=redirect&bpo=35712]: Using NotImplemented in a boolean context has been deprecated. Patch contributed by Josh Rosenberg.

bpo-22490 [https://bugs.python.org/issue?@action=redirect&bpo=22490]: Don't leak environment variable __PYVENV_LAUNCHER__ into the interpreter session on macOS.

Library

bpo-39830 [https://bugs.python.org/issue?@action=redirect&bpo=39830]: Add zipfile.Path to __all__ in the zipfile module.

bpo-40000 [https://bugs.python.org/issue?@action=redirect&bpo=40000]: Improved error messages for validation of ast.Constant nodes. Patch by Batuhan Taskaya.

bpo-39999 [https://bugs.python.org/issue?@action=redirect&bpo=39999]: __module__ of the AST node classes is now set to "ast" instead of "_ast". Added docstrings for dummy AST node classes and deprecated attributes.

bpo-39991 [https://bugs.python.org/issue?@action=redirect&bpo=39991]: uuid.getnode() now skips IPv6 addresses with the same string length than a MAC address (17 characters): only use MAC addresses.

bpo-39988 [https://bugs.python.org/issue?@action=redirect&bpo=39988]: Deprecated ast.AugLoad and ast.AugStore node classes because they are no longer used.

bpo-39656 [https://bugs.python.org/issue?@action=redirect&bpo=39656]: Ensure bin/python3.# is always present in virtual environments on POSIX platforms - by Anthony Sottile.

bpo-39969 [https://bugs.python.org/issue?@action=redirect&bpo=39969]: Deprecated ast.Param node class because it's no longer used. Patch by Batuhan Taskaya.

bpo-39360 [https://bugs.python.org/issue?@action=redirect&bpo=39360]: Ensure all workers exit when finalizing a multiprocessing.Pool implicitly via the module finalization handlers of multiprocessing. This fixes a deadlock situation that can be experienced when the Pool is not properly finalized via the context manager or a call to multiprocessing.Pool.terminate. Patch by Batuhan Taskaya and Pablo Galindo.

bpo-35370 [https://bugs.python.org/issue?@action=redirect&bpo=35370]: sys.settrace(), sys.setprofile() and _lsprof.Profiler.enable() now properly report PySys_Audit() error if "sys.setprofile" or "sys.settrace" audit event is denied.

bpo-39936 [https://bugs.python.org/issue?@action=redirect&bpo=39936]: AIX: Fix _aix_support module when the subprocess is not available, when building Python from scratch. It now uses new private _bootsubprocess module, rather than having two implementations depending if subprocess is available or not. So _aix_support.aix_platform() result is now the same if subprocess is available or not.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: collections.OrderedDict now implements | and |= (PEP 584 [https://peps.python.org/pep-0584/]).

bpo-39652 [https://bugs.python.org/issue?@action=redirect&bpo=39652]: The column name found in sqlite3.Cursor.description is now truncated on the first '[' only if the PARSE_COLNAMES option is set.

bpo-39915 [https://bugs.python.org/issue?@action=redirect&bpo=39915]: Ensure unittest.mock.AsyncMock.await_args_list has call objects in the order of awaited arguments instead of using unittest.mock.Mock.call_args which has the last value of the call. Patch by Karthikeyan Singaravelan.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: Updated os.environ and os.environb to support PEP 584 [https://peps.python.org/pep-0584/]'s merge (|) and update (|=) operators.

bpo-38662 [https://bugs.python.org/issue?@action=redirect&bpo=38662]: The ensurepip module now invokes pip via the runpy module. Hence it is no longer tightly coupled with the internal API of the bundled pip version, allowing easier updates to a newer pip version both internally and for distributors.

bpo-38075 [https://bugs.python.org/issue?@action=redirect&bpo=38075]: Fix the random.Random.seed() method when a bool is passed as the seed.

bpo-39916 [https://bugs.python.org/issue?@action=redirect&bpo=39916]: More reliable use of os.scandir() in Path.glob(). It no longer emits a ResourceWarning when interrupted.

bpo-39850 [https://bugs.python.org/issue?@action=redirect&bpo=39850]: multiprocessing now supports abstract socket addresses (if abstract sockets are supported in the running platform). When creating arbitrary addresses (like when default-constructing multiprocessing.connection.Listener objects) abstract sockets are preferred to avoid the case when the temporary-file-generated address is too large for an AF_UNIX socket address. Patch by Pablo Galindo.

bpo-36287 [https://bugs.python.org/issue?@action=redirect&bpo=36287]: ast.dump() no longer outputs optional fields and attributes with default values. The default values for optional fields and attributes of AST nodes are now set as class attributes (e.g. Constant.kind is set to None).

bpo-39889 [https://bugs.python.org/issue?@action=redirect&bpo=39889]: Fixed ast.unparse() for extended slices containing a single element (e.g. a[i:j,]). Remove redundant tuples when index with a tuple (e.g. a[i, j]).

bpo-39828 [https://bugs.python.org/issue?@action=redirect&bpo=39828]: Fix json.tool to catch BrokenPipeError. Patch by Donghee Na.

bpo-13487 [https://bugs.python.org/issue?@action=redirect&bpo=13487]: Avoid a possible "RuntimeError: dictionary changed size during iteration" from inspect.getmodule() when it tried to loop through sys.modules.

bpo-39674 [https://bugs.python.org/issue?@action=redirect&bpo=39674]: Revert "bpo-37330 [https://bugs.python.org/issue?@action=redirect&bpo=37330]: open() no longer accept 'U' in file mode". The "U" mode of open() is kept in Python 3.9 to ease transition from Python 2.7, but will be removed in Python 3.10.

bpo-28577 [https://bugs.python.org/issue?@action=redirect&bpo=28577]: The hosts method on 32-bit prefix length IPv4Networks and 128-bit prefix IPv6Networks now returns a list containing the single Address instead of an empty list.

bpo-39826 [https://bugs.python.org/issue?@action=redirect&bpo=39826]: Add getConnection method to logging HTTPHandler to enable custom connections.

bpo-39763 [https://bugs.python.org/issue?@action=redirect&bpo=39763]: Reimplement distutils.spawn.spawn function with the subprocess module.

bpo-39794 [https://bugs.python.org/issue?@action=redirect&bpo=39794]: Add --without-decimal-contextvar build option. This enables a thread-local rather than a coroutine local context.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: collections.defaultdict now implements | (PEP 584 [https://peps.python.org/pep-0584/]).

bpo-39517 [https://bugs.python.org/issue?@action=redirect&bpo=39517]: Fix runpy.run_path() when using pathlike objects

bpo-39775 [https://bugs.python.org/issue?@action=redirect&bpo=39775]: Change inspect.Signature.parameters back to collections.OrderedDict. This was changed to dict in Python 3.9.0a4.

bpo-39678 [https://bugs.python.org/issue?@action=redirect&bpo=39678]: Refactor queue_manager in concurrent.futures.ProcessPoolExecutor to make it easier to maintain.

bpo-39764 [https://bugs.python.org/issue?@action=redirect&bpo=39764]: Fix AttributeError when calling get_stack on a PyAsyncGenObject Task

bpo-39769 [https://bugs.python.org/issue?@action=redirect&bpo=39769]: The compileall.compile_dir() function's ddir parameter and the compileall command line flag -d no longer write the wrong pathname to the generated pyc file for submodules beneath the root of the directory tree being compiled. This fixes a regression introduced with Python 3.5.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: types.MappingProxyType objects now support the merge (|) operator from PEP 584 [https://peps.python.org/pep-0584/].

bpo-38691 [https://bugs.python.org/issue?@action=redirect&bpo=38691]: The importlib module now ignores the PYTHONCASEOK environment variable when the -E or -I command line options are being used.

bpo-39719 [https://bugs.python.org/issue?@action=redirect&bpo=39719]: Remove tempfile.SpooledTemporaryFile.softspace() as files no longer have the softspace attribute in Python 3. Patch by Shantanu.

bpo-39667 [https://bugs.python.org/issue?@action=redirect&bpo=39667]: Improve pathlib.Path compatibility on zipfile.Path and correct performance degradation as found in zipp 3.0.

bpo-39638 [https://bugs.python.org/issue?@action=redirect&bpo=39638]: Keep ASDL signatures in the docstrings for AST nodes. Patch by Batuhan Taskaya

bpo-39639 [https://bugs.python.org/issue?@action=redirect&bpo=39639]: Deprecated ast.Suite node class because it's no longer used. Patch by Batuhan Taskaya.

bpo-39609 [https://bugs.python.org/issue?@action=redirect&bpo=39609]: Add thread_name_prefix to default asyncio executor

bpo-39548 [https://bugs.python.org/issue?@action=redirect&bpo=39548]: Fix handling of header in urllib.request.AbstractDigestAuthHandler when the optional qop parameter is not present.

bpo-39509 [https://bugs.python.org/issue?@action=redirect&bpo=39509]: HTTP status codes 103 EARLY_HINTS and 425 TOO_EARLY are added to http.HTTPStatus. Patch by Donghee Na.

bpo-39507 [https://bugs.python.org/issue?@action=redirect&bpo=39507]: Adding HTTP status 418 "I'm a Teapot" to HTTPStatus in http library. Patch by Ross Rhodes.

bpo-39495 [https://bugs.python.org/issue?@action=redirect&bpo=39495]: Remove default value from attrs parameter of xml.etree.ElementTree.TreeBuilder.start() for consistency between Python and C implementations.

bpo-38971 [https://bugs.python.org/issue?@action=redirect&bpo=38971]: Open issue in the BPO indicated a desire to make the implementation of codecs.open() at parity with io.open(), which implements a try/except to assure file stream gets closed before an exception is raised.

bpo-38641 [https://bugs.python.org/issue?@action=redirect&bpo=38641]: Added starred expressions support to return and yield statements for lib2to3. Patch by Vlad Emelianov.

bpo-37534 [https://bugs.python.org/issue?@action=redirect&bpo=37534]: When using minidom module to generate XML documents the ability to add Standalone Document Declaration is added. All the changes are made to generate a document in compliance with Extensible Markup Language (XML) 1.0 (Fifth Edition) W3C Recommendation (available here: https://www.w3.org/TR/xml/#sec-prolog-dtd).

bpo-34788 [https://bugs.python.org/issue?@action=redirect&bpo=34788]: Add support for scoped IPv6 addresses to ipaddress. Patch by Oleksandr Pavliuk.

bpo-34822 [https://bugs.python.org/issue?@action=redirect&bpo=34822]: Simplified AST for subscription. Simple indices are now represented by their value, extended slices are represented as tuples. ast classes Index and ExtSlice are considered deprecated and will be removed in future Python versions. In the meantime, Index(value) now returns a value itself, ExtSlice(slices) returns Tuple(slices, Load()).

Documentation

bpo-39868 [https://bugs.python.org/issue?@action=redirect&bpo=39868]: Updated the Language Reference for PEP 572 [https://peps.python.org/pep-0572/].

bpo-13790 [https://bugs.python.org/issue?@action=redirect&bpo=13790]: Change 'string' to 'specification' in format doc.

bpo-17422 [https://bugs.python.org/issue?@action=redirect&bpo=17422]: The language reference no longer restricts default class namespaces to dicts only.

bpo-39530 [https://bugs.python.org/issue?@action=redirect&bpo=39530]: Fix misleading documentation about mixed-type numeric comparisons.

bpo-39718 [https://bugs.python.org/issue?@action=redirect&bpo=39718]: Update token documentation to reflect additions in Python 3.8

bpo-39677 [https://bugs.python.org/issue?@action=redirect&bpo=39677]: Changed operand name of MAKE_FUNCTION from argc to flags for module dis

Tests

bpo-40019 [https://bugs.python.org/issue?@action=redirect&bpo=40019]: test_gdb now skips tests if it detects that gdb failed to read debug information because the Python binary is optimized.

bpo-27807 [https://bugs.python.org/issue?@action=redirect&bpo=27807]: test_site.test_startup_imports() is now skipped if a path of sys.path contains a .pth file.

bpo-26067 [https://bugs.python.org/issue?@action=redirect&bpo=26067]: Do not fail test_shutil test_chown test when uid or gid of user cannot be resolved to a name.

bpo-39855 [https://bugs.python.org/issue?@action=redirect&bpo=39855]: test_subprocess.test_user() now skips the test on an user name if the user name doesn't exist. For example, skip the test if the user "nobody" doesn't exist on Linux.

Build

bpo-39761 [https://bugs.python.org/issue?@action=redirect&bpo=39761]: Fix build with DTrace but without additional DFLAGS.

bpo-39763 [https://bugs.python.org/issue?@action=redirect&bpo=39763]: setup.py now uses a basic implementation of the subprocess module if the subprocess module is not available: before required C extension modules are built.

bpo-1294959 [https://bugs.python.org/issue?@action=redirect&bpo=1294959]: Add --with-platlibdir option to the configure script: name of the platform-specific library directory, stored in the new sys.platlibdir attribute. It is used to build the path of platform-specific extension modules and the path of the standard library. It is equal to "lib" on most platforms. On Fedora and SuSE, it is equal to "lib64" on 64-bit platforms. Patch by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner.

Windows

bpo-39930 [https://bugs.python.org/issue?@action=redirect&bpo=39930]: Ensures the required vcruntime140.dll is included in install packages.

bpo-39847 [https://bugs.python.org/issue?@action=redirect&bpo=39847]: Avoid hang when computer is hibernated whilst waiting for a mutex (for lock-related objects from threading) around 49-day uptime.

bpo-38597 [https://bugs.python.org/issue?@action=redirect&bpo=38597]: distutils will no longer statically link vcruntime140.dll when a redistributable version is unavailable. All future releases of CPython will include a copy of this DLL to ensure distributed extensions can continue to load.

bpo-38380 [https://bugs.python.org/issue?@action=redirect&bpo=38380]: Update Windows builds to use SQLite 3.31.1

bpo-39789 [https://bugs.python.org/issue?@action=redirect&bpo=39789]: Update Windows release build machines to Visual Studio 2019 (MSVC 14.2).

bpo-34803 [https://bugs.python.org/issue?@action=redirect&bpo=34803]: Package for nuget.org now includes repository reference and bundled icon image.

macOS

bpo-38380 [https://bugs.python.org/issue?@action=redirect&bpo=38380]: Update macOS builds to use SQLite 3.31.1

IDLE

bpo-27115 [https://bugs.python.org/issue?@action=redirect&bpo=27115]: For 'Go to Line', use a Query box subclass with IDLE standard behavior and improved error checking.

bpo-39885 [https://bugs.python.org/issue?@action=redirect&bpo=39885]: Since clicking to get an IDLE context menu moves the cursor, any text selection should be and now is cleared.

bpo-39852 [https://bugs.python.org/issue?@action=redirect&bpo=39852]: Edit "Go to line" now clears any selection, preventing accidental deletion. It also updates Ln and Col on the status bar.

bpo-39781 [https://bugs.python.org/issue?@action=redirect&bpo=39781]: Selecting code context lines no longer causes a jump.

Tools/Demos

bpo-36184 [https://bugs.python.org/issue?@action=redirect&bpo=36184]: Port python-gdb.py to FreeBSD. python-gdb.py now checks for "take_gil" function name to check if a frame tries to acquire the GIL, instead of checking for "pthread_cond_timedwait" which is specific to Linux and can be a different condition than the GIL.

bpo-38080 [https://bugs.python.org/issue?@action=redirect&bpo=38080]: Added support to fix getproxies in the lib2to3.fixes.fix_urllib module. Patch by José Roberto Meza Cabrera.

C API

bpo-40024 [https://bugs.python.org/issue?@action=redirect&bpo=40024]: Add PyModule_AddType() helper function: add a type to a module. Patch by Donghee Na.

bpo-39946 [https://bugs.python.org/issue?@action=redirect&bpo=39946]: Remove _PyRuntime.getframe hook and remove _PyThreadState_GetFrame macro which was an alias to _PyRuntime.getframe. They were only exposed by the internal C API. Remove also PyThreadFrameGetter type.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Add PyThreadState_GetFrame() function: get the current frame of a Python thread state.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Add _PyArg_NoKwnames helper function. Patch by Donghee Na.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Add PyThreadState_GetInterpreter(): get the interpreter of a Python thread state.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Add PyInterpreterState_Get() function to the limited C API.

bpo-35370 [https://bugs.python.org/issue?@action=redirect&bpo=35370]: If PySys_Audit() fails in PyEval_SetProfile() or PyEval_SetTrace(), log the error as an unraisable exception.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Move the static inline function flavor of Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() to the internal C API: they access PyThreadState attributes. The limited C API provides regular functions which hide implementation details.

bpo-39947 [https://bugs.python.org/issue?@action=redirect&bpo=39947]: Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer access PyThreadState attributes, but call new private _PyTrash_begin() and _PyTrash_end() functions which hide implementation details.

bpo-39884 [https://bugs.python.org/issue?@action=redirect&bpo=39884]: PyDescr_NewMethod() and PyCFunction_NewEx() now include the method name in the SystemError "bad call flags" error message to ease debug.

bpo-39877 [https://bugs.python.org/issue?@action=redirect&bpo=39877]: Deprecated PyEval_InitThreads() and PyEval_ThreadsInitialized(). Calling PyEval_InitThreads() now does nothing.

bpo-38249 [https://bugs.python.org/issue?@action=redirect&bpo=38249]: Py_UNREACHABLE is now implemented with __builtin_unreachable() and analogs in release mode.

bpo-38643 [https://bugs.python.org/issue?@action=redirect&bpo=38643]: PyNumber_ToBase() now raises a SystemError instead of crashing when called with invalid base.

bpo-39882 [https://bugs.python.org/issue?@action=redirect&bpo=39882]: The Py_FatalError() function is replaced with a macro which logs automatically the name of the current function, unless the Py_LIMITED_API macro is defined.

bpo-39824 [https://bugs.python.org/issue?@action=redirect&bpo=39824]: Extension modules: m_traverse, m_clear and m_free functions of PyModuleDef are no longer called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, these functions are not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

Extension modules without module state (m_size <= 0) are not affected.

bpo-38913 [https://bugs.python.org/issue?@action=redirect&bpo=38913]: Fixed segfault in Py_BuildValue() called with a format containing "#" and undefined PY_SSIZE_T_CLEAN whwn an exception is set.

bpo-38500 [https://bugs.python.org/issue?@action=redirect&bpo=38500]: Add a private API to get and set the frame evaluation function: add _PyInterpreterState_GetEvalFrameFunc() and _PyInterpreterState_SetEvalFrameFunc() C functions. The _PyFrameEvalFunction function type now takes a tstate parameter.

Python 3.9.0 alpha 4

Release date: 2020-02-25

Security

bpo-39184 [https://bugs.python.org/issue?@action=redirect&bpo=39184]: Add audit events to functions in fcntl, msvcrt, os, resource, shutil, signal and syslog.

bpo-39401 [https://bugs.python.org/issue?@action=redirect&bpo=39401]: Avoid unsafe DLL load at startup on Windows 7 and earlier.

bpo-39184 [https://bugs.python.org/issue?@action=redirect&bpo=39184]: Add audit events to command execution functions in os and pty modules.

Core and Builtins

bpo-39382 [https://bugs.python.org/issue?@action=redirect&bpo=39382]: Fix a use-after-free in the single inheritance path of issubclass(), when the __bases__ of an object has a single reference, and so does its first item. Patch by Yonatan Goldschmidt.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Update clinic tool to use Py_IS_TYPE(). Patch by Donghee Na.

bpo-39619 [https://bugs.python.org/issue?@action=redirect&bpo=39619]: Enable use of os.chroot() on HP-UX systems.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Add Py_IS_TYPE() static inline function to check whether the object o type is type.

bpo-39606 [https://bugs.python.org/issue?@action=redirect&bpo=39606]: Fix regression caused by fix for bpo-39386 [https://bugs.python.org/issue?@action=redirect&bpo=39386], that prevented calling aclose on an async generator that had already been closed or exhausted.

bpo-39579 [https://bugs.python.org/issue?@action=redirect&bpo=39579]: Change the ending column offset of Attribute nodes constructed in ast_for_dotted_name to point at the end of the current node and not at the end of the last NAME node.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _crypt extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _contextvars extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-39510 [https://bugs.python.org/issue?@action=redirect&bpo=39510]: Fix segfault in readinto() method on closed BufferedReader.

bpo-39502 [https://bugs.python.org/issue?@action=redirect&bpo=39502]: Fix time.localtime() on 64-bit AIX to support years before 1902 and after 2038. Patch by M Felt.

bpo-39492 [https://bugs.python.org/issue?@action=redirect&bpo=39492]: Fix a reference cycle in the C Pickler that was preventing the garbage collection of deleted, pickled objects.

bpo-39453 [https://bugs.python.org/issue?@action=redirect&bpo=39453]: Fixed a possible crash in list.__contains__() when a list is changed during comparing items. Patch by Donghee Na.

bpo-39434 [https://bugs.python.org/issue?@action=redirect&bpo=39434]: floor division of float operation now has a better performance. Also the message of ZeroDivisionError for this operation is updated. Patch by Donghee Na.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _codecs extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _bz2 extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _abc extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-39320 [https://bugs.python.org/issue?@action=redirect&bpo=39320]: Replace two complex bytecodes for building dicts with two simpler ones. The new bytecodes DICT_MERGE and DICT_UPDATE have been added The old bytecodes BUILD_MAP_UNPACK and BUILD_MAP_UNPACK_WITH_CALL have been removed.

bpo-39219 [https://bugs.python.org/issue?@action=redirect&bpo=39219]: Syntax errors raised in the tokenizer now always set correct "text" and "offset" attributes.

bpo-36051 [https://bugs.python.org/issue?@action=redirect&bpo=36051]: Drop the GIL during large bytes.join operations. Patch by Bruce Merry.

bpo-38960 [https://bugs.python.org/issue?@action=redirect&bpo=38960]: Fix DTrace build issues on FreeBSD. Patch by David Carlier.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: Speed up calls to range() by about 30%, by using the PEP 590 vectorcall calling convention. Patch by Mark Shannon.

bpo-36144 [https://bugs.python.org/issue?@action=redirect&bpo=36144]: dict (and collections.UserDict) objects now support PEP 584's merge (|) and update (|=) operators. Patch by Brandt Bucher.

bpo-32856 [https://bugs.python.org/issue?@action=redirect&bpo=32856]: Optimized the idiom for assignment a temporary variable in comprehensions. Now for y in [expr] in comprehensions is as fast as a simple assignment y = expr.

Library

bpo-30566 [https://bugs.python.org/issue?@action=redirect&bpo=30566]: Fix IndexError when trying to decode an invalid string with punycode codec.

bpo-39649 [https://bugs.python.org/issue?@action=redirect&bpo=39649]: Remove obsolete check for __args__ in bdb.Bdb.format_stack_entry.

bpo-39648 [https://bugs.python.org/issue?@action=redirect&bpo=39648]: Expanded math.gcd() and math.lcm() to handle multiple arguments.

bpo-39681 [https://bugs.python.org/issue?@action=redirect&bpo=39681]: Fix a regression where the C pickle module wouldn't allow unpickling from a file-like object that doesn't expose a readinto() method.

bpo-35950 [https://bugs.python.org/issue?@action=redirect&bpo=35950]: Raise io.UnsupportedOperation in io.BufferedReader.truncate() when it is called on a read-only io.BufferedReader instance.

bpo-39479 [https://bugs.python.org/issue?@action=redirect&bpo=39479]: Add math.lcm() function: least common multiple.

bpo-39674 [https://bugs.python.org/issue?@action=redirect&bpo=39674]: Revert "Do not expose abstract collection classes in the collections module" change (bpo-25988 [https://bugs.python.org/issue?@action=redirect&bpo=25988]). Aliases to ABC like collections.Mapping are kept in Python 3.9 to ease transition from Python 2.7, but will be removed in Python 3.10.

bpo-39104 [https://bugs.python.org/issue?@action=redirect&bpo=39104]: Fix hanging ProcessPoolExcutor on shutdown(wait=False) when a task has failed pickling.

bpo-39627 [https://bugs.python.org/issue?@action=redirect&bpo=39627]: Fixed TypedDict totality check for inherited keys.

bpo-39474 [https://bugs.python.org/issue?@action=redirect&bpo=39474]: Fixed starting position of AST for expressions like (a)(b), (a)[b] and (a).b.

bpo-21016 [https://bugs.python.org/issue?@action=redirect&bpo=21016]: The pydoc and trace modules now use the sysconfig module to get the path to the Python standard library, to support uncommon installation path like /usr/lib64/python3.9/ on Fedora. Patch by Jan Matějek.

bpo-39590 [https://bugs.python.org/issue?@action=redirect&bpo=39590]: Collections.deque now holds strong references during deque.__contains__ and deque.count, fixing crashes.

bpo-39586 [https://bugs.python.org/issue?@action=redirect&bpo=39586]: The distutils bdist_msi command is deprecated in Python 3.9, use bdist_wheel (wheel packages) instead.

bpo-39595 [https://bugs.python.org/issue?@action=redirect&bpo=39595]: Improved performance of zipfile.Path for files with a large number of entries. Also improved performance and fixed minor issue as published with importlib_metadata 1.5 [https://importlib-metadata.readthedocs.io/en/latest/history.html#v1-5-0].

bpo-39350 [https://bugs.python.org/issue?@action=redirect&bpo=39350]: Fix regression in fractions.Fraction if the numerator and/or the denominator is an int subclass. The math.gcd() function is now used to normalize the numerator and denominator. math.gcd() always return a int type. Previously, the GCD type depended on numerator and denominator.

bpo-39567 [https://bugs.python.org/issue?@action=redirect&bpo=39567]: Added audit for os.walk(), os.fwalk(), pathlib.Path.glob() and pathlib.Path.rglob().

bpo-39559 [https://bugs.python.org/issue?@action=redirect&bpo=39559]: Remove unused, undocumented argument getters from uuid.getnode()

bpo-38149 [https://bugs.python.org/issue?@action=redirect&bpo=38149]: sys.audit() is now called only once per call of glob.glob() and glob.iglob().

bpo-39546 [https://bugs.python.org/issue?@action=redirect&bpo=39546]: Fix a regression in ArgumentParser where allow_abbrev=False was ignored for long options that used a prefix character other than "-".

bpo-39450 [https://bugs.python.org/issue?@action=redirect&bpo=39450]: Striped whitespace from docstring before returning it from unittest.case.shortDescription().

bpo-12915 [https://bugs.python.org/issue?@action=redirect&bpo=12915]: A new function resolve_name has been added to the pkgutil module. This resolves a string of the form 'a.b.c.d' or 'a.b:c.d' to an object. In the example, a.b is a package/module and c.d is an object within that package/module reached via recursive attribute access.

bpo-39353 [https://bugs.python.org/issue?@action=redirect&bpo=39353]: The binascii.crc_hqx() function is no longer deprecated.

bpo-39493 [https://bugs.python.org/issue?@action=redirect&bpo=39493]: Mark typing.IO.closed as a property

bpo-39491 [https://bugs.python.org/issue?@action=redirect&bpo=39491]: Add typing.Annotated and include_extras parameter to typing.get_type_hints() as part of PEP 593 [https://peps.python.org/pep-0593/]. Patch by Till Varoquaux, documentation by Till Varoquaux and Konstantin Kashin.

bpo-39485 [https://bugs.python.org/issue?@action=redirect&bpo=39485]: Fix a bug in unittest.mock.create_autospec() that would complain about the wrong number of arguments for custom descriptors defined in an extension module returning functions.

bpo-38932 [https://bugs.python.org/issue?@action=redirect&bpo=38932]: Mock fully resets child objects on reset_mock(). Patch by Vegard Stikbakke

bpo-39082 [https://bugs.python.org/issue?@action=redirect&bpo=39082]: Allow AsyncMock to correctly patch static/class methods

bpo-39432 [https://bugs.python.org/issue?@action=redirect&bpo=39432]: Implement PEP-489 algorithm for non-ascii "PyInit_..." symbol names in distutils to make it export the correct init symbol also on Windows.

bpo-18819 [https://bugs.python.org/issue?@action=redirect&bpo=18819]: Omit devmajor and devminor fields for non-device files in tarfile archives, enabling bit-for-bit compatibility with GNU tar(1).

bpo-39349 [https://bugs.python.org/issue?@action=redirect&bpo=39349]: Added a new cancel_futures parameter to concurrent.futures.Executor.shutdown() that cancels all pending futures which have not started running, instead of waiting for them to complete before shutting down the executor.

bpo-39274 [https://bugs.python.org/issue?@action=redirect&bpo=39274]: bool(fraction.Fraction) now returns a boolean even if (numerator != 0) does not return a boolean (ex: numpy number).

bpo-34793 [https://bugs.python.org/issue?@action=redirect&bpo=34793]: Remove support for with (await asyncio.lock): and with (yield from asyncio.lock):. The same is correct for asyncio.Condition and asyncio.Semaphore.

bpo-25597 [https://bugs.python.org/issue?@action=redirect&bpo=25597]: Ensure, if wraps is supplied to unittest.mock.MagicMock, it is used to calculate return values for the magic methods instead of using the default return values. Patch by Karthikeyan Singaravelan.

bpo-36350 [https://bugs.python.org/issue?@action=redirect&bpo=36350]: inspect.Signature.parameters and inspect.BoundArguments.arguments are now dicts instead of OrderedDicts. Patch contributed by Rémi Lapeyre.

bpo-35727 [https://bugs.python.org/issue?@action=redirect&bpo=35727]: Fix sys.exit() and sys.exit(None) exit code propagation when used in multiprocessing.Process.

bpo-32173 [https://bugs.python.org/issue?@action=redirect&bpo=32173]: * Add lazycache function to __all__. * Use dict.clear to clear the cache. * Refactoring getline function and checkcache function.

Documentation

bpo-17422 [https://bugs.python.org/issue?@action=redirect&bpo=17422]: The language reference now specifies restrictions on class namespaces. Adapted from a patch by Ethan Furman.

bpo-39572 [https://bugs.python.org/issue?@action=redirect&bpo=39572]: Updated documentation of total flag of TypedDict.

bpo-39654 [https://bugs.python.org/issue?@action=redirect&bpo=39654]: In pyclbr doc, update 'class' to 'module' where appropriate and add readmodule comment. Patch by Hakan Çelik.

bpo-39153 [https://bugs.python.org/issue?@action=redirect&bpo=39153]: Clarify refcounting semantics for the following functions: - PyObject_SetItem - PyMapping_SetItemString - PyDict_SetItem - PyDict_SetItemString

bpo-39392 [https://bugs.python.org/issue?@action=redirect&bpo=39392]: Explain that when filling with turtle, overlap regions may be left unfilled.

bpo-39369 [https://bugs.python.org/issue?@action=redirect&bpo=39369]: Update mmap readline method description. The fact that the readline method does update the file position should not be ignored since this might give the impression for the programmer that it doesn't update it.

bpo-9056 [https://bugs.python.org/issue?@action=redirect&bpo=9056]: Include subsection in TOC for PDF version of docs.

Tests

bpo-38325 [https://bugs.python.org/issue?@action=redirect&bpo=38325]: Skip tests on non-BMP characters of test_winconsoleio.

bpo-39502 [https://bugs.python.org/issue?@action=redirect&bpo=39502]: Skip test_zipfile.test_add_file_after_2107() if time.localtime() fails with OverflowError. It is the case on AIX 6.1 for example.

Build

bpo-39489 [https://bugs.python.org/issue?@action=redirect&bpo=39489]: Remove COUNT_ALLOCS special build.

Windows

bpo-39553 [https://bugs.python.org/issue?@action=redirect&bpo=39553]: Delete unused code related to SxS manifests.

bpo-39439 [https://bugs.python.org/issue?@action=redirect&bpo=39439]: Honor the Python path when a virtualenv is active on Windows.

bpo-39393 [https://bugs.python.org/issue?@action=redirect&bpo=39393]: Improve the error message when attempting to load a DLL with unresolved dependencies.

bpo-38883 [https://bugs.python.org/issue?@action=redirect&bpo=38883]: home() and expanduser() on Windows now prefer USERPROFILE and no longer use HOME, which is not normally set for regular user accounts. This makes them again behave like os.path.expanduser(), which was changed to ignore HOME in 3.8, see bpo-36264 [https://bugs.python.org/issue?@action=redirect&bpo=36264].

bpo-39185 [https://bugs.python.org/issue?@action=redirect&bpo=39185]: The build.bat script has additional options for very-quiet output (-q) and very-verbose output (-vv)

IDLE

bpo-39663 [https://bugs.python.org/issue?@action=redirect&bpo=39663]: Add tests for pyparse find_good_parse_start().

bpo-39600 [https://bugs.python.org/issue?@action=redirect&bpo=39600]: In the font configuration window, remove duplicated font names.

bpo-30780 [https://bugs.python.org/issue?@action=redirect&bpo=30780]: Add remaining configdialog tests for buttons and highlights and keys tabs.

bpo-39388 [https://bugs.python.org/issue?@action=redirect&bpo=39388]: IDLE Settings Cancel button now cancels pending changes

bpo-38792 [https://bugs.python.org/issue?@action=redirect&bpo=38792]: Close an IDLE shell calltip if a KeyboardInterrupt or shell restart occurs. Patch by Zackery Spytz.

C API

bpo-35081 [https://bugs.python.org/issue?@action=redirect&bpo=35081]: Move the bytes_methods.h header file to the internal C API as pycore_bytes_methods.h: it only contains private symbols (prefixed by _Py), except of the PyDoc_STRVAR_shared() macro.

bpo-35081 [https://bugs.python.org/issue?@action=redirect&bpo=35081]: Move the dtoa.h header file to the internal C API as pycore_dtoa.h: it only contains private functions (prefixed by _Py). The math and cmath modules must now be compiled with the Py_BUILD_CORE macro defined.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Add Py_SET_SIZE() function to set the size of an object.

bpo-39500 [https://bugs.python.org/issue?@action=redirect&bpo=39500]: PyUnicode_IsIdentifier() does not call Py_FatalError() anymore if the string is not ready.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Add Py_SET_TYPE() function to set the type of an object.

bpo-39573 [https://bugs.python.org/issue?@action=redirect&bpo=39573]: Add a Py_SET_REFCNT() function to set the reference counter of an object.

bpo-39542 [https://bugs.python.org/issue?@action=redirect&bpo=39542]: Convert PyType_HasFeature(), PyType_Check() and PyType_CheckExact() macros to static inline functions.

bpo-39542 [https://bugs.python.org/issue?@action=redirect&bpo=39542]: In the limited C API, PyObject_INIT() and PyObject_INIT_VAR() are now defined as aliases to PyObject_Init() and PyObject_InitVar() to make their implementation opaque. It avoids to leak implementation details in the limited C API. Exclude the following functions from the limited C API: _Py_NewReference(), _Py_ForgetReference(), _PyTraceMalloc_NewReference() and _Py_GetRefTotal().

bpo-39542 [https://bugs.python.org/issue?@action=redirect&bpo=39542]: Exclude trashcan mechanism from the limited C API: it requires access to PyTypeObject and PyThreadState structure fields, whereas these structures are opaque in the limited C API.

bpo-39511 [https://bugs.python.org/issue?@action=redirect&bpo=39511]: The PyThreadState_Clear() function now calls the PyThreadState.on_delete callback. Previously, that happened in PyThreadState_Delete().

bpo-38076 [https://bugs.python.org/issue?@action=redirect&bpo=38076]: Fix to clear the interpreter state only after clearing module globals to guarantee module state access from C Extensions during runtime destruction

bpo-39245 [https://bugs.python.org/issue?@action=redirect&bpo=39245]: The Vectorcall API (PEP 590) was made public, adding the functions PyObject_Vectorcall, PyObject_VectorcallMethod, PyVectorcall_Function, PyObject_CallOneArg, PyObject_CallMethodNoArgs, PyObject_CallMethodOneArg, PyObject_FastCallDict, and the flag Py_TPFLAGS_HAVE_VECTORCALL.

Python 3.9.0 alpha 3

Release date: 2020-01-24

Core and Builtins

bpo-39427 [https://bugs.python.org/issue?@action=redirect&bpo=39427]: Document all possibilities for the -X options in the command line help section. Patch by Pablo Galindo.

bpo-39421 [https://bugs.python.org/issue?@action=redirect&bpo=39421]: Fix possible crashes when operating with the functions in the heapq module and custom comparison operators.

bpo-39386 [https://bugs.python.org/issue?@action=redirect&bpo=39386]: Prevent double awaiting of async iterator.

bpo-17005 [https://bugs.python.org/issue?@action=redirect&bpo=17005]: Add functools.TopologicalSorter to the functools module to offers functionality to perform topological sorting of graphs. Patch by Pablo Galindo, Tim Peters and Larry Hastings.

bpo-39320 [https://bugs.python.org/issue?@action=redirect&bpo=39320]: Replace four complex bytecodes for building sequences with three simpler ones.

The following four bytecodes have been removed:

BUILD_LIST_UNPACK

BUILD_TUPLE_UNPACK

BUILD_SET_UNPACK

BUILD_TUPLE_UNPACK_WITH_CALL

The following three bytecodes have been added:

LIST_TO_TUPLE

LIST_EXTEND

SET_UPDATE

bpo-39336 [https://bugs.python.org/issue?@action=redirect&bpo=39336]: Import loaders which publish immutable module objects can now publish immutable packages in addition to individual modules.

bpo-39322 [https://bugs.python.org/issue?@action=redirect&bpo=39322]: Added a new function gc.is_finalized() to check if an object has been finalized by the garbage collector. Patch by Pablo Galindo.

bpo-39048 [https://bugs.python.org/issue?@action=redirect&bpo=39048]: Improve the displayed error message when incorrect types are passed to async with statements by looking up the __aenter__() special method before the __aexit__() special method when entering an asynchronous context manager. Patch by Géry Ogam.

bpo-39235 [https://bugs.python.org/issue?@action=redirect&bpo=39235]: Fix AST end location for lone generator expression in function call, e.g. f(i for i in a).

bpo-39209 [https://bugs.python.org/issue?@action=redirect&bpo=39209]: Correctly handle multi-line tokens in interactive mode. Patch by Pablo Galindo.

bpo-1635741 [https://bugs.python.org/issue?@action=redirect&bpo=1635741]: Port _json extension module to multiphase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

bpo-39216 [https://bugs.python.org/issue?@action=redirect&bpo=39216]: Fix constant folding optimization for positional only arguments - by Anthony Sottile.

bpo-39215 [https://bugs.python.org/issue?@action=redirect&bpo=39215]: Fix SystemError when nested function has annotation on positional-only argument - by Anthony Sottile.

bpo-39200 [https://bugs.python.org/issue?@action=redirect&bpo=39200]: Correct the error message when calling the min() or max() with no arguments. Patch by Donghee Na.

bpo-39200 [https://bugs.python.org/issue?@action=redirect&bpo=39200]: Correct the error message when trying to construct range objects with no arguments. Patch by Pablo Galindo.

bpo-39166 [https://bugs.python.org/issue?@action=redirect&bpo=39166]: Fix incorrect line execution reporting in trace functions when tracing the last iteration of asynchronous for loops. Patch by Pablo Galindo.

bpo-39114 [https://bugs.python.org/issue?@action=redirect&bpo=39114]: Fix incorrect line execution reporting in trace functions when tracing exception handlers with name binding. Patch by Pablo Galindo.

bpo-39156 [https://bugs.python.org/issue?@action=redirect&bpo=39156]: Split the COMPARE_OP bytecode instruction into four distinct instructions.

COMPARE_OP for rich comparisons

IS_OP for 'is' and 'is not' tests

CONTAINS_OP for 'in' and 'is not' tests

JUMP_IF_NOT_EXC_MATCH for checking exceptions in 'try-except' statements.

This improves the clarity of the interpreter and should provide a modest speedup.

bpo-38588 [https://bugs.python.org/issue?@action=redirect&bpo=38588]: Fix possible crashes in dict and list when calling PyObject_RichCompareBool().

bpo-13601 [https://bugs.python.org/issue?@action=redirect&bpo=13601]: By default, sys.stderr is line-buffered now, even if stderr is redirected to a file. You can still make sys.stderr unbuffered by passing the -u command-line option or setting the PYTHONUNBUFFERED environment variable.

(Contributed by Jendrik Seipp in bpo-13601 [https://bugs.python.org/issue?@action=redirect&bpo=13601].)

bpo-38610 [https://bugs.python.org/issue?@action=redirect&bpo=38610]: Fix possible crashes in several list methods by holding strong references to list elements when calling PyObject_RichCompareBool().

bpo-32021 [https://bugs.python.org/issue?@action=redirect&bpo=32021]: Include brotli .br encoding in mimetypes encodings_map

Library

bpo-39430 [https://bugs.python.org/issue?@action=redirect&bpo=39430]: Fixed race condition in lazy imports in tarfile.

bpo-39413 [https://bugs.python.org/issue?@action=redirect&bpo=39413]: The os.unsetenv() function is now also available on Windows.

bpo-39390 [https://bugs.python.org/issue?@action=redirect&bpo=39390]: Fixed a regression with the ignore callback of shutil.copytree(). The argument types are now str and List[str] again.

bpo-39395 [https://bugs.python.org/issue?@action=redirect&bpo=39395]: The os.putenv() and os.unsetenv() functions are now always available.

bpo-39406 [https://bugs.python.org/issue?@action=redirect&bpo=39406]: If setenv() C function is available, os.putenv() is now implemented with setenv() instead of putenv(), so Python doesn't have to handle the environment variable memory.

bpo-39396 [https://bugs.python.org/issue?@action=redirect&bpo=39396]: Fix math.nextafter(-0.0, +0.0) on AIX 7.1.

bpo-29435 [https://bugs.python.org/issue?@action=redirect&bpo=29435]: Allow tarfile.is_tarfile() to be used with file and file-like objects, like zipfile.is_zipfile(). Patch by William Woodruff.

bpo-39377 [https://bugs.python.org/issue?@action=redirect&bpo=39377]: Removed encoding option from json.loads(). It has been deprecated since Python 3.1.

bpo-39389 [https://bugs.python.org/issue?@action=redirect&bpo=39389]: Write accurate compression level metadata in gzip archives, rather than always signaling maximum compression.

bpo-39366 [https://bugs.python.org/issue?@action=redirect&bpo=39366]: The previously deprecated xpath() and xgtitle() methods of nntplib.NNTP have been removed.

bpo-39357 [https://bugs.python.org/issue?@action=redirect&bpo=39357]: Remove the buffering parameter of bz2.BZ2File. Since Python 3.0, it was ignored and using it was emitting DeprecationWarning. Pass an open file object, to control how the file is opened. The compresslevel parameter becomes keyword-only.

bpo-39353 [https://bugs.python.org/issue?@action=redirect&bpo=39353]: Deprecate binhex4 and hexbin4 standards. Deprecate the binhex module and the following binascii functions: b2a_hqx(), a2b_hqx(), rlecode_hqx(), rledecode_hqx(), crc_hqx().

bpo-39351 [https://bugs.python.org/issue?@action=redirect&bpo=39351]: Remove base64.encodestring() and base64.decodestring(), aliases deprecated since Python 3.1: use base64.encodebytes() and base64.decodebytes() instead.

bpo-39350 [https://bugs.python.org/issue?@action=redirect&bpo=39350]: Remove fractions.gcd() function, deprecated since Python 3.5 (bpo-22486 [https://bugs.python.org/issue?@action=redirect&bpo=22486]): use math.gcd() instead.

bpo-39329 [https://bugs.python.org/issue?@action=redirect&bpo=39329]: LMTP constructor now has an optional timeout parameter. Patch by Donghee Na.

bpo-39313 [https://bugs.python.org/issue?@action=redirect&bpo=39313]: Add a new exec_function option (--exec-function in the CLI) to RefactoringTool for making exec a function. Patch by Batuhan Taskaya.

bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259]: FTP_TLS and FTP_TLS now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259]: SMTP and SMTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

bpo-39310 [https://bugs.python.org/issue?@action=redirect&bpo=39310]: Add math.ulp(): return the value of the least significant bit of a float.

bpo-39297 [https://bugs.python.org/issue?@action=redirect&bpo=39297]: Improved performance of importlib.metadata distribution discovery and resilients to inaccessible sys.path entries (importlib_metadata v1.4.0).

bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259]: NNTP and NNTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

bpo-38901 [https://bugs.python.org/issue?@action=redirect&bpo=38901]: When you specify prompt='.' or equivalently python -m venv --prompt . ... the basename of the current directory is used to set the created venv's prompt when it's activated.

bpo-39288 [https://bugs.python.org/issue?@action=redirect&bpo=39288]: Add math.nextafter(): return the next floating-point value after x towards y.

bpo-39259 [https://bugs.python.org/issue?@action=redirect&bpo=39259]: POP3 and POP3_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

bpo-39242 [https://bugs.python.org/issue?@action=redirect&bpo=39242]: Updated the Gmane domain from news.gmane.org to news.gmane.io which is used for examples of NNTP news reader server and nntplib tests.

bpo-35292 [https://bugs.python.org/issue?@action=redirect&bpo=35292]: Proxy the SimpleHTTPRequestHandler.guess_type to mimetypes.guess_type so the mimetypes.init is called lazily to avoid unnecessary costs when http.server module is imported.

bpo-39239 [https://bugs.python.org/issue?@action=redirect&bpo=39239]: The select.epoll.unregister() method no longer ignores the EBADF error.

bpo-38907 [https://bugs.python.org/issue?@action=redirect&bpo=38907]: In http.server script, restore binding to IPv4 on Windows.

bpo-39152 [https://bugs.python.org/issue?@action=redirect&bpo=39152]: Fix ttk.Scale.configure([name]) to return configuration tuple for name or all options. Giovanni Lombardo contributed part of the patch.

bpo-39198 [https://bugs.python.org/issue?@action=redirect&bpo=39198]: If an exception were to be thrown in Logger.isEnabledFor (say, by asyncio timeouts or stopit) , the logging global lock may not be released appropriately, resulting in deadlock. This change wraps that block of code with try...finally to ensure the lock is released.

bpo-39191 [https://bugs.python.org/issue?@action=redirect&bpo=39191]: Perform a check for running loop before starting a new task in loop.run_until_complete() to fail fast; it prevents the side effect of new task spawning before exception raising.

bpo-38871 [https://bugs.python.org/issue?@action=redirect&bpo=38871]: Correctly parenthesize filter-based statements that contain lambda expressions in lib2to3. Patch by Donghee Na.

bpo-39142 [https://bugs.python.org/issue?@action=redirect&bpo=39142]: A change was made to logging.config.dictConfig to avoid converting instances of named tuples to ConvertingTuple. It's assumed that named tuples are too specialised to be treated like ordinary tuples; if a user of named tuples requires ConvertingTuple functionality, they will have to implement that themselves in their named tuple class.

bpo-39158 [https://bugs.python.org/issue?@action=redirect&bpo=39158]: ast.literal_eval() now supports empty sets.

bpo-39129 [https://bugs.python.org/issue?@action=redirect&bpo=39129]: Fix import path for asyncio.TimeoutError

bpo-39057 [https://bugs.python.org/issue?@action=redirect&bpo=39057]: urllib.request.proxy_bypass_environment() now ignores leading dots and no longer ignores a trailing newline.

bpo-39056 [https://bugs.python.org/issue?@action=redirect&bpo=39056]: Fixed handling invalid warning category in the -W option. No longer import the re module if it is not needed.

bpo-39055 [https://bugs.python.org/issue?@action=redirect&bpo=39055]: base64.b64decode() with validate=True raises now a binascii.Error if the input ends with a single \n.

bpo-21600 [https://bugs.python.org/issue?@action=redirect&bpo=21600]: Fix mock.patch.stopall() to stop active patches that were created with mock.patch.dict().

bpo-39019 [https://bugs.python.org/issue?@action=redirect&bpo=39019]: Implement dummy __class_getitem__ for tempfile.SpooledTemporaryFile.

bpo-39019 [https://bugs.python.org/issue?@action=redirect&bpo=39019]: Implement dummy __class_getitem__ for subprocess.Popen, subprocess.CompletedProcess

bpo-38914 [https://bugs.python.org/issue?@action=redirect&bpo=38914]: Adjusted the wording of the warning issued by distutils' check command when the author and maintainer fields are supplied but no corresponding e-mail field (author_email or maintainer_email) is found. The wording now reflects the fact that these fields are suggested, but not required. Patch by Juergen Gmach.

bpo-38878 [https://bugs.python.org/issue?@action=redirect&bpo=38878]: Fixed __subclasshook__ of os.PathLike to return a correct result upon inheritance. Patch by Bar Harel.

bpo-38615 [https://bugs.python.org/issue?@action=redirect&bpo=38615]: IMAP4 and IMAP4_SSL now have an optional timeout parameter for their constructors. Also, the open() method now has an optional timeout parameter with this change. The overridden methods of IMAP4_SSL and IMAP4_stream were applied to this change. Patch by Donghee Na.

bpo-35182 [https://bugs.python.org/issue?@action=redirect&bpo=35182]: Fixed Popen.communicate() subsequent call crash when the child process has already closed any piped standard stream, but still continues to be running. Patch by Andriy Maletsky.

bpo-38630 [https://bugs.python.org/issue?@action=redirect&bpo=38630]: On Unix, subprocess.Popen.send_signal() now polls the process status. Polling reduces the risk of sending a signal to the wrong process if the process completed, the subprocess.Popen.returncode attribute is still None, and the pid has been reassigned (recycled) to a new different process.

bpo-38536 [https://bugs.python.org/issue?@action=redirect&bpo=38536]: Removes trailing space in formatted currency with international=True and a locale with symbol following value. E.g. locale.currency(12.34, international=True) returned '12,34 EUR ' instead of '12,34 EUR'.

bpo-38473 [https://bugs.python.org/issue?@action=redirect&bpo=38473]: Use signature from inner mock for autospecced methods attached with unittest.mock.attach_mock(). Patch by Karthikeyan Singaravelan.

bpo-38361 [https://bugs.python.org/issue?@action=redirect&bpo=38361]: Fixed an issue where ident could include a leading path separator when syslog.openlog() was called without arguments.

bpo-38293 [https://bugs.python.org/issue?@action=redirect&bpo=38293]: Add copy.copy() and copy.deepcopy() support to property() objects.

bpo-37958 [https://bugs.python.org/issue?@action=redirect&bpo=37958]: Added the pstats.Stats.get_profile_dict() method to return the profile data as a StatsProfile instance.

bpo-28367 [https://bugs.python.org/issue?@action=redirect&bpo=28367]: Termios magic constants for the following baud rates: - B500000 - B576000 - B921600 - B1000000 - B1152000 - B1500000 - B2000000 - B2500000 - B3000000 - B3500000 - B4000000 Patch by Andrey Smirnov

Documentation

bpo-39381 [https://bugs.python.org/issue?@action=redirect&bpo=39381]: Mention in docs that asyncio.get_event_loop() implicitly creates new event loop only if called from the main thread.

bpo-38918 [https://bugs.python.org/issue?@action=redirect&bpo=38918]: Add an entry for __module__ in the "function" & "method" sections of the inspect docs' Types and members table.

bpo-3530 [https://bugs.python.org/issue?@action=redirect&bpo=3530]: In the ast module documentation, fix a misleading NodeTransformer example and add advice on when to use the fix_missing_locations function.

Build

bpo-39395 [https://bugs.python.org/issue?@action=redirect&bpo=39395]: On non-Windows platforms, the setenv() and unsetenv() functions are now required to build Python.

bpo-39160 [https://bugs.python.org/issue?@action=redirect&bpo=39160]: Updated the documentation in ./configure --help to show default values, reference documentation where required and add additional explanation where needed.

bpo-39144 [https://bugs.python.org/issue?@action=redirect&bpo=39144]: The ctags and etags build targets both include Modules/_ctypes and Python standard library source files.

IDLE

bpo-39050 [https://bugs.python.org/issue?@action=redirect&bpo=39050]: Make IDLE Settings dialog Help button work again.

bpo-34118 [https://bugs.python.org/issue?@action=redirect&bpo=34118]: Tag memoryview, range, and tuple as classes, the same as list, etcetera, in the library manual built-in functions list.

bpo-32989 [https://bugs.python.org/issue?@action=redirect&bpo=32989]: Add tests for editor newline_and_indent_event method. Remove dead code from pyparse find_good_parse_start method.

C API

bpo-39372 [https://bugs.python.org/issue?@action=redirect&bpo=39372]: Clean header files of interfaces defined but with no implementation. The public API symbols being removed are: _PyBytes_InsertThousandsGroupingLocale, _PyBytes_InsertThousandsGrouping, _Py_InitializeFromArgs, _Py_InitializeFromWideArgs, _PyFloat_Repr, _PyFloat_Digits, _PyFloat_DigitsInit, PyFrame_ExtendStack, _PyAIterWrapper_Type, PyNullImporter_Type, PyCmpWrapper_Type, PySortWrapper_Type, PyNoArgsFunction.

bpo-39164 [https://bugs.python.org/issue?@action=redirect&bpo=39164]: Add a private _PyErr_GetExcInfo() function to retrieve exception information of the specified Python thread state.

Python 3.9.0 alpha 2

Release date: 2019-12-18

Security

bpo-38945 [https://bugs.python.org/issue?@action=redirect&bpo=38945]: Newline characters have been escaped when performing uu encoding to prevent them from overflowing into to content section of the encoded file. This prevents malicious or accidental modification of data during the decoding process.

bpo-37228 [https://bugs.python.org/issue?@action=redirect&bpo=37228]: Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint() is no longer supported. This is because of the behavior of SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228 [https://bugs.python.org/issue?@action=redirect&bpo=37228].)

bpo-38804 [https://bugs.python.org/issue?@action=redirect&bpo=38804]: Fixes a ReDoS vulnerability in http.cookiejar. Patch by Ben Caller.

Core and Builtins

bpo-39028 [https://bugs.python.org/issue?@action=redirect&bpo=39028]: Slightly improve the speed of keyword argument parsing with many kwargs by strengthening the assumption that kwargs are interned strings.

bpo-39080 [https://bugs.python.org/issue?@action=redirect&bpo=39080]: Fix the value of end_col_offset for Starred Expression AST nodes when they are among the elements in the args attribute of Call AST nodes.

bpo-39031 [https://bugs.python.org/issue?@action=redirect&bpo=39031]: When parsing an "elif" node, lineno and col_offset of the node now point to the "elif" keyword and not to its condition, making it consistent with the "if" node. Patch by Lysandros Nikolaou.

bpo-20443 [https://bugs.python.org/issue?@action=redirect&bpo=20443]: In Python 3.9.0a1, sys.argv[0] was made an absolute path if a filename was specified on the command line. Revert this change, since most users expect sys.argv to be unmodified.

bpo-39008 [https://bugs.python.org/issue?@action=redirect&bpo=39008]: PySys_Audit() now requires Py_ssize_t to be used for size arguments in the format string, regardless of whether PY_SSIZE_T_CLEAN was defined at include time.

bpo-38673 [https://bugs.python.org/issue?@action=redirect&bpo=38673]: In REPL mode, don't switch to PS2 if the line starts with comment or whitespace. Based on work by Batuhan Taşkaya.

bpo-38922 [https://bugs.python.org/issue?@action=redirect&bpo=38922]: Calling replace on a code object now raises the code.__new__ audit event.

bpo-38920 [https://bugs.python.org/issue?@action=redirect&bpo=38920]: Add audit hooks for when sys.excepthook() and sys.unraisablehook() are invoked.

bpo-38892 [https://bugs.python.org/issue?@action=redirect&bpo=38892]: Improve documentation for audit events table and functions.

bpo-38852 [https://bugs.python.org/issue?@action=redirect&bpo=38852]: Set the thread stack size to 8 Mb for debug builds on android platforms.

bpo-38858 [https://bugs.python.org/issue?@action=redirect&bpo=38858]: Each Python subinterpreter now has its own "small integer singletons": numbers in [-5; 257] range. It is no longer possible to change the number of small integers at build time by overriding NSMALLNEGINTS and NSMALLPOSINTS macros: macros should now be modified manually in pycore_pystate.h header file.

bpo-36854 [https://bugs.python.org/issue?@action=redirect&bpo=36854]: The garbage collector state becomes per interpreter (PyInterpreterState.gc), rather than being global (_PyRuntimeState.gc).

bpo-38835 [https://bugs.python.org/issue?@action=redirect&bpo=38835]: The PyFPE_START_PROTECT() and PyFPE_END_PROTECT() macros are empty: they have been doing nothing for the last year, so stop using them.

bpo-38328 [https://bugs.python.org/issue?@action=redirect&bpo=38328]: Sped up the creation time of constant list and set displays. Patch by Brandt Bucher.

bpo-38707 [https://bugs.python.org/issue?@action=redirect&bpo=38707]: MainThread.native_id is now correctly reset in child processes spawned using multiprocessing.Process, instead of retaining the parent's value.

bpo-38629 [https://bugs.python.org/issue?@action=redirect&bpo=38629]: Added __floor__ and __ceil__ methods to float object. Patch by Batuhan Taşkaya.

bpo-27145 [https://bugs.python.org/issue?@action=redirect&bpo=27145]: int + int and int - int operators can now return small integer singletons. Patch by hongweipeng.

bpo-38021 [https://bugs.python.org/issue?@action=redirect&bpo=38021]: Provide a platform tag for AIX that is sufficient for PEP425 binary distribution identification. Patch by Michael Felt.

bpo-35409 [https://bugs.python.org/issue?@action=redirect&bpo=35409]: Ignore GeneratorExit exceptions when throwing an exception into the aclose coroutine of an asynchronous generator.

bpo-33387 [https://bugs.python.org/issue?@action=redirect&bpo=33387]: Removed WITH_CLEANUP_START, WITH_CLEANUP_FINISH, BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Replaced with RERAISE and WITH_EXCEPT_START bytecodes. The compiler now generates different code for exceptional and non-exceptional branches for 'with' and 'try-except' statements. For 'try-finally' statements the 'finally' block is replicated for each exit from the 'try' body.

Library

bpo-39033 [https://bugs.python.org/issue?@action=redirect&bpo=39033]: Fix NameError in zipimport. Patch by Karthikeyan Singaravelan.

bpo-39022 [https://bugs.python.org/issue?@action=redirect&bpo=39022]: Update importlib.metadata to include improvements from importlib_metadata 1.3 including better serialization of EntryPoints and improved documentation for custom finders.

bpo-39006 [https://bugs.python.org/issue?@action=redirect&bpo=39006]: Fix asyncio when the ssl module is missing: only check for ssl.SSLSocket instance if the ssl module is available.

bpo-38708 [https://bugs.python.org/issue?@action=redirect&bpo=38708]: Fix a potential IndexError in email parser when parsing an empty msg-id.

bpo-38698 [https://bugs.python.org/issue?@action=redirect&bpo=38698]: Add a new InvalidMessageID token to email parser to represent invalid Message-ID headers. Also, add defects when there is remaining value after parsing the header.

bpo-38994 [https://bugs.python.org/issue?@action=redirect&bpo=38994]: Implement __class_getitem__ for os.PathLike, pathlib.Path.

bpo-38979 [https://bugs.python.org/issue?@action=redirect&bpo=38979]: Return class from ContextVar.__class_getitem__ to simplify subclassing.

bpo-38978 [https://bugs.python.org/issue?@action=redirect&bpo=38978]: Implement __class_getitem__ on asyncio objects (Future, Task, Queue). Patch by Batuhan Taskaya.

bpo-38916 [https://bugs.python.org/issue?@action=redirect&bpo=38916]: array.array: Remove tostring() and fromstring() methods. They were aliases to tobytes() and frombytes(), deprecated since Python 3.2.

bpo-38986 [https://bugs.python.org/issue?@action=redirect&bpo=38986]: Make repr of C accelerated TaskWakeupMethWrapper the same as of pure Python version.

bpo-38982 [https://bugs.python.org/issue?@action=redirect&bpo=38982]: Fix asyncio PidfdChildWatcher: handle waitpid() error. If waitpid() is called elsewhere, waitpid() call fails with ChildProcessError: use return code 255 in this case, and log a warning. It ensures that the pidfd file descriptor is closed if this error occurs.

bpo-38529 [https://bugs.python.org/issue?@action=redirect&bpo=38529]: Drop too noisy asyncio warning about deletion of a stream without explicit .close() call.

bpo-27413 [https://bugs.python.org/issue?@action=redirect&bpo=27413]: Added ability to pass through ensure_ascii options to json.dumps in the json.tool command-line interface.

bpo-38634 [https://bugs.python.org/issue?@action=redirect&bpo=38634]: The readline module now detects if Python is linked to libedit at runtime on all platforms. Previously, the check was only done on macOS.

bpo-33684 [https://bugs.python.org/issue?@action=redirect&bpo=33684]: Fix json.tool failed to read a JSON file with non-ASCII characters when locale encoding is not UTF-8.

bpo-38698 [https://bugs.python.org/issue?@action=redirect&bpo=38698]: Prevent UnboundLocalError to pop up in parse_message_id.

parse_message_id() was improperly using a token defined inside an exception handler, which was raising UnboundLocalError on parsing an invalid value. Patch by Claudiu Popa.

bpo-38927 [https://bugs.python.org/issue?@action=redirect&bpo=38927]: Use python -m pip instead of pip to upgrade dependencies in venv.

bpo-26730 [https://bugs.python.org/issue?@action=redirect&bpo=26730]: Fix SpooledTemporaryFile.rollover() might corrupt the file when it is in text mode. Patch by Serhiy Storchaka.

bpo-38881 [https://bugs.python.org/issue?@action=redirect&bpo=38881]: random.choices() now raises a ValueError when all the weights are zero.

bpo-38876 [https://bugs.python.org/issue?@action=redirect&bpo=38876]: Raise pickle.UnpicklingError when loading an item from memo for invalid input.

The previous code was raising a KeyError for both the Python and C implementation. This was caused by the specified index of an invalid input which did not exist in the memo structure, where the pickle stores what objects it has seen. The malformed input would have caused either a BINGET or LONG_BINGET load from the memo, leading to a KeyError as the determined index was bogus. Patch by Claudiu Popa.

bpo-38688 [https://bugs.python.org/issue?@action=redirect&bpo=38688]: Calling func:shutil.copytree to copy a directory tree from one directory to another subdirectory resulted in an endless loop and a RecursionError. A fix was added to consume an iterator and create the list of the entries to be copied, avoiding the recursion for newly created directories. Patch by Bruno P. Kinoshita.

bpo-38863 [https://bugs.python.org/issue?@action=redirect&bpo=38863]: Improve is_cgi() function in http.server, which enables processing the case that cgi directory is a child of another directory other than root.

bpo-37838 [https://bugs.python.org/issue?@action=redirect&bpo=37838]: typing.get_type_hints() properly handles functions decorated with functools.wraps().

bpo-38870 [https://bugs.python.org/issue?@action=redirect&bpo=38870]: Expose ast.unparse() as a function of the ast module that can be used to unparse an ast.AST object and produce a string with code that would produce an equivalent ast.AST object when parsed. Patch by Pablo Galindo and Batuhan Taskaya.

bpo-38859 [https://bugs.python.org/issue?@action=redirect&bpo=38859]: AsyncMock now returns StopAsyncIteration on the exhaustion of a side_effects iterable. Since PEP-479 its Impossible to raise a StopIteration exception from a coroutine.

bpo-38857 [https://bugs.python.org/issue?@action=redirect&bpo=38857]: AsyncMock fix for return values that are awaitable types. This also covers side_effect iterable values that happened to be awaitable, and wraps callables that return an awaitable type. Before these awaitables were being awaited instead of being returned as is.

bpo-38834 [https://bugs.python.org/issue?@action=redirect&bpo=38834]: typing.TypedDict subclasses now track which keys are optional using the __required_keys__ and __optional_keys__ attributes, to enable runtime validation by downstream projects. Patch by Zac Hatfield-Dodds.

bpo-38821 [https://bugs.python.org/issue?@action=redirect&bpo=38821]: Fix unhandled exceptions in argparse when internationalizing error messages for arguments with nargs set to special (non-integer) values. Patch by Federico Bond.

bpo-38820 [https://bugs.python.org/issue?@action=redirect&bpo=38820]: Make Python compatible with OpenSSL 3.0.0. ssl.SSLSocket.getpeercert() no longer returns IPv6 addresses with a trailing new line.

bpo-38811 [https://bugs.python.org/issue?@action=redirect&bpo=38811]: Fix an unhandled exception in pathlib when os.link() is missing. Patch by Toke Høiland-Jørgensen.

bpo-38686 [https://bugs.python.org/issue?@action=redirect&bpo=38686]: Added support for multiple qop values in urllib.request.AbstractDigestAuthHandler.

bpo-38712 [https://bugs.python.org/issue?@action=redirect&bpo=38712]: Add the Linux-specific signal.pidfd_send_signal() function, which allows sending a signal to a process identified by a file descriptor rather than a pid.

bpo-38348 [https://bugs.python.org/issue?@action=redirect&bpo=38348]: Add -i and --indent (indentation level), and --no-type-comments (type comments) command line options to ast parsing tool.

bpo-37523 [https://bugs.python.org/issue?@action=redirect&bpo=37523]: Change zipfile.ZipExtFile to raise ValueError when trying to access the underlying file object after it has been closed. This new behavior is consistent with how accessing closed files is handled in other parts of Python.

bpo-38045 [https://bugs.python.org/issue?@action=redirect&bpo=38045]: Improve the performance of enum._decompose() in enum. Patch by hongweipeng.

bpo-36820 [https://bugs.python.org/issue?@action=redirect&bpo=36820]: Break cycle generated when saving an exception in socket.py, codeop.py and dyld.py as they keep alive not only the exception but user objects through the __traceback__ attribute. Patch by Mario Corchero.

bpo-36406 [https://bugs.python.org/issue?@action=redirect&bpo=36406]: Handle namespace packages in doctest. Patch by Karthikeyan Singaravelan.

bpo-34776 [https://bugs.python.org/issue?@action=redirect&bpo=34776]: Fix dataclasses to support forward references in type annotations

bpo-20928 [https://bugs.python.org/issue?@action=redirect&bpo=20928]: ElementTree supports recursive XInclude processing. Patch by Stefan Behnel.

bpo-29636 [https://bugs.python.org/issue?@action=redirect&bpo=29636]: Add whitespace options for formatting JSON with the json.tool CLI. The following mutually exclusive options are now supported: --indent for setting the indent level in spaces; --tab for indenting with tabs; --no-indent for suppressing newlines; and --compact for suppressing all whitespace. The default behavior remains the same as --indent=4.

Documentation

bpo-38928 [https://bugs.python.org/issue?@action=redirect&bpo=38928]: Correct when venv's upgrade_dependencies() and --upgrade-deps are added.

bpo-38899 [https://bugs.python.org/issue?@action=redirect&bpo=38899]: Update documentation to state that to activate virtual environments under fish one should use source, not . as documented at https://fishshell.com/docs/current/cmds/source.html.

bpo-22377 [https://bugs.python.org/issue?@action=redirect&bpo=22377]: Improves documentation of the values that datetime.datetime.strptime() accepts for %Z. Patch by Karl Dubost.

Tests

bpo-38546 [https://bugs.python.org/issue?@action=redirect&bpo=38546]: Fix test_ressources_gced_in_workers() of test_concurrent_futures: explicitly stop the manager to prevent leaking a child process running in the background after the test completes.

bpo-38546 [https://bugs.python.org/issue?@action=redirect&bpo=38546]: Multiprocessing and concurrent.futures tests now stop the resource tracker process when tests complete.

bpo-38614 [https://bugs.python.org/issue?@action=redirect&bpo=38614]: Replace hardcoded timeout constants in tests with new test.support constants: LOOPBACK_TIMEOUT, INTERNET_TIMEOUT, SHORT_TIMEOUT and LONG_TIMEOUT. It becomes easier to adjust these four timeout constants for all tests at once, rather than having to adjust every single test file.

bpo-38547 [https://bugs.python.org/issue?@action=redirect&bpo=38547]: Fix test_pty: if the process is the session leader, closing the master file descriptor raises a SIGHUP signal: simply ignore SIGHUP when running the tests.

bpo-38992 [https://bugs.python.org/issue?@action=redirect&bpo=38992]: Fix a test for math.fsum() that was failing due to constant folding.

bpo-38991 [https://bugs.python.org/issue?@action=redirect&bpo=38991]: test.support: run_python_until_end(), assert_python_ok() and assert_python_failure() functions no longer strip whitespaces from stderr. Remove test.support.strip_python_stderr() function.

bpo-38965 [https://bugs.python.org/issue?@action=redirect&bpo=38965]: Fix test_faulthandler on GCC 10. Use the "volatile" keyword in faulthandler._stack_overflow() to prevent tail call optimization on any compiler, rather than relying on compiler specific pragma.

bpo-38875 [https://bugs.python.org/issue?@action=redirect&bpo=38875]: test_capi: trashcan tests now require the test "cpu" resource.

bpo-38841 [https://bugs.python.org/issue?@action=redirect&bpo=38841]: Skip asyncio test_create_datagram_endpoint_existing_sock_unix on platforms lacking a functional bind() for named unix domain sockets.

bpo-38692 [https://bugs.python.org/issue?@action=redirect&bpo=38692]: Skip the test_posix.test_pidfd_open() test if os.pidfd_open() fails with a PermissionError. This situation can happen in a Linux sandbox using a syscall whitelist which doesn't allow the pidfd_open() syscall yet.

bpo-38839 [https://bugs.python.org/issue?@action=redirect&bpo=38839]: Fix some unused functions in tests. Patch by Adam Johnson.

bpo-38669 [https://bugs.python.org/issue?@action=redirect&bpo=38669]: Raise TypeError when passing target as a string with unittest.mock.patch.object().

bpo-37957 [https://bugs.python.org/issue?@action=redirect&bpo=37957]: test.regrtest now can receive a list of test patterns to ignore (using the -i/--ignore argument) or a file with a list of patterns to ignore (using the --ignore-file argument). Patch by Pablo Galindo.

Build

bpo-37404 [https://bugs.python.org/issue?@action=redirect&bpo=37404]: asyncio now raises TypeError when calling incompatible methods with an ssl.SSLSocket socket. Patch by Ido Michael.

bpo-36500 [https://bugs.python.org/issue?@action=redirect&bpo=36500]: Added an optional "regen" project to the Visual Studio solution that will regenerate all grammar, tokens, and opcodes.

Windows

bpo-39007 [https://bugs.python.org/issue?@action=redirect&bpo=39007]: Add auditing events to functions in winreg.

bpo-33125 [https://bugs.python.org/issue?@action=redirect&bpo=33125]: Add support for building and releasing Windows ARM64 packages.

macOS

bpo-37931 [https://bugs.python.org/issue?@action=redirect&bpo=37931]: Fixed a crash on OSX dynamic builds that occurred when re-initializing the posix module after a Py_Finalize if the environment had changed since the previous import posix. Patch by Benoît Hudson.

IDLE

bpo-38944 [https://bugs.python.org/issue?@action=redirect&bpo=38944]: Escape key now closes IDLE completion windows. Patch by Johnny Najera.

bpo-38943 [https://bugs.python.org/issue?@action=redirect&bpo=38943]: Fix IDLE autocomplete windows not always appearing on some systems. Patch by Johnny Najera.

bpo-38862 [https://bugs.python.org/issue?@action=redirect&bpo=38862]: 'Strip Trailing Whitespace' on the Format menu removes extra newlines at the end of non-shell files.

bpo-38636 [https://bugs.python.org/issue?@action=redirect&bpo=38636]: Fix IDLE Format menu tab toggle and file indent width. These functions (default shortcuts Alt-T and Alt-U) were mistakenly disabled in 3.7.5 and 3.8.0.

C API

bpo-38896 [https://bugs.python.org/issue?@action=redirect&bpo=38896]: Remove PyUnicode_ClearFreeList() function: the Unicode free list has been removed in Python 3.3.

bpo-37340 [https://bugs.python.org/issue?@action=redirect&bpo=37340]: Remove PyMethod_ClearFreeList() and PyCFunction_ClearFreeList() functions: the free lists of bound method objects have been removed.

bpo-38835 [https://bugs.python.org/issue?@action=redirect&bpo=38835]: Exclude PyFPE_START_PROTECT() and PyFPE_END_PROTECT() macros of pyfpe.h from Py_LIMITED_API (stable API).

Python 3.9.0 alpha 1

Release date: 2019-11-19

Security

bpo-38722 [https://bugs.python.org/issue?@action=redirect&bpo=38722]: runpy now uses io.open_code() to open code files. Patch by Jason Killen.

bpo-38622 [https://bugs.python.org/issue?@action=redirect&bpo=38622]: Add additional audit events for the ctypes module.

bpo-38418 [https://bugs.python.org/issue?@action=redirect&bpo=38418]: Fixes audit event for os.system() to be named os.system.

bpo-38243 [https://bugs.python.org/issue?@action=redirect&bpo=38243]: Escape the server title of xmlrpc.server.DocXMLRPCServer when rendering the document page as HTML. (Contributed by Donghee Na in bpo-38243 [https://bugs.python.org/issue?@action=redirect&bpo=38243].)

bpo-38174 [https://bugs.python.org/issue?@action=redirect&bpo=38174]: Update vendorized expat library version to 2.2.8, which resolves CVE 2019-15903 [https://www.cve.org/CVERecord?id=CVE-2019-15903].

bpo-37764 [https://bugs.python.org/issue?@action=redirect&bpo=37764]: Fixes email._header_value_parser.get_unstructured going into an infinite loop for a specific case in which the email header does not have trailing whitespace, and the case in which it contains an invalid encoded word. Patch by Ashwin Ramaswami.

bpo-37461 [https://bugs.python.org/issue?@action=redirect&bpo=37461]: Fix an infinite loop when parsing specially crafted email headers. Patch by Abhilash Raj.

bpo-37363 [https://bugs.python.org/issue?@action=redirect&bpo=37363]: Adds audit events for the range of supported run commands (see 命令列與環境).

bpo-37463 [https://bugs.python.org/issue?@action=redirect&bpo=37463]: ssl.match_hostname() no longer accepts IPv4 addresses with additional text after the address and only quad-dotted notation without trailing whitespaces. Some inet_aton() implementations ignore whitespace and all data after whitespace, e.g. '127.0.0.1 whatever'.

bpo-37363 [https://bugs.python.org/issue?@action=redirect&bpo=37363]: Adds audit events for ensurepip, ftplib, glob, imaplib, nntplib, pdb, poplib, shutil, smtplib, sqlite3, subprocess, telnetlib, tempfile and webbrowser, as well as os.listdir(), os.scandir() and breakpoint().

bpo-37364 [https://bugs.python.org/issue?@action=redirect&bpo=37364]: io.open_code() is now used when reading .pth files.

bpo-34631 [https://bugs.python.org/issue?@action=redirect&bpo=34631]: Updated OpenSSL to 1.1.1c in Windows installer

bpo-34155 [https://bugs.python.org/issue?@action=redirect&bpo=34155]: Fix parsing of invalid email addresses with more than one @ (e.g. a@b@c.com.) to not return the part before 2nd @ as valid email address. Patch by maxking & jpic.

Core and Builtins

bpo-38631 [https://bugs.python.org/issue?@action=redirect&bpo=38631]: Replace Py_FatalError() call with a regular RuntimeError exception in float.__getformat__().

bpo-38639 [https://bugs.python.org/issue?@action=redirect&bpo=38639]: Optimized math.floor(), math.ceil() and math.trunc() for floats.

bpo-38640 [https://bugs.python.org/issue?@action=redirect&bpo=38640]: Fixed a bug in the compiler that was causing to raise in the presence of break statements and continue statements inside always false while loops. Patch by Pablo Galindo.

bpo-38613 [https://bugs.python.org/issue?@action=redirect&bpo=38613]: Optimized some set operations (e.g. |, ^, and -) of dict_keys. d.keys() | other was slower than set(d) | other but they are almost same performance for now.

bpo-28029 [https://bugs.python.org/issue?@action=redirect&bpo=28029]: "".replace("", s, n) now returns s instead of an empty string for all non-zero n. There are similar changes for bytes and bytearray objects.

bpo-38535 [https://bugs.python.org/issue?@action=redirect&bpo=38535]: Fixed line numbers and column offsets for AST nodes for calls without arguments in decorators.

bpo-38525 [https://bugs.python.org/issue?@action=redirect&bpo=38525]: Fix a segmentation fault when using reverse iterators of empty dict objects. Patch by Donghee Na and Inada Naoki.

bpo-38465 [https://bugs.python.org/issue?@action=redirect&bpo=38465]: bytearray, array and mmap objects allow now to export more than 2**31 buffers at a time.

bpo-38469 [https://bugs.python.org/issue?@action=redirect&bpo=38469]: Fixed a bug where the scope of named expressions was not being resolved correctly in the presence of the global keyword. Patch by Pablo Galindo.

bpo-38437 [https://bugs.python.org/issue?@action=redirect&bpo=38437]: Activate the GC_DEBUG macro for debug builds of the interpreter (when Py_DEBUG is set). Patch by Pablo Galindo.

bpo-38379 [https://bugs.python.org/issue?@action=redirect&bpo=38379]: When the garbage collector makes a collection in which some objects resurrect (they are reachable from outside the isolated cycles after the finalizers have been executed), do not block the collection of all objects that are still unreachable. Patch by Pablo Galindo and Tim Peters.

bpo-38379 [https://bugs.python.org/issue?@action=redirect&bpo=38379]: When cyclic garbage collection (gc) runs finalizers that resurrect unreachable objects, the current gc run ends, without collecting any cyclic trash. However, the statistics reported by collect() and get_stats() claimed that all cyclic trash found was collected, and that the resurrected objects were collected. Changed the stats to report that none were collected.

bpo-38392 [https://bugs.python.org/issue?@action=redirect&bpo=38392]: In debug mode, PyObject_GC_Track() now calls tp_traverse() of the object type to ensure that the object is valid: test that objects visited by tp_traverse() are valid.

bpo-38210 [https://bugs.python.org/issue?@action=redirect&bpo=38210]: Remove unnecessary intersection and update set operation in dictview with empty set. (Contributed by Donghee Na in bpo-38210 [https://bugs.python.org/issue?@action=redirect&bpo=38210].)

bpo-38402 [https://bugs.python.org/issue?@action=redirect&bpo=38402]: Check the error from the system's underlying crypt or crypt_r.

bpo-37474 [https://bugs.python.org/issue?@action=redirect&bpo=37474]: On FreeBSD, Python no longer calls fedisableexcept() at startup to control the floating-point control mode. The call became useless since FreeBSD 6: it became the default mode.

bpo-38006 [https://bugs.python.org/issue?@action=redirect&bpo=38006]: Fix a bug due to the interaction of weakrefs and the cyclic garbage collector. We must clear any weakrefs in garbage in order to prevent their callbacks from executing and causing a crash.

bpo-38317 [https://bugs.python.org/issue?@action=redirect&bpo=38317]: Fix warnings options priority: PyConfig.warnoptions has the highest priority, as stated in the PEP 587 [https://peps.python.org/pep-0587/].

bpo-38310 [https://bugs.python.org/issue?@action=redirect&bpo=38310]: Predict BUILD_MAP_UNPACK_WITH_CALL -> CALL_FUNCTION_EX opcode pairs in the main interpreter loop. Patch by Brandt Bucher.

bpo-36871 [https://bugs.python.org/issue?@action=redirect&bpo=36871]: Improve error handling for the assert_has_calls and assert_has_awaits methods of mocks. Fixed a bug where any errors encountered while binding the expected calls to the mock's spec were silently swallowed, leading to misleading error output.

bpo-11410 [https://bugs.python.org/issue?@action=redirect&bpo=11410]: Better control over symbol visibility is provided through use of the visibility attributes available in gcc >= 4.0, provided in a uniform way across POSIX and Windows. The POSIX build files have been updated to compile with -fvisibility=hidden, minimising exported symbols.

bpo-38219 [https://bugs.python.org/issue?@action=redirect&bpo=38219]: Optimized the dict constructor and the update() method for the case when the argument is a dict.

bpo-38236 [https://bugs.python.org/issue?@action=redirect&bpo=38236]: Python now dumps path configuration if it fails to import the Python codecs of the filesystem and stdio encodings.

bpo-38013 [https://bugs.python.org/issue?@action=redirect&bpo=38013]: Allow to call async_generator_athrow().throw(...) even for non-started async generator helper. It fixes annoying warning at the end of asyncio.run() call.

bpo-38124 [https://bugs.python.org/issue?@action=redirect&bpo=38124]: Fix an off-by-one error in PyState_AddModule that could cause out-of-bounds memory access.

bpo-38116 [https://bugs.python.org/issue?@action=redirect&bpo=38116]: The select module is now PEP-384 compliant and no longer has static state

bpo-38113 [https://bugs.python.org/issue?@action=redirect&bpo=38113]: ast module updated to PEP-384 and all statics removed

bpo-38076 [https://bugs.python.org/issue?@action=redirect&bpo=38076]: The struct module is now PEP-384 compatible

bpo-38075 [https://bugs.python.org/issue?@action=redirect&bpo=38075]: The random module is now PEP-384 compatible

bpo-38074 [https://bugs.python.org/issue?@action=redirect&bpo=38074]: zlib module made PEP-384 compatible

bpo-38073 [https://bugs.python.org/issue?@action=redirect&bpo=38073]: Make pwd extension module PEP-384 compatible

bpo-38072 [https://bugs.python.org/issue?@action=redirect&bpo=38072]: grp module made PEP-384 compatible

bpo-38069 [https://bugs.python.org/issue?@action=redirect&bpo=38069]: Make _posixsubprocess PEP-384 compatible

bpo-38071 [https://bugs.python.org/issue?@action=redirect&bpo=38071]: Make termios extension module PEP-384 compatible

bpo-38005 [https://bugs.python.org/issue?@action=redirect&bpo=38005]: Fixed comparing and creating of InterpreterID and ChannelID.

bpo-36946 [https://bugs.python.org/issue?@action=redirect&bpo=36946]: Fix possible signed integer overflow when handling slices. Patch by hongweipeng.

bpo-37994 [https://bugs.python.org/issue?@action=redirect&bpo=37994]: Fixed silencing arbitrary errors if an attribute lookup fails in several sites. Only AttributeError should be silenced.

bpo-8425 [https://bugs.python.org/issue?@action=redirect&bpo=8425]: Optimize set difference_update for the case when the other set is much larger than the base set. (Suggested by Evgeny Kapun with code contributed by Michele Orrù).

bpo-37966 [https://bugs.python.org/issue?@action=redirect&bpo=37966]: The implementation of is_normalized() has been greatly sped up on strings that aren't normalized, by implementing the full normalization-quick-check algorithm from the Unicode standard.

bpo-37947 [https://bugs.python.org/issue?@action=redirect&bpo=37947]: Adjust correctly the recursion level in the symtable generation for named expressions. Patch by Pablo Galindo.

bpo-37812 [https://bugs.python.org/issue?@action=redirect&bpo=37812]: The CHECK_SMALL_INT macro used inside Object/longobject.c has been replaced with an explicit return at each call site.

bpo-37751 [https://bugs.python.org/issue?@action=redirect&bpo=37751]: Fix codecs.lookup() to normalize the encoding name the same way than encodings.normalize_encoding(), except that codecs.lookup() also converts the name to lower case.

bpo-37830 [https://bugs.python.org/issue?@action=redirect&bpo=37830]: Fixed compilation of break and continue in the finally block when the corresponding try block contains return with a non-constant value.

bpo-20490 [https://bugs.python.org/issue?@action=redirect&bpo=20490]: Improve import error message for partially initialized module on circular from imports - by Anthony Sottile.

bpo-37840 [https://bugs.python.org/issue?@action=redirect&bpo=37840]: Fix handling of negative indices in sq_item of bytearray. Patch by Sergey Fedoseev.

bpo-37802 [https://bugs.python.org/issue?@action=redirect&bpo=37802]: Slightly improve performance of PyLong_FromUnsignedLong(), PyLong_FromUnsignedLongLong() and PyLong_FromSize_t(). Patch by Sergey Fedoseev.

bpo-37409 [https://bugs.python.org/issue?@action=redirect&bpo=37409]: Ensure explicit relative imports from interactive sessions and scripts (having no parent package) always raise ImportError, rather than treating the current module as the package. Patch by Ben Lewis.

bpo-32912 [https://bugs.python.org/issue?@action=redirect&bpo=32912]: Reverted bpo-32912 [https://bugs.python.org/issue?@action=redirect&bpo=32912]: emitting SyntaxWarning instead of DeprecationWarning for invalid escape sequences in string and bytes literals.

bpo-37757 [https://bugs.python.org/issue?@action=redirect&bpo=37757]: PEP 572 [https://peps.python.org/pep-0572/]: As described in the PEP, assignment expressions now raise SyntaxError when their interaction with comprehension scoping results in an ambiguous target scope.

The TargetScopeError subclass originally proposed by the PEP has been removed in favour of just raising regular syntax errors for the disallowed cases.

bpo-36279 [https://bugs.python.org/issue?@action=redirect&bpo=36279]: Fix potential use of uninitialized memory in os.wait3().

bpo-36311 [https://bugs.python.org/issue?@action=redirect&bpo=36311]: Decoding bytes objects larger than 2GiB is faster and no longer fails when a multibyte characters spans a chunk boundary.

bpo-34880 [https://bugs.python.org/issue?@action=redirect&bpo=34880]: The assert statement now works properly if the AssertionError exception is being shadowed. Patch by Zackery Spytz.

bpo-37340 [https://bugs.python.org/issue?@action=redirect&bpo=37340]: Removed object cache (free_list) for bound method objects. Temporary bound method objects are less used than before thanks to the LOAD_METHOD opcode and the _PyObject_VectorcallMethod C API.

bpo-37648 [https://bugs.python.org/issue?@action=redirect&bpo=37648]: Fixed minor inconsistency in list.__contains__(), tuple.__contains__() and a few other places. The collection's item is now always at the left and the needle is on the right of ==.

bpo-37444 [https://bugs.python.org/issue?@action=redirect&bpo=37444]: Update differing exception between builtins.__import__() and importlib.__import__().

bpo-37619 [https://bugs.python.org/issue?@action=redirect&bpo=37619]: When adding a wrapper descriptor from one class to a different class (for example, setting __add__ = str.__add__ on an int subclass), an exception is correctly raised when the operator is called.

bpo-37593 [https://bugs.python.org/issue?@action=redirect&bpo=37593]: Swap the positions of the posonlyargs and args parameters in the constructor of ast.parameters nodes.

bpo-37543 [https://bugs.python.org/issue?@action=redirect&bpo=37543]: Optimized pymalloc for non PGO build.

bpo-37537 [https://bugs.python.org/issue?@action=redirect&bpo=37537]: Compute allocated pymalloc blocks inside _Py_GetAllocatedBlocks(). This slows down _Py_GetAllocatedBlocks() but gives a small speedup to _PyObject_Malloc() and _PyObject_Free().

bpo-37467 [https://bugs.python.org/issue?@action=redirect&bpo=37467]: Fix sys.excepthook() and PyErr_Display() if a filename is a bytes string. For example, for a SyntaxError exception where the filename attribute is a bytes string.

bpo-37433 [https://bugs.python.org/issue?@action=redirect&bpo=37433]: Fix SyntaxError indicator printing too many spaces for multi-line strings - by Anthony Sottile.

bpo-37417 [https://bugs.python.org/issue?@action=redirect&bpo=37417]: bytearray.extend() now correctly handles errors that arise during iteration. Patch by Brandt Bucher.

bpo-37414 [https://bugs.python.org/issue?@action=redirect&bpo=37414]: The undocumented sys.callstats() function has been removed. Since Python 3.7, it was deprecated and always returned None. It required a special build option CALL_PROFILE which was already removed in Python 3.7.

bpo-37392 [https://bugs.python.org/issue?@action=redirect&bpo=37392]: Remove sys.getcheckinterval() and sys.setcheckinterval() functions. They were deprecated since Python 3.2. Use sys.getswitchinterval() and sys.setswitchinterval() instead. Remove also check_interval field of the PyInterpreterState structure.

bpo-37388 [https://bugs.python.org/issue?@action=redirect&bpo=37388]: In development mode and in debug build, encoding and errors arguments are now checked on string encoding and decoding operations. Examples: open(), str.encode() and bytes.decode().

By default, for best performances, the errors argument is only checked at the first encoding/decoding error, and the encoding argument is sometimes ignored for empty strings.

bpo-37348 [https://bugs.python.org/issue?@action=redirect&bpo=37348]: Optimized decoding short ASCII string with UTF-8 and ascii codecs. b"foo".decode() is about 15% faster. Patch by Inada Naoki.

bpo-24214 [https://bugs.python.org/issue?@action=redirect&bpo=24214]: Improved support of the surrogatepass error handler in the UTF-8 and UTF-16 incremental decoders.

bpo-37330 [https://bugs.python.org/issue?@action=redirect&bpo=37330]: open(), io.open(), codecs.open() and fileinput.FileInput no longer accept 'U' ("universal newline") in the file mode. This flag was deprecated since Python 3.3.

bpo-35224 [https://bugs.python.org/issue?@action=redirect&bpo=35224]: Reverse evaluation order of key: value in dict comprehensions as proposed in PEP 572. I.e. in {k: v for ...}, k will be evaluated before v.

bpo-37316 [https://bugs.python.org/issue?@action=redirect&bpo=37316]: Fix the PySys_Audit() call in mmap.mmap.

bpo-37300 [https://bugs.python.org/issue?@action=redirect&bpo=37300]: Remove an unnecessary Py_XINCREF in classobject.c.

bpo-37269 [https://bugs.python.org/issue?@action=redirect&bpo=37269]: Fix a bug in the peephole optimizer that was not treating correctly constant conditions with binary operators. Patch by Pablo Galindo.

bpo-20443 [https://bugs.python.org/issue?@action=redirect&bpo=20443]: Python now gets the absolute path of the script filename specified on the command line (ex: "python3 script.py"): the __file__ attribute of the __main__ module and sys.path[0] become an absolute path, rather than a relative path.

bpo-37257 [https://bugs.python.org/issue?@action=redirect&bpo=37257]: Python's small object allocator (obmalloc.c) now allows (no more than) one empty arena to remain available for immediate reuse, without returning it to the OS. This prevents thrashing in simple loops where an arena could be created and destroyed anew on each iteration.

bpo-37231 [https://bugs.python.org/issue?@action=redirect&bpo=37231]: The dispatching of type slots to special methods (for example calling __mul__ when doing x * y) has been made faster.

bpo-36974 [https://bugs.python.org/issue?@action=redirect&bpo=36974]: Implemented separate vectorcall functions for every calling convention of builtin functions and methods. This improves performance for calls.

bpo-37213 [https://bugs.python.org/issue?@action=redirect&bpo=37213]: Handle correctly negative line offsets in the peephole optimizer. Patch by Pablo Galindo.

bpo-37219 [https://bugs.python.org/issue?@action=redirect&bpo=37219]: Remove erroneous optimization for empty set differences.

bpo-15913 [https://bugs.python.org/issue?@action=redirect&bpo=15913]: Implement PyBuffer_SizeFromFormat() function (previously documented but not implemented): call struct.calcsize(). Patch by Joannah Nanjekye.

bpo-36922 [https://bugs.python.org/issue?@action=redirect&bpo=36922]: Slot functions optimize any callable with Py_TPFLAGS_METHOD_DESCRIPTOR instead of only instances of function.

bpo-36974 [https://bugs.python.org/issue?@action=redirect&bpo=36974]: The slot tp_vectorcall_offset is inherited unconditionally to support super().__call__() when the base class uses vectorcall.

bpo-37160 [https://bugs.python.org/issue?@action=redirect&bpo=37160]: threading.get_native_id() now also supports NetBSD.

bpo-37077 [https://bugs.python.org/issue?@action=redirect&bpo=37077]: Add threading.get_native_id() support for AIX. Patch by M. Felt

bpo-36781 [https://bugs.python.org/issue?@action=redirect&bpo=36781]: sum() has been optimized for boolean values.

bpo-34556 [https://bugs.python.org/issue?@action=redirect&bpo=34556]: Add --upgrade-deps to venv module. Patch by Cooper Ry Lees

bpo-20523 [https://bugs.python.org/issue?@action=redirect&bpo=20523]: pdb.Pdb supports ~/.pdbrc in Windows 7. Patch by Tim Hopper and Dan Lidral-Porter.

bpo-35551 [https://bugs.python.org/issue?@action=redirect&bpo=35551]: Updated encodings: - Removed the "tis260" encoding, which was an alias for the nonexistent "tactis" codec. - Added "mac_centeuro" as an alias for the mac_latin2 encoding.

bpo-19072 [https://bugs.python.org/issue?@action=redirect&bpo=19072]: The classmethod decorator can now wrap other descriptors such as property objects. Adapted from a patch written by Graham Dumpleton.

bpo-27575 [https://bugs.python.org/issue?@action=redirect&bpo=27575]: Improve speed of dictview intersection by directly using set intersection logic. Patch by David Su.

bpo-30773 [https://bugs.python.org/issue?@action=redirect&bpo=30773]: Prohibit parallel running of aclose() / asend() / athrow(). Fix ag_running to reflect the actual running status of the AG.

Library

bpo-36589 [https://bugs.python.org/issue?@action=redirect&bpo=36589]: The curses.update_lines_cols() function now returns None instead of 1 on success.

bpo-38807 [https://bugs.python.org/issue?@action=redirect&bpo=38807]: Update TypeError messages for os.path.join() to include os.PathLike objects as acceptable input types.

bpo-38724 [https://bugs.python.org/issue?@action=redirect&bpo=38724]: Add a repr for subprocess.Popen objects. Patch by Andrey Doroschenko.

bpo-38786 [https://bugs.python.org/issue?@action=redirect&bpo=38786]: pydoc now recognizes and parses HTTPS URLs. Patch by python273.

bpo-38785 [https://bugs.python.org/issue?@action=redirect&bpo=38785]: Prevent asyncio from crashing if parent __init__ is not called from a constructor of object derived from asyncio.Future.

bpo-38723 [https://bugs.python.org/issue?@action=redirect&bpo=38723]: pdb now uses io.open_code() to trigger auditing events.

bpo-27805 [https://bugs.python.org/issue?@action=redirect&bpo=27805]: Allow opening pipes and other non-seekable files in append mode with open().

bpo-38438 [https://bugs.python.org/issue?@action=redirect&bpo=38438]: Simplify the argparse usage message for nargs="*".

bpo-38761 [https://bugs.python.org/issue?@action=redirect&bpo=38761]: WeakSet is now registered as a collections.abc.MutableSet.

bpo-38716 [https://bugs.python.org/issue?@action=redirect&bpo=38716]: logging: change RotatingHandler namer and rotator to class-level attributes. This stops __init__ from setting them to None in the case where a subclass defines them with eponymous methods.

bpo-38713 [https://bugs.python.org/issue?@action=redirect&bpo=38713]: Add os.P_PIDFD constant, which may be passed to os.waitid() to wait on a Linux process file descriptor.

bpo-38692 [https://bugs.python.org/issue?@action=redirect&bpo=38692]: Add asyncio.PidfdChildWatcher, a Linux-specific child watcher implementation that polls process file descriptors.

bpo-38692 [https://bugs.python.org/issue?@action=redirect&bpo=38692]: Expose the Linux pidfd_open syscall as os.pidfd_open().

bpo-38602 [https://bugs.python.org/issue?@action=redirect&bpo=38602]: Added constants F_OFD_GETLK, F_OFD_SETLK and F_OFD_SETLKW to the fcntl module. Patch by Donghee Na.

bpo-38334 [https://bugs.python.org/issue?@action=redirect&bpo=38334]: Fixed seeking backward on an encrypted zipfile.ZipExtFile.

bpo-38312 [https://bugs.python.org/issue?@action=redirect&bpo=38312]: Add curses.get_escdelay(), curses.set_escdelay(), curses.get_tabsize(), and curses.set_tabsize() functions - by Anthony Sottile.

bpo-38586 [https://bugs.python.org/issue?@action=redirect&bpo=38586]: Now fileConfig() correctly sets the .name of handlers loaded.

bpo-38565 [https://bugs.python.org/issue?@action=redirect&bpo=38565]: Add new cache_parameters() method for functools.lru_cache() to better support pickling.

bpo-34679 [https://bugs.python.org/issue?@action=redirect&bpo=34679]: asynci.ProactorEventLoop.close() now only calls signal.set_wakeup_fd() in the main thread.

bpo-31202 [https://bugs.python.org/issue?@action=redirect&bpo=31202]: The case the result of pathlib.WindowsPath.glob() matches now the case of the pattern for literal parts.

bpo-36321 [https://bugs.python.org/issue?@action=redirect&bpo=36321]: Remove misspelled attribute. The 3.8 changelog noted that this would be removed in 3.9.

bpo-38521 [https://bugs.python.org/issue?@action=redirect&bpo=38521]: Fixed erroneous equality comparison in statistics.NormalDist().

bpo-38493 [https://bugs.python.org/issue?@action=redirect&bpo=38493]: Added CLD_KILLED and CLD_STOPPED for si_code. Patch by Donghee Na.

bpo-38478 [https://bugs.python.org/issue?@action=redirect&bpo=38478]: Fixed a bug in inspect.signature.bind() that was causing it to fail when handling a keyword argument with same name as positional-only parameter. Patch by Pablo Galindo.

bpo-33604 [https://bugs.python.org/issue?@action=redirect&bpo=33604]: Fixed hmac.new and hmac.HMAC to raise TypeError instead of ValueError when the digestmod parameter, now required in 3.8, is omitted. Also clarified the hmac module documentation and docstrings.

bpo-38378 [https://bugs.python.org/issue?@action=redirect&bpo=38378]: Parameters out and in of os.sendfile() was renamed to out_fd and in_fd.

bpo-38417 [https://bugs.python.org/issue?@action=redirect&bpo=38417]: Added support for setting the umask in the child process to the subprocess module on POSIX systems.

bpo-38449 [https://bugs.python.org/issue?@action=redirect&bpo=38449]: Revert PR 15522, which introduces a regression in mimetypes.guess_type() due to improper handling of filenames as urls.

bpo-38431 [https://bugs.python.org/issue?@action=redirect&bpo=38431]: Fix __repr__ method for dataclasses.InitVar to support typing objects, patch by Samuel Colvin.

bpo-38109 [https://bugs.python.org/issue?@action=redirect&bpo=38109]: Add missing stat.S_IFDOOR, stat.S_IFPORT, stat.S_IFWHT, stat.S_ISDOOR(), stat.S_ISPORT(), and stat.S_ISWHT() values to the Python implementation of stat.

bpo-38422 [https://bugs.python.org/issue?@action=redirect&bpo=38422]: Clarify docstrings of pathlib suffix(es)

bpo-38405 [https://bugs.python.org/issue?@action=redirect&bpo=38405]: Nested subclasses of typing.NamedTuple are now pickleable.

bpo-38332 [https://bugs.python.org/issue?@action=redirect&bpo=38332]: Prevent KeyError thrown by _encoded_words.decode() when given an encoded-word with invalid content-type encoding from propagating all the way to email.message.get().

bpo-38371 [https://bugs.python.org/issue?@action=redirect&bpo=38371]: Deprecated the split() method in _tkinter.TkappType in favour of the splitlist() method which has more consistent and predictable behavior.

bpo-38341 [https://bugs.python.org/issue?@action=redirect&bpo=38341]: Add smtplib.SMTPNotSupportedError to the smtplib exported names.

bpo-38319 [https://bugs.python.org/issue?@action=redirect&bpo=38319]: sendfile() used in socket and shutil modules was raising OverflowError for files >= 2GiB on 32-bit architectures. (patch by Giampaolo Rodola)

bpo-38242 [https://bugs.python.org/issue?@action=redirect&bpo=38242]: Revert the new asyncio Streams API

bpo-13153 [https://bugs.python.org/issue?@action=redirect&bpo=13153]: OS native encoding is now used for converting between Python strings and Tcl objects. This allows to display, copy and paste to clipboard emoji and other non-BMP characters. Converting strings from Tcl to Python and back now never fails (except MemoryError).

bpo-38019 [https://bugs.python.org/issue?@action=redirect&bpo=38019]: Correctly handle pause/resume reading of closed asyncio unix pipe.

bpo-38163 [https://bugs.python.org/issue?@action=redirect&bpo=38163]: Child mocks will now detect their type as either synchronous or asynchronous, asynchronous child mocks will be AsyncMocks and synchronous child mocks will be either MagicMock or Mock (depending on their parent type).

bpo-38161 [https://bugs.python.org/issue?@action=redirect&bpo=38161]: Removes _AwaitEvent from AsyncMock.

bpo-38216 [https://bugs.python.org/issue?@action=redirect&bpo=38216]: Allow the rare code that wants to send invalid http requests from the http.client library a way to do so. The fixes for bpo-30458 [https://bugs.python.org/issue?@action=redirect&bpo=30458] led to breakage for some projects that were relying on this ability to test their own behavior in the face of bad requests.

bpo-28286 [https://bugs.python.org/issue?@action=redirect&bpo=28286]: Deprecate opening GzipFile for writing implicitly. Always specify the mode argument for writing.

bpo-38108 [https://bugs.python.org/issue?@action=redirect&bpo=38108]: Any synchronous magic methods on an AsyncMock now return a MagicMock. Any asynchronous magic methods on a MagicMock now return an AsyncMock.

bpo-38265 [https://bugs.python.org/issue?@action=redirect&bpo=38265]: Update the length parameter of os.pread() to accept Py_ssize_t instead of int.

bpo-38112 [https://bugs.python.org/issue?@action=redirect&bpo=38112]: compileall has a higher default recursion limit and new command-line arguments for path manipulation, symlinks handling, and multiple optimization levels.

bpo-38248 [https://bugs.python.org/issue?@action=redirect&bpo=38248]: asyncio: Fix inconsistent immediate Task cancellation

bpo-38237 [https://bugs.python.org/issue?@action=redirect&bpo=38237]: The arguments for the builtin pow function are more descriptive. They can now also be passed in as keywords.

bpo-34002 [https://bugs.python.org/issue?@action=redirect&bpo=34002]: Improve efficiency in parts of email package by changing while-pop to a for loop, using isdisjoint instead of set intersections.

bpo-38191 [https://bugs.python.org/issue?@action=redirect&bpo=38191]: Constructors of NamedTuple and TypedDict types now accept arbitrary keyword argument names, including "cls", "self", "typename", "_typename", "fields" and "_fields".

bpo-38155 [https://bugs.python.org/issue?@action=redirect&bpo=38155]: Add __all__ to datetime. Patch by Tahia Khan.

bpo-38185 [https://bugs.python.org/issue?@action=redirect&bpo=38185]: Fixed case-insensitive string comparison in sqlite3.Row indexing.

bpo-38136 [https://bugs.python.org/issue?@action=redirect&bpo=38136]: Changes AsyncMock call count and await count to be two different counters. Now await count only counts when a coroutine has been awaited, not when it has been called, and vice-versa. Update the documentation around this.

bpo-37828 [https://bugs.python.org/issue?@action=redirect&bpo=37828]: Fix default mock name in unittest.mock.Mock.assert_called() exceptions. Patch by Abraham Toriz Cruz.

bpo-38175 [https://bugs.python.org/issue?@action=redirect&bpo=38175]: Fix a memory leak in comparison of sqlite3.Row objects.

bpo-33936 [https://bugs.python.org/issue?@action=redirect&bpo=33936]: _hashlib no longer calls obsolete OpenSSL initialization function with OpenSSL 1.1.0+.

bpo-34706 [https://bugs.python.org/issue?@action=redirect&bpo=34706]: Preserve subclassing in inspect.Signature.from_callable.

bpo-38153 [https://bugs.python.org/issue?@action=redirect&bpo=38153]: Names of hashing algorithms from OpenSSL are now normalized to follow Python's naming conventions. For example OpenSSL uses sha3-512 instead of sha3_512 or blake2b512 instead of blake2b.

bpo-38115 [https://bugs.python.org/issue?@action=redirect&bpo=38115]: Fix a bug in dis.findlinestarts() where it would return invalid bytecode offsets. Document that a code object's co_lnotab can contain invalid bytecode offsets.

bpo-38148 [https://bugs.python.org/issue?@action=redirect&bpo=38148]: Add slots to asyncio transport classes, which can reduce memory usage.

bpo-38142 [https://bugs.python.org/issue?@action=redirect&bpo=38142]: The _hashlib OpenSSL wrapper extension module is now PEP-384 compliant.

bpo-9216 [https://bugs.python.org/issue?@action=redirect&bpo=9216]: hashlib constructors now support usedforsecurity flag to signal that a hashing algorithm is not used in a security context.

bpo-36991 [https://bugs.python.org/issue?@action=redirect&bpo=36991]: Fixes a potential incorrect AttributeError exception escaping ZipFile.extract() in some unsupported input error situations.

bpo-38134 [https://bugs.python.org/issue?@action=redirect&bpo=38134]: Remove obsolete copy of PBKDF2_HMAC_fast. All supported OpenSSL versions contain a fast implementation.

bpo-38132 [https://bugs.python.org/issue?@action=redirect&bpo=38132]: The OpenSSL hashlib wrapper uses a simpler implementation. Several Macros and pointless caches are gone. The hash name now comes from OpenSSL's EVP. The algorithm name stays the same, except it is now always lower case.

bpo-38008 [https://bugs.python.org/issue?@action=redirect&bpo=38008]: Fix parent class check in protocols to correctly identify the module that provides a builtin protocol, instead of assuming they all come from the collections.abc module

bpo-34037 [https://bugs.python.org/issue?@action=redirect&bpo=34037]: For asyncio, add a new coroutine loop.shutdown_default_executor(). The new coroutine provides an API to schedule an executor shutdown that waits on the threadpool to finish closing. Also, asyncio.run() has been updated to utilize the new coroutine. Patch by Kyle Stanley.

bpo-37405 [https://bugs.python.org/issue?@action=redirect&bpo=37405]: Fixed regression bug for socket.getsockname() for non-CAN_ISOTP AF_CAN address family sockets by returning a 1-tuple instead of string.

bpo-38121 [https://bugs.python.org/issue?@action=redirect&bpo=38121]: Update parameter names on functions in importlib.metadata matching the changes in the 0.22 release of importlib_metadata.

bpo-38110 [https://bugs.python.org/issue?@action=redirect&bpo=38110]: The os.closewalk() implementation now uses the libc fdwalk() API on platforms where it is available.

bpo-38093 [https://bugs.python.org/issue?@action=redirect&bpo=38093]: Fixes AsyncMock so it doesn't crash when used with AsyncContextManagers or AsyncIterators.

bpo-37488 [https://bugs.python.org/issue?@action=redirect&bpo=37488]: Add warning to datetime.utctimetuple(), datetime.utcnow() and datetime.utcfromtimestamp() .

bpo-35640 [https://bugs.python.org/issue?@action=redirect&bpo=35640]: Allow passing a path-like object as directory argument to the http.server.SimpleHTTPRequestHandler class. Patch by Géry Ogam.

bpo-38086 [https://bugs.python.org/issue?@action=redirect&bpo=38086]: Update importlib.metadata with changes from importlib_metadata 0.21 [https://gitlab.com/python-devs/importlib_metadata/blob/0.21/importlib_metadata/docs/changelog.rst].

bpo-37251 [https://bugs.python.org/issue?@action=redirect&bpo=37251]: Remove __code__ check in AsyncMock that incorrectly evaluated function specs as async objects but failed to evaluate classes with __await__ but no __code__ attribute defined as async objects.

bpo-38037 [https://bugs.python.org/issue?@action=redirect&bpo=38037]: Fix reference counters in the signal module.

bpo-38066 [https://bugs.python.org/issue?@action=redirect&bpo=38066]: Hide internal asyncio.Stream methods: feed_eof(), feed_data(), set_exception() and set_transport().

bpo-38059 [https://bugs.python.org/issue?@action=redirect&bpo=38059]: inspect.py now uses sys.exit() instead of exit()

bpo-38049 [https://bugs.python.org/issue?@action=redirect&bpo=38049]: Added command-line interface for the ast module.

bpo-37953 [https://bugs.python.org/issue?@action=redirect&bpo=37953]: In typing, improved the __hash__ and __eq__ methods for ForwardReferences.

bpo-38026 [https://bugs.python.org/issue?@action=redirect&bpo=38026]: Fixed inspect.getattr_static() used isinstance while it should avoid dynamic lookup.

bpo-35923 [https://bugs.python.org/issue?@action=redirect&bpo=35923]: Update importlib.machinery.BuiltinImporter to use loader._ORIGIN instead of a hardcoded value. Patch by Donghee Na.

bpo-38010 [https://bugs.python.org/issue?@action=redirect&bpo=38010]: In importlib.metadata sync with importlib_metadata 0.20, clarifying behavior of files() and fixing issue where only one requirement was returned for requires() on dist-info packages.

bpo-38006 [https://bugs.python.org/issue?@action=redirect&bpo=38006]: weakref.WeakValueDictionary defines a local remove() function used as callback for weak references. This function was created with a closure. Modify the implementation to avoid the closure.

bpo-37995 [https://bugs.python.org/issue?@action=redirect&bpo=37995]: Added the indent option to ast.dump() which allows it to produce a multiline indented output.

bpo-34410 [https://bugs.python.org/issue?@action=redirect&bpo=34410]: Fixed a crash in the tee() iterator when re-enter it. RuntimeError is now raised in this case.

bpo-37140 [https://bugs.python.org/issue?@action=redirect&bpo=37140]: Fix a ctypes regression of Python 3.8. When a ctypes.Structure is passed by copy to a function, ctypes internals created a temporary object which had the side effect of calling the structure finalizer (__del__) twice. The Python semantics requires a finalizer to be called exactly once. Fix ctypes internals to no longer call the finalizer twice.

bpo-37587 [https://bugs.python.org/issue?@action=redirect&bpo=37587]: _json.scanstring is now up to 3x faster when there are many backslash escaped characters in the JSON string.

bpo-37834 [https://bugs.python.org/issue?@action=redirect&bpo=37834]: Prevent shutil.rmtree exception when built on non-Windows system without fd system call support, like older versions of macOS.

bpo-10978 [https://bugs.python.org/issue?@action=redirect&bpo=10978]: Semaphores and BoundedSemaphores can now release more than one waiting thread at a time.

bpo-37972 [https://bugs.python.org/issue?@action=redirect&bpo=37972]: Subscripts to the unittest.mock.call objects now receive the same chaining mechanism as any other custom attributes, so that the following usage no longer raises a TypeError:

call().foo().__getitem__('bar')

Patch by blhsing

bpo-37965 [https://bugs.python.org/issue?@action=redirect&bpo=37965]: Fix C compiler warning caused by distutils.ccompiler.CCompiler.has_function.

bpo-37964 [https://bugs.python.org/issue?@action=redirect&bpo=37964]: Add F_GETPATH command to fcntl.

bpo-37960 [https://bugs.python.org/issue?@action=redirect&bpo=37960]: repr() of buffered and text streams now silences only expected exceptions when get the value of "name" and "mode" attributes.

bpo-37961 [https://bugs.python.org/issue?@action=redirect&bpo=37961]: Add a total_nframe field to the traces collected by the tracemalloc module. This field indicates the original number of frames before it was truncated.

bpo-37951 [https://bugs.python.org/issue?@action=redirect&bpo=37951]: Most features of the subprocess module now work again in subinterpreters. Only preexec_fn is restricted in subinterpreters.

bpo-36205 [https://bugs.python.org/issue?@action=redirect&bpo=36205]: Fix the rusage implementation of time.process_time() to correctly report the sum of the system and user CPU time.

bpo-37950 [https://bugs.python.org/issue?@action=redirect&bpo=37950]: Fix ast.dump() when call with incompletely initialized node.

bpo-34679 [https://bugs.python.org/issue?@action=redirect&bpo=34679]: Restores instantiation of Windows IOCP event loops from the non-main thread.

bpo-36917 [https://bugs.python.org/issue?@action=redirect&bpo=36917]: Add default implementation of the ast.NodeVisitor.visit_Constant() method which emits a deprecation warning and calls corresponding methods visit_Num(), visit_Str(), etc.

bpo-37798 [https://bugs.python.org/issue?@action=redirect&bpo=37798]: Update test_statistics.py to verify that the statistics module works well for both C and Python implementations. Patch by Donghee Na

bpo-26589 [https://bugs.python.org/issue?@action=redirect&bpo=26589]: Added a new status code to the http module: 451 UNAVAILABLE_FOR_LEGAL_REASONS

bpo-37915 [https://bugs.python.org/issue?@action=redirect&bpo=37915]: Fix a segmentation fault that appeared when comparing instances of datetime.timezone and datetime.tzinfo objects. Patch by Pablo Galindo.

bpo-32554 [https://bugs.python.org/issue?@action=redirect&bpo=32554]: Deprecate having random.seed() call hash on arbitrary types.

bpo-9938 [https://bugs.python.org/issue?@action=redirect&bpo=9938]: Add optional keyword argument exit_on_error for ArgumentParser.

bpo-37851 [https://bugs.python.org/issue?@action=redirect&bpo=37851]: The faulthandler module no longer allocates its alternative stack at Python startup. Now the stack is only allocated at the first faulthandler usage.

bpo-32793 [https://bugs.python.org/issue?@action=redirect&bpo=32793]: Fix a duplicated debug message when smtplib.SMTP.connect() is called.

bpo-37885 [https://bugs.python.org/issue?@action=redirect&bpo=37885]: venv: Don't generate unset variable warning on deactivate.

bpo-37868 [https://bugs.python.org/issue?@action=redirect&bpo=37868]: Fix dataclasses.is_dataclass when given an instance that never raises AttributeError in __getattr__. That is, an object that returns something for __dataclass_fields__ even if it's not a dataclass.

bpo-37811 [https://bugs.python.org/issue?@action=redirect&bpo=37811]: Fix socket module's socket.connect(address) function being unable to establish connection in case of interrupted system call. The problem was observed on all OSes which poll(2) system call can take only non-negative integers and -1 as a timeout value.

bpo-37863 [https://bugs.python.org/issue?@action=redirect&bpo=37863]: Optimizations for Fraction.__hash__ suggested by Tim Peters.

bpo-21131 [https://bugs.python.org/issue?@action=redirect&bpo=21131]: Fix faulthandler.register(chain=True) stack. faulthandler now allocates a dedicated stack of SIGSTKSZ*2 bytes, instead of just SIGSTKSZ bytes. Calling the previous signal handler in faulthandler signal handler uses more than SIGSTKSZ bytes of stack memory on some platforms.

bpo-37798 [https://bugs.python.org/issue?@action=redirect&bpo=37798]: Add C fastpath for statistics.NormalDist.inv_cdf() Patch by Donghee Na

bpo-37804 [https://bugs.python.org/issue?@action=redirect&bpo=37804]: Remove the deprecated method threading.Thread.isAlive(). Patch by Donghee Na.

bpo-37819 [https://bugs.python.org/issue?@action=redirect&bpo=37819]: Add Fraction.as_integer_ratio() to match the corresponding methods in bool, int, float, and decimal.

bpo-14465 [https://bugs.python.org/issue?@action=redirect&bpo=14465]: Add an xml.etree.ElementTree.indent() function for pretty-printing XML trees. Contributed by Stefan Behnel.

bpo-37810 [https://bugs.python.org/issue?@action=redirect&bpo=37810]: Fix difflib ? hint in diff output when dealing with tabs. Patch by Anthony Sottile.

bpo-37772 [https://bugs.python.org/issue?@action=redirect&bpo=37772]: In zipfile.Path, when adding implicit dirs, ensure that ancestral directories are added and that duplicates are excluded.

bpo-18578 [https://bugs.python.org/issue?@action=redirect&bpo=18578]: Renamed and documented test.bytecode_helper as test.support.bytecode_helper. Patch by Joannah Nanjekye.

bpo-37785 [https://bugs.python.org/issue?@action=redirect&bpo=37785]: Fix xgettext warnings in argparse.

bpo-34488 [https://bugs.python.org/issue?@action=redirect&bpo=34488]: writelines() method of io.BytesIO is now slightly faster when many small lines are passed. Patch by Sergey Fedoseev.

bpo-37449 [https://bugs.python.org/issue?@action=redirect&bpo=37449]: ensurepip now uses importlib.resources.read_binary() to read data instead of pkgutil.get_data(). Patch by Joannah Nanjekye.

bpo-28292 [https://bugs.python.org/issue?@action=redirect&bpo=28292]: Mark calendar.py helper functions as being private. The follows PEP 8 guidance to maintain the style conventions in the module and it addresses a known case of user confusion.

bpo-18049 [https://bugs.python.org/issue?@action=redirect&bpo=18049]: Add definition of THREAD_STACK_SIZE for AIX in Python/thread_pthread.h The default thread stacksize caused crashes with the default recursion limit Patch by M Felt

bpo-37742 [https://bugs.python.org/issue?@action=redirect&bpo=37742]: The logging.getLogger() API now returns the root logger when passed the name 'root', whereas previously it returned a non-root logger named 'root'. This could affect cases where user code explicitly wants a non-root logger named 'root', or instantiates a logger using logging.getLogger(__name__) in some top-level module called 'root.py'.

bpo-37738 [https://bugs.python.org/issue?@action=redirect&bpo=37738]: Fix the implementation of curses addch(str, color_pair): pass the color pair to setcchar(), instead of always passing 0 as the color pair.

bpo-37723 [https://bugs.python.org/issue?@action=redirect&bpo=37723]: Fix performance regression on regular expression parsing with huge character sets. Patch by Yann Vaginay.

bpo-35943 [https://bugs.python.org/issue?@action=redirect&bpo=35943]: The function PyImport_GetModule() now ensures any module it returns is fully initialized. Patch by Joannah Nanjekye.

bpo-32178 [https://bugs.python.org/issue?@action=redirect&bpo=32178]: Fix IndexError in email package when trying to parse invalid address fields starting with :.

bpo-37268 [https://bugs.python.org/issue?@action=redirect&bpo=37268]: The parser module is deprecated and will be removed in future versions of Python.

bpo-11953 [https://bugs.python.org/issue?@action=redirect&bpo=11953]: Completing WSA* error codes in socket.

bpo-37685 [https://bugs.python.org/issue?@action=redirect&bpo=37685]: Fixed comparisons of datetime.timedelta and datetime.timezone.

bpo-37697 [https://bugs.python.org/issue?@action=redirect&bpo=37697]: Synchronize importlib.metadata with importlib_metadata 0.19 [https://gitlab.com/python-devs/importlib_metadata/-/milestones/20], improving handling of EGG-INFO files and fixing a crash when entry point names contained colons.

bpo-37695 [https://bugs.python.org/issue?@action=redirect&bpo=37695]: Correct curses.unget_wch() error message. Patch by Anthony Sottile.

bpo-37689 [https://bugs.python.org/issue?@action=redirect&bpo=37689]: Add is_relative_to() in PurePath to determine whether or not one path is relative to another.

bpo-29553 [https://bugs.python.org/issue?@action=redirect&bpo=29553]: Fixed argparse.ArgumentParser.format_usage() for mutually exclusive groups. Patch by Andrew Nester.

bpo-37691 [https://bugs.python.org/issue?@action=redirect&bpo=37691]: Let math.dist() accept coordinates as sequences (or iterables) rather than just tuples.

bpo-37685 [https://bugs.python.org/issue?@action=redirect&bpo=37685]: Fixed __eq__, __lt__ etc implementations in some classes. They now return NotImplemented for unsupported type of the other operand. This allows the other operand to play role (for example the equality comparison with ANY will return True).

bpo-37354 [https://bugs.python.org/issue?@action=redirect&bpo=37354]: Make Activate.ps1 Powershell script static to allow for signing it.

bpo-37664 [https://bugs.python.org/issue?@action=redirect&bpo=37664]: Update wheels bundled with ensurepip (pip 19.2.3 and setuptools 41.2.0)

bpo-37663 [https://bugs.python.org/issue?@action=redirect&bpo=37663]: Bring consistency to venv shell activation scripts by always using __VENV_PROMPT__.

bpo-37642 [https://bugs.python.org/issue?@action=redirect&bpo=37642]: Allowed the pure Python implementation of datetime.timezone to represent sub-minute offsets close to minimum and maximum boundaries, specifically in the ranges (23:59, 24:00) and (-23:59, 24:00). Patch by Ngalim Siregar

bpo-36161 [https://bugs.python.org/issue?@action=redirect&bpo=36161]: In posix, use ttyname_r instead of ttyname for thread safety.

bpo-36324 [https://bugs.python.org/issue?@action=redirect&bpo=36324]: Make internal attributes for statistics.NormalDist() private.

bpo-37555 [https://bugs.python.org/issue?@action=redirect&bpo=37555]: Fix NonCallableMock._call_matcher returning tuple instead of _Call object when self._spec_signature exists. Patch by Elizabeth Uselton

bpo-29446 [https://bugs.python.org/issue?@action=redirect&bpo=29446]: Make from tkinter import * import only the expected objects.

bpo-16970 [https://bugs.python.org/issue?@action=redirect&bpo=16970]: Adding a value error when an invalid value in passed to nargs Patch by Robert Leenders

bpo-34443 [https://bugs.python.org/issue?@action=redirect&bpo=34443]: Exceptions from enum now use the __qualname of the enum class in the exception message instead of the __name__.

bpo-37491 [https://bugs.python.org/issue?@action=redirect&bpo=37491]: Fix IndexError when parsing email headers with unexpectedly ending bare-quoted string value. Patch by Abhilash Raj.

bpo-37587 [https://bugs.python.org/issue?@action=redirect&bpo=37587]: Make json.loads faster for long strings. (Patch by Marco Paolini)

bpo-18378 [https://bugs.python.org/issue?@action=redirect&bpo=18378]: Recognize "UTF-8" as a valid value for LC_CTYPE in locale._parse_localename.

bpo-37579 [https://bugs.python.org/issue?@action=redirect&bpo=37579]: Return NotImplemented in Python implementation of __eq__ for timedelta and time when the other object being compared is not of the same type to match C implementation. Patch by Karthikeyan Singaravelan.

bpo-21478 [https://bugs.python.org/issue?@action=redirect&bpo=21478]: Record calls to parent when autospecced object is attached to a mock using unittest.mock.attach_mock(). Patch by Karthikeyan Singaravelan.

bpo-37531 [https://bugs.python.org/issue?@action=redirect&bpo=37531]: "python3 -m test -jN --timeout=TIMEOUT" now kills a worker process if it runs longer than TIMEOUT seconds.

bpo-37482 [https://bugs.python.org/issue?@action=redirect&bpo=37482]: Fix serialization of display name in originator or destination address fields with both encoded words and special chars.

bpo-36993 [https://bugs.python.org/issue?@action=redirect&bpo=36993]: Improve error reporting for corrupt zip files with bad zip64 extra data. Patch by Daniel Hillier.

bpo-37502 [https://bugs.python.org/issue?@action=redirect&bpo=37502]: pickle.loads() no longer raises TypeError when the buffers argument is set to None

bpo-37520 [https://bugs.python.org/issue?@action=redirect&bpo=37520]: Correct behavior for zipfile.Path.parent when the path object identifies a subdirectory.

bpo-18374 [https://bugs.python.org/issue?@action=redirect&bpo=18374]: Fix the .col_offset attribute of nested ast.BinOp instances which had a too large value in some situations.

bpo-37424 [https://bugs.python.org/issue?@action=redirect&bpo=37424]: Fixes a possible hang when using a timeout on subprocess.run() while capturing output. If the child process spawned its own children or otherwise connected its stdout or stderr handles with another process, we could hang after the timeout was reached and our child was killed when attempting to read final output from the pipes.

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: Fix multiprocessing.util.get_temp_dir() finalizer: clear also the 'tempdir' configuration of the current process, so next call to get_temp_dir() will create a new temporary directory, rather than reusing the removed temporary directory.

bpo-37481 [https://bugs.python.org/issue?@action=redirect&bpo=37481]: The distutils bdist_wininst command is deprecated in Python 3.8, use bdist_wheel (wheel packages) instead.

bpo-37479 [https://bugs.python.org/issue?@action=redirect&bpo=37479]: When Enum.__str__ is overridden in a derived class, the override will be used by Enum.__format__ regardless of whether mixin classes are present.

bpo-37440 [https://bugs.python.org/issue?@action=redirect&bpo=37440]: http.client now enables TLS 1.3 post-handshake authentication for default context or if a cert_file is passed to HTTPSConnection.

bpo-37437 [https://bugs.python.org/issue?@action=redirect&bpo=37437]: Update vendorized expat version to 2.2.7.

bpo-37428 [https://bugs.python.org/issue?@action=redirect&bpo=37428]: SSLContext.post_handshake_auth = True no longer sets SSL_VERIFY_POST_HANDSHAKE verify flag for client connections. Although the option is documented as ignored for clients, OpenSSL implicitly enables cert chain validation when the flag is set.

bpo-37420 [https://bugs.python.org/issue?@action=redirect&bpo=37420]: os.sched_setaffinity() now correctly handles errors that arise during iteration over its mask argument. Patch by Brandt Bucher.

bpo-37412 [https://bugs.python.org/issue?@action=redirect&bpo=37412]: The os.getcwdb() function now uses the UTF-8 encoding on Windows, rather than the ANSI code page: see PEP 529 [https://peps.python.org/pep-0529/] for the rationale. The function is no longer deprecated on Windows.

bpo-37406 [https://bugs.python.org/issue?@action=redirect&bpo=37406]: The sqlite3 module now raises TypeError, rather than ValueError, if operation argument type is not str: execute(), executemany() and calling a connection.

bpo-29412 [https://bugs.python.org/issue?@action=redirect&bpo=29412]: Fix IndexError in parsing a header value ending unexpectedly. Patch by Abhilash Raj.

bpo-36546 [https://bugs.python.org/issue?@action=redirect&bpo=36546]: The dist argument for statistics.quantiles() is now positional only. The current name doesn't reflect that the argument can be either a dataset or a distribution. Marking the parameter as positional avoids confusion and makes it possible to change the name later.

bpo-37394 [https://bugs.python.org/issue?@action=redirect&bpo=37394]: Fix a bug that was causing the queue module to fail if the accelerator module was not available. Patch by Pablo Galindo.

bpo-37376 [https://bugs.python.org/issue?@action=redirect&bpo=37376]: pprint now has support for types.SimpleNamespace. Patch by Carl Bordum Hansen.

bpo-26967 [https://bugs.python.org/issue?@action=redirect&bpo=26967]: An ArgumentParser with allow_abbrev=False no longer disables grouping of short flags, such as -vv, but only disables abbreviation of long flags as documented. Patch by Zac Hatfield-Dodds.

bpo-37212 [https://bugs.python.org/issue?@action=redirect&bpo=37212]: unittest.mock.call() now preserves the order of keyword arguments in repr output. Patch by Karthikeyan Singaravelan.

bpo-37372 [https://bugs.python.org/issue?@action=redirect&bpo=37372]: Fix error unpickling datetime.time objects from Python 2 with seconds>=24. Patch by Justin Blanchard.

bpo-37345 [https://bugs.python.org/issue?@action=redirect&bpo=37345]: Add formal support for UDPLITE sockets. Support was present before, but it is now easier to detect support with hasattr(socket, 'IPPROTO_UDPLITE') and there are constants defined for each of the values needed: socket.IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, and UDPLITE_RECV_CSCOV. Patch by Gabe Appleton.

bpo-37358 [https://bugs.python.org/issue?@action=redirect&bpo=37358]: Optimized functools.partial by using vectorcall.

bpo-37347 [https://bugs.python.org/issue?@action=redirect&bpo=37347]: sqlite3.Connection.create_aggregate(), sqlite3.Connection.create_function(), sqlite3.Connection.set_authorizer(), sqlite3.Connection.set_progress_handler() sqlite3.Connection.set_trace_callback() methods lead to segfaults if some of these methods are called twice with an equal object but not the same. Now callbacks are stored more carefully. Patch by Aleksandr Balezin.

bpo-37163 [https://bugs.python.org/issue?@action=redirect&bpo=37163]: The obj argument of dataclasses.replace() is positional-only now.

bpo-37085 [https://bugs.python.org/issue?@action=redirect&bpo=37085]: Add the optional Linux SocketCAN Broadcast Manager constants, used as flags to configure the BCM behaviour, in the socket module. Patch by Karl Ding.

bpo-37328 [https://bugs.python.org/issue?@action=redirect&bpo=37328]: HTMLParser.unescape is removed. It was undocumented and deprecated since Python 3.4.

bpo-37305 [https://bugs.python.org/issue?@action=redirect&bpo=37305]: Add .webmanifest -> application/manifest+json to list of recognized file types and content type headers

bpo-37320 [https://bugs.python.org/issue?@action=redirect&bpo=37320]: aifc.openfp() alias to aifc.open(), sunau.openfp() alias to sunau.open(), and wave.openfp() alias to wave.open() have been removed. They were deprecated since Python 3.7.

bpo-37315 [https://bugs.python.org/issue?@action=redirect&bpo=37315]: Deprecated accepting floats with integral value (like 5.0) in math.factorial().

bpo-37312 [https://bugs.python.org/issue?@action=redirect&bpo=37312]: _dummy_thread and dummy_threading modules have been removed. These modules were deprecated since Python 3.7 which requires threading support.

bpo-33972 [https://bugs.python.org/issue?@action=redirect&bpo=33972]: Email with single part but content-type set to multipart/* doesn't raise AttributeError anymore.

bpo-37280 [https://bugs.python.org/issue?@action=redirect&bpo=37280]: Use threadpool for reading from file for sendfile fallback mode.

bpo-37279 [https://bugs.python.org/issue?@action=redirect&bpo=37279]: Fix asyncio sendfile support when sendfile sends extra data in fallback mode.

bpo-19865 [https://bugs.python.org/issue?@action=redirect&bpo=19865]: ctypes.create_unicode_buffer() now also supports non-BMP characters on platforms with 16-bit wchar_t (for example, Windows and AIX).

bpo-37266 [https://bugs.python.org/issue?@action=redirect&bpo=37266]: In a subinterpreter, spawning a daemon thread now raises an exception. Daemon threads were never supported in subinterpreters. Previously, the subinterpreter finalization crashed with a Python fatal error if a daemon thread was still running.

bpo-37210 [https://bugs.python.org/issue?@action=redirect&bpo=37210]: Allow pure Python implementation of pickle to work even when the C _pickle module is unavailable.

bpo-21872 [https://bugs.python.org/issue?@action=redirect&bpo=21872]: Fix lzma: module decompresses data incompletely. When decompressing a FORMAT_ALONE format file, and it doesn't have the end marker, sometimes the last one to dozens bytes can't be output. Patch by Ma Lin.

bpo-35922 [https://bugs.python.org/issue?@action=redirect&bpo=35922]: Fix RobotFileParser.crawl_delay() and RobotFileParser.request_rate() to return None rather than raise AttributeError when no relevant rule is defined in the robots.txt file. Patch by Rémi Lapeyre.

bpo-35766 [https://bugs.python.org/issue?@action=redirect&bpo=35766]: Change the format of feature_version to be a (major, minor) tuple.

bpo-36607 [https://bugs.python.org/issue?@action=redirect&bpo=36607]: Eliminate RuntimeError raised by asyncio.all_tasks() if internal tasks weak set is changed by another thread during iteration.

bpo-18748 [https://bugs.python.org/issue?@action=redirect&bpo=18748]: _pyio.IOBase destructor now does nothing if getting the closed attribute fails to better mimic _io.IOBase finalizer.

bpo-36402 [https://bugs.python.org/issue?@action=redirect&bpo=36402]: Fix a race condition at Python shutdown when waiting for threads. Wait until the Python thread state of all non-daemon threads get deleted (join all non-daemon threads), rather than just wait until non-daemon Python threads complete.

bpo-37206 [https://bugs.python.org/issue?@action=redirect&bpo=37206]: Default values which cannot be represented as Python objects no longer improperly represented as None in function signatures.

bpo-37111 [https://bugs.python.org/issue?@action=redirect&bpo=37111]: Added encoding and errors keyword parameters to logging.basicConfig.

bpo-12144 [https://bugs.python.org/issue?@action=redirect&bpo=12144]: Ensure cookies with expires attribute are handled in CookieJar.make_cookies().

bpo-34886 [https://bugs.python.org/issue?@action=redirect&bpo=34886]: Fix an unintended ValueError from subprocess.run() when checking for conflicting input and stdin or capture_output and stdout or stderr args when they were explicitly provided but with None values within a passed in **kwargs dict rather than as passed directly by name. Patch contributed by Rémi Lapeyre.

bpo-37173 [https://bugs.python.org/issue?@action=redirect&bpo=37173]: The exception message for inspect.getfile() now correctly reports the passed class rather than the builtins module.

bpo-37178 [https://bugs.python.org/issue?@action=redirect&bpo=37178]: Give math.perm() a one argument form that means the same as math.factorial().

bpo-37178 [https://bugs.python.org/issue?@action=redirect&bpo=37178]: For math.perm(n, k), let k default to n, giving the same result as factorial.

bpo-37165 [https://bugs.python.org/issue?@action=redirect&bpo=37165]: Converted _collections._count_elements to use the Argument Clinic.

bpo-34767 [https://bugs.python.org/issue?@action=redirect&bpo=34767]: Do not always create a collections.deque in asyncio.Lock.

bpo-37158 [https://bugs.python.org/issue?@action=redirect&bpo=37158]: Speed-up statistics.fmean() by switching from a function to a generator.

bpo-34282 [https://bugs.python.org/issue?@action=redirect&bpo=34282]: Remove Enum._convert method, deprecated in 3.8.

bpo-37150 [https://bugs.python.org/issue?@action=redirect&bpo=37150]: argparse._ActionsContainer.add_argument now throws error, if someone accidentally pass FileType class object instead of instance of FileType as type argument.

bpo-28724 [https://bugs.python.org/issue?@action=redirect&bpo=28724]: The socket module now has the socket.send_fds() and socket.recv.fds() methods. Contributed by Joannah Nanjekye, Shinya Okano and Victor Stinner.

bpo-35621 [https://bugs.python.org/issue?@action=redirect&bpo=35621]: Support running asyncio subprocesses when execution event loop in a thread on UNIX.

bpo-36520 [https://bugs.python.org/issue?@action=redirect&bpo=36520]: Lengthy email headers with UTF-8 characters are now properly encoded when they are folded. Patch by Jeffrey Kintscher.

bpo-30835 [https://bugs.python.org/issue?@action=redirect&bpo=30835]: Fixed a bug in email parsing where a message with invalid bytes in content-transfer-encoding of a multipart message can cause an AttributeError. Patch by Andrew Donnellan.

bpo-31163 [https://bugs.python.org/issue?@action=redirect&bpo=31163]: pathlib.Path instance's rename and replace methods now return the new Path instance.

bpo-25068 [https://bugs.python.org/issue?@action=redirect&bpo=25068]: urllib.request.ProxyHandler now lowercases the keys of the passed dictionary.

bpo-26185 [https://bugs.python.org/issue?@action=redirect&bpo=26185]: Fix repr() on empty ZipInfo object. Patch by Mickaël Schoentgen.

bpo-21315 [https://bugs.python.org/issue?@action=redirect&bpo=21315]: Email headers containing RFC2047 encoded words are parsed despite the missing whitespace, and a defect registered. Also missing trailing whitespace after encoded words is now registered as a defect.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Port test_datetime to VxWorks: skip zoneinfo tests on VxWorks

bpo-35805 [https://bugs.python.org/issue?@action=redirect&bpo=35805]: Add parser for Message-ID header and add it to default HeaderRegistry. This should prevent folding of Message-ID using RFC 2048 encoded words.

bpo-36871 [https://bugs.python.org/issue?@action=redirect&bpo=36871]: Ensure method signature is used instead of constructor signature of a class while asserting mock object against method calls. Patch by Karthikeyan Singaravelan.

bpo-35070 [https://bugs.python.org/issue?@action=redirect&bpo=35070]: posix.getgrouplist() now works correctly when the user belongs to NGROUPS_MAX supplemental groups. Patch by Jeffrey Kintscher.

bpo-31783 [https://bugs.python.org/issue?@action=redirect&bpo=31783]: Fix race condition in ThreadPoolExecutor when worker threads are created during interpreter shutdown.

bpo-36582 [https://bugs.python.org/issue?@action=redirect&bpo=36582]: Fix UserString.encode() to correctly return bytes rather than a UserString instance.

bpo-32424 [https://bugs.python.org/issue?@action=redirect&bpo=32424]: Deprecate xml.etree.ElementTree.Element.copy() in favor of copy.copy().

Patch by Gordon P. Hemsley

bpo-36564 [https://bugs.python.org/issue?@action=redirect&bpo=36564]: Fix infinite loop in email header folding logic that would be triggered when an email policy's max_line_length is not long enough to include the required markup and any values in the message. Patch by Paul Ganssle

bpo-36543 [https://bugs.python.org/issue?@action=redirect&bpo=36543]: Removed methods Element.getchildren(), Element.getiterator() and ElementTree.getiterator() and the xml.etree.cElementTree module.

bpo-36409 [https://bugs.python.org/issue?@action=redirect&bpo=36409]: Remove the old plistlib API deprecated in Python 3.4

bpo-36302 [https://bugs.python.org/issue?@action=redirect&bpo=36302]: distutils sorts source file lists so that Extension .so files build more reproducibly by default

bpo-36250 [https://bugs.python.org/issue?@action=redirect&bpo=36250]: Ignore ValueError from signal with interaction in non-main thread.

bpo-36046 [https://bugs.python.org/issue?@action=redirect&bpo=36046]: Added user, group and extra_groups parameters to the subprocess.Popen constructor. Patch by Patrick McLean.

bpo-32627 [https://bugs.python.org/issue?@action=redirect&bpo=32627]: Fix compile error when _uuid headers conflicting included.

bpo-35800 [https://bugs.python.org/issue?@action=redirect&bpo=35800]: Deprecate smtpd.MailmanProxy ready for future removal.

bpo-35168 [https://bugs.python.org/issue?@action=redirect&bpo=35168]: shlex.shlex.punctuation_chars is now a read-only property.

bpo-8538 [https://bugs.python.org/issue?@action=redirect&bpo=8538]: Add support for boolean actions like --foo and --no-foo to argparse. Patch contributed by Rémi Lapeyre.

bpo-20504 [https://bugs.python.org/issue?@action=redirect&bpo=20504]: Fixes a bug in cgi module when a multipart/form-data request has no Content-Length header.

bpo-25988 [https://bugs.python.org/issue?@action=redirect&bpo=25988]: The abstract base classes in collections.abc no longer are exposed in the regular collections module.

bpo-11122 [https://bugs.python.org/issue?@action=redirect&bpo=11122]: Distutils won't check for rpmbuild in specified paths only.

bpo-34775 [https://bugs.python.org/issue?@action=redirect&bpo=34775]: Division handling of PurePath now returns NotImplemented instead of raising a TypeError when passed something other than an instance of str or PurePath. Patch by Roger Aiudi.

bpo-34749 [https://bugs.python.org/issue?@action=redirect&bpo=34749]: binascii.a2b_base64() is now up to 2 times faster. Patch by Sergey Fedoseev.

bpo-34519 [https://bugs.python.org/issue?@action=redirect&bpo=34519]: Add additional aliases for HP Roman 8. Patch by Michael Osipov.

bpo-28009 [https://bugs.python.org/issue?@action=redirect&bpo=28009]: Fix uuid.getnode() on platforms with '.' as MAC Addr delimiter as well fix for MAC Addr format that omits a leading 0 in MAC Addr values. Currently, AIX is the only know platform with these settings. Patch by Michael Felt.

bpo-30618 [https://bugs.python.org/issue?@action=redirect&bpo=30618]: Add readlink(). Patch by Girts Folkmanis.

bpo-32498 [https://bugs.python.org/issue?@action=redirect&bpo=32498]: Made urllib.parse.unquote() accept bytes in addition to strings. Patch by Stein Karlsen.

bpo-33348 [https://bugs.python.org/issue?@action=redirect&bpo=33348]: lib2to3 now recognizes expressions after * and ** like in f(*[] or []).

bpo-32689 [https://bugs.python.org/issue?@action=redirect&bpo=32689]: Update shutil.move() function to allow for Path objects to be used as source argument. Patch by Emily Morehouse and Maxwell "5.13b" McKinnon.

bpo-32820 [https://bugs.python.org/issue?@action=redirect&bpo=32820]: Added __format__ to IPv4 and IPv6 classes. Always outputs a fully zero-padded string. Supports b/x/n modifiers (bin/hex/native format). Native format for IPv4 is bin, native format for IPv6 is hex. Also supports '#' and '_' modifiers.

bpo-27657 [https://bugs.python.org/issue?@action=redirect&bpo=27657]: Fix urllib.parse.urlparse() with numeric paths. A string like "path:80" is no longer parsed as a path but as a scheme ("path") and a path ("80").

bpo-4963 [https://bugs.python.org/issue?@action=redirect&bpo=4963]: Fixed non-deterministic behavior related to mimetypes extension mapping and module reinitialization.

Documentation

bpo-21767 [https://bugs.python.org/issue?@action=redirect&bpo=21767]: Explicitly mention abc support in functools.singledispatch

bpo-38816 [https://bugs.python.org/issue?@action=redirect&bpo=38816]: Provides more details about the interaction between fork() and CPython's runtime, focusing just on the C-API. This includes cautions about where fork() should and shouldn't be called.

bpo-38351 [https://bugs.python.org/issue?@action=redirect&bpo=38351]: Modernize email examples from %-formatting to f-strings.

bpo-38778 [https://bugs.python.org/issue?@action=redirect&bpo=38778]: Document the fact that RuntimeError is raised if os.fork() is called in a subinterpreter.

bpo-38592 [https://bugs.python.org/issue?@action=redirect&bpo=38592]: Add Brazilian Portuguese to the language switcher at Python Documentation website.

bpo-38294 [https://bugs.python.org/issue?@action=redirect&bpo=38294]: Add list of no-longer-escaped chars to re.escape documentation

bpo-38053 [https://bugs.python.org/issue?@action=redirect&bpo=38053]: Modernized the plistlib documentation

bpo-26868 [https://bugs.python.org/issue?@action=redirect&bpo=26868]: Fix example usage of PyModule_AddObject() to properly handle errors.

bpo-36797 [https://bugs.python.org/issue?@action=redirect&bpo=36797]: Fix a dead link in the distutils API Reference.

bpo-37977 [https://bugs.python.org/issue?@action=redirect&bpo=37977]: Warn more strongly and clearly about pickle insecurity

bpo-37979 [https://bugs.python.org/issue?@action=redirect&bpo=37979]: Added a link to dateutil.parser.isoparse in the datetime.fromisoformat documentation. Patch by Paul Ganssle

bpo-12707 [https://bugs.python.org/issue?@action=redirect&bpo=12707]: Deprecate info(), geturl(), getcode() methods in favor of the headers, url, and status properties, respectively, for HTTPResponse and addinfourl. Also deprecate the code attribute of addinfourl in favor of the status attribute. Patch by Ashwin Ramaswami

bpo-37937 [https://bugs.python.org/issue?@action=redirect&bpo=37937]: Mention frame.f_trace in sys.settrace() docs.

bpo-37878 [https://bugs.python.org/issue?@action=redirect&bpo=37878]: Make PyThreadState_DeleteCurrent() Internal.

bpo-37759 [https://bugs.python.org/issue?@action=redirect&bpo=37759]: Beginning edits to Whatsnew 3.8

bpo-37726 [https://bugs.python.org/issue?@action=redirect&bpo=37726]: Stop recommending getopt in the tutorial for command line argument parsing and promote argparse.

bpo-32910 [https://bugs.python.org/issue?@action=redirect&bpo=32910]: Remove implementation-specific behaviour of how venv's Deactivate works.

bpo-37256 [https://bugs.python.org/issue?@action=redirect&bpo=37256]: Fix wording of arguments for Request in urllib.request

bpo-37284 [https://bugs.python.org/issue?@action=redirect&bpo=37284]: Add a brief note to indicate that any new sys.implementation required attributes must go through the PEP process.

bpo-30088 [https://bugs.python.org/issue?@action=redirect&bpo=30088]: Documented that mailbox.Maildir constructor doesn't attempt to verify the maildir folder layout correctness. Patch by Sviatoslav Sydorenko.

bpo-37521 [https://bugs.python.org/issue?@action=redirect&bpo=37521]: Fix importlib examples to insert any newly created modules via importlib.util.module_from_spec() immediately into sys.modules instead of after calling loader.exec_module().

Thanks to Benjamin Mintz for finding the bug.

bpo-37456 [https://bugs.python.org/issue?@action=redirect&bpo=37456]: Slash ('/') is now part of syntax.

bpo-37487 [https://bugs.python.org/issue?@action=redirect&bpo=37487]: Fix PyList_GetItem index description to include 0.

bpo-37149 [https://bugs.python.org/issue?@action=redirect&bpo=37149]: Replace the dead link to the Tkinter 8.5 reference by John Shipman, New Mexico Tech, with a link to the archive.org copy.

bpo-37478 [https://bugs.python.org/issue?@action=redirect&bpo=37478]: Added possible exceptions to the description of os.chdir().

bpo-34903 [https://bugs.python.org/issue?@action=redirect&bpo=34903]: Documented that in datetime.datetime.strptime(), the leading zero in some two-digit formats is optional. Patch by Mike Gleen.

bpo-36260 [https://bugs.python.org/issue?@action=redirect&bpo=36260]: Add decompression pitfalls to zipfile module documentation.

bpo-37004 [https://bugs.python.org/issue?@action=redirect&bpo=37004]: In the documentation for difflib, a note was added explicitly warning that the results of SequenceMatcher's ratio method may depend on the order of the input strings.

bpo-36960 [https://bugs.python.org/issue?@action=redirect&bpo=36960]: Restructured the datetime docs in the interest of making them more user-friendly and improving readability. Patch by Brad Solomon.

bpo-36487 [https://bugs.python.org/issue?@action=redirect&bpo=36487]: Make C-API docs clear about what the "main" interpreter is.

bpo-23460 [https://bugs.python.org/issue?@action=redirect&bpo=23460]: The documentation for decimal string formatting using the :g specifier has been updated to reflect the correct exponential notation cutoff point. Original patch contributed by Tuomas Suutari.

bpo-35803 [https://bugs.python.org/issue?@action=redirect&bpo=35803]: Document and test that tempfile functions may accept a path-like object for the dir argument. Patch by Anthony Sottile.

bpo-33944 [https://bugs.python.org/issue?@action=redirect&bpo=33944]: Added a note about the intended use of code in .pth files.

bpo-34293 [https://bugs.python.org/issue?@action=redirect&bpo=34293]: Fix the Doc/Makefile regarding PAPER environment variable and PDF builds

bpo-25237 [https://bugs.python.org/issue?@action=redirect&bpo=25237]: Add documentation for tkinter modules

Tests

bpo-38614 [https://bugs.python.org/issue?@action=redirect&bpo=38614]: Fix test_communicate() of test_asyncio.test_subprocess: use support.LONG_TIMEOUT (5 minutes), instead of just 1 minute.

bpo-38614 [https://bugs.python.org/issue?@action=redirect&bpo=38614]: Add timeout constants to test.support: LOOPBACK_TIMEOUT, INTERNET_TIMEOUT, SHORT_TIMEOUT and LONG_TIMEOUT.

bpo-38502 [https://bugs.python.org/issue?@action=redirect&bpo=38502]: test.regrtest now uses process groups in the multiprocessing mode (-jN command line option) if process groups are available: if os.setsid() and os.killpg() functions are available.

bpo-35998 [https://bugs.python.org/issue?@action=redirect&bpo=35998]: Fix a race condition in test_asyncio.test_start_tls_server_1(). Previously, there was a race condition between the test main() function which replaces the protocol and the test ServerProto protocol which sends ANSWER once it gets HELLO. Now, only the test main() function is responsible to send data, ServerProto no longer sends data.

bpo-38470 [https://bugs.python.org/issue?@action=redirect&bpo=38470]: Fix test_compileall.test_compile_dir_maxlevels() on Windows without long path support: only create 3 subdirectories instead of between 20 and 100 subdirectories.

bpo-37531 [https://bugs.python.org/issue?@action=redirect&bpo=37531]: On timeout, regrtest no longer attempts to call popen.communicate() again: it can hang until all child processes using stdout and stderr pipes completes. Kill the worker process and ignores its output. Change also the faulthandler timeout of the main process from 1 minute to 5 minutes, for Python slowest buildbots.

bpo-38239 [https://bugs.python.org/issue?@action=redirect&bpo=38239]: Fix test_gdb for Link Time Optimization (LTO) builds.

bpo-38275 [https://bugs.python.org/issue?@action=redirect&bpo=38275]: test_ssl now handles disabled TLS/SSL versions better. OpenSSL's crypto policy and run-time settings are recognized and tests for disabled versions are skipped. Tests also accept more TLS minimum_versions for platforms that override OpenSSL's default with strict settings.

bpo-38271 [https://bugs.python.org/issue?@action=redirect&bpo=38271]: The private keys for test_ssl were encrypted with 3DES in traditional PKCS#5 format. 3DES and the digest algorithm of PKCS#5 are blocked by some strict crypto policies. Use PKCS#8 format with AES256 encryption instead.

bpo-38270 [https://bugs.python.org/issue?@action=redirect&bpo=38270]: test.support now has a helper function to check for availability of a hash digest function. Several tests are refactored avoid MD5 and use SHA256 instead. Other tests are marked to use MD5 and skipped when MD5 is disabled.

bpo-37123 [https://bugs.python.org/issue?@action=redirect&bpo=37123]: Multiprocessing test test_mymanager() now also expects -SIGTERM, not only exitcode 0. BaseManager._finalize_manager() sends SIGTERM to the manager process if it takes longer than 1 second to stop, which happens on slow buildbots.

bpo-38212 [https://bugs.python.org/issue?@action=redirect&bpo=38212]: Multiprocessing tests: increase test_queue_feeder_donot_stop_onexc() timeout from 1 to 60 seconds.

bpo-38117 [https://bugs.python.org/issue?@action=redirect&bpo=38117]: Test with OpenSSL 1.1.1d

bpo-38018 [https://bugs.python.org/issue?@action=redirect&bpo=38018]: Increase code coverage for multiprocessing.shared_memory.

bpo-37805 [https://bugs.python.org/issue?@action=redirect&bpo=37805]: Add tests for json.dump(..., skipkeys=True). Patch by Donghee Na.

bpo-37531 [https://bugs.python.org/issue?@action=redirect&bpo=37531]: Enhance regrtest multiprocess timeout: write a message when killing a worker process, catch popen.kill() and popen.wait() exceptions, put a timeout on the second call to popen.communicate().

bpo-37876 [https://bugs.python.org/issue?@action=redirect&bpo=37876]: Add tests for ROT-13 codec.

bpo-36833 [https://bugs.python.org/issue?@action=redirect&bpo=36833]: Added tests for PyDateTime_xxx_GET_xxx() macros of the C API of the datetime module. Patch by Joannah Nanjekye.

bpo-37558 [https://bugs.python.org/issue?@action=redirect&bpo=37558]: Fix test_shared_memory_cleaned_after_process_termination name handling

bpo-37526 [https://bugs.python.org/issue?@action=redirect&bpo=37526]: Add test.support.catch_threading_exception(): context manager catching threading.Thread exception using threading.excepthook().

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: test_concurrent_futures now explicitly stops the ForkServer instance if it's running.

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: multiprocessing tests now stop the ForkServer instance if it's running: close the "alive" file descriptor to ask the server to stop and then remove its UNIX address.

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: test_distutils.test_build_ext() is now able to remove the temporary directory on Windows: don't import the newly built C extension ("xx") in the current process, but test it in a separated process.

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: test_concurrent_futures now cleans up multiprocessing to remove immediately temporary directories created by multiprocessing.util.get_temp_dir().

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: test_winconsoleio doesn't leak a temporary file anymore: use tempfile.TemporaryFile() to remove it when the test completes.

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: multiprocessing tests now explicitly call _run_finalizers() to immediately remove temporary directories created by tests.

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: urllib.request tests now call urlcleanup() to remove temporary files created by urlretrieve() tests and to clear the _opener global variable set by urlopen() and functions calling indirectly urlopen().

bpo-37472 [https://bugs.python.org/issue?@action=redirect&bpo=37472]: Remove Lib/test/outstanding_bugs.py.

bpo-37199 [https://bugs.python.org/issue?@action=redirect&bpo=37199]: Fix test failures when IPv6 is unavailable or disabled.

bpo-19696 [https://bugs.python.org/issue?@action=redirect&bpo=19696]: Replace deprecated method "random.choose" with "random.choice" in "test_pkg_import.py".

bpo-37335 [https://bugs.python.org/issue?@action=redirect&bpo=37335]: Remove no longer necessary code from c locale coercion tests

bpo-37421 [https://bugs.python.org/issue?@action=redirect&bpo=37421]: Fix test_shutil to no longer leak temporary files.

bpo-37411 [https://bugs.python.org/issue?@action=redirect&bpo=37411]: Fix test_wsgiref.testEnviron() to no longer depend on the environment variables (don't fail if "X" variable is set).

bpo-37400 [https://bugs.python.org/issue?@action=redirect&bpo=37400]: Fix test_os.test_chown(): use os.getgroups() rather than grp.getgrall() to get groups. Rename also the test to test_chown_gid().

bpo-37359 [https://bugs.python.org/issue?@action=redirect&bpo=37359]: Add --cleanup option to python3 -m test to remove test_python_* directories of previous failed jobs. Add "make cleantest" to run python3 -m test --cleanup.

bpo-37362 [https://bugs.python.org/issue?@action=redirect&bpo=37362]: test_gdb no longer fails if it gets an "unexpected" message on stderr: it now ignores stderr. The purpose of test_gdb is to test that python-gdb.py commands work as expected, not to test gdb.

bpo-35998 [https://bugs.python.org/issue?@action=redirect&bpo=35998]: Avoid TimeoutError in test_asyncio: test_start_tls_server_1()

bpo-37278 [https://bugs.python.org/issue?@action=redirect&bpo=37278]: Fix test_asyncio ProactorLoopCtrlC: join the thread to prevent leaking a running thread and leaking a reference.

bpo-37261 [https://bugs.python.org/issue?@action=redirect&bpo=37261]: Fix test.support.catch_unraisable_exception(): its __exit__() method now ignores unraisable exception raised when clearing its unraisable attribute.

bpo-37069 [https://bugs.python.org/issue?@action=redirect&bpo=37069]: regrtest now uses sys.unraisablehook() to mark a test as "environment altered" (ENV_CHANGED) if it emits an "unraisable exception". Moreover, regrtest logs a warning in this case.

Use python3 -m test --fail-env-changed to catch unraisable exceptions in tests.

bpo-37252 [https://bugs.python.org/issue?@action=redirect&bpo=37252]: Fix assertions in test_close and test_events_mask_overflow devpoll tests.

bpo-37169 [https://bugs.python.org/issue?@action=redirect&bpo=37169]: Rewrite _PyObject_IsFreed() unit tests.

bpo-37153 [https://bugs.python.org/issue?@action=redirect&bpo=37153]: test_venv.test_multiprocessing() now explicitly calls pool.terminate() to wait until the pool completes.

bpo-34001 [https://bugs.python.org/issue?@action=redirect&bpo=34001]: Make test_ssl pass with LibreSSL. LibreSSL handles minimum and maximum TLS version differently than OpenSSL.

bpo-36919 [https://bugs.python.org/issue?@action=redirect&bpo=36919]: Make test_source_encoding.test_issue2301 implementation independent. The test will work now for both CPython and IronPython.

bpo-30202 [https://bugs.python.org/issue?@action=redirect&bpo=30202]: Update test.test_importlib.test_abc to test find_spec().

bpo-28009 [https://bugs.python.org/issue?@action=redirect&bpo=28009]: Modify the test_uuid logic to test when a program is available AND can be used to obtain a MACADDR as basis for an UUID. Patch by M. Felt

bpo-34596 [https://bugs.python.org/issue?@action=redirect&bpo=34596]: Fallback to a default reason when unittest.skip() is uncalled. Patch by Naitree Zhu.

Build

bpo-38809 [https://bugs.python.org/issue?@action=redirect&bpo=38809]: On Windows, build scripts will now recognize and use python.exe from an active virtual env.

bpo-38684 [https://bugs.python.org/issue?@action=redirect&bpo=38684]: Fix _hashlib build when Blake2 is disabled, but OpenSSL supports it.

bpo-38468 [https://bugs.python.org/issue?@action=redirect&bpo=38468]: Misc/python-config.in now uses getvar() for all still existing sysconfig.get_config_var() calls. Patch by Joannah Nanjekye.

bpo-37415 [https://bugs.python.org/issue?@action=redirect&bpo=37415]: Fix stdatomic.h header check for ICC compiler: the ICC implementation lacks atomic_uintptr_t type which is needed by Python.

bpo-38301 [https://bugs.python.org/issue?@action=redirect&bpo=38301]: In Solaris family, we must be sure to use -D_REENTRANT. Patch by Jesús Cea Avión.

bpo-36002 [https://bugs.python.org/issue?@action=redirect&bpo=36002]: Locate llvm-profdata and llvm-ar binaries using AC_PATH_TOOL rather than AC_PATH_TARGET_TOOL.

bpo-37936 [https://bugs.python.org/issue?@action=redirect&bpo=37936]: The .gitignore file systematically keeps "rooted", with a non-trailing slash, all the rules that are meant to apply to files in a specific place in the repo. Previously, when the intended file to ignore happened to be at the root of the repo, we'd most often accidentally also ignore files and directories with the same name anywhere in the tree.

bpo-37760 [https://bugs.python.org/issue?@action=redirect&bpo=37760]: The Tools/unicode/makeunicodedata.py script, which is used for converting information from the Unicode Character Database into generated code and data used by the methods of str and by the unicodedata module, now handles each character's data as a dataclass with named attributes, rather than a length-18 list of different fields.

bpo-37936 [https://bugs.python.org/issue?@action=redirect&bpo=37936]: The .gitignore file no longer applies to any files that are in fact tracked in the Git repository. Patch by Greg Price.

bpo-37725 [https://bugs.python.org/issue?@action=redirect&bpo=37725]: Change "clean" makefile target to also clean the program guided optimization (PGO) data. Previously you would have to use "make clean" and "make profile-removal", or "make clobber".

bpo-37707 [https://bugs.python.org/issue?@action=redirect&bpo=37707]: Mark some individual tests to skip when --pgo is used. The tests marked increase the PGO task time significantly and likely don't help improve optimization of the final executable.

bpo-36044 [https://bugs.python.org/issue?@action=redirect&bpo=36044]: Reduce the number of unit tests run for the PGO generation task. This speeds up the task by a factor of about 15x. Running the full unit test suite is slow. This change may result in a slightly less optimized build since not as many code branches will be executed. If you are willing to wait for the much slower build, the old behavior can be restored using './configure [..] PROFILE_TASK="-m test --pgo-extended"'. We make no guarantees as to which PGO task set produces a faster build. Users who care should run their own relevant benchmarks as results can depend on the environment, workload, and compiler tool chain.

bpo-37468 [https://bugs.python.org/issue?@action=redirect&bpo=37468]: make install no longer installs wininst-*.exe files used by distutils bdist_wininst: bdist_wininst only works on Windows.

bpo-37189 [https://bugs.python.org/issue?@action=redirect&bpo=37189]: Many PyRun_XXX() functions like PyRun_String() were no longer exported in libpython38.dll by mistake. Export them again to fix the ABI compatibility.

bpo-25361 [https://bugs.python.org/issue?@action=redirect&bpo=25361]: Enables use of SSE2 instructions in Windows 32-bit build.

bpo-36210 [https://bugs.python.org/issue?@action=redirect&bpo=36210]: Update optional extension module detection for AIX. ossaudiodev and spwd are not applicable for AIX, and are no longer reported as missing. 3rd-party packaging of ncurses (with ASIS support) conflicts with officially supported AIX curses library, so configure AIX to use libcurses.a. However, skip trying to build _curses_panel.

patch by M Felt

Windows

bpo-38589 [https://bugs.python.org/issue?@action=redirect&bpo=38589]: Fixes HTML Help shortcut when Windows is not installed to C drive

bpo-38453 [https://bugs.python.org/issue?@action=redirect&bpo=38453]: Ensure ntpath.realpath() correctly resolves relative paths.

bpo-38519 [https://bugs.python.org/issue?@action=redirect&bpo=38519]: Restores the internal C headers that were missing from the nuget.org and Microsoft Store packages.

bpo-38492 [https://bugs.python.org/issue?@action=redirect&bpo=38492]: Remove pythonw.exe dependency on the Microsoft C++ runtime.

bpo-38344 [https://bugs.python.org/issue?@action=redirect&bpo=38344]: Fix error message in activate.bat

bpo-38359 [https://bugs.python.org/issue?@action=redirect&bpo=38359]: Ensures pyw.exe launcher reads correct registry key.

bpo-38355 [https://bugs.python.org/issue?@action=redirect&bpo=38355]: Fixes ntpath.realpath failing on sys.executable.

bpo-38117 [https://bugs.python.org/issue?@action=redirect&bpo=38117]: Update bundled OpenSSL to 1.1.1d

bpo-38092 [https://bugs.python.org/issue?@action=redirect&bpo=38092]: Reduce overhead when using multiprocessing in a Windows virtual environment.

bpo-38133 [https://bugs.python.org/issue?@action=redirect&bpo=38133]: Allow py.exe launcher to locate installations from the Microsoft Store and improve display of active virtual environments.

bpo-38114 [https://bugs.python.org/issue?@action=redirect&bpo=38114]: The pip.ini is no longer included in the Nuget package.

bpo-32592 [https://bugs.python.org/issue?@action=redirect&bpo=32592]: Set Windows 8 as the minimum required version for API support

bpo-36634 [https://bugs.python.org/issue?@action=redirect&bpo=36634]: os.cpu_count() now returns active processors rather than maximum processors.

bpo-36634 [https://bugs.python.org/issue?@action=redirect&bpo=36634]: venv activate.bat now works when the existing variables contain double quote characters.

bpo-38081 [https://bugs.python.org/issue?@action=redirect&bpo=38081]: Prevent error calling os.path.realpath() on 'NUL'.

bpo-38087 [https://bugs.python.org/issue?@action=redirect&bpo=38087]: Fix case sensitivity in test_pathlib and test_ntpath.

bpo-38088 [https://bugs.python.org/issue?@action=redirect&bpo=38088]: Fixes distutils not finding vcruntime140.dll with only the v142 toolset installed.

bpo-37283 [https://bugs.python.org/issue?@action=redirect&bpo=37283]: Ensure command-line and unattend.xml setting override previously detected states in Windows installer.

bpo-38030 [https://bugs.python.org/issue?@action=redirect&bpo=38030]: Fixes os.stat() failing for block devices on Windows

bpo-38020 [https://bugs.python.org/issue?@action=redirect&bpo=38020]: Fixes potential crash when calling os.readlink() (or indirectly through realpath()) on a file that is not a supported link.

bpo-37705 [https://bugs.python.org/issue?@action=redirect&bpo=37705]: Improve the implementation of winerror_to_errno().

bpo-37549 [https://bugs.python.org/issue?@action=redirect&bpo=37549]: os.dup() no longer fails for standard streams on Windows 7.

bpo-1311 [https://bugs.python.org/issue?@action=redirect&bpo=1311]: The nul file on Windows now returns True from exists() and a valid result from os.stat() with S_IFCHR set.

bpo-9949 [https://bugs.python.org/issue?@action=redirect&bpo=9949]: Enable support for following symlinks in os.realpath().

bpo-37834 [https://bugs.python.org/issue?@action=redirect&bpo=37834]: Treat all name surrogate reparse points on Windows in os.lstat() and other reparse points as regular files in os.stat().

bpo-36266 [https://bugs.python.org/issue?@action=redirect&bpo=36266]: Add the module name in the formatted error message when DLL load fail happens during module import in _PyImport_FindSharedFuncptrWindows(). Patch by Srinivas Nyayapati.

bpo-25172 [https://bugs.python.org/issue?@action=redirect&bpo=25172]: Trying to import the crypt module on Windows will result in an ImportError with a message explaining that the module isn't supported on Windows. On other platforms, if the underlying _crypt module is not available, the ImportError will include a message explaining the problem.

bpo-37778 [https://bugs.python.org/issue?@action=redirect&bpo=37778]: Fixes the icons used for file associations to the Microsoft Store package.

bpo-37734 [https://bugs.python.org/issue?@action=redirect&bpo=37734]: Fix use of registry values to launch Python from Microsoft Store app.

bpo-37702 [https://bugs.python.org/issue?@action=redirect&bpo=37702]: Fix memory leak on Windows in creating an SSLContext object or running urllib.request.urlopen('https://...').

bpo-37672 [https://bugs.python.org/issue?@action=redirect&bpo=37672]: Switch Windows Store package's pip to use bundled pip.ini instead of PIP_USER variable.

bpo-10945 [https://bugs.python.org/issue?@action=redirect&bpo=10945]: Officially drop support for creating bdist_wininst installers on non-Windows systems.

bpo-37445 [https://bugs.python.org/issue?@action=redirect&bpo=37445]: Include the FORMAT_MESSAGE_IGNORE_INSERTS flag in FormatMessageW() calls.

bpo-37369 [https://bugs.python.org/issue?@action=redirect&bpo=37369]: Fixes path for sys.executable when running from the Microsoft Store.

bpo-37380 [https://bugs.python.org/issue?@action=redirect&bpo=37380]: Don't collect unfinished processes with subprocess._active on Windows to cleanup later. Patch by Ruslan Kuprieiev.

bpo-37351 [https://bugs.python.org/issue?@action=redirect&bpo=37351]: Removes libpython38.a from standard Windows distribution.

bpo-35360 [https://bugs.python.org/issue?@action=redirect&bpo=35360]: Update Windows builds to use SQLite 3.28.0.

bpo-37267 [https://bugs.python.org/issue?@action=redirect&bpo=37267]: On Windows, os.dup() no longer creates an inheritable fd when handling a character file.

bpo-36779 [https://bugs.python.org/issue?@action=redirect&bpo=36779]: Ensure time.tzname is correct on Windows when the active code page is set to CP_UTF7 or CP_UTF8.

bpo-32587 [https://bugs.python.org/issue?@action=redirect&bpo=32587]: Make winreg.REG_MULTI_SZ support zero-length strings.

bpo-28269 [https://bugs.python.org/issue?@action=redirect&bpo=28269]: Replace use of strcasecmp() for the system function _stricmp(). Patch by Minmin Gong.

bpo-36590 [https://bugs.python.org/issue?@action=redirect&bpo=36590]: Add native Bluetooth RFCOMM support to socket module.

macOS

bpo-38117 [https://bugs.python.org/issue?@action=redirect&bpo=38117]: Updated OpenSSL to 1.1.1d in macOS installer.

bpo-38089 [https://bugs.python.org/issue?@action=redirect&bpo=38089]: Move Azure Pipelines to latest VM versions and make macOS tests optional

bpo-18049 [https://bugs.python.org/issue?@action=redirect&bpo=18049]: Increase the default stack size of threads from 5MB to 16MB on macOS, to match the stack size of the main thread. This avoids crashes on deep recursion in threads.

bpo-34602 [https://bugs.python.org/issue?@action=redirect&bpo=34602]: Avoid test suite failures on macOS by no longer calling resource.setrlimit to increase the process stack size limit at runtime. The runtime change is no longer needed since the interpreter is being built with a larger default stack size.

bpo-35360 [https://bugs.python.org/issue?@action=redirect&bpo=35360]: Update macOS installer to use SQLite 3.28.0.

bpo-34631 [https://bugs.python.org/issue?@action=redirect&bpo=34631]: Updated OpenSSL to 1.1.1c in macOS installer.

IDLE

bpo-26353 [https://bugs.python.org/issue?@action=redirect&bpo=26353]: Stop adding newline when saving an IDLE shell window.

bpo-4630 [https://bugs.python.org/issue?@action=redirect&bpo=4630]: Add an option to toggle IDLE's cursor blink for shell, editor, and output windows. See Settings, General, Window Preferences, Cursor Blink. Patch by Zackery Spytz.

bpo-38598 [https://bugs.python.org/issue?@action=redirect&bpo=38598]: Do not try to compile IDLE shell or output windows

bpo-36698 [https://bugs.python.org/issue?@action=redirect&bpo=36698]: IDLE no longer fails when write non-encodable characters to stderr. It now escapes them with a backslash, as the regular Python interpreter. Added the errors field to the standard streams.

bpo-35379 [https://bugs.python.org/issue?@action=redirect&bpo=35379]: When exiting IDLE, catch any AttributeError. One happens when EditorWindow.close is called twice. Printing a traceback, when IDLE is run from a terminal, is useless and annoying.

bpo-38183 [https://bugs.python.org/issue?@action=redirect&bpo=38183]: To avoid problems, test_idle ignores the user config directory. It no longer tries to create or access .idlerc or any files within. Users must run IDLE to discover problems with saving settings.

bpo-38077 [https://bugs.python.org/issue?@action=redirect&bpo=38077]: IDLE no longer adds 'argv' to the user namespace when initializing it. This bug only affected 3.7.4 and 3.8.0b2 to 3.8.0b4.

bpo-38041 [https://bugs.python.org/issue?@action=redirect&bpo=38041]: Shell restart lines now fill the window width, always start with '=', and avoid wrapping unnecessarily. The line will still wrap if the included file name is long relative to the width.

bpo-35771 [https://bugs.python.org/issue?@action=redirect&bpo=35771]: To avoid occasional spurious test_idle failures on slower machines, increase the hover_delay in test_tooltip.

bpo-37824 [https://bugs.python.org/issue?@action=redirect&bpo=37824]: Properly handle user input warnings in IDLE shell. Cease turning SyntaxWarnings into SyntaxErrors.

bpo-37929 [https://bugs.python.org/issue?@action=redirect&bpo=37929]: IDLE Settings dialog now closes properly when there is no shell window.

bpo-37902 [https://bugs.python.org/issue?@action=redirect&bpo=37902]: Add mousewheel scrolling for IDLE module, path, and stack browsers. Patch by George Zhang.

bpo-37849 [https://bugs.python.org/issue?@action=redirect&bpo=37849]: Fixed completions list appearing too high or low when shown above the current line.

bpo-36419 [https://bugs.python.org/issue?@action=redirect&bpo=36419]: Refactor IDLE autocomplete and improve testing.

bpo-37748 [https://bugs.python.org/issue?@action=redirect&bpo=37748]: Reorder the Run menu. Put the most common choice, Run Module, at the top.

bpo-37692 [https://bugs.python.org/issue?@action=redirect&bpo=37692]: Improve highlight config sample with example shell interaction and better labels for shell elements.

bpo-37628 [https://bugs.python.org/issue?@action=redirect&bpo=37628]: Settings dialog no longer expands with font size.

bpo-37627 [https://bugs.python.org/issue?@action=redirect&bpo=37627]: Initialize the Customize Run dialog with the command line arguments most recently entered before. The user can optionally edit before submitting them.

bpo-33610 [https://bugs.python.org/issue?@action=redirect&bpo=33610]: Fix code context not showing the correct context when first toggled on.

bpo-37530 [https://bugs.python.org/issue?@action=redirect&bpo=37530]: Optimize code context to reduce unneeded background activity. Font and highlight changes now occur along with text changes instead of after a random delay.

bpo-27452 [https://bugs.python.org/issue?@action=redirect&bpo=27452]: Cleanup config.py by inlining RemoveFile and simplifying the handling of file in CreateConfigHandlers.

bpo-37325 [https://bugs.python.org/issue?@action=redirect&bpo=37325]: Fix tab focus traversal order for help source and custom run dialogs.

bpo-37321 [https://bugs.python.org/issue?@action=redirect&bpo=37321]: Both subprocess connection error messages now refer to the 'Startup failure' section of the IDLE doc.

bpo-17535 [https://bugs.python.org/issue?@action=redirect&bpo=17535]: Add optional line numbers for IDLE editor windows. Windows open without line numbers unless set otherwise in the General tab of the configuration dialog.

bpo-26806 [https://bugs.python.org/issue?@action=redirect&bpo=26806]: To compensate for stack frames added by IDLE and avoid possible problems with low recursion limits, add 30 to limits in the user code execution process. Subtract 30 when reporting recursion limits to make this addition mostly transparent.

bpo-37177 [https://bugs.python.org/issue?@action=redirect&bpo=37177]: Properly 'attach' search dialogs to their main window so that they behave like other dialogs and do not get hidden behind their main window.

bpo-37039 [https://bugs.python.org/issue?@action=redirect&bpo=37039]: Adjust "Zoom Height" to individual screens by momentarily maximizing the window on first use with a particular screen. Changing screen settings may invalidate the saved height. While a window is maximized, "Zoom Height" has no effect.

bpo-35763 [https://bugs.python.org/issue?@action=redirect&bpo=35763]: Make calltip reminder about '/' meaning positional-only less obtrusive by only adding it when there is room on the first line.

bpo-5680 [https://bugs.python.org/issue?@action=redirect&bpo=5680]: Add 'Run... Customized' to the Run menu to run a module with customized settings. Any 'command line arguments' entered are added to sys.argv. One can suppress the normal Shell main module restart.

bpo-36390 [https://bugs.python.org/issue?@action=redirect&bpo=36390]: Gather Format menu functions into format.py. Combine paragraph.py, rstrip.py, and format methods from editor.py.

Tools/Demos

bpo-38118 [https://bugs.python.org/issue?@action=redirect&bpo=38118]: Update Valgrind suppression file to ignore a false alarm in PyUnicode_Decode() when using GCC builtin strcmp().

bpo-38347 [https://bugs.python.org/issue?@action=redirect&bpo=38347]: pathfix.py: Assume all files that end on '.py' are Python scripts when working recursively.

bpo-37803 [https://bugs.python.org/issue?@action=redirect&bpo=37803]: pdb's --help and --version long options now work.

bpo-37942 [https://bugs.python.org/issue?@action=redirect&bpo=37942]: Improve ArgumentClinic converter for floats.

bpo-37704 [https://bugs.python.org/issue?@action=redirect&bpo=37704]: Remove Tools/scripts/h2py.py: use cffi to access a C API in Python.

bpo-37675 [https://bugs.python.org/issue?@action=redirect&bpo=37675]: 2to3 now works when run from a zipped standard library.

bpo-37034 [https://bugs.python.org/issue?@action=redirect&bpo=37034]: Argument Clinic now uses the argument name on errors with keyword-only argument instead of their position. Patch contributed by Rémi Lapeyre.

bpo-37064 [https://bugs.python.org/issue?@action=redirect&bpo=37064]: Add option -k to pathscript.py script: preserve shebang flags. Add option -a to pathscript.py script: add flags.

C API

bpo-37633 [https://bugs.python.org/issue?@action=redirect&bpo=37633]: Re-export some function compatibility wrappers for macros in pythonrun.h.

bpo-38644 [https://bugs.python.org/issue?@action=redirect&bpo=38644]: Provide Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() as regular functions for the limited API. Previously, there were defined as macros, but these macros didn't work with the limited API which cannot access PyThreadState.recursion_depth field. Remove _Py_CheckRecursionLimit from the stable ABI.

bpo-38650 [https://bugs.python.org/issue?@action=redirect&bpo=38650]: The global variable PyStructSequence_UnnamedField is now a constant and refers to a constant string.

bpo-38540 [https://bugs.python.org/issue?@action=redirect&bpo=38540]: Fixed possible leak in PyArg_Parse() and similar functions for format units "es#" and "et#" when the macro PY_SSIZE_T_CLEAN is not defined.

bpo-38395 [https://bugs.python.org/issue?@action=redirect&bpo=38395]: Fix a crash in weakref.proxy objects due to incorrect lifetime management when calling some associated methods that may delete the last reference to object being referenced by the proxy. Patch by Pablo Galindo.

bpo-36389 [https://bugs.python.org/issue?@action=redirect&bpo=36389]: The _PyObject_CheckConsistency() function is now also available in release mode. For example, it can be used to debug a crash in the visit_decref() function of the GC.

bpo-38266 [https://bugs.python.org/issue?@action=redirect&bpo=38266]: Revert the removal of PyThreadState_DeleteCurrent() with documentation.

bpo-38303 [https://bugs.python.org/issue?@action=redirect&bpo=38303]: Update audioop extension module to use the stable ABI (PEP-384). Patch by Tyler Kieft.

bpo-38234 [https://bugs.python.org/issue?@action=redirect&bpo=38234]: Py_SetPath() now sets sys.executable to the program full path (Py_GetProgramFullPath()) rather than to the program name (Py_GetProgramName()).

bpo-38234 [https://bugs.python.org/issue?@action=redirect&bpo=38234]: Python ignored arguments passed to Py_SetPath(), Py_SetPythonHome() and Py_SetProgramName(): fix Python initialization to use specified arguments.

bpo-38205 [https://bugs.python.org/issue?@action=redirect&bpo=38205]: The Py_UNREACHABLE() macro now calls Py_FatalError().

bpo-38140 [https://bugs.python.org/issue?@action=redirect&bpo=38140]: Make dict and weakref offsets opaque for C heap types by passing the offsets through PyMemberDef

bpo-15088 [https://bugs.python.org/issue?@action=redirect&bpo=15088]: The C function PyGen_NeedsFinalizing has been removed. It was not documented, tested or used anywhere within CPython after the implementation of PEP 442 [https://peps.python.org/pep-0442/]. Patch by Joannah Nanjekye. (Patch by Joannah Nanjekye)

bpo-36763 [https://bugs.python.org/issue?@action=redirect&bpo=36763]: Options added by PySys_AddXOption() are now handled the same way than PyConfig.xoptions and command line -X options.

bpo-37926 [https://bugs.python.org/issue?@action=redirect&bpo=37926]: Fix a crash in PySys_SetArgvEx(0, NULL, 0).

bpo-37879 [https://bugs.python.org/issue?@action=redirect&bpo=37879]: Fix subtype_dealloc to suppress the type decref when the base type is a C heap type

bpo-37645 [https://bugs.python.org/issue?@action=redirect&bpo=37645]: Add _PyObject_FunctionStr() to get a user-friendly string representation of a function-like object. Patch by Jeroen Demeyer.

bpo-29548 [https://bugs.python.org/issue?@action=redirect&bpo=29548]: The functions PyEval_CallObject, PyEval_CallFunction, PyEval_CallMethod and PyEval_CallObjectWithKeywords are deprecated. Use PyObject_Call() and its variants instead.

bpo-37151 [https://bugs.python.org/issue?@action=redirect&bpo=37151]: PyCFunction_Call is now a deprecated alias of PyObject_Call().

bpo-37540 [https://bugs.python.org/issue?@action=redirect&bpo=37540]: The vectorcall protocol now requires that the caller passes only strings as keyword names.

bpo-37207 [https://bugs.python.org/issue?@action=redirect&bpo=37207]: The vectorcall protocol is now enabled for type objects: set tp_vectorcall to a vectorcall function to be used instead of tp_new and tp_init when calling the class itself.

bpo-21120 [https://bugs.python.org/issue?@action=redirect&bpo=21120]: Exclude Python-ast.h, ast.h and asdl.h from the limited API.

bpo-37483 [https://bugs.python.org/issue?@action=redirect&bpo=37483]: Add new function _PyObject_CallOneArg for calling an object with one positional argument.

bpo-36763 [https://bugs.python.org/issue?@action=redirect&bpo=36763]: Add PyConfig_SetWideStringList() function.

bpo-37337 [https://bugs.python.org/issue?@action=redirect&bpo=37337]: Add fast functions for calling methods: _PyObject_VectorcallMethod(), _PyObject_CallMethodNoArgs() and _PyObject_CallMethodOneArg().

bpo-28805 [https://bugs.python.org/issue?@action=redirect&bpo=28805]: The METH_FASTCALL calling convention has been documented.

bpo-37221 [https://bugs.python.org/issue?@action=redirect&bpo=37221]: The new function PyCode_NewWithPosOnlyArgs() allows to create code objects like PyCode_New(), but with an extra posonlyargcount parameter for indicating the number of positonal-only arguments.

bpo-37215 [https://bugs.python.org/issue?@action=redirect&bpo=37215]: Fix dtrace issue introduce by bpo-36842 [https://bugs.python.org/issue?@action=redirect&bpo=36842]

bpo-37194 [https://bugs.python.org/issue?@action=redirect&bpo=37194]: Add a new public PyObject_CallNoArgs() function to the C API: call a callable Python object without any arguments. It is the most efficient way to call a callback without any argument. On x86-64, for example, PyObject_CallFunctionObjArgs(func, NULL) allocates 960 bytes on the stack per call, whereas PyObject_CallNoArgs(func) only allocates 624 bytes per call.

bpo-37170 [https://bugs.python.org/issue?@action=redirect&bpo=37170]: Fix the cast on error in PyLong_AsUnsignedLongLongMask().

bpo-35381 [https://bugs.python.org/issue?@action=redirect&bpo=35381]: Convert posixmodule.c statically allocated types DirEntryType and ScandirIteratorType to heap-allocated types.

bpo-34331 [https://bugs.python.org/issue?@action=redirect&bpo=34331]: Use singular/plural noun in error message when instantiating an abstract class with non-overridden abstract method(s).

Python 3.8.0 beta 1

Release date: 2019-06-04

Security

bpo-35907 [https://bugs.python.org/issue?@action=redirect&bpo=35907]: CVE 2019-9948 [https://www.cve.org/CVERecord?id=CVE-2019-9948]: Avoid file reading by disallowing local-file:// and local_file:// URL schemes in URLopener().open() and URLopener().retrieve() of urllib.request.

bpo-33529 [https://bugs.python.org/issue?@action=redirect&bpo=33529]: Prevent fold function used in email header encoding from entering infinite loop when there are too many non-ASCII characters in a header.

bpo-33164 [https://bugs.python.org/issue?@action=redirect&bpo=33164]: Updated blake2 implementation which uses secure memset implementation provided by platform.

Core and Builtins

bpo-35814 [https://bugs.python.org/issue?@action=redirect&bpo=35814]: Allow unpacking in the right hand side of annotated assignments. In particular, t: Tuple[int, ...] = x, y, *z is now allowed.

bpo-37126 [https://bugs.python.org/issue?@action=redirect&bpo=37126]: All structseq objects are now tracked by the garbage collector. Patch by Pablo Galindo.

bpo-37122 [https://bugs.python.org/issue?@action=redirect&bpo=37122]: Make the co_argcount attribute of code objects represent the total number of positional arguments (including positional-only arguments). The value of co_posonlyargcount can be used to distinguish which arguments are positional only, and the difference (co_argcount - co_posonlyargcount) is the number of positional-or-keyword arguments. Patch by Pablo Galindo.

bpo-20092 [https://bugs.python.org/issue?@action=redirect&bpo=20092]: Constructors of int, float and complex will now use the __index__() special method, if available and the corresponding method __int__(), __float__() or __complex__() is not available.

bpo-37087 [https://bugs.python.org/issue?@action=redirect&bpo=37087]: Add native thread ID (TID) support to OpenBSD.

bpo-26219 [https://bugs.python.org/issue?@action=redirect&bpo=26219]: Implemented per opcode cache mechanism and LOAD_GLOBAL instruction use it. LOAD_GLOBAL is now about 40% faster. Contributed by Yury Selivanov, and Inada Naoki.

bpo-37072 [https://bugs.python.org/issue?@action=redirect&bpo=37072]: Fix crash in PyAST_FromNodeObject() when flags is NULL.

bpo-37029 [https://bugs.python.org/issue?@action=redirect&bpo=37029]: Freeing a great many small objects could take time quadratic in the number of arenas, due to using linear search to keep obmalloc.c's list of usable arenas sorted by order of number of free memory pools. This is accomplished without search now, leaving the worst-case time linear in the number of arenas. For programs where this quite visibly matters (typically with more than 100 thousand small objects alive simultaneously), this can greatly reduce the time needed to release their memory.

bpo-26423 [https://bugs.python.org/issue?@action=redirect&bpo=26423]: Fix possible overflow in wrap_lenfunc() when sizeof(long) < sizeof(Py_ssize_t) (e.g., 64-bit Windows).

bpo-37050 [https://bugs.python.org/issue?@action=redirect&bpo=37050]: Improve the AST for "debug" f-strings, which use '=' to print out the source of the expression being evaluated. Delete expr_text from the FormattedValue node, and instead use a Constant string node (possibly merged with adjacent constant expressions inside the f-string).

bpo-22385 [https://bugs.python.org/issue?@action=redirect&bpo=22385]: The bytes.hex, bytearray.hex, and memoryview.hex methods as well as the binascii.hexlify and b2a_hex functions now have the ability to include an optional separator between hex bytes. This functionality was inspired by MicroPython's hexlify implementation.

bpo-26836 [https://bugs.python.org/issue?@action=redirect&bpo=26836]: Add os.memfd_create().

bpo-37032 [https://bugs.python.org/issue?@action=redirect&bpo=37032]: Added new replace() method to the code type (types.CodeType).

bpo-37007 [https://bugs.python.org/issue?@action=redirect&bpo=37007]: Implement socket.if_nameindex(), socket.if_nametoindex(), and socket.if_indextoname() on Windows.

bpo-36829 [https://bugs.python.org/issue?@action=redirect&bpo=36829]: PyErr_WriteUnraisable() now creates a traceback object if there is no current traceback. Moreover, call PyErr_NormalizeException() and PyException_SetTraceback() to normalize the exception value. Ignore any error.

bpo-36878 [https://bugs.python.org/issue?@action=redirect&bpo=36878]: Only accept text after # type: ignore if the first character is ASCII. This is to disallow things like # type: ignoreé.

bpo-36878 [https://bugs.python.org/issue?@action=redirect&bpo=36878]: Store text appearing after a # type: ignore comment in the AST. For example a type ignore like # type: ignore[E1000] will have the string "[E1000]" stored in its AST node.

bpo-2180 [https://bugs.python.org/issue?@action=redirect&bpo=2180]: Treat line continuation at EOF as a SyntaxError by Anthony Sottile.

bpo-36907 [https://bugs.python.org/issue?@action=redirect&bpo=36907]: Fix a crash when calling a C function with a keyword dict (f(**kwargs)) and changing the dict kwargs while that function is running.

bpo-36946 [https://bugs.python.org/issue?@action=redirect&bpo=36946]: Fix possible signed integer overflow when handling slices.

bpo-36826 [https://bugs.python.org/issue?@action=redirect&bpo=36826]: Add NamedExpression kind support to ast_unparse.c

bpo-1875 [https://bugs.python.org/issue?@action=redirect&bpo=1875]: A SyntaxError is now raised if a code blocks that will be optimized away (e.g. if conditions that are always false) contains syntax errors. Patch by Pablo Galindo.

bpo-36027 [https://bugs.python.org/issue?@action=redirect&bpo=36027]: Allow computation of modular inverses via three-argument pow: the second argument is now permitted to be negative in the case where the first and third arguments are relatively prime.

bpo-36861 [https://bugs.python.org/issue?@action=redirect&bpo=36861]: Update the Unicode database to version 12.1.0.

bpo-28866 [https://bugs.python.org/issue?@action=redirect&bpo=28866]: Avoid caching attributes of classes which type defines mro() to avoid a hard cache invalidation problem.

bpo-36851 [https://bugs.python.org/issue?@action=redirect&bpo=36851]: The FrameType stack is now correctly cleaned up if the execution ends with a return and the stack is not empty.

bpo-34616 [https://bugs.python.org/issue?@action=redirect&bpo=34616]: The compile() builtin functions now support the ast.PyCF_ALLOW_TOP_LEVEL_AWAIT flag, which allow to compile sources that contains top-level await, async with or async for. This is useful to evaluate async-code from with an already async functions; for example in a custom REPL.

bpo-36842 [https://bugs.python.org/issue?@action=redirect&bpo=36842]: Implement PEP 578, adding sys.audit, io.open_code and related APIs.

bpo-27639 [https://bugs.python.org/issue?@action=redirect&bpo=27639]: Correct return type for UserList slicing operations. Patch by Michael Blahay, Erick Cervantes, and vaultah

bpo-36737 [https://bugs.python.org/issue?@action=redirect&bpo=36737]: Move PyRuntimeState.warnings into per-interpreter state (via "module state").

bpo-36793 [https://bugs.python.org/issue?@action=redirect&bpo=36793]: Removed __str__ implementations from builtin types bool, int, float, complex and few classes from the standard library. They now inherit __str__() from object.

bpo-36817 [https://bugs.python.org/issue?@action=redirect&bpo=36817]: Add a = feature f-strings for debugging. This can precede !s, !r, or !a. It produces the text of the expression, followed by an equal sign, followed by the repr of the value of the expression. So f'{3*9+15=}' would be equal to the string '3*9+15=42'. If = is specified, the default conversion is set to !r, unless a format spec is given, in which case the formatting behavior is unchanged, and __format__ will be used.

bpo-24048 [https://bugs.python.org/issue?@action=redirect&bpo=24048]: Save the live exception during import.c's remove_module().

bpo-27987 [https://bugs.python.org/issue?@action=redirect&bpo=27987]: pymalloc returns memory blocks aligned by 16 bytes, instead of 8 bytes, on 64-bit platforms to conform x86-64 ABI. Recent compilers assume this alignment more often. Patch by Inada Naoki.

bpo-36601 [https://bugs.python.org/issue?@action=redirect&bpo=36601]: A long-since-meaningless check for getpid() == main_pid was removed from Python's internal C signal handler.

bpo-36594 [https://bugs.python.org/issue?@action=redirect&bpo=36594]: Fix incorrect use of %p in format strings. Patch by Zackery Spytz.

bpo-36045 [https://bugs.python.org/issue?@action=redirect&bpo=36045]: builtins.help() now prefixes async for async functions.

bpo-36084 [https://bugs.python.org/issue?@action=redirect&bpo=36084]: Add native thread ID (TID) to threading.Thread objects (supported platforms: Windows, FreeBSD, Linux, macOS)

bpo-36035 [https://bugs.python.org/issue?@action=redirect&bpo=36035]: Added fix for broken symlinks in combination with pathlib

bpo-35983 [https://bugs.python.org/issue?@action=redirect&bpo=35983]: Added new trashcan macros to deal with a double deallocation that could occur when the tp_dealloc of a subclass calls the tp_dealloc of a base class and that base class uses the trashcan mechanism. Patch by Jeroen Demeyer.

bpo-20602 [https://bugs.python.org/issue?@action=redirect&bpo=20602]: Do not clear sys.flags and sys.float_info during shutdown. Patch by Zackery Spytz.

bpo-26826 [https://bugs.python.org/issue?@action=redirect&bpo=26826]: Expose copy_file_range() as a low level API in the os module.

bpo-32388 [https://bugs.python.org/issue?@action=redirect&bpo=32388]: Remove cross-version binary compatibility requirement in tp_flags.

bpo-31862 [https://bugs.python.org/issue?@action=redirect&bpo=31862]: Port binascii to PEP 489 multiphase initialization. Patch by Marcel Plch.

Library

bpo-37128 [https://bugs.python.org/issue?@action=redirect&bpo=37128]: Added math.perm().

bpo-37120 [https://bugs.python.org/issue?@action=redirect&bpo=37120]: Add SSLContext.num_tickets to control the number of TLSv1.3 session tickets.

bpo-12202 [https://bugs.python.org/issue?@action=redirect&bpo=12202]: Fix the error handling in msilib.SummaryInformation.GetProperty(). Patch by Zackery Spytz.

bpo-26835 [https://bugs.python.org/issue?@action=redirect&bpo=26835]: The fcntl module now contains file sealing constants for sealing of memfds.

bpo-29262 [https://bugs.python.org/issue?@action=redirect&bpo=29262]: Add get_origin() and get_args() introspection helpers to typing module.

bpo-12639 [https://bugs.python.org/issue?@action=redirect&bpo=12639]: msilib.Directory.start_component() no longer fails if keyfile is not None.

bpo-36999 [https://bugs.python.org/issue?@action=redirect&bpo=36999]: Add the asyncio.Task.get_coro() method to publicly expose the tasks's coroutine object.

bpo-35246 [https://bugs.python.org/issue?@action=redirect&bpo=35246]: Make asyncio.create_subprocess_exec() accept path-like arguments.

bpo-35279 [https://bugs.python.org/issue?@action=redirect&bpo=35279]: Change default max_workers of ThreadPoolExecutor from cpu_count() * 5 to min(32, cpu_count() + 4). Previous value was unreasonably large on many cores machines.

bpo-37076 [https://bugs.python.org/issue?@action=redirect&bpo=37076]: _thread.start_new_thread() now logs uncaught exception raised by the function using sys.unraisablehook(), rather than sys.excepthook(), so the hook gets access to the function which raised the exception.

bpo-33725 [https://bugs.python.org/issue?@action=redirect&bpo=33725]: On macOS, the multiprocessing module now uses spawn start method by default.

bpo-37054 [https://bugs.python.org/issue?@action=redirect&bpo=37054]: Fix destructor _pyio.BytesIO and _pyio.TextIOWrapper: initialize their _buffer attribute as soon as possible (in the class body), because it's used by __del__() which calls close().

bpo-37058 [https://bugs.python.org/issue?@action=redirect&bpo=37058]: PEP 544: Add Protocol and @runtime_checkable to the typing module.

bpo-36933 [https://bugs.python.org/issue?@action=redirect&bpo=36933]: The functions sys.set_coroutine_wrapper and sys.get_coroutine_wrapper that were deprecated and marked for removal in 3.8 have been removed.

bpo-37047 [https://bugs.python.org/issue?@action=redirect&bpo=37047]: Handle late binding and attribute access in unittest.mock.AsyncMock setup for autospeccing. Document newly implemented async methods in unittest.mock.MagicMock.

bpo-37049 [https://bugs.python.org/issue?@action=redirect&bpo=37049]: PEP 589: Add TypedDict to the typing module.

bpo-37046 [https://bugs.python.org/issue?@action=redirect&bpo=37046]: PEP 586: Add Literal to the typing module.

bpo-37045 [https://bugs.python.org/issue?@action=redirect&bpo=37045]: PEP 591: Add Final qualifier and @final decorator to the typing module.

bpo-37035 [https://bugs.python.org/issue?@action=redirect&bpo=37035]: Don't log OSError based exceptions if a fatal error has occurred in asyncio transport. Peer can generate almost any OSError, user cannot avoid these exceptions by fixing own code. Errors are still propagated to user code, it's just logging them is pointless and pollute asyncio logs.

bpo-37001 [https://bugs.python.org/issue?@action=redirect&bpo=37001]: symtable.symtable() now accepts the same input types for source code as the built-in compile() function. Patch by Dino Viehland.

bpo-37028 [https://bugs.python.org/issue?@action=redirect&bpo=37028]: Implement asyncio REPL

bpo-37027 [https://bugs.python.org/issue?@action=redirect&bpo=37027]: Return safe to use proxy socket object from transport.get_extra_info('socket')

bpo-32528 [https://bugs.python.org/issue?@action=redirect&bpo=32528]: Make asyncio.CancelledError a BaseException.

This will address the common mistake many asyncio users make: an "except Exception" clause breaking Tasks cancellation.

In addition to this change, we stop inheriting asyncio.TimeoutError and asyncio.InvalidStateError from their concurrent.futures.* counterparts. There's no point for these exceptions to share the inheritance chain.

bpo-1230540 [https://bugs.python.org/issue?@action=redirect&bpo=1230540]: Add a new threading.excepthook() function which handles uncaught threading.Thread.run() exception. It can be overridden to control how uncaught threading.Thread.run() exceptions are handled.

bpo-36996 [https://bugs.python.org/issue?@action=redirect&bpo=36996]: Handle unittest.mock.patch() used as a decorator on async functions.

bpo-37008 [https://bugs.python.org/issue?@action=redirect&bpo=37008]: Add support for calling next() with the mock resulting from unittest.mock.mock_open()

bpo-27737 [https://bugs.python.org/issue?@action=redirect&bpo=27737]: Allow whitespace only header encoding in email.header - by Batuhan Taskaya

bpo-36969 [https://bugs.python.org/issue?@action=redirect&bpo=36969]: PDB command args now display positional only arguments. Patch contributed by Rémi Lapeyre.

bpo-36969 [https://bugs.python.org/issue?@action=redirect&bpo=36969]: PDB command args now display keyword only arguments. Patch contributed by Rémi Lapeyre.

bpo-36983 [https://bugs.python.org/issue?@action=redirect&bpo=36983]: Add missing names to typing.__all__: ChainMap, ForwardRef, OrderedDict - by Anthony Sottile.

bpo-36972 [https://bugs.python.org/issue?@action=redirect&bpo=36972]: Add SupportsIndex protocol to the typing module to allow type checking to detect classes that can be passed to hex(), oct() and bin().

bpo-32972 [https://bugs.python.org/issue?@action=redirect&bpo=32972]: Implement unittest.IsolatedAsyncioTestCase to help testing asyncio-based code.

bpo-36952 [https://bugs.python.org/issue?@action=redirect&bpo=36952]: fileinput.input() and fileinput.FileInput bufsize argument has been removed (was deprecated and ignored since Python 3.6), and as a result the mode and openhook arguments have been made keyword-only.

bpo-36952 [https://bugs.python.org/issue?@action=redirect&bpo=36952]: Starting with Python 3.3, importing ABCs from collections is deprecated, and import should be done from collections.abc. Still being able to import from collections was marked for removal in 3.8, but has been delayed to 3.9; documentation and DeprecationWarning clarified.

bpo-36949 [https://bugs.python.org/issue?@action=redirect&bpo=36949]: Implement __repr__ for WeakSet objects.

bpo-36948 [https://bugs.python.org/issue?@action=redirect&bpo=36948]: Fix NameError in urllib.request.URLopener.retrieve(). Patch by Karthikeyan Singaravelan.

bpo-33524 [https://bugs.python.org/issue?@action=redirect&bpo=33524]: Fix the folding of email header when the max_line_length is 0 or None and the header contains non-ascii characters. Contributed by Licht Takeuchi (@Licht-T).

bpo-24564 [https://bugs.python.org/issue?@action=redirect&bpo=24564]: shutil.copystat() now ignores errno.EINVAL on os.setxattr() which may occur when copying files on filesystems without extended attributes support.

Original patch by Giampaolo Rodola, updated by Ying Wang.

bpo-36888 [https://bugs.python.org/issue?@action=redirect&bpo=36888]: Python child processes can now access the status of their parent process using multiprocessing.process.parent_process

bpo-36921 [https://bugs.python.org/issue?@action=redirect&bpo=36921]: Deprecate @coroutine for sake of async def.

bpo-25652 [https://bugs.python.org/issue?@action=redirect&bpo=25652]: Fix bug in __rmod__ of UserString - by Batuhan Taskaya.

bpo-36916 [https://bugs.python.org/issue?@action=redirect&bpo=36916]: Remove a message about an unhandled exception in a task when writer.write() is used without await and writer.drain() fails with an exception.

bpo-36889 [https://bugs.python.org/issue?@action=redirect&bpo=36889]: Introduce asyncio.Stream class that merges asyncio.StreamReader and asyncio.StreamWriter functionality. asyncio.Stream can work in readonly, writeonly and readwrite modes. Provide asyncio.connect(), asyncio.connect_unix(), asyncio.connect_read_pipe() and asyncio.connect_write_pipe() factories to open asyncio.Stream connections. Provide asyncio.StreamServer and UnixStreamServer to serve servers with asyncio.Stream API. Modify asyncio.create_subprocess_shell() and asyncio.create_subprocess_exec() to use asyncio.Stream instead of deprecated StreamReader and StreamWriter. Deprecate asyncio.StreamReader and asyncio.StreamWriter. Deprecate usage of private classes, e.g. asyncio.FlowControlMixing and asyncio.StreamReaderProtocol outside of asyncio package.

bpo-36845 [https://bugs.python.org/issue?@action=redirect&bpo=36845]: Added validation of integer prefixes to the construction of IP networks and interfaces in the ipaddress module.

bpo-23378 [https://bugs.python.org/issue?@action=redirect&bpo=23378]: Add an extend action to argparser.

bpo-36867 [https://bugs.python.org/issue?@action=redirect&bpo=36867]: Fix a bug making a SharedMemoryManager instance and its parent process use two separate resource_tracker processes.

bpo-23896 [https://bugs.python.org/issue?@action=redirect&bpo=23896]: Adds a grammar to lib2to3.pygram that contains exec as a function not as statement.

bpo-36895 [https://bugs.python.org/issue?@action=redirect&bpo=36895]: The function time.clock() was deprecated in 3.3 in favor of time.perf_counter() and marked for removal in 3.8, it has removed.

bpo-35545 [https://bugs.python.org/issue?@action=redirect&bpo=35545]: Fix asyncio discarding IPv6 scopes when ensuring hostname resolutions internally

bpo-36887 [https://bugs.python.org/issue?@action=redirect&bpo=36887]: Add new function math.isqrt() to compute integer square roots.

bpo-34632 [https://bugs.python.org/issue?@action=redirect&bpo=34632]: Introduce the importlib.metadata module with (provisional) support for reading metadata from third-party packages.

bpo-36878 [https://bugs.python.org/issue?@action=redirect&bpo=36878]: When using type_comments=True in ast.parse, treat # type: ignore followed by a non-alphanumeric character and then arbitrary text as a type ignore, instead of requiring nothing but whitespace or another comment. This is to permit formations such as # type: ignore[E1000].

bpo-36778 [https://bugs.python.org/issue?@action=redirect&bpo=36778]: cp65001 encoding (Windows code page 65001) becomes an alias to utf_8 encoding.

bpo-36867 [https://bugs.python.org/issue?@action=redirect&bpo=36867]: The multiprocessing.resource_tracker replaces the multiprocessing.semaphore_tracker module. Other than semaphores, resource_tracker also tracks shared_memory segments.

bpo-30262 [https://bugs.python.org/issue?@action=redirect&bpo=30262]: The Cache and Statement objects of the sqlite3 module are not exposed to the user. Patch by Aviv Palivoda.

bpo-24538 [https://bugs.python.org/issue?@action=redirect&bpo=24538]: In shutil.copystat(), first copy extended file attributes and then file permissions, since extended attributes can only be set on the destination while it is still writeable.

bpo-36829 [https://bugs.python.org/issue?@action=redirect&bpo=36829]: Add new sys.unraisablehook() function which can be overridden to control how "unraisable exceptions" are handled. It is called when an exception has occurred but there is no way for Python to handle it. For example, when a destructor raises an exception or during garbage collection (gc.collect()).

bpo-36832 [https://bugs.python.org/issue?@action=redirect&bpo=36832]: Introducing zipfile.Path, a pathlib-compatible wrapper for traversing zip files.

bpo-36814 [https://bugs.python.org/issue?@action=redirect&bpo=36814]: Fix an issue where os.posix_spawnp() would incorrectly raise a TypeError when file_actions is None.

bpo-33110 [https://bugs.python.org/issue?@action=redirect&bpo=33110]: Handle exceptions raised by functions added by concurrent.futures add_done_callback correctly when the Future has already completed.

bpo-26903 [https://bugs.python.org/issue?@action=redirect&bpo=26903]: Limit max_workers in ProcessPoolExecutor to 61 to work around a WaitForMultipleObjects limitation.

bpo-36813 [https://bugs.python.org/issue?@action=redirect&bpo=36813]: Fix QueueListener to call queue.task_done() upon stopping. Patch by Bar Harel.

bpo-36806 [https://bugs.python.org/issue?@action=redirect&bpo=36806]: Forbid creation of asyncio stream objects like StreamReader, StreamWriter, Process, and their protocols outside of asyncio package.

bpo-36802 [https://bugs.python.org/issue?@action=redirect&bpo=36802]: Provide both sync and async calls for StreamWriter.write() and StreamWriter.close()

bpo-36801 [https://bugs.python.org/issue?@action=redirect&bpo=36801]: Properly handle SSL connection closing in asyncio StreamWriter.drain() call.

bpo-36785 [https://bugs.python.org/issue?@action=redirect&bpo=36785]: Implement PEP 574 (pickle protocol 5 with out-of-band buffers).

bpo-36772 [https://bugs.python.org/issue?@action=redirect&bpo=36772]: functools.lru_cache() can now be used as a straight decorator in addition to its existing usage as a function that returns a decorator.

bpo-6584 [https://bugs.python.org/issue?@action=redirect&bpo=6584]: Add a BadGzipFile exception to the gzip module.

bpo-36748 [https://bugs.python.org/issue?@action=redirect&bpo=36748]: Optimized write buffering in C implementation of TextIOWrapper. Writing ASCII string to TextIOWrapper with ascii, latin1, or utf-8 encoding is about 20% faster. Patch by Inada Naoki.

bpo-8138 [https://bugs.python.org/issue?@action=redirect&bpo=8138]: Don't mark wsgiref.simple_server.SimpleServer as multi-threaded since wsgiref.simple_server.WSGIServer is single-threaded.

bpo-22640 [https://bugs.python.org/issue?@action=redirect&bpo=22640]: py_compile.compile() now supports silent mode. Patch by Joannah Nanjekye

bpo-29183 [https://bugs.python.org/issue?@action=redirect&bpo=29183]: Fix double exceptions in wsgiref.handlers.BaseHandler by calling its close() method only when no exception is raised.

bpo-36548 [https://bugs.python.org/issue?@action=redirect&bpo=36548]: Improved the repr of regular expression flags.

bpo-36542 [https://bugs.python.org/issue?@action=redirect&bpo=36542]: The signature of Python functions can now be overridden by specifying the __text_signature__ attribute.

bpo-36533 [https://bugs.python.org/issue?@action=redirect&bpo=36533]: Reinitialize logging.Handler locks in forked child processes instead of attempting to acquire them all in the parent before forking only to be released in the child process. The acquire/release pattern was leading to deadlocks in code that has implemented any form of chained logging handlers that depend upon one another as the lock acquisition order cannot be guaranteed.

bpo-35252 [https://bugs.python.org/issue?@action=redirect&bpo=35252]: Throw a TypeError instead of an AssertionError when using an invalid type annotation with singledispatch.

bpo-35900 [https://bugs.python.org/issue?@action=redirect&bpo=35900]: Allow reduction methods to return a 6-item tuple where the 6th item specifies a custom state-setting method that's called instead of the regular __setstate__ method.

bpo-35900 [https://bugs.python.org/issue?@action=redirect&bpo=35900]: enable custom reduction callback registration for functions and classes in _pickle.c, using the new Pickler's attribute reducer_override

bpo-36368 [https://bugs.python.org/issue?@action=redirect&bpo=36368]: Fix a bug crashing SharedMemoryManager instances in interactive sessions after a ctrl-c (KeyboardInterrupt) was sent

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix mmap fail for VxWorks

bpo-27497 [https://bugs.python.org/issue?@action=redirect&bpo=27497]: csv.DictWriter.writeheader() now returns the return value of the underlying csv.Writer.writerow() method. Patch contributed by Ashish Nitin Patil.

bpo-36239 [https://bugs.python.org/issue?@action=redirect&bpo=36239]: Parsing .mo files now ignores comments starting and ending with #-#-#-#-#.

bpo-26707 [https://bugs.python.org/issue?@action=redirect&bpo=26707]: Enable plistlib to read and write binary plist files that were created as a KeyedArchive file. Specifically, this allows the plistlib to process 0x80 tokens as UID objects.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Add posix module support for VxWorks.

bpo-35125 [https://bugs.python.org/issue?@action=redirect&bpo=35125]: Asyncio: Remove inner callback on outer cancellation in shield

bpo-35721 [https://bugs.python.org/issue?@action=redirect&bpo=35721]: Fix asyncio.SelectorEventLoop.subprocess_exec() leaks file descriptors if Popen fails and called with stdin=subprocess.PIPE. Patch by Niklas Fiekas.

bpo-31855 [https://bugs.python.org/issue?@action=redirect&bpo=31855]: unittest.mock.mock_open() results now respects the argument of read([size]). Patch contributed by Rémi Lapeyre.

bpo-35431 [https://bugs.python.org/issue?@action=redirect&bpo=35431]: Implement math.comb() that returns binomial coefficient, that computes the number of ways to choose k items from n items without repetition and without order. Patch by Yash Aggarwal and Keller Fuchs.

bpo-26660 [https://bugs.python.org/issue?@action=redirect&bpo=26660]: Fixed permission errors in TemporaryDirectory clean up. Previously TemporaryDirectory.cleanup() failed when non-writeable or non-searchable files or directories were created inside a temporary directory.

bpo-34271 [https://bugs.python.org/issue?@action=redirect&bpo=34271]: Add debugging helpers to ssl module. It's now possible to dump key material and to trace TLS protocol. The default and stdlib contexts also support SSLKEYLOGFILE env var.

bpo-26467 [https://bugs.python.org/issue?@action=redirect&bpo=26467]: Added AsyncMock to support using unittest to mock asyncio coroutines. Patch by Lisa Roach.

bpo-33569 [https://bugs.python.org/issue?@action=redirect&bpo=33569]: dataclasses.InitVar: Exposes the type used to create the init var.

bpo-34424 [https://bugs.python.org/issue?@action=redirect&bpo=34424]: Fix serialization of messages containing encoded strings when the policy.linesep is set to a multi-character string. Patch by Jens Troeger.

bpo-34303 [https://bugs.python.org/issue?@action=redirect&bpo=34303]: Performance of functools.reduce() is slightly improved. Patch by Sergey Fedoseev.

bpo-33361 [https://bugs.python.org/issue?@action=redirect&bpo=33361]: Fix a bug in codecs.StreamRecoder where seeking might leave old data in a buffer and break subsequent read calls. Patch by Ammar Askar.

bpo-22454 [https://bugs.python.org/issue?@action=redirect&bpo=22454]: The shlex module now exposes shlex.join(), the inverse of shlex.split(). Patch by Bo Bayles.

bpo-31922 [https://bugs.python.org/issue?@action=redirect&bpo=31922]: asyncio.AbstractEventLoop.create_datagram_endpoint(): Do not connect UDP socket when broadcast is allowed. This allows to receive replies after a UDP broadcast.

bpo-24882 [https://bugs.python.org/issue?@action=redirect&bpo=24882]: Change ThreadPoolExecutor to use existing idle threads before spinning up new ones.

bpo-31961 [https://bugs.python.org/issue?@action=redirect&bpo=31961]: Added support for bytes and path-like objects in subprocess.Popen() on Windows. The args parameter now accepts a path-like object if shell is False and a sequence containing bytes and path-like objects. The executable parameter now accepts a bytes and path-like object. The cwd parameter now accepts a bytes object. Based on patch by Anders Lorentsen.

bpo-33123 [https://bugs.python.org/issue?@action=redirect&bpo=33123]: pathlib.Path.unlink now accepts a missing_ok parameter to avoid a FileNotFoundError from being raised. Patch by Robert Buchholz.

bpo-32941 [https://bugs.python.org/issue?@action=redirect&bpo=32941]: Allow mmap.mmap objects to access the madvise() system call (through mmap.mmap.madvise()).

bpo-22102 [https://bugs.python.org/issue?@action=redirect&bpo=22102]: Added support for ZIP files with disks set to 0. Such files are commonly created by builtin tools on Windows when use ZIP64 extension. Patch by Francisco Facioni.

bpo-32515 [https://bugs.python.org/issue?@action=redirect&bpo=32515]: trace.py can now run modules via python3 -m trace -t --module module_name

bpo-32299 [https://bugs.python.org/issue?@action=redirect&bpo=32299]: Changed unittest.mock.patch.dict() to return the patched dictionary when used as context manager. Patch by Vadim Tsander.

bpo-27141 [https://bugs.python.org/issue?@action=redirect&bpo=27141]: Added a __copy__() to collections.UserList and collections.UserDict in order to correctly implement shallow copying of the objects. Patch by Bar Harel.

bpo-31829 [https://bugs.python.org/issue?@action=redirect&bpo=31829]: \r, \0 and \x1a (end-of-file on Windows) are now escaped in protocol 0 pickles of Unicode strings. This allows to load them without loss from files open in text mode in Python 2.

bpo-23395 [https://bugs.python.org/issue?@action=redirect&bpo=23395]: _thread.interrupt_main() now avoids setting the Python error status if the SIGINT signal is ignored or not handled by Python.

Documentation

bpo-36896 [https://bugs.python.org/issue?@action=redirect&bpo=36896]: Clarify that some types have unstable constructor signature between Python versions.

bpo-36686 [https://bugs.python.org/issue?@action=redirect&bpo=36686]: Improve documentation of the stdin, stdout, and stderr arguments of the asyncio.subprocess_exec function to specify which values are supported. Also mention that decoding as text is not supported.

Add a few tests to verify that the various values passed to the std* arguments actually work.

bpo-36984 [https://bugs.python.org/issue?@action=redirect&bpo=36984]: Improve version added references in typing module - by Anthony Sottile.

bpo-36868 [https://bugs.python.org/issue?@action=redirect&bpo=36868]: What's new now mentions SSLContext.hostname_checks_common_name instead of SSLContext.host_flags.

bpo-35924 [https://bugs.python.org/issue?@action=redirect&bpo=35924]: Add a note to the curses.addstr() documentation to warn that multiline strings can cause segfaults because of an ncurses bug.

bpo-36783 [https://bugs.python.org/issue?@action=redirect&bpo=36783]: Added C API Documentation for Time_FromTimeAndFold and PyDateTime_FromDateAndTimeAndFold as per PEP 495. Patch by Edison Abahurire.

bpo-36797 [https://bugs.python.org/issue?@action=redirect&bpo=36797]: More of the legacy distutils documentation has been either pruned, or else more clearly marked as being retained solely until the setuptools documentation covers it independently.

bpo-22865 [https://bugs.python.org/issue?@action=redirect&bpo=22865]: Add detail to the documentation on the pty.spawn function.

bpo-35397 [https://bugs.python.org/issue?@action=redirect&bpo=35397]: Remove deprecation and document urllib.parse.unwrap(). Patch contributed by Rémi Lapeyre.

bpo-32995 [https://bugs.python.org/issue?@action=redirect&bpo=32995]: Added the context variable in glossary.

bpo-33519 [https://bugs.python.org/issue?@action=redirect&bpo=33519]: Clarify that copy() is not part of the MutableSequence ABC.

bpo-33482 [https://bugs.python.org/issue?@action=redirect&bpo=33482]: Make codecs.StreamRecoder.writelines take a list of bytes.

bpo-25735 [https://bugs.python.org/issue?@action=redirect&bpo=25735]: Added documentation for func factorial to indicate that returns integer values

bpo-20285 [https://bugs.python.org/issue?@action=redirect&bpo=20285]: Expand object.__doc__ (docstring) to make it clearer. Modify pydoc.py so that help(object) lists object methods (for other classes, help omits methods of the object base class.)

Tests

bpo-37069 [https://bugs.python.org/issue?@action=redirect&bpo=37069]: Modify test_coroutines, test_cprofile, test_generators, test_raise, test_ssl and test_yield_from to use test.support.catch_unraisable_exception() rather than test.support.captured_stderr().

bpo-37098 [https://bugs.python.org/issue?@action=redirect&bpo=37098]: Fix test_memfd_create on older Linux Kernels.

bpo-37081 [https://bugs.python.org/issue?@action=redirect&bpo=37081]: Test with OpenSSL 1.1.1c

bpo-36829 [https://bugs.python.org/issue?@action=redirect&bpo=36829]: Add test.support.catch_unraisable_exception(): context manager catching unraisable exception using sys.unraisablehook().

bpo-36915 [https://bugs.python.org/issue?@action=redirect&bpo=36915]: The main regrtest process now always removes all temporary directories of worker processes even if they crash or if they are killed on KeyboardInterrupt (CTRL+c).

bpo-36719 [https://bugs.python.org/issue?@action=redirect&bpo=36719]: "python3 -m test -jN ..." now continues the execution of next tests when a worker process crash (CHILD_ERROR state). Previously, the test suite stopped immediately. Use --failfast to stop at the first error.

bpo-36816 [https://bugs.python.org/issue?@action=redirect&bpo=36816]: Update Lib/test/selfsigned_pythontestdotnet.pem to match self-signed.pythontest.net's new TLS certificate.

bpo-35925 [https://bugs.python.org/issue?@action=redirect&bpo=35925]: Skip httplib and nntplib networking tests when they would otherwise fail due to a modern OS or distro with a default OpenSSL policy of rejecting connections to servers with weak certificates.

bpo-36782 [https://bugs.python.org/issue?@action=redirect&bpo=36782]: Add tests for several C API functions in the datetime module. Patch by Edison Abahurire.

bpo-36342 [https://bugs.python.org/issue?@action=redirect&bpo=36342]: Fix test_multiprocessing in test_venv if platform lacks functioning sem_open.

Build

bpo-36721 [https://bugs.python.org/issue?@action=redirect&bpo=36721]: To embed Python into an application, a new --embed option must be passed to python3-config --libs --embed to get -lpython3.8 (link the application to libpython). To support both 3.8 and older, try python3-config --libs --embed first and fallback to python3-config --libs (without --embed) if the previous command fails.

Add a pkg-config python-3.8-embed module to embed Python into an application: pkg-config python-3.8-embed --libs includes -lpython3.8. To support both 3.8 and older, try pkg-config python-X.Y-embed --libs first and fallback to pkg-config python-X.Y --libs (without --embed) if the previous command fails (replace X.Y with the Python version).

On the other hand, pkg-config python3.8 --libs no longer contains -lpython3.8. C extensions must not be linked to libpython (except on Android, case handled by the script); this change is backward incompatible on purpose.

bpo-36786 [https://bugs.python.org/issue?@action=redirect&bpo=36786]: "make install" now runs compileall in parallel.

Windows

bpo-36965 [https://bugs.python.org/issue?@action=redirect&bpo=36965]: include of STATUS_CONTROL_C_EXIT without depending on MSC compiler

bpo-35926 [https://bugs.python.org/issue?@action=redirect&bpo=35926]: Update to OpenSSL 1.1.1b for Windows.

bpo-29883 [https://bugs.python.org/issue?@action=redirect&bpo=29883]: Add Windows support for UDP transports for the Proactor Event Loop. Patch by Adam Meily.

bpo-33407 [https://bugs.python.org/issue?@action=redirect&bpo=33407]: The Py_DEPRECATED() macro has been implemented for MSVC.

macOS

bpo-36231 [https://bugs.python.org/issue?@action=redirect&bpo=36231]: Support building Python on macOS without /usr/include installed. As of macOS 10.14, system header files are only available within an SDK provided by either the Command Line Tools or the Xcode app.

IDLE

bpo-35610 [https://bugs.python.org/issue?@action=redirect&bpo=35610]: Replace now redundant .context_use_ps1 with .prompt_last_line. This finishes change started in bpo-31858 [https://bugs.python.org/issue?@action=redirect&bpo=31858].

bpo-37038 [https://bugs.python.org/issue?@action=redirect&bpo=37038]: Make idlelib.run runnable; add test clause.

bpo-36958 [https://bugs.python.org/issue?@action=redirect&bpo=36958]: Print any argument other than None or int passed to SystemExit or sys.exit().

bpo-36807 [https://bugs.python.org/issue?@action=redirect&bpo=36807]: When saving a file, call os.fsync() so bits are flushed to e.g. USB drive.

bpo-32411 [https://bugs.python.org/issue?@action=redirect&bpo=32411]: In browser.py, remove extraneous sorting by line number since dictionary was created in line number order.

Tools/Demos

bpo-37053 [https://bugs.python.org/issue?@action=redirect&bpo=37053]: Handle strings like u"bar" correctly in Tools/parser/unparse.py. Patch by Chih-Hsuan Yen.

C API

bpo-36763 [https://bugs.python.org/issue?@action=redirect&bpo=36763]: Implement the PEP 587 [https://peps.python.org/pep-0587/] "Python Initialization Configuration".

bpo-36379 [https://bugs.python.org/issue?@action=redirect&bpo=36379]: Fix crashes when attempting to use the modulo parameter when __ipow__ is implemented in C.

bpo-37107 [https://bugs.python.org/issue?@action=redirect&bpo=37107]: Update PyObject_CallMethodObjArgs() and _PyObject_CallMethodIdObjArgs to use _PyObject_GetMethod to avoid creating a bound method object in many cases. Patch by Michael J. Sullivan.

bpo-36974 [https://bugs.python.org/issue?@action=redirect&bpo=36974]: Implement PEP 590 [https://peps.python.org/pep-0590/]: Vectorcall: a fast calling protocol for CPython. This is a new protocol to optimize calls of custom callable objects.

bpo-36763 [https://bugs.python.org/issue?@action=redirect&bpo=36763]: Py_Main() now returns the exitcode rather than calling Py_Exit(exitcode) when calling PyErr_Print() if the current exception type is SystemExit.

bpo-36922 [https://bugs.python.org/issue?@action=redirect&bpo=36922]: Add new type flag Py_TPFLAGS_METHOD_DESCRIPTOR for objects behaving like unbound methods. These are objects supporting the optimization given by the LOAD_METHOD/CALL_METHOD opcodes. See PEP 590.

bpo-36728 [https://bugs.python.org/issue?@action=redirect&bpo=36728]: The PyEval_ReInitThreads() function has been removed from the C API. It should not be called explicitly: use PyOS_AfterFork_Child() instead.

Python 3.8.0 alpha 4

Release date: 2019-05-06

Security

bpo-36742 [https://bugs.python.org/issue?@action=redirect&bpo=36742]: Fixes mishandling of pre-normalization characters in urlsplit().

bpo-30458 [https://bugs.python.org/issue?@action=redirect&bpo=30458]: Address CVE 2019-9740 [https://www.cve.org/CVERecord?id=CVE-2019-9740] by disallowing URL paths with embedded whitespace or control characters through into the underlying http client request. Such potentially malicious header injection URLs now cause an http.client.InvalidURL exception to be raised.

bpo-35755 [https://bugs.python.org/issue?@action=redirect&bpo=35755]: shutil.which() now uses os.confstr("CS_PATH") if available and if the PATH environment variable is not set. Remove also the current directory from posixpath.defpath. On Unix, shutil.which() and the subprocess module no longer search the executable in the current directory if the PATH environment variable is not set.

Core and Builtins

bpo-36722 [https://bugs.python.org/issue?@action=redirect&bpo=36722]: In debug build, import now also looks for C extensions compiled in release mode and for C extensions compiled in the stable ABI.

bpo-32849 [https://bugs.python.org/issue?@action=redirect&bpo=32849]: Fix Python Initialization code on FreeBSD to detect properly when stdin file descriptor (fd 0) is invalid.

bpo-36623 [https://bugs.python.org/issue?@action=redirect&bpo=36623]: Remove parser headers and related function declarations that lack implementations after the removal of pgen.

bpo-20180 [https://bugs.python.org/issue?@action=redirect&bpo=20180]: dict.pop() is now up to 33% faster thanks to Argument Clinic. Patch by Inada Naoki.

bpo-36611 [https://bugs.python.org/issue?@action=redirect&bpo=36611]: Debug memory allocators: disable serialno field by default from debug hooks on Python memory allocators to reduce the memory footprint by 5%. Enable tracemalloc to get the traceback where a memory block has been allocated when a fatal memory error is logged to decide where to put a breakpoint. Compile Python with PYMEM_DEBUG_SERIALNO defined to get back the field.

bpo-36588 [https://bugs.python.org/issue?@action=redirect&bpo=36588]: On AIX, sys.platform doesn't contain the major version anymore. Always return 'aix', instead of 'aix3' .. 'aix7'. Since older Python versions include the version number, it is recommended to always use sys.platform.startswith('aix'). Contributed by M. Felt.

bpo-36549 [https://bugs.python.org/issue?@action=redirect&bpo=36549]: Change str.capitalize to use titlecase for the first character instead of uppercase.

bpo-36540 [https://bugs.python.org/issue?@action=redirect&bpo=36540]: Implement PEP 570 [https://peps.python.org/pep-0570/] (Python positional-only parameters). Patch by Pablo Galindo.

bpo-36475 [https://bugs.python.org/issue?@action=redirect&bpo=36475]: PyEval_AcquireLock() and PyEval_AcquireThread() now terminate the current thread if called while the interpreter is finalizing, making them consistent with PyEval_RestoreThread(), Py_END_ALLOW_THREADS(), and PyGILState_Ensure().

bpo-36504 [https://bugs.python.org/issue?@action=redirect&bpo=36504]: Fix signed integer overflow in _ctypes.c's PyCArrayType_new().

bpo-20844 [https://bugs.python.org/issue?@action=redirect&bpo=20844]: Fix running script with encoding cookie and LF line ending may fail on Windows.

bpo-24214 [https://bugs.python.org/issue?@action=redirect&bpo=24214]: Fixed support of the surrogatepass error handler in the UTF-8 incremental decoder.

bpo-36452 [https://bugs.python.org/issue?@action=redirect&bpo=36452]: Changing dict keys during iteration of the dict itself, keys(), values(), or items() will now be detected in certain corner cases where keys are deleted/added so that the number of keys isn't changed. A RuntimeError will be raised after len(dict) iterations. Contributed by Thomas Perl.

bpo-36459 [https://bugs.python.org/issue?@action=redirect&bpo=36459]: Fix a possible double PyMem_FREE() due to tokenizer.c's tok_nextc().

bpo-36433 [https://bugs.python.org/issue?@action=redirect&bpo=36433]: Fixed TypeError message in classmethoddescr_call.

bpo-36430 [https://bugs.python.org/issue?@action=redirect&bpo=36430]: Fix a possible reference leak in itertools.count().

bpo-36440 [https://bugs.python.org/issue?@action=redirect&bpo=36440]: Include node names in ParserError messages, instead of numeric IDs. Patch by A. Skrobov.

bpo-36143 [https://bugs.python.org/issue?@action=redirect&bpo=36143]: Regenerate keyword from the Grammar and Tokens file using pgen. Patch by Pablo Galindo.

bpo-18372 [https://bugs.python.org/issue?@action=redirect&bpo=18372]: Add missing PyObject_GC_Track() calls in the pickle module. Patch by Zackery Spytz.

Library

bpo-35952 [https://bugs.python.org/issue?@action=redirect&bpo=35952]: Fix pythoninfo when the compiler is missing.

bpo-28238 [https://bugs.python.org/issue?@action=redirect&bpo=28238]: The .find*() methods of xml.etree.ElementTree can now search for wildcards like {*}tag and {ns}* that match a tag in any namespace or all tags in a namespace. Patch by Stefan Behnel.

bpo-26978 [https://bugs.python.org/issue?@action=redirect&bpo=26978]: pathlib.path.link_to() is now implemented. It creates a hard link pointing to a path.

bpo-1613500 [https://bugs.python.org/issue?@action=redirect&bpo=1613500]: fileinput.FileInput now uses the input file mode to correctly set the output file mode (previously it was hardcoded to 'w') when inplace=True is passed to its constructor.

bpo-36734 [https://bugs.python.org/issue?@action=redirect&bpo=36734]: Fix compilation of faulthandler.c on HP-UX. Initialize stack_t current_stack to zero using memset().

bpo-13611 [https://bugs.python.org/issue?@action=redirect&bpo=13611]: The xml.etree.ElementTree packages gained support for C14N 2.0 serialisation. Patch by Stefan Behnel.

bpo-36669 [https://bugs.python.org/issue?@action=redirect&bpo=36669]: Add missing matrix multiplication operator support to weakref.proxy.

bpo-36676 [https://bugs.python.org/issue?@action=redirect&bpo=36676]: The XMLParser() in xml.etree.ElementTree provides namespace prefix context to the parser target if it defines the callback methods "start_ns()" and/or "end_ns()". Patch by Stefan Behnel.

bpo-36673 [https://bugs.python.org/issue?@action=redirect&bpo=36673]: The TreeBuilder and XMLPullParser in xml.etree.ElementTree gained support for parsing comments and processing instructions. Patch by Stefan Behnel.

bpo-36650 [https://bugs.python.org/issue?@action=redirect&bpo=36650]: The C version of functools.lru_cache() was treating calls with an empty **kwargs dictionary as being distinct from calls with no keywords at all. This did not result in an incorrect answer, but it did trigger an unexpected cache miss.

bpo-28552 [https://bugs.python.org/issue?@action=redirect&bpo=28552]: Fix distutils.sysconfig if sys.executable is None or an empty string: use os.getcwd() to initialize project_base. Fix also the distutils build command: don't use sys.executable if it is None or an empty string.

bpo-35755 [https://bugs.python.org/issue?@action=redirect&bpo=35755]: shutil.which() and distutils.spawn.find_executable now use os.confstr("CS_PATH") if available instead of os.defpath, if the PATH environment variable is not set. Moreover, don't use os.confstr("CS_PATH") nor os.defpath if the PATH environment variable is set to an empty string.

bpo-25430 [https://bugs.python.org/issue?@action=redirect&bpo=25430]: improve performance of IPNetwork.__contains__()

bpo-30485 [https://bugs.python.org/issue?@action=redirect&bpo=30485]: Path expressions in xml.etree.ElementTree can now avoid explicit namespace prefixes for tags (or the "{namespace}tag" notation) by passing a default namespace with an empty string prefix.

bpo-36613 [https://bugs.python.org/issue?@action=redirect&bpo=36613]: Fix asyncio wait() not removing callback if exception

bpo-36598 [https://bugs.python.org/issue?@action=redirect&bpo=36598]: Fix isinstance check for Mock objects with spec when the code is executed under tracing. Patch by Karthikeyan Singaravelan.

bpo-18748 [https://bugs.python.org/issue?@action=redirect&bpo=18748]: In development mode (-X dev) and in debug build, the io.IOBase destructor now logs close() exceptions. These exceptions are silent by default in release mode.

bpo-36575 [https://bugs.python.org/issue?@action=redirect&bpo=36575]: The _lsprof module now uses internal timer same to time.perf_counter() by default. gettimeofday(2) was used on Unix. New timer has better resolution on most Unix platforms and timings are no longer impacted by system clock updates since perf_counter() is monotonic. Patch by Inada Naoki.

bpo-33461 [https://bugs.python.org/issue?@action=redirect&bpo=33461]: json.loads now emits DeprecationWarning when encoding option is specified. Patch by Matthias Bussonnier.

bpo-36559 [https://bugs.python.org/issue?@action=redirect&bpo=36559]: The random module now prefers the lean internal _sha512 module over hashlib for seed(version=2) to optimize import time.

bpo-17561 [https://bugs.python.org/issue?@action=redirect&bpo=17561]: Set backlog=None as the default for socket.create_server.

bpo-34373 [https://bugs.python.org/issue?@action=redirect&bpo=34373]: Fix time.mktime() error handling on AIX for year before 1970.

bpo-36232 [https://bugs.python.org/issue?@action=redirect&bpo=36232]: Improve error message when trying to open existing DBM database that actually doesn't exist. Patch by Marco Rougeth.

bpo-36546 [https://bugs.python.org/issue?@action=redirect&bpo=36546]: Add statistics.quantiles()

bpo-36050 [https://bugs.python.org/issue?@action=redirect&bpo=36050]: Optimized http.client.HTTPResponse.read() for large response. Patch by Inada Naoki.

bpo-36522 [https://bugs.python.org/issue?@action=redirect&bpo=36522]: If debuglevel is set to >0 in http.client, print all values for headers with multiple values for the same header name. Patch by Matt Houglum.

bpo-36492 [https://bugs.python.org/issue?@action=redirect&bpo=36492]: Deprecated passing required arguments like func as keyword arguments in functions which should accept arbitrary keyword arguments and pass them to other function. Arbitrary keyword arguments (even with names "self" and "func") can now be passed to these functions if the required arguments are passed as positional arguments.

bpo-27181 [https://bugs.python.org/issue?@action=redirect&bpo=27181]: Add statistics.geometric_mean().

bpo-30427 [https://bugs.python.org/issue?@action=redirect&bpo=30427]: os.path.normcase() relies on os.fspath() to check the type of its argument. Redundant checks have been removed from its posixpath.normcase() and ntpath.normcase() implementations. Patch by Wolfgang Maier.

bpo-36385 [https://bugs.python.org/issue?@action=redirect&bpo=36385]: Stop rejecting IPv4 octets for being ambiguously octal. Leading zeros are ignored, and no longer are assumed to specify octal octets. Octets are always decimal numbers. Octets must still be no more than three digits, including leading zeroes.

bpo-36434 [https://bugs.python.org/issue?@action=redirect&bpo=36434]: Errors during writing to a ZIP file no longer prevent to properly close it.

bpo-36407 [https://bugs.python.org/issue?@action=redirect&bpo=36407]: Fixed wrong indentation writing for CDATA section in xml.dom.minidom. Patch by Vladimir Surjaninov.

bpo-36326 [https://bugs.python.org/issue?@action=redirect&bpo=36326]: inspect.getdoc() can now find docstrings for member objects when __slots__ is a dictionary.

bpo-36366 [https://bugs.python.org/issue?@action=redirect&bpo=36366]: Calling stop() on an unstarted or stopped unittest.mock.patch() object will now return None instead of raising RuntimeError, making the method idempotent. Patch by Karthikeyan Singaravelan.

bpo-36348 [https://bugs.python.org/issue?@action=redirect&bpo=36348]: The imap.IMAP4.logout() method no longer ignores silently arbitrary exceptions.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Add time module support and fix test_time failures for VxWorks.

bpo-36227 [https://bugs.python.org/issue?@action=redirect&bpo=36227]: Added support for keyword arguments default_namespace and xml_declaration in functions ElementTree.tostring() and ElementTree.tostringlist().

bpo-36004 [https://bugs.python.org/issue?@action=redirect&bpo=36004]: Added new alternate constructors datetime.date.fromisocalendar() and datetime.datetime.fromisocalendar(), which construct date objects from ISO year, week number and weekday; these are the inverse of each class's isocalendar method. Patch by Paul Ganssle.

bpo-35936 [https://bugs.python.org/issue?@action=redirect&bpo=35936]: modulefinder no longer depends on the deprecated imp module, and the initializer for modulefinder.ModuleFinder now has immutable default arguments. Patch by Brandt Bucher.

bpo-35376 [https://bugs.python.org/issue?@action=redirect&bpo=35376]: modulefinder correctly handles modules that have the same name as a bad package. Patch by Brandt Bucher.

bpo-17396 [https://bugs.python.org/issue?@action=redirect&bpo=17396]: modulefinder no longer crashes when encountering syntax errors in followed imports. Patch by Brandt Bucher.

bpo-35934 [https://bugs.python.org/issue?@action=redirect&bpo=35934]: Added create_server() and has_dualstack_ipv6() convenience functions to automate the necessary tasks usually involved when creating a server socket, including accepting both IPv4 and IPv6 connections on the same socket. (Contributed by Giampaolo Rodola in bpo-17561 [https://bugs.python.org/issue?@action=redirect&bpo=17561].)

bpo-23078 [https://bugs.python.org/issue?@action=redirect&bpo=23078]: Add support for classmethod() and staticmethod() to unittest.mock.create_autospec(). Initial patch by Felipe Ochoa.

bpo-35416 [https://bugs.python.org/issue?@action=redirect&bpo=35416]: Fix potential resource warnings in distutils. Patch by Mickaël Schoentgen.

bpo-25451 [https://bugs.python.org/issue?@action=redirect&bpo=25451]: Add transparency methods to tkinter.PhotoImage. Patch by Zackery Spytz.

bpo-35082 [https://bugs.python.org/issue?@action=redirect&bpo=35082]: Don't return deleted attributes when calling dir on a unittest.mock.Mock.

bpo-34547 [https://bugs.python.org/issue?@action=redirect&bpo=34547]: wsgiref.handlers.BaseHandler now handles abrupt client connection terminations gracefully. Patch by Petter Strandmark.

bpo-31658 [https://bugs.python.org/issue?@action=redirect&bpo=31658]: xml.sax.parse() now supports path-like. Patch by Mickaël Schoentgen.

bpo-34139 [https://bugs.python.org/issue?@action=redirect&bpo=34139]: Remove stale unix datagram socket before binding

bpo-33530 [https://bugs.python.org/issue?@action=redirect&bpo=33530]: Implemented Happy Eyeballs in asyncio.create_connection(). Added two new arguments, happy_eyeballs_delay and interleave, to specify Happy Eyeballs behavior.

bpo-33291 [https://bugs.python.org/issue?@action=redirect&bpo=33291]: Do not raise AttributeError when calling the inspect functions isgeneratorfunction, iscoroutinefunction, isasyncgenfunction on a method created from an arbitrary callable. Instead, return False.

bpo-31310 [https://bugs.python.org/issue?@action=redirect&bpo=31310]: Fix the multiprocessing.semaphore_tracker so it is reused by child processes

bpo-31292 [https://bugs.python.org/issue?@action=redirect&bpo=31292]: Fix setup.py check --restructuredtext for files containing include directives.

Documentation

bpo-36625 [https://bugs.python.org/issue?@action=redirect&bpo=36625]: Remove obsolete comments from docstrings in fractions.Fraction

bpo-30840 [https://bugs.python.org/issue?@action=redirect&bpo=30840]: Document relative imports

bpo-36523 [https://bugs.python.org/issue?@action=redirect&bpo=36523]: Add docstring for io.IOBase.writelines().

bpo-36425 [https://bugs.python.org/issue?@action=redirect&bpo=36425]: New documentation translation: Simplified Chinese [https://docs.python.org/zh-cn/].

bpo-36345 [https://bugs.python.org/issue?@action=redirect&bpo=36345]: Avoid the duplication of code from Tools/scripts/serve.py in using the literalinclude directive for the basic wsgiref-based web server in the documentation of wsgiref. Contributed by Stéphane Wirtel.

bpo-36345 [https://bugs.python.org/issue?@action=redirect&bpo=36345]: Using the code of the Tools/scripts/serve.py script as an example in the wsgiref documentation. Contributed by Stéphane Wirtel.

bpo-36157 [https://bugs.python.org/issue?@action=redirect&bpo=36157]: Added documentation for PyInterpreterState_Main().

bpo-33043 [https://bugs.python.org/issue?@action=redirect&bpo=33043]: Updates the docs.python.org page with the addition of a 'Contributing to Docs' link at the end of the page (between 'Reporting Bugs' and 'About Documentation'). Updates the 'Found a Bug' page with additional links and information in the Documentation Bugs section.

bpo-35581 [https://bugs.python.org/issue?@action=redirect&bpo=35581]: @typing.type_check_only now allows type stubs to mark functions and classes not available during runtime.

bpo-33832 [https://bugs.python.org/issue?@action=redirect&bpo=33832]: Add glossary entry for 'magic method'.

bpo-32913 [https://bugs.python.org/issue?@action=redirect&bpo=32913]: Added re.Match.groupdict example to regex HOWTO.

Tests

bpo-36719 [https://bugs.python.org/issue?@action=redirect&bpo=36719]: regrtest now always detects uncollectable objects. Previously, the check was only enabled by --findleaks. The check now also works with -jN/--multiprocess N. --findleaks becomes a deprecated alias to --fail-env-changed.

bpo-36725 [https://bugs.python.org/issue?@action=redirect&bpo=36725]: When using multiprocessing mode (-jN), regrtest now better reports errors if a worker process fails, and it exits immediately on a worker thread failure or when interrupted.

bpo-36454 [https://bugs.python.org/issue?@action=redirect&bpo=36454]: Change test_time.test_monotonic() to test only the lower bound of elapsed time after a sleep command rather than the upper bound. This prevents unnecessary test failures on slow buildbots. Patch by Victor Stinner.

bpo-32424 [https://bugs.python.org/issue?@action=redirect&bpo=32424]: Improve test coverage for xml.etree.ElementTree. Patch by Gordon P. Hemsley.

bpo-32424 [https://bugs.python.org/issue?@action=redirect&bpo=32424]: Fix typo in test_cyclic_gc() test for xml.etree.ElementTree. Patch by Gordon P. Hemsley.

bpo-36635 [https://bugs.python.org/issue?@action=redirect&bpo=36635]: Add a new _testinternalcapi module to test the internal C API.

bpo-36629 [https://bugs.python.org/issue?@action=redirect&bpo=36629]: Fix test_imap4_host_default_value() of test_imaplib: catch also errno.ENETUNREACH error.

bpo-36611 [https://bugs.python.org/issue?@action=redirect&bpo=36611]: Fix test_sys.test_getallocatedblocks() when tracemalloc is enabled.

bpo-36560 [https://bugs.python.org/issue?@action=redirect&bpo=36560]: Fix reference leak hunting in regrtest: compute also deltas (of reference count, allocated memory blocks, file descriptor count) during warmup, to ensure that everything is initialized before starting to hunt reference leaks.

bpo-36565 [https://bugs.python.org/issue?@action=redirect&bpo=36565]: Fix reference hunting (python3 -m test -R 3:3) when Python has no built-in abc module.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Port test_resource to VxWorks: skip tests cases setting RLIMIT_FSIZE and RLIMIT_CPU.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix test_tabnanny on VxWorks: adjust ENOENT error message.

bpo-36436 [https://bugs.python.org/issue?@action=redirect&bpo=36436]: Fix _testcapi.pymem_buffer_overflow(): handle memory allocation failure.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Fix test_utf8_mode on VxWorks: Python always use UTF-8 on VxWorks.

bpo-36341 [https://bugs.python.org/issue?@action=redirect&bpo=36341]: Fix tests that may fail with PermissionError upon calling bind() on AF_UNIX sockets.

Build

bpo-36747 [https://bugs.python.org/issue?@action=redirect&bpo=36747]: Remove the stale scriptsinstall Makefile target.

bpo-21536 [https://bugs.python.org/issue?@action=redirect&bpo=21536]: On Unix, C extensions are no longer linked to libpython except on Android and Cygwin.

It is now possible for a statically linked Python to load a C extension built using a shared library Python.

When Python is embedded, libpython must not be loaded with RTLD_LOCAL, but RTLD_GLOBAL instead. Previously, using RTLD_LOCAL, it was already not possible to load C extensions which were not linked to libpython, such as C extensions of the standard library built by the *shared* section of Modules/Setup.

distutils, python-config and python-config.py have been modified.

bpo-36707 [https://bugs.python.org/issue?@action=redirect&bpo=36707]: ./configure --with-pymalloc no longer adds the m flag to SOABI (sys.implementation.cache_tag). Enabling or disabling pymalloc has no impact on the ABI.

bpo-36635 [https://bugs.python.org/issue?@action=redirect&bpo=36635]: Change PyAPI_FUNC(type), PyAPI_DATA(type) and PyMODINIT_FUNC macros of pyport.h when Py_BUILD_CORE_MODULE is defined. The Py_BUILD_CORE_MODULE define must be now be used to build a C extension as a dynamic library accessing Python internals: export the PyInit_xxx() function in DLL exports on Windows.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Don't build the _crypt extension on VxWorks.

bpo-36618 [https://bugs.python.org/issue?@action=redirect&bpo=36618]: Add -fmax-type-align=8 to CFLAGS when clang compiler is detected. The pymalloc memory allocator aligns memory on 8 bytes. On x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS instruction which can lead to segmentation fault. Instruct clang that Python is limited to alignment on 8 bytes to use MOVUPS instruction instead: slower but don't trigger a SIGSEGV if the memory is not aligned on 16 bytes. Sadly, the flag must be added to CFLAGS and not just CFLAGS_NODIST, since third party C extensions can have the same issue.

bpo-36605 [https://bugs.python.org/issue?@action=redirect&bpo=36605]: make tags and make TAGS now also parse Modules/_io/*.c and Modules/_io/*.h.

bpo-36465 [https://bugs.python.org/issue?@action=redirect&bpo=36465]: Release builds and debug builds are now ABI compatible: defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro, which introduces the only ABI incompatibility. The Py_TRACE_REFS macro, which adds the sys.getobjects() function and the PYTHONDUMPREFS environment variable, can be set using the new ./configure --with-trace-refs build option.

bpo-36577 [https://bugs.python.org/issue?@action=redirect&bpo=36577]: setup.py now correctly reports missing OpenSSL headers and libraries again.

bpo-36544 [https://bugs.python.org/issue?@action=redirect&bpo=36544]: Fix regression introduced in bpo-36146 [https://bugs.python.org/issue?@action=redirect&bpo=36146] refactoring setup.py

bpo-36508 [https://bugs.python.org/issue?@action=redirect&bpo=36508]: python-config --ldflags no longer includes flags of the LINKFORSHARED variable. The LINKFORSHARED variable must only be used to build executables.

bpo-36503 [https://bugs.python.org/issue?@action=redirect&bpo=36503]: Remove references to "aix3" and "aix4". Patch by M. Felt.

Windows

bpo-35920 [https://bugs.python.org/issue?@action=redirect&bpo=35920]: Added platform.win32_edition() and platform.win32_is_iot(). Added support for cross-compiling packages for Windows ARM32. Skip tests that are not expected to work on Windows IoT Core ARM32.

bpo-36649 [https://bugs.python.org/issue?@action=redirect&bpo=36649]: Remove trailing spaces for registry keys when installed via the Store.

bpo-34144 [https://bugs.python.org/issue?@action=redirect&bpo=34144]: Fixed activate.bat to correctly update codepage when chcp.com returns dots in output. Patch by Lorenz Mende.

bpo-36509 [https://bugs.python.org/issue?@action=redirect&bpo=36509]: Added preset-iot layout for Windows IoT ARM containers. This layout doesn't contain UI components like tkinter or IDLE. It also doesn't contain files to support on-target builds since Windows ARM32 builds must be cross-compiled when using MSVC.

bpo-35941 [https://bugs.python.org/issue?@action=redirect&bpo=35941]: enum_certificates function of the ssl module now returns certificates from all available certificate stores inside windows in a query instead of returning only certificates from the system wide certificate store. This includes certificates from these certificate stores: local machine, local machine enterprise, local machine group policy, current user, current user group policy, services, users. ssl.enum_crls() function is changed in the same way to return all certificate revocation lists inside the windows certificate revocation list stores.

bpo-36441 [https://bugs.python.org/issue?@action=redirect&bpo=36441]: Fixes creating a venv when debug binaries are installed.

bpo-36085 [https://bugs.python.org/issue?@action=redirect&bpo=36085]: Enable better DLL resolution on Windows by using safe DLL search paths and adding os.add_dll_directory().

bpo-36010 [https://bugs.python.org/issue?@action=redirect&bpo=36010]: Add the venv standard library module to the nuget distribution for Windows.

bpo-29515 [https://bugs.python.org/issue?@action=redirect&bpo=29515]: Add the following socket module constants on Windows: IPPROTO_AH IPPROTO_CBT IPPROTO_DSTOPTS IPPROTO_EGP IPPROTO_ESP IPPROTO_FRAGMENT IPPROTO_GGP IPPROTO_HOPOPTS IPPROTO_ICLFXBM IPPROTO_ICMPV6 IPPROTO_IDP IPPROTO_IGMP IPPROTO_IGP IPPROTO_IPV4 IPPROTO_IPV6 IPPROTO_L2TP IPPROTO_MAX IPPROTO_ND IPPROTO_NONE IPPROTO_PGM IPPROTO_PIM IPPROTO_PUP IPPROTO_RDP IPPROTO_ROUTING IPPROTO_SCTP IPPROTO_ST

bpo-35947 [https://bugs.python.org/issue?@action=redirect&bpo=35947]: Added current version of libffi to cpython-source-deps. Change _ctypes to use current version of libffi on Windows.

bpo-34060 [https://bugs.python.org/issue?@action=redirect&bpo=34060]: Report system load when running test suite on Windows. Patch by Ammar Askar. Based on prior work by Jeremy Kloth.

bpo-31512 [https://bugs.python.org/issue?@action=redirect&bpo=31512]: With the Windows 10 Creators Update, non-elevated users can now create symlinks as long as the computer has Developer Mode enabled.

macOS

bpo-34602 [https://bugs.python.org/issue?@action=redirect&bpo=34602]: Avoid failures setting macOS stack resource limit with resource.setrlimit. This reverts an earlier fix for bpo-18075 [https://bugs.python.org/issue?@action=redirect&bpo=18075] which forced a non-default stack size when building the interpreter executable on macOS.

IDLE

bpo-36429 [https://bugs.python.org/issue?@action=redirect&bpo=36429]: Fix starting IDLE with pyshell. Add idlelib.pyshell alias at top; remove pyshell alias at bottom. Remove obsolete __name__=='__main__' command.

Tools/Demos

bpo-14546 [https://bugs.python.org/issue?@action=redirect&bpo=14546]: Fix the argument handling in Tools/scripts/lll.py.

C API

bpo-36763 [https://bugs.python.org/issue?@action=redirect&bpo=36763]: Fix memory leak in Py_SetStandardStreamEncoding(): release memory if the function is called twice.

bpo-36641 [https://bugs.python.org/issue?@action=redirect&bpo=36641]: PyDoc_VAR(name) and PyDoc_STRVAR(name, str) now create static const char name[] instead of static char name[]. Patch by Inada Naoki.

bpo-36389 [https://bugs.python.org/issue?@action=redirect&bpo=36389]: Change the value of CLEANBYTE, DEADDYTE and FORBIDDENBYTE internal constants used by debug hooks on Python memory allocators (PyMem_SetupDebugHooks() function). Byte patterns 0xCB, 0xDB and 0xFB have been replaced with 0xCD, 0xDD and 0xFD to use the same values than Windows CRT debug malloc() and free().

bpo-36443 [https://bugs.python.org/issue?@action=redirect&bpo=36443]: Since Python 3.7.0, calling Py_DecodeLocale() before Py_Initialize() produces mojibake if the LC_CTYPE locale is coerced and/or if the UTF-8 Mode is enabled by the user configuration. The LC_CTYPE coercion and UTF-8 Mode are now disabled by default to fix the mojibake issue. They must now be enabled explicitly (opt-in) using the new _Py_PreInitialize() API with _PyPreConfig.

bpo-36025 [https://bugs.python.org/issue?@action=redirect&bpo=36025]: Fixed an accidental change to the datetime C API where the arguments to the PyDate_FromTimestamp() function were incorrectly interpreted as a single timestamp rather than an arguments tuple, which causes existing code to start raising TypeError. The backwards-incompatible change was only present in alpha releases of Python 3.8. Patch by Paul Ganssle.

bpo-35810 [https://bugs.python.org/issue?@action=redirect&bpo=35810]: Modify PyObject_Init to correctly increase the refcount of heap-allocated Type objects. Also fix the refcounts of the heap-allocated types that were either doing this manually or not decreasing the type's refcount in tp_dealloc

Python 3.8.0 alpha 3

Release date: 2019-03-25

Security

bpo-36216 [https://bugs.python.org/issue?@action=redirect&bpo=36216]: Changes urlsplit() to raise ValueError when the URL contains characters that decompose under IDNA encoding (NFKC-normalization) into characters that affect how the URL is parsed.

bpo-35121 [https://bugs.python.org/issue?@action=redirect&bpo=35121]: Don't send cookies of domain A without Domain attribute to domain B when domain A is a suffix match of domain B while using a cookiejar with http.cookiejar.DefaultCookiePolicy policy. Patch by Karthikeyan Singaravelan.

Core and Builtins

bpo-36421 [https://bugs.python.org/issue?@action=redirect&bpo=36421]: Fix a possible double decref in _ctypes.c's PyCArrayType_new().

bpo-36412 [https://bugs.python.org/issue?@action=redirect&bpo=36412]: Fix a possible crash when creating a new dictionary.

bpo-36398 [https://bugs.python.org/issue?@action=redirect&bpo=36398]: Fix a possible crash in structseq_repr().

bpo-36256 [https://bugs.python.org/issue?@action=redirect&bpo=36256]: Fix bug in parsermodule when parsing a state in a DFA that has two or more arcs with labels of the same type. Patch by Pablo Galindo.

bpo-36365 [https://bugs.python.org/issue?@action=redirect&bpo=36365]: repr(structseq) is no longer limited to 512 bytes.

bpo-36374 [https://bugs.python.org/issue?@action=redirect&bpo=36374]: Fix a possible null pointer dereference in merge_consts_recursive(). Patch by Zackery Spytz.

bpo-36236 [https://bugs.python.org/issue?@action=redirect&bpo=36236]: At Python initialization, the current directory is no longer prepended to sys.path if it has been removed.

bpo-36352 [https://bugs.python.org/issue?@action=redirect&bpo=36352]: Python initialization now fails with an error, rather than silently truncating paths, if a path is too long.

bpo-36301 [https://bugs.python.org/issue?@action=redirect&bpo=36301]: Python initialization now fails if decoding pybuilddir.txt configuration file fails at startup.

bpo-36333 [https://bugs.python.org/issue?@action=redirect&bpo=36333]: Fix leak in _PyRuntimeState_Fini. Contributed by Stéphane Wirtel.

bpo-36332 [https://bugs.python.org/issue?@action=redirect&bpo=36332]: The builtin compile() can now handle AST objects that contain assignment expressions. Patch by Pablo Galindo.

bpo-36282 [https://bugs.python.org/issue?@action=redirect&bpo=36282]: Improved error message for too much positional arguments in some builtin functions.

bpo-30040 [https://bugs.python.org/issue?@action=redirect&bpo=30040]: New empty dict uses fewer memory for now. It used more memory than empty dict created by dict.clear(). And empty dict creation and deletion is about 2x faster. Patch by Inada Naoki.

bpo-36262 [https://bugs.python.org/issue?@action=redirect&bpo=36262]: Fix an unlikely memory leak on conversion from string to float in the function _Py_dg_strtod() used by float(str), complex(str), pickle.load(), marshal.load(), etc.

bpo-36252 [https://bugs.python.org/issue?@action=redirect&bpo=36252]: Update Unicode databases to version 12.0.0.

bpo-36218 [https://bugs.python.org/issue?@action=redirect&bpo=36218]: Fix a segfault occurring when sorting a list of heterogeneous values. Patch contributed by Rémi Lapeyre and Elliot Gorokhovsky.

bpo-36188 [https://bugs.python.org/issue?@action=redirect&bpo=36188]: Cleaned up left-over vestiges of Python 2 unbound method handling in method objects and documentation. Patch by Martijn Pieters

bpo-36124 [https://bugs.python.org/issue?@action=redirect&bpo=36124]: Add a new interpreter-specific dict and expose it in the C-API via PyInterpreterState_GetDict(). This parallels PyThreadState_GetDict(). However, extension modules should continue using PyModule_GetState() for their own internal per-interpreter state.

bpo-35975 [https://bugs.python.org/issue?@action=redirect&bpo=35975]: Add a feature_version flag to ast.parse() (documented) and compile() (hidden) that allows tweaking the parser to support older versions of the grammar. In particular, if feature_version is 5 or 6, the hacks for the async and await keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than NAME tokens that the parser driver recognizes.)

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Use UTF-8 as the system encoding on VxWorks.

bpo-36048 [https://bugs.python.org/issue?@action=redirect&bpo=36048]: The __index__() special method will be used instead of __int__() for implicit conversion of Python numbers to C integers. Using the __int__() method in implicit conversions has been deprecated.

bpo-35808 [https://bugs.python.org/issue?@action=redirect&bpo=35808]: Retire pgen and use a modified version of pgen2 to generate the parser. Patch by Pablo Galindo.

Library

bpo-36401 [https://bugs.python.org/issue?@action=redirect&bpo=36401]: The class documentation created by pydoc now has a separate section for readonly properties.

bpo-36320 [https://bugs.python.org/issue?@action=redirect&bpo=36320]: The typing.NamedTuple() class has deprecated the _field_types attribute in favor of the __annotations__ attribute which carried the same information. Also, both attributes were converted from OrderedDict to a regular dict.

bpo-34745 [https://bugs.python.org/issue?@action=redirect&bpo=34745]: Fix asyncio ssl memory issues caused by circular references

bpo-36324 [https://bugs.python.org/issue?@action=redirect&bpo=36324]: Add method to statistics.NormalDist for computing the inverse cumulative normal distribution.

bpo-36321 [https://bugs.python.org/issue?@action=redirect&bpo=36321]: collections.namedtuple() misspelled the name of an attribute. To be consistent with typing.NamedTuple, the attribute name should have been "_field_defaults" instead of "_fields_defaults". For backwards compatibility, both spellings are now created. The misspelled version may be removed in the future.

bpo-36297 [https://bugs.python.org/issue?@action=redirect&bpo=36297]: "unicode_internal" codec is removed. It was deprecated since Python 3.3. Patch by Inada Naoki.

bpo-36298 [https://bugs.python.org/issue?@action=redirect&bpo=36298]: Raise ModuleNotFoundError in pyclbr when a module can't be found. Thanks to 'mental' for the bug report.

bpo-36268 [https://bugs.python.org/issue?@action=redirect&bpo=36268]: Switch the default format used for writing tars with tarfile to the modern POSIX.1-2001 pax standard, from the vendor-specific GNU. Contributed by C.A.M. Gerlach.

bpo-36285 [https://bugs.python.org/issue?@action=redirect&bpo=36285]: Fix integer overflows in the array module. Patch by Stephan Hohe.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Add _signal module support for VxWorks.

bpo-36272 [https://bugs.python.org/issue?@action=redirect&bpo=36272]: logging does not silently ignore RecursionError anymore. Patch contributed by Rémi Lapeyre.

bpo-36280 [https://bugs.python.org/issue?@action=redirect&bpo=36280]: Add a kind field to ast.Constant. It is 'u' if the literal has a 'u' prefix (i.e. a Python 2 style unicode literal), else None.

bpo-35931 [https://bugs.python.org/issue?@action=redirect&bpo=35931]: The pdb debug command now gracefully handles all exceptions.

bpo-36251 [https://bugs.python.org/issue?@action=redirect&bpo=36251]: Fix format strings used for stderrprinter and re.Match reprs. Patch by Stephan Hohe.

bpo-36235 [https://bugs.python.org/issue?@action=redirect&bpo=36235]: Fix CFLAGS in customize_compiler() of distutils.sysconfig: when the CFLAGS environment variable is defined, don't override CFLAGS variable with the OPT variable anymore. Initial patch written by David Malcolm.

bpo-35807 [https://bugs.python.org/issue?@action=redirect&bpo=35807]: Update ensurepip to install pip 19.0.3 and setuptools 40.8.0.

bpo-36139 [https://bugs.python.org/issue?@action=redirect&bpo=36139]: Release GIL when closing mmap objects.

bpo-36179 [https://bugs.python.org/issue?@action=redirect&bpo=36179]: Fix two unlikely reference leaks in _hashopenssl. The leaks only occur in out-of-memory cases.

bpo-36169 [https://bugs.python.org/issue?@action=redirect&bpo=36169]: Add overlap() method to statistics.NormalDist. Computes the overlapping coefficient for two normal distributions.

bpo-36103 [https://bugs.python.org/issue?@action=redirect&bpo=36103]: Default buffer size used by shutil.copyfileobj() is changed from 16 KiB to 64 KiB on non-Windows platform to reduce system call overhead. Contributed by Inada Naoki.

bpo-36130 [https://bugs.python.org/issue?@action=redirect&bpo=36130]: Fix pdb with skip=... when stepping into a frame without a __name__ global. Patch by Anthony Sottile.

bpo-35652 [https://bugs.python.org/issue?@action=redirect&bpo=35652]: shutil.copytree(copy_function=...) erroneously pass DirEntry instead of a path string.

bpo-35178 [https://bugs.python.org/issue?@action=redirect&bpo=35178]: Ensure custom warnings.formatwarning() function can receive line as positional argument. Based on patch by Tashrif Billah.

bpo-36106 [https://bugs.python.org/issue?@action=redirect&bpo=36106]: Resolve potential name clash with libm's sinpi(). Patch by Dmitrii Pasechnik.

bpo-36091 [https://bugs.python.org/issue?@action=redirect&bpo=36091]: Clean up reference to async generator in Lib/types. Patch by Henry Chen.

bpo-36043 [https://bugs.python.org/issue?@action=redirect&bpo=36043]: FileCookieJar supports path-like object. Contributed by Stéphane Wirtel

bpo-35899 [https://bugs.python.org/issue?@action=redirect&bpo=35899]: Enum has been fixed to correctly handle empty strings and strings with non-Latin characters (ie. 'α', 'א') without crashing. Original patch contributed by Maxwell. Assisted by Stéphane Wirtel.

bpo-21269 [https://bugs.python.org/issue?@action=redirect&bpo=21269]: Add args and kwargs properties to mock call objects. Contributed by Kumar Akshay.

bpo-30670 [https://bugs.python.org/issue?@action=redirect&bpo=30670]: pprint.pp has been added to pretty-print objects with dictionary keys being sorted with their insertion order by default. Parameter sort_dicts has been added to pprint.pprint, pprint.pformat and pprint.PrettyPrinter. Contributed by Rémi Lapeyre.

bpo-35843 [https://bugs.python.org/issue?@action=redirect&bpo=35843]: Implement __getitem__ for _NamespacePath. Patch by Anthony Sottile.

bpo-35802 [https://bugs.python.org/issue?@action=redirect&bpo=35802]: Clean up code which checked presence of os.stat / os.lstat / os.chmod which are always present. Patch by Anthony Sottile.

bpo-35715 [https://bugs.python.org/issue?@action=redirect&bpo=35715]: Librates the return value of a ProcessPoolExecutor _process_worker after it's no longer needed to free memory

bpo-35493 [https://bugs.python.org/issue?@action=redirect&bpo=35493]: Use multiprocessing.connection.wait() instead of polling each 0.2 seconds for worker updates in multiprocessing.Pool. Patch by Pablo Galindo.

bpo-35661 [https://bugs.python.org/issue?@action=redirect&bpo=35661]: Store the venv prompt in pyvenv.cfg.

bpo-35121 [https://bugs.python.org/issue?@action=redirect&bpo=35121]: Don't set cookie for a request when the request path is a prefix match of the cookie's path attribute but doesn't end with "/". Patch by Karthikeyan Singaravelan.

bpo-21478 [https://bugs.python.org/issue?@action=redirect&bpo=21478]: Calls to a child function created with unittest.mock.create_autospec() should propagate to the parent. Patch by Karthikeyan Singaravelan.

bpo-35198 [https://bugs.python.org/issue?@action=redirect&bpo=35198]: Fix C++ extension compilation on AIX

Documentation

bpo-36329 [https://bugs.python.org/issue?@action=redirect&bpo=36329]: Declare the path of the Python binary for the usage of Tools/scripts/serve.py when executing make -C Doc/ serve. Contributed by Stéphane Wirtel

bpo-36138 [https://bugs.python.org/issue?@action=redirect&bpo=36138]: Improve documentation about converting datetime.timedelta to scalars.

bpo-21314 [https://bugs.python.org/issue?@action=redirect&bpo=21314]: A new entry was added to the Core Language Section of the Programming FAQ, which explaines the usage of slash(/) in the signature of a function. Patch by Lysandros Nikolaou

Tests

bpo-36234 [https://bugs.python.org/issue?@action=redirect&bpo=36234]: test_posix.PosixUidGidTests: add tests for invalid uid/gid type (str). Initial patch written by David Malcolm.

bpo-29571 [https://bugs.python.org/issue?@action=redirect&bpo=29571]: Fix test_re.test_locale_flag(): use locale.getpreferredencoding() rather than locale.getlocale() to get the locale encoding. With some locales, locale.getlocale() returns the wrong encoding.

bpo-36123 [https://bugs.python.org/issue?@action=redirect&bpo=36123]: Fix race condition in test_socket.

Build

bpo-36356 [https://bugs.python.org/issue?@action=redirect&bpo=36356]: Fix leaks that led to build failure when configured with address sanitizer.

bpo-36146 [https://bugs.python.org/issue?@action=redirect&bpo=36146]: Add TEST_EXTENSIONS constant to setup.py to allow to not build test extensions like _testcapi.

bpo-36146 [https://bugs.python.org/issue?@action=redirect&bpo=36146]: Fix setup.py on macOS: only add /usr/include/ffi to include directories of _ctypes, not for all extensions.

bpo-31904 [https://bugs.python.org/issue?@action=redirect&bpo=31904]: Enable build system to cross-build for VxWorks RTOS.

Windows

bpo-36312 [https://bugs.python.org/issue?@action=redirect&bpo=36312]: Fixed decoders for the following code pages: 50220, 50221, 50222, 50225, 50227, 50229, 57002 through 57011, 65000 and 42.

bpo-36264 [https://bugs.python.org/issue?@action=redirect&bpo=36264]: Don't honor POSIX HOME in os.path.expanduser on windows. Patch by Anthony Sottile.

bpo-24643 [https://bugs.python.org/issue?@action=redirect&bpo=24643]: Fix name collisions due to #define timezone _timezone in PC/pyconfig.h.

IDLE

bpo-36405 [https://bugs.python.org/issue?@action=redirect&bpo=36405]: Use dict unpacking in idlelib.

bpo-36396 [https://bugs.python.org/issue?@action=redirect&bpo=36396]: Remove fgBg param of idlelib.config.GetHighlight(). This param was only used twice and changed the return type.

bpo-36176 [https://bugs.python.org/issue?@action=redirect&bpo=36176]: Fix IDLE autocomplete & calltip popup colors. Prevent conflicts with Linux dark themes (and slightly darken calltip background).

bpo-23205 [https://bugs.python.org/issue?@action=redirect&bpo=23205]: For the grep module, add tests for findfiles, refactor findfiles to be a module-level function, and refactor findfiles to use os.walk.

bpo-23216 [https://bugs.python.org/issue?@action=redirect&bpo=23216]: Add docstrings to IDLE search modules.

bpo-36152 [https://bugs.python.org/issue?@action=redirect&bpo=36152]: Remove colorizer.ColorDelegator.close_when_done and the corresponding argument of .close(). In IDLE, both have always been None or False since 2007.

bpo-32129 [https://bugs.python.org/issue?@action=redirect&bpo=32129]: Avoid blurry IDLE application icon on macOS with Tk 8.6. Patch by Kevin Walzer.

bpo-36096 [https://bugs.python.org/issue?@action=redirect&bpo=36096]: Refactor class variables to instance variables in colorizer.

bpo-30348 [https://bugs.python.org/issue?@action=redirect&bpo=30348]: Increase test coverage of idlelib.autocomplete by 30%. Patch by Louie Lu

Tools/Demos

bpo-35132 [https://bugs.python.org/issue?@action=redirect&bpo=35132]: Fix py-list and py-bt commands of python-gdb.py on gdb7.

bpo-32217 [https://bugs.python.org/issue?@action=redirect&bpo=32217]: Fix freeze script on Windows.

C API

bpo-36381 [https://bugs.python.org/issue?@action=redirect&bpo=36381]: Raise DeprecationWarning when '#' formats are used for building or parsing values without PY_SSIZE_T_CLEAN.

bpo-36142 [https://bugs.python.org/issue?@action=redirect&bpo=36142]: The whole coreconfig.h header is now excluded from Py_LIMITED_API. Move functions definitions into a new internal pycore_coreconfig.h header.

Python 3.8.0 alpha 2

Release date: 2019-02-25

Core and Builtins

bpo-36052 [https://bugs.python.org/issue?@action=redirect&bpo=36052]: Raise a SyntaxError when assigning a value to __debug__ with the Assignment Operator. Contributed by Stéphane Wirtel and Pablo Galindo.

bpo-36012 [https://bugs.python.org/issue?@action=redirect&bpo=36012]: Doubled the speed of class variable writes. When a non-dunder attribute was updated, there was an unnecessary call to update slots.

bpo-35942 [https://bugs.python.org/issue?@action=redirect&bpo=35942]: The error message emitted when returning invalid types from __fspath__ in interfaces that allow passing PathLike objects has been improved and now it does explain the origin of the error.

bpo-36016 [https://bugs.python.org/issue?@action=redirect&bpo=36016]: gc.get_objects can now receive an optional parameter indicating a generation to get objects from. Patch by Pablo Galindo.

bpo-1054041 [https://bugs.python.org/issue?@action=redirect&bpo=1054041]: When the main interpreter exits due to an uncaught KeyboardInterrupt, the process now exits in the appropriate manner for its parent process to detect that a SIGINT or ^C terminated the process. This allows shells and batch scripts to understand that the user has asked them to stop.

bpo-35992 [https://bugs.python.org/issue?@action=redirect&bpo=35992]: Fix __class_getitem__() not being called on a class with a custom non-subscriptable metaclass.

bpo-35993 [https://bugs.python.org/issue?@action=redirect&bpo=35993]: Fix a crash on fork when using subinterpreters. Contributed by Stéphane Wirtel

bpo-35991 [https://bugs.python.org/issue?@action=redirect&bpo=35991]: Fix a potential double free in Modules/_randommodule.c.

bpo-35961 [https://bugs.python.org/issue?@action=redirect&bpo=35961]: Fix a crash in slice_richcompare(): use strong references rather than stolen references for the two temporary internal tuples.

bpo-35911 [https://bugs.python.org/issue?@action=redirect&bpo=35911]: Enable the creation of cell objects by adding a cell.__new__ method, and expose the type cell in Lib/types.py under the name CellType. Patch by Pierre Glaser.

bpo-12822 [https://bugs.python.org/issue?@action=redirect&bpo=12822]: Use monotonic clock for pthread_cond_timedwait when pthread_condattr_setclock and CLOCK_MONOTONIC are available.

bpo-15248 [https://bugs.python.org/issue?@action=redirect&bpo=15248]: The compiler emits now syntax warnings in the case when a comma is likely missed before tuple or list.

bpo-35886 [https://bugs.python.org/issue?@action=redirect&bpo=35886]: The implementation of PyInterpreterState has been moved into the internal header files (guarded by Py_BUILD_CORE).

bpo-31506 [https://bugs.python.org/issue?@action=redirect&bpo=31506]: Clarify the errors reported when object.__new__ and object.__init__ receive more than one argument. Contributed by Sanyam Khurana.

bpo-35724 [https://bugs.python.org/issue?@action=redirect&bpo=35724]: Signal-handling is now guaranteed to happen relative to the main interpreter.

bpo-33608 [https://bugs.python.org/issue?@action=redirect&bpo=33608]: We added a new internal _Py_AddPendingCall() that operates relative to the provided interpreter. This allows us to use the existing implementation to ask another interpreter to do work that cannot be done in the current interpreter, like decref an object the other interpreter owns. The existing Py_AddPendingCall() only operates relative to the main interpreter.

bpo-33989 [https://bugs.python.org/issue?@action=redirect&bpo=33989]: Fix a possible crash in list.sort() when sorting objects with ob_type->tp_richcompare == NULL. Patch by Zackery Spytz.

Library

bpo-35512 [https://bugs.python.org/issue?@action=redirect&bpo=35512]: unittest.mock.patch.dict() used as a decorator with string target resolves the target during function call instead of during decorator construction. Patch by Karthikeyan Singaravelan.

bpo-36018 [https://bugs.python.org/issue?@action=redirect&bpo=36018]: Add statistics.NormalDist, a tool for creating and manipulating normal distributions of random variable. Features a composite class that treats the mean and standard deviation of measurement data as single entity.

bpo-35904 [https://bugs.python.org/issue?@action=redirect&bpo=35904]: Added statistics.fmean() as a faster, floating-point variant of the existing mean() function.

bpo-35918 [https://bugs.python.org/issue?@action=redirect&bpo=35918]: Removed broken has_key method from multiprocessing.managers.SyncManager.dict. Contributed by Rémi Lapeyre.

bpo-18283 [https://bugs.python.org/issue?@action=redirect&bpo=18283]: Add support for bytes to shutil.which().

bpo-35960 [https://bugs.python.org/issue?@action=redirect&bpo=35960]: Fix dataclasses.field() throwing away empty mapping objects passed as metadata.

bpo-35500 [https://bugs.python.org/issue?@action=redirect&bpo=35500]: Write expected and actual call parameters on separate lines in unittest.mock.Mock.assert_called_with() assertion errors. Contributed by Susan Su.

bpo-35931 [https://bugs.python.org/issue?@action=redirect&bpo=35931]: The pdb debug command now gracefully handles syntax errors.

bpo-24209 [https://bugs.python.org/issue?@action=redirect&bpo=24209]: In http.server script, rely on getaddrinfo to bind to preferred address based on the bind parameter. Now default bind or binding to a name may bind to IPv6 or dual-stack, depending on the environment.

bpo-35321 [https://bugs.python.org/issue?@action=redirect&bpo=35321]: Set __spec__.origin of _frozen_importlib to frozen so that it matches the behavior of _frozen_importlib_external. Patch by Nina Zakharenko.

bpo-35378 [https://bugs.python.org/issue?@action=redirect&bpo=35378]: Fix a reference issue inside multiprocessing.Pool that caused the pool to remain alive if it was deleted without being closed or terminated explicitly. A new strong reference is added to the pool iterators to link the lifetime of the pool to the lifetime of its iterators so the pool does not get destroyed if a pool iterator is still alive.

bpo-34294 [https://bugs.python.org/issue?@action=redirect&bpo=34294]: re module, fix wrong capturing groups in rare cases. re.search(), re.findall(), re.sub() and other functions that scan through string looking for a match, should reset capturing groups between two match attempts. Patch by Ma Lin.

bpo-35615 [https://bugs.python.org/issue?@action=redirect&bpo=35615]: weakref: Fix a RuntimeError when copying a WeakKeyDictionary or a WeakValueDictionary, due to some keys or values disappearing while iterating.

bpo-35606 [https://bugs.python.org/issue?@action=redirect&bpo=35606]: Implement math.prod() as analogous function to sum() that returns the product of a 'start' value (default: 1) times an iterable of numbers. Patch by Pablo Galindo.

bpo-32417 [https://bugs.python.org/issue?@action=redirect&bpo=32417]: Performing arithmetic between datetime.datetime subclasses and datetime.timedelta now returns an object of the same type as the datetime.datetime subclass. As a result, datetime.datetime.astimezone() and alternate constructors like datetime.datetime.now() and datetime.fromtimestamp() called with a tz argument now also retain their subclass.

bpo-35153 [https://bugs.python.org/issue?@action=redirect&bpo=35153]: Add headers optional keyword-only parameter to xmlrpc.client.ServerProxy, xmlrpc.client.Transport and xmlrpc.client.SafeTransport. Patch by Cédric Krier.

bpo-34572 [https://bugs.python.org/issue?@action=redirect&bpo=34572]: Fix C implementation of pickle.loads to use importlib's locking mechanisms, and thereby avoid using partially loaded modules. Patch by Tim Burgess.

Documentation

bpo-36083 [https://bugs.python.org/issue?@action=redirect&bpo=36083]: Fix formatting of --check-hash-based-pycs options in the manpage Synopsis.

bpo-36007 [https://bugs.python.org/issue?@action=redirect&bpo=36007]: Bump minimum sphinx version to 1.8. Patch by Anthony Sottile.

bpo-22062 [https://bugs.python.org/issue?@action=redirect&bpo=22062]: Update documentation and docstrings for pathlib. Original patch by Mike Short.

Tests

bpo-27313 [https://bugs.python.org/issue?@action=redirect&bpo=27313]: Avoid test_ttk_guionly ComboboxTest failure with macOS Cocoa Tk.

bpo-36019 [https://bugs.python.org/issue?@action=redirect&bpo=36019]: Add test.support.TEST_HTTP_URL and replace references of http://www.example.com by this new constant. Contributed by Stéphane Wirtel.

bpo-36037 [https://bugs.python.org/issue?@action=redirect&bpo=36037]: Fix test_ssl for strict OpenSSL configuration like RHEL8 strict crypto policy. Use older TLS version for minimum TLS version of the server SSL context if needed, to test TLS version older than default minimum TLS version.

bpo-35798 [https://bugs.python.org/issue?@action=redirect&bpo=35798]: Added test.support.check_syntax_warning().

bpo-35505 [https://bugs.python.org/issue?@action=redirect&bpo=35505]: Make test_imap4_host_default_value independent on whether the local IMAP server is running.

bpo-35917 [https://bugs.python.org/issue?@action=redirect&bpo=35917]: multiprocessing: provide unit tests for SyncManager and SharedMemoryManager classes + all the shareable types which are supposed to be supported by them. (patch by Giampaolo Rodola)

bpo-35704 [https://bugs.python.org/issue?@action=redirect&bpo=35704]: Skip test_shutil.test_unpack_archive_xztar to prevent a MemoryError on 32-bit AIX when MAXDATA setting is less than 0x20000000.

Patch by Michael Felt (aixtools)

bpo-34720 [https://bugs.python.org/issue?@action=redirect&bpo=34720]: Assert m_state != NULL to mimic GC traversal functions that do not correctly handle module creation when the module state has not been created.

Windows

bpo-35976 [https://bugs.python.org/issue?@action=redirect&bpo=35976]: Added ARM build support to Windows build files in PCBuild.

bpo-35692 [https://bugs.python.org/issue?@action=redirect&bpo=35692]: pathlib no longer raises when checking file and directory existence on drives that are not ready

bpo-35872 [https://bugs.python.org/issue?@action=redirect&bpo=35872]: Uses the base Python executable when invoking venv in a virtual environment

bpo-35873 [https://bugs.python.org/issue?@action=redirect&bpo=35873]: Prevents venv paths being inherited by child processes

bpo-35299 [https://bugs.python.org/issue?@action=redirect&bpo=35299]: Fix sysconfig detection of the source directory and distutils handling of pyconfig.h during PGO profiling

IDLE

bpo-24310 [https://bugs.python.org/issue?@action=redirect&bpo=24310]: IDLE -- Document settings dialog font tab sample.

bpo-35833 [https://bugs.python.org/issue?@action=redirect&bpo=35833]: Revise IDLE doc for control codes sent to Shell. Add a code example block.

bpo-35689 [https://bugs.python.org/issue?@action=redirect&bpo=35689]: Add docstrings and unittests for colorizer.py.

Python 3.8.0 alpha 1

Release date: 2019-02-03

Security

bpo-35746 [https://bugs.python.org/issue?@action=redirect&bpo=35746]: CVE 2019-5010 [https://www.cve.org/CVERecord?id=CVE-2019-5010]: Fix a NULL pointer deref in ssl module. The cert parser did not handle CRL distribution points with empty DP or URI correctly. A malicious or buggy certificate can result into segfault. Vulnerability (TALOS-2018-0758) reported by Colin Read and Nicolas Edet of Cisco.

bpo-34812 [https://bugs.python.org/issue?@action=redirect&bpo=34812]: The -I command line option (run Python in isolated mode) is now also copied by the multiprocessing and distutils modules when spawning child processes. Previously, only -E and -s options (enabled by -I) were copied.

bpo-34791 [https://bugs.python.org/issue?@action=redirect&bpo=34791]: The xml.sax and xml.dom.domreg no longer use environment variables to override parser implementations when sys.flags.ignore_environment is set by -E or -I arguments.

bpo-17239 [https://bugs.python.org/issue?@action=redirect&bpo=17239]: The xml.sax and xml.dom.minidom parsers no longer processes external entities by default. External DTD and ENTITY declarations no longer load files or create network connections.

bpo-34623 [https://bugs.python.org/issue?@action=redirect&bpo=34623]: CVE 2018-14647 [https://www.cve.org/CVERecord?id=CVE-2018-14647]: The C accelerated _elementtree module now initializes hash randomization salt from _Py_HashSecret instead of libexpat's default CSPRNG.

bpo-34405 [https://bugs.python.org/issue?@action=redirect&bpo=34405]: Updated to OpenSSL 1.1.0i for Windows builds.

bpo-33871 [https://bugs.python.org/issue?@action=redirect&bpo=33871]: Fixed sending the part of the file in os.sendfile() on macOS. Using the trailers argument could cause sending more bytes from the input file than was specified.

bpo-32533 [https://bugs.python.org/issue?@action=redirect&bpo=32533]: Fixed thread-safety of error handling in _ssl.

bpo-33136 [https://bugs.python.org/issue?@action=redirect&bpo=33136]: Harden ssl module against LibreSSL CVE 2018-8970 [https://www.cve.org/CVERecord?id=CVE-2018-8970]. X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new test ensures that NULL bytes are not allowed.

bpo-33001 [https://bugs.python.org/issue?@action=redirect&bpo=33001]: Minimal fix to prevent buffer overrun in os.symlink on Windows

bpo-32981 [https://bugs.python.org/issue?@action=redirect&bpo=32981]: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE 2018-1060 [https://www.cve.org/CVERecord?id=CVE-2018-1060] and CVE 2018-1061 [https://www.cve.org/CVERecord?id=CVE-2018-1061]. Patch by Jamie Davis.

bpo-28414 [https://bugs.python.org/issue?@action=redirect&bpo=28414]: The ssl module now allows users to perform their own IDN en/decoding when using SNI.

Core and Builtins

bpo-35877 [https://bugs.python.org/issue?@action=redirect&bpo=35877]: Make parenthesis optional for named expressions in while statement. Patch by Karthikeyan Singaravelan.

bpo-35814 [https://bugs.python.org/issue?@action=redirect&bpo=35814]: Allow same right hand side expressions in annotated assignments as in normal ones. In particular, x: Tuple[int, int] = 1, 2 (without parentheses on the right) is now allowed.

bpo-35766 [https://bugs.python.org/issue?@action=redirect&bpo=35766]: Add the option to parse PEP 484 type comments in the ast module. (Off by default.) This is merging the key functionality of the third party fork thereof, [typed_ast](https://github.com/python/typed_ast).

bpo-35713 [https://bugs.python.org/issue?@action=redirect&bpo=35713]: Reorganize Python initialization to get working exceptions and sys.stderr earlier.

bpo-33416 [https://bugs.python.org/issue?@action=redirect&bpo=33416]: Add end line and end column position information to the Python AST nodes. This is a C-level backwards incompatible change.

bpo-35720 [https://bugs.python.org/issue?@action=redirect&bpo=35720]: Fixed a minor memory leak in pymain_parse_cmdline_impl function in Modules/main.c

bpo-35634 [https://bugs.python.org/issue?@action=redirect&bpo=35634]: func(**kwargs) will now raise an error when kwargs is a mapping containing multiple entries with the same key. An error was already raised when other keyword arguments are passed before **kwargs since Python 3.6.

bpo-35623 [https://bugs.python.org/issue?@action=redirect&bpo=35623]: Fix a crash when sorting very long lists. Patch by Stephan Hohe.

bpo-35214 [https://bugs.python.org/issue?@action=redirect&bpo=35214]: clang Memory Sanitizer build instrumentation was added to work around false positives from posix, socket, time, test_io, and test_faulthandler.

bpo-35560 [https://bugs.python.org/issue?@action=redirect&bpo=35560]: Fix an assertion error in format() in debug build for floating-point formatting with "n" format, zero padding and small width. Release build is not impacted. Patch by Karthikeyan Singaravelan.

bpo-35552 [https://bugs.python.org/issue?@action=redirect&bpo=35552]: Format characters %s and %V in PyUnicode_FromFormat() and %s in PyBytes_FromFormat() no longer read memory past the limit if precision is specified.

bpo-35504 [https://bugs.python.org/issue?@action=redirect&bpo=35504]: Fix segfaults and SystemErrors when deleting certain attributes. Patch by Zackery Spytz.

bpo-35504 [https://bugs.python.org/issue?@action=redirect&bpo=35504]: Fixed a SystemError when delete the characters_written attribute of an OSError.

bpo-35494 [https://bugs.python.org/issue?@action=redirect&bpo=35494]: Improved syntax error messages for unbalanced parentheses in f-string.

bpo-35444 [https://bugs.python.org/issue?@action=redirect&bpo=35444]: Fixed error handling in pickling methods when fail to look up builtin "getattr". Sped up pickling iterators.

bpo-35436 [https://bugs.python.org/issue?@action=redirect&bpo=35436]: Fix various issues with memory allocation error handling. Patch by Zackery Spytz.

bpo-35423 [https://bugs.python.org/issue?@action=redirect&bpo=35423]: Separate the signal handling trigger in the eval loop from the "pending calls" machinery. There is no semantic change and the difference in performance is insignificant.

bpo-35357 [https://bugs.python.org/issue?@action=redirect&bpo=35357]: Internal attributes' names of unittest.mock._Call and unittest.mock.MagicProxy (name, parent & from_kall) are now prefixed with _mock_ in order to prevent clashes with widely used object attributes. Fixed minor typo in test function name.

bpo-35372 [https://bugs.python.org/issue?@action=redirect&bpo=35372]: Fixed the code page decoder for input longer than 2 GiB containing undecodable bytes.

bpo-35336 [https://bugs.python.org/issue?@action=redirect&bpo=35336]: Fix PYTHONCOERCECLOCALE=1 environment variable: only coerce the C locale if the LC_CTYPE locale is "C".

bpo-31241 [https://bugs.python.org/issue?@action=redirect&bpo=31241]: The lineno and col_offset attributes of AST nodes for list comprehensions, generator expressions and tuples are now point to the opening parenthesis or square brace. For tuples without parenthesis they point to the position of the first item.

bpo-33954 [https://bugs.python.org/issue?@action=redirect&bpo=33954]: For str.format(), float.__format__() and complex.__format__() methods for non-ASCII decimal point when using the "n" formatter.

bpo-35269 [https://bugs.python.org/issue?@action=redirect&bpo=35269]: Fix a possible segfault involving a newly created coroutine. Patch by Zackery Spytz.

bpo-35224 [https://bugs.python.org/issue?@action=redirect&bpo=35224]: Implement PEP 572 [https://peps.python.org/pep-0572/] (assignment expressions). Patch by Emily Morehouse.

bpo-32492 [https://bugs.python.org/issue?@action=redirect&bpo=32492]: Speed up namedtuple() attribute access by 1.6x using a C fast-path for the name descriptors. Patch by Pablo Galindo.

bpo-35214 [https://bugs.python.org/issue?@action=redirect&bpo=35214]: Fixed an out of bounds memory access when parsing a truncated unicode escape sequence at the end of a string such as '\N'. It would read one byte beyond the end of the memory allocation.

bpo-35214 [https://bugs.python.org/issue?@action=redirect&bpo=35214]: The interpreter and extension modules have had annotations added so that they work properly under clang's Memory Sanitizer. A new configure flag --with-memory-sanitizer has been added to make test builds of this nature easier to perform.

bpo-35193 [https://bugs.python.org/issue?@action=redirect&bpo=35193]: Fix an off by one error in the bytecode peephole optimizer where it could read bytes beyond the end of bounds of an array when removing unreachable code. This bug was present in every release of Python 3.6 and 3.7 until now.

bpo-35169 [https://bugs.python.org/issue?@action=redirect&bpo=35169]: Improved error messages for forbidden assignments.

bpo-34022 [https://bugs.python.org/issue?@action=redirect&bpo=34022]: Fix handling of hash-based bytecode files in zipimport. Patch by Elvis Pranskevichus.

bpo-28401 [https://bugs.python.org/issue?@action=redirect&bpo=28401]: Debug builds will no longer to attempt to import extension modules built for the ABI as they were never compatible to begin with. Patch by Stefano Rivera.

bpo-29341 [https://bugs.python.org/issue?@action=redirect&bpo=29341]: Clarify in the docstrings of os methods that path-like objects are also accepted as input parameters.

bpo-35050 [https://bugs.python.org/issue?@action=redirect&bpo=35050]: socket: Fix off-by-one bug in length check for AF_ALG name and type.

bpo-29743 [https://bugs.python.org/issue?@action=redirect&bpo=29743]: Raise ValueError instead of OverflowError in case of a negative _length_ in a ctypes.Array subclass. Also raise TypeError instead of AttributeError for non-integer _length_. Original patch by Oren Milman.

bpo-16806 [https://bugs.python.org/issue?@action=redirect&bpo=16806]: Fix lineno and col_offset for multi-line string tokens.

bpo-35029 [https://bugs.python.org/issue?@action=redirect&bpo=35029]: SyntaxWarning raised as an exception at code generation time will be now replaced with a SyntaxError for better error reporting.

bpo-34983 [https://bugs.python.org/issue?@action=redirect&bpo=34983]: Expose symtable.Symbol.is_nonlocal() in the symtable module. Patch by Pablo Galindo.

bpo-34974 [https://bugs.python.org/issue?@action=redirect&bpo=34974]: bytes and bytearray constructors no longer convert unexpected exceptions (e.g. MemoryError and KeyboardInterrupt) to TypeError.

bpo-34939 [https://bugs.python.org/issue?@action=redirect&bpo=34939]: Allow annotated names in module namespace that are declared global before the annotation happens. Patch by Pablo Galindo.

bpo-34973 [https://bugs.python.org/issue?@action=redirect&bpo=34973]: Fixed crash in bytes() when the list argument is mutated while it is iterated.

bpo-34876 [https://bugs.python.org/issue?@action=redirect&bpo=34876]: The lineno and col_offset attributes of the AST for decorated function and class refer now to the position of the corresponding def, async def and class instead of the position of the first decorator. This leads to more correct line reporting in tracing. This is the only case when the position of child AST nodes can precede the position of the parent AST node.

bpo-34879 [https://bugs.python.org/issue?@action=redirect&bpo=34879]: Fix a possible null pointer dereference in bytesobject.c. Patch by Zackery Spytz.

bpo-34784 [https://bugs.python.org/issue?@action=redirect&bpo=34784]: Fix the implementation of PyStructSequence_NewType in order to create heap allocated StructSequences.

bpo-32912 [https://bugs.python.org/issue?@action=redirect&bpo=32912]: A SyntaxWarning is now emitted instead of a DeprecationWarning for invalid escape sequences in string and bytes literals.

bpo-34854 [https://bugs.python.org/issue?@action=redirect&bpo=34854]: Fixed a crash in compiling string annotations containing a lambda with a keyword-only argument that doesn't have a default value.

bpo-34850 [https://bugs.python.org/issue?@action=redirect&bpo=34850]: The compiler now produces a SyntaxWarning when identity checks (is and is not) are used with certain types of literals (e.g. strings, ints). These can often work by accident in CPython, but are not guaranteed by the language spec. The warning advises users to use equality tests (== and !=) instead.

bpo-34824 [https://bugs.python.org/issue?@action=redirect&bpo=34824]: Fix a possible null pointer dereference in Modules/_ssl.c. Patch by Zackery Spytz.

bpo-30156 [https://bugs.python.org/issue?@action=redirect&bpo=30156]: The C function property_descr_get() uses a "cached" tuple to optimize function calls. But this tuple can be discovered in debug mode with sys.getobjects(). Remove the optimization, it's not really worth it and it causes 3 different crashes last years.

bpo-34762 [https://bugs.python.org/issue?@action=redirect&bpo=34762]: Fix contextvars C API to use PyObject* pointer types.

bpo-34751 [https://bugs.python.org/issue?@action=redirect&bpo=34751]: The hash function for tuples is now based on xxHash which gives better collision results on (formerly) pathological cases. Additionally, on 64-bit systems it improves tuple hashes in general. Patch by Jeroen Demeyer with substantial contributions by Tim Peters.

bpo-34735 [https://bugs.python.org/issue?@action=redirect&bpo=34735]: Fix a memory leak in Modules/timemodule.c. Patch by Zackery Spytz.

bpo-34683 [https://bugs.python.org/issue?@action=redirect&bpo=34683]: Fixed a bug where some SyntaxError error pointed to locations that were off-by-one.

bpo-34651 [https://bugs.python.org/issue?@action=redirect&bpo=34651]: Only allow the main interpreter to fork. The avoids the possibility of affecting the main interpreter, which is critical to operation of the runtime.

bpo-34653 [https://bugs.python.org/issue?@action=redirect&bpo=34653]: Remove unused function PyParser_SimpleParseStringFilename.

bpo-32236 [https://bugs.python.org/issue?@action=redirect&bpo=32236]: Warn that line buffering is not supported if open() is called with binary mode and buffering=1.

bpo-34641 [https://bugs.python.org/issue?@action=redirect&bpo=34641]: Further restrict the syntax of the left-hand side of keyword arguments in function calls. In particular, f((keyword)=arg) is now disallowed.

bpo-34637 [https://bugs.python.org/issue?@action=redirect&bpo=34637]: Make the start argument to sum() visible as a keyword argument.

bpo-1621 [https://bugs.python.org/issue?@action=redirect&bpo=1621]: Do not assume signed integer overflow behavior (C undefined behavior) when performing set hash table resizing.

bpo-34588 [https://bugs.python.org/issue?@action=redirect&bpo=34588]: Fix an off-by-one in the recursive call pruning feature of traceback formatting.

bpo-34485 [https://bugs.python.org/issue?@action=redirect&bpo=34485]: On Windows, the LC_CTYPE is now set to the user preferred locale at startup. Previously, the LC_CTYPE locale was "C" at startup, but changed when calling setlocale(LC_CTYPE, "") or setlocale(LC_ALL, "").

bpo-34485 [https://bugs.python.org/issue?@action=redirect&bpo=34485]: Standard streams like sys.stdout now use the "surrogateescape" error handler, instead of "strict", on the POSIX locale (when the C locale is not coerced and the UTF-8 Mode is disabled).

bpo-34485 [https://bugs.python.org/issue?@action=redirect&bpo=34485]: Fix the error handler of standard streams like sys.stdout: PYTHONIOENCODING=":" is now ignored instead of setting the error handler to "strict".

bpo-34485 [https://bugs.python.org/issue?@action=redirect&bpo=34485]: Python now gets the locale encoding with C code to initialize the encoding of standard streams like sys.stdout. Moreover, the encoding is now initialized to the Python codec name to get a normalized encoding name and to ensure that the codec is loaded. The change avoids importing _bootlocale and _locale modules at startup by default.

bpo-34527 [https://bugs.python.org/issue?@action=redirect&bpo=34527]: On FreeBSD, Py_DecodeLocale() and Py_EncodeLocale() now also forces the ASCII encoding if the LC_CTYPE locale is "POSIX", not only if the LC_CTYPE locale is "C".

bpo-34527 [https://bugs.python.org/issue?@action=redirect&bpo=34527]: The UTF-8 Mode is now also enabled by the "POSIX" locale, not only by the "C" locale.

bpo-34403 [https://bugs.python.org/issue?@action=redirect&bpo=34403]: On HP-UX with C or POSIX locale, sys.getfilesystemencoding() now returns "ascii" instead of "roman8" (when the UTF-8 Mode is disabled and the C locale is not coerced).

bpo-34523 [https://bugs.python.org/issue?@action=redirect&bpo=34523]: The Python filesystem encoding is now read earlier during the Python initialization.

bpo-12458 [https://bugs.python.org/issue?@action=redirect&bpo=12458]: Tracebacks show now correct line number for subexpressions in multiline expressions. Tracebacks show now the line number of the first line for multiline expressions instead of the line number of the last subexpression.

bpo-34408 [https://bugs.python.org/issue?@action=redirect&bpo=34408]: Prevent a null pointer dereference and resource leakage in PyInterpreterState_New().

bpo-34400 [https://bugs.python.org/issue?@action=redirect&bpo=34400]: Fix undefined behavior in parsetok.c. Patch by Zackery Spytz.

bpo-33073 [https://bugs.python.org/issue?@action=redirect&bpo=33073]: Added as_integer_ratio to ints to make them more interoperable with floats.

bpo-34377 [https://bugs.python.org/issue?@action=redirect&bpo=34377]: Update valgrind suppression list to use _PyObject_Free/_PyObject_Realloc instead of PyObject_Free/PyObject_Realloc.

bpo-34353 [https://bugs.python.org/issue?@action=redirect&bpo=34353]: Added the "socket" option in the stat.filemode() Python implementation to match the C implementation.

bpo-34320 [https://bugs.python.org/issue?@action=redirect&bpo=34320]: Fix dict(od) didn't copy iteration order of OrderedDict.

bpo-34113 [https://bugs.python.org/issue?@action=redirect&bpo=34113]: Fixed crash on debug builds when opcode stack was adjusted with negative numbers. Patch by Constantin Petrisor.

bpo-34100 [https://bugs.python.org/issue?@action=redirect&bpo=34100]: Compiler now merges constants in tuples and frozensets recursively. Code attributes like co_names are merged too.

bpo-34151 [https://bugs.python.org/issue?@action=redirect&bpo=34151]: Performance of list concatenation, repetition and slicing operations is slightly improved. Patch by Sergey Fedoseev.

bpo-34170 [https://bugs.python.org/issue?@action=redirect&bpo=34170]: -X dev: it is now possible to override the memory allocator using PYTHONMALLOC even if the developer mode is enabled.

bpo-33237 [https://bugs.python.org/issue?@action=redirect&bpo=33237]: Improved AttributeError message for partially initialized module.

bpo-34149 [https://bugs.python.org/issue?@action=redirect&bpo=34149]: Fix min and max functions to get default behavior when key is None.

bpo-34125 [https://bugs.python.org/issue?@action=redirect&bpo=34125]: Profiling of unbound built-in methods now works when **kwargs is given.

bpo-34141 [https://bugs.python.org/issue?@action=redirect&bpo=34141]: Optimized pickling atomic types (None, bool, int, float, bytes, str).

bpo-34126 [https://bugs.python.org/issue?@action=redirect&bpo=34126]: Fix crashes when profiling certain invalid calls of unbound methods. Patch by Jeroen Demeyer.

bpo-24618 [https://bugs.python.org/issue?@action=redirect&bpo=24618]: Fixed reading invalid memory when create the code object with too small varnames tuple or too large argument counts.

bpo-34068 [https://bugs.python.org/issue?@action=redirect&bpo=34068]: In io.IOBase.close(), ensure that the closed attribute is not set with a live exception. Patch by Zackery Spytz and Serhiy Storchaka.

bpo-34087 [https://bugs.python.org/issue?@action=redirect&bpo=34087]: Fix buffer overflow while converting unicode to numeric values.

bpo-34080 [https://bugs.python.org/issue?@action=redirect&bpo=34080]: Fixed a memory leak in the compiler when it raised some uncommon errors during tokenizing.

bpo-34066 [https://bugs.python.org/issue?@action=redirect&bpo=34066]: Disabled interruption by Ctrl-C between calling open() and entering a with block in with open().

bpo-34042 [https://bugs.python.org/issue?@action=redirect&bpo=34042]: Fix dict.copy() to maintain correct total refcount (as reported by sys.gettotalrefcount()).

bpo-33418 [https://bugs.python.org/issue?@action=redirect&bpo=33418]: Fix potential memory leak in function object when it creates reference cycle.

bpo-33985 [https://bugs.python.org/issue?@action=redirect&bpo=33985]: Implement contextvars.ContextVar.name attribute.

bpo-33956 [https://bugs.python.org/issue?@action=redirect&bpo=33956]: Update vendored Expat library copy to version 2.2.5.

bpo-24596 [https://bugs.python.org/issue?@action=redirect&bpo=24596]: Decref the module object in PyRun_SimpleFileExFlags() before calling PyErr_Print(). Patch by Zackery Spytz.

bpo-33451 [https://bugs.python.org/issue?@action=redirect&bpo=33451]: Close directly executed pyc files before calling PyEval_EvalCode().

bpo-1617161 [https://bugs.python.org/issue?@action=redirect&bpo=1617161]: The hash of BuiltinMethodType instances (methods of built-in classes) now depends on the hash of the identity of __self__ instead of its value. The hash and equality of ModuleType and MethodWrapperType instances (methods of user-defined classes and some methods of built-in classes like str.__add__) now depend on the hash and equality of the identity of __self__ instead of its value. MethodWrapperType instances no longer support ordering.

bpo-33824 [https://bugs.python.org/issue?@action=redirect&bpo=33824]: Fix "LC_ALL=C python3.7 -V": reset properly the command line parser when the encoding changes after reading the Python configuration.

bpo-33803 [https://bugs.python.org/issue?@action=redirect&bpo=33803]: Fix a crash in hamt.c caused by enabling GC tracking for an object that hadn't all of its fields set to NULL.

bpo-33738 [https://bugs.python.org/issue?@action=redirect&bpo=33738]: Seven macro incompatibilities with the Limited API were fixed, and the macros PyIter_Check(), PyIndex_Check() and PyExceptionClass_Name() were added as functions. A script for automatic macro checks was added.

bpo-33786 [https://bugs.python.org/issue?@action=redirect&bpo=33786]: Fix asynchronous generators to handle GeneratorExit in athrow() correctly

bpo-30167 [https://bugs.python.org/issue?@action=redirect&bpo=30167]: PyRun_SimpleFileExFlags removes __cached__ from module in addition to __file__.

bpo-33706 [https://bugs.python.org/issue?@action=redirect&bpo=33706]: Fix a crash in Python initialization when parsing the command line options. Thanks Christoph Gohlke for the bug report and the fix!

bpo-33597 [https://bugs.python.org/issue?@action=redirect&bpo=33597]: Reduce PyGC_Head size from 3 words to 2 words.

bpo-30654 [https://bugs.python.org/issue?@action=redirect&bpo=30654]: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

bpo-33622 [https://bugs.python.org/issue?@action=redirect&bpo=33622]: Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc.garbage list. PyGC_Collect() can now be called when an exception is set and preserves it.

bpo-33462 [https://bugs.python.org/issue?@action=redirect&bpo=33462]: Make dict and dict views reversible. Patch by Rémi Lapeyre.

bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722]: A RuntimeError is now raised when the custom metaclass doesn't provide the __classcell__ entry in the namespace passed to type.__new__. A DeprecationWarning was emitted in Python 3.6--3.7.

bpo-33499 [https://bugs.python.org/issue?@action=redirect&bpo=33499]: Add PYTHONPYCACHEPREFIX environment variable and -X pycache_prefix command-line option to set an alternate root directory for writing module bytecode cache files.

bpo-25711 [https://bugs.python.org/issue?@action=redirect&bpo=25711]: The zipimport module has been rewritten in pure Python.

bpo-33509 [https://bugs.python.org/issue?@action=redirect&bpo=33509]: Fix module_globals parameter of warnings.warn_explicit(): don't crash if module_globals is not a dict.

bpo-31849 [https://bugs.python.org/issue?@action=redirect&bpo=31849]: Fix signed/unsigned comparison warning in pyhash.c.

bpo-33475 [https://bugs.python.org/issue?@action=redirect&bpo=33475]: Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation.

bpo-20104 [https://bugs.python.org/issue?@action=redirect&bpo=20104]: Added support for the setpgroup, resetids, setsigmask, setsigdef and scheduler parameters of posix_spawn. Patch by Pablo Galindo.

bpo-33391 [https://bugs.python.org/issue?@action=redirect&bpo=33391]: Fix a leak in set_symmetric_difference().

bpo-33363 [https://bugs.python.org/issue?@action=redirect&bpo=33363]: Raise a SyntaxError for async with and async for statements outside of async functions.

bpo-28055 [https://bugs.python.org/issue?@action=redirect&bpo=28055]: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

bpo-33128 [https://bugs.python.org/issue?@action=redirect&bpo=33128]: Fix a bug that causes PathFinder to appear twice on sys.meta_path. Patch by Pablo Galindo Salgado.

bpo-33331 [https://bugs.python.org/issue?@action=redirect&bpo=33331]: Modules imported last are now cleared first at interpreter shutdown.

bpo-33312 [https://bugs.python.org/issue?@action=redirect&bpo=33312]: Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by adjusting how the internal struct _dictkeysobject shared keys structure is declared.

bpo-33305 [https://bugs.python.org/issue?@action=redirect&bpo=33305]: Improved syntax error messages for invalid numerical literals.

bpo-33306 [https://bugs.python.org/issue?@action=redirect&bpo=33306]: Improved syntax error messages for unbalanced parentheses.

bpo-33234 [https://bugs.python.org/issue?@action=redirect&bpo=33234]: The list constructor will pre-size and not over-allocate when the input length is known.

bpo-33270 [https://bugs.python.org/issue?@action=redirect&bpo=33270]: Intern the names for all anonymous code objects. Patch by Zackery Spytz.

bpo-30455 [https://bugs.python.org/issue?@action=redirect&bpo=30455]: The C and Python code and the documentation related to tokens are now generated from a single source file Grammar/Tokens.

bpo-33176 [https://bugs.python.org/issue?@action=redirect&bpo=33176]: Add a toreadonly() method to memoryviews.

bpo-33231 [https://bugs.python.org/issue?@action=redirect&bpo=33231]: Fix potential memory leak in normalizestring().

bpo-33205 [https://bugs.python.org/issue?@action=redirect&bpo=33205]: Change dict growth function from round_up_to_power_2(used*2+hashtable_size/2) to round_up_to_power_2(used*3). Previously, dict is shrunk only when used == 0. Now dict has more chance to be shrunk.

bpo-29922 [https://bugs.python.org/issue?@action=redirect&bpo=29922]: Improved error messages in 'async with' when __aenter__() or __aexit__() return non-awaitable object.

bpo-33199 [https://bugs.python.org/issue?@action=redirect&bpo=33199]: Fix ma_version_tag in dict implementation is uninitialized when copying from key-sharing dict.

bpo-33053 [https://bugs.python.org/issue?@action=redirect&bpo=33053]: When using the -m switch, sys.path[0] is now explicitly expanded as the starting working directory, rather than being left as the empty path (which allows imports from the current working directory at the time of the import)

bpo-33138 [https://bugs.python.org/issue?@action=redirect&bpo=33138]: Changed standard error message for non-pickleable and non-copyable types. It now says "cannot pickle" instead of "can't pickle" or "cannot serialize".

bpo-33018 [https://bugs.python.org/issue?@action=redirect&bpo=33018]: Improve consistency of errors raised by issubclass() when called with a non-class and an abstract base class as the first and second arguments, respectively. Patch by Josh Bronson.

bpo-33083 [https://bugs.python.org/issue?@action=redirect&bpo=33083]: math.factorial no longer accepts arguments that are not int-like. Patch by Pablo Galindo.

bpo-33041 [https://bugs.python.org/issue?@action=redirect&bpo=33041]: Added new opcode END_ASYNC_FOR and fixes the following issues:

Setting global StopAsyncIteration no longer breaks async for loops.

Jumping into an async for loop is now disabled.

Jumping out of an async for loop no longer corrupts the stack.

bpo-25750 [https://bugs.python.org/issue?@action=redirect&bpo=25750]: Fix rare Python crash due to bad refcounting in type_getattro() if a descriptor deletes itself from the class. Patch by Jeroen Demeyer.

bpo-33041 [https://bugs.python.org/issue?@action=redirect&bpo=33041]: Fixed bytecode generation for "async for" with a complex target. A StopAsyncIteration raised on assigning or unpacking will be now propagated instead of stopping the iteration.

bpo-33026 [https://bugs.python.org/issue?@action=redirect&bpo=33026]: Fixed jumping out of "with" block by setting f_lineno.

bpo-33005 [https://bugs.python.org/issue?@action=redirect&bpo=33005]: Fix a crash on fork when using a custom memory allocator (ex: using PYTHONMALLOC env var). _PyGILState_Reinit() and _PyInterpreterState_Enable() now use the default RAW memory allocator to allocate a new interpreters mutex on fork.

bpo-32911 [https://bugs.python.org/issue?@action=redirect&bpo=32911]: Due to unexpected compatibility issues discovered during downstream beta testing, reverted bpo-29463 [https://bugs.python.org/issue?@action=redirect&bpo=29463]. docstring field is removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes which was added in 3.7a1. Docstring expression is restored as a first statement in their body. Based on patch by Inada Naoki.

bpo-17288 [https://bugs.python.org/issue?@action=redirect&bpo=17288]: Prevent jumps from 'return' and 'exception' trace events.

bpo-32946 [https://bugs.python.org/issue?@action=redirect&bpo=32946]: Importing names from already imported module with "from ... import ..." is now 30% faster if the module is not a package.

bpo-32932 [https://bugs.python.org/issue?@action=redirect&bpo=32932]: Make error message more revealing when there are non-str objects in __all__.

bpo-32925 [https://bugs.python.org/issue?@action=redirect&bpo=32925]: Optimized iterating and containing test for literal lists consisting of non-constants: x in [a, b] and for x in [a, b]. The case of all constant elements already was optimized.

bpo-32889 [https://bugs.python.org/issue?@action=redirect&bpo=32889]: Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range.

bpo-32836 [https://bugs.python.org/issue?@action=redirect&bpo=32836]: Don't use temporary variables in cases of list/dict/set comprehensions

bpo-31356 [https://bugs.python.org/issue?@action=redirect&bpo=31356]: Remove the new API added in bpo-31356 [https://bugs.python.org/issue?@action=redirect&bpo=31356] (gc.ensure_disabled() context manager).

bpo-32305 [https://bugs.python.org/issue?@action=redirect&bpo=32305]: For namespace packages, ensure that both __file__ and __spec__.origin are set to None.

bpo-32303 [https://bugs.python.org/issue?@action=redirect&bpo=32303]: Make sure __spec__.loader matches __loader__ for namespace packages.

bpo-32711 [https://bugs.python.org/issue?@action=redirect&bpo=32711]: Fix the warning messages for Python/ast_unparse.c. Patch by Stéphane Wirtel

bpo-32583 [https://bugs.python.org/issue?@action=redirect&bpo=32583]: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

bpo-32489 [https://bugs.python.org/issue?@action=redirect&bpo=32489]: A continue statement is now allowed in the finally clause.

bpo-17611 [https://bugs.python.org/issue?@action=redirect&bpo=17611]: Simplified the interpreter loop by moving the logic of unrolling the stack of blocks into the compiler. The compiler emits now explicit instructions for adjusting the stack of values and calling the cleaning up code for break, continue and return.

Removed opcodes BREAK_LOOP, CONTINUE_LOOP, SETUP_LOOP and SETUP_EXCEPT. Added new opcodes ROT_FOUR, BEGIN_FINALLY and CALL_FINALLY and POP_FINALLY. Changed the behavior of END_FINALLY and WITH_CLEANUP_START.

bpo-32285 [https://bugs.python.org/issue?@action=redirect&bpo=32285]: New function unicodedata.is_normalized, which can check whether a string is in a specific normal form.

bpo-10544 [https://bugs.python.org/issue?@action=redirect&bpo=10544]: Yield expressions are now disallowed in comprehensions and generator expressions except the expression for the outermost iterable.

bpo-32117 [https://bugs.python.org/issue?@action=redirect&bpo=32117]: Iterable unpacking is now allowed without parentheses in yield and return statements, e.g. yield 1, 2, 3, *rest. Thanks to David Cuthbert for the change and Jordan Chapman for added tests.

bpo-31902 [https://bugs.python.org/issue?@action=redirect&bpo=31902]: Fix the col_offset attribute for ast nodes ast.AsyncFor, ast.AsyncFunctionDef, and ast.AsyncWith. Previously, col_offset pointed to the keyword after async.

bpo-25862 [https://bugs.python.org/issue?@action=redirect&bpo=25862]: Fix assertion failures in the tell() method of io.TextIOWrapper. Patch by Zackery Spytz.

bpo-21983 [https://bugs.python.org/issue?@action=redirect&bpo=21983]: Fix a crash in ctypes.cast() in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

bpo-31577 [https://bugs.python.org/issue?@action=redirect&bpo=31577]: Fix a crash in os.utime() in case of a bad ns argument. Patch by Oren Milman.

bpo-29832 [https://bugs.python.org/issue?@action=redirect&bpo=29832]: Remove references to 'getsockaddrarg' from various socket error messages. Patch by Oren Milman.

Library

bpo-35845 [https://bugs.python.org/issue?@action=redirect&bpo=35845]: Add 'order' parameter to memoryview.tobytes().

bpo-35864 [https://bugs.python.org/issue?@action=redirect&bpo=35864]: The _asdict() method for collections.namedtuple now returns a regular dict instead of an OrderedDict.

bpo-35537 [https://bugs.python.org/issue?@action=redirect&bpo=35537]: An ExitStack is now used internally within subprocess.Popen to clean up pipe file handles. No behavior change in normal operation. But if closing one handle were ever to cause an exception, the others will now be closed instead of leaked. (patch by Giampaolo Rodola)

bpo-35847 [https://bugs.python.org/issue?@action=redirect&bpo=35847]: RISC-V needed the CTYPES_PASS_BY_REF_HACK. Fixes ctypes Structure test_pass_by_value.

bpo-35813 [https://bugs.python.org/issue?@action=redirect&bpo=35813]: Shared memory submodule added to multiprocessing to avoid need for serialization between processes

bpo-35780 [https://bugs.python.org/issue?@action=redirect&bpo=35780]: Fix lru_cache() errors arising in recursive, reentrant, or multi-threaded code. These errors could result in orphan links and in the cache being trapped in a state with fewer than the specified maximum number of links. Fix handling of negative maxsize which should have been treated as zero. Fix errors in toggling the "full" status flag. Fix misordering of links when errors are encountered. Sync-up the C code and pure Python code for the space saving path in functions with a single positional argument. In this common case, the space overhead of an lru cache entry is reduced by almost half. Fix counting of cache misses. In error cases, the miss count was out of sync with the actual number of times the underlying user function was called.

bpo-35537 [https://bugs.python.org/issue?@action=redirect&bpo=35537]: os.posix_spawn() and os.posix_spawnp() now have a setsid parameter.

bpo-23846 [https://bugs.python.org/issue?@action=redirect&bpo=23846]: asyncio.ProactorEventLoop now catches and logs send errors when the self-pipe is full.

bpo-34323 [https://bugs.python.org/issue?@action=redirect&bpo=34323]: asyncio: Enhance IocpProactor.close() log: wait 1 second before the first log, then log every second. Log also the number of seconds since close() was called.

bpo-35674 [https://bugs.python.org/issue?@action=redirect&bpo=35674]: Add a new os.posix_spawnp() function. Patch by Joannah Nanjekye.

bpo-35733 [https://bugs.python.org/issue?@action=redirect&bpo=35733]: ast.Constant(boolean) no longer an instance of ast.Num. Patch by Anthony Sottile.

bpo-35726 [https://bugs.python.org/issue?@action=redirect&bpo=35726]: QueueHandler.prepare() now makes a copy of the record before modifying and enqueueing it, to avoid affecting other handlers in the chain.

bpo-35719 [https://bugs.python.org/issue?@action=redirect&bpo=35719]: Sped up multi-argument math functions atan2(), copysign(), remainder() and hypot() by 1.3--2.5 times.

bpo-35717 [https://bugs.python.org/issue?@action=redirect&bpo=35717]: Fix KeyError exception raised when using enums and compile. Patch contributed by Rémi Lapeyre.

bpo-35699 [https://bugs.python.org/issue?@action=redirect&bpo=35699]: Fixed detection of Visual Studio Build Tools 2017 in distutils

bpo-32710 [https://bugs.python.org/issue?@action=redirect&bpo=32710]: Fix memory leaks in asyncio ProactorEventLoop on overlapped operation failure.

bpo-35702 [https://bugs.python.org/issue?@action=redirect&bpo=35702]: The time.CLOCK_UPTIME_RAW constant is now available for macOS 10.12.

bpo-32710 [https://bugs.python.org/issue?@action=redirect&bpo=32710]: Fix a memory leak in asyncio in the ProactorEventLoop when ReadFile() or WSASend() overlapped operation fail immediately: release the internal buffer.

bpo-35682 [https://bugs.python.org/issue?@action=redirect&bpo=35682]: Fix asyncio.ProactorEventLoop.sendfile(): don't attempt to set the result of an internal future if it's already done.

bpo-35283 [https://bugs.python.org/issue?@action=redirect&bpo=35283]: Add a deprecated warning for the threading.Thread.isAlive() method. Patch by Donghee Na.

bpo-35664 [https://bugs.python.org/issue?@action=redirect&bpo=35664]: Improve operator.itemgetter() performance by 33% with optimized argument handling and with adding a fast path for the common case of a single non-negative integer index into a tuple (which is the typical use case in the standard library).

bpo-35643 [https://bugs.python.org/issue?@action=redirect&bpo=35643]: Fixed a SyntaxWarning: invalid escape sequence in Modules/_sha3/cleanup.py. Patch by Mickaël Schoentgen.

bpo-35619 [https://bugs.python.org/issue?@action=redirect&bpo=35619]: Improved support of custom data descriptors in help() and pydoc.

bpo-28503 [https://bugs.python.org/issue?@action=redirect&bpo=28503]: The crypt module now internally uses the crypt_r() library function instead of crypt() when available.

bpo-35614 [https://bugs.python.org/issue?@action=redirect&bpo=35614]: Fixed help() on metaclasses. Patch by Sanyam Khurana.

bpo-35568 [https://bugs.python.org/issue?@action=redirect&bpo=35568]: Expose raise(signum) as raise_signal

bpo-35588 [https://bugs.python.org/issue?@action=redirect&bpo=35588]: The floor division and modulo operations and the divmod() function on fractions.Fraction types are 2--4x faster. Patch by Stefan Behnel.

bpo-35585 [https://bugs.python.org/issue?@action=redirect&bpo=35585]: Speed-up building enums by value, e.g. http.HTTPStatus(200).

bpo-30561 [https://bugs.python.org/issue?@action=redirect&bpo=30561]: random.gammavariate(1.0, beta) now computes the same result as random.expovariate(1.0 / beta). This synchronizes the two algorithms and eliminates some idiosyncrasies in the old implementation. It does however produce a difference stream of random variables than it used to.

bpo-35537 [https://bugs.python.org/issue?@action=redirect&bpo=35537]: The subprocess module can now use the os.posix_spawn() function in some cases for better performance.

bpo-35526 [https://bugs.python.org/issue?@action=redirect&bpo=35526]: Delaying the 'joke' of barry_as_FLUFL.mandatory to Python version 4.0

bpo-35523 [https://bugs.python.org/issue?@action=redirect&bpo=35523]: Remove ctypes callback workaround: no longer create a callback at startup. Avoid SELinux alert on import ctypes and import uuid.

bpo-31784 [https://bugs.python.org/issue?@action=redirect&bpo=31784]: uuid.uuid1() now calls time.time_ns() rather than int(time.time() * 1e9).

bpo-35513 [https://bugs.python.org/issue?@action=redirect&bpo=35513]: TextTestRunner of unittest.runner now uses time.perf_counter() rather than time.time() to measure the execution time of a test: time.time() can go backwards, whereas time.perf_counter() is monotonic.

bpo-35502 [https://bugs.python.org/issue?@action=redirect&bpo=35502]: Fixed reference leaks in xml.etree.ElementTree.TreeBuilder in case of unfinished building of the tree (in particular when an error was raised during parsing XML).

bpo-35348 [https://bugs.python.org/issue?@action=redirect&bpo=35348]: Make platform.architecture() parsing of file command output more reliable: add the -b option to the file command to omit the filename, force the usage of the C locale, and search also the "shared object" pattern.

bpo-35491 [https://bugs.python.org/issue?@action=redirect&bpo=35491]: multiprocessing: Add Pool.__repr__() and enhance BaseProcess.__repr__() (add pid and parent pid) to ease debugging. Pool state constant values are now strings instead of integers, for example RUN value becomes 'RUN' instead of 0.

bpo-35477 [https://bugs.python.org/issue?@action=redirect&bpo=35477]: multiprocessing.Pool.__enter__() now fails if the pool is not running: with pool: fails if used more than once.

bpo-31446 [https://bugs.python.org/issue?@action=redirect&bpo=31446]: Copy command line that was passed to CreateProcessW since this function can change the content of the input buffer.

bpo-35471 [https://bugs.python.org/issue?@action=redirect&bpo=35471]: Python 2.4 dropped MacOS 9 support. The macpath module was deprecated in Python 3.7. The module is now removed.

bpo-23057 [https://bugs.python.org/issue?@action=redirect&bpo=23057]: Unblock Proactor event loop when keyboard interrupt is received on Windows

bpo-35052 [https://bugs.python.org/issue?@action=redirect&bpo=35052]: Fix xml.dom.minidom cloneNode() on a document with an entity: pass the correct arguments to the user data handler of an entity.

bpo-20239 [https://bugs.python.org/issue?@action=redirect&bpo=20239]: Allow repeated assignment deletion of unittest.mock.Mock attributes. Patch by Pablo Galindo.

bpo-17185 [https://bugs.python.org/issue?@action=redirect&bpo=17185]: Set __signature__ on mock for inspect to get signature. Patch by Karthikeyan Singaravelan.

bpo-35445 [https://bugs.python.org/issue?@action=redirect&bpo=35445]: Memory errors during creating posix.environ no longer ignored.

bpo-35415 [https://bugs.python.org/issue?@action=redirect&bpo=35415]: Validate fileno= argument to socket.socket().

bpo-35424 [https://bugs.python.org/issue?@action=redirect&bpo=35424]: multiprocessing.Pool destructor now emits ResourceWarning if the pool is still running.

bpo-35330 [https://bugs.python.org/issue?@action=redirect&bpo=35330]: When a Mock instance was used to wrap an object, if side_effect is used in one of the mocks of it methods, don't call the original implementation and return the result of using the side effect the same way that it is done with return_value.

bpo-35346 [https://bugs.python.org/issue?@action=redirect&bpo=35346]: Drop Mac OS 9 and Rhapsody support from the platform module. Rhapsody last release was in 2000. Mac OS 9 last release was in 2001.

bpo-10496 [https://bugs.python.org/issue?@action=redirect&bpo=10496]: check_environ() of distutils.utils now catches KeyError on calling pwd.getpwuid(): don't create the HOME environment variable in this case.

bpo-10496 [https://bugs.python.org/issue?@action=redirect&bpo=10496]: posixpath.expanduser() now returns the input path unchanged if the HOME environment variable is not set and the current user has no home directory (if the current user identifier doesn't exist in the password database). This change fix the site module if the current user doesn't exist in the password database (if the user has no home directory).

bpo-35389 [https://bugs.python.org/issue?@action=redirect&bpo=35389]: platform.libc_ver() now uses os.confstr('CS_GNU_LIBC_VERSION') if available and the executable parameter is not set.

bpo-35394 [https://bugs.python.org/issue?@action=redirect&bpo=35394]: Add empty slots to asyncio abstract protocols.

bpo-35310 [https://bugs.python.org/issue?@action=redirect&bpo=35310]: Fix a bug in select.select() where, in some cases, the file descriptor sequences were returned unmodified after a signal interruption, even though the file descriptors might not be ready yet. select.select() will now always return empty lists if a timeout has occurred. Patch by Oran Avraham.

bpo-35380 [https://bugs.python.org/issue?@action=redirect&bpo=35380]: Enable TCP_NODELAY on Windows for proactor asyncio event loop.

bpo-35341 [https://bugs.python.org/issue?@action=redirect&bpo=35341]: Add generic version of collections.OrderedDict to the typing module. Patch by Ismo Toijala.

bpo-35371 [https://bugs.python.org/issue?@action=redirect&bpo=35371]: Fixed possible crash in os.utime() on Windows when pass incorrect arguments.

bpo-35346 [https://bugs.python.org/issue?@action=redirect&bpo=35346]: platform.uname() now redirects stderr to os.devnull when running external programs like cmd /c ver.

bpo-35066 [https://bugs.python.org/issue?@action=redirect&bpo=35066]: Previously, calling the strftime() method on a datetime object with a trailing '%' in the format string would result in an exception. However, this only occurred when the datetime C module was being used; the python implementation did not match this behavior. Datetime is now PEP-399 compliant, and will not throw an exception on a trailing '%'.

bpo-35345 [https://bugs.python.org/issue?@action=redirect&bpo=35345]: The function platform.popen has been removed, it was deprecated since Python 3.3: use os.popen() instead.

bpo-35344 [https://bugs.python.org/issue?@action=redirect&bpo=35344]: On macOS, platform.platform() now uses platform.mac_ver(), if it returns a non-empty release string, to get the macOS version rather than the darwin version.

bpo-35312 [https://bugs.python.org/issue?@action=redirect&bpo=35312]: Make lib2to3.pgen2.parse.ParseError round-trip pickle-able. Patch by Anthony Sottile.

bpo-35308 [https://bugs.python.org/issue?@action=redirect&bpo=35308]: Fix regression in webbrowser where default browsers may be preferred over browsers in the BROWSER environment variable.

bpo-24746 [https://bugs.python.org/issue?@action=redirect&bpo=24746]: Avoid stripping trailing whitespace in doctest fancy diff. Original patch by R. David Murray & Jairo Trad. Enhanced by Sanyam Khurana.

bpo-28604 [https://bugs.python.org/issue?@action=redirect&bpo=28604]: locale.localeconv() now sets temporarily the LC_CTYPE locale to the LC_MONETARY locale if the two locales are different and monetary strings are non-ASCII. This temporary change affects other threads.

bpo-35277 [https://bugs.python.org/issue?@action=redirect&bpo=35277]: Update ensurepip to install pip 18.1 and setuptools 40.6.2.

bpo-24209 [https://bugs.python.org/issue?@action=redirect&bpo=24209]: Adds IPv6 support when invoking http.server directly.

bpo-35226 [https://bugs.python.org/issue?@action=redirect&bpo=35226]: Recursively check arguments when testing for equality of unittest.mock.call objects and add note that tracking of parameters used to create ancestors of mocks in mock_calls is not possible.

bpo-29564 [https://bugs.python.org/issue?@action=redirect&bpo=29564]: The warnings module now suggests to enable tracemalloc if the source is specified, the tracemalloc module is available, but tracemalloc is not tracing memory allocations.

bpo-35189 [https://bugs.python.org/issue?@action=redirect&bpo=35189]: Modify the following fnctl function to retry if interrupted by a signal (EINTR): flock, lockf, fnctl

bpo-30064 [https://bugs.python.org/issue?@action=redirect&bpo=30064]: Use add_done_callback() in sock_* asyncio API to unsubscribe reader/writer early on calcellation.

bpo-35186 [https://bugs.python.org/issue?@action=redirect&bpo=35186]: Removed the "built with" comment added when setup.py upload is used with either bdist_rpm or bdist_dumb.

bpo-35152 [https://bugs.python.org/issue?@action=redirect&bpo=35152]: Allow sending more than 2 GB at once on a multiprocessing connection on non-Windows systems.

bpo-35062 [https://bugs.python.org/issue?@action=redirect&bpo=35062]: Fix incorrect parsing of io.IncrementalNewlineDecoder's translate argument.

bpo-35065 [https://bugs.python.org/issue?@action=redirect&bpo=35065]: Remove StreamReaderProtocol._untrack_reader. The call to _untrack_reader is currently performed too soon, causing the protocol to forget about the reader before connection_lost can run and feed the EOF to the reader.

bpo-34160 [https://bugs.python.org/issue?@action=redirect&bpo=34160]: ElementTree and minidom now preserve the attribute order specified by the user.

bpo-35079 [https://bugs.python.org/issue?@action=redirect&bpo=35079]: Improve difflib.SequenceManager.get_matching_blocks doc by adding 'non-overlapping' and changing '!=' to '<'.

bpo-33710 [https://bugs.python.org/issue?@action=redirect&bpo=33710]: Deprecated l*gettext() functions and methods in the gettext module. They return encoded bytes instead of Unicode strings and are artifacts from Python 2 times. Also deprecated functions and methods related to setting the charset for l*gettext() functions and methods.

bpo-35017 [https://bugs.python.org/issue?@action=redirect&bpo=35017]: socketserver.BaseServer.serve_forever() now exits immediately if it's shutdown() method is called while it is polling for new events.

bpo-35024 [https://bugs.python.org/issue?@action=redirect&bpo=35024]: importlib no longer logs wrote <bytecode path> redundantly after (created|could not create) <bytecode path> is already logged. Patch by Quentin Agren.

bpo-35047 [https://bugs.python.org/issue?@action=redirect&bpo=35047]: unittest.mock now includes mock calls in exception messages if assert_not_called, assert_called_once, or assert_called_once_with fails. Patch by Petter Strandmark.

bpo-31047 [https://bugs.python.org/issue?@action=redirect&bpo=31047]: Fix ntpath.abspath regression where it didn't remove a trailing separator on Windows. Patch by Tim Graham.

bpo-35053 [https://bugs.python.org/issue?@action=redirect&bpo=35053]: tracemalloc now tries to update the traceback when an object is reused from a "free list" (optimization for faster object creation, used by the builtin list type for example).

bpo-31553 [https://bugs.python.org/issue?@action=redirect&bpo=31553]: Add the --json-lines option to json.tool. Patch by hongweipeng.

bpo-34794 [https://bugs.python.org/issue?@action=redirect&bpo=34794]: Fixed a leak in Tkinter when pass the Python wrapper around Tcl_Obj back to Tcl/Tk.

bpo-34909 [https://bugs.python.org/issue?@action=redirect&bpo=34909]: Enum: fix grandchildren subclassing when parent mixed with concrete data types.

bpo-35022 [https://bugs.python.org/issue?@action=redirect&bpo=35022]: unittest.mock.MagicMock now supports the __fspath__ method (from os.PathLike).

bpo-35008 [https://bugs.python.org/issue?@action=redirect&bpo=35008]: Fixed references leaks when call the __setstate__() method of xml.etree.ElementTree.Element in the C implementation for already initialized element.

bpo-23420 [https://bugs.python.org/issue?@action=redirect&bpo=23420]: Verify the value for the parameter '-s' of the cProfile CLI. Patch by Robert Kuska

bpo-33947 [https://bugs.python.org/issue?@action=redirect&bpo=33947]: dataclasses now handle recursive reprs without raising RecursionError.

bpo-34890 [https://bugs.python.org/issue?@action=redirect&bpo=34890]: Make inspect.iscoroutinefunction(), inspect.isgeneratorfunction() and inspect.isasyncgenfunction() work with functools.partial(). Patch by Pablo Galindo.

bpo-34521 [https://bugs.python.org/issue?@action=redirect&bpo=34521]: Use socket.CMSG_SPACE() to calculate ancillary data size instead of socket.CMSG_LEN() in multiprocessing.reduction.recvfds() as RFC 3542 [https://datatracker.ietf.org/doc/html/rfc3542.html] requires the use of the former for portable applications.

bpo-31522 [https://bugs.python.org/issue?@action=redirect&bpo=31522]: The mailbox.mbox.get_string function from_ parameter can now successfully be set to a non-default value.

bpo-34970 [https://bugs.python.org/issue?@action=redirect&bpo=34970]: Protect tasks weak set manipulation in asyncio.all_tasks()

bpo-34969 [https://bugs.python.org/issue?@action=redirect&bpo=34969]: gzip: Add --fast, --best on the gzip CLI, these parameters will be used for the fast compression method (quick) or the best method compress (slower, but smaller file). Also, change the default compression level to 6 (tradeoff).

bpo-16965 [https://bugs.python.org/issue?@action=redirect&bpo=16965]: The 2to3 execfile fixer now opens the file with mode 'rb'. Patch by Zackery Spytz.

bpo-34966 [https://bugs.python.org/issue?@action=redirect&bpo=34966]: pydoc now supports aliases not only to methods defined in the end class, but also to inherited methods. The docstring is not duplicated for aliases.

bpo-34926 [https://bugs.python.org/issue?@action=redirect&bpo=34926]: mimetypes.MimeTypes.guess_type() now accepts path-like object in addition to url strings. Patch by Mayank Asthana.

bpo-23831 [https://bugs.python.org/issue?@action=redirect&bpo=23831]: Add moveto() method to the tkinter.Canvas widget. Patch by Juliette Monsel.

bpo-34941 [https://bugs.python.org/issue?@action=redirect&bpo=34941]: Methods find(), findtext() and findall() of the Element class in the xml.etree.ElementTree module are now able to find children which are instances of Element subclasses.

bpo-32680 [https://bugs.python.org/issue?@action=redirect&bpo=32680]: smtplib.SMTP objects now always have a sock attribute present

bpo-34769 [https://bugs.python.org/issue?@action=redirect&bpo=34769]: Fix for async generators not finalizing when event loop is in debug mode and garbage collector runs in another thread.

bpo-34936 [https://bugs.python.org/issue?@action=redirect&bpo=34936]: Fix TclError in tkinter.Spinbox.selection_element(). Patch by Juliette Monsel.

bpo-34829 [https://bugs.python.org/issue?@action=redirect&bpo=34829]: Add methods selection_from, selection_range, selection_present and selection_to to the tkinter.Spinbox for consistency with the tkinter.Entry widget. Patch by Juliette Monsel.

bpo-34911 [https://bugs.python.org/issue?@action=redirect&bpo=34911]: Added secure_protocols argument to http.cookiejar.DefaultCookiePolicy to allow for tweaking of protocols and also to add support by default for wss, the secure websocket protocol.

bpo-34922 [https://bugs.python.org/issue?@action=redirect&bpo=34922]: Fixed integer overflow in the digest() and hexdigest() methods for the SHAKE algorithm in the hashlib module.

bpo-34925 [https://bugs.python.org/issue?@action=redirect&bpo=34925]: 25% speedup in argument parsing for the functions in the bisect module.

bpo-34900 [https://bugs.python.org/issue?@action=redirect&bpo=34900]: Fixed unittest.TestCase.debug() when used to call test methods with subtests. Patch by Bruno Oliveira.

bpo-34844 [https://bugs.python.org/issue?@action=redirect&bpo=34844]: logging.Formatter enhancement - Ensure styles and fmt matches in logging.Formatter - Added validate method in each format style class: StrFormatStyle, PercentStyle, StringTemplateStyle. - This method is called in the constructor of logging.Formatter class - Also re-raise the KeyError in the format method of each style class, so it would a bit clear that it's an error with the invalid format fields.

bpo-34897 [https://bugs.python.org/issue?@action=redirect&bpo=34897]: Adjust test.support.missing_compiler_executable check so that a nominal command name of "" is ignored. Patch by Michael Felt.

bpo-34871 [https://bugs.python.org/issue?@action=redirect&bpo=34871]: Fix inspect module polluted sys.modules when parsing __text_signature__ of callable.

bpo-34898 [https://bugs.python.org/issue?@action=redirect&bpo=34898]: Add mtime argument to gzip.compress for reproducible output. Patch by Guo Ci Teo.

bpo-28441 [https://bugs.python.org/issue?@action=redirect&bpo=28441]: On Cygwin and MinGW, ensure that sys.executable always includes the full filename in the path, including the .exe suffix (unless it is a symbolic link).

bpo-34866 [https://bugs.python.org/issue?@action=redirect&bpo=34866]: Adding max_num_fields to cgi.FieldStorage to make DOS attacks harder by limiting the number of MiniFieldStorage objects created by FieldStorage.

bpo-34711 [https://bugs.python.org/issue?@action=redirect&bpo=34711]: http.server ensures it reports HTTPStatus.NOT_FOUND when the local path ends with "/" and is not a directory, even if the underlying OS (e.g. AIX) accepts such paths as a valid file reference. Patch by Michael Felt.

bpo-34872 [https://bugs.python.org/issue?@action=redirect&bpo=34872]: Fix self-cancellation in C implementation of asyncio.Task

bpo-34849 [https://bugs.python.org/issue?@action=redirect&bpo=34849]: Don't log waiting for selector.select in asyncio loop iteration. The waiting is pretty normal for any asyncio program, logging its time just adds a noise to logs without any useful information provided.

bpo-34022 [https://bugs.python.org/issue?@action=redirect&bpo=34022]: The SOURCE_DATE_EPOCH environment variable no longer overrides the value of the invalidation_mode argument to py_compile.compile(), and determines its default value instead.

bpo-34819 [https://bugs.python.org/issue?@action=redirect&bpo=34819]: Use a monotonic clock to compute timeouts in Executor.map() and as_completed(), in order to prevent timeouts from deviating when the system clock is adjusted.

bpo-34758 [https://bugs.python.org/issue?@action=redirect&bpo=34758]: Add .wasm -> application/wasm to list of recognized file types and content type headers

bpo-34789 [https://bugs.python.org/issue?@action=redirect&bpo=34789]: xml.sax.make_parser() now accepts any iterable as its parser_list argument. Patch by Andrés Delfino.

bpo-34334 [https://bugs.python.org/issue?@action=redirect&bpo=34334]: In QueueHandler, clear exc_text from LogRecord to prevent traceback from being written twice.

bpo-34687 [https://bugs.python.org/issue?@action=redirect&bpo=34687]: On Windows, asyncio now uses ProactorEventLoop, instead of SelectorEventLoop, by default.

bpo-5950 [https://bugs.python.org/issue?@action=redirect&bpo=5950]: Support reading zip files with archive comments in zipimport.

bpo-32892 [https://bugs.python.org/issue?@action=redirect&bpo=32892]: The parser now represents all constants as ast.Constant instead of using specific constant AST types (Num, Str, Bytes, NameConstant and Ellipsis). These classes are considered deprecated and will be removed in future Python versions.

bpo-34728 [https://bugs.python.org/issue?@action=redirect&bpo=34728]: Add deprecation warning when loop is used in methods: asyncio.sleep, asyncio.wait and asyncio.wait_for.

bpo-34738 [https://bugs.python.org/issue?@action=redirect&bpo=34738]: ZIP files created by distutils will now include entries for directories.

bpo-34659 [https://bugs.python.org/issue?@action=redirect&bpo=34659]: Add an optional initial argument to itertools.accumulate().

bpo-29577 [https://bugs.python.org/issue?@action=redirect&bpo=29577]: Support multiple mixin classes when creating Enums.

bpo-34670 [https://bugs.python.org/issue?@action=redirect&bpo=34670]: Add SSLContext.post_handshake_auth and SSLSocket.verify_client_post_handshake for TLS 1.3's post handshake authentication feature.

bpo-32718 [https://bugs.python.org/issue?@action=redirect&bpo=32718]: The Activate.ps1 script from venv works with PowerShell Core 6.1 and is now available under all operating systems.

bpo-31177 [https://bugs.python.org/issue?@action=redirect&bpo=31177]: Fix bug that prevented using reset_mock on mock instances with deleted attributes

bpo-34672 [https://bugs.python.org/issue?@action=redirect&bpo=34672]: Add a workaround, so the 'Z' time.strftime() specifier on the musl C library can work in some cases.

bpo-34666 [https://bugs.python.org/issue?@action=redirect&bpo=34666]: Implement asyncio.StreamWriter.awrite and asyncio.StreamWriter.aclose() coroutines. Methods are needed for providing a consistent stream API with control flow switched on by default.

bpo-6721 [https://bugs.python.org/issue?@action=redirect&bpo=6721]: Acquire the logging module's commonly used internal locks while fork()ing to avoid deadlocks in the child process.

bpo-34658 [https://bugs.python.org/issue?@action=redirect&bpo=34658]: Fix a rare interpreter unhandled exception state SystemError only seen when using subprocess with a preexec_fn while an after_parent handler has been registered with os.register_at_fork and the fork system call fails.

bpo-34652 [https://bugs.python.org/issue?@action=redirect&bpo=34652]: Ensure os.lchmod() is never defined on Linux.

bpo-34638 [https://bugs.python.org/issue?@action=redirect&bpo=34638]: Store a weak reference to stream reader to break strong references loop between reader and protocol. It allows to detect and close the socket if the stream is deleted (garbage collected) without close() call.

bpo-34536 [https://bugs.python.org/issue?@action=redirect&bpo=34536]: Enum._missing_: raise ValueError if None returned and TypeError if non-member is returned.

bpo-34636 [https://bugs.python.org/issue?@action=redirect&bpo=34636]: Speed up re scanning of many non-matching characters for s w and d within bytes objects. (microoptimization)

bpo-24412 [https://bugs.python.org/issue?@action=redirect&bpo=24412]: Add addModuleCleanup() and addClassCleanup() to unittest to support cleanups for setUpModule() and setUpClass(). Patch by Lisa Roach.

bpo-34630 [https://bugs.python.org/issue?@action=redirect&bpo=34630]: Don't log SSL certificate errors in asyncio code (connection error logging is skipped already).

bpo-32490 [https://bugs.python.org/issue?@action=redirect&bpo=32490]: Prevent filename duplication in subprocess exception messages. Patch by Zackery Spytz.

bpo-34363 [https://bugs.python.org/issue?@action=redirect&bpo=34363]: dataclasses.asdict() and .astuple() now handle namedtuples correctly.

bpo-34625 [https://bugs.python.org/issue?@action=redirect&bpo=34625]: Update vendorized expat library version to 2.2.6.

bpo-32270 [https://bugs.python.org/issue?@action=redirect&bpo=32270]: The subprocess module no longer mistakenly closes redirected fds even when they were in pass_fds when outside of the default {0, 1, 2} set.

bpo-34622 [https://bugs.python.org/issue?@action=redirect&bpo=34622]: Create a dedicated asyncio.CancelledError, asyncio.InvalidStateError and asyncio.TimeoutError exception classes. Inherit them from corresponding exceptions from concurrent.futures package. Extract asyncio exceptions into a separate file.

bpo-34610 [https://bugs.python.org/issue?@action=redirect&bpo=34610]: Fixed iterator of multiprocessing.managers.DictProxy.

bpo-34421 [https://bugs.python.org/issue?@action=redirect&bpo=34421]: Fix distutils logging for non-ASCII strings. This caused installation issues on Windows.

bpo-34604 [https://bugs.python.org/issue?@action=redirect&bpo=34604]: Fix possible mojibake in the error message of pwd.getpwnam and grp.getgrnam using string representation because of invisible characters or trailing whitespaces. Patch by William Grzybowski.

bpo-30977 [https://bugs.python.org/issue?@action=redirect&bpo=30977]: Make uuid.UUID use __slots__ to reduce its memory footprint. Based on original patch by Wouter Bolsterlee.

bpo-34574 [https://bugs.python.org/issue?@action=redirect&bpo=34574]: OrderedDict iterators are not exhausted during pickling anymore. Patch by Sergey Fedoseev.

bpo-8110 [https://bugs.python.org/issue?@action=redirect&bpo=8110]: Refactored subprocess to check for Windows-specific modules rather than sys.platform == 'win32'.

bpo-34530 [https://bugs.python.org/issue?@action=redirect&bpo=34530]: distutils.spawn.find_executable() now falls back on os.defpath if the PATH environment variable is not set.

bpo-34563 [https://bugs.python.org/issue?@action=redirect&bpo=34563]: On Windows, fix multiprocessing.Connection for very large read: fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than INT_MAX (usually 2**31-1).

bpo-34558 [https://bugs.python.org/issue?@action=redirect&bpo=34558]: Correct typo in Lib/ctypes/_aix.py

bpo-34282 [https://bugs.python.org/issue?@action=redirect&bpo=34282]: Move Enum._convert to EnumMeta._convert_ and fix enum members getting shadowed by parent attributes.

bpo-22872 [https://bugs.python.org/issue?@action=redirect&bpo=22872]: When the queue is closed, ValueError is now raised by multiprocessing.Queue.put() and multiprocessing.Queue.get() instead of AssertionError and OSError, respectively. Patch by Zackery Spytz.

bpo-34515 [https://bugs.python.org/issue?@action=redirect&bpo=34515]: Fix parsing non-ASCII identifiers in lib2to3.pgen2.tokenize (PEP 3131 [https://peps.python.org/pep-3131/]).

bpo-13312 [https://bugs.python.org/issue?@action=redirect&bpo=13312]: Avoids a possible integer underflow (undefined behavior) in the time module's year handling code when passed a very low negative year value.

bpo-34472 [https://bugs.python.org/issue?@action=redirect&bpo=34472]: Improved compatibility for streamed files in zipfile. Previously an optional signature was not being written and certain ZIP applications were not supported. Patch by Silas Sewell.

bpo-34454 [https://bugs.python.org/issue?@action=redirect&bpo=34454]: Fix the .fromisoformat() methods of datetime types crashing when given unicode with non-UTF-8-encodable code points. Specifically, datetime.fromisoformat() now accepts surrogate unicode code points used as the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.

bpo-6700 [https://bugs.python.org/issue?@action=redirect&bpo=6700]: Fix inspect.getsourcelines for module level frames/tracebacks. Patch by Vladimir Matveev.

bpo-34171 [https://bugs.python.org/issue?@action=redirect&bpo=34171]: Running the trace module no longer creates the trace.cover file.

bpo-34441 [https://bugs.python.org/issue?@action=redirect&bpo=34441]: Fix crash when an ABC-derived class with invalid __subclasses__ is passed as the second argument to issubclass(). Patch by Alexey Izbyshev.

bpo-34427 [https://bugs.python.org/issue?@action=redirect&bpo=34427]: Fix infinite loop in a.extend(a) for MutableSequence subclasses.

bpo-34412 [https://bugs.python.org/issue?@action=redirect&bpo=34412]: Make signal.strsignal() work on HP-UX. Patch by Michael Osipov.

bpo-20849 [https://bugs.python.org/issue?@action=redirect&bpo=20849]: shutil.copytree now accepts a new dirs_exist_ok keyword argument. Patch by Josh Bronson.

bpo-31715 [https://bugs.python.org/issue?@action=redirect&bpo=31715]: Associate .mjs file extension with application/javascript MIME Type.

bpo-34384 [https://bugs.python.org/issue?@action=redirect&bpo=34384]: os.readlink() now accepts path-like and bytes objects on Windows.

bpo-22602 [https://bugs.python.org/issue?@action=redirect&bpo=22602]: The UTF-7 decoder now raises UnicodeDecodeError for ill-formed sequences starting with "+" (as specified in RFC 2152). Patch by Zackery Spytz.

bpo-2122 [https://bugs.python.org/issue?@action=redirect&bpo=2122]: The mmap.flush() method now returns None on success, raises an exception on error under all platforms.

bpo-34341 [https://bugs.python.org/issue?@action=redirect&bpo=34341]: Appending to the ZIP archive with the ZIP64 extension no longer grows the size of extra fields of existing entries.

bpo-34333 [https://bugs.python.org/issue?@action=redirect&bpo=34333]: Fix %-formatting in pathlib.PurePath.with_suffix() when formatting an error message.

bpo-18540 [https://bugs.python.org/issue?@action=redirect&bpo=18540]: The imaplib.IMAP4 and imaplib.IMAP4_SSL classes now resolve to the local host IP correctly when the default value of host parameter ('') is used.

bpo-26502 [https://bugs.python.org/issue?@action=redirect&bpo=26502]: Implement traceback.FrameSummary.__len__() method to preserve compatibility with the old tuple API.

bpo-34318 [https://bugs.python.org/issue?@action=redirect&bpo=34318]: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() no longer success if the passed callable is None. They no longer ignore unknown keyword arguments in the context manager mode. A DeprecationWarning was raised in these cases since Python 3.5.

bpo-9372 [https://bugs.python.org/issue?@action=redirect&bpo=9372]: Deprecate __getitem__() methods of xml.dom.pulldom.DOMEventStream, wsgiref.util.FileWrapper and fileinput.FileInput.

bpo-33613 [https://bugs.python.org/issue?@action=redirect&bpo=33613]: Fix a race condition in multiprocessing.semaphore_tracker when the tracker receives SIGINT before it can register signal handlers for ignoring it.

bpo-34248 [https://bugs.python.org/issue?@action=redirect&bpo=34248]: Report filename in the exception raised when the database file cannot be opened by dbm.gnu.open() and dbm.ndbm.open() due to OS-related error. Patch by Zsolt Cserna.

bpo-33089 [https://bugs.python.org/issue?@action=redirect&bpo=33089]: Add math.dist() to compute the Euclidean distance between two points.

bpo-34246 [https://bugs.python.org/issue?@action=redirect&bpo=34246]: smtplib.SMTP.send_message() no longer modifies the content of the mail_options argument. Patch by Pablo S. Blum de Aguiar.

bpo-31047 [https://bugs.python.org/issue?@action=redirect&bpo=31047]: Fix ntpath.abspath for invalid paths on windows. Patch by Franz Woellert.

bpo-32321 [https://bugs.python.org/issue?@action=redirect&bpo=32321]: Add pure Python fallback for functools.reduce. Patch by Robert Wright.

bpo-34270 [https://bugs.python.org/issue?@action=redirect&bpo=34270]: The default asyncio task class now always has a name which can be get or set using two new methods (get_name() and set_name()) and is visible in the repr() output. An initial name can also be set using the new name keyword argument to asyncio.create_task() or the create_task() method of the event loop. If no initial name is set, the default Task implementation generates a name like Task-1 using a monotonic counter.

bpo-34263 [https://bugs.python.org/issue?@action=redirect&bpo=34263]: asyncio's event loop will not pass timeouts longer than one day to epoll/select etc.

bpo-34035 [https://bugs.python.org/issue?@action=redirect&bpo=34035]: Fix several AttributeError in zipfile seek() methods. Patch by Mickaël Schoentgen.

bpo-32215 [https://bugs.python.org/issue?@action=redirect&bpo=32215]: Fix performance regression in sqlite3 when a DML statement appeared in a different line than the rest of the SQL query.

bpo-34075 [https://bugs.python.org/issue?@action=redirect&bpo=34075]: Deprecate passing non-ThreadPoolExecutor instances to AbstractEventLoop.set_default_executor().

bpo-34251 [https://bugs.python.org/issue?@action=redirect&bpo=34251]: Restore msilib.Win64 to preserve backwards compatibility since it's already used by distutils' bdist_msi command.

bpo-19891 [https://bugs.python.org/issue?@action=redirect&bpo=19891]: Ignore errors caused by missing / non-writable homedir while writing history during exit of an interactive session. Patch by Anthony Sottile.

bpo-33089 [https://bugs.python.org/issue?@action=redirect&bpo=33089]: Enhanced math.hypot() to support more than two dimensions.

bpo-34228 [https://bugs.python.org/issue?@action=redirect&bpo=34228]: tracemalloc: PYTHONTRACEMALLOC=0 environment variable and -X tracemalloc=0 command line option are now allowed to disable explicitly tracemalloc at startup.

bpo-13041 [https://bugs.python.org/issue?@action=redirect&bpo=13041]: Use shutil.get_terminal_size() to calculate the terminal width correctly in the argparse.HelpFormatter class. Initial patch by Zbyszek Jędrzejewski-Szmek.

bpo-34213 [https://bugs.python.org/issue?@action=redirect&bpo=34213]: Allow frozen dataclasses to have a field named "object". Previously this conflicted with an internal use of "object".

bpo-34052 [https://bugs.python.org/issue?@action=redirect&bpo=34052]: sqlite3.Connection.create_aggregate(), sqlite3.Connection.create_function(), sqlite3.Connection.set_authorizer(), sqlite3.Connection.set_progress_handler() methods raises TypeError when unhashable objects are passed as callable. These methods now don't pass such objects to SQLite API. Previous behavior could lead to segfaults. Patch by Sergey Fedoseev.

bpo-34197 [https://bugs.python.org/issue?@action=redirect&bpo=34197]: Attributes skipinitialspace, doublequote and strict of the dialect attribute of the csv reader are now bool instances instead of integers 0 or 1.

bpo-32788 [https://bugs.python.org/issue?@action=redirect&bpo=32788]: Errors other than TypeError raised in methods __adapt__() and __conform__() in the sqlite3 module are now propagated to the user.

bpo-21446 [https://bugs.python.org/issue?@action=redirect&bpo=21446]: The reload fixer now uses importlib.reload() instead of deprecated imp.reload().

bpo-940286 [https://bugs.python.org/issue?@action=redirect&bpo=940286]: pydoc's Helper.showtopic() method now prints the cross references of a topic correctly.

bpo-34164 [https://bugs.python.org/issue?@action=redirect&bpo=34164]: base64.b32decode() could raise UnboundLocalError or OverflowError for incorrect padding. Now it always raises base64.Error in these cases.

bpo-33729 [https://bugs.python.org/issue?@action=redirect&bpo=33729]: Fixed issues with arguments parsing in hashlib.

bpo-34097 [https://bugs.python.org/issue?@action=redirect&bpo=34097]: ZipFile can zip files older than 1980-01-01 and newer than 2107-12-31 using a new strict_timestamps parameter at the cost of setting the timestamp to the limit.

bpo-34108 [https://bugs.python.org/issue?@action=redirect&bpo=34108]: Remove extraneous CR in 2to3 refactor.

bpo-34070 [https://bugs.python.org/issue?@action=redirect&bpo=34070]: Make sure to only check if the handle is a tty, when opening a file with buffering=-1.

bpo-27494 [https://bugs.python.org/issue?@action=redirect&bpo=27494]: Reverted bpo-27494 [https://bugs.python.org/issue?@action=redirect&bpo=27494]. 2to3 rejects now a trailing comma in generator expressions.

bpo-33967 [https://bugs.python.org/issue?@action=redirect&bpo=33967]: functools.singledispatch now raises TypeError instead of IndexError when no positional arguments are passed.

bpo-34041 [https://bugs.python.org/issue?@action=redirect&bpo=34041]: Add the parameter deterministic to the sqlite3.Connection.create_function() method. Patch by Sergey Fedoseev.

bpo-34056 [https://bugs.python.org/issue?@action=redirect&bpo=34056]: Ensure the loader shim created by imp.load_module always returns bytes from its get_data() function. This fixes using imp.load_module with PEP 552 [https://peps.python.org/pep-0552/] hash-based pycs.

bpo-34054 [https://bugs.python.org/issue?@action=redirect&bpo=34054]: The multiprocessing module now uses the monotonic clock time.monotonic() instead of the system clock time.time() to implement timeout.

bpo-34043 [https://bugs.python.org/issue?@action=redirect&bpo=34043]: Optimize tarfile uncompress performance about 15% when gzip is used.

bpo-34044 [https://bugs.python.org/issue?@action=redirect&bpo=34044]: subprocess.Popen now copies the startupinfo argument to leave it unchanged: it will modify the copy, so that the same STARTUPINFO object can be used multiple times.

bpo-34010 [https://bugs.python.org/issue?@action=redirect&bpo=34010]: Fixed a performance regression for reading streams with tarfile. The buffered read should use a list, instead of appending to a bytes object.

bpo-34019 [https://bugs.python.org/issue?@action=redirect&bpo=34019]: webbrowser: Correct the arguments passed to Opera Browser when opening a new URL using the webbrowser module. Patch by Bumsik Kim.

bpo-34003 [https://bugs.python.org/issue?@action=redirect&bpo=34003]: csv.DictReader now creates dicts instead of OrderedDicts. Patch by Michael Selik.

bpo-33978 [https://bugs.python.org/issue?@action=redirect&bpo=33978]: Closed existing logging handlers before reconfiguration via fileConfig and dictConfig. Patch by Karthikeyan Singaravelan.

bpo-14117 [https://bugs.python.org/issue?@action=redirect&bpo=14117]: Make minor tweaks to turtledemo. The 'wikipedia' example is now 'rosette', describing what it draws. The 'penrose' print output is reduced. The'1024' output of 'tree' is eliminated.

bpo-33974 [https://bugs.python.org/issue?@action=redirect&bpo=33974]: Fixed passing lists and tuples of strings containing special characters ", \, {, } and \n as options to ttk widgets.

bpo-27500 [https://bugs.python.org/issue?@action=redirect&bpo=27500]: Fix getaddrinfo to resolve IPv6 addresses correctly.

bpo-24567 [https://bugs.python.org/issue?@action=redirect&bpo=24567]: Improve random.choices() to handle subnormal input weights that could occasionally trigger an IndexError.

bpo-33871 [https://bugs.python.org/issue?@action=redirect&bpo=33871]: Fixed integer overflow in os.readv(), os.writev(), os.preadv() and os.pwritev() and in os.sendfile() with headers or trailers arguments (on BSD-based OSes and macOS).

bpo-25007 [https://bugs.python.org/issue?@action=redirect&bpo=25007]: Add copy.copy() and copy.deepcopy() support to zlib compressors and decompressors. Patch by Zackery Spytz.

bpo-33929 [https://bugs.python.org/issue?@action=redirect&bpo=33929]: multiprocessing: Fix a race condition in Popen of multiprocessing.popen_spawn_win32. The child process now duplicates the read end of pipe instead of "stealing" it. Previously, the read end of pipe was "stolen" by the child process, but it leaked a handle if the child process had been terminated before it could steal the handle from the parent process.

bpo-33899 [https://bugs.python.org/issue?@action=redirect&bpo=33899]: Tokenize module now implicitly emits a NEWLINE when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. Contributed by Ammar Askar.

bpo-33897 [https://bugs.python.org/issue?@action=redirect&bpo=33897]: Added a 'force' keyword argument to logging.basicConfig().

bpo-33695 [https://bugs.python.org/issue?@action=redirect&bpo=33695]: shutil.copytree() uses os.scandir() function and all copy functions depending from it use cached os.stat() values. The speedup for copying a directory with 8000 files is around +9% on Linux, +20% on Windows and + 30% on a Windows SMB share. Also the number of os.stat() syscalls is reduced by 38% making shutil.copytree() especially faster on network filesystems. (Contributed by Giampaolo Rodola' in bpo-33695 [https://bugs.python.org/issue?@action=redirect&bpo=33695].)

bpo-33916 [https://bugs.python.org/issue?@action=redirect&bpo=33916]: bz2 and lzma: When Decompressor.__init__() is called twice, free the old lock to not leak memory.

bpo-32568 [https://bugs.python.org/issue?@action=redirect&bpo=32568]: Make select.epoll() and its documentation consistent regarding sizehint and flags.

bpo-33833 [https://bugs.python.org/issue?@action=redirect&bpo=33833]: Fixed bug in asyncio where ProactorSocketTransport logs AssertionError if force closed during write.

bpo-33663 [https://bugs.python.org/issue?@action=redirect&bpo=33663]: Convert content length to string before putting to header.

bpo-33721 [https://bugs.python.org/issue?@action=redirect&bpo=33721]: os.path functions that return a boolean result like exists(), lexists(), isdir(), isfile(), islink(), and ismount(), and pathlib.Path methods that return a boolean result like exists(), is_dir(), is_file(), is_mount(), is_symlink(), is_block_device(), is_char_device(), is_fifo(), is_socket() now return False instead of raising ValueError or its subclasses UnicodeEncodeError and UnicodeDecodeError for paths that contain characters or bytes unrepresentable at the OS level.

bpo-26544 [https://bugs.python.org/issue?@action=redirect&bpo=26544]: Fixed implementation of platform.libc_ver(). It almost always returned version '2.9' for glibc.

bpo-33843 [https://bugs.python.org/issue?@action=redirect&bpo=33843]: Remove deprecated cgi.escape, cgi.parse_qs and cgi.parse_qsl.

bpo-33842 [https://bugs.python.org/issue?@action=redirect&bpo=33842]: Remove tarfile.filemode which is deprecated since Python 3.3.

bpo-30167 [https://bugs.python.org/issue?@action=redirect&bpo=30167]: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

bpo-33805 [https://bugs.python.org/issue?@action=redirect&bpo=33805]: Improve error message of dataclasses.replace() when an InitVar is not specified

bpo-33687 [https://bugs.python.org/issue?@action=redirect&bpo=33687]: Fix the call to os.chmod() for uu.decode() if a mode is given or decoded. Patch by Timo Furrer.

bpo-33812 [https://bugs.python.org/issue?@action=redirect&bpo=33812]: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

bpo-32108 [https://bugs.python.org/issue?@action=redirect&bpo=32108]: In configparser, don't clear section when it is assigned to itself.

bpo-27397 [https://bugs.python.org/issue?@action=redirect&bpo=27397]: Make email module properly handle invalid-length base64 strings.

bpo-33578 [https://bugs.python.org/issue?@action=redirect&bpo=33578]: Implement multibyte encoder/decoder state methods

bpo-30805 [https://bugs.python.org/issue?@action=redirect&bpo=30805]: Avoid race condition with debug logging

bpo-33476 [https://bugs.python.org/issue?@action=redirect&bpo=33476]: Fix _header_value_parser.py when address group is missing final ';'. Contributed by Enrique Perez-Terron

bpo-33694 [https://bugs.python.org/issue?@action=redirect&bpo=33694]: asyncio: Fix a race condition causing data loss on pause_reading()/resume_reading() when using the ProactorEventLoop.

bpo-32493 [https://bugs.python.org/issue?@action=redirect&bpo=32493]: Correct test for uuid_enc_be availability in configure.ac. Patch by Michael Felt.

bpo-33792 [https://bugs.python.org/issue?@action=redirect&bpo=33792]: Add asyncio.WindowsSelectorEventLoopPolicy and asyncio.WindowsProactorEventLoopPolicy.

bpo-33274 [https://bugs.python.org/issue?@action=redirect&bpo=33274]: W3C DOM Level 1 specifies return value of Element.removeAttributeNode() as "The Attr node that was removed." xml.dom.minidom now complies with this requirement.

bpo-33778 [https://bugs.python.org/issue?@action=redirect&bpo=33778]: Update unicodedata's database to Unicode version 11.0.0.

bpo-33165 [https://bugs.python.org/issue?@action=redirect&bpo=33165]: Added a stacklevel parameter to logging calls to allow use of wrapper/helper functions for logging APIs.

bpo-33770 [https://bugs.python.org/issue?@action=redirect&bpo=33770]: improve base64 exception message for encoded inputs of invalid length

bpo-33769 [https://bugs.python.org/issue?@action=redirect&bpo=33769]: asyncio/start_tls: Fix error message; cancel callbacks in case of an unhandled error; mark SSLTransport as closed if it is aborted.

bpo-33767 [https://bugs.python.org/issue?@action=redirect&bpo=33767]: The concatenation (+) and repetition (*) sequence operations now raise TypeError instead of SystemError when performed on mmap.mmap objects. Patch by Zackery Spytz.

bpo-33734 [https://bugs.python.org/issue?@action=redirect&bpo=33734]: asyncio/ssl: Fix AttributeError, increase default handshake timeout

bpo-31014 [https://bugs.python.org/issue?@action=redirect&bpo=31014]: Fixed creating a controller for webbrowser when a user specifies a path to an entry in the BROWSER environment variable. Based on patch by John Still.

bpo-2504 [https://bugs.python.org/issue?@action=redirect&bpo=2504]: Add gettext.pgettext() and variants.

bpo-33197 [https://bugs.python.org/issue?@action=redirect&bpo=33197]: Add description property for _ParameterKind

bpo-32751 [https://bugs.python.org/issue?@action=redirect&bpo=32751]: When cancelling the task due to a timeout, asyncio.wait_for() will now wait until the cancellation is complete.

bpo-32684 [https://bugs.python.org/issue?@action=redirect&bpo=32684]: Fix gather to propagate cancellation of itself even with return_exceptions.

bpo-33654 [https://bugs.python.org/issue?@action=redirect&bpo=33654]: Support protocol type switching in SSLTransport.set_protocol().

bpo-33674 [https://bugs.python.org/issue?@action=redirect&bpo=33674]: Pause the transport as early as possible to further reduce the risk of data_received() being called before connection_made().

bpo-33671 [https://bugs.python.org/issue?@action=redirect&bpo=33671]: shutil.copyfile(), shutil.copy(), shutil.copy2(), shutil.copytree() and shutil.move() use platform-specific fast-copy syscalls on Linux and macOS in order to copy the file more efficiently. On Windows shutil.copyfile() uses a bigger default buffer size (1 MiB instead of 16 KiB) and a memoryview()-based variant of shutil.copyfileobj() is used. The speedup for copying a 512MiB file is about +26% on Linux, +50% on macOS and +40% on Windows. Also, much less CPU cycles are consumed. (Contributed by Giampaolo Rodola' in bpo-25427 [https://bugs.python.org/issue?@action=redirect&bpo=25427].)

bpo-33674 [https://bugs.python.org/issue?@action=redirect&bpo=33674]: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

bpo-31647 [https://bugs.python.org/issue?@action=redirect&bpo=31647]: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it's already closed raises AttributeError.

bpo-32610 [https://bugs.python.org/issue?@action=redirect&bpo=32610]: Make asyncio.all_tasks() return only pending tasks.

bpo-32410 [https://bugs.python.org/issue?@action=redirect&bpo=32410]: Avoid blocking on file IO in sendfile fallback code

bpo-33469 [https://bugs.python.org/issue?@action=redirect&bpo=33469]: Fix RuntimeError after closing loop that used run_in_executor

bpo-33672 [https://bugs.python.org/issue?@action=redirect&bpo=33672]: Fix Task.__repr__ crash with Cython's bogus coroutines

bpo-33654 [https://bugs.python.org/issue?@action=redirect&bpo=33654]: Fix transport.set_protocol() to support switching between asyncio.Protocol and asyncio.BufferedProtocol. Fix loop.start_tls() to work with asyncio.BufferedProtocols.

bpo-33652 [https://bugs.python.org/issue?@action=redirect&bpo=33652]: Pickles of type variables and subscripted generics are now future-proof and compatible with older Python versions.

bpo-32493 [https://bugs.python.org/issue?@action=redirect&bpo=32493]: Fixed uuid.uuid1() on FreeBSD.

bpo-33238 [https://bugs.python.org/issue?@action=redirect&bpo=33238]: Add InvalidStateError to concurrent.futures. Future.set_result and Future.set_exception now raise InvalidStateError if the futures are not pending or running. Patch by Jason Haydaman.

bpo-33618 [https://bugs.python.org/issue?@action=redirect&bpo=33618]: Finalize and document preliminary and experimental TLS 1.3 support with OpenSSL 1.1.1

bpo-33625 [https://bugs.python.org/issue?@action=redirect&bpo=33625]: Release GIL on grp.getgrnam, grp.getgrgid, pwd.getpwnam and pwd.getpwuid if reentrant variants of these functions are available. Patch by William Grzybowski.

bpo-33623 [https://bugs.python.org/issue?@action=redirect&bpo=33623]: Fix possible SIGSGV when asyncio.Future is created in __del__

bpo-11874 [https://bugs.python.org/issue?@action=redirect&bpo=11874]: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

bpo-30877 [https://bugs.python.org/issue?@action=redirect&bpo=30877]: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

bpo-33604 [https://bugs.python.org/issue?@action=redirect&bpo=33604]: Remove HMAC default to md5 marked for removal in 3.8 (removal originally planned in 3.6, bump to 3.8 in PR 7062).

bpo-33582 [https://bugs.python.org/issue?@action=redirect&bpo=33582]: Emit a deprecation warning for inspect.formatargspec

bpo-21145 [https://bugs.python.org/issue?@action=redirect&bpo=21145]: Add functools.cached_property decorator, for computed properties cached for the life of the instance.

bpo-33570 [https://bugs.python.org/issue?@action=redirect&bpo=33570]: Change TLS 1.3 cipher suite settings for compatibility with OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers enabled by default.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Do not simplify arguments to typing.Union. Now Union[Manager, Employee] is not simplified to Employee at runtime. Such simplification previously caused several bugs and limited possibilities for introspection.

bpo-12486 [https://bugs.python.org/issue?@action=redirect&bpo=12486]: tokenize.generate_tokens() is now documented as a public API to tokenize unicode strings. It was previously present but undocumented.

bpo-33540 [https://bugs.python.org/issue?@action=redirect&bpo=33540]: Add a new block_on_close class attribute to ForkingMixIn and ThreadingMixIn classes of socketserver.

bpo-33548 [https://bugs.python.org/issue?@action=redirect&bpo=33548]: tempfile._candidate_tempdir_list should consider common TEMP locations

bpo-33109 [https://bugs.python.org/issue?@action=redirect&bpo=33109]: argparse subparsers are once again not required by default, reverting the change in behavior introduced by bpo-26510 [https://bugs.python.org/issue?@action=redirect&bpo=26510] in 3.7.0a2.

bpo-33541 [https://bugs.python.org/issue?@action=redirect&bpo=33541]: Remove unused private method _strptime.LocaleTime.__pad (a.k.a. _LocaleTime__pad).

bpo-33536 [https://bugs.python.org/issue?@action=redirect&bpo=33536]: dataclasses.make_dataclass now checks for invalid field names and duplicate fields. Also, added a check for invalid field specifications.

bpo-33542 [https://bugs.python.org/issue?@action=redirect&bpo=33542]: Prevent uuid.get_node from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

bpo-26819 [https://bugs.python.org/issue?@action=redirect&bpo=26819]: Fix race condition with ReadTransport.resume_reading in Windows proactor event loop.

Fix failure in typing.get_type_hints() when ClassVar was provided as a string forward reference.

bpo-33516 [https://bugs.python.org/issue?@action=redirect&bpo=33516]: unittest.mock.MagicMock now supports the __round__ magic method.

bpo-28612 [https://bugs.python.org/issue?@action=redirect&bpo=28612]: Added support for Site Maps to urllib's RobotFileParser as RobotFileParser.site_maps(). Patch by Lady Red, based on patch by Peter Wirtz.

bpo-28167 [https://bugs.python.org/issue?@action=redirect&bpo=28167]: Remove platform.linux_distribution, which was deprecated since 3.5.

bpo-33504 [https://bugs.python.org/issue?@action=redirect&bpo=33504]: Switch the default dictionary implementation for configparser from collections.OrderedDict to the standard dict type.

bpo-33505 [https://bugs.python.org/issue?@action=redirect&bpo=33505]: Optimize asyncio.ensure_future() by reordering if checks: 1.17x faster.

bpo-33497 [https://bugs.python.org/issue?@action=redirect&bpo=33497]: Add errors param to cgi.parse_multipart and make an encoding in FieldStorage use the given errors (needed for Twisted). Patch by Amber Brown.

bpo-29235 [https://bugs.python.org/issue?@action=redirect&bpo=29235]: The cProfile.Profile class can now be used as a context manager. Patch by Scott Sanderson.

bpo-33495 [https://bugs.python.org/issue?@action=redirect&bpo=33495]: Change dataclasses.Fields repr to use the repr of each of its members, instead of str. This makes it more clear what each field actually represents. This is especially true for the 'type' member.

bpo-26103 [https://bugs.python.org/issue?@action=redirect&bpo=26103]: Correct inspect.isdatadescriptor to look for __set__ or __delete__. Patch by Aaron Hall.

bpo-29209 [https://bugs.python.org/issue?@action=redirect&bpo=29209]: Removed the doctype() method and the html parameter of the constructor of XMLParser. The doctype() method defined in a subclass will no longer be called. Deprecated methods getchildren() and getiterator() in the ElementTree module emit now a DeprecationWarning instead of PendingDeprecationWarning.

bpo-33453 [https://bugs.python.org/issue?@action=redirect&bpo=33453]: Fix dataclasses to work if using literal string type annotations or if using PEP 563 "Postponed Evaluation of Annotations". Only specific string prefixes are detected for both ClassVar ("ClassVar" and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Minor fixes in typing module: add annotations to NamedTuple.__new__, pass *args and **kwds in Generic.__new__. Original PRs by Paulius Šarka and Chad Dombrova.

bpo-33365 [https://bugs.python.org/issue?@action=redirect&bpo=33365]: Print the header values besides the header keys instead just the header keys if debuglevel is set to >0 in http.client. Patch by Marco Strigl.

bpo-20087 [https://bugs.python.org/issue?@action=redirect&bpo=20087]: Updated alias mapping with glibc 2.27 supported locales.

bpo-33422 [https://bugs.python.org/issue?@action=redirect&bpo=33422]: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

bpo-28167 [https://bugs.python.org/issue?@action=redirect&bpo=28167]: The function platform.linux_distribution and platform.dist now trigger a DeprecationWarning and have been marked for removal in Python 3.8

bpo-33281 [https://bugs.python.org/issue?@action=redirect&bpo=33281]: Fix ctypes.util.find_library regression on macOS.

bpo-33311 [https://bugs.python.org/issue?@action=redirect&bpo=33311]: Text and html output generated by cgitb does not display parentheses if the current call is done directly in the module. Patch by Stéphane Blondon.

bpo-27300 [https://bugs.python.org/issue?@action=redirect&bpo=27300]: The file classes in tempfile now accept an errors parameter that complements the already existing encoding. Patch by Stephan Hohe.

bpo-32933 [https://bugs.python.org/issue?@action=redirect&bpo=32933]: unittest.mock.mock_open() now supports iteration over the file contents. Patch by Tony Flury.

bpo-33217 [https://bugs.python.org/issue?@action=redirect&bpo=33217]: Raise TypeError when looking up non-Enum objects in Enum classes and Enum members.

bpo-33197 [https://bugs.python.org/issue?@action=redirect&bpo=33197]: Update error message when constructing invalid inspect.Parameters Patch by Donghee Na.

bpo-33383 [https://bugs.python.org/issue?@action=redirect&bpo=33383]: Fixed crash in the get() method of the dbm.ndbm database object when it is called with a single argument.

bpo-33375 [https://bugs.python.org/issue?@action=redirect&bpo=33375]: The warnings module now finds the Python file associated with a warning from the code object, rather than the frame's global namespace. This is consistent with how tracebacks and pdb find filenames, and should work better for dynamically executed code.

bpo-33336 [https://bugs.python.org/issue?@action=redirect&bpo=33336]: imaplib now allows MOVE command in IMAP4.uid() (RFC 6851: IMAP MOVE Extension) and potentially as a name of supported method of IMAP4 object.

bpo-32455 [https://bugs.python.org/issue?@action=redirect&bpo=32455]: Added jump parameter to dis.stack_effect().

bpo-27485 [https://bugs.python.org/issue?@action=redirect&bpo=27485]: Rename and deprecate undocumented functions in urllib.parse().

bpo-33332 [https://bugs.python.org/issue?@action=redirect&bpo=33332]: Add signal.valid_signals() to expose the POSIX sigfillset() functionality.

bpo-33251 [https://bugs.python.org/issue?@action=redirect&bpo=33251]: ConfigParser.items() was fixed so that key-value pairs passed in via vars() are not included in the resulting output.

bpo-33329 [https://bugs.python.org/issue?@action=redirect&bpo=33329]: Fix multiprocessing regression on newer glibcs

bpo-33334 [https://bugs.python.org/issue?@action=redirect&bpo=33334]: dis.stack_effect() now supports all defined opcodes including NOP and EXTENDED_ARG.

bpo-991266 [https://bugs.python.org/issue?@action=redirect&bpo=991266]: Fix quoting of the Comment attribute of http.cookies.SimpleCookie.

bpo-33131 [https://bugs.python.org/issue?@action=redirect&bpo=33131]: Upgrade bundled version of pip to 10.0.1.

bpo-33308 [https://bugs.python.org/issue?@action=redirect&bpo=33308]: Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info=False and col_info=True.

bpo-23403 [https://bugs.python.org/issue?@action=redirect&bpo=23403]: lib2to3 now uses pickle protocol 4 for pre-computed grammars.

bpo-33266 [https://bugs.python.org/issue?@action=redirect&bpo=33266]: lib2to3 now recognizes rf'...' strings.

bpo-11594 [https://bugs.python.org/issue?@action=redirect&bpo=11594]: Ensure line-endings are respected when using lib2to3.

bpo-33254 [https://bugs.python.org/issue?@action=redirect&bpo=33254]: Have importlib.resources.contents() and importlib.abc.ResourceReader.contents() return an iterable instead of an iterator.

bpo-33265 [https://bugs.python.org/issue?@action=redirect&bpo=33265]: contextlib.ExitStack and contextlib.AsyncExitStack now use a method instead of a wrapper function for exit callbacks.

bpo-33263 [https://bugs.python.org/issue?@action=redirect&bpo=33263]: Fix FD leak in _SelectorSocketTransport Patch by Vlad Starostin.

bpo-33256 [https://bugs.python.org/issue?@action=redirect&bpo=33256]: Fix display of <module> call in the html produced by cgitb.html(). Patch by Stéphane Blondon.

bpo-33144 [https://bugs.python.org/issue?@action=redirect&bpo=33144]: random.Random() and its subclassing mechanism got optimized to check only once at class/subclass instantiation time whether its getrandbits() method can be relied on by other methods, including randrange(), for the generation of arbitrarily large random integers. Patch by Wolfgang Maier.

bpo-33185 [https://bugs.python.org/issue?@action=redirect&bpo=33185]: Fixed regression when running pydoc with the -m switch. (The regression was introduced in 3.7.0b3 by the resolution of bpo-33053 [https://bugs.python.org/issue?@action=redirect&bpo=33053])

This fix also changed pydoc to add os.getcwd() to sys.path when necessary, rather than adding ".".

bpo-29613 [https://bugs.python.org/issue?@action=redirect&bpo=29613]: Added support for the SameSite cookie flag to the http.cookies module.

bpo-33169 [https://bugs.python.org/issue?@action=redirect&bpo=33169]: Delete entries of None in sys.path_importer_cache when importlib.machinery.invalidate_caches() is called.

bpo-33203 [https://bugs.python.org/issue?@action=redirect&bpo=33203]: random.Random.choice() now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits() implementation.

bpo-33224 [https://bugs.python.org/issue?@action=redirect&bpo=33224]: Update difflib.mdiff() for PEP 479 [https://peps.python.org/pep-0479/]. Convert an uncaught StopIteration in a generator into a return-statement.

bpo-33209 [https://bugs.python.org/issue?@action=redirect&bpo=33209]: End framing at the end of C implementation of pickle.Pickler.dump().

bpo-32861 [https://bugs.python.org/issue?@action=redirect&bpo=32861]: The urllib.robotparser's __str__ representation now includes wildcard entries and the "Crawl-delay" and "Request-rate" fields. Also removes extra newlines that were being appended to the end of the string. Patch by Michael Lazar.

bpo-23403 [https://bugs.python.org/issue?@action=redirect&bpo=23403]: DEFAULT_PROTOCOL in pickle was bumped to 4. Protocol 4 is described in PEP 3154 [https://peps.python.org/pep-3154/] and available since Python 3.4. It offers better performance and smaller size compared to protocol 3 introduced in Python 3.0.

bpo-20104 [https://bugs.python.org/issue?@action=redirect&bpo=20104]: Improved error handling and fixed a reference leak in os.posix_spawn().

bpo-33106 [https://bugs.python.org/issue?@action=redirect&bpo=33106]: Deleting a key from a read-only dbm database raises module specific error instead of KeyError.

bpo-33175 [https://bugs.python.org/issue?@action=redirect&bpo=33175]: In dataclasses, Field.__set_name__ now looks up the __set_name__ special method on the class, not the instance, of the default value.

bpo-32380 [https://bugs.python.org/issue?@action=redirect&bpo=32380]: Create functools.singledispatchmethod to support generic single dispatch on descriptors and methods.

bpo-33141 [https://bugs.python.org/issue?@action=redirect&bpo=33141]: Have Field objects pass through __set_name__ to their default values, if they have their own __set_name__.

bpo-33096 [https://bugs.python.org/issue?@action=redirect&bpo=33096]: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

bpo-32873 [https://bugs.python.org/issue?@action=redirect&bpo=32873]: Treat type variables and special typing forms as immutable by copy and pickle. This fixes several minor issues and inconsistencies, and improves backwards compatibility with Python 3.6.

bpo-33134 [https://bugs.python.org/issue?@action=redirect&bpo=33134]: When computing dataclass's __hash__, use the lookup table to contain the function which returns the __hash__ value. This is an improvement over looking up a string, and then testing that string to see what to do.

bpo-33127 [https://bugs.python.org/issue?@action=redirect&bpo=33127]: The ssl module now compiles with LibreSSL 2.7.1.

bpo-32505 [https://bugs.python.org/issue?@action=redirect&bpo=32505]: Raise TypeError if a member variable of a dataclass is of type Field, but doesn't have a type annotation.

bpo-33078 [https://bugs.python.org/issue?@action=redirect&bpo=33078]: Fix the failure on OSX caused by the tests relying on sem_getvalue

bpo-33116 [https://bugs.python.org/issue?@action=redirect&bpo=33116]: Add 'Field' to dataclasses.__all__.

bpo-32896 [https://bugs.python.org/issue?@action=redirect&bpo=32896]: Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class.

bpo-33100 [https://bugs.python.org/issue?@action=redirect&bpo=33100]: Dataclasses: If a field has a default value that's a MemberDescriptorType, then it's from that field being in __slots__, not an actual default value.

bpo-32953 [https://bugs.python.org/issue?@action=redirect&bpo=32953]: If a non-dataclass inherits from a frozen dataclass, allow attributes to be added to the derived class. Only attributes from the frozen dataclass cannot be assigned to. Require all dataclasses in a hierarchy to be either all frozen or all non-frozen.

bpo-33097 [https://bugs.python.org/issue?@action=redirect&bpo=33097]: Raise RuntimeError when executor.submit is called during interpreter shutdown.

bpo-32968 [https://bugs.python.org/issue?@action=redirect&bpo=32968]: Modulo and floor division involving Fraction and float should return float.

bpo-33061 [https://bugs.python.org/issue?@action=redirect&bpo=33061]: Add missing NoReturn to __all__ in typing.py

bpo-33078 [https://bugs.python.org/issue?@action=redirect&bpo=33078]: Fix the size handling in multiprocessing.Queue when a pickling error occurs.

bpo-33064 [https://bugs.python.org/issue?@action=redirect&bpo=33064]: lib2to3 now properly supports trailing commas after *args and **kwargs in function signatures.

bpo-33056 [https://bugs.python.org/issue?@action=redirect&bpo=33056]: FIX properly close leaking fds in concurrent.futures.ProcessPoolExecutor.

bpo-33021 [https://bugs.python.org/issue?@action=redirect&bpo=33021]: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

bpo-31804 [https://bugs.python.org/issue?@action=redirect&bpo=31804]: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

bpo-33034 [https://bugs.python.org/issue?@action=redirect&bpo=33034]: Providing an explicit error message when casting the port property to anything that is not an integer value using urlparse() and urlsplit(). Patch by Matt Eaton.

bpo-30249 [https://bugs.python.org/issue?@action=redirect&bpo=30249]: Improve struct.unpack_from() exception messages for problems with the buffer size and offset.

bpo-33037 [https://bugs.python.org/issue?@action=redirect&bpo=33037]: Skip sending/receiving data after SSL transport closing.

bpo-27683 [https://bugs.python.org/issue?@action=redirect&bpo=27683]: Fix a regression in ipaddress that result of hosts() is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

bpo-22674 [https://bugs.python.org/issue?@action=redirect&bpo=22674]: Add the strsignal() function in the signal module that returns the system description of the given signal, as returned by strsignal(3).

bpo-32999 [https://bugs.python.org/issue?@action=redirect&bpo=32999]: Fix C implementation of ABC.__subclasscheck__(cls, subclass) crashed when subclass is not a type object.

bpo-33009 [https://bugs.python.org/issue?@action=redirect&bpo=33009]: Fix inspect.signature() for single-parameter partialmethods.

bpo-32969 [https://bugs.python.org/issue?@action=redirect&bpo=32969]: Expose several missing constants in zlib and fix corresponding documentation.

bpo-32056 [https://bugs.python.org/issue?@action=redirect&bpo=32056]: Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules aifc, wave and sunau.

bpo-32970 [https://bugs.python.org/issue?@action=redirect&bpo=32970]: Improved disassembly of the MAKE_FUNCTION instruction.

bpo-32844 [https://bugs.python.org/issue?@action=redirect&bpo=32844]: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

bpo-32960 [https://bugs.python.org/issue?@action=redirect&bpo=32960]: For dataclasses, disallow inheriting frozen from non-frozen classes, and also disallow inheriting non-frozen from frozen classes. This restriction will be relaxed at a future date.

bpo-32713 [https://bugs.python.org/issue?@action=redirect&bpo=32713]: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

bpo-32257 [https://bugs.python.org/issue?@action=redirect&bpo=32257]: The ssl module now contains OP_NO_RENEGOTIATION constant, available with OpenSSL 1.1.0h or 1.1.1.

bpo-32951 [https://bugs.python.org/issue?@action=redirect&bpo=32951]: Direct instantiation of SSLSocket and SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were suppose to use ssl.wrap_socket() or SSLContext.

bpo-32929 [https://bugs.python.org/issue?@action=redirect&bpo=32929]: Remove the tri-state parameter "hash", and add the boolean "unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, raise TypeError. If unsafe_hash is False, add a __hash__ based on the values of eq= and frozen=. The unsafe_hash=False behavior is the same as the old hash=None behavior. unsafe_hash=False is the default, just as hash=None used to be.

bpo-32947 [https://bugs.python.org/issue?@action=redirect&bpo=32947]: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future compatibility with OpenSSL 1.1.1.

bpo-32146 [https://bugs.python.org/issue?@action=redirect&bpo=32146]: Document the interaction between frozen executables and the spawn and forkserver start methods in multiprocessing.

bpo-30622 [https://bugs.python.org/issue?@action=redirect&bpo=30622]: The ssl module now detects missing NPN support in LibreSSL.

bpo-32922 [https://bugs.python.org/issue?@action=redirect&bpo=32922]: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

bpo-32759 [https://bugs.python.org/issue?@action=redirect&bpo=32759]: Free unused arenas in multiprocessing.heap.

bpo-32859 [https://bugs.python.org/issue?@action=redirect&bpo=32859]: In os.dup2, don't check every call whether the dup3 syscall exists or not.

bpo-32556 [https://bugs.python.org/issue?@action=redirect&bpo=32556]: nt._getfinalpathname, nt._getvolumepathname and nt._getdiskusage now correctly convert from bytes.

bpo-21060 [https://bugs.python.org/issue?@action=redirect&bpo=21060]: Rewrite confusing message from setup.py upload from "No dist file created in earlier command" to the more helpful "Must create and upload files in one command".

bpo-32857 [https://bugs.python.org/issue?@action=redirect&bpo=32857]: In tkinter, after_cancel(None) now raises a ValueError instead of canceling the first scheduled function. Patch by Cheryl Sabella.

bpo-32852 [https://bugs.python.org/issue?@action=redirect&bpo=32852]: Make sure sys.argv remains as a list when running trace.

bpo-31333 [https://bugs.python.org/issue?@action=redirect&bpo=31333]: _abc module is added. It is a speedup module with C implementations for various functions and methods in abc. Creating an ABC subclass and calling isinstance or issubclass with an ABC subclass are up to 1.5x faster. In addition, this makes Python start-up up to 10% faster.

Note that the new implementation hides internal registry and caches, previously accessible via private attributes _abc_registry, _abc_cache, and _abc_negative_cache. There are three debugging helper methods that can be used instead _dump_registry, _abc_registry_clear, and _abc_caches_clear.

bpo-32841 [https://bugs.python.org/issue?@action=redirect&bpo=32841]: Fixed asyncio.Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

bpo-32819 [https://bugs.python.org/issue?@action=redirect&bpo=32819]: ssl.match_hostname() has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses. Error reporting for invalid wildcards has been improved.

bpo-19675 [https://bugs.python.org/issue?@action=redirect&bpo=19675]: multiprocessing.Pool no longer leaks processes if its initialization fails.

bpo-32394 [https://bugs.python.org/issue?@action=redirect&bpo=32394]: socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version Windows during run-time.

bpo-31787 [https://bugs.python.org/issue?@action=redirect&bpo=31787]: Fixed refleaks of __init__() methods in various modules. (Contributed by Oren Milman)

bpo-30157 [https://bugs.python.org/issue?@action=redirect&bpo=30157]: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

bpo-30688 [https://bugs.python.org/issue?@action=redirect&bpo=30688]: Added support of \N{name} escapes in regular expressions. Based on patch by Jonathan Eunice.

bpo-32792 [https://bugs.python.org/issue?@action=redirect&bpo=32792]: collections.ChainMap() preserves the order of the underlying mappings.

bpo-32775 [https://bugs.python.org/issue?@action=redirect&bpo=32775]: fnmatch.translate() no longer produces patterns which contain set operations. Sets starting with '[' or containing '--', '&&', '~~' or '||' will be interpreted differently in regular expressions in future versions. Currently they emit warnings. fnmatch.translate() now avoids producing patterns containing such sets by accident.

bpo-32622 [https://bugs.python.org/issue?@action=redirect&bpo=32622]: Implement native fast sendfile for Windows proactor event loop.

bpo-32777 [https://bugs.python.org/issue?@action=redirect&bpo=32777]: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

bpo-32647 [https://bugs.python.org/issue?@action=redirect&bpo=32647]: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

bpo-32749 [https://bugs.python.org/issue?@action=redirect&bpo=32749]: A dbm.dumb database opened with flags 'r' is now read-only. dbm.dumb.open() with flags 'r' and 'w' no longer creates a database if it does not exist.

bpo-32741 [https://bugs.python.org/issue?@action=redirect&bpo=32741]: Implement asyncio.TimerHandle.when() method.

bpo-32691 [https://bugs.python.org/issue?@action=redirect&bpo=32691]: Use mod_spec.parent when running modules with pdb

bpo-32734 [https://bugs.python.org/issue?@action=redirect&bpo=32734]: Fixed asyncio.Lock() safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

bpo-32727 [https://bugs.python.org/issue?@action=redirect&bpo=32727]: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

bpo-31453 [https://bugs.python.org/issue?@action=redirect&bpo=31453]: Add TLSVersion constants and SSLContext.maximum_version / minimum_version attributes. The new API wraps OpenSSL 1.1 https://web.archive.org/web/20180309043602/https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html feature.

bpo-24334 [https://bugs.python.org/issue?@action=redirect&bpo=24334]: Internal implementation details of ssl module were cleaned up. The SSLSocket has one less layer of indirection. Owner and session information are now handled by the SSLSocket and SSLObject constructor. Channel binding implementation has been simplified.

bpo-31848 [https://bugs.python.org/issue?@action=redirect&bpo=31848]: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

bpo-32585 [https://bugs.python.org/issue?@action=redirect&bpo=32585]: Add Ttk spinbox widget to tkinter.ttk. Patch by Alan D Moore.

bpo-32512 [https://bugs.python.org/issue?@action=redirect&bpo=32512]: profile CLI accepts -m module_name as an alternative to script path.

bpo-8525 [https://bugs.python.org/issue?@action=redirect&bpo=8525]: help() on a type now displays builtin subclasses. This is intended primarily to help with notification of more specific exception subclasses.

Patch by Sanyam Khurana.

bpo-31639 [https://bugs.python.org/issue?@action=redirect&bpo=31639]: http.server now exposes a ThreadingHTTPServer class and uses it when the module is run with -m to cope with web browsers pre-opening sockets.

bpo-29877 [https://bugs.python.org/issue?@action=redirect&bpo=29877]: compileall: import ProcessPoolExecutor only when needed, preventing hangs on low resource platforms

bpo-32221 [https://bugs.python.org/issue?@action=redirect&bpo=32221]: Various functions returning tuple containing IPv6 addresses now omit %scope part since the same information is already encoded in scopeid tuple item. Especially this speeds up socket.recvfrom() when it receives multicast packet since useless resolving of network interface name is omitted.

bpo-32147 [https://bugs.python.org/issue?@action=redirect&bpo=32147]: binascii.unhexlify() is now up to 2 times faster. Patch by Sergey Fedoseev.

bpo-30693 [https://bugs.python.org/issue?@action=redirect&bpo=30693]: The TarFile class now recurses directories in a reproducible way.

bpo-30693 [https://bugs.python.org/issue?@action=redirect&bpo=30693]: The ZipFile class now recurses directories in a reproducible way.

bpo-31680 [https://bugs.python.org/issue?@action=redirect&bpo=31680]: Added curses.ncurses_version.

bpo-31908 [https://bugs.python.org/issue?@action=redirect&bpo=31908]: Fix output of cover files for trace module command-line tool. Previously emitted cover files only when --missing option was used. Patch by Michael Selik.

bpo-31608 [https://bugs.python.org/issue?@action=redirect&bpo=31608]: Raise a TypeError instead of crashing if a collections.deque subclass returns a non-deque from __new__. Patch by Oren Milman.

bpo-31425 [https://bugs.python.org/issue?@action=redirect&bpo=31425]: Add support for sockets of the AF_QIPCRTR address family, supported by the Linux kernel. This is used to communicate with services, such as GPS or radio, running on Qualcomm devices. Patch by Bjorn Andersson.

bpo-22005 [https://bugs.python.org/issue?@action=redirect&bpo=22005]: Implemented unpickling instances of datetime, date and time pickled by Python 2. encoding='latin1' should be used for successful decoding.

bpo-27645 [https://bugs.python.org/issue?@action=redirect&bpo=27645]: sqlite3.Connection now exposes a backup method, if the underlying SQLite library is at version 3.6.11 or higher. Patch by Lele Gaifax.

bpo-16865 [https://bugs.python.org/issue?@action=redirect&bpo=16865]: Support arrays >=2GiB in ctypes. Patch by Segev Finer.

bpo-31508 [https://bugs.python.org/issue?@action=redirect&bpo=31508]: Removed support of arguments in tkinter.ttk.Treeview.selection. It was deprecated in 3.6. Use specialized methods like selection_set for changing the selection.

bpo-29456 [https://bugs.python.org/issue?@action=redirect&bpo=29456]: Fix bugs in hangul normalization: u1176, u11a7 and u11c3

Documentation

bpo-21257 [https://bugs.python.org/issue?@action=redirect&bpo=21257]: Document http.client.parse_headers().

bpo-34764 [https://bugs.python.org/issue?@action=redirect&bpo=34764]: Improve example of iter() with 2nd sentinel argument.

bpo-35564 [https://bugs.python.org/issue?@action=redirect&bpo=35564]: Explicitly set master_doc variable in conf.py for compliance with Sphinx 2.0

bpo-35511 [https://bugs.python.org/issue?@action=redirect&bpo=35511]: Specified that profile.Profile class doesn't not support enable or disable methods. Also, elaborated that Profile object as a context manager is only supported in cProfile module.

bpo-10536 [https://bugs.python.org/issue?@action=redirect&bpo=10536]: Enhance the gettext docs. Patch by Éric Araujo

bpo-35089 [https://bugs.python.org/issue?@action=redirect&bpo=35089]: Remove mention of typing.io and typing.re. Their types should be imported from typing directly.

bpo-35038 [https://bugs.python.org/issue?@action=redirect&bpo=35038]: Fix the documentation about an unexisting f_restricted attribute in the frame object. Patch by Stéphane Wirtel

bpo-35042 [https://bugs.python.org/issue?@action=redirect&bpo=35042]: Replace PEP XYZ by the pep role and allow to use the direct links to the PEPs.

bpo-35044 [https://bugs.python.org/issue?@action=redirect&bpo=35044]: Fix the documentation with the role exc for the appropriated exception. Patch by Stéphane Wirtel

bpo-35035 [https://bugs.python.org/issue?@action=redirect&bpo=35035]: Rename documentation for email.utils to email.utils.rst.

bpo-34967 [https://bugs.python.org/issue?@action=redirect&bpo=34967]: Use app.add_object_type() instead of the deprecated Sphinx function app.description_unit()

bpo-34913 [https://bugs.python.org/issue?@action=redirect&bpo=34913]: Add documentation about the new command line interface of the gzip module.

bpo-32174 [https://bugs.python.org/issue?@action=redirect&bpo=32174]: chm document displays non-ASCII characters properly on some MBCS Windows systems.

bpo-11233 [https://bugs.python.org/issue?@action=redirect&bpo=11233]: Create availability directive for documentation. Original patch by Georg Brandl.

bpo-34790 [https://bugs.python.org/issue?@action=redirect&bpo=34790]: Document how passing coroutines to asyncio.wait() can be confusing.

bpo-34552 [https://bugs.python.org/issue?@action=redirect&bpo=34552]: Make clear that == operator sometimes is equivalent to is. The <, <=, > and >= operators are only defined where they make sense.

bpo-28617 [https://bugs.python.org/issue?@action=redirect&bpo=28617]: Fixed info in the stdtypes docs concerning the types that support membership tests.

bpo-20177 [https://bugs.python.org/issue?@action=redirect&bpo=20177]: Migrate datetime.date.fromtimestamp to Argument Clinic. Patch by Tim Hoffmann.

bpo-34065 [https://bugs.python.org/issue?@action=redirect&bpo=34065]: Fix wrongly written basicConfig documentation markup syntax

bpo-33460 [https://bugs.python.org/issue?@action=redirect&bpo=33460]: replaced ellipsis with correct error codes in tutorial chapter 3.

bpo-33847 [https://bugs.python.org/issue?@action=redirect&bpo=33847]: Add '@' operator entry to index.

bpo-33409 [https://bugs.python.org/issue?@action=redirect&bpo=33409]: Clarified the relationship between PEP 538 [https://peps.python.org/pep-0538/]'s PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

bpo-33197 [https://bugs.python.org/issue?@action=redirect&bpo=33197]: Add versionadded tag to the documentation of ParameterKind.description

bpo-17045 [https://bugs.python.org/issue?@action=redirect&bpo=17045]: Improve the C-API doc for PyTypeObject. This includes adding several quick-reference tables and a lot of missing slot/typedef entries. The existing entries were also cleaned up with a slightly more consistent format.

bpo-33736 [https://bugs.python.org/issue?@action=redirect&bpo=33736]: Improve the documentation of asyncio.open_connection(), asyncio.start_server() and their UNIX socket counterparts.

bpo-23859 [https://bugs.python.org/issue?@action=redirect&bpo=23859]: Document that asyncio.wait() does not cancel its futures on timeout.

bpo-32436 [https://bugs.python.org/issue?@action=redirect&bpo=32436]: Document PEP 567 [https://peps.python.org/pep-0567/] changes to asyncio.

bpo-33604 [https://bugs.python.org/issue?@action=redirect&bpo=33604]: Update HMAC md5 default to a DeprecationWarning, bump removal to 3.8.

bpo-33594 [https://bugs.python.org/issue?@action=redirect&bpo=33594]: Document getargspec, from_function and from_builtin as deprecated in their respective docstring, and include version since deprecation in DeprecationWarning message.

bpo-33503 [https://bugs.python.org/issue?@action=redirect&bpo=33503]: Fix broken pypi link

bpo-33421 [https://bugs.python.org/issue?@action=redirect&bpo=33421]: Add missing documentation for typing.AsyncContextManager.

bpo-33487 [https://bugs.python.org/issue?@action=redirect&bpo=33487]: BZ2file now emit a DeprecationWarning when buffering=None is passed, the deprecation message and documentation also now explicitly state it is deprecated since 3.0.

bpo-33378 [https://bugs.python.org/issue?@action=redirect&bpo=33378]: Add Korean language switcher for https://docs.python.org/3/

bpo-33276 [https://bugs.python.org/issue?@action=redirect&bpo=33276]: Clarify that the __path__ attribute on modules cannot be just any value.

bpo-33201 [https://bugs.python.org/issue?@action=redirect&bpo=33201]: Modernize documentation for writing C extension types.

bpo-33195 [https://bugs.python.org/issue?@action=redirect&bpo=33195]: Deprecate Py_UNICODE usage in c-api/arg document. Py_UNICODE related APIs are deprecated since Python 3.3, but it is missed in the document.

bpo-33126 [https://bugs.python.org/issue?@action=redirect&bpo=33126]: Document PyBuffer_ToContiguous().

bpo-27212 [https://bugs.python.org/issue?@action=redirect&bpo=27212]: Modify documentation for the islice() recipe to consume initial values up to the start index.

bpo-28247 [https://bugs.python.org/issue?@action=redirect&bpo=28247]: Update zipapp documentation to describe how to make standalone applications.

bpo-18802 [https://bugs.python.org/issue?@action=redirect&bpo=18802]: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

bpo-27428 [https://bugs.python.org/issue?@action=redirect&bpo=27428]: Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder. (Patch by Himanshu Lakhara)

bpo-28124 [https://bugs.python.org/issue?@action=redirect&bpo=28124]: The ssl module function ssl.wrap_socket() has been de-emphasized and deprecated in favor of the more secure and efficient SSLContext.wrap_socket() method.

bpo-17232 [https://bugs.python.org/issue?@action=redirect&bpo=17232]: Clarify docs for -O and -OO. Patch by Terry Reedy.

bpo-32436 [https://bugs.python.org/issue?@action=redirect&bpo=32436]: Add documentation for the contextvars module (PEP 567).

bpo-32800 [https://bugs.python.org/issue?@action=redirect&bpo=32800]: Update link to w3c doc for xml default namespaces.

bpo-11015 [https://bugs.python.org/issue?@action=redirect&bpo=11015]: Update test.support documentation.

bpo-32613 [https://bugs.python.org/issue?@action=redirect&bpo=32613]: Update the faq/windows.html to use the py command from PEP 397 instead of python.

bpo-8722 [https://bugs.python.org/issue?@action=redirect&bpo=8722]: Document __getattr__() behavior when property get() method raises AttributeError.

bpo-32614 [https://bugs.python.org/issue?@action=redirect&bpo=32614]: Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation.

bpo-20709 [https://bugs.python.org/issue?@action=redirect&bpo=20709]: Remove the paragraph where we explain that os.utime() does not support a directory as path under Windows. Patch by Jan-Philip Gehrcke

bpo-32722 [https://bugs.python.org/issue?@action=redirect&bpo=32722]: Remove the bad example in the tutorial of the Generator Expression. Patch by Stéphane Wirtel

bpo-31972 [https://bugs.python.org/issue?@action=redirect&bpo=31972]: Improve docstrings for pathlib.PurePath subclasses.

bpo-30607 [https://bugs.python.org/issue?@action=redirect&bpo=30607]: Use the externalized python-docs-theme package when building the documentation.

bpo-8243 [https://bugs.python.org/issue?@action=redirect&bpo=8243]: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

bpo-32337 [https://bugs.python.org/issue?@action=redirect&bpo=32337]: Update documentation related with dict order.

bpo-25041 [https://bugs.python.org/issue?@action=redirect&bpo=25041]: Document AF_PACKET in the socket module.

bpo-31432 [https://bugs.python.org/issue?@action=redirect&bpo=31432]: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

Tests

bpo-35772 [https://bugs.python.org/issue?@action=redirect&bpo=35772]: Fix sparse file tests of test_tarfile on ppc64 with the tmpfs filesystem. Fix the function testing if the filesystem supports sparse files: create a file which contains data and "holes", instead of creating a file which contains no data. tmpfs effective block size is a page size (tmpfs lives in the page cache). RHEL uses 64 KiB pages on aarch64, ppc64, ppc64le, only s390x and x86_64 use 4 KiB pages, whereas the test punch holes of 4 KiB.

bpo-35045 [https://bugs.python.org/issue?@action=redirect&bpo=35045]: Make ssl tests less strict and also accept TLSv1 as system default. The changes unbreaks test_min_max_version on Fedora 29.

bpo-32710 [https://bugs.python.org/issue?@action=redirect&bpo=32710]: test_asyncio/test_sendfile.py now resets the event loop policy using tearDownModule() as done in other tests, to prevent a warning when running tests on Windows.

bpo-33717 [https://bugs.python.org/issue?@action=redirect&bpo=33717]: test.pythoninfo now logs information of all clocks, not only time.time() and time.perf_counter().

bpo-35488 [https://bugs.python.org/issue?@action=redirect&bpo=35488]: Add a test to pathlib's Path.match() to verify it does not support glob-style ** recursive pattern matching.

bpo-31731 [https://bugs.python.org/issue?@action=redirect&bpo=31731]: Fix a race condition in check_interrupted_write() of test_io: create directly the thread with SIGALRM signal blocked, rather than blocking the signal later from the thread. Previously, it was possible that the thread gets the signal before the signal is blocked.

bpo-35424 [https://bugs.python.org/issue?@action=redirect&bpo=35424]: Fix test_multiprocessing_main_handling: use multiprocessing.Pool with a context manager and then explicitly join the pool.

bpo-35519 [https://bugs.python.org/issue?@action=redirect&bpo=35519]: Rename test.bisect module to test.bisect_cmd to avoid conflict with bisect module when running directly a test like ./python Lib/test/test_xmlrpc.py.

bpo-35513 [https://bugs.python.org/issue?@action=redirect&bpo=35513]: Replace time.time() with time.monotonic() in tests to measure time delta.

bpo-34279 [https://bugs.python.org/issue?@action=redirect&bpo=34279]: test.support.run_unittest() no longer raise TestDidNotRun if the test result contains skipped tests. The exception is now only raised if no test have been run and no test have been skipped.

bpo-35412 [https://bugs.python.org/issue?@action=redirect&bpo=35412]: Add testcase to test_future4: check unicode literal.

bpo-26704 [https://bugs.python.org/issue?@action=redirect&bpo=26704]: Added test demonstrating double-patching of an instance method. Patch by Anthony Sottile.

bpo-33725 [https://bugs.python.org/issue?@action=redirect&bpo=33725]: test_multiprocessing_fork may crash on recent versions of macOS. Until the issue is resolved, skip the test on macOS.

bpo-35352 [https://bugs.python.org/issue?@action=redirect&bpo=35352]: Modify test_asyncio to use the certificate set from the test directory.

bpo-35317 [https://bugs.python.org/issue?@action=redirect&bpo=35317]: Fix mktime() overflow error in test_email: run test_localtime_daylight_true_dst_true() and test_localtime_daylight_false_dst_true() with a specific timezone.

bpo-21263 [https://bugs.python.org/issue?@action=redirect&bpo=21263]: After several reports that test_gdb does not work properly on macOS and since gdb is not shipped by default anymore, test_gdb is now skipped on macOS when LLVM Clang has been used to compile Python. Patch by Lysandros Nikolaou

bpo-34279 [https://bugs.python.org/issue?@action=redirect&bpo=34279]: regrtest issue a warning when no tests have been executed in a particular test file. Also, a new final result state is issued if no test have been executed across all test files. Patch by Pablo Galindo.

bpo-34962 [https://bugs.python.org/issue?@action=redirect&bpo=34962]: make docstest in Doc now passes., and is enforced in CI

bpo-23596 [https://bugs.python.org/issue?@action=redirect&bpo=23596]: Use argparse for the command line of the gzip module. Patch by Antony Lee

bpo-34537 [https://bugs.python.org/issue?@action=redirect&bpo=34537]: Fix test_gdb.test_strings() when LC_ALL=C and GDB was compiled with Python 3.6 or earlier.

bpo-34587 [https://bugs.python.org/issue?@action=redirect&bpo=34587]: test_socket: Remove RDSTest.testCongestion(). The test tries to fill the receiver's socket buffer and expects an error. But the RDS protocol doesn't require that. Moreover, the Linux implementation of RDS expects that the producer of the messages reduces its rate, it's not the role of the receiver to trigger an error. The test fails on Fedora 28 by design, so just remove it.

bpo-34661 [https://bugs.python.org/issue?@action=redirect&bpo=34661]: Fix test_shutil if unzip doesn't support -t.

bpo-34200 [https://bugs.python.org/issue?@action=redirect&bpo=34200]: Fixed non-deterministic flakiness of test_pkg by not using the scary test.support.module_cleanup() logic to save and restore sys.modules contents between test cases.

bpo-34569 [https://bugs.python.org/issue?@action=redirect&bpo=34569]: The experimental PEP 554 data channels now correctly pass negative PyLong objects between subinterpreters on 32-bit systems. Patch by Michael Felt.

bpo-34594 [https://bugs.python.org/issue?@action=redirect&bpo=34594]: Fix usage of hardcoded errno values in the tests.

bpo-34579 [https://bugs.python.org/issue?@action=redirect&bpo=34579]: Fix test_embed for AIX Patch by Michael Felt

bpo-34542 [https://bugs.python.org/issue?@action=redirect&bpo=34542]: Use 3072 RSA keys and SHA-256 signature for test certs and keys.

bpo-11193 [https://bugs.python.org/issue?@action=redirect&bpo=11193]: Remove special condition for AIX in test_subprocess.test_undecodable_env

bpo-34347 [https://bugs.python.org/issue?@action=redirect&bpo=34347]: Fix test_utf8_mode.test_cmd_line for AIX

bpo-34490 [https://bugs.python.org/issue?@action=redirect&bpo=34490]: On AIX with AF_UNIX family sockets getsockname() does not provide 'sockname', so skip calls to transport.get_extra_info('sockname')

bpo-34391 [https://bugs.python.org/issue?@action=redirect&bpo=34391]: Fix ftplib test for TLS 1.3 by reading from data socket.

bpo-11192 [https://bugs.python.org/issue?@action=redirect&bpo=11192]: Fix test_socket on AIX 6.1 and later IPv6 zone id supports only supported by inet_pton6_zone(). Switch to runtime-based platform.system() to establish current platform rather than build-time based sys.platform()

bpo-34399 [https://bugs.python.org/issue?@action=redirect&bpo=34399]: Update all RSA keys and DH params to use at least 2048 bits.

bpo-34373 [https://bugs.python.org/issue?@action=redirect&bpo=34373]: Fix test_mktime and test_pthread_getcpuclickid tests for AIX Add range checking for _PyTime_localtime for AIX Patch by Michael Felt

bpo-11191 [https://bugs.python.org/issue?@action=redirect&bpo=11191]: Skip the distutils test 'test_search_cpp' when using XLC as compiler patch by aixtools (Michael Felt)

Improved an error message when mock assert_has_calls fails.

bpo-33746 [https://bugs.python.org/issue?@action=redirect&bpo=33746]: Fix test_unittest when run in verbose mode.

bpo-33901 [https://bugs.python.org/issue?@action=redirect&bpo=33901]: Fix test_dbm_gnu on macOS with gdbm 1.15: add a larger value to make sure that the file size changes.

bpo-33873 [https://bugs.python.org/issue?@action=redirect&bpo=33873]: Fix a bug in regrtest that caused an extra test to run if --huntrleaks/-R was used. Exit with error in case that invalid parameters are specified to --huntrleaks/-R (at least one warmup run and one repetition must be used).

bpo-33562 [https://bugs.python.org/issue?@action=redirect&bpo=33562]: Check that a global asyncio event loop policy is not left behind by any tests.

bpo-33655 [https://bugs.python.org/issue?@action=redirect&bpo=33655]: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

bpo-32962 [https://bugs.python.org/issue?@action=redirect&bpo=32962]: Fixed test_gdb when Python is compiled with flags -mcet -fcf-protection -O0.

bpo-33358 [https://bugs.python.org/issue?@action=redirect&bpo=33358]: Fix test_embed.test_pre_initialization_sys_options() when the interpreter is built with --enable-shared.

bpo-32872 [https://bugs.python.org/issue?@action=redirect&bpo=32872]: Avoid regrtest compatibility issue with namespace packages.

bpo-32517 [https://bugs.python.org/issue?@action=redirect&bpo=32517]: Fix failing test_asyncio on macOS 10.12.2+ due to transport of KqueueSelector loop was not being closed.

bpo-32663 [https://bugs.python.org/issue?@action=redirect&bpo=32663]: Making sure the SMTPUTF8SimTests class of tests gets run in test_smtplib.py.

bpo-27643 [https://bugs.python.org/issue?@action=redirect&bpo=27643]: Test_C test case needs "signed short" bitfields, but the IBM XLC compiler (on AIX) does not support this Skip the code and test when AIX and XLC are used

Applicable to Python2-2.7 and later

bpo-19417 [https://bugs.python.org/issue?@action=redirect&bpo=19417]: Add test_bdb.py.

bpo-31809 [https://bugs.python.org/issue?@action=redirect&bpo=31809]: Add tests to verify connection with secp ECDH curves.

Build

bpo-34691 [https://bugs.python.org/issue?@action=redirect&bpo=34691]: The _contextvars module is now built into the core Python library on Windows.

bpo-35683 [https://bugs.python.org/issue?@action=redirect&bpo=35683]: Improved Azure Pipelines build steps and now verifying layouts correctly

bpo-35642 [https://bugs.python.org/issue?@action=redirect&bpo=35642]: Remove asynciomodule.c from pythoncore.vcxproj

bpo-35550 [https://bugs.python.org/issue?@action=redirect&bpo=35550]: Fix incorrect Solaris #ifdef checks to look for __sun && __SVR4 instead of sun when compiling.

bpo-35499 [https://bugs.python.org/issue?@action=redirect&bpo=35499]: make profile-opt no longer replaces CFLAGS_NODIST with CFLAGS. It now adds profile-guided optimization (PGO) flags to CFLAGS_NODIST: existing CFLAGS_NODIST flags are kept.

bpo-35257 [https://bugs.python.org/issue?@action=redirect&bpo=35257]: Avoid leaking the linker flags from Link Time Optimizations (LTO) into distutils when compiling C extensions.

bpo-35351 [https://bugs.python.org/issue?@action=redirect&bpo=35351]: When building Python with clang and LTO, LTO flags are no longer passed into CFLAGS to build third-party C extensions through distutils.

bpo-35139 [https://bugs.python.org/issue?@action=redirect&bpo=35139]: Fix a compiler error when statically linking pyexpat in Modules/Setup.

bpo-35059 [https://bugs.python.org/issue?@action=redirect&bpo=35059]: PCbuild: Set InlineFunctionExpansion to OnlyExplicitInline ("/Ob1" option) in pyproject.props in Debug mode to expand functions marked as inline. This change should make Python compiled in Debug mode a little bit faster on Windows.

bpo-35011 [https://bugs.python.org/issue?@action=redirect&bpo=35011]: Restores the use of pyexpatns.h to isolate our embedded copy of the expat C library so that its symbols do not conflict at link or dynamic loading time with an embedding application or other extension modules with their own version of libexpat.

bpo-28015 [https://bugs.python.org/issue?@action=redirect&bpo=28015]: Have --with-lto works correctly with clang.

bpo-34765 [https://bugs.python.org/issue?@action=redirect&bpo=34765]: Update the outdated install-sh file to the latest revision from automake v1.16.1

bpo-34585 [https://bugs.python.org/issue?@action=redirect&bpo=34585]: Check for floating-point byte order in configure.ac using compilation tests instead of executing code, so that these checks work in cross-compiled builds.

bpo-34710 [https://bugs.python.org/issue?@action=redirect&bpo=34710]: Fixed SSL module build with OpenSSL & pedantic CFLAGS.

bpo-34582 [https://bugs.python.org/issue?@action=redirect&bpo=34582]: Add JUnit XML output for regression tests and update Azure DevOps builds.

bpo-34081 [https://bugs.python.org/issue?@action=redirect&bpo=34081]: Make Sphinx warnings as errors in the Docs Makefile.

bpo-34555 [https://bugs.python.org/issue?@action=redirect&bpo=34555]: Fix for case where it was not possible to have both HAVE_LINUX_VM_SOCKETS_H and HAVE_SOCKADDR_ALG be undefined.

bpo-33015 [https://bugs.python.org/issue?@action=redirect&bpo=33015]: Fix an undefined behaviour in the pthread implementation of PyThread_start_new_thread(): add a function wrapper to always return NULL.

bpo-34245 [https://bugs.python.org/issue?@action=redirect&bpo=34245]: The Python shared library is now installed with write permission (mode 0755), which is the standard way of installing such libraries.

bpo-34121 [https://bugs.python.org/issue?@action=redirect&bpo=34121]: Fix detection of C11 atomic support on clang.

bpo-32430 [https://bugs.python.org/issue?@action=redirect&bpo=32430]: Rename Modules/Setup.dist to Modules/Setup, and remove the necessity to copy the former manually to the latter when updating the local source tree.

bpo-30345 [https://bugs.python.org/issue?@action=redirect&bpo=30345]: Add -g to LDFLAGS when compiling with LTO to get debug symbols.

bpo-5755 [https://bugs.python.org/issue?@action=redirect&bpo=5755]: Move -Wstrict-prototypes option to CFLAGS_NODIST from OPT. This option emitted annoying warnings when building extension modules written in C++.

bpo-33614 [https://bugs.python.org/issue?@action=redirect&bpo=33614]: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

bpo-33648 [https://bugs.python.org/issue?@action=redirect&bpo=33648]: The --with-c-locale-warning configuration flag has been removed. It has had no effect for about a year.

bpo-33522 [https://bugs.python.org/issue?@action=redirect&bpo=33522]: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

bpo-33512 [https://bugs.python.org/issue?@action=redirect&bpo=33512]: configure's check for "long double" has been simplified

bpo-33483 [https://bugs.python.org/issue?@action=redirect&bpo=33483]: C compiler is now correctly detected from the standard environment variables. --without-gcc and --with-icc options have been removed.

bpo-33394 [https://bugs.python.org/issue?@action=redirect&bpo=33394]: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

bpo-33393 [https://bugs.python.org/issue?@action=redirect&bpo=33393]: Update config.guess and config.sub files.

bpo-33377 [https://bugs.python.org/issue?@action=redirect&bpo=33377]: Add new triplets for mips r6 and riscv variants (used in extension suffixes).

bpo-32232 [https://bugs.python.org/issue?@action=redirect&bpo=32232]: By default, modules configured in Modules/Setup are no longer built with -DPy_BUILD_CORE. Instead, modules that specifically need that preprocessor definition include it in their individual entries.

bpo-33182 [https://bugs.python.org/issue?@action=redirect&bpo=33182]: The embedding tests can once again be built with clang 6.0

bpo-33163 [https://bugs.python.org/issue?@action=redirect&bpo=33163]: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

bpo-33012 [https://bugs.python.org/issue?@action=redirect&bpo=33012]: gcc 8 has added a new warning heuristic to detect invalid function casts and a stock python build seems to hit that warning quite often. The most common is the cast of a METH_NOARGS function (that uses just one argument) to a PyCFunction. Fix this by adding a dummy argument to all functions that implement METH_NOARGS.

bpo-32898 [https://bugs.python.org/issue?@action=redirect&bpo=32898]: Fix the python debug build when using COUNT_ALLOCS.

bpo-29442 [https://bugs.python.org/issue?@action=redirect&bpo=29442]: Replace optparse with argparse in setup.py

Windows

bpo-35890 [https://bugs.python.org/issue?@action=redirect&bpo=35890]: Fix API calling consistency of GetVersionEx and wcstok.

bpo-32560 [https://bugs.python.org/issue?@action=redirect&bpo=32560]: The py launcher now forwards its STARTUPINFO structure to child processes.

bpo-35854 [https://bugs.python.org/issue?@action=redirect&bpo=35854]: Fix EnvBuilder and --symlinks in venv on Windows

bpo-35811 [https://bugs.python.org/issue?@action=redirect&bpo=35811]: Avoid propagating venv settings when launching via py.exe

bpo-35797 [https://bugs.python.org/issue?@action=redirect&bpo=35797]: Fix default executable used by the multiprocessing module

bpo-35758 [https://bugs.python.org/issue?@action=redirect&bpo=35758]: Allow building on ARM with MSVC.

bpo-29734 [https://bugs.python.org/issue?@action=redirect&bpo=29734]: Fix handle leaks in os.stat on Windows.

bpo-35596 [https://bugs.python.org/issue?@action=redirect&bpo=35596]: Use unchecked PYCs for the embeddable distro to avoid zipimport restrictions.

bpo-35596 [https://bugs.python.org/issue?@action=redirect&bpo=35596]: Fix vcruntime140.dll being added to embeddable distro multiple times.

bpo-35402 [https://bugs.python.org/issue?@action=redirect&bpo=35402]: Update Windows build to use Tcl and Tk 8.6.9

bpo-35401 [https://bugs.python.org/issue?@action=redirect&bpo=35401]: Updates Windows build to OpenSSL 1.1.0j

bpo-34977 [https://bugs.python.org/issue?@action=redirect&bpo=34977]: venv on Windows will now use a python.exe redirector rather than copying the actual binaries from the base environment.

bpo-34977 [https://bugs.python.org/issue?@action=redirect&bpo=34977]: Adds support for building a Windows App Store package

bpo-35067 [https://bugs.python.org/issue?@action=redirect&bpo=35067]: Remove _distutils_findvs module and use vswhere.exe instead.

bpo-32557 [https://bugs.python.org/issue?@action=redirect&bpo=32557]: Allow shutil.disk_usage to take a file path on Windows

bpo-34770 [https://bugs.python.org/issue?@action=redirect&bpo=34770]: Fix a possible null pointer dereference in pyshellext.cpp.

bpo-34603 [https://bugs.python.org/issue?@action=redirect&bpo=34603]: Fix returning structs from functions produced by MSVC

bpo-34581 [https://bugs.python.org/issue?@action=redirect&bpo=34581]: Guard MSVC-specific code in socketmodule.c with #ifdef _MSC_VER.

bpo-34532 [https://bugs.python.org/issue?@action=redirect&bpo=34532]: Fixes exit code of list version arguments for py.exe.

bpo-34062 [https://bugs.python.org/issue?@action=redirect&bpo=34062]: Fixed the '--list' and '--list-paths' arguments for the py.exe launcher

bpo-34225 [https://bugs.python.org/issue?@action=redirect&bpo=34225]: Ensure INCLUDE and LIB directories do not end with a backslash.

bpo-34011 [https://bugs.python.org/issue?@action=redirect&bpo=34011]: A suite of code has been changed which copied across DLLs and init.tcl from the running Python location into a venv being created. These copies are needed only when running from a Python source build, and the copying code is now only run when that is the case, rather than whenever a venv is created.

bpo-34006 [https://bugs.python.org/issue?@action=redirect&bpo=34006]: Revert line length limit for Windows help docs. The line-length limit is not needed because the pages appear in a separate app rather than on a browser tab. It can also interact badly with the DPI setting.

bpo-31546 [https://bugs.python.org/issue?@action=redirect&bpo=31546]: Restore running PyOS_InputHook while waiting for user input at the prompt. The restores integration of interactive GUI windows (such as Matplotlib figures) with the prompt on Windows.

bpo-30237 [https://bugs.python.org/issue?@action=redirect&bpo=30237]: Output error when ReadConsole is canceled by CancelSynchronousIo instead of crashing.

bpo-33895 [https://bugs.python.org/issue?@action=redirect&bpo=33895]: GIL is released while calling functions that acquire Windows loader lock.

bpo-33720 [https://bugs.python.org/issue?@action=redirect&bpo=33720]: Reduces maximum marshal recursion depth on release builds.

bpo-29097 [https://bugs.python.org/issue?@action=redirect&bpo=29097]: Fix bug where datetime.fromtimestamp() erroneously throws an OSError on Windows for values between 0 and 86400. Patch by Ammar Askar.

bpo-33316 [https://bugs.python.org/issue?@action=redirect&bpo=33316]: PyThread_release_lock always fails

bpo-33184 [https://bugs.python.org/issue?@action=redirect&bpo=33184]: Update Windows installer to use OpenSSL 1.1.0h.

bpo-32890 [https://bugs.python.org/issue?@action=redirect&bpo=32890]: Fix usage of GetLastError() instead of errno in os.execve() and os.truncate().

bpo-33016 [https://bugs.python.org/issue?@action=redirect&bpo=33016]: Fix potential use of uninitialized memory in nt._getfinalpathname

bpo-32903 [https://bugs.python.org/issue?@action=redirect&bpo=32903]: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

bpo-32901 [https://bugs.python.org/issue?@action=redirect&bpo=32901]: Update Tcl and Tk versions to 8.6.8

bpo-31966 [https://bugs.python.org/issue?@action=redirect&bpo=31966]: Fixed WindowsConsoleIO.write() for writing empty data.

bpo-32409 [https://bugs.python.org/issue?@action=redirect&bpo=32409]: Ensures activate.bat can handle Unicode contents.

bpo-32457 [https://bugs.python.org/issue?@action=redirect&bpo=32457]: Improves handling of denormalized executable path when launching Python.

bpo-32370 [https://bugs.python.org/issue?@action=redirect&bpo=32370]: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

bpo-29248 [https://bugs.python.org/issue?@action=redirect&bpo=29248]: Fix os.readlink() on Windows, which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

bpo-1104 [https://bugs.python.org/issue?@action=redirect&bpo=1104]: Correctly handle string length in msilib.SummaryInfo.GetProperty() to prevent it from truncating the last character.

macOS

bpo-35401 [https://bugs.python.org/issue?@action=redirect&bpo=35401]: Update macOS installer to use OpenSSL 1.1.0j.

bpo-35025 [https://bugs.python.org/issue?@action=redirect&bpo=35025]: Properly guard the use of the CLOCK_GETTIME et al. macros in timemodule on macOS.

bpo-24658 [https://bugs.python.org/issue?@action=redirect&bpo=24658]: On macOS, fix reading from and writing into a file with a size larger than 2 GiB.

bpo-34405 [https://bugs.python.org/issue?@action=redirect&bpo=34405]: Update to OpenSSL 1.1.0i for macOS installer builds.

bpo-33635 [https://bugs.python.org/issue?@action=redirect&bpo=33635]: In macOS stat on some file descriptors (/dev/fd/3 f.e) will result in bad file descriptor OSError. Guard against this exception was added in is_dir, is_file and similar methods. DirEntry.is_dir can also throw this exception so _RecursiveWildcardSelector._iterate_directories was also extended with the same error ignoring pattern.

bpo-13631 [https://bugs.python.org/issue?@action=redirect&bpo=13631]: The .editrc file in user's home directory is now processed correctly during the readline initialization through editline emulation on macOS.

bpo-33184 [https://bugs.python.org/issue?@action=redirect&bpo=33184]: Update macOS installer build to use OpenSSL 1.1.0h.

bpo-32726 [https://bugs.python.org/issue?@action=redirect&bpo=32726]: Build and link with private copy of Tcl/Tk 8.6 for the macOS 10.6+ installer. The 10.9+ installer variant already does this. This means that the Python 3.7 provided by the python.org macOS installers no longer need or use any external versions of Tcl/Tk, either system-provided or user-installed, such as ActiveTcl.

bpo-32901 [https://bugs.python.org/issue?@action=redirect&bpo=32901]: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

bpo-31903 [https://bugs.python.org/issue?@action=redirect&bpo=31903]: In _scproxy, drop the GIL when calling into SystemConfiguration to avoid deadlocks.

IDLE

bpo-35770 [https://bugs.python.org/issue?@action=redirect&bpo=35770]: IDLE macosx deletes Options => Configure IDLE. It previously deleted Window => Zoom Height by mistake. (Zoom Height is now on the Options menu). On Mac, the settings dialog is accessed via Preferences on the IDLE menu.

bpo-35769 [https://bugs.python.org/issue?@action=redirect&bpo=35769]: Change IDLE's new file name from 'Untitled' to 'untitled'

bpo-35660 [https://bugs.python.org/issue?@action=redirect&bpo=35660]: Fix imports in idlelib.window.

bpo-35641 [https://bugs.python.org/issue?@action=redirect&bpo=35641]: Proper format calltip when the function has no docstring.

bpo-33987 [https://bugs.python.org/issue?@action=redirect&bpo=33987]: Use ttk Frame for ttk widgets.

bpo-34055 [https://bugs.python.org/issue?@action=redirect&bpo=34055]: Fix erroneous 'smart' indents and newlines in IDLE Shell.

bpo-35591 [https://bugs.python.org/issue?@action=redirect&bpo=35591]: Find Selection now works when selection not found.

bpo-35196 [https://bugs.python.org/issue?@action=redirect&bpo=35196]: Speed up squeezer line counting.

bpo-35598 [https://bugs.python.org/issue?@action=redirect&bpo=35598]: Update config_key: use PEP 8 names and ttk widgets, make some objects global, and add tests.

bpo-28097 [https://bugs.python.org/issue?@action=redirect&bpo=28097]: Add Previous/Next History entries to Shell menu.

bpo-35208 [https://bugs.python.org/issue?@action=redirect&bpo=35208]: Squeezer now properly counts wrapped lines before newlines.

bpo-35555 [https://bugs.python.org/issue?@action=redirect&bpo=35555]: Gray out Code Context menu entry when it's not applicable.

bpo-35521 [https://bugs.python.org/issue?@action=redirect&bpo=35521]: Document the IDLE editor code context feature. Add some internal references within the IDLE doc.

bpo-22703 [https://bugs.python.org/issue?@action=redirect&bpo=22703]: The Code Context menu label now toggles between Show/Hide Code Context. The Zoom Height menu now toggles between Zoom/Restore Height. Zoom Height has moved from the Window menu to the Options menu.

bpo-35213 [https://bugs.python.org/issue?@action=redirect&bpo=35213]: Where appropriate, use 'macOS' in idlelib.

bpo-34864 [https://bugs.python.org/issue?@action=redirect&bpo=34864]: On macOS, warn if the system preference "Prefer tabs when opening documents" is set to "Always".

bpo-34864 [https://bugs.python.org/issue?@action=redirect&bpo=34864]: Document two IDLE on MacOS issues. The System Preferences Dock "prefer tabs always" setting disables some IDLE features. Menus are a bit different than as described for Windows and Linux.

bpo-35202 [https://bugs.python.org/issue?@action=redirect&bpo=35202]: Remove unused imports from lib/idlelib

bpo-33000 [https://bugs.python.org/issue?@action=redirect&bpo=33000]: Document that IDLE's shell has no line limit. A program that runs indefinitely can overfill memory.

bpo-23220 [https://bugs.python.org/issue?@action=redirect&bpo=23220]: Explain how IDLE's Shell displays output.

bpo-35099 [https://bugs.python.org/issue?@action=redirect&bpo=35099]: Improve the doc about IDLE running user code. The section is renamed from "IDLE -- console differences" is renamed "Running user code". It mostly covers the implications of using custom sys.stdxxx objects.

bpo-35097 [https://bugs.python.org/issue?@action=redirect&bpo=35097]: Add IDLE doc subsection explaining editor windows. Topics include opening, title and status bar, .py* extension, and running.

bpo-35093 [https://bugs.python.org/issue?@action=redirect&bpo=35093]: Document the IDLE document viewer in the IDLE doc. Add a paragraph in "Help and preferences", "Help sources" subsection.

bpo-35088 [https://bugs.python.org/issue?@action=redirect&bpo=35088]: Update idlelib.help.copy_string docstring. We now use git and backporting instead of hg and forward merging.

bpo-35087 [https://bugs.python.org/issue?@action=redirect&bpo=35087]: Update idlelib help files for the current doc build. The main change is the elimination of chapter-section numbers.

bpo-34548 [https://bugs.python.org/issue?@action=redirect&bpo=34548]: Use configured color theme for read-only text views.

bpo-1529353 [https://bugs.python.org/issue?@action=redirect&bpo=1529353]: Enable "squeezing" of long outputs in the shell, to avoid performance degradation and to clean up the history without losing it. Squeezed outputs may be copied, viewed in a separate window, and "unsqueezed".

bpo-34047 [https://bugs.python.org/issue?@action=redirect&bpo=34047]: Fixed mousewheel scrolling direction on macOS.

bpo-34275 [https://bugs.python.org/issue?@action=redirect&bpo=34275]: Make IDLE calltips always visible on Mac. Some MacOS-tk combinations need .update_idletasks(). Patch by Kevin Walzer.

bpo-34120 [https://bugs.python.org/issue?@action=redirect&bpo=34120]: Fix unresponsiveness after closing certain windows and dialogs.

bpo-33975 [https://bugs.python.org/issue?@action=redirect&bpo=33975]: Avoid small type when running htests. Since part of the purpose of human-viewed tests is to determine that widgets look right, it is important that they look the same for testing as when running IDLE.

bpo-33905 [https://bugs.python.org/issue?@action=redirect&bpo=33905]: Add test for idlelib.stackview.StackBrowser.

bpo-33924 [https://bugs.python.org/issue?@action=redirect&bpo=33924]: Change mainmenu.menudefs key 'windows' to 'window'. Every other menudef key is lowercase version of main menu entry.

bpo-33906 [https://bugs.python.org/issue?@action=redirect&bpo=33906]: Rename idlelib.windows as window Match Window on the main menu and remove last plural module name.

bpo-33917 [https://bugs.python.org/issue?@action=redirect&bpo=33917]: Fix and document idlelib/idle_test/template.py. The revised file compiles, runs, and tests OK. idle_test/README.txt explains how to use it to create new IDLE test files.

bpo-33904 [https://bugs.python.org/issue?@action=redirect&bpo=33904]: IDLE: In rstrip, rename class RstripExtension as Rstrip

bpo-33907 [https://bugs.python.org/issue?@action=redirect&bpo=33907]: For consistency and clarity, rename an IDLE module and classes. Module calltips and its class CallTips are now calltip and Calltip. In module calltip_w, class CallTip is now CalltipWindow.

bpo-33856 [https://bugs.python.org/issue?@action=redirect&bpo=33856]: Add "help" in the welcome message of IDLE

bpo-33839 [https://bugs.python.org/issue?@action=redirect&bpo=33839]: IDLE: refactor ToolTip and CallTip and add documentation and tests

bpo-33855 [https://bugs.python.org/issue?@action=redirect&bpo=33855]: Minimally test all IDLE modules. Add missing files, import module, instantiate classes, and check coverage. Check existing files.

bpo-33656 [https://bugs.python.org/issue?@action=redirect&bpo=33656]: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.

bpo-33768 [https://bugs.python.org/issue?@action=redirect&bpo=33768]: Clicking on a context line moves that line to the top of the editor window.

bpo-33763 [https://bugs.python.org/issue?@action=redirect&bpo=33763]: IDLE: Use read-only text widget for code context instead of label widget.

bpo-33664 [https://bugs.python.org/issue?@action=redirect&bpo=33664]: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.

bpo-33679 [https://bugs.python.org/issue?@action=redirect&bpo=33679]: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.

bpo-33642 [https://bugs.python.org/issue?@action=redirect&bpo=33642]: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

bpo-33628 [https://bugs.python.org/issue?@action=redirect&bpo=33628]: IDLE: Cleanup codecontext.py and its test.

bpo-33564 [https://bugs.python.org/issue?@action=redirect&bpo=33564]: IDLE's code context now recognizes async as a block opener.

bpo-21474 [https://bugs.python.org/issue?@action=redirect&bpo=21474]: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.

bpo-33204 [https://bugs.python.org/issue?@action=redirect&bpo=33204]: IDLE: consistently color invalid string prefixes. A 'u' string prefix cannot be paired with either 'r' or 'f'. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

bpo-32984 [https://bugs.python.org/issue?@action=redirect&bpo=32984]: Set __file__ while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, -s runs a file named in environmental variable IDLESTARTUP or PYTHONSTARTUP; -r file runs file. Python sets __file__ to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the -n option.

bpo-32940 [https://bugs.python.org/issue?@action=redirect&bpo=32940]: Simplify and rename StringTranslatePseudoMapping in pyparse.

bpo-32916 [https://bugs.python.org/issue?@action=redirect&bpo=32916]: Change str to code in pyparse.

bpo-32905 [https://bugs.python.org/issue?@action=redirect&bpo=32905]: Remove unused code in pyparse module.

bpo-32874 [https://bugs.python.org/issue?@action=redirect&bpo=32874]: Add tests for pyparse.

bpo-32837 [https://bugs.python.org/issue?@action=redirect&bpo=32837]: Using the system and place-dependent default encoding for open() is a bad idea for IDLE's system and location-independent files.

bpo-32826 [https://bugs.python.org/issue?@action=redirect&bpo=32826]: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to 'ascii' because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.

bpo-32831 [https://bugs.python.org/issue?@action=redirect&bpo=32831]: Add docstrings and tests for codecontext.

bpo-32765 [https://bugs.python.org/issue?@action=redirect&bpo=32765]: Update configdialog General tab docstring to add new widgets to the widget list.

Tools/Demos

bpo-35884 [https://bugs.python.org/issue?@action=redirect&bpo=35884]: Add a benchmark script for timing various ways to access variables: Tools/scripts/var_access_benchmark.py.

bpo-34989 [https://bugs.python.org/issue?@action=redirect&bpo=34989]: python-gdb.py now handles errors on computing the line number of a Python frame.

bpo-20260 [https://bugs.python.org/issue?@action=redirect&bpo=20260]: Argument Clinic now has non-bitwise unsigned int converters.

bpo-32962 [https://bugs.python.org/issue?@action=redirect&bpo=32962]: python-gdb now catches UnicodeDecodeError exceptions when calling string().

bpo-32962 [https://bugs.python.org/issue?@action=redirect&bpo=32962]: python-gdb now catches ValueError on read_var(): when Python has no debug symbols for example.

bpo-33189 [https://bugs.python.org/issue?@action=redirect&bpo=33189]: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.

bpo-31920 [https://bugs.python.org/issue?@action=redirect&bpo=31920]: Fixed handling directories as arguments in the pygettext script. Based on patch by Oleg Krasnikov.

bpo-29673 [https://bugs.python.org/issue?@action=redirect&bpo=29673]: Fix pystackv and pystack gdbinit macros.

bpo-25427 [https://bugs.python.org/issue?@action=redirect&bpo=25427]: Remove the pyvenv script in favor of python3 -m venv in order to lower confusion as to what Python interpreter a virtual environment will be created for.

bpo-32885 [https://bugs.python.org/issue?@action=redirect&bpo=32885]: Add an -n flag for Tools/scripts/pathfix.py to disable automatic backup creation (files with ~ suffix).

bpo-32222 [https://bugs.python.org/issue?@action=redirect&bpo=32222]: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

bpo-31583 [https://bugs.python.org/issue?@action=redirect&bpo=31583]: Fix 2to3 for using with --add-suffix option but without --output-dir option for relative path to files in current directory.

C API

bpo-35713 [https://bugs.python.org/issue?@action=redirect&bpo=35713]: The PyByteArray_Init() and PyByteArray_Fini() functions have been removed. They did nothing since Python 2.7.4 and Python 3.2.0, were excluded from the limited API (stable ABI), and were not documented.

bpo-33817 [https://bugs.python.org/issue?@action=redirect&bpo=33817]: Fixed _PyBytes_Resize() for empty bytes objects.

bpo-35322 [https://bugs.python.org/issue?@action=redirect&bpo=35322]: Fix memory leak in PyUnicode_EncodeLocale() and PyUnicode_EncodeFSDefault() on error handling.

bpo-35059 [https://bugs.python.org/issue?@action=redirect&bpo=35059]: The following C macros have been converted to static inline functions: Py_INCREF(), Py_DECREF(), Py_XINCREF(), Py_XDECREF(), PyObject_INIT(), PyObject_INIT_VAR().

bpo-35296 [https://bugs.python.org/issue?@action=redirect&bpo=35296]: make install now also installs the internal API: Include/internal/*.h header files.

bpo-35081 [https://bugs.python.org/issue?@action=redirect&bpo=35081]: Internal APIs surrounded by #ifdef Py_BUILD_CORE have been moved from Include/*.h headers to new header files Include/internal/pycore_*.h.

bpo-35259 [https://bugs.python.org/issue?@action=redirect&bpo=35259]: Conditionally declare Py_FinalizeEx() (new in 3.6) based on Py_LIMITED_API. Patch by Arthur Neufeld.

bpo-35081 [https://bugs.python.org/issue?@action=redirect&bpo=35081]: The _PyObject_GC_TRACK() and _PyObject_GC_UNTRACK() macros have been removed from the public C API.

bpo-35134 [https://bugs.python.org/issue?@action=redirect&bpo=35134]: Creation of a new Include/cpython/ subdirectory.

bpo-34725 [https://bugs.python.org/issue?@action=redirect&bpo=34725]: Adds _Py_SetProgramFullPath so embedders may override sys.executable

bpo-34910 [https://bugs.python.org/issue?@action=redirect&bpo=34910]: Ensure that PyObject_Print() always returns -1 on error. Patch by Zackery Spytz.

bpo-34523 [https://bugs.python.org/issue?@action=redirect&bpo=34523]: Py_DecodeLocale() and Py_EncodeLocale() now use the UTF-8 encoding on Windows if Py_LegacyWindowsFSEncodingFlag is zero.

bpo-34193 [https://bugs.python.org/issue?@action=redirect&bpo=34193]: Fix pluralization in TypeError messages in getargs.c and typeobject.c: '1 argument' instead of '1 arguments' and '1 element' instead of '1 elements'.

bpo-34127 [https://bugs.python.org/issue?@action=redirect&bpo=34127]: Return grammatically correct error message based on argument count. Patch by Karthikeyan Singaravelan.

bpo-23927 [https://bugs.python.org/issue?@action=redirect&bpo=23927]: Fixed SystemError in PyArg_ParseTupleAndKeywords() when the w* format unit is used for optional parameter.

bpo-32455 [https://bugs.python.org/issue?@action=redirect&bpo=32455]: Added PyCompile_OpcodeStackEffectWithJump().

bpo-34008 [https://bugs.python.org/issue?@action=redirect&bpo=34008]: Py_Main() can again be called after Py_Initialize(), as in Python 3.6.

bpo-32500 [https://bugs.python.org/issue?@action=redirect&bpo=32500]: Fixed error messages for PySequence_Size(), PySequence_GetItem(), PySequence_SetItem() and PySequence_DelItem() called with a mapping and PyMapping_Size() called with a sequence.

bpo-33818 [https://bugs.python.org/issue?@action=redirect&bpo=33818]: PyExceptionClass_Name() will now return const char * instead of char *.

bpo-33042 [https://bugs.python.org/issue?@action=redirect&bpo=33042]: Embedding applications may once again call PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to calling Py_Initialize.

bpo-32374 [https://bugs.python.org/issue?@action=redirect&bpo=32374]: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

bpo-30863 [https://bugs.python.org/issue?@action=redirect&bpo=30863]: PyUnicode_AsWideChar() and PyUnicode_AsWideCharString() no longer cache the wchar_t* representation of string objects.

Python 3.7.0 final

Release date: 2018-06-27

Library

bpo-33851 [https://bugs.python.org/issue?@action=redirect&bpo=33851]: Fix ast.get_docstring() for a node that lacks a docstring.

C API

bpo-33932 [https://bugs.python.org/issue?@action=redirect&bpo=33932]: Calling Py_Initialize() twice does nothing, instead of failing with a fatal error: restore the Python 3.6 behaviour.

Python 3.7.0 release candidate 1

Release date: 2018-06-12

Core and Builtins

bpo-33803 [https://bugs.python.org/issue?@action=redirect&bpo=33803]: Fix a crash in hamt.c caused by enabling GC tracking for an object that hadn't all of its fields set to NULL.

bpo-33706 [https://bugs.python.org/issue?@action=redirect&bpo=33706]: Fix a crash in Python initialization when parsing the command line options. Thanks Christoph Gohlke for the bug report and the fix!

bpo-30654 [https://bugs.python.org/issue?@action=redirect&bpo=30654]: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

bpo-31849 [https://bugs.python.org/issue?@action=redirect&bpo=31849]: Fix signed/unsigned comparison warning in pyhash.c.

Library

bpo-30167 [https://bugs.python.org/issue?@action=redirect&bpo=30167]: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

bpo-33812 [https://bugs.python.org/issue?@action=redirect&bpo=33812]: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

bpo-30805 [https://bugs.python.org/issue?@action=redirect&bpo=30805]: Avoid race condition with debug logging

bpo-33694 [https://bugs.python.org/issue?@action=redirect&bpo=33694]: asyncio: Fix a race condition causing data loss on pause_reading()/resume_reading() when using the ProactorEventLoop.

bpo-32493 [https://bugs.python.org/issue?@action=redirect&bpo=32493]: Correct test for uuid_enc_be availability in configure.ac. Patch by Michael Felt.

bpo-33792 [https://bugs.python.org/issue?@action=redirect&bpo=33792]: Add asyncio.WindowsSelectorEventLoopPolicy and asyncio.WindowsProactorEventLoopPolicy.

bpo-33778 [https://bugs.python.org/issue?@action=redirect&bpo=33778]: Update unicodedata's database to Unicode version 11.0.0.

bpo-33770 [https://bugs.python.org/issue?@action=redirect&bpo=33770]: improve base64 exception message for encoded inputs of invalid length

bpo-33769 [https://bugs.python.org/issue?@action=redirect&bpo=33769]: asyncio/start_tls: Fix error message; cancel callbacks in case of an unhandled error; mark SSLTransport as closed if it is aborted.

bpo-33767 [https://bugs.python.org/issue?@action=redirect&bpo=33767]: The concatenation (+) and repetition (*) sequence operations now raise TypeError instead of SystemError when performed on mmap.mmap objects. Patch by Zackery Spytz.

bpo-33734 [https://bugs.python.org/issue?@action=redirect&bpo=33734]: asyncio/ssl: Fix AttributeError, increase default handshake timeout

bpo-11874 [https://bugs.python.org/issue?@action=redirect&bpo=11874]: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

bpo-33582 [https://bugs.python.org/issue?@action=redirect&bpo=33582]: Emit a deprecation warning for inspect.formatargspec

Documentation

bpo-33409 [https://bugs.python.org/issue?@action=redirect&bpo=33409]: Clarified the relationship between PEP 538 [https://peps.python.org/pep-0538/]'s PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

bpo-33736 [https://bugs.python.org/issue?@action=redirect&bpo=33736]: Improve the documentation of asyncio.open_connection(), asyncio.start_server() and their UNIX socket counterparts.

bpo-31432 [https://bugs.python.org/issue?@action=redirect&bpo=31432]: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

Build

bpo-5755 [https://bugs.python.org/issue?@action=redirect&bpo=5755]: Move -Wstrict-prototypes option to CFLAGS_NODIST from OPT. This option emitted annoying warnings when building extension modules written in C++.

Windows

bpo-33720 [https://bugs.python.org/issue?@action=redirect&bpo=33720]: Reduces maximum marshal recursion depth on release builds.

IDLE

bpo-33656 [https://bugs.python.org/issue?@action=redirect&bpo=33656]: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.

bpo-33768 [https://bugs.python.org/issue?@action=redirect&bpo=33768]: Clicking on a context line moves that line to the top of the editor window.

bpo-33763 [https://bugs.python.org/issue?@action=redirect&bpo=33763]: IDLE: Use read-only text widget for code context instead of label widget.

bpo-33664 [https://bugs.python.org/issue?@action=redirect&bpo=33664]: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.

bpo-33679 [https://bugs.python.org/issue?@action=redirect&bpo=33679]: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.

bpo-33642 [https://bugs.python.org/issue?@action=redirect&bpo=33642]: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

Python 3.7.0 beta 5

Release date: 2018-05-30

Core and Builtins

bpo-33622 [https://bugs.python.org/issue?@action=redirect&bpo=33622]: Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc.garbage list. PyGC_Collect() can now be called when an exception is set and preserves it.

bpo-33509 [https://bugs.python.org/issue?@action=redirect&bpo=33509]: Fix module_globals parameter of warnings.warn_explicit(): don't crash if module_globals is not a dict.

bpo-20104 [https://bugs.python.org/issue?@action=redirect&bpo=20104]: The new os.posix_spawn added in 3.7.0b1 was removed as we are still working on what the API should look like. Expect this in 3.8 instead.

bpo-33475 [https://bugs.python.org/issue?@action=redirect&bpo=33475]: Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation.

bpo-33391 [https://bugs.python.org/issue?@action=redirect&bpo=33391]: Fix a leak in set_symmetric_difference().

bpo-28055 [https://bugs.python.org/issue?@action=redirect&bpo=28055]: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

bpo-32911 [https://bugs.python.org/issue?@action=redirect&bpo=32911]: Due to unexpected compatibility issues discovered during downstream beta testing, reverted bpo-29463 [https://bugs.python.org/issue?@action=redirect&bpo=29463]. docstring field is removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes which was added in 3.7a1. Docstring expression is restored as a first statement in their body. Based on patch by Inada Naoki.

bpo-21983 [https://bugs.python.org/issue?@action=redirect&bpo=21983]: Fix a crash in ctypes.cast() in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

Library

bpo-32751 [https://bugs.python.org/issue?@action=redirect&bpo=32751]: When cancelling the task due to a timeout, asyncio.wait_for() will now wait until the cancellation is complete.

bpo-32684 [https://bugs.python.org/issue?@action=redirect&bpo=32684]: Fix gather to propagate cancellation of itself even with return_exceptions.

bpo-33654 [https://bugs.python.org/issue?@action=redirect&bpo=33654]: Support protocol type switching in SSLTransport.set_protocol().

bpo-33674 [https://bugs.python.org/issue?@action=redirect&bpo=33674]: Pause the transport as early as possible to further reduce the risk of data_received() being called before connection_made().

bpo-33674 [https://bugs.python.org/issue?@action=redirect&bpo=33674]: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

bpo-31647 [https://bugs.python.org/issue?@action=redirect&bpo=31647]: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it's already closed raises AttributeError.

bpo-32610 [https://bugs.python.org/issue?@action=redirect&bpo=32610]: Make asyncio.all_tasks() return only pending tasks.

bpo-32410 [https://bugs.python.org/issue?@action=redirect&bpo=32410]: Avoid blocking on file IO in sendfile fallback code

bpo-33469 [https://bugs.python.org/issue?@action=redirect&bpo=33469]: Fix RuntimeError after closing loop that used run_in_executor

bpo-33672 [https://bugs.python.org/issue?@action=redirect&bpo=33672]: Fix Task.__repr__ crash with Cython's bogus coroutines

bpo-33654 [https://bugs.python.org/issue?@action=redirect&bpo=33654]: Fix transport.set_protocol() to support switching between asyncio.Protocol and asyncio.BufferedProtocol. Fix loop.start_tls() to work with asyncio.BufferedProtocols.

bpo-33652 [https://bugs.python.org/issue?@action=redirect&bpo=33652]: Pickles of type variables and subscripted generics are now future-proof and compatible with older Python versions.

bpo-32493 [https://bugs.python.org/issue?@action=redirect&bpo=32493]: Fixed uuid.uuid1() on FreeBSD.

bpo-33618 [https://bugs.python.org/issue?@action=redirect&bpo=33618]: Finalize and document preliminary and experimental TLS 1.3 support with OpenSSL 1.1.1

bpo-33623 [https://bugs.python.org/issue?@action=redirect&bpo=33623]: Fix possible SIGSGV when asyncio.Future is created in __del__

bpo-30877 [https://bugs.python.org/issue?@action=redirect&bpo=30877]: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

bpo-33570 [https://bugs.python.org/issue?@action=redirect&bpo=33570]: Change TLS 1.3 cipher suite settings for compatibility with OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers enabled by default.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Do not simplify arguments to typing.Union. Now Union[Manager, Employee] is not simplified to Employee at runtime. Such simplification previously caused several bugs and limited possibilities for introspection.

bpo-33540 [https://bugs.python.org/issue?@action=redirect&bpo=33540]: Add a new block_on_close class attribute to ForkingMixIn and ThreadingMixIn classes of socketserver.

bpo-33548 [https://bugs.python.org/issue?@action=redirect&bpo=33548]: tempfile._candidate_tempdir_list should consider common TEMP locations

bpo-33109 [https://bugs.python.org/issue?@action=redirect&bpo=33109]: argparse subparsers are once again not required by default, reverting the change in behavior introduced by bpo-26510 [https://bugs.python.org/issue?@action=redirect&bpo=26510] in 3.7.0a2.

bpo-33536 [https://bugs.python.org/issue?@action=redirect&bpo=33536]: dataclasses.make_dataclass now checks for invalid field names and duplicate fields. Also, added a check for invalid field specifications.

bpo-33542 [https://bugs.python.org/issue?@action=redirect&bpo=33542]: Prevent uuid.get_node from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

bpo-26819 [https://bugs.python.org/issue?@action=redirect&bpo=26819]: Fix race condition with ReadTransport.resume_reading in Windows proactor event loop.

Fix failure in typing.get_type_hints() when ClassVar was provided as a string forward reference.

bpo-33505 [https://bugs.python.org/issue?@action=redirect&bpo=33505]: Optimize asyncio.ensure_future() by reordering if checks: 1.17x faster.

bpo-33497 [https://bugs.python.org/issue?@action=redirect&bpo=33497]: Add errors param to cgi.parse_multipart and make an encoding in FieldStorage use the given errors (needed for Twisted). Patch by Amber Brown.

bpo-33495 [https://bugs.python.org/issue?@action=redirect&bpo=33495]: Change dataclasses.Fields repr to use the repr of each of its members, instead of str. This makes it more clear what each field actually represents. This is especially true for the 'type' member.

bpo-33453 [https://bugs.python.org/issue?@action=redirect&bpo=33453]: Fix dataclasses to work if using literal string type annotations or if using PEP 563 "Postponed Evaluation of Annotations". Only specific string prefixes are detected for both ClassVar ("ClassVar" and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Minor fixes in typing module: add annotations to NamedTuple.__new__, pass *args and **kwds in Generic.__new__. Original PRs by Paulius Šarka and Chad Dombrova.

bpo-20087 [https://bugs.python.org/issue?@action=redirect&bpo=20087]: Updated alias mapping with glibc 2.27 supported locales.

bpo-33422 [https://bugs.python.org/issue?@action=redirect&bpo=33422]: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

bpo-28167 [https://bugs.python.org/issue?@action=redirect&bpo=28167]: The function platform.linux_distribution and platform.dist now trigger a DeprecationWarning and have been marked for removal in Python 3.8

bpo-33197 [https://bugs.python.org/issue?@action=redirect&bpo=33197]: Update error message when constructing invalid inspect.Parameters Patch by Donghee Na.

bpo-33263 [https://bugs.python.org/issue?@action=redirect&bpo=33263]: Fix FD leak in _SelectorSocketTransport Patch by Vlad Starostin.

bpo-32861 [https://bugs.python.org/issue?@action=redirect&bpo=32861]: The urllib.robotparser's __str__ representation now includes wildcard entries and the "Crawl-delay" and "Request-rate" fields. Patch by Michael Lazar.

bpo-32257 [https://bugs.python.org/issue?@action=redirect&bpo=32257]: The ssl module now contains OP_NO_RENEGOTIATION constant, available with OpenSSL 1.1.0h or 1.1.1.

bpo-16865 [https://bugs.python.org/issue?@action=redirect&bpo=16865]: Support arrays >=2GiB in ctypes. Patch by Segev Finer.

Documentation

bpo-23859 [https://bugs.python.org/issue?@action=redirect&bpo=23859]: Document that asyncio.wait() does not cancel its futures on timeout.

bpo-32436 [https://bugs.python.org/issue?@action=redirect&bpo=32436]: Document PEP 567 [https://peps.python.org/pep-0567/] changes to asyncio.

bpo-33604 [https://bugs.python.org/issue?@action=redirect&bpo=33604]: Update HMAC md5 default to a DeprecationWarning, bump removal to 3.8.

bpo-33503 [https://bugs.python.org/issue?@action=redirect&bpo=33503]: Fix broken pypi link

bpo-33421 [https://bugs.python.org/issue?@action=redirect&bpo=33421]: Add missing documentation for typing.AsyncContextManager.

Tests

bpo-33655 [https://bugs.python.org/issue?@action=redirect&bpo=33655]: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

bpo-32604 [https://bugs.python.org/issue?@action=redirect&bpo=32604]: Remove the _xxsubinterpreters module (meant for testing) and associated helpers. This module was originally added recently in 3.7b1.

Build

bpo-33614 [https://bugs.python.org/issue?@action=redirect&bpo=33614]: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

bpo-33522 [https://bugs.python.org/issue?@action=redirect&bpo=33522]: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

bpo-33012 [https://bugs.python.org/issue?@action=redirect&bpo=33012]: Add -Wno-cast-function-type for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists.

macOS

bpo-13631 [https://bugs.python.org/issue?@action=redirect&bpo=13631]: The .editrc file in user's home directory is now processed correctly during the readline initialization through editline emulation on macOS.

IDLE

bpo-33628 [https://bugs.python.org/issue?@action=redirect&bpo=33628]: IDLE: Cleanup codecontext.py and its test.

bpo-33564 [https://bugs.python.org/issue?@action=redirect&bpo=33564]: IDLE's code context now recognizes async as a block opener.

bpo-32831 [https://bugs.python.org/issue?@action=redirect&bpo=32831]: Add docstrings and tests for codecontext.

Python 3.7.0 beta 4

Release date: 2018-05-02

Core and Builtins

bpo-33363 [https://bugs.python.org/issue?@action=redirect&bpo=33363]: Raise a SyntaxError for async with and async for statements outside of async functions.

bpo-33128 [https://bugs.python.org/issue?@action=redirect&bpo=33128]: Fix a bug that causes PathFinder to appear twice on sys.meta_path. Patch by Pablo Galindo Salgado.

bpo-33312 [https://bugs.python.org/issue?@action=redirect&bpo=33312]: Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by adjusting how the internal struct _dictkeysobject shared keys structure is declared.

bpo-33231 [https://bugs.python.org/issue?@action=redirect&bpo=33231]: Fix potential memory leak in normalizestring().

bpo-33205 [https://bugs.python.org/issue?@action=redirect&bpo=33205]: Change dict growth function from round_up_to_power_2(used*2+hashtable_size/2) to round_up_to_power_2(used*3). Previously, dict is shrunk only when used == 0. Now dict has more chance to be shrunk.

bpo-29922 [https://bugs.python.org/issue?@action=redirect&bpo=29922]: Improved error messages in 'async with' when __aenter__() or __aexit__() return non-awaitable object.

bpo-33199 [https://bugs.python.org/issue?@action=redirect&bpo=33199]: Fix ma_version_tag in dict implementation is uninitialized when copying from key-sharing dict.

Library

bpo-33281 [https://bugs.python.org/issue?@action=redirect&bpo=33281]: Fix ctypes.util.find_library regression on macOS.

bpo-33383 [https://bugs.python.org/issue?@action=redirect&bpo=33383]: Fixed crash in the get() method of the dbm.ndbm database object when it is called with a single argument.

bpo-33329 [https://bugs.python.org/issue?@action=redirect&bpo=33329]: Fix multiprocessing regression on newer glibcs

bpo-991266 [https://bugs.python.org/issue?@action=redirect&bpo=991266]: Fix quoting of the Comment attribute of http.cookies.SimpleCookie.

bpo-33131 [https://bugs.python.org/issue?@action=redirect&bpo=33131]: Upgrade bundled version of pip to 10.0.1.

bpo-33308 [https://bugs.python.org/issue?@action=redirect&bpo=33308]: Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info=False and col_info=True.

bpo-33266 [https://bugs.python.org/issue?@action=redirect&bpo=33266]: lib2to3 now recognizes rf'...' strings.

bpo-11594 [https://bugs.python.org/issue?@action=redirect&bpo=11594]: Ensure line-endings are respected when using lib2to3.

bpo-33254 [https://bugs.python.org/issue?@action=redirect&bpo=33254]: Have importlib.resources.contents() and importlib.abc.ResourceReader.contents() return an iterable instead of an iterator.

bpo-33256 [https://bugs.python.org/issue?@action=redirect&bpo=33256]: Fix display of <module> call in the html produced by cgitb.html(). Patch by Stéphane Blondon.

bpo-33185 [https://bugs.python.org/issue?@action=redirect&bpo=33185]: Fixed regression when running pydoc with the -m switch. (The regression was introduced in 3.7.0b3 by the resolution of bpo-33053 [https://bugs.python.org/issue?@action=redirect&bpo=33053]) This fix also changed pydoc to add os.getcwd() to sys.path when necessary, rather than adding ".".

bpo-33169 [https://bugs.python.org/issue?@action=redirect&bpo=33169]: Delete entries of None in sys.path_importer_cache when importlib.machinery.invalidate_caches() is called.

bpo-33217 [https://bugs.python.org/issue?@action=redirect&bpo=33217]: Deprecate looking up non-Enum objects in Enum classes and Enum members (will raise TypeError in 3.8+).

bpo-33203 [https://bugs.python.org/issue?@action=redirect&bpo=33203]: random.Random.choice() now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits() implementation.

bpo-33224 [https://bugs.python.org/issue?@action=redirect&bpo=33224]: Update difflib.mdiff() for PEP 479 [https://peps.python.org/pep-0479/]. Convert an uncaught StopIteration in a generator into a return-statement.

bpo-33209 [https://bugs.python.org/issue?@action=redirect&bpo=33209]: End framing at the end of C implementation of pickle.Pickler.dump().

bpo-20104 [https://bugs.python.org/issue?@action=redirect&bpo=20104]: Improved error handling and fixed a reference leak in os.posix_spawn().

bpo-33175 [https://bugs.python.org/issue?@action=redirect&bpo=33175]: In dataclasses, Field.__set_name__ now looks up the __set_name__ special method on the class, not the instance, of the default value.

bpo-33097 [https://bugs.python.org/issue?@action=redirect&bpo=33097]: Raise RuntimeError when executor.submit is called during interpreter shutdown.

bpo-31908 [https://bugs.python.org/issue?@action=redirect&bpo=31908]: Fix output of cover files for trace module command-line tool. Previously emitted cover files only when --missing option was used. Patch by Michael Selik.

Documentation

bpo-33378 [https://bugs.python.org/issue?@action=redirect&bpo=33378]: Add Korean language switcher for https://docs.python.org/3/

bpo-33276 [https://bugs.python.org/issue?@action=redirect&bpo=33276]: Clarify that the __path__ attribute on modules cannot be just any value.

bpo-33201 [https://bugs.python.org/issue?@action=redirect&bpo=33201]: Modernize documentation for writing C extension types.

bpo-33195 [https://bugs.python.org/issue?@action=redirect&bpo=33195]: Deprecate Py_UNICODE usage in c-api/arg document. Py_UNICODE related APIs are deprecated since Python 3.3, but it is missed in the document.

bpo-8243 [https://bugs.python.org/issue?@action=redirect&bpo=8243]: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

bpo-32337 [https://bugs.python.org/issue?@action=redirect&bpo=32337]: Update documentation related with dict order.

Tests

bpo-33358 [https://bugs.python.org/issue?@action=redirect&bpo=33358]: Fix test_embed.test_pre_initialization_sys_options() when the interpreter is built with --enable-shared.

Build

bpo-33394 [https://bugs.python.org/issue?@action=redirect&bpo=33394]: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

bpo-33393 [https://bugs.python.org/issue?@action=redirect&bpo=33393]: Update config.guess and config.sub files.

bpo-33377 [https://bugs.python.org/issue?@action=redirect&bpo=33377]: Add new triplets for mips r6 and riscv variants (used in extension suffixes).

bpo-32232 [https://bugs.python.org/issue?@action=redirect&bpo=32232]: By default, modules configured in Modules/Setup are no longer built with -DPy_BUILD_CORE. Instead, modules that specifically need that preprocessor definition include it in their individual entries.

bpo-33182 [https://bugs.python.org/issue?@action=redirect&bpo=33182]: The embedding tests can once again be built with clang 6.0

Windows

bpo-33184 [https://bugs.python.org/issue?@action=redirect&bpo=33184]: Update Windows installer to use OpenSSL 1.1.0h.

macOS

bpo-33184 [https://bugs.python.org/issue?@action=redirect&bpo=33184]: Update macOS installer build to use OpenSSL 1.1.0h.

IDLE

bpo-21474 [https://bugs.python.org/issue?@action=redirect&bpo=21474]: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.

bpo-33204 [https://bugs.python.org/issue?@action=redirect&bpo=33204]: IDLE: consistently color invalid string prefixes. A 'u' string prefix cannot be paired with either 'r' or 'f'. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

Tools/Demos

bpo-33189 [https://bugs.python.org/issue?@action=redirect&bpo=33189]: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.

bpo-31920 [https://bugs.python.org/issue?@action=redirect&bpo=31920]: Fixed handling directories as arguments in the pygettext script. Based on patch by Oleg Krasnikov.

bpo-29673 [https://bugs.python.org/issue?@action=redirect&bpo=29673]: Fix pystackv and pystack gdbinit macros.

bpo-31583 [https://bugs.python.org/issue?@action=redirect&bpo=31583]: Fix 2to3 for using with --add-suffix option but without --output-dir option for relative path to files in current directory.

Python 3.7.0 beta 3

Release date: 2018-03-29

Security

bpo-33136 [https://bugs.python.org/issue?@action=redirect&bpo=33136]: Harden ssl module against LibreSSL CVE 2018-8970 [https://www.cve.org/CVERecord?id=CVE-2018-8970]. X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new test ensures that NULL bytes are not allowed.

bpo-33001 [https://bugs.python.org/issue?@action=redirect&bpo=33001]: Minimal fix to prevent buffer overrun in os.symlink on Windows

bpo-32981 [https://bugs.python.org/issue?@action=redirect&bpo=32981]: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE 2018-1060 [https://www.cve.org/CVERecord?id=CVE-2018-1060] and CVE 2018-1061 [https://www.cve.org/CVERecord?id=CVE-2018-1061]. Patch by Jamie Davis.

Core and Builtins

bpo-33053 [https://bugs.python.org/issue?@action=redirect&bpo=33053]: When using the -m switch, sys.path[0] is now explicitly expanded as the starting working directory, rather than being left as the empty path (which allows imports from the current working directory at the time of the import)

bpo-33018 [https://bugs.python.org/issue?@action=redirect&bpo=33018]: Improve consistency of errors raised by issubclass() when called with a non-class and an abstract base class as the first and second arguments, respectively. Patch by Josh Bronson.

bpo-33041 [https://bugs.python.org/issue?@action=redirect&bpo=33041]: Fixed jumping when the function contains an async for loop.

bpo-33026 [https://bugs.python.org/issue?@action=redirect&bpo=33026]: Fixed jumping out of "with" block by setting f_lineno.

bpo-33005 [https://bugs.python.org/issue?@action=redirect&bpo=33005]: Fix a crash on fork when using a custom memory allocator (ex: using PYTHONMALLOC env var). _PyGILState_Reinit() and _PyInterpreterState_Enable() now use the default RAW memory allocator to allocate a new interpreters mutex on fork.

bpo-17288 [https://bugs.python.org/issue?@action=redirect&bpo=17288]: Prevent jumps from 'return' and 'exception' trace events.

bpo-32836 [https://bugs.python.org/issue?@action=redirect&bpo=32836]: Don't use temporary variables in cases of list/dict/set comprehensions

Library

bpo-33141 [https://bugs.python.org/issue?@action=redirect&bpo=33141]: Have Field objects pass through __set_name__ to their default values, if they have their own __set_name__.

bpo-33096 [https://bugs.python.org/issue?@action=redirect&bpo=33096]: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

bpo-32873 [https://bugs.python.org/issue?@action=redirect&bpo=32873]: Treat type variables and special typing forms as immutable by copy and pickle. This fixes several minor issues and inconsistencies, and improves backwards compatibility with Python 3.6.

bpo-33134 [https://bugs.python.org/issue?@action=redirect&bpo=33134]: When computing dataclass's __hash__, use the lookup table to contain the function which returns the __hash__ value. This is an improvement over looking up a string, and then testing that string to see what to do.

bpo-33127 [https://bugs.python.org/issue?@action=redirect&bpo=33127]: The ssl module now compiles with LibreSSL 2.7.1.

bpo-32505 [https://bugs.python.org/issue?@action=redirect&bpo=32505]: Raise TypeError if a member variable of a dataclass is of type Field, but doesn't have a type annotation.

bpo-33078 [https://bugs.python.org/issue?@action=redirect&bpo=33078]: Fix the failure on OSX caused by the tests relying on sem_getvalue

bpo-33116 [https://bugs.python.org/issue?@action=redirect&bpo=33116]: Add 'Field' to dataclasses.__all__.

bpo-32896 [https://bugs.python.org/issue?@action=redirect&bpo=32896]: Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class.

bpo-33100 [https://bugs.python.org/issue?@action=redirect&bpo=33100]: Dataclasses: If a field has a default value that's a MemberDescriptorType, then it's from that field being in __slots__, not an actual default value.

bpo-32953 [https://bugs.python.org/issue?@action=redirect&bpo=32953]: If a non-dataclass inherits from a frozen dataclass, allow attributes to be added to the derived class. Only attributes from the frozen dataclass cannot be assigned to. Require all dataclasses in a hierarchy to be either all frozen or all non-frozen.

bpo-33061 [https://bugs.python.org/issue?@action=redirect&bpo=33061]: Add missing NoReturn to __all__ in typing.py

bpo-33078 [https://bugs.python.org/issue?@action=redirect&bpo=33078]: Fix the size handling in multiprocessing.Queue when a pickling error occurs.

bpo-33064 [https://bugs.python.org/issue?@action=redirect&bpo=33064]: lib2to3 now properly supports trailing commas after *args and **kwargs in function signatures.

bpo-33056 [https://bugs.python.org/issue?@action=redirect&bpo=33056]: FIX properly close leaking fds in concurrent.futures.ProcessPoolExecutor.

bpo-33021 [https://bugs.python.org/issue?@action=redirect&bpo=33021]: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

bpo-31804 [https://bugs.python.org/issue?@action=redirect&bpo=31804]: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

bpo-33037 [https://bugs.python.org/issue?@action=redirect&bpo=33037]: Skip sending/receiving data after SSL transport closing.

bpo-27683 [https://bugs.python.org/issue?@action=redirect&bpo=27683]: Fix a regression in ipaddress that result of hosts() is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

bpo-32999 [https://bugs.python.org/issue?@action=redirect&bpo=32999]: Fix C implementation of ABC.__subclasscheck__(cls, subclass) crashed when subclass is not a type object.

bpo-33009 [https://bugs.python.org/issue?@action=redirect&bpo=33009]: Fix inspect.signature() for single-parameter partialmethods.

bpo-32969 [https://bugs.python.org/issue?@action=redirect&bpo=32969]: Expose several missing constants in zlib and fix corresponding documentation.

bpo-32056 [https://bugs.python.org/issue?@action=redirect&bpo=32056]: Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules aifc, wave and sunau.

bpo-32844 [https://bugs.python.org/issue?@action=redirect&bpo=32844]: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

bpo-32857 [https://bugs.python.org/issue?@action=redirect&bpo=32857]: In tkinter, after_cancel(None) now raises a ValueError instead of canceling the first scheduled function. Patch by Cheryl Sabella.

bpo-31639 [https://bugs.python.org/issue?@action=redirect&bpo=31639]: http.server now exposes a ThreadedHTTPServer class and uses it when the module is run with -m to cope with web browsers pre-opening sockets.

bpo-27645 [https://bugs.python.org/issue?@action=redirect&bpo=27645]: sqlite3.Connection now exposes a backup method, if the underlying SQLite library is at version 3.6.11 or higher. Patch by Lele Gaifax.

Documentation

bpo-33126 [https://bugs.python.org/issue?@action=redirect&bpo=33126]: Document PyBuffer_ToContiguous().

bpo-27212 [https://bugs.python.org/issue?@action=redirect&bpo=27212]: Modify documentation for the islice() recipe to consume initial values up to the start index.

bpo-28247 [https://bugs.python.org/issue?@action=redirect&bpo=28247]: Update zipapp documentation to describe how to make standalone applications.

bpo-18802 [https://bugs.python.org/issue?@action=redirect&bpo=18802]: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

bpo-27428 [https://bugs.python.org/issue?@action=redirect&bpo=27428]: Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder. (Patch by Himanshu Lakhara)

Tests

bpo-32872 [https://bugs.python.org/issue?@action=redirect&bpo=32872]: Avoid regrtest compatibility issue with namespace packages.

bpo-32517 [https://bugs.python.org/issue?@action=redirect&bpo=32517]: Fix failing test_asyncio on macOS 10.12.2+ due to transport of KqueueSelector loop was not being closed.

bpo-19417 [https://bugs.python.org/issue?@action=redirect&bpo=19417]: Add test_bdb.py.

Build

bpo-33163 [https://bugs.python.org/issue?@action=redirect&bpo=33163]: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

Windows

bpo-33016 [https://bugs.python.org/issue?@action=redirect&bpo=33016]: Fix potential use of uninitialized memory in nt._getfinalpathname

bpo-32903 [https://bugs.python.org/issue?@action=redirect&bpo=32903]: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

macOS

bpo-32726 [https://bugs.python.org/issue?@action=redirect&bpo=32726]: Build and link with private copy of Tcl/Tk 8.6 for the macOS 10.6+ installer. The 10.9+ installer variant already does this. This means that the Python 3.7 provided by the python.org macOS installers no longer need or use any external versions of Tcl/Tk, either system-provided or user-installed, such as ActiveTcl.

IDLE

bpo-32984 [https://bugs.python.org/issue?@action=redirect&bpo=32984]: Set __file__ while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, -s runs a file named in environmental variable IDLESTARTUP or PYTHONSTARTUP; -r file runs file. Python sets __file__ to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the -n option.

bpo-32940 [https://bugs.python.org/issue?@action=redirect&bpo=32940]: Simplify and rename StringTranslatePseudoMapping in pyparse.

Tools/Demos

bpo-32885 [https://bugs.python.org/issue?@action=redirect&bpo=32885]: Add an -n flag for Tools/scripts/pathfix.py to disable automatic backup creation (files with ~ suffix).

C API

bpo-33042 [https://bugs.python.org/issue?@action=redirect&bpo=33042]: Embedding applications may once again call PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to calling Py_Initialize.

bpo-32374 [https://bugs.python.org/issue?@action=redirect&bpo=32374]: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

Python 3.7.0 beta 2

Release date: 2018-02-27

Security

bpo-28414 [https://bugs.python.org/issue?@action=redirect&bpo=28414]: The ssl module now allows users to perform their own IDN en/decoding when using SNI.

Core and Builtins

bpo-32889 [https://bugs.python.org/issue?@action=redirect&bpo=32889]: Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range.

bpo-31356 [https://bugs.python.org/issue?@action=redirect&bpo=31356]: Remove the new API added in bpo-31356 [https://bugs.python.org/issue?@action=redirect&bpo=31356] (gc.ensure_disabled() context manager).

bpo-32305 [https://bugs.python.org/issue?@action=redirect&bpo=32305]: For namespace packages, ensure that both __file__ and __spec__.origin are set to None.

bpo-32303 [https://bugs.python.org/issue?@action=redirect&bpo=32303]: Make sure __spec__.loader matches __loader__ for namespace packages.

bpo-32711 [https://bugs.python.org/issue?@action=redirect&bpo=32711]: Fix the warning messages for Python/ast_unparse.c. Patch by Stéphane Wirtel

bpo-32583 [https://bugs.python.org/issue?@action=redirect&bpo=32583]: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

Library

bpo-32960 [https://bugs.python.org/issue?@action=redirect&bpo=32960]: For dataclasses, disallow inheriting frozen from non-frozen classes, and also disallow inheriting non-frozen from frozen classes. This restriction will be relaxed at a future date.

bpo-32713 [https://bugs.python.org/issue?@action=redirect&bpo=32713]: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

bpo-32951 [https://bugs.python.org/issue?@action=redirect&bpo=32951]: Direct instantiation of SSLSocket and SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were suppose to use ssl.wrap_socket() or SSLContext.

bpo-32929 [https://bugs.python.org/issue?@action=redirect&bpo=32929]: Remove the tri-state parameter "hash", and add the boolean "unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, raise TypeError. If unsafe_hash is False, add a __hash__ based on the values of eq= and frozen=. The unsafe_hash=False behavior is the same as the old hash=None behavior. unsafe_hash=False is the default, just as hash=None used to be.

bpo-32947 [https://bugs.python.org/issue?@action=redirect&bpo=32947]: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future compatibility with OpenSSL 1.1.1.

bpo-30622 [https://bugs.python.org/issue?@action=redirect&bpo=30622]: The ssl module now detects missing NPN support in LibreSSL.

bpo-32922 [https://bugs.python.org/issue?@action=redirect&bpo=32922]: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

bpo-32859 [https://bugs.python.org/issue?@action=redirect&bpo=32859]: In os.dup2, don't check every call whether the dup3 syscall exists or not.

bpo-32556 [https://bugs.python.org/issue?@action=redirect&bpo=32556]: nt._getfinalpathname, nt._getvolumepathname and nt._getdiskusage now correctly convert from bytes.

bpo-25988 [https://bugs.python.org/issue?@action=redirect&bpo=25988]: Emit a DeprecationWarning when using or importing an ABC directly from collections rather than from collections.abc.

bpo-21060 [https://bugs.python.org/issue?@action=redirect&bpo=21060]: Rewrite confusing message from setup.py upload from "No dist file created in earlier command" to the more helpful "Must create and upload files in one command".

bpo-32852 [https://bugs.python.org/issue?@action=redirect&bpo=32852]: Make sure sys.argv remains as a list when running trace.

bpo-31333 [https://bugs.python.org/issue?@action=redirect&bpo=31333]: _abc module is added. It is a speedup module with C implementations for various functions and methods in abc. Creating an ABC subclass and calling isinstance or issubclass with an ABC subclass are up to 1.5x faster. In addition, this makes Python start-up up to 10% faster. Note that the new implementation hides internal registry and caches, previously accessible via private attributes _abc_registry, _abc_cache, and _abc_negative_cache. There are three debugging helper methods that can be used instead _dump_registry, _abc_registry_clear, and _abc_caches_clear.

bpo-32841 [https://bugs.python.org/issue?@action=redirect&bpo=32841]: Fixed asyncio.Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

bpo-32819 [https://bugs.python.org/issue?@action=redirect&bpo=32819]: ssl.match_hostname() has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses. Error reporting for invalid wildcards has been improved.

bpo-32394 [https://bugs.python.org/issue?@action=redirect&bpo=32394]: socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version Windows during run-time.

bpo-31787 [https://bugs.python.org/issue?@action=redirect&bpo=31787]: Fixed refleaks of __init__() methods in various modules. (Contributed by Oren Milman)

bpo-30157 [https://bugs.python.org/issue?@action=redirect&bpo=30157]: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

bpo-32792 [https://bugs.python.org/issue?@action=redirect&bpo=32792]: collections.ChainMap() preserves the order of the underlying mappings.

bpo-32775 [https://bugs.python.org/issue?@action=redirect&bpo=32775]: fnmatch.translate() no longer produces patterns which contain set operations. Sets starting with '[' or containing '--', '&&', '~~' or '||' will be interpreted differently in regular expressions in future versions. Currently they emit warnings. fnmatch.translate() now avoids producing patterns containing such sets by accident.

bpo-32622 [https://bugs.python.org/issue?@action=redirect&bpo=32622]: Implement native fast sendfile for Windows proactor event loop.

bpo-32777 [https://bugs.python.org/issue?@action=redirect&bpo=32777]: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

bpo-32647 [https://bugs.python.org/issue?@action=redirect&bpo=32647]: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

bpo-32741 [https://bugs.python.org/issue?@action=redirect&bpo=32741]: Implement asyncio.TimerHandle.when() method.

bpo-32691 [https://bugs.python.org/issue?@action=redirect&bpo=32691]: Use mod_spec.parent when running modules with pdb

bpo-32734 [https://bugs.python.org/issue?@action=redirect&bpo=32734]: Fixed asyncio.Lock() safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

bpo-32727 [https://bugs.python.org/issue?@action=redirect&bpo=32727]: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

bpo-31453 [https://bugs.python.org/issue?@action=redirect&bpo=31453]: Add TLSVersion constants and SSLContext.maximum_version / minimum_version attributes. The new API wraps OpenSSL 1.1 https://web.archive.org/web/20180309043602/https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html feature.

bpo-24334 [https://bugs.python.org/issue?@action=redirect&bpo=24334]: Internal implementation details of ssl module were cleaned up. The SSLSocket has one less layer of indirection. Owner and session information are now handled by the SSLSocket and SSLObject constructor. Channel binding implementation has been simplified.

bpo-31848 [https://bugs.python.org/issue?@action=redirect&bpo=31848]: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

bpo-32585 [https://bugs.python.org/issue?@action=redirect&bpo=32585]: Add Ttk spinbox widget to tkinter.ttk. Patch by Alan D Moore.

bpo-32221 [https://bugs.python.org/issue?@action=redirect&bpo=32221]: Various functions returning tuple containing IPv6 addresses now omit %scope part since the same information is already encoded in scopeid tuple item. Especially this speeds up socket.recvfrom() when it receives multicast packet since useless resolving of network interface name is omitted.

bpo-30693 [https://bugs.python.org/issue?@action=redirect&bpo=30693]: The TarFile class now recurses directories in a reproducible way.

bpo-30693 [https://bugs.python.org/issue?@action=redirect&bpo=30693]: The ZipFile class now recurses directories in a reproducible way.

Documentation

bpo-28124 [https://bugs.python.org/issue?@action=redirect&bpo=28124]: The ssl module function ssl.wrap_socket() has been de-emphasized and deprecated in favor of the more secure and efficient SSLContext.wrap_socket() method.

bpo-17232 [https://bugs.python.org/issue?@action=redirect&bpo=17232]: Clarify docs for -O and -OO. Patch by Terry Reedy.

bpo-32436 [https://bugs.python.org/issue?@action=redirect&bpo=32436]: Add documentation for the contextvars module (PEP 567).

bpo-32800 [https://bugs.python.org/issue?@action=redirect&bpo=32800]: Update link to w3c doc for xml default namespaces.

bpo-11015 [https://bugs.python.org/issue?@action=redirect&bpo=11015]: Update test.support documentation.

bpo-8722 [https://bugs.python.org/issue?@action=redirect&bpo=8722]: Document __getattr__() behavior when property get() method raises AttributeError.

bpo-32614 [https://bugs.python.org/issue?@action=redirect&bpo=32614]: Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation.

bpo-31972 [https://bugs.python.org/issue?@action=redirect&bpo=31972]: Improve docstrings for pathlib.PurePath subclasses.

Tests

bpo-31809 [https://bugs.python.org/issue?@action=redirect&bpo=31809]: Add tests to verify connection with secp ECDH curves.

Build

bpo-32898 [https://bugs.python.org/issue?@action=redirect&bpo=32898]: Fix the python debug build when using COUNT_ALLOCS.

Windows

bpo-32901 [https://bugs.python.org/issue?@action=redirect&bpo=32901]: Update Tcl and Tk versions to 8.6.8

bpo-31966 [https://bugs.python.org/issue?@action=redirect&bpo=31966]: Fixed WindowsConsoleIO.write() for writing empty data.

bpo-32409 [https://bugs.python.org/issue?@action=redirect&bpo=32409]: Ensures activate.bat can handle Unicode contents.

bpo-32457 [https://bugs.python.org/issue?@action=redirect&bpo=32457]: Improves handling of denormalized executable path when launching Python.

bpo-32370 [https://bugs.python.org/issue?@action=redirect&bpo=32370]: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

bpo-29248 [https://bugs.python.org/issue?@action=redirect&bpo=29248]: Fix os.readlink() on Windows, which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

macOS

bpo-32901 [https://bugs.python.org/issue?@action=redirect&bpo=32901]: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

IDLE

bpo-32916 [https://bugs.python.org/issue?@action=redirect&bpo=32916]: Change str to code in pyparse.

bpo-32905 [https://bugs.python.org/issue?@action=redirect&bpo=32905]: Remove unused code in pyparse module.

bpo-32874 [https://bugs.python.org/issue?@action=redirect&bpo=32874]: Add tests for pyparse.

bpo-32837 [https://bugs.python.org/issue?@action=redirect&bpo=32837]: Using the system and place-dependent default encoding for open() is a bad idea for IDLE's system and location-independent files.

bpo-32826 [https://bugs.python.org/issue?@action=redirect&bpo=32826]: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to 'ascii' because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.

bpo-32765 [https://bugs.python.org/issue?@action=redirect&bpo=32765]: Update configdialog General tab docstring to add new widgets to the widget list.

Tools/Demos

bpo-32222 [https://bugs.python.org/issue?@action=redirect&bpo=32222]: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

Python 3.7.0 beta 1

Release date: 2018-01-30

Core and Builtins

bpo-32703 [https://bugs.python.org/issue?@action=redirect&bpo=32703]: Fix coroutine's ResourceWarning when there's an active error set when it's being finalized.

bpo-32650 [https://bugs.python.org/issue?@action=redirect&bpo=32650]: Pdb and other debuggers dependent on bdb.py will correctly step over (next command) native coroutines. Patch by Pablo Galindo.

bpo-28685 [https://bugs.python.org/issue?@action=redirect&bpo=28685]: Optimize list.sort() and sorted() by using type specialized comparisons when possible.

bpo-32685 [https://bugs.python.org/issue?@action=redirect&bpo=32685]: Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi-colon instead of a newline. Patch by Nitish Chandra.

bpo-32697 [https://bugs.python.org/issue?@action=redirect&bpo=32697]: Python now explicitly preserves the definition order of keyword-only parameters. It's always preserved their order, but this behavior was never guaranteed before; this behavior is now guaranteed and tested.

bpo-32690 [https://bugs.python.org/issue?@action=redirect&bpo=32690]: The locals() dictionary now displays in the lexical order that variables were defined. Previously, the order was reversed.

bpo-32677 [https://bugs.python.org/issue?@action=redirect&bpo=32677]: Add .isascii() method to str, bytes and bytearray. It can be used to test that string contains only ASCII characters.

bpo-32670 [https://bugs.python.org/issue?@action=redirect&bpo=32670]: Enforce PEP 479 [https://peps.python.org/pep-0479/] for all code. This means that manually raising a StopIteration exception from a generator is prohibited for all code, regardless of whether 'from __future__ import generator_stop' was used or not.

bpo-32591 [https://bugs.python.org/issue?@action=redirect&bpo=32591]: Added built-in support for tracking the origin of coroutine objects; see sys.set_coroutine_origin_tracking_depth and CoroutineType.cr_origin. This replaces the asyncio debug mode's use of coroutine wrapping for native coroutine objects.

bpo-31368 [https://bugs.python.org/issue?@action=redirect&bpo=31368]: Expose preadv and pwritev system calls in the os module. Patch by Pablo Galindo

bpo-32544 [https://bugs.python.org/issue?@action=redirect&bpo=32544]: hasattr(obj, name) and getattr(obj, name, default) are about 4 times faster than before when name is not found and obj doesn't override __getattr__ or __getattribute__.

bpo-26163 [https://bugs.python.org/issue?@action=redirect&bpo=26163]: Improved frozenset() hash to create more distinct hash values when faced with datasets containing many similar values.

bpo-32550 [https://bugs.python.org/issue?@action=redirect&bpo=32550]: Remove the STORE_ANNOTATION bytecode.

bpo-20104 [https://bugs.python.org/issue?@action=redirect&bpo=20104]: Expose posix_spawn as a low level API in the os module. (removed before 3.7.0rc1)

bpo-24340 [https://bugs.python.org/issue?@action=redirect&bpo=24340]: Fixed estimation of the code stack size.

bpo-32436 [https://bugs.python.org/issue?@action=redirect&bpo=32436]: Implement PEP 567 [https://peps.python.org/pep-0567/] Context Variables.

bpo-18533 [https://bugs.python.org/issue?@action=redirect&bpo=18533]: repr() on a dict containing its own values() or items() no longer raises RecursionError; OrderedDict similarly. Instead, use ..., as for other recursive structures. Patch by Ben North.

bpo-20891 [https://bugs.python.org/issue?@action=redirect&bpo=20891]: Py_Initialize() now creates the GIL. The GIL is no longer created "on demand" to fix a race condition when PyGILState_Ensure() is called in a non-Python thread.

bpo-32028 [https://bugs.python.org/issue?@action=redirect&bpo=32028]: Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls. Patch by Sanyam Khurana.

bpo-31179 [https://bugs.python.org/issue?@action=redirect&bpo=31179]: Make dict.copy() up to 5.5 times faster.

bpo-31113 [https://bugs.python.org/issue?@action=redirect&bpo=31113]: Get rid of recursion in the compiler for normal control flow.

Library

bpo-25988 [https://bugs.python.org/issue?@action=redirect&bpo=25988]: Deprecate exposing the contents of collections.abc in the regular collections module.

bpo-31429 [https://bugs.python.org/issue?@action=redirect&bpo=31429]: The default cipher suite selection of the ssl module now uses a blacklist approach rather than a hard-coded whitelist. Python no longer re-enables ciphers that have been blocked by OpenSSL security update. Default cipher suite selection can be configured on compile time.

bpo-30306 [https://bugs.python.org/issue?@action=redirect&bpo=30306]: contextlib.contextmanager now releases the arguments passed to the underlying generator as soon as the context manager is entered. Previously it would keep them alive for as long as the context manager was alive, even when not being used as a function decorator. Patch by Martin Teichmann.

bpo-21417 [https://bugs.python.org/issue?@action=redirect&bpo=21417]: Added support for setting the compression level for zipfile.ZipFile.

bpo-32251 [https://bugs.python.org/issue?@action=redirect&bpo=32251]: Implement asyncio.BufferedProtocol (provisional API).

bpo-32513 [https://bugs.python.org/issue?@action=redirect&bpo=32513]: In dataclasses, allow easier overriding of dunder methods without specifying decorator parameters.

bpo-32660 [https://bugs.python.org/issue?@action=redirect&bpo=32660]: termios makes available FIONREAD, FIONCLEX, FIOCLEX, FIOASYNC and FIONBIO also under Solaris/derivatives.

bpo-27931 [https://bugs.python.org/issue?@action=redirect&bpo=27931]: Fix email address header parsing error when the username is an empty quoted string. Patch by Xiang Zhang.

bpo-32659 [https://bugs.python.org/issue?@action=redirect&bpo=32659]: Under Solaris and derivatives, os.stat_result provides a st_fstype attribute.

bpo-32662 [https://bugs.python.org/issue?@action=redirect&bpo=32662]: Implement Server.start_serving(), Server.serve_forever(), and Server.is_serving() methods. Add 'start_serving' keyword parameter to loop.create_server() and loop.create_unix_server().

bpo-32391 [https://bugs.python.org/issue?@action=redirect&bpo=32391]: Implement asyncio.StreamWriter.wait_closed() and asyncio.StreamWriter.is_closing() methods

bpo-32643 [https://bugs.python.org/issue?@action=redirect&bpo=32643]: Make Task._step, Task._wakeup and Future._schedule_callbacks methods private.

bpo-32630 [https://bugs.python.org/issue?@action=redirect&bpo=32630]: Refactor decimal module to use contextvars to store decimal context.

bpo-32622 [https://bugs.python.org/issue?@action=redirect&bpo=32622]: Add asyncio.AbstractEventLoop.sendfile() method.

bpo-32304 [https://bugs.python.org/issue?@action=redirect&bpo=32304]: distutils' upload command no longer corrupts tar files ending with a CR byte, and no longer tries to convert CR to CRLF in any of the upload text fields.

bpo-32502 [https://bugs.python.org/issue?@action=redirect&bpo=32502]: uuid.uuid1 no longer raises an exception if a 64-bit hardware address is encountered.

bpo-32596 [https://bugs.python.org/issue?@action=redirect&bpo=32596]: concurrent.futures imports ThreadPoolExecutor and ProcessPoolExecutor lazily (using PEP 562 [https://peps.python.org/pep-0562/]). It makes import asyncio about 15% faster because asyncio uses only ThreadPoolExecutor by default.

bpo-31801 [https://bugs.python.org/issue?@action=redirect&bpo=31801]: Add _ignore_ to Enum so temporary variables can be used during class construction without being turned into members.

bpo-32576 [https://bugs.python.org/issue?@action=redirect&bpo=32576]: Use queue.SimpleQueue() in places where it can be invoked from a weakref callback.

bpo-32574 [https://bugs.python.org/issue?@action=redirect&bpo=32574]: Fix memory leak in asyncio.Queue, when the queue has limited size and it is full, the cancellation of queue.put() can cause a memory leak. Patch by: José Melero.

bpo-32521 [https://bugs.python.org/issue?@action=redirect&bpo=32521]: The nis module is now compatible with new libnsl and headers location.

bpo-32467 [https://bugs.python.org/issue?@action=redirect&bpo=32467]: collections.abc.ValuesView now inherits from collections.abc.Collection.

bpo-32473 [https://bugs.python.org/issue?@action=redirect&bpo=32473]: Improve ABCMeta._dump_registry() output readability

bpo-32102 [https://bugs.python.org/issue?@action=redirect&bpo=32102]: New argument capture_output for subprocess.run

bpo-32521 [https://bugs.python.org/issue?@action=redirect&bpo=32521]: glibc has removed Sun RPC. Use replacement libtirpc headers and library in nis module.

bpo-32493 [https://bugs.python.org/issue?@action=redirect&bpo=32493]: UUID module fixes build for FreeBSD/OpenBSD

bpo-32503 [https://bugs.python.org/issue?@action=redirect&bpo=32503]: Pickling with protocol 4 no longer creates too small frames.

bpo-29237 [https://bugs.python.org/issue?@action=redirect&bpo=29237]: Create enum for pstats sorting options

bpo-32454 [https://bugs.python.org/issue?@action=redirect&bpo=32454]: Add close(fd) function to the socket module.

bpo-25942 [https://bugs.python.org/issue?@action=redirect&bpo=25942]: The subprocess module is now more graceful when handling a Ctrl-C KeyboardInterrupt during subprocess.call, subprocess.run, or a Popen context manager. It now waits a short amount of time for the child (presumed to have also gotten the SIGINT) to exit, before continuing the KeyboardInterrupt exception handling. This still includes a SIGKILL in the call() and run() APIs, but at least the child had a chance first.

bpo-32433 [https://bugs.python.org/issue?@action=redirect&bpo=32433]: The hmac module now has hmac.digest(), which provides an optimized HMAC digest.

bpo-28134 [https://bugs.python.org/issue?@action=redirect&bpo=28134]: Sockets now auto-detect family, type and protocol from file descriptor by default.

bpo-32404 [https://bugs.python.org/issue?@action=redirect&bpo=32404]: Fix bug where datetime.datetime.fromtimestamp() did not call __new__ in datetime.datetime subclasses.

bpo-32403 [https://bugs.python.org/issue?@action=redirect&bpo=32403]: Improved speed of datetime.date and datetime.datetime alternate constructors.

bpo-32228 [https://bugs.python.org/issue?@action=redirect&bpo=32228]: Ensure that truncate() preserves the file position (as reported by tell()) after writes longer than the buffer size.

bpo-32410 [https://bugs.python.org/issue?@action=redirect&bpo=32410]: Implement loop.sock_sendfile for asyncio event loop.

bpo-22908 [https://bugs.python.org/issue?@action=redirect&bpo=22908]: Added seek and tell to the ZipExtFile class. This only works if the file object used to open the zipfile is seekable.

bpo-32373 [https://bugs.python.org/issue?@action=redirect&bpo=32373]: Add socket.getblocking() method.

bpo-32248 [https://bugs.python.org/issue?@action=redirect&bpo=32248]: Add importlib.resources and importlib.abc.ResourceReader as the unified API for reading resources contained within packages. Loaders wishing to support resource reading must implement the get_resource_reader() method. File-based and zipimport-based loaders both implement these APIs. importlib.abc.ResourceLoader is deprecated in favor of these new APIs.

bpo-32320 [https://bugs.python.org/issue?@action=redirect&bpo=32320]: collections.namedtuple() now supports default values.

bpo-29302 [https://bugs.python.org/issue?@action=redirect&bpo=29302]: Add contextlib.AsyncExitStack. Patch by Alexander Mohr and Ilya Kulakov.

bpo-31961 [https://bugs.python.org/issue?@action=redirect&bpo=31961]: Removed in Python 3.7.0b2. The args argument of subprocess.Popen can now be a path-like object. If args is given as a sequence, it's first element can now be a path-like object as well.

bpo-31900 [https://bugs.python.org/issue?@action=redirect&bpo=31900]: The locale.localeconv() function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep byte strings if they are non-ASCII or longer than 1 byte, and the LC_NUMERIC locale is different than the LC_CTYPE locale. This temporary change affects other threads. Same change for the str.format() method when formatting a number (int, float, float and subclasses) with the n type (ex: '{:n}'.format(1234)).

bpo-31853 [https://bugs.python.org/issue?@action=redirect&bpo=31853]: Use super().method instead of socket.method in SSLSocket. They were there most likely for legacy reasons.

bpo-31399 [https://bugs.python.org/issue?@action=redirect&bpo=31399]: The ssl module now uses OpenSSL's X509_VERIFY_PARAM_set1_host() and X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses. Subject common name fallback can be disabled with SSLContext.hostname_checks_common_name.

bpo-14976 [https://bugs.python.org/issue?@action=redirect&bpo=14976]: Add a queue.SimpleQueue class, an unbounded FIFO queue with a reentrant C implementation of put().

Documentation

bpo-32724 [https://bugs.python.org/issue?@action=redirect&bpo=32724]: Add references to some commands in the documentation of Pdb. Patch by Stéphane Wirtel

bpo-32649 [https://bugs.python.org/issue?@action=redirect&bpo=32649]: Complete the C API documentation, profiling and tracing part with the newly added per-opcode events.

bpo-17799 [https://bugs.python.org/issue?@action=redirect&bpo=17799]: Explain real behaviour of sys.settrace and sys.setprofile and their C-API counterparts regarding which type of events are received in each function. Patch by Pablo Galindo Salgado.

Tests

bpo-32721 [https://bugs.python.org/issue?@action=redirect&bpo=32721]: Fix test_hashlib to not fail if the _md5 module is not built.

bpo-28414 [https://bugs.python.org/issue?@action=redirect&bpo=28414]: Add test cases for IDNA 2003 and 2008 host names. IDNA 2003 internationalized host names are working since bpo-31399 [https://bugs.python.org/issue?@action=redirect&bpo=31399] has landed. IDNA 2008 are still broken.

bpo-32604 [https://bugs.python.org/issue?@action=redirect&bpo=32604]: Add a new "_xxsubinterpreters" extension module that exposes the existing subinterpreter C-API and a new cross-interpreter data sharing mechanism. The module is primarily intended for more thorough testing of the existing subinterpreter support. Note that the _xxsubinterpreters module has been removed in 3.7.0rc1.

bpo-32602 [https://bugs.python.org/issue?@action=redirect&bpo=32602]: Add test certs and test for ECDSA cert and EC/RSA dual mode.

bpo-32549 [https://bugs.python.org/issue?@action=redirect&bpo=32549]: On Travis CI, Python now Compiles and uses a local copy of OpenSSL 1.1.0g for testing.

Build

bpo-32635 [https://bugs.python.org/issue?@action=redirect&bpo=32635]: Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system.

bpo-32598 [https://bugs.python.org/issue?@action=redirect&bpo=32598]: Use autoconf to detect OpenSSL libs, headers and supported features. The ax_check_openssl M4 macro uses pkg-config to locate OpenSSL and falls back to manual search.

bpo-32593 [https://bugs.python.org/issue?@action=redirect&bpo=32593]: Drop support of FreeBSD 9 and older.

bpo-29708 [https://bugs.python.org/issue?@action=redirect&bpo=29708]: If the SOURCE_DATE_EPOCH environment variable is set, py_compile will always create hash-based .pyc files.

Windows

bpo-32588 [https://bugs.python.org/issue?@action=redirect&bpo=32588]: Create standalone _distutils_findvs module and add missing _queue module to installer.

bpo-29911 [https://bugs.python.org/issue?@action=redirect&bpo=29911]: Ensure separate Modify and Uninstall buttons are displayed.

bpo-32507 [https://bugs.python.org/issue?@action=redirect&bpo=32507]: Use app-local UCRT install rather than the proper update for old versions of Windows.

macOS

bpo-32726 [https://bugs.python.org/issue?@action=redirect&bpo=32726]: Provide an additional, more modern macOS installer variant that supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied third-party libraries to OpenSSL 1.1.0g and to SQLite 3.22.0. The 10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.

bpo-28440 [https://bugs.python.org/issue?@action=redirect&bpo=28440]: No longer add /Library/Python/3.x/site-packages to sys.path for macOS framework builds to avoid future conflicts.

C API

bpo-32681 [https://bugs.python.org/issue?@action=redirect&bpo=32681]: Fix uninitialized variable 'res' in the C implementation of os.dup2. Patch by Stéphane Wirtel

bpo-10381 [https://bugs.python.org/issue?@action=redirect&bpo=10381]: Add C API access to the datetime.timezone constructor and datetime.timezone.UTC singleton.

Python 3.7.0 alpha 4

Release date: 2018-01-08

Core and Builtins

bpo-31975 [https://bugs.python.org/issue?@action=redirect&bpo=31975]: The default warning filter list now starts with a "default::DeprecationWarning:__main__" entry, so deprecation warnings are once again shown by default in single-file scripts and at the interactive prompt.

bpo-32226 [https://bugs.python.org/issue?@action=redirect&bpo=32226]: __class_getitem__ is now an automatic class method.

bpo-32399 [https://bugs.python.org/issue?@action=redirect&bpo=32399]: Add AIX uuid library support for RFC4122 using uuid_create() in libc.a

bpo-32390 [https://bugs.python.org/issue?@action=redirect&bpo=32390]: Fix the compilation failure on AIX after the f_fsid field has been added to the object returned by os.statvfs() (bpo-32143 [https://bugs.python.org/issue?@action=redirect&bpo=32143]). Original patch by Michael Felt.

bpo-32379 [https://bugs.python.org/issue?@action=redirect&bpo=32379]: Make MRO computation faster when a class inherits from a single base.

bpo-32259 [https://bugs.python.org/issue?@action=redirect&bpo=32259]: The error message of a TypeError raised when unpack non-iterable is now more specific.

bpo-27169 [https://bugs.python.org/issue?@action=redirect&bpo=27169]: The __debug__ constant is now optimized out at compile time. This fixes also bpo-22091 [https://bugs.python.org/issue?@action=redirect&bpo=22091].

bpo-32329 [https://bugs.python.org/issue?@action=redirect&bpo=32329]: The -R option now turns on hash randomization when the PYTHONHASHSEED environment variable is set to 0. Previously, the option was ignored. Moreover, sys.flags.hash_randomization is now properly set to 0 when hash randomization is turned off by PYTHONHASHSEED=0.

bpo-30416 [https://bugs.python.org/issue?@action=redirect&bpo=30416]: The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding. Increased limits for constants that can be produced in constant folding.

bpo-32282 [https://bugs.python.org/issue?@action=redirect&bpo=32282]: Fix an unnecessary ifdef in the include of VersionHelpers.h in socketmodule on Windows.

bpo-30579 [https://bugs.python.org/issue?@action=redirect&bpo=30579]: Implement TracebackType.__new__ to allow Python-level creation of traceback objects, and make TracebackType.tb_next mutable.

bpo-32260 [https://bugs.python.org/issue?@action=redirect&bpo=32260]: Don't byte swap the input keys to the SipHash algorithm on big-endian platforms. This should ensure siphash gives consistent results across platforms.

bpo-31506 [https://bugs.python.org/issue?@action=redirect&bpo=31506]: Improve the error message logic for object.__new__ and object.__init__. Patch by Sanyam Khurana.

bpo-20361 [https://bugs.python.org/issue?@action=redirect&bpo=20361]: -b and -bb now inject 'default::BytesWarning' and error::BytesWarning entries into sys.warnoptions, ensuring that they take precedence over any other warning filters configured via the -W option or the PYTHONWARNINGS environment variable.

bpo-32230 [https://bugs.python.org/issue?@action=redirect&bpo=32230]: -X dev now injects a 'default' entry into sys.warnoptions, ensuring that it behaves identically to actually passing -Wdefault at the command line.

bpo-29240 [https://bugs.python.org/issue?@action=redirect&bpo=29240]: Add a new UTF-8 mode: implementation of the PEP 540 [https://peps.python.org/pep-0540/].

bpo-32226 [https://bugs.python.org/issue?@action=redirect&bpo=32226]: PEP 560 [https://peps.python.org/pep-0560/]: Add support for __mro_entries__ and __class_getitem__. Implemented by Ivan Levkivskyi.

bpo-32225 [https://bugs.python.org/issue?@action=redirect&bpo=32225]: PEP 562 [https://peps.python.org/pep-0562/]: Add support for module __getattr__ and __dir__. Implemented by Ivan Levkivskyi.

bpo-31901 [https://bugs.python.org/issue?@action=redirect&bpo=31901]: The atexit module now has its callback stored per interpreter.

bpo-31650 [https://bugs.python.org/issue?@action=redirect&bpo=31650]: Implement PEP 552 [https://peps.python.org/pep-0552/] (Deterministic pycs). Python now supports invalidating bytecode cache files bashed on a source content hash rather than source last-modified time.

bpo-29469 [https://bugs.python.org/issue?@action=redirect&bpo=29469]: Move constant folding from bytecode layer to AST layer. Original patch by Eugene Toder.

Library

bpo-32506 [https://bugs.python.org/issue?@action=redirect&bpo=32506]: Now that dict is defined as keeping insertion order, drop OrderedDict and just use plain dict.

bpo-32279 [https://bugs.python.org/issue?@action=redirect&bpo=32279]: Add params to dataclasses.make_dataclasses(): init, repr, eq, order, hash, and frozen. Pass them through to dataclass().

bpo-32278 [https://bugs.python.org/issue?@action=redirect&bpo=32278]: Make type information optional on dataclasses.make_dataclass(). If omitted, the string 'typing.Any' is used.

bpo-32499 [https://bugs.python.org/issue?@action=redirect&bpo=32499]: Add dataclasses.is_dataclass(obj), which returns True if obj is a dataclass or an instance of one.

bpo-32468 [https://bugs.python.org/issue?@action=redirect&bpo=32468]: Improve frame repr() to mention filename, code name and current line number.

bpo-23749 [https://bugs.python.org/issue?@action=redirect&bpo=23749]: asyncio: Implement loop.start_tls()

bpo-32441 [https://bugs.python.org/issue?@action=redirect&bpo=32441]: Return the new file descriptor (i.e., the second argument) from os.dup2. Previously, None was always returned.

bpo-32422 [https://bugs.python.org/issue?@action=redirect&bpo=32422]: functools.lru_cache uses less memory (3 words for each cached key) and takes about 1/3 time for cyclic GC.

bpo-31721 [https://bugs.python.org/issue?@action=redirect&bpo=31721]: Prevent Python crash from happening when Future._log_traceback is set to True manually. Now it can only be set to False, or a ValueError is raised.

bpo-32415 [https://bugs.python.org/issue?@action=redirect&bpo=32415]: asyncio: Add Task.get_loop() and Future.get_loop()

bpo-26133 [https://bugs.python.org/issue?@action=redirect&bpo=26133]: Don't unsubscribe signals in asyncio UNIX event loop on interpreter shutdown.

bpo-32363 [https://bugs.python.org/issue?@action=redirect&bpo=32363]: Make asyncio.Task.set_exception() and set_result() raise NotImplementedError. Task._step() and Future.__await__() raise proper exceptions when they are in an invalid state, instead of raising an AssertionError.

bpo-32357 [https://bugs.python.org/issue?@action=redirect&bpo=32357]: Optimize asyncio.iscoroutine() and loop.create_task() for non-native coroutines (e.g. async/await compiled with Cython). 'loop.create_task(python_coroutine)' used to be 20% faster than 'loop.create_task(cython_coroutine)'. Now, the latter is as fast.

bpo-32356 [https://bugs.python.org/issue?@action=redirect&bpo=32356]: asyncio.transport.resume_reading() and pause_reading() are now idempotent. New transport.is_reading() method is added.

bpo-32355 [https://bugs.python.org/issue?@action=redirect&bpo=32355]: Optimize asyncio.gather(); now up to 15% faster.

bpo-32351 [https://bugs.python.org/issue?@action=redirect&bpo=32351]: Use fastpath in asyncio.sleep if delay<0 (2x boost)

bpo-32348 [https://bugs.python.org/issue?@action=redirect&bpo=32348]: Optimize asyncio.Future schedule/add/remove callback. The optimization shows 3-6% performance improvements of async/await code.

bpo-32331 [https://bugs.python.org/issue?@action=redirect&bpo=32331]: Fix socket.settimeout() and socket.setblocking() to keep socket.type as is. Fix socket.socket() constructor to reset any bit flags applied to socket's type. This change only affects OSes that have SOCK_NONBLOCK and/or SOCK_CLOEXEC.

bpo-32248 [https://bugs.python.org/issue?@action=redirect&bpo=32248]: Add importlib.abc.ResourceReader as an ABC for loaders to provide a unified API for reading resources contained within packages. Also add importlib.resources as the port of importlib_resources.

bpo-32311 [https://bugs.python.org/issue?@action=redirect&bpo=32311]: Implement asyncio.create_task(coro) shortcut

bpo-32327 [https://bugs.python.org/issue?@action=redirect&bpo=32327]: Convert asyncio functions that were documented as coroutines to coroutines. Affected functions: loop.sock_sendall, loop.sock_recv, loop.sock_accept, loop.getaddrinfo, loop.getnameinfo.

bpo-32323 [https://bugs.python.org/issue?@action=redirect&bpo=32323]: urllib.parse.urlsplit() does not convert zone-id (scope) to lower case for scoped IPv6 addresses in hostnames now.

bpo-32302 [https://bugs.python.org/issue?@action=redirect&bpo=32302]: Fix bdist_wininst of distutils for CRT v142: it binary compatible with CRT v140.

bpo-29711 [https://bugs.python.org/issue?@action=redirect&bpo=29711]: Fix stop_serving in asyncio proactor loop kill all listening servers

bpo-32308 [https://bugs.python.org/issue?@action=redirect&bpo=32308]: re.sub() now replaces empty matches adjacent to a previous non-empty match.

bpo-29970 [https://bugs.python.org/issue?@action=redirect&bpo=29970]: Abort asyncio SSLProtocol connection if handshake not complete within 10 seconds.

bpo-32314 [https://bugs.python.org/issue?@action=redirect&bpo=32314]: Implement asyncio.run().

bpo-17852 [https://bugs.python.org/issue?@action=redirect&bpo=17852]: Revert incorrect fix based on misunderstanding of _Py_PyAtExit() semantics.

bpo-32296 [https://bugs.python.org/issue?@action=redirect&bpo=32296]: Implement asyncio._get_running_loop() and get_event_loop() in C. This makes them 4x faster.

bpo-32250 [https://bugs.python.org/issue?@action=redirect&bpo=32250]: Implement asyncio.current_task() and asyncio.all_tasks(). Add helpers intended to be used by alternative task implementations: asyncio._register_task, asyncio._enter_task, asyncio._leave_task and asyncio._unregister_task. Deprecate asyncio.Task.current_task() and asyncio.Task.all_tasks().

bpo-32255 [https://bugs.python.org/issue?@action=redirect&bpo=32255]: A single empty field is now always quoted when written into a CSV file. This allows to distinguish an empty row from a row consisting of a single empty field. Patch by Licht Takeuchi.

bpo-32277 [https://bugs.python.org/issue?@action=redirect&bpo=32277]: Raise NotImplementedError instead of SystemError on platforms where chmod(..., follow_symlinks=False) is not supported. Patch by Anthony Sottile.

bpo-30050 [https://bugs.python.org/issue?@action=redirect&bpo=30050]: New argument warn_on_full_buffer to signal.set_wakeup_fd lets you control whether Python prints a warning on stderr when the wakeup fd buffer overflows.

bpo-29137 [https://bugs.python.org/issue?@action=redirect&bpo=29137]: The fpectl library has been removed. It was never enabled by default, never worked correctly on x86-64, and it changed the Python ABI in ways that caused unexpected breakage of C extensions.

bpo-32273 [https://bugs.python.org/issue?@action=redirect&bpo=32273]: Move asyncio.test_utils to test.test_asyncio.

bpo-32272 [https://bugs.python.org/issue?@action=redirect&bpo=32272]: Remove asyncio.async() function.

bpo-32269 [https://bugs.python.org/issue?@action=redirect&bpo=32269]: Add asyncio.get_running_loop() function.

bpo-32265 [https://bugs.python.org/issue?@action=redirect&bpo=32265]: All class and static methods of builtin types now are correctly classified by inspect.classify_class_attrs() and grouped in pydoc output. Added types.ClassMethodDescriptorType for unbound class methods of builtin types.

bpo-32253 [https://bugs.python.org/issue?@action=redirect&bpo=32253]: Deprecate yield from lock, await lock, with (yield from lock) and with await lock for asyncio synchronization primitives.

bpo-22589 [https://bugs.python.org/issue?@action=redirect&bpo=22589]: Changed MIME type of .bmp from 'image/x-ms-bmp' to 'image/bmp'

bpo-32193 [https://bugs.python.org/issue?@action=redirect&bpo=32193]: Convert asyncio to use async/await syntax. Old styled yield from is still supported too.

bpo-32206 [https://bugs.python.org/issue?@action=redirect&bpo=32206]: Add support to run modules with pdb

bpo-32227 [https://bugs.python.org/issue?@action=redirect&bpo=32227]: functools.singledispatch now supports registering implementations using type annotations.

bpo-15873 [https://bugs.python.org/issue?@action=redirect&bpo=15873]: Added new alternate constructors datetime.datetime.fromisoformat(), datetime.time.fromisoformat() and datetime.date.fromisoformat() as the inverse operation of each classes's respective isoformat methods.

bpo-32199 [https://bugs.python.org/issue?@action=redirect&bpo=32199]: The getnode() ip getter now uses 'ip link' instead of 'ip link list'.

bpo-32143 [https://bugs.python.org/issue?@action=redirect&bpo=32143]: os.statvfs() includes the f_fsid field from statvfs(2)

bpo-26439 [https://bugs.python.org/issue?@action=redirect&bpo=26439]: Fix ctypes.util.find_library() for AIX by implementing ctypes._aix.find_library() Patch by: Michael Felt

bpo-31993 [https://bugs.python.org/issue?@action=redirect&bpo=31993]: The pickler now uses less memory when serializing large bytes and str objects into a file. Pickles created with protocol 4 will require less memory for unpickling large bytes and str objects.

bpo-27456 [https://bugs.python.org/issue?@action=redirect&bpo=27456]: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

bpo-31778 [https://bugs.python.org/issue?@action=redirect&bpo=31778]: ast.literal_eval() is now more strict. Addition and subtraction of arbitrary numbers no longer allowed.

bpo-31802 [https://bugs.python.org/issue?@action=redirect&bpo=31802]: Importing native path module (posixpath, ntpath) now works even if the os module still is not imported.

bpo-30241 [https://bugs.python.org/issue?@action=redirect&bpo=30241]: Add contextlib.AbstractAsyncContextManager. Patch by Jelle Zijlstra.

bpo-31699 [https://bugs.python.org/issue?@action=redirect&bpo=31699]: Fix deadlocks in concurrent.futures.ProcessPoolExecutor when task arguments or results cause pickling or unpickling errors. This should make sure that calls to the ProcessPoolExecutor API always eventually return.

bpo-15216 [https://bugs.python.org/issue?@action=redirect&bpo=15216]: TextIOWrapper.reconfigure() supports changing encoding, errors, and newline.

Documentation

bpo-32418 [https://bugs.python.org/issue?@action=redirect&bpo=32418]: Add get_loop() method to Server and AbstractServer classes.

Tests

bpo-32252 [https://bugs.python.org/issue?@action=redirect&bpo=32252]: Fix faulthandler_suppress_crash_report() used to prevent core dump files when testing crashes. getrlimit() returns zero on success.

bpo-32002 [https://bugs.python.org/issue?@action=redirect&bpo=32002]: Adjust C locale coercion testing for the empty locale and POSIX locale cases to more readily adjust to platform dependent behaviour.

Windows

bpo-19764 [https://bugs.python.org/issue?@action=redirect&bpo=19764]: Implement support for subprocess.Popen(close_fds=True) on Windows. Patch by Segev Finer.

Tools/Demos

bpo-24960 [https://bugs.python.org/issue?@action=redirect&bpo=24960]: 2to3 and lib2to3 can now read pickled grammar files using pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and lib2to3 work when run from a zipfile.

C API

bpo-32030 [https://bugs.python.org/issue?@action=redirect&bpo=32030]: Py_Initialize() doesn't reset the memory allocators to default if the PYTHONMALLOC environment variable is not set.

bpo-29084 [https://bugs.python.org/issue?@action=redirect&bpo=29084]: Undocumented C API for OrderedDict has been excluded from the limited C API. It was added by mistake and actually never worked in the limited C API.

bpo-32264 [https://bugs.python.org/issue?@action=redirect&bpo=32264]: Moved the pygetopt.h header into internal/, since it has no public APIs.

bpo-32241 [https://bugs.python.org/issue?@action=redirect&bpo=32241]: Py_SetProgramName() and Py_SetPythonHome() now take the const wchar * arguments instead of wchar *.

Python 3.7.0 alpha 3

Release date: 2017-12-05

Core and Builtins

bpo-32176 [https://bugs.python.org/issue?@action=redirect&bpo=32176]: co_flags.CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars, rather than needing to be set correctly by the caller. This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function.

bpo-10544 [https://bugs.python.org/issue?@action=redirect&bpo=10544]: Yield expressions are now deprecated in comprehensions and generator expressions. They are still permitted in the definition of the outermost iterable, as that is evaluated directly in the enclosing scope.

bpo-32137 [https://bugs.python.org/issue?@action=redirect&bpo=32137]: The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow.

bpo-32096 [https://bugs.python.org/issue?@action=redirect&bpo=32096]: Revert memory allocator changes in the C API: move structures back from _PyRuntime to Objects/obmalloc.c. The memory allocators are once again initialized statically, and so PyMem_RawMalloc() and Py_DecodeLocale() can be called before _PyRuntime_Initialize().

bpo-32043 [https://bugs.python.org/issue?@action=redirect&bpo=32043]: Add a new "developer mode": new "-X dev" command line option to enable debug checks at runtime.

bpo-32023 [https://bugs.python.org/issue?@action=redirect&bpo=32023]: SyntaxError is now correctly raised when a generator expression without parenthesis is used instead of an inheritance list in a class definition. The duplication of the parentheses can be omitted only on calls.

bpo-32012 [https://bugs.python.org/issue?@action=redirect&bpo=32012]: SyntaxError is now correctly raised when a generator expression without parenthesis is passed as an argument, but followed by a trailing comma. A generator expression always needs to be directly inside a set of parentheses and cannot have a comma on either side.

bpo-28180 [https://bugs.python.org/issue?@action=redirect&bpo=28180]: A new internal _Py_SetLocaleFromEnv(category) helper function has been added in order to improve the consistency of behaviour across different libc implementations (e.g. Android doesn't support setting the locale from the environment by default).

bpo-31949 [https://bugs.python.org/issue?@action=redirect&bpo=31949]: Fixed several issues in printing tracebacks (PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks. Setting sys.tracebacklimit to None now causes using the default limit. Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit. Fixed integer overflows in the case of more than 2**31 traceback items on Windows. Fixed output errors handling.

bpo-30696 [https://bugs.python.org/issue?@action=redirect&bpo=30696]: Fix the interactive interpreter looping endlessly when no memory.

bpo-20047 [https://bugs.python.org/issue?@action=redirect&bpo=20047]: Bytearray methods partition() and rpartition() now accept only bytes-like objects as separator, as documented. In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator.

bpo-21720 [https://bugs.python.org/issue?@action=redirect&bpo=21720]: BytesWarning no longer emitted when the fromlist argument of __import__() or the __all__ attribute of the module contain bytes instances.

bpo-31845 [https://bugs.python.org/issue?@action=redirect&bpo=31845]: Environment variables are once more read correctly at interpreter startup.

bpo-28936 [https://bugs.python.org/issue?@action=redirect&bpo=28936]: Ensure that lexically first syntax error involving a parameter and global or nonlocal is detected first at a given scope. Patch by Ivan Levkivskyi.

bpo-31825 [https://bugs.python.org/issue?@action=redirect&bpo=31825]: Fixed OverflowError in the 'unicode-escape' codec and in codecs.escape_decode() when decode an escaped non-ascii byte.

bpo-31618 [https://bugs.python.org/issue?@action=redirect&bpo=31618]: The per-frame tracing logic added in 3.7a1 has been altered so that frame->f_lineno is updated before either "line" or "opcode" events are emitted. Previously, opcode events were emitted first, and therefore would occasionally see stale line numbers on the frame. The behavior of this feature has changed slightly as a result: when both f_trace_lines and f_trace_opcodes are enabled, line events now occur first.

bpo-28603 [https://bugs.python.org/issue?@action=redirect&bpo=28603]: Print the full context/cause chain of exceptions on interpreter exit, even if an exception in the chain is unhashable or compares equal to later ones. Patch by Zane Bitter.

bpo-31786 [https://bugs.python.org/issue?@action=redirect&bpo=31786]: Fix timeout rounding in the select module to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

bpo-31781 [https://bugs.python.org/issue?@action=redirect&bpo=31781]: Prevent crashes when calling methods of an uninitialized zipimport.zipimporter object. Patch by Oren Milman.

bpo-30399 [https://bugs.python.org/issue?@action=redirect&bpo=30399]: Standard repr() of BaseException with a single argument no longer contains redundant trailing comma.

bpo-31626 [https://bugs.python.org/issue?@action=redirect&bpo=31626]: Fixed a bug in debug memory allocator. There was a write to freed memory after shrinking a memory block.

bpo-30817 [https://bugs.python.org/issue?@action=redirect&bpo=30817]: PyErr_PrintEx() clears now the ignored exception that may be raised by _PySys_SetObjectId(), for example when no memory.

Library

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Two minor fixes for typing module: allow shallow copying instances of generic classes, improve interaction of __init_subclass__ with generics. Original PRs by Ivan Levkivskyi.

bpo-32214 [https://bugs.python.org/issue?@action=redirect&bpo=32214]: PEP 557, Data Classes. Provides a decorator which adds boilerplate methods to classes which use type annotations so specify fields.

bpo-27240 [https://bugs.python.org/issue?@action=redirect&bpo=27240]: The header folding algorithm for the new email policies has been rewritten, which also fixes bpo-30788 [https://bugs.python.org/issue?@action=redirect&bpo=30788], bpo-31831 [https://bugs.python.org/issue?@action=redirect&bpo=31831], and bpo-32182 [https://bugs.python.org/issue?@action=redirect&bpo=32182]. In particular, RFC2231 folding is now done correctly.

bpo-32186 [https://bugs.python.org/issue?@action=redirect&bpo=32186]: io.FileIO.readall() and io.FileIO.read() now release the GIL when getting the file size. Fixed hang of all threads with inaccessible NFS server. Patch by Nir Soffer.

bpo-32101 [https://bugs.python.org/issue?@action=redirect&bpo=32101]: Add sys.flags.dev_mode flag

bpo-32154 [https://bugs.python.org/issue?@action=redirect&bpo=32154]: The asyncio.windows_utils.socketpair() function has been removed: use directly socket.socketpair() which is available on all platforms since Python 3.5 (before, it wasn't available on Windows). asyncio.windows_utils.socketpair() was just an alias to socket.socketpair on Python 3.5 and newer.

bpo-32089 [https://bugs.python.org/issue?@action=redirect&bpo=32089]: warnings: In development (-X dev) and debug mode (pydebug build), use the "default" action for ResourceWarning, rather than the "always" action, in the default warnings filters.

bpo-32107 [https://bugs.python.org/issue?@action=redirect&bpo=32107]: uuid.getnode() now preferentially returns universally administered MAC addresses if available, over locally administered MAC addresses. This makes a better guarantee for global uniqueness of UUIDs returned from uuid.uuid1(). If only locally administered MAC addresses are available, the first such one found is returned.

bpo-23033 [https://bugs.python.org/issue?@action=redirect&bpo=23033]: Wildcard is now supported in hostname when it is one and only character in the left most segment of hostname in second argument of ssl.match_hostname(). Patch by Mandeep Singh.

bpo-12239 [https://bugs.python.org/issue?@action=redirect&bpo=12239]: Make msilib.SummaryInformation.GetProperty() return None when the value of property is VT_EMPTY. Initial patch by Mark Mc Mahon.

bpo-28334 [https://bugs.python.org/issue?@action=redirect&bpo=28334]: Use os.path.expanduser() to find the ~/.netrc file in netrc.netrc. If it does not exist, FileNotFoundError is raised. Patch by Dimitri Merejkowsky.

bpo-32121 [https://bugs.python.org/issue?@action=redirect&bpo=32121]: Made tracemalloc.Traceback behave more like the traceback module, sorting the frames from oldest to most recent. Traceback.format() now accepts negative limit, truncating the result to the abs(limit) oldest frames. To get the old behaviour, one can use the new most_recent_first argument to Traceback.format(). (Patch by Jesse Bakker.)

bpo-31325 [https://bugs.python.org/issue?@action=redirect&bpo=31325]: Fix wrong usage of collections.namedtuple() in the RobotFileParser.parse() method. Initial patch by Robin Wellner.

bpo-12382 [https://bugs.python.org/issue?@action=redirect&bpo=12382]: msilib.OpenDatabase() now raises a better exception message when it couldn't open or create an MSI file. Initial patch by William Tisäter.

bpo-19610 [https://bugs.python.org/issue?@action=redirect&bpo=19610]: setup() now warns about invalid types for some fields. The distutils.dist.Distribution class now warns when classifiers, keywords and platforms fields are not specified as a list or a string.

bpo-32071 [https://bugs.python.org/issue?@action=redirect&bpo=32071]: Added the -k command-line option to python -m unittest to run only tests that match the given pattern(s).

bpo-10049 [https://bugs.python.org/issue?@action=redirect&bpo=10049]: Added nullcontext no-op context manager to contextlib. This provides a simpler and faster alternative to ExitStack() when handling optional context managers.

bpo-28684 [https://bugs.python.org/issue?@action=redirect&bpo=28684]: The new test.support.skip_unless_bind_unix_socket() decorator is used here to skip asyncio tests that fail because the platform lacks a functional bind() function for unix domain sockets (as it is the case for non root users on the recent Android versions that run now SELinux in enforcing mode).

bpo-32110 [https://bugs.python.org/issue?@action=redirect&bpo=32110]: codecs.StreamReader.read(n) now returns not more than n characters/bytes for non-negative n. This makes it compatible with read() methods of other file-like objects.

bpo-27535 [https://bugs.python.org/issue?@action=redirect&bpo=27535]: The warnings module doesn't leak memory anymore in the hidden warnings registry for the "ignore" action of warnings filters. warn_explicit() function doesn't add the warning key to the registry anymore for the "ignore" action.

bpo-32088 [https://bugs.python.org/issue?@action=redirect&bpo=32088]: warnings: When Python is build is debug mode (Py_DEBUG), DeprecationWarning, PendingDeprecationWarning and ImportWarning warnings are now displayed by default.

bpo-1647489 [https://bugs.python.org/issue?@action=redirect&bpo=1647489]: Fixed searching regular expression patterns that could match an empty string. Non-empty string can now be correctly found after matching an empty string.

bpo-25054 [https://bugs.python.org/issue?@action=redirect&bpo=25054]: Added support of splitting on a pattern that could match an empty string.

bpo-32072 [https://bugs.python.org/issue?@action=redirect&bpo=32072]: Fixed issues with binary plists: Fixed saving bytearrays. Identical objects will be saved only once. Equal references will be load as identical objects. Added support for saving and loading recursive data structures.

bpo-32069 [https://bugs.python.org/issue?@action=redirect&bpo=32069]: Drop legacy SSL transport from asyncio, ssl.MemoryBIO is always used anyway.

bpo-32066 [https://bugs.python.org/issue?@action=redirect&bpo=32066]: asyncio: Support pathlib.Path in create_unix_connection; sock arg should be optional

bpo-32046 [https://bugs.python.org/issue?@action=redirect&bpo=32046]: Updates 2to3 to convert from operator.isCallable(obj) to callable(obj). Patch by Donghee Na.

bpo-32018 [https://bugs.python.org/issue?@action=redirect&bpo=32018]: inspect.signature should follow PEP 8 [https://peps.python.org/pep-0008/], if the parameter has an annotation and a default value. Patch by Donghee Na.

bpo-32025 [https://bugs.python.org/issue?@action=redirect&bpo=32025]: Add time.thread_time() and time.thread_time_ns()

bpo-32037 [https://bugs.python.org/issue?@action=redirect&bpo=32037]: Integers that fit in a signed 32-bit integer will be now pickled with protocol 0 using the INT opcode. This will decrease the size of a pickle, speed up pickling and unpickling, and make these integers be unpickled as int instances in Python 2.

bpo-32034 [https://bugs.python.org/issue?@action=redirect&bpo=32034]: Make asyncio.IncompleteReadError and LimitOverrunError pickleable.

bpo-32015 [https://bugs.python.org/issue?@action=redirect&bpo=32015]: Fixed the looping of asyncio in the case of reconnection the socket during waiting async read/write from/to the socket.

bpo-32011 [https://bugs.python.org/issue?@action=redirect&bpo=32011]: Restored support of loading marshal files with the TYPE_INT64 code. These files can be produced in Python 2.7.

bpo-28369 [https://bugs.python.org/issue?@action=redirect&bpo=28369]: Enhance add_reader/writer check that socket is not used by some transport. Before, only cases when add_reader/writer were called with an int FD were supported. Now the check is implemented correctly for all file-like objects.

bpo-31976 [https://bugs.python.org/issue?@action=redirect&bpo=31976]: Fix race condition when flushing a file is slow, which can cause a segfault if closing the file from another thread.

bpo-31985 [https://bugs.python.org/issue?@action=redirect&bpo=31985]: Formally deprecated aifc.openfp, sunau.openfp, and wave.openfp. Since change 7bc817d5ba917528e8bd07ec461c635291e7b06a in 1993, openfp in each of the three modules had been pointing to that module's open function as a matter of backwards compatibility, though it had been both untested and undocumented.

bpo-21862 [https://bugs.python.org/issue?@action=redirect&bpo=21862]: cProfile command line now accepts -m module_name as an alternative to script path. Patch by Sanyam Khurana.

bpo-31970 [https://bugs.python.org/issue?@action=redirect&bpo=31970]: Reduce performance overhead of asyncio debug mode.

bpo-31843 [https://bugs.python.org/issue?@action=redirect&bpo=31843]: database argument of sqlite3.connect() now accepts a path-like object, instead of just a string.

bpo-31945 [https://bugs.python.org/issue?@action=redirect&bpo=31945]: Add Configurable blocksize to HTTPConnection and HTTPSConnection for improved upload throughput. Patch by Nir Soffer.

bpo-31943 [https://bugs.python.org/issue?@action=redirect&bpo=31943]: Add a cancelled() method to asyncio.Handle. Patch by Marat Sharafutdinov.

bpo-9678 [https://bugs.python.org/issue?@action=redirect&bpo=9678]: Fixed determining the MAC address in the uuid module: Using ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and OpenBSD. Based on patch by Takayuki Shimizukawa.

bpo-30057 [https://bugs.python.org/issue?@action=redirect&bpo=30057]: Fix potential missed signal in signal.signal().

bpo-31933 [https://bugs.python.org/issue?@action=redirect&bpo=31933]: Fix Blake2 params leaf_size and node_offset on big endian platforms. Patch by Jack O'Connor.

bpo-21423 [https://bugs.python.org/issue?@action=redirect&bpo=21423]: Add an initializer argument to {Process,Thread}PoolExecutor

bpo-31927 [https://bugs.python.org/issue?@action=redirect&bpo=31927]: Fixed compilation of the socket module on NetBSD 8. Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD.

bpo-27666 [https://bugs.python.org/issue?@action=redirect&bpo=27666]: Fixed stack corruption in curses.box() and curses.ungetmouse() when the size of types chtype or mmask_t is less than the size of C long. curses.box() now accepts characters as arguments. Based on patch by Steve Fink.

bpo-31917 [https://bugs.python.org/issue?@action=redirect&bpo=31917]: Add 3 new clock identifiers: time.CLOCK_BOOTTIME, time.CLOCK_PROF and time.CLOCK_UPTIME.

bpo-31897 [https://bugs.python.org/issue?@action=redirect&bpo=31897]: plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions.

bpo-25720 [https://bugs.python.org/issue?@action=redirect&bpo=25720]: Fix the method for checking pad state of curses WINDOW. Patch by Masayuki Yamamoto.

bpo-31893 [https://bugs.python.org/issue?@action=redirect&bpo=31893]: Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD. Fixed the comparison of the kqueue_event objects.

bpo-31891 [https://bugs.python.org/issue?@action=redirect&bpo=31891]: Fixed building the curses module on NetBSD.

bpo-31884 [https://bugs.python.org/issue?@action=redirect&bpo=31884]: added required constants to subprocess module for setting priority on windows

bpo-28281 [https://bugs.python.org/issue?@action=redirect&bpo=28281]: Remove year (1-9999) limits on the Calendar.weekday() function. Patch by Mark Gollahon.

bpo-31702 [https://bugs.python.org/issue?@action=redirect&bpo=31702]: crypt.mksalt() now allows to specify the number of rounds for SHA-256 and SHA-512 hashing.

bpo-30639 [https://bugs.python.org/issue?@action=redirect&bpo=30639]: inspect.getfile() no longer computes the repr of unknown objects to display in an error message, to protect against badly behaved custom reprs.

bpo-30768 [https://bugs.python.org/issue?@action=redirect&bpo=30768]: Fix the pthread+semaphore implementation of PyThread_acquire_lock_timed() when called with timeout > 0 and intr_flag=0: recompute the timeout if sem_timedwait() is interrupted by a signal (EINTR). See also the PEP 475 [https://peps.python.org/pep-0475/].

bpo-31854 [https://bugs.python.org/issue?@action=redirect&bpo=31854]: Add mmap.ACCESS_DEFAULT constant.

bpo-31834 [https://bugs.python.org/issue?@action=redirect&bpo=31834]: Use optimized code for BLAKE2 only with SSSE3+. The pure SSE2 implementation is slower than the pure C reference implementation.

bpo-28292 [https://bugs.python.org/issue?@action=redirect&bpo=28292]: Calendar.itermonthdates() will now consistently raise an exception when a date falls outside of the 0001-01-01 through 9999-12-31 range. To support applications that cannot tolerate such exceptions, the new methods itermonthdays3() and itermonthdays4() are added. The new methods return tuples and are not restricted by the range supported by datetime.date.

bpo-28564 [https://bugs.python.org/issue?@action=redirect&bpo=28564]: The shutil.rmtree() function has been sped up to 20--40%. This was done using the os.scandir() function.

bpo-28416 [https://bugs.python.org/issue?@action=redirect&bpo=28416]: Instances of pickle.Pickler subclass with the persistent_id() method and pickle.Unpickler subclass with the persistent_load() method no longer create reference cycles.

bpo-31653 [https://bugs.python.org/issue?@action=redirect&bpo=31653]: Don't release the GIL if we can acquire a multiprocessing semaphore immediately.

bpo-28326 [https://bugs.python.org/issue?@action=redirect&bpo=28326]: Fix multiprocessing.Process when stdout and/or stderr is closed or None.

bpo-20825 [https://bugs.python.org/issue?@action=redirect&bpo=20825]: Add subnet_of and superset_of containment tests to ipaddress.IPv6Network and ipaddress.IPv4Network. Patch by Michel Albert and Cheryl Sabella.

bpo-31827 [https://bugs.python.org/issue?@action=redirect&bpo=31827]: Remove the os.stat_float_times() function. It was introduced in Python 2.3 for backward compatibility with Python 2.2, and was deprecated since Python 3.1.

bpo-31756 [https://bugs.python.org/issue?@action=redirect&bpo=31756]: Add a subprocess.Popen(text=False) keyword argument to subprocess functions to be more explicit about when the library should attempt to decode outputs into text. Patch by Andrew Clegg.

bpo-31819 [https://bugs.python.org/issue?@action=redirect&bpo=31819]: Add AbstractEventLoop.sock_recv_into().

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: If nested log adapters are used, the inner process() methods are no longer omitted.

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: The manager property on LoggerAdapter objects is now properly settable.

bpo-31806 [https://bugs.python.org/issue?@action=redirect&bpo=31806]: Fix timeout rounding in time.sleep(), threading.Lock.acquire() and socket.socket.settimeout() to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

bpo-31803 [https://bugs.python.org/issue?@action=redirect&bpo=31803]: time.clock() and time.get_clock_info('clock') now emit a DeprecationWarning warning.

bpo-31800 [https://bugs.python.org/issue?@action=redirect&bpo=31800]: Extended support for parsing UTC offsets. strptime '%z' can now parse the output generated by datetime.isoformat, including seconds and microseconds.

bpo-28603 [https://bugs.python.org/issue?@action=redirect&bpo=28603]: traceback: Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context/cause chain is unhashable. Patch by Zane Bitter.

bpo-30541 [https://bugs.python.org/issue?@action=redirect&bpo=30541]: Add new function to seal a mock and prevent the automatically creation of child mocks. Patch by Mario Corchero.

bpo-31784 [https://bugs.python.org/issue?@action=redirect&bpo=31784]: Implement the PEP 564 [https://peps.python.org/pep-0564/], add new 6 new functions with nanosecond resolution to the time module: clock_gettime_ns(), clock_settime_ns(), monotonic_ns(), perf_counter_ns(), process_time_ns(), time_ns().

bpo-30143 [https://bugs.python.org/issue?@action=redirect&bpo=30143]: 2to3 now generates a code that uses abstract collection classes from collections.abc rather than collections.

bpo-31770 [https://bugs.python.org/issue?@action=redirect&bpo=31770]: Prevent a crash when calling the __init__() method of a sqlite3.Cursor object more than once. Patch by Oren Milman.

bpo-31764 [https://bugs.python.org/issue?@action=redirect&bpo=31764]: Prevent a crash in sqlite3.Cursor.close() in case the Cursor object is uninitialized. Patch by Oren Milman.

bpo-31752 [https://bugs.python.org/issue?@action=redirect&bpo=31752]: Fix possible crash in timedelta constructor called with custom integers.

bpo-31620 [https://bugs.python.org/issue?@action=redirect&bpo=31620]: an empty asyncio.Queue now doesn't leak memory when queue.get pollers timeout

bpo-31690 [https://bugs.python.org/issue?@action=redirect&bpo=31690]: Allow the flags re.ASCII, re.LOCALE, and re.UNICODE to be used as group flags for regular expressions.

bpo-30349 [https://bugs.python.org/issue?@action=redirect&bpo=30349]: FutureWarning is now emitted if a regular expression contains character set constructs that will change semantically in the future (nested sets and set operations).

bpo-31664 [https://bugs.python.org/issue?@action=redirect&bpo=31664]: Added support for the Blowfish hashing in the crypt module.

bpo-31632 [https://bugs.python.org/issue?@action=redirect&bpo=31632]: Fix method set_protocol() of class _SSLProtocolTransport in asyncio module. This method was previously modifying a wrong reference to the protocol.

bpo-15037 [https://bugs.python.org/issue?@action=redirect&bpo=15037]: Added a workaround for getkey() in curses for ncurses 5.7 and earlier.

bpo-31307 [https://bugs.python.org/issue?@action=redirect&bpo=31307]: Allow use of bytes objects for arguments to configparser.ConfigParser.read(). Patch by Vincent Michel.

bpo-31334 [https://bugs.python.org/issue?@action=redirect&bpo=31334]: Fix poll.poll([timeout]) in the select module for arbitrary negative timeouts on all OSes where it can only be a non-negative integer or -1. Patch by Riccardo Coccioli.

bpo-31310 [https://bugs.python.org/issue?@action=redirect&bpo=31310]: multiprocessing's semaphore tracker should be launched again if crashed.

bpo-31308 [https://bugs.python.org/issue?@action=redirect&bpo=31308]: Make multiprocessing's forkserver process immune to Ctrl-C and other user interruptions. If it crashes, restart it when necessary.

bpo-31245 [https://bugs.python.org/issue?@action=redirect&bpo=31245]: Added support for AF_UNIX socket in asyncio create_datagram_endpoint.

bpo-30553 [https://bugs.python.org/issue?@action=redirect&bpo=30553]: Add HTTP/2 status code 421 (Misdirected Request) to http.HTTPStatus. Patch by Vitor Pereira.

Documentation

bpo-32105 [https://bugs.python.org/issue?@action=redirect&bpo=32105]: Added asyncio.BaseEventLoop.connect_accepted_socket versionadded marker.

Tests

bpo-31380 [https://bugs.python.org/issue?@action=redirect&bpo=31380]: Skip test_httpservers test_undecodable_file on macOS: fails on APFS.

bpo-31705 [https://bugs.python.org/issue?@action=redirect&bpo=31705]: Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the kernel 4.5.

bpo-32138 [https://bugs.python.org/issue?@action=redirect&bpo=32138]: Skip on Android test_faulthandler tests that raise SIGSEGV and remove the test.support.requires_android_level decorator.

bpo-32136 [https://bugs.python.org/issue?@action=redirect&bpo=32136]: The runtime embedding tests have been split out from Lib/test/test_capi.py into a new Lib/test/test_embed.py file.

bpo-28668 [https://bugs.python.org/issue?@action=redirect&bpo=28668]: test.support.requires_multiprocessing_queue is removed. Skip tests with test.support.import_module('multiprocessing.synchronize') instead when the semaphore implementation is broken or missing.

bpo-32126 [https://bugs.python.org/issue?@action=redirect&bpo=32126]: Skip test_get_event_loop_new_process in test.test_asyncio.test_events when sem_open() is not functional.

bpo-31174 [https://bugs.python.org/issue?@action=redirect&bpo=31174]: Fix test_tools.test_unparse: DirectoryTestCase now stores the names sample to always test the same files. It prevents false alarms when hunting reference leaks.

Build

bpo-28538 [https://bugs.python.org/issue?@action=redirect&bpo=28538]: Revert the previous changes, the if_nameindex structure is defined by Unified Headers.

bpo-28762 [https://bugs.python.org/issue?@action=redirect&bpo=28762]: Revert the last commit, the F_LOCK macro is defined by Android Unified Headers.

bpo-29040 [https://bugs.python.org/issue?@action=redirect&bpo=29040]: Support building Android with Unified Headers. The first NDK release to support Unified Headers is android-ndk-r14.

bpo-32059 [https://bugs.python.org/issue?@action=redirect&bpo=32059]: detect_modules() in setup.py now also searches the sysroot paths when cross-compiling.

bpo-31957 [https://bugs.python.org/issue?@action=redirect&bpo=31957]: Fixes Windows SDK version detection when building for Windows.

bpo-31609 [https://bugs.python.org/issue?@action=redirect&bpo=31609]: Fixes quotes in PCbuild/clean.bat

bpo-31934 [https://bugs.python.org/issue?@action=redirect&bpo=31934]: Abort the build when building out of a not clean source tree.

bpo-31926 [https://bugs.python.org/issue?@action=redirect&bpo=31926]: Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and/or method in a .c file with the same name.

bpo-28791 [https://bugs.python.org/issue?@action=redirect&bpo=28791]: Update Windows builds to use SQLite 3.21.0.

bpo-28791 [https://bugs.python.org/issue?@action=redirect&bpo=28791]: Update OS X installer to use SQLite 3.21.0.

bpo-28643 [https://bugs.python.org/issue?@action=redirect&bpo=28643]: Record profile-opt build progress with stamp files.

bpo-31866 [https://bugs.python.org/issue?@action=redirect&bpo=31866]: Finish removing support for AtheOS.

Windows

bpo-1102 [https://bugs.python.org/issue?@action=redirect&bpo=1102]: Return None when View.Fetch() returns ERROR_NO_MORE_ITEMS instead of raising MSIError. Initial patch by Anthony Tuininga.

bpo-31944 [https://bugs.python.org/issue?@action=redirect&bpo=31944]: Fixes Modify button in Apps and Features dialog.

bpo-20486 [https://bugs.python.org/issue?@action=redirect&bpo=20486]: Implement the Database.Close() method to help closing MSI database objects.

bpo-31857 [https://bugs.python.org/issue?@action=redirect&bpo=31857]: Make the behavior of USE_STACKCHECK deterministic in a multi-threaded environment.

macOS

bpo-31392 [https://bugs.python.org/issue?@action=redirect&bpo=31392]: Update macOS installer to use OpenSSL 1.0.2m

IDLE

bpo-32207 [https://bugs.python.org/issue?@action=redirect&bpo=32207]: Improve tk event exception tracebacks in IDLE. When tk event handling is driven by IDLE's run loop, a confusing and distracting queue.EMPTY traceback context is no longer added to tk event exception tracebacks. The traceback is now the same as when event handling is driven by user code. Patch based on a suggestion by Serhiy Storchaka.

bpo-32164 [https://bugs.python.org/issue?@action=redirect&bpo=32164]: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet in configdialog was replaced by ttk.Notebook.

bpo-32100 [https://bugs.python.org/issue?@action=redirect&bpo=32100]: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch mostly by Cheryl Sabella.

bpo-31858 [https://bugs.python.org/issue?@action=redirect&bpo=31858]: IDLE -- Restrict shell prompt manipulation to the shell. Editor and output windows only see an empty last prompt line. This simplifies the code and fixes a minor bug when newline is inserted. Sys.ps1, if present, is read on Shell start-up, but is not set or changed.

bpo-31860 [https://bugs.python.org/issue?@action=redirect&bpo=31860]: The font sample in the IDLE configuration dialog is now editable. Changes persist while IDLE remains open

bpo-31836 [https://bugs.python.org/issue?@action=redirect&bpo=31836]: Test_code_module now passes if run after test_idle, which sets ps1. The code module uses sys.ps1 if present or sets it to '>>> ' if not. Test_code_module now properly tests both behaviors. Ditto for ps2.

bpo-28603 [https://bugs.python.org/issue?@action=redirect&bpo=28603]: Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable. Patch by Zane Bitter.

bpo-13802 [https://bugs.python.org/issue?@action=redirect&bpo=13802]: Use non-Latin characters in the IDLE's Font settings sample. Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane, tcl/tk will use other fonts that define a character. The expanded example give users of non-Latin characters a better idea of what they might see in IDLE's shell and editors. To make room for the expanded sample, frames on the Font tab are re-arranged. The Font/Tabs help explains a bit about the additions.

Tools/Demos

bpo-32159 [https://bugs.python.org/issue?@action=redirect&bpo=32159]: Remove CVS and Subversion tools: remove svneol.py and treesync.py scripts. CPython migrated from CVS to Subversion, to Mercurial, and then to Git. CVS and Subversion are no longer used to develop CPython.

bpo-30722 [https://bugs.python.org/issue?@action=redirect&bpo=30722]: Make redemo work with Python 3.6 and newer versions. Also, remove the LOCALE option since it doesn't work with string patterns in Python 3. Patch by Christoph Sarnowski.

C API

bpo-20891 [https://bugs.python.org/issue?@action=redirect&bpo=20891]: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in a non-Python thread before PyEval_InitThreads(), only call PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

bpo-32125 [https://bugs.python.org/issue?@action=redirect&bpo=32125]: The Py_UseClassExceptionsFlag flag has been removed. It was deprecated and wasn't used anymore since Python 2.0.

bpo-25612 [https://bugs.python.org/issue?@action=redirect&bpo=25612]: Move the current exception state from the frame object to the co-routine. This simplifies the interpreter and fixes a couple of obscure bugs caused by having swap exception state when entering or exiting a generator.

bpo-23699 [https://bugs.python.org/issue?@action=redirect&bpo=23699]: Add Py_RETURN_RICHCOMPARE macro to reduce boilerplate code in rich comparison functions.

bpo-30697 [https://bugs.python.org/issue?@action=redirect&bpo=30697]: The PyExc_RecursionErrorInst singleton is removed and PyErr_NormalizeException() does not use it anymore. This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter. See also bpo-22898 [https://bugs.python.org/issue?@action=redirect&bpo=22898].

Python 3.7.0 alpha 2

Release date: 2017-10-16

Core and Builtins

bpo-31558 [https://bugs.python.org/issue?@action=redirect&bpo=31558]: gc.freeze() is a new API that allows for moving all objects currently tracked by the garbage collector to a permanent generation, effectively removing them from future collection events. This can be used to protect those objects from having their PyGC_Head mutated. In effect, this enables great copy-on-write stability at fork().

bpo-31642 [https://bugs.python.org/issue?@action=redirect&bpo=31642]: Restored blocking "from package import module" by setting sys.modules["package.module"] to None.

bpo-31708 [https://bugs.python.org/issue?@action=redirect&bpo=31708]: Allow use of asynchronous generator expressions in synchronous functions.

bpo-31709 [https://bugs.python.org/issue?@action=redirect&bpo=31709]: Drop support of asynchronous __aiter__.

bpo-30404 [https://bugs.python.org/issue?@action=redirect&bpo=30404]: The -u option now makes the stdout and stderr streams unbuffered rather than line-buffered.

bpo-31619 [https://bugs.python.org/issue?@action=redirect&bpo=31619]: Fixed a ValueError when convert a string with large number of underscores to integer with binary base.

bpo-31602 [https://bugs.python.org/issue?@action=redirect&bpo=31602]: Fix an assertion failure in zipimporter.get_source() in case of a bad zlib.decompress(). Patch by Oren Milman.

bpo-31592 [https://bugs.python.org/issue?@action=redirect&bpo=31592]: Fixed an assertion failure in Python parser in case of a bad unicodedata.normalize(). Patch by Oren Milman.

bpo-31588 [https://bugs.python.org/issue?@action=redirect&bpo=31588]: Raise a TypeError with a helpful error message when class creation fails due to a metaclass with a bad __prepare__() method. Patch by Oren Milman.

bpo-31574 [https://bugs.python.org/issue?@action=redirect&bpo=31574]: Importlib was instrumented with two dtrace probes to profile import timing.

bpo-31566 [https://bugs.python.org/issue?@action=redirect&bpo=31566]: Fix an assertion failure in _warnings.warn() in case of a bad __name__ global. Patch by Oren Milman.

bpo-31506 [https://bugs.python.org/issue?@action=redirect&bpo=31506]: Improved the error message logic for object.__new__ and object.__init__.

bpo-31505 [https://bugs.python.org/issue?@action=redirect&bpo=31505]: Fix an assertion failure in json, in case _json.make_encoder() received a bad encoder() argument. Patch by Oren Milman.

bpo-31492 [https://bugs.python.org/issue?@action=redirect&bpo=31492]: Fix assertion failures in case of failing to import from a module with a bad __name__ attribute, and in case of failing to access an attribute of such a module. Patch by Oren Milman.

bpo-31478 [https://bugs.python.org/issue?@action=redirect&bpo=31478]: Fix an assertion failure in _random.Random.seed() in case the argument has a bad __abs__() method. Patch by Oren Milman.

bpo-31336 [https://bugs.python.org/issue?@action=redirect&bpo=31336]: Speed up class creation by 10-20% by reducing the overhead in the necessary special method lookups. Patch by Stefan Behnel.

bpo-31415 [https://bugs.python.org/issue?@action=redirect&bpo=31415]: Add -X importtime option to show how long each import takes. It can be used to optimize application's startup time. Support the PYTHONPROFILEIMPORTTIME as an equivalent way to enable this.

bpo-31410 [https://bugs.python.org/issue?@action=redirect&bpo=31410]: Optimized calling wrapper and classmethod descriptors.

bpo-31353 [https://bugs.python.org/issue?@action=redirect&bpo=31353]: PEP 553 [https://peps.python.org/pep-0553/] - Add a new built-in called breakpoint() which calls sys.breakpointhook(). By default this imports pdb and calls pdb.set_trace(), but users may override sys.breakpointhook() to call whatever debugger they want. The original value of the hook is saved in sys.__breakpointhook__.

bpo-17852 [https://bugs.python.org/issue?@action=redirect&bpo=17852]: Maintain a list of open buffered files, flush them before exiting the interpreter. Based on a patch from Armin Rigo.

bpo-31315 [https://bugs.python.org/issue?@action=redirect&bpo=31315]: Fix an assertion failure in imp.create_dynamic(), when spec.name is not a string. Patch by Oren Milman.

bpo-31311 [https://bugs.python.org/issue?@action=redirect&bpo=31311]: Fix a crash in the __setstate__() method of ctypes._CData, in case of a bad __dict__. Patch by Oren Milman.

bpo-31293 [https://bugs.python.org/issue?@action=redirect&bpo=31293]: Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio() method. Patch by Oren Milman.

bpo-31285 [https://bugs.python.org/issue?@action=redirect&bpo=31285]: Fix an assertion failure in warnings.warn_explicit, when the return value of the received loader's get_source() has a bad splitlines() method. Patch by Oren Milman.

bpo-30406 [https://bugs.python.org/issue?@action=redirect&bpo=30406]: Make async and await proper keywords, as specified in PEP 492 [https://peps.python.org/pep-0492/].

Library

bpo-30058 [https://bugs.python.org/issue?@action=redirect&bpo=30058]: Fixed buffer overflow in select.kqueue.control().

bpo-31672 [https://bugs.python.org/issue?@action=redirect&bpo=31672]: idpattern in string.Template matched some non-ASCII characters. Now it uses -i regular expression local flag to avoid non-ASCII characters.

bpo-31701 [https://bugs.python.org/issue?@action=redirect&bpo=31701]: On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

bpo-31728 [https://bugs.python.org/issue?@action=redirect&bpo=31728]: Prevent crashes in _elementtree due to unsafe cleanup of Element.text and Element.tail. Patch by Oren Milman.

bpo-31671 [https://bugs.python.org/issue?@action=redirect&bpo=31671]: Now re.compile() converts passed RegexFlag to normal int object before compiling. bm_regex_compile benchmark shows 14% performance improvements.

bpo-30397 [https://bugs.python.org/issue?@action=redirect&bpo=30397]: The types of compiled regular objects and match objects are now exposed as re.Pattern and re.Match. This adds information in pydoc output for the re module.

bpo-31675 [https://bugs.python.org/issue?@action=redirect&bpo=31675]: Fixed memory leaks in Tkinter's methods splitlist() and split() when pass a string larger than 2 GiB.

bpo-31673 [https://bugs.python.org/issue?@action=redirect&bpo=31673]: Fixed typo in the name of Tkinter's method adderrorinfo().

bpo-31648 [https://bugs.python.org/issue?@action=redirect&bpo=31648]: Improvements to path predicates in ElementTree: Allow whitespace around predicate parts, i.e. "[a = 'text']" instead of requiring the less readable "[a='text']". Add support for text comparison of the current node, like "[.='text']". Patch by Stefan Behnel.

bpo-30806 [https://bugs.python.org/issue?@action=redirect&bpo=30806]: Fix the string representation of a netrc object.

bpo-31638 [https://bugs.python.org/issue?@action=redirect&bpo=31638]: Add optional argument compressed to zipapp.create_archive, and add option --compress to the command line interface of zipapp.

bpo-25351 [https://bugs.python.org/issue?@action=redirect&bpo=25351]: Avoid venv activate failures with undefined variables

bpo-20519 [https://bugs.python.org/issue?@action=redirect&bpo=20519]: Avoid ctypes use (if possible) and improve import time for uuid.

bpo-28293 [https://bugs.python.org/issue?@action=redirect&bpo=28293]: The regular expression cache is no longer completely dumped when it is full.

bpo-31596 [https://bugs.python.org/issue?@action=redirect&bpo=31596]: Added pthread_getcpuclockid() to the time module

bpo-27494 [https://bugs.python.org/issue?@action=redirect&bpo=27494]: Make 2to3 accept a trailing comma in generator expressions. For example, set(x for x in [],) is now allowed.

bpo-30347 [https://bugs.python.org/issue?@action=redirect&bpo=30347]: Stop crashes when concurrently iterate over itertools.groupby() iterators.

bpo-30346 [https://bugs.python.org/issue?@action=redirect&bpo=30346]: An iterator produced by itertools.groupby() iterator now becomes exhausted after advancing the groupby iterator.

bpo-31556 [https://bugs.python.org/issue?@action=redirect&bpo=31556]: Cancel asyncio.wait_for future faster if timeout <= 0

bpo-31540 [https://bugs.python.org/issue?@action=redirect&bpo=31540]: Allow passing a context object in concurrent.futures.ProcessPoolExecutor constructor. Also, free job resources in concurrent.futures.ProcessPoolExecutor earlier to improve memory usage when a worker waits for new jobs.

bpo-31516 [https://bugs.python.org/issue?@action=redirect&bpo=31516]: threading.current_thread() should not return a dummy thread at shutdown.

bpo-31525 [https://bugs.python.org/issue?@action=redirect&bpo=31525]: In the sqlite module, require the sqlite3_prepare_v2 API. Thus, the sqlite module now requires sqlite version at least 3.3.9.

bpo-26510 [https://bugs.python.org/issue?@action=redirect&bpo=26510]: argparse subparsers are now required by default. This matches behaviour in Python 2. For optional subparsers, use the new parameter add_subparsers(required=False). Patch by Anthony Sottile. (As of 3.7.0rc1, the default was changed to not required as had been the case since Python 3.3.)

bpo-27541 [https://bugs.python.org/issue?@action=redirect&bpo=27541]: Reprs of subclasses of some collection and iterator classes (bytearray, array.array, collections.deque, collections.defaultdict, itertools.count, itertools.repeat) now contain actual type name instead of hardcoded names of the base class.

bpo-31351 [https://bugs.python.org/issue?@action=redirect&bpo=31351]: python -m ensurepip now exits with non-zero exit code if pip bootstrapping has failed.

bpo-31389 [https://bugs.python.org/issue?@action=redirect&bpo=31389]: pdb.set_trace() now takes an optional keyword-only argument header. If given, this is printed to the console just before debugging begins.

Documentation

bpo-31537 [https://bugs.python.org/issue?@action=redirect&bpo=31537]: Fix incorrect usage of get_history_length in readline documentation example code. Patch by Brad Smith.

bpo-30085 [https://bugs.python.org/issue?@action=redirect&bpo=30085]: The operator functions without double underscores are preferred for clarity. The one with underscores are only kept for back-compatibility.

Build

bpo-31696 [https://bugs.python.org/issue?@action=redirect&bpo=31696]: Improve compiler version information in sys.version when Python is built with Clang.

bpo-31625 [https://bugs.python.org/issue?@action=redirect&bpo=31625]: Stop using ranlib on static libraries. Instead, we assume ar supports the 's' flag.

bpo-31624 [https://bugs.python.org/issue?@action=redirect&bpo=31624]: Remove support for BSD/OS.

bpo-22140 [https://bugs.python.org/issue?@action=redirect&bpo=22140]: Prevent double substitution of prefix in python-config.sh.

bpo-31569 [https://bugs.python.org/issue?@action=redirect&bpo=31569]: Correct PCBuild/ case to PCbuild/ in build scripts and documentation.

bpo-31536 [https://bugs.python.org/issue?@action=redirect&bpo=31536]: Avoid wholesale rebuild after make regen-all if nothing changed.

IDLE

bpo-31460 [https://bugs.python.org/issue?@action=redirect&bpo=31460]: Simplify the API of IDLE's Module Browser. Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window. Passing a full file name instead of pieces assumed to come from a .py file opens the possibility of browsing python files that do not end in .py.

bpo-31649 [https://bugs.python.org/issue?@action=redirect&bpo=31649]: IDLE - Make _htest, _utest parameters keyword only.

bpo-31559 [https://bugs.python.org/issue?@action=redirect&bpo=31559]: Remove test order dependence in idle_test.test_browser.

bpo-31459 [https://bugs.python.org/issue?@action=redirect&bpo=31459]: Rename IDLE's module browser from Class Browser to Module Browser. The original module-level class and method browser became a module browser, with the addition of module-level functions, years ago. Nested classes and functions were added yesterday. For back-compatibility, the virtual event <<open-class-browser>>, which appears on the Keys tab of the Settings dialog, is not changed. Patch by Cheryl Sabella.

bpo-31500 [https://bugs.python.org/issue?@action=redirect&bpo=31500]: Default fonts now are scaled on HiDPI displays.

bpo-1612262 [https://bugs.python.org/issue?@action=redirect&bpo=1612262]: IDLE module browser now shows nested classes and functions. Original patches for code and tests by Guilherme Polo and Cheryl Sabella, respectively.

C API

bpo-28280 [https://bugs.python.org/issue?@action=redirect&bpo=28280]: Make PyMapping_Keys(), PyMapping_Values() and PyMapping_Items() always return a list (rather than a list or a tuple). Patch by Oren Milman.

bpo-31532 [https://bugs.python.org/issue?@action=redirect&bpo=31532]: Fix memory corruption due to allocator mix in getpath.c between Py_GetPath() and Py_SetPath()

bpo-25658 [https://bugs.python.org/issue?@action=redirect&bpo=25658]: Implement PEP 539 [https://peps.python.org/pep-0539/] for Thread Specific Storage (TSS) API: it is a new Thread Local Storage (TLS) API to CPython which would supersede use of the existing TLS API within the CPython interpreter, while deprecating the existing API. PEP written by Erik M. Bray, patch by Masayuki Yamamoto.

Python 3.7.0 alpha 1

Release date: 2017-09-19

Security

bpo-29781 [https://bugs.python.org/issue?@action=redirect&bpo=29781]: SSLObject.version() now correctly returns None when handshake over BIO has not been performed yet.

bpo-29505 [https://bugs.python.org/issue?@action=redirect&bpo=29505]: Add fuzz tests for float(str), int(str), unicode(str); for oss-fuzz.

bpo-30947 [https://bugs.python.org/issue?@action=redirect&bpo=30947]: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

bpo-30730 [https://bugs.python.org/issue?@action=redirect&bpo=30730]: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.

bpo-30694 [https://bugs.python.org/issue?@action=redirect&bpo=30694]: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE 2017-9233 [https://www.cve.org/CVERecord?id=CVE-2017-9233] (External entity infinite loop DoS), CVE 2016-9063 [https://www.cve.org/CVERecord?id=CVE-2016-9063] (Integer overflow, re-fix), CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718] (Fix regression bugs from 2.2.0's fix to CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718]) and CVE 2012-0876 [https://www.cve.org/CVERecord?id=CVE-2012-0876] (Counter hash flooding with SipHash). Note: the CVE 2016-5300 [https://www.cve.org/CVERecord?id=CVE-2016-5300] (Use os-specific entropy sources like getrandom) doesn't impact Python, since Python already gets entropy from the OS to set the expat secret using XML_SetHashSalt().

bpo-30500 [https://bugs.python.org/issue?@action=redirect&bpo=30500]: Fix urllib.parse.splithost() to correctly parse fragments. For example, splithost('//127.0.0.1#@evil.com/') now correctly returns the 127.0.0.1 host, instead of treating @evil.com as the host in an authentication (login@host).

bpo-29591 [https://bugs.python.org/issue?@action=redirect&bpo=29591]: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718] and CVE 2016-4472 [https://www.cve.org/CVERecord?id=CVE-2016-4472]. See https://sourceforge.net/p/expat/bugs/537/ for more information.

Core and Builtins

bpo-31490 [https://bugs.python.org/issue?@action=redirect&bpo=31490]: Fix an assertion failure in ctypes class definition, in case the class has an attribute whose name is specified in _anonymous_ but not in _fields_. Patch by Oren Milman.

bpo-31471 [https://bugs.python.org/issue?@action=redirect&bpo=31471]: Fix an assertion failure in subprocess.Popen() on Windows, in case the env argument has a bad keys() method. Patch by Oren Milman.

bpo-31418 [https://bugs.python.org/issue?@action=redirect&bpo=31418]: Fix an assertion failure in PyErr_WriteUnraisable() in case of an exception with a bad __module__ attribute. Patch by Oren Milman.

bpo-31416 [https://bugs.python.org/issue?@action=redirect&bpo=31416]: Fix assertion failures in case of a bad warnings.filters or warnings.defaultaction. Patch by Oren Milman.

bpo-28411 [https://bugs.python.org/issue?@action=redirect&bpo=28411]: Change direct usage of PyInterpreterState.modules to PyImport_GetModuleDict(). Also introduce more uniformity in other code that deals with sys.modules. This helps reduce complications when working on sys.modules.

bpo-28411 [https://bugs.python.org/issue?@action=redirect&bpo=28411]: Switch to the abstract API when dealing with PyInterpreterState.modules. This allows later support for all dict subclasses and other Mapping implementations. Also add a PyImport_GetModule() function to reduce a bunch of duplicated code.

bpo-31411 [https://bugs.python.org/issue?@action=redirect&bpo=31411]: Raise a TypeError instead of SystemError in case warnings.onceregistry is not a dictionary. Patch by Oren Milman.

bpo-31344 [https://bugs.python.org/issue?@action=redirect&bpo=31344]: For finer control of tracing behaviour when testing the interpreter, two new frame attributes have been added to control the emission of particular trace events: f_trace_lines (True by default) to turn off per-line trace events; and f_trace_opcodes (False by default) to turn on per-opcode trace events.

bpo-31373 [https://bugs.python.org/issue?@action=redirect&bpo=31373]: Fix several possible instances of undefined behavior due to floating-point demotions.

bpo-30465 [https://bugs.python.org/issue?@action=redirect&bpo=30465]: Location information (lineno and col_offset) in f-strings is now (mostly) correct. This fixes tools like flake8 from showing warnings on the wrong line (typically the first line of the file).

bpo-30860 [https://bugs.python.org/issue?@action=redirect&bpo=30860]: Consolidate CPython's global runtime state under a single struct. This improves discoverability of the runtime state.

bpo-31347 [https://bugs.python.org/issue?@action=redirect&bpo=31347]: Fix possible undefined behavior in _PyObject_FastCall_Prepend.

bpo-31343 [https://bugs.python.org/issue?@action=redirect&bpo=31343]: Include sys/sysmacros.h for major(), minor(), and makedev(). GNU C library plans to remove the functions from sys/types.h.

bpo-31291 [https://bugs.python.org/issue?@action=redirect&bpo=31291]: Fix an assertion failure in zipimport.zipimporter.get_data on Windows, when the return value of pathname.replace('/','\\') isn't a string. Patch by Oren Milman.

bpo-31271 [https://bugs.python.org/issue?@action=redirect&bpo=31271]: Fix an assertion failure in the write() method of io.TextIOWrapper, when the encoder doesn't return a bytes object. Patch by Oren Milman.

bpo-31243 [https://bugs.python.org/issue?@action=redirect&bpo=31243]: Fix a crash in some methods of io.TextIOWrapper, when the decoder's state is invalid. Patch by Oren Milman.

bpo-30721 [https://bugs.python.org/issue?@action=redirect&bpo=30721]: print now shows correct usage hint for using Python 2 redirection syntax. Patch by Sanyam Khurana.

bpo-31070 [https://bugs.python.org/issue?@action=redirect&bpo=31070]: Fix a race condition in importlib _get_module_lock().

bpo-30747 [https://bugs.python.org/issue?@action=redirect&bpo=30747]: Add a non-dummy implementation of _Py_atomic_store and _Py_atomic_load on MSVC.

bpo-31095 [https://bugs.python.org/issue?@action=redirect&bpo=31095]: Fix potential crash during GC caused by tp_dealloc which doesn't call PyObject_GC_UnTrack().

bpo-31071 [https://bugs.python.org/issue?@action=redirect&bpo=31071]: Avoid masking original TypeError in call with * unpacking when other arguments are passed.

bpo-30978 [https://bugs.python.org/issue?@action=redirect&bpo=30978]: str.format_map() now passes key lookup exceptions through. Previously any exception was replaced with a KeyError exception.

bpo-30808 [https://bugs.python.org/issue?@action=redirect&bpo=30808]: Use _Py_atomic API for concurrency-sensitive signal state.

bpo-30876 [https://bugs.python.org/issue?@action=redirect&bpo=30876]: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

bpo-30703 [https://bugs.python.org/issue?@action=redirect&bpo=30703]: Improve signal delivery. Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions. The tests I'm adding here fail without the rest of the patch, on Linux and OS X. This means our signal delivery logic had defects (some signals could be lost).

bpo-30765 [https://bugs.python.org/issue?@action=redirect&bpo=30765]: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

bpo-31161 [https://bugs.python.org/issue?@action=redirect&bpo=31161]: Make sure the 'Missing parentheses' syntax error message is only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

bpo-30814 [https://bugs.python.org/issue?@action=redirect&bpo=30814]: Fixed a race condition when import a submodule from a package.

bpo-30736 [https://bugs.python.org/issue?@action=redirect&bpo=30736]: The internal unicodedata database has been upgraded to Unicode 10.0.

bpo-30604 [https://bugs.python.org/issue?@action=redirect&bpo=30604]: Move co_extra_freefuncs from per-thread to per-interpreter to avoid crashes.

bpo-30597 [https://bugs.python.org/issue?@action=redirect&bpo=30597]: print now shows expected input in custom error message when used as a Python 2 statement. Patch by Sanyam Khurana.

bpo-30682 [https://bugs.python.org/issue?@action=redirect&bpo=30682]: Removed a too-strict assertion that failed for certain f-strings, such as eval("f'\n'") and eval("f'\r'").

bpo-30501 [https://bugs.python.org/issue?@action=redirect&bpo=30501]: The compiler now produces more optimal code for complex condition expressions in the "if", "while" and "assert" statement, the "if" expression, and generator expressions and comprehensions.

bpo-28180 [https://bugs.python.org/issue?@action=redirect&bpo=28180]: Implement PEP 538 [https://peps.python.org/pep-0538/] (legacy C locale coercion). This means that when a suitable coercion target locale is available, both the core interpreter and locale-aware C extensions will assume the use of UTF-8 as the default text encoding, rather than ASCII.

bpo-30486 [https://bugs.python.org/issue?@action=redirect&bpo=30486]: Allows setting cell values for __closure__. Patch by Lisa Roach.

bpo-30537 [https://bugs.python.org/issue?@action=redirect&bpo=30537]: itertools.islice now accepts integer-like objects (having an __index__ method) as start, stop, and slice arguments

bpo-25324 [https://bugs.python.org/issue?@action=redirect&bpo=25324]: Tokens needed for parsing in Python moved to C. COMMENT, NL and ENCODING. This way the tokens and tok_names in the token module don't get changed when you import the tokenize module.

bpo-29104 [https://bugs.python.org/issue?@action=redirect&bpo=29104]: Fixed parsing backslashes in f-strings.

bpo-27945 [https://bugs.python.org/issue?@action=redirect&bpo=27945]: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

bpo-25794 [https://bugs.python.org/issue?@action=redirect&bpo=25794]: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

bpo-30039 [https://bugs.python.org/issue?@action=redirect&bpo=30039]: If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested 'yield from' or 'await' calls, it's now correctly delivered to the innermost frame.

bpo-28974 [https://bugs.python.org/issue?@action=redirect&bpo=28974]: object.__format__(x, '') is now equivalent to str(x) rather than format(str(self), '').

bpo-30024 [https://bugs.python.org/issue?@action=redirect&bpo=30024]: Circular imports involving absolute imports with binding a submodule to a name are now supported.

bpo-12414 [https://bugs.python.org/issue?@action=redirect&bpo=12414]: sys.getsizeof() on a code object now returns the sizes which includes the code struct and sizes of objects which it references. Patch by Donghee Na.

bpo-29839 [https://bugs.python.org/issue?@action=redirect&bpo=29839]: len() now raises ValueError rather than OverflowError if __len__() returned a large negative integer.

bpo-11913 [https://bugs.python.org/issue?@action=redirect&bpo=11913]: README.rst is now included in the list of distutils standard READMEs and therefore included in source distributions.

bpo-29914 [https://bugs.python.org/issue?@action=redirect&bpo=29914]: Fixed default implementations of __reduce__ and __reduce_ex__(). object.__reduce__() no longer takes arguments, object.__reduce_ex__() now requires one argument.

bpo-29949 [https://bugs.python.org/issue?@action=redirect&bpo=29949]: Fix memory usage regression of set and frozenset object.

bpo-29935 [https://bugs.python.org/issue?@action=redirect&bpo=29935]: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

bpo-29816 [https://bugs.python.org/issue?@action=redirect&bpo=29816]: Shift operation now has less opportunity to raise OverflowError. ValueError always is raised rather than OverflowError for negative counts. Shifting zero with non-negative count always returns zero.

bpo-24821 [https://bugs.python.org/issue?@action=redirect&bpo=24821]: Fixed the slowing down to 25 times in the searching of some unlucky Unicode characters.

bpo-29102 [https://bugs.python.org/issue?@action=redirect&bpo=29102]: Add a unique ID to PyInterpreterState. This makes it easier to identify each subinterpreter.

bpo-29894 [https://bugs.python.org/issue?@action=redirect&bpo=29894]: The deprecation warning is emitted if __complex__ returns an instance of a strict subclass of complex. In a future versions of Python this can be an error.

bpo-29859 [https://bugs.python.org/issue?@action=redirect&bpo=29859]: Show correct error messages when any of the pthread_* calls in thread_pthread.h fails.

bpo-29849 [https://bugs.python.org/issue?@action=redirect&bpo=29849]: Fix a memory leak when an ImportError is raised during from import.

bpo-28856 [https://bugs.python.org/issue?@action=redirect&bpo=28856]: Fix an oversight that %b format for bytes should support objects follow the buffer protocol.

bpo-29723 [https://bugs.python.org/issue?@action=redirect&bpo=29723]: The sys.path[0] initialization change for bpo-29139 [https://bugs.python.org/issue?@action=redirect&bpo=29139] caused a regression by revealing an inconsistency in how sys.path is initialized when executing __main__ from a zipfile, directory, or other import location. The interpreter now consistently avoids ever adding the import location's parent directory to sys.path, and ensures no other sys.path entries are inadvertently modified when inserting the import location named on the command line.

bpo-29568 [https://bugs.python.org/issue?@action=redirect&bpo=29568]: Escaped percent "%%" in the format string for classic string formatting no longer allows any characters between two percents.

bpo-29714 [https://bugs.python.org/issue?@action=redirect&bpo=29714]: Fix a regression that bytes format may fail when containing zero bytes inside.

bpo-29695 [https://bugs.python.org/issue?@action=redirect&bpo=29695]: bool(), float(), list() and tuple() no longer take keyword arguments. The first argument of int() can now be passes only as positional argument.

bpo-28893 [https://bugs.python.org/issue?@action=redirect&bpo=28893]: Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__.

bpo-28876 [https://bugs.python.org/issue?@action=redirect&bpo=28876]: bool(range) works even if len(range) raises OverflowError.

bpo-29683 [https://bugs.python.org/issue?@action=redirect&bpo=29683]: Fixes to memory allocation in _PyCode_SetExtra. Patch by Brian Coleman.

bpo-29684 [https://bugs.python.org/issue?@action=redirect&bpo=29684]: Fix minor regression of PyEval_CallObjectWithKeywords. It should raise TypeError when kwargs is not a dict. But it might cause segv when args=NULL and kwargs is not a dict.

bpo-28598 [https://bugs.python.org/issue?@action=redirect&bpo=28598]: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

bpo-29607 [https://bugs.python.org/issue?@action=redirect&bpo=29607]: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by Matthieu Dartiailh.

bpo-29602 [https://bugs.python.org/issue?@action=redirect&bpo=29602]: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

bpo-29347 [https://bugs.python.org/issue?@action=redirect&bpo=29347]: Fixed possibly dereferencing undefined pointers when creating weakref objects.

bpo-29463 [https://bugs.python.org/issue?@action=redirect&bpo=29463]: Add docstring field to Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes. docstring is not first stmt in their body anymore. It affects co_firstlineno and co_lnotab of code object for module and class. (Reverted in bpo-32911 [https://bugs.python.org/issue?@action=redirect&bpo=32911].)

bpo-29438 [https://bugs.python.org/issue?@action=redirect&bpo=29438]: Fixed use-after-free problem in key sharing dict.

bpo-29546 [https://bugs.python.org/issue?@action=redirect&bpo=29546]: Set the 'path' and 'name' attribute on ImportError for from ... import ....

bpo-29546 [https://bugs.python.org/issue?@action=redirect&bpo=29546]: Improve from-import error message with location

bpo-29478 [https://bugs.python.org/issue?@action=redirect&bpo=29478]: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

bpo-29319 [https://bugs.python.org/issue?@action=redirect&bpo=29319]: Prevent RunMainFromImporter overwriting sys.path[0].

bpo-29337 [https://bugs.python.org/issue?@action=redirect&bpo=29337]: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

bpo-29327 [https://bugs.python.org/issue?@action=redirect&bpo=29327]: Fixed a crash when pass the iterable keyword argument to sorted().

bpo-29034 [https://bugs.python.org/issue?@action=redirect&bpo=29034]: Fix memory leak and use-after-free in os module (path_converter).

bpo-29159 [https://bugs.python.org/issue?@action=redirect&bpo=29159]: Fix regression in bytes(x) when x.__index__() raises Exception.

bpo-29049 [https://bugs.python.org/issue?@action=redirect&bpo=29049]: Call _PyObject_GC_TRACK() lazily when calling Python function. Calling function is up to 5% faster.

bpo-28927 [https://bugs.python.org/issue?@action=redirect&bpo=28927]: bytes.fromhex() and bytearray.fromhex() now ignore all ASCII whitespace, not only spaces. Patch by Robert Xiao.

bpo-28932 [https://bugs.python.org/issue?@action=redirect&bpo=28932]: Do not include <sys/random.h> if it does not exist.

bpo-25677 [https://bugs.python.org/issue?@action=redirect&bpo=25677]: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

bpo-29000 [https://bugs.python.org/issue?@action=redirect&bpo=29000]: Fixed bytes formatting of octals with zero padding in alternate form.

bpo-18896 [https://bugs.python.org/issue?@action=redirect&bpo=18896]: Python function can now have more than 255 parameters. collections.namedtuple() now supports tuples with more than 255 elements.

bpo-28596 [https://bugs.python.org/issue?@action=redirect&bpo=28596]: The preferred encoding is UTF-8 on Android. Patch written by Chi Hsuan Yen.

bpo-22257 [https://bugs.python.org/issue?@action=redirect&bpo=22257]: Clean up interpreter startup (see PEP 432 [https://peps.python.org/pep-0432/]).

bpo-26919 [https://bugs.python.org/issue?@action=redirect&bpo=26919]: On Android, operating system data is now always encoded/decoded to/from UTF-8, instead of the locale encoding to avoid inconsistencies with os.fsencode() and os.fsdecode() which are already using UTF-8.

bpo-28991 [https://bugs.python.org/issue?@action=redirect&bpo=28991]: functools.lru_cache() was susceptible to an obscure reentrancy bug triggerable by a monkey-patched len() function.

bpo-28147 [https://bugs.python.org/issue?@action=redirect&bpo=28147]: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table. Patch written by INADA Naoki.

bpo-28739 [https://bugs.python.org/issue?@action=redirect&bpo=28739]: f-string expressions are no longer accepted as docstrings and by ast.literal_eval() even if they do not include expressions.

bpo-28512 [https://bugs.python.org/issue?@action=redirect&bpo=28512]: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

bpo-28918 [https://bugs.python.org/issue?@action=redirect&bpo=28918]: Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined.

bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722]: Rather than silently producing a class that doesn't support zero-argument super() in methods, failing to pass the new __classcell__ namespace entry up to type.__new__ now results in a DeprecationWarning and a class that supports zero-argument super().

bpo-28797 [https://bugs.python.org/issue?@action=redirect&bpo=28797]: Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.

bpo-28799 [https://bugs.python.org/issue?@action=redirect&bpo=28799]: Remove the PyEval_GetCallStats() function and deprecate the untested and undocumented sys.callstats() function. Remove the CALL_PROFILE special build: use the sys.setprofile() function, cProfile or profile to profile function calls.

bpo-12844 [https://bugs.python.org/issue?@action=redirect&bpo=12844]: More than 255 arguments can now be passed to a function.

bpo-28782 [https://bugs.python.org/issue?@action=redirect&bpo=28782]: Fix a bug in the implementation yield from when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (bpo-26647 [https://bugs.python.org/issue?@action=redirect&bpo=26647]).

bpo-28774 [https://bugs.python.org/issue?@action=redirect&bpo=28774]: Fix error position of the unicode error in ASCII and Latin1 encoders when a string returned by the error handler contains multiple non-encodable characters (non-ASCII for the ASCII codec, characters out of the U+0000-U+00FF range for Latin1).

bpo-28731 [https://bugs.python.org/issue?@action=redirect&bpo=28731]: Optimize _PyDict_NewPresized() to create correct size dict. Improve speed of dict literal with constant keys up to 30%.

bpo-28532 [https://bugs.python.org/issue?@action=redirect&bpo=28532]: Show sys.version when -V option is supplied twice.

bpo-27100 [https://bugs.python.org/issue?@action=redirect&bpo=27100]: The with-statement now checks for __enter__ before it checks for __exit__. This gives less confusing error messages when both methods are missing. Patch by Jonathan Ellington.

bpo-28746 [https://bugs.python.org/issue?@action=redirect&bpo=28746]: Fix the set_inheritable() file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands.

bpo-26920 [https://bugs.python.org/issue?@action=redirect&bpo=26920]: Fix not getting the locale's charset upon initializing the interpreter, on platforms that do not have langinfo.

bpo-28648 [https://bugs.python.org/issue?@action=redirect&bpo=28648]: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

bpo-28665 [https://bugs.python.org/issue?@action=redirect&bpo=28665]: Improve speed of the STORE_DEREF opcode by 40%.

bpo-19398 [https://bugs.python.org/issue?@action=redirect&bpo=19398]: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

bpo-28621 [https://bugs.python.org/issue?@action=redirect&bpo=28621]: Sped up converting int to float by reusing faster bits counting implementation. Patch by Adrian Wielgosik.

bpo-28580 [https://bugs.python.org/issue?@action=redirect&bpo=28580]: Optimize iterating split table values. Patch by Xiang Zhang.

bpo-28583 [https://bugs.python.org/issue?@action=redirect&bpo=28583]: PyDict_SetDefault didn't combine split table when needed. Patch by Xiang Zhang.

bpo-28128 [https://bugs.python.org/issue?@action=redirect&bpo=28128]: Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs. Patch by Serhiy Storchaka and Eric Smith.

bpo-28509 [https://bugs.python.org/issue?@action=redirect&bpo=28509]: dict.update() no longer allocate unnecessary large memory.

bpo-28426 [https://bugs.python.org/issue?@action=redirect&bpo=28426]: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

bpo-28517 [https://bugs.python.org/issue?@action=redirect&bpo=28517]: Fixed of-by-one error in the peephole optimizer that caused keeping unreachable code.

bpo-28214 [https://bugs.python.org/issue?@action=redirect&bpo=28214]: Improved exception reporting for problematic __set_name__ attributes.

bpo-23782 [https://bugs.python.org/issue?@action=redirect&bpo=23782]: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

bpo-28183 [https://bugs.python.org/issue?@action=redirect&bpo=28183]: Optimize and cleanup dict iteration.

bpo-26081 [https://bugs.python.org/issue?@action=redirect&bpo=26081]: Added C implementation of asyncio.Future. Original patch by Yury Selivanov.

bpo-28379 [https://bugs.python.org/issue?@action=redirect&bpo=28379]: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: Creating instances of range_iterator by calling range_iterator type now is disallowed. Calling iter() on range instance is the only way. Patch by Oren Milman.

bpo-26906 [https://bugs.python.org/issue?@action=redirect&bpo=26906]: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

bpo-18287 [https://bugs.python.org/issue?@action=redirect&bpo=18287]: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

bpo-24098 [https://bugs.python.org/issue?@action=redirect&bpo=24098]: Fixed possible crash when AST is changed in process of compiling it.

bpo-28201 [https://bugs.python.org/issue?@action=redirect&bpo=28201]: Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits.

bpo-28350 [https://bugs.python.org/issue?@action=redirect&bpo=28350]: String constants with null character no longer interned.

bpo-26617 [https://bugs.python.org/issue?@action=redirect&bpo=26617]: Fix crash when GC runs during weakref callbacks.

bpo-27942 [https://bugs.python.org/issue?@action=redirect&bpo=27942]: String constants now interned recursively in tuples and frozensets.

bpo-28289 [https://bugs.python.org/issue?@action=redirect&bpo=28289]: ImportError.__init__ now resets not specified attributes.

bpo-21578 [https://bugs.python.org/issue?@action=redirect&bpo=21578]: Fixed misleading error message when ImportError called with invalid keyword args.

bpo-28203 [https://bugs.python.org/issue?@action=redirect&bpo=28203]: Fix incorrect type in complex(1.0, {2:3}) error message. Patch by Soumya Sharma.

bpo-28086 [https://bugs.python.org/issue?@action=redirect&bpo=28086]: Single var-positional argument of tuple subtype was passed unscathed to the C-defined function. Now it is converted to exact tuple.

bpo-28214 [https://bugs.python.org/issue?@action=redirect&bpo=28214]: Now __set_name__ is looked up on the class instead of the instance.

bpo-27955 [https://bugs.python.org/issue?@action=redirect&bpo=27955]: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

bpo-28192 [https://bugs.python.org/issue?@action=redirect&bpo=28192]: Don't import readline in isolated mode.

bpo-27441 [https://bugs.python.org/issue?@action=redirect&bpo=27441]: Remove some redundant assignments to ob_size in longobject.c. Thanks Oren Milman.

bpo-27222 [https://bugs.python.org/issue?@action=redirect&bpo=27222]: Clean up redundant code in long_rshift function. Thanks Oren Milman.

Upgrade internal unicode databases to Unicode version 9.0.0.

bpo-28131 [https://bugs.python.org/issue?@action=redirect&bpo=28131]: Fix a regression in zipimport's compile_source(). zipimport should use the same optimization level as the interpreter.

bpo-28126 [https://bugs.python.org/issue?@action=redirect&bpo=28126]: Replace Py_MEMCPY with memcpy(). Visual Studio can properly optimize memcpy().

bpo-28120 [https://bugs.python.org/issue?@action=redirect&bpo=28120]: Fix dict.pop() for split dictionary when trying to remove a "pending key" (Not yet inserted in split-table). Patch by Xiang Zhang.

bpo-26182 [https://bugs.python.org/issue?@action=redirect&bpo=26182]: Raise DeprecationWarning when async and await keywords are used as variable/attribute/class/function name.

bpo-26182 [https://bugs.python.org/issue?@action=redirect&bpo=26182]: Fix a refleak in code that raises DeprecationWarning.

bpo-28721 [https://bugs.python.org/issue?@action=redirect&bpo=28721]: Fix asynchronous generators aclose() and athrow() to handle StopAsyncIteration propagation properly.

bpo-26110 [https://bugs.python.org/issue?@action=redirect&bpo=26110]: Speed-up method calls: add LOAD_METHOD and CALL_METHOD opcodes.

Library

bpo-31499 [https://bugs.python.org/issue?@action=redirect&bpo=31499]: xml.etree: Fix a crash when a parser is part of a reference cycle.

bpo-31482 [https://bugs.python.org/issue?@action=redirect&bpo=31482]: random.seed() now works with bytes in version=1

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: typing.get_type_hints now finds the right globalns for classes and modules by default (when no globalns was specified by the caller).

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Speed improvements to the typing module. Original PRs by Ivan Levkivskyi and Mitar.

bpo-31544 [https://bugs.python.org/issue?@action=redirect&bpo=31544]: The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser().

bpo-31234 [https://bugs.python.org/issue?@action=redirect&bpo=31234]: socket.create_connection() now fixes manually a reference cycle: clear the variable storing the last exception on success.

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: LoggerAdapter objects can now be nested.

bpo-31431 [https://bugs.python.org/issue?@action=redirect&bpo=31431]: SSLContext.check_hostname now automatically sets SSLContext.verify_mode to ssl.CERT_REQUIRED instead of failing with a ValueError.

bpo-31233 [https://bugs.python.org/issue?@action=redirect&bpo=31233]: socketserver.ThreadingMixIn now keeps a list of non-daemonic threads to wait until all these threads complete in server_close().

bpo-28638 [https://bugs.python.org/issue?@action=redirect&bpo=28638]: Changed the implementation strategy for collections.namedtuple() to substantially reduce the use of exec() in favor of precomputed methods. As a result, the verbose parameter and _source attribute are no longer supported. The benefits include 1) having a smaller memory footprint for applications using multiple named tuples, 2) faster creation of the named tuple class (approx 4x to 6x depending on how it is measured), and 3) minor speed-ups for instance creation using __new__, _make, and _replace. (The primary patch contributor is Jelle Zijlstra with further improvements by INADA Naoki, Serhiy Storchaka, and Raymond Hettinger.)

bpo-31400 [https://bugs.python.org/issue?@action=redirect&bpo=31400]: Improves SSL error handling to avoid losing error numbers.

bpo-27629 [https://bugs.python.org/issue?@action=redirect&bpo=27629]: Make return types of SSLContext.wrap_bio() and SSLContext.wrap_socket() customizable.

bpo-28958 [https://bugs.python.org/issue?@action=redirect&bpo=28958]: ssl.SSLContext() now uses OpenSSL error information when a context cannot be instantiated.

bpo-28182 [https://bugs.python.org/issue?@action=redirect&bpo=28182]: The SSL module now raises SSLCertVerificationError when OpenSSL fails to verify the peer's certificate. The exception contains more information about the error.

bpo-27340 [https://bugs.python.org/issue?@action=redirect&bpo=27340]: SSLSocket.sendall() now uses memoryview to create slices of data. This fixes support for all bytes-like object. It is also more efficient and avoids costly copies.

bpo-14191 [https://bugs.python.org/issue?@action=redirect&bpo=14191]: A new function argparse.ArgumentParser.parse_intermixed_args provides the ability to parse command lines where there user intermixes options and positional arguments.

bpo-31178 [https://bugs.python.org/issue?@action=redirect&bpo=31178]: Fix string concatenation bug in rare error path in the subprocess module

bpo-31350 [https://bugs.python.org/issue?@action=redirect&bpo=31350]: Micro-optimize asyncio._get_running_loop() to become up to 10% faster.

bpo-31170 [https://bugs.python.org/issue?@action=redirect&bpo=31170]: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

bpo-29136 [https://bugs.python.org/issue?@action=redirect&bpo=29136]: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

bpo-1198569 [https://bugs.python.org/issue?@action=redirect&bpo=1198569]: string.Template subclasses can optionally define braceidpattern if they want to specify different placeholder patterns inside and outside the braces. If None (the default) it falls back to idpattern.

bpo-31326 [https://bugs.python.org/issue?@action=redirect&bpo=31326]: concurrent.futures.ProcessPoolExecutor.shutdown() now explicitly closes the call queue. Moreover, shutdown(wait=True) now also join the call queue thread, to prevent leaking a dangling thread.

bpo-27144 [https://bugs.python.org/issue?@action=redirect&bpo=27144]: The map() and as_completed() iterators in concurrent.futures now avoid keeping a reference to yielded objects.

bpo-31281 [https://bugs.python.org/issue?@action=redirect&bpo=31281]: Fix fileinput.FileInput(files, inplace=True) when files contain pathlib.Path objects.

bpo-10746 [https://bugs.python.org/issue?@action=redirect&bpo=10746]: Fix ctypes producing wrong PEP 3118 [https://peps.python.org/pep-3118/] type codes for integer types.

bpo-27584 [https://bugs.python.org/issue?@action=redirect&bpo=27584]: AF_VSOCK has been added to the socket interface which allows communication between virtual machines and their host.

bpo-22536 [https://bugs.python.org/issue?@action=redirect&bpo=22536]: The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found.

bpo-29741 [https://bugs.python.org/issue?@action=redirect&bpo=29741]: Update some methods in the _pyio module to also accept integer types. Patch by Oren Milman.

bpo-31249 [https://bugs.python.org/issue?@action=redirect&bpo=31249]: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object.

bpo-31247 [https://bugs.python.org/issue?@action=redirect&bpo=31247]: xmlrpc.server now explicitly breaks reference cycles when using sys.exc_info() in code handling exceptions.

bpo-23835 [https://bugs.python.org/issue?@action=redirect&bpo=23835]: configparser: reading defaults in the ConfigParser() constructor is now using read_dict(), making its behavior consistent with the rest of the parser. Non-string keys and values in the defaults dictionary are now being implicitly converted to strings. Patch by James Tocknell.

bpo-31238 [https://bugs.python.org/issue?@action=redirect&bpo=31238]: pydoc: the stop() method of the private ServerThread class now waits until DocServer.serve_until_quit() completes and then explicitly sets its docserver attribute to None to break a reference cycle.

bpo-5001 [https://bugs.python.org/issue?@action=redirect&bpo=5001]: Many asserts in multiprocessing are now more informative, and some error types have been changed to more specific ones.

bpo-31109 [https://bugs.python.org/issue?@action=redirect&bpo=31109]: Convert zipimport to use Argument Clinic.

bpo-30102 [https://bugs.python.org/issue?@action=redirect&bpo=30102]: The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function detects CPU features and enables optimizations on some CPU architectures such as POWER8. Patch is based on research from Gustavo Serra Scalet.

bpo-18966 [https://bugs.python.org/issue?@action=redirect&bpo=18966]: Non-daemonic threads created by a multiprocessing.Process are now joined on child exit.

bpo-31183 [https://bugs.python.org/issue?@action=redirect&bpo=31183]: dis now works with asynchronous generator and coroutine objects. Patch by George Collins based on diagnosis by Luciano Ramalho.

bpo-5001 [https://bugs.python.org/issue?@action=redirect&bpo=5001]: There are a number of uninformative asserts in the multiprocessing module, as noted in issue 5001. This change fixes two of the most potentially problematic ones, since they are in error-reporting code, in the multiprocessing.managers.convert_to_error function. (It also makes more informative a ValueError message.) The only potentially problematic change is that the AssertionError is now a TypeError; however, this should also help distinguish it from an AssertionError being reported by the function/its caller (such as in issue 31169). - Patch by Allen W. Smith (drallensmith on github).

bpo-31185 [https://bugs.python.org/issue?@action=redirect&bpo=31185]: Fixed miscellaneous errors in asyncio speedup module.

bpo-31151 [https://bugs.python.org/issue?@action=redirect&bpo=31151]: socketserver.ForkingMixIn.server_close() now waits until all child processes completed to prevent leaking zombie processes.

bpo-31072 [https://bugs.python.org/issue?@action=redirect&bpo=31072]: Add an include_file parameter to zipapp.create_archive()

bpo-24700 [https://bugs.python.org/issue?@action=redirect&bpo=24700]: Optimize array.array comparison. It is now from 10x up to 70x faster when comparing arrays holding values of the same integer type.

bpo-31135 [https://bugs.python.org/issue?@action=redirect&bpo=31135]: ttk: fix the destroy() method of LabeledScale and OptionMenu classes. Call the parent destroy() method even if the used attribute doesn't exist. The LabeledScale.destroy() method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets.

bpo-31107 [https://bugs.python.org/issue?@action=redirect&bpo=31107]: Fix copyreg._slotnames() mangled attribute calculation for classes whose name begins with an underscore. Patch by Shane Harvey.

bpo-31080 [https://bugs.python.org/issue?@action=redirect&bpo=31080]: Allow logging.config.fileConfig to accept kwargs and/or args.

bpo-30897 [https://bugs.python.org/issue?@action=redirect&bpo=30897]: pathlib.Path objects now include an is_mount() method (only implemented on POSIX). This is similar to os.path.ismount(p). Patch by Cooper Ry Lees.

bpo-31061 [https://bugs.python.org/issue?@action=redirect&bpo=31061]: Fixed a crash when using asyncio and threads.

bpo-30987 [https://bugs.python.org/issue?@action=redirect&bpo=30987]: Added support for CAN ISO-TP protocol in the socket module.

bpo-30522 [https://bugs.python.org/issue?@action=redirect&bpo=30522]: Added a setStream method to logging.StreamHandler to allow the stream to be set after creation.

bpo-30502 [https://bugs.python.org/issue?@action=redirect&bpo=30502]: Fix handling of long oids in ssl. Based on patch by Christian Heimes.

bpo-5288 [https://bugs.python.org/issue?@action=redirect&bpo=5288]: Support tzinfo objects with sub-minute offsets.

bpo-30919 [https://bugs.python.org/issue?@action=redirect&bpo=30919]: Fix shared memory performance regression in multiprocessing in 3.x. Shared memory used anonymous memory mappings in 2.x, while 3.x mmaps actual files. Try to be careful to do as little disk I/O as possible.

bpo-26732 [https://bugs.python.org/issue?@action=redirect&bpo=26732]: Fix too many fds in processes started with the "forkserver" method. A child process would inherit as many fds as the number of still-running children.

bpo-29403 [https://bugs.python.org/issue?@action=redirect&bpo=29403]: Fix unittest.mock's autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

bpo-30961 [https://bugs.python.org/issue?@action=redirect&bpo=30961]: Fix decrementing a borrowed reference in tracemalloc.

bpo-19896 [https://bugs.python.org/issue?@action=redirect&bpo=19896]: Fix multiprocessing.sharedctypes to recognize typecodes 'q' and 'Q'.

bpo-30946 [https://bugs.python.org/issue?@action=redirect&bpo=30946]: Remove obsolete code in readline module for platforms where GNU readline is older than 2.1 or where select() is not available.

bpo-25684 [https://bugs.python.org/issue?@action=redirect&bpo=25684]: Change ttk.OptionMenu radiobuttons to be unique across instances of OptionMenu.

bpo-30886 [https://bugs.python.org/issue?@action=redirect&bpo=30886]: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

bpo-29854 [https://bugs.python.org/issue?@action=redirect&bpo=29854]: Fix segfault in readline when using readline's history-size option. Patch by Nir Soffer.

bpo-30794 [https://bugs.python.org/issue?@action=redirect&bpo=30794]: Added multiprocessing.Process.kill method to terminate using the SIGKILL signal on Unix.

bpo-30319 [https://bugs.python.org/issue?@action=redirect&bpo=30319]: socket.close() now ignores ECONNRESET error.

bpo-30828 [https://bugs.python.org/issue?@action=redirect&bpo=30828]: Fix out of bounds write in asyncio.CFuture.remove_done_callback().

bpo-30302 [https://bugs.python.org/issue?@action=redirect&bpo=30302]: Use keywords in the repr of datetime.timedelta.

bpo-30807 [https://bugs.python.org/issue?@action=redirect&bpo=30807]: signal.setitimer() may disable the timer when passed a tiny value. Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

bpo-30441 [https://bugs.python.org/issue?@action=redirect&bpo=30441]: Fix bug when modifying os.environ while iterating over it

bpo-29585 [https://bugs.python.org/issue?@action=redirect&bpo=29585]: Avoid importing sysconfig from site to improve startup speed. Python startup is about 5% faster on Linux and 30% faster on macOS.

bpo-29293 [https://bugs.python.org/issue?@action=redirect&bpo=29293]: Add missing parameter "n" on multiprocessing.Condition.notify(). The doc claims multiprocessing.Condition behaves like threading.Condition, but its notify() method lacked the optional "n" argument (to specify the number of sleepers to wake up) that threading.Condition.notify() accepts.

bpo-30532 [https://bugs.python.org/issue?@action=redirect&bpo=30532]: Fix email header value parser dropping folding white space in certain cases.

bpo-30596 [https://bugs.python.org/issue?@action=redirect&bpo=30596]: Add a close() method to multiprocessing.Process.

bpo-9146 [https://bugs.python.org/issue?@action=redirect&bpo=9146]: Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library. As in some special FIPS-140 build environments.

bpo-29169 [https://bugs.python.org/issue?@action=redirect&bpo=29169]: Update zlib to 1.2.11.

bpo-30119 [https://bugs.python.org/issue?@action=redirect&bpo=30119]: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Donghee Na.

bpo-30879 [https://bugs.python.org/issue?@action=redirect&bpo=30879]: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

bpo-30746 [https://bugs.python.org/issue?@action=redirect&bpo=30746]: Prohibited the '=' character in environment variable names in os.putenv() and os.spawn*().

bpo-30664 [https://bugs.python.org/issue?@action=redirect&bpo=30664]: The description of a unittest subtest now preserves the order of keyword arguments of TestCase.subTest().

bpo-21071 [https://bugs.python.org/issue?@action=redirect&bpo=21071]: struct.Struct.format type is now str instead of bytes.

bpo-29212 [https://bugs.python.org/issue?@action=redirect&bpo=29212]: Fix concurrent.futures.thread.ThreadPoolExecutor threads to have a non repr() based thread name by default when no thread_name_prefix is supplied. They will now identify themselves as "ThreadPoolExecutor-y_n".

bpo-29755 [https://bugs.python.org/issue?@action=redirect&bpo=29755]: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

bpo-30616 [https://bugs.python.org/issue?@action=redirect&bpo=30616]: Functional API of enum allows to create empty enums. Patched by Donghee Na

bpo-30038 [https://bugs.python.org/issue?@action=redirect&bpo=30038]: Fix race condition between signal delivery and wakeup file descriptor. Patch by Nathaniel Smith.

bpo-23894 [https://bugs.python.org/issue?@action=redirect&bpo=23894]: lib2to3 now recognizes rb'...' and f'...' strings.

bpo-24744 [https://bugs.python.org/issue?@action=redirect&bpo=24744]: pkgutil.walk_packages function now raises ValueError if path is a string. Patch by Sanyam Khurana.

bpo-24484 [https://bugs.python.org/issue?@action=redirect&bpo=24484]: Avoid race condition in multiprocessing cleanup.

bpo-30589 [https://bugs.python.org/issue?@action=redirect&bpo=30589]: Fix multiprocessing.Process.exitcode to return the opposite of the signal number when the process is killed by a signal (instead of 255) when using the "forkserver" method.

bpo-28994 [https://bugs.python.org/issue?@action=redirect&bpo=28994]: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

bpo-30508 [https://bugs.python.org/issue?@action=redirect&bpo=30508]: Don't log exceptions if Task/Future "cancel()" method was called.

bpo-30645 [https://bugs.python.org/issue?@action=redirect&bpo=30645]: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

bpo-11822 [https://bugs.python.org/issue?@action=redirect&bpo=11822]: The dis.dis() function now is able to disassemble nested code objects.

bpo-30624 [https://bugs.python.org/issue?@action=redirect&bpo=30624]: selectors does not take KeyboardInterrupt and SystemExit into account, leaving a fd in a bad state in case of error. Patch by Giampaolo Rodola'.

bpo-30595 [https://bugs.python.org/issue?@action=redirect&bpo=30595]: multiprocessing.Queue.get() with a timeout now polls its reader in non-blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

bpo-30605 [https://bugs.python.org/issue?@action=redirect&bpo=30605]: re.compile() no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier. Patch by Roy Williams.

bpo-29870 [https://bugs.python.org/issue?@action=redirect&bpo=29870]: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

bpo-29743 [https://bugs.python.org/issue?@action=redirect&bpo=29743]: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

bpo-27585 [https://bugs.python.org/issue?@action=redirect&bpo=27585]: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

bpo-30014 [https://bugs.python.org/issue?@action=redirect&bpo=30014]: modify() method of poll(), epoll() and devpoll() based classes of selectors module is around 10% faster. Patch by Giampaolo Rodola'.

bpo-30418 [https://bugs.python.org/issue?@action=redirect&bpo=30418]: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

bpo-30463 [https://bugs.python.org/issue?@action=redirect&bpo=30463]: Added empty __slots__ to abc.ABC. This allows subclassers to deny __dict__ and __weakref__ creation. Patch by Aaron Hall.

bpo-30520 [https://bugs.python.org/issue?@action=redirect&bpo=30520]: Loggers are now pickleable.

bpo-30557 [https://bugs.python.org/issue?@action=redirect&bpo=30557]: faulthandler now correctly filters and displays exception codes on Windows

bpo-30526 [https://bugs.python.org/issue?@action=redirect&bpo=30526]: Add TextIOWrapper.reconfigure() and a TextIOWrapper.write_through attribute.

bpo-30245 [https://bugs.python.org/issue?@action=redirect&bpo=30245]: Fix possible overflow when organize struct.pack_into error message. Patch by Yuan Liu.

bpo-30378 [https://bugs.python.org/issue?@action=redirect&bpo=30378]: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

bpo-16500 [https://bugs.python.org/issue?@action=redirect&bpo=16500]: Allow registering at-fork handlers.

bpo-30470 [https://bugs.python.org/issue?@action=redirect&bpo=30470]: Deprecate invalid ctypes call protection on Windows. Patch by Mariatta Wijaya.

bpo-30414 [https://bugs.python.org/issue?@action=redirect&bpo=30414]: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

bpo-30003 [https://bugs.python.org/issue?@action=redirect&bpo=30003]: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

bpo-30149 [https://bugs.python.org/issue?@action=redirect&bpo=30149]: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Donghee Na.

bpo-30436 [https://bugs.python.org/issue?@action=redirect&bpo=30436]: importlib.find_spec() raises ModuleNotFoundError instead of AttributeError if the specified parent module is not a package (i.e. lacks a __path__ attribute).

bpo-30301 [https://bugs.python.org/issue?@action=redirect&bpo=30301]: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

bpo-30375 [https://bugs.python.org/issue?@action=redirect&bpo=30375]: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

bpo-30329 [https://bugs.python.org/issue?@action=redirect&bpo=30329]: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

bpo-29196 [https://bugs.python.org/issue?@action=redirect&bpo=29196]: Removed previously deprecated in Python 2.4 classes Plist, Dict and _InternalDict in the plistlib module. Dict values in the result of functions readPlist() and readPlistFromBytes() are now normal dicts. You no longer can use attribute access to access items of these dictionaries.

bpo-9850 [https://bugs.python.org/issue?@action=redirect&bpo=9850]: The macpath is now deprecated and will be removed in Python 3.8.

bpo-30299 [https://bugs.python.org/issue?@action=redirect&bpo=30299]: Compiling regular expression in debug mode on CPython now displays the compiled bytecode in human readable form.

bpo-30048 [https://bugs.python.org/issue?@action=redirect&bpo=30048]: Fixed Task.cancel() can be ignored when the task is running coroutine and the coroutine returned without any more await.

bpo-30266 [https://bugs.python.org/issue?@action=redirect&bpo=30266]: contextlib.AbstractContextManager now supports anti-registration by setting __enter__ = None or __exit__ = None, following the pattern introduced in bpo-25958 [https://bugs.python.org/issue?@action=redirect&bpo=25958]. Patch by Jelle Zijlstra.

bpo-30340 [https://bugs.python.org/issue?@action=redirect&bpo=30340]: Enhanced regular expressions optimization. This increased the performance of matching some patterns up to 25 times.

bpo-30298 [https://bugs.python.org/issue?@action=redirect&bpo=30298]: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. '(?i)(?s)...'). In verbose mode whitespaces and comments now are allowed before and between inline modifiers (e.g. '(?x) (?i) (?s)...').

bpo-30285 [https://bugs.python.org/issue?@action=redirect&bpo=30285]: Optimized case-insensitive matching and searching of regular expressions.

bpo-29990 [https://bugs.python.org/issue?@action=redirect&bpo=29990]: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

bpo-29979 [https://bugs.python.org/issue?@action=redirect&bpo=29979]: rewrite cgi.parse_multipart, reusing the FieldStorage class and making its results consistent with those of FieldStorage for multipart/form-data requests. Patch by Pierre Quentel.

bpo-30243 [https://bugs.python.org/issue?@action=redirect&bpo=30243]: Removed the __init__ methods of _json's scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

bpo-30215 [https://bugs.python.org/issue?@action=redirect&bpo=30215]: Compiled regular expression objects with the re.LOCALE flag no longer depend on the locale at compile time. Only the locale at matching time affects the result of matching.

bpo-30185 [https://bugs.python.org/issue?@action=redirect&bpo=30185]: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

bpo-30103 [https://bugs.python.org/issue?@action=redirect&bpo=30103]: binascii.b2a_uu() and uu.encode() now support using '`' as zero instead of space.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

bpo-30205 [https://bugs.python.org/issue?@action=redirect&bpo=30205]: Fix getsockname() for unbound AF_UNIX sockets on Linux.

bpo-30228 [https://bugs.python.org/issue?@action=redirect&bpo=30228]: The seek() and tell() methods of io.FileIO now set the internal seekable attribute to avoid one syscall on open() (in buffered or text mode).

bpo-30190 [https://bugs.python.org/issue?@action=redirect&bpo=30190]: unittest's assertAlmostEqual and assertNotAlmostEqual provide a better message in case of failure which includes the difference between left and right arguments. (patch by Giampaolo Rodola')

bpo-30101 [https://bugs.python.org/issue?@action=redirect&bpo=30101]: Add support for curses.A_ITALIC.

bpo-29822 [https://bugs.python.org/issue?@action=redirect&bpo=29822]: inspect.isabstract() now works during __init_subclass__. Patch by Nate Soares.

bpo-29960 [https://bugs.python.org/issue?@action=redirect&bpo=29960]: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

bpo-30070 [https://bugs.python.org/issue?@action=redirect&bpo=30070]: Fixed leaks and crashes in errors handling in the parser module.

bpo-22352 [https://bugs.python.org/issue?@action=redirect&bpo=22352]: Column widths in the output of dis.dis() are now adjusted for large line numbers and instruction offsets.

bpo-30061 [https://bugs.python.org/issue?@action=redirect&bpo=30061]: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

bpo-30218 [https://bugs.python.org/issue?@action=redirect&bpo=30218]: Fix PathLike support for shutil.unpack_archive. Patch by Jelle Zijlstra.

bpo-10076 [https://bugs.python.org/issue?@action=redirect&bpo=10076]: Compiled regular expression and match objects in the re module now support copy.copy() and copy.deepcopy() (they are considered atomic).

bpo-30068 [https://bugs.python.org/issue?@action=redirect&bpo=30068]: _io._IOBase.readlines will check if it's closed first when hint is present.

bpo-29694 [https://bugs.python.org/issue?@action=redirect&bpo=29694]: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

bpo-29692 [https://bugs.python.org/issue?@action=redirect&bpo=29692]: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

bpo-26187 [https://bugs.python.org/issue?@action=redirect&bpo=26187]: Test that sqlite3 trace callback is not called multiple times when schema is changing. Indirectly fixed by switching to use sqlite3_prepare_v2() in bpo-9303 [https://bugs.python.org/issue?@action=redirect&bpo=9303]. Patch by Aviv Palivoda.

bpo-30017 [https://bugs.python.org/issue?@action=redirect&bpo=30017]: Allowed calling the close() method of the zip entry writer object multiple times. Writing to a closed writer now always produces a ValueError.

bpo-29998 [https://bugs.python.org/issue?@action=redirect&bpo=29998]: Pickling and copying ImportError now preserves name and path attributes.

bpo-29995 [https://bugs.python.org/issue?@action=redirect&bpo=29995]: re.escape() now escapes only regex special characters.

bpo-29962 [https://bugs.python.org/issue?@action=redirect&bpo=29962]: Add math.remainder operation, implementing remainder as specified in IEEE 754.

bpo-29649 [https://bugs.python.org/issue?@action=redirect&bpo=29649]: Improve struct.pack_into() exception messages for problems with the buffer size and offset. Patch by Andrew Nester.

bpo-29654 [https://bugs.python.org/issue?@action=redirect&bpo=29654]: Support If-Modified-Since HTTP header (browser cache). Patch by Pierre Quentel.

bpo-29931 [https://bugs.python.org/issue?@action=redirect&bpo=29931]: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

bpo-29953 [https://bugs.python.org/issue?@action=redirect&bpo=29953]: Fixed memory leaks in the replace() method of datetime and time objects when pass out of bound fold argument.

bpo-29942 [https://bugs.python.org/issue?@action=redirect&bpo=29942]: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

bpo-10030 [https://bugs.python.org/issue?@action=redirect&bpo=10030]: Sped up reading encrypted ZIP files by 2 times.

bpo-29204 [https://bugs.python.org/issue?@action=redirect&bpo=29204]: Element.getiterator() and the html parameter of XMLParser() were deprecated only in the documentation (since Python 3.2 and 3.4 correspondingly). Now using them emits a deprecation warning.

bpo-27863 [https://bugs.python.org/issue?@action=redirect&bpo=27863]: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

bpo-25996 [https://bugs.python.org/issue?@action=redirect&bpo=25996]: Added support of file descriptors in os.scandir() on Unix. os.fwalk() is sped up by 2 times by using os.scandir().

bpo-28699 [https://bugs.python.org/issue?@action=redirect&bpo=28699]: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

bpo-23890 [https://bugs.python.org/issue?@action=redirect&bpo=23890]: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

bpo-29901 [https://bugs.python.org/issue?@action=redirect&bpo=29901]: The zipapp module now supports general path-like objects, not just pathlib.Path.

bpo-25803 [https://bugs.python.org/issue?@action=redirect&bpo=25803]: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

bpo-29861 [https://bugs.python.org/issue?@action=redirect&bpo=29861]: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

bpo-19930 [https://bugs.python.org/issue?@action=redirect&bpo=19930]: The mode argument of os.makedirs() no longer affects the file permission bits of newly created intermediate-level directories.

bpo-29884 [https://bugs.python.org/issue?@action=redirect&bpo=29884]: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

bpo-25455 [https://bugs.python.org/issue?@action=redirect&bpo=25455]: Fixed crashes in repr of recursive buffered file-like objects.

bpo-29800 [https://bugs.python.org/issue?@action=redirect&bpo=29800]: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

bpo-8256 [https://bugs.python.org/issue?@action=redirect&bpo=8256]: Fixed possible failing or crashing input() if attributes "encoding" or "errors" of sys.stdin or sys.stdout are not set or are not strings.

bpo-28692 [https://bugs.python.org/issue?@action=redirect&bpo=28692]: Using non-integer value for selecting a plural form in gettext is now deprecated.

bpo-26121 [https://bugs.python.org/issue?@action=redirect&bpo=26121]: Use C library implementation for math functions erf() and erfc().

bpo-29619 [https://bugs.python.org/issue?@action=redirect&bpo=29619]: os.stat() and os.DirEntry.inode() now convert inode (st_ino) using unsigned integers.

bpo-28298 [https://bugs.python.org/issue?@action=redirect&bpo=28298]: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting big intables (objects that have __int__) as elements.

bpo-29645 [https://bugs.python.org/issue?@action=redirect&bpo=29645]: Speed up importing the webbrowser module. webbrowser.register() is now thread-safe.

bpo-28231 [https://bugs.python.org/issue?@action=redirect&bpo=28231]: The zipfile module now accepts path-like objects for external paths.

bpo-26915 [https://bugs.python.org/issue?@action=redirect&bpo=26915]: index() and count() methods of collections.abc.Sequence now check identity before checking equality when do comparisons.

bpo-28682 [https://bugs.python.org/issue?@action=redirect&bpo=28682]: Added support for bytes paths in os.fwalk().

bpo-29728 [https://bugs.python.org/issue?@action=redirect&bpo=29728]: Add new socket.TCP_NOTSENT_LOWAT (Linux 3.12) constant. Patch by Nathaniel J. Smith.

bpo-29623 [https://bugs.python.org/issue?@action=redirect&bpo=29623]: Allow use of path-like object as a single argument in ConfigParser.read(). Patch by David Ellis.

bpo-9303 [https://bugs.python.org/issue?@action=redirect&bpo=9303]: Migrate sqlite3 module to _v2 API. Patch by Aviv Palivoda.

bpo-28963 [https://bugs.python.org/issue?@action=redirect&bpo=28963]: Fix out of bound iteration in asyncio.Future.remove_done_callback implemented in C.

bpo-29704 [https://bugs.python.org/issue?@action=redirect&bpo=29704]: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

bpo-29271 [https://bugs.python.org/issue?@action=redirect&bpo=29271]: Fix Task.current_task and Task.all_tasks implemented in C to accept None argument as their pure Python implementation.

bpo-29703 [https://bugs.python.org/issue?@action=redirect&bpo=29703]: Fix asyncio to support instantiation of new event loops in child processes.

bpo-29615 [https://bugs.python.org/issue?@action=redirect&bpo=29615]: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

bpo-7769 [https://bugs.python.org/issue?@action=redirect&bpo=7769]: Method register_function() of xmlrpc.server.SimpleXMLRPCDispatcher and its subclasses can now be used as a decorator.

bpo-29376 [https://bugs.python.org/issue?@action=redirect&bpo=29376]: Fix assertion error in threading._DummyThread.is_alive().

bpo-28624 [https://bugs.python.org/issue?@action=redirect&bpo=28624]: Add a test that checks that cwd parameter of Popen() accepts PathLike objects. Patch by Sayan Chowdhury.

bpo-28518 [https://bugs.python.org/issue?@action=redirect&bpo=28518]: Start a transaction implicitly before a DML statement. Patch by Aviv Palivoda.

bpo-29742 [https://bugs.python.org/issue?@action=redirect&bpo=29742]: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

bpo-16285 [https://bugs.python.org/issue?@action=redirect&bpo=16285]: urllib.parse.quote is now based on RFC 3986 and hence includes '~' in the set of characters that is not quoted by default. Patch by Christian Theune and Ratnadeep Debnath.

bpo-29532 [https://bugs.python.org/issue?@action=redirect&bpo=29532]: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

bpo-29110 [https://bugs.python.org/issue?@action=redirect&bpo=29110]: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

bpo-22807 [https://bugs.python.org/issue?@action=redirect&bpo=22807]: Add uuid.SafeUUID and uuid.UUID.is_safe to relay information from the platform about whether generated UUIDs are generated with a multiprocessing safe method.

bpo-29576 [https://bugs.python.org/issue?@action=redirect&bpo=29576]: Improve some deprecations in importlib. Some deprecated methods now emit DeprecationWarnings and have better descriptive messages.

bpo-29534 [https://bugs.python.org/issue?@action=redirect&bpo=29534]: Fixed different behaviour of Decimal.from_float() for _decimal and _pydecimal. Thanks Andrew Nester.

bpo-10379 [https://bugs.python.org/issue?@action=redirect&bpo=10379]: locale.format_string now supports the 'monetary' keyword argument, and locale.format is deprecated.

bpo-29851 [https://bugs.python.org/issue?@action=redirect&bpo=29851]: importlib.reload() now raises ModuleNotFoundError if the module lacks a spec.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

bpo-29100 [https://bugs.python.org/issue?@action=redirect&bpo=29100]: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

bpo-29416 [https://bugs.python.org/issue?@action=redirect&bpo=29416]: Prevent infinite loop in pathlib.Path.mkdir

bpo-29444 [https://bugs.python.org/issue?@action=redirect&bpo=29444]: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

bpo-29377 [https://bugs.python.org/issue?@action=redirect&bpo=29377]: Add WrapperDescriptorType, MethodWrapperType, and MethodDescriptorType built-in types to types module. Original patch by Manuel Krebber.

bpo-29218 [https://bugs.python.org/issue?@action=redirect&bpo=29218]: Unused install_misc command is now removed. It has been documented as unused since 2000. Patch by Eric N. Vander Weele.

bpo-29368 [https://bugs.python.org/issue?@action=redirect&bpo=29368]: The extend() method is now called instead of the append() method when unpickle collections.deque and other list-like objects. This can speed up unpickling to 2 times.

bpo-29338 [https://bugs.python.org/issue?@action=redirect&bpo=29338]: The help of a builtin or extension class now includes the constructor signature if __text_signature__ is provided for the class.

bpo-29335 [https://bugs.python.org/issue?@action=redirect&bpo=29335]: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

bpo-29290 [https://bugs.python.org/issue?@action=redirect&bpo=29290]: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

bpo-28735 [https://bugs.python.org/issue?@action=redirect&bpo=28735]: Fixed the comparison of mock.MagickMock with mock.ANY.

bpo-29197 [https://bugs.python.org/issue?@action=redirect&bpo=29197]: Removed deprecated function ntpath.splitunc().

bpo-29210 [https://bugs.python.org/issue?@action=redirect&bpo=29210]: Removed support of deprecated argument "exclude" in tarfile.TarFile.add().

bpo-29219 [https://bugs.python.org/issue?@action=redirect&bpo=29219]: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

bpo-29192 [https://bugs.python.org/issue?@action=redirect&bpo=29192]: Removed deprecated features in the http.cookies module.

bpo-29193 [https://bugs.python.org/issue?@action=redirect&bpo=29193]: A format string argument for string.Formatter.format() is now positional-only.

bpo-29195 [https://bugs.python.org/issue?@action=redirect&bpo=29195]: Removed support of deprecated undocumented keyword arguments in methods of regular expression objects.

bpo-28969 [https://bugs.python.org/issue?@action=redirect&bpo=28969]: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments.

bpo-20804 [https://bugs.python.org/issue?@action=redirect&bpo=20804]: The unittest.mock.sentinel attributes now preserve their identity when they are copied or pickled.

bpo-29142 [https://bugs.python.org/issue?@action=redirect&bpo=29142]: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

bpo-28961 [https://bugs.python.org/issue?@action=redirect&bpo=28961]: Fix unittest.mock._Call helper: don't ignore the name parameter anymore. Patch written by Jiajun Huang.

bpo-15812 [https://bugs.python.org/issue?@action=redirect&bpo=15812]: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

bpo-28985 [https://bugs.python.org/issue?@action=redirect&bpo=28985]: Update authorizer constants in sqlite3 module. Patch by Dingyuan Wang.

bpo-29079 [https://bugs.python.org/issue?@action=redirect&bpo=29079]: Prevent infinite loop in pathlib.resolve() on Windows

bpo-13051 [https://bugs.python.org/issue?@action=redirect&bpo=13051]: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

bpo-9770 [https://bugs.python.org/issue?@action=redirect&bpo=9770]: curses.ascii predicates now work correctly with negative integers.

bpo-28427 [https://bugs.python.org/issue?@action=redirect&bpo=28427]: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

bpo-28923 [https://bugs.python.org/issue?@action=redirect&bpo=28923]: Remove editor artifacts from Tix.py.

bpo-28871 [https://bugs.python.org/issue?@action=redirect&bpo=28871]: Fixed a crash when deallocate deep ElementTree.

bpo-19542 [https://bugs.python.org/issue?@action=redirect&bpo=19542]: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

bpo-20191 [https://bugs.python.org/issue?@action=redirect&bpo=20191]: Fixed a crash in resource.prlimit() when passing a sequence that doesn't own its elements as limits.

bpo-16255 [https://bugs.python.org/issue?@action=redirect&bpo=16255]: subprocess.Popen uses /system/bin/sh on Android as the shell, instead of /bin/sh.

bpo-28779 [https://bugs.python.org/issue?@action=redirect&bpo=28779]: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

bpo-26937 [https://bugs.python.org/issue?@action=redirect&bpo=26937]: The chown() method of the tarfile.TarFile class does not fail now when the grp module cannot be imported, as for example on Android platforms.

bpo-28847 [https://bugs.python.org/issue?@action=redirect&bpo=28847]: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed. A deprecation warning is now emitted if the index file is missed and recreated in the 'r' and 'w' modes (will be an error in future Python releases).

bpo-27030 [https://bugs.python.org/issue?@action=redirect&bpo=27030]: Unknown escapes consisting of '\' and an ASCII letter in re.sub() replacement templates regular expressions now are errors.

bpo-28835 [https://bugs.python.org/issue?@action=redirect&bpo=28835]: Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overridden inside the context manager.

bpo-27172 [https://bugs.python.org/issue?@action=redirect&bpo=27172]: To assist with upgrades from 2.7, the previously documented deprecation of inspect.getfullargspec() has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.

bpo-28740 [https://bugs.python.org/issue?@action=redirect&bpo=28740]: Add sys.getandroidapilevel(): return the build time API version of Android as an integer. Function only available on Android.

bpo-26273 [https://bugs.python.org/issue?@action=redirect&bpo=26273]: Add new socket.TCP_CONGESTION (Linux 2.6.13) and socket.TCP_USER_TIMEOUT (Linux 2.6.37) constants. Patch written by Omar Sandoval.

bpo-28752 [https://bugs.python.org/issue?@action=redirect&bpo=28752]: Restored the __reduce__() methods of datetime objects.

bpo-28727 [https://bugs.python.org/issue?@action=redirect&bpo=28727]: Regular expression patterns, _sre.SRE_Pattern objects created by re.compile(), become comparable (only x==y and x!=y operators). This change should fix the bpo-18383 [https://bugs.python.org/issue?@action=redirect&bpo=18383]: don't duplicate warning filters when the warnings module is reloaded (thing usually only done in unit tests).

bpo-20572 [https://bugs.python.org/issue?@action=redirect&bpo=20572]: Remove the subprocess.Popen.wait endtime parameter. It was deprecated in 3.4 and undocumented prior to that.

bpo-25659 [https://bugs.python.org/issue?@action=redirect&bpo=25659]: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

bpo-28548 [https://bugs.python.org/issue?@action=redirect&bpo=28548]: In the "http.server" module, parse the protocol version if possible, to avoid using HTTP 0.9 in some error responses.

bpo-19717 [https://bugs.python.org/issue?@action=redirect&bpo=19717]: Makes Path.resolve() succeed on paths that do not exist. Patch by Vajrasky Kok

bpo-28563 [https://bugs.python.org/issue?@action=redirect&bpo=28563]: Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module. The expression parser now supports exact syntax supported by GNU gettext.

bpo-28387 [https://bugs.python.org/issue?@action=redirect&bpo=28387]: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

bpo-27517 [https://bugs.python.org/issue?@action=redirect&bpo=27517]: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

bpo-28549 [https://bugs.python.org/issue?@action=redirect&bpo=28549]: Fixed segfault in curses's addch() with ncurses6.

bpo-28449 [https://bugs.python.org/issue?@action=redirect&bpo=28449]: tarfile.open() with mode "r" or "r:" now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

bpo-23262 [https://bugs.python.org/issue?@action=redirect&bpo=23262]: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

bpo-24241 [https://bugs.python.org/issue?@action=redirect&bpo=24241]: The webbrowser in an X environment now prefers using the default browser directly. Also, the webbrowser register() function now has a documented 'preferred' argument, to specify browsers to be returned by get() with no arguments. Patch by David Steele

bpo-27939 [https://bugs.python.org/issue?@action=redirect&bpo=27939]: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

bpo-28255 [https://bugs.python.org/issue?@action=redirect&bpo=28255]: calendar.TextCalendar.prweek() no longer prints a space after a weeks's calendar. calendar.TextCalendar.pryear() no longer prints redundant newline after a year's calendar. Based on patch by Xiang Zhang.

bpo-28255 [https://bugs.python.org/issue?@action=redirect&bpo=28255]: calendar.TextCalendar.prmonth() no longer prints a space at the start of new line after printing a month's calendar. Patch by Xiang Zhang.

bpo-20491 [https://bugs.python.org/issue?@action=redirect&bpo=20491]: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

bpo-28353 [https://bugs.python.org/issue?@action=redirect&bpo=28353]: os.fwalk() no longer fails on broken links.

bpo-28430 [https://bugs.python.org/issue?@action=redirect&bpo=28430]: Fix iterator of C implemented asyncio.Future doesn't accept non-None value is passed to it.send(val).

bpo-27025 [https://bugs.python.org/issue?@action=redirect&bpo=27025]: Generated names for Tkinter widgets now start by the "!" prefix for readability.

bpo-25464 [https://bugs.python.org/issue?@action=redirect&bpo=25464]: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

bpo-28488 [https://bugs.python.org/issue?@action=redirect&bpo=28488]: shutil.make_archive() no longer adds entry "./" to ZIP archive.

bpo-25953 [https://bugs.python.org/issue?@action=redirect&bpo=25953]: re.sub() now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string. Error message for invalid group reference now includes the group index and the position of the reference. Based on patch by SilentGhost.

bpo-28469 [https://bugs.python.org/issue?@action=redirect&bpo=28469]: timeit now uses the sequence 1, 2, 5, 10, 20, 50,... instead of 1, 10, 100,... for autoranging.

bpo-28115 [https://bugs.python.org/issue?@action=redirect&bpo=28115]: Command-line interface of the zipfile module now uses argparse. Added support of long options.

bpo-18219 [https://bugs.python.org/issue?@action=redirect&bpo=18219]: Optimize csv.DictWriter for large number of columns. Patch by Mariatta Wijaya.

bpo-28448 [https://bugs.python.org/issue?@action=redirect&bpo=28448]: Fix C implemented asyncio.Future didn't work on Windows.

bpo-23214 [https://bugs.python.org/issue?@action=redirect&bpo=23214]: In the "io" module, the argument to BufferedReader and BytesIO's read1() methods is now optional and can be -1, matching the BufferedIOBase specification.

bpo-28480 [https://bugs.python.org/issue?@action=redirect&bpo=28480]: Fix error building socket module when multithreading is disabled.

bpo-28240 [https://bugs.python.org/issue?@action=redirect&bpo=28240]: timeit: remove -c/--clock and -t/--time command line options which were deprecated since Python 3.3.

bpo-28240 [https://bugs.python.org/issue?@action=redirect&bpo=28240]: timeit now repeats the benchmarks 5 times instead of only 3 to make benchmarks more reliable.

bpo-28240 [https://bugs.python.org/issue?@action=redirect&bpo=28240]: timeit autorange now uses a single loop iteration if the benchmark takes less than 10 seconds, instead of 10 iterations. "python3 -m timeit -s 'import time' 'time.sleep(1)'" now takes 4 seconds instead of 40 seconds.

Distutils.sdist now looks for README and setup.py files with case sensitivity. This behavior matches that found in Setuptools 6.0 and later. See setuptools 100 [https://github.com/pypa/setuptools/issues/100] for rationale.

bpo-24452 [https://bugs.python.org/issue?@action=redirect&bpo=24452]: Make webbrowser support Chrome on Mac OS X. Patch by Ned Batchelder.

bpo-20766 [https://bugs.python.org/issue?@action=redirect&bpo=20766]: Fix references leaked by pdb in the handling of SIGINT handlers.

bpo-27998 [https://bugs.python.org/issue?@action=redirect&bpo=27998]: Fixed bytes path support in os.scandir() on Windows. Patch by Eryk Sun.

bpo-28317 [https://bugs.python.org/issue?@action=redirect&bpo=28317]: The disassembler now decodes FORMAT_VALUE argument.

bpo-28380 [https://bugs.python.org/issue?@action=redirect&bpo=28380]: unittest.mock Mock autospec functions now properly support assert_called, assert_not_called, and assert_called_once.

bpo-28229 [https://bugs.python.org/issue?@action=redirect&bpo=28229]: lzma module now supports pathlib.

bpo-28321 [https://bugs.python.org/issue?@action=redirect&bpo=28321]: Fixed writing non-BMP characters with binary format in plistlib.

bpo-28225 [https://bugs.python.org/issue?@action=redirect&bpo=28225]: bz2 module now supports pathlib. Initial patch by Ethan Furman.

bpo-28227 [https://bugs.python.org/issue?@action=redirect&bpo=28227]: gzip now supports pathlib. Patch by Ethan Furman.

bpo-28332 [https://bugs.python.org/issue?@action=redirect&bpo=28332]: Deprecated silent truncations in socket.htons and socket.ntohs. Original patch by Oren Milman.

bpo-27358 [https://bugs.python.org/issue?@action=redirect&bpo=27358]: Optimized merging var-keyword arguments and improved error message when passing a non-mapping as a var-keyword argument.

bpo-28257 [https://bugs.python.org/issue?@action=redirect&bpo=28257]: Improved error message when passing a non-iterable as a var-positional argument. Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

bpo-28322 [https://bugs.python.org/issue?@action=redirect&bpo=28322]: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

bpo-28228 [https://bugs.python.org/issue?@action=redirect&bpo=28228]: imghdr now supports pathlib.

bpo-28226 [https://bugs.python.org/issue?@action=redirect&bpo=28226]: compileall now supports pathlib.

bpo-28314 [https://bugs.python.org/issue?@action=redirect&bpo=28314]: Fix function declaration (C flags) for the getiterator() method of xml.etree.ElementTree.Element.

bpo-28148 [https://bugs.python.org/issue?@action=redirect&bpo=28148]: Stop using localtime() and gmtime() in the time module. Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r, but available on all platforms. Patch by Ed Schouten.

bpo-28253 [https://bugs.python.org/issue?@action=redirect&bpo=28253]: Fixed calendar functions for extreme months: 0001-01 and 9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so that they don't call itermonthdates() which can cause datetime.date under/overflow.

bpo-28275 [https://bugs.python.org/issue?@action=redirect&bpo=28275]: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

bpo-27897 [https://bugs.python.org/issue?@action=redirect&bpo=27897]: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

bpo-18844 [https://bugs.python.org/issue?@action=redirect&bpo=18844]: random.choices() now has k as a keyword-only argument to improve the readability of common cases and come into line with the signature used in other languages.

bpo-18893 [https://bugs.python.org/issue?@action=redirect&bpo=18893]: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

bpo-27611 [https://bugs.python.org/issue?@action=redirect&bpo=27611]: Fixed support of default root window in the tkinter.tix module. Added the master parameter in the DisplayStyle constructor.

bpo-27348 [https://bugs.python.org/issue?@action=redirect&bpo=27348]: In the traceback module, restore the formatting of exception messages like "Exception: None". This fixes a regression introduced in 3.5a2.

bpo-25651 [https://bugs.python.org/issue?@action=redirect&bpo=25651]: Allow false values to be used for msg parameter of subTest().

bpo-27778 [https://bugs.python.org/issue?@action=redirect&bpo=27778]: Fix a memory leak in os.getrandom() when the getrandom() is interrupted by a signal and a signal handler raises a Python exception.

bpo-28200 [https://bugs.python.org/issue?@action=redirect&bpo=28200]: Fix memory leak on Windows in the os module (fix path_converter() function).

bpo-25400 [https://bugs.python.org/issue?@action=redirect&bpo=25400]: RobotFileParser now correctly returns default values for crawl_delay and request_rate. Initial patch by Peter Wirtz.

bpo-27932 [https://bugs.python.org/issue?@action=redirect&bpo=27932]: Prevent memory leak in win32_ver().

Fix UnboundLocalError in socket._sendfile_use_sendfile.

bpo-28075 [https://bugs.python.org/issue?@action=redirect&bpo=28075]: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

bpo-22493 [https://bugs.python.org/issue?@action=redirect&bpo=22493]: Warning message emitted by using inline flags in the middle of regular expression now contains a (truncated) regex pattern. Patch by Tim Graham.

bpo-25270 [https://bugs.python.org/issue?@action=redirect&bpo=25270]: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

bpo-28181 [https://bugs.python.org/issue?@action=redirect&bpo=28181]: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

bpo-25895 [https://bugs.python.org/issue?@action=redirect&bpo=25895]: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

bpo-28114 [https://bugs.python.org/issue?@action=redirect&bpo=28114]: Fix a crash in parse_envlist() when env contains byte strings. Patch by Eryk Sun.

bpo-27599 [https://bugs.python.org/issue?@action=redirect&bpo=27599]: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

bpo-27906 [https://bugs.python.org/issue?@action=redirect&bpo=27906]: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

bpo-28174 [https://bugs.python.org/issue?@action=redirect&bpo=28174]: Handle when SO_REUSEPORT isn't properly supported. Patch by Seth Michael Larson.

bpo-26654 [https://bugs.python.org/issue?@action=redirect&bpo=26654]: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

bpo-26909 [https://bugs.python.org/issue?@action=redirect&bpo=26909]: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

bpo-28176 [https://bugs.python.org/issue?@action=redirect&bpo=28176]: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

bpo-27759 [https://bugs.python.org/issue?@action=redirect&bpo=27759]: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

bpo-28325 [https://bugs.python.org/issue?@action=redirect&bpo=28325]: Remove vestigial MacOS 9 macurl2path module and its tests.

bpo-28368 [https://bugs.python.org/issue?@action=redirect&bpo=28368]: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

bpo-28369 [https://bugs.python.org/issue?@action=redirect&bpo=28369]: Raise RuntimeError when transport's FD is used with add_reader, add_writer, etc.

bpo-28370 [https://bugs.python.org/issue?@action=redirect&bpo=28370]: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

bpo-28371 [https://bugs.python.org/issue?@action=redirect&bpo=28371]: Deprecate passing asyncio.Handles to run_in_executor.

bpo-28372 [https://bugs.python.org/issue?@action=redirect&bpo=28372]: Fix asyncio to support formatting of non-python coroutines.

bpo-28399 [https://bugs.python.org/issue?@action=redirect&bpo=28399]: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

bpo-27972 [https://bugs.python.org/issue?@action=redirect&bpo=27972]: Prohibit Tasks to await on themselves.

bpo-24142 [https://bugs.python.org/issue?@action=redirect&bpo=24142]: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.

bpo-29581 [https://bugs.python.org/issue?@action=redirect&bpo=29581]: ABCMeta.__new__ now accepts **kwargs, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares.

bpo-25532 [https://bugs.python.org/issue?@action=redirect&bpo=25532]: inspect.unwrap() will now only try to unwrap an object sys.getrecursionlimit() times, to protect against objects which create a new object on every attribute access.

bpo-30177 [https://bugs.python.org/issue?@action=redirect&bpo=30177]: path.resolve(strict=False) no longer cuts the path after the first element not present in the filesystem. Patch by Antoine Pietri.

Documentation

bpo-31294 [https://bugs.python.org/issue?@action=redirect&bpo=31294]: Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3.

bpo-21649 [https://bugs.python.org/issue?@action=redirect&bpo=21649]: Add RFC 7525 and Mozilla server side TLS links to SSL documentation.

bpo-31128 [https://bugs.python.org/issue?@action=redirect&bpo=31128]: Allow the pydoc server to bind to arbitrary hostnames.

bpo-30803 [https://bugs.python.org/issue?@action=redirect&bpo=30803]: Clarify doc on truth value testing. Original patch by Peter Thomassen.

bpo-30176 [https://bugs.python.org/issue?@action=redirect&bpo=30176]: Add missing attribute related constants in curses documentation.

bpo-30052 [https://bugs.python.org/issue?@action=redirect&bpo=30052]: the link targets for bytes() and bytearray() are now their respective type definitions, rather than the corresponding builtin function entries. Use bytes and bytearray to reference the latter. In order to ensure this and future cross-reference updates are applied automatically, the daily documentation builds now disable the default output caching features in Sphinx.

bpo-26985 [https://bugs.python.org/issue?@action=redirect&bpo=26985]: Add missing info of code object in inspect documentation.

bpo-19824 [https://bugs.python.org/issue?@action=redirect&bpo=19824]: Improve the documentation for, and links to, template strings by emphasizing their utility for internationalization, and by clarifying some usage constraints. (See also: bpo-20314 [https://bugs.python.org/issue?@action=redirect&bpo=20314], bpo-12518 [https://bugs.python.org/issue?@action=redirect&bpo=12518])

bpo-28929 [https://bugs.python.org/issue?@action=redirect&bpo=28929]: Link the documentation to its source file on GitHub.

bpo-25008 [https://bugs.python.org/issue?@action=redirect&bpo=25008]: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

bpo-26355 [https://bugs.python.org/issue?@action=redirect&bpo=26355]: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

bpo-29349 [https://bugs.python.org/issue?@action=redirect&bpo=29349]: Fix Python 2 syntax in code for building the documentation.

bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722]: The data model reference and the porting section in the 3.6 What's New guide now cover the additional __classcell__ handling needed for custom metaclasses to fully support PEP 487 [https://peps.python.org/pep-0487/] and zero-argument super().

bpo-28513 [https://bugs.python.org/issue?@action=redirect&bpo=28513]: Documented command-line interface of zipfile.

Tests

bpo-29639 [https://bugs.python.org/issue?@action=redirect&bpo=29639]: test.support.HOST is now "localhost", a new HOSTv4 constant has been added for your 127.0.0.1 needs, similar to the existing HOSTv6 constant.

bpo-31320 [https://bugs.python.org/issue?@action=redirect&bpo=31320]: Silence traceback in test_ssl

bpo-31346 [https://bugs.python.org/issue?@action=redirect&bpo=31346]: Prefer PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER protocols for SSLContext.

bpo-25674 [https://bugs.python.org/issue?@action=redirect&bpo=25674]: Remove sha256.tbs-internet.com ssl test

bpo-30715 [https://bugs.python.org/issue?@action=redirect&bpo=30715]: Address ALPN callback changes for OpenSSL 1.1.0f. The latest version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

bpo-30822 [https://bugs.python.org/issue?@action=redirect&bpo=30822]: regrtest: Exclude tzdata from regrtest --all. When running the test suite using --use=all / -u all, exclude tzdata since it makes test_datetime too slow (15-20 min on some buildbots) which then times out on some buildbots. Fix also regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

bpo-30695 [https://bugs.python.org/issue?@action=redirect&bpo=30695]: Add the set_nomemory(start, stop) and remove_mem_hooks() functions to the _testcapi module.

bpo-30357 [https://bugs.python.org/issue?@action=redirect&bpo=30357]: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

bpo-30197 [https://bugs.python.org/issue?@action=redirect&bpo=30197]: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn't exist) now will be assigned to the target of the "as" clause, if there is one.

bpo-24932 [https://bugs.python.org/issue?@action=redirect&bpo=24932]: Use proper command line parsing in _testembed

bpo-28950 [https://bugs.python.org/issue?@action=redirect&bpo=28950]: Disallow -j0 to be combined with -T/-l in regrtest command line arguments.

bpo-28683 [https://bugs.python.org/issue?@action=redirect&bpo=28683]: Fix the tests that bind() a unix socket and raise PermissionError on Android for a non-root user.

bpo-26936 [https://bugs.python.org/issue?@action=redirect&bpo=26936]: Fix the test_socket failures on Android - getservbyname(), getservbyport() and getaddrinfo() are broken on some Android API levels.

bpo-28666 [https://bugs.python.org/issue?@action=redirect&bpo=28666]: Now test.support.rmtree is able to remove unwritable or unreadable directories.

bpo-23839 [https://bugs.python.org/issue?@action=redirect&bpo=23839]: Various caches now are cleared before running every test file.

bpo-26944 [https://bugs.python.org/issue?@action=redirect&bpo=26944]: Fix test_posix for Android where 'id -G' is entirely wrong or missing the effective gid.

bpo-28409 [https://bugs.python.org/issue?@action=redirect&bpo=28409]: regrtest: fix the parser of command line arguments.

bpo-28217 [https://bugs.python.org/issue?@action=redirect&bpo=28217]: Adds _testconsole module to test console input.

bpo-26939 [https://bugs.python.org/issue?@action=redirect&bpo=26939]: Add the support.setswitchinterval() function to fix test_functools hanging on the Android armv7 qemu emulator.

Build

bpo-31354 [https://bugs.python.org/issue?@action=redirect&bpo=31354]: Allow --with-lto to be used on all builds, not just make profile-opt.

bpo-31370 [https://bugs.python.org/issue?@action=redirect&bpo=31370]: Remove support for building --without-threads. This option is not really useful anymore in the 21st century. Removing lots of conditional paths allows us to simplify the code base, including in difficult to maintain low-level internal code.

bpo-31341 [https://bugs.python.org/issue?@action=redirect&bpo=31341]: Per PEP 11 [https://peps.python.org/pep-0011/], support for the IRIX operating system was removed.

bpo-30854 [https://bugs.python.org/issue?@action=redirect&bpo=30854]: Fix compile error when compiling --without-threads. Patch by Masayuki Yamamoto.

bpo-30687 [https://bugs.python.org/issue?@action=redirect&bpo=30687]: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

bpo-20210 [https://bugs.python.org/issue?@action=redirect&bpo=20210]: Support the disabled marker in Setup files. Extension modules listed after this marker are not built at all, neither by the Makefile nor by setup.py.

bpo-29941 [https://bugs.python.org/issue?@action=redirect&bpo=29941]: Add --with-assertions configure flag to explicitly enable C assert() checks. Defaults to off. --with-pydebug implies --with-assertions.

bpo-28787 [https://bugs.python.org/issue?@action=redirect&bpo=28787]: Fix out-of-tree builds of Python when configured with --with--dtrace.

bpo-29243 [https://bugs.python.org/issue?@action=redirect&bpo=29243]: Prevent unnecessary rebuilding of Python during make test, make install and some other make targets when configured with --enable-optimizations.

bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404]: Don't regenerate generated files based on file modification time anymore: the action is now explicit. Replace make touch with make regen-all.

bpo-29643 [https://bugs.python.org/issue?@action=redirect&bpo=29643]: Fix --enable-optimization didn't work.

bpo-27593 [https://bugs.python.org/issue?@action=redirect&bpo=27593]: sys.version and the platform module python_build(), python_branch(), and python_revision() functions now use git information rather than hg when building from a repo.

bpo-29572 [https://bugs.python.org/issue?@action=redirect&bpo=29572]: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

bpo-27659 [https://bugs.python.org/issue?@action=redirect&bpo=27659]: Prohibit implicit C function declarations: use -Werror=implicit-function-declaration when possible (GCC and Clang, but it depends on the compiler version). Patch written by Chi Hsuan Yen.

bpo-29384 [https://bugs.python.org/issue?@action=redirect&bpo=29384]: Remove old Be OS helper scripts.

bpo-26851 [https://bugs.python.org/issue?@action=redirect&bpo=26851]: Set Android compilation and link flags.

bpo-28768 [https://bugs.python.org/issue?@action=redirect&bpo=28768]: Fix implicit declaration of function _setmode. Patch by Masayuki Yamamoto

bpo-29080 [https://bugs.python.org/issue?@action=redirect&bpo=29080]: Removes hard dependency on hg.exe from PCBuild/build.bat

bpo-23903 [https://bugs.python.org/issue?@action=redirect&bpo=23903]: Added missed names to PC/python3.def.

bpo-28762 [https://bugs.python.org/issue?@action=redirect&bpo=28762]: lockf() is available on Android API level 24, but the F_LOCK macro is not defined in android-ndk-r13.

bpo-28538 [https://bugs.python.org/issue?@action=redirect&bpo=28538]: Fix the compilation error that occurs because if_nameindex() is available on Android API level 24, but the if_nameindex structure is not defined.

bpo-20211 [https://bugs.python.org/issue?@action=redirect&bpo=20211]: Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths. Original patch by Thomas Petazzoni.

bpo-28849 [https://bugs.python.org/issue?@action=redirect&bpo=28849]: Do not define sys.implementation._multiarch on Android.

bpo-10656 [https://bugs.python.org/issue?@action=redirect&bpo=10656]: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

bpo-26359 [https://bugs.python.org/issue?@action=redirect&bpo=26359]: Rename --with-optimiations to --enable-optimizations.

bpo-28444 [https://bugs.python.org/issue?@action=redirect&bpo=28444]: Fix missing extensions modules when cross compiling.

bpo-28208 [https://bugs.python.org/issue?@action=redirect&bpo=28208]: Update Windows build and OS X installers to use SQLite 3.14.2.

bpo-28248 [https://bugs.python.org/issue?@action=redirect&bpo=28248]: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

bpo-21124 [https://bugs.python.org/issue?@action=redirect&bpo=21124]: Fix building the _struct module on Cygwin by passing NULL instead of &PyType_Type to PyVarObject_HEAD_INIT. Patch by Masayuki Yamamoto.

bpo-13756 [https://bugs.python.org/issue?@action=redirect&bpo=13756]: Fix building extensions modules on Cygwin. Patch by Roumen Petrov, based on original patch by Jason Tishler.

bpo-21085 [https://bugs.python.org/issue?@action=redirect&bpo=21085]: Add configure check for siginfo_t.si_band, which Cygwin does not provide. Patch by Masayuki Yamamoto with review and rebase by Erik Bray.

bpo-28258 [https://bugs.python.org/issue?@action=redirect&bpo=28258]: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

bpo-26661 [https://bugs.python.org/issue?@action=redirect&bpo=26661]: setup.py now detects system libffi with multiarch wrapper.

bpo-27979 [https://bugs.python.org/issue?@action=redirect&bpo=27979]: A full copy of libffi is no longer bundled for use when building _ctypes on non-OSX UNIX platforms. An installed copy of libffi is now required when building _ctypes on such platforms.

bpo-15819 [https://bugs.python.org/issue?@action=redirect&bpo=15819]: Remove redundant include search directory option for building outside the source tree.

bpo-28676 [https://bugs.python.org/issue?@action=redirect&bpo=28676]: Prevent missing 'getentropy' declaration warning on macOS. Patch by Gareth Rees.

Windows

bpo-31392 [https://bugs.python.org/issue?@action=redirect&bpo=31392]: Update Windows build to use OpenSSL 1.1.0f

bpo-30389 [https://bugs.python.org/issue?@action=redirect&bpo=30389]: Adds detection of Visual Studio 2017 to distutils on Windows.

bpo-31358 [https://bugs.python.org/issue?@action=redirect&bpo=31358]: zlib is no longer bundled in the CPython source, instead it is downloaded on demand just like bz2, lzma, OpenSSL, Tcl/Tk, and SQLite.

bpo-31340 [https://bugs.python.org/issue?@action=redirect&bpo=31340]: Change to building with MSVC v141 (included with Visual Studio 2017)

bpo-30581 [https://bugs.python.org/issue?@action=redirect&bpo=30581]: os.cpu_count() now returns the correct number of processors on Windows when the number of logical processors is greater than 64.

bpo-30916 [https://bugs.python.org/issue?@action=redirect&bpo=30916]: Pre-build OpenSSL, Tcl and Tk and include the binaries in the build.

bpo-30731 [https://bugs.python.org/issue?@action=redirect&bpo=30731]: Add a missing xmlns to python.manifest so that it matches the schema.

bpo-30291 [https://bugs.python.org/issue?@action=redirect&bpo=30291]: Allow requiring 64-bit interpreters from py.exe using -64 suffix. Contributed by Steve (Gadget) Barnes.

bpo-30362 [https://bugs.python.org/issue?@action=redirect&bpo=30362]: Adds list options (-0, -0p) to py.exe launcher. Contributed by Steve Barnes.

bpo-23451 [https://bugs.python.org/issue?@action=redirect&bpo=23451]: Fix socket deprecation warnings in socketmodule.c. Patch by Segev Finer.

bpo-30450 [https://bugs.python.org/issue?@action=redirect&bpo=30450]: The build process on Windows no longer depends on Subversion, instead pulling external code from GitHub via a Python script. If Python 3.6 is not found on the system (via py -3.6), NuGet is used to download a copy of 32-bit Python.

bpo-29579 [https://bugs.python.org/issue?@action=redirect&bpo=29579]: Removes readme.txt from the installer.

bpo-25778 [https://bugs.python.org/issue?@action=redirect&bpo=25778]: winreg does not truncate string correctly (Patch by Eryk Sun)

bpo-28896 [https://bugs.python.org/issue?@action=redirect&bpo=28896]: Deprecate WindowsRegistryFinder and disable it by default

bpo-28522 [https://bugs.python.org/issue?@action=redirect&bpo=28522]: Fixes mishandled buffer reallocation in getpathp.c

bpo-28402 [https://bugs.python.org/issue?@action=redirect&bpo=28402]: Adds signed catalog files for stdlib on Windows.

bpo-28333 [https://bugs.python.org/issue?@action=redirect&bpo=28333]: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk Sun)

bpo-28251 [https://bugs.python.org/issue?@action=redirect&bpo=28251]: Improvements to help manuals on Windows.

bpo-28110 [https://bugs.python.org/issue?@action=redirect&bpo=28110]: launcher.msi has different product codes between 32-bit and 64-bit

bpo-28161 [https://bugs.python.org/issue?@action=redirect&bpo=28161]: Opening CON for write access fails

bpo-28162 [https://bugs.python.org/issue?@action=redirect&bpo=28162]: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z

bpo-28163 [https://bugs.python.org/issue?@action=redirect&bpo=28163]: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

bpo-28164 [https://bugs.python.org/issue?@action=redirect&bpo=28164]: _PyIO_get_console_type fails for various paths

bpo-28137 [https://bugs.python.org/issue?@action=redirect&bpo=28137]: Renames Windows path file to ._pth

bpo-28138 [https://bugs.python.org/issue?@action=redirect&bpo=28138]: Windows ._pth file should allow import site

IDLE

bpo-31493 [https://bugs.python.org/issue?@action=redirect&bpo=31493]: IDLE code context -- fix code update and font update timers. Canceling timers prevents a warning message when test_idle completes.

bpo-31488 [https://bugs.python.org/issue?@action=redirect&bpo=31488]: IDLE - Update non-key options in former extension classes. When applying configdialog changes, call .reload for each feature class. Change ParenMatch so updated options affect existing instances attached to existing editor windows.

bpo-31477 [https://bugs.python.org/issue?@action=redirect&bpo=31477]: IDLE - Improve rstrip entry in doc. Strip trailing whitespace strips more than blank spaces. Multiline string literals are not skipped.

bpo-31480 [https://bugs.python.org/issue?@action=redirect&bpo=31480]: IDLE - make tests pass with zzdummy extension disabled by default.

bpo-31421 [https://bugs.python.org/issue?@action=redirect&bpo=31421]: Document how IDLE runs tkinter programs. IDLE calls tcl/tk update in the background in order to make live interaction and experimentation with tkinter applications much easier.

bpo-31414 [https://bugs.python.org/issue?@action=redirect&bpo=31414]: IDLE -- fix tk entry box tests by deleting first. Adding to an int entry is not the same as deleting and inserting because int('') will fail.

bpo-31051 [https://bugs.python.org/issue?@action=redirect&bpo=31051]: Rearrange IDLE configdialog GenPage into Window, Editor, and Help sections.

bpo-30617 [https://bugs.python.org/issue?@action=redirect&bpo=30617]: IDLE - Add docstrings and tests for outwin subclass of editor. Move some data and functions from the class to module level. Patch by Cheryl Sabella.

bpo-31287 [https://bugs.python.org/issue?@action=redirect&bpo=31287]: IDLE - Do not modify tkinter.message in test_configdialog.

bpo-27099 [https://bugs.python.org/issue?@action=redirect&bpo=27099]: Convert IDLE's built-in 'extensions' to regular features. About 10 IDLE features were implemented as supposedly optional extensions. Their different behavior could be confusing or worse for users and not good for maintenance. Hence the conversion. The main difference for users is that user configurable key bindings for builtin features are now handled uniformly. Now, editing a binding in a keyset only affects its value in the keyset. All bindings are defined together in the system-specific default keysets in config-extensions.def. All custom keysets are saved as a whole in config-extension.cfg. All take effect as soon as one clicks Apply or Ok. The affected events are '<<force-open-completions>>', '<<expand-word>>', '<<force-open-calltip>>', '<<flash-paren>>', '<<format-paragraph>>', '<<run-module>>', '<<check-module>>', and '<<zoom-height>>'. Any (global) customizations made before 3.6.3 will not affect their keyset-specific customization after 3.6.3. and vice versa. Initial patch by Charles Wohlganger.

bpo-31206 [https://bugs.python.org/issue?@action=redirect&bpo=31206]: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by Cheryl Sabella.

bpo-31001 [https://bugs.python.org/issue?@action=redirect&bpo=31001]: Add tests for configdialog highlight tab. Patch by Cheryl Sabella.

bpo-31205 [https://bugs.python.org/issue?@action=redirect&bpo=31205]: IDLE: Factor KeysPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

bpo-31130 [https://bugs.python.org/issue?@action=redirect&bpo=31130]: IDLE -- stop leaks in test_configdialog. Initial patch by Victor Stinner.

bpo-31002 [https://bugs.python.org/issue?@action=redirect&bpo=31002]: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

bpo-19903 [https://bugs.python.org/issue?@action=redirect&bpo=19903]: IDLE: Calltips use inspect.signature instead of inspect.getfullargspec. This improves calltips for builtins converted to use Argument Clinic. Patch by Louie Lu.

bpo-31083 [https://bugs.python.org/issue?@action=redirect&bpo=31083]: IDLE - Add an outline of a TabPage class in configdialog. Update existing classes to match outline. Initial patch by Cheryl Sabella.

bpo-31050 [https://bugs.python.org/issue?@action=redirect&bpo=31050]: Factor GenPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

bpo-31004 [https://bugs.python.org/issue?@action=redirect&bpo=31004]: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly modified tests continue to pass. Fix General tests. Patch mostly by Cheryl Sabella.

bpo-30781 [https://bugs.python.org/issue?@action=redirect&bpo=30781]: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan Reedy and Cheryl Sabella.

bpo-31060 [https://bugs.python.org/issue?@action=redirect&bpo=31060]: IDLE - Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes.

bpo-30853 [https://bugs.python.org/issue?@action=redirect&bpo=30853]: IDLE -- Factor a VarTrace class out of ConfigDialog. Instance tracers manages pairs consisting of a tk variable and a callback function. When tracing is turned on, setting the variable calls the function. Test coverage for the new class is 100%.

bpo-31003 [https://bugs.python.org/issue?@action=redirect&bpo=31003]: IDLE: Add more tests for General tab.

bpo-30993 [https://bugs.python.org/issue?@action=redirect&bpo=30993]: IDLE - Improve configdialog font page and tests. In configdialog: Document causal pathways in create_font_tab docstring. Simplify some attribute names. Move set_samples calls to var_changed_font (idea from Cheryl Sabella). Move related functions to positions after the create widgets function. In test_configdialog: Fix test_font_set so not order dependent. Fix renamed test_indent_scale so it tests the widget. Adjust tests for movement of set_samples call. Add tests for load functions. Put all font tests in one class and tab indent tests in another. Except for two lines, these tests completely cover the related functions.

bpo-30981 [https://bugs.python.org/issue?@action=redirect&bpo=30981]: IDLE -- Add more configdialog font page tests.

bpo-28523 [https://bugs.python.org/issue?@action=redirect&bpo=28523]: IDLE: replace 'colour' with 'color' in configdialog.

bpo-30917 [https://bugs.python.org/issue?@action=redirect&bpo=30917]: Add tests for idlelib.config.IdleConf. Increase coverage from 46% to 96%. Patch by Louie Lu.

bpo-30934 [https://bugs.python.org/issue?@action=redirect&bpo=30934]: Document coverage details for idlelib tests. Add section to idlelib/idle-test/README.txt. Include check that branches are taken both ways. Exclude IDLE-specific code that does not run during unit tests.

bpo-30913 [https://bugs.python.org/issue?@action=redirect&bpo=30913]: IDLE: Document ConfigDialog tk Vars, methods, and widgets in docstrings This will facilitate improving the dialog and splitting up the class. Original patch by Cheryl Sabella.

bpo-30899 [https://bugs.python.org/issue?@action=redirect&bpo=30899]: IDLE: Add tests for ConfigParser subclasses in config. Patch by Louie Lu.

bpo-30881 [https://bugs.python.org/issue?@action=redirect&bpo=30881]: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

bpo-30851 [https://bugs.python.org/issue?@action=redirect&bpo=30851]: IDLE: Remove unused variables in configdialog. One is a duplicate, one is set but cannot be altered by users. Patch by Cheryl Sabella.

bpo-30870 [https://bugs.python.org/issue?@action=redirect&bpo=30870]: IDLE: In Settings dialog, select font with Up, Down keys as well as mouse. Initial patch by Louie Lu.

bpo-8231 [https://bugs.python.org/issue?@action=redirect&bpo=8231]: IDLE: call config.IdleConf.GetUserCfgDir only once.

bpo-30779 [https://bugs.python.org/issue?@action=redirect&bpo=30779]: IDLE: Factor ConfigChanges class from configdialog, put in config; test. * In config, put dump test code in a function; run it and unittest in 'if __name__ == '__main__'. * Add class config.ConfigChanges based on changes_class_v4.py on bpo issue. * Add class test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise configdialog to use ConfigChanges; see tracker msg297804. * Revise test_configdialog to match configdialog changes. * Remove configdialog functions unused or moved to ConfigChanges. Cheryl Sabella contributed parts of the patch.

bpo-30777 [https://bugs.python.org/issue?@action=redirect&bpo=30777]: IDLE: configdialog - Add docstrings and fix comments. Patch by Cheryl Sabella.

bpo-30495 [https://bugs.python.org/issue?@action=redirect&bpo=30495]: IDLE: Improve textview with docstrings, PEP8 names, and more tests. Patch by Cheryl Sabella.

bpo-30723 [https://bugs.python.org/issue?@action=redirect&bpo=30723]: IDLE: Make several improvements to parenmatch. Add 'parens' style to highlight both opener and closer. Make 'default' style, which is not default, a synonym for 'opener'. Make time-delay work the same with all styles. Add help for config dialog extensions tab, including help for parenmatch. Add new tests. Original patch by Charles Wohlganger.

bpo-30674 [https://bugs.python.org/issue?@action=redirect&bpo=30674]: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

bpo-21519 [https://bugs.python.org/issue?@action=redirect&bpo=21519]: IDLE's basic custom key entry dialog now detects duplicates properly. Original patch by Saimadhav Heblikar.

bpo-29910 [https://bugs.python.org/issue?@action=redirect&bpo=29910]: IDLE no longer deletes a character after commenting out a region by a key shortcut. Add return 'break' for this and other potential conflicts between IDLE and default key bindings.

bpo-30728 [https://bugs.python.org/issue?@action=redirect&bpo=30728]: Review and change idlelib.configdialog names. Lowercase method and attribute names. Replace 'colour' with 'color', expand overly cryptic names, delete unneeded underscores. Replace import * with specific imports. Patches by Cheryl Sabella.

bpo-6739 [https://bugs.python.org/issue?@action=redirect&bpo=6739]: IDLE: Verify user-entered key sequences by trying to bind them with tk. Add tests for all 3 validation functions. Original patch by G Polo. Tests added by Cheryl Sabella.

bpo-15786 [https://bugs.python.org/issue?@action=redirect&bpo=15786]: Fix several problems with IDLE's autocompletion box. The following should now work: clicking on selection box items; using the scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no longer happen. Patch by Louie Lu.

bpo-25514 [https://bugs.python.org/issue?@action=redirect&bpo=25514]: Add doc subsubsection about IDLE failure to start. Popup no-connection message directs users to this section.

bpo-30642 [https://bugs.python.org/issue?@action=redirect&bpo=30642]: Fix reference leaks in IDLE tests. Patches by Louie Lu and Terry Jan Reedy.

bpo-30495 [https://bugs.python.org/issue?@action=redirect&bpo=30495]: Add docstrings for textview.py and use PEP8 names. Patches by Cheryl Sabella and Terry Jan Reedy.

bpo-30290 [https://bugs.python.org/issue?@action=redirect&bpo=30290]: Help-about: use pep8 names and add tests. Increase coverage to 100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

bpo-30303 [https://bugs.python.org/issue?@action=redirect&bpo=30303]: Add _utest option to textview; add new tests. Increase coverage to 100%. Patches by Louie Lu and Terry Jan Reedy.

bpo-29071 [https://bugs.python.org/issue?@action=redirect&bpo=29071]: IDLE colors f-string prefixes (but not invalid ur prefixes).

bpo-28572 [https://bugs.python.org/issue?@action=redirect&bpo=28572]: Add 10% to coverage of IDLE's test_configdialog. Update and augment description of the configuration system.

Tools/Demos

bpo-30983 [https://bugs.python.org/issue?@action=redirect&bpo=30983]: gdb integration commands (py-bt, etc.) work on optimized shared builds now, too. PEP 523 [https://peps.python.org/pep-0523/] introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non-debug shared builds. This broke the ability to use py-bt, py-up, and a few other Python-specific gdb integrations. The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python-gdb.py. Original patch by Bruno "Polaco" Penteado.

bpo-29748 [https://bugs.python.org/issue?@action=redirect&bpo=29748]: Added the slice index converter in Argument Clinic.

bpo-24037 [https://bugs.python.org/issue?@action=redirect&bpo=24037]: Argument Clinic now uses the converter bool(accept={int}) rather than int for semantical booleans. This avoids repeating the default value for Python and C and will help in converting to bool in future.

bpo-29367 [https://bugs.python.org/issue?@action=redirect&bpo=29367]: python-gdb.py now supports also method-wrapper (wrapperobject) objects.

bpo-28023 [https://bugs.python.org/issue?@action=redirect&bpo=28023]: Fix python-gdb.py didn't support new dict implementation.

bpo-15369 [https://bugs.python.org/issue?@action=redirect&bpo=15369]: The pybench and pystone microbenchmark have been removed from Tools. Please use the new Python benchmark suite https://github.com/python/pyperformance which is more reliable and includes a portable version of pybench working on Python 2 and Python 3.

bpo-28102 [https://bugs.python.org/issue?@action=redirect&bpo=28102]: The zipfile module CLI now prints usage to stderr. Patch by Stephen J. Turnbull.

C API

bpo-31338 [https://bugs.python.org/issue?@action=redirect&bpo=31338]: Added the Py_UNREACHABLE() macro for code paths which are never expected to be reached. This and a few other useful macros are now documented in the C API manual.

bpo-30832 [https://bugs.python.org/issue?@action=redirect&bpo=30832]: Remove own implementation for thread-local storage. CPython has provided the own implementation for thread-local storage (TLS) on Python/thread.c, it's used in the case which a platform has not supplied native TLS. However, currently all supported platforms (Windows and pthreads) have provided native TLS and defined the Py_HAVE_NATIVE_TLS macro with unconditional in any case.

bpo-30708 [https://bugs.python.org/issue?@action=redirect&bpo=30708]: PyUnicode_AsWideCharString() now raises a ValueError if the second argument is NULL and the wchar_t* string contains null characters.

bpo-16500 [https://bugs.python.org/issue?@action=redirect&bpo=16500]: Deprecate PyOS_AfterFork() and add PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

bpo-6532 [https://bugs.python.org/issue?@action=redirect&bpo=6532]: The type of results of PyThread_start_new_thread() and PyThread_get_thread_ident(), and the id parameter of PyThreadState_SetAsyncExc() changed from "long" to "unsigned long".

bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867]: Function PySlice_GetIndicesEx() is deprecated and replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher. Added functions PySlice_Unpack() and PySlice_AdjustIndices().

bpo-29083 [https://bugs.python.org/issue?@action=redirect&bpo=29083]: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

bpo-28769 [https://bugs.python.org/issue?@action=redirect&bpo=28769]: The result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8() is now of type const char * rather of char *.

bpo-29058 [https://bugs.python.org/issue?@action=redirect&bpo=29058]: All stable API extensions added after Python 3.2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API.

bpo-28822 [https://bugs.python.org/issue?@action=redirect&bpo=28822]: The index parameters start and end of PyUnicode_FindChar() are now adjusted to behave like str[start:end].

bpo-28808 [https://bugs.python.org/issue?@action=redirect&bpo=28808]: PyUnicode_CompareWithASCIIString() now never raises exceptions.

bpo-28761 [https://bugs.python.org/issue?@action=redirect&bpo=28761]: The fields name and doc of structures PyMemberDef, PyGetSetDef, PyStructSequence_Field, PyStructSequence_Desc, and wrapperbase are now of type const char * rather of char *.

bpo-28748 [https://bugs.python.org/issue?@action=redirect&bpo=28748]: Private variable _Py_PackageContext is now of type const char * rather of char *.

bpo-19569 [https://bugs.python.org/issue?@action=redirect&bpo=19569]: Compiler warnings are now emitted if use most of deprecated functions.

bpo-28426 [https://bugs.python.org/issue?@action=redirect&bpo=28426]: Deprecated undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and PyUnicode_AsEncodedUnicode().

Python 3.6.6 final

Release date: 2018-06-27

There were no new changes in version 3.6.6.

Python 3.6.6 release candidate 1

Release date: 2018-06-11

Core and Builtins

bpo-33786 [https://bugs.python.org/issue?@action=redirect&bpo=33786]: Fix asynchronous generators to handle GeneratorExit in athrow() correctly

bpo-30654 [https://bugs.python.org/issue?@action=redirect&bpo=30654]: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

bpo-33622 [https://bugs.python.org/issue?@action=redirect&bpo=33622]: Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc.garbage list. PyGC_Collect() can now be called when an exception is set and preserves it.

bpo-31849 [https://bugs.python.org/issue?@action=redirect&bpo=31849]: Fix signed/unsigned comparison warning in pyhash.c.

bpo-33391 [https://bugs.python.org/issue?@action=redirect&bpo=33391]: Fix a leak in set_symmetric_difference().

bpo-28055 [https://bugs.python.org/issue?@action=redirect&bpo=28055]: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

bpo-33231 [https://bugs.python.org/issue?@action=redirect&bpo=33231]: Fix potential memory leak in normalizestring().

bpo-29922 [https://bugs.python.org/issue?@action=redirect&bpo=29922]: Improved error messages in 'async with' when __aenter__() or __aexit__() return non-awaitable object.

bpo-33199 [https://bugs.python.org/issue?@action=redirect&bpo=33199]: Fix ma_version_tag in dict implementation is uninitialized when copying from key-sharing dict.

bpo-33041 [https://bugs.python.org/issue?@action=redirect&bpo=33041]: Fixed jumping when the function contains an async for loop.

bpo-32282 [https://bugs.python.org/issue?@action=redirect&bpo=32282]: Fix an unnecessary ifdef in the include of VersionHelpers.h in socketmodule on Windows.

bpo-21983 [https://bugs.python.org/issue?@action=redirect&bpo=21983]: Fix a crash in ctypes.cast() in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

Library

bpo-30167 [https://bugs.python.org/issue?@action=redirect&bpo=30167]: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

bpo-33812 [https://bugs.python.org/issue?@action=redirect&bpo=33812]: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

bpo-30805 [https://bugs.python.org/issue?@action=redirect&bpo=30805]: Avoid race condition with debug logging

bpo-33767 [https://bugs.python.org/issue?@action=redirect&bpo=33767]: The concatenation (+) and repetition (*) sequence operations now raise TypeError instead of SystemError when performed on mmap.mmap objects. Patch by Zackery Spytz.

bpo-32684 [https://bugs.python.org/issue?@action=redirect&bpo=32684]: Fix gather to propagate cancellation of itself even with return_exceptions.

bpo-33674 [https://bugs.python.org/issue?@action=redirect&bpo=33674]: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

bpo-31647 [https://bugs.python.org/issue?@action=redirect&bpo=31647]: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it's already closed raises AttributeError.

bpo-33672 [https://bugs.python.org/issue?@action=redirect&bpo=33672]: Fix Task.__repr__ crash with Cython's bogus coroutines

bpo-33469 [https://bugs.python.org/issue?@action=redirect&bpo=33469]: Fix RuntimeError after closing loop that used run_in_executor

bpo-11874 [https://bugs.python.org/issue?@action=redirect&bpo=11874]: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

bpo-30877 [https://bugs.python.org/issue?@action=redirect&bpo=30877]: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

bpo-33548 [https://bugs.python.org/issue?@action=redirect&bpo=33548]: tempfile._candidate_tempdir_list should consider common TEMP locations

bpo-33542 [https://bugs.python.org/issue?@action=redirect&bpo=33542]: Prevent uuid.get_node from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

bpo-26819 [https://bugs.python.org/issue?@action=redirect&bpo=26819]: Fix race condition with ReadTransport.resume_reading in Windows proactor event loop.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Minor fixes in typing module: add annotations to NamedTuple.__new__, pass *args and **kwds in Generic.__new__. Original PRs by Paulius Šarka and Chad Dombrova.

bpo-20087 [https://bugs.python.org/issue?@action=redirect&bpo=20087]: Updated alias mapping with glibc 2.27 supported locales.

bpo-33422 [https://bugs.python.org/issue?@action=redirect&bpo=33422]: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

bpo-33197 [https://bugs.python.org/issue?@action=redirect&bpo=33197]: Update error message when constructing invalid inspect.Parameters Patch by Donghee Na.

bpo-33383 [https://bugs.python.org/issue?@action=redirect&bpo=33383]: Fixed crash in the get() method of the dbm.ndbm database object when it is called with a single argument.

bpo-33329 [https://bugs.python.org/issue?@action=redirect&bpo=33329]: Fix multiprocessing regression on newer glibcs

bpo-991266 [https://bugs.python.org/issue?@action=redirect&bpo=991266]: Fix quoting of the Comment attribute of http.cookies.SimpleCookie.

bpo-33131 [https://bugs.python.org/issue?@action=redirect&bpo=33131]: Upgrade bundled version of pip to 10.0.1.

bpo-33308 [https://bugs.python.org/issue?@action=redirect&bpo=33308]: Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info=False and col_info=True.

bpo-33263 [https://bugs.python.org/issue?@action=redirect&bpo=33263]: Fix FD leak in _SelectorSocketTransport Patch by Vlad Starostin.

bpo-33256 [https://bugs.python.org/issue?@action=redirect&bpo=33256]: Fix display of <module> call in the html produced by cgitb.html(). Patch by Stéphane Blondon.

bpo-33203 [https://bugs.python.org/issue?@action=redirect&bpo=33203]: random.Random.choice() now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits() implementation.

bpo-33224 [https://bugs.python.org/issue?@action=redirect&bpo=33224]: Update difflib.mdiff() for PEP 479 [https://peps.python.org/pep-0479/]. Convert an uncaught StopIteration in a generator into a return-statement.

bpo-33209 [https://bugs.python.org/issue?@action=redirect&bpo=33209]: End framing at the end of C implementation of pickle.Pickler.dump().

bpo-32861 [https://bugs.python.org/issue?@action=redirect&bpo=32861]: The urllib.robotparser's __str__ representation now includes wildcard entries and the "Crawl-delay" and "Request-rate" fields. Patch by Michael Lazar.

bpo-33096 [https://bugs.python.org/issue?@action=redirect&bpo=33096]: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

bpo-33127 [https://bugs.python.org/issue?@action=redirect&bpo=33127]: The ssl module now compiles with LibreSSL 2.7.1.

bpo-33021 [https://bugs.python.org/issue?@action=redirect&bpo=33021]: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

bpo-27683 [https://bugs.python.org/issue?@action=redirect&bpo=27683]: Fix a regression in ipaddress that result of hosts() is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

bpo-32844 [https://bugs.python.org/issue?@action=redirect&bpo=32844]: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

bpo-31908 [https://bugs.python.org/issue?@action=redirect&bpo=31908]: Fix output of cover files for trace module command-line tool. Previously emitted cover files only when --missing option was used. Patch by Michael Selik.

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: If nested log adapters are used, the inner process() methods are no longer omitted.

bpo-16865 [https://bugs.python.org/issue?@action=redirect&bpo=16865]: Support arrays >=2GiB in ctypes. Patch by Segev Finer.

bpo-31238 [https://bugs.python.org/issue?@action=redirect&bpo=31238]: pydoc: the stop() method of the private ServerThread class now waits until DocServer.serve_until_quit() completes and then explicitly sets its docserver attribute to None to break a reference cycle.

Documentation

bpo-33503 [https://bugs.python.org/issue?@action=redirect&bpo=33503]: Fix broken pypi link

bpo-33421 [https://bugs.python.org/issue?@action=redirect&bpo=33421]: Add missing documentation for typing.AsyncContextManager.

bpo-33378 [https://bugs.python.org/issue?@action=redirect&bpo=33378]: Add Korean language switcher for https://docs.python.org/3/

bpo-33276 [https://bugs.python.org/issue?@action=redirect&bpo=33276]: Clarify that the __path__ attribute on modules cannot be just any value.

bpo-33201 [https://bugs.python.org/issue?@action=redirect&bpo=33201]: Modernize documentation for writing C extension types.

bpo-33195 [https://bugs.python.org/issue?@action=redirect&bpo=33195]: Deprecate Py_UNICODE usage in c-api/arg document. Py_UNICODE related APIs are deprecated since Python 3.3, but it is missed in the document.

bpo-33126 [https://bugs.python.org/issue?@action=redirect&bpo=33126]: Document PyBuffer_ToContiguous().

bpo-27212 [https://bugs.python.org/issue?@action=redirect&bpo=27212]: Modify documentation for the islice() recipe to consume initial values up to the start index.

bpo-28247 [https://bugs.python.org/issue?@action=redirect&bpo=28247]: Update zipapp documentation to describe how to make standalone applications.

bpo-18802 [https://bugs.python.org/issue?@action=redirect&bpo=18802]: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

bpo-27428 [https://bugs.python.org/issue?@action=redirect&bpo=27428]: Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder. (Patch by Himanshu Lakhara)

bpo-8243 [https://bugs.python.org/issue?@action=redirect&bpo=8243]: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

bpo-31432 [https://bugs.python.org/issue?@action=redirect&bpo=31432]: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

Tests

bpo-33655 [https://bugs.python.org/issue?@action=redirect&bpo=33655]: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

bpo-19417 [https://bugs.python.org/issue?@action=redirect&bpo=19417]: Add test_bdb.py.

Build

bpo-5755 [https://bugs.python.org/issue?@action=redirect&bpo=5755]: Move -Wstrict-prototypes option to CFLAGS_NODIST from OPT. This option emitted annoying warnings when building extension modules written in C++.

bpo-33614 [https://bugs.python.org/issue?@action=redirect&bpo=33614]: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

bpo-33522 [https://bugs.python.org/issue?@action=redirect&bpo=33522]: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

bpo-33012 [https://bugs.python.org/issue?@action=redirect&bpo=33012]: Add -Wno-cast-function-type for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists.

bpo-33394 [https://bugs.python.org/issue?@action=redirect&bpo=33394]: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

Windows

bpo-33184 [https://bugs.python.org/issue?@action=redirect&bpo=33184]: Update Windows installer to OpenSSL 1.0.2o.

macOS

bpo-33184 [https://bugs.python.org/issue?@action=redirect&bpo=33184]: Update macOS installer build to use OpenSSL 1.0.2o.

IDLE

bpo-33656 [https://bugs.python.org/issue?@action=redirect&bpo=33656]: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.

bpo-33768 [https://bugs.python.org/issue?@action=redirect&bpo=33768]: Clicking on a context line moves that line to the top of the editor window.

bpo-33763 [https://bugs.python.org/issue?@action=redirect&bpo=33763]: IDLE: Use read-only text widget for code context instead of label widget.

bpo-33664 [https://bugs.python.org/issue?@action=redirect&bpo=33664]: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.

bpo-33679 [https://bugs.python.org/issue?@action=redirect&bpo=33679]: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.

bpo-33642 [https://bugs.python.org/issue?@action=redirect&bpo=33642]: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

bpo-33628 [https://bugs.python.org/issue?@action=redirect&bpo=33628]: IDLE: Cleanup codecontext.py and its test.

bpo-33564 [https://bugs.python.org/issue?@action=redirect&bpo=33564]: IDLE's code context now recognizes async as a block opener.

bpo-29706 [https://bugs.python.org/issue?@action=redirect&bpo=29706]: IDLE now colors async and await as keywords in 3.6. They become full keywords in 3.7.

bpo-21474 [https://bugs.python.org/issue?@action=redirect&bpo=21474]: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.

bpo-33204 [https://bugs.python.org/issue?@action=redirect&bpo=33204]: IDLE: consistently color invalid string prefixes. A 'u' string prefix cannot be paired with either 'r' or 'f'. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

bpo-32831 [https://bugs.python.org/issue?@action=redirect&bpo=32831]: Add docstrings and tests for codecontext.

Tools/Demos

bpo-33189 [https://bugs.python.org/issue?@action=redirect&bpo=33189]: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.

bpo-31920 [https://bugs.python.org/issue?@action=redirect&bpo=31920]: Fixed handling directories as arguments in the pygettext script. Based on patch by Oleg Krasnikov.

bpo-29673 [https://bugs.python.org/issue?@action=redirect&bpo=29673]: Fix pystackv and pystack gdbinit macros.

bpo-32885 [https://bugs.python.org/issue?@action=redirect&bpo=32885]: Add an -n flag for Tools/scripts/pathfix.py to disable automatic backup creation (files with ~ suffix).

bpo-31583 [https://bugs.python.org/issue?@action=redirect&bpo=31583]: Fix 2to3 for using with --add-suffix option but without --output-dir option for relative path to files in current directory.

C API

bpo-32374 [https://bugs.python.org/issue?@action=redirect&bpo=32374]: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

Python 3.6.5 final

Release date: 2018-03-28

Tests

bpo-32872 [https://bugs.python.org/issue?@action=redirect&bpo=32872]: Avoid regrtest compatibility issue with namespace packages.

Build

bpo-33163 [https://bugs.python.org/issue?@action=redirect&bpo=33163]: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

Python 3.6.5 release candidate 1

Release date: 2018-03-13

Security

bpo-33001 [https://bugs.python.org/issue?@action=redirect&bpo=33001]: Minimal fix to prevent buffer overrun in os.symlink on Windows

bpo-32981 [https://bugs.python.org/issue?@action=redirect&bpo=32981]: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE 2018-1060 [https://www.cve.org/CVERecord?id=CVE-2018-1060] and CVE 2018-1061 [https://www.cve.org/CVERecord?id=CVE-2018-1061]. Patch by Jamie Davis.

Core and Builtins

bpo-33026 [https://bugs.python.org/issue?@action=redirect&bpo=33026]: Fixed jumping out of "with" block by setting f_lineno.

bpo-17288 [https://bugs.python.org/issue?@action=redirect&bpo=17288]: Prevent jumps from 'return' and 'exception' trace events.

bpo-32889 [https://bugs.python.org/issue?@action=redirect&bpo=32889]: Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range.

bpo-32650 [https://bugs.python.org/issue?@action=redirect&bpo=32650]: Pdb and other debuggers dependent on bdb.py will correctly step over (next command) native coroutines. Patch by Pablo Galindo.

bpo-32685 [https://bugs.python.org/issue?@action=redirect&bpo=32685]: Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi-colon instead of a newline. Patch by Nitish Chandra.

bpo-32583 [https://bugs.python.org/issue?@action=redirect&bpo=32583]: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

bpo-26163 [https://bugs.python.org/issue?@action=redirect&bpo=26163]: Improved frozenset() hash to create more distinct hash values when faced with datasets containing many similar values.

bpo-27169 [https://bugs.python.org/issue?@action=redirect&bpo=27169]: The __debug__ constant is now optimized out at compile time. This fixes also bpo-22091 [https://bugs.python.org/issue?@action=redirect&bpo=22091].

bpo-32329 [https://bugs.python.org/issue?@action=redirect&bpo=32329]: sys.flags.hash_randomization is now properly set to 0 when hash randomization is turned off by PYTHONHASHSEED=0.

bpo-30416 [https://bugs.python.org/issue?@action=redirect&bpo=30416]: The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding.

bpo-18533 [https://bugs.python.org/issue?@action=redirect&bpo=18533]: repr() on a dict containing its own values() or items() no longer raises RecursionError; OrderedDict similarly. Instead, use ..., as for other recursive structures. Patch by Ben North.

bpo-32028 [https://bugs.python.org/issue?@action=redirect&bpo=32028]: Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls. Patch by Sanyam Khurana.

bpo-32137 [https://bugs.python.org/issue?@action=redirect&bpo=32137]: The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow.

Library

bpo-33064 [https://bugs.python.org/issue?@action=redirect&bpo=33064]: lib2to3 now properly supports trailing commas after *args and **kwargs in function signatures.

bpo-31804 [https://bugs.python.org/issue?@action=redirect&bpo=31804]: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

bpo-33037 [https://bugs.python.org/issue?@action=redirect&bpo=33037]: Skip sending/receiving data after SSL transport closing.

bpo-30353 [https://bugs.python.org/issue?@action=redirect&bpo=30353]: Fix ctypes pass-by-value for structs on 64-bit Cygwin/MinGW.

bpo-33009 [https://bugs.python.org/issue?@action=redirect&bpo=33009]: Fix inspect.signature() for single-parameter partialmethods.

bpo-32969 [https://bugs.python.org/issue?@action=redirect&bpo=32969]: Expose several missing constants in zlib and fix corresponding documentation.

bpo-32713 [https://bugs.python.org/issue?@action=redirect&bpo=32713]: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

bpo-30622 [https://bugs.python.org/issue?@action=redirect&bpo=30622]: The ssl module now detects missing NPN support in LibreSSL.

bpo-32922 [https://bugs.python.org/issue?@action=redirect&bpo=32922]: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

bpo-32859 [https://bugs.python.org/issue?@action=redirect&bpo=32859]: In os.dup2, don't check every call whether the dup3 syscall exists or not.

bpo-21060 [https://bugs.python.org/issue?@action=redirect&bpo=21060]: Rewrite confusing message from setup.py upload from "No dist file created in earlier command" to the more helpful "Must create and upload files in one command".

bpo-32857 [https://bugs.python.org/issue?@action=redirect&bpo=32857]: In tkinter, after_cancel(None) now raises a ValueError instead of canceling the first scheduled function. Patch by Cheryl Sabella.

bpo-32852 [https://bugs.python.org/issue?@action=redirect&bpo=32852]: Make sure sys.argv remains as a list when running trace.

bpo-32841 [https://bugs.python.org/issue?@action=redirect&bpo=32841]: Fixed asyncio.Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

bpo-31787 [https://bugs.python.org/issue?@action=redirect&bpo=31787]: Fixed refleaks of __init__() methods in various modules. (Contributed by Oren Milman)

bpo-30157 [https://bugs.python.org/issue?@action=redirect&bpo=30157]: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

bpo-32394 [https://bugs.python.org/issue?@action=redirect&bpo=32394]: socket: Remove TCP_FASTOPEN, TCP_KEEPCNT flags on older version Windows during run-time.

bpo-32777 [https://bugs.python.org/issue?@action=redirect&bpo=32777]: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

bpo-32647 [https://bugs.python.org/issue?@action=redirect&bpo=32647]: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

bpo-32734 [https://bugs.python.org/issue?@action=redirect&bpo=32734]: Fixed asyncio.Lock() safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

bpo-32727 [https://bugs.python.org/issue?@action=redirect&bpo=32727]: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

bpo-27931 [https://bugs.python.org/issue?@action=redirect&bpo=27931]: Fix email address header parsing error when the username is an empty quoted string. Patch by Xiang Zhang.

bpo-32304 [https://bugs.python.org/issue?@action=redirect&bpo=32304]: distutils' upload command no longer corrupts tar files ending with a CR byte, and no longer tries to convert CR to CRLF in any of the upload text fields.

bpo-32502 [https://bugs.python.org/issue?@action=redirect&bpo=32502]: uuid.uuid1 no longer raises an exception if a 64-bit hardware address is encountered.

bpo-31848 [https://bugs.python.org/issue?@action=redirect&bpo=31848]: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

bpo-32555 [https://bugs.python.org/issue?@action=redirect&bpo=32555]: On FreeBSD and Solaris, os.strerror() now always decode the byte string from the current locale encoding, rather than using ASCII/surrogateescape in some cases.

bpo-32521 [https://bugs.python.org/issue?@action=redirect&bpo=32521]: The nis module is now compatible with new libnsl and headers location.

bpo-32473 [https://bugs.python.org/issue?@action=redirect&bpo=32473]: Improve ABCMeta._dump_registry() output readability

bpo-32521 [https://bugs.python.org/issue?@action=redirect&bpo=32521]: glibc has removed Sun RPC. Use replacement libtirpc headers and library in nis module.

bpo-32228 [https://bugs.python.org/issue?@action=redirect&bpo=32228]: Ensure that truncate() preserves the file position (as reported by tell()) after writes longer than the buffer size.

bpo-26133 [https://bugs.python.org/issue?@action=redirect&bpo=26133]: Don't unsubscribe signals in asyncio UNIX event loop on interpreter shutdown.

bpo-32185 [https://bugs.python.org/issue?@action=redirect&bpo=32185]: The SSL module no longer sends IP addresses in SNI TLS extension on platforms with OpenSSL 1.0.2+ or inet_pton.

bpo-32323 [https://bugs.python.org/issue?@action=redirect&bpo=32323]: urllib.parse.urlsplit() does not convert zone-id (scope) to lower case for scoped IPv6 addresses in hostnames now.

bpo-32302 [https://bugs.python.org/issue?@action=redirect&bpo=32302]: Fix bdist_wininst of distutils for CRT v142: it binary compatible with CRT v140.

bpo-32255 [https://bugs.python.org/issue?@action=redirect&bpo=32255]: A single empty field is now always quoted when written into a CSV file. This allows to distinguish an empty row from a row consisting of a single empty field. Patch by Licht Takeuchi.

bpo-32277 [https://bugs.python.org/issue?@action=redirect&bpo=32277]: Raise NotImplementedError instead of SystemError on platforms where chmod(..., follow_symlinks=False) is not supported. Patch by Anthony Sottile.

bpo-32199 [https://bugs.python.org/issue?@action=redirect&bpo=32199]: The getnode() ip getter now uses 'ip link' instead of 'ip link list'.

bpo-27456 [https://bugs.python.org/issue?@action=redirect&bpo=27456]: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

bpo-31900 [https://bugs.python.org/issue?@action=redirect&bpo=31900]: The locale.localeconv() function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep byte strings if they are non-ASCII or longer than 1 byte, and the LC_NUMERIC locale is different than the LC_CTYPE locale. This temporary change affects other threads. Same change for the str.format() method when formatting a number (int, float, float and subclasses) with the n type (ex: '{:n}'.format(1234)).

bpo-31802 [https://bugs.python.org/issue?@action=redirect&bpo=31802]: Importing native path module (posixpath, ntpath) now works even if the os module still is not imported.

Documentation

bpo-17232 [https://bugs.python.org/issue?@action=redirect&bpo=17232]: Clarify docs for -O and -OO. Patch by Terry Reedy.

bpo-32800 [https://bugs.python.org/issue?@action=redirect&bpo=32800]: Update link to w3c doc for xml default namespaces.

bpo-8722 [https://bugs.python.org/issue?@action=redirect&bpo=8722]: Document __getattr__() behavior when property get() method raises AttributeError.

bpo-32614 [https://bugs.python.org/issue?@action=redirect&bpo=32614]: Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation.

bpo-31972 [https://bugs.python.org/issue?@action=redirect&bpo=31972]: Improve docstrings for pathlib.PurePath subclasses.

bpo-17799 [https://bugs.python.org/issue?@action=redirect&bpo=17799]: Explain real behaviour of sys.settrace and sys.setprofile and their C-API counterparts regarding which type of events are received in each function. Patch by Pablo Galindo Salgado.

Tests

bpo-32517 [https://bugs.python.org/issue?@action=redirect&bpo=32517]: Fix failing test_asyncio on macOS 10.12.2+ due to transport of KqueueSelector loop was not being closed.

bpo-32721 [https://bugs.python.org/issue?@action=redirect&bpo=32721]: Fix test_hashlib to not fail if the _md5 module is not built.

bpo-32252 [https://bugs.python.org/issue?@action=redirect&bpo=32252]: Fix faulthandler_suppress_crash_report() used to prevent core dump files when testing crashes. getrlimit() returns zero on success.

bpo-31518 [https://bugs.python.org/issue?@action=redirect&bpo=31518]: Debian Unstable has disabled TLS 1.0 and 1.1 for SSLv23_METHOD(). Change TLS/SSL protocol of some tests to PROTOCOL_TLS or PROTOCOL_TLSv1_2 to make them pass on Debian.

Build

bpo-32635 [https://bugs.python.org/issue?@action=redirect&bpo=32635]: Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system.

Windows

bpo-33016 [https://bugs.python.org/issue?@action=redirect&bpo=33016]: Fix potential use of uninitialized memory in nt._getfinalpathname

bpo-32903 [https://bugs.python.org/issue?@action=redirect&bpo=32903]: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

bpo-31966 [https://bugs.python.org/issue?@action=redirect&bpo=31966]: Fixed WindowsConsoleIO.write() for writing empty data.

bpo-32409 [https://bugs.python.org/issue?@action=redirect&bpo=32409]: Ensures activate.bat can handle Unicode contents.

bpo-32457 [https://bugs.python.org/issue?@action=redirect&bpo=32457]: Improves handling of denormalized executable path when launching Python.

bpo-32370 [https://bugs.python.org/issue?@action=redirect&bpo=32370]: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

bpo-29248 [https://bugs.python.org/issue?@action=redirect&bpo=29248]: Fix os.readlink() on Windows, which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

bpo-32588 [https://bugs.python.org/issue?@action=redirect&bpo=32588]: Create standalone _distutils_findvs module.

macOS

bpo-32726 [https://bugs.python.org/issue?@action=redirect&bpo=32726]: Provide an additional, more modern macOS installer variant that supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied third-party libraries to OpenSSL 1.0.2n, XZ 5.2.3, and SQLite 3.22.0. The 10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.8.

IDLE

bpo-32984 [https://bugs.python.org/issue?@action=redirect&bpo=32984]: Set __file__ while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, -s runs a file named in environmental variable IDLESTARTUP or PYTHONSTARTUP; -r file runs file. Python sets __file__ to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the -n option.

bpo-32940 [https://bugs.python.org/issue?@action=redirect&bpo=32940]: Simplify and rename StringTranslatePseudoMapping in pyparse.

bpo-32916 [https://bugs.python.org/issue?@action=redirect&bpo=32916]: Change str to code in pyparse.

bpo-32905 [https://bugs.python.org/issue?@action=redirect&bpo=32905]: Remove unused code in pyparse module.

bpo-32874 [https://bugs.python.org/issue?@action=redirect&bpo=32874]: Add tests for pyparse.

bpo-32837 [https://bugs.python.org/issue?@action=redirect&bpo=32837]: Using the system and place-dependent default encoding for open() is a bad idea for IDLE's system and location-independent files.

bpo-32826 [https://bugs.python.org/issue?@action=redirect&bpo=32826]: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to 'ascii' because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.

bpo-32765 [https://bugs.python.org/issue?@action=redirect&bpo=32765]: Update configdialog General tab docstring to add new widgets to the widget list.

Tools/Demos

bpo-24960 [https://bugs.python.org/issue?@action=redirect&bpo=24960]: 2to3 and lib2to3 can now read pickled grammar files using pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and lib2to3 work when run from a zipfile.

bpo-32222 [https://bugs.python.org/issue?@action=redirect&bpo=32222]: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

C API

bpo-29084 [https://bugs.python.org/issue?@action=redirect&bpo=29084]: Undocumented C API for OrderedDict has been excluded from the limited C API. It was added by mistake and actually never worked in the limited C API.

Python 3.6.4 final

Release date: 2017-12-18

There were no new code changes in version 3.6.4 since v3.6.4rc1.

Python 3.6.4 release candidate 1

Release date: 2017-12-05

Core and Builtins

bpo-32176 [https://bugs.python.org/issue?@action=redirect&bpo=32176]: co_flags.CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars, rather than needing to be set correctly by the caller. This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function.

bpo-31949 [https://bugs.python.org/issue?@action=redirect&bpo=31949]: Fixed several issues in printing tracebacks (PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks. Setting sys.tracebacklimit to None now causes using the default limit. Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit. Fixed integer overflows in the case of more than 2**31 traceback items on Windows. Fixed output errors handling.

bpo-30696 [https://bugs.python.org/issue?@action=redirect&bpo=30696]: Fix the interactive interpreter looping endlessly when no memory.

bpo-20047 [https://bugs.python.org/issue?@action=redirect&bpo=20047]: Bytearray methods partition() and rpartition() now accept only bytes-like objects as separator, as documented. In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator.

bpo-31852 [https://bugs.python.org/issue?@action=redirect&bpo=31852]: Fix a segmentation fault caused by a combination of the async soft keyword and continuation lines.

bpo-21720 [https://bugs.python.org/issue?@action=redirect&bpo=21720]: BytesWarning no longer emitted when the fromlist argument of __import__() or the __all__ attribute of the module contain bytes instances.

bpo-31825 [https://bugs.python.org/issue?@action=redirect&bpo=31825]: Fixed OverflowError in the 'unicode-escape' codec and in codecs.escape_decode() when decode an escaped non-ascii byte.

bpo-28603 [https://bugs.python.org/issue?@action=redirect&bpo=28603]: Print the full context/cause chain of exceptions on interpreter exit, even if an exception in the chain is unhashable or compares equal to later ones. Patch by Zane Bitter.

bpo-31786 [https://bugs.python.org/issue?@action=redirect&bpo=31786]: Fix timeout rounding in the select module to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

bpo-31642 [https://bugs.python.org/issue?@action=redirect&bpo=31642]: Restored blocking "from package import module" by setting sys.modules["package.module"] to None.

bpo-31626 [https://bugs.python.org/issue?@action=redirect&bpo=31626]: Fixed a bug in debug memory allocator. There was a write to freed memory after shrinking a memory block.

bpo-31619 [https://bugs.python.org/issue?@action=redirect&bpo=31619]: Fixed a ValueError when convert a string with large number of underscores to integer with binary base.

bpo-31592 [https://bugs.python.org/issue?@action=redirect&bpo=31592]: Fixed an assertion failure in Python parser in case of a bad unicodedata.normalize(). Patch by Oren Milman.

bpo-31588 [https://bugs.python.org/issue?@action=redirect&bpo=31588]: Raise a TypeError with a helpful error message when class creation fails due to a metaclass with a bad __prepare__() method. Patch by Oren Milman.

bpo-31566 [https://bugs.python.org/issue?@action=redirect&bpo=31566]: Fix an assertion failure in _warnings.warn() in case of a bad __name__ global. Patch by Oren Milman.

bpo-31505 [https://bugs.python.org/issue?@action=redirect&bpo=31505]: Fix an assertion failure in json, in case _json.make_encoder() received a bad encoder() argument. Patch by Oren Milman.

bpo-31492 [https://bugs.python.org/issue?@action=redirect&bpo=31492]: Fix assertion failures in case of failing to import from a module with a bad __name__ attribute, and in case of failing to access an attribute of such a module. Patch by Oren Milman.

bpo-31490 [https://bugs.python.org/issue?@action=redirect&bpo=31490]: Fix an assertion failure in ctypes class definition, in case the class has an attribute whose name is specified in _anonymous_ but not in _fields_. Patch by Oren Milman.

bpo-31478 [https://bugs.python.org/issue?@action=redirect&bpo=31478]: Fix an assertion failure in _random.Random.seed() in case the argument has a bad __abs__() method. Patch by Oren Milman.

bpo-31315 [https://bugs.python.org/issue?@action=redirect&bpo=31315]: Fix an assertion failure in imp.create_dynamic(), when spec.name is not a string. Patch by Oren Milman.

bpo-31311 [https://bugs.python.org/issue?@action=redirect&bpo=31311]: Fix a crash in the __setstate__() method of ctypes._CData, in case of a bad __dict__. Patch by Oren Milman.

bpo-31293 [https://bugs.python.org/issue?@action=redirect&bpo=31293]: Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio() method. Patch by Oren Milman.

bpo-31285 [https://bugs.python.org/issue?@action=redirect&bpo=31285]: Fix an assertion failure in warnings.warn_explicit, when the return value of the received loader's get_source() has a bad splitlines() method. Patch by Oren Milman.

bpo-30817 [https://bugs.python.org/issue?@action=redirect&bpo=30817]: PyErr_PrintEx() clears now the ignored exception that may be raised by _PySys_SetObjectId(), for example when no memory.

Library

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Two minor fixes for typing module: allow shallow copying instances of generic classes, improve interaction of __init_subclass__ with generics. Original PRs by Ivan Levkivskyi.

bpo-27240 [https://bugs.python.org/issue?@action=redirect&bpo=27240]: The header folding algorithm for the new email policies has been rewritten, which also fixes bpo-30788 [https://bugs.python.org/issue?@action=redirect&bpo=30788], bpo-31831 [https://bugs.python.org/issue?@action=redirect&bpo=31831], and bpo-32182 [https://bugs.python.org/issue?@action=redirect&bpo=32182]. In particular, RFC2231 folding is now done correctly.

bpo-32186 [https://bugs.python.org/issue?@action=redirect&bpo=32186]: io.FileIO.readall() and io.FileIO.read() now release the GIL when getting the file size. Fixed hang of all threads with inaccessible NFS server. Patch by Nir Soffer.

bpo-12239 [https://bugs.python.org/issue?@action=redirect&bpo=12239]: Make msilib.SummaryInformation.GetProperty() return None when the value of property is VT_EMPTY. Initial patch by Mark Mc Mahon.

bpo-31325 [https://bugs.python.org/issue?@action=redirect&bpo=31325]: Fix wrong usage of collections.namedtuple() in the RobotFileParser.parse() method. Initial patch by Robin Wellner.

bpo-12382 [https://bugs.python.org/issue?@action=redirect&bpo=12382]: msilib.OpenDatabase() now raises a better exception message when it couldn't open or create an MSI file. Initial patch by William Tisäter.

bpo-32110 [https://bugs.python.org/issue?@action=redirect&bpo=32110]: codecs.StreamReader.read(n) now returns not more than n characters/bytes for non-negative n. This makes it compatible with read() methods of other file-like objects.

bpo-32072 [https://bugs.python.org/issue?@action=redirect&bpo=32072]: Fixed issues with binary plists: Fixed saving bytearrays. Identical objects will be saved only once. Equal references will be load as identical objects. Added support for saving and loading recursive data structures.

bpo-32034 [https://bugs.python.org/issue?@action=redirect&bpo=32034]: Make asyncio.IncompleteReadError and LimitOverrunError pickleable.

bpo-32015 [https://bugs.python.org/issue?@action=redirect&bpo=32015]: Fixed the looping of asyncio in the case of reconnection the socket during waiting async read/write from/to the socket.

bpo-32011 [https://bugs.python.org/issue?@action=redirect&bpo=32011]: Restored support of loading marshal files with the TYPE_INT64 code. These files can be produced in Python 2.7.

bpo-31970 [https://bugs.python.org/issue?@action=redirect&bpo=31970]: Reduce performance overhead of asyncio debug mode.

bpo-9678 [https://bugs.python.org/issue?@action=redirect&bpo=9678]: Fixed determining the MAC address in the uuid module: Using ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and OpenBSD. Based on patch by Takayuki Shimizukawa.

bpo-30057 [https://bugs.python.org/issue?@action=redirect&bpo=30057]: Fix potential missed signal in signal.signal().

bpo-31933 [https://bugs.python.org/issue?@action=redirect&bpo=31933]: Fix Blake2 params leaf_size and node_offset on big endian platforms. Patch by Jack O'Connor.

bpo-31927 [https://bugs.python.org/issue?@action=redirect&bpo=31927]: Fixed compilation of the socket module on NetBSD 8. Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD.

bpo-27666 [https://bugs.python.org/issue?@action=redirect&bpo=27666]: Fixed stack corruption in curses.box() and curses.ungetmouse() when the size of types chtype or mmask_t is less than the size of C long. curses.box() now accepts characters as arguments. Based on patch by Steve Fink.

bpo-31897 [https://bugs.python.org/issue?@action=redirect&bpo=31897]: plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions.

bpo-25720 [https://bugs.python.org/issue?@action=redirect&bpo=25720]: Fix the method for checking pad state of curses WINDOW. Patch by Masayuki Yamamoto.

bpo-31893 [https://bugs.python.org/issue?@action=redirect&bpo=31893]: Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD. Fixed the comparison of the kqueue_event objects.

bpo-31891 [https://bugs.python.org/issue?@action=redirect&bpo=31891]: Fixed building the curses module on NetBSD.

bpo-28416 [https://bugs.python.org/issue?@action=redirect&bpo=28416]: Instances of pickle.Pickler subclass with the persistent_id() method and pickle.Unpickler subclass with the persistent_load() method no longer create reference cycles.

bpo-28326 [https://bugs.python.org/issue?@action=redirect&bpo=28326]: Fix multiprocessing.Process when stdout and/or stderr is closed or None.

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: If nested log adapters are used, the inner process() methods are no longer omitted.

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: The manager property on LoggerAdapter objects is now properly settable.

bpo-31806 [https://bugs.python.org/issue?@action=redirect&bpo=31806]: Fix timeout rounding in time.sleep(), threading.Lock.acquire() and socket.socket.settimeout() to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

bpo-28603 [https://bugs.python.org/issue?@action=redirect&bpo=28603]: traceback: Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context/cause chain is unhashable. Patch by Zane Bitter.

bpo-30058 [https://bugs.python.org/issue?@action=redirect&bpo=30058]: Fixed buffer overflow in select.kqueue.control().

bpo-31770 [https://bugs.python.org/issue?@action=redirect&bpo=31770]: Prevent a crash when calling the __init__() method of a sqlite3.Cursor object more than once. Patch by Oren Milman.

bpo-31672 [https://bugs.python.org/issue?@action=redirect&bpo=31672]: idpattern in string.Template matched some non-ASCII characters. Now it uses -i regular expression local flag to avoid non-ASCII characters.

bpo-31764 [https://bugs.python.org/issue?@action=redirect&bpo=31764]: Prevent a crash in sqlite3.Cursor.close() in case the Cursor object is uninitialized. Patch by Oren Milman.

bpo-31752 [https://bugs.python.org/issue?@action=redirect&bpo=31752]: Fix possible crash in timedelta constructor called with custom integers.

bpo-31701 [https://bugs.python.org/issue?@action=redirect&bpo=31701]: On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

bpo-31728 [https://bugs.python.org/issue?@action=redirect&bpo=31728]: Prevent crashes in _elementtree due to unsafe cleanup of Element.text and Element.tail. Patch by Oren Milman.

bpo-31620 [https://bugs.python.org/issue?@action=redirect&bpo=31620]: an empty asyncio.Queue now doesn't leak memory when queue.get pollers timeout

bpo-31632 [https://bugs.python.org/issue?@action=redirect&bpo=31632]: Fix method set_protocol() of class _SSLProtocolTransport in asyncio module. This method was previously modifying a wrong reference to the protocol.

bpo-31675 [https://bugs.python.org/issue?@action=redirect&bpo=31675]: Fixed memory leaks in Tkinter's methods splitlist() and split() when pass a string larger than 2 GiB.

bpo-31673 [https://bugs.python.org/issue?@action=redirect&bpo=31673]: Fixed typo in the name of Tkinter's method adderrorinfo().

bpo-30806 [https://bugs.python.org/issue?@action=redirect&bpo=30806]: Fix the string representation of a netrc object.

bpo-15037 [https://bugs.python.org/issue?@action=redirect&bpo=15037]: Added a workaround for getkey() in curses for ncurses 5.7 and earlier.

bpo-25351 [https://bugs.python.org/issue?@action=redirect&bpo=25351]: Avoid venv activate failures with undefined variables

bpo-25532 [https://bugs.python.org/issue?@action=redirect&bpo=25532]: inspect.unwrap() will now only try to unwrap an object sys.getrecursionlimit() times, to protect against objects which create a new object on every attribute access.

bpo-30347 [https://bugs.python.org/issue?@action=redirect&bpo=30347]: Stop crashes when concurrently iterate over itertools.groupby() iterators.

bpo-31516 [https://bugs.python.org/issue?@action=redirect&bpo=31516]: threading.current_thread() should not return a dummy thread at shutdown.

bpo-31351 [https://bugs.python.org/issue?@action=redirect&bpo=31351]: python -m ensurepip now exits with non-zero exit code if pip bootstrapping has failed.

bpo-31482 [https://bugs.python.org/issue?@action=redirect&bpo=31482]: random.seed() now works with bytes in version=1

bpo-31334 [https://bugs.python.org/issue?@action=redirect&bpo=31334]: Fix poll.poll([timeout]) in the select module for arbitrary negative timeouts on all OSes where it can only be a non-negative integer or -1. Patch by Riccardo Coccioli.

bpo-31310 [https://bugs.python.org/issue?@action=redirect&bpo=31310]: multiprocessing's semaphore tracker should be launched again if crashed.

bpo-31308 [https://bugs.python.org/issue?@action=redirect&bpo=31308]: Make multiprocessing's forkserver process immune to Ctrl-C and other user interruptions. If it crashes, restart it when necessary.

Documentation

bpo-32105 [https://bugs.python.org/issue?@action=redirect&bpo=32105]: Added asyncio.BaseEventLoop.connect_accepted_socket versionadded marker.

bpo-31537 [https://bugs.python.org/issue?@action=redirect&bpo=31537]: Fix incorrect usage of get_history_length in readline documentation example code. Patch by Brad Smith.

bpo-30085 [https://bugs.python.org/issue?@action=redirect&bpo=30085]: The operator functions without double underscores are preferred for clarity. The one with underscores are only kept for back-compatibility.

Tests

bpo-31380 [https://bugs.python.org/issue?@action=redirect&bpo=31380]: Skip test_httpservers test_undecodable_file on macOS: fails on APFS.

bpo-31705 [https://bugs.python.org/issue?@action=redirect&bpo=31705]: Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the kernel 4.5.

bpo-31174 [https://bugs.python.org/issue?@action=redirect&bpo=31174]: Fix test_tools.test_unparse: DirectoryTestCase now stores the names sample to always test the same files. It prevents false alarms when hunting reference leaks.

bpo-30695 [https://bugs.python.org/issue?@action=redirect&bpo=30695]: Add the set_nomemory(start, stop) and remove_mem_hooks() functions to the _testcapi module.

Build

bpo-32059 [https://bugs.python.org/issue?@action=redirect&bpo=32059]: detect_modules() in setup.py now also searches the sysroot paths when cross-compiling.

bpo-31957 [https://bugs.python.org/issue?@action=redirect&bpo=31957]: Fixes Windows SDK version detection when building for Windows.

bpo-31609 [https://bugs.python.org/issue?@action=redirect&bpo=31609]: Fixes quotes in PCbuild/clean.bat

bpo-31934 [https://bugs.python.org/issue?@action=redirect&bpo=31934]: Abort the build when building out of a not clean source tree.

bpo-31926 [https://bugs.python.org/issue?@action=redirect&bpo=31926]: Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and/or method in a .c file with the same name.

bpo-28791 [https://bugs.python.org/issue?@action=redirect&bpo=28791]: Update Windows builds to use SQLite 3.21.0.

bpo-28791 [https://bugs.python.org/issue?@action=redirect&bpo=28791]: Update OS X installer to use SQLite 3.21.0.

bpo-22140 [https://bugs.python.org/issue?@action=redirect&bpo=22140]: Prevent double substitution of prefix in python-config.sh.

bpo-31536 [https://bugs.python.org/issue?@action=redirect&bpo=31536]: Avoid wholesale rebuild after make regen-all if nothing changed.

Windows

bpo-1102 [https://bugs.python.org/issue?@action=redirect&bpo=1102]: Return None when View.Fetch() returns ERROR_NO_MORE_ITEMS instead of raising MSIError. Initial patch by Anthony Tuininga.

bpo-31944 [https://bugs.python.org/issue?@action=redirect&bpo=31944]: Fixes Modify button in Apps and Features dialog.

macOS

bpo-31392 [https://bugs.python.org/issue?@action=redirect&bpo=31392]: Update macOS installer to use OpenSSL 1.0.2m

IDLE

bpo-32207 [https://bugs.python.org/issue?@action=redirect&bpo=32207]: Improve tk event exception tracebacks in IDLE. When tk event handling is driven by IDLE's run loop, a confusing and distracting queue.EMPTY traceback context is no longer added to tk event exception tracebacks. The traceback is now the same as when event handling is driven by user code. Patch based on a suggestion by Serhiy Storchaka.

bpo-32164 [https://bugs.python.org/issue?@action=redirect&bpo=32164]: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet in configdialog was replaced by ttk.Notebook.

bpo-32100 [https://bugs.python.org/issue?@action=redirect&bpo=32100]: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch mostly by Cheryl Sabella.

bpo-31858 [https://bugs.python.org/issue?@action=redirect&bpo=31858]: IDLE -- Restrict shell prompt manipulation to the shell. Editor and output windows only see an empty last prompt line. This simplifies the code and fixes a minor bug when newline is inserted. Sys.ps1, if present, is read on Shell start-up, but is not set or changed.

bpo-31860 [https://bugs.python.org/issue?@action=redirect&bpo=31860]: The font sample in the IDLE configuration dialog is now editable. Changes persist while IDLE remains open

bpo-31836 [https://bugs.python.org/issue?@action=redirect&bpo=31836]: Test_code_module now passes if run after test_idle, which sets ps1. The code module uses sys.ps1 if present or sets it to '>>> ' if not. Test_code_module now properly tests both behaviors. Ditto for ps2.

bpo-28603 [https://bugs.python.org/issue?@action=redirect&bpo=28603]: Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable. Patch by Zane Bitter.

bpo-13802 [https://bugs.python.org/issue?@action=redirect&bpo=13802]: Use non-Latin characters in the IDLE's Font settings sample. Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane, tcl/tk will use other fonts that define a character. The expanded example give users of non-Latin characters a better idea of what they might see in IDLE's shell and editors. To make room for the expanded sample, frames on the Font tab are re-arranged. The Font/Tabs help explains a bit about the additions.

bpo-31460 [https://bugs.python.org/issue?@action=redirect&bpo=31460]: Simplify the API of IDLE's Module Browser. Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window. Passing a full file name instead of pieces assumed to come from a .py file opens the possibility of browsing python files that do not end in .py.

bpo-31649 [https://bugs.python.org/issue?@action=redirect&bpo=31649]: IDLE - Make _htest, _utest parameters keyword only.

bpo-31559 [https://bugs.python.org/issue?@action=redirect&bpo=31559]: Remove test order dependence in idle_test.test_browser.

bpo-31459 [https://bugs.python.org/issue?@action=redirect&bpo=31459]: Rename IDLE's module browser from Class Browser to Module Browser. The original module-level class and method browser became a module browser, with the addition of module-level functions, years ago. Nested classes and functions were added yesterday. For back-compatibility, the virtual event <<open-class-browser>>, which appears on the Keys tab of the Settings dialog, is not changed. Patch by Cheryl Sabella.

bpo-31500 [https://bugs.python.org/issue?@action=redirect&bpo=31500]: Default fonts now are scaled on HiDPI displays.

bpo-1612262 [https://bugs.python.org/issue?@action=redirect&bpo=1612262]: IDLE module browser now shows nested classes and functions. Original patches for code and tests by Guilherme Polo and Cheryl Sabella, respectively.

Tools/Demos

bpo-30722 [https://bugs.python.org/issue?@action=redirect&bpo=30722]: Make redemo work with Python 3.6 and newer versions. Also, remove the LOCALE option since it doesn't work with string patterns in Python 3. Patch by Christoph Sarnowski.

C API

bpo-20891 [https://bugs.python.org/issue?@action=redirect&bpo=20891]: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in a non-Python thread before PyEval_InitThreads(), only call PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

bpo-31532 [https://bugs.python.org/issue?@action=redirect&bpo=31532]: Fix memory corruption due to allocator mix in getpath.c between Py_GetPath() and Py_SetPath()

bpo-30697 [https://bugs.python.org/issue?@action=redirect&bpo=30697]: The PyExc_RecursionErrorInst singleton is removed and PyErr_NormalizeException() does not use it anymore. This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter. See also bpo-22898 [https://bugs.python.org/issue?@action=redirect&bpo=22898].

Python 3.6.3 final

Release date: 2017-10-03

Library

bpo-31641 [https://bugs.python.org/issue?@action=redirect&bpo=31641]: Re-allow arbitrary iterables in concurrent.futures.as_completed(). Fixes regression in 3.6.3rc1.

Build

bpo-31662 [https://bugs.python.org/issue?@action=redirect&bpo=31662]: Fix typos in Windows uploadrelease.bat script. Fix Windows Doc build issues in Doc/make.bat.

bpo-31423 [https://bugs.python.org/issue?@action=redirect&bpo=31423]: Fix building the PDF documentation with newer versions of Sphinx.

Python 3.6.3 release candidate 1

Release date: 2017-09-18

Security

bpo-29781 [https://bugs.python.org/issue?@action=redirect&bpo=29781]: SSLObject.version() now correctly returns None when handshake over BIO has not been performed yet.

bpo-30947 [https://bugs.python.org/issue?@action=redirect&bpo=30947]: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

Core and Builtins

bpo-31471 [https://bugs.python.org/issue?@action=redirect&bpo=31471]: Fix an assertion failure in subprocess.Popen() on Windows, in case the env argument has a bad keys() method. Patch by Oren Milman.

bpo-31418 [https://bugs.python.org/issue?@action=redirect&bpo=31418]: Fix an assertion failure in PyErr_WriteUnraisable() in case of an exception with a bad __module__ attribute. Patch by Oren Milman.

bpo-31416 [https://bugs.python.org/issue?@action=redirect&bpo=31416]: Fix assertion failures in case of a bad warnings.filters or warnings.defaultaction. Patch by Oren Milman.

bpo-31411 [https://bugs.python.org/issue?@action=redirect&bpo=31411]: Raise a TypeError instead of SystemError in case warnings.onceregistry is not a dictionary. Patch by Oren Milman.

bpo-31373 [https://bugs.python.org/issue?@action=redirect&bpo=31373]: Fix several possible instances of undefined behavior due to floating-point demotions.

bpo-30465 [https://bugs.python.org/issue?@action=redirect&bpo=30465]: Location information (lineno and col_offset) in f-strings is now (mostly) correct. This fixes tools like flake8 from showing warnings on the wrong line (typically the first line of the file).

bpo-31343 [https://bugs.python.org/issue?@action=redirect&bpo=31343]: Include sys/sysmacros.h for major(), minor(), and makedev(). GNU C library plans to remove the functions from sys/types.h.

bpo-31291 [https://bugs.python.org/issue?@action=redirect&bpo=31291]: Fix an assertion failure in zipimport.zipimporter.get_data on Windows, when the return value of pathname.replace('/','\\') isn't a string. Patch by Oren Milman.

bpo-31271 [https://bugs.python.org/issue?@action=redirect&bpo=31271]: Fix an assertion failure in the write() method of io.TextIOWrapper, when the encoder doesn't return a bytes object. Patch by Oren Milman.

bpo-31243 [https://bugs.python.org/issue?@action=redirect&bpo=31243]: Fix a crash in some methods of io.TextIOWrapper, when the decoder's state is invalid. Patch by Oren Milman.

bpo-30721 [https://bugs.python.org/issue?@action=redirect&bpo=30721]: print now shows correct usage hint for using Python 2 redirection syntax. Patch by Sanyam Khurana.

bpo-31070 [https://bugs.python.org/issue?@action=redirect&bpo=31070]: Fix a race condition in importlib _get_module_lock().

bpo-31095 [https://bugs.python.org/issue?@action=redirect&bpo=31095]: Fix potential crash during GC caused by tp_dealloc which doesn't call PyObject_GC_UnTrack().

bpo-31071 [https://bugs.python.org/issue?@action=redirect&bpo=31071]: Avoid masking original TypeError in call with * unpacking when other arguments are passed.

bpo-30978 [https://bugs.python.org/issue?@action=redirect&bpo=30978]: str.format_map() now passes key lookup exceptions through. Previously any exception was replaced with a KeyError exception.

bpo-30808 [https://bugs.python.org/issue?@action=redirect&bpo=30808]: Use _Py_atomic API for concurrency-sensitive signal state.

bpo-30876 [https://bugs.python.org/issue?@action=redirect&bpo=30876]: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

bpo-30703 [https://bugs.python.org/issue?@action=redirect&bpo=30703]: Improve signal delivery. Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions. The tests I'm adding here fail without the rest of the patch, on Linux and OS X. This means our signal delivery logic had defects (some signals could be lost).

bpo-30765 [https://bugs.python.org/issue?@action=redirect&bpo=30765]: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

bpo-31161 [https://bugs.python.org/issue?@action=redirect&bpo=31161]: Make sure the 'Missing parentheses' syntax error message is only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

bpo-30814 [https://bugs.python.org/issue?@action=redirect&bpo=30814]: Fixed a race condition when import a submodule from a package.

bpo-30597 [https://bugs.python.org/issue?@action=redirect&bpo=30597]: print now shows expected input in custom error message when used as a Python 2 statement. Patch by Sanyam Khurana.

Library

bpo-31499 [https://bugs.python.org/issue?@action=redirect&bpo=31499]: xml.etree: Fix a crash when a parser is part of a reference cycle.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: typing.get_type_hints now finds the right globalns for classes and modules by default (when no globalns was specified by the caller).

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Speed improvements to the typing module. Original PRs by Ivan Levkivskyi and Mitar.

bpo-31544 [https://bugs.python.org/issue?@action=redirect&bpo=31544]: The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser().

bpo-31234 [https://bugs.python.org/issue?@action=redirect&bpo=31234]: socket.create_connection() now fixes manually a reference cycle: clear the variable storing the last exception on success.

bpo-31457 [https://bugs.python.org/issue?@action=redirect&bpo=31457]: LoggerAdapter objects can now be nested.

bpo-31400 [https://bugs.python.org/issue?@action=redirect&bpo=31400]: Improves SSL error handling to avoid losing error numbers.

bpo-28958 [https://bugs.python.org/issue?@action=redirect&bpo=28958]: ssl.SSLContext() now uses OpenSSL error information when a context cannot be instantiated.

bpo-27340 [https://bugs.python.org/issue?@action=redirect&bpo=27340]: SSLSocket.sendall() now uses memoryview to create slices of data. This fixes support for all bytes-like object. It is also more efficient and avoids costly copies.

bpo-31178 [https://bugs.python.org/issue?@action=redirect&bpo=31178]: Fix string concatenation bug in rare error path in the subprocess module

bpo-31350 [https://bugs.python.org/issue?@action=redirect&bpo=31350]: Micro-optimize asyncio._get_running_loop() to become up to 10% faster.

bpo-31170 [https://bugs.python.org/issue?@action=redirect&bpo=31170]: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

bpo-29136 [https://bugs.python.org/issue?@action=redirect&bpo=29136]: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

bpo-29212 [https://bugs.python.org/issue?@action=redirect&bpo=29212]: Fix concurrent.futures.thread.ThreadPoolExecutor threads to have a non repr() based thread name by default when no thread_name_prefix is supplied. They will now identify themselves as "ThreadPoolExecutor-y_n".

bpo-9146 [https://bugs.python.org/issue?@action=redirect&bpo=9146]: Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library. As in some special FIPS-140 build environments.

bpo-27144 [https://bugs.python.org/issue?@action=redirect&bpo=27144]: The map() and as_completed() iterators in concurrent.futures now avoid keeping a reference to yielded objects.

bpo-10746 [https://bugs.python.org/issue?@action=redirect&bpo=10746]: Fix ctypes producing wrong PEP 3118 [https://peps.python.org/pep-3118/] type codes for integer types.

bpo-22536 [https://bugs.python.org/issue?@action=redirect&bpo=22536]: The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found.

bpo-31249 [https://bugs.python.org/issue?@action=redirect&bpo=31249]: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object.

bpo-31247 [https://bugs.python.org/issue?@action=redirect&bpo=31247]: xmlrpc.server now explicitly breaks reference cycles when using sys.exc_info() in code handling exceptions.

bpo-30102 [https://bugs.python.org/issue?@action=redirect&bpo=30102]: The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function detects CPU features and enables optimizations on some CPU architectures such as POWER8. Patch is based on research from Gustavo Serra Scalet.

bpo-31185 [https://bugs.python.org/issue?@action=redirect&bpo=31185]: Fixed miscellaneous errors in asyncio speedup module.

bpo-31135 [https://bugs.python.org/issue?@action=redirect&bpo=31135]: ttk: fix the destroy() method of LabeledScale and OptionMenu classes. Call the parent destroy() method even if the used attribute doesn't exist. The LabeledScale.destroy() method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets.

bpo-31107 [https://bugs.python.org/issue?@action=redirect&bpo=31107]: Fix copyreg._slotnames() mangled attribute calculation for classes whose name begins with an underscore. Patch by Shane Harvey.

bpo-31061 [https://bugs.python.org/issue?@action=redirect&bpo=31061]: Fixed a crash when using asyncio and threads.

bpo-30502 [https://bugs.python.org/issue?@action=redirect&bpo=30502]: Fix handling of long oids in ssl. Based on patch by Christian Heimes.

bpo-30119 [https://bugs.python.org/issue?@action=redirect&bpo=30119]: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Donghee Na.

bpo-30595 [https://bugs.python.org/issue?@action=redirect&bpo=30595]: multiprocessing.Queue.get() with a timeout now polls its reader in non-blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout.

bpo-29403 [https://bugs.python.org/issue?@action=redirect&bpo=29403]: Fix unittest.mock's autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

bpo-30961 [https://bugs.python.org/issue?@action=redirect&bpo=30961]: Fix decrementing a borrowed reference in tracemalloc.

bpo-25684 [https://bugs.python.org/issue?@action=redirect&bpo=25684]: Change ttk.OptionMenu radiobuttons to be unique across instances of OptionMenu.

bpo-30886 [https://bugs.python.org/issue?@action=redirect&bpo=30886]: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

bpo-29854 [https://bugs.python.org/issue?@action=redirect&bpo=29854]: Fix segfault in readline when using readline's history-size option. Patch by Nir Soffer.

bpo-30319 [https://bugs.python.org/issue?@action=redirect&bpo=30319]: socket.close() now ignores ECONNRESET error.

bpo-30828 [https://bugs.python.org/issue?@action=redirect&bpo=30828]: Fix out of bounds write in asyncio.CFuture.remove_done_callback().

bpo-30807 [https://bugs.python.org/issue?@action=redirect&bpo=30807]: signal.setitimer() may disable the timer when passed a tiny value. Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

bpo-30441 [https://bugs.python.org/issue?@action=redirect&bpo=30441]: Fix bug when modifying os.environ while iterating over it

bpo-30532 [https://bugs.python.org/issue?@action=redirect&bpo=30532]: Fix email header value parser dropping folding white space in certain cases.

bpo-30879 [https://bugs.python.org/issue?@action=redirect&bpo=30879]: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

bpo-30746 [https://bugs.python.org/issue?@action=redirect&bpo=30746]: Prohibited the '=' character in environment variable names in os.putenv() and os.spawn*().

bpo-29755 [https://bugs.python.org/issue?@action=redirect&bpo=29755]: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

Documentation

bpo-31294 [https://bugs.python.org/issue?@action=redirect&bpo=31294]: Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3.

bpo-21649 [https://bugs.python.org/issue?@action=redirect&bpo=21649]: Add RFC 7525 and Mozilla server side TLS links to SSL documentation.

bpo-30803 [https://bugs.python.org/issue?@action=redirect&bpo=30803]: Clarify doc on truth value testing. Original patch by Peter Thomassen.

Tests

bpo-31320 [https://bugs.python.org/issue?@action=redirect&bpo=31320]: Silence traceback in test_ssl

bpo-25674 [https://bugs.python.org/issue?@action=redirect&bpo=25674]: Remove sha256.tbs-internet.com ssl test

bpo-30715 [https://bugs.python.org/issue?@action=redirect&bpo=30715]: Address ALPN callback changes for OpenSSL 1.1.0f. The latest version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

bpo-30822 [https://bugs.python.org/issue?@action=redirect&bpo=30822]: regrtest: Exclude tzdata from regrtest --all. When running the test suite using --use=all / -u all, exclude tzdata since it makes test_datetime too slow (15-20 min on some buildbots) which then times out on some buildbots. Fix also regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

Build

bpo-30854 [https://bugs.python.org/issue?@action=redirect&bpo=30854]: Fix compile error when compiling --without-threads. Patch by Masayuki Yamamoto.

Windows

bpo-30389 [https://bugs.python.org/issue?@action=redirect&bpo=30389]: Adds detection of Visual Studio 2017 to distutils on Windows.

bpo-31340 [https://bugs.python.org/issue?@action=redirect&bpo=31340]: Change to building with MSVC v141 (included with Visual Studio 2017)

bpo-30581 [https://bugs.python.org/issue?@action=redirect&bpo=30581]: os.cpu_count() now returns the correct number of processors on Windows when the number of logical processors is greater than 64.

bpo-30731 [https://bugs.python.org/issue?@action=redirect&bpo=30731]: Add a missing xmlns to python.manifest so that it matches the schema.

IDLE

bpo-31493 [https://bugs.python.org/issue?@action=redirect&bpo=31493]: IDLE code context -- fix code update and font update timers. Canceling timers prevents a warning message when test_idle completes.

bpo-31488 [https://bugs.python.org/issue?@action=redirect&bpo=31488]: IDLE - Update non-key options in former extension classes. When applying configdialog changes, call .reload for each feature class. Change ParenMatch so updated options affect existing instances attached to existing editor windows.

bpo-31477 [https://bugs.python.org/issue?@action=redirect&bpo=31477]: IDLE - Improve rstrip entry in doc. Strip trailing whitespace strips more than blank spaces. Multiline string literals are not skipped.

bpo-31480 [https://bugs.python.org/issue?@action=redirect&bpo=31480]: IDLE - make tests pass with zzdummy extension disabled by default.

bpo-31421 [https://bugs.python.org/issue?@action=redirect&bpo=31421]: Document how IDLE runs tkinter programs. IDLE calls tcl/tk update in the background in order to make live interaction and experimentation with tkinter applications much easier.

bpo-31414 [https://bugs.python.org/issue?@action=redirect&bpo=31414]: IDLE -- fix tk entry box tests by deleting first. Adding to an int entry is not the same as deleting and inserting because int('') will fail.

bpo-31051 [https://bugs.python.org/issue?@action=redirect&bpo=31051]: Rearrange IDLE configdialog GenPage into Window, Editor, and Help sections.

bpo-30617 [https://bugs.python.org/issue?@action=redirect&bpo=30617]: IDLE - Add docstrings and tests for outwin subclass of editor. Move some data and functions from the class to module level. Patch by Cheryl Sabella.

bpo-31287 [https://bugs.python.org/issue?@action=redirect&bpo=31287]: IDLE - Do not modify tkinter.message in test_configdialog.

bpo-27099 [https://bugs.python.org/issue?@action=redirect&bpo=27099]: Convert IDLE's built-in 'extensions' to regular features. About 10 IDLE features were implemented as supposedly optional extensions. Their different behavior could be confusing or worse for users and not good for maintenance. Hence the conversion. The main difference for users is that user configurable key bindings for builtin features are now handled uniformly. Now, editing a binding in a keyset only affects its value in the keyset. All bindings are defined together in the system-specific default keysets in config-extensions.def. All custom keysets are saved as a whole in config-extension.cfg. All take effect as soon as one clicks Apply or Ok. The affected events are '<<force-open-completions>>', '<<expand-word>>', '<<force-open-calltip>>', '<<flash-paren>>', '<<format-paragraph>>', '<<run-module>>', '<<check-module>>', and '<<zoom-height>>'. Any (global) customizations made before 3.6.3 will not affect their keyset-specific customization after 3.6.3. and vice versa. Initial patch by Charles Wohlganger.

bpo-31206 [https://bugs.python.org/issue?@action=redirect&bpo=31206]: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by Cheryl Sabella.

bpo-31001 [https://bugs.python.org/issue?@action=redirect&bpo=31001]: Add tests for configdialog highlight tab. Patch by Cheryl Sabella.

bpo-31205 [https://bugs.python.org/issue?@action=redirect&bpo=31205]: IDLE: Factor KeysPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

bpo-31130 [https://bugs.python.org/issue?@action=redirect&bpo=31130]: IDLE -- stop leaks in test_configdialog. Initial patch by Victor Stinner.

bpo-31002 [https://bugs.python.org/issue?@action=redirect&bpo=31002]: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

bpo-19903 [https://bugs.python.org/issue?@action=redirect&bpo=19903]: IDLE: Calltips use inspect.signature instead of inspect.getfullargspec. This improves calltips for builtins converted to use Argument Clinic. Patch by Louie Lu.

bpo-31083 [https://bugs.python.org/issue?@action=redirect&bpo=31083]: IDLE - Add an outline of a TabPage class in configdialog. Update existing classes to match outline. Initial patch by Cheryl Sabella.

bpo-31050 [https://bugs.python.org/issue?@action=redirect&bpo=31050]: Factor GenPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

bpo-31004 [https://bugs.python.org/issue?@action=redirect&bpo=31004]: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly modified tests continue to pass. Fix General tests. Patch mostly by Cheryl Sabella.

bpo-30781 [https://bugs.python.org/issue?@action=redirect&bpo=30781]: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan Reedy and Cheryl Sabella.

bpo-31060 [https://bugs.python.org/issue?@action=redirect&bpo=31060]: IDLE - Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes.

bpo-30853 [https://bugs.python.org/issue?@action=redirect&bpo=30853]: IDLE -- Factor a VarTrace class out of ConfigDialog. Instance tracers manages pairs consisting of a tk variable and a callback function. When tracing is turned on, setting the variable calls the function. Test coverage for the new class is 100%.

bpo-31003 [https://bugs.python.org/issue?@action=redirect&bpo=31003]: IDLE: Add more tests for General tab.

bpo-30993 [https://bugs.python.org/issue?@action=redirect&bpo=30993]: IDLE - Improve configdialog font page and tests. In configdialog: Document causal pathways in create_font_tab docstring. Simplify some attribute names. Move set_samples calls to var_changed_font (idea from Cheryl Sabella). Move related functions to positions after the create widgets function. In test_configdialog: Fix test_font_set so not order dependent. Fix renamed test_indent_scale so it tests the widget. Adjust tests for movement of set_samples call. Add tests for load functions. Put all font tests in one class and tab indent tests in another. Except for two lines, these tests completely cover the related functions.

bpo-30981 [https://bugs.python.org/issue?@action=redirect&bpo=30981]: IDLE -- Add more configdialog font page tests.

bpo-28523 [https://bugs.python.org/issue?@action=redirect&bpo=28523]: IDLE: replace 'colour' with 'color' in configdialog.

bpo-30917 [https://bugs.python.org/issue?@action=redirect&bpo=30917]: Add tests for idlelib.config.IdleConf. Increase coverage from 46% to 96%. Patch by Louie Lu.

bpo-30934 [https://bugs.python.org/issue?@action=redirect&bpo=30934]: Document coverage details for idlelib tests. Add section to idlelib/idle-test/README.txt. Include check that branches are taken both ways. Exclude IDLE-specific code that does not run during unit tests.

bpo-30913 [https://bugs.python.org/issue?@action=redirect&bpo=30913]: IDLE: Document ConfigDialog tk Vars, methods, and widgets in docstrings This will facilitate improving the dialog and splitting up the class. Original patch by Cheryl Sabella.

bpo-30899 [https://bugs.python.org/issue?@action=redirect&bpo=30899]: IDLE: Add tests for ConfigParser subclasses in config. Patch by Louie Lu.

bpo-30881 [https://bugs.python.org/issue?@action=redirect&bpo=30881]: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

bpo-30851 [https://bugs.python.org/issue?@action=redirect&bpo=30851]: IDLE: Remove unused variables in configdialog. One is a duplicate, one is set but cannot be altered by users. Patch by Cheryl Sabella.

bpo-30870 [https://bugs.python.org/issue?@action=redirect&bpo=30870]: IDLE: In Settings dialog, select font with Up, Down keys as well as mouse. Initial patch by Louie Lu.

bpo-8231 [https://bugs.python.org/issue?@action=redirect&bpo=8231]: IDLE: call config.IdleConf.GetUserCfgDir only once.

bpo-30779 [https://bugs.python.org/issue?@action=redirect&bpo=30779]: IDLE: Factor ConfigChanges class from configdialog, put in config; test. * In config, put dump test code in a function; run it and unittest in 'if __name__ == '__main__'. * Add class config.ConfigChanges based on changes_class_v4.py on bpo issue. * Add class test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise configdialog to use ConfigChanges; see tracker msg297804. * Revise test_configdialog to match configdialog changes. * Remove configdialog functions unused or moved to ConfigChanges. Cheryl Sabella contributed parts of the patch.

bpo-30777 [https://bugs.python.org/issue?@action=redirect&bpo=30777]: IDLE: configdialog - Add docstrings and fix comments. Patch by Cheryl Sabella.

bpo-30495 [https://bugs.python.org/issue?@action=redirect&bpo=30495]: IDLE: Improve textview with docstrings, PEP8 names, and more tests. Patch by Cheryl Sabella.

bpo-30723 [https://bugs.python.org/issue?@action=redirect&bpo=30723]: IDLE: Make several improvements to parenmatch. Add 'parens' style to highlight both opener and closer. Make 'default' style, which is not default, a synonym for 'opener'. Make time-delay work the same with all styles. Add help for config dialog extensions tab, including help for parenmatch. Add new tests. Original patch by Charles Wohlganger.

bpo-30674 [https://bugs.python.org/issue?@action=redirect&bpo=30674]: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

bpo-21519 [https://bugs.python.org/issue?@action=redirect&bpo=21519]: IDLE's basic custom key entry dialog now detects duplicates properly. Original patch by Saimadhav Heblikar.

bpo-29910 [https://bugs.python.org/issue?@action=redirect&bpo=29910]: IDLE no longer deletes a character after commenting out a region by a key shortcut. Add return 'break' for this and other potential conflicts between IDLE and default key bindings.

bpo-30728 [https://bugs.python.org/issue?@action=redirect&bpo=30728]: Review and change idlelib.configdialog names. Lowercase method and attribute names. Replace 'colour' with 'color', expand overly cryptic names, delete unneeded underscores. Replace import * with specific imports. Patches by Cheryl Sabella.

bpo-6739 [https://bugs.python.org/issue?@action=redirect&bpo=6739]: IDLE: Verify user-entered key sequences by trying to bind them with tk. Add tests for all 3 validation functions. Original patch by G Polo. Tests added by Cheryl Sabella.

Tools/Demos

bpo-30983 [https://bugs.python.org/issue?@action=redirect&bpo=30983]: gdb integration commands (py-bt, etc.) work on optimized shared builds now, too. PEP 523 [https://peps.python.org/pep-0523/] introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non-debug shared builds. This broke the ability to use py-bt, py-up, and a few other Python-specific gdb integrations. The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python-gdb.py. Original patch by Bruno "Polaco" Penteado.

Python 3.6.2 final

Release date: 2017-07-17

No changes since release candidate 2

Python 3.6.2 release candidate 2

Release date: 2017-07-07

Security

bpo-30730 [https://bugs.python.org/issue?@action=redirect&bpo=30730]: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.

bpo-30694 [https://bugs.python.org/issue?@action=redirect&bpo=30694]: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE 2017-9233 [https://www.cve.org/CVERecord?id=CVE-2017-9233] (External entity infinite loop DoS), CVE 2016-9063 [https://www.cve.org/CVERecord?id=CVE-2016-9063] (Integer overflow, re-fix), CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718] (Fix regression bugs from 2.2.0's fix to CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718]) and CVE 2012-0876 [https://www.cve.org/CVERecord?id=CVE-2012-0876] (Counter hash flooding with SipHash). Note: the CVE 2016-5300 [https://www.cve.org/CVERecord?id=CVE-2016-5300] (Use os-specific entropy sources like getrandom) doesn't impact Python, since Python already gets entropy from the OS to set the expat secret using XML_SetHashSalt().

bpo-30500 [https://bugs.python.org/issue?@action=redirect&bpo=30500]: Fix urllib.parse.splithost() to correctly parse fragments. For example, splithost('//127.0.0.1#@evil.com/') now correctly returns the 127.0.0.1 host, instead of treating @evil.com as the host in an authentication (login@host).

Python 3.6.2 release candidate 1

Release date: 2017-06-17

Security

bpo-29591 [https://bugs.python.org/issue?@action=redirect&bpo=29591]: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718] and CVE 2016-4472 [https://www.cve.org/CVERecord?id=CVE-2016-4472]. See https://sourceforge.net/p/expat/bugs/537/ for more information.

Core and Builtins

bpo-30682 [https://bugs.python.org/issue?@action=redirect&bpo=30682]: Removed a too-strict assertion that failed for certain f-strings, such as eval("f'\n'") and eval("f'\r'").

bpo-30604 [https://bugs.python.org/issue?@action=redirect&bpo=30604]: Move co_extra_freefuncs to not be per-thread to avoid crashes

bpo-29104 [https://bugs.python.org/issue?@action=redirect&bpo=29104]: Fixed parsing backslashes in f-strings.

bpo-27945 [https://bugs.python.org/issue?@action=redirect&bpo=27945]: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

bpo-25794 [https://bugs.python.org/issue?@action=redirect&bpo=25794]: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

bpo-30039 [https://bugs.python.org/issue?@action=redirect&bpo=30039]: If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested 'yield from' or 'await' calls, it's now correctly delivered to the innermost frame.

bpo-12414 [https://bugs.python.org/issue?@action=redirect&bpo=12414]: sys.getsizeof() on a code object now returns the sizes which includes the code struct and sizes of objects which it references. Patch by Donghee Na.

bpo-29949 [https://bugs.python.org/issue?@action=redirect&bpo=29949]: Fix memory usage regression of set and frozenset object.

bpo-29935 [https://bugs.python.org/issue?@action=redirect&bpo=29935]: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

bpo-29859 [https://bugs.python.org/issue?@action=redirect&bpo=29859]: Show correct error messages when any of the pthread_* calls in thread_pthread.h fails.

bpo-28876 [https://bugs.python.org/issue?@action=redirect&bpo=28876]: bool(range) works even if len(range) raises OverflowError.

bpo-29600 [https://bugs.python.org/issue?@action=redirect&bpo=29600]: Fix wrapping coroutine return values in StopIteration.

bpo-28856 [https://bugs.python.org/issue?@action=redirect&bpo=28856]: Fix an oversight that %b format for bytes should support objects follow the buffer protocol.

bpo-29714 [https://bugs.python.org/issue?@action=redirect&bpo=29714]: Fix a regression that bytes format may fail when containing zero bytes inside.

bpo-29478 [https://bugs.python.org/issue?@action=redirect&bpo=29478]: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

Library

bpo-30616 [https://bugs.python.org/issue?@action=redirect&bpo=30616]: Functional API of enum allows to create empty enums. Patched by Donghee Na

bpo-30038 [https://bugs.python.org/issue?@action=redirect&bpo=30038]: Fix race condition between signal delivery and wakeup file descriptor. Patch by Nathaniel Smith.

bpo-23894 [https://bugs.python.org/issue?@action=redirect&bpo=23894]: lib2to3 now recognizes rb'...' and f'...' strings.

bpo-23890 [https://bugs.python.org/issue?@action=redirect&bpo=23890]: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

bpo-30149 [https://bugs.python.org/issue?@action=redirect&bpo=30149]: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Donghee Na.

bpo-30645 [https://bugs.python.org/issue?@action=redirect&bpo=30645]: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

bpo-29931 [https://bugs.python.org/issue?@action=redirect&bpo=29931]: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

bpo-30605 [https://bugs.python.org/issue?@action=redirect&bpo=30605]: re.compile() no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier. Patch by Roy Williams.

bpo-24484 [https://bugs.python.org/issue?@action=redirect&bpo=24484]: Avoid race condition in multiprocessing cleanup (#2159)

bpo-28994 [https://bugs.python.org/issue?@action=redirect&bpo=28994]: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

bpo-30508 [https://bugs.python.org/issue?@action=redirect&bpo=30508]: Don't log exceptions if Task/Future "cancel()" method was called.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

bpo-29870 [https://bugs.python.org/issue?@action=redirect&bpo=29870]: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

bpo-29743 [https://bugs.python.org/issue?@action=redirect&bpo=29743]: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

bpo-27585 [https://bugs.python.org/issue?@action=redirect&bpo=27585]: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

bpo-30418 [https://bugs.python.org/issue?@action=redirect&bpo=30418]: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

bpo-29822 [https://bugs.python.org/issue?@action=redirect&bpo=29822]: inspect.isabstract() now works during __init_subclass__. Patch by Nate Soares.

bpo-29581 [https://bugs.python.org/issue?@action=redirect&bpo=29581]: ABCMeta.__new__ now accepts **kwargs, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares.

bpo-30557 [https://bugs.python.org/issue?@action=redirect&bpo=30557]: faulthandler now correctly filters and displays exception codes on Windows

bpo-30378 [https://bugs.python.org/issue?@action=redirect&bpo=30378]: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

bpo-29960 [https://bugs.python.org/issue?@action=redirect&bpo=29960]: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

bpo-30414 [https://bugs.python.org/issue?@action=redirect&bpo=30414]: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

bpo-30003 [https://bugs.python.org/issue?@action=redirect&bpo=30003]: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

bpo-30301 [https://bugs.python.org/issue?@action=redirect&bpo=30301]: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

bpo-30329 [https://bugs.python.org/issue?@action=redirect&bpo=30329]: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

bpo-30375 [https://bugs.python.org/issue?@action=redirect&bpo=30375]: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

bpo-30048 [https://bugs.python.org/issue?@action=redirect&bpo=30048]: Fixed Task.cancel() can be ignored when the task is running coroutine and the coroutine returned without any more await.

bpo-30266 [https://bugs.python.org/issue?@action=redirect&bpo=30266]: contextlib.AbstractContextManager now supports anti-registration by setting __enter__ = None or __exit__ = None, following the pattern introduced in bpo-25958 [https://bugs.python.org/issue?@action=redirect&bpo=25958]. Patch by Jelle Zijlstra.

bpo-30298 [https://bugs.python.org/issue?@action=redirect&bpo=30298]: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. '(?i)(?s)...'). In verbose mode whitespaces and comments now are allowed before and between inline modifiers (e.g. '(?x) (?i) (?s)...').

bpo-29990 [https://bugs.python.org/issue?@action=redirect&bpo=29990]: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

bpo-26293 [https://bugs.python.org/issue?@action=redirect&bpo=26293]: Change resulted because of zipfile breakage. (See also: bpo-29094 [https://bugs.python.org/issue?@action=redirect&bpo=29094])

bpo-30243 [https://bugs.python.org/issue?@action=redirect&bpo=30243]: Removed the __init__ methods of _json's scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

bpo-30185 [https://bugs.python.org/issue?@action=redirect&bpo=30185]: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

bpo-30205 [https://bugs.python.org/issue?@action=redirect&bpo=30205]: Fix getsockname() for unbound AF_UNIX sockets on Linux.

bpo-30070 [https://bugs.python.org/issue?@action=redirect&bpo=30070]: Fixed leaks and crashes in errors handling in the parser module.

bpo-30061 [https://bugs.python.org/issue?@action=redirect&bpo=30061]: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

bpo-30017 [https://bugs.python.org/issue?@action=redirect&bpo=30017]: Allowed calling the close() method of the zip entry writer object multiple times. Writing to a closed writer now always produces a ValueError.

bpo-30068 [https://bugs.python.org/issue?@action=redirect&bpo=30068]: _io._IOBase.readlines will check if it's closed first when hint is present.

bpo-29694 [https://bugs.python.org/issue?@action=redirect&bpo=29694]: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

bpo-29692 [https://bugs.python.org/issue?@action=redirect&bpo=29692]: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

bpo-29998 [https://bugs.python.org/issue?@action=redirect&bpo=29998]: Pickling and copying ImportError now preserves name and path attributes.

bpo-29953 [https://bugs.python.org/issue?@action=redirect&bpo=29953]: Fixed memory leaks in the replace() method of datetime and time objects when pass out of bound fold argument.

bpo-29942 [https://bugs.python.org/issue?@action=redirect&bpo=29942]: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

bpo-27863 [https://bugs.python.org/issue?@action=redirect&bpo=27863]: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

bpo-28699 [https://bugs.python.org/issue?@action=redirect&bpo=28699]: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

bpo-25803 [https://bugs.python.org/issue?@action=redirect&bpo=25803]: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

bpo-29861 [https://bugs.python.org/issue?@action=redirect&bpo=29861]: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

bpo-29884 [https://bugs.python.org/issue?@action=redirect&bpo=29884]: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

bpo-25455 [https://bugs.python.org/issue?@action=redirect&bpo=25455]: Fixed crashes in repr of recursive buffered file-like objects.

bpo-29800 [https://bugs.python.org/issue?@action=redirect&bpo=29800]: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

bpo-29742 [https://bugs.python.org/issue?@action=redirect&bpo=29742]: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

bpo-8256 [https://bugs.python.org/issue?@action=redirect&bpo=8256]: Fixed possible failing or crashing input() if attributes "encoding" or "errors" of sys.stdin or sys.stdout are not set or are not strings.

bpo-28298 [https://bugs.python.org/issue?@action=redirect&bpo=28298]: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting big intables (objects that have __int__) as elements. Patch by Oren Milman.

bpo-28231 [https://bugs.python.org/issue?@action=redirect&bpo=28231]: The zipfile module now accepts path-like objects for external paths.

bpo-26915 [https://bugs.python.org/issue?@action=redirect&bpo=26915]: index() and count() methods of collections.abc.Sequence now check identity before checking equality when do comparisons.

bpo-29615 [https://bugs.python.org/issue?@action=redirect&bpo=29615]: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

bpo-30177 [https://bugs.python.org/issue?@action=redirect&bpo=30177]: path.resolve(strict=False) no longer cuts the path after the first element not present in the filesystem. Patch by Antoine Pietri.

IDLE

bpo-15786 [https://bugs.python.org/issue?@action=redirect&bpo=15786]: Fix several problems with IDLE's autocompletion box. The following should now work: clicking on selection box items; using the scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no longer happen. Patch by Louie Lu.

bpo-25514 [https://bugs.python.org/issue?@action=redirect&bpo=25514]: Add doc subsubsection about IDLE failure to start. Popup no-connection message directs users to this section.

bpo-30642 [https://bugs.python.org/issue?@action=redirect&bpo=30642]: Fix reference leaks in IDLE tests. Patches by Louie Lu and Terry Jan Reedy.

bpo-30495 [https://bugs.python.org/issue?@action=redirect&bpo=30495]: Add docstrings for textview.py and use PEP8 names. Patches by Cheryl Sabella and Terry Jan Reedy.

bpo-30290 [https://bugs.python.org/issue?@action=redirect&bpo=30290]: Help-about: use pep8 names and add tests. Increase coverage to 100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

bpo-30303 [https://bugs.python.org/issue?@action=redirect&bpo=30303]: Add _utest option to textview; add new tests. Increase coverage to 100%. Patches by Louie Lu and Terry Jan Reedy.

C API

bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867]: Function PySlice_GetIndicesEx() no longer replaced with a macro if Py_LIMITED_API is not set.

Build

bpo-29941 [https://bugs.python.org/issue?@action=redirect&bpo=29941]: Add --with-assertions configure flag to explicitly enable C assert() checks. Defaults to off. --with-pydebug implies --with-assertions.

bpo-28787 [https://bugs.python.org/issue?@action=redirect&bpo=28787]: Fix out-of-tree builds of Python when configured with --with--dtrace.

bpo-29243 [https://bugs.python.org/issue?@action=redirect&bpo=29243]: Prevent unnecessary rebuilding of Python during make test, make install and some other make targets when configured with --enable-optimizations.

bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404]: Don't regenerate generated files based on file modification time anymore: the action is now explicit. Replace make touch with make regen-all.

bpo-29643 [https://bugs.python.org/issue?@action=redirect&bpo=29643]: Fix --enable-optimization didn't work.

Documentation

bpo-30176 [https://bugs.python.org/issue?@action=redirect&bpo=30176]: Add missing attribute related constants in curses documentation.

bpo-30052 [https://bugs.python.org/issue?@action=redirect&bpo=30052]: the link targets for bytes() and bytearray() are now their respective type definitions, rather than the corresponding builtin function entries. Use bytes and bytearray to reference the latter. In order to ensure this and future cross-reference updates are applied automatically, the daily documentation builds now disable the default output caching features in Sphinx.

bpo-26985 [https://bugs.python.org/issue?@action=redirect&bpo=26985]: Add missing info of code object in inspect documentation.

Tools/Demos

bpo-29367 [https://bugs.python.org/issue?@action=redirect&bpo=29367]: python-gdb.py now supports also method-wrapper (wrapperobject) objects.

Tests

bpo-30357 [https://bugs.python.org/issue?@action=redirect&bpo=30357]: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

bpo-30197 [https://bugs.python.org/issue?@action=redirect&bpo=30197]: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn't exist) now will be assigned to the target of the "as" clause, if there is one.

Windows

bpo-30687 [https://bugs.python.org/issue?@action=redirect&bpo=30687]: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

bpo-30450 [https://bugs.python.org/issue?@action=redirect&bpo=30450]: The build process on Windows no longer depends on Subversion, instead pulling external code from GitHub via a Python script. If Python 3.6 is not found on the system (via py -3.6), NuGet is used to download a copy of 32-bit Python.

Python 3.6.1 final

Release date: 2017-03-21

Core and Builtins

bpo-29723 [https://bugs.python.org/issue?@action=redirect&bpo=29723]: The sys.path[0] initialization change for bpo-29139 [https://bugs.python.org/issue?@action=redirect&bpo=29139] caused a regression by revealing an inconsistency in how sys.path is initialized when executing __main__ from a zipfile, directory, or other import location. The interpreter now consistently avoids ever adding the import location's parent directory to sys.path, and ensures no other sys.path entries are inadvertently modified when inserting the import location named on the command line.

Build

bpo-27593 [https://bugs.python.org/issue?@action=redirect&bpo=27593]: fix format of git information used in sys.version

Fix incompatible comment in python.h

Python 3.6.1 release candidate 1

Release date: 2017-03-04

Core and Builtins

bpo-28893 [https://bugs.python.org/issue?@action=redirect&bpo=28893]: Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__.

bpo-29683 [https://bugs.python.org/issue?@action=redirect&bpo=29683]: Fixes to memory allocation in _PyCode_SetExtra. Patch by Brian Coleman.

bpo-29684 [https://bugs.python.org/issue?@action=redirect&bpo=29684]: Fix minor regression of PyEval_CallObjectWithKeywords. It should raise TypeError when kwargs is not a dict. But it might cause segv when args=NULL and kwargs is not a dict.

bpo-28598 [https://bugs.python.org/issue?@action=redirect&bpo=28598]: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

bpo-29607 [https://bugs.python.org/issue?@action=redirect&bpo=29607]: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by Matthieu Dartiailh.

bpo-29602 [https://bugs.python.org/issue?@action=redirect&bpo=29602]: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

bpo-29347 [https://bugs.python.org/issue?@action=redirect&bpo=29347]: Fixed possibly dereferencing undefined pointers when creating weakref objects.

bpo-29438 [https://bugs.python.org/issue?@action=redirect&bpo=29438]: Fixed use-after-free problem in key sharing dict.

bpo-29319 [https://bugs.python.org/issue?@action=redirect&bpo=29319]: Prevent RunMainFromImporter overwriting sys.path[0].

bpo-29337 [https://bugs.python.org/issue?@action=redirect&bpo=29337]: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

bpo-29327 [https://bugs.python.org/issue?@action=redirect&bpo=29327]: Fixed a crash when pass the iterable keyword argument to sorted().

bpo-29034 [https://bugs.python.org/issue?@action=redirect&bpo=29034]: Fix memory leak and use-after-free in os module (path_converter).

bpo-29159 [https://bugs.python.org/issue?@action=redirect&bpo=29159]: Fix regression in bytes(x) when x.__index__() raises Exception.

bpo-28932 [https://bugs.python.org/issue?@action=redirect&bpo=28932]: Do not include <sys/random.h> if it does not exist.

bpo-25677 [https://bugs.python.org/issue?@action=redirect&bpo=25677]: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

bpo-29000 [https://bugs.python.org/issue?@action=redirect&bpo=29000]: Fixed bytes formatting of octals with zero padding in alternate form.

bpo-26919 [https://bugs.python.org/issue?@action=redirect&bpo=26919]: On Android, operating system data is now always encoded/decoded to/from UTF-8, instead of the locale encoding to avoid inconsistencies with os.fsencode() and os.fsdecode() which are already using UTF-8.

bpo-28991 [https://bugs.python.org/issue?@action=redirect&bpo=28991]: functools.lru_cache() was susceptible to an obscure reentrancy bug triggerable by a monkey-patched len() function.

bpo-28739 [https://bugs.python.org/issue?@action=redirect&bpo=28739]: f-string expressions are no longer accepted as docstrings and by ast.literal_eval() even if they do not include expressions.

bpo-28512 [https://bugs.python.org/issue?@action=redirect&bpo=28512]: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

bpo-28918 [https://bugs.python.org/issue?@action=redirect&bpo=28918]: Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined.

bpo-28731 [https://bugs.python.org/issue?@action=redirect&bpo=28731]: Optimize _PyDict_NewPresized() to create correct size dict. Improve speed of dict literal with constant keys up to 30%.

Library

bpo-29169 [https://bugs.python.org/issue?@action=redirect&bpo=29169]: Update zlib to 1.2.11.

bpo-29623 [https://bugs.python.org/issue?@action=redirect&bpo=29623]: Allow use of path-like object as a single argument in ConfigParser.read(). Patch by David Ellis.

bpo-28963 [https://bugs.python.org/issue?@action=redirect&bpo=28963]: Fix out of bound iteration in asyncio.Future.remove_done_callback implemented in C.

bpo-29704 [https://bugs.python.org/issue?@action=redirect&bpo=29704]: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

bpo-29271 [https://bugs.python.org/issue?@action=redirect&bpo=29271]: Fix Task.current_task and Task.all_tasks implemented in C to accept None argument as their pure Python implementation.

bpo-29703 [https://bugs.python.org/issue?@action=redirect&bpo=29703]: Fix asyncio to support instantiation of new event loops in child processes.

bpo-29376 [https://bugs.python.org/issue?@action=redirect&bpo=29376]: Fix assertion error in threading._DummyThread.is_alive().

bpo-28624 [https://bugs.python.org/issue?@action=redirect&bpo=28624]: Add a test that checks that cwd parameter of Popen() accepts PathLike objects. Patch by Sayan Chowdhury.

bpo-28518 [https://bugs.python.org/issue?@action=redirect&bpo=28518]: Start a transaction implicitly before a DML statement. Patch by Aviv Palivoda.

bpo-29532 [https://bugs.python.org/issue?@action=redirect&bpo=29532]: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

bpo-29110 [https://bugs.python.org/issue?@action=redirect&bpo=29110]: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

bpo-29100 [https://bugs.python.org/issue?@action=redirect&bpo=29100]: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

bpo-29519 [https://bugs.python.org/issue?@action=redirect&bpo=29519]: Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs.

bpo-29416 [https://bugs.python.org/issue?@action=redirect&bpo=29416]: Prevent infinite loop in pathlib.Path.mkdir

bpo-29444 [https://bugs.python.org/issue?@action=redirect&bpo=29444]: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

bpo-29335 [https://bugs.python.org/issue?@action=redirect&bpo=29335]: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

bpo-29290 [https://bugs.python.org/issue?@action=redirect&bpo=29290]: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

bpo-28735 [https://bugs.python.org/issue?@action=redirect&bpo=28735]: Fixed the comparison of mock.MagickMock with mock.ANY.

bpo-29316 [https://bugs.python.org/issue?@action=redirect&bpo=29316]: Restore the provisional status of typing module, add corresponding note to documentation. Patch by Ivan L.

bpo-29219 [https://bugs.python.org/issue?@action=redirect&bpo=29219]: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

bpo-29011 [https://bugs.python.org/issue?@action=redirect&bpo=29011]: Fix an important omission by adding Deque to the typing module.

bpo-28969 [https://bugs.python.org/issue?@action=redirect&bpo=28969]: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments.

bpo-29142 [https://bugs.python.org/issue?@action=redirect&bpo=29142]: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

bpo-28961 [https://bugs.python.org/issue?@action=redirect&bpo=28961]: Fix unittest.mock._Call helper: don't ignore the name parameter anymore. Patch written by Jiajun Huang.

bpo-29203 [https://bugs.python.org/issue?@action=redirect&bpo=29203]: functools.lru_cache() now respects PEP 468 [https://peps.python.org/pep-0468/] and preserves the order of keyword arguments. f(a=1, b=2) is now cached separately from f(b=2, a=1) since both calls could potentially give different results.

bpo-15812 [https://bugs.python.org/issue?@action=redirect&bpo=15812]: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

bpo-29094 [https://bugs.python.org/issue?@action=redirect&bpo=29094]: Offsets in a ZIP file created with extern file object and modes "w" and "x" now are relative to the start of the file.

bpo-29085 [https://bugs.python.org/issue?@action=redirect&bpo=29085]: Allow random.Random.seed() to use high quality OS randomness rather than the pid and time.

bpo-29061 [https://bugs.python.org/issue?@action=redirect&bpo=29061]: Fixed bug in secrets.randbelow() which would hang when given a negative input. Patch by Brendan Donegan.

bpo-29079 [https://bugs.python.org/issue?@action=redirect&bpo=29079]: Prevent infinite loop in pathlib.resolve() on Windows

bpo-13051 [https://bugs.python.org/issue?@action=redirect&bpo=13051]: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

bpo-29119 [https://bugs.python.org/issue?@action=redirect&bpo=29119]: Fix weakrefs in the pure python version of collections.OrderedDict move_to_end() method. Contributed by Andra Bogildea.

bpo-9770 [https://bugs.python.org/issue?@action=redirect&bpo=9770]: curses.ascii predicates now work correctly with negative integers.

bpo-28427 [https://bugs.python.org/issue?@action=redirect&bpo=28427]: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

bpo-28923 [https://bugs.python.org/issue?@action=redirect&bpo=28923]: Remove editor artifacts from Tix.py.

bpo-29055 [https://bugs.python.org/issue?@action=redirect&bpo=29055]: Neaten-up empty population error on random.choice() by suppressing the upstream exception.

bpo-28871 [https://bugs.python.org/issue?@action=redirect&bpo=28871]: Fixed a crash when deallocate deep ElementTree.

bpo-19542 [https://bugs.python.org/issue?@action=redirect&bpo=19542]: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

bpo-20191 [https://bugs.python.org/issue?@action=redirect&bpo=20191]: Fixed a crash in resource.prlimit() when passing a sequence that doesn't own its elements as limits.

bpo-28779 [https://bugs.python.org/issue?@action=redirect&bpo=28779]: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

bpo-28847 [https://bugs.python.org/issue?@action=redirect&bpo=28847]: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.

bpo-26937 [https://bugs.python.org/issue?@action=redirect&bpo=26937]: The chown() method of the tarfile.TarFile class does not fail now when the grp module cannot be imported, as for example on Android platforms.

IDLE

bpo-29071 [https://bugs.python.org/issue?@action=redirect&bpo=29071]: IDLE colors f-string prefixes (but not invalid ur prefixes).

bpo-28572 [https://bugs.python.org/issue?@action=redirect&bpo=28572]: Add 10% to coverage of IDLE's test_configdialog. Update and augment description of the configuration system.

Windows

bpo-29579 [https://bugs.python.org/issue?@action=redirect&bpo=29579]: Removes readme.txt from the installer

bpo-29326 [https://bugs.python.org/issue?@action=redirect&bpo=29326]: Ignores blank lines in ._pth files (Patch by Alexey Izbyshev)

bpo-28164 [https://bugs.python.org/issue?@action=redirect&bpo=28164]: Correctly handle special console filenames (patch by Eryk Sun)

bpo-29409 [https://bugs.python.org/issue?@action=redirect&bpo=29409]: Implement PEP 529 [https://peps.python.org/pep-0529/] for io.FileIO (Patch by Eryk Sun)

bpo-29392 [https://bugs.python.org/issue?@action=redirect&bpo=29392]: Prevent crash when passing invalid arguments into msvcrt module.

bpo-25778 [https://bugs.python.org/issue?@action=redirect&bpo=25778]: winreg does not truncate string correctly (Patch by Eryk Sun)

bpo-28896 [https://bugs.python.org/issue?@action=redirect&bpo=28896]: Deprecate WindowsRegistryFinder and disable it by default.

C API

bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867]: Function PySlice_GetIndicesEx() is replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.

bpo-29083 [https://bugs.python.org/issue?@action=redirect&bpo=29083]: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

bpo-29058 [https://bugs.python.org/issue?@action=redirect&bpo=29058]: All stable API extensions added after Python 3.2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API.

Documentation

bpo-28929 [https://bugs.python.org/issue?@action=redirect&bpo=28929]: Link the documentation to its source file on GitHub.

bpo-25008 [https://bugs.python.org/issue?@action=redirect&bpo=25008]: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

bpo-26355 [https://bugs.python.org/issue?@action=redirect&bpo=26355]: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

bpo-29349 [https://bugs.python.org/issue?@action=redirect&bpo=29349]: Fix Python 2 syntax in code for building the documentation.

Tests

bpo-28087 [https://bugs.python.org/issue?@action=redirect&bpo=28087]: Skip test_asyncore and test_eintr poll failures on macOS. Skip some tests of select.poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions.

bpo-29571 [https://bugs.python.org/issue?@action=redirect&bpo=29571]: to match the behaviour of the re.LOCALE flag, test_re.test_locale_flag now uses locale.getpreferredencoding(False) to determine the candidate encoding for the test regex (allowing it to correctly skip the test when the default locale encoding is a multi-byte encoding)

bpo-28950 [https://bugs.python.org/issue?@action=redirect&bpo=28950]: Disallow -j0 to be combined with -T/-l in regrtest command line arguments.

bpo-28683 [https://bugs.python.org/issue?@action=redirect&bpo=28683]: Fix the tests that bind() a unix socket and raise PermissionError on Android for a non-root user.

bpo-26939 [https://bugs.python.org/issue?@action=redirect&bpo=26939]: Add the support.setswitchinterval() function to fix test_functools hanging on the Android armv7 qemu emulator.

Build

bpo-27593 [https://bugs.python.org/issue?@action=redirect&bpo=27593]: sys.version and the platform module python_build(), python_branch(), and python_revision() functions now use git information rather than hg when building from a repo.

bpo-29572 [https://bugs.python.org/issue?@action=redirect&bpo=29572]: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

bpo-26851 [https://bugs.python.org/issue?@action=redirect&bpo=26851]: Set Android compilation and link flags.

bpo-28768 [https://bugs.python.org/issue?@action=redirect&bpo=28768]: Fix implicit declaration of function _setmode. Patch by Masayuki Yamamoto

bpo-29080 [https://bugs.python.org/issue?@action=redirect&bpo=29080]: Removes hard dependency on hg.exe from PCBuild/build.bat

bpo-23903 [https://bugs.python.org/issue?@action=redirect&bpo=23903]: Added missed names to PC/python3.def.

bpo-28762 [https://bugs.python.org/issue?@action=redirect&bpo=28762]: lockf() is available on Android API level 24, but the F_LOCK macro is not defined in android-ndk-r13.

bpo-28538 [https://bugs.python.org/issue?@action=redirect&bpo=28538]: Fix the compilation error that occurs because if_nameindex() is available on Android API level 24, but the if_nameindex structure is not defined.

bpo-20211 [https://bugs.python.org/issue?@action=redirect&bpo=20211]: Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths. Original patch by Thomas Petazzoni.

bpo-28849 [https://bugs.python.org/issue?@action=redirect&bpo=28849]: Do not define sys.implementation._multiarch on Android.

Python 3.6.0 final

Release date: 2016-12-23

No changes since release candidate 2

Python 3.6.0 release candidate 2

Release date: 2016-12-16

Core and Builtins

bpo-28147 [https://bugs.python.org/issue?@action=redirect&bpo=28147]: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table. Patch written by INADA Naoki.

bpo-28990 [https://bugs.python.org/issue?@action=redirect&bpo=28990]: Fix asyncio SSL hanging if connection is closed before handshake is completed. (Patch by HoHo-Ho)

Tools/Demos

bpo-28770 [https://bugs.python.org/issue?@action=redirect&bpo=28770]: Fix python-gdb.py for fastcalls.

Windows

bpo-28896 [https://bugs.python.org/issue?@action=redirect&bpo=28896]: Deprecate WindowsRegistryFinder.

Build

bpo-28898 [https://bugs.python.org/issue?@action=redirect&bpo=28898]: Prevent gdb build errors due to HAVE_LONG_LONG redefinition.

Python 3.6.0 release candidate 1

Release date: 2016-12-06

Core and Builtins

bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722]: Rather than silently producing a class that doesn't support zero-argument super() in methods, failing to pass the new __classcell__ namespace entry up to type.__new__ now results in a DeprecationWarning and a class that supports zero-argument super().

bpo-28797 [https://bugs.python.org/issue?@action=redirect&bpo=28797]: Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.

bpo-28782 [https://bugs.python.org/issue?@action=redirect&bpo=28782]: Fix a bug in the implementation yield from when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (bpo-26647 [https://bugs.python.org/issue?@action=redirect&bpo=26647]).

Library

bpo-27030 [https://bugs.python.org/issue?@action=redirect&bpo=27030]: Unknown escapes in re.sub() replacement template are allowed again. But they still are deprecated and will be disabled in 3.7.

bpo-28835 [https://bugs.python.org/issue?@action=redirect&bpo=28835]: Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overridden inside the context manager.

bpo-27172 [https://bugs.python.org/issue?@action=redirect&bpo=27172]: To assist with upgrades from 2.7, the previously documented deprecation of inspect.getfullargspec() has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.

bpo-26273 [https://bugs.python.org/issue?@action=redirect&bpo=26273]: Add new socket.TCP_CONGESTION (Linux 2.6.13) and socket.TCP_USER_TIMEOUT (Linux 2.6.37) constants. Patch written by Omar Sandoval.

bpo-24142 [https://bugs.python.org/issue?@action=redirect&bpo=24142]: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.

bpo-28843 [https://bugs.python.org/issue?@action=redirect&bpo=28843]: Fix asyncio C Task to handle exceptions __traceback__.

C API

bpo-28808 [https://bugs.python.org/issue?@action=redirect&bpo=28808]: PyUnicode_CompareWithASCIIString() now never raises exceptions.

Documentation

bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722]: The data model reference and the porting section in the What's New guide now cover the additional __classcell__ handling needed for custom metaclasses to fully support PEP 487 [https://peps.python.org/pep-0487/] and zero-argument super().

Tools/Demos

bpo-28023 [https://bugs.python.org/issue?@action=redirect&bpo=28023]: Fix python-gdb.py didn't support new dict implementation.

Python 3.6.0 beta 4

Release date: 2016-11-21

Core and Builtins

bpo-28532 [https://bugs.python.org/issue?@action=redirect&bpo=28532]: Show sys.version when -V option is supplied twice.

bpo-27100 [https://bugs.python.org/issue?@action=redirect&bpo=27100]: The with-statement now checks for __enter__ before it checks for __exit__. This gives less confusing error messages when both methods are missing. Patch by Jonathan Ellington.

bpo-28746 [https://bugs.python.org/issue?@action=redirect&bpo=28746]: Fix the set_inheritable() file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands.

bpo-26920 [https://bugs.python.org/issue?@action=redirect&bpo=26920]: Fix not getting the locale's charset upon initializing the interpreter, on platforms that do not have langinfo.

bpo-28648 [https://bugs.python.org/issue?@action=redirect&bpo=28648]: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

bpo-19398 [https://bugs.python.org/issue?@action=redirect&bpo=19398]: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

bpo-28665 [https://bugs.python.org/issue?@action=redirect&bpo=28665]: Improve speed of the STORE_DEREF opcode by 40%.

bpo-28583 [https://bugs.python.org/issue?@action=redirect&bpo=28583]: PyDict_SetDefault didn't combine split table when needed. Patch by Xiang Zhang.

bpo-27243 [https://bugs.python.org/issue?@action=redirect&bpo=27243]: Change PendingDeprecationWarning -> DeprecationWarning. As it was agreed in the issue, __aiter__ returning an awaitable should result in PendingDeprecationWarning in 3.5 and in DeprecationWarning in 3.6.

bpo-26182 [https://bugs.python.org/issue?@action=redirect&bpo=26182]: Fix a refleak in code that raises DeprecationWarning.

bpo-28721 [https://bugs.python.org/issue?@action=redirect&bpo=28721]: Fix asynchronous generators aclose() and athrow() to handle StopAsyncIteration propagation properly.

Library

bpo-28752 [https://bugs.python.org/issue?@action=redirect&bpo=28752]: Restored the __reduce__() methods of datetime objects.

bpo-28727 [https://bugs.python.org/issue?@action=redirect&bpo=28727]: Regular expression patterns, _sre.SRE_Pattern objects created by re.compile(), become comparable (only x==y and x!=y operators). This change should fix the bpo-18383 [https://bugs.python.org/issue?@action=redirect&bpo=18383]: don't duplicate warning filters when the warnings module is reloaded (thing usually only done in unit tests).

bpo-20572 [https://bugs.python.org/issue?@action=redirect&bpo=20572]: The subprocess.Popen.wait method's undocumented endtime parameter now raises a DeprecationWarning.

bpo-25659 [https://bugs.python.org/issue?@action=redirect&bpo=25659]: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

bpo-19717 [https://bugs.python.org/issue?@action=redirect&bpo=19717]: Makes Path.resolve() succeed on paths that do not exist. Patch by Vajrasky Kok

bpo-28563 [https://bugs.python.org/issue?@action=redirect&bpo=28563]: Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module. The expression parser now supports exact syntax supported by GNU gettext.

bpo-28387 [https://bugs.python.org/issue?@action=redirect&bpo=28387]: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

bpo-28600 [https://bugs.python.org/issue?@action=redirect&bpo=28600]: Optimize loop.call_soon.

bpo-28613 [https://bugs.python.org/issue?@action=redirect&bpo=28613]: Fix get_event_loop() return the current loop if called from coroutines/callbacks.

bpo-28634 [https://bugs.python.org/issue?@action=redirect&bpo=28634]: Fix asyncio.isfuture() to support unittest.Mock.

bpo-26081 [https://bugs.python.org/issue?@action=redirect&bpo=26081]: Fix refleak in _asyncio.Future.__iter__().throw.

bpo-28639 [https://bugs.python.org/issue?@action=redirect&bpo=28639]: Fix inspect.isawaitable to always return bool Patch by Justin Mayfield.

bpo-28652 [https://bugs.python.org/issue?@action=redirect&bpo=28652]: Make loop methods reject socket kinds they do not support.

bpo-28653 [https://bugs.python.org/issue?@action=redirect&bpo=28653]: Fix a refleak in functools.lru_cache.

bpo-28703 [https://bugs.python.org/issue?@action=redirect&bpo=28703]: Fix asyncio.iscoroutinefunction to handle Mock objects.

bpo-28704 [https://bugs.python.org/issue?@action=redirect&bpo=28704]: Fix create_unix_server to support Path-like objects (PEP 519).

bpo-28720 [https://bugs.python.org/issue?@action=redirect&bpo=28720]: Add collections.abc.AsyncGenerator.

Documentation

bpo-28513 [https://bugs.python.org/issue?@action=redirect&bpo=28513]: Documented command-line interface of zipfile.

Tests

bpo-28666 [https://bugs.python.org/issue?@action=redirect&bpo=28666]: Now test.support.rmtree is able to remove unwritable or unreadable directories.

bpo-23839 [https://bugs.python.org/issue?@action=redirect&bpo=23839]: Various caches now are cleared before running every test file.

Build

bpo-10656 [https://bugs.python.org/issue?@action=redirect&bpo=10656]: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

bpo-26359 [https://bugs.python.org/issue?@action=redirect&bpo=26359]: Rename --with-optimiations to --enable-optimizations.

bpo-28676 [https://bugs.python.org/issue?@action=redirect&bpo=28676]: Prevent missing 'getentropy' declaration warning on macOS. Patch by Gareth Rees.

Python 3.6.0 beta 3

Release date: 2016-10-31

Core and Builtins

bpo-28128 [https://bugs.python.org/issue?@action=redirect&bpo=28128]: Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs. Patch by Serhiy Storchaka and Eric Smith.

bpo-28509 [https://bugs.python.org/issue?@action=redirect&bpo=28509]: dict.update() no longer allocate unnecessary large memory.

bpo-28426 [https://bugs.python.org/issue?@action=redirect&bpo=28426]: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

bpo-28517 [https://bugs.python.org/issue?@action=redirect&bpo=28517]: Fixed of-by-one error in the peephole optimizer that caused keeping unreachable code.

bpo-28214 [https://bugs.python.org/issue?@action=redirect&bpo=28214]: Improved exception reporting for problematic __set_name__ attributes.

bpo-23782 [https://bugs.python.org/issue?@action=redirect&bpo=23782]: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

bpo-28471 [https://bugs.python.org/issue?@action=redirect&bpo=28471]: Fix "Python memory allocator called without holding the GIL" crash in socket.setblocking.

Library

bpo-27517 [https://bugs.python.org/issue?@action=redirect&bpo=27517]: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

bpo-28549 [https://bugs.python.org/issue?@action=redirect&bpo=28549]: Fixed segfault in curses's addch() with ncurses6.

bpo-28449 [https://bugs.python.org/issue?@action=redirect&bpo=28449]: tarfile.open() with mode "r" or "r:" now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

bpo-23262 [https://bugs.python.org/issue?@action=redirect&bpo=23262]: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

bpo-27939 [https://bugs.python.org/issue?@action=redirect&bpo=27939]: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

bpo-18844 [https://bugs.python.org/issue?@action=redirect&bpo=18844]: The various ways of specifying weights for random.choices() now produce the same result sequences.

bpo-28255 [https://bugs.python.org/issue?@action=redirect&bpo=28255]: calendar.TextCalendar().prmonth() no longer prints a space at the start of new line after printing a month's calendar. Patch by Xiang Zhang.

bpo-20491 [https://bugs.python.org/issue?@action=redirect&bpo=20491]: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

bpo-28353 [https://bugs.python.org/issue?@action=redirect&bpo=28353]: os.fwalk() no longer fails on broken links.

bpo-28430 [https://bugs.python.org/issue?@action=redirect&bpo=28430]: Fix iterator of C implemented asyncio.Future doesn't accept non-None value is passed to it.send(val).

bpo-27025 [https://bugs.python.org/issue?@action=redirect&bpo=27025]: Generated names for Tkinter widgets now start by the "!" prefix for readability.

bpo-25464 [https://bugs.python.org/issue?@action=redirect&bpo=25464]: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

bpo-28488 [https://bugs.python.org/issue?@action=redirect&bpo=28488]: shutil.make_archive() no longer adds entry "./" to ZIP archive.

bpo-25953 [https://bugs.python.org/issue?@action=redirect&bpo=25953]: re.sub() now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string. Error message for invalid group reference now includes the group index and the position of the reference. Based on patch by SilentGhost.

bpo-18219 [https://bugs.python.org/issue?@action=redirect&bpo=18219]: Optimize csv.DictWriter for large number of columns. Patch by Mariatta Wijaya.

bpo-28448 [https://bugs.python.org/issue?@action=redirect&bpo=28448]: Fix C implemented asyncio.Future didn't work on Windows.

bpo-28480 [https://bugs.python.org/issue?@action=redirect&bpo=28480]: Fix error building socket module when multithreading is disabled.

bpo-24452 [https://bugs.python.org/issue?@action=redirect&bpo=24452]: Make webbrowser support Chrome on Mac OS X.

bpo-20766 [https://bugs.python.org/issue?@action=redirect&bpo=20766]: Fix references leaked by pdb in the handling of SIGINT handlers.

bpo-28492 [https://bugs.python.org/issue?@action=redirect&bpo=28492]: Fix how StopIteration exception is raised in _asyncio.Future.

bpo-28500 [https://bugs.python.org/issue?@action=redirect&bpo=28500]: Fix asyncio to handle async gens GC from another thread.

bpo-26923 [https://bugs.python.org/issue?@action=redirect&bpo=26923]: Fix asyncio.Gather to refuse being cancelled once all children are done. Patch by Johannes Ebke.

bpo-26796 [https://bugs.python.org/issue?@action=redirect&bpo=26796]: Don't configure the number of workers for default threadpool executor. Initial patch by Hans Lawrenz.

bpo-28544 [https://bugs.python.org/issue?@action=redirect&bpo=28544]: Implement asyncio.Task in C.

Windows

bpo-28522 [https://bugs.python.org/issue?@action=redirect&bpo=28522]: Fixes mishandled buffer reallocation in getpathp.c

Build

bpo-28444 [https://bugs.python.org/issue?@action=redirect&bpo=28444]: Fix missing extensions modules when cross compiling.

bpo-28208 [https://bugs.python.org/issue?@action=redirect&bpo=28208]: Update Windows build and OS X installers to use SQLite 3.14.2.

bpo-28248 [https://bugs.python.org/issue?@action=redirect&bpo=28248]: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

Tests

bpo-26944 [https://bugs.python.org/issue?@action=redirect&bpo=26944]: Fix test_posix for Android where 'id -G' is entirely wrong or missing the effective gid.

bpo-28409 [https://bugs.python.org/issue?@action=redirect&bpo=28409]: regrtest: fix the parser of command line arguments.

Python 3.6.0 beta 2

Release date: 2016-10-10

Core and Builtins

bpo-28183 [https://bugs.python.org/issue?@action=redirect&bpo=28183]: Optimize and cleanup dict iteration.

bpo-26081 [https://bugs.python.org/issue?@action=redirect&bpo=26081]: Added C implementation of asyncio.Future. Original patch by Yury Selivanov.

bpo-28379 [https://bugs.python.org/issue?@action=redirect&bpo=28379]: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: Creating instances of range_iterator by calling range_iterator type now is deprecated. Patch by Oren Milman.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: The constructor of range_iterator now checks that step is not 0. Patch by Oren Milman.

bpo-26906 [https://bugs.python.org/issue?@action=redirect&bpo=26906]: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

bpo-18287 [https://bugs.python.org/issue?@action=redirect&bpo=18287]: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

bpo-24098 [https://bugs.python.org/issue?@action=redirect&bpo=24098]: Fixed possible crash when AST is changed in process of compiling it.

bpo-28201 [https://bugs.python.org/issue?@action=redirect&bpo=28201]: Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits.

bpo-28350 [https://bugs.python.org/issue?@action=redirect&bpo=28350]: String constants with null character no longer interned.

bpo-26617 [https://bugs.python.org/issue?@action=redirect&bpo=26617]: Fix crash when GC runs during weakref callbacks.

bpo-27942 [https://bugs.python.org/issue?@action=redirect&bpo=27942]: String constants now interned recursively in tuples and frozensets.

bpo-21578 [https://bugs.python.org/issue?@action=redirect&bpo=21578]: Fixed misleading error message when ImportError called with invalid keyword args.

bpo-28203 [https://bugs.python.org/issue?@action=redirect&bpo=28203]: Fix incorrect type in complex(1.0, {2:3}) error message. Patch by Soumya Sharma.

bpo-28086 [https://bugs.python.org/issue?@action=redirect&bpo=28086]: Single var-positional argument of tuple subtype was passed unscathed to the C-defined function. Now it is converted to exact tuple.

bpo-28214 [https://bugs.python.org/issue?@action=redirect&bpo=28214]: Now __set_name__ is looked up on the class instead of the instance.

bpo-27955 [https://bugs.python.org/issue?@action=redirect&bpo=27955]: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

bpo-28192 [https://bugs.python.org/issue?@action=redirect&bpo=28192]: Don't import readline in isolated mode.

Upgrade internal unicode databases to Unicode version 9.0.0.

bpo-28131 [https://bugs.python.org/issue?@action=redirect&bpo=28131]: Fix a regression in zipimport's compile_source(). zipimport should use the same optimization level as the interpreter.

bpo-28126 [https://bugs.python.org/issue?@action=redirect&bpo=28126]: Replace Py_MEMCPY with memcpy(). Visual Studio can properly optimize memcpy().

bpo-28120 [https://bugs.python.org/issue?@action=redirect&bpo=28120]: Fix dict.pop() for split dictionary when trying to remove a "pending key" (Not yet inserted in split-table). Patch by Xiang Zhang.

bpo-26182 [https://bugs.python.org/issue?@action=redirect&bpo=26182]: Raise DeprecationWarning when async and await keywords are used as variable/attribute/class/function name.

Library

bpo-27998 [https://bugs.python.org/issue?@action=redirect&bpo=27998]: Fixed bytes path support in os.scandir() on Windows. Patch by Eryk Sun.

bpo-28317 [https://bugs.python.org/issue?@action=redirect&bpo=28317]: The disassembler now decodes FORMAT_VALUE argument.

bpo-26293 [https://bugs.python.org/issue?@action=redirect&bpo=26293]: Fixed writing ZIP files that starts not from the start of the file. Offsets in ZIP file now are relative to the start of the archive in conforming to the specification.

bpo-28380 [https://bugs.python.org/issue?@action=redirect&bpo=28380]: unittest.mock Mock autospec functions now properly support assert_called, assert_not_called, and assert_called_once.

bpo-27181 [https://bugs.python.org/issue?@action=redirect&bpo=27181]: remove statistics.geometric_mean and defer until 3.7.

bpo-28229 [https://bugs.python.org/issue?@action=redirect&bpo=28229]: lzma module now supports pathlib.

bpo-28321 [https://bugs.python.org/issue?@action=redirect&bpo=28321]: Fixed writing non-BMP characters with binary format in plistlib.

bpo-28225 [https://bugs.python.org/issue?@action=redirect&bpo=28225]: bz2 module now supports pathlib. Initial patch by Ethan Furman.

bpo-28227 [https://bugs.python.org/issue?@action=redirect&bpo=28227]: gzip now supports pathlib. Patch by Ethan Furman.

bpo-27358 [https://bugs.python.org/issue?@action=redirect&bpo=27358]: Optimized merging var-keyword arguments and improved error message when passing a non-mapping as a var-keyword argument.

bpo-28257 [https://bugs.python.org/issue?@action=redirect&bpo=28257]: Improved error message when passing a non-iterable as a var-positional argument. Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

bpo-28322 [https://bugs.python.org/issue?@action=redirect&bpo=28322]: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

bpo-28228 [https://bugs.python.org/issue?@action=redirect&bpo=28228]: imghdr now supports pathlib.

bpo-28226 [https://bugs.python.org/issue?@action=redirect&bpo=28226]: compileall now supports pathlib.

bpo-28314 [https://bugs.python.org/issue?@action=redirect&bpo=28314]: Fix function declaration (C flags) for the getiterator() method of xml.etree.ElementTree.Element.

bpo-28148 [https://bugs.python.org/issue?@action=redirect&bpo=28148]: Stop using localtime() and gmtime() in the time module. Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r, but available on all platforms. Patch by Ed Schouten.

bpo-28253 [https://bugs.python.org/issue?@action=redirect&bpo=28253]: Fixed calendar functions for extreme months: 0001-01 and 9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so that they don't call itermonthdates() which can cause datetime.date under/overflow.

bpo-28275 [https://bugs.python.org/issue?@action=redirect&bpo=28275]: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

bpo-27897 [https://bugs.python.org/issue?@action=redirect&bpo=27897]: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

bpo-18844 [https://bugs.python.org/issue?@action=redirect&bpo=18844]: random.choices() now has k as a keyword-only argument to improve the readability of common cases and come into line with the signature used in other languages.

bpo-18893 [https://bugs.python.org/issue?@action=redirect&bpo=18893]: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

bpo-27611 [https://bugs.python.org/issue?@action=redirect&bpo=27611]: Fixed support of default root window in the tkinter.tix module. Added the master parameter in the DisplayStyle constructor.

bpo-27348 [https://bugs.python.org/issue?@action=redirect&bpo=27348]: In the traceback module, restore the formatting of exception messages like "Exception: None". This fixes a regression introduced in 3.5a2.

bpo-25651 [https://bugs.python.org/issue?@action=redirect&bpo=25651]: Allow false values to be used for msg parameter of subTest().

bpo-27778 [https://bugs.python.org/issue?@action=redirect&bpo=27778]: Fix a memory leak in os.getrandom() when the getrandom() is interrupted by a signal and a signal handler raises a Python exception.

bpo-28200 [https://bugs.python.org/issue?@action=redirect&bpo=28200]: Fix memory leak on Windows in the os module (fix path_converter() function).

bpo-25400 [https://bugs.python.org/issue?@action=redirect&bpo=25400]: RobotFileParser now correctly returns default values for crawl_delay and request_rate. Initial patch by Peter Wirtz.

bpo-27932 [https://bugs.python.org/issue?@action=redirect&bpo=27932]: Prevent memory leak in win32_ver().

Fix UnboundLocalError in socket._sendfile_use_sendfile.

bpo-28075 [https://bugs.python.org/issue?@action=redirect&bpo=28075]: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

bpo-22493 [https://bugs.python.org/issue?@action=redirect&bpo=22493]: Warning message emitted by using inline flags in the middle of regular expression now contains a (truncated) regex pattern. Patch by Tim Graham.

bpo-25270 [https://bugs.python.org/issue?@action=redirect&bpo=25270]: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

bpo-28181 [https://bugs.python.org/issue?@action=redirect&bpo=28181]: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

bpo-25895 [https://bugs.python.org/issue?@action=redirect&bpo=25895]: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

bpo-28114 [https://bugs.python.org/issue?@action=redirect&bpo=28114]: Fix a crash in parse_envlist() when env contains byte strings. Patch by Eryk Sun.

bpo-27599 [https://bugs.python.org/issue?@action=redirect&bpo=27599]: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

bpo-27906 [https://bugs.python.org/issue?@action=redirect&bpo=27906]: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

bpo-28174 [https://bugs.python.org/issue?@action=redirect&bpo=28174]: Handle when SO_REUSEPORT isn't properly supported. Patch by Seth Michael Larson.

bpo-26654 [https://bugs.python.org/issue?@action=redirect&bpo=26654]: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

bpo-26909 [https://bugs.python.org/issue?@action=redirect&bpo=26909]: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

bpo-28176 [https://bugs.python.org/issue?@action=redirect&bpo=28176]: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

bpo-27759 [https://bugs.python.org/issue?@action=redirect&bpo=27759]: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

bpo-28368 [https://bugs.python.org/issue?@action=redirect&bpo=28368]: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

bpo-28369 [https://bugs.python.org/issue?@action=redirect&bpo=28369]: Raise RuntimeError when transport's FD is used with add_reader, add_writer, etc.

bpo-28370 [https://bugs.python.org/issue?@action=redirect&bpo=28370]: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

bpo-28371 [https://bugs.python.org/issue?@action=redirect&bpo=28371]: Deprecate passing asyncio.Handles to run_in_executor.

bpo-28372 [https://bugs.python.org/issue?@action=redirect&bpo=28372]: Fix asyncio to support formatting of non-python coroutines.

bpo-28399 [https://bugs.python.org/issue?@action=redirect&bpo=28399]: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

bpo-27972 [https://bugs.python.org/issue?@action=redirect&bpo=27972]: Prohibit Tasks to await on themselves.

Windows

bpo-28402 [https://bugs.python.org/issue?@action=redirect&bpo=28402]: Adds signed catalog files for stdlib on Windows.

bpo-28333 [https://bugs.python.org/issue?@action=redirect&bpo=28333]: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk Sun)

bpo-28251 [https://bugs.python.org/issue?@action=redirect&bpo=28251]: Improvements to help manuals on Windows.

bpo-28110 [https://bugs.python.org/issue?@action=redirect&bpo=28110]: launcher.msi has different product codes between 32-bit and 64-bit

bpo-28161 [https://bugs.python.org/issue?@action=redirect&bpo=28161]: Opening CON for write access fails

bpo-28162 [https://bugs.python.org/issue?@action=redirect&bpo=28162]: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z

bpo-28163 [https://bugs.python.org/issue?@action=redirect&bpo=28163]: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

bpo-28164 [https://bugs.python.org/issue?@action=redirect&bpo=28164]: _PyIO_get_console_type fails for various paths

bpo-28137 [https://bugs.python.org/issue?@action=redirect&bpo=28137]: Renames Windows path file to ._pth

bpo-28138 [https://bugs.python.org/issue?@action=redirect&bpo=28138]: Windows ._pth file should allow import site

C API

bpo-28426 [https://bugs.python.org/issue?@action=redirect&bpo=28426]: Deprecated undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and PyUnicode_AsEncodedUnicode().

Build

bpo-28258 [https://bugs.python.org/issue?@action=redirect&bpo=28258]: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

bpo-26661 [https://bugs.python.org/issue?@action=redirect&bpo=26661]: setup.py now detects system libffi with multiarch wrapper.

bpo-15819 [https://bugs.python.org/issue?@action=redirect&bpo=15819]: Remove redundant include search directory option for building outside the source tree.

Tests

bpo-28217 [https://bugs.python.org/issue?@action=redirect&bpo=28217]: Adds _testconsole module to test console input.

Python 3.6.0 beta 1

Release date: 2016-09-12

Core and Builtins

bpo-23722 [https://bugs.python.org/issue?@action=redirect&bpo=23722]: The __class__ cell used by zero-argument super() is now initialized from type.__new__ rather than __build_class__, so class methods relying on that will now work correctly when called from metaclass methods during class creation. Patch by Martin Teichmann.

bpo-25221 [https://bugs.python.org/issue?@action=redirect&bpo=25221]: Fix corrupted result from PyLong_FromLong(0) when Python is compiled with NSMALLPOSINTS = 0.

bpo-27080 [https://bugs.python.org/issue?@action=redirect&bpo=27080]: Implement formatting support for PEP 515 [https://peps.python.org/pep-0515/]. Initial patch by Chris Angelico.

bpo-27199 [https://bugs.python.org/issue?@action=redirect&bpo=27199]: In tarfile, expose copyfileobj bufsize to improve throughput. Patch by Jason Fried.

bpo-27948 [https://bugs.python.org/issue?@action=redirect&bpo=27948]: In f-strings, only allow backslashes inside the braces (where the expressions are). This is a breaking change from the 3.6 alpha releases, where backslashes are allowed anywhere in an f-string. Also, require that expressions inside f-strings be enclosed within literal braces, and not escapes like f'\x7b"hi"\x7d'.

bpo-28046 [https://bugs.python.org/issue?@action=redirect&bpo=28046]: Remove platform-specific directories from sys.path.

bpo-28071 [https://bugs.python.org/issue?@action=redirect&bpo=28071]: Add early-out for differencing from an empty set.

bpo-25758 [https://bugs.python.org/issue?@action=redirect&bpo=25758]: Prevents zipimport from unnecessarily encoding a filename (patch by Eryk Sun)

bpo-25856 [https://bugs.python.org/issue?@action=redirect&bpo=25856]: The __module__ attribute of extension classes and functions now is interned. This leads to more compact pickle data with protocol 4.

bpo-27213 [https://bugs.python.org/issue?@action=redirect&bpo=27213]: Rework CALL_FUNCTION* opcodes to produce shorter and more efficient bytecode. Patch by Demur Rumed, design by Serhiy Storchaka, reviewed by Serhiy Storchaka and Victor Stinner.

bpo-26331 [https://bugs.python.org/issue?@action=redirect&bpo=26331]: Implement tokenizing support for PEP 515 [https://peps.python.org/pep-0515/]. Patch by Georg Brandl.

bpo-27999 [https://bugs.python.org/issue?@action=redirect&bpo=27999]: Make "global after use" a SyntaxError, and ditto for nonlocal. Patch by Ivan Levkivskyi.

bpo-28003 [https://bugs.python.org/issue?@action=redirect&bpo=28003]: Implement PEP 525 [https://peps.python.org/pep-0525/] -- Asynchronous Generators.

bpo-27985 [https://bugs.python.org/issue?@action=redirect&bpo=27985]: Implement PEP 526 [https://peps.python.org/pep-0526/] -- Syntax for Variable Annotations. Patch by Ivan Levkivskyi.

bpo-26058 [https://bugs.python.org/issue?@action=redirect&bpo=26058]: Add a new private version to the builtin dict type, incremented at each dictionary creation and at each dictionary change. Implementation of the PEP 509.

bpo-27364 [https://bugs.python.org/issue?@action=redirect&bpo=27364]: A backslash-character pair that is not a valid escape sequence now generates a DeprecationWarning. Patch by Emanuel Barry.

bpo-27350 [https://bugs.python.org/issue?@action=redirect&bpo=27350]: dict implementation is changed like PyPy. It is more compact and preserves insertion order. (Concept developed by Raymond Hettinger and patch by Inada Naoki.)

bpo-27911 [https://bugs.python.org/issue?@action=redirect&bpo=27911]: Remove unnecessary error checks in exec_builtin_or_dynamic().

bpo-27078 [https://bugs.python.org/issue?@action=redirect&bpo=27078]: Added BUILD_STRING opcode. Optimized f-strings evaluation.

bpo-17884 [https://bugs.python.org/issue?@action=redirect&bpo=17884]: Python now requires systems with inttypes.h and stdint.h

bpo-27961 [https://bugs.python.org/issue?@action=redirect&bpo=27961]: Require platforms to support long long. Python hasn't compiled without long long for years, so this is basically a formality.

bpo-27355 [https://bugs.python.org/issue?@action=redirect&bpo=27355]: Removed support for Windows CE. It was never finished, and Windows CE is no longer a relevant platform for Python.

Implement PEP 523 [https://peps.python.org/pep-0523/].

bpo-27870 [https://bugs.python.org/issue?@action=redirect&bpo=27870]: A left shift of zero by a large integer no longer attempts to allocate large amounts of memory.

bpo-25402 [https://bugs.python.org/issue?@action=redirect&bpo=25402]: In int-to-decimal-string conversion, improve the estimate of the intermediate memory required, and remove an unnecessarily strict overflow check. Patch by Serhiy Storchaka.

bpo-27214 [https://bugs.python.org/issue?@action=redirect&bpo=27214]: In long_invert, be more careful about modifying object returned by long_add, and remove an unnecessary check for small longs. Thanks Oren Milman for analysis and patch.

bpo-27506 [https://bugs.python.org/issue?@action=redirect&bpo=27506]: Support passing the bytes/bytearray.translate() "delete" argument by keyword.

bpo-27812 [https://bugs.python.org/issue?@action=redirect&bpo=27812]: Properly clear out a generator's frame's backreference to the generator to prevent crashes in frame.clear().

bpo-27811 [https://bugs.python.org/issue?@action=redirect&bpo=27811]: Fix a crash when a coroutine that has not been awaited is finalized with warnings-as-errors enabled.

bpo-27587 [https://bugs.python.org/issue?@action=redirect&bpo=27587]: Fix another issue found by PVS-Studio: Null pointer check after use of 'def' in _PyState_AddModule(). Initial patch by Christian Heimes.

bpo-27792 [https://bugs.python.org/issue?@action=redirect&bpo=27792]: The modulo operation applied to bool and other int subclasses now always returns an int. Previously the return type depended on the input values. Patch by Xiang Zhang.

bpo-26984 [https://bugs.python.org/issue?@action=redirect&bpo=26984]: int() now always returns an instance of exact int.

bpo-25604 [https://bugs.python.org/issue?@action=redirect&bpo=25604]: Fix a minor bug in integer true division; this bug could potentially have caused off-by-one-ulp results on platforms with unreliable ldexp implementations.

bpo-24254 [https://bugs.python.org/issue?@action=redirect&bpo=24254]: Make class definition namespace ordered by default.

bpo-27662 [https://bugs.python.org/issue?@action=redirect&bpo=27662]: Fix an overflow check in List_New: the original code was checking against Py_SIZE_MAX instead of the correct upper bound of Py_SSIZE_T_MAX. Patch by Xiang Zhang.

bpo-27782 [https://bugs.python.org/issue?@action=redirect&bpo=27782]: Multi-phase extension module import now correctly allows the m_methods field to be used to add module level functions to instances of non-module types returned from Py_create_mod. Patch by Xiang Zhang.

bpo-27936 [https://bugs.python.org/issue?@action=redirect&bpo=27936]: The round() function accepted a second None argument for some types but not for others. Fixed the inconsistency by accepting None for all numeric types.

bpo-27487 [https://bugs.python.org/issue?@action=redirect&bpo=27487]: Warn if a submodule argument to "python -m" or runpy.run_module() is found in sys.modules after parent packages are imported, but before the submodule is executed.

bpo-27157 [https://bugs.python.org/issue?@action=redirect&bpo=27157]: Make only type() itself accept the one-argument form. Patch by Eryk Sun and Emanuel Barry.

bpo-27558 [https://bugs.python.org/issue?@action=redirect&bpo=27558]: Fix a SystemError in the implementation of "raise" statement. In a brand new thread, raise a RuntimeError since there is no active exception to reraise. Patch written by Xiang Zhang.

bpo-28008 [https://bugs.python.org/issue?@action=redirect&bpo=28008]: Implement PEP 530 [https://peps.python.org/pep-0530/] -- asynchronous comprehensions.

bpo-27942 [https://bugs.python.org/issue?@action=redirect&bpo=27942]: Fix memory leak in codeobject.c

Library

bpo-28732 [https://bugs.python.org/issue?@action=redirect&bpo=28732]: Fix crash in os.spawnv() with no elements in args

bpo-28485 [https://bugs.python.org/issue?@action=redirect&bpo=28485]: Always raise ValueError for negative compileall.compile_dir(workers=...) parameter, even when multithreading is unavailable.

bpo-28037 [https://bugs.python.org/issue?@action=redirect&bpo=28037]: Use sqlite3_get_autocommit() instead of setting Connection->inTransaction manually.

bpo-25283 [https://bugs.python.org/issue?@action=redirect&bpo=25283]: Attributes tm_gmtoff and tm_zone are now available on all platforms in the return values of time.localtime() and time.gmtime().

bpo-24454 [https://bugs.python.org/issue?@action=redirect&bpo=24454]: Regular expression match object groups are now accessible using __getitem__. "mo[x]" is equivalent to "mo.group(x)".

bpo-10740 [https://bugs.python.org/issue?@action=redirect&bpo=10740]: sqlite3 no longer implicitly commit an open transaction before DDL statements.

bpo-17941 [https://bugs.python.org/issue?@action=redirect&bpo=17941]: Add a module parameter to collections.namedtuple().

bpo-22493 [https://bugs.python.org/issue?@action=redirect&bpo=22493]: Inline flags now should be used only at the start of the regular expression. Deprecation warning is emitted if uses them in the middle of the regular expression.

bpo-26885 [https://bugs.python.org/issue?@action=redirect&bpo=26885]: xmlrpc now supports unmarshalling additional data types used by Apache XML-RPC implementation for numerics and None.

bpo-28070 [https://bugs.python.org/issue?@action=redirect&bpo=28070]: Fixed parsing inline verbose flag in regular expressions.

bpo-19500 [https://bugs.python.org/issue?@action=redirect&bpo=19500]: Add client-side SSL session resumption to the ssl module.

bpo-28022 [https://bugs.python.org/issue?@action=redirect&bpo=28022]: Deprecate ssl-related arguments in favor of SSLContext. The deprecation include manual creation of SSLSocket and certfile/keyfile (or similar) in ftplib, httplib, imaplib, smtplib, poplib and urllib.

bpo-28043 [https://bugs.python.org/issue?@action=redirect&bpo=28043]: SSLContext has improved default settings: OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION, OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE and HIGH ciphers without MD5.

bpo-24693 [https://bugs.python.org/issue?@action=redirect&bpo=24693]: Changed some RuntimeError's in the zipfile module to more appropriate types. Improved some error messages and debugging output.

bpo-17909 [https://bugs.python.org/issue?@action=redirect&bpo=17909]: json.load and json.loads now support binary input encoded as UTF-8, UTF-16 or UTF-32. Patch by Serhiy Storchaka.

bpo-27137 [https://bugs.python.org/issue?@action=redirect&bpo=27137]: the pure Python fallback implementation of functools.partial now matches the behaviour of its accelerated C counterpart for subclassing, pickling and text representation purposes. Patch by Emanuel Barry and Serhiy Storchaka.

Fix possible integer overflows and crashes in the mmap module with unusual usage patterns.

bpo-1703178 [https://bugs.python.org/issue?@action=redirect&bpo=1703178]: Fix the ability to pass the --link-objects option to the distutils build_ext command.

bpo-28019 [https://bugs.python.org/issue?@action=redirect&bpo=28019]: itertools.count() no longer rounds non-integer step in range between 1.0 and 2.0 to 1.

bpo-18401 [https://bugs.python.org/issue?@action=redirect&bpo=18401]: Pdb now supports the 'readrc' keyword argument to control whether .pdbrc files should be read. Patch by Martin Matusiak and Sam Kimbrel.

bpo-25969 [https://bugs.python.org/issue?@action=redirect&bpo=25969]: Update the lib2to3 grammar to handle the unpacking generalizations added in 3.5.

bpo-14977 [https://bugs.python.org/issue?@action=redirect&bpo=14977]: mailcap now respects the order of the lines in the mailcap files ("first match"), as required by RFC 1542. Patch by Michael Lazar.

bpo-28082 [https://bugs.python.org/issue?@action=redirect&bpo=28082]: Convert re flag constants to IntFlag.

bpo-28025 [https://bugs.python.org/issue?@action=redirect&bpo=28025]: Convert all ssl module constants to IntEnum and IntFlags. SSLContext properties now return flags and enums.

bpo-23591 [https://bugs.python.org/issue?@action=redirect&bpo=23591]: Add Flag, IntFlag, and auto() to enum module.

bpo-433028 [https://bugs.python.org/issue?@action=redirect&bpo=433028]: Added support of modifier spans in regular expressions.

bpo-24594 [https://bugs.python.org/issue?@action=redirect&bpo=24594]: Validates persist parameter when opening MSI database

bpo-17582 [https://bugs.python.org/issue?@action=redirect&bpo=17582]: xml.etree.ElementTree nows preserves whitespaces in attributes (Patch by Duane Griffin. Reviewed and approved by Stefan Behnel.)

bpo-28047 [https://bugs.python.org/issue?@action=redirect&bpo=28047]: Fixed calculation of line length used for the base64 CTE in the new email policies.

bpo-27576 [https://bugs.python.org/issue?@action=redirect&bpo=27576]: Fix call order in OrderedDict.__init__().

email.generator.DecodedGenerator now supports the policy keyword.

bpo-28027 [https://bugs.python.org/issue?@action=redirect&bpo=28027]: Remove undocumented modules from Lib/plat-*: IN, CDROM, DLFCN, TYPES, CDIO, and STROPTS.

bpo-27445 [https://bugs.python.org/issue?@action=redirect&bpo=27445]: Don't pass str(_charset) to MIMEText.set_payload(). Patch by Claude Paroz.

bpo-24277 [https://bugs.python.org/issue?@action=redirect&bpo=24277]: The new email API is no longer provisional, and the docs have been reorganized and rewritten to emphasize the new API.

bpo-22450 [https://bugs.python.org/issue?@action=redirect&bpo=22450]: urllib now includes an Accept: */* header among the default headers. This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved.

lib2to3.pgen3.driver.load_grammar() now creates a stable cache file between runs given the same Grammar.txt input regardless of the hash randomization setting.

bpo-28005 [https://bugs.python.org/issue?@action=redirect&bpo=28005]: Allow ImportErrors in encoding implementation to propagate.

bpo-26667 [https://bugs.python.org/issue?@action=redirect&bpo=26667]: Support path-like objects in importlib.util.

bpo-27570 [https://bugs.python.org/issue?@action=redirect&bpo=27570]: Avoid zero-length memcpy() etc calls with null source pointers in the "ctypes" and "array" modules.

bpo-22233 [https://bugs.python.org/issue?@action=redirect&bpo=22233]: Break email header lines only on the RFC specified CR and LF characters, not on arbitrary unicode line breaks. This also fixes a bug in HTTP header parsing.

bpo-27331 [https://bugs.python.org/issue?@action=redirect&bpo=27331]: The email.mime classes now all accept an optional policy keyword.

bpo-27988 [https://bugs.python.org/issue?@action=redirect&bpo=27988]: Fix email iter_attachments incorrect mutation of payload list.

bpo-16113 [https://bugs.python.org/issue?@action=redirect&bpo=16113]: Add SHA-3 and SHAKE support to hashlib module.

Eliminate a tautological-pointer-compare warning in _scproxy.c.

bpo-27776 [https://bugs.python.org/issue?@action=redirect&bpo=27776]: The os.urandom() function does now block on Linux 3.17 and newer until the system urandom entropy pool is initialized to increase the security. This change is part of the PEP 524 [https://peps.python.org/pep-0524/].

bpo-27778 [https://bugs.python.org/issue?@action=redirect&bpo=27778]: Expose the Linux getrandom() syscall as a new os.getrandom() function. This change is part of the PEP 524 [https://peps.python.org/pep-0524/].

bpo-27691 [https://bugs.python.org/issue?@action=redirect&bpo=27691]: Fix ssl module's parsing of GEN_RID subject alternative name fields in X.509 certs.

bpo-18844 [https://bugs.python.org/issue?@action=redirect&bpo=18844]: Add random.choices().

bpo-25761 [https://bugs.python.org/issue?@action=redirect&bpo=25761]: Improved error reporting about truncated pickle data in C implementation of unpickler. UnpicklingError is now raised instead of AttributeError and ValueError in some cases.

bpo-26798 [https://bugs.python.org/issue?@action=redirect&bpo=26798]: Add BLAKE2 (blake2b and blake2s) to hashlib.

bpo-26032 [https://bugs.python.org/issue?@action=redirect&bpo=26032]: Optimized globbing in pathlib by using os.scandir(); it is now about 1.5--4 times faster.

bpo-25596 [https://bugs.python.org/issue?@action=redirect&bpo=25596]: Optimized glob() and iglob() functions in the glob module; they are now about 3--6 times faster.

bpo-27928 [https://bugs.python.org/issue?@action=redirect&bpo=27928]: Add scrypt (password-based key derivation function) to hashlib module (requires OpenSSL 1.1.0).

bpo-27850 [https://bugs.python.org/issue?@action=redirect&bpo=27850]: Remove 3DES from ssl module's default cipher list to counter measure sweet32 attack (CVE 2016-2183 [https://www.cve.org/CVERecord?id=CVE-2016-2183]).

bpo-27766 [https://bugs.python.org/issue?@action=redirect&bpo=27766]: Add ChaCha20 Poly1305 to ssl module's default cipher list. (Required OpenSSL 1.1.0 or LibreSSL).

bpo-25387 [https://bugs.python.org/issue?@action=redirect&bpo=25387]: Check return value of winsound.MessageBeep.

bpo-27866 [https://bugs.python.org/issue?@action=redirect&bpo=27866]: Add SSLContext.get_ciphers() method to get a list of all enabled ciphers.

bpo-27744 [https://bugs.python.org/issue?@action=redirect&bpo=27744]: Add AF_ALG (Linux Kernel crypto) to socket module.

bpo-26470 [https://bugs.python.org/issue?@action=redirect&bpo=26470]: Port ssl and hashlib module to OpenSSL 1.1.0.

bpo-11620 [https://bugs.python.org/issue?@action=redirect&bpo=11620]: Fix support for SND_MEMORY in winsound.PlaySound. Based on a patch by Tim Lesher.

bpo-11734 [https://bugs.python.org/issue?@action=redirect&bpo=11734]: Add support for IEEE 754 half-precision floats to the struct module. Based on a patch by Eli Stevens.

bpo-27919 [https://bugs.python.org/issue?@action=redirect&bpo=27919]: Deprecated extra_path distribution option in distutils packaging.

bpo-23229 [https://bugs.python.org/issue?@action=redirect&bpo=23229]: Add new cmath constants: cmath.inf and cmath.nan to match math.inf and math.nan, and also cmath.infj and cmath.nanj to match the format used by complex repr.

bpo-27842 [https://bugs.python.org/issue?@action=redirect&bpo=27842]: The csv.DictReader now returns rows of type OrderedDict. (Contributed by Steve Holden.)

Remove support for passing a file descriptor to os.access. It never worked but previously didn't raise.

bpo-12885 [https://bugs.python.org/issue?@action=redirect&bpo=12885]: Fix error when distutils encounters symlink.

bpo-27881 [https://bugs.python.org/issue?@action=redirect&bpo=27881]: Fixed possible bugs when setting sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

bpo-27861 [https://bugs.python.org/issue?@action=redirect&bpo=27861]: Fixed a crash in sqlite3.Connection.cursor() when a factory creates not a cursor. Patch by Xiang Zhang.

bpo-19884 [https://bugs.python.org/issue?@action=redirect&bpo=19884]: Avoid spurious output on OS X with Gnu Readline.

bpo-27706 [https://bugs.python.org/issue?@action=redirect&bpo=27706]: Restore deterministic behavior of random.Random().seed() for string seeds using seeding version 1. Allows sequences of calls to random() to exactly match those obtained in Python 2. Patch by Nofar Schnider.

bpo-10513 [https://bugs.python.org/issue?@action=redirect&bpo=10513]: Fix a regression in Connection.commit(). Statements should not be reset after a commit.

bpo-12319 [https://bugs.python.org/issue?@action=redirect&bpo=12319]: Chunked transfer encoding support added to http.client.HTTPConnection requests. The urllib.request.AbstractHTTPHandler class does not enforce a Content-Length header any more. If a HTTP request has a file or iterable body, but no Content-Length header, the library now falls back to use chunked transfer-encoding.

A new version of typing.py from https://github.com/python/typing: - Collection (only for 3.6) (bpo-27598 [https://bugs.python.org/issue?@action=redirect&bpo=27598]) - Add FrozenSet to __all__ (upstream #261) - fix crash in _get_type_vars() (upstream #259) - Remove the dict constraint in ForwardRef._eval_type (upstream #252)

bpo-27832 [https://bugs.python.org/issue?@action=redirect&bpo=27832]: Make _normalize parameter to Fraction constructor keyword-only, so that Fraction(2, 3, 4) now raises TypeError.

bpo-27539 [https://bugs.python.org/issue?@action=redirect&bpo=27539]: Fix unnormalised Fraction.__pow__ result in the case of negative exponent and negative base.

bpo-21718 [https://bugs.python.org/issue?@action=redirect&bpo=21718]: cursor.description is now available for queries using CTEs.

bpo-27819 [https://bugs.python.org/issue?@action=redirect&bpo=27819]: In distutils sdists, simply produce the "gztar" (gzipped tar format) distributions on all platforms unless "formats" is supplied.

bpo-2466 [https://bugs.python.org/issue?@action=redirect&bpo=2466]: posixpath.ismount now correctly recognizes mount points which the user does not have permission to access.

bpo-9998 [https://bugs.python.org/issue?@action=redirect&bpo=9998]: On Linux, ctypes.util.find_library now looks in LD_LIBRARY_PATH for shared libraries.

bpo-27573 [https://bugs.python.org/issue?@action=redirect&bpo=27573]: exit message for code.interact is now configurable.

bpo-27930 [https://bugs.python.org/issue?@action=redirect&bpo=27930]: Improved behaviour of logging.handlers.QueueListener. Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch.

bpo-6766 [https://bugs.python.org/issue?@action=redirect&bpo=6766]: Distributed reference counting added to multiprocessing to support nesting of shared values / proxy objects.

bpo-21201 [https://bugs.python.org/issue?@action=redirect&bpo=21201]: Improves readability of multiprocessing error message. Thanks to Wojciech Walczak for patch.

asyncio: Add set_protocol / get_protocol to Transports.

bpo-27456 [https://bugs.python.org/issue?@action=redirect&bpo=27456]: asyncio: Set TCP_NODELAY by default.

IDLE

bpo-15308 [https://bugs.python.org/issue?@action=redirect&bpo=15308]: Add 'interrupt execution' (^C) to Shell menu. Patch by Roger Serwy, updated by Bayard Randel.

bpo-27922 [https://bugs.python.org/issue?@action=redirect&bpo=27922]: Stop IDLE tests from 'flashing' gui widgets on the screen.

bpo-27891 [https://bugs.python.org/issue?@action=redirect&bpo=27891]: Consistently group and sort imports within idlelib modules.

bpo-17642 [https://bugs.python.org/issue?@action=redirect&bpo=17642]: add larger font sizes for classroom projection.

Add version to title of IDLE help window.

bpo-25564 [https://bugs.python.org/issue?@action=redirect&bpo=25564]: In section on IDLE -- console differences, mention that using exec means that __builtins__ is defined for each statement.

bpo-27821 [https://bugs.python.org/issue?@action=redirect&bpo=27821]: Fix 3.6.0a3 regression that prevented custom key sets from being selected when no custom theme was defined.

C API

bpo-26900 [https://bugs.python.org/issue?@action=redirect&bpo=26900]: Excluded underscored names and other private API from limited API.

bpo-26027 [https://bugs.python.org/issue?@action=redirect&bpo=26027]: Add support for path-like objects in PyUnicode_FSConverter() & PyUnicode_FSDecoder().

Tests

bpo-27427 [https://bugs.python.org/issue?@action=redirect&bpo=27427]: Additional tests for the math module. Patch by Francisco Couzo.

bpo-27953 [https://bugs.python.org/issue?@action=redirect&bpo=27953]: Skip math and cmath tests that fail on OS X 10.4 due to a poor libm implementation of tan.

bpo-26040 [https://bugs.python.org/issue?@action=redirect&bpo=26040]: Improve test_math and test_cmath coverage and rigour. Patch by Jeff Allen.

bpo-27787 [https://bugs.python.org/issue?@action=redirect&bpo=27787]: Call gc.collect() before checking each test for "dangling threads", since the dangling threads are weak references.

Build

bpo-27566 [https://bugs.python.org/issue?@action=redirect&bpo=27566]: Fix clean target in freeze makefile (patch by Lisa Roach)

bpo-27705 [https://bugs.python.org/issue?@action=redirect&bpo=27705]: Update message in validate_ucrtbase.py

bpo-27976 [https://bugs.python.org/issue?@action=redirect&bpo=27976]: Deprecate building _ctypes with the bundled copy of libffi on non-OSX UNIX platforms.

bpo-27983 [https://bugs.python.org/issue?@action=redirect&bpo=27983]: Cause lack of llvm-profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when --with-optimizations is enabled. Also improve our ability to find the llvm-profdata tool on MacOS and some Linuxes.

bpo-21590 [https://bugs.python.org/issue?@action=redirect&bpo=21590]: Support for DTrace and SystemTap probes.

bpo-26307 [https://bugs.python.org/issue?@action=redirect&bpo=26307]: The profile-opt build now applies PGO to the built-in modules.

bpo-26359 [https://bugs.python.org/issue?@action=redirect&bpo=26359]: Add the --with-optimizations flag to turn on LTO and PGO build support when available.

bpo-27917 [https://bugs.python.org/issue?@action=redirect&bpo=27917]: Set platform triplets for Android builds.

bpo-25825 [https://bugs.python.org/issue?@action=redirect&bpo=25825]: Update references to the $(LIBPL) installation path on AIX. This path was changed in 3.2a4.

Update OS X installer to use SQLite 3.14.1 and XZ 5.2.2.

bpo-21122 [https://bugs.python.org/issue?@action=redirect&bpo=21122]: Fix LTO builds on OS X.

bpo-17128 [https://bugs.python.org/issue?@action=redirect&bpo=17128]: Build OS X installer with a private copy of OpenSSL. Also provide a sample Install Certificates command script to install a set of root certificates from the third-party certifi module.

Tools/Demos

bpo-27952 [https://bugs.python.org/issue?@action=redirect&bpo=27952]: Get Tools/scripts/fixcid.py working with Python 3 and the current "re" module, avoid invalid Python backslash escapes, and fix a bug parsing escaped C quote signs.

Windows

bpo-28065 [https://bugs.python.org/issue?@action=redirect&bpo=28065]: Update xz dependency to 5.2.2 and build it from source.

bpo-25144 [https://bugs.python.org/issue?@action=redirect&bpo=25144]: Ensures TargetDir is set before continuing with custom install.

bpo-1602 [https://bugs.python.org/issue?@action=redirect&bpo=1602]: Windows console doesn't input or print Unicode (PEP 528)

bpo-27781 [https://bugs.python.org/issue?@action=redirect&bpo=27781]: Change file system encoding on Windows to UTF-8 (PEP 529)

bpo-27731 [https://bugs.python.org/issue?@action=redirect&bpo=27731]: Opt-out of MAX_PATH on Windows 10

bpo-6135 [https://bugs.python.org/issue?@action=redirect&bpo=6135]: Adds encoding and errors parameters to subprocess.

bpo-27959 [https://bugs.python.org/issue?@action=redirect&bpo=27959]: Adds oem encoding, alias ansi to mbcs, move aliasmbcs to codec lookup.

bpo-27982 [https://bugs.python.org/issue?@action=redirect&bpo=27982]: The functions of the winsound module now accept keyword arguments.

bpo-20366 [https://bugs.python.org/issue?@action=redirect&bpo=20366]: Build full text search support into SQLite on Windows.

bpo-27756 [https://bugs.python.org/issue?@action=redirect&bpo=27756]: Adds new icons for Python files and processes on Windows. Designs by Cherry Wang.

bpo-27883 [https://bugs.python.org/issue?@action=redirect&bpo=27883]: Update sqlite to 3.14.1.0 on Windows.

Python 3.6.0 alpha 4

Release date: 2016-08-15

Core and Builtins

bpo-27704 [https://bugs.python.org/issue?@action=redirect&bpo=27704]: Optimized creating bytes and bytearray from byte-like objects and iterables. Speed up to 3 times for short objects. Original patch by Naoki Inada.

bpo-26823 [https://bugs.python.org/issue?@action=redirect&bpo=26823]: Large sections of repeated lines in tracebacks are now abbreviated as "[Previous line repeated {count} more times]" by the builtin traceback rendering. Patch by Emanuel Barry.

bpo-27574 [https://bugs.python.org/issue?@action=redirect&bpo=27574]: Decreased an overhead of parsing keyword arguments in functions implemented with using Argument Clinic.

bpo-22557 [https://bugs.python.org/issue?@action=redirect&bpo=22557]: Now importing already imported modules is up to 2.5 times faster.

bpo-17596 [https://bugs.python.org/issue?@action=redirect&bpo=17596]: Include <wincrypt.h> to help with Min GW building.

bpo-17599 [https://bugs.python.org/issue?@action=redirect&bpo=17599]: On Windows, rename the privately defined REPARSE_DATA_BUFFER structure to avoid conflicting with the definition from Min GW.

bpo-27507 [https://bugs.python.org/issue?@action=redirect&bpo=27507]: Add integer overflow check in bytearray.extend(). Patch by Xiang Zhang.

bpo-27581 [https://bugs.python.org/issue?@action=redirect&bpo=27581]: Don't rely on wrapping for overflow check in PySequence_Tuple(). Patch by Xiang Zhang.

bpo-1621 [https://bugs.python.org/issue?@action=redirect&bpo=1621]: Avoid signed integer overflow in list and tuple operations. Patch by Xiang Zhang.

bpo-27419 [https://bugs.python.org/issue?@action=redirect&bpo=27419]: Standard __import__() no longer look up "__import__" in globals or builtins for importing submodules or "from import". Fixed a crash if raise a warning about unabling to resolve package from __spec__ or __package__.

bpo-27083 [https://bugs.python.org/issue?@action=redirect&bpo=27083]: Respect the PYTHONCASEOK environment variable under Windows.

bpo-27514 [https://bugs.python.org/issue?@action=redirect&bpo=27514]: Make having too many statically nested blocks a SyntaxError instead of SystemError.

bpo-27366 [https://bugs.python.org/issue?@action=redirect&bpo=27366]: Implemented PEP 487 [https://peps.python.org/pep-0487/] (Simpler customization of class creation). Upon subclassing, the __init_subclass__ classmethod is called on the base class. Descriptors are initialized with __set_name__ after class creation.

Library

bpo-26027 [https://bugs.python.org/issue?@action=redirect&bpo=26027]: Add PEP 519 [https://peps.python.org/pep-0519/]/__fspath__() support to the os and os.path modules. Includes code from Jelle Zijlstra. (See also: bpo-27524 [https://bugs.python.org/issue?@action=redirect&bpo=27524])

bpo-27598 [https://bugs.python.org/issue?@action=redirect&bpo=27598]: Add Collections to collections.abc. Patch by Ivan Levkivskyi, docs by Neil Girdhar.

bpo-25958 [https://bugs.python.org/issue?@action=redirect&bpo=25958]: Support "anti-registration" of special methods from various ABCs, like __hash__, __iter__ or __len__. All these (and several more) can be set to None in an implementation class and the behavior will be as if the method is not defined at all. (Previously, this mechanism existed only for __hash__, to make mutable classes unhashable.) Code contributed by Andrew Barnert and Ivan Levkivskyi.

bpo-16764 [https://bugs.python.org/issue?@action=redirect&bpo=16764]: Support keyword arguments to zlib.decompress(). Patch by Xiang Zhang.

bpo-27736 [https://bugs.python.org/issue?@action=redirect&bpo=27736]: Prevent segfault after interpreter re-initialization due to ref count problem introduced in code for bpo-27038 [https://bugs.python.org/issue?@action=redirect&bpo=27038] in 3.6.0a3. Patch by Xiang Zhang.

bpo-25628 [https://bugs.python.org/issue?@action=redirect&bpo=25628]: The verbose and rename parameters for collections.namedtuple are now keyword-only.

bpo-12345 [https://bugs.python.org/issue?@action=redirect&bpo=12345]: Add mathematical constant tau to math and cmath. See also PEP 628 [https://peps.python.org/pep-0628/].

bpo-26823 [https://bugs.python.org/issue?@action=redirect&bpo=26823]: traceback.StackSummary.format now abbreviates large sections of repeated lines as "[Previous line repeated {count} more times]" (this change then further affects other traceback display operations in the module). Patch by Emanuel Barry.

bpo-27664 [https://bugs.python.org/issue?@action=redirect&bpo=27664]: Add to concurrent.futures.thread.ThreadPoolExecutor() the ability to specify a thread name prefix.

bpo-27181 [https://bugs.python.org/issue?@action=redirect&bpo=27181]: Add geometric_mean and harmonic_mean to statistics module.

bpo-27573 [https://bugs.python.org/issue?@action=redirect&bpo=27573]: code.interact now prints an message when exiting.

bpo-6422 [https://bugs.python.org/issue?@action=redirect&bpo=6422]: Add autorange method to timeit.Timer objects.

bpo-27773 [https://bugs.python.org/issue?@action=redirect&bpo=27773]: Correct some memory management errors server_hostname in _ssl.wrap_socket().

bpo-26750 [https://bugs.python.org/issue?@action=redirect&bpo=26750]: unittest.mock.create_autospec() now works properly for subclasses of property() and other data descriptors. Removes the never publicly used, never documented unittest.mock.DescriptorTypes tuple.

bpo-26754 [https://bugs.python.org/issue?@action=redirect&bpo=26754]: Undocumented support of general bytes-like objects as path in compile() and similar functions is now deprecated.

bpo-26800 [https://bugs.python.org/issue?@action=redirect&bpo=26800]: Undocumented support of general bytes-like objects as paths in os functions is now deprecated.

bpo-26981 [https://bugs.python.org/issue?@action=redirect&bpo=26981]: Add _order_ compatibility shim to enum.Enum for Python 2/3 code bases.

bpo-27661 [https://bugs.python.org/issue?@action=redirect&bpo=27661]: Added tzinfo keyword argument to datetime.combine.

In the curses module, raise an error if window.getstr() or window.instr() is passed a negative value.

bpo-27783 [https://bugs.python.org/issue?@action=redirect&bpo=27783]: Fix possible usage of uninitialized memory in operator.methodcaller.

bpo-27774 [https://bugs.python.org/issue?@action=redirect&bpo=27774]: Fix possible Py_DECREF on unowned object in _sre.

bpo-27760 [https://bugs.python.org/issue?@action=redirect&bpo=27760]: Fix possible integer overflow in binascii.b2a_qp.

bpo-27758 [https://bugs.python.org/issue?@action=redirect&bpo=27758]: Fix possible integer overflow in the _csv module for large record lengths.

bpo-27568 [https://bugs.python.org/issue?@action=redirect&bpo=27568]: Prevent HTTPoxy attack (CVE 2016-1000110 [https://www.cve.org/CVERecord?id=CVE-2016-1000110]). Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates that the script is in CGI mode.

bpo-7063 [https://bugs.python.org/issue?@action=redirect&bpo=7063]: Remove dead code from the "array" module's slice handling. Patch by Chuck.

bpo-27656 [https://bugs.python.org/issue?@action=redirect&bpo=27656]: Do not assume sched.h defines any SCHED_* constants.

bpo-27130 [https://bugs.python.org/issue?@action=redirect&bpo=27130]: In the "zlib" module, fix handling of large buffers (typically 4 GiB) when compressing and decompressing. Previously, inputs were limited to 4 GiB, and compression and decompression operations did not properly handle results of 4 GiB.

bpo-24773 [https://bugs.python.org/issue?@action=redirect&bpo=24773]: Implemented PEP 495 [https://peps.python.org/pep-0495/] (Local Time Disambiguation).

Expose the EPOLLEXCLUSIVE constant (when it is defined) in the select module.

bpo-27567 [https://bugs.python.org/issue?@action=redirect&bpo=27567]: Expose the EPOLLRDHUP and POLLRDHUP constants in the select module.

bpo-1621 [https://bugs.python.org/issue?@action=redirect&bpo=1621]: Avoid signed int negation overflow in the "audioop" module.

bpo-27533 [https://bugs.python.org/issue?@action=redirect&bpo=27533]: Release GIL in nt._isdir

bpo-17711 [https://bugs.python.org/issue?@action=redirect&bpo=17711]: Fixed unpickling by the persistent ID with protocol 0. Original patch by Alexandre Vassalotti.

bpo-27522 [https://bugs.python.org/issue?@action=redirect&bpo=27522]: Avoid an unintentional reference cycle in email.feedparser.

bpo-27512 [https://bugs.python.org/issue?@action=redirect&bpo=27512]: Fix a segfault when os.fspath() called an __fspath__() method that raised an exception. Patch by Xiang Zhang.

IDLE

bpo-27714 [https://bugs.python.org/issue?@action=redirect&bpo=27714]: text_textview and test_autocomplete now pass when re-run in the same process. This occurs when test_idle fails when run with the -w option but without -jn. Fix warning from test_config.

bpo-27621 [https://bugs.python.org/issue?@action=redirect&bpo=27621]: Put query response validation error messages in the query box itself instead of in a separate messagebox. Redo tests to match. Add Mac OSX refinements. Original patch by Mark Roseman.

bpo-27620 [https://bugs.python.org/issue?@action=redirect&bpo=27620]: Escape key now closes Query box as cancelled.

bpo-27609 [https://bugs.python.org/issue?@action=redirect&bpo=27609]: IDLE: tab after initial whitespace should tab, not autocomplete. This fixes problem with writing docstrings at least twice indented.

bpo-27609 [https://bugs.python.org/issue?@action=redirect&bpo=27609]: Explicitly return None when there are also non-None returns. In a few cases, reverse a condition and eliminate a return.

bpo-25507 [https://bugs.python.org/issue?@action=redirect&bpo=25507]: IDLE no longer runs buggy code because of its tkinter imports. Users must include the same imports required to run directly in Python.

bpo-27173 [https://bugs.python.org/issue?@action=redirect&bpo=27173]: Add 'IDLE Modern Unix' to the built-in key sets. Make the default key set depend on the platform. Add tests for the changes to the config module.

bpo-27452 [https://bugs.python.org/issue?@action=redirect&bpo=27452]: add line counter and crc to IDLE configHandler test dump.

Tests

bpo-25805 [https://bugs.python.org/issue?@action=redirect&bpo=25805]: Skip a test in test_pkgutil as needed that doesn't work when __name__ == __main__. Patch by SilentGhost.

bpo-27472 [https://bugs.python.org/issue?@action=redirect&bpo=27472]: Add test.support.unix_shell as the path to the default shell.

bpo-27369 [https://bugs.python.org/issue?@action=redirect&bpo=27369]: In test_pyexpat, avoid testing an error message detail that changed in Expat 2.2.0.

bpo-27594 [https://bugs.python.org/issue?@action=redirect&bpo=27594]: Prevent assertion error when running test_ast with coverage enabled: ensure code object has a valid first line number. Patch suggested by Ivan Levkivskyi.

Windows

bpo-27647 [https://bugs.python.org/issue?@action=redirect&bpo=27647]: Update bundled Tcl/Tk to 8.6.6.

bpo-27610 [https://bugs.python.org/issue?@action=redirect&bpo=27610]: Adds PEP 514 [https://peps.python.org/pep-0514/] metadata to Windows installer

bpo-27469 [https://bugs.python.org/issue?@action=redirect&bpo=27469]: Adds a shell extension to the launcher so that drag and drop works correctly.

bpo-27309 [https://bugs.python.org/issue?@action=redirect&bpo=27309]: Enables proper Windows styles in python[w].exe manifest.

Build

bpo-27713 [https://bugs.python.org/issue?@action=redirect&bpo=27713]: Suppress spurious build warnings when updating importlib's bootstrap files. Patch by Xiang Zhang

bpo-25825 [https://bugs.python.org/issue?@action=redirect&bpo=25825]: Correct the references to Modules/python.exp, which is required on AIX. The references were accidentally changed in 3.5.0a1.

bpo-27453 [https://bugs.python.org/issue?@action=redirect&bpo=27453]: CPP invocation in configure must use CPPFLAGS. Patch by Chi Hsuan Yen.

bpo-27641 [https://bugs.python.org/issue?@action=redirect&bpo=27641]: The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross-compiled.

bpo-26662 [https://bugs.python.org/issue?@action=redirect&bpo=26662]: Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build.

bpo-10910 [https://bugs.python.org/issue?@action=redirect&bpo=10910]: Avoid C++ compilation errors on FreeBSD and OS X. Also update FreedBSD version checks for the original ctype UTF-8 workaround.

Python 3.6.0 alpha 3

Release date: 2016-07-11

Security

bpo-27278 [https://bugs.python.org/issue?@action=redirect&bpo=27278]: Fix os.urandom() implementation using getrandom() on Linux. Truncate size to INT_MAX and loop until we collected enough random bytes, instead of casting a directly Py_ssize_t to int.

bpo-22636 [https://bugs.python.org/issue?@action=redirect&bpo=22636]: Avoid shell injection problems with ctypes.util.find_library().

Core and Builtins

bpo-27473 [https://bugs.python.org/issue?@action=redirect&bpo=27473]: Fixed possible integer overflow in bytes and bytearray concatenations. Patch by Xiang Zhang.

bpo-23034 [https://bugs.python.org/issue?@action=redirect&bpo=23034]: The output of a special Python build with defined COUNT_ALLOCS, SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default. It can be re-enabled using the "-X showalloccount" option. It now outputs to stderr instead of stdout.

bpo-27443 [https://bugs.python.org/issue?@action=redirect&bpo=27443]: __length_hint__() of bytearray iterators no longer return a negative integer for a resized bytearray.

bpo-27007 [https://bugs.python.org/issue?@action=redirect&bpo=27007]: The fromhex() class methods of bytes and bytearray subclasses now return an instance of corresponding subclass.

Library

bpo-26844 [https://bugs.python.org/issue?@action=redirect&bpo=26844]: Fix error message for imp.find_module() to refer to 'path' instead of 'name'. Patch by Lev Maximov.

bpo-23804 [https://bugs.python.org/issue?@action=redirect&bpo=23804]: Fix SSL zero-length recv() calls to not block and not raise an error about unclean EOF.

bpo-27466 [https://bugs.python.org/issue?@action=redirect&bpo=27466]: Change time format returned by http.cookie.time2netscape, confirming the netscape cookie format and making it consistent with documentation.

bpo-21708 [https://bugs.python.org/issue?@action=redirect&bpo=21708]: Deprecated dbm.dumb behavior that differs from common dbm behavior: creating a database in 'r' and 'w' modes and modifying a database in 'r' mode.

bpo-26721 [https://bugs.python.org/issue?@action=redirect&bpo=26721]: Change the socketserver.StreamRequestHandler.wfile attribute to implement BufferedIOBase. In particular, the write() method no longer does partial writes.

bpo-22115 [https://bugs.python.org/issue?@action=redirect&bpo=22115]: Added methods trace_add, trace_remove and trace_info in the tkinter.Variable class. They replace old methods trace_variable, trace, trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not work in future versions of Tcl. Fixed old tracing methods: trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now always returns a list of pairs of strings, tracing in the "u" mode now works.

bpo-26243 [https://bugs.python.org/issue?@action=redirect&bpo=26243]: Only the level argument to zlib.compress() is keyword argument now. The first argument is positional-only.

bpo-27038 [https://bugs.python.org/issue?@action=redirect&bpo=27038]: Expose the DirEntry type as os.DirEntry. Code patch by Jelle Zijlstra.

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Update os.fspath()/PyOS_FSPath() to check the return value of __fspath__() to be either str or bytes.

bpo-18726 [https://bugs.python.org/issue?@action=redirect&bpo=18726]: All optional parameters of the dump(), dumps(), load() and loads() functions and JSONEncoder and JSONDecoder class constructors in the json module are now keyword-only.

bpo-27319 [https://bugs.python.org/issue?@action=redirect&bpo=27319]: Methods selection_set(), selection_add(), selection_remove() and selection_toggle() of ttk.TreeView now allow passing multiple items as multiple arguments instead of passing them as a tuple. Deprecated undocumented ability of calling the selection() method with arguments.

bpo-27079 [https://bugs.python.org/issue?@action=redirect&bpo=27079]: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().

bpo-27294 [https://bugs.python.org/issue?@action=redirect&bpo=27294]: Numerical state in the repr for Tkinter event objects is now represented as a combination of known flags.

bpo-27177 [https://bugs.python.org/issue?@action=redirect&bpo=27177]: Match objects in the re module now support index-like objects as group indices. Based on patches by Jeroen Demeyer and Xiang Zhang.

bpo-26754 [https://bugs.python.org/issue?@action=redirect&bpo=26754]: Some functions (compile() etc) accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

bpo-26536 [https://bugs.python.org/issue?@action=redirect&bpo=26536]: socket.ioctl now supports SIO_LOOPBACK_FAST_PATH. Patch by Daniel Stokes.

bpo-27048 [https://bugs.python.org/issue?@action=redirect&bpo=27048]: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

bpo-27330 [https://bugs.python.org/issue?@action=redirect&bpo=27330]: Fixed possible leaks in the ctypes module.

bpo-27238 [https://bugs.python.org/issue?@action=redirect&bpo=27238]: Got rid of bare excepts in the turtle module. Original patch by Jelle Zijlstra.

bpo-27122 [https://bugs.python.org/issue?@action=redirect&bpo=27122]: When an exception is raised within the context being managed by a contextlib.ExitStack() and one of the exit stack generators catches and raises it in a chain, do not re-raise the original exception when exiting, let the new chained one through. This avoids the PEP 479 [https://peps.python.org/pep-0479/] bug described in issue25782.

bpo-16864 [https://bugs.python.org/issue?@action=redirect&bpo=16864]: sqlite3.Cursor.lastrowid now supports REPLACE statement. Initial patch by Alex LordThorsen.

bpo-26386 [https://bugs.python.org/issue?@action=redirect&bpo=26386]: Fixed ttk.TreeView selection operations with item id's containing spaces.

bpo-8637 [https://bugs.python.org/issue?@action=redirect&bpo=8637]: Honor a pager set by the env var MANPAGER (in preference to one set by the env var PAGER).

bpo-16182 [https://bugs.python.org/issue?@action=redirect&bpo=16182]: Fix various functions in the "readline" module to use the locale encoding, and fix get_begidx() and get_endidx() to return code point indexes.

bpo-27392 [https://bugs.python.org/issue?@action=redirect&bpo=27392]: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

IDLE

bpo-27477 [https://bugs.python.org/issue?@action=redirect&bpo=27477]: IDLE search dialogs now use ttk widgets.

bpo-27173 [https://bugs.python.org/issue?@action=redirect&bpo=27173]: Add 'IDLE Modern Unix' to the built-in key sets. Make the default key set depend on the platform. Add tests for the changes to the config module.

bpo-27452 [https://bugs.python.org/issue?@action=redirect&bpo=27452]: make command line "idle-test> python test_help.py" work. __file__ is relative when python is started in the file's directory.

bpo-27452 [https://bugs.python.org/issue?@action=redirect&bpo=27452]: add line counter and crc to IDLE configHandler test dump.

bpo-27380 [https://bugs.python.org/issue?@action=redirect&bpo=27380]: IDLE: add query.py with base Query dialog and ttk widgets. Module had subclasses SectionName, ModuleName, and HelpSource, which are used to get information from users by configdialog and file =>Load Module. Each subclass has itw own validity checks. Using ModuleName allows users to edit bad module names instead of starting over. Add tests and delete the two files combined into the new one.

bpo-27372 [https://bugs.python.org/issue?@action=redirect&bpo=27372]: Test_idle no longer changes the locale.

bpo-27365 [https://bugs.python.org/issue?@action=redirect&bpo=27365]: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

bpo-27245 [https://bugs.python.org/issue?@action=redirect&bpo=27245]: IDLE: Cleanly delete custom themes and key bindings. Previously, when IDLE was started from a console or by import, a cascade of warnings was emitted. Patch by Serhiy Storchaka.

bpo-24137 [https://bugs.python.org/issue?@action=redirect&bpo=24137]: Run IDLE, test_idle, and htest with tkinter default root disabled. Fix code and tests that fail with this restriction. Fix htests to not create a second and redundant root and mainloop.

bpo-27310 [https://bugs.python.org/issue?@action=redirect&bpo=27310]: Fix IDLE.app failure to launch on OS X due to vestigial import.

C API

bpo-26754 [https://bugs.python.org/issue?@action=redirect&bpo=26754]: PyUnicode_FSDecoder() accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

Build

bpo-28066 [https://bugs.python.org/issue?@action=redirect&bpo=28066]: Fix the logic that searches build directories for generated include files when building outside the source tree.

bpo-27442 [https://bugs.python.org/issue?@action=redirect&bpo=27442]: Expose the Android API level that python was built against, in sysconfig.get_config_vars() as 'ANDROID_API_LEVEL'.

bpo-27434 [https://bugs.python.org/issue?@action=redirect&bpo=27434]: The interpreter that runs the cross-build, found in PATH, must now be of the same feature version (e.g. 3.6) as the source being built.

bpo-26930 [https://bugs.python.org/issue?@action=redirect&bpo=26930]: Update Windows builds to use OpenSSL 1.0.2h.

bpo-23968 [https://bugs.python.org/issue?@action=redirect&bpo=23968]: Rename the platform directory from plat-$(MACHDEP) to plat-$(PLATFORM_TRIPLET). Rename the config directory (LIBPL) from config-$(LDVERSION) to config-$(LDVERSION)-$(PLATFORM_TRIPLET). Install the platform specific _sysconfigdata module into the platform directory and rename it to include the ABIFLAGS.

Don't use largefile support for GNU/Hurd.

Tools/Demos

bpo-27332 [https://bugs.python.org/issue?@action=redirect&bpo=27332]: Fixed the type of the first argument of module-level functions generated by Argument Clinic. Patch by Petr Viktorin.

bpo-27418 [https://bugs.python.org/issue?@action=redirect&bpo=27418]: Fixed Tools/importbench/importbench.py.

Documentation

bpo-19489 [https://bugs.python.org/issue?@action=redirect&bpo=19489]: Moved the search box from the sidebar to the header and footer of each page. Patch by Ammar Askar.

bpo-27285 [https://bugs.python.org/issue?@action=redirect&bpo=27285]: Update documentation to reflect the deprecation of pyvenv and normalize on the term "virtual environment". Patch by Steve Piercy.

Tests

bpo-27027 [https://bugs.python.org/issue?@action=redirect&bpo=27027]: Added test.support.is_android that is True when this is an Android build.

Python 3.6.0 alpha 2

Release date: 2016-06-13

Security

bpo-26556 [https://bugs.python.org/issue?@action=redirect&bpo=26556]: Update expat to 2.1.1, fixes CVE 2015-1283 [https://www.cve.org/CVERecord?id=CVE-2015-1283].

Fix TLS stripping vulnerability in smtplib, CVE 2016-0772 [https://www.cve.org/CVERecord?id=CVE-2016-0772]. Reported by Team Oststrom.

bpo-26839 [https://bugs.python.org/issue?@action=redirect&bpo=26839]: On Linux, os.urandom() now calls getrandom() with GRND_NONBLOCK to fall back on reading /dev/urandom if the urandom entropy pool is not initialized yet. Patch written by Colm Buckley.

Core and Builtins

bpo-27095 [https://bugs.python.org/issue?@action=redirect&bpo=27095]: Simplified MAKE_FUNCTION and removed MAKE_CLOSURE opcodes. Patch by Demur Rumed.

bpo-27190 [https://bugs.python.org/issue?@action=redirect&bpo=27190]: Raise NotSupportedError if sqlite3 is older than 3.3.1. Patch by Dave Sawyer.

bpo-27286 [https://bugs.python.org/issue?@action=redirect&bpo=27286]: Fixed compiling BUILD_MAP_UNPACK_WITH_CALL opcode. Calling function with generalized unpacking (PEP 448) and conflicting keyword names could cause undefined behavior.

bpo-27140 [https://bugs.python.org/issue?@action=redirect&bpo=27140]: Added BUILD_CONST_KEY_MAP opcode.

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Add support for os.PathLike objects to open() (part of PEP 519 [https://peps.python.org/pep-0519/]).

bpo-27066 [https://bugs.python.org/issue?@action=redirect&bpo=27066]: Fixed SystemError if a custom opener (for open()) returns a negative number without setting an exception.

bpo-26983 [https://bugs.python.org/issue?@action=redirect&bpo=26983]: float() now always return an instance of exact float. The deprecation warning is emitted if __float__ returns an instance of a strict subclass of float. In a future versions of Python this can be an error.

bpo-27097 [https://bugs.python.org/issue?@action=redirect&bpo=27097]: Python interpreter is now about 7% faster due to optimized instruction decoding. Based on patch by Demur Rumed.

bpo-26647 [https://bugs.python.org/issue?@action=redirect&bpo=26647]: Python interpreter now uses 16-bit wordcode instead of bytecode. Patch by Demur Rumed.

bpo-23275 [https://bugs.python.org/issue?@action=redirect&bpo=23275]: Allow assigning to an empty target list in round brackets: () = iterable.

bpo-27243 [https://bugs.python.org/issue?@action=redirect&bpo=27243]: Update the __aiter__ protocol: instead of returning an awaitable that resolves to an asynchronous iterator, the asynchronous iterator should be returned directly. Doing the former will trigger a PendingDeprecationWarning.

Library

Comment out socket (SO_REUSEPORT) and posix (O_SHLOCK, O_EXLOCK) constants exposed on the API which are not implemented on GNU/Hurd. They would not work at runtime anyway.

bpo-27025 [https://bugs.python.org/issue?@action=redirect&bpo=27025]: Generated names for Tkinter widgets are now more meaningful and recognizable.

bpo-25455 [https://bugs.python.org/issue?@action=redirect&bpo=25455]: Fixed crashes in repr of recursive ElementTree.Element and functools.partial objects.

bpo-27294 [https://bugs.python.org/issue?@action=redirect&bpo=27294]: Improved repr for Tkinter event objects.

bpo-20508 [https://bugs.python.org/issue?@action=redirect&bpo=20508]: Improve exception message of IPv{4,6}Network.__getitem__. Patch by Gareth Rees.

bpo-21386 [https://bugs.python.org/issue?@action=redirect&bpo=21386]: Implement missing IPv4Address.is_global property. It was documented since 07a5610bae9d. Initial patch by Roger Luethi.

bpo-27029 [https://bugs.python.org/issue?@action=redirect&bpo=27029]: Removed deprecated support of universal newlines mode from ZipFile.open().

bpo-27030 [https://bugs.python.org/issue?@action=redirect&bpo=27030]: Unknown escapes consisting of '\' and an ASCII letter in regular expressions now are errors. The re.LOCALE flag now can be used only with bytes patterns.

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Add os.PathLike support to DirEntry (part of PEP 519 [https://peps.python.org/pep-0519/]). Initial patch by Jelle Zijlstra.

bpo-20900 [https://bugs.python.org/issue?@action=redirect&bpo=20900]: distutils register command now decodes HTTP responses correctly. Initial patch by ingrid.

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Add os.PathLike support to pathlib, removing its provisional status (part of PEP 519). Initial patch by Dusty Phillips.

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Add support for os.PathLike objects to os.fsencode() and os.fsdecode() (part of PEP 519 [https://peps.python.org/pep-0519/]).

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Introduce os.PathLike and os.fspath() (part of PEP 519 [https://peps.python.org/pep-0519/]).

A new version of typing.py provides several new classes and features: @overload outside stubs, Reversible, DefaultDict, Text, ContextManager, Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some of the new features are not yet implemented in mypy or other static analyzers). Also classes for PEP 492 [https://peps.python.org/pep-0492/] (Awaitable, AsyncIterable, AsyncIterator) have been added (in fact they made it into 3.5.1 but were never mentioned).

bpo-25738 [https://bugs.python.org/issue?@action=redirect&bpo=25738]: Stop http.server.BaseHTTPRequestHandler.send_error() from sending a message body for 205 Reset Content. Also, don't send Content header fields in responses that don't have a body. Patch by Susumu Koshiba.

bpo-21313 [https://bugs.python.org/issue?@action=redirect&bpo=21313]: Fix the "platform" module to tolerate when sys.version contains truncated build information.

bpo-23883 [https://bugs.python.org/issue?@action=redirect&bpo=23883]: Added missing APIs to __all__ to match the documented APIs for the following modules: cgi, mailbox, mimetypes, plistlib and smtpd. Patches by Jacek Kołodziej.

bpo-27164 [https://bugs.python.org/issue?@action=redirect&bpo=27164]: In the zlib module, allow decompressing raw Deflate streams with a predefined zdict. Based on patch by Xiang Zhang.

bpo-24291 [https://bugs.python.org/issue?@action=redirect&bpo=24291]: Fix wsgiref.simple_server.WSGIRequestHandler to completely write data to the client. Previously it could do partial writes and truncate data. Also, wsgiref.handler.ServerHandler can now handle stdout doing partial writes, but this is deprecated.

bpo-21272 [https://bugs.python.org/issue?@action=redirect&bpo=21272]: Use _sysconfigdata.py to initialize distutils.sysconfig.

bpo-19611 [https://bugs.python.org/issue?@action=redirect&bpo=19611]: inspect now reports the implicit .0 parameters generated by the compiler for comprehension and generator expression scopes as if they were positional-only parameters called implicit0. Patch by Jelle Zijlstra.

bpo-26809 [https://bugs.python.org/issue?@action=redirect&bpo=26809]: Add __all__ to string. Patch by Emanuel Barry.

bpo-26373 [https://bugs.python.org/issue?@action=redirect&bpo=26373]: subprocess.Popen.communicate now correctly ignores BrokenPipeError when the child process dies before .communicate() is called in more/all circumstances.

signal, socket, and ssl module IntEnum constant name lookups now return a consistent name for values having multiple names. Ex: signal.Signals(6) now refers to itself as signal.SIGALRM rather than flipping between that and signal.SIGIOT based on the interpreter's hash randomization seed.

bpo-27167 [https://bugs.python.org/issue?@action=redirect&bpo=27167]: Clarify the subprocess.CalledProcessError error message text when the child process died due to a signal.

bpo-25931 [https://bugs.python.org/issue?@action=redirect&bpo=25931]: Don't define socketserver.Forking* names on platforms such as Windows that do not support os.fork().

bpo-21776 [https://bugs.python.org/issue?@action=redirect&bpo=21776]: distutils.upload now correctly handles HTTPError. Initial patch by Claudiu Popa.

bpo-26526 [https://bugs.python.org/issue?@action=redirect&bpo=26526]: Replace custom parse tree validation in the parser module with a simple DFA validator.

bpo-27114 [https://bugs.python.org/issue?@action=redirect&bpo=27114]: Fix SSLContext._load_windows_store_certs fails with PermissionError

bpo-18383 [https://bugs.python.org/issue?@action=redirect&bpo=18383]: Avoid creating duplicate filters when using filterwarnings and simplefilter. Based on patch by Alex Shkop.

bpo-23026 [https://bugs.python.org/issue?@action=redirect&bpo=23026]: winreg.QueryValueEx() now return an integer for REG_QWORD type.

bpo-26741 [https://bugs.python.org/issue?@action=redirect&bpo=26741]: subprocess.Popen destructor now emits a ResourceWarning warning if the child process is still running.

bpo-27056 [https://bugs.python.org/issue?@action=redirect&bpo=27056]: Optimize pickle.load() and pickle.loads(), up to 10% faster to deserialize a lot of small objects.

bpo-21271 [https://bugs.python.org/issue?@action=redirect&bpo=21271]: New keyword only parameters in reset_mock call.

IDLE

bpo-5124 [https://bugs.python.org/issue?@action=redirect&bpo=5124]: Paste with text selected now replaces the selection on X11. This matches how paste works on Windows, Mac, most modern Linux apps, and ttk widgets. Original patch by Serhiy Storchaka.

bpo-24750 [https://bugs.python.org/issue?@action=redirect&bpo=24750]: Switch all scrollbars in IDLE to ttk versions. Where needed, minimal tests are added to cover changes.

bpo-24759 [https://bugs.python.org/issue?@action=redirect&bpo=24759]: IDLE requires tk 8.5 and availability ttk widgets. Delete now unneeded tk version tests and code for older versions. Add test for IDLE syntax colorizer.

bpo-27239 [https://bugs.python.org/issue?@action=redirect&bpo=27239]: idlelib.macosx.isXyzTk functions initialize as needed.

bpo-27262 [https://bugs.python.org/issue?@action=redirect&bpo=27262]: move Aqua unbinding code, which enable context menus, to macosx.

bpo-24759 [https://bugs.python.org/issue?@action=redirect&bpo=24759]: Make clear in idlelib.idle_test.__init__ that the directory is a private implementation of test.test_idle and tool for maintainers.

bpo-27196 [https://bugs.python.org/issue?@action=redirect&bpo=27196]: Stop 'ThemeChanged' warnings when running IDLE tests. These persisted after other warnings were suppressed in #20567. Apply Serhiy Storchaka's update_idletasks solution to four test files. Record this additional advice in idle_test/README.txt

bpo-20567 [https://bugs.python.org/issue?@action=redirect&bpo=20567]: Revise idle_test/README.txt with advice about avoiding tk warning messages from tests. Apply advice to several IDLE tests.

bpo-24225 [https://bugs.python.org/issue?@action=redirect&bpo=24225]: Update idlelib/README.txt with new file names and event handlers.

bpo-27156 [https://bugs.python.org/issue?@action=redirect&bpo=27156]: Remove obsolete code not used by IDLE.

bpo-27117 [https://bugs.python.org/issue?@action=redirect&bpo=27117]: Make colorizer htest and turtledemo work with dark themes. Move code for configuring text widget colors to a new function.

bpo-24225 [https://bugs.python.org/issue?@action=redirect&bpo=24225]: Rename many idlelib/*.py and idle_test/test_*.py files. Edit files to replace old names with new names when the old name referred to the module rather than the class it contained. See the issue and IDLE section in What's New in 3.6 for more.

bpo-26673 [https://bugs.python.org/issue?@action=redirect&bpo=26673]: When tk reports font size as 0, change to size 10. Such fonts on Linux prevented the configuration dialog from opening.

bpo-21939 [https://bugs.python.org/issue?@action=redirect&bpo=21939]: Add test for IDLE's percolator. Original patch by Saimadhav Heblikar.

bpo-21676 [https://bugs.python.org/issue?@action=redirect&bpo=21676]: Add test for IDLE's replace dialog. Original patch by Saimadhav Heblikar.

bpo-18410 [https://bugs.python.org/issue?@action=redirect&bpo=18410]: Add test for IDLE's search dialog. Original patch by Westley Martínez.

bpo-21703 [https://bugs.python.org/issue?@action=redirect&bpo=21703]: Add test for undo delegator. Patch mostly by Saimadhav Heblikar .

bpo-27044 [https://bugs.python.org/issue?@action=redirect&bpo=27044]: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

bpo-23977 [https://bugs.python.org/issue?@action=redirect&bpo=23977]: Add more asserts to test_delegator.

Documentation

bpo-16484 [https://bugs.python.org/issue?@action=redirect&bpo=16484]: Change the default PYTHONDOCS URL to "https:", and fix the resulting links to use lowercase. Patch by Sean Rodman, test by Kaushik Nadikuditi.

bpo-24136 [https://bugs.python.org/issue?@action=redirect&bpo=24136]: Document the new PEP 448 [https://peps.python.org/pep-0448/] unpacking syntax of 3.5.

bpo-22558 [https://bugs.python.org/issue?@action=redirect&bpo=22558]: Add remaining doc links to source code for Python-coded modules. Patch by Yoni Lavi.

Tests

bpo-25285 [https://bugs.python.org/issue?@action=redirect&bpo=25285]: regrtest now uses subprocesses when the -j1 command line option is used: each test file runs in a fresh child process. Before, the -j1 option was ignored.

bpo-25285 [https://bugs.python.org/issue?@action=redirect&bpo=25285]: Tools/buildbot/test.bat script now uses -j1 by default to run each test file in fresh child process.

Windows

bpo-27064 [https://bugs.python.org/issue?@action=redirect&bpo=27064]: The py.exe launcher now defaults to Python 3. The Windows launcher py.exe no longer prefers an installed Python 2 version over Python 3 by default when used interactively.

bpo-17500 [https://bugs.python.org/issue?@action=redirect&bpo=17500]: Remove unused and outdated icons. (See also: https://github.com/python/pythondotorg/issues/945)

Build

bpo-27229 [https://bugs.python.org/issue?@action=redirect&bpo=27229]: Fix the cross-compiling pgen rule for in-tree builds. Patch by Xavier de Gaye.

bpo-26930 [https://bugs.python.org/issue?@action=redirect&bpo=26930]: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2h.

C API

bpo-27186 [https://bugs.python.org/issue?@action=redirect&bpo=27186]: Add the PyOS_FSPath() function (part of PEP 519 [https://peps.python.org/pep-0519/]).

bpo-26282 [https://bugs.python.org/issue?@action=redirect&bpo=26282]: PyArg_ParseTupleAndKeywords() now supports positional-only parameters.

Tools/Demos

bpo-26282 [https://bugs.python.org/issue?@action=redirect&bpo=26282]: Argument Clinic now supports positional-only and keyword parameters in the same function.

Python 3.6.0 alpha 1

Release date: 2016-05-16

Security

bpo-26657 [https://bugs.python.org/issue?@action=redirect&bpo=26657]: Fix directory traversal vulnerability with http.server on Windows. This fixes a regression that was introduced in 3.3.4rc1 and 3.4.0rc1. Based on patch by Philipp Hagemeister.

bpo-26313 [https://bugs.python.org/issue?@action=redirect&bpo=26313]: ssl.py _load_windows_store_certs fails if windows cert store is empty. Patch by Baji.

bpo-25939 [https://bugs.python.org/issue?@action=redirect&bpo=25939]: On Windows open the cert store readonly in ssl.enum_certificates.

Core and Builtins

bpo-20041 [https://bugs.python.org/issue?@action=redirect&bpo=20041]: Fixed TypeError when frame.f_trace is set to None. Patch by Xavier de Gaye.

bpo-26168 [https://bugs.python.org/issue?@action=redirect&bpo=26168]: Fixed possible refleaks in failing Py_BuildValue() with the "N" format unit.

bpo-26991 [https://bugs.python.org/issue?@action=redirect&bpo=26991]: Fix possible refleak when creating a function with annotations.

bpo-27039 [https://bugs.python.org/issue?@action=redirect&bpo=27039]: Fixed bytearray.remove() for values greater than 127. Based on patch by Joe Jevnik.

bpo-23640 [https://bugs.python.org/issue?@action=redirect&bpo=23640]: int.from_bytes() no longer bypasses constructors for subclasses.

bpo-27005 [https://bugs.python.org/issue?@action=redirect&bpo=27005]: Optimized the float.fromhex() class method for exact float. It is now 2 times faster.

bpo-18531 [https://bugs.python.org/issue?@action=redirect&bpo=18531]: Single var-keyword argument of dict subtype was passed unscathed to the C-defined function. Now it is converted to exact dict.

bpo-26811 [https://bugs.python.org/issue?@action=redirect&bpo=26811]: gc.get_objects() no longer contains a broken tuple with NULL pointer.

bpo-20120 [https://bugs.python.org/issue?@action=redirect&bpo=20120]: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.

bpo-26249 [https://bugs.python.org/issue?@action=redirect&bpo=26249]: Memory functions of the PyMem_Malloc() domain (PYMEM_DOMAIN_MEM) now use the pymalloc allocator rather than system malloc(). Applications calling PyMem_Malloc() without holding the GIL can now crash: use PYTHONMALLOC=debug environment variable to validate the usage of memory allocators in your application.

bpo-26802 [https://bugs.python.org/issue?@action=redirect&bpo=26802]: Optimize function calls only using unpacking like func(*tuple) (no other positional argument, no keyword): avoid copying the tuple. Patch written by Joe Jevnik.

bpo-26659 [https://bugs.python.org/issue?@action=redirect&bpo=26659]: Make the builtin slice type support cycle collection.

bpo-26718 [https://bugs.python.org/issue?@action=redirect&bpo=26718]: super.__init__ no longer leaks memory if called multiple times. NOTE: A direct call of super.__init__ is not endorsed!

bpo-27138 [https://bugs.python.org/issue?@action=redirect&bpo=27138]: Fix the doc comment for FileFinder.find_spec().

bpo-27147 [https://bugs.python.org/issue?@action=redirect&bpo=27147]: Mention PEP 420 [https://peps.python.org/pep-0420/] in the importlib docs.

bpo-25339 [https://bugs.python.org/issue?@action=redirect&bpo=25339]: PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout.

bpo-26494 [https://bugs.python.org/issue?@action=redirect&bpo=26494]: Fixed crash on iterating exhausting iterators. Affected classes are generic sequence iterators, iterators of str, bytes, bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding views and os.scandir() iterator.

bpo-26574 [https://bugs.python.org/issue?@action=redirect&bpo=26574]: Optimize bytes.replace(b'', b'.') and bytearray.replace(b'', b'.'). Patch written by Josh Snider.

bpo-26581 [https://bugs.python.org/issue?@action=redirect&bpo=26581]: If coding cookie is specified multiple times on a line in Python source code file, only the first one is taken to account.

bpo-19711 [https://bugs.python.org/issue?@action=redirect&bpo=19711]: Add tests for reloading namespace packages.

bpo-21099 [https://bugs.python.org/issue?@action=redirect&bpo=21099]: Switch applicable importlib tests to use PEP 451 [https://peps.python.org/pep-0451/] API.

bpo-26563 [https://bugs.python.org/issue?@action=redirect&bpo=26563]: Debug hooks on Python memory allocators now raise a fatal error if functions of the PyMem_Malloc() family are called without holding the GIL.

bpo-26564 [https://bugs.python.org/issue?@action=redirect&bpo=26564]: On error, the debug hooks on Python memory allocators now use the tracemalloc module to get the traceback where a memory block was allocated.

bpo-26558 [https://bugs.python.org/issue?@action=redirect&bpo=26558]: The debug hooks on Python memory allocator PyObject_Malloc() now detect when functions are called without holding the GIL.

bpo-26516 [https://bugs.python.org/issue?@action=redirect&bpo=26516]: Add PYTHONMALLOC environment variable to set the Python memory allocators and/or install debug hooks.

bpo-26516 [https://bugs.python.org/issue?@action=redirect&bpo=26516]: The PyMem_SetupDebugHooks() function can now also be used on Python compiled in release mode.

bpo-26516 [https://bugs.python.org/issue?@action=redirect&bpo=26516]: The PYTHONMALLOCSTATS environment variable can now also be used on Python compiled in release mode. It now has no effect if set to an empty string.

bpo-26516 [https://bugs.python.org/issue?@action=redirect&bpo=26516]: In debug mode, debug hooks are now also installed on Python memory allocators when Python is configured without pymalloc.

bpo-26464 [https://bugs.python.org/issue?@action=redirect&bpo=26464]: Fix str.translate() when string is ASCII and first replacements removes character, but next replacement uses a non-ASCII character or a string longer than 1 character. Regression introduced in Python 3.5.0.

bpo-22836 [https://bugs.python.org/issue?@action=redirect&bpo=22836]: Ensure exception reports from PyErr_Display() and PyErr_WriteUnraisable() are sensible even when formatting them produces secondary errors. This affects the reports produced by sys.__excepthook__() and when __del__() raises an exception.

bpo-26302 [https://bugs.python.org/issue?@action=redirect&bpo=26302]: Correct behavior to reject comma as a legal character for cookie names.

bpo-26136 [https://bugs.python.org/issue?@action=redirect&bpo=26136]: Upgrade the warning when a generator raises StopIteration from PendingDeprecationWarning to DeprecationWarning. Patch by Anish Shah.

bpo-26204 [https://bugs.python.org/issue?@action=redirect&bpo=26204]: The compiler now ignores all constant statements: bytes, str, int, float, complex, name constants (None, False, True), Ellipsis and ast.Constant; not only str and int. For example, 1.0 is now ignored in def f(): 1.0.

bpo-4806 [https://bugs.python.org/issue?@action=redirect&bpo=4806]: Avoid masking the original TypeError exception when using star (*) unpacking in function calls. Based on patch by Hagen Fürstenau and Daniel Urban.

bpo-26146 [https://bugs.python.org/issue?@action=redirect&bpo=26146]: Add a new kind of AST node: ast.Constant. It can be used by external AST optimizers, but the compiler does not emit directly such node.

bpo-23601 [https://bugs.python.org/issue?@action=redirect&bpo=23601]: Sped-up allocation of dict key objects by using Python's small object allocator. (Contributed by Julian Taylor.)

bpo-18018 [https://bugs.python.org/issue?@action=redirect&bpo=18018]: Import raises ImportError instead of SystemError if a relative import is attempted without a known parent package.

bpo-25843 [https://bugs.python.org/issue?@action=redirect&bpo=25843]: When compiling code, don't merge constants if they are equal but have a different types. For example, f1, f2 = lambda: 1, lambda: 1.0 is now correctly compiled to two different functions: f1() returns 1 (int) and f2() returns 1.0 (float), even if 1 and 1.0 are equal.

bpo-26107 [https://bugs.python.org/issue?@action=redirect&bpo=26107]: The format of the co_lnotab attribute of code objects changes to support negative line number delta.

bpo-26154 [https://bugs.python.org/issue?@action=redirect&bpo=26154]: Add a new private _PyThreadState_UncheckedGet() function to get the current Python thread state, but don't issue a fatal error if it is NULL. This new function must be used instead of accessing directly the _PyThreadState_Current variable. The variable is no more exposed since Python 3.5.1 to hide the exact implementation of atomic C types, to avoid compiler issues.

bpo-25791 [https://bugs.python.org/issue?@action=redirect&bpo=25791]: If __package__ != __spec__.parent or if neither __package__ or __spec__ are defined then ImportWarning is raised.

bpo-22995 [https://bugs.python.org/issue?@action=redirect&bpo=22995]: [UPDATE] Comment out the one of the pickleability tests in _PyObject_GetState() due to regressions observed in Cython-based projects.

bpo-25961 [https://bugs.python.org/issue?@action=redirect&bpo=25961]: Disallowed null characters in the type name.

bpo-25973 [https://bugs.python.org/issue?@action=redirect&bpo=25973]: Fix segfault when an invalid nonlocal statement binds a name starting with two underscores.

bpo-22995 [https://bugs.python.org/issue?@action=redirect&bpo=22995]: Instances of extension types with a state that aren't subclasses of list or dict and haven't implemented any pickle-related methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or __getstate__), can no longer be pickled. Including memoryview.

bpo-20440 [https://bugs.python.org/issue?@action=redirect&bpo=20440]: Massive replacing unsafe attribute setting code with special macro Py_SETREF.

bpo-25766 [https://bugs.python.org/issue?@action=redirect&bpo=25766]: Special method __bytes__() now works in str subclasses.

bpo-25421 [https://bugs.python.org/issue?@action=redirect&bpo=25421]: __sizeof__ methods of builtin types now use dynamic basic size. This allows sys.getsize() to work correctly with their subclasses with __slots__ defined.

bpo-25709 [https://bugs.python.org/issue?@action=redirect&bpo=25709]: Fixed problem with in-place string concatenation and utf-8 cache.

bpo-5319 [https://bugs.python.org/issue?@action=redirect&bpo=5319]: New Py_FinalizeEx() API allowing Python to set an exit status of 120 on failure to flush buffered streams.

bpo-25485 [https://bugs.python.org/issue?@action=redirect&bpo=25485]: telnetlib.Telnet is now a context manager.

bpo-24097 [https://bugs.python.org/issue?@action=redirect&bpo=24097]: Fixed crash in object.__reduce__() if slot name is freed inside __getattr__.

bpo-24731 [https://bugs.python.org/issue?@action=redirect&bpo=24731]: Fixed crash on converting objects with special methods __bytes__, __trunc__, and __float__ returning instances of subclasses of bytes, int, and float to subclasses of bytes, int, and float correspondingly.

bpo-25630 [https://bugs.python.org/issue?@action=redirect&bpo=25630]: Fix a possible segfault during argument parsing in functions that accept filesystem paths.

bpo-23564 [https://bugs.python.org/issue?@action=redirect&bpo=23564]: Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child. The bug had no actual impact as subprocess.py already avoided it.

bpo-25388 [https://bugs.python.org/issue?@action=redirect&bpo=25388]: Fixed tokenizer crash when processing undecodable source code with a null byte.

bpo-25462 [https://bugs.python.org/issue?@action=redirect&bpo=25462]: The hash of the key now is calculated only once in most operations in C implementation of OrderedDict.

bpo-22995 [https://bugs.python.org/issue?@action=redirect&bpo=22995]: Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__.

bpo-24802 [https://bugs.python.org/issue?@action=redirect&bpo=24802]: Avoid buffer overreads when int(), float(), compile(), exec() and eval() are passed bytes-like objects. These objects are not necessarily terminated by a null byte, but the functions assumed they were.

bpo-25555 [https://bugs.python.org/issue?@action=redirect&bpo=25555]: Fix parser and AST: fill lineno and col_offset of "arg" node when compiling AST from Python objects.

bpo-24726 [https://bugs.python.org/issue?@action=redirect&bpo=24726]: Fixed a crash and leaking NULL in repr() of OrderedDict that was mutated by direct calls of dict methods.

bpo-25449 [https://bugs.python.org/issue?@action=redirect&bpo=25449]: Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation.

bpo-25395 [https://bugs.python.org/issue?@action=redirect&bpo=25395]: Fixed crash when highly nested OrderedDict structures were garbage collected.

bpo-25401 [https://bugs.python.org/issue?@action=redirect&bpo=25401]: Optimize bytes.fromhex() and bytearray.fromhex(): they are now between 2x and 3.5x faster.

bpo-25399 [https://bugs.python.org/issue?@action=redirect&bpo=25399]: Optimize bytearray % args using the new private _PyBytesWriter API. Formatting is now between 2.5 and 5 times faster.

bpo-25274 [https://bugs.python.org/issue?@action=redirect&bpo=25274]: sys.setrecursionlimit() now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth. Modify also the "lower-water mark" formula to make it monotonic. This mark is used to decide when the overflowed flag of the thread state is reset.

bpo-24402 [https://bugs.python.org/issue?@action=redirect&bpo=24402]: Fix input() to prompt to the redirected stdout when sys.stdout.fileno() fails.

bpo-25349 [https://bugs.python.org/issue?@action=redirect&bpo=25349]: Optimize bytes % args using the new private _PyBytesWriter API. Formatting is now up to 2 times faster.

bpo-24806 [https://bugs.python.org/issue?@action=redirect&bpo=24806]: Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance.

bpo-25301 [https://bugs.python.org/issue?@action=redirect&bpo=25301]: The UTF-8 decoder is now up to 15 times as fast for error handlers: ignore, replace and surrogateescape.

bpo-24848 [https://bugs.python.org/issue?@action=redirect&bpo=24848]: Fixed a number of bugs in UTF-7 decoding of misformed data.

bpo-25267 [https://bugs.python.org/issue?@action=redirect&bpo=25267]: The UTF-8 encoder is now up to 75 times as fast for error handlers: ignore, replace, surrogateescape, surrogatepass. Patch co-written with Serhiy Storchaka.

bpo-25280 [https://bugs.python.org/issue?@action=redirect&bpo=25280]: Import trace messages emitted in verbose (-v) mode are no longer formatted twice.

bpo-25227 [https://bugs.python.org/issue?@action=redirect&bpo=25227]: Optimize ASCII and latin1 encoders with the surrogateescape error handler: the encoders are now up to 3 times as fast. Initial patch written by Serhiy Storchaka.

bpo-25003 [https://bugs.python.org/issue?@action=redirect&bpo=25003]: On Solaris 11.3 or newer, os.urandom() now uses the getrandom() function instead of the getentropy() function. The getentropy() function is blocking to generate very good quality entropy, os.urandom() doesn't need such high-quality entropy.

bpo-9232 [https://bugs.python.org/issue?@action=redirect&bpo=9232]: Modify Python's grammar to allow trailing commas in the argument list of a function declaration. For example, "def f(*, a = 3,): pass" is now legal. Patch from Mark Dickinson.

bpo-24965 [https://bugs.python.org/issue?@action=redirect&bpo=24965]: Implement PEP 498 [https://peps.python.org/pep-0498/] "Literal String Interpolation". This allows you to embed expressions inside f-strings, which are converted to normal strings at run time. Given x=3, then f'value={x}' == 'value=3'. Patch by Eric V. Smith.

bpo-26478 [https://bugs.python.org/issue?@action=redirect&bpo=26478]: Fix semantic bugs when using binary operators with dictionary views and tuples.

bpo-26171 [https://bugs.python.org/issue?@action=redirect&bpo=26171]: Fix possible integer overflow and heap corruption in zipimporter.get_data().

bpo-25660 [https://bugs.python.org/issue?@action=redirect&bpo=25660]: Fix TAB key behaviour in REPL with readline.

bpo-26288 [https://bugs.python.org/issue?@action=redirect&bpo=26288]: Optimize PyLong_AsDouble.

bpo-26289 [https://bugs.python.org/issue?@action=redirect&bpo=26289]: Optimize floor and modulo division for single-digit longs. Microbenchmarks show 2-2.5x improvement. Built-in 'divmod' function is now also ~10% faster. (See also: bpo-26315 [https://bugs.python.org/issue?@action=redirect&bpo=26315])

bpo-25887 [https://bugs.python.org/issue?@action=redirect&bpo=25887]: Raise a RuntimeError when a coroutine object is awaited more than once.

Library

bpo-27057 [https://bugs.python.org/issue?@action=redirect&bpo=27057]: Fix os.set_inheritable() on Android, ioctl() is blocked by SELinux and fails with EACCESS. The function now falls back to fcntl(). Patch written by Michał Bednarski.

bpo-27014 [https://bugs.python.org/issue?@action=redirect&bpo=27014]: Fix infinite recursion using typing.py. Thanks to Kalle Tuure!

bpo-27031 [https://bugs.python.org/issue?@action=redirect&bpo=27031]: Removed dummy methods in Tkinter widget classes: tk_menuBar() and tk_bindForTraversal().

bpo-14132 [https://bugs.python.org/issue?@action=redirect&bpo=14132]: Fix urllib.request redirect handling when the target only has a query string. Original fix by Ján Janech.

bpo-17214 [https://bugs.python.org/issue?@action=redirect&bpo=17214]: The "urllib.request" module now percent-encodes non-ASCII bytes found in redirect target URLs. Some servers send Location header fields with non-ASCII bytes, but "http.client" requires the request target to be ASCII-encodable, otherwise a UnicodeEncodeError is raised. Based on patch by Christian Heimes.

bpo-27033 [https://bugs.python.org/issue?@action=redirect&bpo=27033]: The default value of the decode_data parameter for smtpd.SMTPChannel and smtpd.SMTPServer constructors is changed to False.

bpo-27034 [https://bugs.python.org/issue?@action=redirect&bpo=27034]: Removed deprecated class asynchat.fifo.

bpo-26870 [https://bugs.python.org/issue?@action=redirect&bpo=26870]: Added readline.set_auto_history(), which can stop entries being automatically added to the history list. Based on patch by Tyler Crompton.

bpo-26039 [https://bugs.python.org/issue?@action=redirect&bpo=26039]: zipfile.ZipFile.open() can now be used to write data into a ZIP file, as well as for extracting data. Patch by Thomas Kluyver.

bpo-26892 [https://bugs.python.org/issue?@action=redirect&bpo=26892]: Honor debuglevel flag in urllib.request.HTTPHandler. Patch contributed by Chi Hsuan Yen.

bpo-22274 [https://bugs.python.org/issue?@action=redirect&bpo=22274]: In the subprocess module, allow stderr to be redirected to stdout even when stdout is not redirected. Patch by Akira Li.

bpo-26807 [https://bugs.python.org/issue?@action=redirect&bpo=26807]: mock_open 'files' no longer error on readline at end of file. Patch from Yolanda Robla.

bpo-25745 [https://bugs.python.org/issue?@action=redirect&bpo=25745]: Fixed leaking a userptr in curses panel destructor.

bpo-26977 [https://bugs.python.org/issue?@action=redirect&bpo=26977]: Removed unnecessary, and ignored, call to sum of squares helper in statistics.pvariance.

bpo-26002 [https://bugs.python.org/issue?@action=redirect&bpo=26002]: Use bisect in statistics.median instead of a linear search. Patch by Upendra Kuma.

bpo-25974 [https://bugs.python.org/issue?@action=redirect&bpo=25974]: Make use of new Decimal.as_integer_ratio() method in statistics module. Patch by Stefan Krah.

bpo-26996 [https://bugs.python.org/issue?@action=redirect&bpo=26996]: Add secrets module as described in PEP 506 [https://peps.python.org/pep-0506/].

bpo-26881 [https://bugs.python.org/issue?@action=redirect&bpo=26881]: The modulefinder module now supports extended opcode arguments.

bpo-23815 [https://bugs.python.org/issue?@action=redirect&bpo=23815]: Fixed crashes related to directly created instances of types in _tkinter and curses.panel modules.

bpo-17765 [https://bugs.python.org/issue?@action=redirect&bpo=17765]: weakref.ref() no longer silently ignores keyword arguments. Patch by Georg Brandl.

bpo-26873 [https://bugs.python.org/issue?@action=redirect&bpo=26873]: xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result.

bpo-26915 [https://bugs.python.org/issue?@action=redirect&bpo=26915]: The __contains__ methods in the collections ABCs now check for identity before checking equality. This better matches the behavior of the concrete classes, allows sensible handling of NaNs, and makes it easier to reason about container invariants.

bpo-26711 [https://bugs.python.org/issue?@action=redirect&bpo=26711]: Fixed the comparison of plistlib.Data with other types.

bpo-24114 [https://bugs.python.org/issue?@action=redirect&bpo=24114]: Fix an uninitialized variable in ctypes.util. The bug only occurs on SunOS when the ctypes implementation searches for the crle program. Patch by Xiang Zhang. Tested on SunOS by Kees Bos.

bpo-26864 [https://bugs.python.org/issue?@action=redirect&bpo=26864]: In urllib.request, change the proxy bypass host checking against no_proxy to be case-insensitive, and to not match unrelated host names that happen to have a bypassed hostname as a suffix. Patch by Xiang Zhang.

bpo-24902 [https://bugs.python.org/issue?@action=redirect&bpo=24902]: Print server URL on http.server startup. Initial patch by Felix Kaiser.

bpo-25788 [https://bugs.python.org/issue?@action=redirect&bpo=25788]: fileinput.hook_encoded() now supports an "errors" argument for passing to open. Original patch by Joseph Hackman.

bpo-26634 [https://bugs.python.org/issue?@action=redirect&bpo=26634]: recursive_repr() now sets __qualname__ of wrapper. Patch by Xiang Zhang.

bpo-26804 [https://bugs.python.org/issue?@action=redirect&bpo=26804]: urllib.request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones. Patch contributed by Hans-Peter Jansen.

bpo-26837 [https://bugs.python.org/issue?@action=redirect&bpo=26837]: assertSequenceEqual() now correctly outputs non-stringified differing items (like bytes in the -b mode). This affects assertListEqual() and assertTupleEqual().

bpo-26041 [https://bugs.python.org/issue?@action=redirect&bpo=26041]: Remove "will be removed in Python 3.7" from deprecation messages of platform.dist() and platform.linux_distribution(). Patch by Kumaripaba Miyurusara Athukorala.

bpo-26822 [https://bugs.python.org/issue?@action=redirect&bpo=26822]: itemgetter, attrgetter and methodcaller objects no longer silently ignore keyword arguments.

bpo-26733 [https://bugs.python.org/issue?@action=redirect&bpo=26733]: Disassembling a class now disassembles class and static methods. Patch by Xiang Zhang.

bpo-26801 [https://bugs.python.org/issue?@action=redirect&bpo=26801]: Fix error handling in shutil.get_terminal_size(), catch AttributeError instead of NameError. Patch written by Emanuel Barry.

bpo-24838 [https://bugs.python.org/issue?@action=redirect&bpo=24838]: tarfile's ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf-8.

bpo-26717 [https://bugs.python.org/issue?@action=redirect&bpo=26717]: Stop encoding Latin-1-ized WSGI paths with UTF-8. Patch by Anthony Sottile.

bpo-26782 [https://bugs.python.org/issue?@action=redirect&bpo=26782]: Add STARTUPINFO to subprocess.__all__ on Windows.

bpo-26404 [https://bugs.python.org/issue?@action=redirect&bpo=26404]: Add context manager to socketserver. Patch by Aviv Palivoda.

bpo-26735 [https://bugs.python.org/issue?@action=redirect&bpo=26735]: Fix os.urandom() on Solaris 11.3 and newer when reading more than 1,024 bytes: call getrandom() multiple times with a limit of 1024 bytes per call.

bpo-26585 [https://bugs.python.org/issue?@action=redirect&bpo=26585]: Eliminate http.server._quote_html() and use html.escape(quote=False). Patch by Xiang Zhang.

bpo-26685 [https://bugs.python.org/issue?@action=redirect&bpo=26685]: Raise OSError if closing a socket fails.

bpo-16329 [https://bugs.python.org/issue?@action=redirect&bpo=16329]: Add .webm to mimetypes.types_map. Patch by Giampaolo Rodola'.

bpo-13952 [https://bugs.python.org/issue?@action=redirect&bpo=13952]: Add .csv to mimetypes.types_map. Patch by Geoff Wilson.

bpo-26587 [https://bugs.python.org/issue?@action=redirect&bpo=26587]: the site module now allows .pth files to specify files to be added to sys.path (e.g. zip files).

bpo-25609 [https://bugs.python.org/issue?@action=redirect&bpo=25609]: Introduce contextlib.AbstractContextManager and typing.ContextManager.

bpo-26709 [https://bugs.python.org/issue?@action=redirect&bpo=26709]: Fixed Y2038 problem in loading binary PLists.

bpo-23735 [https://bugs.python.org/issue?@action=redirect&bpo=23735]: Handle terminal resizing with Readline 6.3+ by installing our own SIGWINCH handler. Patch by Eric Price.

bpo-25951 [https://bugs.python.org/issue?@action=redirect&bpo=25951]: Change SSLSocket.sendall() to return None, as explicitly documented for plain socket objects. Patch by Aviv Palivoda.

bpo-26586 [https://bugs.python.org/issue?@action=redirect&bpo=26586]: In http.server, respond with "413 Request header fields too large" if there are too many header fields to parse, rather than killing the connection and raising an unhandled exception. Patch by Xiang Zhang.

bpo-26676 [https://bugs.python.org/issue?@action=redirect&bpo=26676]: Added missing XMLPullParser to ElementTree.__all__.

bpo-22854 [https://bugs.python.org/issue?@action=redirect&bpo=22854]: Change BufferedReader.writable() and BufferedWriter.readable() to always return False.

bpo-26492 [https://bugs.python.org/issue?@action=redirect&bpo=26492]: Exhausted iterator of array.array now conforms with the behavior of iterators of other mutable sequences: it lefts exhausted even if iterated array is extended.

bpo-26641 [https://bugs.python.org/issue?@action=redirect&bpo=26641]: doctest.DocFileTest and doctest.testfile() now support packages (module split into multiple directories) for the package parameter.

bpo-25195 [https://bugs.python.org/issue?@action=redirect&bpo=25195]: Fix a regression in mock.MagicMock. _Call is a subclass of tuple (changeset 3603bae63c13 only works for classes) so we need to implement __ne__ ourselves. Patch by Andrew Plummer.

bpo-26644 [https://bugs.python.org/issue?@action=redirect&bpo=26644]: Raise ValueError rather than SystemError when a negative length is passed to SSLSocket.recv() or read().

bpo-23804 [https://bugs.python.org/issue?@action=redirect&bpo=23804]: Fix SSL recv(0) and read(0) methods to return zero bytes instead of up to 1024.

bpo-26616 [https://bugs.python.org/issue?@action=redirect&bpo=26616]: Fixed a bug in datetime.astimezone() method.

bpo-26637 [https://bugs.python.org/issue?@action=redirect&bpo=26637]: The importlib module now emits an ImportError rather than a TypeError if __import__() is tried during the Python shutdown process but sys.path is already cleared (set to None).

bpo-21925 [https://bugs.python.org/issue?@action=redirect&bpo=21925]: warnings.formatwarning() now catches exceptions when calling linecache.getline() and tracemalloc.get_object_traceback() to be able to log ResourceWarning emitted late during the Python shutdown process.

bpo-23848 [https://bugs.python.org/issue?@action=redirect&bpo=23848]: On Windows, faulthandler.enable() now also installs an exception handler to dump the traceback of all Python threads on any Windows exception, not only on UNIX signals (SIGSEGV, SIGFPE, SIGABRT).

bpo-26530 [https://bugs.python.org/issue?@action=redirect&bpo=26530]: Add C functions _PyTraceMalloc_Track() and _PyTraceMalloc_Untrack() to track memory blocks using the tracemalloc module. Add _PyTraceMalloc_GetTraceback() to get the traceback of an object.

bpo-26588 [https://bugs.python.org/issue?@action=redirect&bpo=26588]: The _tracemalloc now supports tracing memory allocations of multiple address spaces (domains).

bpo-24266 [https://bugs.python.org/issue?@action=redirect&bpo=24266]: Ctrl+C during Readline history search now cancels the search mode when compiled with Readline 7.

bpo-26590 [https://bugs.python.org/issue?@action=redirect&bpo=26590]: Implement a safe finalizer for the _socket.socket type. It now releases the GIL to close the socket.

bpo-18787 [https://bugs.python.org/issue?@action=redirect&bpo=18787]: spwd.getspnam() now raises a PermissionError if the user doesn't have privileges.

bpo-26560 [https://bugs.python.org/issue?@action=redirect&bpo=26560]: Avoid potential ValueError in BaseHandler.start_response. Initial patch by Peter Inglesby.

bpo-26567 [https://bugs.python.org/issue?@action=redirect&bpo=26567]: Add a new function PyErr_ResourceWarning() function to pass the destroyed object. Add a source attribute to warnings.WarningMessage. Add warnings._showwarnmsg() which uses tracemalloc to get the traceback where source object was allocated.

bpo-26569 [https://bugs.python.org/issue?@action=redirect&bpo=26569]: Fix pyclbr.readmodule() and pyclbr.readmodule_ex() to support importing packages.

bpo-26499 [https://bugs.python.org/issue?@action=redirect&bpo=26499]: Account for remaining Content-Length in HTTPResponse.readline() and read1(). Based on patch by Silent Ghost. Also document that HTTPResponse now supports these methods.

bpo-25320 [https://bugs.python.org/issue?@action=redirect&bpo=25320]: Handle sockets in directories unittest discovery is scanning. Patch from Victor van den Elzen.

bpo-16181 [https://bugs.python.org/issue?@action=redirect&bpo=16181]: cookiejar.http2time() now returns None if year is higher than datetime.MAXYEAR.

bpo-26513 [https://bugs.python.org/issue?@action=redirect&bpo=26513]: Fixes platform module detection of Windows Server

bpo-23718 [https://bugs.python.org/issue?@action=redirect&bpo=23718]: Fixed parsing time in week 0 before Jan 1. Original patch by Tamás Bence Gedai.

bpo-26323 [https://bugs.python.org/issue?@action=redirect&bpo=26323]: Add Mock.assert_called() and Mock.assert_called_once() methods to unittest.mock. Patch written by Amit Saha.

bpo-20589 [https://bugs.python.org/issue?@action=redirect&bpo=20589]: Invoking Path.owner() and Path.group() on Windows now raise NotImplementedError instead of ImportError.

bpo-26177 [https://bugs.python.org/issue?@action=redirect&bpo=26177]: Fixed the keys() method for Canvas and Scrollbar widgets.

bpo-15068 [https://bugs.python.org/issue?@action=redirect&bpo=15068]: Got rid of excessive buffering in fileinput. The bufsize parameter is now deprecated and ignored.

bpo-19475 [https://bugs.python.org/issue?@action=redirect&bpo=19475]: Added an optional argument timespec to the datetime isoformat() method to choose the precision of the time component.

bpo-2202 [https://bugs.python.org/issue?@action=redirect&bpo=2202]: Fix UnboundLocalError in AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu Dupuy.

bpo-26167 [https://bugs.python.org/issue?@action=redirect&bpo=26167]: Minimized overhead in copy.copy() and copy.deepcopy(). Optimized copying and deepcopying bytearrays, NotImplemented, slices, short lists, tuples, dicts, sets.

bpo-25718 [https://bugs.python.org/issue?@action=redirect&bpo=25718]: Fixed pickling and copying the accumulate() iterator with total is None.

bpo-26475 [https://bugs.python.org/issue?@action=redirect&bpo=26475]: Fixed debugging output for regular expressions with the (?x) flag.

bpo-26482 [https://bugs.python.org/issue?@action=redirect&bpo=26482]: Allowed pickling recursive dequeues.

bpo-26335 [https://bugs.python.org/issue?@action=redirect&bpo=26335]: Make mmap.write() return the number of bytes written like other write methods. Patch by Jakub Stasiak.

bpo-26457 [https://bugs.python.org/issue?@action=redirect&bpo=26457]: Fixed the subnets() methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length. Based on patch by Xiang Zhang.

bpo-26385 [https://bugs.python.org/issue?@action=redirect&bpo=26385]: Remove the file if the internal open() call in NamedTemporaryFile() fails. Patch by Silent Ghost.

bpo-26402 [https://bugs.python.org/issue?@action=redirect&bpo=26402]: Fix XML-RPC client to retry when the server shuts down a persistent connection. This was a regression related to the new http.client.RemoteDisconnected exception in 3.5.0a4.

bpo-25913 [https://bugs.python.org/issue?@action=redirect&bpo=25913]: Leading <~ is optional now in base64.a85decode() with adobe=True. Patch by Swati Jaiswal.

bpo-26186 [https://bugs.python.org/issue?@action=redirect&bpo=26186]: Remove an invalid type check in importlib.util.LazyLoader.

bpo-26367 [https://bugs.python.org/issue?@action=redirect&bpo=26367]: importlib.__import__() raises ImportError like builtins.__import__() when level is specified but without an accompanying package specified.

bpo-26309 [https://bugs.python.org/issue?@action=redirect&bpo=26309]: In the "socketserver" module, shut down the request (closing the connected socket) when verify_request() returns false. Patch by Aviv Palivoda.

bpo-23430 [https://bugs.python.org/issue?@action=redirect&bpo=23430]: Change the socketserver module to only catch exceptions raised from a request handler that are derived from Exception (instead of BaseException). Therefore SystemExit and KeyboardInterrupt no longer trigger the handle_error() method, and will now to stop a single-threaded server.

bpo-25995 [https://bugs.python.org/issue?@action=redirect&bpo=25995]: os.walk() no longer uses FDs proportional to the tree depth.

bpo-25994 [https://bugs.python.org/issue?@action=redirect&bpo=25994]: Added the close() method and the support of the context manager protocol for the os.scandir() iterator.

bpo-23992 [https://bugs.python.org/issue?@action=redirect&bpo=23992]: multiprocessing: make MapResult not fail-fast upon exception.

bpo-26243 [https://bugs.python.org/issue?@action=redirect&bpo=26243]: Support keyword arguments to zlib.compress(). Patch by Aviv Palivoda.

bpo-26117 [https://bugs.python.org/issue?@action=redirect&bpo=26117]: The os.scandir() iterator now closes file descriptor not only when the iteration is finished, but when it was failed with error.

bpo-25949 [https://bugs.python.org/issue?@action=redirect&bpo=25949]: __dict__ for an OrderedDict instance is now created only when needed.

bpo-25911 [https://bugs.python.org/issue?@action=redirect&bpo=25911]: Restored support of bytes paths in os.walk() on Windows.

bpo-26045 [https://bugs.python.org/issue?@action=redirect&bpo=26045]: Add UTF-8 suggestion to error message when posting a non-Latin-1 string with http.client.

bpo-26039 [https://bugs.python.org/issue?@action=redirect&bpo=26039]: Added zipfile.ZipInfo.from_file() and zipinfo.ZipInfo.is_dir(). Patch by Thomas Kluyver.

bpo-12923 [https://bugs.python.org/issue?@action=redirect&bpo=12923]: Reset FancyURLopener's redirect counter even if there is an exception. Based on patches by Brian Brazil and Daniel Rocco.

bpo-25945 [https://bugs.python.org/issue?@action=redirect&bpo=25945]: Fixed a crash when unpickle the functools.partial object with wrong state. Fixed a leak in failed functools.partial constructor. "args" and "keywords" attributes of functools.partial have now always types tuple and dict correspondingly.

bpo-26202 [https://bugs.python.org/issue?@action=redirect&bpo=26202]: copy.deepcopy() now correctly copies range() objects with non-atomic attributes.

bpo-23076 [https://bugs.python.org/issue?@action=redirect&bpo=23076]: Path.glob() now raises a ValueError if it's called with an invalid pattern. Patch by Thomas Nyberg.

bpo-19883 [https://bugs.python.org/issue?@action=redirect&bpo=19883]: Fixed possible integer overflows in zipimport.

bpo-26227 [https://bugs.python.org/issue?@action=redirect&bpo=26227]: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex() functions of the socket module now decode the hostname from the ANSI code page rather than UTF-8.

bpo-26099 [https://bugs.python.org/issue?@action=redirect&bpo=26099]: The site module now writes an error into stderr if sitecustomize module can be imported but executing the module raise an ImportError. Same change for usercustomize.

bpo-26147 [https://bugs.python.org/issue?@action=redirect&bpo=26147]: xmlrpc now works with strings not encodable with used non-UTF-8 encoding.

bpo-25935 [https://bugs.python.org/issue?@action=redirect&bpo=25935]: Garbage collector now breaks reference loops with OrderedDict.

bpo-16620 [https://bugs.python.org/issue?@action=redirect&bpo=16620]: Fixed AttributeError in msilib.Directory.glob().

bpo-26013 [https://bugs.python.org/issue?@action=redirect&bpo=26013]: Added compatibility with broken protocol 2 pickles created in old Python 3 versions (3.4.3 and lower).

bpo-26129 [https://bugs.python.org/issue?@action=redirect&bpo=26129]: Deprecated accepting non-integers in grp.getgrgid().

bpo-25850 [https://bugs.python.org/issue?@action=redirect&bpo=25850]: Use cross-compilation by default for 64-bit Windows.

bpo-25822 [https://bugs.python.org/issue?@action=redirect&bpo=25822]: Add docstrings to the fields of urllib.parse results. Patch contributed by Swati Jaiswal.

bpo-22642 [https://bugs.python.org/issue?@action=redirect&bpo=22642]: Convert trace module option parsing mechanism to argparse. Patch contributed by SilentGhost.

bpo-24705 [https://bugs.python.org/issue?@action=redirect&bpo=24705]: Fix sysconfig._parse_makefile not expanding ${} vars appearing before $() vars.

bpo-26069 [https://bugs.python.org/issue?@action=redirect&bpo=26069]: Remove the deprecated apis in the trace module.

bpo-22138 [https://bugs.python.org/issue?@action=redirect&bpo=22138]: Fix mock.patch behavior when patching descriptors. Restore original values after patching. Patch contributed by Sean McCully.

bpo-25672 [https://bugs.python.org/issue?@action=redirect&bpo=25672]: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so.

bpo-26012 [https://bugs.python.org/issue?@action=redirect&bpo=26012]: Don't traverse into symlinks for ** pattern in pathlib.Path.[r]glob().

bpo-24120 [https://bugs.python.org/issue?@action=redirect&bpo=24120]: Ignore PermissionError when traversing a tree with pathlib.Path.[r]glob(). Patch by Ulrich Petri.

bpo-21815 [https://bugs.python.org/issue?@action=redirect&bpo=21815]: Accept ] characters in the data portion of imap responses, in order to handle the flags with square brackets accepted and produced by servers such as gmail.

bpo-25447 [https://bugs.python.org/issue?@action=redirect&bpo=25447]: fileinput now uses sys.stdin as-is if it does not have a buffer attribute (restores backward compatibility).

bpo-25971 [https://bugs.python.org/issue?@action=redirect&bpo=25971]: Optimized creating Fractions from floats by 2 times and from Decimals by 3 times.

bpo-25802 [https://bugs.python.org/issue?@action=redirect&bpo=25802]: Document as deprecated the remaining implementations of importlib.abc.Loader.load_module().

bpo-25928 [https://bugs.python.org/issue?@action=redirect&bpo=25928]: Add Decimal.as_integer_ratio().

bpo-25447 [https://bugs.python.org/issue?@action=redirect&bpo=25447]: Copying the lru_cache() wrapper object now always works, independently from the type of the wrapped object (by returning the original object unchanged).

bpo-25768 [https://bugs.python.org/issue?@action=redirect&bpo=25768]: Have the functions in compileall return booleans instead of ints and add proper documentation and tests for the return values.

bpo-24103 [https://bugs.python.org/issue?@action=redirect&bpo=24103]: Fixed possible use after free in ElementTree.XMLPullParser.

bpo-25860 [https://bugs.python.org/issue?@action=redirect&bpo=25860]: os.fwalk() no longer skips remaining directories when error occurs. Original patch by Samson Lee.

bpo-25914 [https://bugs.python.org/issue?@action=redirect&bpo=25914]: Fixed and simplified OrderedDict.__sizeof__.

bpo-25869 [https://bugs.python.org/issue?@action=redirect&bpo=25869]: Optimized deepcopying ElementTree; it is now 20 times faster.

bpo-25873 [https://bugs.python.org/issue?@action=redirect&bpo=25873]: Optimized iterating ElementTree. Iterating elements Element.iter() is now 40% faster, iterating text Element.itertext() is now up to 2.5 times faster.

bpo-25902 [https://bugs.python.org/issue?@action=redirect&bpo=25902]: Fixed various refcount issues in ElementTree iteration.

bpo-22227 [https://bugs.python.org/issue?@action=redirect&bpo=22227]: The TarFile iterator is reimplemented using generator. This implementation is simpler that using class.

bpo-25638 [https://bugs.python.org/issue?@action=redirect&bpo=25638]: Optimized ElementTree.iterparse(); it is now 2x faster. Optimized ElementTree parsing; it is now 10% faster.

bpo-25761 [https://bugs.python.org/issue?@action=redirect&bpo=25761]: Improved detecting errors in broken pickle data.

bpo-25717 [https://bugs.python.org/issue?@action=redirect&bpo=25717]: Restore the previous behaviour of tolerating most fstat() errors when opening files. This was a regression in 3.5a1, and stopped anonymous temporary files from working in special cases.

bpo-24903 [https://bugs.python.org/issue?@action=redirect&bpo=24903]: Fix regression in number of arguments compileall accepts when '-d' is specified. The check on the number of arguments has been dropped completely as it never worked correctly anyway.

bpo-25764 [https://bugs.python.org/issue?@action=redirect&bpo=25764]: In the subprocess module, preserve any exception caused by fork() failure when preexec_fn is used.

bpo-25771 [https://bugs.python.org/issue?@action=redirect&bpo=25771]: Tweak the exception message for importlib.util.resolve_name() when 'package' isn't specified but necessary.

bpo-6478 [https://bugs.python.org/issue?@action=redirect&bpo=6478]: _strptime's regexp cache now is reset after changing timezone with time.tzset().

bpo-14285 [https://bugs.python.org/issue?@action=redirect&bpo=14285]: When executing a package with the "python -m package" option, and package initialization fails, a proper traceback is now reported. The "runpy" module now lets exceptions from package initialization pass back to the caller, rather than raising ImportError.

bpo-19771 [https://bugs.python.org/issue?@action=redirect&bpo=19771]: Also in runpy and the "-m" option, omit the irrelevant message ". . . is a package and cannot be directly executed" if the package could not even be initialized (e.g. due to a bad *.pyc file).

bpo-25177 [https://bugs.python.org/issue?@action=redirect&bpo=25177]: Fixed problem with the mean of very small and very large numbers. As a side effect, statistics.mean and statistics.variance should be significantly faster.

bpo-25718 [https://bugs.python.org/issue?@action=redirect&bpo=25718]: Fixed copying object with state with boolean value is false.

bpo-10131 [https://bugs.python.org/issue?@action=redirect&bpo=10131]: Fixed deep copying of minidom documents. Based on patch by Marian Ganisin.

bpo-7990 [https://bugs.python.org/issue?@action=redirect&bpo=7990]: dir() on ElementTree.Element now lists properties: "tag", "text", "tail" and "attrib". Original patch by Santoso Wijaya.

bpo-25725 [https://bugs.python.org/issue?@action=redirect&bpo=25725]: Fixed a reference leak in pickle.loads() when unpickling invalid data including tuple instructions.

bpo-25663 [https://bugs.python.org/issue?@action=redirect&bpo=25663]: In the Readline completer, avoid listing duplicate global names, and search the global namespace before searching builtins.

bpo-25688 [https://bugs.python.org/issue?@action=redirect&bpo=25688]: Fixed file leak in ElementTree.iterparse() raising an error.

bpo-23914 [https://bugs.python.org/issue?@action=redirect&bpo=23914]: Fixed SystemError raised by unpickler on broken pickle data.

bpo-25691 [https://bugs.python.org/issue?@action=redirect&bpo=25691]: Fixed crash on deleting ElementTree.Element attributes.

bpo-25624 [https://bugs.python.org/issue?@action=redirect&bpo=25624]: ZipFile now always writes a ZIP_STORED header for directory entries. Patch by Dingyuan Wang.

bpo-25626 [https://bugs.python.org/issue?@action=redirect&bpo=25626]: Change three zlib functions to accept sizes that fit in Py_ssize_t, but internally cap those sizes to UINT_MAX. This resolves a regression in 3.5 where GzipFile.read() failed to read chunks larger than 2 or 4 GiB. The change affects the zlib.Decompress.decompress() max_length parameter, the zlib.decompress() bufsize parameter, and the zlib.Decompress.flush() length parameter.

bpo-25583 [https://bugs.python.org/issue?@action=redirect&bpo=25583]: Avoid incorrect errors raised by os.makedirs(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

bpo-25593 [https://bugs.python.org/issue?@action=redirect&bpo=25593]: Change semantics of EventLoop.stop() in asyncio.

bpo-6973 [https://bugs.python.org/issue?@action=redirect&bpo=6973]: When we know a subprocess.Popen process has died, do not allow the send_signal(), terminate(), or kill() methods to do anything as they could potentially signal a different process.

bpo-23883 [https://bugs.python.org/issue?@action=redirect&bpo=23883]: Added missing APIs to __all__ to match the documented APIs for the following modules: calendar, csv, enum, fileinput, ftplib, logging, optparse, tarfile, threading and wave. Also added a test.support.check__all__() helper. Patches by Jacek Kołodziej, Mauro S. M. Rodrigues and Joel Taddei.

bpo-25590 [https://bugs.python.org/issue?@action=redirect&bpo=25590]: In the Readline completer, only call getattr() once per attribute. Also complete names of attributes such as properties and slots which are listed by dir() but not yet created on an instance.

bpo-25498 [https://bugs.python.org/issue?@action=redirect&bpo=25498]: Fix a crash when garbage-collecting ctypes objects created by wrapping a memoryview. This was a regression made in 3.5a1. Based on patch by Eryksun.

bpo-25584 [https://bugs.python.org/issue?@action=redirect&bpo=25584]: Added "escape" to the __all__ list in the glob module.

bpo-25584 [https://bugs.python.org/issue?@action=redirect&bpo=25584]: Fixed recursive glob() with patterns starting with **.

bpo-25446 [https://bugs.python.org/issue?@action=redirect&bpo=25446]: Fix regression in smtplib's AUTH LOGIN support.

bpo-18010 [https://bugs.python.org/issue?@action=redirect&bpo=18010]: Fix the pydoc web server's module search function to handle exceptions from importing packages.

bpo-25554 [https://bugs.python.org/issue?@action=redirect&bpo=25554]: Got rid of circular references in regular expression parsing.

bpo-18973 [https://bugs.python.org/issue?@action=redirect&bpo=18973]: Command-line interface of the calendar module now uses argparse instead of optparse.

bpo-25510 [https://bugs.python.org/issue?@action=redirect&bpo=25510]: fileinput.FileInput.readline() now returns b'' instead of '' at the end if the FileInput was opened with binary mode. Patch by Ryosuke Ito.

bpo-25503 [https://bugs.python.org/issue?@action=redirect&bpo=25503]: Fixed inspect.getdoc() for inherited docstrings of properties. Original patch by John Mark Vandenberg.

bpo-25515 [https://bugs.python.org/issue?@action=redirect&bpo=25515]: Always use os.urandom as a source of randomness in uuid.uuid4.

bpo-21827 [https://bugs.python.org/issue?@action=redirect&bpo=21827]: Fixed textwrap.dedent() for the case when largest common whitespace is a substring of smallest leading whitespace. Based on patch by Robert Li.

bpo-25447 [https://bugs.python.org/issue?@action=redirect&bpo=25447]: The lru_cache() wrapper objects now can be copied and pickled (by returning the original object unchanged).

bpo-25390 [https://bugs.python.org/issue?@action=redirect&bpo=25390]: typing: Don't crash on Union[str, Pattern].

bpo-25441 [https://bugs.python.org/issue?@action=redirect&bpo=25441]: asyncio: Raise error from drain() when socket is closed.

bpo-25410 [https://bugs.python.org/issue?@action=redirect&bpo=25410]: Cleaned up and fixed minor bugs in C implementation of OrderedDict.

bpo-25411 [https://bugs.python.org/issue?@action=redirect&bpo=25411]: Improved Unicode support in SMTPHandler through better use of the email package. Thanks to user simon04 for the patch.

Move the imp module from a PendingDeprecationWarning to DeprecationWarning.

bpo-25407 [https://bugs.python.org/issue?@action=redirect&bpo=25407]: Remove mentions of the formatter module being removed in Python 3.6.

bpo-25406 [https://bugs.python.org/issue?@action=redirect&bpo=25406]: Fixed a bug in C implementation of OrderedDict.move_to_end() that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict.

bpo-25382 [https://bugs.python.org/issue?@action=redirect&bpo=25382]: pickletools.dis() now outputs implicit memo index for the MEMOIZE opcode.

bpo-25357 [https://bugs.python.org/issue?@action=redirect&bpo=25357]: Add an optional newline parameter to binascii.b2a_base64(). base64.b64encode() uses it to avoid a memory copy.

bpo-24164 [https://bugs.python.org/issue?@action=redirect&bpo=24164]: Objects that need calling __new__ with keyword arguments, can now be pickled using pickle protocols older than protocol version 4.

bpo-25364 [https://bugs.python.org/issue?@action=redirect&bpo=25364]: zipfile now works in threads disabled builds.

bpo-25328 [https://bugs.python.org/issue?@action=redirect&bpo=25328]: smtpd's SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true.

bpo-16099 [https://bugs.python.org/issue?@action=redirect&bpo=16099]: RobotFileParser now supports Crawl-delay and Request-rate extensions. Patch by Nikolay Bogoychev.

bpo-25316 [https://bugs.python.org/issue?@action=redirect&bpo=25316]: distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed.

bpo-25380 [https://bugs.python.org/issue?@action=redirect&bpo=25380]: Fixed protocol for the STACK_GLOBAL opcode in pickletools.opcodes.

bpo-23972 [https://bugs.python.org/issue?@action=redirect&bpo=23972]: Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket. Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O/S is 'posix' (except if the platform is Cygwin). Patch by Chris Laws.

bpo-25304 [https://bugs.python.org/issue?@action=redirect&bpo=25304]: Add asyncio.run_coroutine_threadsafe(). This lets you submit a coroutine to a loop from another thread, returning a concurrent.futures.Future. By Vincent Michel.

bpo-25232 [https://bugs.python.org/issue?@action=redirect&bpo=25232]: Fix CGIRequestHandler to split the query from the URL at the first question mark (?) rather than the last. Patch from Xiang Zhang.

bpo-24657 [https://bugs.python.org/issue?@action=redirect&bpo=24657]: Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path. Patch from Xiang Zhang.

bpo-25287 [https://bugs.python.org/issue?@action=redirect&bpo=25287]: Don't add crypt.METHOD_CRYPT to crypt.methods if it's not supported. Check if it is supported, it may not be supported on OpenBSD for example.

bpo-23600 [https://bugs.python.org/issue?@action=redirect&bpo=23600]: Default implementation of tzinfo.fromutc() was returning wrong results in some cases.

bpo-25203 [https://bugs.python.org/issue?@action=redirect&bpo=25203]: Failed readline.set_completer_delims() no longer left the module in inconsistent state.

bpo-25011 [https://bugs.python.org/issue?@action=redirect&bpo=25011]: rlcompleter now omits private and special attribute names unless the prefix starts with underscores.

bpo-25209 [https://bugs.python.org/issue?@action=redirect&bpo=25209]: rlcompleter now can add a space or a colon after completed keyword.

bpo-22241 [https://bugs.python.org/issue?@action=redirect&bpo=22241]: timezone.utc name is now plain 'UTC', not 'UTC-00:00'.

bpo-23517 [https://bugs.python.org/issue?@action=redirect&bpo=23517]: fromtimestamp() and utcfromtimestamp() methods of datetime.datetime now round microseconds to nearest with ties going to nearest even integer (ROUND_HALF_EVEN), as round(float), instead of rounding towards -Infinity (ROUND_FLOOR).

bpo-23552 [https://bugs.python.org/issue?@action=redirect&bpo=23552]: Timeit now warns when there is substantial (4x) variance between best and worst times. Patch from Serhiy Storchaka.

bpo-24633 [https://bugs.python.org/issue?@action=redirect&bpo=24633]: site-packages/README -> README.txt.

bpo-24879 [https://bugs.python.org/issue?@action=redirect&bpo=24879]: help() and pydoc can now list named tuple fields in the order they were defined rather than alphabetically. The ordering is determined by the _fields attribute if present.

bpo-24874 [https://bugs.python.org/issue?@action=redirect&bpo=24874]: Improve speed of itertools.cycle() and make its pickle more compact.

Fix crash in itertools.cycle.__setstate__() when the first argument wasn't a list.

bpo-20059 [https://bugs.python.org/issue?@action=redirect&bpo=20059]: urllib.parse raises ValueError on all invalid ports. Patch by Martin Panter.

bpo-24360 [https://bugs.python.org/issue?@action=redirect&bpo=24360]: Improve __repr__ of argparse.Namespace() for invalid identifiers. Patch by Matthias Bussonnier.

bpo-23426 [https://bugs.python.org/issue?@action=redirect&bpo=23426]: run_setup was broken in distutils. Patch from Alexander Belopolsky.

bpo-13938 [https://bugs.python.org/issue?@action=redirect&bpo=13938]: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.

bpo-2091 [https://bugs.python.org/issue?@action=redirect&bpo=2091]: open() accepted a 'U' mode string containing '+', but 'U' can only be used with 'r'. Patch from Jeff Balogh and John O'Connor.

bpo-8585 [https://bugs.python.org/issue?@action=redirect&bpo=8585]: improved tests for zipimporter2. Patch from Mark Lawrence.

bpo-18622 [https://bugs.python.org/issue?@action=redirect&bpo=18622]: unittest.mock.mock_open().reset_mock would recurse infinitely. Patch from Nicola Palumbo and Laurent De Buyst.

bpo-24426 [https://bugs.python.org/issue?@action=redirect&bpo=24426]: Fast searching optimization in regular expressions now works for patterns that starts with capturing groups. Fast searching optimization now can't be disabled at compile time.

bpo-23661 [https://bugs.python.org/issue?@action=redirect&bpo=23661]: unittest.mock side_effects can now be exceptions again. This was a regression vs Python 3.4. Patch from Ignacio Rossi

bpo-13248 [https://bugs.python.org/issue?@action=redirect&bpo=13248]: Remove deprecated inspect.getmoduleinfo function.

bpo-25578 [https://bugs.python.org/issue?@action=redirect&bpo=25578]: Fix (another) memory leak in SSLSocket.getpeercer().

bpo-25530 [https://bugs.python.org/issue?@action=redirect&bpo=25530]: Disable the vulnerable SSLv3 protocol by default when creating ssl.SSLContext.

bpo-25569 [https://bugs.python.org/issue?@action=redirect&bpo=25569]: Fix memory leak in SSLSocket.getpeercert().

bpo-25471 [https://bugs.python.org/issue?@action=redirect&bpo=25471]: Sockets returned from accept() shouldn't appear to be nonblocking.

bpo-25319 [https://bugs.python.org/issue?@action=redirect&bpo=25319]: When threading.Event is reinitialized, the underlying condition should use a regular lock rather than a recursive lock.

Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu Davis.

bpo-26050 [https://bugs.python.org/issue?@action=redirect&bpo=26050]: Add asyncio.StreamReader.readuntil() method. Patch by Марк Коренберг.

bpo-25924 [https://bugs.python.org/issue?@action=redirect&bpo=25924]: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X versions 10.5 or higher. Original patch by A. Jesse Jiryu Davis.

bpo-26406 [https://bugs.python.org/issue?@action=redirect&bpo=26406]: Avoid unnecessary serialization of getaddrinfo(3) calls on current versions of OpenBSD and NetBSD. Patch by A. Jesse Jiryu Davis.

bpo-26848 [https://bugs.python.org/issue?@action=redirect&bpo=26848]: Fix asyncio/subprocess.communicate() to handle empty input. Patch by Jack O'Connor.

bpo-27040 [https://bugs.python.org/issue?@action=redirect&bpo=27040]: Add loop.get_exception_handler method

bpo-27041 [https://bugs.python.org/issue?@action=redirect&bpo=27041]: asyncio: Add loop.create_future method

IDLE

bpo-20640 [https://bugs.python.org/issue?@action=redirect&bpo=20640]: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav Heblikar.

In the 'IDLE-console differences' section of the IDLE doc, clarify how running with IDLE affects sys.modules and the standard streams.

bpo-25507 [https://bugs.python.org/issue?@action=redirect&bpo=25507]: fix incorrect change in IOBinding that prevented printing. Augment IOBinding htest to include all major IOBinding functions.

bpo-25905 [https://bugs.python.org/issue?@action=redirect&bpo=25905]: Revert unwanted conversion of ' to ’ RIGHT SINGLE QUOTATION MARK in README.txt and open this and NEWS.txt with 'ascii'. Re-encode CREDITS.txt to utf-8 and open it with 'utf-8'.

bpo-15348 [https://bugs.python.org/issue?@action=redirect&bpo=15348]: Stop the debugger engine (normally in a user process) before closing the debugger window (running in the IDLE process). This prevents the RuntimeErrors that were being caught and ignored.

bpo-24455 [https://bugs.python.org/issue?@action=redirect&bpo=24455]: Prevent IDLE from hanging when a) closing the shell while the debugger is active (15347); b) closing the debugger with the [X] button (15348); and c) activating the debugger when already active (24455). The patch by Mark Roseman does this by making two changes. 1. Suspend and resume the gui.interaction method with the tcl vwait mechanism intended for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow any existing interaction to terminate first.

Change 'The program' to 'Your program' in an IDLE 'kill program?' message to make it clearer that the program referred to is the currently running user program, not IDLE itself.

bpo-24750 [https://bugs.python.org/issue?@action=redirect&bpo=24750]: Improve the appearance of the IDLE editor window status bar. Patch by Mark Roseman.

bpo-25313 [https://bugs.python.org/issue?@action=redirect&bpo=25313]: Change the handling of new built-in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark. Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

bpo-24782 [https://bugs.python.org/issue?@action=redirect&bpo=24782]: Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog. The former tabs are now a sorted list. Patch by Mark Roseman.

bpo-22726 [https://bugs.python.org/issue?@action=redirect&bpo=22726]: Re-activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme.

bpo-24820 [https://bugs.python.org/issue?@action=redirect&bpo=24820]: IDLE now has an 'IDLE Dark' built-in text color theme. It is more or less IDLE Classic inverted, with a cobalt blue background. Strings, comments, keywords, ... are still green, red, orange, ... . To use it with IDLEs released before November 2015, hit the 'Save as New Custom Theme' button and enter a new name, such as 'Custom Dark'. The custom theme will work with any IDLE release, and can be modified.

bpo-25224 [https://bugs.python.org/issue?@action=redirect&bpo=25224]: README.txt is now an idlelib index for IDLE developers and curious users. The previous user content is now in the IDLE doc chapter. 'IDLE' now means 'Integrated Development and Learning Environment'.

bpo-24820 [https://bugs.python.org/issue?@action=redirect&bpo=24820]: Users can now set breakpoint colors in Settings -> Custom Highlighting. Original patch by Mark Roseman.

bpo-24972 [https://bugs.python.org/issue?@action=redirect&bpo=24972]: Inactive selection background now matches active selection background, as configured by users, on all systems. Found items are now always highlighted on Windows. Initial patch by Mark Roseman.

bpo-24570 [https://bugs.python.org/issue?@action=redirect&bpo=24570]: Idle: make calltip and completion boxes appear on Macs affected by a tk regression. Initial patch by Mark Roseman.

bpo-24988 [https://bugs.python.org/issue?@action=redirect&bpo=24988]: Idle ScrolledList context menus (used in debugger) now work on Mac Aqua. Patch by Mark Roseman.

bpo-24801 [https://bugs.python.org/issue?@action=redirect&bpo=24801]: Make right-click for context menu work on Mac Aqua. Patch by Mark Roseman.

bpo-25173 [https://bugs.python.org/issue?@action=redirect&bpo=25173]: Associate tkinter messageboxes with a specific widget. For Mac OSX, make them a 'sheet'. Patch by Mark Roseman.

bpo-25198 [https://bugs.python.org/issue?@action=redirect&bpo=25198]: Enhance the initial html viewer now used for Idle Help. Properly indent fixed-pitch text (patch by Mark Roseman). Give code snippet a very Sphinx-like light blueish-gray background. Re-use initial width and height set by users for shell and editor. When the Table of Contents (TOC) menu is used, put the section header at the top of the screen.

bpo-25225 [https://bugs.python.org/issue?@action=redirect&bpo=25225]: Condense and rewrite Idle doc section on text colors.

bpo-21995 [https://bugs.python.org/issue?@action=redirect&bpo=21995]: Explain some differences between IDLE and console Python.

bpo-22820 [https://bugs.python.org/issue?@action=redirect&bpo=22820]: Explain need for print when running file from Idle editor.

bpo-25224 [https://bugs.python.org/issue?@action=redirect&bpo=25224]: Doc: augment Idle feature list and no-subprocess section.

bpo-25219 [https://bugs.python.org/issue?@action=redirect&bpo=25219]: Update doc for Idle command line options. Some were missing and notes were not correct.

bpo-24861 [https://bugs.python.org/issue?@action=redirect&bpo=24861]: Most of idlelib is private and subject to change. Use idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

bpo-25199 [https://bugs.python.org/issue?@action=redirect&bpo=25199]: Idle: add synchronization comments for future maintainers.

bpo-16893 [https://bugs.python.org/issue?@action=redirect&bpo=16893]: Replace help.txt with help.html for Idle doc display. The new idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks better than help.txt and will better document Idle as released. The tkinter html viewer that works for this file was written by Rose Roseman. The now unused EditorWindow.HelpDialog class and helt.txt file are deprecated.

bpo-24199 [https://bugs.python.org/issue?@action=redirect&bpo=24199]: Deprecate unused idlelib.idlever with possible removal in 3.6.

bpo-24790 [https://bugs.python.org/issue?@action=redirect&bpo=24790]: Remove extraneous code (which also create 2 & 3 conflicts).

Documentation

bpo-26736 [https://bugs.python.org/issue?@action=redirect&bpo=26736]: Used HTTPS for external links in the documentation if possible.

bpo-6953 [https://bugs.python.org/issue?@action=redirect&bpo=6953]: Rework the Readline module documentation to group related functions together, and add more details such as what underlying Readline functions and variables are accessed.

bpo-23606 [https://bugs.python.org/issue?@action=redirect&bpo=23606]: Adds note to ctypes documentation regarding cdll.msvcrt.

bpo-24952 [https://bugs.python.org/issue?@action=redirect&bpo=24952]: Clarify the default size argument of stack_size() in the "threading" and "_thread" modules. Patch from Mattip.

bpo-26014 [https://bugs.python.org/issue?@action=redirect&bpo=26014]: Update 3.x packaging documentation: * "See also" links to the new docs are now provided in the legacy pages * links to setuptools documentation have been updated

Tests

bpo-21916 [https://bugs.python.org/issue?@action=redirect&bpo=21916]: Added tests for the turtle module. Patch by ingrid, Gregory Loyse and Jelle Zijlstra.

bpo-26295 [https://bugs.python.org/issue?@action=redirect&bpo=26295]: When using "python3 -m test --testdir=TESTDIR", regrtest doesn't add "test." prefix to test module names.

bpo-26523 [https://bugs.python.org/issue?@action=redirect&bpo=26523]: The multiprocessing thread pool (multiprocessing.dummy.Pool) was untested.

bpo-26015 [https://bugs.python.org/issue?@action=redirect&bpo=26015]: Added new tests for pickling iterators of mutable sequences.

bpo-26325 [https://bugs.python.org/issue?@action=redirect&bpo=26325]: Added test.support.check_no_resource_warning() to check that no ResourceWarning is emitted.

bpo-25940 [https://bugs.python.org/issue?@action=redirect&bpo=25940]: Changed test_ssl to use its internal local server more. This avoids relying on svn.python.org, which recently changed root certificate.

bpo-25616 [https://bugs.python.org/issue?@action=redirect&bpo=25616]: Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict.

bpo-25449 [https://bugs.python.org/issue?@action=redirect&bpo=25449]: Added tests for OrderedDict subclasses.

bpo-25188 [https://bugs.python.org/issue?@action=redirect&bpo=25188]: Add -P/--pgo to test.regrtest to suppress error output when running the test suite for the purposes of a PGO build. Initial patch by Alecsandru Patrascu.

bpo-22806 [https://bugs.python.org/issue?@action=redirect&bpo=22806]: Add python -m test --list-tests command to list tests.

bpo-18174 [https://bugs.python.org/issue?@action=redirect&bpo=18174]: python -m test --huntrleaks ... now also checks for leak of file descriptors. Patch written by Richard Oudkerk.

bpo-25260 [https://bugs.python.org/issue?@action=redirect&bpo=25260]: Fix python -m test --coverage on Windows. Remove the list of ignored directories.

PCbuild\rt.bat now accepts an unlimited number of arguments to pass along to regrtest.py. Previously there was a limit of 9.

bpo-26583 [https://bugs.python.org/issue?@action=redirect&bpo=26583]: Skip test_timestamp_overflow in test_import if bytecode files cannot be written.

Build

bpo-21277 [https://bugs.python.org/issue?@action=redirect&bpo=21277]: Don't try to link _ctypes with a ffi_convenience library.

bpo-26884 [https://bugs.python.org/issue?@action=redirect&bpo=26884]: Fix linking extension modules for cross builds. Patch by Xavier de Gaye.

bpo-26932 [https://bugs.python.org/issue?@action=redirect&bpo=26932]: Fixed support of RTLD_* constants defined as enum values, not via macros (in particular on Android). Patch by Chi Hsuan Yen.

bpo-22359 [https://bugs.python.org/issue?@action=redirect&bpo=22359]: Disable the rules for running _freeze_importlib and pgen when cross-compiling. The output of these programs is normally saved with the source code anyway, and is still regenerated when doing a native build. Patch by Xavier de Gaye.

bpo-21668 [https://bugs.python.org/issue?@action=redirect&bpo=21668]: Link audioop, _datetime, _ctypes_test modules to libm, except on Mac OS X. Patch written by Chi Hsuan Yen.

bpo-25702 [https://bugs.python.org/issue?@action=redirect&bpo=25702]: A --with-lto configure option has been added that will enable link time optimizations at build time during a make profile-opt. Some compilers and toolchains are known to not produce stable code when using LTO, be sure to test things thoroughly before relying on it. It can provide a few % speed up over profile-opt alone.

bpo-26624 [https://bugs.python.org/issue?@action=redirect&bpo=26624]: Adds validation of ucrtbase[d].dll version with warning for old versions.

bpo-17603 [https://bugs.python.org/issue?@action=redirect&bpo=17603]: Avoid error about nonexistent fileblocks.o file by using a lower-level check for st_blocks in struct stat.

bpo-26079 [https://bugs.python.org/issue?@action=redirect&bpo=26079]: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern Thiel.

bpo-26465 [https://bugs.python.org/issue?@action=redirect&bpo=26465]: Update Windows builds to use OpenSSL 1.0.2g.

bpo-25348 [https://bugs.python.org/issue?@action=redirect&bpo=25348]: Added --pgo and --pgo-job arguments to PCbuild\build.bat for building with Profile-Guided Optimization. The old PCbuild\build_pgo.bat script is removed.

bpo-25827 [https://bugs.python.org/issue?@action=redirect&bpo=25827]: Add support for building with ICC to configure, including a new --with-icc flag.

bpo-25696 [https://bugs.python.org/issue?@action=redirect&bpo=25696]: Fix installation of Python on UNIX with make -j9.

bpo-24986 [https://bugs.python.org/issue?@action=redirect&bpo=24986]: It is now possible to build Python on Windows without errors when external libraries are not available.

bpo-24421 [https://bugs.python.org/issue?@action=redirect&bpo=24421]: Compile Modules/_math.c once, before building extensions. Previously it could fail to compile properly if the math and cmath builds were concurrent.

bpo-26465 [https://bugs.python.org/issue?@action=redirect&bpo=26465]: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2g.

bpo-26268 [https://bugs.python.org/issue?@action=redirect&bpo=26268]: Update Windows builds to use OpenSSL 1.0.2f.

bpo-25136 [https://bugs.python.org/issue?@action=redirect&bpo=25136]: Support Apple Xcode 7's new textual SDK stub libraries.

bpo-24324 [https://bugs.python.org/issue?@action=redirect&bpo=24324]: Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc-4.5.

Windows

bpo-27053 [https://bugs.python.org/issue?@action=redirect&bpo=27053]: Updates make_zip.py to correctly generate library ZIP file.

bpo-26268 [https://bugs.python.org/issue?@action=redirect&bpo=26268]: Update the prepare_ssl.py script to handle OpenSSL releases that don't include the contents of the include directory (that is, 1.0.2e and later).

bpo-26071 [https://bugs.python.org/issue?@action=redirect&bpo=26071]: bdist_wininst created binaries fail to start and find 32bit Python

bpo-26073 [https://bugs.python.org/issue?@action=redirect&bpo=26073]: Update the list of magic numbers in launcher

bpo-26065 [https://bugs.python.org/issue?@action=redirect&bpo=26065]: Excludes venv from library when generating embeddable distro.

bpo-25022 [https://bugs.python.org/issue?@action=redirect&bpo=25022]: Removed very outdated PC/example_nt/ directory.

Tools/Demos

bpo-26799 [https://bugs.python.org/issue?@action=redirect&bpo=26799]: Fix python-gdb.py: don't get C types once when the Python code is loaded, but get C types on demand. The C types can change if python-gdb.py is loaded before the Python executable. Patch written by Thomas Ilsche.

bpo-26271 [https://bugs.python.org/issue?@action=redirect&bpo=26271]: Fix the Freeze tool to properly use flags passed through configure. Patch by Daniel Shaulov.

bpo-26489 [https://bugs.python.org/issue?@action=redirect&bpo=26489]: Add dictionary unpacking support to Tools/parser/unparse.py. Patch by Guo Ci Teo.

bpo-26316 [https://bugs.python.org/issue?@action=redirect&bpo=26316]: Fix variable name typo in Argument Clinic.

bpo-25440 [https://bugs.python.org/issue?@action=redirect&bpo=25440]: Fix output of python-config --extension-suffix.

bpo-25154 [https://bugs.python.org/issue?@action=redirect&bpo=25154]: The pyvenv script has been deprecated in favour of python3 -m venv.

C API

bpo-26312 [https://bugs.python.org/issue?@action=redirect&bpo=26312]: SystemError is now raised in all programming bugs with using PyArg_ParseTupleAndKeywords(). RuntimeError did raised before in some programming bugs.

bpo-26198 [https://bugs.python.org/issue?@action=redirect&bpo=26198]: ValueError is now raised instead of TypeError on buffer overflow in parsing "es#" and "et#" format units. SystemError is now raised instead of TypeError on programmatical error in parsing format string.

Python 3.5.5 final

Release date: 2018-02-04

There were no new changes in version 3.5.5.

Python 3.5.5 release candidate 1

Release date: 2018-01-23

Security

bpo-32551 [https://bugs.python.org/issue?@action=redirect&bpo=32551]: The sys.path[0] initialization change for bpo-29139 [https://bugs.python.org/issue?@action=redirect&bpo=29139] caused a regression by revealing an inconsistency in how sys.path is initialized when executing __main__ from a zipfile, directory, or other import location. This is considered a potential security issue, as it may lead to privileged processes unexpectedly loading code from user controlled directories in situations where that was not previously the case. The interpreter now consistently avoids ever adding the import location's parent directory to sys.path, and ensures no other sys.path entries are inadvertently modified when inserting the import location named on the command line. (Originally reported as bpo-29723 [https://bugs.python.org/issue?@action=redirect&bpo=29723] against Python 3.6rc1, but it was missed at the time that the then upcoming Python 3.5.4 release would also be affected)

bpo-30657 [https://bugs.python.org/issue?@action=redirect&bpo=30657]: Fixed possible integer overflow in PyBytes_DecodeEscape, CVE 2017-1000158 [https://www.cve.org/CVERecord?id=CVE-2017-1000158]. Original patch by Jay Bosamiya; rebased to Python 3 by Miro Hrončok.

bpo-30947 [https://bugs.python.org/issue?@action=redirect&bpo=30947]: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

Core and Builtins

bpo-31095 [https://bugs.python.org/issue?@action=redirect&bpo=31095]: Fix potential crash during GC caused by tp_dealloc which doesn't call PyObject_GC_UnTrack().

Library

bpo-32072 [https://bugs.python.org/issue?@action=redirect&bpo=32072]: Fixed issues with binary plists: Fixed saving bytearrays. Identical objects will be saved only once. Equal references will be load as identical objects. Added support for saving and loading recursive data structures.

bpo-31170 [https://bugs.python.org/issue?@action=redirect&bpo=31170]: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

Python 3.5.4 final

Release date: 2017-08-07

Library

bpo-30119 [https://bugs.python.org/issue?@action=redirect&bpo=30119]: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Donghee Na.

Python 3.5.4 release candidate 1

Release date: 2017-07-23

Security

bpo-30730 [https://bugs.python.org/issue?@action=redirect&bpo=30730]: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.

bpo-30694 [https://bugs.python.org/issue?@action=redirect&bpo=30694]: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE 2017-9233 [https://www.cve.org/CVERecord?id=CVE-2017-9233] (External entity infinite loop DoS), CVE 2016-9063 [https://www.cve.org/CVERecord?id=CVE-2016-9063] (Integer overflow, re-fix), CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718] (Fix regression bugs from 2.2.0's fix to CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718]) and CVE 2012-0876 [https://www.cve.org/CVERecord?id=CVE-2012-0876] (Counter hash flooding with SipHash). Note: the CVE 2016-5300 [https://www.cve.org/CVERecord?id=CVE-2016-5300] (Use os-specific entropy sources like getrandom) doesn't impact Python, since Python already gets entropy from the OS to set the expat secret using XML_SetHashSalt().

bpo-30500 [https://bugs.python.org/issue?@action=redirect&bpo=30500]: Fix urllib.parse.splithost() to correctly parse fragments. For example, splithost('//127.0.0.1#@evil.com/') now correctly returns the 127.0.0.1 host, instead of treating @evil.com as the host in an authentication (login@host).

bpo-29591 [https://bugs.python.org/issue?@action=redirect&bpo=29591]: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE 2016-0718 [https://www.cve.org/CVERecord?id=CVE-2016-0718] and CVE 2016-4472 [https://www.cve.org/CVERecord?id=CVE-2016-4472]. See https://sourceforge.net/p/expat/bugs/537/ for more information.

Core and Builtins

bpo-30876 [https://bugs.python.org/issue?@action=redirect&bpo=30876]: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

bpo-30765 [https://bugs.python.org/issue?@action=redirect&bpo=30765]: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

bpo-27945 [https://bugs.python.org/issue?@action=redirect&bpo=27945]: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

bpo-25794 [https://bugs.python.org/issue?@action=redirect&bpo=25794]: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

bpo-29935 [https://bugs.python.org/issue?@action=redirect&bpo=29935]: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

bpo-28876 [https://bugs.python.org/issue?@action=redirect&bpo=28876]: bool(range) works even if len(range) raises OverflowError.

bpo-29600 [https://bugs.python.org/issue?@action=redirect&bpo=29600]: Fix wrapping coroutine return values in StopIteration.

bpo-29537 [https://bugs.python.org/issue?@action=redirect&bpo=29537]: Restore runtime compatibility with bytecode files generated by CPython 3.5.0 to 3.5.2, and adjust the eval loop to avoid the problems that could be caused by the malformed variant of the BUILD_MAP_UNPACK_WITH_CALL opcode that they may contain. Patch by Petr Viktorin, Serhiy Storchaka, and Nick Coghlan.

bpo-28598 [https://bugs.python.org/issue?@action=redirect&bpo=28598]: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

bpo-29602 [https://bugs.python.org/issue?@action=redirect&bpo=29602]: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

bpo-29347 [https://bugs.python.org/issue?@action=redirect&bpo=29347]: Fixed possibly dereferencing undefined pointers when creating weakref objects.

bpo-29438 [https://bugs.python.org/issue?@action=redirect&bpo=29438]: Fixed use-after-free problem in key sharing dict.

bpo-29319 [https://bugs.python.org/issue?@action=redirect&bpo=29319]: Prevent RunMainFromImporter overwriting sys.path[0].

bpo-29337 [https://bugs.python.org/issue?@action=redirect&bpo=29337]: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

bpo-29478 [https://bugs.python.org/issue?@action=redirect&bpo=29478]: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

Library

bpo-29403 [https://bugs.python.org/issue?@action=redirect&bpo=29403]: Fix unittest.mock's autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

bpo-30961 [https://bugs.python.org/issue?@action=redirect&bpo=30961]: Fix decrementing a borrowed reference in tracemalloc.

bpo-30886 [https://bugs.python.org/issue?@action=redirect&bpo=30886]: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

bpo-29854 [https://bugs.python.org/issue?@action=redirect&bpo=29854]: Fix segfault in readline when using readline's history-size option. Patch by Nir Soffer.

bpo-30807 [https://bugs.python.org/issue?@action=redirect&bpo=30807]: signal.setitimer() may disable the timer when passed a tiny value. Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

bpo-30441 [https://bugs.python.org/issue?@action=redirect&bpo=30441]: Fix bug when modifying os.environ while iterating over it

bpo-30532 [https://bugs.python.org/issue?@action=redirect&bpo=30532]: Fix email header value parser dropping folding white space in certain cases.

bpo-29169 [https://bugs.python.org/issue?@action=redirect&bpo=29169]: Update zlib to 1.2.11.

bpo-30879 [https://bugs.python.org/issue?@action=redirect&bpo=30879]: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

bpo-30746 [https://bugs.python.org/issue?@action=redirect&bpo=30746]: Prohibited the '=' character in environment variable names in os.putenv() and os.spawn*().

bpo-29755 [https://bugs.python.org/issue?@action=redirect&bpo=29755]: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

bpo-30645 [https://bugs.python.org/issue?@action=redirect&bpo=30645]: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

bpo-23890 [https://bugs.python.org/issue?@action=redirect&bpo=23890]: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

bpo-30149 [https://bugs.python.org/issue?@action=redirect&bpo=30149]: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Donghee Na.

bpo-29931 [https://bugs.python.org/issue?@action=redirect&bpo=29931]: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

bpo-24484 [https://bugs.python.org/issue?@action=redirect&bpo=24484]: Avoid race condition in multiprocessing cleanup.

bpo-28994 [https://bugs.python.org/issue?@action=redirect&bpo=28994]: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

bpo-30508 [https://bugs.python.org/issue?@action=redirect&bpo=30508]: Don't log exceptions if Task/Future "cancel()" method was called.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

bpo-29870 [https://bugs.python.org/issue?@action=redirect&bpo=29870]: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

bpo-29743 [https://bugs.python.org/issue?@action=redirect&bpo=29743]: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

bpo-27585 [https://bugs.python.org/issue?@action=redirect&bpo=27585]: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

bpo-30418 [https://bugs.python.org/issue?@action=redirect&bpo=30418]: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

bpo-30378 [https://bugs.python.org/issue?@action=redirect&bpo=30378]: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

bpo-29960 [https://bugs.python.org/issue?@action=redirect&bpo=29960]: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

bpo-30414 [https://bugs.python.org/issue?@action=redirect&bpo=30414]: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

bpo-30003 [https://bugs.python.org/issue?@action=redirect&bpo=30003]: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

bpo-30301 [https://bugs.python.org/issue?@action=redirect&bpo=30301]: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

bpo-30329 [https://bugs.python.org/issue?@action=redirect&bpo=30329]: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

bpo-30375 [https://bugs.python.org/issue?@action=redirect&bpo=30375]: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

bpo-30048 [https://bugs.python.org/issue?@action=redirect&bpo=30048]: Fixed Task.cancel() can be ignored when the task is running coroutine and the coroutine returned without any more await.

bpo-29990 [https://bugs.python.org/issue?@action=redirect&bpo=29990]: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

bpo-26293 [https://bugs.python.org/issue?@action=redirect&bpo=26293]: Change resulted because of zipfile breakage. (See also: bpo-29094 [https://bugs.python.org/issue?@action=redirect&bpo=29094])

bpo-30243 [https://bugs.python.org/issue?@action=redirect&bpo=30243]: Removed the __init__ methods of _json's scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

bpo-30185 [https://bugs.python.org/issue?@action=redirect&bpo=30185]: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

bpo-30205 [https://bugs.python.org/issue?@action=redirect&bpo=30205]: Fix getsockname() for unbound AF_UNIX sockets on Linux.

bpo-30070 [https://bugs.python.org/issue?@action=redirect&bpo=30070]: Fixed leaks and crashes in errors handling in the parser module.

bpo-30061 [https://bugs.python.org/issue?@action=redirect&bpo=30061]: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

bpo-30068 [https://bugs.python.org/issue?@action=redirect&bpo=30068]: _io._IOBase.readlines will check if it's closed first when hint is present.

bpo-29694 [https://bugs.python.org/issue?@action=redirect&bpo=29694]: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

bpo-29692 [https://bugs.python.org/issue?@action=redirect&bpo=29692]: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

bpo-29998 [https://bugs.python.org/issue?@action=redirect&bpo=29998]: Pickling and copying ImportError now preserves name and path attributes.

bpo-29942 [https://bugs.python.org/issue?@action=redirect&bpo=29942]: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

bpo-27863 [https://bugs.python.org/issue?@action=redirect&bpo=27863]: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

bpo-28699 [https://bugs.python.org/issue?@action=redirect&bpo=28699]: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

bpo-25803 [https://bugs.python.org/issue?@action=redirect&bpo=25803]: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

bpo-29861 [https://bugs.python.org/issue?@action=redirect&bpo=29861]: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

bpo-29884 [https://bugs.python.org/issue?@action=redirect&bpo=29884]: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

bpo-25455 [https://bugs.python.org/issue?@action=redirect&bpo=25455]: Fixed crashes in repr of recursive buffered file-like objects.

bpo-29800 [https://bugs.python.org/issue?@action=redirect&bpo=29800]: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

bpo-29742 [https://bugs.python.org/issue?@action=redirect&bpo=29742]: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

bpo-8256 [https://bugs.python.org/issue?@action=redirect&bpo=8256]: Fixed possible failing or crashing input() if attributes "encoding" or "errors" of sys.stdin or sys.stdout are not set or are not strings.

bpo-28298 [https://bugs.python.org/issue?@action=redirect&bpo=28298]: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting big intables (objects that have __int__) as elements. Patch by Oren Milman.

bpo-29615 [https://bugs.python.org/issue?@action=redirect&bpo=29615]: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

bpo-29704 [https://bugs.python.org/issue?@action=redirect&bpo=29704]: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

bpo-29703 [https://bugs.python.org/issue?@action=redirect&bpo=29703]: Fix asyncio to support instantiation of new event loops in child processes.

bpo-29376 [https://bugs.python.org/issue?@action=redirect&bpo=29376]: Fix assertion error in threading._DummyThread.is_alive().

bpo-29110 [https://bugs.python.org/issue?@action=redirect&bpo=29110]: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

bpo-28961 [https://bugs.python.org/issue?@action=redirect&bpo=28961]: Fix unittest.mock._Call helper: don't ignore the name parameter anymore. Patch written by Jiajun Huang.

bpo-29532 [https://bugs.python.org/issue?@action=redirect&bpo=29532]: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

bpo-28556 [https://bugs.python.org/issue?@action=redirect&bpo=28556]: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

bpo-29100 [https://bugs.python.org/issue?@action=redirect&bpo=29100]: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

bpo-29519 [https://bugs.python.org/issue?@action=redirect&bpo=29519]: Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs.

bpo-29416 [https://bugs.python.org/issue?@action=redirect&bpo=29416]: Prevent infinite loop in pathlib.Path.mkdir

bpo-29444 [https://bugs.python.org/issue?@action=redirect&bpo=29444]: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

bpo-29335 [https://bugs.python.org/issue?@action=redirect&bpo=29335]: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

bpo-29290 [https://bugs.python.org/issue?@action=redirect&bpo=29290]: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

bpo-28735 [https://bugs.python.org/issue?@action=redirect&bpo=28735]: Fixed the comparison of mock.MagickMock with mock.ANY.

bpo-29011 [https://bugs.python.org/issue?@action=redirect&bpo=29011]: Fix an important omission by adding Deque to the typing module.

bpo-29219 [https://bugs.python.org/issue?@action=redirect&bpo=29219]: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

bpo-28969 [https://bugs.python.org/issue?@action=redirect&bpo=28969]: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments.

bpo-29142 [https://bugs.python.org/issue?@action=redirect&bpo=29142]: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

Documentation

bpo-30176 [https://bugs.python.org/issue?@action=redirect&bpo=30176]: Add missing attribute related constants in curses documentation.

bpo-26985 [https://bugs.python.org/issue?@action=redirect&bpo=26985]: Add missing info of code object in inspect documentation.

bpo-28929 [https://bugs.python.org/issue?@action=redirect&bpo=28929]: Link the documentation to its source file on GitHub.

bpo-25008 [https://bugs.python.org/issue?@action=redirect&bpo=25008]: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

bpo-26355 [https://bugs.python.org/issue?@action=redirect&bpo=26355]: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

bpo-29349 [https://bugs.python.org/issue?@action=redirect&bpo=29349]: Fix Python 2 syntax in code for building the documentation.

Tests

bpo-30822 [https://bugs.python.org/issue?@action=redirect&bpo=30822]: Fix regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

bpo-30383 [https://bugs.python.org/issue?@action=redirect&bpo=30383]: regrtest: Enhance regrtest and backport features from the master branch. Add options: --coverage, --testdir, --list-tests (list test files, don't run them), --list-cases (list test identifiers, don't run them, bpo-30523 [https://bugs.python.org/issue?@action=redirect&bpo=30523]), --matchfile (load a list of test filters from a text file, bpo-30540 [https://bugs.python.org/issue?@action=redirect&bpo=30540]), --slowest (alias to --slow). Enhance output: add timestamp, test result, currently running tests, "Tests result: xxx" summary with total duration, etc. Fix reference leak hunting in regrtest, --huntrleaks: regrtest now warms up caches, create explicitly all internal singletons which are created on demand to prevent false positives when checking for reference leaks. (bpo-30675 [https://bugs.python.org/issue?@action=redirect&bpo=30675]).

bpo-30357 [https://bugs.python.org/issue?@action=redirect&bpo=30357]: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

bpo-28087 [https://bugs.python.org/issue?@action=redirect&bpo=28087]: Skip test_asyncore and test_eintr poll failures on macOS. Skip some tests of select.poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions.

bpo-30197 [https://bugs.python.org/issue?@action=redirect&bpo=30197]: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn't exist) now will be assigned to the target of the "as" clause, if there is one.

bpo-29571 [https://bugs.python.org/issue?@action=redirect&bpo=29571]: to match the behaviour of the re.LOCALE flag, test_re.test_locale_flag now uses locale.getpreferredencoding(False) to determine the candidate encoding for the test regex (allowing it to correctly skip the test when the default locale encoding is a multi-byte encoding)

Build

bpo-29243 [https://bugs.python.org/issue?@action=redirect&bpo=29243]: Prevent unnecessary rebuilding of Python during make test, make install and some other make targets when configured with --enable-optimizations.

bpo-23404 [https://bugs.python.org/issue?@action=redirect&bpo=23404]: Don't regenerate generated files based on file modification time anymore: the action is now explicit. Replace make touch with make regen-all.

bpo-29643 [https://bugs.python.org/issue?@action=redirect&bpo=29643]: Fix --enable-optimization didn't work.

Windows

bpo-30687 [https://bugs.python.org/issue?@action=redirect&bpo=30687]: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

bpo-29392 [https://bugs.python.org/issue?@action=redirect&bpo=29392]: Prevent crash when passing invalid arguments into msvcrt module.

C API

bpo-27867 [https://bugs.python.org/issue?@action=redirect&bpo=27867]: Function PySlice_GetIndicesEx() is replaced with a macro if Py_LIMITED_API is set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.

bpo-29083 [https://bugs.python.org/issue?@action=redirect&bpo=29083]: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

Python 3.5.3 final

Release date: 2017-01-17

There were no code changes between 3.5.3rc1 and 3.5.3 final.

Python 3.5.3 release candidate 1

Release date: 2017-01-02

Security

bpo-27278 [https://bugs.python.org/issue?@action=redirect&bpo=27278]: Fix os.urandom() implementation using getrandom() on Linux. Truncate size to INT_MAX and loop until we collected enough random bytes, instead of casting a directly Py_ssize_t to int.

bpo-22636 [https://bugs.python.org/issue?@action=redirect&bpo=22636]: Avoid shell injection problems with ctypes.util.find_library().

Core and Builtins

bpo-29073 [https://bugs.python.org/issue?@action=redirect&bpo=29073]: bytearray formatting no longer truncates on first null byte.

bpo-28932 [https://bugs.python.org/issue?@action=redirect&bpo=28932]: Do not include <sys/random.h> if it does not exist.

bpo-28147 [https://bugs.python.org/issue?@action=redirect&bpo=28147]: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table.

bpo-25677 [https://bugs.python.org/issue?@action=redirect&bpo=25677]: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

bpo-29000 [https://bugs.python.org/issue?@action=redirect&bpo=29000]: Fixed bytes formatting of octals with zero padding in alternate form.

bpo-28512 [https://bugs.python.org/issue?@action=redirect&bpo=28512]: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

bpo-28991 [https://bugs.python.org/issue?@action=redirect&bpo=28991]: functools.lru_cache() was susceptible to an obscure reentrancy bug caused by a monkey-patched len() function.

bpo-28648 [https://bugs.python.org/issue?@action=redirect&bpo=28648]: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

bpo-19398 [https://bugs.python.org/issue?@action=redirect&bpo=19398]: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

bpo-28426 [https://bugs.python.org/issue?@action=redirect&bpo=28426]: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

bpo-23782 [https://bugs.python.org/issue?@action=redirect&bpo=23782]: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

bpo-28379 [https://bugs.python.org/issue?@action=redirect&bpo=28379]: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

bpo-28376 [https://bugs.python.org/issue?@action=redirect&bpo=28376]: The constructor of range_iterator now checks that step is not 0. Patch by Oren Milman.

bpo-26906 [https://bugs.python.org/issue?@action=redirect&bpo=26906]: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

bpo-18287 [https://bugs.python.org/issue?@action=redirect&bpo=18287]: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

bpo-24098 [https://bugs.python.org/issue?@action=redirect&bpo=24098]: Fixed possible crash when AST is changed in process of compiling it.

bpo-28350 [https://bugs.python.org/issue?@action=redirect&bpo=28350]: String constants with null character no longer interned.

bpo-26617 [https://bugs.python.org/issue?@action=redirect&bpo=26617]: Fix crash when GC runs during weakref callbacks.

bpo-27942 [https://bugs.python.org/issue?@action=redirect&bpo=27942]: String constants now interned recursively in tuples and frozensets.

bpo-21578 [https://bugs.python.org/issue?@action=redirect&bpo=21578]: Fixed misleading error message when ImportError called with invalid keyword args.

bpo-28203 [https://bugs.python.org/issue?@action=redirect&bpo=28203]: Fix incorrect type in error message from complex(1.0, {2:3}). Patch by Soumya Sharma.

bpo-27955 [https://bugs.python.org/issue?@action=redirect&bpo=27955]: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

bpo-28131 [https://bugs.python.org/issue?@action=redirect&bpo=28131]: Fix a regression in zipimport's compile_source(). zipimport should use the same optimization level as the interpreter.

bpo-25221 [https://bugs.python.org/issue?@action=redirect&bpo=25221]: Fix corrupted result from PyLong_FromLong(0) when Python is compiled with NSMALLPOSINTS = 0.

bpo-25758 [https://bugs.python.org/issue?@action=redirect&bpo=25758]: Prevents zipimport from unnecessarily encoding a filename (patch by Eryk Sun)

bpo-28189 [https://bugs.python.org/issue?@action=redirect&bpo=28189]: dictitems_contains no longer swallows compare errors. (Patch by Xiang Zhang)

bpo-27812 [https://bugs.python.org/issue?@action=redirect&bpo=27812]: Properly clear out a generator's frame's backreference to the generator to prevent crashes in frame.clear().

bpo-27811 [https://bugs.python.org/issue?@action=redirect&bpo=27811]: Fix a crash when a coroutine that has not been awaited is finalized with warnings-as-errors enabled.

bpo-27587 [https://bugs.python.org/issue?@action=redirect&bpo=27587]: Fix another issue found by PVS-Studio: Null pointer check after use of 'def' in _PyState_AddModule(). Initial patch by Christian Heimes.

bpo-26020 [https://bugs.python.org/issue?@action=redirect&bpo=26020]: set literal evaluation order did not match documented behaviour.

bpo-27782 [https://bugs.python.org/issue?@action=redirect&bpo=27782]: Multi-phase extension module import now correctly allows the m_methods field to be used to add module level functions to instances of non-module types returned from Py_create_mod. Patch by Xiang Zhang.

bpo-27936 [https://bugs.python.org/issue?@action=redirect&bpo=27936]: The round() function accepted a second None argument for some types but not for others. Fixed the inconsistency by accepting None for all numeric types.

bpo-27487 [https://bugs.python.org/issue?@action=redirect&bpo=27487]: Warn if a submodule argument to "python -m" or runpy.run_module() is found in sys.modules after parent packages are imported, but before the submodule is executed.

bpo-27558 [https://bugs.python.org/issue?@action=redirect&bpo=27558]: Fix a SystemError in the implementation of "raise" statement. In a brand new thread, raise a RuntimeError since there is no active exception to reraise. Patch written by Xiang Zhang.

bpo-27419 [https://bugs.python.org/issue?@action=redirect&bpo=27419]: Standard __import__() no longer look up "__import__" in globals or builtins for importing submodules or "from import". Fixed handling an error of non-string package name.

bpo-27083 [https://bugs.python.org/issue?@action=redirect&bpo=27083]: Respect the PYTHONCASEOK environment variable under Windows.

bpo-27514 [https://bugs.python.org/issue?@action=redirect&bpo=27514]: Make having too many statically nested blocks a SyntaxError instead of SystemError.

bpo-27473 [https://bugs.python.org/issue?@action=redirect&bpo=27473]: Fixed possible integer overflow in bytes and bytearray concatenations. Patch by Xiang Zhang.

bpo-27507 [https://bugs.python.org/issue?@action=redirect&bpo=27507]: Add integer overflow check in bytearray.extend(). Patch by Xiang Zhang.

bpo-27581 [https://bugs.python.org/issue?@action=redirect&bpo=27581]: Don't rely on wrapping for overflow check in PySequence_Tuple(). Patch by Xiang Zhang.

bpo-27443 [https://bugs.python.org/issue?@action=redirect&bpo=27443]: __length_hint__() of bytearray iterators no longer return a negative integer for a resized bytearray.

bpo-27942 [https://bugs.python.org/issue?@action=redirect&bpo=27942]: Fix memory leak in codeobject.c

Library

bpo-15812 [https://bugs.python.org/issue?@action=redirect&bpo=15812]: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

bpo-29094 [https://bugs.python.org/issue?@action=redirect&bpo=29094]: Offsets in a ZIP file created with extern file object and modes "w" and "x" now are relative to the start of the file.

bpo-13051 [https://bugs.python.org/issue?@action=redirect&bpo=13051]: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

bpo-29119 [https://bugs.python.org/issue?@action=redirect&bpo=29119]: Fix weakrefs in the pure python version of collections.OrderedDict move_to_end() method. Contributed by Andra Bogildea.

bpo-9770 [https://bugs.python.org/issue?@action=redirect&bpo=9770]: curses.ascii predicates now work correctly with negative integers.

bpo-28427 [https://bugs.python.org/issue?@action=redirect&bpo=28427]: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

bpo-28923 [https://bugs.python.org/issue?@action=redirect&bpo=28923]: Remove editor artifacts from Tix.py.

bpo-28871 [https://bugs.python.org/issue?@action=redirect&bpo=28871]: Fixed a crash when deallocate deep ElementTree.

bpo-19542 [https://bugs.python.org/issue?@action=redirect&bpo=19542]: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

bpo-20191 [https://bugs.python.org/issue?@action=redirect&bpo=20191]: Fixed a crash in resource.prlimit() when pass a sequence that doesn't own its elements as limits.

bpo-28779 [https://bugs.python.org/issue?@action=redirect&bpo=28779]: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

bpo-28847 [https://bugs.python.org/issue?@action=redirect&bpo=28847]: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.

bpo-25659 [https://bugs.python.org/issue?@action=redirect&bpo=25659]: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

bpo-28732 [https://bugs.python.org/issue?@action=redirect&bpo=28732]: Fix crash in os.spawnv() with no elements in args

bpo-28485 [https://bugs.python.org/issue?@action=redirect&bpo=28485]: Always raise ValueError for negative compileall.compile_dir(workers=...) parameter, even when multithreading is unavailable.

bpo-28387 [https://bugs.python.org/issue?@action=redirect&bpo=28387]: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

bpo-27517 [https://bugs.python.org/issue?@action=redirect&bpo=27517]: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

bpo-28549 [https://bugs.python.org/issue?@action=redirect&bpo=28549]: Fixed segfault in curses's addch() with ncurses6.

bpo-28449 [https://bugs.python.org/issue?@action=redirect&bpo=28449]: tarfile.open() with mode "r" or "r:" now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

bpo-23262 [https://bugs.python.org/issue?@action=redirect&bpo=23262]: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

bpo-27939 [https://bugs.python.org/issue?@action=redirect&bpo=27939]: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

bpo-28255 [https://bugs.python.org/issue?@action=redirect&bpo=28255]: calendar.TextCalendar().prmonth() no longer prints a space at the start of new line after printing a month's calendar. Patch by Xiang Zhang.

bpo-20491 [https://bugs.python.org/issue?@action=redirect&bpo=20491]: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

bpo-28353 [https://bugs.python.org/issue?@action=redirect&bpo=28353]: os.fwalk() no longer fails on broken links.

bpo-25464 [https://bugs.python.org/issue?@action=redirect&bpo=25464]: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

bpo-28488 [https://bugs.python.org/issue?@action=redirect&bpo=28488]: shutil.make_archive() no longer add entry "./" to ZIP archive.

bpo-24452 [https://bugs.python.org/issue?@action=redirect&bpo=24452]: Make webbrowser support Chrome on Mac OS X.

bpo-20766 [https://bugs.python.org/issue?@action=redirect&bpo=20766]: Fix references leaked by pdb in the handling of SIGINT handlers.

bpo-26293 [https://bugs.python.org/issue?@action=redirect&bpo=26293]: Fixed writing ZIP files that starts not from the start of the file. Offsets in ZIP file now are relative to the start of the archive in conforming to the specification.

bpo-28321 [https://bugs.python.org/issue?@action=redirect&bpo=28321]: Fixed writing non-BMP characters with binary format in plistlib.

bpo-28322 [https://bugs.python.org/issue?@action=redirect&bpo=28322]: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

Fix possible integer overflows and crashes in the mmap module with unusual usage patterns.

bpo-1703178 [https://bugs.python.org/issue?@action=redirect&bpo=1703178]: Fix the ability to pass the --link-objects option to the distutils build_ext command.

bpo-28253 [https://bugs.python.org/issue?@action=redirect&bpo=28253]: Fixed calendar functions for extreme months: 0001-01 and 9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so that they don't call itermonthdates() which can cause datetime.date under/overflow.

bpo-28275 [https://bugs.python.org/issue?@action=redirect&bpo=28275]: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

bpo-27897 [https://bugs.python.org/issue?@action=redirect&bpo=27897]: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

bpo-18893 [https://bugs.python.org/issue?@action=redirect&bpo=18893]: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

bpo-27611 [https://bugs.python.org/issue?@action=redirect&bpo=27611]: Fixed support of default root window in the tkinter.tix module.

bpo-27348 [https://bugs.python.org/issue?@action=redirect&bpo=27348]: In the traceback module, restore the formatting of exception messages like "Exception: None". This fixes a regression introduced in 3.5a2.

bpo-25651 [https://bugs.python.org/issue?@action=redirect&bpo=25651]: Allow false values to be used for msg parameter of subTest().

bpo-27932 [https://bugs.python.org/issue?@action=redirect&bpo=27932]: Prevent memory leak in win32_ver().

Fix UnboundLocalError in socket._sendfile_use_sendfile.

bpo-28075 [https://bugs.python.org/issue?@action=redirect&bpo=28075]: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

bpo-25270 [https://bugs.python.org/issue?@action=redirect&bpo=25270]: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

bpo-28181 [https://bugs.python.org/issue?@action=redirect&bpo=28181]: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

bpo-25895 [https://bugs.python.org/issue?@action=redirect&bpo=25895]: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

bpo-27599 [https://bugs.python.org/issue?@action=redirect&bpo=27599]: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

bpo-19003 [https://bugs.python.org/issue?@action=redirect&bpo=19003]: m email.generator now replaces only \r and/or \n line endings, per the RFC, instead of all unicode line endings.

bpo-28019 [https://bugs.python.org/issue?@action=redirect&bpo=28019]: itertools.count() no longer rounds non-integer step in range between 1.0 and 2.0 to 1.

bpo-25969 [https://bugs.python.org/issue?@action=redirect&bpo=25969]: Update the lib2to3 grammar to handle the unpacking generalizations added in 3.5.

bpo-14977 [https://bugs.python.org/issue?@action=redirect&bpo=14977]: mailcap now respects the order of the lines in the mailcap files ("first match"), as required by RFC 1542. Patch by Michael Lazar.

bpo-24594 [https://bugs.python.org/issue?@action=redirect&bpo=24594]: Validates persist parameter when opening MSI database

bpo-17582 [https://bugs.python.org/issue?@action=redirect&bpo=17582]: xml.etree.ElementTree nows preserves whitespaces in attributes (Patch by Duane Griffin. Reviewed and approved by Stefan Behnel.)

bpo-28047 [https://bugs.python.org/issue?@action=redirect&bpo=28047]: Fixed calculation of line length used for the base64 CTE in the new email policies.

bpo-27445 [https://bugs.python.org/issue?@action=redirect&bpo=27445]: Don't pass str(_charset) to MIMEText.set_payload(). Patch by Claude Paroz.

bpo-22450 [https://bugs.python.org/issue?@action=redirect&bpo=22450]: urllib now includes an Accept: */* header among the default headers. This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved.

lib2to3.pgen3.driver.load_grammar() now creates a stable cache file between runs given the same Grammar.txt input regardless of the hash randomization setting.

bpo-27570 [https://bugs.python.org/issue?@action=redirect&bpo=27570]: Avoid zero-length memcpy() etc calls with null source pointers in the "ctypes" and "array" modules.

bpo-22233 [https://bugs.python.org/issue?@action=redirect&bpo=22233]: Break email header lines only on the RFC specified CR and LF characters, not on arbitrary unicode line breaks. This also fixes a bug in HTTP header parsing.

bpo-27988 [https://bugs.python.org/issue?@action=redirect&bpo=27988]: Fix email iter_attachments incorrect mutation of payload list.

bpo-27691 [https://bugs.python.org/issue?@action=redirect&bpo=27691]: Fix ssl module's parsing of GEN_RID subject alternative name fields in X.509 certs.

bpo-27850 [https://bugs.python.org/issue?@action=redirect&bpo=27850]: Remove 3DES from ssl module's default cipher list to counter measure sweet32 attack (CVE 2016-2183 [https://www.cve.org/CVERecord?id=CVE-2016-2183]).

bpo-27766 [https://bugs.python.org/issue?@action=redirect&bpo=27766]: Add ChaCha20 Poly1305 to ssl module's default cipher list. (Required OpenSSL 1.1.0 or LibreSSL).

bpo-26470 [https://bugs.python.org/issue?@action=redirect&bpo=26470]: Port ssl and hashlib module to OpenSSL 1.1.0.

Remove support for passing a file descriptor to os.access. It never worked but previously didn't raise.

bpo-12885 [https://bugs.python.org/issue?@action=redirect&bpo=12885]: Fix error when distutils encounters symlink.

bpo-27881 [https://bugs.python.org/issue?@action=redirect&bpo=27881]: Fixed possible bugs when setting sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

bpo-27861 [https://bugs.python.org/issue?@action=redirect&bpo=27861]: Fixed a crash in sqlite3.Connection.cursor() when a factory creates not a cursor. Patch by Xiang Zhang.

bpo-19884 [https://bugs.python.org/issue?@action=redirect&bpo=19884]: Avoid spurious output on OS X with Gnu Readline.

bpo-27706 [https://bugs.python.org/issue?@action=redirect&bpo=27706]: Restore deterministic behavior of random.Random().seed() for string seeds using seeding version 1. Allows sequences of calls to random() to exactly match those obtained in Python 2. Patch by Nofar Schnider.

bpo-10513 [https://bugs.python.org/issue?@action=redirect&bpo=10513]: Fix a regression in Connection.commit(). Statements should not be reset after a commit.

A new version of typing.py from https://github.com/python/typing: Collection (only for 3.6) (bpo-27598 [https://bugs.python.org/issue?@action=redirect&bpo=27598]). Add FrozenSet to __all__ (upstream #261). Fix crash in _get_type_vars() (upstream #259). Remove the dict constraint in ForwardRef._eval_type (upstream #252).

bpo-27539 [https://bugs.python.org/issue?@action=redirect&bpo=27539]: Fix unnormalised Fraction.__pow__ result in the case of negative exponent and negative base.

bpo-21718 [https://bugs.python.org/issue?@action=redirect&bpo=21718]: cursor.description is now available for queries using CTEs.

bpo-2466 [https://bugs.python.org/issue?@action=redirect&bpo=2466]: posixpath.ismount now correctly recognizes mount points which the user does not have permission to access.

bpo-27773 [https://bugs.python.org/issue?@action=redirect&bpo=27773]: Correct some memory management errors server_hostname in _ssl.wrap_socket().

bpo-26750 [https://bugs.python.org/issue?@action=redirect&bpo=26750]: unittest.mock.create_autospec() now works properly for subclasses of property() and other data descriptors.

In the curses module, raise an error if window.getstr() or window.instr() is passed a negative value.

bpo-27783 [https://bugs.python.org/issue?@action=redirect&bpo=27783]: Fix possible usage of uninitialized memory in operator.methodcaller.

bpo-27774 [https://bugs.python.org/issue?@action=redirect&bpo=27774]: Fix possible Py_DECREF on unowned object in _sre.

bpo-27760 [https://bugs.python.org/issue?@action=redirect&bpo=27760]: Fix possible integer overflow in binascii.b2a_qp.

bpo-27758 [https://bugs.python.org/issue?@action=redirect&bpo=27758]: Fix possible integer overflow in the _csv module for large record lengths.

bpo-27568 [https://bugs.python.org/issue?@action=redirect&bpo=27568]: Prevent HTTPoxy attack (CVE 2016-1000110 [https://www.cve.org/CVERecord?id=CVE-2016-1000110]). Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates that the script is in CGI mode.

bpo-27656 [https://bugs.python.org/issue?@action=redirect&bpo=27656]: Do not assume sched.h defines any SCHED_* constants.

bpo-27130 [https://bugs.python.org/issue?@action=redirect&bpo=27130]: In the "zlib" module, fix handling of large buffers (typically 4 GiB) when compressing and decompressing. Previously, inputs were limited to 4 GiB, and compression and decompression operations did not properly handle results of 4 GiB.

bpo-27533 [https://bugs.python.org/issue?@action=redirect&bpo=27533]: Release GIL in nt._isdir

bpo-17711 [https://bugs.python.org/issue?@action=redirect&bpo=17711]: Fixed unpickling by the persistent ID with protocol 0. Original patch by Alexandre Vassalotti.

bpo-27522 [https://bugs.python.org/issue?@action=redirect&bpo=27522]: Avoid an unintentional reference cycle in email.feedparser.

bpo-26844 [https://bugs.python.org/issue?@action=redirect&bpo=26844]: Fix error message for imp.find_module() to refer to 'path' instead of 'name'. Patch by Lev Maximov.

bpo-23804 [https://bugs.python.org/issue?@action=redirect&bpo=23804]: Fix SSL zero-length recv() calls to not block and not raise an error about unclean EOF.

bpo-27466 [https://bugs.python.org/issue?@action=redirect&bpo=27466]: Change time format returned by http.cookie.time2netscape, confirming the netscape cookie format and making it consistent with documentation.

bpo-26664 [https://bugs.python.org/issue?@action=redirect&bpo=26664]: Fix activate.fish by removing mis-use of $.

bpo-22115 [https://bugs.python.org/issue?@action=redirect&bpo=22115]: Fixed tracing Tkinter variables: trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now always returns a list of pairs of strings, tracing in the "u" mode now works.

Fix a scoping issue in importlib.util.LazyLoader which triggered an UnboundLocalError when lazy-loading a module that was already put into sys.modules.

bpo-27079 [https://bugs.python.org/issue?@action=redirect&bpo=27079]: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().

bpo-26754 [https://bugs.python.org/issue?@action=redirect&bpo=26754]: Some functions (compile() etc) accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

bpo-27048 [https://bugs.python.org/issue?@action=redirect&bpo=27048]: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

bpo-27330 [https://bugs.python.org/issue?@action=redirect&bpo=27330]: Fixed possible leaks in the ctypes module.

bpo-27238 [https://bugs.python.org/issue?@action=redirect&bpo=27238]: Got rid of bare excepts in the turtle module. Original patch by Jelle Zijlstra.

bpo-27122 [https://bugs.python.org/issue?@action=redirect&bpo=27122]: When an exception is raised within the context being managed by a contextlib.ExitStack() and one of the exit stack generators catches and raises it in a chain, do not re-raise the original exception when exiting, let the new chained one through. This avoids the PEP 479 [https://peps.python.org/pep-0479/] bug described in issue25782.

bpo-26386 [https://bugs.python.org/issue?@action=redirect&bpo=26386]: Fixed ttk.TreeView selection operations with item id's containing spaces.

bpo-16182 [https://bugs.python.org/issue?@action=redirect&bpo=16182]: Fix various functions in the "readline" module to use the locale encoding, and fix get_begidx() and get_endidx() to return code point indexes.

bpo-27392 [https://bugs.python.org/issue?@action=redirect&bpo=27392]: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

bpo-27930 [https://bugs.python.org/issue?@action=redirect&bpo=27930]: Improved behaviour of logging.handlers.QueueListener. Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch.

bpo-21201 [https://bugs.python.org/issue?@action=redirect&bpo=21201]: Improves readability of multiprocessing error message. Thanks to Wojciech Walczak for patch.

bpo-27456 [https://bugs.python.org/issue?@action=redirect&bpo=27456]: asyncio: Set TCP_NODELAY by default.

bpo-27906 [https://bugs.python.org/issue?@action=redirect&bpo=27906]: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

bpo-28174 [https://bugs.python.org/issue?@action=redirect&bpo=28174]: Handle when SO_REUSEPORT isn't properly supported. Patch by Seth Michael Larson.

bpo-26654 [https://bugs.python.org/issue?@action=redirect&bpo=26654]: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

bpo-26909 [https://bugs.python.org/issue?@action=redirect&bpo=26909]: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

bpo-28176 [https://bugs.python.org/issue?@action=redirect&bpo=28176]: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

bpo-27759 [https://bugs.python.org/issue?@action=redirect&bpo=27759]: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

bpo-28368 [https://bugs.python.org/issue?@action=redirect&bpo=28368]: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

bpo-28369 [https://bugs.python.org/issue?@action=redirect&bpo=28369]: Raise RuntimeError when transport's FD is used with add_reader, add_writer, etc.

bpo-28370 [https://bugs.python.org/issue?@action=redirect&bpo=28370]: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

bpo-28371 [https://bugs.python.org/issue?@action=redirect&bpo=28371]: Deprecate passing asyncio.Handles to run_in_executor.

bpo-28372 [https://bugs.python.org/issue?@action=redirect&bpo=28372]: Fix asyncio to support formatting of non-python coroutines.

bpo-28399 [https://bugs.python.org/issue?@action=redirect&bpo=28399]: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

bpo-27972 [https://bugs.python.org/issue?@action=redirect&bpo=27972]: Prohibit Tasks to await on themselves.

bpo-26923 [https://bugs.python.org/issue?@action=redirect&bpo=26923]: Fix asyncio.Gather to refuse being cancelled once all children are done. Patch by Johannes Ebke.

bpo-26796 [https://bugs.python.org/issue?@action=redirect&bpo=26796]: Don't configure the number of workers for default threadpool executor. Initial patch by Hans Lawrenz.

bpo-28600 [https://bugs.python.org/issue?@action=redirect&bpo=28600]: Optimize loop.call_soon().

bpo-28613 [https://bugs.python.org/issue?@action=redirect&bpo=28613]: Fix get_event_loop() return the current loop if called from coroutines/callbacks.

bpo-28639 [https://bugs.python.org/issue?@action=redirect&bpo=28639]: Fix inspect.isawaitable to always return bool Patch by Justin Mayfield.

bpo-28652 [https://bugs.python.org/issue?@action=redirect&bpo=28652]: Make loop methods reject socket kinds they do not support.

bpo-28653 [https://bugs.python.org/issue?@action=redirect&bpo=28653]: Fix a refleak in functools.lru_cache.

bpo-28703 [https://bugs.python.org/issue?@action=redirect&bpo=28703]: Fix asyncio.iscoroutinefunction to handle Mock objects.

bpo-24142 [https://bugs.python.org/issue?@action=redirect&bpo=24142]: Reading a corrupt config file left the parser in an invalid state. Original patch by Florian Höch.

bpo-28990 [https://bugs.python.org/issue?@action=redirect&bpo=28990]: Fix SSL hanging if connection is closed before handshake completed. (Patch by HoHo-Ho)

IDLE

bpo-15308 [https://bugs.python.org/issue?@action=redirect&bpo=15308]: Add 'interrupt execution' (^C) to Shell menu. Patch by Roger Serwy, updated by Bayard Randel.

bpo-27922 [https://bugs.python.org/issue?@action=redirect&bpo=27922]: Stop IDLE tests from 'flashing' gui widgets on the screen.

Add version to title of IDLE help window.

bpo-25564 [https://bugs.python.org/issue?@action=redirect&bpo=25564]: In section on IDLE -- console differences, mention that using exec means that __builtins__ is defined for each statement.

bpo-27714 [https://bugs.python.org/issue?@action=redirect&bpo=27714]: text_textview and test_autocomplete now pass when re-run in the same process. This occurs when test_idle fails when run with the -w option but without -jn. Fix warning from test_config.

bpo-25507 [https://bugs.python.org/issue?@action=redirect&bpo=25507]: IDLE no longer runs buggy code because of its tkinter imports. Users must include the same imports required to run directly in Python.

bpo-27452 [https://bugs.python.org/issue?@action=redirect&bpo=27452]: add line counter and crc to IDLE configHandler test dump.

bpo-27365 [https://bugs.python.org/issue?@action=redirect&bpo=27365]: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

bpo-27245 [https://bugs.python.org/issue?@action=redirect&bpo=27245]: IDLE: Cleanly delete custom themes and key bindings. Previously, when IDLE was started from a console or by import, a cascade of warnings was emitted. Patch by Serhiy Storchaka.

C API

bpo-28808 [https://bugs.python.org/issue?@action=redirect&bpo=28808]: PyUnicode_CompareWithASCIIString() now never raises exceptions.

bpo-26754 [https://bugs.python.org/issue?@action=redirect&bpo=26754]: PyUnicode_FSDecoder() accepted a filename argument encoded as an iterable of integers. Now only strings and bytes-like objects are accepted.

Documentation

bpo-28513 [https://bugs.python.org/issue?@action=redirect&bpo=28513]: Documented command-line interface of zipfile.

Tests

bpo-28950 [https://bugs.python.org/issue?@action=redirect&bpo=28950]: Disallow -j0 to be combined with -T/-l/-M in regrtest command line arguments.

bpo-28666 [https://bugs.python.org/issue?@action=redirect&bpo=28666]: Now test.support.rmtree is able to remove unwritable or unreadable directories.

bpo-23839 [https://bugs.python.org/issue?@action=redirect&bpo=23839]: Various caches now are cleared before running every test file.

bpo-28409 [https://bugs.python.org/issue?@action=redirect&bpo=28409]: regrtest: fix the parser of command line arguments.

bpo-27787 [https://bugs.python.org/issue?@action=redirect&bpo=27787]: Call gc.collect() before checking each test for "dangling threads", since the dangling threads are weak references.

bpo-27369 [https://bugs.python.org/issue?@action=redirect&bpo=27369]: In test_pyexpat, avoid testing an error message detail that changed in Expat 2.2.0.

Tools/Demos

bpo-27952 [https://bugs.python.org/issue?@action=redirect&bpo=27952]: Get Tools/scripts/fixcid.py working with Python 3 and the current "re" module, avoid invalid Python backslash escapes, and fix a bug parsing escaped C quote signs.

bpo-27332 [https://bugs.python.org/issue?@action=redirect&bpo=27332]: Fixed the type of the first argument of module-level functions generated by Argument Clinic. Patch by Petr Viktorin.

bpo-27418 [https://bugs.python.org/issue?@action=redirect&bpo=27418]: Fixed Tools/importbench/importbench.py.

Windows

bpo-28251 [https://bugs.python.org/issue?@action=redirect&bpo=28251]: Improvements to help manuals on Windows.

bpo-28110 [https://bugs.python.org/issue?@action=redirect&bpo=28110]: launcher.msi has different product codes between 32-bit and 64-bit

bpo-25144 [https://bugs.python.org/issue?@action=redirect&bpo=25144]: Ensures TargetDir is set before continuing with custom install.

bpo-27469 [https://bugs.python.org/issue?@action=redirect&bpo=27469]: Adds a shell extension to the launcher so that drag and drop works correctly.

bpo-27309 [https://bugs.python.org/issue?@action=redirect&bpo=27309]: Enabled proper Windows styles in python[w].exe manifest.

Build

bpo-29080 [https://bugs.python.org/issue?@action=redirect&bpo=29080]: Removes hard dependency on hg.exe from PCBuild/build.bat

bpo-23903 [https://bugs.python.org/issue?@action=redirect&bpo=23903]: Added missed names to PC/python3.def.

bpo-10656 [https://bugs.python.org/issue?@action=redirect&bpo=10656]: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

bpo-26359 [https://bugs.python.org/issue?@action=redirect&bpo=26359]: Rename --with-optimiations to --enable-optimizations.

bpo-28444 [https://bugs.python.org/issue?@action=redirect&bpo=28444]: Fix missing extensions modules when cross compiling.

bpo-28248 [https://bugs.python.org/issue?@action=redirect&bpo=28248]: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

bpo-28258 [https://bugs.python.org/issue?@action=redirect&bpo=28258]: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

bpo-26661 [https://bugs.python.org/issue?@action=redirect&bpo=26661]: setup.py now detects system libffi with multiarch wrapper.

bpo-28066 [https://bugs.python.org/issue?@action=redirect&bpo=28066]: Fix the logic that searches build directories for generated include files when building outside the source tree.

bpo-15819 [https://bugs.python.org/issue?@action=redirect&bpo=15819]: Remove redundant include search directory option for building outside the source tree.

bpo-27566 [https://bugs.python.org/issue?@action=redirect&bpo=27566]: Fix clean target in freeze makefile (patch by Lisa Roach)

bpo-27705 [https://bugs.python.org/issue?@action=redirect&bpo=27705]: Update message in validate_ucrtbase.py

bpo-27983 [https://bugs.python.org/issue?@action=redirect&bpo=27983]: Cause lack of llvm-profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when --with-optimizations is enabled. Also improve our ability to find the llvm-profdata tool on MacOS and some Linuxes.

bpo-26307 [https://bugs.python.org/issue?@action=redirect&bpo=26307]: The profile-opt build now applies PGO to the built-in modules.

bpo-26359 [https://bugs.python.org/issue?@action=redirect&bpo=26359]: Add the --with-optimizations configure flag.

bpo-27713 [https://bugs.python.org/issue?@action=redirect&bpo=27713]: Suppress spurious build warnings when updating importlib's bootstrap files. Patch by Xiang Zhang

bpo-25825 [https://bugs.python.org/issue?@action=redirect&bpo=25825]: Correct the references to Modules/python.exp and ld_so_aix, which are required on AIX. This updates references to an installation path that was changed in 3.2a4, and undoes changed references to the build tree that were made in 3.5.0a1.

bpo-27453 [https://bugs.python.org/issue?@action=redirect&bpo=27453]: CPP invocation in configure must use CPPFLAGS. Patch by Chi Hsuan Yen.

bpo-27641 [https://bugs.python.org/issue?@action=redirect&bpo=27641]: The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross-compiled.

bpo-26662 [https://bugs.python.org/issue?@action=redirect&bpo=26662]: Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build.

bpo-10910 [https://bugs.python.org/issue?@action=redirect&bpo=10910]: Avoid C++ compilation errors on FreeBSD and OS X. Also update FreedBSD version checks for the original ctype UTF-8 workaround.

bpo-28676 [https://bugs.python.org/issue?@action=redirect&bpo=28676]: Prevent missing 'getentropy' declaration warning on macOS. Patch by Gareth Rees.

Python 3.5.2 final

Release date: 2016-06-26

Core and Builtins

bpo-26930 [https://bugs.python.org/issue?@action=redirect&bpo=26930]: Update Windows builds to use OpenSSL 1.0.2h.

Tests

bpo-26867 [https://bugs.python.org/issue?@action=redirect&bpo=26867]: Ubuntu's openssl OP_NO_SSLv3 is forced on by default; fix test.

IDLE

bpo-27365 [https://bugs.python.org/issue?@action=redirect&bpo=27365]: Allow non-ascii in idlelib/NEWS.txt - minimal part for 3.5.2.

Python 3.5.2 release candidate 1

Release date: 2016-06-12

Security

bpo-26556 [https://bugs.python.org/issue?@action=redirect&bpo=26556]: Update expat to 2.1.1, fixes CVE 2015-1283 [https://www.cve.org/CVERecord?id=CVE-2015-1283].

Fix TLS stripping vulnerability in smtplib, CVE 2016-0772 [https://www.cve.org/CVERecord?id=CVE-2016-0772]. Reported by Team Oststrom.

bpo-26839 [https://bugs.python.org/issue?@action=redirect&bpo=26839]: On Linux, os.urandom() now calls getrandom() with GRND_NONBLOCK to fall back on reading /dev/urandom if the urandom entropy pool is not initialized yet. Patch written by Colm Buckley.

bpo-26657 [https://bugs.python.org/issue?@action=redirect&bpo=26657]: Fix directory traversal vulnerability with http.server on Windows. This fixes a regression that was introduced in 3.3.4rc1 and 3.4.0rc1. Based on patch by Philipp Hagemeister.

bpo-26313 [https://bugs.python.org/issue?@action=redirect&bpo=26313]: ssl.py _load_windows_store_certs fails if windows cert store is empty. Patch by Baji.

bpo-25939 [https://bugs.python.org/issue?@action=redirect&bpo=25939]: On Windows open the cert store readonly in ssl.enum_certificates.

Core and Builtins

bpo-27066 [https://bugs.python.org/issue?@action=redirect&bpo=27066]: Fixed SystemError if a custom opener (for open()) returns a negative number without setting an exception.

bpo-20041 [https://bugs.python.org/issue?@action=redirect&bpo=20041]: Fixed TypeError when frame.f_trace is set to None. Patch by Xavier de Gaye.

bpo-26168 [https://bugs.python.org/issue?@action=redirect&bpo=26168]: Fixed possible refleaks in failing Py_BuildValue() with the "N" format unit.

bpo-26991 [https://bugs.python.org/issue?@action=redirect&bpo=26991]: Fix possible refleak when creating a function with annotations.

bpo-27039 [https://bugs.python.org/issue?@action=redirect&bpo=27039]: Fixed bytearray.remove() for values greater than 127. Patch by Joe Jevnik.

bpo-23640 [https://bugs.python.org/issue?@action=redirect&bpo=23640]: int.from_bytes() no longer bypasses constructors for subclasses.

bpo-26811 [https://bugs.python.org/issue?@action=redirect&bpo=26811]: gc.get_objects() no longer contains a broken tuple with NULL pointer.

bpo-20120 [https://bugs.python.org/issue?@action=redirect&bpo=20120]: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.

bpo-26659 [https://bugs.python.org/issue?@action=redirect&bpo=26659]: Make the builtin slice type support cycle collection.

bpo-26718 [https://bugs.python.org/issue?@action=redirect&bpo=26718]: super.__init__ no longer leaks memory if called multiple times. NOTE: A direct call of super.__init__ is not endorsed!

bpo-25339 [https://bugs.python.org/issue?@action=redirect&bpo=25339]: PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout.

bpo-26494 [https://bugs.python.org/issue?@action=redirect&bpo=26494]: Fixed crash on iterating exhausting iterators. Affected classes are generic sequence iterators, iterators of str, bytes, bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding views and os.scandir() iterator.

bpo-26581 [https://bugs.python.org/issue?@action=redirect&bpo=26581]: If coding cookie is specified multiple times on a line in Python source code file, only the first one is taken to account.

bpo-26464 [https://bugs.python.org/issue?@action=redirect&bpo=26464]: Fix str.translate() when string is ASCII and first replacements removes character, but next replacement uses a non-ASCII character or a string longer than 1 character. Regression introduced in Python 3.5.0.

bpo-22836 [https://bugs.python.org/issue?@action=redirect&bpo=22836]: Ensure exception reports from PyErr_Display() and PyErr_WriteUnraisable() are sensible even when formatting them produces secondary errors. This affects the reports produced by sys.__excepthook__() and when __del__() raises an exception.

bpo-26302 [https://bugs.python.org/issue?@action=redirect&bpo=26302]: Correct behavior to reject comma as a legal character for cookie names.

bpo-4806 [https://bugs.python.org/issue?@action=redirect&bpo=4806]: Avoid masking the original TypeError exception when using star (*) unpacking in function calls. Based on patch by Hagen Fürstenau and Daniel Urban.

bpo-27138 [https://bugs.python.org/issue?@action=redirect&bpo=27138]: Fix the doc comment for FileFinder.find_spec().

bpo-26154 [https://bugs.python.org/issue?@action=redirect&bpo=26154]: Add a new private _PyThreadState_UncheckedGet() function to get the current Python thread state, but don't issue a fatal error if it is NULL. This new function must be used instead of accessing directly the _PyThreadState_Current variable. The variable is no more exposed since Python 3.5.1 to hide the exact implementation of atomic C types, to avoid compiler issues.

bpo-26194 [https://bugs.python.org/issue?@action=redirect&bpo=26194]: Deque.insert() gave odd results for bounded deques that had reached their maximum size. Now an IndexError will be raised when attempting to insert into a full deque.

bpo-25843 [https://bugs.python.org/issue?@action=redirect&bpo=25843]: When compiling code, don't merge constants if they are equal but have a different types. For example, f1, f2 = lambda: 1, lambda: 1.0 is now correctly compiled to two different functions: f1() returns 1 (int) and f2() returns 1.0 (int), even if 1 and 1.0 are equal.

bpo-22995 [https://bugs.python.org/issue?@action=redirect&bpo=22995]: [UPDATE] Comment out the one of the pickleability tests in _PyObject_GetState() due to regressions observed in Cython-based projects.

bpo-25961 [https://bugs.python.org/issue?@action=redirect&bpo=25961]: Disallowed null characters in the type name.

bpo-25973 [https://bugs.python.org/issue?@action=redirect&bpo=25973]: Fix segfault when an invalid nonlocal statement binds a name starting with two underscores.

bpo-22995 [https://bugs.python.org/issue?@action=redirect&bpo=22995]: Instances of extension types with a state that aren't subclasses of list or dict and haven't implemented any pickle-related methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or __getstate__), can no longer be pickled. Including memoryview.

bpo-20440 [https://bugs.python.org/issue?@action=redirect&bpo=20440]: Massive replacing unsafe attribute setting code with special macro Py_SETREF.

bpo-25766 [https://bugs.python.org/issue?@action=redirect&bpo=25766]: Special method __bytes__() now works in str subclasses.

bpo-25421 [https://bugs.python.org/issue?@action=redirect&bpo=25421]: __sizeof__ methods of builtin types now use dynamic basic size. This allows sys.getsize() to work correctly with their subclasses with __slots__ defined.

bpo-25709 [https://bugs.python.org/issue?@action=redirect&bpo=25709]: Fixed problem with in-place string concatenation and utf-8 cache.

bpo-27147 [https://bugs.python.org/issue?@action=redirect&bpo=27147]: Mention PEP 420 [https://peps.python.org/pep-0420/] in the importlib docs.

bpo-24097 [https://bugs.python.org/issue?@action=redirect&bpo=24097]: Fixed crash in object.__reduce__() if slot name is freed inside __getattr__.

bpo-24731 [https://bugs.python.org/issue?@action=redirect&bpo=24731]: Fixed crash on converting objects with special methods __bytes__, __trunc__, and __float__ returning instances of subclasses of bytes, int, and float to subclasses of bytes, int, and float correspondingly.

bpo-26478 [https://bugs.python.org/issue?@action=redirect&bpo=26478]: Fix semantic bugs when using binary operators with dictionary views and tuples.

bpo-26171 [https://bugs.python.org/issue?@action=redirect&bpo=26171]: Fix possible integer overflow and heap corruption in zipimporter.get_data().

bpo-25660 [https://bugs.python.org/issue?@action=redirect&bpo=25660]: Fix TAB key behaviour in REPL with readline.

bpo-25887 [https://bugs.python.org/issue?@action=redirect&bpo=25887]: Raise a RuntimeError when a coroutine object is awaited more than once.

bpo-27243 [https://bugs.python.org/issue?@action=redirect&bpo=27243]: Update the __aiter__ protocol: instead of returning an awaitable that resolves to an asynchronous iterator, the asynchronous iterator should be returned directly. Doing the former will trigger a PendingDeprecationWarning.

Library

bpo-21386 [https://bugs.python.org/issue?@action=redirect&bpo=21386]: Implement missing IPv4Address.is_global property. It was documented since 07a5610bae9d. Initial patch by Roger Luethi.

bpo-20900 [https://bugs.python.org/issue?@action=redirect&bpo=20900]: distutils register command now decodes HTTP responses correctly. Initial patch by ingrid.

A new version of typing.py provides several new classes and features: @overload outside stubs, Reversible, DefaultDict, Text, ContextManager, Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some of the new features are not yet implemented in mypy or other static analyzers). Also classes for PEP 492 [https://peps.python.org/pep-0492/] (Awaitable, AsyncIterable, AsyncIterator) have been added (in fact they made it into 3.5.1 but were never mentioned).

bpo-25738 [https://bugs.python.org/issue?@action=redirect&bpo=25738]: Stop http.server.BaseHTTPRequestHandler.send_error() from sending a message body for 205 Reset Content. Also, don't send Content header fields in responses that don't have a body. Patch by Susumu Koshiba.

bpo-21313 [https://bugs.python.org/issue?@action=redirect&bpo=21313]: Fix the "platform" module to tolerate when sys.version contains truncated build information.

bpo-27164 [https://bugs.python.org/issue?@action=redirect&bpo=27164]: In the zlib module, allow decompressing raw Deflate streams with a predefined zdict. Based on patch by Xiang Zhang.

bpo-24291 [https://bugs.python.org/issue?@action=redirect&bpo=24291]: Fix wsgiref.simple_server.WSGIRequestHandler to completely write data to the client. Previously it could do partial writes and truncate data. Also, wsgiref.handler.ServerHandler can now handle stdout doing partial writes, but this is deprecated.

bpo-26809 [https://bugs.python.org/issue?@action=redirect&bpo=26809]: Add __all__ to string. Patch by Emanuel Barry.

bpo-26373 [https://bugs.python.org/issue?@action=redirect&bpo=26373]: subprocess.Popen.communicate now correctly ignores BrokenPipeError when the child process dies before .communicate() is called in more/all circumstances.

bpo-21776 [https://bugs.python.org/issue?@action=redirect&bpo=21776]: distutils.upload now correctly handles HTTPError. Initial patch by Claudiu Popa.

bpo-27114 [https://bugs.python.org/issue?@action=redirect&bpo=27114]: Fix SSLContext._load_windows_store_certs fails with PermissionError

bpo-18383 [https://bugs.python.org/issue?@action=redirect&bpo=18383]: Avoid creating duplicate filters when using filterwarnings and simplefilter. Based on patch by Alex Shkop.

bpo-27057 [https://bugs.python.org/issue?@action=redirect&bpo=27057]: Fix os.set_inheritable() on Android, ioctl() is blocked by SELinux and fails with EACCESS. The function now falls back to fcntl(). Patch written by Michał Bednarski.

bpo-27014 [https://bugs.python.org/issue?@action=redirect&bpo=27014]: Fix infinite recursion using typing.py. Thanks to Kalle Tuure!

bpo-14132 [https://bugs.python.org/issue?@action=redirect&bpo=14132]: Fix urllib.request redirect handling when the target only has a query string. Original fix by Ján Janech.

bpo-17214 [https://bugs.python.org/issue?@action=redirect&bpo=17214]: The "urllib.request" module now percent-encodes non-ASCII bytes found in redirect target URLs. Some servers send Location header fields with non-ASCII bytes, but "http.client" requires the request target to be ASCII-encodable, otherwise a UnicodeEncodeError is raised. Based on patch by Christian Heimes.

bpo-26892 [https://bugs.python.org/issue?@action=redirect&bpo=26892]: Honor debuglevel flag in urllib.request.HTTPHandler. Patch contributed by Chi Hsuan Yen.

bpo-22274 [https://bugs.python.org/issue?@action=redirect&bpo=22274]: In the subprocess module, allow stderr to be redirected to stdout even when stdout is not redirected. Patch by Akira Li.

bpo-26807 [https://bugs.python.org/issue?@action=redirect&bpo=26807]: mock_open 'files' no longer error on readline at end of file. Patch from Yolanda Robla.

bpo-25745 [https://bugs.python.org/issue?@action=redirect&bpo=25745]: Fixed leaking a userptr in curses panel destructor.

bpo-26977 [https://bugs.python.org/issue?@action=redirect&bpo=26977]: Removed unnecessary, and ignored, call to sum of squares helper in statistics.pvariance.

bpo-26881 [https://bugs.python.org/issue?@action=redirect&bpo=26881]: The modulefinder module now supports extended opcode arguments.

bpo-23815 [https://bugs.python.org/issue?@action=redirect&bpo=23815]: Fixed crashes related to directly created instances of types in _tkinter and curses.panel modules.

bpo-17765 [https://bugs.python.org/issue?@action=redirect&bpo=17765]: weakref.ref() no longer silently ignores keyword arguments. Patch by Georg Brandl.

bpo-26873 [https://bugs.python.org/issue?@action=redirect&bpo=26873]: xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result.

bpo-26711 [https://bugs.python.org/issue?@action=redirect&bpo=26711]: Fixed the comparison of plistlib.Data with other types.

bpo-24114 [https://bugs.python.org/issue?@action=redirect&bpo=24114]: Fix an uninitialized variable in ctypes.util. The bug only occurs on SunOS when the ctypes implementation searches for the crle program. Patch by Xiang Zhang. Tested on SunOS by Kees Bos.

bpo-26864 [https://bugs.python.org/issue?@action=redirect&bpo=26864]: In urllib.request, change the proxy bypass host checking against no_proxy to be case-insensitive, and to not match unrelated host names that happen to have a bypassed hostname as a suffix. Patch by Xiang Zhang.

bpo-26634 [https://bugs.python.org/issue?@action=redirect&bpo=26634]: recursive_repr() now sets __qualname__ of wrapper. Patch by Xiang Zhang.

bpo-26804 [https://bugs.python.org/issue?@action=redirect&bpo=26804]: urllib.request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones. Patch contributed by Hans-Peter Jansen.

bpo-26837 [https://bugs.python.org/issue?@action=redirect&bpo=26837]: assertSequenceEqual() now correctly outputs non-stringified differing items (like bytes in the -b mode). This affects assertListEqual() and assertTupleEqual().

bpo-26041 [https://bugs.python.org/issue?@action=redirect&bpo=26041]: Remove "will be removed in Python 3.7" from deprecation messages of platform.dist() and platform.linux_distribution(). Patch by Kumaripaba Miyurusara Athukorala.

bpo-26822 [https://bugs.python.org/issue?@action=redirect&bpo=26822]: itemgetter, attrgetter and methodcaller objects no longer silently ignore keyword arguments.

bpo-26733 [https://bugs.python.org/issue?@action=redirect&bpo=26733]: Disassembling a class now disassembles class and static methods. Patch by Xiang Zhang.

bpo-26801 [https://bugs.python.org/issue?@action=redirect&bpo=26801]: Fix error handling in shutil.get_terminal_size(), catch AttributeError instead of NameError. Patch written by Emanuel Barry.

bpo-24838 [https://bugs.python.org/issue?@action=redirect&bpo=24838]: tarfile's ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf-8.

bpo-26717 [https://bugs.python.org/issue?@action=redirect&bpo=26717]: Stop encoding Latin-1-ized WSGI paths with UTF-8. Patch by Anthony Sottile.

bpo-26735 [https://bugs.python.org/issue?@action=redirect&bpo=26735]: Fix os.urandom() on Solaris 11.3 and newer when reading more than 1,024 bytes: call getrandom() multiple times with a limit of 1024 bytes per call.

bpo-16329 [https://bugs.python.org/issue?@action=redirect&bpo=16329]: Add .webm to mimetypes.types_map. Patch by Giampaolo Rodola'.

bpo-13952 [https://bugs.python.org/issue?@action=redirect&bpo=13952]: Add .csv to mimetypes.types_map. Patch by Geoff Wilson.

bpo-26709 [https://bugs.python.org/issue?@action=redirect&bpo=26709]: Fixed Y2038 problem in loading binary PLists.

bpo-23735 [https://bugs.python.org/issue?@action=redirect&bpo=23735]: Handle terminal resizing with Readline 6.3+ by installing our own SIGWINCH handler. Patch by Eric Price.

bpo-26586 [https://bugs.python.org/issue?@action=redirect&bpo=26586]: In http.server, respond with "413 Request header fields too large" if there are too many header fields to parse, rather than killing the connection and raising an unhandled exception. Patch by Xiang Zhang.

bpo-22854 [https://bugs.python.org/issue?@action=redirect&bpo=22854]: Change BufferedReader.writable() and BufferedWriter.readable() to always return False.

bpo-25195 [https://bugs.python.org/issue?@action=redirect&bpo=25195]: Fix a regression in mock.MagicMock. _Call is a subclass of tuple (changeset 3603bae63c13 only works for classes) so we need to implement __ne__ ourselves. Patch by Andrew Plummer.

bpo-26644 [https://bugs.python.org/issue?@action=redirect&bpo=26644]: Raise ValueError rather than SystemError when a negative length is passed to SSLSocket.recv() or read().

bpo-23804 [https://bugs.python.org/issue?@action=redirect&bpo=23804]: Fix SSL recv(0) and read(0) methods to return zero bytes instead of up to 1024.

bpo-26616 [https://bugs.python.org/issue?@action=redirect&bpo=26616]: Fixed a bug in datetime.astimezone() method.

bpo-21925 [https://bugs.python.org/issue?@action=redirect&bpo=21925]: warnings.formatwarning() now catches exceptions on linecache.getline(...) to be able to log ResourceWarning emitted late during the Python shutdown process.

bpo-24266 [https://bugs.python.org/issue?@action=redirect&bpo=24266]: Ctrl+C during Readline history search now cancels the search mode when compiled with Readline 7.

bpo-26560 [https://bugs.python.org/issue?@action=redirect&bpo=26560]: Avoid potential ValueError in BaseHandler.start_response. Initial patch by Peter Inglesby.

bpo-26569 [https://bugs.python.org/issue?@action=redirect&bpo=26569]: Fix pyclbr.readmodule() and pyclbr.readmodule_ex() to support importing packages.

bpo-26499 [https://bugs.python.org/issue?@action=redirect&bpo=26499]: Account for remaining Content-Length in HTTPResponse.readline() and read1(). Based on patch by Silent Ghost. Also document that HTTPResponse now supports these methods.

bpo-25320 [https://bugs.python.org/issue?@action=redirect&bpo=25320]: Handle sockets in directories unittest discovery is scanning. Patch from Victor van den Elzen.

bpo-16181 [https://bugs.python.org/issue?@action=redirect&bpo=16181]: cookiejar.http2time() now returns None if year is higher than datetime.MAXYEAR.

bpo-26513 [https://bugs.python.org/issue?@action=redirect&bpo=26513]: Fixes platform module detection of Windows Server

bpo-23718 [https://bugs.python.org/issue?@action=redirect&bpo=23718]: Fixed parsing time in week 0 before Jan 1. Original patch by Tamás Bence Gedai.

bpo-20589 [https://bugs.python.org/issue?@action=redirect&bpo=20589]: Invoking Path.owner() and Path.group() on Windows now raise NotImplementedError instead of ImportError.

bpo-26177 [https://bugs.python.org/issue?@action=redirect&bpo=26177]: Fixed the keys() method for Canvas and Scrollbar widgets.

bpo-15068 [https://bugs.python.org/issue?@action=redirect&bpo=15068]: Got rid of excessive buffering in the fileinput module. The bufsize parameter is no longer used.

bpo-2202 [https://bugs.python.org/issue?@action=redirect&bpo=2202]: Fix UnboundLocalError in AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu Dupuy.

bpo-25718 [https://bugs.python.org/issue?@action=redirect&bpo=25718]: Fixed pickling and copying the accumulate() iterator with total is None.

bpo-26475 [https://bugs.python.org/issue?@action=redirect&bpo=26475]: Fixed debugging output for regular expressions with the (?x) flag.

bpo-26457 [https://bugs.python.org/issue?@action=redirect&bpo=26457]: Fixed the subnets() methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length. Based on patch by Xiang Zhang.

bpo-26385 [https://bugs.python.org/issue?@action=redirect&bpo=26385]: Remove the file if the internal open() call in NamedTemporaryFile() fails. Patch by Silent Ghost.

bpo-26402 [https://bugs.python.org/issue?@action=redirect&bpo=26402]: Fix XML-RPC client to retry when the server shuts down a persistent connection. This was a regression related to the new http.client.RemoteDisconnected exception in 3.5.0a4.

bpo-25913 [https://bugs.python.org/issue?@action=redirect&bpo=25913]: Leading <~ is optional now in base64.a85decode() with adobe=True. Patch by Swati Jaiswal.

bpo-26186 [https://bugs.python.org/issue?@action=redirect&bpo=26186]: Remove an invalid type check in importlib.util.LazyLoader.

bpo-26367 [https://bugs.python.org/issue?@action=redirect&bpo=26367]: importlib.__import__() raises SystemError like builtins.__import__() when level is specified but without an accompanying package specified.

bpo-26309 [https://bugs.python.org/issue?@action=redirect&bpo=26309]: In the "socketserver" module, shut down the request (closing the connected socket) when verify_request() returns false. Patch by Aviv Palivoda.

bpo-25995 [https://bugs.python.org/issue?@action=redirect&bpo=25995]: os.walk() no longer uses FDs proportional to the tree depth.

bpo-26117 [https://bugs.python.org/issue?@action=redirect&bpo=26117]: The os.scandir() iterator now closes file descriptor not only when the iteration is finished, but when it was failed with error.

bpo-25911 [https://bugs.python.org/issue?@action=redirect&bpo=25911]: Restored support of bytes paths in os.walk() on Windows.

bpo-26045 [https://bugs.python.org/issue?@action=redirect&bpo=26045]: Add UTF-8 suggestion to error message when posting a non-Latin-1 string with http.client.

bpo-12923 [https://bugs.python.org/issue?@action=redirect&bpo=12923]: Reset FancyURLopener's redirect counter even if there is an exception. Based on patches by Brian Brazil and Daniel Rocco.

bpo-25945 [https://bugs.python.org/issue?@action=redirect&bpo=25945]: Fixed a crash when unpickle the functools.partial object with wrong state. Fixed a leak in failed functools.partial constructor. "args" and "keywords" attributes of functools.partial have now always types tuple and dict correspondingly.

bpo-26202 [https://bugs.python.org/issue?@action=redirect&bpo=26202]: copy.deepcopy() now correctly copies range() objects with non-atomic attributes.

bpo-23076 [https://bugs.python.org/issue?@action=redirect&bpo=23076]: Path.glob() now raises a ValueError if it's called with an invalid pattern. Patch by Thomas Nyberg.

bpo-19883 [https://bugs.python.org/issue?@action=redirect&bpo=19883]: Fixed possible integer overflows in zipimport.

bpo-26227 [https://bugs.python.org/issue?@action=redirect&bpo=26227]: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex() functions of the socket module now decode the hostname from the ANSI code page rather than UTF-8.

bpo-26147 [https://bugs.python.org/issue?@action=redirect&bpo=26147]: xmlrpc now works with strings not encodable with used non-UTF-8 encoding.

bpo-25935 [https://bugs.python.org/issue?@action=redirect&bpo=25935]: Garbage collector now breaks reference loops with OrderedDict.

bpo-16620 [https://bugs.python.org/issue?@action=redirect&bpo=16620]: Fixed AttributeError in msilib.Directory.glob().

bpo-26013 [https://bugs.python.org/issue?@action=redirect&bpo=26013]: Added compatibility with broken protocol 2 pickles created in old Python 3 versions (3.4.3 and lower).

bpo-25850 [https://bugs.python.org/issue?@action=redirect&bpo=25850]: Use cross-compilation by default for 64-bit Windows.

bpo-17633 [https://bugs.python.org/issue?@action=redirect&bpo=17633]: Improve zipimport's support for namespace packages.

bpo-24705 [https://bugs.python.org/issue?@action=redirect&bpo=24705]: Fix sysconfig._parse_makefile not expanding ${} vars appearing before $() vars.

bpo-22138 [https://bugs.python.org/issue?@action=redirect&bpo=22138]: Fix mock.patch behavior when patching descriptors. Restore original values after patching. Patch contributed by Sean McCully.

bpo-25672 [https://bugs.python.org/issue?@action=redirect&bpo=25672]: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so.

bpo-26012 [https://bugs.python.org/issue?@action=redirect&bpo=26012]: Don't traverse into symlinks for ** pattern in pathlib.Path.[r]glob().

bpo-24120 [https://bugs.python.org/issue?@action=redirect&bpo=24120]: Ignore PermissionError when traversing a tree with pathlib.Path.[r]glob(). Patch by Ulrich Petri.

bpo-25447 [https://bugs.python.org/issue?@action=redirect&bpo=25447]: fileinput now uses sys.stdin as-is if it does not have a buffer attribute (restores backward compatibility).

bpo-25447 [https://bugs.python.org/issue?@action=redirect&bpo=25447]: Copying the lru_cache() wrapper object now always works, independently from the type of the wrapped object (by returning the original object unchanged).

bpo-24103 [https://bugs.python.org/issue?@action=redirect&bpo=24103]: Fixed possible use after free in ElementTree.XMLPullParser.

bpo-25860 [https://bugs.python.org/issue?@action=redirect&bpo=25860]: os.fwalk() no longer skips remaining directories when error occurs. Original patch by Samson Lee.

bpo-25914 [https://bugs.python.org/issue?@action=redirect&bpo=25914]: Fixed and simplified OrderedDict.__sizeof__.

bpo-25902 [https://bugs.python.org/issue?@action=redirect&bpo=25902]: Fixed various refcount issues in ElementTree iteration.

bpo-25717 [https://bugs.python.org/issue?@action=redirect&bpo=25717]: Restore the previous behaviour of tolerating most fstat() errors when opening files. This was a regression in 3.5a1, and stopped anonymous temporary files from working in special cases.

bpo-24903 [https://bugs.python.org/issue?@action=redirect&bpo=24903]: Fix regression in number of arguments compileall accepts when '-d' is specified. The check on the number of arguments has been dropped completely as it never worked correctly anyway.

bpo-25764 [https://bugs.python.org/issue?@action=redirect&bpo=25764]: In the subprocess module, preserve any exception caused by fork() failure when preexec_fn is used.

bpo-6478 [https://bugs.python.org/issue?@action=redirect&bpo=6478]: _strptime's regexp cache now is reset after changing timezone with time.tzset().

bpo-14285 [https://bugs.python.org/issue?@action=redirect&bpo=14285]: When executing a package with the "python -m package" option, and package initialization fails, a proper traceback is now reported. The "runpy" module now lets exceptions from package initialization pass back to the caller, rather than raising ImportError.

bpo-19771 [https://bugs.python.org/issue?@action=redirect&bpo=19771]: Also in runpy and the "-m" option, omit the irrelevant message ". . . is a package and cannot be directly executed" if the package could not even be initialized (e.g. due to a bad *.pyc file).

bpo-25177 [https://bugs.python.org/issue?@action=redirect&bpo=25177]: Fixed problem with the mean of very small and very large numbers. As a side effect, statistics.mean and statistics.variance should be significantly faster.

bpo-25718 [https://bugs.python.org/issue?@action=redirect&bpo=25718]: Fixed copying object with state with boolean value is false.

bpo-10131 [https://bugs.python.org/issue?@action=redirect&bpo=10131]: Fixed deep copying of minidom documents. Based on patch by Marian Ganisin.

bpo-25725 [https://bugs.python.org/issue?@action=redirect&bpo=25725]: Fixed a reference leak in pickle.loads() when unpickling invalid data including tuple instructions.

bpo-25663 [https://bugs.python.org/issue?@action=redirect&bpo=25663]: In the Readline completer, avoid listing duplicate global names, and search the global namespace before searching builtins.

bpo-25688 [https://bugs.python.org/issue?@action=redirect&bpo=25688]: Fixed file leak in ElementTree.iterparse() raising an error.

bpo-23914 [https://bugs.python.org/issue?@action=redirect&bpo=23914]: Fixed SystemError raised by unpickler on broken pickle data.

bpo-25691 [https://bugs.python.org/issue?@action=redirect&bpo=25691]: Fixed crash on deleting ElementTree.Element attributes.

bpo-25624 [https://bugs.python.org/issue?@action=redirect&bpo=25624]: ZipFile now always writes a ZIP_STORED header for directory entries. Patch by Dingyuan Wang.

Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu Davis.

bpo-26050 [https://bugs.python.org/issue?@action=redirect&bpo=26050]: Add asyncio.StreamReader.readuntil() method. Patch by Марк Коренберг.

bpo-25924 [https://bugs.python.org/issue?@action=redirect&bpo=25924]: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X versions 10.5 or higher. Original patch by A. Jesse Jiryu Davis.

bpo-26406 [https://bugs.python.org/issue?@action=redirect&bpo=26406]: Avoid unnecessary serialization of getaddrinfo(3) calls on current versions of OpenBSD and NetBSD. Patch by A. Jesse Jiryu Davis.

bpo-26848 [https://bugs.python.org/issue?@action=redirect&bpo=26848]: Fix asyncio/subprocess.communicate() to handle empty input. Patch by Jack O'Connor.

bpo-27040 [https://bugs.python.org/issue?@action=redirect&bpo=27040]: Add loop.get_exception_handler method

bpo-27041 [https://bugs.python.org/issue?@action=redirect&bpo=27041]: asyncio: Add loop.create_future method

bpo-27223 [https://bugs.python.org/issue?@action=redirect&bpo=27223]: asyncio: Fix _read_ready and _write_ready to respect _conn_lost. Patch by Łukasz Langa.

bpo-22970 [https://bugs.python.org/issue?@action=redirect&bpo=22970]: asyncio: Fix inconsistency cancelling Condition.wait. Patch by David Coles.

IDLE

bpo-5124 [https://bugs.python.org/issue?@action=redirect&bpo=5124]: Paste with text selected now replaces the selection on X11. This matches how paste works on Windows, Mac, most modern Linux apps, and ttk widgets. Original patch by Serhiy Storchaka.

bpo-24759 [https://bugs.python.org/issue?@action=redirect&bpo=24759]: Make clear in idlelib.idle_test.__init__ that the directory is a private implementation of test.test_idle and tool for maintainers.

bpo-27196 [https://bugs.python.org/issue?@action=redirect&bpo=27196]: Stop 'ThemeChanged' warnings when running IDLE tests. These persisted after other warnings were suppressed in #20567. Apply Serhiy Storchaka's update_idletasks solution to four test files. Record this additional advice in idle_test/README.txt

bpo-20567 [https://bugs.python.org/issue?@action=redirect&bpo=20567]: Revise idle_test/README.txt with advice about avoiding tk warning messages from tests. Apply advice to several IDLE tests.

bpo-27117 [https://bugs.python.org/issue?@action=redirect&bpo=27117]: Make colorizer htest and turtledemo work with dark themes. Move code for configuring text widget colors to a new function.

bpo-26673 [https://bugs.python.org/issue?@action=redirect&bpo=26673]: When tk reports font size as 0, change to size 10. Such fonts on Linux prevented the configuration dialog from opening.

bpo-21939 [https://bugs.python.org/issue?@action=redirect&bpo=21939]: Add test for IDLE's percolator. Original patch by Saimadhav Heblikar.

bpo-21676 [https://bugs.python.org/issue?@action=redirect&bpo=21676]: Add test for IDLE's replace dialog. Original patch by Saimadhav Heblikar.

bpo-18410 [https://bugs.python.org/issue?@action=redirect&bpo=18410]: Add test for IDLE's search dialog. Original patch by Westley Martínez.

bpo-21703 [https://bugs.python.org/issue?@action=redirect&bpo=21703]: Add test for IDLE's undo delegator. Original patch by Saimadhav Heblikar .

bpo-27044 [https://bugs.python.org/issue?@action=redirect&bpo=27044]: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

bpo-23977 [https://bugs.python.org/issue?@action=redirect&bpo=23977]: Add more asserts to test_delegator.

bpo-20640 [https://bugs.python.org/issue?@action=redirect&bpo=20640]: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav Heblikar.

In the 'IDLE-console differences' section of the IDLE doc, clarify how running with IDLE affects sys.modules and the standard streams.

bpo-25507 [https://bugs.python.org/issue?@action=redirect&bpo=25507]: fix incorrect change in IOBinding that prevented printing. Augment IOBinding htest to include all major IOBinding functions.

bpo-25905 [https://bugs.python.org/issue?@action=redirect&bpo=25905]: Revert unwanted conversion of ' to ’ RIGHT SINGLE QUOTATION MARK in README.txt and open this and NEWS.txt with 'ascii'. Re-encode CREDITS.txt to utf-8 and open it with 'utf-8'.

Documentation

bpo-19489 [https://bugs.python.org/issue?@action=redirect&bpo=19489]: Moved the search box from the sidebar to the header and footer of each page. Patch by Ammar Askar.

bpo-24136 [https://bugs.python.org/issue?@action=redirect&bpo=24136]: Document the new PEP 448 [https://peps.python.org/pep-0448/] unpacking syntax of 3.5.

bpo-26736 [https://bugs.python.org/issue?@action=redirect&bpo=26736]: Used HTTPS for external links in the documentation if possible.

bpo-6953 [https://bugs.python.org/issue?@action=redirect&bpo=6953]: Rework the Readline module documentation to group related functions together, and add more details such as what underlying Readline functions and variables are accessed.

bpo-23606 [https://bugs.python.org/issue?@action=redirect&bpo=23606]: Adds note to ctypes documentation regarding cdll.msvcrt.

bpo-25500 [https://bugs.python.org/issue?@action=redirect&bpo=25500]: Fix documentation to not claim that __import__ is searched for in the global scope.

bpo-26014 [https://bugs.python.org/issue?@action=redirect&bpo=26014]: Update 3.x packaging documentation: * "See also" links to the new docs are now provided in the legacy pages * links to setuptools documentation have been updated

Tests

bpo-21916 [https://bugs.python.org/issue?@action=redirect&bpo=21916]: Added tests for the turtle module. Patch by ingrid, Gregory Loyse and Jelle Zijlstra.

bpo-26523 [https://bugs.python.org/issue?@action=redirect&bpo=26523]: The multiprocessing thread pool (multiprocessing.dummy.Pool) was untested.

bpo-26015 [https://bugs.python.org/issue?@action=redirect&bpo=26015]: Added new tests for pickling iterators of mutable sequences.

bpo-26325 [https://bugs.python.org/issue?@action=redirect&bpo=26325]: Added test.support.check_no_resource_warning() to check that no ResourceWarning is emitted.

bpo-25940 [https://bugs.python.org/issue?@action=redirect&bpo=25940]: Changed test_ssl to use self-signed.pythontest.net. This avoids relying on svn.python.org, which recently changed root certificate.

bpo-25616 [https://bugs.python.org/issue?@action=redirect&bpo=25616]: Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict.

bpo-26583 [https://bugs.python.org/issue?@action=redirect&bpo=26583]: Skip test_timestamp_overflow in test_import if bytecode files cannot be written.

Build

bpo-26884 [https://bugs.python.org/issue?@action=redirect&bpo=26884]: Fix linking extension modules for cross builds. Patch by Xavier de Gaye.

bpo-22359 [https://bugs.python.org/issue?@action=redirect&bpo=22359]: Disable the rules for running _freeze_importlib and pgen when cross-compiling. The output of these programs is normally saved with the source code anyway, and is still regenerated when doing a native build. Patch by Xavier de Gaye.

bpo-27229 [https://bugs.python.org/issue?@action=redirect&bpo=27229]: Fix the cross-compiling pgen rule for in-tree builds. Patch by Xavier de Gaye.

bpo-21668 [https://bugs.python.org/issue?@action=redirect&bpo=21668]: Link audioop, _datetime, _ctypes_test modules to libm, except on Mac OS X. Patch written by Xavier de Gaye.

bpo-25702 [https://bugs.python.org/issue?@action=redirect&bpo=25702]: A --with-lto configure option has been added that will enable link time optimizations at build time during a make profile-opt. Some compilers and toolchains are known to not produce stable code when using LTO, be sure to test things thoroughly before relying on it. It can provide a few % speed up over profile-opt alone.

bpo-26624 [https://bugs.python.org/issue?@action=redirect&bpo=26624]: Adds validation of ucrtbase[d].dll version with warning for old versions.

bpo-17603 [https://bugs.python.org/issue?@action=redirect&bpo=17603]: Avoid error about nonexistent fileblocks.o file by using a lower-level check for st_blocks in struct stat.

bpo-26079 [https://bugs.python.org/issue?@action=redirect&bpo=26079]: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern Thiel.

bpo-26465 [https://bugs.python.org/issue?@action=redirect&bpo=26465]: Update Windows builds to use OpenSSL 1.0.2g.

bpo-24421 [https://bugs.python.org/issue?@action=redirect&bpo=24421]: Compile Modules/_math.c once, before building extensions. Previously it could fail to compile properly if the math and cmath builds were concurrent.

bpo-25348 [https://bugs.python.org/issue?@action=redirect&bpo=25348]: Added --pgo and --pgo-job arguments to PCbuild\build.bat for building with Profile-Guided Optimization. The old PCbuild\build_pgo.bat script is now deprecated, and simply calls PCbuild\build.bat --pgo %*.

bpo-25827 [https://bugs.python.org/issue?@action=redirect&bpo=25827]: Add support for building with ICC to configure, including a new --with-icc flag.

bpo-25696 [https://bugs.python.org/issue?@action=redirect&bpo=25696]: Fix installation of Python on UNIX with make -j9.

bpo-26930 [https://bugs.python.org/issue?@action=redirect&bpo=26930]: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2h.

bpo-26268 [https://bugs.python.org/issue?@action=redirect&bpo=26268]: Update Windows builds to use OpenSSL 1.0.2f.

bpo-25136 [https://bugs.python.org/issue?@action=redirect&bpo=25136]: Support Apple Xcode 7's new textual SDK stub libraries.

bpo-24324 [https://bugs.python.org/issue?@action=redirect&bpo=24324]: Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc-4.5.

Windows

bpo-27053 [https://bugs.python.org/issue?@action=redirect&bpo=27053]: Updates make_zip.py to correctly generate library ZIP file.

bpo-26268 [https://bugs.python.org/issue?@action=redirect&bpo=26268]: Update the prepare_ssl.py script to handle OpenSSL releases that don't include the contents of the include directory (that is, 1.0.2e and later).

bpo-26071 [https://bugs.python.org/issue?@action=redirect&bpo=26071]: bdist_wininst created binaries fail to start and find 32bit Python

bpo-26073 [https://bugs.python.org/issue?@action=redirect&bpo=26073]: Update the list of magic numbers in launcher

bpo-26065 [https://bugs.python.org/issue?@action=redirect&bpo=26065]: Excludes venv from library when generating embeddable distro.

bpo-17500 [https://bugs.python.org/issue?@action=redirect&bpo=17500]: Remove unused and outdated icons. (See also: https://github.com/python/pythondotorg/issues/945)

Tools/Demos

bpo-26799 [https://bugs.python.org/issue?@action=redirect&bpo=26799]: Fix python-gdb.py: don't get C types once when the Python code is loaded, but get C types on demand. The C types can change if python-gdb.py is loaded before the Python executable. Patch written by Thomas Ilsche.

bpo-26271 [https://bugs.python.org/issue?@action=redirect&bpo=26271]: Fix the Freeze tool to properly use flags passed through configure. Patch by Daniel Shaulov.

bpo-26489 [https://bugs.python.org/issue?@action=redirect&bpo=26489]: Add dictionary unpacking support to Tools/parser/unparse.py. Patch by Guo Ci Teo.

bpo-26316 [https://bugs.python.org/issue?@action=redirect&bpo=26316]: Fix variable name typo in Argument Clinic.

Python 3.5.1 final

Release date: 2015-12-06

Core and Builtins

bpo-25709 [https://bugs.python.org/issue?@action=redirect&bpo=25709]: Fixed problem with in-place string concatenation and utf-8 cache.

Windows

bpo-25715 [https://bugs.python.org/issue?@action=redirect&bpo=25715]: Python 3.5.1 installer shows wrong upgrade path and incorrect logic for launcher detection.

Python 3.5.1 release candidate 1

Release date: 2015-11-22

Core and Builtins

bpo-25630 [https://bugs.python.org/issue?@action=redirect&bpo=25630]: Fix a possible segfault during argument parsing in functions that accept filesystem paths.

bpo-23564 [https://bugs.python.org/issue?@action=redirect&bpo=23564]: Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child. The bug had no actual impact as subprocess.py already avoided it.

bpo-25388 [https://bugs.python.org/issue?@action=redirect&bpo=25388]: Fixed tokenizer crash when processing undecodable source code with a null byte.

bpo-25462 [https://bugs.python.org/issue?@action=redirect&bpo=25462]: The hash of the key now is calculated only once in most operations in C implementation of OrderedDict.

bpo-22995 [https://bugs.python.org/issue?@action=redirect&bpo=22995]: Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__.

bpo-25555 [https://bugs.python.org/issue?@action=redirect&bpo=25555]: Fix parser and AST: fill lineno and col_offset of "arg" node when compiling AST from Python objects.

bpo-24802 [https://bugs.python.org/issue?@action=redirect&bpo=24802]: Avoid buffer overreads when int(), float(), compile(), exec() and eval() are passed bytes-like objects. These objects are not necessarily terminated by a null byte, but the functions assumed they were.

bpo-24726 [https://bugs.python.org/issue?@action=redirect&bpo=24726]: Fixed a crash and leaking NULL in repr() of OrderedDict that was mutated by direct calls of dict methods.

bpo-25449 [https://bugs.python.org/issue?@action=redirect&bpo=25449]: Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation.

bpo-25395 [https://bugs.python.org/issue?@action=redirect&bpo=25395]: Fixed crash when highly nested OrderedDict structures were garbage collected.

bpo-25274 [https://bugs.python.org/issue?@action=redirect&bpo=25274]: sys.setrecursionlimit() now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth. Modify also the "lower-water mark" formula to make it monotonic. This mark is used to decide when the overflowed flag of the thread state is reset.

bpo-24402 [https://bugs.python.org/issue?@action=redirect&bpo=24402]: Fix input() to prompt to the redirected stdout when sys.stdout.fileno() fails.

bpo-24806 [https://bugs.python.org/issue?@action=redirect&bpo=24806]: Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance.

bpo-24848 [https://bugs.python.org/issue?@action=redirect&bpo=24848]: Fixed a number of bugs in UTF-7 decoding of misformed data.

bpo-25280 [https://bugs.python.org/issue?@action=redirect&bpo=25280]: Import trace messages emitted in verbose (-v) mode are no longer formatted twice.

bpo-25003 [https://bugs.python.org/issue?@action=redirect&bpo=25003]: On Solaris 11.3 or newer, os.urandom() now uses the getrandom() function instead of the getentropy() function. The getentropy() function is blocking to generate very good quality entropy, os.urandom() doesn't need such high-quality entropy.

bpo-25182 [https://bugs.python.org/issue?@action=redirect&bpo=25182]: The stdprinter (used as sys.stderr before the io module is imported at startup) now uses the backslashreplace error handler.

bpo-25131 [https://bugs.python.org/issue?@action=redirect&bpo=25131]: Make the line number and column offset of set/dict literals and comprehensions correspond to the opening brace.

bpo-25150 [https://bugs.python.org/issue?@action=redirect&bpo=25150]: Hide the private _Py_atomic_xxx symbols from the public Python.h header to fix a compilation error with OpenMP. PyThreadState_GET() becomes an alias to PyThreadState_Get() to avoid ABI incompatibilities.

Library

bpo-25626 [https://bugs.python.org/issue?@action=redirect&bpo=25626]: Change three zlib functions to accept sizes that fit in Py_ssize_t, but internally cap those sizes to UINT_MAX. This resolves a regression in 3.5 where GzipFile.read() failed to read chunks larger than 2 or 4 GiB. The change affects the zlib.Decompress.decompress() max_length parameter, the zlib.decompress() bufsize parameter, and the zlib.Decompress.flush() length parameter.

bpo-25583 [https://bugs.python.org/issue?@action=redirect&bpo=25583]: Avoid incorrect errors raised by os.makedirs(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

bpo-25593 [https://bugs.python.org/issue?@action=redirect&bpo=25593]: Change semantics of EventLoop.stop() in asyncio.

bpo-6973 [https://bugs.python.org/issue?@action=redirect&bpo=6973]: When we know a subprocess.Popen process has died, do not allow the send_signal(), terminate(), or kill() methods to do anything as they could potentially signal a different process.

bpo-25590 [https://bugs.python.org/issue?@action=redirect&bpo=25590]: In the Readline completer, only call getattr() once per attribute.

bpo-25498 [https://bugs.python.org/issue?@action=redirect&bpo=25498]: Fix a crash when garbage-collecting ctypes objects created by wrapping a memoryview. This was a regression made in 3.5a1. Based on patch by Eryksun.

bpo-25584 [https://bugs.python.org/issue?@action=redirect&bpo=25584]: Added "escape" to the __all__ list in the glob module.

bpo-25584 [https://bugs.python.org/issue?@action=redirect&bpo=25584]: Fixed recursive glob() with patterns starting with **.

bpo-25446 [https://bugs.python.org/issue?@action=redirect&bpo=25446]: Fix regression in smtplib's AUTH LOGIN support.

bpo-18010 [https://bugs.python.org/issue?@action=redirect&bpo=18010]: Fix the pydoc web server's module search function to handle exceptions from importing packages.

bpo-25554 [https://bugs.python.org/issue?@action=redirect&bpo=25554]: Got rid of circular references in regular expression parsing.

bpo-25510 [https://bugs.python.org/issue?@action=redirect&bpo=25510]: fileinput.FileInput.readline() now returns b'' instead of '' at the end if the FileInput was opened with binary mode. Patch by Ryosuke Ito.

bpo-25503 [https://bugs.python.org/issue?@action=redirect&bpo=25503]: Fixed inspect.getdoc() for inherited docstrings of properties. Original patch by John Mark Vandenberg.

bpo-25515 [https://bugs.python.org/issue?@action=redirect&bpo=25515]: Always use os.urandom as a source of randomness in uuid.uuid4.

bpo-21827 [https://bugs.python.org/issue?@action=redirect&bpo=21827]: Fixed textwrap.dedent() for the case when largest common whitespace is a substring of smallest leading whitespace. Based on patch by Robert Li.

bpo-25447 [https://bugs.python.org/issue?@action=redirect&bpo=25447]: The lru_cache() wrapper objects now can be copied and pickled (by returning the original object unchanged).

bpo-25390 [https://bugs.python.org/issue?@action=redirect&bpo=25390]: typing: Don't crash on Union[str, Pattern].

bpo-25441 [https://bugs.python.org/issue?@action=redirect&bpo=25441]: asyncio: Raise error from drain() when socket is closed.

bpo-25410 [https://bugs.python.org/issue?@action=redirect&bpo=25410]: Cleaned up and fixed minor bugs in C implementation of OrderedDict.

bpo-25411 [https://bugs.python.org/issue?@action=redirect&bpo=25411]: Improved Unicode support in SMTPHandler through better use of the email package. Thanks to user simon04 for the patch.

bpo-25407 [https://bugs.python.org/issue?@action=redirect&bpo=25407]: Remove mentions of the formatter module being removed in Python 3.6.

bpo-25406 [https://bugs.python.org/issue?@action=redirect&bpo=25406]: Fixed a bug in C implementation of OrderedDict.move_to_end() that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict.

bpo-25364 [https://bugs.python.org/issue?@action=redirect&bpo=25364]: zipfile now works in threads disabled builds.

bpo-25328 [https://bugs.python.org/issue?@action=redirect&bpo=25328]: smtpd's SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true.

bpo-25316 [https://bugs.python.org/issue?@action=redirect&bpo=25316]: distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed.

bpo-25380 [https://bugs.python.org/issue?@action=redirect&bpo=25380]: Fixed protocol for the STACK_GLOBAL opcode in pickletools.opcodes.

bpo-23972 [https://bugs.python.org/issue?@action=redirect&bpo=23972]: Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket. Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O/S is 'posix' (except if the platform is Cygwin). Patch by Chris Laws.

bpo-25304 [https://bugs.python.org/issue?@action=redirect&bpo=25304]: Add asyncio.run_coroutine_threadsafe(). This lets you submit a coroutine to a loop from another thread, returning a concurrent.futures.Future. By Vincent Michel.

bpo-25232 [https://bugs.python.org/issue?@action=redirect&bpo=25232]: Fix CGIRequestHandler to split the query from the URL at the first question mark (?) rather than the last. Patch from Xiang Zhang.

bpo-24657 [https://bugs.python.org/issue?@action=redirect&bpo=24657]: Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path. Patch from Xiang Zhang.

bpo-24483 [https://bugs.python.org/issue?@action=redirect&bpo=24483]: C implementation of functools.lru_cache() now calculates key's hash only once.

bpo-22958 [https://bugs.python.org/issue?@action=redirect&bpo=22958]: Constructor and update method of weakref.WeakValueDictionary now accept the self and the dict keyword arguments.

bpo-22609 [https://bugs.python.org/issue?@action=redirect&bpo=22609]: Constructor of collections.UserDict now accepts the self keyword argument.

bpo-25111 [https://bugs.python.org/issue?@action=redirect&bpo=25111]: Fixed comparison of traceback.FrameSummary.

bpo-25262 [https://bugs.python.org/issue?@action=redirect&bpo=25262]: Added support for BINBYTES8 opcode in Python implementation of unpickler. Highest 32 bits of 64-bit size for BINUNICODE8 and BINBYTES8 opcodes no longer silently ignored on 32-bit platforms in C implementation.

bpo-25034 [https://bugs.python.org/issue?@action=redirect&bpo=25034]: Fix string.Formatter problem with auto-numbering and nested format_specs. Patch by Anthon van der Neut.

bpo-25233 [https://bugs.python.org/issue?@action=redirect&bpo=25233]: Rewrite the guts of asyncio.Queue and asyncio.Semaphore to be more understandable and correct.

bpo-25203 [https://bugs.python.org/issue?@action=redirect&bpo=25203]: Failed readline.set_completer_delims() no longer left the module in inconsistent state.

bpo-23600 [https://bugs.python.org/issue?@action=redirect&bpo=23600]: Default implementation of tzinfo.fromutc() was returning wrong results in some cases.

bpo-23329 [https://bugs.python.org/issue?@action=redirect&bpo=23329]: Allow the ssl module to be built with older versions of LibreSSL.

Prevent overflow in _Unpickler_Read.

bpo-25047 [https://bugs.python.org/issue?@action=redirect&bpo=25047]: The XML encoding declaration written by Element Tree now respects the letter case given by the user. This restores the ability to write encoding names in uppercase like "UTF-8", which worked in Python 2.

bpo-25135 [https://bugs.python.org/issue?@action=redirect&bpo=25135]: Make deque_clear() safer by emptying the deque before clearing. This helps avoid possible reentrancy issues.

bpo-19143 [https://bugs.python.org/issue?@action=redirect&bpo=19143]: platform module now reads Windows version from kernel32.dll to avoid compatibility shims.

bpo-25092 [https://bugs.python.org/issue?@action=redirect&bpo=25092]: Fix datetime.strftime() failure when errno was already set to EINVAL.

bpo-23517 [https://bugs.python.org/issue?@action=redirect&bpo=23517]: Fix rounding in fromtimestamp() and utcfromtimestamp() methods of datetime.datetime: microseconds are now rounded to nearest with ties going to nearest even integer (ROUND_HALF_EVEN), instead of being rounding towards minus infinity (ROUND_FLOOR). It's important that these methods use the same rounding mode than datetime.timedelta to keep the property: (datetime(1970,1,1) + timedelta(seconds=t)) == datetime.utcfromtimestamp(t). It also the rounding mode used by round(float) for example.

bpo-25155 [https://bugs.python.org/issue?@action=redirect&bpo=25155]: Fix datetime.datetime.now() and datetime.datetime.utcnow() on Windows to support date after year 2038. It was a regression introduced in Python 3.5.0.

bpo-25108 [https://bugs.python.org/issue?@action=redirect&bpo=25108]: Omitted internal frames in traceback functions print_stack(), format_stack(), and extract_stack() called without arguments.

bpo-25118 [https://bugs.python.org/issue?@action=redirect&bpo=25118]: Fix a regression of Python 3.5.0 in os.waitpid() on Windows.

bpo-24684 [https://bugs.python.org/issue?@action=redirect&bpo=24684]: socket.socket.getaddrinfo() now calls PyUnicode_AsEncodedString() instead of calling the encode() method of the host, to handle correctly custom string with an encode() method which doesn't return a byte string. The encoder of the IDNA codec is now called directly instead of calling the encode() method of the string.

bpo-25060 [https://bugs.python.org/issue?@action=redirect&bpo=25060]: Correctly compute stack usage of the BUILD_MAP opcode.

bpo-24857 [https://bugs.python.org/issue?@action=redirect&bpo=24857]: Comparing call_args to a long sequence now correctly returns a boolean result instead of raising an exception. Patch by A Kaptur.

bpo-23144 [https://bugs.python.org/issue?@action=redirect&bpo=23144]: Make sure that HTMLParser.feed() returns all the data, even when convert_charrefs is True.

bpo-24982 [https://bugs.python.org/issue?@action=redirect&bpo=24982]: shutil.make_archive() with the "zip" format now adds entries for directories (including empty directories) in ZIP file.

bpo-25019 [https://bugs.python.org/issue?@action=redirect&bpo=25019]: Fixed a crash caused by setting non-string key of expat parser. Based on patch by John Leitch.

bpo-16180 [https://bugs.python.org/issue?@action=redirect&bpo=16180]: Exit pdb if file has syntax error, instead of trapping user in an infinite loop. Patch by Xavier de Gaye.

bpo-24891 [https://bugs.python.org/issue?@action=redirect&bpo=24891]: Fix a race condition at Python startup if the file descriptor of stdin (0), stdout (1) or stderr (2) is closed while Python is creating sys.stdin, sys.stdout and sys.stderr objects. These attributes are now set to None if the creation of the object failed, instead of raising an OSError exception. Initial patch written by Marco Paolini.

bpo-24992 [https://bugs.python.org/issue?@action=redirect&bpo=24992]: Fix error handling and a race condition (related to garbage collection) in collections.OrderedDict constructor.

bpo-24881 [https://bugs.python.org/issue?@action=redirect&bpo=24881]: Fixed setting binary mode in Python implementation of FileIO on Windows and Cygwin. Patch from Akira Li.

bpo-25578 [https://bugs.python.org/issue?@action=redirect&bpo=25578]: Fix (another) memory leak in SSLSocket.getpeercer().

bpo-25530 [https://bugs.python.org/issue?@action=redirect&bpo=25530]: Disable the vulnerable SSLv3 protocol by default when creating ssl.SSLContext.

bpo-25569 [https://bugs.python.org/issue?@action=redirect&bpo=25569]: Fix memory leak in SSLSocket.getpeercert().

bpo-25471 [https://bugs.python.org/issue?@action=redirect&bpo=25471]: Sockets returned from accept() shouldn't appear to be nonblocking.

bpo-25319 [https://bugs.python.org/issue?@action=redirect&bpo=25319]: When threading.Event is reinitialized, the underlying condition should use a regular lock rather than a recursive lock.

bpo-21112 [https://bugs.python.org/issue?@action=redirect&bpo=21112]: Fix regression in unittest.expectedFailure on subclasses. Patch from Berker Peksag.

bpo-24764 [https://bugs.python.org/issue?@action=redirect&bpo=24764]: cgi.FieldStorage.read_multi() now ignores the Content-Length header in part headers. Patch written by Peter Landry and reviewed by Pierre Quentel.

bpo-24913 [https://bugs.python.org/issue?@action=redirect&bpo=24913]: Fix overrun error in deque.index(). Found by John Leitch and Bryce Darling.

bpo-24774 [https://bugs.python.org/issue?@action=redirect&bpo=24774]: Fix docstring in http.server.test. Patch from Chiu-Hsiang Hsu.

bpo-21159 [https://bugs.python.org/issue?@action=redirect&bpo=21159]: Improve message in configparser.InterpolationMissingOptionError. Patch from Łukasz Langa.

bpo-20362 [https://bugs.python.org/issue?@action=redirect&bpo=20362]: Honour TestCase.longMessage correctly in assertRegex. Patch from Ilia Kurenkov.

bpo-23572 [https://bugs.python.org/issue?@action=redirect&bpo=23572]: Fixed functools.singledispatch on classes with false metaclasses. Patch by Ethan Furman.

asyncio: ensure_future() now accepts awaitable objects.

IDLE

bpo-15348 [https://bugs.python.org/issue?@action=redirect&bpo=15348]: Stop the debugger engine (normally in a user process) before closing the debugger window (running in the IDLE process). This prevents the RuntimeErrors that were being caught and ignored.

bpo-24455 [https://bugs.python.org/issue?@action=redirect&bpo=24455]: Prevent IDLE from hanging when a) closing the shell while the debugger is active (15347); b) closing the debugger with the [X] button (15348); and c) activating the debugger when already active (24455). The patch by Mark Roseman does this by making two changes. 1. Suspend and resume the gui.interaction method with the tcl vwait mechanism intended for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow any existing interaction to terminate first.

Change 'The program' to 'Your program' in an IDLE 'kill program?' message to make it clearer that the program referred to is the currently running user program, not IDLE itself.

bpo-24750 [https://bugs.python.org/issue?@action=redirect&bpo=24750]: Improve the appearance of the IDLE editor window status bar. Patch by Mark Roseman.

bpo-25313 [https://bugs.python.org/issue?@action=redirect&bpo=25313]: Change the handling of new built-in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark. Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

bpo-24782 [https://bugs.python.org/issue?@action=redirect&bpo=24782]: Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog. The former tabs are now a sorted list. Patch by Mark Roseman.

bpo-22726 [https://bugs.python.org/issue?@action=redirect&bpo=22726]: Re-activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme.

bpo-24820 [https://bugs.python.org/issue?@action=redirect&bpo=24820]: IDLE now has an 'IDLE Dark' built-in text color theme. It is more or less IDLE Classic inverted, with a cobalt blue background. Strings, comments, keywords, ... are still green, red, orange, ... . To use it with IDLEs released before November 2015, hit the 'Save as New Custom Theme' button and enter a new name, such as 'Custom Dark'. The custom theme will work with any IDLE release, and can be modified.

bpo-25224 [https://bugs.python.org/issue?@action=redirect&bpo=25224]: README.txt is now an idlelib index for IDLE developers and curious users. The previous user content is now in the IDLE doc chapter. 'IDLE' now means 'Integrated Development and Learning Environment'.

bpo-24820 [https://bugs.python.org/issue?@action=redirect&bpo=24820]: Users can now set breakpoint colors in Settings -> Custom Highlighting. Original patch by Mark Roseman.

bpo-24972 [https://bugs.python.org/issue?@action=redirect&bpo=24972]: Inactive selection background now matches active selection background, as configured by users, on all systems. Found items are now always highlighted on Windows. Initial patch by Mark Roseman.

bpo-24570 [https://bugs.python.org/issue?@action=redirect&bpo=24570]: Idle: make calltip and completion boxes appear on Macs affected by a tk regression. Initial patch by Mark Roseman.

bpo-24988 [https://bugs.python.org/issue?@action=redirect&bpo=24988]: Idle ScrolledList context menus (used in debugger) now work on Mac Aqua. Patch by Mark Roseman.

bpo-24801 [https://bugs.python.org/issue?@action=redirect&bpo=24801]: Make right-click for context menu work on Mac Aqua. Patch by Mark Roseman.

bpo-25173 [https://bugs.python.org/issue?@action=redirect&bpo=25173]: Associate tkinter messageboxes with a specific widget. For Mac OSX, make them a 'sheet'. Patch by Mark Roseman.

bpo-25198 [https://bugs.python.org/issue?@action=redirect&bpo=25198]: Enhance the initial html viewer now used for Idle Help. Properly indent fixed-pitch text (patch by Mark Roseman). Give code snippet a very Sphinx-like light blueish-gray background. Re-use initial width and height set by users for shell and editor. When the Table of Contents (TOC) menu is used, put the section header at the top of the screen.

bpo-25225 [https://bugs.python.org/issue?@action=redirect&bpo=25225]: Condense and rewrite Idle doc section on text colors.

bpo-21995 [https://bugs.python.org/issue?@action=redirect&bpo=21995]: Explain some differences between IDLE and console Python.

bpo-22820 [https://bugs.python.org/issue?@action=redirect&bpo=22820]: Explain need for print when running file from Idle editor.

bpo-25224 [https://bugs.python.org/issue?@action=redirect&bpo=25224]: Doc: augment Idle feature list and no-subprocess section.

bpo-25219 [https://bugs.python.org/issue?@action=redirect&bpo=25219]: Update doc for Idle command line options. Some were missing and notes were not correct.

bpo-24861 [https://bugs.python.org/issue?@action=redirect&bpo=24861]: Most of idlelib is private and subject to change. Use idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

bpo-25199 [https://bugs.python.org/issue?@action=redirect&bpo=25199]: Idle: add synchronization comments for future maintainers.

bpo-16893 [https://bugs.python.org/issue?@action=redirect&bpo=16893]: Replace help.txt with help.html for Idle doc display. The new idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks better than help.txt and will better document Idle as released. The tkinter html viewer that works for this file was written by Mark Roseman. The now unused EditorWindow.HelpDialog class and helt.txt file are deprecated.

bpo-24199 [https://bugs.python.org/issue?@action=redirect&bpo=24199]: Deprecate unused idlelib.idlever with possible removal in 3.6.

bpo-24790 [https://bugs.python.org/issue?@action=redirect&bpo=24790]: Remove extraneous code (which also create 2 & 3 conflicts).

Documentation

bpo-22558 [https://bugs.python.org/issue?@action=redirect&bpo=22558]: Add remaining doc links to source code for Python-coded modules. Patch by Yoni Lavi.

bpo-12067 [https://bugs.python.org/issue?@action=redirect&bpo=12067]: Rewrite Comparisons section in the Expressions chapter of the language reference. Some of the details of comparing mixed types were incorrect or ambiguous. NotImplemented is only relevant at a lower level than the Expressions chapter. Added details of comparing range() objects, and default behaviour and consistency suggestions for user-defined classes. Patch from Andy Maier.

bpo-24952 [https://bugs.python.org/issue?@action=redirect&bpo=24952]: Clarify the default size argument of stack_size() in the "threading" and "_thread" modules. Patch from Mattip.

bpo-23725 [https://bugs.python.org/issue?@action=redirect&bpo=23725]: Overhaul tempfile docs. Note deprecated status of mktemp. Patch from Zbigniew Jędrzejewski-Szmek.

bpo-24808 [https://bugs.python.org/issue?@action=redirect&bpo=24808]: Update the types of some PyTypeObject fields. Patch by Joseph Weston.

bpo-22812 [https://bugs.python.org/issue?@action=redirect&bpo=22812]: Fix unittest discovery examples. Patch from Pam McA'Nulty.

Tests

bpo-25449 [https://bugs.python.org/issue?@action=redirect&bpo=25449]: Added tests for OrderedDict subclasses.

bpo-25099 [https://bugs.python.org/issue?@action=redirect&bpo=25099]: Make test_compileall not fail when an entry on sys.path cannot be written to (commonly seen in administrative installs on Windows).

bpo-23919 [https://bugs.python.org/issue?@action=redirect&bpo=23919]: Prevents assert dialogs appearing in the test suite.

PCbuild\rt.bat now accepts an unlimited number of arguments to pass along to regrtest.py. Previously there was a limit of 9.

Build

bpo-24915 [https://bugs.python.org/issue?@action=redirect&bpo=24915]: Add LLVM support for PGO builds and use the test suite to generate the profile data. Initial patch by Alecsandru Patrascu of Intel.

bpo-24910 [https://bugs.python.org/issue?@action=redirect&bpo=24910]: Windows MSIs now have unique display names.

bpo-24986 [https://bugs.python.org/issue?@action=redirect&bpo=24986]: It is now possible to build Python on Windows without errors when external libraries are not available.

Windows

bpo-25450 [https://bugs.python.org/issue?@action=redirect&bpo=25450]: Updates shortcuts to start Python in installation directory.

bpo-25164 [https://bugs.python.org/issue?@action=redirect&bpo=25164]: Changes default all-users install directory to match per-user directory.

bpo-25143 [https://bugs.python.org/issue?@action=redirect&bpo=25143]: Improves installer error messages for unsupported platforms.

bpo-25163 [https://bugs.python.org/issue?@action=redirect&bpo=25163]: Display correct directory in installer when using non-default settings.

bpo-25361 [https://bugs.python.org/issue?@action=redirect&bpo=25361]: Disables use of SSE2 instructions in Windows 32-bit build

bpo-25089 [https://bugs.python.org/issue?@action=redirect&bpo=25089]: Adds logging to installer for case where launcher is not selected on upgrade.

bpo-25165 [https://bugs.python.org/issue?@action=redirect&bpo=25165]: Windows uninstallation should not remove launcher if other versions remain

bpo-25112 [https://bugs.python.org/issue?@action=redirect&bpo=25112]: py.exe launcher is missing icons

bpo-25102 [https://bugs.python.org/issue?@action=redirect&bpo=25102]: Windows installer does not precompile for -O or -OO.

bpo-25081 [https://bugs.python.org/issue?@action=redirect&bpo=25081]: Makes Back button in installer go back to upgrade page when upgrading.

bpo-25091 [https://bugs.python.org/issue?@action=redirect&bpo=25091]: Increases font size of the installer.

bpo-25126 [https://bugs.python.org/issue?@action=redirect&bpo=25126]: Clarifies that the non-web installer will download some components.

bpo-25213 [https://bugs.python.org/issue?@action=redirect&bpo=25213]: Restores requestedExecutionLevel to manifest to disable UAC virtualization.

bpo-25022 [https://bugs.python.org/issue?@action=redirect&bpo=25022]: Removed very outdated PC/example_nt/ directory.

Tools/Demos

bpo-25440 [https://bugs.python.org/issue?@action=redirect&bpo=25440]: Fix output of python-config --extension-suffix.

Python 3.5.0 final

Release date: 2015-09-13

Build

bpo-25071 [https://bugs.python.org/issue?@action=redirect&bpo=25071]: Windows installer should not require TargetDir parameter when installing quietly.

Python 3.5.0 release candidate 4

Release date: 2015-09-09

Library

bpo-25029 [https://bugs.python.org/issue?@action=redirect&bpo=25029]: Fixes MemoryError in test_strptime.

Build

bpo-25027 [https://bugs.python.org/issue?@action=redirect&bpo=25027]: Reverts partial-static build options and adds vcruntime140.dll to Windows installation.

Python 3.5.0 release candidate 3

Release date: 2015-09-07

Core and Builtins

bpo-24305 [https://bugs.python.org/issue?@action=redirect&bpo=24305]: Prevent import subsystem stack frames from being counted by the warnings.warn(stacklevel=) parameter.

bpo-24912 [https://bugs.python.org/issue?@action=redirect&bpo=24912]: Prevent __class__ assignment to immutable built-in objects.

bpo-24975 [https://bugs.python.org/issue?@action=redirect&bpo=24975]: Fix AST compilation for PEP 448 [https://peps.python.org/pep-0448/] syntax.

Library

bpo-24917 [https://bugs.python.org/issue?@action=redirect&bpo=24917]: time_strftime() buffer over-read.

bpo-24748 [https://bugs.python.org/issue?@action=redirect&bpo=24748]: To resolve a compatibility problem found with py2exe and pywin32, imp.load_dynamic() once again ignores previously loaded modules to support Python modules replacing themselves with extension modules. Patch by Petr Viktorin.

bpo-24635 [https://bugs.python.org/issue?@action=redirect&bpo=24635]: Fixed a bug in typing.py where isinstance([], typing.Iterable) would return True once, then False on subsequent calls.

bpo-24989 [https://bugs.python.org/issue?@action=redirect&bpo=24989]: Fixed buffer overread in BytesIO.readline() if a position is set beyond size. Based on patch by John Leitch.

bpo-24913 [https://bugs.python.org/issue?@action=redirect&bpo=24913]: Fix overrun error in deque.index(). Found by John Leitch and Bryce Darling.

Python 3.5.0 release candidate 2

Release date: 2015-08-25

Core and Builtins

bpo-24769 [https://bugs.python.org/issue?@action=redirect&bpo=24769]: Interpreter now starts properly when dynamic loading is disabled. Patch by Petr Viktorin.

bpo-21167 [https://bugs.python.org/issue?@action=redirect&bpo=21167]: NAN operations are now handled correctly when python is compiled with ICC even if -fp-model strict is not specified.

bpo-24492 [https://bugs.python.org/issue?@action=redirect&bpo=24492]: A "package" lacking a __name__ attribute when trying to perform a from .. import ... statement will trigger an ImportError instead of an AttributeError.

Library

bpo-24847 [https://bugs.python.org/issue?@action=redirect&bpo=24847]: Removes vcruntime140.dll dependency from Tcl/Tk.

bpo-24839 [https://bugs.python.org/issue?@action=redirect&bpo=24839]: platform._syscmd_ver raises DeprecationWarning

bpo-24867 [https://bugs.python.org/issue?@action=redirect&bpo=24867]: Fix Task.get_stack() for 'async def' coroutines

Python 3.5.0 release candidate 1

Release date: 2015-08-09

Core and Builtins

bpo-24667 [https://bugs.python.org/issue?@action=redirect&bpo=24667]: Resize odict in all cases that the underlying dict resizes.

Library

bpo-24824 [https://bugs.python.org/issue?@action=redirect&bpo=24824]: Signatures of codecs.encode() and codecs.decode() now are compatible with pydoc.

bpo-24634 [https://bugs.python.org/issue?@action=redirect&bpo=24634]: Importing uuid should not try to load libc on Windows

bpo-24798 [https://bugs.python.org/issue?@action=redirect&bpo=24798]: _msvccompiler.py doesn't properly support manifests

bpo-4395 [https://bugs.python.org/issue?@action=redirect&bpo=4395]: Better testing and documentation of binary operators. Patch by Martin Panter.

bpo-23973 [https://bugs.python.org/issue?@action=redirect&bpo=23973]: Update typing.py from GitHub repo.

bpo-23004 [https://bugs.python.org/issue?@action=redirect&bpo=23004]: mock_open() now reads binary data correctly when the type of read_data is bytes. Initial patch by Aaron Hill.

bpo-23888 [https://bugs.python.org/issue?@action=redirect&bpo=23888]: Handle fractional time in cookie expiry. Patch by ssh.

bpo-23652 [https://bugs.python.org/issue?@action=redirect&bpo=23652]: Make it possible to compile the select module against the libc headers from the Linux Standard Base, which do not include some EPOLL macros. Patch by Matt Frank.

bpo-22932 [https://bugs.python.org/issue?@action=redirect&bpo=22932]: Fix timezones in email.utils.formatdate. Patch from Dmitry Shachnev.

bpo-23779 [https://bugs.python.org/issue?@action=redirect&bpo=23779]: imaplib raises TypeError if authenticator tries to abort. Patch from Craig Holmquist.

bpo-23319 [https://bugs.python.org/issue?@action=redirect&bpo=23319]: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch written by Matthieu Gautier.

bpo-23254 [https://bugs.python.org/issue?@action=redirect&bpo=23254]: Document how to close the TCPServer listening socket. Patch from Martin Panter.

bpo-19450 [https://bugs.python.org/issue?@action=redirect&bpo=19450]: Update Windows and OS X installer builds to use SQLite 3.8.11.

bpo-17527 [https://bugs.python.org/issue?@action=redirect&bpo=17527]: Add PATCH to wsgiref.validator. Patch from Luca Sbardella.

bpo-24791 [https://bugs.python.org/issue?@action=redirect&bpo=24791]: Fix grammar regression for call syntax: 'g(*a or b)'.

IDLE

bpo-23672 [https://bugs.python.org/issue?@action=redirect&bpo=23672]: Allow Idle to edit and run files with astral chars in name. Patch by Mohd Sanad Zaki Rizvi.

bpo-24745 [https://bugs.python.org/issue?@action=redirect&bpo=24745]: Idle editor default font. Switch from Courier to platform-sensitive TkFixedFont. This should not affect current customized font selections. If there is a problem, edit $HOME/.idlerc/config-main.cfg and remove 'fontxxx' entries from [Editor Window]. Patch by Mark Roseman.

bpo-21192 [https://bugs.python.org/issue?@action=redirect&bpo=21192]: Idle editor. When a file is run, put its name in the restart bar. Do not print false prompts. Original patch by Adnan Umer.

bpo-13884 [https://bugs.python.org/issue?@action=redirect&bpo=13884]: Idle menus. Remove tearoff lines. Patch by Roger Serwy.

Documentation

bpo-24129 [https://bugs.python.org/issue?@action=redirect&bpo=24129]: Clarify the reference documentation for name resolution. This includes removing the assumption that readers will be familiar with the name resolution scheme Python used prior to the introduction of lexical scoping for function namespaces. Patch by Ivan Levkivskyi.

bpo-20769 [https://bugs.python.org/issue?@action=redirect&bpo=20769]: Improve reload() docs. Patch by Dorian Pula.

bpo-23589 [https://bugs.python.org/issue?@action=redirect&bpo=23589]: Remove duplicate sentence from the FAQ. Patch by Yongzhi Pan.

bpo-24729 [https://bugs.python.org/issue?@action=redirect&bpo=24729]: Correct IO tutorial to match implementation regarding encoding parameter to open function.

Tests

bpo-24751 [https://bugs.python.org/issue?@action=redirect&bpo=24751]: When running regrtest with the -w command line option, a test run is no longer marked as a failure if all tests succeed when re-run.

Python 3.5.0 beta 4

Release date: 2015-07-26

Core and Builtins

bpo-23573 [https://bugs.python.org/issue?@action=redirect&bpo=23573]: Restored optimization of bytes.rfind() and bytearray.rfind() for single-byte argument on Linux.

bpo-24569 [https://bugs.python.org/issue?@action=redirect&bpo=24569]: Make PEP 448 [https://peps.python.org/pep-0448/] dictionary evaluation more consistent.

bpo-24583 [https://bugs.python.org/issue?@action=redirect&bpo=24583]: Fix crash when set is mutated while being updated.

bpo-24407 [https://bugs.python.org/issue?@action=redirect&bpo=24407]: Fix crash when dict is mutated while being updated.

bpo-24619 [https://bugs.python.org/issue?@action=redirect&bpo=24619]: New approach for tokenizing async/await. As a consequence, it is now possible to have one-line 'async def foo(): await ..' functions.

bpo-24687 [https://bugs.python.org/issue?@action=redirect&bpo=24687]: Plug refleak on SyntaxError in function parameters annotations.

bpo-15944 [https://bugs.python.org/issue?@action=redirect&bpo=15944]: memoryview: Allow arbitrary formats when casting to bytes. Patch by Martin Panter.

Library

bpo-23441 [https://bugs.python.org/issue?@action=redirect&bpo=23441]: rcompleter now prints a tab character instead of displaying possible completions for an empty word. Initial patch by Martin Sekera.

bpo-24683 [https://bugs.python.org/issue?@action=redirect&bpo=24683]: Fixed crashes in _json functions called with arguments of inappropriate type.

bpo-21697 [https://bugs.python.org/issue?@action=redirect&bpo=21697]: shutil.copytree() now correctly handles symbolic links that point to directories. Patch by Eduardo Seabra and Thomas Kluyver.

bpo-14373 [https://bugs.python.org/issue?@action=redirect&bpo=14373]: Fixed segmentation fault when gc.collect() is called during constructing lru_cache (C implementation).

bpo-24695 [https://bugs.python.org/issue?@action=redirect&bpo=24695]: Fix a regression in traceback.print_exception(). If exc_traceback is None we shouldn't print a traceback header like described in the documentation.

bpo-24620 [https://bugs.python.org/issue?@action=redirect&bpo=24620]: Random.setstate() now validates the value of state last element.

bpo-22485 [https://bugs.python.org/issue?@action=redirect&bpo=22485]: Fixed an issue that caused inspect.getsource to return incorrect results on nested functions.

bpo-22153 [https://bugs.python.org/issue?@action=redirect&bpo=22153]: Improve unittest docs. Patch from Martin Panter and evilzero.

bpo-24580 [https://bugs.python.org/issue?@action=redirect&bpo=24580]: Symbolic group references to open group in re patterns now are explicitly forbidden as well as numeric group references.

bpo-24206 [https://bugs.python.org/issue?@action=redirect&bpo=24206]: Fixed __eq__ and __ne__ methods of inspect classes.

bpo-24631 [https://bugs.python.org/issue?@action=redirect&bpo=24631]: Fixed regression in the timeit module with multiline setup.

bpo-18622 [https://bugs.python.org/issue?@action=redirect&bpo=18622]: unittest.mock.mock_open().reset_mock would recurse infinitely. Patch from Nicola Palumbo and Laurent De Buyst.

bpo-23661 [https://bugs.python.org/issue?@action=redirect&bpo=23661]: unittest.mock side_effects can now be exceptions again. This was a regression vs Python 3.4. Patch from Ignacio Rossi

bpo-24608 [https://bugs.python.org/issue?@action=redirect&bpo=24608]: chunk.Chunk.read() now always returns bytes, not str.

bpo-18684 [https://bugs.python.org/issue?@action=redirect&bpo=18684]: Fixed reading out of the buffer in the re module.

bpo-24259 [https://bugs.python.org/issue?@action=redirect&bpo=24259]: tarfile now raises a ReadError if an archive is truncated inside a data segment.

bpo-15014 [https://bugs.python.org/issue?@action=redirect&bpo=15014]: SMTP.auth() and SMTP.login() now support RFC 4954's optional initial-response argument to the SMTP AUTH command.

bpo-24669 [https://bugs.python.org/issue?@action=redirect&bpo=24669]: Fix inspect.getsource() for 'async def' functions. Patch by Kai Groner.

bpo-24688 [https://bugs.python.org/issue?@action=redirect&bpo=24688]: ast.get_docstring() for 'async def' functions.

Build

bpo-24603 [https://bugs.python.org/issue?@action=redirect&bpo=24603]: Update Windows builds and OS X 10.5 installer to use OpenSSL 1.0.2d.

Python 3.5.0 beta 3

Release date: 2015-07-05

Core and Builtins

bpo-24467 [https://bugs.python.org/issue?@action=redirect&bpo=24467]: Fixed possible buffer over-read in bytearray. The bytearray object now always allocates place for trailing null byte and it's buffer now is always null-terminated.

Upgrade to Unicode 8.0.0.

bpo-24345 [https://bugs.python.org/issue?@action=redirect&bpo=24345]: Add Py_tp_finalize slot for the stable ABI.

bpo-24400 [https://bugs.python.org/issue?@action=redirect&bpo=24400]: Introduce a distinct type for PEP 492 [https://peps.python.org/pep-0492/] coroutines; add types.CoroutineType, inspect.getcoroutinestate, inspect.getcoroutinelocals; coroutines no longer use CO_GENERATOR flag; sys.set_coroutine_wrapper works only for 'async def' coroutines; inspect.iscoroutine no longer uses collections.abc.Coroutine, it's intended to test for pure 'async def' coroutines only; add new opcode: GET_YIELD_FROM_ITER; fix generators wrapper used in types.coroutine to be instance of collections.abc.Generator; collections.abc.Awaitable and collections.abc.Coroutine can no longer be used to detect generator-based coroutines--use inspect.isawaitable instead.

bpo-24450 [https://bugs.python.org/issue?@action=redirect&bpo=24450]: Add gi_yieldfrom to generators and cr_await to coroutines. Contributed by Benno Leslie and Yury Selivanov.

bpo-19235 [https://bugs.python.org/issue?@action=redirect&bpo=19235]: Add new RecursionError exception. Patch by Georg Brandl.

Library

bpo-21750 [https://bugs.python.org/issue?@action=redirect&bpo=21750]: mock_open.read_data can now be read from each instance, as it could in Python 3.3.

bpo-24552 [https://bugs.python.org/issue?@action=redirect&bpo=24552]: Fix use after free in an error case of the _pickle module.

bpo-24514 [https://bugs.python.org/issue?@action=redirect&bpo=24514]: tarfile now tolerates number fields consisting of only whitespace.

bpo-19176 [https://bugs.python.org/issue?@action=redirect&bpo=19176]: Fixed doctype() related bugs in C implementation of ElementTree. A deprecation warning no longer issued by XMLParser subclass with default doctype() method. Direct call of doctype() now issues a warning. Parser's doctype() now is not called if target's doctype() is called. Based on patch by Martin Panter.

bpo-20387 [https://bugs.python.org/issue?@action=redirect&bpo=20387]: Restore semantic round-trip correctness in tokenize/untokenize for tab-indented blocks.

bpo-24456 [https://bugs.python.org/issue?@action=redirect&bpo=24456]: Fixed possible buffer over-read in adpcm2lin() and lin2adpcm() functions of the audioop module.

bpo-24336 [https://bugs.python.org/issue?@action=redirect&bpo=24336]: The contextmanager decorator now works with functions with keyword arguments called "func" and "self". Patch by Martin Panter.

bpo-24522 [https://bugs.python.org/issue?@action=redirect&bpo=24522]: Fix possible integer overflow in json accelerator module.

bpo-24489 [https://bugs.python.org/issue?@action=redirect&bpo=24489]: ensure a previously set C errno doesn't disturb cmath.polar().

bpo-24408 [https://bugs.python.org/issue?@action=redirect&bpo=24408]: Fixed AttributeError in measure() and metrics() methods of tkinter.Font.

bpo-14373 [https://bugs.python.org/issue?@action=redirect&bpo=14373]: C implementation of functools.lru_cache() now can be used with methods.

bpo-24347 [https://bugs.python.org/issue?@action=redirect&bpo=24347]: Set KeyError if PyDict_GetItemWithError returns NULL.

bpo-24348 [https://bugs.python.org/issue?@action=redirect&bpo=24348]: Drop superfluous incref/decref.

bpo-24359 [https://bugs.python.org/issue?@action=redirect&bpo=24359]: Check for changed OrderedDict size during iteration.

bpo-24368 [https://bugs.python.org/issue?@action=redirect&bpo=24368]: Support keyword arguments in OrderedDict methods.

bpo-24362 [https://bugs.python.org/issue?@action=redirect&bpo=24362]: Simplify the C OrderedDict fast nodes resize logic.

bpo-24377 [https://bugs.python.org/issue?@action=redirect&bpo=24377]: Fix a ref leak in OrderedDict.__repr__.

bpo-24369 [https://bugs.python.org/issue?@action=redirect&bpo=24369]: Defend against key-changes during iteration.

Tests

bpo-24373 [https://bugs.python.org/issue?@action=redirect&bpo=24373]: _testmultiphase and xxlimited now use tp_traverse and tp_finalize to avoid reference leaks encountered when combining tp_dealloc with PyType_FromSpec (see bpo-16690 [https://bugs.python.org/issue?@action=redirect&bpo=16690] for details)

Documentation

bpo-24458 [https://bugs.python.org/issue?@action=redirect&bpo=24458]: Update documentation to cover multi-phase initialization for extension modules (PEP 489). Patch by Petr Viktorin.

bpo-24351 [https://bugs.python.org/issue?@action=redirect&bpo=24351]: Clarify what is meant by "identifier" in the context of string.Template instances.

Build

bpo-24432 [https://bugs.python.org/issue?@action=redirect&bpo=24432]: Update Windows builds and OS X 10.5 installer to use OpenSSL 1.0.2c.

Python 3.5.0 beta 2

Release date: 2015-05-31

Core and Builtins

bpo-24284 [https://bugs.python.org/issue?@action=redirect&bpo=24284]: The startswith and endswith methods of the str class no longer return True when finding the empty string and the indexes are completely out of range.

bpo-24115 [https://bugs.python.org/issue?@action=redirect&bpo=24115]: Update uses of PyObject_IsTrue(), PyObject_Not(), PyObject_IsInstance(), PyObject_RichCompareBool() and _PyDict_Contains() to check for and handle errors correctly.

bpo-24328 [https://bugs.python.org/issue?@action=redirect&bpo=24328]: Fix importing one character extension modules.

bpo-11205 [https://bugs.python.org/issue?@action=redirect&bpo=11205]: In dictionary displays, evaluate the key before the value.

bpo-24285 [https://bugs.python.org/issue?@action=redirect&bpo=24285]: Fixed regression that prevented importing extension modules from inside packages. Patch by Petr Viktorin.

Library

bpo-23247 [https://bugs.python.org/issue?@action=redirect&bpo=23247]: Fix a crash in the StreamWriter.reset() of CJK codecs.

bpo-24270 [https://bugs.python.org/issue?@action=redirect&bpo=24270]: Add math.isclose() and cmath.isclose() functions as per PEP 485 [https://peps.python.org/pep-0485/]. Contributed by Chris Barker and Tal Einat.

bpo-5633 [https://bugs.python.org/issue?@action=redirect&bpo=5633]: Fixed timeit when the statement is a string and the setup is not.

bpo-24326 [https://bugs.python.org/issue?@action=redirect&bpo=24326]: Fixed audioop.ratecv() with non-default weightB argument. Original patch by David Moore.

bpo-16991 [https://bugs.python.org/issue?@action=redirect&bpo=16991]: Add a C implementation of OrderedDict.

bpo-23934 [https://bugs.python.org/issue?@action=redirect&bpo=23934]: Fix inspect.signature to fail correctly for builtin types lacking signature information. Initial patch by James Powell.

Python 3.5.0 beta 1

Release date: 2015-05-24

Core and Builtins

bpo-24276 [https://bugs.python.org/issue?@action=redirect&bpo=24276]: Fixed optimization of property descriptor getter.

bpo-24268 [https://bugs.python.org/issue?@action=redirect&bpo=24268]: PEP 489: Multi-phase extension module initialization. Patch by Petr Viktorin.

bpo-23955 [https://bugs.python.org/issue?@action=redirect&bpo=23955]: Add pyvenv.cfg option to suppress registry/environment lookup for generating sys.path on Windows.

bpo-24257 [https://bugs.python.org/issue?@action=redirect&bpo=24257]: Fixed system error in the comparison of faked types.SimpleNamespace.

bpo-22939 [https://bugs.python.org/issue?@action=redirect&bpo=22939]: Fixed integer overflow in iterator object. Patch by Clement Rouault.

bpo-23985 [https://bugs.python.org/issue?@action=redirect&bpo=23985]: Fix a possible buffer overrun when deleting a slice from the front of a bytearray and then appending some other bytes data.

bpo-24102 [https://bugs.python.org/issue?@action=redirect&bpo=24102]: Fixed exception type checking in standard error handlers.

bpo-15027 [https://bugs.python.org/issue?@action=redirect&bpo=15027]: The UTF-32 encoder is now 3x to 7x faster.

bpo-23290 [https://bugs.python.org/issue?@action=redirect&bpo=23290]: Optimize set_merge() for cases where the target is empty. (Contributed by Serhiy Storchaka.)

bpo-2292 [https://bugs.python.org/issue?@action=redirect&bpo=2292]: PEP 448: Additional Unpacking Generalizations.

bpo-24096 [https://bugs.python.org/issue?@action=redirect&bpo=24096]: Make warnings.warn_explicit more robust against mutation of the warnings.filters list.

bpo-23996 [https://bugs.python.org/issue?@action=redirect&bpo=23996]: Avoid a crash when a delegated generator raises an unnormalized StopIteration exception. Patch by Stefan Behnel.

bpo-23910 [https://bugs.python.org/issue?@action=redirect&bpo=23910]: Optimize property() getter calls. Patch by Joe Jevnik.

bpo-23911 [https://bugs.python.org/issue?@action=redirect&bpo=23911]: Move path-based importlib bootstrap code to a separate frozen module.

bpo-24192 [https://bugs.python.org/issue?@action=redirect&bpo=24192]: Fix namespace package imports.

bpo-24022 [https://bugs.python.org/issue?@action=redirect&bpo=24022]: Fix tokenizer crash when processing undecodable source code.

bpo-9951 [https://bugs.python.org/issue?@action=redirect&bpo=9951]: Added a hex() method to bytes, bytearray, and memoryview.

bpo-22906 [https://bugs.python.org/issue?@action=redirect&bpo=22906]: PEP 479: Change StopIteration handling inside generators.

bpo-24017 [https://bugs.python.org/issue?@action=redirect&bpo=24017]: PEP 492: Coroutines with async and await syntax.

Library

bpo-14373 [https://bugs.python.org/issue?@action=redirect&bpo=14373]: Added C implementation of functools.lru_cache(). Based on patches by Matt Joiner and Alexey Kachayev.

bpo-24230 [https://bugs.python.org/issue?@action=redirect&bpo=24230]: The tempfile module now accepts bytes for prefix, suffix and dir parameters and returns bytes in such situations (matching the os module APIs).

bpo-22189 [https://bugs.python.org/issue?@action=redirect&bpo=22189]: collections.UserString now supports __getnewargs__(), __rmod__(), casefold(), format_map(), isprintable(), and maketrans(). Patch by Joe Jevnik.

bpo-24244 [https://bugs.python.org/issue?@action=redirect&bpo=24244]: Prevents termination when an invalid format string is encountered on Windows in strftime.

bpo-23973 [https://bugs.python.org/issue?@action=redirect&bpo=23973]: PEP 484: Add the typing module.

bpo-23086 [https://bugs.python.org/issue?@action=redirect&bpo=23086]: The collections.abc.Sequence() abstract base class added start and stop parameters to the index() mixin. Patch by Devin Jeanpierre.

bpo-20035 [https://bugs.python.org/issue?@action=redirect&bpo=20035]: Replaced the tkinter._fix module used for setting up the Tcl/Tk environment on Windows with a private function in the _tkinter module that makes no permanent changes to the environment.

bpo-24257 [https://bugs.python.org/issue?@action=redirect&bpo=24257]: Fixed segmentation fault in sqlite3.Row constructor with faked cursor type.

bpo-15836 [https://bugs.python.org/issue?@action=redirect&bpo=15836]: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() assertments now check the type of the first argument to prevent possible user error. Based on patch by Daniel Wagner-Hall.

bpo-9858 [https://bugs.python.org/issue?@action=redirect&bpo=9858]: Add missing method stubs to _io.RawIOBase. Patch by Laura Rupprecht.

bpo-22955 [https://bugs.python.org/issue?@action=redirect&bpo=22955]: attrgetter, itemgetter and methodcaller objects in the operator module now support pickling. Added readable and evaluable repr for these objects. Based on patch by Josh Rosenberg.

bpo-22107 [https://bugs.python.org/issue?@action=redirect&bpo=22107]: tempfile.gettempdir() and tempfile.mkdtemp() now try again when a directory with the chosen name already exists on Windows as well as on Unix. tempfile.mkstemp() now fails early if parent directory is not valid (not exists or is a file) on Windows.

bpo-23780 [https://bugs.python.org/issue?@action=redirect&bpo=23780]: Improved error message in os.path.join() with single argument.

bpo-6598 [https://bugs.python.org/issue?@action=redirect&bpo=6598]: Increased time precision and random number range in email.utils.make_msgid() to strengthen the uniqueness of the message ID.

bpo-24091 [https://bugs.python.org/issue?@action=redirect&bpo=24091]: Fixed various crashes in corner cases in C implementation of ElementTree.

bpo-21931 [https://bugs.python.org/issue?@action=redirect&bpo=21931]: msilib.FCICreate() now raises TypeError in the case of a bad argument instead of a ValueError with a bogus FCI error number. Patch by Jeffrey Armstrong.

bpo-13866 [https://bugs.python.org/issue?@action=redirect&bpo=13866]: quote_via argument added to urllib.parse.urlencode.

bpo-20098 [https://bugs.python.org/issue?@action=redirect&bpo=20098]: New mangle_from policy option for email, default True for compat32, but False for all other policies.

bpo-24211 [https://bugs.python.org/issue?@action=redirect&bpo=24211]: The email library now supports RFC 6532: it can generate headers using utf-8 instead of encoded words.

bpo-16314 [https://bugs.python.org/issue?@action=redirect&bpo=16314]: Added support for the LZMA compression in distutils.

bpo-21804 [https://bugs.python.org/issue?@action=redirect&bpo=21804]: poplib now supports RFC 6856 (UTF8).

bpo-18682 [https://bugs.python.org/issue?@action=redirect&bpo=18682]: Optimized pprint functions for builtin scalar types.

bpo-22027 [https://bugs.python.org/issue?@action=redirect&bpo=22027]: smtplib now supports RFC 6531 (SMTPUTF8).

bpo-23488 [https://bugs.python.org/issue?@action=redirect&bpo=23488]: Random generator objects now consume 2x less memory on 64-bit.

bpo-1322 [https://bugs.python.org/issue?@action=redirect&bpo=1322]: platform.dist() and platform.linux_distribution() functions are now deprecated. Initial patch by Vajrasky Kok.

bpo-22486 [https://bugs.python.org/issue?@action=redirect&bpo=22486]: Added the math.gcd() function. The fractions.gcd() function now is deprecated. Based on patch by Mark Dickinson.

bpo-24064 [https://bugs.python.org/issue?@action=redirect&bpo=24064]: Property() docstrings are now writeable. (Patch by Berker Peksag.)

bpo-22681 [https://bugs.python.org/issue?@action=redirect&bpo=22681]: Added support for the koi8_t encoding.

bpo-22682 [https://bugs.python.org/issue?@action=redirect&bpo=22682]: Added support for the kz1048 encoding.

bpo-23796 [https://bugs.python.org/issue?@action=redirect&bpo=23796]: peek and read1 methods of BufferedReader now raise ValueError if they called on a closed object. Patch by John Hergenroeder.

bpo-21795 [https://bugs.python.org/issue?@action=redirect&bpo=21795]: smtpd now supports the 8BITMIME extension whenever the new decode_data constructor argument is set to False.

bpo-24155 [https://bugs.python.org/issue?@action=redirect&bpo=24155]: optimize heapq.heapify() for better cache performance when heapifying large lists.

bpo-21800 [https://bugs.python.org/issue?@action=redirect&bpo=21800]: imaplib now supports RFC 5161 (enable), RFC 6855 (utf8/internationalized email) and automatically encodes non-ASCII usernames and passwords to UTF8.

bpo-20274 [https://bugs.python.org/issue?@action=redirect&bpo=20274]: When calling a _sqlite.Connection, it now complains if passed any keyword arguments. Previously it silently ignored them.

bpo-20274 [https://bugs.python.org/issue?@action=redirect&bpo=20274]: Remove ignored and erroneous "kwargs" parameters from three METH_VARARGS methods on _sqlite.Connection.

bpo-24134 [https://bugs.python.org/issue?@action=redirect&bpo=24134]: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() checks now emits a deprecation warning when callable is None or keyword arguments except msg is passed in the context manager mode.

bpo-24018 [https://bugs.python.org/issue?@action=redirect&bpo=24018]: Add a collections.abc.Generator abstract base class. Contributed by Stefan Behnel.

bpo-23880 [https://bugs.python.org/issue?@action=redirect&bpo=23880]: Tkinter's getint() and getdouble() now support Tcl_Obj. Tkinter's getdouble() now supports any numbers (in particular int).

bpo-22619 [https://bugs.python.org/issue?@action=redirect&bpo=22619]: Added negative limit support in the traceback module. Based on patch by Dmitry Kazakov.

bpo-24094 [https://bugs.python.org/issue?@action=redirect&bpo=24094]: Fix possible crash in json.encode with poorly behaved dict subclasses.

bpo-9246 [https://bugs.python.org/issue?@action=redirect&bpo=9246]: On POSIX, os.getcwd() now supports paths longer than 1025 bytes. Patch written by William Orr.

bpo-17445 [https://bugs.python.org/issue?@action=redirect&bpo=17445]: add difflib.diff_bytes() to support comparison of byte strings (fixes a regression from Python 2).

bpo-23917 [https://bugs.python.org/issue?@action=redirect&bpo=23917]: Fall back to sequential compilation when ProcessPoolExecutor doesn't exist. Patch by Claudiu Popa.

bpo-23008 [https://bugs.python.org/issue?@action=redirect&bpo=23008]: Fixed resolving attributes with boolean value is False in pydoc.

Fix asyncio issue 235: LifoQueue and PriorityQueue's put didn't increment unfinished tasks (this bug was introduced when JoinableQueue was merged with Queue).

bpo-23908 [https://bugs.python.org/issue?@action=redirect&bpo=23908]: os functions now reject paths with embedded null character on Windows instead of silently truncating them.

bpo-23728 [https://bugs.python.org/issue?@action=redirect&bpo=23728]: binascii.crc_hqx() could return an integer outside of the range 0-0xffff for empty data.

bpo-23887 [https://bugs.python.org/issue?@action=redirect&bpo=23887]: urllib.error.HTTPError now has a proper repr() representation. Patch by Berker Peksag.

asyncio: New event loop APIs: set_task_factory() and get_task_factory().

asyncio: async() function is deprecated in favour of ensure_future().

bpo-24178 [https://bugs.python.org/issue?@action=redirect&bpo=24178]: asyncio.Lock, Condition, Semaphore, and BoundedSemaphore support new 'async with' syntax. Contributed by Yury Selivanov.

bpo-24179 [https://bugs.python.org/issue?@action=redirect&bpo=24179]: Support 'async for' for asyncio.StreamReader. Contributed by Yury Selivanov.

bpo-24184 [https://bugs.python.org/issue?@action=redirect&bpo=24184]: Add AsyncIterator and AsyncIterable ABCs to collections.abc. Contributed by Yury Selivanov.

bpo-22547 [https://bugs.python.org/issue?@action=redirect&bpo=22547]: Implement informative __repr__ for inspect.BoundArguments. Contributed by Yury Selivanov.

bpo-24190 [https://bugs.python.org/issue?@action=redirect&bpo=24190]: Implement inspect.BoundArgument.apply_defaults() method. Contributed by Yury Selivanov.

bpo-20691 [https://bugs.python.org/issue?@action=redirect&bpo=20691]: Add 'follow_wrapped' argument to inspect.Signature.from_callable() and inspect.signature(). Contributed by Yury Selivanov.

bpo-24248 [https://bugs.python.org/issue?@action=redirect&bpo=24248]: Deprecate inspect.Signature.from_function() and inspect.Signature.from_builtin().

bpo-23898 [https://bugs.python.org/issue?@action=redirect&bpo=23898]: Fix inspect.classify_class_attrs() to support attributes with overloaded __eq__ and __bool__. Patch by Mike Bayer.

bpo-24298 [https://bugs.python.org/issue?@action=redirect&bpo=24298]: Fix inspect.signature() to correctly unwrap wrappers around bound methods.

IDLE

bpo-23184 [https://bugs.python.org/issue?@action=redirect&bpo=23184]: remove unused names and imports in idlelib. Initial patch by Al Sweigart.

Tests

bpo-21520 [https://bugs.python.org/issue?@action=redirect&bpo=21520]: test_zipfile no longer fails if the word 'bad' appears anywhere in the name of the current directory.

bpo-9517 [https://bugs.python.org/issue?@action=redirect&bpo=9517]: Move script_helper into the support package. Patch by Christie Wilson.

Documentation

bpo-22155 [https://bugs.python.org/issue?@action=redirect&bpo=22155]: Add File Handlers subsection with createfilehandler to tkinter doc. Remove obsolete example from FAQ. Patch by Martin Panter.

bpo-24029 [https://bugs.python.org/issue?@action=redirect&bpo=24029]: Document the name binding behavior for submodule imports.

bpo-24077 [https://bugs.python.org/issue?@action=redirect&bpo=24077]: Fix typo in man page for -I command option: -s, not -S

Tools/Demos

bpo-24000 [https://bugs.python.org/issue?@action=redirect&bpo=24000]: Improved Argument Clinic's mapping of converters to legacy "format units". Updated the documentation to match.

bpo-24001 [https://bugs.python.org/issue?@action=redirect&bpo=24001]: Argument Clinic converters now use accept={type} instead of types={'type'} to specify the types the converter accepts.

bpo-23330 [https://bugs.python.org/issue?@action=redirect&bpo=23330]: h2py now supports arbitrary filenames in #include.

bpo-24031 [https://bugs.python.org/issue?@action=redirect&bpo=24031]: make patchcheck now supports git checkouts, too.

Python 3.5.0 alpha 4

Release date: 2015-04-19

Core and Builtins

bpo-22980 [https://bugs.python.org/issue?@action=redirect&bpo=22980]: Under Linux, GNU/KFreeBSD and the Hurd, C extensions now include the architecture triplet in the extension name, to make it easy to test builds for different ABIs in the same working tree. Under OS X, the extension name now includes PEP 3149 [https://peps.python.org/pep-3149/]-style information.

bpo-22631 [https://bugs.python.org/issue?@action=redirect&bpo=22631]: Added Linux-specific socket constant CAN_RAW_FD_FRAMES. Patch courtesy of Joe Jevnik.

bpo-23731 [https://bugs.python.org/issue?@action=redirect&bpo=23731]: Implement PEP 488 [https://peps.python.org/pep-0488/]: removal of .pyo files.

bpo-23726 [https://bugs.python.org/issue?@action=redirect&bpo=23726]: Don't enable GC for user subclasses of non-GC types that don't add any new fields. Patch by Eugene Toder.

bpo-23309 [https://bugs.python.org/issue?@action=redirect&bpo=23309]: Avoid a deadlock at shutdown if a daemon thread is aborted while it is holding a lock to a buffered I/O object, and the main thread tries to use the same I/O object (typically stdout or stderr). A fatal error is emitted instead.

bpo-22977 [https://bugs.python.org/issue?@action=redirect&bpo=22977]: Fixed formatting Windows error messages on Wine. Patch by Martin Panter.

bpo-23466 [https://bugs.python.org/issue?@action=redirect&bpo=23466]: %c, %o, %x, and %X in bytes formatting now raise TypeError on non-integer input.

bpo-24044 [https://bugs.python.org/issue?@action=redirect&bpo=24044]: Fix possible null pointer dereference in list.sort in out of memory conditions.

bpo-21354 [https://bugs.python.org/issue?@action=redirect&bpo=21354]: PyCFunction_New function is exposed by python DLL again.

Library

bpo-23840 [https://bugs.python.org/issue?@action=redirect&bpo=23840]: tokenize.open() now closes the temporary binary file on error to fix a resource warning.

bpo-16914 [https://bugs.python.org/issue?@action=redirect&bpo=16914]: new debuglevel 2 in smtplib adds timestamps to debug output.

bpo-7159 [https://bugs.python.org/issue?@action=redirect&bpo=7159]: urllib.request now supports sending auth credentials automatically after the first 401. This enhancement is a superset of the enhancement from bpo-19494 [https://bugs.python.org/issue?@action=redirect&bpo=19494] and supersedes that change.

bpo-23703 [https://bugs.python.org/issue?@action=redirect&bpo=23703]: Fix a regression in urljoin() introduced in 901e4e52b20a. Patch by Demian Brecht.

bpo-4254 [https://bugs.python.org/issue?@action=redirect&bpo=4254]: Adds _curses.update_lines_cols(). Patch by Arnon Yaari

bpo-19933 [https://bugs.python.org/issue?@action=redirect&bpo=19933]: Provide default argument for ndigits in round. Patch by Vajrasky Kok.

bpo-23193 [https://bugs.python.org/issue?@action=redirect&bpo=23193]: Add a numeric_owner parameter to tarfile.TarFile.extract and tarfile.TarFile.extractall. Patch by Michael Vogt and Eric Smith.

bpo-23342 [https://bugs.python.org/issue?@action=redirect&bpo=23342]: Add a subprocess.run() function than returns a CalledProcess instance for a more consistent API than the existing call* functions.

bpo-21217 [https://bugs.python.org/issue?@action=redirect&bpo=21217]: inspect.getsourcelines() now tries to compute the start and end lines from the code object, fixing an issue when a lambda function is used as decorator argument. Patch by Thomas Ballinger and Allison Kaptur.

bpo-24521 [https://bugs.python.org/issue?@action=redirect&bpo=24521]: Fix possible integer overflows in the pickle module.

bpo-22931 [https://bugs.python.org/issue?@action=redirect&bpo=22931]: Allow '[' and ']' in cookie values.

The keywords attribute of functools.partial is now always a dictionary.

bpo-23811 [https://bugs.python.org/issue?@action=redirect&bpo=23811]: Add missing newline to the PyCompileError error message. Patch by Alex Shkop.

bpo-21116 [https://bugs.python.org/issue?@action=redirect&bpo=21116]: Avoid blowing memory when allocating a multiprocessing shared array that's larger than 50% of the available RAM. Patch by Médéric Boquien.

bpo-22982 [https://bugs.python.org/issue?@action=redirect&bpo=22982]: Improve BOM handling when seeking to multiple positions of a writable text file.

bpo-23464 [https://bugs.python.org/issue?@action=redirect&bpo=23464]: Removed deprecated asyncio JoinableQueue.

bpo-23529 [https://bugs.python.org/issue?@action=redirect&bpo=23529]: Limit the size of decompressed data when reading from GzipFile, BZ2File or LZMAFile. This defeats denial of service attacks using compressed bombs (i.e. compressed payloads which decompress to a huge size). Patch by Martin Panter and Nikolaus Rath.

bpo-21859 [https://bugs.python.org/issue?@action=redirect&bpo=21859]: Added Python implementation of io.FileIO.

bpo-23865 [https://bugs.python.org/issue?@action=redirect&bpo=23865]: close() methods in multiple modules now are idempotent and more robust at shutdown. If they need to release multiple resources, all are released even if errors occur.

bpo-23400 [https://bugs.python.org/issue?@action=redirect&bpo=23400]: Raise same exception on both Python 2 and 3 if sem_open is not available. Patch by Davin Potts.

bpo-10838 [https://bugs.python.org/issue?@action=redirect&bpo=10838]: The subprocess now module includes SubprocessError and TimeoutError in its list of exported names for the users wild enough to use from subprocess import *.

bpo-23411 [https://bugs.python.org/issue?@action=redirect&bpo=23411]: Added DefragResult, ParseResult, SplitResult, DefragResultBytes, ParseResultBytes, and SplitResultBytes to urllib.parse.__all__. Patch by Martin Panter.

bpo-23881 [https://bugs.python.org/issue?@action=redirect&bpo=23881]: urllib.request.ftpwrapper constructor now closes the socket if the FTP connection failed to fix a ResourceWarning.

bpo-23853 [https://bugs.python.org/issue?@action=redirect&bpo=23853]: socket.socket.sendall() does no more reset the socket timeout each time data is sent successfully. The socket timeout is now the maximum total duration to send all data.

bpo-22721 [https://bugs.python.org/issue?@action=redirect&bpo=22721]: An order of multiline pprint output of set or dict containing orderable and non-orderable elements no longer depends on iteration order of set or dict.

bpo-15133 [https://bugs.python.org/issue?@action=redirect&bpo=15133]: _tkinter.tkapp.getboolean() now supports Tcl_Obj and always returns bool. tkinter.BooleanVar now validates input values (accepted bool, int, str, and Tcl_Obj). tkinter.BooleanVar.get() now always returns bool.

bpo-10590 [https://bugs.python.org/issue?@action=redirect&bpo=10590]: xml.sax.parseString() now supports string argument.

bpo-23338 [https://bugs.python.org/issue?@action=redirect&bpo=23338]: Fixed formatting ctypes error messages on Cygwin. Patch by Makoto Kato.

bpo-15582 [https://bugs.python.org/issue?@action=redirect&bpo=15582]: inspect.getdoc() now follows inheritance chains.

bpo-2175 [https://bugs.python.org/issue?@action=redirect&bpo=2175]: SAX parsers now support a character stream of InputSource object.

bpo-16840 [https://bugs.python.org/issue?@action=redirect&bpo=16840]: Tkinter now supports 64-bit integers added in Tcl 8.4 and arbitrary precision integers added in Tcl 8.5.

bpo-23834 [https://bugs.python.org/issue?@action=redirect&bpo=23834]: Fix socket.sendto(), use the C Py_ssize_t type to store the result of sendto() instead of the C int type.

bpo-23618 [https://bugs.python.org/issue?@action=redirect&bpo=23618]: socket.socket.connect() now waits until the connection completes instead of raising InterruptedError if the connection is interrupted by signals, signal handlers don't raise an exception and the socket is blocking or has a timeout. socket.socket.connect() still raise InterruptedError for non-blocking sockets.

bpo-21526 [https://bugs.python.org/issue?@action=redirect&bpo=21526]: Tkinter now supports new boolean type in Tcl 8.5.

bpo-23836 [https://bugs.python.org/issue?@action=redirect&bpo=23836]: Fix the faulthandler module to handle reentrant calls to its signal handlers.

bpo-23838 [https://bugs.python.org/issue?@action=redirect&bpo=23838]: linecache now clears the cache and returns an empty result on MemoryError.

bpo-10395 [https://bugs.python.org/issue?@action=redirect&bpo=10395]: Added os.path.commonpath(). Implemented in posixpath and ntpath. Based on patch by Rafik Draoui.

bpo-23611 [https://bugs.python.org/issue?@action=redirect&bpo=23611]: Serializing more "lookupable" objects (such as unbound methods or nested classes) now are supported with pickle protocols < 4.

bpo-13583 [https://bugs.python.org/issue?@action=redirect&bpo=13583]: sqlite3.Row now supports slice indexing.

bpo-18473 [https://bugs.python.org/issue?@action=redirect&bpo=18473]: Fixed 2to3 and 3to2 compatible pickle mappings. Fixed ambiguous reverse mappings. Added many new mappings. Import mapping is no longer applied to modules already mapped with full name mapping.

bpo-23485 [https://bugs.python.org/issue?@action=redirect&bpo=23485]: select.select() is now retried automatically with the recomputed timeout when interrupted by a signal, except if the signal handler raises an exception. This change is part of the PEP 475 [https://peps.python.org/pep-0475/].

bpo-23752 [https://bugs.python.org/issue?@action=redirect&bpo=23752]: When built from an existing file descriptor, io.FileIO() now only calls fstat() once. Before fstat() was called twice, which was not necessary.

bpo-23704 [https://bugs.python.org/issue?@action=redirect&bpo=23704]: collections.deque() objects now support __add__, __mul__, and __imul__().

bpo-23171 [https://bugs.python.org/issue?@action=redirect&bpo=23171]: csv.Writer.writerow() now supports arbitrary iterables.

bpo-23745 [https://bugs.python.org/issue?@action=redirect&bpo=23745]: The new email header parser now handles duplicate MIME parameter names without error, similar to how get_param behaves.

bpo-22117 [https://bugs.python.org/issue?@action=redirect&bpo=22117]: Fix os.utime(), it now rounds the timestamp towards minus infinity (-inf) instead of rounding towards zero.

bpo-23310 [https://bugs.python.org/issue?@action=redirect&bpo=23310]: Fix MagicMock's initializer to work with __methods__, just like configure_mock(). Patch by Kasia Jachim.

Build

bpo-23817 [https://bugs.python.org/issue?@action=redirect&bpo=23817]: FreeBSD now uses "1.0" in the SOVERSION as other operating systems, instead of just "1".

bpo-23501 [https://bugs.python.org/issue?@action=redirect&bpo=23501]: Argument Clinic now generates code into separate files by default.

Tests

bpo-23799 [https://bugs.python.org/issue?@action=redirect&bpo=23799]: Added test.support.start_threads() for running and cleaning up multiple threads.

bpo-22390 [https://bugs.python.org/issue?@action=redirect&bpo=22390]: test.regrtest now emits a warning if temporary files or directories are left after running a test.

Tools/Demos

bpo-18128 [https://bugs.python.org/issue?@action=redirect&bpo=18128]: pygettext now uses standard +NNNN format in the POT-Creation-Date header.

bpo-23935 [https://bugs.python.org/issue?@action=redirect&bpo=23935]: Argument Clinic's understanding of format units accepting bytes, bytearrays, and buffers is now consistent with both the documentation and the implementation.

bpo-23944 [https://bugs.python.org/issue?@action=redirect&bpo=23944]: Argument Clinic now wraps long impl prototypes at column 78.

bpo-20586 [https://bugs.python.org/issue?@action=redirect&bpo=20586]: Argument Clinic now ensures that functions without docstrings have signatures.

bpo-23492 [https://bugs.python.org/issue?@action=redirect&bpo=23492]: Argument Clinic now generates argument parsing code with PyArg_Parse instead of PyArg_ParseTuple if possible.

bpo-23500 [https://bugs.python.org/issue?@action=redirect&bpo=23500]: Argument Clinic is now smarter about generating the "#ifndef" (empty) definition of the methoddef macro: it's only generated once, even if Argument Clinic processes the same symbol multiple times, and it's emitted at the end of all processing rather than immediately after the first use.

C API

bpo-23998 [https://bugs.python.org/issue?@action=redirect&bpo=23998]: PyImport_ReInitLock() now checks for lock allocation error

Python 3.5.0 alpha 3

Release date: 2015-03-28

Core and Builtins

bpo-23573 [https://bugs.python.org/issue?@action=redirect&bpo=23573]: Increased performance of string search operations (str.find, str.index, str.count, the in operator, str.split, str.partition) with arguments of different kinds (UCS1, UCS2, UCS4).

bpo-23753 [https://bugs.python.org/issue?@action=redirect&bpo=23753]: Python doesn't support anymore platforms without stat() or fstat(), these functions are always required.

bpo-23681 [https://bugs.python.org/issue?@action=redirect&bpo=23681]: The -b option now affects comparisons of bytes with int.

bpo-23632 [https://bugs.python.org/issue?@action=redirect&bpo=23632]: Memoryviews now allow tuple indexing (including for multi-dimensional memoryviews).

bpo-23192 [https://bugs.python.org/issue?@action=redirect&bpo=23192]: Fixed generator lambdas. Patch by Bruno Cauet.

bpo-23629 [https://bugs.python.org/issue?@action=redirect&bpo=23629]: Fix the default __sizeof__ implementation for variable-sized objects.

Library

bpo-14260 [https://bugs.python.org/issue?@action=redirect&bpo=14260]: The groupindex attribute of regular expression pattern object now is non-modifiable mapping.

bpo-23792 [https://bugs.python.org/issue?@action=redirect&bpo=23792]: Ignore KeyboardInterrupt when the pydoc pager is active. This mimics the behavior of the standard unix pagers, and prevents pipepager from shutting down while the pager itself is still running.

bpo-23775 [https://bugs.python.org/issue?@action=redirect&bpo=23775]: pprint() of OrderedDict now outputs the same representation as repr().

bpo-23765 [https://bugs.python.org/issue?@action=redirect&bpo=23765]: Removed IsBadStringPtr calls in ctypes

bpo-22364 [https://bugs.python.org/issue?@action=redirect&bpo=22364]: Improved some re error messages using regex for hints.

bpo-23742 [https://bugs.python.org/issue?@action=redirect&bpo=23742]: ntpath.expandvars() no longer loses unbalanced single quotes.

bpo-21717 [https://bugs.python.org/issue?@action=redirect&bpo=21717]: The zipfile.ZipFile.open function now supports 'x' (exclusive creation) mode.

bpo-21802 [https://bugs.python.org/issue?@action=redirect&bpo=21802]: The reader in BufferedRWPair now is closed even when closing writer failed in BufferedRWPair.close().

bpo-23622 [https://bugs.python.org/issue?@action=redirect&bpo=23622]: Unknown escapes in regular expressions that consist of '\' and ASCII letter now raise a deprecation warning and will be forbidden in Python 3.6.

bpo-23671 [https://bugs.python.org/issue?@action=redirect&bpo=23671]: string.Template now allows specifying the "self" parameter as a keyword argument. string.Formatter now allows specifying the "self" and the "format_string" parameters as keyword arguments.

bpo-23502 [https://bugs.python.org/issue?@action=redirect&bpo=23502]: The pprint module now supports mapping proxies.

bpo-17530 [https://bugs.python.org/issue?@action=redirect&bpo=17530]: pprint now wraps long bytes objects and bytearrays.

bpo-22687 [https://bugs.python.org/issue?@action=redirect&bpo=22687]: Fixed some corner cases in breaking words in tetxtwrap. Got rid of quadratic complexity in breaking long words.

bpo-4727 [https://bugs.python.org/issue?@action=redirect&bpo=4727]: The copy module now uses pickle protocol 4 (PEP 3154) and supports copying of instances of classes whose __new__ method takes keyword-only arguments.

bpo-23491 [https://bugs.python.org/issue?@action=redirect&bpo=23491]: Added a zipapp module to support creating executable zip file archives of Python code. Registered ".pyz" and ".pyzw" extensions on Windows for these archives (PEP 441).

bpo-23657 [https://bugs.python.org/issue?@action=redirect&bpo=23657]: Avoid explicit checks for str in zipapp, adding support for pathlib.Path objects as arguments.

bpo-23688 [https://bugs.python.org/issue?@action=redirect&bpo=23688]: Added support of arbitrary bytes-like objects and avoided unnecessary copying of memoryview in gzip.GzipFile.write(). Original patch by Wolfgang Maier.

bpo-23252 [https://bugs.python.org/issue?@action=redirect&bpo=23252]: Added support for writing ZIP files to unseekable streams.

bpo-23647 [https://bugs.python.org/issue?@action=redirect&bpo=23647]: Increase imaplib's MAXLINE to accommodate modern mailbox sizes.

bpo-23539 [https://bugs.python.org/issue?@action=redirect&bpo=23539]: If body is None, http.client.HTTPConnection.request now sets Content-Length to 0 for PUT, POST, and PATCH headers to avoid 411 errors from some web servers.

bpo-22351 [https://bugs.python.org/issue?@action=redirect&bpo=22351]: The nntplib.NNTP constructor no longer leaves the connection and socket open until the garbage collector cleans them up. Patch by Martin Panter.

bpo-23704 [https://bugs.python.org/issue?@action=redirect&bpo=23704]: collections.deque() objects now support methods for index(), insert(), and copy(). This allows deques to be registered as a MutableSequence and it improves their substitutability for lists.

bpo-23715 [https://bugs.python.org/issue?@action=redirect&bpo=23715]: signal.sigwaitinfo() and signal.sigtimedwait() are now retried when interrupted by a signal not in the sigset parameter, if the signal handler does not raise an exception. signal.sigtimedwait() recomputes the timeout with a monotonic clock when it is retried.

bpo-23001 [https://bugs.python.org/issue?@action=redirect&bpo=23001]: Few functions in modules mmap, ossaudiodev, socket, ssl, and codecs, that accepted only read-only bytes-like object now accept writable bytes-like object too.

bpo-23646 [https://bugs.python.org/issue?@action=redirect&bpo=23646]: If time.sleep() is interrupted by a signal, the sleep is now retried with the recomputed delay, except if the signal handler raises an exception (PEP 475).

bpo-23136 [https://bugs.python.org/issue?@action=redirect&bpo=23136]: _strptime now uniformly handles all days in week 0, including Dec 30 of previous year. Based on patch by Jim Carroll.

bpo-23700 [https://bugs.python.org/issue?@action=redirect&bpo=23700]: Iterator of NamedTemporaryFile now keeps a reference to NamedTemporaryFile instance. Patch by Bohuslav Kabrda.

bpo-22903 [https://bugs.python.org/issue?@action=redirect&bpo=22903]: The fake test case created by unittest.loader when it fails importing a test module is now picklable.

bpo-22181 [https://bugs.python.org/issue?@action=redirect&bpo=22181]: On Linux, os.urandom() now uses the new getrandom() syscall if available, syscall introduced in the Linux kernel 3.17. It is more reliable and more secure, because it avoids the need of a file descriptor and waits until the kernel has enough entropy.

bpo-2211 [https://bugs.python.org/issue?@action=redirect&bpo=2211]: Updated the implementation of the http.cookies.Morsel class. Setting attributes key, value and coded_value directly now is deprecated. update() and setdefault() now transform and check keys. Comparing for equality now takes into account attributes key, value and coded_value. copy() now returns a Morsel, not a dict. repr() now contains all attributes. Optimized checking keys and quoting values. Added new tests. Original patch by Demian Brecht.

bpo-18983 [https://bugs.python.org/issue?@action=redirect&bpo=18983]: Allow selection of output units in timeit. Patch by Julian Gindi.

bpo-23631 [https://bugs.python.org/issue?@action=redirect&bpo=23631]: Fix traceback.format_list when a traceback has been mutated.

bpo-23568 [https://bugs.python.org/issue?@action=redirect&bpo=23568]: Add rdivmod support to MagicMock() objects. Patch by Håkan Lövdahl.

bpo-2052 [https://bugs.python.org/issue?@action=redirect&bpo=2052]: Add charset parameter to HtmlDiff.make_file().

bpo-23668 [https://bugs.python.org/issue?@action=redirect&bpo=23668]: Support os.truncate and os.ftruncate on Windows.

bpo-23138 [https://bugs.python.org/issue?@action=redirect&bpo=23138]: Fixed parsing cookies with absent keys or values in cookiejar. Patch by Demian Brecht.

bpo-23051 [https://bugs.python.org/issue?@action=redirect&bpo=23051]: multiprocessing.Pool methods imap() and imap_unordered() now handle exceptions raised by an iterator. Patch by Alon Diamant and Davin Potts.

bpo-23581 [https://bugs.python.org/issue?@action=redirect&bpo=23581]: Add matmul support to MagicMock. Patch by Håkan Lövdahl.

bpo-23566 [https://bugs.python.org/issue?@action=redirect&bpo=23566]: enable(), register(), dump_traceback() and dump_traceback_later() functions of faulthandler now accept file descriptors. Patch by Wei Wu.

bpo-22928 [https://bugs.python.org/issue?@action=redirect&bpo=22928]: Disabled HTTP header injections in http.client. Original patch by Demian Brecht.

bpo-23615 [https://bugs.python.org/issue?@action=redirect&bpo=23615]: Modules bz2, tarfile and tokenize now can be reloaded with imp.reload(). Patch by Thomas Kluyver.

bpo-23605 [https://bugs.python.org/issue?@action=redirect&bpo=23605]: os.walk() now calls os.scandir() instead of os.listdir(). The usage of os.scandir() reduces the number of calls to os.stat(). Initial patch written by Ben Hoyt.

Build

bpo-23585 [https://bugs.python.org/issue?@action=redirect&bpo=23585]: make patchcheck will ensure the interpreter is built.

Tests

bpo-23583 [https://bugs.python.org/issue?@action=redirect&bpo=23583]: Added tests for standard IO streams in IDLE.

bpo-22289 [https://bugs.python.org/issue?@action=redirect&bpo=22289]: Prevent test_urllib2net failures due to ftp connection timeout.

Tools/Demos

bpo-22826 [https://bugs.python.org/issue?@action=redirect&bpo=22826]: The result of open() in Tools/freeze/bkfile.py is now better compatible with regular files (in particular it now supports the context management protocol).

Python 3.5.0 alpha 2

Release date: 2015-03-09

Core and Builtins

bpo-23571 [https://bugs.python.org/issue?@action=redirect&bpo=23571]: PyObject_Call() and PyCFunction_Call() now raise a SystemError if a function returns a result and raises an exception. The SystemError is chained to the previous exception.

Library

bpo-22524 [https://bugs.python.org/issue?@action=redirect&bpo=22524]: New os.scandir() function, part of the PEP 471 [https://peps.python.org/pep-0471/]: "os.scandir() function -- a better and faster directory iterator". Patch written by Ben Hoyt.

bpo-23103 [https://bugs.python.org/issue?@action=redirect&bpo=23103]: Reduced the memory consumption of IPv4Address and IPv6Address.

bpo-21793 [https://bugs.python.org/issue?@action=redirect&bpo=21793]: BaseHTTPRequestHandler again logs response code as numeric, not as stringified enum. Patch by Demian Brecht.

bpo-23476 [https://bugs.python.org/issue?@action=redirect&bpo=23476]: In the ssl module, enable OpenSSL's X509_V_FLAG_TRUSTED_FIRST flag on certificate stores when it is available.

bpo-23576 [https://bugs.python.org/issue?@action=redirect&bpo=23576]: Avoid stalling in SSL reads when EOF has been reached in the SSL layer but the underlying connection hasn't been closed.

bpo-23504 [https://bugs.python.org/issue?@action=redirect&bpo=23504]: Added an __all__ to the types module.

bpo-23563 [https://bugs.python.org/issue?@action=redirect&bpo=23563]: Optimized utility functions in urllib.parse.

bpo-7830 [https://bugs.python.org/issue?@action=redirect&bpo=7830]: Flatten nested functools.partial.

bpo-20204 [https://bugs.python.org/issue?@action=redirect&bpo=20204]: Added the __module__ attribute to _tkinter classes.

bpo-19980 [https://bugs.python.org/issue?@action=redirect&bpo=19980]: Improved help() for non-recognized strings. help('') now shows the help on str. help('help') now shows the help on help(). Original patch by Mark Lawrence.

bpo-23521 [https://bugs.python.org/issue?@action=redirect&bpo=23521]: Corrected pure python implementation of timedelta division. Eliminated OverflowError from timedelta * float for some floats; Corrected rounding in timedelta true division.

bpo-21619 [https://bugs.python.org/issue?@action=redirect&bpo=21619]: Popen objects no longer leave a zombie after exit in the with statement if the pipe was broken. Patch by Martin Panter.

bpo-22936 [https://bugs.python.org/issue?@action=redirect&bpo=22936]: Make it possible to show local variables in tracebacks for both the traceback module and unittest.

bpo-15955 [https://bugs.python.org/issue?@action=redirect&bpo=15955]: Add an option to limit the output size in bz2.decompress(). Patch by Nikolaus Rath.

bpo-6639 [https://bugs.python.org/issue?@action=redirect&bpo=6639]: Module-level turtle functions no longer raise TclError after closing the window.

bpo-814253 [https://bugs.python.org/issue?@action=redirect&bpo=814253]: Group references and conditional group references now work in lookbehind assertions in regular expressions. (See also: bpo-9179 [https://bugs.python.org/issue?@action=redirect&bpo=9179])

bpo-23215 [https://bugs.python.org/issue?@action=redirect&bpo=23215]: Multibyte codecs with custom error handlers that ignores errors consumed too much memory and raised SystemError or MemoryError. Original patch by Aleksi Torhamo.

bpo-5700 [https://bugs.python.org/issue?@action=redirect&bpo=5700]: io.FileIO() called flush() after closing the file. flush() was not called in close() if closefd=False.

bpo-23374 [https://bugs.python.org/issue?@action=redirect&bpo=23374]: Fixed pydoc failure with non-ASCII files when stdout encoding differs from file system encoding (e.g. on Mac OS).

bpo-23481 [https://bugs.python.org/issue?@action=redirect&bpo=23481]: Remove RC4 from the SSL module's default cipher list.

bpo-21548 [https://bugs.python.org/issue?@action=redirect&bpo=21548]: Fix pydoc.synopsis() and pydoc.apropos() on modules with empty docstrings.

bpo-22885 [https://bugs.python.org/issue?@action=redirect&bpo=22885]: Fixed arbitrary code execution vulnerability in the dbm.dumb module. Original patch by Claudiu Popa.

bpo-23239 [https://bugs.python.org/issue?@action=redirect&bpo=23239]: ssl.match_hostname() now supports matching of IP addresses.

bpo-23146 [https://bugs.python.org/issue?@action=redirect&bpo=23146]: Fix mishandling of absolute Windows paths with forward slashes in pathlib.

bpo-23096 [https://bugs.python.org/issue?@action=redirect&bpo=23096]: Pickle representation of floats with protocol 0 now is the same for both Python and C implementations.

bpo-19105 [https://bugs.python.org/issue?@action=redirect&bpo=19105]: pprint now more efficiently uses free space at the right.

bpo-14910 [https://bugs.python.org/issue?@action=redirect&bpo=14910]: Add allow_abbrev parameter to argparse.ArgumentParser. Patch by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.

bpo-21717 [https://bugs.python.org/issue?@action=redirect&bpo=21717]: tarfile.open() now supports 'x' (exclusive creation) mode.

bpo-23344 [https://bugs.python.org/issue?@action=redirect&bpo=23344]: marshal.dumps() is now 20-25% faster on average.

bpo-20416 [https://bugs.python.org/issue?@action=redirect&bpo=20416]: marshal.dumps() with protocols 3 and 4 is now 40-50% faster on average.

bpo-23421 [https://bugs.python.org/issue?@action=redirect&bpo=23421]: Fixed compression in tarfile CLI. Patch by wdv4758h.

bpo-23367 [https://bugs.python.org/issue?@action=redirect&bpo=23367]: Fix possible overflows in the unicodedata module.

bpo-23361 [https://bugs.python.org/issue?@action=redirect&bpo=23361]: Fix possible overflow in Windows subprocess creation code.

logging.handlers.QueueListener now takes a respect_handler_level keyword argument which, if set to True, will pass messages to handlers taking handler levels into account.

bpo-19705 [https://bugs.python.org/issue?@action=redirect&bpo=19705]: turtledemo now has a visual sorting algorithm demo. Original patch from Jason Yeo.

bpo-23801 [https://bugs.python.org/issue?@action=redirect&bpo=23801]: Fix issue where cgi.FieldStorage did not always ignore the entire preamble to a multipart body.

Build

bpo-23445 [https://bugs.python.org/issue?@action=redirect&bpo=23445]: pydebug builds now use "gcc -Og" where possible, to make the resulting executable faster.

bpo-23686 [https://bugs.python.org/issue?@action=redirect&bpo=23686]: Update OS X 10.5 installer build to use OpenSSL 1.0.2a.

C API

bpo-20204 [https://bugs.python.org/issue?@action=redirect&bpo=20204]: Deprecation warning is now raised for builtin types without the __module__ attribute.

Windows

bpo-23465 [https://bugs.python.org/issue?@action=redirect&bpo=23465]: Implement PEP 486 [https://peps.python.org/pep-0486/] - Make the Python Launcher aware of virtual environments. Patch by Paul Moore.

bpo-23437 [https://bugs.python.org/issue?@action=redirect&bpo=23437]: Make user scripts directory versioned on Windows. Patch by Paul Moore.

Python 3.5.0 alpha 1

Release date: 2015-02-08

Core and Builtins

bpo-23285 [https://bugs.python.org/issue?@action=redirect&bpo=23285]: PEP 475 - EINTR handling.

bpo-22735 [https://bugs.python.org/issue?@action=redirect&bpo=22735]: Fix many edge cases (including crashes) involving custom mro() implementations.

bpo-22896 [https://bugs.python.org/issue?@action=redirect&bpo=22896]: Avoid using PyObject_AsCharBuffer(), PyObject_AsReadBuffer() and PyObject_AsWriteBuffer().

bpo-21295 [https://bugs.python.org/issue?@action=redirect&bpo=21295]: Revert some changes (bpo-16795 [https://bugs.python.org/issue?@action=redirect&bpo=16795]) to AST line numbers and column offsets that constituted a regression.

bpo-22986 [https://bugs.python.org/issue?@action=redirect&bpo=22986]: Allow changing an object's __class__ between a dynamic type and static type in some cases.

bpo-15859 [https://bugs.python.org/issue?@action=redirect&bpo=15859]: PyUnicode_EncodeFSDefault(), PyUnicode_EncodeMBCS() and PyUnicode_EncodeCodePage() now raise an exception if the object is not a Unicode object. For PyUnicode_EncodeFSDefault(), it was already the case on platforms other than Windows. Patch written by Campbell Barton.

bpo-21408 [https://bugs.python.org/issue?@action=redirect&bpo=21408]: The default __ne__() now returns NotImplemented if __eq__() returned NotImplemented. Original patch by Martin Panter.

bpo-23321 [https://bugs.python.org/issue?@action=redirect&bpo=23321]: Fixed a crash in str.decode() when error handler returned replacement string longer than malformed input data.

bpo-22286 [https://bugs.python.org/issue?@action=redirect&bpo=22286]: The "backslashreplace" error handlers now works with decoding and translating.

bpo-23253 [https://bugs.python.org/issue?@action=redirect&bpo=23253]: Delay-load ShellExecute[AW] in os.startfile for reduced startup overhead on Windows.

bpo-22038 [https://bugs.python.org/issue?@action=redirect&bpo=22038]: pyatomic.h now uses stdatomic.h or GCC built-in functions for atomic memory access if available. Patch written by Vitor de Lima and Gustavo Temple.

bpo-20284 [https://bugs.python.org/issue?@action=redirect&bpo=20284]: %-interpolation (aka printf) formatting added for bytes and bytearray.

bpo-23048 [https://bugs.python.org/issue?@action=redirect&bpo=23048]: Fix jumping out of an infinite while loop in the pdb.

bpo-20335 [https://bugs.python.org/issue?@action=redirect&bpo=20335]: bytes constructor now raises TypeError when encoding or errors is specified with non-string argument. Based on patch by Renaud Blanch.

bpo-22834 [https://bugs.python.org/issue?@action=redirect&bpo=22834]: If the current working directory ends up being set to a non-existent directory then import will no longer raise FileNotFoundError.

bpo-22869 [https://bugs.python.org/issue?@action=redirect&bpo=22869]: Move the interpreter startup & shutdown code to a new dedicated pylifecycle.c module

bpo-22847 [https://bugs.python.org/issue?@action=redirect&bpo=22847]: Improve method cache efficiency.

bpo-22335 [https://bugs.python.org/issue?@action=redirect&bpo=22335]: Fix crash when trying to enlarge a bytearray to 0x7fffffff bytes on a 32-bit platform.

bpo-22653 [https://bugs.python.org/issue?@action=redirect&bpo=22653]: Fix an assertion failure in debug mode when doing a reentrant dict insertion in debug mode.

bpo-22643 [https://bugs.python.org/issue?@action=redirect&bpo=22643]: Fix integer overflow in Unicode case operations (upper, lower, title, swapcase, casefold).

bpo-17636 [https://bugs.python.org/issue?@action=redirect&bpo=17636]: Circular imports involving relative imports are now supported.

bpo-22604 [https://bugs.python.org/issue?@action=redirect&bpo=22604]: Fix assertion error in debug mode when dividing a complex number by (nan+0j).

bpo-21052 [https://bugs.python.org/issue?@action=redirect&bpo=21052]: Do not raise ImportWarning when sys.path_hooks or sys.meta_path are set to None.

bpo-16518 [https://bugs.python.org/issue?@action=redirect&bpo=16518]: Use 'bytes-like object required' in error messages that previously used the far more cryptic "'x' does not support the buffer protocol.

bpo-22470 [https://bugs.python.org/issue?@action=redirect&bpo=22470]: Fixed integer overflow issues in "backslashreplace", "xmlcharrefreplace", and "surrogatepass" error handlers.

bpo-22540 [https://bugs.python.org/issue?@action=redirect&bpo=22540]: speed up PyObject_IsInstance and PyObject_IsSubclass in the common case that the second argument has metaclass type.

bpo-18711 [https://bugs.python.org/issue?@action=redirect&bpo=18711]: Add a new PyErr_FormatV function, similar to PyErr_Format but accepting a va_list argument.

bpo-22520 [https://bugs.python.org/issue?@action=redirect&bpo=22520]: Fix overflow checking when generating the repr of a unicode object.

bpo-22519 [https://bugs.python.org/issue?@action=redirect&bpo=22519]: Fix overflow checking in PyBytes_Repr.

bpo-22518 [https://bugs.python.org/issue?@action=redirect&bpo=22518]: Fix integer overflow issues in latin-1 encoding.

bpo-16324 [https://bugs.python.org/issue?@action=redirect&bpo=16324]: _charset parameter of MIMEText now also accepts email.charset.Charset instances. Initial patch by Claude Paroz.

bpo-1764286 [https://bugs.python.org/issue?@action=redirect&bpo=1764286]: Fix inspect.getsource() to support decorated functions. Patch by Claudiu Popa.

bpo-18554 [https://bugs.python.org/issue?@action=redirect&bpo=18554]: os.__all__ includes posix functions.

bpo-21391 [https://bugs.python.org/issue?@action=redirect&bpo=21391]: Use os.path.abspath in the shutil module.

bpo-11471 [https://bugs.python.org/issue?@action=redirect&bpo=11471]: avoid generating a JUMP_FORWARD instruction at the end of an if-block if there is no else-clause. Original patch by Eugene Toder.

bpo-22215 [https://bugs.python.org/issue?@action=redirect&bpo=22215]: Now ValueError is raised instead of TypeError when str or bytes argument contains not permitted null character or byte.

bpo-22258 [https://bugs.python.org/issue?@action=redirect&bpo=22258]: Fix the internal function set_inheritable() on Illumos. This platform exposes the function ioctl(FIOCLEX), but calling it fails with errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable() now falls back to the slower fcntl() (F_GETFD and then F_SETFD).

bpo-21389 [https://bugs.python.org/issue?@action=redirect&bpo=21389]: Displaying the __qualname__ of the underlying function in the repr of a bound method.

bpo-22206 [https://bugs.python.org/issue?@action=redirect&bpo=22206]: Using pthread, PyThread_create_key() now sets errno to ENOMEM and returns -1 (error) on integer overflow.

bpo-20184 [https://bugs.python.org/issue?@action=redirect&bpo=20184]: Argument Clinic based signature introspection added for 30 of the builtin functions.

bpo-22116 [https://bugs.python.org/issue?@action=redirect&bpo=22116]: C functions and methods (of the 'builtin_function_or_method' type) can now be weakref'ed. Patch by Wei Wu.

bpo-22077 [https://bugs.python.org/issue?@action=redirect&bpo=22077]: Improve index error messages for bytearrays, bytes, lists, and tuples by adding 'or slices'. Added ', not <typename>' for bytearrays. Original patch by Claudiu Popa.

bpo-20179 [https://bugs.python.org/issue?@action=redirect&bpo=20179]: Apply Argument Clinic to bytes and bytearray. Patch by Tal Einat.

bpo-22082 [https://bugs.python.org/issue?@action=redirect&bpo=22082]: Clear interned strings in slotdefs.

Upgrade Unicode database to Unicode 7.0.0.

bpo-21897 [https://bugs.python.org/issue?@action=redirect&bpo=21897]: Fix a crash with the f_locals attribute with closure variables when frame.clear() has been called.

bpo-21205 [https://bugs.python.org/issue?@action=redirect&bpo=21205]: Add a new __qualname__ attribute to generator, the qualified name, and use it in the representation of a generator (repr(gen)). The default name of the generator (__name__ attribute) is now get from the function instead of the code. Use gen.gi_code.co_name to get the name of the code.

bpo-21669 [https://bugs.python.org/issue?@action=redirect&bpo=21669]: With the aid of heuristics in SyntaxError.__init__, the parser now attempts to generate more meaningful (or at least more search engine friendly) error messages when "exec" and "print" are used as statements.

bpo-21642 [https://bugs.python.org/issue?@action=redirect&bpo=21642]: In the conditional if-else expression, allow an integer written with no space between itself and the else keyword (e.g. True if 42else False) to be valid syntax.

bpo-21523 [https://bugs.python.org/issue?@action=redirect&bpo=21523]: Fix over-pessimistic computation of the stack effect of some opcodes in the compiler. This also fixes a quadratic compilation time issue noticeable when compiling code with a large number of "and" and "or" operators.

bpo-21418 [https://bugs.python.org/issue?@action=redirect&bpo=21418]: Fix a crash in the builtin function super() when called without argument and without current frame (ex: embedded Python).

bpo-21425 [https://bugs.python.org/issue?@action=redirect&bpo=21425]: Fix flushing of standard streams in the interactive interpreter.

bpo-21435 [https://bugs.python.org/issue?@action=redirect&bpo=21435]: In rare cases, when running finalizers on objects in cyclic trash a bad pointer dereference could occur due to a subtle flaw in internal iteration logic.

bpo-21377 [https://bugs.python.org/issue?@action=redirect&bpo=21377]: PyBytes_Concat() now tries to concatenate in-place when the first argument has a reference count of 1. Patch by Nikolaus Rath.

bpo-20355 [https://bugs.python.org/issue?@action=redirect&bpo=20355]: -W command line options now have higher priority than the PYTHONWARNINGS environment variable. Patch by Arfrever.

bpo-21274 [https://bugs.python.org/issue?@action=redirect&bpo=21274]: Define PATH_MAX for GNU/Hurd in Python/pythonrun.c.

bpo-20904 [https://bugs.python.org/issue?@action=redirect&bpo=20904]: Support setting FPU precision on m68k.

bpo-21209 [https://bugs.python.org/issue?@action=redirect&bpo=21209]: Fix sending tuples to custom generator objects with the yield from syntax.

bpo-21193 [https://bugs.python.org/issue?@action=redirect&bpo=21193]: pow(a, b, c) now raises ValueError rather than TypeError when b is negative. Patch by Josh Rosenberg.

bpo-21176 [https://bugs.python.org/issue?@action=redirect&bpo=21176]: PEP 465: Add the '@' operator for matrix multiplication.

bpo-21134 [https://bugs.python.org/issue?@action=redirect&bpo=21134]: Fix segfault when str is called on an uninitialized UnicodeEncodeError, UnicodeDecodeError, or UnicodeTranslateError object.

bpo-19537 [https://bugs.python.org/issue?@action=redirect&bpo=19537]: Fix PyUnicode_DATA() alignment under m68k. Patch by Andreas Schwab.

bpo-20929 [https://bugs.python.org/issue?@action=redirect&bpo=20929]: Add a type cast to avoid shifting a negative number.

bpo-20731 [https://bugs.python.org/issue?@action=redirect&bpo=20731]: Properly position in source code files even if they are opened in text mode. Patch by Serhiy Storchaka.

bpo-20637 [https://bugs.python.org/issue?@action=redirect&bpo=20637]: Key-sharing now also works for instance dictionaries of subclasses. Patch by Peter Ingebretson.

bpo-8297 [https://bugs.python.org/issue?@action=redirect&bpo=8297]: Attributes missing from modules now include the module name in the error text. Original patch by ysj.ray.

bpo-19995 [https://bugs.python.org/issue?@action=redirect&bpo=19995]: %c, %o, %x, and %X now raise TypeError on non-integer input.

bpo-19655 [https://bugs.python.org/issue?@action=redirect&bpo=19655]: The ASDL parser - used by the build process to generate code for managing the Python AST in C - was rewritten. The new parser is self contained and does not require to carry long the spark.py parser-generator library; spark.py was removed from the source base.

bpo-12546 [https://bugs.python.org/issue?@action=redirect&bpo=12546]: Allow \x00 to be used as a fill character when using str, int, float, and complex __format__ methods.

bpo-20480 [https://bugs.python.org/issue?@action=redirect&bpo=20480]: Add ipaddress.reverse_pointer. Patch by Leon Weber.

bpo-13598 [https://bugs.python.org/issue?@action=redirect&bpo=13598]: Modify string.Formatter to support auto-numbering of replacement fields. It now matches the behavior of str.format() in this regard. Patches by Phil Elson and Ramchandra Apte.

bpo-8931 [https://bugs.python.org/issue?@action=redirect&bpo=8931]: Make alternate formatting ('#') for type 'c' raise an exception. In versions prior to 3.5, '#' with 'c' had no effect. Now specifying it is an error. Patch by Torsten Landschoff.

bpo-23165 [https://bugs.python.org/issue?@action=redirect&bpo=23165]: Perform overflow checks before allocating memory in the _Py_char2wchar function.

Library

bpo-23399 [https://bugs.python.org/issue?@action=redirect&bpo=23399]: pyvenv creates relative symlinks where possible.

bpo-20289 [https://bugs.python.org/issue?@action=redirect&bpo=20289]: cgi.FieldStorage() now supports the context management protocol.

bpo-13128 [https://bugs.python.org/issue?@action=redirect&bpo=13128]: Print response headers for CONNECT requests when debuglevel > 0. Patch by Demian Brecht.

bpo-15381 [https://bugs.python.org/issue?@action=redirect&bpo=15381]: Optimized io.BytesIO to make less allocations and copyings.

bpo-22818 [https://bugs.python.org/issue?@action=redirect&bpo=22818]: Splitting on a pattern that could match an empty string now raises a warning. Patterns that can only match empty strings are now rejected.

bpo-23099 [https://bugs.python.org/issue?@action=redirect&bpo=23099]: Closing io.BytesIO with exported buffer is rejected now to prevent corrupting exported buffer.

bpo-23326 [https://bugs.python.org/issue?@action=redirect&bpo=23326]: Removed __ne__ implementations. Since fixing default __ne__ implementation in bpo-21408 [https://bugs.python.org/issue?@action=redirect&bpo=21408] they are redundant.

bpo-23363 [https://bugs.python.org/issue?@action=redirect&bpo=23363]: Fix possible overflow in itertools.permutations.

bpo-23364 [https://bugs.python.org/issue?@action=redirect&bpo=23364]: Fix possible overflow in itertools.product.

bpo-23366 [https://bugs.python.org/issue?@action=redirect&bpo=23366]: Fixed possible integer overflow in itertools.combinations.

bpo-23369 [https://bugs.python.org/issue?@action=redirect&bpo=23369]: Fixed possible integer overflow in _json.encode_basestring_ascii.

bpo-23353 [https://bugs.python.org/issue?@action=redirect&bpo=23353]: Fix the exception handling of generators in PyEval_EvalFrameEx(). At entry, save or swap the exception state even if PyEval_EvalFrameEx() is called with throwflag=0. At exit, the exception state is now always restored or swapped, not only if why is WHY_YIELD or WHY_RETURN. Patch co-written with Antoine Pitrou.

bpo-14099 [https://bugs.python.org/issue?@action=redirect&bpo=14099]: Restored support of writing ZIP files to tellable but non-seekable streams.

bpo-14099 [https://bugs.python.org/issue?@action=redirect&bpo=14099]: Writing to ZipFile and reading multiple ZipExtFiles is threadsafe now.

bpo-19361 [https://bugs.python.org/issue?@action=redirect&bpo=19361]: JSON decoder now raises JSONDecodeError instead of ValueError.

bpo-18518 [https://bugs.python.org/issue?@action=redirect&bpo=18518]: timeit now rejects statements which can't be compiled outside a function or a loop (e.g. "return" or "break").

bpo-23094 [https://bugs.python.org/issue?@action=redirect&bpo=23094]: Fixed readline with frames in Python implementation of pickle.

bpo-23268 [https://bugs.python.org/issue?@action=redirect&bpo=23268]: Fixed bugs in the comparison of ipaddress classes.

bpo-21408 [https://bugs.python.org/issue?@action=redirect&bpo=21408]: Removed incorrect implementations of __ne__() which didn't returned NotImplemented if __eq__() returned NotImplemented. The default __ne__() now works correctly.

bpo-19996 [https://bugs.python.org/issue?@action=redirect&bpo=19996]: email.feedparser.FeedParser now handles (malformed) headers with no key rather than assuming the body has started.

bpo-20188 [https://bugs.python.org/issue?@action=redirect&bpo=20188]: Support Application-Layer Protocol Negotiation (ALPN) in the ssl module.

bpo-23133 [https://bugs.python.org/issue?@action=redirect&bpo=23133]: Pickling of ipaddress objects now produces more compact and portable representation.

bpo-23248 [https://bugs.python.org/issue?@action=redirect&bpo=23248]: Update ssl error codes from latest OpenSSL git master.

bpo-23266 [https://bugs.python.org/issue?@action=redirect&bpo=23266]: Much faster implementation of ipaddress.collapse_addresses() when there are many non-consecutive addresses.

bpo-23098 [https://bugs.python.org/issue?@action=redirect&bpo=23098]: 64-bit dev_t is now supported in the os module.

bpo-21817 [https://bugs.python.org/issue?@action=redirect&bpo=21817]: When an exception is raised in a task submitted to a ProcessPoolExecutor, the remote traceback is now displayed in the parent process. Patch by Claudiu Popa.

bpo-15955 [https://bugs.python.org/issue?@action=redirect&bpo=15955]: Add an option to limit output size when decompressing LZMA data. Patch by Nikolaus Rath and Martin Panter.

bpo-23250 [https://bugs.python.org/issue?@action=redirect&bpo=23250]: In the http.cookies module, capitalize "HttpOnly" and "Secure" as they are written in the standard.

bpo-23063 [https://bugs.python.org/issue?@action=redirect&bpo=23063]: In the distutils' check command, fix parsing of reST with code or code-block directives.

bpo-23209 [https://bugs.python.org/issue?@action=redirect&bpo=23209]: selectors.BaseSelector.get_key() now raises a RuntimeError if the selector is closed. And selectors.BaseSelector.close() now clears its internal reference to the selector mapping to break a reference cycle. Initial patch written by Martin Richard. (See also: bpo-23225 [https://bugs.python.org/issue?@action=redirect&bpo=23225])

bpo-17911 [https://bugs.python.org/issue?@action=redirect&bpo=17911]: Provide a way to seed the linecache for a PEP-302 module without actually loading the code.

bpo-17911 [https://bugs.python.org/issue?@action=redirect&bpo=17911]: Provide a new object API for traceback, including the ability to not lookup lines at all until the traceback is actually rendered, without any trace of the original objects being kept alive.

bpo-19777 [https://bugs.python.org/issue?@action=redirect&bpo=19777]: Provide a home() classmethod on Path objects. Contributed by Victor Salgado and Mayank Tripathi.

bpo-23206 [https://bugs.python.org/issue?@action=redirect&bpo=23206]: Make json.dumps(..., ensure_ascii=False) as fast as the default case of ensure_ascii=True. Patch by Naoki Inada.

bpo-23185 [https://bugs.python.org/issue?@action=redirect&bpo=23185]: Add math.inf and math.nan constants.

bpo-23186 [https://bugs.python.org/issue?@action=redirect&bpo=23186]: Add ssl.SSLObject.shared_ciphers() and ssl.SSLSocket.shared_ciphers() to fetch the client's list ciphers sent at handshake.

bpo-23143 [https://bugs.python.org/issue?@action=redirect&bpo=23143]: Remove compatibility with OpenSSLs older than 0.9.8.

bpo-23132 [https://bugs.python.org/issue?@action=redirect&bpo=23132]: Improve performance and introspection support of comparison methods created by functool.total_ordering.

bpo-19776 [https://bugs.python.org/issue?@action=redirect&bpo=19776]: Add an expanduser() method on Path objects.

bpo-23112 [https://bugs.python.org/issue?@action=redirect&bpo=23112]: Fix SimpleHTTPServer to correctly carry the query string and fragment when it redirects to add a trailing slash.

bpo-21793 [https://bugs.python.org/issue?@action=redirect&bpo=21793]: Added http.HTTPStatus enums (i.e. HTTPStatus.OK, HTTPStatus.NOT_FOUND). Patch by Demian Brecht.

bpo-23093 [https://bugs.python.org/issue?@action=redirect&bpo=23093]: In the io, module allow more operations to work on detached streams.

bpo-23111 [https://bugs.python.org/issue?@action=redirect&bpo=23111]: In the ftplib, make ssl.PROTOCOL_SSLv23 the default protocol version.

bpo-22585 [https://bugs.python.org/issue?@action=redirect&bpo=22585]: On OpenBSD 5.6 and newer, os.urandom() now calls getentropy(), instead of reading /dev/urandom, to get pseudo-random bytes.

bpo-19104 [https://bugs.python.org/issue?@action=redirect&bpo=19104]: pprint now produces evaluable output for wrapped strings.

bpo-23071 [https://bugs.python.org/issue?@action=redirect&bpo=23071]: Added missing names to codecs.__all__. Patch by Martin Panter.

bpo-22783 [https://bugs.python.org/issue?@action=redirect&bpo=22783]: Pickling now uses the NEWOBJ opcode instead of the NEWOBJ_EX opcode if possible.

bpo-15513 [https://bugs.python.org/issue?@action=redirect&bpo=15513]: Added a __sizeof__ implementation for pickle classes.

bpo-19858 [https://bugs.python.org/issue?@action=redirect&bpo=19858]: pickletools.optimize() now aware of the MEMOIZE opcode, can produce more compact result and no longer produces invalid output if input data contains MEMOIZE opcodes together with PUT or BINPUT opcodes.

bpo-22095 [https://bugs.python.org/issue?@action=redirect&bpo=22095]: Fixed HTTPConnection.set_tunnel with default port. The port value in the host header was set to "None". Patch by Demian Brecht.

bpo-23016 [https://bugs.python.org/issue?@action=redirect&bpo=23016]: A warning no longer produces an AttributeError when the program is run with pythonw.exe.

bpo-21775 [https://bugs.python.org/issue?@action=redirect&bpo=21775]: shutil.copytree(): fix crash when copying to VFAT. An exception handler assumed that OSError objects always have a 'winerror' attribute. That is not the case, so the exception handler itself raised AttributeError when run on Linux (and, presumably, any other non-Windows OS). Patch by Greg Ward.

bpo-1218234 [https://bugs.python.org/issue?@action=redirect&bpo=1218234]: Fix inspect.getsource() to load updated source of reloaded module. Initial patch by Berker Peksag.

bpo-21740 [https://bugs.python.org/issue?@action=redirect&bpo=21740]: Support wrapped callables in doctest. Patch by Claudiu Popa.

bpo-23009 [https://bugs.python.org/issue?@action=redirect&bpo=23009]: Make sure selectors.EpollSelector.select() works when no FD is registered.

bpo-22959 [https://bugs.python.org/issue?@action=redirect&bpo=22959]: In the constructor of http.client.HTTPSConnection, prefer the context's check_hostname attribute over the check_hostname parameter.

bpo-22696 [https://bugs.python.org/issue?@action=redirect&bpo=22696]: Add function sys.is_finalizing() to know about interpreter shutdown.

bpo-16043 [https://bugs.python.org/issue?@action=redirect&bpo=16043]: Add a default limit for the amount of data xmlrpclib.gzip_decode will return. This resolves CVE 2013-1753 [https://www.cve.org/CVERecord?id=CVE-2013-1753].

bpo-14099 [https://bugs.python.org/issue?@action=redirect&bpo=14099]: ZipFile.open() no longer reopen the underlying file. Objects returned by ZipFile.open() can now operate independently of the ZipFile even if the ZipFile was created by passing in a file-like object as the first argument to the constructor.

bpo-22966 [https://bugs.python.org/issue?@action=redirect&bpo=22966]: Fix __pycache__ pyc file name clobber when pyc_compile is asked to compile a source file containing multiple dots in the source file name.

bpo-21971 [https://bugs.python.org/issue?@action=redirect&bpo=21971]: Update turtledemo doc and add module to the index.

bpo-21032 [https://bugs.python.org/issue?@action=redirect&bpo=21032]: Fixed socket leak if HTTPConnection.getresponse() fails. Original patch by Martin Panter.

bpo-22407 [https://bugs.python.org/issue?@action=redirect&bpo=22407]: Deprecated the use of re.LOCALE flag with str patterns or re.ASCII. It was newer worked.

bpo-22902 [https://bugs.python.org/issue?@action=redirect&bpo=22902]: The "ip" command is now used on Linux to determine MAC address in uuid.getnode(). Patch by Bruno Cauet.

bpo-22960 [https://bugs.python.org/issue?@action=redirect&bpo=22960]: Add a context argument to xmlrpclib.ServerProxy constructor.

bpo-22389 [https://bugs.python.org/issue?@action=redirect&bpo=22389]: Add contextlib.redirect_stderr().

bpo-21356 [https://bugs.python.org/issue?@action=redirect&bpo=21356]: Make ssl.RAND_egd() optional to support LibreSSL. The availability of the function is checked during the compilation. Patch written by Bernard Spil.

bpo-22915 [https://bugs.python.org/issue?@action=redirect&bpo=22915]: SAX parser now supports files opened with file descriptor or bytes path.

bpo-22609 [https://bugs.python.org/issue?@action=redirect&bpo=22609]: Constructors and update methods of mapping classes in the collections module now accept the self keyword argument.

bpo-22940 [https://bugs.python.org/issue?@action=redirect&bpo=22940]: Add readline.append_history_file.

bpo-19676 [https://bugs.python.org/issue?@action=redirect&bpo=19676]: Added the "namereplace" error handler.

bpo-22788 [https://bugs.python.org/issue?@action=redirect&bpo=22788]: Add context parameter to logging.handlers.HTTPHandler.

bpo-22921 [https://bugs.python.org/issue?@action=redirect&bpo=22921]: Allow SSLContext to take the hostname parameter even if OpenSSL doesn't support SNI.

bpo-22894 [https://bugs.python.org/issue?@action=redirect&bpo=22894]: TestCase.subTest() would cause the test suite to be stopped when in failfast mode, even in the absence of failures.

bpo-22796 [https://bugs.python.org/issue?@action=redirect&bpo=22796]: HTTP cookie parsing is now stricter, in order to protect against potential injection attacks.

bpo-22370 [https://bugs.python.org/issue?@action=redirect&bpo=22370]: Windows detection in pathlib is now more robust.

bpo-22841 [https://bugs.python.org/issue?@action=redirect&bpo=22841]: Reject coroutines in asyncio add_signal_handler(). Patch by Ludovic.Gasc.

bpo-19494 [https://bugs.python.org/issue?@action=redirect&bpo=19494]: Added urllib.request.HTTPBasicPriorAuthHandler. Patch by Matej Cepl.

bpo-22578 [https://bugs.python.org/issue?@action=redirect&bpo=22578]: Added attributes to the re.error class.

bpo-22849 [https://bugs.python.org/issue?@action=redirect&bpo=22849]: Fix possible double free in the io.TextIOWrapper constructor.

bpo-12728 [https://bugs.python.org/issue?@action=redirect&bpo=12728]: Different Unicode characters having the same uppercase but different lowercase are now matched in case-insensitive regular expressions.

bpo-22821 [https://bugs.python.org/issue?@action=redirect&bpo=22821]: Fixed fcntl() with integer argument on 64-bit big-endian platforms.

bpo-21650 [https://bugs.python.org/issue?@action=redirect&bpo=21650]: Add an --sort-keys option to json.tool CLI.

bpo-22824 [https://bugs.python.org/issue?@action=redirect&bpo=22824]: Updated reprlib output format for sets to use set literals. Patch contributed by Berker Peksag.

bpo-22824 [https://bugs.python.org/issue?@action=redirect&bpo=22824]: Updated reprlib output format for arrays to display empty arrays without an unnecessary empty list. Suggested by Serhiy Storchaka.

bpo-22406 [https://bugs.python.org/issue?@action=redirect&bpo=22406]: Fixed the uu_codec codec incorrectly ported to 3.x. Based on patch by Martin Panter.

bpo-17293 [https://bugs.python.org/issue?@action=redirect&bpo=17293]: uuid.getnode() now determines MAC address on AIX using netstat. Based on patch by Aivars Kalvāns.

bpo-22769 [https://bugs.python.org/issue?@action=redirect&bpo=22769]: Fixed ttk.Treeview.tag_has() when called without arguments.

bpo-22417 [https://bugs.python.org/issue?@action=redirect&bpo=22417]: Verify certificates by default in httplib (PEP 476).

bpo-22775 [https://bugs.python.org/issue?@action=redirect&bpo=22775]: Fixed unpickling of http.cookies.SimpleCookie with protocol 2 and above. Patch by Tim Graham.

bpo-22776 [https://bugs.python.org/issue?@action=redirect&bpo=22776]: Brought excluded code into the scope of a try block in SysLogHandler.emit().

bpo-22665 [https://bugs.python.org/issue?@action=redirect&bpo=22665]: Add missing get_terminal_size and SameFileError to shutil.__all__.

bpo-6623 [https://bugs.python.org/issue?@action=redirect&bpo=6623]: Remove deprecated Netrc class in the ftplib module. Patch by Matt Chaput.

bpo-17381 [https://bugs.python.org/issue?@action=redirect&bpo=17381]: Fixed handling of case-insensitive ranges in regular expressions.

bpo-22410 [https://bugs.python.org/issue?@action=redirect&bpo=22410]: Module level functions in the re module now cache compiled locale-dependent regular expressions taking into account the locale.

bpo-22759 [https://bugs.python.org/issue?@action=redirect&bpo=22759]: Query methods on pathlib.Path() (exists(), is_dir(), etc.) now return False when the underlying stat call raises NotADirectoryError.

bpo-8876 [https://bugs.python.org/issue?@action=redirect&bpo=8876]: distutils now falls back to copying files when hard linking doesn't work. This allows use with special filesystems such as VirtualBox shared folders.

bpo-22217 [https://bugs.python.org/issue?@action=redirect&bpo=22217]: Implemented reprs of classes in the zipfile module.

bpo-22457 [https://bugs.python.org/issue?@action=redirect&bpo=22457]: Honour load_tests in the start_dir of discovery.

bpo-18216 [https://bugs.python.org/issue?@action=redirect&bpo=18216]: gettext now raises an error when a .mo file has an unsupported major version number. Patch by Aaron Hill.

bpo-13918 [https://bugs.python.org/issue?@action=redirect&bpo=13918]: Provide a locale.delocalize() function which can remove locale-specific number formatting from a string representing a number, without then converting it to a specific type. Patch by Cédric Krier.

bpo-22676 [https://bugs.python.org/issue?@action=redirect&bpo=22676]: Make the pickling of global objects which don't have a __module__ attribute less slow.

bpo-18853 [https://bugs.python.org/issue?@action=redirect&bpo=18853]: Fixed ResourceWarning in shlex.__nain__.

bpo-9351 [https://bugs.python.org/issue?@action=redirect&bpo=9351]: Defaults set with set_defaults on an argparse subparser are no longer ignored when also set on the parent parser.

bpo-7559 [https://bugs.python.org/issue?@action=redirect&bpo=7559]: unittest test loading ImportErrors are reported as import errors with their import exception rather than as attribute errors after the import has already failed.

bpo-19746 [https://bugs.python.org/issue?@action=redirect&bpo=19746]: Make it possible to examine the errors from unittest discovery without executing the test suite. The new errors attribute on TestLoader exposes these non-fatal errors encountered during discovery.

bpo-21991 [https://bugs.python.org/issue?@action=redirect&bpo=21991]: Make email.headerregistry's header 'params' attributes be read-only (MappingProxyType). Previously the dictionary was modifiable but a new one was created on each access of the attribute.

bpo-22638 [https://bugs.python.org/issue?@action=redirect&bpo=22638]: SSLv3 is now disabled throughout the standard library. It can still be enabled by instantiating a SSLContext manually.

bpo-22641 [https://bugs.python.org/issue?@action=redirect&bpo=22641]: In asyncio, the default SSL context for client connections is now created using ssl.create_default_context(), for stronger security.

bpo-17401 [https://bugs.python.org/issue?@action=redirect&bpo=17401]: Include closefd in io.FileIO repr.

bpo-21338 [https://bugs.python.org/issue?@action=redirect&bpo=21338]: Add silent mode for compileall. quiet parameters of compile_{dir, file, path} functions now have a multilevel value. Also, -q option of the CLI now have a multilevel value. Patch by Thomas Kluyver.

bpo-20152 [https://bugs.python.org/issue?@action=redirect&bpo=20152]: Convert the array and cmath modules to Argument Clinic.

bpo-18643 [https://bugs.python.org/issue?@action=redirect&bpo=18643]: Add socket.socketpair() on Windows.

bpo-22435 [https://bugs.python.org/issue?@action=redirect&bpo=22435]: Fix a file descriptor leak when socketserver bind fails.

bpo-13096 [https://bugs.python.org/issue?@action=redirect&bpo=13096]: Fixed segfault in CTypes POINTER handling of large values.

bpo-11694 [https://bugs.python.org/issue?@action=redirect&bpo=11694]: Raise ConversionError in xdrlib as documented. Patch by Filip Gruszczyński and Claudiu Popa.

bpo-19380 [https://bugs.python.org/issue?@action=redirect&bpo=19380]: Optimized parsing of regular expressions.

bpo-1519638 [https://bugs.python.org/issue?@action=redirect&bpo=1519638]: Now unmatched groups are replaced with empty strings in re.sub() and re.subn().

bpo-18615 [https://bugs.python.org/issue?@action=redirect&bpo=18615]: sndhdr.what/whathdr now return a namedtuple.

bpo-22462 [https://bugs.python.org/issue?@action=redirect&bpo=22462]: Fix pyexpat's creation of a dummy frame to make it appear in exception tracebacks.

bpo-21965 [https://bugs.python.org/issue?@action=redirect&bpo=21965]: Add support for in-memory SSL to the ssl module. Patch by Geert Jansen.

bpo-21173 [https://bugs.python.org/issue?@action=redirect&bpo=21173]: Fix len() on a WeakKeyDictionary when .clear() was called with an iterator alive.

bpo-11866 [https://bugs.python.org/issue?@action=redirect&bpo=11866]: Eliminated race condition in the computation of names for new threads.

bpo-21905 [https://bugs.python.org/issue?@action=redirect&bpo=21905]: Avoid RuntimeError in pickle.whichmodule() when sys.modules is mutated while iterating. Patch by Olivier Grisel.

bpo-11271 [https://bugs.python.org/issue?@action=redirect&bpo=11271]: concurrent.futures.Executor.map() now takes a chunksize argument to allow batching of tasks in child processes and improve performance of ProcessPoolExecutor. Patch by Dan O'Reilly.

bpo-21883 [https://bugs.python.org/issue?@action=redirect&bpo=21883]: os.path.join() and os.path.relpath() now raise a TypeError with more helpful error message for unsupported or mismatched types of arguments.

bpo-22219 [https://bugs.python.org/issue?@action=redirect&bpo=22219]: The zipfile module CLI now adds entries for directories (including empty directories) in ZIP file.

bpo-22449 [https://bugs.python.org/issue?@action=redirect&bpo=22449]: In the ssl.SSLContext.load_default_certs, consult the environmental variables SSL_CERT_DIR and SSL_CERT_FILE on Windows.

bpo-22508 [https://bugs.python.org/issue?@action=redirect&bpo=22508]: The email.__version__ variable has been removed; the email code is no longer shipped separately from the stdlib, and __version__ hasn't been updated in several releases.

bpo-20076 [https://bugs.python.org/issue?@action=redirect&bpo=20076]: Added non derived UTF-8 aliases to locale aliases table.

bpo-20079 [https://bugs.python.org/issue?@action=redirect&bpo=20079]: Added locales supported in glibc 2.18 to locale alias table.

bpo-20218 [https://bugs.python.org/issue?@action=redirect&bpo=20218]: Added convenience methods read_text/write_text and read_bytes/ write_bytes to pathlib.Path objects.

bpo-22396 [https://bugs.python.org/issue?@action=redirect&bpo=22396]: On 32-bit AIX platform, don't expose os.posix_fadvise() nor os.posix_fallocate() because their prototypes in system headers are wrong.

bpo-22517 [https://bugs.python.org/issue?@action=redirect&bpo=22517]: When an io.BufferedRWPair object is deallocated, clear its weakrefs.

bpo-22437 [https://bugs.python.org/issue?@action=redirect&bpo=22437]: Number of capturing groups in regular expression is no longer limited by 100.

bpo-17442 [https://bugs.python.org/issue?@action=redirect&bpo=17442]: InteractiveInterpreter now displays the full chained traceback in its showtraceback method, to match the built in interactive interpreter.

bpo-23392 [https://bugs.python.org/issue?@action=redirect&bpo=23392]: Added tests for marshal C API that works with FILE*.

bpo-10510 [https://bugs.python.org/issue?@action=redirect&bpo=10510]: distutils register and upload methods now use HTML standards compliant CRLF line endings.

bpo-9850 [https://bugs.python.org/issue?@action=redirect&bpo=9850]: Fixed macpath.join() for empty first component. Patch by Oleg Oshmyan.

bpo-5309 [https://bugs.python.org/issue?@action=redirect&bpo=5309]: distutils' build and build_ext commands now accept a -j option to enable parallel building of extension modules.

bpo-22448 [https://bugs.python.org/issue?@action=redirect&bpo=22448]: Improve canceled timer handles cleanup to prevent unbound memory usage. Patch by Joshua Moore-Oliva.

bpo-22427 [https://bugs.python.org/issue?@action=redirect&bpo=22427]: TemporaryDirectory no longer attempts to clean up twice when used in the with statement in generator.

bpo-22362 [https://bugs.python.org/issue?@action=redirect&bpo=22362]: Forbidden ambiguous octal escapes out of range 0-0o377 in regular expressions.

bpo-20912 [https://bugs.python.org/issue?@action=redirect&bpo=20912]: Now directories added to ZIP file have correct Unix and MS-DOS directory attributes.

bpo-21866 [https://bugs.python.org/issue?@action=redirect&bpo=21866]: ZipFile.close() no longer writes ZIP64 central directory records if allowZip64 is false.

bpo-22278 [https://bugs.python.org/issue?@action=redirect&bpo=22278]: Fix urljoin problem with relative urls, a regression observed after changes to issue22118 were submitted.

bpo-22415 [https://bugs.python.org/issue?@action=redirect&bpo=22415]: Fixed debugging output of the GROUPREF_EXISTS opcode in the re module. Removed trailing spaces in debugging output.

bpo-22423 [https://bugs.python.org/issue?@action=redirect&bpo=22423]: Unhandled exception in thread no longer causes unhandled AttributeError when sys.stderr is None.

bpo-21332 [https://bugs.python.org/issue?@action=redirect&bpo=21332]: Ensure that bufsize=1 in subprocess.Popen() selects line buffering, rather than block buffering. Patch by Akira Li.

bpo-21091 [https://bugs.python.org/issue?@action=redirect&bpo=21091]: Fix API bug: email.message.EmailMessage.is_attachment is now a method.

bpo-21079 [https://bugs.python.org/issue?@action=redirect&bpo=21079]: Fix email.message.EmailMessage.is_attachment to return the correct result when the header has parameters as well as a value.

bpo-22247 [https://bugs.python.org/issue?@action=redirect&bpo=22247]: Add NNTPError to nntplib.__all__.

bpo-22366 [https://bugs.python.org/issue?@action=redirect&bpo=22366]: urllib.request.urlopen will accept a context object (SSLContext) as an argument which will then be used for HTTPS connection. Patch by Alex Gaynor.

bpo-4180 [https://bugs.python.org/issue?@action=redirect&bpo=4180]: The warnings registries are now reset when the filters are modified.

bpo-22419 [https://bugs.python.org/issue?@action=redirect&bpo=22419]: Limit the length of incoming HTTP request in wsgiref server to 65536 bytes and send a 414 error code for higher lengths. Patch contributed by Devin Cook.

Lax cookie parsing in http.cookies could be a security issue when combined with non-standard cookie handling in some web browsers. Reported by Sergey Bobrov.

bpo-20537 [https://bugs.python.org/issue?@action=redirect&bpo=20537]: logging methods now accept an exception instance as well as a Boolean value or exception tuple. Thanks to Yury Selivanov for the patch.

bpo-22384 [https://bugs.python.org/issue?@action=redirect&bpo=22384]: An exception in Tkinter callback no longer crashes the program when it is run with pythonw.exe.

bpo-22168 [https://bugs.python.org/issue?@action=redirect&bpo=22168]: Prevent turtle AttributeError with non-default Canvas on OS X.

bpo-21147 [https://bugs.python.org/issue?@action=redirect&bpo=21147]: sqlite3 now raises an exception if the request contains a null character instead of truncating it. Based on patch by Victor Stinner.

bpo-13968 [https://bugs.python.org/issue?@action=redirect&bpo=13968]: The glob module now supports recursive search in subdirectories using the ** pattern.

bpo-21951 [https://bugs.python.org/issue?@action=redirect&bpo=21951]: Fixed a crash in Tkinter on AIX when called Tcl command with empty string or tuple argument.

bpo-21951 [https://bugs.python.org/issue?@action=redirect&bpo=21951]: Tkinter now most likely raises MemoryError instead of crash if the memory allocation fails.

bpo-22338 [https://bugs.python.org/issue?@action=redirect&bpo=22338]: Fix a crash in the json module on memory allocation failure.

bpo-12410 [https://bugs.python.org/issue?@action=redirect&bpo=12410]: imaplib.IMAP4 now supports the context management protocol. Original patch by Tarek Ziadé.

bpo-21270 [https://bugs.python.org/issue?@action=redirect&bpo=21270]: We now override tuple methods in mock.call objects so that they can be used as normal call attributes.

bpo-16662 [https://bugs.python.org/issue?@action=redirect&bpo=16662]: load_tests() is now unconditionally run when it is present in a package's __init__.py. TestLoader.loadTestsFromModule() still accepts use_load_tests, but it is deprecated and ignored. A new keyword-only attribute pattern is added and documented. Patch given by Robert Collins, tweaked by Barry Warsaw.

bpo-22226 [https://bugs.python.org/issue?@action=redirect&bpo=22226]: First letter no longer is stripped from the "status" key in the result of Treeview.heading().

bpo-19524 [https://bugs.python.org/issue?@action=redirect&bpo=19524]: Fixed resource leak in the HTTP connection when an invalid response is received. Patch by Martin Panter.

bpo-20421 [https://bugs.python.org/issue?@action=redirect&bpo=20421]: Add a .version() method to SSL sockets exposing the actual protocol version in use.

bpo-19546 [https://bugs.python.org/issue?@action=redirect&bpo=19546]: configparser exceptions no longer expose implementation details. Chained KeyErrors are removed, which leads to cleaner tracebacks. Patch by Claudiu Popa.

bpo-22051 [https://bugs.python.org/issue?@action=redirect&bpo=22051]: turtledemo no longer reloads examples to re-run them. Initialization of variables and gui setup should be done in main(), which is called each time a demo is run, but not on import.

bpo-21933 [https://bugs.python.org/issue?@action=redirect&bpo=21933]: Turtledemo users can change the code font size with a menu selection or control(command) '-' or '+' or control-mousewheel. Original patch by Lita Cho.

bpo-21597 [https://bugs.python.org/issue?@action=redirect&bpo=21597]: The separator between the turtledemo text pane and the drawing canvas can now be grabbed and dragged with a mouse. The code text pane can be widened to easily view or copy the full width of the text. The canvas can be widened on small screens. Original patches by Jan Kanis and Lita Cho.

bpo-18132 [https://bugs.python.org/issue?@action=redirect&bpo=18132]: Turtledemo buttons no longer disappear when the window is shrunk. Original patches by Jan Kanis and Lita Cho.

bpo-22043 [https://bugs.python.org/issue?@action=redirect&bpo=22043]: time.monotonic() is now always available. threading.Lock.acquire(), threading.RLock.acquire() and socket operations now use a monotonic clock, instead of the system clock, when a timeout is used.

bpo-21527 [https://bugs.python.org/issue?@action=redirect&bpo=21527]: Add a default number of workers to ThreadPoolExecutor equal to 5 times the number of CPUs. Patch by Claudiu Popa.

bpo-22216 [https://bugs.python.org/issue?@action=redirect&bpo=22216]: smtplib now resets its state more completely after a quit. The most obvious consequence of the previous behavior was a STARTTLS failure during a connect/starttls/quit/connect/starttls sequence.

bpo-22098 [https://bugs.python.org/issue?@action=redirect&bpo=22098]: ctypes' BigEndianStructure and LittleEndianStructure now define an empty __slots__ so that subclasses don't always get an instance dict. Patch by Claudiu Popa.

bpo-22185 [https://bugs.python.org/issue?@action=redirect&bpo=22185]: Fix an occasional RuntimeError in threading.Condition.wait() caused by mutation of the waiters queue without holding the lock. Patch by Doug Zongker.

bpo-22287 [https://bugs.python.org/issue?@action=redirect&bpo=22287]: On UNIX, _PyTime_gettimeofday() now uses clock_gettime(CLOCK_REALTIME) if available. As a side effect, Python now depends on the librt library on Solaris and on Linux (only with glibc older than 2.17).

bpo-22182 [https://bugs.python.org/issue?@action=redirect&bpo=22182]: Use e.args to unpack exceptions correctly in distutils.file_util.move_file. Patch by Claudiu Popa.

The webbrowser module now uses subprocess's start_new_session=True rather than a potentially risky preexec_fn=os.setsid call.

bpo-22042 [https://bugs.python.org/issue?@action=redirect&bpo=22042]: signal.set_wakeup_fd(fd) now raises an exception if the file descriptor is in blocking mode.

bpo-16808 [https://bugs.python.org/issue?@action=redirect&bpo=16808]: inspect.stack() now returns a named tuple instead of a tuple. Patch by Daniel Shahaf.

bpo-22236 [https://bugs.python.org/issue?@action=redirect&bpo=22236]: Fixed Tkinter images copying operations in NoDefaultRoot mode.

bpo-2527 [https://bugs.python.org/issue?@action=redirect&bpo=2527]: Add a globals argument to timeit functions, in order to override the globals namespace in which the timed code is executed. Patch by Ben Roberts.

bpo-22118 [https://bugs.python.org/issue?@action=redirect&bpo=22118]: Switch urllib.parse to use RFC 3986 semantics for the resolution of relative URLs, rather than RFCs 1808 and 2396. Patch by Demian Brecht.

bpo-21549 [https://bugs.python.org/issue?@action=redirect&bpo=21549]: Added the "members" parameter to TarFile.list().

bpo-19628 [https://bugs.python.org/issue?@action=redirect&bpo=19628]: Allow compileall recursion depth to be specified with a -r option.

bpo-15696 [https://bugs.python.org/issue?@action=redirect&bpo=15696]: Add a __sizeof__ implementation for mmap objects on Windows.

bpo-22068 [https://bugs.python.org/issue?@action=redirect&bpo=22068]: Avoided reference loops with Variables and Fonts in Tkinter.

bpo-22165 [https://bugs.python.org/issue?@action=redirect&bpo=22165]: SimpleHTTPRequestHandler now supports undecodable file names.

bpo-15381 [https://bugs.python.org/issue?@action=redirect&bpo=15381]: Optimized line reading in io.BytesIO.

bpo-8797 [https://bugs.python.org/issue?@action=redirect&bpo=8797]: Raise HTTPError on failed Basic Authentication immediately. Initial patch by Sam Bull.

bpo-20729 [https://bugs.python.org/issue?@action=redirect&bpo=20729]: Restored the use of lazy iterkeys()/itervalues()/iteritems() in the mailbox module.

bpo-21448 [https://bugs.python.org/issue?@action=redirect&bpo=21448]: Changed FeedParser feed() to avoid O(n²) behavior when parsing long line. Original patch by Raymond Hettinger.

bpo-22184 [https://bugs.python.org/issue?@action=redirect&bpo=22184]: The functools LRU Cache decorator factory now gives an earlier and clearer error message when the user forgets the required parameters.

bpo-17923 [https://bugs.python.org/issue?@action=redirect&bpo=17923]: glob() patterns ending with a slash no longer match non-dirs on AIX. Based on patch by Delhallt.

bpo-21725 [https://bugs.python.org/issue?@action=redirect&bpo=21725]: Added support for RFC 6531 (SMTPUTF8) in smtpd.

bpo-22176 [https://bugs.python.org/issue?@action=redirect&bpo=22176]: Update the ctypes module's libffi to v3.1. This release adds support for the Linux AArch64 and POWERPC ELF ABIv2 little endian architectures.

bpo-5411 [https://bugs.python.org/issue?@action=redirect&bpo=5411]: Added support for the "xztar" format in the shutil module.

bpo-21121 [https://bugs.python.org/issue?@action=redirect&bpo=21121]: Don't force 3rd party C extensions to be built with -Werror=declaration-after-statement.

bpo-21975 [https://bugs.python.org/issue?@action=redirect&bpo=21975]: Fixed crash when using uninitialized sqlite3.Row (in particular when unpickling pickled sqlite3.Row). sqlite3.Row is now initialized in the __new__() method.

bpo-20170 [https://bugs.python.org/issue?@action=redirect&bpo=20170]: Convert posixmodule to use Argument Clinic.

bpo-21539 [https://bugs.python.org/issue?@action=redirect&bpo=21539]: Add an exists_ok argument to Pathlib.mkdir() to mimic mkdir -p and os.makedirs() functionality. When true, ignore FileExistsErrors. Patch by Berker Peksag.

bpo-22127 [https://bugs.python.org/issue?@action=redirect&bpo=22127]: Bypass IDNA for pure-ASCII host names in the socket module (in particular for numeric IPs).

bpo-21047 [https://bugs.python.org/issue?@action=redirect&bpo=21047]: set the default value for the convert_charrefs argument of HTMLParser to True. Patch by Berker Peksag.

Add an __all__ to html.entities.

bpo-15114 [https://bugs.python.org/issue?@action=redirect&bpo=15114]: the strict mode and argument of HTMLParser, HTMLParser.error, and the HTMLParserError exception have been removed.

bpo-22085 [https://bugs.python.org/issue?@action=redirect&bpo=22085]: Dropped support of Tk 8.3 in Tkinter.

bpo-21580 [https://bugs.python.org/issue?@action=redirect&bpo=21580]: Now Tkinter correctly handles bytes arguments passed to Tk. In particular this allows initializing images from binary data.

bpo-22003 [https://bugs.python.org/issue?@action=redirect&bpo=22003]: When initialized from a bytes object, io.BytesIO() now defers making a copy until it is mutated, improving performance and memory use on some use cases. Patch by David Wilson.

bpo-22018 [https://bugs.python.org/issue?@action=redirect&bpo=22018]: On Windows, signal.set_wakeup_fd() now also supports sockets. A side effect is that Python depends to the WinSock library.

bpo-22054 [https://bugs.python.org/issue?@action=redirect&bpo=22054]: Add os.get_blocking() and os.set_blocking() functions to get and set the blocking mode of a file descriptor (False if the O_NONBLOCK flag is set, True otherwise). These functions are not available on Windows.

bpo-17172 [https://bugs.python.org/issue?@action=redirect&bpo=17172]: Make turtledemo start as active on OS X even when run with subprocess. Patch by Lita Cho.

bpo-21704 [https://bugs.python.org/issue?@action=redirect&bpo=21704]: Fix build error for _multiprocessing when semaphores are not available. Patch by Arfrever Frehtes Taifersar Arahesis.

bpo-20173 [https://bugs.python.org/issue?@action=redirect&bpo=20173]: Convert sha1, sha256, sha512 and md5 to ArgumentClinic. Patch by Vajrasky Kok.

Fix repr(_socket.socket) on Windows 64-bit: don't fail with OverflowError on closed socket. repr(socket.socket) already works fine.

bpo-22033 [https://bugs.python.org/issue?@action=redirect&bpo=22033]: Reprs of most Python implemented classes now contain actual class name instead of hardcoded one.

bpo-21947 [https://bugs.python.org/issue?@action=redirect&bpo=21947]: The dis module can now disassemble generator-iterator objects based on their gi_code attribute. Patch by Clement Rouault.

bpo-16133 [https://bugs.python.org/issue?@action=redirect&bpo=16133]: The asynchat.async_chat.handle_read() method now ignores BlockingIOError exceptions.

bpo-22044 [https://bugs.python.org/issue?@action=redirect&bpo=22044]: Fixed premature DECREF in call_tzinfo_method. Patch by Tom Flanagan.

bpo-19884 [https://bugs.python.org/issue?@action=redirect&bpo=19884]: readline: Disable the meta modifier key if stdout is not a terminal to not write the ANSI sequence "\033[1034h" into stdout. This sequence is used on some terminal (ex: TERM=xterm-256color") to enable support of 8 bit characters.

bpo-4350 [https://bugs.python.org/issue?@action=redirect&bpo=4350]: Removed a number of out-of-dated and non-working for a long time Tkinter methods.

bpo-6167 [https://bugs.python.org/issue?@action=redirect&bpo=6167]: Scrollbar.activate() now returns the name of active element if the argument is not specified. Scrollbar.set() now always accepts only 2 arguments.

bpo-15275 [https://bugs.python.org/issue?@action=redirect&bpo=15275]: Clean up and speed up the ntpath module.

bpo-21888 [https://bugs.python.org/issue?@action=redirect&bpo=21888]: plistlib's load() and loads() now work if the fmt parameter is specified.

bpo-22032 [https://bugs.python.org/issue?@action=redirect&bpo=22032]: __qualname__ instead of __name__ is now always used to format fully qualified class names of Python implemented classes.

bpo-22031 [https://bugs.python.org/issue?@action=redirect&bpo=22031]: Reprs now always use hexadecimal format with the "0x" prefix when contain an id in form " at 0x...".

bpo-22018 [https://bugs.python.org/issue?@action=redirect&bpo=22018]: signal.set_wakeup_fd() now raises an OSError instead of a ValueError on fstat() failure.

bpo-21044 [https://bugs.python.org/issue?@action=redirect&bpo=21044]: tarfile.open() now handles fileobj with an integer 'name' attribute. Based on patch by Antoine Pietri.

bpo-21966 [https://bugs.python.org/issue?@action=redirect&bpo=21966]: Respect -q command-line option when code module is ran.

bpo-19076 [https://bugs.python.org/issue?@action=redirect&bpo=19076]: Don't pass the redundant 'file' argument to self.error().

bpo-16382 [https://bugs.python.org/issue?@action=redirect&bpo=16382]: Improve exception message of warnings.warn() for bad category. Initial patch by Phil Elson.

bpo-21932 [https://bugs.python.org/issue?@action=redirect&bpo=21932]: os.read() now uses a Py_ssize_t() type instead of int for the size to support reading more than 2 GB at once. On Windows, the size is truncated to INT_MAX. As any call to os.read(), the OS may read less bytes than the number of requested bytes.

bpo-21942 [https://bugs.python.org/issue?@action=redirect&bpo=21942]: Fixed source file viewing in pydoc's server mode on Windows.

bpo-11259 [https://bugs.python.org/issue?@action=redirect&bpo=11259]: asynchat.async_chat().set_terminator() now raises a ValueError if the number of received bytes is negative.

bpo-12523 [https://bugs.python.org/issue?@action=redirect&bpo=12523]: asynchat.async_chat.push() now raises a TypeError if it doesn't get a bytes string

bpo-21707 [https://bugs.python.org/issue?@action=redirect&bpo=21707]: Add missing kwonlyargcount argument to ModuleFinder.replace_paths_in_code().

bpo-20639 [https://bugs.python.org/issue?@action=redirect&bpo=20639]: calling Path.with_suffix('') allows removing the suffix again. Patch by July Tikhonov.

bpo-21714 [https://bugs.python.org/issue?@action=redirect&bpo=21714]: Disallow the construction of invalid paths using Path.with_name(). Original patch by Antony Lee.

bpo-15014 [https://bugs.python.org/issue?@action=redirect&bpo=15014]: Added 'auth' method to smtplib to make implementing auth mechanisms simpler, and used it internally in the login method.

bpo-21151 [https://bugs.python.org/issue?@action=redirect&bpo=21151]: Fixed a segfault in the winreg module when None is passed as a REG_BINARY value to SetValueEx. Patch by John Ehresman.

bpo-21090 [https://bugs.python.org/issue?@action=redirect&bpo=21090]: io.FileIO.readall() does not ignore I/O errors anymore. Before, it ignored I/O errors if at least the first C call read() succeed.

bpo-5800 [https://bugs.python.org/issue?@action=redirect&bpo=5800]: headers parameter of wsgiref.headers.Headers is now optional. Initial patch by Pablo Torres Navarrete and SilentGhost.

bpo-21781 [https://bugs.python.org/issue?@action=redirect&bpo=21781]: ssl.RAND_add() now supports strings longer than 2 GB.

bpo-21679 [https://bugs.python.org/issue?@action=redirect&bpo=21679]: Prevent extraneous fstat() calls during open(). Patch by Bohuslav Kabrda.

bpo-21863 [https://bugs.python.org/issue?@action=redirect&bpo=21863]: cProfile now displays the module name of C extension functions, in addition to their own name.

bpo-11453 [https://bugs.python.org/issue?@action=redirect&bpo=11453]: asyncore: emit a ResourceWarning when an unclosed file_wrapper object is destroyed. The destructor now closes the file if needed. The close() method can now be called twice: the second call does nothing.

bpo-21858 [https://bugs.python.org/issue?@action=redirect&bpo=21858]: Better handling of Python exceptions in the sqlite3 module.

bpo-21476 [https://bugs.python.org/issue?@action=redirect&bpo=21476]: Make sure the email.parser.BytesParser TextIOWrapper is discarded after parsing, so the input file isn't unexpectedly closed.

bpo-20295 [https://bugs.python.org/issue?@action=redirect&bpo=20295]: imghdr now recognizes OpenEXR format images.

bpo-21729 [https://bugs.python.org/issue?@action=redirect&bpo=21729]: Used the "with" statement in the dbm.dumb module to ensure files closing. Patch by Claudiu Popa.

bpo-21491 [https://bugs.python.org/issue?@action=redirect&bpo=21491]: socketserver: Fix a race condition in child processes reaping.

bpo-21719 [https://bugs.python.org/issue?@action=redirect&bpo=21719]: Added the st_file_attributes field to os.stat_result on Windows.

bpo-21832 [https://bugs.python.org/issue?@action=redirect&bpo=21832]: Require named tuple inputs to be exact strings.

bpo-21722 [https://bugs.python.org/issue?@action=redirect&bpo=21722]: The distutils "upload" command now exits with a non-zero return code when uploading fails. Patch by Martin Dengler.

bpo-21723 [https://bugs.python.org/issue?@action=redirect&bpo=21723]: asyncio.Queue: support any type of number (ex: float) for the maximum size. Patch written by Vajrasky Kok.

bpo-21711 [https://bugs.python.org/issue?@action=redirect&bpo=21711]: support for "site-python" directories has now been removed from the site module (it was deprecated in 3.4).

bpo-17552 [https://bugs.python.org/issue?@action=redirect&bpo=17552]: new socket.sendfile() method allowing a file to be sent over a socket by using high-performance os.sendfile() on UNIX. Patch by Giampaolo Rodola'.

bpo-18039 [https://bugs.python.org/issue?@action=redirect&bpo=18039]: dbm.dump.open() now always creates a new database when the flag has the value 'n'. Patch by Claudiu Popa.

bpo-21326 [https://bugs.python.org/issue?@action=redirect&bpo=21326]: Add a new is_closed() method to asyncio.BaseEventLoop. run_forever() and run_until_complete() methods of asyncio.BaseEventLoop now raise an exception if the event loop was closed.

bpo-21766 [https://bugs.python.org/issue?@action=redirect&bpo=21766]: Prevent a security hole in CGIHTTPServer by URL unquoting paths before checking for a CGI script at that path.

bpo-21310 [https://bugs.python.org/issue?@action=redirect&bpo=21310]: Fixed possible resource leak in failed open().

bpo-21256 [https://bugs.python.org/issue?@action=redirect&bpo=21256]: Printout of keyword args should be in deterministic order in a mock function call. This will help to write better doctests.

bpo-21677 [https://bugs.python.org/issue?@action=redirect&bpo=21677]: Fixed chaining nonnormalized exceptions in io close() methods.

bpo-11709 [https://bugs.python.org/issue?@action=redirect&bpo=11709]: Fix the pydoc.help function to not fail when sys.stdin is not a valid file.

bpo-21515 [https://bugs.python.org/issue?@action=redirect&bpo=21515]: tempfile.TemporaryFile now uses os.O_TMPFILE flag is available.

bpo-13223 [https://bugs.python.org/issue?@action=redirect&bpo=13223]: Fix pydoc.writedoc so that the HTML documentation for methods that use 'self' in the example code is generated correctly.

bpo-21463 [https://bugs.python.org/issue?@action=redirect&bpo=21463]: In urllib.request, fix pruning of the FTP cache.

bpo-21618 [https://bugs.python.org/issue?@action=redirect&bpo=21618]: The subprocess module could fail to close open fds that were inherited by the calling process and already higher than POSIX resource limits would otherwise allow. On systems with a functioning /proc/self/fd or /dev/fd interface the max is now ignored and all fds are closed.

bpo-20383 [https://bugs.python.org/issue?@action=redirect&bpo=20383]: Introduce importlib.util.module_from_spec() as the preferred way to create a new module.

bpo-21552 [https://bugs.python.org/issue?@action=redirect&bpo=21552]: Fixed possible integer overflow of too long string lengths in the tkinter module on 64-bit platforms.

bpo-14315 [https://bugs.python.org/issue?@action=redirect&bpo=14315]: The zipfile module now ignores extra fields in the central directory that are too short to be parsed instead of letting a struct.unpack error bubble up as this "bad data" appears in many real world zip files in the wild and is ignored by other zip tools.

bpo-13742 [https://bugs.python.org/issue?@action=redirect&bpo=13742]: Added "key" and "reverse" parameters to heapq.merge(). (First draft of patch contributed by Simon Sapin.)

bpo-21402 [https://bugs.python.org/issue?@action=redirect&bpo=21402]: tkinter.ttk now works when default root window is not set.

bpo-3015 [https://bugs.python.org/issue?@action=redirect&bpo=3015]: _tkinter.create() now creates tkapp object with wantobjects=1 by default.

bpo-10203 [https://bugs.python.org/issue?@action=redirect&bpo=10203]: sqlite3.Row now truly supports sequence protocol. In particular it supports reverse() and negative indices. Original patch by Claudiu Popa.

bpo-18807 [https://bugs.python.org/issue?@action=redirect&bpo=18807]: If copying (no symlinks) specified for a venv, then the python interpreter aliases (python, python3) are now created by copying rather than symlinking.

bpo-20197 [https://bugs.python.org/issue?@action=redirect&bpo=20197]: Added support for the WebP image type in the imghdr module. Patch by Fabrice Aneche and Claudiu Popa.

bpo-21513 [https://bugs.python.org/issue?@action=redirect&bpo=21513]: Speedup some properties of IP addresses (IPv4Address, IPv6Address) such as .is_private or .is_multicast.

bpo-21137 [https://bugs.python.org/issue?@action=redirect&bpo=21137]: Improve the repr for threading.Lock() and its variants by showing the "locked" or "unlocked" status. Patch by Berker Peksag.

bpo-21538 [https://bugs.python.org/issue?@action=redirect&bpo=21538]: The plistlib module now supports loading of binary plist files when reference or offset size is not a power of two.

bpo-21455 [https://bugs.python.org/issue?@action=redirect&bpo=21455]: Add a default backlog to socket.listen().

bpo-21525 [https://bugs.python.org/issue?@action=redirect&bpo=21525]: Most Tkinter methods which accepted tuples now accept lists too.

bpo-22166 [https://bugs.python.org/issue?@action=redirect&bpo=22166]: With the assistance of a new internal _codecs._forget_codec helping function, test_codecs now clears the encoding caches to avoid the appearance of a reference leak

bpo-22236 [https://bugs.python.org/issue?@action=redirect&bpo=22236]: Tkinter tests now don't reuse default root window. New root window is created for every test class.

bpo-10744 [https://bugs.python.org/issue?@action=redirect&bpo=10744]: Fix PEP 3118 [https://peps.python.org/pep-3118/] format strings on ctypes objects with a nontrivial shape.

bpo-20826 [https://bugs.python.org/issue?@action=redirect&bpo=20826]: Optimize ipaddress.collapse_addresses().

bpo-21487 [https://bugs.python.org/issue?@action=redirect&bpo=21487]: Optimize ipaddress.summarize_address_range() and ipaddress.{IPv4Network,IPv6Network}.subnets().

bpo-21486 [https://bugs.python.org/issue?@action=redirect&bpo=21486]: Optimize parsing of netmasks in ipaddress.IPv4Network and ipaddress.IPv6Network.

bpo-13916 [https://bugs.python.org/issue?@action=redirect&bpo=13916]: Disallowed the surrogatepass error handler for non UTF-* encodings.

bpo-20998 [https://bugs.python.org/issue?@action=redirect&bpo=20998]: Fixed re.fullmatch() of repeated single character pattern with ignore case. Original patch by Matthew Barnett.

bpo-21075 [https://bugs.python.org/issue?@action=redirect&bpo=21075]: fileinput.FileInput now reads bytes from standard stream if binary mode is specified. Patch by Sam Kimbrel.

bpo-19775 [https://bugs.python.org/issue?@action=redirect&bpo=19775]: Add a samefile() method to pathlib Path objects. Initial patch by Vajrasky Kok.

bpo-21226 [https://bugs.python.org/issue?@action=redirect&bpo=21226]: Set up modules properly in PyImport_ExecCodeModuleObject (and friends).

bpo-21398 [https://bugs.python.org/issue?@action=redirect&bpo=21398]: Fix a unicode error in the pydoc pager when the documentation contains characters not encodable to the stdout encoding.

bpo-16531 [https://bugs.python.org/issue?@action=redirect&bpo=16531]: ipaddress.IPv4Network and ipaddress.IPv6Network now accept an (address, netmask) tuple argument, so as to easily construct network objects from existing addresses.

bpo-21156 [https://bugs.python.org/issue?@action=redirect&bpo=21156]: importlib.abc.InspectLoader.source_to_code() is now a staticmethod.

bpo-21424 [https://bugs.python.org/issue?@action=redirect&bpo=21424]: Simplified and optimized heaqp.nlargest() and nmsmallest() to make fewer tuple comparisons.

bpo-21396 [https://bugs.python.org/issue?@action=redirect&bpo=21396]: Fix TextIOWrapper(..., write_through=True) to not force a flush() on the underlying binary stream. Patch by akira.

bpo-18314 [https://bugs.python.org/issue?@action=redirect&bpo=18314]: Unlink now removes junctions on Windows. Patch by Kim Gräsman

bpo-21088 [https://bugs.python.org/issue?@action=redirect&bpo=21088]: Bugfix for curses.window.addch() regression in 3.4.0. In porting to Argument Clinic, the first two arguments were reversed.

bpo-21407 [https://bugs.python.org/issue?@action=redirect&bpo=21407]: _decimal: The module now supports function signatures.

bpo-10650 [https://bugs.python.org/issue?@action=redirect&bpo=10650]: Remove the non-standard 'watchexp' parameter from the Decimal.quantize() method in the Python version. It had never been present in the C version.

bpo-21469 [https://bugs.python.org/issue?@action=redirect&bpo=21469]: Reduced the risk of false positives in robotparser by checking to make sure that robots.txt has been read or does not exist prior to returning True in can_fetch().

bpo-19414 [https://bugs.python.org/issue?@action=redirect&bpo=19414]: Have the OrderedDict mark deleted links as unusable. This gives an early failure if the link is deleted during iteration.

bpo-21421 [https://bugs.python.org/issue?@action=redirect&bpo=21421]: Add __slots__ to the MappingViews ABC. Patch by Josh Rosenberg.

bpo-21101 [https://bugs.python.org/issue?@action=redirect&bpo=21101]: Eliminate double hashing in the C speed-up code for collections.Counter().

bpo-21321 [https://bugs.python.org/issue?@action=redirect&bpo=21321]: itertools.islice() now releases the reference to the source iterator when the slice is exhausted. Patch by Anton Afanasyev.

bpo-21057 [https://bugs.python.org/issue?@action=redirect&bpo=21057]: TextIOWrapper now allows the underlying binary stream's read() or read1() method to return an arbitrary bytes-like object (such as a memoryview). Patch by Nikolaus Rath.

bpo-20951 [https://bugs.python.org/issue?@action=redirect&bpo=20951]: SSLSocket.send() now raises either SSLWantReadError or SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0. Patch by Nikolaus Rath.

bpo-13248 [https://bugs.python.org/issue?@action=redirect&bpo=13248]: removed previously deprecated asyncore.dispatcher __getattr__ cheap inheritance hack.

bpo-9815 [https://bugs.python.org/issue?@action=redirect&bpo=9815]: assertRaises now tries to clear references to local variables in the exception's traceback.

bpo-19940 [https://bugs.python.org/issue?@action=redirect&bpo=19940]: ssl.cert_time_to_seconds() now interprets the given time string in the UTC timezone (as specified in RFC 5280), not the local timezone.

bpo-13204 [https://bugs.python.org/issue?@action=redirect&bpo=13204]: Calling sys.flags.__new__ would crash the interpreter, now it raises a TypeError.

bpo-19385 [https://bugs.python.org/issue?@action=redirect&bpo=19385]: Make operations on a closed dbm.dumb database always raise the same exception.

bpo-21207 [https://bugs.python.org/issue?@action=redirect&bpo=21207]: Detect when the os.urandom cached fd has been closed or replaced, and open it anew.

bpo-21291 [https://bugs.python.org/issue?@action=redirect&bpo=21291]: subprocess's Popen.wait() is now thread safe so that multiple threads may be calling wait() or poll() on a Popen instance at the same time without losing the Popen.returncode value.

bpo-21127 [https://bugs.python.org/issue?@action=redirect&bpo=21127]: Path objects can now be instantiated from str subclass instances (such as numpy.str_).

bpo-15002 [https://bugs.python.org/issue?@action=redirect&bpo=15002]: urllib.response object to use _TemporaryFileWrapper (and _TemporaryFileCloser) facility. Provides a better way to handle file descriptor close. Patch contributed by Christian Theune.

bpo-12220 [https://bugs.python.org/issue?@action=redirect&bpo=12220]: mindom now raises a custom ValueError indicating it doesn't support spaces in URIs instead of letting a 'split' ValueError bubble up.

bpo-21068 [https://bugs.python.org/issue?@action=redirect&bpo=21068]: The ssl.PROTOCOL* constants are now enum members.

bpo-21276 [https://bugs.python.org/issue?@action=redirect&bpo=21276]: posixmodule: Don't define USE_XATTRS on KFreeBSD and the Hurd.

bpo-21262 [https://bugs.python.org/issue?@action=redirect&bpo=21262]: New method assert_not_called for Mock. It raises AssertionError if the mock has been called.

bpo-21238 [https://bugs.python.org/issue?@action=redirect&bpo=21238]: New keyword argument unsafe to Mock. It raises AttributeError in case of an attribute startswith assert or assret.

bpo-20896 [https://bugs.python.org/issue?@action=redirect&bpo=20896]: ssl.get_server_certificate() now uses PROTOCOL_SSLv23, not PROTOCOL_SSLv3, for maximum compatibility.

bpo-21239 [https://bugs.python.org/issue?@action=redirect&bpo=21239]: patch.stopall() didn't work deterministically when the same name was patched more than once.

bpo-21203 [https://bugs.python.org/issue?@action=redirect&bpo=21203]: Updated fileConfig and dictConfig to remove inconsistencies. Thanks to Jure Koren for the patch.

bpo-21222 [https://bugs.python.org/issue?@action=redirect&bpo=21222]: Passing name keyword argument to mock.create_autospec now works.

bpo-21197 [https://bugs.python.org/issue?@action=redirect&bpo=21197]: Add lib64 -> lib symlink in venvs on 64-bit non-OS X POSIX.

bpo-17498 [https://bugs.python.org/issue?@action=redirect&bpo=17498]: Some SMTP servers disconnect after certain errors, violating strict RFC conformance. Instead of losing the error code when we issue the subsequent RSET, smtplib now returns the error code and defers raising the SMTPServerDisconnected error until the next command is issued.

bpo-17826 [https://bugs.python.org/issue?@action=redirect&bpo=17826]: setting an iterable side_effect on a mock function created by create_autospec now works. Patch by Kushal Das.

bpo-7776 [https://bugs.python.org/issue?@action=redirect&bpo=7776]: Fix Host: header and reconnection when using http.client.HTTPConnection.set_tunnel(). Patch by Nikolaus Rath.

bpo-20968 [https://bugs.python.org/issue?@action=redirect&bpo=20968]: unittest.mock.MagicMock now supports division. Patch by Johannes Baiter.

bpo-21529 [https://bugs.python.org/issue?@action=redirect&bpo=21529]: Fix arbitrary memory access in JSONDecoder.raw_decode with a negative second parameter. Bug reported by Guido Vranken. (See also: CVE 2014-4616 [https://www.cve.org/CVERecord?id=CVE-2014-4616])

bpo-21169 [https://bugs.python.org/issue?@action=redirect&bpo=21169]: getpass now handles non-ascii characters that the input stream encoding cannot encode by re-encoding using the replace error handler.

bpo-21171 [https://bugs.python.org/issue?@action=redirect&bpo=21171]: Fixed undocumented filter API of the rot13 codec. Patch by Berker Peksag.

bpo-20539 [https://bugs.python.org/issue?@action=redirect&bpo=20539]: Improved math.factorial error message for large positive inputs and changed exception type (OverflowError -> ValueError) for large negative inputs.

bpo-21172 [https://bugs.python.org/issue?@action=redirect&bpo=21172]: isinstance check relaxed from dict to collections.Mapping.

bpo-21155 [https://bugs.python.org/issue?@action=redirect&bpo=21155]: asyncio.EventLoop.create_unix_server() now raises a ValueError if path and sock are specified at the same time.

bpo-21136 [https://bugs.python.org/issue?@action=redirect&bpo=21136]: Avoid unnecessary normalization of Fractions resulting from power and other operations. Patch by Raymond Hettinger.

bpo-17621 [https://bugs.python.org/issue?@action=redirect&bpo=17621]: Introduce importlib.util.LazyLoader.

bpo-21076 [https://bugs.python.org/issue?@action=redirect&bpo=21076]: signal module constants were turned into enums. Patch by Giampaolo Rodola'.

bpo-20636 [https://bugs.python.org/issue?@action=redirect&bpo=20636]: Improved the repr of Tkinter widgets.

bpo-19505 [https://bugs.python.org/issue?@action=redirect&bpo=19505]: The items, keys, and values views of OrderedDict now support reverse iteration using reversed().

bpo-21149 [https://bugs.python.org/issue?@action=redirect&bpo=21149]: Improved thread-safety in logging cleanup during interpreter shutdown. Thanks to Devin Jeanpierre for the patch.

bpo-21058 [https://bugs.python.org/issue?@action=redirect&bpo=21058]: Fix a leak of file descriptor in tempfile.NamedTemporaryFile(), close the file descriptor if io.open() fails

bpo-21200 [https://bugs.python.org/issue?@action=redirect&bpo=21200]: Return None from pkgutil.get_loader() when __spec__ is missing.

bpo-21013 [https://bugs.python.org/issue?@action=redirect&bpo=21013]: Enhance ssl.create_default_context() when used for server side sockets to provide better security by default.

bpo-20145 [https://bugs.python.org/issue?@action=redirect&bpo=20145]: assertRaisesRegex and assertWarnsRegex now raise a TypeError if the second argument is not a string or compiled regex.

bpo-20633 [https://bugs.python.org/issue?@action=redirect&bpo=20633]: Replace relative import by absolute import.

bpo-20980 [https://bugs.python.org/issue?@action=redirect&bpo=20980]: Stop wrapping exception when using ThreadPool.

bpo-21082 [https://bugs.python.org/issue?@action=redirect&bpo=21082]: In os.makedirs, do not set the process-wide umask. Note this changes behavior of makedirs when exist_ok=True.

bpo-20990 [https://bugs.python.org/issue?@action=redirect&bpo=20990]: Fix issues found by pyflakes for multiprocessing.

bpo-21015 [https://bugs.python.org/issue?@action=redirect&bpo=21015]: SSL contexts will now automatically select an elliptic curve for ECDH key exchange on OpenSSL 1.0.2 and later, and otherwise default to "prime256v1".

bpo-21000 [https://bugs.python.org/issue?@action=redirect&bpo=21000]: Improve the command-line interface of json.tool.

bpo-20995 [https://bugs.python.org/issue?@action=redirect&bpo=20995]: Enhance default ciphers used by the ssl module to enable better security and prioritize perfect forward secrecy.

bpo-20884 [https://bugs.python.org/issue?@action=redirect&bpo=20884]: Don't assume that __file__ is defined on importlib.__init__.

bpo-21499 [https://bugs.python.org/issue?@action=redirect&bpo=21499]: Ignore __builtins__ in several test_importlib.test_api tests.

bpo-20627 [https://bugs.python.org/issue?@action=redirect&bpo=20627]: xmlrpc.client.ServerProxy is now a context manager.

bpo-19165 [https://bugs.python.org/issue?@action=redirect&bpo=19165]: The formatter module now raises DeprecationWarning instead of PendingDeprecationWarning.

bpo-13936 [https://bugs.python.org/issue?@action=redirect&bpo=13936]: Remove the ability of datetime.time instances to be considered false in boolean contexts.

bpo-18931 [https://bugs.python.org/issue?@action=redirect&bpo=18931]: selectors module now supports /dev/poll on Solaris. Patch by Giampaolo Rodola'.

bpo-19977 [https://bugs.python.org/issue?@action=redirect&bpo=19977]: When the LC_TYPE locale is the POSIX locale (C locale), sys.stdin and sys.stdout are now using the surrogateescape error handler, instead of the strict error handler.

bpo-20574 [https://bugs.python.org/issue?@action=redirect&bpo=20574]: Implement incremental decoder for cp65001 code (Windows code page 65001, Microsoft UTF-8).

bpo-20879 [https://bugs.python.org/issue?@action=redirect&bpo=20879]: Delay the initialization of encoding and decoding tables for base32, ascii85 and base85 codecs in the base64 module, and delay the initialization of the unquote_to_bytes() table of the urllib.parse module, to not waste memory if these modules are not used.

bpo-19157 [https://bugs.python.org/issue?@action=redirect&bpo=19157]: Include the broadcast address in the usable hosts for IPv6 in ipaddress.

bpo-11599 [https://bugs.python.org/issue?@action=redirect&bpo=11599]: When an external command (e.g. compiler) fails, distutils now prints out the whole command line (instead of just the command name) if the environment variable DISTUTILS_DEBUG is set.

bpo-4931 [https://bugs.python.org/issue?@action=redirect&bpo=4931]: distutils should not produce unhelpful "error: None" messages anymore. distutils.util.grok_environment_error is kept but doc-deprecated.

bpo-20875 [https://bugs.python.org/issue?@action=redirect&bpo=20875]: Prevent possible gzip "'read' is not defined" NameError. Patch by Claudiu Popa.

bpo-11558 [https://bugs.python.org/issue?@action=redirect&bpo=11558]: email.message.Message.attach now returns a more useful error message if attach is called on a message for which is_multipart is False.

bpo-20283 [https://bugs.python.org/issue?@action=redirect&bpo=20283]: RE pattern methods now accept the string keyword parameters as documented. The pattern and source keyword parameters are left as deprecated aliases.

bpo-20778 [https://bugs.python.org/issue?@action=redirect&bpo=20778]: Fix modulefinder to work with bytecode-only modules.

bpo-20791 [https://bugs.python.org/issue?@action=redirect&bpo=20791]: copy.copy() now doesn't make a copy when the input is a bytes object. Initial patch by Peter Otten.

bpo-19748 [https://bugs.python.org/issue?@action=redirect&bpo=19748]: On AIX, time.mktime() now raises an OverflowError for year outsize range [1902; 2037].

bpo-19573 [https://bugs.python.org/issue?@action=redirect&bpo=19573]: inspect.signature: Use enum for parameter kind constants.

bpo-20726 [https://bugs.python.org/issue?@action=redirect&bpo=20726]: inspect.signature: Make Signature and Parameter picklable.

bpo-17373 [https://bugs.python.org/issue?@action=redirect&bpo=17373]: Add inspect.Signature.from_callable method.

bpo-20378 [https://bugs.python.org/issue?@action=redirect&bpo=20378]: Improve repr of inspect.Signature and inspect.Parameter.

bpo-20816 [https://bugs.python.org/issue?@action=redirect&bpo=20816]: Fix inspect.getcallargs() to raise correct TypeError for missing keyword-only arguments. Patch by Jeremiah Lowin.

bpo-20817 [https://bugs.python.org/issue?@action=redirect&bpo=20817]: Fix inspect.getcallargs() to fail correctly if more than 3 arguments are missing. Patch by Jeremiah Lowin.

bpo-6676 [https://bugs.python.org/issue?@action=redirect&bpo=6676]: Ensure a meaningful exception is raised when attempting to parse more than one XML document per pyexpat xmlparser instance. (Original patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with suggested wording by David Gutteridge)

bpo-21117 [https://bugs.python.org/issue?@action=redirect&bpo=21117]: Fix inspect.signature to better support functools.partial. Due to the specifics of functools.partial implementation, positional-or-keyword arguments passed as keyword arguments become keyword-only.

bpo-20334 [https://bugs.python.org/issue?@action=redirect&bpo=20334]: inspect.Signature and inspect.Parameter are now hashable. Thanks to Antony Lee for bug reports and suggestions.

bpo-15916 [https://bugs.python.org/issue?@action=redirect&bpo=15916]: doctest.DocTestSuite returns an empty unittest.TestSuite instead of raising ValueError if it finds no tests

bpo-21209 [https://bugs.python.org/issue?@action=redirect&bpo=21209]: Fix asyncio.tasks.CoroWrapper to workaround a bug in yield-from implementation in CPythons prior to 3.4.1.

asyncio: Add gi_{frame,running,code} properties to CoroWrapper (upstream bpo-163 [https://bugs.python.org/issue?@action=redirect&bpo=163]).

bpo-21311 [https://bugs.python.org/issue?@action=redirect&bpo=21311]: Avoid exception in _osx_support with non-standard compiler configurations. Patch by John Szakmeister.

bpo-11571 [https://bugs.python.org/issue?@action=redirect&bpo=11571]: Ensure that the turtle window becomes the topmost window when launched on OS X.

bpo-21801 [https://bugs.python.org/issue?@action=redirect&bpo=21801]: Validate that __signature__ is None or an instance of Signature.

bpo-21923 [https://bugs.python.org/issue?@action=redirect&bpo=21923]: Prevent AttributeError in distutils.sysconfig.customize_compiler due to possible uninitialized _config_vars.

bpo-21323 [https://bugs.python.org/issue?@action=redirect&bpo=21323]: Fix http.server to again handle scripts in CGI subdirectories, broken by the fix for security bpo-19435 [https://bugs.python.org/issue?@action=redirect&bpo=19435]. Patch by Zach Byrne.

bpo-22733 [https://bugs.python.org/issue?@action=redirect&bpo=22733]: Fix ffi_prep_args not zero-extending argument values correctly on 64-bit Windows.

bpo-23302 [https://bugs.python.org/issue?@action=redirect&bpo=23302]: Default to TCP_NODELAY=1 upon establishing an HTTPConnection. Removed use of hard-coded MSS as it's an optimization that's no longer needed with Nagle disabled.

IDLE

bpo-20577 [https://bugs.python.org/issue?@action=redirect&bpo=20577]: Configuration of the max line length for the FormatParagraph extension has been moved from the General tab of the Idle preferences dialog to the FormatParagraph tab of the Config Extensions dialog. Patch by Tal Einat.

bpo-16893 [https://bugs.python.org/issue?@action=redirect&bpo=16893]: Update Idle doc chapter to match current Idle and add new information.

bpo-3068 [https://bugs.python.org/issue?@action=redirect&bpo=3068]: Add Idle extension configuration dialog to Options menu. Changes are written to HOME/.idlerc/config-extensions.cfg. Original patch by Tal Einat.

bpo-16233 [https://bugs.python.org/issue?@action=redirect&bpo=16233]: A module browser (File : Class Browser, Alt+C) requires an editor window with a filename. When Class Browser is requested otherwise, from a shell, output window, or 'Untitled' editor, Idle no longer displays an error box. It now pops up an Open Module box (Alt+M). If a valid name is entered and a module is opened, a corresponding browser is also opened.

bpo-4832 [https://bugs.python.org/issue?@action=redirect&bpo=4832]: Save As to type Python files automatically adds .py to the name you enter (even if your system does not display it). Some systems automatically add .txt when type is Text files.

bpo-21986 [https://bugs.python.org/issue?@action=redirect&bpo=21986]: Code objects are not normally pickled by the pickle module. To match this, they are no longer pickled when running under Idle.

bpo-17390 [https://bugs.python.org/issue?@action=redirect&bpo=17390]: Adjust Editor window title; remove 'Python', move version to end.

bpo-14105 [https://bugs.python.org/issue?@action=redirect&bpo=14105]: Idle debugger breakpoints no longer disappear when inserting or deleting lines.

bpo-17172 [https://bugs.python.org/issue?@action=redirect&bpo=17172]: Turtledemo can now be run from Idle. Currently, the entry is on the Help menu, but it may move to Run. Patch by Ramchandra Apt and Lita Cho.

bpo-21765 [https://bugs.python.org/issue?@action=redirect&bpo=21765]: Add support for non-ascii identifiers to HyperParser.

bpo-21940 [https://bugs.python.org/issue?@action=redirect&bpo=21940]: Add unittest for WidgetRedirector. Initial patch by Saimadhav Heblikar.

bpo-18592 [https://bugs.python.org/issue?@action=redirect&bpo=18592]: Add unittest for SearchDialogBase. Patch by Phil Webster.

bpo-21694 [https://bugs.python.org/issue?@action=redirect&bpo=21694]: Add unittest for ParenMatch. Patch by Saimadhav Heblikar.

bpo-21686 [https://bugs.python.org/issue?@action=redirect&bpo=21686]: add unittest for HyperParser. Original patch by Saimadhav Heblikar.

bpo-12387 [https://bugs.python.org/issue?@action=redirect&bpo=12387]: Add missing upper(lower)case versions of default Windows key bindings for Idle so Caps Lock does not disable them. Patch by Roger Serwy.

bpo-21695 [https://bugs.python.org/issue?@action=redirect&bpo=21695]: Closing a Find-in-files output window while the search is still in progress no longer closes Idle.

bpo-18910 [https://bugs.python.org/issue?@action=redirect&bpo=18910]: Add unittest for textView. Patch by Phil Webster.

bpo-18292 [https://bugs.python.org/issue?@action=redirect&bpo=18292]: Add unittest for AutoExpand. Patch by Saihadhav Heblikar.

bpo-18409 [https://bugs.python.org/issue?@action=redirect&bpo=18409]: Add unittest for AutoComplete. Patch by Phil Webster.

bpo-21477 [https://bugs.python.org/issue?@action=redirect&bpo=21477]: htest.py - Improve framework, complete set of tests. Patches by Saimadhav Heblikar

bpo-18104 [https://bugs.python.org/issue?@action=redirect&bpo=18104]: Add idlelib/idle_test/htest.py with a few sample tests to begin consolidating and improving human-validated tests of Idle. Change other files as needed to work with htest. Running the module as __main__ runs all tests.

bpo-21139 [https://bugs.python.org/issue?@action=redirect&bpo=21139]: Change default paragraph width to 72, the PEP 8 [https://peps.python.org/pep-0008/] recommendation.

bpo-21284 [https://bugs.python.org/issue?@action=redirect&bpo=21284]: Paragraph reformat test passes after user changes reformat width.

bpo-17654 [https://bugs.python.org/issue?@action=redirect&bpo=17654]: Ensure IDLE menus are customized properly on OS X for non-framework builds and for all variants of Tk.

bpo-23180 [https://bugs.python.org/issue?@action=redirect&bpo=23180]: Rename IDLE "Windows" menu item to "Window". Patch by Al Sweigart.

Build

bpo-15506 [https://bugs.python.org/issue?@action=redirect&bpo=15506]: Use standard PKG_PROG_PKG_CONFIG autoconf macro in the configure script.

bpo-22935 [https://bugs.python.org/issue?@action=redirect&bpo=22935]: Allow the ssl module to be compiled if openssl doesn't support SSL 3.

bpo-22592 [https://bugs.python.org/issue?@action=redirect&bpo=22592]: Drop support of the Borland C compiler to build Python. The distutils module still supports it to build extensions.

bpo-22591 [https://bugs.python.org/issue?@action=redirect&bpo=22591]: Drop support of MS-DOS, especially of the DJGPP compiler (MS-DOS port of GCC).

bpo-16537 [https://bugs.python.org/issue?@action=redirect&bpo=16537]: Check whether self.extensions is empty in setup.py. Patch by Jonathan Hosmer.

bpo-22359 [https://bugs.python.org/issue?@action=redirect&bpo=22359]: Remove incorrect uses of recursive make. Patch by Jonas Wagner.

bpo-21958 [https://bugs.python.org/issue?@action=redirect&bpo=21958]: Define HAVE_ROUND when building with Visual Studio 2013 and above. Patch by Zachary Turner.

bpo-18093 [https://bugs.python.org/issue?@action=redirect&bpo=18093]: the programs that embed the CPython runtime are now in a separate "Programs" directory, rather than being kept in the Modules directory.

bpo-15759 [https://bugs.python.org/issue?@action=redirect&bpo=15759]: "make suspicious", "make linkcheck" and "make doctest" in Doc/ now display special message when and only when there are failures.

bpo-21141 [https://bugs.python.org/issue?@action=redirect&bpo=21141]: The Windows build process no longer attempts to find Perl, instead relying on OpenSSL source being configured and ready to build. The PCbuild\build_ssl.py script has been re-written and re-named to PCbuild\prepare_ssl.py, and takes care of configuring OpenSSL source for both 32 and 64 bit platforms. OpenSSL sources obtained from svn.python.org will always be pre-configured and ready to build.

bpo-21037 [https://bugs.python.org/issue?@action=redirect&bpo=21037]: Add a build option to enable AddressSanitizer support.

bpo-19962 [https://bugs.python.org/issue?@action=redirect&bpo=19962]: The Windows build process now creates "python.bat" in the root of the source tree, which passes all arguments through to the most recently built interpreter.

bpo-21285 [https://bugs.python.org/issue?@action=redirect&bpo=21285]: Refactor and fix curses configure check to always search in a ncursesw directory.

bpo-15234 [https://bugs.python.org/issue?@action=redirect&bpo=15234]: For BerkeleyDB and Sqlite, only add the found library and include directories if they aren't already being searched. This avoids an explicit runtime library dependency.

bpo-17861 [https://bugs.python.org/issue?@action=redirect&bpo=17861]: Tools/scripts/generate_opcode_h.py automatically regenerates Include/opcode.h from Lib/opcode.py if the latter gets any change.

bpo-20644 [https://bugs.python.org/issue?@action=redirect&bpo=20644]: OS X installer build support for documentation build changes in 3.4.1: assume externally supplied sphinx-build is available in /usr/bin.

bpo-20022 [https://bugs.python.org/issue?@action=redirect&bpo=20022]: Eliminate use of deprecated bundlebuilder in OS X builds.

bpo-15968 [https://bugs.python.org/issue?@action=redirect&bpo=15968]: Incorporated Tcl, Tk, and Tix builds into the Windows build solution.

bpo-17095 [https://bugs.python.org/issue?@action=redirect&bpo=17095]: Fix Modules/Setup shared support.

bpo-21811 [https://bugs.python.org/issue?@action=redirect&bpo=21811]: Anticipated fixes to support OS X versions > 10.9.

bpo-21166 [https://bugs.python.org/issue?@action=redirect&bpo=21166]: Prevent possible segfaults and other random failures of python --generate-posix-vars in pybuilddir.txt build target.

bpo-18096 [https://bugs.python.org/issue?@action=redirect&bpo=18096]: Fix library order returned by python-config.

bpo-17219 [https://bugs.python.org/issue?@action=redirect&bpo=17219]: Add library build dir for Python extension cross-builds.

bpo-22919 [https://bugs.python.org/issue?@action=redirect&bpo=22919]: Windows build updated to support VC 14.0 (Visual Studio 2015), which will be used for the official release.

bpo-21236 [https://bugs.python.org/issue?@action=redirect&bpo=21236]: Build _msi.pyd with cabinet.lib instead of fci.lib

bpo-17128 [https://bugs.python.org/issue?@action=redirect&bpo=17128]: Use private version of OpenSSL for OS X 10.5+ installer.

C API

bpo-14203 [https://bugs.python.org/issue?@action=redirect&bpo=14203]: Remove obsolete support for view==NULL in PyBuffer_FillInfo(), bytearray_getbuffer(), bytesiobuf_getbuffer() and array_buffer_getbuf(). All functions now raise BufferError in that case.

bpo-22445 [https://bugs.python.org/issue?@action=redirect&bpo=22445]: PyBuffer_IsContiguous() now implements precise contiguity tests, compatible with NumPy's NPY_RELAXED_STRIDES_CHECKING compilation flag. Previously the function reported false negatives for corner cases.

bpo-22079 [https://bugs.python.org/issue?@action=redirect&bpo=22079]: PyType_Ready() now checks that statically allocated type has no dynamically allocated bases.

bpo-22453 [https://bugs.python.org/issue?@action=redirect&bpo=22453]: Removed non-documented macro PyObject_REPR().

bpo-18395 [https://bugs.python.org/issue?@action=redirect&bpo=18395]: Rename _Py_char2wchar() to Py_DecodeLocale(), rename _Py_wchar2char() to Py_EncodeLocale(), and document these functions.

bpo-21233 [https://bugs.python.org/issue?@action=redirect&bpo=21233]: Add new C functions: PyMem_RawCalloc(), PyMem_Calloc(), PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) is now using calloc() instead of malloc() for large objects which is faster and use less memory.

bpo-20942 [https://bugs.python.org/issue?@action=redirect&bpo=20942]: PyImport_ImportFrozenModuleObject() no longer sets __file__ to match what importlib does; this affects _frozen_importlib as well as any module loaded using imp.init_frozen().

Documentation

bpo-19548 [https://bugs.python.org/issue?@action=redirect&bpo=19548]: Update the codecs module documentation to better cover the distinction between text encodings and other codecs, together with other clarifications. Patch by Martin Panter.

bpo-22394 [https://bugs.python.org/issue?@action=redirect&bpo=22394]: Doc/Makefile now supports make venv PYTHON=../python to create a venv for generating the documentation, e.g., make html PYTHON=venv/bin/python3.

bpo-21514 [https://bugs.python.org/issue?@action=redirect&bpo=21514]: The documentation of the json module now refers to new JSON RFC 7159 instead of obsoleted RFC 4627.

bpo-21777 [https://bugs.python.org/issue?@action=redirect&bpo=21777]: The binary sequence methods on bytes and bytearray are now documented explicitly, rather than assuming users will be able to derive the expected behaviour from the behaviour of the corresponding str methods.

bpo-6916 [https://bugs.python.org/issue?@action=redirect&bpo=6916]: undocument deprecated asynchat.fifo class.

bpo-17386 [https://bugs.python.org/issue?@action=redirect&bpo=17386]: Expanded functionality of the Doc/make.bat script to make it much more comparable to Doc/Makefile.

bpo-21312 [https://bugs.python.org/issue?@action=redirect&bpo=21312]: Update the thread_foobar.h template file to include newer threading APIs. Patch by Jack McCracken.

bpo-21043 [https://bugs.python.org/issue?@action=redirect&bpo=21043]: Remove the recommendation for specific CA organizations and to mention the ability to load the OS certificates.

bpo-20765 [https://bugs.python.org/issue?@action=redirect&bpo=20765]: Add missing documentation for PurePath.with_name() and PurePath.with_suffix().

bpo-19407 [https://bugs.python.org/issue?@action=redirect&bpo=19407]: New package installation and distribution guides based on the Python Packaging Authority tools. Existing guides have been retained as legacy links from the distutils docs, as they still contain some required reference material for tool developers that isn't recorded anywhere else.

bpo-19697 [https://bugs.python.org/issue?@action=redirect&bpo=19697]: Document cases where __main__.__spec__ is None.

Tests

bpo-18982 [https://bugs.python.org/issue?@action=redirect&bpo=18982]: Add tests for CLI of the calendar module.

bpo-19548 [https://bugs.python.org/issue?@action=redirect&bpo=19548]: Added some additional checks to test_codecs to ensure that statements in the updated documentation remain accurate. Patch by Martin Panter.

bpo-22838 [https://bugs.python.org/issue?@action=redirect&bpo=22838]: All test_re tests now work with unittest test discovery.

bpo-22173 [https://bugs.python.org/issue?@action=redirect&bpo=22173]: Update lib2to3 tests to use unittest test discovery.

bpo-16000 [https://bugs.python.org/issue?@action=redirect&bpo=16000]: Convert test_curses to use unittest.

bpo-21456 [https://bugs.python.org/issue?@action=redirect&bpo=21456]: Skip two tests in test_urllib2net.py if _ssl module not present. Patch by Remi Pointel.

bpo-20746 [https://bugs.python.org/issue?@action=redirect&bpo=20746]: Fix test_pdb to run in refleak mode (-R). Patch by Xavier de Gaye.

bpo-22060 [https://bugs.python.org/issue?@action=redirect&bpo=22060]: test_ctypes has been somewhat cleaned up and simplified; it now uses unittest test discovery to find its tests.

bpo-22104 [https://bugs.python.org/issue?@action=redirect&bpo=22104]: regrtest.py no longer holds a reference to the suite of tests loaded from test modules that don't define test_main().

bpo-22111 [https://bugs.python.org/issue?@action=redirect&bpo=22111]: Assorted cleanups in test_imaplib. Patch by Milan Oberkirch.

bpo-22002 [https://bugs.python.org/issue?@action=redirect&bpo=22002]: Added load_package_tests function to test.support and used it to implement/augment test discovery in test_asyncio, test_email, test_importlib, test_json, and test_tools.

bpo-21976 [https://bugs.python.org/issue?@action=redirect&bpo=21976]: Fix test_ssl to accept LibreSSL version strings. Thanks to William Orr.

bpo-21918 [https://bugs.python.org/issue?@action=redirect&bpo=21918]: Converted test_tools from a module to a package containing separate test files for each tested script.

bpo-9554 [https://bugs.python.org/issue?@action=redirect&bpo=9554]: Use modern unittest features in test_argparse. Initial patch by Denver Coneybeare and Radu Voicilas.

bpo-20155 [https://bugs.python.org/issue?@action=redirect&bpo=20155]: Changed HTTP method names in failing tests in test_httpservers so that packet filtering software (specifically Windows Base Filtering Engine) does not interfere with the transaction semantics expected by the tests.

bpo-19493 [https://bugs.python.org/issue?@action=redirect&bpo=19493]: Refactored the ctypes test package to skip tests explicitly rather than silently.

bpo-18492 [https://bugs.python.org/issue?@action=redirect&bpo=18492]: All resources are now allowed when tests are not run by regrtest.py.

bpo-21634 [https://bugs.python.org/issue?@action=redirect&bpo=21634]: Fix pystone micro-benchmark: use floor division instead of true division to benchmark integers instead of floating-point numbers. Set pystone version to 1.2. Patch written by Lennart Regebro.

bpo-21605 [https://bugs.python.org/issue?@action=redirect&bpo=21605]: Added tests for Tkinter images.

bpo-21493 [https://bugs.python.org/issue?@action=redirect&bpo=21493]: Added test for ntpath.expanduser(). Original patch by Claudiu Popa.

bpo-19925 [https://bugs.python.org/issue?@action=redirect&bpo=19925]: Added tests for the spwd module. Original patch by Vajrasky Kok.

bpo-21522 [https://bugs.python.org/issue?@action=redirect&bpo=21522]: Added Tkinter tests for Listbox.itemconfigure(), PanedWindow.paneconfigure(), and Menu.entryconfigure().

bpo-17756 [https://bugs.python.org/issue?@action=redirect&bpo=17756]: Fix test_code test when run from the installed location.

bpo-17752 [https://bugs.python.org/issue?@action=redirect&bpo=17752]: Fix distutils tests when run from the installed location.

bpo-18604 [https://bugs.python.org/issue?@action=redirect&bpo=18604]: Consolidated checks for GUI availability. All platforms now at least check whether Tk can be instantiated when the GUI resource is requested.

bpo-21275 [https://bugs.python.org/issue?@action=redirect&bpo=21275]: Fix a socket test on KFreeBSD.

bpo-21223 [https://bugs.python.org/issue?@action=redirect&bpo=21223]: Pass test_site/test_startup_imports when some of the extensions are built as builtins.

bpo-20635 [https://bugs.python.org/issue?@action=redirect&bpo=20635]: Added tests for Tk geometry managers.

Add test case for freeze.

bpo-20743 [https://bugs.python.org/issue?@action=redirect&bpo=20743]: Fix a reference leak in test_tcl.

bpo-21097 [https://bugs.python.org/issue?@action=redirect&bpo=21097]: Move test_namespace_pkgs into test_importlib.

bpo-21503 [https://bugs.python.org/issue?@action=redirect&bpo=21503]: Use test_both() consistently in test_importlib.

bpo-20939 [https://bugs.python.org/issue?@action=redirect&bpo=20939]: Avoid various network test failures due to new redirect of http://www.python.org/ to https://www.python.org: use http://www.example.com instead.

bpo-20668 [https://bugs.python.org/issue?@action=redirect&bpo=20668]: asyncio tests no longer rely on tests.txt file. (Patch by Vajrasky Kok)

bpo-21093 [https://bugs.python.org/issue?@action=redirect&bpo=21093]: Prevent failures of ctypes test_macholib on OS X if a copy of libz exists in $HOME/lib or /usr/local/lib.

bpo-22770 [https://bugs.python.org/issue?@action=redirect&bpo=22770]: Prevent some Tk segfaults on OS X when running gui tests.

bpo-23211 [https://bugs.python.org/issue?@action=redirect&bpo=23211]: Workaround test_logging failure on some OS X 10.6 systems.

bpo-23345 [https://bugs.python.org/issue?@action=redirect&bpo=23345]: Prevent test_ssl failures with large OpenSSL patch level values (like 0.9.8zc).

Tools/Demos

bpo-22314 [https://bugs.python.org/issue?@action=redirect&bpo=22314]: pydoc now works when the LINES environment variable is set.

bpo-22615 [https://bugs.python.org/issue?@action=redirect&bpo=22615]: Argument Clinic now supports the "type" argument for the int converter. This permits using the int converter with enums and typedefs.

bpo-20076 [https://bugs.python.org/issue?@action=redirect&bpo=20076]: The makelocalealias.py script no longer ignores UTF-8 mapping.

bpo-20079 [https://bugs.python.org/issue?@action=redirect&bpo=20079]: The makelocalealias.py script now can parse the SUPPORTED file from glibc sources and supports command line options for source paths.

bpo-22201 [https://bugs.python.org/issue?@action=redirect&bpo=22201]: Command-line interface of the zipfile module now correctly extracts ZIP files with directory entries. Patch by Ryan Wilson.

bpo-22120 [https://bugs.python.org/issue?@action=redirect&bpo=22120]: For functions using an unsigned integer return converter, Argument Clinic now generates a cast to that type for the comparison to -1 in the generated code. (This suppresses a compilation warning.)

bpo-18974 [https://bugs.python.org/issue?@action=redirect&bpo=18974]: Tools/scripts/diff.py now uses argparse instead of optparse.

bpo-21906 [https://bugs.python.org/issue?@action=redirect&bpo=21906]: Make Tools/scripts/md5sum.py work in Python 3. Patch by Zachary Ware.

bpo-21629 [https://bugs.python.org/issue?@action=redirect&bpo=21629]: Fix Argument Clinic's "--converters" feature.

Add support for yield from to 2to3.

Add support for the PEP 465 [https://peps.python.org/pep-0465/] matrix multiplication operator to 2to3.

bpo-16047 [https://bugs.python.org/issue?@action=redirect&bpo=16047]: Fix module exception list and __file__ handling in freeze. Patch by Meador Inge.

bpo-11824 [https://bugs.python.org/issue?@action=redirect&bpo=11824]: Consider ABI tags in freeze. Patch by Meador Inge.

bpo-20535 [https://bugs.python.org/issue?@action=redirect&bpo=20535]: PYTHONWARNING no longer affects the run_tests.py script. Patch by Arfrever Frehtes Taifersar Arahesis.

Windows

bpo-23260 [https://bugs.python.org/issue?@action=redirect&bpo=23260]: Update Windows installer

The bundled version of Tcl/Tk has been updated to 8.6.3. The most visible result of this change is the addition of new native file dialogs when running on Windows Vista or newer. See Tcl/Tk's TIP 432 for more information. Also, this version of Tcl/Tk includes support for Windows 10.

bpo-17896 [https://bugs.python.org/issue?@action=redirect&bpo=17896]: The Windows build scripts now expect external library sources to be in PCbuild\..\externals rather than PCbuild\..\...

bpo-17717 [https://bugs.python.org/issue?@action=redirect&bpo=17717]: The Windows build scripts now use a copy of NASM pulled from svn.python.org to build OpenSSL.

bpo-21907 [https://bugs.python.org/issue?@action=redirect&bpo=21907]: Improved the batch scripts provided for building Python.

bpo-22644 [https://bugs.python.org/issue?@action=redirect&bpo=22644]: The bundled version of OpenSSL has been updated to 1.0.1j.

bpo-10747 [https://bugs.python.org/issue?@action=redirect&bpo=10747]: Use versioned labels in the Windows start menu. Patch by Olive Kilburn.

bpo-22980 [https://bugs.python.org/issue?@action=redirect&bpo=22980]: .pyd files with a version and platform tag (for example, ".cp35-win32.pyd") will now be loaded in preference to those without tags.

(For information about older versions, consult the HISTORY file.)

Python 教學

小訣竅

這份教學是為了那些對 Python 語言有興趣的程式設計師而設計的，不是對於程式設計新手的入門教學。

Python 是一種易學、功能強大的程式語言。它有高效能的高階資料結構，也有簡單但有效的方法去實現物件導向程式設計。Python 優雅的語法和動態型別，結合其直譯特性，使它成為眾多領域和大多數平臺上，撰寫腳本和快速開發應用程式的理想語言。

使用者可以自由且免費地從 Python 官網上 (https://www.python.org/) 取得各大平台上用的 Python 直譯器和標準函式庫，下載其源碼或二進位形式執行檔，同時，也可以將其自由地散佈。另外，Python 官網也提供了許多自由且免費的第三方 Python 模組、程式與工具、以及額外說明文件，有興趣的使用者，可在官網上找到相關的發行版本與連結網址。

使用 C 或 C++（或其他可被 C 呼叫的程式語言），可以很容易在 Python 直譯器內新增功能函式及資料型別。同時，對可讓使用者自製功能的應用程式來說，Python 也適合作為其擴充用介面語言 (extension language)。

這份教學將非常規地介紹 Python 語言與系統的基本概念及功能。請注意，它預期你對程式設計有基本的了解。實際用 Python 直譯器進行實際操作將有助於學習，但所有範例都是獨立完整的，所以這份教學也可以離線閱讀。

若想了解 Python 標準物件和模組的描述，請參閱 Python 標準函式庫 (Standard Library)。在 Python 語言參考手冊 中，你可以學到 Python 語言更正規的定義。想用 C 或 C++ 寫延伸套件 (extensions) 的讀者，請閱讀 擴充和嵌入 Python 直譯器 和 Python/C API 參考手冊 。此外，市面上也能找到更深入的 Python 學習書。

這份教學中，我們不會介紹每一個功能，甚至，也不打算介紹完每一個常用功能。取而代之，我們的重心將放在介紹 Python 中最值得一提的那些功能，幫助你了解 Python 語言的特色與風格。讀完教學後，你將有能力閱讀和撰寫 Python 模組與程式，也做好進一步學習 Python 標準函式庫 (Standard Library) 中各類型的 Python 函式庫模組的準備。

術語表 頁面也值得細讀。

1. 淺嘗滋味

2. 使用 Python 直譯器

2.1. 啟動直譯器

2.1.1. 傳遞引數

2.1.2. 互動模式

2.2. 直譯器與它的環境

2.2.1. 原始碼的字元編碼 (encoding)

3. 一個非正式的 Python 簡介

3.1. 把 Python 當作計算機使用

3.1.1. 數字 (Number)

3.1.2. 文字

3.1.3. List（串列）

3.2. 初探程式設計的前幾步

4. 深入了解流程控制

4.1. if 陳述式

4.2. for 陳述式

4.3. range() 函式

4.4. break 和 continue 陳述式

4.5. 迴圈的 else 子句

4.6. pass 陳述式

4.7. match 陳述式

4.8. 定義函式 (function)

4.9. 深入了解函式定義

4.9.1. 預設引數值

4.9.2. 關鍵字引數

4.9.3. 特殊參數

4.9.3.1. 位置或關鍵字引數 (Positional-or-Keyword Arguments)

4.9.3.2. 僅限位置參數 (Positional-Only Parameters)

4.9.3.3. 僅限關鍵字引數 (Keyword-Only Arguments)

4.9.3.4. 函式範例

4.9.3.5. 回顧

4.9.4. 任意引數列表 (Arbitrary Argument Lists)

4.9.5. 拆解引數列表（Unpacking Argument Lists）

4.9.6. Lambda 運算式

4.9.7. 說明文件字串 (Documentation Strings)

4.9.8. 函式註釋 (Function Annotations)

4.10. 間奏曲：程式碼風格 (Coding Style)

5. 資料結構

5.1. 進一步了解 List（串列）

5.1.1. 將 List 作為 Stack（堆疊）使用

5.1.2. 將 List 作為 Queue（佇列）使用

5.1.3. List Comprehensions（串列綜合運算）

5.1.4. 巢狀的 List Comprehensions

5.2. del 陳述式

5.3. Tuples 和序列 (Sequences)

5.4. 集合 (Sets)

5.5. 字典（Dictionary）

5.6. 迴圈技巧

5.7. 深入了解條件 (Condition)

5.8. 序列和其他資料類型之比較

6. 模組 (Module)

6.1. 深入了解模組

6.1.1. 把模組當作腳本執行

6.1.2. 模組的搜尋路徑

6.1.3. 「編譯」Python 檔案

6.2. 標準模組

6.3. dir() 函式

6.4. 套件 (Package)

6.4.1. 從套件中 import *

6.4.2. 套件內引用

6.4.3. 多目錄中的套件

7. 輸入和輸出

7.1. 更華麗的輸出格式

7.1.1. 格式化的字串文本 (Formatted String Literals)

7.1.2. 字串的 format() method

7.1.3. 手動格式化字串

7.1.4. 格式化字串的舊方法

7.2. 讀寫檔案

7.2.1. 檔案物件的 method

7.2.2. 使用 json 儲存結構化資料

8. 錯誤和例外

8.1. 語法錯誤 (Syntax Error)

8.2. 例外 (Exception)

8.3. 處理例外

8.4. 引發例外

8.5. 例外鏈接 (Exception Chaining)

8.6. 使用者自定的例外

8.7. 定義清理動作

8.8. 預定義的清理動作

8.9. 引發及處理多個無關的例外

8.10. 用註解使例外更詳細

9. Class（類別）

9.1. 關於名稱與物件的一段話

9.2. Python 作用域 (Scope) 及命名空間 (Namespace)

9.2.1. 作用域和命名空間的範例

9.3. 初見 class

9.3.1. Class definition（類別定義）語法

9.3.2. Class 物件

9.3.3. 實例物件

9.3.4. Method 物件

9.3.5. Class 及實例變數

9.4. 隨意的備註

9.5. 繼承 (Inheritance)

9.5.1. 多重繼承

9.6. 私有變數

9.7. 補充說明

9.8. 疊代器 (Iterator)

9.9. 產生器 (Generator)

9.10. 產生器運算式

10. Python 標準函式庫概覽

10.1. 作業系統介面

10.2. 檔案之萬用字元 (File Wildcards)

10.3. 命令列引數

10.4. 錯誤輸出重新導向與程式終止

10.5. 字串樣式比對

10.6. 數學相關

10.7. 網路存取

10.8. 日期與時間

10.9. 資料壓縮

10.10. 效能量測

10.11. 品質控管

10.12. 標準模組庫

11. Python 標準函式庫概覽——第二部份

11.1. 輸出格式化 (Output Formatting)

11.2. 模板化 (Templating)

11.3. 二進制資料記錄編排 (Binary Data Record Layouts)

11.4. 多執行緒 (Multi-threading)

11.5. 日誌記錄 (Logging)

11.6. 弱引用 (Weak References)

11.7. 使用於 List 的工具

11.8. 十進制浮點數運算 (Decimal Floating-Point Arithmetic)

12. 虛擬環境與套件

12.1. 簡介

12.2. 建立虛擬環境

12.3. 用 pip 管理套件

13. 現在可以來學習些什麼？

14. 互動式輸入編輯和歷史記錄替換

14.1. Tab 鍵自動完成 (Tab Completion) 和歷史記錄編輯 (History Editing)

14.2. 互動式直譯器的替代方案

15. 浮點數運算：問題與限制

15.1. 表示法誤差 (Representation Error)

16. 附錄

16.1. 互動模式

16.1.1. 錯誤處理

16.1.2. 可執行的 Python 腳本

16.1.3. 互動式啟動檔案

16.1.4. 客製化模組

1. 淺嘗滋味

如果你經常在電腦上工作，最終總能發現有些工作你會想要自動化。舉例來說，你會想在很多文字檔案裡做相同的搜尋取代，或者是用個複雜的規則重新命名或整理一群照片。也有可能你想寫個自己的小資料庫，一個專門的 GUI 應用程式，或一個小遊戲。

如果你是一個職業軟體開發者，你可能要操作數個 C/C++/Java 程式庫，卻覺得平常寫程式碼、編譯、測試、再編譯的流程太慢；有可能你正為了一個程式庫撰寫一套測試集，但發現寫測試單調乏味；也有可能你正在開發一個能使用某一語言擴充的程式，但並不想要為了這程式特別設計一個全新的擴充語言。

在上述的例子中，Python 正是你合適的語言。

也許你可以為了某些任務而寫個 Unix shell 腳本或者 Windows 批次檔來處理，但 shell 腳本最適合於搬動檔案或更動文字內容，而不適於圖形應用程式或遊戲。你可以為此寫個 C/C++/Java 程式，但僅僅是完成個草稿也需要很長的開發時間。相較而言，Python 更易於使用，並能在 Windows、macOS、Unix 作業系統上執行，且能更快速地幫助你完成工作。

Python 即便易用也是個貨真價實的程式語言。它提供比 shell 腳本、批次檔更多樣的程式架構與更多的支援。另一方面，Python 提供比 C 更豐富的錯誤檢查。相較於 C，Python 作為一個「非常高階的程式語言」，它內建了高階的資料型別如彈性的陣列與字典。因為這些多用途的資料型別，Python 適用解決比 Awk（甚至是 Perl）能處理的更多問題上。至少在許多事情中，使用 Python 處理起來跟其他語言是同樣容易的。

Python 允許你把程式切割成許多模組 (module) 並將他們重複運用至其他 Python 程式中。Python 自帶了一個很大集合的標準模組，它們能做為你程式的基礎——或把它們當作一開始學寫 Python 程式的範例。有些模組提供了如檔案 I/O、系統呼叫、socket 的功能，甚至提供了 Tk 等圖形介面工具庫 (GUI toolkit) 的介面。

Python 是個直譯式語言，因為不需要編譯與連結，能為你在開發過程中省下可觀的時間。它的直譯器能互動地使用，因此能很方便地實驗每個語言的功能、寫些用完即丟的程式、幫助測試一些從細部開始開發的函式。它也是個好用的計算機。

Python 讓程式寫得精簡並易讀。用 Python 實作的程式長度往往遠比用 C、C++、Java 實作的短。這有以下幾個原因：

Python 高階的資料型別能在一陳述式 (statement) 中表達很複雜的操作；

陳述式的段落以縮排為區隔而非括號；

不需要宣告變數和引數。

Python 是可擴充的：如果你會寫 C 程式，那麼要加個新的內建函式或模組到直譯器中是很容易的。無論是為了用最快速的執行速度完成一些關鍵的操作，或是讓 Python 連結到一些僅以二進位形式 (binary form) 釋出的程式庫（例如特定供應商的繪圖程式庫）。如果你想更多這樣的結合，你其實也可以把 Python 直譯器連結到用 C 寫的應用程式，並在該應用程式中使用 Python 寫擴充或者作為下達指令的語言。

順帶一提，這個語言是以 BBC 的戲劇《Monty Python's Flying Circus》命名，與爬蟲類完全沒有關係。在說明文件中引用他們的喜劇不但沒問題，這甚至是個被鼓勵的行為！

如果你現在已經躍躍欲試，你會想了解 Python 更多細節，而學習語言的最好方式就是直接使用它。接下來這個教學就將帶領你，一邊閱讀，一邊將所學用在 Python 直譯器中玩耍。

在下個章節中，將會解說如何使用該直譯器。這也許只是個普通的資訊，但你必須試著操作接下來呈現的範例。

接下來的教學裡，將會透過許多範例介紹 Python 語言與其系統的諸多特色。一開始是簡單的運算式 (expression)、陳述式 (statement) 和資料型別 (data type)；接著是函式 (function) 與模組 (module)；最後會接觸一些較進階的主題如例外 (exception) 與使用者定義類別 (class)。

2. 使用 Python 直譯器

2.1. 啟動直譯器

在有安裝的機器上 Python 直譯器通常是被安裝在 /usr/local/bin/python3.14；把 /usr/local/bin 放在 Unix shell 的搜尋路徑中就可以透過輸入命令來啟動它：

python3.14

能啟動 Python [1]。因為直譯器存放的目錄是個安裝選項，其他的目錄也是有可能的；請洽談在地的 Python 達人或者系統管理員。（例如：/usr/local/python 是個很常見的另類存放路徑。）

Windows 系統中，從 Microsoft Store 安裝 Python 後，就可以使用 python3.14 命令了。如果安裝了 py.exe launcher ，則可以使用 py 命令。請參閱 Python 安裝管理員 了解其他啟動 Python 的方式。

在主提示字元輸入一個 end-of-file 字元（在 Unix 上為 Control-D；在 Windows 上為 Control-Z）會使得直譯器以零退出狀況 (zero exit status) 離開。如果上述的做法沒有效，也可以輸入 quit() 命令離開直譯器。

直譯器的命令列編輯功能有很多，在大多數系統上包含：互動編輯、歷史取代、命令補完等功能。最快檢查有無支援命令列編輯的方法為：在第一個 Python 提示字元後輸入 Control-P，如果出現嗶嗶聲，就代表有支援；見附錄互動式輸入編輯和歷史記錄替換介紹相關的快速鍵。如果什麼事都沒有發生，或者出現一個 ^P，就代表並沒有命令列編輯功能；此時只能使用 backspace 去除該行的字元。

這個直譯器使用起來像是 Unix shell：如果它被呼叫時連結至一個 tty 裝置，它會互動式地讀取並執行命令；如果被呼叫時給定檔名為引數或者使用 stdin 傳入檔案內容，它會將這個檔案視為腳本來閱讀。

另一個啟動直譯器的方式為 python -c command [arg] ...，它會執行在 command 裡的陳述式（們），行為如同 shell 的 -c 選項。因為 Python 的陳述式包含空白等 shell 用到的特殊字元，通常建議用引號把 command 包起來。

有些 Python 模組使用上如腳本般一樣方便。透過 python -m module [arg] ... 可以執行 module 模組的原始碼，就如同直接傳入那個模組的完整路徑一樣的行為。

當要執行一個腳本檔時，有時候會希望在腳本結束時進入互動模式。這可以透過在腳本前加入 -i 選項來達成。

所有命令列可用的選項都詳記在命令列與環境。

2.1.1. 傳遞引數

當直譯器收到腳本的名稱和額外的引數後，他們會轉換為由字串所組成的 list（串列）並指派給 sys 模組的 argv 變數。你可以執行 import sys 取得這個串列。這個串列的長度至少為一；當沒有給任何腳本名稱和引數時， sys.argv[0] 為空字串。當腳本名為 '-'（指標準輸入）時， sys.argv[0] 為 '-'。當使用 -c command 時， sys.argv[0] 為 '-c'。當使用 -m module 時， sys.argv[0] 為該模組存在的完整路徑。其餘非 -c command 或 -m module 的選項不會被 Python 直譯器吸收掉，而是留在 sys.argv 變數中給後續的 command 或 module 使用。

2.1.2. 互動模式

當命令從終端 (tty) 被讀取時，直譯器被稱為在互動模式（interactive mode）中。在這種模式中，會顯示主提示字元，提示輸入下一條命令，主提示字元通常用三個大於號（>>>）表示；輸入連續行時，顯示次要提示字元，預設是三個點（...）。進入直譯器時，首先顯示歡迎訊息、版本訊息、版權聲明，然後才是提示字元：

$ python3.14
Python 3.14 (default, April 4 2024, 09:25:04)
[GCC 10.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

接續多行的情況出現在需要多行才能建立完整指令時。舉例來說，像是 if 陳述式：

>>> the_world_is_flat = True
>>> if the_world_is_flat:
...     print("Be careful not to fall off!")
...
Be careful not to fall off!

更多有關互動模式的使用，請見互動模式。

2.2. 直譯器與它的環境

2.2.1. 原始碼的字元編碼 (encoding)

預設 Python 原始碼檔案的字元編碼使用 UTF-8。在這個編碼中，世界上多數語言的文字可以同時被使用在字串內容、識別名 (identifier) 及註解中 --- 雖然在標準函式庫中只使用 ASCII 字元作為識別名，這也是個任何 portable 程式碼需遵守的慣例。如果要正確地顯示所有字元，你的編輯器需要能夠認識檔案為 UTF-8，並且需要能顯示檔案中所有字元的字型。

如果不使用預設編碼，則要聲明檔案的編碼，檔案的第一行要寫成特殊註解。語法如下：

# -*- coding: encoding -*-

其中， encoding 可以是 Python 支援的任意一種 codecs。

比如，聲明使用 Windows-1252 編碼，原始碼檔案要寫成：

# -*- coding: cp1252 -*-

第一行的規則也有一種例外情況，在原始碼以 UNIX "shebang" line 行開頭時。此時，編碼聲明要寫在檔案的第二行。例如：

#!/usr/bin/env python3
# -*- coding: cp1252 -*-

註腳

[1]

在 Unix 中，Python 3.x 直譯器預設安裝不會以 python 作為執行檔名稱，以避免與現有的 Python 2.x 執行檔名稱衝突。

3. 一個非正式的 Python 簡介

在下面的例子中，輸入與輸出的區別在於有無提示字元（prompt，>>> 和 ...）：如果要重做範例，你必須在提示字元出現的時候，輸入提示字元後方的所有內容；那些非提示字元開始的文字行是直譯器的輸出。注意到在範例中，若出現單行只有次提示字元時，代表該行你必須直接換行；這被使用在多行指令結束輸入時。

你可以使用 "Copy" 按鈕（當游標移至程式碼範例上方或點選程式碼範例時，它會出現在右上角），這會去除提示字元並略過輸出，讓你可以複製貼上輸入行到你的直譯器。

在本手冊中的許多範例中，即便他們為互動式地輸入，仍然包含註解。Python 中的註解 (comments) 由 hash 字元 # 開始一直到該行結束。註解可以從該行之首、空白後、或程式碼之後開始，但不會出現在字串文本 (string literal) 之中。hash 字元在字串文本之中時仍視為一 hash 字元。因為註解只是用來說明程式而不會被 Python 解讀，在練習範例時不一定要輸入。

一些範例如下：

# 這是第一個註解
spam = 1  # 這是第二個註解
          # ... 現在是第三個！
text = "# 這不是註解，因為它在引號內。"

3.1. 把 Python 當作計算機使用

讓我們來試試一些簡單的 Python 指令。啟動直譯器並等待第一個主提示字元 >>> 出現。（應該不會等太久）

3.1.1. 數字 (Number)

直譯器如同一台簡單的計算機：你可以輸入一個 expression（運算式），它會寫出該式的值。Expression 的語法可以使用：運算子 +、-、* 和 / 可以用來執行運算；括號 () 可以用來分群。例如：

>>> 2 + 2
4
>>> 50 - 5*6
20
>>> (50 - 5*6) / 4
5.0
>>> 8 / 5  # 除法總是回傳浮點數
1.6

整數數字（即 2、4、20）為 int 型別，數字有小數點部份的（即 5.0、1.6）為 float 型別。我們將在之後的教學中看到更多數字相關的型別。

除法 (/) 永遠回傳一個 float。如果要做 floor division 並拿到整數的結果，你可以使用 // 運算子；計算餘數可以使用 %：

>>> 17 / 3  # 傳統除法回傳浮點數
5.666666666666667
>>>
>>> 17 // 3  # 下取整除法捨棄小數部分
5
>>> 17 % 3  # % 運算子回傳除法的餘數
2
>>> 5 * 3 + 2  # 下取整商 * 除數 + 餘數
17

在 Python 中，計算冪次 (powers) 可以使用 ** 運算子 [1]：

>>> 5 ** 2  # 5 的平方
25
>>> 2 ** 7  # 2 的 7 次方
128

等於符號 (=) 可以用於為變數賦值。賦值完之後，在下個指示字元前並不會顯示任何結果：

>>> width = 20
>>> height = 5 * 9
>>> width * height
900

如果一個變數未被「定義 (defined)」（即變數未被賦值），試著使用它時會出現一個錯誤：

>>> n  # 嘗試存取未定義的變數
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'n' is not defined

浮點數的運算有完善的支援，運算子 (operator) 遇上混合的運算元 (operand) 時會把整數的運算元轉換為浮點數：

>>> 4 * 3.75 - 1
14.0

在互動式模式中，最後一個印出的運算式的結果會被指派至變數 _ 中。這表示當你把 Python 當作桌上計算機使用者，要接續計算變得容易許多：

>>> tax = 12.5 / 100
>>> price = 100.50
>>> price * tax
12.5625
>>> price + _
113.0625
>>> round(_, 2)
113.06

這個變數應該被使用者視為只能讀取。不應該明確地為它賦值 --- 你可以創一個獨立但名稱相同的本地變數來覆蓋掉預設變數和它的神奇行為。

除了 int 和 float，Python 還支援了其他的數字型別，包含 Decimal 和 Fraction。Python 亦內建支援複數 (complex numbers)，並使用 j 和 J 後綴來指定虛數的部份（即 3+5j）。

3.1.2. 文字

Python 可以操作文本（由 str 型別表示，即所謂的「字串 (strings)」）和數字。這包括字元 "!"、單詞 "rabbit"、名稱 "Paris"、句子 "Got your back." 等等。"Yay! :)"。它們可以用單引號 ('...') 或雙引號 ("...") 括起來，會具有相同的結果 [2]。

>>> 'spam eggs'  # 單引號
'spam eggs'
>>> "Paris rabbit got your back :)! Yay!"  # 雙引號
'Paris rabbit got your back :)! Yay!'
>>> '1975'  # 以引號包含的數字和數值也是字串
'1975'

要引用引文，我們需要在其前面加上 \ 來「跳脫」它。或者我們也可以使用其他種類的引號：

>>> 'doesn\'t'  # 用 \' 來跳脫單引號...
"doesn't"
>>> "doesn't"  # ...或改用雙引號
"doesn't"
>>> '"Yes," they said.'
'"Yes," they said.'
>>> "\"Yes,\" they said."
'"Yes," they said.'
>>> '"Isn\'t," they said.'
'"Isn\'t," they said.'

在 Python shell 中，字串定義和輸出字串可能看起來不同。print() 函式透過省略引號並印出跳脫字元和特殊字元來生成更具可讀性的輸出：

>>> s = 'First line.\nSecond line.'  # \n 表示換行
>>> s  # 沒有 print()，特殊字元會包含在字串中
'First line.\nSecond line.'
>>> print(s)  # 有 print()，特殊字元會被直譯，所以 \n 會產生新的一行
First line.
Second line.

如果你不希望字元前出現 \ 就被當成特殊字元時，可以改使用 raw string，在第一個包圍引號前加上 r ：

>>> print('C:\some\name')  # 這裡 \n 表示換行！
C:\some
ame
>>> print(r'C:\some\name')  # 注意引號前的 r
C:\some\name

原始字串有一個微妙的地方：原始字串可能不會以奇數個 \ 字元結尾；請參閱常見問答集來了解更多資訊和解決方法。

字串文本可以跨越數行。其中一方式是使用三個重複引號："""...""" 或 '''...'''。此時換行字元會被自動加入字串值中，但也可以在換行前加入 \ 來取消這個行為。在以下的例子中，最初的換行符不會被包含：

>>> print("""\
... Usage: thingy [OPTIONS]
...      -h                        Display this usage message
...      -H hostname               Hostname to connect to
... """)
Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to

>>>

字串可以使用 + 運算子連接 (concatenate)，並用 * 重複該字串的內容：

>>> # 3 次 'un'，接著是 'ium'
>>> 3 * 'un' + 'ium'
'unununium'

兩個以上相鄰的字串文本（string literal，即被引號包圍的字串）會被自動連接起來：

>>> 'Py' 'thon'
'Python'

當你想要分段一個非常長的字串時，兩相鄰字串值自動連接的特性十分有用：

>>> text = ('Put several strings within parentheses '
...         'to have them joined together.')
>>> text
'Put several strings within parentheses to have them joined together.'

但這特性只限於兩相鄰的字串值間，而非兩相鄰變數或運算式：

>>> prefix = 'Py'
>>> prefix 'thon'  # 無法串接變數和字串字面值
  File "<stdin>", line 1
    prefix 'thon'
           ^^^^^^
SyntaxError: invalid syntax
>>> ('un' * 3) 'ium'
  File "<stdin>", line 1
    ('un' * 3) 'ium'
               ^^^^^
SyntaxError: invalid syntax

如果要連接變數們或一個變數與一個字串值，使用 +：

>>> prefix + 'thon'
'Python'

字串可以被「索引 indexed」(下標，即 subscripted)，第一個字元的索引值為 0。沒有獨立表示字元的型別；一個字元就是一個大小為 1 的字串：

>>> word = 'Python'
>>> word[0]  # 位置 0 的字元
'P'
>>> word[5]  # 位置 5 的字元
'n'

索引值可以是負的，此時改成從右開始計數：

>>> word[-1]  # 最後一個字元
'n'
>>> word[-2]  # 倒數第二個字元
'o'
>>> word[-6]
'P'

注意到因為 -0 等同於 0，負的索引值由 -1 開始。

除了索引外，字串亦支援「切片 slicing」。索引用來拿到單獨的字元，而切片則可以讓你拿到一個子字串 (substring)：

>>> word[0:2]  # 從位置 0 (包含) 到 2 (不包含) 的字元
'Py'
>>> word[2:5]  # 從位置 2 (包含) 到 5 (不包含) 的字元
'tho'

切片索引 (slice indices) 有很常用的預設值，省略起點索引值時預設為 0，而省略第二個索引值時預設整個字串被包含在 slice 中：

>>> word[:2]   # 從開頭到位置 2 (不包含) 的字元
'Py'
>>> word[4:]   # 從位置 4 (包含) 到結尾的字元
'on'
>>> word[-2:]  # 從倒數第二個 (包含) 到結尾的字元
'on'

注意到起點永遠被包含，而結尾永遠不被包含。這確保了 s[:i] + s[i:] 永遠等於 s：

>>> word[:2] + word[2:]
'Python'
>>> word[:4] + word[4:]
'Python'

這裡有個簡單記住 slice 是如何運作的方式。想像 slice 的索引值指著字元們之間，其中第一個字元的左側邊緣由 0 計數。則 n 個字元的字串中最後一個字元的右側邊緣會有索引值 n，例如：

 +---+---+---+---+---+---+
 | P | y | t | h | o | n |
 +---+---+---+---+---+---+
 0   1   2   3   4   5   6
-6  -5  -4  -3  -2  -1

第一行數字給定字串索引值為 0...6 的位置；第二行則標示了負索引值的位置。由 i 至 j 的 slice 包含了標示 i 和 j 邊緣間的所有字元。

對非負數的索引值而言，一個 slice 的長度等於其索引值之差，如果索引值落在字串邊界內。例如，word[1:3] 的長度是 2。

嘗試使用一個過大的索引值會造成錯誤：

>>> word[42]  # 這只有六個字母
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range

然而，超出範圍的索引值在 slice 中會被妥善的處理：

>>> word[4:42]
'on'
>>> word[42:]
''

Python 字串無法被改變 --- 它們是 immutable。因此，嘗試對字串中某個索引位置賦值會產生錯誤：

>>> word[0] = 'J'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment
>>> word[2:] = 'py'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment

如果你需要一個不一樣的字串，你必須建立一個新的：

>>> 'J' + word[1:]
'Jython'
>>> word[:2] + 'py'
'Pypy'

內建的函式 len() 回傳一個字串的長度：

>>> s = 'supercalifragilisticexpialidocious'
>>> len(s)
34

也參考

Text Sequence Type --- str

字串是 sequence 型別的範例之一，並支援該型別常用的操作。

字串方法

字串支援非常多種基本轉換和搜尋的 method（方法）。

f-string（f 字串）

包含有運算式的字串文本。

格式化文字語法

關於透過 str.format() 字串格式化 (string formatting) 的資訊。

printf-style String Formatting

在字串為 % 運算子的左運算元時，將觸發舊的字串格式化操作，更多的細節在本連結中介紹。

3.1.3. List（串列）

Python 理解數種複合型資料型別，用來組合不同的數值。當中最多樣變化的型別為 list，可以寫成一系列以逗號分隔的數值（稱之元素，即 item），包含在方括號之中。List 可以包合不同型別的元素，但通常這些元素會有相同的型別：

>>> squares = [1, 4, 9, 16, 25]
>>> squares
[1, 4, 9, 16, 25]

如同字串（以及其他內建的 sequence 型別），list 可以被索引和切片 (slice)：

>>> squares[0]  # 索引回傳項目
1
>>> squares[-1]
25
>>> squares[-3:]  # 切片回傳新串列
[9, 16, 25]

List 對支援如接合 (concatenation) 等操作：

>>> squares + [36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

不同於字串是 immutable，list 是 mutable 型別，即改變 list 的內容是可能的：

>>> cubes = [1, 8, 27, 65, 125]  # 這裡有問題
>>> 4 ** 3  # 4 的立方是 64，不是 65！
64
>>> cubes[3] = 64  # 替換錯誤的值
>>> cubes
[1, 8, 27, 64, 125]

你也可以在 list 的最後加入新元素，透過使用 list.append() 方法（我們稍後會看到更多方法的說明）：

>>> cubes.append(216)  # 加入 6 的立方
>>> cubes.append(7 ** 3)  # 以及 7 的立方
>>> cubes
[1, 8, 27, 64, 125, 216, 343]

Python 中的簡單賦值永遠不會複製資料。當你將 list 指派給變數時，該變數會參照現有 list。任何透過一個變數對 list 所做的更改都將能夠透過參照該變數的所有其他變數看到。

>>> rgb = ["Red", "Green", "Blue"]
>>> rgba = rgb
>>> id(rgb) == id(rgba)  # 它們參照到同一物件
True
>>> rgba.append("Alph")
>>> rgb
["Red", "Green", "Blue", "Alph"]

所有切片操作都會回傳一個新的 list ，包含要求的元素。這意謂著以下這個切片回傳了原本 list 的淺複製：

>>> correct_rgba = rgba[:]
>>> correct_rgba[-1] = "Alpha"
>>> correct_rgba
["Red", "Green", "Blue", "Alpha"]
>>> rgba
["Red", "Green", "Blue", "Alph"]

也可以對 slice 賦值，這能改變 list 的大小，甚至是清空一個 list：

>>> letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> letters
['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> # replace some values
>>> letters[2:5] = ['C', 'D', 'E']
>>> letters
['a', 'b', 'C', 'D', 'E', 'f', 'g']
>>> # now remove them
>>> letters[2:5] = []
>>> letters
['a', 'b', 'f', 'g']
>>> # 透過將所有元素替換為空串列的方式來清空串列
>>> letters[:] = []
>>> letters
[]

內建的函式 len() 亦可以作用在 list 上：

>>> letters = ['a', 'b', 'c', 'd']
>>> len(letters)
4

也可以嵌套多層 list （建立 list 包含其他 list），例如：

>>> a = ['a', 'b', 'c']
>>> n = [1, 2, 3]
>>> x = [a, n]
>>> x
[['a', 'b', 'c'], [1, 2, 3]]
>>> x[0]
['a', 'b', 'c']
>>> x[0][1]
'b'

3.2. 初探程式設計的前幾步

當然，我們可以用 Python 來處理比 2 加 2 更複雜的工作。例如，我們可以印出費氏數列 [https://zh.wikipedia.org/zh-tw/%E6%96%90%E6%B3%A2%E9%82%A3%E5%A5%91%E6%95%B0%E5%88%97]的首幾項序列：

>>> # 費波那契數列
>>> # 以兩個元素的和來決定下一個元素
>>> a, b = 0, 1
>>> while a < 10:
...     print(a)
...     a, b = b, a+b
...
0
1
1
2
3
5
8

這例子引入了許多新的特性。

第一行出現了多重賦值：變數 a 與 b 同時得到了新的值 0 與 1。在最後一行同樣的賦值再被使用了一次，示範了等號的右項運算 (expression) 會先被計算 (evaluate)，賦值再發生。右項的運算式由左至右依序被計算。

while 迴圈只要它的條件為真（此範例：a < 10），將會一直重複執行。在 Python 中如同 C 語言，任何非零的整數值為真 (true)；零為假 (false)。條件可以是字串、list、甚至是任何序列型別；任何非零長度的序列為真，空的序列即為假。本例子使用的條件是個簡單的比較。標準的比較運算子 (comparison operators) 使用如同 C 語言一樣的符號：<（小於）、>（大於）、==（等於）、<=（小於等於）、>=（大於等於）以及 !=（不等於）。

迴圈的主體會縮排：縮排在 Python 中用來關連一群陳述式。在互動式提示字元中，你必須在迴圈內的每一行一開始鍵入 tab 或者（數個）空白來維持縮排。實務上，你會先在文字編輯器中準備好比較複雜的輸入；多數編輯器都有自動縮排的功能。當一個複合陳述式以互動地方式輸入，必須在結束時多加一行空行來代表結束（因為語法剖析器無法判斷你何時輸入複合陳述的最後一行）。注意在一個縮排段落內的縮排方式與數量必須維持一致。

print() 函式印出它接收到引數（們）的值。不同於先前僅我們寫下想要的運算（像是先前的計算機範例），它可以處理複數個引數、浮點數數值和字串。印出的字串將不帶有引號，並且不同項目間會插入一個空白，因此可以讓你容易格式化輸出，例如：

>>> i = 256*256
>>> print('The value of i is', i)
The value of i is 65536

關鍵字引數 end 可以被用來避免額外的換行符加入到輸出中，或者以不同的字串結束輸出：

>>> a, b = 0, 1
>>> while a < 1000:
...     print(a, end=',')
...     a, b = b, a+b
...
0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,

註解

[1]

因為 ** 擁有較 - 高的優先次序，-3**2 會被解釋為 -(3**2) 並得到 -9。如果要避免這樣的優先順序以得到 9，你可以使用 (-3)**2。

[2]

不像其他語言，特殊符號如 \n 在單 ('...') 和雙 ("...") 引號中有相同的意思。兩種引號的唯一差別，在於使用單引號時，不需要跳脫 "（但必須跳脫 \'），反之亦同。

4. 深入了解流程控制

除了剛才介紹的 while，這章節還會介紹一些 Python 的陳述式語法。

4.1. if 陳述式

或許最常見的陳述式種類就是 if 了。舉例來說：

>>> x = int(input("Please enter an integer: "))
Please enter an integer: 42
>>> if x < 0:
...     x = 0
...     print('Negative changed to zero')
... elif x == 0:
...     print('Zero')
... elif x == 1:
...     print('Single')
... else:
...     print('More')
...
More

在陳述式中，可以沒有或有許多個 elif 敘述，且 else 敘述並不是必要的。關鍵字 elif 是「else if」的縮寫，用來避免過多的縮排。一個 if ... elif ... elif ... 序列可以用來替代其他程式語言中的 switch 或 case 陳述式。

如果你要將同一個值與多個常數進行比較，或者檢查特定的型別或屬性，你可能會發現 match 陳述式也很有用。更多的細節，請參閱 match 陳述式。

4.2. for 陳述式

在 Python 中的 for 陳述式有點不同於在 C 或 Pascal 中的慣用方式。相較於只能疊代 (iterate) 一個等差數列（如 Pascal），或給予使用者定義疊代步驟與終止條件（如 C），Python 的 for 陳述式疊代任何序列（list 或者字串）的元素，順序與它們出現在序列中的順序相同。例如（無意雙關）：

>>> # 測量一些字串：
>>> words = ['cat', 'window', 'defenestrate']
>>> for w in words:
...     print(w, len(w))
...
cat 3
window 6
defenestrate 12

在疊代一個集合的同時修改該集合的內容，很難取得想要的結果。比較直觀的替代方式，是疊代該集合的副本，或建立一個新的集合：

# 建立一個範例集合
users = {'Hans': 'active', 'Éléonore': 'inactive', '景太郎': 'active'}

# 策略：對副本進行疊代
for user, status in users.copy().items():
    if status == 'inactive':
        del users[user]

# 策略：建立一個新集合
active_users = {}
for user, status in users.items():
    if status == 'active':
        active_users[user] = status

4.3. range() 函式

如果你需要疊代一個數列的話，使用內建 range() 函式就很方便。它可以生成一等差數列：

>>> for i in range(5):
...     print(i)
...
0
1
2
3
4

給定的結束值永遠不會出現在生成的序列中；range(10) 生成的 10 個數值，即對應存取一個長度為 10 的序列內每一個項目的索引值。也可以讓 range 從其他數值開始計數，或者給定不同的公差（甚至為負；有時稱之為 step）：

>>> list(range(5, 10))
[5, 6, 7, 8, 9]

>>> list(range(0, 10, 3))
[0, 3, 6, 9]

>>> list(range(-10, -100, -30))
[-10, -40, -70]

欲疊代一個序列的索引值，你可以搭配使用 range() 和 len() 如下：

>>> a = ['Mary', 'had', 'a', 'little', 'lamb']
>>> for i in range(len(a)):
...     print(i, a[i])
...
0 Mary
1 had
2 a
3 little
4 lamb

然而，在多數的情況，使用 enumerate() 函式將更為方便，詳見迴圈技巧。

如果直接印出一個 range 則會出現奇怪的輸出：

>>> range(10)
range(0, 10)

在很多情況下，由 range() 回傳的物件表現得像是一個 list（串列）一樣，但實際上它並不是。它是一個在疊代時能夠回傳所要求的序列中所有項目的物件，但它不會真正建出這個序列的 list，以節省空間。

我們稱這樣的物件為 iterable（可疊代物件），意即能作為函式及架構中可以一直取得項目直到取盡的對象。我們已經了解 for 陳述式就是如此的架構，另一個使用 iterable 的函式範例是 sum()：

>>> sum(range(4))  # 0 + 1 + 2 + 3
6

待會我們可以看到更多回傳 iterable 和使用 iterable 為引數的函式。在資料結構章節中，我們會討論更多關於 list() 的細節。

4.4. break 和 continue 陳述式

break 陳述式，終止包含它的最內部 for 或 while 迴圈：

>>> for n in range(2, 10):
...     for x in range(2, n):
...         if n % x == 0:
...             print(f"{n} equals {x} * {n//x}")
...             break
...
4 equals 2 * 2
6 equals 2 * 3
8 equals 2 * 4
9 equals 3 * 3

continue 陳述式讓所屬的迴圈繼續執行下個疊代：

>>> for num in range(2, 10):
...     if num % 2 == 0:
...         print(f"Found an even number {num}")
...         continue
...     print(f"Found an odd number {num}")
...
Found an even number 2
Found an odd number 3
Found an even number 4
Found an odd number 5
Found an even number 6
Found an odd number 7
Found an even number 8
Found an odd number 9

4.5. 迴圈的 else 子句

在 for 或 while 迴圈中，break 陳述句可能與 else 子句配對。如果迴圈完成而沒有執行 break，else 子句會被執行。

在 for 迴圈中，else 子句會在迴圈完成最終的疊代後執行。

在 while 迴圈中，它會在迴圈條件變為 false 後執行。

在任何一種迴圈中，如果迴圈由 break 終止，則不會執行 else 子句。當然其他提早結束迴圈的方式（例如 return 或引發例外）也會跳過 else 子句的執行。

下面的 for 迴圈對此進行了舉例說明，該迴圈用以搜尋質數：

>>> for n in range(2, 10):
...     for x in range(2, n):
...         if n % x == 0:
...             print(n, 'equals', x, '*', n//x)
...             break
...     else:
...         # 迴圈結束但沒有找到因數
...         print(n, 'is a prime number')
...
2 is a prime number
3 is a prime number
4 equals 2 * 2
5 is a prime number
6 equals 2 * 3
7 is a prime number
8 equals 2 * 4
9 equals 3 * 3

（沒錯，這是正確的程式碼。請看仔細：else 子句屬於 for 迴圈，並非 if 陳述式。）

理解 else 子句的一個方法是將它想像成與迴圈內的 if 配對。當迴圈執行時，它會運行如 if/if/if/else 的序列。if 在迴圈內，會遇到多次。如果條件曾經為真，break 就會發生。如果條件從未為真，迴圈外的 else 子句就會執行。

當 else 子句用於迴圈時，相較於搭配 if 陳述式使用，它的行為與 try 陳述式中的 else 子句更為相似：try 陳述式的 else 子句在沒有發生例外 (exception) 時執行，而迴圈的 else 子句在沒有任何 break 發生時執行。更多有關 try 陳述式和例外的介紹，見處理例外。

4.6. pass 陳述式

pass 陳述式不執行任何動作。它可用在語法上需要一個陳述式但程式不需要執行任何動作的時候。例如：

>>> while True:
...     pass  # 忙碌等待鍵盤中斷 (Ctrl+C)
...

這經常用於建立簡單的 class（類別）：

>>> class MyEmptyClass:
...     pass
...

pass 亦可作為一個函式或條件判斷主體的預留位置，在你撰寫新的程式碼時讓你保持在更抽象的思維層次。pass 會直接被忽略：

>>> def initlog(*args):
...     pass   # 記得要實作這個！
...

在最後這個例子中，許多人會使用刪節號字面值 ... 來取代 pass。這種用法對 Python 並沒有特殊的意義，且並非語言定義的一部分（你也可以在這裡使用任何常數運算式），但 ... 也慣例上被用作預留主體 (placeholder body)。見 Ellipsis 物件。

4.7. match 陳述式

match 陳述式會拿取一個運算式，並將其值與多個連續的模式 (pattern) 進行比較，這些模式是以一個或多個 case 區塊來表示。表面上，這類似 C、Java 或 JavaScript（以及許多其他語言）中的 switch 陳述式，但它與 Rust 或 Haskell 等語言中的模式匹配 (pattern matching) 更為相近。只有第一個匹配成功的模式會被執行，而它也可以將成分（序列元素或物件屬性）從值中提取到變數中。如果沒有任何的 case 匹配成功，則不會執行任何的分支。

最簡單的形式，是將一個主題值 (subject value) 與一個或多個字面值 (literal) 進行比較：

def http_error(status):
    match status:
        case 400:
            return "Bad request"
        case 404:
            return "Not found"
        case 418:
            return "I'm a teapot"
        case _:
            return "Something's wrong with the internet"

請注意最後一段：「變數名稱」_ 是作為通用字元 (wildcard)的角色，且永遠不會匹配失敗。

你可以使用 |（「或」）來將多個字面值組合在單一模式中：

case 401 | 403 | 404:
    return "Not allowed"

模式可以看起來像是拆解賦值 (unpacking assignment)，且可以用來連結變數：

# point 是一個 (x, y) 元組
match point:
    case (0, 0):
        print("Origin")
    case (0, y):
        print(f"Y={y}")
    case (x, 0):
        print(f"X={x}")
    case (x, y):
        print(f"X={x}, Y={y}")
    case _:
        raise ValueError("Not a point")

請仔細研究那個例子！第一個模式有兩個字面值，可以想作是之前所述的字面值模式的延伸。但是接下來的兩個模式結合了一個字面值和一個變數，且該變數繫結 (bind) 了來自主題 (point) 的一個值。第四個模式會擷取兩個值，這使得它在概念上類似於拆解賦值 (x, y) = point。

如果你要用 class 來結構化你的資料，你可以使用該 class 的名稱加上一個引數列表，類似一個建構式 (constructor)，但它能夠將屬性擷取到變數中：

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

def where_is(point):
    match point:
        case Point(x=0, y=0):
            print("Origin")
        case Point(x=0, y=y):
            print(f"Y={y}")
        case Point(x=x, y=0):
            print(f"X={x}")
        case Point():
            print("Somewhere else")
        case _:
            print("Not a point")

你可以將位置參數 (positional parameter) 與一些能夠排序其屬性的內建 class（例如 dataclasses）一起使用。你也可以透過在 class 中設定特殊屬性 __match_args__，來定義模式中屬性們的特定位置。如果它被設定為 ("x", "y")，則以下的模式都是等價的（且都會將屬性 y 連結到變數 var）：

Point(1, var)
Point(1, y=var)
Point(x=1, y=var)
Point(y=var, x=1)

理解模式的一種推薦方法，是將它們看作是你會放在賦值 (assignment) 左側內容的一種延伸形式，這樣就可以了解哪些變數會被設為何值。只有獨立的名稱（像是上面的 var）能被 match 陳述式賦值。點分隔名稱（如 foo.bar）、屬性名稱（上面的 x= 及 y=）或 class 名稱（由它們後面的 "(...)" 被辨識，如上面的 Point）則永遠無法被賦值。

模式可以任意地被巢套 (nested)。例如，如果我們有一個由某些點所組成的簡短 list，我們就可以像這樣加入 __match_args__ 來對它進行匹配：

class Point:
    __match_args__ = ('x', 'y')
    def __init__(self, x, y):
        self.x = x
        self.y = y

match points:
    case []:
        print("No points")
    case [Point(0, 0)]:
        print("The origin")
    case [Point(x, y)]:
        print(f"Single point {x}, {y}")
    case [Point(0, y1), Point(0, y2)]:
        print(f"Two on the Y axis at {y1}, {y2}")
    case _:
        print("Something else")

我們可以在模式中加入一個 if 子句，稱為「防護 (guard)」。如果該防護為假，則 match 會繼續嘗試下一個 case 區塊。請注意，值的擷取會發生在防護的評估之前：

match point:
    case Point(x, y) if x == y:
        print(f"Y=X at {x}")
    case Point(x, y):
        print(f"Not on the diagonal")

此種陳述式的其他幾個重要特色：

與拆解賦值的情況類似，tuple（元組）和 list 模式具有完全相同的意義，而且實際上可以匹配任意的序列。一個重要的例外，是它們不能匹配疊代器 (iterator) 或字串。

序列模式 (sequence pattern) 可支援擴充拆解 (extended unpacking)：[x, y, *rest] 與 (x, y, *rest) 的作用類似於拆解賦值。* 後面的名稱也可以是 _，所以 (x, y, *_) 會匹配一個至少兩項的序列，且不會連結那兩項以外的其餘項。

對映模式 (mapping pattern)：{"bandwidth": b, "latency": l} 能從一個 dictionary（字典）中擷取 "bandwidth" 及 "latency" 的值。與序列模式不同，額外的鍵 (key) 會被忽略。一種像是 **rest 的拆解方式，也是可被支援的。（但 **_ 則是多餘的做法，所以它並不被允許。）

使用關鍵字 as 可以擷取子模式 (subpattern)：

case (Point(x1, y1), Point(x2, y2) as p2): ...

將會擷取輸入的第二個元素作為 p2（只要該輸入是一個由兩個點所組成的序列）。

大部分的字面值是藉由相等性 (equality) 來比較，但是單例物件 (singleton) True、False 和 None 是藉由標識值 (identity) 來比較。

模式可以使用附名常數 (named constant)。這些模式必須是點分隔名稱，以免它們被解釋為擷取變數：

from enum import Enum
class Color(Enum):
    RED = 'red'
    GREEN = 'green'
    BLUE = 'blue'

color = Color(input("Enter your choice of 'red', 'blue' or 'green': "))

match color:
    case Color.RED:
        print("I see red!")
    case Color.GREEN:
        print("Grass is green")
    case Color.BLUE:
        print("I'm feeling the blues :(")

關於更詳細的解釋和其他範例，你可以閱讀 PEP 636 [https://peps.python.org/pep-0636/]，它是以教學的格式編寫而成。

4.8. 定義函式 (function)

我們可以建立一個函式來產生費式數列到任何一個上界：

>>> def fib(n):    # 寫出小於 n 的費氏數列
...     """印出小於 n 的費氏數列。"""
...     a, b = 0, 1
...     while a < n:
...         print(a, end=' ')
...         a, b = b, a+b
...     print()
...
>>> # 現在呼叫我們剛才定義的函式：
>>> fib(2000)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597

關鍵字 def 介紹一個函式的定義。它之後必須連著該函式的名稱和置於括號之中的一串參數。自下一行起，所有縮排的陳述式成為該函式的主體。

一個函式的第一個陳述式可以是一個字串文本；該字串文本被視為該函式的說明文件字串，即 docstring。（關於 docstring 的細節請參見說明文件字串 (Documentation Strings)段落。）有些工具可以使用 docstring 來自動產生線上或可列印的文件，或讓使用者能以互動的方式在原始碼中瀏覽文件。在原始碼中加入 docstring 是個好慣例，應該養成這樣的習慣。

函式執行時會建立一個新的符號表 (symbol table) 來儲存該函式內的區域變數 (local variable)。更精確地說，所有在函式內的變數賦值都會把該值儲存在一個區域符號表。然而，在引用一個變數時，會先從區域符號表開始搜尋，其次為外層函式的區域符號表，其次為全域符號表 (global symbol table)，最後為所有內建的名稱。因此，在函式中，全域變數及外層函式變數雖然可以被引用，但無法被直接賦值（除非全域變數是在 global 陳述式中被定義，或外層函式變數在 nonlocal 陳述式中被定義）。

在一個函式被呼叫的時候，實際傳入的參數（引數）會被加入至該函式的區域符號表。因此，引數傳入的方式為傳值呼叫 (call by value)（這裡傳遞的值永遠是一個物件的參照 (reference)，而不是該物件的值）。 [1] 當一個函式呼叫別的函式或遞迴呼叫它自己時，在被呼叫的函式中會建立一個新的區域符號表。

函式定義時，會把該函式名稱加入至目前的符號表。函式名稱的值帶有一個型別，並被直譯器辨識為使用者自定函式 (user-defined function)。該值可以被指定給別的變數名，使該變數名也可以被當作函式使用。這是常見的重新命名方式：

>>> fib
<function fib at 10042ed0>
>>> f = fib
>>> f(100)
0 1 1 2 3 5 8 13 21 34 55 89

如果你是來自別的語言，你可能不同意 fib 是個函式，而是個程序 (procedure)，因為它並沒有回傳值。實際上，即使一個函式缺少一個 return 陳述式，它亦有一個固定的回傳值。這個值稱為 None（它是一個內建名稱）。在直譯器中單獨使用 None 時，通常不會被顯示。你可以使用 print() 來看到它：

>>> fib(0)
>>> print(fib(0))
None

如果要寫一個函式回傳費式數列的 list 而不是直接印出它，這也很容易：

>>> def fib2(n):  # 回傳到 n 為止的費氏數列
...     """回傳包含到 n 為止的費氏數列的串列。"""
...     result = []
...     a, b = 0, 1
...     while a < n:
...         result.append(a)    # 見下方
...         a, b = b, a+b
...     return result
...
>>> f100 = fib2(100)    # 呼叫它
>>> f100                # 寫出結果
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]

這個例子一樣示範了一些新的 Python 特性：

return 陳述式會讓一個函式回傳一個值。單獨使用 return 不外加一個運算式作為引數時會回傳 None。一個函式執行到結束也會回傳 None。

result.append(a) 陳述式呼叫了一個 list 物件 result 的 method（方法）。method 為「屬於」一個物件的函式，命名規則為 obj.methodname，其中 obj 為某個物件（亦可為一運算式），而 methodname 為該 method 的名稱，並由該物件的型別所定義。不同的型別定義不同的 method。不同型別的 method 可以擁有一樣的名稱而不會讓 Python 混淆。（你可以使用 class（類別）定義自己的物件型別和 method，見 Class（類別））範例中的 append() method 定義在 list 物件中；它會在該 list 的末端加入一個新的元素。這個例子等同於 result = result + [a]，但更有效率。

4.9. 深入了解函式定義

定義函式時使用的引數 (argument) 數量是可變的。總共有三種可以組合使用的形式。

4.9.1. 預設引數值

為一個或多個引數指定預設值是很有用的方式。函式建立後，可以用比定義時更少的引數呼叫該函式。例如：

def ask_ok(prompt, retries=4, reminder='Please try again!'):
    while True:
        reply = input(prompt)
        if reply in {'y', 'ye', 'yes'}:
            return True
        if reply in {'n', 'no', 'nop', 'nope'}:
            return False
        retries = retries - 1
        if retries < 0:
            raise ValueError('invalid user response')
        print(reminder)

該函式可以用以下幾種方式被呼叫：

只給必要引數：ask_ok('Do you really want to quit?')

給予一個選擇性引數：ask_ok('OK to overwrite the file?', 2)

給予所有引數：ask_ok('OK to overwrite the file?', 2, 'Come on, only yes or no!')

此例也使用了關鍵字 in，用於測試序列中是否包含某個特定值。

預設值是在函式定義當下，於定義時的作用域中求值，所以：

i = 5

def f(arg=i):
    print(arg)

i = 6
f()

將會輸出 5。

重要警告：預設值只求值一次。當預設值為可變物件，例如 list、dictionary（字典）或許多類別實例時，會產生不同的結果。例如，以下函式於後續呼叫時會累積曾經傳遞的引數：

def f(a, L=[]):
    L.append(a)
    return L

print(f(1))
print(f(2))
print(f(3))

將會輸出：

[1]
[1, 2]
[1, 2, 3]

如果不想在後續呼叫之間共用預設值，應以如下方式編寫函式：

def f(a, L=None):
    if L is None:
        L = []
    L.append(a)
    return L

4.9.2. 關鍵字引數

函式也可以使用關鍵字引數，以 kwarg=value 的形式呼叫。舉例來說，以下函式：

def parrot(voltage, state='a stiff', action='voom', type='Norwegian Blue'):
    print("-- This parrot wouldn't", action, end=' ')
    print("if you put", voltage, "volts through it.")
    print("-- Lovely plumage, the", type)
    print("-- It's", state, "!")

接受一個必要引數 (voltage) 和三個選擇性引數 (state，action，和 type)。該函式可用下列任一方式呼叫：

parrot(1000)                                          # 1 個位置引數
parrot(voltage=1000)                                  # 1 個關鍵字引數
parrot(voltage=1000000, action='VOOOOOM')             # 2 個關鍵字引數
parrot(action='VOOOOOM', voltage=1000000)             # 2 個關鍵字引數
parrot('a million', 'bereft of life', 'jump')         # 3 個位置引數
parrot('a thousand', state='pushing up the daisies')  # 1 個位置引數、1 個關鍵字引數

但以下呼叫方式都無效：

parrot()                     # 缺少必要引數
parrot(voltage=5.0, 'dead')  # 關鍵字引數後面的非關鍵字引數
parrot(110, voltage=220)     # 同一個引數有重複值
parrot(actor='John Cleese')  # 未知的關鍵字引數

函式呼叫時，關鍵字引數 (keyword argument) 必須在位置引數 (positional argument) 後面。所有傳遞的關鍵字引數都必須匹配一個可被函式接受的引數（actor 不是 parrot 函式的有效引數），而關鍵字引數的順序並不重要。此規則也包括必要引數，（parrot(voltage=1000) 也有效）。一個引數不可多次被賦值，下面就是一個因此限制而無效的例子：

>>> def function(a):
...     pass
...
>>> function(0, a=0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: function() got multiple values for argument 'a'

當最後一個參數為 **name 形式時，它接收一個 dictionary（字典，詳見 Mapping Types --- dict），該字典包含所有可對應形式參數以外的關鍵字引數。**name 可以與 *name 參數（下一小節介紹）組合使用，*name 接收一個 tuple，該 tuple 包含一般參數以外的位置引數（*name 必須出現在 **name 前面）。例如，若我們定義這樣的函式：

def cheeseshop(kind, *arguments, **keywords):
    print("-- Do you have any", kind, "?")
    print("-- I'm sorry, we're all out of", kind)
    for arg in arguments:
        print(arg)
    print("-" * 40)
    for kw in keywords:
        print(kw, ":", keywords[kw])

它可以被如此呼叫：

cheeseshop("Limburger", "It's very runny, sir.",
           "It's really very, VERY runny, sir.",
           shopkeeper="Michael Palin",
           client="John Cleese",
           sketch="Cheese Shop Sketch")

輸出結果如下：

-- Do you have any Limburger ?
-- I'm sorry, we're all out of Limburger
It's very runny, sir.
It's really very, VERY runny, sir.
----------------------------------------
shopkeeper : Michael Palin
client : John Cleese
sketch : Cheese Shop Sketch

注意，關鍵字引數的輸出順序與呼叫函式時被提供的順序必定一致。

4.9.3. 特殊參數

在預設情況，引數能以位置或明確地以關鍵字傳遞给 Python 函式。為了程式的可讀性及效能，限制引數的傳遞方式是合理的，如此，開發者只需查看函式定義，即可確定各項目是按位置，按位置或關鍵字，還是按關鍵字傳遞。

函式定義可能如以下樣式：

def f(pos1, pos2, /, pos_or_kwd, *, kwd1, kwd2):
      -----------    ----------     ----------
        |             |                  |
        |        Positional or keyword   |
        |                                - Keyword only
         -- Positional only

/ 和 * 是選擇性的。這些符號若被使用，是表明引數被傳遞給函式的參數種類：僅限位置、位置或關鍵字、僅限關鍵字。關鍵字參數也稱為附名參數 (named parameters)。

4.9.3.1. 位置或關鍵字引數 (Positional-or-Keyword Arguments)

若函式定義中未使用 / 和 * 時，引數可以按位置或關鍵字傳遞給函式。

4.9.3.2. 僅限位置參數 (Positional-Only Parameters)

此處再詳述一些細節，特定參數可以標記為僅限位置。若參數為僅限位置時，它們的順序很重要，且這些參數不能用關鍵字傳遞。僅限位置參數必須放在 /（斜線）之前。/ 用於在邏輯上分開僅限位置參數與其餘參數。如果函式定義中沒有 /，則表示沒有任何僅限位置參數。

/ 後面的參數可以是位置或關鍵字或僅限關鍵字參數。

4.9.3.3. 僅限關鍵字引數 (Keyword-Only Arguments)

要把參數標記為僅限關鍵字，表明參數必須以關鍵字引數傳遞，必須在引數列表中第一個僅限關鍵字參數前放上 *。

4.9.3.4. 函式範例

請看以下的函式定義範例，注意 / 和 * 記號：

>>> def standard_arg(arg):
...     print(arg)
...
>>> def pos_only_arg(arg, /):
...     print(arg)
...
>>> def kwd_only_arg(*, arg):
...     print(arg)
...
>>> def combined_example(pos_only, /, standard, *, kwd_only):
...     print(pos_only, standard, kwd_only)

第一個函式定義 standard_arg 是我們最熟悉的形式，對呼叫方式沒有任何限制，可以按位置或關鍵字傳遞引數：

>>> standard_arg(2)
2

>>> standard_arg(arg=2)
2

第二個函式 pos_only_arg 的函式定義中有 /，因此僅限使用位置參數：

>>> pos_only_arg(1)
1

>>> pos_only_arg(arg=1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: pos_only_arg() got some positional-only arguments passed as keyword arguments: 'arg'

第三個函式 kwd_only_arg 的函式定義透過 * 表明僅限關鍵字引數：

>>> kwd_only_arg(3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: kwd_only_arg() takes 0 positional arguments but 1 was given

>>> kwd_only_arg(arg=3)
3

最後一個函式在同一個函式定義中，使用了全部三種呼叫方式：

>>> combined_example(1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: combined_example() takes 2 positional arguments but 3 were given

>>> combined_example(1, 2, kwd_only=3)
1 2 3

>>> combined_example(1, standard=2, kwd_only=3)
1 2 3

>>> combined_example(pos_only=1, standard=2, kwd_only=3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: combined_example() got some positional-only arguments passed as keyword arguments: 'pos_only'

最後，請看這個函式定義，如果 **kwds 內有 name 這個鍵，可能與位置引數 name 產生潛在衝突：

def foo(name, **kwds):
    return 'name' in kwds

呼叫該函式不可能回傳 True，因為關鍵字 'name' 永遠是連結在第一個參數。例如：

>>> foo(1, **{'name': 2})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() got multiple values for argument 'name'
>>>

使用 /（僅限位置引數）後，就可以了。函式定義會允許 name 當作位置引數，而 'name' 也可以當作關鍵字引數中的鍵：

>>> def foo(name, /, **kwds):
...     return 'name' in kwds
...
>>> foo(1, **{'name': 2})
True

換句話說，僅限位置參數的名稱可以在 **kwds 中使用，而不產生歧義。

4.9.3.5. 回顧

此用例決定哪些參數可以用於函式定義：

def f(pos1, pos2, /, pos_or_kwd, *, kwd1, kwd2):

說明：

如果不想讓使用者使用參數名稱，請使用僅限位置。當參數名稱沒有實際意義時，若你想控制引數在函式呼叫的排列順序，或同時使用位置參數和任意關鍵字時，這種方式很有用。

當參數名稱有意義，且明確的名稱可讓函式定義更易理解，或是你不希望使用者依賴引數被傳遞時的位置時，請使用僅限關鍵字。

對於應用程式介面 (API)，使用僅限位置，以防止未來參數名稱被修改時造成 API 的中斷性變更。

4.9.4. 任意引數列表 (Arbitrary Argument Lists)

最後，有個較不常用的選項，是規定函式被呼叫時，可以使用任意數量的引數。這些引數會被包裝進一個 tuple 中（詳見 Tuples 和序列 (Sequences)）。在可變數量的引數之前，可能有零個或多個普通引數：

def write_multiple_items(file, separator, *args):
    file.write(separator.join(args))

通常，這些 variadic（可變的）引數會出現在參數列表的最末端，這樣它們就可以把所有傳遞給函式的剩餘輸入引數都撈起來。出現在 *args 參數後面的任何參數必須是「僅限關鍵字」引數，意即它們只能作為關鍵字引數，而不能用作位置引數。

>>> def concat(*args, sep="/"):
...     return sep.join(args)
...
>>> concat("earth", "mars", "venus")
'earth/mars/venus'
>>> concat("earth", "mars", "venus", sep=".")
'earth.mars.venus'

4.9.5. 拆解引數列表（Unpacking Argument Lists）

當引數們已經存在一個 list 或 tuple 裡，但為了滿足一個需要個別位置引數的函式呼叫，而去拆解它們時，情況就剛好相反。例如，內建的 range() 函式要求分開的 start 和 stop 引數。如果這些引數不是分開的，則要在呼叫函式時，用 * 運算子把引數們從 list 或 tuple 中拆解出來：

>>> list(range(3, 6))            # 使用分離引數的一般呼叫
[3, 4, 5]
>>> args = [3, 6]
>>> list(range(*args))            # 以從串列解包而得的引數呼叫
[3, 4, 5]

同樣地，dictionary（字典）可以用 ** 運算子傳遞關鍵字引數：

>>> def parrot(voltage, state='a stiff', action='voom'):
...     print("-- This parrot wouldn't", action, end=' ')
...     print("if you put", voltage, "volts through it.", end=' ')
...     print("E's", state, "!")
...
>>> d = {"voltage": "four million", "state": "bleedin' demised", "action": "VOOM"}
>>> parrot(**d)
-- This parrot wouldn't VOOM if you put four million volts through it. E's bleedin' demised !

4.9.6. Lambda 運算式

lambda 關鍵字用於建立小巧的匿名函式。lambda a, b: a+b 函式回傳兩個引數的和。Lambda 函式可用於任何需要函式物件的地方。在語法上，它們被限定只能是單一運算式。在語義上，它就是一個普通函式定義的語法糖 (syntactic sugar)。與巢狀函式定義一樣，lambda 函式可以從包含它的作用域中引用變數：

>>> def make_incrementor(n):
...     return lambda x: x + n
...
>>> f = make_incrementor(42)
>>> f(0)
42
>>> f(1)
43

上面的例子用 lambda 運算式回傳了一個函式。另外的用法是傳遞一個小函式當作引數。舉例來說，list.sort() 接受一個鍵排序函式 key，這個函式可以是 lambda 函式：

>>> pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
>>> pairs.sort(key=lambda pair: pair[1])
>>> pairs
[(4, 'four'), (1, 'one'), (3, 'three'), (2, 'two')]

4.9.7. 說明文件字串 (Documentation Strings)

以下是關於說明文件字串內容和格式的慣例。

第一行都是一段關於此物件目的之簡短摘要。為保持簡潔，不應在這裡明確地陳述物件的名稱或型別，因為有其他方法可以達到相同目的（除非該名稱剛好是一個描述函式運算的動詞）。這一行應以大寫字母開頭，以句號結尾。

文件字串為多行時，第二行應為空白行，在視覺上將摘要與其餘描述分開。後面幾行可包含一或多個段落，描述此物件的呼叫慣例、副作用等。

當多行字串字面值作為模組、類別或函式的說明字串時，Python 剖析器會去除其縮排。

下面是多行說明字串的一個範例：

>>> def my_function():
...     """不做任何事，但有文件說明。
...
...     它真的什麼都不做：
...     """
...     pass
...
>>> print(my_function.__doc__)
不做任何事，但有文件說明。

它真的什麼都不做：

    >>> my_function()
    >>>

4.9.8. 函式註釋 (Function Annotations)

函式註釋是選擇性的元資料（metadata）資訊，描述使用者定義函式所使用的型別（更多資訊詳見 PEP 3107 [https://peps.python.org/pep-3107/] 和 PEP 484 [https://peps.python.org/pep-0484/]）。

註釋以 dictionary（字典）的形式存放在函式的 __annotations__ 屬性中，且不會影響函式的任何其他部分。參數註釋的定義方式是在參數名稱後加一個冒號，冒號後面跟著一個對註釋求值的運算式。回傳註釋的定義方式是在參數列表和 def 陳述式結尾的冒號中間，用一個 -> 文字接著一個運算式。以下範例註釋了一個必要引數、一個選擇性引數，以及回傳值：

>>> def f(ham: str, eggs: str = 'eggs') -> str:
...     print("Annotations:", f.__annotations__)
...     print("Arguments:", ham, eggs)
...     return ham + ' and ' + eggs
...
>>> f('spam')
Annotations: {'ham': <class 'str'>, 'return': <class 'str'>, 'eggs': <class 'str'>}
Arguments: spam eggs
'spam and eggs'

4.10. 間奏曲：程式碼風格 (Coding Style)

現在你即將要寫更長、更複雜的 Python 程式，是時候討論一下編碼樣式了。大多數語言都能以不同的樣式被書寫（或更精確地說，被格式化），而有些樣式比其他的更具可讀性。能讓其他人輕鬆閱讀你的程式碼永遠是一個好主意，而使用優良的編碼樣式對此有極大的幫助。

對於 Python，大多數的專案都遵循 PEP 8 [https://peps.python.org/pep-0008/] 的樣式指南；它推行的編碼樣式相當可讀且賞心悅目。每個 Python 開發者都應該花點時間研讀；這裡是該指南的核心重點：

用 4 個空格縮排，不要用 tab 鍵。

4 個空格是小縮排（容許更大的巢套深度）和大縮排（較易閱讀）之間的折衷方案。Tab 鍵會造成混亂，最好別用。

換行，使一行不超過 79 個字元。

換行能讓使用小顯示器的使用者方便閱讀，也可以在較大顯示器上並排陳列多個程式碼檔案。

用空行分隔函式和 class（類別），及函式內較大塊的程式碼。

如果可以，把註解放在單獨一行。

使用說明字串。

運算子前後、逗號後要加空格，但不要直接放在括號內側：a = f(1, 2) + g(3, 4)。

Class 和函式的命名樣式要一致；按慣例，命名 class 用 UpperCamelCase（駝峰式大小寫），命名函式與 method 用 lowercase_with_underscores（小寫加底線）。永遠用 self 作為 method 第一個引數的名稱（關於 class 和 method，詳見 初見 class）。

若程式碼是為了用於國際環境時，不要用花俏的編碼。Python 預設的 UTF-8 或甚至普通的 ASCII，就可以勝任各種情況。

同樣地，若不同語言使用者閱讀或維護程式碼的可能性微乎其微，就不要在命名時使用非 ASCII 字元。

註解

[1]

實際上，傳址呼叫 (call by object reference) 的說法可能較為貼切。因為，若傳遞的是一個可變物件時，呼叫者將看得見被呼叫者對物件做出的任何改變（例如被插入 list 內的新項目）。

5. 資料結構

這個章節將會更深入的介紹一些你已經學過的東西的細節上，並且加入一些你還沒有接觸過的部分。

5.1. 進一步了解 List（串列）

List（串列）這個資料型別具有更多方法。下面條列了 list 物件的所有 method：

list.append(x)

將一個新的項目加到 list 的尾端。與 a[len(a):] = [x] 類似。

list.extend(iterable)

將 iterable（可疊代物件）接到 list 的尾端。與 a[len(a):] = iterable 類似。

list.insert(i, x)

將一個項目插入至 list 中給定的位置。第一個引數為插入處前元素的索引值，所以 a.insert(0, x) 會插入在 list 首位，而 a.insert(len(a), x) 則相當於 a.append(x)。

list.remove(x)

刪除 list 中第一個值等於 x 的元素。若 list 中無此元素則會觸發 ValueError。

list.pop([i])

移除 list 中給定位置的項目，並回傳它。如果沒有指定位置， a.pop() 將會移除 list 中最後的項目並回傳它。若 list 是空的或是索引值超出範圍，則會引發 IndexError 例外。

list.clear()

刪除 list 中所有項目。與 del a[:] 類似。

list.index(x[, start[, end]])

回傳 list 中第一個出現 x 的（從零開始的）索引值。若 list 中無此項目，則丟出 ValueError 錯誤。

引數 start 和 end 的定義跟在 slice 表示法中相同，搜尋的動作被這兩個引數限定在 list 中特定的子序列。但要注意的是，回傳的索引值是從 list 的開頭開始算，而不是從 start 開始算。

list.count(x)

回傳 x 在 list 中所出現的次數。

list.sort(*, key=None, reverse=False)

將 list 中的項目排序。（可使用引數來進行客製化的排序，請參考 sorted() 部分的解釋）

list.reverse()

將 list 中的項目前後順序反過來。

list.copy()

回傳一個淺複製 (shallow copy) 的 list。與 a[:] 類似。

以下是一個使用到許多 list 物件方法的例子：

>>> fruits = ['orange', 'apple', 'pear', 'banana', 'kiwi', 'apple', 'banana']
>>> fruits.count('apple')
2
>>> fruits.count('tangerine')
0
>>> fruits.index('banana')
3
>>> fruits.index('banana', 4)  # 從位置 4 開始找到下一個 banana
6
>>> fruits.reverse()
>>> fruits
['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange']
>>> fruits.append('grape')
>>> fruits
['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange', 'grape']
>>> fruits.sort()
>>> fruits
['apple', 'apple', 'banana', 'banana', 'grape', 'kiwi', 'orange', 'pear']
>>> fruits.pop()
'pear'

你可能會注意到一些方法，像是 insert、remove 或者是 sort，並沒有印出回傳值，事實上，他們回傳預設值 None [1]。這是一個用於 Python 中所有可變資料結構的設計法則。

另外你可能也會發現，不是所有資料都可以被排序或比較。例如，[None, 'hello', 10] 就不可排序，因為整數不能與字串比較，而 None 不能與其他型別比較。有些型別根本就沒有被定義彼此之間的大小順序，例如，3+4j < 5+7j 就是一個無效的比較。

5.1.1. 將 List 作為 Stack（堆疊）使用

List 的操作方法使得它非常簡單可以用來實作 stack（堆疊）。Stack 為一個遵守最後加入元素最先被取回（後進先出，"last-in, first-out"）規則的資料結構。你可以使用方法 append() 將一個項目放到堆疊的頂層。而使用方法 pop() 且不給定索引值去取得堆疊最上面的項目。舉例而言：

>>> stack = [3, 4, 5]
>>> stack.append(6)
>>> stack.append(7)
>>> stack
[3, 4, 5, 6, 7]
>>> stack.pop()
7
>>> stack
[3, 4, 5, 6]
>>> stack.pop()
6
>>> stack.pop()
5
>>> stack
[3, 4]

5.1.2. 將 List 作為 Queue（佇列）使用

我們也可以將 list 當作 queue（佇列）使用，即最先加入元素最先被取回（先進先出，"first-in, first-out"）的資料結構。然而，list 在這種使用方式下效率較差。使用 append 和 pop 來加入和取出尾端的元素較快，而使用 insert 和 pop 來插入和取出頭端的元素較慢（因為其他元素都需要挪動一格）。

如果要實作 queue，請使用 collections.deque，其被設計成能快速的從頭尾兩端加入和取出。例如：

>>> from collections import deque
>>> queue = deque(["Eric", "John", "Michael"])
>>> queue.append("Terry")           # Terry 加進來
>>> queue.append("Graham")          # Graham 加進來
>>> queue.popleft()                 # 第一個加進來的現在離開
'Eric'
>>> queue.popleft()                 # 第二個加進來的現在離開
'John'
>>> queue                           # queue 裡剩下的會按照加進來的順序排列
deque(['Michael', 'Terry', 'Graham'])

5.1.3. List Comprehensions（串列綜合運算）

List comprehension（串列綜合運算）讓你可以用簡潔的方法建立 list。常見的應用是基於一個序列或 iterable（可疊代物件），將每一個元素經過某個運算的結果串接起來成為新的 list，或是建立一個子序列，其每一個元素皆滿足一個特定的條件。

舉例來說，假設我們要建立一個「平方的 list」：

>>> squares = []
>>> for x in range(10):
...     squares.append(x**2)
...
>>> squares
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

注意這是建立（或覆寫）一個變數叫 x，其在迴圈結束後仍然存在。我們可以這樣產生平方串列而不造成任何 side effects（副作用）：

squares = list(map(lambda x: x**2, range(10)))

或與此相等的：

squares = [x**2 for x in range(10)]

這樣更簡潔和易讀。

一個 list comprehension 的組成，是在一對方括號內，放入一個 expression（運算式）、一個 for 子句、再接著零個或多個 for 或 if 子句。結果會是一個新的 list，內容是在後面的 for 和 if 子句情境下，對前面運算式求值的結果。例如，這個 list comprehension 組合了兩個 list 中彼此相異的元素：

>>> [(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]

而它就等於：

>>> combs = []
>>> for x in [1,2,3]:
...     for y in [3,1,4]:
...         if x != y:
...             combs.append((x, y))
...
>>> combs
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]

注意 for 和 if 在這兩段程式裡的順序是相同的。

如果 expression 是一個 tuple（例如上面例子中的 (x, y)），它必須加上括號：

>>> vec = [-4, -2, 0, 2, 4]
>>> # 建立一個值加倍的新串列
>>> [x*2 for x in vec]
[-8, -4, 0, 4, 8]
>>> # 過濾串列以排除負數
>>> [x for x in vec if x >= 0]
[0, 2, 4]
>>> # 對所有元素套用函式
>>> [abs(x) for x in vec]
[4, 2, 0, 2, 4]
>>> # 對每個元素呼叫方法
>>> freshfruit = ['  banana', '  loganberry ', 'passion fruit  ']
>>> [weapon.strip() for weapon in freshfruit]
['banana', 'loganberry', 'passion fruit']
>>> # 建立像 (數字, 平方) 的 2-元組串列
>>> [(x, x**2) for x in range(6)]
[(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]
>>> # 元組必須加上括號，否則會產生錯誤
>>> [x, x**2 for x in range(6)]
  File "<stdin>", line 1
    [x, x**2 for x in range(6)]
     ^^^^^^^
SyntaxError: did you forget parentheses around the comprehension target?
>>> # flatten a list using a listcomp with two 'for'
>>> vec = [[1,2,3], [4,5,6], [7,8,9]]
>>> [num for elem in vec for num in elem]
[1, 2, 3, 4, 5, 6, 7, 8, 9]

List comprehensions 可以含有複雜的 expression 和巢狀的函式：

>>> from math import pi
>>> [str(round(pi, i)) for i in range(1, 6)]
['3.1', '3.14', '3.142', '3.1416', '3.14159']

5.1.4. 巢狀的 List Comprehensions

在 list comprehesion 中開頭的 expression 可以是任何形式的 expression，包括再寫一個 list comprehension。

考慮以下表示 3x4 矩陣的範例，使用 list 包含 3 個長度為 4 的 list ：

>>> matrix = [
...     [1, 2, 3, 4],
...     [5, 6, 7, 8],
...     [9, 10, 11, 12],
... ]

以下的 list comprehesion 會將矩陣的行與列作轉置：

>>> [[row[i] for row in matrix] for i in range(4)]
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]

如同我們在上一節看到的，內部的 list comprehension 會依據後面的 for 環境被求值，所以這個例子就等於：

>>> transposed = []
>>> for i in range(4):
...     transposed.append([row[i] for row in matrix])
...
>>> transposed
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]

而它也和這一段相同：

>>> transposed = []
>>> for i in range(4):
...     # 下面這三行實作了巢狀的 listcomp
...     transposed_row = []
...     for row in matrix:
...         transposed_row.append(row[i])
...     transposed.append(transposed_row)
...
>>> transposed
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]

在實際運用上，我們傾向於使用內建函式 (built-in functions) 而不是複雜的流程控制陳述式。在這個例子中，使用 zip() 函式會非常有效率：

>>> list(zip(*matrix))
[(1, 5, 9), (2, 6, 10), (3, 7, 11), (4, 8, 12)]

關於星號的更多細節，請參考拆解引數列表（Unpacking Argument Lists）。

5.2. del 陳述式

有一個方法可以藉由索引而不是值來刪除 list 中的項目：del 陳述式。這和 pop() method 傳回一個值不同，del 陳述式可以用來刪除 list 中的片段或者清空整個 list（我們之前藉由指派一個空的 list 給想刪除的片段來完成這件事）。例如：

>>> a = [-1, 1, 66.25, 333, 333, 1234.5]
>>> del a[0]
>>> a
[1, 66.25, 333, 333, 1234.5]
>>> del a[2:4]
>>> a
[1, 66.25, 1234.5]
>>> del a[:]
>>> a
[]

del 也可以用來刪除整個變數：

>>> del a

刪除之後，對 a 的參照將會造成錯誤（至少在另一個值又被指派到它之前）。我們將在後面看到更多關於 del 的其他用法。

5.3. Tuples 和序列 (Sequences)

我們看到 list 和字串 (string) 有許多共同的特性，像是索引操作 (indexing) 以及切片操作 (slicing) 。他們是序列資料類型中的兩個例子（請參考Sequence Types --- list, tuple, range）。由於 Python 是個持續發展中的語言，未來可能還會有其他的序列資料類型加入。接著要介紹是下一個標準序列資料類型：tuple。

一個 tuple 是由若干個值藉由逗號區隔而組成，例如：

>>> t = 12345, 54321, 'hello!'
>>> t[0]
12345
>>> t
(12345, 54321, 'hello!')
>>> # Tuple 可以為巢狀的：
>>> u = t, (1, 2, 3, 4, 5)
>>> u
((12345, 54321, 'hello!'), (1, 2, 3, 4, 5))
>>> # Tuple 為不可變的：
>>> t[0] = 88888
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> # but they can contain mutable objects:
>>> v = ([1, 2, 3], [3, 2, 1])
>>> v
([1, 2, 3], [3, 2, 1])

如同我們看到的，被輸出的 tuple 總是以括號包著，如此巢狀的 tuple 才能被正確的直譯 (interpret)；他們可以是以被括號包著或不被包著的方式當作輸入，雖然括號的使用常常是有其必要的（譬如此 tuple 是一個較大的運算式的一部分）。指派東西給 tuple 中的個別項目是不行的，但是可以建立含有可變物件（譬如 list）的 tuple。

雖然 tuple 和 list 看起來很類似，但是他們通常用在不同的情況與不同目的。 tuple 是 immutable（不可變的），通常儲存異質的元素序列，並可經由拆解 (unpacking)（請參考本節後段）或索引 (indexing) 來存取（或者在使用 namedtuples 的時候藉由屬性 (attribute) 來存取）。List 是 mutable（可變的），其元素通常是同質的且可藉由疊代整個 list 來存取。

一個特別的議題是，關於建立一個含有 0 個或 1 個項目的 tuple：語法上會採納一些奇怪的用法。空的 tuple 藉由一對空括號來建立；含有一個項目的 tuple 經由一個值加上一個逗點來建立（用括號把一個單一的值包住是不夠的）。醜，但有效率。例如：

>>> empty = ()
>>> singleton = 'hello',    # <-- 注意後面有個逗號
>>> len(empty)
0
>>> len(singleton)
1
>>> singleton
('hello',)

陳述式 t = 12345, 54321, 'hello!' 就是一個 tuple packing 的例子：12345，54321 和 'hello!' 一起被放進 tuple 裡。反向操作也可以：

>>> x, y, z = t

這個正是我們所說序列拆解 (sequence unpacking)，可運用在任何位在等號右邊的序列。序列拆解要求等號左邊的變數數量必須與等號右邊的序列中的元素數量相同。注意，多重指派就只是 tuple packing 和序列拆解的結合而已。

5.4. 集合 (Sets)

Python 也包含了集合 (sets)的資料型別。Set 是一種無序且不含重複元素的集合。基本的用途包括成員測試和消除重複的項目。集合物件也支援像是聯集、交集、差集和對稱差集等數學運算。

大括號或 set() 函式都可以用來建立 set。注意：要建立一個空的 set，你必須使用 set() 而不是 {}；後者會建立一個空的 dictionary，一種我們將在下一節討論的資料結構。

這裡是一個簡單的演示：

>>> basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}
>>> print(basket)                      # 確認重複值已被移除
{'orange', 'banana', 'pear', 'apple'}
>>> 'orange' in basket                 # 快速成員測試
True
>>> 'crabgrass' in basket
False

>>> # 示範對兩個字的唯一字母進行集合運算
>>>
>>> a = set('abracadabra')
>>> b = set('alacazam')
>>> a                                  # a 中的唯一字母
{'a', 'r', 'b', 'c', 'd'}
>>> a - b                              # 在 a 中但不在 b 中的字母
{'r', 'd', 'b'}
>>> a | b                              # 在 a 或 b 或兩者中的字母
{'a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'}
>>> a & b                              # 同時在 a 和 b 中的字母
{'a', 'c'}
>>> a ^ b                              # 在 a 或 b 中但不在兩者中的字母
{'r', 'd', 'b', 'm', 'z', 'l'}

和 list comprehensions 類似，也有 set comprehensions（集合綜合運算）：

>>> a = {x for x in 'abracadabra' if x not in 'abc'}
>>> a
{'r', 'd'}

5.5. 字典（Dictionary）

下一個常用的 Python 內建資料類型為 dictionary（請參考Mapping Types --- dict）。 Dictionary 有時被稱為「關聯記憶體」(associative memories) 或「關聯陣列」(associative arrays)。不像序列是由一個範圍內的數字當作索引，dictionary 是由鍵 (key) 來當索引，鍵可以是任何不可變的類型；字串和數字都可以當作鍵。Tuple 也可以當作鍵，如果他們只含有字串、數字或 tuple；若一個 tuple 直接或間接地含有任何可變的物件，它就不能當作鍵。你無法使用 list 當作鍵，因為 list 可以經由索引指派 (index assignment)、切片指派 (slice assignment) 或是像 append() 和 extend() 等方法被修改。

思考 dictionary 最好的方式是把它想成是一組鍵值對 (key: value pair) 的 set，其中鍵在同一個 dictionary 裡必須是獨一無二的。使用一對大括號可建立一個空的 dictionary：{}。將一串由逗號分隔的鍵值對置於大括號則可初始化字典的鍵值對。這同樣也是字典輸出時的格式。

Dictionary 主要的操作為藉由鍵來儲存一個值並且可藉由該鍵來取出該值。也可以使用 del 來刪除鍵值對。如果我們使用用過的鍵來儲存，該鍵所對應的較舊的值會被覆蓋。

使用下標 (d[key]) 來取出一個不存在的鍵所對應的值會引發 KeyError。為了避免在存取一個可能不存在的鍵時發生這個錯誤，可以改用 get() 方法，如果該鍵不存在於字典中，該方法會回傳 None（或者一個指定的預設值）。

對 dictionary 使用 list(d) 會得到一個包含該字典所有鍵的 list，其排列順序為插入時的順序。（若想要排序，則使用 sorted(d) 代替即可）。如果想確認一個鍵是否已存在於字典中，可使用關鍵字 in。

這是個使用一個 dictionary 的簡單範例：

>>> tel = {'jack': 4098, 'sape': 4139}
>>> tel['guido'] = 4127
>>> tel
{'jack': 4098, 'sape': 4139, 'guido': 4127}
>>> tel['jack']
4098
>>> tel['irv']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'irv'
>>> print(tel.get('irv'))
None
>>> del tel['sape']
>>> tel['irv'] = 4127
>>> tel
{'jack': 4098, 'guido': 4127, 'irv': 4127}
>>> list(tel)
['jack', 'guido', 'irv']
>>> sorted(tel)
['guido', 'irv', 'jack']
>>> 'guido' in tel
True
>>> 'jack' not in tel
False

函式 dict() 可直接透過一串鍵值對序列來建立 dictionary：

>>> dict([('sape', 4139), ('guido', 4127), ('jack', 4098)])
{'sape': 4139, 'guido': 4127, 'jack': 4098}

此外，dict comprehensions 也可以透過任意鍵與值的運算式來建立 dictionary ：

>>> {x: x**2 for x in (2, 4, 6)}
{2: 4, 4: 16, 6: 36}

當鍵是簡單的字串時，使用關鍵字引數 (keyword arguments) 有時會較為簡潔：

>>> dict(sape=4139, guido=4127, jack=4098)
{'sape': 4139, 'guido': 4127, 'jack': 4098}

5.6. 迴圈技巧

當對 dictionary 作迴圈時，鍵以及其對應的值可以藉由使用 items() method 來同時取得：

>>> knights = {'gallahad': 'the pure', 'robin': 'the brave'}
>>> for k, v in knights.items():
...     print(k, v)
...
gallahad the pure
robin the brave

當對序列作迴圈時，位置索引及其對應的值可以藉由使用 enumerate() 函式來同時取得：

>>> for i, v in enumerate(['tic', 'tac', 'toe']):
...     print(i, v)
...
0 tic
1 tac
2 toe

要同時對兩個以上的序列作迴圈，可以將其以成對的方式放入 zip() 函式：

>>> questions = ['name', 'quest', 'favorite color']
>>> answers = ['lancelot', 'the holy grail', 'blue']
>>> for q, a in zip(questions, answers):
...     print('What is your {0}?  It is {1}.'.format(q, a))
...
What is your name?  It is lancelot.
What is your quest?  It is the holy grail.
What is your favorite color?  It is blue.

要對序列作反向的迴圈，首先先寫出正向的序列，再對其使用 reversed() 函式：

>>> for i in reversed(range(1, 10, 2)):
...     print(i)
...
9
7
5
3
1

要以迴圈對序列作排序，使用 sorted() 函式會得到一個新的經排序過的 list ，但不會改變原本的序列：

>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> for i in sorted(basket):
...     print(i)
...
apple
apple
banana
orange
orange
pear

對序列使用 set() 可去除重複元素。對序列使用 sorted() 加上 set()，則是對經過排序後的非重複元素跑迴圈的慣用方法：

>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> for f in sorted(set(basket)):
...     print(f)
...
apple
banana
orange
pear

有時我們會想要以迴圈來改變的一個 list，但是，通常建立一個新的 list 會更簡單且安全：

>>> import math
>>> raw_data = [56.2, float('NaN'), 51.7, 55.3, 52.5, float('NaN'), 47.8]
>>> filtered_data = []
>>> for value in raw_data:
...     if not math.isnan(value):
...         filtered_data.append(value)
...
>>> filtered_data
[56.2, 51.7, 55.3, 52.5, 47.8]

5.7. 深入了解條件 (Condition)

使用在 while 和 if 陳述式的條件句可以包含任何運算子，而不是只有比較運算子 (comparisons) 。

比較運算子 in 和 not in 用於隸屬資格檢測，在容器中檢查一個值是否存在（或不存在）。運算子 is 和 is not 比較兩個物件是否真的是相同的物件。所有比較運算子的優先度都相同且都低於數值運算子。

比較運算是可以串連在一起的。例如， a < b == c 就是在測試 a 是否小於 b 和 b 是否等於 c。

比較運算可以結合布林運算子 and 和 or，且一個比較運算的結果（或任何其他布林運算式）可以加上 not 來否定。這些運算子的優先度都比比較運算子還低，其中，not 的優先度最高，or 的優先度最低，因此 A and not B or C 等同於 (A and (not B)) or C。一如往常，括號可以用來表示任何想要的組合。

布林運算子 and 和 or 也被稱為短路 (short-circuit) 運算子：會將其引數從左至右進行運算，當結果出現時即結束運算。例如，若 A 和 C 為真但 B 為假，則 A and B and C 的運算並不會執行到 C。當運算結果被當成一般值而非布林值時，短路運算子的回傳值為最後被求值的引數。

將一個比較運算或其他布林運算式的結果指派給一個變數是可以的。例如：

>>> string1, string2, string3 = '', 'Trondheim', 'Hammer Dance'
>>> non_null = string1 or string2 or string3
>>> non_null
'Trondheim'

注意，Python 與 C 語言不一樣，在運算式裡進行指派必須外顯地使用海象運算子 :=。 這樣做避免了在 C 語言裡常見的一種問題：想要打 == 卻在運算式裡輸入 =。

5.8. 序列和其他資料類型之比較

序列物件通常可以拿來和其他相同類型的物件做比較。這種比較使用詞典式 (lexicographical) 順序：首先比較各自最前面的那項，若不相同，便可決定結果；若相同，則比較下一項，以此類推，直到其中一個序列完全用完。如果被拿出來比較的兩項本身又是相同的序列類型，則詞典式比較會遞迴地執行。如果兩個序列所有的項目都相等，則此兩個序列被認為是相等的。如果其中一個序列是另一個的子序列，則較短的那個序列為較小的序列。字串的詞典式順序使用 Unicode 的編碼位置 (code point) 編號來排序個別字元。以下是一些相同序列類型的比較：

(1, 2, 3)              < (1, 2, 4)
[1, 2, 3]              < [1, 2, 4]
'ABC' < 'C' < 'Pascal' < 'Python'
(1, 2, 3, 4)           < (1, 2, 4)
(1, 2)                 < (1, 2, -1)
(1, 2, 3)             == (1.0, 2.0, 3.0)
(1, 2, ('aa', 'ab'))   < (1, 2, ('abc', 'a'), 4)

注意，若使用 < 或 > 來比較不同類型的物件是合法的，表示物件擁有適當的比較方法。例如，混合的數值類型是根據它們數值來做比較，所以 0 等於 0.0，等等。否則直譯器會選擇丟出一個 TypeError 錯誤而不是提供一個任意的排序。

註解

[1]

其他語言可以回傳變更後的物件，這就允許 method 的串連，例如 d->insert("a")->remove("b")->sort();。

6. 模組 (Module)

如果從 Python 直譯器離開後又再次進入，之前（幫函式或變數）做的定義都會消失。因此，想要寫一些比較長的程式時，你最好使用編輯器來準備要輸入給直譯器的內容，並且用該檔案來運行它。這就是一個腳本 (script)。隨著你的程式越變越長，你可能會想要把它分開成幾個檔案，讓它比較好維護。你可能也會想用一個你之前已經在其他程式寫好的函式，但不想要複製該函式的原始定義到所有使用它的程式裡。

為了支援這一點，Python 有一種方法可以將定義放入檔案中，並在互動模式下的直譯器中使用它們。這種檔案稱為模組 (module)；模組中的定義可以被 import 到其他模組中，或是被 import 至主 (main) 模組（在最頂層執行的腳本，以及互動模式下，所使用的變數集合）。

模組是指包含 Python 定義和語句的檔案，檔案名稱是模組名稱加上 .py。在模組中，模組的名稱（作為字串）會是全域變數 __name__ 的值。例如，用你喜歡的文字編輯器在資料夾中創一個名為 fibo.py 的檔案，內容如下：

# 費波那契數模組

def fib(n):
    """寫出費波那契數列至第 n 位。"""
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()

def fib2(n):
    """回傳費波那契數列至第 n 位。"""
    result = []
    a, b = 0, 1
    while a < n:
        result.append(a)
        a, b = b, a+b
    return result

現在進入 Python 直譯器並用以下指令 import 這個模組：

>>> import fibo

這並不會將 fibo 中定義的函式名稱直接加入目前的 namespace 中（詳情請見 Python 作用域 (Scope) 及命名空間 (Namespace)）；它只會加入 fibo 的模組名稱。使用此模組名稱，就可以存取函式：

>>> fibo.fib(1000)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987
>>> fibo.fib2(100)
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
>>> fibo.__name__
'fibo'

如果你打算經常使用其中某個函式，可以將其指定至區域變數：

>>> fib = fibo.fib
>>> fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

6.1. 深入了解模組

模組可以包含可執行的陳述式以及函式的定義。這些陳述式是作為模組的初始化，它們只會在第一次被 import 時才會執行。[1]（如果檔案被當成腳本執行，也會執行它們）。

每個模組都有它自己的私有命名空間 (namespace)，模組內定義的函式會把該模組的私有符號表當成全域命名空間使用。因此，模組的作者可以在模組中使用全域變數，而不必擔心和使用者的全域變數發生意外的名稱衝突。另一方面，如果你知道自己在做什麼，你可以用這個方式取用模組的全域變數，以和引用函式一樣的寫法，modname.itemname。

在一個模組中可以 import 其他模組。把所有的 import 陳述式放在模組（就這邊來說，腳本也是一樣）的最開頭是個慣例，但並沒有強制。如放置在模組的最高層（不在任何函式或 class 中），被 import 的模組名稱將被加入全域命名空間中。

import 陳述式有另一種變形寫法，可以直接將名稱從欲 import 的模組，直接 import 至原模組的命名空間中。例如：

>>> from fibo import fib, fib2
>>> fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

在 import 之後的名稱會被導入，但定義該函式的整個模組名稱並不會被引入在區域命名空間中（因此，示例中的 fibo 未被定義）。

甚至還有另一種變形寫法，可以 import 模組定義的所有名稱：

>>> from fibo import *
>>> fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

這個寫法會 import 模組中所有的名稱，除了使用底線 (_) 開頭的名稱。大多數情況下，Python 程式設計師不大使用這個功能，因為它在直譯器中引入了一組未知的名稱，並且可能覆蓋了某些你已經定義的內容。

請注意，一般情況下並不建議從模組或套件中 import * 的做法，因為它通常會導致可讀性較差的程式碼。但若是使用它來在互動模式中節省打字時間，則是可以接受的。

如果模組名稱後面出現 as，則 as 之後的名稱將直接和被 import 模組綁定在一起。

>>> import fibo as fib
>>> fib.fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

這個 import 方式和 import fibo 實質上是一樣的，唯一的差別是現在要用 fib 使用模組。

在使用 from 時也可以用同樣的方式獲得類似的效果：

>>> from fibo import fib as fibonacci
>>> fibonacci(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

備註

出於效率原因，每個模組在每個直譯器 session 中僅會被 import 一次。因此，如果你更改了模組，則必須重啟直譯器——或者，如果只是一個想要在互動模式下測試的模組，可以使用 importlib.reload()。例如：import importlib; importlib.reload(modulename)。

6.1.1. 把模組當作腳本執行

當使用以下內容運行 Python 模組時：

python fibo.py <arguments>

如同使用 import 指令，模組中的程式碼會被執行，但 __name__ 被設為 "__main__"。這意味著，透過在模組的末尾添加以下程式碼：

if __name__ == "__main__":
    import sys
    fib(int(sys.argv[1]))

你可以將檔案作為腳本也同時可以作為被 import 的模組，因為剖析 (parse) 命令列的程式碼只會在當模組是「主」檔案時，才會執行：

$ python fibo.py 50
0 1 1 2 3 5 8 13 21 34

如果此模組是被 import 的，則該段程式碼不會被執行：

>>> import fibo
>>>

這通常是用來為模組提供方便的使用者介面，或者用於測試目的（執行測試套件時，以腳本的方式執行模組）。

6.1.2. 模組的搜尋路徑

Import 一個名為 spam 的模組時，直譯器首先會搜尋具有該名稱的內建模組。模組名稱列在 sys.builtin_module_names 當中。如果找不到，接下來會在變數 sys.path 所給定的資料夾清單之中，搜尋一個名為 spam.py 的檔案。sys.path 從這些位置開始進行初始化：

輸入腳本所位在的資料夾（如未指定檔案時，則是目前資料夾）。

PYTHONPATH（一連串和 shell 變數 PATH 的語法相同的資料夾名稱）。

與安裝相關的預設值（按慣例會包含一個 site-packages 資料夾，它是由 site 模組所處理）。

在 sys.path 模組搜尋路徑的初始化 有更多的細節。

備註

在支援符號連結 (symlink) 的檔案系統中，輸入腳本的所在資料夾是在跟隨符號連結之後才被計算的。換言之，包含符號連結的資料夾並沒有增加到模組的搜尋路徑中。

初始化之後，Python 程式可以修改 sys.path。執行中腳本的所在資料夾會在搜尋路徑的開頭，在標準函式庫路徑之前。這代表該資料夾中的腳本會優先被載入，而不是函式庫資料夾中相同名稱的模組。除非是有意要做這樣的替換，否則這是一個錯誤。 請參見標準模組以瞭解更多資訊。

6.1.3. 「編譯」Python 檔案

為了加快載入模組的速度，Python 將每個模組的編譯版本暫存在 __pycache__ 資料夾下，並命名為 module.version.pyc， 這裡的 version 是編譯後的檔案的格式名稱，且名稱通常會包含 Python 的版本編號。例如，在 CPython 3.3 中，spam.py 的編譯版本將被暫存為 __pycache__/spam.cpython-33.pyc。此命名準則可以讓來自不同版本的編譯模組和 Python 的不同版本同時共存。

Python 根據原始碼最後修改的日期，檢查編譯版本是否過期而需要重新編譯。這是一個完全自動的過程。另外，編譯後的模組獨立於平台，因此不同架構的作業系統之間可以共用同一函式庫。

Python 在兩種情況下不檢查快取 (cache)。首先，它總是重新編譯且不儲存直接從命令列載入的模組的結果。第二，如果沒有源模組，則不會檢查快取。要支援非源模組（僅編譯）的發布，編譯後的模組必須位於原始資料夾中，並且不能有源模組。

一些給專家的秘訣：

可以在 Python 指令上使用開關參數 (switch) -O 或 -OO 來減小已編譯模組的大小。開關參數 -O 刪除 assert（斷言）陳述式，而 -OO 同時刪除 assert 陳述式和 __doc__ 字串。由於有些程式可能依賴於上述這些內容，因此只有在你知道自己在做什麼時，才應使用此參數。「已最佳化」模組有 opt- 標記，且通常較小。未來的版本可能會改變最佳化的效果。

讀取 .pyc 檔案時，程式的執行速度並不會比讀取 .py 檔案快。唯一比較快的地方是載入的速度。

模組 compileall 可以為資料夾中的所有模組建立 .pyc 檔。

更多的細節，包括決策流程圖，請參考PEP 3147 [https://peps.python.org/pep-3147/]。

6.2. 標準模組

Python 附帶了一個標準模組庫，詳細的介紹在另一份文件，稱為「Python 函式庫參考手冊」（簡稱為「函式庫參考手冊」）。有些模組是直譯器中內建的；它們使一些不屬於語言核心但依然內建的運算得以存取，其目的是為了提高效率，或提供作業系統基本操作（例如系統呼叫）。這些模組的集合是一個組態選項，它們取決於底層平台。例如：winreg 模組僅供 Windows 使用。值得注意的模組是 sys，它被內建在每個 Python 直譯器中。變數 sys.ps1 和 sys.ps2 則用來定義主、次提示字元的字串：

>>> import sys
>>> sys.ps1
'>>> '
>>> sys.ps2
'... '
>>> sys.ps1 = 'C> '
C> print('Yuck!')
Yuck!
C>

只有直譯器在互動模式時，才需要定義這兩個變數。

變數 sys.path 是一個字串 list，它決定直譯器的模組搜尋路徑。它的初始值為環境變數 PYTHONPATH 中提取的預設路徑，或是當 PYTHONPATH 未設定時，從內建預設值提取。你可以用標準的 list 操作修改該變數：

>>> import sys
>>> sys.path.append('/ufs/guido/lib/python')

6.3. dir() 函式

內建函式 dir() 用於找出模組定義的所有名稱。它回傳一個排序後的字串 list：

>>> import fibo, sys
>>> dir(fibo)
['__name__', 'fib', 'fib2']
>>> dir(sys)
['__breakpointhook__', '__displayhook__', '__doc__', '__excepthook__',
 '__interactivehook__', '__loader__', '__name__', '__package__', '__spec__',
 '__stderr__', '__stdin__', '__stdout__', '__unraisablehook__',
 '_clear_type_cache', '_current_frames', '_debugmallocstats', '_framework',
 '_getframe', '_git', '_home', '_xoptions', 'abiflags', 'addaudithook',
 'api_version', 'argv', 'audit', 'base_exec_prefix', 'base_prefix',
 'breakpointhook', 'builtin_module_names', 'byteorder', 'call_tracing',
 'callstats', 'copyright', 'displayhook', 'dont_write_bytecode', 'exc_info',
 'excepthook', 'exec_prefix', 'executable', 'exit', 'flags', 'float_info',
 'float_repr_style', 'get_asyncgen_hooks', 'get_coroutine_origin_tracking_depth',
 'getallocatedblocks', 'getdefaultencoding', 'getdlopenflags',
 'getfilesystemencodeerrors', 'getfilesystemencoding', 'getprofile',
 'getrecursionlimit', 'getrefcount', 'getsizeof', 'getswitchinterval',
 'gettrace', 'hash_info', 'hexversion', 'implementation', 'int_info',
 'intern', 'is_finalizing', 'last_traceback', 'last_type', 'last_value',
 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks',
 'path_importer_cache', 'platform', 'prefix', 'ps1', 'ps2', 'pycache_prefix',
 'set_asyncgen_hooks', 'set_coroutine_origin_tracking_depth', 'setdlopenflags',
 'setprofile', 'setrecursionlimit', 'setswitchinterval', 'settrace', 'stderr',
 'stdin', 'stdout', 'thread_info', 'unraisablehook', 'version', 'version_info',
 'warnoptions']

沒有給引數時，dir() 列出目前已定義的名稱：

>>> a = [1, 2, 3, 4, 5]
>>> import fibo
>>> fib = fibo.fib
>>> dir()
['__builtins__', '__name__', 'a', 'fib', 'fibo', 'sys']

請注意，它列出所有類型的名稱：變數、模組、函式等。

dir() 不會列出內建函式和變數的名稱。如果你想要列出它們，它們被定義在標準模組 builtins 內：

>>> import builtins
>>> dir(builtins)
['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException',
 'BlockingIOError', 'BrokenPipeError', 'BufferError', 'BytesWarning',
 'ChildProcessError', 'ConnectionAbortedError', 'ConnectionError',
 'ConnectionRefusedError', 'ConnectionResetError', 'DeprecationWarning',
 'EOFError', 'Ellipsis', 'EnvironmentError', 'Exception', 'False',
 'FileExistsError', 'FileNotFoundError', 'FloatingPointError',
 'FutureWarning', 'GeneratorExit', 'IOError', 'ImportError',
 'ImportWarning', 'IndentationError', 'IndexError', 'InterruptedError',
 'IsADirectoryError', 'KeyError', 'KeyboardInterrupt', 'LookupError',
 'MemoryError', 'NameError', 'None', 'NotADirectoryError', 'NotImplemented',
 'NotImplementedError', 'OSError', 'OverflowError',
 'PendingDeprecationWarning', 'PermissionError', 'ProcessLookupError',
 'ReferenceError', 'ResourceWarning', 'RuntimeError', 'RuntimeWarning',
 'StopIteration', 'SyntaxError', 'SyntaxWarning', 'SystemError',
 'SystemExit', 'TabError', 'TimeoutError', 'True', 'TypeError',
 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError',
 'UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning',
 'ValueError', 'Warning', 'ZeroDivisionError', '_', '__build_class__',
 '__debug__', '__doc__', '__import__', '__name__', '__package__', 'abs',
 'all', 'any', 'ascii', 'bin', 'bool', 'bytearray', 'bytes', 'callable',
 'chr', 'classmethod', 'compile', 'complex', 'copyright', 'credits',
 'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'exec', 'exit',
 'filter', 'float', 'format', 'frozenset', 'getattr', 'globals', 'hasattr',
 'hash', 'help', 'hex', 'id', 'input', 'int', 'isinstance', 'issubclass',
 'iter', 'len', 'license', 'list', 'locals', 'map', 'max', 'memoryview',
 'min', 'next', 'object', 'oct', 'open', 'ord', 'pow', 'print', 'property',
 'quit', 'range', 'repr', 'reversed', 'round', 'set', 'setattr', 'slice',
 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'vars',
 'zip']

6.4. 套件 (Package)

套件是一種使用「點分隔模組名稱」組織 Python 模組命名空間的方法。例如，模組名稱 A.B 表示套件 A 中名為 B 的子模組。正如模組使用時，不同模組的作者不需擔心與其他模組的全域變數名稱重複，點分隔模組名稱的使用，也讓多模組套件（像 NumPy 或 Pillow）的作者們不須擔心其他套件的模組名稱。

假設你想設計一個能統一處理音訊檔案及音訊數據的模組集（「套件」）。因為音訊檔案有很多的不同的格式（通常以它們的副檔名來辨識，例如：.wav、.aiff、.au），因此，為了不同檔案格式之間的轉換，你會需要建立和維護一個不斷增長的模組集合。為了要達成對音訊數據的許多不同作業（例如，音訊混合、增加回聲、套用等化器功能、創造人工立體音效），你將編寫一系列無止盡的模組來執行這些作業。以下是你的套件可能的架構（以階層式檔案系統的方式表示）：

sound/                          Top-level package
      __init__.py               Initialize the sound package
      formats/                  Subpackage for file format conversions
              __init__.py
              wavread.py
              wavwrite.py
              aiffread.py
              aiffwrite.py
              auread.py
              auwrite.py
              ...
      effects/                  Subpackage for sound effects
              __init__.py
              echo.py
              surround.py
              reverse.py
              ...
      filters/                  Subpackage for filters
              __init__.py
              equalizer.py
              vocoder.py
              karaoke.py
              ...

Import 套件時，Python 會搜尋 sys.path 裡的目錄，尋找套件的子目錄。

目錄中必須含有 __init__.py 檔案，才會被 Pyhon 當成套件（除非有使用 namespace package，為一個相對進階的功能）；這樣可以避免一些以常用名稱命名（例如 string）的目錄，無意中隱藏了較晚出現在模組搜尋路徑中的有效模組。在最簡單的情況，__init__.py 可以只是一個空白檔案；但它也可以執行套件的初始化程式碼，或設置 __all__ 變數，之後會詳述。

套件使用者可以從套件中 import 個別模組，例如：

import sound.effects.echo

這樣就載入了子模組 sound.effects.echo。引用時必須用它的全名：

sound.effects.echo.echofilter(input, output, delay=0.7, atten=4)

另一種 import 子模組的方法是：

from sound.effects import echo

這段程式碼一樣可以載入子模組 echo，並且不加套件前綴也可以使用，因此能以如下方式使用：

echo.echofilter(input, output, delay=0.7, atten=4)

另一種變化是直接 import 所需的函式或變數：

from sound.effects.echo import echofilter

同樣地，這樣也會載入子模組 echo，但它的函式 echofilter() 就可以直接使用：

echofilter(input, output, delay=0.7, atten=4)

請注意，使用 from package import item 時，item 可以是套件的子模組（或子套件），也可以是套件中被定義的名稱，像是函式、class （類別）或變數。import 陳述式首先測試套件中有沒有定義該 item；如果沒有，則會假設它是模組，並嘗試載入。如果還是找不到 item，則會引發 ImportError 例外。

相反地，使用 import item.subitem.subsubitem 語法時，除了最後一項之外，每一項都必須是套件；最後一項可以是模組或套件，但不能是前一項中定義的 class、函式或變數。

6.4.1. 從套件中 import *

當使用者寫下 from sound.effects import * 時，會發生什麼事？理想情況下，我們可能希望程式碼會去檔案系統，尋找套件中存在的子模組，並將它們全部 import。這會花費較長的時間，且 import 子模組的過程可能會有不必要的副作用，這些副作用只有在明確地 import 子模組時才會發生。

唯一的解法是由套件作者為套件提供明確的索引。import 陳述式使用以下慣例：如果套件的 __init__.py 程式碼有定義一個名為 __all__ 的 list，若遇到 from package import * 的時候，它就會是要被 import 的模組名稱。發布套件的新版本時，套件作者可自行決定是否更新此 list。如果套件作者認為沒有人會從他的套件中 import *，他也可能會決定不支援這個 list。舉例來說，sound/effects/__init__.py 檔案可包含以下程式碼：

__all__ = ["echo", "surround", "reverse"]

意思是，from sound.effects import * 將會 import sound.effects 套件中，這三個被提名的子模組。

請注意，子模組可能會被區域定義 (locally defined) 的名稱遮蔽。例如，如果你在 sound/effects/__init__.py 檔案中新增了一個 reverse 函式，則 from sound.effects import * 只會引入兩個子模組 echo 和 surround，但不是 reverse 子模組，因為它被區域定義的 reverse 函式遮蔽了：

__all__ = [
    "echo",      # 指向 'echo.py' 檔案
    "surround",  # 指向 'surround.py' 檔案
    "reverse",   # !!! 現在指向 'reverse' 函式 !!!
]

def reverse(msg: str):  #  <-- 在 'from sound.effects import *' 的情況下
    return msg[::-1]    #     這個名稱遮蔽了 'reverse.py' 子模組

如果 __all__ 沒有被定義，from sound.effects import * 陳述式並不會把 sound.effects 套件中所有子模組都 import 到目前的命名空間；它只保證 sound.effects 套件有被 import（可能會運行 __init__.py 中的初始化程式碼），然後 import 套件中被定義的全部名稱。這包含 __init__.py 定義（以及被明確載入的子模組）的任何名稱。它也包括任何之前被 import 陳述式明確載入的套件子模組。請看以下程式碼：

import sound.effects.echo
import sound.effects.surround
from sound.effects import *

此例中，當 from...import 陳述式被執行時，echo 和 surround 模組被 import 進目前的命名空間，因為它們是在 sound.effects 套件裡定義的。（當 __all__ 有被定義時，這規則也有效。）

雖然，有些特定模組的設計，讓你使用 import * 時，該模組只會輸出遵循特定樣式的名稱，但在正式環境 (production) 的程式碼中這仍然被視為是不良習慣。

記住，使用 from package import specific_submodule 不會有任何問題！實際上，這是推薦用法，除非 import 的模組需要用到的子模組和其他套件的子模組同名。

6.4.2. 套件內引用

當套件的結構為多個子套件的組合時（如同範例中的 sound 套件），可以使用「絕對 (absolute) import」，引用同層套件中的子模組。例如，要在 sound.filters.vocoder 模組中使用 sound.effects 中的 echo 模組時，可以用 from sound.effects import echo。

你也可以用 from module import name 的 import 陳述式，編寫「相對 (relative) import」。這些 import 使用前導句號指示相對 import 中的目前套件和母套件。例如，在 urround 模組中，你可以使用：

from . import echo
from .. import formats
from ..filters import equalizer

請注意，相對 import 的運作是以目前模組的套件名稱為依據。因為主模組並沒有套件，所以如果一個模組預期被用作 Python 應用程式的主模組，那它必須永遠使用絕對引入。

6.4.3. 多目錄中的套件

套件也支援一個特殊屬性 __path__。它在初始化時是一個字串的序列的 __init__.py 檔案所在的目錄名稱，初始化時機是在這個檔案的程式碼被執行之前。這個變數可以被修改，但這樣做會影響將來對套件內的模組和子套件的搜尋。

雖然這個特色不太常被需要，但它可用於擴充套件中的模組集合。

註解

[1]

實際上，函式定義也是「被執行」的「陳述式」；在執行模組階層的函式定義時，會將函式名稱加到模組的全域命名空間。

7. 輸入和輸出

有數種方式可以顯示程式的輸出；資料可以以人類易讀的形式印出，或是寫入檔案以供未來所使用。這章節會討論幾種不同的方式。

7.1. 更華麗的輸出格式

目前為止我們已經學過兩種寫值的方式：運算式陳述 (expression statements) 與 print() 函式。（第三種方法是使用檔案物件的 write() 方法；標準輸出的檔案是使用 sys.stdout 來達成的。詳細的資訊請參考對應的函式庫說明。）

通常你會想要對輸出格式有更多地控制，而不是僅列印出以空格隔開的值。以下是幾種格式化輸出的方式。

要使用格式化字串文本 (formatted string literals)，需在字串開始前的引號或連續三個引號前加上 f 或 F。你可以在這個字串中使用 { 與 } 包夾 Python 的運算式，引用變數或其他字面值 (literal values)。

>>> year = 2016
>>> event = 'Referendum'
>>> f'Results of the {year} {event}'
'Results of the 2016 Referendum'

字串的 str.format() method 需要更多手動操作。你還是可以用 { 和 } 標示欲替代變數的位置，且可給予詳細的格式指令，但你也需提供要被格式化的資訊。在以下程式碼區塊中，有兩個如何格式化變數的範例：

>>> yes_votes = 42_572_654
>>> total_votes = 85_705_149
>>> percentage = yes_votes / total_votes
>>> '{:-9} YES votes  {:2.2%}'.format(yes_votes, percentage)
' 42572654 YES votes  49.67%'

請注意 yes_votes 如何對於負數用空格和負號填補。該範例還會列出 percentage 乘以 100，並保留 2 位小數且後面跟著一個百分號（有關詳細資訊，請參閱 格式規格 (Format Specification) 迷你語言）。

最後，你還可以自己用字串切片 (slicing) 和串接 (concatenation) 操作，完成所有的字串處理，建立任何你能想像的排版格式。字串型別有一些 method，能以給定的欄寬填補字串，這些運算也很有用。

如果你不需要華麗的輸出，只想快速顯示變數以進行除錯，可以用 repr() 或 str() 函式把任何的值轉換為字串。

str() 函式的用意是回傳一個人類易讀的表示法，而 repr() 的用意是產生直譯器可讀取的表示法（如果沒有等效的語法，則造成 SyntaxError）。如果物件沒有人類易讀的特定表示法，str() 會回傳與 repr() 相同的值。有許多的值，像是數字，或 list 及 dictionary 等結構，使用這兩個函式會有相同的表示法。而字串，則較為特別，有兩種不同的表示法。

一些範例：

>>> s = 'Hello, world.'
>>> str(s)
'Hello, world.'
>>> repr(s)
"'Hello, world.'"
>>> str(1/7)
'0.14285714285714285'
>>> x = 10 * 3.25
>>> y = 200 * 200
>>> s = 'The value of x is ' + repr(x) + ', and y is ' + repr(y) + '...'
>>> print(s)
The value of x is 32.5, and y is 40000...
>>> # 字串的 repr() 會加上字串引號和反斜線：
>>> hello = 'hello, world\n'
>>> hellos = repr(hello)
>>> print(hellos)
'hello, world\n'
>>> # repr() 的引數可以是任何 Python 物件：
>>> repr((x, y, ('spam', 'eggs')))
"(32.5, 40000, ('spam', 'eggs'))"

string 模組包含一個基於正規表示式 (regular expressions)、透過 string.Template 的簡單模板化手段的支援。這提供了另一種將值替換到字串中的方式，使用像 $x 這樣的佔位符號，並用來自字典的值取代它們。這種語法較易用，但它在格式化方面提供的控制較少。

7.1.1. 格式化的字串文本 (Formatted String Literals)

格式化的字串文本（簡稱為 f-字串），透過在字串加入前綴 f 或 F，並將運算式編寫為 {expression}，讓你可以在字串內加入 Python 運算式的值。

格式說明符 (format specifier) 是選擇性的，寫在運算式後面，可以更好地控制值的格式化方式。以下範例將 pi 捨入到小數點後三位：

>>> import math
>>> print(f'The value of pi is approximately {math.pi:.3f}.')
The value of pi is approximately 3.142.

在 ':' 後傳遞一個整數，可以設定該欄位至少為幾個字元寬，常用於將每一欄對齊。

>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678}
>>> for name, phone in table.items():
...     print(f'{name:10} ==> {phone:10d}')
...
Sjoerd     ==>       4127
Jack       ==>       4098
Dcab       ==>       7678

還有一些修飾符號可以在格式化前先將值轉換過。'!a' 會套用 ascii()，'!s' 會套用 str()，'!r' 會套用 repr()：

>>> animals = 'eels'
>>> print(f'My hovercraft is full of {animals}.')
My hovercraft is full of eels.
>>> print(f'My hovercraft is full of {animals!r}.')
My hovercraft is full of 'eels'.

= 說明符可用於將一個運算式擴充為該運算式的文字、一個等號、以及對該運算式求值 (evaluate) 後的表示法：

>>> bugs = 'roaches'
>>> count = 13
>>> area = 'living room'
>>> print(f'Debugging {bugs=} {count=} {area=}')
Debugging bugs='roaches' count=13 area='living room'

更多關於 = 說明符的資訊請見自文件性運算式 (self-documenting expressions)。若要參考這些格式化字串的規格，詳見 格式規格 (Format Specification) 迷你語言 參考指南。

7.1.2. 字串的 format() method

str.format() method 的基本用法如下：

>>> print('We are the {} who say "{}!"'.format('knights', 'Ni'))
We are the knights who say "Ni!"

大括號及其內的字元（稱為格式欄位）會被取代為傳遞給 str.format() method 的物件。大括號中的數字表示該物件在傳遞給 str.format() method 時所在的位置。

>>> print('{0} and {1}'.format('spam', 'eggs'))
spam and eggs
>>> print('{1} and {0}'.format('spam', 'eggs'))
eggs and spam

如果在 str.format() method 中使用關鍵字引數，可以使用引數名稱去引用它們的值。

>>> print('This {food} is {adjective}.'.format(
...       food='spam', adjective='absolutely horrible'))
This spam is absolutely horrible.

位置引數和關鍵字引數可以任意組合：

>>> print('The story of {0}, {1}, and {other}.'.format('Bill', 'Manfred',
...                                                    other='Georg'))
The story of Bill, Manfred, and Georg.

如果你有一個不想分割的長格式化字串，比較好的方式是按名稱而不是按位置來引用變數。這項操作可以透過傳遞字典 (dict)，並用方括號 '[]' 使用鍵 (key) 來輕鬆完成。

>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678}
>>> print('Jack: {0[Jack]:d}; Sjoerd: {0[Sjoerd]:d}; '
...       'Dcab: {0[Dcab]:d}'.format(table))
Jack: 4098; Sjoerd: 4127; Dcab: 8637678

用 '**' 符號，把 table 字典當作關鍵字引數來傳遞，也有一樣的結果。

>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678}
>>> print('Jack: {Jack:d}; Sjoerd: {Sjoerd:d}; Dcab: {Dcab:d}'.format(**table))
Jack: 4098; Sjoerd: 4127; Dcab: 8637678

與內建函式 vars() 組合使用時，這種方式特別實用。該函式可以回傳一個包含所有區域變數的 dictionary：

>>> table = {k: str(v) for k, v in vars().items()}
>>> message = " ".join([f'{k}: ' + '{' + k +'};' for k in table.keys()])
>>> print(message.format(**table))
__name__: __main__; __doc__: None; __package__: None; __loader__: ...

例如，下面的程式碼產生一組排列整齊的欄，列出整數及其平方與立方：

>>> for x in range(1, 11):
...     print('{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x))
...
 1   1    1
 2   4    8
 3   9   27
 4  16   64
 5  25  125
 6  36  216
 7  49  343
 8  64  512
 9  81  729
10 100 1000

關於使用 str.format() 進行字串格式化的完整概述，請見格式化文字語法。

7.1.3. 手動格式化字串

下面是以手動格式化完成的同一個平方及立方的表：

>>> for x in range(1, 11):
...     print(repr(x).rjust(2), repr(x*x).rjust(3), end=' ')
...     # 注意前一列使用的 'end'
...     print(repr(x*x*x).rjust(4))
...
 1   1    1
 2   4    8
 3   9   27
 4  16   64
 5  25  125
 6  36  216
 7  49  343
 8  64  512
 9  81  729
10 100 1000

（請注意，使用 print() 讓每欄之間加入一個空格的方法：這種方法總是在其引數間加入空格。）

字串物件的 str.rjust() method 透過在左側填補空格，使字串以給定的欄寬進行靠右對齊。類似的 method 還有 str.ljust() 和 str.center()。這些 method 不寫入任何內容，只回傳一個新字串，如果輸入的字串太長，它們不會截斷字串，而是不做任何改變地回傳；雖然這樣會弄亂欄的編排，但這通常還是比另一種情況好，那種情況會讓值變得不正確。（如果你真的想截斷字串，可以加入像 x.ljust(n)[:n] 這樣的切片運算。）

另一種 method 是 str.zfill()，可在數值字串的左邊填補零，且能識別正負號：

>>> '12'.zfill(5)
'00012'
>>> '-3.14'.zfill(7)
'-003.14'
>>> '3.14159265359'.zfill(5)
'3.14159265359'

7.1.4. 格式化字串的舊方法

% 運算子（modulo，模數）也可用於字串格式化。在 format % values 中（其中 format 是個字串），format 內的 % 轉換規格會被 values 的零個或多個元素所取代。此運算常被稱為字串插值 (string interpolation)。例如：

>>> import math
>>> print('The value of pi is approximately %5.3f.' % math.pi)
The value of pi is approximately 3.142.

更多資訊請見 printf-style String Formatting小節。

7.2. 讀寫檔案

open() 回傳一個 file object，而它最常使用的兩個位置引數和一個關鍵字引數是：open(filename, mode, encoding=None)

>>> f = open('workfile', 'w', encoding="utf-8")

第一個引數是一個包含檔案名稱的字串。第二個引數是另一個字串，包含了描述檔案使用方式的幾個字元。mode 為 'r' 時，表示以唯讀模式開啟檔案；為 'w' 時，表示以唯寫模式開啟檔案（已存在的同名檔案會被抹除）；為 'a' 時，以附加內容為目的開啟檔案，任何寫入檔案的資料會自動被加入到檔案的結尾。'r+' 可以開啟檔案並進行讀取和寫入。mode 引數是選擇性的，若省略時會預設為 'r'。

通常，檔案以 text mode 開啟，意即，從檔案中讀取或寫入字串時，都以特定編碼方式 encoding 進行編碼。如未指定 encoding，則預設值會取決於系統平台（見 open()）。因為 UTF-8 是現時的標準，除非你很清楚該用什麼編碼，否則推薦使用 encoding="utf-8"。在 mode 後面加上 'b' 會以 binary mode（二進制模式）開啟檔案，二進制模式資料以 bytes 物件的形式被讀寫。以二進制模式開啟檔案時不可以指定 encoding。

在文字模式 (text mode) 下，讀取時會預設把平台特定的行尾符號（Unix 上為 \n，Windows 上為 \r\n）轉換為 \n。在文字模式下寫入時，預設會把 \n 出現之處轉換回平台特定的行尾符號。這種在幕後對檔案資料的修改方式對文字檔案來說沒有問題，但會毀壞像是 JPEG 或 EXE 檔案中的二進制資料。在讀寫此類檔案時，注意一定要使用二進制模式。

在處理檔案物件時，使用 with 關鍵字是個好習慣。優點是，當它的套件結束後，即使在某個時刻引發了例外，檔案仍會正確地被關閉。使用 with 也比寫等效的 try-finally 區塊，來得簡短許多：

>>> with open('workfile', encoding="utf-8") as f:
...     read_data = f.read()

>>> # 我們可以檢查確認該檔案已經自動被關閉。
>>> f.closed
True

如果你沒有使用 with 關鍵字，則應呼叫 f.close() 關閉檔案，可以立即釋放被它所使用的系統資源。

警告

呼叫 f.write() 時，若未使用 with 關鍵字或呼叫 f.close()，即使程式成功退出，也可能導致 f.write() 的引數沒有被完全寫入硬碟。

不論是透過 with 陳述式，或呼叫 f.close() 關閉一個檔案物件之後，嘗試使用該檔案物件將會自動失效。

>>> f.close()
>>> f.read()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file.

7.2.1. 檔案物件的 method

本節其餘的範例皆假設一個名為 f 的檔案物件已被建立。

要讀取檔案的內容，可呼叫 f.read(size)，它可讀取一部份的資料，並以字串（文字模式）或位元組串物件（二進制模式）形式回傳。size 是個選擇性的數字引數。當 size 被省略或為負數時，檔案的全部內容會被讀取並回傳；如果檔案是機器記憶體容量的兩倍大時，這會是你的問題。否則，最多只有等同於 size 數量的字元（文字模式）或 size 數量的位元組串（二進制模式）會被讀取及回傳。如果之前已經到達檔案的末端，f.read() 會回傳空字串（''）。

>>> f.read()
'This is the entire file.\n'
>>> f.read()
''

f.readline() 從檔案中讀取單獨一行；換行字元（\n）會被留在字串的結尾，只有當檔案末端不是換行字元時，它才會在檔案的最後一行被省略。這種方式讓回傳值清晰明確；只要 f.readline() 回傳一個空字串，就表示已經到達了檔案末端，而空白行的表示法是 '\n'，也就是只含一個換行字元的字串。

>>> f.readline()
'This is the first line of the file.\n'
>>> f.readline()
'Second line of the file\n'
>>> f.readline()
''

想從檔案中讀取多行時，可以對檔案物件進行迴圈。這種方法能有效地使用記憶體、快速，且程式碼簡潔：

>>> for line in f:
...     print(line, end='')
...
This is the first line of the file.
Second line of the file

如果你想把一個檔案的所有行讀進一個 list 裡，可以用 list(f) 或 f.readlines()。

f.write(string) 把 string 的內容寫入檔案，並回傳寫入的字元數。

>>> f.write('This is a test\n')
15

寫入其他類型的物件之前，要先把它們轉換為字串（文字模式）或位元組串物件（二進制模式）：

>>> value = ('the answer', 42)
>>> s = str(value)  # 將元組轉換成字串
>>> f.write(s)
18

f.tell() 回傳一個整數，它給出檔案物件在檔案中的目前位置，在二進制模式下表示為檔案開始至今的位元組數，在文字模式下表示為一個意義不明的數字。

使用 f.seek(offset, whence) 可以改變檔案物件的位置。位置計算方法是從一個參考點增加 offset 的偏移量；參考點則由引數 whence 來選擇。當 whence 值為 0 時，表示使用檔案開頭，1 表示使用目前的檔案位置，2 表示使用檔案末端作為參考點。whence 可省略，其預設值為 0，即以檔案開頭作為參考點。

>>> f = open('workfile', 'rb+')
>>> f.write(b'0123456789abcdef')
16
>>> f.seek(5)      # 跳到檔案中的第六個位元組
5
>>> f.read(1)
b'5'
>>> f.seek(-3, 2)  # 跳到結尾前的第三個位元組
13
>>> f.read(1)
b'd'

在文字檔案（開啟時模式字串未加入 b 的檔案）中，只允許以檔案開頭為參考點進行尋找（但 seek(0, 2) 尋找檔案最末端是例外），且只有從 f.tell() 回傳的值，或是 0，才是有效的 offset 值。其他任何 offset 值都會產生未定義的行為。

檔案物件還有一些附加的 method，像是較不常使用的 isatty() 和 truncate()；檔案物件的完整指南詳見程式庫參考手冊。

7.2.2. 使用 json 儲存結構化資料

字串可以簡單地從檔案中被寫入和讀取。數字則稍嫌麻煩，因為 read() method 只回傳字串，這些字串必須傳遞給像 int() 這樣的函式，它接受 '123' 這樣的字串，並回傳數值 123。當你想儲存像是巢狀 list 和 dictionary（字典）等複雜的資料類型時，手動剖析 (parsing) 和序列化 (serializing) 就變得複雜。

相較於讓使用者不斷地編寫和除錯程式碼才能把複雜的資料類型儲存到檔案，Python 支援一個普及的資料交換格式，稱為 JSON (JavaScript Object Notation) [https://json.org]。標準模組 json 可接收 Python 資料階層，並將它們轉換為字串表示法；這個過程稱為 serializing（序列化）。從字串表示法中重建資料則稱為 deserializing（反序列化）。在序列化和反序列化之間，表示物件的字串可以被儲存在檔案或資料中，或透過網路連接發送到遠端的機器。

備註

JSON 格式經常地使用於現代應用程式的資料交換。許多程序設計師早已對它耳熟能詳，使它成為提升互操作性 (interoperability) 的好選擇。

如果你有一個物件 x，只需一行簡單的程式碼即可檢視它的 JSON 字串表示法：

>>> import json
>>> x = [1, 'simple', 'list']
>>> json.dumps(x)
'[1, "simple", "list"]'

dumps() 函式有一個變體，稱為 dump()，它單純地將物件序列化為 text file。因此，如果 f 是一個為了寫入而開啟的 text file 物件，我們可以這樣做：

json.dump(x, f)

若 f 是一個已開啟、可讀取的 binary file 或 text file 物件，要再次解碼物件的話：

x = json.load(f)

備註

JSON 檔案必須以 UTF-8 格式編碼。在開啟 JSON 檔案以作為一個可讀取與寫入的 text file 時，要用 encoding="utf-8"。

這種簡單的序列化技術可以處理 list 和 dictionary，但要在 JSON 中序列化任意的 class（類別）實例，則需要一些額外的工作。json 模組的參考資料包含對此的說明。

也參考

pickle - pickle 模組

與 JSON 不同，pickle 是一種允許對任意的複雜 Python 物件進行序列化的協定。因此，它為 Python 所特有，不能用於與其他語言編寫的應用程式溝通。在預設情況，它也是不安全的：如果資料是由手段高明的攻擊者精心設計，將這段來自於不受信任來源的 pickle 資料反序列化，可以執行任意的程式碼。

8. 錯誤和例外

到目前為止還沒有提到錯誤訊息，但如果你嘗試運行範例，你可能會發現一些錯誤訊息。常見的（至少）兩種不同的錯誤類別為：語法錯誤 (syntax error) 和例外 (exception)。

8.1. 語法錯誤 (Syntax Error)

語法錯誤又稱剖析錯誤 (parsing error)，它或許是學習 Python 的過程最常聽見的抱怨：

>>> while True print('Hello world')
  File "<stdin>", line 1
    while True print('Hello world')
               ^^^^^
SyntaxError: invalid syntax

剖析器 (parser) 會重複犯錯的那一行，並用一個小箭頭指向該行檢測到錯誤的地方，但請注意這並非都會是應該去修改的地方。此例中，錯誤是在 print() 函式中被檢測到，因為在它前面少了一個冒號 (':')。

檔案名稱（此例中為 <stdin>）和列號會被印出來，所以如果訊息是來自一個檔案時，就可以知道去哪裡找問題。

8.2. 例外 (Exception)

即使一段陳述式或運算式使用了正確的語法，嘗試執行時仍可能導致錯誤。執行時檢測到的錯誤稱為例外，例外不一定都很嚴重：你很快就能學會在 Python 程式中如何處理它們。不過大多數的例外不會被程式處理，並且會顯示如下的錯誤訊息：

>>> 10 * (1/0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    10 * (1/0)
          ~^~
ZeroDivisionError: division by zero
>>> 4 + spam*3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    4 + spam*3
        ^^^^
NameError: name 'spam' is not defined
>>> '2' + 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    '2' + 2
    ~~~~^~~
TypeError: can only concatenate str (not "int") to str

錯誤訊息的最後一行指示發生了什麼事。例外有不同的類型，而類型名稱會作為訊息的一部份被印出。範例中的例外類型為：ZeroDivisionError、NameError 和 TypeError。作為例外類型被印出的字串，就是發生的內建例外 (built-in exception) 的名稱。所有的內建例外都是如此運作，但對於使用者自定的例外則不一定需要遵守（雖然這是一個有用的慣例）。標準例外名稱是內建的識別字 (identifier)，不是保留關鍵字 (reserved keyword)。

此行其餘部分，根據例外的類型及導致例外的原因，說明例外的細節。

錯誤訊息的開頭，用堆疊回溯 (stack traceback) 的形式顯示發生例外的語境。一般來說，它含有一個列出源程式碼行 (source line) 的堆疊回溯；但它不會顯示從標準輸入中讀取的程式碼。

內建的例外章節列出內建的例外及它們的意義。

8.3. 處理例外

編寫程式處理選定的例外是可行的。以下範例會要求使用者輸入內容，直到有效的整數被輸入為止，但它允許使用者中斷程式（使用 Control-C 或作業系統支援的指令）；請注意，由使用者產生的程式中斷會引發 KeyboardInterrupt 例外信號。

>>> while True:
...     try:
...         x = int(input("Please enter a number: "))
...         break
...     except ValueError:
...         print("Oops!  That was no valid number.  Try again...")
...

try 陳述式運作方式如下。

首先，執行 try 子句（try 和 except 關鍵字之間的陳述式）。

如果沒有發生例外，則 except 子句會被跳過，try 陳述式執行完畢。

如果執行 try 子句時發生了例外，則該子句中剩下的部分會被跳過。如果例外的類型與 except 關鍵字後面的例外名稱相符，則 except 子句被執行，然後，繼續執行 try/except 區塊之後的程式碼。

如果發生的例外未符合 except 子句 中的例外名稱，則將其傳遞到外層的 try 陳述式；如果仍無法找到處理者，則它是一個未處理例外 (unhandled exception)，執行將停止，並顯示錯誤訊息。

try 陳述式可以有不只一個 except 子句，為不同的例外指定處理者，而最多只有一個處理者會被執行。處理者只處理對應的 try 子句中發生的例外，而不會處理同一 try 陳述式裡其他處理者內的例外。一個 except 子句可以用一組括號內的 tuple 列舉多個例外，例如：

... except (RuntimeError, TypeError, NameError):
...     pass

except 子句中的一個類別符合該類別本身或它的衍生類別的例外（但不是反過來 -- 列出一個衍生類別的 except 子句不會符合它的基底類別的例外）。例如，以下程式碼會按照 B、C、D 的順序印出：

class B(Exception):
    pass

class C(B):
    pass

class D(C):
    pass

for cls in [B, C, D]:
    try:
        raise cls()
    except D:
        print("D")
    except C:
        print("C")
    except B:
        print("B")

請注意，如果 except 子句的順序被反轉（把 except B 放到第一個），則會印出 B、B、B ——第一個符合的 except 子句會被觸發。

當例外發生時，它可能有相關聯的值，也就是例外的引數。引數的存在與否及它的類型，是取決於例外的類型。

except 子句可以在例外名稱後面指定一個變數。這個變數被綁定到一個例外實例 (instance)，其引數通常儲存在 args 屬性中。為了方便，內建例外型別定義了 __str__() 以印出所有引數而不需顯式地取用 .args：

>>> try:
...     raise Exception('spam', 'eggs')
... except Exception as inst:
...     print(type(inst))    # 例外的型別
...     print(inst.args)     # 儲存在 .args 中的引數
...     print(inst)          # __str__ 使得引數可以直接被印出，
...                          # 但可能在例外的子類別中被覆蓋
...     x, y = inst.args     # 解包引數
...     print('x =', x)
...     print('y =', y)
...
<class 'Exception'>
('spam', 'eggs')
('spam', 'eggs')
x = spam
y = eggs

例外的 __str__() 輸出會被印在未處理例外訊息的最後一部分（「細節」）。

BaseException 是由全部的例外所共用的 base class。它的 subclass（子類別）之一，Exception，則是所有非嚴重例外 (non-fatal exception) 的 base class。有些例外不是 Exception 的 subclass，而它們通常不會被處理，因為它們是用來指示程式應該終止。這些例外包括了由 sys.exit() 所引發的 SystemExit，以及當使用者想要中斷程式時所引發的 KeyboardInterrupt。

Exception 可以用作通配符 (wildcard) 來捕獲（幾乎）所有的例外。然而，比較好的做法是盡可能具體地說明我們打算處理的例外類型，並容許任何非預期例外的傳遞 (propagate)。

處理 Exception 的最常見模式，是先將該例外印出或記錄，然後再重新引發它（也允許一個呼叫函式 (caller) 來處理該例外）：

import sys

try:
    f = open('myfile.txt')
    s = f.readline()
    i = int(s.strip())
except OSError as err:
    print("OS error:", err)
except ValueError:
    print("Could not convert data to an integer.")
except Exception as err:
    print(f"Unexpected {err=}, {type(err)=}")
    raise

try ... except 陳述式有一個選擇性的 else 子句，使用時，該子句必須放在所有 except 子句之後。如果一段程式碼必須被執行，但 try 子句又沒有引發例外時，這個子句很有用。例如：

for arg in sys.argv[1:]:
    try:
        f = open(arg, 'r')
    except OSError:
        print('cannot open', arg)
    else:
        print(arg, 'has', len(f.readlines()), 'lines')
        f.close()

使用 else 子句比向 try 子句添加額外的程式碼要好，因為這可以避免意外地捕獲不是由 try ... except 陳述式保護的程式碼所引發的例外。

例外的處理者不僅處理 try 子句內立即發生的例外，還處理 try 子句內（即使是間接地）呼叫的函式內部發生的例外。例如：

>>> def this_fails():
...     x = 1/0
...
>>> try:
...     this_fails()
... except ZeroDivisionError as err:
...     print('Handling run-time error:', err)
...
Handling run-time error: division by zero

8.4. 引發例外

raise 陳述式可讓程式設計師強制引發指定的例外。例如：

>>> raise NameError('HiThere')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    raise NameError('HiThere')
NameError: HiThere

raise 唯一的引數就是要引發的例外。該引數必須是一個例外實例或例外 class（衍生自 BaseException 的 class，例如 Exception 與它的 subclass）。如果一個例外 class 被傳遞，它會不含引數地呼叫它的建構函式 (constructor) ，使它被自動建立實例 (implicitly instantiated)：

raise ValueError  # 'raise ValueError()' 的簡寫

如果你只想判斷是否引發了例外，但並不打算處理它，則可以使用簡單的 raise 陳述式來重新引發該例外：

>>> try:
...     raise NameError('HiThere')
... except NameError:
...     print('An exception flew by!')
...     raise
...
An exception flew by!
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    raise NameError('HiThere')
NameError: HiThere

8.5. 例外鏈接 (Exception Chaining)

如果在 except 段落內部發生了一個未處理的例外，則它會讓這個將要被處理的例外附加在後，並將其包含在錯誤訊息中：

>>> try:
...     open("database.sqlite")
... except OSError:
...     raise RuntimeError("unable to handle error")
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    open("database.sqlite")
    ~~~~^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'database.sqlite'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
    raise RuntimeError("unable to handle error")
RuntimeError: unable to handle error

為了表明一個例外是另一個例外直接造成的結果，raise 陳述式容許一個選擇性的 from 子句：

# exc 必須是例外實例或 None。
raise RuntimeError from exc

要變換例外時，這種方式很有用。例如：

>>> def func():
...     raise ConnectionError
...
>>> try:
...     func()
... except ConnectionError as exc:
...     raise RuntimeError('Failed to open database') from exc
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    func()
    ~~~~^^
  File "<stdin>", line 2, in func
ConnectionError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
    raise RuntimeError('Failed to open database') from exc
RuntimeError: Failed to open database

它也容許使用慣用語 from None 來停用自動例外鏈接：

>>> try:
...     open('database.sqlite')
... except OSError:
...     raise RuntimeError from None
...
Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
    raise RuntimeError from None
RuntimeError

更多關於鏈接機制的資訊，詳見內建的例外。

8.6. 使用者自定的例外

程式可以透過建立新的例外 class 來命名自己的例外（深入了解 Python class，詳見Class（類別））。不論是直接還是間接地，例外通常應該從 Exception class 衍生出來。

例外 class 可被定義來做任何其他 class 能夠做的事，但通常會讓它維持簡單，只提供一些屬性，讓關於錯誤的資訊可被例外的處理者抽取出來。

大多數的例外定義，都會以「Error」作為名稱結尾，類似於標準例外的命名。

許多標準模組會定義它們自己的例外，以報告在其定義的函式中發生的錯誤。

8.7. 定義清理動作

try 陳述式有另一個選擇性子句，用於定義在所有情況下都必須被執行的清理動作。例如：

>>> try:
...     raise KeyboardInterrupt
... finally:
...     print('Goodbye, world!')
...
Goodbye, world!
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    raise KeyboardInterrupt
KeyboardInterrupt

如果 finally 子句存在，則 finally 子句會是 try 陳述式結束前執行的最後一項任務。不論 try 陳述式是否產生例外，都會執行 finally 子句。以下幾點將探討例外發生時，比較複雜的情況：

若一個例外發生於 try 子句的執行過程，則該例外會被某個 except 子句處理。如果該例外沒有被 except 子句處理，它會在 finally 子句執行後被重新引發。

一個例外可能發生於 except 或 else 子句的執行過程。同樣地，該例外會在 finally 子句執行後被重新引發。

如果 finally 子句執行 break、continue 或 return 陳述式，則例外不會被重新引發。這可能會令人困惑，因此不建議這麼做。從 3.14 版本開始，編譯器會為此發出 SyntaxWarning（詳見 PEP 765 [https://peps.python.org/pep-0765/]）。

如果 try 陳述式遇到 break、continue 或 return 陳述式，則 finally 子句會在執行 break、continue 或 return 陳述式之前先執行。

如果 finally 子句中包含 return 陳述式，則回傳值會是來自 finally 子句的 return 陳述式的回傳值，而不是來自 try 子句的 return 陳述式的回傳值。這可能會令人困惑，因此不建議這麼做。從 3.14 版本開始，編譯器會為此發出 SyntaxWarning（詳見 PEP 765 [https://peps.python.org/pep-0765/]）。

例如：

>>> def bool_return():
...     try:
...         return True
...     finally:
...         return False
...
>>> bool_return()
False

另一個比較複雜的範例：

>>> def divide(x, y):
...     try:
...         result = x / y
...     except ZeroDivisionError:
...         print("division by zero!")
...     else:
...         print("result is", result)
...     finally:
...         print("executing finally clause")
...
>>> divide(2, 1)
result is 2.0
executing finally clause
>>> divide(2, 0)
division by zero!
executing finally clause
>>> divide("2", "1")
executing finally clause
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    divide("2", "1")
    ~~~~~~^^^^^^^^^^
  File "<stdin>", line 3, in divide
    result = x / y
             ~~^~~
TypeError: unsupported operand type(s) for /: 'str' and 'str'

如你所見，finally 子句在任何情況下都會被執行。兩個字串相除所引發的 TypeError 沒有被 except 子句處理，因此會在 finally 子句執行後被重新引發。

在真實應用程式中，finally 子句對於釋放外部資源（例如檔案或網路連線）很有用，無論該資源的使用是否成功。

8.8. 預定義的清理動作

某些物件定義了在物件不再被需要時的標準清理動作，無論使用該物件的作業是成功或失敗。請看以下範例，它嘗試開啟一個檔案，並印出檔案內容至螢幕。

for line in open("myfile.txt"):
    print(line, end="")

這段程式碼的問題在於，執行完該程式碼後，它讓檔案在一段不確定的時間內處於開啟狀態。在簡單腳本中這不是問題，但對於較大的應用程式來說可能會是個問題。with 陳述式讓物件（例如檔案）在被使用時，能保證它們總是及時、正確地被清理。

with open("myfile.txt") as f:
    for line in f:
        print(line, end="")

陳述式執行完畢後，就算是在處理內容時遇到問題，檔案 f 總是會被關閉。和檔案一樣，提供預定義清理動作的物件會在說明文件中表明這一點。

8.9. 引發及處理多個無關的例外

在某些情況下，必須回報已經發生的多個例外。在並行框架 (concurrency framework) 中經常會出現這種情況，當平行的 (parallel) 某些任務可能已經失效，但還有其他用例 (use case) 希望能繼續執行並收集多個例外，而不是只有引發第一個例外時。

內建的 ExceptionGroup 會包裝一個例外實例 (exception instance) 的 list（串列），使得它們可以一起被引發。由於它本身就是一個例外，因此它也可以像任何其他例外一樣被捕獲。

>>> def f():
...     excs = [OSError('error 1'), SystemError('error 2')]
...     raise ExceptionGroup('there were problems', excs)
...
>>> f()
  + Exception Group Traceback (most recent call last):
  |   File "<stdin>", line 1, in <module>
  |     f()
  |     ~^^
  |   File "<stdin>", line 3, in f
  |     raise ExceptionGroup('there were problems', excs)
  | ExceptionGroup: there were problems (2 sub-exceptions)
  +-+---------------- 1 ----------------
    | OSError: error 1
    +---------------- 2 ----------------
    | SystemError: error 2
    +------------------------------------
>>> try:
...     f()
... except Exception as e:
...     print(f'caught {type(e)}: e')
...
caught <class 'ExceptionGroup'>: e
>>>

若使用 except* 代替 except，我們可以選擇性地只處理該群組中與特定類型匹配的例外。在以下範例中，展示了一個巢狀的例外群組 (exception group)，每個 except* 子句分別從該群組中提取一個特定類型的例外，同時讓所有其他的例外都傳遞到其他子句，最後再被重新引發。

>>> def f():
...     raise ExceptionGroup(
...         "group1",
...         [
...             OSError(1),
...             SystemError(2),
...             ExceptionGroup(
...                 "group2",
...                 [
...                     OSError(3),
...                     RecursionError(4)
...                 ]
...             )
...         ]
...     )
...
>>> try:
...     f()
... except* OSError as e:
...     print("There were OSErrors")
... except* SystemError as e:
...     print("There were SystemErrors")
...
There were OSErrors
There were SystemErrors
  + Exception Group Traceback (most recent call last):
  |   File "<stdin>", line 2, in <module>
  |     f()
  |     ~^^
  |   File "<stdin>", line 2, in f
  |     raise ExceptionGroup(
  |     ...<12 lines>...
  |     )
  | ExceptionGroup: group1 (1 sub-exception)
  +-+---------------- 1 ----------------
    | ExceptionGroup: group2 (1 sub-exception)
    +-+---------------- 1 ----------------
      | RecursionError: 4
      +------------------------------------
>>>

請注意，被巢套在例外群組中的例外必須是實例，而不是類型。這是因為在實務上，這些例外通常是已經被程式引發並捕獲的例外，類似以下的模式：

>>> excs = []
... for test in tests:
...     try:
...         test.run()
...     except Exception as e:
...         excs.append(e)
...
>>> if excs:
...    raise ExceptionGroup("Test Failures", excs)
...

8.10. 用註解使例外更詳細

當一個例外是為了被引發而建立時，它通常會伴隨著一些資訊被初始化，這些資訊描述了當下發生的錯誤。在某些情況，在例外被捕獲之後添加資訊會很有用。為此，例外具有一個 add_note(note) method（方法），它可以接受一個字串並將其添加到例外的註解清單中。標準的回溯呈現會在例外之後列出所有的註解，並按照其被添加的順序來排列。

>>> try:
...     raise TypeError('bad type')
... except Exception as e:
...     e.add_note('Add some information')
...     e.add_note('Add some more information')
...     raise
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    raise TypeError('bad type')
TypeError: bad type
Add some information
Add some more information
>>>

例如，在將例外收集到例外群組中時，我們可能希望為各個錯誤添加一些上下文的資訊。在以下範例中，群組中的每個例外都有一條註解，指示此錯誤是在何時發生。

>>> def f():
...     raise OSError('operation failed')
...
>>> excs = []
>>> for i in range(3):
...     try:
...         f()
...     except Exception as e:
...         e.add_note(f'Happened in Iteration {i+1}')
...         excs.append(e)
...
>>> raise ExceptionGroup('We have some problems', excs)
  + Exception Group Traceback (most recent call last):
  |   File "<stdin>", line 1, in <module>
  |     raise ExceptionGroup('We have some problems', excs)
  | ExceptionGroup: We have some problems (3 sub-exceptions)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   File "<stdin>", line 3, in <module>
    |     f()
    |     ~^^
    |   File "<stdin>", line 2, in f
    |     raise OSError('operation failed')
    | OSError: operation failed
    | Happened in Iteration 1
    +---------------- 2 ----------------
    | Traceback (most recent call last):
    |   File "<stdin>", line 3, in <module>
    |     f()
    |     ~^^
    |   File "<stdin>", line 2, in f
    |     raise OSError('operation failed')
    | OSError: operation failed
    | Happened in Iteration 2
    +---------------- 3 ----------------
    | Traceback (most recent call last):
    |   File "<stdin>", line 3, in <module>
    |     f()
    |     ~^^
    |   File "<stdin>", line 2, in f
    |     raise OSError('operation failed')
    | OSError: operation failed
    | Happened in Iteration 3
    +------------------------------------
>>>

9. Class（類別）

Class 提供了一種結合資料與功能的手段。建立一個 class 將會新增一個物件的型別 (type)，並且允許建立該型別的新實例 (instance)。每一個 class 實例可以擁有一些維持該實例狀態的屬性 (attribute)。Class 實例也可以有一些（由其 class 所定義的）method（方法），用於修改該實例的狀態。

與其他程式語言相比，Python 的 class 機制為 class 增加了最少的新語法跟語意。他混合了 C++ 和 Modula-3 的 class 機制。Python 的 class 提供了所有物件導向程式設計 (Object Oriented Programming) 的標準特色：class 繼承機制允許多個 base class（基底類別），一個 derived class（衍生類別）可以覆寫 (override) 其 base class 的任何 method，且一個 method 可以用相同的名稱呼叫其 base class 的 method。物件可以包含任意數量及任意種類的資料。如同模組一樣，class 也具有 Python 的動態特性：他們在執行期 (runtime) 被建立，且可以在建立之後被修改。

在 C++ 的術語中，class 成員（包含資料成員）通常都是公開的（除了以下內容：私有變數），而所有的成員函式都是虛擬的。如同在 Modula-3 中一樣，Python 並沒有提供簡寫可以從物件的 method 裡參照其成員：method 函式與一個外顯的 (explicit)、第一個代表物件的引數被宣告，而此引數是在呼叫時隱性地 (implicitly) 被提供。如同在 Smalltak 中，class 都是物件，這為 import 及重新命名提供了語意。不像 C++ 和 Modula-3，Pyhon 內建的型別可以被使用者以 base class 用於其他擴充 (extension)。另外，如同在 C++ 中，大多數有著特別語法的內建運算子（算術運算子、下標等）都可以為了 class 實例而被重新定義。

（由於缺乏普遍能接受的術語來討論 class，我偶爾會使用 Smalltalk 和 C++ 的術語。我會使用 Modula-3 的術語，因為它比 C++ 更接近 Python 的物件導向語意，但我預期比較少的讀者會聽過它。）

9.1. 關於名稱與物件的一段話

物件有個體性 (individuality)，且多個名稱（在多個作用域 (scope) ）可以被連結到相同的物件。這在其他語言中被稱為別名 (aliasing)。初次接觸 Python 時通常不會注意這件事，而在處理不可變的基本型別（數值、字串、tuple）時，它也可以安全地被忽略。然而，別名在含有可變物件（如 list（串列）、dictionary（字典）、和大多數其他的型別）的 Python 程式碼語意中，可能會有意外的效果。這通常有利於程式，因為別名在某些方面表現得像指標 (pointer)。舉例來說，在實作時傳遞一個物件是便宜的，因為只有指標被傳遞；假如函式修改了一個作為引數傳遞的物件，呼叫函式者 (caller) 能夠見到這些改變——這消除了在 Pascal 中兩個相異引數傳遞機制的需求。

9.2. Python 作用域 (Scope) 及命名空間 (Namespace)

在介紹 class 之前，我必須先告訴你一些關於 Python 作用域的規則。Class definition（類別定義）以命名空間展現了一些俐落的技巧，而你需要了解作用域和命名空間的運作才能完整理解正在發生的事情。順帶一提，關於這個主題的知識對任何進階的 Python 程式設計師都是很有用的。

讓我們從一些定義開始。

命名空間是從名稱到物件的對映。大部分的命名空間現在都是以 Python 的 dictionary 被實作，但通常不會以任何方式被察覺（除了性能），且它可能會在未來改變。命名空間的例子有：內建名稱的集合（包含如 abs() 的函式，和內建的例外名稱）；模組中的全域 (global) 名稱；和在函式呼叫中的區域 (local) 名稱。某種意義上，物件中的屬性集合也會形成一個命名空間。關於命名空間的重要一點是，不同命名空間中的名稱之間絕對沒有關係；舉例來說，兩個不一樣的模組都可以定義一個 maximize 函式而不會混淆——模組的使用者必須為它加上前綴 (prefix) 模組名稱。

順帶一提，我使用屬性 (attribute) 這個字，統稱句號 (dot) 後面的任何名稱——例如，運算式中的 z.real，real 是物件 z 的一個屬性。嚴格來說，模組中名稱的參照都是屬性參照：在運算式 modname.funcname 中，modname 是模組物件而 funcname 是它的屬性。在這種情況下，模組的屬性和模組中定義的全域名稱碰巧有一個直接的對映：他們共享了相同的命名空間！[1]

屬性可以是唯讀的或可寫的。在後者的情況下，對屬性的賦值是可能的。模組屬性是可寫的：你可以寫 modname.the_answer = 42。可寫屬性也可以用 del 陳述式刪除。例如，del modname.the_answer 將從名為 modname 的物件中刪除屬性 the_answer。

命名空間在不同的時刻被建立，並且有不同的壽命。當 Python 直譯器啟動時，含有內建名稱的命名空間會被建立，並且永遠不會被刪除。當模組定義被讀入時，模組的全域命名空間會被建立；一般情況下，模組的命名空間也會持續到直譯器結束。被直譯器的頂層呼叫 (top-level invocation) 執行的陳述式，不論是從腳本檔案讀取的或是互動模式中的，會被視為一個稱為 __main__ 的模組的一部分，因此它們具有自己的全域命名空間。（內建名稱實際上也存在一個模組中，它被稱為 builtins。）

函式的區域命名空間是在呼叫函式時建立的，而當函式回傳，或引發了未在函式中處理的例外時，此命名空間將會被刪除。（實際上，忘記是描述實際發生的事情的更好方法。） 當然，每個遞迴呼叫 (recursive invocation) 都有自己的區域命名空間。

作用域是 Python 程式中的一個文本區域 (textual region)，在此區域，命名空間是可直接存取的。這裡的「可直接存取的」意思是，對一個名稱的非限定參照 (unqualified reference) 可以在命名空間內嘗試尋找該名稱。

儘管作用域是靜態地被決定，但它們是動態地被使用的。在執行期間內的任何時間點，都會有 3 或 4 個巢狀的作用域，其命名空間是可以被直接存取的：

最內層作用域，會最先被搜尋，而它包含了區域名稱

任何外圍函式 (enclosing function) 的作用域，會從最近的外圍作用域開始搜尋，它包含了非區域 (non-local) 和非全域 (non-global) 的名稱

倒數第二個作用域，包含目前模組的全域名稱

最外面的作用域（最後搜尋），是包含內建名稱的命名空間

如果一個名稱被宣告為全域，則所有的參照和賦值將直接轉到包含模組全域名稱的倒數第二個作用域。要重新連結最內層作用域以外找到的變數，可以使用 nonlocal 陳述式；如果那些變數沒有被宣告為 nonlocal，則它們會是唯讀的（嘗試寫入這樣的變數只會在最內層的作用域內建立一個新的區域變數，同名的外部變數則維持不變）。

通常，區域作用域會參照（文本的）目前函式的區域名稱。在函式外部，區域作用域與全域作用域參照相同的命名空間：模組的命名空間。然而，Class definition 會在區域作用域中放置另一個命名空間。

務必要了解，作用域是按文本被決定的：在模組中定義的函式，其全域作用域便是該模組的命名空間，無論函式是從何處或以什麼別名被呼叫。另一方面，對名稱的實際搜尋是在執行時期 (run time) 動態完成的——但是，語言定義的發展，正朝向在「編譯」時期 (compile time) 的靜態名稱解析 (static name resolution)，所以不要太依賴動態名稱解析 (dynamic name resolution)！ （事實上，局部變數已經是靜態地被決定。）

一個 Python 的特殊癖好是——假如沒有 global 或 nonlocal 陳述式的效果——名稱的賦值 (assignment) 都會指向最內層作用域。賦值不會複製資料——它們只會把名稱連結至物件。刪除也是一樣：陳述式 del x 會從區域作用域參照的命名空間移除 x 的連結。事實上，引入新名稱的所有運算都使用區域作用域：特別是 import 陳述式和函式定義，會連結區域作用域內的模組或函式名稱。

global 陳述式可以用來表示特定變數存活在全域作用域，應該被重新綁定到那裡；nonlocal 陳述式表示特定變數存活在外圍作用域內，應該被重新綁定到那裡。

9.2.1. 作用域和命名空間的範例

這是一個範例，演示如何參照不同的作用域和命名空間，以及 global 和 nonlocal 如何影響變數的綁定：

def scope_test():
    def do_local():
        spam = "local spam"

    def do_nonlocal():
        nonlocal spam
        spam = "nonlocal spam"

    def do_global():
        global spam
        spam = "global spam"

    spam = "test spam"
    do_local()
    print("After local assignment:", spam)
    do_nonlocal()
    print("After nonlocal assignment:", spam)
    do_global()
    print("After global assignment:", spam)

scope_test()
print("In global scope:", spam)

範例程式碼的輸出是：

After local assignment: test spam
After nonlocal assignment: nonlocal spam
After global assignment: nonlocal spam
In global scope: global spam

請注意，區域賦值（預設情況）不會改變 scope_test 對 spam 的連結。nonlocal 賦值改變了 scope_test 對 spam 的連結，而 global 賦值改變了模組層次的連結。

你還可以發現，在 global 賦值之前，沒有對 spam 的連結。

9.3. 初見 class

Class 採用一些新的語法，三個新的物件型別，以及一些新的語意。

9.3.1. Class definition（類別定義）語法

Class definition 最簡單的形式如下：

class ClassName:
    <statement-1>
    .
    .
    .
    <statement-N>

Class definition，如同函式定義（def 陳述式），必須在它們有任何效果前先執行。（你可以想像把 class definition 放在一個 if 陳述式的分支，或在函式裡。）

在實作時，class definition 內的陳述式通常會是函式定義，但其他陳述式也是允許的，有時很有用——我們稍後會回到這裡。Class 中的函式定義通常會有一個獨特的引數列表形式，取決於 method 的呼叫慣例——再一次地，這將會在稍後解釋。

當進入 class definition，一個新的命名空間將會被建立，並且作為區域作用域——因此，所有區域變數的賦值將進入這個新的命名空間。特別是，函式定義會在這裡連結新函式的名稱。

正常地（從結尾處）離開 class definition 時，一個 class 物件會被建立。基本上這是一個包裝器 (wrapper)，裝著 class definition 建立的命名空間內容；我們將在下一節中更加了解 class 物件。原始的區域作用域（在進入 class definition 之前已生效的作用域）會恢復，在此 class 物件會被連結到 class definition 標頭中給出的 class 名稱（在範例中為 ClassName）。

9.3.2. Class 物件

Class 物件支援兩種運算：屬性參照 (attribute reference) 和實例化 (instantiation)。

屬性參照使用 Python 中所有屬性參照的標準語法：obj.name。有效的屬性名稱是 class 物件被建立時，class 的命名空間中所有的名稱。所以，如果 class definition 看起來像這樣：

class MyClass:
    """一個簡單的類別範例"""
    i = 12345

    def f(self):
        return 'hello world'

那麼 MyClass.i 和 MyClass.f 都是有效的屬性參照，會分別回傳一個整數和一個函式物件。Class 屬性也可以被指派 (assign)，所以你可以透過賦值改變 MyClass.i 的值。__doc__ 也是一個有效的屬性，會回傳屬於該 class 的說明字串 (docstring)："A simple example class"。

Class 實例化使用了函式記法 (function notation)。就好像 class 物件是一個沒有參數的函式，它回傳一個新的 class 實例。例如（假設是上述的 class）：

x = MyClass()

建立 class 的一個新實例，並將此物件指派給區域變數 x。

實例化運算（「呼叫」一個 class 物件）會建立一個空的物件。許多 class 喜歡在建立物件時有著自訂的特定實例初始狀態。因此，class 可以定義一個名為 __init__() 的特別 method，像這樣：

def __init__(self):
    self.data = []

當 class 定義了 __init__() method，class 實例化會為新建的 class 實例自動叫用 __init__()。所以在這個範例中，一個新的、初始化的實例可以如此獲得：

x = MyClass()

當然，__init__() method 可能為了更多的彈性而有引數。在這種情況下，要給 class 實例化運算子的引數會被傳遞給 __init__()。例如：

>>> class Complex:
...     def __init__(self, realpart, imagpart):
...         self.r = realpart
...         self.i = imagpart
...
>>> x = Complex(3.0, -4.5)
>>> x.r, x.i
(3.0, -4.5)

9.3.3. 實例物件

現在，我們可以如何處理實例物件？實例物件能理解的唯一運算就是屬性參照。有兩種有效的屬性名稱：資料屬性 (data attribute) 和 method。

資料屬性對應 Smalltalk 中的「實例變數」，以及 C++ 中的「資料成員」。資料屬性不需要被宣告；和區域變數一樣，它們在第一次被賦值時就會立即存在。例如，如果 x 是 MyClass 在上述例子中建立的實例，下面的程式碼將印出值 16，而不留下蹤跡：

x.counter = 1
while x.counter < 10:
    x.counter = x.counter * 2
print(x.counter)
del x.counter

另一種執行個體屬性參考是 方法 (method)。方法是"屬於"一個物件的函式。

實例物件的有效 method 名稱取決於其 class。根據定義，一個 class 中所有的函式物件屬性，就定義了實例的對應 method。所以在我們的例子中，x.f 是一個有效的 method 參照，因為 MyClass.f 是一個函式，但 x.i 不是，因為 MyClass.i 不是。但 x.f 與 MyClass.f 是不一樣的——它是一個 method 物件，而不是函式物件。

9.3.4. Method 物件

通常，一個 method 在它被連結後隨即被呼叫：

x.f()

如果像上面一樣 x = MyClass()，這將回傳字串 'hello world'。然而，並沒有必要立即呼叫一個 method：x.f 是一個 method 物件，並且可以被儲藏起來，之後再被呼叫。舉例來說：

xf = x.f
while True:
    print(xf())

將會持續印出 hello world 直到天荒地老。

當一個 method 被呼叫時究竟會發生什麼事？你可能已經注意到 x.f() 被呼叫時沒有任何的引數，儘管 f() 的函式定義有指定一個引數。這個引數發生了什麼事？當一個需要引數的函式被呼叫而沒有給任何引數時，Python 肯定會引發例外——即使該引數實際上沒有被使用...

事實上，你可能已經猜到了答案：method 的特殊之處在於，實例物件會作為函式中的第一個引數被傳遞。在我們的例子中，x.f() 這個呼叫等同於 MyClass.f(x)。一般來說，呼叫一個有 n 個引數的 method，等同於呼叫一個對應函式，其引數列表 (argument list) 被建立時，會在第一個引數前插入該 method 的實例物件。

一般來說，方法的工作原理如下。當一個實例的非資料屬性被參照時，將會搜尋該實例的 class。如果該名稱是一個有效的 class 屬性，而且是一個函式物件，則對實例物件和函式物件的參照都會被打包到方法物件中。當使用引數串列呼叫方法物件時，會根據實例物件和引數串列來建構一個新的引數串列，並使用該新引數串列來呼叫函式物件。

9.3.5. Class 及實例變數

一般來說，實例變數用於每一個實例的獨特資料，而 class 變數用於該 class 的所有實例共享的屬性和 method：

class Dog:

    kind = 'canine'         # 所有實例共享的類別變數

    def __init__(self, name):
        self.name = name    # 每個實例獨有的實例變數

>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.kind                  # 為所有 Dog 實例所共享
'canine'
>>> e.kind                  # 為所有 Dog 實例所共享
'canine'
>>> d.name                  # d 獨有
'Fido'
>>> e.name                  # e 獨有
'Buddy'

如同在關於名稱與物件的一段話的討論，共享的資料若涉及 mutable 物件，如 list 和 dictionary，可能會產生意外的影響。舉例來說，下列程式碼的 tricks list 不應該作為一個 class 變數使用，因為這個 list 將會被所有的 Dog 實例所共享：

class Dog:

    tricks = []             # 誤用類別變數

    def __init__(self, name):
        self.name = name

    def add_trick(self, trick):
        self.tricks.append(trick)

>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.add_trick('roll over')
>>> e.add_trick('play dead')
>>> d.tricks                # 出乎意料地被所有 dog 共享
['roll over', 'play dead']

正確的 class 設計應該使用實例變數：

class Dog:

    def __init__(self, name):
        self.name = name
        self.tricks = []    # 為每一個 dog 建立空 list

    def add_trick(self, trick):
        self.tricks.append(trick)

>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.add_trick('roll over')
>>> e.add_trick('play dead')
>>> d.tricks
['roll over']
>>> e.tricks
['play dead']

9.4. 隨意的備註

如果屬性名稱同時出現在一個實例和一個 class 中，則屬性的尋找會以實例為優先：

>>> class Warehouse:
...    purpose = 'storage'
...    region = 'west'
...
>>> w1 = Warehouse()
>>> print(w1.purpose, w1.region)
storage west
>>> w2 = Warehouse()
>>> w2.region = 'east'
>>> print(w2.purpose, w2.region)
storage east

資料屬性可能被 method 或是被物件的一般使用者（「用戶端」）所參照。也就是說，class 不可用於實作純粹抽象的資料型別。事實上，在 Python 中沒有任何可能的方法，可強制隱藏資料——這都是基於慣例。（另一方面，以 C 編寫的 Python 實作可以完全隱藏實作細節並且在必要時控制物件的存取；這可以被以 C 編寫的 Python 擴充所使用。）

用戶端應該小心使用資料屬性——用戶端可能會因為覆寫他們的資料屬性，而破壞了被 method 維護的不變性。注意，用戶端可以增加他們自己的資料屬性到實例物件，但不影響 method 的有效性，只要避免名稱衝突即可——再一次提醒，命名慣例可以在這裡節省很多麻煩。

在 method 中參照資料屬性（或其他 method！）是沒有簡寫的。我發現這實際上增加了 method 的可閱讀性：在瀏覽 method 時，絕不會混淆區域變數和實例變數。

通常，方法的第一個引數稱為 self。這僅僅只是一個慣例：self 這個名字對 Python 來說完全沒有特別的意義。但請注意，如果不遵循慣例，你的程式碼可能對其他 Python 程式設計師來說可讀性較低，此外，也可以想像一個可能因信任此慣例而編寫的 class 瀏覽器 (browser) 程式。

任何一個作為 class 屬性的函式物件都為該 class 的實例定義了一個相應的 method。函式定義不一定要包含在 class definition 的文本中：將函式物件指定給 class 中的區域變數也是可以的。例如：

# 在類別以外定義的函式
def f1(self, x, y):
    return min(x, x+y)

class C:
    f = f1

    def g(self):
        return 'hello world'

    h = g

現在 f、g 和 h 都是 class C 的屬性，並指向函式物件，所以他們都是class C 實例的 method —— h 與 g 是完全一樣的。請注意，這種做法通常只會使該程式的讀者感到困惑。

Method 可以藉由使用 self 引數的 method 屬性，呼叫其他 method：

class Bag:
    def __init__(self):
        self.data = []

    def add(self, x):
        self.data.append(x)

    def addtwice(self, x):
        self.add(x)
        self.add(x)

Method 可以用與一般函式相同的方式參照全域名稱。與 method 相關的全域作用域，就是包含其定義的模組。（class 永遠不會被用作全域作用域。）雖然人們很少有在 method 中使用全域資料的充分理由，但全域作用域仍有許多合法的使用：比方說，被 import 至全域作用域的函式和模組，可以被 method 以及在該作用域中定義的函式和 class 所使用。通常，包含 method 的 class，它本身就是被定義在這個全域作用域，在下一節，我們將看到 method 想要參照自己的 class 的一些好原因。

每個值都是一個物件，因此都具有一個 class，也可以稱為它的 type（型別）。它以 object.__class__ 被儲存。

9.5. 繼承 (Inheritance)

當然，如果沒有支援繼承，「class」這個語言特色就不值得被稱為 class。一個 derived class（衍生類別）定義的語法看起來如下：

class DerivedClassName(BaseClassName):
    <statement-1>
    .
    .
    .
    <statement-N>

名稱 BaseClassName 必須被定義於作用域可及的命名空間，且該作用域要包含 derived class 定義。要代替 base class（基底類別）的名稱，用其他任意的運算式也是被允許的。這會很有用，例如，當一個 base class 是在另一個模組中被定義時：

class DerivedClassName(modname.BaseClassName):

執行 derived class 定義的過程，與執行 base class 相同。當 class 物件被建構時，base class 會被記住。這是用於解析屬性參照：如果一個要求的屬性無法在該 class 中找到，則會繼續在 base class 中搜尋。假如該 base class 本身也是衍生自其他 class，則這個規則會遞迴地被應用。

關於 derived class 的實例化並沒有特別之處：DerivedClassName() 會建立該 class 的一個新實例。Method 的參照被解析如下：對應的 class 屬性會被搜尋，如果需要，沿著 base class 的繼承鍊往下走，如果這產生了一個函式物件，則該 method 的參照是有效的。

Derived class 可以覆寫其 base class 的 method。因為 method 在呼叫同一個物件的其他 method 時沒有特別的特權，所以當 base class 的一個 method 在呼叫相同 base class 中定義的另一個 method 時，最終可能會呼叫到一個覆寫它的 derived class 中的 method。（給 C++ 程式設計師：Python 中所有 method 實際上都是 virtual。）

一個在 derived class 覆寫的 method 可能事實上是想要擴充而非單純取代 base class 中相同名稱的 method。要直接呼叫 base class 的 method 有一個簡單的方法：只要呼叫 BaseClassName.methodname(self, arguments)。這有時對用戶端也很有用。（請注意，只有在 base class 在全域作用域可以用 BaseClassName 被存取時，這方法才有效。）

Python 有兩個內建函式可以用於繼承：

使用 isinstance() 判斷一個實例的型別：isinstance(obj, int) 只有在 obj.__class__ 是 int 或衍伸自 int 時，結果才會是 True。

使用 issubclass() 判斷 class 繼承：issubclass(bool, int) 會是 True，因為 bool 是 int 的 subclass（子類別）。但是，issubclass(float, int) 是 False，因為 float 並不是 int 的 subclass。

9.5.1. 多重繼承

Python 也支援多重繼承的形式。一個有多個 base class 的 class definition 看起來像這樣子：

class DerivedClassName(Base1, Base2, Base3):
    <statement-1>
    .
    .
    .
    <statement-N>

在大多數情況下，最簡單的例子裡，你可以這樣思考，對於繼承自 parent class（父類別）的屬性，其搜尋規則為：深度優先、從左到右、在階層裡重疊的相同 class 中不重複搜尋。因此，假如有一個屬性在 DerivedClassName 沒有被找到，則在 Base1 搜尋它，接著（遞迴地）在 Base1 的 base class 中搜尋，假如在那裡又沒有找到的話，會在 Base2 搜尋，依此類推。

事實上，它稍微複雜一些；method 的解析順序是動態地變化，以支援對 super() 的合作呼叫。這個方式在其他的多重繼承語言中，稱為呼叫下一個方法 (call-next-method)，且比在單一繼承語言中的 super call（超級呼叫）來得更強大。

動態排序是必要的，因為多重繼承的所有情況都表現一或多的菱形關係（其中至少一個 parent class 可以從最底層 class 透過多個路徑存取）。例如，所有的 class 都繼承自 object，因此任何多重繼承的情況都提供了多個到達 object 的路徑。為了避免 base class 被多次存取，動態演算法以這些方式將搜尋順序線性化 (linearize)：保留每個 class 中規定的從左到右的順序、對每個 parent 只會呼叫一次、使用單調的 (monotonic) 方式（意思是，一個 class 可以被 subclassed（子類別化），而不會影響其 parent 的搜尋優先順序）。總之，這些特性使設計出可靠又可擴充、具有多重繼承的 class 成為可能。更多資訊，請見 Python 2.3 方法解析順序。

9.6. 私有變數

「私有」(private) 實例變數，指的是不在物件內部便無法存取的變數，這在 Python 中是不存在的。但是，大多數 Python 的程式碼都遵守一個慣例：前綴為一個底線的名稱（如：_spam）應被視為 API （應用程式介面）的非公有 (non-public) 部分（無論它是函式、方法或是資料成員）。這被視為一個實作細節，如有調整，亦不另行通知。

既然 class 私有的成員已有一個有效的用例（即避免名稱與 subclass 定義的名稱衝突），這種機制也存在另一個有限的支援，稱為 name mangling（名稱修飾）。任何格式為 __spam（至少兩個前導下底線，最多一個尾隨下底線）的物件名稱 (identifier) 會被文本地被替換為 _classname__spam，在此 classname 就是去掉前導下底線的目前 class 名稱。只要這個修飾是在 class 的定義之中發生，它就會在不考慮該物件名稱的語法位置的情況下完成。

也參考

參閱私有名稱修飾規格的詳情與特殊情況。

名稱修飾對於讓 subclass 覆寫 method 而不用破壞 class 內部的 method 呼叫，是有幫助的。舉例來說：

class Mapping:
    def __init__(self, iterable):
        self.items_list = []
        self.__update(iterable)

    def update(self, iterable):
        for item in iterable:
            self.items_list.append(item)

    __update = update   # 原始 update() 方法的私有副本

class MappingSubclass(Mapping):

    def update(self, keys, values):
        # 為 update() 提供新的函式簽名
        # 但不會破壞 __init__()
        for item in zip(keys, values):
            self.items_list.append(item)

在上例中，就算在 MappingSubclass 當中加入 __update 識別符，也能順利運作，因為在 Mapping class 中，它會被替換為 _Mapping__update，而在 MappingSubclass class 中，它會被替換為 _MappingSubclass__update。

請注意，修飾規則是被設計來避免意外；它仍可能存取或修改一個被視為私有的變數。這在特殊情況下甚至可能很有用，例如在除錯器 (debugger)。

另外也注意，傳遞給 exec() 或 eval() 的程式碼不會把叫用 class 的名稱視為目前的 class；這和 global 陳述式的效果類似，該效果同樣僅限於整體被位元組編譯後 (byte-compiled) 的程式碼。同樣的限制適用於 getattr()，setattr() 和 delattr()，以及直接參照 __dict__ 時。

9.7. 補充說明

如果有一種資料型別，類似於 Pascal 的「record」或 C 的「struct」，可以將一些有名稱的資料項目捆綁在一起，有時候這會很有用。符合語言習慣的做法是使用 dataclasses：

from dataclasses import dataclass

@dataclass
class Employee:
    name: str
    dept: str
    salary: int

>>> john = Employee('john', 'computer lab', 1000)
>>> john.dept
'computer lab'
>>> john.salary
1000

用來處理特殊抽象資料型別的一段 Python 程式碼，經常能以傳遞一個 class 來替代，此 class 模擬該資料型別的多種 method。例如，如果你有一個函式，它會從一個檔案物件來格式化某些資料，你也可以定義一個有 read() 和 readline() method 的 class 作為替代方式，從字串緩衝區取得資料，並將其作為引數來傳遞。

實例的 method 物件也具有屬性：m.__self__ 就是帶有 method m() 的實例物件，而 m.__func__ 則是該 method 所對應的函式物件。

9.8. 疊代器 (Iterator)

到目前為止，你可能已經注意到大多數的容器 (container) 物件都可以使用 for 陳述式來進行迴圈：

for element in [1, 2, 3]:
    print(element)
for element in (1, 2, 3):
    print(element)
for key in {'one':1, 'two':2}:
    print(key)
for char in "123":
    print(char)
for line in open("myfile.txt"):
    print(line, end='')

這種存取風格清晰、簡潔且方便。疊代器的使用在 Python 中處處可見且用法一致。在幕後，for 陳述式會在容器物件上呼叫 iter()。該函式回傳一個疊代器物件，此物件定義了 __next__() method，而此 method 會逐一存取容器中的元素。當元素用盡時，__next__() 將引發 StopIteration 例外，來通知 for 終止迴圈。你可以使用內建函式 next() 來呼叫 __next__() method；這個例子展示了它的運作方式：

>>> s = 'abc'
>>> it = iter(s)
>>> it
<str_iterator object at 0x10c90e650>
>>> next(it)
'a'
>>> next(it)
'b'
>>> next(it)
'c'
>>> next(it)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    next(it)
StopIteration

看過疊代器協定的幕後機制後，在你的 class 加入疊代器的行為就很容易了。定義一個 __iter__() method 來回傳一個帶有 __next__() method 的物件。如果 class 已定義了 __next__()，則 __iter__() 可以只回傳 self：

class Reverse:
    """用於向後迴圈遍歷序列的疊代器。"""
    def __init__(self, data):
        self.data = data
        self.index = len(data)

    def __iter__(self):
        return self

    def __next__(self):
        if self.index == 0:
            raise StopIteration
        self.index = self.index - 1
        return self.data[self.index]

>>> rev = Reverse('spam')
>>> iter(rev)
<__main__.Reverse object at 0x00A1DB50>
>>> for char in rev:
...     print(char)
...
m
a
p
s

9.9. 產生器 (Generator)

產生器是一個用於建立疊代器的簡單而強大的工具。它們的寫法和常規的函式一樣，但當它們要回傳資料時，會使用 yield 陳述式。每次在產生器上呼叫 next() 時，它會從上次離開的位置恢復執行（它會記得所有資料值以及上一個被執行的陳述式）。以下範例顯示，建立產生器可以相當地容易：

def reverse(data):
    for index in range(len(data)-1, -1, -1):
        yield data[index]

>>> for char in reverse('golf'):
...     print(char)
...
f
l
o
g

任何可以用產生器來完成的事，也能用以 class 為基礎的疊代器來完成，如同前一節的描述。而讓產生器的程式碼更為精簡的原因是，__iter__() 和 __next__() method 會自動被建立。

另一個關鍵的特性在於，區域變數和執行狀態會在每次呼叫之間自動被儲存。這使得該函式比使用 self.index 和 self.data 這種實例變數的方式更容易編寫且更為清晰。

除了會自動建立 method 和儲存程式狀態，當產生器終止時，它們還會自動引發 StopIteration。這些特性結合在一起，使建立疊代器能與編寫常規函式一樣容易。

9.10. 產生器運算式

某些簡單的產生器可以寫成如運算式一般的簡潔程式碼，所用的語法類似 list comprehension（串列綜合運算），但外層為括號而非方括號。這種運算式被設計用於產生器將立即被外圍函式 (enclosing function) 所使用的情況。產生器運算式與完整的產生器定義相比，程式碼較精簡但功能較少，也比等效的 list comprehension 更為節省記憶體。

例如：

>>> sum(i*i for i in range(10))                 # 平方和
285

>>> xvec = [10, 20, 30]
>>> yvec = [7, 5, 3]
>>> sum(x*y for x,y in zip(xvec, yvec))         # 向量內積
260

>>> unique_words = set(word for line in page  for word in line.split())

>>> valedictorian = max((student.gpa, student.name) for student in graduates)

>>> data = 'golf'
>>> list(data[i] for i in range(len(data)-1, -1, -1))
['f', 'l', 'o', 'g']

註解

[1]

有一個例外。模組物件有一個秘密的唯讀屬性，稱為 __dict__，它回傳用於實作模組命名空間的 dictionary；__dict__ 這個名稱是一個屬性但不是全域名稱。顯然，使用此屬性將違反命名空間實作的抽象化，而應該僅限用於事後除錯器 (post-mortem debugger) 之類的東西。

10. Python 標準函式庫概覽

10.1. 作業系統介面

os 模組提供了數十個與作業系統溝通的函式：

>>> import os
>>> os.getcwd()      # 回傳目前的工作目錄
'C:\\Python314'
>>> os.chdir('/server/accesslogs')   # 改變目前的工作目錄
>>> os.system('mkdir today')   # 在系統 shell 中執行 mkdir 指令
0

務必使用 import os 而非 from os import *。這將避免因系統不同而有實作差異的 os.open() 覆蓋內建函式 open()。

在使用 os 諸如此類大型模組時搭配內建函式 dir() 和 help() 是非常有用的：

>>> import os
>>> dir(os)
<returns a list of all module functions>
>>> help(os)
<returns an extensive manual page created from the module's docstrings>

對於日常檔案和目錄管理任務，shutil 模組提供了更容易使用的高階介面：

>>> import shutil
>>> shutil.copyfile('data.db', 'archive.db')
'archive.db'
>>> shutil.move('/build/executables', 'installdir')
'installdir'

10.2. 檔案之萬用字元 (File Wildcards)

glob 模組提供了一函式可以從目錄萬用字元中搜尋並產生檔案列表：

>>> import glob
>>> glob.glob('*.py')
['primes.py', 'random.py', 'quote.py']

10.3. 命令列引數

通用工具腳本常需要處理命令列引數。這些引數會以 list（串列）形式存放在 sys 模組的 argv 屬性中。例如以下 demo.py 檔案：

# demo.py 檔案
import sys
print(sys.argv)

以下是在命令列運行 python demo.py one two three 的輸出：

['demo.py', 'one', 'two', 'three']

argparse 模組提供了一種更複雜的機制來處理命令列引數。以下腳本可擷取一個或多個檔案名稱，並可選擇要顯示的行數：

import argparse

parser = argparse.ArgumentParser(
    prog='top',
    description='Show top lines from each file')
parser.add_argument('filenames', nargs='+')
parser.add_argument('-l', '--lines', type=int, default=10)
args = parser.parse_args()
print(args)

當 python top.py --lines=5 alpha.txt beta.txt 在命令列執行時，該腳本會將 args.lines 設為 5，並將 args.filenames 設為 ['alpha.txt', 'beta.txt']。

10.4. 錯誤輸出重新導向與程式終止

sys 模組也有 stdin，stdout，和 stderr 等屬性。即使當 stdout 被重新導向時，後者 stderr 可輸出警告和錯誤訊息：

>>> sys.stderr.write('Warning, log file not found starting a new one\n')
Warning, log file not found starting a new one

終止腳本最直接的方式就是利用 sys.exit()。

10.5. 字串樣式比對

re 模組提供正規表示式 (regular expression) 做進階的字串處理。當要處理複雜的比對以及操作時，正規表示式是簡潔且經過最佳化的解決方案：

>>> import re
>>> re.findall(r'\bf[a-z]*', 'which foot or hand fell fastest')
['foot', 'fell', 'fastest']
>>> re.sub(r'(\b[a-z]+) \1', r'\1', 'cat in the the hat')
'cat in the hat'

當只需要簡單的字串操作時，因為可讀性以及方便除錯，字串本身的 method 是比較建議的：

>>> 'tea for too'.replace('too', 'two')
'tea for two'

10.6. 數學相關

math 模組提供了 C 函式庫中底層的浮點數運算的函式：

>>> import math
>>> math.cos(math.pi / 4)
0.70710678118654757
>>> math.log(1024, 2)
10.0

random 模組提供了隨機選擇的工具：

>>> import random
>>> random.choice(['apple', 'pear', 'banana'])
'apple'
>>> random.sample(range(100), 10)   # 不重複抽樣
[30, 83, 16, 4, 8, 81, 41, 50, 18, 33]
>>> random.random()    # 區間 [0.0, 1.0) 中的隨機浮點數
0.17970987693706186
>>> random.randrange(6)    # 從 range(6) 中隨機選擇整數
4

statistics 模組提供了替數值資料計算基本統計量（包括平均、中位數、變異量數等）的功能：

>>> import statistics
>>> data = [2.75, 1.75, 1.25, 0.25, 0.5, 1.25, 3.5]
>>> statistics.mean(data)
1.6071428571428572
>>> statistics.median(data)
1.25
>>> statistics.variance(data)
1.3720238095238095

SciPy 專案 <https://scipy.org> 上也有許多數值計算相關的模組。

10.7. 網路存取

Python 中有許多存取網路以及處理網路協定。最簡單的兩個例子包括 urllib.request 模組可以從網址抓取資料以及 smtplib 可以用來寄郵件：

>>> from urllib.request import urlopen
>>> with urlopen('https://docs.python.org/3/') as response:
...     for line in response:
...         line = line.decode()             # 將 bytes 轉換為 str
...         if 'updated' in line:
...             print(line.rstrip())         # 移除最後面的換行符號
...
      Last updated on Nov 11, 2025 (20:11 UTC).

>>> import smtplib
>>> server = smtplib.SMTP('localhost')
>>> server.sendmail('soothsayer@example.org', 'jcaesar@example.org',
... """To: jcaesar@example.org
... From: soothsayer@example.org
...
... Beware the Ides of March.
... """)
>>> server.quit()

（注意第二個例子中需要在本地端執行一個郵件伺服器。）

10.8. 日期與時間

datetime 模組提供許多 class 可以操作日期以及時間，從簡單從複雜都有。模組支援日期與時間的運算，而實作的重點是有效率的成員擷取以達到輸出格式化以及操作。模組也提供支援時區換算的類別。

>>> # 能夠輕易建立與格式化
>>> from datetime import date
>>> now = date.today()
>>> now
datetime.date(2003, 12, 2)
>>> now.strftime("%m-%d-%y. %d %b %Y is a %A on the %d day of %B.")
'12-02-03. 02 Dec 2003 is a Tuesday on the 02 day of December.'

>>> # 支援運算
>>> birthday = date(1964, 7, 31)
>>> age = now - birthday
>>> age.days
14368

10.9. 資料壓縮

常見的解壓縮以及壓縮格式都有直接支援的模組。包括：zlib、gzip、bz2、lzma、zipfile 以及 tarfile。

>>> import zlib
>>> s = b'witch which has which witches wrist watch'
>>> len(s)
41
>>> t = zlib.compress(s)
>>> len(t)
37
>>> zlib.decompress(t)
b'witch which has which witches wrist watch'
>>> zlib.crc32(s)
226805979

10.10. 效能量測

有一些 Python 使用者很想了解同個問題的不同實作方法的效能差異。Python 提供了評估效能差異的工具。

舉例來說，有人可能會試著用 tuple 的打包機制來交換引數代替傳統的方式。timeit 模組可以迅速地展示效能的進步：

>>> from timeit import Timer
>>> Timer('t=a; a=b; b=t', 'a=1; b=2').timeit()
0.57535828626024577
>>> Timer('a,b = b,a', 'a=1; b=2').timeit()
0.54962537085770791

相對於 timeit 模組提供這麼細的粒度，profile 模組以及 pstats 模組則提供了一些在大型的程式碼識別時間使用上關鍵的區塊 (time critical section) 的工具。

10.11. 品質控管

達到高品質軟體的一個方法，是在開發時對每個函式寫測試，以及在開發過程中要不斷地跑這些測試。

doctest 模組提供了一個工具，掃描模組並根據程式中內嵌的文件字串執行測試。撰寫測試如同簡單地將它的呼叫及輸出結果剪下並貼上到文件字串中。透過提供範例給使用者，它強化了說明文件，並允許 doctest 模組確認程式碼的結果與說明文件一致：

def average(values):
    """計算數字串列的算術平均數。

    >>> print(average([20, 30, 70]))
    40.0
    """
    return sum(values) / len(values)

import doctest
doctest.testmod()   # 自動驗證內嵌的測試

unittest 模組不像 doctest 模組這般容易，但是它讓你可以在另外一個檔案裡撰寫更完整的測試集：

import unittest

class TestStatisticalFunctions(unittest.TestCase):

    def test_average(self):
        self.assertEqual(average([20, 30, 70]), 40.0)
        self.assertEqual(round(average([1, 5, 7]), 1), 4.3)
        with self.assertRaises(ZeroDivisionError):
            average([])
        with self.assertRaises(TypeError):
            average(20, 30, 70)

unittest.main()  # 從命令列呼叫會執行所有測試

10.12. 標準模組庫

"Batteries included" 是 Python 的設計哲學。這個理念可以透過使用它的大型套件，感受複雜與強大的功能，來得到印證。例如：

使用 xmlrpc.client 和 xmlrpc.server 模組使實作遠端程序呼叫變得更為容易。即使模組名稱裡有 XML，使用者並不需要直接操作 XML 檔案或事先具備相關知識。

函式庫 email 套件用來管理 MIME 和其他 RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] 相關電子郵件訊息的文件。相異於 smtplib 和 poplib 這些實際用來發送與接收訊息的模組，email 套件擁有更完整的工具集，可用於建立與解碼複雜訊息結構（包含附件檔案）以及實作編碼與標頭協定。

json 套件對 JSON 資料交換格式的剖析，提供強大的支援。csv 模組則提供直接讀寫 CSV（以逗號分隔值的檔案格式，通常資料庫和電子表格都有支援）。xml.etree.ElementTree、xml.dom 與 xml.sax 套件則支援 XML 的處理。綜觀所有，這些模組和套件都簡化了 Python 應用程式與其他工具之間的資料交換。

sqlite3 模組是 SQLite 資料庫函式庫的一層包裝，提供一個具持久性的資料庫，可以使用稍微非標準的 SQL 語法來對它進行更新與存取。

有數種支援國際化的模組，包括 gettext、locale 和 codecs 等套件。

11. Python 標準函式庫概覽——第二部份

第二部分涵蓋更多支援專業程式設計所需要的進階模組。這些模組很少出現在小腳本中。

11.1. 輸出格式化 (Output Formatting)

reprlib 模組提供了一個 repr() 的版本，專門用來以簡短的形式顯示大型或深層的巢狀容器：

>>> import reprlib
>>> reprlib.repr(set('supercalifragilisticexpialidocious'))
"{'a', 'c', 'd', 'e', 'f', 'g', ...}"

pprint 模組能對內建和使用者自定的物件提供更複雜的列印控制，並且是以直譯器可讀的方式。當結果超過一行時，「漂亮的印表機」會加入換行和縮排，以更清楚地顯示資料結構：

>>> import pprint
>>> t = [[[['black', 'cyan'], 'white', ['green', 'red']], [['magenta',
...     'yellow'], 'blue']]]
...
>>> pprint.pprint(t, width=30)
[[[['black', 'cyan'],
   'white',
   ['green', 'red']],
  [['magenta', 'yellow'],
   'blue']]]

textwrap 模組能夠格式化文本的段落，以符合指定的螢幕寬度：

>>> import textwrap
>>> doc = """The wrap() method is just like fill() except that it returns
... a list of strings instead of one big string with newlines to separate
... the wrapped lines."""
...
>>> print(textwrap.fill(doc, width=40))
The wrap() method is just like fill()
except that it returns a list of strings
instead of one big string with newlines
to separate the wrapped lines.

locale 模組能存取一個含有特定文化相關資料格式的資料庫。locale 模組的 format 函式有一個 grouping 屬性，可直接以群分隔符 (group separator) 將數字格式化：

>>> import locale
>>> locale.setlocale(locale.LC_ALL, 'English_United States.1252')
'English_United States.1252'
>>> conv = locale.localeconv()          # 取得慣例的對映
>>> x = 1234567.8
>>> locale.format_string("%d", x, grouping=True)
'1,234,567'
>>> locale.format_string("%s%.*f", (conv['currency_symbol'],
...                      conv['frac_digits'], x), grouping=True)
'$1,234,567.80'

11.2. 模板化 (Templating)

string 模組包含一個多功能的 Template class，提供的簡化語法適合使用者進行編輯時使用。它容許使用者客製化自己的應用程式，但不必對原應用程式做出變更。

格式化方式是使用佔位符號名稱 (placeholder name)，它是由 $ 加上合法的 Python 識別符（字母、數字和下底線）構成。使用大括號包覆佔位符號以允許在後面接上更多的字母和數字而無需插入空格。使用 $$ 將會跳脫為單一字元 $：

>>> from string import Template
>>> t = Template('${village}folk send $$10 to $cause.')
>>> t.substitute(village='Nottingham', cause='the ditch fund')
'Nottinghamfolk send $10 to the ditch fund.'

如果在 dictionary 或關鍵字引數中未提供某個佔位符號的值，那麼 substitute() method 將引發 KeyError。對於郵件合併 (mail-merge) 類型的應用程式，使用者提供的資料有可能是不完整的，此時使用 safe_substitute() method 會更適當——如果資料有缺少，它會保持佔位符號不變：

>>> t = Template('Return the $item to $owner.')
>>> d = dict(item='unladen swallow')
>>> t.substitute(d)
Traceback (most recent call last):
  ...
KeyError: 'owner'
>>> t.safe_substitute(d)
'Return the unladen swallow to $owner.'

Template 的 subclass（子類別）可以指定自訂的分隔符號 (delimiter)。例如，一個相片瀏覽器的批次重新命名功能，可以選擇用百分號作為現在日期、照片序號或檔案格式的佔位符號：

>>> import time, os.path
>>> photofiles = ['img_1074.jpg', 'img_1076.jpg', 'img_1077.jpg']
>>> class BatchRename(Template):
...     delimiter = '%'
...
>>> fmt = input('Enter rename style (%d-date %n-seqnum %f-format):  ')
Enter rename style (%d-date %n-seqnum %f-format):  Ashley_%n%f

>>> t = BatchRename(fmt)
>>> date = time.strftime('%d%b%y')
>>> for i, filename in enumerate(photofiles):
...     base, ext = os.path.splitext(filename)
...     newname = t.substitute(d=date, n=i, f=ext)
...     print('{0} --> {1}'.format(filename, newname))

img_1074.jpg --> Ashley_0.jpg
img_1076.jpg --> Ashley_1.jpg
img_1077.jpg --> Ashley_2.jpg

模板化的另一個應用，是將程式邏輯與多樣的輸出格式細節分離開來。這樣就可以為 XML 檔案、純文字報表和 HTML 網路報表替換自訂的模板。

11.3. 二進制資料記錄編排 (Binary Data Record Layouts)

struct 模組提供了 pack() 和 unpack() 函式，用於處理可變動長度的二進制記錄格式。以下範例說明，如何在不使用 zipfile 模組的情況下，使用迴圈瀏覽一個 ZIP 檔案中的標頭資訊 (header information)。壓縮程式碼 "H" 和 "I" 分別代表兩個和四個位元組的無符號數 (unsigned number)。"<" 表示它們是標準大小，並使用小端 (little-endian) 位元組順序：

import struct

with open('myfile.zip', 'rb') as f:
    data = f.read()

start = 0
for i in range(3):                      # 顯示前 3 個檔案標頭
    start += 14
    fields = struct.unpack('<IIIHH', data[start:start+16])
    crc32, comp_size, uncomp_size, filenamesize, extra_size = fields

    start += 16
    filename = data[start:start+filenamesize]
    start += filenamesize
    extra = data[start:start+extra_size]
    print(filename, hex(crc32), comp_size, uncomp_size)

    start += extra_size + comp_size     # 跳到下一個標頭

11.4. 多執行緒 (Multi-threading)

執行緒是一種用來對非順序相依 (sequentially dependent) 的多個任務進行解耦 (decoupling) 的技術。當其他任務在背景執行時，多執行緒可以用來提升應用程式在接收使用者輸入時的反應能力。一個相關的用例是，運行 I/O 的同時，在另一個執行緒中進行計算。

以下程式碼顯示了高階的 threading 模組如何在背景運行任務，而主程式同時繼續運行：

import threading, zipfile

class AsyncZip(threading.Thread):
    def __init__(self, infile, outfile):
        threading.Thread.__init__(self)
        self.infile = infile
        self.outfile = outfile

    def run(self):
        f = zipfile.ZipFile(self.outfile, 'w', zipfile.ZIP_DEFLATED)
        f.write(self.infile)
        f.close()
        print('Finished background zip of:', self.infile)

background = AsyncZip('mydata.txt', 'myarchive.zip')
background.start()
print('The main program continues to run in foreground.')

background.join()    # 等待背景任務結束
print('Main program waited until background was done.')

多執行緒應用程式的主要挑戰是，要協調多個彼此共享資料或資源的執行緒。為此，threading 模組提供了多個同步處理原始物件 (synchronization primitive)，包括鎖 (lock)、事件 (event)、條件變數 (condition variable) 和號誌 (semaphore)。

儘管這些工具很強大，但很小的設計錯誤也可能導致一些難以重現的問題。所以，任務協調的首選方法是，把所有對資源的存取集中到單一的執行緒中，然後使用 queue 模組向該執行緒饋送來自其他執行緒的請求。應用程式若使用 Queue 物件進行執行緒間的通信和協調，會更易於設計、更易讀、更可靠。

11.5. 日誌記錄 (Logging)

logging 模組提供功能齊全且富彈性的日誌記錄系統。在最簡單的情況下，日誌訊息會被發送到檔案或 sys.stderr：

import logging
logging.debug('Debugging information')
logging.info('Informational message')
logging.warning('Warning:config file %s not found', 'server.conf')
logging.error('Error occurred')
logging.critical('Critical error -- shutting down')

這會產生以下輸出：

WARNING:root:Warning:config file server.conf not found
ERROR:root:Error occurred
CRITICAL:root:Critical error -- shutting down

在預設情況，資訊和除錯訊息不會被顯示，其輸出會被發送到標準錯誤 (standard error)。其他輸出選項包括，將訊息轉發到電子郵件、資料報 (datagram)、網路插座 (socket) 或 HTTP 伺服器。新的過濾器可以根據訊息的優先順序，選擇不同的路由 (routing) 方式：DEBUG、INFO、WARNING、ERROR 及 CRITICAL。

日誌記錄系統可以直接從 Python 配置，也可以透過載入使用者可編輯的配置檔案以進行客製化的日誌記錄，而無須對應用程式做出變更。

11.6. 弱引用 (Weak References)

Python 會自動進行記憶體管理（對大多數物件進行參照計數 (reference counting) 並使用 garbage collection 來消除循環參照）。當一個參照從記憶體被移除後不久，該記憶體就會被釋出。

此方式對大多數應用程式來說都沒問題，但偶爾也需要在物件仍然被其他物件所使用時持續追蹤它們。可惜的是，儘管只是追蹤它們，也會建立一個使它們永久化 (permanent) 的參照。weakref 模組提供的工具可以不必建立參照就能追蹤物件。當該物件不再被需要時，它會自動從一個弱引用表 (weakref table) 中被移除，並為弱引用物件觸發一個回呼 (callback)。典型的應用包括暫存 (cache) 那些成本較為昂貴的物件：

>>> import weakref, gc
>>> class A:
...     def __init__(self, value):
...         self.value = value
...     def __repr__(self):
...         return str(self.value)
...
>>> a = A(10)                   # 建立一個參照
>>> d = weakref.WeakValueDictionary()
>>> d['primary'] = a            # 不會建立參照
>>> d['primary']                # 如果物件仍然存在則取得它
10
>>> del a                       # 移除一個參照
>>> gc.collect()                # 立即執行垃圾回收
0
>>> d['primary']                # 項目被自動移除
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    d['primary']                # 項目被自動移除
  File "C:/python314/lib/weakref.py", line 46, in __getitem__
    o = self.data[key]()
KeyError: 'primary'

11.7. 使用於 List 的工具

許多對於資料結構的需求，可以透過內建的 list（串列）型別來滿足。但是，有時也會根據效能的各種取捨，需要一些替代的實作。

array 模組提供了一個 array 物件，它像是 list，但只能儲存同類的資料且能緊密地儲存。下面的範例展示一個數值陣列 (array)，以兩個位元組的無符號二進數 (unsigned binary numbers) 為儲存單位（類型碼為 "H"），而在 Python 整數物件的正規 list 中，每個項目通常使用 16 個位元組：

>>> from array import array
>>> a = array('H', [4000, 10, 700, 22222])
>>> sum(a)
26932
>>> a[1:3]
array('H', [10, 700])

collections 模組提供了一個 deque 物件，它像是 list，但從左側加入 (append) 和彈出 (pop) 的速度較快，而在中間查找的速度則較慢。這種物件適用於實作佇列 (queue) 和廣度優先搜尋法 (breadth first tree search)：

>>> from collections import deque
>>> d = deque(["task1", "task2", "task3"])
>>> d.append("task4")
>>> print("Handling", d.popleft())
Handling task1

unsearched = deque([starting_node])
def breadth_first_search(unsearched):
    node = unsearched.popleft()
    for m in gen_moves(node):
        if is_goal(m):
            return m
        unsearched.append(m)

除了替代的 list 實作以外，函式庫也提供了其他工具，例如 bisect 模組，具有能夠操作 sorted list（已排序串列）的函式：

>>> import bisect
>>> scores = [(100, 'perl'), (200, 'tcl'), (400, 'lua'), (500, 'python')]
>>> bisect.insort(scores, (300, 'ruby'))
>>> scores
[(100, 'perl'), (200, 'tcl'), (300, 'ruby'), (400, 'lua'), (500, 'python')]

heapq 模組提供了一些函式，能基於正規 list 來實作堆積 (heap)。最小值的項目會永遠保持在位置零。對於一些需要多次存取最小元素，但不想要對整個 list 進行排序的應用程式來說，這會很有用：

>>> from heapq import heapify, heappop, heappush
>>> data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
>>> heapify(data)                      # 將串列重新排列為堆積順序
>>> heappush(data, -5)                 # 加入新項目
>>> [heappop(data) for i in range(3)]  # 取得三個最小的項目
[-5, 0, 1]

11.8. 十進制浮點數運算 (Decimal Floating-Point Arithmetic)

decimal 模組提供了一個 Decimal 資料類型，用於十進制浮點數運算。相較於內建的二進制浮點數 float 實作，該 class 特別適用於下列情境

金融應用程式及其他需要準確十進位制表示法的應用，

對於精確度 (precision) 的控制，

控制四捨五入，以滿足法律或監管規範，

追蹤有效的小數位數 (decimal place)，或

使用者會期望計算結果與手工計算相符的應用程式。

例如，要計算 70 美分的手機充電加上 5% 稅金的總價，使用十進制浮點數和二進制浮點數，會算出不同的答案。如果把計算結果四捨五入到最接近的美分，兩者的差異會更顯著：

>>> from decimal import *
>>> round(Decimal('0.70') * Decimal('1.05'), 2)
Decimal('0.74')
>>> round(.70 * 1.05, 2)
0.73

Decimal 的運算結果會保留尾部的零，也會根據有兩個有效位數的被乘數自動推斷出有四個有效位數的乘積。Decimal 可以重現手工計算的結果，以避免產生二進制浮點數無法準確表示十進制數值時會導致的問題。

準確的表示法使得 Decimal class 能夠執行對於二進制浮點數不適用的模數計算和相等性檢測：

>>> Decimal('1.00') % Decimal('.10')
Decimal('0.00')
>>> 1.00 % 0.10
0.09999999999999995

>>> sum([Decimal('0.1')]*10) == Decimal('1.0')
True
>>> 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 == 1.0
False

decimal 模組可提供運算中需要的足夠精確度：

>>> getcontext().prec = 36
>>> Decimal(1) / Decimal(7)
Decimal('0.142857142857142857142857142857142857')

12. 虛擬環境與套件

12.1. 簡介

Python 應用程式通常會用到不在標準函式庫的套件和模組。應用程式有時候會需要某個特定版本的函式庫，因為這個應用程式可能需要某個特殊的臭蟲修正，或是這個應用程式是根據該函式庫特定版本的介面所撰寫。

這意味著不太可能安裝一套 Python 就可以滿足所有應用程式的要求。如果應用程式 A 需要一個特定的模組的 1.0 版，但另外一個應用程式 B 需要 2.0 版，那麼這整個需求不管安裝 1.0 或是 2.0 都會衝突，以致於應用程式無法使用。

解決方案是建立一個虛擬環境 (virtual environment)，這是一個獨立的資料夾，並且裡面裝好了特定版本的 Python，以及一系列相關的套件。

不同的應用程式可以使用不同的虛擬環境。以前述中需要被解決的例子中，應用程式 A 能夠擁有它自己的虛擬環境，並且是裝好 1.0 版，然而應用程式 B 則可以是用另外一個有 2.0 版的虛擬環境。要是應用程式 B 需要某個函式庫被升級到 3.0 版，這並不會影響到應用程式 A 的環境。

12.2. 建立虛擬環境

用來建立與管理虛擬環境的模組叫做 venv。venv 將安裝執行命令的 Python 版本（如 --version 選項所報告的）。例如使用 python3.12 執行命令將安裝 3.12 版本。

在建立虛擬環境的時候，在你決定要放該虛擬環境的資料夾之後，以腳本 (script) 執行 venv 模組並且給定資料夾路徑：

python -m venv tutorial-env

如果 tutorial-env 不存在的話，這會建立 tutorial-env 資料夾，並且也會在裡面建立一個有 Python 直譯器的複本以及不同的支援檔案的資料夾。

虛擬環境的常用資料夾位置是 .venv。這個名稱通常會使該資料夾在你的 shell 中保持隱藏，因此這樣命名既可以解釋資料夾存在的原因，也不會造成任何困擾。它還能防止與某些工具所支援的 .env 環境變數定義檔案發生衝突。

一旦你建立了一個虛擬環境，你可以啟動它。

在 Windows 系統中，使用：

tutorial-env\Scripts\activate

在 Unix 或 MacOS 系統，使用：

source tutorial-env/bin/activate

（這段程式碼適用於 bash shell。如果你是用 csh 或者 fish shell，應當使用替代的 activate.csh 與 activate.fish 腳本。）

啟動虛擬環境會改變你的 shell 提示字元來顯示你正在使用的虛擬環境，並且修改環境以讓你在執行 python 的時候可以得到特定的 Python 版本，例如：

$ source ~/envs/tutorial-env/bin/activate
(tutorial-env) $ python
Python 3.5.1 (default, May  6 2016, 10:59:36)
  ...
>>> import sys
>>> sys.path
['', '/usr/local/lib/python35.zip', ...,
'~/envs/tutorial-env/lib/python3.5/site-packages']
>>>

要停用虛擬環境，輸入：

deactivate

於終端機中。

12.3. 用 pip 管理套件

你可以使用一個叫做 pip 的程式來安裝、升級和移除套件。pip 預設會從 Python Package Index [https://pypi.org] 安裝套件。你可以透過你的網頁瀏覽器瀏覽 Python Package Index。

pip 有好幾個子命令："install"、"uninstall"、"freeze" 等等。（可以參考安裝 Python 模組指南，來取得 pip 的完整說明文件。）

你可以透過指定套件名字來安裝最新版本的套件：

(tutorial-env) $ python -m pip install novas
Collecting novas
  Downloading novas-3.1.1.3.tar.gz (136kB)
Installing collected packages: novas
  Running setup.py install for novas
Successfully installed novas-3.1.1.3

你也可以透過在套件名稱之後接上 == 和版號來指定特定版本：

(tutorial-env) $ python -m pip install requests==2.6.0
Collecting requests==2.6.0
  Using cached requests-2.6.0-py2.py3-none-any.whl
Installing collected packages: requests
Successfully installed requests-2.6.0

要是你重新執行此命令，pip 會知道該版本已經安裝過，然後什麼也不做。你可以提供不同的版本號碼來取得該版本，或是可以執行 python -m pip install --upgrade 來把套件升級到最新的版本：

(tutorial-env) $ python -m pip install --upgrade requests
Collecting requests
Installing collected packages: requests
  Found existing installation: requests 2.6.0
    Uninstalling requests-2.6.0:
      Successfully uninstalled requests-2.6.0
Successfully installed requests-2.7.0

python -m pip uninstall 後面接一個或是多個套件名稱可以從虛擬環境中移除套件。

python -m pip show 可以顯示一個特定套件的資訊：

(tutorial-env) $ python -m pip show requests
---
Metadata-Version: 2.0
Name: requests
Version: 2.7.0
Summary: Python HTTP for Humans.
Home-page: http://python-requests.org
Author: Kenneth Reitz
Author-email: me@kennethreitz.com
License: Apache 2.0
Location: /Users/akuchling/envs/tutorial-env/lib/python3.4/site-packages
Requires:

python -m pip list 會顯示虛擬環境中所有已經安裝的套件：

(tutorial-env) $ python -m pip list
novas (3.1.1.3)
numpy (1.9.2)
pip (7.0.3)
requests (2.7.0)
setuptools (16.0)

python -m pip freeze 可以複製一整個已經安裝的套件清單，但是輸出使用 python -m pip install 可以讀懂的格式。一個常見的慣例是放這整個清單到一個叫做 requirements.txt 的檔案：

(tutorial-env) $ python -m pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
novas==3.1.1.3
numpy==1.9.2
requests==2.7.0

requirements.txt 可以提交到版本控制，並且作為釋出應用程式的一部分。使用者可以透過 install -r 安裝對應的的套件：

(tutorial-env) $ python -m pip install -r requirements.txt
Collecting novas==3.1.1.3 (from -r requirements.txt (line 1))
  ...
Collecting numpy==1.9.2 (from -r requirements.txt (line 2))
  ...
Collecting requests==2.7.0 (from -r requirements.txt (line 3))
  ...
Installing collected packages: novas, numpy, requests
  Running setup.py install for novas
Successfully installed novas-3.1.1.3 numpy-1.9.2 requests-2.7.0

pip 還有更多功能。可以參考安裝 Python 模組指南，來取得完整的 pip 說明文件。當你撰寫了一個套件並且想要讓它在 Python Package Index 上可以取得的話，可以參考 Python packaging user guide [https://packaging.python.org/en/latest/tutorials/packaging-projects/]。

13. 現在可以來學習些什麼？

閱讀本教學可能增強你對於使用 Python 的興趣——你應該非常渴望使用 Python 來解決在現實生活中所遭遇的問題。該從哪裡學習更多呢？

本教學是 Python 文件中的一部分。這份文件集裡頭的其他文件包含：

Python 標準函式庫 (Standard Library)：

你該好好的瀏覽這份手冊，它提供了完整（但簡潔）的參考素材像是型別、函式與標準函式庫裡的模組。標準的 Python 發行版本會包含大量的附加程式碼。有些模組可以讀取 Unix 信箱、透過 HTTP 來檢索文件、產生亂數、分析命令列選項、壓縮資料、及許多其他任務。瀏覽函式庫參考手冊可以讓你了解有哪些模組可以用。

安裝 Python 模組：說明與解釋如何安裝其他 Python 使用者所編寫的模組。

Python 語言參考手冊：Python 語法以及語意的詳細說明。這份文件閱讀起來會有些吃力，但作為一個語言本身的完整指南是非常有用的。

更多 Python 的資源：

https://www.python.org：Python 的主要網站。它包含程式碼、文件以及連結到 Python 相關聯的網頁。

https://docs.python.org：快速存取 Python 的文件。

https://pypi.org：Python 套件索引 (Python Package Index)，之前也被暱稱為 Cheese Shop [1]，彙總了使用者開發 Python 模組的索引，並提供模組能夠被下載。一旦開始發佈相關程式碼，你可以將開發的作品註冊到這裡並且讓其他人找到。

https://code.activestate.com/recipes/langs/python/：Python Cookbook 是一個相當大的程式碼集，包含程式碼範例、較大的模組以及有用的腳本。特別值得注意的貢獻則被收集在一本名為 Python Cookbook (O'Reilly & Associates, ISBN 0-596-00797-3.) 的書籍中。

https://pyvideo.org 從研討會與使用者群組聚會裡收集與 Python 相關的影片連結。

https://scipy.org：The Scientific Python 專案是一個包含用於高速陣列運算與操作的模組，以及用於如線性代數、傅利葉變換、非線性求解器、隨機數分佈、統計分析等一系列的套件。

對於 Python 相關的疑問與問題回報，你可以張貼到新聞群組comp.lang.python，或將它們寄至 python-list@python.org 的郵寄清單 (mailing list)。新聞群組和郵寄清單是個閘道，因此張貼到其中的郵件都將自動轉發給另一個。每天會有數以百計的內容，詢問（和回答）問題、建議新功能與發佈新的模組。郵寄清單會存檔在 https://mail.python.org/pipermail/。

在張貼之前，請先確認問題是否在常見問題（也被稱為 FAQ）這個清單內。FAQ 會回答出現很多次的問題及解答，有很多問題甚至已經包含解決問題的方法。

註腳

[1]

「Cheese Shop（起司店）」是 Monty Python 的一個短劇：一位顧客進入一家起司店，但無論他要哪種起司，店員都說沒有貨。

14. 互動式輸入編輯和歷史記錄替換

有些版本的 Python 直譯器支援目前輸入內容的編輯和歷史記錄的替換 (history substitution)，類似在 Korn shell 和 GNU Bash shell 中的功能。這個功能是用 GNU Readline [https://tiswww.case.edu/php/chet/readline/rltop.html] 函式庫來實作，它支援多種編輯的風格。這個函式庫有它自己的說明文件，在這裡我們就不重複了。

14.1. Tab 鍵自動完成 (Tab Completion) 和歷史記錄編輯 (History Editing)

在直譯器啟動的時候，變數和模組名稱的自動完成功能會被自動啟用，所以可以用 Tab 鍵來叫用自動完成函式；它會查看 Python 的陳述式名稱、目前區域變數名稱和可用模組名稱。對於像是 string.a 的點分隔運算式 (dotted expression)，它會對最後一個 '.' 之前的運算式求值，然後根據求值結果物件的屬性，給予自動完成的建議。請注意，如果一個物件有 __getattr__() method（方法），同時又是該運算式的一部份，這樣可能會執行應用程式定義的程式碼。預設設定也會把你的指令歷史記錄儲存在你的使用者資料夾內，一個名為 .python_history 的檔案中。在下一次啟動互動式直譯器時，這些歷史記錄依然可以被使用。

14.2. 互動式直譯器的替代方案

與早期版本的直譯器相比，上述功能的出現的確是一個巨大的進步；但還是有一些願望沒有被實現：如果能在每次換行時給予適當的縮排建議（剖析器 (parser) 知道下一行是否需要縮排標記 (INDENT token)），那就更棒了。自動完成機制可能會使用直譯器的符號表。若有一個命令能夠檢查（或甚至建議）括號、引號和其他符號的匹配，那也會很有用。

有一個功能增強的互動式直譯器替代方案，已經存在一段時間，稱為 IPython [https://ipython.org/]，它具有 Tab 鍵自動完成、物件探索和進階歷史記錄管理等特色。它也可以完全客製化並被嵌入到其他應用程式中。另一個類似的增強型互動式環境，稱為 bpython [https://bpython-interpreter.org/]。

15. 浮點數運算：問題與限制

在計算機架構中，浮點數 (floating-point number) 是以基數為 2（二進位）的小數表示。例如說，在十進位小數中 0.625 可被分為 6/10 + 2/100 + 5/1000，同樣的道理，二進位小數 0.101 可被分為 1/2 + 0/4 + 1/8。這兩個小數有相同的數值，而唯一真正的不同在於前者以十進位表示，後者以二進位表示。

不幸的是，大多數十進位小數無法精準地以二進位小數表示。一般的結果為，你輸入的十進位浮點數只能由實際儲存在計算機中的二進位浮點數近似。

在十進位中，這個問題更容易被理解。以分數 1/3 為例，你可以將其近似為十進位小數：

0.3

或者，更好的近似：

0.33

或者，更好的近似：

0.333

依此類推，不論你使用多少位數表示小數，最後的結果都無法精準地表示 1/3，但你還是能越來越精準地表示 1/3。

同樣的道理，不論你願意以多少位數表示二進位小數，十進位小數 0.1 都無法被二進位小數精準地表達。在二進位小數中，1/10 會是一個無限循環小數：

0.0001100110011001100110011001100110011001100110011...

只要你停在任何有限的位數，你就只會得到近似值。而現在大多數的計算機中，浮點數是透過二進位分數近似的，其中分子是從最高有效位元開始，用 53 個位元表示，分母則是以二為底的指數。在 1/10 的例子中，二進位分數為 3602879701896397 / 2 ** 55，而這樣的表示十分地接近，但不完全等同於 1/10 的真正數值。

由於數值顯示的方式，很多使用者並沒有發現數值是個近似值。Python 只會印出一個十進位近似值，其近似了儲存在計算機中的二進位近似值的真正十進位數值。在大多數的計算機中，如果 Python 真的會印出完整的十進位數值，其表示儲存在計算機中的 0.1 的二進位近似值，它將顯示為：

>>> 0.1
0.1000000000000000055511151231257827021181583404541015625

這比一般人感到有用的位數還多，所以 Python 將位數保持在可以接受的範圍，只顯示捨入後的數值：

>>> 1 / 10
0.1

一定要記住，雖然印出的數字看起來是精準的 1/10，但真正儲存的數值是能表示的二進位分數中，最接近精準數值的數。

有趣的是，有許多不同的十進位數，共用同一個最接近的二進位近似分數。例如說：數字 0.1 和 0.10000000000000001 和 0.1000000000000000055511151231257827021181583404541015625，都由 3602879701896397 / 2 ** 55 近似。由於這三個十進位數值共用同一個近似值，任何一個數值都可以被顯示，同時保持 eval(repr(x)) == x。

歷史上，Python 的提示字元 (prompt) 與內建的 repr() 函式會選擇上段說明中有 17 個有效位元的數：0.10000000000000001。從 Python 3.1 版開始，Python（在大部分的系統上）現在能選擇其中最短的數並簡單地顯示為 0.1。

注意，這是二進位浮點數理所當然的特性，並不是 Python 的錯誤 (bug)，更不是你程式碼的錯誤。只要程式語言有支援硬體的浮點數運算，你將會看到同樣的事情出現在其中（雖然有些程式語言預設不會顯示該差異，有些甚至是在所有的輸出模式中都不會顯示。）

為求更優雅的輸出，你可能想要使用字串的格式化 (string formatting) 產生限定的有效位數：

>>> format(math.pi, '.12g')  # 給出 12 個有效位數
'3.14159265359'

>>> format(math.pi, '.2f')   # 小數點後給出 2 位數字
'3.14'

>>> repr(math.pi)
'3.141592653589793'

要了解一件很重要的事，在真正意義上，浮點數的表示是一種幻覺：你基本上在捨入真正機器數值所展示的值。

這種幻覺可能會產生下一個幻覺。舉例來說，因為 0.1 不是真正的 1/10，把三個 0.1 的值相加，也不會產生精準的 0.3：

>>> 0.1 + 0.1 + 0.1 == 0.3
False

同時，因為 0.1 不能再更接近精準的 1/10，還有 0.3 不能再更接近精準的 3/10，預先用 round() 函式捨入並不會有幫助：

>>> round(0.1, 1) + round(0.1, 1) + round(0.1, 1) == round(0.3, 1)
False

雖然數字不會再更接近他們的精準數值，但 math.isclose() 函式可以用來比較不精確的值：

>>> math.isclose(0.1 + 0.1 + 0.1, 0.3)
True

或者，可以使用 round() 函式來比較粗略的近似值：

>>> round(math.pi, ndigits=2) == round(22 / 7, ndigits=2)
True

二進位浮點數架構下還有很多這樣的意外。底下的「表示法誤差 (Representation Error)」章節，詳細地解釋了「0.1」的問題。Examples of Floating Point Problems（浮點數問題範例） [https://jvns.ca/blog/2023/01/13/examples-of-floating-point-problems/]一文提供了二進位浮點數的作用方式與現實中這類常見問題的摘錄。如果想要其他常見問題的更完整描述，可以參考 The Perils of Floating Point（浮點數的風險） [http://www.indowsway.com/floatingpoint.htm]。

如同上文的末段所述，「這個問題並沒有簡單的答案。」不過，也不必對浮點過度擔心！Python 的 float（浮點數）運算中的誤差，是從浮點硬體繼承而來，而在大多數的計算機上，每次運算的誤差範圍不會大於 2**53 分之 1。這對大多數的任務來說已經相當足夠，但你需要記住，它並非十進位運算，且每一次 float 運算都可能會承受新的捨入誤差。

雖然浮點運算確實存在一些問題，但在一般情況下，如果你只是把最終結果的顯示值，以十進位方式捨入至預期的位數，那麼仍會得到你預期的結果。str() 通常就能滿足要求，而若想要更細緻的控制，可參閱格式化文字語法中關於 str.format() method（方法）的格式說明符號。

對於需要精準十進位表示法的用例，可以試著用 decimal 模組，它可實作適用於會計應用程式與高精確度應用程式的十進位運算。

另一種支援精準運算的格式為 fractions 模組，該模組基於有理數來實作運算（因此可以精確表示像 1/3 這樣的數字）。

如果你是浮點運算的重度使用者，你應該看一下 NumPy 套件，以及由 SciPy 專案提供的許多用於數學和統計學運算的其他套件。請參閱 <https://scipy.org>。

在罕見情況下，當你真的想知道一個 float 的精準值，Python 提供的工具可協助達成。float.as_integer_ratio() method 可將一個 float 的值表示為分數：

>>> x = 3.14159
>>> x.as_integer_ratio()
(3537115888337719, 1125899906842624)

由於該比率是精準的，它可無損地再現該原始值：

>>> x == 3537115888337719 / 1125899906842624
True

float.hex() method 以十六進位（基數為 16）表示 float，一樣可以給出你的電腦所儲存的精準值：

>>> x.hex()
'0x1.921f9f01b866ep+1'

這種精確的十六進位表示法可用於精準地重建 float 值：

>>> x == float.fromhex('0x1.921f9f01b866ep+1')
True

由於該表示法是精準的，因此適用於在不同版本的 Python 之間可靠地傳送數值（獨立於系統平台），並與支援相同格式的其他語言（如 JAVA 和 C99）交換資料。

另一個有用的工具是 sum() 函式，能在計算總和時幫忙減少精確度的損失。當數值被加到運行中的總計值時，它會追蹤「失去的位數 (lost digits)」。這可以明顯改善總體準確度 (overall accuracy)，使得誤差不至於累積到影響最終總計值的程度：

>>> 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 == 1.0
False
>>> sum([0.1] * 10) == 1.0
True

math.fsum() 更進一步將數值被加到運行總計中的總計時追蹤所有「失去的位數」，以便結果僅有一次捨入。這比 sum() 慢，但在不常見的情況下會更準確，在這種情況下，大量輸入大多相互抵消，最終的總和會接近於零：

>>> arr = [-0.10430216751806065, -266310978.67179024, 143401161448607.16,
...        -143401161400469.7, 266262841.31058735, -0.003244936839808227]
>>> float(sum(map(Fraction, arr)))   # 單次四捨五入的精確加總
8.042173697819788e-13
>>> math.fsum(arr)                   # 單次四捨五入
8.042173697819788e-13
>>> sum(arr)                         # 在擴展精度中進行多次捨入
8.042178034628478e-13
>>> total = 0.0
>>> for x in arr:
...     total += x                   # 在標準精度中進行多次捨入
...
>>> total                            # 直接相加沒有正確的數字
-0.0051575902860057365

15.1. 表示法誤差 (Representation Error)

本節將會詳細解釋「0.1」的例子，並說明你自己要如何對類似案例執行精準的分析。 以下假設你對二進位浮點表示法已有基本程度的熟悉。

Representation error（表示法誤差）是指在真實情況中，有些（實際上是大多數）十進位小數並不能精準地以二進位（基數為 2）小數表示。這是 Python（或 Perl、C、C++、JAVA、Fortran 和其他許多）通常不會顯示你期望的精準十進位數字的主要原因。

為什麼呢？因為 1/10 無法精準地以一個二進位小數來表示。至少自從 2000 年以來，幾乎所有的計算機皆使用 IEEE-754 浮點數運算標準，並且幾乎所有的平台都以 IEEE 754 binary64 標準中的「雙精度 (double precision)」來作為 Python 的 float。IEEE 754 binary64 的值包含 53 位元的精度，所以在輸入時，電腦會努力把 0.1 轉換到最接近的分數，以 J/2**N 的形式表示，此處 J 是一個正好包含 53 位元的整數。可以將：

1 / 10 ~= J / (2**N)

重寫為：

J ~= 2**N / 10

而前面提到 J 有精準的 53 位元（即 >= 2**52 但 < 2**53），所以 N 的最佳數值是 56：

>>> 2**52 <=  2**56 // 10  < 2**53
True

意即，要使 J 正好有 53 位元，則 56 會是 N 的唯一值。而 J 最有可能的數值就是經過捨入後的該商數：

>>> q, r = divmod(2**56, 10)
>>> r
6

由於餘數超過 10 的一半，所以最佳的近似值是透過進位而得：

>>> q+1
7205759403792794

所以，在 IEEE 754 雙精度下，1/10 的最佳近似值是：

7205759403792794 / 2 ** 56

將分子和分母同除以二，會約分為：

3602879701896397 / 2 ** 55

請注意，由於我們有進位，所以這實際上比 1/10 大了一點；如果我們沒有進位，商數將會有點小於 1/10。但在任何情況下都不可能是精準的 1/10！

所以電腦從來沒有「看到」1/10：它看到的是上述的精準分數，也就是它能得到的 IEEE 754 double 最佳近似值：

>>> 0.1 * 2 ** 55
3602879701896397.0

如果將該分數乘以 10**55，則可以看到該值以 55 個十進位數字顯示：

>>> 3602879701896397 * 10 ** 55 // 2 ** 55
1000000000000000055511151231257827021181583404541015625

這表示儲存在電腦中的精準數值等於十進位值 0.1000000000000000055511151231257827021181583404541015625。與其顯示完整的十進位數值，許多語言（包括 Python 的舊版本）選擇將結果捨入至 17 個有效位數：

>>> format(0.1, '.17f')
'0.10000000000000001'

fractions 與 decimal 模組能使這些計算變得容易：

>>> from decimal import Decimal
>>> from fractions import Fraction

>>> Fraction.from_float(0.1)
Fraction(3602879701896397, 36028797018963968)

>>> (0.1).as_integer_ratio()
(3602879701896397, 36028797018963968)

>>> Decimal.from_float(0.1)
Decimal('0.1000000000000000055511151231257827021181583404541015625')

>>> format(Decimal.from_float(0.1), '.17')
'0.10000000000000001'

16. 附錄

16.1. 互動模式

互動式 REPL 有兩種變體。經典的基本解釋器在所有平台上都支援，具有最低限度的行控制能力（line control capabilities）。

自 Python 3.13 起，預設會使用新的互動式 shell。這個 shell 支援顏色、多行編輯、歷史瀏覽和貼上模式。要停用顏色，請參閱 Controlling color 以取得詳細資訊。功能鍵提供了一些額外的功能。F1 進入互動式幫助瀏覽器 pydoc。F2 允許瀏覽命令列歷史，且不會有輸出，也不會有 >>> 和 ... 提示。F3 進入「貼上模式」，這使得貼上較大的程式碼區塊更容易。按 F3 可以返回正常提示。

使用新的互動 shell 時， 請輸入 exit 或 quit 來離開 shell。不需要在這些指令後面加上呼叫括號。

如果不需要新的互動式 shell， 可以透過 PYTHON_BASIC_REPL 環境變數來停用它。

16.1.1. 錯誤處理

當一個錯誤發生時，直譯器會印出一個錯誤訊息和堆疊回溯。在互動模式下，它將返回主提示字元；當輸入來自檔案時，它在印出堆疊回溯後以非零退出狀態 (nonzero exit status) 退出。(由 except 子句在 try 陳述式中處理的例外在這種情況下不是錯誤。) 有些錯誤是無條件嚴重的，會導致非零退出狀態；這適用於內部不一致和一些記憶體耗盡的情況。所有的錯誤訊息都被寫入標準錯誤輸出；被執行指令的正常輸出被寫入標準輸出。

向主提示字元或次提示字元輸入中斷字元（通常是 Control-C 或 Delete ）會取消輸入並回傳到主提示字元。[1] 在指令執行過程中輸入一個中斷，會引發 KeyboardInterrupt 例外，但可以透過 try 陳述式來處理。

16.1.2. 可執行的 Python 腳本

在類 BSD 的 Unix 系統上，Python 腳本可以直接執行，就像 shell 腳本一樣，透過放置以下這行：

#!/usr/bin/env python3

（假設直譯器在用戶的 PATH 上）在腳本的開頭並給檔案一個可執行模式。#! 必須是檔案的前兩個字元。在某些平台上，第一行必須以 Unix 樣式的換行 ('\n') 結尾，而不是 Windows ('\r\n') 換行。請注意，井號 '#' 用於在 Python 中開始註解。

可以使用 chmod 指令為腳本賦予可執行模式或權限。

$ chmod +x myscript.py

在 Windows 系統上，沒有「可執行模式」的概念。Python 安裝程式會自動將 .py 檔案與 python.exe 聯繫起來，這樣雙擊 Python 檔案就會作為腳本運行。副檔名也可以是 .pyw，在這種情況下，通常會出現的控制台視窗會被隱藏。

16.1.3. 互動式啟動檔案

當你互動式地使用 Python 時，每次啟動直譯器時執行一些標準指令是非常方便的。你可以透過設置一個名為 PYTHONSTARTUP 的環境變數來實現，該變數是一個包含啟動指令的檔案名。它的功能類似 Unix shell 的 .profile 。

這個檔案只在互動模式中被讀取，當 Python 從腳本中讀取指令時，此檔案不會被讀取，當 /dev/tty 作為指令的明確來源時也不會（否則表現得像互動模式）。它在執行互動式指令的同一命名空間中執行，因此它所定義或 import 的物件可以在互動模式中不加限定地使用。你也可以在這個檔案中改變 sys.ps1 和 sys.ps2 等提示字元。

如果你想從目前目錄中讀取一個額外的啟動檔案，你可以在全域啟動檔案中使用類似 if os.path.isfile('.pythonrc.py'): exec(open('.pythonrc.py').read() 的程式碼設定這個行為。如果你想在一個腳本中使用啟動檔案，你必須在腳本中明確地這樣做：

import os
filename = os.environ.get('PYTHONSTARTUP')
if filename and os.path.isfile(filename):
    with open(filename) as fobj:
        startup_file = fobj.read()
    exec(startup_file)

16.1.4. 客製化模組

Python 提供了兩個鉤子 (hook) 讓你可以將它客製化： sitecustomize 和 usercustomize 。要看它是如何運作的，你首先需要找到你的 site-packages 的位置。啟動 Python 並運行這段程式碼：

>>> import site
>>> site.getusersitepackages()
'/home/user/.local/lib/python3.x/site-packages'

現在，你可以在該目錄中建立一個名為 usercustomize.py 的檔案，並將你想要的任何內容放入其中。它會影響 Python 的每次呼叫，除非它以 -s 選項啟動以禁用自動 import 。

sitecustomize 的運作方式相同，但通常是由電腦的管理員在全域 site-packages 目錄下建立，並在 usercustomize 之前 import 。更多細節請參閱 site 模組的文件。

註解

[1]

GNU Readline 套件的一個問題可能會阻止這一點。

Python 的設置與使用

這部分的說明文件是關於在不同平台上設定 Python 環境的綜合資訊、直譯器的呼叫，以及讓 Python 更容易使用的一些方法。

1. 命令列與環境

1.1. 命令列

1.2. 環境變數

2. 在 Unix 平臺上使用 Python

2.1. 獲得並安裝 Python 的最新版本

2.2. 建置 Python

2.3. 與 Python 相關的路徑和檔案

2.4. 雜項

2.5. 客製化 OpenSSL

3. 配置 Python

3.1. 建置需求

3.2. 產生的檔案

3.3. 設定選項

3.4. Python 建置系統

3.5. Compiler and linker flags

4. 在 Windows 上使用 Python

4.1. Python 安裝管理員

4.2. The embeddable package

4.3. nuget.org 套件

4.4. Alternative bundles

4.5. Supported Windows versions

4.6. Removing the MAX_PATH limitation

4.7. UTF-8 模式

4.8. 找尋模組

4.9. 額外的模組

4.10. 編譯 Python 在 Windows

4.11. The full installer (deprecated)

4.12. Python launcher for Windows (deprecated)

5. 於 macOS 使用 Python

5.1. Using Python for macOS from python.org

5.2. Alternative Distributions

5.3. 安裝額外的 Python 套件

5.4. 開發 GUI 程式

5.5. 進階主題

5.6. 其他資源

6. 在 Android 上使用 Python

6.1. 將 Python 加入 Android 應用程式

6.2. 建置用於 Android 的 Python 套件

7. 在 iOS 上使用 Python

7.1. Python at runtime on iOS

7.2. Installing Python on iOS

7.3. App Store Compliance

8. 編輯器與 IDE

8.1. IDLE --- Python 編輯器與 shell

8.2. 其他編輯器與 IDE

1. 命令列與環境

The CPython interpreter scans the command line and the environment for various settings.

CPython 實作細節： Other implementations' command line schemes may differ. See 可選實作 for further resources.

1.1. 命令列

When invoking Python, you may specify any of these options:

python [-bBdEhiIOPqRsSuvVWx?] [-c command | -m module-name | script | - ] [args]

The most common use case is, of course, a simple invocation of a script:

python myscript.py

1.1.1. 介面選項

The interpreter interface resembles that of the UNIX shell, but provides some additional methods of invocation:

When called with standard input connected to a tty device, it prompts for commands and executes them until an EOF (an end-of-file character, you can produce that with Ctrl-D on UNIX or Ctrl-Z, Enter on Windows) is read. For more on interactive mode, see 互動模式.

When called with a file name argument or with a file as standard input, it reads and executes a script from that file.

When called with a directory name argument, it reads and executes an appropriately named script from that directory.

When called with -c command, it executes the Python statement(s) given as command. Here command may contain multiple statements separated by newlines. Leading whitespace is significant in Python statements!

When called with -m module-name, the given module is located on the Python module path and executed as a script.

In non-interactive mode, the entire input is parsed before it is executed.

An interface option terminates the list of options consumed by the interpreter, all consecutive arguments will end up in sys.argv -- note that the first element, subscript zero (sys.argv[0]), is a string reflecting the program's source.

-c <command>

Execute the Python code in command. command can be one or more statements separated by newlines, with significant leading whitespace as in normal module code.

If this option is given, the first element of sys.argv will be "-c" and the current directory will be added to the start of sys.path (allowing modules in that directory to be imported as top level modules).

引發一個附帶引數 command 的稽核事件 cpython.run_command。

在 3.14 版的變更: command is automatically dedented before execution.

-m <module-name>

Search sys.path for the named module and execute its contents as the __main__ module.

Since the argument is a module name, you must not give a file extension (.py). The module name should be a valid absolute Python module name, but the implementation may not always enforce this (e.g. it may allow you to use a name that includes a hyphen).

Package names (including namespace packages) are also permitted. When a package name is supplied instead of a normal module, the interpreter will execute <pkg>.__main__ as the main module. This behaviour is deliberately similar to the handling of directories and zipfiles that are passed to the interpreter as the script argument.

備註

This option cannot be used with built-in modules and extension modules written in C, since they do not have Python module files. However, it can still be used for precompiled modules, even if the original source file is not available.

If this option is given, the first element of sys.argv will be the full path to the module file (while the module file is being located, the first element will be set to "-m"). As with the -c option, the current directory will be added to the start of sys.path.

-I option can be used to run the script in isolated mode where sys.path contains neither the current directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too.

Many standard library modules contain code that is invoked on their execution as a script. An example is the timeit module:

python -m timeit -s "setup here" "benchmarked code here"
python -m timeit -h # for details

引發一個附帶引數 module-name 的稽核事件 cpython.run_module。

也參考

runpy.run_module()

Equivalent functionality directly available to Python code

PEP 338 [https://peps.python.org/pep-0338/] -- Executing modules as scripts

在 3.1 版的變更: Supply the package name to run a __main__ submodule.

在 3.4 版的變更: namespace packages are also supported

-

Read commands from standard input (sys.stdin). If standard input is a terminal, -i is implied.

If this option is given, the first element of sys.argv will be "-" and the current directory will be added to the start of sys.path.

引發一個不附帶引數的稽核事件 cpython.run_stdin。

<script>

Execute the Python code contained in script, which must be a filesystem path (absolute or relative) referring to either a Python file, a directory containing a __main__.py file, or a zipfile containing a __main__.py file.

If this option is given, the first element of sys.argv will be the script name as given on the command line.

If the script name refers directly to a Python file, the directory containing that file is added to the start of sys.path, and the file is executed as the __main__ module.

If the script name refers to a directory or zipfile, the script name is added to the start of sys.path and the __main__.py file in that location is executed as the __main__ module.

-I option can be used to run the script in isolated mode where sys.path contains neither the script's directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too.

引發一個附帶引數 filename 的稽核事件 cpython.run_file。

也參考

runpy.run_path()

Equivalent functionality directly available to Python code

If no interface option is given, -i is implied, sys.argv[0] is an empty string ("") and the current directory will be added to the start of sys.path. Also, tab-completion and history editing is automatically enabled, if available on your platform (see Readline configuration).

也參考

啟動直譯器

在 3.4 版的變更: Automatic enabling of tab-completion and history editing.

1.1.2. Generic options

-?

-h

--help

Print a short description of all command line options and corresponding environment variables and exit.

--help-env

Print a short description of Python-specific environment variables and exit.

在 3.11 版被加入.

--help-xoptions

Print a description of implementation-specific -X options and exit.

在 3.11 版被加入.

--help-all

印出完整使用資訊並離開。

在 3.11 版被加入.

-V

--version

Print the Python version number and exit. Example output could be:

Python 3.8.0b2+

When given twice, print more information about the build, like:

Python 3.8.0b2+ (3.8:0c076caaa8, Apr 20 2019, 21:55:00)
[GCC 6.2.0 20161005]

在 3.6 版被加入: -VV 選項

1.1.3. Miscellaneous options

-b

Issue a warning when converting bytes or bytearray to str without specifying encoding or comparing bytes or bytearray with str or bytes with int. Issue an error when the option is given twice (-bb).

在 3.5 版的變更: Affects also comparisons of bytes with int.

-B

If given, Python won't try to write .pyc files on the import of source modules. See also PYTHONDONTWRITEBYTECODE.

--check-hash-based-pycs default|always|never

Control the validation behavior of hash-based .pyc files. See Cached bytecode invalidation. When set to default, checked and unchecked hash-based bytecode cache files are validated according to their default semantics. When set to always, all hash-based .pyc files, whether checked or unchecked, are validated against their corresponding source file. When set to never, hash-based .pyc files are not validated against their corresponding source files.

The semantics of timestamp-based .pyc files are unaffected by this option.

-d

Turn on parser debugging output (for expert only). See also the PYTHONDEBUG environment variable.

This option requires a debug build of Python, otherwise it's ignored.

-E

Ignore all PYTHON* environment variables, e.g. PYTHONPATH and PYTHONHOME, that might be set.

另請參閱 -P 和 -I (isolated) 選項。

-i

Enter interactive mode after execution.

Using the -i option will enter interactive mode in any of the following circumstances:

When a script is passed as first argument

When the -c option is used

When the -m option is used

Interactive mode will start even when sys.stdin does not appear to be a terminal. The PYTHONSTARTUP file is not read.

This can be useful to inspect global variables or a stack trace when a script raises an exception. See also PYTHONINSPECT.

-I

Run Python in isolated mode. This also implies -E, -P and -s options.

In isolated mode sys.path contains neither the script's directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too. Further restrictions may be imposed to prevent the user from injecting malicious code.

在 3.4 版被加入.

-O

Remove assert statements and any code conditional on the value of __debug__. Augment the filename for compiled (bytecode) files by adding .opt-1 before the .pyc extension (see PEP 488 [https://peps.python.org/pep-0488/]). See also PYTHONOPTIMIZE.

在 3.5 版的變更: 根據 PEP 488 [https://peps.python.org/pep-0488/] 修改 .pyc 檔案名稱。

-OO

Do -O and also discard docstrings. Augment the filename for compiled (bytecode) files by adding .opt-2 before the .pyc extension (see PEP 488 [https://peps.python.org/pep-0488/]).

在 3.5 版的變更: 根據 PEP 488 [https://peps.python.org/pep-0488/] 修改 .pyc 檔案名稱。

-P

Don't prepend a potentially unsafe path to sys.path:

python -m module command line: Don't prepend the current working directory.

python script.py command line: Don't prepend the script's directory. If it's a symbolic link, resolve symbolic links.

python -c code and python (REPL) command lines: Don't prepend an empty string, which means the current working directory.

See also the PYTHONSAFEPATH environment variable, and -E and -I (isolated) options.

在 3.11 版被加入.

-q

Don't display the copyright and version messages even in interactive mode.

在 3.2 版被加入.

-R

Turn on hash randomization. This option only has an effect if the PYTHONHASHSEED environment variable is set to anything other than random, since hash randomization is enabled by default.

On previous versions of Python, this option turns on hash randomization, so that the __hash__() values of str and bytes objects are "salted" with an unpredictable random value. Although they remain constant within an individual Python process, they are not predictable between repeated invocations of Python.

Hash randomization is intended to provide protection against a denial-of-service caused by carefully chosen inputs that exploit the worst case performance of a dict construction, O(n²) complexity. See http://ocert.org/advisories/ocert-2011-003.html for details.

PYTHONHASHSEED allows you to set a fixed value for the hash seed secret.

在 3.2.3 版被加入.

在 3.7 版的變更: The option is no longer ignored.

-s

Don't add the user site-packages directory to sys.path.

另請參閱 PYTHONNOUSERSITE。

也參考

PEP 370 [https://peps.python.org/pep-0370/] -- Per user site-packages directory

-S

Disable the import of the module site and the site-dependent manipulations of sys.path that it entails. Also disable these manipulations if site is explicitly imported later (call site.main() if you want them to be triggered).

-u

Force the stdout and stderr streams to be unbuffered. This option has no effect on the stdin stream.

另請參閱 PYTHONUNBUFFERED。

在 3.7 版的變更: The text layer of the stdout and stderr streams now is unbuffered.

-v

Print a message each time a module is initialized, showing the place (filename or built-in module) from which it is loaded. When given twice (-vv), print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit.

在 3.10 版的變更: The site module reports the site-specific paths and .pth files being processed.

另請參閱 PYTHONVERBOSE。

-W arg

Warning control. Python's warning machinery by default prints warning messages to sys.stderr.

The simplest settings apply a particular action unconditionally to all warnings emitted by a process (even those that are otherwise ignored by default):

-Wdefault  # Warn once per call location
-Werror    # Convert to exceptions
-Walways   # Warn every time
-Wall      # Same as -Walways
-Wmodule   # Warn once per calling module
-Wonce     # Warn once per Python process
-Wignore   # Never warn

The action names can be abbreviated as desired and the interpreter will resolve them to the appropriate action name. For example, -Wi is the same as -Wignore.

完整的引數形式為：

action:message:category:module:lineno

Empty fields match all values; trailing empty fields may be omitted. For example -W ignore::DeprecationWarning ignores all DeprecationWarning warnings.

The action field is as explained above but only applies to warnings that match the remaining fields.

The message field must match the whole warning message; this match is case-insensitive.

The category field matches the warning category (ex: DeprecationWarning). This must be a class name; the match test whether the actual warning category of the message is a subclass of the specified warning category.

The module field matches the (fully qualified) module name; this match is case-sensitive.

The lineno field matches the line number, where zero matches all line numbers and is thus equivalent to an omitted line number.

Multiple -W options can be given; when a warning matches more than one option, the action for the last matching option is performed. Invalid -W options are ignored (though, a warning message is printed about invalid options when the first warning is issued).

Warnings can also be controlled using the PYTHONWARNINGS environment variable and from within a Python program using the warnings module. For example, the warnings.filterwarnings() function can be used to use a regular expression on the warning message.

See 警告過濾器 and 描述警告過濾器 for more details.

-x

Skip the first line of the source, allowing use of non-Unix forms of #!cmd. This is intended for a DOS specific hack only.

-X

Reserved for various implementation-specific options. CPython currently defines the following possible values:

-X faulthandler to enable faulthandler. See also PYTHONFAULTHANDLER.

在 3.3 版被加入.

-X showrefcount to output the total reference count and number of used memory blocks when the program finishes or after each statement in the interactive interpreter. This only works on debug builds.

在 3.4 版被加入.

-X tracemalloc to start tracing Python memory allocations using the tracemalloc module. By default, only the most recent frame is stored in a traceback of a trace. Use -X tracemalloc=NFRAME to start tracing with a traceback limit of NFRAME frames. See tracemalloc.start() and PYTHONTRACEMALLOC for more information.

在 3.4 版被加入.

-X int_max_str_digits configures the integer string conversion length limitation. See also PYTHONINTMAXSTRDIGITS.

在 3.11 版被加入.

-X importtime to show how long each import takes. It shows module name, cumulative time (including nested imports) and self time (excluding nested imports). Note that its output may be broken in multi-threaded application. Typical usage is python -X importtime -c 'import asyncio'.

-X importtime=2 enables additional output that indicates when an imported module has already been loaded. In such cases, the string cached will be printed in both time columns.

另請參閱 PYTHONPROFILEIMPORTTIME。

在 3.7 版被加入.

在 3.14 版的變更: Added -X importtime=2 to also trace imports of loaded modules, and reserved values other than 1 and 2 for future use.

-X dev: enable Python Development Mode, introducing additional runtime checks that are too expensive to be enabled by default. See also PYTHONDEVMODE.

在 3.7 版被加入.

-X utf8 enables the Python UTF-8 Mode. -X utf8=0 explicitly disables Python UTF-8 Mode (even when it would otherwise activate automatically). See also PYTHONUTF8.

在 3.7 版被加入.

-X pycache_prefix=PATH enables writing .pyc files to a parallel tree rooted at the given directory instead of to the code tree. See also PYTHONPYCACHEPREFIX.

在 3.8 版被加入.

-X warn_default_encoding issues a EncodingWarning when the locale-specific default encoding is used for opening files. See also PYTHONWARNDEFAULTENCODING.

在 3.10 版被加入.

-X no_debug_ranges disables the inclusion of the tables mapping extra location information (end line, start column offset and end column offset) to every instruction in code objects. This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks. See also PYTHONNODEBUGRANGES.

在 3.11 版被加入.

-X frozen_modules determines whether or not frozen modules are ignored by the import machinery. A value of on means they get imported and off means they are ignored. The default is on if this is an installed Python (the normal case). If it's under development (running from the source tree) then the default is off. Note that the importlib_bootstrap and importlib_bootstrap_external frozen modules are always used, even if this flag is set to off. See also PYTHON_FROZEN_MODULES.

在 3.11 版被加入.

-X perf enables support for the Linux perf profiler. When this option is provided, the perf profiler will be able to report Python calls. This option is only available on some platforms and will do nothing if is not supported on the current system. The default value is "off". See also PYTHONPERFSUPPORT and Python 對 Linux perf 分析器的支援.

在 3.12 版被加入.

-X perf_jit enables support for the Linux perf profiler with DWARF support. When this option is provided, the perf profiler will be able to report Python calls using DWARF information. This option is only available on some platforms and will do nothing if is not supported on the current system. The default value is "off". See also PYTHON_PERF_JIT_SUPPORT and Python 對 Linux perf 分析器的支援.

在 3.13 版被加入.

-X disable_remote_debug disables the remote debugging support as described in PEP 768 [https://peps.python.org/pep-0768/]. This includes both the functionality to schedule code for execution in another process and the functionality to receive code for execution in the current process.

This option is only available on some platforms and will do nothing if is not supported on the current system. See also PYTHON_DISABLE_REMOTE_DEBUG and PEP 768 [https://peps.python.org/pep-0768/].

在 3.14 版被加入.

-X cpu_count=n overrides os.cpu_count(), os.process_cpu_count(), and multiprocessing.cpu_count(). n must be greater than or equal to 1. This option may be useful for users who need to limit CPU resources of a container system. See also PYTHON_CPU_COUNT. If n is default, nothing is overridden.

在 3.13 版被加入.

-X presite=package.module specifies a module that should be imported before the site module is executed and before the __main__ module exists. Therefore, the imported module isn't __main__. This can be used to execute code early during Python initialization. Python needs to be built in debug mode for this option to exist. See also PYTHON_PRESITE.

在 3.13 版被加入.

-X gil=0,1 forces the GIL to be disabled or enabled, respectively. Setting to 0 is only available in builds configured with --disable-gil. See also PYTHON_GIL and Free-threaded CPython.

在 3.13 版被加入.

-X thread_inherit_context=0,1 causes Thread to, by default, use a copy of context of the caller of Thread.start() when starting. Otherwise, threads will start with an empty context. If unset, the value of this option defaults to 1 on free-threaded builds and to 0 otherwise. See also PYTHON_THREAD_INHERIT_CONTEXT.

在 3.14 版被加入.

-X context_aware_warnings=0,1 causes the warnings.catch_warnings context manager to use a ContextVar to store warnings filter state. If unset, the value of this option defaults to 1 on free-threaded builds and to 0 otherwise. See also PYTHON_CONTEXT_AWARE_WARNINGS.

在 3.14 版被加入.

-X tlbc=0,1 enables (1, the default) or disables (0) thread-local bytecode in builds configured with --disable-gil. When disabled, this also disables the specializing interpreter. See also PYTHON_TLBC.

在 3.14 版被加入.

It also allows passing arbitrary values and retrieving them through the sys._xoptions dictionary.

在 3.2 版被加入.

在 3.9 版的變更: 移除 -X showalloccount 選項。

在 3.10 版的變更: 移除 -X oldparser 選項。

在 3.14 版被移除: -J is no longer reserved for use by Jython [https://www.jython.org/], and now has no special meaning.

1.1.4. Controlling color

The Python interpreter is configured by default to use colors to highlight output in certain situations such as when displaying tracebacks. This behavior can be controlled by setting different environment variables.

Setting the environment variable TERM to dumb will disable color.

If the FORCE_COLOR [https://force-color.org/] environment variable is set, then color will be enabled regardless of the value of TERM. This is useful on CI systems which aren’t terminals but can still display ANSI escape sequences.

If the NO_COLOR [https://no-color.org/] environment variable is set, Python will disable all color in the output. This takes precedence over FORCE_COLOR.

All these environment variables are used also by other tools to control color output. To control the color output only in the Python interpreter, the PYTHON_COLORS environment variable can be used. This variable takes precedence over NO_COLOR, which in turn takes precedence over FORCE_COLOR.

1.2. 環境變數

These environment variables influence Python's behavior, they are processed before the command-line switches other than -E or -I. It is customary that command-line switches override environmental variables where there is a conflict.

PYTHONHOME

Change the location of the standard Python libraries. By default, the libraries are searched in prefix/lib/pythonversion and exec_prefix/lib/pythonversion, where prefix and exec_prefix are installation-dependent directories, both defaulting to /usr/local.

When PYTHONHOME is set to a single directory, its value replaces both prefix and exec_prefix. To specify different values for these, set PYTHONHOME to prefix:exec_prefix.

PYTHONPATH

Augment the default search path for module files. The format is the same as the shell's PATH: one or more directory pathnames separated by os.pathsep (e.g. colons on Unix or semicolons on Windows). Non-existent directories are silently ignored.

In addition to normal directories, individual PYTHONPATH entries may refer to zipfiles containing pure Python modules (in either source or compiled form). Extension modules cannot be imported from zipfiles.

The default search path is installation dependent, but generally begins with prefix/lib/pythonversion (see PYTHONHOME above). It is always appended to PYTHONPATH.

An additional directory will be inserted in the search path in front of PYTHONPATH as described above under 介面選項. The search path can be manipulated from within a Python program as the variable sys.path.

PYTHONSAFEPATH

If this is set to a non-empty string, don't prepend a potentially unsafe path to sys.path: see the -P option for details.

在 3.11 版被加入.

PYTHONPLATLIBDIR

If this is set to a non-empty string, it overrides the sys.platlibdir value.

在 3.9 版被加入.

PYTHONSTARTUP

If this is the name of a readable file, the Python commands in that file are executed before the first prompt is displayed in interactive mode. The file is executed in the same namespace where interactive commands are executed so that objects defined or imported in it can be used without qualification in the interactive session. You can also change the prompts sys.ps1 and sys.ps2 and the hook sys.__interactivehook__ in this file.

引發一個附帶呼叫啟動時的檔案名稱為引數的稽核事件 cpython.run_startup。

PYTHONOPTIMIZE

If this is set to a non-empty string it is equivalent to specifying the -O option. If set to an integer, it is equivalent to specifying -O multiple times.

PYTHONBREAKPOINT

If this is set, it names a callable using dotted-path notation. The module containing the callable will be imported and then the callable will be run by the default implementation of sys.breakpointhook() which itself is called by built-in breakpoint(). If not set, or set to the empty string, it is equivalent to the value "pdb.set_trace". Setting this to the string "0" causes the default implementation of sys.breakpointhook() to do nothing but return immediately.

在 3.7 版被加入.

PYTHONDEBUG

If this is set to a non-empty string it is equivalent to specifying the -d option. If set to an integer, it is equivalent to specifying -d multiple times.

This environment variable requires a debug build of Python, otherwise it's ignored.

PYTHONINSPECT

If this is set to a non-empty string it is equivalent to specifying the -i option.

This variable can also be modified by Python code using os.environ to force inspect mode on program termination.

引發一個不附帶引數的稽核事件 cpython.run_stdin。

在 3.12.5 版的變更: (also 3.11.10, 3.10.15, 3.9.20, and 3.8.20) Emits audit events.

在 3.13 版的變更: Uses PyREPL if possible, in which case PYTHONSTARTUP is also executed. Emits audit events.

PYTHONUNBUFFERED

If this is set to a non-empty string it is equivalent to specifying the -u option.

PYTHONVERBOSE

If this is set to a non-empty string it is equivalent to specifying the -v option. If set to an integer, it is equivalent to specifying -v multiple times.

PYTHONCASEOK

If this is set, Python ignores case in import statements. This only works on Windows and macOS.

PYTHONDONTWRITEBYTECODE

If this is set to a non-empty string, Python won't try to write .pyc files on the import of source modules. This is equivalent to specifying the -B option.

PYTHONPYCACHEPREFIX

If this is set, Python will write .pyc files in a mirror directory tree at this path, instead of in __pycache__ directories within the source tree. This is equivalent to specifying the -X pycache_prefix=PATH option.

在 3.8 版被加入.

PYTHONHASHSEED

If this variable is not set or set to random, a random value is used to seed the hashes of str and bytes objects.

If PYTHONHASHSEED is set to an integer value, it is used as a fixed seed for generating the hash() of the types covered by the hash randomization.

Its purpose is to allow repeatable hashing, such as for selftests for the interpreter itself, or to allow a cluster of python processes to share hash values.

The integer must be a decimal number in the range [0,4294967295]. Specifying the value 0 will disable hash randomization.

在 3.2.3 版被加入.

PYTHONINTMAXSTRDIGITS

If this variable is set to an integer, it is used to configure the interpreter's global integer string conversion length limitation.

在 3.11 版被加入.

PYTHONIOENCODING

If this is set before running the interpreter, it overrides the encoding used for stdin/stdout/stderr, in the syntax encodingname:errorhandler. Both the encodingname and the :errorhandler parts are optional and have the same meaning as in str.encode().

For stderr, the :errorhandler part is ignored; the handler will always be 'backslashreplace'.

在 3.4 版的變更: The encodingname part is now optional.

在 3.6 版的變更: On Windows, the encoding specified by this variable is ignored for interactive console buffers unless PYTHONLEGACYWINDOWSSTDIO is also specified. Files and pipes redirected through the standard streams are not affected.

PYTHONNOUSERSITE

If this is set, Python won't add the user site-packages directory to sys.path.

也參考

PEP 370 [https://peps.python.org/pep-0370/] -- Per user site-packages directory

PYTHONUSERBASE

Defines the user base directory, which is used to compute the path of the user site-packages directory and installation paths for python -m pip install --user.

也參考

PEP 370 [https://peps.python.org/pep-0370/] -- Per user site-packages directory

PYTHONEXECUTABLE

If this environment variable is set, sys.argv[0] will be set to its value instead of the value got through the C runtime. Only works on macOS.

PYTHONWARNINGS

This is equivalent to the -W option. If set to a comma separated string, it is equivalent to specifying -W multiple times, with filters later in the list taking precedence over those earlier in the list.

The simplest settings apply a particular action unconditionally to all warnings emitted by a process (even those that are otherwise ignored by default):

PYTHONWARNINGS=default  # Warn once per call location
PYTHONWARNINGS=error    # Convert to exceptions
PYTHONWARNINGS=always   # Warn every time
PYTHONWARNINGS=all      # Same as PYTHONWARNINGS=always
PYTHONWARNINGS=module   # Warn once per calling module
PYTHONWARNINGS=once     # Warn once per Python process
PYTHONWARNINGS=ignore   # Never warn

See 警告過濾器 and 描述警告過濾器 for more details.

PYTHONFAULTHANDLER

If this environment variable is set to a non-empty string, faulthandler.enable() is called at startup: install a handler for SIGSEGV, SIGFPE, SIGABRT, SIGBUS and SIGILL signals to dump the Python traceback. This is equivalent to -X faulthandler option.

在 3.3 版被加入.

PYTHONTRACEMALLOC

If this environment variable is set to a non-empty string, start tracing Python memory allocations using the tracemalloc module. The value of the variable is the maximum number of frames stored in a traceback of a trace. For example, PYTHONTRACEMALLOC=1 stores only the most recent frame. See the tracemalloc.start() function for more information. This is equivalent to setting the -X tracemalloc option.

在 3.4 版被加入.

PYTHONPROFILEIMPORTTIME

If this environment variable is set to 1, Python will show how long each import takes. If set to 2, Python will include output for imported modules that have already been loaded. This is equivalent to setting the -X importtime option.

在 3.7 版被加入.

在 3.14 版的變更: Added PYTHONPROFILEIMPORTTIME=2 to also trace imports of loaded modules.

PYTHONASYNCIODEBUG

If this environment variable is set to a non-empty string, enable the debug mode of the asyncio module.

在 3.4 版被加入.

PYTHONMALLOC

Set the Python memory allocators and/or install debug hooks.

Set the family of memory allocators used by Python:

default: use the default memory allocators.

malloc: use the malloc() function of the C library for all domains (PYMEM_DOMAIN_RAW, PYMEM_DOMAIN_MEM, PYMEM_DOMAIN_OBJ).

pymalloc: use the pymalloc allocator for PYMEM_DOMAIN_MEM and PYMEM_DOMAIN_OBJ domains and use the malloc() function for the PYMEM_DOMAIN_RAW domain.

mimalloc: use the mimalloc allocator for PYMEM_DOMAIN_MEM and PYMEM_DOMAIN_OBJ domains and use the malloc() function for the PYMEM_DOMAIN_RAW domain.

Install debug hooks:

debug: install debug hooks on top of the default memory allocators.

malloc_debug: same as malloc but also install debug hooks.

pymalloc_debug: same as pymalloc but also install debug hooks.

mimalloc_debug: same as mimalloc but also install debug hooks.

在 3.6 版被加入.

在 3.7 版的變更: Added the "default" allocator.

PYTHONMALLOCSTATS

If set to a non-empty string, Python will print statistics of the pymalloc memory allocator every time a new pymalloc object arena is created, and on shutdown.

This variable is ignored if the PYTHONMALLOC environment variable is used to force the malloc() allocator of the C library, or if Python is configured without pymalloc support.

在 3.6 版的變更: This variable can now also be used on Python compiled in release mode. It now has no effect if set to an empty string.

PYTHONLEGACYWINDOWSFSENCODING

If set to a non-empty string, the default filesystem encoding and error handler mode will revert to their pre-3.6 values of 'mbcs' and 'replace', respectively. Otherwise, the new defaults 'utf-8' and 'surrogatepass' are used.

This may also be enabled at runtime with sys._enablelegacywindowsfsencoding().

可用性: Windows.

在 3.6 版被加入: 更多細節請見 PEP 529 [https://peps.python.org/pep-0529/]。

PYTHONLEGACYWINDOWSSTDIO

If set to a non-empty string, does not use the new console reader and writer. This means that Unicode characters will be encoded according to the active console code page, rather than using utf-8.

This variable is ignored if the standard streams are redirected (to files or pipes) rather than referring to console buffers.

可用性: Windows.

在 3.6 版被加入.

PYTHONCOERCECLOCALE

If set to the value 0, causes the main Python command line application to skip coercing the legacy ASCII-based C and POSIX locales to a more capable UTF-8 based alternative.

If this variable is not set (or is set to a value other than 0), the LC_ALL locale override environment variable is also not set, and the current locale reported for the LC_CTYPE category is either the default C locale, or else the explicitly ASCII-based POSIX locale, then the Python CLI will attempt to configure the following locales for the LC_CTYPE category in the order listed before loading the interpreter runtime:

C.UTF-8

C.utf8

UTF-8

If setting one of these locale categories succeeds, then the LC_CTYPE environment variable will also be set accordingly in the current process environment before the Python runtime is initialized. This ensures that in addition to being seen by both the interpreter itself and other locale-aware components running in the same process (such as the GNU readline library), the updated setting is also seen in subprocesses (regardless of whether or not those processes are running a Python interpreter), as well as in operations that query the environment rather than the current C locale (such as Python's own locale.getdefaultlocale()).

Configuring one of these locales (either explicitly or via the above implicit locale coercion) automatically enables the surrogateescape error handler for sys.stdin and sys.stdout (sys.stderr continues to use backslashreplace as it does in any other locale). This stream handling behavior can be overridden using PYTHONIOENCODING as usual.

For debugging purposes, setting PYTHONCOERCECLOCALE=warn will cause Python to emit warning messages on stderr if either the locale coercion activates, or else if a locale that would have triggered coercion is still active when the Python runtime is initialized.

Also note that even when locale coercion is disabled, or when it fails to find a suitable target locale, PYTHONUTF8 will still activate by default in legacy ASCII-based locales. Both features must be disabled in order to force the interpreter to use ASCII instead of UTF-8 for system interfaces.

可用性: Unix.

在 3.7 版被加入: 更多細節請見 PEP 538 [https://peps.python.org/pep-0538/]。

PYTHONDEVMODE

If this environment variable is set to a non-empty string, enable Python Development Mode, introducing additional runtime checks that are too expensive to be enabled by default. This is equivalent to setting the -X dev option.

在 3.7 版被加入.

PYTHONUTF8

如果設為 1，則啟用 Python UTF-8 Mode。

如果設為 0，則停用 Python UTF-8 Mode。

Setting any other non-empty string causes an error during interpreter initialisation.

在 3.7 版被加入.

PYTHONWARNDEFAULTENCODING

If this environment variable is set to a non-empty string, issue a EncodingWarning when the locale-specific default encoding is used.

細節請見 選擇性加入的編碼警告。

在 3.10 版被加入.

PYTHONNODEBUGRANGES

If this variable is set, it disables the inclusion of the tables mapping extra location information (end line, start column offset and end column offset) to every instruction in code objects. This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks.

在 3.11 版被加入.

PYTHONPERFSUPPORT

If this variable is set to a nonzero value, it enables support for the Linux perf profiler so Python calls can be detected by it.

If set to 0, disable Linux perf profiler support.

See also the -X perf command-line option and Python 對 Linux perf 分析器的支援.

在 3.12 版被加入.

PYTHON_PERF_JIT_SUPPORT

If this variable is set to a nonzero value, it enables support for the Linux perf profiler so Python calls can be detected by it using DWARF information.

If set to 0, disable Linux perf profiler support.

See also the -X perf_jit command-line option and Python 對 Linux perf 分析器的支援.

在 3.13 版被加入.

PYTHON_DISABLE_REMOTE_DEBUG

If this variable is set to a non-empty string, it disables the remote debugging feature described in PEP 768 [https://peps.python.org/pep-0768/]. This includes both the functionality to schedule code for execution in another process and the functionality to receive code for execution in the current process.

另請參閱 -X disable_remote_debug 命令列選項。

在 3.14 版被加入.

PYTHON_CPU_COUNT

If this variable is set to a positive integer, it overrides the return values of os.cpu_count() and os.process_cpu_count().

另請參閱 -X cpu_count 命令列選項。

在 3.13 版被加入.

PYTHON_FROZEN_MODULES

If this variable is set to on or off, it determines whether or not frozen modules are ignored by the import machinery. A value of on means they get imported and off means they are ignored. The default is on for non-debug builds (the normal case) and off for debug builds. Note that the importlib_bootstrap and importlib_bootstrap_external frozen modules are always used, even if this flag is set to off.

另請參閱 -X frozen_modules 命令列選項。

在 3.13 版被加入.

PYTHON_COLORS

If this variable is set to 1, the interpreter will colorize various kinds of output. Setting it to 0 deactivates this behavior. See also Controlling color.

在 3.13 版被加入.

PYTHON_BASIC_REPL

If this variable is set to any value, the interpreter will not attempt to load the Python-based REPL that requires readline, and will instead use the traditional parser-based REPL.

在 3.13 版被加入.

PYTHON_HISTORY

This environment variable can be used to set the location of a .python_history file (by default, it is .python_history in the user's home directory).

在 3.13 版被加入.

PYTHON_GIL

If this variable is set to 1, the global interpreter lock (GIL) will be forced on. Setting it to 0 forces the GIL off (needs Python configured with the --disable-gil build option).

See also the -X gil command-line option, which takes precedence over this variable, and Free-threaded CPython.

在 3.13 版被加入.

PYTHON_THREAD_INHERIT_CONTEXT

If this variable is set to 1 then Thread will, by default, use a copy of context of the caller of Thread.start() when starting. Otherwise, new threads will start with an empty context. If unset, this variable defaults to 1 on free-threaded builds and to 0 otherwise. See also -X thread_inherit_context.

在 3.14 版被加入.

PYTHON_CONTEXT_AWARE_WARNINGS

If set to 1 then the warnings.catch_warnings context manager will use a ContextVar to store warnings filter state. If unset, this variable defaults to 1 on free-threaded builds and to 0 otherwise. See -X context_aware_warnings.

在 3.14 版被加入.

PYTHON_JIT

On builds where experimental just-in-time compilation is available, this variable can force the JIT to be disabled (0) or enabled (1) at interpreter startup.

在 3.13 版被加入.

PYTHON_TLBC

If set to 1 enables thread-local bytecode. If set to 0 thread-local bytecode and the specializing interpreter are disabled. Only applies to builds configured with --disable-gil.

另請參閱 -X tlbc 命令列選項。

在 3.14 版被加入.

1.2.1. 除錯模式變數

PYTHONDUMPREFS

If set, Python will dump objects and reference counts still alive after shutting down the interpreter.

Needs Python configured with the --with-trace-refs build option.

PYTHONDUMPREFSFILE

If set, Python will dump objects and reference counts still alive after shutting down the interpreter into a file under the path given as the value to this environment variable.

Needs Python configured with the --with-trace-refs build option.

在 3.11 版被加入.

PYTHON_PRESITE

If this variable is set to a module, that module will be imported early in the interpreter lifecycle, before the site module is executed, and before the __main__ module is created. Therefore, the imported module is not treated as __main__.

This can be used to execute code early during Python initialization.

To import a submodule, use package.module as the value, like in an import statement.

See also the -X presite command-line option, which takes precedence over this variable.

Needs Python configured with the --with-pydebug build option.

在 3.13 版被加入.

2. 在 Unix 平臺上使用 Python

2.1. 獲得並安裝 Python 的最新版本

2.1.1. 在 Linux 上

在大多數 Linux 發行版上會預先安裝 Python，並作為一個套件提供給所有其他使用者。但是發行版提供的套件可能沒有你想要使用的某些功能，這時你可以選擇從原始碼編譯最新版本的 Python。

如果最新版的 Python 沒有預先安裝，並且不在發行版提供的儲存庫 (repository) 中，你可以輕鬆地為自己使用的發行版建立套件。參閱以下連結：

也參考

https://www.debian.org/doc/manuals/maint-guide/first.en.html

對於 Debian 使用者

https://en.opensuse.org/Portal:Packaging

對於 OpenSuse 使用者

https://docs.fedoraproject.org/en-US/package-maintainers/Packaging_Tutorial_GNU_Hello/

對於 Fedora 使用者

https://slackbook.org/html/package-management-making-packages.html

對於 Slackware 使用者

2.1.1.1. 安裝 IDLE

在某些情況下，IDLE 可能不會包含在你的 Python 安裝中。

對於 Debian 和 Ubuntu 使用者：

sudo apt update
sudo apt install idle

對於 Fedora、RHEL 和 CentOS 使用者：

sudo dnf install python3-idle

對於 SUSE 和 OpenSUSE 使用者：

sudo zypper install python3-idle

對於 Alpine Linux 使用者：

sudo apk add python3-idle

2.1.2. 在 FreeBSD 和 OpenBSD 上

FreeBSD 使用者應使用以下命令增加套件：

pkg install python3

OpenBSD 使用者應使用以下命令增加套件：

pkg_add -r python

pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/<insert your architecture here>/python-<version>.tgz

例如 i386 使用者要取得 Python 2.5.1 的可用版本：

pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/i386/python-2.5.1p2.tgz

2.2. 建置 Python

也參考

If you want to contribute to CPython, refer to the devguide [https://devguide.python.org/getting-started/setup-building/], which includes build instructions and other tips on setting up environment.

如果你想自己編譯 CPython，首先要做的是取得原始碼 [https://www.python.org/downloads/source/]。你可以下載最新版本的原始碼，也可以直接提取最新的 clone（克隆） [https://devguide.python.org/setup/#get-the-source-code]。你還需要安裝建置需求。

建置過程由幾個常用命令組成：

./configure
make
make install

特定 Unix 平臺的配置選項和注意事項通常會詳細地記錄在 Python 原始碼樹 (source tree) 根目錄下的 README.rst [https://github.com/python/cpython/tree/3.14/README.rst] 檔案中。

警告

make install 可以覆蓋或偽裝 python3 二進位制檔案。因此，建議使用 make altinstall 而不是 make install，因為它只安裝 exec_prefix/bin/pythonversion。

2.3. 與 Python 相關的路徑和檔案

這取決於本地安裝慣例；prefix 和 exec_prefix 相依於安裝方式，應被直譯來讓 GNU 軟體使用；它們也可能相同。

例如，在大多數 Linux 系統上，兩者的預設值皆是 /usr。

檔案/目錄

含意

exec_prefix/bin/python3

直譯器的推薦位置。

prefix/lib/pythonversion、exec_prefix/lib/pythonversion

包含標準模組目錄的推薦位置。

prefix/include/pythonversion、exec_prefix/include/pythonversion

包含開發 Python 擴充套件和嵌入直譯器所需 include 檔案之目錄的推薦位置。

2.4. 雜項

要在 Unix 上使用 Python 腳本，你需要讓他們是可執行的 (executable)，例如用

$ chmod +x script

並在腳本的頂部放一個合適的 Shebang。以下通常是個好選擇：

#!/usr/bin/env python3

將在整個 PATH 中搜尋 Python 直譯器。然而某些 Unix 系統可能沒有 env 命令，因此你可能需要將 /usr/bin/python3 寫死 (hardcode) 成直譯器路徑。

要在 Python 腳本中使用 shell 命令，請見 subprocess 模組。

2.5. 客製化 OpenSSL

要使用你所選擇發行商 (vendor) 的 OpenSSL 配置和系統信任儲存區 (system trust store)，請找到包含 openssl.cnf 檔案的目錄或位於 /etc 的符號連結 (symlink)。在大多數發行版上，該檔案會是在 /etc/ssl 或者 /etc/pki/tls 中。該目錄亦應包含一個 cert.pem 檔案和/或一個 certs 目錄。

$ find /etc/ -name openssl.cnf -printf "%h\n"
/etc/ssl

下載、建置並安裝 OpenSSL。請確保你使用 install_sw 而不是 install。install_sw 的目標不會覆蓋 openssl.cnf。

$ curl -O https://www.openssl.org/source/openssl-VERSION.tar.gz
$ tar xzf openssl-VERSION
$ pushd openssl-VERSION
$ ./config \
    --prefix=/usr/local/custom-openssl \
    --libdir=lib \
    --openssldir=/etc/ssl
$ make -j1 depend
$ make -j8
$ make install_sw
$ popd

使用客製化 OpenSSL 建置 Python（參見配置 --with-openssl 和 --with-openssl-rpath 選項）

$ pushd python-3.x.x
$ ./configure -C \
    --with-openssl=/usr/local/custom-openssl \
    --with-openssl-rpath=auto \
    --prefix=/usr/local/python-3.x.x
$ make -j8
$ make altinstall

備註

OpenSSL 的修補釋出版 (patch releases) 具有向後相容的 ABI。你不需要重新編譯 Python 來更新 OpenSSL。使用一個新的版本來替代客製化 OpenSSL 安裝版就可以了。

3. 配置 Python

3.1. 建置需求

要建置 CPython，你將需要：

一個 C11 [https://en.cppreference.com/w/c/11] 編譯器。選擇性 C11 功能 [https://en.wikipedia.org/wiki/C11_(C_standard_revision)#Optional_features]並非必要。

在 Windows 上需要 Microsoft Visual Studio 2017 或更新版本。

支援 IEEE 754 [https://en.wikipedia.org/wiki/IEEE_754] 浮點數與浮點數非數值 (NaN) [https://en.wikipedia.org/wiki/NaN#Floating_point]。

thread 的支援。

在 3.5 版的變更: 在 Windows 上現在需要 Visual Studio 2015 或更新版本。

在 3.6 版的變更: Selected C99 features, like <stdint.h> and static inline functions, are now required.

在 3.7 版的變更: 執行緒支援現在是必要的。

在 3.11 版的變更: 現在需要 C11 編譯器、IEEE 754 和 NaN 支援。在 Windows 上需要 Visual Studio 2017 或更新版本。

See also PEP 7 [https://peps.python.org/pep-0007/] "Style Guide for C Code" and PEP 11 [https://peps.python.org/pep-0011/] "CPython platform support".

3.1.1. 可選模組的需求

Some optional modules of the standard library require third-party libraries installed for development (for example, header files must be available).

Missing requirements are reported in the configure output. Modules that are missing due to missing dependencies are listed near the end of the make output, sometimes using an internal name, for example, _ctypes for ctypes module.

If you distribute a CPython interpreter without optional modules, it's best practice to advise users, who generally expect that standard library modules are available.

建置可選模組的依賴項目為：

Dependency

Minimum version

Python 模組

libbz2 [https://sourceware.org/bzip2/]

bz2

libffi [https://sourceware.org/libffi/]

建議使用 3.3.0 版本

ctypes

liblzma [https://tukaani.org/xz/]

lzma

libmpdec [https://www.bytereef.org/mpdecimal/doc/libmpdec/]

2.5.0

decimal [1]

libreadline [https://tiswww.case.edu/php/chet/readline/rltop.html] 或 libedit [https://www.thrysoee.dk/editline/] [2]

readline

libuuid [https://linux.die.net/man/3/libuuid]

_uuid [3]

ncurses [https://gnu.org/software/ncurses/ncurses.html] [4]

curses

OpenSSL [https://openssl-library.org/]

3.0.18 recommended

(1.1.1 minimum)

ssl、hashlib [5]

SQLite [https://sqlite.org/]

3.15.2

sqlite3

Tcl/Tk [https://www.tcl-lang.org/]

8.5.12

tkinter、IDLE、turtle

zlib [https://www.zlib.net]

1.2.2.1

zlib、gzip、ensurepip

zstd [https://facebook.github.io/zstd/]

1.4.5

compression.zstd

[1]

If libmpdec is not available, the decimal module will use a pure-Python implementation. See --with-system-libmpdec for details.

[2]

See --with-readline for choosing the backend for the readline module.

[3]

The uuid module uses _uuid to generate "safe" UUIDs. See the module documentation for details.

[4]

The curses module requires the libncurses or libncursesw library. The curses.panel module additionally requires the libpanel or libpanelw library.

[5]

If OpenSSL is not available, the hashlib module will use bundled implementations of several hash functions. See --with-builtin-hashlib-hashes for forcing usage of OpenSSL.

Note that the table does not include all optional modules; in particular, platform-specific modules like winreg are not listed here.

也參考

The devguide [https://devguide.python.org/getting-started/setup-building/#install-dependencies] includes a full list of dependencies required to build all modules and instructions on how to install them on common platforms.

--with-system-expat allows building with an external libexpat [https://libexpat.github.io/] library.

Options for third-party dependencies

在 3.1 版的變更: tkinter 現在需要 Tcl/Tk version 8.3.1。

在 3.5 版的變更: tkinter 現在需要 Tcl/Tk version 8.4。

在 3.7 版的變更: hashlib 和 ssl 現在需要 OpenSSL 1.0.2。

在 3.10 版的變更: hashlib 和 ssl 現在需要 OpenSSL 1.1.1。sqlite3 現在需要 SQLite 3.7.15。

在 3.11 版的變更: tkinter 現在需要 Tcl/Tk version 8.5.12。

在 3.13 版的變更: sqlite3 現在會需要 SQLite 3.15.2。

3.2. 產生的檔案

To reduce build dependencies, Python source code contains multiple generated files. Commands to regenerate all generated files:

make regen-all
make regen-stdlib-module-names
make regen-limited-abi
make regen-configure

The Makefile.pre.in file documents generated files, their inputs, and tools used to regenerate them. Search for regen-* make targets.

3.2.1. 設定腳本

The make regen-configure command regenerates the aclocal.m4 file and the configure script using the Tools/build/regen-configure.sh shell script which uses an Ubuntu container to get the same tools versions and have a reproducible output.

The container is optional, the following command can be run locally:

autoreconf -ivf -Werror

The generated files can change depending on the exact versions of the tools used. The container that CPython uses has Autoconf [https://gnu.org/software/autoconf] 2.72, aclocal from Automake [https://www.gnu.org/software/automake] 1.16.5, and pkg-config [https://www.freedesktop.org/wiki/Software/pkg-config/] 1.8.1.

在 3.13 版的變更: Autoconf 2.71 and aclocal 1.16.5 and are now used to regenerate configure.

在 3.14 版的變更: 現在使用 Autoconf 2.72 來重新產生 configure。

3.3. 設定選項

使用以下命令列出所有 configure 腳本選項：

./configure --help

請見 Python 原始碼發行版中的 Misc/SpecialBuilds.txt。

3.3.1. 一般選項

--enable-loadable-sqlite-extensions

Support loadable extensions in the _sqlite extension module (default is no) of the sqlite3 module.

請見 sqlite3 模組的 sqlite3.Connection.enable_load_extension() 方法。

在 3.6 版被加入.

--disable-ipv6

停用 IPv6 支援（如果支援的話預設是啟用的），請見 socket 模組。

--enable-big-digits=[15|30]

Define the size in bits of Python int digits: 15 or 30 bits.

By default, the digit size is 30.

將 PYLONG_BITS_IN_DIGIT 定義為 15 或 30。

參閱 sys.int_info.bits_per_digit。

--with-suffix=SUFFIX

將 Python 執行檔的後綴設定為 SUFFIX。

在 Windows 和 macOS 上預設的後綴是 .exe （python.exe 執行檔）、在 Emscripten node 上為 .js、在 Emscripten 瀏覽器為 .html、在 WASI 上為 .wasm，以及在其他平台為空字串（python 執行檔）。

在 3.11 版的變更: 在 WASM 平台上預設的後綴是 .js、.html 或 .wasm 中的一個。

--with-tzpath=<list of absolute paths separated by pathsep>

Select the default time zone search path for zoneinfo.TZPATH. See the Compile-time configuration of the zoneinfo module.

預設值：/usr/share/zoneinfo:/usr/lib/zoneinfo:/usr/share/lib/zoneinfo:/etc/zoneinfo。

請見 os.pathsep 路徑分隔符號。

在 3.9 版被加入.

--without-decimal-contextvar

Build the _decimal extension module using a thread-local context rather than a coroutine-local context (default), see the decimal module.

請見 decimal.HAVE_CONTEXTVAR 與 contextvars 模組。

在 3.9 版被加入.

--with-dbmliborder=<list of backend names>

Override order to check db backends for the dbm module

A valid value is a colon (:) separated string with the backend names:

ndbm;

gdbm;

bdb.

--without-c-locale-coercion

Disable C locale coercion to a UTF-8 based locale (enabled by default).

不要定義 PY_COERCE_C_LOCALE 巨集。

請見 PYTHONCOERCECLOCALE 與 PEP 538 [https://peps.python.org/pep-0538/]。

--with-platlibdir=DIRNAME

Python 函式庫目錄名稱（預設為 lib ）。

Fedora 和 SuSE 在 64 位元平台上使用 lib64。

參閱 sys.platlibdir。

在 3.9 版被加入.

--with-wheel-pkg-dir=PATH

Directory of wheel packages used by the ensurepip module (none by default).

Some Linux distribution packaging policies recommend against bundling dependencies. For example, Fedora installs wheel packages in the /usr/share/python-wheels/ directory and don't install the ensurepip._bundled package.

在 3.10 版被加入.

--with-pkg-config=[check|yes|no]

Whether configure should use pkg-config to detect build dependencies.

check（預設）：pkg-config 是可選的

yes：pkg-config 是必要的

no：即使存在也不使用 pkg-config 來配置

在 3.11 版被加入.

--enable-pystats

Turn on internal Python performance statistics gathering.

By default, statistics gathering is off. Use python3 -X pystats command or set PYTHONSTATS=1 environment variable to turn on statistics gathering at Python startup.

At Python exit, dump statistics if statistics gathering was on and not cleared.

效果：

新增 -X pystats 命令列選項。

新增 PYTHONSTATS 環境變數。

定義 Py_STATS 巨集。

新增函式到 sys 模組。

sys._stats_on()：啟用統計資料收集。

sys._stats_off()：關閉統計資料收集。

sys._stats_clear()：清除統計資料。

sys._stats_dump()：將統計資料轉儲到檔案，並清除統計資料。

統計資料將被轉儲到 /tmp/py_stats/ (Unix) 或 C:\temp\py_stats\ (Windows) 中的任意（可能是唯一的）檔案。如果該目錄不存在，結果將被列印到 stderr。

使用 Tools/scripts/summarize_stats.py 來讀取統計資料。

Statistics:

Opcode:

Specialization: success, failure, hit, deferred, miss, deopt, failures;

Execution count;

Pair count.

Call:

Inlined Python calls;

PyEval calls;

Frames pushed;

Frame object created;

Eval calls: vector, generator, legacy, function VECTORCALL, build class, slot, function "ex", API, method.

物件：

incref and decref;

interpreter incref and decref;

allocations: all, 512 bytes, 4 kiB, big;

free;

to/from free lists;

dictionary materialized/dematerialized;

type cache;

最佳化嘗試；

optimization traces created/executed;

uops executed.

垃圾回收器：

垃圾回收；

Objects visited;

Objects collected.

在 3.11 版被加入.

--disable-gil

Enables support for running Python without the global interpreter lock (GIL): free threading build.

Defines the Py_GIL_DISABLED macro and adds "t" to sys.abiflags.

細節請參見 Free-threaded CPython。

在 3.13 版被加入.

--enable-experimental-jit=[no|yes|yes-off|interpreter]

Indicate how to integrate the experimental just-in-time compiler.

no: Don't build the JIT.

yes: Enable the JIT. To disable it at runtime, set the environment variable PYTHON_JIT=0.

yes-off: Build the JIT, but disable it by default. To enable it at runtime, set the environment variable PYTHON_JIT=1.

interpreter: Enable the "JIT interpreter" (only useful for those debugging the JIT itself). To disable it at runtime, set the environment variable PYTHON_JIT=0.

--enable-experimental-jit=no is the default behavior if the option is not provided, and --enable-experimental-jit is shorthand for --enable-experimental-jit=yes. See Tools/jit/README.md for more information, including how to install the necessary build-time dependencies.

備註

When building CPython with JIT enabled, ensure that your system has Python 3.11 or later installed.

在 3.13 版被加入.

PKG_CONFIG

Path to pkg-config utility.

PKG_CONFIG_LIBDIR

PKG_CONFIG_PATH

pkg-config 選項。

3.3.2. C 編譯器選項。

CC

C 編譯器指令。

CFLAGS

C 編譯器旗標。

CPP

C 預處理器指令。

CPPFLAGS

C 預處理器旗標，例如：-Iinclude_dir。

3.3.3. Linker options

LDFLAGS

Linker flags, e.g. -Llibrary_directory.

LIBS

Libraries to pass to the linker, e.g. -llibrary.

MACHDEP

Name for machine-dependent library files.

3.3.4. Options for third-party dependencies

在 3.11 版被加入.

BZIP2_CFLAGS

BZIP2_LIBS

C compiler and linker flags to link Python to libbz2, used by bz2 module, overriding pkg-config.

CURSES_CFLAGS

CURSES_LIBS

C compiler and linker flags for libncurses or libncursesw, used by curses module, overriding pkg-config.

GDBM_CFLAGS

GDBM_LIBS

C compiler and linker flags for gdbm.

LIBEDIT_CFLAGS

LIBEDIT_LIBS

C compiler and linker flags for libedit, used by readline module, overriding pkg-config.

LIBFFI_CFLAGS

LIBFFI_LIBS

C compiler and linker flags for libffi, used by ctypes module, overriding pkg-config.

LIBMPDEC_CFLAGS

LIBMPDEC_LIBS

C compiler and linker flags for libmpdec, used by decimal module, overriding pkg-config.

備註

These environment variables have no effect unless --with-system-libmpdec is specified.

LIBLZMA_CFLAGS

LIBLZMA_LIBS

C compiler and linker flags for liblzma, used by lzma module, overriding pkg-config.

LIBREADLINE_CFLAGS

LIBREADLINE_LIBS

C compiler and linker flags for libreadline, used by readline module, overriding pkg-config.

LIBSQLITE3_CFLAGS

LIBSQLITE3_LIBS

C compiler and linker flags for libsqlite3, used by sqlite3 module, overriding pkg-config.

LIBUUID_CFLAGS

LIBUUID_LIBS

C compiler and linker flags for libuuid, used by uuid module, overriding pkg-config.

LIBZSTD_CFLAGS

LIBZSTD_LIBS

C compiler and linker flags for libzstd, used by compression.zstd module, overriding pkg-config.

在 3.14 版被加入.

PANEL_CFLAGS

PANEL_LIBS

C compiler and linker flags for PANEL, overriding pkg-config.

C compiler and linker flags for libpanel or libpanelw, used by curses.panel module, overriding pkg-config.

TCLTK_CFLAGS

TCLTK_LIBS

C compiler and linker flags for TCLTK, overriding pkg-config.

ZLIB_CFLAGS

ZLIB_LIBS

C compiler and linker flags for libzlib, used by gzip module, overriding pkg-config.

3.3.5. WebAssembly 選項

--enable-wasm-dynamic-linking

Turn on dynamic linking support for WASM.

Dynamic linking enables dlopen. File size of the executable increases due to limited dead code elimination and additional features.

在 3.11 版被加入.

--enable-wasm-pthreads

Turn on pthreads support for WASM.

在 3.11 版被加入.

3.3.6. 安裝選項

--prefix=PREFIX

Install architecture-independent files in PREFIX. On Unix, it defaults to /usr/local.

這個值可以在 runtime 使用 sys.prefix 取得。

As an example, one can use --prefix="$HOME/.local/" to install a Python in its home directory.

--exec-prefix=EPREFIX

Install architecture-dependent files in EPREFIX, defaults to --prefix.

這個值可以在 runtime 使用 sys.exec_prefix 取得

--disable-test-modules

Don't build nor install test modules, like the test package or the _testcapi extension module (built and installed by default).

在 3.10 版被加入.

--with-ensurepip=[upgrade|install|no]

選擇在 Python 安裝時執行的 ensurepip 命令：

upgrade （預設）：執行 python -m ensurepip --altinstall --upgrade 命令。

install：執行 python -m ensurepip --altinstall 命令；

no：不要執行 ensurepip；

在 3.6 版被加入.

3.3.7. 效能選項

Configuring Python using --enable-optimizations --with-lto (PGO + LTO) is recommended for best performance. The experimental --enable-bolt flag can also be used to improve performance.

--enable-optimizations

Enable Profile Guided Optimization (PGO) using PROFILE_TASK (disabled by default).

The C compiler Clang requires llvm-profdata program for PGO. On macOS, GCC also requires it: GCC is just an alias to Clang on macOS.

Disable also semantic interposition in libpython if --enable-shared and GCC is used: add -fno-semantic-interposition to the compiler and linker flags.

備註

During the build, you may encounter compiler warnings about profile data not being available for some source files. These warnings are harmless, as only a subset of the code is exercised during profile data acquisition. To disable these warnings on Clang, manually suppress them by adding -Wno-profile-instr-unprofiled to CFLAGS.

在 3.6 版被加入.

在 3.10 版的變更: 在 GCC 上使用 -fno-semantic-interposition。

PROFILE_TASK

Environment variable used in the Makefile: Python command line arguments for the PGO generation task.

預設值：-m test --pgo --timeout=$(TESTTIMEOUT)。

在 3.8 版被加入.

在 3.13 版的變更: Task failure is no longer ignored silently.

--with-lto=[full|thin|no|yes]

Enable Link Time Optimization (LTO) in any build (disabled by default).

The C compiler Clang requires llvm-ar for LTO (ar on macOS), as well as an LTO-aware linker (ld.gold or lld).

在 3.6 版被加入.

在 3.11 版被加入: To use ThinLTO feature, use --with-lto=thin on Clang.

在 3.12 版的變更: Use ThinLTO as the default optimization policy on Clang if the compiler accepts the flag.

--enable-bolt

Enable usage of the BOLT post-link binary optimizer [https://github.com/llvm/llvm-project/tree/main/bolt] (disabled by default).

BOLT is part of the LLVM project but is not always included in their binary distributions. This flag requires that llvm-bolt and merge-fdata are available.

BOLT is still a fairly new project so this flag should be considered experimental for now. Because this tool operates on machine code its success is dependent on a combination of the build environment + the other optimization configure args + the CPU architecture, and not all combinations are supported. BOLT versions before LLVM 16 are known to crash BOLT under some scenarios. Use of LLVM 16 or newer for BOLT optimization is strongly encouraged.

The BOLT_INSTRUMENT_FLAGS and BOLT_APPLY_FLAGS configure variables can be defined to override the default set of arguments for llvm-bolt to instrument and apply BOLT data to binaries, respectively.

在 3.12 版被加入.

BOLT_APPLY_FLAGS

Arguments to llvm-bolt when creating a BOLT optimized binary [https://github.com/facebookarchive/BOLT].

在 3.12 版被加入.

BOLT_INSTRUMENT_FLAGS

Arguments to llvm-bolt when instrumenting binaries.

在 3.12 版被加入.

--with-computed-gotos

Enable computed gotos in evaluation loop (enabled by default on supported compilers).

--with-tail-call-interp

Enable interpreters using tail calls in CPython. If enabled, enabling PGO (--enable-optimizations) is highly recommended. This option specifically requires a C compiler with proper tail call support, and the preserve_none [https://clang.llvm.org/docs/AttributeReference.html#preserve-none] calling convention. For example, Clang 19 and newer supports this feature.

在 3.14 版被加入.

--without-mimalloc

Disable the fast mimalloc allocator (enabled by default).

另請參閱 PYTHONMALLOC 環境變數。

--without-pymalloc

Disable the specialized Python memory allocator pymalloc (enabled by default).

另請參閱 PYTHONMALLOC 環境變數。

--without-doc-strings

Disable static documentation strings to reduce the memory footprint (enabled by default). Documentation strings defined in Python are not affected.

不要定義 WITH_DOC_STRINGS 巨集。

請見 PyDoc_STRVAR() 巨集。

--enable-profiling

Enable C-level code profiling with gprof (disabled by default).

--with-strict-overflow

Add -fstrict-overflow to the C compiler flags (by default we add -fno-strict-overflow instead).

--without-remote-debug

Deactivate remote debugging support described in PEP 768 [https://peps.python.org/pep-0768/] (enabled by default). When this flag is provided the code that allows the interpreter to schedule the execution of a Python file in a separate process as described in PEP 768 [https://peps.python.org/pep-0768/] is not compiled. This includes both the functionality to schedule code to be executed and the functionality to receive code to be executed.

Py_REMOTE_DEBUG

This macro is defined by default, unless Python is configured with --without-remote-debug.

Note that even if the macro is defined, remote debugging may not be available (for example, on an incompatible platform).

在 3.14 版被加入.

3.3.8. Python Debug Build

A debug build is Python built with the --with-pydebug configure option.

Effects of a debug build:

Display all warnings by default: the list of default warning filters is empty in the warnings module.

新增 d 到 sys.abiflags。

新增 sys.gettotalrefcount() 函式。

新增 -X showrefcount 命令列選項。

Add -d command line option and PYTHONDEBUG environment variable to debug the parser.

Add support for the __lltrace__ variable: enable low-level tracing in the bytecode evaluation loop if the variable is defined.

Install debug hooks on memory allocators to detect buffer overflow and other memory errors.

定義 Py_DEBUG 和 Py_REF_DEBUG 巨集。

Add runtime checks: code surrounded by #ifdef Py_DEBUG and #endif. Enable assert(...) and _PyObject_ASSERT(...) assertions: don't set the NDEBUG macro (see also the --with-assertions configure option). Main runtime checks:

Add sanity checks on the function arguments.

Unicode and int objects are created with their memory filled with a pattern to detect usage of uninitialized objects.

Ensure that functions which can clear or replace the current exception are not called with an exception raised.

Check that deallocator functions don't change the current exception.

The garbage collector (gc.collect() function) runs some basic checks on objects consistency.

The Py_SAFE_DOWNCAST() macro checks for integer underflow and overflow when downcasting from wide types to narrow types.

See also the Python Development Mode and the --with-trace-refs configure option.

在 3.8 版的變更: Release builds and debug builds are now ABI compatible: defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro (see the --with-trace-refs option).

3.3.9. 偵錯選項

--with-pydebug

以偵錯模式建置 Python：定義 Py_DEBUG 巨集（預設不啟用）。

--with-trace-refs

以偵錯為目的啟用參照追蹤（預設不啟用）。

效果：

定義 Py_TRACE_REFS 巨集。

新增 sys.getobjects() 函式。

新增 PYTHONDUMPREFS 環境變數。

PYTHONDUMPREFS 環境變數可以用來在 Python 結束時轉儲仍然有效的物件和參照計數。

不追蹤靜態配置的物件。

在 3.8 版被加入.

在 3.13 版的變更: 這個建置現在與發佈版本建置和偵錯建置具有 ABI 相容性。

--with-assertions

啟用 C 斷言建置（預設不啟用）：assert(...); 和 _PyObject_ASSERT(...);。

如果設定，NDEBUG 巨集不會在 OPT 編譯器變數中定義。

另請參閱 --with-pydebug 選項（debug build），它也啟用了斷言。

在 3.6 版被加入.

--with-valgrind

啟用 Valgrind 支援（預設不啟用）。

--with-dtrace

啟用 DTrace 支援（預設不啟用）。

請參閱使用 DTrace 和 SystemTap 檢測 CPython。

在 3.6 版被加入.

--with-address-sanitizer

Enable AddressSanitizer memory error detector, asan (default is no). To improve ASan detection capabilities you may also want to combine this with --without-pymalloc to disable the specialized small-object allocator whose allocations are not tracked by ASan.

在 3.6 版被加入.

--with-memory-sanitizer

啟用 MemorySanitizer 分配錯誤偵測器 msan（預設不啟用）。

在 3.6 版被加入.

--with-undefined-behavior-sanitizer

啟用 UndefinedBehaviorSanitizer 未定義行為偵測器 ubsan（預設不啟用）。

在 3.6 版被加入.

--with-thread-sanitizer

啟用 ThreadSanitizer 資料競爭偵測器 tsan（預設不啟用）。

在 3.13 版被加入.

3.3.10. Linker options

--enable-shared

啟用建置共享 Python 函式庫：libpython（預設不啟用）。

--without-static-libpython

不要建置 libpythonMAJOR.MINOR.a 並且不要安裝 python.o（預設會建置並啟用）。

在 3.10 版被加入.

3.3.11. 函式庫選項

--with-libs='lib1 ...'

Link against additional libraries (default is no).

--with-system-expat

使用已安裝的 expat 函式庫建置 pyexpat 模組（預設不建置）。

--with-system-libmpdec

使用已安裝的 mpdecimal 函式庫建置 _decimal 擴充模組，請參閱 decimal 模組（預設建置）。

在 3.3 版被加入.

在 3.13 版的變更: 預設使用已安裝的 mpdecimal 函式庫。

在 3.15 版的變更: A bundled copy of the library will no longer be selected implicitly if an installed mpdecimal library is not found. In Python 3.15 only, it can still be selected explicitly using --with-system-libmpdec=no or --without-system-libmpdec.

自從版本 3.13 後不推薦使用，將會自版本 3.16 中移除。: Python 3.16 不再隨附 mpdecimal 函式庫的原始碼副本。

也參考

LIBMPDEC_CFLAGS 和 LIBMPDEC_LIBS。

--with-readline=readline|editline

Designate a backend library for the readline module.

readline: Use readline as the backend.

editline: Use editline as the backend.

在 3.10 版被加入.

--without-readline

不要建置 readline 模組（預設會建置）。

不要定義 HAVE_LIBREADLINE 巨集。

在 3.10 版被加入.

--with-libm=STRING

Override libm math library to STRING (default is system-dependent).

--with-libc=STRING

Override libc C library to STRING (default is system-dependent).

--with-openssl=DIR

OpenSSL 目錄的根目錄。

在 3.7 版被加入.

--with-openssl-rpath=[no|auto|DIR]

Set runtime library directory (rpath) for OpenSSL libraries:

no (default): don't set rpath;

auto: auto-detect rpath from --with-openssl and pkg-config;

DIR: set an explicit rpath.

在 3.10 版被加入.

3.3.12. 安全性選項

--with-hash-algorithm=[fnv|siphash13|siphash24]

Select hash algorithm for use in Python/pyhash.c:

siphash13（預設）；

siphash24；

fnv。

在 3.4 版被加入.

在 3.11 版被加入: siphash13 is added and it is the new default.

--with-builtin-hashlib-hashes=md5,sha1,sha256,sha512,sha3,blake2

內建雜湊模組：

md5；

sha1；

sha256；

sha512；

sha3 (with shake);

blake2。

在 3.9 版被加入.

--with-ssl-default-suites=[python|openssl|STRING]

Override the OpenSSL default cipher suites string:

python (default): use Python's preferred selection;

openssl: leave OpenSSL's defaults untouched;

STRING: use a custom string

請見 ssl 模組。

在 3.7 版被加入.

在 3.10 版的變更: The settings python and STRING also set TLS 1.2 as minimum protocol version.

--disable-safety

Disable compiler options that are recommended by OpenSSF [https://github.com/ossf/wg-best-practices-os-developers/blob/main/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.md] for security reasons with no performance overhead. If this option is not enabled, CPython will be built based on safety compiler options with no slow down. When this option is enabled, CPython will not be built with the compiler options listed below.

The following compiler options are disabled with --disable-safety:

-fstack-protector-strong [https://github.com/ossf/wg-best-practices-os-developers/blob/main/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.md#enable-run-time-checks-for-stack-based-buffer-overflows]: Enable run-time checks for stack-based buffer overflows.

-Wtrampolines [https://github.com/ossf/wg-best-practices-os-developers/blob/main/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.md#enable-warning-about-trampolines-that-require-executable-stacks]: Enable warnings about trampolines that require executable stacks.

在 3.14 版被加入.

--enable-slower-safety

Enable compiler options that are recommended by OpenSSF [https://github.com/ossf/wg-best-practices-os-developers/blob/main/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.md] for security reasons which require overhead. If this option is not enabled, CPython will not be built based on safety compiler options which performance impact. When this option is enabled, CPython will be built with the compiler options listed below.

The following compiler options are enabled with --enable-slower-safety:

-D_FORTIFY_SOURCE=3 [https://github.com/ossf/wg-best-practices-os-developers/blob/main/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.md#fortify-sources-for-unsafe-libc-usage-and-buffer-overflows]: Fortify sources with compile- and run-time checks for unsafe libc usage and buffer overflows.

在 3.14 版被加入.

3.3.13. macOS 選項

參閱 Mac/README.rst [https://github.com/python/cpython/tree/3.14/Mac/README.rst]。

--enable-universalsdk

--enable-universalsdk=SDKDIR

Create a universal binary build. SDKDIR specifies which macOS SDK should be used to perform the build (default is no).

--enable-framework

--enable-framework=INSTALLDIR

Create a Python.framework rather than a traditional Unix install. Optional INSTALLDIR specifies the installation path (default is no).

--with-universal-archs=ARCH

Specify the kind of universal binary that should be created. This option is only valid when --enable-universalsdk is set.

選項：

universal2（x86-64 與 arm64）；

32-bit（PPC 與 i386）；

64-bit（PPC64 與 x86-64）；

3-way（i386、PPC 與 x86-64）；

intel（i386 與 x86-64）；

intel-32（i386）；

intel-64（x86-64）；

all（PPC、i386、PPC64 與 x86-64）。

Note that values for this configuration item are not the same as the identifiers used for universal binary wheels on macOS. See the Python Packaging User Guide for details on the packaging platform compatibility tags used on macOS [https://packaging.python.org/en/latest/specifications/platform-compatibility-tags/#macos]

--with-framework-name=FRAMEWORK

Specify the name for the python framework on macOS only valid when --enable-framework is set (default: Python).

--with-app-store-compliance

--with-app-store-compliance=PATCH-FILE

The Python standard library contains strings that are known to trigger automated inspection tool errors when submitted for distribution by the macOS and iOS App Stores. If enabled, this option will apply the list of patches that are known to correct app store compliance. A custom patch file can also be specified. This option is disabled by default.

在 3.13 版被加入.

3.3.14. iOS 選項

參閱 iOS/README.rst [https://github.com/python/cpython/tree/3.14/iOS/README.rst]。

--enable-framework=INSTALLDIR

Create a Python.framework. Unlike macOS, the INSTALLDIR argument specifying the installation path is mandatory.

--with-framework-name=FRAMEWORK

指定框架的名稱（預設值：Python）。

3.3.15. Cross Compiling Options

Cross compiling, also known as cross building, can be used to build Python for another CPU architecture or platform. Cross compiling requires a Python interpreter for the build platform. The version of the build Python must match the version of the cross compiled host Python.

--build=BUILD

configure for building on BUILD, usually guessed by config.guess.

--host=HOST

cross-compile to build programs to run on HOST (target platform)

--with-build-python=path/to/python

path to build python binary for cross compiling

在 3.11 版被加入.

CONFIG_SITE=file

An environment variable that points to a file with configure overrides.

範例 config.site 檔案：

# config.site-aarch64
ac_cv_buggy_getaddrinfo=no
ac_cv_file__dev_ptmx=yes
ac_cv_file__dev_ptc=no

HOSTRUNNER

Program to run CPython for the host platform for cross-compilation.

在 3.11 版被加入.

Cross compiling example:

CONFIG_SITE=config.site-aarch64 ../configure \
    --build=x86_64-pc-linux-gnu \
    --host=aarch64-unknown-linux-gnu \
    --with-build-python=../x86_64/python

3.4. Python 建置系統

3.4.1. 建置系統的主要檔案

configure.ac => configure；

Makefile.pre.in => Makefile（由 configure 建立）；

pyconfig.h（由 configure 建立）；

Modules/Setup: C extensions built by the Makefile using Module/makesetup shell script;

3.4.2. 主要建置步驟

C 檔案（.c）被建置為目的檔（.o）。

A static libpython library (.a) is created from objects files.

python.o and the static libpython library are linked into the final python program.

C extensions are built by the Makefile (see Modules/Setup).

3.4.3. 主要 Makefile 目標

3.4.3.1. make

For the most part, when rebuilding after editing some code or refreshing your checkout from upstream, all you need to do is execute make, which (per Make's semantics) builds the default target, the first one defined in the Makefile. By tradition (including in the CPython project) this is usually the all target. The configure script expands an autoconf variable, @DEF_MAKE_ALL_RULE@ to describe precisely which targets make all will build. The three choices are:

profile-opt（使用 --enable-optimizations 配置）

build_wasm (chosen if the host platform matches wasm32-wasi* or wasm32-emscripten)

build_all（未明確使用其他選項進行配置）

Depending on the most recent source file changes, Make will rebuild any targets (object files and executables) deemed out-of-date, including running configure again if necessary. Source/target dependencies are many and maintained manually however, so Make sometimes doesn't have all the information necessary to correctly detect all targets which need to be rebuilt. Depending on which targets aren't rebuilt, you might experience a number of problems. If you have build or test problems which you can't otherwise explain, make clean && make should work around most dependency problems, at the expense of longer build times.

3.4.3.2. make platform

Build the python program, but don't build the standard library extension modules. This generates a file named platform which contains a single line describing the details of the build platform, e.g., macosx-14.3-arm64-3.12 or linux-x86_64-3.13.

3.4.3.3. make profile-opt

Build Python using profile-guided optimization (PGO). You can use the configure --enable-optimizations option to make this the default target of the make command (make all or just make).

3.4.3.4. make clean

移除建置的檔案。

3.4.3.5. make distclean

In addition to the work done by make clean, remove files created by the configure script. configure will have to be run before building again. [6]

3.4.3.6. make install

建置 all 目標並安裝 Python。

3.4.3.7. make test

Build the all target and run the Python test suite with the --fast-ci option without GUI tests. Variables:

TESTOPTS：額外的 regrtest 命令列選項。

TESTPYTHONOPTS：額外的 Python 命令列選項。

TESTTIMEOUT：秒數表示的超時設定（預設值：10 分鐘）。

3.4.3.8. make ci

This is similar to make test, but uses the -ugui to also run GUI tests.

在 3.14 版被加入.

3.4.3.9. make buildbottest

This is similar to make test, but uses the --slow-ci option and default timeout of 20 minutes, instead of --fast-ci option.

3.4.3.10. make regen-all

Regenerate (almost) all generated files. These include (but are not limited to) bytecode cases, and parser generator file. make regen-stdlib-module-names and autoconf must be run separately for the remaining generated files.

3.4.4. C 擴充模組

Some C extensions are built as built-in modules, like the sys module. They are built with the Py_BUILD_CORE_BUILTIN macro defined. Built-in modules have no __file__ attribute:

>>> import sys
>>> sys
<module 'sys' (built-in)>
>>> sys.__file__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'sys' has no attribute '__file__'

Other C extensions are built as dynamic libraries, like the _asyncio module. They are built with the Py_BUILD_CORE_MODULE macro defined. Example on Linux x86-64:

>>> import _asyncio
>>> _asyncio
<module '_asyncio' from '/usr/lib64/python3.9/lib-dynload/_asyncio.cpython-39-x86_64-linux-gnu.so'>
>>> _asyncio.__file__
'/usr/lib64/python3.9/lib-dynload/_asyncio.cpython-39-x86_64-linux-gnu.so'

Modules/Setup is used to generate Makefile targets to build C extensions. At the beginning of the files, C extensions are built as built-in modules. Extensions defined after the *shared* marker are built as dynamic libraries.

The PyAPI_FUNC(), PyAPI_DATA() and PyMODINIT_FUNC macros of Include/exports.h are defined differently depending if the Py_BUILD_CORE_MODULE macro is defined:

如果定義了 Py_BUILD_CORE_MODULE，則使用 Py_EXPORTED_SYMBOL

否則使用 Py_IMPORTED_SYMBOL。

If the Py_BUILD_CORE_BUILTIN macro is used by mistake on a C extension built as a shared library, its PyInit_xxx() function is not exported, causing an ImportError on import.

3.5. Compiler and linker flags

Options set by the ./configure script and environment variables and used by Makefile.

3.5.1. 預處理器旗標

CONFIGURE_CPPFLAGS

Value of CPPFLAGS variable passed to the ./configure script.

在 3.6 版被加入.

CPPFLAGS

(Objective) C/C++ preprocessor flags, e.g. -Iinclude_dir if you have headers in a nonstandard directory include_dir.

Both CPPFLAGS and LDFLAGS need to contain the shell's value to be able to build extension modules using the directories specified in the environment variables.

BASECPPFLAGS

在 3.4 版被加入.

PY_CPPFLAGS

Extra preprocessor flags added for building the interpreter object files.

Default: $(BASECPPFLAGS) -I. -I$(srcdir)/Include $(CONFIGURE_CPPFLAGS) $(CPPFLAGS).

在 3.2 版被加入.

3.5.2. 編譯器旗標

CC

C 編譯器指令。

範例：gcc -pthread。

CXX

C++ 編譯器指令。

範例：g++ -pthread。

CFLAGS

C 編譯器旗標。

CFLAGS_NODIST

CFLAGS_NODIST is used for building the interpreter and stdlib C extensions. Use it when a compiler flag should not be part of CFLAGS once Python is installed (gh-65320 [https://github.com/python/cpython/issues/65320]).

In particular, CFLAGS should not contain:

the compiler flag -I (for setting the search path for include files). The -I flags are processed from left to right, and any flags in CFLAGS would take precedence over user- and package-supplied -I flags.

hardening flags such as -Werror because distributions cannot control whether packages installed by users conform to such heightened standards.

在 3.5 版被加入.

COMPILEALL_OPTS

Options passed to the compileall command line when building PYC files in make install. Default: -j0.

在 3.12 版被加入.

EXTRA_CFLAGS

額外的 C 編譯器旗標。

CONFIGURE_CFLAGS

Value of CFLAGS variable passed to the ./configure script.

在 3.2 版被加入.

CONFIGURE_CFLAGS_NODIST

Value of CFLAGS_NODIST variable passed to the ./configure script.

在 3.5 版被加入.

BASECFLAGS

基本編譯器旗標。

OPT

最佳化旗標。

CFLAGS_ALIASING

Strict or non-strict aliasing flags used to compile Python/dtoa.c.

在 3.7 版被加入.

CCSHARED

用於建置共享函式庫的編譯器旗標。

例如說 -fPIC 被使用於 Linux 與 BSD 上。

CFLAGSFORSHARED

用於建置直譯器目的檔的額外 C 旗標。

預設值：當使用 --enable-shared 時為 $(CCSHARED)，否則為空字串。

PY_CFLAGS

預設值：$(BASECFLAGS) $(OPT) $(CONFIGURE_CFLAGS) $(CFLAGS) $(EXTRA_CFLAGS)。

PY_CFLAGS_NODIST

預設值：$(CONFIGURE_CFLAGS_NODIST) $(CFLAGS_NODIST) -I$(srcdir)/Include/internal。

在 3.5 版被加入.

PY_STDMODULE_CFLAGS

用於建置直譯器目的檔的 C 旗標。

預設值：$(PY_CFLAGS) $(PY_CFLAGS_NODIST) $(PY_CPPFLAGS) $(CFLAGSFORSHARED)。

在 3.7 版被加入.

PY_CORE_CFLAGS

預設值：$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE。

在 3.2 版被加入.

PY_BUILTIN_MODULE_CFLAGS

Compiler flags to build a standard library extension module as a built-in module, like the posix module.

預設值：$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN。

在 3.8 版被加入.

PURIFY

Purify command. Purify is a memory debugger program.

預設值：空字串（未使用）。

3.5.3. Linker flags

LINKCC

Linker command used to build programs like python and _testembed.

預設值：$(PURIFY) $(CC)。

CONFIGURE_LDFLAGS

Value of LDFLAGS variable passed to the ./configure script.

Avoid assigning CFLAGS, LDFLAGS, etc. so users can use them on the command line to append to these values without stomping the pre-set values.

在 3.2 版被加入.

LDFLAGS_NODIST

LDFLAGS_NODIST is used in the same manner as CFLAGS_NODIST. Use it when a linker flag should not be part of LDFLAGS once Python is installed (gh-65320 [https://github.com/python/cpython/issues/65320]).

In particular, LDFLAGS should not contain:

the compiler flag -L (for setting the search path for libraries). The -L flags are processed from left to right, and any flags in LDFLAGS would take precedence over user- and package-supplied -L flags.

CONFIGURE_LDFLAGS_NODIST

Value of LDFLAGS_NODIST variable passed to the ./configure script.

在 3.8 版被加入.

LDFLAGS

Linker flags, e.g. -Llib_dir if you have libraries in a nonstandard directory lib_dir.

Both CPPFLAGS and LDFLAGS need to contain the shell's value to be able to build extension modules using the directories specified in the environment variables.

LIBS

Linker flags to pass libraries to the linker when linking the Python executable.

範例：-lrt。

LDSHARED

建置共享函式庫的指令。

預設值：@LDSHARED@ $(PY_LDFLAGS)。

BLDSHARED

建置 libpython 共享函式庫的指令。

預設值：@BLDSHARED@ $(PY_CORE_LDFLAGS)。

PY_LDFLAGS

預設值：$(CONFIGURE_LDFLAGS) $(LDFLAGS)。

PY_LDFLAGS_NODIST

預設值：$(CONFIGURE_LDFLAGS_NODIST) $(LDFLAGS_NODIST)。

在 3.8 版被加入.

PY_CORE_LDFLAGS

Linker flags used for building the interpreter object files.

在 3.8 版被加入.

註腳

[6]

git clean -fdx is an even more extreme way to "clean" your checkout. It removes all files not known to Git. When bug hunting using git bisect, this is recommended between probes [https://github.com/python/cpython/issues/114505#issuecomment-1907021718] to guarantee a completely clean build. Use with care, as it will delete all files not checked into Git, including your new, uncommitted work.

4. 在 Windows 上使用 Python

This document aims to give an overview of Windows-specific behaviour you should know about when using Python on Microsoft Windows.

Unlike most Unix systems and services, Windows does not include a system supported installation of Python. Instead, Python can be obtained from a number of distributors, including directly from the CPython team. Each Python distribution will have its own benefits and drawbacks, however, consistency with other tools you are using is generally a worthwhile benefit. Before committing to the process described here, we recommend investigating your existing tools to see if they can provide Python directly.

To obtain Python from the CPython team, use the Python Install Manager. This is a standalone tool that makes Python available as global commands on your Windows machine, integrates with the system, and supports updates over time. You can download the Python Install Manager from python.org/downloads [https://www.python.org/downloads/] or through the Microsoft Store app [https://apps.microsoft.com/detail/9NQ7512CXL7T].

Once you have installed the Python Install Manager, the global python command can be used from any terminal to launch your current latest version of Python. This version may change over time as you add or remove different versions, and the py list command will show which is current.

In general, we recommend that you create a virtual environment for each project and run <env>\Scripts\Activate in your terminal to use it. This provides isolation between projects, consistency over time, and ensures that additional commands added by packages are also available in your session. Create a virtual environment using python -m venv <env path>.

If the python or py commands do not seem to be working, please see the Troubleshooting section below. There are sometimes additional manual steps required to configure your PC.

Apart from using the Python install manager, Python can also be obtained as NuGet packages. See nuget.org 套件 below for more information on these packages.

The embeddable distros are minimal packages of Python suitable for embedding into larger applications. They can be installed using the Python install manager. See The embeddable package below for more information on these packages.

4.1. Python 安裝管理員

4.1.1. 安裝

The Python install manager can be installed from the Microsoft Store app [https://apps.microsoft.com/detail/9NQ7512CXL7T] or downloaded and installed from python.org/downloads [https://www.python.org/downloads/]. The two versions are identical.

To install through the Store, simply click "Install". After it has completed, open a terminal and type python to get started.

To install the file downloaded from python.org, either double-click and select "Install", or run Add-AppxPackage <path to MSIX> in Windows Powershell.

After installation, the python, py, and pymanager commands should be available. If you have existing installations of Python, or you have modified your PATH variable, you may need to remove them or undo the modifications. See Troubleshooting for more help with fixing non-working commands.

When you first install a runtime, you will likely be prompted to add a directory to your PATH. This is optional, if you prefer to use the py command, but is offered for those who prefer the full range of aliases (such as python3.14.exe) to be available. The directory will be %LocalAppData%\Python\bin by default, but may be customized by an administrator. Click Start and search for "Edit environment variables for your account" for the system settings page to add the path.

Each Python runtime you install will have its own directory for scripts. These also need to be added to PATH if you want to use them.

The Python install manager will be automatically updated to new releases. This does not affect any installs of Python runtimes. Uninstalling the Python install manager does not uninstall any Python runtimes.

If you are not able to install an MSIX in your context, for example, you are using automated deployment software that does not support it, or are targeting Windows Server 2019, please see 進階安裝 below for more information.

4.1.2. 基本使用

The recommended command for launching Python is python, which will either launch the version requested by the script being launched, an active virtual environment, or the default installed version, which will be the latest stable release unless configured otherwise. If no version is specifically requested and no runtimes are installed at all, the current latest release will be installed automatically.

For all scenarios involving multiple runtime versions, the recommended command is py. This may be used anywhere in place of python or the older py.exe launcher. By default, py matches the behaviour of python, but also allows command line options to select a specific version as well as subcommands to manage installations. These are detailed below.

Because the py command may already be taken by the previous version, there is also an unambiguous pymanager command. Scripted installs that are intending to use Python install manager should consider using pymanager, due to the lower chance of encountering a conflict with existing installs. The only difference between the two commands is when running without any arguments: py will launch your default interpreter, while pymanager will display help (pymanager exec ... provides equivalent behaviour to py ...).

Each of these commands also has a windowed version that avoids creating a console window. These are pyw, pythonw and pymanagerw. A python3 command is also included that mimics the python command. It is intended to catch accidental uses of the typical POSIX command on Windows, but is not meant to be widely used or recommended.

To launch your default runtime, run python or py with the arguments you want to be passed to the runtime (such as script files or the module to launch):

$> py
...
$> python my-script.py
...
$> py -m this
...

The default runtime can be overridden with the PYTHON_MANAGER_DEFAULT environment variable, or a configuration file. See 設定 for information about configuration settings.

To launch a specific runtime, the py command accepts a -V:<TAG> option. This option must be specified before any others. The tag is part or all of the identifier for the runtime; for those from the CPython team, it looks like the version, potentially with the platform. For compatibility, the V: may be omitted in cases where the tag refers to an official release and starts with 3.

$> py -V:3.14 ...
$> py -V:3-arm64 ...

Runtimes from other distributors may require the company to be included as well. This should be separated from the tag by a slash, and may be a prefix. Specifying the company is optional when it is PythonCore, and specifying the tag is optional (but not the slash) when you want the latest release from a specific company.

$> py -V:Distributor\1.0 ...
$> py -V:distrib/ ...

If no version is specified, but a script file is passed, the script will be inspected for a shebang line. This is a special format for the first line in a file that allows overriding the command. See Shebang lines for more information. When there is no shebang line, or it cannot be resolved, the script will be launched with the default runtime.

If you are running in an active virtual environment, have not requested a particular version, and there is no shebang line, the default runtime will be that virtual environment. In this scenario, the python command was likely already overridden and none of these checks occurred. However, this behaviour ensures that the py command can be used interchangeably.

When no runtimes are installed, any launch command will try to install the requested version and launch it. However, after any version is installed, only the py exec ... and pymanager exec ... commands will install if the requested version is absent. Other forms of commands will display an error and direct you to use py install first.

4.1.3. Command help

The py help command will display the full list of supported commands, along with their options. Any command may be passed the -? option to display its help, or its name passed to py help.

$> py help
$> py help install
$> py install /?

All commands support some common options, which will be shown by py help. These options must be specified after any subcommand. Specifying -v or --verbose will increase the amount of output shown, and -vv will increase it further for debugging purposes. Passing -q or --quiet will reduce output, and -qq will reduce it further.

The --config=<PATH> option allows specifying a configuration file to override multiple settings at once. See 設定 below for more information about these files.

4.1.4. 列出 runtimes

$> py list [-f=|--format=<FMT>] [-1|--one] [--online|-s=|--source=<URL>] [<TAG>...]

The list of installed runtimes can be seen using py list. A filter may be added in the form of one or more tags (with or without company specifier), and each may include a <, <=, >= or > prefix to restrict to a range.

A range of formats are supported, and can be passed as the --format=<FMT> or -f <FMT> option. Formats include table (a user friendly table view), csv (comma-separated table), json (a single JSON blob), jsonl (one JSON blob per result), exe (just the executable path), prefix (just the prefix path).

The --one or -1 option only displays a single result. If the default runtime is included, it will be the one. Otherwise, the "best" result is shown ("best" is deliberately vaguely defined, but will usually be the most recent version). The result shown by py list --one <TAG> will match the runtime that would be launched by py -V:<TAG>.

The --only-managed option excludes results that were not installed by the Python install manager. This is useful when determining which runtimes may be updated or uninstalled through the py command.

The --online option is short for passing --source=<URL> with the default source. Passing either of these options will search the online index for runtimes that can be installed. The result shown by py list --online --one <TAG> will match the runtime that would be installed by py install <TAG>.

$> py list --online 3.14

For compatibility with the old launcher, the --list, --list-paths, -0 and -0p commands (e.g. py -0p) are retained. They do not allow additional options, and will produce legacy formatted output.

4.1.5. 安裝 runtimes

$> py install [-s=|--source=<URL>] [-f|--force] [-u|--update] [--dry-run] [<TAG>...]

New runtime versions may be added using py install. One or more tags may be specified, and the special tag default may be used to select the default. Ranges are not supported for installation.

The --source=<URL> option allows overriding the online index that is used to obtain runtimes. This may be used with an offline index, as shown in 離線安裝.

Passing --force will ignore any cached files and remove any existing install to replace it with the specified one.

Passing --update will replace existing installs if the new version is newer. Otherwise, they will be left. If no tags are provided with --update, all installs managed by the Python install manager will be updated if newer versions are available. Updates will remove any modifications made to the install, including globally installed packages, but virtual environments will continue to work.

Passing --dry-run will generate output and logs, but will not modify any installs.

In addition to the above options, the --target option will extract the runtime to the specified directory instead of doing a normal install. This is useful for embedding runtimes into larger applications. Unlike a normal install, py will not be aware of the extracted runtime, and no Start menu or other shortcuts will be created. To launch the runtime, directly execute the main executable (typically python.exe) in the target directory.

$> py install ... [-t=|--target=<PATH>] <TAG>

The py exec command will install the requested runtime if it is not already present. This is controlled by the automatic_install configuration (PYTHON_MANAGER_AUTOMATIC_INSTALL), and is enabled by default. If no runtimes are available at all, all launch commands will do an automatic install if the configuration setting allows. This is to ensure a good experience for new users, but should not generally be relied on rather than using the py exec command or explicit install commands.

4.1.6. 離線安裝

To perform offline installs of Python, you will need to first create an offline index on a machine that has network access.

$> py install --download=<PATH> ... <TAG>...

The --download=<PATH> option will download the packages for the listed tags and create a directory containing them and an index.json file suitable for later installation. This entire directory can be moved to the offline machine and used to install one or more of the bundled runtimes:

$> py install --source="<PATH>\index.json" <TAG>...

The Python install manager can be installed by downloading its installer and moving it to another machine before installing.

Alternatively, the ZIP files in an offline index directory can simply be transferred to another machine and extracted. This will not register the install in any way, and so it must be launched by directly referencing the executables in the extracted directory, but it is sometimes a preferable approach in cases where installing the Python install manager is not possible or convenient.

In this way, Python runtimes can be installed and managed on a machine without access to the internet.

4.1.7. 解除安裝 runtimes

$> py uninstall [-y|--yes] <TAG>...

Runtimes may be removed using the py uninstall command. One or more tags must be specified. Ranges are not supported here.

The --yes option bypasses the confirmation prompt before uninstalling.

Instead of passing tags individually, the --purge option may be specified. This will remove all runtimes managed by the Python install manager, including cleaning up the Start menu, registry, and any download caches. Runtimes that were not installed by the Python install manager will not be impacted, and neither will manually created configuration files.

$> py uninstall [-y|--yes] --purge

The Python install manager can be uninstalled through the Windows "Installed apps" settings page. This does not remove any runtimes, and they will still be usable, though the global python and py commands will be removed. Reinstalling the Python install manager will allow you to manage these runtimes again. To completely clean up all Python runtimes, run with --purge before uninstalling the Python install manager.

4.1.8. 設定

Python install manager is configured with a hierarchy of configuration files, environment variables, command-line options, and registry settings. In general, configuration files have the ability to configure everything, including the location of other configuration files, while registry settings are administrator-only and will override configuration files. Command-line options override all other settings, but not every option is available.

This section will describe the defaults, but be aware that modified or overridden installs may resolve settings differently.

A global configuration file may be configured by an administrator, and would be read first. The user configuration file is stored at %AppData%\Python\pymanager.json (note that this location is under Roaming, not Local) and is read next, overwriting any settings from earlier files. An additional configuration file may be specified as the PYTHON_MANAGER_CONFIG environment variable or the --config command line option (but not both). These locations may be modified by administrative customization options listed later.

The following settings are those that are considered likely to be modified in normal use. Later sections list those that are intended for administrative customization.

Standard configuration options

Config Key

Environment Variable

描述

default_tag

PYTHON_MANAGER_DEFAULT

The preferred default version to launch or install. By default, this is interpreted as the most recent non-prerelease version from the CPython team.

default_platform

PYTHON_MANAGER_DEFAULT_PLATFORM

The preferred default platform to launch or install. This is treated as a suffix to the specified tag, such that py -V:3.14 would prefer an install for 3.14-64 if it exists (and default_platform is -64), but will use 3.14 if no tagged install exists.

logs_dir

PYTHON_MANAGER_LOGS

The location where log files are written. By default, %TEMP%.

automatic_install

PYTHON_MANAGER_AUTOMATIC_INSTALL

True to allow automatic installs when using py exec to launch (or py when no runtimes are installed yet). Other commands will not automatically install, regardless of this setting. By default, true.

include_unmanaged

PYTHON_MANAGER_INCLUDE_UNMANAGED

True to allow listing and launching runtimes that were not installed by the Python install manager, or false to exclude them. By default, true.

shebang_can_run_anything

PYTHON_MANAGER_SHEBANG_CAN_RUN_ANYTHING

True to allow shebangs in .py files to launch applications other than Python runtimes, or false to prevent it. By default, true.

log_level

PYMANAGER_VERBOSE、PYMANAGER_DEBUG

Set the default level of output (0-50). By default, 20. Lower values produce more output. The environment variables are boolean, and may produce additional output during startup that is later suppressed by other configuration.

confirm

PYTHON_MANAGER_CONFIRM

True to confirm certain actions before taking them (such as uninstall), or false to skip the confirmation. By default, true.

install.source

PYTHON_MANAGER_SOURCE_URL

Override the index feed to obtain new installs from.

list.format

PYTHON_MANAGER_LIST_FORMAT

Specify the default format used by the py list command. By default, table.

install_dir

(none)

Specify the root directory that runtimes will be installed into. If you change this setting, previously installed runtimes will not be usable unless you move them to the new location.

global_dir

(none)

Specify the directory where global commands (such as python3.14.exe) are stored. This directory should be added to your PATH to make the commands available from your terminal.

download_dir

(none)

Specify the directory where downloaded files are stored. This directory is a temporary cache, and can be cleaned up from time to time.

Dotted names should be nested inside JSON objects, for example, list.format would be specified as {"list": {"format": "table"}}.

4.1.9. Shebang lines

If the first line of a script file starts with #!, it is known as a "shebang" line. Linux and other Unix like operating systems have native support for such lines and they are commonly used on such systems to indicate how a script should be executed. The python and py commands allow the same facilities to be used with Python scripts on Windows.

To allow shebang lines in Python scripts to be portable between Unix and Windows, a number of 'virtual' commands are supported to specify which interpreter to use. The supported virtual commands are:

/usr/bin/env <ALIAS>

/usr/bin/env -S <ALIAS>

/usr/bin/<ALIAS>

/usr/local/bin/<ALIAS>

<ALIAS>

For example, if the first line of your script starts with

#! /usr/bin/python

The default Python or an active virtual environment will be located and used. As many Python scripts written to work on Unix will already have this line, you should find these scripts can be used by the launcher without modification. If you are writing a new script on Windows which you hope will be useful on Unix, you should use one of the shebang lines starting with /usr.

Any of the above virtual commands can have <ALIAS> replaced by an alias from an installed runtime. That is, any command generated in the global aliases directory (which you may have added to your PATH environment variable) can be used in a shebang, even if it is not on your PATH. This allows the use of shebangs like /usr/bin/python3.12 to select a particular runtime.

If no runtimes are installed, or if automatic installation is enabled, the requested runtime will be installed if necessary. See 設定 for information about configuration settings.

The /usr/bin/env form of shebang line will also search the PATH environment variable for unrecognized commands. This corresponds to the behaviour of the Unix env program, which performs the same search, but prefers launching known Python commands. A warning may be displayed when searching for arbitrary executables, and this search may be disabled by the shebang_can_run_anything configuration option.

Shebang lines that do not match any of patterns are treated as Windows executable paths that are absolute or relative to the directory containing the script file. This is a convenience for Windows-only scripts, such as those generated by an installer, since the behavior is not compatible with Unix-style shells. These paths may be quoted, and may include multiple arguments, after which the path to the script and any additional arguments will be appended. This functionality may be disabled by the shebang_can_run_anything configuration option.

備註

The behaviour of shebangs in the Python install manager is subtly different from the previous py.exe launcher, and the old configuration options no longer apply. If you are specifically reliant on the old behaviour or configuration, we recommend installing the legacy launcher [https://www.python.org/ftp/python/3.14.0/win32/launcher.msi]. The legacy launcher's py command will override PyManager's one by default, and you will need to use pymanager commands for installing and uninstalling.

4.1.10. 進階安裝

For situations where an MSIX cannot be installed, such as some older administrative distribution platforms, there is an MSI available from the python.org downloads page. This MSI has no user interface, and can only perform per-machine installs to its default location in Program Files. It will attempt to modify the system PATH environment variable to include this install location, but be sure to validate this on your configuration.

備註

Windows Server 2019 is the only version of Windows that CPython supports that does not support MSIX. For Windows Server 2019, you should use the MSI.

Be aware that the MSI package does not bundle any runtimes, and so is not suitable for installs into offline environments without also creating an offline install index. See 離線安裝 and Administrative configuration for information on handling these scenarios.

Runtimes installed by the MSI are shared with those installed by the MSIX, and are all per-user only. The Python install manager does not support installing runtimes per-machine. To emulate a per-machine install, you can use py install --target=<shared location> as administrator and add your own system-wide modifications to PATH, the registry, or the Start menu.

When the MSIX is installed, but commands are not available in the PATH environment variable, they can be found under %LocalAppData%\Microsoft\WindowsApps\PythonSoftwareFoundation.PythonManager_3847v3x7pw1km or %LocalAppData%\Microsoft\WindowsApps\PythonSoftwareFoundation.PythonManager_qbz5n2kfra8p0, depending on whether it was installed from python.org or through the Windows Store. Attempting to run the executable directly from Program Files is not recommended.

To programmatically install the Python install manager, it is easiest to use WinGet, which is included with all supported versions of Windows:

$> winget install 9NQ7512CXL7T -e --accept-package-agreements --disable-interactivity

# Optionally run the configuration checker and accept all changes
$> py install --configure -y

To download the Python install manager and install on another machine, the following WinGet command will download the required files from the Store to your Downloads directory (add -d <location> to customize the output location). This also generates a YAML file that appears to be unnecessary, as the downloaded MSIX can be installed by launching or using the commands below.

$> winget download 9NQ7512CXL7T -e --skip-license --accept-package-agreements --accept-source-agreements

To programmatically install or uninstall an MSIX using only PowerShell, the Add-AppxPackage [https://learn.microsoft.com/powershell/module/appx/add-appxpackage] and Remove-AppxPackage [https://learn.microsoft.com/powershell/module/appx/remove-appxpackage] PowerShell cmdlets are recommended:

$> Add-AppxPackage C:\Downloads\python-manager-25.0.msix
...
$> Get-AppxPackage PythonSoftwareFoundation.PythonManager | Remove-AppxPackage

The latest release can be downloaded and installed by Windows by passing the AppInstaller file to the Add-AppxPackage command. This installs using the MSIX on python.org, and is only recommended for cases where installing via the Store (interactively or using WinGet) is not possible.

$> Add-AppxPackage -AppInstallerFile https://www.python.org/ftp/python/pymanager/pymanager.appinstaller

Other tools and APIs may also be used to provision an MSIX package for all users on a machine, but Python does not consider this a supported scenario. We suggest looking into the PowerShell Add-AppxProvisionedPackage [https://learn.microsoft.com/powershell/module/dism/add-appxprovisionedpackage] cmdlet, the native Windows PackageManager [https://learn.microsoft.com/uwp/api/windows.management.deployment.packagemanager] class, or the documentation and support for your deployment tool.

Regardless of the install method, users will still need to install their own copies of Python itself, as there is no way to trigger those installs without being a logged in user. When using the MSIX, the latest version of Python will be available for all users to install without network access.

Note that the MSIX downloadable from the Store and from the Python website are subtly different and cannot be installed at the same time. Wherever possible, we suggest using the above WinGet commands to download the package from the Store to reduce the risk of setting up conflicting installs. There are no licensing restrictions on the Python install manager that would prevent using the Store package in this way.

4.1.11. Administrative configuration

There are a number of options that may be useful for administrators to override configuration of the Python install manager. These can be used to provide local caching, disable certain shortcut types, override bundled content. All of the above configuration options may be set, as well as those below.

Configuration options may be overridden in the registry by setting values under HKEY_LOCAL_MACHINE\Software\Policies\Python\PyManager, where the value name matches the configuration key and the value type is REG_SZ. Note that this key can itself be customized, but only by modifying the core config file distributed with the Python install manager. We recommend, however, that registry values are used only to set base_config to a JSON file containing the full set of overrides. Registry key overrides will replace any other configured setting, while base_config allows users to further modify settings they may need.

Note that most settings with environment variables support those variables because their default setting specifies the variable. If you override them, the environment variable will no longer work, unless you override it with another one. For example, the default value of confirm is literally %PYTHON_MANAGER_CONFIRM%, which will resolve the variable at load time. If you override the value to yes, then the environment variable will no longer be used. If you override the value to %CONFIRM%, then that environment variable will be used instead.

Configuration settings that are paths are interpreted as relative to the directory containing the configuration file that specified them.

Administrative configuration options

Config Key

描述

base_config

The highest priority configuration file to read. Note that only the built-in configuration file and the registry can modify this setting.

user_config

The second configuration file to read.

additional_config

The third configuration file to read.

registry_override_key

Registry location to check for overrides. Note that only the built-in configuration file can modify this setting.

bundled_dir

Read-only directory containing locally cached files.

install.fallback_source

Path or URL to an index to consult when the main index cannot be accessed.

install.enable_shortcut_kinds

Comma-separated list of shortcut kinds to allow (e.g. "pep514,start"). Enabled shortcuts may still be disabled by disable_shortcut_kinds.

install.disable_shortcut_kinds

Comma-separated list of shortcut kinds to exclude (e.g. "pep514,start"). Disabled shortcuts are not reactivated by enable_shortcut_kinds.

pep514_root

Registry location to read and write PEP 514 entries into. By default, HKEY_CURRENT_USER\Software\Python.

start_folder

Start menu folder to write shortcuts into. By default, Python. This path is relative to the user's Programs folder.

virtual_env

Path to the active virtual environment. By default, this is %VIRTUAL_ENV%, but may be set empty to disable venv detection.

shebang_can_run_anything_silently

True to suppress visible warnings when a shebang launches an application other than a Python runtime.

4.1.12. Installing free-threaded binaries

在 3.13 版被加入.

Pre-built distributions of the free-threaded build are available by installing tags with the t suffix.

$> py install 3.14t
$> py install 3.14t-arm64
$> py install 3.14t-32

This will install and register as normal. If you have no other runtimes installed, then python will launch this one. Otherwise, you will need to use py -V:3.14t ... or, if you have added the global aliases directory to your PATH environment variable, the python3.14t.exe commands.

4.1.13. Troubleshooting

If your Python install manager does not seem to be working correctly, please work through these tests and fixes to see if it helps. If not, please report an issue at our bug tracker [https://github.com/python/pymanager/issues], including any relevant log files (written to your %TEMP% directory by default).

Troubleshooting

Symptom

Things to try

python gives me a "command not found" error or opens the Store app when I type it in my terminal.

Did you install the Python install manager?

Click Start, open "Manage app execution aliases", and check that the aliases for "Python (default)" are enabled. If they already are, try disabling and re-enabling to refresh the command. The "Python (default windowed)" and "Python install manager" commands may also need refreshing.

Check that the py and pymanager commands work.

Ensure your PATH variable contains the entry for %UserProfile%\AppData\Local\Microsoft\WindowsApps. The operating system includes this entry once by default, after other user paths. If removed, shortcuts will not be found.

py gives me a "command not found" error when I type it in my terminal.

Did you install the Python install manager?

Click Start, open "Manage app execution aliases", and check that the aliases for "Python (default)" are enabled. If they already are, try disabling and re-enabling to refresh the command. The "Python (default windowed)" and "Python install manager" commands may also need refreshing.

Ensure your PATH variable contains the entry for %UserProfile%\AppData\Local\Microsoft\WindowsApps. The operating system includes this entry once by default, after other user paths. If removed, shortcuts will not be found.

py gives me a "can't open file" error when I type commands in my terminal.

This usually means you have the legacy launcher installed and it has priority over the Python install manager. To remove, click Start, open "Installed apps", search for "Python launcher" and uninstall it.

python doesn't launch the same runtime as py

Click Start, open "Installed apps", look for any existing Python runtimes, and either remove them or Modify and disable the PATH options.

Click Start, open "Manage app execution aliases", and check that your python.exe alias is set to "Python (default)"

python and py don't launch the runtime I expect

Check your PYTHON_MANAGER_DEFAULT environment variable or default_tag configuration. The py list command will show your default based on these settings.

Installs that are managed by the Python install manager will be chosen ahead of unmanaged installs. Use py install to install the runtime you expect, or configure your default tag.

Prerelease and experimental installs that are not managed by the Python install manager may be chosen ahead of stable releases. Configure your default tag or uninstall the prerelease runtime and reinstall it using py install.

pythonw or pyw don't launch the same runtime as python or py

Click Start, open "Manage app execution aliases", and check that your pythonw.exe and pyw.exe aliases are consistent with your others.

pip gives me a "command not found" error when I type it in my terminal.

Have you activated a virtual environment? Run the .venv\Scripts\activate script in your terminal to activate.

The package may be available but missing the generated executable. We recommend using the python -m pip command instead, or alternatively the python -m pip install --force pip command will recreate the executables and show you the path to add to PATH. These scripts are separated for each runtime, and so you may need to add multiple paths.

Typing script-name.py in the terminal opens in a new window.

This is a known limitation of the operating system. Either specify py before the script name, create a batch file containing @py "%~dpn0.py" %* with the same name as the script, or install the legacy launcher [https://www.python.org/ftp/python/3.14.0/win32/launcher.msi] and select it as the association for scripts.

Drag-dropping files onto a script doesn't work

This is a known limitation of the operating system. It is supported with the legacy launcher [https://www.python.org/ftp/python/3.14.0/win32/launcher.msi], or with the Python install manager when installed from the MSI.

I have installed the Python install manager multiple times.

It is possible to install from the Store or WinGet, from the MSIX on the Python website, and from the MSI, all at once. They are all compatible and will share configuration and runtimes.

See the earlier 進階安裝 section for ways to uninstall the install manager other than the typical Installed Apps (Add and Remove Programs) settings page.

My old py.ini settings no longer work.

The new Python install manager no longer supports this configuration file or its settings, and so it will be ignored. See 設定 for information about configuration settings.

4.2. The embeddable package

在 3.5 版被加入.

The embedded distribution is a ZIP file containing a minimal Python environment. It is intended for acting as part of another application, rather than being directly accessed by end-users.

To install an embedded distribution, we recommend using py install with the --target option:

$> py install 3.14-embed --target=<directory>

When extracted, the embedded distribution is (almost) fully isolated from the user's system, including environment variables, system registry settings, and installed packages. The standard library is included as pre-compiled and optimized .pyc files in a ZIP, and python3.dll, python313.dll, python.exe and pythonw.exe are all provided. Tcl/tk (including all dependents, such as Idle), pip and the Python documentation are not included.

A default ._pth file is included, which further restricts the default search paths (as described below in 找尋模組). This file is intended for embedders to modify as necessary.

Third-party packages should be installed by the application installer alongside the embedded distribution. Using pip to manage dependencies as for a regular Python installation is not supported with this distribution, though with some care it may be possible to include and use pip for automatic updates. In general, third-party packages should be treated as part of the application ("vendoring") so that the developer can ensure compatibility with newer versions before providing updates to users.

The two recommended use cases for this distribution are described below.

4.2.1. Python 應用程式

An application written in Python does not necessarily require users to be aware of that fact. The embedded distribution may be used in this case to include a private version of Python in an install package. Depending on how transparent it should be (or conversely, how professional it should appear), there are two options.

Using a specialized executable as a launcher requires some coding, but provides the most transparent experience for users. With a customized launcher, there are no obvious indications that the program is running on Python: icons can be customized, company and version information can be specified, and file associations behave properly. In most cases, a custom launcher should simply be able to call Py_Main with a hard-coded command line.

The simpler approach is to provide a batch file or generated shortcut that directly calls the python.exe or pythonw.exe with the required command-line arguments. In this case, the application will appear to be Python and not its actual name, and users may have trouble distinguishing it from other running Python processes or file associations.

With the latter approach, packages should be installed as directories alongside the Python executable to ensure they are available on the path. With the specialized launcher, packages can be located in other locations as there is an opportunity to specify the search path before launching the application.

4.2.2. 嵌入 Python

Applications written in native code often require some form of scripting language, and the embedded Python distribution can be used for this purpose. In general, the majority of the application is in native code, and some part will either invoke python.exe or directly use python3.dll. For either case, extracting the embedded distribution to a subdirectory of the application installation is sufficient to provide a loadable Python interpreter.

As with the application use, packages can be installed to any location as there is an opportunity to specify search paths before initializing the interpreter. Otherwise, there is no fundamental differences between using the embedded distribution and a regular installation.

4.3. nuget.org 套件

在 3.5.2 版被加入.

The nuget.org package is a reduced size Python environment intended for use on continuous integration and build systems that do not have a system-wide install of Python. While nuget is "the package manager for .NET", it also works perfectly fine for packages containing build-time tools.

Visit nuget.org [https://www.nuget.org/] for the most up-to-date information on using nuget. What follows is a summary that is sufficient for Python developers.

The nuget.exe command line tool may be downloaded directly from https://aka.ms/nugetclidl, for example, using curl or PowerShell. With the tool, the latest version of Python for 64-bit or 32-bit machines is installed using:

nuget.exe install python -ExcludeVersion -OutputDirectory .
nuget.exe install pythonx86 -ExcludeVersion -OutputDirectory .

To select a particular version, add a -Version 3.x.y. The output directory may be changed from ., and the package will be installed into a subdirectory. By default, the subdirectory is named the same as the package, and without the -ExcludeVersion option this name will include the specific version installed. Inside the subdirectory is a tools directory that contains the Python installation:

# Without -ExcludeVersion
> .\python.3.5.2\tools\python.exe -V
Python 3.5.2

# With -ExcludeVersion
> .\python\tools\python.exe -V
Python 3.5.2

In general, nuget packages are not upgradeable, and newer versions should be installed side-by-side and referenced using the full path. Alternatively, delete the package directory manually and install it again. Many CI systems will do this automatically if they do not preserve files between builds.

Alongside the tools directory is a build\native directory. This contains a MSBuild properties file python.props that can be used in a C++ project to reference the Python install. Including the settings will automatically use the headers and import libraries in your build.

The package information pages on nuget.org are www.nuget.org/packages/python [https://www.nuget.org/packages/python] for the 64-bit version, www.nuget.org/packages/pythonx86 [https://www.nuget.org/packages/pythonx86] for the 32-bit version, and www.nuget.org/packages/pythonarm64 [https://www.nuget.org/packages/pythonarm64] for the ARM64 version

4.3.1. Free-threaded packages

在 3.13 版被加入.

Packages containing free-threaded binaries are named python-freethreaded [https://www.nuget.org/packages/python-freethreaded] for the 64-bit version, pythonx86-freethreaded [https://www.nuget.org/packages/pythonx86-freethreaded] for the 32-bit version, and pythonarm64-freethreaded [https://www.nuget.org/packages/pythonarm64-freethreaded] for the ARM64 version. These packages contain both the python3.13t.exe and python.exe entry points, both of which run free threaded.

4.4. Alternative bundles

Besides the standard CPython distribution, there are modified packages including additional functionality. The following is a list of popular versions and their key features:

ActivePython [https://www.activestate.com/products/python/]

Installer with multi-platform compatibility, documentation, PyWin32

Anaconda [https://www.anaconda.com/download/]

Popular scientific modules (such as numpy, scipy and pandas) and the conda package manager.

Enthought Deployment Manager [https://assets.enthought.com/downloads/edm/]

"The Next Generation Python Environment and Package Manager".

Previously Enthought provided Canopy, but it reached end of life in 2016 [https://support.enthought.com/hc/en-us/articles/360038600051-Canopy-GUI-end-of-life-transition-to-the-Enthought-Deployment-Manager-EDM-and-Visual-Studio-Code].

WinPython [https://winpython.github.io/]

Windows-specific distribution with prebuilt scientific packages and tools for building packages.

Note that these packages may not include the latest versions of Python or other libraries, and are not maintained or supported by the core Python team.

4.5. Supported Windows versions

As specified in PEP 11 [https://peps.python.org/pep-0011/], a Python release only supports a Windows platform while Microsoft considers the platform under extended support. This means that Python 3.14 supports Windows 10 and newer. If you require Windows 7 support, please install Python 3.8. If you require Windows 8.1 support, please install Python 3.12.

4.6. Removing the MAX_PATH limitation

Windows historically has limited path lengths to 260 characters. This meant that paths longer than this would not resolve and errors would result.

In the latest versions of Windows, this limitation can be expanded to over 32,000 characters. Your administrator will need to activate the "Enable Win32 long paths" group policy, or set LongPathsEnabled to 1 in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem.

This allows the open() function, the os module and most other path functionality to accept and return paths longer than 260 characters.

After changing the above option and rebooting, no further configuration is required.

4.7. UTF-8 模式

在 3.7 版被加入.

Windows still uses legacy encodings for the system encoding (the ANSI Code Page). Python uses it for the default encoding of text files (e.g. locale.getencoding()).

This may cause issues because UTF-8 is widely used on the internet and most Unix systems, including WSL (Windows Subsystem for Linux).

You can use the Python UTF-8 Mode to change the default text encoding to UTF-8. You can enable the Python UTF-8 Mode via the -X utf8 command line option, or the PYTHONUTF8=1 environment variable. See PYTHONUTF8 for enabling UTF-8 mode, and Python 安裝管理員 for how to modify environment variables.

When the Python UTF-8 Mode is enabled, you can still use the system encoding (the ANSI Code Page) via the "mbcs" codec.

Note that adding PYTHONUTF8=1 to the default environment variables will affect all Python 3.7+ applications on your system. If you have any Python 3.7+ applications which rely on the legacy system encoding, it is recommended to set the environment variable temporarily or use the -X utf8 command line option.

備註

Even when UTF-8 mode is disabled, Python uses UTF-8 by default on Windows for:

Console I/O including standard I/O (see PEP 528 [https://peps.python.org/pep-0528/] for details).

The filesystem encoding (see PEP 529 [https://peps.python.org/pep-0529/] for details).

4.8. 找尋模組

These notes supplement the description at sys.path 模組搜尋路徑的初始化 with detailed Windows notes.

When no ._pth file is found, this is how sys.path is populated on Windows:

An empty entry is added at the start, which corresponds to the current directory.

If the environment variable PYTHONPATH exists, as described in 環境變數, its entries are added next. Note that on Windows, paths in this variable must be separated by semicolons, to distinguish them from the colon used in drive identifiers (C:\ etc.).

Additional "application paths" can be added in the registry as subkeys of \SOFTWARE\Python\PythonCore{version}\PythonPath under both the HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE hives. Subkeys which have semicolon-delimited path strings as their default value will cause each path to be added to sys.path. (Note that all known installers only use HKLM, so HKCU is typically empty.)

If the environment variable PYTHONHOME is set, it is assumed as "Python Home". Otherwise, the path of the main Python executable is used to locate a "landmark file" (either Lib\os.py or pythonXY.zip) to deduce the "Python Home". If a Python home is found, the relevant sub-directories added to sys.path (Lib, plat-win, etc) are based on that folder. Otherwise, the core Python path is constructed from the PythonPath stored in the registry.

If the Python Home cannot be located, no PYTHONPATH is specified in the environment, and no registry entries can be found, a default path with relative entries is used (e.g. .\Lib;.\plat-win, etc).

If a pyvenv.cfg file is found alongside the main executable or in the directory one level above the executable, the following variations apply:

If home is an absolute path and PYTHONHOME is not set, this path is used instead of the path to the main executable when deducing the home location.

最終這所有的結果為：

When running python.exe, or any other .exe in the main Python directory (either an installed version, or directly from the PCbuild directory), the core path is deduced, and the core paths in the registry are ignored. Other "application paths" in the registry are always read.

When Python is hosted in another .exe (different directory, embedded via COM, etc), the "Python Home" will not be deduced, so the core path from the registry is used. Other "application paths" in the registry are always read.

If Python can't find its home and there are no registry value (frozen .exe, some very strange installation setup) you get a path with some default, but relative, paths.

For those who want to bundle Python into their application or distribution, the following advice will prevent conflicts with other installations:

Include a ._pth file alongside your executable containing the directories to include. This will ignore paths listed in the registry and environment variables, and also ignore site unless import site is listed.

If you are loading python3.dll or python37.dll in your own executable, explicitly set PyConfig.module_search_paths before Py_InitializeFromConfig().

Clear and/or overwrite PYTHONPATH and set PYTHONHOME before launching python.exe from your application.

If you cannot use the previous suggestions (for example, you are a distribution that allows people to run python.exe directly), ensure that the landmark file (Lib\os.py) exists in your install directory. (Note that it will not be detected inside a ZIP file, but a correctly named ZIP file will be detected instead.)

These will ensure that the files in a system-wide installation will not take precedence over the copy of the standard library bundled with your application. Otherwise, your users may experience problems using your application. Note that the first suggestion is the best, as the others may still be susceptible to non-standard paths in the registry and user site-packages.

在 3.6 版的變更: Add ._pth file support and removes applocal option from pyvenv.cfg.

在 3.6 版的變更: Add pythonXX.zip as a potential landmark when directly adjacent to the executable.

在 3.6 版之後被棄用: Modules specified in the registry under Modules (not PythonPath) may be imported by importlib.machinery.WindowsRegistryFinder. This finder is enabled on Windows in 3.6.0 and earlier, but may need to be explicitly added to sys.meta_path in the future.

4.9. 額外的模組

Even though Python aims to be portable among all platforms, there are features that are unique to Windows. A couple of modules, both in the standard library and external, and snippets exist to use these features.

The Windows-specific standard modules are documented in MS Windows 特有服務.

4.9.1. PyWin32

The PyWin32 [https://pypi.org/project/PyWin32/] module by Mark Hammond is a collection of modules for advanced Windows-specific support. This includes utilities for:

Component Object Model [https://learn.microsoft.com/windows/win32/com/component-object-model--com--portal] (COM)

Win32 API 呼叫

登錄檔（Registry）

事件日誌（Event log）

Microsoft Foundation Classes [https://learn.microsoft.com/cpp/mfc/mfc-desktop-applications] (MFC) user interfaces

PythonWin [https://web.archive.org/web/20060524042422/https://www.python.org/windows/pythonwin/] is a sample MFC application shipped with PyWin32. It is an embeddable IDE with a built-in debugger.

也參考

Win32 How Do I...? [https://timgolden.me.uk/python/win32_how_do_i.html]

由 Tim Golden 所著

Python and COM [https://www.boddie.org.uk/python/COM.html]

由 David 與 Paul Boddie 所著

4.9.2. cx_Freeze

cx_Freeze [https://cx-freeze.readthedocs.io/en/latest/] wraps Python scripts into executable Windows programs (*.exe files). When you have done this, you can distribute your application without requiring your users to install Python.

4.10. 編譯 Python 在 Windows

If you want to compile CPython yourself, first thing you should do is get the source [https://www.python.org/downloads/source/]. You can download either the latest release's source or just grab a fresh checkout [https://devguide.python.org/setup/#get-the-source-code].

The source tree contains a build solution and project files for Microsoft Visual Studio, which is the compiler used to build the official Python releases. These files are in the PCbuild directory.

Check PCbuild/readme.txt for general information on the build process.

For extension modules, consult 建置 Windows 上的 C 和 C++ 擴充.

4.11. The full installer (deprecated)

在 3.14 版之後被棄用: This installer is deprecated since 3.14 and will not be produced for Python 3.16 or later. See Python 安裝管理員 for the modern installer.

4.11.1. 安裝步驟

Four Python 3.14 installers are available for download - two each for the 32-bit and 64-bit versions of the interpreter. The web installer is a small initial download, and it will automatically download the required components as necessary. The offline installer includes the components necessary for a default installation and only requires an internet connection for optional features. See 無下載安裝 for other ways to avoid downloading during installation.

After starting the installer, one of two options may be selected:

如果你選擇「馬上安裝」：

You will not need to be an administrator (unless a system update for the C Runtime Library is required or you install the Python 安裝管理員 for all users)

Python will be installed into your user directory

The Python 安裝管理員 will be installed according to the option at the bottom of the first page

The standard library, test suite, launcher and pip will be installed

如果選擇，安裝目錄將被加入到你的 PATH

安裝捷徑將只能被目前使用者所看見

選擇「客製化安裝」將允許你選擇所需的項目進行安裝，安裝位置與其他選擇或安裝後的所需進行的動作。你將需要使用此選項「除錯特徵」或「二進位方式」進行安裝。

To perform an all-users installation, you should select "Customize installation". In this case:

You may be required to provide administrative credentials or approval

Python will be installed into the Program Files directory

The Python 安裝管理員 will be installed into the Windows directory

Optional features may be selected during installation

The standard library can be pre-compiled to bytecode

If selected, the install directory will be added to the system PATH

捷徑將被所有使用者所見

4.11.2. Removing the MAX_PATH limitation

Windows historically has limited path lengths to 260 characters. This meant that paths longer than this would not resolve and errors would result.

In the latest versions of Windows, this limitation can be expanded to approximately 32,000 characters. Your administrator will need to activate the "Enable Win32 long paths" group policy, or set LongPathsEnabled to 1 in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem.

This allows the open() function, the os module and most other path functionality to accept and return paths longer than 260 characters.

After changing the above option, no further configuration is required.

在 3.6 版的變更: Support for long paths was enabled in Python.

4.11.3. 無使用者介面安裝

All of the options available in the installer UI can also be specified from the command line, allowing scripted installers to replicate an installation on many machines without user interaction. These options may also be set without suppressing the UI in order to change some of the defaults.

The following options (found by executing the installer with /?) can be passed into the installer:

名稱

描述

/passive

to display progress without requiring user interaction

/quiet

to install/uninstall without displaying any UI

/simple

to prevent user customization

/uninstall

to remove Python (without confirmation)

/layout [directory]

to pre-download all components

/log [filename]

to specify log files location

All other options are passed as name=value, where the value is usually 0 to disable a feature, 1 to enable a feature, or a path. The full list of available options is shown below.

名稱

描述

預設

InstallAllUsers

Perform a system-wide installation.

0

TargetDir

安裝目錄

Selected based on InstallAllUsers

DefaultAllUsersTargetDir

The default installation directory for all-user installs

%ProgramFiles%\Python X.Y or %ProgramFiles(x86)%\Python X.Y

DefaultJustForMeTargetDir

The default install directory for just-for-me installs

%LocalAppData%\Programs\Python\PythonXY or %LocalAppData%\Programs\Python\PythonXY-32 or %LocalAppData%\Programs\Python\PythonXY-64

DefaultCustomTargetDir

The default custom install directory displayed in the UI

(empty)

AssociateFiles

如果啟動器也被安裝，建立檔案關聯。

1

CompileAll

編譯所有 .py 檔案為 .pyc。

0

PrependPath

Prepend install and Scripts directories to PATH and add .PY to PATHEXT

0

AppendPath

Append install and Scripts directories to PATH and add .PY to PATHEXT

0

Shortcuts

Create shortcuts for the interpreter, documentation and IDLE if installed.

1

Include_doc

安裝Python文件

1

Include_debug

Install debug binaries

0

Include_dev

Install developer headers and libraries. Omitting this may lead to an unusable installation.

1

Include_exe

Install python.exe and related files. Omitting this may lead to an unusable installation.

1

Include_launcher

安裝 Python 安裝管理員。

1

InstallLauncherAllUsers

Installs the launcher for all users. Also requires Include_launcher to be set to 1

1

Include_lib

Install standard library and extension modules. Omitting this may lead to an unusable installation.

1

Include_pip

Install bundled pip and setuptools

1

Include_symbols

Install debugging symbols (*.pdb)

0

Include_tcltk

Install Tcl/Tk support and IDLE

1

Include_test

Install standard library test suite

1

Include_tools

Install utility scripts

1

LauncherOnly

Only installs the launcher. This will override most other options.

0

SimpleInstall

Disable most install UI

0

SimpleInstallDescription

A custom message to display when the simplified install UI is used.

(empty)

For example, to silently install a default, system-wide Python installation, you could use the following command (from an elevated command prompt):

python-3.9.0.exe /quiet InstallAllUsers=1 PrependPath=1 Include_test=0

To allow users to easily install a personal copy of Python without the test suite, you could provide a shortcut with the following command. This will display a simplified initial page and disallow customization:

python-3.9.0.exe InstallAllUsers=0 Include_launcher=0 Include_test=0
    SimpleInstall=1 SimpleInstallDescription="Just for me, no test suite."

(Note that omitting the launcher also omits file associations, and is only recommended for per-user installs when there is also a system-wide installation that included the launcher.)

The options listed above can also be provided in a file named unattend.xml alongside the executable. This file specifies a list of options and values. When a value is provided as an attribute, it will be converted to a number if possible. Values provided as element text are always left as strings. This example file sets the same options as the previous example:

<Options>
    <Option Name="InstallAllUsers" Value="no" />
    <Option Name="Include_launcher" Value="0" />
    <Option Name="Include_test" Value="no" />
    <Option Name="SimpleInstall" Value="yes" />
    <Option Name="SimpleInstallDescription">Just for me, no test suite</Option>
</Options>

4.11.4. 無下載安裝

As some features of Python are not included in the initial installer download, selecting those features may require an internet connection. To avoid this need, all possible components may be downloaded on-demand to create a complete layout that will no longer require an internet connection regardless of the selected features. Note that this download may be bigger than required, but where a large number of installations are going to be performed it is very useful to have a locally cached copy.

Execute the following command from Command Prompt to download all possible required files. Remember to substitute python-3.9.0.exe for the actual name of your installer, and to create layouts in their own directories to avoid collisions between files with the same name.

python-3.9.0.exe /layout [optional target directory]

You may also specify the /quiet option to hide the progress display.

4.11.5. Modifying an install

Once Python has been installed, you can add or remove features through the Programs and Features tool that is part of Windows. Select the Python entry and choose "Uninstall/Change" to open the installer in maintenance mode.

"Modify" allows you to add or remove features by modifying the checkboxes - unchanged checkboxes will not install or remove anything. Some options cannot be changed in this mode, such as the install directory; to modify these, you will need to remove and then reinstall Python completely.

"Repair" will verify all the files that should be installed using the current settings and replace any that have been removed or modified.

"Uninstall" will remove Python entirely, with the exception of the Python 安裝管理員, which has its own entry in Programs and Features.

4.11.6. Installing free-threaded binaries

在 3.13 版被加入.

To install pre-built binaries with free-threading enabled (see PEP 703 [https://peps.python.org/pep-0703/]), you should select "Customize installation". The second page of options includes the "Download free-threaded binaries" checkbox.

Selecting this option will download and install additional binaries to the same location as the main Python install. The main executable is called python3.13t.exe, and other binaries either receive a t suffix or a full ABI suffix. Python source files and bundled third-party dependencies are shared with the main install.

The free-threaded version is registered as a regular Python install with the tag 3.13t (with a -32 or -arm64 suffix as normal for those platforms). This allows tools to discover it, and for the Python 安裝管理員 to support py.exe -3.13t. Note that the launcher will interpret py.exe -3 (or a python3 shebang) as "the latest 3.x install", which will prefer the free-threaded binaries over the regular ones, while py.exe -3.13 will not. If you use the short style of option, you may prefer to not install the free-threaded binaries at this time.

To specify the install option at the command line, use Include_freethreaded=1. See 無下載安裝 for instructions on pre-emptively downloading the additional binaries for offline install. The options to include debug symbols and binaries also apply to the free-threaded builds.

Free-threaded binaries are also available on nuget.org.

4.12. Python launcher for Windows (deprecated)

在 3.14 版之後被棄用: The launcher and this documentation have been superseded by the Python Install Manager described above. This is preserved temporarily for historical interest.

在 3.3 版被加入.

The Python launcher for Windows is a utility which aids in locating and executing of different Python versions. It allows scripts (or the command-line) to indicate a preference for a specific Python version, and will locate and execute that version.

Unlike the PATH variable, the launcher will correctly select the most appropriate version of Python. It will prefer per-user installations over system-wide ones, and orders by language version rather than using the most recently installed version.

The launcher was originally specified in PEP 397 [https://peps.python.org/pep-0397/].

4.12.1. 開始

4.12.1.1. From the command-line

在 3.6 版的變更.

System-wide installations of Python 3.3 and later will put the launcher on your PATH. The launcher is compatible with all available versions of Python, so it does not matter which version is installed. To check that the launcher is available, execute the following command in Command Prompt:

py

You should find that the latest version of Python you have installed is started - it can be exited as normal, and any additional command-line arguments specified will be sent directly to Python.

If you have multiple versions of Python installed (e.g., 3.7 and 3.14) you will have noticed that Python 3.14 was started - to launch Python 3.7, try the command:

py -3.7

If you want the latest version of Python 2 you have installed, try the command:

py -2

If you see the following error, you do not have the launcher installed:

'py' is not recognized as an internal or external command,
operable program or batch file.

指令：

py --list

displays the currently installed version(s) of Python.

The -x.y argument is the short form of the -V:Company/Tag argument, which allows selecting a specific Python runtime, including those that may have come from somewhere other than python.org. Any runtime registered by following PEP 514 [https://peps.python.org/pep-0514/] will be discoverable. The --list command lists all available runtimes using the -V: format.

When using the -V: argument, specifying the Company will limit selection to runtimes from that provider, while specifying only the Tag will select from all providers. Note that omitting the slash implies a tag:

# Select any '3.*' tagged runtime
py -V:3

# Select any 'PythonCore' released runtime
py -V:PythonCore/

# Select PythonCore's latest Python 3 runtime
py -V:PythonCore/3

The short form of the argument (-3) only ever selects from core Python releases, and not other distributions. However, the longer form (-V:3) will select from any.

The Company is matched on the full string, case-insensitive. The Tag is matched on either the full string, or a prefix, provided the next character is a dot or a hyphen. This allows -V:3.1 to match 3.1-32, but not 3.10. Tags are sorted using numerical ordering (3.10 is newer than 3.1), but are compared using text (-V:3.01 does not match 3.1).

4.12.1.2. 虛擬環境（Virtual environment）

在 3.5 版被加入.

If the launcher is run with no explicit Python version specification, and a virtual environment (created with the standard library venv module or the external virtualenv tool) active, the launcher will run the virtual environment's interpreter rather than the global one. To run the global interpreter, either deactivate the virtual environment, or explicitly specify the global Python version.

4.12.1.3. From a script

Let's create a test Python script - create a file called hello.py with the following contents

#! python
import sys
sys.stdout.write("hello from Python %s\n" % (sys.version,))

From the directory in which hello.py lives, execute the command:

py hello.py

You should notice the version number of your latest Python 2.x installation is printed. Now try changing the first line to be:

#! python3

Re-executing the command should now print the latest Python 3.x information. As with the above command-line examples, you can specify a more explicit version qualifier. Assuming you have Python 3.7 installed, try changing the first line to #! python3.7 and you should find the 3.7 version information printed.

Note that unlike interactive use, a bare "python" will use the latest version of Python 2.x that you have installed. This is for backward compatibility and for compatibility with Unix, where the command python typically refers to Python 2.

4.12.1.4. 從檔案關聯

The launcher should have been associated with Python files (i.e. .py, .pyw, .pyc files) when it was installed. This means that when you double-click on one of these files from Windows explorer the launcher will be used, and therefore you can use the same facilities described above to have the script specify the version which should be used.

The key benefit of this is that a single launcher can support multiple Python versions at the same time depending on the contents of the first line.

4.12.2. Shebang lines

If the first line of a script file starts with #!, it is known as a "shebang" line. Linux and other Unix like operating systems have native support for such lines and they are commonly used on such systems to indicate how a script should be executed. This launcher allows the same facilities to be used with Python scripts on Windows and the examples above demonstrate their use.

To allow shebang lines in Python scripts to be portable between Unix and Windows, this launcher supports a number of 'virtual' commands to specify which interpreter to use. The supported virtual commands are:

/usr/bin/env

/usr/bin/python

/usr/local/bin/python

python

For example, if the first line of your script starts with

#! /usr/bin/python

The default Python or an active virtual environment will be located and used. As many Python scripts written to work on Unix will already have this line, you should find these scripts can be used by the launcher without modification. If you are writing a new script on Windows which you hope will be useful on Unix, you should use one of the shebang lines starting with /usr.

Any of the above virtual commands can be suffixed with an explicit version (either just the major version, or the major and minor version). Furthermore the 32-bit version can be requested by adding "-32" after the minor version. I.e. /usr/bin/python3.7-32 will request usage of the 32-bit Python 3.7. If a virtual environment is active, the version will be ignored and the environment will be used.

在 3.7 版被加入: Beginning with python launcher 3.7 it is possible to request 64-bit version by the "-64" suffix. Furthermore it is possible to specify a major and architecture without minor (i.e. /usr/bin/python3-64).

在 3.11 版的變更: The "-64" suffix is deprecated, and now implies "any architecture that is not provably i386/32-bit". To request a specific environment, use the new -V:TAG argument with the complete tag.

在 3.13 版的變更: Virtual commands referencing python now prefer an active virtual environment rather than searching PATH. This handles cases where the shebang specifies /usr/bin/env python3 but python3.exe is not present in the active environment.

The /usr/bin/env form of shebang line has one further special property. Before looking for installed Python interpreters, this form will search the executable PATH for a Python executable matching the name provided as the first argument. This corresponds to the behaviour of the Unix env program, which performs a PATH search. If an executable matching the first argument after the env command cannot be found, but the argument starts with python, it will be handled as described for the other virtual commands. The environment variable PYLAUNCHER_NO_SEARCH_PATH may be set (to any value) to skip this search of PATH.

Shebang lines that do not match any of these patterns are looked up in the [commands] section of the launcher's .INI file. This may be used to handle certain commands in a way that makes sense for your system. The name of the command must be a single argument (no spaces in the shebang executable), and the value substituted is the full path to the executable (additional arguments specified in the .INI will be quoted as part of the filename).

[commands]
/bin/xpython=C:\Program Files\XPython\python.exe

Any commands not found in the .INI file are treated as Windows executable paths that are absolute or relative to the directory containing the script file. This is a convenience for Windows-only scripts, such as those generated by an installer, since the behavior is not compatible with Unix-style shells. These paths may be quoted, and may include multiple arguments, after which the path to the script and any additional arguments will be appended.

4.12.3. Arguments in shebang lines

The shebang lines can also specify additional options to be passed to the Python interpreter. For example, if you have a shebang line:

#! /usr/bin/python -v

Then Python will be started with the -v option

4.12.4. Customization

4.12.4.1. Customization via INI files

Two .ini files will be searched by the launcher - py.ini in the current user's application data directory (%LOCALAPPDATA% or $env:LocalAppData) and py.ini in the same directory as the launcher. The same .ini files are used for both the 'console' version of the launcher (i.e. py.exe) and for the 'windows' version (i.e. pyw.exe).

Customization specified in the "application directory" will have precedence over the one next to the executable, so a user, who may not have write access to the .ini file next to the launcher, can override commands in that global .ini file.

4.12.4.2. Customizing default Python versions

In some cases, a version qualifier can be included in a command to dictate which version of Python will be used by the command. A version qualifier starts with a major version number and can optionally be followed by a period ('.') and a minor version specifier. Furthermore it is possible to specify if a 32 or 64 bit implementation shall be requested by adding "-32" or "-64".

For example, a shebang line of #!python has no version qualifier, while #!python3 has a version qualifier which specifies only a major version.

If no version qualifiers are found in a command, the environment variable PY_PYTHON can be set to specify the default version qualifier. If it is not set, the default is "3". The variable can specify any value that may be passed on the command line, such as "3", "3.7", "3.7-32" or "3.7-64". (Note that the "-64" option is only available with the launcher included with Python 3.7 or newer.)

If no minor version qualifiers are found, the environment variable PY_PYTHON{major} (where {major} is the current major version qualifier as determined above) can be set to specify the full version. If no such option is found, the launcher will enumerate the installed Python versions and use the latest minor release found for the major version, which is likely, although not guaranteed, to be the most recently installed version in that family.

On 64-bit Windows with both 32-bit and 64-bit implementations of the same (major.minor) Python version installed, the 64-bit version will always be preferred. This will be true for both 32-bit and 64-bit implementations of the launcher - a 32-bit launcher will prefer to execute a 64-bit Python installation of the specified version if available. This is so the behavior of the launcher can be predicted knowing only what versions are installed on the PC and without regard to the order in which they were installed (i.e., without knowing whether a 32 or 64-bit version of Python and corresponding launcher was installed last). As noted above, an optional "-32" or "-64" suffix can be used on a version specifier to change this behaviour.

範例：

If no relevant options are set, the commands python and python2 will use the latest Python 2.x version installed and the command python3 will use the latest Python 3.x installed.

The command python3.7 will not consult any options at all as the versions are fully specified.

If PY_PYTHON=3, the commands python and python3 will both use the latest installed Python 3 version.

If PY_PYTHON=3.7-32, the command python will use the 32-bit implementation of 3.7 whereas the command python3 will use the latest installed Python (PY_PYTHON was not considered at all as a major version was specified.)

If PY_PYTHON=3 and PY_PYTHON3=3.7, the commands python and python3 will both use specifically 3.7

In addition to environment variables, the same settings can be configured in the .INI file used by the launcher. The section in the INI file is called [defaults] and the key name will be the same as the environment variables without the leading PY_ prefix (and note that the key names in the INI file are case insensitive.) The contents of an environment variable will override things specified in the INI file.

舉例來說：

Setting PY_PYTHON=3.7 is equivalent to the INI file containing:

[defaults]
python=3.7

Setting PY_PYTHON=3 and PY_PYTHON3=3.7 is equivalent to the INI file containing:

[defaults]
python=3
python3=3.7

4.12.5. Diagnostics

If an environment variable PYLAUNCHER_DEBUG is set (to any value), the launcher will print diagnostic information to stderr (i.e. to the console). While this information manages to be simultaneously verbose and terse, it should allow you to see what versions of Python were located, why a particular version was chosen and the exact command-line used to execute the target Python. It is primarily intended for testing and debugging.

4.12.6. Dry run

If an environment variable PYLAUNCHER_DRYRUN is set (to any value), the launcher will output the command it would have run, but will not actually launch Python. This may be useful for tools that want to use the launcher to detect and then launch Python directly. Note that the command written to standard output is always encoded using UTF-8, and may not render correctly in the console.

4.12.7. 安裝隨選

If an environment variable PYLAUNCHER_ALLOW_INSTALL is set (to any value), and the requested Python version is not installed but is available on the Microsoft Store, the launcher will attempt to install it. This may require user interaction to complete, and you may need to run the command again.

An additional PYLAUNCHER_ALWAYS_INSTALL variable causes the launcher to always try to install Python, even if it is detected. This is mainly intended for testing (and should be used with PYLAUNCHER_DRYRUN).

4.12.8. Return codes

The following exit codes may be returned by the Python launcher. Unfortunately, there is no way to distinguish these from the exit code of Python itself.

The names of codes are as used in the sources, and are only for reference. There is no way to access or resolve them apart from reading this page. Entries are listed in alphabetical order of names.

名稱

Value

描述

RC_BAD_VENV_CFG

107

A pyvenv.cfg was found but is corrupt.

RC_CREATE_PROCESS

101

Failed to launch Python.

RC_INSTALLING

111

An install was started, but the command will need to be re-run after it completes.

RC_INTERNAL_ERROR

109

Unexpected error. Please report a bug.

RC_NO_COMMANDLINE

108

Unable to obtain command line from the operating system.

RC_NO_PYTHON

103

Unable to locate the requested version.

RC_NO_VENV_CFG

106

A pyvenv.cfg was required but not found.

5. 於 macOS 使用 Python

This document aims to give an overview of macOS-specific behavior you should know about to get started with Python on Mac computers. Python on a Mac running macOS is very similar to Python on other Unix-derived platforms, but there are some differences in installation and some features.

There are various ways to obtain and install Python for macOS. Pre-built versions of the most recent versions of Python are available from a number of distributors. Much of this document describes use of the Pythons provided by the CPython release team for download from the python.org website [https://www.python.org/downloads/]. See Alternative Distributions for some other options.

5.1. Using Python for macOS from python.org

5.1.1. 安裝步驟

For current Python versions [https://www.python.org/downloads/] (other than those in security status), the release team produces a Python for macOS installer package for each new release. A list of available installers is available here [https://www.python.org/downloads/macos/]. We recommend using the most recent supported Python version where possible. Current installers provide a universal2 binary [https://en.wikipedia.org/wiki/Universal_binary] build of Python which runs natively on all Macs (Apple Silicon and Intel) that are supported by a wide range of macOS versions, currently typically from at least macOS 10.15 Catalina on.

The downloaded file is a standard macOS installer package file (.pkg). File integrity information (checksum, size, sigstore signature, etc) for each file is included on the release download page. Installer packages and their contents are signed and notarized with Python Software Foundation Apple Developer ID certificates to meet macOS Gatekeeper requirements [https://support.apple.com/en-us/102445].

For a default installation, double-click on the downloaded installer package file. This should launch the standard macOS Installer app and display the first of several installer windows steps.

Clicking on the Continue button brings up the Read Me for this installer. Besides other important information, the Read Me documents which Python version is going to be installed and on what versions of macOS it is supported. You may need to scroll through to read the whole file. By default, this Read Me will also be installed in /Applications/Python 3.14/ and available to read anytime.

Clicking on Continue proceeds to display the license for Python and for other included software. You will then need to Agree to the license terms before proceeding to the next step. This license file will also be installed and available to be read later.

After the license terms are accepted, the next step is the Installation Type display. For most uses, the standard set of installation operations is appropriate.

By pressing the Customize button, you can choose to omit or select certain package components of the installer. Click on each package name to see a description of what it installs. To also install support for the optional free-threaded feature, see Installing Free-threaded Binaries.

In either case, clicking Install will begin the install process by asking permission to install new software. A macOS user name with Administrator privilege is needed as the installed Python will be available to all users of the Mac.

When the installation is complete, the Summary window will appear.

Double-click on the Install Certificates.command icon or file in the /Applications/Python 3.14/ window to complete the installation.

This will open a temporary Terminal shell window that will use the new Python to download and install SSL root certificates for its use.

If Successfully installed certifi and update complete appears in the terminal window, the installation is complete. Close this terminal window and the installer window.

預設安裝會包含：

會有一個 Python 3.14 資料夾在你的 Applications 資料夾中。在這裡你可以找到 IDLE，它是作為官方 Python 發行版標準組成的開發環境；以及 Python Launcher，它負責處理在 Finder [https://support.apple.com/en-us/HT201732] 中雙擊 Python 腳本的操作。

/Library/Frameworks/Python.framework 框架，包括 Python 可執行檔案 (executable) 和函式庫 (library)。安裝程式將此位置新增到 shell 路徑。要解除安裝 Python ，你可以移除這三個東西。Python 可執行檔案的符號連結 (symlink) 則放在 /usr/local/bin/ 中。

備註

Recent versions of macOS include a python3 command in /usr/bin/python3 that links to a usually older and incomplete version of Python provided by and for use by the Apple development tools, Xcode or the Command Line Tools for Xcode. You should never modify or attempt to delete this installation, as it is Apple-controlled and is used by Apple-provided or third-party software. If you choose to install a newer Python version from python.org, you will have two different but functional Python installations on your computer that can co-exist. The default installer options should ensure that its python3 will be used instead of the system python3.

5.1.2. 如何執行 Python 腳本

There are two ways to invoke the Python interpreter. If you are familiar with using a Unix shell in a terminal window, you can invoke python3.14 or python3 optionally followed by one or more command line options (described in 命令列與環境). The Python tutorial also has a useful section on using Python interactively from a shell.

You can also invoke the interpreter through an integrated development environment. IDLE --- Python 編輯器與 shell is a basic editor and interpreter environment which is included with the standard distribution of Python. IDLE includes a Help menu that allows you to access Python documentation. If you are completely new to Python, you can read the tutorial introduction in that document.

There are many other editors and IDEs available, see 編輯器與 IDE for more information.

To run a Python script file from the terminal window, you can invoke the interpreter with the name of the script file:

python3.14 myscript.py

從 Finder 執行你的腳本時，你可以：

把它拖曳到 Python Launcher

透過 Finder Info 視窗選擇 Python Launcher 作為開啟腳本（或任何 .py 腳本）的預設應用程式，然後雙擊腳本。Python Launcher 有各種用來控制腳本啟動方式的選項。拖曳選項可以讓你一次更改多個選項，或使用其 Preferences 選單以全域性地更改內容。

Be aware that running the script directly from the macOS Finder might produce different results than when running from a terminal window as the script will not be run in the usual shell environment including any setting of environment variables in shell profiles. And, as with any other script or program, be certain of what you are about to run.

5.2. Alternative Distributions

Besides the standard python.org for macOS installer, there are third-party distributions for macOS that may include additional functionality. Some popular distributions and their key features:

ActivePython [https://www.activestate.com/products/python/]

Installer with multi-platform compatibility, documentation

Anaconda [https://www.anaconda.com/download/]

Popular scientific modules (such as numpy, scipy, and pandas) and the conda package manager.

Homebrew [https://brew.sh]

Package manager for macOS including multiple versions of Python and many third-party Python-based packages (including numpy, scipy, and pandas).

MacPorts [https://www.macports.org]

Another package manager for macOS including multiple versions of Python and many third-party Python-based packages. May include pre-built versions of Python and many packages for older versions of macOS.

Note that distributions might not include the latest versions of Python or other libraries, and are not maintained or supported by the core Python team.

5.3. 安裝額外的 Python 套件

更多資訊請見 Python Packaging User Guide [https://packaging.python.org/en/latest/tutorials/installing-packages/]。

5.4. 開發 GUI 程式

於 Mac 上使用 Python 來建立 GUI 應用程式有許多選項。

標準的 Python GUI 工具套件是基於跨平臺 Tk 工具套件 (https://www.tcl.tk) 的 tkinter。macOS 原生版本的 Tk 有包含於安裝程式中。

PyObjC 是一個 Apple Objective-C/Cocoa 框架的 Python 繫結 (binding)。有關 PyObjC 的資訊請見 pyobjc [https://pypi.org/project/pyobjc/]。

有許多替代 macOS GUI 工具套件可用，包含：

PySide [https://www.qt.io/qt-for-python]：Qt GUI 工具包 [https://wiki.qt.io/Qt_for_Python]的官方 Python 繫結。

PyQt [https://riverbankcomputing.com/software/pyqt/]：Qt 的替代 Python 繫結。

Kivy [https://kivy.org]：一個支援桌面和行動平臺的跨平臺 GUI 工具包。

Toga [https://toga.readthedocs.io]：BeeWare 專案 [https://beeware.org]的一部分；支援桌面、行動、網頁和控制台應用程式。

wxPython [https://wxpython.org]：一個支援桌面作業系統的跨平臺工具包。

5.5. 進階主題

5.5.1. Installing Free-threaded Binaries

在 3.13 版被加入.

The python.org Python for macOS installer package can optionally install an additional build of Python 3.14 that supports PEP 703 [https://peps.python.org/pep-0703/], the free-threading feature (running with the global interpreter lock disabled). Check the release page on python.org for possible updated information.

The free-threaded mode is working and continues to be improved, but there is some additional overhead in single-threaded workloads compared to the regular build. Additionally, third-party packages, in particular ones with an extension module, may not be ready for use in a free-threaded build, and will re-enable the GIL. Therefore, the support for free-threading is not installed by default. It is packaged as a separate install option, available by clicking the Customize button on the Installation Type step of the installer as described above.

If the box next to the Free-threaded Python package name is checked, a separate PythonT.framework will also be installed alongside the normal Python.framework in /Library/Frameworks. This configuration allows a free-threaded Python 3.14 build to co-exist on your system with a traditional (GIL only) Python 3.14 build with minimal risk while installing or testing. This installation layout may change in future releases.

Known cautions and limitations:

The UNIX command-line tools package, which is selected by default, will install links in /usr/local/bin for python3.14t, the free-threaded interpreter, and python3.14t-config, a configuration utility which may be useful for package builders. Since /usr/local/bin is typically included in your shell PATH, in most cases no changes to your PATH environment variables should be needed to use python3.14t.

For this release, the Shell profile updater package and the Update Shell Profile.command in /Applications/Python 3.14/ do not support the free-threaded package.

The free-threaded build and the traditional build have separate search paths and separate site-packages directories so, by default, if you need a package available in both builds, it may need to be installed in both. The free-threaded package will install a separate instance of pip for use with python3.14t.

To install a package using pip without a venv:

python3.14t -m pip install <package_name>

When working with multiple Python environments, it is usually safest and easiest to create and use virtual environments. This can avoid possible command name conflicts and confusion about which Python is in use:

python3.14t -m venv <venv_name>

然後 activate。

執行 free-threaded（自由執行緒）版本的 IDLE：

python3.14t -m idlelib

The interpreters in both builds respond to the same PYTHON environment variables which may have unexpected results, for example, if you have PYTHONPATH set in a shell profile. If necessary, there are command line options like -E to ignore these environment variables.

The free-threaded build links to the third-party shared libraries, such as OpenSSL and Tk, installed in the traditional framework. This means that both builds also share one set of trust certificates as installed by the Install Certificates.command script, thus it only needs to be run once.

If you cannot depend on the link in /usr/local/bin pointing to the python.org free-threaded python3.14t (for example, if you want to install your own version there or some other distribution does), you can explicitly set your shell PATH environment variable to include the PythonT framework bin directory:

export PATH="/Library/Frameworks/PythonT.framework/Versions/3.14/bin":"$PATH"

The traditional framework installation by default does something similar, except for Python.framework. Be aware that having both framework bin directories in PATH can lead to confusion if there are duplicate names like python3.14 in both; which one is actually used depends on the order they appear in PATH. The which python3.x or which python3.xt commands can show which path is being used. Using virtual environments can help avoid such ambiguities. Another option might be to create a shell alias to the desired interpreter, like:

alias py3.14="/Library/Frameworks/Python.framework/Versions/3.14/bin/python3.14"
alias py3.14t="/Library/Frameworks/PythonT.framework/Versions/3.14/bin/python3.14t"

5.5.2. 使用命令列安裝

If you want to use automation to install the python.org installer package (rather than by using the familiar macOS Installer GUI app), the macOS command line installer utility lets you select non-default options, too. If you are not familiar with installer, it can be somewhat cryptic (see man installer for more information). As an example, the following shell snippet shows one way to do it, using the 3.14.0b2 release and selecting the free-threaded interpreter option:

RELEASE="python-3.140b2-macos11.pkg"

# download installer pkg
curl -O https://www.python.org/ftp/python/3.14.0/${RELEASE}

# create installer choicechanges to customize the install:
#    enable the PythonTFramework-3.14 package
#    while accepting the other defaults (install all other packages)
cat > ./choicechanges.plist <<EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<array>
        <dict>
                <key>attributeSetting</key>
                <integer>1</integer>
                <key>choiceAttribute</key>
                <string>selected</string>
                <key>choiceIdentifier</key>
                <string>org.python.Python.PythonTFramework-3.14</string>
        </dict>
</array>
</plist>
EOF

sudo installer -pkg ./${RELEASE} -applyChoiceChangesXML ./choicechanges.plist -target /

You can then test that both installer builds are now available with something like:

$ # test that the free-threaded interpreter was installed if the Unix Command Tools package was enabled
$ /usr/local/bin/python3.14t -VV
Python 3.14.0b2 free-threading build (v3.14.0b2:3a83b172af, Jun  5 2024, 12:57:31) [Clang 15.0.0 (clang-1500.3.9.4)]
$ #    and the traditional interpreter
$ /usr/local/bin/python3.14 -VV
Python 3.14.0b2 (v3.14.0b2:3a83b172af, Jun  5 2024, 12:50:24) [Clang 15.0.0 (clang-1500.3.9.4)]
$ # test that they are also available without the prefix if /usr/local/bin is on $PATH
$ python3.14t -VV
Python 3.14.0b2 free-threading build (v3.14.0b2:3a83b172af, Jun  5 2024, 12:57:31) [Clang 15.0.0 (clang-1500.3.9.4)]
$ python3.14 -VV
Python 3.14.0b2 (v3.14.0b2:3a83b172af, Jun  5 2024, 12:50:24) [Clang 15.0.0 (clang-1500.3.9.4)]

備註

Current python.org installers only install to fixed locations like /Library/Frameworks/, /Applications, and /usr/local/bin. You cannot use the installer -domain option to install to other locations.

5.5.3. 發行 Python 應用程式

A range of tools exist for converting your Python code into a standalone distributable application:

py2app [https://pypi.org/project/py2app/]：支援從 Python 專案打包成 macOS .app。

Briefcase [https://briefcase.readthedocs.io]：BeeWare 專案 [https://beeware.org]的一部分；支援建立 macOS .app 的跨平台打包工具，亦為管理簽署和驗證 (notarization) 的工具。

PyInstaller [https://pyinstaller.org/]：一個跨平臺打包工具，可以將單一檔案或資料夾打包成可分發的檔案。

5.5.4. App Store Compliance

Apps submitted for distribution through the macOS App Store must pass Apple's app review process. This process includes a set of automated validation rules that inspect the submitted application bundle for problematic code.

The Python standard library contains some code that is known to violate these automated rules. While these violations appear to be false positives, Apple's review rules cannot be challenged. Therefore, it is necessary to modify the Python standard library for an app to pass App Store review.

The Python source tree contains a patch file [https://github.com/python/cpython/tree/3.14/Mac/Resources/app-store-compliance.patch] that will remove all code that is known to cause issues with the App Store review process. This patch is applied automatically when CPython is configured with the --with-app-store-compliance option.

This patch is not normally required to use CPython on a Mac; nor is it required if you are distributing an app outside the macOS App Store. It is only required if you are using the macOS App Store as a distribution channel.

5.6. 其他資源

The python.org Help page [https://www.python.org/about/help/] has links to many useful resources. The Pythonmac-SIG mailing list [https://www.python.org/community/sigs/current/pythonmac-sig/] is another support resource specifically for Python users and developers on the Mac.

6. 在 Android 上使用 Python

Android 上的 Python 與桌面版的 Python 不同。在桌面版上，Python 通常作為系統資源安裝，供該台電腦上的任何使用者使用。使用者通常透過執行 python 可執行檔並在互動式提示字元中輸入指令，或是直接執行 Python 腳本與 Python 互動。

在 Android 上，沒有將其安裝為系統資源的概念。唯一的軟體單位是 "app"。也沒有可以執行 python 可執行檔的控制台，或與 Python REPL 互動。

因此，在 Android 上使用 Python 的唯一方式就是以嵌入模式運作 - 也就是撰寫一個原生的 Android 應用程式，使用 libpython 嵌入 Python 直譯器，並透過 Python 嵌入式 API 呼叫 Python 程式碼。完整的 Python 直譯器、標準函式庫，以及你所有的 Python 程式碼，都會被打包進你的應用程式，供該應用程式使用。

Python 的標準函式庫在 Android 上有一些明顯的缺漏與限制。詳情請參考 API 可用性指南。

6.1. 將 Python 加入 Android 應用程式

大多數的應用程式開發者應該使用下面其中一種工具，這些工具能提供更輕鬆的使用體驗：

Briefcase [https://briefcase.readthedocs.io]，由 BeeWare 專案提供

Buildozer [https://buildozer.readthedocs.io]，由 Kivy 專案提供

Chaquopy [https://chaquo.com/chaquopy]

pyqtdeploy [https://www.riverbankcomputing.com/static/Docs/pyqtdeploy/]

Termux [https://termux.dev/en/]

如果你確定要全部手動操作，請繼續閱讀。你可以將 testbed app [https://github.com/python/cpython/tree/3.14/Android/testbed] 作為參考；下面的每個步驟都包含相關檔案的連結。

首先，取得一個用於 Android 的 Python 建置：

最簡單的方式是從 python.org [https://www.python.org/downloads/android/] 下載 Android 版本。下面提到的 prefix 目錄位於套件的最上層。

或者如果你想自行建置它，請依照 Android/README.md [https://github.com/python/cpython/tree/3.14/Android/README.md] 中的操作。prefix 目錄將會建立在 cross-build/HOST 底下。

在你的 build.gradle [https://github.com/python/cpython/tree/3.14/Android/testbed/app/build.gradle.kts] 檔案中加入程式碼，將以下項目複製到你的專案中。除了你自己的 Python 程式碼外，其他項目都可以從 prefix/lib 複製：

在你的 JNI 函式庫：

libpython*.*.so

lib*_python.so（外部函式庫，例如 OpenSSL）

在你的資產：

python*.*（Python 標準函式庫）

python*.*/site-packages（你自己的 Python 程式碼）

在你的應用程式中加入程式碼，以 解壓縮資產到檔案系統 [https://github.com/python/cpython/tree/3.14/Android/testbed/app/src/main/java/org/python/testbed/MainActivity.kt]。

在你的應用程式中加入程式碼，以 嵌入模式啟動 Python [https://github.com/python/cpython/tree/3.14/Android/testbed/app/src/main/c/main_activity.c]。這需要透過 JNI 呼叫的 C 語言程式碼。

6.2. 建置用於 Android 的 Python 套件

Python 套件可以為 Android 建置成 wheels 並發布到 PyPI。建議使用的工具是 cibuildwheel [https://cibuildwheel.pypa.io/en/stable/platforms/#android]，它會自動設定交叉編譯環境、建置 wheel，以及在模擬器上測試等所有細節。

7. 在 iOS 上使用 Python

作者:

Russell Keith-Magee (2024-03)

Python on iOS is unlike Python on desktop platforms. On a desktop platform, Python is generally installed as a system resource that can be used by any user of that computer. Users then interact with Python by running a python executable and entering commands at an interactive prompt, or by running a Python script.

On iOS, there is no concept of installing as a system resource. The only unit of software distribution is an "app". There is also no console where you could run a python executable, or interact with a Python REPL.

As a result, the only way you can use Python on iOS is in embedded mode - that is, by writing a native iOS application, and embedding a Python interpreter using libPython, and invoking Python code using the Python embedding API. The full Python interpreter, the standard library, and all your Python code is then packaged as a standalone bundle that can be distributed via the iOS App Store.

If you're looking to experiment for the first time with writing an iOS app in Python, projects such as BeeWare [https://beeware.org] and Kivy [https://kivy.org] will provide a much more approachable user experience. These projects manage the complexities associated with getting an iOS project running, so you only need to deal with the Python code itself.

7.1. Python at runtime on iOS

7.1.1. iOS version compatibility

The minimum supported iOS version is specified at compile time, using the --host option to configure. By default, when compiled for iOS, Python will be compiled with a minimum supported iOS version of 13.0. To use a different minimum iOS version, provide the version number as part of the --host argument - for example, --host=arm64-apple-ios15.4-simulator would compile an ARM64 simulator build with a deployment target of 15.4.

7.1.2. Platform identification

When executing on iOS, sys.platform will report as ios. This value will be returned on an iPhone or iPad, regardless of whether the app is running on the simulator or a physical device.

Information about the specific runtime environment, including the iOS version, device model, and whether the device is a simulator, can be obtained using platform.ios_ver(). platform.system() will report iOS or iPadOS, depending on the device.

os.uname() reports kernel-level details; it will report a name of Darwin.

7.1.3. Standard library availability

The Python standard library has some notable omissions and restrictions on iOS. See the API availability guide for iOS for details.

7.1.4. Binary extension modules

One notable difference about iOS as a platform is that App Store distribution imposes hard requirements on the packaging of an application. One of these requirements governs how binary extension modules are distributed.

The iOS App Store requires that all binary modules in an iOS app must be dynamic libraries, contained in a framework with appropriate metadata, stored in the Frameworks folder of the packaged app. There can be only a single binary per framework, and there can be no executable binary material outside the Frameworks folder.

This conflicts with the usual Python approach for distributing binaries, which allows a binary extension module to be loaded from any location on sys.path. To ensure compliance with App Store policies, an iOS project must post-process any Python packages, converting .so binary modules into individual standalone frameworks with appropriate metadata and signing. For details on how to perform this post-processing, see the guide for adding Python to your project.

To help Python discover binaries in their new location, the original .so file on sys.path is replaced with a .fwork file. This file is a text file containing the location of the framework binary, relative to the app bundle. To allow the framework to resolve back to the original location, the framework must contain a .origin file that contains the location of the .fwork file, relative to the app bundle.

For example, consider the case of an import from foo.bar import _whiz, where _whiz is implemented with the binary module sources/foo/bar/_whiz.abi3.so, with sources being the location registered on sys.path, relative to the application bundle. This module must be distributed as Frameworks/foo.bar._whiz.framework/foo.bar._whiz (creating the framework name from the full import path of the module), with an Info.plist file in the .framework directory identifying the binary as a framework. The foo.bar._whiz module would be represented in the original location with a sources/foo/bar/_whiz.abi3.fwork marker file, containing the path Frameworks/foo.bar._whiz/foo.bar._whiz. The framework would also contain Frameworks/foo.bar._whiz.framework/foo.bar._whiz.origin, containing the path to the .fwork file.

When running on iOS, the Python interpreter will install an AppleFrameworkLoader that is able to read and import .fwork files. Once imported, the __file__ attribute of the binary module will report as the location of the .fwork file. However, the ModuleSpec for the loaded module will report the origin as the location of the binary in the framework folder.

7.1.5. Compiler stub binaries

Xcode doesn't expose explicit compilers for iOS; instead, it uses an xcrun script that resolves to a full compiler path (e.g., xcrun --sdk iphoneos clang to get the clang for an iPhone device). However, using this script poses two problems:

The output of xcrun includes paths that are machine specific, resulting in a sysconfig module that cannot be shared between users; and

It results in CC/CPP/LD/AR definitions that include spaces. There is a lot of C ecosystem tooling that assumes that you can split a command line at the first space to get the path to the compiler executable; this isn't the case when using xcrun.

To avoid these problems, Python provided stubs for these tools. These stubs are shell script wrappers around the underingly xcrun tools, distributed in a bin folder distributed alongside the compiled iOS framework. These scripts are relocatable, and will always resolve to the appropriate local system paths. By including these scripts in the bin folder that accompanies a framework, the contents of the sysconfig module becomes useful for end-users to compile their own modules. When compiling third-party Python modules for iOS, you should ensure these stub binaries are on your path.

7.2. Installing Python on iOS

7.2.1. Tools for building iOS apps

Building for iOS requires the use of Apple's Xcode tooling. It is strongly recommended that you use the most recent stable release of Xcode. This will require the use of the most (or second-most) recently released macOS version, as Apple does not maintain Xcode for older macOS versions. The Xcode Command Line Tools are not sufficient for iOS development; you need a full Xcode install.

If you want to run your code on the iOS simulator, you'll also need to install an iOS Simulator Platform. You should be prompted to select an iOS Simulator Platform when you first run Xcode. Alternatively, you can add an iOS Simulator Platform by selecting from the Platforms tab of the Xcode Settings panel.

7.2.2. Adding Python to an iOS project

Python can be added to any iOS project, using either Swift or Objective C. The following examples will use Objective C; if you are using Swift, you may find a library like PythonKit [https://github.com/pvieito/PythonKit] to be helpful.

To add Python to an iOS Xcode project:

Build or obtain a Python XCFramework. See the instructions in Apple/iOS/README.md [https://github.com/python/cpython/tree/3.14/Apple/iOS/README.md] (in the CPython source distribution) for details on how to build a Python XCFramework. At a minimum, you will need a build that supports arm64-apple-ios, plus one of either arm64-apple-ios-simulator or x86_64-apple-ios-simulator.

Drag the XCframework into your iOS project. In the following instructions, we'll assume you've dropped the XCframework into the root of your project; however, you can use any other location that you want by adjusting paths as needed.

Add your application code as a folder in your Xcode project. In the following instructions, we'll assume that your user code is in a folder named app in the root of your project; you can use any other location by adjusting paths as needed. Ensure that this folder is associated with your app target.

Select the app target by selecting the root node of your Xcode project, then the target name in the sidebar that appears.

In the "General" settings, under "Frameworks, Libraries and Embedded Content", add Python.xcframework, with "Embed & Sign" selected.

In the "Build Settings" tab, modify the following:

建置選項

User Script Sandboxing: No

Enable Testability: Yes

Search Paths

Framework Search Paths: $(PROJECT_DIR)

Header Search Paths: "$(BUILT_PRODUCTS_DIR)/Python.framework/Headers"

Apple Clang - Warnings - All languages

Quoted Include In Framework Header: No

Add a build step that processes the Python standard library, and your own Python binary dependencies. In the "Build Phases" tab, add a new "Run Script" build step before the "Embed Frameworks" step, but after the "Copy Bundle Resources" step. Name the step "Process Python libraries", disable the "Based on dependency analysis" checkbox, and set the script content to:

set -e
source $PROJECT_DIR/Python.xcframework/build/build_utils.sh
install_python Python.xcframework app

If you have placed your XCframework somewhere other than the root of your project, modify the path to the first argument.

Add Objective C code to initialize and use a Python interpreter in embedded mode. You should ensure that:

UTF-8 mode (PyPreConfig.utf8_mode) is enabled;

Buffered stdio (PyConfig.buffered_stdio) is disabled;

Writing bytecode (PyConfig.write_bytecode) is disabled;

Signal handlers (PyConfig.install_signal_handlers) are enabled;

System logging (PyConfig.use_system_logger) is enabled (optional, but strongly recommended; this is enabled by default);

PYTHONHOME for the interpreter is configured to point at the python subfolder of your app's bundle; and

The PYTHONPATH for the interpreter includes:

the python/lib/python3.X subfolder of your app's bundle,

the python/lib/python3.X/lib-dynload subfolder of your app's bundle, and

the app subfolder of your app's bundle

Your app's bundle location can be determined using [[NSBundle mainBundle] resourcePath].

Steps 7 and 8 of these instructions assume that you have a single folder of pure Python application code, named app. If you have third-party binary modules in your app, some additional steps will be required:

You need to ensure that any folders containing third-party binaries are either associated with the app target, or are explicitly copied as part of step 7. Step 7 should also purge any binaries that are not appropriate for the platform a specific build is targeting (i.e., delete any device binaries if you're building an app targeting the simulator).

If you're using a separate folder for third-party packages, ensure that folder is added to the end of the call to install_python in step 7, and as part of the PYTHONPATH configuration in step 8.

If any of the folders that contain third-party packages will contain .pth files, you should add that folder as a site directory (using site.addsitedir()), rather than adding to PYTHONPATH or sys.path directly.

7.2.3. Testing a Python package

The CPython source tree contains a testbed project [https://github.com/python/cpython/tree/3.14/Apple/iOS/testbed] that is used to run the CPython test suite on the iOS simulator. This testbed can also be used as a testbed project for running your Python library's test suite on iOS.

After building or obtaining an iOS XCFramework (see Apple/iOS/README.md [https://github.com/python/cpython/tree/3.14/Apple/iOS/README.md] for details), create a clone of the Python iOS testbed project. If you used the Apple build script to build the XCframework, you can run:

$ python cross-build/iOS/testbed clone --app <path/to/module1> --app <path/to/module2> app-testbed

Or, if you've sourced your own XCframework, by running:

$ python Apple/testbed clone --platform iOS --framework <path/to/Python.xcframework> --app <path/to/module1> --app <path/to/module2> app-testbed

Any folders specified with the --app flag will be copied into the cloned testbed project. The resulting testbed will be created in the app-testbed folder. In this example, the module1 and module2 would be importable modules at runtime. If your project has additional dependencies, they can be installed into the app-testbed/Testbed/app_packages folder (using pip install --target app-testbed/Testbed/app_packages or similar).

You can then use the app-testbed folder to run the test suite for your app, For example, if module1.tests was the entry point to your test suite, you could run:

$ python app-testbed run -- module1.tests

This is the equivalent of running python -m module1.tests on a desktop Python build. Any arguments after the -- will be passed to the testbed as if they were arguments to python -m on a desktop machine.

You can also open the testbed project in Xcode by running:

$ open app-testbed/iOSTestbed.xcodeproj

This will allow you to use the full Xcode suite of tools for debugging.

The arguments used to run the test suite are defined as part of the test plan. To modify the test plan, select the test plan node of the project tree (it should be the first child of the root node), and select the "Configurations" tab. Modify the "Arguments Passed On Launch" value to change the testing arguments.

The test plan also disables parallel testing, and specifies the use of the Testbed.lldbinit file for providing configuration of the debugger. The default debugger configuration disables automatic breakpoints on the SIGINT, SIGUSR1, SIGUSR2, and SIGXFSZ signals.

7.3. App Store Compliance

The only mechanism for distributing apps to third-party iOS devices is to submit the app to the iOS App Store; apps submitted for distribution must pass Apple's app review process. This process includes a set of automated validation rules that inspect the submitted application bundle for problematic code. There are some steps that must be taken to ensure that your app will be able to pass these validation steps.

7.3.1. Incompatible code in the standard library

The Python standard library contains some code that is known to violate these automated rules. While these violations appear to be false positives, Apple's review rules cannot be challenged; so, it is necessary to modify the Python standard library for an app to pass App Store review.

The Python source tree contains a patch file [https://github.com/python/cpython/tree/3.14/Mac/Resources/app-store-compliance.patch] that will remove all code that is known to cause issues with the App Store review process. This patch is applied automatically when building for iOS.

7.3.2. Privacy manifests

In April 2025, Apple introduced a requirement for certain third-party libraries to provide a Privacy Manifest [https://developer.apple.com/support/third-party-SDK-requirements]. As a result, if you have a binary module that uses one of the affected libraries, you must provide an .xcprivacy file for that library. OpenSSL is one library affected by this requirement, but there are others.

If you produce a binary module named mymodule.so, and use you the Xcode build script described in step 7 above, you can place a mymodule.xcprivacy file next to mymodule.so, and the privacy manifest will be installed into the required location when the binary module is converted into a framework.

8. 編輯器與 IDE

There are a number of IDEs that support Python programming language. Many editors and IDEs provide syntax highlighting, debugging tools, and PEP 8 [https://peps.python.org/pep-0008/] checks.

8.1. IDLE --- Python 編輯器與 shell

IDLE is Python’s Integrated Development and Learning Environment and is generally bundled with Python installs. If you are on Linux and do not have IDLE installed see Installing IDLE on Linux. For more information see the IDLE docs.

8.2. 其他編輯器與 IDE

Python's community wiki has information submitted by the community on Editors and IDEs. Please go to Python Editors [https://wiki.python.org/moin/PythonEditors] and Integrated Development Environments [https://wiki.python.org/moin/IntegratedDevelopmentEnvironments] for a comprehensive list.

Python 語言參考手冊

這份參考手冊會描述 Python 語言的語法及「核心語意」。它雖然簡潔，但也盡量保持精確並完整。關於非必要的 (non-essential) 內建物件型別、內建函式及模組的語意，則在 Python 標準函式庫 (Standard Library) 中說明。關於此語言的非正式介紹，請參閱 Python 教學。對於 C 或 C++ 程式設計師，還有另外兩個手冊：擴充和嵌入 Python 直譯器以高階的視野說明如何編寫 Python 擴充模組，而 Python/C API 參考手冊則詳細說明 C/C++ 程式設計師可用的介面。

1. 簡介

1.1. 可選實作

1.2. 標示法

2. 詞法分析

2.1. Line structure

2.2. Other tokens

2.3. Names (identifiers and keywords)

2.4. Literals

2.5. String and Bytes literals

2.6. Numeric literals

2.7. Operators and delimiters

3. 資料模型

3.1. 物件、數值和型別

3.2. 標準型別階層

3.3. Special method names

3.4. 協程

4. 執行模型

4.1. Structure of a program

4.2. Naming and binding

4.3. 例外

4.4. Runtime Components

5. 模組引入系統

5.1. importlib

5.2. 套件

5.3. 搜尋

5.4. 載入

5.5. The Path Based Finder

5.6. Replacing the standard import system

5.7. Package Relative Imports

5.8. Special considerations for __main__

5.9. References

6. 運算式

6.1. Arithmetic conversions

6.2. Atoms

6.3. Primaries

6.4. Await expression

6.5. The power operator

6.6. Unary arithmetic and bitwise operations

6.7. Binary arithmetic operations

6.8. Shifting operations

6.9. Binary bitwise operations

6.10. Comparisons

6.11. Boolean operations

6.12. Assignment expressions

6.13. Conditional expressions

6.14. Lambdas

6.15. Expression lists

6.16. Evaluation order

6.17. Operator precedence

7. 簡單陳述式

7.1. Expression statements

7.2. Assignment statements

7.3. assert 陳述式

7.4. pass 陳述式

7.5. del 陳述式

7.6. return 陳述式

7.7. yield 陳述式

7.8. raise 陳述式

7.9. break 陳述式

7.10. continue 陳述式

7.11. import 陳述式

7.12. global 陳述式

7.13. nonlocal 陳述式

7.14. type 陳述式

8. 複合陳述式

8.1. if 陳述式

8.2. while 陳述式

8.3. for 陳述式

8.4. try 陳述式

8.5. with 陳述式

8.6. match 陳述式

8.7. 函式定義

8.8. 類別定義

8.9. 協程

8.10. Type parameter lists

8.11. 註釋

9. 最高層級元件

9.1. 完整的 Python 程式

9.2. 檔案輸入

9.3. 互動式輸入

9.4. 運算式輸入

10. 完整的文法規格書

1. 簡介

這份參考手冊將會描述 Python 的程式語言特性，而非用於教學。

在我想要盡可能精確表達的同時，除了語法和詞法分析部分，我仍選擇使用英語來描述這些特性，而不是透過形式化的規格。如此一來，這份文件對於一般讀者來說將更容易理解，只是某些意思表達會有模糊之處。因此，如果你是來自火星，並想要僅僅藉由這份文件來重新實作 Python，你可能有些時候必須猜測做出判斷——事實上，你很有可能實作出一個不同的語言。另一方面，如果你已經在使用 Python，並且好奇這個語言的某個特定領域的精確規則為何，那麼你一定能在這份手冊裡找到它們。而如果你想要看到關於這語言更形式化的一個定義，也許你可以自告奮勇——或是發明一台複製機器。:-)

在一份語言的參考文件中加入太多實作細節，是很危險的——這些細節將來可能變化，同一個語言的其他實作也可能有不一樣的運作方式。然而，CPython 是一個廣泛使用的 Python 實作（儘管其他可選的實作也在持續得到更多支援），而有時候它的一些特別古怪之處確實值得提及，尤其當那樣的實作作法帶來了額外限制。基於這個原因，手冊內你會發現簡短的實作細節說明散落在各處。

每一個 Python 實作都附帶內建模組和標準模組。它們都被記錄於 Python 標準函式庫 (Standard Library) 文件中。一些內建模組因為和語言定義有深刻的交互影響，之後也將提及。

1.1. 可選實作

儘管已有一個 Python 實作是目前最廣為流傳，仍存在其他種類的實作適合不同需求的族群所使用。

知名的實作如下：

CPython

以 C 語言開發，是 Python 一開始的實作，同時也是維護程度最好的。新的語言功能通常會先在這裡問世。

Jython

基於 Java 所實作的 Python。這個實作可以作為針對 Java 應用程式的腳本語言，或是用它來從 Java 函式庫建立應用程式。它也經常用於撰寫 Java 函式庫的測試。如需更多資訊，請參閱 Jython 網站 [https://www.jython.org/]。

Python for .NET

這個實作實際上使用 CPython 的實作內容，但它是託管式的 .NET 應用程式，也使得 .NET 函式庫可用。它是由 Brian Lloyd 所設計。如需更多資訊，請參閱 Python.NET 首頁 [https://pythonnet.github.io/]。

IronPython

另一個基於 .NET 的 Python 實作選項。不像 Python.NET，這是一個會產出中繼語言 (IL) 的完整 Python 實作，並會將 Python 程式碼直接編譯為 .NET 組件。它由 Jython 的原始設計者 Jim Hugunin 所設計。如需更多資訊，請參閱 IronPython 網站 [https://ironpython.net/]。

PyPy

一個完全透過 Python 來撰寫的 Python 實作。它有一些其他實作所沒有的進階特性，像是它支援無堆疊 Python 以及採用即時編譯器。額外資訊可參閱 PyPy 專案網站 [https://pypy.org/]。

上述每一個實作都和這份手冊裡所描述的 Python 語言有些許不同，可能需要特定的、在標準 Python 文件涵蓋內容以外的資訊才能掌握。如果在使用它們時有需要瞭解更多，請參閱特定實作的相關文件。

1.2. 標示法

為了描述詞法分析和語法，我使用了混合 EBNF [https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form] 和 PEG [https://en.wikipedia.org/wiki/Parsing_expression_grammar] 的文法標記系統。例如：

name:   letter (letter | digit | "_")*
letter: "a"..."z" | "A"..."Z"
digit:  "0"..."9"

在這個例子裡，第一行說明 name 是由一個 letter 接續零或多個 letter、digit 或底線所組成。而 letter 則是 'a' 到 'z'、A 到 Z 之中任一個單一字元；digit 是 0 到 9 之中的單一字元。

每一條規則的開頭即規則名稱（用來識別被定義的規則），接著一個分號 :。分號右側是由下列語法元素所構成的規則定義 ：

name：表示另一條規則的名稱。只要可行，它也會是一個連到規則定義的連結。

TOKEN：大寫的名稱代表的是 token。就這裡文法定義的目的而言，token 和規則的意義是相同的。

"text"、'text'：單引號或雙引號內的文字必須完全相符，不含外面的引號。依據 text 的意義，會決定使用何種引號 ：

'if'：單引號內的文字為 關鍵字。

"case"：雙引號內的文字為 軟關鍵字。

'@'：單引號內的非字母（非 letter）符號為 OP token，也就是 分隔符號 或 運算子。

e1 e2：僅由空白所開的多個項目代表一個序列。這裡，e1 之後必須以 e2 接續。

e1 | e2：垂直槓符號用來隔開可匹配的項目。它代表 PEG 的「有序選擇」——如果 e1 已匹配，那麼 e2 便不考慮。在傳統的 PEG 文法裡，使用的是斜線 / 而非垂直槓。如需更多背景細節，可參考 PEP 617 [https://peps.python.org/pep-0617/]。

e*：星號表示星號前的項目重複零次或多次。

e+：同樣方式，加號表示重複一次或多次。

[e]：以方括號包圍的元素意謂零次或一次。換句話說，方括號裡的元素為選擇性的。

e?：問號的用途和方括號一樣，表示問號前的項目是選擇性的。

(e)：括號用於分組。

以下的表示法僅會用於詞法定義。

"a"..."z"：兩個字面值字元由三個點隔開，表示在此界定範圍內（含）任一個 ASCII 字元皆合文法。

<...>：角括號內的文字片語是對匹配符號（例如，<除了 "\" 以外的任何 ASCII 字元>）的非正式說明，或是在附近段落有解釋的縮寫（例如 <Lu>）。

有些定義會採用預查作法，也就是指定位置的元素必須（或必須不）匹配，但不消耗任何輸入：

&e：正向預查，也就是 e 必須匹配

!e：負向預查，也就是 e 必須不匹配

一元運算子（*、+、?）跟元素的繫結關係最緊密；垂直槓 (|) 的則最鬆散。

空格的用途只在於隔開 token。

通常而言，規則長度都在一行以內，但太長的規則也可以換行表示：

literal: stringliteral | bytesliteral
         | integer | floatnumber | imagnumber

或者，規則可以呈現為第一行以分號結束，而每一種可匹配選項皆在新一行以垂直槓開頭表示。例如：

literal:
   | stringliteral
   | bytesliteral
   | integer
   | floatnumber
   | imagnumber

這不代表一開始有一個空白匹配選項。

1.2.1. 詞法和語法定義

詞法 (lexical) 和語法 (syntactic) 分析是有一些差異的：lexical analyzer 處理的對象是輸入來源的各個字元，而剖析器 （語法分析器）處理的則是詞法分析產生的 tokens 串流。然而在某些時候，這兩個階段的確切分界會是 CPython 實作細節的問題。

實務上，這兩個的差異在於：在詞法定義裡，任何空格都是有影響的。詞法分析器捨棄了那些無法轉換成 token（例如 token.INDENT 或 NEWLINE）的空白。語法定義才接著處理這些 tokens，而非來源字元。

這份手冊裡不管是為了定義還是風格表現，都使用了同樣的 BNF 文法。在下一個章節（詞法分析）裡所有 BNF 的使用都是詞法定義；在那之後的章節裡則是語法定義。

2. 詞法分析

A Python program is read by a parser. Input to the parser is a stream of tokens, generated by the lexical analyzer (also known as the tokenizer). This chapter describes how the lexical analyzer produces these tokens.

The lexical analyzer determines the program text's encoding (UTF-8 by default), and decodes the text into source characters. If the text cannot be decoded, a SyntaxError is raised.

Next, the lexical analyzer uses the source characters to generate a stream of tokens. The type of a generated token generally depends on the next source character to be processed. Similarly, other special behavior of the analyzer depends on the first source character that hasn't yet been processed. The following table gives a quick summary of these source characters, with links to sections that contain more information.

字元

Next token (or other relevant documentation)

space（空白）

tab（定位字元）

formfeed

空白字元

CR, LF

New line

Indentation

反斜線 (\)

Explicit line joining

(Also significant in string escape sequences)

hash (#)

Comment

quote (', ")

String literal

ASCII letter (a-z, A-Z)

非 ASCII 字元

Name

Prefixed string or bytes literal

底線 (_)

Name

(Can also be part of numeric literals)

number (0-9)

Numeric literal

dot (.)

Numeric literal

Operator

question mark (?)

dollar ($)

backquote (​`​)

控制字元

Error (outside string literals and comments)

other printing character

Operator or delimiter

end of file

End marker

2.1. Line structure

A Python program is divided into a number of logical lines.

2.1.1. Logical lines

The end of a logical line is represented by the token NEWLINE. Statements cannot cross logical line boundaries except where NEWLINE is allowed by the syntax (e.g., between statements in compound statements). A logical line is constructed from one or more physical lines by following the explicit or implicit line joining rules.

2.1.2. Physical lines

A physical line is a sequence of characters terminated by one the following end-of-line sequences:

the Unix form using ASCII LF (linefeed),

the Windows form using the ASCII sequence CR LF (return followed by linefeed),

the 'Classic Mac OS [https://en.wikipedia.org/wiki/Classic_Mac_OS]' form using the ASCII CR (return) character.

Regardless of platform, each of these sequences is replaced by a single ASCII LF (linefeed) character. (This is done even inside string literals.) Each line can use any of the sequences; they do not need to be consistent within a file.

The end of input also serves as an implicit terminator for the final physical line.

Formally:

newline: <ASCII LF> | <ASCII CR> <ASCII LF> | <ASCII CR>

2.1.3. Comments

A comment starts with a hash character (#) that is not part of a string literal, and ends at the end of the physical line. A comment signifies the end of the logical line unless the implicit line joining rules are invoked. Comments are ignored by the syntax.

2.1.4. Encoding declarations

If a comment in the first or second line of the Python script matches the regular expression coding[=:]\s*([-\w.]+), this comment is processed as an encoding declaration; the first group of this expression names the encoding of the source code file. The encoding declaration must appear on a line of its own. If it is the second line, the first line must also be a comment-only line. The recommended forms of an encoding expression are

# -*- coding: <encoding-name> -*-

which is recognized also by GNU Emacs, and

# vim:fileencoding=<encoding-name>

which is recognized by Bram Moolenaar's VIM.

If no encoding declaration is found, the default encoding is UTF-8. If the implicit or explicit encoding of a file is UTF-8, an initial UTF-8 byte-order mark (b'\xef\xbb\xbf') is ignored rather than being a syntax error.

If an encoding is declared, the encoding name must be recognized by Python (see 標準編碼). The encoding is used for all lexical analysis, including string literals, comments and identifiers.

All lexical analysis, including string literals, comments and identifiers, works on Unicode text decoded using the source encoding. Any Unicode code point, except the NUL control character, can appear in Python source.

source_character:  <any Unicode code point, except NUL>

2.1.5. Explicit line joining

Two or more physical lines may be joined into logical lines using backslash characters (\), as follows: when a physical line ends in a backslash that is not part of a string literal or comment, it is joined with the following forming a single logical line, deleting the backslash and the following end-of-line character. For example:

if 1900 < year < 2100 and 1 <= month <= 12 \
   and 1 <= day <= 31 and 0 <= hour < 24 \
   and 0 <= minute < 60 and 0 <= second < 60:   # 看起來像個有效日期
        return 1

A line ending in a backslash cannot carry a comment. A backslash does not continue a comment. A backslash does not continue a token except for string literals (i.e., tokens other than string literals cannot be split across physical lines using a backslash). A backslash is illegal elsewhere on a line outside a string literal.

2.1.6. Implicit line joining

Expressions in parentheses, square brackets or curly braces can be split over more than one physical line without using backslashes. For example:

month_names = ['Januari', 'Februari', 'Maart',      # 這些是
               'April',   'Mei',      'Juni',       # 荷蘭文的
               'Juli',    'Augustus', 'September',  # 一年之中
               'Oktober', 'November', 'December']   # 月份名稱

Implicitly continued lines can carry comments. The indentation of the continuation lines is not important. Blank continuation lines are allowed. There is no NEWLINE token between implicit continuation lines. Implicitly continued lines can also occur within triple-quoted strings (see below); in that case they cannot carry comments.

2.1.7. Blank lines

A logical line that contains only spaces, tabs, formfeeds and possibly a comment, is ignored (i.e., no NEWLINE token is generated). During interactive input of statements, handling of a blank line may differ depending on the implementation of the read-eval-print loop. In the standard interactive interpreter, an entirely blank logical line (that is, one containing not even whitespace or a comment) terminates a multi-line statement.

2.1.8. Indentation

Leading whitespace (spaces and tabs) at the beginning of a logical line is used to compute the indentation level of the line, which in turn is used to determine the grouping of statements.

Tabs are replaced (from left to right) by one to eight spaces such that the total number of characters up to and including the replacement is a multiple of eight (this is intended to be the same rule as used by Unix). The total number of spaces preceding the first non-blank character then determines the line's indentation. Indentation cannot be split over multiple physical lines using backslashes; the whitespace up to the first backslash determines the indentation.

Indentation is rejected as inconsistent if a source file mixes tabs and spaces in a way that makes the meaning dependent on the worth of a tab in spaces; a TabError is raised in that case.

Cross-platform compatibility note: because of the nature of text editors on non-UNIX platforms, it is unwise to use a mixture of spaces and tabs for the indentation in a single source file. It should also be noted that different platforms may explicitly limit the maximum indentation level.

A formfeed character may be present at the start of the line; it will be ignored for the indentation calculations above. Formfeed characters occurring elsewhere in the leading whitespace have an undefined effect (for instance, they may reset the space count to zero).

The indentation levels of consecutive lines are used to generate INDENT and DEDENT tokens, using a stack, as follows.

Before the first line of the file is read, a single zero is pushed on the stack; this will never be popped off again. The numbers pushed on the stack will always be strictly increasing from bottom to top. At the beginning of each logical line, the line's indentation level is compared to the top of the stack. If it is equal, nothing happens. If it is larger, it is pushed on the stack, and one INDENT token is generated. If it is smaller, it must be one of the numbers occurring on the stack; all numbers on the stack that are larger are popped off, and for each number popped off a DEDENT token is generated. At the end of the file, a DEDENT token is generated for each number remaining on the stack that is larger than zero.

Here is an example of a correctly (though confusingly) indented piece of Python code:

def perm(l):
        # Compute the list of all permutations of l
    if len(l) <= 1:
                  return [l]
    r = []
    for i in range(len(l)):
             s = l[:i] + l[i+1:]
             p = perm(s)
             for x in p:
              r.append(l[i:i+1] + x)
    return r

The following example shows various indentation errors:

 def perm(l):                       # error: first line indented
for i in range(len(l)):             # error: not indented
    s = l[:i] + l[i+1:]
        p = perm(l[:i] + l[i+1:])   # error: unexpected indent
        for x in p:
                r.append(l[i:i+1] + x)
            return r                # error: inconsistent dedent

(Actually, the first three errors are detected by the parser; only the last error is found by the lexical analyzer --- the indentation of return r does not match a level popped off the stack.)

2.1.9. Whitespace between tokens

Except at the beginning of a logical line or in string literals, the whitespace characters space, tab and formfeed can be used interchangeably to separate tokens:

whitespace:  ' ' | tab | formfeed

Whitespace is needed between two tokens only if their concatenation could otherwise be interpreted as a different token. For example, ab is one token, but a b is two tokens. However, +a and + a both produce two tokens, + and a, as +a is not a valid token.

2.1.10. End marker

At the end of non-interactive input, the lexical analyzer generates an ENDMARKER token.

2.2. Other tokens

Besides NEWLINE, INDENT and DEDENT, the following categories of tokens exist: identifiers and keywords (NAME), literals (such as NUMBER and STRING), and other symbols (operators and delimiters, OP). Whitespace characters (other than logical line terminators, discussed earlier) are not tokens, but serve to delimit tokens. Where ambiguity exists, a token comprises the longest possible string that forms a legal token, when read from left to right.

2.3. Names (identifiers and keywords)

NAME tokens represent identifiers, keywords, and soft keywords.

Names are composed of the following characters:

uppercase and lowercase letters (A-Z and a-z),

底線 (_)，

digits (0 through 9), which cannot appear as the first character, and

non-ASCII characters. Valid names may only contain "letter-like" and "digit-like" characters; see 名稱中的非 ASCII 字元 for details.

Names must contain at least one character, but have no upper length limit. Case is significant.

Formally, names are described by the following lexical definitions:

NAME:          name_start name_continue*
name_start:    "a"..."z" | "A"..."Z" | "_" | <non-ASCII character>
name_continue: name_start | "0"..."9"
identifier:    <NAME, except keywords>

Note that not all names matched by this grammar are valid; see 名稱中的非 ASCII 字元 for details.

2.3.1. 關鍵字

The following names are used as reserved words, or keywords of the language, and cannot be used as ordinary identifiers. They must be spelled exactly as written here:

False      await      else       import     pass
None       break      except     in         raise
True       class      finally    is         return
and        continue   for        lambda     try
as         def        from       nonlocal   while
assert     del        global     not        with
async      elif       if         or         yield

2.3.2. 軟關鍵字

在 3.10 版被加入.

Some names are only reserved under specific contexts. These are known as soft keywords:

match, case, and _, when used in the match statement.

type, when used in the type statement.

These syntactically act as keywords in their specific contexts, but this distinction is done at the parser level, not when tokenizing.

As soft keywords, their use in the grammar is possible while still preserving compatibility with existing code that uses these names as identifier names.

在 3.12 版的變更: type 現在是軟關鍵字。

2.3.3. Reserved classes of identifiers

Certain classes of identifiers (besides keywords) have special meanings. These classes are identified by the patterns of leading and trailing underscore characters:

_*

Not imported by from module import *.

_

In a case pattern within a match statement, _ is a soft keyword that denotes a wildcard.

Separately, the interactive interpreter makes the result of the last evaluation available in the variable _. (It is stored in the builtins module, alongside built-in functions like print.)

Elsewhere, _ is a regular identifier. It is often used to name "special" items, but it is not special to Python itself.

備註

The name _ is often used in conjunction with internationalization; refer to the documentation for the gettext module for more information on this convention.

It is also commonly used for unused variables.

__*__

System-defined names, informally known as "dunder" names. These names are defined by the interpreter and its implementation (including the standard library). Current system names are discussed in the Special method names section and elsewhere. More will likely be defined in future versions of Python. Any use of __*__ names, in any context, that does not follow explicitly documented use, is subject to breakage without warning.

__*

Class-private names. Names in this category, when used within the context of a class definition, are re-written to use a mangled form to help avoid name clashes between "private" attributes of base and derived classes. See section Identifiers (Names).

2.3.4. 名稱中的非 ASCII 字元

Names that contain non-ASCII characters need additional normalization and validation beyond the rules and grammar explained above. For example, ř_1, 蛇, or साँप are valid names, but r〰2, €, or 🐍 are not.

This section explains the exact rules.

All names are converted into the normalization form [https://www.unicode.org/reports/tr15/#Norm_Forms] NFKC while parsing. This means that, for example, some typographic variants of characters are converted to their "basic" form. For example, ﬁⁿₐˡᵢᶻₐᵗᵢᵒₙ normalizes to finalization, so Python treats them as the same name:

>>> ﬁⁿₐˡᵢᶻₐᵗᵢᵒₙ = 3
>>> finalization
3

備註

Normalization is done at the lexical level only. Run-time functions that take names as strings generally do not normalize their arguments. For example, the variable defined above is accessible at run time in the globals() dictionary as globals()["finalization"] but not globals()["ﬁⁿₐˡᵢᶻₐᵗᵢᵒₙ"].

Similarly to how ASCII-only names must contain only letters, digits and the underscore, and cannot start with a digit, a valid name must start with a character in the "letter-like" set xid_start, and the remaining characters must be in the "letter- and digit-like" set xid_continue.

These sets based on the XID_Start and XID_Continue sets as defined by the Unicode standard annex UAX-31 [https://www.unicode.org/reports/tr31/]. Python's xid_start additionally includes the underscore (_). Note that Python does not necessarily conform to UAX-31 [https://www.unicode.org/reports/tr31/].

A non-normative listing of characters in the XID_Start and XID_Continue sets as defined by Unicode is available in the DerivedCoreProperties.txt [https://www.unicode.org/Public/16.0.0/ucd/DerivedCoreProperties.txt] file in the Unicode Character Database. For reference, the construction rules for the xid_* sets are given below.

The set id_start is defined as the union of:

Unicode category <Lu> - uppercase letters (includes A to Z)

Unicode category <Ll> - lowercase letters (includes a to z)

Unicode category <Lt> - titlecase letters

Unicode category <Lm> - modifier letters

Unicode category <Lo> - other letters

Unicode category <Nl> - letter numbers

{"_"} - 底線

<Other_ID_Start> - an explicit set of characters in PropList.txt [https://www.unicode.org/Public/16.0.0/ucd/PropList.txt] to support backwards compatibility

The set xid_start then closes this set under NFKC normalization, by removing all characters whose normalization is not of the form id_start id_continue*.

The set id_continue is defined as the union of:

id_start (see above)

Unicode category <Nd> - decimal numbers (includes 0 to 9)

Unicode category <Pc> - connector punctuations

Unicode category <Mn> - nonspacing marks

Unicode category <Mc> - spacing combining marks

<Other_ID_Continue> - another explicit set of characters in PropList.txt [https://www.unicode.org/Public/16.0.0/ucd/PropList.txt] to support backwards compatibility

Again, xid_continue closes this set under NFKC normalization.

Unicode categories use the version of the Unicode Character Database as included in the unicodedata module.

也參考

PEP 3131 [https://peps.python.org/pep-3131/] -- Supporting Non-ASCII Identifiers

PEP 672 [https://peps.python.org/pep-0672/] -- Unicode-related Security Considerations for Python

2.4. Literals

Literals are notations for constant values of some built-in types.

In terms of lexical analysis, Python has string, bytes and numeric literals.

Other "literals" are lexically denoted using keywords (None, True, False) and the special ellipsis token (...).

2.5. String and Bytes literals

String literals are text enclosed in single quotes (') or double quotes ("). For example:

"spam"
'eggs'

The quote used to start the literal also terminates it, so a string literal can only contain the other quote (except with escape sequences, see below). For example:

'Say "Hello", please.'
"Don't do that!"

Except for this limitation, the choice of quote character (' or ") does not affect how the literal is parsed.

Inside a string literal, the backslash (\) character introduces an escape sequence, which has special meaning depending on the character after the backslash. For example, \" denotes the double quote character, and does not end the string:

>>> print("Say \"Hello\" to everyone!")
Say "Hello" to everyone!

See escape sequences below for a full list of such sequences, and more details.

2.5.1. 三引號字串

Strings can also be enclosed in matching groups of three single or double quotes. These are generally referred to as triple-quoted strings:

"""這是一個三引號字串。"""

In triple-quoted literals, unescaped quotes are allowed (and are retained), except that three unescaped quotes in a row terminate the literal, if they are of the same kind (' or ") used at the start:

"""這個字串裡面有 "引號"。"""

Unescaped newlines are also allowed and retained:

'''This triple-quoted string
continues on the next line.'''

2.5.2. String prefixes

String literals can have an optional prefix that influences how the content of the literal is parsed, for example:

b"data"
f'{result=}'

The allowed prefixes are:

b: Bytes literal

r: Raw string

f: Formatted string literal ("f-string")

t: Template string literal ("t-string")

u: No effect (allowed for backwards compatibility)

See the linked sections for details on each type.

Prefixes are case-insensitive (for example, 'B' works the same as 'b'). The 'r' prefix can be combined with 'f', 't' or 'b', so 'fr', 'rf', 'tr', 'rt', 'br', and 'rb' are also valid prefixes.

在 3.3 版被加入: The 'rb' prefix of raw bytes literals has been added as a synonym of 'br'.

Support for the unicode legacy literal (u'value') was reintroduced to simplify the maintenance of dual Python 2.x and 3.x codebases. See PEP 414 [https://peps.python.org/pep-0414/] for more information.

2.5.3. Formal grammar

String literals, except "f-strings" and "t-strings", are described by the following lexical definitions.

These definitions use negative lookaheads (!) to indicate that an ending quote ends the literal.

STRING:          [stringprefix] (stringcontent)
stringprefix:    <("r" | "u" | "b" | "br" | "rb"), case-insensitive>
stringcontent:
   | "'''" ( !"'''" longstringitem)* "'''"
   | '"""' ( !'"""' longstringitem)* '"""'
   | "'" ( !"'" stringitem)* "'"
   | '"' ( !'"' stringitem)* '"'
stringitem:      stringchar | stringescapeseq
stringchar:      <any source_character, except backslash and newline>
longstringitem:  stringitem | newline
stringescapeseq: "\" <any source_character>

Note that as in all lexical definitions, whitespace is significant. In particular, the prefix (if any) must be immediately followed by the starting quote.

2.5.4. 跳脫序列

Unless an 'r' or 'R' prefix is present, escape sequences in string and bytes literals are interpreted according to rules similar to those used by Standard C. The recognized escape sequences are:

Escape Sequence

含義

\<newline>

Ignored end of line

\\

Backslash

\'

Single quote

\"

Double quote

\a

ASCII Bell (BEL)

\b

ASCII Backspace (BS)

\f

ASCII Formfeed (FF)

\n

ASCII Linefeed (LF)

\r

ASCII Carriage Return (CR)

\t

ASCII Horizontal Tab (TAB)

\v

ASCII Vertical Tab (VT)

\ooo

八進位字元

\xhh

十六進位字元

\N{name}

Named Unicode character

\uxxxx

Hexadecimal Unicode character

\Uxxxxxxxx

Hexadecimal Unicode character

2.5.4.1. Ignored end of line

A backslash can be added at the end of a line to ignore the newline:

>>> 'This string will not include \
... backslashes or newline characters.'
'This string will not include backslashes or newline characters.'

The same result can be achieved using triple-quoted strings, or parentheses and string literal concatenation.

2.5.4.2. 跳脫字元

To include a backslash in a non-raw Python string literal, it must be doubled. The \\ escape sequence denotes a single backslash character:

>>> print('C:\\Program Files')
C:\Program Files

Similarly, the \' and \" sequences denote the single and double quote character, respectively:

>>> print('\' and \"')
' and "

2.5.4.3. 八進位字元

The sequence \ooo denotes a character with the octal (base 8) value ooo:

>>> '\120'
'P'

Up to three octal digits (0 through 7) are accepted.

In a bytes literal, character means a byte with the given value. In a string literal, it means a Unicode character with the given value.

在 3.11 版的變更: Octal escapes with value larger than 0o377 (255) produce a DeprecationWarning.

在 3.12 版的變更: Octal escapes with value larger than 0o377 (255) produce a SyntaxWarning. In a future Python version they will raise a SyntaxError.

2.5.4.4. 十六進位字元

The sequence \xhh denotes a character with the hex (base 16) value hh:

>>> '\x50'
'P'

與標準 C 不同，這裡需要剛好兩個十六進位數字。

In a bytes literal, character means a byte with the given value. In a string literal, it means a Unicode character with the given value.

2.5.4.5. Named Unicode character

The sequence \N{name} denotes a Unicode character with the given name:

>>> '\N{LATIN CAPITAL LETTER P}'
'P'
>>> '\N{SNAKE}'
'🐍'

This sequence cannot appear in bytes literals.

在 3.3 版的變更: 已新增對名稱別名 (name alias) [https://www.unicode.org/Public/16.0.0/ucd/NameAliases.txt]的支援。

2.5.4.6. 十六進位 Unicode 字元

These sequences \uxxxx and \Uxxxxxxxx denote the Unicode character with the given hex (base 16) value. Exactly four digits are required for \u; exactly eight digits are required for \U. The latter can encode any Unicode character.

>>> '\u1234'
'ሴ'
>>> '\U0001f40d'
'🐍'

These sequences cannot appear in bytes literals.

2.5.4.7. 無法辨識的跳脫序列

Unlike in Standard C, all unrecognized escape sequences are left in the string unchanged, that is, the backslash is left in the result:

>>> print('\q')
\q
>>> list('\q')
['\\', 'q']

Note that for bytes literals, the escape sequences only recognized in string literals (\N..., \u..., \U...) fall into the category of unrecognized escapes.

在 3.6 版的變更: Unrecognized escape sequences produce a DeprecationWarning.

在 3.12 版的變更: Unrecognized escape sequences produce a SyntaxWarning. In a future Python version they will raise a SyntaxError.

2.5.5. 位元組常數

Bytes literals are always prefixed with 'b' or 'B'; they produce an instance of the bytes type instead of the str type. They may only contain ASCII characters; bytes with a numeric value of 128 or greater must be expressed with escape sequences (typically 十六進位字元 or 八進位字元):

>>> b'\x89PNG\r\n\x1a\n'
b'\x89PNG\r\n\x1a\n'
>>> list(b'\x89PNG\r\n\x1a\n')
[137, 80, 78, 71, 13, 10, 26, 10]

Similarly, a zero byte must be expressed using an escape sequence (typically \0 or \x00).

2.5.6. 原始字串常數

Both string and bytes literals may optionally be prefixed with a letter 'r' or 'R'; such constructs are called raw string literals and raw bytes literals respectively and treat backslashes as literal characters. As a result, in raw string literals, escape sequences are not treated specially:

>>> r'\d{4}-\d{2}-\d{2}'
'\\d{4}-\\d{2}-\\d{2}'

Even in a raw literal, quotes can be escaped with a backslash, but the backslash remains in the result; for example, r"\"" is a valid string literal consisting of two characters: a backslash and a double quote; r"\" is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, a raw literal cannot end in a single backslash (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the literal, not as a line continuation.

2.5.7. f-string（f 字串）

在 3.6 版被加入.

在 3.7 版的變更: The await and async for can be used in expressions within f-strings.

在 3.8 版的變更: Added the debug specifier (=)

在 3.12 版的變更: Many restrictions on expressions within f-strings have been removed. Notably, nested strings, comments, and backslashes are now permitted.

A formatted string literal or f-string is a string literal that is prefixed with 'f' or 'F'. Unlike other string literals, f-strings do not have a constant value. They may contain replacement fields delimited by curly braces {}. Replacement fields contain expressions which are evaluated at run time. For example:

>>> who = 'nobody'
>>> nationality = 'Spanish'
>>> f'{who.title()} expects the {nationality} Inquisition!'
'Nobody expects the Spanish Inquisition!'

Any doubled curly braces ({{ or }}) outside replacement fields are replaced with the corresponding single curly brace:

>>> print(f'{{...}}')
{...}

Other characters outside replacement fields are treated like in ordinary string literals. This means that escape sequences are decoded (except when a literal is also marked as a raw string), and newlines are possible in triple-quoted f-strings:

>>> name = 'Galahad'
>>> favorite_color = 'blue'
>>> print(f'{name}:\t{favorite_color}')
Galahad:       blue
>>> print(rf"C:\Users\{name}")
C:\Users\Galahad
>>> print(f'''Three shall be the number of the counting
... and the number of the counting shall be three.''')
Three shall be the number of the counting
and the number of the counting shall be three.

Expressions in formatted string literals are treated like regular Python expressions. Each expression is evaluated in the context where the formatted string literal appears, in order from left to right. An empty expression is not allowed, and both lambda and assignment expressions := must be surrounded by explicit parentheses:

>>> f'{(half := 1/2)}, {half * 42}'
'0.5, 21.0'

Reusing the outer f-string quoting type inside a replacement field is permitted:

>>> a = dict(x=2)
>>> f"abc {a["x"]} def"
'abc 2 def'

Backslashes are also allowed in replacement fields and are evaluated the same way as in any other context:

>>> a = ["a", "b", "c"]
>>> print(f"List a contains:\n{"\n".join(a)}")
List a contains:
a
b
c

It is possible to nest f-strings:

>>> name = 'world'
>>> f'Repeated:{f' hello {name}' * 3}'
'Repeated: hello world hello world hello world'

Portable Python programs should not use more than 5 levels of nesting.

CPython 實作細節： CPython does not limit nesting of f-strings.

Replacement expressions can contain newlines in both single-quoted and triple-quoted f-strings and they can contain comments. Everything that comes after a # inside a replacement field is a comment (even closing braces and quotes). This means that replacement fields with comments must be closed in a different line:

>>> a = 2
>>> f"abc{a  # This comment  }"  continues until the end of the line
...       + 3}"
'abc5'

After the expression, replacement fields may optionally contain:

a debug specifier -- an equal sign (=), optionally surrounded by whitespace on one or both sides;

a conversion specifier -- !s, !r or !a; and/or

a format specifier prefixed with a colon (:).

See the Standard Library section on f-strings for details on how these fields are evaluated.

As that section explains, format specifiers are passed as the second argument to the format() function to format a replacement field value. For example, they can be used to specify a field width and padding characters using the Format Specification Mini-Language:

>>> number = 14.3
>>> f'{number:20.7f}'
'          14.3000000'

Top-level format specifiers may include nested replacement fields:

>>> field_size = 20
>>> precision = 7
>>> f'{number:{field_size}.{precision}f}'
'          14.3000000'

These nested fields may include their own conversion fields and format specifiers:

>>> number = 3
>>> f'{number:{field_size}}'
'                   3'
>>> f'{number:{field_size:05}}'
'00000000000000000003'

However, these nested fields may not include more deeply nested replacement fields.

Formatted string literals cannot be used as docstrings, even if they do not include expressions:

>>> def foo():
...     f"Not a docstring"
...
>>> print(foo.__doc__)
None

也參考

PEP 498 [https://peps.python.org/pep-0498/] -- Literal String Interpolation

PEP 701 [https://peps.python.org/pep-0701/] -- Syntactic formalization of f-strings

str.format(), which uses a related format string mechanism.

2.5.8. t-string（t 字串）

在 3.14 版被加入.

A template string literal or t-string is a string literal that is prefixed with 't' or 'T'. These strings follow the same syntax rules as formatted string literals. For differences in evaluation rules, see the Standard Library section on t-strings

2.5.9. Formal grammar for f-strings

F-strings are handled partly by the lexical analyzer, which produces the tokens FSTRING_START, FSTRING_MIDDLE and FSTRING_END, and partly by the parser, which handles expressions in the replacement field. The exact way the work is split is a CPython implementation detail.

Correspondingly, the f-string grammar is a mix of lexical and syntactic definitions.

Whitespace is significant in these situations:

There may be no whitespace in FSTRING_START (between the prefix and quote).

Whitespace in FSTRING_MIDDLE is part of the literal string contents.

In fstring_replacement_field, if f_debug_specifier is present, all whitespace after the opening brace until the f_debug_specifier, as well as whitespace immediately following f_debug_specifier, is retained as part of the expression.

CPython 實作細節： The expression is not handled in the tokenization phase; it is retrieved from the source code using locations of the { token and the token after =.

The FSTRING_MIDDLE definition uses negative lookaheads (!) to indicate special characters (backslash, newline, {, }) and sequences (f_quote).

fstring:    FSTRING_START fstring_middle* FSTRING_END

FSTRING_START:      fstringprefix ("'" | '"' | "'''" | '"""')
FSTRING_END:        f_quote
fstringprefix:      <("f" | "fr" | "rf"), case-insensitive>
f_debug_specifier:  '='
f_quote:            <the quote character(s) used in FSTRING_START>

fstring_middle:
   | fstring_replacement_field
   | FSTRING_MIDDLE
FSTRING_MIDDLE:
   | (!"\" !newline !'{' !'}' !f_quote) source_character
   | stringescapeseq
   | "{{"
   | "}}"
   | <newline, in triple-quoted f-strings only>
fstring_replacement_field:
   | '{' f_expression [f_debug_specifier] [fstring_conversion]
         [fstring_full_format_spec] '}'
fstring_conversion:
   | "!" ("s" | "r" | "a")
fstring_full_format_spec:
   | ':' fstring_format_spec*
fstring_format_spec:
   | FSTRING_MIDDLE
   | fstring_replacement_field
f_expression:
   | ','.(conditional_expression | "*" or_expr)+ [","]
   | yield_expression

備註

In the above grammar snippet, the f_quote and FSTRING_MIDDLE rules are context-sensitive -- they depend on the contents of FSTRING_START of the nearest enclosing fstring.

Constructing a more traditional formal grammar from this template is left as an exercise for the reader.

The grammar for t-strings is identical to the one for f-strings, with t instead of f at the beginning of rule and token names and in the prefix.

tstring:    TSTRING_START tstring_middle* TSTRING_END

<rest of the t-string grammar is omitted; see above>

2.6. Numeric literals

NUMBER tokens represent numeric literals, of which there are three types: integers, floating-point numbers, and imaginary numbers.

NUMBER: integer | floatnumber | imagnumber

The numeric value of a numeric literal is the same as if it were passed as a string to the int, float or complex class constructor, respectively. Note that not all valid inputs for those constructors are also valid literals.

Numeric literals do not include a sign; a phrase like -1 is actually an expression composed of the unary operator '-' and the literal 1.

2.6.1. Integer literals

Integer literals denote whole numbers. For example:

7
3
2147483647

There is no limit for the length of integer literals apart from what can be stored in available memory:

7922816251426433759354395033679228162514264337593543950336

Underscores can be used to group digits for enhanced readability, and are ignored for determining the numeric value of the literal. For example, the following literals are equivalent:

100_000_000_000
100000000000
1_00_00_00_00_000

Underscores can only occur between digits. For example, _123, 321_, and 123__321 are not valid literals.

Integers can be specified in binary (base 2), octal (base 8), or hexadecimal (base 16) using the prefixes 0b, 0o and 0x, respectively. Hexadecimal digits 10 through 15 are represented by letters A-F, case-insensitive. For example:

0b100110111
0b_1110_0101
0o177
0o377
0xdeadbeef
0xDead_Beef

An underscore can follow the base specifier. For example, 0x_1f is a valid literal, but 0_x1f and 0x__1f are not.

Leading zeros in a non-zero decimal number are not allowed. For example, 0123 is not a valid literal. This is for disambiguation with C-style octal literals, which Python used before version 3.0.

Formally, integer literals are described by the following lexical definitions:

integer:      decinteger | bininteger | octinteger | hexinteger | zerointeger
decinteger:   nonzerodigit (["_"] digit)*
bininteger:   "0" ("b" | "B") (["_"] bindigit)+
octinteger:   "0" ("o" | "O") (["_"] octdigit)+
hexinteger:   "0" ("x" | "X") (["_"] hexdigit)+
zerointeger:  "0"+ (["_"] "0")*
nonzerodigit: "1"..."9"
digit:        "0"..."9"
bindigit:     "0" | "1"
octdigit:     "0"..."7"
hexdigit:     digit | "a"..."f" | "A"..."F"

在 3.6 版的變更: Underscores are now allowed for grouping purposes in literals.

2.6.2. 浮點數常數 (Floating-point literals)

Floating-point (float) literals, such as 3.14 or 1.5, denote approximations of real numbers.

They consist of integer and fraction parts, each composed of decimal digits. The parts are separated by a decimal point, .:

2.71828
4.0

Unlike in integer literals, leading zeros are allowed. For example, 077.010 is legal, and denotes the same number as 77.01.

As in integer literals, single underscores may occur between digits to help readability:

96_485.332_123
3.14_15_93

Either of these parts, but not both, can be empty. For example:

10.  # （相當於 10.0）
.001  # （相當於 0.001）

Optionally, the integer and fraction may be followed by an exponent: the letter e or E, followed by an optional sign, + or -, and a number in the same format as the integer and fraction parts. The e or E represents "times ten raised to the power of":

1.0e3  # (represents 1.0×10³, or 1000.0)
1.166e-5  # (represents 1.166×10⁻⁵, or 0.00001166)
6.02214076e+23  # (represents 6.02214076×10²³, or 602214076000000000000000.)

In floats with only integer and exponent parts, the decimal point may be omitted:

1e3  # （相當於 1.e3 和 1.0e3）
0e0  # （相當於 0.）

Formally, floating-point literals are described by the following lexical definitions:

floatnumber:
   | digitpart "." [digitpart] [exponent]
   | "." digitpart [exponent]
   | digitpart exponent
digitpart: digit (["_"] digit)*
exponent:  ("e" | "E") ["+" | "-"] digitpart

在 3.6 版的變更: Underscores are now allowed for grouping purposes in literals.

2.6.3. Imaginary literals

Python has complex number objects, but no complex literals. Instead, imaginary literals denote complex numbers with a zero real part.

For example, in math, the complex number 3+4.2i is written as the real number 3 added to the imaginary number 4.2i. Python uses a similar syntax, except the imaginary unit is written as j rather than i:

3+4.2j

This is an expression composed of the integer literal 3, the operator '+', and the imaginary literal 4.2j. Since these are three separate tokens, whitespace is allowed between them:

3 + 4.2j

No whitespace is allowed within each token. In particular, the j suffix, may not be separated from the number before it.

The number before the j has the same syntax as a floating-point literal. Thus, the following are valid imaginary literals:

4.2j
3.14j
10.j
.001j
1e100j
3.14e-10j
3.14_15_93j

Unlike in a floating-point literal the decimal point can be omitted if the imaginary number only has an integer part. The number is still evaluated as a floating-point number, not an integer:

10j
0j
1000000000000000000000000j   # 相當於 1e+24j

The j suffix is case-insensitive. That means you can use J instead:

3.14J   # equivalent to 3.14j

Formally, imaginary literals are described by the following lexical definition:

imagnumber: (floatnumber | digitpart) ("j" | "J")

2.7. Operators and delimiters

The following grammar defines operator and delimiter tokens, that is, the generic OP token type. A list of these tokens and their names is also available in the token module documentation.

OP:
   | assignment_operator
   | bitwise_operator
   | comparison_operator
   | enclosing_delimiter
   | other_delimiter
   | arithmetic_operator
   | "..."
   | other_op

assignment_operator:   "+=" | "-=" | "*=" | "**=" | "/="  | "//=" | "%=" |
                       "&=" | "|=" | "^=" | "<<=" | ">>=" | "@="  | ":="
bitwise_operator:      "&"  | "|"  | "^"  | "~"   | "<<"  | ">>"
comparison_operator:   "<=" | ">=" | "<"  | ">"   | "=="  | "!="
enclosing_delimiter:   "("  | ")"  | "["  | "]"   | "{"   | "}"
other_delimiter:       ","  | ":"  | "!"  | ";"   | "="   | "->"
arithmetic_operator:   "+"  | "-"  | "**" | "*"   | "//"  | "/"   | "%"
other_op:              "."  | "@"

備註

Generally, operators are used to combine expressions, while delimiters serve other purposes. However, there is no clear, formal distinction between the two categories.

Some tokens can serve as either operators or delimiters, depending on usage. For example, * is both the multiplication operator and a delimiter used for sequence unpacking, and @ is both the matrix multiplication and a delimiter that introduces decorators.

For some tokens, the distinction is unclear. For example, some people consider ., (, and ) to be delimiters, while others see the getattr() operator and the function call operator(s).

Some of Python's operators, like and, or, and not in, use keyword tokens rather than "symbols" (operator tokens).

A sequence of three consecutive periods (...) has a special meaning as an Ellipsis literal.

3. 資料模型

3.1. 物件、數值和型別

物件 是 Python 為資料的抽象表示方式。一個 Python 程式當中的所有資料皆由物件或物件之間的關係來呈現。程式碼也都是以物件呈現的。

每個物件都有一個識別性、型別，和數值。物件的識別性在物件建立後永遠不會改變；你也可以把它想成是該物件在記憶體中的位址。is 運算子會比較兩個物件的識別性是否相同；id() 函式則會回傳代表一個該物件的識別性的整數。

在 CPython 當中，id(x) 就是 x 所儲存在的記憶體位址。

一個物件的型別決定了該物件所支援的操作（例如「它有長度嗎？」），也同時定義該型別的物件能夠擁有的數值。type() 函式會回傳一個物件的型別（而該型別本身也是一個物件）。如同它的識別性，一個物件的型別 (type) 也是不可變的。[1]

某些物件的數值可被改變，這種物件稱作「可變的」(mutable)；建立後數值不能變更的物件則稱作「不可變的」(immutable)。（不可變的容器物件中如果包含對於可變物件的參照，則後者的數值改變的時候前者的數值也會跟著一起改變；這種時候該容器仍會被當成是不可變的，因為它包含的物件集合仍然無法變更。因此可變或不可變嚴格說起並不等同於數值是否能被改變，它的定義有其他不明顯的細節。）一個物件是否為可變取決於它的型別；舉例來說，數字、字串和 tuple 是不可變的，而字典與串列則是可變的。

物件永遠不會被明示的摧毀；但當它們變得不再能夠存取的時候可能會被作為垃圾回收。每個實作都能延後垃圾回收或是乾脆忽略它 --- 垃圾回收如何進行完全取決於各個實作，只要沒有被回收的物件仍是可達的。

CPython 目前使用一種參照計數的方案，並提供可選的循環連結垃圾延遲偵測，這個方案會在大部分物件變得不可存取時馬上回收它們，但不保證能夠回收包含循環參照的垃圾。關於控制循環垃圾回收的資訊請見 gc 模組的說明文件。其他實作的行為不會相同，CPython 也有可能改變，因此請不要仰賴物件在變得不可存取時能夠馬上被最終化（亦即你應該總是明確關閉檔案）。

請注意，使用一個實作的追蹤或除錯工具可能會讓原本能夠回收的物件被維持存活。也請注意，使用 try...except 陳述式來抓捕例外也可能會讓物件維持存活。

某些物件包含對於「外部」資源的參照，像是開啟的檔案或是視窗。基本上這些資源會在物件被回收時釋放，但因為垃圾回收不保證會發生，這種物件也會提供明確釋放外部資源的方式 --- 通常是 close() method。強烈建議各個程式明確關閉這種物件。try...finally 陳述式與 with 陳述式提供進行明確關閉的方便手段。

某些物件包含對於其他物件的參照；這種物件被叫做「容器」。容器的範例有 tuple、串列與字典。這些參照是容器的數值的一部分。通常當我們提到容器的數值的時候，我們指的是其中包含的物件的數值，而不是它們的識別性；但當我們提到容器是否可變的時候，我們指的是直接包含在其中的物件的識別性。因此，如果一個不可變的容器（像一個 tuple）包含對於可變物件的參照，該可變物件被變更時該容器的數值也會跟著變更。

型別幾乎影響物件行為的所有面向。就連物件識別性的重要性某種程度上也受型別影響：對於不可變的型別，計算新數值的操作可能其實會回傳一個某個相同型別且相同數值的現存物件的參照；對於可變型別這則不會發生。舉例來說，在進行 a = 1; b = 1 之後，a 和 b 可能會參照同一個物件，也可能不會，取決於所使用的實作。這是因為 int 是不可變的型別，因此 1 的參照可以重複利用。這個行為取決於所使用的實作，因此不應該依賴它，但在進行物件識別性測試的時候還是需要注意有這件事情。而在進行 c = []; d = [] 之後，c 和 d 則保證會參照兩個不同、獨特、且新建立的空白串列。（請注意，e = f = [] 則會將同一個物件同時指派給 e 和 f。）

3.2. 標準型別階層

Below is a list of the types that are built into Python. Extension modules (written in C, Java, or other languages, depending on the implementation) can define additional types. Future versions of Python may add types to the type hierarchy (e.g., rational numbers, efficiently stored arrays of integers, etc.), although such additions will often be provided via the standard library instead.

Some of the type descriptions below contain a paragraph listing 'special attributes.' These are attributes that provide access to the implementation and are not intended for general use. Their definition may change in the future.

3.2.1. None

這個型別只有一個數值。只有一個物件有這個數值。這個物件由內建名稱 None 存取。它用來在許多情況下代表數值不存在，例如沒有明確回傳任何東西的函式就會回傳這個物件。它的真值是 false。

3.2.2. NotImplemented

這個型別只有一個數值。只有一個物件有這個數值。這個物件由內建名稱 NotImplemented 存取。數字方法和 rich comparison 方法應該在沒有為所提供的運算元實作該操作的時候回傳這個數值。（直譯器接下來則會依運算子嘗試反轉的操作或是其他的後備方案。）它不應該在預期布林值的情境中被計算。

更多細節請見 實作算術操作。

在 3.9 版的變更: Evaluating NotImplemented in a boolean context was deprecated.

在 3.14 版的變更: 在預期布林值的情境中計算 NotImplemented 現在會引發 TypeError。它先前會計算為 True，並自 Python 3.9 起會發出 DeprecationWarning。

3.2.3. Ellipsis

這個型別只有一個數值。只有一個物件有這個數值。這個物件由文本 ... 或內建名稱 Ellipsis 存取。它的真值是 true。

3.2.4. numbers.Number

These are created by numeric literals and returned as results by arithmetic operators and arithmetic built-in functions. Numeric objects are immutable; once created their value never changes. Python numbers are of course strongly related to mathematical numbers, but subject to the limitations of numerical representation in computers.

The string representations of the numeric classes, computed by __repr__() and __str__(), have the following properties:

They are valid numeric literals which, when passed to their class constructor, produce an object having the value of the original numeric.

The representation is in base 10, when possible.

Leading zeros, possibly excepting a single zero before a decimal point, are not shown.

Trailing zeros, possibly excepting a single zero after a decimal point, are not shown.

A sign is shown only when the number is negative.

Python distinguishes between integers, floating-point numbers, and complex numbers:

3.2.4.1. numbers.Integral

These represent elements from the mathematical set of integers (positive and negative).

備註

The rules for integer representation are intended to give the most meaningful interpretation of shift and mask operations involving negative integers.

There are two types of integers:

Integers (int)

These represent numbers in an unlimited range, subject to available (virtual) memory only. For the purpose of shift and mask operations, a binary representation is assumed, and negative numbers are represented in a variant of 2's complement which gives the illusion of an infinite string of sign bits extending to the left.

Booleans (bool)

These represent the truth values False and True. The two objects representing the values False and True are the only Boolean objects. The Boolean type is a subtype of the integer type, and Boolean values behave like the values 0 and 1, respectively, in almost all contexts, the exception being that when converted to a string, the strings "False" or "True" are returned, respectively.

3.2.4.2. numbers.Real (float)

These represent machine-level double precision floating-point numbers. You are at the mercy of the underlying machine architecture (and C or Java implementation) for the accepted range and handling of overflow. Python does not support single-precision floating-point numbers; the savings in processor and memory usage that are usually the reason for using these are dwarfed by the overhead of using objects in Python, so there is no reason to complicate the language with two kinds of floating-point numbers.

3.2.4.3. numbers.Complex (complex)

These represent complex numbers as a pair of machine-level double precision floating-point numbers. The same caveats apply as for floating-point numbers. The real and imaginary parts of a complex number z can be retrieved through the read-only attributes z.real and z.imag.

3.2.5. Sequences

These represent finite ordered sets indexed by non-negative numbers. The built-in function len() returns the number of items of a sequence. When the length of a sequence is n, the index set contains the numbers 0, 1, ..., n-1. Item i of sequence a is selected by a[i]. Some sequences, including built-in sequences, interpret negative subscripts by adding the sequence length. For example, a[-2] equals a[n-2], the second to last item of sequence a with length n.

Sequences also support slicing: a[i:j] selects all items with index k such that i <= k < j. When used as an expression, a slice is a sequence of the same type. The comment above about negative indexes also applies to negative slice positions.

Some sequences also support "extended slicing" with a third "step" parameter: a[i:j:k] selects all items of a with index x where x = i + n*k, n >= 0 and i <= x < j.

Sequences are distinguished according to their mutability:

3.2.5.1. Immutable sequences

An object of an immutable sequence type cannot change once it is created. (If the object contains references to other objects, these other objects may be mutable and may be changed; however, the collection of objects directly referenced by an immutable object cannot change.)

The following types are immutable sequences:

字串 (String)

A string is a sequence of values that represent Unicode code points. All the code points in the range U+0000 - U+10FFFF can be represented in a string. Python doesn't have a char type; instead, every code point in the string is represented as a string object with length 1. The built-in function ord() converts a code point from its string form to an integer in the range 0 - 10FFFF; chr() converts an integer in the range 0 - 10FFFF to the corresponding length 1 string object. str.encode() can be used to convert a str to bytes using the given text encoding, and bytes.decode() can be used to achieve the opposite.

Tuple（元組）

The items of a tuple are arbitrary Python objects. Tuples of two or more items are formed by comma-separated lists of expressions. A tuple of one item (a 'singleton') can be formed by affixing a comma to an expression (an expression by itself does not create a tuple, since parentheses must be usable for grouping of expressions). An empty tuple can be formed by an empty pair of parentheses.

位元組

A bytes object is an immutable array. The items are 8-bit bytes, represented by integers in the range 0 <= x < 256. Bytes literals (like b'abc') and the built-in bytes() constructor can be used to create bytes objects. Also, bytes objects can be decoded to strings via the decode() method.

3.2.5.2. 可變序列

Mutable sequences can be changed after they are created. The subscription and slicing notations can be used as the target of assignment and del (delete) statements.

備註

The collections and array module provide additional examples of mutable sequence types.

There are currently two intrinsic mutable sequence types:

List（串列）

The items of a list are arbitrary Python objects. Lists are formed by placing a comma-separated list of expressions in square brackets. (Note that there are no special cases needed to form lists of length 0 or 1.)

位元組陣列

A bytearray object is a mutable array. They are created by the built-in bytearray() constructor. Aside from being mutable (and hence unhashable), byte arrays otherwise provide the same interface and functionality as immutable bytes objects.

3.2.6. Set（集合）型別

These represent unordered, finite sets of unique, immutable objects. As such, they cannot be indexed by any subscript. However, they can be iterated over, and the built-in function len() returns the number of items in a set. Common uses for sets are fast membership testing, removing duplicates from a sequence, and computing mathematical operations such as intersection, union, difference, and symmetric difference.

For set elements, the same immutability rules apply as for dictionary keys. Note that numeric types obey the normal rules for numeric comparison: if two numbers compare equal (e.g., 1 and 1.0), only one of them can be contained in a set.

There are currently two intrinsic set types:

Set（集合）

These represent a mutable set. They are created by the built-in set() constructor and can be modified afterwards by several methods, such as add().

Frozen set（凍結集合）

These represent an immutable set. They are created by the built-in frozenset() constructor. As a frozenset is immutable and hashable, it can be used again as an element of another set, or as a dictionary key.

3.2.7. 對映

These represent finite sets of objects indexed by arbitrary index sets. The subscript notation a[k] selects the item indexed by k from the mapping a; this can be used in expressions and as the target of assignments or del statements. The built-in function len() returns the number of items in a mapping.

There is currently a single intrinsic mapping type:

3.2.7.1. 字典

These represent finite sets of objects indexed by nearly arbitrary values. The only types of values not acceptable as keys are values containing lists or dictionaries or other mutable types that are compared by value rather than by object identity, the reason being that the efficient implementation of dictionaries requires a key's hash value to remain constant. Numeric types used for keys obey the normal rules for numeric comparison: if two numbers compare equal (e.g., 1 and 1.0) then they can be used interchangeably to index the same dictionary entry.

Dictionaries preserve insertion order, meaning that keys will be produced in the same order they were added sequentially over the dictionary. Replacing an existing key does not change the order, however removing a key and re-inserting it will add it to the end instead of keeping its old place.

Dictionaries are mutable; they can be created by the {} notation (see section Dictionary displays).

The extension modules dbm.ndbm and dbm.gnu provide additional examples of mapping types, as does the collections module.

在 3.7 版的變更: Dictionaries did not preserve insertion order in versions of Python before 3.6. In CPython 3.6, insertion order was preserved, but it was considered an implementation detail at that time rather than a language guarantee.

3.2.8. 可呼叫型別

These are the types to which the function call operation (see section Calls) can be applied:

3.2.8.1. 自訂函式

A user-defined function object is created by a function definition (see section 函式定義). It should be called with an argument list containing the same number of items as the function's formal parameter list.

3.2.8.1.1. 特殊唯讀屬性

屬性

含義

function.__builtins__

A reference to the dictionary that holds the function's builtins namespace.

在 3.10 版被加入.

function.__globals__

A reference to the dictionary that holds the function's global variables -- the global namespace of the module in which the function was defined.

function.__closure__

None or a tuple of cells that contain bindings for the names specified in the co_freevars attribute of the function's code object.

A cell object has the attribute cell_contents. This can be used to get the value of the cell, as well as set the value.

3.2.8.1.2. 特殊可寫屬性

Most of these attributes check the type of the assigned value:

屬性

含義

function.__doc__

函式的文件字串，若不可用則為 None。

function.__name__

The function's name. See also: __name__ attributes.

function.__qualname__

The function's qualified name. See also: __qualname__ attributes.

在 3.3 版被加入.

function.__module__

The name of the module the function was defined in, or None if unavailable.

function.__defaults__

A tuple containing default parameter values for those parameters that have defaults, or None if no parameters have a default value.

function.__code__

代表編譯函式主體的程式碼物件。

function.__dict__

The namespace supporting arbitrary function attributes. See also: __dict__ attributes.

function.__annotations__

A dictionary containing annotations of parameters. The keys of the dictionary are the parameter names, and 'return' for the return annotation, if provided. See also: object.__annotations__.

在 3.14 版的變更: Annotations are now lazily evaluated. See PEP 649 [https://peps.python.org/pep-0649/].

function.__annotate__

The annotate function for this function, or None if the function has no annotations. See object.__annotate__.

在 3.14 版被加入.

function.__kwdefaults__

A dictionary containing defaults for keyword-only parameters.

function.__type_params__

A tuple containing the type parameters of a generic function.

在 3.12 版被加入.

Function objects also support getting and setting arbitrary attributes, which can be used, for example, to attach metadata to functions. Regular attribute dot-notation is used to get and set such attributes.

CPython 實作細節： CPython's current implementation only supports function attributes on user-defined functions. Function attributes on built-in functions may be supported in the future.

Additional information about a function's definition can be retrieved from its code object (accessible via the __code__ attribute).

3.2.8.2. 實例方法

An instance method object combines a class, a class instance and any callable object (normally a user-defined function).

特殊唯讀屬性：

method.__self__

Refers to the class instance object to which the method is bound

method.__func__

Refers to the original function object

method.__doc__

The method's documentation (same as method.__func__.__doc__). A string if the original function had a docstring, else None.

method.__name__

The name of the method (same as method.__func__.__name__)

method.__module__

The name of the module the method was defined in, or None if unavailable.

Methods also support accessing (but not setting) the arbitrary function attributes on the underlying function object.

User-defined method objects may be created when getting an attribute of a class (perhaps via an instance of that class), if that attribute is a user-defined function object or a classmethod object.

When an instance method object is created by retrieving a user-defined function object from a class via one of its instances, its __self__ attribute is the instance, and the method object is said to be bound. The new method's __func__ attribute is the original function object.

When an instance method object is created by retrieving a classmethod object from a class or instance, its __self__ attribute is the class itself, and its __func__ attribute is the function object underlying the class method.

When an instance method object is called, the underlying function (__func__) is called, inserting the class instance (__self__) in front of the argument list. For instance, when C is a class which contains a definition for a function f(), and x is an instance of C, calling x.f(1) is equivalent to calling C.f(x, 1).

When an instance method object is derived from a classmethod object, the "class instance" stored in __self__ will actually be the class itself, so that calling either x.f(1) or C.f(1) is equivalent to calling f(C,1) where f is the underlying function.

It is important to note that user-defined functions which are attributes of a class instance are not converted to bound methods; this only happens when the function is an attribute of the class.

3.2.8.3. 產生器函式

A function or method which uses the yield statement (see section yield 陳述式) is called a generator function. Such a function, when called, always returns an iterator object which can be used to execute the body of the function: calling the iterator's iterator.__next__() method will cause the function to execute until it provides a value using the yield statement. When the function executes a return statement or falls off the end, a StopIteration exception is raised and the iterator will have reached the end of the set of values to be returned.

3.2.8.4. Coroutine（協程）函式

A function or method which is defined using async def is called a coroutine function. Such a function, when called, returns a coroutine object. It may contain await expressions, as well as async with and async for statements. See also the 協程物件 section.

3.2.8.5. 非同步產生器函式

A function or method which is defined using async def and which uses the yield statement is called a asynchronous generator function. Such a function, when called, returns an asynchronous iterator object which can be used in an async for statement to execute the body of the function.

Calling the asynchronous iterator's aiterator.__anext__ method will return an awaitable which when awaited will execute until it provides a value using the yield expression. When the function executes an empty return statement or falls off the end, a StopAsyncIteration exception is raised and the asynchronous iterator will have reached the end of the set of values to be yielded.

3.2.8.6. 內建函式

一個內建函式物件是一個 C 函式的 wrapper。內建函式的範例有 len() 和 math.sin()（math 是一個標準的內建模組）。內建函式的引數數量與其型別由其包裝的 C 函式所決定。特殊唯讀屬性：

__doc__ 是函式的文件字串，若不可用則為 None。請見 function.__doc__。

__name__ 是函式的名稱。請見 function.__name__。

__self__ is set to None (but see the next item).

__module__ is the name of the module the function was defined in or None if unavailable. See function.__module__.

3.2.8.7. 內建方法

This is really a different disguise of a built-in function, this time containing an object passed to the C function as an implicit extra argument. An example of a built-in method is alist.append(), assuming alist is a list object. In this case, the special read-only attribute __self__ is set to the object denoted by alist. (The attribute has the same semantics as it does with other instance methods.)

3.2.8.8. Classes

Classes are callable. These objects normally act as factories for new instances of themselves, but variations are possible for class types that override __new__(). The arguments of the call are passed to __new__() and, in the typical case, to __init__() to initialize the new instance.

3.2.8.9. 類別實例

Instances of arbitrary classes can be made callable by defining a __call__() method in their class.

3.2.9. 模組

Modules are a basic organizational unit of Python code, and are created by the import system as invoked either by the import statement, or by calling functions such as importlib.import_module() and built-in __import__(). A module object has a namespace implemented by a dictionary object (this is the dictionary referenced by the __globals__ attribute of functions defined in the module). Attribute references are translated to lookups in this dictionary, e.g., m.x is equivalent to m.__dict__["x"]. A module object does not contain the code object used to initialize the module (since it isn't needed once the initialization is done).

Attribute assignment updates the module's namespace dictionary, e.g., m.x = 1 is equivalent to m.__dict__["x"] = 1.

3.2.9.1. Import-related attributes on module objects

Module objects have the following attributes that relate to the import system. When a module is created using the machinery associated with the import system, these attributes are filled in based on the module's spec, before the loader executes and loads the module.

To create a module dynamically rather than using the import system, it's recommended to use importlib.util.module_from_spec(), which will set the various import-controlled attributes to appropriate values. It's also possible to use the types.ModuleType constructor to create modules directly, but this technique is more error-prone, as most attributes must be manually set on the module object after it has been created when using this approach.

警示

With the exception of __name__, it is strongly recommended that you rely on __spec__ and its attributes instead of any of the other individual attributes listed in this subsection. Note that updating an attribute on __spec__ will not update the corresponding attribute on the module itself:

>>> import typing
>>> typing.__name__, typing.__spec__.name
('typing', 'typing')
>>> typing.__spec__.name = 'spelling'
>>> typing.__name__, typing.__spec__.name
('typing', 'spelling')
>>> typing.__name__ = 'keyboard_smashing'
>>> typing.__name__, typing.__spec__.name
('keyboard_smashing', 'spelling')

module.__name__

The name used to uniquely identify the module in the import system. For a directly executed module, this will be set to "__main__".

This attribute must be set to the fully qualified name of the module. It is expected to match the value of module.__spec__.name.

module.__spec__

A record of the module's import-system-related state.

Set to the module spec that was used when importing the module. See 模組規格 for more details.

在 3.4 版被加入.

module.__package__

The package a module belongs to.

If the module is top-level (that is, not a part of any specific package) then the attribute should be set to '' (the empty string). Otherwise, it should be set to the name of the module's package (which can be equal to module.__name__ if the module itself is a package). See PEP 366 [https://peps.python.org/pep-0366/] for further details.

This attribute is used instead of __name__ to calculate explicit relative imports for main modules. It defaults to None for modules created dynamically using the types.ModuleType constructor; use importlib.util.module_from_spec() instead to ensure the attribute is set to a str.

It is strongly recommended that you use module.__spec__.parent instead of module.__package__. __package__ is now only used as a fallback if __spec__.parent is not set, and this fallback path is deprecated.

在 3.4 版的變更: This attribute now defaults to None for modules created dynamically using the types.ModuleType constructor. Previously the attribute was optional.

在 3.6 版的變更: The value of __package__ is expected to be the same as __spec__.parent. __package__ is now only used as a fallback during import resolution if __spec__.parent is not defined.

在 3.10 版的變更: ImportWarning is raised if an import resolution falls back to __package__ instead of __spec__.parent.

在 3.12 版的變更: Raise DeprecationWarning instead of ImportWarning when falling back to __package__ during import resolution.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: __package__ will cease to be set or taken into consideration by the import system or standard library.

module.__loader__

The loader object that the import machinery used to load the module.

This attribute is mostly useful for introspection, but can be used for additional loader-specific functionality, for example getting data associated with a loader.

__loader__ defaults to None for modules created dynamically using the types.ModuleType constructor; use importlib.util.module_from_spec() instead to ensure the attribute is set to a loader object.

It is strongly recommended that you use module.__spec__.loader instead of module.__loader__.

在 3.4 版的變更: This attribute now defaults to None for modules created dynamically using the types.ModuleType constructor. Previously the attribute was optional.

自從版本 3.12 後不推薦使用，將會自版本 3.16 中移除。: 在模組上設定 __loader__ 而沒有設定 __spec__.loader 的做法已被棄用。在 Python 3.16 中，引入系統或標準函式庫將不再設定或考慮 __loader__。

module.__path__

A (possibly empty) sequence of strings enumerating the locations where the package's submodules will be found. Non-package modules should not have a __path__ attribute. See __path__ attributes on modules for more details.

It is strongly recommended that you use module.__spec__.submodule_search_locations instead of module.__path__.

module.__file__

module.__cached__

__file__ and __cached__ are both optional attributes that may or may not be set. Both attributes should be a str when they are available.

__file__ indicates the pathname of the file from which the module was loaded (if loaded from a file), or the pathname of the shared library file for extension modules loaded dynamically from a shared library. It might be missing for certain types of modules, such as C modules that are statically linked into the interpreter, and the import system may opt to leave it unset if it has no semantic meaning (for example, a module loaded from a database).

If __file__ is set then the __cached__ attribute might also be set, which is the path to any compiled version of the code (for example, a byte-compiled file). The file does not need to exist to set this attribute; the path can simply point to where the compiled file would exist (see PEP 3147 [https://peps.python.org/pep-3147/]).

Note that __cached__ may be set even if __file__ is not set. However, that scenario is quite atypical. Ultimately, the loader is what makes use of the module spec provided by the finder (from which __file__ and __cached__ are derived). So if a loader can load from a cached module but otherwise does not load from a file, that atypical scenario may be appropriate.

It is strongly recommended that you use module.__spec__.cached instead of module.__cached__.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Setting __cached__ on a module while failing to set __spec__.cached is deprecated. In Python 3.15, __cached__ will cease to be set or taken into consideration by the import system or standard library.

3.2.9.2. 模組物件的其他可寫入屬性

As well as the import-related attributes listed above, module objects also have the following writable attributes:

module.__doc__

模組的文件字串，若不可用則為 None。請見 __doc__ attributes。

module.__annotations__

A dictionary containing variable annotations collected during module body execution. For best practices on working with __annotations__, see annotationlib.

在 3.14 版的變更: Annotations are now lazily evaluated. See PEP 649 [https://peps.python.org/pep-0649/].

module.__annotate__

The annotate function for this module, or None if the module has no annotations. See also: __annotate__ attributes.

在 3.14 版被加入.

3.2.9.3. 模組字典

Module objects also have the following special read-only attribute:

module.__dict__

The module's namespace as a dictionary object. Uniquely among the attributes listed here, __dict__ cannot be accessed as a global variable from within a module; it can only be accessed as an attribute on module objects.

CPython 實作細節： Because of the way CPython clears module dictionaries, the module dictionary will be cleared when the module falls out of scope even if the dictionary still has live references. To avoid this, copy the dictionary or keep the module around while using its dictionary directly.

3.2.10. Custom classes

Custom class types are typically created by class definitions (see section 類別定義). A class has a namespace implemented by a dictionary object. Class attribute references are translated to lookups in this dictionary, e.g., C.x is translated to C.__dict__["x"] (although there are a number of hooks which allow for other means of locating attributes). When the attribute name is not found there, the attribute search continues in the base classes. This search of the base classes uses the C3 method resolution order which behaves correctly even in the presence of 'diamond' inheritance structures where there are multiple inheritance paths leading back to a common ancestor. Additional details on the C3 MRO used by Python can be found at Python 2.3 方法解析順序.

When a class attribute reference (for class C, say) would yield a class method object, it is transformed into an instance method object whose __self__ attribute is C. When it would yield a staticmethod object, it is transformed into the object wrapped by the static method object. See section 實作描述器 for another way in which attributes retrieved from a class may differ from those actually contained in its __dict__.

Class attribute assignments update the class's dictionary, never the dictionary of a base class.

A class object can be called (see above) to yield a class instance (see below).

3.2.10.1. 特殊屬性

屬性

含義

type.__name__

The class's name. See also: __name__ attributes.

type.__qualname__

The class's qualified name. See also: __qualname__ attributes.

type.__module__

The name of the module in which the class was defined.

type.__dict__

A mapping proxy providing a read-only view of the class's namespace. See also: __dict__ attributes.

type.__bases__

A tuple containing the class's bases. In most cases, for a class defined as class X(A, B, C), X.__bases__ will be exactly equal to (A, B, C).

type.__base__

CPython 實作細節： The single base class in the inheritance chain that is responsible for the memory layout of instances. This attribute corresponds to tp_base at the C level.

type.__doc__

The class's documentation string, or None if undefined. Not inherited by subclasses.

type.__annotations__

A dictionary containing variable annotations collected during class body execution. See also: __annotations__ attributes.

For best practices on working with __annotations__, please see annotationlib. Use annotationlib.get_annotations() instead of accessing this attribute directly.

警告

Accessing the __annotations__ attribute directly on a class object may return annotations for the wrong class, specifically in certain cases where the class, its base class, or a metaclass is defined under from __future__ import annotations. See 749 [https://peps.python.org/pep-0749/#pep749-metaclasses] for details.

This attribute does not exist on certain builtin classes. On user-defined classes without __annotations__, it is an empty dictionary.

在 3.14 版的變更: Annotations are now lazily evaluated. See PEP 649 [https://peps.python.org/pep-0649/].

type.__annotate__()

The annotate function for this class, or None if the class has no annotations. See also: __annotate__ attributes.

在 3.14 版被加入.

type.__type_params__

A tuple containing the type parameters of a generic class.

在 3.12 版被加入.

type.__static_attributes__

A tuple containing names of attributes of this class which are assigned through self.X from any function in its body.

在 3.13 版被加入.

type.__firstlineno__

The line number of the first line of the class definition, including decorators. Setting the __module__ attribute removes the __firstlineno__ item from the type's dictionary.

在 3.13 版被加入.

type.__mro__

The tuple of classes that are considered when looking for base classes during method resolution.

3.2.10.2. 特殊方法

In addition to the special attributes described above, all Python classes also have the following two methods available:

type.mro()

This method can be overridden by a metaclass to customize the method resolution order for its instances. It is called at class instantiation, and its result is stored in __mro__.

type.__subclasses__()

Each class keeps a list of weak references to its immediate subclasses. This method returns a list of all those references still alive. The list is in definition order. Example:

>>> class A: pass
>>> class B(A): pass
>>> A.__subclasses__()
[<class 'B'>]

3.2.11. 類別實例

A class instance is created by calling a class object (see above). A class instance has a namespace implemented as a dictionary which is the first place in which attribute references are searched. When an attribute is not found there, and the instance's class has an attribute by that name, the search continues with the class attributes. If a class attribute is found that is a user-defined function object, it is transformed into an instance method object whose __self__ attribute is the instance. Static method and class method objects are also transformed; see above under "Classes". See section 實作描述器 for another way in which attributes of a class retrieved via its instances may differ from the objects actually stored in the class's __dict__. If no class attribute is found, and the object's class has a __getattr__() method, that is called to satisfy the lookup.

Attribute assignments and deletions update the instance's dictionary, never a class's dictionary. If the class has a __setattr__() or __delattr__() method, this is called instead of updating the instance dictionary directly.

Class instances can pretend to be numbers, sequences, or mappings if they have methods with certain special names. See section Special method names.

3.2.11.1. 特殊屬性

object.__class__

The class to which a class instance belongs.

object.__dict__

A dictionary or other mapping object used to store an object's (writable) attributes. Not all instances have a __dict__ attribute; see the section on __slots__ for more details.

3.2.12. I/O objects (also known as file objects)

A file object represents an open file. Various shortcuts are available to create file objects: the open() built-in function, and also os.popen(), os.fdopen(), and the makefile() method of socket objects (and perhaps by other functions or methods provided by extension modules).

The objects sys.stdin, sys.stdout and sys.stderr are initialized to file objects corresponding to the interpreter's standard input, output and error streams; they are all open in text mode and therefore follow the interface defined by the io.TextIOBase abstract class.

3.2.13. Internal types

A few types used internally by the interpreter are exposed to the user. Their definitions may change with future versions of the interpreter, but they are mentioned here for completeness.

3.2.13.1. 程式碼物件

Code objects represent byte-compiled executable Python code, or bytecode. The difference between a code object and a function object is that the function object contains an explicit reference to the function's globals (the module in which it was defined), while a code object contains no context; also the default argument values are stored in the function object, not in the code object (because they represent values calculated at run-time). Unlike function objects, code objects are immutable and contain no references (directly or indirectly) to mutable objects.

3.2.13.1.1. 特殊唯讀屬性

codeobject.co_name

函式名稱

codeobject.co_qualname

The fully qualified function name

在 3.11 版被加入.

codeobject.co_argcount

The total number of positional parameters (including positional-only parameters and parameters with default values) that the function has

codeobject.co_posonlyargcount

The number of positional-only parameters (including arguments with default values) that the function has

codeobject.co_kwonlyargcount

The number of keyword-only parameters (including arguments with default values) that the function has

codeobject.co_nlocals

The number of local variables used by the function (including parameters)

codeobject.co_varnames

A tuple containing the names of the local variables in the function (starting with the parameter names)

codeobject.co_cellvars

A tuple containing the names of local variables that are referenced from at least one nested scope inside the function

codeobject.co_freevars

A tuple containing the names of free (closure) variables that a nested scope references in an outer scope. See also function.__closure__.

Note: references to global and builtin names are not included.

codeobject.co_code

A string representing the sequence of bytecode instructions in the function

codeobject.co_consts

A tuple containing the literals used by the bytecode in the function

codeobject.co_names

A tuple containing the names used by the bytecode in the function

codeobject.co_filename

The name of the file from which the code was compiled

codeobject.co_firstlineno

The line number of the first line of the function

codeobject.co_lnotab

A string encoding the mapping from bytecode offsets to line numbers. For details, see the source code of the interpreter.

在 3.12 版之後被棄用: This attribute of code objects is deprecated, and may be removed in Python 3.15.

codeobject.co_stacksize

The required stack size of the code object

codeobject.co_flags

An integer encoding a number of flags for the interpreter.

The following flag bits are defined for co_flags: bit 0x04 is set if the function uses the *arguments syntax to accept an arbitrary number of positional arguments; bit 0x08 is set if the function uses the **keywords syntax to accept arbitrary keyword arguments; bit 0x20 is set if the function is a generator. See Code Objects Bit Flags for details on the semantics of each flags that might be present.

Future feature declarations (for example, from __future__ import division) also use bits in co_flags to indicate whether a code object was compiled with a particular feature enabled. See compiler_flag.

Other bits in co_flags are reserved for internal use.

If a code object represents a function and has a docstring, the CO_HAS_DOCSTRING bit is set in co_flags and the first item in co_consts is the docstring of the function.

3.2.13.1.2. 用於程式碼物件的方法

codeobject.co_positions()

Returns an iterable over the source code positions of each bytecode instruction in the code object.

The iterator returns tuples containing the (start_line, end_line, start_column, end_column). The i-th tuple corresponds to the position of the source code that compiled to the i-th code unit. Column information is 0-indexed utf-8 byte offsets on the given source line.

This positional information can be missing. A non-exhaustive lists of cases where this may happen:

Running the interpreter with -X no_debug_ranges.

Loading a pyc file compiled while using -X no_debug_ranges.

Position tuples corresponding to artificial instructions.

Line and column numbers that can't be represented due to implementation specific limitations.

When this occurs, some or all of the tuple elements can be None.

在 3.11 版被加入.

備註

This feature requires storing column positions in code objects which may result in a small increase of disk usage of compiled Python files or interpreter memory usage. To avoid storing the extra information and/or deactivate printing the extra traceback information, the -X no_debug_ranges command line flag or the PYTHONNODEBUGRANGES environment variable can be used.

codeobject.co_lines()

Returns an iterator that yields information about successive ranges of bytecodes. Each item yielded is a (start, end, lineno) tuple:

start (an int) represents the offset (inclusive) of the start of the bytecode range

end (an int) represents the offset (exclusive) of the end of the bytecode range

lineno is an int representing the line number of the bytecode range, or None if the bytecodes in the given range have no line number

The items yielded will have the following properties:

The first range yielded will have a start of 0.

The (start, end) ranges will be non-decreasing and consecutive. That is, for any pair of tuples, the start of the second will be equal to the end of the first.

No range will be backwards: end >= start for all triples.

The last tuple yielded will have end equal to the size of the bytecode.

Zero-width ranges, where start == end, are allowed. Zero-width ranges are used for lines that are present in the source code, but have been eliminated by the bytecode compiler.

在 3.10 版被加入.

也參考

PEP 626 [https://peps.python.org/pep-0626/] - Precise line numbers for debugging and other tools.

The PEP that introduced the co_lines() method.

codeobject.replace(**kwargs)

Return a copy of the code object with new values for the specified fields.

Code objects are also supported by the generic function copy.replace().

在 3.8 版被加入.

3.2.13.2. Frame objects

Frame objects represent execution frames. They may occur in traceback objects, and are also passed to registered trace functions.

3.2.13.2.1. 特殊唯讀屬性

frame.f_back

Points to the previous stack frame (towards the caller), or None if this is the bottom stack frame

frame.f_code

在這個 frame 中執行的程式碼物件 (code object)。存取這個屬性會引發一個附帶引數 obj 與 "f_code" 的稽核事件 object.__getattr__。

frame.f_locals

The mapping used by the frame to look up local variables. If the frame refers to an optimized scope, this may return a write-through proxy object.

在 3.13 版的變更: Return a proxy for optimized scopes.

frame.f_globals

The dictionary used by the frame to look up global variables

frame.f_builtins

The dictionary used by the frame to look up built-in (intrinsic) names

frame.f_lasti

The "precise instruction" of the frame object (this is an index into the bytecode string of the code object)

frame.f_generator

The generator or coroutine object that owns this frame, or None if the frame is a normal function.

在 3.14 版被加入.

3.2.13.2.2. 特殊可寫屬性

frame.f_trace

If not None, this is a function called for various events during code execution (this is used by debuggers). Normally an event is triggered for each new source line (see f_trace_lines).

frame.f_trace_lines

Set this attribute to False to disable triggering a tracing event for each source line.

frame.f_trace_opcodes

Set this attribute to True to allow per-opcode events to be requested. Note that this may lead to undefined interpreter behaviour if exceptions raised by the trace function escape to the function being traced.

frame.f_lineno

The current line number of the frame -- writing to this from within a trace function jumps to the given line (only for the bottom-most frame). A debugger can implement a Jump command (aka Set Next Statement) by writing to this attribute.

3.2.13.2.3. Frame object methods

Frame objects support one method:

frame.clear()

This method clears all references to local variables held by the frame. Also, if the frame belonged to a generator, the generator is finalized. This helps break reference cycles involving frame objects (for example when catching an exception and storing its traceback for later use).

RuntimeError is raised if the frame is currently executing or suspended.

在 3.4 版被加入.

在 3.13 版的變更: Attempting to clear a suspended frame raises RuntimeError (as has always been the case for executing frames).

3.2.13.3. Traceback objects

Traceback objects represent the stack trace of an exception. A traceback object is implicitly created when an exception occurs, and may also be explicitly created by calling types.TracebackType.

在 3.7 版的變更: Traceback objects can now be explicitly instantiated from Python code.

For implicitly created tracebacks, when the search for an exception handler unwinds the execution stack, at each unwound level a traceback object is inserted in front of the current traceback. When an exception handler is entered, the stack trace is made available to the program. (See section try 陳述式.) It is accessible as the third item of the tuple returned by sys.exc_info(), and as the __traceback__ attribute of the caught exception.

When the program contains no suitable handler, the stack trace is written (nicely formatted) to the standard error stream; if the interpreter is interactive, it is also made available to the user as sys.last_traceback.

For explicitly created tracebacks, it is up to the creator of the traceback to determine how the tb_next attributes should be linked to form a full stack trace.

特殊唯讀屬性：

traceback.tb_frame

Points to the execution frame of the current level.

存取此屬性會引發一個附帶引數 obj 與 "tb_frame" 的稽核事件 object.__getattr__。

traceback.tb_lineno

Gives the line number where the exception occurred

traceback.tb_lasti

Indicates the "precise instruction".

The line number and last instruction in the traceback may differ from the line number of its frame object if the exception occurred in a try statement with no matching except clause or with a finally clause.

traceback.tb_next

The special writable attribute tb_next is the next level in the stack trace (towards the frame where the exception occurred), or None if there is no next level.

在 3.7 版的變更: 此屬性現在可寫入

3.2.13.4. Slice objects

Slice objects are used to represent slices for __getitem__() methods. They are also created by the built-in slice() function.

Special read-only attributes: start is the lower bound; stop is the upper bound; step is the step value; each is None if omitted. These attributes can have any type.

Slice objects support one method:

slice.indices(self, length)

This method takes a single integer argument length and computes information about the slice that the slice object would describe if applied to a sequence of length items. It returns a tuple of three integers; respectively these are the start and stop indices and the step or stride length of the slice. Missing or out-of-bounds indices are handled in a manner consistent with regular slices.

3.2.13.5. Static method objects

Static method objects provide a way of defeating the transformation of function objects to method objects described above. A static method object is a wrapper around any other object, usually a user-defined method object. When a static method object is retrieved from a class or a class instance, the object actually returned is the wrapped object, which is not subject to any further transformation. Static method objects are also callable. Static method objects are created by the built-in staticmethod() constructor.

3.2.13.6. Class method objects

A class method object, like a static method object, is a wrapper around another object that alters the way in which that object is retrieved from classes and class instances. The behaviour of class method objects upon such retrieval is described above, under "instance methods". Class method objects are created by the built-in classmethod() constructor.

3.3. Special method names

A class can implement certain operations that are invoked by special syntax (such as arithmetic operations or subscripting and slicing) by defining methods with special names. This is Python's approach to operator overloading, allowing classes to define their own behavior with respect to language operators. For instance, if a class defines a method named __getitem__(), and x is an instance of this class, then x[i] is roughly equivalent to type(x).__getitem__(x, i). Except where mentioned, attempts to execute an operation raise an exception when no appropriate method is defined (typically AttributeError or TypeError).

Setting a special method to None indicates that the corresponding operation is not available. For example, if a class sets __iter__() to None, the class is not iterable, so calling iter() on its instances will raise a TypeError (without falling back to __getitem__()). [2]

When implementing a class that emulates any built-in type, it is important that the emulation only be implemented to the degree that it makes sense for the object being modelled. For example, some sequences may work well with retrieval of individual elements, but extracting a slice may not make sense. (One example of this is the NodeList interface in the W3C's Document Object Model.)

3.3.1. Basic customization

object.__new__(cls[, ...])

Called to create a new instance of class cls. __new__() is a static method (special-cased so you need not declare it as such) that takes the class of which an instance was requested as its first argument. The remaining arguments are those passed to the object constructor expression (the call to the class). The return value of __new__() should be the new object instance (usually an instance of cls).

Typical implementations create a new instance of the class by invoking the superclass's __new__() method using super().__new__(cls[, ...]) with appropriate arguments and then modifying the newly created instance as necessary before returning it.

If __new__() is invoked during object construction and it returns an instance of cls, then the new instance’s __init__() method will be invoked like __init__(self[, ...]), where self is the new instance and the remaining arguments are the same as were passed to the object constructor.

If __new__() does not return an instance of cls, then the new instance's __init__() method will not be invoked.

__new__() is intended mainly to allow subclasses of immutable types (like int, str, or tuple) to customize instance creation. It is also commonly overridden in custom metaclasses in order to customize class creation.

object.__init__(self[, ...])

Called after the instance has been created (by __new__()), but before it is returned to the caller. The arguments are those passed to the class constructor expression. If a base class has an __init__() method, the derived class's __init__() method, if any, must explicitly call it to ensure proper initialization of the base class part of the instance; for example: super().__init__([args...]).

Because __new__() and __init__() work together in constructing objects (__new__() to create it, and __init__() to customize it), no non-None value may be returned by __init__(); doing so will cause a TypeError to be raised at runtime.

object.__del__(self)

Called when the instance is about to be destroyed. This is also called a finalizer or (improperly) a destructor. If a base class has a __del__() method, the derived class's __del__() method, if any, must explicitly call it to ensure proper deletion of the base class part of the instance.

It is possible (though not recommended!) for the __del__() method to postpone destruction of the instance by creating a new reference to it. This is called object resurrection. It is implementation-dependent whether __del__() is called a second time when a resurrected object is about to be destroyed; the current CPython implementation only calls it once.

It is not guaranteed that __del__() methods are called for objects that still exist when the interpreter exits. weakref.finalize provides a straightforward way to register a cleanup function to be called when an object is garbage collected.

備註

del x doesn't directly call x.__del__() --- the former decrements the reference count for x by one, and the latter is only called when x's reference count reaches zero.

CPython 實作細節： It is possible for a reference cycle to prevent the reference count of an object from going to zero. In this case, the cycle will be later detected and deleted by the cyclic garbage collector. A common cause of reference cycles is when an exception has been caught in a local variable. The frame's locals then reference the exception, which references its own traceback, which references the locals of all frames caught in the traceback.

也參考

gc 模組的文件。

警告

Due to the precarious circumstances under which __del__() methods are invoked, exceptions that occur during their execution are ignored, and a warning is printed to sys.stderr instead. In particular:

__del__() can be invoked when arbitrary code is being executed, including from any arbitrary thread. If __del__() needs to take a lock or invoke any other blocking resource, it may deadlock as the resource may already be taken by the code that gets interrupted to execute __del__().

__del__() can be executed during interpreter shutdown. As a consequence, the global variables it needs to access (including other modules) may already have been deleted or set to None. Python guarantees that globals whose name begins with a single underscore are deleted from their module before other globals are deleted; if no other references to such globals exist, this may help in assuring that imported modules are still available at the time when the __del__() method is called.

object.__repr__(self)

Called by the repr() built-in function to compute the "official" string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment). If this is not possible, a string of the form <...some useful description...> should be returned. The return value must be a string object. If a class defines __repr__() but not __str__(), then __repr__() is also used when an "informal" string representation of instances of that class is required.

This is typically used for debugging, so it is important that the representation is information-rich and unambiguous. A default implementation is provided by the object class itself.

object.__str__(self)

Called by str(object), the default __format__() implementation, and the built-in function print(), to compute the "informal" or nicely printable string representation of an object. The return value must be a str object.

This method differs from object.__repr__() in that there is no expectation that __str__() return a valid Python expression: a more convenient or concise representation can be used.

The default implementation defined by the built-in type object calls object.__repr__().

object.__bytes__(self)

Called by bytes to compute a byte-string representation of an object. This should return a bytes object. The object class itself does not provide this method.

object.__format__(self, format_spec)

Called by the format() built-in function, and by extension, evaluation of formatted string literals and the str.format() method, to produce a "formatted" string representation of an object. The format_spec argument is a string that contains a description of the formatting options desired. The interpretation of the format_spec argument is up to the type implementing __format__(), however most classes will either delegate formatting to one of the built-in types, or use a similar formatting option syntax.

See 格式規格 (Format Specification) 迷你語言 for a description of the standard formatting syntax.

回傳值必須是個字串物件。

The default implementation by the object class should be given an empty format_spec string. It delegates to __str__().

在 3.4 版的變更: The __format__ method of object itself raises a TypeError if passed any non-empty string.

在 3.7 版的變更: object.__format__(x, '') is now equivalent to str(x) rather than format(str(x), '').

object.__lt__(self, other)

object.__le__(self, other)

object.__eq__(self, other)

object.__ne__(self, other)

object.__gt__(self, other)

object.__ge__(self, other)

These are the so-called "rich comparison" methods. The correspondence between operator symbols and method names is as follows: x<y calls x.__lt__(y), x<=y calls x.__le__(y), x==y calls x.__eq__(y), x!=y calls x.__ne__(y), x>y calls x.__gt__(y), and x>=y calls x.__ge__(y).

A rich comparison method may return the singleton NotImplemented if it does not implement the operation for a given pair of arguments. By convention, False and True are returned for a successful comparison. However, these methods can return any value, so if the comparison operator is used in a Boolean context (e.g., in the condition of an if statement), Python will call bool() on the value to determine if the result is true or false.

By default, object implements __eq__() by using is, returning NotImplemented in the case of a false comparison: True if x is y else NotImplemented. For __ne__(), by default it delegates to __eq__() and inverts the result unless it is NotImplemented. There are no other implied relationships among the comparison operators or default implementations; for example, the truth of (x<y or x==y) does not imply x<=y. To automatically generate ordering operations from a single root operation, see functools.total_ordering().

By default, the object class provides implementations consistent with Value comparisons: equality compares according to object identity, and order comparisons raise TypeError. Each default method may generate these results directly, but may also return NotImplemented.

See the paragraph on __hash__() for some important notes on creating hashable objects which support custom comparison operations and are usable as dictionary keys.

There are no swapped-argument versions of these methods (to be used when the left argument does not support the operation but the right argument does); rather, __lt__() and __gt__() are each other's reflection, __le__() and __ge__() are each other's reflection, and __eq__() and __ne__() are their own reflection. If the operands are of different types, and the right operand's type is a direct or indirect subclass of the left operand's type, the reflected method of the right operand has priority, otherwise the left operand's method has priority. Virtual subclassing is not considered.

When no appropriate method returns any value other than NotImplemented, the == and != operators will fall back to is and is not, respectively.

object.__hash__(self)

Called by built-in function hash() and for operations on members of hashed collections including set, frozenset, and dict. The __hash__() method should return an integer. The only required property is that objects which compare equal have the same hash value; it is advised to mix together the hash values of the components of the object that also play a part in comparison of objects by packing them into a tuple and hashing the tuple. Example:

def __hash__(self):
    return hash((self.name, self.nick, self.color))

備註

hash() truncates the value returned from an object's custom __hash__() method to the size of a Py_ssize_t. This is typically 8 bytes on 64-bit builds and 4 bytes on 32-bit builds. If an object's __hash__() must interoperate on builds of different bit sizes, be sure to check the width on all supported builds. An easy way to do this is with python -c "import sys; print(sys.hash_info.width)".

If a class does not define an __eq__() method it should not define a __hash__() operation either; if it defines __eq__() but not __hash__(), its instances will not be usable as items in hashable collections. If a class defines mutable objects and implements an __eq__() method, it should not implement __hash__(), since the implementation of hashable collections requires that a key's hash value is immutable (if the object's hash value changes, it will be in the wrong hash bucket).

User-defined classes have __eq__() and __hash__() methods by default (inherited from the object class); with them, all objects compare unequal (except with themselves) and x.__hash__() returns an appropriate value such that x == y implies both that x is y and hash(x) == hash(y).

A class that overrides __eq__() and does not define __hash__() will have its __hash__() implicitly set to None. When the __hash__() method of a class is None, instances of the class will raise an appropriate TypeError when a program attempts to retrieve their hash value, and will also be correctly identified as unhashable when checking isinstance(obj, collections.abc.Hashable).

If a class that overrides __eq__() needs to retain the implementation of __hash__() from a parent class, the interpreter must be told this explicitly by setting __hash__ = <ParentClass>.__hash__.

If a class that does not override __eq__() wishes to suppress hash support, it should include __hash__ = None in the class definition. A class which defines its own __hash__() that explicitly raises a TypeError would be incorrectly identified as hashable by an isinstance(obj, collections.abc.Hashable) call.

備註

By default, the __hash__() values of str and bytes objects are "salted" with an unpredictable random value. Although they remain constant within an individual Python process, they are not predictable between repeated invocations of Python.

This is intended to provide protection against a denial-of-service caused by carefully chosen inputs that exploit the worst case performance of a dict insertion, O(n²) complexity. See http://ocert.org/advisories/ocert-2011-003.html for details.

Changing hash values affects the iteration order of sets. Python has never made guarantees about this ordering (and it typically varies between 32-bit and 64-bit builds).

另請參閱 PYTHONHASHSEED。

在 3.3 版的變更: Hash randomization is enabled by default.

object.__bool__(self)

Called to implement truth value testing and the built-in operation bool(); should return False or True. When this method is not defined, __len__() is called, if it is defined, and the object is considered true if its result is nonzero. If a class defines neither __len__() nor __bool__() (which is true of the object class itself), all its instances are considered true.

3.3.2. Customizing attribute access

The following methods can be defined to customize the meaning of attribute access (use of, assignment to, or deletion of x.name) for class instances.

object.__getattr__(self, name)

Called when the default attribute access fails with an AttributeError (either __getattribute__() raises an AttributeError because name is not an instance attribute or an attribute in the class tree for self; or __get__() of a name property raises AttributeError). This method should either return the (computed) attribute value or raise an AttributeError exception. The object class itself does not provide this method.

Note that if the attribute is found through the normal mechanism, __getattr__() is not called. (This is an intentional asymmetry between __getattr__() and __setattr__().) This is done both for efficiency reasons and because otherwise __getattr__() would have no way to access other attributes of the instance. Note that at least for instance variables, you can take total control by not inserting any values in the instance attribute dictionary (but instead inserting them in another object). See the __getattribute__() method below for a way to actually get total control over attribute access.

object.__getattribute__(self, name)

Called unconditionally to implement attribute accesses for instances of the class. If the class also defines __getattr__(), the latter will not be called unless __getattribute__() either calls it explicitly or raises an AttributeError. This method should return the (computed) attribute value or raise an AttributeError exception. In order to avoid infinite recursion in this method, its implementation should always call the base class method with the same name to access any attributes it needs, for example, object.__getattribute__(self, name).

備註

This method may still be bypassed when looking up special methods as the result of implicit invocation via language syntax or built-in functions. See Special method lookup.

For certain sensitive attribute accesses, raises an auditing event object.__getattr__ with arguments obj and name.

object.__setattr__(self, name, value)

Called when an attribute assignment is attempted. This is called instead of the normal mechanism (i.e. store the value in the instance dictionary). name is the attribute name, value is the value to be assigned to it.

If __setattr__() wants to assign to an instance attribute, it should call the base class method with the same name, for example, object.__setattr__(self, name, value).

For certain sensitive attribute assignments, raises an auditing event object.__setattr__ with arguments obj, name, value.

object.__delattr__(self, name)

Like __setattr__() but for attribute deletion instead of assignment. This should only be implemented if del obj.name is meaningful for the object.

For certain sensitive attribute deletions, raises an auditing event object.__delattr__ with arguments obj and name.

object.__dir__(self)

Called when dir() is called on the object. An iterable must be returned. dir() converts the returned iterable to a list and sorts it.

3.3.2.1. Customizing module attribute access

module.__getattr__()

module.__dir__()

Special names __getattr__ and __dir__ can be also used to customize access to module attributes. The __getattr__ function at the module level should accept one argument which is the name of an attribute and return the computed value or raise an AttributeError. If an attribute is not found on a module object through the normal lookup, i.e. object.__getattribute__(), then __getattr__ is searched in the module __dict__ before raising an AttributeError. If found, it is called with the attribute name and the result is returned.

The __dir__ function should accept no arguments, and return an iterable of strings that represents the names accessible on module. If present, this function overrides the standard dir() search on a module.

module.__class__

For a more fine grained customization of the module behavior (setting attributes, properties, etc.), one can set the __class__ attribute of a module object to a subclass of types.ModuleType. For example:

import sys
from types import ModuleType

class VerboseModule(ModuleType):
    def __repr__(self):
        return f'Verbose {self.__name__}'

    def __setattr__(self, attr, value):
        print(f'Setting {attr}...')
        super().__setattr__(attr, value)

sys.modules[__name__].__class__ = VerboseModule

備註

Defining module __getattr__ and setting module __class__ only affect lookups made using the attribute access syntax -- directly accessing the module globals (whether by code within the module, or via a reference to the module's globals dictionary) is unaffected.

在 3.5 版的變更: __class__ 模組屬性現在是可寫入的。

在 3.7 版被加入: __getattr__ 和 __dir__ 模組屬性。

也參考

PEP 562 [https://peps.python.org/pep-0562/] - 模組 __getattr__ 和 __dir__

Describes the __getattr__ and __dir__ functions on modules.

3.3.2.2. 實作描述器

The following methods only apply when an instance of the class containing the method (a so-called descriptor class) appears in an owner class (the descriptor must be in either the owner's class dictionary or in the class dictionary for one of its parents). In the examples below, "the attribute" refers to the attribute whose name is the key of the property in the owner class' __dict__. The object class itself does not implement any of these protocols.

object.__get__(self, instance, owner=None)

Called to get the attribute of the owner class (class attribute access) or of an instance of that class (instance attribute access). The optional owner argument is the owner class, while instance is the instance that the attribute was accessed through, or None when the attribute is accessed through the owner.

This method should return the computed attribute value or raise an AttributeError exception.

PEP 252 [https://peps.python.org/pep-0252/] specifies that __get__() is callable with one or two arguments. Python's own built-in descriptors support this specification; however, it is likely that some third-party tools have descriptors that require both arguments. Python's own __getattribute__() implementation always passes in both arguments whether they are required or not.

object.__set__(self, instance, value)

Called to set the attribute on an instance instance of the owner class to a new value, value.

Note, adding __set__() or __delete__() changes the kind of descriptor to a "data descriptor". See Invoking Descriptors for more details.

object.__delete__(self, instance)

Called to delete the attribute on an instance instance of the owner class.

Instances of descriptors may also have the __objclass__ attribute present:

object.__objclass__

The attribute __objclass__ is interpreted by the inspect module as specifying the class where this object was defined (setting this appropriately can assist in runtime introspection of dynamic class attributes). For callables, it may indicate that an instance of the given type (or a subclass) is expected or required as the first positional argument (for example, CPython sets this attribute for unbound methods that are implemented in C).

3.3.2.3. Invoking Descriptors

In general, a descriptor is an object attribute with "binding behavior", one whose attribute access has been overridden by methods in the descriptor protocol: __get__(), __set__(), and __delete__(). If any of those methods are defined for an object, it is said to be a descriptor.

The default behavior for attribute access is to get, set, or delete the attribute from an object's dictionary. For instance, a.x has a lookup chain starting with a.__dict__['x'], then type(a).__dict__['x'], and continuing through the base classes of type(a) excluding metaclasses.

However, if the looked-up value is an object defining one of the descriptor methods, then Python may override the default behavior and invoke the descriptor method instead. Where this occurs in the precedence chain depends on which descriptor methods were defined and how they were called.

The starting point for descriptor invocation is a binding, a.x. How the arguments are assembled depends on a:

直接呼叫

The simplest and least common call is when user code directly invokes a descriptor method: x.__get__(a).

Instance Binding

If binding to an object instance, a.x is transformed into the call: type(a).__dict__['x'].__get__(a, type(a)).

Class Binding

If binding to a class, A.x is transformed into the call: A.__dict__['x'].__get__(None, A).

Super Binding

A dotted lookup such as super(A, a).x searches a.__class__.__mro__ for a base class B following A and then returns B.__dict__['x'].__get__(a, A). If not a descriptor, x is returned unchanged.

For instance bindings, the precedence of descriptor invocation depends on which descriptor methods are defined. A descriptor can define any combination of __get__(), __set__() and __delete__(). If it does not define __get__(), then accessing the attribute will return the descriptor object itself unless there is a value in the object's instance dictionary. If the descriptor defines __set__() and/or __delete__(), it is a data descriptor; if it defines neither, it is a non-data descriptor. Normally, data descriptors define both __get__() and __set__(), while non-data descriptors have just the __get__() method. Data descriptors with __get__() and __set__() (and/or __delete__()) defined always override a redefinition in an instance dictionary. In contrast, non-data descriptors can be overridden by instances.

Python methods (including those decorated with @staticmethod and @classmethod) are implemented as non-data descriptors. Accordingly, instances can redefine and override methods. This allows individual instances to acquire behaviors that differ from other instances of the same class.

The property() function is implemented as a data descriptor. Accordingly, instances cannot override the behavior of a property.

3.3.2.4. __slots__

__slots__ allow us to explicitly declare data members (like properties) and deny the creation of __dict__ and __weakref__ (unless explicitly declared in __slots__ or available in a parent.)

The space saved over using __dict__ can be significant. Attribute lookup speed can be significantly improved as well.

object.__slots__

This class variable can be assigned a string, iterable, or sequence of strings with variable names used by instances. __slots__ reserves space for the declared variables and prevents the automatic creation of __dict__ and __weakref__ for each instance.

Notes on using __slots__:

When inheriting from a class without __slots__, the __dict__ and __weakref__ attribute of the instances will always be accessible.

Without a __dict__ variable, instances cannot be assigned new variables not listed in the __slots__ definition. Attempts to assign to an unlisted variable name raises AttributeError. If dynamic assignment of new variables is desired, then add '__dict__' to the sequence of strings in the __slots__ declaration.

Without a __weakref__ variable for each instance, classes defining __slots__ do not support weak references to its instances. If weak reference support is needed, then add '__weakref__' to the sequence of strings in the __slots__ declaration.

__slots__ are implemented at the class level by creating descriptors for each variable name. As a result, class attributes cannot be used to set default values for instance variables defined by __slots__; otherwise, the class attribute would overwrite the descriptor assignment.

The action of a __slots__ declaration is not limited to the class where it is defined. __slots__ declared in parents are available in child classes. However, instances of a child subclass will get a __dict__ and __weakref__ unless the subclass also defines __slots__ (which should only contain names of any additional slots).

If a class defines a slot also defined in a base class, the instance variable defined by the base class slot is inaccessible (except by retrieving its descriptor directly from the base class). This renders the meaning of the program undefined. In the future, a check may be added to prevent this.

TypeError will be raised if nonempty __slots__ are defined for a class derived from a "variable-length" built-in type such as int, bytes, and tuple.

Any non-string iterable may be assigned to __slots__.

If a dictionary is used to assign __slots__, the dictionary keys will be used as the slot names. The values of the dictionary can be used to provide per-attribute docstrings that will be recognised by inspect.getdoc() and displayed in the output of help().

__class__ assignment works only if both classes have the same __slots__.

Multiple inheritance with multiple slotted parent classes can be used, but only one parent is allowed to have attributes created by slots (the other bases must have empty slot layouts) - violations raise TypeError.

If an iterator is used for __slots__ then a descriptor is created for each of the iterator's values. However, the __slots__ attribute will be an empty iterator.

3.3.3. Customizing class creation

Whenever a class inherits from another class, __init_subclass__() is called on the parent class. This way, it is possible to write classes which change the behavior of subclasses. This is closely related to class decorators, but where class decorators only affect the specific class they're applied to, __init_subclass__ solely applies to future subclasses of the class defining the method.

classmethod object.__init_subclass__(cls)

This method is called whenever the containing class is subclassed. cls is then the new subclass. If defined as a normal instance method, this method is implicitly converted to a class method.

Keyword arguments which are given to a new class are passed to the parent class's __init_subclass__. For compatibility with other classes using __init_subclass__, one should take out the needed keyword arguments and pass the others over to the base class, as in:

class Philosopher:
    def __init_subclass__(cls, /, default_name, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.default_name = default_name

class AustralianPhilosopher(Philosopher, default_name="Bruce"):
    pass

The default implementation object.__init_subclass__ does nothing, but raises an error if it is called with any arguments.

備註

The metaclass hint metaclass is consumed by the rest of the type machinery, and is never passed to __init_subclass__ implementations. The actual metaclass (rather than the explicit hint) can be accessed as type(cls).

在 3.6 版被加入.

When a class is created, type.__new__() scans the class variables and makes callbacks to those with a __set_name__() hook.

object.__set_name__(self, owner, name)

Automatically called at the time the owning class owner is created. The object has been assigned to name in that class:

class A:
    x = C()  # 自動呼叫：x.__set_name__(A, 'x')

If the class variable is assigned after the class is created, __set_name__() will not be called automatically. If needed, __set_name__() can be called directly:

class A:
   pass

c = C()
A.x = c                  # The hook is not called
c.__set_name__(A, 'x')   # Manually invoke the hook

更多細節請見 Creating the class object。

在 3.6 版被加入.

3.3.3.1. Metaclasses

By default, classes are constructed using type(). The class body is executed in a new namespace and the class name is bound locally to the result of type(name, bases, namespace).

The class creation process can be customized by passing the metaclass keyword argument in the class definition line, or by inheriting from an existing class that included such an argument. In the following example, both MyClass and MySubclass are instances of Meta:

class Meta(type):
    pass

class MyClass(metaclass=Meta):
    pass

class MySubclass(MyClass):
    pass

Any other keyword arguments that are specified in the class definition are passed through to all metaclass operations described below.

When a class definition is executed, the following steps occur:

MRO entries are resolved;

the appropriate metaclass is determined;

the class namespace is prepared;

the class body is executed;

the class object is created.

3.3.3.2. Resolving MRO entries

object.__mro_entries__(self, bases)

If a base that appears in a class definition is not an instance of type, then an __mro_entries__() method is searched on the base. If an __mro_entries__() method is found, the base is substituted with the result of a call to __mro_entries__() when creating the class. The method is called with the original bases tuple passed to the bases parameter, and must return a tuple of classes that will be used instead of the base. The returned tuple may be empty: in these cases, the original base is ignored.

也參考

types.resolve_bases()

Dynamically resolve bases that are not instances of type.

types.get_original_bases()

Retrieve a class's "original bases" prior to modifications by __mro_entries__().

PEP 560 [https://peps.python.org/pep-0560/]

Core support for typing module and generic types.

3.3.3.3. Determining the appropriate metaclass

The appropriate metaclass for a class definition is determined as follows:

if no bases and no explicit metaclass are given, then type() is used;

if an explicit metaclass is given and it is not an instance of type(), then it is used directly as the metaclass;

if an instance of type() is given as the explicit metaclass, or bases are defined, then the most derived metaclass is used.

The most derived metaclass is selected from the explicitly specified metaclass (if any) and the metaclasses (i.e. type(cls)) of all specified base classes. The most derived metaclass is one which is a subtype of all of these candidate metaclasses. If none of the candidate metaclasses meets that criterion, then the class definition will fail with TypeError.

3.3.3.4. Preparing the class namespace

Once the appropriate metaclass has been identified, then the class namespace is prepared. If the metaclass has a __prepare__ attribute, it is called as namespace = metaclass.__prepare__(name, bases, **kwds) (where the additional keyword arguments, if any, come from the class definition). The __prepare__ method should be implemented as a classmethod. The namespace returned by __prepare__ is passed in to __new__, but when the final class object is created the namespace is copied into a new dict.

If the metaclass has no __prepare__ attribute, then the class namespace is initialised as an empty ordered mapping.

也參考

PEP 3115 [https://peps.python.org/pep-3115/] - Metaclasses in Python 3000

Introduced the __prepare__ namespace hook

3.3.3.5. Executing the class body

The class body is executed (approximately) as exec(body, globals(), namespace). The key difference from a normal call to exec() is that lexical scoping allows the class body (including any methods) to reference names from the current and outer scopes when the class definition occurs inside a function.

However, even when the class definition occurs inside the function, methods defined inside the class still cannot see names defined at the class scope. Class variables must be accessed through the first parameter of instance or class methods, or through the implicit lexically scoped __class__ reference described in the next section.

3.3.3.6. Creating the class object

Once the class namespace has been populated by executing the class body, the class object is created by calling metaclass(name, bases, namespace, **kwds) (the additional keywords passed here are the same as those passed to __prepare__).

This class object is the one that will be referenced by the zero-argument form of super(). __class__ is an implicit closure reference created by the compiler if any methods in a class body refer to either __class__ or super. This allows the zero argument form of super() to correctly identify the class being defined based on lexical scoping, while the class or instance that was used to make the current call is identified based on the first argument passed to the method.

CPython 實作細節： In CPython 3.6 and later, the __class__ cell is passed to the metaclass as a __classcell__ entry in the class namespace. If present, this must be propagated up to the type.__new__ call in order for the class to be initialised correctly. Failing to do so will result in a RuntimeError in Python 3.8.

When using the default metaclass type, or any metaclass that ultimately calls type.__new__, the following additional customization steps are invoked after creating the class object:

The type.__new__ method collects all of the attributes in the class namespace that define a __set_name__() method;

Those __set_name__ methods are called with the class being defined and the assigned name of that particular attribute;

The __init_subclass__() hook is called on the immediate parent of the new class in its method resolution order.

After the class object is created, it is passed to the class decorators included in the class definition (if any) and the resulting object is bound in the local namespace as the defined class.

When a new class is created by type.__new__, the object provided as the namespace parameter is copied to a new ordered mapping and the original object is discarded. The new copy is wrapped in a read-only proxy, which becomes the __dict__ attribute of the class object.

也參考

PEP 3135 [https://peps.python.org/pep-3135/] - New super

Describes the implicit __class__ closure reference

3.3.3.7. Uses for metaclasses

The potential uses for metaclasses are boundless. Some ideas that have been explored include enum, logging, interface checking, automatic delegation, automatic property creation, proxies, frameworks, and automatic resource locking/synchronization.

3.3.4. Customizing instance and subclass checks

The following methods are used to override the default behavior of the isinstance() and issubclass() built-in functions.

In particular, the metaclass abc.ABCMeta implements these methods in order to allow the addition of Abstract Base Classes (ABCs) as "virtual base classes" to any class or type (including built-in types), including other ABCs.

type.__instancecheck__(self, instance)

Return true if instance should be considered a (direct or indirect) instance of class. If defined, called to implement isinstance(instance, class).

type.__subclasscheck__(self, subclass)

Return true if subclass should be considered a (direct or indirect) subclass of class. If defined, called to implement issubclass(subclass, class).

Note that these methods are looked up on the type (metaclass) of a class. They cannot be defined as class methods in the actual class. This is consistent with the lookup of special methods that are called on instances, only in this case the instance is itself a class.

也參考

PEP 3119 [https://peps.python.org/pep-3119/] - Introducing Abstract Base Classes

Includes the specification for customizing isinstance() and issubclass() behavior through __instancecheck__() and __subclasscheck__(), with motivation for this functionality in the context of adding Abstract Base Classes (see the abc module) to the language.

3.3.5. Emulating generic types

When using type annotations, it is often useful to parameterize a generic type using Python's square-brackets notation. For example, the annotation list[int] might be used to signify a list in which all the elements are of type int.

也參考

PEP 484 [https://peps.python.org/pep-0484/] - 型別提示

引入 Python 的型別註釋框架

泛型別名型別

Documentation for objects representing parameterized generic classes

泛型, user-defined generics and typing.Generic

Documentation on how to implement generic classes that can be parameterized at runtime and understood by static type-checkers.

A class can generally only be parameterized if it defines the special class method __class_getitem__().

classmethod object.__class_getitem__(cls, key)

Return an object representing the specialization of a generic class by type arguments found in key.

When defined on a class, __class_getitem__() is automatically a class method. As such, there is no need for it to be decorated with @classmethod when it is defined.

3.3.5.1. The purpose of __class_getitem__

The purpose of __class_getitem__() is to allow runtime parameterization of standard-library generic classes in order to more easily apply type hints to these classes.

To implement custom generic classes that can be parameterized at runtime and understood by static type-checkers, users should either inherit from a standard library class that already implements __class_getitem__(), or inherit from typing.Generic, which has its own implementation of __class_getitem__().

Custom implementations of __class_getitem__() on classes defined outside of the standard library may not be understood by third-party type-checkers such as mypy. Using __class_getitem__() on any class for purposes other than type hinting is discouraged.

3.3.5.2. __class_getitem__ versus __getitem__

Usually, the subscription of an object using square brackets will call the __getitem__() instance method defined on the object's class. However, if the object being subscribed is itself a class, the class method __class_getitem__() may be called instead. __class_getitem__() should return a GenericAlias object if it is properly defined.

Presented with the expression obj[x], the Python interpreter follows something like the following process to decide whether __getitem__() or __class_getitem__() should be called:

from inspect import isclass

def subscribe(obj, x):
    """Return the result of the expression 'obj[x]'"""

    class_of_obj = type(obj)

    # If the class of obj defines __getitem__,
    # call class_of_obj.__getitem__(obj, x)
    if hasattr(class_of_obj, '__getitem__'):
        return class_of_obj.__getitem__(obj, x)

    # Else, if obj is a class and defines __class_getitem__,
    # call obj.__class_getitem__(x)
    elif isclass(obj) and hasattr(obj, '__class_getitem__'):
        return obj.__class_getitem__(x)

    # Else, raise an exception
    else:
        raise TypeError(
            f"'{class_of_obj.__name__}' object is not subscriptable"
        )

In Python, all classes are themselves instances of other classes. The class of a class is known as that class's metaclass, and most classes have the type class as their metaclass. type does not define __getitem__(), meaning that expressions such as list[int], dict[str, float] and tuple[str, bytes] all result in __class_getitem__() being called:

>>> # list has class "type" as its metaclass, like most classes:
>>> type(list)
<class 'type'>
>>> type(dict) == type(list) == type(tuple) == type(str) == type(bytes)
True
>>> # "list[int]" calls "list.__class_getitem__(int)"
>>> list[int]
list[int]
>>> # list.__class_getitem__ returns a GenericAlias object:
>>> type(list[int])
<class 'types.GenericAlias'>

However, if a class has a custom metaclass that defines __getitem__(), subscribing the class may result in different behaviour. An example of this can be found in the enum module:

>>> from enum import Enum
>>> class Menu(Enum):
...     """A breakfast menu"""
...     SPAM = 'spam'
...     BACON = 'bacon'
...
>>> # Enum classes have a custom metaclass:
>>> type(Menu)
<class 'enum.EnumMeta'>
>>> # EnumMeta defines __getitem__,
>>> # so __class_getitem__ is not called,
>>> # and the result is not a GenericAlias object:
>>> Menu['SPAM']
<Menu.SPAM: 'spam'>
>>> type(Menu['SPAM'])
<enum 'Menu'>

也參考

PEP 560 [https://peps.python.org/pep-0560/] - Core Support for typing module and generic types

Introducing __class_getitem__(), and outlining when a subscription results in __class_getitem__() being called instead of __getitem__()

3.3.6. Emulating callable objects

object.__call__(self[, args...])

Called when the instance is "called" as a function; if this method is defined, x(arg1, arg2, ...) roughly translates to type(x).__call__(x, arg1, ...). The object class itself does not provide this method.

3.3.7. Emulating container types

The following methods can be defined to implement container objects. None of them are provided by the object class itself. Containers usually are sequences (such as lists or tuples) or mappings (like dictionaries), but can represent other containers as well. The first set of methods is used either to emulate a sequence or to emulate a mapping; the difference is that for a sequence, the allowable keys should be the integers k for which 0 <= k < N where N is the length of the sequence, or slice objects, which define a range of items. It is also recommended that mappings provide the methods keys(), values(), items(), get(), clear(), setdefault(), pop(), popitem(), copy(), and update() behaving similar to those for Python's standard dictionary objects. The collections.abc module provides a MutableMapping abstract base class to help create those methods from a base set of __getitem__(), __setitem__(), __delitem__(), and keys().

Mutable sequences should provide methods append(), clear(), count(), extend(), index(), insert(), pop(), remove(), and reverse(), like Python standard list objects. Finally, sequence types should implement addition (meaning concatenation) and multiplication (meaning repetition) by defining the methods __add__(), __radd__(), __iadd__(), __mul__(), __rmul__() and __imul__() described below; they should not define other numerical operators.

It is recommended that both mappings and sequences implement the __contains__() method to allow efficient use of the in operator; for mappings, in should search the mapping's keys; for sequences, it should search through the values. It is further recommended that both mappings and sequences implement the __iter__() method to allow efficient iteration through the container; for mappings, __iter__() should iterate through the object's keys; for sequences, it should iterate through the values.

object.__len__(self)

Called to implement the built-in function len(). Should return the length of the object, an integer >= 0. Also, an object that doesn't define a __bool__() method and whose __len__() method returns zero is considered to be false in a Boolean context.

CPython 實作細節： In CPython, the length is required to be at most sys.maxsize. If the length is larger than sys.maxsize some features (such as len()) may raise OverflowError. To prevent raising OverflowError by truth value testing, an object must define a __bool__() method.

object.__length_hint__(self)

Called to implement operator.length_hint(). Should return an estimated length for the object (which may be greater or less than the actual length). The length must be an integer >= 0. The return value may also be NotImplemented, which is treated the same as if the __length_hint__ method didn't exist at all. This method is purely an optimization and is never required for correctness.

在 3.4 版被加入.

備註

Slicing is done exclusively with the following three methods. A call like

a[1:2] = b

is translated to

a[slice(1, 2, None)] = b

and so forth. Missing slice items are always filled in with None.

object.__getitem__(self, key)

Called to implement evaluation of self[key]. For sequence types, the accepted keys should be integers. Optionally, they may support slice objects as well. Negative index support is also optional. If key is of an inappropriate type, TypeError may be raised; if key is a value outside the set of indexes for the sequence (after any special interpretation of negative values), IndexError should be raised. For mapping types, if key is missing (not in the container), KeyError should be raised.

備註

for loops expect that an IndexError will be raised for illegal indexes to allow proper detection of the end of the sequence.

備註

When subscripting a class, the special class method __class_getitem__() may be called instead of __getitem__(). See __class_getitem__ versus __getitem__ for more details.

object.__setitem__(self, key, value)

Called to implement assignment to self[key]. Same note as for __getitem__(). This should only be implemented for mappings if the objects support changes to the values for keys, or if new keys can be added, or for sequences if elements can be replaced. The same exceptions should be raised for improper key values as for the __getitem__() method.

object.__delitem__(self, key)

Called to implement deletion of self[key]. Same note as for __getitem__(). This should only be implemented for mappings if the objects support removal of keys, or for sequences if elements can be removed from the sequence. The same exceptions should be raised for improper key values as for the __getitem__() method.

object.__missing__(self, key)

Called by dict.__getitem__() to implement self[key] for dict subclasses when key is not in the dictionary.

object.__iter__(self)

This method is called when an iterator is required for a container. This method should return a new iterator object that can iterate over all the objects in the container. For mappings, it should iterate over the keys of the container.

object.__reversed__(self)

Called (if present) by the reversed() built-in to implement reverse iteration. It should return a new iterator object that iterates over all the objects in the container in reverse order.

If the __reversed__() method is not provided, the reversed() built-in will fall back to using the sequence protocol (__len__() and __getitem__()). Objects that support the sequence protocol should only provide __reversed__() if they can provide an implementation that is more efficient than the one provided by reversed().

The membership test operators (in and not in) are normally implemented as an iteration through a container. However, container objects can supply the following special method with a more efficient implementation, which also does not require the object be iterable.

object.__contains__(self, item)

Called to implement membership test operators. Should return true if item is in self, false otherwise. For mapping objects, this should consider the keys of the mapping rather than the values or the key-item pairs.

For objects that don't define __contains__(), the membership test first tries iteration via __iter__(), then the old sequence iteration protocol via __getitem__(), see this section in the language reference.

3.3.8. Emulating numeric types

The following methods can be defined to emulate numeric objects. Methods corresponding to operations that are not supported by the particular kind of number implemented (e.g., bitwise operations for non-integral numbers) should be left undefined.

object.__add__(self, other)

object.__sub__(self, other)

object.__mul__(self, other)

object.__matmul__(self, other)

object.__truediv__(self, other)

object.__floordiv__(self, other)

object.__mod__(self, other)

object.__divmod__(self, other)

object.__pow__(self, other[, modulo])

object.__lshift__(self, other)

object.__rshift__(self, other)

object.__and__(self, other)

object.__xor__(self, other)

object.__or__(self, other)

These methods are called to implement the binary arithmetic operations (+, -, *, @, /, //, %, divmod(), pow(), **, <<, >>, &, ^, |). For instance, to evaluate the expression x + y, where x is an instance of a class that has an __add__() method, type(x).__add__(x, y) is called. The __divmod__() method should be the equivalent to using __floordiv__() and __mod__(); it should not be related to __truediv__(). Note that __pow__() should be defined to accept an optional third argument if the three-argument version of the built-in pow() function is to be supported.

If one of those methods does not support the operation with the supplied arguments, it should return NotImplemented.

object.__radd__(self, other)

object.__rsub__(self, other)

object.__rmul__(self, other)

object.__rmatmul__(self, other)

object.__rtruediv__(self, other)

object.__rfloordiv__(self, other)

object.__rmod__(self, other)

object.__rdivmod__(self, other)

object.__rpow__(self, other[, modulo])

object.__rlshift__(self, other)

object.__rrshift__(self, other)

object.__rand__(self, other)

object.__rxor__(self, other)

object.__ror__(self, other)

These methods are called to implement the binary arithmetic operations (+, -, *, @, /, //, %, divmod(), pow(), **, <<, >>, &, ^, |) with reflected (swapped) operands. These functions are only called if the operands are of different types, when the left operand does not support the corresponding operation [3], or the right operand's class is derived from the left operand's class. [4] For instance, to evaluate the expression x - y, where y is an instance of a class that has an __rsub__() method, type(y).__rsub__(y, x) is called if type(x).__sub__(x, y) returns NotImplemented or type(y) is a subclass of type(x). [5]

Note that __rpow__() should be defined to accept an optional third argument if the three-argument version of the built-in pow() function is to be supported.

在 3.14 版的變更: Three-argument pow() now try calling __rpow__() if necessary. Previously it was only called in two-argument pow() and the binary power operator.

備註

If the right operand's type is a subclass of the left operand's type and that subclass provides a different implementation of the reflected method for the operation, this method will be called before the left operand's non-reflected method. This behavior allows subclasses to override their ancestors' operations.

object.__iadd__(self, other)

object.__isub__(self, other)

object.__imul__(self, other)

object.__imatmul__(self, other)

object.__itruediv__(self, other)

object.__ifloordiv__(self, other)

object.__imod__(self, other)

object.__ipow__(self, other[, modulo])

object.__ilshift__(self, other)

object.__irshift__(self, other)

object.__iand__(self, other)

object.__ixor__(self, other)

object.__ior__(self, other)

These methods are called to implement the augmented arithmetic assignments (+=, -=, *=, @=, /=, //=, %=, **=, <<=, >>=, &=, ^=, |=). These methods should attempt to do the operation in-place (modifying self) and return the result (which could be, but does not have to be, self). If a specific method is not defined, or if that method returns NotImplemented, the augmented assignment falls back to the normal methods. For instance, if x is an instance of a class with an __iadd__() method, x += y is equivalent to x = x.__iadd__(y) . If __iadd__() does not exist, or if x.__iadd__(y) returns NotImplemented, x.__add__(y) and y.__radd__(x) are considered, as with the evaluation of x + y. In certain situations, augmented assignment can result in unexpected errors (see 為什麼 a_tuple[i] += ['item'] 做加法時會引發例外？), but this behavior is in fact part of the data model.

object.__neg__(self)

object.__pos__(self)

object.__abs__(self)

object.__invert__(self)

Called to implement the unary arithmetic operations (-, +, abs() and ~).

object.__complex__(self)

object.__int__(self)

object.__float__(self)

Called to implement the built-in functions complex(), int() and float(). Should return a value of the appropriate type.

object.__index__(self)

Called to implement operator.index(), and whenever Python needs to losslessly convert the numeric object to an integer object (such as in slicing, or in the built-in bin(), hex() and oct() functions). Presence of this method indicates that the numeric object is an integer type. Must return an integer.

If __int__(), __float__() and __complex__() are not defined then corresponding built-in functions int(), float() and complex() fall back to __index__().

object.__round__(self[, ndigits])

object.__trunc__(self)

object.__floor__(self)

object.__ceil__(self)

Called to implement the built-in function round() and math functions trunc(), floor() and ceil(). Unless ndigits is passed to __round__() all these methods should return the value of the object truncated to an Integral (typically an int).

在 3.14 版的變更: int() no longer delegates to the __trunc__() method.

3.3.9. With 陳述式的情境管理器

A context manager is an object that defines the runtime context to be established when executing a with statement. The context manager handles the entry into, and the exit from, the desired runtime context for the execution of the block of code. Context managers are normally invoked using the with statement (described in section with 陳述式), but can also be used by directly invoking their methods.

Typical uses of context managers include saving and restoring various kinds of global state, locking and unlocking resources, closing opened files, etc.

For more information on context managers, see 情境管理器型別. The object class itself does not provide the context manager methods.

object.__enter__(self)

Enter the runtime context related to this object. The with statement will bind this method's return value to the target(s) specified in the as clause of the statement, if any.

object.__exit__(self, exc_type, exc_value, traceback)

Exit the runtime context related to this object. The parameters describe the exception that caused the context to be exited. If the context was exited without an exception, all three arguments will be None.

If an exception is supplied, and the method wishes to suppress the exception (i.e., prevent it from being propagated), it should return a true value. Otherwise, the exception will be processed normally upon exit from this method.

Note that __exit__() methods should not reraise the passed-in exception; this is the caller's responsibility.

也參考

PEP 343 [https://peps.python.org/pep-0343/] - "with" 陳述式

The specification, background, and examples for the Python with statement.

3.3.10. Customizing positional arguments in class pattern matching

When using a class name in a pattern, positional arguments in the pattern are not allowed by default, i.e. case MyClass(x, y) is typically invalid without special support in MyClass. To be able to use that kind of pattern, the class needs to define a __match_args__ attribute.

object.__match_args__

This class variable can be assigned a tuple of strings. When this class is used in a class pattern with positional arguments, each positional argument will be converted into a keyword argument, using the corresponding value in __match_args__ as the keyword. The absence of this attribute is equivalent to setting it to ().

For example, if MyClass.__match_args__ is ("left", "center", "right") that means that case MyClass(x, y) is equivalent to case MyClass(left=x, center=y). Note that the number of arguments in the pattern must be smaller than or equal to the number of elements in __match_args__; if it is larger, the pattern match attempt will raise a TypeError.

在 3.10 版被加入.

也參考

PEP 634 [https://peps.python.org/pep-0634/] - Structural Pattern Matching

The specification for the Python match statement.

3.3.11. Emulating buffer types

The buffer protocol provides a way for Python objects to expose efficient access to a low-level memory array. This protocol is implemented by builtin types such as bytes and memoryview, and third-party libraries may define additional buffer types.

While buffer types are usually implemented in C, it is also possible to implement the protocol in Python.

object.__buffer__(self, flags)

Called when a buffer is requested from self (for example, by the memoryview constructor). The flags argument is an integer representing the kind of buffer requested, affecting for example whether the returned buffer is read-only or writable. inspect.BufferFlags provides a convenient way to interpret the flags. The method must return a memoryview object.

object.__release_buffer__(self, buffer)

Called when a buffer is no longer needed. The buffer argument is a memoryview object that was previously returned by __buffer__(). The method must release any resources associated with the buffer. This method should return None. Buffer objects that do not need to perform any cleanup are not required to implement this method.

在 3.12 版被加入.

也參考

PEP 688 [https://peps.python.org/pep-0688/] - Making the buffer protocol accessible in Python

Introduces the Python __buffer__ and __release_buffer__ methods.

collections.abc.Buffer

ABC for buffer types.

3.3.12. Annotations

Functions, classes, and modules may contain annotations, which are a way to associate information (usually type hints) with a symbol.

object.__annotations__

This attribute contains the annotations for an object. It is lazily evaluated, so accessing the attribute may execute arbitrary code and raise exceptions. If evaluation is successful, the attribute is set to a dictionary mapping from variable names to annotations.

在 3.14 版的變更: Annotations are now lazily evaluated.

object.__annotate__(format)

An annotate function. Returns a new dictionary object mapping attribute/parameter names to their annotation values.

Takes a format parameter specifying the format in which annotations values should be provided. It must be a member of the annotationlib.Format enum, or an integer with a value corresponding to a member of the enum.

If an annotate function doesn't support the requested format, it must raise NotImplementedError. Annotate functions must always support VALUE format; they must not raise NotImplementedError() when called with this format.

When called with VALUE format, an annotate function may raise NameError; it must not raise NameError when called requesting any other format.

If an object does not have any annotations, __annotate__ should preferably be set to None (it can’t be deleted), rather than set to a function that returns an empty dict.

在 3.14 版被加入.

也參考

PEP 649 [https://peps.python.org/pep-0649/] --- Deferred evaluation of annotation using descriptors

Introduces lazy evaluation of annotations and the __annotate__ function.

3.3.13. Special method lookup

For custom classes, implicit invocations of special methods are only guaranteed to work correctly if defined on an object's type, not in the object's instance dictionary. That behaviour is the reason why the following code raises an exception:

>>> class C:
...     pass
...
>>> c = C()
>>> c.__len__ = lambda: 5
>>> len(c)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object of type 'C' has no len()

The rationale behind this behaviour lies with a number of special methods such as __hash__() and __repr__() that are implemented by all objects, including type objects. If the implicit lookup of these methods used the conventional lookup process, they would fail when invoked on the type object itself:

>>> 1 .__hash__() == hash(1)
True
>>> int.__hash__() == hash(int)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: descriptor '__hash__' of 'int' object needs an argument

Incorrectly attempting to invoke an unbound method of a class in this way is sometimes referred to as 'metaclass confusion', and is avoided by bypassing the instance when looking up special methods:

>>> type(1).__hash__(1) == hash(1)
True
>>> type(int).__hash__(int) == hash(int)
True

In addition to bypassing any instance attributes in the interest of correctness, implicit special method lookup generally also bypasses the __getattribute__() method even of the object's metaclass:

>>> class Meta(type):
...     def __getattribute__(*args):
...         print("Metaclass getattribute invoked")
...         return type.__getattribute__(*args)
...
>>> class C(object, metaclass=Meta):
...     def __len__(self):
...         return 10
...     def __getattribute__(*args):
...         print("Class getattribute invoked")
...         return object.__getattribute__(*args)
...
>>> c = C()
>>> c.__len__()                 # Explicit lookup via instance
Class getattribute invoked
10
>>> type(c).__len__(c)          # Explicit lookup via type
Metaclass getattribute invoked
10
>>> len(c)                      # Implicit lookup
10

Bypassing the __getattribute__() machinery in this fashion provides significant scope for speed optimisations within the interpreter, at the cost of some flexibility in the handling of special methods (the special method must be set on the class object itself in order to be consistently invoked by the interpreter).

3.4. 協程

3.4.1. Awaitable Objects

An awaitable object generally implements an __await__() method. Coroutine objects returned from async def functions are awaitable.

備註

The generator iterator objects returned from generators decorated with types.coroutine() are also awaitable, but they do not implement __await__().

object.__await__(self)

Must return an iterator. Should be used to implement awaitable objects. For instance, asyncio.Future implements this method to be compatible with the await expression. The object class itself is not awaitable and does not provide this method.

備註

The language doesn't place any restriction on the type or value of the objects yielded by the iterator returned by __await__, as this is specific to the implementation of the asynchronous execution framework (e.g. asyncio) that will be managing the awaitable object.

在 3.5 版被加入.

也參考

PEP 492 [https://peps.python.org/pep-0492/] for additional information about awaitable objects.

3.4.2. 協程物件

Coroutine objects are awaitable objects. A coroutine's execution can be controlled by calling __await__() and iterating over the result. When the coroutine has finished executing and returns, the iterator raises StopIteration, and the exception's value attribute holds the return value. If the coroutine raises an exception, it is propagated by the iterator. Coroutines should not directly raise unhandled StopIteration exceptions.

Coroutines also have the methods listed below, which are analogous to those of generators (see Generator-iterator methods). However, unlike generators, coroutines do not directly support iteration.

在 3.5.2 版的變更: It is a RuntimeError to await on a coroutine more than once.

coroutine.send(value)

Starts or resumes execution of the coroutine. If value is None, this is equivalent to advancing the iterator returned by __await__(). If value is not None, this method delegates to the send() method of the iterator that caused the coroutine to suspend. The result (return value, StopIteration, or other exception) is the same as when iterating over the __await__() return value, described above.

coroutine.throw(value)

coroutine.throw(type[, value[, traceback]])

Raises the specified exception in the coroutine. This method delegates to the throw() method of the iterator that caused the coroutine to suspend, if it has such a method. Otherwise, the exception is raised at the suspension point. The result (return value, StopIteration, or other exception) is the same as when iterating over the __await__() return value, described above. If the exception is not caught in the coroutine, it propagates back to the caller.

在 3.12 版的變更: The second signature (type[, value[, traceback]]) is deprecated and may be removed in a future version of Python.

coroutine.close()

Causes the coroutine to clean itself up and exit. If the coroutine is suspended, this method first delegates to the close() method of the iterator that caused the coroutine to suspend, if it has such a method. Then it raises GeneratorExit at the suspension point, causing the coroutine to immediately clean itself up. Finally, the coroutine is marked as having finished executing, even if it was never started.

Coroutine objects are automatically closed using the above process when they are about to be destroyed.

3.4.3. Asynchronous Iterators

An asynchronous iterator can call asynchronous code in its __anext__ method.

Asynchronous iterators can be used in an async for statement.

The object class itself does not provide these methods.

object.__aiter__(self)

Must return an asynchronous iterator object.

object.__anext__(self)

Must return an awaitable resulting in a next value of the iterator. Should raise a StopAsyncIteration error when the iteration is over.

An example of an asynchronous iterable object:

class Reader:
    async def readline(self):
        ...

    def __aiter__(self):
        return self

    async def __anext__(self):
        val = await self.readline()
        if val == b'':
            raise StopAsyncIteration
        return val

在 3.5 版被加入.

在 3.7 版的變更: Prior to Python 3.7, __aiter__() could return an awaitable that would resolve to an asynchronous iterator.

Starting with Python 3.7, __aiter__() must return an asynchronous iterator object. Returning anything else will result in a TypeError error.

3.4.4. Asynchronous Context Managers

An asynchronous context manager is a context manager that is able to suspend execution in its __aenter__ and __aexit__ methods.

Asynchronous context managers can be used in an async with statement.

The object class itself does not provide these methods.

object.__aenter__(self)

Semantically similar to __enter__(), the only difference being that it must return an awaitable.

object.__aexit__(self, exc_type, exc_value, traceback)

Semantically similar to __exit__(), the only difference being that it must return an awaitable.

An example of an asynchronous context manager class:

class AsyncContextManager:
    async def __aenter__(self):
        await log('entering context')

    async def __aexit__(self, exc_type, exc, tb):
        await log('exiting context')

在 3.5 版被加入.

註解

[1]

It is possible in some cases to change an object's type, under certain controlled conditions. It generally isn't a good idea though, since it can lead to some very strange behaviour if it is handled incorrectly.

[2]

The __hash__(), __iter__(), __reversed__(), __contains__(), __class_getitem__() and __fspath__() methods have special handling for this. Others will still raise a TypeError, but may do so by relying on the behavior that None is not callable.

[3]

"Does not support" here means that the class has no such method, or the method returns NotImplemented. Do not set the method to None if you want to force fallback to the right operand's reflected method—that will instead have the opposite effect of explicitly blocking such fallback.

[4]

For operands of the same type, it is assumed that if the non-reflected method (such as __add__()) fails then the operation is not supported, which is why the reflected method is not called.

[5]

If the right operand's type is a subclass of the left operand's type, the reflected method having precedence allows subclasses to override their ancestors' operations.

4. 執行模型

4.1. Structure of a program

A Python program is constructed from code blocks. A block is a piece of Python program text that is executed as a unit. The following are blocks: a module, a function body, and a class definition. Each command typed interactively is a block. A script file (a file given as standard input to the interpreter or specified as a command line argument to the interpreter) is a code block. A script command (a command specified on the interpreter command line with the -c option) is a code block. A module run as a top level script (as module __main__) from the command line using a -m argument is also a code block. The string argument passed to the built-in functions eval() and exec() is a code block.

A code block is executed in an execution frame. A frame contains some administrative information (used for debugging) and determines where and how execution continues after the code block's execution has completed.

4.2. Naming and binding

4.2.1. Binding of names

Names refer to objects. Names are introduced by name binding operations.

The following constructs bind names:

formal parameters to functions,

class definitions,

function definitions,

assignment expressions,

targets that are identifiers if occurring in an assignment:

for loop header,

after as in a with statement, except clause, except* clause, or in the as-pattern in structural pattern matching,

in a capture pattern in structural pattern matching

import 陳述式。

type 陳述式。

type parameter lists.

The import statement of the form from ... import * binds all names defined in the imported module, except those beginning with an underscore. This form may only be used at the module level.

A target occurring in a del statement is also considered bound for this purpose (though the actual semantics are to unbind the name).

Each assignment or import statement occurs within a block defined by a class or function definition or at the module level (the top-level code block).

If a name is bound in a block, it is a local variable of that block, unless declared as nonlocal or global. If a name is bound at the module level, it is a global variable. (The variables of the module code block are local and global.) If a variable is used in a code block but not defined there, it is a free variable.

Each occurrence of a name in the program text refers to the binding of that name established by the following name resolution rules.

4.2.2. Resolution of names

A scope defines the visibility of a name within a block. If a local variable is defined in a block, its scope includes that block. If the definition occurs in a function block, the scope extends to any blocks contained within the defining one, unless a contained block introduces a different binding for the name.

When a name is used in a code block, it is resolved using the nearest enclosing scope. The set of all such scopes visible to a code block is called the block's environment.

When a name is not found at all, a NameError exception is raised. If the current scope is a function scope, and the name refers to a local variable that has not yet been bound to a value at the point where the name is used, an UnboundLocalError exception is raised. UnboundLocalError is a subclass of NameError.

If a name binding operation occurs anywhere within a code block, all uses of the name within the block are treated as references to the current block. This can lead to errors when a name is used within a block before it is bound. This rule is subtle. Python lacks declarations and allows name binding operations to occur anywhere within a code block. The local variables of a code block can be determined by scanning the entire text of the block for name binding operations. See the FAQ entry on UnboundLocalError for examples.

If the global statement occurs within a block, all uses of the names specified in the statement refer to the bindings of those names in the top-level namespace. Names are resolved in the top-level namespace by searching the global namespace, i.e. the namespace of the module containing the code block, and the builtins namespace, the namespace of the module builtins. The global namespace is searched first. If the names are not found there, the builtins namespace is searched next. If the names are also not found in the builtins namespace, new variables are created in the global namespace. The global statement must precede all uses of the listed names.

The global statement has the same scope as a name binding operation in the same block. If the nearest enclosing scope for a free variable contains a global statement, the free variable is treated as a global.

The nonlocal statement causes corresponding names to refer to previously bound variables in the nearest enclosing function scope. SyntaxError is raised at compile time if the given name does not exist in any enclosing function scope. Type parameters cannot be rebound with the nonlocal statement.

The namespace for a module is automatically created the first time a module is imported. The main module for a script is always called __main__.

Class definition blocks and arguments to exec() and eval() are special in the context of name resolution. A class definition is an executable statement that may use and define names. These references follow the normal rules for name resolution with an exception that unbound local variables are looked up in the global namespace. The namespace of the class definition becomes the attribute dictionary of the class. The scope of names defined in a class block is limited to the class block; it does not extend to the code blocks of methods. This includes comprehensions and generator expressions, but it does not include annotation scopes, which have access to their enclosing class scopes. This means that the following will fail:

class A:
    a = 42
    b = list(a + i for i in range(10))

However, the following will succeed:

class A:
    type Alias = Nested
    class Nested: pass

print(A.Alias.__value__)  # <type 'A.Nested'>

4.2.3. 註釋作用域 (annotation scopes)

Annotations, type parameter lists and type statements introduce annotation scopes, which behave mostly like function scopes, but with some exceptions discussed below.

Annotation scopes are used in the following contexts:

Function annotations.

Variable annotations.

Type parameter lists for generic type aliases.

Type parameter lists for generic functions. A generic function's annotations are executed within the annotation scope, but its defaults and decorators are not.

Type parameter lists for generic classes. A generic class's base classes and keyword arguments are executed within the annotation scope, but its decorators are not.

The bounds, constraints, and default values for type parameters (lazily evaluated).

The value of type aliases (lazily evaluated).

Annotation scopes differ from function scopes in the following ways:

Annotation scopes have access to their enclosing class namespace. If an annotation scope is immediately within a class scope, or within another annotation scope that is immediately within a class scope, the code in the annotation scope can use names defined in the class scope as if it were executed directly within the class body. This contrasts with regular functions defined within classes, which cannot access names defined in the class scope.

Expressions in annotation scopes cannot contain yield, yield from, await, or := expressions. (These expressions are allowed in other scopes contained within the annotation scope.)

Names defined in annotation scopes cannot be rebound with nonlocal statements in inner scopes. This includes only type parameters, as no other syntactic elements that can appear within annotation scopes can introduce new names.

While annotation scopes have an internal name, that name is not reflected in the qualified name of objects defined within the scope. Instead, the __qualname__ of such objects is as if the object were defined in the enclosing scope.

在 3.12 版被加入: Annotation scopes were introduced in Python 3.12 as part of PEP 695 [https://peps.python.org/pep-0695/].

在 3.13 版的變更: Annotation scopes are also used for type parameter defaults, as introduced by PEP 696 [https://peps.python.org/pep-0696/].

在 3.14 版的變更: Annotation scopes are now also used for annotations, as specified in PEP 649 [https://peps.python.org/pep-0649/] and PEP 749 [https://peps.python.org/pep-0749/].

4.2.4. Lazy evaluation

Most annotation scopes are lazily evaluated. This includes annotations, the values of type aliases created through the type statement, and the bounds, constraints, and default values of type variables created through the type parameter syntax. This means that they are not evaluated when the type alias or type variable is created, or when the object carrying annotations is created. Instead, they are only evaluated when necessary, for example when the __value__ attribute on a type alias is accessed.

舉例來說：

>>> type Alias = 1/0
>>> Alias.__value__
Traceback (most recent call last):
  ...
ZeroDivisionError: division by zero
>>> def func[T: 1/0](): pass
>>> T = func.__type_params__[0]
>>> T.__bound__
Traceback (most recent call last):
  ...
ZeroDivisionError: division by zero

Here the exception is raised only when the __value__ attribute of the type alias or the __bound__ attribute of the type variable is accessed.

This behavior is primarily useful for references to types that have not yet been defined when the type alias or type variable is created. For example, lazy evaluation enables creation of mutually recursive type aliases:

from typing import Literal

type SimpleExpr = int | Parenthesized
type Parenthesized = tuple[Literal["("], Expr, Literal[")"]]
type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", "-"], Expr]

Lazily evaluated values are evaluated in annotation scope, which means that names that appear inside the lazily evaluated value are looked up as if they were used in the immediately enclosing scope.

在 3.12 版被加入.

4.2.5. Builtins and restricted execution

CPython 實作細節： Users should not touch __builtins__; it is strictly an implementation detail. Users wanting to override values in the builtins namespace should import the builtins module and modify its attributes appropriately.

The builtins namespace associated with the execution of a code block is actually found by looking up the name __builtins__ in its global namespace; this should be a dictionary or a module (in the latter case the module's dictionary is used). By default, when in the __main__ module, __builtins__ is the built-in module builtins; when in any other module, __builtins__ is an alias for the dictionary of the builtins module itself.

4.2.6. Interaction with dynamic features

Name resolution of free variables occurs at runtime, not at compile time. This means that the following code will print 42:

i = 10
def f():
    print(i)
i = 42
f()

The eval() and exec() functions do not have access to the full environment for resolving names. Names may be resolved in the local and global namespaces of the caller. Free variables are not resolved in the nearest enclosing namespace, but in the global namespace. [1] The exec() and eval() functions have optional arguments to override the global and local namespace. If only one namespace is specified, it is used for both.

4.3. 例外

Exceptions are a means of breaking out of the normal flow of control of a code block in order to handle errors or other exceptional conditions. An exception is raised at the point where the error is detected; it may be handled by the surrounding code block or by any code block that directly or indirectly invoked the code block where the error occurred.

The Python interpreter raises an exception when it detects a run-time error (such as division by zero). A Python program can also explicitly raise an exception with the raise statement. Exception handlers are specified with the try ... except statement. The finally clause of such a statement can be used to specify cleanup code which does not handle the exception, but is executed whether an exception occurred or not in the preceding code.

Python uses the "termination" model of error handling: an exception handler can find out what happened and continue execution at an outer level, but it cannot repair the cause of the error and retry the failing operation (except by re-entering the offending piece of code from the top).

When an exception is not handled at all, the interpreter terminates execution of the program, or returns to its interactive main loop. In either case, it prints a stack traceback, except when the exception is SystemExit.

Exceptions are identified by class instances. The except clause is selected depending on the class of the instance: it must reference the class of the instance or a non-virtual base class thereof. The instance can be received by the handler and can carry additional information about the exceptional condition.

備註

Exception messages are not part of the Python API. Their contents may change from one version of Python to the next without warning and should not be relied on by code which will run under multiple versions of the interpreter.

See also the description of the try statement in section try 陳述式 and raise statement in section raise 陳述式.

4.4. Runtime Components

4.4.1. General Computing Model

Python's execution model does not operate in a vacuum. It runs on a host machine and through that host's runtime environment, including its operating system (OS), if there is one. When a program runs, the conceptual layers of how it runs on the host look something like this:

host machine

process (global resources)

thread (runs machine code)

Each process represents a program running on the host. Think of each process itself as the data part of its program. Think of the process' threads as the execution part of the program. This distinction will be important to understand the conceptual Python runtime.

The process, as the data part, is the execution context in which the program runs. It mostly consists of the set of resources assigned to the program by the host, including memory, signals, file handles, sockets, and environment variables.

Processes are isolated and independent from one another. (The same is true for hosts.) The host manages the process' access to its assigned resources, in addition to coordinating between processes.

Each thread represents the actual execution of the program's machine code, running relative to the resources assigned to the program's process. It's strictly up to the host how and when that execution takes place.

From the point of view of Python, a program always starts with exactly one thread. However, the program may grow to run in multiple simultaneous threads. Not all hosts support multiple threads per process, but most do. Unlike processes, threads in a process are not isolated and independent from one another. Specifically, all threads in a process share all of the process' resources.

The fundamental point of threads is that each one does run independently, at the same time as the others. That may be only conceptually at the same time ("concurrently") or physically ("in parallel"). Either way, the threads effectively run at a non-synchronized rate.

備註

That non-synchronized rate means none of the process' memory is guaranteed to stay consistent for the code running in any given thread. Thus multi-threaded programs must take care to coordinate access to intentionally shared resources. Likewise, they must take care to be absolutely diligent about not accessing any other resources in multiple threads; otherwise two threads running at the same time might accidentally interfere with each other's use of some shared data. All this is true for both Python programs and the Python runtime.

The cost of this broad, unstructured requirement is the tradeoff for the kind of raw concurrency that threads provide. The alternative to the required discipline generally means dealing with non-deterministic bugs and data corruption.

4.4.2. Python Runtime Model

The same conceptual layers apply to each Python program, with some extra data layers specific to Python:

host machine

process (global resources)

Python global runtime (state)

Python interpreter (state)

thread (runs Python bytecode and "C-API")

Python thread state

At the conceptual level: when a Python program starts, it looks exactly like that diagram, with one of each. The runtime may grow to include multiple interpreters, and each interpreter may grow to include multiple thread states.

備註

A Python implementation won't necessarily implement the runtime layers distinctly or even concretely. The only exception is places where distinct layers are directly specified or exposed to users, like through the threading module.

備註

The initial interpreter is typically called the "main" interpreter. Some Python implementations, like CPython, assign special roles to the main interpreter.

Likewise, the host thread where the runtime was initialized is known as the "main" thread. It may be different from the process' initial thread, though they are often the same. In some cases "main thread" may be even more specific and refer to the initial thread state. A Python runtime might assign specific responsibilities to the main thread, such as handling signals.

As a whole, the Python runtime consists of the global runtime state, interpreters, and thread states. The runtime ensures all that state stays consistent over its lifetime, particularly when used with multiple host threads.

The global runtime, at the conceptual level, is just a set of interpreters. While those interpreters are otherwise isolated and independent from one another, they may share some data or other resources. The runtime is responsible for managing these global resources safely. The actual nature and management of these resources is implementation-specific. Ultimately, the external utility of the global runtime is limited to managing interpreters.

In contrast, an "interpreter" is conceptually what we would normally think of as the (full-featured) "Python runtime". When machine code executing in a host thread interacts with the Python runtime, it calls into Python in the context of a specific interpreter.

備註

The term "interpreter" here is not the same as the "bytecode interpreter", which is what regularly runs in threads, executing compiled Python code.

In an ideal world, "Python runtime" would refer to what we currently call "interpreter". However, it's been called "interpreter" at least since introduced in 1997 (CPython:a027efa5b [https://github.com/python/cpython/commit/a027efa5b]).

Each interpreter completely encapsulates all of the non-process-global, non-thread-specific state needed for the Python runtime to work. Notably, the interpreter's state persists between uses. It includes fundamental data like sys.modules. The runtime ensures multiple threads using the same interpreter will safely share it between them.

A Python implementation may support using multiple interpreters at the same time in the same process. They are independent and isolated from one another. For example, each interpreter has its own sys.modules.

For thread-specific runtime state, each interpreter has a set of thread states, which it manages, in the same way the global runtime contains a set of interpreters. It can have thread states for as many host threads as it needs. It may even have multiple thread states for the same host thread, though that isn't as common.

Each thread state, conceptually, has all the thread-specific runtime data an interpreter needs to operate in one host thread. The thread state includes the current raised exception and the thread's Python call stack. It may include other thread-specific resources.

備註

The term "Python thread" can sometimes refer to a thread state, but normally it means a thread created using the threading module.

Each thread state, over its lifetime, is always tied to exactly one interpreter and exactly one host thread. It will only ever be used in that thread and with that interpreter.

Multiple thread states may be tied to the same host thread, whether for different interpreters or even the same interpreter. However, for any given host thread, only one of the thread states tied to it can be used by the thread at a time.

Thread states are isolated and independent from one another and don't share any data, except for possibly sharing an interpreter and objects or other resources belonging to that interpreter.

Once a program is running, new Python threads can be created using the threading module (on platforms and Python implementations that support threads). Additional processes can be created using the os, subprocess, and multiprocessing modules. Interpreters can be created and used with the interpreters module. Coroutines (async) can be run using asyncio in each interpreter, typically only in a single thread (often the main thread).

註解

[1]

This limitation occurs because the code that is executed by these operations is not available at the time the module is compiled.

5. 模組引入系統

一個 module 中的 Python 程式碼透過 importing 的過程來存取另一個模組中的程式碼。import 陳述式是叫用 (invoke) 引入機制最常見的方法，但這不是唯一的方法。函式如 importlib.import_module() 以及內建函式 __import__() 也可以用來叫用引入機制。

import 陳述式結合了兩個操作：首先搜尋指定的模組，然後將搜尋結果繫結到本地作用域中的一個名稱。import 陳述式的搜尋操作被定義為一個對 __import__() 函式的呼叫，並帶有相應的引數。__import__() 的回傳值用於執行 import 陳述式的名稱繫結操作。有關名稱繫結操作的詳細資訊，請參見 import 陳述式。

直接呼叫 __import__() 只會執行模組搜尋操作，以及在找到時執行模組的建立操作。雖然某些副作用可能會發生，例如引入父套件 (parent package)，以及更新各種快取（包括 sys.modules），但只有 import 陳述式會執行名稱繫結操作。

當執行 import 陳述式時，會呼叫內建的 __import__() 函式。其他叫用引入系統的機制（如 importlib.import_module()）可以選擇略過 __import__()，並使用它們自己的解決方案來實作引入語意。

當模組首次被引入時，Python 會搜尋該模組，若找到則會建立一個模組物件 [1]，並對其進行初始化。如果找不到指定的模組，則會引發 ModuleNotFoundError。當引入機制被叫用時，Python 會實作各種策略來搜尋指定的模組。這些策略可以透過使用以下章節描述的各種 hook（掛鉤）來修改和擴展。

在 3.3 版的變更: 引入系統已被更新，以完全實作 PEP 302 [https://peps.python.org/pep-0302/] 的第二階段。不再有隱式引入機制——完整的引入系統已透過 sys.meta_path 公開。此外，原生命名空間套件支援（請參閱 PEP 420 [https://peps.python.org/pep-0420/]）也已被實作。

5.1. importlib

importlib 模組提供了豐富的 API 來與引入系統互動。例如，importlib.import_module() 提供了一個比內建的 __import__() 更推薦且更簡單的 API 來叫用引入機制。更多詳細資訊請參閱 importlib 函式庫文件。

5.2. 套件

Python 只有一種類型的模組物件，且所有模組，無論其是使用 Python、C 還是其他語言實作，都是這種類型。為了幫助組織模組並提供命名階層，Python 導入了套件的概念。

你可以將套件視為檔案系統中的目錄，模組則是目錄中的檔案，但不要過於字面地理解這個比喻，因為套件和模組不一定來自檔案系統。為了方便解釋，我們將使用這個目錄和檔案的比喻。就像檔案系統目錄一樣，套件是分層組織的，套件本身可以包含子套件以及一般模組。

請記住，所有的套件都是模組，但並非所有模組都是套件。換句話說，套件只是一種特殊的模組。具體來說，任何包含 __path__ 屬性的模組都被視為套件。

所有模組都有一個名稱。子套件的名稱與其父套件名稱之間用一個點來分隔，類似於 Python 的標準屬性存取語法。因此，你可能會有一個名為 email 的套件，該套件又有一個名為 email.mime 的子套件，並且該子套件中有一個名為 email.mime.text 的模組。

5.2.1. 一般套件

Python 定義了兩種類型的套件，一般套件和命名空間套件。一般套件是 Python 3.2 及更早版本中存在的傳統套件。一般套件通常實作成一個包含 __init__.py 檔案的目錄。當引入一般套件時，該 __init__.py 檔案會被隱式執行，其定義的物件會繫結到該套件的命名空間中的名稱。__init__.py 檔案可以包含與任何其他模組相同的 Python 程式碼，並且 Python 會在引入時為該模組增加一些額外的屬性。

例如，以下檔案系統布置定義了一個頂層的 parent 套件，該套件包含三個子套件：

parent/
    __init__.py
    one/
        __init__.py
    two/
        __init__.py
    three/
        __init__.py

引入 parent.one 將隱式執行 parent/__init__.py 和 parent/one/__init__.py。隨後引入 parent.two 或 parent.three 將分別執行 parent/two/__init__.py 和 parent/three/__init__.py。

5.2.2. 命名空間套件

命名空間套件是由不同的部分 組成的，每個部分都為父套件提供一個子套件。這些部分可以位於檔案系統上的不同位置。部分可能也存在於壓縮檔案中、網路上，或 Python 在引入時搜尋的任何其他地方。命名空間套件不一定直接對應於檔案系統中的對象；它們可能是沒有具體表示的虛擬模組。

命名空間套件的 __path__ 屬性不使用普通的串列。它們使用自訂的可疊代型別，當父套件的路徑（或頂層套件的 sys.path）發生變化時，會在下一次引入嘗試時自動執行新一輪的套件部分搜尋。

在命名空間套件中，不存在 parent/__init__.py 檔案。實際上，在引入搜尋過程中可能會找到多個 parent 目錄，每個目錄由不同的部分提供。因此，parent/one 可能與 parent/two 不會實際位於一起。在這種情況下，每當引入頂層 parent 套件或其子套件之一時，Python 會為頂層 parent 套件建立一個命名空間套件。

有關命名空間套件的規範，請參見 PEP 420 [https://peps.python.org/pep-0420/]。

5.3. 搜尋

在開始搜尋之前，Python 需要被引入模組（或套件，但在本討論中，兩者的區別無關緊要）的完整限定名稱 (qualified name)。此名稱可能來自 import 陳述式的各種引數，或來自 importlib.import_module() 或 __import__() 函式的參數。

此名稱將在引入搜尋的各個階段中使用，並且它可能是指向子模組的點分隔路徑，例如 foo.bar.baz。在這種情況下，Python 會首先嘗試引入 foo，然後是 foo.bar，最後是 foo.bar.baz。如果任何中間引入失敗，則會引發 ModuleNotFoundError。

5.3.1. 模組快取

在引入搜尋過程中首先檢查的地方是 sys.modules。此對映用作所有先前引入過的模組的快取，包括中間路徑。因此，如果 foo.bar.baz 之前已被引入，sys.modules 將包含 foo、foo.bar 和 foo.bar.baz 的條目。每個鍵的值都是相應的模組物件。

在引入過程中，會在 sys.modules 中查找模組名稱，如果存在，則相關的值為滿足此引入的模組，此引入過程即完成。然而，如果值是 None，則會引發 ModuleNotFoundError。如果模組名稱不存在，Python 會繼續搜尋該模組。

sys.modules 是可寫入的。刪除一個鍵可能不會銷毀相關聯的模組（因為其他模組可能持有對它的參照），但會使指定的模組的快取條目失效，導致 Python 在下一次引入該模組時重新搜尋。也可以將鍵賦值為 None，這會強制下一次引入該模組時引發 ModuleNotFoundError。

但請注意，如果你保留了對模組物件的參照，並在 sys.modules 中使其快取條目失效，然後重新引入指定的模組，這兩個模組物件將不會相同。相比之下，importlib.reload() 會重用相同的模組物件，並透過重新執行模組的程式碼來簡單地重新初始化模組內容。

5.3.2. 尋檢器 (Finder) 與載入器 (Loader)

如果在 sys.modules 中找不到指定的模組，則會叫用 Python 的引入協定來尋找並載入該模組。這個協定由兩個概念性物件組成，尋檢器 和載入器。尋檢器的任務是使用其已知的策略來確定是否能找到命名模組。實作這兩個介面的物件稱為引入器 (importer) ——當它們發現可以載入所請求的模組時，會回傳它們自己。

Python 包含多個預設的尋檢器和引入器。第一個尋檢器知道如何定位內建模組，第二個尋檢器知道如何定位凍結模組。第三個預設尋檢器會在 import path 中搜尋模組。import path 是一個位置的列表，這些位置可能是檔案系統路徑或壓縮檔案，也可以擴展以搜尋任何可定位的資源，例如由 URL 識別的資源。

引入機制是可擴展的，因此可以增加新的尋檢器來擴展模組搜尋的範圍和作用域。

尋檢器實際上不會載入模組。如果它們能找到指定的模組，它們會回傳一個模組規格，這是一個模組的引入相關資訊的封裝，引入機制會在載入模組時使用這些資訊。

以下各節將更詳細地描述尋檢器和載入器的協定，包括如何建立和註冊新的尋檢器和載入器來擴展引入機制。

在 3.4 版的變更: Python 在之前的版本中，尋檢器會直接回傳載入器，而現在它們回傳的是包含載入器的模組規格。載入器仍在引入過程中使用，但其責任減少了。

5.3.3. 引入掛鉤 (Import hooks)

引入機制的設計是可擴展的；其主要機制是引入掛鉤。引入掛鉤有兩種類型：元掛鉤 (meta hooks) 和引入路徑掛鉤。

元掛鉤會在引入處理的開始階段被呼叫，除了查找 sys.modules 快取外，其他引入處理還未發生時就會呼叫。這允許元掛鉤覆蓋 sys.path 的處理、凍結模組，甚至是內建模組。元掛鉤透過將新的尋檢器物件添加到 sys.meta_path 中來註冊，具體描述請參閱以下段落。

引入路徑掛鉤被視為 sys.path（或 package.__path__）處理過程的一部分來呼叫，當遇到與其相關聯的路徑項目時就會被觸發。引入路徑掛鉤透過將新的可呼叫對象增加到 sys.path_hooks 中來註冊，具體描述請參閱以下段落。

5.3.4. 元路徑

當在 sys.modules 中找不到命名模組時，Python 接下來會搜尋 sys.meta_path，其中包含一個元路徑尋檢器物件串列。這些尋檢器會依次被查詢，看它們是否知道如何處理命名模組。元路徑尋檢器必須實作一個名為 find_spec() 的方法，該方法接收三個引數：名稱、引入路徑和（可選的）目標模組。元路徑尋檢器可以使用任何策略來確定它是否能處理命名模組。

如果元路徑尋檢器知道如何處理命名模組，它會回傳一個規格物件。如果它無法處理命名模組，則回傳 None。如果 sys.meta_path 的處理到達串列的末尾仍未回傳規格，則會引發 ModuleNotFoundError。任何其他引發的例外將直接向上傳播，並中止引入過程。

元路徑尋檢器的 find_spec() 方法會以兩個或三個引數來呼叫。第一個是被引入模組的完全限定名稱，例如 foo.bar.baz。第二個引數是用於模組搜尋的路徑條目。對於頂層模組，第二個引數是 None，但對於子模組或子套件，第二個引數是父套件的 __path__ 屬性的值。如果無法存取相應的 __path__ 屬性，將引發 ModuleNotFoundError。第三個引數是一個現有的模組物件，該物件將成為後續載入的目標。引入系統只會在重新載入時傳入目標模組。

對於一個引入請求，元路徑可能會被遍歷多次。例如，假設參與的模組都沒有被快取，則引入 foo.bar.baz 將首先執行頂層引入，對每個元路徑尋檢器（mpf）呼叫 mpf.find_spec("foo", None, None)。當 foo 被引入後，將再次藉由遍歷元路徑引入 foo.bar，並呼叫 mpf.find_spec("foo.bar", foo.__path__, None)。當 foo.bar 被引入後，最後一次遍歷會呼叫 mpf.find_spec("foo.bar.baz", foo.bar.__path__, None)。

一些元路徑尋檢器僅支援頂層引入。當第二個引數傳入 None 以外的值時，這些引入器將始終回傳 None。

Python 的預設 sys.meta_path 有三個元路徑尋檢器，一個知道如何引入內建模組，一個知道如何引入凍結模組，還有一個知道如何從 import path 引入模組（即 path based finder）。

在 3.4 版的變更: 元路徑尋檢器的 find_spec() 方法取代了 find_module()，後者現在已被棄用。雖然它將繼續正常工作，但引入機制僅在尋檢器未實作 find_spec() 時才會嘗試使用它。

在 3.10 版的變更: 引入系統現在使用 find_module() 時將引發 ImportWarning。

在 3.12 版的變更: find_module() 已被移除。請改用 find_spec()。

5.4. 載入

如果找到模組規格，引入機制會在載入模組時使用該規格（以及它包含的載入器）。以下是引入過程中載入部分的大致情況：

module = None
if spec.loader is not None and hasattr(spec.loader, 'create_module'):
    # 這裡假設載入器上也會定義 'exec_module'
    module = spec.loader.create_module(spec)
if module is None:
    module = ModuleType(spec.name)
# 與引入相關的模組屬性會在此處設定：
_init_module_attrs(spec, module)

if spec.loader is None:
    # 不支援
    raise ImportError
if spec.origin is None and spec.submodule_search_locations is not None:
    # 命名空間套件
    sys.modules[spec.name] = module
elif not hasattr(spec.loader, 'exec_module'):
    module = spec.loader.load_module(spec.name)
else:
    sys.modules[spec.name] = module
    try:
        spec.loader.exec_module(module)
    except BaseException:
        try:
            del sys.modules[spec.name]
        except KeyError:
            pass
        raise
return sys.modules[spec.name]

請注意下列細節：

如果 sys.modules 中已存在具有給定名稱的模組物件，引入會已回傳該物件。

在載入器執行模組程式碼之前，模組將已存在於 sys.modules 中。這一點至關重要，因為模組程式碼可能會（直接或間接）引入自己；事先將其增加到 sys.modules 可以預防類似無限遞迴以及多次重複載入等情形。

如果載入失敗，只有載入失敗的模組會從 sys.modules 中刪除。任何已存在於 sys.modules 快取中的模組，以及任何在載入失敗前成功載入的模組，都必須保留在快取中。此情形與重新載入不同，在重新載入時，即使載入失敗的模組也會保留在 sys.modules 中。

模組建立後、在執行之前，引入機制會設置與引入相關的模組屬性（在上面的偽程式碼範例中為 "_init_module_attrs"），具體內容在之後的段落會總結。

模組執行是載入過程中的關鍵時刻，此時模組的命名空間會被新增名稱。執行過程完全交由載入器處理，由其決定如何新增以及新增什麼。

在載入過程中建立並傳遞給 exec_module() 的模組，可能不會是引入結束時回傳的模組 [2]。

在 3.4 版的變更: 引入系統已接管載入器的模板 (boilerplate) 責任。之前是由 importlib.abc.Loader.load_module() 方法執行的。

5.4.1. 載入器

模組載入器提供了載入的關鍵功能：模組執行。引入機制會以單一引數（即要執行的模組物件）呼叫 importlib.abc.Loader.exec_module() 方法。任何從 exec_module() 回傳的值都會被忽略。

載入器必須滿足以下要求：

如果模組是 Python 模組（而非內建模組或動態載入的擴充），載入器應在模組的全域命名空間 (module.__dict__) 中執行該模組的程式碼。

如果載入器無法執行該模組，應引發 ImportError。不過，在 exec_module() 中引發的任何其他例外也會被傳播。

在許多情況下，尋檢器和載入器可以是同一個物件；在這種情況下，find_spec() 方法只需回傳一個載入器設為 self 的規格即可。

模組載入器可以選擇透過實作 create_module() 方法，在載入過程中建立模組物件。該方法接受一個引數，即模組規格，並回傳在載入過程中要使用的新的模組物件。create_module() 不需要在模組物件上設定任何屬性。如果該方法回傳 None，引入機制將自行建立新的模組。

在 3.4 版被加入: 載入器的 create_module() 方法。

在 3.4 版的變更: load_module() 方法已被 exec_module() 取代，引入機制已承擔所有載入的模板責任。

為了與現有的載入器相容，引入機制會在載入器未實作 exec_module() 且存在 load_module() 方法時使用該方法。然而，load_module() 已被棄用，載入器應改為實作 exec_module()。

load_module() 方法除了執行模組外，還必須實作上述全部的模板載入功能。所有相同的限制依然適用，並且還有一些額外的說明：

如果 sys.modules 中已存在具有給定名稱的模組物件，載入器必須使用該模組（否則 importlib.reload() 將無法正常運作）。如果命名模組不存在於 sys.modules 中，載入器必須建立一個新的模組物件並將其新增至 sys.modules。

在載入器執行模組程式碼之前，該模組必須已存在於 sys.modules 中，以防止無限遞迴或多次載入。

如果載入失敗，載入器必須移除已經插入到 sys.modules 中的任何模組，但只能移除失敗的模組（們），且僅在載入器本身明確載入這些模組時才需移除。

在 3.5 版的變更: 當 exec_module() 已定義但未定義 create_module() 時，將引發 DeprecationWarning。

在 3.6 版的變更: 當 exec_module() 已定義但未定義 create_module() 時，將引發 ImportError。

在 3.10 版的變更: 使用 load_module() 將引發 ImportWarning。

5.4.2. 子模組

當使用任何機制（例如 importlib APIs、import 或 import-from 陳述式，或內建的 __import__()）載入子模組時，會將子模組物件繫結到父模組的命名空間中。例如，如果套件 spam 有一個子模組 foo，則在引入 spam.foo 之後，spam 將擁有一個名為 foo 的屬性，該屬性繫結到子模組。我們假設你有以下的目錄結構：

spam/
    __init__.py
    foo.py

並且 spam/__init__.py 中包含以下程式碼：

from .foo import Foo

那麼執行以下程式碼會將 foo 和 Foo 的名稱繫結到 spam 模組中：

>>> import spam
>>> spam.foo
<module 'spam.foo' from '/tmp/imports/spam/foo.py'>
>>> spam.Foo
<class 'spam.foo.Foo'>

鑑於 Python 相似的名稱繫結規則，這可能看起來有些出人意料，但這實際上是引入系統的一個基本特性。不變的是如果你擁有 sys.modules['spam'] 和 sys.modules['spam.foo']（就像上述引入後那樣），那麼後者必須作為前者的 foo 屬性出現。

5.4.3. 模組規格

引入機制在引入過程中使用有關每個模組的各種資訊，尤其是在載入之前。大多數資訊對所有模組來說都是通用的。模組規格的目的是以每個模組為基礎封裝這些與引入相關的資訊。

在引入過程中使用規格允許在引入系統的各個組件之間傳遞狀態，例如在建立模組規格的尋檢器和執行該規格的載入器之間傳遞。最重要的是，這允許引入機制執行載入的模板操作，而在沒有模組規格的情況下，這些操作則是載入器的責任。

模組的規格以 module.__spec__ 的形式公開。適當地設定 __spec__ 同樣適用於在直譯器啟動期間初始化的模組。唯一的例外是 __main__，其中 __spec__ 會在某些情況下被設定成 None。

有關模組規格內容的詳細資訊，請參閱 ModuleSpec。

在 3.4 版被加入.

5.4.4. __path__ attributes on modules

The __path__ attribute should be a (possibly empty) sequence of strings enumerating the locations where the package's submodules will be found. By definition, if a module has a __path__ attribute, it is a package.

A package's __path__ attribute is used during imports of its subpackages. Within the import machinery, it functions much the same as sys.path, i.e. providing a list of locations to search for modules during import. However, __path__ is typically much more constrained than sys.path.

The same rules used for sys.path also apply to a package's __path__. sys.path_hooks (described below) are consulted when traversing a package's __path__.

A package's __init__.py file may set or alter the package's __path__ attribute, and this was typically the way namespace packages were implemented prior to PEP 420 [https://peps.python.org/pep-0420/]. With the adoption of PEP 420 [https://peps.python.org/pep-0420/], namespace packages no longer need to supply __init__.py files containing only __path__ manipulation code; the import machinery automatically sets __path__ correctly for the namespace package.

5.4.5. Module reprs

By default, all modules have a usable repr, however depending on the attributes set above, and in the module's spec, you can more explicitly control the repr of module objects.

If the module has a spec (__spec__), the import machinery will try to generate a repr from it. If that fails or there is no spec, the import system will craft a default repr using whatever information is available on the module. It will try to use the module.__name__, module.__file__, and module.__loader__ as input into the repr, with defaults for whatever information is missing.

Here are the exact rules used:

If the module has a __spec__ attribute, the information in the spec is used to generate the repr. The "name", "loader", "origin", and "has_location" attributes are consulted.

If the module has a __file__ attribute, this is used as part of the module's repr.

If the module has no __file__ but does have a __loader__ that is not None, then the loader's repr is used as part of the module's repr.

Otherwise, just use the module's __name__ in the repr.

在 3.12 版的變更: Use of module_repr(), having been deprecated since Python 3.4, was removed in Python 3.12 and is no longer called during the resolution of a module's repr.

5.4.6. Cached bytecode invalidation

Before Python loads cached bytecode from a .pyc file, it checks whether the cache is up-to-date with the source .py file. By default, Python does this by storing the source's last-modified timestamp and size in the cache file when writing it. At runtime, the import system then validates the cache file by checking the stored metadata in the cache file against the source's metadata.

Python also supports "hash-based" cache files, which store a hash of the source file's contents rather than its metadata. There are two variants of hash-based .pyc files: checked and unchecked. For checked hash-based .pyc files, Python validates the cache file by hashing the source file and comparing the resulting hash with the hash in the cache file. If a checked hash-based cache file is found to be invalid, Python regenerates it and writes a new checked hash-based cache file. For unchecked hash-based .pyc files, Python simply assumes the cache file is valid if it exists. Hash-based .pyc files validation behavior may be overridden with the --check-hash-based-pycs flag.

在 3.7 版的變更: Added hash-based .pyc files. Previously, Python only supported timestamp-based invalidation of bytecode caches.

5.5. The Path Based Finder

As mentioned previously, Python comes with several default meta path finders. One of these, called the path based finder (PathFinder), searches an import path, which contains a list of path entries. Each path entry names a location to search for modules.

The path based finder itself doesn't know how to import anything. Instead, it traverses the individual path entries, associating each of them with a path entry finder that knows how to handle that particular kind of path.

The default set of path entry finders implement all the semantics for finding modules on the file system, handling special file types such as Python source code (.py files), Python byte code (.pyc files) and shared libraries (e.g. .so files). When supported by the zipimport module in the standard library, the default path entry finders also handle loading all of these file types (other than shared libraries) from zipfiles.

Path entries need not be limited to file system locations. They can refer to URLs, database queries, or any other location that can be specified as a string.

The path based finder provides additional hooks and protocols so that you can extend and customize the types of searchable path entries. For example, if you wanted to support path entries as network URLs, you could write a hook that implements HTTP semantics to find modules on the web. This hook (a callable) would return a path entry finder supporting the protocol described below, which was then used to get a loader for the module from the web.

A word of warning: this section and the previous both use the term finder, distinguishing between them by using the terms meta path finder and path entry finder. These two types of finders are very similar, support similar protocols, and function in similar ways during the import process, but it's important to keep in mind that they are subtly different. In particular, meta path finders operate at the beginning of the import process, as keyed off the sys.meta_path traversal.

By contrast, path entry finders are in a sense an implementation detail of the path based finder, and in fact, if the path based finder were to be removed from sys.meta_path, none of the path entry finder semantics would be invoked.

5.5.1. Path entry finders

The path based finder is responsible for finding and loading Python modules and packages whose location is specified with a string path entry. Most path entries name locations in the file system, but they need not be limited to this.

As a meta path finder, the path based finder implements the find_spec() protocol previously described, however it exposes additional hooks that can be used to customize how modules are found and loaded from the import path.

Three variables are used by the path based finder, sys.path, sys.path_hooks and sys.path_importer_cache. The __path__ attributes on package objects are also used. These provide additional ways that the import machinery can be customized.

sys.path contains a list of strings providing search locations for modules and packages. It is initialized from the PYTHONPATH environment variable and various other installation- and implementation-specific defaults. Entries in sys.path can name directories on the file system, zip files, and potentially other "locations" (see the site module) that should be searched for modules, such as URLs, or database queries. Only strings should be present on sys.path; all other data types are ignored.

The path based finder is a meta path finder, so the import machinery begins the import path search by calling the path based finder's find_spec() method as described previously. When the path argument to find_spec() is given, it will be a list of string paths to traverse - typically a package's __path__ attribute for an import within that package. If the path argument is None, this indicates a top level import and sys.path is used.

The path based finder iterates over every entry in the search path, and for each of these, looks for an appropriate path entry finder (PathEntryFinder) for the path entry. Because this can be an expensive operation (e.g. there may be stat() call overheads for this search), the path based finder maintains a cache mapping path entries to path entry finders. This cache is maintained in sys.path_importer_cache (despite the name, this cache actually stores finder objects rather than being limited to importer objects). In this way, the expensive search for a particular path entry location's path entry finder need only be done once. User code is free to remove cache entries from sys.path_importer_cache forcing the path based finder to perform the path entry search again.

If the path entry is not present in the cache, the path based finder iterates over every callable in sys.path_hooks. Each of the path entry hooks in this list is called with a single argument, the path entry to be searched. This callable may either return a path entry finder that can handle the path entry, or it may raise ImportError. An ImportError is used by the path based finder to signal that the hook cannot find a path entry finder for that path entry. The exception is ignored and import path iteration continues. The hook should expect either a string or bytes object; the encoding of bytes objects is up to the hook (e.g. it may be a file system encoding, UTF-8, or something else), and if the hook cannot decode the argument, it should raise ImportError.

If sys.path_hooks iteration ends with no path entry finder being returned, then the path based finder's find_spec() method will store None in sys.path_importer_cache (to indicate that there is no finder for this path entry) and return None, indicating that this meta path finder could not find the module.

If a path entry finder is returned by one of the path entry hook callables on sys.path_hooks, then the following protocol is used to ask the finder for a module spec, which is then used when loading the module.

The current working directory -- denoted by an empty string -- is handled slightly differently from other entries on sys.path. First, if the current working directory cannot be determined or is found not to exist, no value is stored in sys.path_importer_cache. Second, the value for the current working directory is looked up fresh for each module lookup. Third, the path used for sys.path_importer_cache and returned by importlib.machinery.PathFinder.find_spec() will be the actual current working directory and not the empty string.

5.5.2. Path entry finder protocol

In order to support imports of modules and initialized packages and also to contribute portions to namespace packages, path entry finders must implement the find_spec() method.

find_spec() takes two arguments: the fully qualified name of the module being imported, and the (optional) target module. find_spec() returns a fully populated spec for the module. This spec will always have "loader" set (with one exception).

To indicate to the import machinery that the spec represents a namespace portion, the path entry finder sets submodule_search_locations to a list containing the portion.

在 3.4 版的變更: find_spec() replaced find_loader() and find_module(), both of which are now deprecated, but will be used if find_spec() is not defined.

Older path entry finders may implement one of these two deprecated methods instead of find_spec(). The methods are still respected for the sake of backward compatibility. However, if find_spec() is implemented on the path entry finder, the legacy methods are ignored.

find_loader() takes one argument, the fully qualified name of the module being imported. find_loader() returns a 2-tuple where the first item is the loader and the second item is a namespace portion.

For backwards compatibility with other implementations of the import protocol, many path entry finders also support the same, traditional find_module() method that meta path finders support. However path entry finder find_module() methods are never called with a path argument (they are expected to record the appropriate path information from the initial call to the path hook).

The find_module() method on path entry finders is deprecated, as it does not allow the path entry finder to contribute portions to namespace packages. If both find_loader() and find_module() exist on a path entry finder, the import system will always call find_loader() in preference to find_module().

在 3.10 版的變更: Calls to find_module() and find_loader() by the import system will raise ImportWarning.

在 3.12 版的變更: find_module() 和 find_loader() 已被移除。

5.6. Replacing the standard import system

The most reliable mechanism for replacing the entire import system is to delete the default contents of sys.meta_path, replacing them entirely with a custom meta path hook.

If it is acceptable to only alter the behaviour of import statements without affecting other APIs that access the import system, then replacing the builtin __import__() function may be sufficient.

To selectively prevent the import of some modules from a hook early on the meta path (rather than disabling the standard import system entirely), it is sufficient to raise ModuleNotFoundError directly from find_spec() instead of returning None. The latter indicates that the meta path search should continue, while raising an exception terminates it immediately.

5.7. Package Relative Imports

Relative imports use leading dots. A single leading dot indicates a relative import, starting with the current package. Two or more leading dots indicate a relative import to the parent(s) of the current package, one level per dot after the first. For example, given the following package layout:

package/
    __init__.py
    subpackage1/
        __init__.py
        moduleX.py
        moduleY.py
    subpackage2/
        __init__.py
        moduleZ.py
    moduleA.py

In either subpackage1/moduleX.py or subpackage1/__init__.py, the following are valid relative imports:

from .moduleY import spam
from .moduleY import spam as ham
from . import moduleY
from ..subpackage1 import moduleY
from ..subpackage2.moduleZ import eggs
from ..moduleA import foo

Absolute imports may use either the import <> or from <> import <> syntax, but relative imports may only use the second form; the reason for this is that:

import XXX.YYY.ZZZ

should expose XXX.YYY.ZZZ as a usable expression, but .moduleY is not a valid expression.

5.8. Special considerations for __main__

The __main__ module is a special case relative to Python's import system. As noted elsewhere, the __main__ module is directly initialized at interpreter startup, much like sys and builtins. However, unlike those two, it doesn't strictly qualify as a built-in module. This is because the manner in which __main__ is initialized depends on the flags and other options with which the interpreter is invoked.

5.8.1. __main__.__spec__

Depending on how __main__ is initialized, __main__.__spec__ gets set appropriately or to None.

When Python is started with the -m option, __spec__ is set to the module spec of the corresponding module or package. __spec__ is also populated when the __main__ module is loaded as part of executing a directory, zipfile or other sys.path entry.

In the remaining cases __main__.__spec__ is set to None, as the code used to populate the __main__ does not correspond directly with an importable module:

interactive prompt

-c 選項

running from stdin

running directly from a source or bytecode file

Note that __main__.__spec__ is always None in the last case, even if the file could technically be imported directly as a module instead. Use the -m switch if valid module metadata is desired in __main__.

Note also that even when __main__ corresponds with an importable module and __main__.__spec__ is set accordingly, they're still considered distinct modules. This is due to the fact that blocks guarded by if __name__ == "__main__": checks only execute when the module is used to populate the __main__ namespace, and not during normal import.

5.9. References

The import machinery has evolved considerably since Python's early days. The original specification for packages [https://www.python.org/doc/essays/packages/] is still available to read, although some details have changed since the writing of that document.

The original specification for sys.meta_path was PEP 302 [https://peps.python.org/pep-0302/], with subsequent extension in PEP 420 [https://peps.python.org/pep-0420/].

PEP 420 [https://peps.python.org/pep-0420/] introduced namespace packages for Python 3.3. PEP 420 [https://peps.python.org/pep-0420/] also introduced the find_loader() protocol as an alternative to find_module().

PEP 366 [https://peps.python.org/pep-0366/] describes the addition of the __package__ attribute for explicit relative imports in main modules.

PEP 328 [https://peps.python.org/pep-0328/] introduced absolute and explicit relative imports and initially proposed __name__ for semantics PEP 366 [https://peps.python.org/pep-0366/] would eventually specify for __package__.

PEP 338 [https://peps.python.org/pep-0338/] defines executing modules as scripts.

PEP 451 [https://peps.python.org/pep-0451/] adds the encapsulation of per-module import state in spec objects. It also off-loads most of the boilerplate responsibilities of loaders back onto the import machinery. These changes allow the deprecation of several APIs in the import system and also addition of new methods to finders and loaders.

註解

[1]

參閱 types.ModuleType。

[2]

The importlib implementation avoids using the return value directly. Instead, it gets the module object by looking the module name up in sys.modules. The indirect effect of this is that an imported module may replace itself in sys.modules. This is implementation-specific behavior that is not guaranteed to work in other Python implementations.

6. 運算式

This chapter explains the meaning of the elements of expressions in Python.

Syntax Notes: In this and the following chapters, extended BNF notation will be used to describe syntax, not lexical analysis. When (one alternative of) a syntax rule has the form

name: othername

and no semantics are given, the semantics of this form of name are the same as for othername.

6.1. Arithmetic conversions

When a description of an arithmetic operator below uses the phrase "the numeric arguments are converted to a common real type", this means that the operator implementation for built-in types works as follows:

If both arguments are complex numbers, no conversion is performed;

if either argument is a complex or a floating-point number, the other is converted to a floating-point number;

otherwise, both must be integers and no conversion is necessary.

Some additional rules apply for certain operators (e.g., a string as a left argument to the '%' operator). Extensions must define their own conversion behavior.

6.2. Atoms

Atoms are the most basic elements of expressions. The simplest atoms are identifiers or literals. Forms enclosed in parentheses, brackets or braces are also categorized syntactically as atoms. The syntax for atoms is:

atom:      identifier | literal | enclosure
enclosure: parenth_form | list_display | dict_display | set_display
           | generator_expression | yield_atom

6.2.1. Identifiers (Names)

An identifier occurring as an atom is a name. See section Names (identifiers and keywords) for lexical definition and section Naming and binding for documentation of naming and binding.

When the name is bound to an object, evaluation of the atom yields that object. When a name is not bound, an attempt to evaluate it raises a NameError exception.

6.2.1.1. Private name mangling

When an identifier that textually occurs in a class definition begins with two or more underscore characters and does not end in two or more underscores, it is considered a private name of that class.

也參考

The class specifications.

More precisely, private names are transformed to a longer form before code is generated for them. If the transformed name is longer than 255 characters, implementation-defined truncation may happen.

The transformation is independent of the syntactical context in which the identifier is used but only the following private identifiers are mangled:

Any name used as the name of a variable that is assigned or read or any name of an attribute being accessed.

The __name__ attribute of nested functions, classes, and type aliases is however not mangled.

The name of imported modules, e.g., __spam in import __spam. If the module is part of a package (i.e., its name contains a dot), the name is not mangled, e.g., the __foo in import __foo.bar is not mangled.

The name of an imported member, e.g., __f in from spam import __f.

The transformation rule is defined as follows:

The class name, with leading underscores removed and a single leading underscore inserted, is inserted in front of the identifier, e.g., the identifier __spam occurring in a class named Foo, _Foo or __Foo is transformed to _Foo__spam.

If the class name consists only of underscores, the transformation is the identity, e.g., the identifier __spam occurring in a class named _ or __ is left as is.

6.2.2. Literals

Python supports string and bytes literals and various numeric literals:

literal: strings | NUMBER

Evaluation of a literal yields an object of the given type (string, bytes, integer, floating-point number, complex number) with the given value. The value may be approximated in the case of floating-point and imaginary (complex) literals. See section Literals for details. See section String literal concatenation for details on strings.

All literals correspond to immutable data types, and hence the object's identity is less important than its value. Multiple evaluations of literals with the same value (either the same occurrence in the program text or a different occurrence) may obtain the same object or a different object with the same value.

6.2.2.1. String literal concatenation

Multiple adjacent string or bytes literals (delimited by whitespace), possibly using different quoting conventions, are allowed, and their meaning is the same as their concatenation:

>>> "hello" 'world'
"helloworld"

Formally:

strings: ( STRING | fstring)+ | tstring+

This feature is defined at the syntactical level, so it only works with literals. To concatenate string expressions at run time, the '+' operator may be used:

>>> greeting = "Hello"
>>> space = " "
>>> name = "Blaise"
>>> print(greeting + space + name)   # 不是：print(greeting space name)
Hello Blaise

Literal concatenation can freely mix raw strings, triple-quoted strings, and formatted string literals. For example:

>>> "Hello" r', ' f"{name}!"
"Hello, Blaise!"

This feature can be used to reduce the number of backslashes needed, to split long strings conveniently across long lines, or even to add comments to parts of strings. For example:

re.compile("[A-Za-z_]"       # letter or underscore
           "[A-Za-z0-9_]*"   # letter, digit or underscore
          )

However, bytes literals may only be combined with other byte literals; not with string literals of any kind. Also, template string literals may only be combined with other template string literals:

>>> t"Hello" t"{name}!"
Template(strings=('Hello', '!'), interpolations=(...))

6.2.3. Parenthesized forms

A parenthesized form is an optional expression list enclosed in parentheses:

parenth_form: "(" [starred_expression] ")"

A parenthesized expression list yields whatever that expression list yields: if the list contains at least one comma, it yields a tuple; otherwise, it yields the single expression that makes up the expression list.

An empty pair of parentheses yields an empty tuple object. Since tuples are immutable, the same rules as for literals apply (i.e., two occurrences of the empty tuple may or may not yield the same object).

Note that tuples are not formed by the parentheses, but rather by use of the comma. The exception is the empty tuple, for which parentheses are required --- allowing unparenthesized "nothing" in expressions would cause ambiguities and allow common typos to pass uncaught.

6.2.4. Displays for lists, sets and dictionaries

For constructing a list, a set or a dictionary Python provides special syntax called "displays", each of them in two flavors:

either the container contents are listed explicitly, or

they are computed via a set of looping and filtering instructions, called a comprehension.

Common syntax elements for comprehensions are:

comprehension: assignment_expression comp_for
comp_for:      ["async"] "for" target_list "in" or_test [comp_iter]
comp_iter:     comp_for | comp_if
comp_if:       "if" or_test [comp_iter]

The comprehension consists of a single expression followed by at least one for clause and zero or more for or if clauses. In this case, the elements of the new container are those that would be produced by considering each of the for or if clauses a block, nesting from left to right, and evaluating the expression to produce an element each time the innermost block is reached.

However, aside from the iterable expression in the leftmost for clause, the comprehension is executed in a separate implicitly nested scope. This ensures that names assigned to in the target list don't "leak" into the enclosing scope.

The iterable expression in the leftmost for clause is evaluated directly in the enclosing scope and then passed as an argument to the implicitly nested scope. Subsequent for clauses and any filter condition in the leftmost for clause cannot be evaluated in the enclosing scope as they may depend on the values obtained from the leftmost iterable. For example: [x*y for x in range(10) for y in range(x, x+10)].

To ensure the comprehension always results in a container of the appropriate type, yield and yield from expressions are prohibited in the implicitly nested scope.

Since Python 3.6, in an async def function, an async for clause may be used to iterate over a asynchronous iterator. A comprehension in an async def function may consist of either a for or async for clause following the leading expression, may contain additional for or async for clauses, and may also use await expressions.

If a comprehension contains async for clauses, or if it contains await expressions or other asynchronous comprehensions anywhere except the iterable expression in the leftmost for clause, it is called an asynchronous comprehension. An asynchronous comprehension may suspend the execution of the coroutine function in which it appears. See also PEP 530 [https://peps.python.org/pep-0530/].

在 3.6 版被加入: Asynchronous comprehensions were introduced.

在 3.8 版的變更: yield and yield from prohibited in the implicitly nested scope.

在 3.11 版的變更: Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions. Outer comprehensions implicitly become asynchronous.

6.2.5. List displays

A list display is a possibly empty series of expressions enclosed in square brackets:

list_display: "[" [flexible_expression_list | comprehension] "]"

A list display yields a new list object, the contents being specified by either a list of expressions or a comprehension. When a comma-separated list of expressions is supplied, its elements are evaluated from left to right and placed into the list object in that order. When a comprehension is supplied, the list is constructed from the elements resulting from the comprehension.

6.2.6. Set displays

A set display is denoted by curly braces and distinguishable from dictionary displays by the lack of colons separating keys and values:

set_display: "{" (flexible_expression_list | comprehension) "}"

A set display yields a new mutable set object, the contents being specified by either a sequence of expressions or a comprehension. When a comma-separated list of expressions is supplied, its elements are evaluated from left to right and added to the set object. When a comprehension is supplied, the set is constructed from the elements resulting from the comprehension.

An empty set cannot be constructed with {}; this literal constructs an empty dictionary.

6.2.7. Dictionary displays

A dictionary display is a possibly empty series of dict items (key/value pairs) enclosed in curly braces:

dict_display:       "{" [dict_item_list | dict_comprehension] "}"
dict_item_list:     dict_item ("," dict_item)* [","]
dict_item:          expression ":" expression | "**" or_expr
dict_comprehension: expression ":" expression comp_for

A dictionary display yields a new dictionary object.

If a comma-separated sequence of dict items is given, they are evaluated from left to right to define the entries of the dictionary: each key object is used as a key into the dictionary to store the corresponding value. This means that you can specify the same key multiple times in the dict item list, and the final dictionary's value for that key will be the last one given.

A double asterisk ** denotes dictionary unpacking. Its operand must be a mapping. Each mapping item is added to the new dictionary. Later values replace values already set by earlier dict items and earlier dictionary unpackings.

在 3.5 版被加入: Unpacking into dictionary displays, originally proposed by PEP 448 [https://peps.python.org/pep-0448/].

A dict comprehension, in contrast to list and set comprehensions, needs two expressions separated with a colon followed by the usual "for" and "if" clauses. When the comprehension is run, the resulting key and value elements are inserted in the new dictionary in the order they are produced.

Restrictions on the types of the key values are listed earlier in section 標準型別階層. (To summarize, the key type should be hashable, which excludes all mutable objects.) Clashes between duplicate keys are not detected; the last value (textually rightmost in the display) stored for a given key value prevails.

在 3.8 版的變更: Prior to Python 3.8, in dict comprehensions, the evaluation order of key and value was not well-defined. In CPython, the value was evaluated before the key. Starting with 3.8, the key is evaluated before the value, as proposed by PEP 572 [https://peps.python.org/pep-0572/].

6.2.8. Generator expressions

A generator expression is a compact generator notation in parentheses:

generator_expression: "(" expression comp_for ")"

A generator expression yields a new generator object. Its syntax is the same as for comprehensions, except that it is enclosed in parentheses instead of brackets or curly braces.

Variables used in the generator expression are evaluated lazily when the __next__() method is called for the generator object (in the same fashion as normal generators). However, the iterable expression in the leftmost for clause is immediately evaluated, and the iterator is immediately created for that iterable, so that an error produced while creating the iterator will be emitted at the point where the generator expression is defined, rather than at the point where the first value is retrieved. Subsequent for clauses and any filter condition in the leftmost for clause cannot be evaluated in the enclosing scope as they may depend on the values obtained from the leftmost iterable. For example: (x*y for x in range(10) for y in range(x, x+10)).

The parentheses can be omitted on calls with only one argument. See section Calls for details.

To avoid interfering with the expected operation of the generator expression itself, yield and yield from expressions are prohibited in the implicitly defined generator.

If a generator expression contains either async for clauses or await expressions it is called an asynchronous generator expression. An asynchronous generator expression returns a new asynchronous generator object, which is an asynchronous iterator (see Asynchronous Iterators).

在 3.6 版被加入: Asynchronous generator expressions were introduced.

在 3.7 版的變更: Prior to Python 3.7, asynchronous generator expressions could only appear in async def coroutines. Starting with 3.7, any function can use asynchronous generator expressions.

在 3.8 版的變更: yield and yield from prohibited in the implicitly nested scope.

6.2.9. Yield expressions

yield_atom:       "(" yield_expression ")"
yield_from:       "yield" "from" expression
yield_expression: "yield" yield_list | yield_from

The yield expression is used when defining a generator function or an asynchronous generator function and thus can only be used in the body of a function definition. Using a yield expression in a function's body causes that function to be a generator function, and using it in an async def function's body causes that coroutine function to be an asynchronous generator function. For example:

def gen():  # 定義一個產生器函式
    yield 123

async def agen(): # 定義一個非同步產生器函式
    yield 123

Due to their side effects on the containing scope, yield expressions are not permitted as part of the implicitly defined scopes used to implement comprehensions and generator expressions.

在 3.8 版的變更: Yield expressions prohibited in the implicitly nested scopes used to implement comprehensions and generator expressions.

Generator functions are described below, while asynchronous generator functions are described separately in section 非同步產生器函式.

When a generator function is called, it returns an iterator known as a generator. That generator then controls the execution of the generator function. The execution starts when one of the generator's methods is called. At that time, the execution proceeds to the first yield expression, where it is suspended again, returning the value of yield_list to the generator's caller, or None if yield_list is omitted. By suspended, we mean that all local state is retained, including the current bindings of local variables, the instruction pointer, the internal evaluation stack, and the state of any exception handling. When the execution is resumed by calling one of the generator's methods, the function can proceed exactly as if the yield expression were just another external call. The value of the yield expression after resuming depends on the method which resumed the execution. If __next__() is used (typically via either a for or the next() builtin) then the result is None. Otherwise, if send() is used, then the result will be the value passed in to that method.

All of this makes generator functions quite similar to coroutines; they yield multiple times, they have more than one entry point and their execution can be suspended. The only difference is that a generator function cannot control where the execution should continue after it yields; the control is always transferred to the generator's caller.

Yield expressions are allowed anywhere in a try construct. If the generator is not resumed before it is finalized (by reaching a zero reference count or by being garbage collected), the generator-iterator's close() method will be called, allowing any pending finally clauses to execute.

When yield from <expr> is used, the supplied expression must be an iterable. The values produced by iterating that iterable are passed directly to the caller of the current generator's methods. Any values passed in with send() and any exceptions passed in with throw() are passed to the underlying iterator if it has the appropriate methods. If this is not the case, then send() will raise AttributeError or TypeError, while throw() will just raise the passed in exception immediately.

When the underlying iterator is complete, the value attribute of the raised StopIteration instance becomes the value of the yield expression. It can be either set explicitly when raising StopIteration, or automatically when the subiterator is a generator (by returning a value from the subgenerator).

在 3.3 版的變更: Added yield from <expr> to delegate control flow to a subiterator.

The parentheses may be omitted when the yield expression is the sole expression on the right hand side of an assignment statement.

也參考

PEP 255 [https://peps.python.org/pep-0255/] - Simple Generators

The proposal for adding generators and the yield statement to Python.

PEP 342 [https://peps.python.org/pep-0342/] - Coroutines via Enhanced Generators

The proposal to enhance the API and syntax of generators, making them usable as simple coroutines.

PEP 380 [https://peps.python.org/pep-0380/] - Syntax for Delegating to a Subgenerator

The proposal to introduce the yield_from syntax, making delegation to subgenerators easy.

PEP 525 [https://peps.python.org/pep-0525/] - Asynchronous Generators

The proposal that expanded on PEP 492 [https://peps.python.org/pep-0492/] by adding generator capabilities to coroutine functions.

6.2.9.1. Generator-iterator methods

This subsection describes the methods of a generator iterator. They can be used to control the execution of a generator function.

Note that calling any of the generator methods below when the generator is already executing raises a ValueError exception.

generator.__next__()

Starts the execution of a generator function or resumes it at the last executed yield expression. When a generator function is resumed with a __next__() method, the current yield expression always evaluates to None. The execution then continues to the next yield expression, where the generator is suspended again, and the value of the yield_list is returned to __next__()'s caller. If the generator exits without yielding another value, a StopIteration exception is raised.

This method is normally called implicitly, e.g. by a for loop, or by the built-in next() function.

generator.send(value)

Resumes the execution and "sends" a value into the generator function. The value argument becomes the result of the current yield expression. The send() method returns the next value yielded by the generator, or raises StopIteration if the generator exits without yielding another value. When send() is called to start the generator, it must be called with None as the argument, because there is no yield expression that could receive the value.

generator.throw(value)

generator.throw(type[, value[, traceback]])

Raises an exception at the point where the generator was paused, and returns the next value yielded by the generator function. If the generator exits without yielding another value, a StopIteration exception is raised. If the generator function does not catch the passed-in exception, or raises a different exception, then that exception propagates to the caller.

In typical use, this is called with a single exception instance similar to the way the raise keyword is used.

For backwards compatibility, however, the second signature is supported, following a convention from older versions of Python. The type argument should be an exception class, and value should be an exception instance. If the value is not provided, the type constructor is called to get an instance. If traceback is provided, it is set on the exception, otherwise any existing __traceback__ attribute stored in value may be cleared.

在 3.12 版的變更: The second signature (type[, value[, traceback]]) is deprecated and may be removed in a future version of Python.

generator.close()

Raises a GeneratorExit exception at the point where the generator function was paused (equivalent to calling throw(GeneratorExit)). The exception is raised by the yield expression where the generator was paused. If the generator function catches the exception and returns a value, this value is returned from close(). If the generator function is already closed, or raises GeneratorExit (by not catching the exception), close() returns None. If the generator yields a value, a RuntimeError is raised. If the generator raises any other exception, it is propagated to the caller. If the generator has already exited due to an exception or normal exit, close() returns None and has no other effect.

在 3.13 版的變更: If a generator returns a value upon being closed, the value is returned by close().

6.2.9.2. 模組

Here is a simple example that demonstrates the behavior of generators and generator functions:

>>> def echo(value=None):
...     print("Execution starts when 'next()' is called for the first time.")
...     try:
...         while True:
...             try:
...                 value = (yield value)
...             except Exception as e:
...                 value = e
...     finally:
...         print("Don't forget to clean up when 'close()' is called.")
...
>>> generator = echo(1)
>>> print(next(generator))
Execution starts when 'next()' is called for the first time.
1
>>> print(next(generator))
None
>>> print(generator.send(2))
2
>>> generator.throw(TypeError, "spam")
TypeError('spam',)
>>> generator.close()
Don't forget to clean up when 'close()' is called.

For examples using yield from, see PEP 380: Syntax for Delegating to a Subgenerator in "What's New in Python."

6.2.9.3. 非同步產生器函式

The presence of a yield expression in a function or method defined using async def further defines the function as an asynchronous generator function.

When an asynchronous generator function is called, it returns an asynchronous iterator known as an asynchronous generator object. That object then controls the execution of the generator function. An asynchronous generator object is typically used in an async for statement in a coroutine function analogously to how a generator object would be used in a for statement.

Calling one of the asynchronous generator's methods returns an awaitable object, and the execution starts when this object is awaited on. At that time, the execution proceeds to the first yield expression, where it is suspended again, returning the value of yield_list to the awaiting coroutine. As with a generator, suspension means that all local state is retained, including the current bindings of local variables, the instruction pointer, the internal evaluation stack, and the state of any exception handling. When the execution is resumed by awaiting on the next object returned by the asynchronous generator's methods, the function can proceed exactly as if the yield expression were just another external call. The value of the yield expression after resuming depends on the method which resumed the execution. If __anext__() is used then the result is None. Otherwise, if asend() is used, then the result will be the value passed in to that method.

If an asynchronous generator happens to exit early by break, the caller task being cancelled, or other exceptions, the generator's async cleanup code will run and possibly raise exceptions or access context variables in an unexpected context--perhaps after the lifetime of tasks it depends, or during the event loop shutdown when the async-generator garbage collection hook is called. To prevent this, the caller must explicitly close the async generator by calling aclose() method to finalize the generator and ultimately detach it from the event loop.

In an asynchronous generator function, yield expressions are allowed anywhere in a try construct. However, if an asynchronous generator is not resumed before it is finalized (by reaching a zero reference count or by being garbage collected), then a yield expression within a try construct could result in a failure to execute pending finally clauses. In this case, it is the responsibility of the event loop or scheduler running the asynchronous generator to call the asynchronous generator-iterator's aclose() method and run the resulting coroutine object, thus allowing any pending finally clauses to execute.

To take care of finalization upon event loop termination, an event loop should define a finalizer function which takes an asynchronous generator-iterator and presumably calls aclose() and executes the coroutine. This finalizer may be registered by calling sys.set_asyncgen_hooks(). When first iterated over, an asynchronous generator-iterator will store the registered finalizer to be called upon finalization. For a reference example of a finalizer method see the implementation of asyncio.Loop.shutdown_asyncgens in Lib/asyncio/base_events.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/base_events.py].

The expression yield from <expr> is a syntax error when used in an asynchronous generator function.

6.2.9.4. Asynchronous generator-iterator methods

This subsection describes the methods of an asynchronous generator iterator, which are used to control the execution of a generator function.

async agen.__anext__()

Returns an awaitable which when run starts to execute the asynchronous generator or resumes it at the last executed yield expression. When an asynchronous generator function is resumed with an __anext__() method, the current yield expression always evaluates to None in the returned awaitable, which when run will continue to the next yield expression. The value of the yield_list of the yield expression is the value of the StopIteration exception raised by the completing coroutine. If the asynchronous generator exits without yielding another value, the awaitable instead raises a StopAsyncIteration exception, signalling that the asynchronous iteration has completed.

This method is normally called implicitly by a async for loop.

async agen.asend(value)

Returns an awaitable which when run resumes the execution of the asynchronous generator. As with the send() method for a generator, this "sends" a value into the asynchronous generator function, and the value argument becomes the result of the current yield expression. The awaitable returned by the asend() method will return the next value yielded by the generator as the value of the raised StopIteration, or raises StopAsyncIteration if the asynchronous generator exits without yielding another value. When asend() is called to start the asynchronous generator, it must be called with None as the argument, because there is no yield expression that could receive the value.

async agen.athrow(value)

async agen.athrow(type[, value[, traceback]])

Returns an awaitable that raises an exception of type type at the point where the asynchronous generator was paused, and returns the next value yielded by the generator function as the value of the raised StopIteration exception. If the asynchronous generator exits without yielding another value, a StopAsyncIteration exception is raised by the awaitable. If the generator function does not catch the passed-in exception, or raises a different exception, then when the awaitable is run that exception propagates to the caller of the awaitable.

在 3.12 版的變更: The second signature (type[, value[, traceback]]) is deprecated and may be removed in a future version of Python.

async agen.aclose()

Returns an awaitable that when run will throw a GeneratorExit into the asynchronous generator function at the point where it was paused. If the asynchronous generator function then exits gracefully, is already closed, or raises GeneratorExit (by not catching the exception), then the returned awaitable will raise a StopIteration exception. Any further awaitables returned by subsequent calls to the asynchronous generator will raise a StopAsyncIteration exception. If the asynchronous generator yields a value, a RuntimeError is raised by the awaitable. If the asynchronous generator raises any other exception, it is propagated to the caller of the awaitable. If the asynchronous generator has already exited due to an exception or normal exit, then further calls to aclose() will return an awaitable that does nothing.

6.3. Primaries

Primaries represent the most tightly bound operations of the language. Their syntax is:

primary: atom | attributeref | subscription | slicing | call

6.3.1. Attribute references

An attribute reference is a primary followed by a period and a name:

attributeref: primary "." identifier

The primary must evaluate to an object of a type that supports attribute references, which most objects do. This object is then asked to produce the attribute whose name is the identifier. The type and value produced is determined by the object. Multiple evaluations of the same attribute reference may yield different objects.

This production can be customized by overriding the __getattribute__() method or the __getattr__() method. The __getattribute__() method is called first and either returns a value or raises AttributeError if the attribute is not available.

If an AttributeError is raised and the object has a __getattr__() method, that method is called as a fallback.

6.3.2. Subscriptions

The subscription of an instance of a container class will generally select an element from the container. The subscription of a generic class will generally return a GenericAlias object.

subscription: primary "[" flexible_expression_list "]"

When an object is subscripted, the interpreter will evaluate the primary and the expression list.

The primary must evaluate to an object that supports subscription. An object may support subscription through defining one or both of __getitem__() and __class_getitem__(). When the primary is subscripted, the evaluated result of the expression list will be passed to one of these methods. For more details on when __class_getitem__ is called instead of __getitem__, see __class_getitem__ versus __getitem__.

If the expression list contains at least one comma, or if any of the expressions are starred, the expression list will evaluate to a tuple containing the items of the expression list. Otherwise, the expression list will evaluate to the value of the list's sole member.

在 3.11 版的變更: Expressions in an expression list may be starred. See PEP 646 [https://peps.python.org/pep-0646/].

For built-in objects, there are two types of objects that support subscription via __getitem__():

Mappings. If the primary is a mapping, the expression list must evaluate to an object whose value is one of the keys of the mapping, and the subscription selects the value in the mapping that corresponds to that key. An example of a builtin mapping class is the dict class.

Sequences. If the primary is a sequence, the expression list must evaluate to an int or a slice (as discussed in the following section). Examples of builtin sequence classes include the str, list and tuple classes.

The formal syntax makes no special provision for negative indices in sequences. However, built-in sequences all provide a __getitem__() method that interprets negative indices by adding the length of the sequence to the index so that, for example, x[-1] selects the last item of x. The resulting value must be a nonnegative integer less than the number of items in the sequence, and the subscription selects the item whose index is that value (counting from zero). Since the support for negative indices and slicing occurs in the object's __getitem__() method, subclasses overriding this method will need to explicitly add that support.

A string is a special kind of sequence whose items are characters. A character is not a separate data type but a string of exactly one character.

6.3.3. Slicings

A slicing selects a range of items in a sequence object (e.g., a string, tuple or list). Slicings may be used as expressions or as targets in assignment or del statements. The syntax for a slicing:

slicing:      primary "[" slice_list "]"
slice_list:   slice_item ("," slice_item)* [","]
slice_item:   expression | proper_slice
proper_slice: [lower_bound] ":" [upper_bound] [ ":" [stride] ]
lower_bound:  expression
upper_bound:  expression
stride:       expression

There is ambiguity in the formal syntax here: anything that looks like an expression list also looks like a slice list, so any subscription can be interpreted as a slicing. Rather than further complicating the syntax, this is disambiguated by defining that in this case the interpretation as a subscription takes priority over the interpretation as a slicing (this is the case if the slice list contains no proper slice).

The semantics for a slicing are as follows. The primary is indexed (using the same __getitem__() method as normal subscription) with a key that is constructed from the slice list, as follows. If the slice list contains at least one comma, the key is a tuple containing the conversion of the slice items; otherwise, the conversion of the lone slice item is the key. The conversion of a slice item that is an expression is that expression. The conversion of a proper slice is a slice object (see section 標準型別階層) whose start, stop and step attributes are the values of the expressions given as lower bound, upper bound and stride, respectively, substituting None for missing expressions.

6.3.4. Calls

A call calls a callable object (e.g., a function) with a possibly empty series of arguments:

call:                 primary "(" [argument_list [","] | comprehension] ")"
argument_list:        positional_arguments ["," starred_and_keywords]
                        ["," keywords_arguments]
                      | starred_and_keywords ["," keywords_arguments]
                      | keywords_arguments
positional_arguments: positional_item ("," positional_item)*
positional_item:      assignment_expression | "*" expression
starred_and_keywords: ("*" expression | keyword_item)
                      ("," "*" expression | "," keyword_item)*
keywords_arguments:   (keyword_item | "**" expression)
                      ("," keyword_item | "," "**" expression)*
keyword_item:         identifier "=" expression

An optional trailing comma may be present after the positional and keyword arguments but does not affect the semantics.

The primary must evaluate to a callable object (user-defined functions, built-in functions, methods of built-in objects, class objects, methods of class instances, and all objects having a __call__() method are callable). All argument expressions are evaluated before the call is attempted. Please refer to section 函式定義 for the syntax of formal parameter lists.

If keyword arguments are present, they are first converted to positional arguments, as follows. First, a list of unfilled slots is created for the formal parameters. If there are N positional arguments, they are placed in the first N slots. Next, for each keyword argument, the identifier is used to determine the corresponding slot (if the identifier is the same as the first formal parameter name, the first slot is used, and so on). If the slot is already filled, a TypeError exception is raised. Otherwise, the argument is placed in the slot, filling it (even if the expression is None, it fills the slot). When all arguments have been processed, the slots that are still unfilled are filled with the corresponding default value from the function definition. (Default values are calculated, once, when the function is defined; thus, a mutable object such as a list or dictionary used as default value will be shared by all calls that don't specify an argument value for the corresponding slot; this should usually be avoided.) If there are any unfilled slots for which no default value is specified, a TypeError exception is raised. Otherwise, the list of filled slots is used as the argument list for the call.

CPython 實作細節： An implementation may provide built-in functions whose positional parameters do not have names, even if they are 'named' for the purpose of documentation, and which therefore cannot be supplied by keyword. In CPython, this is the case for functions implemented in C that use PyArg_ParseTuple() to parse their arguments.

If there are more positional arguments than there are formal parameter slots, a TypeError exception is raised, unless a formal parameter using the syntax *identifier is present; in this case, that formal parameter receives a tuple containing the excess positional arguments (or an empty tuple if there were no excess positional arguments).

If any keyword argument does not correspond to a formal parameter name, a TypeError exception is raised, unless a formal parameter using the syntax **identifier is present; in this case, that formal parameter receives a dictionary containing the excess keyword arguments (using the keywords as keys and the argument values as corresponding values), or a (new) empty dictionary if there were no excess keyword arguments.

If the syntax *expression appears in the function call, expression must evaluate to an iterable. Elements from these iterables are treated as if they were additional positional arguments. For the call f(x1, x2, *y, x3, x4), if y evaluates to a sequence y1, ..., yM, this is equivalent to a call with M+4 positional arguments x1, x2, y1, ..., yM, x3, x4.

A consequence of this is that although the *expression syntax may appear after explicit keyword arguments, it is processed before the keyword arguments (and any **expression arguments -- see below). So:

>>> def f(a, b):
...     print(a, b)
...
>>> f(b=1, *(2,))
2 1
>>> f(a=1, *(2,))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: f() got multiple values for keyword argument 'a'
>>> f(1, *(2,))
1 2

It is unusual for both keyword arguments and the *expression syntax to be used in the same call, so in practice this confusion does not often arise.

If the syntax **expression appears in the function call, expression must evaluate to a mapping, the contents of which are treated as additional keyword arguments. If a parameter matching a key has already been given a value (by an explicit keyword argument, or from another unpacking), a TypeError exception is raised.

When **expression is used, each key in this mapping must be a string. Each value from the mapping is assigned to the first formal parameter eligible for keyword assignment whose name is equal to the key. A key need not be a Python identifier (e.g. "max-temp °F" is acceptable, although it will not match any formal parameter that could be declared). If there is no match to a formal parameter the key-value pair is collected by the ** parameter, if there is one, or if there is not, a TypeError exception is raised.

Formal parameters using the syntax *identifier or **identifier cannot be used as positional argument slots or as keyword argument names.

在 3.5 版的變更: Function calls accept any number of * and ** unpackings, positional arguments may follow iterable unpackings (*), and keyword arguments may follow dictionary unpackings (**). Originally proposed by PEP 448 [https://peps.python.org/pep-0448/].

A call always returns some value, possibly None, unless it raises an exception. How this value is computed depends on the type of the callable object.

If it is---

a user-defined function:

The code block for the function is executed, passing it the argument list. The first thing the code block will do is bind the formal parameters to the arguments; this is described in section 函式定義. When the code block executes a return statement, this specifies the return value of the function call. If execution reaches the end of the code block without executing a return statement, the return value is None.

a built-in function or method:

The result is up to the interpreter; see 內建函式 for the descriptions of built-in functions and methods.

a class object:

A new instance of that class is returned.

a class instance method:

The corresponding user-defined function is called, with an argument list that is one longer than the argument list of the call: the instance becomes the first argument.

a class instance:

The class must define a __call__() method; the effect is then the same as if that method was called.

6.4. Await expression

Suspend the execution of coroutine on an awaitable object. Can only be used inside a coroutine function.

await_expr: "await" primary

在 3.5 版被加入.

6.5. The power operator

The power operator binds more tightly than unary operators on its left; it binds less tightly than unary operators on its right. The syntax is:

power: (await_expr | primary) ["**" u_expr]

Thus, in an unparenthesized sequence of power and unary operators, the operators are evaluated from right to left (this does not constrain the evaluation order for the operands): -1**2 results in -1.

The power operator has the same semantics as the built-in pow() function, when called with two arguments: it yields its left argument raised to the power of its right argument. The numeric arguments are first converted to a common type, and the result is of that type.

For int operands, the result has the same type as the operands unless the second argument is negative; in that case, all arguments are converted to float and a float result is delivered. For example, 10**2 returns 100, but 10**-2 returns 0.01.

Raising 0.0 to a negative power results in a ZeroDivisionError. Raising a negative number to a fractional power results in a complex number. (In earlier versions it raised a ValueError.)

This operation can be customized using the special __pow__() and __rpow__() methods.

6.6. Unary arithmetic and bitwise operations

All unary arithmetic and bitwise operations have the same priority:

u_expr: power | "-" u_expr | "+" u_expr | "~" u_expr

The unary - (minus) operator yields the negation of its numeric argument; the operation can be overridden with the __neg__() special method.

The unary + (plus) operator yields its numeric argument unchanged; the operation can be overridden with the __pos__() special method.

The unary ~ (invert) operator yields the bitwise inversion of its integer argument. The bitwise inversion of x is defined as -(x+1). It only applies to integral numbers or to custom objects that override the __invert__() special method.

In all three cases, if the argument does not have the proper type, a TypeError exception is raised.

6.7. Binary arithmetic operations

The binary arithmetic operations have the conventional priority levels. Note that some of these operations also apply to certain non-numeric types. Apart from the power operator, there are only two levels, one for multiplicative operators and one for additive operators:

m_expr: u_expr | m_expr "*" u_expr | m_expr "@" m_expr |
        m_expr "//" u_expr | m_expr "/" u_expr |
        m_expr "%" u_expr
a_expr: m_expr | a_expr "+" m_expr | a_expr "-" m_expr

The * (multiplication) operator yields the product of its arguments. The arguments must either both be numbers, or one argument must be an integer and the other must be a sequence. In the former case, the numbers are converted to a common real type and then multiplied together. In the latter case, sequence repetition is performed; a negative repetition factor yields an empty sequence.

This operation can be customized using the special __mul__() and __rmul__() methods.

在 3.14 版的變更: If only one operand is a complex number, the other operand is converted to a floating-point number.

The @ (at) operator is intended to be used for matrix multiplication. No builtin Python types implement this operator.

This operation can be customized using the special __matmul__() and __rmatmul__() methods.

在 3.5 版被加入.

The / (division) and // (floor division) operators yield the quotient of their arguments. The numeric arguments are first converted to a common type. Division of integers yields a float, while floor division of integers results in an integer; the result is that of mathematical division with the 'floor' function applied to the result. Division by zero raises the ZeroDivisionError exception.

The division operation can be customized using the special __truediv__() and __rtruediv__() methods. The floor division operation can be customized using the special __floordiv__() and __rfloordiv__() methods.

The % (modulo) operator yields the remainder from the division of the first argument by the second. The numeric arguments are first converted to a common type. A zero right argument raises the ZeroDivisionError exception. The arguments may be floating-point numbers, e.g., 3.14%0.7 equals 0.34 (since 3.14 equals 4*0.7 + 0.34.) The modulo operator always yields a result with the same sign as its second operand (or zero); the absolute value of the result is strictly smaller than the absolute value of the second operand [1].

The floor division and modulo operators are connected by the following identity: x == (x//y)*y + (x%y). Floor division and modulo are also connected with the built-in function divmod(): divmod(x, y) == (x//y, x%y). [2].

In addition to performing the modulo operation on numbers, the % operator is also overloaded by string objects to perform old-style string formatting (also known as interpolation). The syntax for string formatting is described in the Python Library Reference, section printf-style String Formatting.

The modulo operation can be customized using the special __mod__() and __rmod__() methods.

The floor division operator, the modulo operator, and the divmod() function are not defined for complex numbers. Instead, convert to a floating-point number using the abs() function if appropriate.

The + (addition) operator yields the sum of its arguments. The arguments must either both be numbers or both be sequences of the same type. In the former case, the numbers are converted to a common real type and then added together. In the latter case, the sequences are concatenated.

This operation can be customized using the special __add__() and __radd__() methods.

在 3.14 版的變更: If only one operand is a complex number, the other operand is converted to a floating-point number.

The - (subtraction) operator yields the difference of its arguments. The numeric arguments are first converted to a common real type.

This operation can be customized using the special __sub__() and __rsub__() methods.

在 3.14 版的變更: If only one operand is a complex number, the other operand is converted to a floating-point number.

6.8. Shifting operations

The shifting operations have lower priority than the arithmetic operations:

shift_expr: a_expr | shift_expr ("<<" | ">>") a_expr

These operators accept integers as arguments. They shift the first argument to the left or right by the number of bits given by the second argument.

The left shift operation can be customized using the special __lshift__() and __rlshift__() methods. The right shift operation can be customized using the special __rshift__() and __rrshift__() methods.

A right shift by n bits is defined as floor division by pow(2,n). A left shift by n bits is defined as multiplication with pow(2,n).

6.9. Binary bitwise operations

Each of the three bitwise operations has a different priority level:

and_expr: shift_expr | and_expr "&" shift_expr
xor_expr: and_expr | xor_expr "^" and_expr
or_expr:  xor_expr | or_expr "|" xor_expr

The & operator yields the bitwise AND of its arguments, which must be integers or one of them must be a custom object overriding __and__() or __rand__() special methods.

The ^ operator yields the bitwise XOR (exclusive OR) of its arguments, which must be integers or one of them must be a custom object overriding __xor__() or __rxor__() special methods.

The | operator yields the bitwise (inclusive) OR of its arguments, which must be integers or one of them must be a custom object overriding __or__() or __ror__() special methods.

6.10. Comparisons

Unlike C, all comparison operations in Python have the same priority, which is lower than that of any arithmetic, shifting or bitwise operation. Also unlike C, expressions like a < b < c have the interpretation that is conventional in mathematics:

comparison:    or_expr (comp_operator or_expr)*
comp_operator: "<" | ">" | "==" | ">=" | "<=" | "!="
               | "is" ["not"] | ["not"] "in"

Comparisons yield boolean values: True or False. Custom rich comparison methods may return non-boolean values. In this case Python will call bool() on such value in boolean contexts.

Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once (but in both cases z is not evaluated at all when x < y is found to be false).

Formally, if a, b, c, ..., y, z are expressions and op1, op2, ..., opN are comparison operators, then a op1 b op2 c ... y opN z is equivalent to a op1 b and b op2 c and ... y opN z, except that each expression is evaluated at most once.

Note that a op1 b op2 c doesn't imply any kind of comparison between a and c, so that, e.g., x < y > z is perfectly legal (though perhaps not pretty).

6.10.1. Value comparisons

The operators <, >, ==, >=, <=, and != compare the values of two objects. The objects do not need to have the same type.

Chapter 物件、數值和型別 states that objects have a value (in addition to type and identity). The value of an object is a rather abstract notion in Python: For example, there is no canonical access method for an object's value. Also, there is no requirement that the value of an object should be constructed in a particular way, e.g. comprised of all its data attributes. Comparison operators implement a particular notion of what the value of an object is. One can think of them as defining the value of an object indirectly, by means of their comparison implementation.

Because all types are (direct or indirect) subtypes of object, they inherit the default comparison behavior from object. Types can customize their comparison behavior by implementing rich comparison methods like __lt__(), described in Basic customization.

The default behavior for equality comparison (== and !=) is based on the identity of the objects. Hence, equality comparison of instances with the same identity results in equality, and equality comparison of instances with different identities results in inequality. A motivation for this default behavior is the desire that all objects should be reflexive (i.e. x is y implies x == y).

A default order comparison (<, >, <=, and >=) is not provided; an attempt raises TypeError. A motivation for this default behavior is the lack of a similar invariant as for equality.

The behavior of the default equality comparison, that instances with different identities are always unequal, may be in contrast to what types will need that have a sensible definition of object value and value-based equality. Such types will need to customize their comparison behavior, and in fact, a number of built-in types have done that.

The following list describes the comparison behavior of the most important built-in types.

Numbers of built-in numeric types (數值型別 --- int、float、complex) and of the standard library types fractions.Fraction and decimal.Decimal can be compared within and across their types, with the restriction that complex numbers do not support order comparison. Within the limits of the types involved, they compare mathematically (algorithmically) correct without loss of precision.

The not-a-number values float('NaN') and decimal.Decimal('NaN') are special. Any ordered comparison of a number to a not-a-number value is false. A counter-intuitive implication is that not-a-number values are not equal to themselves. For example, if x = float('NaN'), 3 < x, x < 3 and x == x are all false, while x != x is true. This behavior is compliant with IEEE 754.

None and NotImplemented are singletons. PEP 8 [https://peps.python.org/pep-0008/] advises that comparisons for singletons should always be done with is or is not, never the equality operators.

Binary sequences (instances of bytes or bytearray) can be compared within and across their types. They compare lexicographically using the numeric values of their elements.

Strings (instances of str) compare lexicographically using the numerical Unicode code points (the result of the built-in function ord()) of their characters. [3]

Strings and binary sequences cannot be directly compared.

Sequences (instances of tuple, list, or range) can be compared only within each of their types, with the restriction that ranges do not support order comparison. Equality comparison across these types results in inequality, and ordering comparison across these types raises TypeError.

Sequences compare lexicographically using comparison of corresponding elements. The built-in containers typically assume identical objects are equal to themselves. That lets them bypass equality tests for identical objects to improve performance and to maintain their internal invariants.

Lexicographical comparison between built-in collections works as follows:

For two collections to compare equal, they must be of the same type, have the same length, and each pair of corresponding elements must compare equal (for example, [1,2] == (1,2) is false because the type is not the same).

Collections that support order comparison are ordered the same as their first unequal elements (for example, [1,2,x] <= [1,2,y] has the same value as x <= y). If a corresponding element does not exist, the shorter collection is ordered first (for example, [1,2] < [1,2,3] is true).

Mappings (instances of dict) compare equal if and only if they have equal (key, value) pairs. Equality comparison of the keys and values enforces reflexivity.

Order comparisons (<, >, <=, and >=) raise TypeError.

Sets (instances of set or frozenset) can be compared within and across their types.

They define order comparison operators to mean subset and superset tests. Those relations do not define total orderings (for example, the two sets {1,2} and {2,3} are not equal, nor subsets of one another, nor supersets of one another). Accordingly, sets are not appropriate arguments for functions which depend on total ordering (for example, min(), max(), and sorted() produce undefined results given a list of sets as inputs).

Comparison of sets enforces reflexivity of its elements.

Most other built-in types have no comparison methods implemented, so they inherit the default comparison behavior.

User-defined classes that customize their comparison behavior should follow some consistency rules, if possible:

Equality comparison should be reflexive. In other words, identical objects should compare equal:

x is y implies x == y

Comparison should be symmetric. In other words, the following expressions should have the same result:

x == y 和 y == x

x != y 和 y != x

x < y 和 y > x

x <= y 和 y >= x

Comparison should be transitive. The following (non-exhaustive) examples illustrate that:

x > y and y > z 暗示了 x > z

x < y and y <= z 暗示了 x < z

Inverse comparison should result in the boolean negation. In other words, the following expressions should have the same result:

x == y 和 not x != y

x < y and not x >= y (for total ordering)

x > y and not x <= y (for total ordering)

The last two expressions apply to totally ordered collections (e.g. to sequences, but not to sets or mappings). See also the total_ordering() decorator.

The hash() result should be consistent with equality. Objects that are equal should either have the same hash value, or be marked as unhashable.

Python does not enforce these consistency rules. In fact, the not-a-number values are an example for not following these rules.

6.10.2. Membership test operations

The operators in and not in test for membership. x in s evaluates to True if x is a member of s, and False otherwise. x not in s returns the negation of x in s. All built-in sequences and set types support this as well as dictionary, for which in tests whether the dictionary has a given key. For container types such as list, tuple, set, frozenset, dict, or collections.deque, the expression x in y is equivalent to any(x is e or x == e for e in y).

For the string and bytes types, x in y is True if and only if x is a substring of y. An equivalent test is y.find(x) != -1. Empty strings are always considered to be a substring of any other string, so "" in "abc" will return True.

For user-defined classes which define the __contains__() method, x in y returns True if y.__contains__(x) returns a true value, and False otherwise.

For user-defined classes which do not define __contains__() but do define __iter__(), x in y is True if some value z, for which the expression x is z or x == z is true, is produced while iterating over y. If an exception is raised during the iteration, it is as if in raised that exception.

Lastly, the old-style iteration protocol is tried: if a class defines __getitem__(), x in y is True if and only if there is a non-negative integer index i such that x is y[i] or x == y[i], and no lower integer index raises the IndexError exception. (If any other exception is raised, it is as if in raised that exception).

The operator not in is defined to have the inverse truth value of in.

6.10.3. Identity comparisons

The operators is and is not test for an object's identity: x is y is true if and only if x and y are the same object. An Object's identity is determined using the id() function. x is not y yields the inverse truth value. [4]

6.11. Boolean operations

or_test:  and_test | or_test "or" and_test
and_test: not_test | and_test "and" not_test
not_test: comparison | "not" not_test

In the context of Boolean operations, and also when expressions are used by control flow statements, the following values are interpreted as false: False, None, numeric zero of all types, and empty strings and containers (including strings, tuples, lists, dictionaries, sets and frozensets). All other values are interpreted as true. User-defined objects can customize their truth value by providing a __bool__() method.

The operator not yields True if its argument is false, False otherwise.

The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.

The expression x or y first evaluates x; if x is true, its value is returned; otherwise, y is evaluated and the resulting value is returned.

Note that neither and nor or restrict the value and type they return to False and True, but rather return the last evaluated argument. This is sometimes useful, e.g., if s is a string that should be replaced by a default value if it is empty, the expression s or 'foo' yields the desired value. Because not has to create a new value, it returns a boolean value regardless of the type of its argument (for example, not 'foo' produces False rather than ''.)

6.12. Assignment expressions

assignment_expression: [identifier ":="] expression

An assignment expression (sometimes also called a "named expression" or "walrus") assigns an expression to an identifier, while also returning the value of the expression.

One common use case is when handling matched regular expressions:

if matching := pattern.search(data):
    do_something(matching)

Or, when processing a file stream in chunks:

while chunk := file.read(9000):
    process(chunk)

Assignment expressions must be surrounded by parentheses when used as expression statements and when used as sub-expressions in slicing, conditional, lambda, keyword-argument, and comprehension-if expressions and in assert, with, and assignment statements. In all other places where they can be used, parentheses are not required, including in if and while statements.

在 3.8 版被加入: See PEP 572 [https://peps.python.org/pep-0572/] for more details about assignment expressions.

6.13. Conditional expressions

conditional_expression: or_test ["if" or_test "else" expression]
expression:             conditional_expression | lambda_expr

A conditional expression (sometimes called a "ternary operator") is an alternative to the if-else statement. As it is an expression, it returns a value and can appear as a sub-expression.

The expression x if C else y first evaluates the condition, C rather than x. If C is true, x is evaluated and its value is returned; otherwise, y is evaluated and its value is returned.

See PEP 308 [https://peps.python.org/pep-0308/] for more details about conditional expressions.

6.14. Lambdas

lambda_expr: "lambda" [parameter_list] ":" expression

Lambda expressions (sometimes called lambda forms) are used to create anonymous functions. The expression lambda parameters: expression yields a function object. The unnamed object behaves like a function object defined with:

def <lambda>(parameters):
    return expression

See section 函式定義 for the syntax of parameter lists. Note that functions created with lambda expressions cannot contain statements or annotations.

6.15. Expression lists

starred_expression:       "*" or_expr | expression
flexible_expression:      assignment_expression | starred_expression
flexible_expression_list: flexible_expression ("," flexible_expression)* [","]
starred_expression_list:  starred_expression ("," starred_expression)* [","]
expression_list:          expression ("," expression)* [","]
yield_list:               expression_list | starred_expression "," [starred_expression_list]

Except when part of a list or set display, an expression list containing at least one comma yields a tuple. The length of the tuple is the number of expressions in the list. The expressions are evaluated from left to right.

An asterisk * denotes iterable unpacking. Its operand must be an iterable. The iterable is expanded into a sequence of items, which are included in the new tuple, list, or set, at the site of the unpacking.

在 3.5 版被加入: Iterable unpacking in expression lists, originally proposed by PEP 448 [https://peps.python.org/pep-0448/].

在 3.11 版被加入: Any item in an expression list may be starred. See PEP 646 [https://peps.python.org/pep-0646/].

A trailing comma is required only to create a one-item tuple, such as 1,; it is optional in all other cases. A single expression without a trailing comma doesn't create a tuple, but rather yields the value of that expression. (To create an empty tuple, use an empty pair of parentheses: ().)

6.16. Evaluation order

Python evaluates expressions from left to right. Notice that while evaluating an assignment, the right-hand side is evaluated before the left-hand side.

In the following lines, expressions will be evaluated in the arithmetic order of their suffixes:

expr1, expr2, expr3, expr4
(expr1, expr2, expr3, expr4)
{expr1: expr2, expr3: expr4}
expr1 + expr2 * (expr3 - expr4)
expr1(expr2, expr3, *expr4, **expr5)
expr3, expr4 = expr1, expr2

6.17. Operator precedence

The following table summarizes the operator precedence in Python, from highest precedence (most binding) to lowest precedence (least binding). Operators in the same box have the same precedence. Unless the syntax is explicitly given, operators are binary. Operators in the same box group left to right (except for exponentiation and conditional expressions, which group from right to left).

Note that comparisons, membership tests, and identity tests, all have the same precedence and have a left-to-right chaining feature as described in the Comparisons section.

運算子

描述

(expressions...),

[expressions...], {key: value...}, {expressions...}

Binding or parenthesized expression, list display, dictionary display, set display

x[index], x[index:index], x(arguments...), x.attribute

Subscription, slicing, call, attribute reference

await x

Await expression

**

Exponentiation [5]

+x, -x, ~x

Positive, negative, bitwise NOT

*, @, /, //, %

Multiplication, matrix multiplication, division, floor division, remainder [6]

+, -

Addition and subtraction

<<, >>

Shifts

&

Bitwise AND

^

Bitwise XOR

|

Bitwise OR

in, not in, is, is not, <, <=, >, >=, !=, ==

Comparisons, including membership tests and identity tests

not x

Boolean NOT

and

Boolean AND

or

Boolean OR

if -- else

Conditional expression

lambda

Lambda expression

:=

Assignment expression

註解

[1]

While abs(x%y) < abs(y) is true mathematically, for floats it may not be true numerically due to roundoff. For example, and assuming a platform on which a Python float is an IEEE 754 double-precision number, in order that -1e-100 % 1e100 have the same sign as 1e100, the computed result is -1e-100 + 1e100, which is numerically exactly equal to 1e100. The function math.fmod() returns a result whose sign matches the sign of the first argument instead, and so returns -1e-100 in this case. Which approach is more appropriate depends on the application.

[2]

If x is very close to an exact integer multiple of y, it's possible for x//y to be one larger than (x-x%y)//y due to rounding. In such cases, Python returns the latter result, in order to preserve that divmod(x,y)[0] * y + x % y be very close to x.

[3]

The Unicode standard distinguishes between code points (e.g. U+0041) and abstract characters (e.g. "LATIN CAPITAL LETTER A"). While most abstract characters in Unicode are only represented using one code point, there is a number of abstract characters that can in addition be represented using a sequence of more than one code point. For example, the abstract character "LATIN CAPITAL LETTER C WITH CEDILLA" can be represented as a single precomposed character at code position U+00C7, or as a sequence of a base character at code position U+0043 (LATIN CAPITAL LETTER C), followed by a combining character at code position U+0327 (COMBINING CEDILLA).

The comparison operators on strings compare at the level of Unicode code points. This may be counter-intuitive to humans. For example, "\u00C7" == "\u0043\u0327" is False, even though both strings represent the same abstract character "LATIN CAPITAL LETTER C WITH CEDILLA".

To compare strings at the level of abstract characters (that is, in a way intuitive to humans), use unicodedata.normalize().

[4]

Due to automatic garbage-collection, free lists, and the dynamic nature of descriptors, you may notice seemingly unusual behaviour in certain uses of the is operator, like those involving comparisons between instance methods, or constants. Check their documentation for more info.

[5]

The power operator ** binds less tightly than an arithmetic or bitwise unary operator on its right, that is, 2**-1 is 0.5.

[6]

The % operator is also used for string formatting; the same precedence applies.

7. 簡單陳述式

A simple statement is comprised within a single logical line. Several simple statements may occur on a single line separated by semicolons. The syntax for simple statements is:

simple_stmt: expression_stmt
             | assert_stmt
             | assignment_stmt
             | augmented_assignment_stmt
             | annotated_assignment_stmt
             | pass_stmt
             | del_stmt
             | return_stmt
             | yield_stmt
             | raise_stmt
             | break_stmt
             | continue_stmt
             | import_stmt
             | future_stmt
             | global_stmt
             | nonlocal_stmt
             | type_stmt

7.1. Expression statements

Expression statements are used (mostly interactively) to compute and write a value, or (usually) to call a procedure (a function that returns no meaningful result; in Python, procedures return the value None). Other uses of expression statements are allowed and occasionally useful. The syntax for an expression statement is:

expression_stmt: starred_expression

An expression statement evaluates the expression list (which may be a single expression).

In interactive mode, if the value is not None, it is converted to a string using the built-in repr() function and the resulting string is written to standard output on a line by itself (except if the result is None, so that procedure calls do not cause any output.)

7.2. Assignment statements

Assignment statements are used to (re)bind names to values and to modify attributes or items of mutable objects:

assignment_stmt: (target_list "=")+ (starred_expression | yield_expression)
target_list:     target ("," target)* [","]
target:          identifier
                 | "(" [target_list] ")"
                 | "[" [target_list] "]"
                 | attributeref
                 | subscription
                 | slicing
                 | "*" target

(See section Primaries for the syntax definitions for attributeref, subscription, and slicing.)

An assignment statement evaluates the expression list (remember that this can be a single expression or a comma-separated list, the latter yielding a tuple) and assigns the single resulting object to each of the target lists, from left to right.

Assignment is defined recursively depending on the form of the target (list). When a target is part of a mutable object (an attribute reference, subscription or slicing), the mutable object must ultimately perform the assignment and decide about its validity, and may raise an exception if the assignment is unacceptable. The rules observed by various types and the exceptions raised are given with the definition of the object types (see section 標準型別階層).

Assignment of an object to a target list, optionally enclosed in parentheses or square brackets, is recursively defined as follows.

If the target list is a single target with no trailing comma, optionally in parentheses, the object is assigned to that target.

Else:

If the target list contains one target prefixed with an asterisk, called a "starred" target: The object must be an iterable with at least as many items as there are targets in the target list, minus one. The first items of the iterable are assigned, from left to right, to the targets before the starred target. The final items of the iterable are assigned to the targets after the starred target. A list of the remaining items in the iterable is then assigned to the starred target (the list can be empty).

Else: The object must be an iterable with the same number of items as there are targets in the target list, and the items are assigned, from left to right, to the corresponding targets.

Assignment of an object to a single target is recursively defined as follows.

If the target is an identifier (name):

If the name does not occur in a global or nonlocal statement in the current code block: the name is bound to the object in the current local namespace.

Otherwise: the name is bound to the object in the global namespace or the outer namespace determined by nonlocal, respectively.

The name is rebound if it was already bound. This may cause the reference count for the object previously bound to the name to reach zero, causing the object to be deallocated and its destructor (if it has one) to be called.

If the target is an attribute reference: The primary expression in the reference is evaluated. It should yield an object with assignable attributes; if this is not the case, TypeError is raised. That object is then asked to assign the assigned object to the given attribute; if it cannot perform the assignment, it raises an exception (usually but not necessarily AttributeError).

Note: If the object is a class instance and the attribute reference occurs on both sides of the assignment operator, the right-hand side expression, a.x can access either an instance attribute or (if no instance attribute exists) a class attribute. The left-hand side target a.x is always set as an instance attribute, creating it if necessary. Thus, the two occurrences of a.x do not necessarily refer to the same attribute: if the right-hand side expression refers to a class attribute, the left-hand side creates a new instance attribute as the target of the assignment:

class Cls:
    x = 3             # class variable
inst = Cls()
inst.x = inst.x + 1   # writes inst.x as 4 leaving Cls.x as 3

This description does not necessarily apply to descriptor attributes, such as properties created with property().

If the target is a subscription: The primary expression in the reference is evaluated. It should yield either a mutable sequence object (such as a list) or a mapping object (such as a dictionary). Next, the subscript expression is evaluated.

If the primary is a mutable sequence object (such as a list), the subscript must yield an integer. If it is negative, the sequence's length is added to it. The resulting value must be a nonnegative integer less than the sequence's length, and the sequence is asked to assign the assigned object to its item with that index. If the index is out of range, IndexError is raised (assignment to a subscripted sequence cannot add new items to a list).

If the primary is a mapping object (such as a dictionary), the subscript must have a type compatible with the mapping's key type, and the mapping is then asked to create a key/value pair which maps the subscript to the assigned object. This can either replace an existing key/value pair with the same key value, or insert a new key/value pair (if no key with the same value existed).

For user-defined objects, the __setitem__() method is called with appropriate arguments.

If the target is a slicing: The primary expression in the reference is evaluated. It should yield a mutable sequence object (such as a list). The assigned object should be a sequence object of the same type. Next, the lower and upper bound expressions are evaluated, insofar they are present; defaults are zero and the sequence's length. The bounds should evaluate to integers. If either bound is negative, the sequence's length is added to it. The resulting bounds are clipped to lie between zero and the sequence's length, inclusive. Finally, the sequence object is asked to replace the slice with the items of the assigned sequence. The length of the slice may be different from the length of the assigned sequence, thus changing the length of the target sequence, if the target sequence allows it.

CPython 實作細節： In the current implementation, the syntax for targets is taken to be the same as for expressions, and invalid syntax is rejected during the code generation phase, causing less detailed error messages.

Although the definition of assignment implies that overlaps between the left-hand side and the right-hand side are 'simultaneous' (for example a, b = b, a swaps two variables), overlaps within the collection of assigned-to variables occur left-to-right, sometimes resulting in confusion. For instance, the following program prints [0, 2]:

x = [0, 1]
i = 0
i, x[i] = 1, 2         # i 先被更新，然後 x[i] 再被更新
print(x)

也參考

PEP 3132 [https://peps.python.org/pep-3132/] - Extended Iterable Unpacking

The specification for the *target feature.

7.2.1. 擴增賦值陳述式

Augmented assignment is the combination, in a single statement, of a binary operation and an assignment statement:

augmented_assignment_stmt: augtarget augop (expression_list | yield_expression)
augtarget:                 identifier | attributeref | subscription | slicing
augop:                     "+=" | "-=" | "*=" | "@=" | "/=" | "//=" | "%=" | "**="
                           | ">>=" | "<<=" | "&=" | "^=" | "|="

(See section Primaries for the syntax definitions of the last three symbols.)

An augmented assignment evaluates the target (which, unlike normal assignment statements, cannot be an unpacking) and the expression list, performs the binary operation specific to the type of assignment on the two operands, and assigns the result to the original target. The target is only evaluated once.

An augmented assignment statement like x += 1 can be rewritten as x = x + 1 to achieve a similar, but not exactly equal effect. In the augmented version, x is only evaluated once. Also, when possible, the actual operation is performed in-place, meaning that rather than creating a new object and assigning that to the target, the old object is modified instead.

Unlike normal assignments, augmented assignments evaluate the left-hand side before evaluating the right-hand side. For example, a[i] += f(x) first looks-up a[i], then it evaluates f(x) and performs the addition, and lastly, it writes the result back to a[i].

With the exception of assigning to tuples and multiple targets in a single statement, the assignment done by augmented assignment statements is handled the same way as normal assignments. Similarly, with the exception of the possible in-place behavior, the binary operation performed by augmented assignment is the same as the normal binary operations.

For targets which are attribute references, the same caveat about class and instance attributes applies as for regular assignments.

7.2.2. 註釋賦值陳述式

註釋 賦值是將變數或屬性註釋與可選的賦值陳述式結合在一個陳述式中：

annotated_assignment_stmt: augtarget ":" expression
                           ["=" (starred_expression | yield_expression)]

The difference from normal Assignment statements is that only a single target is allowed.

The assignment target is considered "simple" if it consists of a single name that is not enclosed in parentheses. For simple assignment targets, if in class or module scope, the annotations are gathered in a lazily evaluated annotation scope. The annotations can be evaluated using the __annotations__ attribute of a class or module, or using the facilities in the annotationlib module.

If the assignment target is not simple (an attribute, subscript node, or parenthesized name), the annotation is never evaluated.

If a name is annotated in a function scope, then this name is local for that scope. Annotations are never evaluated and stored in function scopes.

If the right hand side is present, an annotated assignment performs the actual assignment as if there was no annotation present. If the right hand side is not present for an expression target, then the interpreter evaluates the target except for the last __setitem__() or __setattr__() call.

也參考

PEP 526 [https://peps.python.org/pep-0526/] - Syntax for Variable Annotations

The proposal that added syntax for annotating the types of variables (including class variables and instance variables), instead of expressing them through comments.

PEP 484 [https://peps.python.org/pep-0484/] - 型別提示

The proposal that added the typing module to provide a standard syntax for type annotations that can be used in static analysis tools and IDEs.

在 3.8 版的變更: Now annotated assignments allow the same expressions in the right hand side as regular assignments. Previously, some expressions (like un-parenthesized tuple expressions) caused a syntax error.

在 3.14 版的變更: Annotations are now lazily evaluated in a separate annotation scope. If the assignment target is not simple, annotations are never evaluated.

7.3. assert 陳述式

Assert statements are a convenient way to insert debugging assertions into a program:

assert_stmt: "assert" expression ["," expression]

The simple form, assert expression, is equivalent to

if __debug__:
    if not expression: raise AssertionError

The extended form, assert expression1, expression2, is equivalent to

if __debug__:
    if not expression1: raise AssertionError(expression2)

These equivalences assume that __debug__ and AssertionError refer to the built-in variables with those names. In the current implementation, the built-in variable __debug__ is True under normal circumstances, False when optimization is requested (command line option -O). The current code generator emits no code for an assert statement when optimization is requested at compile time. Note that it is unnecessary to include the source code for the expression that failed in the error message; it will be displayed as part of the stack trace.

Assignments to __debug__ are illegal. The value for the built-in variable is determined when the interpreter starts.

7.4. pass 陳述式

pass_stmt: "pass"

pass is a null operation --- when it is executed, nothing happens. It is useful as a placeholder when a statement is required syntactically, but no code needs to be executed, for example:

def f(arg): pass    # 一個（還）沒有實作的函式

class C: pass       # 一個（還）沒有方法的類別

7.5. del 陳述式

del_stmt: "del" target_list

Deletion is recursively defined very similar to the way assignment is defined. Rather than spelling it out in full details, here are some hints.

Deletion of a target list recursively deletes each target, from left to right.

Deletion of a name removes the binding of that name from the local or global namespace, depending on whether the name occurs in a global statement in the same code block. Trying to delete an unbound name raises a NameError exception.

Deletion of attribute references, subscriptions and slicings is passed to the primary object involved; deletion of a slicing is in general equivalent to assignment of an empty slice of the right type (but even this is determined by the sliced object).

在 3.2 版的變更: Previously it was illegal to delete a name from the local namespace if it occurs as a free variable in a nested block.

7.6. return 陳述式

return_stmt: "return" [expression_list]

return may only occur syntactically nested in a function definition, not within a nested class definition.

If an expression list is present, it is evaluated, else None is substituted.

return leaves the current function call with the expression list (or None) as return value.

When return passes control out of a try statement with a finally clause, that finally clause is executed before really leaving the function.

In a generator function, the return statement indicates that the generator is done and will cause StopIteration to be raised. The returned value (if any) is used as an argument to construct StopIteration and becomes the StopIteration.value attribute.

In an asynchronous generator function, an empty return statement indicates that the asynchronous generator is done and will cause StopAsyncIteration to be raised. A non-empty return statement is a syntax error in an asynchronous generator function.

7.7. yield 陳述式

yield_stmt: yield_expression

A yield statement is semantically equivalent to a yield expression. The yield statement can be used to omit the parentheses that would otherwise be required in the equivalent yield expression statement. For example, the yield statements

yield <expr>
yield from <expr>

are equivalent to the yield expression statements

(yield <expr>)
(yield from <expr>)

Yield expressions and statements are only used when defining a generator function, and are only used in the body of the generator function. Using yield in a function definition is sufficient to cause that definition to create a generator function instead of a normal function.

For full details of yield semantics, refer to the Yield expressions section.

7.8. raise 陳述式

raise_stmt: "raise" [expression ["from" expression]]

If no expressions are present, raise re-raises the exception that is currently being handled, which is also known as the active exception. If there isn't currently an active exception, a RuntimeError exception is raised indicating that this is an error.

Otherwise, raise evaluates the first expression as the exception object. It must be either a subclass or an instance of BaseException. If it is a class, the exception instance will be obtained when needed by instantiating the class with no arguments.

The type of the exception is the exception instance's class, the value is the instance itself.

A traceback object is normally created automatically when an exception is raised and attached to it as the __traceback__ attribute. You can create an exception and set your own traceback in one step using the with_traceback() exception method (which returns the same exception instance, with its traceback set to its argument), like so:

raise Exception("foo occurred").with_traceback(tracebackobj)

The from clause is used for exception chaining: if given, the second expression must be another exception class or instance. If the second expression is an exception instance, it will be attached to the raised exception as the __cause__ attribute (which is writable). If the expression is an exception class, the class will be instantiated and the resulting exception instance will be attached to the raised exception as the __cause__ attribute. If the raised exception is not handled, both exceptions will be printed:

>>> try:
...     print(1 / 0)
... except Exception as exc:
...     raise RuntimeError("Something bad happened") from exc
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    print(1 / 0)
          ~~^~~
ZeroDivisionError: division by zero

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
    raise RuntimeError("Something bad happened") from exc
RuntimeError: Something bad happened

A similar mechanism works implicitly if a new exception is raised when an exception is already being handled. An exception may be handled when an except or finally clause, or a with statement, is used. The previous exception is then attached as the new exception's __context__ attribute:

>>> try:
...     print(1 / 0)
... except:
...     raise RuntimeError("Something bad happened")
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
    print(1 / 0)
          ~~^~~
ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
    raise RuntimeError("Something bad happened")
RuntimeError: Something bad happened

Exception chaining can be explicitly suppressed by specifying None in the from clause:

>>> try:
...     print(1 / 0)
... except:
...     raise RuntimeError("Something bad happened") from None
...
Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
RuntimeError: Something bad happened

Additional information on exceptions can be found in section 例外, and information about handling exceptions is in section try 陳述式.

在 3.3 版的變更: None 現在允許作為 raise X from Y 中的 Y。

Added the __suppress_context__ attribute to suppress automatic display of the exception context.

在 3.11 版的變更: If the traceback of the active exception is modified in an except clause, a subsequent raise statement re-raises the exception with the modified traceback. Previously, the exception was re-raised with the traceback it had when it was caught.

7.9. break 陳述式

break_stmt: "break"

break may only occur syntactically nested in a for or while loop, but not nested in a function or class definition within that loop.

It terminates the nearest enclosing loop, skipping the optional else clause if the loop has one.

If a for loop is terminated by break, the loop control target keeps its current value.

When break passes control out of a try statement with a finally clause, that finally clause is executed before really leaving the loop.

7.10. continue 陳述式

continue_stmt: "continue"

continue may only occur syntactically nested in a for or while loop, but not nested in a function or class definition within that loop. It continues with the next cycle of the nearest enclosing loop.

When continue passes control out of a try statement with a finally clause, that finally clause is executed before really starting the next loop cycle.

7.11. import 陳述式

import_stmt:     "import" module ["as" identifier] ("," module ["as" identifier])*
                 | "from" relative_module "import" identifier ["as" identifier]
                 ("," identifier ["as" identifier])*
                 | "from" relative_module "import" "(" identifier ["as" identifier]
                 ("," identifier ["as" identifier])* [","] ")"
                 | "from" relative_module "import" "*"
module:          (identifier ".")* identifier
relative_module: "."* module | "."+

The basic import statement (no from clause) is executed in two steps:

find a module, loading and initializing it if necessary

define a name or names in the local namespace for the scope where the import statement occurs.

When the statement contains multiple clauses (separated by commas) the two steps are carried out separately for each clause, just as though the clauses had been separated out into individual import statements.

The details of the first step, finding and loading modules, are described in greater detail in the section on the import system, which also describes the various types of packages and modules that can be imported, as well as all the hooks that can be used to customize the import system. Note that failures in this step may indicate either that the module could not be located, or that an error occurred while initializing the module, which includes execution of the module's code.

If the requested module is retrieved successfully, it will be made available in the local namespace in one of three ways:

If the module name is followed by as, then the name following as is bound directly to the imported module.

If no other name is specified, and the module being imported is a top level module, the module's name is bound in the local namespace as a reference to the imported module

If the module being imported is not a top level module, then the name of the top level package that contains the module is bound in the local namespace as a reference to the top level package. The imported module must be accessed using its full qualified name rather than directly

The from form uses a slightly more complex process:

find the module specified in the from clause, loading and initializing it if necessary;

for each of the identifiers specified in the import clauses:

check if the imported module has an attribute by that name

if not, attempt to import a submodule with that name and then check the imported module again for that attribute

if the attribute is not found, ImportError is raised.

otherwise, a reference to that value is stored in the local namespace, using the name in the as clause if it is present, otherwise using the attribute name

範例：

import foo                 # foo imported and bound locally
import foo.bar.baz         # foo, foo.bar, and foo.bar.baz imported, foo bound locally
import foo.bar.baz as fbb  # foo, foo.bar, and foo.bar.baz imported, foo.bar.baz bound as fbb
from foo.bar import baz    # foo, foo.bar, and foo.bar.baz imported, foo.bar.baz bound as baz
from foo import attr       # foo imported and foo.attr bound as attr

If the list of identifiers is replaced by a star ('*'), all public names defined in the module are bound in the local namespace for the scope where the import statement occurs.

The public names defined by a module are determined by checking the module's namespace for a variable named __all__; if defined, it must be a sequence of strings which are names defined or imported by that module. The names given in __all__ are all considered public and are required to exist. If __all__ is not defined, the set of public names includes all names found in the module's namespace which do not begin with an underscore character ('_'). __all__ should contain the entire public API. It is intended to avoid accidentally exporting items that are not part of the API (such as library modules which were imported and used within the module).

The wild card form of import --- from module import * --- is only allowed at the module level. Attempting to use it in class or function definitions will raise a SyntaxError.

When specifying what module to import you do not have to specify the absolute name of the module. When a module or package is contained within another package it is possible to make a relative import within the same top package without having to mention the package name. By using leading dots in the specified module or package after from you can specify how high to traverse up the current package hierarchy without specifying exact names. One leading dot means the current package where the module making the import exists. Two dots means up one package level. Three dots is up two levels, etc. So if you execute from . import mod from a module in the pkg package then you will end up importing pkg.mod. If you execute from ..subpkg2 import mod from within pkg.subpkg1 you will import pkg.subpkg2.mod. The specification for relative imports is contained in the Package Relative Imports section.

importlib.import_module() is provided to support applications that determine dynamically the modules to be loaded.

引發一個附帶引數 module、filename、sys.path、sys.meta_path、sys.path_hooks 的稽核事件 import。

7.11.1. Future statements

A future statement is a directive to the compiler that a particular module should be compiled using syntax or semantics that will be available in a specified future release of Python where the feature becomes standard.

The future statement is intended to ease migration to future versions of Python that introduce incompatible changes to the language. It allows use of the new features on a per-module basis before the release in which the feature becomes standard.

future_stmt: "from" "__future__" "import" feature ["as" identifier]
             ("," feature ["as" identifier])*
             | "from" "__future__" "import" "(" feature ["as" identifier]
             ("," feature ["as" identifier])* [","] ")"
feature:     identifier

A future statement must appear near the top of the module. The only lines that can appear before a future statement are:

the module docstring (if any),

comments,

blank lines, and

other future statements.

The only feature that requires using the future statement is annotations (see PEP 563 [https://peps.python.org/pep-0563/]).

All historical features enabled by the future statement are still recognized by Python 3. The list includes absolute_import, division, generators, generator_stop, unicode_literals, print_function, nested_scopes and with_statement. They are all redundant because they are always enabled, and only kept for backwards compatibility.

A future statement is recognized and treated specially at compile time: Changes to the semantics of core constructs are often implemented by generating different code. It may even be the case that a new feature introduces new incompatible syntax (such as a new reserved word), in which case the compiler may need to parse the module differently. Such decisions cannot be pushed off until runtime.

For any given release, the compiler knows which feature names have been defined, and raises a compile-time error if a future statement contains a feature not known to it.

The direct runtime semantics are the same as for any import statement: there is a standard module __future__, described later, and it will be imported in the usual way at the time the future statement is executed.

The interesting runtime semantics depend on the specific feature enabled by the future statement.

Note that there is nothing special about the statement:

import __future__ [as name]

That is not a future statement; it's an ordinary import statement with no special semantics or syntax restrictions.

Code compiled by calls to the built-in functions exec() and compile() that occur in a module M containing a future statement will, by default, use the new syntax or semantics associated with the future statement. This can be controlled by optional arguments to compile() --- see the documentation of that function for details.

A future statement typed at an interactive interpreter prompt will take effect for the rest of the interpreter session. If an interpreter is started with the -i option, is passed a script name to execute, and the script includes a future statement, it will be in effect in the interactive session started after the script is executed.

也參考

PEP 236 [https://peps.python.org/pep-0236/] - Back to the __future__

The original proposal for the __future__ mechanism.

7.12. global 陳述式

global_stmt: "global" identifier ("," identifier)*

The global statement causes the listed identifiers to be interpreted as globals. It would be impossible to assign to a global variable without global, although free variables may refer to globals without being declared global.

The global statement applies to the entire current scope (module, function body or class definition). A SyntaxError is raised if a variable is used or assigned to prior to its global declaration in the scope.

At the module level, all variables are global, so a global statement has no effect. However, variables must still not be used or assigned to prior to their global declaration. This requirement is relaxed in the interactive prompt (REPL).

Programmer's note: global is a directive to the parser. It applies only to code parsed at the same time as the global statement. In particular, a global statement contained in a string or code object supplied to the built-in exec() function does not affect the code block containing the function call, and code contained in such a string is unaffected by global statements in the code containing the function call. The same applies to the eval() and compile() functions.

7.13. nonlocal 陳述式

nonlocal_stmt: "nonlocal" identifier ("," identifier)*

When the definition of a function or class is nested (enclosed) within the definitions of other functions, its nonlocal scopes are the local scopes of the enclosing functions. The nonlocal statement causes the listed identifiers to refer to names previously bound in nonlocal scopes. It allows encapsulated code to rebind such nonlocal identifiers. If a name is bound in more than one nonlocal scope, the nearest binding is used. If a name is not bound in any nonlocal scope, or if there is no nonlocal scope, a SyntaxError is raised.

The nonlocal statement applies to the entire scope of a function or class body. A SyntaxError is raised if a variable is used or assigned to prior to its nonlocal declaration in the scope.

也參考

PEP 3104 [https://peps.python.org/pep-3104/] - Access to Names in Outer Scopes

The specification for the nonlocal statement.

Programmer's note: nonlocal is a directive to the parser and applies only to code parsed along with it. See the note for the global statement.

7.14. type 陳述式

type_stmt: 'type' identifier [type_params] "=" expression

The type statement declares a type alias, which is an instance of typing.TypeAliasType.

For example, the following statement creates a type alias:

type Point = tuple[float, float]

This code is roughly equivalent to:

annotation-def VALUE_OF_Point():
    return tuple[float, float]
Point = typing.TypeAliasType("Point", VALUE_OF_Point())

annotation-def indicates an annotation scope, which behaves mostly like a function, but with several small differences.

The value of the type alias is evaluated in the annotation scope. It is not evaluated when the type alias is created, but only when the value is accessed through the type alias's __value__ attribute (see Lazy evaluation). This allows the type alias to refer to names that are not yet defined.

Type aliases may be made generic by adding a type parameter list after the name. See Generic type aliases for more.

type is a soft keyword.

在 3.12 版被加入.

也參考

PEP 695 [https://peps.python.org/pep-0695/] - Type Parameter Syntax

Introduced the type statement and syntax for generic classes and functions.

8. 複合陳述式

Compound statements contain (groups of) other statements; they affect or control the execution of those other statements in some way. In general, compound statements span multiple lines, although in simple incarnations a whole compound statement may be contained in one line.

The if, while and for statements implement traditional control flow constructs. try specifies exception handlers and/or cleanup code for a group of statements, while the with statement allows the execution of initialization and finalization code around a block of code. Function and class definitions are also syntactically compound statements.

A compound statement consists of one or more 'clauses.' A clause consists of a header and a 'suite.' The clause headers of a particular compound statement are all at the same indentation level. Each clause header begins with a uniquely identifying keyword and ends with a colon. A suite is a group of statements controlled by a clause. A suite can be one or more semicolon-separated simple statements on the same line as the header, following the header's colon, or it can be one or more indented statements on subsequent lines. Only the latter form of a suite can contain nested compound statements; the following is illegal, mostly because it wouldn't be clear to which if clause a following else clause would belong:

if test1: if test2: print(x)

Also note that the semicolon binds tighter than the colon in this context, so that in the following example, either all or none of the print() calls are executed:

if x < y < z: print(x); print(y); print(z)

Summarizing:

compound_stmt: if_stmt
               | while_stmt
               | for_stmt
               | try_stmt
               | with_stmt
               | match_stmt
               | funcdef
               | classdef
               | async_with_stmt
               | async_for_stmt
               | async_funcdef
suite:         stmt_list NEWLINE | NEWLINE INDENT statement+ DEDENT
statement:     stmt_list NEWLINE | compound_stmt
stmt_list:     simple_stmt (";" simple_stmt)* [";"]

Note that statements always end in a NEWLINE possibly followed by a DEDENT. Also note that optional continuation clauses always begin with a keyword that cannot start a statement, thus there are no ambiguities (the 'dangling else' problem is solved in Python by requiring nested if statements to be indented).

The formatting of the grammar rules in the following sections places each clause on a separate line for clarity.

8.1. if 陳述式

The if statement is used for conditional execution:

if_stmt: "if" assignment_expression ":" suite
         ("elif" assignment_expression ":" suite)*
         ["else" ":" suite]

It selects exactly one of the suites by evaluating the expressions one by one until one is found to be true (see section Boolean operations for the definition of true and false); then that suite is executed (and no other part of the if statement is executed or evaluated). If all expressions are false, the suite of the else clause, if present, is executed.

8.2. while 陳述式

The while statement is used for repeated execution as long as an expression is true:

while_stmt: "while" assignment_expression ":" suite
            ["else" ":" suite]

This repeatedly tests the expression and, if it is true, executes the first suite; if the expression is false (which may be the first time it is tested) the suite of the else clause, if present, is executed and the loop terminates.

A break statement executed in the first suite terminates the loop without executing the else clause's suite. A continue statement executed in the first suite skips the rest of the suite and goes back to testing the expression.

8.3. for 陳述式

The for statement is used to iterate over the elements of a sequence (such as a string, tuple or list) or other iterable object:

for_stmt: "for" target_list "in" starred_expression_list ":" suite
          ["else" ":" suite]

The starred_expression_list expression is evaluated once; it should yield an iterable object. An iterator is created for that iterable. The first item provided by the iterator is then assigned to the target list using the standard rules for assignments (see Assignment statements), and the suite is executed. This repeats for each item provided by the iterator. When the iterator is exhausted, the suite in the else clause, if present, is executed, and the loop terminates.

A break statement executed in the first suite terminates the loop without executing the else clause's suite. A continue statement executed in the first suite skips the rest of the suite and continues with the next item, or with the else clause if there is no next item.

The for-loop makes assignments to the variables in the target list. This overwrites all previous assignments to those variables including those made in the suite of the for-loop:

for i in range(10):
    print(i)
    i = 5             # this will not affect the for-loop
                      # because i will be overwritten with the next
                      # index in the range

Names in the target list are not deleted when the loop is finished, but if the sequence is empty, they will not have been assigned to at all by the loop. Hint: the built-in type range() represents immutable arithmetic sequences of integers. For instance, iterating range(3) successively yields 0, 1, and then 2.

在 3.11 版的變更: Starred elements are now allowed in the expression list.

8.4. try 陳述式

The try statement specifies exception handlers and/or cleanup code for a group of statements:

try_stmt:  try1_stmt | try2_stmt | try3_stmt
try1_stmt: "try" ":" suite
           ("except" [expression ["as" identifier]] ":" suite)+
           ["else" ":" suite]
           ["finally" ":" suite]
try2_stmt: "try" ":" suite
           ("except" "*" expression ["as" identifier] ":" suite)+
           ["else" ":" suite]
           ["finally" ":" suite]
try3_stmt: "try" ":" suite
           "finally" ":" suite

Additional information on exceptions can be found in section 例外, and information on using the raise statement to generate exceptions may be found in section raise 陳述式.

在 3.14 版的變更: Support for optionally dropping grouping parentheses when using multiple exception types. See PEP 758 [https://peps.python.org/pep-0758/].

8.4.1. except 子句

The except clause(s) specify one or more exception handlers. When no exception occurs in the try clause, no exception handler is executed. When an exception occurs in the try suite, a search for an exception handler is started. This search inspects the except clauses in turn until one is found that matches the exception. An expression-less except clause, if present, must be last; it matches any exception.

For an except clause with an expression, the expression must evaluate to an exception type or a tuple of exception types. Parentheses can be dropped if multiple exception types are provided and the as clause is not used. The raised exception matches an except clause whose expression evaluates to the class or a non-virtual base class of the exception object, or to a tuple that contains such a class.

If no except clause matches the exception, the search for an exception handler continues in the surrounding code and on the invocation stack. [1]

If the evaluation of an expression in the header of an except clause raises an exception, the original search for a handler is canceled and a search starts for the new exception in the surrounding code and on the call stack (it is treated as if the entire try statement raised the exception).

When a matching except clause is found, the exception is assigned to the target specified after the as keyword in that except clause, if present, and the except clause's suite is executed. All except clauses must have an executable block. When the end of this block is reached, execution continues normally after the entire try statement. (This means that if two nested handlers exist for the same exception, and the exception occurs in the try clause of the inner handler, the outer handler will not handle the exception.)

When an exception has been assigned using as target, it is cleared at the end of the except clause. This is as if

except E as N:
    foo

was translated to

except E as N:
    try:
        foo
    finally:
        del N

This means the exception must be assigned to a different name to be able to refer to it after the except clause. Exceptions are cleared because with the traceback attached to them, they form a reference cycle with the stack frame, keeping all locals in that frame alive until the next garbage collection occurs.

Before an except clause's suite is executed, the exception is stored in the sys module, where it can be accessed from within the body of the except clause by calling sys.exception(). When leaving an exception handler, the exception stored in the sys module is reset to its previous value:

>>> print(sys.exception())
None
>>> try:
...     raise TypeError
... except:
...     print(repr(sys.exception()))
...     try:
...          raise ValueError
...     except:
...         print(repr(sys.exception()))
...     print(repr(sys.exception()))
...
TypeError()
ValueError()
TypeError()
>>> print(sys.exception())
None

8.4.2. except* 子句

The except* clause(s) specify one or more handlers for groups of exceptions (BaseExceptionGroup instances). A try statement can have either except or except* clauses, but not both. The exception type for matching is mandatory in the case of except*, so except*: is a syntax error. The type is interpreted as in the case of except, but matching is performed on the exceptions contained in the group that is being handled. An TypeError is raised if a matching type is a subclass of BaseExceptionGroup, because that would have ambiguous semantics.

When an exception group is raised in the try block, each except* clause splits (see split()) it into the subgroups of matching and non-matching exceptions. If the matching subgroup is not empty, it becomes the handled exception (the value returned from sys.exception()) and assigned to the target of the except* clause (if there is one). Then, the body of the except* clause executes. If the non-matching subgroup is not empty, it is processed by the next except* in the same manner. This continues until all exceptions in the group have been matched, or the last except* clause has run.

After all except* clauses execute, the group of unhandled exceptions is merged with any exceptions that were raised or re-raised from within except* clauses. This merged exception group propagates on.:

>>> try:
...     raise ExceptionGroup("eg",
...         [ValueError(1), TypeError(2), OSError(3), OSError(4)])
... except* TypeError as e:
...     print(f'caught {type(e)} with nested {e.exceptions}')
... except* OSError as e:
...     print(f'caught {type(e)} with nested {e.exceptions}')
...
caught <class 'ExceptionGroup'> with nested (TypeError(2),)
caught <class 'ExceptionGroup'> with nested (OSError(3), OSError(4))
  + Exception Group Traceback (most recent call last):
  |   File "<doctest default[0]>", line 2, in <module>
  |     raise ExceptionGroup("eg",
  |         [ValueError(1), TypeError(2), OSError(3), OSError(4)])
  | ExceptionGroup: eg (1 sub-exception)
  +-+---------------- 1 ----------------
    | ValueError: 1
    +------------------------------------

If the exception raised from the try block is not an exception group and its type matches one of the except* clauses, it is caught and wrapped by an exception group with an empty message string. This ensures that the type of the target e is consistently BaseExceptionGroup:

>>> try:
...     raise BlockingIOError
... except* BlockingIOError as e:
...     print(repr(e))
...
ExceptionGroup('', (BlockingIOError(),))

break, continue and return cannot appear in an except* clause.

8.4.3. else 子句

The optional else clause is executed if the control flow leaves the try suite, no exception was raised, and no return, continue, or break statement was executed. Exceptions in the else clause are not handled by the preceding except clauses.

8.4.4. finally 子句

If finally is present, it specifies a 'cleanup' handler. The try clause is executed, including any except and else clauses. If an exception occurs in any of the clauses and is not handled, the exception is temporarily saved. The finally clause is executed. If there is a saved exception it is re-raised at the end of the finally clause. If the finally clause raises another exception, the saved exception is set as the context of the new exception. If the finally clause executes a return, break or continue statement, the saved exception is discarded. For example, this function returns 42.

def f():
    try:
        1/0
    finally:
        return 42

The exception information is not available to the program during execution of the finally clause.

When a return, break or continue statement is executed in the try suite of a try...finally statement, the finally clause is also executed 'on the way out.'

The return value of a function is determined by the last return statement executed. Since the finally clause always executes, a return statement executed in the finally clause will always be the last one executed. The following function returns 'finally'.

def foo():
    try:
        return 'try'
    finally:
        return 'finally'

在 3.8 版的變更: Prior to Python 3.8, a continue statement was illegal in the finally clause due to a problem with the implementation.

在 3.14 版的變更: The compiler emits a SyntaxWarning when a return, break or continue appears in a finally block (see PEP 765 [https://peps.python.org/pep-0765/]).

8.5. with 陳述式

The with statement is used to wrap the execution of a block with methods defined by a context manager (see section With 陳述式的情境管理器). This allows common try...except...finally usage patterns to be encapsulated for convenient reuse.

with_stmt:          "with" ( "(" with_stmt_contents ","? ")" | with_stmt_contents ) ":" suite
with_stmt_contents: with_item ("," with_item)*
with_item:          expression ["as" target]

The execution of the with statement with one "item" proceeds as follows:

The context expression (the expression given in the with_item) is evaluated to obtain a context manager.

The context manager's __enter__() is loaded for later use.

The context manager's __exit__() is loaded for later use.

The context manager's __enter__() method is invoked.

If a target was included in the with statement, the return value from __enter__() is assigned to it.

備註

The with statement guarantees that if the __enter__() method returns without an error, then __exit__() will always be called. Thus, if an error occurs during the assignment to the target list, it will be treated the same as an error occurring within the suite would be. See step 7 below.

The suite is executed.

The context manager's __exit__() method is invoked. If an exception caused the suite to be exited, its type, value, and traceback are passed as arguments to __exit__(). Otherwise, three None arguments are supplied.

If the suite was exited due to an exception, and the return value from the __exit__() method was false, the exception is reraised. If the return value was true, the exception is suppressed, and execution continues with the statement following the with statement.

If the suite was exited for any reason other than an exception, the return value from __exit__() is ignored, and execution proceeds at the normal location for the kind of exit that was taken.

以下程式碼：

with EXPRESSION as TARGET:
    SUITE

在語義上等同於：

manager = (EXPRESSION)
enter = type(manager).__enter__
exit = type(manager).__exit__
value = enter(manager)
hit_except = False

try:
    TARGET = value
    SUITE
except:
    hit_except = True
    if not exit(manager, *sys.exc_info()):
        raise
finally:
    if not hit_except:
        exit(manager, None, None, None)

With more than one item, the context managers are processed as if multiple with statements were nested:

with A() as a, B() as b:
    SUITE

在語義上等同於：

with A() as a:
    with B() as b:
        SUITE

You can also write multi-item context managers in multiple lines if the items are surrounded by parentheses. For example:

with (
    A() as a,
    B() as b,
):
    SUITE

在 3.1 版的變更: Support for multiple context expressions.

在 3.10 版的變更: Support for using grouping parentheses to break the statement in multiple lines.

也參考

PEP 343 [https://peps.python.org/pep-0343/] - "with" 陳述式

The specification, background, and examples for the Python with statement.

8.6. match 陳述式

在 3.10 版被加入.

The match statement is used for pattern matching. Syntax:

match_stmt:   'match' subject_expr ":" NEWLINE INDENT case_block+ DEDENT
subject_expr: `!star_named_expression` "," `!star_named_expressions`?
              | `!named_expression`
case_block:   'case' patterns [guard] ":" `!block`

備註

This section uses single quotes to denote soft keywords.

Pattern matching takes a pattern as input (following case) and a subject value (following match). The pattern (which may contain subpatterns) is matched against the subject value. The outcomes are:

A match success or failure (also termed a pattern success or failure).

Possible binding of matched values to a name. The prerequisites for this are further discussed below.

The match and case keywords are soft keywords.

也參考

PEP 634 [https://peps.python.org/pep-0634/] -- Structural Pattern Matching: Specification

PEP 636 [https://peps.python.org/pep-0636/] -- Structural Pattern Matching: Tutorial

8.6.1. Overview

Here's an overview of the logical flow of a match statement:

The subject expression subject_expr is evaluated and a resulting subject value obtained. If the subject expression contains a comma, a tuple is constructed using the standard rules.

Each pattern in a case_block is attempted to match with the subject value. The specific rules for success or failure are described below. The match attempt can also bind some or all of the standalone names within the pattern. The precise pattern binding rules vary per pattern type and are specified below. Name bindings made during a successful pattern match outlive the executed block and can be used after the match statement.

備註

During failed pattern matches, some subpatterns may succeed. Do not rely on bindings being made for a failed match. Conversely, do not rely on variables remaining unchanged after a failed match. The exact behavior is dependent on implementation and may vary. This is an intentional decision made to allow different implementations to add optimizations.

If the pattern succeeds, the corresponding guard (if present) is evaluated. In this case all name bindings are guaranteed to have happened.

If the guard evaluates as true or is missing, the block inside case_block is executed.

Otherwise, the next case_block is attempted as described above.

If there are no further case blocks, the match statement is completed.

備註

Users should generally never rely on a pattern being evaluated. Depending on implementation, the interpreter may cache values or use other optimizations which skip repeated evaluations.

A sample match statement:

>>> flag = False
>>> match (100, 200):
...    case (100, 300):  # Mismatch: 200 != 300
...        print('Case 1')
...    case (100, 200) if flag:  # Successful match, but guard fails
...        print('Case 2')
...    case (100, y):  # Matches and binds y to 200
...        print(f'Case 3, y: {y}')
...    case _:  # Pattern not attempted
...        print('Case 4, I match anything!')
...
Case 3, y: 200

In this case, if flag is a guard. Read more about that in the next section.

8.6.2. Guards

guard: "if" `!named_expression`

A guard (which is part of the case) must succeed for code inside the case block to execute. It takes the form: if followed by an expression.

The logical flow of a case block with a guard follows:

Check that the pattern in the case block succeeded. If the pattern failed, the guard is not evaluated and the next case block is checked.

If the pattern succeeded, evaluate the guard.

If the guard condition evaluates as true, the case block is selected.

If the guard condition evaluates as false, the case block is not selected.

If the guard raises an exception during evaluation, the exception bubbles up.

Guards are allowed to have side effects as they are expressions. Guard evaluation must proceed from the first to the last case block, one at a time, skipping case blocks whose pattern(s) don't all succeed. (I.e., guard evaluation must happen in order.) Guard evaluation must stop once a case block is selected.

8.6.3. Irrefutable Case Blocks

An irrefutable case block is a match-all case block. A match statement may have at most one irrefutable case block, and it must be last.

A case block is considered irrefutable if it has no guard and its pattern is irrefutable. A pattern is considered irrefutable if we can prove from its syntax alone that it will always succeed. Only the following patterns are irrefutable:

AS Patterns whose left-hand side is irrefutable

OR Patterns containing at least one irrefutable pattern

Capture Patterns

Wildcard Patterns

parenthesized irrefutable patterns

8.6.4. Patterns

備註

This section uses grammar notations beyond standard EBNF:

the notation SEP.RULE+ is shorthand for RULE (SEP RULE)*

the notation !RULE is shorthand for a negative lookahead assertion

The top-level syntax for patterns is:

patterns:       open_sequence_pattern | pattern
pattern:        as_pattern | or_pattern
closed_pattern: | literal_pattern
                | capture_pattern
                | wildcard_pattern
                | value_pattern
                | group_pattern
                | sequence_pattern
                | mapping_pattern
                | class_pattern

The descriptions below will include a description "in simple terms" of what a pattern does for illustration purposes (credits to Raymond Hettinger for a document that inspired most of the descriptions). Note that these descriptions are purely for illustration purposes and may not reflect the underlying implementation. Furthermore, they do not cover all valid forms.

8.6.4.1. OR Patterns

An OR pattern is two or more patterns separated by vertical bars |. Syntax:

or_pattern: "|".closed_pattern+

Only the final subpattern may be irrefutable, and each subpattern must bind the same set of names to avoid ambiguity.

An OR pattern matches each of its subpatterns in turn to the subject value, until one succeeds. The OR pattern is then considered successful. Otherwise, if none of the subpatterns succeed, the OR pattern fails.

In simple terms, P1 | P2 | ... will try to match P1, if it fails it will try to match P2, succeeding immediately if any succeeds, failing otherwise.

8.6.4.2. AS Patterns

An AS pattern matches an OR pattern on the left of the as keyword against a subject. Syntax:

as_pattern: or_pattern "as" capture_pattern

If the OR pattern fails, the AS pattern fails. Otherwise, the AS pattern binds the subject to the name on the right of the as keyword and succeeds. capture_pattern cannot be a _.

In simple terms P as NAME will match with P, and on success it will set NAME = <subject>.

8.6.4.3. Literal Patterns

A literal pattern corresponds to most literals in Python. Syntax:

literal_pattern: signed_number
                 | signed_number "+" NUMBER
                 | signed_number "-" NUMBER
                 | strings
                 | "None"
                 | "True"
                 | "False"
signed_number:   ["-"] NUMBER

The rule strings and the token NUMBER are defined in the standard Python grammar. Triple-quoted strings are supported. Raw strings and byte strings are supported. f-string（f 字串） and t-string（t 字串） are not supported.

The forms signed_number '+' NUMBER and signed_number '-' NUMBER are for expressing complex numbers; they require a real number on the left and an imaginary number on the right. E.g. 3 + 4j.

In simple terms, LITERAL will succeed only if <subject> == LITERAL. For the singletons None, True and False, the is operator is used.

8.6.4.4. Capture Patterns

A capture pattern binds the subject value to a name. Syntax:

capture_pattern: !'_' NAME

A single underscore _ is not a capture pattern (this is what !'_' expresses). It is instead treated as a wildcard_pattern.

In a given pattern, a given name can only be bound once. E.g. case x, x: ... is invalid while case [x] | x: ... is allowed.

Capture patterns always succeed. The binding follows scoping rules established by the assignment expression operator in PEP 572 [https://peps.python.org/pep-0572/]; the name becomes a local variable in the closest containing function scope unless there's an applicable global or nonlocal statement.

In simple terms NAME will always succeed and it will set NAME = <subject>.

8.6.4.5. Wildcard Patterns

A wildcard pattern always succeeds (matches anything) and binds no name. Syntax:

wildcard_pattern: '_'

_ is a soft keyword within any pattern, but only within patterns. It is an identifier, as usual, even within match subject expressions, guards, and case blocks.

In simple terms, _ will always succeed.

8.6.4.6. Value Patterns

A value pattern represents a named value in Python. Syntax:

value_pattern: attr
attr:          name_or_attr "." NAME
name_or_attr:  attr | NAME

The dotted name in the pattern is looked up using standard Python name resolution rules. The pattern succeeds if the value found compares equal to the subject value (using the == equality operator).

In simple terms NAME1.NAME2 will succeed only if <subject> == NAME1.NAME2

備註

If the same value occurs multiple times in the same match statement, the interpreter may cache the first value found and reuse it rather than repeat the same lookup. This cache is strictly tied to a given execution of a given match statement.

8.6.4.7. Group Patterns

A group pattern allows users to add parentheses around patterns to emphasize the intended grouping. Otherwise, it has no additional syntax. Syntax:

group_pattern: "(" pattern ")"

In simple terms (P) has the same effect as P.

8.6.4.8. Sequence Patterns

A sequence pattern contains several subpatterns to be matched against sequence elements. The syntax is similar to the unpacking of a list or tuple.

sequence_pattern:       "[" [maybe_sequence_pattern] "]"
                        | "(" [open_sequence_pattern] ")"
open_sequence_pattern:  maybe_star_pattern "," [maybe_sequence_pattern]
maybe_sequence_pattern: ",".maybe_star_pattern+ ","?
maybe_star_pattern:     star_pattern | pattern
star_pattern:           "*" (capture_pattern | wildcard_pattern)

There is no difference if parentheses or square brackets are used for sequence patterns (i.e. (...) vs [...] ).

備註

A single pattern enclosed in parentheses without a trailing comma (e.g. (3 | 4)) is a group pattern. While a single pattern enclosed in square brackets (e.g. [3 | 4]) is still a sequence pattern.

At most one star subpattern may be in a sequence pattern. The star subpattern may occur in any position. If no star subpattern is present, the sequence pattern is a fixed-length sequence pattern; otherwise it is a variable-length sequence pattern.

The following is the logical flow for matching a sequence pattern against a subject value:

If the subject value is not a sequence [2], the sequence pattern fails.

If the subject value is an instance of str, bytes or bytearray the sequence pattern fails.

The subsequent steps depend on whether the sequence pattern is fixed or variable-length.

If the sequence pattern is fixed-length:

If the length of the subject sequence is not equal to the number of subpatterns, the sequence pattern fails

Subpatterns in the sequence pattern are matched to their corresponding items in the subject sequence from left to right. Matching stops as soon as a subpattern fails. If all subpatterns succeed in matching their corresponding item, the sequence pattern succeeds.

Otherwise, if the sequence pattern is variable-length:

If the length of the subject sequence is less than the number of non-star subpatterns, the sequence pattern fails.

The leading non-star subpatterns are matched to their corresponding items as for fixed-length sequences.

If the previous step succeeds, the star subpattern matches a list formed of the remaining subject items, excluding the remaining items corresponding to non-star subpatterns following the star subpattern.

Remaining non-star subpatterns are matched to their corresponding subject items, as for a fixed-length sequence.

備註

The length of the subject sequence is obtained via len() (i.e. via the __len__() protocol). This length may be cached by the interpreter in a similar manner as value patterns.

In simple terms [P1, P2, P3, ... , P<N>] matches only if all the following happens:

check <subject> is a sequence

len(subject) == <N>

P1 matches <subject>[0] (note that this match can also bind names)

P2 matches <subject>[1] (note that this match can also bind names)

... and so on for the corresponding pattern/element.

8.6.4.9. Mapping Patterns

A mapping pattern contains one or more key-value patterns. The syntax is similar to the construction of a dictionary. Syntax:

mapping_pattern:     "{" [items_pattern] "}"
items_pattern:       ",".key_value_pattern+ ","?
key_value_pattern:   (literal_pattern | value_pattern) ":" pattern
                     | double_star_pattern
double_star_pattern: "**" capture_pattern

At most one double star pattern may be in a mapping pattern. The double star pattern must be the last subpattern in the mapping pattern.

Duplicate keys in mapping patterns are disallowed. Duplicate literal keys will raise a SyntaxError. Two keys that otherwise have the same value will raise a ValueError at runtime.

The following is the logical flow for matching a mapping pattern against a subject value:

If the subject value is not a mapping [3],the mapping pattern fails.

If every key given in the mapping pattern is present in the subject mapping, and the pattern for each key matches the corresponding item of the subject mapping, the mapping pattern succeeds.

If duplicate keys are detected in the mapping pattern, the pattern is considered invalid. A SyntaxError is raised for duplicate literal values; or a ValueError for named keys of the same value.

備註

Key-value pairs are matched using the two-argument form of the mapping subject's get() method. Matched key-value pairs must already be present in the mapping, and not created on-the-fly via __missing__() or __getitem__().

In simple terms {KEY1: P1, KEY2: P2, ... } matches only if all the following happens:

check <subject> is a mapping

KEY1 in <subject>

P1 matches <subject>[KEY1]

... and so on for the corresponding KEY/pattern pair.

8.6.4.10. Class Patterns

A class pattern represents a class and its positional and keyword arguments (if any). Syntax:

class_pattern:       name_or_attr "(" [pattern_arguments ","?] ")"
pattern_arguments:   positional_patterns ["," keyword_patterns]
                     | keyword_patterns
positional_patterns: ",".pattern+
keyword_patterns:    ",".keyword_pattern+
keyword_pattern:     NAME "=" pattern

The same keyword should not be repeated in class patterns.

The following is the logical flow for matching a class pattern against a subject value:

If name_or_attr is not an instance of the builtin type , raise TypeError.

If the subject value is not an instance of name_or_attr (tested via isinstance()), the class pattern fails.

If no pattern arguments are present, the pattern succeeds. Otherwise, the subsequent steps depend on whether keyword or positional argument patterns are present.

For a number of built-in types (specified below), a single positional subpattern is accepted which will match the entire subject; for these types keyword patterns also work as for other types.

If only keyword patterns are present, they are processed as follows, one by one:

The keyword is looked up as an attribute on the subject.

If this raises an exception other than AttributeError, the exception bubbles up.

If this raises AttributeError, the class pattern has failed.

Else, the subpattern associated with the keyword pattern is matched against the subject's attribute value. If this fails, the class pattern fails; if this succeeds, the match proceeds to the next keyword.

If all keyword patterns succeed, the class pattern succeeds.

If any positional patterns are present, they are converted to keyword patterns using the __match_args__ attribute on the class name_or_attr before matching:

The equivalent of getattr(cls, "__match_args__", ()) is called.

If this raises an exception, the exception bubbles up.

If the returned value is not a tuple, the conversion fails and TypeError is raised.

If there are more positional patterns than len(cls.__match_args__), TypeError is raised.

Otherwise, positional pattern i is converted to a keyword pattern using __match_args__[i] as the keyword. __match_args__[i] must be a string; if not TypeError is raised.

If there are duplicate keywords, TypeError is raised.

也參考

Customizing positional arguments in class pattern matching

Once all positional patterns have been converted to keyword patterns, the match proceeds as if there were only keyword patterns.

For the following built-in types the handling of positional subpatterns is different:

bool

bytearray

bytes

dict

float

frozenset

int

list

set

str

tuple

These classes accept a single positional argument, and the pattern there is matched against the whole object rather than an attribute. For example int(0|1) matches the value 0, but not the value 0.0.

In simple terms CLS(P1, attr=P2) matches only if the following happens:

isinstance(<subject>, CLS)

convert P1 to a keyword pattern using CLS.__match_args__

For each keyword argument attr=P2:

hasattr(<subject>, "attr")

P2 matches <subject>.attr

... and so on for the corresponding keyword argument/pattern pair.

也參考

PEP 634 [https://peps.python.org/pep-0634/] -- Structural Pattern Matching: Specification

PEP 636 [https://peps.python.org/pep-0636/] -- Structural Pattern Matching: Tutorial

8.7. 函式定義

A function definition defines a user-defined function object (see section 標準型別階層):

funcdef:                   [decorators] "def" funcname [type_params] "(" [parameter_list] ")"
                           ["->" expression] ":" suite
decorators:                decorator+
decorator:                 "@" assignment_expression NEWLINE
parameter_list:            defparameter ("," defparameter)* "," "/" ["," [parameter_list_no_posonly]]
                             | parameter_list_no_posonly
parameter_list_no_posonly: defparameter ("," defparameter)* ["," [parameter_list_starargs]]
                           | parameter_list_starargs
parameter_list_starargs:   "*" [star_parameter] ("," defparameter)* ["," [parameter_star_kwargs]]
                           | "*" ("," defparameter)+ ["," [parameter_star_kwargs]]
                           | parameter_star_kwargs
parameter_star_kwargs:     "**" parameter [","]
parameter:                 identifier [":" expression]
star_parameter:            identifier [":" ["*"] expression]
defparameter:              parameter ["=" expression]
funcname:                  identifier

A function definition is an executable statement. Its execution binds the function name in the current local namespace to a function object (a wrapper around the executable code for the function). This function object contains a reference to the current global namespace as the global namespace to be used when the function is called.

The function definition does not execute the function body; this gets executed only when the function is called. [4]

A function definition may be wrapped by one or more decorator expressions. Decorator expressions are evaluated when the function is defined, in the scope that contains the function definition. The result must be a callable, which is invoked with the function object as the only argument. The returned value is bound to the function name instead of the function object. Multiple decorators are applied in nested fashion. For example, the following code

@f1(arg)
@f2
def func(): pass

大致等價於：

def func(): pass
func = f1(arg)(f2(func))

except that the original function is not temporarily bound to the name func.

在 3.9 版的變更: Functions may be decorated with any valid assignment_expression. Previously, the grammar was much more restrictive; see PEP 614 [https://peps.python.org/pep-0614/] for details.

A list of type parameters may be given in square brackets between the function's name and the opening parenthesis for its parameter list. This indicates to static type checkers that the function is generic. At runtime, the type parameters can be retrieved from the function's __type_params__ attribute. See Generic functions for more.

在 3.12 版的變更: Type parameter lists are new in Python 3.12.

When one or more parameters have the form parameter = expression, the function is said to have "default parameter values." For a parameter with a default value, the corresponding argument may be omitted from a call, in which case the parameter's default value is substituted. If a parameter has a default value, all following parameters up until the "*" must also have a default value --- this is a syntactic restriction that is not expressed by the grammar.

Default parameter values are evaluated from left to right when the function definition is executed. This means that the expression is evaluated once, when the function is defined, and that the same "pre-computed" value is used for each call. This is especially important to understand when a default parameter value is a mutable object, such as a list or a dictionary: if the function modifies the object (e.g. by appending an item to a list), the default parameter value is in effect modified. This is generally not what was intended. A way around this is to use None as the default, and explicitly test for it in the body of the function, e.g.:

def whats_on_the_telly(penguin=None):
    if penguin is None:
        penguin = []
    penguin.append("property of the zoo")
    return penguin

Function call semantics are described in more detail in section Calls. A function call always assigns values to all parameters mentioned in the parameter list, either from positional arguments, from keyword arguments, or from default values. If the form "*identifier" is present, it is initialized to a tuple receiving any excess positional parameters, defaulting to the empty tuple. If the form "**identifier" is present, it is initialized to a new ordered mapping receiving any excess keyword arguments, defaulting to a new empty mapping of the same type. Parameters after "*" or "*identifier" are keyword-only parameters and may only be passed by keyword arguments. Parameters before "/" are positional-only parameters and may only be passed by positional arguments.

在 3.8 版的變更: The / function parameter syntax may be used to indicate positional-only parameters. See PEP 570 [https://peps.python.org/pep-0570/] for details.

Parameters may have an annotation of the form ": expression" following the parameter name. Any parameter may have an annotation, even those of the form *identifier or **identifier. (As a special case, parameters of the form *identifier may have an annotation ": *expression".) Functions may have "return" annotation of the form "-> expression" after the parameter list. These annotations can be any valid Python expression. The presence of annotations does not change the semantics of a function. See 註釋 for more information on annotations.

在 3.11 版的變更: Parameters of the form "*identifier" may have an annotation ": *expression". See PEP 646 [https://peps.python.org/pep-0646/].

It is also possible to create anonymous functions (functions not bound to a name), for immediate use in expressions. This uses lambda expressions, described in section Lambdas. Note that the lambda expression is merely a shorthand for a simplified function definition; a function defined in a "def" statement can be passed around or assigned to another name just like a function defined by a lambda expression. The "def" form is actually more powerful since it allows the execution of multiple statements and annotations.

Programmer's note: Functions are first-class objects. A "def" statement executed inside a function definition defines a local function that can be returned or passed around. Free variables used in the nested function can access the local variables of the function containing the def. See section Naming and binding for details.

也參考

PEP 3107 [https://peps.python.org/pep-3107/] - Function Annotations

The original specification for function annotations.

PEP 484 [https://peps.python.org/pep-0484/] - 型別提示

定義註釋的標準意義：型別提示。

PEP 526 [https://peps.python.org/pep-0526/] - 變數註釋的語法

Ability to type hint variable declarations, including class variables and instance variables.

PEP 563 [https://peps.python.org/pep-0563/] - Postponed Evaluation of Annotations

Support for forward references within annotations by preserving annotations in a string form at runtime instead of eager evaluation.

PEP 318 [https://peps.python.org/pep-0318/] - Decorators for Functions and Methods

Function and method decorators were introduced. Class decorators were introduced in PEP 3129 [https://peps.python.org/pep-3129/].

8.8. 類別定義

A class definition defines a class object (see section 標準型別階層):

classdef:    [decorators] "class" classname [type_params] [inheritance] ":" suite
inheritance: "(" [argument_list] ")"
classname:   identifier

A class definition is an executable statement. The inheritance list usually gives a list of base classes (see Metaclasses for more advanced uses), so each item in the list should evaluate to a class object which allows subclassing. Classes without an inheritance list inherit, by default, from the base class object; hence,

class Foo:
    pass

is equivalent to

class Foo(object):
    pass

The class's suite is then executed in a new execution frame (see Naming and binding), using a newly created local namespace and the original global namespace. (Usually, the suite contains mostly function definitions.) When the class's suite finishes execution, its execution frame is discarded but its local namespace is saved. [5] A class object is then created using the inheritance list for the base classes and the saved local namespace for the attribute dictionary. The class name is bound to this class object in the original local namespace.

The order in which attributes are defined in the class body is preserved in the new class's __dict__. Note that this is reliable only right after the class is created and only for classes that were defined using the definition syntax.

Class creation can be customized heavily using metaclasses.

Classes can also be decorated: just like when decorating functions,

@f1(arg)
@f2
class Foo: pass

大致等價於：

class Foo: pass
Foo = f1(arg)(f2(Foo))

The evaluation rules for the decorator expressions are the same as for function decorators. The result is then bound to the class name.

在 3.9 版的變更: Classes may be decorated with any valid assignment_expression. Previously, the grammar was much more restrictive; see PEP 614 [https://peps.python.org/pep-0614/] for details.

A list of type parameters may be given in square brackets immediately after the class's name. This indicates to static type checkers that the class is generic. At runtime, the type parameters can be retrieved from the class's __type_params__ attribute. See Generic classes for more.

在 3.12 版的變更: Type parameter lists are new in Python 3.12.

Programmer's note: Variables defined in the class definition are class attributes; they are shared by instances. Instance attributes can be set in a method with self.name = value. Both class and instance attributes are accessible through the notation "self.name", and an instance attribute hides a class attribute with the same name when accessed in this way. Class attributes can be used as defaults for instance attributes, but using mutable values there can lead to unexpected results. Descriptors can be used to create instance variables with different implementation details.

也參考

PEP 3115 [https://peps.python.org/pep-3115/] - Metaclasses in Python 3000

The proposal that changed the declaration of metaclasses to the current syntax, and the semantics for how classes with metaclasses are constructed.

PEP 3129 [https://peps.python.org/pep-3129/] - 類別裝飾器

The proposal that added class decorators. Function and method decorators were introduced in PEP 318 [https://peps.python.org/pep-0318/].

8.9. 協程

在 3.5 版被加入.

8.9.1. 協程函式定義

async_funcdef: [decorators] "async" "def" funcname "(" [parameter_list] ")"
               ["->" expression] ":" suite

Execution of Python coroutines can be suspended and resumed at many points (see coroutine). await expressions, async for and async with can only be used in the body of a coroutine function.

Functions defined with async def syntax are always coroutine functions, even if they do not contain await or async keywords.

It is a SyntaxError to use a yield from expression inside the body of a coroutine function.

一個協程函式範例：

async def func(param1, param2):
    do_stuff()
    await some_coroutine()

在 3.7 版的變更: await and async are now keywords; previously they were only treated as such inside the body of a coroutine function.

8.9.2. async for 陳述式

async_for_stmt: "async" for_stmt

An asynchronous iterable provides an __aiter__ method that directly returns an asynchronous iterator, which can call asynchronous code in its __anext__ method.

The async for statement allows convenient iteration over asynchronous iterables.

以下程式碼：

async for TARGET in ITER:
    SUITE
else:
    SUITE2

Is semantically equivalent to:

iter = (ITER)
iter = type(iter).__aiter__(iter)
running = True

while running:
    try:
        TARGET = await type(iter).__anext__(iter)
    except StopAsyncIteration:
        running = False
    else:
        SUITE
else:
    SUITE2

更多細節請見 __aiter__() 與 __anext__()。

It is a SyntaxError to use an async for statement outside the body of a coroutine function.

8.9.3. async with 陳述式

async_with_stmt: "async" with_stmt

An asynchronous context manager is a context manager that is able to suspend execution in its enter and exit methods.

以下程式碼：

async with EXPRESSION as TARGET:
    SUITE

在語義上等同於：

manager = (EXPRESSION)
aenter = type(manager).__aenter__
aexit = type(manager).__aexit__
value = await aenter(manager)
hit_except = False

try:
    TARGET = value
    SUITE
except:
    hit_except = True
    if not await aexit(manager, *sys.exc_info()):
        raise
finally:
    if not hit_except:
        await aexit(manager, None, None, None)

更多細節請見 __aenter__() 與 __aexit__()。

It is a SyntaxError to use an async with statement outside the body of a coroutine function.

也參考

PEP 492 [https://peps.python.org/pep-0492/] - Coroutines with async and await syntax

The proposal that made coroutines a proper standalone concept in Python, and added supporting syntax.

8.10. Type parameter lists

在 3.12 版被加入.

在 3.13 版的變更: Support for default values was added (see PEP 696 [https://peps.python.org/pep-0696/]).

type_params:  "[" type_param ("," type_param)* "]"
type_param:   typevar | typevartuple | paramspec
typevar:      identifier (":" expression)? ("=" expression)?
typevartuple: "*" identifier ("=" expression)?
paramspec:    "**" identifier ("=" expression)?

Functions (including coroutines), classes and type aliases may contain a type parameter list:

def max[T](args: list[T]) -> T:
    ...

async def amax[T](args: list[T]) -> T:
    ...

class Bag[T]:
    def __iter__(self) -> Iterator[T]:
        ...

    def add(self, arg: T) -> None:
        ...

type ListOrSet[T] = list[T] | set[T]

Semantically, this indicates that the function, class, or type alias is generic over a type variable. This information is primarily used by static type checkers, and at runtime, generic objects behave much like their non-generic counterparts.

Type parameters are declared in square brackets ([]) immediately after the name of the function, class, or type alias. The type parameters are accessible within the scope of the generic object, but not elsewhere. Thus, after a declaration def func[T](): pass, the name T is not available in the module scope. Below, the semantics of generic objects are described with more precision. The scope of type parameters is modeled with a special function (technically, an annotation scope) that wraps the creation of the generic object.

Generic functions, classes, and type aliases have a __type_params__ attribute listing their type parameters.

Type parameters come in three kinds:

typing.TypeVar, introduced by a plain name (e.g., T). Semantically, this represents a single type to a type checker.

typing.TypeVarTuple, introduced by a name prefixed with a single asterisk (e.g., *Ts). Semantically, this stands for a tuple of any number of types.

typing.ParamSpec, introduced by a name prefixed with two asterisks (e.g., **P). Semantically, this stands for the parameters of a callable.

typing.TypeVar declarations can define bounds and constraints with a colon (:) followed by an expression. A single expression after the colon indicates a bound (e.g. T: int). Semantically, this means that the typing.TypeVar can only represent types that are a subtype of this bound. A parenthesized tuple of expressions after the colon indicates a set of constraints (e.g. T: (str, bytes)). Each member of the tuple should be a type (again, this is not enforced at runtime). Constrained type variables can only take on one of the types in the list of constraints.

For typing.TypeVars declared using the type parameter list syntax, the bound and constraints are not evaluated when the generic object is created, but only when the value is explicitly accessed through the attributes __bound__ and __constraints__. To accomplish this, the bounds or constraints are evaluated in a separate annotation scope.

typing.TypeVarTuples and typing.ParamSpecs cannot have bounds or constraints.

All three flavors of type parameters can also have a default value, which is used when the type parameter is not explicitly provided. This is added by appending a single equals sign (=) followed by an expression. Like the bounds and constraints of type variables, the default value is not evaluated when the object is created, but only when the type parameter's __default__ attribute is accessed. To this end, the default value is evaluated in a separate annotation scope. If no default value is specified for a type parameter, the __default__ attribute is set to the special sentinel object typing.NoDefault.

The following example indicates the full set of allowed type parameter declarations:

def overly_generic[
   SimpleTypeVar,
   TypeVarWithDefault = int,
   TypeVarWithBound: int,
   TypeVarWithConstraints: (str, bytes),
   *SimpleTypeVarTuple = (int, float),
   **SimpleParamSpec = (str, bytearray),
](
   a: SimpleTypeVar,
   b: TypeVarWithDefault,
   c: TypeVarWithBound,
   d: Callable[SimpleParamSpec, TypeVarWithConstraints],
   *e: SimpleTypeVarTuple,
): ...

8.10.1. Generic functions

Generic functions are declared as follows:

def func[T](arg: T): ...

語法大致等價於：

annotation-def TYPE_PARAMS_OF_func():
    T = typing.TypeVar("T")
    def func(arg: T): ...
    func.__type_params__ = (T,)
    return func
func = TYPE_PARAMS_OF_func()

Here annotation-def indicates an annotation scope, which is not actually bound to any name at runtime. (One other liberty is taken in the translation: the syntax does not go through attribute access on the typing module, but creates an instance of typing.TypeVar directly.)

The annotations of generic functions are evaluated within the annotation scope used for declaring the type parameters, but the function's defaults and decorators are not.

The following example illustrates the scoping rules for these cases, as well as for additional flavors of type parameters:

@decorator
def func[T: int, *Ts, **P](*args: *Ts, arg: Callable[P, T] = some_default):
    ...

Except for the lazy evaluation of the TypeVar bound, this is equivalent to:

DEFAULT_OF_arg = some_default

annotation-def TYPE_PARAMS_OF_func():

    annotation-def BOUND_OF_T():
        return int
    # In reality, BOUND_OF_T() is evaluated only on demand.
    T = typing.TypeVar("T", bound=BOUND_OF_T())

    Ts = typing.TypeVarTuple("Ts")
    P = typing.ParamSpec("P")

    def func(*args: *Ts, arg: Callable[P, T] = DEFAULT_OF_arg):
        ...

    func.__type_params__ = (T, Ts, P)
    return func
func = decorator(TYPE_PARAMS_OF_func())

The capitalized names like DEFAULT_OF_arg are not actually bound at runtime.

8.10.2. Generic classes

Generic classes are declared as follows:

class Bag[T]: ...

語法大致等價於：

annotation-def TYPE_PARAMS_OF_Bag():
    T = typing.TypeVar("T")
    class Bag(typing.Generic[T]):
        __type_params__ = (T,)
        ...
    return Bag
Bag = TYPE_PARAMS_OF_Bag()

Here again annotation-def (not a real keyword) indicates an annotation scope, and the name TYPE_PARAMS_OF_Bag is not actually bound at runtime.

Generic classes implicitly inherit from typing.Generic. The base classes and keyword arguments of generic classes are evaluated within the type scope for the type parameters, and decorators are evaluated outside that scope. This is illustrated by this example:

@decorator
class Bag(Base[T], arg=T): ...

這等價於：

annotation-def TYPE_PARAMS_OF_Bag():
    T = typing.TypeVar("T")
    class Bag(Base[T], typing.Generic[T], arg=T):
        __type_params__ = (T,)
        ...
    return Bag
Bag = decorator(TYPE_PARAMS_OF_Bag())

8.10.3. Generic type aliases

The type statement can also be used to create a generic type alias:

type ListOrSet[T] = list[T] | set[T]

Except for the lazy evaluation of the value, this is equivalent to:

annotation-def TYPE_PARAMS_OF_ListOrSet():
    T = typing.TypeVar("T")

    annotation-def VALUE_OF_ListOrSet():
        return list[T] | set[T]
    # In reality, the value is lazily evaluated
    return typing.TypeAliasType("ListOrSet", VALUE_OF_ListOrSet(), type_params=(T,))
ListOrSet = TYPE_PARAMS_OF_ListOrSet()

Here, annotation-def (not a real keyword) indicates an annotation scope. The capitalized names like TYPE_PARAMS_OF_ListOrSet are not actually bound at runtime.

8.11. 註釋

在 3.14 版的變更: Annotations are now lazily evaluated by default.

Variables and function parameters may carry annotations, created by adding a colon after the name, followed by an expression:

x: annotation = 1
def f(param: annotation): ...

Functions may also carry a return annotation following an arrow:

def f() -> annotation: ...

Annotations are conventionally used for type hints, but this is not enforced by the language, and in general annotations may contain arbitrary expressions. The presence of annotations does not change the runtime semantics of the code, except if some mechanism is used that introspects and uses the annotations (such as dataclasses or functools.singledispatch()).

By default, annotations are lazily evaluated in an annotation scope. This means that they are not evaluated when the code containing the annotation is evaluated. Instead, the interpreter saves information that can be used to evaluate the annotation later if requested. The annotationlib module provides tools for evaluating annotations.

If the future statement from __future__ import annotations is present, all annotations are instead stored as strings:

>>> from __future__ import annotations
>>> def f(param: annotation): ...
>>> f.__annotations__
{'param': 'annotation'}

This future statement will be deprecated and removed in a future version of Python, but not before Python 3.13 reaches its end of life (see PEP 749 [https://peps.python.org/pep-0749/]). When it is used, introspection tools like annotationlib.get_annotations() and typing.get_type_hints() are less likely to be able to resolve annotations at runtime.

註解

[1]

The exception is propagated to the invocation stack unless there is a finally clause which happens to raise another exception. That new exception causes the old one to be lost.

[2]

In pattern matching, a sequence is defined as one of the following:

a class that inherits from collections.abc.Sequence

a Python class that has been registered as collections.abc.Sequence

a builtin class that has its (CPython) Py_TPFLAGS_SEQUENCE bit set

a class that inherits from any of the above

The following standard library classes are sequences:

array.array

collections.deque

list

memoryview

range

tuple

備註

Subject values of type str, bytes, and bytearray do not match sequence patterns.

[3]

In pattern matching, a mapping is defined as one of the following:

a class that inherits from collections.abc.Mapping

a Python class that has been registered as collections.abc.Mapping

a builtin class that has its (CPython) Py_TPFLAGS_MAPPING bit set

a class that inherits from any of the above

The standard library classes dict and types.MappingProxyType are mappings.

[4]

A string literal appearing as the first statement in the function body is transformed into the function's __doc__ attribute and therefore the function's docstring.

[5]

A string literal appearing as the first statement in the class body is transformed into the namespace's __doc__ item and therefore the class's docstring.

9. 最高層級元件

Python 直譯器可以從多種來源獲得輸入：作為標準輸入或程式引數自腳本傳入、以互動式鍵入、自模組原始檔引入等等。這一章將給出在這些情況下所用的語法。

9.1. 完整的 Python 程式

雖然語言規範描述不必規定語言直譯器是如何被叫用（invoke）的，但對完整的 Python 程式加以說明還是很有用的。一個完整的 Python 程式會在最小初始化環境中被執行：所有內建和標準模組均為可用，但均處於未初始化狀態，只有 sys（各種系統服務）、builtins（內建函式、例外和 None）和 __main__ 除外。後者用於為完整程式的執行提供區域性和全域性命名空間 (namespace)。

用於一個完整 Python 程式的語法，即下節所描述的檔案輸入。

直譯器也可以透過互動模式被叫用；在此情況下，它並不讀取和執行一個完整程式，而是每讀取一條陳述式就執行一次（可能為複合陳述式）。此時的初始環境與一個完整程式的相同；每條陳述式會在 __main__ 的命名空間中被執行。

一個完整程式可透過三種形式被傳遞給直譯器：使用 -c 字串命令列選項、使用一個檔案作為第一個命令列引數、或者使用標準輸入。如果檔案或標準輸入是一個 tty 裝置，直譯器會進入互動模式；否則它會將檔案當作一個完整程式來執行。

9.2. 檔案輸入

所有從非互動式檔案讀取的輸入都具有相同的形式：

file_input: (NEWLINE | statement)* ENDMARKER

此語法用於下列幾種情況：

剖析一個完整 Python 程式時（從檔案或字串）；

剖析一個模組時；

剖析一個傳遞给 exec() 函數的字串時；

9.3. 互動式輸入

互動模式下的輸入使用以下語法進行剖析：

interactive_input: [stmt_list] NEWLINE | compound_stmt NEWLINE | ENDMARKER

注意在互動模式下，一條（最高層級）複合陳述式最後必須帶有一個空行；這能夠幫助剖析器確定輸入已經結束。

9.4. 運算式輸入

eval() 被用於運算式輸入，它會忽略開頭的空白。傳遞給 eval() 的字串引數必須具有以下形式：

eval_input: expression_list NEWLINE* ENDMARKER

10. 完整的文法規格書

這是完整的 Python 文法，是直接從用來產生 CPython 剖析器的文法衍生出來的（請參閱 Grammar/python.gram [https://github.com/python/cpython/tree/3.14/Grammar/python.gram]）。這裡的版本省略了與程式碼產生和錯誤復原相關的細節。

這裡使用的標示法與前面文件相同，並在標示法部分中進行了說明。除有一個額外的複雜性：

~（「切斷」）：提交至目前的替代方案；無法剖析會使規則失敗。

Python 主要使用切斷來進行最佳化或改善錯誤訊息。它們在下面的列表中常看起來沒用。

切斷目前不會出現在括號、方括號、預查和類似的地方。它們在這些情境中的行為是故意未指定的。

# Python 的 PEG 文法

# ========================= 文法的開始 =========================

# 通用文法結構與規則
#
# * 雙引號（"）字串表示軟關鍵字 (SOFT KEYWORDS)
# * 單引號（'）字串表示關鍵字 (KEYWORDS)
# * 大寫名稱 (NAME) 表示 Grammar/Tokens 檔案中的語彙符號 (token)
# * 以 "invalid_" 開頭的規則名稱用於專門的語法錯誤
#     - 這些規則不會在剖析器的第一遍剖析中使用。
#     - 只有當第一遍剖析失敗時，才會執行包含無效規則的第二遍。
#     - 如果剖析器在第二階段因泛用語法錯誤而失敗，
#       則會使用第一遍泛用失敗的位置（這可避免因無效規則
#       而報告錯誤的位置）。
#     - 涉及無效規則的替代方案的順序很重要
#       （就像 PEG 中的任何規則一樣）。
#
# 文法語法（更多資訊請參閱 PEP 617）：
#
# rule_name: expression
#   在規則名稱後面可以選擇性地包含型別，用來指定對應此規則的
#   C 或 Python 函式的回傳型別：
# rule_name[return_type]: expression
#   如果省略回傳型別，則在 C 中回傳 void *，並在 Python 中回傳 Any。
# e1 e2
#   匹配 e1，然後匹配 e2。
# e1 | e2
#   匹配 e1 或 e2。
#   為了格式化目的，第一個替代選項也可以出現在規則名稱後的下一行。
#   在這種情況下，必須在第一個替代選項之前使用 |，如下所示：
#       rule_name[return_type]:
#            | first_alt
#            | second_alt
# ( e )
#   匹配 e（也允許在群組中使用其他運算子，如 '(e)*'）
# [ e ] or e?
#   可選地匹配 e。
# e*
#   匹配零個或多個 e。
# e+
#   匹配一個或多個 e。
# s.e+
#   匹配一個或多個 e，以 s 分隔。產生的剖析樹不包含分隔符號。
#   這在其他方面與 (e (s e)*) 相同。
# &e
#   如果可以剖析 e 則成功，但不消耗任何輸入。
# !e
#   如果可以剖析 e 則失敗，但不消耗任何輸入。
# ~
#   提交到目前的替代選項，即使剖析失敗。
# &&e
#   急切剖析 e。如果無法剖析 e，剖析器將不會回溯 (backtrack)，並會立即
#   引發 SyntaxError 失敗。
#

# 起始規則
# =======

file: [statements] ENDMARKER
interactive: statement_newline
eval: expressions NEWLINE* ENDMARKER
func_type: '(' [type_expressions] ')' '->' expression NEWLINE* ENDMARKER

# 一般陳述式
# =========

statements: statement+

statement:
    | compound_stmt
    | simple_stmts

single_compound_stmt:
    | compound_stmt

statement_newline:
    | single_compound_stmt NEWLINE
    | simple_stmts
    | NEWLINE
    | ENDMARKER

simple_stmts:
    | simple_stmt !';' NEWLINE  # Not needed, there for speedup
    | ';'.simple_stmt+ [';'] NEWLINE

# 註：賦值必須在運算式之前，否則剖析簡單賦值時會引發 SyntaxError。
simple_stmt:
    | assignment
    | type_alias
    | star_expressions
    | return_stmt
    | import_stmt
    | raise_stmt
    | pass_stmt
    | del_stmt
    | yield_stmt
    | assert_stmt
    | break_stmt
    | continue_stmt
    | global_stmt
    | nonlocal_stmt

compound_stmt:
    | function_def
    | if_stmt
    | class_def
    | with_stmt
    | for_stmt
    | try_stmt
    | while_stmt
    | match_stmt

# 簡單陳述式
# =========

# 註：annotated_rhs 可以用 'yield' 開頭；yield_expr 必須以 'yield' 開頭
assignment:
    | NAME ':' expression ['=' annotated_rhs ]
    | ('(' single_target ')'
         | single_subscript_attribute_target) ':' expression ['=' annotated_rhs ]
    | (star_targets '=' )+ annotated_rhs !'=' [TYPE_COMMENT]
    | single_target augassign ~ annotated_rhs

annotated_rhs: yield_expr | star_expressions

augassign:
    | '+='
    | '-='
    | '*='
    | '@='
    | '/='
    | '%='
    | '&='
    | '|='
    | '^='
    | '<<='
    | '>>='
    | '**='
    | '//='

return_stmt:
    | 'return' [star_expressions]

raise_stmt:
    | 'raise' expression ['from' expression ]
    | 'raise'

pass_stmt:
    | 'pass'

break_stmt:
    | 'break'

continue_stmt:
    | 'continue'

global_stmt: 'global' ','.NAME+

nonlocal_stmt: 'nonlocal' ','.NAME+

del_stmt:
    | 'del' del_targets &(';' | NEWLINE)

yield_stmt: yield_expr

assert_stmt: 'assert' expression [',' expression ]

import_stmt:
    | import_name
    | import_from

# Import 陳述式
# ------------

import_name: 'import' dotted_as_names
# 注意以下部分：('.' | '...') 是必須的，因為 '...' 是被 tokenize 為 ELLIPSIS
import_from:
    | 'from' ('.' | '...')* dotted_name 'import' import_from_targets
    | 'from' ('.' | '...')+ 'import' import_from_targets
import_from_targets:
    | '(' import_from_as_names [','] ')'
    | import_from_as_names !','
    | '*'
import_from_as_names:
    | ','.import_from_as_name+
import_from_as_name:
    | NAME ['as' NAME ]

dotted_as_names:
    | ','.dotted_as_name+
dotted_as_name:
    | dotted_name ['as' NAME ]

dotted_name:
    | dotted_name '.' NAME
    | NAME

# 複合陳述式
# ========

# 共用元素
# -------

block:
    | NEWLINE INDENT statements DEDENT
    | simple_stmts

decorators: ('@' named_expression NEWLINE )+

# 類別定義
# -------

class_def:
    | decorators class_def_raw
    | class_def_raw

class_def_raw:
    | 'class' NAME [type_params] ['(' [arguments] ')' ] ':' block

# 函式定義
# -------

function_def:
    | decorators function_def_raw
    | function_def_raw

function_def_raw:
    | 'def' NAME [type_params] '(' [params] ')' ['->' expression ] ':' [func_type_comment] block
    | 'async' 'def' NAME [type_params] '(' [params] ')' ['->' expression ] ':' [func_type_comment] block

# 函式參數
# -------

params:
    | parameters

parameters:
    | slash_no_default param_no_default* param_with_default* [star_etc]
    | slash_with_default param_with_default* [star_etc]
    | param_no_default+ param_with_default* [star_etc]
    | param_with_default+ [star_etc]
    | star_etc

# 這裡有些重複，因為我們不能寫 (',' | &')')，
# 這是因為我們（尚）不支援空替代方案。

slash_no_default:
    | param_no_default+ '/' ','
    | param_no_default+ '/' &')'
slash_with_default:
    | param_no_default* param_with_default+ '/' ','
    | param_no_default* param_with_default+ '/' &')'

star_etc:
    | '*' param_no_default param_maybe_default* [kwds]
    | '*' param_no_default_star_annotation param_maybe_default* [kwds]
    | '*' ',' param_maybe_default+ [kwds]
    | kwds

kwds:
    | '**' param_no_default

# 一個參數。這 *包含* 後面的逗號和型別註解。
#
# 有三種風格：
# - 沒有預設值
# - 有預設值
# - 可能有預設值
#
# 每種都有兩種替代形式，用以處理型別註解：
# - 以逗號結尾，後面接可選的型別註解
# - 沒有逗號，可選的型別註解，後面必須接右括號
# 後者是用於沒有尾隨逗號的最後一個參數。
#

param_no_default:
    | param ',' TYPE_COMMENT?
    | param TYPE_COMMENT? &')'
param_no_default_star_annotation:
    | param_star_annotation ',' TYPE_COMMENT?
    | param_star_annotation TYPE_COMMENT? &')'
param_with_default:
    | param default ',' TYPE_COMMENT?
    | param default TYPE_COMMENT? &')'
param_maybe_default:
    | param default? ',' TYPE_COMMENT?
    | param default? TYPE_COMMENT? &')'
param: NAME annotation?
param_star_annotation: NAME star_annotation
annotation: ':' expression
star_annotation: ':' star_expression
default: '=' expression  | invalid_default

# If 陳述式
# --------

if_stmt:
    | 'if' named_expression ':' block elif_stmt
    | 'if' named_expression ':' block [else_block]
elif_stmt:
    | 'elif' named_expression ':' block elif_stmt
    | 'elif' named_expression ':' block [else_block]
else_block:
    | 'else' ':' block

# While 陳述式
# -----------

while_stmt:
    | 'while' named_expression ':' block [else_block]

# For 陳述式
# ---------

for_stmt:
    | 'for' star_targets 'in' ~ star_expressions ':' [TYPE_COMMENT] block [else_block]
    | 'async' 'for' star_targets 'in' ~ star_expressions ':' [TYPE_COMMENT] block [else_block]

# With 陳述式
# ----------

with_stmt:
    | 'with' '(' ','.with_item+ ','? ')' ':' [TYPE_COMMENT] block
    | 'with' ','.with_item+ ':' [TYPE_COMMENT] block
    | 'async' 'with' '(' ','.with_item+ ','? ')' ':' block
    | 'async' 'with' ','.with_item+ ':' [TYPE_COMMENT] block

with_item:
    | expression 'as' star_target &(',' | ')' | ':')
    | expression

# Try 陳述式
# ---------

try_stmt:
    | 'try' ':' block finally_block
    | 'try' ':' block except_block+ [else_block] [finally_block]
    | 'try' ':' block except_star_block+ [else_block] [finally_block]

# Except 陳述式
# ------------

except_block:
    | 'except' expression ':' block
    | 'except' expression 'as' NAME ':' block
    | 'except' expressions ':' block
    | 'except' ':' block
except_star_block:
    | 'except' '*' expression ':' block
    | 'except' '*' expression 'as' NAME ':' block
    | 'except' '*' expressions ':' block
finally_block:
    | 'finally' ':' block

# Match 陳述式
# -----------

match_stmt:
    | "match" subject_expr ':' NEWLINE INDENT case_block+ DEDENT

subject_expr:
    | star_named_expression ',' star_named_expressions?
    | named_expression

case_block:
    | "case" patterns guard? ':' block

guard: 'if' named_expression

patterns:
    | open_sequence_pattern
    | pattern

pattern:
    | as_pattern
    | or_pattern

as_pattern:
    | or_pattern 'as' pattern_capture_target

or_pattern:
    | '|'.closed_pattern+

closed_pattern:
    | literal_pattern
    | capture_pattern
    | wildcard_pattern
    | value_pattern
    | group_pattern
    | sequence_pattern
    | mapping_pattern
    | class_pattern

# 字面值模式被用於相等性和識別字限制
literal_pattern:
    | signed_number !('+' | '-')
    | complex_number
    | strings
    | 'None'
    | 'True'
    | 'False'

# 字面值運算式被用於限制允許的對映模式鍵
literal_expr:
    | signed_number !('+' | '-')
    | complex_number
    | strings
    | 'None'
    | 'True'
    | 'False'

complex_number:
    | signed_real_number '+' imaginary_number
    | signed_real_number '-' imaginary_number

signed_number:
    | NUMBER
    | '-' NUMBER

signed_real_number:
    | real_number
    | '-' real_number

real_number:
    | NUMBER

imaginary_number:
    | NUMBER

capture_pattern:
    | pattern_capture_target

pattern_capture_target:
    | !"_" NAME !('.' | '(' | '=')

wildcard_pattern:
    | "_"

value_pattern:
    | attr !('.' | '(' | '=')

attr:
    | name_or_attr '.' NAME

name_or_attr:
    | attr
    | NAME

group_pattern:
    | '(' pattern ')'

sequence_pattern:
    | '[' maybe_sequence_pattern? ']'
    | '(' open_sequence_pattern? ')'

open_sequence_pattern:
    | maybe_star_pattern ',' maybe_sequence_pattern?

maybe_sequence_pattern:
    | ','.maybe_star_pattern+ ','?

maybe_star_pattern:
    | star_pattern
    | pattern

star_pattern:
    | '*' pattern_capture_target
    | '*' wildcard_pattern

mapping_pattern:
    | '{' '}'
    | '{' double_star_pattern ','? '}'
    | '{' items_pattern ',' double_star_pattern ','? '}'
    | '{' items_pattern ','? '}'

items_pattern:
    | ','.key_value_pattern+

key_value_pattern:
    | (literal_expr | attr) ':' pattern

double_star_pattern:
    | '**' pattern_capture_target

class_pattern:
    | name_or_attr '(' ')'
    | name_or_attr '(' positional_patterns ','? ')'
    | name_or_attr '(' keyword_patterns ','? ')'
    | name_or_attr '(' positional_patterns ',' keyword_patterns ','? ')'

positional_patterns:
    | ','.pattern+

keyword_patterns:
    | ','.keyword_pattern+

keyword_pattern:
    | NAME '=' pattern

# Type 陳述式
# ----------

type_alias:
    | "type" NAME [type_params] '=' expression

# Type 參數宣告
# ------------

type_params:
    | '[' type_param_seq ']'

type_param_seq: ','.type_param+ [',']

type_param:
    | NAME [type_param_bound] [type_param_default]
    | '*' NAME [type_param_starred_default]
    | '**' NAME [type_param_default]

type_param_bound: ':' expression
type_param_default: '=' expression
type_param_starred_default: '=' star_expression

# 運算式
# -----

expressions:
    | expression (',' expression )+ [',']
    | expression ','
    | expression

expression:
    | disjunction 'if' disjunction 'else' expression
    | disjunction
    | lambdef

yield_expr:
    | 'yield' 'from' expression
    | 'yield' [star_expressions]

star_expressions:
    | star_expression (',' star_expression )+ [',']
    | star_expression ','
    | star_expression

star_expression:
    | '*' bitwise_or
    | expression

star_named_expressions: ','.star_named_expression+ [',']

star_named_expression:
    | '*' bitwise_or
    | named_expression

assignment_expression:
    | NAME ':=' ~ expression

named_expression:
    | assignment_expression
    | expression !':='

disjunction:
    | conjunction ('or' conjunction )+
    | conjunction

conjunction:
    | inversion ('and' inversion )+
    | inversion

inversion:
    | 'not' inversion
    | comparison

# 比較運算子
# --------

comparison:
    | bitwise_or compare_op_bitwise_or_pair+
    | bitwise_or

compare_op_bitwise_or_pair:
    | eq_bitwise_or
    | noteq_bitwise_or
    | lte_bitwise_or
    | lt_bitwise_or
    | gte_bitwise_or
    | gt_bitwise_or
    | notin_bitwise_or
    | in_bitwise_or
    | isnot_bitwise_or
    | is_bitwise_or

eq_bitwise_or: '==' bitwise_or
noteq_bitwise_or:
    | ('!=' ) bitwise_or
lte_bitwise_or: '<=' bitwise_or
lt_bitwise_or: '<' bitwise_or
gte_bitwise_or: '>=' bitwise_or
gt_bitwise_or: '>' bitwise_or
notin_bitwise_or: 'not' 'in' bitwise_or
in_bitwise_or: 'in' bitwise_or
isnot_bitwise_or: 'is' 'not' bitwise_or
is_bitwise_or: 'is' bitwise_or

# 位元運算子
# --------

bitwise_or:
    | bitwise_or '|' bitwise_xor
    | bitwise_xor

bitwise_xor:
    | bitwise_xor '^' bitwise_and
    | bitwise_and

bitwise_and:
    | bitwise_and '&' shift_expr
    | shift_expr

shift_expr:
    | shift_expr '<<' sum
    | shift_expr '>>' sum
    | sum

# 算術運算子
# --------

sum:
    | sum '+' term
    | sum '-' term
    | term

term:
    | term '*' factor
    | term '/' factor
    | term '//' factor
    | term '%' factor
    | term '@' factor
    | factor

factor:
    | '+' factor
    | '-' factor
    | '~' factor
    | power

power:
    | await_primary '**' factor
    | await_primary

# 主要元素
# -------

# 主要元素是像 "obj.something.something", "obj[something]", "obj(something)", "obj" ... 這樣的東西

await_primary:
    | 'await' primary
    | primary

primary:
    | primary '.' NAME
    | primary genexp
    | primary '(' [arguments] ')'
    | primary '[' slices ']'
    | atom

slices:
    | slice !','
    | ','.(slice | starred_expression)+ [',']

slice:
    | [expression] ':' [expression] [':' [expression] ]
    | named_expression

atom:
    | NAME
    | 'True'
    | 'False'
    | 'None'
    | strings
    | NUMBER
    | (tuple | group | genexp)
    | (list | listcomp)
    | (dict | set | dictcomp | setcomp)
    | '...'

group:
    | '(' (yield_expr | named_expression) ')'

# Lambda 函式
# ----------

lambdef:
    | 'lambda' [lambda_params] ':' expression

lambda_params:
    | lambda_parameters

# lambda_parameters 等複製了參數但沒有註釋
# 或型別註解，而且如果參數後面沒有逗號，我們預期會有
# 冒號，而不是右括號。（更多資訊請參見上面的參數部分。）
#
lambda_parameters:
    | lambda_slash_no_default lambda_param_no_default* lambda_param_with_default* [lambda_star_etc]
    | lambda_slash_with_default lambda_param_with_default* [lambda_star_etc]
    | lambda_param_no_default+ lambda_param_with_default* [lambda_star_etc]
    | lambda_param_with_default+ [lambda_star_etc]
    | lambda_star_etc

lambda_slash_no_default:
    | lambda_param_no_default+ '/' ','
    | lambda_param_no_default+ '/' &':'

lambda_slash_with_default:
    | lambda_param_no_default* lambda_param_with_default+ '/' ','
    | lambda_param_no_default* lambda_param_with_default+ '/' &':'

lambda_star_etc:
    | '*' lambda_param_no_default lambda_param_maybe_default* [lambda_kwds]
    | '*' ',' lambda_param_maybe_default+ [lambda_kwds]
    | lambda_kwds

lambda_kwds:
    | '**' lambda_param_no_default

lambda_param_no_default:
    | lambda_param ','
    | lambda_param &':'
lambda_param_with_default:
    | lambda_param default ','
    | lambda_param default &':'
lambda_param_maybe_default:
    | lambda_param default? ','
    | lambda_param default? &':'
lambda_param: NAME

# 字面值
# =====

fstring_middle:
    | fstring_replacement_field
    | FSTRING_MIDDLE
fstring_replacement_field:
    | '{' annotated_rhs '='? [fstring_conversion] [fstring_full_format_spec] '}'
fstring_conversion:
    | "!" NAME
fstring_full_format_spec:
    | ':' fstring_format_spec*
fstring_format_spec:
    | FSTRING_MIDDLE
    | fstring_replacement_field
fstring:
    | FSTRING_START fstring_middle* FSTRING_END

tstring_format_spec_replacement_field:
    | '{' annotated_rhs '='? [fstring_conversion] [tstring_full_format_spec] '}'
tstring_format_spec:
    | TSTRING_MIDDLE
    | tstring_format_spec_replacement_field
tstring_full_format_spec:
    | ':' tstring_format_spec*
tstring_replacement_field:
    | '{' annotated_rhs '='? [fstring_conversion] [tstring_full_format_spec] '}'
tstring_middle:
    | tstring_replacement_field
    | TSTRING_MIDDLE
tstring:
    | TSTRING_START tstring_middle* TSTRING_END

string: STRING
strings:
    | (fstring|string)+
    | tstring+

list:
    | '[' [star_named_expressions] ']'

tuple:
    | '(' [star_named_expression ',' [star_named_expressions]  ] ')'

set: '{' star_named_expressions '}'

# 字典
# ----

dict:
    | '{' [double_starred_kvpairs] '}'

double_starred_kvpairs: ','.double_starred_kvpair+ [',']

double_starred_kvpair:
    | '**' bitwise_or
    | kvpair

kvpair: expression ':' expression

# 綜合運算式與產生器
# ---------------------------

for_if_clauses:
    | for_if_clause+

for_if_clause:
    | 'async' 'for' star_targets 'in' ~ disjunction ('if' disjunction )*
    | 'for' star_targets 'in' ~ disjunction ('if' disjunction )*

listcomp:
    | '[' named_expression for_if_clauses ']'

setcomp:
    | '{' named_expression for_if_clauses '}'

genexp:
    | '(' ( assignment_expression | expression !':=') for_if_clauses ')'

dictcomp:
    | '{' kvpair for_if_clauses '}'

# 函式呼叫引數
# ==========

arguments:
    | args [','] &')'

args:
    | ','.(starred_expression | ( assignment_expression | expression !':=') !'=')+ [',' kwargs ]
    | kwargs

kwargs:
    | ','.kwarg_or_starred+ ',' ','.kwarg_or_double_starred+
    | ','.kwarg_or_starred+
    | ','.kwarg_or_double_starred+

starred_expression:
    | '*' expression

kwarg_or_starred:
    | NAME '=' expression
    | starred_expression

kwarg_or_double_starred:
    | NAME '=' expression
    | '**' expression

# 賦值目標
# =======

# 泛用目標
# -------

# 注意：star_targets 可能包含 *bitwise_or，targets 則不可以。
star_targets:
    | star_target !','
    | star_target (',' star_target )* [',']

star_targets_list_seq: ','.star_target+ [',']

star_targets_tuple_seq:
    | star_target (',' star_target )+ [',']
    | star_target ','

star_target:
    | '*' (!'*' star_target)
    | target_with_star_atom

target_with_star_atom:
    | t_primary '.' NAME !t_lookahead
    | t_primary '[' slices ']' !t_lookahead
    | star_atom

star_atom:
    | NAME
    | '(' target_with_star_atom ')'
    | '(' [star_targets_tuple_seq] ')'
    | '[' [star_targets_list_seq] ']'

single_target:
    | single_subscript_attribute_target
    | NAME
    | '(' single_target ')'

single_subscript_attribute_target:
    | t_primary '.' NAME !t_lookahead
    | t_primary '[' slices ']' !t_lookahead

t_primary:
    | t_primary '.' NAME &t_lookahead
    | t_primary '[' slices ']' &t_lookahead
    | t_primary genexp &t_lookahead
    | t_primary '(' [arguments] ')' &t_lookahead
    | atom &t_lookahead

t_lookahead: '(' | '[' | '.'

# del 陳述式的目標
# --------------

del_targets: ','.del_target+ [',']

del_target:
    | t_primary '.' NAME !t_lookahead
    | t_primary '[' slices ']' !t_lookahead
    | del_t_atom

del_t_atom:
    | NAME
    | '(' del_target ')'
    | '(' [del_targets] ')'
    | '[' [del_targets] ']'

# 型別元素
# -------

# type_expressions 允許 */** 但會忽略他們
type_expressions:
    | ','.expression+ ',' '*' expression ',' '**' expression
    | ','.expression+ ',' '*' expression
    | ','.expression+ ',' '**' expression
    | '*' expression ',' '**' expression
    | '*' expression
    | '**' expression
    | ','.expression+

func_type_comment:
    | NEWLINE TYPE_COMMENT &(NEWLINE INDENT)   # 後面必須接縮排區塊
    | TYPE_COMMENT

# ========================= 文法結束 ===========================

# ========================= 無效規則開始 =======================

# 從這裡開始是用於無效語法的規則，具有專門的錯誤訊息
invalid_arguments:
    | ((','.(starred_expression | ( assignment_expression | expression !':=') !'=')+ ',' kwargs) | kwargs) ',' ','.(starred_expression !'=')+
    | expression for_if_clauses ',' [args | expression for_if_clauses]
    | NAME '=' expression for_if_clauses
    | (args ',')? NAME '=' &(',' | ')')
    | args for_if_clauses
    | args ',' expression for_if_clauses
    | args ',' args
invalid_kwarg:
    | ('True'|'False'|'None') '='
    | NAME '=' expression for_if_clauses
    | !(NAME '=') expression '='
    | '**' expression '=' expression

# 重要：請注意 "_without_invalid" 後綴會導致該規則不呼叫其下的無效規則
expression_without_invalid:
    | disjunction 'if' disjunction 'else' expression
    | disjunction
    | lambdef
invalid_legacy_expression:
    | NAME !'(' star_expressions

invalid_type_param:
    | '*' NAME ':' expression
    | '**' NAME ':' expression

invalid_expression:
   |  STRING (!STRING expression_without_invalid)+ STRING
    # !(NAME STRING) 不匹配所以我們不會去顯示有著像是 kf"dsfsdf" 無效字串前綴的錯誤
    # 軟關鍵字也需要被忽略，因為它們可以被剖析為 NAME NAME
   | !(NAME STRING | SOFT_KEYWORD) disjunction expression_without_invalid
   | disjunction 'if' disjunction !('else'|':')
   | disjunction 'if' disjunction 'else' !expression
   | (pass_stmt|break_stmt|continue_stmt) 'if' disjunction 'else' simple_stmt
   | 'lambda' [lambda_params] ':' &FSTRING_MIDDLE
   | 'lambda' [lambda_params] ':' &TSTRING_MIDDLE

invalid_named_expression:
    | expression ':=' expression
    | NAME '=' bitwise_or !('='|':=')
    | !(list|tuple|genexp|'True'|'None'|'False') bitwise_or '=' bitwise_or !('='|':=')

invalid_assignment:
        RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
            a,
            "only single target (not %s) can be annotated",
            _PyPegen_get_expr_name(a)
        )}
    | star_named_expression ',' star_named_expressions* ':' expression
    | expression ':' expression
    | (star_targets '=')* star_expressions '='
    | (star_targets '=')* yield_expr '='
    | star_expressions augassign annotated_rhs
invalid_ann_assign_target:
    | list
    | tuple
invalid_del_stmt:
    | 'del' star_expressions
invalid_block:
    | NEWLINE !INDENT
invalid_comprehension:
    | ('[' | '(' | '{') starred_expression for_if_clauses
    | ('[' | '{') star_named_expression ',' star_named_expressions for_if_clauses
    | ('[' | '{') star_named_expression ',' for_if_clauses
invalid_dict_comprehension:
    | '{' '**' bitwise_or for_if_clauses '}'
invalid_parameters:
    | "/" ','
    | (slash_no_default | slash_with_default) param_maybe_default* '/'
        RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "parameter without a default follows parameter with a default") }
    | param_no_default* '(' param_no_default+ ','? ')'
    | (slash_no_default | slash_with_default)? param_maybe_default* '*' (',' | param_no_default) param_maybe_default* '/'
    | param_maybe_default+ '/' '*'
invalid_default:
    | '=' &(')'|',')
invalid_star_etc:
    | '*' (')' | ',' (')' | '**'))
    | '*' ',' TYPE_COMMENT
    | '*' param '='
    | '*' (param_no_default | ',') param_maybe_default* '*' (param_no_default | ',')
invalid_kwds:
    | '**' param '='
    | '**' param ',' param
    | '**' param ',' ('*'|'**'|'/')
invalid_parameters_helper: # 這是為了避免型別錯誤而存在的規則
    | slash_with_default
    | param_with_default+
invalid_lambda_parameters:
    | "/" ','
    | (lambda_slash_no_default | lambda_slash_with_default) lambda_param_maybe_default* '/'
        RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "parameter without a default follows parameter with a default") }
    | lambda_param_no_default* '(' ','.lambda_param+ ','? ')'
    | (lambda_slash_no_default | lambda_slash_with_default)? lambda_param_maybe_default* '*' (',' | lambda_param_no_default) lambda_param_maybe_default* '/'
    | lambda_param_maybe_default+ '/' '*'
invalid_lambda_parameters_helper:
    | lambda_slash_with_default
    | lambda_param_with_default+
invalid_lambda_star_etc:
    | '*' (':' | ',' (':' | '**'))
    | '*' lambda_param '='
    | '*' (lambda_param_no_default | ',') lambda_param_maybe_default* '*' (lambda_param_no_default | ',')
invalid_lambda_kwds:
    | '**' lambda_param '='
    | '**' lambda_param ',' lambda_param
    | '**' lambda_param ',' ('*'|'**'|'/')
invalid_double_type_comments:
    | TYPE_COMMENT NEWLINE TYPE_COMMENT NEWLINE INDENT
invalid_with_item:
    | expression 'as' expression &(',' | ')' | ':')

invalid_for_if_clause:
    | 'async'? 'for' (bitwise_or (',' bitwise_or)* [',']) !'in'

invalid_for_target:
    | 'async'? 'for' star_expressions

invalid_group:
    | '(' starred_expression ')'
    | '(' '**' expression ')'
invalid_import:
    | 'import' ','.dotted_name+ 'from' dotted_name
    | 'import' NEWLINE
invalid_dotted_as_name:
    | dotted_name 'as' !(NAME (',' | ')' | ';' | NEWLINE)) expression
invalid_import_from_as_name:
    | NAME 'as' !(NAME (',' | ')' | ';' | NEWLINE)) expression

invalid_import_from_targets:
    | import_from_as_names ',' NEWLINE
    | NEWLINE

invalid_with_stmt:
    | ['async'] 'with' ','.(expression ['as' star_target])+ NEWLINE
    | ['async'] 'with' '(' ','.(expressions ['as' star_target])+ ','? ')' NEWLINE
invalid_with_stmt_indent:
    | ['async'] 'with' ','.(expression ['as' star_target])+ ':' NEWLINE !INDENT
    | ['async'] 'with' '(' ','.(expressions ['as' star_target])+ ','? ')' ':' NEWLINE !INDENT

invalid_try_stmt:
    | 'try' ':' NEWLINE !INDENT
    | 'try' ':' block !('except' | 'finally')
    | 'try' ':' block* except_block+ 'except' '*' expression ['as' NAME] ':'
    | 'try' ':' block* except_star_block+ 'except' [expression ['as' NAME]] ':'
invalid_except_stmt:
    | 'except' expression ',' expressions 'as' NAME  ':'
    | 'except' expression ['as' NAME ] NEWLINE
    | 'except' NEWLINE
    | 'except' expression 'as' expression ':' block
invalid_except_star_stmt:
    | 'except' '*' expression ',' expressions 'as' NAME  ':'
    | 'except' '*' expression ['as' NAME ] NEWLINE
    | 'except' '*' (NEWLINE | ':')
    | 'except' '*' expression 'as' expression ':' block
invalid_finally_stmt:
    | 'finally' ':' NEWLINE !INDENT
invalid_except_stmt_indent:
    | 'except' expression ['as' NAME ] ':' NEWLINE !INDENT
    | 'except' ':' NEWLINE !INDENT
invalid_except_star_stmt_indent:
    | 'except' '*' expression ['as' NAME ] ':' NEWLINE !INDENT
invalid_match_stmt:
    | "match" subject_expr NEWLINE
    | "match" subject_expr ':' NEWLINE !INDENT
invalid_case_block:
    | "case" patterns guard? NEWLINE
    | "case" patterns guard? ':' NEWLINE !INDENT
invalid_as_pattern:
    | or_pattern 'as' "_"
    | or_pattern 'as' expression
invalid_class_pattern:
        PyPegen_first_item(a, pattern_ty),
        PyPegen_last_item(a, pattern_ty),
        "positional patterns follow keyword patterns") }
invalid_class_argument_pattern:
    | [positional_patterns ','] keyword_patterns ',' positional_patterns
invalid_if_stmt:
    | 'if' named_expression NEWLINE
    | 'if' named_expression ':' NEWLINE !INDENT
invalid_elif_stmt:
    | 'elif' named_expression NEWLINE
    | 'elif' named_expression ':' NEWLINE !INDENT
invalid_else_stmt:
    | 'else' ':' NEWLINE !INDENT
    | 'else' ':' block 'elif'
invalid_while_stmt:
    | 'while' named_expression NEWLINE
    | 'while' named_expression ':' NEWLINE !INDENT
invalid_for_stmt:
    | ['async'] 'for' star_targets 'in' star_expressions NEWLINE
    | ['async'] 'for' star_targets 'in' star_expressions ':' NEWLINE !INDENT
invalid_def_raw:
    | ['async'] 'def' NAME [type_params] '(' [params] ')' ['->' expression] ':' NEWLINE !INDENT
    | ['async'] 'def' NAME [type_params] '(' [params] ')' ['->' expression] ':' [func_type_comment] block
invalid_class_def_raw:
    | 'class' NAME [type_params] ['(' [arguments] ')'] NEWLINE
    | 'class' NAME [type_params] ['(' [arguments] ')'] ':' NEWLINE !INDENT

invalid_double_starred_kvpairs:
    | expression ':' '*' bitwise_or
    | expression ':' &('}'|',')
invalid_kvpair:
    | expression !(':')
    | expression ':' '*' bitwise_or
    | expression ':' &('}'|',')
invalid_starred_expression_unpacking:
    | '*' expression '=' expression
invalid_starred_expression:
    | '*'

invalid_fstring_replacement_field:
    | '{' '='
    | '{' '!'
    | '{' ':'
    | '{' '}' '") }
    | '
    | '{' annotated_rhs !('=' | '!' | ':' | '}') '") }
    | '') '") }
    | '') '") }
    | '' ', or format specs") }
    | '{' annotated_rhs '='? ['!' NAME] !'}' '") }

invalid_fstring_conversion_character:
    | '!' &(':' | '}')
    | '!' !NAME

invalid_tstring_replacement_field:
    | '{' '='
    | '{' '!'
    | '{' ':'
    | '{' '}' '") }
    | '
    | '{' annotated_rhs !('=' | '!' | ':' | '}') '") }
    | '') '") }
    | '') '") }
    | '' ', or format specs") }
    | '{' annotated_rhs '='? ['!' NAME] !'}' '") }

invalid_tstring_conversion_character:
    | '!' &(':' | '}')
    | '!' !NAME

invalid_string_tstring_concat:
    | (fstring|string)+ tstring
    | tstring+ (fstring|string)

invalid_arithmetic:
    | sum ('+'|'-'|'*'|'/'|'%'|'//'|'@') 'not' inversion
invalid_factor:
    | ('+' | '-' | '~') 'not' factor

invalid_type_params:
    | '[' ']'

Python 標準函式庫 (Standard Library)

Python 語言參考手冊說明 Python 這門語言確切的文法及語意，而這份函式庫參考手冊則是說明隨著 Python 一起發佈的標準函式庫，除此之外，其內容也包含一些時常出現在 Python 發佈版本中的非必要套件。

Python 的標準函式庫是非常龐大的，其提供了如下所述極多且涵蓋用途極廣的許多模組。包含一些用 C 語言撰寫，可以操作像是檔案讀寫等系統相關功能的內建模組，當然也有用 Python 撰寫，並使用標準解法解決許多常見問題的模組。其中有些模組則是特別針對 Python 的可攜性去設計的，為此特地將一些平台特殊相依性的功能抽象化成可跨平台的 API。

Python 的 Windows 安裝檔基本上包含整個標準函式庫，且通常也包含許多附加的組件；而在類 Unix 作業系統方面，Python 通常是以一系列的套件被安裝，因此對於某些或全部的可選組件，可能都必須使用該作業系統提供的套件管理工具來安裝。

在標準函式庫之外，還有成千上萬且不斷增加的組件（從個別的程式、模組、套件到完整的應用程式開發框架），可以從 Python 套件索引 (Python Package Index) [https://pypi.org] 中取得。

簡介

可用性之標註

內建函式

內建常數

由 site module（模組）所添增的常數

內建型別

真值檢測

Boolean（布林）運算 --- and, or, not

比較運算

數值型別 --- int、float、complex

Boolean 型別 - bool

疊代器型別

Sequence Types --- list, tuple, range

Text and Binary Sequence Type Methods Summary

Text Sequence Type --- str

Binary Sequence Types --- bytes, bytearray, memoryview

Set Types --- set, frozenset

Mapping Types --- dict

情境管理器型別

型別註釋的型別 --- 泛型別名 (Generic Alias)、聯合 (Union)

其他內建型別

特殊屬性

Integer string conversion length limitation

內建的例外

例外的情境

繼承自內建的例外

基底類別 (base classes)

實體例外

警告

例外群組

例外階層

文本處理 (Text Processing) 服務

string --- 常見的字串操作

string.templatelib --- 對模板字串字面值的支援

re --- 正規表示式 (regular expression) 操作

difflib --- 計算差異的輔助工具

textwrap --- 文字包裝與填充

unicodedata --- Unicode 資料庫

stringprep --- 網際網路字串的準備

readline --- GNU readline 介面

rlcompleter --- GNU readline 的補全函式

二進位資料服務

struct --- 將位元組直譯為打包起來的二進位資料

codecs --- 編解碼器註冊表和基底類別

資料型別

datetime --- 日期與時間的基本型別

zoneinfo --- IANA 時區支援

calendar --- 日曆相關函式

collections --- 容器資料型別

collections.abc --- 容器的抽象基底類別

heapq --- 堆積佇列 (heap queue) 演算法

bisect --- 陣列二分演算法 (Array bisection algorithm)

array --- 高效率的數值型陣列

weakref --- 弱參照

types --- 動態型別建立與內建型別名稱

copy --- 淺層 (shallow) 和深層 (deep) 複製操作

pprint --- 資料美化列印器

reprlib --- repr() 的替代實作

enum --- 對列舉的支援

graphlib —-- 使用類圖 (graph-like) 結構進行操作的功能

數值與數學模組

numbers --- 數值的抽象基底類別

math --- 數學函式

cmath --- 複數的數學函式

decimal --- 十進位固定點和浮點運算

fractions --- 有理數

random --- 產生偽隨機數

statistics --- 數學統計函式

函式程式設計模組

itertools --- 建立產生高效率迴圈之疊代器的函式

functools --- 可呼叫物件上的高階函式與操作

operator --- 標準運算子替代函式

檔案與目錄存取

pathlib --- 物件導向檔案系統路徑

os.path --- 常見的路徑名操作

stat --- 直譯 stat() 的結果

filecmp --- 檔案與目錄比較

tempfile --- 生成臨時檔案和目錄

glob --- Unix 風格的路徑名稱模式擴展

fnmatch --- Unix 檔案名稱模式比對

linecache --- 隨機存取文字列

shutil — 高階檔案操作

資料持久性 (Data Persistence)

pickle --- Python 物件序列化

copyreg --- 註冊 pickle 支援函式

shelve --- Python object persistence

marshal --- 內部 Python 物件序列化

dbm --- Unix "databases" 的介面

sqlite3 --- SQLite 資料庫的 DB-API 2.0 介面

資料壓縮與保存

compression 套件

compression.zstd --- 與 Zstandard 格式相容的壓縮

zlib --- 相容於 gzip 的壓縮

gzip --- gzip 檔案的支援

bz2 --- bzip2 壓縮的支援

lzma --- 使用 LZMA 演算法進行壓縮

zipfile --- 處理 ZIP 封存檔案

tarfile --- 讀取與寫入 tar 封存檔案

檔案格式

csv --- CSV 檔案讀取及寫入

configparser --- 設定檔剖析器

tomllib --- 剖析 TOML 檔案

netrc --- netrc 檔案處理

plistlib --- 產生和剖析 Apple .plist 檔案

加密服務

hashlib --- 安全雜湊與訊息摘要

hmac --- 基於金鑰雜湊的訊息驗證

secrets --- 產生用於管理機密的安全亂數

通用作業系統服務

os --- 各種作業系統介面

io — 處理資料串流的核心工具

time --- 時間存取與轉換

logging --- Python 的日誌記錄工具

logging.config --- 日誌記錄配置

logging.handlers --- 日誌紀錄處理器

platform --- 對底層平臺識別資料的存取

errno --- 標準 errno 系統符號

ctypes --- 用於 Python 的外部函式庫

命令列介面函式庫

argparse --- 命令列選項、引數和子命令的剖析器

optparse --- 命令列選項剖析器

getpass --- 可攜式密碼輸入工具

fileinput --- 逐列疊代多個輸入串流

curses --- 字元儲存格顯示的終端處理

curses.textpad --- Text input widget for curses programs

curses.ascii --- ASCII 字元的工具程式

curses.panel --- curses 的面板堆疊擴充

cmd --- 以列為導向的命令直譯器支援

並行執行 (Concurrent Execution)

threading --- 基於執行緒的平行性

multiprocessing --- 以行程為基礎的平行性

multiprocessing.shared_memory --- 對於共享記憶體的跨行程直接存取

concurrent 套件

concurrent.futures --- 啟動平行任務

concurrent.interpreters --- 在同一個行程中使用多個直譯器

subprocess --- 子行程管理

sched --- 事件排程器

queue --- 同步佇列 (synchronized queue) 類別

contextvars --- 情境變數

_thread --- 低階執行緒 API

網路與行程間通訊

asyncio --- 非同步 I/O

socket — 低階網路介面

ssl --- socket 物件的 TLS/SSL 包裝器

select --- 等待 I/O 完成

selectors --- 高階 I/O 多工

signal --- 設定非同步事件的處理函式

mmap --- 記憶體對映檔案的支援

網際網路資料處理

email --- 郵件和 MIME 處理套件

json --- JSON 編碼器與解碼器

mailbox --- 以各種格式操作郵件信箱

mimetypes --- 將檔案名稱對映到 MIME 類型

base64 --- Base16、Base32、Base64、Base85 資料編碼

binascii --- 在二進位制和 ASCII 之間轉換

quopri --- 編碼和解碼 MIME 可列印字元資料

結構化標記處理工具

html --- 超文本標記語言 (HTML) 支援

html.parser --- 簡單的 HTML 和 XHTML 剖析器

html.entities --- HTML 一般實體的定義

XML 處理模組

xml.etree.cElementTree --- ElementTree XML API

xml.dom --- Document 物件模型 API

xml.dom.minidom --- 最小的 DOM 實作

xml.dom.pulldom --- 支援建置部分 DOM 樹

xml.sax --- SAX2 剖析器支援

xml.sax.handler --- SAX 處理函式的基本類別

xml.sax.saxutils --- SAX 工具程式

xml.sax.xmlreader --- XML 剖析器的介面

xml.parsers.expat --- 使用 Expat 進行快速 XML 剖析

網路協定 (Internet protocols) 及支援

webbrowser --- 方便的網頁瀏覽器控制器

wsgiref --- WSGI 工具與參考實作

urllib --- URL 處理模組

urllib.request --- 用來開啟 URLs 的可擴充函式庫

urllib.response --- Response classes used by urllib

urllib.parse --- 將 URL 剖析成元件

urllib.error --- urllib.request 引發的例外類別

urllib.robotparser --- robots.txt 的剖析器

http --- HTTP 模組

http.client --- HTTP 協定用戶端

ftplib --- FTP 協定用戶端

poplib --- POP3 協定用戶端

imaplib --- IMAP4 協定用戶端

smtplib --- SMTP 協定用戶端

uuid --- RFC 9562 定義的 UUID 物件

socketserver --- 用於網路伺服器的框架

http.server — HTTP 伺服器

http.cookies --- HTTP 狀態管理

http.cookiejar --- HTTP 用戶端的 Cookie 處理

xmlrpc --- XMLRPC 伺服器與用戶模組

xmlrpc.client --- XML-RPC 用戶端存取

xmlrpc.server --- 基本 XML-RPC 伺服器

ipaddress --- IPv4/IPv6 操作函式庫

多媒體服務

wave --- 讀寫 WAV 檔案

colorsys --- 顏色系統間的轉換

國際化

gettext --- 多語言國際化服務

locale --- 國際化服務

以 Tk 打造圖形使用者介面 (Graphical User Interfaces)

tkinter --- Tcl/Tk 的 Python 介面

tkinter.colorchooser --- 顏色選擇對話框

tkinter.font --- Tkinter 字型包裝器

Tkinter 對話框

tkinter.messagebox --- Tkinter 訊息提示

tkinter.scrolledtext --- 捲動文字小工具

tkinter.dnd --- 拖放支援

tkinter.ttk --- Tk 主題化小工具

IDLE --- Python 編輯器與 shell

turtle --- 龜圖學 (Turtle graphics)

開發工具

typing --- 支援型別提示

pydoc --- 文件產生器與線上幫助系統

Python 開發模式

doctest --- 測試互動式 Python 範例

unittest --- 單元測試框架

unittest.mock — mock 物件函式庫

unittest.mock --- 入門指南

test --- Python 的回歸測試 (regression tests) 套件

test.support --- Python 測試套件的工具

test.support.socket_helper --- 用於 socket 測試的工具

test.support.script_helper --- 用於 Python 執行測試的工具

test.support.bytecode_helper --- 用於測試位元組碼能正確產生的支援工具

test.support.threading_helper --- Utilities for threading tests

test.support.os_helper --- 用於 os 測試的工具

test.support.import_helper --- 用於 import 測試的工具

test.support.warnings_helper --- 用於 warnings 測試的工具

除錯與效能分析

稽核事件表

bdb --- 偵錯器框架

faulthandler --- 傾印 Python 回溯

pdb --- Python 偵錯器

Python 的分析器

timeit --- 測量小量程式片段的執行時間

trace --- 追蹤或追查 Python 陳述式執行

tracemalloc --- 追蹤記憶體配置

軟體封裝與發布

ensurepip --- pip 安裝器的初始建置 (bootstrapping)

venv --- 建立虛擬環境

zipapp —-- 管理可執行的 Python zip 封存檔案

Python Runtime 服務

sys --- 系統特定的參數與函式

sys.monitoring --- 執行事件監控

sysconfig --- 提供 Python 設定資訊的存取

builtins --- 內建物件

__main__ --- 頂層程式碼環境

warnings --- 警告控制

dataclasses --- Data Classes

contextlib --- with 陳述式工具程式

abc --- 抽象基底類別

atexit --- 退出處理函式

traceback --- 列印或取得堆疊回溯 (stack traceback)

__future__ --- Future 陳述式定義

gc --- 垃圾回收器介面 (Garbage Collector interface)

inspect --- 檢視活動物件

annotationlib --- 用於自我檢查註釋的功能

site --- Site-specific configuration hook

自訂 Python 直譯器

code --- 直譯器基底類別

codeop --- 編譯 Python 程式碼

引入模組

zipimport --- 從 Zip 封存檔案匯入模組

pkgutil --- 套件擴充工具程式

modulefinder --- 搜尋腳本所使用的模組

runpy --- 定位並執行 Python 模組

importlib --- import 的實作

importlib.resources -- 套件資源的讀取、開啟與存取

importlib.resources.abc -- 資源的抽象基底類別

importlib.metadata -- 存取套件的元資料

sys.path 模組搜尋路徑的初始化

Python 語言服務

ast --- 抽象語法樹 (Abstract Syntax Trees)

symtable --- 存取編譯器的符號表

token --- 與 Python 剖析樹一起使用的常數

keyword --- 檢驗 Python 關鍵字

tokenize --- Tokenizer for Python source

tabnanny --- 偵測不良縮排

pyclbr --- Python 模組瀏覽器支援

py_compile — 編譯 Python 來源檔案

compileall --- 位元組編譯 Python 函式庫

dis --- Python bytecode 的反組譯器

pickletools --- pickle 開發者的工具

MS Windows 特有服務

msvcrt --- MS VC++ runtime 提供的有用例程

winreg --- Windows 註冊表存取

winsound --- Windows 的音效播放介面

Unix 特有服務

shlex --- 簡單的語法分析

posix --- 最常見的 POSIX 系統呼叫

pwd --- 密碼資料庫

grp --- 群組資料庫

termios --- POSIX 風格 tty 控制

tty --- 終端機控制函式

pty --- 偽終端工具

fcntl --- fcntl 和 ioctl 系統呼叫

resource --- 資源使用資訊

syslog --- Unix syslog 函式庫例程

模組命令列介面

已被取代的模組

getopt --- 用於命令列選項的 C 風格剖析器

已移除的模組

安全性注意事項

簡介

「Python 函式庫」包含了許多不同的部分。

函式庫中包括被視為程式語言「核心」部分的資料型別，像是數字 (number) 或是串列 (list)。對於這些型別，Python 核心對這些字面值 (literal) 的形式做定義，並對它們的語意制定了一些限制，但在此同時卻不把文字對應的語意完全定義。（另一方面，Python 在語法面上有確實的定義，例如拼字或是運算元次序）

Python 函式庫也囊括了內建函式與例外處理——這些物件都可以不用透過 import 陳述式來引入 Python 程式中就能使用。函式庫中有部份是被 Python 核心所定義的，但在這裡僅解釋最核心的語意部分。

整個函式庫中包含了許多模組，有許多方法可以從函式庫中取用這些模組。有些模組是以 C 語言撰寫並建置於 Python 編譯器之中，其他的是由 Python 撰寫並以源碼的方式 (source form) 引入。有些模組提供的功能是專屬於 Python 的，像是把 stack trace 印出來；有些則是針對特定作業系統，去試著存取特定硬體；還有些提供對特定應用的功能與操作介面，像是 World Wide Web。模組的使用情況會因機器與 Python 的版本而不同，部分模組是開放所有版本以及 Port 的 Python 來使用的，但有些會因系統支援或需求在某些版本或系統下無法使用，甚至有些僅限在特定的設定環境下才能使用。

這個手冊會「深入淺出」地介紹 Python 函式庫。它會先介紹一些內建函式、資料型態、和一些例外處理，再來一章章的主題式介紹相關模組。

這代表如果你從這個手冊的最開始讀起，並在感到無聊時跳到下一個章節，你仍然可以得到一個對 Python 函式庫所支援的模組與其合理應用的概觀。當然，你沒有必要像是在讀一本小說一樣讀這本手冊——你可以快速瀏覽目錄（在手冊的最前頭）、或是你可以利用最後面的索引來查詢特定的函式或模組。最後，如果你享受閱讀一些隨機的主題，你可以選擇一個隨機的數字並開始閱讀（見 random 模組) 。不管你想要以什麼順序來閱讀這個手冊，內建函式會是一個很好的入門，因為手冊中其他章節都預設你已經對這個章節有一定的熟悉程度。

讓我們開始吧！

可用性之標註

如果出現「適用：Unix」標註，則代表該函式普遍存在於 Unix 系統中，但這並不保證其存在於某特定作業系統。

如果沒有分別標註的話，有標明「適用：Unix」標註的所有函式也都於 macOS、iOS 和 Android 上支援，因其建於 Unix 核心之上。

If an availability note contains both a minimum Kernel version and a minimum libc version, then both conditions must hold. For example a feature with note Availability: Linux >= 3.17 with glibc >= 2.27 requires both Linux 3.17 or newer and glibc 2.27 or newer.

WebAssembly 平台

The WebAssembly [https://webassembly.org/] platforms wasm32-emscripten (Emscripten [https://emscripten.org/]) and wasm32-wasi (WASI [https://wasi.dev/]) provide a subset of POSIX APIs. WebAssembly runtimes and browsers are sandboxed and have limited access to the host and external resources. Any Python standard library module that uses processes, threading, networking, signals, or other forms of inter-process communication (IPC), is either not available or may not work as on other Unix-like systems. File I/O, file system, and Unix permission-related functions are restricted, too. Emscripten does not permit blocking I/O. Other blocking operations like sleep() block the browser event loop.

The properties and behavior of Python on WebAssembly platforms depend on the Emscripten [https://emscripten.org/]-SDK or WASI [https://wasi.dev/]-SDK version, WASM runtimes (browser, NodeJS, wasmtime [https://wasmtime.dev/]), and Python build time flags. WebAssembly, Emscripten, and WASI are evolving standards; some features like networking may be supported in the future.

For Python in the browser, users should consider Pyodide [https://pyodide.org/] or PyScript [https://pyscript.net/]. PyScript is built on top of Pyodide, which itself is built on top of CPython and Emscripten. Pyodide provides access to browsers' JavaScript and DOM APIs as well as limited networking capabilities with JavaScript's XMLHttpRequest and Fetch APIs.

Process-related APIs are not available or always fail with an error. That includes APIs that spawn new processes (fork(), execve()), wait for processes (waitpid()), send signals (kill()), or otherwise interact with processes. The subprocess is importable but does not work.

The socket module is available, but is limited and behaves differently from other platforms. On Emscripten, sockets are always non-blocking and require additional JavaScript code and helpers on the server to proxy TCP through WebSockets; see Emscripten Networking [https://emscripten.org/docs/porting/networking.html] for more information. WASI snapshot preview 1 only permits sockets from an existing file descriptor.

Some functions are stubs that either don't do anything and always return hardcoded values.

Functions related to file descriptors, file permissions, file ownership, and links are limited and don't support some operations. For example, WASI does not permit symlinks with absolute file names.

行動平台

Android and iOS are, in most respects, POSIX operating systems. File I/O, socket handling, and threading all behave as they would on any POSIX operating system. However, there are several major differences:

Mobile platforms can only use Python in "embedded" mode. There is no Python REPL, and no ability to use separate executables such as python or pip. To add Python code to your mobile app, you must use the Python embedding API. For more details, see 在 Android 上使用 Python and 在 iOS 上使用 Python.

Subprocesses:

On Android, creating subprocesses is possible but officially unsupported [https://issuetracker.google.com/issues/128554619#comment4]. In particular, Android does not support any part of the System V IPC API, so multiprocessing is not available.

An iOS app cannot use any form of subprocessing, multiprocessing, or inter-process communication. If an iOS app attempts to create a subprocess, the process creating the subprocess will either lock up, or crash. An iOS app has no visibility of other applications that are running, nor any ability to communicate with other running applications, outside of the iOS-specific APIs that exist for this purpose.

Mobile apps have limited access to modify system resources (such as the system clock). These resources will often be readable, but attempts to modify those resources will usually fail.

Console input and output:

On Android, the native stdout and stderr are not connected to anything, so Python installs its own streams which redirect messages to the system log. These can be seen under the tags python.stdout and python.stderr respectively.

iOS apps have a limited concept of console output. stdout and stderr exist, and content written to stdout and stderr will be visible in logs when running in Xcode, but this content won't be recorded in the system log. If a user who has installed your app provides their app logs as a diagnostic aid, they will not include any detail written to stdout or stderr.

Mobile apps have no usable stdin at all. While apps can display an on-screen keyboard, this is a software feature, not something that is attached to stdin.

As a result, Python modules that involve console manipulation (such as curses and readline) are not available on mobile platforms.

內建函式

Python 直譯器有內建多個可隨時使用的函式和型別。以下按照英文字母排序列出。

內建函式

A

abs()

aiter()

all()

anext()

any()

ascii()

B

bin()

bool()

breakpoint()

bytearray()

bytes()

C

callable()

chr()

classmethod()

compile()

complex()

D

delattr()

dict()

dir()

divmod()

E

enumerate()

eval()

exec()

F

filter()

float()

format()

frozenset()

G

getattr()

globals()

H

hasattr()

hash()

help()

hex()

I

id()

input()

int()

isinstance()

issubclass()

iter()

L

len()

list()

locals()

M

map()

max()

memoryview()

min()

N

next()

O

object()

oct()

open()

ord()

P

pow()

print()

property()

R

range()

repr()

reversed()

round()

S

set()

setattr()

slice()

sorted()

staticmethod()

str()

sum()

super()

T

tuple()

type()

V

vars()

Z

zip()

_

__import__()

abs(number, /)

回傳一個數的絕對值，引數可以是整數、浮點數或有實現 __abs__() 的物件。如果引數是一個複數，回傳它的純量（大小）。

aiter(async_iterable, /)

回傳 非同步疊代器 做為 非同步可疊代物件。相當於呼叫 x.__aiter__()。

注意：與 iter() 不同，aiter() 沒有兩個引數的變體。

在 3.10 版被加入.

all(iterable, /)

如果 iterable 的所有元素皆為真（或 iterable 為空）則回傳 True。等價於：

def all(iterable):
    for element in iterable:
        if not element:
            return False
    return True

awaitable anext(async_iterator, /)

awaitable anext(async_iterator, default, /)

當進入 await 時，從給定的 asynchronous iterator 中回傳下一個項目（item），疊代完畢則回傳 default 。

這是內建函式 next() 的非同步版本，其行為類似於：

呼叫 async_iterator 的 __anext__() 方法，回傳 awaitable。等待返回疊代器的下一個值。如果指定 default，當疊代器結束時會返回該值，否則會引發 StopAsyncIteration 。

在 3.10 版被加入.

any(iterable, /)

如果 iterable 的任一元素為真，回傳 True。如果 iterable 是空的，則回傳 False。等價於：

def any(iterable):
    for element in iterable:
        if element:
            return True
    return False

ascii(object, /)

就像函式 repr()，回傳一個表示物件的字串，但是 repr() 回傳的字串中非 ASCII 編碼的字元會被跳脫 (escape)，像是 \x、\u 和 \U。這個函式生成的字串和 Python 2 的 repr() 回傳的結果相似。

bin(integer, /)

將一個整數轉變為一個前綴為 "0b" 的二進位制字串。結果是一個有效的 Python 運算式。如果 integer 不是 Python 的 int 物件，那它需要定義 __index__() method 回傳一個整數。舉例來說：

>>> bin(3)
'0b11'
>>> bin(-10)
'-0b1010'

如果不一定需要 "0b" 前綴，還可以使用如下的方法。

>>> format(14, '#b'), format(14, 'b')
('0b1110', '1110')
>>> f'{14:#b}', f'{14:b}'
('0b1110', '1110')

See also enum.bin() to represent negative values as twos-complement.

可參考 format() 取得更多資訊。

class bool(object=False, /)

回傳一個布林值，即 True 或者 False。引數會使用標準的真值測試程序來轉換。如果引數為假或者被省略，則回傳 False；其他情況回傳 True。bool class（類別）是 int 的 subclass（子類別）（參見 數值型別 --- int、float、complex），其他 class 不能繼承自它。它只有 False 和 True 兩個實例（參見 Boolean 型別 - bool）。

在 3.7 版的變更: 現在為僅限位置參數。

breakpoint(*args, **kws)

這個函式將呼叫 sys.breakpointhook() 函式，並將 args 和 kws 傳遞給它。這將有效地讓你在特定的呼叫點進入除錯器。預設情況下，sys.breakpointhook() 呼叫 pdb.set_trace() 不須帶任何引數。這樣的設計是為了方便使用者，讓他們不需要額外地導入 pdb 模組或輸入太多程式就可以進入除錯器。然而，可以將 sys.breakpointhook() 設置為其他函式，並且 breakpoint() 將自動呼叫該函式，讓你進入所選擇的除錯器。如果無法存取 sys.breakpointhook() 這個函式，則此函式將引發 RuntimeError。

預設情況下，breakpoint() 的行為可以透過 PYTHONBREAKPOINT 環境變數來更改。有關使用詳情，請參考 sys.breakpointhook()。

請注意，如果 sys.breakpointhook() 被替換了，則無法保證此功能。

引發一個附帶引數 breakpointhook 的稽核事件 builtins.breakpoint。

在 3.7 版被加入.

class bytearray(source=b'')

class bytearray(source, encoding, errors='strict')

回傳一個新的 bytes 陣列。bytearray class 是一個可變的整數序列，包含範圍為 0 <= x < 256 的整數。它有可變序列大部分常見的 method（如在 可變序列型別 中所述），同時也有 bytes 型別大部分的 method，參見 Bytes 和 Bytearray 的操作。

選擇性參數 source 可以被用來以不同的方式初始化陣列：

如果是一個 string，你必須提供 encoding 參數（以及選擇性地提供 errors ）；bytearray() 會使用 str.encode() method 來將 string 轉變成 bytes。

如果是一個 integer，陣列則會有該數值的長度，並以 null bytes 來當作初始值。

如果是一個符合 buffer 介面的物件，該物件的唯讀 buffer 會被用來初始化 bytes 陣列。

如果是一個 iterable，它的元素必須是範圍為 0 <= x < 256 的整數，並且會被用作陣列的初始值。

如果沒有引數，則建立長度為 0 的陣列。

可參考 Binary Sequence Types --- bytes, bytearray, memoryview 和 Bytearray 物件。

class bytes(source=b'')

class bytes(source, encoding, errors='strict')

回傳一個新的 "bytes" 物件，會是一個元素是範圍為 0 <= x < 256 整數的不可變序列。bytes 是 bytearray 的不可變版本 — 它的同樣具備不改變物件的 method，也有相同的索引和切片操作。

因此，建構函式的引數和 bytearray() 相同。

Bytes 物件還可以用文字建立，參見 String and Bytes literals。

可參考 Binary Sequence Types --- bytes, bytearray, memoryview、Bytes Objects 和 Bytes 和 Bytearray 的操作。

callable(object, /)

如果引數 object 是可呼叫的，回傳 True，否則回傳 False。如果回傳 True，呼叫仍可能會失敗；但如果回傳 False，則呼叫 object 肯定會失敗。注意 class 是可呼叫的（呼叫 class 會回傳一個新的實例）；如果實例的 class 有定義 __call__() method，則它是可呼叫的。

在 3.2 版被加入: 這個函式一開始在 Python 3.0 被移除，但在 Python 3.2 又被重新加入。

chr(codepoint, /)

回傳代表有特定 Unicode 編碼位置字元的字串。例如，chr(97) 回傳字串 'a'，而 chr(8364) 回傳字串 '€'。這是 ord() 的逆函式。

引數的有效範圍是 0 到 1,114,111（16 進制表示為 0x10FFFF）。如果它超過這個範圍，會引發 ValueError。

@classmethod

把一個 method 封裝成 class method（類別方法）。

一個 class method 把自己的 class 作為第一個引數，就像一個實例 method 把實例自己作為第一個引數。請用以下慣例來宣告 class method：

class C:
    @classmethod
    def f(cls, arg1, arg2): ...

@classmethod 語法是一個函式 decorator — 參見 函式定義 中關於函式定義的詳細介紹。

一個 class method 可以在 class（如 C.f()）或實例（如 C().f()）上呼叫。實例除了它的 class 資訊，其他都會被忽略。如果一個 class method 在 subclass 上呼叫，subclass 會作為第一個引數傳入。

Class method 和 C++ 與 Java 的 static method 是有區別的。如果你想瞭解 static method，請看本節的 staticmethod()。關於 class method 的更多資訊，請參考標準型別階層。

在 3.9 版的變更: Class methods 現在可以包裝其他描述器，例如 property()

在 3.10 版的變更: Class method 現在繼承了 method 屬性（__module__、__name__、__qualname__、__doc__ 和 __annotations__），並擁有一個新的 __wrapped__ 屬性。

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。: Class methods 不能再包裝其他的描述器，例如 property()。

compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)

將 source 編譯成程式碼或 AST 物件。程式碼物件可以被 exec() 或 eval() 執行。source 可以是一般的字串、bytes 字串、或者 AST 物件。參見 ast module（模組）的說明文件瞭解如何使用 AST 物件。

filename 引數必須是程式碼的檔名；如果程式碼不是從檔案中讀取，可以傳入一些可辨識的值（經常會使用 '<string>' 來替代）。

mode 引數指定了編譯程式碼時必須用的模式。如果 source 是一系列的陳述式，可以是 'exec'；如果是單一運算式，可以是 'eval'；如果是單個互動式陳述式，可以是 'single'（在最後一種情況下，如果運算式執行結果不是 None 則會被印出來）。

可選引數 flags 和 dont_inherit 控制啟用哪個編譯器選項以及允許哪個未來功能。如果兩者都不存在（或兩者都為零），則會呼叫與 compile() 相同旗標的程式碼來編譯。如果給定 flags 引數而未給定 dont_inherit（或為零）則無論如何都會使用由 flags 引數所指定的編譯器選項和未來陳述式。如果 dont_inherit 是一個非零整數，則使用 flags 引數 -- 周圍程式碼中的旗標（未來功能和編譯器選項）將被忽略。

編譯器選項和 future 陳述式使用 bits 來表示，可以一起被位元操作 OR 來表示複數個選項。需要被具體定義特徵的位元域可以透過 __future__ module 中 _Feature 實例中的 compiler_flag 屬性來獲得。編譯器旗標可以在 ast module 中搜尋有 PyCF_ 前綴的名稱。

引數 optimize 用來指定編譯器的最佳化級別；預設值 -1 選擇與直譯器的 -O 選項相同的最佳化級別。其他級別為 0（沒有最佳化；__debug__ 為真值）、1（assert 被刪除，__debug__ 為假值）或 2（說明字串 (docstring) 也被刪除）。

如果編譯的原始碼無效，此函式會引發 SyntaxError 或 ValueError。

如果你想解析 Python 程式碼為 AST 運算式，請參閱 ast.parse()。

引發一個附帶引數 source、filename 的稽核事件 compile。此事件也可能由隱式編譯 (implicit compilation) 所引發。

備註

在 'single' 或 'eval' 模式編譯多行程式碼時，輸入必須以至少一個換行符結尾。這使 code module 更容易檢測陳述式的完整性。

警告

如果編譯足夠大或者足夠複雜的字串成 AST 物件時，Python 直譯器會因為 Python AST 編譯器的 stack 深度限制而崩潰。

在 3.2 版的變更: 允許使用 Windows 和 Mac 的換行符號。此外，在 'exec' 模式不需要以換行符號結尾。增加了 optimize 參數。

在 3.5 版的變更: 在之前的版本，source 中包含 null bytes 會引發 TypeError。

在 3.8 版被加入: ast.PyCF_ALLOW_TOP_LEVEL_AWAIT 現在可以傳遞旗標以啟用對頂層 await、async for 和 async with 的支援。

class complex(number=0, /)

class complex(string, /)

class complex(real=0, imag=0)

Convert a single string or number to a complex number, or create a complex number from real and imaginary parts.

例如：

>>> complex('+1.23')
(1.23+0j)
>>> complex('-4.5j')
-4.5j
>>> complex('-1.23+4.5j')
(-1.23+4.5j)
>>> complex('\t( -1.23+4.5J )\n')
(-1.23+4.5j)
>>> complex('-Infinity+NaNj')
(-inf+nanj)
>>> complex(1.23)
(1.23+0j)
>>> complex(imag=-4.5)
-4.5j
>>> complex(-1.23, 4.5)
(-1.23+4.5j)

If the argument is a string, it must contain either a real part (in the same format as for float()) or an imaginary part (in the same format but with a 'j' or 'J' suffix), or both real and imaginary parts (the sign of the imaginary part is mandatory in this case). The string can optionally be surrounded by whitespaces and the round parentheses '(' and ')', which are ignored. The string must not contain whitespace between '+', '-', the 'j' or 'J' suffix, and the decimal number. For example, complex('1+2j') is fine, but complex('1 + 2j') raises ValueError. More precisely, the input must conform to the complexvalue production rule in the following grammar, after parentheses and leading and trailing whitespace characters are removed:

complexvalue: floatvalue |
              floatvalue ("j" | "J") |
              floatvalue sign absfloatvalue ("j" | "J")

如果引數是一個數字，則建構函式會像 int 和 float 一樣進行數值轉換。對於一個普通的 Python 物件 x，complex(x) 會委派給 x.__complex__()。如果 __complex__() 未定義，則會回退 (fall back) 到 __float__()。如果 __float__() 未定義，則會再回退到 __index__()。

If two arguments are provided or keyword arguments are used, each argument may be any numeric type (including complex). If both arguments are real numbers, return a complex number with the real component real and the imaginary component imag. If both arguments are complex numbers, return a complex number with the real component real.real-imag.imag and the imaginary component real.imag+imag.real. If one of arguments is a real number, only its real component is used in the above expressions.

See also complex.from_number() which only accepts a single numeric argument.

If all arguments are omitted, returns 0j.

複數型別在 數值型別 --- int、float、complex 中有相關描述。

在 3.6 版的變更: 可以使用底線將程式碼文字中的數字進行分組。

在 3.8 版的變更: 如果 __complex__() 和 __float__() 未定義，則會回退到 __index__()。

在 3.14 版之後被棄用: Passing a complex number as the real or imag argument is now deprecated; it should only be passed as a single positional argument.

delattr(object, name, /)

這是 setattr() 相關的函式。引數是一個物件和一個字串，該字串必須是物件中某個屬性名稱。如果物件允許，該函式將刪除指定的屬性。例如 delattr(x, 'foobar') 等價於 del x.foobar。name 不必是個 Python 識別符 (identifier)（請見 setattr()）。

class dict(**kwargs)

class dict(mapping, /, **kwargs)

class dict(iterable, /, **kwargs)

建立一個新的 dictionary（字典）。dict 物件是一個 dictionary class。參見 dict 和 Mapping Types --- dict 來瞭解這個 class。

其他容器型別，請參見內建的 list、set 和 tuple class，以及 collections module。

dir()

dir(object, /)

如果沒有引數，則回傳目前區域作用域 (local scope) 中的名稱列表。如果有引數，它會嘗試回傳該物件的有效屬性列表。

如果物件有一個名為 __dir__() 的 method，那麼該 method 將被呼叫，並且必須回傳一個屬性列表。這允許實現自訂 __getattr__() 或 __getattribute__() 函式的物件能夠自訂 dir() 來報告它們的屬性。

如果物件不提供 __dir__()，這個函式會嘗試從物件已定義的 __dict__ 屬性和型別物件收集資訊。結果列表並不總是完整的，如果物件有自訂 __getattr__()，那結果可能不準確。

預設的 dir() 機制對不同型別的物件有不同行為，它會試圖回傳最相關而非最完整的資訊：

如果物件是 module 物件，則列表包含 module 的屬性名稱。

如果物件是型別或 class 物件，則列表包含它們的屬性名稱，並且遞迴查詢其基礎的所有屬性。

否則，包含物件的屬性名稱列表、它的 class 屬性名稱，並且遞迴查詢它的 class 的所有基礎 class 的屬性。

回傳的列表按字母表排序，例如：

>>> import struct
>>> dir()   # show the names in the module namespace
['__builtins__', '__name__', 'struct']
>>> dir(struct)   # show the names in the struct module
['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
 '__initializing__', '__loader__', '__name__', '__package__',
 '_clearcache', 'calcsize', 'error', 'pack', 'pack_into',
 'unpack', 'unpack_from']
>>> class Shape:
...     def __dir__(self):
...         return ['area', 'perimeter', 'location']
...
>>> s = Shape()
>>> dir(s)
['area', 'location', 'perimeter']

備註

因為 dir() 主要是為了便於在互動式提示字元時使用，所以它會試圖回傳人們感興趣的名稱集合，而不是試圖保證結果的嚴格性或一致性，它具體的行為也可能在不同版本之間改變。例如，當引數是一個 class 時，metaclass 的屬性不包含在結果列表中。

divmod(a, b, /)

它將兩個（非複數）數字作為引數，並在執行整數除法時回傳一對商和餘數。對於混合運算元型別，適用二進位算術運算子的規則。對於整數，運算結果和 (a // b, a % b) 一致。對於浮點數，運算結果是 (q, a % b)，q 通常是 math.floor(a / b) 但可能會比 1 小。在任何情況下，q * b + a % b 和 a 基本相等，如果 a % b 非零，則它的符號和 b 一樣，且 0 <= abs(a % b) < abs(b)。

enumerate(iterable, start=0)

回傳一個列舉 (enumerate) 物件。iterable 必須是一個序列、iterator 或其他支援疊代的物件。enumerate() 回傳之 iterator 的 __next__() method 回傳一個 tuple（元組），裡面包含一個計數值（從 start 開始，預設為 0）和透過疊代 iterable 獲得的值。

>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]

等價於：

def enumerate(iterable, start=0):
    n = start
    for elem in iterable:
        yield n, elem
        n += 1

eval(source, /, globals=None, locals=None)

參數:

source (str | code object) -- A Python expression.

globals (dict | None) -- The global namespace (default: None).

locals (mapping | None) -- The local namespace (default: None).

回傳:

The result of the evaluated expression.

引發:

Syntax errors are reported as exceptions.

警告

This function executes arbitrary code. Calling it with user-supplied input may lead to security vulnerabilities.

source 引數會被視為一條 Python 運算式（技術上而言，是條件列表）來剖析及求值，而 globals 和 locals 對映分別用作全域和區域命名空間。如果 globals dictionary 存在但缺少 __builtins__ 的鍵值，那 source 被剖析之前，將為該鍵插入對內建 builtins module dictionary 的引用。這麼一來，在將 __builtins__ dictionary 傳入 eval() 之前，你可以透過將它插入 globals 來控制你需要哪些內建函式來執行程式碼。如果 locals 對映被省略，那它的預設值是 globals dictionary。如果兩個對映都被省略，則以在 eval() 被呼叫的環境中的 globals 和 locals 執行原始碼。請注意，eval() 在封閉 (enclosing) 環境中無法存取巢狀作用域 (non-locals)，除非呼叫 eval() 的作用域已經有參照它們（例如透過 nonlocal 陳述式）。

範例：

>>> x = 1
>>> eval('x+1')
2

這個函式也可以用來執行任意程式碼物件（如被 compile() 建立的那些）。這種情況下，傳入的引數是程式碼物件而不是字串。如果編譯該物件時的 mode 引數是 'exec'，那麼 eval() 回傳值為 None。

提示：exec() 函式支援動態執行陳述式。globals() 和 locals() 函式分別回傳目前的全域性和局部性 dictionary，它們對於將引數傳遞給 eval() 或 exec() 可能會方便許多。

如果給定來源是一個字串，那麼其前後的空格和定位字元會被移除。

另外可以參閱 ast.literal_eval()，該函式可以安全執行僅包含文字的運算式字串。

引發一個附帶程式碼物件為引數的稽核事件 exec。也可能會引發程式碼編譯事件。

在 3.13 版的變更: The globals and locals arguments can now be passed as keywords.

在 3.13 版的變更: The semantics of the default locals namespace have been adjusted as described for the locals() builtin.

exec(source, /, globals=None, locals=None, *, closure=None)

警告

This function executes arbitrary code. Calling it with user-supplied input may lead to security vulnerabilities.

這個函式支援動態執行 Python 程式碼。source 必須是字串或者程式碼物件。如果是字串，那麼該字串將被剖析為一系列 Python 陳述式並執行（除非發生語法錯誤）。[1] 如果是程式碼物件，它將被直接執行。無論哪種情況，被執行的程式碼都需要和檔案輸入一樣是有效的（可參閱語言參考手冊中關於檔案輸入的章節）。請注意，即使在傳遞給 exec() 函式的程式碼的上下文中，nonlocal、yield 和 return 陳述式也不能在函式之外使用。該函式回傳值是 None。

無論哪種情況，如果省略了選擇性的部分，程式碼將在目前作用域內執行。如果只提供了 globals 引數，就必須是 dictionary 型別（且不能是 dictionary 的子類別），而且會被用作全域和區域變數。如果同時提供了 globals 和 locals，它們分別被用作全域和區域變數。如果提供了 locals，則它可以是任何對映物件。請記住在 module 層級中全域和區域變數是相同的 dictionary。

備註

When exec gets two separate objects as globals and locals, the code will be executed as if it were embedded in a class definition. This means functions and classes defined in the executed code will not be able to access variables assigned at the top level (as the "top level" variables are treated as class variables in a class definition).

如果 globals dictionary 不包含 __builtins__ 鍵值，則將為該鍵插入對內建 builtins module dictionary 的引用。這麼一來，在將 __builtins__ dictionary 傳入 exec() 之前，你可以透過將它插入 globals 來控制你需要哪些內建函式來執行程式碼。

closure 引數會指定一個閉包 (closure) — 它是一個 cellvar（格變數）的 tuple。只有在 object 是一個含有自由（閉包）變數 (free (closure) variables) 的程式碼物件時，它才有效。Tuple 的長度必須與程式碼物件的 co_freevars 屬性完全匹配。

引發一個附帶程式碼物件為引數的稽核事件 exec。也可能會引發程式碼編譯事件。

備註

內建 globals() 和 locals() 函式各自回傳目前的全域和區域命名空間，因此可以將它們傳遞給 exec() 的第二個和第三個引數以供後續使用。

備註

預設情況下，locals 的行為如下面 locals() 函式描述的一樣。如果你想在 exec() 函式回傳時知道程式碼對 locals 的變動，請明確地傳遞 locals dictionary 。

在 3.11 版的變更: 增加了 closure 參數。

在 3.13 版的變更: The globals and locals arguments can now be passed as keywords.

在 3.13 版的變更: The semantics of the default locals namespace have been adjusted as described for the locals() builtin.

filter(function, iterable, /)

用 iterable 中函式 function 為 True 的那些元素，構建一個新的 iterator。iterable 可以是一個序列、一個支援疊代的容器、或一個 iterator。如果 function 是 None，則會假設它是一個識別性函式，即 iterable 中所有假值元素會被移除。

請注意，filter(function, iterable) 相當於一個生成器運算式，當 function 不是 None 的時候為 (item for item in iterable if function(item))；function 是 None 的時候為 (item for item in iterable if item)。

請參閱 itertools.filterfalse()，只有 function 為 false 時才選取 iterable 中元素的互補函式。

class float(number=0.0, /)

class float(string, /)

回傳從數字或字串生成的浮點數。

例如：

>>> float('+1.23')
1.23
>>> float('   -12345\n')
-12345.0
>>> float('1e-003')
0.001
>>> float('+1E6')
1000000.0
>>> float('-Infinity')
-inf

如果引數是字串，則它必須是包含十進位制數字的字串，字串前面可以有符號，之前也可以有空格。選擇性的符號有 '+' 和 '-'；'+' 對建立的值沒有影響。引數也可以是 NaN（非數字）或正負無窮大的字串。確切地說，除去首尾的空格後，輸入必須遵循以下語法中 floatvalue 的生成規則：

sign:          "+" | "-"
infinity:      "Infinity" | "inf"
nan:           "nan"
digit:         <a Unicode decimal digit, i.e. characters in Unicode general category Nd>
digitpart:     digit (["_"] digit)*
number:        [digitpart] "." digitpart | digitpart ["."]
exponent:      ("e" | "E") [sign] digitpart
floatnumber:   number [exponent]
absfloatvalue: floatnumber | infinity | nan
floatvalue:    [sign] absfloatvalue

字母大小寫不影響，例如，"inf"、"Inf"、"INFINITY"、"iNfINity" 都可以表示正無窮大。

否則，如果引數是整數或浮點數，則回傳具有相同值（在 Python 浮點精度範圍內）的浮點數。如果引數在 Python 浮點精度範圍外，則會引發 OverflowError。

對於一般的 Python 物件 x，float(x) 會委派給 x.__float__()。如果未定義 __float__() 則會回退到 __index__()。

See also float.from_number() which only accepts a numeric argument.

如果沒有引數，則回傳 0.0。

數值型別 --- int、float、complex 描述了浮點數型別。

在 3.6 版的變更: 可以使用底線將程式碼文字中的數字進行分組。

在 3.7 版的變更: 現在為僅限位置參數。

在 3.8 版的變更: 如果 __float__() 未定義，則會回退到 __index__()。

format(value, format_spec='', /)

將 value 轉換為 format_spec 控制的 "格式化" 表示。format_spec 的解釋取決於 value 引數的型別，但是大多數內建型別使用標準格式化語法：格式規格 (Format Specification) 迷你語言。

預設的 format_spec 是一個空字串，它通常和呼叫 str(value) 的效果相同。

呼叫 format(value, format_spec) 會轉換成 type(value).__format__(value, format_spec)，當搜尋 value 的 __format__() method 時，會忽略實例中的字典。如果搜尋到 object 這個 method 但 format_spec 不為空，或是 format_spec 或回傳值不是字串，則會引發 TypeError。

在 3.4 版的變更: 當 format_spec 不是空字串時，object().__format__(format_spec) 會引發 TypeError。

class frozenset(iterable=(), /)

回傳一個新的 frozenset 物件，它包含選擇性引數 iterable 中的元素。frozenset 是一個內建的 class。有關此 class 的文件，請參閱 frozenset 和 Set Types --- set, frozenset。

請參閱內建的 set、list、tuple 和 dict class，以及 collections module 來了解其它的容器。

getattr(object, name, /)

getattr(object, name, default, /)

回傳 object 之具名屬性的值。name 必須是字串。如果該字串是物件屬性之一的名稱，則回傳該屬性的值。例如，getattr(x, 'foobar') 等同於 x.foobar。如果指定的屬性不存在，且提供了 default 值，則回傳其值，否則引發 AttributeError。name 不必是個 Python 識別符 (identifier)（請見 setattr()）。

備註

由於私有名稱改編 (private name mangling) 是發生在編譯期，因此你必須手動改編私有屬性（有兩個前導底線的屬性）的名稱，才能使用 getattr() 來取得它。

globals()

回傳代表目前 module 命名空間的 dictionary。對於在函式中的程式碼來說，這在定義函式時設定且不論該函式是在何處呼叫都會保持相同。

hasattr(object, name, /)

該引數是一個物件和一個字串。如果字串是物件屬性之一的名稱，則回傳 True，否則回傳 False。（此功能是透過呼叫 getattr(object, name) 並檢查是否引發 AttributeError 來實作的。）

hash(object, /)

回傳該物件的雜湊值（如果它有的話）。雜湊值是整數。它們在 dictionary 查詢元素時用來快速比較 dictionary 的鍵。相同大小的數字數值有相同的雜湊值（即使它們型別不同，如 1 和 1.0）。

備註

請注意，如果物件帶有自訂的 __hash__() 方法，hash() 將根據運行機器的位元長度來截斷回傳值。

help()

help(request)

啟動內建的幫助系統（此函式主要以互動式使用）。如果沒有引數，直譯器控制台裡會啟動互動式幫助系統。如果引數是一個字串，則會在 module、函式、class、method、關鍵字或說明文件主題中搜尋該字串，並在控制台上列印幫助資訊。如果引數是其他任意物件，則會生成該物件的幫助頁。

請注意，呼叫 help() 時，如果斜線 (/) 出現在函式的參數列表中，這表示斜線前面的參數是僅限位置 (positional-only) 參數。有關更多資訊，請參閱常見問答集中的僅限位置參數條目。

此函式會被 site module 加入到內建命名空間。

在 3.4 版的變更: 對於 pydoc 和 inspect 的變更，使得可呼叫物件回報的的簽名 (signature) 更加全面和一致。

hex(integer, /)

將整數轉換為以 "0x" 為前綴的小寫十六進位制字串。如果 integer 不是 Python int 物件，則必須定義一個 __index__() method 並且回傳一個整數。舉例來說：

>>> hex(255)
'0xff'
>>> hex(-42)
'-0x2a'

如果要將整數轉換為大寫或小寫的十六進位制字串，並可選擇有無 "0x" 前綴，則可以使用如下方法：

>>> '%#x' % 255, '%x' % 255, '%X' % 255
('0xff', 'ff', 'FF')
>>> format(255, '#x'), format(255, 'x'), format(255, 'X')
('0xff', 'ff', 'FF')
>>> f'{255:#x}', f'{255:x}', f'{255:X}'
('0xff', 'ff', 'FF')

可參考 format() 取得更多資訊。

另請參閱 int() 將十六進位制字串轉換為以 16 為基數的整數。

備註

如果要取得浮點數的十六進位制字串形式，請使用 float.hex() method。

id(object, /)

回傳物件的 "識別性" 。該值是一個整數，在此物件的生命週期中保證是唯一且恆定的。兩個生命期不重疊的物件可能具有相同的 id() 值。

這是該物件在記憶體中的位址。

引發一個附帶引數 id 的稽核事件 builtins.id。

input()

input(prompt, /)

如果有提供 prompt 引數，則將其寫入標準輸出，末尾不帶換行符。接下來，該函式從輸入中讀取一行，將其轉換為字串（去除末尾的換行符）並回傳。當讀取到 EOF 時，則引發 EOFError。例如：

>>> s = input('--> ')
--> Monty Python's Flying Circus
>>> s
"Monty Python's Flying Circus"

如果載入了 readline module，input() 將使用它來提供複雜的行編輯和歷史記錄功能。

引發一個附帶讀取輸入前的引數 prompt 的稽核事件 builtins.input。

引發一個附帶成功讀取結果的稽核事件 builtins.input/result。

class int(number=0, /)

class int(string, /, base=10)

Return an integer object constructed from a number or a string, or return 0 if no arguments are given.

例如：

>>> int(123.45)
123
>>> int('123')
123
>>> int('   -12_345\n')
-12345
>>> int('FACE', 16)
64206
>>> int('0xface', 0)
64206
>>> int('01110011', base=2)
115

如果引數定義了 __int__()，則 int(x) 會回傳 x.__int__()。如果引數定義了 __index__() 則回傳 x.__index__()。對於浮點數，則會向零的方向無條件捨去。

如果引數不是數字或如果有給定 base，則它必須是個字串、bytes 或 bytearray 實例，表示基數 (radix) base 中的整數。可選地，字串之前可以有 + 或 -（中間沒有空格）、可有個前導的零、也可被空格包圍、或在數字間有單一底線。

一個 n 進制的整數字串，包含各個代表 0 到 n-1 的數字，0–9 可以用任何 Unicode 十進制數字表示，10–35 可以用 a 到 z（或 A 到 Z）表示。預設的 base 是 10。允許的進位制有 0、2–36。2、8、16 進位制的字串可以在程式碼中用 0b/0B、0o/0O、0x/0X 前綴來表示，如同程式碼中的整數文字。進位制為 0 的字串將以和程式碼整數字面值 (integer literal in code) 類似的方式來直譯，最後由前綴決定的結果會是 2、8、10、16 進制中的一個，所以 int('010', 0) 是非法的，但 int('010') 和 int('010', 8) 是有效的。

整數型別定義請參閱數值型別 --- int、float、complex。

在 3.4 版的變更: 如果 base 不是 int 的實例，但 base 物件有 base.__index__ method，則會呼叫該 method 來取得此進位制所需的整數。以前的版本使用 base.__int__ 而不是 base.__index__。

在 3.6 版的變更: 可以使用底線將程式碼文字中的數字進行分組。

在 3.7 版的變更: 第一個參數為僅限位置參數。

在 3.8 版的變更: 如果未定義 __int__() 則會回退到 __index__()。

在 3.11 版的變更: int 的字串輸入和字串表示法可以被限制，以避免阻斷服務攻擊 (denial of service attack)。在字串 x 轉換為 int 時已超出限制，或是在 int 轉換為字串時將會超出限制時，會引發 ValueError。請參閱整數字串轉換的長度限制說明文件。

在 3.14 版的變更: int() 不再委派給 __trunc__() method。

isinstance(object, classinfo, /)

如果 object 引數是 classinfo 引數的實例，或者是（直接、間接或 virtual）subclass 的實例，則回傳 True。如果 object 不是給定型別的物件，函式始終回傳 False。如果 classinfo 是包含物件型別的 tuple（或多個遞迴 tuple）或一個包含多種型別的 聯合型別 (Union Type)，若 object 是其中的任何一個物件的實例則回傳 True。如果 classinfo 既不是型別，也不是型別 tuple 或型別的遞迴 tuple，那麼會引發 TypeError 異常。若是先前檢查已經成功，TypeError 可能不會再因為不合格的型別而被引發。

在 3.10 版的變更: classinfo 可以是一個 聯合型別 (Union Type)。

issubclass(class, classinfo, /)

如果 class 是 classinfo 的 subclass（直接、間接或 virtual），則回傳 True。classinfo 可以是 class 物件的 tuple（或遞迴地其他類似 tuple）或是一個 聯合型別 (Union Type)，此時若 class 是 classinfo 中任一元素的 subclass 時則回傳 True。其他情況，會引發 TypeError。

在 3.10 版的變更: classinfo 可以是一個 聯合型別 (Union Type)。

iter(iterable, /)

iter(callable, sentinel, /)

回傳一個 iterator 物件。根據是否存在第二個引數，第一個引數的意義是非常不同的。如果沒有第二個引數，該單一引數必須是支援 iterable 協定（有 __iter__() method）的集合物件，或必須支援序列協定（有 __getitem__() 方法，且數字引數從 0 開始）。如果它不支援這些協定，會引發 TypeError。如果有第二個引數 sentinel，那麼第一引數必須是可呼叫的物件，這種情況下生成的 iterator，每次疊代呼叫 __next__() 時會不帶引數地呼叫 callable；如果回傳的結果是 sentinel 則引發 StopIteration，否則回傳呼叫結果。

另請參閱 疊代器型別。

iter() 的第二種形式有一個好用的應用，是能夠建立一個區塊閱讀器 (block-reader)。例如，從二進位資料庫檔案中讀取固定寬度的區塊，直到檔案的結尾：

from functools import partial
with open('mydata.db', 'rb') as f:
    for block in iter(partial(f.read, 64), b''):
        process_block(block)

len(object, /)

回傳物件的長度（元素個數）。引數可以是序列（如 string、bytes、tuple、list 或 range）或集合（如 dictionary、set 或 frozen set）。

如果物件長度大於 sys.maxsize，像是 range(2 ** 100)，則 len 會引發 OverflowError。

class list(iterable=(), /)

除了是函式，list 也是可變序列型別，詳情請參閱 List（串列） 和 Sequence Types --- list, tuple, range。

locals()

Return a mapping object representing the current local symbol table, with variable names as the keys, and their currently bound references as the values.

At module scope, as well as when using exec() or eval() with a single namespace, this function returns the same namespace as globals().

At class scope, it returns the namespace that will be passed to the metaclass constructor.

When using exec() or eval() with separate local and global arguments, it returns the local namespace passed in to the function call.

In all of the above cases, each call to locals() in a given frame of execution will return the same mapping object. Changes made through the mapping object returned from locals() will be visible as assigned, reassigned, or deleted local variables, and assigning, reassigning, or deleting local variables will immediately affect the contents of the returned mapping object.

In an optimized scope (including functions, generators, and coroutines), each call to locals() instead returns a fresh dictionary containing the current bindings of the function's local variables and any nonlocal cell references. In this case, name binding changes made via the returned dict are not written back to the corresponding local variables or nonlocal cell references, and assigning, reassigning, or deleting local variables and nonlocal cell references does not affect the contents of previously returned dictionaries.

Calling locals() as part of a comprehension in a function, generator, or coroutine is equivalent to calling it in the containing scope, except that the comprehension's initialised iteration variables will be included. In other scopes, it behaves as if the comprehension were running as a nested function.

Calling locals() as part of a generator expression is equivalent to calling it in a nested generator function.

在 3.12 版的變更: The behaviour of locals() in a comprehension has been updated as described in PEP 709 [https://peps.python.org/pep-0709/].

在 3.13 版的變更: As part of PEP 667 [https://peps.python.org/pep-0667/], the semantics of mutating the mapping objects returned from this function are now defined. The behavior in optimized scopes is now as described above. Aside from being defined, the behaviour in other scopes remains unchanged from previous versions.

map(function, iterable, /, *iterables, strict=False)

產生一個將 function 應用於 iterable 中所有項目並 yield 回傳結果的疊代器。如果傳遞了額外的 iterables 引數，則 function 必須接受相同個數的引數，且 function 會平行地被應用於所有可疊代物件的項目。當有多個可疊代物件時，項目最少的可疊代物件耗盡時疊代器也會結束。如果 strict 為 True 且其中一個可疊代物件在其他可疊代物件之前耗盡，則會拋出 ValueError。如果函式的輸入已經被編排為引數的元組，請參閱 itertools.starmap()。

在 3.14 版的變更: 增加了 strict 參數。

max(iterable, /, *, key=None)

max(iterable, /, *, default, key=None)

max(arg1, arg2, /, *args, key=None)

回傳 iterable 中最大的元素，或者回傳兩個以上的引數中最大的。

如果只提供了一個位置引數，它必須是個 iterable，iterable 中最大的元素會被回傳。如果提供了兩個或以上的位置引數，則回傳最大的位置引數。

這個函式有兩個選擇性的僅限關鍵字引數。key 引數能指定單一引數所使用的排序函式，如同 list.sort() 的使用方式。default 引數是當 iterable 為空時回傳的物件。如果 iterable 為空，並且沒有提供 default，則會引發 ValueError。

如果有多個最大元素，則此函式將回傳第一個找到的。這和其他穩定排序工具如 sorted(iterable, key=keyfunc, reverse=True)[0] 和 heapq.nlargest(1, iterable, key=keyfunc) 一致。

在 3.4 版的變更: 新增 default 僅限關鍵字參數。

在 3.8 版的變更: key 可以為 None。

class memoryview(object)

回傳由給定的引數所建立之「memory view（記憶體檢視）」物件。有關詳細資訊，請參閱Memory Views。

min(iterable, /, *, key=None)

min(iterable, /, *, default, key=None)

min(arg1, arg2, /, *args, key=None)

回傳 iterable 中最小的元素，或者回傳兩個以上的引數中最小的。

如果只提供了一個位置引數，它必須是 iterable，iterable 中最小的元素會被回傳。如果提供了兩個以上的位置引數，則回傳最小的位置引數。

這個函式有兩個選擇性的僅限關鍵字引數。key 引數能指定單一引數所使用的排序函式，如同 list.sort() 的使用方式。default 引數是當 iterable 為空時回傳的物件。如果 iterable 為空，並且沒有提供 default，則會引發 ValueError。

如果有多個最小元素，則此函式將回傳第一個找到的。這和其他穩定排序工具如 sorted(iterable, key=keyfunc)[0] 和 heapq.nsmallest(1, iterable, key=keyfunc) 一致。

在 3.4 版的變更: 新增 default 僅限關鍵字參數。

在 3.8 版的變更: key 可以為 None。

next(iterator, /)

next(iterator, default, /)

透過呼叫 iterator 的 __next__() method 取得下一個元素。如果 iterator 耗盡，則回傳給定的預設值 default，如果沒有預設值則引發 StopIteration。

class object

這是所有其他 class 的基礎，它具有所有 Python class 實例的通用 method。當建構函式被呼叫時，它會回傳一個新的沒有特徵 (featureless) 的物件。這個建構函式不接受任何引數。

備註

由於 object 實例沒有 __dict__ 屬性，因此無法將任意屬性賦給 object 的實例。

oct(integer, /)

將一個整數轉變為一個前綴為 "0o" 的八進位制字串。回傳結果是一個有效的 Python 運算式。如果 integer 不是 Python 的 int 物件，那它需要定義 __index__() method 回傳一個整數。舉例來說：

>>> oct(8)
'0o10'
>>> oct(-56)
'-0o70'

如果要將整數轉換為八進位制字串，不論是否具備 "0o" 前綴，都可以使用下面的方法。

>>> '%#o' % 10, '%o' % 10
('0o12', '12')
>>> format(10, '#o'), format(10, 'o')
('0o12', '12')
>>> f'{10:#o}', f'{10:o}'
('0o12', '12')

可參考 format() 取得更多資訊。

open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

開啟 file 並回傳對應的檔案物件。如果該檔案不能開啟，則引發 OSError。關於使用此函式的更多方法，請參閱讀寫檔案。

file 是一個類路徑物件，是將被開啟之檔案的路徑（絕對路徑或目前工作目錄的相對路徑），或是要被包裝 (wrap) 檔案的整數檔案描述器 (file descriptor)。（如果有給定檔案描述器，它會隨著回傳的 I/O 物件關閉而關閉，除非 closefd 被設為 False。）

mode 是一個選擇性字串，用於指定開啟檔案的模式。預設值是 'r'，這意味著它以文字模式開啟並讀取。其他常見模式有：寫入 'w'（會捨去已經存在的檔案）、唯一性建立 'x'、追加寫入 'a'（在一些 Unix 系統上，無論目前的檔案指標在什麼位置，所有 寫入都會追加到檔案末尾）。在文字模式，如果沒有指定 encoding，則根據電腦平臺來決定使用的編碼：呼叫 locale.getencoding() 來取得目前的本地編碼。（要讀取和寫入原始 bytes，請使用二進位制模式且不要指定 encoding。）可用的模式有：

字元

意義

'r'

讀取（預設）

'w'

寫入，會先清除檔案內容

'x'

唯一性建立，如果文件已存在則會失敗

'a'

寫入，如果檔案存在則在其末端附加內容

'b'

二進制模式

't'

文字模式（預設）

'+'

更新（讀取並寫入）

預設的模式是 'r'（開啟並讀取文字，同 'rt'）。'w+' 和 'w+b' 模式會開啟並清除檔案。'r+' 和 'r+b' 模式會開啟且保留檔案內容。

如總覽中所述，Python 能區分二進制和文字的 I/O。在二進制模式下開啟的檔案（mode 引數中含有 'b'）會將其內容以 bytes 物件回傳，而不進行任何解碼。在文字模式（預設情況，或當 mode 引數中含有 't'），檔案的內容會以 str 回傳，其位元組已經先被解碼，使用的是取決於平台的編碼系統或是給定的 encoding。

備註

Python 不會使用底層作業系統對於文字檔案的操作概念；所有的處理都是由 Python 獨自完成的，因此能獨立於不同平台。

buffering 是一個選擇性的整數，用於設定緩衝策略。傳入 0 表示關閉緩衝（僅在二進制模式下被允許），1 表示行緩衝（line buffering，僅在文字模式下可用），而 >1 的整數是指示一個大小固定的區塊緩衝區 (chunk buffer)，其位元組的數量。請注意，此類指定緩衝區大小的方式適用於二進制緩衝 I/O，但是 TextIOWrapper（以 mode='r+' 開啟的檔案）會有另一種緩衝方式。若要在 TextIOWrapper 中停用緩衝，可考慮使用 io.TextIOWrapper.reconfigure() 的 write_through 旗標。若未給定 buffering 引數，則預設的緩衝策略會運作如下：

二進位檔案會以固定大小的區塊進行緩衝；緩衝區的大小為 max(min(blocksize, 8 MiB), DEFAULT_BUFFER_SIZE)，當裝置區塊大小可用時。在大多數系統上，緩衝區的長度通常為 128 KB。

「互動式」文字檔（isatty() 回傳 True 的檔案）會使用列緩衝。其他文字檔則使用上述的二進制檔案緩衝策略。

encoding 是用於解碼或編碼檔案的編碼系統之名稱。它只應該在文字模式下使用。預設的編碼系統會取決於平台（根據 locale.getencoding() 回傳的內容），但 Python 支援的任何 text encoding（文字編碼）都是可以使用的。關於支援的編碼系統清單，請參閱 codecs module。

errors 是一個選擇性的字串，用於指定要如何處理編碼和解碼的錯誤——它不能在二進制模式下使用。有許多不同的標準錯誤處理程式（error handler，在Error Handlers有列出清單），不過任何已註冊到 codecs.register_error() 的錯誤處理程式名稱也都是有效的。標準的名稱包括：

'strict' 如果發生編碼錯誤，則引發 ValueError 例外。預設值 None 也有相同的效果。

'ignore' 忽略錯誤。請注意，忽略編碼錯誤可能導致資料遺失。

'replace' 會在格式不正確的資料位置插入一個替換標誌（像是 '?'）。

'surrogateescape' 會將任何不正確的位元組表示為低位代理碼元 (low surrogate code unit)，範圍從 U+DC80 到 U+DCFF。在寫入資料時，這些代理碼元將會被還原回 surrogateescape 錯誤處理程式當時所處理的那些相同位元組。這對於處理未知編碼方式的檔案會很好用。

'xmlcharrefreplace' 僅在寫入檔案時可支援。編碼系統不支援的字元會被替換為適當的 XML 字元參考 (character reference) &#nnn;。

'backslashreplace' 會用 Python 的反斜線跳脫序列 (backslashed escape sequence) 替換格式不正確的資料。

'namereplace'（也僅在寫入時支援）會將不支援的字元替換為 \N{...} 跳脫序列。

newline 會決定如何剖析資料串流 (stream) 中的換行字元。它可以是 None、''、'\n'、'\r' 或 '\r\n'。它的運作規則如下：

從資料串流讀取輸入時，如果 newline 是 None，則會啟用通用換行模式。輸入資料中的行結尾可以是 '\n'、'\r' 或 '\r\n'，這些符號會被轉換為 '\n' 之後再回傳給呼叫方。如果是 ''，也會啟用通用換行模式，但在回傳給呼叫方時，行尾符號不會被轉換。如果它是任何其他有效的值，則輸入資料的行只會由給定的字串做結尾，且在回傳給呼叫方時，行尾符號不會被轉換。

將輸出寫入資料串流時，如果 newline 是 None，則被寫入的任何 '\n' 字元都會轉換為系統預設的行分隔符號 os.linesep。如果 newline 是 '' 或 '\n'，則不做任何轉換。如果 newline 是任何其他有效的值，則寫入的任何 '\n' 字元都將轉換為給定的字串。

如果 closefd 是 False，且給定的 file 引數是一個檔案描述器而不是檔名，則當檔案關閉時，底層的檔案描述器會保持開啟狀態。如果有給定一個檔名，則 closefd 必須是 True（預設值）；否則將引發錯誤。

透過以 opener 傳遞一個可呼叫物件，就可以自訂開啟函式。然後透過以引數 (file, flags) 呼叫 opener，就能取得檔案物件的底層檔案描述器。opener 必須回傳一個開啟的檔案描述器（將 os.open 作為 opener 傳入，在功能上的結果會相當於傳入 None）。

新建立的檔案是不可繼承的。

下面的範例使用 os.open() 函式回傳值當作 dir_fd 的參數，從給定的目錄中用相對路徑開啟檔案：

>>> import os
>>> dir_fd = os.open('somedir', os.O_RDONLY)
>>> def opener(path, flags):
...     return os.open(path, flags, dir_fd=dir_fd)
...
>>> with open('spamspam.txt', 'w', opener=opener) as f:
...     print('This will be written to somedir/spamspam.txt', file=f)
...
>>> os.close(dir_fd)  # don't leak a file descriptor

open() 函式回傳的 file object 型別取決於模式。當 open() 是在文字模式中開啟檔案時（'w'、'r'、'wt'、'rt' 等），它會回傳 io.TextIOBase 的一個 subclass（具體來說，就是 io.TextIOWrapper）。使用有緩衝的二進制模式開啟檔案時，回傳的 class 則會是 io.BufferedIOBase 的 subclass。確切的 class 各不相同：在讀取的二進制模式，它會回傳 io.BufferedReader；在寫入和附加的二進制模式，它會回傳 io.BufferedWriter，而在讀／寫模式，它會回傳 io.BufferedRandom。當緩衝被停用時，會回傳原始資料串流 io.FileIO，它是 io.RawIOBase 的一個 subclass。

另請參閱檔案操作模組，例如 fileinput、io（定義了 open() 的 module ）、os、os.path、tempfile 以及 shutil。

引發一個附帶引數 path、mode、flags 的稽核事件 open。

mode 和 flags 引數可能會被原始的呼叫所修改或推論 (infer)。

在 3.3 版的變更:

新增 opener 參數。

新增 'x' 模式。

過去引發的 IOError，現在是 OSError 的別名。

如果檔案已存在但使用了唯一性建立模式 ('x')，現在會引發 FileExistsError。

在 3.4 版的變更:

檔案在此版本開始是不可繼承的。

在 3.5 版的變更:

如果系統呼叫被中斷，但訊號處理程式沒有引發例外，此函式現在會重試系統呼叫，而不是引發 InterruptedError 例外（原因詳見 PEP 475 [https://peps.python.org/pep-0475/]）。

增加了 'namereplace' 錯誤處理程式。

在 3.6 版的變更:

增加對於實作 os.PathLike 物件的支援。

在 Windows 上，開啟一個控制臺緩衝區可能會回傳 io.RawIOBase 的 subclass，而不是 io.FileIO。

在 3.11 版的變更: 'U' 模式被移除。

ord(character, /)

Return the ordinal value of a character.

如果引數是單字元字串，則回傳該字元的 Unicode 編碼位置。例如 ord('a') 回傳整數 97、ord('€')（歐元符號）回傳 8364。這是 chr() 的逆函式。

If the argument is a bytes or bytearray object of length 1, return its single byte value. For example, ord(b'a') returns the integer 97.

pow(base, exp, mod=None)

回傳 base 的 exp 次方；如果 mod 存在，則回傳 base 的 exp 次方對 mod 取餘數（比直接呼叫 pow(base, exp) % mod 計算更高效）。兩個引數形式的 pow(exp, exp) 等價於次方運算子：base**exp。

當引數為內建數值型別且運算元型別為混合型別時，會套用二元算術運算子的強制轉型 (coercion) 規則。對於 int 運算元，運算結果會（在強制轉型後）與運算元的型別相同，除非第二個引數是負數；在這種情況下，所有的引數都會被轉換為浮點數並得到浮點數的結果。例如，pow(10, 2) 會回傳 100，但 pow(10, -2) 會回傳 0.01。如果底數 (base) 是型別為 int 或 float 的負數且指數 (exponent) 為非整數，則會傳回複數結果。例如 pow(-9, 0.5) 會回傳一個接近 3j 的值。然而，如果底數 (base) 是型別為 int 或 float 的負數且指數為整數，則會傳回浮點數結果。例如 pow(-9, 2.0) 會回傳 81.0。

對於 int 運算元 base 和 exp，如果有給定 mod，則 mod 也必須是整數型別，且 mod 必須不為零。如果有給定 mod 且 exp 為負，則 base 必須與 mod 互質。在這種情況下，會回傳 pow(inv_base, -exp, mod)，其中 inv_base 是 base 對 mod 的模倒數 (inverse modulo)。

以下是一個計算 38 對 97 取模倒數的範例：

>>> pow(38, -1, mod=97)
23
>>> 23 * 38 % 97 == 1
True

在 3.8 版的變更: 對於 int 運算元，現在 pow 的三引數形式允許第二個引數為負數，也容許模倒數的計算。

在 3.8 版的變更: 允許關鍵字引數。在此之前只支援位置引數。

print(*objects, sep=' ', end='\n', file=None, flush=False)

將 objects 列印到文字資料串流 file，用 sep 分隔並以 end 結尾。如果有給定 sep、end、file 和 flush，那麼它們必須是關鍵字引數的形式。

所有的非關鍵字引數都會像是 str() 操作一樣地被轉換為字串，並寫入資料串流，彼此以 sep 分隔，並以 end 結尾。sep 和 end 都必須是字串；它們也可以是 None，這表示使用預設值。如果沒有給定 objects，print() 就只會寫入 end。

file 引數必須是一個有 write(string) method 的物件；如果沒有給定或被設為 None，則將使用 sys.stdout。因為要列印的引數會被轉換為文字字串，所以 print() 不能用於二進位模式的檔案物件。對於此類物件，請改用 file.write(...)。

輸出緩衝通常會由 file 決定。但是如果 flush 為 true，則資料串流會被強制清除。

在 3.3 版的變更: 增加了 flush 關鍵字引數。

class property(fget=None, fset=None, fdel=None, doc=None)

回傳 property 屬性。

fget 是一個用於取得屬性值的函式，fset 是一個用於設定屬性值的函式，fdel 是一個用於刪除屬性值的函式，而 doc 會為該屬性建立一個說明字串。

一個典型的用途是定義一個受管理的屬性 x：

class C:
    def __init__(self):
        self._x = None

    def getx(self):
        return self._x

    def setx(self, value):
        self._x = value

    def delx(self):
        del self._x

    x = property(getx, setx, delx, "I'm the 'x' property.")

如果 c 是 C 的一個實例，則 c.x 將會叫用取得器 (getter)，c.x = value 會呼叫設定器 (setter)，而 del c.x 會叫用刪除器 (deleter)。

如果有給定 doc，它將會是 property 屬性的說明字串。否則，property 會複製 fget 的說明字串（如果它存在的話）。這樣一來，就能夠輕鬆地使用 property() 作為裝飾器來建立唯讀屬性：

class Parrot:
    def __init__(self):
        self._voltage = 100000

    @property
    def voltage(self):
        """Get the current voltage."""
        return self._voltage

The @property decorator turns the voltage() method into a "getter" for a read-only attribute with the same name, and it sets the docstring for voltage to "Get the current voltage."

@getter

@setter

@deleter

A property object has getter, setter, and deleter methods usable as decorators that create a copy of the property with the corresponding accessor function set to the decorated function. This is best explained with an example:

class C:
    def __init__(self):
        self._x = None

    @property
    def x(self):
        """I'm the 'x' property."""
        return self._x

    @x.setter
    def x(self, value):
        self._x = value

    @x.deleter
    def x(self):
        del self._x

This code is exactly equivalent to the first example. Be sure to give the additional functions the same name as the original property (x in this case.)

The returned property object also has the attributes fget, fset, and fdel corresponding to the constructor arguments.

在 3.5 版的變更: The docstrings of property objects are now writeable.

__name__

Attribute holding the name of the property. The name of the property can be changed at runtime.

在 3.13 版被加入.

class range(stop, /)

class range(start, stop, step=1, /)

Rather than being a function, range is actually an immutable sequence type, as documented in Ranges and Sequence Types --- list, tuple, range.

repr(object, /)

Return a string containing a printable representation of an object. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval(); otherwise, the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object. A class can control what this function returns for its instances by defining a __repr__() method. If sys.displayhook() is not accessible, this function will raise RuntimeError.

This class has a custom representation that can be evaluated:

class Person:
   def __init__(self, name, age):
      self.name = name
      self.age = age

   def __repr__(self):
      return f"Person('{self.name}', {self.age})"

reversed(object, /)

Return a reverse iterator. The argument must be an object which has a __reversed__() method or supports the sequence protocol (the __len__() method and the __getitem__() method with integer arguments starting at 0).

round(number, ndigits=None)

Return number rounded to ndigits precision after the decimal point. If ndigits is omitted or is None, it returns the nearest integer to its input.

For the built-in types supporting round(), values are rounded to the closest multiple of 10 to the power minus ndigits; if two multiples are equally close, rounding is done toward the even choice (so, for example, both round(0.5) and round(-0.5) are 0, and round(1.5) is 2). Any integer value is valid for ndigits (positive, zero, or negative). The return value is an integer if ndigits is omitted or None. Otherwise, the return value has the same type as number.

For a general Python object number, round delegates to number.__round__.

備註

The behavior of round() for floats can be surprising: for example, round(2.675, 2) gives 2.67 instead of the expected 2.68. This is not a bug: it's a result of the fact that most decimal fractions can't be represented exactly as a float. See 浮點數運算：問題與限制 for more information.

class set(iterable=(), /)

Return a new set object, optionally with elements taken from iterable. set is a built-in class. See set and Set Types --- set, frozenset for documentation about this class.

For other containers see the built-in frozenset, list, tuple, and dict classes, as well as the collections module.

setattr(object, name, value, /)

This is the counterpart of getattr(). The arguments are an object, a string, and an arbitrary value. The string may name an existing attribute or a new attribute. The function assigns the value to the attribute, provided the object allows it. For example, setattr(x, 'foobar', 123) is equivalent to x.foobar = 123.

name need not be a Python identifier as defined in Names (identifiers and keywords) unless the object chooses to enforce that, for example in a custom __getattribute__() or via __slots__. An attribute whose name is not an identifier will not be accessible using the dot notation, but is accessible through getattr() etc..

備註

Since private name mangling happens at compilation time, one must manually mangle a private attribute's (attributes with two leading underscores) name in order to set it with setattr().

class slice(stop, /)

class slice(start, stop, step=None, /)

Return a slice object representing the set of indices specified by range(start, stop, step). The start and step arguments default to None.

Slice objects have read-only data attributes start, stop, and step which merely return the argument values (or their default). They have no other explicit functionality; however, they are used by NumPy and other third-party packages.

start

stop

step

Slice objects are also generated when extended indexing syntax is used. For example: a[start:stop:step] or a[start:stop, i]. See itertools.islice() for an alternate version that returns an iterator.

在 3.12 版的變更: Slice objects are now hashable (provided start, stop, and step are hashable).

sorted(iterable, /, *, key=None, reverse=False)

Return a new sorted list from the items in iterable.

有兩個選擇性引數，只能使用關鍵字引數來指定。

key specifies a function of one argument that is used to extract a comparison key from each element in iterable (for example, key=str.lower). The default value is None (compare the elements directly).

reverse is a boolean value. If set to True, then the list elements are sorted as if each comparison were reversed.

Use functools.cmp_to_key() to convert an old-style cmp function to a key function.

The built-in sorted() function is guaranteed to be stable. A sort is stable if it guarantees not to change the relative order of elements that compare equal --- this is helpful for sorting in multiple passes (for example, sort by department, then by salary grade).

The sort algorithm uses only < comparisons between items. While defining an __lt__() method will suffice for sorting, PEP 8 [https://peps.python.org/pep-0008/] recommends that all six rich comparisons be implemented. This will help avoid bugs when using the same data with other ordering tools such as max() that rely on a different underlying method. Implementing all six comparisons also helps avoid confusion for mixed type comparisons which can call the reflected __gt__() method.

For sorting examples and a brief sorting tutorial, see 排序技法.

@staticmethod

Transform a method into a static method.

A static method does not receive an implicit first argument. To declare a static method, use this idiom:

class C:
    @staticmethod
    def f(arg1, arg2, argN): ...

@staticmethod 語法是一個函式 decorator - 參見 函式定義 中的詳細介紹。

A static method can be called either on the class (such as C.f()) or on an instance (such as C().f()). Moreover, the static method descriptor is also callable, so it can be used in the class definition (such as f()).

Static methods in Python are similar to those found in Java or C++. Also, see classmethod() for a variant that is useful for creating alternate class constructors.

Like all decorators, it is also possible to call staticmethod as a regular function and do something with its result. This is needed in some cases where you need a reference to a function from a class body and you want to avoid the automatic transformation to instance method. For these cases, use this idiom:

def regular_function():
    ...

class C:
    method = staticmethod(regular_function)

關於 static method 的更多資訊，請參考 標準型別階層。

在 3.10 版的變更: Static method 現在繼承了 method 屬性（__module__、__name__、__qualname__、__doc__ 和 __annotations__），並擁有一個新的 __wrapped__ 屬性，且為如一般函式的可呼叫物件。

class str(*, encoding='utf-8', errors='strict')

class str(object)

class str(object, encoding, errors='strict')

class str(object, *, errors)

Return a str version of object. See str() for details.

str is the built-in string class. For general information about strings, see Text Sequence Type --- str.

sum(iterable, /, start=0)

Sums start and the items of an iterable from left to right and returns the total. The iterable's items are normally numbers, and the start value is not allowed to be a string.

For some use cases, there are good alternatives to sum(). The preferred, fast way to concatenate a sequence of strings is by calling ''.join(sequence). To add floating-point values with extended precision, see math.fsum(). To concatenate a series of iterables, consider using itertools.chain().

在 3.8 版的變更: start 參數可被指定為關鍵字引數。

在 3.12 版的變更: Summation of floats switched to an algorithm that gives higher accuracy and better commutativity on most builds.

在 3.14 版的變更: Added specialization for summation of complexes, using same algorithm as for summation of floats.

class super

class super(type, object_or_type=None, /)

Return a proxy object that delegates method calls to a parent or sibling class of type. This is useful for accessing inherited methods that have been overridden in a class.

The object_or_type determines the method resolution order to be searched. The search starts from the class right after the type.

For example, if __mro__ of object_or_type is D -> B -> C -> A -> object and the value of type is B, then super() searches C -> A -> object.

The __mro__ attribute of the class corresponding to object_or_type lists the method resolution search order used by both getattr() and super(). The attribute is dynamic and can change whenever the inheritance hierarchy is updated.

If the second argument is omitted, the super object returned is unbound. If the second argument is an object, isinstance(obj, type) must be true. If the second argument is a type, issubclass(type2, type) must be true (this is useful for classmethods).

When called directly within an ordinary method of a class, both arguments may be omitted ("zero-argument super()"). In this case, type will be the enclosing class, and obj will be the first argument of the immediately enclosing function (typically self). (This means that zero-argument super() will not work as expected within nested functions, including generator expressions, which implicitly create nested functions.)

There are two typical use cases for super. In a class hierarchy with single inheritance, super can be used to refer to parent classes without naming them explicitly, thus making the code more maintainable. This use closely parallels the use of super in other programming languages.

The second use case is to support cooperative multiple inheritance in a dynamic execution environment. This use case is unique to Python and is not found in statically compiled languages or languages that only support single inheritance. This makes it possible to implement "diamond diagrams" where multiple base classes implement the same method. Good design dictates that such implementations have the same calling signature in every case (because the order of calls is determined at runtime, because that order adapts to changes in the class hierarchy, and because that order can include sibling classes that are unknown prior to runtime).

For both use cases, a typical superclass call looks like this:

class C(B):
    def method(self, arg):
        super().method(arg)    # This does the same thing as:
                               # super(C, self).method(arg)

In addition to method lookups, super() also works for attribute lookups. One possible use case for this is calling descriptors in a parent or sibling class.

Note that super() is implemented as part of the binding process for explicit dotted attribute lookups such as super().__getitem__(name). It does so by implementing its own __getattribute__() method for searching classes in a predictable order that supports cooperative multiple inheritance. Accordingly, super() is undefined for implicit lookups using statements or operators such as super()[name].

Also note that, aside from the zero argument form, super() is not limited to use inside methods. The two argument form specifies the arguments exactly and makes the appropriate references. The zero argument form only works inside a class definition, as the compiler fills in the necessary details to correctly retrieve the class being defined, as well as accessing the current instance for ordinary methods.

For practical suggestions on how to design cooperative classes using super(), see guide to using super() [https://rhettinger.wordpress.com/2011/05/26/super-considered-super/].

在 3.14 版的變更: super objects are now pickleable and copyable.

class tuple(iterable=(), /)

Rather than being a function, tuple is actually an immutable sequence type, as documented in Tuple（元組） and Sequence Types --- list, tuple, range.

class type(object, /)

class type(name, bases, dict, /, **kwargs)

With one argument, return the type of an object. The return value is a type object and generally the same object as returned by object.__class__.

The isinstance() built-in function is recommended for testing the type of an object, because it takes subclasses into account.

With three arguments, return a new type object. This is essentially a dynamic form of the class statement. The name string is the class name and becomes the __name__ attribute. The bases tuple contains the base classes and becomes the __bases__ attribute; if empty, object, the ultimate base of all classes, is added. The dict dictionary contains attribute and method definitions for the class body; it may be copied or wrapped before becoming the __dict__ attribute. The following two statements create identical type objects:

>>> class X:
...     a = 1
...
>>> X = type('X', (), dict(a=1))

另請參閱：

Documentation on attributes and methods on classes.

Type Objects

Keyword arguments provided to the three argument form are passed to the appropriate metaclass machinery (usually __init_subclass__()) in the same way that keywords in a class definition (besides metaclass) would.

另請參閱 Customizing class creation。

在 3.6 版的變更: Subclasses of type which don't override type.__new__ may no longer use the one-argument form to get the type of an object.

vars()

vars(object, /)

Return the __dict__ attribute for a module, class, instance, or any other object with a __dict__ attribute.

Objects such as modules and instances have an updateable __dict__ attribute; however, other objects may have write restrictions on their __dict__ attributes (for example, classes use a types.MappingProxyType to prevent direct dictionary updates).

Without an argument, vars() acts like locals().

A TypeError exception is raised if an object is specified but it doesn't have a __dict__ attribute (for example, if its class defines the __slots__ attribute).

在 3.13 版的變更: The result of calling this function without an argument has been updated as described for the locals() builtin.

zip(*iterables, strict=False)

Iterate over several iterables in parallel, producing tuples with an item from each one.

例如：

>>> for item in zip([1, 2, 3], ['sugar', 'spice', 'everything nice']):
...     print(item)
...
(1, 'sugar')
(2, 'spice')
(3, 'everything nice')

More formally: zip() returns an iterator of tuples, where the i-th tuple contains the i-th element from each of the argument iterables.

Another way to think of zip() is that it turns rows into columns, and columns into rows. This is similar to transposing a matrix [https://en.wikipedia.org/wiki/Transpose].

zip() is lazy: The elements won't be processed until the iterable is iterated on, e.g. by a for loop or by wrapping in a list.

One thing to consider is that the iterables passed to zip() could have different lengths; sometimes by design, and sometimes because of a bug in the code that prepared these iterables. Python offers three different approaches to dealing with this issue:

By default, zip() stops when the shortest iterable is exhausted. It will ignore the remaining items in the longer iterables, cutting off the result to the length of the shortest iterable:

>>> list(zip(range(3), ['fee', 'fi', 'fo', 'fum']))
[(0, 'fee'), (1, 'fi'), (2, 'fo')]

zip() is often used in cases where the iterables are assumed to be of equal length. In such cases, it's recommended to use the strict=True option. Its output is the same as regular zip():

>>> list(zip(('a', 'b', 'c'), (1, 2, 3), strict=True))
[('a', 1), ('b', 2), ('c', 3)]

Unlike the default behavior, it raises a ValueError if one iterable is exhausted before the others:

>>> for item in zip(range(3), ['fee', 'fi', 'fo', 'fum'], strict=True):
...     print(item)
...
(0, 'fee')
(1, 'fi')
(2, 'fo')
Traceback (most recent call last):
  ...
ValueError: zip() argument 2 is longer than argument 1

Without the strict=True argument, any bug that results in iterables of different lengths will be silenced, possibly manifesting as a hard-to-find bug in another part of the program.

Shorter iterables can be padded with a constant value to make all the iterables have the same length. This is done by itertools.zip_longest().

Edge cases: With a single iterable argument, zip() returns an iterator of 1-tuples. With no arguments, it returns an empty iterator.

Tips and tricks:

The left-to-right evaluation order of the iterables is guaranteed. This makes possible an idiom for clustering a data series into n-length groups using zip(*[iter(s)]*n, strict=True). This repeats the same iterator n times so that each output tuple has the result of n calls to the iterator. This has the effect of dividing the input into n-length chunks.

zip() in conjunction with the * operator can be used to unzip a list:

>>> x = [1, 2, 3]
>>> y = [4, 5, 6]
>>> list(zip(x, y))
[(1, 4), (2, 5), (3, 6)]
>>> x2, y2 = zip(*zip(x, y))
>>> x == list(x2) and y == list(y2)
True

在 3.10 版的變更: 增加了 strict 引數。

__import__(name, globals=None, locals=None, fromlist=(), level=0)

備註

This is an advanced function that is not needed in everyday Python programming, unlike importlib.import_module().

This function is invoked by the import statement. It can be replaced (by importing the builtins module and assigning to builtins.__import__) in order to change semantics of the import statement, but doing so is strongly discouraged as it is usually simpler to use import hooks (see PEP 302 [https://peps.python.org/pep-0302/]) to attain the same goals and does not cause issues with code which assumes the default import implementation is in use. Direct use of __import__() is also discouraged in favor of importlib.import_module().

The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name. The standard implementation does not use its locals argument at all and uses its globals only to determine the package context of the import statement.

level specifies whether to use absolute or relative imports. 0 (the default) means only perform absolute imports. Positive values for level indicate the number of parent directories to search relative to the directory of the module calling __import__() (see PEP 328 [https://peps.python.org/pep-0328/] for the details).

When the name variable is of the form package.module, normally, the top-level package (the name up till the first dot) is returned, not the module named by name. However, when a non-empty fromlist argument is given, the module named by name is returned.

For example, the statement import spam results in bytecode resembling the following code:

spam = __import__('spam', globals(), locals(), [], 0)

The statement import spam.ham results in this call:

spam = __import__('spam.ham', globals(), locals(), [], 0)

Note how __import__() returns the toplevel module here because this is the object that is bound to a name by the import statement.

On the other hand, the statement from spam.ham import eggs, sausage as saus results in

_temp = __import__('spam.ham', globals(), locals(), ['eggs', 'sausage'], 0)
eggs = _temp.eggs
saus = _temp.sausage

Here, the spam.ham module is returned from __import__(). From this object, the names to import are retrieved and assigned to their respective names.

If you simply want to import a module (potentially within a package) by name, use importlib.import_module().

在 3.3 版的變更: Negative values for level are no longer supported (which also changes the default value to 0).

在 3.9 版的變更: When the command line options -E or -I are being used, the environment variable PYTHONCASEOK is now ignored.

註腳

[1]

剖析器只接受 Unix 風格的行結束符。如果你從檔案中讀取程式碼，請確保用換行符號轉換模式轉換 Windows 或 Mac 風格的換行符號。

內建常數

有一小部分的常數存在於內建命名空間中。他們是：

False

在 bool 型別中的 false 值。對於 False 的賦值是不合法的，並且會拋出 SyntaxError。

True

在 bool 型別中的 true 值。對於 True 的賦值是不合法的，並且會拋出 SyntaxError。

None

型別 NoneType 的唯一值。None 經常被使用來表達缺少值，例如未傳送預設的引數至函式時，相對應參數即會被賦予 None。對於 None 的賦值是不合法的，並且會拋出 SyntaxError。None 是型別 NoneType 的唯一實例。

NotImplemented

會被二元特殊方法 (binary special methods)（如：__eq__()、__lt__()、__add__()、__rsub__() 等）所回傳的特殊值，代表著該運算沒有針對其他型別的實作。同理也可以被原地二元特殊方法 (in-place binary special methods) （如：__imul__()、__iand__() 等）回傳。它不應該被作為 boolean（布林）來解讀。NotImplemented 是型別 types.NotImplementedType 的唯一實例。

備註

當一個二元 (binary) 或原地 (in-place) 方法回傳 NotImplemented，直譯器會嘗試反映該操作到其他型別（或是其他後備 (fallback)，取決於是哪種運算子）。如果所有的常識都回傳 NotImplemented，直譯器會拋出適當的例外。不正確的回傳 NotImplemented 會造成誤導的錯誤訊息或是 NotImplemented 值被傳回到 Python 程式碼中。

請參見 實作算術操作 以找到更多範例。

警示

NotImplemented 與 NotImplementedError 並不一樣且不可互換。這個常數只能用於上述的情況；欲知更多如何正確使用它們的細節，請參見 NotImplementedError。

在 3.9 版的變更: 在 boolean（布林）上下文中對 NotImplemented 求值的操作已被棄用。

在 3.14 版的變更: 在 boolean 上下文中解讀 NotImplemented 現在會引發 TypeError。過去自 Python 3.9 以來，這會被解讀成 True，並發出 DeprecationWarning

Ellipsis

與刪節號 "..." 字面相同，是一個經常被用來表示某些東西被省略的物件。對於 Ellipsis 的賦值是可能的，但對於 ... 的賦值會引發 SyntaxError。Ellipsis 是型別 types.EllipsisType 的唯一實例。

__debug__

如果 Python 沒有被以 -O 選項啟動，則此常數為 true。請參見 assert 陳述式。

備註

None，False，True，以及 __debug__ 都是不能被重新賦值的（任何對它們的賦值，即使是屬性的名稱，也會拋出 SyntaxError）。因此，它們可以被視為”真正的”常數。

由 site module（模組）所添增的常數

site module（模組）（在啟動期間自動 import ，除非有給予 -S 指令行選項）會添增一些常數到內建命名空間 (built-in namespace) 中。它們在互動式直譯器中是很有幫助的，但不應該在程式 (programs) 中被使用。

quit(code=None)

exit(code=None)

當印出物件時，會印出一個訊息："Use quit() or Ctrl-D (i.e. EOF) to exit"。當直接在互動式直譯器中存取或作為函式呼叫時，會引發 SystemExit 並帶有指定的返回碼（exit code）。

help

當印出此物件時，會印出訊息 "Type help() for interactive help, or help(object) for help about object."，並在互動式直譯器中直接存取時，會叫用內建的幫助系統（參見 help()）。

copyright

credits

當印出或是呼叫此物件時，分別會印出版權與致謝的文字。

license

當印出此物件時，會印出訊息 "Type license() to see the full license text"，並在呼叫時以分頁形式印出完整的許可證文字（一次一整個畫面）。

內建型別

以下章節描述了直譯器中內建的標準型別。

主要內建型別為數字、序列、對映、class（類別）、實例和例外。

有些集合類別是 mutable（可變的）。那些用於原地 (in-place) 加入、移除或重新排列其成員且不回傳特定項的 method（方法），也只會回傳 None 而非集合實例自己。

某些操作已被多種物件型別支援；特別是實務上所有物件都已經可以做相等性比較、真值檢測及被轉換為字串（使用 repr() 函式或稍有差異的 str() 函式），後者為當物件傳入 print() 函式印出時在背後被呼叫的函式。

真值檢測

任何物件都可以進行檢測以判斷是否為真值，以便在 if 或 while 條件中使用，或是作為如下所述 boolean（布林）運算之運算元所用。

預設情況下，一個物件會被視為真值，除非它的 class 定義了會回傳 False 的 __bool__() method 或是定義了會回傳零的 __len__() method。[1] 如果其中一個 method 在被呼叫時引發例外，該例外將會被傳播，且該物件不具有真值（例如 NotImplemented）。以下列出了大部分會被視為 false 的內建物件：

定義為 false 之常數：None 與 False

任何數值型別的零：0、0.0、0j、Decimal(0)、Fraction(0, 1)

空的序列和集合：''、()、[]、{}、set()、range(0)

除非另有特別說明，產生 boolean 結果的操作或內建函式都會回傳 0 或 False 作為假值、1 或 True 作為真值。（重要例外： boolean 運算 or 和 and 回傳的是其中一個運算元。）

Boolean（布林）運算 --- and, or, not

下方為 Boolean 運算，按優先順序排序：

運算

結果

註解

x or y

假如 x 為真，則 x，否則 y

(1)

x and y

假如 x 為假，則 x，否則 y

(2)

not x

假如 x 為假，則 True，否則 False

(3)

註解：

這是一個短路運算子，所以他只有在第一個引數為假時，才會對第二個引數求值。

這是一個短路運算子，所以他只有在第一個引數為真時，才會對第二個引數求值。

not 比非 Boolean 運算子有較低的優先權，因此 not a == b 可直譯為 not (a == b)，而 a == not b 會導致語法錯誤。

比較運算

在 Python 裡共有 8 種比較運算。他們的優先順序都相同（皆優先於 Boolean 運算）。比較運算可以任意的串連；例如，x < y <= z 等同於 x < y and y <= z，差異只在於前者的 y 只有被求值一次（但在這兩個例子中，當 x < y 為假時，z 皆不會被求值）。

這個表格統整所有比較運算：

運算

含義

<

小於

<=

小於等於

>

大於

>=

大於等於

==

等於

!=

不等於

is

物件識別性

is not

否定的物件識別性

除非有另外聲明，不同型別的物件不能進行相等比較。運算子 == 總有定義，但在某些物件型別（例如，class 物件）時，運算子會等同於 is。其他運算子 <、<=、> 及 >= 皆僅在有意義的部分有所定義；例如，當其中一個引數為複數時，將引發一個 TypeError 的例外。

一個 class 的非相同實例通常會比較為不相等，除非 class 有定義 __eq__() method。

一個 class 的實例不可以與其他相同 class 的實例或其他物件型別進行排序，除非 class 定義足夠的 method ，包含 __lt__()、__le__()、__gt__() 及 __ge__()（一般來說，使用 __lt__() 及 __eq__() 就可以滿足常規意義上的比較運算子）。

無法自訂 is 與 is not 運算子的行為；這兩個運算子也可以運用在任意兩個物件且不會引發例外。

此外，擁有相同的語法優先序的 in 及 not in 兩種運算皆被可疊代物件或者有實作 __contains__() method 的型別所支援。

數值型別 --- int、float、complex

數值型別共有三種：整數、浮點數 及 複數。此外，Boolean 為整數中的一個子型別。整數有無限的精度。浮點數通常使用 C 裡面的 double 實作。關於在你程式所運作的機器上之浮點數的精度及內部表示法可以在 sys.float_info 進行查找。複數包含實數及虛數的部分，這兩部分各自是一個浮點數。若要從一個複數 z 提取這兩部分，需使用 z.real 及 z.imag。（標準函式庫包含額外的數值型別，像是 fractions.Fraction 表示有理數，而 decimal.Decimal 表示可由使用者制定精度的浮點數。）

數字是由字面數值或內建公式及運算子的結果所產生的。未經修飾的字面數值（含十六進位、八進位及二進位數值）會 yield 整數。包含小數點或指數符號的字面數值會 yield 浮點數。在數值後面加上 'j' 或是 'J' 會 yield 一個虛數（意即一個實數為 0 的複數）。你也可以將整數與浮點數相加以得到一個有實部與虛部的複數。

建構函式： int()、float() 及 complex() 可以用來產生特定型別的數字。

Python 完全支援混和運算：當一個二元運算子的運算元有不同數值型別時，「較窄」型別的運算元會被拓寬到另一個型別的運算元；在此處，整數窄於浮點數。複數及實數運算元的運算是由一般的數學公式所定義，例如：

x + complex(u, v) = complex(x + u, v)
x * complex(u, v) = complex(x * u, x * v)

A comparison between numbers of different types behaves as though the exact values of those numbers were being compared. [2]

所有數值型別（除複數外）皆支援以下的運算（有關運算的先後順序，詳見 Operator precedence）：

運算

結果

註解

完整文件

x + y

x 及 y 的加總

x - y

x 及 y 的相減

x * y

x 及 y 的相乘

x / y

x 及 y 相除之商

x // y

x 及 y 的整數除法

(1)(2)

x % y

x / y 的餘數

(2)

-x

x 的負數

+x

x 不變

abs(x)

x 的絕對值或量 (magnitude)

abs()

int(x)

將 x 轉為整數

(3)(6)

int()

float(x)

將 x 轉為浮點數

(4)(6)

float()

complex(re, im)

一個複數，其實部為 re，虛部為 im。im 預設為零。

(6)

complex()

c.conjugate()

為複數 c 的共軛複數

divmod(x, y)

一對 (x // y, x % y)

(2)

divmod()

pow(x, y)

x 的 y 次方

(5)

pow()

x ** y

x 的 y 次方

(5)

註解：

也被稱為整數除法。對於型別為 int 的運算元來說，結果之型別會是 int。對於型別為 float 的運算元來說，結果之型別會是 float。一般來說，結果會是一個整數，但其型別不一定會是 int。結果總是會往負無窮大的方向取整數值： 1//2 為 0、(-1)//2 為 -1、1//(-2) 為 -1 及 (-1)//(-2) 為 0。

不可用於複數。在適當情形下，可使用 abs() 轉換為浮點數。

從 float 轉換為 int 會導致截斷並排除小數部分。詳見 math.floor() 及 math.ceil() 以了解更多轉換方式。

浮點數也接受帶有可選的前綴 "+" 及 "-" 的 "nan" 及 "inf" 字串，其分別代表非數字（NaN）及正負無窮。

Python 將 pow(0, 0) 及 0 ** 0 定義為 1 這是程式語言的普遍做法。

字面數值接受包含數字 0 到 9 或任何等效的 Unicode 字元（具有 Nd 屬性的 code points（編碼位置））。

請參閱 Unicode 標準 [https://unicode.org/Public/UNIDATA/extracted/DerivedNumericType.txt]以了解具有 Nd 屬性的 code points 完整列表。

所有 numbers.Real 型別（int 及 float）也適用下列運算：

運算

結果

math.trunc(x)

x 截斷為 Integral

round(x[, n])

x 進位至小數點後第 n 位，使用偶數捨入法。若省略 n ，則預設為 0。

math.floor(x)

小於等於 x 的最大 Integral

math.ceil(x)

大於等於 x 的最小 Integral

關於其他數值運算請詳見 math 及 cmath modules（模組）。

整數型別的位元運算

位元運算只對整數有意義。位元運算的計算結果就如同對二的補數執行無窮多個符號位元。

二元位元運算的優先順序皆低於數字運算，但高於比較運算；一元運算 ~ 與其他一元數值運算有一致的優先順序（+ 及 -）。

這個表格列出所有位元運算並以優先順序由先至後排序。

運算

結果

註解

x | y

x 及 y 的位元 或

(4)

x ^ y

x 及 y 的位元 邏輯互斥或

(4)

x & y

x 及 y 的位元 與

(4)

x << n

x 往左移動 n 個位元

(1)(2)

x >> n

x 往右移動 n 個位元

(1)(3)

~x

反轉 x 的位元

註解：

負數位移是不被允許並會引發 ValueError 的錯誤。

向左移動 n 個位元等同於乘以 pow(2, n)。

向右移動 n 個位元等同於向下除法除以 pow(2, n)。

在有限的二的補數表示法中執行這些計算（一個有效位元寬度為 1 + max(x.bit_length(), y.bit_length()) 或以上）並至少有一個額外的符號擴展位元，便足以得到與無窮多個符號位元相同的結果。

整數型別的附加方法

整數型別實作了 numbers.Integral 抽象基底類別。此外，它提供了一些方法：

int.bit_length()

回傳以二進位表示一個整數所需要的位元數，不包括符號及首位的零：

>>> n = -37
>>> bin(n)
'-0b100101'
>>> n.bit_length()
6

更準確來說，若 x 非為零，則 x.bit_length() 會得出滿足 2**(k-1) <= abs(x) < 2**k 的單一正整數 k。同樣地，當 abs(x) 足夠小到能正確地取得捨入的對數，則 k = 1 + int(log(abs(x), 2))。若 x 為零，則 x.bit_length() 會回傳 0。

等同於：

def bit_length(self):
    s = bin(self)       # binary representation:  bin(-37) --> '-0b100101'
    s = s.lstrip('-0b') # remove leading zeros and minus sign
    return len(s)       # len('100101') --> 6

在 3.1 版被加入.

int.bit_count()

回傳在絕對值表示的二進位中 1 的個數。這也被稱作母體計數。舉例來說：

>>> n = 19
>>> bin(n)
'0b10011'
>>> n.bit_count()
3
>>> (-n).bit_count()
3

等同於：

def bit_count(self):
    return bin(self).count("1")

在 3.10 版被加入.

int.to_bytes(length=1, byteorder='big', *, signed=False)

回傳表示一個整數的一列位元組。

>>> (1024).to_bytes(2, byteorder='big')
b'\x04\x00'
>>> (1024).to_bytes(10, byteorder='big')
b'\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00'
>>> (-1024).to_bytes(10, byteorder='big', signed=True)
b'\xff\xff\xff\xff\xff\xff\xff\xff\xfc\x00'
>>> x = 1000
>>> x.to_bytes((x.bit_length() + 7) // 8, byteorder='little')
b'\xe8\x03'

此整數會使用 length 位元組表示，並且預設為 1。如果該整數無法用給定的位元組數來表示，則會引發 OverflowError。

byteorder 引數決定了用來表示整數的位元組順序並且預設為 "big"。如果 byteorder 是 "big"，最重要的位元組位於位元組陣列的開頭。如果 byteorder 是 "little"，最重要的位元組位於位元組陣列的結尾。

signed 引數決定是否使用二的補數來表示整數。如果 signed 是 False 並且給定了一個負整數，則會引發 OverflowError。signed 的預設值是 False。

預設值可以方便地將一個整數轉換為單一位元組物件：

>>> (65).to_bytes()
b'A'

然而，使用預設引數時，不要嘗試轉換大於 255 的值，否則你將會得到一個 OverflowError。

等同於：

def to_bytes(n, length=1, byteorder='big', signed=False):
    if byteorder == 'little':
        order = range(length)
    elif byteorder == 'big':
        order = reversed(range(length))
    else:
        raise ValueError("byteorder must be either 'little' or 'big'")

    return bytes((n >> i*8) & 0xff for i in order)

在 3.2 版被加入.

在 3.11 版的變更: 為 length 和 byteorder 添加了預設引數值。

classmethod int.from_bytes(bytes, byteorder='big', *, signed=False)

回傳由給定的位元組陣列表示的整數。

>>> int.from_bytes(b'\x00\x10', byteorder='big')
16
>>> int.from_bytes(b'\x00\x10', byteorder='little')
4096
>>> int.from_bytes(b'\xfc\x00', byteorder='big', signed=True)
-1024
>>> int.from_bytes(b'\xfc\x00', byteorder='big', signed=False)
64512
>>> int.from_bytes([255, 0, 0], byteorder='big')
16711680

引數 bytes 必須是一個類位元組物件或是一個產生位元組的可疊代物件。

byteorder 引數決定了用來表示整數的位元組順序並且預設為 "big"。如果 byteorder 是 "big"，最重要的位元組位於位元組陣列的開頭。如果 byteorder 是 "little"，最重要的位元組位於位元組陣列的結尾。若要請求主機系統的本機位元組順序，請使用 sys.byteorder 作為位元組順序值。

signed 引數指示是否使用二的補數來表示整數。

等同於：

def from_bytes(bytes, byteorder='big', signed=False):
    if byteorder == 'little':
        little_ordered = list(bytes)
    elif byteorder == 'big':
        little_ordered = list(reversed(bytes))
    else:
        raise ValueError("byteorder must be either 'little' or 'big'")

    n = sum(b << i*8 for i, b in enumerate(little_ordered))
    if signed and little_ordered and (little_ordered[-1] & 0x80):
        n -= 1 << 8*len(little_ordered)

    return n

在 3.2 版被加入.

在 3.11 版的變更: 為 byteorder 添加了預設引數值。

int.as_integer_ratio()

回傳一對整數，其比率等於原始整數並且有一個正分母。整數（整個數值）的整數比率總是整數作為分子，並且 1 作為分母。

在 3.8 版被加入.

int.is_integer()

回傳 True。為了與 float.is_integer() 的鴨子型別相容而存在。

在 3.12 版被加入.

浮點數的附加方法

浮點數型別實作了 numbers.Real 抽象基底類別。浮點數也有下列附加方法。

classmethod float.from_number(x)

Class method to return a floating-point number constructed from a number x.

If the argument is an integer or a floating-point number, a floating-point number with the same value (within Python's floating-point precision) is returned. If the argument is outside the range of a Python float, an OverflowError will be raised.

For a general Python object x, float.from_number(x) delegates to x.__float__(). If __float__() is not defined then it falls back to __index__().

在 3.14 版被加入.

float.as_integer_ratio()

回傳一對整數，其比率完全等於原始浮點數。比率是在最低條件下並且有一個正分母。在無窮大時引發 OverflowError，在 NaN 時引發 ValueError。

float.is_integer()

如果浮點數實例是有限的並且具有整數值，則回傳 True，否則回傳 False：

>>> (-2.0).is_integer()
True
>>> (3.2).is_integer()
False

兩個 methods 皆支援十六進位字串之間的轉換。由於 Python 的浮點數內部以二進位數值儲存，將浮點數轉換為或從 十進位 字串通常涉及一個小的四捨五入誤差。相反地，十六進位字串允許精確表示和指定浮點數。這在除錯和數值工作中可能會有用。

float.hex()

回傳浮點數的十六進位字串表示。對於有限浮點數，此表示方式總是包含一個前導 0x 及一個尾部 p 和指數。

classmethod float.fromhex(s)

Class method 回傳由十六進位字串 s 表示的浮點數。字串 s 可能有前導及尾部的空白。

請注意 float.hex() 是一個實例 method，而 float.fromhex() 是一個 class method。

一個十六進位字串的形式如下：

[sign] ['0x'] integer ['.' fraction] ['p' exponent]

其中可選的 sign 可以是 + 或 -，integer 和 fraction 是十六進位數字的字串，而 exponent 是一個十進位整數並且有一個可選的前導符號。大小寫不重要，並且整數或小數部分至少有一個十六進位數字。這個語法與 C99 標準的第 6.4.4.2 節指定的語法相似，也與 Java 1.5 以後的語法相似。特別是 float.hex() 的輸出可用作 C 或 Java 程式碼中的十六進位浮點數文字，並且 C 的 %a 格式字元或 Java 的 Double.toHexString 產生的十六進位字串可被 float.fromhex() 接受。

請注意指數是以十進位而非十六進位寫入，並且它給出了乘以係數的 2 的次方。例如，十六進位字串 0x3.a7p10 表示浮點數 (3 + 10./16 + 7./16**2) * 2.0**10，或 3740.0：

>>> float.fromhex('0x3.a7p10')
3740.0

對 3740.0 應用反向轉換會給出一個不同的十六進位字串，它表示相同的數字：

>>> float.hex(3740.0)
'0x1.d380000000000p+11'

複數的附加方法

complex 型別實作了 numbers.Complex 抽象基底類別。complex 也有下列附加方法。

classmethod complex.from_number(x)

將一個數字轉換為複數的類別方法。

For a general Python object x, complex.from_number(x) delegates to x.__complex__(). If __complex__() is not defined then it falls back to __float__(). If __float__() is not defined then it falls back to __index__().

在 3.14 版被加入.

數值型別的雜湊

對於數字 x 和 y，可能是不同型別，當 x == y 時，hash(x) == hash(y) 是一個要求（ 詳見 __hash__() method 的文件以獲得更多細節）。為了實作的便利性和效率跨越各種數值型別（包括 int、float、decimal.Decimal 和 fractions.Fraction）Python 的數值型別的雜湊是基於一個數學函式，它對於任何有理數都是定義的，因此適用於所有 int 和 fractions.Fraction 的實例，以及所有有限的 float 和 decimal.Decimal 的實例。基本上，這個函式是由簡化的 modulo（模數） P 給出的一個固定的質數 P。P 的值作為 sys.hash_info 的 modulus 屬性提供給 Python。

目前在具有 32 位元 C longs 的機器上所使用的質數是 P = 2**31 - 1，而在具有 64 位元 C longs 的機器上為 P = 2**61 - 1 。

以下是詳細的規則：

如果 x = m / n 是一個非負的有理數，並且 n 不可被 P 整除，則將 hash(x) 定義為 m * invmod(n, P) % P。其中 invmod(n, P) 為 n 對模數 P 的倒數。

如果 x = m / n 是一個非負的有理數，並且 n 可被 P 整除（但 m 不行），則 n 沒有 inverse modulo（模倒數） P ，並且不適用於上述規則；在這種情況下，將 hash(x) 定義為常數值 sys.hash_info.inf。

如果 x = m / n 是一個負的有理數，則將 hash(x) 定義為 -hash(-x)。如果結果的雜湊是 -1，則將其替換為 -2。

特定值 sys.hash_info.inf 和 -sys.hash_info.inf （分別）被用作正無窮大或負無窮大的雜湊值。

對於一個 complex 值 z，實部和虛部的雜湊值藉由 hash(z.real) + sys.hash_info.imag * hash(z.imag) 的計算進行組合，對 2**sys.hash_info.width 取模數使其介於 range(-2**(sys.hash_info.width - 1), 2**(sys.hash_info.width - 1))。同樣地，如果結果是 -1，則將其替換為 -2。

為了闡明上述規則，這裡有一些 Python 程式碼範例，等同於內建的雜湊，用於計算有理數、float 或 complex 的雜湊：

import sys, math

def hash_fraction(m, n):
    """Compute the hash of a rational number m / n.

    Assumes m and n are integers, with n positive.
    Equivalent to hash(fractions.Fraction(m, n)).

    """
    P = sys.hash_info.modulus
    # Remove common factors of P.  (Unnecessary if m and n already coprime.)
    while m % P == n % P == 0:
        m, n = m // P, n // P

    if n % P == 0:
        hash_value = sys.hash_info.inf
    else:
        # Fermat's Little Theorem: pow(n, P-1, P) is 1, so
        # pow(n, P-2, P) gives the inverse of n modulo P.
        hash_value = (abs(m) % P) * pow(n, P - 2, P) % P
    if m < 0:
        hash_value = -hash_value
    if hash_value == -1:
        hash_value = -2
    return hash_value

def hash_float(x):
    """Compute the hash of a float x."""

    if math.isnan(x):
        return object.__hash__(x)
    elif math.isinf(x):
        return sys.hash_info.inf if x > 0 else -sys.hash_info.inf
    else:
        return hash_fraction(*x.as_integer_ratio())

def hash_complex(z):
    """Compute the hash of a complex number z."""

    hash_value = hash_float(z.real) + sys.hash_info.imag * hash_float(z.imag)
    # do a signed reduction modulo 2**sys.hash_info.width
    M = 2**(sys.hash_info.width - 1)
    hash_value = (hash_value & (M - 1)) - (hash_value & M)
    if hash_value == -1:
        hash_value = -2
    return hash_value

Boolean 型別 - bool

Boolean 值代表 truth values（真值）。bool 型別有兩個常數實例：True 和 False。

內建函式 bool() 將任何值轉換為 boolean 值，如果該值可以被直譯為一個 truth value（真值）（見上面的真值檢測章節）。

對於邏輯運算，使用 boolean 運算子 and、or 和 not。當將位元運算子 &、|、^ 應用於兩個 boolean 值時，它們會回傳一個等同於邏輯運算 "and"、"or"、"xor" 的 boolean 值。然而，應該優先使用邏輯運算子 and、or 和 != 而不是 &、| 和 ^。

在 3.12 版之後被棄用: 位元反轉運算子 ~ 的使用已被棄用並且將在 Python 3.16 中引發錯誤。

bool 是 int 的子類別（見數值型別 --- int、float、complex）。在許多數值情境中，False 和 True 分別像整數 0 和 1 一樣。然而，不鼓勵依賴這一點；請使用 int() 進行顯式轉換。

疊代器型別

Python 支援對容器的疊代概念。這是實作兩種不同的 methods；這些方法被用於允許使用者定義的 classes 以支援疊代。序列則總是支援這些疊代 methods，在下方有更詳細的描述。

需要為容器物件定義一個 method 來提供可疊代物件支援：

container.__iter__()

回傳一個疊代器物件。該物件需要支援下述的疊代器協定。如果一個容器支援不同型別的疊代，則可以提供額外的 methods 來專門請求這些疊代型別的疊代器。（支援多種形式疊代的物件的一個例子是支援廣度優先和深度優先遍歷的樹結構。）此 method 對應 Python/C API 中 Python 物件的型別結構的 tp_iter 插槽。

疊代器物件本身需要支援下列兩個 methods，他們一起形成了 疊代器協定：

iterator.__iter__()

回傳疊代器物件本身。這是為了允許容器和疊代器都可以與 for 和 in 在陳述式中使用。此 method 對應於 Python/C API 中 Python 物件的型別結構的 tp_iter 插槽。

iterator.__next__()

從疊代器回傳下一個項目。如果沒有更多項目，則引發 StopIteration 例外。此 method 對應於 Python/C API 中Python 物件的型別結構的 tp_iternext 插槽。

Python 定義了幾個疊代器物件來支援對一般和特定序列型別、字典和其他更專門的形式的疊代。這些特定型別除了實作疊代器協定外並不重要。

一旦疊代器的 __next__() method 引發 StopIteration，則它必須在後續呼叫中繼續這樣做。不遵守此屬性的實作被認為是有問題的。

Generator Types

Python's generators provide a convenient way to implement the iterator protocol. If a container object's __iter__() method is implemented as a generator, it will automatically return an iterator object (technically, a generator object) supplying the __iter__() and __next__() methods. More information about generators can be found in the documentation for the yield expression.

Sequence Types --- list, tuple, range

There are three basic sequence types: lists, tuples, and range objects. Additional sequence types tailored for processing of binary data and text strings are described in dedicated sections.

Common Sequence Operations

The operations in the following table are supported by most sequence types, both mutable and immutable. The collections.abc.Sequence ABC is provided to make it easier to correctly implement these operations on custom sequence types.

This table lists the sequence operations sorted in ascending priority. In the table, s and t are sequences of the same type, n, i, j and k are integers and x is an arbitrary object that meets any type and value restrictions imposed by s.

The in and not in operations have the same priorities as the comparison operations. The + (concatenation) and * (repetition) operations have the same priority as the corresponding numeric operations. [3]

運算

結果

註解

x in s

如果 s 的一個項目等於 x 則為 True，否則為 False

(1)

x not in s

如果 s 的一個項目等於 x 則為 False，否則為 True

(1)

s + t

s 和 t 的串接

(6)(7)

s * n 或 n * s

等同於將 s 加到自己 n 次

(2)(7)

s[i]

s 的第 i 項，起始為 0

(3)(8)

s[i:j]

slice of s from i to j

(3)(4)

s[i:j:k]

slice of s from i to j with step k

(3)(5)

len(s)

s 的長度

min(s)

s 中最小的項目

max(s)

s 中最大的項目

Sequences of the same type also support comparisons. In particular, tuples and lists are compared lexicographically by comparing corresponding elements. This means that to compare equal, every element must compare equal and the two sequences must be of the same type and have the same length. (For full details see Comparisons in the language reference.)

Forward and reversed iterators over mutable sequences access values using an index. That index will continue to march forward (or backward) even if the underlying sequence is mutated. The iterator terminates only when an IndexError or a StopIteration is encountered (or when the index drops below zero).

註解：

While the in and not in operations are used only for simple containment testing in the general case, some specialised sequences (such as str, bytes and bytearray) also use them for subsequence testing:

>>> "gg" in "eggs"
True

Values of n less than 0 are treated as 0 (which yields an empty sequence of the same type as s). Note that items in the sequence s are not copied; they are referenced multiple times. This often haunts new Python programmers; consider:

>>> lists = [[]] * 3
>>> lists
[[], [], []]
>>> lists[0].append(3)
>>> lists
[[3], [3], [3]]

What has happened is that [[]] is a one-element list containing an empty list, so all three elements of [[]] * 3 are references to this single empty list. Modifying any of the elements of lists modifies this single list. You can create a list of different lists this way:

>>> lists = [[] for i in range(3)]
>>> lists[0].append(3)
>>> lists[1].append(5)
>>> lists[2].append(7)
>>> lists
[[3], [5], [7]]

Further explanation is available in the FAQ entry 如何建立多維度串列？.

If i or j is negative, the index is relative to the end of sequence s: len(s) + i or len(s) + j is substituted. But note that -0 is still 0.

The slice of s from i to j is defined as the sequence of items with index k such that i <= k < j.

假如 i 被省略或為 None，則使用 0。

假如 j 被省略或為 None，則使用 len(s)。

假如 i 或 j 小於 -len(s)，則使用 0。

假如 i 或 j 大於 len(s)，則使用 len(s)。

假如 i 大於或等於 j，則該切片為空。

The slice of s from i to j with step k is defined as the sequence of items with index x = i + n*k such that 0 <= n < (j-i)/k. In other words, the indices are i, i+k, i+2*k, i+3*k and so on, stopping when j is reached (but never including j). When k is positive, i and j are reduced to len(s) if they are greater. When k is negative, i and j are reduced to len(s) - 1 if they are greater. If i or j are omitted or None, they become "end" values (which end depends on the sign of k). Note, k cannot be zero. If k is None, it is treated like 1.

Concatenating immutable sequences always results in a new object. This means that building up a sequence by repeated concatenation will have a quadratic runtime cost in the total sequence length. To get a linear runtime cost, you must switch to one of the alternatives below:

if concatenating str objects, you can build a list and use str.join() at the end or else write to an io.StringIO instance and retrieve its value when complete

if concatenating bytes objects, you can similarly use bytes.join() or io.BytesIO, or you can do in-place concatenation with a bytearray object. bytearray objects are mutable and have an efficient overallocation mechanism

if concatenating tuple objects, extend a list instead

for other types, investigate the relevant class documentation

Some sequence types (such as range) only support item sequences that follow specific patterns, and hence don't support sequence concatenation or repetition.

An IndexError is raised if i is outside the sequence range.

序列方法

序列型別也支援以下方法：

sequence.count(value, /)

回傳 sequence 中 value 出現的總次數。

sequence.index(value[, start[, stop])

回傳 sequence 中 value 首次出現的索引。

當 value 不在 sequence 中時引發 ValueError。

The start or stop arguments allow for efficient searching of subsections of the sequence, beginning at start and ending at stop. This is roughly equivalent to start + sequence[start:stop].index(value), only without copying any data.

警示

Not all sequence types support passing the start and stop arguments.

不可變序列型別

The only operation that immutable sequence types generally implement that is not also implemented by mutable sequence types is support for the hash() built-in.

This support allows immutable sequences, such as tuple instances, to be used as dict keys and stored in set and frozenset instances.

Attempting to hash an immutable sequence that contains unhashable values will result in TypeError.

可變序列型別

The operations in the following table are defined on mutable sequence types. The collections.abc.MutableSequence ABC is provided to make it easier to correctly implement these operations on custom sequence types.

In the table s is an instance of a mutable sequence type, t is any iterable object and x is an arbitrary object that meets any type and value restrictions imposed by s (for example, bytearray only accepts integers that meet the value restriction 0 <= x <= 255).

運算

結果

註解

s[i] = x

item i of s is replaced by x

del s[i]

移除 s 中的項目 i

s[i:j] = t

slice of s from i to j is replaced by the contents of the iterable t

del s[i:j]

移除串列中 s[i:j] 的元素（和 s[i:j] = [] 相同）

s[i:j:k] = t

s[i:j:k] 的元素被 t 的元素取代

(1)

del s[i:j:k]

移除串列中 s[i:j:k] 的元素

s += t

extends s with the contents of t (for the most part the same as s[len(s):len(s)] = t)

s *= n

updates s with its contents repeated n times

(2)

註解：

If k is not equal to 1, t must have the same length as the slice it is replacing.

The value n is an integer, or an object implementing __index__(). Zero and negative values of n clear the sequence. Items in the sequence are not copied; they are referenced multiple times, as explained for s * n under Common Sequence Operations.

可變序列方法

可變序列型別也支援以下方法：

sequence.append(value, /)

Append value to the end of the sequence This is equivalent to writing seq[len(seq):len(seq)] = [value].

sequence.clear()

在 3.3 版被加入.

移除 sequence 中的所有項目，這和 del sequence[:] 相同。

sequence.copy()

在 3.3 版被加入.

建立 sequence 的淺層複製，這和 sequence[:] 相同。

提示

The copy() method is not part of the MutableSequence ABC, but most concrete mutable sequence types provide it.

sequence.extend(iterable, /)

Extend sequence with the contents of iterable. For the most part, this is the same as writing seq[len(seq):len(seq)] = iterable.

sequence.insert(index, value, /)

Insert value into sequence at the given index. This is equivalent to writing sequence[index:index] = [value].

sequence.pop(index=-1, /)

Retrieve the item at index and also removes it from sequence. By default, the last item in sequence is removed and returned.

sequence.remove(value, /)

Remove the first item from sequence where sequence[i] == value.

當 value 不在 sequence 中時引發 ValueError。

sequence.reverse()

Reverse the items of sequence in place. This method maintains economy of space when reversing a large sequence. To remind users that it operates by side-effect, it returns None.

List（串列）

Lists are mutable sequences, typically used to store collections of homogeneous items (where the precise degree of similarity will vary by application).

class list(iterable=(), /)

Lists may be constructed in several ways:

Using a pair of square brackets to denote the empty list: []

Using square brackets, separating items with commas: [a], [a, b, c]

使用串列綜合運算式：[x for x in iterable]

使用型別建構函式：list() 或 list(iterable)

The constructor builds a list whose items are the same and in the same order as iterable's items. iterable may be either a sequence, a container that supports iteration, or an iterator object. If iterable is already a list, a copy is made and returned, similar to iterable[:]. For example, list('abc') returns ['a', 'b', 'c'] and list( (1, 2, 3) ) returns [1, 2, 3]. If no argument is given, the constructor creates a new empty list, [].

Many other operations also produce lists, including the sorted() built-in.

Lists implement all of the common and mutable sequence operations. Lists also provide the following additional method:

sort(*, key=None, reverse=False)

This method sorts the list in place, using only < comparisons between items. Exceptions are not suppressed - if any comparison operations fail, the entire sort operation will fail (and the list will likely be left in a partially modified state).

sort() accepts two arguments that can only be passed by keyword (keyword-only arguments):

key specifies a function of one argument that is used to extract a comparison key from each list element (for example, key=str.lower). The key corresponding to each item in the list is calculated once and then used for the entire sorting process. The default value of None means that list items are sorted directly without calculating a separate key value.

The functools.cmp_to_key() utility is available to convert a 2.x style cmp function to a key function.

reverse is a boolean value. If set to True, then the list elements are sorted as if each comparison were reversed.

This method modifies the sequence in place for economy of space when sorting a large sequence. To remind users that it operates by side effect, it does not return the sorted sequence (use sorted() to explicitly request a new sorted list instance).

The sort() method is guaranteed to be stable. A sort is stable if it guarantees not to change the relative order of elements that compare equal --- this is helpful for sorting in multiple passes (for example, sort by department, then by salary grade).

For sorting examples and a brief sorting tutorial, see 排序技法.

CPython 實作細節： While a list is being sorted, the effect of attempting to mutate, or even inspect, the list is undefined. The C implementation of Python makes the list appear empty for the duration, and raises ValueError if it can detect that the list has been mutated during a sort.

Thread safety

Reading a single element from a list is atomic:

lst[i]   # list.__getitem__

The following methods traverse the list and use atomic reads of each item to perform their function. That means that they may return results affected by concurrent modifications:

item in lst
lst.index(item)
lst.count(item)

All of the above methods/operations are also lock-free. They do not block concurrent modifications. Other operations that hold a lock will not block these from observing intermediate states.

All other operations from here on block using the per-object lock.

Writing a single item via lst[i] = x is safe to call from multiple threads and will not corrupt the list.

The following operations return new objects and appear atomic to other threads:

lst1 + lst2    # concatenates two lists into a new list
x * lst        # repeats lst x times into a new list
lst.copy()     # returns a shallow copy of the list

Methods that only operate on a single elements with no shifting required are atomic:

lst.append(x)  # append to the end of the list, no shifting required
lst.pop()      # pop element from the end of the list, no shifting required

The clear() method is also atomic. Other threads cannot observe elements being removed.

The sort() method is not atomic. Other threads cannot observe intermediate states during sorting, but the list appears empty for the duration of the sort.

The following operations may allow lock-free operations to observe intermediate states since they modify multiple elements in place:

lst.insert(idx, item)  # shifts elements
lst.pop(idx)           # idx not at the end of the list, shifts elements
lst *= x               # copies elements in place

The remove() method may allow concurrent modifications since element comparison may execute arbitrary Python code (via __eq__()).

extend() is safe to call from multiple threads. However, its guarantees depend on the iterable passed to it. If it is a list, a tuple, a set, a frozenset, a dict or a dictionary view object (but not their subclasses), the extend operation is safe from concurrent modifications to the iterable. Otherwise, an iterator is created which can be concurrently modified by another thread. The same applies to inplace concatenation of a list with other iterables when using lst += iterable.

Similarly, assigning to a list slice with lst[i:j] = iterable is safe to call from multiple threads, but iterable is only locked when it is also a list (but not its subclasses).

Operations that involve multiple accesses, as well as iteration, are never atomic. For example:

# NOT atomic: read-modify-write
lst[i] = lst[i] + 1

# NOT atomic: check-then-act
if lst:
    item = lst.pop()

# NOT thread-safe: iteration while modifying
for item in lst:
    process(item)  # another thread may modify lst

Consider external synchronization when sharing list instances across threads. See Python 自由執行緒的支援 for more information.

Tuple（元組）

Tuples are immutable sequences, typically used to store collections of heterogeneous data (such as the 2-tuples produced by the enumerate() built-in). Tuples are also used for cases where an immutable sequence of homogeneous data is needed (such as allowing storage in a set or dict instance).

class tuple(iterable=(), /)

元組可以以多種方式建構：

使用一對圓括號表示空元組：()

使用末尾的逗號表示單元素元組：a, 或 (a,)

使用逗號分隔項目：a, b, c 或 (a, b, c)

Using the tuple() built-in: tuple() or tuple(iterable)

The constructor builds a tuple whose items are the same and in the same order as iterable's items. iterable may be either a sequence, a container that supports iteration, or an iterator object. If iterable is already a tuple, it is returned unchanged. For example, tuple('abc') returns ('a', 'b', 'c') and tuple( [1, 2, 3] ) returns (1, 2, 3). If no argument is given, the constructor creates a new empty tuple, ().

Note that it is actually the comma which makes a tuple, not the parentheses. The parentheses are optional, except in the empty tuple case, or when they are needed to avoid syntactic ambiguity. For example, f(a, b, c) is a function call with three arguments, while f((a, b, c)) is a function call with a 3-tuple as the sole argument.

Tuples implement all of the common sequence operations.

For heterogeneous collections of data where access by name is clearer than access by index, collections.namedtuple() may be a more appropriate choice than a simple tuple object.

Ranges

The range type represents an immutable sequence of numbers and is commonly used for looping a specific number of times in for loops.

class range(stop, /)

class range(start, stop, step=1, /)

The arguments to the range constructor must be integers (either built-in int or any object that implements the __index__() special method). If the step argument is omitted, it defaults to 1. If the start argument is omitted, it defaults to 0. If step is zero, ValueError is raised.

For a positive step, the contents of a range r are determined by the formula r[i] = start + step*i where i >= 0 and r[i] < stop.

For a negative step, the contents of the range are still determined by the formula r[i] = start + step*i, but the constraints are i >= 0 and r[i] > stop.

A range object will be empty if r[0] does not meet the value constraint. Ranges do support negative indices, but these are interpreted as indexing from the end of the sequence determined by the positive indices.

Ranges containing absolute values larger than sys.maxsize are permitted but some features (such as len()) may raise OverflowError.

Range examples:

>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(1, 11))
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> list(range(0, 30, 5))
[0, 5, 10, 15, 20, 25]
>>> list(range(0, 10, 3))
[0, 3, 6, 9]
>>> list(range(0, -10, -1))
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
>>> list(range(0))
[]
>>> list(range(1, 0))
[]

Ranges implement all of the common sequence operations except concatenation and repetition (due to the fact that range objects can only represent sequences that follow a strict pattern and repetition and concatenation will usually violate that pattern).

start

The value of the start parameter (or 0 if the parameter was not supplied)

stop

The value of the stop parameter

step

The value of the step parameter (or 1 if the parameter was not supplied)

The advantage of the range type over a regular list or tuple is that a range object will always take the same (small) amount of memory, no matter the size of the range it represents (as it only stores the start, stop and step values, calculating individual items and subranges as needed).

Range objects implement the collections.abc.Sequence ABC, and provide features such as containment tests, element index lookup, slicing and support for negative indices (see Sequence Types --- list, tuple, range):

>>> r = range(0, 20, 2)
>>> r
range(0, 20, 2)
>>> 11 in r
False
>>> 10 in r
True
>>> r.index(10)
5
>>> r[5]
10
>>> r[:5]
range(0, 10, 2)
>>> r[-1]
18

Testing range objects for equality with == and != compares them as sequences. That is, two range objects are considered equal if they represent the same sequence of values. (Note that two range objects that compare equal might have different start, stop and step attributes, for example range(0) == range(2, 1, 3) or range(0, 3, 2) == range(0, 4, 2).)

在 3.2 版的變更: Implement the Sequence ABC. Support slicing and negative indices. Test int objects for membership in constant time instead of iterating through all items.

在 3.3 版的變更: Define '==' and '!=' to compare range objects based on the sequence of values they define (instead of comparing based on object identity).

Added the start, stop and step attributes.

也參考

The linspace recipe [https://code.activestate.com/recipes/579000-equally-spaced-numbers-linspace/] shows how to implement a lazy version of range suitable for floating-point applications.

Text and Binary Sequence Type Methods Summary

The following table summarizes the text and binary sequence types methods by category.

分類

str 方法

bytes 和 bytearray 方法

格式化

str.format()

str.format_map()

f-string（f 字串）

printf-style String Formatting

printf-style Bytes Formatting

搜尋和取代

str.find()

str.rfind()

bytes.find()

bytes.rfind()

str.index()

str.rindex()

bytes.index()

bytes.rindex()

str.startswith()

bytes.startswith()

str.endswith()

bytes.endswith()

str.count()

bytes.count()

str.replace()

bytes.replace()

分割和連接

str.split()

str.rsplit()

bytes.split()

bytes.rsplit()

str.splitlines()

bytes.splitlines()

str.partition()

bytes.partition()

str.rpartition()

bytes.rpartition()

str.join()

bytes.join()

字串分類

str.isalpha()

bytes.isalpha()

str.isdecimal()

str.isdigit()

bytes.isdigit()

str.isnumeric()

str.isalnum()

bytes.isalnum()

str.isidentifier()

str.islower()

bytes.islower()

str.isupper()

bytes.isupper()

str.istitle()

bytes.istitle()

str.isspace()

bytes.isspace()

str.isprintable()

大小寫操作

str.lower()

bytes.lower()

str.upper()

bytes.upper()

str.casefold()

str.capitalize()

bytes.capitalize()

str.title()

bytes.title()

str.swapcase()

bytes.swapcase()

填充和去除空白

str.ljust()

str.rjust()

bytes.ljust()

bytes.rjust()

str.center()

bytes.center()

str.expandtabs()

bytes.expandtabs()

str.strip()

bytes.strip()

str.lstrip()

str.rstrip()

bytes.lstrip()

bytes.rstrip()

翻譯和編碼

str.translate()

bytes.translate()

str.maketrans()

bytes.maketrans()

str.encode()

bytes.decode()

Text Sequence Type --- str

Textual data in Python is handled with str objects, or strings. Strings are immutable sequences of Unicode code points. String literals are written in a variety of ways:

Single quotes: 'allows embedded "double" quotes'

Double quotes: "allows embedded 'single' quotes"

Triple quoted: '''Three single quotes''', """Three double quotes"""

Triple quoted strings may span multiple lines - all associated whitespace will be included in the string literal.

String literals that are part of a single expression and have only whitespace between them will be implicitly converted to a single string literal. That is, ("spam " "eggs") == "spam eggs".

See String and Bytes literals for more about the various forms of string literal, including supported escape sequences, and the r ("raw") prefix that disables most escape sequence processing.

Strings may also be created from other objects using the str constructor.

Since there is no separate "character" type, indexing a string produces strings of length 1. That is, for a non-empty string s, s[0] == s[0:1].

There is also no mutable string type, but str.join() or io.StringIO can be used to efficiently construct strings from multiple fragments.

在 3.3 版的變更: For backwards compatibility with the Python 2 series, the u prefix is once again permitted on string literals. It has no effect on the meaning of string literals and cannot be combined with the r prefix.

class str(*, encoding='utf-8', errors='strict')

class str(object)

class str(object, encoding, errors='strict')

class str(object, *, errors)

Return a string version of object. If object is not provided, returns the empty string. Otherwise, the behavior of str() depends on whether encoding or errors is given, as follows.

If neither encoding nor errors is given, str(object) returns type(object).__str__(object), which is the "informal" or nicely printable string representation of object. For string objects, this is the string itself. If object does not have a __str__() method, then str() falls back to returning repr(object).

If at least one of encoding or errors is given, object should be a bytes-like object (e.g. bytes or bytearray). In this case, if object is a bytes (or bytearray) object, then str(bytes, encoding, errors) is equivalent to bytes.decode(encoding, errors). Otherwise, the bytes object underlying the buffer object is obtained before calling bytes.decode(). See Binary Sequence Types --- bytes, bytearray, memoryview and 緩衝協定 (Buffer Protocol) for information on buffer objects.

Passing a bytes object to str() without the encoding or errors arguments falls under the first case of returning the informal string representation (see also the -b command-line option to Python). For example:

>>> str(b'Zoot!')
"b'Zoot!'"

For more information on the str class and its methods, see Text Sequence Type --- str and the 字串方法 section below. To output formatted strings, see the f-string（f 字串） and 格式化文字語法 sections. In addition, see the 文本處理 (Text Processing) 服務 section.

字串方法

Strings implement all of the common sequence operations, along with the additional methods described below.

Strings also support two styles of string formatting, one providing a large degree of flexibility and customization (see str.format(), 格式化文字語法 and 自訂字串格式) and the other based on C printf style formatting that handles a narrower range of types and is slightly harder to use correctly, but is often faster for the cases it can handle (printf-style String Formatting).

The 文本處理 (Text Processing) 服務 section of the standard library covers a number of other modules that provide various text related utilities (including regular expression support in the re module).

str.capitalize()

Return a copy of the string with its first character capitalized and the rest lowercased.

在 3.8 版的變更: The first character is now put into titlecase rather than uppercase. This means that characters like digraphs will only have their first letter capitalized, instead of the full character.

str.casefold()

Return a casefolded copy of the string. Casefolded strings may be used for caseless matching.

Casefolding is similar to lowercasing but more aggressive because it is intended to remove all case distinctions in a string. For example, the German lowercase letter 'ß' is equivalent to "ss". Since it is already lowercase, lower() would do nothing to 'ß'; casefold() converts it to "ss". For example:

>>> 'straße'.lower()
'straße'
>>> 'straße'.casefold()
'strasse'

The casefolding algorithm is described in section 3.13 'Default Case Folding' of the Unicode Standard [https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-3/#G33992].

在 3.3 版被加入.

str.center(width, fillchar=' ', /)

Return centered in a string of length width. Padding is done using the specified fillchar (default is an ASCII space). The original string is returned if width is less than or equal to len(s). For example:

>>> 'Python'.center(10)
'  Python  '
>>> 'Python'.center(10, '-')
'--Python--'
>>> 'Python'.center(4)
'Python'

str.count(sub[, start[, end]])

Return the number of non-overlapping occurrences of substring sub in the range [start, end]. Optional arguments start and end are interpreted as in slice notation.

If sub is empty, returns the number of empty strings between characters which is the length of the string plus one. For example:

>>> 'spam, spam, spam'.count('spam')
3
>>> 'spam, spam, spam'.count('spam', 5)
2
>>> 'spam, spam, spam'.count('spam', 5, 10)
1
>>> 'spam, spam, spam'.count('eggs')
0
>>> 'spam, spam, spam'.count('')
17

str.encode(encoding='utf-8', errors='strict')

Return the string encoded to bytes.

encoding defaults to 'utf-8'; see 標準編碼 for possible values.

errors controls how encoding errors are handled. If 'strict' (the default), a UnicodeError exception is raised. Other possible values are 'ignore', 'replace', 'xmlcharrefreplace', 'backslashreplace' and any other name registered via codecs.register_error(). See Error Handlers for details.

For performance reasons, the value of errors is not checked for validity unless an encoding error actually occurs, Python 開發模式 is enabled or a debug build is used. For example:

>>> encoded_str_to_bytes = 'Python'.encode()
>>> type(encoded_str_to_bytes)
<class 'bytes'>
>>> encoded_str_to_bytes
b'Python'

在 3.1 版的變更: 新增關鍵字引數的支援。

在 3.9 版的變更: The value of the errors argument is now checked in Python 開發模式 and in debug mode.

str.endswith(suffix[, start[, end]])

Return True if the string ends with the specified suffix, otherwise return False. suffix can also be a tuple of suffixes to look for. With optional start, test beginning at that position. With optional end, stop comparing at that position. Using start and end is equivalent to str[start:end].endswith(suffix). For example:

>>> 'Python'.endswith('on')
True
>>> 'a tuple of suffixes'.endswith(('at', 'in'))
False
>>> 'a tuple of suffixes'.endswith(('at', 'es'))
True
>>> 'Python is amazing'.endswith('is', 0, 9)
True

另請參閱 startswith() 和 removesuffix()。

str.expandtabs(tabsize=8)

Return a copy of the string where all tab characters are replaced by one or more spaces, depending on the current column and the given tab size. Tab positions occur every tabsize characters (default is 8, giving tab positions at columns 0, 8, 16 and so on). To expand the string, the current column is set to zero and the string is examined character by character. If the character is a tab (\t), one or more space characters are inserted in the result until the current column is equal to the next tab position. (The tab character itself is not copied.) If the character is a newline (\n) or return (\r), it is copied and the current column is reset to zero. Any other character is copied unchanged and the current column is incremented by one regardless of how the character is represented when printed. For example:

>>> '01\t012\t0123\t01234'.expandtabs()
'01      012     0123    01234'
>>> '01\t012\t0123\t01234'.expandtabs(4)
'01  012 0123    01234'
>>> print('01\t012\n0123\t01234'.expandtabs(4))
01  012
0123    01234

str.find(sub[, start[, end]])

Return the lowest index in the string where substring sub is found within the slice s[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 if sub is not found. For example:

>>> 'spam, spam, spam'.find('sp')
0
>>> 'spam, spam, spam'.find('sp', 5)
6

另請參閱 rfind() 和 index()。

備註

The find() method should be used only if you need to know the position of sub. To check if sub is a substring or not, use the in operator:

>>> 'Py' in 'Python'
True

str.format(*args, **kwargs)

Perform a string formatting operation. The string on which this method is called can contain literal text or replacement fields delimited by braces {}. Each replacement field contains either the numeric index of a positional argument, or the name of a keyword argument. Returns a copy of the string where each replacement field is replaced with the string value of the corresponding argument. For example:

>>> "The sum of 1 + 2 is {0}".format(1+2)
'The sum of 1 + 2 is 3'
>>> "The sum of {a} + {b} is {answer}".format(answer=1+2, a=1, b=2)
'The sum of 1 + 2 is 3'
>>> "{1} expects the {0} Inquisition!".format("Spanish", "Nobody")
'Nobody expects the Spanish Inquisition!'

See 格式化文字語法 for a description of the various formatting options that can be specified in format strings.

備註

When formatting a number (int, float, complex, decimal.Decimal and subclasses) with the n type (ex: '{:n}'.format(1234)), the function temporarily sets the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep fields of localeconv() if they are non-ASCII or longer than 1 byte, and the LC_NUMERIC locale is different than the LC_CTYPE locale. This temporary change affects other threads.

在 3.7 版的變更: When formatting a number with the n type, the function sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale in some cases.

str.format_map(mapping, /)

Similar to str.format(**mapping), except that mapping is used directly and not copied to a dict. This is useful if for example mapping is a dict subclass:

>>> class Default(dict):
...     def __missing__(self, key):
...         return key
...
>>> '{name} was born in {country}'.format_map(Default(name='Guido'))
'Guido was born in country'

在 3.2 版被加入.

str.index(sub[, start[, end]])

Like find(), but raise ValueError when the substring is not found. For example:

>>> 'spam, spam, spam'.index('eggs')
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    'spam, spam, spam'.index('eggs')
    ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
ValueError: substring not found

另請參閱 rindex()。

str.isalnum()

Return True if all characters in the string are alphanumeric and there is at least one character, False otherwise. A character c is alphanumeric if one of the following returns True: c.isalpha(), c.isdecimal(), c.isdigit(), or c.isnumeric().

str.isalpha()

Return True if all characters in the string are alphabetic and there is at least one character, False otherwise. Alphabetic characters are those characters defined in the Unicode character database as "Letter", i.e., those with general category property being one of "Lm", "Lt", "Lu", "Ll", or "Lo". Note that this is different from the Alphabetic property defined in the section 4.10 'Letters, Alphabetic, and Ideographic' of the Unicode Standard [https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-4/#G91002]. For example:

>>> 'Letters and spaces'.isalpha()
False
>>> 'LettersOnly'.isalpha()
True
>>> 'µ'.isalpha()  # 非 ASCII 字元也可以被視為字母
True

請參閱 Unicode Properties。

str.isascii()

Return True if the string is empty or all characters in the string are ASCII, False otherwise. ASCII characters have code points in the range U+0000-U+007F. For example:

>>> 'ASCII characters'.isascii()
True
>>> 'µ'.isascii()
False

在 3.7 版被加入.

str.isdecimal()

Return True if all characters in the string are decimal characters and there is at least one character, False otherwise. Decimal characters are those that can be used to form numbers in base 10, such as U+0660, ARABIC-INDIC DIGIT ZERO. Formally a decimal character is a character in the Unicode General Category "Nd". For example:

>>> '0123456789'.isdecimal()
True
>>> '٠١٢٣٤٥٦٧٨٩'.isdecimal()  # 阿拉伯-印度數字零到九
True
>>> 'alphabetic'.isdecimal()
False

str.isdigit()

Return True if all characters in the string are digits and there is at least one character, False otherwise. Digits include decimal characters and digits that need special handling, such as the compatibility superscript digits. This covers digits which cannot be used to form numbers in base 10, like the Kharosthi numbers. Formally, a digit is a character that has the property value Numeric_Type=Digit or Numeric_Type=Decimal.

str.isidentifier()

Return True if the string is a valid identifier according to the language definition, section Names (identifiers and keywords).

keyword.iskeyword() can be used to test whether string s is a reserved identifier, such as def and class.

範例：

>>> from keyword import iskeyword

>>> 'hello'.isidentifier(), iskeyword('hello')
(True, False)
>>> 'def'.isidentifier(), iskeyword('def')
(True, True)

str.islower()

Return True if all cased characters [4] in the string are lowercase and there is at least one cased character, False otherwise.

str.isnumeric()

Return True if all characters in the string are numeric characters, and there is at least one character, False otherwise. Numeric characters include digit characters, and all characters that have the Unicode numeric value property, e.g. U+2155, VULGAR FRACTION ONE FIFTH. Formally, numeric characters are those with the property value Numeric_Type=Digit, Numeric_Type=Decimal or Numeric_Type=Numeric. For example:

>>> '0123456789'.isnumeric()
True
>>> '٠١٢٣٤٥٦٧٨٩'.isnumeric()  # 阿拉伯-印度數字零到九
True
>>> '⅕'.isnumeric()  # 普通分數五分之一
True
>>> '²'.isdecimal(), '²'.isdigit(),  '²'.isnumeric()
(False, True, True)

也請參閱 isdecimal() 和 isdigit()。數字字元是十進位數字的超集。

str.isprintable()

Return True if all characters in the string are printable, False if it contains at least one non-printable character.

Here "printable" means the character is suitable for repr() to use in its output; "non-printable" means that repr() on built-in types will hex-escape the character. It has no bearing on the handling of strings written to sys.stdout or sys.stderr.

The printable characters are those which in the Unicode character database (see unicodedata) have a general category in group Letter, Mark, Number, Punctuation, or Symbol (L, M, N, P, or S); plus the ASCII space 0x20. Nonprintable characters are those in group Separator or Other (Z or C), except the ASCII space.

舉例來說：

>>> ''.isprintable(), ' '.isprintable()
(True, True)
>>> '\t'.isprintable(), '\n'.isprintable()
(False, False)

str.isspace()

Return True if there are only whitespace characters in the string and there is at least one character, False otherwise.

A character is whitespace if in the Unicode character database (see unicodedata), either its general category is Zs ("Separator, space"), or its bidirectional class is one of WS, B, or S.

str.istitle()

Return True if the string is a titlecased string and there is at least one character, for example uppercase characters may only follow uncased characters and lowercase characters only cased ones. Return False otherwise.

舉例來說：

>>> 'Spam, Spam, Spam'.istitle()
True
>>> 'spam, spam, spam'.istitle()
False
>>> 'SPAM, SPAM, SPAM'.istitle()
False

另請參閱 title()。

str.isupper()

Return True if all cased characters [4] in the string are uppercase and there is at least one cased character, False otherwise.

>>> 'BANANA'.isupper()
True
>>> 'banana'.isupper()
False
>>> 'baNana'.isupper()
False
>>> ' '.isupper()
False

str.join(iterable, /)

Return a string which is the concatenation of the strings in iterable. A TypeError will be raised if there are any non-string values in iterable, including bytes objects. The separator between elements is the string providing this method. For example:

>>> ', '.join(['spam', 'spam', 'spam'])
'spam, spam, spam'
>>> '-'.join('Python')
'P-y-t-h-o-n'

另請參閱 split()。

str.ljust(width, fillchar=' ', /)

Return the string left justified in a string of length width. Padding is done using the specified fillchar (default is an ASCII space). The original string is returned if width is less than or equal to len(s).

舉例來說：

>>> 'Python'.ljust(10)
'Python    '
>>> 'Python'.ljust(10, '.')
'Python....'
>>> 'Monty Python'.ljust(10, '.')
'Monty Python'

另請參閱 rjust()。

str.lower()

Return a copy of the string with all the cased characters [4] converted to lowercase. For example:

>>> 'Lower Method Example'.lower()
'lower method example'

The lowercasing algorithm used is described in section 3.13 'Default Case Folding' of the Unicode Standard [https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-3/#G33992].

str.lstrip(chars=None, /)

Return a copy of the string with leading characters removed. The chars argument is a string specifying the set of characters to be removed. If omitted or None, the chars argument defaults to removing whitespace. The chars argument is not a prefix; rather, all combinations of its values are stripped:

>>> '   spacious   '.lstrip()
'spacious   '
>>> 'www.example.com'.lstrip('cmowz.')
'example.com'

See str.removeprefix() for a method that will remove a single prefix string rather than all of a set of characters. For example:

>>> 'Arthur: three!'.lstrip('Arthur: ')
'ee!'
>>> 'Arthur: three!'.removeprefix('Arthur: ')
'three!'

static str.maketrans(dict, /)

static str.maketrans(from, to, remove='', /)

This static method returns a translation table usable for str.translate().

If there is only one argument, it must be a dictionary mapping Unicode ordinals (integers) or characters (strings of length 1) to Unicode ordinals, strings (of arbitrary lengths) or None. Character keys will then be converted to ordinals.

If there are two arguments, they must be strings of equal length, and in the resulting dictionary, each character in from will be mapped to the character at the same position in to. If there is a third argument, it must be a string, whose characters will be mapped to None in the result.

str.partition(sep, /)

Split the string at the first occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing the string itself, followed by two empty strings.

str.removeprefix(prefix, /)

If the string starts with the prefix string, return string[len(prefix):]. Otherwise, return a copy of the original string:

>>> 'TestHook'.removeprefix('Test')
'Hook'
>>> 'BaseTestCase'.removeprefix('Test')
'BaseTestCase'

在 3.9 版被加入.

另請參閱 removesuffix() 和 startswith()。

str.removesuffix(suffix, /)

If the string ends with the suffix string and that suffix is not empty, return string[:-len(suffix)]. Otherwise, return a copy of the original string:

>>> 'MiscTests'.removesuffix('Tests')
'Misc'
>>> 'TmpDirMixin'.removesuffix('Tests')
'TmpDirMixin'

在 3.9 版被加入.

另請參閱 removeprefix() 和 endswith()。

str.replace(old, new, /, count=-1)

Return a copy of the string with all occurrences of substring old replaced by new. If count is given, only the first count occurrences are replaced. If count is not specified or -1, then all occurrences are replaced. For example:

>>> 'spam, spam, spam'.replace('spam', 'eggs')
'eggs, eggs, eggs'
>>> 'spam, spam, spam'.replace('spam', 'eggs', 1)
'eggs, spam, spam'

在 3.13 版的變更: count 現在作為關鍵字引數被支援。

str.rfind(sub[, start[, end]])

Return the highest index in the string where substring sub is found, such that sub is contained within s[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 on failure. For example:

>>> 'spam, spam, spam'.rfind('sp')
12
>>> 'spam, spam, spam'.rfind('sp', 0, 10)
6

另請參閱 find() 和 rindex()。

str.rindex(sub[, start[, end]])

Like rfind() but raises ValueError when the substring sub is not found.

str.rjust(width, fillchar=' ', /)

Return the string right justified in a string of length width. Padding is done using the specified fillchar (default is an ASCII space). The original string is returned if width is less than or equal to len(s).

str.rpartition(sep, /)

Split the string at the last occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing two empty strings, followed by the string itself.

舉例來說：

>>> 'Monty Python'.rpartition(' ')
('Monty', ' ', 'Python')
>>> "Monty Python's Flying Circus".rpartition(' ')
("Monty Python's Flying", ' ', 'Circus')
>>> 'Monty Python'.rpartition('-')
('', '', 'Monty Python')

另請參閱 partition()。

str.rsplit(sep=None, maxsplit=-1)

Return a list of the words in the string, using sep as the delimiter string. If maxsplit is given, at most maxsplit splits are done, the rightmost ones. If sep is not specified or None, any whitespace string is a separator. Except for splitting from the right, rsplit() behaves like split() which is described in detail below.

str.rstrip(chars=None, /)

Return a copy of the string with trailing characters removed. The chars argument is a string specifying the set of characters to be removed. If omitted or None, the chars argument defaults to removing whitespace. The chars argument is not a suffix; rather, all combinations of its values are stripped:

>>> '   spacious   '.rstrip()
'   spacious'
>>> 'mississippi'.rstrip('ipz')
'mississ'

See str.removesuffix() for a method that will remove a single suffix string rather than all of a set of characters. For example:

>>> 'Monty Python'.rstrip(' Python')
'M'
>>> 'Monty Python'.removesuffix(' Python')
'Monty'

str.split(sep=None, maxsplit=-1)

Return a list of the words in the string, using sep as the delimiter string. If maxsplit is given, at most maxsplit splits are done (thus, the list will have at most maxsplit+1 elements). If maxsplit is not specified or -1, then there is no limit on the number of splits (all possible splits are made).

If sep is given, consecutive delimiters are not grouped together and are deemed to delimit empty strings (for example, '1,,2'.split(',') returns ['1', '', '2']). The sep argument may consist of multiple characters as a single delimiter (to split with multiple delimiters, use re.split()). Splitting an empty string with a specified separator returns [''].

舉例來說：

>>> '1,2,3'.split(',')
['1', '2', '3']
>>> '1,2,3'.split(',', maxsplit=1)
['1', '2,3']
>>> '1,2,,3,'.split(',')
['1', '2', '', '3', '']
>>> '1<>2<>3<4'.split('<>')
['1', '2', '3<4']

If sep is not specified or is None, a different splitting algorithm is applied: runs of consecutive whitespace are regarded as a single separator, and the result will contain no empty strings at the start or end if the string has leading or trailing whitespace. Consequently, splitting an empty string or a string consisting of just whitespace with a None separator returns [].

舉例來說：

>>> '1 2 3'.split()
['1', '2', '3']
>>> '1 2 3'.split(maxsplit=1)
['1', '2 3']
>>> '   1   2   3   '.split()
['1', '2', '3']

If sep is not specified or is None and maxsplit is 0, only leading runs of consecutive whitespace are considered.

舉例來說：

>>> "".split(None, 0)
[]
>>> "   ".split(None, 0)
[]
>>> "   foo   ".split(maxsplit=0)
['foo   ']

另請參閱 join()。

str.splitlines(keepends=False)

Return a list of the lines in the string, breaking at line boundaries. Line breaks are not included in the resulting list unless keepends is given and true.

This method splits on the following line boundaries. In particular, the boundaries are a superset of universal newlines.

Representation

描述

\n

Line Feed

\r

Carriage Return

\r\n

Carriage Return + Line Feed

\v 或 \x0b

Line Tabulation

\f 或 \x0c

Form Feed

\x1c

File Separator

\x1d

Group Separator

\x1e

Record Separator

\x85

Next Line (C1 Control Code)

\u2028

Line Separator

\u2029

Paragraph Separator

在 3.2 版的變更: \v and \f added to list of line boundaries.

舉例來說：

>>> 'ab c\n\nde fg\rkl\r\n'.splitlines()
['ab c', '', 'de fg', 'kl']
>>> 'ab c\n\nde fg\rkl\r\n'.splitlines(keepends=True)
['ab c\n', '\n', 'de fg\r', 'kl\r\n']

Unlike split() when a delimiter string sep is given, this method returns an empty list for the empty string, and a terminal line break does not result in an extra line:

>>> "".splitlines()
[]
>>> "One line\n".splitlines()
['One line']

For comparison, split('\n') gives:

>>> ''.split('\n')
['']
>>> 'Two lines\n'.split('\n')
['Two lines', '']

str.startswith(prefix[, start[, end]])

Return True if string starts with the prefix, otherwise return False. prefix can also be a tuple of prefixes to look for. With optional start, test string beginning at that position. With optional end, stop comparing string at that position.

str.strip(chars=None, /)

Return a copy of the string with the leading and trailing characters removed. The chars argument is a string specifying the set of characters to be removed. If omitted or None, the chars argument defaults to removing whitespace. The chars argument is not a prefix or suffix; rather, all combinations of its values are stripped:

>>> '   spacious   '.strip()
'spacious'
>>> 'www.example.com'.strip('cmowz.')
'example'

The outermost leading and trailing chars argument values are stripped from the string. Characters are removed from the leading end until reaching a string character that is not contained in the set of characters in chars. A similar action takes place on the trailing end. For example:

>>> comment_string = '#....... Section 3.2.1 Issue #32 .......'
>>> comment_string.strip('.#! ')
'Section 3.2.1 Issue #32'

str.swapcase()

Return a copy of the string with uppercase characters converted to lowercase and vice versa. Note that it is not necessarily true that s.swapcase().swapcase() == s.

str.title()

Return a titlecased version of the string where words start with an uppercase character and the remaining characters are lowercase.

舉例來說：

>>> 'Hello world'.title()
'Hello World'

The algorithm uses a simple language-independent definition of a word as groups of consecutive letters. The definition works in many contexts but it means that apostrophes in contractions and possessives form word boundaries, which may not be the desired result:

>>> "they're bill's friends from the UK".title()
"They'Re Bill'S Friends From The Uk"

The string.capwords() function does not have this problem, as it splits words on spaces only.

Alternatively, a workaround for apostrophes can be constructed using regular expressions:

>>> import re
>>> def titlecase(s):
...     return re.sub(r"[A-Za-z]+('[A-Za-z]+)?",
...                   lambda mo: mo.group(0).capitalize(),
...                   s)
...
>>> titlecase("they're bill's friends.")
"They're Bill's Friends."

另請參閱 istitle()。

str.translate(table, /)

Return a copy of the string in which each character has been mapped through the given translation table. The table must be an object that implements indexing via __getitem__(), typically a mapping or sequence. When indexed by a Unicode ordinal (an integer), the table object can do any of the following: return a Unicode ordinal or a string, to map the character to one or more other characters; return None, to delete the character from the return string; or raise a LookupError exception, to map the character to itself.

You can use str.maketrans() to create a translation map from character-to-character mappings in different formats.

See also the codecs module for a more flexible approach to custom character mappings.

str.upper()

Return a copy of the string with all the cased characters [4] converted to uppercase. Note that s.upper().isupper() might be False if s contains uncased characters or if the Unicode category of the resulting character(s) is not "Lu" (Letter, uppercase), but e.g. "Lt" (Letter, titlecase).

The uppercasing algorithm used is described in section 3.13 'Default Case Folding' of the Unicode Standard [https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-3/#G33992].

str.zfill(width, /)

Return a copy of the string left filled with ASCII '0' digits to make a string of length width. A leading sign prefix ('+'/'-') is handled by inserting the padding after the sign character rather than before. The original string is returned if width is less than or equal to len(s).

舉例來說：

>>> "42".zfill(5)
'00042'
>>> "-42".zfill(5)
'-0042'

Formatted String Literals (f-strings)

在 3.6 版被加入.

在 3.7 版的變更: The await and async for can be used in expressions within f-strings.

在 3.8 版的變更: Added the debug specifier (=)

在 3.12 版的變更: Many restrictions on expressions within f-strings have been removed. Notably, nested strings, comments, and backslashes are now permitted.

An f-string (formally a formatted string literal) is a string literal that is prefixed with f or F. This type of string literal allows embedding the results of arbitrary Python expressions within replacement fields, which are delimited by curly brackets ({}). Each replacement field must contain an expression, optionally followed by:

a debug specifier -- an equal sign (=);

a conversion specifier -- !s, !r or !a; and/or

a format specifier prefixed with a colon (:).

See the Lexical Analysis section on f-strings for details on the syntax of these fields.

Debug specifier

在 3.8 版被加入.

If a debug specifier -- an equal sign (=) -- appears after the replacement field expression, the resulting f-string will contain the expression's source, the equal sign, and the value of the expression. This is often useful for debugging:

>>> number = 14.3
>>> f'{number=}'
'number=14.3'

Whitespace before, inside and after the expression, as well as whitespace after the equal sign, is significant --- it is retained in the result:

>>> f'{ number  -  4  = }'
' number  -  4  = 10.3'

Conversion specifier

By default, the value of a replacement field expression is converted to a string using str():

>>> from fractions import Fraction
>>> one_third = Fraction(1, 3)
>>> f'{one_third}'
'1/3'

When a debug specifier but no format specifier is used, the default conversion instead uses repr():

>>> f'{one_third = }'
'one_third = Fraction(1, 3)'

The conversion can be specified explicitly using one of these specifiers:

!s 用於 str()

!r 用於 repr()

!a 用於 ascii()

舉例來說：

>>> str(one_third)
'1/3'
>>> repr(one_third)
'Fraction(1, 3)'

>>> f'{one_third!s} is {one_third!r}'
'1/3 is Fraction(1, 3)'

>>> string = "¡kočka 😸!"
>>> ascii(string)
"'\\xa1ko\\u010dka \\U0001f638!'"

>>> f'{string = !a}'
"string = '\\xa1ko\\u010dka \\U0001f638!'"

Format specifier

After the expression has been evaluated, and possibly converted using an explicit conversion specifier, it is formatted using the format() function. If the replacement field includes a format specifier introduced by a colon (:), the specifier is passed to format() as the second argument. The result of format() is then used as the final value for the replacement field. For example:

>>> from fractions import Fraction
>>> one_third = Fraction(1, 3)
>>> f'{one_third:.6f}'
'0.333333'
>>> f'{one_third:_^+10}'
'___+1/3___'
>>> >>> f'{one_third!r:_^20}'
'___Fraction(1, 3)___'
>>> f'{one_third = :~>10}~'
'one_third = ~~~~~~~1/3~'

模板字串字面值 (t-strings)

An t-string (formally a template string literal) is a string literal that is prefixed with t or T.

These strings follow the same syntax and evaluation rules as formatted string literals, with for the following differences:

Rather than evaluating to a str object, template string literals evaluate to a string.templatelib.Template object.

The format() protocol is not used. Instead, the format specifier and conversions (if any) are passed to a new Interpolation object that is created for each evaluated expression. It is up to code that processes the resulting Template object to decide how to handle format specifiers and conversions.

Format specifiers containing nested replacement fields are evaluated eagerly, prior to being passed to the Interpolation object. For instance, an interpolation of the form {amount:.{precision}f} will evaluate the inner expression {precision} to determine the value of the format_spec attribute. If precision were to be 2, the resulting format specifier would be '.2f'.

When the equals sign '=' is provided in an interpolation expression, the text of the expression is appended to the literal string that precedes the relevant interpolation. This includes the equals sign and any surrounding whitespace. The Interpolation instance for the expression will be created as normal, except that conversion will be set to 'r' (repr()) by default. If an explicit conversion or format specifier are provided, this will override the default behaviour.

printf-style String Formatting

備註

The formatting operations described here exhibit a variety of quirks that lead to a number of common errors (such as failing to display tuples and dictionaries correctly).

Using formatted string literals, the str.format() interface, or string.Template may help avoid these errors. Each of these alternatives provides their own trade-offs and benefits of simplicity, flexibility, and/or extensibility.

String objects have one unique built-in operation: the % operator (modulo). This is also known as the string formatting or interpolation operator. Given format % values (where format is a string), % conversion specifications in format are replaced with zero or more elements of values. The effect is similar to using the sprintf() function in the C language. For example:

>>> print('%s has %d quote types.' % ('Python', 2))
Python has 2 quote types.

If format requires a single argument, values may be a single non-tuple object. [5] Otherwise, values must be a tuple with exactly the number of items specified by the format string, or a single mapping object (for example, a dictionary).

A conversion specifier contains two or more characters and has the following components, which must occur in this order:

The '%' character, which marks the start of the specifier.

Mapping key (optional), consisting of a parenthesised sequence of characters (for example, (somename)).

Conversion flags (optional), which affect the result of some conversion types.

Minimum field width (optional). If specified as an '*' (asterisk), the actual width is read from the next element of the tuple in values, and the object to convert comes after the minimum field width and optional precision.

Precision (optional), given as a '.' (dot) followed by the precision. If specified as '*' (an asterisk), the actual precision is read from the next element of the tuple in values, and the value to convert comes after the precision.

Length modifier (optional).

Conversion type.

When the right argument is a dictionary (or other mapping type), then the formats in the string must include a parenthesised mapping key into that dictionary inserted immediately after the '%' character. The mapping key selects the value to be formatted from the mapping. For example:

>>> print('%(language)s has %(number)03d quote types.' %
...       {'language': "Python", "number": 2})
Python has 002 quote types.

In this case no * specifiers may occur in a format (since they require a sequential parameter list).

The conversion flag characters are:

Flag

含義

'#'

The value conversion will use the "alternate form" (where defined below).

'0'

The conversion will be zero padded for numeric values.

'-'

The converted value is left adjusted (overrides the '0' conversion if both are given).

' '

(a space) A blank should be left before a positive number (or empty string) produced by a signed conversion.

'+'

A sign character ('+' or '-') will precede the conversion (overrides a "space" flag).

A length modifier (h, l, or L) may be present, but is ignored as it is not necessary for Python -- so e.g. %ld is identical to %d.

The conversion types are:

Conversion

含義

註解

'd'

Signed integer decimal.

'i'

Signed integer decimal.

'o'

Signed octal value.

(1)

'u'

Obsolete type -- it is identical to 'd'.

(6)

'x'

Signed hexadecimal (lowercase).

(2)

'X'

Signed hexadecimal (uppercase).

(2)

'e'

Floating-point exponential format (lowercase).

(3)

'E'

Floating-point exponential format (uppercase).

(3)

'f'

Floating-point decimal format.

(3)

'F'

Floating-point decimal format.

(3)

'g'

Floating-point format. Uses lowercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.

(4)

'G'

Floating-point format. Uses uppercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.

(4)

'c'

Single character (accepts integer or single character string).

'r'

String (converts any Python object using repr()).

(5)

's'

String (converts any Python object using str()).

(5)

'a'

String (converts any Python object using ascii()).

(5)

'%'

No argument is converted, results in a '%' character in the result.

註解：

The alternate form causes a leading octal specifier ('0o') to be inserted before the first digit.

The alternate form causes a leading '0x' or '0X' (depending on whether the 'x' or 'X' format was used) to be inserted before the first digit.

The alternate form causes the result to always contain a decimal point, even if no digits follow it.

The precision determines the number of digits after the decimal point and defaults to 6.

The alternate form causes the result to always contain a decimal point, and trailing zeroes are not removed as they would otherwise be.

The precision determines the number of significant digits before and after the decimal point and defaults to 6.

If precision is N, the output is truncated to N characters.

參閱 PEP 237 [https://peps.python.org/pep-0237/]。

Since Python strings have an explicit length, %s conversions do not assume that '\0' is the end of the string.

在 3.1 版的變更: %f conversions for numbers whose absolute value is over 1e50 are no longer replaced by %g conversions.

Binary Sequence Types --- bytes, bytearray, memoryview

The core built-in types for manipulating binary data are bytes and bytearray. They are supported by memoryview which uses the buffer protocol to access the memory of other binary objects without needing to make a copy.

The array module supports efficient storage of basic data types like 32-bit integers and IEEE754 double-precision floating values.

Bytes Objects

Bytes objects are immutable sequences of single bytes. Since many major binary protocols are based on the ASCII text encoding, bytes objects offer several methods that are only valid when working with ASCII compatible data and are closely related to string objects in a variety of other ways.

class bytes(source=b'')

class bytes(source, encoding, errors='strict')

Firstly, the syntax for bytes literals is largely the same as that for string literals, except that a b prefix is added:

Single quotes: b'still allows embedded "double" quotes'

Double quotes: b"still allows embedded 'single' quotes"

Triple quoted: b'''3 single quotes''', b"""3 double quotes"""

Only ASCII characters are permitted in bytes literals (regardless of the declared source code encoding). Any binary values over 127 must be entered into bytes literals using the appropriate escape sequence.

As with string literals, bytes literals may also use a r prefix to disable processing of escape sequences. See String and Bytes literals for more about the various forms of bytes literal, including supported escape sequences.

While bytes literals and representations are based on ASCII text, bytes objects actually behave like immutable sequences of integers, with each value in the sequence restricted such that 0 <= x < 256 (attempts to violate this restriction will trigger ValueError). This is done deliberately to emphasise that while many binary formats include ASCII based elements and can be usefully manipulated with some text-oriented algorithms, this is not generally the case for arbitrary binary data (blindly applying text processing algorithms to binary data formats that are not ASCII compatible will usually lead to data corruption).

In addition to the literal forms, bytes objects can be created in a number of other ways:

A zero-filled bytes object of a specified length: bytes(10)

From an iterable of integers: bytes(range(20))

Copying existing binary data via the buffer protocol: bytes(obj)

另見內建的 bytes。

Since 2 hexadecimal digits correspond precisely to a single byte, hexadecimal numbers are a commonly used format for describing binary data. Accordingly, the bytes type has an additional class method to read data in that format:

classmethod fromhex(string, /)

This bytes class method returns a bytes object, decoding the given string object. The string must contain two hexadecimal digits per byte, with ASCII whitespace being ignored.

>>> bytes.fromhex('2Ef0 F1f2  ')
b'.\xf0\xf1\xf2'

在 3.7 版的變更: bytes.fromhex() now skips all ASCII whitespace in the string, not just spaces.

在 3.14 版的變更: bytes.fromhex() now accepts ASCII bytes and bytes-like objects as input.

A reverse conversion function exists to transform a bytes object into its hexadecimal representation.

hex(*, bytes_per_sep=1)

hex(sep, bytes_per_sep=1)

Return a string object containing two hexadecimal digits for each byte in the instance.

>>> b'\xf0\xf1\xf2'.hex()
'f0f1f2'

If you want to make the hex string easier to read, you can specify a single character separator sep parameter to include in the output. By default, this separator will be included between each byte. A second optional bytes_per_sep parameter controls the spacing. Positive values calculate the separator position from the right, negative values from the left.

>>> value = b'\xf0\xf1\xf2'
>>> value.hex('-')
'f0-f1-f2'
>>> value.hex('_', 2)
'f0_f1f2'
>>> b'UUDDLRLRAB'.hex(' ', -4)
'55554444 4c524c52 4142'

在 3.5 版被加入.

在 3.8 版的變更: bytes.hex() now supports optional sep and bytes_per_sep parameters to insert separators between bytes in the hex output.

Since bytes objects are sequences of integers (akin to a tuple), for a bytes object b, b[0] will be an integer, while b[0:1] will be a bytes object of length 1. (This contrasts with text strings, where both indexing and slicing will produce a string of length 1)

The representation of bytes objects uses the literal format (b'...') since it is often more useful than e.g. bytes([46, 46, 46]). You can always convert a bytes object into a list of integers using list(b).

Bytearray 物件

bytearray objects are a mutable counterpart to bytes objects.

class bytearray(source=b'')

class bytearray(source, encoding, errors='strict')

There is no dedicated literal syntax for bytearray objects, instead they are always created by calling the constructor:

建立一個空的實例：bytearray()

Creating a zero-filled instance with a given length: bytearray(10)

From an iterable of integers: bytearray(range(20))

Copying existing binary data via the buffer protocol: bytearray(b'Hi!')

As bytearray objects are mutable, they support the mutable sequence operations in addition to the common bytes and bytearray operations described in Bytes 和 Bytearray 的操作.

另見內建的 bytearray。

Since 2 hexadecimal digits correspond precisely to a single byte, hexadecimal numbers are a commonly used format for describing binary data. Accordingly, the bytearray type has an additional class method to read data in that format:

classmethod fromhex(string, /)

This bytearray class method returns bytearray object, decoding the given string object. The string must contain two hexadecimal digits per byte, with ASCII whitespace being ignored.

>>> bytearray.fromhex('2Ef0 F1f2  ')
bytearray(b'.\xf0\xf1\xf2')

在 3.7 版的變更: bytearray.fromhex() now skips all ASCII whitespace in the string, not just spaces.

在 3.14 版的變更: bytearray.fromhex() now accepts ASCII bytes and bytes-like objects as input.

A reverse conversion function exists to transform a bytearray object into its hexadecimal representation.

hex(*, bytes_per_sep=1)

hex(sep, bytes_per_sep=1)

Return a string object containing two hexadecimal digits for each byte in the instance.

>>> bytearray(b'\xf0\xf1\xf2').hex()
'f0f1f2'

在 3.5 版被加入.

在 3.8 版的變更: Similar to bytes.hex(), bytearray.hex() now supports optional sep and bytes_per_sep parameters to insert separators between bytes in the hex output.

resize(size, /)

Resize the bytearray to contain size bytes. size must be greater than or equal to 0.

If the bytearray needs to shrink, bytes beyond size are truncated.

If the bytearray needs to grow, all new bytes, those beyond size, will be set to null bytes.

等同於：

>>> def resize(ba, size):
...     if len(ba) > size:
...         del ba[size:]
...     else:
...         ba += b'\0' * (size - len(ba))

範例：

>>> shrink = bytearray(b'abc')
>>> shrink.resize(1)
>>> (shrink, len(shrink))
(bytearray(b'a'), 1)
>>> grow = bytearray(b'abc')
>>> grow.resize(5)
>>> (grow, len(grow))
(bytearray(b'abc\x00\x00'), 5)

在 3.14 版被加入.

Since bytearray objects are sequences of integers (akin to a list), for a bytearray object b, b[0] will be an integer, while b[0:1] will be a bytearray object of length 1. (This contrasts with text strings, where both indexing and slicing will produce a string of length 1)

The representation of bytearray objects uses the bytes literal format (bytearray(b'...')) since it is often more useful than e.g. bytearray([46, 46, 46]). You can always convert a bytearray object into a list of integers using list(b).

Bytes 和 Bytearray 的操作

Both bytes and bytearray objects support the common sequence operations. They interoperate not just with operands of the same type, but with any bytes-like object. Due to this flexibility, they can be freely mixed in operations without causing errors. However, the return type of the result may depend on the order of operands.

備註

The methods on bytes and bytearray objects don't accept strings as their arguments, just as the methods on strings don't accept bytes as their arguments. For example, you have to write:

a = "abc"
b = a.replace("a", "f")

和：

a = b"abc"
b = a.replace(b"a", b"f")

Some bytes and bytearray operations assume the use of ASCII compatible binary formats, and hence should be avoided when working with arbitrary binary data. These restrictions are covered below.

備註

Using these ASCII based operations to manipulate binary data that is not stored in an ASCII based format may lead to data corruption.

The following methods on bytes and bytearray objects can be used with arbitrary binary data.

bytes.count(sub[, start[, end]])

bytearray.count(sub[, start[, end]])

Return the number of non-overlapping occurrences of subsequence sub in the range [start, end]. Optional arguments start and end are interpreted as in slice notation.

The subsequence to search for may be any bytes-like object or an integer in the range 0 to 255.

If sub is empty, returns the number of empty slices between characters which is the length of the bytes object plus one.

在 3.3 版的變更: Also accept an integer in the range 0 to 255 as the subsequence.

bytes.removeprefix(prefix, /)

bytearray.removeprefix(prefix, /)

If the binary data starts with the prefix string, return bytes[len(prefix):]. Otherwise, return a copy of the original binary data:

>>> b'TestHook'.removeprefix(b'Test')
b'Hook'
>>> b'BaseTestCase'.removeprefix(b'Test')
b'BaseTestCase'

prefix 可以是任何的 bytes-like object。

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

在 3.9 版被加入.

bytes.removesuffix(suffix, /)

bytearray.removesuffix(suffix, /)

If the binary data ends with the suffix string and that suffix is not empty, return bytes[:-len(suffix)]. Otherwise, return a copy of the original binary data:

>>> b'MiscTests'.removesuffix(b'Tests')
b'Misc'
>>> b'TmpDirMixin'.removesuffix(b'Tests')
b'TmpDirMixin'

The suffix may be any bytes-like object.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

在 3.9 版被加入.

bytes.decode(encoding='utf-8', errors='strict')

bytearray.decode(encoding='utf-8', errors='strict')

Return the bytes decoded to a str.

encoding defaults to 'utf-8'; see 標準編碼 for possible values.

errors controls how decoding errors are handled. If 'strict' (the default), a UnicodeError exception is raised. Other possible values are 'ignore', 'replace', and any other name registered via codecs.register_error(). See Error Handlers for details.

For performance reasons, the value of errors is not checked for validity unless a decoding error actually occurs, Python 開發模式 is enabled or a debug build is used.

備註

Passing the encoding argument to str allows decoding any bytes-like object directly, without needing to make a temporary bytes or bytearray object.

在 3.1 版的變更: 新增關鍵字引數的支援。

在 3.9 版的變更: The value of the errors argument is now checked in Python 開發模式 and in debug mode.

bytes.endswith(suffix[, start[, end]])

bytearray.endswith(suffix[, start[, end]])

Return True if the binary data ends with the specified suffix, otherwise return False. suffix can also be a tuple of suffixes to look for. With optional start, test beginning at that position. With optional end, stop comparing at that position.

The suffix(es) to search for may be any bytes-like object.

bytes.find(sub[, start[, end]])

bytearray.find(sub[, start[, end]])

Return the lowest index in the data where the subsequence sub is found, such that sub is contained in the slice s[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 if sub is not found.

The subsequence to search for may be any bytes-like object or an integer in the range 0 to 255.

備註

The find() method should be used only if you need to know the position of sub. To check if sub is a substring or not, use the in operator:

>>> b'Py' in b'Python'
True

在 3.3 版的變更: Also accept an integer in the range 0 to 255 as the subsequence.

bytes.index(sub[, start[, end]])

bytearray.index(sub[, start[, end]])

Like find(), but raise ValueError when the subsequence is not found.

The subsequence to search for may be any bytes-like object or an integer in the range 0 to 255.

在 3.3 版的變更: Also accept an integer in the range 0 to 255 as the subsequence.

bytes.join(iterable, /)

bytearray.join(iterable, /)

Return a bytes or bytearray object which is the concatenation of the binary data sequences in iterable. A TypeError will be raised if there are any values in iterable that are not bytes-like objects, including str objects. The separator between elements is the contents of the bytes or bytearray object providing this method.

static bytes.maketrans(from, to, /)

static bytearray.maketrans(from, to, /)

This static method returns a translation table usable for bytes.translate() that will map each character in from into the character at the same position in to; from and to must both be bytes-like objects and have the same length.

在 3.1 版被加入.

bytes.partition(sep, /)

bytearray.partition(sep, /)

Split the sequence at the first occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself or its bytearray copy, and the part after the separator. If the separator is not found, return a 3-tuple containing a copy of the original sequence, followed by two empty bytes or bytearray objects.

The separator to search for may be any bytes-like object.

bytes.replace(old, new, count=-1, /)

bytearray.replace(old, new, count=-1, /)

Return a copy of the sequence with all occurrences of subsequence old replaced by new. If the optional argument count is given, only the first count occurrences are replaced.

The subsequence to search for and its replacement may be any bytes-like object.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.rfind(sub[, start[, end]])

bytearray.rfind(sub[, start[, end]])

Return the highest index in the sequence where the subsequence sub is found, such that sub is contained within s[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 on failure.

The subsequence to search for may be any bytes-like object or an integer in the range 0 to 255.

在 3.3 版的變更: Also accept an integer in the range 0 to 255 as the subsequence.

bytes.rindex(sub[, start[, end]])

bytearray.rindex(sub[, start[, end]])

Like rfind() but raises ValueError when the subsequence sub is not found.

The subsequence to search for may be any bytes-like object or an integer in the range 0 to 255.

在 3.3 版的變更: Also accept an integer in the range 0 to 255 as the subsequence.

bytes.rpartition(sep, /)

bytearray.rpartition(sep, /)

Split the sequence at the last occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself or its bytearray copy, and the part after the separator. If the separator is not found, return a 3-tuple containing two empty bytes or bytearray objects, followed by a copy of the original sequence.

The separator to search for may be any bytes-like object.

bytes.startswith(prefix[, start[, end]])

bytearray.startswith(prefix[, start[, end]])

Return True if the binary data starts with the specified prefix, otherwise return False. prefix can also be a tuple of prefixes to look for. With optional start, test beginning at that position. With optional end, stop comparing at that position.

The prefix(es) to search for may be any bytes-like object.

bytes.translate(table, /, delete=b'')

bytearray.translate(table, /, delete=b'')

Return a copy of the bytes or bytearray object where all bytes occurring in the optional argument delete are removed, and the remaining bytes have been mapped through the given translation table, which must be a bytes object of length 256.

You can use the bytes.maketrans() method to create a translation table.

Set the table argument to None for translations that only delete characters:

>>> b'read this short text'.translate(None, b'aeiou')
b'rd ths shrt txt'

在 3.6 版的變更: 支援 delete 關鍵字引數。

The following methods on bytes and bytearray objects have default behaviours that assume the use of ASCII compatible binary formats, but can still be used with arbitrary binary data by passing appropriate arguments. Note that all of the bytearray methods in this section do not operate in place, and instead produce new objects.

bytes.center(width, fillbyte=b' ', /)

bytearray.center(width, fillbyte=b' ', /)

Return a copy of the object centered in a sequence of length width. Padding is done using the specified fillbyte (default is an ASCII space). For bytes objects, the original sequence is returned if width is less than or equal to len(s).

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.ljust(width, fillbyte=b' ', /)

bytearray.ljust(width, fillbyte=b' ', /)

Return a copy of the object left justified in a sequence of length width. Padding is done using the specified fillbyte (default is an ASCII space). For bytes objects, the original sequence is returned if width is less than or equal to len(s).

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.lstrip(bytes=None, /)

bytearray.lstrip(bytes=None, /)

Return a copy of the sequence with specified leading bytes removed. The bytes argument is a binary sequence specifying the set of byte values to be removed. If omitted or None, the bytes argument defaults to removing ASCII whitespace. The bytes argument is not a prefix; rather, all combinations of its values are stripped:

>>> b'   spacious   '.lstrip()
b'spacious   '
>>> b'www.example.com'.lstrip(b'cmowz.')
b'example.com'

The binary sequence of byte values to remove may be any bytes-like object. See removeprefix() for a method that will remove a single prefix string rather than all of a set of characters. For example:

>>> b'Arthur: three!'.lstrip(b'Arthur: ')
b'ee!'
>>> b'Arthur: three!'.removeprefix(b'Arthur: ')
b'three!'

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.rjust(width, fillbyte=b' ', /)

bytearray.rjust(width, fillbyte=b' ', /)

Return a copy of the object right justified in a sequence of length width. Padding is done using the specified fillbyte (default is an ASCII space). For bytes objects, the original sequence is returned if width is less than or equal to len(s).

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.rsplit(sep=None, maxsplit=-1)

bytearray.rsplit(sep=None, maxsplit=-1)

Split the binary sequence into subsequences of the same type, using sep as the delimiter string. If maxsplit is given, at most maxsplit splits are done, the rightmost ones. If sep is not specified or None, any subsequence consisting solely of ASCII whitespace is a separator. Except for splitting from the right, rsplit() behaves like split() which is described in detail below.

bytes.rstrip(bytes=None, /)

bytearray.rstrip(bytes=None, /)

Return a copy of the sequence with specified trailing bytes removed. The bytes argument is a binary sequence specifying the set of byte values to be removed. If omitted or None, the bytes argument defaults to removing ASCII whitespace. The bytes argument is not a suffix; rather, all combinations of its values are stripped:

>>> b'   spacious   '.rstrip()
b'   spacious'
>>> b'mississippi'.rstrip(b'ipz')
b'mississ'

The binary sequence of byte values to remove may be any bytes-like object. See removesuffix() for a method that will remove a single suffix string rather than all of a set of characters. For example:

>>> b'Monty Python'.rstrip(b' Python')
b'M'
>>> b'Monty Python'.removesuffix(b' Python')
b'Monty'

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.split(sep=None, maxsplit=-1)

bytearray.split(sep=None, maxsplit=-1)

Split the binary sequence into subsequences of the same type, using sep as the delimiter string. If maxsplit is given and non-negative, at most maxsplit splits are done (thus, the list will have at most maxsplit+1 elements). If maxsplit is not specified or is -1, then there is no limit on the number of splits (all possible splits are made).

If sep is given, consecutive delimiters are not grouped together and are deemed to delimit empty subsequences (for example, b'1,,2'.split(b',') returns [b'1', b'', b'2']). The sep argument may consist of a multibyte sequence as a single delimiter. Splitting an empty sequence with a specified separator returns [b''] or [bytearray(b'')] depending on the type of object being split. The sep argument may be any bytes-like object.

舉例來說：

>>> b'1,2,3'.split(b',')
[b'1', b'2', b'3']
>>> b'1,2,3'.split(b',', maxsplit=1)
[b'1', b'2,3']
>>> b'1,2,,3,'.split(b',')
[b'1', b'2', b'', b'3', b'']
>>> b'1<>2<>3<4'.split(b'<>')
[b'1', b'2', b'3<4']

If sep is not specified or is None, a different splitting algorithm is applied: runs of consecutive ASCII whitespace are regarded as a single separator, and the result will contain no empty strings at the start or end if the sequence has leading or trailing whitespace. Consequently, splitting an empty sequence or a sequence consisting solely of ASCII whitespace without a specified separator returns [].

舉例來說：

>>> b'1 2 3'.split()
[b'1', b'2', b'3']
>>> b'1 2 3'.split(maxsplit=1)
[b'1', b'2 3']
>>> b'   1   2   3   '.split()
[b'1', b'2', b'3']

bytes.strip(bytes=None, /)

bytearray.strip(bytes=None, /)

Return a copy of the sequence with specified leading and trailing bytes removed. The bytes argument is a binary sequence specifying the set of byte values to be removed. If omitted or None, the bytes argument defaults to removing ASCII whitespace. The bytes argument is not a prefix or suffix; rather, all combinations of its values are stripped:

>>> b'   spacious   '.strip()
b'spacious'
>>> b'www.example.com'.strip(b'cmowz.')
b'example'

The binary sequence of byte values to remove may be any bytes-like object.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

The following methods on bytes and bytearray objects assume the use of ASCII compatible binary formats and should not be applied to arbitrary binary data. Note that all of the bytearray methods in this section do not operate in place, and instead produce new objects.

bytes.capitalize()

bytearray.capitalize()

Return a copy of the sequence with each byte interpreted as an ASCII character, and the first byte capitalized and the rest lowercased. Non-ASCII byte values are passed through unchanged.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.expandtabs(tabsize=8)

bytearray.expandtabs(tabsize=8)

Return a copy of the sequence where all ASCII tab characters are replaced by one or more ASCII spaces, depending on the current column and the given tab size. Tab positions occur every tabsize bytes (default is 8, giving tab positions at columns 0, 8, 16 and so on). To expand the sequence, the current column is set to zero and the sequence is examined byte by byte. If the byte is an ASCII tab character (b'\t'), one or more space characters are inserted in the result until the current column is equal to the next tab position. (The tab character itself is not copied.) If the current byte is an ASCII newline (b'\n') or carriage return (b'\r'), it is copied and the current column is reset to zero. Any other byte value is copied unchanged and the current column is incremented by one regardless of how the byte value is represented when printed:

>>> b'01\t012\t0123\t01234'.expandtabs()
b'01      012     0123    01234'
>>> b'01\t012\t0123\t01234'.expandtabs(4)
b'01  012 0123    01234'

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.isalnum()

bytearray.isalnum()

Return True if all bytes in the sequence are alphabetical ASCII characters or ASCII decimal digits and the sequence is not empty, False otherwise. Alphabetic ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'. ASCII decimal digits are those byte values in the sequence b'0123456789'.

舉例來說：

>>> b'ABCabc1'.isalnum()
True
>>> b'ABC abc1'.isalnum()
False

bytes.isalpha()

bytearray.isalpha()

Return True if all bytes in the sequence are alphabetic ASCII characters and the sequence is not empty, False otherwise. Alphabetic ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.

舉例來說：

>>> b'ABCabc'.isalpha()
True
>>> b'ABCabc1'.isalpha()
False

bytes.isascii()

bytearray.isascii()

Return True if the sequence is empty or all bytes in the sequence are ASCII, False otherwise. ASCII bytes are in the range 0-0x7F.

在 3.7 版被加入.

bytes.isdigit()

bytearray.isdigit()

Return True if all bytes in the sequence are ASCII decimal digits and the sequence is not empty, False otherwise. ASCII decimal digits are those byte values in the sequence b'0123456789'.

舉例來說：

>>> b'1234'.isdigit()
True
>>> b'1.23'.isdigit()
False

bytes.islower()

bytearray.islower()

Return True if there is at least one lowercase ASCII character in the sequence and no uppercase ASCII characters, False otherwise.

舉例來說：

>>> b'hello world'.islower()
True
>>> b'Hello world'.islower()
False

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

bytes.isspace()

bytearray.isspace()

Return True if all bytes in the sequence are ASCII whitespace and the sequence is not empty, False otherwise. ASCII whitespace characters are those byte values in the sequence b' \t\n\r\x0b\f' (space, tab, newline, carriage return, vertical tab, form feed).

bytes.istitle()

bytearray.istitle()

Return True if the sequence is ASCII titlecase and the sequence is not empty, False otherwise. See bytes.title() for more details on the definition of "titlecase".

舉例來說：

>>> b'Hello World'.istitle()
True
>>> b'Hello world'.istitle()
False

bytes.isupper()

bytearray.isupper()

Return True if there is at least one uppercase alphabetic ASCII character in the sequence and no lowercase ASCII characters, False otherwise.

舉例來說：

>>> b'HELLO WORLD'.isupper()
True
>>> b'Hello world'.isupper()
False

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

bytes.lower()

bytearray.lower()

Return a copy of the sequence with all the uppercase ASCII characters converted to their corresponding lowercase counterpart.

舉例來說：

>>> b'Hello World'.lower()
b'hello world'

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.splitlines(keepends=False)

bytearray.splitlines(keepends=False)

Return a list of the lines in the binary sequence, breaking at ASCII line boundaries. This method uses the universal newlines approach to splitting lines. Line breaks are not included in the resulting list unless keepends is given and true.

舉例來說：

>>> b'ab c\n\nde fg\rkl\r\n'.splitlines()
[b'ab c', b'', b'de fg', b'kl']
>>> b'ab c\n\nde fg\rkl\r\n'.splitlines(keepends=True)
[b'ab c\n', b'\n', b'de fg\r', b'kl\r\n']

Unlike split() when a delimiter string sep is given, this method returns an empty list for the empty string, and a terminal line break does not result in an extra line:

>>> b"".split(b'\n'), b"Two lines\n".split(b'\n')
([b''], [b'Two lines', b''])
>>> b"".splitlines(), b"One line\n".splitlines()
([], [b'One line'])

bytes.swapcase()

bytearray.swapcase()

Return a copy of the sequence with all the lowercase ASCII characters converted to their corresponding uppercase counterpart and vice-versa.

舉例來說：

>>> b'Hello World'.swapcase()
b'hELLO wORLD'

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

Unlike str.swapcase(), it is always the case that bin.swapcase().swapcase() == bin for the binary versions. Case conversions are symmetrical in ASCII, even though that is not generally true for arbitrary Unicode code points.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.title()

bytearray.title()

Return a titlecased version of the binary sequence where words start with an uppercase ASCII character and the remaining characters are lowercase. Uncased byte values are left unmodified.

舉例來說：

>>> b'Hello world'.title()
b'Hello World'

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'. All other byte values are uncased.

The algorithm uses a simple language-independent definition of a word as groups of consecutive letters. The definition works in many contexts but it means that apostrophes in contractions and possessives form word boundaries, which may not be the desired result:

>>> b"they're bill's friends from the UK".title()
b"They'Re Bill'S Friends From The Uk"

A workaround for apostrophes can be constructed using regular expressions:

>>> import re
>>> def titlecase(s):
...     return re.sub(rb"[A-Za-z]+('[A-Za-z]+)?",
...                   lambda mo: mo.group(0)[0:1].upper() +
...                              mo.group(0)[1:].lower(),
...                   s)
...
>>> titlecase(b"they're bill's friends.")
b"They're Bill's Friends."

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.upper()

bytearray.upper()

Return a copy of the sequence with all the lowercase ASCII characters converted to their corresponding uppercase counterpart.

舉例來說：

>>> b'Hello World'.upper()
b'HELLO WORLD'

Lowercase ASCII characters are those byte values in the sequence b'abcdefghijklmnopqrstuvwxyz'. Uppercase ASCII characters are those byte values in the sequence b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

bytes.zfill(width, /)

bytearray.zfill(width, /)

Return a copy of the sequence left filled with ASCII b'0' digits to make a sequence of length width. A leading sign prefix (b'+'/ b'-') is handled by inserting the padding after the sign character rather than before. For bytes objects, the original sequence is returned if width is less than or equal to len(seq).

舉例來說：

>>> b"42".zfill(5)
b'00042'
>>> b"-42".zfill(5)
b'-0042'

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

printf-style Bytes Formatting

備註

The formatting operations described here exhibit a variety of quirks that lead to a number of common errors (such as failing to display tuples and dictionaries correctly). If the value being printed may be a tuple or dictionary, wrap it in a tuple.

Bytes objects (bytes/bytearray) have one unique built-in operation: the % operator (modulo). This is also known as the bytes formatting or interpolation operator. Given format % values (where format is a bytes object), % conversion specifications in format are replaced with zero or more elements of values. The effect is similar to using the sprintf() in the C language.

If format requires a single argument, values may be a single non-tuple object. [5] Otherwise, values must be a tuple with exactly the number of items specified by the format bytes object, or a single mapping object (for example, a dictionary).

A conversion specifier contains two or more characters and has the following components, which must occur in this order:

The '%' character, which marks the start of the specifier.

Mapping key (optional), consisting of a parenthesised sequence of characters (for example, (somename)).

Conversion flags (optional), which affect the result of some conversion types.

Minimum field width (optional). If specified as an '*' (asterisk), the actual width is read from the next element of the tuple in values, and the object to convert comes after the minimum field width and optional precision.

Precision (optional), given as a '.' (dot) followed by the precision. If specified as '*' (an asterisk), the actual precision is read from the next element of the tuple in values, and the value to convert comes after the precision.

Length modifier (optional).

Conversion type.

When the right argument is a dictionary (or other mapping type), then the formats in the bytes object must include a parenthesised mapping key into that dictionary inserted immediately after the '%' character. The mapping key selects the value to be formatted from the mapping. For example:

>>> print(b'%(language)s has %(number)03d quote types.' %
...       {b'language': b"Python", b"number": 2})
b'Python has 002 quote types.'

In this case no * specifiers may occur in a format (since they require a sequential parameter list).

The conversion flag characters are:

Flag

含義

'#'

The value conversion will use the "alternate form" (where defined below).

'0'

The conversion will be zero padded for numeric values.

'-'

The converted value is left adjusted (overrides the '0' conversion if both are given).

' '

(a space) A blank should be left before a positive number (or empty string) produced by a signed conversion.

'+'

A sign character ('+' or '-') will precede the conversion (overrides a "space" flag).

A length modifier (h, l, or L) may be present, but is ignored as it is not necessary for Python -- so e.g. %ld is identical to %d.

The conversion types are:

Conversion

含義

註解

'd'

Signed integer decimal.

'i'

Signed integer decimal.

'o'

Signed octal value.

(1)

'u'

Obsolete type -- it is identical to 'd'.

(8)

'x'

Signed hexadecimal (lowercase).

(2)

'X'

Signed hexadecimal (uppercase).

(2)

'e'

Floating-point exponential format (lowercase).

(3)

'E'

Floating-point exponential format (uppercase).

(3)

'f'

Floating-point decimal format.

(3)

'F'

Floating-point decimal format.

(3)

'g'

Floating-point format. Uses lowercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.

(4)

'G'

Floating-point format. Uses uppercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.

(4)

'c'

Single byte (accepts integer or single byte objects).

'b'

Bytes (any object that follows the buffer protocol or has __bytes__()).

(5)

's'

's' is an alias for 'b' and should only be used for Python2/3 code bases.

(6)

'a'

Bytes (converts any Python object using repr(obj).encode('ascii', 'backslashreplace')).

(5)

'r'

'r' is an alias for 'a' and should only be used for Python2/3 code bases.

(7)

'%'

No argument is converted, results in a '%' character in the result.

註解：

The alternate form causes a leading octal specifier ('0o') to be inserted before the first digit.

The alternate form causes a leading '0x' or '0X' (depending on whether the 'x' or 'X' format was used) to be inserted before the first digit.

The alternate form causes the result to always contain a decimal point, even if no digits follow it.

The precision determines the number of digits after the decimal point and defaults to 6.

The alternate form causes the result to always contain a decimal point, and trailing zeroes are not removed as they would otherwise be.

The precision determines the number of significant digits before and after the decimal point and defaults to 6.

If precision is N, the output is truncated to N characters.

b'%s' 已被棄用，但在 3.x 系列中不會被移除。

b'%r' 已被棄用，但在 3.x 系列中不會被移除。

參閱 PEP 237 [https://peps.python.org/pep-0237/]。

備註

The bytearray version of this method does not operate in place - it always produces a new object, even if no changes were made.

也參考

PEP 461 [https://peps.python.org/pep-0461/] - Adding % formatting to bytes and bytearray

在 3.5 版被加入.

Memory Views

memoryview objects allow Python code to access the internal data of an object that supports the buffer protocol without copying.

class memoryview(object)

Create a memoryview that references object. object must support the buffer protocol. Built-in objects that support the buffer protocol include bytes and bytearray.

A memoryview has the notion of an element, which is the atomic memory unit handled by the originating object. For many simple types such as bytes and bytearray, an element is a single byte, but other types such as array.array may have bigger elements.

len(view) is equal to the length of tolist, which is the nested list representation of the view. If view.ndim = 1, this is equal to the number of elements in the view.

在 3.12 版的變更: If view.ndim == 0, len(view) now raises TypeError instead of returning 1.

The itemsize attribute will give you the number of bytes in a single element.

A memoryview supports slicing and indexing to expose its data. One-dimensional slicing will result in a subview:

>>> v = memoryview(b'abcefg')
>>> v[1]
98
>>> v[-1]
103
>>> v[1:4]
<memory at 0x7f3ddc9f4350>
>>> bytes(v[1:4])
b'bce'

If format is one of the native format specifiers from the struct module, indexing with an integer or a tuple of integers is also supported and returns a single element with the correct type. One-dimensional memoryviews can be indexed with an integer or a one-integer tuple. Multi-dimensional memoryviews can be indexed with tuples of exactly ndim integers where ndim is the number of dimensions. Zero-dimensional memoryviews can be indexed with the empty tuple.

Here is an example with a non-byte format:

>>> import array
>>> a = array.array('l', [-11111111, 22222222, -33333333, 44444444])
>>> m = memoryview(a)
>>> m[0]
-11111111
>>> m[-1]
44444444
>>> m[::2].tolist()
[-11111111, -33333333]

If the underlying object is writable, the memoryview supports one-dimensional slice assignment. Resizing is not allowed:

>>> data = bytearray(b'abcefg')
>>> v = memoryview(data)
>>> v.readonly
False
>>> v[0] = ord(b'z')
>>> data
bytearray(b'zbcefg')
>>> v[1:4] = b'123'
>>> data
bytearray(b'z123fg')
>>> v[2:3] = b'spam'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: memoryview assignment: lvalue and rvalue have different structures
>>> v[2:6] = b'spam'
>>> data
bytearray(b'z1spam')

One-dimensional memoryviews of hashable (read-only) types with formats 'B', 'b' or 'c' are also hashable. The hash is defined as hash(m) == hash(m.tobytes()):

>>> v = memoryview(b'abcefg')
>>> hash(v) == hash(b'abcefg')
True
>>> hash(v[2:4]) == hash(b'ce')
True
>>> hash(v[::-2]) == hash(b'abcefg'[::-2])
True

在 3.3 版的變更: One-dimensional memoryviews can now be sliced. One-dimensional memoryviews with formats 'B', 'b' or 'c' are now hashable.

在 3.4 版的變更: memoryview is now registered automatically with collections.abc.Sequence

在 3.5 版的變更: memoryviews can now be indexed with tuple of integers.

在 3.14 版的變更: memoryview is now a generic type.

memoryview 有幾個方法：

__eq__(exporter)

A memoryview and a PEP 3118 [https://peps.python.org/pep-3118/] exporter are equal if their shapes are equivalent and if all corresponding values are equal when the operands' respective format codes are interpreted using struct syntax.

For the subset of struct format strings currently supported by tolist(), v and w are equal if v.tolist() == w.tolist():

>>> import array
>>> a = array.array('I', [1, 2, 3, 4, 5])
>>> b = array.array('d', [1.0, 2.0, 3.0, 4.0, 5.0])
>>> c = array.array('b', [5, 3, 1])
>>> x = memoryview(a)
>>> y = memoryview(b)
>>> x == a == y == b
True
>>> x.tolist() == a.tolist() == y.tolist() == b.tolist()
True
>>> z = y[::-2]
>>> z == c
True
>>> z.tolist() == c.tolist()
True

If either format string is not supported by the struct module, then the objects will always compare as unequal (even if the format strings and buffer contents are identical):

>>> from ctypes import BigEndianStructure, c_long
>>> class BEPoint(BigEndianStructure):
...     _fields_ = [("x", c_long), ("y", c_long)]
...
>>> point = BEPoint(100, 200)
>>> a = memoryview(point)
>>> b = memoryview(point)
>>> a == point
False
>>> a == b
False

Note that, as with floating-point numbers, v is w does not imply v == w for memoryview objects.

在 3.3 版的變更: Previous versions compared the raw memory disregarding the item format and the logical array structure.

tobytes(order='C')

Return the data in the buffer as a bytestring. This is equivalent to calling the bytes constructor on the memoryview.

>>> m = memoryview(b"abc")
>>> m.tobytes()
b'abc'
>>> bytes(m)
b'abc'

For non-contiguous arrays the result is equal to the flattened list representation with all elements converted to bytes. tobytes() supports all format strings, including those that are not in struct module syntax.

在 3.8 版被加入: order can be {'C', 'F', 'A'}. When order is 'C' or 'F', the data of the original array is converted to C or Fortran order. For contiguous views, 'A' returns an exact copy of the physical memory. In particular, in-memory Fortran order is preserved. For non-contiguous views, the data is converted to C first. order=None is the same as order='C'.

hex(*, bytes_per_sep=1)

hex(sep, bytes_per_sep=1)

Return a string object containing two hexadecimal digits for each byte in the buffer.

>>> m = memoryview(b"abc")
>>> m.hex()
'616263'

在 3.5 版被加入.

在 3.8 版的變更: Similar to bytes.hex(), memoryview.hex() now supports optional sep and bytes_per_sep parameters to insert separators between bytes in the hex output.

tolist()

Return the data in the buffer as a list of elements.

>>> memoryview(b'abc').tolist()
[97, 98, 99]
>>> import array
>>> a = array.array('d', [1.1, 2.2, 3.3])
>>> m = memoryview(a)
>>> m.tolist()
[1.1, 2.2, 3.3]

在 3.3 版的變更: tolist() now supports all single character native formats in struct module syntax as well as multi-dimensional representations.

toreadonly()

Return a readonly version of the memoryview object. The original memoryview object is unchanged.

>>> m = memoryview(bytearray(b'abc'))
>>> mm = m.toreadonly()
>>> mm.tolist()
[97, 98, 99]
>>> mm[0] = 42
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot modify read-only memory
>>> m[0] = 43
>>> mm.tolist()
[43, 98, 99]

在 3.8 版被加入.

release()

Release the underlying buffer exposed by the memoryview object. Many objects take special actions when a view is held on them (for example, a bytearray would temporarily forbid resizing); therefore, calling release() is handy to remove these restrictions (and free any dangling resources) as soon as possible.

After this method has been called, any further operation on the view raises a ValueError (except release() itself which can be called multiple times):

>>> m = memoryview(b'abc')
>>> m.release()
>>> m[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: operation forbidden on released memoryview object

The context management protocol can be used for a similar effect, using the with statement:

>>> with memoryview(b'abc') as m:
...     m[0]
...
97
>>> m[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: operation forbidden on released memoryview object

在 3.2 版被加入.

cast(format, /)

cast(format, shape, /)

Cast a memoryview to a new format or shape. shape defaults to [byte_length//new_itemsize], which means that the result view will be one-dimensional. The return value is a new memoryview, but the buffer itself is not copied. Supported casts are 1D -> C-contiguous and C-contiguous -> 1D.

The destination format is restricted to a single element native format in struct syntax. One of the formats must be a byte format ('B', 'b' or 'c'). The byte length of the result must be the same as the original length. Note that all byte lengths may depend on the operating system.

Cast 1D/long to 1D/unsigned bytes:

>>> import array
>>> a = array.array('l', [1,2,3])
>>> x = memoryview(a)
>>> x.format
'l'
>>> x.itemsize
8
>>> len(x)
3
>>> x.nbytes
24
>>> y = x.cast('B')
>>> y.format
'B'
>>> y.itemsize
1
>>> len(y)
24
>>> y.nbytes
24

Cast 1D/unsigned bytes to 1D/char:

>>> b = bytearray(b'zyz')
>>> x = memoryview(b)
>>> x[0] = b'a'
Traceback (most recent call last):
  ...
TypeError: memoryview: invalid type for format 'B'
>>> y = x.cast('c')
>>> y[0] = b'a'
>>> b
bytearray(b'ayz')

Cast 1D/bytes to 3D/ints to 1D/signed char:

>>> import struct
>>> buf = struct.pack("i"*12, *list(range(12)))
>>> x = memoryview(buf)
>>> y = x.cast('i', shape=[2,2,3])
>>> y.tolist()
[[[0, 1, 2], [3, 4, 5]], [[6, 7, 8], [9, 10, 11]]]
>>> y.format
'i'
>>> y.itemsize
4
>>> len(y)
2
>>> y.nbytes
48
>>> z = y.cast('b')
>>> z.format
'b'
>>> z.itemsize
1
>>> len(z)
48
>>> z.nbytes
48

Cast 1D/unsigned long to 2D/unsigned long:

>>> buf = struct.pack("L"*6, *list(range(6)))
>>> x = memoryview(buf)
>>> y = x.cast('L', shape=[2,3])
>>> len(y)
2
>>> y.nbytes
48
>>> y.tolist()
[[0, 1, 2], [3, 4, 5]]

在 3.3 版被加入.

在 3.5 版的變更: The source format is no longer restricted when casting to a byte view.

count(value, /)

計算 value 的出現次數

在 3.14 版被加入.

index(value, start=0, stop=sys.maxsize, /)

Return the index of the first occurrence of value (at or after index start and before index stop).

在找不到 value 時引發 ValueError。

在 3.14 版被加入.

There are also several readonly attributes available:

obj

memoryview 的底層物件：

>>> b  = bytearray(b'xyz')
>>> m = memoryview(b)
>>> m.obj is b
True

在 3.3 版被加入.

nbytes

nbytes == product(shape) * itemsize == len(m.tobytes()). This is the amount of space in bytes that the array would use in a contiguous representation. It is not necessarily equal to len(m):

>>> import array
>>> a = array.array('i', [1,2,3,4,5])
>>> m = memoryview(a)
>>> len(m)
5
>>> m.nbytes
20
>>> y = m[::2]
>>> len(y)
3
>>> y.nbytes
12
>>> len(y.tobytes())
12

Multi-dimensional arrays:

>>> import struct
>>> buf = struct.pack("d"*12, *[1.5*x for x in range(12)])
>>> x = memoryview(buf)
>>> y = x.cast('d', shape=[3,4])
>>> y.tolist()
[[0.0, 1.5, 3.0, 4.5], [6.0, 7.5, 9.0, 10.5], [12.0, 13.5, 15.0, 16.5]]
>>> len(y)
3
>>> y.nbytes
96

在 3.3 版被加入.

readonly

A bool indicating whether the memory is read only.

format

A string containing the format (in struct module style) for each element in the view. A memoryview can be created from exporters with arbitrary format strings, but some methods (e.g. tolist()) are restricted to native single element formats.

在 3.3 版的變更: format 'B' is now handled according to the struct module syntax. This means that memoryview(b'abc')[0] == b'abc'[0] == 97.

itemsize

The size in bytes of each element of the memoryview:

>>> import array, struct
>>> m = memoryview(array.array('H', [32000, 32001, 32002]))
>>> m.itemsize
2
>>> m[0]
32000
>>> struct.calcsize('H') == m.itemsize
True

ndim

An integer indicating how many dimensions of a multi-dimensional array the memory represents.

shape

A tuple of integers the length of ndim giving the shape of the memory as an N-dimensional array.

在 3.3 版的變更: An empty tuple instead of None when ndim = 0.

strides

A tuple of integers the length of ndim giving the size in bytes to access each element for each dimension of the array.

在 3.3 版的變更: An empty tuple instead of None when ndim = 0.

suboffsets

Used internally for PIL-style arrays. The value is informational only.

c_contiguous

A bool indicating whether the memory is C-contiguous.

在 3.3 版被加入.

f_contiguous

A bool indicating whether the memory is Fortran contiguous.

在 3.3 版被加入.

contiguous

A bool indicating whether the memory is contiguous.

在 3.3 版被加入.

Set Types --- set, frozenset

A set object is an unordered collection of distinct hashable objects. Common uses include membership testing, removing duplicates from a sequence, and computing mathematical operations such as intersection, union, difference, and symmetric difference. (For other containers see the built-in dict, list, and tuple classes, and the collections module.)

Like other collections, sets support x in set, len(set), and for x in set. Being an unordered collection, sets do not record element position or order of insertion. Accordingly, sets do not support indexing, slicing, or other sequence-like behavior.

There are currently two built-in set types, set and frozenset. The set type is mutable --- the contents can be changed using methods like add() and remove(). Since it is mutable, it has no hash value and cannot be used as either a dictionary key or as an element of another set. The frozenset type is immutable and hashable --- its contents cannot be altered after it is created; it can therefore be used as a dictionary key or as an element of another set.

Non-empty sets (not frozensets) can be created by placing a comma-separated list of elements within braces, for example: {'jack', 'sjoerd'}, in addition to the set constructor.

The constructors for both classes work the same:

class set(iterable=(), /)

class frozenset(iterable=(), /)

Return a new set or frozenset object whose elements are taken from iterable. The elements of a set must be hashable. To represent sets of sets, the inner sets must be frozenset objects. If iterable is not specified, a new empty set is returned.

集合可以以多種方式建立：

Use a comma-separated list of elements within braces: {'jack', 'sjoerd'}

Use a set comprehension: {c for c in 'abracadabra' if c not in 'abc'}

Use the type constructor: set(), set('foobar'), set(['a', 'b', 'foo'])

Instances of set and frozenset provide the following operations:

len(s)

Return the number of elements in set s (cardinality of s).

x in s

Test x for membership in s.

x not in s

Test x for non-membership in s.

frozenset.isdisjoint(other, /)

set.isdisjoint(other, /)

Return True if the set has no elements in common with other. Sets are disjoint if and only if their intersection is the empty set.

frozenset.issubset(other, /)

set.issubset(other, /)

set <= other

Test whether every element in the set is in other.

set < other

Test whether the set is a proper subset of other, that is, set <= other and set != other.

frozenset.issuperset(other, /)

set.issuperset(other, /)

set >= other

Test whether every element in other is in the set.

set > other

Test whether the set is a proper superset of other, that is, set >= other and set != other.

frozenset.union(*others)

set.union(*others)

set | other | ...

Return a new set with elements from the set and all others.

frozenset.intersection(*others)

set.intersection(*others)

set & other & ...

Return a new set with elements common to the set and all others.

frozenset.difference(*others)

set.difference(*others)

set - other - ...

Return a new set with elements in the set that are not in the others.

frozenset.symmetric_difference(other, /)

set.symmetric_difference(other, /)

set ^ other

Return a new set with elements in either the set or other but not both.

frozenset.copy()

set.copy()

Return a shallow copy of the set.

Note, the non-operator versions of union(), intersection(), difference(), symmetric_difference(), issubset(), and issuperset() methods will accept any iterable as an argument. In contrast, their operator based counterparts require their arguments to be sets. This precludes error-prone constructions like set('abc') & 'cbs' in favor of the more readable set('abc').intersection('cbs').

Both set and frozenset support set to set comparisons. Two sets are equal if and only if every element of each set is contained in the other (each is a subset of the other). A set is less than another set if and only if the first set is a proper subset of the second set (is a subset, but is not equal). A set is greater than another set if and only if the first set is a proper superset of the second set (is a superset, but is not equal).

Instances of set are compared to instances of frozenset based on their members. For example, set('abc') == frozenset('abc') returns True and so does set('abc') in set([frozenset('abc')]).

The subset and equality comparisons do not generalize to a total ordering function. For example, any two nonempty disjoint sets are not equal and are not subsets of each other, so all of the following return False: a<b, a==b, or a>b.

Since sets only define partial ordering (subset relationships), the output of the list.sort() method is undefined for lists of sets.

Set elements, like dictionary keys, must be hashable.

Binary operations that mix set instances with frozenset return the type of the first operand. For example: frozenset('ab') | set('bc') returns an instance of frozenset.

The following table lists operations available for set that do not apply to immutable instances of frozenset:

set.update(*others)

set |= other | ...

Update the set, adding elements from all others.

set.intersection_update(*others)

set &= other & ...

Update the set, keeping only elements found in it and all others.

set.difference_update(*others)

set -= other | ...

Update the set, removing elements found in others.

set.symmetric_difference_update(other, /)

set ^= other

Update the set, keeping only elements found in either set, but not in both.

set.add(elem, /)

將元素 elem 加入集合。

set.remove(elem, /)

Remove element elem from the set. Raises KeyError if elem is not contained in the set.

set.discard(elem, /)

如果 elem 存在於集合中則將其移除。

set.pop()

Remove and return an arbitrary element from the set. Raises KeyError if the set is empty.

set.clear()

從集合中移除所有元素。

Note, the non-operator versions of the update(), intersection_update(), difference_update(), and symmetric_difference_update() methods will accept any iterable as an argument.

Note, the elem argument to the __contains__(), remove(), and discard() methods may be a set. To support searching for an equivalent frozenset, a temporary one is created from elem.

Mapping Types --- dict

A mapping object maps hashable values to arbitrary objects. Mappings are mutable objects. There is currently only one standard mapping type, the dictionary. (For other containers see the built-in list, set, and tuple classes, and the collections module.)

A dictionary's keys are almost arbitrary values. Values that are not hashable, that is, values containing lists, dictionaries or other mutable types (that are compared by value rather than by object identity) may not be used as keys. Values that compare equal (such as 1, 1.0, and True) can be used interchangeably to index the same dictionary entry.

class dict(**kwargs)

class dict(mapping, /, **kwargs)

class dict(iterable, /, **kwargs)

Return a new dictionary initialized from an optional positional argument and a possibly empty set of keyword arguments.

字典可以用數種方式建立：

Use a comma-separated list of key: value pairs within braces: {'jack': 4098, 'sjoerd': 4127} or {4098: 'jack', 4127: 'sjoerd'}

Use a dict comprehension: {}, {x: x ** 2 for x in range(10)}

Use the type constructor: dict(), dict([('foo', 100), ('bar', 200)]), dict(foo=100, bar=200)

If no positional argument is given, an empty dictionary is created. If a positional argument is given and it defines a keys() method, a dictionary is created by calling __getitem__() on the argument with each returned key from the method. Otherwise, the positional argument must be an iterable object. Each item in the iterable must itself be an iterable with exactly two elements. The first element of each item becomes a key in the new dictionary, and the second element the corresponding value. If a key occurs more than once, the last value for that key becomes the corresponding value in the new dictionary.

If keyword arguments are given, the keyword arguments and their values are added to the dictionary created from the positional argument. If a key being added is already present, the value from the keyword argument replaces the value from the positional argument.

Dictionaries compare equal if and only if they have the same (key, value) pairs (regardless of ordering). Order comparisons ('<', '<=', '>=', '>') raise TypeError. To illustrate dictionary creation and equality, the following examples all return a dictionary equal to {"one": 1, "two": 2, "three": 3}:

>>> a = dict(one=1, two=2, three=3)
>>> b = {'one': 1, 'two': 2, 'three': 3}
>>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))
>>> d = dict([('two', 2), ('one', 1), ('three', 3)])
>>> e = dict({'three': 3, 'one': 1, 'two': 2})
>>> f = dict({'one': 1, 'three': 3}, two=2)
>>> a == b == c == d == e == f
True

Providing keyword arguments as in the first example only works for keys that are valid Python identifiers. Otherwise, any valid keys can be used.

Dictionaries preserve insertion order. Note that updating a key does not affect the order. Keys added after deletion are inserted at the end.

>>> d = {"one": 1, "two": 2, "three": 3, "four": 4}
>>> d
{'one': 1, 'two': 2, 'three': 3, 'four': 4}
>>> list(d)
['one', 'two', 'three', 'four']
>>> list(d.values())
[1, 2, 3, 4]
>>> d["one"] = 42
>>> d
{'one': 42, 'two': 2, 'three': 3, 'four': 4}
>>> del d["two"]
>>> d["two"] = None
>>> d
{'one': 42, 'three': 3, 'four': 4, 'two': None}

在 3.7 版的變更: Dictionary order is guaranteed to be insertion order. This behavior was an implementation detail of CPython from 3.6.

These are the operations that dictionaries support (and therefore, custom mapping types should support too):

list(d)

Return a list of all the keys used in the dictionary d.

len(d)

Return the number of items in the dictionary d.

d[key]

Return the item of d with key key. Raises a KeyError if key is not in the map.

If a subclass of dict defines a method __missing__() and key is not present, the d[key] operation calls that method with the key key as argument. The d[key] operation then returns or raises whatever is returned or raised by the __missing__(key) call. No other operations or methods invoke __missing__(). If __missing__() is not defined, KeyError is raised. __missing__() must be a method; it cannot be an instance variable:

>>> class Counter(dict):
...     def __missing__(self, key):
...         return 0
...
>>> c = Counter()
>>> c['red']
0
>>> c['red'] += 1
>>> c['red']
1

The example above shows part of the implementation of collections.Counter. A different __missing__() method is used by collections.defaultdict.

d[key] = value

將 d[key] 設為 value。

del d[key]

從 d 中移除 d[key]。若 key 不在對映中則引發 KeyError。

key in d

若 d 有鍵 key 則回傳 True，否則回傳 False。

key not in d

等價於 not key in d。

iter(d)

Return an iterator over the keys of the dictionary. This is a shortcut for iter(d.keys()).

clear()

從字典中移除所有項目。

copy()

Return a shallow copy of the dictionary.

classmethod fromkeys(iterable, value=None, /)

Create a new dictionary with keys from iterable and values set to value.

fromkeys() is a class method that returns a new dictionary. value defaults to None. All of the values refer to just a single instance, so it generally doesn't make sense for value to be a mutable object such as an empty list. To get distinct values, use a dict comprehension instead.

get(key, default=None, /)

Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.

items()

Return a new view of the dictionary's items ((key, value) pairs). See the documentation of view objects.

keys()

Return a new view of the dictionary's keys. See the documentation of view objects.

pop(key, /)

pop(key, default, /)

If key is in the dictionary, remove it and return its value, else return default. If default is not given and key is not in the dictionary, a KeyError is raised.

popitem()

Remove and return a (key, value) pair from the dictionary. Pairs are returned in LIFO order.

popitem() is useful to destructively iterate over a dictionary, as often used in set algorithms. If the dictionary is empty, calling popitem() raises a KeyError.

在 3.7 版的變更: LIFO order is now guaranteed. In prior versions, popitem() would return an arbitrary key/value pair.

reversed(d)

Return a reverse iterator over the keys of the dictionary. This is a shortcut for reversed(d.keys()).

在 3.8 版被加入.

setdefault(key, default=None, /)

If key is in the dictionary, return its value. If not, insert key with a value of default and return default. default defaults to None.

update(**kwargs)

update(mapping, /, **kwargs)

update(iterable, /, **kwargs)

Update the dictionary with the key/value pairs from mapping or iterable and kwargs, overwriting existing keys. Return None.

update() accepts either another object with a keys() method (in which case __getitem__() is called with every key returned from the method) or an iterable of key/value pairs (as tuples or other iterables of length two). If keyword arguments are specified, the dictionary is then updated with those key/value pairs: d.update(red=1, blue=2).

values()

Return a new view of the dictionary's values. See the documentation of view objects.

An equality comparison between one dict.values() view and another will always return False. This also applies when comparing dict.values() to itself:

>>> d = {'a': 1}
>>> d.values() == d.values()
False

d | other

Create a new dictionary with the merged keys and values of d and other, which must both be dictionaries. The values of other take priority when d and other share keys.

在 3.9 版被加入.

d |= other

Update the dictionary d with keys and values from other, which may be either a mapping or an iterable of key/value pairs. The values of other take priority when d and other share keys.

在 3.9 版被加入.

Dictionaries and dictionary views are reversible.

>>> d = {"one": 1, "two": 2, "three": 3, "four": 4}
>>> d
{'one': 1, 'two': 2, 'three': 3, 'four': 4}
>>> list(reversed(d))
['four', 'three', 'two', 'one']
>>> list(reversed(d.values()))
[4, 3, 2, 1]
>>> list(reversed(d.items()))
[('four', 4), ('three', 3), ('two', 2), ('one', 1)]

在 3.8 版的變更: Dictionaries are now reversible.

也參考

types.MappingProxyType can be used to create a read-only view of a dict.

字典視圖物件

The objects returned by dict.keys(), dict.values() and dict.items() are view objects. They provide a dynamic view on the dictionary's entries, which means that when the dictionary changes, the view reflects these changes.

Dictionary views can be iterated over to yield their respective data, and support membership tests:

len(dictview)

Return the number of entries in the dictionary.

iter(dictview)

Return an iterator over the keys, values or items (represented as tuples of (key, value)) in the dictionary.

Keys and values are iterated over in insertion order. This allows the creation of (value, key) pairs using zip(): pairs = zip(d.values(), d.keys()). Another way to create the same list is pairs = [(v, k) for (k, v) in d.items()].

Iterating views while adding or deleting entries in the dictionary may raise a RuntimeError or fail to iterate over all entries.

在 3.7 版的變更: Dictionary order is guaranteed to be insertion order.

x in dictview

Return True if x is in the underlying dictionary's keys, values or items (in the latter case, x should be a (key, value) tuple).

reversed(dictview)

Return a reverse iterator over the keys, values or items of the dictionary. The view will be iterated in reverse order of the insertion.

在 3.8 版的變更: Dictionary views are now reversible.

dictview.mapping

Return a types.MappingProxyType that wraps the original dictionary to which the view refers.

在 3.10 版被加入.

Keys views are set-like since their entries are unique and hashable. Items views also have set-like operations since the (key, value) pairs are unique and the keys are hashable. If all values in an items view are hashable as well, then the items view can interoperate with other sets. (Values views are not treated as set-like since the entries are generally not unique.) For set-like views, all of the operations defined for the abstract base class collections.abc.Set are available (for example, ==, <, or ^). While using set operators, set-like views accept any iterable as the other operand, unlike sets which only accept sets as the input.

An example of dictionary view usage:

>>> dishes = {'eggs': 2, 'sausage': 1, 'bacon': 1, 'spam': 500}
>>> keys = dishes.keys()
>>> values = dishes.values()

>>> # iteration
>>> n = 0
>>> for val in values:
...     n += val
...
>>> print(n)
504

>>> # keys and values are iterated over in the same order (insertion order)
>>> list(keys)
['eggs', 'sausage', 'bacon', 'spam']
>>> list(values)
[2, 1, 1, 500]

>>> # view objects are dynamic and reflect dict changes
>>> del dishes['eggs']
>>> del dishes['sausage']
>>> list(keys)
['bacon', 'spam']

>>> # set operations
>>> keys & {'eggs', 'bacon', 'salad'}
{'bacon'}
>>> keys ^ {'sausage', 'juice'} == {'juice', 'sausage', 'bacon', 'spam'}
True
>>> keys | ['juice', 'juice', 'juice'] == {'bacon', 'spam', 'juice'}
True

>>> # get back a read-only proxy for the original dictionary
>>> values.mapping
mappingproxy({'bacon': 1, 'spam': 500})
>>> values.mapping['spam']
500

情境管理器型別

Python 的 with 陳述式支援了由情境管理器定義之 runtime 情境的概念，要使用兩個方法來實作，該方法讓使用者定義類別能夠去定義 runtime 情境，且該情境在執行陳述式主體 (statement body) 之前進入、在陳述式結束時退出：

contextmanager.__enter__()

輸入 runtime 情境並回傳此物件或者與 runtime 情境相關的另一個物件。此方法回傳的值有被綁定到使用此情境管理器的 with 陳述式的 as 子句中的識別字。

一個會回傳自己的情境管理器範例是 file object。檔案物件從 __enter__() 回傳自己，以允許將 open() 用作 with 陳述式中的情境運算式。

一個會回傳相關物件的情境管理器範例是由 decimal.localcontext() 回傳的管理器。這些管理器將有效的十進位情境設定為原始十進位情境的副本，然後回傳該副本。這允許對 with 陳述式主體中的目前十進位情境進行更改，而不會影響 with 陳述式外部的程式碼。

contextmanager.__exit__(exc_type, exc_val, exc_tb)

退出 runtime 情境並回傳布林旗標以表示是否應抑制曾發生的任何例外。如果在執行 with 陳述式主體時發生例外，則引數包含例外型別、值和回溯 (traceback) 資訊。否則，所有三個引數都是 None。

從此方法回傳 true 值將導致 with 陳述式抑制例外並繼續執行緊接著 with 陳述式之後的陳述式。否則，該例外將在該方法執行完畢後繼續傳播 (propagate)。

If this method raises an exception while handling an earlier exception from the with block, the new exception is raised, and the original exception is stored in its __context__ attribute.

傳入的例外不應明確重新引發 - 取而代之的是，此方法應回傳 false 值以指示該方法已成功完成且不希望抑制引發的例外。這讓情境管理程式碼能輕鬆檢測 __exit__() 方法是否曾實際失敗過。

Python 定義了多個情境管理器來支援簡單的執行緒同步、檔案或其他物件的提示關閉以及對有效十進位算術情境的更簡單操作。除了情境管理協定的實作之外，不會對特定型別進行特殊處理。更多範例請參閱 contextlib 模組。

Python 的 generator 和 contextlib.contextmanager 裝飾器提供了一種便捷的方法來實作這些協定。如果產生器函式以 contextlib.contextmanager 裝飾器裝飾，它將回傳一個有實作出需要的 __enter__() 和 __exit__() 方法的情境管理器，而不是由未裝飾產生器函式產生的疊代器。

請注意，Python/C API 中 Python 物件的型別結構中的任何方法都沒有特定的槽。想要定義這些方法的擴充型別必須將它們作為普通的 Python 可存取方法提供。與設定 runtime 情境的開銷相比，單一類別字典查找的開銷可以忽略不計。

型別註釋的型別 --- 泛型別名 (Generic Alias)、聯合 (Union)

型別註釋 的核心內建型別是泛型別名和聯合。

泛型別名型別

GenericAlias 物件通常是透過下標 (subscripting) 一個類別來建立的。它們最常與容器類別 一起使用，像是 list 或 dict。例如 list[int] 是一個 GenericAlias 物件，它是透過使用引數 int 來下標 list 類別而建立的。GenericAlias 物件主要會與型別註釋 一起使用。

備註

通常只有當類別有實作特殊方法 __class_getitem__() 時才可以去下標該類別。

將一個 GenericAlias 物件用作 generic type 的代理，實作參數化泛型 (parameterized generics)。

對於一個容器類別，提供給該類別的下標引數可以代表物件所包含元素的型別。例如 set[bytes] 可以用於型別註釋來表示一個 set，其中所有元素的型別都是 bytes。

對於定義 __class_getitem__() 但不是容器的類別，提供給該類別的下標引數通常會指示物件上有定義的一個或多個方法的回傳型別。例如正規表示式可以用於 str 和 bytes 資料型別：

如果 x = re.search('foo', 'foo')，x 將會是一個 re.Match 物件，其中 x.group(0) 和 x[0] 的回傳值都是 str 型別。我們就可以用 GenericAlias re.Match[str] 在型別註釋中表示這種物件。

如果 y = re.search(b'bar', b'bar')（注意 bytes 的 b）， y 也會是 re.Match 的實例，但 y.group(0) 和 y[0] 的回傳值的型別都是 bytes。在型別註釋中，我們將用 re.Match[bytes] 來表示各種 re.Match 物件。

GenericAlias 物件是 types.GenericAlias 類別的實例，也可以用來直接建立 GenericAlias 物件。

T[X, Y, ...]

建立一個 GenericAlias 來表示一個型別 T，其以型別 X、Y 等（取決於所使用的 T）來參數化。例如，一個函式需要一個包含 float 元素的 list：

def average(values: list[float]) -> float:
    return sum(values) / len(values)

對映物件的另一個範例，使用 dict，它是一個泛型型別，需要兩個型別參數，分別表示鍵型別和值型別。在此範例中，函式需要一個 dict，其帶有 str 型別的鍵和 int 型別的值：

def send_post_request(url: str, body: dict[str, int]) -> None:
    ...

內建函式 isinstance() 和 issubclass() 不接受 GenericAlias 型別作為第二個引數：

>>> isinstance([1, 2], list[str])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: isinstance() argument 2 cannot be a parameterized generic

Python runtime 不強制執行型別註釋。這也擴展到泛型型別及其型別參數。當從 GenericAlias 建立容器物件時，不會檢查容器中元素的型別。例如，不鼓勵使用以下程式碼，但 runtime 不會出現錯誤：

>>> t = list[str]
>>> t([1, 2, 3])
[1, 2, 3]

此外，參數化泛型在物件建立期間會擦除 (erase) 型別參數：

>>> t = list[str]
>>> type(t)
<class 'types.GenericAlias'>

>>> l = t()
>>> type(l)
<class 'list'>

在泛型上呼叫 repr() 或 str() 會顯示參數化型別：

>>> repr(list[int])
'list[int]'

>>> str(list[int])
'list[int]'

為防止像是 dict[str][str] 的錯誤出現，泛型容器的 __getitem__() 方法會在這種情況下引發例外：

>>> dict[str][str]
Traceback (most recent call last):
  ...
TypeError: dict[str] is not a generic class

然而當使用型別變數 (type variable) 時，此類運算式是有效的。索引的元素數量必須與 GenericAlias 物件的 __args__ 中的型別變數項目一樣多：

>>> from typing import TypeVar
>>> Y = TypeVar('Y')
>>> dict[str, Y][int]
dict[str, int]

標準泛型類別

以下標準函式庫類別有支援參數化泛型。此列表並非詳盡無遺。

tuple

list

dict

set

frozenset

type

asyncio.Future

asyncio.Task

collections.deque

collections.defaultdict

collections.OrderedDict

collections.Counter

collections.ChainMap

collections.abc.Awaitable

collections.abc.Coroutine

collections.abc.AsyncIterable

collections.abc.AsyncIterator

collections.abc.AsyncGenerator

collections.abc.Iterable

collections.abc.Iterator

collections.abc.Generator

collections.abc.Reversible

collections.abc.Container

collections.abc.Collection

collections.abc.Callable

collections.abc.Set

collections.abc.MutableSet

collections.abc.Mapping

collections.abc.MutableMapping

collections.abc.Sequence

collections.abc.MutableSequence

collections.abc.ByteString

collections.abc.MappingView

collections.abc.KeysView

collections.abc.ItemsView

collections.abc.ValuesView

contextlib.AbstractContextManager

contextlib.AbstractAsyncContextManager

dataclasses.Field

functools.cached_property

functools.partialmethod

os.PathLike

queue.LifoQueue

queue.Queue

queue.PriorityQueue

queue.SimpleQueue

re.Pattern

re.Match

shelve.BsdDbShelf

shelve.DbfilenameShelf

shelve.Shelf

types.MappingProxyType

weakref.WeakKeyDictionary

weakref.WeakMethod

weakref.WeakSet

weakref.WeakValueDictionary

GenericAlias 物件的特殊屬性

所有參數化泛型都有實作特殊的唯讀屬性。

genericalias.__origin__

此屬性指向非參數化泛型類別：

>>> list[int].__origin__
<class 'list'>

genericalias.__args__

此屬性是傳遞給泛型類別之原始 __class_getitem__() 的泛型型別 tuple（長度可以為 1）：

>>> dict[str, list[int]].__args__
(<class 'str'>, list[int])

genericalias.__parameters__

此屬性是個會被延遲計算 (lazily computed) 的元組（可能為空），包含了在 __args__ 中找得到的不重複型別變數：

>>> from typing import TypeVar

>>> T = TypeVar('T')
>>> list[T].__parameters__
(~T,)

備註

具有 typing.ParamSpec 參數的一個 GenericAlias 物件在替換後可能沒有正確的 __parameters__，因為 typing.ParamSpec 主要用於靜態型別檢查。

genericalias.__unpacked__

如果別名已使用 * 運算子解包 (unpack) 則為 true 的布林值（請參閱 TypeVarTuple）。

在 3.11 版被加入.

也參考

PEP 484 [https://peps.python.org/pep-0484/] - 型別提示

引入 Python 的型別註釋框架。

PEP 585 [https://peps.python.org/pep-0585/] - 標準集合 (Standard Collections) 中的型別提示泛型

引入原生參數化標準函式庫類別的能力，前提是它們有實作特殊的類別方法 __class_getitem__()。

泛型、使用者定義泛型和 typing.Generic

有關如何實作可以在 runtime 參數化並能被靜態型別檢查器理解的泛型類別的文件。

在 3.9 版被加入.

聯合型別 (Union Type)

一個聯合物件可以保存多個型別物件 (type object)之 |（位元 or）運算的值。這些型別主要用於型別註釋 (type annotation)。與下標 typing.Union 相比，聯合型別運算式可以讓型別提示語法更清晰簡潔。

X | Y | ...

定義一個包含 X、Y 等型別的聯合物件。X | Y 表示 X 或 Y。它相當於 typing.Union[X, Y]。舉例來說，下列函式需要一個型別為 int 或 float 的引數：

def square(number: int | float) -> int | float:
    return number ** 2

備註

不能在 runtime 使用 | 運算元 (operand) 來定義有一個以上的成員為向前參照 (forward reference) 的聯合。例如 int | "Foo"，其中 "Foo" 是對未定義類別的參照，將在 runtime 失敗。對於包含向前參照的聯合，請將整個運算式以字串呈現，例如 "int | Foo"。

union_object == other

聯合物件可以與其他聯合物件一起進行相等性測試。細節如下：

聯合的聯合會被扁平化：

(int | str) | float == int | str | float

冗餘型別會被刪除：

int | str | int == int | str

比較聯合時，順序會被忽略：

int | str == str | int

它會建立 typing.Union 的實例：

int | str == typing.Union[int, str]
type(int | str) is typing.Union

可選型別可以表示為與 None 的聯合：

str | None == typing.Optional[str]

isinstance(obj, union_object)

issubclass(obj, union_object)

聯合物件也支援 isinstance() 和 issubclass() 的呼叫：

>>> isinstance("", int | str)
True

然而聯合物件中的參數化泛型則無法被檢查：

>>> isinstance(1, int | list[int])  # short-circuit evaluation
True
>>> isinstance([1], int | list[int])
Traceback (most recent call last):
  ...
TypeError: isinstance() argument 2 cannot be a parameterized generic

構成聯合物件的對使用者公開型別 (user-exposed type) 可以透過 typing.Union 存取並用於 isinstance() 檢查：

>>> import typing
>>> isinstance(int | str, typing.Union)
True
>>> typing.Union()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot create 'typing.Union' instances

備註

新增了型別物件的 __or__() 方法來支援 X | Y 語法。如果元類別有實作 __or__()，則 Union 可以覆寫 (override) 它：

>>> class M(type):
...     def __or__(self, other):
...         return "Hello"
...
>>> class C(metaclass=M):
...     pass
...
>>> C | int
'Hello'
>>> int | C
int | C

也參考

PEP 604 [https://peps.python.org/pep-0604/] -- PEP 提出 X | Y 語法和聯合型別。

在 3.10 版被加入.

在 3.14 版的變更: Union objects are now instances of typing.Union. Previously, they were instances of types.UnionType, which remains an alias for typing.Union.

其他內建型別

The interpreter supports several other kinds of objects. Most of these support only one or two operations.

模組

The only special operation on a module is attribute access: m.name, where m is a module and name accesses a name defined in m's symbol table. Module attributes can be assigned to. (Note that the import statement is not, strictly speaking, an operation on a module object; import foo does not require a module object named foo to exist, rather it requires an (external) definition for a module named foo somewhere.)

A special attribute of every module is __dict__. This is the dictionary containing the module's symbol table. Modifying this dictionary will actually change the module's symbol table, but direct assignment to the __dict__ attribute is not possible (you can write m.__dict__['a'] = 1, which defines m.a to be 1, but you can't write m.__dict__ = {}). Modifying __dict__ directly is not recommended.

Modules built into the interpreter are written like this: <module 'sys' (built-in)>. If loaded from a file, they are written as <module 'os' from '/usr/local/lib/pythonX.Y/os.pyc'>.

類別與類別實例

請見 物件、數值和型別 和 類別定義。

函式

Function objects are created by function definitions. The only operation on a function object is to call it: func(argument-list).

There are really two flavors of function objects: built-in functions and user-defined functions. Both support the same operation (to call the function), but the implementation is different, hence the different object types.

更多資訊請見 函式定義。

方法

Methods are functions that are called using the attribute notation. There are two flavors: built-in methods (such as append() on lists) and class instance method. Built-in methods are described with the types that support them.

If you access a method (a function defined in a class namespace) through an instance, you get a special object: a bound method (also called instance method) object. When called, it will add the self argument to the argument list. Bound methods have two special read-only attributes: m.__self__ is the object on which the method operates, and m.__func__ is the function implementing the method. Calling m(arg-1, arg-2, ..., arg-n) is completely equivalent to calling m.__func__(m.__self__, arg-1, arg-2, ..., arg-n).

Like function objects, bound method objects support getting arbitrary attributes. However, since method attributes are actually stored on the underlying function object (method.__func__), setting method attributes on bound methods is disallowed. Attempting to set an attribute on a method results in an AttributeError being raised. In order to set a method attribute, you need to explicitly set it on the underlying function object:

>>> class C:
...     def method(self):
...         pass
...
>>> c = C()
>>> c.method.whoami = 'my name is method'  # 不得設定於方法
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'method' object has no attribute 'whoami'
>>> c.method.__func__.whoami = 'my name is method'
>>> c.method.whoami
'my name is method'

更多資訊請見 實例方法。

程式碼物件

Code objects are used by the implementation to represent "pseudo-compiled" executable Python code such as a function body. They differ from function objects because they don't contain a reference to their global execution environment. Code objects are returned by the built-in compile() function and can be extracted from function objects through their __code__ attribute. See also the code module.

存取 __code__ 會引發一個附帶引數 obj 與 "__code__" 的稽核事件 object.__getattr__。

A code object can be executed or evaluated by passing it (instead of a source string) to the exec() or eval() built-in functions.

更多資訊請見 標準型別階層。

Type Objects

Type objects represent the various object types. An object's type is accessed by the built-in function type(). There are no special operations on types. The standard module types defines names for all standard built-in types.

Types are written like this: <class 'int'>.

Null 物件

This object is returned by functions that don't explicitly return a value. It supports no special operations. There is exactly one null object, named None (a built-in name). type(None)() produces the same singleton.

它被寫為 None。

Ellipsis 物件

This object is commonly used to indicate that something is omitted. It supports no special operations. There is exactly one ellipsis object, named Ellipsis (a built-in name). type(Ellipsis)() produces the Ellipsis singleton.

它被寫為 Ellipsis 或 ...。

In typical use, ... as the Ellipsis object appears in a few different places, for instance:

In type annotations, such as callable arguments or tuple elements.

As the body of a function instead of a pass statement.

In third-party libraries, such as Numpy's slicing and striding [https://numpy.org/doc/stable/user/basics.indexing.html#slicing-and-striding].

Python also uses three dots in ways that are not Ellipsis objects, for instance:

Doctest's ELLIPSIS, as a pattern for missing content.

The default Python prompt of the interactive shell when partial input is incomplete.

Lastly, the Python documentation often uses three dots in conventional English usage to mean omitted content, even in code examples that also use them as the Ellipsis.

NotImplemented 物件

This object is returned from comparisons and binary operations when they are asked to operate on types they don't support. See Comparisons for more information. There is exactly one NotImplemented object. type(NotImplemented)() produces the singleton instance.

它被寫為 NotImplemented。

內部物件

See 標準型別階層 for this information. It describes stack frame objects, traceback objects, and slice objects.

特殊屬性

The implementation adds a few special read-only attributes to several object types, where they are relevant. Some of these are not reported by the dir() built-in function.

definition.__name__

The name of the class, function, method, descriptor, or generator instance.

definition.__qualname__

The qualified name of the class, function, method, descriptor, or generator instance.

在 3.3 版被加入.

definition.__module__

The name of the module in which a class or function was defined.

definition.__doc__

The documentation string of a class or function, or None if undefined.

definition.__type_params__

The type parameters of generic classes, functions, and type aliases. For classes and functions that are not generic, this will be an empty tuple.

在 3.12 版被加入.

Integer string conversion length limitation

CPython has a global limit for converting between int and str to mitigate denial of service attacks. This limit only applies to decimal or other non-power-of-two number bases. Hexadecimal, octal, and binary conversions are unlimited. The limit can be configured.

The int type in CPython is an arbitrary length number stored in binary form (commonly known as a "bignum"). There exists no algorithm that can convert a string to a binary integer or a binary integer to a string in linear time, unless the base is a power of 2. Even the best known algorithms for base 10 have sub-quadratic complexity. Converting a large value such as int('1' * 500_000) can take over a second on a fast CPU.

Limiting conversion size offers a practical way to avoid CVE 2020-10735 [https://www.cve.org/CVERecord?id=CVE-2020-10735].

The limit is applied to the number of digit characters in the input or output string when a non-linear conversion algorithm would be involved. Underscores and the sign are not counted towards the limit.

When an operation would exceed the limit, a ValueError is raised:

>>> import sys
>>> sys.set_int_max_str_digits(4300)  # Illustrative, this is the default.
>>> _ = int('2' * 5432)
Traceback (most recent call last):
...
ValueError: Exceeds the limit (4300 digits) for integer string conversion: value has 5432 digits; use sys.set_int_max_str_digits() to increase the limit
>>> i = int('2' * 4300)
>>> len(str(i))
4300
>>> i_squared = i*i
>>> len(str(i_squared))
Traceback (most recent call last):
...
ValueError: Exceeds the limit (4300 digits) for integer string conversion; use sys.set_int_max_str_digits() to increase the limit
>>> len(hex(i_squared))
7144
>>> assert int(hex(i_squared), base=16) == i*i  # Hexadecimal is unlimited.

The default limit is 4300 digits as provided in sys.int_info.default_max_str_digits. The lowest limit that can be configured is 640 digits as provided in sys.int_info.str_digits_check_threshold.

Verification:

>>> import sys
>>> assert sys.int_info.default_max_str_digits == 4300, sys.int_info
>>> assert sys.int_info.str_digits_check_threshold == 640, sys.int_info
>>> msg = int('578966293710682886880994035146873798396722250538762761564'
...           '9252925514383915483333812743580549779436104706260696366600'
...           '571186405732').to_bytes(53, 'big')
...

在 3.11 版被加入.

受影響的 API

此限制僅適用於 int 與 str 或 bytes 之間可能較慢的轉換：

int(string) 以預設的 10 為底。

int(string, base) 用於所有非 2 冪次方的底。

str(integer)。

repr(integer)。

any other string conversion to base 10, for example f"{integer}", "{}".format(integer), or b"%d" % integer.

The limitations do not apply to functions with a linear algorithm:

int(string, base) 以 2、4、8、16 或 32 為底。

int.from_bytes() 和 int.to_bytes()。

hex()、oct()、bin()。

格式規格 (Format Specification) 迷你語言 用於十六進位、八進位和二進位數字。

str 轉換為 float。

str 轉換為 decimal.Decimal。

設定限制

Before Python starts up you can use an environment variable or an interpreter command line flag to configure the limit:

PYTHONINTMAXSTRDIGITS, e.g. PYTHONINTMAXSTRDIGITS=640 python3 to set the limit to 640 or PYTHONINTMAXSTRDIGITS=0 python3 to disable the limitation.

-X int_max_str_digits，例如 python3 -X int_max_str_digits=640

sys.flags.int_max_str_digits contains the value of PYTHONINTMAXSTRDIGITS or -X int_max_str_digits. If both the env var and the -X option are set, the -X option takes precedence. A value of -1 indicates that both were unset, thus a value of sys.int_info.default_max_str_digits was used during initialization.

From code, you can inspect the current limit and set a new one using these sys APIs:

sys.get_int_max_str_digits() and sys.set_int_max_str_digits() are a getter and setter for the interpreter-wide limit. Subinterpreters have their own limit.

Information about the default and minimum can be found in sys.int_info:

sys.int_info.default_max_str_digits is the compiled-in default limit.

sys.int_info.str_digits_check_threshold is the lowest accepted value for the limit (other than 0 which disables it).

在 3.11 版被加入.

警示

Setting a low limit can lead to problems. While rare, code exists that contains integer constants in decimal in their source that exceed the minimum threshold. A consequence of setting the limit is that Python source code containing decimal integer literals longer than the limit will encounter an error during parsing, usually at startup time or import time or even at installation time - anytime an up to date .pyc does not already exist for the code. A workaround for source that contains such large constants is to convert them to 0x hexadecimal form as it has no limit.

Test your application thoroughly if you use a low limit. Ensure your tests run with the limit set early via the environment or flag so that it applies during startup and even during any installation step that may invoke Python to precompile .py sources to .pyc files.

建議的配置

The default sys.int_info.default_max_str_digits is expected to be reasonable for most applications. If your application requires a different limit, set it from your main entry point using Python version agnostic code as these APIs were added in security patch releases in versions before 3.12.

範例：

>>> import sys
>>> if hasattr(sys, "set_int_max_str_digits"):
...     upper_bound = 68000
...     lower_bound = 4004
...     current_limit = sys.get_int_max_str_digits()
...     if current_limit == 0 or current_limit > upper_bound:
...         sys.set_int_max_str_digits(upper_bound)
...     elif current_limit < lower_bound:
...         sys.set_int_max_str_digits(lower_bound)

If you need to disable it entirely, set it to 0.

註腳

[1]

Additional information on these special methods may be found in the Python Reference Manual (Basic customization).

[2]

As a consequence, the list [1, 2] is considered equal to [1.0, 2.0], and similarly for tuples.

[3]

They must have since the parser can't tell the type of the operands.

[4] (1,2,3,4)

Cased characters are those with general category property being one of "Lu" (Letter, uppercase), "Ll" (Letter, lowercase), or "Lt" (Letter, titlecase).

[5] (1,2)

To format only a tuple you should therefore provide a singleton tuple whose only element is the tuple to be formatted.

內建的例外

在 Python 中，所有例外必須是從 BaseException 衍生的類別的實例。在陳述式 try 搭配 except 子句裡提到一個特定的類別時，那個子句也會處理任何從該類別衍生的例外類別（但不會處理該類別衍生自的例外類別）。兩個不是由子類別關係關聯起來的例外類別永遠不相等，就算它們有相同的名稱也是如此。

此章節裡列出的內建例外可以從直譯器或內建函式產生。除了特別提到的地方之外，它們會有一個關聯值表示錯誤發生的詳細原因。這可能是一個字串，或者是一些資訊項目組成的元組（例如一個錯誤代碼及一個解釋該代碼的字串）。這個關聯值通常當作引數傳遞給例外類別的建構函式。

使用者的程式碼可以引發內建例外。這可以用來測試例外處理器或者用來回報一個錯誤條件，就像直譯器會引發相同例外的情況；但需要注意的是沒有任何方式可以避免使用者的程式碼引發不適當的錯誤。

可以從內建的例外類別定義新的例外子類別；程式設計師被鼓勵從 Exception 類別或其子類別衍生新的例外，而不是從 BaseException 來衍生。更多關於定義例外的資訊可以在 Python 教學中的使用者自定的例外裡取得。

例外的情境

三個例外物件上的屬性提供關於引發此例外的情境的資訊：

BaseException.__context__

BaseException.__cause__

BaseException.__suppress_context__

當引發一個新的例外而同時有另一個例外已經正在被處理時，這個新例外的 __context__ 屬性會自動被設成那個已處理的例外。當使用 except 或 finally 子句或 with 陳述式的時候例外會被處理。

這個隱含的例外情境可以透過使用 from 搭配 raise 來補充明確的原因：

raise new_exc from original_exc

在 from 後面的運算式必須是一個例外或 None。它將會被設定成所引發例外的 __cause__。設定 __cause__ 也隱含地設定 __suppress_context__ 屬性為 True，因此使用 raise new_exc from None 實際上會以新的例外取代舊的例外以利於顯示（例如轉換 KeyError 為 AttributeError），同時保持舊的例外可以透過 __context__ 取得以方便 debug 的時候檢查。

預設的回溯 (traceback) 顯示程式碼會顯示這些連鎖的例外 (chained exception) 加上例外本身的回溯。當存在的時候，在 __cause__ 中明確地連鎖的例外總是會被顯示。而在 __context__ 中隱含地連鎖的例外只有當 __cause__ 是 None 且 __suppress_context__ 是 false 時才會顯示。

在任一種情況下，例外本身總是會顯示在任何連鎖例外的後面，因此回溯的最後一列總是顯示最後一個被引發的例外。

繼承自內建的例外

使用者的程式碼可以建立繼承自例外型別的子類別。建議一次只繼承一種例外型別以避免在基底類別之間如何處理 args 屬性的任何可能衝突，以及可能的記憶體佈局 (memory layout) 不相容。

為了效率，大部分的內建例外使用 C 來實作，參考 Objects/exceptions.c [https://github.com/python/cpython/tree/3.14/Objects/exceptions.c]。一些例外有客製化的記憶體佈局，使其不可能建立一個繼承多種例外型別的子類別。型別的記憶體佈局是實作細節且可能會在不同 Python 版本間改變，造成未來新的衝突。因此，總之建議避免繼承多種例外型別。

基底類別 (base classes)

以下的例外大部分被用在當作其他例外的基底類別。

exception BaseException

所有內建例外的基底類別。這不是為了讓使用者定義的類別直接繼承（可以使用 Exception）。如果在這個類別的實例上呼叫 str()，會回傳實例的引數的表示，或者沒有引數的時候會回傳空字串。

args

提供給該例外建構函式的引數元組。一些內建的例外（像是 OSError）預期接受特定數量的引數並賦予該元組的每一個元素一個特別的意義，其他例外則通常用一個提供錯誤訊息的單一字串來呼叫。

with_traceback(tb)

此方法設定 tb 為該例外的新的回溯並回傳該例外物件。在 PEP 3134 [https://peps.python.org/pep-3134/] 的例外連鎖功能變得可用之前，此方法曾被更普遍使用。下面的範例顯示我們如何將 SomeException 的實例轉換為 OtherException 的實例同時保留回溯。一旦被引發，目前的 frame 會被加進 OtherException 的回溯，就像原來 SomeException 的回溯會發生的一樣，我們允許它被傳遞給呼叫者：

try:
    ...
except SomeException:
    tb = sys.exception().__traceback__
    raise OtherException(...).with_traceback(tb)

__traceback__

可寫入的欄位，儲存關聯到該例外的回溯物件。也可以參考 raise 陳述式。

add_note(note)

新增字串 note 到例外的備註，在標準的回溯裡，備註出現在例外字串的後面。如果 note 不是字串則引發 TypeError。

在 3.11 版被加入.

__notes__

該例外的備註串列，使用 add_note() 來新增。此屬性在 add_note() 被呼叫的時候建立。

在 3.11 版被加入.

exception Exception

所有內建、非系統退出 (non-system-exiting) 的例外都衍生自此類別。所有使用者定義的例外應該也要衍生自此類別。

exception ArithmeticError

各種運算錯誤所引發的那些內建例外：OverflowError、ZeroDivisionError、FloatingPointError 的基底類別。

exception BufferError

當緩衝 (buffer) 相關的操作無法被執行時會引發此例外。

exception LookupError

當使用在對映或序列上的鍵或索引是無效的時候所引發的例外：IndexError、KeyError 的基底類別。這可以被 codecs.lookup() 直接引發。

實體例外

以下的例外是通常會被引發的例外。

exception AssertionError

當 assert 陳述式失敗的時候被引發。

exception AttributeError

當屬性參照（參考 Attribute references）或賦值失敗的時候被引發。（當物件根本不支援屬性參照或屬性賦值的時候，TypeError 會被引發。）

可選的僅限關鍵字引數 name 和 obj 會設定對應的屬性：

name

嘗試被存取的屬性名稱。

obj

存取指定屬性的物件。

在 3.10 版的變更: 新增 name 與 obj 屬性。

exception EOFError

當 input() 函式在沒有讀到任何資料而到達檔案結尾 (end-of-file, EOF) 條件的時候被引發。（注意：io.IOBase.read() 和 io.IOBase.readline() 方法當達到 EOF 時會回傳空字串。）

exception FloatingPointError

目前沒有被使用。

exception GeneratorExit

當 generator 或 coroutine 被關閉的時候被引發；參考 generator.close() 和 coroutine.close()。此例外直接繼承自 BaseException 而不是 Exception，因為技術上來說這不是一個錯誤。

exception ImportError

當 import 陳述式嘗試載入模組遇到問題的時候會被引發。當 from ... import 裡的 "from list" 包含找不到的名稱時也會被引發。

可選的僅限關鍵字引數 name 和 path 設定對應的屬性：

name

嘗試引入 (import) 的模組名稱。

path

觸發此例外的任何檔案的路徑。

在 3.3 版的變更: 新增 name 與 path 屬性。

exception ModuleNotFoundError

ImportError 的子類別，當模組不能被定位的時候會被 import 所引發。當在 sys.modules 裡找到 None 時也會被引發。

在 3.6 版被加入.

exception IndexError

當序列的索引超出範圍的時候會被引發。（切片索引 (slice indices) 會默默地被截短使其能落在允許的範圍內；如果索引不是整數，TypeError 會被引發。）

exception KeyError

當對映（字典）的鍵無法在已存在的鍵的集合中被找到時會被引發。

exception KeyboardInterrupt

當使用者輸入中斷鍵 (interrupt key)（一般來說是 Control-C 或 Delete）時會被引發。在執行過程中，會定期檢查是否產生中斷。此例外繼承自 BaseException 以防止意外地被捕捉 Exception 的程式碼所捕捉，而因此讓直譯器無法結束。

備註

捕捉 KeyboardInterrupt 需要特殊的考量。因為它可以在無法預期的時間點被引發，可能在某些情況下讓正在跑的程式處在一個不一致的狀態。一般來說最好讓 KeyboardInterrupt 越快結束程式越好，或者完全避免引發它。（參考 訊號處理程式與例外的說明。）

exception MemoryError

當一個操作用光了記憶體但情況還可能被修復 (rescued)（透過刪除一些物件）的時候被引發。關聯值是一個字串，表示什麼類型的（內部）操作用光了記憶體。需注意的是因為底層的記憶體管理架構（C 的 malloc() 函式），直譯器可能無法總是完整地從該情況中修復；僅管如此，它還是引發例外以讓堆疊回溯可以被印出，以防原因出在失控的程式。

exception NameError

當找不到本地或全域的名稱時會被引發。這只應用在不合格的名稱 (unqualified name) 上。關聯值是一個錯誤訊息，包含那個無法被找到的名稱。

可選的僅限關鍵字引數 name 設定對應的屬性：

name

嘗試被存取的變數名稱。

在 3.10 版的變更: 新增 name 屬性。

exception NotImplementedError

此例外衍生自 RuntimeError。在使用者定義的基礎類別裡，當抽象方法要求衍生類別覆寫該方法時應該要引發此例外，或者當類別正在開發中，可用此例外表示還需要加入真正的實作。

備註

此例外不應該用來表示根本沒有要支援的運算子或方法 ── 在這個情況下可以讓該運算子或方法保持未定義，或者如果是子類別的話將其設成 None。

警示

NotImplementedError 和 NotImplemented 並不是可互換的。這個例外只能用在上面描述的情況；參考 NotImplemented 裡關於內建常數正確使用方法的細節。

exception OSError([arg])

exception OSError(errno, strerror[, filename[, winerror[, filename2]]])

當系統函式回傳系統相關錯誤，包含像"找不到檔案"或"硬碟已滿"的 I/O 失敗會引發此例外（而非不合法的引數或其他次要的錯誤）。

建構函式的第二種形式會設定以下描述的相對應屬性。如果沒有給定則屬性預設為 None。為了向後相容，如果傳入三個引數，args 屬性只會是包含建構函式前兩個引數的雙元素元組。

如同下面的作業系統例外所描述，實際上建構函式通常回傳 OSError 的子類別。會依據最後 errno 的值決定特定子類別。這個行為只發生在直接建構 OSError 或透過別名，且產生子類別的時候不會被繼承。

errno

從 C 變數 errno 而來的數值錯誤代碼。

winerror

在 Windows 下，這會提供你原生的 Windows 錯誤代碼。而 errno 屬性是一個該原生錯誤代碼對於 POSIX 來說的近似翻譯。

在 Windows 下，如果建構函式引數 winerror 是整數，則 errno 屬性會根據該 Windows 錯誤代碼來決定，且 errno 引數會被忽略。在其他平台上，winerror 引數會被忽略，而 winerror 屬性會不存在。

strerror

作業系統提供的對應錯誤訊息。在 POSIX 下會使用 C 函式 perror() 做格式化，而在 Windows 下會使用 FormatMessage()。

filename

filename2

對於包含檔案系統路徑的例外（像是 open() 或 os.unlink()），filename 是傳入函式的檔案名稱。對於包含兩個檔案系統路徑的函式（像是 os.rename()），filename2 對應到傳入函式的第二個檔案名稱。

在 3.3 版的變更: EnvironmentError、IOError、WindowsError、socket.error、select.error 及 mmap.error 已合併進 OSError，而建構函式可能會回傳子類別。

在 3.4 版的變更: filename 屬性現在是傳入函式的原始檔名，而不是從檔案系統編碼和錯誤處理函式編碼或解碼過的名稱。並且新增 filename2 建構函式引數與屬性。

exception OverflowError

當運算操作的結果太大而無法表示的時候會引發此例外。這不會發生在整數上（會改成引發 MemoryError 而不是放棄）。然而，因為一些歷史因素，OverflowError 有時候會因為整數在要求範圍之外而引發。因為在 C 裡面缺乏浮點數例外處理的標準化，大部分的浮點數運算都沒有被檢查。

exception PythonFinalizationError

此例外衍生自 RuntimeError。當一個操作在直譯器關閉（也稱作 Python 最終化 (Python finalization））期間被阻塞會引發此例外。

在 Python 最終化期間，能夠以 PythonFinalizationError 被阻塞的操作範例：

建立新的 Python 執行緒。

Joining a running daemon thread.

os.fork()。

也可以參閱 sys.is_finalizing() 函式。

在 3.13 版被加入: 在之前，會引發一般的 RuntimeError。

在 3.14 版的變更: threading.Thread.join() can now raise this exception.

exception RecursionError

此例外衍生自 RuntimeError。當直譯器偵測到超過最大的遞迴深度（參考 sys.getrecursionlimit()）時會引發此例外。

在 3.5 版被加入: 在之前，會引發一般的 RuntimeError。

exception ReferenceError

當一個被 weakref.proxy() 函式建立的弱參照代理 (weak reference proxy) 被用來存取已經被垃圾回收 (garbage collected) 的參照物屬性時會引發此例外。更多關於弱參照的資訊參考 weakref 模組。

exception RuntimeError

當偵測到一個不屬於任何其他種類的錯誤時會引發此例外。關聯值是一個表示確切什麼地方出錯的字串。

exception StopIteration

會被內建函式 next() 及 iterator 的 __next__() 方法引發，用來表示疊代器沒有更多項目可以產生。

value

此例外物件有單一屬性 value，當建構此例外時會以引數給定，預設為 None。

當 generator 或 coroutine 函式回傳時，新的 StopIteration 實例會被引發，而該函式的回傳值會被用來當作此例外建構函式的 value 參數。

如果產生器程式直接或間接引發 StopIteration，則其會被轉換成 RuntimeError（保留 StopIteration 作為新例外的成因）。

在 3.3 版的變更: 新增 value 屬性且產生器函式可以用它來回傳值。

在 3.5 版的變更: 透過 from __future__ import generator_stop 引入 RuntimeError 的轉換，參考 PEP 479 [https://peps.python.org/pep-0479/]。

在 3.7 版的變更: 預設對所有程式啟用 PEP 479 [https://peps.python.org/pep-0479/]：在產生器引發的 StopIteration 錯誤會轉換成 RuntimeError。

exception StopAsyncIteration

此例外必須被 asynchronous iterator 物件的 __anext__() 方法引發來停止疊代。

在 3.5 版被加入.

exception SyntaxError(message, details)

當剖析器遇到語法錯誤時會引發此例外。這可能發生在 import 陳述式、在呼叫內建函式 compile()、exec() 或 eval() 的時候，或者在讀取初始腳本或標準輸入（也包含互動式）的時候。

例外實例的 str() 只回傳錯誤訊息。Details 是個元組，其成員也能夠以分開的屬性取得。

filename

發生語法錯誤所在的檔案名稱。

lineno

發生錯誤所在檔案的列號。這是以 1 開始的索引：檔案第一列的 lineno 是 1。

offset

發生錯誤所在該列的欄號 (column)。這是以 1 開始的索引：該列第一個字元的 offset 是 1。

text

涉及該錯誤的原始程式碼文字。

end_lineno

發生錯誤所在檔案的結束列號。這是以 1 開始的索引：檔案第一列的 lineno 是 1。

end_offset

發生錯誤所在該結束列的欄號。這是以 1 開始的索引：該列第一個字元的 offset 是 1。

對於發生在 f-string 欄位的錯誤，訊息會以 "f-string: " 為前綴，而偏移量 (offset) 是從替代運算式建構的文字的偏移量。例如編譯 f'Bad {a b} field' 會得到這個 args 屬性：('f-string: ...', ('', 1, 2, '(a b)n', 1, 5))。

在 3.10 版的變更: 新增 end_lineno 與 end_offset 屬性。

exception IndentationError

與不正確的縮排有關的語法錯誤的基礎類別。這是 SyntaxError 的子類別。

exception TabError

當縮排包含製表符號 (tab) 和空白的不一致用法時會引發此例外。這是 IndentationError 的子類別。

exception SystemError

當直譯器找到一個內部錯誤，但該情況看起來沒有嚴重到要讓它放棄所有的希望時會引發此例外。關聯值是一個表示什麼地方出錯的字串（以低階的方式表達）。在 CPython 中，這可能是因為錯誤地使用 Python 的 C API，例如回傳一個 NULL 值而沒有設定例外。

如果你確定這個例外不是你的或者所用套件的錯，你應該向你的 Python 直譯器作者或維護者回報此錯誤。務必要回報該 Python 直譯器的版本（sys.version；這也會在互動式 Python 會話的開頭被印出）、確切的錯誤訊息（該例外的關聯值）及如果可能的話，觸發此錯誤的程式來源。

exception SystemExit

此例外會被 sys.exit() 函式引發。它繼承自 BaseException 而不是 Exception 因此不會被捕捉 Exception 的程式意外地捕捉。這允許例外可以正確地向上傳遞並導致直譯器結束。當它未被處理時，Python 直譯器會結束；不會印出堆疊回溯。建構函式接受跟傳入 sys.exit() 一樣的可選引數。如果該值是整數，它會指定系統的結束狀態（傳入 C 的 exit() 函式）；如果它是 None，結束狀態會是 0；如果它是其他型別（例如字串），則物件的值會被印出而結束狀態是 1。

對 sys.exit() 的呼叫會轉譯成例外讓負責清理的處理函式（try 陳述式的 finally 子句）可以被執行，且讓除錯器可以在不冒著失去控制的風險下執行腳本。如果在絕對有必要立即結束的情況（例如在子行程呼叫完 os.fork() 之後 ）可以使用 os._exit() 函式。

code

傳入建構函式的結束狀態或錯誤訊息。（預設是 None。 ）

exception TypeError

當一個操作或函式被用在不適合的型別的物件時會引發此例外。關聯值是一個字串，提供關於不相符型別的細節。

此例外可能被使用者程式碼引發，以表示並不支援物件上所嘗試的操作，且本來就無意這樣做。如果一個物件有意要支援某個給定的操作但尚未提供實作，該引發的正確例外是 NotImplementedError。

傳入錯誤型別的引數（例如當預期傳入 int 卻傳入 list）應該要導致 TypeError，但傳入帶有錯誤值的引數（例如超出預期範圍的數值）應該要導致 ValueError。

exception UnboundLocalError

當在函式或方法裡引用某個區域變數，但該變數尚未被繫結到任何值的時候會引發此例外。這是 NameError 的子類別。

exception UnicodeError

當 Unicode 相關的編碼或解碼錯誤發生時會引發此例外。這是 ValueError 的子類別。

UnicodeError 有屬性描述編碼或解碼錯誤。例如 err.object[err.start:err.end] 會提供讓編解碼器失敗的具體無效輸入。

encoding

引發錯誤的編碼名稱。

reason

描述特定編解碼器錯誤的字串。

object

編解碼器嘗試編碼或解碼的物件。

start

在 object 中無效資料的開始索引。

This value should not be negative as it is interpreted as an absolute offset but this constraint is not enforced at runtime.

end

在 object 中最後的無效資料後的索引。

This value should not be negative as it is interpreted as an absolute offset but this constraint is not enforced at runtime.

exception UnicodeEncodeError

在編碼當中發生 Unicode 相關錯誤時會引發此例外。這是 UnicodeError 的子類別。

exception UnicodeDecodeError

在解碼當中發生 Unicode 相關錯誤時會引發此例外。這是 UnicodeError 的子類別。

exception UnicodeTranslateError

在轉譯當中發生 Unicode 相關錯誤時會引發此例外。這是 UnicodeError 的子類別。

exception ValueError

當一個操作或函式收到引數是正確型別但是不適合的值，且該情況無法被更精確的例外例如 IndexError 所描述時會引發此例外。

exception ZeroDivisionError

當除法或模數運算 (modulo operation) 的第二個引數是 0 的時候會引發此例外。關聯值是一個字串，表示運算元及運算的類型。

以下例外是為了相容於之前版本而保留；從 Python 3.3 開始，它們是 OSError 的別名。

exception EnvironmentError

exception IOError

exception WindowsError

僅限於在 Windows 中使用。

作業系統例外

以下的例外是 OSError 的子類別，它們根據系統錯誤代碼來引發。

exception BlockingIOError

當設置為非阻塞操作的物件（例如 socket）上的操作將要阻塞時會引發此例外。對應到 errno EAGAIN、EALREADY、EWOULDBLOCK 及 EINPROGRESS。

除了 OSError 的那些屬性之外，BlockingIOError 有多一個屬性：

characters_written

一個整數，內容為在其阻塞之前，已寫進串流的位元組數。當使用 io 模組裡的緩衝 I/O 類別時這個屬性是可用的。

exception ChildProcessError

當子行程上的操作失敗時會引發此例外。對應到 errno ECHILD。

exception ConnectionError

連線相關問題的基礎類別。

子類別有 BrokenPipeError、ConnectionAbortedError、ConnectionRefusedError 及 ConnectionResetError。

exception BrokenPipeError

ConnectionError 的子類別，當嘗試寫入管道 (pipe) 同時另一端已經被關閉時會引發此例外，或者當嘗試寫入已關閉寫入的 socket 時也會引發。對應到 errno EPIPE 及 ESHUTDOWN。

exception ConnectionAbortedError

ConnectionError 的子類別。當一個連線的嘗試被對等端點 (peer) 中斷時會引發此例外。對應到 errno ECONNABORTED。

exception ConnectionRefusedError

ConnectionError 的子類別。當一個連線的嘗試被對等端點拒絕時會引發此例外。對應到 errno ECONNREFUSED。

exception ConnectionResetError

ConnectionError 的子類別。當一個連線被對等端點重置時會引發此例外。對應到 errno ECONNRESET。

exception FileExistsError

當嘗試建立已存在的檔案或目錄時會引發此例外。對應到 errno EEXIST。

exception FileNotFoundError

當請求不存在的檔案或目錄時會引發此例外。對應到 errno ENOENT。

exception InterruptedError

當系統呼叫被傳入的信號中斷時會引發此例外。對應到 errno EINTR。

在 3.5 版的變更: 現在當 syscall 被信號中斷時 Python 會重試系統呼叫而不會引發 InterruptedError，除非信號處理器引發例外（理由可參考 PEP 475 [https://peps.python.org/pep-0475/]）。

exception IsADirectoryError

當在目錄上請求檔案操作（例如 os.remove()）時會引發此例外。對應到 errno EISDIR。

exception NotADirectoryError

當在某個不是目錄的東西上請求目錄操作（例如 os.listdir()）時會引發此例外。在大多數的 POSIX 平台上，如果嘗試操作開啟或遍歷一個當作目錄的非目錄檔案也會引發此例外。對應到 errno ENOTDIR。

exception PermissionError

當嘗試執行一個沒有合乎存取權限的操作時會引發此例外 — 例如檔案系統權限。對應到 errno EACCES、EPERM 及 ENOTCAPABLE。

在 3.11.1 版的變更: WASI 的 ENOTCAPABLE 現在對應到 PermissionError。

exception ProcessLookupError

當給定的行程不存在時會引發此例外。對應到 errno ESRCH。

exception TimeoutError

當系統函式在系統層級超時會引發此例外。對應到 errno ETIMEDOUT。

在 3.3 版被加入: 加入以上所有的 OSError 子類別。

也參考

PEP 3151 [https://peps.python.org/pep-3151/] — 改寫作業系統與 IO 例外階層

警告

以下的例外是當作警告的種類使用；更多細節參考 警告類別 文件。

exception Warning

警告種類的基礎類別。

exception UserWarning

使用者程式碼產生的警告的基礎類別。

exception DeprecationWarning

關於已棄用功能的警告的基礎類別，且當那些警告是針對其他 Python 開發者。

會被預設的警告過濾器忽略，在 __main__ 模組裡除外 (PEP 565 [https://peps.python.org/pep-0565/])。啟用 Python 開發模式會顯示此警告。

棄用原則描述在 PEP 387 [https://peps.python.org/pep-0387/] 裡。

exception PendingDeprecationWarning

關於過時且預期未來要被棄用，但目前尚未被棄用的功能的警告的基礎類別。

因為發出關於可能即將被棄用的警告是不尋常的，此類別很少被使用，而對已經被棄用的情況會優先使用 DeprecationWarning。

會被預設的警告過濾器忽略。啟用 Python 開發模式會顯示此警告。

棄用原則描述在 PEP 387 [https://peps.python.org/pep-0387/] 裡。

exception SyntaxWarning

關於可疑語法的警告的基礎類別。

This warning is typically emitted when compiling Python source code, and usually won't be reported when running already compiled code.

exception RuntimeWarning

關於可疑執行環境行為的警告的基礎類別。

exception FutureWarning

關於已棄用功能的警告的基礎類別，且當那些警告是針對以 Python 寫的應用程式的終端使用者。

exception ImportWarning

關於在模組引入的可能錯誤的警告的基礎類別。

會被預設的警告過濾器忽略。啟用 Python 開發模式會顯示此警告。

exception UnicodeWarning

Unicode 相關警告的基礎類別。

exception EncodingWarning

編碼相關警告的基礎類別。

細節參考選擇性加入的編碼警告。

在 3.10 版被加入.

exception BytesWarning

bytes 及 bytearray 相關警告的基礎類別。

exception ResourceWarning

資源用法相關警告的基礎類別。

會被預設的警告過濾器忽略。啟用 Python 開發模式會顯示此警告。

在 3.2 版被加入.

例外群組

當需要引發多個不相關例外時會使用下列的類別。它們是例外階層的一部分所以可以像所有其他例外一樣使用 except 來處理。此外，它們會以包含的例外型別為基礎來比對其子群組而被 except* 辨認出來。

exception ExceptionGroup(msg, excs)

exception BaseExceptionGroup(msg, excs)

這兩個例外型別都將例外包裝在序列 excs 中。msg 參數必須是字串。這兩個類別的差異是 BaseExceptionGroup 擴充了 BaseException 且可以包裝任何例外，而 ExceptionGroup 擴充了 Exception 且只能包裝 Exception 的子類別。這個設計使得 except Exception 可以捕捉 ExceptionGroup 但不能捕捉 BaseExceptionGroup。

如果所有包含的例外都是 Exception 實例，BaseExceptionGroup 建構函式會回傳 ExceptionGroup 而不是 BaseExceptionGroup，因此可以被使用來讓這樣的選擇自動化。另一方面來說，如果任何包含的例外不是 Exception 的子類別，ExceptionGroup 建構函式會引發 TypeError。

message

建構函式的 msg 引數。這是一個唯讀的屬性。

exceptions

指定給建構函式 excs 序列中的例外組成的元組。這是一個唯讀的屬性。

subgroup(condition)

回傳只包含從現有群組比對到 condition 的例外的例外群組，或者當結果為空時回傳 None。

條件式可以是一個例外型別或是例外型別的元組，在此情況下，每個例外都會使用與 except 子句中使用的相同檢查方法來檢查是否有匹配。條件式也可以是一個可呼叫物件（除了型別物件之外），其接受一個例外作為單一引數，而如果該例外應該在子群組中就回傳 true。

現有例外的巢狀結構會保留在結果裡，其 message、__traceback__、__cause__、__context__ 及 __notes__ 欄位的值也一樣。空的巢狀群組會從結果裡排除。

條件會對巢狀例外群組裡的所有例外做檢查，包括頂層及任何巢狀的例外群組。如果條件對這樣的例外群組為 true，它會被完整包含在結果裡。

在 3.13 版被加入: condition 可以是任何不是型別物件的可呼叫物件。

split(condition)

像 subgroup() 一樣，但回傳一對 (match, rest)，其中 match 是 subgroup(condition) 而 rest 是剩下沒有比對到的部分。

derive(excs)

回傳有相同 message 但將例外包裝在 excs 的例外群組。

此方法被 subgroup() 及 split() 使用，被用來在各種情境下拆分例外群組。子類別需要覆寫它來讓 subgroup() 及 split() 回傳子類別而不是 ExceptionGroup 的實例。

subgroup() 及 split() 會從原始的例外群組複製 __traceback__、__cause__、__context__ 和 __notes__ 欄位到 derive() 所回傳的例外群組上，因此這些欄位不需要被 derive() 更新。

>>> class MyGroup(ExceptionGroup):
...     def derive(self, excs):
...         return MyGroup(self.message, excs)
...
>>> e = MyGroup("eg", [ValueError(1), TypeError(2)])
>>> e.add_note("a note")
>>> e.__context__ = Exception("context")
>>> e.__cause__ = Exception("cause")
>>> try:
...    raise e
... except Exception as e:
...    exc = e
...
>>> match, rest = exc.split(ValueError)
>>> exc, exc.__context__, exc.__cause__, exc.__notes__
(MyGroup('eg', [ValueError(1), TypeError(2)]), Exception('context'), Exception('cause'), ['a note'])
>>> match, match.__context__, match.__cause__, match.__notes__
(MyGroup('eg', [ValueError(1)]), Exception('context'), Exception('cause'), ['a note'])
>>> rest, rest.__context__, rest.__cause__, rest.__notes__
(MyGroup('eg', [TypeError(2)]), Exception('context'), Exception('cause'), ['a note'])
>>> exc.__traceback__ is match.__traceback__ is rest.__traceback__
True

需注意 BaseExceptionGroup 定義了 __new__()，因此需要不同建構函式簽名的子類別需要覆寫它而不是 __init__()。例如下面定義了一個例外群組子類別接受 exit_code 並從中建構群組的訊息。：

class Errors(ExceptionGroup):
   def __new__(cls, errors, exit_code):
      self = super().__new__(Errors, f"exit code: {exit_code}", errors)
      self.exit_code = exit_code
      return self

   def derive(self, excs):
      return Errors(excs, self.exit_code)

像 ExceptionGroup 一樣，任何 BaseExceptionGroup 的子類別且也是 Exception 的子類別只能包裝 Exception 的實例。

在 3.11 版被加入.

例外階層

內建例外的類別階層如下：

BaseException
 ├── BaseExceptionGroup
 ├── GeneratorExit
 ├── KeyboardInterrupt
 ├── SystemExit
 └── Exception
      ├── ArithmeticError
      │    ├── FloatingPointError
      │    ├── OverflowError
      │    └── ZeroDivisionError
      ├── AssertionError
      ├── AttributeError
      ├── BufferError
      ├── EOFError
      ├── ExceptionGroup [BaseExceptionGroup]
      ├── ImportError
      │    └── ModuleNotFoundError
      ├── LookupError
      │    ├── IndexError
      │    └── KeyError
      ├── MemoryError
      ├── NameError
      │    └── UnboundLocalError
      ├── OSError
      │    ├── BlockingIOError
      │    ├── ChildProcessError
      │    ├── ConnectionError
      │    │    ├── BrokenPipeError
      │    │    ├── ConnectionAbortedError
      │    │    ├── ConnectionRefusedError
      │    │    └── ConnectionResetError
      │    ├── FileExistsError
      │    ├── FileNotFoundError
      │    ├── InterruptedError
      │    ├── IsADirectoryError
      │    ├── NotADirectoryError
      │    ├── PermissionError
      │    ├── ProcessLookupError
      │    └── TimeoutError
      ├── ReferenceError
      ├── RuntimeError
      │    ├── NotImplementedError
      │    ├── PythonFinalizationError
      │    └── RecursionError
      ├── StopAsyncIteration
      ├── StopIteration
      ├── SyntaxError
      │    └── IndentationError
      │         └── TabError
      ├── SystemError
      ├── TypeError
      ├── ValueError
      │    └── UnicodeError
      │         ├── UnicodeDecodeError
      │         ├── UnicodeEncodeError
      │         └── UnicodeTranslateError
      └── Warning
           ├── BytesWarning
           ├── DeprecationWarning
           ├── EncodingWarning
           ├── FutureWarning
           ├── ImportWarning
           ├── PendingDeprecationWarning
           ├── ResourceWarning
           ├── RuntimeWarning
           ├── SyntaxWarning
           ├── UnicodeWarning
           └── UserWarning

文本處理 (Text Processing) 服務

本章節介紹的模組 (module) 提供了廣泛的字串操作與其他文本處理服務。

在 二進位資料服務 下所描述的 codecs 模組也與文本處理高度相關。另外也請參閱在 Text Sequence Type --- str 中所描述的 Python 內建字串型別。

string --- 常見的字串操作

字串常數

自訂字串格式

格式化文字語法

格式規格 (Format Specification) 迷你語言

格式範例

模板字串 ($-strings)

輔助函式

string.templatelib --- 對模板字串字面值的支援

模板字串

Types

Helper functions

re --- 正規表示式 (regular expression) 操作

正規表示式語法

模組內容

旗標

函式

例外

正規表示式物件

Match Objects

Regular Expression Examples

Checking for a Pair

模擬 scanf()

search() vs. match()

Making a Phonebook

Text Munging

Finding all Adverbs

Finding all Adverbs and their Positions

Raw String Notation

Writing a Tokenizer

difflib --- 計算差異的輔助工具

SequenceMatcher 物件

SequenceMatcher 範例

Differ Objects

Differ Example

difflib 的命令列介面

ndiff 範例：

textwrap --- 文字包裝與填充

unicodedata --- Unicode 資料庫

stringprep --- 網際網路字串的準備

readline --- GNU readline 介面

Init file

Line buffer

History file

History list

Startup hooks

Completion

範例

rlcompleter --- GNU readline 的補全函式

string --- 常見的字串操作

原始碼：Lib/string/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/string/__init__.py]

也參考

Text Sequence Type --- str

字串方法

字串常數

此模組中定義的常數為：

string.ascii_letters

下文描述的 ascii_lowercase 和 ascii_uppercase 常數的串接，該值不依賴於區域設定。

string.ascii_lowercase

小寫字母 'abcdefghijklmnopqrstuvwxyz'。該值與地區設定無關且不會改變。

string.ascii_uppercase

大寫字母 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'。此值與地區設定無關且不會改變。

string.digits

字串 '0123456789'。

string.hexdigits

字串 '0123456789abcdefABCDEF'。

string.octdigits

字串 '01234567'。

string.punctuation

在 C 語言中被視為標點符號的 ASCII 字元的字串：!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~。

string.printable

ASCII 字元的字串被 Python 是為可被列印輸出的。這是 digits、ascii_letters、punctuation 和 whitespace 的組合。

備註

By design, string.printable.isprintable() returns False. In particular, string.printable is not printable in the POSIX sense (see LC_CTYPE [https://manpages.debian.org/locale(5)]).

string.whitespace

包含所有 ASCII 字元的字串都視為空白字元 (whitespace)。 包含空格 (space)、製表符號 (tab)、換行符號 (linefeed)、return、換頁符號 (formfeed) 和垂直製表符號 (vertical tab) 這些字元。

自訂字串格式

透過 PEP 3101 [https://peps.python.org/pep-3101/] 中描述的 format() 方法，內建字串類別提供了進行複雜變數替換和數值格式化的能力。string 模組中的 Formatter 類別模組可讓你使用與內建 format() 方法相同的實作來建立和自訂你自己的字串格式化行為。

class string.Formatter

Formatter 類別有以下的公開方法：

format(format_string, /, *args, **kwargs)

主要的 API 方法。它接收一個格式字串及一組任意的位置引數與關鍵字引數，是呼叫 vformat() 的包裝器 (wrapper)。

在 3.7 版的變更: 現在格式字串引數是僅限位置參數。

vformat(format_string, args, kwargs)

This function does the actual work of formatting. It is exposed as a separate function for cases where you want to pass in a predefined dictionary of arguments, rather than unpacking and repacking the dictionary as individual arguments using the *args and **kwargs syntax. vformat() does the work of breaking up the format string into character data and replacement fields. It calls the various methods described below.

In addition, the Formatter defines a number of methods that are intended to be replaced by subclasses:

parse(format_string)

將 format_string 放入迴圈，並回傳一個可疊代物件，其元素為 (literal_text, field_name, format_spec, conversion)。這會被 vformat() 用於將字串裁切為字面文本或替換欄位。

The values in the tuple conceptually represent a span of literal text followed by a single replacement field. If there is no literal text (which can happen if two replacement fields occur consecutively), then literal_text will be a zero-length string. If there is no replacement field, then the values of field_name, format_spec and conversion will be None. The value of field_name is unmodified and auto-numbering of non-numbered positional fields is done by vformat().

get_field(field_name, args, kwargs)

Given field_name, convert it to an object to be formatted. Auto-numbering of field_name returned from parse() is done by vformat() before calling this method. Returns a tuple (obj, used_key). The default version takes strings of the form defined in PEP 3101 [https://peps.python.org/pep-3101/], such as "0[name]" or "label.title". args and kwargs are as passed in to vformat(). The return value used_key has the same meaning as the key parameter to get_value().

get_value(key, args, kwargs)

Retrieve a given field value. The key argument will be either an integer or a string. If it is an integer, it represents the index of the positional argument in args; if it is a string, then it represents a named argument in kwargs.

The args parameter is set to the list of positional arguments to vformat(), and the kwargs parameter is set to the dictionary of keyword arguments.

For compound field names, these functions are only called for the first component of the field name; subsequent components are handled through normal attribute and indexing operations.

So for example, the field expression '0.name' would cause get_value() to be called with a key argument of 0. The name attribute will be looked up after get_value() returns by calling the built-in getattr() function.

If the index or keyword refers to an item that does not exist, then an IndexError or KeyError should be raised.

check_unused_args(used_args, args, kwargs)

Implement checking for unused arguments if desired. The arguments to this function is the set of all argument keys that were actually referred to in the format string (integers for positional arguments, and strings for named arguments), and a reference to the args and kwargs that was passed to vformat. The set of unused args can be calculated from these parameters. check_unused_args() is assumed to raise an exception if the check fails.

format_field(value, format_spec)

format_field() simply calls the global format() built-in. The method is provided so that subclasses can override it.

convert_field(value, conversion)

Converts the value (returned by get_field()) given a conversion type (as in the tuple returned by the parse() method). The default version understands 's' (str), 'r' (repr) and 'a' (ascii) conversion types.

格式化文字語法

The str.format() method and the Formatter class share the same syntax for format strings (although in the case of Formatter, subclasses can define their own format string syntax). The syntax is related to that of formatted string literals and template string literals, but it is less sophisticated and, in particular, does not support arbitrary expressions in interpolations.

Format strings contain "replacement fields" surrounded by curly braces {}. Anything that is not contained in braces is considered literal text, which is copied unchanged to the output. If you need to include a brace character in the literal text, it can be escaped by doubling: {{ and }}.

The grammar for a replacement field is as follows:

replacement_field: "{" [field_name] ["!" conversion] [":" format_spec] "}"
field_name:        arg_name ("." attribute_name | "[" element_index "]")*
arg_name:          [identifier | digit+]
attribute_name:    identifier
element_index:     digit+ | index_string
index_string:      <any source character except "]"> +
conversion:        "r" | "s" | "a"
format_spec:       format-spec:format_spec

In less formal terms, the replacement field can start with a field_name that specifies the object whose value is to be formatted and inserted into the output instead of the replacement field. The field_name is optionally followed by a conversion field, which is preceded by an exclamation point '!', and a format_spec, which is preceded by a colon ':'. These specify a non-default format for the replacement value.

另請參閱 格式規格 (Format Specification) 迷你語言 部份。

The field_name itself begins with an arg_name that is either a number or a keyword. If it's a number, it refers to a positional argument, and if it's a keyword, it refers to a named keyword argument. An arg_name is treated as a number if a call to str.isdecimal() on the string would return true. If the numerical arg_names in a format string are 0, 1, 2, ... in sequence, they can all be omitted (not just some) and the numbers 0, 1, 2, ... will be automatically inserted in that order. Because arg_name is not quote-delimited, it is not possible to specify arbitrary dictionary keys (e.g., the strings '10' or ':-]') within a format string. The arg_name can be followed by any number of index or attribute expressions. An expression of the form '.name' selects the named attribute using getattr(), while an expression of the form '[index]' does an index lookup using __getitem__().

在 3.1 版的變更: The positional argument specifiers can be omitted for str.format(), so '{} {}'.format(a, b) is equivalent to '{0} {1}'.format(a, b).

在 3.4 版的變更: The positional argument specifiers can be omitted for Formatter.

Some simple format string examples:

"First, thou shalt count to {0}"  # References first positional argument
"Bring me a {}"                   # Implicitly references the first positional argument
"From {} to {}"                   # Same as "From {0} to {1}"
"My quest is {name}"              # References keyword argument 'name'
"Weight in tons {0.weight}"       # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}"   # First element of keyword argument 'players'.

The conversion field causes a type coercion before formatting. Normally, the job of formatting a value is done by the __format__() method of the value itself. However, in some cases it is desirable to force a type to be formatted as a string, overriding its own definition of formatting. By converting the value to a string before calling __format__(), the normal formatting logic is bypassed.

目前支援三種轉換旗標：'!s' 會對該值呼叫 str()，'!r' 會對該值呼叫 repr()，而 '!a' 則會對該值呼叫 ascii()。

一些範例：

"Harold's a clever {0!s}"        # Calls str() on the argument first
"Bring out the holy {name!r}"    # Calls repr() on the argument first
"More {!a}"                      # Calls ascii() on the argument first

format_spec 欄位描述了值的呈現規格，例如欄位寬度、對齊、填充 (padding)、小數精度等細節資訊。每種值類型都可以定義自己的「格式化迷你語言 (formatting mini-language)」或對 format_spec 的解釋。

大多數內建型別都支援常見的格式化迷你語言，下一節將會詳細說明。

format_spec 欄位還可以在其內部包含巢狀的替換欄位。這些巢狀的替換欄位可能包含欄位名稱、轉換旗標、格式規格描述，但是不允許再更深層的巢狀結構。format_spec 內部的替換欄位會在 format_spec 字串被直譯前被替換。這讓數值的格式能夠被動態地指定。

範例請見 格式範例。

格式規格 (Format Specification) 迷你語言

「格式規格」在格式字串 (format string) 中包含的替換欄位中使用，以定義各個值如何被呈現（請參考 格式化文字語法、f-string（f 字串） 和 t-string（t 字串））。它們也能夠直接傳遞給內建的 format() 函式。每個可格式化型別 (formattable type) 可以定義格式規格如何被直譯。

大部分內建型別為了格式規格實作了下列選項，不過有些選項只被數值型別支援。

一般來說，輸入空格式規格會產生和對值呼叫 str() 函式相同的結果，非空的格式規格才會修改結果。

標準格式說明符號 (standard format specifier) 的一般型式如下：

format_spec:             [options][width_and_precision][type]
options:                 [[fill]align][sign]["z"]["#"]["0"]
fill:                    <any character>
align:                   "<" | ">" | "=" | "^"
sign:                    "+" | "-" | " "
width_and_precision:     [width_with_grouping][precision_with_grouping]
width_with_grouping:     [width][grouping]
precision_with_grouping: "." [precision][grouping] | "." grouping
width:                   digit+
precision:               digit+
grouping:                "," | "_"
type:                    "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g"
                         | "G" | "n" | "o" | "s" | "x" | "X" | "%"

如果給定了一個有效的 align 值，則可以在它之前加一個 fill 字元，且該字元可為任意字元，若不加的話預設為空格。使用格式字串或 str.format() 時是無法在其中使用大括號（"{" 或 "}"）作為 fill 字元的，但仍可透過巢狀替換欄位的方式插入大括號。此限制不影響 format() 函式。

The meaning of the various alignment options is as follows:

選項

含義

'<'

強制欄位在可用空間內靠左對齊（這是大多數物件的預設值）。

'>'

強制欄位在可用空間內靠右對齊（這是數字的預設值）。

'='

Forces the padding to be placed after the sign (if any) but before the digits. This is used for printing fields in the form '+000000120'. This alignment option is only valid for numeric types, excluding complex. It becomes the default for numbers when '0' immediately precedes the field width.

'^'

強制欄位在可用空間內置中。

請注意，除非有定義了最小欄位寬度，否則欄位寬度將始終與填充它的資料大小相同，故在該情況下的對齊選項是沒有意義的。

sign 選項只適用於數字型別，並可為以下之一：

選項

含義

'+'

表示正數與負數均需使用符號。

'-'

表示正數應使用前導空格，負數應使用減號。

空格

表示正數應使用前導空格，負數應使用減號。

The 'z' option coerces negative zero floating-point values to positive zero after rounding to the format precision. This option is only valid for floating-point presentation types.

在 3.11 版的變更: 新增 'z' 選項（請見 PEP 682 [https://peps.python.org/pep-0682/]）。

The '#' option causes the "alternate form" to be used for the conversion. The alternate form is defined differently for different types. This option is only valid for integer, float and complex types. For integers, when binary, octal, or hexadecimal output is used, this option adds the respective prefix '0b', '0o', '0x', or '0X' to the output value. For float and complex the alternate form causes the result of the conversion to always contain a decimal-point character, even if no digits follow it. Normally, a decimal-point character appears in the result of these conversions only if a digit follows it. In addition, for 'g' and 'G' conversions, trailing zeros are not removed from the result.

width 是一個十進位整數，定義了最小總欄位寬度，包括任何前綴、分隔符號和其他格式字元。如果未指定，則欄位寬度將由內容決定。

當未給予明確的對齊指示，在 width 欄位前面填入零 ('0') 字元將會為 complex 以外的數值型別啟用有符號察覺的零填充 (sign-aware zero-padding)。這相當於使用 '0' 為 fill 字元且對齊類型為 '='。

在 3.10 版的變更: 在 width 欄位前面加上 '0' 不再影響字串的預設對齊方式。

precision 是一個十進位整數，指定表示類型 'f' 和 'F' 的小數點後應顯示多少位，或表示類型 'g' 或 'G' 的小數點前後應顯示多少位。對於字串表示類型，該欄位指定最大欄位大小 - 換言之，將使用欄位中的多少字元。整數表示類型不允許使用 precision。

The grouping option after width and precision fields specifies a digit group separator for the integral and fractional parts of a number respectively. It can be one of the following:

選項

含義

','

Inserts a comma every 3 digits for integer presentation type 'd' and floating-point presentation types, excluding 'n'. For other presentation types, this option is not supported.

'_'

在整數表示型別 'd' 和浮點數表示型別中，每 3 位數插入一個底線，這不包括 'n'。對於整數表示型別 'b'，'o'，'x' 和 'X'，每 4 位數字會插入底線。對於其他表示型別來說此選項並不支援。

For a locale aware separator, use the 'n' presentation type instead.

在 3.1 版的變更: 新增 ',' 選項（請見 PEP 378 [https://peps.python.org/pep-0378/]）。

在 3.6 版的變更: 新增 '_' 選項（請見 PEP 515 [https://peps.python.org/pep-0515/]）。

在 3.14 版的變更: Support the grouping option for the fractional part.

最終，型別決定了資料將會如何呈現

可用的字串表示型別有：

型別

含義

's'

String format. This is the default type for strings and may be omitted.

None

與 's' 相同。

The available integer presentation types are:

型別

含義

'b'

Binary format. Outputs the number in base 2.

'c'

Character. Converts the integer to the corresponding unicode character before printing.

'd'

Decimal Integer. Outputs the number in base 10.

'o'

Octal format. Outputs the number in base 8.

'x'

十六進位格式。輸出以 16 為基數的數字，9 以上的數字使用小寫字母。

'X'

十六進位格式。輸出以 16 為基數的數字，9 以上的數字使用大寫字母。如果指定了 '#'，則前綴 '0x' 也會被轉成大寫的 '0X'。

'n'

Number. This is the same as 'd', except that it uses the current locale setting to insert the appropriate digit group separators.

None

與 'd' 相同。

In addition to the above presentation types, integers can be formatted with the floating-point presentation types listed below (except 'n' and None). When doing so, float() is used to convert the integer to a floating-point number before formatting.

The available presentation types for float and Decimal values are:

型別

含義

'e'

Scientific notation. For a given precision p, formats the number in scientific notation with the letter 'e' separating the coefficient from the exponent. The coefficient has one digit before and p digits after the decimal point, for a total of p + 1 significant digits. With no precision given, uses a precision of 6 digits after the decimal point for float, and shows all coefficient digits for Decimal. If p=0, the decimal point is omitted unless the # option is used.

For float, the exponent always contains at least two digits, and is zero if the value is zero.

'E'

Scientific notation. Same as 'e' except it uses an upper case 'E' as the separator character.

'f'

Fixed-point notation. For a given precision p, formats the number as a decimal number with exactly p digits following the decimal point. With no precision given, uses a precision of 6 digits after the decimal point for float, and uses a precision large enough to show all coefficient digits for Decimal. If p=0, the decimal point is omitted unless the # option is used.

'F'

Fixed-point notation. Same as 'f', but converts nan to NAN and inf to INF.

'g'

General format. For a given precision p >= 1, this rounds the number to p significant digits and then formats the result in either fixed-point format or in scientific notation, depending on its magnitude. A precision of 0 is treated as equivalent to a precision of 1.

The precise rules are as follows: suppose that the result formatted with presentation type 'e' and precision p-1 would have exponent exp. Then, if m <= exp < p, where m is -4 for floats and -6 for Decimals, the number is formatted with presentation type 'f' and precision p-1-exp. Otherwise, the number is formatted with presentation type 'e' and precision p-1. In both cases insignificant trailing zeros are removed from the significand, and the decimal point is also removed if there are no remaining digits following it, unless the '#' option is used.

With no precision given, uses a precision of 6 significant digits for float. For Decimal, the coefficient of the result is formed from the coefficient digits of the value; scientific notation is used for values smaller than 1e-6 in absolute value and values where the place value of the least significant digit is larger than 1, and fixed-point notation is used otherwise.

Positive and negative infinity, positive and negative zero, and nans, are formatted as inf, -inf, 0, -0 and nan respectively, regardless of the precision.

'G'

General format. Same as 'g' except switches to 'E' if the number gets too large. The representations of infinity and NaN are uppercased, too.

'n'

Number. This is the same as 'g', except that it uses the current locale setting to insert the appropriate digit group separators for the integral part of a number.

'%'

Percentage. Multiplies the number by 100 and displays in fixed ('f') format, followed by a percent sign.

None

For float this is like the 'g' type, except that when fixed-point notation is used to format the result, it always includes at least one digit past the decimal point, and switches to the scientific notation when exp >= p - 1. When the precision is not specified, the latter will be as large as needed to represent the given value faithfully.

For Decimal, this is the same as either 'g' or 'G' depending on the value of context.capitals for the current decimal context.

The overall effect is to match the output of str() as altered by the other format modifiers.

The result should be correctly rounded to a given precision p of digits after the decimal point. The rounding mode for float matches that of the round() builtin. For Decimal, the rounding mode of the current context will be used.

The available presentation types for complex are the same as those for float ('%' is not allowed). Both the real and imaginary components of a complex number are formatted as floating-point numbers, according to the specified presentation type. They are separated by the mandatory sign of the imaginary part, the latter being terminated by a j suffix. If the presentation type is missing, the result will match the output of str() (complex numbers with a non-zero real part are also surrounded by parentheses), possibly altered by other format modifiers.

格式範例

本節包含 str.format() 語法以及與舊式 % 格式的比較。

此語法在大多情況下與舊式的 % 格式類似，只是增加了 {} 和 : 來取代 %。例如，'%03.2f' 可以改寫為 '{:03.2f}'。

新的語法還支援新的選項，將在以下的範例中說明。

按位置存取引數：

>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
>>> '{}, {}, {}'.format('a', 'b', 'c')  # 3.1+ only
'a, b, c'
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc')      # 解包引數序列
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad')   # 引數索引可以重複
'abracadabra'

按名稱存取引數：

>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)
'Coordinates: 37.24N, -115.81W'

存取引數的屬性：

>>> c = 3-5j
>>> ('The complex number {0} is formed from the real part {0.real} '
...  'and the imaginary part {0.imag}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point:
...     def __init__(self, x, y):
...         self.x, self.y = x, y
...     def __str__(self):
...         return 'Point({self.x}, {self.y})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)'

存取引數的內容：

>>> coord = (3, 5)
>>> 'X: {0[0]};  Y: {0[1]}'.format(coord)
'X: 3;  Y: 5'

替換 %s 和 %r：

>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"

對齊文字以及指定寬度：

>>> '{:<30}'.format('left aligned')
'left aligned                  '
>>> '{:>30}'.format('right aligned')
'                 right aligned'
>>> '{:^30}'.format('centered')
'           centered           '
>>> '{:*^30}'.format('centered')  # use '*' as a fill char
'***********centered***********'

替換 %+f、%-f 和 % f 以及指定正負號：

>>> '{:+f}; {:+f}'.format(3.14, -3.14)  # 總會顯示
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14)  # 若為正數則顯示空格
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14)  # 只顯示負號 -- 與 '{:f}; {:f}' 相同
'3.140000; -3.140000'

替換 %x 和 %o 並將其值轉換為不同的進位制：

>>> # format also supports binary numbers
>>> "int: {0:d};  hex: {0:x};  oct: {0:o};  bin: {0:b}".format(42)
'int: 42;  hex: 2a;  oct: 52;  bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}".format(42)
'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'

使用逗號或底線作為數字分組分隔符號：

>>> '{:,}'.format(1234567890)
'1,234,567,890'
>>> '{:_}'.format(1234567890)
'1_234_567_890'
>>> '{:_b}'.format(1234567890)
'100_1001_1001_0110_0000_0010_1101_0010'
>>> '{:_x}'.format(1234567890)
'4996_02d2'
>>> '{:_}'.format(123456789.123456789)
'123_456_789.12345679'
>>> '{:.,}'.format(123456789.123456789)
'123456789.123,456,79'
>>> '{:,._}'.format(123456789.123456789)
'123,456,789.123_456_79'

表示為百分比：

>>> points = 19
>>> total = 22
>>> 'Correct answers: {:.2%}'.format(points/total)
'Correct answers: 86.36%'

作為特定型別格式：

>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'

巢狀引數及更多複雜範例：

>>> for align, text in zip('<^>', ['left', 'center', 'right']):
...     '{0:{fill}{align}16}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12):
...     for base in 'dXob':
...         print('{0:{width}{base}}'.format(num, base=base, width=width), end=' ')
...     print()
...
    5     5     5   101
    6     6     6   110
    7     7     7   111
    8     8    10  1000
    9     9    11  1001
   10     A    12  1010
   11     B    13  1011

模板字串 ($-strings)

備註

The feature described here was introduced in Python 2.4; a simple templating method based upon regular expressions. It predates str.format(), formatted string literals, and template string literals.

It is unrelated to template string literals (t-strings), which were introduced in Python 3.14. These evaluate to string.templatelib.Template objects, found in the string.templatelib module.

模板字串提供如 PEP 292 [https://peps.python.org/pep-0292/] 所述更簡單的字串替換。模板字串的主要用例是國際化 (i18n)，因為在這種情況下，更簡單的語法和功能使得它比其他 Python 內建字串格式化工具更容易翻譯。基於模板字串建構的 i18n 函式庫範例，請參閱 flufl.i18n [https://flufli18n.readthedocs.io/en/latest/] 套件。

Template strings support $-based substitutions, using the following rules:

$$ is an escape; it is replaced with a single $.

$identifier names a substitution placeholder matching a mapping key of "identifier". By default, "identifier" is restricted to any case-insensitive ASCII alphanumeric string (including underscores) that starts with an underscore or ASCII letter. The first non-identifier character after the $ character terminates this placeholder specification.

${identifier} is equivalent to $identifier. It is required when valid identifier characters follow the placeholder but are not part of the placeholder, such as "${noun}ification".

Any other appearance of $ in the string will result in a ValueError being raised.

The string module provides a Template class that implements these rules. The methods of Template are:

class string.Template(template)

The constructor takes a single argument which is the template string.

substitute(mapping={}, /, **kwds)

進行模板替換，並回傳一個新的字串。 mapping 是任何有金鑰並符合模板裡佔位符號的字典型物件。或者如果關鍵字就是佔位符號時，你也可以改提供關鍵字引數。當 mapping 跟 kwds 同時給定並存在重複時，kwds 的佔位符號會被優先使用。

safe_substitute(mapping={}, /, **kwds)

類似於 substitute()，但如果 mapping 與 kwds 中缺少佔位符號的話，原始的佔位符號會完整地出現在結果字串裡，而不會引發 KeyError 例外。此外，與 substitute() 不同的是，任何包含 $ 的字句會直接回傳 $ 而非引發 ValueError。

雖然仍可能發生其他例外，但這個方法被認為是「安全」的，因為它總是試圖回傳一個有用的字串而不是引發例外。從另一個角度來看，safe_substitute() 可能並非完全安全，因為它會默默忽略格式錯誤的模板，這些模板包含了多餘的左右定界符、不匹配的括號，或者不是有效的 Python 識別字的佔位符號。

is_valid()

如果模板有將導致 substitute() 引發 ValueError 的無效佔位符號，就會回傳 False。

在 3.11 版被加入.

get_identifiers()

回傳模板中有效識別字的串列，按照它們首次出現的順序，並忽略任何無效的識別字。

在 3.11 版被加入.

Template 實例也提供一個公開的資料屬性：

template

這是傳遞給建構函式 template 引數的物件。一般來說，你不應該改變它，但並沒有強制設定成唯讀。

以下是如何使用 Template 的一個範例：

>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
'tim likes kung pao'
>>> d = dict(who='tim')
>>> Template('Give $who $100').substitute(d)
Traceback (most recent call last):
...
ValueError: Invalid placeholder in string: line 1, col 11
>>> Template('$who likes $what').substitute(d)
Traceback (most recent call last):
...
KeyError: 'what'
>>> Template('$who likes $what').safe_substitute(d)
'tim likes $what'

進階用法：你可以衍生 Template 類別來自訂佔位符號語法、左右定界符字元，或者用於剖析模板字串的正規表示式。你可以透過覆寫這些類別屬性來達成：

delimiter -- 這是描述引入左右定界符的文字字串。預設值是 $。請注意這不是正規表示式，因為實作會在需要時對這個字串呼叫 re.escape()。也請注意你不能在建立類別後修改左右定界符。（意即在子類別的命名空間中必須設置不同的左右定界符）

idpattern -- This is the regular expression describing the pattern for non-braced placeholders. The default value is the regular expression (?a:[_a-z][_a-z0-9]*). If this is given and braceidpattern is None this pattern will also apply to braced placeholders.

備註

Since default flags is re.IGNORECASE, pattern [a-z] can match with some non-ASCII characters. That's why we use the local a flag here.

在 3.7 版的變更: braceidpattern can be used to define separate patterns used inside and outside the braces.

braceidpattern -- This is like idpattern but describes the pattern for braced placeholders. Defaults to None which means to fall back to idpattern (i.e. the same pattern is used both inside and outside braces). If given, this allows you to define different patterns for braced and unbraced placeholders.

在 3.7 版被加入.

flags -- The regular expression flags that will be applied when compiling the regular expression used for recognizing substitutions. The default value is re.IGNORECASE. Note that re.VERBOSE will always be added to the flags, so custom idpatterns must follow conventions for verbose regular expressions.

在 3.2 版被加入.

Alternatively, you can provide the entire regular expression pattern by overriding the class attribute pattern. If you do this, the value must be a regular expression object with four named capturing groups. The capturing groups correspond to the rules given above, along with the invalid placeholder rule:

escaped -- 此群組與跳脫序列匹配，例如在預設模式下為 $$。

named -- 此群組與不帶大括號的佔位符號名稱匹配；它不應包含擷取群組中的左右定界符號。

braced -- 此群組與大括號括起來的佔位符號名稱匹配；它不應在擷取群組中包含左右定界符或大括號。

invalid -- 此群組與任何其他左右定界符模式（通常是單一左右定界符）匹配，且它應該出現在正規表示式的最後。

當此模式有匹配於模板但這些命名組中卻有任一個不匹配，此類別的方法將引發 ValueError。

輔助函式

string.capwords(s, sep=None)

使用 str.split() 將引數分割為字詞，使用 str.capitalize() 將每個單字大寫，並使用 str.join() 將大寫字詞連接起來。如果可選的第二引數 sep 不存在或為 None，則連續的空白字元將替換為單一空格，並且刪除前導和尾隨空白；在其他情況下則使用 sep 來分割和連接單字。

string.templatelib --- 對模板字串字面值的支援

原始碼：Lib/string/templatelib.py [https://github.com/python/cpython/tree/3.14/Lib/string/templatelib.py]

也參考

格式字串

Template string literal (t-string) syntax

PEP 750 [https://peps.python.org/pep-0750/]

模板字串

在 3.14 版被加入.

Template strings are a mechanism for custom string processing. They have the full flexibility of Python's f-string（f 字串）, but return a Template instance that gives access to the static and interpolated (in curly brackets) parts of a string before they are combined.

To write a t-string, use a 't' prefix instead of an 'f', like so:

>>> pi = 3.14
>>> t't-strings are new in Python {pi!s}!'
Template(
   strings=('t-strings are new in Python ', '!'),
   interpolations=(Interpolation(3.14, 'pi', 's', ''),)
)

Types

class string.templatelib.Template

The Template class describes the contents of a template string. It is immutable, meaning that attributes of a template cannot be reassigned.

The most common way to create a Template instance is to use the template string literal syntax. This syntax is identical to that of f-strings, except that it uses a t prefix in place of an f:

>>> cheese = 'Red Leicester'
>>> template = t"We're fresh out of {cheese}, sir."
>>> type(template)
<class 'string.templatelib.Template'>

Templates are stored as sequences of literal strings and dynamic interpolations. A values attribute holds the values of the interpolations:

>>> cheese = 'Camembert'
>>> template = t'Ah! We do have {cheese}.'
>>> template.strings
('Ah! We do have ', '.')
>>> template.interpolations
(Interpolation('Camembert', ...),)
>>> template.values
('Camembert',)

The strings tuple has one more element than interpolations and values; the interpolations “belong” between the strings. This may be easier to understand when tuples are aligned

template.strings:  ('Ah! We do have ',              '.')
template.values:   (                   'Camembert',    )

Attributes

strings: tuple[str, ...]

A tuple of the static strings in the template.

>>> cheese = 'Camembert'
>>> template = t'Ah! We do have {cheese}.'
>>> template.strings
('Ah! We do have ', '.')

Empty strings are included in the tuple:

>>> response = 'We do have '
>>> cheese = 'Camembert'
>>> template = t'Ah! {response}{cheese}.'
>>> template.strings
('Ah! ', '', '.')

The strings tuple is never empty, and always contains one more string than the interpolations and values tuples:

>>> t''.strings
('',)
>>> t''.values
()
>>> t'{'cheese'}'.strings
('', '')
>>> t'{'cheese'}'.values
('cheese',)

interpolations: tuple[Interpolation, ...]

A tuple of the interpolations in the template.

>>> cheese = 'Camembert'
>>> template = t'Ah! We do have {cheese}.'
>>> template.interpolations
(Interpolation('Camembert', 'cheese', None, ''),)

The interpolations tuple may be empty and always contains one fewer values than the strings tuple:

>>> t'Red Leicester'.interpolations
()

values: tuple[object, ...]

A tuple of all interpolated values in the template.

>>> cheese = 'Camembert'
>>> template = t'Ah! We do have {cheese}.'
>>> template.values
('Camembert',)

The values tuple always has the same length as the interpolations tuple. It is always equivalent to tuple(i.value for i in template.interpolations).

方法

__new__(*args: str | Interpolation)

While literal syntax is the most common way to create a Template, it is also possible to create them directly using the constructor:

>>> from string.templatelib import Interpolation, Template
>>> cheese = 'Camembert'
>>> template = Template(
...     'Ah! We do have ', Interpolation(cheese, 'cheese'), '.'
... )
>>> list(template)
['Ah! We do have ', Interpolation('Camembert', 'cheese', None, ''), '.']

If multiple strings are passed consecutively, they will be concatenated into a single value in the strings attribute. For example, the following code creates a Template with a single final string:

>>> from string.templatelib import Template
>>> template = Template('Ah! We do have ', 'Camembert', '.')
>>> template.strings
('Ah! We do have Camembert.',)

If multiple interpolations are passed consecutively, they will be treated as separate interpolations and an empty string will be inserted between them. For example, the following code creates a template with empty placeholders in the strings attribute:

>>> from string.templatelib import Interpolation, Template
>>> template = Template(
...     Interpolation('Camembert', 'cheese'),
...     Interpolation('.', 'punctuation'),
... )
>>> template.strings
('', '', '')

iter(template)

Iterate over the template, yielding each non-empty string and Interpolation in the correct order:

>>> cheese = 'Camembert'
>>> list(t'Ah! We do have {cheese}.')
['Ah! We do have ', Interpolation('Camembert', 'cheese', None, ''), '.']

警示

Empty strings are not included in the iteration:

>>> response = 'We do have '
>>> cheese = 'Camembert'
>>> list(t'Ah! {response}{cheese}.')
['Ah! ',
 Interpolation('We do have ', 'response', None, ''),
 Interpolation('Camembert', 'cheese', None, ''),
 '.']

template + other

template += other

Concatenate this template with another, returning a new Template instance:

>>> cheese = 'Camembert'
>>> list(t'Ah! ' + t'We do have {cheese}.')
['Ah! We do have ', Interpolation('Camembert', 'cheese', None, ''), '.']

Concatenating a Template and a str is not supported. This is because it is unclear whether the string should be treated as a static string or an interpolation. If you want to concatenate a Template with a string, you should either wrap the string directly in a Template (to treat it as a static string) or use an Interpolation (to treat it as dynamic):

>>> from string.templatelib import Interpolation, Template
>>> template = t'Ah! '
>>> # Treat 'We do have ' as a static string
>>> template += Template('We do have ')
>>> # Treat cheese as an interpolation
>>> cheese = 'Camembert'
>>> template += Template(Interpolation(cheese, 'cheese'))
>>> list(template)
['Ah! We do have ', Interpolation('Camembert', 'cheese', None, '')]

class string.templatelib.Interpolation

The Interpolation type represents an expression inside a template string. It is immutable, meaning that attributes of an interpolation cannot be reassigned.

Interpolations support pattern matching, allowing you to match against their attributes with the match statement:

>>> from string.templatelib import Interpolation
>>> interpolation = t'{1. + 2.:.2f}'.interpolations[0]
>>> interpolation
Interpolation(3.0, '1. + 2.', None, '.2f')
>>> match interpolation:
...     case Interpolation(value, expression, conversion, format_spec):
...         print(value, expression, conversion, format_spec, sep=' | ')
...
3.0 | 1. + 2. | None | .2f

Attributes

value: object

The evaluated value of the interpolation.

>>> t'{1 + 2}'.interpolations[0].value
3

expression: str

For interpolations created by t-string literals, expression is the expression text found inside the curly brackets ({ & }), including any whitespace, excluding the curly brackets themselves, and ending before the first !, :, or = if any is present. For manually created interpolations, expression is the arbitrary string provided when constructing the interpolation instance.

We recommend using valid Python expressions or the empty string for the expression field of manually created Interpolation instances, although this is not enforced at runtime.

>>> t'{1 + 2}'.interpolations[0].expression
'1 + 2'

conversion: Literal['a', 'r', 's'] | None

The conversion to apply to the value, or None.

The conversion is the optional conversion to apply to the value:

>>> t'{1 + 2!a}'.interpolations[0].conversion
'a'

備註

Unlike f-strings, where conversions are applied automatically, the expected behavior with t-strings is that code that processes the Template will decide how to interpret and whether to apply the conversion. For convenience, the convert() function can be used to mimic f-string conversion semantics.

format_spec: str

The format specification to apply to the value.

The format_spec is an optional, arbitrary string used as the format specification to present the value:

>>> t'{1 + 2:.2f}'.interpolations[0].format_spec
'.2f'

備註

Unlike f-strings, where format specifications are applied automatically via the format() protocol, the expected behavior with t-strings is that code that processes the interpolation will decide how to interpret and whether to apply the format specification. As a result, format_spec values in interpolations can be arbitrary strings, including those that do not conform to the format() protocol.

方法

__new__(value: object, expression: str, conversion: Literal['a', 'r', 's'] | None = None, format_spec: str = '')

Create a new Interpolation object from component parts.

參數:

value -- The evaluated, in-scope result of the interpolation.

expression -- The text of a valid Python expression, or an empty string.

conversion -- The conversion to be used, one of None, 'a', 'r', or 's'.

format_spec -- An optional, arbitrary string used as the format specification to present the value.

Helper functions

string.templatelib.convert(obj, /, conversion)

Applies formatted string literal conversion semantics to the given object obj. This is frequently useful for custom template string processing logic.

Three conversion flags are currently supported:

's' which calls str() on the value (like !s),

'r' which calls repr() (like !r), and

'a' which calls ascii() (like !a).

If the conversion flag is None, obj is returned unchanged.

re --- 正規表示式 (regular expression) 操作

原始碼：Lib/re/ [https://github.com/python/cpython/tree/3.14/Lib/re/]

此模組提供類似於 Perl 中正規表示式的匹配操作。

被搜尋的模式 (pattern) 與字串可以是 Unicode 字串 (str)，也可以是 8-bit 字串 (bytes)。然而，Unicode 字串和 8-bit 字串不能混用：也就是，你不能用 byte 模式匹配 Unicode 字串，反之亦然；同樣地，替換時，用來替換的字串必須與模式和搜尋字串是相同的型別 (type)。

正規表示式使用反斜線字元 ('\') 表示特別的形式，或是使用特殊字元而不觸發它們的特殊意義。這與 Python 在字串文本 (literal) 中，為了相同目的使用同一個字元的做法相衝突；舉例來說，為了匹配一個反斜線字面值，可能需要寫 '\\\\' 當作模式字串，因為正規表示式必須是 \\，而且每個反斜線在一個普通的 Python 字串文本中必須表示為 \\。另外，請注意在 Python 的字串文本中使用反斜線的任何無效跳脫序列目前會產生一個 SyntaxWarning，而在未來這會變成一個 SyntaxError。儘管它對正規表示式是一個有效的跳脫序列，這種行為也會發生。

解決方法是對正規表示式模式使用 Python 的原始字串符號；反斜線在一個以 'r' 為前綴的字串文本中不會被用任何特別的方式處理。所以 r"\n" 是一個兩個字元的字串，包含 '\' 和 'n'，同時 "\n" 是一個單個字元的字串，包含一個換行符號。通常模式在 Python 程式中會使用這個原始字串符號表示。

請務必注意到大部分的正規表示式操作是可以在模組層級的函式和 compiled regular expressions 中的方法使用的。這些函式是個捷徑且讓你不需要先編譯一個正規表示式物件，但是會缺少一些微調參數。

也參考

第三方的 regex [https://pypi.org/project/regex/] 模組，有著和標準函式庫 re 模組相容的 API，但是提供額外的功能以及更完整的 Unicode 支援。

正規表示式語法

一個正規表示式（或 RE）會指定一組匹配它的字串；這個模組的函式讓你可以檢查一個特定的字串是否匹配給定的正規表示式（或是給定的正規表示式是否匹配特定的字串，說到底是一樣的）。

正規表示式可以被連接 (concatenated) 成新的正規表示式；如果 A 和 B 都是正規表示式，則 AB 也是一個正規表示式。一般來說，如果一個字串 p 與 A 匹配，並且另一個字串 q 與 B 匹配，則字串 pq 會匹配 AB。或：這在以下情況下不成立：A*或 *B 包含低優先順序的運算子；或 A 和 B 之間的邊界條件 (boundary conditions)；或是有編號群組 (numbered group) 的參照。因此，複雜的正規表示式可以輕鬆地從此處提到的簡單原始正規表示式建立。關於正規表示式的理論和實作，請參考 Friedl 書 [Frie09]，或任何有關建構編譯器的書籍。

一個簡短的正規表示式格式解釋如下。如需更多資訊或以較平易的方式了解，請參閱 如何使用正規表示式。

正規表示式可以包含特殊和一般字元。大多數一般字元，如 'A'、'a' 或 '0' 是最簡單的正規表示式；它們只匹配它們自己。你可以連接一般字元，讓 last 匹配字串 'last'。（在本節的其餘部分，我們會用通常沒有引號的 這種特殊樣式 來書寫正規表示式，而被匹配的字串會 '在單引號中'。）

某些字元是特殊的，像 '|' 或 '('。特殊字元會代表一般字元的類別，或是會影響它們周圍正規表示式的解讀方法。

重複運算子或量詞 (quantifiers)（*, +, ?, {m,n} 等）不能直接嵌套使用。這樣避免了和非貪婪修飾符號後綴 ? 和其他實作中的修飾符號的模糊性。要在一個重複正規表示式內添加第二個重複，可以使用括號。例如：正規表示式 (?:a{6})* 會匹配任何六的倍數個 a 字元。

特殊字元包含：

.

（點） 在預設模式下，這會匹配除換行符號外的任何字元。如果指定了 DOTALL 旗標，這會匹配包含換行符號的任何字元。無論旗標為何，(?s:.) 都會匹配任何字元。

^

（插入符號） 會匹配字串的開頭，並且在 MULTILINE 模式下，也會立即匹配緊接在每個換行符號之後的位置。

$

匹配字串的結尾或是字串結尾的換行符號之前，並且在 MULTILINE 模式下會匹配換行符號之前的位置。foo 會匹配 'foo' 和 'foobar'，而正規表示式 foo$ 只會匹配 'foo'。更有趣的是，在 'foo1\nfoo2\n' 中搜尋 foo.$，正常情況下會匹配 'foo2'，但是在 MULTILINE 模式下會匹配 'foo1'；在 'foo\n' 中搜尋單一個 $ 會找到兩個（空的）匹配：一個在換行符號之前，一個在字串結尾。

*

使得到的正規表示式匹配前面正規表示式的 0 或多次的重複，盡可能多次的重複。ab* 會匹配 'a'、'ab'，或後面跟著任何數量個 'b' 的 'a'。

+

使得到的正規表示式匹配前面正規表示式的 1 或多次的重複。ab+ 會匹配後面跟著任何非零數量個 'b' 的 'a'；它不會匹配 'a'。

?

使得到的正規表示式匹配前面正規表示式的 0 或 1 次的重複。ab? 會匹配 'a' 或 'ab'。

*?, +?, ??

量詞 (quantifier) '*'、'+' 和 '?' 都是 greedy（貪婪的）；它們會盡可能地匹配更多文字。有時候這種行為不是預期的；如果正規表示式 <.*> 被用來匹配 '<a> b <c>'，它會匹配整個字串，而不只是 '<a>'。在量詞後添加 ? 會讓他以 non-greedy（非貪婪的）或 minimal（最小的）方式進行匹配；盡可能匹配更少的字元。使用正規表示式 <.*?> 只會匹配到 '<a>'。

*+, ++, ?+

類似於量詞 '*'、'+' 和 '?'，添加了 '+' 的量詞也會盡可能多次的匹配。然而，不同於真正的貪婪量詞，這些量詞在接續的正規表示式匹配失敗時不允許回溯 (back-tracking)。這些量詞被稱為 possessive （佔有的）量詞。例如，a*a 會匹配 'aaaa'，因為 a* 會匹配全部 4 個 'a'，但是在遇到最後的 'a' 時，此正規表示式會回溯，以讓 a* 最終可以總共匹配 3 個 'a'，而第四個 'a' 會被最後的 'a' 匹配。然而，當 a*+a 被用來匹配 'aaaa' 時， a*+ 會匹配全部 4 個 'a'，但是當最終的 'a' 在尋找更多字元匹配失敗時，此正規表示式不能回溯並會因此匹配失敗。x*+、x++ 和 x?+ 分別等同於 (?>x*)、(?>x+) 和 (?>x?)。

在 3.11 版被加入.

{m}

指定應該恰好匹配 m 個前面的正規表示式；太少的匹配會造成整個正規表示式匹配失敗。例如，a{6} 會匹配恰好六個 'a' 字元，但不匹配五個。

{m,n}

使得到的正規表示式重複匹配前面的正規表示式 m 到 n 次，並嘗試盡可能多次的匹配。例如，a{3,5} 會匹配 3 到 5 個 'a' 字元。忽略 m 會指定下限為零，且忽略 n 會指定無限大的上限。舉例來說，a{4,}b 會匹配 'aaaab' 或一千個 'a' 字元加上一個 'b'，但是不匹配 'aaab'。不可以忽略逗號，否則量詞會與前述的形式混淆。

{m,n}?

使得到的正規表示式重複匹配前面的正規表示式 m 到 n 次，嘗試盡可能更少次的匹配。這是上一個量詞的非貪婪版本。例如，對六個字元的字串 'aaaaaa'，a{3,5} 會匹配 5 個 'a' 字元，而 a{3,5}? 只會匹配 3 個字元。

{m,n}+

使得到的正規表示式重複匹配前面的正規表示式 m 到 n 次，並嘗試盡可能更多次的匹配而不建立任何回溯點。這是上述量詞的佔有版本。例如，對六個字元的字串 'aaaaaa'，a{3,5}+aa 嘗試匹配 5 個 'a' 字元，然後需要再 2 個 'a'，會需要比可用的字元更多所以失敗，而 a{3,5}aa 會捕捉到 5 個 'a'，然後回溯成 4 個 'a'，接著最後兩個 'a' 會被模式中最後的 aa 匹配。x{m,n}+ 等同於 (?>x{m,n})。

在 3.11 版被加入.

\

用來跳脫特殊字元（允許你匹配如 '*'、'?' 等字元），或是表示一個特殊序列；特殊序列將在下方討論。

如果你沒有使用原始字串來表示正規表示式，請記得 Python 也會使用反斜線作為字串文本的跳脫序列；如果 Python 的剖析器辨認不出該跳脫序列，反斜線和接續的字元將會被包含在得到的字串中。然而，如果 Python 能辨認出該序列，反斜線應該要被重複兩次。這很複雜並且難以理解，所以強烈建議，除了最簡單的正規表示式，都應該使用原始字串。

[]

用來表示一個字元集合。在一個集合中：

字元可以獨立列出，例如： [amk] 會匹配 'a'、'm' 或 'k'。

可以透過給定兩個字元並且使用 '-' 分隔它們來表示一個範圍的字元，例如 [a-z] 會匹配任何 ASCII 小寫字母，[0-5][0-9] 會匹配所有從 00 到 59 的兩位數字，而 [0-9A-Fa-f] 會匹配任何十六進位數字。如果 - 被跳脫了（如： [a\-z]） 或是放在第一或最後一個位置（如： [-a] 或 [a-]），它將會匹配字面的 '-'。

除反斜線外的特殊字元會在集合內失去它們的特殊意義。例如，[(+*)] 會匹配任何字面字元 '('、'+'、'*'，或 ')'。

反斜線可能用於跳脫集合內具有特殊意義的字元，像是 '-'、']'、'^' 和 '\\' 本身，或是表示一個代表單一字元的特殊序列，像是 \xa0 或 \n 或一個字元類別，如 \w 或 \S（定義如下）。請注意，\b 代表單一個 "backspace" 字元，而不是在集合外代表的字元邊界，且像是 \1 的數值跳脫總是代表八進位數字的跳脫，而不是群組的參照。不匹配單一字元的特殊序列是不被允許的，像是 \A 和 \Z。

不在範圍內的字元可以透過取集合的補集 (complement) <complementing> 匹配。如果集合中的第一個字元是 '^'，所有不在集合內的字元都會被匹配。例如， [^5] 會匹配任何除了 '5' 的字元，而 [^^] 會匹配任何除了 '^' 的字元。如果 ^ 不是集合中的第一個字元的話，沒有特殊意義。

要在集合中匹配字面的 ']'，在前面加上一個反斜線，或是將它放在集合中的最前面。例如，[()[\]{}] 和 []()[{}] 都會匹配右方括號、左方括號、花括號和括號。

未來可能會支援 Unicode Technical Standard #18 [https://unicode.org/reports/tr18/] 中的嵌套集合與集合操作。這會改變語法，所以為了促進這個改變，暫時會在模糊的情況下引發 FutureWarning。包含了以字面 '[' 開頭，或是包含字面的字元序列 '--'、'&&'、'~~' 和 '||' 的集合。為了避免警告，請用反斜線跳脫它們。

在 3.7 版的變更: 如果一個字元集合包含了其語義未來會被改變的結構，FutureWarning 會被引發。

|

A|B，其中 A 和 B 可以為任何正規表示式，會創造出一個匹配 A 或是 B 的正規表示式。任何數量的正規表示式可以像這樣用 '|' 分隔。這也可以用在群組（見下文）中。當目標字串被掃描時，被 '|' 分隔的正規表示式會被從左到右嘗試。當一個模式完全匹配時，那條分支就被接受了。這代表一旦 A 匹配了，B 就不會被進一步測試，就算它會讓整個匹配更長。換句話說，'|' 永遠不是貪婪的。要匹配字面的 '|'，使用 \|，或是將它包圍在一個字元類別中，就像 [|]。

(...)

匹配括號中的任何正規表示式，並且表示一個群組的開始和結束；群組的內容可以在執行匹配後取得，並且在後續的字串可以使用 \number 特殊序列來匹配，如下所述。要匹配字面的 '(' 或 ')'，用 \( 或 \)，或是將它們包圍在一個字元類別中： [(、[)]。

(?...)

這是一個擴充表示法（否則一個 '?' 接著一個 '(' 是沒有意義的）。'?' 後面的第一個字元決定了這個結構的意義和進一步的語法。擴充通常不會創造新的群組；(?P<name>...) 是這個規則的唯一例外。以下是目前支援的擴充。

(?aiLmsux)

（集合 'a'、'i'、'L'、'm'、's'、'u'、 'x' 中的一或多個字母。）該群組會匹配空字串；這些字母會為整個正規表示式設定對應的旗標。

re.A（僅限 ASCII 字元匹配）

re.I（忽略大小寫）

re.L（依賴區域設定）

re.M（多行）

re.S（點會匹配所有字元）

re.U（匹配 Unicode）

re.X（詳盡模式）

（這些旗標在 模組內容 中說明。）如果你想將旗標當作正規表示式的一部分，而不是傳遞一個 flag 引數給 re.compile() 函式的話，這會有幫助。旗標應該首先在正規表示式字串中使用。

在 3.11 版的變更: 此結構只能用於正規表示式的開頭。

(?:...)

一個非捕捉版本的普通括號。匹配括號內的任何正規表示式，但是被群組匹配到的子字串不能在執行匹配後被取得，或是在之後的模式中被參照。

(?aiLmsux-imsx:...)

（集合 'a'、'i'、'L'、'm'、's'、'u'、'x' 中的零或多個字母，選擇性地接著 '-'，並接著一或多個 'i'、'm'、's'、'x' 中的字母。）該字母集合會為那一部分的正規表示式設定或是移除對應的旗標。

re.A（僅限 ASCII 字元匹配）

re.I（忽略大小寫）

re.L（依賴區域設定）

re.M（多行）

re.S（點會匹配所有字元）

re.U（匹配 Unicode）

re.X（詳盡模式）

（這些旗標在 模組內容 中說明。）

字母 'a'、'L' 和 'u' 在被當作嵌入旗標時是互斥的，所以它們不能被組合使用或是接在 '-' 後面。相反地，當它們其中一個出現在嵌入群組時，它會覆蓋括號中群組的匹配模式。在 Unicode 模式中，(?a:...) 會切換到僅匹配 ASCII 模式，且 (?u:...) 會切換到 Unicode 匹配模式（預設）。在位元組模式，(?L:...) 會切換到依賴區域設定 (locale) 的匹配，且 (?a:...) 會切換到僅匹配 ASCII 模式（預設）。這個覆蓋只會在嵌入群組中作用，而原本的匹配模式會在群組外恢復。

在 3.6 版被加入.

在 3.7 版的變更: 字母 'a'、'L' 和 'u' 也可以被用在群組中。

(?>...)

嘗試將 ... 視為獨立的正規表示式進行匹配，且若成功則會繼續匹配後續的模式。如果後續模式匹配失敗，則回溯堆疊 (stack) 只能還原 (unwound) 到 (?>...) 之前，因為一旦退出了，這個也叫做原子群組 (atomic group) 的正規表示式，已經丟棄了它自己的所有回溯點 (stack point)。因此，(?>.*). 永遠不會匹配任何內容，因為 .* 會先盡可能匹配所有的字元，接著沒有任何剩餘內容可以匹配，導致最終的 . 匹配失敗。因為原子群組中沒有儲存回溯點，而且群組之前也沒有回溯點，整個正規表示式都會匹配失敗。

在 3.11 版被加入.

(?P<name>...)

類似於一般的括號，但是這個群組匹配的子字串可以透過符號群組名稱 name 存取。群組名稱必須是有效的 Python 識別字 (identifier)，並且在 bytes 模式中，它們只能包含 ASCII 範圍中的位元組。每個群組名稱在正規表示式中只能定義一次。一個符號群組同時也是一個編號群組，只是等同於該群組沒有名稱。

命名群組 (named groups) 可以在三種情境下被參照。如果該模式是 (?P<quote>['"]).*?(?P=quote)（也就是匹配一個用單引號或雙引號包圍的字串）：

對 "quote" 群組參照的情境

參照方式

在同一個模式中

(?P=quote)（如上例所示）

\1

在處理匹配物件 m 時

m.group('quote')

m.end('quote')（等）

在被當成 re.sub() 的 repl 引數傳入的字串中

\g<quote>

\g<1>

\1

在 3.12 版的變更: 在 bytes 模式中，群組的名稱只能包含 ASCII 範圍中的位元組（b'\x00'-b'\x7f'）。

(?P=name)

對於命名群組的反向參照；它會匹配任何之前被命名為 name 的群組所匹配到的文字。

(?#...)

一個註解；括號中的內容會被忽略。

(?=...)

如果字串接下來可以匹配 ... 才會成功匹配，但是並不會消耗任何字串。這被稱作 lookahead assertion。例如，Isaac (?=Asimov) 只在後面跟著 'Asimov' 時才會匹配 'Isaac '。

(?!...)

如果字串接下來不匹配 ...，才會成功匹配。這是一個負向預查斷言 (negative lookahead assertion) <negative lookahead assertion>。例如，Isaac (?!Asimov) 只在後面不跟著 'Asimov' 時才會匹配 'Isaac '。

(?<=...)

如果目前位置前方的字串能夠匹配 ...，可以成功匹配。這叫做正向回查斷言 (positive lookbehind assertion) <positive lookbehind assertion>。(?<=abc)def 會在 'abcdef' 中找到一個匹配，因為回查會向後 3 個字元，並檢查是否能匹配包含的模式。這個包含的模式只能匹配固定長度的字串，代表 abc 或 a|b 是被允許的，但是 a* 和 a{3,4} 不被允許。請注意，使用正向回查斷言開頭的模式不會匹配被搜尋字串的開頭；你更可能想要使用 search() 函式而不是 match() 函式：

>>> import re
>>> m = re.search('(?<=abc)def', 'abcdef')
>>> m.group(0)
'def'

這個範例在尋找連字號後的單字：

>>> m = re.search(r'(?<=-)\w+', 'spam-egg')
>>> m.group(0)
'egg'

在 3.5 版的變更: 新增固定長度群組參照的支援。

(?<!...)

如果目前位置前方的字串不能夠匹配 ...，可以成功匹配。這叫做負向回查斷言 (negative lookbehind assertion) <negative lookbehind assertion>。類似於正向回查斷言，包含的模式只能匹配固定長度的字串。使用負向回查斷言開頭的模式可以匹配被搜尋字串的開頭。

(?(id/name)yes-pattern|no-pattern)

如果給定 id 或 name 的群組存在，會嘗試匹配 yes-pattern，否則會匹配 no-pattern。no-pattern 是可選的並且可以省略。例如，(<)?(\w+@\w+(?:\.\w+)+)(?(1)>|$) 是一個不好的電子郵件匹配模式，它會匹配 '<user@host.com>' 和 'user@host.com'，但不會匹配 '<user@host.com' 以及 'user@host.com>'。

在 3.12 版的變更: 群組 id 只能包含 ASCII 數字。在 bytes 模式中，群組 name 只能包含 ASCII 範圍中的位元組 (b'\x00'-b'\x7f')。

特殊序列由 '\' 和下列清單的一個字元組成。如果序列中的一般字元不是一個 ASCII 數字或是一個 ASCII 字母，那麼產生的的正規表示式會匹配第二個字元。例如，\$ 會匹配字元 '$'。

\number

匹配相同數字群組中的內容。群組會從 1 開始編號。例如，(.+) \1 會匹配 'the the' 或 '55 55'，但不會匹配 'thethe'（注意群組後的空格）。這個特殊序列只能用來匹配前 99 個群組之一。如果 number 的第一位數是 0，或是 number 有 3 個八進位位數，它就不會被解讀成匹配群組，而是解讀成八進位數值 number 的字元。在一個字元類別中的 '[' 和 ']'，所有數值的跳脫字元都會被當作字元。

\A

只在字串的開頭匹配。

\b

匹配空字串，但是只在一個單字的開頭或結尾。一個單字被定義為一個單字字元的序列。請注意在正式情況下，\b 被定義為 \w 和一個 \W 字元的邊界（或是反之亦然），或是在 \w 和字串的開頭或結尾之間。這表示 r'\bat\b' 會匹配 'at'、'at.'、'(at)'，以及 'as at ay'，但是不匹配 'attempt' 或 'atlas'。

預設的單字字元在 Unicode（字串）模式中，是 Unicode 字母數字 (alphanumerics) 和底線，但是這可以透過使用 ASCII 旗標來改變。如果使用了 LOCALE 旗標，單字的邊界會由目前的區域設定決定。

備註

在字元範圍中，為了與 Python 的字串文本的相容性，\b 表示 backspace 字元。

\B

匹配空字串，但是只有在空字串不在單字的開頭或結尾時匹配。這表示 r'at\B' 會匹配 'athens'、'atom'、'attorney'，但是不匹配 'at'、'at.' 或 'at!'。\B 是 \b 的相反，所以 Unicode（字串）模式中的單字字元是 Unicode 字母、數字或底線，不過這可以透過使用 ASCII 旗標來改變。如果使用了 LOCALE 旗標，單字的邊界會由目前的區域設定決定。

在 3.14 版的變更: \B 現在會匹配空的輸入字串。

\d

對於 Unicode（字串）模式：

匹配任何 Unicode 十進位數字（也就是 Unicode 字元類別中的任何字元 [Nd] [https://www.unicode.org/versions/Unicode15.0.0/ch04.pdf#G134153]）。這包含了 [0-9]，以及許多許多其他的數字字元。

如果使用了 ASCII 旗標，匹配 [0-9]。

對於 8 位元（位元組）模式：

匹配任何 ASCII 字元集合中的十進位數字；這等同於 [0-9]。

\D

匹配任何不是十進位數字的字元。這是 \d 的相反。

如果使用了 ASCII 旗標，會匹配 [^0-9]。

\s

對於 Unicode（字串）模式：

匹配 Unicode 空格字元（在 str.isspace() 中定義）。包含 [ \t\n\r\f\v]，還有許多其他的字元，例如許多語言的排版規則中要求的不換行空格。

如果使用了 ASCII 旗標，匹配 [ \t\n\r\f\v]。

對於 8 位元（位元組）模式：

匹配 ASCII 字元集合中認定的空格；這等同於 [ \t\n\r\f\v]。

\S

匹配任何不是空格字元的字元。這是 \s 的相反。

如果使用了 ASCII 旗標，匹配 [^ \t\n\r\f\v]。

\w

對於 Unicode（字串）模式：

匹配 Unicode 單字字元；這包含全部 Unicode 的字母數字字元（在 str.isalnum() 中定義），以及底線 (_)。

如果使用了 ASCII 旗標，匹配 [a-zA-Z0-9_]。

對於 8 位元（位元組）模式：

匹配在 ASCII 字元集合中被認定為字母或數字的字元；這等同於 [a-zA-Z0-9_]。如果使用了 LOCALE 旗標，會匹配目前區域設定中被認定為字母或數字的字元，以及底線。

\W

匹配任何不是單字字元的字元。這是 \w 的相反。預設情況下，會匹配任何不是底線 (_)，並且 str.isalnum() 會回傳 False 的字元。

如果使用了 ASCII 旗標，會匹配 [^a-zA-Z0-9_]。

如果使用了 LOCALE 旗標，會匹配目前區域中不是字母數字，也不是底線的字元。

\z

只在字串的結尾匹配。

在 3.14 版被加入.

\Z

和 \z 相同。為了與舊版的 Python 相容而保留。

大多數 Python 的字串文本支援的跳脫序列也能被正規表示式剖析器接受：

\a      \b      \f      \n
\N      \r      \t      \u
\U      \v      \x      \\

（請注意 \b 被用來表示單字邊界，並且只在字元類別內表示 "backspace"。）

'\u'、'\U'，和 '\N' 跳脫序列只會在 Unicode（字串）模式中可辨認。在位元組模式中，它們是錯誤。未知的跳脫 ASCII 字母被保留於未來使用，並且會被當成錯誤。

八進位數的跳脫被有限地包含在內。如果第一個數字是一個 0，或是如果有三個八進位數字，它就會被當作是一個八進位跳脫。否則，它是一個群組參照。至於字串文本，八進位跳脫最多只能包含三個數字。

在 3.3 版的變更: '\u' 和 '\U' 跳脫序列已經被添加。

在 3.6 版的變更: 由 '\' 和一個 ASCII 字母組成的未知跳脫現在會是錯誤。

在 3.8 版的變更: '\N{name}' 跳脫序列已經被添加。如同字串文本，它會展開成命名的 Unicode 字元（如 '\N{EM DASH}'）。

模組內容

The module defines several functions, constants, and an exception. Some of the functions are simplified versions of the full featured methods for compiled regular expressions. Most non-trivial applications always use the compiled form.

旗標

在 3.6 版的變更: Flag 常數現在是 RegexFlag 的實例，其為 enum.IntFlag 的子類別。

class re.RegexFlag

包含下列正規表示式選項的一個 enum.IntFlag 類別。

在 3.11 版被加入: - added to __all__

re.A

re.ASCII

使 \w、\W、\b、\B、\d、\D、\s 和 \S 執行僅限 ASCII 的匹配，而不是完整的 Unicode 匹配。這只對 Unicode（字串）模式有意義，並且在位元組模式中會被忽略。

對應到內嵌旗標 (?a)。

備註

為了向後相容，U 旗標仍然存在，但是在 Python 3 中是多餘的，因為對於 str 模式，匹配預設是 Unicode，並且不允許位元組模式進行 Unicode 匹配。UNICODE 和內嵌旗標 (?u) 也是類似的冗餘。

re.DEBUG

顯示關於已編譯表示式的偵錯資訊。

沒有對應的內嵌旗標。

re.I

re.IGNORECASE

執行不區分大小寫的匹配；像是 [A-Z] 這樣的表示式也會匹配小寫字母。完整的 Unicode 匹配（例如 Ü 匹配 ü）也能正常運作，除非使用了 ASCII 旗標來停用非 ASCII 的匹配。除非也使用了 LOCALE 旗標，否則目前的區域設定不會改變這個旗標的效果。

對應到內嵌旗標 (?i)。

請注意，當 Unicode 模式 [a-z] 或 [A-Z] 與 IGNORECASE 旗標結合使用時，它們會匹配 52 個 ASCII 字母和另外 4 個非 ASCII 字母：'İ' (U+0130，帶點的大寫拉丁字母 I)、'ı' （U+0131，無點的小寫拉丁字母 i）、'ſ' （U+017F，拉丁小寫長 s）和 'K' （U+212A，開爾文符號）。如果使用了 ASCII 旗標，則只會匹配字母 'a' 到 'z' 和 'A' 到 'Z'。

re.L

re.LOCALE

使 \w、\W、\b、\B 和不區分大小寫的匹配依賴於目前的區域設定。這個旗標只能用在位元組模式中。

對應到內嵌旗標 (?L)。

警告

不建議使用這個旗標；請考慮使用 Unicode 匹配。區域設定機制非常不可靠，因為它一次只處理一種「文化」，並且只適用於 8 位元的區域設定。Unicode 匹配在 Unicode（字串）模式中預設是啟用的，並且能夠處理不同的區域設定和語言。

在 3.6 版的變更: LOCALE 只能用在位元組模式中，並且與 ASCII 不相容。

在 3.7 版的變更: 使用 LOCALE 旗標的已編譯正規表示式物件不再依賴於編譯時的區域設定。只有匹配時的區域設定會影響匹配的結果。

re.M

re.MULTILINE

當指定時，模式字元 '^' 會在字串的開頭以及每一行的開頭（緊接在每個換行符號之後）匹配；而模式字元 '$' 會在字串的結尾以及每一行的結尾（緊接在每個換行符號之前）匹配。預設情況下，'^' 只會在字串的開頭匹配，而 '$' 只會在字串的結尾以及字串結尾（如果有的話）緊接在換行符號之前匹配。

對應到內嵌旗標 (?m)。

re.NOFLAG

表示沒有應用任何旗標，值為 0。這個旗標可以用作函式關鍵字引數的預設值，或是作為一個基底值，將會有條件地與其他旗標進行 OR 運算。作為預設值使用的範例：

def myfunc(text, flag=re.NOFLAG):
    return re.match(text, flag)

在 3.11 版被加入.

re.S

re.DOTALL

使 '.' 特殊字元能夠匹配任何字元，包括換行符號；如果沒有這個旗標，'.' 只會匹配除了換行符號以外的任何字元。

對應到內嵌旗標 (?s)。

re.U

re.UNICODE

在 Python 3 中，Unicode 字元在 str 模式中預設會被匹配。因此這個旗標是多餘的，沒有任何效果，並且僅為了向後相容而保留。

請參閱 ASCII 以將匹配限制為 ASCII 字元。

re.X

re.VERBOSE

這個旗標透過讓你在視覺上分隔模式的邏輯區塊並添加註解，使你能夠撰寫看起來更好且更易讀的正規表示式。模式中的空白會被忽略，除非在字元類別中，或是前面有一個未跳脫的反斜線，或是在像是 *?、(?: 或 (?P<...> 這樣的標記中。例如，(? : 和 * ? 是不允許的。當一行包含一個不在字元類別中且前面沒有未跳脫反斜線的 # 時，從最左邊的這個 # 到行尾的所有字元都會被忽略。

這表示下面兩個匹配十進位數字的正規表示式物件在功能上是相等的：

a = re.compile(r"""\d +  # 整數部分
                   \.    # 小數點
                   \d *  # 一些小數位""", re.X)
b = re.compile(r"\d+\.\d*")

對應到內嵌旗標 (?x)。

函式

re.compile(pattern, flags=0)

將正規表示式模式編譯成正規表示式物件，可以使用它的 match()、search() 等方法來匹配，如下所述。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

序列為：

prog = re.compile(pattern)
result = prog.match(string)

等價於：

result = re.match(pattern, string)

但是當表示式在單一程式中多次使用時，使用 re.compile() 並保存產生的正規表示式物件以供重複使用會更有效率。

備註

傳遞給 re.compile() 之最新模式的編譯版本和模組層級匹配函式都會被快取，因此一次僅使用幾個正規表示式的程式不必去擔心編譯正規表示式。

re.search(pattern, string, flags=0)

掃描 string 以尋找正規表示式 pattern 產生匹配的第一個位置，並回傳對應的 Match。如果字串中沒有與模式匹配的位置則回傳 None；請注意，這與在字串中的某個點查找零長度匹配不同。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

re.match(pattern, string, flags=0)

如果 string 開頭的零個或多個字元與正規表示式 pattern 匹配，則回傳對應的 Match。如果字串與模式不匹配，則回傳 None；請注意，這與零長度匹配不同。

請注意，即使在 MULTILINE 模式 (mode) 下，re.match() 只會於字串的開頭匹配，而非每行的開頭。

如果你想在 string 中的任何位置找到匹配項，請使用 search()（另請參閱 search() vs. match()）。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

re.fullmatch(pattern, string, flags=0)

如果整個 string 與正規表示式 pattern 匹配，則回傳對應的 Match。如果字串與模式不匹配，則回傳 None；請注意，這與零長度匹配不同。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

在 3.4 版被加入.

re.split(pattern, string, maxsplit=0, flags=0)

依 pattern 的出現次數拆分 string。如果在 pattern 中使用捕獲括號，則模式中所有群組的文字也會作為結果串列的一部分回傳。如果 maxsplit 非零，則最多發生 maxsplit 次拆分，並且字串的其餘部分會作為串列的最終元素回傳。

>>> re.split(r'\W+', 'Words, words, words.')
['Words', 'words', 'words', '']
>>> re.split(r'(\W+)', 'Words, words, words.')
['Words', ', ', 'words', ', ', 'words', '.', '']
>>> re.split(r'\W+', 'Words, words, words.', maxsplit=1)
['Words', 'words, words.']
>>> re.split('[a-f]+', '0a3B9', flags=re.IGNORECASE)
['0', '3', '9']

如果分隔符號中有捕獲群組並且它在字串的開頭匹配，則結果將以空字串開頭。這同樣適用於字串的結尾：

>>> re.split(r'(\W+)', '...words, words...')
['', '...', 'words', ', ', 'words', '...', '']

如此一來，分隔符號元件始終可以在結果串列中的相同相對索引處找到。

Adjacent empty matches are not possible, but an empty match can occur immediately after a non-empty match.

>>> re.split(r'\b', 'Words, words, words.')
['', 'Words', ', ', 'words', ', ', 'words', '.']
>>> re.split(r'\W*', '...words...')
['', '', 'w', 'o', 'r', 'd', 's', '', '']
>>> re.split(r'(\W*)', '...words...')
['', '...', '', '', 'w', '', 'o', '', 'r', '', 'd', '', 's', '...', '', '', '']

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

在 3.1 版的變更: 新增可選旗標引數。

在 3.7 版的變更: 新增了對可以匹配空字串之模式進行拆分的支援。

在 3.13 版之後被棄用: 將 maxsplit 和 flags 作為位置引數傳遞的用法已被棄用。在未來的 Python 版本中，它們將會是僅限關鍵字參數。

re.findall(pattern, string, flags=0)

以字串或元組串列的形式回傳 string 中 pattern 的所有非重疊匹配項。從左到右掃描 string，並按找到的順序回傳符合項目。結果中會包含空匹配項。

結果取決於模式中捕獲群組的數量。如果沒有群組，則回傳與整個模式匹配的字串串列。如果恰好存在一個群組，則回傳與該群組匹配的字串串列。如果存在多個群組，則回傳與群組匹配的字串元組串列。非捕獲群組則不影響結果的形式。

>>> re.findall(r'\bf[a-z]*', 'which foot or hand fell fastest')
['foot', 'fell', 'fastest']
>>> re.findall(r'(\w+)=(\d+)', 'set width=20 and height=10')
[('width', '20'), ('height', '10')]

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

在 3.7 版的變更: 非空匹配現在可以剛好在前一個空匹配的後面開始。

re.finditer(pattern, string, flags=0)

回傳一個 iterator，在 string 中的 RE pattern 的所有非重疊匹配上 yield Match 物件。從左到右掃描 string，並按找到的順序回傳匹配項目。結果中包含空匹配項。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

在 3.7 版的變更: 非空匹配現在可以剛好在前一個空匹配的後面開始。

re.sub(pattern, repl, string, count=0, flags=0)

回傳透過以替換 repl 取代 string 中最左邊不重疊出現的 pattern 所獲得的字串。如果未找到該模式，則不改變 string 並回傳。repl 可以是字串或函式；如果它是字串，則處理其中的任何反斜線跳脫。也就是說 \n 會被轉換為單一換行符、\r 會被轉換為回車符 (carriage return) 等等。ASCII 字母的未知跳脫符會被保留以供將來使用並被視為錯誤。其他未知跳脫符例如 \& 會被單獨保留。例如 \6 的反向參照將被替換為模式中第 6 組匹配的子字串。例如：

>>> re.sub(r'def\s+([a-zA-Z_][a-zA-Z_0-9]*)\s*\(\s*\):',
...        r'static PyObject*\npy_\1(void)\n{',
...        'def myfunc():')
'static PyObject*\npy_myfunc(void)\n{'

如果 repl 是一個函式，則 pattern 的每個不重疊出現之處都會呼叫它。此函式接收單一 Match 引數，並回傳替換字串。例如：

>>> def dashrepl(matchobj):
...     if matchobj.group(0) == '-': return ' '
...     else: return '-'
...
>>> re.sub('-{1,2}', dashrepl, 'pro----gram-files')
'pro--gram files'
>>> re.sub(r'\sAND\s', ' & ', 'Baked Beans And Spam', flags=re.IGNORECASE)
'Baked Beans & Spam'

此模式可以是字串或 Pattern。

可選引數 count 是要替換的模式出現的最大次數；count 必須是非負整數。如果省略或為零，則所有出現的內容都將被替換。

Adjacent empty matches are not possible, but an empty match can occur immediately after a non-empty match. As a result, sub('x*', '-', 'abxd') returns '-a-b--d-' instead of '-a-b-d-'.

在字串型別 repl 引數中，除了上述字元跳脫和反向參照之外，\g<name> 將使用名為 name 的群組所匹配到的子字串，如 (?P<name>...) 所定義的語法。\g<number> 使用對應的群組編號；因此 \g<2> 等價於 \2，但在諸如 \g<2>0 之類的替換中並非模糊不清 (isn't ambiguous)。\20 將被直譯為對群組 20 的參照，而不是對後面跟著字面字元 '0' 的群組 2 的參照。反向參照 \g<0> 會取代以 RE 所匹配到的整個子字串。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

在 3.1 版的變更: 新增可選旗標引數。

在 3.5 版的變更: 不匹配的群組將被替換為空字串。

在 3.6 版的變更: 在由 '\' 和一個 ASCII 字母組成之 pattern 中的未知跳脫符現在為錯誤。

在 3.7 版的變更: 由 '\' 和一個 ASCII 字母組成之 repl 中的未知跳脫符現在為錯誤。非空匹配後可以緊接著出現空匹配。

在 3.12 版的變更: 群組 id 只能包含 ASCII 數字。在 bytes 替換字串中，群組 name 只能包含 ASCII 範圍內的位元組 (b'\x00'-b'\x7f')。

在 3.13 版之後被棄用: 將 count 和 flags 作為位置引數傳遞的用法已被棄用。在未來的 Python 版本中，它們將會是僅限關鍵字參數。

re.subn(pattern, repl, string, count=0, flags=0)

執行與 sub() 相同的操作，但回傳一個元組 (new_string, number_of_subs_made)。

可以透過指定 flags 值來修改正規表示式的行為，值可以是任何 flags 變數，使用位元 OR（bitwise OR、| 運算子）組合。

re.escape(pattern)

對 pattern 中的特殊字元進行跳脫。如果你想要匹配其中可能包含正規表示式元字元 (metacharacter) 的任何文本字串，這會非常有用。例如：

>>> print(re.escape('https://www.python.org'))
https://www\.python\.org

>>> legal_chars = string.ascii_lowercase + string.digits + "!#$%&'*+-.^_`|~:"
>>> print('[%s]+' % re.escape(legal_chars))
[abcdefghijklmnopqrstuvwxyz0123456789!\#\$%\&'\*\+\-\.\^_`\|\~:]+

>>> operators = ['+', '-', '*', '/', '**']
>>> print('|'.join(map(re.escape, sorted(operators, reverse=True))))
/|\-|\+|\*\*|\*

此函式不得用於 sub() 和 subn() 中的替換字串，僅應跳脫反斜線。例如：

>>> digits_re = r'\d+'
>>> sample = '/usr/sbin/sendmail - 0 errors, 12 warnings'
>>> print(re.sub(digits_re, digits_re.replace('\\', r'\\'), sample))
/usr/sbin/sendmail - \d+ errors, \d+ warnings

在 3.3 版的變更: '_' 字元不再被跳脫。

在 3.7 版的變更: Only characters that can have special meaning in a regular expression are escaped. As a result, '!', '"', '%', "'", ',', '/', ':', ';', '<', '=', '>', '@', and "`" are no longer escaped.

re.purge()

清除正規表示式快取。

例外

exception re.PatternError(msg, pattern=None, pos=None)

當傳遞給此處函式之一的字串不是有效的正規表示式（例如它可能包含不匹配的括號）或在編譯或匹配期間發生某些其他錯誤時，將引發例外。如果字串不包含模式匹配項，則絕不是錯誤。PatternError 實例具有以下附加屬性：

msg

未格式化的錯誤訊息。

pattern

正規表示式模式。

pos

pattern 中編譯失敗的索引（可能是 None）。

lineno

對應 pos 的列（可能是 None）。

colno

對應 pos 的欄（可能是 None）。

在 3.5 版的變更: 新增額外屬性。

在 3.13 版的變更: PatternError 最初被命名為 error；後者為了向後相容性而被保留為別名。

正規表示式物件

class re.Pattern

由 re.compile() 回傳的已編譯正規表示式物件。

在 3.9 版的變更: re.Pattern 支援 [] 以表示 Unicode（字串）或位元組模式。請參閱 泛型別名型別。

Pattern.search(string[, pos[, endpos]])

掃描 string 以尋找此正規表示式產生匹配的第一個位置，並回傳對應的 Match。如果字串中沒有與模式匹配的位置則回傳 None；請注意，這與在字串中的某個點查找零長度匹配不同。

可選的第二個參數 pos 提供字串中的索引，表示要從哪裡開始搜尋；預設值為 0。這並不完全等同於對字串進行切片；'^' 模式字元會在字串的實際開頭和換行之後的位置匹配，但不一定是在要開始搜尋的索引處。

可選的參數 endpos 限制了字串將被搜尋的範圍；就好像字串的長度為 endpos 個字元一樣，因此只有從 pos 到 endpos - 1 的字元會被搜尋以尋找匹配項。如果 endpos 小於 pos，則不會找到匹配項；否則，如果 rx 是已編譯的正規表示式物件，則 rx.search(string, 0, 50) 等價於 rx.search(string[:50], 0)。

>>> pattern = re.compile("d")
>>> pattern.search("dog")     # 在索引 0 處匹配
<re.Match object; span=(0, 1), match='d'>
>>> pattern.search("dog", 1)  # 無匹配；搜尋不包含 "d"

Pattern.match(string[, pos[, endpos]])

如果在 string 的開頭處有零個或多個字元與此正規表示式匹配，則回傳對應的 Match。如果字串與模式不匹配，則回傳 None；請注意，這與零長度匹配不同。

可選的 pos 和 endpos 參數與 search() 方法中的參數具有相同的意義。

>>> pattern = re.compile("o")
>>> pattern.match("dog")      # 無匹配，因為 "o" 不在 "dog" 的開頭。
>>> pattern.match("dog", 1)   # 匹配，因為 "o" 是 "dog" 的第二個字元。
<re.Match object; span=(1, 2), match='o'>

如果你想在 string 中的任何位置找到匹配，請改用 search()（另請參閱 search() vs. match()）。

Pattern.fullmatch(string[, pos[, endpos]])

如果整個 string 與此正規表示式匹配，則回傳對應的 Match。如果字串與模式不匹配，則回傳 None；請注意，這與零長度匹配不同。

可選的 pos 和 endpos 參數與 search() 方法中的參數具有相同的意義。

>>> pattern = re.compile("o[gh]")
>>> pattern.fullmatch("dog")      # 無匹配，因為 "o" 不在 "dog" 的開頭。
>>> pattern.fullmatch("ogre")     # 無匹配，因為整個字串不匹配。
>>> pattern.fullmatch("doggie", 1, 3)   # 在給定限制內匹配。
<re.Match object; span=(1, 3), match='og'>

在 3.4 版被加入.

Pattern.split(string, maxsplit=0)

和 split() 函式相同，使用已編譯的模式。

Pattern.findall(string[, pos[, endpos]])

類似於 findall() 函式，使用已編譯的模式，但也接受可選的 pos 和 endpos 參數，這些參數會像 search() 一樣限制搜尋區域。

Pattern.finditer(string[, pos[, endpos]])

類似於 finditer() 函式，使用已編譯的模式，但也接受可選的 pos 和 endpos 參數，這些參數會像 search() 一樣限制搜尋區域。

Pattern.sub(repl, string, count=0)

和 sub() 函式相同，使用已編譯的模式。

Pattern.subn(repl, string, count=0)

和 subn() 函式相同，使用已編譯的模式。

Pattern.flags

正規表示式匹配旗標。這是傳遞給 compile() 的旗標、模式中的任何 (?...) 內嵌旗標以及隱含旗標（例如如果模式是 Unicode 字串則為 UNICODE）的組合。

Pattern.groups

模式中捕獲群組的數量。

Pattern.groupindex

一個字典，將任何由 (?P<id>) 定義的符號群組名稱對映到群組編號。如果模式中未使用符號群組，則字典為空。

Pattern.pattern

從中編譯出模式物件的模式字串。

在 3.7 版的變更: 新增對 copy.copy() 和 copy.deepcopy() 的支援。已編譯的正規表示式物件被視為不可分割的 (atomic)。

Match Objects

Match objects always have a boolean value of True. Since match() and search() return None when there is no match, you can test whether there was a match with a simple if statement:

match = re.search(pattern, string)
if match:
    process(match)

class re.Match

Match object returned by successful matches and searches.

在 3.9 版的變更: re.Match supports [] to indicate a Unicode (str) or bytes match. See 泛型別名型別.

Match.expand(template)

Return the string obtained by doing backslash substitution on the template string template, as done by the sub() method. Escapes such as \n are converted to the appropriate characters, and numeric backreferences (\1, \2) and named backreferences (\g<1>, \g<name>) are replaced by the contents of the corresponding group. The backreference \g<0> will be replaced by the entire match.

在 3.5 版的變更: 不匹配的群組將被替換為空字串。

Match.group([group1, ...])

Returns one or more subgroups of the match. If there is a single argument, the result is a single string; if there are multiple arguments, the result is a tuple with one item per argument. Without arguments, group1 defaults to zero (the whole match is returned). If a groupN argument is zero, the corresponding return value is the entire matching string; if it is in the inclusive range [1..99], it is the string matching the corresponding parenthesized group. If a group number is negative or larger than the number of groups defined in the pattern, an IndexError exception is raised. If a group is contained in a part of the pattern that did not match, the corresponding result is None. If a group is contained in a part of the pattern that matched multiple times, the last match is returned.

>>> m = re.match(r"(\w+) (\w+)", "Isaac Newton, physicist")
>>> m.group(0)       # The entire match
'Isaac Newton'
>>> m.group(1)       # The first parenthesized subgroup.
'Isaac'
>>> m.group(2)       # The second parenthesized subgroup.
'Newton'
>>> m.group(1, 2)    # Multiple arguments give us a tuple.
('Isaac', 'Newton')

If the regular expression uses the (?P<name>...) syntax, the groupN arguments may also be strings identifying groups by their group name. If a string argument is not used as a group name in the pattern, an IndexError exception is raised.

A moderately complicated example:

>>> m = re.match(r"(?P<first_name>\w+) (?P<last_name>\w+)", "Malcolm Reynolds")
>>> m.group('first_name')
'Malcolm'
>>> m.group('last_name')
'Reynolds'

Named groups can also be referred to by their index:

>>> m.group(1)
'Malcolm'
>>> m.group(2)
'Reynolds'

If a group matches multiple times, only the last match is accessible:

>>> m = re.match(r"(..)+", "a1b2c3")  # Matches 3 times.
>>> m.group(1)                        # Returns only the last match.
'c3'

Match.__getitem__(g)

This is identical to m.group(g). This allows easier access to an individual group from a match:

>>> m = re.match(r"(\w+) (\w+)", "Isaac Newton, physicist")
>>> m[0]       # The entire match
'Isaac Newton'
>>> m[1]       # The first parenthesized subgroup.
'Isaac'
>>> m[2]       # The second parenthesized subgroup.
'Newton'

Named groups are supported as well:

>>> m = re.match(r"(?P<first_name>\w+) (?P<last_name>\w+)", "Isaac Newton")
>>> m['first_name']
'Isaac'
>>> m['last_name']
'Newton'

在 3.6 版被加入.

Match.groups(default=None)

Return a tuple containing all the subgroups of the match, from 1 up to however many groups are in the pattern. The default argument is used for groups that did not participate in the match; it defaults to None.

舉例來說：

>>> m = re.match(r"(\d+)\.(\d+)", "24.1632")
>>> m.groups()
('24', '1632')

If we make the decimal place and everything after it optional, not all groups might participate in the match. These groups will default to None unless the default argument is given:

>>> m = re.match(r"(\d+)\.?(\d+)?", "24")
>>> m.groups()      # Second group defaults to None.
('24', None)
>>> m.groups('0')   # Now, the second group defaults to '0'.
('24', '0')

Match.groupdict(default=None)

Return a dictionary containing all the named subgroups of the match, keyed by the subgroup name. The default argument is used for groups that did not participate in the match; it defaults to None. For example:

>>> m = re.match(r"(?P<first_name>\w+) (?P<last_name>\w+)", "Malcolm Reynolds")
>>> m.groupdict()
{'first_name': 'Malcolm', 'last_name': 'Reynolds'}

Match.start([group])

Match.end([group])

Return the indices of the start and end of the substring matched by group; group defaults to zero (meaning the whole matched substring). Return -1 if group exists but did not contribute to the match. For a match object m, and a group g that did contribute to the match, the substring matched by group g (equivalent to m.group(g)) is

m.string[m.start(g):m.end(g)]

Note that m.start(group) will equal m.end(group) if group matched a null string. For example, after m = re.search('b(c?)', 'cba'), m.start(0) is 1, m.end(0) is 2, m.start(1) and m.end(1) are both 2, and m.start(2) raises an IndexError exception.

An example that will remove remove_this from email addresses:

>>> email = "tony@tiremove_thisger.net"
>>> m = re.search("remove_this", email)
>>> email[:m.start()] + email[m.end():]
'tony@tiger.net'

Match.span([group])

For a match m, return the 2-tuple (m.start(group), m.end(group)). Note that if group did not contribute to the match, this is (-1, -1). group defaults to zero, the entire match.

Match.pos

The value of pos which was passed to the search() or match() method of a regex object. This is the index into the string at which the RE engine started looking for a match.

Match.endpos

The value of endpos which was passed to the search() or match() method of a regex object. This is the index into the string beyond which the RE engine will not go.

Match.lastindex

The integer index of the last matched capturing group, or None if no group was matched at all. For example, the expressions (a)b, ((a)(b)), and ((ab)) will have lastindex == 1 if applied to the string 'ab', while the expression (a)(b) will have lastindex == 2, if applied to the same string.

Match.lastgroup

The name of the last matched capturing group, or None if the group didn't have a name, or if no group was matched at all.

Match.re

The regular expression object whose match() or search() method produced this match instance.

Match.string

The string passed to match() or search().

在 3.7 版的變更: Added support of copy.copy() and copy.deepcopy(). Match objects are considered atomic.

Regular Expression Examples

Checking for a Pair

In this example, we'll use the following helper function to display match objects a little more gracefully:

def displaymatch(match):
    if match is None:
        return None
    return '<Match: %r, groups=%r>' % (match.group(), match.groups())

Suppose you are writing a poker program where a player's hand is represented as a 5-character string with each character representing a card, "a" for ace, "k" for king, "q" for queen, "j" for jack, "t" for 10, and "2" through "9" representing the card with that value.

To see if a given string is a valid hand, one could do the following:

>>> valid = re.compile(r"^[a2-9tjqk]{5}$")
>>> displaymatch(valid.match("akt5q"))  # Valid.
"<Match: 'akt5q', groups=()>"
>>> displaymatch(valid.match("akt5e"))  # Invalid.
>>> displaymatch(valid.match("akt"))    # Invalid.
>>> displaymatch(valid.match("727ak"))  # Valid.
"<Match: '727ak', groups=()>"

That last hand, "727ak", contained a pair, or two of the same valued cards. To match this with a regular expression, one could use backreferences as such:

>>> pair = re.compile(r".*(.).*\1")
>>> displaymatch(pair.match("717ak"))     # Pair of 7s.
"<Match: '717', groups=('7',)>"
>>> displaymatch(pair.match("718ak"))     # No pairs.
>>> displaymatch(pair.match("354aa"))     # Pair of aces.
"<Match: '354aa', groups=('a',)>"

To find out what card the pair consists of, one could use the group() method of the match object in the following manner:

>>> pair = re.compile(r".*(.).*\1")
>>> pair.match("717ak").group(1)
'7'

# Error because re.match() returns None, which doesn't have a group() method:
>>> pair.match("718ak").group(1)
Traceback (most recent call last):
  File "<pyshell#23>", line 1, in <module>
    re.match(r".*(.).*\1", "718ak").group(1)
AttributeError: 'NoneType' object has no attribute 'group'

>>> pair.match("354aa").group(1)
'a'

模擬 scanf()

Python does not currently have an equivalent to scanf(). Regular expressions are generally more powerful, though also more verbose, than scanf() format strings. The table below offers some more-or-less equivalent mappings between scanf() format tokens and regular expressions.

scanf() Token

Regular Expression

%c

.

%5c

.{5}

%d

[-+]?\d+

%e, %E, %f, %g

[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?

%i

[-+]?(0[xX][\dA-Fa-f]+|0[0-7]*|\d+)

%o

[-+]?[0-7]+

%s

\S+

%u

\d+

%x、%X

[-+]?(0[xX])?[\dA-Fa-f]+

To extract the filename and numbers from a string like

/usr/sbin/sendmail - 0 errors, 4 warnings

you would use a scanf() format like

%s - %d errors, %d warnings

The equivalent regular expression would be

(\S+) - (\d+) errors, (\d+) warnings

search() vs. match()

Python offers different primitive operations based on regular expressions:

re.match() checks for a match only at the beginning of the string

re.search() checks for a match anywhere in the string (this is what Perl does by default)

re.fullmatch() checks for entire string to be a match

舉例來說：

>>> re.match("c", "abcdef")    # No match
>>> re.search("c", "abcdef")   # Match
<re.Match object; span=(2, 3), match='c'>
>>> re.fullmatch("p.*n", "python") # Match
<re.Match object; span=(0, 6), match='python'>
>>> re.fullmatch("r.*n", "python") # No match

Regular expressions beginning with '^' can be used with search() to restrict the match at the beginning of the string:

>>> re.match("c", "abcdef")    # No match
>>> re.search("^c", "abcdef")  # No match
>>> re.search("^a", "abcdef")  # Match
<re.Match object; span=(0, 1), match='a'>

Note however that in MULTILINE mode match() only matches at the beginning of the string, whereas using search() with a regular expression beginning with '^' will match at the beginning of each line.

>>> re.match("X", "A\nB\nX", re.MULTILINE)  # No match
>>> re.search("^X", "A\nB\nX", re.MULTILINE)  # Match
<re.Match object; span=(4, 5), match='X'>

Making a Phonebook

split() splits a string into a list delimited by the passed pattern. The method is invaluable for converting textual data into data structures that can be easily read and modified by Python as demonstrated in the following example that creates a phonebook.

First, here is the input. Normally it may come from a file, here we are using triple-quoted string syntax

>>> text = """Ross McFluff: 834.345.1254 155 Elm Street
...
... Ronald Heathmore: 892.345.3428 436 Finley Avenue
... Frank Burger: 925.541.7625 662 South Dogwood Way
...
...
... Heather Albrecht: 548.326.4584 919 Park Place"""

The entries are separated by one or more newlines. Now we convert the string into a list with each nonempty line having its own entry:

>>> entries = re.split("\n+", text)
>>> entries
['Ross McFluff: 834.345.1254 155 Elm Street',
'Ronald Heathmore: 892.345.3428 436 Finley Avenue',
'Frank Burger: 925.541.7625 662 South Dogwood Way',
'Heather Albrecht: 548.326.4584 919 Park Place']

Finally, split each entry into a list with first name, last name, telephone number, and address. We use the maxsplit parameter of split() because the address has spaces, our splitting pattern, in it:

>>> [re.split(":? ", entry, maxsplit=3) for entry in entries]
[['Ross', 'McFluff', '834.345.1254', '155 Elm Street'],
['Ronald', 'Heathmore', '892.345.3428', '436 Finley Avenue'],
['Frank', 'Burger', '925.541.7625', '662 South Dogwood Way'],
['Heather', 'Albrecht', '548.326.4584', '919 Park Place']]

The :? pattern matches the colon after the last name, so that it does not occur in the result list. With a maxsplit of 4, we could separate the house number from the street name:

>>> [re.split(":? ", entry, maxsplit=4) for entry in entries]
[['Ross', 'McFluff', '834.345.1254', '155', 'Elm Street'],
['Ronald', 'Heathmore', '892.345.3428', '436', 'Finley Avenue'],
['Frank', 'Burger', '925.541.7625', '662', 'South Dogwood Way'],
['Heather', 'Albrecht', '548.326.4584', '919', 'Park Place']]

Text Munging

sub() replaces every occurrence of a pattern with a string or the result of a function. This example demonstrates using sub() with a function to "munge" text, or randomize the order of all the characters in each word of a sentence except for the first and last characters:

>>> def repl(m):
...     inner_word = list(m.group(2))
...     random.shuffle(inner_word)
...     return m.group(1) + "".join(inner_word) + m.group(3)
...
>>> text = "Professor Abdolmalek, please report your absences promptly."
>>> re.sub(r"(\w)(\w+)(\w)", repl, text)
'Poefsrosr Aealmlobdk, pslaee reorpt your abnseces plmrptoy.'
>>> re.sub(r"(\w)(\w+)(\w)", repl, text)
'Pofsroser Aodlambelk, plasee reoprt yuor asnebces potlmrpy.'

Finding all Adverbs

findall() matches all occurrences of a pattern, not just the first one as search() does. For example, if a writer wanted to find all of the adverbs in some text, they might use findall() in the following manner:

>>> text = "He was carefully disguised but captured quickly by police."
>>> re.findall(r"\w+ly\b", text)
['carefully', 'quickly']

Finding all Adverbs and their Positions

If one wants more information about all matches of a pattern than the matched text, finditer() is useful as it provides Match objects instead of strings. Continuing with the previous example, if a writer wanted to find all of the adverbs and their positions in some text, they would use finditer() in the following manner:

>>> text = "He was carefully disguised but captured quickly by police."
>>> for m in re.finditer(r"\w+ly\b", text):
...     print('%02d-%02d: %s' % (m.start(), m.end(), m.group(0)))
07-16: carefully
40-47: quickly

Raw String Notation

Raw string notation (r"text") keeps regular expressions sane. Without it, every backslash ('\') in a regular expression would have to be prefixed with another one to escape it. For example, the two following lines of code are functionally identical:

>>> re.match(r"\W(.)\1\W", " ff ")
<re.Match object; span=(0, 4), match=' ff '>
>>> re.match("\\W(.)\\1\\W", " ff ")
<re.Match object; span=(0, 4), match=' ff '>

When one wants to match a literal backslash, it must be escaped in the regular expression. With raw string notation, this means r"\\". Without raw string notation, one must use "\\\\", making the following lines of code functionally identical:

>>> re.match(r"\\", r"\\")
<re.Match object; span=(0, 1), match='\\'>
>>> re.match("\\\\", r"\\")
<re.Match object; span=(0, 1), match='\\'>

Writing a Tokenizer

A tokenizer or scanner [https://en.wikipedia.org/wiki/Lexical_analysis] analyzes a string to categorize groups of characters. This is a useful first step in writing a compiler or interpreter.

The text categories are specified with regular expressions. The technique is to combine those into a single master regular expression and to loop over successive matches:

from typing import NamedTuple
import re

class Token(NamedTuple):
    type: str
    value: str
    line: int
    column: int

def tokenize(code):
    keywords = {'IF', 'THEN', 'ENDIF', 'FOR', 'NEXT', 'GOSUB', 'RETURN'}
    token_specification = [
        ('NUMBER',   r'\d+(\.\d*)?'),  # Integer or decimal number
        ('ASSIGN',   r':='),           # Assignment operator
        ('END',      r';'),            # Statement terminator
        ('ID',       r'[A-Za-z]+'),    # Identifiers
        ('OP',       r'[+\-*/]'),      # Arithmetic operators
        ('NEWLINE',  r'\n'),           # Line endings
        ('SKIP',     r'[ \t]+'),       # Skip over spaces and tabs
        ('MISMATCH', r'.'),            # Any other character
    ]
    tok_regex = '|'.join('(?P<%s>%s)' % pair for pair in token_specification)
    line_num = 1
    line_start = 0
    for mo in re.finditer(tok_regex, code):
        kind = mo.lastgroup
        value = mo.group()
        column = mo.start() - line_start
        if kind == 'NUMBER':
            value = float(value) if '.' in value else int(value)
        elif kind == 'ID' and value in keywords:
            kind = value
        elif kind == 'NEWLINE':
            line_start = mo.end()
            line_num += 1
            continue
        elif kind == 'SKIP':
            continue
        elif kind == 'MISMATCH':
            raise RuntimeError(f'{value!r} unexpected on line {line_num}')
        yield Token(kind, value, line_num, column)

statements = '''
    IF quantity THEN
        total := total + price * quantity;
        tax := price * 0.05;
    ENDIF;
'''

for token in tokenize(statements):
    print(token)

The tokenizer produces the following output:

Token(type='IF', value='IF', line=2, column=4)
Token(type='ID', value='quantity', line=2, column=7)
Token(type='THEN', value='THEN', line=2, column=16)
Token(type='ID', value='total', line=3, column=8)
Token(type='ASSIGN', value=':=', line=3, column=14)
Token(type='ID', value='total', line=3, column=17)
Token(type='OP', value='+', line=3, column=23)
Token(type='ID', value='price', line=3, column=25)
Token(type='OP', value='*', line=3, column=31)
Token(type='ID', value='quantity', line=3, column=33)
Token(type='END', value=';', line=3, column=41)
Token(type='ID', value='tax', line=4, column=8)
Token(type='ASSIGN', value=':=', line=4, column=12)
Token(type='ID', value='price', line=4, column=15)
Token(type='OP', value='*', line=4, column=21)
Token(type='NUMBER', value=0.05, line=4, column=23)
Token(type='END', value=';', line=4, column=27)
Token(type='ENDIF', value='ENDIF', line=5, column=4)
Token(type='END', value=';', line=5, column=9)

[Frie09]

Friedl, Jeffrey. Mastering Regular Expressions. 3rd ed., O'Reilly Media, 2009. The third edition of the book no longer covers Python at all, but the first edition covered writing good regular expression patterns in great detail.

difflib --- 計算差異的輔助工具

原始碼：Lib/difflib.py [https://github.com/python/cpython/tree/3.14/Lib/difflib.py]

This module provides classes and functions for comparing sequences. It can be used for example, for comparing files, and can produce information about file differences in various formats, including HTML and context and unified diffs. For comparing directories and files, see also, the filecmp module.

class difflib.SequenceMatcher

This is a flexible class for comparing pairs of sequences of any type, so long as the sequence elements are hashable. The basic algorithm predates, and is a little fancier than, an algorithm published in the late 1980's by Ratcliff and Obershelp under the hyperbolic name "gestalt pattern matching." The idea is to find the longest contiguous matching subsequence that contains no "junk" elements; these "junk" elements are ones that are uninteresting in some sense, such as blank lines or whitespace. (Handling junk is an extension to the Ratcliff and Obershelp algorithm.) The same idea is then applied recursively to the pieces of the sequences to the left and to the right of the matching subsequence. This does not yield minimal edit sequences, but does tend to yield matches that "look right" to people.

Timing: The basic Ratcliff-Obershelp algorithm is cubic time in the worst case and quadratic time in the expected case. SequenceMatcher is quadratic time for the worst case and has expected-case behavior dependent in a complicated way on how many elements the sequences have in common; best case time is linear.

Automatic junk heuristic: SequenceMatcher supports a heuristic that automatically treats certain sequence items as junk. The heuristic counts how many times each individual item appears in the sequence. If an item's duplicates (after the first one) account for more than 1% of the sequence and the sequence is at least 200 items long, this item is marked as "popular" and is treated as junk for the purpose of sequence matching. This heuristic can be turned off by setting the autojunk argument to False when creating the SequenceMatcher.

在 3.2 版的變更: 新增 autojunk 參數。

class difflib.Differ

This is a class for comparing sequences of lines of text, and producing human-readable differences or deltas. Differ uses SequenceMatcher both to compare sequences of lines, and to compare sequences of characters within similar (near-matching) lines.

Each line of a Differ delta begins with a two-letter code:

程式碼

含義

'- '

line unique to sequence 1

'+ '

line unique to sequence 2

'  '

line common to both sequences

'? '

line not present in either input sequence

Lines beginning with '?' attempt to guide the eye to intraline differences, and were not present in either input sequence. These lines can be confusing if the sequences contain whitespace characters, such as spaces, tabs or line breaks.

class difflib.HtmlDiff

This class can be used to create an HTML table (or a complete HTML file containing the table) showing a side by side, line by line comparison of text with inter-line and intra-line change highlights. The table can be generated in either full or contextual difference mode.

The constructor for this class is:

__init__(tabsize=8, wrapcolumn=None, linejunk=None, charjunk=IS_CHARACTER_JUNK)

Initializes instance of HtmlDiff.

tabsize is an optional keyword argument to specify tab stop spacing and defaults to 8.

wrapcolumn is an optional keyword to specify column number where lines are broken and wrapped, defaults to None where lines are not wrapped.

linejunk and charjunk are optional keyword arguments passed into ndiff() (used by HtmlDiff to generate the side by side HTML differences). See ndiff() documentation for argument default values and descriptions.

The following methods are public:

make_file(fromlines, tolines, fromdesc='', todesc='', context=False, numlines=5, *, charset='utf-8')

Compares fromlines and tolines (lists of strings) and returns a string which is a complete HTML file containing a table showing line by line differences with inter-line and intra-line changes highlighted.

fromdesc and todesc are optional keyword arguments to specify from/to file column header strings (both default to an empty string).

context and numlines are both optional keyword arguments. Set context to True when contextual differences are to be shown, else the default is False to show the full files. numlines defaults to 5. When context is True numlines controls the number of context lines which surround the difference highlights. When context is False numlines controls the number of lines which are shown before a difference highlight when using the "next" hyperlinks (setting to zero would cause the "next" hyperlinks to place the next difference highlight at the top of the browser without any leading context).

備註

fromdesc and todesc are interpreted as unescaped HTML and should be properly escaped while receiving input from untrusted sources.

在 3.5 版的變更: charset keyword-only argument was added. The default charset of HTML document changed from 'ISO-8859-1' to 'utf-8'.

make_table(fromlines, tolines, fromdesc='', todesc='', context=False, numlines=5)

Compares fromlines and tolines (lists of strings) and returns a string which is a complete HTML table showing line by line differences with inter-line and intra-line changes highlighted.

The arguments for this method are the same as those for the make_file() method.

difflib.context_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\n')

Compare a and b (lists of strings); return a delta (a generator generating the delta lines) in context diff format.

Context diffs are a compact way of showing just the lines that have changed plus a few lines of context. The changes are shown in a before/after style. The number of context lines is set by n which defaults to three.

By default, the diff control lines (those with *** or ---) are created with a trailing newline. This is helpful so that inputs created from io.IOBase.readlines() result in diffs that are suitable for use with io.IOBase.writelines() since both the inputs and outputs have trailing newlines.

For inputs that do not have trailing newlines, set the lineterm argument to "" so that the output will be uniformly newline free.

The context diff format normally has a header for filenames and modification times. Any or all of these may be specified using strings for fromfile, tofile, fromfiledate, and tofiledate. The modification times are normally expressed in the ISO 8601 format. If not specified, the strings default to blanks.

>>> import sys
>>> from difflib import *
>>> s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
>>> s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
>>> sys.stdout.writelines(context_diff(s1, s2, fromfile='before.py',
...                        tofile='after.py'))
*** before.py
--- after.py
***************
*** 1,4 ****
! bacon
! eggs
! ham
  guido
--- 1,4 ----
! python
! eggy
! hamster
  guido

一個更詳盡的範例請見 difflib 的命令列介面。

difflib.get_close_matches(word, possibilities, n=3, cutoff=0.6)

Return a list of the best "good enough" matches. word is a sequence for which close matches are desired (typically a string), and possibilities is a list of sequences against which to match word (typically a list of strings).

Optional argument n (default 3) is the maximum number of close matches to return; n must be greater than 0.

Optional argument cutoff (default 0.6) is a float in the range [0, 1]. Possibilities that don't score at least that similar to word are ignored.

The best (no more than n) matches among the possibilities are returned in a list, sorted by similarity score, most similar first.

>>> get_close_matches('appel', ['ape', 'apple', 'peach', 'puppy'])
['apple', 'ape']
>>> import keyword
>>> get_close_matches('wheel', keyword.kwlist)
['while']
>>> get_close_matches('pineapple', keyword.kwlist)
[]
>>> get_close_matches('accept', keyword.kwlist)
['except']

difflib.ndiff(a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK)

Compare a and b (lists of strings); return a Differ-style delta (a generator generating the delta lines).

Optional keyword parameters linejunk and charjunk are filtering functions (or None):

linejunk: A function that accepts a single string argument, and returns true if the string is junk, or false if not. The default is None. There is also a module-level function IS_LINE_JUNK(), which filters out lines without visible characters, except for at most one hash character ('#') -- however the underlying SequenceMatcher class does a dynamic analysis of which lines are so frequent as to constitute noise, and this usually works better than using this function.

charjunk: A function that accepts a character (a string of length 1), and returns if the character is junk, or false if not. The default is module-level function IS_CHARACTER_JUNK(), which filters out whitespace characters (a blank or tab; it's a bad idea to include newline in this!).

>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(keepends=True),
...              'ore\ntree\nemu\n'.splitlines(keepends=True))
>>> print(''.join(diff), end="")
- one
?  ^
+ ore
?  ^
- two
- three
?  -
+ tree
+ emu

difflib.restore(sequence, which)

Return one of the two sequences that generated a delta.

Given a sequence produced by Differ.compare() or ndiff(), extract lines originating from file 1 or 2 (parameter which), stripping off line prefixes.

範例：

>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(keepends=True),
...              'ore\ntree\nemu\n'.splitlines(keepends=True))
>>> diff = list(diff) # materialize the generated delta into a list
>>> print(''.join(restore(diff, 1)), end="")
one
two
three
>>> print(''.join(restore(diff, 2)), end="")
ore
tree
emu

difflib.unified_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\n')

Compare a and b (lists of strings); return a delta (a generator generating the delta lines) in unified diff format.

Unified diffs are a compact way of showing just the lines that have changed plus a few lines of context. The changes are shown in an inline style (instead of separate before/after blocks). The number of context lines is set by n which defaults to three.

By default, the diff control lines (those with ---, +++, or @@) are created with a trailing newline. This is helpful so that inputs created from io.IOBase.readlines() result in diffs that are suitable for use with io.IOBase.writelines() since both the inputs and outputs have trailing newlines.

For inputs that do not have trailing newlines, set the lineterm argument to "" so that the output will be uniformly newline free.

The unified diff format normally has a header for filenames and modification times. Any or all of these may be specified using strings for fromfile, tofile, fromfiledate, and tofiledate. The modification times are normally expressed in the ISO 8601 format. If not specified, the strings default to blanks.

>>> s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
>>> s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
>>> sys.stdout.writelines(unified_diff(s1, s2, fromfile='before.py', tofile='after.py'))
--- before.py
+++ after.py
@@ -1,4 +1,4 @@
-bacon
-eggs
-ham
+python
+eggy
+hamster
 guido

一個更詳盡的範例請見 difflib 的命令列介面。

difflib.diff_bytes(dfunc, a, b, fromfile=b'', tofile=b'', fromfiledate=b'', tofiledate=b'', n=3, lineterm=b'\n')

Compare a and b (lists of bytes objects) using dfunc; yield a sequence of delta lines (also bytes) in the format returned by dfunc. dfunc must be a callable, typically either unified_diff() or context_diff().

Allows you to compare data with unknown or inconsistent encoding. All inputs except n must be bytes objects, not str. Works by losslessly converting all inputs (except n) to str, and calling dfunc(a, b, fromfile, tofile, fromfiledate, tofiledate, n, lineterm). The output of dfunc is then converted back to bytes, so the delta lines that you receive have the same unknown/inconsistent encodings as a and b.

在 3.5 版被加入.

difflib.IS_LINE_JUNK(line)

Return True for ignorable lines. The line line is ignorable if line is blank or contains a single '#', otherwise it is not ignorable. Used as a default for parameter linejunk in ndiff() in older versions.

difflib.IS_CHARACTER_JUNK(ch)

Return True for ignorable characters. The character ch is ignorable if ch is a space or tab, otherwise it is not ignorable. Used as a default for parameter charjunk in ndiff().

也參考

Pattern Matching: The Gestalt Approach [https://jacobfilipp.com/DrDobbs/articles/DDJ/1988/8807/8807c/8807c.htm]

Discussion of a similar algorithm by John W. Ratcliff and D. E. Metzener. This was published in Dr. Dobb's Journal in July, 1988.

SequenceMatcher 物件

The SequenceMatcher class has this constructor:

class difflib.SequenceMatcher(isjunk=None, a='', b='', autojunk=True)

Optional argument isjunk must be None (the default) or a one-argument function that takes a sequence element and returns true if and only if the element is "junk" and should be ignored. Passing None for isjunk is equivalent to passing lambda x: False; in other words, no elements are ignored. For example, pass:

lambda x: x in " \t"

if you're comparing lines as sequences of characters, and don't want to synch up on blanks or hard tabs.

The optional arguments a and b are sequences to be compared; both default to empty strings. The elements of both sequences must be hashable.

The optional argument autojunk can be used to disable the automatic junk heuristic.

在 3.2 版的變更: 新增 autojunk 參數。

SequenceMatcher objects get three data attributes: bjunk is the set of elements of b for which isjunk is True; bpopular is the set of non-junk elements considered popular by the heuristic (if it is not disabled); b2j is a dict mapping the remaining elements of b to a list of positions where they occur. All three are reset whenever b is reset with set_seqs() or set_seq2().

在 3.2 版被加入: The bjunk and bpopular attributes.

SequenceMatcher 物件有以下方法：

set_seqs(a, b)

Set the two sequences to be compared.

SequenceMatcher computes and caches detailed information about the second sequence, so if you want to compare one sequence against many sequences, use set_seq2() to set the commonly used sequence once and call set_seq1() repeatedly, once for each of the other sequences.

set_seq1(a)

Set the first sequence to be compared. The second sequence to be compared is not changed.

set_seq2(b)

Set the second sequence to be compared. The first sequence to be compared is not changed.

find_longest_match(alo=0, ahi=None, blo=0, bhi=None)

Find longest matching block in a[alo:ahi] and b[blo:bhi].

If isjunk was omitted or None, find_longest_match() returns (i, j, k) such that a[i:i+k] is equal to b[j:j+k], where alo <= i <= i+k <= ahi and blo <= j <= j+k <= bhi. For all (i', j', k') meeting those conditions, the additional conditions k >= k', i <= i', and if i == i', j <= j' are also met. In other words, of all maximal matching blocks, return one that starts earliest in a, and of all those maximal matching blocks that start earliest in a, return the one that starts earliest in b.

>>> s = SequenceMatcher(None, " abcd", "abcd abcd")
>>> s.find_longest_match(0, 5, 0, 9)
Match(a=0, b=4, size=5)

If isjunk was provided, first the longest matching block is determined as above, but with the additional restriction that no junk element appears in the block. Then that block is extended as far as possible by matching (only) junk elements on both sides. So the resulting block never matches on junk except as identical junk happens to be adjacent to an interesting match.

Here's the same example as before, but considering blanks to be junk. That prevents ' abcd' from matching the ' abcd' at the tail end of the second sequence directly. Instead only the 'abcd' can match, and matches the leftmost 'abcd' in the second sequence:

>>> s = SequenceMatcher(lambda x: x==" ", " abcd", "abcd abcd")
>>> s.find_longest_match(0, 5, 0, 9)
Match(a=1, b=0, size=4)

If no blocks match, this returns (alo, blo, 0).

This method returns a named tuple Match(a, b, size).

在 3.9 版的變更: 新增預設引數。

get_matching_blocks()

Return list of triples describing non-overlapping matching subsequences. Each triple is of the form (i, j, n), and means that a[i:i+n] == b[j:j+n]. The triples are monotonically increasing in i and j.

The last triple is a dummy, and has the value (len(a), len(b), 0). It is the only triple with n == 0. If (i, j, n) and (i', j', n') are adjacent triples in the list, and the second is not the last triple in the list, then i+n < i' or j+n < j'; in other words, adjacent triples always describe non-adjacent equal blocks.

>>> s = SequenceMatcher(None, "abxcd", "abcd")
>>> s.get_matching_blocks()
[Match(a=0, b=0, size=2), Match(a=3, b=2, size=2), Match(a=5, b=4, size=0)]

get_opcodes()

Return list of 5-tuples describing how to turn a into b. Each tuple is of the form (tag, i1, i2, j1, j2). The first tuple has i1 == j1 == 0, and remaining tuples have i1 equal to the i2 from the preceding tuple, and, likewise, j1 equal to the previous j2.

The tag values are strings, with these meanings:

Value

含義

'replace'

a[i1:i2] 應該被替換為 b[j1:j2]。

'delete'

a[i1:i2] 應該被刪除。請注意，在這種情況下 j1 == j2。

'insert'

b[j1:j2] should be inserted at a[i1:i1]. Note that i1 == i2 in this case.

'equal'

a[i1:i2] == b[j1:j2] (the sub-sequences are equal).

舉例來說：

>>> a = "qabxcd"
>>> b = "abycdf"
>>> s = SequenceMatcher(None, a, b)
>>> for tag, i1, i2, j1, j2 in s.get_opcodes():
...     print('{:7}   a[{}:{}] --> b[{}:{}] {!r:>8} --> {!r}'.format(
...         tag, i1, i2, j1, j2, a[i1:i2], b[j1:j2]))
delete    a[0:1] --> b[0:0]      'q' --> ''
equal     a[1:3] --> b[0:2]     'ab' --> 'ab'
replace   a[3:4] --> b[2:3]      'x' --> 'y'
equal     a[4:6] --> b[3:5]     'cd' --> 'cd'
insert    a[6:6] --> b[5:6]       '' --> 'f'

get_grouped_opcodes(n=3)

Return a generator of groups with up to n lines of context.

Starting with the groups returned by get_opcodes(), this method splits out smaller change clusters and eliminates intervening ranges which have no changes.

The groups are returned in the same format as get_opcodes().

ratio()

Return a measure of the sequences' similarity as a float in the range [0, 1].

Where T is the total number of elements in both sequences, and M is the number of matches, this is 2.0*M / T. Note that this is 1.0 if the sequences are identical, and 0.0 if they have nothing in common.

This is expensive to compute if get_matching_blocks() or get_opcodes() hasn't already been called, in which case you may want to try quick_ratio() or real_quick_ratio() first to get an upper bound.

備註

Caution: The result of a ratio() call may depend on the order of the arguments. For instance:

>>> SequenceMatcher(None, 'tide', 'diet').ratio()
0.25
>>> SequenceMatcher(None, 'diet', 'tide').ratio()
0.5

quick_ratio()

Return an upper bound on ratio() relatively quickly.

real_quick_ratio()

Return an upper bound on ratio() very quickly.

The three methods that return the ratio of matching to total characters can give different results due to differing levels of approximation, although quick_ratio() and real_quick_ratio() are always at least as large as ratio():

>>> s = SequenceMatcher(None, "abcd", "bcde")
>>> s.ratio()
0.75
>>> s.quick_ratio()
0.75
>>> s.real_quick_ratio()
1.0

SequenceMatcher 範例

This example compares two strings, considering blanks to be "junk":

>>> s = SequenceMatcher(lambda x: x == " ",
...                     "private Thread currentThread;",
...                     "private volatile Thread currentThread;")

ratio() returns a float in [0, 1], measuring the similarity of the sequences. As a rule of thumb, a ratio() value over 0.6 means the sequences are close matches:

>>> print(round(s.ratio(), 3))
0.866

If you're only interested in where the sequences match, get_matching_blocks() is handy:

>>> for block in s.get_matching_blocks():
...     print("a[%d] and b[%d] match for %d elements" % block)
a[0] and b[0] match for 8 elements
a[8] and b[17] match for 21 elements
a[29] and b[38] match for 0 elements

Note that the last tuple returned by get_matching_blocks() is always a dummy, (len(a), len(b), 0), and this is the only case in which the last tuple element (number of elements matched) is 0.

If you want to know how to change the first sequence into the second, use get_opcodes():

>>> for opcode in s.get_opcodes():
...     print("%6s a[%d:%d] b[%d:%d]" % opcode)
 equal a[0:8] b[0:8]
insert a[8:8] b[8:17]
 equal a[8:29] b[17:38]

也參考

The get_close_matches() function in this module which shows how simple code building on SequenceMatcher can be used to do useful work.

Simple version control recipe [https://code.activestate.com/recipes/576729-simple-version-control/] for a small application built with SequenceMatcher.

Differ Objects

Note that Differ-generated deltas make no claim to be minimal diffs. To the contrary, minimal diffs are often counter-intuitive, because they synch up anywhere possible, sometimes accidental matches 100 pages apart. Restricting synch points to contiguous matches preserves some notion of locality, at the occasional cost of producing a longer diff.

Differ 類別有這個建構函式：

class difflib.Differ(linejunk=None, charjunk=None)

Optional keyword parameters linejunk and charjunk are for filter functions (or None):

linejunk: A function that accepts a single string argument, and returns true if the string is junk. The default is None, meaning that no line is considered junk.

charjunk: A function that accepts a single character argument (a string of length 1), and returns true if the character is junk. The default is None, meaning that no character is considered junk.

These junk-filtering functions speed up matching to find differences and do not cause any differing lines or characters to be ignored. Read the description of the find_longest_match() method's isjunk parameter for an explanation.

Differ objects are used (deltas generated) via a single method:

compare(a, b)

Compare two sequences of lines, and generate the delta (a sequence of lines).

Each sequence must contain individual single-line strings ending with newlines. Such sequences can be obtained from the readlines() method of file-like objects. The delta generated also consists of newline-terminated strings, ready to be printed as-is via the writelines() method of a file-like object.

Differ Example

This example compares two texts. First we set up the texts, sequences of individual single-line strings ending with newlines (such sequences can also be obtained from the readlines() method of file-like objects):

>>> text1 = '''  1. Beautiful is better than ugly.
...   2. Explicit is better than implicit.
...   3. Simple is better than complex.
...   4. Complex is better than complicated.
... '''.splitlines(keepends=True)
>>> len(text1)
4
>>> text1[0][-1]
'\n'
>>> text2 = '''  1. Beautiful is better than ugly.
...   3.   Simple is better than complex.
...   4. Complicated is better than complex.
...   5. Flat is better than nested.
... '''.splitlines(keepends=True)

Next we instantiate a Differ object:

>>> d = Differ()

Note that when instantiating a Differ object we may pass functions to filter out line and character "junk." See the Differ() constructor for details.

Finally, we compare the two:

>>> result = list(d.compare(text1, text2))

result is a list of strings, so let's pretty-print it:

>>> from pprint import pprint
>>> pprint(result)
['    1. Beautiful is better than ugly.\n',
 '-   2. Explicit is better than implicit.\n',
 '-   3. Simple is better than complex.\n',
 '+   3.   Simple is better than complex.\n',
 '?     ++\n',
 '-   4. Complex is better than complicated.\n',
 '?            ^                     ---- ^\n',
 '+   4. Complicated is better than complex.\n',
 '?           ++++ ^                      ^\n',
 '+   5. Flat is better than nested.\n']

As a single multi-line string it looks like this:

>>> import sys
>>> sys.stdout.writelines(result)
    1. Beautiful is better than ugly.
-   2. Explicit is better than implicit.
-   3. Simple is better than complex.
+   3.   Simple is better than complex.
?     ++
-   4. Complex is better than complicated.
?            ^                     ---- ^
+   4. Complicated is better than complex.
?           ++++ ^                      ^
+   5. Flat is better than nested.

difflib 的命令列介面

This example shows how to use difflib to create a diff-like utility.

""" Command line interface to difflib.py providing diffs in four formats:

* ndiff:    lists every line and highlights interline changes.
* context:  highlights clusters of changes in a before/after format.
* unified:  highlights clusters of changes in an inline format.
* html:     generates side by side comparison with change highlights.

"""

import sys, os, difflib, argparse
from datetime import datetime, timezone

def file_mtime(path):
    t = datetime.fromtimestamp(os.stat(path).st_mtime,
                               timezone.utc)
    return t.astimezone().isoformat()

def main():

    parser = argparse.ArgumentParser()
    parser.add_argument('-c', action='store_true', default=False,
                        help='Produce a context format diff (default)')
    parser.add_argument('-u', action='store_true', default=False,
                        help='Produce a unified format diff')
    parser.add_argument('-m', action='store_true', default=False,
                        help='Produce HTML side by side diff '
                             '(can use -c and -l in conjunction)')
    parser.add_argument('-n', action='store_true', default=False,
                        help='Produce a ndiff format diff')
    parser.add_argument('-l', '--lines', type=int, default=3,
                        help='Set number of context lines (default 3)')
    parser.add_argument('fromfile')
    parser.add_argument('tofile')
    options = parser.parse_args()

    n = options.lines
    fromfile = options.fromfile
    tofile = options.tofile

    fromdate = file_mtime(fromfile)
    todate = file_mtime(tofile)
    with open(fromfile) as ff:
        fromlines = ff.readlines()
    with open(tofile) as tf:
        tolines = tf.readlines()

    if options.u:
        diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)
    elif options.n:
        diff = difflib.ndiff(fromlines, tolines)
    elif options.m:
        diff = difflib.HtmlDiff().make_file(fromlines,tolines,fromfile,tofile,context=options.c,numlines=n)
    else:
        diff = difflib.context_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)

    sys.stdout.writelines(diff)

if __name__ == '__main__':
    main()

ndiff 範例：

This example shows how to use difflib.ndiff().

"""ndiff [-q] file1 file2
    or
ndiff (-r1 | -r2) < ndiff_output > file1_or_file2

Print a human-friendly file difference report to stdout.  Both inter-
and intra-line differences are noted.  In the second form, recreate file1
(-r1) or file2 (-r2) on stdout, from an ndiff report on stdin.

In the first form, if -q ("quiet") is not specified, the first two lines
of output are

-: file1
+: file2

Each remaining line begins with a two-letter code:

    "- "    line unique to file1
    "+ "    line unique to file2
    "  "    line common to both files
    "? "    line not present in either input file

Lines beginning with "? " attempt to guide the eye to intraline
differences, and were not present in either input file.  These lines can be
confusing if the source files contain tab characters.

The first file can be recovered by retaining only lines that begin with
"  " or "- ", and deleting those 2-character prefixes; use ndiff with -r1.

The second file can be recovered similarly, but by retaining only "  " and
"+ " lines; use ndiff with -r2; or, on Unix, the second file can be
recovered by piping the output through

    sed -n '/^[+ ] /s/^..//p'
"""

__version__ = 1, 7, 0

import difflib, sys

def fail(msg):
    out = sys.stderr.write
    out(msg + "\n\n")
    out(__doc__)
    return 0

# open a file & return the file object; gripe and return 0 if it
# couldn't be opened
def fopen(fname):
    try:
        return open(fname)
    except IOError as detail:
        return fail("couldn't open " + fname + ": " + str(detail))

# open two files & spray the diff to stdout; return false iff a problem
def fcompare(f1name, f2name):
    f1 = fopen(f1name)
    f2 = fopen(f2name)
    if not f1 or not f2:
        return 0

    a = f1.readlines(); f1.close()
    b = f2.readlines(); f2.close()
    for line in difflib.ndiff(a, b):
        print(line, end=' ')

    return 1

# crack args (sys.argv[1:] is normal) & compare;
# return false iff a problem

def main(args):
    import getopt
    try:
        opts, args = getopt.getopt(args, "qr:")
    except getopt.error as detail:
        return fail(str(detail))
    noisy = 1
    qseen = rseen = 0
    for opt, val in opts:
        if opt == "-q":
            qseen = 1
            noisy = 0
        elif opt == "-r":
            rseen = 1
            whichfile = val
    if qseen and rseen:
        return fail("can't specify both -q and -r")
    if rseen:
        if args:
            return fail("no args allowed with -r option")
        if whichfile in ("1", "2"):
            restore(whichfile)
            return 1
        return fail("-r value must be 1 or 2")
    if len(args) != 2:
        return fail("need 2 filename args")
    f1name, f2name = args
    if noisy:
        print('-:', f1name)
        print('+:', f2name)
    return fcompare(f1name, f2name)

# read ndiff output from stdin, and print file1 (which=='1') or
# file2 (which=='2') to stdout

def restore(which):
    restored = difflib.restore(sys.stdin.readlines(), which)
    sys.stdout.writelines(restored)

if __name__ == '__main__':
    main(sys.argv[1:])

textwrap --- 文字包裝與填充

原始碼：Lib/textwrap.py [https://github.com/python/cpython/tree/3.14/Lib/textwrap.py]

The textwrap module provides some convenience functions, as well as TextWrapper, the class that does all the work. If you're just wrapping or filling one or two text strings, the convenience functions should be good enough; otherwise, you should use an instance of TextWrapper for efficiency.

textwrap.wrap(text, width=70, *, initial_indent='', subsequent_indent='', expand_tabs=True, replace_whitespace=True, fix_sentence_endings=False, break_long_words=True, drop_whitespace=True, break_on_hyphens=True, tabsize=8, max_lines=None, placeholder=' [...]')

Wraps the single paragraph in text (a string) so every line is at most width characters long. Returns a list of output lines, without final newlines.

Optional keyword arguments correspond to the instance attributes of TextWrapper, documented below.

See the TextWrapper.wrap() method for additional details on how wrap() behaves.

textwrap.fill(text, width=70, *, initial_indent='', subsequent_indent='', expand_tabs=True, replace_whitespace=True, fix_sentence_endings=False, break_long_words=True, drop_whitespace=True, break_on_hyphens=True, tabsize=8, max_lines=None, placeholder=' [...]')

Wraps the single paragraph in text, and returns a single string containing the wrapped paragraph. fill() is shorthand for

"\n".join(wrap(text, ...))

In particular, fill() accepts exactly the same keyword arguments as wrap().

textwrap.shorten(text, width, *, fix_sentence_endings=False, break_long_words=True, break_on_hyphens=True, placeholder=' [...]')

Collapse and truncate the given text to fit in the given width.

First the whitespace in text is collapsed (all whitespace is replaced by single spaces). If the result fits in the width, it is returned. Otherwise, enough words are dropped from the end so that the remaining words plus the placeholder fit within width:

>>> textwrap.shorten("Hello  world!", width=12)
'Hello world!'
>>> textwrap.shorten("Hello  world!", width=11)
'Hello [...]'
>>> textwrap.shorten("Hello world", width=10, placeholder="...")
'Hello...'

Optional keyword arguments correspond to the instance attributes of TextWrapper, documented below. Note that the whitespace is collapsed before the text is passed to the TextWrapper fill() function, so changing the value of tabsize, expand_tabs, drop_whitespace, and replace_whitespace will have no effect.

在 3.4 版被加入.

textwrap.dedent(text)

Remove any common leading whitespace from every line in text.

This can be used to make triple-quoted strings line up with the left edge of the display, while still presenting them in the source code in indented form.

Note that tabs and spaces are both treated as whitespace, but they are not equal: the lines "  hello" and "\thello" are considered to have no common leading whitespace.

Lines containing only whitespace are ignored in the input and normalized to a single newline character in the output.

舉例來說：

def test():
    # end first line with \ to avoid the empty line!
    s = '''\
    hello
      world
    '''
    print(repr(s))          # prints '    hello\n      world\n    '
    print(repr(dedent(s)))  # prints 'hello\n  world\n'

在 3.14 版的變更: The dedent() function now correctly normalizes blank lines containing only whitespace characters. Previously, the implementation only normalized blank lines containing tabs and spaces.

textwrap.indent(text, prefix, predicate=None)

Add prefix to the beginning of selected lines in text.

Lines are separated by calling text.splitlines(True).

By default, prefix is added to all lines that do not consist solely of whitespace (including any line endings).

舉例來說：

>>> s = 'hello\n\n \nworld'
>>> indent(s, '  ')
'  hello\n\n \n  world'

The optional predicate argument can be used to control which lines are indented. For example, it is easy to add prefix to even empty and whitespace-only lines:

>>> print(indent(s, '+ ', lambda line: True))
+ hello
+
+
+ world

在 3.3 版被加入.

wrap(), fill() and shorten() work by creating a TextWrapper instance and calling a single method on it. That instance is not reused, so for applications that process many text strings using wrap() and/or fill(), it may be more efficient to create your own TextWrapper object.

Text is preferably wrapped on whitespaces and right after the hyphens in hyphenated words; only then will long words be broken if necessary, unless TextWrapper.break_long_words is set to false.

class textwrap.TextWrapper(**kwargs)

The TextWrapper constructor accepts a number of optional keyword arguments. Each keyword argument corresponds to an instance attribute, so for example

wrapper = TextWrapper(initial_indent="* ")

is the same as

wrapper = TextWrapper()
wrapper.initial_indent = "* "

You can reuse the same TextWrapper object many times, and you can change any of its options through direct assignment to instance attributes between uses.

The TextWrapper instance attributes (and keyword arguments to the constructor) are as follows:

width

(default: 70) The maximum length of wrapped lines. As long as there are no individual words in the input text longer than width, TextWrapper guarantees that no output line will be longer than width characters.

expand_tabs

(default: True) If true, then all tab characters in text will be expanded to spaces using the expandtabs() method of text.

tabsize

(default: 8) If expand_tabs is true, then all tab characters in text will be expanded to zero or more spaces, depending on the current column and the given tab size.

在 3.3 版被加入.

replace_whitespace

(default: True) If true, after tab expansion but before wrapping, the wrap() method will replace each whitespace character with a single space. The whitespace characters replaced are as follows: tab, newline, vertical tab, formfeed, and carriage return ('\t\n\v\f\r').

備註

If expand_tabs is false and replace_whitespace is true, each tab character will be replaced by a single space, which is not the same as tab expansion.

備註

If replace_whitespace is false, newlines may appear in the middle of a line and cause strange output. For this reason, text should be split into paragraphs (using str.splitlines() or similar) which are wrapped separately.

drop_whitespace

(default: True) If true, whitespace at the beginning and ending of every line (after wrapping but before indenting) is dropped. Whitespace at the beginning of the paragraph, however, is not dropped if non-whitespace follows it. If whitespace being dropped takes up an entire line, the whole line is dropped.

initial_indent

(default: '') String that will be prepended to the first line of wrapped output. Counts towards the length of the first line. The empty string is not indented.

subsequent_indent

(default: '') String that will be prepended to all lines of wrapped output except the first. Counts towards the length of each line except the first.

fix_sentence_endings

(default: False) If true, TextWrapper attempts to detect sentence endings and ensure that sentences are always separated by exactly two spaces. This is generally desired for text in a monospaced font. However, the sentence detection algorithm is imperfect: it assumes that a sentence ending consists of a lowercase letter followed by one of '.', '!', or '?', possibly followed by one of '"' or "'", followed by a space. One problem with this algorithm is that it is unable to detect the difference between "Dr." in

[...] Dr. Frankenstein's monster [...]

and "Spot." in

[...] See Spot. See Spot run [...]

fix_sentence_endings 預設為 false。

Since the sentence detection algorithm relies on string.lowercase for the definition of "lowercase letter", and a convention of using two spaces after a period to separate sentences on the same line, it is specific to English-language texts.

break_long_words

(default: True) If true, then words longer than width will be broken in order to ensure that no lines are longer than width. If it is false, long words will not be broken, and some lines may be longer than width. (Long words will be put on a line by themselves, in order to minimize the amount by which width is exceeded.)

break_on_hyphens

(default: True) If true, wrapping will occur preferably on whitespaces and right after hyphens in compound words, as it is customary in English. If false, only whitespaces will be considered as potentially good places for line breaks, but you need to set break_long_words to false if you want truly insecable words. Default behaviour in previous versions was to always allow breaking hyphenated words.

max_lines

(default: None) If not None, then the output will contain at most max_lines lines, with placeholder appearing at the end of the output.

在 3.4 版被加入.

placeholder

(default: ' [...]') String that will appear at the end of the output text if it has been truncated.

在 3.4 版被加入.

TextWrapper also provides some public methods, analogous to the module-level convenience functions:

wrap(text)

Wraps the single paragraph in text (a string) so every line is at most width characters long. All wrapping options are taken from instance attributes of the TextWrapper instance. Returns a list of output lines, without final newlines. If the wrapped output has no content, the returned list is empty.

fill(text)

Wraps the single paragraph in text, and returns a single string containing the wrapped paragraph.

unicodedata --- Unicode 資料庫

This module provides access to the Unicode Character Database (UCD) which defines character properties for all Unicode characters. The data contained in this database is compiled from the UCD version 16.0.0 [https://www.unicode.org/Public/16.0.0/ucd].

The module uses the same names and symbols as defined by Unicode Standard Annex #44, "Unicode Character Database" [https://www.unicode.org/reports/tr44/]. It defines the following functions:

也參考

The Unicode HOWTO for more information about Unicode and how to use this module.

unicodedata.lookup(name)

Look up character by name. If a character with the given name is found, return the corresponding character. If not found, KeyError is raised. For example:

>>> unicodedata.lookup('LEFT CURLY BRACKET')
'{'

The characters returned by this function are the same as those produced by \N escape sequence in string literals. For example:

>>> unicodedata.lookup('MIDDLE DOT') == '\N{MIDDLE DOT}'
True

在 3.3 版的變更: 已新增對名稱別名 [1] 和命名序列 [2] 的支援。

unicodedata.name(chr, default=None, /)

Returns the name assigned to the character chr as a string. If no name is defined, default is returned, or, if not given, ValueError is raised. For example:

>>> unicodedata.name('½')
'VULGAR FRACTION ONE HALF'
>>> unicodedata.name('\uFFFF', 'fallback')
'fallback'

unicodedata.decimal(chr, default=None, /)

Returns the decimal value assigned to the character chr as integer. If no such value is defined, default is returned, or, if not given, ValueError is raised. For example:

>>> unicodedata.decimal('\N{ARABIC-INDIC DIGIT NINE}')
9
>>> unicodedata.decimal('\N{SUPERSCRIPT NINE}', -1)
-1

unicodedata.digit(chr, default=None, /)

Returns the digit value assigned to the character chr as integer. If no such value is defined, default is returned, or, if not given, ValueError is raised:

>>> unicodedata.digit('\N{SUPERSCRIPT NINE}')
9

unicodedata.numeric(chr, default=None, /)

Returns the numeric value assigned to the character chr as float. If no such value is defined, default is returned, or, if not given, ValueError is raised:

>>> unicodedata.numeric('½')
0.5

unicodedata.category(chr)

Returns the general category assigned to the character chr as string. General category names consist of two letters. See the General Category Values section of the Unicode Character Database documentation [https://www.unicode.org/reports/tr44/tr44-34.html#General_Category_Values] for a list of category codes. For example:

>>> unicodedata.category('A')  # 'L'etter, 'u'ppercase
'Lu'

unicodedata.bidirectional(chr)

Returns the bidirectional class assigned to the character chr as string. If no such value is defined, an empty string is returned. See the Bidirectional Class Values section of the Unicode Character Database [https://www.unicode.org/reports/tr44/tr44-34.html#Bidi_Class_Values] documentation for a list of bidirectional codes. For example:

>>> unicodedata.bidirectional('\N{ARABIC-INDIC DIGIT SEVEN}') # 'A'rabic, 'N'umber
'AN'

unicodedata.combining(chr)

Returns the canonical combining class assigned to the character chr as integer. Returns 0 if no combining class is defined. See the Canonical Combining Class Values section of the Unicode Character Database [https://www.unicode.org/reports/tr44/tr44-34.html#Canonical_Combining_Class_Values] for more information.

unicodedata.east_asian_width(chr)

Returns the east asian width assigned to the character chr as string. For a list of widths and or more information, see the Unicode Standard Annex #11 [https://www.unicode.org/reports/tr11/tr11-43.html].

unicodedata.mirrored(chr)

Returns the mirrored property assigned to the character chr as integer. Returns 1 if the character has been identified as a "mirrored" character in bidirectional text, 0 otherwise. For example:

>>> unicodedata.mirrored('>')
1

unicodedata.decomposition(chr)

Returns the character decomposition mapping assigned to the character chr as string. An empty string is returned in case no such mapping is defined. For example:

>>> unicodedata.decomposition('Ã')
'0041 0303'

unicodedata.normalize(form, unistr)

Return the normal form form for the Unicode string unistr. Valid values for form are 'NFC', 'NFKC', 'NFD', and 'NFKD'.

The Unicode standard defines various normalization forms of a Unicode string, based on the definition of canonical equivalence and compatibility equivalence. In Unicode, several characters can be expressed in various way. For example, the character U+00C7 (LATIN CAPITAL LETTER C WITH CEDILLA) can also be expressed as the sequence U+0043 (LATIN CAPITAL LETTER C) U+0327 (COMBINING CEDILLA).

For each character, there are two normal forms: normal form C and normal form D. Normal form D (NFD) is also known as canonical decomposition, and translates each character into its decomposed form. Normal form C (NFC) first applies a canonical decomposition, then composes pre-combined characters again.

In addition to these two forms, there are two additional normal forms based on compatibility equivalence. In Unicode, certain characters are supported which normally would be unified with other characters. For example, U+2160 (ROMAN NUMERAL ONE) is really the same thing as U+0049 (LATIN CAPITAL LETTER I). However, it is supported in Unicode for compatibility with existing character sets (for example, gb2312).

The normal form KD (NFKD) will apply the compatibility decomposition, that is, replace all compatibility characters with their equivalents. The normal form KC (NFKC) first applies the compatibility decomposition, followed by the canonical composition.

Even if two unicode strings are normalized and look the same to a human reader, if one has combining characters and the other doesn't, they may not compare equal.

unicodedata.is_normalized(form, unistr)

Return whether the Unicode string unistr is in the normal form form. Valid values for form are 'NFC', 'NFKC', 'NFD', and 'NFKD'.

在 3.8 版被加入.

In addition, the module exposes the following constant:

unicodedata.unidata_version

在此模組中使用的 Unicode 資料庫版本。

unicodedata.ucd_3_2_0

This is an object that has the same methods as the entire module, but uses the Unicode database version 3.2 instead, for applications that require this specific version of the Unicode database (such as IDNA).

註腳

[1]

https://www.unicode.org/Public/16.0.0/ucd/NameAliases.txt

[2]

https://www.unicode.org/Public/16.0.0/ucd/NamedSequences.txt

stringprep --- 網際網路字串的準備

原始碼：Lib/stringprep.py [https://github.com/python/cpython/tree/3.14/Lib/stringprep.py]

在網際網路上識別事物（例如主機名稱）時，通常需要比較這些識別器的「相等性 (equality)」。比較的具體執行方式可能取決於應用程式領域，例如是否應該不區分大小寫。也可能有必要限制可能的識別器，只允許由「可列印 (printable)」字元組成的識別器。

RFC 3454 [https://datatracker.ietf.org/doc/html/rfc3454.html] 定義了在網際網路通訊協定中「準備」Unicode 字串的程序。在傳送字串到網路之前，先使用準備程序處理字串，之後字串就具有特定的規範化 (normalized) 形式。RFC 定義了一系列的表，這些表可以組合成設定檔 (profile)。每個設定檔必須定義它使用哪些表以及 stringprep 程序的哪些其他可選部分是設定檔的一部分。stringprep 配置文件的一個例子是 nameprep，它被用於國際化網域名稱。

stringprep 模組只開放 RFC 3454 [https://datatracker.ietf.org/doc/html/rfc3454.html] 中的表。由於這些表如果以字典或串列的方式來表示的話會非常大，因此模組內部使用 Unicode 字元資料庫。模組原始碼本身是使用 mkstringprep.py 工具來產生的。

因此，這些表是以函式而非資料結構的形式呈現。RFC 中有兩種表：集合 (sets) 和對映 (mappings)。對於集合，stringprep 提供了「特徵函式 (characteristic function)」，也就是如果參數是集合的一部分就回傳 True 的函式。對於對映，它提供了對映函式：給定鍵，它會回傳相關的值。以下是模組中所有可用函式的清單。

stringprep.in_table_a1(code)

判斷 code 是否在 tableA.1（Unicode 3.2 中未指定的編碼位置 (code point)）中。

stringprep.in_table_b1(code)

判斷 code 是否在 tableB.1（通常沒有對映到任何東西）中。

stringprep.map_table_b2(code)

根據 tableB.2（使用 NFKC 形式的大小寫折疊 (case-folding) 對映）回傳 code 的對映值。

stringprep.map_table_b3(code)

根據 tableB.3（使用沒有規範化的大小寫折疊對映）回傳 code 的對映值。

stringprep.in_table_c11(code)

判斷 code 是否在 tableC.1.1（ASCII 空格字元）中。

stringprep.in_table_c12(code)

判斷 code 是否在 tableC.1.2（非 ASCII 空格字元）中。

stringprep.in_table_c11_c12(code)

判斷 code 是否在 tableC.1（空格字元，為 C.1.1 和 C.1.2 的聯集）中。

stringprep.in_table_c21(code)

判斷 code 是否在 tableC.2.1（ASCII 控制字元）中。

stringprep.in_table_c22(code)

判斷 code 是否在 tableC.2.2（非 ASCII 控制字元）中。

stringprep.in_table_c21_c22(code)

判斷 code 是否在 tableC.2（控制字元，為 C.2.1 和 C.2.2 的聯集）中。

stringprep.in_table_c3(code)

判斷 code 是否在 tableC.3（私有使用）中。

stringprep.in_table_c4(code)

判斷 code 是否在 tableC.4（非字元編碼位置）中。

stringprep.in_table_c5(code)

判斷 code 是否在 tableC.5（代理碼）中。

stringprep.in_table_c6(code)

判斷 code 是否在 tableC.6（不適用於純文字）中。

stringprep.in_table_c7(code)

判斷 code 是否在 tableC.7（不適用於規範表示法 (canonical representation)）中。

stringprep.in_table_c8(code)

判斷 code 是否在 tableC.8（變更顯示屬性或已棄用）中。

stringprep.in_table_c9(code)

判斷 code 是否在 tableC.9（標記字元 (tagging characters)）中。

stringprep.in_table_d1(code)

判斷 code 是否在 tableD.1（具有雙向屬性 "R" 或 "AL" 的字元）中。

stringprep.in_table_d2(code)

判斷 code 是否在 tableD.2（具有雙向屬性 "L" 的字元）中。

readline --- GNU readline 介面

The readline module defines a number of functions to facilitate completion and reading/writing of history files from the Python interpreter. This module can be used directly, or via the rlcompleter module, which supports completion of Python identifiers at the interactive prompt. Settings made using this module affect the behaviour of both the interpreter's interactive prompt and the prompts offered by the built-in input() function.

Readline keybindings may be configured via an initialization file, typically .inputrc in your home directory. See Readline Init File [https://tiswww.cwru.edu/php/chet/readline/rluserman.html#Readline-Init-File] in the GNU Readline manual for information about the format and allowable constructs of that file, and the capabilities of the Readline library in general.

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

備註

The underlying Readline library API may be implemented by the editline (libedit) library instead of GNU readline. On macOS the readline module detects which library is being used at run time.

The configuration file for editline is different from that of GNU readline. If you programmatically load configuration strings you can use backend to determine which library is being used.

If you use editline/libedit readline emulation on macOS, the initialization file located in your home directory is named .editrc. For example, the following content in ~/.editrc will turn ON vi keybindings and TAB completion:

python:bind -v
python:bind ^I rl_complete

Also note that different libraries may use different history file formats. When switching the underlying library, existing history files may become unusable.

readline.backend

The name of the underlying Readline library being used, either "readline" or "editline".

在 3.13 版被加入.

Init file

The following functions relate to the init file and user configuration:

readline.parse_and_bind(string)

Execute the init line provided in the string argument. This calls rl_parse_and_bind() in the underlying library.

readline.read_init_file([filename])

Execute a readline initialization file. The default filename is the last filename used. This calls rl_read_init_file() in the underlying library. It raises an auditing event open with the file name if given, and "<readline_init_file>" otherwise, regardless of which file the library resolves.

在 3.14 版的變更: The auditing event was added.

Line buffer

The following functions operate on the line buffer:

readline.get_line_buffer()

Return the current contents of the line buffer (rl_line_buffer in the underlying library).

readline.insert_text(string)

Insert text into the line buffer at the cursor position. This calls rl_insert_text() in the underlying library, but ignores the return value.

readline.redisplay()

Change what's displayed on the screen to reflect the current contents of the line buffer. This calls rl_redisplay() in the underlying library.

History file

The following functions operate on a history file:

readline.read_history_file([filename])

Load a readline history file, and append it to the history list. The default filename is ~/.history. This calls read_history() in the underlying library and raises an auditing event open with the file name if given and "~/.history" otherwise.

在 3.14 版的變更: The auditing event was added.

readline.write_history_file([filename])

Save the history list to a readline history file, overwriting any existing file. The default filename is ~/.history. This calls write_history() in the underlying library and raises an auditing event open with the file name if given and "~/.history" otherwise.

在 3.14 版的變更: The auditing event was added.

readline.append_history_file(nelements[, filename])

Append the last nelements items of history to a file. The default filename is ~/.history. The file must already exist. This calls append_history() in the underlying library. This function only exists if Python was compiled for a version of the library that supports it. It raises an auditing event open with the file name if given and "~/.history" otherwise.

在 3.5 版被加入.

在 3.14 版的變更: The auditing event was added.

readline.get_history_length()

readline.set_history_length(length)

Set or return the desired number of lines to save in the history file. The write_history_file() function uses this value to truncate the history file, by calling history_truncate_file() in the underlying library. Negative values imply unlimited history file size.

History list

The following functions operate on a global history list:

readline.clear_history()

Clear the current history. This calls clear_history() in the underlying library. The Python function only exists if Python was compiled for a version of the library that supports it.

readline.get_current_history_length()

Return the number of items currently in the history. (This is different from get_history_length(), which returns the maximum number of lines that will be written to a history file.)

readline.get_history_item(index)

Return the current contents of history item at index. The item index is one-based. This calls history_get() in the underlying library.

readline.remove_history_item(pos)

Remove history item specified by its position from the history. The position is zero-based. This calls remove_history() in the underlying library.

readline.replace_history_item(pos, line)

Replace history item specified by its position with line. The position is zero-based. This calls replace_history_entry() in the underlying library.

readline.add_history(line)

Append line to the history buffer, as if it was the last line typed. This calls add_history() in the underlying library.

readline.set_auto_history(enabled)

Enable or disable automatic calls to add_history() when reading input via readline. The enabled argument should be a Boolean value that when true, enables auto history, and that when false, disables auto history.

在 3.6 版被加入.

CPython 實作細節： Auto history is enabled by default, and changes to this do not persist across multiple sessions.

Startup hooks

readline.set_startup_hook([function])

Set or remove the function invoked by the rl_startup_hook callback of the underlying library. If function is specified, it will be used as the new hook function; if omitted or None, any function already installed is removed. The hook is called with no arguments just before readline prints the first prompt.

readline.set_pre_input_hook([function])

Set or remove the function invoked by the rl_pre_input_hook callback of the underlying library. If function is specified, it will be used as the new hook function; if omitted or None, any function already installed is removed. The hook is called with no arguments after the first prompt has been printed and just before readline starts reading input characters. This function only exists if Python was compiled for a version of the library that supports it.

Completion

The following functions relate to implementing a custom word completion function. This is typically operated by the Tab key, and can suggest and automatically complete a word being typed. By default, Readline is set up to be used by rlcompleter to complete Python identifiers for the interactive interpreter. If the readline module is to be used with a custom completer, a different set of word delimiters should be set.

readline.set_completer([function])

Set or remove the completer function. If function is specified, it will be used as the new completer function; if omitted or None, any completer function already installed is removed. The completer function is called as function(text, state), for state in 0, 1, 2, ..., until it returns a non-string value. It should return the next possible completion starting with text.

The installed completer function is invoked by the entry_func callback passed to rl_completion_matches() in the underlying library. The text string comes from the first parameter to the rl_attempted_completion_function callback of the underlying library.

readline.get_completer()

Get the completer function, or None if no completer function has been set.

readline.get_completion_type()

Get the type of completion being attempted. This returns the rl_completion_type variable in the underlying library as an integer.

readline.get_begidx()

readline.get_endidx()

Get the beginning or ending index of the completion scope. These indexes are the start and end arguments passed to the rl_attempted_completion_function callback of the underlying library. The values may be different in the same input editing scenario based on the underlying C readline implementation. Ex: libedit is known to behave differently than libreadline.

readline.set_completer_delims(string)

readline.get_completer_delims()

Set or get the word delimiters for completion. These determine the start of the word to be considered for completion (the completion scope). These functions access the rl_completer_word_break_characters variable in the underlying library.

readline.set_completion_display_matches_hook([function])

Set or remove the completion display function. If function is specified, it will be used as the new completion display function; if omitted or None, any completion display function already installed is removed. This sets or clears the rl_completion_display_matches_hook callback in the underlying library. The completion display function is called as function(substitution, [matches], longest_match_length) once each time matches need to be displayed.

範例

The following example demonstrates how to use the readline module's history reading and writing functions to automatically load and save a history file named .python_history from the user's home directory. The code below would normally be executed automatically during interactive sessions from the user's PYTHONSTARTUP file.

import atexit
import os
import readline

histfile = os.path.join(os.path.expanduser("~"), ".python_history")
try:
    readline.read_history_file(histfile)
    # default history len is -1 (infinite), which may grow unruly
    readline.set_history_length(1000)
except FileNotFoundError:
    pass

atexit.register(readline.write_history_file, histfile)

This code is actually automatically run when Python is run in interactive mode (see Readline configuration).

The following example achieves the same goal but supports concurrent interactive sessions, by only appending the new history.

import atexit
import os
import readline
histfile = os.path.join(os.path.expanduser("~"), ".python_history")

try:
    readline.read_history_file(histfile)
    h_len = readline.get_current_history_length()
except FileNotFoundError:
    open(histfile, 'wb').close()
    h_len = 0

def save(prev_h_len, histfile):
    new_h_len = readline.get_current_history_length()
    readline.set_history_length(1000)
    readline.append_history_file(new_h_len - prev_h_len, histfile)
atexit.register(save, h_len, histfile)

The following example extends the code.InteractiveConsole class to support history save/restore.

import atexit
import code
import os
import readline

class HistoryConsole(code.InteractiveConsole):
    def __init__(self, locals=None, filename="<console>",
                 histfile=os.path.expanduser("~/.console-history")):
        code.InteractiveConsole.__init__(self, locals, filename)
        self.init_history(histfile)

    def init_history(self, histfile):
        readline.parse_and_bind("tab: complete")
        if hasattr(readline, "read_history_file"):
            try:
                readline.read_history_file(histfile)
            except FileNotFoundError:
                pass
            atexit.register(self.save_history, histfile)

    def save_history(self, histfile):
        readline.set_history_length(1000)
        readline.write_history_file(histfile)

備註

The new REPL introduced in version 3.13 doesn't support readline. However, readline can still be used by setting the PYTHON_BASIC_REPL environment variable.

rlcompleter --- GNU readline 的補全函式

原始碼：Lib/rlcompleter.py [https://github.com/python/cpython/tree/3.14/Lib/rlcompleter.py]

The rlcompleter module defines a completion function suitable to be passed to set_completer() in the readline module.

When this module is imported on a Unix platform with the readline module available, an instance of the Completer class is automatically created and its complete() method is set as the readline completer. The method provides completion of valid Python identifiers and keywords.

範例：

>>> import rlcompleter
>>> import readline
>>> readline.parse_and_bind("tab: complete")
>>> readline. <TAB PRESSED>
readline.__doc__          readline.get_line_buffer(  readline.read_init_file(
readline.__file__         readline.insert_text(      readline.set_completer(
readline.__name__         readline.parse_and_bind(
>>> readline.

The rlcompleter module is designed for use with Python's interactive mode. Unless Python is run with the -S option, the module is automatically imported and configured (see Readline configuration).

On platforms without readline, the Completer class defined by this module can still be used for custom purposes.

class rlcompleter.Completer

Completer objects have the following method:

complete(text, state)

Return the next possible completion for text.

When called by the readline module, this method is called successively with state == 0, 1, 2, ... until the method returns None.

If called for text that doesn't include a period character ('.'), it will complete from names currently defined in __main__, builtins and keywords (as defined by the keyword module).

If called for a dotted name, it will try to evaluate anything without obvious side-effects (functions will not be evaluated, but it can generate calls to __getattr__()) up to the last part, and find matches for the rest via the dir() function. Any exception raised during the evaluation of the expression is caught, silenced and None is returned.

二進位資料服務

本章所描述的模組提供了一些基本的二進位資料操作服務。而針對二進位資料的其他操作──尤其是關於檔案格式和網路協定的部分──則會在相關章節中詳細描述。

一些在 文本處理 (Text Processing) 服務 中提及的函式庫也可處理 ASCII 相容的二進位格式（例如，re）及所有的二進位資料（例如，difflib）。

此外，請參閱 Python 內建的二進位資料類型的文件，詳情請參考 Binary Sequence Types --- bytes, bytearray, memoryview。

struct --- 將位元組直譯為打包起來的二進位資料

函式與例外

格式字串

位元組順序、大小和對齊

格式字元

範例

應用

原生格式

標準格式

類別

codecs --- 編解碼器註冊表和基底類別

Codec Base Classes

Error Handlers

Stateless Encoding and Decoding

Incremental Encoding and Decoding

IncrementalEncoder 物件

IncrementalDecoder 物件

串流編碼和解碼

StreamWriter 物件

StreamReader 物件

StreamReaderWriter 物件

StreamRecoder 物件

編碼和 Unicode

標準編碼

Python Specific Encodings

Text Encodings

Binary Transforms

Standalone Codec Functions

Text Transforms

encodings --- Encodings package

encodings.idna --- Internationalized Domain Names in Applications

encodings.mbcs --- Windows ANSI 碼頁

encodings.utf_8_sig --- UTF-8 codec with BOM signature

struct --- 將位元組直譯為打包起來的二進位資料

原始碼：Lib/struct.py [https://github.com/python/cpython/tree/3.14/Lib/struct.py]

此模組可在 Python 數值與以 Python bytes 物件表示的 C 結構之間進行轉換。簡潔的格式字串描述了與 Python 數值之間預期的轉換。此模組的函式和物件可用於兩種截然不同的應用程式：與外部來源（檔案或網路連線）的資料交換，或是 Python 應用程式與 C 層之間的資料傳輸。

備註

當未給定前綴字元時會預設為原生模式。它會根據建構 Python 直譯器的平台和編譯器來打包或解包資料。打包給定 C 結構的結果包含填充位元組，以維持相關 C 型別的正確對齊；同樣地，解包時也會考量對齊。相反地，當在外部來源之間傳輸資料時，程式設計師需負責定義位元組順序和元素之間的填充。詳情請參見 位元組順序、大小和對齊。

一些 struct 函式（和 Struct 的方法）接受一個 buffer 引數。這是指實作緩衝協定 (Buffer Protocol) 並提供可讀或可讀寫緩衝區的物件。最常用於此目的的型別是 bytes 和 bytearray，但許多其他可以視為位元組陣列的型別都實作了緩衝區協定，因此它們可以從 bytes 物件讀取或填入資料而無需額外的複製。

函式與例外

此模組定義了以下例外和函式：

exception struct.error

在各種情況下都可能觸發的例外；引數是一個描述錯誤內容的字串。

struct.pack(format, v1, v2, ...)

回傳一個包含依照格式字串 format 打包的數值 v1、v2、... 的位元組物件。引數必須完全符合格式所需的數值。

struct.pack_into(format, buffer, offset, v1, v2, ...)

依照格式字串 format 打包數值 v1、v2、...，並將打包後的位元組寫入可寫緩衝區 buffer 中從位置 offset 開始的地方。請注意 offset 是必要的引數。

struct.unpack(format, buffer)

根據格式字串 format 從緩衝區 buffer（推測是由 pack(format, ...) 打包的）解包。結果是一個元組，即使它只包含一個項目。緩衝區的位元組大小必須符合格式所需的大小，如 calcsize() 所示。

struct.unpack_from(format, /, buffer, offset=0)

根據格式字串 format 從 buffer 的 offset 位置開始解包。即使它只包含一個項目，結果也都是一個元組。緩衝區從位置 offset 開始的位元組大小，必須至少達到格式所需的大小，如 calcsize() 所示。

struct.iter_unpack(format, buffer)

根據格式字串 format 疊代地從緩衝區 buffer 解包。此函式回傳一個疊代器，它會從緩衝區讀取等大小的區塊，直到消耗完所有內容。緩衝區的位元組大小必須是格式所需大小的倍數，如 calcsize() 所示。

每次疊代都會產生 (yield) 出一個由格式字串指定的元組。

在 3.4 版被加入.

struct.calcsize(format)

回傳對應於格式字串 format 的結構大小（因此也是 pack(format, ...) 所產生的位元組物件的大小）。

格式字串

格式字串描述了打包和解包資料時的資料配置 (layout)。它們由格式字元組成，這些字元指定了要打包或解包的資料型別。此外，特殊字元控制位元組順序、大小和對齊。每個格式字串由一個可選的前綴字元組成，描述資料的整體屬性，以及一個或多個描述實際資料值和填充的格式字元。

位元組順序、大小和對齊

預設情況下，C 型別以機器的原生格式和位元組順序表示，並在必要時透過跳過填充位元組來正確對齊（根據 C 編譯器所使用的規則）。選擇此行為使得打包結構的位元組完全對應於相對應 C 結構的記憶體配置。是否使用原生位元組順序和填充或標準格式取決於應用程式。

或者，格式字串的第一個字元可以用來指示打包資料的位元組順序、大小和對齊，如下表所示：

字元

位元組順序

大小

對齊

@

原生

原生

原生

=

原生

標準

無

<

小端序

標準

無

>

大端序

標準

無

!

網路（= 大端序）

標準

無

如果第一個字元不是這些字元之一，則假設為 '@'。

備註

數字 1023（十六進位為 0x3ff）具有以下位元組表示法：

大端序（>）為 03 ff

小端序（<）為 ff 03

Python 範例：

>>> import struct
>>> struct.pack('>h', 1023)
b'\x03\xff'
>>> struct.pack('<h', 1023)
b'\xff\x03'

原生位元組順序是大端序或小端序，會取決於主機系統。例如，Intel x86、AMD64 (x86-64)和 Apple M1 是小端序；IBM z 和許多舊架構是大端序。可使用 sys.byteorder 來檢查你系統的位元組順序。

原生大小和對齊是使用 C 編譯器的 sizeof 運算式來決定的。這總是與原生位元組順序結合使用。

標準大小僅取決於格式字元；請參見格式字元區塊中的表格。

請注意 '@' 和 '=' 之間的差異：兩者都使用原生位元組順序，但後者的大小和對齊是標準化的。

'!' 形式表示網路位元組順序，根據 IETF RFC 1700 [https://datatracker.ietf.org/doc/html/rfc1700] 的定義，它總是大端序。

沒有方法來指示非原生位元組順序（強制位元組交換）；請使用適當的 '<' 或 '>' 選擇。

註解：

填充只會在連續的結構成員之間自動加入。編碼結構的開頭或結尾不會加入填充。

使用非原生大小和對齊時，例如使用 '<'、'>'、'=' 和 '!' 時，不會加入填充。

要將結構的結尾對齊到特定型別的對齊需求，請以該型別的碼結束格式，重複次數為零。請參見範例。

格式字元

格式字元具有以下意義；在給定型別的情況下，C 和 Python 數值之間的轉換應該是顯而易見的。「標準大小」欄位指的是使用標準大小時（即當格式字串以 '<'、'>'、'!' 或 '=' 其中之一開始時）打包數值的位元組大小。使用原生大小時，打包數值的大小取決於平台。

格式

C Type

Python 型別

標準大小

註解

x

填充位元組

無值

(7)

c

char

長度為 1 的位元組

1

b

signed char

整數

1

(1), (2)

B

unsigned char

整數

1

(2)

?

_Bool

bool

1

(1)

h

short

整數

2

(2)

H

unsigned short

整數

2

(2)

i

int

整數

4

(2)

I

unsigned int

整數

4

(2)

l

long

整數

4

(2)

L

unsigned long

整數

4

(2)

q

long long

整數

8

(2)

Q

unsigned long long

整數

8

(2)

n

ssize_t

整數

(3)

N

size_t

整數

(3)

e

(6)

float

2

(4)

f

float

float

4

(4)

d

double

float

8

(4)

F

float complex

complex

8

(10)

D

double complex

complex

16

(10)

s

char[]

位元組

(9)

p

char[]

位元組

(8)

P

void*

整數

(5)

在 3.3 版的變更: 新增 'n' 與 'N' 格式的支援。

在 3.6 版的變更: 新增 'e' 格式的支援。

在 3.14 版的變更: 新增 'F' 與 'D' 格式的支援。

註解：

'?' 轉換碼對應於自 C99 以來 C 標準定義的 _Bool 型別。在標準模式下，它由一個位元組表示。

當嘗試使用任何整數轉換碼打包非整數時，如果非整數具有 __index__() 方法，則會呼叫該方法在打包之前將引數轉換為整數。

在 3.2 版的變更: 新增對非整數使用 __index__() 方法的支援。

'n' 和 'N' 轉換碼僅適用於原生大小（作為預設選擇或使用 '@' 位元組順序字元）。對於標準大小，你可以使用適合你應用程式的其他整數格式。

對於 'f'、'd' 和 'e' 轉換碼，打包表示法使用 IEEE 754 binary32、binary64 或 binary16 格式（分別對應於 'f'、'd' 或 'e'），無論平台使用何種浮點數格式。

'P' 格式字元僅適用於原生位元組順序（作為預設選擇或使用 '@' 位元組順序字元）。位元組順序字元 '=' 根據主機系統選擇使用小端序或大端序。struct 模組不將其解釋為原生順序，因此 'P' 格式不可用。

IEEE 754 binary16「半精度 (half precision)」型別是在 2008 年的 IEEE 754 標準 [https://en.wikipedia.org/wiki/IEEE_754-2008_revision]修訂版中引入的。它有一個符號位元 (sign bit)、5 位元指數和 11 位元精度（明確儲存 10 位元），可以全精度表示大約 6.1e-05 到 6.5e+04 之間的數字。此型別未被 C 編譯器廣泛支援：在典型機器上，unsigned short 可以用於儲存但不能用於數學運算。請參見 Wikipedia 上的半精度浮點數格式 [https://en.wikipedia.org/wiki/Half-precision_floating-point_format]頁面以取得更多資訊。

打包時，'x' 插入一個 NUL 位元組。

'p' 格式字元編碼一個「Pascal 字串」，意思是儲存在固定位元組數中的短、長度可變字串，由計數指定。儲存的第一個位元組是字串的長度，或與 255 間取較小者。字串的位元組在其後。如果傳遞給 pack() 的字串太長（長於計數減 1），則只儲存字串的前 count-1 個位元組。如果字串短於 count-1，則用空位元組填充，使得總共使用恰好 count 個位元組。請注意，對於 unpack()， 'p' 格式字元消耗 count 個位元組，但回傳的字串永遠不能包含超過 255 個位元組。

對於 's' 格式字元，計數被直譯為位元組的長度，而不是像其他格式字元那樣的重複次數；例如，'10s' 表示一個 10 位元組字串，對應於單一 Python 位元組字串，而 '10c' 表示 10 個獨立的單位元組字元元素（例如 cccccccccc），對應於十個不同的 Python 位元組物件。（請參見 範例 以了解具體差異的示範。）如果未給定計數，則預設為 1。打包時，會適當地截斷或用空位元組填充字串以使其適合。解包時，結果位元組物件總是恰好具有指定的位元組數。作為特殊情況，'0s' 表示單一空字串（而 '0c' 表示 0 個字元）。

For the 'F' and 'D' format characters, the packed representation uses the IEEE 754 binary32 and binary64 format for components of the complex number, regardless of the floating-point format used by the platform. Note that complex types (F and D) are available unconditionally, despite complex types being an optional feature in C. As specified in the C11 standard, each complex type is represented by a two-element C array containing, respectively, the real and imaginary parts.

格式字元前面可以加上整數重複次數。例如，格式字串 '4h' 與 'hhhh' 意思完全相同。

格式之間的空白字元會被忽略；但是計數和其格式不能包含空白字元。

當使用整數格式之一（'b'、'B'、'h'、'H'、'i'、'I'、'l'、'L'、'q'、'Q'）打包數值 x 時，如果 x 超出該格式的有效範圍，則會觸發 struct.error。

在 3.1 版的變更: 以前一些整數格式會環繞超出範圍的數值並引發 DeprecationWarning 而不是 struct.error。

對於 '?' 格式字元，回傳值是 True 或 False。打包時，使用引數物件的真值。原生或標準布林值表示法中的 0 或 1 將被打包，解包時任何非零值都將為 True。

範例

備註

原生位元組順序範例（由 '@' 格式前綴或缺少任何前綴字元指定）可能與讀者機器產生的結果不符，因為這取決於平台和編譯器。

使用大端序打包和解包三種不同大小的整數：

>>> from struct import *
>>> pack(">bhl", 1, 2, 3)
b'\x01\x00\x02\x00\x00\x00\x03'
>>> unpack('>bhl', b'\x01\x00\x02\x00\x00\x00\x03')
(1, 2, 3)
>>> calcsize('>bhl')
7

嘗試打包對於定義欄位來說太大的整數：

>>> pack(">h", 99999)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
struct.error: 'h' format requires -32768 <= number <= 32767

示範 's' 和 'c' 格式字元之間的差異：

>>> pack("@ccc", b'1', b'2', b'3')
b'123'
>>> pack("@3s", b'123')
b'123'

解包的欄位可以透過將其指派給變數或將結果包裝在具名元組中來命名：

>>> record = b'raymond   \x32\x12\x08\x01\x08'
>>> name, serialnum, school, gradelevel = unpack('<10sHHb', record)

>>> from collections import namedtuple
>>> Student = namedtuple('Student', 'name serialnum school gradelevel')
>>> Student._make(unpack('<10sHHb', record))
Student(name=b'raymond   ', serialnum=4658, school=264, gradelevel=8)

在原生模式下，格式字元的順序可能會影響大小，因為填充是隱式的。在標準模式下，使用者負責插入任何所需的填充。請注意下面第一個 pack 呼叫中，在打包的 '#' 之後加入了三個 NUL 位元組，以將後續整數對齊到四位元組邊界。在此範例中，輸出是在小端序機器上產生的：

>>> pack('@ci', b'#', 0x12131415)
b'#\x00\x00\x00\x15\x14\x13\x12'
>>> pack('@ic', 0x12131415, b'#')
b'\x15\x14\x13\x12#'
>>> calcsize('@ci')
8
>>> calcsize('@ic')
5

假設平台的 long 對齊到 4 位元組邊界，以下格式 'llh0l' 會在結尾加入兩個填充位元組：

>>> pack('@llh0l', 1, 2, 3)
b'\x00\x00\x00\x01\x00\x00\x00\x02\x00\x03\x00\x00'

也參考

array 模組

同質資料的打包二進位儲存。

json 模組

JSON 編碼器和解碼器。

pickle 模組

Python 物件序列化。

應用

struct 模組有兩種主要應用程式：在應用程式內或使用相同編譯器編譯的另一個應用程式之間進行 Python 和 C 程式碼的資料交換（原生格式），以及使用約定資料配置的應用程式之間的資料交換（標準格式）。一般來說，為這兩個領域建構的格式字串是不同的。

原生格式

當構造模擬原生配置的格式字串時，編譯器和機器架構會決定位元組順序和填充。在這種情況下，應該使用 @ 格式字元來指定原生位元組順序和資料大小。內部填充位元組通常會自動插入。可能需要在格式字串的結尾使用零重複格式碼來向上舍入到正確的位元組邊界，以便正確對齊連續的資料區塊 (chunks)。

考慮這兩個簡單範例（在 64 位元小端序機器上）：

>>> calcsize('@lhl')
24
>>> calcsize('@llh')
18

在第二個格式字串的結尾，如果不使用額外填充，資料不會填充到 8 位元組邊界。零重複格式碼解決了這個問題：

>>> calcsize('@llh0l')
24

'x' 格式碼可以用來指定重複，但對於原生格式來說最好使用像 '0l' 這樣的零重複格式。

預設使用原生位元組順序和對齊，但最好明確使用 '@' 前綴字元。

標準格式

當與你的行程之外的網路或儲存區等交換資料時，要夠精確。指定確切的位元組順序、大小和對齊。不要假設它們與特定機器的原生順序匹配。例如，網路位元組順序是大端序，而許多流行的 CPU 是小端序。透過明確定義這一點，使用者無需關心其程式碼運行的平台細節。第一個字元通常應該是 < 或 >（或 !）。填充是程式設計師的責任。零重複格式字元不會起作用。取而代之的是使用者必須在需要的地方明確加入 'x' 填充位元組。重新檢視上一節的範例，我們有：

>>> calcsize('<qh6xq')
24
>>> pack('<qh6xq', 1, 2, 3) == pack('@lhl', 1, 2, 3)
True
>>> calcsize('@llh')
18
>>> pack('@llh', 1, 2, 3) == pack('<qqh', 1, 2, 3)
True
>>> calcsize('<qqh6x')
24
>>> calcsize('@llh0l')
24
>>> pack('@llh0l', 1, 2, 3) == pack('<qqh6x', 1, 2, 3)
True

上述結果（在 64 位元機器上執行）和在不同機器上執行時不保證會匹配。例如，下面的範例是在 32 位元機器上執行的：

>>> calcsize('<qqh6x')
24
>>> calcsize('@llh0l')
12
>>> pack('@llh0l', 1, 2, 3) == pack('<qqh6x', 1, 2, 3)
False

類別

struct 模組也定義了以下型別：

class struct.Struct(format)

回傳一個新的 Struct 物件，它會根據格式字串 format 寫入和讀取二進位資料。建立一次 Struct 物件並呼叫其方法比使用相同格式呼叫模組層級函式更有效率，因為格式字串只編譯一次。

備註

傳遞給模組層級函式的最近一個格式字串的編譯版本會被快取起來，因此僅使用少數格式字串的程式無需擔心重複使用單一 Struct 實例。

編譯過的 Struct 物件支援以下方法和屬性：

pack(v1, v2, ...)

與 pack() 函式相同，會使用編譯過的格式。（len(result) 將等於 size。）

pack_into(buffer, offset, v1, v2, ...)

與 pack_into() 函式相同，會使用編譯過的格式。

unpack(buffer)

與 unpack() 函式相同，會使用編譯過的格式。緩衝區的位元組大小必須等於 size。

unpack_from(buffer, offset=0)

與 unpack_from() 函式相同，會使用編譯過的格式。緩衝區從位置 offset 開始的位元組大小必須至少為 size。

iter_unpack(buffer)

與 iter_unpack() 函式相同，會使用編譯過的格式。緩衝區的位元組大小必須是 size 的倍數。

在 3.4 版被加入.

format

用於建構此 Struct 物件的格式字串。

在 3.7 版的變更: 格式字串型別現在是 str 而不是 bytes。

size

對應於 format 的結構之計算出的大小（因此也是 pack() 方法所產生的位元組物件的大小）。

在 3.13 版的變更: 結構的 repr() 已經改變。現在是：

>>> Struct('i')
Struct('i')

codecs --- 編解碼器註冊表和基底類別

原始碼：Lib/codecs.py [https://github.com/python/cpython/tree/3.14/Lib/codecs.py]

This module defines base classes for standard Python codecs (encoders and decoders) and provides access to the internal Python codec registry, which manages the codec and error handling lookup process. Most standard codecs are text encodings, which encode text to bytes (and decode bytes to text), but there are also codecs provided that encode text to text, and bytes to bytes. Custom codecs may encode and decode between arbitrary types, but some module features are restricted to be used specifically with text encodings or with codecs that encode to bytes.

這個模組定義了以下函式，用於以任何編解碼器來編碼與解碼：

codecs.encode(obj, encoding='utf-8', errors='strict')

Encodes obj using the codec registered for encoding.

Errors may be given to set the desired error handling scheme. The default error handler is 'strict' meaning that encoding errors raise ValueError (or a more codec specific subclass, such as UnicodeEncodeError). Refer to Codec Base Classes for more information on codec error handling.

codecs.decode(obj, encoding='utf-8', errors='strict')

Decodes obj using the codec registered for encoding.

Errors may be given to set the desired error handling scheme. The default error handler is 'strict' meaning that decoding errors raise ValueError (or a more codec specific subclass, such as UnicodeDecodeError). Refer to Codec Base Classes for more information on codec error handling.

codecs.charmap_build(string)

Return a mapping suitable for encoding with a custom single-byte encoding. Given a str string of up to 256 characters representing a decoding table, returns either a compact internal mapping object EncodingMap or a dictionary mapping character ordinals to byte values. Raises a TypeError on invalid input.

The full details for each codec can also be looked up directly:

codecs.lookup(encoding, /)

Looks up the codec info in the Python codec registry and returns a CodecInfo object as defined below.

Encodings are first looked up in the registry's cache. If not found, the list of registered search functions is scanned. If no CodecInfo object is found, a LookupError is raised. Otherwise, the CodecInfo object is stored in the cache and returned to the caller.

class codecs.CodecInfo(encode, decode, streamreader=None, streamwriter=None, incrementalencoder=None, incrementaldecoder=None, name=None)

Codec details when looking up the codec registry. The constructor arguments are stored in attributes of the same name:

name

編碼的名稱。

encode

decode

The stateless encoding and decoding functions. These must be functions or methods which have the same interface as the encode() and decode() methods of Codec instances (see Codec Interface). The functions or methods are expected to work in a stateless mode.

incrementalencoder

incrementaldecoder

Incremental encoder and decoder classes or factory functions. These have to provide the interface defined by the base classes IncrementalEncoder and IncrementalDecoder, respectively. Incremental codecs can maintain state.

streamwriter

streamreader

Stream writer and reader classes or factory functions. These have to provide the interface defined by the base classes StreamWriter and StreamReader, respectively. Stream codecs can maintain state.

To simplify access to the various codec components, the module provides these additional functions which use lookup() for the codec lookup:

codecs.getencoder(encoding)

Look up the codec for the given encoding and return its encoder function.

Raises a LookupError in case the encoding cannot be found.

codecs.getdecoder(encoding)

Look up the codec for the given encoding and return its decoder function.

Raises a LookupError in case the encoding cannot be found.

codecs.getincrementalencoder(encoding)

Look up the codec for the given encoding and return its incremental encoder class or factory function.

Raises a LookupError in case the encoding cannot be found or the codec doesn't support an incremental encoder.

codecs.getincrementaldecoder(encoding)

Look up the codec for the given encoding and return its incremental decoder class or factory function.

Raises a LookupError in case the encoding cannot be found or the codec doesn't support an incremental decoder.

codecs.getreader(encoding)

Look up the codec for the given encoding and return its StreamReader class or factory function.

Raises a LookupError in case the encoding cannot be found.

codecs.getwriter(encoding)

Look up the codec for the given encoding and return its StreamWriter class or factory function.

Raises a LookupError in case the encoding cannot be found.

Custom codecs are made available by registering a suitable codec search function:

codecs.register(search_function, /)

Register a codec search function. Search functions are expected to take one argument, being the encoding name in all lower case letters with hyphens and spaces converted to underscores, and return a CodecInfo object. In case a search function cannot find a given encoding, it should return None.

在 3.9 版的變更: Hyphens and spaces are converted to underscore.

codecs.unregister(search_function, /)

Unregister a codec search function and clear the registry's cache. If the search function is not registered, do nothing.

在 3.10 版被加入.

While the builtin open() and the associated io module are the recommended approach for working with encoded text files, this module provides additional utility functions and classes that allow the use of a wider range of codecs when working with binary files:

codecs.open(filename, mode='r', encoding=None, errors='strict', buffering=-1)

Open an encoded file using the given mode and return an instance of StreamReaderWriter, providing transparent encoding/decoding. The default file mode is 'r', meaning to open the file in read mode.

備註

If encoding is not None, then the underlying encoded files are always opened in binary mode. No automatic conversion of '\n' is done on reading and writing. The mode argument may be any binary mode acceptable to the built-in open() function; the 'b' is automatically added.

encoding specifies the encoding which is to be used for the file. Any encoding that encodes to and decodes from bytes is allowed, and the data types supported by the file methods depend on the codec used.

errors may be given to define the error handling. It defaults to 'strict' which causes a ValueError to be raised in case an encoding error occurs.

buffering has the same meaning as for the built-in open() function. It defaults to -1 which means that the default buffer size will be used.

在 3.11 版的變更: 已移除 'U' 模式。

在 3.14 版之後被棄用: codecs.open() 已被 open() 取代。

codecs.EncodedFile(file, data_encoding, file_encoding=None, errors='strict')

Return a StreamRecoder instance, a wrapped version of file which provides transparent transcoding. The original file is closed when the wrapped version is closed.

Data written to the wrapped file is decoded according to the given data_encoding and then written to the original file as bytes using file_encoding. Bytes read from the original file are decoded according to file_encoding, and the result is encoded using data_encoding.

If file_encoding is not given, it defaults to data_encoding.

errors may be given to define the error handling. It defaults to 'strict', which causes ValueError to be raised in case an encoding error occurs.

codecs.iterencode(iterator, encoding, errors='strict', **kwargs)

Uses an incremental encoder to iteratively encode the input provided by iterator. iterator must yield str objects. This function is a generator. The errors argument (as well as any other keyword argument) is passed through to the incremental encoder.

This function requires that the codec accept text str objects to encode. Therefore it does not support bytes-to-bytes encoders such as base64_codec.

codecs.iterdecode(iterator, encoding, errors='strict', **kwargs)

Uses an incremental decoder to iteratively decode the input provided by iterator. iterator must yield bytes objects. This function is a generator. The errors argument (as well as any other keyword argument) is passed through to the incremental decoder.

This function requires that the codec accept bytes objects to decode. Therefore it does not support text-to-text encoders such as rot_13, although rot_13 may be used equivalently with iterencode().

codecs.readbuffer_encode(buffer, errors=None, /)

Return a tuple containing the raw bytes of buffer, a buffer-compatible object or str (encoded to UTF-8 before processing), and their length in bytes.

忽略 errors 引數。

>>> codecs.readbuffer_encode(b"Zito")
(b'Zito', 4)

The module also provides the following constants which are useful for reading and writing to platform dependent files:

codecs.BOM

codecs.BOM_BE

codecs.BOM_LE

codecs.BOM_UTF8

codecs.BOM_UTF16

codecs.BOM_UTF16_BE

codecs.BOM_UTF16_LE

codecs.BOM_UTF32

codecs.BOM_UTF32_BE

codecs.BOM_UTF32_LE

These constants define various byte sequences, being Unicode byte order marks (BOMs) for several encodings. They are used in UTF-16 and UTF-32 data streams to indicate the byte order used, and in UTF-8 as a Unicode signature. BOM_UTF16 is either BOM_UTF16_BE or BOM_UTF16_LE depending on the platform's native byte order, BOM is an alias for BOM_UTF16, BOM_LE for BOM_UTF16_LE and BOM_BE for BOM_UTF16_BE. The others represent the BOM in UTF-8 and UTF-32 encodings.

Codec Base Classes

The codecs module defines a set of base classes which define the interfaces for working with codec objects, and can also be used as the basis for custom codec implementations.

Each codec has to define four interfaces to make it usable as codec in Python: stateless encoder, stateless decoder, stream reader and stream writer. The stream reader and writers typically reuse the stateless encoder/decoder to implement the file protocols. Codec authors also need to define how the codec will handle encoding and decoding errors.

Error Handlers

To simplify and standardize error handling, codecs may implement different error handling schemes by accepting the errors string argument:

>>> 'German ß, ♬'.encode(encoding='ascii', errors='backslashreplace')
b'German \\xdf, \\u266c'
>>> 'German ß, ♬'.encode(encoding='ascii', errors='xmlcharrefreplace')
b'German &#223;, &#9836;'

The following error handlers can be used with all Python 標準編碼 codecs:

Value

含義

'strict'

Raise UnicodeError (or a subclass), this is the default. Implemented in strict_errors().

'ignore'

Ignore the malformed data and continue without further notice. Implemented in ignore_errors().

'replace'

Replace with a replacement marker. On encoding, use ? (ASCII character). On decoding, use � (U+FFFD, the official REPLACEMENT CHARACTER). Implemented in replace_errors().

'backslashreplace'

Replace with backslashed escape sequences. On encoding, use hexadecimal form of Unicode code point with formats \xhh \uxxxx \Uxxxxxxxx. On decoding, use hexadecimal form of byte value with format \xhh. Implemented in backslashreplace_errors().

'surrogateescape'

On decoding, replace byte with individual surrogate code ranging from U+DC80 to U+DCFF. This code will then be turned back into the same byte when the 'surrogateescape' error handler is used when encoding the data. (See PEP 383 [https://peps.python.org/pep-0383/] for more.)

The following error handlers are only applicable to encoding (within text encodings):

Value

含義

'xmlcharrefreplace'

Replace with XML/HTML numeric character reference, which is a decimal form of Unicode code point with format &#num;. Implemented in xmlcharrefreplace_errors().

'namereplace'

Replace with \N{...} escape sequences, what appears in the braces is the Name property from Unicode Character Database. Implemented in namereplace_errors().

In addition, the following error handler is specific to the given codecs:

Value

Codecs

含義

'surrogatepass'

utf-8, utf-16, utf-32, utf-16-be, utf-16-le, utf-32-be, utf-32-le

Allow encoding and decoding surrogate code point (U+D800 - U+DFFF) as normal code point. Otherwise these codecs treat the presence of surrogate code point in str as an error.

在 3.1 版被加入: The 'surrogateescape' and 'surrogatepass' error handlers.

在 3.4 版的變更: The 'surrogatepass' error handler now works with utf-16* and utf-32* codecs.

在 3.5 版被加入: The 'namereplace' error handler.

在 3.5 版的變更: The 'backslashreplace' error handler now works with decoding and translating.

The set of allowed values can be extended by registering a new named error handler:

codecs.register_error(name, error_handler, /)

Register the error handling function error_handler under the name name. The error_handler argument will be called during encoding and decoding in case of an error, when name is specified as the errors parameter.

For encoding, error_handler will be called with a UnicodeEncodeError instance, which contains information about the location of the error. The error handler must either raise this or a different exception, or return a tuple with a replacement for the unencodable part of the input and a position where encoding should continue. The replacement may be either str or bytes. If the replacement is bytes, the encoder will simply copy them into the output buffer. If the replacement is a string, the encoder will encode the replacement. Encoding continues on original input at the specified position. Negative position values will be treated as being relative to the end of the input string. If the resulting position is out of bound an IndexError will be raised.

Decoding and translating works similarly, except UnicodeDecodeError or UnicodeTranslateError will be passed to the handler and that the replacement from the error handler will be put into the output directly.

Previously registered error handlers (including the standard error handlers) can be looked up by name:

codecs.lookup_error(name, /)

Return the error handler previously registered under the name name.

Raises a LookupError in case the handler cannot be found.

The following standard error handlers are also made available as module level functions:

codecs.strict_errors(exception)

Implements the 'strict' error handling.

Each encoding or decoding error raises a UnicodeError.

codecs.ignore_errors(exception)

Implements the 'ignore' error handling.

Malformed data is ignored; encoding or decoding is continued without further notice.

codecs.replace_errors(exception)

Implements the 'replace' error handling.

Substitutes ? (ASCII character) for encoding errors or � (U+FFFD, the official REPLACEMENT CHARACTER) for decoding errors.

codecs.backslashreplace_errors(exception)

Implements the 'backslashreplace' error handling.

Malformed data is replaced by a backslashed escape sequence. On encoding, use the hexadecimal form of Unicode code point with formats \xhh \uxxxx \Uxxxxxxxx. On decoding, use the hexadecimal form of byte value with format \xhh.

在 3.5 版的變更: Works with decoding and translating.

codecs.xmlcharrefreplace_errors(exception)

Implements the 'xmlcharrefreplace' error handling (for encoding within text encoding only).

The unencodable character is replaced by an appropriate XML/HTML numeric character reference, which is a decimal form of Unicode code point with format &#num; .

codecs.namereplace_errors(exception)

Implements the 'namereplace' error handling (for encoding within text encoding only).

The unencodable character is replaced by a \N{...} escape sequence. The set of characters that appear in the braces is the Name property from Unicode Character Database. For example, the German lowercase letter 'ß' will be converted to byte sequence \N{LATIN SMALL LETTER SHARP S} .

在 3.5 版被加入.

Stateless Encoding and Decoding

The base Codec class defines these methods which also define the function interfaces of the stateless encoder and decoder:

class codecs.Codec

encode(input, errors='strict')

Encodes the object input and returns a tuple (output object, length consumed). For instance, text encoding converts a string object to a bytes object using a particular character set encoding (e.g., cp1252 or iso-8859-1).

The errors argument defines the error handling to apply. It defaults to 'strict' handling.

The method may not store state in the Codec instance. Use StreamWriter for codecs which have to keep state in order to make encoding efficient.

The encoder must be able to handle zero length input and return an empty object of the output object type in this situation.

decode(input, errors='strict')

Decodes the object input and returns a tuple (output object, length consumed). For instance, for a text encoding, decoding converts a bytes object encoded using a particular character set encoding to a string object.

For text encodings and bytes-to-bytes codecs, input must be a bytes object or one which provides the read-only buffer interface -- for example, buffer objects and memory mapped files.

The errors argument defines the error handling to apply. It defaults to 'strict' handling.

The method may not store state in the Codec instance. Use StreamReader for codecs which have to keep state in order to make decoding efficient.

The decoder must be able to handle zero length input and return an empty object of the output object type in this situation.

Incremental Encoding and Decoding

The IncrementalEncoder and IncrementalDecoder classes provide the basic interface for incremental encoding and decoding. Encoding/decoding the input isn't done with one call to the stateless encoder/decoder function, but with multiple calls to the encode()/decode() method of the incremental encoder/decoder. The incremental encoder/decoder keeps track of the encoding/decoding process during method calls.

The joined output of calls to the encode()/decode() method is the same as if all the single inputs were joined into one, and this input was encoded/decoded with the stateless encoder/decoder.

IncrementalEncoder 物件

The IncrementalEncoder class is used for encoding an input in multiple steps. It defines the following methods which every incremental encoder must define in order to be compatible with the Python codec registry.

class codecs.IncrementalEncoder(errors='strict')

IncrementalEncoder 的建構函式。

All incremental encoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.

The IncrementalEncoder may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for possible values.

The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalEncoder object.

encode(object, final=False)

Encodes object (taking the current state of the encoder into account) and returns the resulting encoded object. If this is the last call to encode() final must be true (the default is false).

reset()

Reset the encoder to the initial state. The output is discarded: call .encode(object, final=True), passing an empty byte or text string if necessary, to reset the encoder and to get the output.

getstate()

Return the current state of the encoder which must be an integer. The implementation should make sure that 0 is the most common state. (States that are more complicated than integers can be converted into an integer by marshaling/pickling the state and encoding the bytes of the resulting string into an integer.)

setstate(state)

Set the state of the encoder to state. state must be an encoder state returned by getstate().

IncrementalDecoder 物件

The IncrementalDecoder class is used for decoding an input in multiple steps. It defines the following methods which every incremental decoder must define in order to be compatible with the Python codec registry.

class codecs.IncrementalDecoder(errors='strict')

IncrementalDecoder 的建構函式。

All incremental decoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.

The IncrementalDecoder may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for possible values.

The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalDecoder object.

decode(object, final=False)

Decodes object (taking the current state of the decoder into account) and returns the resulting decoded object. If this is the last call to decode() final must be true (the default is false). If final is true the decoder must decode the input completely and must flush all buffers. If this isn't possible (e.g. because of incomplete byte sequences at the end of the input) it must initiate error handling just like in the stateless case (which might raise an exception).

reset()

將解碼器重設到初始狀態。

getstate()

Return the current state of the decoder. This must be a tuple with two items, the first must be the buffer containing the still undecoded input. The second must be an integer and can be additional state info. (The implementation should make sure that 0 is the most common additional state info.) If this additional state info is 0 it must be possible to set the decoder to the state which has no input buffered and 0 as the additional state info, so that feeding the previously buffered input to the decoder returns it to the previous state without producing any output. (Additional state info that is more complicated than integers can be converted into an integer by marshaling/pickling the info and encoding the bytes of the resulting string into an integer.)

setstate(state)

Set the state of the decoder to state. state must be a decoder state returned by getstate().

串流編碼和解碼

The StreamWriter and StreamReader classes provide generic working interfaces which can be used to implement new encoding submodules very easily. See encodings.utf_8 for an example of how this is done.

StreamWriter 物件

The StreamWriter class is a subclass of Codec and defines the following methods which every stream writer must define in order to be compatible with the Python codec registry.

class codecs.StreamWriter(stream, errors='strict')

StreamWriter 的建構函式。

All stream writers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.

The stream argument must be a file-like object open for writing text or binary data, as appropriate for the specific codec.

The StreamWriter may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for the standard error handlers the underlying stream codec may support.

The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamWriter object.

write(object)

Writes the object's contents encoded to the stream.

writelines(list)

Writes the concatenated iterable of strings to the stream (possibly by reusing the write() method). Infinite or very large iterables are not supported. The standard bytes-to-bytes codecs do not support this method.

reset()

Resets the codec buffers used for keeping internal state.

Calling this method should ensure that the data on the output is put into a clean state that allows appending of new fresh data without having to rescan the whole stream to recover state.

In addition to the above methods, the StreamWriter must also inherit all other methods and attributes from the underlying stream.

StreamReader 物件

The StreamReader class is a subclass of Codec and defines the following methods which every stream reader must define in order to be compatible with the Python codec registry.

class codecs.StreamReader(stream, errors='strict')

StreamReader 的建構函式。

All stream readers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.

The stream argument must be a file-like object open for reading text or binary data, as appropriate for the specific codec.

The StreamReader may implement different error handling schemes by providing the errors keyword argument. See Error Handlers for the standard error handlers the underlying stream codec may support.

The errors argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamReader object.

The set of allowed values for the errors argument can be extended with register_error().

read(size=-1, chars=-1, firstline=False)

Decodes data from the stream and returns the resulting object.

The chars argument indicates the number of decoded code points or bytes to return. The read() method will never return more data than requested, but it might return less, if there is not enough available.

The size argument indicates the approximate maximum number of encoded bytes or code points to read for decoding. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. This parameter is intended to prevent having to decode huge files in one step.

The firstline flag indicates that it would be sufficient to only return the first line, if there are decoding errors on later lines.

The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size, e.g. if optional encoding endings or state markers are available on the stream, these should be read too.

readline(size=None, keepends=True)

Read one line from the input stream and return the decoded data.

size, if given, is passed as size argument to the stream's read() method.

If keepends is false line-endings will be stripped from the lines returned.

readlines(sizehint=None, keepends=True)

Read all lines available on the input stream and return them as a list of lines.

Line-endings are implemented using the codec's decode() method and are included in the list entries if keepends is true.

sizehint, if given, is passed as the size argument to the stream's read() method.

reset()

Resets the codec buffers used for keeping internal state.

Note that no stream repositioning should take place. This method is primarily intended to be able to recover from decoding errors.

In addition to the above methods, the StreamReader must also inherit all other methods and attributes from the underlying stream.

StreamReaderWriter 物件

The StreamReaderWriter is a convenience class that allows wrapping streams which work in both read and write modes.

The design is such that one can use the factory functions returned by the lookup() function to construct the instance.

class codecs.StreamReaderWriter(stream, Reader, Writer, errors='strict')

Creates a StreamReaderWriter instance. stream must be a file-like object. Reader and Writer must be factory functions or classes providing the StreamReader and StreamWriter interface resp. Error handling is done in the same way as defined for the stream readers and writers.

StreamReaderWriter instances define the combined interfaces of StreamReader and StreamWriter classes. They inherit all other methods and attributes from the underlying stream.

StreamRecoder 物件

The StreamRecoder translates data from one encoding to another, which is sometimes useful when dealing with different encoding environments.

The design is such that one can use the factory functions returned by the lookup() function to construct the instance.

class codecs.StreamRecoder(stream, encode, decode, Reader, Writer, errors='strict')

Creates a StreamRecoder instance which implements a two-way conversion: encode and decode work on the frontend — the data visible to code calling read() and write(), while Reader and Writer work on the backend — the data in stream.

You can use these objects to do transparent transcodings, e.g., from Latin-1 to UTF-8 and back.

stream 引數必須是類檔案物件。

The encode and decode arguments must adhere to the Codec interface. Reader and Writer must be factory functions or classes providing objects of the StreamReader and StreamWriter interface respectively.

Error handling is done in the same way as defined for the stream readers and writers.

StreamRecoder instances define the combined interfaces of StreamReader and StreamWriter classes. They inherit all other methods and attributes from the underlying stream.

編碼和 Unicode

Strings are stored internally as sequences of code points in range U+0000--U+10FFFF. (See PEP 393 [https://peps.python.org/pep-0393/] for more details about the implementation.) Once a string object is used outside of CPU and memory, endianness and how these arrays are stored as bytes become an issue. As with other codecs, serialising a string into a sequence of bytes is known as encoding, and recreating the string from the sequence of bytes is known as decoding. There are a variety of different text serialisation codecs, which are collectivity referred to as text encodings.

The simplest text encoding (called 'latin-1' or 'iso-8859-1') maps the code points 0--255 to the bytes 0x0--0xff, which means that a string object that contains code points above U+00FF can't be encoded with this codec. Doing so will raise a UnicodeEncodeError that looks like the following (although the details of the error message may differ): UnicodeEncodeError: 'latin-1' codec can't encode character '\u1234' in position 3: ordinal not in range(256).

There's another group of encodings (the so called charmap encodings) that choose a different subset of all Unicode code points and how these code points are mapped to the bytes 0x0--0xff. To see how this is done simply open e.g. encodings/cp1252.py (which is an encoding that is used primarily on Windows). There's a string constant with 256 characters that shows you which character is mapped to which byte value.

All of these encodings can only encode 256 of the 1114112 code points defined in Unicode. A simple and straightforward way that can store each Unicode code point, is to store each code point as four consecutive bytes. There are two possibilities: store the bytes in big endian or in little endian order. These two encodings are called UTF-32-BE and UTF-32-LE respectively. Their disadvantage is that if, for example, you use UTF-32-BE on a little endian machine you will always have to swap bytes on encoding and decoding. Python's UTF-16 and UTF-32 codecs avoid this problem by using the platform's native byte order when no BOM is present. Python follows prevailing platform practice, so native-endian data round-trips without redundant byte swapping, even though the Unicode Standard defaults to big-endian when the byte order is unspecified. When these bytes are read by a CPU with a different endianness, the bytes have to be swapped. To be able to detect the endianness of a UTF-16 or UTF-32 byte sequence, a BOM ("Byte Order Mark") is used. This is the Unicode character U+FEFF. This character can be prepended to every UTF-16 or UTF-32 byte sequence. The byte swapped version of this character (0xFFFE) is an illegal character that may not appear in a Unicode text. When the first character of a UTF-16 or UTF-32 byte sequence is U+FFFE, the bytes have to be swapped on decoding.

Unfortunately the character U+FEFF had a second purpose as a ZERO WIDTH NO-BREAK SPACE: a character that has no width and doesn't allow a word to be split. It can e.g. be used to give hints to a ligature algorithm. With Unicode 4.0 using U+FEFF as a ZERO WIDTH NO-BREAK SPACE has been deprecated (with U+2060 (WORD JOINER) assuming this role). Nevertheless Unicode software still must be able to handle U+FEFF in both roles: as a BOM it's a device to determine the storage layout of the encoded bytes, and vanishes once the byte sequence has been decoded into a string; as a ZERO WIDTH NO-BREAK SPACE it's a normal character that will be decoded like any other.

There's another encoding that is able to encode the full range of Unicode characters: UTF-8. UTF-8 is an 8-bit encoding, which means there are no issues with byte order in UTF-8. Each byte in a UTF-8 byte sequence consists of two parts: marker bits (the most significant bits) and payload bits. The marker bits are a sequence of zero to four 1 bits followed by a 0 bit. Unicode characters are encoded like this (with x being payload bits, which when concatenated give the Unicode character):

Range

Encoding

U-00000000 ... U-0000007F

0xxxxxxx

U-00000080 ... U-000007FF

110xxxxx 10xxxxxx

U-00000800 ... U-0000FFFF

1110xxxx 10xxxxxx 10xxxxxx

U-00010000 ... U-0010FFFF

11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

The least significant bit of the Unicode character is the rightmost x bit.

As UTF-8 is an 8-bit encoding no BOM is required and any U+FEFF character in the decoded string (even if it's the first character) is treated as a ZERO WIDTH NO-BREAK SPACE.

Without external information it's impossible to reliably determine which encoding was used for encoding a string. Each charmap encoding can decode any random byte sequence. However that's not possible with UTF-8, as UTF-8 byte sequences have a structure that doesn't allow arbitrary byte sequences. To increase the reliability with which a UTF-8 encoding can be detected, Microsoft invented a variant of UTF-8 (that Python calls "utf-8-sig") for its Notepad program: Before any of the Unicode characters is written to the file, a UTF-8 encoded BOM (which looks like this as a byte sequence: 0xef, 0xbb, 0xbf) is written. As it's rather improbable that any charmap encoded file starts with these byte values (which would e.g. map to

LATIN SMALL LETTER I WITH DIAERESIS

RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK

INVERTED QUESTION MARK

in iso-8859-1), this increases the probability that a utf-8-sig encoding can be correctly guessed from the byte sequence. So here the BOM is not used to be able to determine the byte order used for generating the byte sequence, but as a signature that helps in guessing the encoding. On encoding the utf-8-sig codec will write 0xef, 0xbb, 0xbf as the first three bytes to the file. On decoding utf-8-sig will skip those three bytes if they appear as the first three bytes in the file. In UTF-8, the use of the BOM is discouraged and should generally be avoided.

標準編碼

Python comes with a number of codecs built-in, either implemented as C functions or with dictionaries as mapping tables. The following table lists the codecs by name, together with a few common aliases, and the languages for which the encoding is likely used. Neither the list of aliases nor the list of languages is meant to be exhaustive. Notice that spelling alternatives that only differ in case or use a hyphen instead of an underscore are also valid aliases because they are equivalent when normalized by normalize_encoding(). For example, 'utf-8' is a valid alias for the 'utf_8' codec.

備註

The below table lists the most common aliases, for a complete list refer to the source aliases.py [https://github.com/python/cpython/tree/3.14/Lib/encodings/aliases.py] file.

On Windows, cpXXX codecs are available for all code pages. But only codecs listed in the following table are guarantead to exist on other platforms.

CPython 實作細節： Some common encodings can bypass the codecs lookup machinery to improve performance. These optimization opportunities are only recognized by CPython for a limited set of (case insensitive) aliases: utf-8, utf8, latin-1, latin1, iso-8859-1, iso8859-1, mbcs (Windows only), ascii, us-ascii, utf-16, utf16, utf-32, utf32, and the same using underscores instead of dashes. Using alternative aliases for these encodings may result in slower execution.

在 3.6 版的變更: Optimization opportunity recognized for us-ascii.

Many of the character sets support the same languages. They vary in individual characters (e.g. whether the EURO SIGN is supported or not), and in the assignment of characters to code positions. For the European languages in particular, the following variants typically exist:

an ISO 8859 codeset

a Microsoft Windows code page, which is typically derived from an 8859 codeset, but replaces control characters with additional graphic characters

an IBM EBCDIC code page

an IBM PC code page, which is ASCII compatible

Codec

Aliases

語言

ascii

646, us-ascii

英文

big5

big5-tw, csbig5

繁體中文

big5hkscs

big5-hkscs, hkscs

繁體中文

cp037

IBM037, IBM039

英文

cp273

273, IBM273, csIBM273

德文

在 3.4 版被加入.

cp424

EBCDIC-CP-HE, IBM424

希伯來文

cp437

437, IBM437

英文

cp500

EBCDIC-CP-BE, EBCDIC-CP-CH, IBM500

Western Europe

cp720

阿拉伯文

cp737

希臘文

cp775

IBM775

Baltic languages

cp850

850, IBM850

Western Europe

cp852

852, IBM852

Central and Eastern Europe

cp855

855, IBM855

Belarusian, Bulgarian, Macedonian, Russian, Serbian

cp856

希伯來文

cp857

857, IBM857

土耳其文

cp858

858, IBM858

Western Europe

cp860

860, IBM860

Portuguese

cp861

861, CP-IS, IBM861

Icelandic

cp862

862, IBM862

希伯來文

cp863

863, IBM863

Canadian

cp864

IBM864

阿拉伯文

cp865

865, IBM865

Danish, Norwegian

cp866

866, IBM866

俄羅斯文

cp869

869, CP-GR, IBM869

希臘文

cp874

泰文

cp875

希臘文

cp932

932, ms932, mskanji, ms-kanji, windows-31j

日文

cp949

949, ms949, uhc

韓文

cp950

950, ms950

繁體中文

cp1006

Urdu

cp1026

ibm1026

土耳其文

cp1125

1125, ibm1125, cp866u, ruscii

烏克蘭文

在 3.4 版被加入.

cp1140

ibm1140

Western Europe

cp1250

windows-1250

Central and Eastern Europe

cp1251

windows-1251

Belarusian, Bulgarian, Macedonian, Russian, Serbian

cp1252

windows-1252

Western Europe

cp1253

windows-1253

希臘文

cp1254

windows-1254

土耳其文

cp1255

windows-1255

希伯來文

cp1256

windows-1256

阿拉伯文

cp1257

windows-1257

Baltic languages

cp1258

windows-1258

越南文

euc_jp

eucjp, ujis, u-jis

日文

euc_jis_2004

jisx0213, eucjis2004

日文

euc_jisx0213

eucjisx0213

日文

euc_kr

euckr, korean, ksc5601, ks_c-5601, ks_c-5601-1987, ksx1001, ks_x-1001

韓文

gb2312

chinese, csiso58gb231280, euc-cn, euccn, eucgb2312-cn, gb2312-1980, gb2312-80, iso-ir-58

簡體中文

gbk

936, cp936, ms936

Unified Chinese

gb18030

gb18030-2000

Unified Chinese

hz

hzgb, hz-gb, hz-gb-2312

簡體中文

iso2022_jp

csiso2022jp, iso2022jp, iso-2022-jp

日文

iso2022_jp_1

iso2022jp-1, iso-2022-jp-1

日文

iso2022_jp_2

iso2022jp-2, iso-2022-jp-2

Japanese, Korean, Simplified Chinese, Western Europe, Greek

iso2022_jp_2004

iso2022jp-2004, iso-2022-jp-2004

日文

iso2022_jp_3

iso2022jp-3, iso-2022-jp-3

日文

iso2022_jp_ext

iso2022jp-ext, iso-2022-jp-ext

日文

iso2022_kr

csiso2022kr, iso2022kr, iso-2022-kr

韓文

latin_1

iso-8859-1, iso8859-1, 8859, cp819, latin, latin1, L1

Western Europe

iso8859_2

iso-8859-2, latin2, L2

Central and Eastern Europe

iso8859_3

iso-8859-3, latin3, L3

Esperanto, Maltese

iso8859_4

iso-8859-4, latin4, L4

Northern Europe

iso8859_5

iso-8859-5, cyrillic

Belarusian, Bulgarian, Macedonian, Russian, Serbian

iso8859_6

iso-8859-6, arabic

阿拉伯文

iso8859_7

iso-8859-7, greek, greek8

希臘文

iso8859_8

iso-8859-8, hebrew

希伯來文

iso8859_9

iso-8859-9, latin5, L5

土耳其文

iso8859_10

iso-8859-10, latin6, L6

Nordic languages

iso8859_11

iso-8859-11, thai

泰語

iso8859_13

iso-8859-13, latin7, L7

Baltic languages

iso8859_14

iso-8859-14, latin8, L8

Celtic languages

iso8859_15

iso-8859-15, latin9, L9

Western Europe

iso8859_16

iso-8859-16, latin10, L10

South-Eastern Europe

johab

cp1361, ms1361

韓文

koi8_r

俄羅斯文

koi8_t

Tajik

在 3.5 版被加入.

koi8_u

烏克蘭文

kz1048

kz_1048, strk1048_2002, rk1048

Kazakh

在 3.5 版被加入.

mac_cyrillic

maccyrillic

Belarusian, Bulgarian, Macedonian, Russian, Serbian

mac_greek

macgreek

希臘文

mac_iceland

maciceland

Icelandic

mac_latin2

maclatin2, maccentraleurope, mac_centeuro

Central and Eastern Europe

mac_roman

macroman, macintosh

Western Europe

mac_turkish

macturkish

土耳其文

ptcp154

csptcp154, pt154, cp154, cyrillic-asian

Kazakh

shift_jis

csshiftjis, shiftjis, sjis, s_jis

日文

shift_jis_2004

shiftjis2004, sjis_2004, sjis2004

日文

shift_jisx0213

shiftjisx0213, sjisx0213, s_jisx0213

日文

utf_32

U32, utf32

all languages

utf_32_be

UTF-32BE

all languages

utf_32_le

UTF-32LE

all languages

utf_16

U16, utf16

all languages

utf_16_be

UTF-16BE

all languages

utf_16_le

UTF-16LE

all languages

utf_7

U7, unicode-1-1-utf-7

all languages

utf_8

U8, UTF, utf8, cp65001

all languages

utf_8_sig

all languages

在 3.4 版的變更: The utf-16* and utf-32* encoders no longer allow surrogate code points (U+D800--U+DFFF) to be encoded. The utf-32* decoders no longer decode byte sequences that correspond to surrogate code points.

在 3.8 版的變更: cp65001 現在是 utf_8 的別名。

在 3.14 版的變更: On Windows, cpXXX codecs are now available for all code pages.

Python Specific Encodings

A number of predefined codecs are specific to Python, so their codec names have no meaning outside Python. These are listed in the tables below based on the expected input and output types (note that while text encodings are the most common use case for codecs, the underlying codec infrastructure supports arbitrary data transforms rather than just text encodings). For asymmetric codecs, the stated meaning describes the encoding direction.

Text Encodings

The following codecs provide str to bytes encoding and bytes-like object to str decoding, similar to the Unicode text encodings.

Codec

Aliases

含義

idna

Implement RFC 3490 [https://datatracker.ietf.org/doc/html/rfc3490.html], see also encodings.idna. Only errors='strict' is supported.

mbcs

ansi, dbcs

Windows only: Encode the operand according to the ANSI codepage (CP_ACP).

oem

Windows only: Encode the operand according to the OEM codepage (CP_OEMCP).

在 3.6 版被加入.

palmos

Encoding of PalmOS 3.5.

punycode

Implement RFC 3492 [https://datatracker.ietf.org/doc/html/rfc3492.html]. Stateful codecs are not supported.

raw_unicode_escape

Latin-1 encoding with \uXXXX and \UXXXXXXXX for other code points. Existing backslashes are not escaped in any way. It is used in the Python pickle protocol.

undefined

This Codec should only be used for testing purposes.

Raise an exception for all conversions, even empty strings. The error handler is ignored.

unicode_escape

Encoding suitable as the contents of a Unicode literal in ASCII-encoded Python source code, except that quotes are not escaped. Decode from Latin-1 source code. Beware that Python source code actually uses UTF-8 by default.

在 3.8 版的變更: "unicode_internal" codec is removed.

Binary Transforms

The following codecs provide binary transforms: bytes-like object to bytes mappings. They are not supported by bytes.decode() (which only produces str output).

Codec

Aliases

含義

Encoder / decoder

base64_codec [1]

base64, base_64

Convert the operand to multiline MIME base64 (the result always includes a trailing '\n').

在 3.4 版的變更: accepts any bytes-like object as input for encoding and decoding

base64.encodebytes() / base64.decodebytes()

bz2_codec

bz2

Compress the operand using bz2.

bz2.compress() / bz2.decompress()

hex_codec

hex

Convert the operand to hexadecimal representation, with two digits per byte.

binascii.b2a_hex() / binascii.a2b_hex()

quopri_codec

quopri, quotedprintable, quoted_printable

Convert the operand to MIME quoted printable.

quopri.encode() with quotetabs=True / quopri.decode()

uu_codec

uu

Convert the operand using uuencode.

zlib_codec

zip, zlib

Compress the operand using gzip.

zlib.compress() / zlib.decompress()

[1]

In addition to bytes-like objects, 'base64_codec' also accepts ASCII-only instances of str for decoding

在 3.2 版被加入: Restoration of the binary transforms.

在 3.4 版的變更: Restoration of the aliases for the binary transforms.

Standalone Codec Functions

The following functions provide encoding and decoding functionality similar to codecs, but are not available as named codecs through codecs.encode() or codecs.decode(). They are used internally (for example, by pickle) and behave similarly to the string_escape codec that was removed in Python 3.

codecs.escape_encode(input, errors=None)

Encode input using escape sequences. Similar to how repr() on bytes produces escaped byte values.

input must be a bytes object.

Returns a tuple (output, length) where output is a bytes object and length is the number of bytes consumed.

codecs.escape_decode(input, errors=None)

Decode input from escape sequences back to the original bytes.

input 必須是個 bytes-like object。

Returns a tuple (output, length) where output is a bytes object and length is the number of bytes consumed.

Text Transforms

The following codec provides a text transform: a str to str mapping. It is not supported by str.encode() (which only produces bytes output).

Codec

Aliases

含義

rot_13

rot13

Return the Caesar-cypher encryption of the operand.

在 3.2 版被加入: Restoration of the rot_13 text transform.

在 3.4 版的變更: Restoration of the rot13 alias.

encodings --- Encodings package

This module implements the following functions:

encodings.normalize_encoding(encoding)

Normalize encoding name encoding.

Normalization works as follows: all non-alphanumeric characters except the dot used for Python package names are collapsed and replaced with a single underscore, leading and trailing underscores are removed. For example, '  -;#' becomes '_'.

Note that encoding should be ASCII only.

備註

The following functions should not be used directly, except for testing purposes; codecs.lookup() should be used instead.

encodings.search_function(encoding)

Search for the codec module corresponding to the given encoding name encoding.

This function first normalizes the encoding using normalize_encoding(), then looks for a corresponding alias. It attempts to import a codec module from the encodings package using either the alias or the normalized name. If the module is found and defines a valid getregentry() function that returns a codecs.CodecInfo object, the codec is cached and returned.

If the codec module defines a getaliases() function any returned aliases are registered for future use.

encodings.win32_code_page_search_function(encoding)

Search for a Windows code page encoding encoding of the form cpXXXX.

If the code page is valid and supported, return a codecs.CodecInfo object for it.

可用性: Windows.

在 3.14 版被加入.

This module implements the following exception:

exception encodings.CodecRegistryError

Raised when a codec is invalid or incompatible.

encodings.idna --- Internationalized Domain Names in Applications

This module implements RFC 3490 [https://datatracker.ietf.org/doc/html/rfc3490.html] (Internationalized Domain Names in Applications) and RFC 3492 [https://datatracker.ietf.org/doc/html/rfc3492.html] (Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)). It builds upon the punycode encoding and stringprep.

If you need the IDNA 2008 standard from RFC 5891 [https://datatracker.ietf.org/doc/html/rfc5891.html] and RFC 5895 [https://datatracker.ietf.org/doc/html/rfc5895.html], use the third-party idna [https://pypi.org/project/idna/] module.

These RFCs together define a protocol to support non-ASCII characters in domain names. A domain name containing non-ASCII characters (such as www.Alliancefrançaise.nu) is converted into an ASCII-compatible encoding (ACE, such as www.xn--alliancefranaise-npb.nu). The ACE form of the domain name is then used in all places where arbitrary characters are not allowed by the protocol, such as DNS queries, HTTP Host fields, and so on. This conversion is carried out in the application; if possible invisible to the user: The application should transparently convert Unicode domain labels to IDNA on the wire, and convert back ACE labels to Unicode before presenting them to the user.

Python supports this conversion in several ways: the idna codec performs conversion between Unicode and ACE, separating an input string into labels based on the separator characters defined in section 3.1 of RFC 3490 [https://datatracker.ietf.org/doc/html/rfc3490.html#section-3.1] and converting each label to ACE as required, and conversely separating an input byte string into labels based on the . separator and converting any ACE labels found into unicode. Furthermore, the socket module transparently converts Unicode host names to ACE, so that applications need not be concerned about converting host names themselves when they pass them to the socket module. On top of that, modules that have host names as function parameters, such as http.client and ftplib, accept Unicode host names (http.client then also transparently sends an IDNA hostname in the Host field if it sends that field at all).

When receiving host names from the wire (such as in reverse name lookup), no automatic conversion to Unicode is performed: applications wishing to present such host names to the user should decode them to Unicode.

The module encodings.idna also implements the nameprep procedure, which performs certain normalizations on host names, to achieve case-insensitivity of international domain names, and to unify similar characters. The nameprep functions can be used directly if desired.

encodings.idna.nameprep(label)

Return the nameprepped version of label. The implementation currently assumes query strings, so AllowUnassigned is true.

encodings.idna.ToASCII(label)

Convert a label to ASCII, as specified in RFC 3490 [https://datatracker.ietf.org/doc/html/rfc3490.html]. UseSTD3ASCIIRules is assumed to be false.

encodings.idna.ToUnicode(label)

Convert a label to Unicode, as specified in RFC 3490 [https://datatracker.ietf.org/doc/html/rfc3490.html].

encodings.mbcs --- Windows ANSI 碼頁

這個模組實作了 ANSI 碼頁 (CP_ACP)。

可用性: Windows.

在 3.2 版的變更: Before 3.2, the errors argument was ignored; 'replace' was always used to encode, and 'ignore' to decode.

在 3.3 版的變更: Support any error handler.

encodings.utf_8_sig --- UTF-8 codec with BOM signature

This module implements a variant of the UTF-8 codec. On encoding, a UTF-8 encoded BOM will be prepended to the UTF-8 encoded bytes. For the stateful encoder this is only done once (on the first write to the byte stream). On decoding, an optional UTF-8 encoded BOM at the start of the data will be skipped.

資料型別

本章節所描述的模組 (module) 提供了多樣的專門資料型別，例如日期與時間、固定型別陣列 (fixed-type arrays)、堆積佇列 (heap queues)、雙端佇列 (double-ended queues) 與列舉 (enumerations)。

Python 也有提供一些內建資料型別，特別是 dict、list、set 與 frozenset 和 tuple。str 類別是用來儲存 Unicode 字串，bytes 與 bytearray 類別則是用來儲存二進位制資料。

本章節包含下列模組的文件：

datetime --- 日期與時間的基本型別

Aware and Naive Objects

常數

Available Types

常見屬性

Determining if an Object is Aware or Naive

timedelta 物件

用法範例：timedelta

date 物件

用法範例：date

datetime 物件

用法範例：datetime

time 物件

用法範例：time

tzinfo 物件

timezone 物件

strftime() 與 strptime() 的行為

strftime() 與 strptime() 格式碼

技術細節

zoneinfo --- IANA 時區支援

使用 ZoneInfo

資料來源

設定資料來源

編譯時期設定

環境設定

Runtime 設定

ZoneInfo 類別

字串表示

封裝（Pickle）序列化

函式

全域變數

例外與警告

calendar --- 日曆相關函式

命令列用法

collections --- 容器資料型別

ChainMap 物件

ChainMap 範例和用法

Counter 物件

deque 物件

deque 用法

defaultdict 物件

defaultdict 範例

namedtuple() 擁有具名欄位之 tuple 的工廠函式

OrderedDict 物件

OrderedDict 範例與用法

UserDict 物件

UserList 物件

UserString 物件

collections.abc --- 容器的抽象基底類別

Collections Abstract Base Classes

集合抽象基底類別的詳細描述

Examples and Recipes

heapq --- 堆積佇列 (heap queue) 演算法

基礎範例

Other Applications

優先佇列實作細節

原理

bisect --- 陣列二分演算法 (Array bisection algorithm)

效能考量

搜尋一個已排序的 list

範例

array --- 高效率的數值型陣列

weakref --- 弱參照

弱參照物件

範例

最終化器物件

最終化器與 __del__() 方法的比較

types --- 動態型別建立與內建型別名稱

Dynamic Type Creation

Standard Interpreter Types

Additional Utility Classes and Functions

Coroutine Utility Functions

copy --- 淺層 (shallow) 和深層 (deep) 複製操作

pprint --- 資料美化列印器

函式

PrettyPrinter 物件

範例

reprlib --- repr() 的替代實作

Repr 物件

Subclassing Repr Objects

enum --- 對列舉的支援

模組內容

資料型別

支援的 __dunder__ 名稱

支援的 _sunder_ 名稱

通用項目與裝飾器

備註

graphlib —-- 使用類圖 (graph-like) 結構進行操作的功能

例外

datetime --- 日期與時間的基本型別

原始碼：Lib/datetime.py [https://github.com/python/cpython/tree/3.14/Lib/datetime.py]

datetime 模組提供操作日期與時間的類別。

While date and time arithmetic is supported, the focus of the implementation is on efficient attribute extraction for output formatting and manipulation.

小訣竅

跳轉至格式碼 (format codes)。

也參考

calendar 模組

與日曆相關的一般函式。

time 模組

Time access and conversions.

zoneinfo 模組

Concrete time zones representing the IANA time zone database.

dateutil [https://dateutil.readthedocs.io/en/stable/] 套件

帶有時區與剖析擴充支援的第三方函式庫。

DateType [https://pypi.org/project/DateType/] 套件

Third-party library that introduces distinct static types to e.g. allow static type checkers to differentiate between naive and aware datetimes.

Aware and Naive Objects

Date and time objects may be categorized as "aware" or "naive" depending on whether or not they include time zone information.

With sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, an aware object can locate itself relative to other aware objects. An aware object represents a specific moment in time that is not open to interpretation. [1]

A naive object does not contain enough information to unambiguously locate itself relative to other date/time objects. Whether a naive object represents Coordinated Universal Time (UTC), local time, or time in some other time zone is purely up to the program, just like it is up to the program whether a particular number represents metres, miles, or mass. Naive objects are easy to understand and to work with, at the cost of ignoring some aspects of reality.

For applications requiring aware objects, datetime and time objects have an optional time zone information attribute, tzinfo, that can be set to an instance of a subclass of the abstract tzinfo class. These tzinfo objects capture information about the offset from UTC time, the time zone name, and whether daylight saving time is in effect.

Only one concrete tzinfo class, the timezone class, is supplied by the datetime module. The timezone class can represent simple time zones with fixed offsets from UTC, such as UTC itself or North American EST and EDT time zones. Supporting time zones at deeper levels of detail is up to the application. The rules for time adjustment across the world are more political than rational, change frequently, and there is no standard suitable for every application aside from UTC.

常數

datetime 模組匯出以下常數：

datetime.MINYEAR

The smallest year number allowed in a date or datetime object. MINYEAR is 1.

datetime.MAXYEAR

The largest year number allowed in a date or datetime object. MAXYEAR is 9999.

datetime.UTC

Alias for the UTC time zone singleton datetime.timezone.utc.

在 3.11 版被加入.

Available Types

class datetime.date

An idealized naive date, assuming the current Gregorian calendar always was, and always will be, in effect. Attributes: year, month, and day.

class datetime.time

An idealized time, independent of any particular day, assuming that every day has exactly 24*60*60 seconds. (There is no notion of "leap seconds" here.) Attributes: hour, minute, second, microsecond, and tzinfo.

class datetime.datetime

A combination of a date and a time. Attributes: year, month, day, hour, minute, second, microsecond, and tzinfo.

class datetime.timedelta

表示兩個 datetime 或 date 實例之間時間的差異，以微秒為解析度。

class datetime.tzinfo

An abstract base class for time zone information objects. These are used by the datetime and time classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time).

class datetime.timezone

A class that implements the tzinfo abstract base class as a fixed offset from the UTC.

在 3.2 版被加入.

Objects of these types are immutable.

Subclass relationships:

object
    timedelta
    tzinfo
        timezone
    time
    date
        datetime

常見屬性

The date, datetime, time, and timezone types share these common features:

Objects of these types are immutable.

Objects of these types are hashable, meaning that they can be used as dictionary keys.

Objects of these types support efficient pickling via the pickle module.

Determining if an Object is Aware or Naive

Objects of the date type are always naive.

An object of type time or datetime may be aware or naive.

A datetime object d is aware if both of the following hold:

d.tzinfo 不是 None

d.tzinfo.utcoffset(d) 不會回傳 None

否則 d 會是 naive 的。

A time object t is aware if both of the following hold:

t.tzinfo 不是 None

t.tzinfo.utcoffset(None) 沒有回傳 None。

否則 t 會是 naive 的。

The distinction between aware and naive doesn't apply to timedelta objects.

timedelta 物件

一個 timedelta 物件代表著一段持續時間，即兩個 datetime 或 date 之間的差異。

class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)

All arguments are optional and default to 0. Arguments may be integers or floats, and may be positive or negative.

Only days, seconds and microseconds are stored internally. Arguments are converted to those units:

一毫秒會被轉換為 1000 微秒。

一分鐘會被轉換為 60 秒。

一小時會被轉換為 3600 秒。

一週會被轉換為 7 天。

and days, seconds and microseconds are then normalized so that the representation is unique, with

0 <= microseconds < 1000000

0 <= seconds < 3600*24 (the number of seconds in one day)

-999999999 <= days <= 999999999

The following example illustrates how any arguments besides days, seconds and microseconds are "merged" and normalized into those three resulting attributes:

>>> from datetime import timedelta
>>> delta = timedelta(
...     days=50,
...     seconds=27,
...     microseconds=10,
...     milliseconds=29000,
...     minutes=5,
...     hours=8,
...     weeks=2
... )
>>> # Only days, seconds, and microseconds remain
>>> delta
datetime.timedelta(days=64, seconds=29156, microseconds=10)

If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond using round-half-to-even tiebreaker. If no argument is a float, the conversion and normalization processes are exact (no information is lost).

If the normalized value of days lies outside the indicated range, OverflowError is raised.

Note that normalization of negative values may be surprising at first. For example:

>>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)

Since the string representation of timedelta objects can be confusing, use the following recipe to produce a more readable format:

>>> def pretty_timedelta(td):
...     if td.days >= 0:
...         return str(td)
...     return f'-({-td!s})'
...
>>> d = timedelta(hours=-1)
>>> str(d)  # not human-friendly
'-1 day, 23:00:00'
>>> pretty_timedelta(d)
'-(1:00:00)'

類別屬性：

timedelta.min

The most negative timedelta object, timedelta(-999999999).

timedelta.max

The most positive timedelta object, timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999).

timedelta.resolution

The smallest possible difference between non-equal timedelta objects, timedelta(microseconds=1).

Note that, because of normalization, timedelta.max is greater than -timedelta.min. -timedelta.max is not representable as a timedelta object.

Instance attributes (read-only):

timedelta.days

在 -999,999,999 到 999,999,999 （含）之間

timedelta.seconds

在 0 到 86,399 （含）之間

警示

It is a somewhat common bug for code to unintentionally use this attribute when it is actually intended to get a total_seconds() value instead:

>>> from datetime import timedelta
>>> duration = timedelta(seconds=11235813)
>>> duration.days, duration.seconds
(130, 3813)
>>> duration.total_seconds()
11235813.0

timedelta.microseconds

在 0 到 999,999 （含）之間

Supported operations:

Operation

Result

t1 = t2 + t3

Sum of t2 and t3. Afterwards t1 - t2 == t3 and t1 - t3 == t2 are true. (1)

t1 = t2 - t3

Difference of t2 and t3. Afterwards t1 == t2 - t3 and t2 == t1 + t3 are true. (1)(6)

t1 = t2 * i or t1 = i * t2

Delta multiplied by an integer. Afterwards t1 // i == t2 is true, provided i != 0.

In general, t1  * i == t1 * (i-1) + t1 is true. (1)

t1 = t2 * f or t1 = f * t2

Delta multiplied by a float. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even.

f = t2 / t3

Division (3) of overall duration t2 by interval unit t3. Returns a float object.

t1 = t2 / f or t1 = t2 / i

Delta divided by a float or an int. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even.

t1 = t2 // i or t1 = t2 // t3

The floor is computed and the remainder (if any) is thrown away. In the second case, an integer is returned. (3)

t1 = t2 % t3

The remainder is computed as a timedelta object. (3)

q, r = divmod(t1, t2)

Computes the quotient and the remainder: q = t1 // t2 (3) and r = t1 % t2. q is an integer and r is a timedelta object.

+t1

Returns a timedelta object with the same value. (2)

-t1

等價於 timedelta(-t1.days, -t1.seconds, -t1.microseconds)，也等價於 t1 * -1。 (1)(4)

abs(t)

Equivalent to +t when t.days >= 0, and to -t when t.days < 0. (2)

str(t)

Returns a string in the form [D day[s], ][H]H:MM:SS[.UUUUUU], where D is negative for negative t. (5)

repr(t)

Returns a string representation of the timedelta object as a constructor call with canonical attribute values.

註解：

這是精確的，但可能會溢位。

這是精確的，且不會溢位。

Division by zero raises ZeroDivisionError.

-timedelta.max is not representable as a timedelta object.

String representations of timedelta objects are normalized similarly to their internal representation. This leads to somewhat unusual results for negative timedeltas. For example:

>>> timedelta(hours=-5)
datetime.timedelta(days=-1, seconds=68400)
>>> print(_)
-1 day, 19:00:00

The expression t2 - t3 will always be equal to the expression t2 + (-t3) except when t3 is equal to timedelta.max; in that case the former will produce a result while the latter will overflow.

In addition to the operations listed above, timedelta objects support certain additions and subtractions with date and datetime objects (see below).

在 3.2 版的變更: Floor division and true division of a timedelta object by another timedelta object are now supported, as are remainder operations and the divmod() function. True division and multiplication of a timedelta object by a float object are now supported.

timedelta objects support equality and order comparisons.

In Boolean contexts, a timedelta object is considered to be true if and only if it isn't equal to timedelta(0).

實例方法：

timedelta.total_seconds()

Return the total number of seconds contained in the duration. Equivalent to td / timedelta(seconds=1). For interval units other than seconds, use the division form directly (e.g. td / timedelta(microseconds=1)).

Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy.

在 3.2 版被加入.

用法範例：timedelta

An additional example of normalization:

>>> # Components of another_year add up to exactly 365 days
>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> another_year = timedelta(weeks=40, days=84, hours=23,
...                          minutes=50, seconds=600)
>>> year == another_year
True
>>> year.total_seconds()
31536000.0

Examples of timedelta arithmetic:

>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> ten_years = 10 * year
>>> ten_years
datetime.timedelta(days=3650)
>>> ten_years.days // 365
10
>>> nine_years = ten_years - year
>>> nine_years
datetime.timedelta(days=3285)
>>> three_years = nine_years // 3
>>> three_years, three_years.days // 365
(datetime.timedelta(days=1095), 3)

date 物件

A date object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions.

January 1 of year 1 is called day number 1, January 2 of year 1 is called day number 2, and so on. [2]

class datetime.date(year, month, day)

All arguments are required. Arguments must be integers, in the following ranges:

MINYEAR <= year <= MAXYEAR

1 <= month <= 12

1 <= day <= 該年該月的天數

If an argument outside those ranges is given, ValueError is raised.

Other constructors, all class methods:

classmethod date.today()

回傳目前的本地日期。

這等同於 date.fromtimestamp(time.time())。

classmethod date.fromtimestamp(timestamp)

Return the local date corresponding to the POSIX timestamp, such as is returned by time.time().

This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() function, and OSError on localtime() failure. It's common for this to be restricted to years from 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp().

在 3.3 版的變更: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime() function. Raise OSError instead of ValueError on localtime() failure.

classmethod date.fromordinal(ordinal)

Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1.

ValueError is raised unless 1 <= ordinal <= date.max.toordinal(). For any date d, date.fromordinal(d.toordinal()) == d.

classmethod date.fromisoformat(date_string)

Return a date corresponding to a date_string given in any valid ISO 8601 format, with the following exceptions:

Reduced precision dates are not currently supported (YYYY-MM, YYYY).

Extended date representations are not currently supported (±YYYYYY-MM-DD).

Ordinal dates are not currently supported (YYYY-OOO).

範例：

>>> from datetime import date
>>> date.fromisoformat('2019-12-04')
datetime.date(2019, 12, 4)
>>> date.fromisoformat('20191204')
datetime.date(2019, 12, 4)
>>> date.fromisoformat('2021-W01-1')
datetime.date(2021, 1, 4)

在 3.7 版被加入.

在 3.11 版的變更: Previously, this method only supported the format YYYY-MM-DD.

classmethod date.fromisocalendar(year, week, day)

Return a date corresponding to the ISO calendar date specified by year, week and day. This is the inverse of the function date.isocalendar().

在 3.8 版被加入.

classmethod date.strptime(date_string, format)

Return a date corresponding to date_string, parsed according to format. This is equivalent to:

date(*(time.strptime(date_string, format)[0:3]))

ValueError is raised if the date_string and format can't be parsed by time.strptime() or if it returns a value which isn't a time tuple. See also strftime() 與 strptime() 的行為 and date.fromisoformat().

備註

If format specifies a day of month without a year a DeprecationWarning is emitted. This is to avoid a quadrennial leap year bug in code seeking to parse only a month and day as the default year used in absence of one in the format is not a leap year. Such format values may raise an error as of Python 3.15. The workaround is to always include a year in your format. If parsing date_string values that do not have a year, explicitly add a year that is a leap year before parsing:

>>> from datetime import date
>>> date_string = "02/29"
>>> when = date.strptime(f"{date_string};1984", "%m/%d;%Y")  # 避免閏年錯誤。
>>> when.strftime("%B %d")
'February 29'

在 3.14 版被加入.

類別屬性：

date.min

The earliest representable date, date(MINYEAR, 1, 1).

date.max

The latest representable date, date(MAXYEAR, 12, 31).

date.resolution

The smallest possible difference between non-equal date objects, timedelta(days=1).

Instance attributes (read-only):

date.year

Between MINYEAR and MAXYEAR inclusive.

date.month

在 1 到 12 （含）之間。

date.day

Between 1 and the number of days in the given month of the given year.

Supported operations:

Operation

Result

date2 = date1 + timedelta

date2 will be timedelta.days days after date1. (1)

date2 = date1 - timedelta

Computes date2 such that date2 + timedelta == date1. (2)

timedelta = date1 - date2

(3)

date1 == date2

date1 != date2

Equality comparison. (4)

date1 < date2

date1 > date2

date1 <= date2

date1 >= date2

Order comparison. (5)

註解：

date2 is moved forward in time if timedelta.days > 0, or backward if timedelta.days < 0. Afterward date2 - date1 == timedelta.days. timedelta.seconds and timedelta.microseconds are ignored. OverflowError is raised if date2.year would be smaller than MINYEAR or larger than MAXYEAR.

timedelta.seconds 和 timedelta.microseconds 被忽略。

This is exact, and cannot overflow. timedelta.seconds and timedelta.microseconds are 0, and date2 + timedelta == date1 after.

date objects are equal if they represent the same date.

date objects that are not also datetime instances are never equal to datetime objects, even if they represent the same date.

date1 is considered less than date2 when date1 precedes date2 in time. In other words, date1 < date2 if and only if date1.toordinal() < date2.toordinal().

Order comparison between a date object that is not also a datetime instance and a datetime object raises TypeError.

在 3.13 版的變更: Comparison between datetime object and an instance of the date subclass that is not a datetime subclass no longer converts the latter to date, ignoring the time part and the time zone. The default behavior can be changed by overriding the special comparison methods in subclasses.

In Boolean contexts, all date objects are considered to be true.

實例方法：

date.replace(year=self.year, month=self.month, day=self.day)

Return a new date object with the same values, but with specified parameters updated.

範例：

>>> from datetime import date
>>> d = date(2002, 12, 31)
>>> d.replace(day=26)
datetime.date(2002, 12, 26)

The generic function copy.replace() also supports date objects.

date.timetuple()

回傳一個 time.struct_time，如同 time.localtime() 所回傳。

The hours, minutes and seconds are 0, and the DST flag is -1.

d.timetuple() 等價於：

time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))

where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st.

date.toordinal()

Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d, date.fromordinal(d.toordinal()) == d.

date.weekday()

回傳一個代表星期幾的整數，星期一為 0、星期日為 6。例如 date(2002, 12, 4).weekday() == 2 為星期三。也請參考 isoweekday()。

date.isoweekday()

Return the day of the week as an integer, where Monday is 1 and Sunday is 7. For example, date(2002, 12, 4).isoweekday() == 3, a Wednesday. See also weekday(), isocalendar().

date.isocalendar()

Return a named tuple object with three components: year, week and weekday.

The ISO calendar is a widely used variant of the Gregorian calendar. [3]

The ISO year consists of 52 or 53 full weeks, and where a week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday. This is called week number 1, and the ISO year of that Thursday is the same as its Gregorian year.

For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004:

>>> from datetime import date
>>> date(2003, 12, 29).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=1)
>>> date(2004, 1, 4).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=7)

在 3.9 版的變更: Result changed from a tuple to a named tuple.

date.isoformat()

回傳一以 ISO 8601 格式 YYYY-MM-DD 表示的日期字串：

>>> from datetime import date
>>> date(2002, 12, 4).isoformat()
'2002-12-04'

date.__str__()

For a date d, str(d) is equivalent to d.isoformat().

date.ctime()

Return a string representing the date:

>>> from datetime import date
>>> date(2002, 12, 4).ctime()
'Wed Dec  4 00:00:00 2002'

d.ctime() 等價於：

time.ctime(time.mktime(d.timetuple()))

on platforms where the native C ctime() function (which time.ctime() invokes, but which date.ctime() does not invoke) conforms to the C standard.

date.strftime(format)

Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values. See also strftime() 與 strptime() 的行為 and date.isoformat().

date.__format__(format)

Same as date.strftime(). This makes it possible to specify a format string for a date object in formatted string literals and when using str.format(). See also strftime() 與 strptime() 的行為 and date.isoformat().

用法範例：date

計算一個事件的天數的範例：

>>> import time
>>> from datetime import date
>>> today = date.today()
>>> today
datetime.date(2007, 12, 5)
>>> today == date.fromtimestamp(time.time())
True
>>> my_birthday = date(today.year, 6, 24)
>>> if my_birthday < today:
...     my_birthday = my_birthday.replace(year=today.year + 1)
...
>>> my_birthday
datetime.date(2008, 6, 24)
>>> time_to_birthday = abs(my_birthday - today)
>>> time_to_birthday.days
202

更多 date 的用法範例：

>>> from datetime import date
>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001
>>> d
datetime.date(2002, 3, 11)

>>> # Methods related to formatting string output
>>> d.isoformat()
'2002-03-11'
>>> d.strftime("%d/%m/%y")
'11/03/02'
>>> d.strftime("%A %d. %B %Y")
'Monday 11. March 2002'
>>> d.ctime()
'Mon Mar 11 00:00:00 2002'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")
'The day is 11, the month is March.'

>>> # Methods for to extracting 'components' under different calendars
>>> t = d.timetuple()
>>> for i in t:
...     print(i)
2002                # year
3                   # month
11                  # day
0
0
0
0                   # weekday (0 = Monday)
70                  # 70th day in the year
-1
>>> ic = d.isocalendar()
>>> for i in ic:
...     print(i)
2002                # ISO year
11                  # ISO week number
1                   # ISO day number ( 1 = Monday )

>>> # A date object is immutable; all operations produce a new object
>>> d.replace(year=2005)
datetime.date(2005, 3, 11)

datetime 物件

A datetime object is a single object containing all the information from a date object and a time object.

Like a date object, datetime assumes the current Gregorian calendar extended in both directions; like a time object, datetime assumes there are exactly 3600*24 seconds in every day.

建構函式：

class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

The year, month and day arguments are required. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:

MINYEAR <= year <= MAXYEAR,

1 <= month <= 12,

1 <= day <= number of days in the given month and year,

0 <= hour < 24,

0 <= minute < 60,

0 <= second < 60,

0 <= microsecond < 1000000,

fold in [0, 1]。

If an argument outside those ranges is given, ValueError is raised.

在 3.6 版的變更: 新增 fold 參數。

Other constructors, all class methods:

classmethod datetime.today()

回傳目前的本地日期與時間，且 tzinfo 為 None。

等價於：

datetime.fromtimestamp(time.time())

也請見 now()、fromtimestamp()。

This method is functionally equivalent to now(), but without a tz parameter.

classmethod datetime.now(tz=None)

Return the current local date and time.

如果選用的引數 tz 為 None 或未指定，則會像是 today()，但盡可能提供比透過 time.time() 取得的時間戳記更多位數的資訊（例如，這在有提供 C gettimeofday() 函式的平台上可能可行）。

If tz is not None, it must be an instance of a tzinfo subclass, and the current date and time are converted to tz’s time zone.

This function is preferred over today() and utcnow().

備註

Subsequent calls to datetime.now() may return the same instant depending on the precision of the underlying clock.

classmethod datetime.utcnow()

Return the current UTC date and time, with tzinfo None.

This is like now(), but returns the current UTC date and time, as a naive datetime object. An aware current UTC datetime can be obtained by calling datetime.now(timezone.utc). See also now().

警告

Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing the current time in UTC is by calling datetime.now(timezone.utc).

在 3.12 版之後被棄用: Use datetime.now() with UTC instead.

classmethod datetime.fromtimestamp(timestamp, tz=None)

Return the local date and time corresponding to the POSIX timestamp, such as is returned by time.time(). If optional argument tz is None or not specified, the timestamp is converted to the platform's local date and time, and the returned datetime object is naive.

If tz is not None, it must be an instance of a tzinfo subclass, and the timestamp is converted to tz’s time zone.

fromtimestamp() may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions, and OSError on localtime() or gmtime() failure. It's common for this to be restricted to years in 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp(), and then it's possible to have two timestamps differing by a second that yield identical datetime objects. This method is preferred over utcfromtimestamp().

在 3.3 版的變更: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions. Raise OSError instead of ValueError on localtime() or gmtime() failure.

在 3.6 版的變更: fromtimestamp() may return instances with fold set to 1.

classmethod datetime.utcfromtimestamp(timestamp)

Return the UTC datetime corresponding to the POSIX timestamp, with tzinfo None. (The resulting object is naive.)

This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C gmtime() function, and OSError on gmtime() failure. It's common for this to be restricted to years in 1970 through 2038.

To get an aware datetime object, call fromtimestamp():

datetime.fromtimestamp(timestamp, timezone.utc)

On the POSIX compliant platforms, it is equivalent to the following expression:

datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)

except the latter formula always supports the full years range: between MINYEAR and MAXYEAR inclusive.

警告

Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing a specific timestamp in UTC is by calling datetime.fromtimestamp(timestamp, tz=timezone.utc).

在 3.3 版的變更: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C gmtime() function. Raise OSError instead of ValueError on gmtime() failure.

在 3.12 版之後被棄用: Use datetime.fromtimestamp() with UTC instead.

classmethod datetime.fromordinal(ordinal)

Return the datetime corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1 <= ordinal <= datetime.max.toordinal(). The hour, minute, second and microsecond of the result are all 0, and tzinfo is None.

classmethod datetime.combine(date, time, tzinfo=time.tzinfo)

Return a new datetime object whose date components are equal to the given date object's, and whose time components are equal to the given time object's. If the tzinfo argument is provided, its value is used to set the tzinfo attribute of the result, otherwise the tzinfo attribute of the time argument is used. If the date argument is a datetime object, its time components and tzinfo attributes are ignored.

For any datetime object d, d == datetime.combine(d.date(), d.time(), d.tzinfo).

在 3.6 版的變更: 新增 tzinfo 引數。

classmethod datetime.fromisoformat(date_string)

Return a datetime corresponding to a date_string in any valid ISO 8601 format, with the following exceptions:

Time zone offsets may have fractional seconds.

The T separator may be replaced by any single unicode character.

Fractional hours and minutes are not supported.

Reduced precision dates are not currently supported (YYYY-MM, YYYY).

Extended date representations are not currently supported (±YYYYYY-MM-DD).

Ordinal dates are not currently supported (YYYY-OOO).

範例：

>>> from datetime import datetime
>>> datetime.fromisoformat('2011-11-04')
datetime.datetime(2011, 11, 4, 0, 0)
>>> datetime.fromisoformat('20111104')
datetime.datetime(2011, 11, 4, 0, 0)
>>> datetime.fromisoformat('2011-11-04T00:05:23')
datetime.datetime(2011, 11, 4, 0, 5, 23)
>>> datetime.fromisoformat('2011-11-04T00:05:23Z')
datetime.datetime(2011, 11, 4, 0, 5, 23, tzinfo=datetime.timezone.utc)
>>> datetime.fromisoformat('20111104T000523')
datetime.datetime(2011, 11, 4, 0, 5, 23)
>>> datetime.fromisoformat('2011-W01-2T00:05:23.283')
datetime.datetime(2011, 1, 4, 0, 5, 23, 283000)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283+00:00')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000, tzinfo=datetime.timezone.utc)
>>> datetime.fromisoformat('2011-11-04T00:05:23+04:00')
datetime.datetime(2011, 11, 4, 0, 5, 23,
    tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))

在 3.7 版被加入.

在 3.11 版的變更: Previously, this method only supported formats that could be emitted by date.isoformat() or datetime.isoformat().

classmethod datetime.fromisocalendar(year, week, day)

Return a datetime corresponding to the ISO calendar date specified by year, week and day. The non-date components of the datetime are populated with their normal default values. This is the inverse of the function datetime.isocalendar().

在 3.8 版被加入.

classmethod datetime.strptime(date_string, format)

Return a datetime corresponding to date_string, parsed according to format.

If format does not contain microseconds or time zone information, this is equivalent to:

datetime(*(time.strptime(date_string, format)[0:6]))

ValueError is raised if the date_string and format can't be parsed by time.strptime() or if it returns a value which isn't a time tuple. See also strftime() 與 strptime() 的行為 and datetime.fromisoformat().

在 3.13 版的變更: If format specifies a day of month without a year a DeprecationWarning is now emitted. This is to avoid a quadrennial leap year bug in code seeking to parse only a month and day as the default year used in absence of one in the format is not a leap year. Such format values may raise an error as of Python 3.15. The workaround is to always include a year in your format. If parsing date_string values that do not have a year, explicitly add a year that is a leap year before parsing:

>>> from datetime import datetime
>>> date_string = "02/29"
>>> when = datetime.strptime(f"{date_string};1984", "%m/%d;%Y")  # 避免閏年錯誤。
>>> when.strftime("%B %d")
'February 29'

類別屬性：

datetime.min

The earliest representable datetime, datetime(MINYEAR, 1, 1, tzinfo=None).

datetime.max

The latest representable datetime, datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999, tzinfo=None).

datetime.resolution

The smallest possible difference between non-equal datetime objects, timedelta(microseconds=1).

Instance attributes (read-only):

datetime.year

Between MINYEAR and MAXYEAR inclusive.

datetime.month

在 1 到 12 （含）之間。

datetime.day

Between 1 and the number of days in the given month of the given year.

datetime.hour

In range(24).

datetime.minute

In range(60).

datetime.second

In range(60).

datetime.microsecond

In range(1000000).

datetime.tzinfo

The object passed as the tzinfo argument to the datetime constructor, or None if none was passed.

datetime.fold

In [0, 1]. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The values 0 and 1 represent, respectively, the earlier and later of the two moments with the same wall time representation.

在 3.6 版被加入.

Supported operations:

Operation

Result

datetime2 = datetime1 + timedelta

(1)

datetime2 = datetime1 - timedelta

(2)

timedelta = datetime1 - datetime2

(3)

datetime1 == datetime2

datetime1 != datetime2

Equality comparison. (4)

datetime1 < datetime2

datetime1 > datetime2

datetime1 <= datetime2

datetime1 >= datetime2

Order comparison. (5)

datetime2 is a duration of timedelta removed from datetime1, moving forward in time if timedelta.days > 0, or backward if timedelta.days < 0. The result has the same tzinfo attribute as the input datetime, and datetime2 - datetime1 == timedelta after. OverflowError is raised if datetime2.year would be smaller than MINYEAR or larger than MAXYEAR. Note that no time zone adjustments are done even if the input is an aware object.

Computes the datetime2 such that datetime2 + timedelta == datetime1. As for addition, the result has the same tzinfo attribute as the input datetime, and no time zone adjustments are done even if the input is aware.

Subtraction of a datetime from a datetime is defined only if both operands are naive, or if both are aware. If one is aware and the other is naive, TypeError is raised.

If both are naive, or both are aware and have the same tzinfo attribute, the tzinfo attributes are ignored, and the result is a timedelta object t such that datetime2 + t == datetime1. No time zone adjustments are done in this case.

If both are aware and have different tzinfo attributes, a-b acts as if a and b were first converted to naive UTC datetimes. The result is (a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None) - b.utcoffset()) except that the implementation never overflows.

datetime objects are equal if they represent the same date and time, taking into account the time zone.

Naive and aware datetime objects are never equal.

If both comparands are aware, and have the same tzinfo attribute, the tzinfo and fold attributes are ignored and the base datetimes are compared. If both comparands are aware and have different tzinfo attributes, the comparison acts as comparands were first converted to UTC datetimes except that the implementation never overflows. datetime instances in a repeated interval are never equal to datetime instances in other time zone.

datetime1 is considered less than datetime2 when datetime1 precedes datetime2 in time, taking into account the time zone.

Order comparison between naive and aware datetime objects raises TypeError.

If both comparands are aware, and have the same tzinfo attribute, the tzinfo and fold attributes are ignored and the base datetimes are compared. If both comparands are aware and have different tzinfo attributes, the comparison acts as comparands were first converted to UTC datetimes except that the implementation never overflows.

在 3.3 版的變更: Equality comparisons between aware and naive datetime instances don't raise TypeError.

在 3.13 版的變更: Comparison between datetime object and an instance of the date subclass that is not a datetime subclass no longer converts the latter to date, ignoring the time part and the time zone. The default behavior can be changed by overriding the special comparison methods in subclasses.

實例方法：

datetime.date()

Return date object with same year, month and day.

datetime.time()

Return time object with same hour, minute, second, microsecond and fold. tzinfo is None. See also method timetz().

在 3.6 版的變更: The fold value is copied to the returned time object.

datetime.timetz()

Return time object with same hour, minute, second, microsecond, fold, and tzinfo attributes. See also method time().

在 3.6 版的變更: The fold value is copied to the returned time object.

datetime.replace(year=self.year, month=self.month, day=self.day, hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, *, fold=0)

Return a new datetime object with the same attributes, but with specified parameters updated. Note that tzinfo=None can be specified to create a naive datetime from an aware datetime with no conversion of date and time data.

datetime objects are also supported by generic function copy.replace().

在 3.6 版的變更: 新增 fold 參數。

datetime.astimezone(tz=None)

Return a datetime object with new tzinfo attribute tz, adjusting the date and time data so the result is the same UTC time as self, but in tz's local time.

If provided, tz must be an instance of a tzinfo subclass, and its utcoffset() and dst() methods must not return None. If self is naive, it is presumed to represent time in the system time zone.

If called without arguments (or with tz=None) the system local time zone is assumed for the target time zone. The .tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS.

If self.tzinfo is tz, self.astimezone(tz) is equal to self: no adjustment of date or time data is performed. Else the result is local time in the time zone tz, representing the same UTC time as self: after astz = dt.astimezone(tz), astz - astz.utcoffset() will have the same date and time data as dt - dt.utcoffset().

If you merely want to attach a timezone object tz to a datetime dt without adjustment of date and time data, use dt.replace(tzinfo=tz). If you merely want to remove the timezone object from an aware datetime dt without conversion of date and time data, use dt.replace(tzinfo=None).

Note that the default tzinfo.fromutc() method can be overridden in a tzinfo subclass to affect the result returned by astimezone(). Ignoring error cases, astimezone() acts like:

def astimezone(self, tz):
    if self.tzinfo is tz:
        return self
    # Convert self to UTC, and attach the new timezone object.
    utc = (self - self.utcoffset()).replace(tzinfo=tz)
    # Convert from UTC to tz's local time.
    return tz.fromutc(utc)

在 3.3 版的變更: tz now can be omitted.

在 3.6 版的變更: The astimezone() method can now be called on naive instances that are presumed to represent system local time.

datetime.utcoffset()

If tzinfo is None, returns None, else returns self.tzinfo.utcoffset(self), and raises an exception if the latter doesn't return None or a timedelta object with magnitude less than one day.

在 3.7 版的變更: The UTC offset is not restricted to a whole number of minutes.

datetime.dst()

If tzinfo is None, returns None, else returns self.tzinfo.dst(self), and raises an exception if the latter doesn't return None or a timedelta object with magnitude less than one day.

在 3.7 版的變更: The DST offset is not restricted to a whole number of minutes.

datetime.tzname()

If tzinfo is None, returns None, else returns self.tzinfo.tzname(self), raises an exception if the latter doesn't return None or a string object,

datetime.timetuple()

回傳一個 time.struct_time，如同 time.localtime() 所回傳。

d.timetuple() 等價於：

time.struct_time((d.year, d.month, d.day,
                  d.hour, d.minute, d.second,
                  d.weekday(), yday, dst))

where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st. The tm_isdst flag of the result is set according to the dst() method: tzinfo is None or dst() returns None, tm_isdst is set to -1; else if dst() returns a non-zero value, tm_isdst is set to 1; else tm_isdst is set to 0.

datetime.utctimetuple()

If datetime instance d is naive, this is the same as d.timetuple() except that tm_isdst is forced to 0 regardless of what d.dst() returns. DST is never in effect for a UTC time.

If d is aware, d is normalized to UTC time, by subtracting d.utcoffset(), and a time.struct_time for the normalized time is returned. tm_isdst is forced to 0. Note that an OverflowError may be raised if d.year was MINYEAR or MAXYEAR and UTC adjustment spills over a year boundary.

警告

Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC; as a result, using datetime.utctimetuple() may give misleading results. If you have a naive datetime representing UTC, use datetime.replace(tzinfo=timezone.utc) to make it aware, at which point you can use datetime.timetuple().

datetime.toordinal()

Return the proleptic Gregorian ordinal of the date. The same as self.date().toordinal().

datetime.timestamp()

Return POSIX timestamp corresponding to the datetime instance. The return value is a float similar to that returned by time.time().

Naive datetime instances are assumed to represent local time and this method relies on the platform C mktime() function to perform the conversion. Since datetime supports wider range of values than mktime() on many platforms, this method may raise OverflowError or OSError for times far in the past or far in the future.

For aware datetime instances, the return value is computed as:

(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()

在 3.3 版被加入.

在 3.6 版的變更: The timestamp() method uses the fold attribute to disambiguate the times during a repeated interval.

備註

There is no method to obtain the POSIX timestamp directly from a naive datetime instance representing UTC time. If your application uses this convention and your system time zone is not set to UTC, you can obtain the POSIX timestamp by supplying tzinfo=timezone.utc:

timestamp = dt.replace(tzinfo=timezone.utc).timestamp()

or by calculating the timestamp directly:

timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)

datetime.weekday()

Return the day of the week as an integer, where Monday is 0 and Sunday is 6. The same as self.date().weekday(). See also isoweekday().

datetime.isoweekday()

Return the day of the week as an integer, where Monday is 1 and Sunday is 7. The same as self.date().isoweekday(). See also weekday(), isocalendar().

datetime.isocalendar()

Return a named tuple with three components: year, week and weekday. The same as self.date().isocalendar().

datetime.isoformat(sep='T', timespec='auto')

Return a string representing the date and time in ISO 8601 format:

YYYY-MM-DDTHH:MM:SS.ffffff，如果 microsecond 不是 0

YYYY-MM-DDTHH:MM:SS，如果 microsecond 是 0

如果 utcoffset() 没有回傳 None，則會附加一个字串，給出 UTC 偏移：

YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]，如果 microsecond 不是 0

YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]]，如果 microsecond 是 0

範例：

>>> from datetime import datetime, timezone
>>> datetime(2019, 5, 18, 15, 17, 8, 132263).isoformat()
'2019-05-18T15:17:08.132263'
>>> datetime(2019, 5, 18, 15, 17, tzinfo=timezone.utc).isoformat()
'2019-05-18T15:17:00+00:00'

The optional argument sep (default 'T') is a one-character separator, placed between the date and time portions of the result. For example:

>>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
...     """A time zone with an arbitrary, constant -06:39 offset."""
...     def utcoffset(self, dt):
...         return timedelta(hours=-6, minutes=-39)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'
>>> datetime(2009, 11, 27, microsecond=100, tzinfo=TZ()).isoformat()
'2009-11-27T00:00:00.000100-06:39'

The optional argument timespec specifies the number of additional components of the time to include (the default is 'auto'). It can be one of the following:

'auto': Same as 'seconds' if microsecond is 0, same as 'microseconds' otherwise.

'hours': Include the hour in the two-digit HH format.

'minutes': Include hour and minute in HH:MM format.

'seconds': Include hour, minute, and second in HH:MM:SS format.

'milliseconds': Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.

'microseconds': Include full time in HH:MM:SS.ffffff format.

備註

Excluded time components are truncated, not rounded.

ValueError will be raised on an invalid timespec argument:

>>> from datetime import datetime
>>> datetime.now().isoformat(timespec='minutes')
'2002-12-25T00:00'
>>> dt = datetime(2015, 1, 1, 12, 30, 59, 0)
>>> dt.isoformat(timespec='microseconds')
'2015-01-01T12:30:59.000000'

在 3.6 版的變更: 新增 timespec 參數。

datetime.__str__()

For a datetime instance d, str(d) is equivalent to d.isoformat(' ').

datetime.ctime()

Return a string representing the date and time:

>>> from datetime import datetime
>>> datetime(2002, 12, 4, 20, 30, 40).ctime()
'Wed Dec  4 20:30:40 2002'

The output string will not include time zone information, regardless of whether the input is aware or naive.

d.ctime() 等價於：

time.ctime(time.mktime(d.timetuple()))

on platforms where the native C ctime() function (which time.ctime() invokes, but which datetime.ctime() does not invoke) conforms to the C standard.

datetime.strftime(format)

Return a string representing the date and time, controlled by an explicit format string. See also strftime() 與 strptime() 的行為 and datetime.isoformat().

datetime.__format__(format)

Same as datetime.strftime(). This makes it possible to specify a format string for a datetime object in formatted string literals and when using str.format(). See also strftime() 與 strptime() 的行為 and datetime.isoformat().

用法範例：datetime

更多 datetime 的用法範例：

>>> from datetime import datetime, date, time, timezone

>>> # Using datetime.combine()
>>> d = date(2005, 7, 14)
>>> t = time(12, 30)
>>> datetime.combine(d, t)
datetime.datetime(2005, 7, 14, 12, 30)

>>> # Using datetime.now()
>>> datetime.now()
datetime.datetime(2007, 12, 6, 16, 29, 43, 79043)   # GMT +1
>>> datetime.now(timezone.utc)
datetime.datetime(2007, 12, 6, 15, 29, 43, 79060, tzinfo=datetime.timezone.utc)

>>> # Using datetime.strptime()
>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")
>>> dt
datetime.datetime(2006, 11, 21, 16, 30)

>>> # Using datetime.timetuple() to get tuple of all attributes
>>> tt = dt.timetuple()
>>> for it in tt:
...     print(it)
...
2006    # year
11      # month
21      # day
16      # hour
30      # minute
0       # second
1       # weekday (0 = Monday)
325     # number of days since 1st January
-1      # dst - method tzinfo.dst() returned None

>>> # Date in ISO format
>>> ic = dt.isocalendar()
>>> for it in ic:
...     print(it)
...
2006    # ISO year
47      # ISO week
2       # ISO weekday

>>> # Formatting a datetime
>>> dt.strftime("%A, %d. %B %Y %I:%M%p")
'Tuesday, 21. November 2006 04:30PM'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(dt, "day", "month", "time")
'The day is 21, the month is November, the time is 04:30PM.'

The example below defines a tzinfo subclass capturing time zone information for Kabul, Afghanistan, which used +4 UTC until 1945 and then +4:30 UTC thereafter:

from datetime import timedelta, datetime, tzinfo, timezone

class KabulTz(tzinfo):
    # Kabul used +4 until 1945, when they moved to +4:30
    UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)

    def utcoffset(self, dt):
        if dt.year < 1945:
            return timedelta(hours=4)
        elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
            # An ambiguous ("imaginary") half-hour range representing
            # a 'fold' in time due to the shift from +4 to +4:30.
            # If dt falls in the imaginary range, use fold to decide how
            # to resolve. See PEP495.
            return timedelta(hours=4, minutes=(30 if dt.fold else 0))
        else:
            return timedelta(hours=4, minutes=30)

    def fromutc(self, dt):
        # Follow same validations as in datetime.tzinfo
        if not isinstance(dt, datetime):
            raise TypeError("fromutc() requires a datetime argument")
        if dt.tzinfo is not self:
            raise ValueError("dt.tzinfo is not self")

        # A custom implementation is required for fromutc as
        # the input to this function is a datetime with utc values
        # but with a tzinfo set to self.
        # See datetime.astimezone or fromtimestamp.
        if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
            return dt + timedelta(hours=4, minutes=30)
        else:
            return dt + timedelta(hours=4)

    def dst(self, dt):
        # Kabul does not observe daylight saving time.
        return timedelta(0)

    def tzname(self, dt):
        if dt >= self.UTC_MOVE_DATE:
            return "+04:30"
        return "+04"

Usage of KabulTz from above:

>>> tz1 = KabulTz()

>>> # Datetime before the change
>>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
>>> print(dt1.utcoffset())
4:00:00

>>> # Datetime after the change
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
>>> print(dt2.utcoffset())
4:30:00

>>> # Convert datetime to another time zone
>>> dt3 = dt2.astimezone(timezone.utc)
>>> dt3
datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
>>> dt2
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
>>> dt2 == dt3
True

time 物件

A time object represents a (local) time of day, independent of any particular day, and subject to adjustment via a tzinfo object.

class datetime.time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

All arguments are optional. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:

0 <= hour < 24,

0 <= minute < 60,

0 <= second < 60,

0 <= microsecond < 1000000,

fold in [0, 1]。

If an argument outside those ranges is given, ValueError is raised. All default to 0 except tzinfo, which defaults to None.

類別屬性：

time.min

The earliest representable time, time(0, 0, 0, 0).

time.max

The latest representable time, time(23, 59, 59, 999999).

time.resolution

The smallest possible difference between non-equal time objects, timedelta(microseconds=1), although note that arithmetic on time objects is not supported.

Instance attributes (read-only):

time.hour

In range(24).

time.minute

In range(60).

time.second

In range(60).

time.microsecond

In range(1000000).

time.tzinfo

The object passed as the tzinfo argument to the time constructor, or None if none was passed.

time.fold

In [0, 1]. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The values 0 and 1 represent, respectively, the earlier and later of the two moments with the same wall time representation.

在 3.6 版被加入.

time objects support equality and order comparisons, where a is considered less than b when a precedes b in time.

Naive and aware time objects are never equal. Order comparison between naive and aware time objects raises TypeError.

If both comparands are aware, and have the same tzinfo attribute, the tzinfo and fold attributes are ignored and the base times are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset()).

在 3.3 版的變更: Equality comparisons between aware and naive time instances don't raise TypeError.

In Boolean contexts, a time object is always considered to be true.

在 3.5 版的變更: Before Python 3.5, a time object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See bpo-13936 [https://bugs.python.org/issue?@action=redirect&bpo=13936] for full details.

其他建構函式：

classmethod time.fromisoformat(time_string)

Return a time corresponding to a time_string in any valid ISO 8601 format, with the following exceptions:

Time zone offsets may have fractional seconds.

The leading T, normally required in cases where there may be ambiguity between a date and a time, is not required.

Fractional seconds may have any number of digits (anything beyond 6 will be truncated).

Fractional hours and minutes are not supported.

範例：

>>> from datetime import time
>>> time.fromisoformat('04:23:01')
datetime.time(4, 23, 1)
>>> time.fromisoformat('T04:23:01')
datetime.time(4, 23, 1)
>>> time.fromisoformat('T042301')
datetime.time(4, 23, 1)
>>> time.fromisoformat('04:23:01.000384')
datetime.time(4, 23, 1, 384)
>>> time.fromisoformat('04:23:01,000384')
datetime.time(4, 23, 1, 384)
>>> time.fromisoformat('04:23:01+04:00')
datetime.time(4, 23, 1, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
>>> time.fromisoformat('04:23:01Z')
datetime.time(4, 23, 1, tzinfo=datetime.timezone.utc)
>>> time.fromisoformat('04:23:01+00:00')
datetime.time(4, 23, 1, tzinfo=datetime.timezone.utc)

在 3.7 版被加入.

在 3.11 版的變更: Previously, this method only supported formats that could be emitted by time.isoformat().

classmethod time.strptime(date_string, format)

Return a time corresponding to date_string, parsed according to format.

If format does not contain microseconds or timezone information, this is equivalent to:

time(*(time.strptime(date_string, format)[3:6]))

ValueError is raised if the date_string and format cannot be parsed by time.strptime() or if it returns a value which is not a time tuple. See also strftime() 與 strptime() 的行為 and time.fromisoformat().

在 3.14 版被加入.

實例方法：

time.replace(hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, *, fold=0)

Return a new time with the same values, but with specified parameters updated. Note that tzinfo=None can be specified to create a naive time from an aware time, without conversion of the time data.

time objects are also supported by generic function copy.replace().

在 3.6 版的變更: 新增 fold 參數。

time.isoformat(timespec='auto')

Return a string representing the time in ISO 8601 format, one of:

HH:MM:SS.ffffff, if microsecond is not 0

HH:MM:SS, if microsecond is 0

HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]], if utcoffset() does not return None

HH:MM:SS+HH:MM[:SS[.ffffff]], if microsecond is 0 and utcoffset() does not return None

The optional argument timespec specifies the number of additional components of the time to include (the default is 'auto'). It can be one of the following:

'auto': Same as 'seconds' if microsecond is 0, same as 'microseconds' otherwise.

'hours': Include the hour in the two-digit HH format.

'minutes': Include hour and minute in HH:MM format.

'seconds': Include hour, minute, and second in HH:MM:SS format.

'milliseconds': Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.

'microseconds': Include full time in HH:MM:SS.ffffff format.

備註

Excluded time components are truncated, not rounded.

ValueError will be raised on an invalid timespec argument.

範例：

>>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
'12:34'
>>> dt = time(hour=12, minute=34, second=56, microsecond=0)
>>> dt.isoformat(timespec='microseconds')
'12:34:56.000000'
>>> dt.isoformat(timespec='auto')
'12:34:56'

在 3.6 版的變更: 新增 timespec 參數。

time.__str__()

For a time t, str(t) is equivalent to t.isoformat().

time.strftime(format)

Return a string representing the time, controlled by an explicit format string. See also strftime() 與 strptime() 的行為 and time.isoformat().

time.__format__(format)

Same as time.strftime(). This makes it possible to specify a format string for a time object in formatted string literals and when using str.format(). See also strftime() 與 strptime() 的行為 and time.isoformat().

time.utcoffset()

If tzinfo is None, returns None, else returns self.tzinfo.utcoffset(None), and raises an exception if the latter doesn't return None or a timedelta object with magnitude less than one day.

在 3.7 版的變更: The UTC offset is not restricted to a whole number of minutes.

time.dst()

If tzinfo is None, returns None, else returns self.tzinfo.dst(None), and raises an exception if the latter doesn't return None, or a timedelta object with magnitude less than one day.

在 3.7 版的變更: The DST offset is not restricted to a whole number of minutes.

time.tzname()

If tzinfo is None, returns None, else returns self.tzinfo.tzname(None), or raises an exception if the latter doesn't return None or a string object.

用法範例：time

Examples of working with a time object:

>>> from datetime import time, tzinfo, timedelta
>>> class TZ1(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=1)
...     def dst(self, dt):
...         return timedelta(0)
...     def tzname(self,dt):
...         return "+01:00"
...     def  __repr__(self):
...         return f"{self.__class__.__name__}()"
...
>>> t = time(12, 10, 30, tzinfo=TZ1())
>>> t
datetime.time(12, 10, 30, tzinfo=TZ1())
>>> t.isoformat()
'12:10:30+01:00'
>>> t.dst()
datetime.timedelta(0)
>>> t.tzname()
'+01:00'
>>> t.strftime("%H:%M:%S %Z")
'12:10:30 +01:00'
>>> 'The {} is {:%H:%M}.'.format("time", t)
'The time is 12:10.'

tzinfo 物件

class datetime.tzinfo

This is an abstract base class, meaning that this class should not be instantiated directly. Define a subclass of tzinfo to capture information about a particular time zone.

An instance of (a concrete subclass of) tzinfo can be passed to the constructors for datetime and time objects. The latter objects view their attributes as being in local time, and the tzinfo object supports methods revealing offset of local time from UTC, the name of the time zone, and DST offset, all relative to a date or time object passed to them.

You need to derive a concrete subclass, and (at least) supply implementations of the standard tzinfo methods needed by the datetime methods you use. The datetime module provides timezone, a simple concrete subclass of tzinfo which can represent time zones with fixed offset from UTC such as UTC itself or North American EST and EDT.

Special requirement for pickling: A tzinfo subclass must have an __init__() method that can be called with no arguments, otherwise it can be pickled but possibly not unpickled again. This is a technical requirement that may be relaxed in the future.

A concrete subclass of tzinfo may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware datetime objects. If in doubt, simply implement all of them.

tzinfo.utcoffset(dt)

Return offset of local time from UTC, as a timedelta object that is positive east of UTC. If local time is west of UTC, this should be negative.

This represents the total offset from UTC; for example, if a tzinfo object represents both time zone and DST adjustments, utcoffset() should return their sum. If the UTC offset isn't known, return None. Else the value returned must be a timedelta object strictly between -timedelta(hours=24) and timedelta(hours=24) (the magnitude of the offset must be less than one day). Most implementations of utcoffset() will probably look like one of these two:

return CONSTANT                 # fixed-offset class
return CONSTANT + self.dst(dt)  # daylight-aware class

If utcoffset() does not return None, dst() should not return None either.

The default implementation of utcoffset() raises NotImplementedError.

在 3.7 版的變更: The UTC offset is not restricted to a whole number of minutes.

tzinfo.dst(dt)

Return the daylight saving time (DST) adjustment, as a timedelta object or None if DST information isn't known.

Return timedelta(0) if DST is not in effect. If DST is in effect, return the offset as a timedelta object (see utcoffset() for details). Note that DST offset, if applicable, has already been added to the UTC offset returned by utcoffset(), so there's no need to consult dst() unless you're interested in obtaining DST info separately. For example, datetime.timetuple() calls its tzinfo attribute's dst() method to determine how the tm_isdst flag should be set, and tzinfo.fromutc() calls dst() to account for DST changes when crossing time zones.

An instance tz of a tzinfo subclass that models both standard and daylight times must be consistent in this sense:

tz.utcoffset(dt) - tz.dst(dt)

must return the same result for every datetime dt with dt.tzinfo == tz. For sane tzinfo subclasses, this expression yields the time zone's "standard offset", which should not depend on the date or the time, but only on geographic location. The implementation of datetime.astimezone() relies on this, but cannot detect violations; it's the programmer's responsibility to ensure it. If a tzinfo subclass cannot guarantee this, it may be able to override the default implementation of tzinfo.fromutc() to work correctly with astimezone() regardless.

Most implementations of dst() will probably look like one of these two:

def dst(self, dt):
    # a fixed-offset class:  doesn't account for DST
    return timedelta(0)

或是：

def dst(self, dt):
    # Code to set dston and dstoff to the time zone's DST
    # transition times based on the input dt.year, and expressed
    # in standard local time.

    if dston <= dt.replace(tzinfo=None) < dstoff:
        return timedelta(hours=1)
    else:
        return timedelta(0)

The default implementation of dst() raises NotImplementedError.

在 3.7 版的變更: The DST offset is not restricted to a whole number of minutes.

tzinfo.tzname(dt)

Return the time zone name corresponding to the datetime object dt, as a string. Nothing about string names is defined by the datetime module, and there's no requirement that it mean anything in particular. For example, "GMT", "UTC", "-500", "-5:00", "EDT", "US/Eastern", "America/New York" are all valid replies. Return None if a string name isn't known. Note that this is a method rather than a fixed string primarily because some tzinfo subclasses will wish to return different names depending on the specific value of dt passed, especially if the tzinfo class is accounting for daylight time.

The default implementation of tzname() raises NotImplementedError.

These methods are called by a datetime or time object, in response to their methods of the same names. A datetime object passes itself as the argument, and a time object passes None as the argument. A tzinfo subclass's methods should therefore be prepared to accept a dt argument of None, or of class datetime.

When None is passed, it's up to the class designer to decide the best response. For example, returning None is appropriate if the class wishes to say that time objects don't participate in the tzinfo protocols. It may be more useful for utcoffset(None) to return the standard UTC offset, as there is no other convention for discovering the standard offset.

When a datetime object is passed in response to a datetime method, dt.tzinfo is the same object as self. tzinfo methods can rely on this, unless user code calls tzinfo methods directly. The intent is that the tzinfo methods interpret dt as being in local time, and not need worry about objects in other time zones.

There is one more tzinfo method that a subclass may wish to override:

tzinfo.fromutc(dt)

This is called from the default datetime.astimezone() implementation. When called from that, dt.tzinfo is self, and dt's date and time data are to be viewed as expressing a UTC time. The purpose of fromutc() is to adjust the date and time data, returning an equivalent datetime in self's local time.

Most tzinfo subclasses should be able to inherit the default fromutc() implementation without problems. It's strong enough to handle fixed-offset time zones, and time zones accounting for both standard and daylight time, and the latter even if the DST transition times differ in different years. An example of a time zone the default fromutc() implementation may not handle correctly in all cases is one where the standard offset (from UTC) depends on the specific date and time passed, which can happen for political reasons. The default implementations of astimezone() and fromutc() may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes.

Skipping code for error cases, the default fromutc() implementation acts like:

def fromutc(self, dt):
    # raise ValueError error if dt.tzinfo is not self
    dtoff = dt.utcoffset()
    dtdst = dt.dst()
    # raise ValueError if dtoff is None or dtdst is None
    delta = dtoff - dtdst  # this is self's standard offset
    if delta:
        dt += delta   # convert to standard local time
        dtdst = dt.dst()
        # raise ValueError if dtdst is None
    if dtdst:
        return dt + dtdst
    else:
        return dt

In the following tzinfo_examples.py file there are some examples of tzinfo classes:

from datetime import tzinfo, timedelta, datetime

ZERO = timedelta(0)
HOUR = timedelta(hours=1)
SECOND = timedelta(seconds=1)

# A class capturing the platform's idea of local time.
# (May result in wrong values on historical times in
#  timezones where UTC offset and/or the DST rules had
#  changed in the past.)
import time as _time

STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
    DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
    DSTOFFSET = STDOFFSET

DSTDIFF = DSTOFFSET - STDOFFSET

class LocalTimezone(tzinfo):

    def fromutc(self, dt):
        assert dt.tzinfo is self
        stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND
        args = _time.localtime(stamp)[:6]
        dst_diff = DSTDIFF // SECOND
        # Detect fold
        fold = (args == _time.localtime(stamp - dst_diff))
        return datetime(*args, microsecond=dt.microsecond,
                        tzinfo=self, fold=fold)

    def utcoffset(self, dt):
        if self._isdst(dt):
            return DSTOFFSET
        else:
            return STDOFFSET

    def dst(self, dt):
        if self._isdst(dt):
            return DSTDIFF
        else:
            return ZERO

    def tzname(self, dt):
        return _time.tzname[self._isdst(dt)]

    def _isdst(self, dt):
        tt = (dt.year, dt.month, dt.day,
              dt.hour, dt.minute, dt.second,
              dt.weekday(), 0, 0)
        stamp = _time.mktime(tt)
        tt = _time.localtime(stamp)
        return tt.tm_isdst > 0

Local = LocalTimezone()

# A complete implementation of current DST rules for major US time zones.

def first_sunday_on_or_after(dt):
    days_to_go = 6 - dt.weekday()
    if days_to_go:
        dt += timedelta(days_to_go)
    return dt

# US DST Rules
#
# This is a simplified (i.e., wrong for a few cases) set of rules for US
# DST start and end times. For a complete and up-to-date set of DST rules
# and timezone definitions, visit the Olson Database (or try pytz):
# http://www.twinsun.com/tz/tz-link.htm
# https://sourceforge.net/projects/pytz/ (might not be up-to-date)
#
# In the US, since 2007, DST starts at 2am (standard time) on the second
# Sunday in March, which is the first Sunday on or after Mar 8.
DSTSTART_2007 = datetime(1, 3, 8, 2)
# and ends at 2am (DST time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 2)
# From 1987 to 2006, DST used to start at 2am (standard time) on the first
# Sunday in April and to end at 2am (DST time) on the last
# Sunday of October, which is the first Sunday on or after Oct 25.
DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
DSTEND_1987_2006 = datetime(1, 10, 25, 2)
# From 1967 to 1986, DST used to start at 2am (standard time) on the last
# Sunday in April (the one on or after April 24) and to end at 2am (DST time)
# on the last Sunday of October, which is the first Sunday
# on or after Oct 25.
DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
DSTEND_1967_1986 = DSTEND_1987_2006

def us_dst_range(year):
    # Find start and end times for US DST. For years before 1967, return
    # start = end for no DST.
    if 2006 < year:
        dststart, dstend = DSTSTART_2007, DSTEND_2007
    elif 1986 < year < 2007:
        dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
    elif 1966 < year < 1987:
        dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
    else:
        return (datetime(year, 1, 1), ) * 2

    start = first_sunday_on_or_after(dststart.replace(year=year))
    end = first_sunday_on_or_after(dstend.replace(year=year))
    return start, end

class USTimeZone(tzinfo):

    def __init__(self, hours, reprname, stdname, dstname):
        self.stdoffset = timedelta(hours=hours)
        self.reprname = reprname
        self.stdname = stdname
        self.dstname = dstname

    def __repr__(self):
        return self.reprname

    def tzname(self, dt):
        if self.dst(dt):
            return self.dstname
        else:
            return self.stdname

    def utcoffset(self, dt):
        return self.stdoffset + self.dst(dt)

    def dst(self, dt):
        if dt is None or dt.tzinfo is None:
            # An exception may be sensible here, in one or both cases.
            # It depends on how you want to treat them.  The default
            # fromutc() implementation (called by the default astimezone()
            # implementation) passes a datetime with dt.tzinfo is self.
            return ZERO
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        # Can't compare naive to aware objects, so strip the timezone from
        # dt first.
        dt = dt.replace(tzinfo=None)
        if start + HOUR <= dt < end - HOUR:
            # DST is in effect.
            return HOUR
        if end - HOUR <= dt < end:
            # Fold (an ambiguous hour): use dt.fold to disambiguate.
            return ZERO if dt.fold else HOUR
        if start <= dt < start + HOUR:
            # Gap (a non-existent hour): reverse the fold rule.
            return HOUR if dt.fold else ZERO
        # DST is off.
        return ZERO

    def fromutc(self, dt):
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        start = start.replace(tzinfo=self)
        end = end.replace(tzinfo=self)
        std_time = dt + self.stdoffset
        dst_time = std_time + HOUR
        if end <= dst_time < end + HOUR:
            # Repeated hour
            return std_time.replace(fold=1)
        if std_time < start or dst_time >= end:
            # Standard time
            return std_time
        if start <= std_time < end - HOUR:
            # Daylight saving time
            return dst_time

Eastern  = USTimeZone(-5, "Eastern",  "EST", "EDT")
Central  = USTimeZone(-6, "Central",  "CST", "CDT")
Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
Pacific  = USTimeZone(-8, "Pacific",  "PST", "PDT")

Note that there are unavoidable subtleties twice per year in a tzinfo subclass accounting for both standard and daylight time, at the DST transition points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the minute after 1:59 (EST) on the second Sunday in March, and ends the minute after 1:59 (EDT) on the first Sunday in November:

  UTC   3:MM  4:MM  5:MM  6:MM  7:MM  8:MM
  EST  22:MM 23:MM  0:MM  1:MM  2:MM  3:MM
  EDT  23:MM  0:MM  1:MM  2:MM  3:MM  4:MM

start  22:MM 23:MM  0:MM  1:MM  3:MM  4:MM

  end  23:MM  0:MM  1:MM  1:MM  2:MM  3:MM

When DST starts (the "start" line), the local wall clock leaps from 1:59 to 3:00. A wall time of the form 2:MM doesn't really make sense on that day, so astimezone(Eastern) won't deliver a result with hour == 2 on the day DST begins. For example, at the Spring forward transition of 2016, we get:

>>> from datetime import datetime, timezone
>>> from tzinfo_examples import HOUR, Eastern
>>> u0 = datetime(2016, 3, 13, 5, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname())
...
05:00:00 UTC = 00:00:00 EST
06:00:00 UTC = 01:00:00 EST
07:00:00 UTC = 03:00:00 EDT
08:00:00 UTC = 04:00:00 EDT

When DST ends (the "end" line), there's a potentially worse problem: there's an hour that can't be spelled unambiguously in local wall time: the last hour of daylight time. In Eastern, that's times of the form 5:MM UTC on the day daylight time ends. The local wall clock leaps from 1:59 (daylight time) back to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous. astimezone() mimics the local clock's behavior by mapping two adjacent UTC hours into the same local hour then. In the Eastern example, UTC times of the form 5:MM and 6:MM both map to 1:MM when converted to Eastern, but earlier times have the fold attribute set to 0 and the later times have it set to 1. For example, at the Fall back transition of 2016, we get:

>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0

Note that the datetime instances that differ only by the value of the fold attribute are considered equal in comparisons.

Applications that can't bear wall-time ambiguities should explicitly check the value of the fold attribute or avoid using hybrid tzinfo subclasses; there are no ambiguities when using timezone, or any other fixed-offset tzinfo subclass (such as a class representing only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).

也參考

zoneinfo

The datetime module has a basic timezone class (for handling arbitrary fixed offsets from UTC) and its timezone.utc attribute (a UTC timezone instance).

zoneinfo brings the IANA time zone database (also known as the Olson database) to Python, and its usage is recommended.

IANA 時區資料庫 [https://www.iana.org/time-zones]

The Time Zone Database (often called tz, tzdata or zoneinfo) contains code and data that represent the history of local time for many representative locations around the globe. It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules.

timezone 物件

The timezone class is a subclass of tzinfo, each instance of which represents a time zone defined by a fixed offset from UTC.

Objects of this class cannot be used to represent time zone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time.

class datetime.timezone(offset, name=None)

The offset argument must be specified as a timedelta object representing the difference between the local time and UTC. It must be strictly between -timedelta(hours=24) and timedelta(hours=24), otherwise ValueError is raised.

The name argument is optional. If specified it must be a string that will be used as the value returned by the datetime.tzname() method.

在 3.2 版被加入.

在 3.7 版的變更: The UTC offset is not restricted to a whole number of minutes.

timezone.utcoffset(dt)

Return the fixed value specified when the timezone instance is constructed.

The dt argument is ignored. The return value is a timedelta instance equal to the difference between the local time and UTC.

在 3.7 版的變更: The UTC offset is not restricted to a whole number of minutes.

timezone.tzname(dt)

Return the fixed value specified when the timezone instance is constructed.

If name is not provided in the constructor, the name returned by tzname(dt) is generated from the value of the offset as follows. If offset is timedelta(0), the name is "UTC", otherwise it is a string in the format UTC±HH:MM, where ± is the sign of offset, HH and MM are two digits of offset.hours and offset.minutes respectively.

在 3.6 版的變更: Name generated from offset=timedelta(0) is now plain 'UTC', not 'UTC+00:00'.

timezone.dst(dt)

總是回傳 None。

timezone.fromutc(dt)

Return dt + offset. The dt argument must be an aware datetime instance, with tzinfo set to self.

類別屬性：

timezone.utc

UTC 時區，timezone(timedelta(0))。

strftime() 與 strptime() 的行為

date, datetime, and time objects all support a strftime(format) method, to create a string representing the time under the control of an explicit format string.

Conversely, the date.strptime(), datetime.strptime() and time.strptime() class methods create an object from a string representing the time and a corresponding format string.

The table below provides a high-level comparison of strftime() versus strptime():

strftime

strptime

用法

Convert object to a string according to a given format

Parse a string into an object given a corresponding format

Type of method

實例方法

類別方法

Signature

strftime(format)

strptime(date_string, format)

strftime() 與 strptime() 格式碼

These methods accept format codes that can be used to parse and format dates:

>>> datetime.strptime('31/01/22 23:59:59.999999',
...                   '%d/%m/%y %H:%M:%S.%f')
datetime.datetime(2022, 1, 31, 23, 59, 59, 999999)
>>> _.strftime('%a %d %b %Y, %I:%M%p')
'Mon 31 Jan 2022, 11:59PM'

The following is a list of all the format codes that the 1989 C standard requires, and these work on all platforms with a standard C implementation.

Directive

含義

範例

註解

%a

Weekday as locale's abbreviated name.

Sun, Mon, ..., Sat (en_US);

So, Mo, ..., Sa (de_DE)

(1)

%A

Weekday as locale's full name.

Sunday, Monday, ..., Saturday (en_US);

Sonntag, Montag, ..., Samstag (de_DE)

(1)

%w

Weekday as a decimal number, where 0 is Sunday and 6 is Saturday.

0, 1, ..., 6

%d

Day of the month as a zero-padded decimal number.

01, 02, ..., 31

(9)

%b

Month as locale's abbreviated name.

Jan, Feb, ..., Dec (en_US);

Jan, Feb, ..., Dez (de_DE)

(1)

%B

Month as locale's full name.

January, February, ..., December (en_US);

Januar, Februar, ..., Dezember (de_DE)

(1)

%m

以零填充的並以十進位數字表示的月份。

01, 02, ..., 12

(9)

%y

Year without century as a zero-padded decimal number.

00, 01, ..., 99

(9)

%Y

Year with century as a decimal number.

0001, 0002, ..., 2013, 2014, ..., 9998, 9999

(2)

%H

Hour (24-hour clock) as a zero-padded decimal number.

00, 01, ..., 23

(9)

%I

Hour (12-hour clock) as a zero-padded decimal number.

01, 02, ..., 12

(9)

%p

Locale's equivalent of either AM or PM.

AM, PM (en_US);

am, pm (de_DE)

(1), (3)

%M

Minute as a zero-padded decimal number.

00, 01, ..., 59

(9)

%S

Second as a zero-padded decimal number.

00, 01, ..., 59

(4), (9)

%f

Microsecond as a decimal number, zero-padded to 6 digits.

000000, 000001, ..., 999999

(5)

%z

UTC offset in the form ±HHMM[SS[.ffffff]] (empty string if the object is naive).

(empty), +0000, -0400, +1030, +063415, -030712.345216

(6)

%Z

Time zone name (empty string if the object is naive).

(empty), UTC, GMT

(6)

%j

Day of the year as a zero-padded decimal number.

001, 002, ..., 366

(9)

%U

Week number of the year (Sunday as the first day of the week) as a zero-padded decimal number. All days in a new year preceding the first Sunday are considered to be in week 0.

00, 01, ..., 53

(7), (9)

%W

Week number of the year (Monday as the first day of the week) as a zero-padded decimal number. All days in a new year preceding the first Monday are considered to be in week 0.

00, 01, ..., 53

(7), (9)

%c

Locale's appropriate date and time representation.

Tue Aug 16 21:30:00 1988 (en_US);

Di 16 Aug 21:30:00 1988 (de_DE)

(1)

%x

Locale's appropriate date representation.

08/16/88 (None);

08/16/1988 (en_US);

16.08.1988 (de_DE)

(1)

%X

Locale's appropriate time representation.

21:30:00 (en_US);

21:30:00 (de_DE)

(1)

%%

A literal '%' character.

%

Several additional directives not required by the C89 standard are included for convenience. These parameters all correspond to ISO 8601 date values.

Directive

含義

範例

註解

%G

ISO 8601 year with century representing the year that contains the greater part of the ISO week (%V).

0001, 0002, ..., 2013, 2014, ..., 9998, 9999

(8)

%u

ISO 8601 weekday as a decimal number where 1 is Monday.

1, 2, ..., 7

%V

ISO 8601 week as a decimal number with Monday as the first day of the week. Week 01 is the week containing Jan 4.

01, 02, ..., 53

(8), (9)

%:z

UTC offset in the form ±HH:MM[:SS[.ffffff]] (empty string if the object is naive).

(empty), +00:00, -04:00, +10:30, +06:34:15, -03:07:12.345216

(6)

These may not be available on all platforms when used with the strftime() method. The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above. Calling strptime() with incomplete or ambiguous ISO 8601 directives will raise a ValueError.

The full set of format codes supported varies across platforms, because Python calls the platform C library's strftime() function, and platform variations are common. To see the full set of format codes supported on your platform, consult the strftime(3) [https://manpages.debian.org/strftime(3)] documentation. There are also differences between platforms in handling of unsupported format specifiers.

在 3.6 版被加入: 新增 %G、%u 與 %V。

在 3.12 版被加入: 新增 %:z。

技術細節

Broadly speaking, d.strftime(fmt) acts like the time module's time.strftime(fmt, d.timetuple()) although not all objects support a timetuple() method.

For the datetime.strptime() and date.strptime() class methods, the default value is 1900-01-01T00:00:00.000: any components not specified in the format string will be pulled from the default value.

備註

When used to parse partial dates lacking a year, datetime.strptime() and date.strptime() will raise when encountering February 29 because the default year of 1900 is not a leap year. Always add a default leap year to partial date strings before parsing.

>>> from datetime import datetime
>>> value = "2/29"
>>> datetime.strptime(value, "%m/%d")
Traceback (most recent call last):
...
ValueError: day 29 must be in range 1..28 for month 2 in year 1900
>>> datetime.strptime(f"1904 {value}", "%Y %m/%d")
datetime.datetime(1904, 2, 29, 0, 0)

Using datetime.strptime(date_string, format) is equivalent to:

datetime(*(time.strptime(date_string, format)[0:6]))

except when the format includes sub-second components or time zone offset information, which are supported in datetime.strptime but are discarded by time.strptime.

對 time 物件來說，不應該使用年、月、日的格式碼，因為 time 物件並沒有這些值。如果使用這些格式碼，年份會以 1900 代替、月及日會以 1 代替。

對 date 物件來說，不應該使用時、分、秒、微秒的格式碼，因為 date 物件並沒有這些值。如果使用這些格式碼，這些值都會以 0 代替。

For the same reason, handling of format strings containing Unicode code points that can't be represented in the charset of the current locale is also platform-dependent. On some platforms such code points are preserved intact in the output, while on others strftime may raise UnicodeError or return an empty string instead.

註解：

Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, "month/day/year" versus "day/month/year"), and the output may contain non-ASCII characters.

The strptime() method can parse years in the full [1, 9999] range, but years < 1000 must be zero-filled to 4-digit width.

在 3.2 版的變更: In previous versions, strftime() method was restricted to years >= 1900.

在 3.3 版的變更: In version 3.2, strftime() method was restricted to years >= 1000.

When used with the strptime() method, the %p directive only affects the output hour field if the %I directive is used to parse the hour.

Unlike the time module, the datetime module does not support leap seconds.

When used with the strptime() method, the %f directive accepts from one to six digits and zero pads on the right. %f is an extension to the set of format characters in the C standard (but implemented separately in datetime objects, and therefore always available).

For a naive object, the %z, %:z and %Z format codes are replaced by empty strings.

For an aware object:

%z

utcoffset() is transformed into a string of the form ±HHMM[SS[.ffffff]], where HH is a 2-digit string giving the number of UTC offset hours, MM is a 2-digit string giving the number of UTC offset minutes, SS is a 2-digit string giving the number of UTC offset seconds and ffffff is a 6-digit string giving the number of UTC offset microseconds. The ffffff part is omitted when the offset is a whole number of seconds and both the ffffff and the SS part is omitted when the offset is a whole number of minutes. For example, if utcoffset() returns timedelta(hours=-3, minutes=-30), %z is replaced with the string '-0330'.

在 3.7 版的變更: The UTC offset is not restricted to a whole number of minutes.

在 3.7 版的變更: When the %z directive is provided to the strptime() method, the UTC offsets can have a colon as a separator between hours, minutes and seconds. For example, '+01:00:00' will be parsed as an offset of one hour. In addition, providing 'Z' is identical to '+00:00'.

%:z

Behaves exactly as %z, but has a colon separator added between hours, minutes and seconds.

%Z

In strftime(), %Z is replaced by an empty string if tzname() returns None; otherwise %Z is replaced by the returned value, which must be a string.

strptime() only accepts certain values for %Z:

any value in time.tzname for your machine's locale

the hard-coded values UTC and GMT

So someone living in Japan may have JST, UTC, and GMT as valid values, but probably not EST. It will raise ValueError for invalid values.

在 3.2 版的變更: When the %z directive is provided to the strptime() method, an aware datetime object will be produced. The tzinfo of the result will be set to a timezone instance.

When used with the strptime() method, %U and %W are only used in calculations when the day of the week and the calendar year (%Y) are specified.

Similar to %U and %W, %V is only used in calculations when the day of the week and the ISO year (%G) are specified in a strptime() format string. Also note that %G and %Y are not interchangeable.

When used with the strptime() method, the leading zero is optional for formats %d, %m, %H, %I, %M, %S, %j, %U, %W, and %V. Format %y does require a leading zero.

When parsing a month and day using strptime(), always include a year in the format. If the value you need to parse lacks a year, append an explicit dummy leap year. Otherwise your code will raise an exception when it encounters leap day because the default year used by the parser (1900) is not a leap year. Users run into that bug every leap year.

>>> month_day = "02/29"
>>> datetime.strptime(f"{month_day};1984", "%m/%d;%Y")  # 沒有閏年問題。
datetime.datetime(1984, 2, 29, 0, 0)

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: strptime() calls using a format string containing a day of month without a year now emit a DeprecationWarning. In 3.15 or later we may change this into an error or change the default year to a leap year. See gh-70647 [https://github.com/python/cpython/issues/70647].

註解

[1]

也就是說，我們會忽略相對論的效應

[2]

This matches the definition of the "proleptic Gregorian" calendar in Dershowitz and Reingold's book Calendrical Calculations, where it's the base calendar for all computations. See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems.

[3]

See R. H. van Gent's guide to the mathematics of the ISO 8601 calendar [https://web.archive.org/web/20220531051136/https://webspace.science.uu.nl/~gent0113/calendar/isocalendar.htm] for a good explanation.

zoneinfo --- IANA 時區支援

在 3.9 版被加入.

原始碼：Lib/zoneinfo [https://github.com/python/cpython/tree/3.14/Lib/zoneinfo]

zoneinfo 模組提供了一個具體的時區實作，以支援 PEP 615 [https://peps.python.org/pep-0615/] 中最初指定的 IANA 時區資料庫。預設情況下，如果可用，zoneinfo 會使用系統的時區資料；如果沒有可用的系統時區資料，該函式庫將轉而使用 PyPI 上可用的第一方 tzdata [https://pypi.org/project/tzdata/] 套件。

也參考

datetime 模組

提供了 time 與 datetime 型別，這些型別是設計來與 ZoneInfo 類別一起使用的。

tzdata [https://pypi.org/project/tzdata/] 套件

由 CPython 核心開發者維護的第一方套件，用於透過 PyPI 提供時區資料。

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

使用 ZoneInfo

ZoneInfo 是 datetime.tzinfo 抽象基底類別的一個具體實作，旨在透過建構函式、datetime.replace 方法或 datetime.astimezone 方法附加到 tzinfo：

>>> from zoneinfo import ZoneInfo
>>> from datetime import datetime, timedelta

>>> dt = datetime(2020, 10, 31, 12, tzinfo=ZoneInfo("America/Los_Angeles"))
>>> print(dt)
2020-10-31 12:00:00-07:00

>>> dt.tzname()
'PDT'

以此方式建構的 Datetime 物件與 datetime 運算相容，並能處理日光節約時間轉換而無需進一步干預：

>>> dt_add = dt + timedelta(days=1)

>>> print(dt_add)
2020-11-01 12:00:00-08:00

>>> dt_add.tzname()
'PST'

這些時區也支援 PEP 495 [https://peps.python.org/pep-0495/] 中引入的 fold 屬性。在會引發時間模糊的時差轉換期間（例如日光節約時間到標準時間的轉換），當 fold=0 時，會使用轉換前的時差，而當 fold=1 時，會使用轉換後的時差，例如：

>>> dt = datetime(2020, 11, 1, 1, tzinfo=ZoneInfo("America/Los_Angeles"))
>>> print(dt)
2020-11-01 01:00:00-07:00

>>> print(dt.replace(fold=1))
2020-11-01 01:00:00-08:00

當從另一個時區轉換時，fold 將被設定為正確的值：

>>> from datetime import timezone
>>> LOS_ANGELES = ZoneInfo("America/Los_Angeles")
>>> dt_utc = datetime(2020, 11, 1, 8, tzinfo=timezone.utc)

>>> # 在 PDT 轉換為 PST 之前
>>> print(dt_utc.astimezone(LOS_ANGELES))
2020-11-01 01:00:00-07:00

>>> # 在 PDT 轉換為 PST 之後
>>> print((dt_utc + timedelta(hours=1)).astimezone(LOS_ANGELES))
2020-11-01 01:00:00-08:00

資料來源

zoneinfo 模組不直接提供時區資料，而是從系統時區資料庫或可用的第一方 PyPI 套件 tzdata [https://pypi.org/project/tzdata/] 中提取時區資訊。某些系統，特別是 Windows 系統，沒有可用的 IANA 資料庫，因此對於需要時區資料且目標為跨平台相容性的專案，建議宣告對 tzdata 的依賴。如果系統資料和 tzdata 都不可用，所有對 ZoneInfo 的呼叫都將引發 ZoneInfoNotFoundError 例外。

設定資料來源

當呼叫 ZoneInfo(key) 時，建構函式會先在 TZPATH 中指定的目錄中搜尋符合 key 的檔案，如果失敗，則在 tzdata 套件中尋找符合的項目。此行為可以透過三種方式設定：

未另外指定時的預設 TZPATH 可以在編譯時期設定。

TZPATH 可以使用 環境變數 來設定。

在 runtime，可以使用 reset_tzpath() 函式來操作搜尋路徑。

編譯時期設定

預設的 TZPATH 包含時區資料庫的幾個常見部署位置（Windows 除外，因為 Windows 上沒有時區資料的「眾所周知」位置）。在 POSIX 系統上，下游發行者和從原始碼建置 Python 且知道其系統時區資料部署位置的人，可以透過指定編譯時期選項 TZPATH（或更有可能的是使用 configure 旗標 --with-tzpath）來變更預設時區路徑，它應該是一個由 os.pathsep 分隔的字串。

在所有平台上，設定的值可以透過 sysconfig.get_config_var() 中的 TZPATH 鍵取得。

環境設定

在初始化 TZPATH 時（無論是在引入時，或是在呼叫不帶引數的 reset_tzpath() 時），如果環境變數 PYTHONTZPATH 存在，zoneinfo 模組將使用它來設定搜尋路徑。

PYTHONTZPATH

這是一個由 os.pathsep 分隔的字串，包含要使用的時區搜尋路徑。它必須只包含絕對路徑，而非相對路徑。在 PYTHONTZPATH 中指定的相對路徑元件將不會被使用，但除此之外，指定相對路徑時的行為是實作定義的；CPython 將引發 InvalidTZPathWarning，但其他實作可以自由地靜默忽略錯誤的元件或引發例外。

要讓系統忽略系統資料並改用 tzdata 套件，請設定 PYTHONTZPATH=""。

Runtime 設定

TZ 搜尋路徑也可以在 Runtime 使用 reset_tzpath() 函式進行設定。這通常不是一個建議的操作，儘管在需要使用特定時區路徑（或需要停用對系統時區的存取）的測試函式中使用它是合理的。

ZoneInfo 類別

class zoneinfo.ZoneInfo(key)

一個具體的 datetime.tzinfo 子類別，代表由字串 key 指定的 IANA 時區。對主要建構函式的呼叫將總是回傳比較結果相同的物件；換句話說，除非透過 ZoneInfo.clear_cache() 使快取失效，否則對於所有 key 的值，以下斷言將永遠為真：

a = ZoneInfo(key)
b = ZoneInfo(key)
assert a is b

key 必須是相對、正規化的 POSIX 路徑形式，且不含上層參照。如果傳入不符合規範的鍵，建構函式將引發 ValueError 例外。

如果找不到符合 key 的檔案，建構函式將引發 ZoneInfoNotFoundError 例外。

ZoneInfo 類別有兩個備用建構函式：

classmethod ZoneInfo.from_file(file_obj, /, key=None)

從回傳位元組的類檔案物件（例如以二進位模式開啟的檔案或一個 io.BytesIO 物件）建構一個 ZoneInfo 物件。與主要建構函式不同，這個建構函式總是會建構一個新物件。

key 參數設定了時區的名稱，用於 __str__() 和 __repr__()。

透過此建構函式建立的物件無法被封裝（參閱 pickling）。

ValueError is raised if the data read from file_obj is not a valid TZif file.

classmethod ZoneInfo.no_cache(key)

一個繞過建構函式快取的備用建構函式。它與主要建構函式相同，但每次呼叫都會回傳一個新物件。這對於測試或示範目的最可能有用，但它也可以用來建立一個具有不同快取失效策略的系統。

透過此建構函式建立的物件，在拆封時也會繞過去序列化過程的快取。

警示

使用此建構函式可能會以意想不到的方式改變你的 datetime 物件的語意，只有在你確定需要時才使用它。

以下類別方法也可用：

classmethod ZoneInfo.clear_cache(*, only_keys=None)

一個用於使 ZoneInfo 類別上的快取失效的方法。如果沒有傳入引數，所有快取都會失效，且下一次對每個鍵的主要建構函式呼叫都將回傳一個新的實例。

如果將一個包含鍵名的可疊代物件傳遞給 only_keys 參數，則只有指定的鍵會從快取中移除。傳遞給 only_keys 但在快取中找不到的鍵會被忽略。

警告

呼叫此函式可能會以意想不到的方式改變使用 ZoneInfo 的 datetime 物件的語意；這會修改模組狀態，因此可能產生廣泛的影響。只有在你確定需要時才使用它。

該類別有一個屬性：

ZoneInfo.key

這是一個唯讀 屬性，它回傳傳遞給建構函式的 key 值，該值應為 IANA 時區資料庫中的查詢鍵（例如 America/New_York、Europe/Paris 或 Asia/Tokyo）。

對於從檔案建構且未指定 key 參數的時區，此屬性將被設定為 None。

備註

雖然將這些值暴露給終端使用者是一種相當普遍的做法，但這些值被設計為表示相關時區的主鍵，而不一定是面向使用者的元素。像 CLDR（Unicode 通用地區資料儲存庫）這樣的專案可以用來從這些鍵中取得更友善的使用者字串。

字串表示

在 ZoneInfo 物件上呼叫 str 時回傳的字串表示，預設使用 ZoneInfo.key 屬性（參閱屬性文件中的使用說明）：

>>> zone = ZoneInfo("Pacific/Kwajalein")
>>> str(zone)
'Pacific/Kwajalein'

>>> dt = datetime(2020, 4, 1, 3, 15, tzinfo=zone)
>>> f"{dt.isoformat()} [{dt.tzinfo}]"
'2020-04-01T03:15:00+12:00 [Pacific/Kwajalein]'

對於從檔案建構且未指定 key 參數的物件，str 會轉而呼叫 repr()。ZoneInfo 的 repr 是實作定義的，且不保證在不同版本之間保持穩定，但保證它不會是一個有效的 ZoneInfo 鍵。

封裝（Pickle）序列化

ZoneInfo 物件不是序列化所有轉換資料，而是按鍵進行序列化，而從檔案建構的 ZoneInfo 物件（即使是那些指定了 key 值的物件）也無法被封裝。

ZoneInfo 檔案的行為取決於它的建構方式：

ZoneInfo(key)：當使用主要建構函式建構時，ZoneInfo 物件會按鍵序列化，而在去序列化時，去序列化過程會使用主要建構函式，因此這些物件會與指向相同時區的其他參照是同一個物件。例如，如果 europe_berlin_pkl 是一個包含從 ZoneInfo("Europe/Berlin") 建構並封裝的字串，會預期以下行為：

>>> a = ZoneInfo("Europe/Berlin")
>>> b = pickle.loads(europe_berlin_pkl)
>>> a is b
True

ZoneInfo.no_cache(key)：當從繞過快取的建構函式建構時，ZoneInfo 物件也會按鍵序列化，但在去序列化時，去序列化過程會使用繞過快取的建構函式。如果 europe_berlin_pkl_nc 是一個包含從 ZoneInfo.no_cache("Europe/Berlin") 建構並封裝的字串，會預期以下行為：

>>> a = ZoneInfo("Europe/Berlin")
>>> b = pickle.loads(europe_berlin_pkl_nc)
>>> a is b
False

ZoneInfo.from_file(file_obj, /, key=None)：當從檔案建構時，ZoneInfo 物件在封裝時會引發例外。如果終端使用者想要封裝一個從檔案建構的 ZoneInfo，建議他們使用包裝器型別或自訂序列化函式：可以按鍵序列化，或儲存檔案物件的內容並將其序列化。

這種序列化方法要求所需鍵的時區資料在序列化和去序列化兩端都可用，這與對類別和函式的參照預期存在於序列化和去序列化環境中的方式相似。這也意味著，當在具有不同版本時區資料的環境中拆封一個封裝的 ZoneInfo 時，不保證結果的一致性。

函式

zoneinfo.available_timezones()

取得一個集合，其中包含時區路徑上任何地方可用的所有 IANA 時區的有效鍵。這會在每次呼叫函式時重新計算。

此函式僅包含規範的時區名稱，不包含「特殊」時區，例如 posix/ 和 right/ 目錄下的時區，或 posixrules 時區。

警示

此函式可能會開啟大量檔案，因為確定時區路徑上的檔案是否為有效時區的最佳方法是讀取開頭的「魔術字串」。

備註

這些值並非設計來暴露給終端使用者；對於面向使用者的元素，應用程式應使用像 CLDR（Unicode 通用地區資料儲存庫）這樣的工具來取得更友善的使用者字串。另請參閱關於 ZoneInfo.key 的警示說明。

zoneinfo.reset_tzpath(to=None)

為模組設定或重設時區搜尋路徑（TZPATH）。當不帶引數呼叫時，TZPATH 會被設定為預設值。

呼叫 reset_tzpath 不會使 ZoneInfo 快取失效，因此對主要 ZoneInfo 建構函式的呼叫只會在快取未命中時才使用新的 TZPATH。

to 參數必須是一個由字串或 os.PathLike 組成的 序列，而不是一個字串，其中所有元素都必須是絕對路徑。如果傳入的不是絕對路徑，將會引發 ValueError 例外。

全域變數

zoneinfo.TZPATH

一個表示時區搜尋路徑的唯讀序列 —— 當從一個鍵建構 ZoneInfo 時，該鍵會與 TZPATH 中的每個條目結合，並使用找到的第一個檔案。

TZPATH 只能包含絕對路徑，絕不能包含相對路徑，無論如何設定。

zoneinfo.TZPATH 指向的物件可能會因應對 reset_tzpath() 的呼叫而改變，因此建議使用 zoneinfo.TZPATH，而不是從 zoneinfo 引入 TZPATH 或將一個長生命週期的變數賦值給 zoneinfo.TZPATH。

有關設定時區搜尋路徑的更多資訊，請參閱 設定資料來源。

例外與警告

exception zoneinfo.ZoneInfoNotFoundError

當建構 ZoneInfo 物件因在系統上找不到指定的鍵而失敗時引發。這是 KeyError 的一個子類別。

exception zoneinfo.InvalidTZPathWarning

當 PYTHONTZPATH 包含將被過濾掉的無效元件（例如相對路徑）時引發。

calendar --- 日曆相關函式

原始碼：Lib/calendar.py [https://github.com/python/cpython/tree/3.14/Lib/calendar.py]

這個模組讓你可以像 Unix 的 cal 程式一樣輸出日曆，並額外提供有用的日曆相關函式。這些日曆預設把週一當作一週的第一天，而週日當作最後一天（歐洲的慣例）。可以使用 setfirstweekday() 設定一週的第一天為週日 (6) 或一週的其它任一天，其中指定日期的參數是整數。相關功能參考 datetime 和 time 模組。

這個模組定義的函式和類別使用理想化的日曆，也就是公曆 (Gregorian calendar) 無限往前後兩個方向延伸。這符合 Dershowitz 和 Reingold 在「Calendrical Calculations」這本書定義的「逆推公曆」(proleptic Gregorian)，是做所有計算的基礎日曆。0 及負數年份的解讀跟 ISO 8601 標準裡規定的一樣，0 年是公元前 1 年，-1 年是公元前 2 年依此類推。

class calendar.Calendar(firstweekday=0)

建立 Calendar 物件。firstweekday 是一個指定一週第一天的整數，MONDAY 是 0（預設值），SUNDAY 是 6。

Calendar 物件提供一些方法來為日曆資料的格式化做準備。這個類別本身不做任何格式化，這是子類別的工作。

Calendar 實例有以下方法與屬性：

firstweekday

The first weekday as an integer (0--6).

This property can also be set and read using setfirstweekday() and getfirstweekday() respectively.

getfirstweekday()

Return an int for the current first weekday (0--6).

Identical to reading the firstweekday property.

setfirstweekday(firstweekday)

Set the first weekday to firstweekday, passed as an int (0--6)

Identical to setting the firstweekday property.

iterweekdays()

回傳一個以數字代表一週的每一天的疊代器 (iterator)。疊代器的第一個值和 firstweekday 屬性的值一樣。

itermonthdates(year, month)

回傳一個在 year 年 month (1--12) 月的疊代器。這個疊代器會回傳該月的所有日期（datetime.date 物件）以及在該月之前及之後用來組成完整一週的日期。

itermonthdays(year, month)

類似 itermonthdates()，回傳一個在 year 年 month 月的疊代器，但不受限於 datetime.date 的範圍。回傳的日期單純是該月當日的數字，對於該月之外的日期數字會是 0。

itermonthdays2(year, month)

類似 itermonthdates()，回傳一個在 year 年 month 月的疊代器，但不受限於 datetime.date 的範圍。回傳的日期是一個由該月當日的數字及代表週幾的數字組成的元組。

itermonthdays3(year, month)

類似 itermonthdates()，回傳一個在 year 年 month 月的疊代器，但不受限於 datetime.date 的範圍。回傳的日期是一個由年、月、日的數字組成的元組。

在 3.7 版被加入.

itermonthdays4(year, month)

類似 itermonthdates()，回傳一個在 year 年 month 月的疊代器，但不受限於 datetime.date 的範圍。回傳的日期是一個由年、月、日及代表週幾的數字組成的元組。

在 3.7 版被加入.

monthdatescalendar(year, month)

回傳一個在 year 年 month 月每一週組成的串列。每一週是一個串列，包含七個 datetime.date 物件。

monthdays2calendar(year, month)

回傳一個在 year 年 month 月每一週組成的串列。每一週是一個串列，包含七個該月當日的數字及代表週幾的數字組成的元組。

monthdayscalendar(year, month)

回傳一個在 year 年 month 月每一週組成的串列。每一週是一個串列，包含七個該月當日的數字。

yeardatescalendar(year, width=3)

回傳用來格式化的指定年份的資料。回傳值是月份列的串列，每個月份列最多由 width 個月份組成（預設為 3）。每個月份包含四到六週，每一週包含一到七天，每一天則是一個 datetime.date 物件。

yeardays2calendar(year, width=3)

回傳用來格式化的指定年份的資料（類似 yeardatescalendar()）。每一天是一個該月當日的數字及代表週幾的數字組成的元組，該月外的日期的該月當日數字為 0。

yeardayscalendar(year, width=3)

回傳用來格式化的指定年份的資料（類似 yeardatescalendar()）。每一天是一個該月當日的數字，該月外的日期的該月當日數字為 0。

class calendar.TextCalendar(firstweekday=0)

這個類別用來產生純文字的日曆。

TextCalendar 實例有以下方法：

formatday(theday, weekday, width)

Return a string representing a single day formatted with the given width. If theday is 0, return a string of spaces of the specified width, representing an empty day. The weekday parameter is unused.

formatweek(theweek, w=0)

Return a single week in a string with no newline. If w is provided, it specifies the width of the date columns, which are centered. Depends on the first weekday as specified in the constructor or set by the setfirstweekday() method.

formatweekday(weekday, width)

Return a string representing the name of a single weekday formatted to the specified width. The weekday parameter is an integer representing the day of the week, where 0 is Monday and 6 is Sunday.

formatweekheader(width)

Return a string containing the header row of weekday names, formatted with the given width for each column. The names depend on the locale settings and are padded to the specified width.

formatmonth(theyear, themonth, w=0, l=0)

以多行字串的形式回傳一個月份的日曆。如果給定 w，它會指定置中的日期欄的寬度。如果給定 l，它會指定每一週使用的行數。這個日曆會依據在建構函式中指定或者透過 setfirstweekday() 方法設定的一週的第一天來輸出。

formatmonthname(theyear, themonth, width=0, withyear=True)

Return a string representing the month's name centered within the specified width. If withyear is True, include the year in the output. The theyear and themonth parameters specify the year and month for the name to be formatted respectively.

prmonth(theyear, themonth, w=0, l=0)

印出一個月份的日曆，內容和 formatmonth() 回傳的一樣。

formatyear(theyear, w=2, l=1, c=6, m=3)

以多行字串的形式回傳有 m 欄的一整年的日曆。可選的參數 w、l 及 c 分別是日期欄寬度、每週行數及月份欄中間的空白數。這個日曆會依據在建構函式中指定或者透過 setfirstweekday() 方法設定的一週的第一天來輸出。最早可以產生日曆的年份會依據平台而不同。

pryear(theyear, w=2, l=1, c=6, m=3)

印出一整年的日曆，內容和 formatyear() 回傳的一樣。

class calendar.HTMLCalendar(firstweekday=0)

這個類別用來產生 HTML 日曆。

HTMLCalendar 實例有以下方法：

formatmonth(theyear, themonth, withyear=True)

以 HTML 表格的形式回傳一個月份的日曆。如果 withyear 是 true 則標題會包含年份，否則只會有月份名稱。

formatyear(theyear, width=3)

以 HTML 表格的形式回傳一整年的日曆。width（預設為 3）指定一列有幾個月。

formatyearpage(theyear, width=3, css='calendar.css', encoding=None)

以完整 HTML 頁面的形式回傳一整年的日曆。width（預設為 3）指定一列有幾個月。css 是要使用的 CSS (cascading style sheet) 名稱，可以給 None 表示不使用任何 CSS。encoding 指定輸出使用的編碼（預設使用系統預設編碼）。

formatmonthname(theyear, themonth, withyear=True)

以 HTML 表列的形式回傳一個月份的名稱。如果 withyear 是 true 則該列會包含年份，否則只會有月份名稱。

HTMLCalendar 可以覆寫以下屬性來客製日曆所使用的 CSS 類別：

cssclasses

對應一週每一天 CSS 類別的串列。預設的串列內容為：

cssclasses = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]

可以針對每一天增加更多樣式：

cssclasses = ["mon text-bold", "tue", "wed", "thu", "fri", "sat", "sun red"]

注意這個串列的長度必須是七個項目。

cssclass_noday

跟當月為同一週且屬於前一個或下一個月份的日期使用的 CSS 類別。

在 3.7 版被加入.

cssclasses_weekday_head

在標題列中一週每一天名稱的 CSS 類別的串列。預設內容和 cssclasses 相同。

在 3.7 版被加入.

cssclass_month_head

月份標題的 CSS 類別（由 formatmonthname() 所使用），預設值是 "month"。

在 3.7 版被加入.

cssclass_month

整個月份表格的 CSS 類別（由 formatmonth() 所使用），預設值是 "month"。

在 3.7 版被加入.

cssclass_year

整年表格的 CSS 類別（由 formatyear() 所使用），預設值是 "year"。

在 3.7 版被加入.

cssclass_year_head

整年表格標題的 CSS 類別（由 formatyear() 所使用），預設值是 "year"。

在 3.7 版被加入.

注意雖然上面提到的 CSS 屬性名稱是單數（例如 cssclass_month、cssclass_noday），你可以使用多個以空格隔開的 CSS 類別取代單一 CSS 類別，例如：

"text-bold text-red"

以下是客製化 HTMLCalendar 的範例：

class CustomHTMLCal(calendar.HTMLCalendar):
    cssclasses = [style + " text-nowrap" for style in
                  calendar.HTMLCalendar.cssclasses]
    cssclass_month_head = "text-center month-head"
    cssclass_month = "text-center month"
    cssclass_year = "text-italic lead"

class calendar.LocaleTextCalendar(firstweekday=0, locale=None)

TextCalendar 的子類別，可以在建構函式傳入語系名稱，它會回傳指定語系的月份及一週每一天的名稱。

class calendar.LocaleHTMLCalendar(firstweekday=0, locale=None)

HTMLCalendar 的子類別，可以在建構函式傳入語系名稱，它會回傳指定語系的月份及一週每一天的名稱。

備註

這兩個類別的建構函式、formatweekday() 及 formatmonthname() 方法會把 LC_TIME 語系暫時改成給定的 locale。因為目前的語系是屬於整個行程 (process-wide) 的設定，它們不是執行緒安全的。

這個模組提供以下函式給單純的文字日曆使用。

calendar.setfirstweekday(weekday)

設定一週的第一天（0 是週一、6 是週日）。提供 MONDAY、TUESDAY、WEDNESDAY、THURSDAY、FRIDAY、SATURDAY 及 SUNDAY 可以方便設定。例如設定一週的第一天為週日：

import calendar
calendar.setfirstweekday(calendar.SUNDAY)

calendar.firstweekday()

回傳目前設定的一週的第一天。

calendar.isleap(year)

如果 year 是閏年回傳 True，否則回傳 False。

calendar.leapdays(y1, y2)

回傳從 y1 到 y2（不包含）間有幾個閏年，其中 y1 和 y2 是年份。

這個函式也適用在跨越世紀的時間範圍。

calendar.weekday(year, month, day)

回傳 year 年 (1970--...) month 月 (1--12) day 日 (1--31) 是週幾（0 是星期一）。

calendar.weekheader(n)

回傳包含一週每一天的名稱縮寫的標題。n 指定每一天的字元寬度。

calendar.monthrange(year, month)

回傳指定 year 年 month 月該月第一天代表週幾的數字及該月有多少天。

calendar.monthcalendar(year, month)

回傳代表一個月份日曆的矩陣。每一列為一週；該月以外的日期以 0 表示。每一週以週一開始，除非有使用 setfirstweekday() 改變設定。

calendar.prmonth(theyear, themonth, w=0, l=0)

印出一個月份的日曆，跟 month() 回傳的內容一樣。

calendar.month(theyear, themonth, w=0, l=0)

以多行字串的形式回傳一個月的日曆，使用 TextCalendar 類別的 formatmonth()。

calendar.prcal(year, w=0, l=0, c=6, m=3)

印出一整年的日曆，跟 calendar() 回傳的內容一樣。

calendar.calendar(year, w=2, l=1, c=6, m=3)

以多行字串回傳三欄形式的一整年日曆，使用 TextCalendar 類別的 formatyear()。

calendar.timegm(tuple)

一個跟日曆無關但方便的函式，它接受一個像 time 模組裡的 gmtime() 函式回傳的元組，並回傳對應的 Unix 時間戳，假設從 1970 開始及 POSIX 編碼。事實上，time.gmtime() 和 timegm() 是彼此相反的。

calendar 模組匯出以下資料屬性：

calendar.day_name

以目前語系來表示的一週每一天名稱的序列，其中週一是第 0 天。

>>> import calendar
>>> list(calendar.day_name)
['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

calendar.day_abbr

以目前語系來表示的一週每一天縮寫名稱的序列，其中 Mon 是第 0 天。

>>> import calendar
>>> list(calendar.day_abbr)
['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']

calendar.MONDAY

calendar.TUESDAY

calendar.WEDNESDAY

calendar.THURSDAY

calendar.FRIDAY

calendar.SATURDAY

calendar.SUNDAY

一週每一天的別名，其中 MONDAY 是 0 而 SUNDAY 是 6。

在 3.12 版被加入.

class calendar.Day

將一週中的幾天定義為整數常數的列舉。此列舉的成員將作為 MONDAY 到 SUNDAY 匯出到模組作用域。

在 3.12 版被加入.

calendar.month_name

以目前語系來表示的一年每個月份名稱的序列。它按照一般慣例以數字 1 代表一月，因此它的長度為 13，而 month_name[0] 是空字串。

>>> import calendar
>>> list(calendar.month_name)
['', 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']

calendar.month_abbr

以目前語系來表示的一年每個月份縮寫名稱的序列。它按照一般慣例以數字 1 代表一月，因此它的長度為 13，而 month_abbr[0] 是空字串。

>>> import calendar
>>> list(calendar.month_abbr)
['', 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']

calendar.JANUARY

calendar.FEBRUARY

calendar.MARCH

calendar.APRIL

calendar.MAY

calendar.JUNE

calendar.JULY

calendar.AUGUST

calendar.SEPTEMBER

calendar.OCTOBER

calendar.NOVEMBER

calendar.DECEMBER

一年內每個月的別名，其中 JANUARY 是 1 而 DECEMBER 是 12。

在 3.12 版被加入.

class calendar.Month

將一年中的月份定義為整數常數的列舉。此列舉的成員將作為 JANUARY 到 DECEMBER 匯出到模組作用域。

在 3.12 版被加入.

calendar 模組定義了以下例外：

exception calendar.IllegalMonthError(month)

ValueError 的子類別，當給定的月份數字超出 1-12 範圍（含）時引發。

month

無效的月份號。

exception calendar.IllegalWeekdayError(weekday)

ValueError 的子類別，當給定的週幾的數字超出 0-6（含）範圍時引發。

weekday

無效的週幾編號。

也參考

datetime 模組

日期與時間的物件導向介面，和 time 模組有相似的功能。

time 模組

底層的時間相關函式。

命令列用法

在 2.5 版被加入.

calendar 模組可以作為腳本從命令列執行，並以互動方式列印日曆。

python -m calendar [-h] [-L LOCALE] [-e ENCODING] [-t {text,html}]
                   [-w WIDTH] [-l LINES] [-s SPACING] [-m MONTHS] [-c CSS]
                   [-f FIRST_WEEKDAY] [year] [month]

例如，要列印 2000 年的日曆：

$ python -m calendar 2000
                                  2000

      January                   February                   March
Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
                1  2          1  2  3  4  5  6             1  2  3  4  5
 3  4  5  6  7  8  9       7  8  9 10 11 12 13       6  7  8  9 10 11 12
10 11 12 13 14 15 16      14 15 16 17 18 19 20      13 14 15 16 17 18 19
17 18 19 20 21 22 23      21 22 23 24 25 26 27      20 21 22 23 24 25 26
24 25 26 27 28 29 30      28 29                     27 28 29 30 31
31

       April                      May                       June
Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
                1  2       1  2  3  4  5  6  7                1  2  3  4
 3  4  5  6  7  8  9       8  9 10 11 12 13 14       5  6  7  8  9 10 11
10 11 12 13 14 15 16      15 16 17 18 19 20 21      12 13 14 15 16 17 18
17 18 19 20 21 22 23      22 23 24 25 26 27 28      19 20 21 22 23 24 25
24 25 26 27 28 29 30      29 30 31                  26 27 28 29 30

        July                     August                  September
Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
                1  2          1  2  3  4  5  6                   1  2  3
 3  4  5  6  7  8  9       7  8  9 10 11 12 13       4  5  6  7  8  9 10
10 11 12 13 14 15 16      14 15 16 17 18 19 20      11 12 13 14 15 16 17
17 18 19 20 21 22 23      21 22 23 24 25 26 27      18 19 20 21 22 23 24
24 25 26 27 28 29 30      28 29 30 31               25 26 27 28 29 30
31

      October                   November                  December
Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
                   1             1  2  3  4  5                   1  2  3
 2  3  4  5  6  7  8       6  7  8  9 10 11 12       4  5  6  7  8  9 10
 9 10 11 12 13 14 15      13 14 15 16 17 18 19      11 12 13 14 15 16 17
16 17 18 19 20 21 22      20 21 22 23 24 25 26      18 19 20 21 22 23 24
23 24 25 26 27 28 29      27 28 29 30               25 26 27 28 29 30 31
30 31

接受以下選項：

--help, -h

顯示幫助訊息並退出。

--locale LOCALE, -L LOCALE

用於月份和週幾名稱的語系。預設為英語。

--encoding ENCODING, -e ENCODING

用於輸出的編碼。如有設定 --locale 則必須給定 --encoding。

--type {text,html}, -t {text,html}

將日曆以文字或 HTML 文件的形式印出到終端機。

--first-weekday FIRST_WEEKDAY, -f FIRST_WEEKDAY

一週起始的日子。必須是 0（週一）到 6（週日）之間的數字。預設為 0。

在 3.13 版被加入.

year

印出日曆的年份。預設為目前年份。

month

要列印日曆的指定 year 的月份。必須是 1 到 12 之間的數字，並且只能在文字模式下使用。預設列印全年日曆。

文字模式選項：

--width WIDTH, -w WIDTH

終端機行中日期行的寬度。日期印出在行的中央。任何小於 2 的值都會被忽略。預設為 2。

--lines LINES, -l LINES

終端機列中每週的列數。日期印出時頂部會對齊。任何小於 1 的值都會被忽略。預設為 1。

--spacing SPACING, -s SPACING

行中月份之間的間距。任何小於 2 的值都會被忽略。預設為 6。

--months MONTHS, -m MONTHS

每列印出的月份數量。預設為 3。

在 3.14 版的變更: By default, today's date is highlighted in color and can be controlled using environment variables.

HTML 模式選項：

--css CSS, -c CSS

用於日曆的 CSS 樣式表路徑。這必須是相對於產生之 HTML 的，或者為絕對的 HTTP 或 file:/// URL。

collections --- 容器資料型別

原始碼：Lib/collections/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/collections/__init__.py]

這個模組實作了一些特別的容器資料型別，用來替代 Python 一般內建的容器，例如 dict（字典）、list（串列）、set（集合）和 tuple（元組）。

namedtuple()

用來建立具名欄位的 tuple 子類別的工廠函式

deque

一個類似 list 的容器，可以快速的在頭尾加入 (append) 元素與移除 (pop) 元素

ChainMap

一個類似 dict 的類別，用來為多個對映 (mapping) 建立單一的視圖 (view)

Counter

dict 的子類別，用來計算可雜湊物件的數量

OrderedDict

dict 的子類別，會記錄物件被加入的順序

defaultdict

dict 的子類別，當值不存在 dict 中時會呼叫一個提供預設值的工廠函式

UserDict

dict 物件的包裝器 (wrapper)，簡化了 dict 的子類別化過程

UserList

list 物件的包裝器，簡化了 list 的子類別化過程

UserString

字串物件的包裝器，簡化了字串的子類別化過程

ChainMap 物件

在 3.3 版被加入.

ChainMap（對映鏈結）類別的目的是快速將數個對映連結在一起，讓它們可以被當作一個單元來處理。它通常會比建立一個新的字典並多次呼叫 update() 來得更快。

這個類別可用於模擬巢狀作用域 (nested scopes)，且在模板化 (templating) 時能派上用場。

class collections.ChainMap(*maps)

一個 ChainMap 將多個 dict 或其他對映組合在一起，建立一個獨立、可更新的視圖。如果沒有指定 maps，預設會提供一個空字典讓每個新鏈結都至少有一個對映。

底層的對映儲存於一個 list 中，這個 list 是公開的且可透過 maps 屬性存取或更新，沒有其他狀態 (state)。

檢索 (lookup) 陸續查詢底層對映，直到鍵被找到，然而讀取、更新和刪除就只會對第一個對映操作。

ChainMap 透過參照將底層對映合併，所以當一個底層對映被更新，這些改變也會反映到 ChainMap。

所有常見的字典方法都有支援。此外，還有一個 maps 屬性 (attribute)、一個建立子上下文 (subcontext) 的方法、和一個能夠存取除了第一個以外其他所有對映的特性 (property)：

maps

一個可被更新的對映列表，這個列表是按照被搜尋的順序來排列，在 ChainMap 中它是唯一被儲存的狀態，可被修改來變換搜尋順序。回傳的列表都至少包含一個對映。

new_child(m=None, **kwargs)

回傳包含一個新對映的 ChainMap， 新對映後面接著目前實例的所有現存對映。如果有給定 m，m 會成為那個最前面的新對映；若沒有指定，則會加上一個空 dict，如此一來呼叫 d.new_child() 就等同於 ChainMap({}, *d.maps)。這個方法用於建立子上下文，而保持父對映的不變。

在 3.4 版的變更: 加入可選參數 m。

在 3.10 版的變更: 增加了對關鍵字引數的支援。

parents

回傳一個包含除了第一個以外所有其他對映的新 ChainMap 的特性，可用於需要跳過第一個對映的搜尋。使用情境類似於在巢狀作用域當中使用 nonlocal 關鍵字，也可與內建函式 super() 做類比。引用 d.parents 等同於 ChainMap(*d.maps[1:])。

注意，一個 ChainMap 的疊代順序是透過由後往前掃描對映而定：

>>> baseline = {'music': 'bach', 'art': 'rembrandt'}
>>> adjustments = {'art': 'van gogh', 'opera': 'carmen'}
>>> list(ChainMap(adjustments, baseline))
['music', 'art', 'opera']

這和呼叫 dict.update() 結果的順序一樣是從最後一個對映開始：

>>> combined = baseline.copy()
>>> combined.update(adjustments)
>>> list(combined)
['music', 'art', 'opera']

在 3.9 版的變更: 支援 | 和 |= 運算子，詳見 PEP 584 [https://peps.python.org/pep-0584/]。

也參考

Enthought CodeTools package [https://github.com/enthought/codetools] 中的 MultiContext class [https://github.com/enthought/codetools/blob/4.0.0/codetools/contexts/multi_context.py] 支援在鏈中選定任意對映寫入。

Django 中用於模板的 Context class [https://github.com/django/django/blob/main/django/template/context.py] 是唯讀的對映鏈，也具有加入 (push) 和移除 (pop) 上下文的功能，與 new_child() 方法和 parents 特性類似。

Nested Contexts recipe [https://code.activestate.com/recipes/577434-nested-contexts-a-chain-of-mapping-objects/] 提供了控制是否只對鏈中第一個或其他對映做寫入或其他操作的選項。

一個極度簡化、維讀版本的 Chainmap [https://code.activestate.com/recipes/305268/]。

ChainMap 範例和用法

此章節提供了多種操作 ChainMap 的案例。

模擬 Python 內部檢索鏈結的例子：

import builtins
pylookup = ChainMap(locals(), globals(), vars(builtins))

讓使用者指定的命令列引數優先於環境變數、再優先於預設值的範例：

import os, argparse

defaults = {'color': 'red', 'user': 'guest'}

parser = argparse.ArgumentParser()
parser.add_argument('-u', '--user')
parser.add_argument('-c', '--color')
namespace = parser.parse_args()
command_line_args = {k: v for k, v in vars(namespace).items() if v is not None}

combined = ChainMap(command_line_args, os.environ, defaults)
print(combined['color'])
print(combined['user'])

用 ChainMap 類別模擬巢狀上下文的範例模式：

c = ChainMap()        # Create root context
d = c.new_child()     # Create nested child context
e = c.new_child()     # Child of c, independent from d
e.maps[0]             # Current context dictionary -- like Python's locals()
e.maps[-1]            # Root context -- like Python's globals()
e.parents             # Enclosing context chain -- like Python's nonlocals

d['x'] = 1            # Set value in current context
d['x']                # Get first key in the chain of contexts
del d['x']            # Delete from current context
list(d)               # All nested values
k in d                # Check all nested values
len(d)                # Number of nested values
d.items()             # All nested items
dict(d)               # Flatten into a regular dictionary

ChainMap 類別只對鏈結中第一個對映來做寫入或刪除，但檢索則會掃過整個鏈結。但如果需要對更深層的鍵寫入或刪除，透過定義一個子類別來實作也不困難：

class DeepChainMap(ChainMap):
    'Variant of ChainMap that allows direct updates to inner scopes'

    def __setitem__(self, key, value):
        for mapping in self.maps:
            if key in mapping:
                mapping[key] = value
                return
        self.maps[0][key] = value

    def __delitem__(self, key):
        for mapping in self.maps:
            if key in mapping:
                del mapping[key]
                return
        raise KeyError(key)

>>> d = DeepChainMap({'zebra': 'black'}, {'elephant': 'blue'}, {'lion': 'yellow'})
>>> d['lion'] = 'orange'         # update an existing key two levels down
>>> d['snake'] = 'red'           # new keys get added to the topmost dict
>>> del d['elephant']            # remove an existing key one level down
>>> d                            # display result
DeepChainMap({'zebra': 'black', 'snake': 'red'}, {}, {'lion': 'orange'})

Counter 物件

提供一個支援方便且快速計數的計數器工具，例如：

>>> # Tally occurrences of words in a list
>>> cnt = Counter()
>>> for word in ['red', 'blue', 'red', 'green', 'blue', 'blue']:
...     cnt[word] += 1
...
>>> cnt
Counter({'blue': 3, 'red': 2, 'green': 1})

>>> # Find the ten most common words in Hamlet
>>> import re
>>> words = re.findall(r'\w+', open('hamlet.txt').read().lower())
>>> Counter(words).most_common(10)
[('the', 1143), ('and', 966), ('to', 762), ('of', 669), ('i', 631),
 ('you', 554),  ('a', 546), ('my', 514), ('hamlet', 471), ('in', 451)]

class collections.Counter([iterable-or-mapping])

Counter 是 dict 的子類別，用來計算可雜湊物件的數量。它是將物件與其計數作為字典的鍵值對儲存的集合容器。計數可以是包含 0 與負數的任何整數值。Counter 類別類似其他程式語言中的 bags 或 multisets。

被計數的元素來自一個 iterable 或是被其他的 mapping（或 Counter）初始化：

>>> c = Counter()                           # a new, empty counter
>>> c = Counter('gallahad')                 # a new counter from an iterable
>>> c = Counter({'red': 4, 'blue': 2})      # a new counter from a mapping
>>> c = Counter(cats=4, dogs=8)             # a new counter from keyword args

Counter 物件擁有一個字典的使用介面，除了遇到 Counter 中沒有的值時會回傳計數 0 取代 KeyError 這點不同：

>>> c = Counter(['eggs', 'ham'])
>>> c['bacon']                              # count of a missing element is zero
0

將一個值的計數設為 0 並不會真的從 Counter 中刪除這個元素，要使用 del 來將其刪除：

>>> c['sausage'] = 0                        # counter entry with a zero count
>>> del c['sausage']                        # del actually removes the entry

在 3.1 版被加入.

在 3.7 版的變更: 作為 dict 的子類別，Counter 繼承了記憶插入順序的功能。對 Counter 做數學運算後同樣保留順序性，其結果是依照各個元素在運算元左邊出現的時間先後、再按照運算元右邊出現的時間先後來排列。

除了字典原本就有的方法外，Counter 物件額外支援數個新方法：

elements()

回傳每個元素都重複出現計算次數的 iterator（疊代器）物件，其中元素的回傳順序是依照各元素首次出現的時間先後。如果元素的出現次數小於 1，elements() 方法會忽略這些元素。

>>> c = Counter(a=4, b=2, c=0, d=-2)
>>> sorted(c.elements())
['a', 'a', 'a', 'a', 'b', 'b']

most_common([n])

回傳一個 list，包含出現最多次的 n 個元素及其出現次數，並按照出現次數排序。如果 n 被省略或者為 None，most_common() 會回傳所有 counter 中的元素。出現次數相同的元素會按照首次出現的時間先後來排列：

>>> Counter('abracadabra').most_common(3)
[('a', 5), ('b', 2), ('r', 2)]

subtract([iterable-or-mapping])

減去自一個 iterable 或另一個對映（或 Counter）中的計數元素，行為類似 dict.update() 但是是為了減去計數而非取代其值。輸入和輸出都可以是 0 或是負數。

>>> c = Counter(a=4, b=2, c=0, d=-2)
>>> d = Counter(a=1, b=2, c=3, d=4)
>>> c.subtract(d)
>>> c
Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6})

在 3.2 版被加入.

total()

計算總計數值。

>>> c = Counter(a=10, b=5, c=0)
>>> c.total()
15

在 3.10 版被加入.

通常來說字典方法也可以用於 Counter 物件，除了以下兩個作用方式與計數器不同。

fromkeys(iterable)

此類別方法沒有被實作於 Counter 物件中。

update([iterable-or-mapping])

加上自一個 iterable 計算出的計數或加上另一個 mapping（或 Counter）中的計數，行為類似 dict.update() 但是是為了加上計數而非取代其值。另外，iterable 需要是一串將被計算個數元素的序列，而非元素為 (key, value) 形式的序列。

Counter 支援相等性、子集和超集關係的 rich comparison 運算子：==、!=、<、<=、>、>=。這些檢測會將不存在的元素之計數值當作零，因此 Counter(a=1) == Counter(a=1, b=0) 將回傳真值。

在 3.10 版的變更: 增加了 rich comparison 運算。

在 3.10 版的變更: 在相等性運算中，不存在的元素之計數值會被當作零。在此之前，Counter(a=3) 和 Counter(a=3, b=0) 被視為不同。

使用 Counter 物件的常見使用模式：

c.total()                       # total of all counts
c.clear()                       # reset all counts
list(c)                         # list unique elements
set(c)                          # convert to a set
dict(c)                         # convert to a regular dictionary
c.items()                       # access the (elem, cnt) pairs
Counter(dict(list_of_pairs))    # convert from a list of (elem, cnt) pairs
c.most_common()[:-n-1:-1]       # n least common elements
+c                              # remove zero and negative counts

為結合多個 Counter 物件以產生 multiset（多重集合，擁有大於 0 計數元素的計數器），有提供了幾種數學操作。加法和減法是根據各個對應元素分別將 Counter 加上和減去計數，交集和聯集分別回傳各個元素最小和最大計數，相等性與包含性運算則會比較對應的計數。每一個操作都可以接受輸入帶有正負號的計數，但輸出的 Counter 則會將擁有小於或等於 0 計數的元素剔除。

>>> c = Counter(a=3, b=1)
>>> d = Counter(a=1, b=2)
>>> c + d                       # add two counters together:  c[x] + d[x]
Counter({'a': 4, 'b': 3})
>>> c - d                       # subtract (keeping only positive counts)
Counter({'a': 2})
>>> c & d                       # intersection:  min(c[x], d[x])
Counter({'a': 1, 'b': 1})
>>> c | d                       # union:  max(c[x], d[x])
Counter({'a': 3, 'b': 2})
>>> c == d                      # equality:  c[x] == d[x]
False
>>> c <= d                      # inclusion:  c[x] <= d[x]
False

加減法的一元運算子分別是加上空的 Counter 和從空 Counter 減去的簡寫。

>>> c = Counter(a=2, b=-4)
>>> +c
Counter({'a': 2})
>>> -c
Counter({'b': 4})

在 3.3 版被加入: 開始支援加減一元運算子和 multiset 的原地 (in-place) 操作。

備註

Counter 主要是被設計來操作正整數以當作使用中的計數，但為了某些會用到計數之值為負數或為其他型別的案例中，Counter 也小心地被設計成不會預先排除這些特殊元素。為了輔助使用於上述案例，這一小節記錄了最小範圍和型別限制。

Counter 類別本身是字典的子類別，且不限制其鍵與值。值被用來表示計數，但實際上你可以儲存任何值。

使用 most_common() 方法的唯一條件是其值要是可被排序的。

像是 c[key] += 1 的原地操作中，其值之型別只必須支援加減，所以分數、浮點數、十進位數與其負值都可以使用。同理，update() 和 subtract() 也都允許 0 或負值為輸入或輸出。

Multiset 相關方法只為了處理正值而設計，其輸入允許是 0 或負值但只有正值會被輸出。並無型別限制，但其值的型別須支援加、減及比較運算。

elements() 方法需要其計數為正值，如為 0 或負值則忽略。

也參考

Smalltalk 中的 Bag class [https://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html]。

維基百科上的多重集合 [https://en.wikipedia.org/wiki/Multiset]條目。

C++ multisets [http://www.java2s.com/Tutorial/Cpp/0380__set-multiset/Catalog0380__set-multiset.htm] 教學與範例。

Multiset 的數學運算及其使用時機，參考 Knuth, Donald. The Art of Computer Programming Volume II, Section 4.6.3, Exercise 19。

若要根據給定的元素集合來列舉出所有不重複且擁有指定元素數量的 multiset，請見 itertools.combinations_with_replacement()：

map(Counter, combinations_with_replacement('ABC', 2)) # --> AA AB AC BB BC CC

deque 物件

class collections.deque([iterable[, maxlen]])

回傳一個新的 deque（雙端佇列）物件，將 iterable 中的資料由左至右（使用 append()）加入來做初始化。如果 iterable 並未給定，回傳的則是一個空的 deque。

Deque（發音為 "deck"，為 "double-ended queue" 的簡稱）為 stack 和 queue 的一般化。deque 支援執行緒安全 (thread-safe)，且能夠有效率地節省記憶體在頭和尾加入和移除元素，兩個方向的表現都大致為 O(1) 複雜度。

雖然 list 物件也支援類似操作，但 list 優化了長度固定時的操作，而會改變底層資料的長度及位置的 pop(0) 和 insert(0, v) 操作，記憶體移動則為 O(n) 複雜度。

如果 maxlen 沒有給定或者為 None，deque 可以增長到任意長度；但若有給定的話，deque 的最大長度就會被限制。一個被限制長度的 deque 一但滿了，若在一端加入數個新元素，則同時會在另一端移除相同數量的元素。限定長度的 deque 提供了和 Unix tail filter 類似的功能，可用於追蹤使用者在意的那些最新執行事項或數據源。

Deque 物件支援以下方法：

append(x)

將 x 自 deque 的右側加入。

appendleft(x)

將 x 自 deque 的左側加入。

clear()

將所有元素從 deque 中移除，使其長度為 0。

copy()

建立一個 deque 的淺複製 (shallow copy)。

在 3.5 版被加入.

count(x)

計算 deque 內元素為 x 的個數。

在 3.2 版被加入.

extend(iterable)

將 iterable 引數加入 deque 的右側。

extendleft(iterable)

將 iterable 引數加入 deque 的左側。要注意的是，加入後的元素順序和 iterable 參數是相反的。

index(x[, start[, stop]])

回傳 deque 中 x 的位置（或在索引 start 之後、索引 stop 之前的位置）。回傳第一個匹配的位置，如果沒找到就引發 ValueError。

在 3.5 版被加入.

insert(i, x)

在 deque 位置 i 中插入 x。

如果此插入操作導致 deque 超過其長度上限 maxlen 的話，會引發 IndexError 例外。

在 3.5 版被加入.

pop()

移除並回傳 deque 的最右側元素，若本來就沒有任何元素，則會引發 IndexError。

popleft()

移除並回傳 deque 的最左側元素，若本來就沒有任何元素，則會引發 IndexError。

remove(value)

移除第一個出現的 value，如果沒找到的話就引發一個 ValueError。

reverse()

將 deque 中的元素原地 (in-place) 倒序排列並回傳 None。

在 3.2 版被加入.

rotate(n=1)

將 deque 向右輪轉 n 步。若 n 為負值則向左輪轉。

當 deque 不是空的，向右輪轉一步和 d.appendleft(d.pop()) 有相同意義，而向左輪轉亦等價於 d.append(d.popleft())。

Deque 物件也提供了一個唯讀屬性：

maxlen

Deque 的最大長度，如果不限制長度的話則為 None。

在 3.1 版被加入.

除了以上使用方式，deque 亦支援了疊代、pickle、len(d)、reversed(d)、copy.copy(d)、copy.deepcopy(d)、用 in 運算子來作隸屬資格檢測以及像是 d[0] 的標號引用來取得第一個元素。在兩端做索引存取的複雜度為 O(1) 但越靠近中間則減慢至 O(n)。若想要隨機而快速的存取，使用 list 會較為合適。

自從 3.5 版本起，deque 開始支援 __add__()、__mul__() 和 __imul__()。

範例：

>>> from collections import deque
>>> d = deque('ghi')                 # make a new deque with three items
>>> for elem in d:                   # iterate over the deque's elements
...     print(elem.upper())
G
H
I

>>> d.append('j')                    # add a new entry to the right side
>>> d.appendleft('f')                # add a new entry to the left side
>>> d                                # show the representation of the deque
deque(['f', 'g', 'h', 'i', 'j'])

>>> d.pop()                          # return and remove the rightmost item
'j'
>>> d.popleft()                      # return and remove the leftmost item
'f'
>>> list(d)                          # list the contents of the deque
['g', 'h', 'i']
>>> d[0]                             # peek at leftmost item
'g'
>>> d[-1]                            # peek at rightmost item
'i'

>>> list(reversed(d))                # list the contents of a deque in reverse
['i', 'h', 'g']
>>> 'h' in d                         # search the deque
True
>>> d.extend('jkl')                  # add multiple elements at once
>>> d
deque(['g', 'h', 'i', 'j', 'k', 'l'])
>>> d.rotate(1)                      # right rotation
>>> d
deque(['l', 'g', 'h', 'i', 'j', 'k'])
>>> d.rotate(-1)                     # left rotation
>>> d
deque(['g', 'h', 'i', 'j', 'k', 'l'])

>>> deque(reversed(d))               # make a new deque in reverse order
deque(['l', 'k', 'j', 'i', 'h', 'g'])
>>> d.clear()                        # empty the deque
>>> d.pop()                          # cannot pop from an empty deque
Traceback (most recent call last):
    File "<pyshell#6>", line 1, in -toplevel-
        d.pop()
IndexError: pop from an empty deque

>>> d.extendleft('abc')              # extendleft() reverses the input order
>>> d
deque(['c', 'b', 'a'])

deque 用法

這一章節提供了多種操作 deque 的案例。

被限制長度的 deque 功能類似 Unix 中的 tail filter：

def tail(filename, n=10):
    '回傳檔案的最後 n 行'
    with open(filename) as f:
        return deque(f, n)

另一用法是透過從右邊加入、從左邊移除來維護最近加入元素的 list：

def moving_average(iterable, n=3):
    # moving_average([40, 30, 50, 46, 39, 44]) --> 40.0 42.0 45.0 43.0
    # https://en.wikipedia.org/wiki/Moving_average
    it = iter(iterable)
    d = deque(itertools.islice(it, n-1))
    d.appendleft(0)
    s = sum(d)
    for elem in it:
        s += elem - d.popleft()
        d.append(elem)
        yield s / n

一個輪詢調度器 [https://en.wikipedia.org/wiki/Round-robin_scheduling]可以透過在 deque 中放入 iterator 來實現，值自目前 iterator 的位置 0 取出，如果 iterator 已經消耗完畢就用 popleft() 將其從佇列中移除，否則利用 rotate() 來將其移至佇列尾端：

def roundrobin(*iterables):
    "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
    iterators = deque(map(iter, iterables))
    while iterators:
        try:
            while True:
                yield next(iterators[0])
                iterators.rotate(-1)
        except StopIteration:
            # 移除耗盡的疊代器。
            iterators.popleft()

rotate() 提供了可以用來實作 deque 切片和刪除的方法。舉例來說，用純 Python 實作 del d[n] 需要用 rotate() 來定位要被移除的元素：

def delete_nth(d, n):
    d.rotate(-n)
    d.popleft()
    d.rotate(n)

要實現 deque 切片，可使用近似以下方法：使用 rotate() 來將目標元素移動到 deque 最左側，用 popleft() 移除舊元素並用 extend() 加入新元素，最後再反向 rotate。在這個方法上做小小的更動就能簡單地實現 Forth 風格的 stack 操作，例如 dup、drop、swap、over、pick、rot 和 roll。

defaultdict 物件

class collections.defaultdict(default_factory=None, /[, ...])

回傳一個新的類似字典的物件。defaultdict 是內建類別 dict 的子類別。它覆蓋掉了一個方法並添加了一個可寫入的實例變數。其餘功能與 dict 相同，此文件不再複述。

第一個引數為 default_factory 屬性提供了初始值，他被預設為 None，所有其他的引數（包括關鍵字引數）都會被傳遞給 dict 的建構函式 (constructor)。

defaultdict 物件支援以下 dict 所沒有的方法：

__missing__(key)

如果 default_factory 屬性為 None，呼叫此方法會引發一個附帶引數 key 的 KeyError 例外。

如果 default_factory 不為 None，它會不帶引數地被呼叫來為給定的 key 提供一個預設值，這個值和 key 被作為鍵值對來插入到字典中，並且被此方法所回傳。

如果呼叫 default_factory 時發生例外，則該例外將會保持不變地向外傳遞。

在無法找到所要求的鍵時，此方法會被 dict 類別的 __getitem__() 方法呼叫。無論此方法回傳了值還是引發了例外，都會被 __getitem__() 所傳遞。

注意，__missing__() 不會被 __getitem__() 以外的其他方法呼叫，這意味著 get() 會像一般的 dict 那樣回傳 None 做為預設值，而非使用 default_factory。

defaultdict 物件支援以下實例變數：

default_factory

此屬性為 __missing__() 方法所使用。如果有引數被傳入建構函式，則此屬性會被初始化成第一個引數，如未提供引數則被初始化為 None。

在 3.9 版的變更: 新增合併 (|) 和更新 (|=) 運算子，請見 PEP 584 [https://peps.python.org/pep-0584/]。

defaultdict 範例

使用 list 作為 default_factory 可以很輕鬆地將鍵值對序列轉換為包含 list 之字典：

>>> s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
>>> d = defaultdict(list)
>>> for k, v in s:
...     d[k].append(v)
...
>>> sorted(d.items())
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]

當每個鍵第一次被存取時，它還沒有存在於對映中，所以會自動呼叫 default_factory 方法來回傳一個空的 list 以建立一個條目，list.append() 操作後續會再新增值到這個新的列表裡。當再次存取該鍵時，就如普通字典般操作（回傳該鍵所對應到的 list），list.append() 也會新增另一個值到 list 中。和使用與其等價的 dict.setdefault() 相比，這個技巧更加快速和簡單：

>>> d = {}
>>> for k, v in s:
...     d.setdefault(k, []).append(v)
...
>>> sorted(d.items())
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]

設定 default_factory 為 int 使得 defaultdict 可被用於計數（類似其他語言中的 bag 或 multiset）：

>>> s = 'mississippi'
>>> d = defaultdict(int)
>>> for k in s:
...     d[k] += 1
...
>>> sorted(d.items())
[('i', 4), ('m', 1), ('p', 2), ('s', 4)]

當一個字母首次被存取時，它並不存在於對映中，則 default_factory 函式會呼叫 int() 來提供一個整數 0 作為預設值。後續的增加操作繼續對每個字母做計數。

函式 int() 總是回傳 0，這是常數函式的特殊情況。一個更快、更有彈性的方法是使用 lambda 函式來提供任何常數值（不用一定要是 0）：

>>> def constant_factory(value):
...     return lambda: value
...
>>> d = defaultdict(constant_factory('<missing>'))
>>> d.update(name='John', action='ran')
>>> '%(name)s %(action)s to %(object)s' % d
'John ran to <missing>'

將 default_factory 設為 set 使 defaultdict 可用於構建一個值為 set 的字典：

>>> s = [('red', 1), ('blue', 2), ('red', 3), ('blue', 4), ('red', 1), ('blue', 4)]
>>> d = defaultdict(set)
>>> for k, v in s:
...     d[k].add(v)
...
>>> sorted(d.items())
[('blue', {2, 4}), ('red', {1, 3})]

namedtuple() 擁有具名欄位之 tuple 的工廠函式

Named tuple（具名元組）賦予 tuple 中各個位置意義，使程式碼更有可讀性與自我文件性。它們可以用於任何普通 tuple 可使用的場合，賦予其透過名稱（而非位置索引）來存取欄位的能力。

collections.namedtuple(typename, field_names, *, rename=False, defaults=None, module=None)

回傳一個名為 typename 的新 tuple 子類別。這個新的子類別被用於建立類似 tuple 的物件，可以透過屬性名稱來存取欄位，它同時也是可索引 (indexable) 和可疊代的 (iterable)。子類別實例同樣有文件字串 (docstring)（有類別名稱 typename 和欄位名 field_names）和一個好用的 __repr__() 方法，可將 tuple 內容以 name=value 格式列出。

field_names 是一個像 ['x', 'y'] 一樣的字串序列。field_names 也可以是一個用空白或逗號分隔各個欄位名稱的字串，比如 'x y' 或者 'x, y'。

除了底線開頭以外的其他任何有效 Python 識別字 (identifier) 都可以作為欄位名稱，有效識別字由字母、數字、底線所組成，但不能是數字或底線開頭，也不能是關鍵詞 keyword，例如 class、for、return、global、pass 或 raise。

如果 rename 為真值，無效的欄位名稱會自動被位置名稱取代。比如 ['abc', 'def', 'ghi', 'abc'] 會被轉換成 ['abc', '_1', 'ghi', '_3']，移除了關鍵字 def 和重複欄位名 abc。

defaults 可以為 None 或者是一個預設值的 iterable。因為有預設值的欄位必須出現在那些沒有預設值的欄位之後，defaults 是被應用在右側的引數。例如 fieldnames 為 ['x', 'y', 'z'] 且 defaults 為 (1, 2)，那麼 x 就必須被給定一個引數，y 被預設為 1，z 則被預設為 2。

如果 module 值有被定義，named tuple 的 __module__ 屬性就被設定為該值。

Named tuple 實例中沒有字典，所以它們更加輕量，且和一般 tuple 相比佔用更少記憶體。

要支援 pickle，應將 named tuple 類別賦值給一個符合 typename 的變數。

在 3.1 版的變更: 新增對於 rename 的支援。

在 3.6 版的變更: verbose 和 rename 參數成為僅限關鍵字引數。

在 3.6 版的變更: 新增 module 參數。

在 3.7 版的變更: 移除 verbose 參數和 _source 屬性。

在 3.7 版的變更: 新增 defaults 參數和 _field_defaults 屬性。

>>> # Basic example
>>> Point = namedtuple('Point', ['x', 'y'])
>>> p = Point(11, y=22)     # instantiate with positional or keyword arguments
>>> p[0] + p[1]             # indexable like the plain tuple (11, 22)
33
>>> x, y = p                # unpack like a regular tuple
>>> x, y
(11, 22)
>>> p.x + p.y               # fields also accessible by name
33
>>> p                       # readable __repr__ with a name=value style
Point(x=11, y=22)

Named tuple 在賦予欄位名稱於 csv 或 sqlite3 模組回傳之 tuple 時相當有用：

EmployeeRecord = namedtuple('EmployeeRecord', 'name, age, title, department, paygrade')

import csv
for emp in map(EmployeeRecord._make, csv.reader(open("employees.csv", "rb"))):
    print(emp.name, emp.title)

import sqlite3
conn = sqlite3.connect('/companydata')
cursor = conn.cursor()
cursor.execute('SELECT name, age, title, department, paygrade FROM employees')
for emp in map(EmployeeRecord._make, cursor.fetchall()):
    print(emp.name, emp.title)

除了繼承自 tuple 的方法，named tuple 還支援三個額外的方法和兩個屬性。為了防止欄位名稱有衝突，方法和屬性的名稱以底線開頭。

classmethod somenamedtuple._make(iterable)

從已存在的序列或可疊代物件建立一個新實例的類別方法。

>>> t = [11, 22]
>>> Point._make(t)
Point(x=11, y=22)

somenamedtuple._asdict()

回傳一個將欄位名稱對映至對應值的 dict：

>>> p = Point(x=11, y=22)
>>> p._asdict()
{'x': 11, 'y': 22}

在 3.1 版的變更: 回傳一個 OrderedDict 而非 dict。

在 3.8 版的變更: 回傳一個常規 dict 而非 OrderedDict，自從 Python 3.7 開始，dict 已經保證有順序性，如果需要 OrderedDict 所專屬的特性，推薦的解法是將結果專換成所需的類型：OrderedDict(nt._asdict())。

somenamedtuple._replace(**kwargs)

回傳一個新的 named tuple 實例，並將指定欄位替換為新的值：

>>> p = Point(x=11, y=22)
>>> p._replace(x=33)
Point(x=33, y=22)

>>> for partnum, record in inventory.items():
...     inventory[partnum] = record._replace(price=newprices[partnum], timestamp=time.now())

Named tuples are also supported by generic function copy.replace().

在 3.13 版的變更: Raise TypeError instead of ValueError for invalid keyword arguments.

somenamedtuple._fields

列出 tuple 欄位名稱的字串，用於自我檢查或是從現有 named tuple 建立一個新的 named tuple 型別。

>>> p._fields            # 查看欄位名稱
('x', 'y')

>>> Color = namedtuple('Color', 'red green blue')
>>> Pixel = namedtuple('Pixel', Point._fields + Color._fields)
>>> Pixel(11, 22, 128, 255, 0)
Pixel(x=11, y=22, red=128, green=255, blue=0)

somenamedtuple._field_defaults

將欄位名稱對映至預設值的字典。

>>> Account = namedtuple('Account', ['type', 'balance'], defaults=[0])
>>> Account._field_defaults
{'balance': 0}
>>> Account('premium')
Account(type='premium', balance=0)

要取得這個名稱存於字串的欄位，要使用 getattr() 函式：

>>> getattr(p, 'x')
11

（如拆解引數列表（Unpacking Argument Lists）所述）將一個字典轉換成 named tuple，要使用 ** 雙星號運算子：

>>> d = {'x': 11, 'y': 22}
>>> Point(**d)
Point(x=11, y=22)

因為一個 named tuple 是一個常規的 Python 類別，我們可以很容易的透過子類別來新增或更改功能，以下是如何新增一個計算得到的欄位和固定寬度的輸出列印格式：

>>> class Point(namedtuple('Point', ['x', 'y'])):
...     __slots__ = ()
...     @property
...     def hypot(self):
...         return (self.x ** 2 + self.y ** 2) ** 0.5
...     def __str__(self):
...         return 'Point: x=%6.3f  y=%6.3f  hypot=%6.3f' % (self.x, self.y, self.hypot)

>>> for p in Point(3, 4), Point(14, 5/7):
...     print(p)
Point: x= 3.000  y= 4.000  hypot= 5.000
Point: x=14.000  y= 0.714  hypot=14.018

上面的子類別將 __slots__ 設定為空 tuple，這樣一來就防止了字典實例被建立，因而保持了較低的記憶體用量。

子類別化無法用於增加新的、已被儲存的欄位，應當透過 _fields 屬性以建立一個新的 named tuple 來實現：

>>> Point3D = namedtuple('Point3D', Point._fields + ('z',))

透過直接賦值給 __doc__，可以自訂說明文件字串：

>>> Book = namedtuple('Book', ['id', 'title', 'authors'])
>>> Book.__doc__ += ': Hardcover book in active collection'
>>> Book.id.__doc__ = '13-digit ISBN'
>>> Book.title.__doc__ = 'Title of first printing'
>>> Book.authors.__doc__ = 'List of authors sorted by last name'

在 3.5 版的變更: 文件字串屬性變成可寫入。

也參考

關於為 named tuple 新增型別提示的方法，請參閱 typing.NamedTuple，它運用 class 關鍵字以提供了一個簡潔的表示法：

class Component(NamedTuple):
    part_number: int
    weight: float
    description: Optional[str] = None

關於以 dict 而非 tuple 為底層的可變命名空間，請參考 types.SimpleNamespace()。

dataclasses 模組提供了一個裝飾器和一些函式，用於自動將被生成的特殊方法新增到使用者定義的類別中。

OrderedDict 物件

Ordered dictionary（有序字典）就像常規字典一樣，但有一些與排序操作相關的額外功能，但由於內建的 dict 類別現在已經有記憶插入順序的能力（Python 3.7 中確保了這種新行為），它們變得不那麼重要了。

仍存在一些與 dict 的不同之處：

常規的 dict 被設計成非常擅長於對映相關操作，追蹤插入的順序為次要目標。

OrderedDict 則被設計成擅長於重新排序相關的操作，空間效率、疊代速度和更新操作的效能則為次要設計目標。

OrderedDict 比起 dict 更適合處理頻繁的重新排序操作，如在下方用法中所示，這讓它適合用於多種 LRU cache 的實作中。

OrderedDict 之相等性運算會檢查順序是否相同。

一個一般的 dict 可以用 p == q and all(k1 == k2 for k1, k2 in zip(p, q)) 來效仿有檢查順序的相等性運算。

OrderedDict 類別的 popitem() 方法有不同的函式簽名 (signature)，它接受傳入一個選擇性引數來指定要移除哪個元素。

一個一般的 dict 可以用 d.popitem() 來效仿 OrderedDict 的 od.popitem(last=True)，這保證會移除最右邊（最後一個）的元素。

一個一般的 dict 可以用 (k := next(iter(d)), d.pop(k)) 來效仿 OrderedDict 的 od.popitem(last=False)，若最左邊（第一個）的元素存在，則將其回傳並移除。

OrderedDict 有個 move_to_end() 方法可有效率地將一個元素重新排列到任一端。

一個一般的 dict 可以用 d[k] = d.pop(k) 來效仿 OrderedDict 的 od.move_to_end(k, last=True)，這會將該鍵與其對應到的值移動至最右（最後面）的位置。

一個一般的 dict 沒有和 OrderedDict 的 od.move_to_end(k, last=False) 等價的有效方式，這是將鍵與其對應到的值移動至最左（最前面）位置的方法。

在 Python 3.8 之前，dict 並沒有 __reversed__() 方法。

class collections.OrderedDict([items])

回傳一個 dict 子類別的實例，它具有專門用於重新排列字典順序的方法。

在 3.1 版被加入.

popitem(last=True)

Ordered dictionary 的 popitem() 方法移除並回傳一個鍵值 (key, value) 對。如果 last 為真值，則按 LIFO 後進先出的順序回傳鍵值對，否則就按 FIFO 先進先出的順序回傳鍵值對。

move_to_end(key, last=True)

將現有的 key 移動到 ordered dictionary 的任一端。如果 last 為真值（此為預設值）則將元素移至右端；如果 last 為假值則將元素移至左端。如果 key 不存在則會引發 KeyError：

>>> d = OrderedDict.fromkeys('abcde')
>>> d.move_to_end('b')
>>> ''.join(d)
'acdeb'
>>> d.move_to_end('b', last=False)
>>> ''.join(d)
'bacde'

在 3.2 版被加入.

除了普通的對映方法，ordered dictionary 還支援了透過 reversed() 來做倒序疊代。

OrderedDict 物件之間的相等性運算是會檢查順序是否相同的，大致等價於 list(od1.items())==list(od2.items())。

OrderedDict 物件和其他 Mapping 物件間的相等性運算則像普通字典一樣不考慮順序性，這使得 OrderedDict 可於任何字典可使用的時機中被替換掉。

在 3.5 版的變更: OrderedDict 的項 (item)、鍵與值之視圖現在可透過 reversed() 來倒序疊代。

在 3.6 版的變更: 隨著 PEP 468 [https://peps.python.org/pep-0468/] 被核可，被傳入給 OrderedDict 建構函式與其 update() 方法的關鍵字引數之順序被保留了下來。

在 3.9 版的變更: 新增合併 (|) 和更新 (|=) 運算子，請見 PEP 584 [https://peps.python.org/pep-0584/]。

OrderedDict 範例與用法

建立一個能夠記住鍵最後插入順序的 ordered dictionary 變體很簡單。如果新條目覆蓋了現有條目，則原本插入位置會被更改並移動至末端：

class LastUpdatedOrderedDict(OrderedDict):
    'Store items in the order the keys were last added'

    def __setitem__(self, key, value):
        super().__setitem__(key, value)
        self.move_to_end(key)

OrderedDict 在實現一個 functools.lru_cache() 的變形版本時也非常有用：

from collections import OrderedDict
from time import time

class TimeBoundedLRU:
    "LRU Cache that invalidates and refreshes old entries."

    def __init__(self, func, maxsize=128, maxage=30):
        self.cache = OrderedDict()      # { args : (timestamp, result)}
        self.func = func
        self.maxsize = maxsize
        self.maxage = maxage

    def __call__(self, *args):
        if args in self.cache:
            self.cache.move_to_end(args)
            timestamp, result = self.cache[args]
            if time() - timestamp <= self.maxage:
                return result
        result = self.func(*args)
        self.cache[args] = time(), result
        if len(self.cache) > self.maxsize:
            self.cache.popitem(last=False)
        return result

class MultiHitLRUCache:
    """ LRU cache that defers caching a result until
        it has been requested multiple times.

        To avoid flushing the LRU cache with one-time requests,
        we don't cache until a request has been made more than once.

    """

    def __init__(self, func, maxsize=128, maxrequests=4096, cache_after=1):
        self.requests = OrderedDict()   # { uncached_key : request_count }
        self.cache = OrderedDict()      # { cached_key : function_result }
        self.func = func
        self.maxrequests = maxrequests  # max number of uncached requests
        self.maxsize = maxsize          # max number of stored return values
        self.cache_after = cache_after

    def __call__(self, *args):
        if args in self.cache:
            self.cache.move_to_end(args)
            return self.cache[args]
        result = self.func(*args)
        self.requests[args] = self.requests.get(args, 0) + 1
        if self.requests[args] <= self.cache_after:
            self.requests.move_to_end(args)
            if len(self.requests) > self.maxrequests:
                self.requests.popitem(last=False)
        else:
            self.requests.pop(args, None)
            self.cache[args] = result
            if len(self.cache) > self.maxsize:
                self.cache.popitem(last=False)
        return result

UserDict 物件

UserDict 類別是作為 dict 物件的包裝器。因為已經可以直接自 dict 建立子類別，這個類別的需求已部分被滿足，不過這個類別使用起來更方便，因為被包裝的字典可以作為其屬性來存取。

class collections.UserDict([initialdata])

模擬字典的類別。實例的內容被存於一個字典，可透過 UserDict 的 data 屬性來做存取。如果有提供 initialdata，data 屬性會被初始化為其值；要注意指到 initialdata 的參照不會被保留，使其可被用於其他目的。

除了支援作為對映所需的方法與操作，UserDict 實例提供了以下屬性：

data

一個真實的字典，用於儲存 UserDict 類別的資料內容。

UserList 物件

此類別是 list 物件的包裝器。它是個方便的基礎類別，可繼承它並覆寫現有方法或加入新方法來定義你所需的一個類似於 list 的類別。如此一來，我們可以為 list 加入新的特性。

因為已經可以直接自 list 建立子類別，這個類別的需求已部分被滿足，不過這個類別使用起來更方便，因為被包裝的 list 可以作為其屬性來存取。

class collections.UserList([list])

模擬 list 的類別。實例的內容被存於一個 list，可透過 UserList 的 data 屬性來做存取。實例內容被初始化為 list 的複製，預設為一個空的 list []。list 可以是任何 iterable，例如一個真實的 Python list 或是一個 UserList 物件。

除了支援可變序列的方法與操作，UserList 實例提供了以下屬性：

data

一個真實的 list 物件，用於儲存 UserList 類別的資料內容。

子類別化的條件：UserList 的子類別應該要提供一個不需要引數或一個引數的建構函式。回傳一個新序列的 list 操作會從那些實作出來的類別建立一個實例，為了達成上述目的，它假設建構函式可傳入單一參數來呼叫，該參數即是做為數據來源的一個序列物件。

如果希望一個自此獲得的子類別不遵從上述要求，那所有該類別支援的特殊方法則必須被覆寫；請參考原始碼來理解在這情況下哪些方法是必須提供的。

UserString 物件

UserString 類別是字串物件的包裝器，因為已經可以從 str 直接建立子類別，這個類別的需求已經部分被滿足，不過這個類別使用起來更方便，因為被包裝的字串可以作為其屬性來存取。

class collections.UserString(seq)

模擬字串物件的類別。實例的內容被存於一個字串物件，可透過 UserString 的 data 屬性來做存取。實例內容被初始化為 seq 的複製，seq 引數可以是任何可被內建函式 str() 轉換成字串的物件。

除了支援字串的方法和操作以外，UserString 實例也提供了以下屬性：

data

一個真實的 str 物件，用來儲存 UserString 類別的資料內容。

在 3.5 版的變更: 新增方法 __getnewargs__、__rmod__、casefold、format_map、isprintable 以及 maketrans。

collections.abc --- 容器的抽象基底類別

在 3.3 版被加入: 過去此模組是 collections 模組的一部分。

原始碼：Lib/_collections_abc.py [https://github.com/python/cpython/tree/3.14/Lib/_collections_abc.py]

This module provides abstract base classes that can be used to test whether a class provides a particular interface; for example, whether it is hashable or whether it is a mapping.

An issubclass() or isinstance() test for an interface works in one of three ways.

A newly written class can inherit directly from one of the abstract base classes. The class must supply the required abstract methods. The remaining mixin methods come from inheritance and can be overridden if desired. Other methods may be added as needed:

class C(Sequence):                      # Direct inheritance
    def __init__(self): ...             # Extra method not required by the ABC
    def __getitem__(self, index):  ...  # Required abstract method
    def __len__(self):  ...             # Required abstract method
    def count(self, value): ...         # Optionally override a mixin method

>>> issubclass(C, Sequence)
True
>>> isinstance(C(), Sequence)
True

Existing classes and built-in classes can be registered as "virtual subclasses" of the ABCs. Those classes should define the full API including all of the abstract methods and all of the mixin methods. This lets users rely on issubclass() or isinstance() tests to determine whether the full interface is supported. The exception to this rule is for methods that are automatically inferred from the rest of the API:

class D:                                 # No inheritance
    def __init__(self): ...              # Extra method not required by the ABC
    def __getitem__(self, index):  ...   # Abstract method
    def __len__(self):  ...              # Abstract method
    def count(self, value): ...          # Mixin method
    def index(self, value): ...          # Mixin method

Sequence.register(D)                     # Register instead of inherit

>>> issubclass(D, Sequence)
True
>>> isinstance(D(), Sequence)
True

In this example, class D does not need to define __contains__, __iter__, and __reversed__ because the in-operator, the iteration logic, and the reversed() function automatically fall back to using __getitem__ and __len__.

Some simple interfaces are directly recognizable by the presence of the required methods (unless those methods have been set to None):

class E:
    def __iter__(self): ...
    def __next__(self): ...

>>> issubclass(E, Iterable)
True
>>> isinstance(E(), Iterable)
True

Complex interfaces do not support this last technique because an interface is more than just the presence of method names. Interfaces specify semantics and relationships between methods that cannot be inferred solely from the presence of specific method names. For example, knowing that a class supplies __getitem__, __len__, and __iter__ is insufficient for distinguishing a Sequence from a Mapping.

在 3.9 版被加入: These abstract classes now support []. See 泛型別名型別 and PEP 585 [https://peps.python.org/pep-0585/].

Collections Abstract Base Classes

The collections module offers the following ABCs:

ABC

Inherits from

抽象方法

Mixin Methods

Container [1]

__contains__

Hashable [1]

__hash__

Iterable [1] [2]

__iter__

Iterator [1]

Iterable

__next__

__iter__

Reversible [1]

Iterable

__reversed__

Generator [1]

Iterator

send、throw

close、__iter__、__next__

Sized [1]

__len__

Callable [1]

__call__

Collection [1]

Sized、Iterable、Container

__contains__、__iter__、__len__

Sequence

Reversible, Collection

__getitem__、__len__

__contains__、__iter__、__reversed__、index 和 count

MutableSequence

Sequence

__getitem__、__setitem__、__delitem__、__len__、insert

繼承 Sequence 方法和 append、clear、reverse、extend、pop、remove 和 __iadd__

ByteString

Sequence

__getitem__、__len__

Sequence 的繼承方法

Set

Collection

__contains__、__iter__、__len__

__le__、__lt__、__eq__、__ne__、__gt__、__ge__、__and__、__or__、__sub__、__rsub__、__xor__、__rxor__ 和 isdisjoint

MutableSet

Set

__contains__、__iter__、__len__、add、discard

Inherited Set methods and clear, pop, remove, __ior__, __iand__, __ixor__, and __isub__

Mapping

Collection

__getitem__、__iter__、__len__

__contains__、keys、items、values、get、__eq__ 和 __ne__

MutableMapping

Mapping

__getitem__、__setitem__、__delitem__、__iter__、__len__

Inherited Mapping methods and pop, popitem, clear, update, and setdefault

MappingView

Sized

__init__、__len__ 和 __repr__

ItemsView

MappingView、Set

__contains__、__iter__

KeysView

MappingView、Set

__contains__、__iter__

ValuesView

MappingView、Collection

__contains__、__iter__

Awaitable [1]

__await__

Coroutine [1]

Awaitable

send、throw

close

AsyncIterable [1]

__aiter__

AsyncIterator [1]

AsyncIterable

__anext__

__aiter__

AsyncGenerator [1]

AsyncIterator

asend、athrow

aclose、__aiter__、__anext__

Buffer [1]

__buffer__

註腳

[1] (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15)

These ABCs override __subclasshook__() to support testing an interface by verifying the required methods are present and have not been set to None. This only works for simple interfaces. More complex interfaces require registration or direct subclassing.

[2]

Checking isinstance(obj, Iterable) detects classes that are registered as Iterable or that have an __iter__() method, but it does not detect classes that iterate with the __getitem__() method. The only reliable way to determine whether an object is iterable is to call iter(obj).

集合抽象基底類別的詳細描述

class collections.abc.Container

有提供 __contains__() 方法之類別的 ABC。

class collections.abc.Hashable

有提供 __hash__() 方法之類別的 ABC。

class collections.abc.Sized

有提供 __len__() 方法之類別的 ABC。

class collections.abc.Callable

有提供 __call__() 方法之類別的 ABC。

See 註釋 callable 物件 for details on how to use Callable in type annotations.

class collections.abc.Iterable

有提供 __iter__() 方法之類別的 ABC。

Checking isinstance(obj, Iterable) detects classes that are registered as Iterable or that have an __iter__() method, but it does not detect classes that iterate with the __getitem__() method. The only reliable way to determine whether an object is iterable is to call iter(obj).

class collections.abc.Collection

ABC for sized iterable container classes.

在 3.6 版被加入.

class collections.abc.Iterator

有提供 __iter__() 和 __next__() 方法之類別的 ABC。另請參閱 iterator 的定義。

class collections.abc.Reversible

亦有提供 __reversed__() 方法之可疊代類別的 ABC。

在 3.6 版被加入.

class collections.abc.Generator

ABC for generator classes that implement the protocol defined in PEP 342 [https://peps.python.org/pep-0342/] that extends iterators with the send(), throw() and close() methods.

See Annotating generators and coroutines for details on using Generator in type annotations.

在 3.5 版被加入.

class collections.abc.Sequence

class collections.abc.MutableSequence

class collections.abc.ByteString

唯讀且可變序列的 ABC。

Implementation note: Some of the mixin methods, such as __iter__(), __reversed__(), and index() make repeated calls to the underlying __getitem__() method. Consequently, if __getitem__() is implemented with constant access speed, the mixin methods will have linear performance; however, if the underlying method is linear (as it would be with a linked list), the mixins will have quadratic performance and will likely need to be overridden.

index(value, start=0, stop=None)

回傳 value 的第一個索引。

如果找不到該值，則引發 ValueError。

建議要支援 start 和 stop 引數，但並非必要。

在 3.5 版的變更: The index() method gained support for the stop and start arguments.

自從版本 3.12 後不推薦使用，將會自版本 3.17 中移除。: ByteString ABC 已被棄用。

Use isinstance(obj, collections.abc.Buffer) to test if obj implements the buffer protocol at runtime. For use in type annotations, either use Buffer or a union that explicitly specifies the types your code supports (e.g., bytes | bytearray | memoryview).

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多詳細資訊請參閱 PEP 688 [https://peps.python.org/pep-0688/#current-options]。

class collections.abc.Set

class collections.abc.MutableSet

唯讀且可變集合的 ABC。

class collections.abc.Mapping

class collections.abc.MutableMapping

唯讀且可變對映的 ABC。

class collections.abc.MappingView

class collections.abc.ItemsView

class collections.abc.KeysView

class collections.abc.ValuesView

ABCs for mapping, items, keys, and values views.

class collections.abc.Awaitable

ABC for awaitable objects, which can be used in await expressions. Custom implementations must provide the __await__() method.

Coroutine objects and instances of the Coroutine ABC are all instances of this ABC.

備註

In CPython, generator-based coroutines (generators decorated with @types.coroutine) are awaitables, even though they do not have an __await__() method. Using isinstance(gencoro, Awaitable) for them will return False. Use inspect.isawaitable() to detect them.

在 3.5 版被加入.

class collections.abc.Coroutine

ABC for coroutine compatible classes. These implement the following methods, defined in 協程物件: send(), throw(), and close(). Custom implementations must also implement __await__(). All Coroutine instances are also instances of Awaitable.

備註

In CPython, generator-based coroutines (generators decorated with @types.coroutine) are awaitables, even though they do not have an __await__() method. Using isinstance(gencoro, Coroutine) for them will return False. Use inspect.isawaitable() to detect them.

See Annotating generators and coroutines for details on using Coroutine in type annotations. The variance and order of type parameters correspond to those of Generator.

在 3.5 版被加入.

class collections.abc.AsyncIterable

ABC for classes that provide an __aiter__ method. See also the definition of asynchronous iterable.

在 3.5 版被加入.

class collections.abc.AsyncIterator

ABC for classes that provide __aiter__ and __anext__ methods. See also the definition of asynchronous iterator.

在 3.5 版被加入.

class collections.abc.AsyncGenerator

ABC for asynchronous generator classes that implement the protocol defined in PEP 525 [https://peps.python.org/pep-0525/] and PEP 492 [https://peps.python.org/pep-0492/].

See Annotating generators and coroutines for details on using AsyncGenerator in type annotations.

在 3.6 版被加入.

class collections.abc.Buffer

ABC for classes that provide the __buffer__() method, implementing the buffer protocol. See PEP 688 [https://peps.python.org/pep-0688/].

在 3.12 版被加入.

Examples and Recipes

ABCs allow us to ask classes or instances if they provide particular functionality, for example:

size = None
if isinstance(myvar, collections.abc.Sized):
    size = len(myvar)

Several of the ABCs are also useful as mixins that make it easier to develop classes supporting container APIs. For example, to write a class supporting the full Set API, it is only necessary to supply the three underlying abstract methods: __contains__(), __iter__(), and __len__(). The ABC supplies the remaining methods such as __and__() and isdisjoint():

class ListBasedSet(collections.abc.Set):
    ''' Alternate set implementation favoring space over speed
        and not requiring the set elements to be hashable. '''
    def __init__(self, iterable):
        self.elements = lst = []
        for value in iterable:
            if value not in lst:
                lst.append(value)

    def __iter__(self):
        return iter(self.elements)

    def __contains__(self, value):
        return value in self.elements

    def __len__(self):
        return len(self.elements)

s1 = ListBasedSet('abcdef')
s2 = ListBasedSet('defghi')
overlap = s1 & s2            # The __and__() method is supported automatically

Notes on using Set and MutableSet as a mixin:

Since some set operations create new sets, the default mixin methods need a way to create new instances from an iterable. The class constructor is assumed to have a signature in the form ClassName(iterable). That assumption is factored-out to an internal classmethod called _from_iterable() which calls cls(iterable) to produce a new set. If the Set mixin is being used in a class with a different constructor signature, you will need to override _from_iterable() with a classmethod or regular method that can construct new instances from an iterable argument.

To override the comparisons (presumably for speed, as the semantics are fixed), redefine __le__() and __ge__(), then the other operations will automatically follow suit.

The Set mixin provides a _hash() method to compute a hash value for the set; however, __hash__() is not defined because not all sets are hashable or immutable. To add set hashability using mixins, inherit from both Set() and Hashable(), then define __hash__ = Set._hash.

也參考

OrderedSet recipe [https://code.activestate.com/recipes/576694/] for an example built on MutableSet.

關於 ABC 的更多資訊請見 abc module 和 PEP 3119 [https://peps.python.org/pep-3119/]。

heapq --- 堆積佇列 (heap queue) 演算法

原始碼：Lib/heapq.py [https://github.com/python/cpython/tree/3.14/Lib/heapq.py]

這個模組實作了堆積佇列 (heap queue) 演算法，亦被稱為優先佇列 (priority queue) 演算法。

最小堆積 (min-heap) 是一顆二元樹，樹上每個父節點的值都小於或等於其子節點的值。我們將這種情況稱為堆積性質不變 (heap invariant)。

對於最小堆積，此實作使用串列，對於所有存在的被比較元素，k 都滿足 heap[k] <= heap[2*k+1] 和 heap[k] <= heap[2*k+2]。元素是從零開始計數。最小堆積有一個有趣的性質：最小的元素永遠在根節點 heap[0]。

Max-heaps satisfy the reverse invariant: every parent node has a value greater than any of its children. These are implemented as lists for which maxheap[2*k+1] <= maxheap[k] and maxheap[2*k+2] <= maxheap[k] for all k for which the compared elements exist. The root, maxheap[0], contains the largest element; heap.sort(reverse=True) maintains the max-heap invariant.

heapq API 與教科書上的堆積演算法在兩個方面不同：(a) 我們使用從零開始的索引。這使得節點索引和其子節點索引之間的關係變得不那麼明顯，但由於 Python 使用從零開始的索引，所以這樣更適合。(b) 教科書通常專注於最大堆積，因為它們適合原地排序。我們的實作偏向於最小堆積，因為它們更符合 Python 串列。

這兩個特性使得可以將堆積視為一個普通的 Python 串列而不會有意外：heap[0] 是最小的元素，而 heap.sort() 維持堆積性質不變！

Like list.sort(), this implementation uses only the < operator for comparisons, for both min-heaps and max-heaps.

In the API below, and in this documentation, the unqualified term heap generally refers to a min-heap. The API for max-heaps is named using a _max suffix.

要建立一個堆積，使用初始化為 [] 的串列，或者分別使用 heapify() 或 heapify_max() 函式將現有的串列轉換為最小堆積或最大堆積。

提供了以下針對最小堆積的函式：

heapq.heapify(x)

在線性時間內將串列 x 原地轉換為最小堆積。

heapq.heappush(heap, item)

將值 item 推入 heap，並維持最小堆積性質不變。

heapq.heappop(heap)

從 heap 取出並回傳最小的元素，維持最小堆積性質不變。如果堆積為空，會引發 IndexError。若要在不取出的情況下存取最小元素，請使用 heap[0]。

heapq.heappushpop(heap, item)

將 item 放入 heap ，接著從 heap 取出並回傳最小的元素。這個組合函式比呼叫 heappush() 之後呼叫 heappop() 更有效率。

heapq.heapreplace(heap, item)

從 heap 取出並回傳最小的元素，接著將新的 item 放進heap。heap 的大小不會改變。如果 heap 是空的會產生 IndexError 錯誤。

這個一次完成的操作會比呼叫 heappop() 之後呼叫 heappush() 更有效率，並在維護 heap 的大小不變時更為適當，取出/放入的組合函式一定會從 heap 回傳一個元素並用 item 取代他。

函式的回傳值可能會大於被加入的 item 。如果這不是你期望發生的，可以考慮使用 heappushpop() 替代，他會回傳 heap 的最小值和 item 兩個當中比較小的那個，並將大的留在 heap 內。

提供以下針對最大堆積的函式：

heapq.heapify_max(x)

在線性時間內將串列 x 原地轉換為最大堆積。

在 3.14 版被加入.

heapq.heappush_max(heap, item)

將值 item 推入最大堆積 heap，維持最大堆積性質不變。

在 3.14 版被加入.

heapq.heappop_max(heap)

從最大堆積 heap 取出並回傳最大的元素，維持最大堆積性質不變。如果最大堆積為空，會引發 IndexError。若要在不取出的情況下存取最大元素，請使用 maxheap[0]。

在 3.14 版被加入.

heapq.heappushpop_max(heap, item)

將 item 推入 max-heap heap，然後取出並回傳 heap 中最大的元素。這個組合動作比先呼叫 heappush_max() 再單獨呼叫 heappop_max() 更有效率。

在 3.14 版被加入.

heapq.heapreplace_max(heap, item)

從最大堆積 heap 取出並回傳最大的元素，同時推入新的 item。最大堆積的大小不會改變。如果最大堆積為空，會引發 IndexError。

The value returned may be smaller than the item added. Refer to the analogous function heapreplace() for detailed usage notes.

在 3.14 版被加入.

這個模組也提供三個利用 heap 實作的一般用途函式

heapq.merge(*iterables, key=None, reverse=False)

合併多個已排序的輸入並產生單一且已排序的輸出（舉例：合併來自多個 log 檔中有時間戳記的項目）。回傳一個 iterator 包含已經排序的值。

和 sorted(itertools.chain(*iterables)) 類似但回傳值是一個 iterable ，不會一次把所有資料都放進記憶體中，並且假設每一個輸入都已經（由小到大）排序過了。

有兩個選用參數，指定時必須被當作關鍵字參數指定。

key 參數指定了一個 key function 引數，用來從每一個輸入的元素中決定一個比較的依據。預設的值是 None （直接比較元素）。

reverse 是一個布林值，如果設定為 True ，則輸入的元素將以相反的比較順序進行合併。為了達成類似 sorted(itertools.chain(*iterables), reverse=True) 的行為，所有 iterables 必須由大到小排序。

在 3.5 版的變更: 加入選用參數 key 和 reverse 。

heapq.nlargest(n, iterable, key=None)

回傳一個包含資料 iterable 中前 n 大元素的 list 。如果有指定 key 引數，key 會是只有一個引數的函式，用來從每一個在 iterable 中的元素提取一個比較的依據（例如 key=str.lower ）。效果相當於 sorted(iterable, key=key, reverse=True)[:n] 。

heapq.nsmallest(n, iterable, key=None)

回傳一個包含資料 iterable 中前 n 小元素的 list 。如果有指定 key 引數，key 會是只有一個引數的函式，用來從每一個在 iterable 中的元素提取一個比較的依據（例如 key=str.lower ）。效果相當於 sorted(iterable, key=key)[:n] 。

後兩個函式在 n 值比較小時有最好的表現。對於較大的 n 值，只用 sorted() 函式會更有效率。同樣地，當 n==1 時，使用內建函式 min() 和 max() 會有更好的效率。如果需要重複使用這些函式，可以考慮將 iterable 轉成真正的 heap 。

基礎範例

堆積排序 (heapsort) [https://en.wikipedia.org/wiki/Heapsort] 可以透過將所有的值推入一個 heap，並且從 heap 中一個接一個彈出最小元素來實作：

>>> def heapsort(iterable):
...     h = []
...     for value in iterable:
...         heappush(h, value)
...     return [heappop(h) for i in range(len(h))]
...
>>> heapsort([1, 3, 5, 7, 9, 2, 4, 6, 8, 0])
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

雖然類似 sorted(iterable) ，但跟 sorted() 不同的是，這個實作不是 stable 的排序。

Heap 中的元素可以是 tuple 。這有利於將要比較的值（例如一個 task 的優先度）和主要資料放在一起排序：

>>> h = []
>>> heappush(h, (5, 'write code'))
>>> heappush(h, (7, 'release product'))
>>> heappush(h, (1, 'write spec'))
>>> heappush(h, (3, 'create tests'))
>>> heappop(h)
(1, 'write spec')

Other Applications

Medians [https://en.wikipedia.org/wiki/Median] are a measure of central tendency for a set of numbers. In distributions skewed by outliers, the median provides a more stable estimate than an average (arithmetic mean). A running median is an online algorithm [https://en.wikipedia.org/wiki/Online_algorithm] that updates continuously as new data arrives.

A running median can be efficiently implemented by balancing two heaps, a max-heap for values at or below the midpoint and a min-heap for values above the midpoint. When the two heaps have the same size, the new median is the average of the tops of the two heaps; otherwise, the median is at the top of the larger heap:

def running_median(iterable):
    "Yields the cumulative median of values seen so far."

    lo = []  # max-heap
    hi = []  # min-heap (same size as or one smaller than lo)

    for x in iterable:
        if len(lo) == len(hi):
            heappush_max(lo, heappushpop(hi, x))
            yield lo[0]
        else:
            heappush(hi, heappushpop_max(lo, x))
            yield (lo[0] + hi[0]) / 2

舉例來說：

>>> list(running_median([5.0, 9.0, 4.0, 12.0, 8.0, 9.0]))
[5.0, 7.0, 5.0, 7.0, 8.0, 8.5]

優先佇列實作細節

優先佇列 (priority queue) [https://en.wikipedia.org/wiki/Priority_queue] 是 heap 的常見用途之一，實作優先佇列伴隨著下列挑戰：

排序的穩定性：如何將兩個擁有相同優先次序 (priority) 的 task 按照他們被加入的順序回傳?

Tuple的排序在某些情況下會壞掉，例如當 Tuple (priority, task) 的 priorities 相等且 tasks 沒有一個預設的排序時。

當一個 heap 中 task 的 priority 改變時，如何將它移到 heap 正確的位置上?

或者一個還沒被解決的 task 需要被刪除時，要如何從佇列中找到並刪除指定的 task?

一個針對前兩個問題的解法是：儲存一個包含 priority、entry count 和 task 三個元素的 tuple 。兩個 task 有相同 priority 時，entry count 會讓兩個 task 能根據加入的順序排序。因為沒有任何兩個 task 擁有相同的 entry count，所以永遠不會直接使用 task 做比較。

task 無法比較的另一個解決方案是建立一個包裝器類別，該類別忽略 task 項目，只比較優先等級：

from dataclasses import dataclass, field
from typing import Any

@dataclass(order=True)
class PrioritizedItem:
    priority: int
    item: Any=field(compare=False)

剩下的問題可以藉由找到要刪除的 task 並更改它的 priority 或者直接將它移除。尋找一個 task 可以使用一個 dictionary 指向佇列當中的 entry 。

移除 entry 或更改它的 priority 更為困難，因為這會破壞 heap 的性質。所以一個可行的方案是將原本的 entry 做一個標記表示它已經被刪除，並新增一個擁有新的 priority 的 entry：

pq = []                         # 在 heap 中的 entry 串列
entry_finder = {}               # task 對應到 entry 的對映
REMOVED = '<removed-task>'      # 被刪除的 task 的佔位器
counter = itertools.count()     # 唯一的序列計數

def add_task(task, priority=0):
    '新增一個 task 或更新一個已存在 task 的 priority'
    if task in entry_finder:
        remove_task(task)
    count = next(counter)
    entry = [priority, count, task]
    entry_finder[task] = entry
    heappush(pq, entry)

def remove_task(task):
    '將一個已存在的 task 標記為 REMOVED。如果找不到會引發 KeyError。'
    entry = entry_finder.pop(task)
    entry[-1] = REMOVED

def pop_task():
    '移除並回傳最低 priority 的 task。如果 heap 是空的會引發 KeyError。'
    while pq:
        priority, count, task = heappop(pq)
        if task is not REMOVED:
            del entry_finder[task]
            return task
    raise KeyError('從空的優先佇列中 pop 出元素')

原理

Heap 是一個陣列對於所有從0開始的 index k 都存在性質 a[k] <= a[2*k+1] 和 a[k] <= a[2*k+2] 。為了方便比較，不存在的元素被視為無限大。Heap 的一個有趣的性質是：a[0] 永遠是最小的元素。

上述乍看之下有些奇怪的不變式，是為了實作一個對記憶體來說有效率的方法，其表示方式如同錦標賽一般。下列的數字為 k，而不是 a[k]：

                               0

              1                                 2

      3               4                5               6

  7       8       9       10      11      12      13      14

15 16   17 18   19 20   21 22   23 24   25 26   27 28   29 30

在上面的樹當中，每個單元 k 都會位在 2*k+1 與 2*k+2 上方。如同體育賽事常見的錦標賽般，每個單元可視為其下方兩個單元當中的贏家，我們可以透過追溯整棵樹來找到該贏家曾經對戰過的所有對手。然而，在許多電腦應用中，我們不需要追溯贏家的完整對戰歷史。為了能更有效率地使用記憶體，當一個贏家晉級勝出時，我們用下方較低層級的另一個項目來取代它，至此規則變為一個單元以及它下方兩個單元，包含三個不同項目，但是最上方的單元「勝過」下方兩個單元。

如果能確保滿足這個 heap 的不變式，那麼索引 0 顯然是最終的贏家。移除並找到「下一個」贏家最簡單的演算法為：將一個輸家（例如上圖中的單元 30）移動到位置 0，然後從新的位置 0 不斷與下方的位置交換值來向下傳遞，直到滿足不變式為止。這個過程的複雜度顯然是樹的節點數目的對數級別。透過對所有項目疊代，可以得到一個複雜度為 O(n log n) 的排序。

這種排序有個好處，只要插入的項目沒有「贏過」你最後提取、索引為 0 的元素，你就可以在排序進行的同時有效率地插入新項目。這在模擬情境當中特別有用，其中樹能夠保存所有輸入事件，而「贏」意味著最小排程時間。當一個事件排程其它事件的執行時，因這些事件仍在等待進行，所以很容易將它們插入 heap 當中。因此， heap 是一個實現排程器的優秀資料結構（這就是我用以實作 MIDI 編曲器的方法 :-）。

多種用於實作排程器的結構現今已被廣泛研究，heap 對此非常有用，因為它們速度相當快，且速度幾乎不受其他因素影響，最壞情況與平均狀況差異無幾。也有其它整體說來更有效率的方法，然而它們的最壞情況可能會非常糟糕。

Heap 在為儲存於硬碟上的大量資料進行排序也非常有用。你可能已經知道，大量資料排序涉及 "runs" 的產生（也就是預先排序的序列，其大小通常與 CPU 記憶體的大小有關），之後再對這些 run 合併，而這些合併的過程通常相當巧妙 [1]。很重要的一點是，初始排序產生的 run 越長越好。錦標賽是達成這一點的好方法，若你用所有可用記憶體來舉行一場錦標賽，並透過替換與向下交換來處理所有適配目前 run 的值，那麼對於隨機產生的輸入，將可以產生長度兩倍於記憶體大小的 run。對於已模糊排序過的輸入，效果更好。

此外，若你將索引為 0 的項目輸出至磁碟，並取得一個無法適配目前錦標賽的輸入（因為該值「勝過」最後的輸出值），則該輸入值就無法插入至 heap 當中，因此 heap 的大小會減小。釋放出來的記憶體可以巧妙地立即再被運用，逐步建構出第二個 heap，其大小增加的速度會與第一個 heap 減少的速度一致。當第一個 heap 完全消失時，你可以切換至第二個 heap 開啟一個新 run 。這真是個聰明且相當有效率的做法！

總結來說，heap 是值得了解的有用記憶體結構。我在一些應用中使用它們，我認為能有一個 'heap' 模組是很棒的。:-)

註解

[1]

現今的磁碟平衡演算法因為硬碟查找能力而更加複雜難解。在沒有查找功能的裝置如大型磁帶機，狀況又不一樣了，人們必須機智地確保（遠遠提前）每次於磁帶上移動都盡可能是最有效率的（也就是盡可能更好地「推進」合併的過程）。有些磁帶甚至能夠向後讀取，這也被用來避免倒轉的時間。相信我，真正優秀的磁帶排序看起來相當壯觀！排序一直以來都是一門偉大的藝術！:-)

bisect --- 陣列二分演算法 (Array bisection algorithm)

原始碼：Lib/bisect.py [https://github.com/python/cpython/tree/3.14/Lib/bisect.py]

這個模組維護一個已經排序過的 list ，當我們每次做完插入後不需要再次排序整個 list 。一個很長的 list 的比較操作很花費時間，可以透過線性搜尋或頻繁地詢問來改善。

這個模組被稱為 bisect 是因為它使用基本二分演算法來完成其工作。不像其它搜尋特定值的二分法工具，本模組中的函式旨在定位插入點。因此，這些函式永遠不會呼叫 __eq__() 方法來確認是否找到一個值。相反地，這些函式只呼叫 __lt__() 方法，並在陣列中的值回傳一個插入點。

備註

The functions in this module are not thread-safe. If multiple threads concurrently use bisect functions on the same sequence, this may result in undefined behaviour. Likewise, if the provided sequence is mutated by a different thread while a bisect function is operating on it, the result is undefined. For example, using insort_left() on the same list from multiple threads may result in the list becoming unsorted.

此模組提供下面的函式：

bisect.bisect_left(a, x, lo=0, hi=len(a), *, key=None)

在 a 當中找到一個位置，讓 x 插入後 a 仍然是排序好的。參數 lo 和 hi 用來指定 list 中應該被考慮的子區間，預設是考慮整個 list 。如果 a 裡面已經有 x 出現，插入的位置會在所有 x 的前面（左邊）。回傳值可以被當作 list.insert() 的第一個參數，但列表 a 必須先排序過。

回傳的插入點 ip 將陣列 a 劃分為左右兩個切片，使得對於左切片而言 all(elem < x for elem in a[lo : ip]) 為真，對於右切片而言 all(elem >= x for elem in a[ip : hi]) 為真。

key 可指定一個單一參數的 key function。函式將套用此 function 在陣列所有元素以得到比較值來計算順位。注意此 function 只會套用在陣列中的元素，不會套用在 x。

若 key 為 None，元素將直接進行比較，不會呼叫任何鍵函式。

在 3.10 版的變更: 新增 key 參數。

bisect.bisect_right(a, x, lo=0, hi=len(a), *, key=None)

bisect.bisect(a, x, lo=0, hi=len(a), *, key=None)

類似 bisect_left()，但回傳的插入位置會在所有 a 當中的 x 的後面（右邊）。

回傳的插入點 ip 將陣列 a 劃分為左右兩個切片，使得對於左切片而言 all(elem <= x for elem in a[lo : ip]) 為真，對於右切片而言 all(elem > x for elem in a[ip : hi]) 為真。

在 3.10 版的變更: 新增 key 參數。

bisect.insort_left(a, x, lo=0, hi=len(a), *, key=None)

將元素 x 插入 list a，並維持順序。

此函式先使用 bisect_left() 搜尋插入位置，接著用 insert() 於 a 以將 x 插入，並維持添加元素後的順序。

此函式只有在搜尋時會使用 key 函式，插入時不會。

注意雖然搜尋是 O(log n)，但插入是 O(n)，因此此函式整體時間複雜度是 O(n)。

在 3.10 版的變更: 新增 key 參數。

bisect.insort_right(a, x, lo=0, hi=len(a), *, key=None)

bisect.insort(a, x, lo=0, hi=len(a), *, key=None)

類似 insort_left()，但插入的位置會在所有 a 當中的 x 的後面（右邊）。

此函式先使用 bisect_right() 搜尋插入位置，接著用 insert() 於 a 以將 x 插入，並維持添加元素後的順序。

此函式只有在搜尋時會使用 key 函式，插入時不會。

注意雖然搜尋是 O(log n)，但插入是 O(n)，因此此函式整體時間複雜度是 O(n)。

在 3.10 版的變更: 新增 key 參數。

效能考量

若在需要關注寫入時間的程式當中使用 bisect() 和 insort()，請特別注意幾個事項：

二分法在一段範圍的數值中做搜尋的效率較佳，但若是要存取特定數值，使用字典的表現還是比較好。

insort() 函式的複雜度為 O(n)，因為對數搜尋是以線性時間的插入步驟所主導 (dominate)。

搜尋函式為無狀態的 (stateless)，且鍵函式會在使用過後被丟棄。因此，如果搜尋函式被使用於迴圈當中，鍵函式會不斷被重複呼叫於相同的 list 元素。如果鍵函式執行速度不快，請考慮將其以 functools.cache() 包裝起來以減少重複的計算。另外，也可以透過搜尋預先計算好的鍵列表 (array of precomputed keys) 來定位插入點（如下方範例所示）。

也參考

有序容器 (Sorted Collections) [https://grantjenks.com/docs/sortedcollections/] 是一個使用 bisect 來管理資料之有序集合的高效能模組。

SortedCollection recipe [https://code.activestate.com/recipes/577197-sortedcollection/] 使用二分法來建立一個功能完整的集合類別 (collection class) 並帶有符合直覺的搜尋方法 (search methods) 與支援鍵函式。鍵會預先被計算好，以減少搜尋過程中多餘的鍵函式呼叫。

搜尋一個已排序的 list

上面的 bisect functions 在找到數值插入點上很有用，但一般的數值搜尋任務上就不是那麼的方便。以下的五個函式展示了如何將其轉換成標準的有序列表查找函式：

def index(a, x):
    'Locate the leftmost value exactly equal to x'
    i = bisect_left(a, x)
    if i != len(a) and a[i] == x:
        return i
    raise ValueError

def find_lt(a, x):
    'Find rightmost value less than x'
    i = bisect_left(a, x)
    if i:
        return a[i-1]
    raise ValueError

def find_le(a, x):
    'Find rightmost value less than or equal to x'
    i = bisect_right(a, x)
    if i:
        return a[i-1]
    raise ValueError

def find_gt(a, x):
    'Find leftmost value greater than x'
    i = bisect_right(a, x)
    if i != len(a):
        return a[i]
    raise ValueError

def find_ge(a, x):
    'Find leftmost item greater than or equal to x'
    i = bisect_left(a, x)
    if i != len(a):
        return a[i]
    raise ValueError

範例

bisect() 函式可用於數值表中的查找 (numeric table lookup)，這個範例使用 bisect() 以基於一組有序的數值分界點來為一個考試成績找到相對應的字母等級：90 以上是 'A'、80 到 89 為 'B'，依此類推：

>>> def grade(score, breakpoints=[60, 70, 80, 90], grades='FDCBA'):
...     i = bisect(breakpoints, score)
...     return grades[i]
...
>>> [grade(score) for score in [33, 99, 77, 70, 89, 90, 100]]
['F', 'A', 'C', 'C', 'B', 'A', 'A']

bisect() 與 insort() 函式也適用於內容為 tuples（元組）的 lists，key 引數可被用以取出在數值表中作為排序依據的欄位：

>>> from collections import namedtuple
>>> from operator import attrgetter
>>> from bisect import bisect, insort
>>> from pprint import pprint

>>> Movie = namedtuple('Movie', ('name', 'released', 'director'))

>>> movies = [
...     Movie('Jaws', 1975, 'Spielberg'),
...     Movie('Titanic', 1997, 'Cameron'),
...     Movie('The Birds', 1963, 'Hitchcock'),
...     Movie('Aliens', 1986, 'Cameron')
... ]

>>> # 找到 1960 年後上映的第一部電影
>>> by_year = attrgetter('released')
>>> movies.sort(key=by_year)
>>> movies[bisect(movies, 1960, key=by_year)]
Movie(name='The Birds', released=1963, director='Hitchcock')

>>> # 插入一部電影並保持排序
>>> romance = Movie('Love Story', 1970, 'Hiller')
>>> insort(movies, romance, key=by_year)
>>> pprint(movies)
[Movie(name='The Birds', released=1963, director='Hitchcock'),
 Movie(name='Love Story', released=1970, director='Hiller'),
 Movie(name='Jaws', released=1975, director='Spielberg'),
 Movie(name='Aliens', released=1986, director='Cameron'),
 Movie(name='Titanic', released=1997, director='Cameron')]

如果鍵函式會消耗較多運算資源，那可以在預先計算好的鍵列表中搜尋該紀錄的索引值，以減少重複的函式呼叫：

>>> data = [('red', 5), ('blue', 1), ('yellow', 8), ('black', 0)]
>>> data.sort(key=lambda r: r[1])       # Or use operator.itemgetter(1).
>>> keys = [r[1] for r in data]         # Precompute a list of keys.
>>> data[bisect_left(keys, 0)]
('black', 0)
>>> data[bisect_left(keys, 1)]
('blue', 1)
>>> data[bisect_left(keys, 5)]
('red', 5)
>>> data[bisect_left(keys, 8)]
('yellow', 8)

array --- 高效率的數值型陣列

這個模組定義了一個物件型別，可以簡潔的表達一個包含基本數值的陣列：字元、整數、浮點數。陣列是一個非常類似 list（串列）的序列型別，除了陣列會限制儲存的物件型別。在建立陣列時可以使用一個字元的 type code 來指定儲存的資料型別。以下為有被定義的 type codes：

Type code

C Type

Python Type

所需的最小位元組 (bytes)

註解

'b'

signed char

int

1

'B'

unsigned char

int

1

'u'

wchar_t

Unicode character

2

(1)

'w'

Py_UCS4

Unicode character

4

(2)

'h'

signed short

int

2

'H'

unsigned short

int

2

'i'

signed int

int

2

'I'

unsigned int

int

2

'l'

signed long

int

4

'L'

unsigned long

int

4

'q'

signed long long

int

8

'Q'

unsigned long long

int

8

'f'

float

float

4

'd'

double

float

8

註解：

根據平台的不同，它有可能是 16 位元或者 32 位元。

在 3.9 版的變更: 目前 array('u') 使用 wchar_t 取代已棄用的 Py_UNICODE 作為 C type。這個異動並沒有影響到它的作用，因為自從 Python 3.3 開始 Py_UNICODE 即為 wchar_t 的別名。

自從版本 3.3 後不推薦使用，將會自版本 3.16 中移除。: 請改用 'w' typecode。

在 3.13 版被加入.

實際上數值的表示方法是被機器的架構所決定（更精準地說，被 C 的實作方法決定）。實際的大小可以透過 array.itemsize 屬性存取。

這個模組定義了以下項目：

array.typecodes

一個包含所有可用的 type codes 的字串。

這個模組定義了下方的型別：

class array.array(typecode[, initializer])

一個新的陣列中的元素被 typecode 限制，並由選用的 initializer 參數初始化，initializer 必須是一個 bytes 或 bytearray 物件、一個 Unicode 字串或包含適當型別元素的可疊代物件 (iterable)。

如果給定的是一個 bytes 或 bytearray 物件，新的陣列初始化時會傳入 frombytes() 方法；如為 Unicode 字串則會傳入 fromunicode() 方法；其他情況時， 一個 initializer 的可疊代物件將被傳入 extend() 方法之中來將初始項目新增至陣列。

陣列支援常見的可變序列操作，包含索引 (indexing)、切片 (slicing)、串接 (concatenation)、相乘 (multiplication) 等。當使用切片進行賦值時，賦值的陣列必須具備相同的 type code，其他型別的數值將導致 TypeError。陣列同時也實作了緩衝區介面，可以在任何支援 bytes-like objects 的地方使用。

引發稽核事件 (auditing event) array.__new__ 並附帶引數 typecode、initializer。

typecode

typecode 字元被用在建立陣列時。

itemsize

陣列當中的一個元素在內部需要的位元組長度。

append(x)

新增一個元素 x 到陣列的最尾端。

buffer_info()

回傳一個 tuple (address, length) 表示目前的記憶體位置和陣列儲存元素的緩衝區記憶體長度。緩衝區的長度單位是位元組，並可以用 array.buffer_info()[1] * array.itemsize 計算得到。這偶爾會在底層操作需要記憶體位置的輸出輸入時很有用，例如 ioctl() 指令。只要陣列存在且沒有使用任何更改長度的操作時，回傳的數值就有效。

備註

當使用來自 C 或 C++ 程式碼（這是唯一使得這個資訊有效的途徑）的陣列物件時，更適當的做法是使用陣列物件支援的緩衝區介面。這個方法維護了向後兼容性，並應該在新的程式碼中避免。關於緩衝區介面的文件在緩衝協定 (Buffer Protocol)。

byteswap()

"Byteswap" 所有陣列中的物件。這只有支援物件長度為 1、2、4 或 8 位元組的陣列，其他型別的值會導致 RuntimeError。這在從機器讀取位元順序不同的檔案時很有用。

count(x)

回傳 x 在陣列中出現了幾次。

extend(iterable)

從 iterable 中新增元素到陣列的尾端，如果 iterable 是另一個陣列，它必須有完全相同的 type code，如果不同會導致 TypeError。如果 iterable 不是一個陣列，它必須可以被疊代 (iterable) 且其中的元素必須是可以被加入陣列中的正確型別。

frombytes(buffer)

從 bytes-like object 中新增元素。讀取時會將其內容當作一個機器數值組成的陣列（就像從檔案中使用 fromfile() 方法讀出的資料）。

在 3.2 版被加入: 將 fromstring() 更名為 frombytes()，使其更加清晰易懂。

fromfile(f, n)

從 file object f 讀取 n 個元素（作為機器數值），接著將這些元素加入陣列的最尾端。如果只有少於 n 個有效的元素會導致 EOFError，但有效的元素仍然會被加入陣列中。

fromlist(list)

從 list 中新增元素。這等價於 for x in list: a.append(x)，除了有型別錯誤產生時，陣列會保持原狀不會被更改。

fromunicode(s)

用給定的 Unicode 字串擴展這個陣列。陣列的 type code 必須是 u 或 'w'；其他的型別會導致 ValueError 被引發。使用 array.frombytes(unicodestring.encode(enc)) 來新增 Unicode 資料到一個其他型別的陣列。

index(x[, start[, stop]])

回傳 i 的最小數值，使得 i 成為陣列之中第一次出現 x 的索引。選擇性的引數 start 及 stop 則可以被用來在指定的陣列空間中搜尋 x。如果 x 不存在將導致 ValueError。

在 3.10 版的變更: 新增選擇性的參數 start 及 stop。

insert(i, x)

在位置 i 之前插入一個元素 x。負數的索引值會從陣列尾端開始數。

pop([i])

移除並回傳陣列索引值 i 的元素。選擇性的引數 i 預設為 -1，所以預設會刪除並回傳最後一個元素。

remove(x)

從陣列中刪除第一個出現的 x。

clear()

從陣列中刪除所有元素。

在 3.13 版被加入.

reverse()

反轉陣列中元素的順序。

tobytes()

將陣列轉為另一個機器數值組成的陣列並回傳它的位元組表示（跟用 tofile() 方法寫入檔案時的位元序列相同）。

在 3.2 版被加入: 為了明確性，過去的 tostring() 已更名為 tobytes()。

tofile(f)

將所有元素（作為機器數值）寫入 file object f。

tolist()

不更改元素，將陣列轉為一般的 list。

tounicode()

將陣列轉為一個 Unicode 字串。陣列的型別必須為 u 或 'w'；其他型別的陣列會引發 ValueError。請使用 array.tobytes().decode(enc) 來為其他型別的陣列轉為 Unicode 字串。

陣列物件的字串表示形式為 array(typecode, initializer)。若為空陣列則參數 initializer 被省略，若 typecode 是 'u' 或 'w' 將被表示為 Unicode 字串，其他情況則被表示為由數字組成的 list。只要 array class（類別）透過 from array import array 的方式引入，便能確保該字串表示能透過 eval() 轉換回一個擁有相同型別及數值的陣列。如果它包含相應的浮點值，inf 和 nan 也必須被定義。範例：

array('l')
array('w', 'hello \u2641')
array('l', [1, 2, 3, 4, 5])
array('d', [1.0, 2.0, 3.14, -inf, nan])

也參考

struct 模組

將包含不同資料類型的二進位資料包裝與解開包裝。

NumPy [https://numpy.org/]

NumPy 套件定義了另一個陣列型別

weakref --- 弱參照

原始碼：Lib/weakref.py [https://github.com/python/cpython/tree/3.14/Lib/weakref.py]

weakref 模組允許 Python 程式設計師建立對物件的 弱參照。

在以下文章中，術語 參照目標 (referent) 表示被弱參照所參考的物件。

對物件的弱參照不足以使物件保持存在：當對參照目標的唯一剩下的參照是弱參照時，garbage collection 可以自由地銷毀參照目標並將其記憶體重新用於其他用途。然而，在物件被確實銷毀之前，即使沒有對該物件的強參照 (strong reference)，弱參照也可能會回傳該物件。

弱參照的主要用途是實作保存大型物件的快取或對映，其不希望大型物件僅僅因為它出現在快取或對映中而保持存在。

例如，如果你有許多大型的二進位影像物件，你可能會想要為每個物件關聯 (associate) 一個名稱。如果你使用 Python 字典將名稱對映到影像，或將影像對映到名稱，則影像物件將保持存活，僅因為它們在字典中作為值 (value) 或鍵 (key) 出現。weakref 模組提供的 WeakKeyDictionary 和 WeakValueDictionary 類別是另一種選擇，它們使用弱參照來建構對映，這些對映不會僅因為物件出現在對映物件中而使物件保持存活。例如，如果一個影像物件是 WeakValueDictionary 中的一個值，那麼當對該影像物件最後的參照是弱對映 (weak mapping) 所持有的弱參照時，垃圾回收 (garbage collection) 可以回收該物件，且其對應的條目在弱對映中會被完全地刪除。

WeakKeyDictionary 和 WeakValueDictionary 在其實作中使用弱參照，在弱參照上設定回呼函式，此弱參照在垃圾回收取回鍵或值時通知弱字典。WeakSet 實作了 set 介面，但保留對其元素的弱參照，就像 WeakKeyDictionary 一樣。

finalize 提供了一種直接的方法來註冊在物件被垃圾回收時呼叫的清理函式。這比在原始弱參照上設定回呼函式更容易使用，因為模組在物件被回收前會自動確保最終化器 (finalizer) 保持存活。

大多數程式應該發現使用這些弱容器種類之一或 finalize 就足夠了—通常不需要直接建立自己的弱參照。低層級的機制由 weakref 模組公開，以利於進階用途。

並非所有物件都可以被弱參照。支援弱參照的物件包括類別實例、用 Python （但不是C）編寫的函式、實例方法、集合、凍結集合 (frozenset)、一些檔案物件、產生器、類型物件、socket、陣列、雙向佇列、正規表示式模式物件和程式碼物件。

在 3.2 版的變更: 新增了對 thread.lock、threading.Lock 和程式碼物件的支援。

一些內建型別，例如 list 和 dict 不直接支援弱參照，但可以透過子類別化來支援：

class Dict(dict):
    pass

obj = Dict(red=1, green=2, blue=3)   # 這個物件是可被弱參照的

其他內建型別，例如 tuple 和 int 即使在子類別化時也不支援弱參照。

擴充型別 (extension type) 可以輕易地支援弱參照；請參閱 Weak Reference Support。

當為給定的型別定義 __slots__ 時，弱參照支援將被停用，除非 '__weakref__' 字串也存在於 __slots__ 宣告的字串序列中。詳情請參閱 __slots__ 文件。

class weakref.ref(object[, callback])

回傳對 object 的弱參照。如果參照目標仍存活，則可以透過呼叫參照物件來取回原始物件；如果參照目標已不存活，呼叫參照物件將導致 None 被回傳。如果 callback 被提供而非 None，且回傳的弱參照物件仍存活，那麼當物件即將被最終化 (finalize) 時，回呼將被呼叫；弱參照物件將作為唯一的參數傳遞給回呼；參照物件將不再可用。

為同一個物件建構多個弱參照是可行的。為每個弱參照註冊的回呼將按照最新到最舊註冊的回呼順序來被呼叫。

回呼引發的例外將在標準錯誤輸出中被註明，但無法被傳播；它們的處理方式與物件的 __del__() 方法引發的例外完全相同。

如果 object 是可雜湊的，那麼弱參照就是可雜湊的。即使在 object 被刪除後，它們仍將保留其雜湊值。如果僅在 object 刪除後才第一次呼叫 hash()，則該呼叫將引發 TypeError。

弱參照支援相等性的測試，但不支援排序。如果參照目標仍存活，則兩個參照與其參照目標具有相同的相等關係（無論 callback 如何）。如果任一參照目標已被刪除，則僅當參照物件是同一物件時，參照才相等。

這是一個可子類別化的型別，而不是一個工廠函式。

__callback__

此唯讀屬性回傳目前與弱參照關聯的回呼。如果沒有回呼或弱參照的參照目標已不存活，那麼該屬性的值為 None。

在 3.4 版的變更: 新增 __callback__ 屬性。

weakref.proxy(object[, callback])

回傳一個使用弱參照的 object 的代理 (proxy)。這支援在大多數情境中使用代理，而不需要對弱參照物件明確地取消參照。回傳的物件將具有 ProxyType 或 CallableProxyType 型別，具體取決於 object 是否為可呼叫物件。無論參照目標如何，代理物件都不是 hashable；這避免了與其基本可變物件本質相關的許多問題，並阻止它們作為字典的鍵被使用。callback 與 ref() 函式的同名參數是相同的。

在參照目標被垃圾回收後存取代理物件的屬性會引發 ReferenceError。

在 3.8 版的變更: 提供對代理物件的運算子支援，以包括矩陣乘法運算子 @ 和 @=。

weakref.getweakrefcount(object)

回傳參照 object 的弱參照和代理的數量。

weakref.getweakrefs(object)

回傳參照 object 的所有弱參照和代理物件的一個串列。

class weakref.WeakKeyDictionary([dict])

弱參照鍵的對映類別。當不再有對鍵的強參照時，字典中的條目將被丟棄。這可用於將附加資料與應用程式其他部分擁有的物件相關聯，而無需向這些物件新增屬性。這對於覆蓋屬性存取的物件特別有用。

請注意，當將與現有鍵具有相同值的鍵（但識別性不相等）插入字典時，它會替換該值，但不會替換現有鍵。因此，當刪除對原始鍵的參照時，它也會刪除字典中的條目：

>>> class T(str): pass
...
>>> k1, k2 = T(), T()
>>> d = weakref.WeakKeyDictionary()
>>> d[k1] = 1   # d = {k1: 1}
>>> d[k2] = 2   # d = {k1: 2}
>>> del k1      # d = {}

一個變通的解法是在重新賦值 (reassignment) 之前刪除鍵：

>>> class T(str): pass
...
>>> k1, k2 = T(), T()
>>> d = weakref.WeakKeyDictionary()
>>> d[k1] = 1   # d = {k1: 1}
>>> del d[k1]
>>> d[k2] = 2   # d = {k2: 2}
>>> del k1      # d = {k2: 2}

在 3.9 版的變更: 新增對 | 和 |= 運算子的支援，如 PEP 584 [https://peps.python.org/pep-0584/] 中所說明。

WeakKeyDictionary 物件有一個直接公開內部參照的附加方法。參照在被使用時不保證是 "存活的"，因此在使用之前需要檢查呼叫參照的結果。這可以用來防止建立會導致垃圾回收器保留鍵的時間超過其所需時間的參照。

WeakKeyDictionary.keyrefs()

回傳對鍵的弱參照的可疊代物件。

class weakref.WeakValueDictionary([dict])

弱參照值的對映類別。當不再存在對值的強參照時，字典中的條目將被丟棄。

在 3.9 版的變更: 新增對 | 和 |= 運算子的支援，如 PEP 584 [https://peps.python.org/pep-0584/] 中所說明。

WeakValueDictionary 物件有一個附加方法，它與 WeakKeyDictionary.keyrefs() 方法有相同的問題。

WeakValueDictionary.valuerefs()

回傳對值的弱參照的可疊代物件。

class weakref.WeakSet([elements])

保留對其元素的弱參照的集合類別。當不再存在對某個元素的強參照時，該元素將被丟棄。

class weakref.WeakMethod(method[, callback])

一個特製的 ref 子類別，其模擬對繫結方法 (bound method) （即在類別上定義並在實例上查找的方法）的弱參照。由於繫結方法是短暫存在的，因此標準弱參照無法保留它。WeakMethod 有特殊的程式碼來重新建立繫結方法，直到物件或原始函式死亡：

>>> class C:
...     def method(self):
...         print("method called!")
...
>>> c = C()
>>> r = weakref.ref(c.method)
>>> r()
>>> r = weakref.WeakMethod(c.method)
>>> r()
<bound method C.method of <__main__.C object at 0x7fc859830220>>
>>> r()()
method called!
>>> del c
>>> gc.collect()
0
>>> r()
>>>

callback 與 ref() 函式的同名參數是相同的。

在 3.4 版被加入.

class weakref.finalize(obj, func, /, *args, **kwargs)

回傳可呼叫的最終化器物件，此物件在 obj 被垃圾回收時會被呼叫。與一般的弱參照不同，最終化器將始終存在，直到參照物件被回收為止，從而大大簡化了生命週期管理。

最終化器在被呼叫（明確呼叫或在垃圾回收時）之前被視為存活，之後它就會死亡。呼叫存活的最終化器會回傳 func(*arg, **kwargs) 的計算結果，而呼叫死亡的最終化器會回傳 None。

垃圾回收期間最終化器回呼引發的例外會在標準錯誤輸出中顯示，但無法傳播。它們的處理方式與從物件的 __del__() 方法或弱參照的回呼引發的例外相同。

當程式結束時，除非該最終化器的 atexit 屬性已被設定為 false，否則每個存活的最終化器會被呼叫。它們以與建立相反的順序被呼叫。

當模組的 globals 可能被 None 取代時，最終化器永遠不會在 interpreter shutdown 的後期叫用（invoke）其回呼。

__call__()

如果 self 仍存活，則將其標記為死亡並回傳呼叫 func(*args, **kwargs) 的結果。如果 self 已死亡，則回傳 None。

detach()

如果 self 仍存活，則將其標記為死亡並回傳元組 (obj, func, args, kwargs)。如果 self 已死亡，則回傳 None。

peek()

如果 self 仍存活，則回傳元組 (obj, func, args, kwargs)。如果 self 已死亡，則回傳 None。

alive

如果最終化器仍存活，則屬性為 true，否則為 false。

atexit

一個可寫的布林屬性，預設為 true。當程式結束時，它會呼叫 atexit 為 true 的所有剩餘且仍存活的最終化器。它們以與建立相反的順序被呼叫。

備註

確保 func、args 和 kwargs 不直接或間接擁有對 obj 的任何參照非常重要，否則 obj 將永遠不會被垃圾回收。尤其 func 不應該是 obj 的繫結方法。

在 3.4 版被加入.

weakref.ReferenceType

弱參照物件的型別物件。

weakref.ProxyType

非可呼叫物件的代理的型別物件。

weakref.CallableProxyType

可呼叫物件的代理的型別物件。

weakref.ProxyTypes

包含代理的所有型別物件的序列。這可以讓測試物件是否為代理變得更簡單，而無需依賴命名兩種代理型別。

也參考

PEP 205 [https://peps.python.org/pep-0205/] - 弱參照

此功能的提案和理由，包括早期實作的連結以及其他語言中類似功能的資訊。

弱參照物件

弱參照物件除了 ref.__callback__ 之外沒有任何方法和屬性。弱參照物件允許透過呼叫來取得參照目標（如果它仍然存在）：

>>> import weakref
>>> class Object:
...     pass
...
>>> o = Object()
>>> r = weakref.ref(o)
>>> o2 = r()
>>> o is o2
True

如果參照目標不再存活，則呼叫參照物件將回傳 None：

>>> del o, o2
>>> print(r())
None

應該使用運算式 ref() is not None 來測試弱參照物件是否仍然存活。需要使用參照物件的應用程式程式碼通常應遵循以下模式：

# r is a weak reference object
o = r()
if o is None:
    # referent has been garbage collected
    print("Object has been deallocated; can't frobnicate.")
else:
    print("Object is still live!")
    o.do_something_useful()

使用對「活性 (liveness)」的單獨測試會在執行緒應用程式中建立競爭條件 (race condition)；另一個執行緒可能在弱參照被呼叫之前讓該弱參照失效；上方顯示的慣用作法在執行緒應用程式和單執行緒應用程式中都是安全的。

可以透過子類別化來建立 ref 物件的特殊版本。這在 WeakValueDictionary 的實作中被使用，以減少對映中每個條目的記憶體開銷。這對於將附加資訊與參照相關聯最有用，但也可用於在呼叫上插入附加處理以檢索參照目標。

這個範例展示如何使用 ref 的子類別來儲存有關物件的附加資訊並影響存取參照目標時回傳的值：

import weakref

class ExtendedRef(weakref.ref):
    def __init__(self, ob, callback=None, /, **annotations):
        super().__init__(ob, callback)
        self.__counter = 0
        for k, v in annotations.items():
            setattr(self, k, v)

    def __call__(self):
        """Return a pair containing the referent and the number of
        times the reference has been called.
        """
        ob = super().__call__()
        if ob is not None:
            self.__counter += 1
            ob = (ob, self.__counter)
        return ob

範例

這個簡單的範例展示了應用程式如何使用物件 ID 來檢索它以前見過​​的物件。物件的 ID 之後可以在其他資料結構中使用，而不必強制物件保持存活，但如果這樣做，仍然可以透過 ID 檢索物件。

import weakref

_id2obj_dict = weakref.WeakValueDictionary()

def remember(obj):
    oid = id(obj)
    _id2obj_dict[oid] = obj
    return oid

def id2obj(oid):
    return _id2obj_dict[oid]

最終化器物件

使用 finalize 的最大優點是可以輕鬆註冊回呼，而無需保留回傳的最終化器物件。例如

>>> import weakref
>>> class Object:
...     pass
...
>>> kenny = Object()
>>> weakref.finalize(kenny, print, "You killed Kenny!")
<finalize object at ...; for 'Object' at ...>
>>> del kenny
You killed Kenny!

最終化器也可以直接被呼叫。然而，最終化器最多會叫用回呼一次。

>>> def callback(x, y, z):
...     print("CALLBACK")
...     return x + y + z
...
>>> obj = Object()
>>> f = weakref.finalize(obj, callback, 1, 2, z=3)
>>> assert f.alive
>>> assert f() == 6
CALLBACK
>>> assert not f.alive
>>> f()                     # callback not called because finalizer dead
>>> del obj                 # callback not called because finalizer dead

你可以使用最終化器的 detach() 方法來取消註冊最終化器。這會殺死最終化器並回傳建立建構函式時傳遞給建構函式的引數。

>>> obj = Object()
>>> f = weakref.finalize(obj, callback, 1, 2, z=3)
>>> f.detach()
(<...Object object ...>, <function callback ...>, (1, 2), {'z': 3})
>>> newobj, func, args, kwargs = _
>>> assert not f.alive
>>> assert newobj is obj
>>> assert func(*args, **kwargs) == 6
CALLBACK

除非你將 atexit 屬性設為 False，否則當程式結束時，最終化器將會被呼叫如果其仍然存在。例如

>>> obj = Object()
>>> weakref.finalize(obj, print, "obj dead or exiting")
<finalize object at ...; for 'Object' at ...>
>>> exit()
obj dead or exiting

最終化器與 __del__() 方法的比較

假設我們要建立一個類別，其實例代表臨時目錄。當以下任一事件發生時，應刪除目錄及其內容：

該物件被垃圾回收，

該物件的 remove() 方法被呼叫，或者

程式結束。

我們可以用以下的方式來嘗試使用 __del__() 方法實作該類別：

class TempDir:
    def __init__(self):
        self.name = tempfile.mkdtemp()

    def remove(self):
        if self.name is not None:
            shutil.rmtree(self.name)
            self.name = None

    @property
    def removed(self):
        return self.name is None

    def __del__(self):
        self.remove()

從 Python 3.4 開始，__del__() 方法不再阻止參照循環 (reference cycle) 被垃圾回收，並且在 interpreter shutdown 期間不再強制將模組的 globals 設為 None。所以這段程式碼在 CPython 上應該可以正常運作。

然而，眾所周知，對 __del__() 方法的處理是特地實作的，因為它依賴於直譯器的垃圾回收器實作的內部細節。

更耐用的替代方案可以是定義一個最終化器，其僅參照需要的特定函式和物件，而不是存取物件的完整狀態：

class TempDir:
    def __init__(self):
        self.name = tempfile.mkdtemp()
        self._finalizer = weakref.finalize(self, shutil.rmtree, self.name)

    def remove(self):
        self._finalizer()

    @property
    def removed(self):
        return not self._finalizer.alive

定義如下，我們的最終化器僅接收對適當清理目錄所需的詳細資訊的參照。如果物件從未被垃圾回收，則最終化器仍將在結束時被呼叫。

基於 weakref 的最終化器的另一個優點是它們可用於為定義由第三方控制的類別註冊最終化器，例如在解除安裝模組時執行程式碼：

import weakref, sys
def unloading_module():
    # implicit reference to the module globals from the function body
weakref.finalize(sys.modules[__name__], unloading_module)

備註

如果在程式結束時在常駐的 (daemonic) 執行緒中建立最終化器物件，則最終化器有可能在結束時不會被呼叫。然而，在常駐的執行緒中 atexit.register()、try: ... finally: ... 和 with: ... 也不保證清理會發生。

types --- 動態型別建立與內建型別名稱

原始碼：Lib/types.py [https://github.com/python/cpython/tree/3.14/Lib/types.py]

This module defines utility functions to assist in dynamic creation of new types.

It also defines names for some object types that are used by the standard Python interpreter, but not exposed as builtins like int or str are.

Finally, it provides some additional type-related utility classes and functions that are not fundamental enough to be builtins.

Dynamic Type Creation

types.new_class(name, bases=(), kwds=None, exec_body=None)

Creates a class object dynamically using the appropriate metaclass.

The first three arguments are the components that make up a class definition header: the class name, the base classes (in order), the keyword arguments (such as metaclass).

The exec_body argument is a callback that is used to populate the freshly created class namespace. It should accept the class namespace as its sole argument and update the namespace directly with the class contents. If no callback is provided, it has the same effect as passing in lambda ns: None.

在 3.3 版被加入.

types.prepare_class(name, bases=(), kwds=None)

Calculates the appropriate metaclass and creates the class namespace.

The arguments are the components that make up a class definition header: the class name, the base classes (in order) and the keyword arguments (such as metaclass).

The return value is a 3-tuple: metaclass, namespace, kwds

metaclass is the appropriate metaclass, namespace is the prepared class namespace and kwds is an updated copy of the passed in kwds argument with any 'metaclass' entry removed. If no kwds argument is passed in, this will be an empty dict.

在 3.3 版被加入.

在 3.6 版的變更: The default value for the namespace element of the returned tuple has changed. Now an insertion-order-preserving mapping is used when the metaclass does not have a __prepare__ method.

也參考

Metaclasses

Full details of the class creation process supported by these functions

PEP 3115 [https://peps.python.org/pep-3115/] - Metaclasses in Python 3000

Introduced the __prepare__ namespace hook

types.resolve_bases(bases)

Resolve MRO entries dynamically as specified by PEP 560 [https://peps.python.org/pep-0560/].

This function looks for items in bases that are not instances of type, and returns a tuple where each such object that has an __mro_entries__() method is replaced with an unpacked result of calling this method. If a bases item is an instance of type, or it doesn't have an __mro_entries__() method, then it is included in the return tuple unchanged.

在 3.7 版被加入.

types.get_original_bases(cls, /)

Return the tuple of objects originally given as the bases of cls before the __mro_entries__() method has been called on any bases (following the mechanisms laid out in PEP 560 [https://peps.python.org/pep-0560/]). This is useful for introspecting Generics.

For classes that have an __orig_bases__ attribute, this function returns the value of cls.__orig_bases__. For classes without the __orig_bases__ attribute, cls.__bases__ is returned.

舉例來說：

from typing import TypeVar, Generic, NamedTuple, TypedDict

T = TypeVar("T")
class Foo(Generic[T]): ...
class Bar(Foo[int], float): ...
class Baz(list[str]): ...
Eggs = NamedTuple("Eggs", [("a", int), ("b", str)])
Spam = TypedDict("Spam", {"a": int, "b": str})

assert Bar.__bases__ == (Foo, float)
assert get_original_bases(Bar) == (Foo[int], float)

assert Baz.__bases__ == (list,)
assert get_original_bases(Baz) == (list[str],)

assert Eggs.__bases__ == (tuple,)
assert get_original_bases(Eggs) == (NamedTuple,)

assert Spam.__bases__ == (dict,)
assert get_original_bases(Spam) == (TypedDict,)

assert int.__bases__ == (object,)
assert get_original_bases(int) == (object,)

在 3.12 版被加入.

也參考

PEP 560 [https://peps.python.org/pep-0560/] - Core support for typing module and generic types

Standard Interpreter Types

This module provides names for many of the types that are required to implement a Python interpreter. It deliberately avoids including some of the types that arise only incidentally during processing such as the listiterator type.

Typical use of these names is for isinstance() or issubclass() checks.

If you instantiate any of these types, note that signatures may vary between Python versions.

Standard names are defined for the following types:

types.NoneType

The type of None.

在 3.10 版被加入.

types.FunctionType

types.LambdaType

The type of user-defined functions and functions created by lambda expressions.

引發一個附帶引數 code 的稽核事件 function.__new__。

The audit event only occurs for direct instantiation of function objects, and is not raised for normal compilation.

types.GeneratorType

The type of generator-iterator objects, created by generator functions.

types.CoroutineType

The type of coroutine objects, created by async def functions.

在 3.5 版被加入.

types.AsyncGeneratorType

The type of asynchronous generator-iterator objects, created by asynchronous generator functions.

在 3.6 版被加入.

class types.CodeType(**kwargs)

The type of code objects such as returned by compile().

引發一個附帶引數 code、filename、name、argcount、posonlyargcount、kwonlyargcount、nlocals、stacksize、flags 的稽核事件 code.__new__。

Note that the audited arguments may not match the names or positions required by the initializer. The audit event only occurs for direct instantiation of code objects, and is not raised for normal compilation.

types.CellType

The type for cell objects: such objects are used as containers for a function's closure variables.

在 3.8 版被加入.

types.MethodType

The type of methods of user-defined class instances.

types.BuiltinFunctionType

types.BuiltinMethodType

The type of built-in functions like len() or sys.exit(), and methods of built-in classes. (Here, the term "built-in" means "written in C".)

types.WrapperDescriptorType

The type of methods of some built-in data types and base classes such as object.__init__() or object.__lt__().

在 3.7 版被加入.

types.MethodWrapperType

The type of bound methods of some built-in data types and base classes. For example it is the type of object().__str__.

在 3.7 版被加入.

types.NotImplementedType

The type of NotImplemented.

在 3.10 版被加入.

types.MethodDescriptorType

The type of methods of some built-in data types such as str.join().

在 3.7 版被加入.

types.ClassMethodDescriptorType

The type of unbound class methods of some built-in data types such as dict.__dict__['fromkeys'].

在 3.7 版被加入.

class types.ModuleType(name, doc=None)

The type of modules. The constructor takes the name of the module to be created and optionally its docstring.

也參考

模組物件的文件

Provides details on the special attributes that can be found on instances of ModuleType.

importlib.util.module_from_spec()

Modules created using the ModuleType constructor are created with many of their special attributes unset or set to default values. module_from_spec() provides a more robust way of creating ModuleType instances which ensures the various attributes are set appropriately.

types.EllipsisType

The type of Ellipsis.

在 3.10 版被加入.

class types.GenericAlias(t_origin, t_args)

The type of parameterized generics such as list[int].

t_origin should be a non-parameterized generic class, such as list, tuple or dict. t_args should be a tuple (possibly of length 1) of types which parameterize t_origin:

>>> from types import GenericAlias

>>> list[int] == GenericAlias(list, (int,))
True
>>> dict[str, int] == GenericAlias(dict, (str, int))
True

在 3.9 版被加入.

在 3.9.2 版的變更: This type can now be subclassed.

也參考

Generic Alias Types

In-depth documentation on instances of types.GenericAlias

PEP 585 [https://peps.python.org/pep-0585/] - Type Hinting Generics In Standard Collections

Introducing the types.GenericAlias class

class types.UnionType

The type of union type expressions.

在 3.10 版被加入.

在 3.14 版的變更: This is now an alias for typing.Union.

class types.TracebackType(tb_next, tb_frame, tb_lasti, tb_lineno)

The type of traceback objects such as found in sys.exception().__traceback__.

See the language reference for details of the available attributes and operations, and guidance on creating tracebacks dynamically.

types.FrameType

The type of frame objects such as found in tb.tb_frame if tb is a traceback object.

types.GetSetDescriptorType

The type of objects defined in extension modules with PyGetSetDef, such as FrameType.f_locals or array.array.typecode. This type is used as descriptor for object attributes; it has the same purpose as the property type, but for classes defined in extension modules.

types.MemberDescriptorType

The type of objects defined in extension modules with PyMemberDef, such as datetime.timedelta.days. This type is used as descriptor for simple C data members which use standard conversion functions; it has the same purpose as the property type, but for classes defined in extension modules.

In addition, when a class is defined with a __slots__ attribute, then for each slot, an instance of MemberDescriptorType will be added as an attribute on the class. This allows the slot to appear in the class's __dict__.

CPython 實作細節： In other implementations of Python, this type may be identical to GetSetDescriptorType.

class types.MappingProxyType(mapping)

Read-only proxy of a mapping. It provides a dynamic view on the mapping's entries, which means that when the mapping changes, the view reflects these changes.

在 3.3 版被加入.

在 3.9 版的變更: Updated to support the new union (|) operator from PEP 584 [https://peps.python.org/pep-0584/], which simply delegates to the underlying mapping.

key in proxy

Return True if the underlying mapping has a key key, else False.

proxy[key]

Return the item of the underlying mapping with key key. Raises a KeyError if key is not in the underlying mapping.

iter(proxy)

Return an iterator over the keys of the underlying mapping. This is a shortcut for iter(proxy.keys()).

len(proxy)

Return the number of items in the underlying mapping.

copy()

Return a shallow copy of the underlying mapping.

get(key[, default])

Return the value for key if key is in the underlying mapping, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.

items()

Return a new view of the underlying mapping's items ((key, value) pairs).

keys()

Return a new view of the underlying mapping's keys.

values()

Return a new view of the underlying mapping's values.

reversed(proxy)

Return a reverse iterator over the keys of the underlying mapping.

在 3.9 版被加入.

hash(proxy)

Return a hash of the underlying mapping.

在 3.12 版被加入.

class types.CapsuleType

The type of capsule objects.

在 3.13 版被加入.

Additional Utility Classes and Functions

class types.SimpleNamespace

A simple object subclass that provides attribute access to its namespace, as well as a meaningful repr.

Unlike object, with SimpleNamespace you can add and remove attributes.

SimpleNamespace objects may be initialized in the same way as dict: either with keyword arguments, with a single positional argument, or with both. When initialized with keyword arguments, those are directly added to the underlying namespace. Alternatively, when initialized with a positional argument, the underlying namespace will be updated with key-value pairs from that argument (either a mapping object or an iterable object producing key-value pairs). All such keys must be strings.

The type is roughly equivalent to the following code:

class SimpleNamespace:
    def __init__(self, mapping_or_iterable=(), /, **kwargs):
        self.__dict__.update(mapping_or_iterable)
        self.__dict__.update(kwargs)

    def __repr__(self):
        items = (f"{k}={v!r}" for k, v in self.__dict__.items())
        return "{}({})".format(type(self).__name__, ", ".join(items))

    def __eq__(self, other):
        if isinstance(self, SimpleNamespace) and isinstance(other, SimpleNamespace):
           return self.__dict__ == other.__dict__
        return NotImplemented

SimpleNamespace may be useful as a replacement for class NS: pass. However, for a structured record type use namedtuple() instead.

SimpleNamespace objects are supported by copy.replace().

在 3.3 版被加入.

在 3.9 版的變更: Attribute order in the repr changed from alphabetical to insertion (like dict).

在 3.13 版的變更: Added support for an optional positional argument.

types.DynamicClassAttribute(fget=None, fset=None, fdel=None, doc=None)

Route attribute access on a class to __getattr__.

This is a descriptor, used to define attributes that act differently when accessed through an instance and through a class. Instance access remains normal, but access to an attribute through a class will be routed to the class's __getattr__ method; this is done by raising AttributeError.

This allows one to have properties active on an instance, and have virtual attributes on the class with the same name (see enum.Enum for an example).

在 3.4 版被加入.

Coroutine Utility Functions

types.coroutine(gen_func)

This function transforms a generator function into a coroutine function which returns a generator-based coroutine. The generator-based coroutine is still a generator iterator, but is also considered to be a coroutine object and is awaitable. However, it may not necessarily implement the __await__() method.

If gen_func is a generator function, it will be modified in-place.

If gen_func is not a generator function, it will be wrapped. If it returns an instance of collections.abc.Generator, the instance will be wrapped in an awaitable proxy object. All other types of objects will be returned as is.

在 3.5 版被加入.

copy --- 淺層 (shallow) 和深層 (deep) 複製操作

原始碼：Lib/copy.py [https://github.com/python/cpython/tree/3.14/Lib/copy.py]

Python 的賦值陳述式不複製物件，而是建立目標和物件的繫結 (binding) 關係。對於可變 (mutable) 或包含可變項目 (mutable item) 的集合，有時會需要一份副本來改變特定副本，而不必改變其他副本。本模組提供了通用的淺層複製和深層複製操作（如下所述）。

介面摘要：

copy.copy(obj)

回傳 obj 的淺層複製。

copy.deepcopy(obj[, memo])

回傳 obj 的深層複製。

copy.replace(obj, /, **changes)

Creates a new object of the same type as obj, replacing fields with values from changes.

在 3.13 版被加入.

exception copy.Error

引發針對特定模組的錯誤。

淺層與深層複製的區別僅與複合物件（即包含 list 或類別的實例等其他物件的物件）相關：

淺層複製建構一個新的複合物件，然後（在儘可能的範圍內）將原始物件中找到的物件的參照插入其中。

深層複製建構一個新的複合物件，然後遞迴地將在原始物件裡找到的物件的副本插入其中。

深層複製操作通常存在兩個問題，而淺層複製操作並不存在這些問題：

遞迴物件（直接或間接包含對自身參照的複合物件）可能會導致遞迴迴圈。

由於深層複製會複製所有內容，因此可能會有過多複製（例如應該在副本之間共享的資料）。

deepcopy() 函式用以下方式避免了這些問題：

保留在目前複製過程中已複製的物件的 memo 字典；以及

允許使用者定義的類別複寫 (override) 複製操作或複製的元件集合。

該模組不複製模組、方法、堆疊追蹤（stack trace）、堆疊框（stack frame）、檔案、socket、視窗、陣列以及任何類似的型別。它透過不變更原始物件並將其回傳來（淺層或深層地）"複製"函式和類別；這與 pickle 模組處理這類問題的方式是相似的。

字典的淺層複製可以使用 dict.copy()，而 list 的淺層複製可以透過賦值整個 list 的切片 (slice) 完成，例如，copied_list = original_list[:]。

類別可以使用與操作 pickle 相同的介面來控制複製操作，關於這些方法的描述資訊請參考 pickle 模組。實際上，copy 模組使用的正是從 copyreg 模組中註冊的 pickle 函式。

In order for a class to define its own copy implementation, it can define special methods __copy__() and __deepcopy__().

object.__copy__(self)

Called to implement the shallow copy operation; no additional arguments are passed.

object.__deepcopy__(self, memo)

用來實作深層複製操作；它會傳遞一個引數，即 memo 字典。如果 __deepcopy__ 實現需要建立一個元件的深層複製，它應當呼叫 deepcopy() 函式並以該元件作為第一個引數、以該 memo 字典作為第二個引數。memo 字典應當被當作不透明物件 (opaque object) 來處理

Function copy.replace() is more limited than copy() and deepcopy(), and only supports named tuples created by namedtuple(), dataclasses, and other classes which define method __replace__().

object.__replace__(self, /, **changes)

This method should create a new object of the same type, replacing fields with values from changes.

在 3.13 版被加入.

也參考

pickle 模組

支援物件之狀態檢索 (state retrieval) 和恢復 (restoration) 相關特殊方法的討論。

pprint --- 資料美化列印器

原始碼：Lib/pprint.py [https://github.com/python/cpython/tree/3.14/Lib/pprint.py]

The pprint module provides a capability to "pretty-print" arbitrary Python data structures in a form which can be used as input to the interpreter. If the formatted structures include objects which are not fundamental Python types, the representation may not be loadable. This may be the case if objects such as files, sockets or classes are included, as well as many other objects which are not representable as Python literals.

The formatted representation keeps objects on a single line if it can, and breaks them onto multiple lines if they don't fit within the allowed width, adjustable by the width parameter defaulting to 80 characters.

在 3.9 版的變更: Added support for pretty-printing types.SimpleNamespace.

在 3.10 版的變更: Added support for pretty-printing dataclasses.dataclass.

函式

pprint.pp(object, stream=None, indent=1, width=80, depth=None, *, compact=False, sort_dicts=False, underscore_numbers=False)

Prints the formatted representation of object, followed by a newline. This function may be used in the interactive interpreter instead of the print() function for inspecting values. Tip: you can reassign print = pprint.pp for use within a scope.

參數:

object -- 將被印出的物件。

stream (file-like object | None) -- A file-like object to which the output will be written by calling its write() method. If None (the default), sys.stdout is used.

indent (int) -- The amount of indentation added for each nesting level.

width (int) -- The desired maximum number of characters per line in the output. If a structure cannot be formatted within the width constraint, a best effort will be made.

depth (int | None) -- The number of nesting levels which may be printed. If the data structure being printed is too deep, the next contained level is replaced by .... If None (the default), there is no constraint on the depth of the objects being formatted.

compact (bool) -- Control the way long sequences are formatted. If False (the default), each item of a sequence will be formatted on a separate line, otherwise as many items as will fit within the width will be formatted on each output line.

sort_dicts (bool) -- If True, dictionaries will be formatted with their keys sorted, otherwise they will be displayed in insertion order (the default).

underscore_numbers (bool) -- If True, integers will be formatted with the _ character for a thousands separator, otherwise underscores are not displayed (the default).

>>> import pprint
>>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']
>>> stuff.insert(0, stuff)
>>> pprint.pp(stuff)
[<Recursion on list with id=...>,
 'spam',
 'eggs',
 'lumberjack',
 'knights',
 'ni']

在 3.8 版被加入.

pprint.pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True, underscore_numbers=False)

Alias for pp() with sort_dicts set to True by default, which would automatically sort the dictionaries' keys, you might want to use pp() instead where it is False by default.

pprint.pformat(object, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True, underscore_numbers=False)

Return the formatted representation of object as a string. indent, width, depth, compact, sort_dicts and underscore_numbers are passed to the PrettyPrinter constructor as formatting parameters and their meanings are as described in the documentation above.

pprint.isreadable(object)

Determine if the formatted representation of object is "readable", or can be used to reconstruct the value using eval(). This always returns False for recursive objects.

>>> pprint.isreadable(stuff)
False

pprint.isrecursive(object)

Determine if object requires a recursive representation. This function is subject to the same limitations as noted in saferepr() below and may raise an RecursionError if it fails to detect a recursive object.

pprint.saferepr(object)

Return a string representation of object, protected against recursion in some common data structures, namely instances of dict, list and tuple or subclasses whose __repr__ has not been overridden. If the representation of object exposes a recursive entry, the recursive reference will be represented as <Recursion on typename with id=number>. The representation is not otherwise formatted.

>>> pprint.saferepr(stuff)
"[<Recursion on list with id=...>, 'spam', 'eggs', 'lumberjack', 'knights', 'ni']"

PrettyPrinter 物件

class pprint.PrettyPrinter(indent=1, width=80, depth=None, stream=None, *, compact=False, sort_dicts=True, underscore_numbers=False)

建立一個 PrettyPrinter 實例。

Arguments have the same meaning as for pp(). Note that they are in a different order, and that sort_dicts defaults to True.

>>> import pprint
>>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']
>>> stuff.insert(0, stuff[:])
>>> pp = pprint.PrettyPrinter(indent=4)
>>> pp.pprint(stuff)
[   ['spam', 'eggs', 'lumberjack', 'knights', 'ni'],
    'spam',
    'eggs',
    'lumberjack',
    'knights',
    'ni']
>>> pp = pprint.PrettyPrinter(width=41, compact=True)
>>> pp.pprint(stuff)
[['spam', 'eggs', 'lumberjack',
  'knights', 'ni'],
 'spam', 'eggs', 'lumberjack', 'knights',
 'ni']
>>> tup = ('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead',
... ('parrot', ('fresh fruit',))))))))
>>> pp = pprint.PrettyPrinter(depth=6)
>>> pp.pprint(tup)
('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead', (...)))))))

在 3.4 版的變更: 新增 compact 參數。

在 3.8 版的變更: 新增 sort_dicts 參數。

在 3.10 版的變更: 新增 underscore_numbers 參數。

在 3.11 版的變更: No longer attempts to write to sys.stdout if it is None.

PrettyPrinter 實例有以下方法：

PrettyPrinter.pformat(object)

Return the formatted representation of object. This takes into account the options passed to the PrettyPrinter constructor.

PrettyPrinter.pprint(object)

Print the formatted representation of object on the configured stream, followed by a newline.

The following methods provide the implementations for the corresponding functions of the same names. Using these methods on an instance is slightly more efficient since new PrettyPrinter objects don't need to be created.

PrettyPrinter.isreadable(object)

Determine if the formatted representation of the object is "readable," or can be used to reconstruct the value using eval(). Note that this returns False for recursive objects. If the depth parameter of the PrettyPrinter is set and the object is deeper than allowed, this returns False.

PrettyPrinter.isrecursive(object)

Determine if the object requires a recursive representation.

This method is provided as a hook to allow subclasses to modify the way objects are converted to strings. The default implementation uses the internals of the saferepr() implementation.

PrettyPrinter.format(object, context, maxlevels, level)

Returns three values: the formatted version of object as a string, a flag indicating whether the result is readable, and a flag indicating whether recursion was detected. The first argument is the object to be presented. The second is a dictionary which contains the id() of objects that are part of the current presentation context (direct and indirect containers for object that are affecting the presentation) as the keys; if an object needs to be presented which is already represented in context, the third return value should be True. Recursive calls to the format() method should add additional entries for containers to this dictionary. The third argument, maxlevels, gives the requested limit to recursion; this will be 0 if there is no requested limit. This argument should be passed unmodified to recursive calls. The fourth argument, level, gives the current level; recursive calls should be passed a value less than that of the current call.

範例

To demonstrate several uses of the pp() function and its parameters, let's fetch information about a project from PyPI [https://pypi.org]:

>>> import json
>>> import pprint
>>> from urllib.request import urlopen
>>> with urlopen('https://pypi.org/pypi/sampleproject/1.2.0/json') as resp:
...     project_info = json.load(resp)['info']

In its basic form, pp() shows the whole object:

>>> pprint.pp(project_info)
{'author': 'The Python Packaging Authority',
 'author_email': 'pypa-dev@googlegroups.com',
 'bugtrack_url': None,
 'classifiers': ['Development Status :: 3 - Alpha',
                 'Intended Audience :: Developers',
                 'License :: OSI Approved :: MIT License',
                 'Programming Language :: Python :: 2',
                 'Programming Language :: Python :: 2.6',
                 'Programming Language :: Python :: 2.7',
                 'Programming Language :: Python :: 3',
                 'Programming Language :: Python :: 3.2',
                 'Programming Language :: Python :: 3.3',
                 'Programming Language :: Python :: 3.4',
                 'Topic :: Software Development :: Build Tools'],
 'description': 'A sample Python project\n'
                '=======================\n'
                '\n'
                'This is the description file for the project.\n'
                '\n'
                'The file should use UTF-8 encoding and be written using '
                'ReStructured Text. It\n'
                'will be used to generate the project webpage on PyPI, and '
                'should be written for\n'
                'that purpose.\n'
                '\n'
                'Typical contents for this file would include an overview of '
                'the project, basic\n'
                'usage examples, etc. Generally, including the project '
                'changelog in here is not\n'
                'a good idea, although a simple "What\'s New" section for the '
                'most recent version\n'
                'may be appropriate.',
 'description_content_type': None,
 'docs_url': None,
 'download_url': 'UNKNOWN',
 'downloads': {'last_day': -1, 'last_month': -1, 'last_week': -1},
 'home_page': 'https://github.com/pypa/sampleproject',
 'keywords': 'sample setuptools development',
 'license': 'MIT',
 'maintainer': None,
 'maintainer_email': None,
 'name': 'sampleproject',
 'package_url': 'https://pypi.org/project/sampleproject/',
 'platform': 'UNKNOWN',
 'project_url': 'https://pypi.org/project/sampleproject/',
 'project_urls': {'Download': 'UNKNOWN',
                  'Homepage': 'https://github.com/pypa/sampleproject'},
 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
 'requires_dist': None,
 'requires_python': None,
 'summary': 'A sample Python project',
 'version': '1.2.0'}

The result can be limited to a certain depth (ellipsis is used for deeper contents):

>>> pprint.pp(project_info, depth=1)
{'author': 'The Python Packaging Authority',
 'author_email': 'pypa-dev@googlegroups.com',
 'bugtrack_url': None,
 'classifiers': [...],
 'description': 'A sample Python project\n'
                '=======================\n'
                '\n'
                'This is the description file for the project.\n'
                '\n'
                'The file should use UTF-8 encoding and be written using '
                'ReStructured Text. It\n'
                'will be used to generate the project webpage on PyPI, and '
                'should be written for\n'
                'that purpose.\n'
                '\n'
                'Typical contents for this file would include an overview of '
                'the project, basic\n'
                'usage examples, etc. Generally, including the project '
                'changelog in here is not\n'
                'a good idea, although a simple "What\'s New" section for the '
                'most recent version\n'
                'may be appropriate.',
 'description_content_type': None,
 'docs_url': None,
 'download_url': 'UNKNOWN',
 'downloads': {...},
 'home_page': 'https://github.com/pypa/sampleproject',
 'keywords': 'sample setuptools development',
 'license': 'MIT',
 'maintainer': None,
 'maintainer_email': None,
 'name': 'sampleproject',
 'package_url': 'https://pypi.org/project/sampleproject/',
 'platform': 'UNKNOWN',
 'project_url': 'https://pypi.org/project/sampleproject/',
 'project_urls': {...},
 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
 'requires_dist': None,
 'requires_python': None,
 'summary': 'A sample Python project',
 'version': '1.2.0'}

Additionally, maximum character width can be suggested. If a long object cannot be split, the specified width will be exceeded:

>>> pprint.pp(project_info, depth=1, width=60)
{'author': 'The Python Packaging Authority',
 'author_email': 'pypa-dev@googlegroups.com',
 'bugtrack_url': None,
 'classifiers': [...],
 'description': 'A sample Python project\n'
                '=======================\n'
                '\n'
                'This is the description file for the '
                'project.\n'
                '\n'
                'The file should use UTF-8 encoding and be '
                'written using ReStructured Text. It\n'
                'will be used to generate the project '
                'webpage on PyPI, and should be written '
                'for\n'
                'that purpose.\n'
                '\n'
                'Typical contents for this file would '
                'include an overview of the project, '
                'basic\n'
                'usage examples, etc. Generally, including '
                'the project changelog in here is not\n'
                'a good idea, although a simple "What\'s '
                'New" section for the most recent version\n'
                'may be appropriate.',
 'description_content_type': None,
 'docs_url': None,
 'download_url': 'UNKNOWN',
 'downloads': {...},
 'home_page': 'https://github.com/pypa/sampleproject',
 'keywords': 'sample setuptools development',
 'license': 'MIT',
 'maintainer': None,
 'maintainer_email': None,
 'name': 'sampleproject',
 'package_url': 'https://pypi.org/project/sampleproject/',
 'platform': 'UNKNOWN',
 'project_url': 'https://pypi.org/project/sampleproject/',
 'project_urls': {...},
 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
 'requires_dist': None,
 'requires_python': None,
 'summary': 'A sample Python project',
 'version': '1.2.0'}

reprlib --- repr() 的替代實作

原始碼：Lib/reprlib.py [https://github.com/python/cpython/tree/3.14/Lib/reprlib.py]

The reprlib module provides a means for producing object representations with limits on the size of the resulting strings. This is used in the Python debugger and may be useful in other contexts as well.

This module provides a class, an instance, and a function:

class reprlib.Repr(*, maxlevel=6, maxtuple=6, maxlist=6, maxarray=5, maxdict=4, maxset=6, maxfrozenset=6, maxdeque=6, maxstring=30, maxlong=40, maxother=30, fillvalue='...', indent=None)

Class which provides formatting services useful in implementing functions similar to the built-in repr(); size limits for different object types are added to avoid the generation of representations which are excessively long.

The keyword arguments of the constructor can be used as a shortcut to set the attributes of the Repr instance. Which means that the following initialization:

aRepr = reprlib.Repr(maxlevel=3)

等價於：

aRepr = reprlib.Repr()
aRepr.maxlevel = 3

See section Repr Objects for more information about Repr attributes.

在 3.12 版的變更: Allow attributes to be set via keyword arguments.

reprlib.aRepr

This is an instance of Repr which is used to provide the repr() function described below. Changing the attributes of this object will affect the size limits used by repr() and the Python debugger.

reprlib.repr(obj)

This is the repr() method of aRepr. It returns a string similar to that returned by the built-in function of the same name, but with limits on most sizes.

In addition to size-limiting tools, the module also provides a decorator for detecting recursive calls to __repr__() and substituting a placeholder string instead.

@reprlib.recursive_repr(fillvalue='...')

Decorator for __repr__() methods to detect recursive calls within the same thread. If a recursive call is made, the fillvalue is returned, otherwise, the usual __repr__() call is made. For example:

>>> from reprlib import recursive_repr
>>> class MyList(list):
...     @recursive_repr()
...     def __repr__(self):
...         return '<' + '|'.join(map(repr, self)) + '>'
...
>>> m = MyList('abc')
>>> m.append(m)
>>> m.append('x')
>>> print(m)
<'a'|'b'|'c'|...|'x'>

在 3.2 版被加入.

Repr 物件

Repr instances provide several attributes which can be used to provide size limits for the representations of different object types, and methods which format specific object types.

Repr.fillvalue

This string is displayed for recursive references. It defaults to ....

在 3.11 版被加入.

Repr.maxlevel

Depth limit on the creation of recursive representations. The default is 6.

Repr.maxdict

Repr.maxlist

Repr.maxtuple

Repr.maxset

Repr.maxfrozenset

Repr.maxdeque

Repr.maxarray

Limits on the number of entries represented for the named object type. The default is 4 for maxdict, 5 for maxarray, and 6 for the others.

Repr.maxlong

Maximum number of characters in the representation for an integer. Digits are dropped from the middle. The default is 40.

Repr.maxstring

Limit on the number of characters in the representation of the string. Note that the "normal" representation of the string is used as the character source: if escape sequences are needed in the representation, these may be mangled when the representation is shortened. The default is 30.

Repr.maxother

This limit is used to control the size of object types for which no specific formatting method is available on the Repr object. It is applied in a similar manner as maxstring. The default is 20.

Repr.indent

If this attribute is set to None (the default), the output is formatted with no line breaks or indentation, like the standard repr(). For example:

>>> example = [
...     1, 'spam', {'a': 2, 'b': 'spam eggs', 'c': {3: 4.5, 6: []}}, 'ham']
>>> import reprlib
>>> aRepr = reprlib.Repr()
>>> print(aRepr.repr(example))
[1, 'spam', {'a': 2, 'b': 'spam eggs', 'c': {3: 4.5, 6: []}}, 'ham']

If indent is set to a string, each recursion level is placed on its own line, indented by that string:

>>> aRepr.indent = '-->'
>>> print(aRepr.repr(example))
[
-->1,
-->'spam',
-->{
-->-->'a': 2,
-->-->'b': 'spam eggs',
-->-->'c': {
-->-->-->3: 4.5,
-->-->-->6: [],
-->-->},
-->},
-->'ham',
]

Setting indent to a positive integer value behaves as if it was set to a string with that number of spaces:

>>> aRepr.indent = 4
>>> print(aRepr.repr(example))
[
    1,
    'spam',
    {
        'a': 2,
        'b': 'spam eggs',
        'c': {
            3: 4.5,
            6: [],
        },
    },
    'ham',
]

在 3.12 版被加入.

Repr.repr(obj)

The equivalent to the built-in repr() that uses the formatting imposed by the instance.

Repr.repr1(obj, level)

Recursive implementation used by repr(). This uses the type of obj to determine which formatting method to call, passing it obj and level. The type-specific methods should call repr1() to perform recursive formatting, with level - 1 for the value of level in the recursive call.

Repr.repr_TYPE(obj, level)

Formatting methods for specific types are implemented as methods with a name based on the type name. In the method name, TYPE is replaced by '_'.join(type(obj).__name__.split()). Dispatch to these methods is handled by repr1(). Type-specific methods which need to recursively format a value should call self.repr1(subobj, level - 1).

Subclassing Repr Objects

The use of dynamic dispatching by Repr.repr1() allows subclasses of Repr to add support for additional built-in object types or to modify the handling of types already supported. This example shows how special support for file objects could be added:

import reprlib
import sys

class MyRepr(reprlib.Repr):

    def repr_TextIOWrapper(self, obj, level):
        if obj.name in {'<stdin>', '<stdout>', '<stderr>'}:
            return obj.name
        return repr(obj)

aRepr = MyRepr()
print(aRepr.repr(sys.stdin))         # 印出 '<stdin>'

<stdin>

enum --- 對列舉的支援

在 3.4 版被加入.

原始碼：Lib/enum.py [https://github.com/python/cpython/tree/3.14/Lib/enum.py]

Important

本頁包含 API 的參考資訊。關於教學資訊及更多進階主題的討論請參考

基本教學

進階教學

列舉指南

列舉：

是一組綁定唯一值的代表名稱（成員）

可以用疊代的方式以定義的順序回傳其正式 (canonical)（即非別名）成員

使用 call 語法來透過值回傳成員

使用 index 語法來透過名稱回傳成員

列舉透過 class 語法或函式呼叫的語法來建立：

>>> from enum import Enum

>>> # class 語法
>>> class Color(Enum):
...     RED = 1
...     GREEN = 2
...     BLUE = 3

>>> # 函式語法
>>> Color = Enum('Color', [('RED', 1), ('GREEN', 2), ('BLUE', 3)])

雖然我們可以用 class 語法來建立列舉，列舉並不是標準的 Python 類別。參考列舉有何差異以取得更多細節。

備註

命名方式

Color 類別是一個列舉（或 enum）

Color.RED、Color.GREEN 等屬性是列舉成員（或成員），並且使用上可以看作常數。

列舉成員有名稱和值（Color.RED 的名稱是 RED，Color.BLUE 的值是 3 諸如此類）

模組內容

EnumType

Enum 及其子類別的 type。

Enum

用來建立列舉常數的基礎類別。

IntEnum

用來建立列舉常數的基礎類別，同時也是 int 的子類別。（備註）

StrEnum

用來建立列舉常數的基礎類別，同時也是 str 的子類別。（備註）

Flag

用來建立列舉常數的基礎類別，可以使用位元操作來結合成員且其結果不失去 Flag 的成員資格。

IntFlag

用來建立列舉常數的基礎類別，可以使用位元操作來結合成員且其結果不失去 IntFlag 的成員資格。IntFlag 的成員也是 int 的子類別。（備註）

ReprEnum

由 IntEnum、StrEnum 及 IntFlag 所使用來保留這些混合型別的 str()。

EnumCheck

一個有 CONTINUOUS、NAMED_FLAGS 及 UNIQUE 這些值的列舉，和 verify() 一起使用來確保給定的列舉符合多種限制。

FlagBoundary

一個有 STRICT、CONFORM、EJECT 及 KEEP 這些值的列舉，允許列舉對如何處理非法值做更細微的控制。

EnumDict

dict 的子類別，用於當作 EnumType 的子類別時使用。

auto

列舉成員的實例會被取代成合適的值。StrEnum 預設是小寫版本的成員名稱，其它列舉則預設是 1 且往後遞增。

property()

允許 Enum 成員擁有屬性且不會與成員名稱有衝突。value 及 name 屬性是用這個方式來實作。

unique()

Enum 類別的裝飾器，用來確保任何值只有綁定到一個名稱上。

verify()

Enum 類別的裝飾器，用來檢查列舉上使用者所選的限制。

member()

讓 obj 變成成員。可以當作裝飾器使用。

nonmember()

不讓 obj 變成成員。可以當作裝飾器使用。

global_enum()

修改列舉上的 str() 及 repr() ，讓成員顯示為屬於模組而不是類別，並將該列舉成員匯出到全域命名空間。

show_flag_values()

回傳旗標 (flag) 裡包含的所有 2 的次方的整數串列。

enum.bin()

Like built-in bin(), except negative values are represented in two's complement, and the leading bit always indicates sign (0 implies positive, 1 implies negative).

在 3.6 版被加入: Flag, IntFlag, auto

在 3.11 版被加入: StrEnum, EnumCheck, ReprEnum, FlagBoundary, property, member, nonmember, global_enum, show_flag_values

在 3.13 版被加入: EnumDict

資料型別

class enum.EnumType

EnumType 是 enum 列舉的 metaclass。EnumType 可以有子類別 -- 細節請參考 建立 EnumType 的子類別。

EnumType 負責在最後的列舉上面設定正確的 __repr__()、__str__()、__format__() 及 __reduce__() 方法，以及建立列舉成員、正確處理重複、提供列舉類別的疊代等等。

在 3.11 版被加入: 在 3.11 之前，EnumType 稱作 EnumMeta，其目前仍可作為別名使用。

__call__(cls, value, names=None, *, module=None, qualname=None, type=None, start=1, boundary=None)

這個方法可以用兩種不同的方式呼叫：

查詢已存在的成員：

cls:

所呼叫的列舉類別。

value:

要查詢的值。

使用 cls 列舉來建立新列舉（只有在現有列舉沒有任何成員時）

cls:

所呼叫的列舉類別。

value:

要建立的新列舉的名稱。

names:

新列舉的成員的名稱/值。

module:

新列舉要建立在哪個模組名稱下。

qualname:

這個列舉在模組裡實際上的位置。

type:

新列舉的混合型別。

start:

列舉的第一個整數值（由 auto 所使用）

boundary:

在位元操作時怎麼處理範圍外的值（只有 Flag 會用到）

__contains__(cls, member)

如果 member 屬於 cls 則回傳 True：

>>> some_var = Color.RED
>>> some_var in Color
True
>>> Color.RED.value in Color
True

在 3.12 版的變更: 在 Python 3.12 之前，如果用非列舉成員做屬於檢查 (containment check) 會引發 TypeError。

__dir__(cls)

回傳 ['__class__', '__doc__', '__members__', '__module__'] 及 cls 的成員名稱：

>>> dir(Color)
['BLUE', 'GREEN', 'RED', '__class__', '__contains__', '__doc__', '__getitem__', '__init_subclass__', '__iter__', '__len__', '__members__', '__module__', '__name__', '__qualname__']

__getitem__(cls, name)

回傳 cls 中符合 name 的列舉成員，或引發 KeyError：

>>> Color['BLUE']
<Color.BLUE: 3>

__iter__(cls)

以定義的順序回傳在 cls 中的每個成員：

>>> list(Color)
[<Color.RED: 1>, <Color.GREEN: 2>, <Color.BLUE: 3>]

__len__(cls)

回傳 cls 的成員數量：

>>> len(Color)
3

__members__

回傳每個列舉名稱到其成員的對映，包括別名

__reversed__(cls)

以跟定義相反的順序回傳 cls 的每個成員：

>>> list(reversed(Color))
[<Color.BLUE: 3>, <Color.GREEN: 2>, <Color.RED: 1>]

class enum.Enum

Enum 是所有 enum 列舉的基礎類別。

name

用來定義 Enum 成員的名稱：

>>> Color.BLUE.name
'BLUE'

value

Enum 成員給定的值：

>>> Color.RED.value
1

成員的值，可以在 __new__() 設定。

備註

列舉成員的值

成員的值可以是任何值：int、str 等等。如果實際使用什麼值並不重要，你可以使用 auto 實例，它會為你選擇合適的值。更多細節請參考 auto。

雖然可以使用可變的 (mutable) / 不可雜湊的 (unhashable) 值，例如 dict、list 或可變的 dataclass，它們在建立期間會對效能產生相對於列舉中可變的 / 不可雜湊的值總數量的二次方影響。

_name_

成員名稱。

_value_

成員的值，可以在 __new__() 設定。

_order_

已不再使用，只為了向後相容而保留（類別屬性，在類別建立時移除）

_ignore_

_ignore_ 只有在建立的時候用到，在列舉建立完成後會被移除。

_ignore_ 是一個不會變成成員的名稱串列，在列舉建立完成後其名稱會被移除。範例請參考 TimePeriod。

__dir__(self)

回傳 ['__class__', '__doc__', '__module__', 'name', 'value'] 及任何 self.__class__ 上定義的公開方法：

>>> from enum import Enum
>>> from datetime import date
>>> class Weekday(Enum):
...     MONDAY = 1
...     TUESDAY = 2
...     WEDNESDAY = 3
...     THURSDAY = 4
...     FRIDAY = 5
...     SATURDAY = 6
...     SUNDAY = 7
...     @classmethod
...     def today(cls):
...         print('today is %s' % cls(date.today().isoweekday()).name)
...
>>> dir(Weekday.SATURDAY)
['__class__', '__doc__', '__eq__', '__hash__', '__module__', 'name', 'today', 'value']

_generate_next_value_(name, start, count, last_values)

name:

定義的成員名稱（例如 'RED'）。

start:

列舉的開始值，預設為 1。

count:

已定義的成員數量，不包含目前這一個。

last_values:

一個之前值的串列。

一個 staticmethod，用來決定 auto 下一個要回傳的值的：

>>> from enum import auto, Enum
>>> class PowersOfThree(Enum):
...     @staticmethod
...     def _generate_next_value_(name, start, count, last_values):
...         return 3 ** (count + 1)
...     FIRST = auto()
...     SECOND = auto()
...
>>> PowersOfThree.SECOND.value
9

__init__(self, *args, **kwds)

預設情況下，不執行任何操作。如果在成員賦值中給出多個值，這些值將成為與 __init__ 分別的引數；例如

>>> from enum import Enum
>>> class Weekday(Enum):
...     MONDAY = 1, 'Mon'

Weekday.__init__() 將被稱為 Weekday.__init__(self, 1, 'Mon')

__init_subclass__(cls, **kwds)

一個 classmethod，用來進一步設定後續的子類別，預設不做任何事。

_missing_(cls, value)

一個 classmethod，用來查詢在 cls 裡找不到的值。預設不做任何事，但可以被覆寫以實作客製化的搜尋行為：

>>> from enum import auto, StrEnum
>>> class Build(StrEnum):
...     DEBUG = auto()
...     OPTIMIZED = auto()
...     @classmethod
...     def _missing_(cls, value):
...         value = value.lower()
...         for member in cls:
...             if member.value == value:
...                 return member
...         return None
...
>>> Build.DEBUG.value
'debug'
>>> Build('deBUG')
<Build.DEBUG: 'debug'>

__new__(cls, *args, **kwds)

預設情況下不存在。如果有指定，無論是在列舉類別定義中還是在 mixin 類別中（例如 int），都將傳遞成員賦值中給出的所有值；例如

>>> from enum import Enum
>>> class MyIntEnum(int, Enum):
...     TWENTYSIX = '1a', 16

會產生呼叫 int('1a', 16) 而該成員的值為 26。

備註

當寫自訂的 __new__ 時，不要使用 super().__new__，而是要呼叫適當的 __new__。

__repr__(self)

回傳呼叫 repr() 時使用的字串。預設回傳 Enum 名稱、成員名稱及值，但可以被覆寫：

>>> from enum import auto, Enum
>>> class OtherStyle(Enum):
...     ALTERNATE = auto()
...     OTHER = auto()
...     SOMETHING_ELSE = auto()
...     def __repr__(self):
...         cls_name = self.__class__.__name__
...         return f'{cls_name}.{self.name}'
...
>>> OtherStyle.ALTERNATE, str(OtherStyle.ALTERNATE), f"{OtherStyle.ALTERNATE}"
(OtherStyle.ALTERNATE, 'OtherStyle.ALTERNATE', 'OtherStyle.ALTERNATE')

__str__(self)

回傳呼叫 str() 時使用的字串。預設回傳 Enum 名稱及成員名稱，但可以被覆寫：

>>> from enum import auto, Enum
>>> class OtherStyle(Enum):
...     ALTERNATE = auto()
...     OTHER = auto()
...     SOMETHING_ELSE = auto()
...     def __str__(self):
...         return f'{self.name}'
...
>>> OtherStyle.ALTERNATE, str(OtherStyle.ALTERNATE), f"{OtherStyle.ALTERNATE}"
(<OtherStyle.ALTERNATE: 1>, 'ALTERNATE', 'ALTERNATE')

__format__(self)

回傳呼叫 format() 及 f-string 時使用的字串。預設回傳 __str__() 的回傳值，但可以被覆寫：

>>> from enum import auto, Enum
>>> class OtherStyle(Enum):
...     ALTERNATE = auto()
...     OTHER = auto()
...     SOMETHING_ELSE = auto()
...     def __format__(self, spec):
...         return f'{self.name}'
...
>>> OtherStyle.ALTERNATE, str(OtherStyle.ALTERNATE), f"{OtherStyle.ALTERNATE}"
(<OtherStyle.ALTERNATE: 1>, 'OtherStyle.ALTERNATE', 'ALTERNATE')

備註

Enum 使用 auto 會產生從 1 開始遞增的整數。

在 3.12 版的變更: 新增 Dataclass support

_add_alias_()

新增一個名稱作為現有成員的別名：

>>> Color.RED._add_alias_("ERROR")
>>> Color.ERROR
<Color.RED: 1>

如果該名稱已經被指派給不同的成員，則會引發 NameError。

在 3.13 版被加入.

_add_value_alias_()

新增一個值作為現有成員的別名：

>>> Color.RED._add_value_alias_(42)
>>> Color(42)
<Color.RED: 1>

如果該值已經被連結到不同的成員，則會引發 ValueError。

在 3.13 版被加入.

class enum.IntEnum

IntEnum 和 Enum 一樣，但其成員同時也是整數而可以被用在任何使用整數的地方。如果 IntEnum 成員經過任何整數運算，結果值會失去其列舉狀態。

>>> from enum import IntEnum
>>> class Number(IntEnum):
...     ONE = 1
...     TWO = 2
...     THREE = 3
...
>>> Number.THREE
<Number.THREE: 3>
>>> Number.ONE + Number.TWO
3
>>> Number.THREE + 5
8
>>> Number.THREE == 3
True

備註

IntEnum 使用 auto 會產生從 1 開始遞增的整數。

在 3.11 版的變更: 為了更好地支援現存常數取代 (replacement of existing constants) 的使用情境，__str__() 現在會是 int.__str__()。為了同樣的理由，__format__() 已經是 int.__format__()。

class enum.StrEnum

StrEnum 和 Enum 一樣，但其成員同時也是字串而可以被用在幾乎所有使用字串的地方。StrEnum 成員經過任何字串操作的結果會不再是列舉的一部份。

>>> from enum import StrEnum, auto
>>> class Color(StrEnum):
...     RED = 'r'
...     GREEN = 'g'
...     BLUE = 'b'
...     UNKNOWN = auto()
...
>>> Color.RED
<Color.RED: 'r'>
>>> Color.UNKNOWN
<Color.UNKNOWN: 'unknown'>
>>> str(Color.UNKNOWN)
'unknown'

備註

stdlib 裡有些地方會檢查只能是 str 而不是 str 的子類別（也就是 type(unknown) == str 而不是 isinstance(unknown, str)），在這些地方你需要使用 str(MyStrEnum.MY_MEMBER)。

備註

StrEnum 使用 auto 會產生小寫的成員名稱當作值。

備註

為了更好地支援現存常數取代 (replacement of existing constants) 的使用情境，__str__() 現在會是 str.__str__()。為了同樣的理由，__format__() 也會是 str.__format__()。

在 3.11 版被加入.

class enum.Flag

Flag 與 Enum 相同，但其成員支援位元運算子 & (AND)、| (OR)、^ (XOR) 和 ~ (INVERT)；這些操作的結果是列舉的成員（的別名）。

__contains__(self, value)

如果 value 在 self 裡則回傳 True：

>>> from enum import Flag, auto
>>> class Color(Flag):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...
>>> purple = Color.RED | Color.BLUE
>>> white = Color.RED | Color.GREEN | Color.BLUE
>>> Color.GREEN in purple
False
>>> Color.GREEN in white
True
>>> purple in white
True
>>> white in purple
False

__iter__(self):

回傳所有包含的非別名成員：

>>> list(Color.RED)
[<Color.RED: 1>]
>>> list(purple)
[<Color.RED: 1>, <Color.BLUE: 4>]

在 3.11 版被加入.

__len__(self):

回傳旗標裡的成員數量：

>>> len(Color.GREEN)
1
>>> len(white)
3

在 3.11 版被加入.

__bool__(self):

如果成員在旗標裡則回傳 True，否則回傳 False：

>>> bool(Color.GREEN)
True
>>> bool(white)
True
>>> black = Color(0)
>>> bool(black)
False

__or__(self, other)

回傳和 other 做 OR 過後的二進位旗標：

>>> Color.RED | Color.GREEN
<Color.RED|GREEN: 3>

__and__(self, other)

回傳和 other 做 AND 過後的二進位旗標：

>>> purple & white
<Color.RED|BLUE: 5>
>>> purple & Color.GREEN
<Color: 0>

__xor__(self, other)

回傳和 other 做 XOR 過後的二進位旗標：

>>> purple ^ white
<Color.GREEN: 2>
>>> purple ^ Color.GREEN
<Color.RED|GREEN|BLUE: 7>

__invert__(self):

回傳所有在 type(self) 但不在 self 裡的旗標：

>>> ~white
<Color: 0>
>>> ~purple
<Color.GREEN: 2>
>>> ~Color.RED
<Color.GREEN|BLUE: 6>

_numeric_repr_()

用來格式化任何剩下未命名數值的函式。預設是值的 repr，常見選擇是 hex() 和 oct()。

備註

Flag 使用 auto 會產生從 1 開始 2 的次方的整數。

在 3.11 版的變更: 值為 0 的旗標的 repr() 已改變。現在是：

>>> Color(0)
<Color: 0>

class enum.IntFlag

IntFlag 和 Flag 一樣，但其成員同時也是整數而可以被用在任何使用整數的地方。

>>> from enum import IntFlag, auto
>>> class Color(IntFlag):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...
>>> Color.RED & 2
<Color: 0>
>>> Color.RED | 2
<Color.RED|GREEN: 3>

如果 IntFlag 成員經過任何整數運算，其結果不是 IntFlag：

>>> Color.RED + 2
3

如果 IntFlag 成員經過 Flag 操作且：

結果是合法的 IntFlag：回傳 IntFlag

結果不是合法的 IntFlag：結果會根據 FlagBoundary 的設定

未命名且值為 0 的旗標的 repr() 已改變。現在是：

>>> Color(0)
<Color: 0>

備註

IntFlag 使用 auto 會產生從 1 開始 2 的次方的整數。

在 3.11 版的變更: 為了更好地支援現存常數取代 (replacement of existing constants) 的使用情境，__str__() 現在會是 int.__str__()。為了同樣的理由，__format__() 已經是 int.__format__()。

IntFlag 的反轉 (inversion) 現在會回傳正值，該值是不在給定旗標的所有旗標聯集，而不是一個負值。這符合現有 Flag 的行為。

class enum.ReprEnum

ReprEnum 使用 Enum 的 repr()，但使用混合資料型別的 str()：

對 IntEnum 和 IntFlag 是 int.__str__()

對 StrEnum 是 str.__str__()

繼承 ReprEnum 來保留混合資料型別的 str() / format()，而不是使用 Enum 預設的 str()。

在 3.11 版被加入.

class enum.EnumCheck

EnumCheck 包含 verify() 裝飾器使用的選項，以確保多樣的限制，不符合限制會產生 ValueError。

UNIQUE

確保每個值只有一個名稱：

>>> from enum import Enum, verify, UNIQUE
>>> @verify(UNIQUE)
... class Color(Enum):
...     RED = 1
...     GREEN = 2
...     BLUE = 3
...     CRIMSON = 1
Traceback (most recent call last):
...
ValueError: aliases found in <enum 'Color'>: CRIMSON -> RED

CONTINUOUS

確保在最小值成員跟最大值成員間沒有缺少值：

>>> from enum import Enum, verify, CONTINUOUS
>>> @verify(CONTINUOUS)
... class Color(Enum):
...     RED = 1
...     GREEN = 2
...     BLUE = 5
Traceback (most recent call last):
...
ValueError: invalid enum 'Color': missing values 3, 4

NAMED_FLAGS

確保任何旗標群組 / 遮罩只包含命名旗標 -- 當值是用指定而不是透過 auto() 產生時是很實用的：

>>> from enum import Flag, verify, NAMED_FLAGS
>>> @verify(NAMED_FLAGS)
... class Color(Flag):
...     RED = 1
...     GREEN = 2
...     BLUE = 4
...     WHITE = 15
...     NEON = 31
Traceback (most recent call last):
...
ValueError: invalid Flag 'Color': aliases WHITE and NEON are missing combined values of 0x18 [use enum.show_flag_values(value) for details]

備註

CONTINUOUS 和 NAMED_FLAGS 是設計用來運作在整數值的成員上。

在 3.11 版被加入.

class enum.FlagBoundary

FlagBoundary 控制在 Flag 及其子類別中如何處理範圍外的值。

STRICT

範圍外的值會引發 ValueError。這是 Flag 的預設行為：

>>> from enum import Flag, STRICT, auto
>>> class StrictFlag(Flag, boundary=STRICT):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...
>>> StrictFlag(2**2 + 2**4)
Traceback (most recent call last):
...
ValueError: <flag 'StrictFlag'> invalid value 20
    given 0b0 10100
  allowed 0b0 00111

CONFORM

會移除範圍外的值中的非法值，留下合法的 Flag 值：

>>> from enum import Flag, CONFORM, auto
>>> class ConformFlag(Flag, boundary=CONFORM):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...
>>> ConformFlag(2**2 + 2**4)
<ConformFlag.BLUE: 4>

EJECT

範圍外的值會失去它們的 Flag 成員資格且恢復成 int。

>>> from enum import Flag, EJECT, auto
>>> class EjectFlag(Flag, boundary=EJECT):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...
>>> EjectFlag(2**2 + 2**4)
20

KEEP

範圍外的值會被保留，Flag 成員資格也會被保留。這是 IntFlag 的預設行為：

>>> from enum import Flag, KEEP, auto
>>> class KeepFlag(Flag, boundary=KEEP):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...
>>> KeepFlag(2**2 + 2**4)
<KeepFlag.BLUE|16: 20>

在 3.11 版被加入.

class enum.EnumDict

EnumDict 是 dict 的子類別，用來作為定義列舉類別的命名空間（參見 Preparing the class namespace）。它被公開來使得 EnumType 的子類別能具有進階行為，例如讓每個成員有多個值。它應該在被呼叫時帶上正在建立的列舉類別名稱，否則私有名稱和內部類別將無法被正確處理。

注意只有 MutableMapping 介面（__setitem__() 和 update()）被覆寫。可能可以使用其他 dict 操作來繞過檢查，例如 |=。

member_names

一個成員名稱的串列。

在 3.13 版被加入.

支援的 __dunder__ 名稱

__members__ 是一個唯讀有序的成員名稱：成員項目的對映。只有在類別上可用。

__new__()，如果有指定，它必須建立並回傳列舉成員；適當地設定成員的 _value_ 也是一個很好的主意。一旦所有成員都建立之後就不會再被用到。

支援的 _sunder_ 名稱

_name_ -- 成員名稱

_value_ -- 成員的值；可以在 __new__ 設定

_missing_() -- 當值沒有被找到時會使用的查詢函式；可以被覆寫

_ignore_ -- 一個名稱的串列，可以是 list 或 str，它不會被轉換成成員，且在最後的類別上會被移除

_order_ -- 不再被使用，僅為了向後相容而保留（類別屬性，在類別建立時移除）

_generate_next_value_() -- 用來為列舉成員取得合適的值；可以被覆寫

備註

對標準的 Enum 類別來說，下一個被選擇的值是所看過的最大值加一。

對 Flag 類別來說，下一個被選擇的值是下一個最大的 2 的次方的數字。

_add_alias_() -- 新增一個名稱作為現有成員的別名。

_add_value_alias_() -- 新增一個值作為現有成員的別名。

雖然 _sunder_ 名稱通常保留用於 Enum 類別的進一步開發而不能被使用，但有些是明確允許的：

_repr_*（例如 _repr_html_），例如用於 IPython 的豐富顯示 [https://ipython.readthedocs.io/en/stable/config/integrating.html#rich-display]

在 3.6 版被加入: _missing_、_order_、_generate_next_value_

在 3.7 版被加入: _ignore_

在 3.13 版被加入: _add_alias_、_add_value_alias_、_repr_*

通用項目與裝飾器

class enum.auto

auto 可以用來取代給值。如果使用的話，Enum 系統會呼叫 Enum 的 _generate_next_value_() 來取得合適的值。對 Enum 和 IntEnum 來說，合適的值是最後一個值加一；對 Flag 和 IntFlag 來說，是第一個比最大值還大的 2 的次方的數字；對 StrEnum 來說，是成員名稱的小寫版本。如果混用 auto() 和手動指定值的話要特別注意。

auto 實例只有在最上層的賦值時才會被解析，不論是獨自一個或作為元組的一部分：

FIRST = auto() 可以運作（auto() 會被取代成 1）

SECOND = auto(), -2 可以運作（auto 會被取代成 2, 因此 2, -2 會被用來建立列舉成員 SECOND；

THREE = [auto(), -3] 無法運作（[<auto instance>, -3] 會被用來建立列舉成員 THREE）

在 3.11.1 版的變更: 在之前的版本中，auto() 必須是賦值行裡的唯一內容才能運作正確。

可以覆寫 _generate_next_value_ 來客製 auto 使用的值。

備註

在 3.13 預設 _generate_next_value_ 總是回傳最大的成員值加一，如果任何成員是不相容的型別就會失敗。

@enum.property

和內建的 property 相似的裝飾器，但只專門針對列舉。它允許成員屬性和成員本身有相同名稱。

備註

屬性和成員必須定義在分開的類別裡；例如 value 和 name 屬性定義在 Enum 類別而 Enum 子類別可以定義成員名稱為 value 和 name。

在 3.11 版被加入.

@enum.unique

專門針對列舉的 class 裝飾器。它搜尋列舉的 __members__，蒐集任何它找到的別名；如果有找到任何別名則引發 ValueError 並附上細節：

>>> from enum import Enum, unique
>>> @unique
... class Mistake(Enum):
...     ONE = 1
...     TWO = 2
...     THREE = 3
...     FOUR = 3
...
Traceback (most recent call last):
...
ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE

@enum.verify

專門針對列舉的 class 裝飾器。使用 EnumCheck 裡的成員來指定在裝飾的列舉上應該檢查什麼限制。

在 3.11 版被加入.

@enum.member

列舉所使用的裝飾器：其目標會變成成員。

在 3.11 版被加入.

@enum.nonmember

列舉所使用的裝飾器：其目標不會變成成員。

在 3.11 版被加入.

@enum.global_enum

修改列舉的 str() 及 repr() 的裝飾器，讓成員顯示為屬於模組而不是其類別。應該只有當列舉成員被匯出到模組的全域命名空間才使用（範例請參考 re.RegexFlag）。

在 3.11 版被加入.

enum.show_flag_values(value)

回傳在旗標值中包含的所有 2 的次方的整數串列。

在 3.11 版被加入.

enum.bin(num, max_bits=None)

Like built-in bin(), except negative values are represented in two's complement, and the leading bit always indicates sign (0 implies positive, 1 implies negative).

>>> import enum
>>> enum.bin(10)
'0b0 1010'
>>> enum.bin(~10)   # ~10 is -11
'0b1 0101'

在 3.10 版被加入.

備註

IntEnum、StrEnum 及 IntFlag

這三種列舉型別是設計來直接取代現有以整數及字串為基底的值；因此它們有額外的限制：

__str__ 使用值而不是列舉成員的名稱

__format__ 因為使用 __str__，也會使用值而不是列舉成員的名稱

如果你不需要或不想要這些限制，你可以透過混合 int 或 str 型別來建立自己的基礎類別：

>>> from enum import Enum
>>> class MyIntEnum(int, Enum):
...     pass

或者你也可以在你的列舉重新給定合適的 str()：

>>> from enum import Enum, IntEnum
>>> class MyIntEnum(IntEnum):
...     __str__ = Enum.__str__

graphlib —-- 使用類圖 (graph-like) 結構進行操作的功能

原始碼：Lib/graphlib.py [https://github.com/python/cpython/tree/3.14/Lib/graphlib.py]

class graphlib.TopologicalSorter(graph=None)

提供對包含可雜湊 (hashable) 節點之圖 (graph) 進行拓撲排序 (topologically sort) 的功能。

拓撲排序是圖中頂點 (vertex) 的線性排序，使得對於從頂點 u 到頂點 v 的每條有向邊 (directed edge) u -> v，頂點 u 在排序中會位於頂點 v 之前。例如，圖的頂點可能代表要執行的任務，而邊可能代表一個任務必須在另一個任務之前執行的限制；在此範例中，拓撲排序只是任務的一種有效序列。若且唯若 (if and only if) 圖沒有有向環 (directed cycle) 時，即如果它是個有向無環圖 (directed acyclic graph)，則完整的拓撲排序才是可行的。

如果提供了可選的 graph 引數，它必須是表示有向無環圖的字典，其中鍵是節點，值是圖中該節點的包含所有前驅節點 (predecessor) 之可疊代物件（這些前驅節點具有指向以鍵表示之節點的邊）。可以使用 add() 方法將其他節點新增到圖中。

在一般情況下，對給定的圖執行排序所需的步驟如下：

以選用的初始圖建立 TopologicalSorter 的實例。

在圖中新增其他節點。

呼叫圖的 prepare()。

當 is_active() 為 True 時，疊代 get_ready() 回傳的節點並處理它們。在每個節點完成處理時呼叫 done()。

如果只需要立即對圖中的節點進行排序且不涉及平行性 (parallelism)，則可以直接使用便捷方法 TopologicalSorter.static_order()：

>>> graph = {"D": {"B", "C"}, "C": {"A"}, "B": {"A"}}
>>> ts = TopologicalSorter(graph)
>>> tuple(ts.static_order())
('A', 'C', 'B', 'D')

該類別設計為在節點準備就緒時，簡單支援節點的平行處理。例如：

topological_sorter = TopologicalSorter()

# Add nodes to 'topological_sorter'...

topological_sorter.prepare()
while topological_sorter.is_active():
    for node in topological_sorter.get_ready():
        # Worker threads or processes take nodes to work on off the
        # 'task_queue' queue.
        task_queue.put(node)

    # When the work for a node is done, workers put the node in
    # 'finalized_tasks_queue' so we can get more nodes to work on.
    # The definition of 'is_active()' guarantees that, at this point, at
    # least one node has been placed on 'task_queue' that hasn't yet
    # been passed to 'done()', so this blocking 'get()' must (eventually)
    # succeed.  After calling 'done()', we loop back to call 'get_ready()'
    # again, so put newly freed nodes on 'task_queue' as soon as
    # logically possible.
    node = finalized_tasks_queue.get()
    topological_sorter.done(node)

add(node, *predecessors)

向圖中新增新節點及其前驅節點。node 和 predecessors 中的所有元素都必須是可雜湊的。

如果以相同節點引數多次呼叫，則依賴項的集合將會是傳入的所有依賴項的聯集。

可以新增一個沒有依賴關係的節點（predecessors 未提供）或提供兩次依賴關係。如果有之前未曾提供的節點被包含在 predecessors 中，它將自動新增到沒有前驅節點的圖中。

如果在 prepare() 之後呼叫，則引發 ValueError。

prepare()

將圖標記為已完成並檢查圖中的循環。如果檢測到任何循環，將引發 CycleError，但 get_ready() 仍可用於盡可能獲得更多的節點，直到循環阻塞了進度。呼叫此函式後就無法修改圖，因此無法使用 add() 來新增更多節點。

A ValueError will be raised if the sort has been started by static_order() or get_ready().

在 3.14 版的變更: prepare() can now be called more than once as long as the sort has not started. Previously this raised ValueError.

is_active()

如果可以有更多進度則回傳 True，否則回傳 False。如果循環不阻塞解析 (resolution) 並且仍有節點準備就緒但尚未由 TopologicalSorter.get_ready() 回傳或標記為 TopologicalSorter.done() 的節點數量較 TopologicalSorter.get_ready() 所回傳的少，則可以繼續取得進度。

此類別的 __bool__() 方法遵循此函式，因此以下做法：

if ts.is_active():
    ...

可以簡單地用以下方式替換：

if ts:
    ...

如果呼叫之前沒有先呼叫 prepare() 則引發 ValueError。

done(*nodes)

將 TopologicalSorter.get_ready() 回傳的一組節點標記為已處理，停止阻塞 nodes 中每個節點的任何後繼節點 (successor)，以便將來透過呼叫 TopologicalSorter.get_ready() 回傳。

若沒有和該呼叫一起呼叫 prepare() 或節點還沒有被 get_ready() 回傳，且如果 nodes 中有任何節點已被先前對此方法的呼叫標記為已處理、或者未使用 TopologicalSorter.add() 將節點新增到圖中，則引發 ValueError。

get_ready()

回傳一個包含所有準備就緒節點的 tuple。最初它回傳沒有前驅節點的所有節點，一旦透過呼叫 TopologicalSorter.done() 來將這些節點標記為已處理後，進一步的呼叫將回傳所有其全部前驅節點都已被處理的新節點。若無法取得更多進度，將回傳空 tuple。

如果呼叫之前沒有先呼叫 prepare() 則引發 ValueError。

static_order()

回傳一個可疊代物件，它將按拓撲排序疊代節點。使用此方法時，不應呼叫 prepare() 和 done()。此方法等效於：

def static_order(self):
    self.prepare()
    while self.is_active():
        node_group = self.get_ready()
        yield from node_group
        self.done(*node_group)

回傳的特定順序可能取決於將項目插入圖中的特定順序。例如：

>>> ts = TopologicalSorter()
>>> ts.add(3, 2, 1)
>>> ts.add(1, 0)
>>> print([*ts.static_order()])
[2, 0, 1, 3]

>>> ts2 = TopologicalSorter()
>>> ts2.add(1, 0)
>>> ts2.add(3, 2, 1)
>>> print([*ts2.static_order()])
[0, 2, 1, 3]

這是因為 "0" 和 "2" 在圖中處於同一級別（它們將在對 get_ready() 的同一呼叫中回傳）並且它們之間的順序取決於插入順序。

如果檢測到任何循環，則引發 CycleError。

在 3.9 版被加入.

例外

graphlib 模組定義了以下例外類別：

exception graphlib.CycleError

ValueError 的子類別，如果作用的圖中存在循環則由 TopologicalSorter.prepare() 引發。如果存在多個循環，則只會報告未定義的其中一個並包含在例外中。

檢測到的循環可以透過例外實例的 args 屬性中第二個元素來存取，其為一個節點列表，每個節點在圖中都是列表中下一個節點的直接前驅節點（immediate predecessor，即父節點）。在報告列表中，第一個和最後一個節點將會是相同的，用以明確表示它是循環的。

數值與數學模組

本章所描述的模組提供了數值和與數學相關的函式和資料型別。numbers 模組定義了數值型別的抽象階層結構。math 和 cmath 模組包含了用於浮點數和複數的各種數學函式。decimal 模組支援對十進位數字的精確表示以及任意精度的算術運算。

本章節包含下列的模組：

numbers --- 數值的抽象基底類別

數值的階層

給型別實作者的註記

加入更多數值 ABC

實作算術操作

math --- 數學函式

數論函式

浮點數算術運算

浮點數操作函式

次方、指數與對數函式

總和與乘積函式

角度轉換

三角函式

雙曲函式

特殊函式

常數

cmath --- 複數的數學函式

轉換到極座標和從極座標做轉換

冪函數和對數函數

三角函數

雙曲函數

分類函式

常數

decimal --- 十進位固定點和浮點運算

Quick-start tutorial

Decimal objects

Logical operands

Context objects

常數

Rounding modes

Signals

Floating-point notes

Mitigating round-off error with increased precision

特殊值

Working with threads

Recipes

Decimal FAQ

fractions --- 有理數

random --- 產生偽隨機數

簿記函式 (bookkeeping functions)

回傳位元組的函式

回傳整數的函式

回傳序列的函式

離散分布

實數分布

替代產生器

關於 Reproducibility（復現性）的注意事項

範例

使用方案

命令列用法

命令列範例

statistics --- 數學統計函式

平均值與中央位置量數

離度 (spread) 的測量

兩個輸入之間的關係統計

函式細節

例外

NormalDist 物件

範例與錦囊妙計

經典機率問題

用於模擬的蒙地卡羅 (Monte Carlo) 輸入

近似二項分布

單純貝氏分類器 (Naive bayesian classifier)

numbers --- 數值的抽象基底類別

原始碼：Lib/numbers.py [https://github.com/python/cpython/tree/3.14/Lib/numbers.py]

numbers 模組 (PEP 3141 [https://peps.python.org/pep-3141/]) 定義了數值抽象基底類別 的階層結構，其中逐一定義了更多操作。此模組中定義的型別都不可被實例化。

class numbers.Number

數值階層結構的基礎。如果你只想確認引數 x 是不是數值、並不關心其型別，請使用 isinstance(x, Number)。

數值的階層

class numbers.Complex

這個型別的子類別描述了複數並包含適用於內建 complex 型別的操作。這些操作有：complex 和 bool 的轉換、real、imag、+、-、*、/、**、abs()、conjugate()、== 以及 !=。除 - 和 != 之外所有操作都是抽象的。

real

為抽象的。取得該數值的實數部分。

imag

為抽象的。取得該數值的虛數部分。

abstractmethod conjugate()

為抽象的。回傳共軛複數，例如 (1+3j).conjugate() == (1-3j)。

class numbers.Real

相對於 Complex，Real 加入了只有實數才能進行的操作。

簡單的說，有 float 的轉換、math.trunc()、round()、math.floor()、math.ceil()、divmod()、//、%、 <、<=、>、和 >=。

實數同樣提供 complex()、real、imag 和 conjugate() 的預設值。

class numbers.Rational

Real 的子型別，並增加了 numerator 和 denominator 這兩種特性。它也會提供 float() 的預設值。

numerator 和 denominator 的值必須是 Integral 的實例且 denominator 要是正數。

numerator

為抽象的。該有理數的分子。

denominator

為抽象的。該有理數的分母。

class numbers.Integral

Rational 的子型別，並增加了 int 的轉換操作。為 float()、numerator 和 denominator 提供了預設值。為 pow() 方法增加了求餘 (modulus) 和位元字串運算 (bit-string operations) 的抽象方法：<<、>>、&、^、|、~。

給型別實作者的註記

實作者需注意，相等的數值除了大小相等外，還必須擁有同樣的雜湊值。當使用兩個不同的實數擴充時，這可能是很微妙的。例如，fractions.Fraction 底下的 hash() 實作如下：

def __hash__(self):
    if self.denominator == 1:
        # 正確處理整數。
        return hash(self.numerator)
    # 檢查費時，但絕對正確。
    if self == float(self):
        return hash(float(self))
    else:
        # 使用 tuple 的雜湊值以避免簡單分數上的高碰撞率。
        return hash((self.numerator, self.denominator))

加入更多數值 ABC

當然，還有更多用於數值的 ABC，如果不加入它們就不會有健全的階層。你可以在 Complex 和 Real 中加入 MyFoo，像是：

class MyFoo(Complex): ...
MyFoo.register(Real)

實作算術操作

我們想要實作算術操作，來使得混合模式操作要麼呼叫一個作者知道兩個引數之型別的實作，要麼將其轉換成最接近的內建型別並執行這個操作。對於 Integral 的子型別，這意味著 __add__() 和 __radd__() 必須用如下方式定義：

class MyIntegral(Integral):

    def __add__(self, other):
        if isinstance(other, MyIntegral):
            return do_my_adding_stuff(self, other)
        elif isinstance(other, OtherTypeIKnowAbout):
            return do_my_other_adding_stuff(self, other)
        else:
            return NotImplemented

    def __radd__(self, other):
        if isinstance(other, MyIntegral):
            return do_my_adding_stuff(other, self)
        elif isinstance(other, OtherTypeIKnowAbout):
            return do_my_other_adding_stuff(other, self)
        elif isinstance(other, Integral):
            return int(other) + int(self)
        elif isinstance(other, Real):
            return float(other) + float(self)
        elif isinstance(other, Complex):
            return complex(other) + complex(self)
        else:
            return NotImplemented

Complex 的子類別有 5 種不同的混合型別操作。我將上面提到所有不涉及 MyIntegral 和 OtherTypeIKnowAbout 的程式碼稱作「模板 (boilerplate)」。a 是 Complex 之子型別 A 的實例 (a : A <: Complex)，同時 b : B <: Complex。我將要計算 a + b：

如果 A 有定義成一個接受 b 的 __add__()，不會發生問題。

如果 A 回退成模板程式碼，它將回傳一個來自 __add__() 的值，並喪失讓 B 定義一個更完善的 __radd__() 的機會，因此模板需要回傳一個來自 __add__() 的 NotImplemented。（或者 A 可能完全不實作 __add__()。）

接著看 B 的 __radd__()。如果它接受 a ，不會發生問題。

如果沒有成功回退到模板，就沒有更多的方法可以去嘗試，因此這裡將使用預設的實作。

如果 B <: A，Python 會在 A.__add__ 之前嘗試 B.__radd__。這是可行的，因為它是透過對 A 的理解而實作的，所以這可以在交給 Complex 之前處理好這些實例。

如果 A <: Complex 和 B <: Real 且沒有共享任何其他型別上的理解，那麼適當的共享操作會涉及內建的 complex，並且分別用到 __radd__()，因此 a+b == b+a。

由於大部分對任意給定類型的操作都十分相似的，定義一個為任意給定運算子生成向前 (forward) 與向後 (reverse) 實例的輔助函式可能會非常有用。例如，fractions.Fraction 使用了：

def _operator_fallbacks(monomorphic_operator, fallback_operator):
    def forward(a, b):
        if isinstance(b, (int, Fraction)):
            return monomorphic_operator(a, b)
        elif isinstance(b, float):
            return fallback_operator(float(a), b)
        elif isinstance(b, complex):
            return fallback_operator(complex(a), b)
        else:
            return NotImplemented
    forward.__name__ = '__' + fallback_operator.__name__ + '__'
    forward.__doc__ = monomorphic_operator.__doc__

    def reverse(b, a):
        if isinstance(a, Rational):
            # 包含整數。
            return monomorphic_operator(a, b)
        elif isinstance(a, Real):
            return fallback_operator(float(a), float(b))
        elif isinstance(a, Complex):
            return fallback_operator(complex(a), complex(b))
        else:
            return NotImplemented
    reverse.__name__ = '__r' + fallback_operator.__name__ + '__'
    reverse.__doc__ = monomorphic_operator.__doc__

    return forward, reverse

def _add(a, b):
    """a + b"""
    return Fraction(a.numerator * b.denominator +
                    b.numerator * a.denominator,
                    a.denominator * b.denominator)

__add__, __radd__ = _operator_fallbacks(_add, operator.add)

# ...

math --- 數學函式

此模組提供對常見數學函式與常數的存取，包括於 C 標準中定義的那些。

這些函式不支援複數；若你需要計算複數，請使用 cmath 模組的同名函式。這是因為大多數的使用者並不想學習那麼多理解複數所需的數學概念，所以根據支援複數與否分為兩種函式。收到一個例外而非複數回傳值，有助於程式設計師提早察覺參數中包含非預期的複數，進而從源頭查出導致此情況的原因。

此模組提供下列函式。除非特意註明，否則回傳值皆為浮點數。

數論函式

comb(n, k)

從 n 個物品中不重複且不考慮排序地取出 k 個物品的方法數。

factorial(n)

n 的階乘

gcd(*integers)

整數引數的最大公因數

isqrt(n)

非負整數 n 的整數平方根

lcm(*integers)

整數引數的最小公倍數

perm(n, k)

從 n 個物品中不重複但考慮排序地取出 k 個物品的方法數。

浮點數算術運算

ceil(x)

x 的上取整值，即大於或等於 x 的最小整數

fabs(x)

x 的絕對值。

floor(x)

x 的下取整值，即小於或等於 x 的最大整數

fma(x, y, z)

融合乘加運算：(x * y) + z

fmod(x, y)

除法 x / y 的餘數

modf(x)

x 的小數部分與整數部分

remainder(x, y)

x 相對於 y 的餘數

trunc(x)

x 的整數部分

浮點數操作函式

copysign(x, y)

帶有 y 的正負號的 x 的量值（絕對值）

frexp(x)

x 的尾數與指數

isclose(a, b, rel_tol, abs_tol)

檢查 a 與 b 兩值是否足夠接近

isfinite(x)

檢查 x 是否既非無限值也非 NaN

isinf(x)

檢查 x 是否為正無限或負無限

isnan(x)

檢查 x 是否為 NaN（非數值）

ldexp(x, i)

x * (2**i)，frexp() 的反函式

nextafter(x, y, steps)

從 x 向 y 移動 steps 步的浮點數值

ulp(x)

x 的最低有效位元的值

次方、指數與對數函式

cbrt(x)

x 的立方根

exp(x)

e 的 x 次方

exp2(x)

2 的 x 次方

expm1(x)

e 的 x 次方減 1

log(x, base)

x 以給定底數（預設為 e）的對數

log1p(x)

1+x 的自然對數（以 e 為底）

log2(x)

x 的以 2 為底的對數

log10(x)

x 的以 10 為底的對數

pow(x, y)

x 的 y 次方

sqrt(x)

x 的平方根

總和與乘積函式

dist(p, q)

兩點 p 與 q 之間的歐幾里得距離，各點以座標的可疊代物件表示

fsum(iterable)

輸入 iterable 中所有值的總和

hypot(*coordinates)

座標可疊代物件的歐幾里得範數

prod(iterable, start)

輸入 iterable 中所有元素與 start 起始值的乘積

sumprod(p, q)

兩個可疊代物件 p 與 q 各元素乘積的總和

角度轉換

degrees(x)

將角度 x 從弧度轉換為度

radians(x)

將角度 x 從度轉換為弧度

三角函式

acos(x)

x 的反餘弦

asin(x)

x 的反正弦

atan(x)

x 的反正切

atan2(y, x)

atan(y / x)

cos(x)

x 的餘弦

sin(x)

x 的正弦

tan(x)

x 的正切

雙曲函式

acosh(x)

x 的反雙曲餘弦

asinh(x)

x 的反雙曲正弦

atanh(x)

x 的反雙曲正切

cosh(x)

x 的雙曲餘弦

sinh(x)

x 的雙曲正弦

tanh(x)

x 的雙曲正切

特殊函式

erf(x)

在 x 處的誤差函式 [https://en.wikipedia.org/wiki/Error_function]值

erfc(x)

在 x 處的互補誤差函式 [https://en.wikipedia.org/wiki/Error_function]值

gamma(x)

在 x 處的 Gamma 函式 [https://en.wikipedia.org/wiki/Gamma_function]值

lgamma(x)

在 x 處的 Gamma 函式 [https://en.wikipedia.org/wiki/Gamma_function]絕對值的自然對數

常數

pi

π = 3.141592...

e

e = 2.718281...

tau

τ = 2π = 6.283185...

inf

正無限大

nan

「非數值」（NaN）

數論函式

math.comb(n, k)

回傳從 n 個物品中不重複且不考慮排序地取出 k 個物品的方法數。

當 k <= n 時其值為 n! / (k! * (n - k)!)，否則其值為 0。

因為此值等同於 (1 + x)ⁿ 進行多項式展開後第 k 項的係數，所以又稱為二項式係數。

當任一參數非整數型別時會引發 TypeError。當任一參數為負數時會引發 ValueError。

在 3.8 版被加入.

math.factorial(n)

回傳非負整數 n 的階乘。

在 3.10 版的變更: 現在已經不允許傳入其值為整數的浮點數（如：5.0）。

math.gcd(*integers)

回傳指定整數引數的最大公因數。若存在任一非零引數，回傳值為所有引數共有因數中最大的正整數。若所有引數皆為零，則回傳值為 0。gcd() 若未傳入任何引數也將回傳 0。

在 3.5 版被加入.

在 3.9 版的變更: 新增支援任意數量的引數。先前僅支援兩個引數。

math.isqrt(n)

回傳非負整數 n 的整數平方根。此值為 n 精確平方根經下取整的值，亦等同於滿足 a² ≤ n 的最大整數值 a。

於有些應用程式中，取得滿足 n ≤ a² 的最小整數值 a ── 或者說 n 精確平方根經上取整的值 ── 會更加方便。對正數 n，此值可使用 a = 1 + isqrt(n - 1) 計算。

在 3.8 版被加入.

math.lcm(*integers)

回傳指定整數引數的最小公倍數。若所有引數值皆非零，回傳值為所有引數共有倍數中最小的正整數。若存在任一引數值為零，則回傳值為 0。lcm() 若未傳入任何引數將回傳 1。

在 3.9 版被加入.

math.perm(n, k=None)

回傳從 n 個物品中不重複且考慮排序地取出 k 個物品的方法數。

當 k <= n 時其值為 n! / (n - k)!，否則其值為 0。

若未給定 k 或其值為 None，則 k 值預設為 n，且函式回傳 n!。

當任一參數非整數型別時會引發 TypeError。當任一參數為負數時會引發 ValueError。

在 3.8 版被加入.

浮點數算術運算

math.ceil(x)

回傳 x 經上取整的值，即大於或等於 x 的最小整數。若 x 並非浮點數，此函式將委派給 x.__ceil__，並回傳 Integral 型別的值。

math.fabs(x)

回傳 x 的絕對值。

math.floor(x)

回傳 x 經下取整的值，即小於或等於 x 的最大整數。若 x 並非浮點數，此函式將委派給 x.__floor__，並回傳 Integral 型別的值。

math.fma(x, y, z)

融合乘加運算。回傳 (x * y) + z，用近似於無限精密度及範圍的方式計算，而後一次轉換為 float 格式。此操作通常能提供比運算式 (x * y) + z 更高的精確度。

此函式遵循 IEEE-754 標準中規範的融合乘加（fusedMultiplyAdd）運算。該標準保留一種由實作決定的案例，即 fma(0, inf, nan) 和 fma(inf, 0, nan) 的結果；在這些案例中，math.fma 回傳 NaN 且不會引發例外。

在 3.13 版被加入.

math.fmod(x, y)

回傳 x / y 的浮點數餘數，其以平臺上的 C 函式庫 fmod(x, y) 函式定義。請注意此函式與 Python 運算式 x % y 可能不會回傳相同結果。C 標準要求 fmod(x, y) 的回傳值完全等同（數學定義上，即無限精密度）於 x - n*y，n*為可使回傳值與 *x 同號且量值小於 abs(y) 的整數。Python 運算式 x % y 的回傳值則與 y 同號，且可能無法精確地計算浮點數引數。例如：fmod(-1e-100, 1e100) 的值為 -1e-100，但 Python 運算式 -1e-100 % 1e100 的結果為 1e100-1e-100，此值無法準確地表示成浮點數，並會四捨五入為出乎意料的 1e100。因此，處理浮點數時通常會選擇函式 fmod()，而處理整數時會選擇 Python 運算式 x % y。

math.modf(x)

回傳 x 的小數及整數部分，兩者皆為與 x 同號的浮點數。

請注意 modf() 的呼叫/回傳模式與 C 語言中相應的函式不同：它們接受一個引數並回傳一對值，而非透過一個「輸出參數（output parameter）」傳遞第二個回傳值（Python 沒有那種東西）。

math.remainder(x, y)

回傳 x 對 y 根據 IEEE 754 定義的餘數。對有限數 x 及有限非零數 y，該值為 x - n*y 差值，n 是最接近商數 x / y 的整數。若 x / y 剛好位於兩個連續整數的正中間，n 為最接近的偶數。因此該餘數 r = remainder(x, y) 總是滿足 abs(r) <= 0.5 * abs(y)。

特殊情況遵循 IEEE 754：特別是，對任何有限數 x，remainder(x, math.inf) 的值為 x；對任何非 NaN 值的 x，remainder(x, 0) 及 remainder(math.inf, x) 會引發 ValueError。若取餘數操作的結果為零，則該零值會與 x 同號。

在使用 IEEE 754 浮點標準中二進制浮點數的平台上，此操作的結果必能精準表示，不會出現捨入誤差。

在 3.7 版被加入.

math.trunc(x)

回傳去除小數部分而僅餘整數部分的 x。此函式會向零捨入：若 x 為正值，trunc() 等價於 floor()；若 x 為負值，trunc() 等價於 ceil()。若 x 非浮點數，此函式將委派給 x.__trunc__，而後回傳一 Integral 值。

使用 ceil()、floor() 及 modf() 三個函式時，請注意所有足夠大的浮點數都是精確的整數。Python 的浮點數型別的精密度通常不會超過 53 位元（與 C 語言 double 型別相同），因此當浮點數 x 滿足 abs(x) >= 2**52 時，它必然沒有小數部分。

浮點數操作函式

math.copysign(x, y)

回傳與 x 相同量值（絕對值）且與 y 同號的浮點數。在支援帶符號零的平臺上，copysign(1.0, -0.0) 回傳 -1.0。

math.frexp(x)

以 (m, e) 對的格式回傳 x 的尾數 m 及指數 e。m 是浮點數而 e 是整數，且兩者精確地使 x == m * 2**e。若 x 為零，回傳 (0.0, 0)，否則令 0.5 <= abs(m) < 1。此函式用於以可攜的方式「分割」浮點數內部表示法。

請注意 frexp() 的呼叫/回傳模式與 C 語言中相應的函式不同：它們接受一個引數並回傳一對值，而非透過一個「輸出參數（output parameter）」傳遞第二個回傳值（Python 沒有那種東西）。

math.isclose(a, b, *, rel_tol=1e-09, abs_tol=0.0)

若 a 及 b 兩值足夠接近便回傳 True，否則回傳 False。

兩數是否足夠接近取決於給定的絕對及相對容許偏差 (tolerance)。如果沒有錯誤發生，結果將為：abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)。

rel_tol 為相對容許偏差 ── a 與 b 兩數差的最大容許值，與 a 及 b 兩數的絕對值中較大者相關。例如欲設置 5% 的容許偏差，則傳入 rel_tol=0.05。其預設值為 1e-09，該值可確保兩數於大約 9 個十進數位內相同。rel_tol 須不為負且小於 1.0。

abs_tol 為絕對容許偏差；預設為 0.0 且必須不為負。當比較 x 與 0.0 時，isclose(x, 0) 將計算為 abs(x) <= rel_tol  * abs(x)，此結果對任何非零 x 及小於 1.0 的 rel_tol 而言皆為 False。因此呼叫時應加上適當的正數 abs_tol 引數。

定義於 IEEE 754 浮點標準中的特殊值 NaN、inf 和 -inf 會根據該標準處理。更明確地說，NaN 不會與包含自身在內的任何數字足夠接近，而 inf 及 -inf 皆只與自身接近。

在 3.5 版被加入.

也參考

PEP 485 [https://peps.python.org/pep-0485/] ── 用於測試近似相等的函式

math.isfinite(x)

若 x 不是無限值或 NaN 便回傳 True，否則回傳 False。（注意 0.0 被視為有限數。）

在 3.2 版被加入.

math.isinf(x)

若 x 是正無限值或負無限值便回傳 True，否則回傳 False。

math.isnan(x)

若 x 是 NaN ── 即非數值（NaN, not a number）── 便回傳 True，否則回傳 False。

math.ldexp(x, i)

回傳 x * (2**i)。此函式本質上為 frexp() 的反函式。

math.nextafter(x, y, steps=1)

回傳 x 向 y steps 步的浮點數值。

除非 steps 為零，否則當 x 與 y 相等時回傳 y。

範例：

math.nextafter(x, math.inf) 增加：往正無限。

math.nextafter(x, -math.inf) 減少：往負無限。

math.nextafter(x, 0.0) 靠近零。

math.nextafter(x, math.copysign(math.inf, x)) 遠離零。

另請參閱 math.ulp()。

在 3.9 版被加入.

在 3.12 版的變更: 新增 steps 引數。

math.ulp(x)

回傳浮點數 x 的最低有效位元：

若 x 為 NaN（非數值），回傳 x。

若 x 為負值，回傳 ulp(-x)。

若 x 為正無限值，回傳 x。

若 x 等於零，回傳反正規化可表示的最小正浮點數（此值小於正規化可表示的最小正浮點數 sys.float_info.min）。

若 x 等於可表示的最大正浮點數，回傳 x 的最低有效位元值，使 x-ulp(x) 為第一個小於 x 的浮點數。

否則（當 x 為正有限數），回傳 x 的最低有效位元值，使 x+ulp(x) 為第一個大於 x 的浮點數。

ULP 即最後一位上的單位值（Unit in the Last Place）。

另請參閱 math.nextafter() 及 sys.float_info.epsilon。

在 3.9 版被加入.

次方、指數與對數函式

math.cbrt(x)

回傳 x 的立方根。

在 3.11 版被加入.

math.exp(x)

回傳 e 的 x 次方，其中 e = 2.718281... 為自然對數的底數。此函式通常比 math.e ** x 或 pow(math.e, x) 更為精確。

math.exp2(x)

回傳 2 的 x 次方。

在 3.11 版被加入.

math.expm1(x)

回傳 e 的 x 次方減 1。此處 e 為自然對數的底數。對於較小的浮點數 x，exp(x) - 1 中的減法運算可能導致顯著的精密度損失 [https://en.wikipedia.org/wiki/Loss_of_significance]；expm1() 函式提供了一種能以完整精密度計算此值的方法：

>>> from math import exp, expm1
>>> exp(1e-5) - 1  # gives result accurate to 11 places
1.0000050000069649e-05
>>> expm1(1e-5)    # result accurate to full precision
1.0000050000166668e-05

在 3.2 版被加入.

math.log(x[, base])

傳入一個引數時，回傳 x 的自然對數（以 e 為底）。

傳入兩個引數時，回傳 x 以給定 base 為底的對數，計算方式為 log(x)/log(base)。

math.log1p(x)

回傳 1+x 的自然對數（以 e 為底）。計算結果對於接近零的 x 值是精確的。

math.log2(x)

回傳 x 的以 2 為底的對數。此函式通常比 log(x, 2) 更為精確。

在 3.3 版被加入.

也參考

int.bit_length() 回傳以二進位表示一個整數所需的位元數，不包含正負號及前導零。

math.log10(x)

回傳 x 的以 10 為底的對數。此函式通常比 log(x, 10) 更為精確。

math.pow(x, y)

回傳 x 的 y 次方。例外情況盡可能遵循 IEEE 754 標準。特別是，pow(1.0, x) 和 pow(x, 0.0) 總是回傳 1.0，即使 x 是零或 NaN 也是如此。若 x 和 y 皆為有限數、x 為負數且 y 不是整數，則 pow(x, y) 是未定義的，並會引發 ValueError。

與內建 ** 運算子不同，math.pow() 會將其兩個引數都轉換為 float 型別。若需要計算精確的整數次方，請使用 ** 或內建的 pow() 函式。

在 3.11 版的變更: 特殊情況 pow(0.0, -inf) 和 pow(-0.0, -inf) 已變更為回傳 inf 而非引發 ValueError，以符合 IEEE 754 標準。

math.sqrt(x)

回傳 x 的平方根。

總和與乘積函式

math.dist(p, q)

回傳兩點 p 與 q 之間的歐幾里得距離，各點以座標的序列（或可疊代物件）表示。兩點必須具有相同的維度。

約等價於：

sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))

在 3.8 版被加入.

math.fsum(iterable)

回傳可疊代物件（iterable）中所有值的精確浮點數和。透過追蹤過程中多個部分和（partial sum）以避免精密度損失。

此演算法準確性奠基於保證 IEEE-754 浮點標準及典型奇進偶捨（half-even）模式。於有些非 Windows 平台建置時，底層 C 函式庫使用延伸精密度加法運算，而可能導致對過程中同一部分和重複捨入，並使其最低有效位不如預期。

更深入的討論及兩種替代做法請參閱 ASPN cookbook recipes 精準的浮點數總和 [https://code.activestate.com/recipes/393090/]。

math.hypot(*coordinates)

回傳歐幾里得範數 sqrt(sum(x**2 for x in coordinates))。這是從原點到座標所給定的點之間的向量長度。

對於二維點 (x, y)，這等同於使用畢氏定理計算直角三角形的斜邊，即 sqrt(x*x + y*y)。

在 3.8 版的變更: 新增對 n 維點的支援。先前僅支援二維情況。

在 3.10 版的變更: 改進了演算法的精確度，使最大誤差低於 1 ulp（最後一位上的單位值）。更典型的情況是，結果幾乎總是能正確捨入到 1/2 ulp 以內。

math.prod(iterable, *, start=1)

計算輸入 iterable 中所有元素的乘積。乘積的預設 start 起始值為 1。

當可疊代物件為空時，回傳起始值。此函式專門設計用於數值運算，可能會拒絕非數值型別。

在 3.8 版被加入.

math.sumprod(p, q)

回傳兩個可疊代物件 p 及 q 各值乘積的總和。

若兩個傳入物件長度不同會引發 ValueError。

約等價於：

sum(map(operator.mul, p, q, strict=True))

對浮點數或混合整數及浮點數的傳入物件，其過程中的乘積及總和皆使用延伸精密度計算。

在 3.12 版被加入.

角度轉換

math.degrees(x)

將角度 x 從弧度轉換為度。

math.radians(x)

將角度 x 從度轉換為弧度。

三角函式

math.acos(x)

回傳 x 的反餘弦值，以弧度表示。結果介於 0 與 pi 之間。

math.asin(x)

回傳 x 的反正弦值，以弧度表示。結果介於 -pi/2 與 pi/2 之間。

math.atan(x)

回傳 x 的反正切值，以弧度表示。結果介於 -pi/2 與 pi/2 之間。

math.atan2(y, x)

回傳 atan(y / x)，以弧度表示。結果介於 -pi 與 pi 之間。從原點到點 (x, y) 的平面向量與正 X 軸形成此角度。atan2() 的重點在於它知道兩個輸入的正負號，因此能計算出角度所在的正確象限。例如，atan(1) 和 atan2(1, 1) 都是 pi/4，但 atan2(-1, -1) 是 -3*pi/4。

math.cos(x)

回傳 x 弧度的餘弦值。

math.sin(x)

回傳 x 弧度的正弦值。

math.tan(x)

回傳 x 弧度的正切值。

雙曲函式

雙曲函式 [https://en.wikipedia.org/wiki/Hyperbolic_functions]是三角函式的類似物，但基於雙曲線而非圓。

math.acosh(x)

回傳 x 的反雙曲餘弦值。

math.asinh(x)

回傳 x 的反雙曲正弦值。

math.atanh(x)

回傳 x 的反雙曲正切值。

math.cosh(x)

回傳 x 的雙曲餘弦值。

math.sinh(x)

回傳 x 的雙曲正弦值。

math.tanh(x)

回傳 x 的雙曲正切值。

特殊函式

math.erf(x)

回傳在 x 處的誤差函式 [https://en.wikipedia.org/wiki/Error_function]值。

erf() 函式可用於計算傳統的統計函式，例如累積標準常態分布 [https://en.wikipedia.org/wiki/Cumulative_distribution_function]：

def phi(x):
    '標準常態分布的累積分布函式'
    return (1.0 + erf(x / sqrt(2.0))) / 2.0

在 3.2 版被加入.

math.erfc(x)

回傳在 x 處的互補誤差函式值。互補誤差函式 [https://en.wikipedia.org/wiki/Error_function]定義為 1.0 - erf(x)。此函式用於較大的 x 值，因為在該情況下從一減去會導致顯著性損失 [https://en.wikipedia.org/wiki/Loss_of_significance]。

在 3.2 版被加入.

math.gamma(x)

回傳在 x 處的 Gamma 函式 [https://en.wikipedia.org/wiki/Gamma_function]值。

在 3.2 版被加入.

math.lgamma(x)

回傳在 x 處 Gamma 函式絕對值的自然對數。

在 3.2 版被加入.

常數

math.pi

數學常數 π = 3.141592...，精確至可用精密度。

math.e

數學常數 e = 2.718281...，精確至可用精密度。

math.tau

數學常數 τ = 6.283185...，精確至可用精密度。Tau 是一個圓常數，等於 2π，即圓的周長與半徑的比值。若想了解更多關於 Tau 的資訊，請觀看 Vi Hart 的影片 Pi is (still) Wrong [https://vimeo.com/147792667]，並開始慶祝 Tau 日 [https://tauday.com/]，吃兩倍的派吧！

在 3.6 版被加入.

math.inf

浮點數正無限值。（對於負無限值，請使用 -math.inf。）等同於 float('inf') 的輸出。

在 3.5 版被加入.

math.nan

浮點數「非數值」（NaN）值。等同於 float('nan') 的輸出。根據 IEEE-754 標準 [https://en.wikipedia.org/wiki/IEEE_754]的要求，math.nan 和 float('nan') 不被認為等於任何其他數值，包括它們自身。若要檢查一個數是否為 NaN，請使用 isnan() 函式而非 is 或 ==。範例：

>>> import math
>>> math.nan == math.nan
False
>>> float('nan') == float('nan')
False
>>> math.isnan(math.nan)
True
>>> math.isnan(float('nan'))
True

在 3.5 版被加入.

在 3.11 版的變更: 現在總是可用。

math 模組大部分由平臺 C 數學函式庫的輕量包裝函式組成。例外情況下的行為在適當時遵循 C99 標準的附錄 F。目前的實作會對無效操作（如 sqrt(-1.0) 或 log(0.0)，C99 附錄 F 建議發出無效操作或除以零的訊號）引發 ValueError，並對溢位結果（例如 exp(1000.0)）引發 OverflowError。除非一個或多個輸入引數是 NaN，否則上述函式不會回傳 NaN；在該情況下，大多數函式會回傳 NaN，但（同樣遵循 C99 附錄 F）此規則有一些例外，例如 pow(float('nan'), 0.0) 或 hypot(float('nan'), float('inf'))。

請注意，Python 不會區分訊號型 NaN（signaling NaN）與安靜型 NaN（quiet NaN），且訊號型 NaN 的行為仍未指定。典型的行為是將所有 NaN 視為安靜型 NaN。

也參考

cmath 模組

這些函式的複數版本。

cmath --- 複數的數學函式

本模組提供一些適用於複數的數學函式。本模組中的函式接受整數、浮點數或複數作為引數。它們也接受任何具有 __complex__() 或 __float__() 方法的 Python 物件：這些方法分別用於將物件轉換為複數或浮點數，然後再將函式應用於轉換後的結果。

備註

對於涉及分枝切割 (branch cut) 的函式，我們面臨的問題是決定如何定義在切割本身上的這些函式。遵循 Kahan 的論文 "Branch cuts for complex elementary functions"，以及 C99 的附錄 G 和後來的 C 標準，我們使用零符號來區分分枝切割的兩側：對於沿著（一部分）實數軸的分枝切割，我們查看虛部的符號，而對於沿虛軸的分枝切割，我們則查看實部的符號。

例如 cmath.sqrt() 函式具有一條沿負實軸的分枝切割。 引數 -2-0j 被視為位於分枝切割 下方 處理，因此給出的結果在負虛軸上：

>>> cmath.sqrt(-2-0j)
-1.4142135623730951j

但是引數 -2+0j 會被當成位於分枝切割上方處理：

>>> cmath.sqrt(-2+0j)
1.4142135623730951j

轉換到極座標和從極座標做轉換

phase(z)

回傳 z 的相位角。

polar(z)

回傳 z 在極座標中的表達方式。

rect(r, phi)

透過極座標 r 和 phi 回傳複數 z。

冪函數和對數函數

exp(z)

回傳 e 的 z 次方。

log(z[, base])

回傳 z 以給定 base 為底（預設為 e）的對數。

log10(z)

回傳 z 以 10 為底的對數。

sqrt(z)

回傳 z 的平方根。

三角函數

acos(z)

回傳 z 的反餘弦值。

asin(z)

回傳 z 的反正弦值。

atan(z)

回傳 z 的反正切值。

cos(z)

回傳 z 的餘弦值。

sin(z)

回傳 z 的正弦值。

tan(z)

回傳 z 的正切值。

雙曲函數

acosh(z)

回傳 z 的反雙曲餘弦值。

asinh(z)

回傳 z 的反雙曲正弦值。

atanh(z)

回傳 z 的反雙曲正切值。

cosh(z)

回傳 z 的雙曲餘弦值。

sinh(z)

回傳 z 的雙曲正弦值。

tanh(z)

回傳 z 的雙曲正切值。

分類函數

isfinite(z)

Check if all components of z are finite

isinf(z)

Check if any component of z is infinite

isnan(z)

Check if any component of z is a NaN

isclose(a, b, *, rel_tol, abs_tol)

檢查 a 和 b 的值是否接近

常數

pi

π = 3.141592...

e

e = 2.718281...

tau

τ = 2π = 6.283185...

inf

Positive infinity

infj

Pure imaginary infinity

nan

"Not a number" (NaN)

nanj

Pure imaginary NaN

轉換到極座標和從極座標做轉換

Python 複數 z 是用 直角坐標 或 笛卡爾坐標 儲存在內部的。它完全是由其 實部 z.real 和 虛部 z.imag 所決定。

極座標 提供了另一種表示複數的方法。在極座標中，複數 z 由絕對值 (modulus) r 和相位角 (phase) phi 定義。絕對值 r 是從 z 到原點的距離，而相位角 phi 是從正 x 軸到連接原點到 z 的線段的逆時針角度（以弧度為單位）。

以下的函式可用於原始直角座標與極座標之間的相互轉換。

cmath.phase(z)

以浮點數的形式回傳 z 的相位角（也稱為 z 的 引數 ）。phase(z) 等價於 math.atan2(z.imag, z.real)。結果將位於 [-π, π] 的範圍內，且此操作的分枝切割將位於負實軸上。結果的符號會與 z.imag 的符號相同，即使 z.imag 為零：

>>> phase(-1+0j)
3.141592653589793
>>> phase(-1-0j)
-3.141592653589793

備註

複數 z 的絕對值可以使用內建的 abs() 函式計算。沒有單獨的 cmath 模組函式適用於此操作。

cmath.polar(z)

回傳 z 在極座標中的表達方式。回傳一組數對 (r, phi)， r 是 z 的絕對值， phi 是 z 的相位角。 polar(z) 相當於 (abs(z), phase(z))。

cmath.rect(r, phi)

透過極座標 r 和 phi 回傳複數 z。相當於 complex(r * math.cos(phi), r * math.sin(phi))。

冪函數和對數函數

cmath.exp(z)

回傳 e 的 z 次方，其中 e 是自然對數的底數。

cmath.log(z[, base])

回傳 z 給定 base 的對數。如果未指定 base，則傳回 z 的自然對數。存在一條分枝切割，從 0 沿負實數軸到 -∞。

cmath.log10(z)

回傳 z 以 10 為底的對數。它與 log() 具有相同的分枝切割。

cmath.sqrt(z)

回傳 z 的平方根。它與 log() 具有相同的分枝切割。

三角函數

cmath.acos(z)

回傳 z 的反餘弦值。存在兩條分枝切割：一條是從 1 沿著實數軸向右延伸到 ∞。另一條從 -1 沿實數軸向左延伸到 -∞。

cmath.asin(z)

回傳 z 的反正弦值。它與 acos() 具有相同的分枝切割。

cmath.atan(z)

回傳 z 的反正切值。有兩條分枝切割：一條是從 1j 沿著虛軸延伸到 ∞j。另一條從 -1j 沿著虛軸延伸到 -∞j。

cmath.cos(z)

回傳 z 的餘弦值。

cmath.sin(z)

回傳 z 的正弦值。

cmath.tan(z)

回傳 z 的正切值。

雙曲函數

cmath.acosh(z)

回傳 z 的反雙曲餘弦值。存在一條分枝切割，從 1 沿實數軸向左延伸到 -∞。

cmath.asinh(z)

回傳 z 的反雙曲正弦值。存在兩條分枝切割：一條是從 1j 沿著虛軸延伸到 ∞j。另一條從 -1j 沿著虛軸延伸到 -∞j。

cmath.atanh(z)

回傳 z 的反雙曲正切值。存在兩條分枝切割：一條是從 1 沿著實數軸延伸到 ∞。另一條從 -1 沿著實數軸延伸到 -∞。

cmath.cosh(z)

回傳 z 的反雙曲餘弦值。

cmath.sinh(z)

回傳 z 的反雙曲正弦值。

cmath.tanh(z)

回傳 z 的反雙曲正切值。

分類函式

cmath.isfinite(z)

如果 z 的實部和虛部都是有限的，則回傳 True，否則回傳 False。

在 3.2 版被加入.

cmath.isinf(z)

如果 z 的實部或虛部是無窮大，則回傳 True，否則回傳 False。

cmath.isnan(z)

如果 z 的實部或虛部為 NaN，則回傳 True，否則回傳 False。

cmath.isclose(a, b, *, rel_tol=1e-09, abs_tol=0.0)

如果 a 和 b 的值相互接近，則回傳 True，否則回傳 False。

兩數是否足夠接近取決於給定的絕對及相對容許偏差 (tolerance)。如果沒有錯誤發生，結果將為：abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)。

rel_tol 為相對容許偏差 ── a 與 b 兩數差的最大容許值，與 a 及 b 兩數的絕對值中較大者相關。例如欲設置 5% 的容許偏差，則傳入 rel_tol=0.05。其預設值為 1e-09，該值可確保兩數於大約 9 個十進數位內相同。rel_tol 須不為負且小於 1.0。

abs_tol is the absolute tolerance; it defaults to 0.0 and it must be nonnegative. When comparing x to 0.0, isclose(x, 0) is computed as abs(x) <= rel_tol  * abs(x), which is False for any x and rel_tol less than 1.0. So add an appropriate positive abs_tol argument to the call.

定義於 IEEE 754 浮點標準中的特殊值 NaN、inf 和 -inf 會根據該標準處理。更明確地說，NaN 不會與包含自身在內的任何數字足夠接近，而 inf 及 -inf 皆只與自身接近。

在 3.5 版被加入.

也參考

PEP 485 [https://peps.python.org/pep-0485/] ── 用於測試近似相等的函式

常數

cmath.pi

數學常數 π，作為一個浮點數。

cmath.e

數學常數 e，作為一個浮點數。

cmath.tau

數學常數 τ，作為一個浮點數。

在 3.6 版被加入.

cmath.inf

正無窮大的浮點數。相當於 float('inf')。

在 3.6 版被加入.

cmath.infj

實部為零和虛部為正無窮的複數。相當於 complex(0.0, float('inf'))。

在 3.6 版被加入.

cmath.nan

浮點「非數字」 (NaN) 值。相當於 float('nan')。另請參閱 math.nan。

在 3.6 版被加入.

cmath.nanj

實部為零和虛部為 NaN 的複數。相當於 complex(0.0, float('nan'))。

在 3.6 版被加入.

請注意，函式的選擇與模組 math 的類似，但並不完全相同。擁有兩個模組的原因是有些用戶對複數不感興趣，甚至根本就不知道它們是什麼。他們寧願讓 math.sqrt(-1) 引發異常，也不願它回傳複數。另請注意， cmath 中所定義的函式始終都會回傳複數，即使答案可以表示為實數（在這種情況下，複數的虛部為零）。

關於分枝切割的註釋：它們是沿著給定的不連續函式的曲線。它們是許多複變函數的必要特徵。假設你需要使用複變函數進行計算，你將會了解分枝切割的概念。請參閱幾乎所有關於複變函數的（不是太初級的）書籍以獲得啟發。對於如何正確地基於數值目的選擇分枝切割的相關訊息，以下內容應該是一個很好的參考：

也參考

Kahan, W: Branch cuts for complex elementary functions; or, Much ado about nothing's sign bit. In Iserles, A., and Powell, M. (eds.), The state of the art in numerical analysis. Clarendon Press (1987) pp165--211.

decimal --- 十進位固定點和浮點運算

原始碼：Lib/decimal.py [https://github.com/python/cpython/tree/3.14/Lib/decimal.py]

The decimal module provides support for fast correctly rounded decimal floating-point arithmetic. It offers several advantages over the float datatype:

Decimal "is based on a floating-point model [https://speleotrove.com/decimal/damodel.html#refnumber] which was designed with people in mind, and necessarily has a paramount guiding principle -- computers must provide an arithmetic that works in the same way as the arithmetic that people learn at school." -- excerpt from the decimal arithmetic specification.

Decimal numbers can be represented exactly. In contrast, numbers like 1.1 and 2.2 do not have exact representations in binary floating point. End users typically would not expect 1.1 + 2.2 to display as 3.3000000000000003 as it does with binary floating point.

The exactness carries over into arithmetic. In decimal floating point, 0.1 + 0.1 + 0.1 - 0.3 is exactly equal to zero. In binary floating point, the result is 5.5511151231257827e-017. While near to zero, the differences prevent reliable equality testing and differences can accumulate. For this reason, decimal is preferred in accounting applications which have strict equality invariants.

The decimal module incorporates a notion of significant places so that 1.30 + 1.20 is 2.50. The trailing zero is kept to indicate significance. This is the customary presentation for monetary applications. For multiplication, the "schoolbook" approach uses all the figures in the multiplicands. For instance, 1.3 * 1.2 gives 1.56 while 1.30 * 1.20 gives 1.5600.

Unlike hardware based binary floating point, the decimal module has a user alterable precision (defaulting to 28 places) which can be as large as needed for a given problem:

>>> from decimal import *
>>> getcontext().prec = 6
>>> Decimal(1) / Decimal(7)
Decimal('0.142857')
>>> getcontext().prec = 28
>>> Decimal(1) / Decimal(7)
Decimal('0.1428571428571428571428571429')

Both binary and decimal floating point are implemented in terms of published standards. While the built-in float type exposes only a modest portion of its capabilities, the decimal module exposes all required parts of the standard. When needed, the programmer has full control over rounding and signal handling. This includes an option to enforce exact arithmetic by using exceptions to block any inexact operations.

The decimal module was designed to support "without prejudice, both exact unrounded decimal arithmetic (sometimes called fixed-point arithmetic) and rounded floating-point arithmetic." -- excerpt from the decimal arithmetic specification.

The module design is centered around three concepts: the decimal number, the context for arithmetic, and signals.

A decimal number is immutable. It has a sign, coefficient digits, and an exponent. To preserve significance, the coefficient digits do not truncate trailing zeros. Decimals also include special values such as Infinity, -Infinity, and NaN. The standard also differentiates -0 from +0.

The context for arithmetic is an environment specifying precision, rounding rules, limits on exponents, flags indicating the results of operations, and trap enablers which determine whether signals are treated as exceptions. Rounding options include ROUND_CEILING, ROUND_DOWN, ROUND_FLOOR, ROUND_HALF_DOWN, ROUND_HALF_EVEN, ROUND_HALF_UP, ROUND_UP, and ROUND_05UP.

Signals are groups of exceptional conditions arising during the course of computation. Depending on the needs of the application, signals may be ignored, considered as informational, or treated as exceptions. The signals in the decimal module are: Clamped, InvalidOperation, DivisionByZero, Inexact, Rounded, Subnormal, Overflow, Underflow and FloatOperation.

For each signal there is a flag and a trap enabler. When a signal is encountered, its flag is set to one, then, if the trap enabler is set to one, an exception is raised. Flags are sticky, so the user needs to reset them before monitoring a calculation.

也參考

IBM's General Decimal Arithmetic Specification, The General Decimal Arithmetic Specification [https://speleotrove.com/decimal/decarith.html].

Quick-start tutorial

The usual start to using decimals is importing the module, viewing the current context with getcontext() and, if necessary, setting new values for precision, rounding, or enabled traps:

>>> from decimal import *
>>> getcontext()
Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
        capitals=1, clamp=0, flags=[], traps=[Overflow, DivisionByZero,
        InvalidOperation])

>>> getcontext().prec = 7       # Set a new precision

Decimal instances can be constructed from integers, strings, floats, or tuples. Construction from an integer or a float performs an exact conversion of the value of that integer or float. Decimal numbers include special values such as NaN which stands for "Not a number", positive and negative Infinity, and -0:

>>> getcontext().prec = 28
>>> Decimal(10)
Decimal('10')
>>> Decimal('3.14')
Decimal('3.14')
>>> Decimal(3.14)
Decimal('3.140000000000000124344978758017532527446746826171875')
>>> Decimal((0, (3, 1, 4), -2))
Decimal('3.14')
>>> Decimal(str(2.0 ** 0.5))
Decimal('1.4142135623730951')
>>> Decimal(2) ** Decimal('0.5')
Decimal('1.414213562373095048801688724')
>>> Decimal('NaN')
Decimal('NaN')
>>> Decimal('-Infinity')
Decimal('-Infinity')

If the FloatOperation signal is trapped, accidental mixing of decimals and floats in constructors or ordering comparisons raises an exception:

>>> c = getcontext()
>>> c.traps[FloatOperation] = True
>>> Decimal(3.14)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
decimal.FloatOperation: [<class 'decimal.FloatOperation'>]
>>> Decimal('3.5') < 3.7
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
decimal.FloatOperation: [<class 'decimal.FloatOperation'>]
>>> Decimal('3.5') == 3.5
True

在 3.3 版被加入.

The significance of a new Decimal is determined solely by the number of digits input. Context precision and rounding only come into play during arithmetic operations.

>>> getcontext().prec = 6
>>> Decimal('3.0')
Decimal('3.0')
>>> Decimal('3.1415926535')
Decimal('3.1415926535')
>>> Decimal('3.1415926535') + Decimal('2.7182818285')
Decimal('5.85987')
>>> getcontext().rounding = ROUND_UP
>>> Decimal('3.1415926535') + Decimal('2.7182818285')
Decimal('5.85988')

If the internal limits of the C version are exceeded, constructing a decimal raises InvalidOperation:

>>> Decimal("1e9999999999999999999")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
decimal.InvalidOperation: [<class 'decimal.InvalidOperation'>]

在 3.3 版的變更.

Decimals interact well with much of the rest of Python. Here is a small decimal floating-point flying circus:

>>> data = list(map(Decimal, '1.34 1.87 3.45 2.35 1.00 0.03 9.25'.split()))
>>> max(data)
Decimal('9.25')
>>> min(data)
Decimal('0.03')
>>> sorted(data)
[Decimal('0.03'), Decimal('1.00'), Decimal('1.34'), Decimal('1.87'),
 Decimal('2.35'), Decimal('3.45'), Decimal('9.25')]
>>> sum(data)
Decimal('19.29')
>>> a,b,c = data[:3]
>>> str(a)
'1.34'
>>> float(a)
1.34
>>> round(a, 1)
Decimal('1.3')
>>> int(a)
1
>>> a * 5
Decimal('6.70')
>>> a * b
Decimal('2.5058')
>>> c % a
Decimal('0.77')

Decimals can be formatted (with format() built-in or f-string（f 字串）) in fixed-point or scientific notation, using the same formatting syntax (see 格式規格 (Format Specification) 迷你語言) as builtin float type:

>>> format(Decimal('2.675'), "f")
'2.675'
>>> format(Decimal('2.675'), ".2f")
'2.68'
>>> f"{Decimal('2.675'):.2f}"
'2.68'
>>> format(Decimal('2.675'), ".2e")
'2.68e+0'
>>> with localcontext() as ctx:
...     ctx.rounding = ROUND_DOWN
...     print(format(Decimal('2.675'), ".2f"))
...
2.67

And some mathematical functions are also available to Decimal:

>>> getcontext().prec = 28
>>> Decimal(2).sqrt()
Decimal('1.414213562373095048801688724')
>>> Decimal(1).exp()
Decimal('2.718281828459045235360287471')
>>> Decimal('10').ln()
Decimal('2.302585092994045684017991455')
>>> Decimal('10').log10()
Decimal('1')

The quantize() method rounds a number to a fixed exponent. This method is useful for monetary applications that often round results to a fixed number of places:

>>> Decimal('7.325').quantize(Decimal('.01'), rounding=ROUND_DOWN)
Decimal('7.32')
>>> Decimal('7.325').quantize(Decimal('1.'), rounding=ROUND_UP)
Decimal('8')

As shown above, the getcontext() function accesses the current context and allows the settings to be changed. This approach meets the needs of most applications.

For more advanced work, it may be useful to create alternate contexts using the Context() constructor. To make an alternate active, use the setcontext() function.

In accordance with the standard, the decimal module provides two ready to use standard contexts, BasicContext and ExtendedContext. The former is especially useful for debugging because many of the traps are enabled:

>>> myothercontext = Context(prec=60, rounding=ROUND_HALF_DOWN)
>>> setcontext(myothercontext)
>>> Decimal(1) / Decimal(7)
Decimal('0.142857142857142857142857142857142857142857142857142857142857')

>>> ExtendedContext
Context(prec=9, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
        capitals=1, clamp=0, flags=[], traps=[])
>>> setcontext(ExtendedContext)
>>> Decimal(1) / Decimal(7)
Decimal('0.142857143')
>>> Decimal(42) / Decimal(0)
Decimal('Infinity')

>>> setcontext(BasicContext)
>>> Decimal(42) / Decimal(0)
Traceback (most recent call last):
  File "<pyshell#143>", line 1, in -toplevel-
    Decimal(42) / Decimal(0)
DivisionByZero: x / 0

Contexts also have signal flags for monitoring exceptional conditions encountered during computations. The flags remain set until explicitly cleared, so it is best to clear the flags before each set of monitored computations by using the clear_flags() method.

>>> setcontext(ExtendedContext)
>>> getcontext().clear_flags()
>>> Decimal(355) / Decimal(113)
Decimal('3.14159292')
>>> getcontext()
Context(prec=9, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
        capitals=1, clamp=0, flags=[Inexact, Rounded], traps=[])

The flags entry shows that the rational approximation to pi was rounded (digits beyond the context precision were thrown away) and that the result is inexact (some of the discarded digits were non-zero).

Individual traps are set using the dictionary in the traps attribute of a context:

>>> setcontext(ExtendedContext)
>>> Decimal(1) / Decimal(0)
Decimal('Infinity')
>>> getcontext().traps[DivisionByZero] = 1
>>> Decimal(1) / Decimal(0)
Traceback (most recent call last):
  File "<pyshell#112>", line 1, in -toplevel-
    Decimal(1) / Decimal(0)
DivisionByZero: x / 0

Most programs adjust the current context only once, at the beginning of the program. And, in many applications, data is converted to Decimal with a single cast inside a loop. With context set and decimals created, the bulk of the program manipulates the data no differently than with other Python numeric types.

Decimal objects

class decimal.Decimal(value='0', context=None)

Construct a new Decimal object based from value.

value can be an integer, string, tuple, float, or another Decimal object. If no value is given, returns Decimal('0'). If value is a string, it should conform to the decimal numeric string syntax after leading and trailing whitespace characters, as well as underscores throughout, are removed:

sign           ::=  '+' | '-'
digit          ::=  '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
indicator      ::=  'e' | 'E'
digits         ::=  digit [digit]...
decimal-part   ::=  digits '.' [digits] | ['.'] digits
exponent-part  ::=  indicator [sign] digits
infinity       ::=  'Infinity' | 'Inf'
nan            ::=  'NaN' [digits] | 'sNaN' [digits]
numeric-value  ::=  decimal-part [exponent-part] | infinity
numeric-string ::=  [sign] numeric-value | [sign] nan

Other Unicode decimal digits are also permitted where digit appears above. These include decimal digits from various other alphabets (for example, Arabic-Indic and Devanāgarī digits) along with the fullwidth digits '\uff10' through '\uff19'. Case is not significant, so, for example, inf, Inf, INFINITY, and iNfINity are all acceptable spellings for positive infinity.

If value is a tuple, it should have three components, a sign (0 for positive or 1 for negative), a tuple of digits, and an integer exponent. For example, Decimal((0, (1, 4, 1, 4), -3)) returns Decimal('1.414').

If value is a float, the binary floating-point value is losslessly converted to its exact decimal equivalent. This conversion can often require 53 or more digits of precision. For example, Decimal(float('1.1')) converts to Decimal('1.100000000000000088817841970012523233890533447265625').

The context precision does not affect how many digits are stored. That is determined exclusively by the number of digits in value. For example, Decimal('3.00000') records all five zeros even if the context precision is only three.

The purpose of the context argument is determining what to do if value is a malformed string. If the context traps InvalidOperation, an exception is raised; otherwise, the constructor returns a new Decimal with the value of NaN.

Once constructed, Decimal objects are immutable.

在 3.2 版的變更: The argument to the constructor is now permitted to be a float instance.

在 3.3 版的變更: float arguments raise an exception if the FloatOperation trap is set. By default the trap is off.

在 3.6 版的變更: Underscores are allowed for grouping, as with integral and floating-point literals in code.

Decimal floating-point objects share many properties with the other built-in numeric types such as float and int. All of the usual math operations and special methods apply. Likewise, decimal objects can be copied, pickled, printed, used as dictionary keys, used as set elements, compared, sorted, and coerced to another type (such as float or int).

There are some small differences between arithmetic on Decimal objects and arithmetic on integers and floats. When the remainder operator % is applied to Decimal objects, the sign of the result is the sign of the dividend rather than the sign of the divisor:

>>> (-7) % 4
1
>>> Decimal(-7) % Decimal(4)
Decimal('-3')

The integer division operator // behaves analogously, returning the integer part of the true quotient (truncating towards zero) rather than its floor, so as to preserve the usual identity x == (x // y) * y + x % y:

>>> -7 // 4
-2
>>> Decimal(-7) // Decimal(4)
Decimal('-1')

The % and // operators implement the remainder and divide-integer operations (respectively) as described in the specification.

Decimal objects cannot generally be combined with floats or instances of fractions.Fraction in arithmetic operations: an attempt to add a Decimal to a float, for example, will raise a TypeError. However, it is possible to use Python's comparison operators to compare a Decimal instance x with another number y. This avoids confusing results when doing equality comparisons between numbers of different types.

在 3.2 版的變更: Mixed-type comparisons between Decimal instances and other numeric types are now fully supported.

In addition to the standard numeric properties, decimal floating-point objects also have a number of specialized methods:

adjusted()

Return the adjusted exponent after shifting out the coefficient's rightmost digits until only the lead digit remains: Decimal('321e+5').adjusted() returns seven. Used for determining the position of the most significant digit with respect to the decimal point.

as_integer_ratio()

Return a pair (n, d) of integers that represent the given Decimal instance as a fraction, in lowest terms and with a positive denominator:

>>> Decimal('-3.14').as_integer_ratio()
(-157, 50)

The conversion is exact. Raise OverflowError on infinities and ValueError on NaNs.

在 3.6 版被加入.

as_tuple()

Return a named tuple representation of the number: DecimalTuple(sign, digits, exponent).

canonical()

Return the canonical encoding of the argument. Currently, the encoding of a Decimal instance is always canonical, so this operation returns its argument unchanged.

compare(other, context=None)

Compare the values of two Decimal instances. compare() returns a Decimal instance, and if either operand is a NaN then the result is a NaN:

a or b is a NaN  ==> Decimal('NaN')
a < b            ==> Decimal('-1')
a == b           ==> Decimal('0')
a > b            ==> Decimal('1')

compare_signal(other, context=None)

This operation is identical to the compare() method, except that all NaNs signal. That is, if neither operand is a signaling NaN then any quiet NaN operand is treated as though it were a signaling NaN.

compare_total(other, context=None)

Compare two operands using their abstract representation rather than their numerical value. Similar to the compare() method, but the result gives a total ordering on Decimal instances. Two Decimal instances with the same numeric value but different representations compare unequal in this ordering:

>>> Decimal('12.0').compare_total(Decimal('12'))
Decimal('-1')

Quiet and signaling NaNs are also included in the total ordering. The result of this function is Decimal('0') if both operands have the same representation, Decimal('-1') if the first operand is lower in the total order than the second, and Decimal('1') if the first operand is higher in the total order than the second operand. See the specification for details of the total order.

This operation is unaffected by context and is quiet: no flags are changed and no rounding is performed. As an exception, the C version may raise InvalidOperation if the second operand cannot be converted exactly.

compare_total_mag(other, context=None)

Compare two operands using their abstract representation rather than their value as in compare_total(), but ignoring the sign of each operand. x.compare_total_mag(y) is equivalent to x.copy_abs().compare_total(y.copy_abs()).

This operation is unaffected by context and is quiet: no flags are changed and no rounding is performed. As an exception, the C version may raise InvalidOperation if the second operand cannot be converted exactly.

conjugate()

Just returns self, this method is only to comply with the Decimal Specification.

copy_abs()

Return the absolute value of the argument. This operation is unaffected by the context and is quiet: no flags are changed and no rounding is performed.

copy_negate()

Return the negation of the argument. This operation is unaffected by the context and is quiet: no flags are changed and no rounding is performed.

copy_sign(other, context=None)

Return a copy of the first operand with the sign set to be the same as the sign of the second operand. For example:

>>> Decimal('2.3').copy_sign(Decimal('-1.5'))
Decimal('-2.3')

This operation is unaffected by context and is quiet: no flags are changed and no rounding is performed. As an exception, the C version may raise InvalidOperation if the second operand cannot be converted exactly.

exp(context=None)

Return the value of the (natural) exponential function e**x at the given number. The result is correctly rounded using the ROUND_HALF_EVEN rounding mode.

>>> Decimal(1).exp()
Decimal('2.718281828459045235360287471')
>>> Decimal(321).exp()
Decimal('2.561702493119680037517373933E+139')

classmethod from_float(f, /)

Alternative constructor that only accepts instances of float or int.

Note Decimal.from_float(0.1) is not the same as Decimal('0.1'). Since 0.1 is not exactly representable in binary floating point, the value is stored as the nearest representable value which is 0x1.999999999999ap-4. That equivalent value in decimal is 0.1000000000000000055511151231257827021181583404541015625.

備註

From Python 3.2 onwards, a Decimal instance can also be constructed directly from a float.

>>> Decimal.from_float(0.1)
Decimal('0.1000000000000000055511151231257827021181583404541015625')
>>> Decimal.from_float(float('nan'))
Decimal('NaN')
>>> Decimal.from_float(float('inf'))
Decimal('Infinity')
>>> Decimal.from_float(float('-inf'))
Decimal('-Infinity')

在 3.1 版被加入.

classmethod from_number(number, /)

Alternative constructor that only accepts instances of float, int or Decimal, but not strings or tuples.

>>> Decimal.from_number(314)
Decimal('314')
>>> Decimal.from_number(0.1)
Decimal('0.1000000000000000055511151231257827021181583404541015625')
>>> Decimal.from_number(Decimal('3.14'))
Decimal('3.14')

在 3.14 版被加入.

fma(other, third, context=None)

Fused multiply-add. Return self*other+third with no rounding of the intermediate product self*other.

>>> Decimal(2).fma(3, 5)
Decimal('11')

is_canonical()

Return True if the argument is canonical and False otherwise. Currently, a Decimal instance is always canonical, so this operation always returns True.

is_finite()

Return True if the argument is a finite number, and False if the argument is an infinity or a NaN.

is_infinite()

Return True if the argument is either positive or negative infinity and False otherwise.

is_nan()

Return True if the argument is a (quiet or signaling) NaN and False otherwise.

is_normal(context=None)

Return True if the argument is a normal finite number. Return False if the argument is zero, subnormal, infinite or a NaN.

is_qnan()

Return True if the argument is a quiet NaN, and False otherwise.

is_signed()

Return True if the argument has a negative sign and False otherwise. Note that zeros and NaNs can both carry signs.

is_snan()

Return True if the argument is a signaling NaN and False otherwise.

is_subnormal(context=None)

Return True if the argument is subnormal, and False otherwise.

is_zero()

Return True if the argument is a (positive or negative) zero and False otherwise.

ln(context=None)

Return the natural (base e) logarithm of the operand. The result is correctly rounded using the ROUND_HALF_EVEN rounding mode.

log10(context=None)

Return the base ten logarithm of the operand. The result is correctly rounded using the ROUND_HALF_EVEN rounding mode.

logb(context=None)

For a nonzero number, return the adjusted exponent of its operand as a Decimal instance. If the operand is a zero then Decimal('-Infinity') is returned and the DivisionByZero flag is raised. If the operand is an infinity then Decimal('Infinity') is returned.

logical_and(other, context=None)

logical_and() is a logical operation which takes two logical operands (see Logical operands). The result is the digit-wise and of the two operands.

logical_invert(context=None)

logical_invert() is a logical operation. The result is the digit-wise inversion of the operand.

logical_or(other, context=None)

logical_or() is a logical operation which takes two logical operands (see Logical operands). The result is the digit-wise or of the two operands.

logical_xor(other, context=None)

logical_xor() is a logical operation which takes two logical operands (see Logical operands). The result is the digit-wise exclusive or of the two operands.

max(other, context=None)

Like max(self, other) except that the context rounding rule is applied before returning and that NaN values are either signaled or ignored (depending on the context and whether they are signaling or quiet).

max_mag(other, context=None)

Similar to the max() method, but the comparison is done using the absolute values of the operands.

min(other, context=None)

Like min(self, other) except that the context rounding rule is applied before returning and that NaN values are either signaled or ignored (depending on the context and whether they are signaling or quiet).

min_mag(other, context=None)

Similar to the min() method, but the comparison is done using the absolute values of the operands.

next_minus(context=None)

Return the largest number representable in the given context (or in the current thread's context if no context is given) that is smaller than the given operand.

next_plus(context=None)

Return the smallest number representable in the given context (or in the current thread's context if no context is given) that is larger than the given operand.

next_toward(other, context=None)

If the two operands are unequal, return the number closest to the first operand in the direction of the second operand. If both operands are numerically equal, return a copy of the first operand with the sign set to be the same as the sign of the second operand.

normalize(context=None)

Used for producing canonical values of an equivalence class within either the current context or the specified context.

This has the same semantics as the unary plus operation, except that if the final result is finite it is reduced to its simplest form, with all trailing zeros removed and its sign preserved. That is, while the coefficient is non-zero and a multiple of ten the coefficient is divided by ten and the exponent is incremented by 1. Otherwise (the coefficient is zero) the exponent is set to 0. In all cases the sign is unchanged.

For example, Decimal('32.100') and Decimal('0.321000e+2') both normalize to the equivalent value Decimal('32.1').

Note that rounding is applied before reducing to simplest form.

In the latest versions of the specification, this operation is also known as reduce.

number_class(context=None)

Return a string describing the class of the operand. The returned value is one of the following ten strings.

"-Infinity", indicating that the operand is negative infinity.

"-Normal", indicating that the operand is a negative normal number.

"-Subnormal", indicating that the operand is negative and subnormal.

"-Zero", indicating that the operand is a negative zero.

"+Zero", indicating that the operand is a positive zero.

"+Subnormal", indicating that the operand is positive and subnormal.

"+Normal", indicating that the operand is a positive normal number.

"+Infinity", indicating that the operand is positive infinity.

"NaN", indicating that the operand is a quiet NaN (Not a Number).

"sNaN", indicating that the operand is a signaling NaN.

quantize(exp, rounding=None, context=None)

Return a value equal to the first operand after rounding and having the exponent of the second operand.

>>> Decimal('1.41421356').quantize(Decimal('1.000'))
Decimal('1.414')

Unlike other operations, if the length of the coefficient after the quantize operation would be greater than precision, then an InvalidOperation is signaled. This guarantees that, unless there is an error condition, the quantized exponent is always equal to that of the right-hand operand.

Also unlike other operations, quantize never signals Underflow, even if the result is subnormal and inexact.

If the exponent of the second operand is larger than that of the first then rounding may be necessary. In this case, the rounding mode is determined by the rounding argument if given, else by the given context argument; if neither argument is given the rounding mode of the current thread's context is used.

An error is returned whenever the resulting exponent is greater than Emax or less than Etiny().

radix()

Return Decimal(10), the radix (base) in which the Decimal class does all its arithmetic. Included for compatibility with the specification.

remainder_near(other, context=None)

Return the remainder from dividing self by other. This differs from self % other in that the sign of the remainder is chosen so as to minimize its absolute value. More precisely, the return value is self - n * other where n is the integer nearest to the exact value of self / other, and if two integers are equally near then the even one is chosen.

If the result is zero then its sign will be the sign of self.

>>> Decimal(18).remainder_near(Decimal(10))
Decimal('-2')
>>> Decimal(25).remainder_near(Decimal(10))
Decimal('5')
>>> Decimal(35).remainder_near(Decimal(10))
Decimal('-5')

rotate(other, context=None)

Return the result of rotating the digits of the first operand by an amount specified by the second operand. The second operand must be an integer in the range -precision through precision. The absolute value of the second operand gives the number of places to rotate. If the second operand is positive then rotation is to the left; otherwise rotation is to the right. The coefficient of the first operand is padded on the left with zeros to length precision if necessary. The sign and exponent of the first operand are unchanged.

same_quantum(other, context=None)

Test whether self and other have the same exponent or whether both are NaN.

This operation is unaffected by context and is quiet: no flags are changed and no rounding is performed. As an exception, the C version may raise InvalidOperation if the second operand cannot be converted exactly.

scaleb(other, context=None)

Return the first operand with exponent adjusted by the second. Equivalently, return the first operand multiplied by 10**other. The second operand must be an integer.

shift(other, context=None)

Return the result of shifting the digits of the first operand by an amount specified by the second operand. The second operand must be an integer in the range -precision through precision. The absolute value of the second operand gives the number of places to shift. If the second operand is positive then the shift is to the left; otherwise the shift is to the right. Digits shifted into the coefficient are zeros. The sign and exponent of the first operand are unchanged.

sqrt(context=None)

Return the square root of the argument to full precision.

to_eng_string(context=None)

Convert to a string, using engineering notation if an exponent is needed.

Engineering notation has an exponent which is a multiple of 3. This can leave up to 3 digits to the left of the decimal place and may require the addition of either one or two trailing zeros.

For example, this converts Decimal('123E+1') to Decimal('1.23E+3').

to_integral(rounding=None, context=None)

Identical to the to_integral_value() method. The to_integral name has been kept for compatibility with older versions.

to_integral_exact(rounding=None, context=None)

Round to the nearest integer, signaling Inexact or Rounded as appropriate if rounding occurs. The rounding mode is determined by the rounding parameter if given, else by the given context. If neither parameter is given then the rounding mode of the current context is used.

to_integral_value(rounding=None, context=None)

Round to the nearest integer without signaling Inexact or Rounded. If given, applies rounding; otherwise, uses the rounding method in either the supplied context or the current context.

Decimal numbers can be rounded using the round() function:

round(number)

round(number, ndigits)

If ndigits is not given or None, returns the nearest int to number, rounding ties to even, and ignoring the rounding mode of the Decimal context. Raises OverflowError if number is an infinity or ValueError if it is a (quiet or signaling) NaN.

If ndigits is an int, the context's rounding mode is respected and a Decimal representing number rounded to the nearest multiple of Decimal('1E-ndigits') is returned; in this case, round(number, ndigits) is equivalent to self.quantize(Decimal('1E-ndigits')). Returns Decimal('NaN') if number is a quiet NaN. Raises InvalidOperation if number is an infinity, a signaling NaN, or if the length of the coefficient after the quantize operation would be greater than the current context's precision. In other words, for the non-corner cases:

if ndigits is positive, return number rounded to ndigits decimal places;

if ndigits is zero, return number rounded to the nearest integer;

if ndigits is negative, return number rounded to the nearest multiple of 10**abs(ndigits).

舉例來說：

>>> from decimal import Decimal, getcontext, ROUND_DOWN
>>> getcontext().rounding = ROUND_DOWN
>>> round(Decimal('3.75'))     # context rounding ignored
4
>>> round(Decimal('3.5'))      # round-ties-to-even
4
>>> round(Decimal('3.75'), 0)  # uses the context rounding
Decimal('3')
>>> round(Decimal('3.75'), 1)
Decimal('3.7')
>>> round(Decimal('3.75'), -1)
Decimal('0E+1')

Logical operands

The logical_and(), logical_invert(), logical_or(), and logical_xor() methods expect their arguments to be logical operands. A logical operand is a Decimal instance whose exponent and sign are both zero, and whose digits are all either 0 or 1.

Context objects

Contexts are environments for arithmetic operations. They govern precision, set rules for rounding, determine which signals are treated as exceptions, and limit the range for exponents.

Each thread has its own current context which is accessed or changed using the getcontext() and setcontext() functions:

decimal.getcontext()

Return the current context for the active thread.

decimal.setcontext(c, /)

Set the current context for the active thread to c.

You can also use the with statement and the localcontext() function to temporarily change the active context.

decimal.localcontext(ctx=None, **kwargs)

Return a context manager that will set the current context for the active thread to a copy of ctx on entry to the with-statement and restore the previous context when exiting the with-statement. If no context is specified, a copy of the current context is used. The kwargs argument is used to set the attributes of the new context.

For example, the following code sets the current decimal precision to 42 places, performs a calculation, and then automatically restores the previous context:

from decimal import localcontext

with localcontext() as ctx:
    ctx.prec = 42   # Perform a high precision calculation
    s = calculate_something()
s = +s  # Round the final result back to the default precision

Using keyword arguments, the code would be the following:

from decimal import localcontext

with localcontext(prec=42) as ctx:
    s = calculate_something()
s = +s

Raises TypeError if kwargs supplies an attribute that Context doesn't support. Raises either TypeError or ValueError if kwargs supplies an invalid value for an attribute.

在 3.11 版的變更: localcontext() now supports setting context attributes through the use of keyword arguments.

decimal.IEEEContext(bits)

Return a context object initialized to the proper values for one of the IEEE interchange formats. The argument must be a multiple of 32 and less than IEEE_CONTEXT_MAX_BITS.

在 3.14 版被加入.

New contexts can also be created using the Context constructor described below. In addition, the module provides three pre-made contexts:

decimal.BasicContext

This is a standard context defined by the General Decimal Arithmetic Specification. Precision is set to nine. Rounding is set to ROUND_HALF_UP. All flags are cleared. All traps are enabled (treated as exceptions) except Inexact, Rounded, and Subnormal.

Because many of the traps are enabled, this context is useful for debugging.

decimal.ExtendedContext

This is a standard context defined by the General Decimal Arithmetic Specification. Precision is set to nine. Rounding is set to ROUND_HALF_EVEN. All flags are cleared. No traps are enabled (so that exceptions are not raised during computations).

Because the traps are disabled, this context is useful for applications that prefer to have result value of NaN or Infinity instead of raising exceptions. This allows an application to complete a run in the presence of conditions that would otherwise halt the program.

decimal.DefaultContext

This context is used by the Context constructor as a prototype for new contexts. Changing a field (such a precision) has the effect of changing the default for new contexts created by the Context constructor.

This context is most useful in multi-threaded environments. Changing one of the fields before threads are started has the effect of setting system-wide defaults. Changing the fields after threads have started is not recommended as it would require thread synchronization to prevent race conditions.

In single threaded environments, it is preferable to not use this context at all. Instead, simply create contexts explicitly as described below.

The default values are Context.prec=28, Context.rounding=ROUND_HALF_EVEN, and enabled traps for Overflow, InvalidOperation, and DivisionByZero.

In addition to the three supplied contexts, new contexts can be created with the Context constructor.

class decimal.Context(prec=None, rounding=None, Emin=None, Emax=None, capitals=None, clamp=None, flags=None, traps=None)

Creates a new context. If a field is not specified or is None, the default values are copied from the DefaultContext. If the flags field is not specified or is None, all flags are cleared.

prec

An integer in the range [1, MAX_PREC] that sets the precision for arithmetic operations in the context.

rounding

One of the constants listed in the section Rounding Modes.

traps

flags

Lists of any signals to be set. Generally, new contexts should only set traps and leave the flags clear.

Emin

Emax

Integers specifying the outer limits allowable for exponents. Emin must be in the range [MIN_EMIN, 0], Emax in the range [0, MAX_EMAX].

capitals

Either 0 or 1 (the default). If set to 1, exponents are printed with a capital E; otherwise, a lowercase e is used: Decimal('6.02e+23').

clamp

Either 0 (the default) or 1. If set to 1, the exponent e of a Decimal instance representable in this context is strictly limited to the range Emin - prec + 1 <= e <= Emax - prec + 1. If clamp is 0 then a weaker condition holds: the adjusted exponent of the Decimal instance is at most Emax. When clamp is 1, a large normal number will, where possible, have its exponent reduced and a corresponding number of zeros added to its coefficient, in order to fit the exponent constraints; this preserves the value of the number but loses information about significant trailing zeros. For example:

>>> Context(prec=6, Emax=999, clamp=1).create_decimal('1.23e999')
Decimal('1.23000E+999')

A clamp value of 1 allows compatibility with the fixed-width decimal interchange formats specified in IEEE 754.

The Context class defines several general purpose methods as well as a large number of methods for doing arithmetic directly in a given context. In addition, for each of the Decimal methods described above (with the exception of the adjusted() and as_tuple() methods) there is a corresponding Context method. For example, for a Context instance C and Decimal instance x, C.exp(x) is equivalent to x.exp(context=C). Each Context method accepts a Python integer (an instance of int) anywhere that a Decimal instance is accepted.

clear_flags()

Resets all of the flags to 0.

clear_traps()

Resets all of the traps to 0.

在 3.3 版被加入.

copy()

Return a duplicate of the context.

copy_decimal(num, /)

Return a copy of the Decimal instance num.

create_decimal(num='0', /)

Creates a new Decimal instance from num but using self as context. Unlike the Decimal constructor, the context precision, rounding method, flags, and traps are applied to the conversion.

This is useful because constants are often given to a greater precision than is needed by the application. Another benefit is that rounding immediately eliminates unintended effects from digits beyond the current precision. In the following example, using unrounded inputs means that adding zero to a sum can change the result:

>>> getcontext().prec = 3
>>> Decimal('3.4445') + Decimal('1.0023')
Decimal('4.45')
>>> Decimal('3.4445') + Decimal(0) + Decimal('1.0023')
Decimal('4.44')

This method implements the to-number operation of the IBM specification. If the argument is a string, no leading or trailing whitespace or underscores are permitted.

create_decimal_from_float(f, /)

Creates a new Decimal instance from a float f but rounding using self as the context. Unlike the Decimal.from_float() class method, the context precision, rounding method, flags, and traps are applied to the conversion.

>>> context = Context(prec=5, rounding=ROUND_DOWN)
>>> context.create_decimal_from_float(math.pi)
Decimal('3.1415')
>>> context = Context(prec=5, traps=[Inexact])
>>> context.create_decimal_from_float(math.pi)
Traceback (most recent call last):
    ...
decimal.Inexact: None

在 3.1 版被加入.

Etiny()

Returns a value equal to Emin - prec + 1 which is the minimum exponent value for subnormal results. When underflow occurs, the exponent is set to Etiny.

Etop()

回傳一個等於 Emax - prec + 1 的值。

The usual approach to working with decimals is to create Decimal instances and then apply arithmetic operations which take place within the current context for the active thread. An alternative approach is to use context methods for calculating within a specific context. The methods are similar to those for the Decimal class and are only briefly recounted here.

abs(x, /)

回傳 x 的絕對值。

add(x, y, /)

回傳 x 與 y 的和。

canonical(x, /)

回傳相同的 Decimal 物件 x。

compare(x, y, /)

Compares x and y numerically.

compare_signal(x, y, /)

Compares the values of the two operands numerically.

compare_total(x, y, /)

Compares two operands using their abstract representation.

compare_total_mag(x, y, /)

Compares two operands using their abstract representation, ignoring sign.

copy_abs(x, /)

Returns a copy of x with the sign set to 0.

copy_negate(x, /)

Returns a copy of x with the sign inverted.

copy_sign(x, y, /)

將 y 的正負號複製到 x。

divide(x, y, /)

回傳 x 除以 y。

divide_int(x, y, /)

Return x divided by y, truncated to an integer.

divmod(x, y, /)

Divides two numbers and returns the integer part of the result.

exp(x, /)

回傳 e ** x。

fma(x, y, z, /)

回傳 x 乘以 y，再加上 z。

is_canonical(x, /)

Returns True if x is canonical; otherwise returns False.

is_finite(x, /)

如果 x 是有限的則回傳 True；否則回傳 False。

is_infinite(x, /)

如果 x 是無限大則回傳 True；否則回傳 False。

is_nan(x, /)

如果 x 是 qNaN 或 sNaN 則回傳 True；否則回傳 False。

is_normal(x, /)

如果 x 是正規數 (normal number) 則回傳 True；否則回傳 False。

is_qnan(x, /)

如果 x 是安靜型 NaN (quiet NaN) 則回傳 True；否則回傳 False。

is_signed(x, /)

如果 x 是負數則回傳 True；否則回傳 False。

is_snan(x, /)

如果 x 是訊號型 NaN (signaling NaN) 則回傳 True；否則回傳 False。

is_subnormal(x, /)

如果 x 是次正規數 (subnormal) 則回傳 True；否則回傳 False。

is_zero(x, /)

如果 x 是零則回傳 True；否則回傳 False。

ln(x, /)

回傳 x 的自然對數（以 e 為底）。

log10(x, /)

回傳 x 的以 10 為底的對數。

logb(x, /)

回傳運算元最高有效位數（MSD）數值的指數。

logical_and(x, y, /)

將每個運算元的位數套用邏輯運算 and。

logical_invert(x, /)

Invert all the digits in x.

logical_or(x, y, /)

Applies the logical operation or between each operand's digits.

logical_xor(x, y, /)

Applies the logical operation xor between each operand's digits.

max(x, y, /)

Compares two values numerically and returns the maximum.

max_mag(x, y, /)

Compares the values numerically with their sign ignored.

min(x, y, /)

Compares two values numerically and returns the minimum.

min_mag(x, y, /)

Compares the values numerically with their sign ignored.

minus(x, /)

Minus corresponds to the unary prefix minus operator in Python.

multiply(x, y, /)

Return the product of x and y.

next_minus(x, /)

Returns the largest representable number smaller than x.

next_plus(x, /)

Returns the smallest representable number larger than x.

next_toward(x, y, /)

Returns the number closest to x, in direction towards y.

normalize(x, /)

Reduces x to its simplest form.

number_class(x, /)

Returns an indication of the class of x.

plus(x, /)

Plus corresponds to the unary prefix plus operator in Python. This operation applies the context precision and rounding, so it is not an identity operation.

power(x, y, modulo=None)

Return x to the power of y, reduced modulo modulo if given.

With two arguments, compute x**y. If x is negative then y must be integral. The result will be inexact unless y is integral and the result is finite and can be expressed exactly in 'precision' digits. The rounding mode of the context is used. Results are always correctly rounded in the Python version.

Decimal(0) ** Decimal(0) results in InvalidOperation, and if InvalidOperation is not trapped, then results in Decimal('NaN').

在 3.3 版的變更: The C module computes power() in terms of the correctly rounded exp() and ln() functions. The result is well-defined but only "almost always correctly rounded".

With three arguments, compute (x**y) % modulo. For the three argument form, the following restrictions on the arguments hold:

all three arguments must be integral

y must be nonnegative

at least one of x or y must be nonzero

modulo must be nonzero and have at most 'precision' digits

The value resulting from Context.power(x, y, modulo) is equal to the value that would be obtained by computing (x**y) % modulo with unbounded precision, but is computed more efficiently. The exponent of the result is zero, regardless of the exponents of x, y and modulo. The result is always exact.

quantize(x, y, /)

Returns a value equal to x (rounded), having the exponent of y.

radix()

Just returns 10, as this is Decimal, :)

remainder(x, y, /)

Returns the remainder from integer division.

The sign of the result, if non-zero, is the same as that of the original dividend.

remainder_near(x, y, /)

Returns x - y * n, where n is the integer nearest the exact value of x / y (if the result is 0 then its sign will be the sign of x).

rotate(x, y, /)

Returns a rotated copy of x, y times.

same_quantum(x, y, /)

如果兩個運算元有相同的指數則回傳 True。

scaleb(x, y, /)

Returns the first operand after adding the second value its exp.

shift(x, y, /)

Returns a shifted copy of x, y times.

sqrt(x, /)

Square root of a non-negative number to context precision.

subtract(x, y, /)

Return the difference between x and y.

to_eng_string(x, /)

Convert to a string, using engineering notation if an exponent is needed.

Engineering notation has an exponent which is a multiple of 3. This can leave up to 3 digits to the left of the decimal place and may require the addition of either one or two trailing zeros.

to_integral_exact(x, /)

Rounds to an integer.

to_sci_string(x, /)

Converts a number to a string using scientific notation.

常數

The constants in this section are only relevant for the C module. They are also included in the pure Python version for compatibility.

32 位元

64 位元

decimal.MAX_PREC

425000000

999999999999999999

decimal.MAX_EMAX

425000000

999999999999999999

decimal.MIN_EMIN

-425000000

-999999999999999999

decimal.MIN_ETINY

-849999999

-1999999999999999997

decimal.IEEE_CONTEXT_MAX_BITS

256

512

decimal.HAVE_THREADS

The value is True. Deprecated, because Python now always has threads.

在 3.9 版之後被棄用.

decimal.HAVE_CONTEXTVAR

The default value is True. If Python is configured using the --without-decimal-contextvar option, the C version uses a thread-local rather than a coroutine-local context and the value is False. This is slightly faster in some nested context scenarios.

在 3.8.3 版被加入.

Rounding modes

decimal.ROUND_CEILING

Round towards Infinity.

decimal.ROUND_DOWN

Round towards zero.

decimal.ROUND_FLOOR

Round towards -Infinity.

decimal.ROUND_HALF_DOWN

Round to nearest with ties going towards zero.

decimal.ROUND_HALF_EVEN

Round to nearest with ties going to nearest even integer.

decimal.ROUND_HALF_UP

Round to nearest with ties going away from zero.

decimal.ROUND_UP

Round away from zero.

decimal.ROUND_05UP

Round away from zero if last digit after rounding towards zero would have been 0 or 5; otherwise round towards zero.

Signals

Signals represent conditions that arise during computation. Each corresponds to one context flag and one context trap enabler.

The context flag is set whenever the condition is encountered. After the computation, flags may be checked for informational purposes (for instance, to determine whether a computation was exact). After checking the flags, be sure to clear all flags before starting the next computation.

If the context's trap enabler is set for the signal, then the condition causes a Python exception to be raised. For example, if the DivisionByZero trap is set, then a DivisionByZero exception is raised upon encountering the condition.

class decimal.Clamped

Altered an exponent to fit representation constraints.

Typically, clamping occurs when an exponent falls outside the context's Emin and Emax limits. If possible, the exponent is reduced to fit by adding zeros to the coefficient.

class decimal.DecimalException

Base class for other signals and a subclass of ArithmeticError.

class decimal.DivisionByZero

Signals the division of a non-infinite number by zero.

Can occur with division, modulo division, or when raising a number to a negative power. If this signal is not trapped, returns Infinity or -Infinity with the sign determined by the inputs to the calculation.

class decimal.Inexact

Indicates that rounding occurred and the result is not exact.

Signals when non-zero digits were discarded during rounding. The rounded result is returned. The signal flag or trap is used to detect when results are inexact.

class decimal.InvalidOperation

An invalid operation was performed.

Indicates that an operation was requested that does not make sense. If not trapped, returns NaN. Possible causes include:

Infinity - Infinity
0 * Infinity
Infinity / Infinity
x % 0
Infinity % x
sqrt(-x) and x > 0
0 ** 0
x ** (non-integer)
x ** Infinity

class decimal.Overflow

Numerical overflow.

Indicates the exponent is larger than Context.Emax after rounding has occurred. If not trapped, the result depends on the rounding mode, either pulling inward to the largest representable finite number or rounding outward to Infinity. In either case, Inexact and Rounded are also signaled.

class decimal.Rounded

Rounding occurred though possibly no information was lost.

Signaled whenever rounding discards digits; even if those digits are zero (such as rounding 5.00 to 5.0). If not trapped, returns the result unchanged. This signal is used to detect loss of significant digits.

class decimal.Subnormal

Exponent was lower than Emin prior to rounding.

Occurs when an operation result is subnormal (the exponent is too small). If not trapped, returns the result unchanged.

class decimal.Underflow

Numerical underflow with result rounded to zero.

Occurs when a subnormal result is pushed to zero by rounding. Inexact and Subnormal are also signaled.

class decimal.FloatOperation

Enable stricter semantics for mixing floats and Decimals.

If the signal is not trapped (default), mixing floats and Decimals is permitted in the Decimal constructor, create_decimal() and all comparison operators. Both conversion and comparisons are exact. Any occurrence of a mixed operation is silently recorded by setting FloatOperation in the context flags. Explicit conversions with from_float() or create_decimal_from_float() do not set the flag.

Otherwise (the signal is trapped), only equality comparisons and explicit conversions are silent. All other mixed operations raise FloatOperation.

The following table summarizes the hierarchy of signals:

exceptions.ArithmeticError(exceptions.Exception)
    DecimalException
        Clamped
        DivisionByZero(DecimalException, exceptions.ZeroDivisionError)
        Inexact
            Overflow(Inexact, Rounded)
            Underflow(Inexact, Rounded, Subnormal)
        InvalidOperation
        Rounded
        Subnormal
        FloatOperation(DecimalException, exceptions.TypeError)

Floating-point notes

Mitigating round-off error with increased precision

The use of decimal floating point eliminates decimal representation error (making it possible to represent 0.1 exactly); however, some operations can still incur round-off error when non-zero digits exceed the fixed precision.

The effects of round-off error can be amplified by the addition or subtraction of nearly offsetting quantities resulting in loss of significance. Knuth provides two instructive examples where rounded floating-point arithmetic with insufficient precision causes the breakdown of the associative and distributive properties of addition:

# Examples from Seminumerical Algorithms, Section 4.2.2.
>>> from decimal import Decimal, getcontext
>>> getcontext().prec = 8

>>> u, v, w = Decimal(11111113), Decimal(-11111111), Decimal('7.51111111')
>>> (u + v) + w
Decimal('9.5111111')
>>> u + (v + w)
Decimal('10')

>>> u, v, w = Decimal(20000), Decimal(-6), Decimal('6.0000003')
>>> (u*v) + (u*w)
Decimal('0.01')
>>> u * (v+w)
Decimal('0.0060000')

The decimal module makes it possible to restore the identities by expanding the precision sufficiently to avoid loss of significance:

>>> getcontext().prec = 20
>>> u, v, w = Decimal(11111113), Decimal(-11111111), Decimal('7.51111111')
>>> (u + v) + w
Decimal('9.51111111')
>>> u + (v + w)
Decimal('9.51111111')
>>>
>>> u, v, w = Decimal(20000), Decimal(-6), Decimal('6.0000003')
>>> (u*v) + (u*w)
Decimal('0.0060000')
>>> u * (v+w)
Decimal('0.0060000')

特殊值

The number system for the decimal module provides special values including NaN, sNaN, -Infinity, Infinity, and two zeros, +0 and -0.

Infinities can be constructed directly with: Decimal('Infinity'). Also, they can arise from dividing by zero when the DivisionByZero signal is not trapped. Likewise, when the Overflow signal is not trapped, infinity can result from rounding beyond the limits of the largest representable number.

The infinities are signed (affine) and can be used in arithmetic operations where they get treated as very large, indeterminate numbers. For instance, adding a constant to infinity gives another infinite result.

Some operations are indeterminate and return NaN, or if the InvalidOperation signal is trapped, raise an exception. For example, 0/0 returns NaN which means "not a number". This variety of NaN is quiet and, once created, will flow through other computations always resulting in another NaN. This behavior can be useful for a series of computations that occasionally have missing inputs --- it allows the calculation to proceed while flagging specific results as invalid.

A variant is sNaN which signals rather than remaining quiet after every operation. This is a useful return value when an invalid result needs to interrupt a calculation for special handling.

The behavior of Python's comparison operators can be a little surprising where a NaN is involved. A test for equality where one of the operands is a quiet or signaling NaN always returns False (even when doing Decimal('NaN')==Decimal('NaN')), while a test for inequality always returns True. An attempt to compare two Decimals using any of the <, <=, > or >= operators will raise the InvalidOperation signal if either operand is a NaN, and return False if this signal is not trapped. Note that the General Decimal Arithmetic specification does not specify the behavior of direct comparisons; these rules for comparisons involving a NaN were taken from the IEEE 854 standard (see Table 3 in section 5.7). To ensure strict standards-compliance, use the compare() and compare_signal() methods instead.

The signed zeros can result from calculations that underflow. They keep the sign that would have resulted if the calculation had been carried out to greater precision. Since their magnitude is zero, both positive and negative zeros are treated as equal and their sign is informational.

In addition to the two signed zeros which are distinct yet equal, there are various representations of zero with differing precisions yet equivalent in value. This takes a bit of getting used to. For an eye accustomed to normalized floating-point representations, it is not immediately obvious that the following calculation returns a value equal to zero:

>>> 1 / Decimal('Infinity')
Decimal('0E-1000026')

Working with threads

The getcontext() function accesses a different Context object for each thread. Having separate thread contexts means that threads may make changes (such as getcontext().prec=10) without interfering with other threads.

Likewise, the setcontext() function automatically assigns its target to the current thread.

If setcontext() has not been called before getcontext(), then getcontext() will automatically create a new context for use in the current thread. New context objects have default values set from the decimal.DefaultContext object.

The sys.flags.thread_inherit_context flag affects the context for new threads. If the flag is false, new threads will start with an empty context. In this case, getcontext() will create a new context object when called and use the default values from DefaultContext. If the flag is true, new threads will start with a copy of context from the caller of threading.Thread.start().

To control the defaults so that each thread will use the same values throughout the application, directly modify the DefaultContext object. This should be done before any threads are started so that there won't be a race condition between threads calling getcontext(). For example:

# Set applicationwide defaults for all threads about to be launched
DefaultContext.prec = 12
DefaultContext.rounding = ROUND_DOWN
DefaultContext.traps = ExtendedContext.traps.copy()
DefaultContext.traps[InvalidOperation] = 1
setcontext(DefaultContext)

# Afterwards, the threads can be started
t1.start()
t2.start()
t3.start()
 . . .

Recipes

Here are a few recipes that serve as utility functions and that demonstrate ways to work with the Decimal class:

def moneyfmt(value, places=2, curr='', sep=',', dp='.',
             pos='', neg='-', trailneg=''):
    """Convert Decimal to a money formatted string.

    places:  required number of places after the decimal point
    curr:    optional currency symbol before the sign (may be blank)
    sep:     optional grouping separator (comma, period, space, or blank)
    dp:      decimal point indicator (comma or period)
             only specify as blank when places is zero
    pos:     optional sign for positive numbers: '+', space or blank
    neg:     optional sign for negative numbers: '-', '(', space or blank
    trailneg:optional trailing minus indicator:  '-', ')', space or blank

    >>> d = Decimal('-1234567.8901')
    >>> moneyfmt(d, curr='$')
    '-$1,234,567.89'
    >>> moneyfmt(d, places=0, sep='.', dp='', neg='', trailneg='-')
    '1.234.568-'
    >>> moneyfmt(d, curr='$', neg='(', trailneg=')')
    '($1,234,567.89)'
    >>> moneyfmt(Decimal(123456789), sep=' ')
    '123 456 789.00'
    >>> moneyfmt(Decimal('-0.02'), neg='<', trailneg='>')
    '<0.02>'

    """
    q = Decimal(10) ** -places      # 2 places --> '0.01'
    sign, digits, exp = value.quantize(q).as_tuple()
    result = []
    digits = list(map(str, digits))
    build, next = result.append, digits.pop
    if sign:
        build(trailneg)
    for i in range(places):
        build(next() if digits else '0')
    if places:
        build(dp)
    if not digits:
        build('0')
    i = 0
    while digits:
        build(next())
        i += 1
        if i == 3 and digits:
            i = 0
            build(sep)
    build(curr)
    build(neg if sign else pos)
    return ''.join(reversed(result))

def pi():
    """Compute Pi to the current precision.

    >>> print(pi())
    3.141592653589793238462643383

    """
    getcontext().prec += 2  # extra digits for intermediate steps
    three = Decimal(3)      # substitute "three=3.0" for regular floats
    lasts, t, s, n, na, d, da = 0, three, 3, 1, 0, 0, 24
    while s != lasts:
        lasts = s
        n, na = n+na, na+8
        d, da = d+da, da+32
        t = (t * n) / d
        s += t
    getcontext().prec -= 2
    return +s               # unary plus applies the new precision

def exp(x):
    """Return e raised to the power of x.  Result type matches input type.

    >>> print(exp(Decimal(1)))
    2.718281828459045235360287471
    >>> print(exp(Decimal(2)))
    7.389056098930650227230427461
    >>> print(exp(2.0))
    7.38905609893
    >>> print(exp(2+0j))
    (7.38905609893+0j)

    """
    getcontext().prec += 2
    i, lasts, s, fact, num = 0, 0, 1, 1, 1
    while s != lasts:
        lasts = s
        i += 1
        fact *= i
        num *= x
        s += num / fact
    getcontext().prec -= 2
    return +s

def cos(x):
    """Return the cosine of x as measured in radians.

    The Taylor series approximation works best for a small value of x.
    For larger values, first compute x = x % (2 * pi).

    >>> print(cos(Decimal('0.5')))
    0.8775825618903727161162815826
    >>> print(cos(0.5))
    0.87758256189
    >>> print(cos(0.5+0j))
    (0.87758256189+0j)

    """
    getcontext().prec += 2
    i, lasts, s, fact, num, sign = 0, 0, 1, 1, 1, 1
    while s != lasts:
        lasts = s
        i += 2
        fact *= i * (i-1)
        num *= x * x
        sign *= -1
        s += num / fact * sign
    getcontext().prec -= 2
    return +s

def sin(x):
    """Return the sine of x as measured in radians.

    The Taylor series approximation works best for a small value of x.
    For larger values, first compute x = x % (2 * pi).

    >>> print(sin(Decimal('0.5')))
    0.4794255386042030002732879352
    >>> print(sin(0.5))
    0.479425538604
    >>> print(sin(0.5+0j))
    (0.479425538604+0j)

    """
    getcontext().prec += 2
    i, lasts, s, fact, num, sign = 1, 0, x, 1, x, 1
    while s != lasts:
        lasts = s
        i += 2
        fact *= i * (i-1)
        num *= x * x
        sign *= -1
        s += num / fact * sign
    getcontext().prec -= 2
    return +s

Decimal FAQ

Q: It is cumbersome to type decimal.Decimal('1234.5'). Is there a way to minimize typing when using the interactive interpreter?

A: Some users abbreviate the constructor to just a single letter:

>>> D = decimal.Decimal
>>> D('1.23') + D('3.45')
Decimal('4.68')

Q: In a fixed-point application with two decimal places, some inputs have many places and need to be rounded. Others are not supposed to have excess digits and need to be validated. What methods should be used?

A: The quantize() method rounds to a fixed number of decimal places. If the Inexact trap is set, it is also useful for validation:

>>> TWOPLACES = Decimal(10) ** -2       # same as Decimal('0.01')

>>> # Round to two places
>>> Decimal('3.214').quantize(TWOPLACES)
Decimal('3.21')

>>> # Validate that a number does not exceed two places
>>> Decimal('3.21').quantize(TWOPLACES, context=Context(traps=[Inexact]))
Decimal('3.21')

>>> Decimal('3.214').quantize(TWOPLACES, context=Context(traps=[Inexact]))
Traceback (most recent call last):
   ...
Inexact: None

Q: Once I have valid two place inputs, how do I maintain that invariant throughout an application?

A: Some operations like addition, subtraction, and multiplication by an integer will automatically preserve fixed point. Others operations, like division and non-integer multiplication, will change the number of decimal places and need to be followed-up with a quantize() step:

>>> a = Decimal('102.72')           # Initial fixed-point values
>>> b = Decimal('3.17')
>>> a + b                           # Addition preserves fixed-point
Decimal('105.89')
>>> a - b
Decimal('99.55')
>>> a * 42                          # So does integer multiplication
Decimal('4314.24')
>>> (a * b).quantize(TWOPLACES)     # Must quantize non-integer multiplication
Decimal('325.62')
>>> (b / a).quantize(TWOPLACES)     # And quantize division
Decimal('0.03')

In developing fixed-point applications, it is convenient to define functions to handle the quantize() step:

>>> def mul(x, y, fp=TWOPLACES):
...     return (x * y).quantize(fp)
...
>>> def div(x, y, fp=TWOPLACES):
...     return (x / y).quantize(fp)

>>> mul(a, b)                       # Automatically preserve fixed-point
Decimal('325.62')
>>> div(b, a)
Decimal('0.03')

Q: There are many ways to express the same value. The numbers 200, 200.000, 2E2, and .02E+4 all have the same value at various precisions. Is there a way to transform them to a single recognizable canonical value?

A: The normalize() method maps all equivalent values to a single representative:

>>> values = map(Decimal, '200 200.000 2E2 .02E+4'.split())
>>> [v.normalize() for v in values]
[Decimal('2E+2'), Decimal('2E+2'), Decimal('2E+2'), Decimal('2E+2')]

Q: When does rounding occur in a computation?

A: It occurs after the computation. The philosophy of the decimal specification is that numbers are considered exact and are created independent of the current context. They can even have greater precision than current context. Computations process with those exact inputs and then rounding (or other context operations) is applied to the result of the computation:

>>> getcontext().prec = 5
>>> pi = Decimal('3.1415926535')   # More than 5 digits
>>> pi                             # All digits are retained
Decimal('3.1415926535')
>>> pi + 0                         # Rounded after an addition
Decimal('3.1416')
>>> pi - Decimal('0.00005')        # Subtract unrounded numbers, then round
Decimal('3.1415')
>>> pi + 0 - Decimal('0.00005').   # Intermediate values are rounded
Decimal('3.1416')

Q: Some decimal values always print with exponential notation. Is there a way to get a non-exponential representation?

A: For some values, exponential notation is the only way to express the number of significant places in the coefficient. For example, expressing 5.0E+3 as 5000 keeps the value constant but cannot show the original's two-place significance.

If an application does not care about tracking significance, it is easy to remove the exponent and trailing zeroes, losing significance, but keeping the value unchanged:

>>> def remove_exponent(d):
...     return d.quantize(Decimal(1)) if d == d.to_integral() else d.normalize()

>>> remove_exponent(Decimal('5E+3'))
Decimal('5000')

Q: Is there a way to convert a regular float to a Decimal?

A: Yes, any binary floating-point number can be exactly expressed as a Decimal though an exact conversion may take more precision than intuition would suggest:

>>> Decimal(math.pi)
Decimal('3.141592653589793115997963468544185161590576171875')

Q: Within a complex calculation, how can I make sure that I haven't gotten a spurious result because of insufficient precision or rounding anomalies.

A: The decimal module makes it easy to test results. A best practice is to re-run calculations using greater precision and with various rounding modes. Widely differing results indicate insufficient precision, rounding mode issues, ill-conditioned inputs, or a numerically unstable algorithm.

Q: I noticed that context precision is applied to the results of operations but not to the inputs. Is there anything to watch out for when mixing values of different precisions?

A: Yes. The principle is that all values are considered to be exact and so is the arithmetic on those values. Only the results are rounded. The advantage for inputs is that "what you type is what you get". A disadvantage is that the results can look odd if you forget that the inputs haven't been rounded:

>>> getcontext().prec = 3
>>> Decimal('3.104') + Decimal('2.104')
Decimal('5.21')
>>> Decimal('3.104') + Decimal('0.000') + Decimal('2.104')
Decimal('5.20')

The solution is either to increase precision or to force rounding of inputs using the unary plus operation:

>>> getcontext().prec = 3
>>> +Decimal('1.23456789')      # unary plus triggers rounding
Decimal('1.23')

Alternatively, inputs can be rounded upon creation using the Context.create_decimal() method:

>>> Context(prec=5, rounding=ROUND_DOWN).create_decimal('1.2345678')
Decimal('1.2345')

Q: Is the CPython implementation fast for large numbers?

A: Yes. In the CPython and PyPy3 implementations, the C/CFFI versions of the decimal module integrate the high speed libmpdec [https://www.bytereef.org/mpdecimal/doc/libmpdec/index.html] library for arbitrary precision correctly rounded decimal floating-point arithmetic [1]. libmpdec uses Karatsuba multiplication [https://en.wikipedia.org/wiki/Karatsuba_algorithm] for medium-sized numbers and the Number Theoretic Transform [https://en.wikipedia.org/wiki/Discrete_Fourier_transform_(general)#Number-theoretic_transform] for very large numbers.

The context must be adapted for exact arbitrary precision arithmetic. Emin and Emax should always be set to the maximum values, clamp should always be 0 (the default). Setting prec requires some care.

The easiest approach for trying out bignum arithmetic is to use the maximum value for prec as well [2]:

>>> setcontext(Context(prec=MAX_PREC, Emax=MAX_EMAX, Emin=MIN_EMIN))
>>> x = Decimal(2) ** 256
>>> x / 128
Decimal('904625697166532776746648320380374280103671755200316906558262375061821325312')

For inexact results, MAX_PREC is far too large on 64-bit platforms and the available memory will be insufficient:

>>> Decimal(1) / 3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
MemoryError

On systems with overallocation (e.g. Linux), a more sophisticated approach is to adjust prec to the amount of available RAM. Suppose that you have 8GB of RAM and expect 10 simultaneous operands using a maximum of 500MB each:

>>> import sys
>>>
>>> # Maximum number of digits for a single operand using 500MB in 8-byte words
>>> # with 19 digits per word (4-byte and 9 digits for the 32-bit build):
>>> maxdigits = 19 * ((500 * 1024**2) // 8)
>>>
>>> # Check that this works:
>>> c = Context(prec=maxdigits, Emax=MAX_EMAX, Emin=MIN_EMIN)
>>> c.traps[Inexact] = True
>>> setcontext(c)
>>>
>>> # Fill the available precision with nines:
>>> x = Decimal(0).logical_invert() * 9
>>> sys.getsizeof(x)
524288112
>>> x + 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  decimal.Inexact: [<class 'decimal.Inexact'>]

In general (and especially on systems without overallocation), it is recommended to estimate even tighter bounds and set the Inexact trap if all calculations are expected to be exact.

[1]

在 3.3 版被加入.

[2]

在 3.9 版的變更: This approach now works for all exact results except for non-integer powers.

fractions --- 有理數

原始碼：Lib/fractions.py [https://github.com/python/cpython/tree/3.14/Lib/fractions.py]

The fractions module provides support for rational number arithmetic.

A Fraction instance can be constructed from a pair of rational numbers, from a single number, or from a string.

class fractions.Fraction(numerator=0, denominator=1)

class fractions.Fraction(number)

class fractions.Fraction(string)

The first version requires that numerator and denominator are instances of numbers.Rational and returns a new Fraction instance with a value equal to numerator/denominator. If denominator is zero, it raises a ZeroDivisionError.

The second version requires that number is an instance of numbers.Rational or has the as_integer_ratio() method (this includes float and decimal.Decimal). It returns a Fraction instance with exactly the same value. Assumed, that the as_integer_ratio() method returns a pair of coprime integers and last one is positive. Note that due to the usual issues with binary point (see 浮點數運算：問題與限制), the argument to Fraction(1.1) is not exactly equal to 11/10, and so Fraction(1.1) does not return Fraction(11, 10) as one might expect. (But see the documentation for the limit_denominator() method below.)

The last version of the constructor expects a string. The usual form for this instance is:

[sign] numerator ['/' denominator]

where the optional sign may be either '+' or '-' and numerator and denominator (if present) are strings of decimal digits (underscores may be used to delimit digits as with integral literals in code). In addition, any string that represents a finite value and is accepted by the float constructor is also accepted by the Fraction constructor. In either form the input string may also have leading and/or trailing whitespace. Here are some examples:

>>> from fractions import Fraction
>>> Fraction(16, -10)
Fraction(-8, 5)
>>> Fraction(123)
Fraction(123, 1)
>>> Fraction()
Fraction(0, 1)
>>> Fraction('3/7')
Fraction(3, 7)
>>> Fraction(' -3/7 ')
Fraction(-3, 7)
>>> Fraction('1.414213 \t\n')
Fraction(1414213, 1000000)
>>> Fraction('-.125')
Fraction(-1, 8)
>>> Fraction('7e-6')
Fraction(7, 1000000)
>>> Fraction(2.25)
Fraction(9, 4)
>>> Fraction(1.1)
Fraction(2476979795053773, 2251799813685248)
>>> from decimal import Decimal
>>> Fraction(Decimal('1.1'))
Fraction(11, 10)

The Fraction class inherits from the abstract base class numbers.Rational, and implements all of the methods and operations from that class. Fraction instances are hashable, and should be treated as immutable. In addition, Fraction has the following properties and methods:

在 3.2 版的變更: Fraction 建構函式現在可接受 float 和 decimal.Decimal 實例。

在 3.9 版的變更: The math.gcd() function is now used to normalize the numerator and denominator. math.gcd() always returns an int type. Previously, the GCD type depended on numerator and denominator.

在 3.11 版的變更: Underscores are now permitted when creating a Fraction instance from a string, following PEP 515 [https://peps.python.org/pep-0515/] rules.

在 3.11 版的變更: Fraction implements __int__ now to satisfy typing.SupportsInt instance checks.

在 3.12 版的變更: Space is allowed around the slash for string inputs: Fraction('2 / 3').

在 3.12 版的變更: Fraction instances now support float-style formatting, with presentation types "e", "E", "f", "F", "g", "G" and "%"".

在 3.13 版的變更: Formatting of Fraction instances without a presentation type now supports fill, alignment, sign handling, minimum width and grouping.

在 3.14 版的變更: Fraction 建構函式現在可接受任何具有 as_integer_ratio() 方法的物件。

numerator

Numerator of the Fraction in lowest term.

denominator

Denominator of the Fraction in lowest terms. Guaranteed to be positive.

as_integer_ratio()

Return a tuple of two integers, whose ratio is equal to the original Fraction. The ratio is in lowest terms and has a positive denominator.

在 3.8 版被加入.

is_integer()

Return True if the Fraction is an integer.

在 3.12 版被加入.

classmethod from_float(f)

Alternative constructor which only accepts instances of float or numbers.Integral. Beware that Fraction.from_float(0.3) is not the same value as Fraction(3, 10).

備註

From Python 3.2 onwards, you can also construct a Fraction instance directly from a float.

classmethod from_decimal(dec)

Alternative constructor which only accepts instances of decimal.Decimal or numbers.Integral.

備註

From Python 3.2 onwards, you can also construct a Fraction instance directly from a decimal.Decimal instance.

classmethod from_number(number)

Alternative constructor which only accepts instances of numbers.Integral, numbers.Rational, float or decimal.Decimal, and objects with the as_integer_ratio() method, but not strings.

在 3.14 版被加入.

limit_denominator(max_denominator=1000000)

Finds and returns the closest Fraction to self that has denominator at most max_denominator. This method is useful for finding rational approximations to a given floating-point number:

>>> from fractions import Fraction
>>> Fraction('3.1415926535897932').limit_denominator(1000)
Fraction(355, 113)

or for recovering a rational number that's represented as a float:

>>> from math import pi, cos
>>> Fraction(cos(pi/3))
Fraction(4503599627370497, 9007199254740992)
>>> Fraction(cos(pi/3)).limit_denominator()
Fraction(1, 2)
>>> Fraction(1.1).limit_denominator()
Fraction(11, 10)

__floor__()

Returns the greatest int <= self. This method can also be accessed through the math.floor() function:

>>> from math import floor
>>> floor(Fraction(355, 113))
3

__ceil__()

Returns the least int >= self. This method can also be accessed through the math.ceil() function.

__round__()

__round__(ndigits)

The first version returns the nearest int to self, rounding half to even. The second version rounds self to the nearest multiple of Fraction(1, 10**ndigits) (logically, if ndigits is negative), again rounding half toward even. This method can also be accessed through the round() function.

__format__(format_spec, /)

Provides support for formatting of Fraction instances via the str.format() method, the format() built-in function, or Formatted string literals.

If the format_spec format specification string does not end with one of the presentation types 'e', 'E', 'f', 'F', 'g', 'G' or '%' then formatting follows the general rules for fill, alignment, sign handling, minimum width, and grouping as described in the format specification mini-language. The "alternate form" flag '#' is supported: if present, it forces the output string to always include an explicit denominator, even when the value being formatted is an exact integer. The zero-fill flag '0' is not supported.

If the format_spec format specification string ends with one of the presentation types 'e', 'E', 'f', 'F', 'g', 'G' or '%' then formatting follows the rules outlined for the float type in the 格式規格 (Format Specification) 迷你語言 section.

Here are some examples:

>>> from fractions import Fraction
>>> format(Fraction(103993, 33102), '_')
'103_993/33_102'
>>> format(Fraction(1, 7), '.^+10')
'...+1/7...'
>>> format(Fraction(3, 1), '')
'3'
>>> format(Fraction(3, 1), '#')
'3/1'
>>> format(Fraction(1, 7), '.40g')
'0.1428571428571428571428571428571428571429'
>>> format(Fraction('1234567.855'), '_.2f')
'1_234_567.86'
>>> f"{Fraction(355, 113):*>20.6e}"
'********3.141593e+00'
>>> old_price, new_price = 499, 672
>>> "{:.2%} price increase".format(Fraction(new_price, old_price) - 1)
'34.67% price increase'

也參考

numbers 模組

The abstract base classes making up the numeric tower.

random --- 產生偽隨機數

原始碼：Lib/random.py [https://github.com/python/cpython/tree/3.14/Lib/random.py]

本章中所提及的 module（模組）用來實現各種分佈的虛擬隨機數產生器。

對於整數，可以從範圍中進行均勻選擇。對於序列，有一個隨機元素的均勻選擇，一個用來原地 (in-place) 產生隨機排列清單的函式，以及一個用來隨機取樣不重置的函式。

在實數線上，有一些函式用於處理均勻分佈、常態分佈（高斯分佈）、對數常態分佈、負指數分佈、gamma 分佈和 Beta 分佈。對於產生角度分佈，可以使用馮·米塞斯分佈 (von Mises distribution)。

幾乎所有 module 函式都相依於基本函式 random()，此函式在半開放範圍 0.0 <= X < 1.0 內均勻地產生一個隨機 float（浮點數）。Python 使用 Mersenne Twister（梅森旋轉演算法）作為核心的產生器，它產生 53 位元精度 float，其週期為 2**19937-1，透過 C 語言進行底層的實作既快速又支援執行緒安全 (threadsafe)。Mersenne Twister 是現存最廣泛被驗證的隨機數產生器之一，但是基於完全確定性，它並不適合所有目的，並且完全不適合加密目的。

該 module 提供的函式實際上是 random.Random class（類別）中一個隱藏實例的綁定方法 (bound method)。你可以實例化自己的 Random 實例，以得到不共享狀態的產生器。

如果你想使用你自己設計的基本產生器，Random 也可以進行子類別化 (subclass)。有關詳細資訊，請參考該類別的文件。

random module 也提供了 SystemRandom class，使用系統函式 os.urandom() 從作業系統提供的來源產生隨機數。

警告

本章所提及的虛擬隨機數產生器不應該使用於安全目的。有關安全性或加密用途，請參考 secrets module。

也參考

M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-dimensionally equidistributed uniform pseudorandom number generator", ACM Transactions on Modeling and Computer Simulation Vol. 8, No. 1, January pp.3--30 1998.

進位互補乘法 (Complementary-Multiply-with-Carry) 用法 [https://code.activestate.com/recipes/576707-long-period-random-number-generator/]，可作為隨機數產生器的一個可相容替代方案，具有較長的週期和相對簡單的更新操作。

備註

全域隨機數產生器和 Random 的實例是執行緒安全的。然而，在自由執行緒構建中，對全域產生器或同一 Random 實例的並行呼叫可能會遇到爭用和性能不佳。請考慮改為每個執行緒使用單獨的 Random 實例。

簿記函式 (bookkeeping functions)

random.seed(a=None, version=2)

初始化隨機數產生器。

如果 a 被省略或為 None，則使用目前系統時間。如果隨機來源由作業系統提供，則使用它們而不是系統時間（有關可用性的詳細資訊，請參考 os.urandom() 函式）。

如果 a 為 int（整數），則直接使用其絕對值。

如使用版本 2（預設值），str、bytes 或 bytearray 物件將轉換為 int，並使用其所有位元。

若使用版本 1（為復現於舊版本 Python 中產生隨機序列而提供），str 和 bytes 的演算法會產生範圍更窄的種子 (seed)。

在 3.2 版的變更: 移至版本 2 方案，該方案使用字串種子中的所有位元。

在 3.11 版的變更: seed 必須是以下型別之一：None、int、float、str、bytes、bytearray。

random.getstate()

回傳一個物件，捕獲產生器的目前內部狀態。此物件可以傳遞給 setstate() 以恢復狀態。

random.setstate(state)

state 應該要從之前對 getstate() 的呼叫中獲得，並且以 setstate() 將產生器的內部狀態恢復到呼叫 getstate() 時的狀態。

回傳位元組的函式

random.randbytes(n)

產生 n 個隨機位元組。

此方法不應使用於產生安全性權杖 (Token)。請改用 secrets.token_bytes()。

在 3.9 版被加入.

回傳整數的函式

random.randrange(stop)

random.randrange(start, stop[, step])

傳回從 range(start, stop, step) 中隨機選擇的元素。

這大致相當於 choice(range(start, stop, step))，但支援任意大的範圍，並針對常見情況進行了最佳化。

位置引數模式與 range() 函式相符。

不應使用關鍵字引數，因為它們可能會以意想不到的方式被直譯。例如 randrange(start=100) 會被直譯為 randrange(0, 100, 1)。

在 3.2 版的變更: randrange() 在產生均勻分佈的值方面更為複雜。以前，它使用像 int(random()*n) 這樣的樣式，這可能會產生稍微不均勻的分佈。

在 3.12 版的變更: 已經不再支援非整數類型到等效整數的自動轉換。像是 randrange(10.0) 和 randrange(Fraction(10, 1)) 的呼叫將會引發 TypeError。

random.randint(a, b)

回傳一個隨機整數 N，使得 a <= N <= b。為 randrange(a, b+1) 的別名。

random.getrandbits(k)

回傳一個具有 k 個隨機位元的非負 Python 整數。此方法會隨 Mersenne Twister 產生器一起提供，一些其他的產生器也可能將其作為 API 的可選部分。如果可用，getrandbits() 使 randrange() 能夠處理任意大的範圍。

在 3.9 版的變更: 此方法現在接受 k 為零。

回傳序列的函式

random.choice(seq)

從非空序列 seq 回傳一個隨機元素。如果 seq 為空，則引發 IndexError。

random.choices(population, weights=None, *, cum_weights=None, k=1)

回傳從 population 中重置取樣出的一個大小為 k 的元素 list。如果 population 為空，則引發 IndexError。

如果指定了 weights 序列，則根據相對權重進行選擇。另外，如果給定 cum_weights 序列，則根據累積權重進行選擇（可能使用 itertools.accumulate() 計算）。例如，相對權重 [10, 5, 30, 5] 等同於累積權重 [10, 15, 45, 50]。在內部，相對權重在進行選擇之前會轉換為累積權重，因此提供累積權重可以節省工作。

如果既未指定 weights 也未指定 cum_weights，則以相等的機率進行選擇。如果提供了加權序列，則該序列的長度必須與 population 序列的長度相同。它是一個 TypeError 來指定 weights 和 cum_weights。

weights 或 cum_weights 可以使用任何與 random() 所回傳的 float 值（包括整數、float 和分數，但不包括小數）交互操作 (interoperates) 的數值類型。權重假定為非負數和有限的。如果所有權重均為零，則引發 ValueError。

對於給定的種子，具有相等權重的 choices() 函式通常產生與重複呼叫 choice() 不同的序列。choices() 使用的演算法使用浮點運算來實現內部一致性和速度。choice() 使用的演算法預設為整數運算和重複選擇，以避免捨入誤差產生的小偏差。

在 3.6 版被加入.

在 3.9 版的變更: 如果所有權重均為零，則引發 ValueError。

random.shuffle(x)

將序列 x 原地 (in place) 隨機打亂位置。

要打亂一個不可變的序列並回傳一個新的被打亂的 list（串列），請使用 sample(x, k=len(x))。

請注意，即使對於較小的 len(x)，x 的置換總數也會快速成長到大於大多數隨機數產生器的週期。這意味著長序列的大多數置換永遠無法產生。例如，長度為 2080 的序列是 Mersenne Twister 隨機數產生器週期內可以容納的最大序列。

在 3.11 版的變更: 移除可選參數 random。

random.sample(population, k, *, counts=None)

回傳從母體序列中選擇出的一個包含獨特元素、長度為 k 的 list。用於不重置的隨機取樣。

回傳包含母體元素的新清單，同時保持原始母體不變。產生的清單按選擇順序排列，因此所有子切片也會是有效的隨機樣本。這允許抽獎獲獎者（樣本）分為大獎和第二名獲獎者（子切片）。

母體成員不必是 hashable 或唯一的。如果母體包含重複項，則每次出現都是樣本中可能出現的一個選擇。

可以一次指定一個重複元素，也可以使用可選的僅關鍵字 counts 參數指定重複元素。例如 sample(['red', 'blue'], counts=[4, 2], k=5) 等同於 sample(['red', 'red', 'red', 'red', 'blue', 'blue'], k=5)。

若要從整數範圍中選擇範例，請使用 range() 物件作為引數。這對於從大型母體中取樣特別快速且節省空間：sample(range(10000000), k=60)。

如果樣本大小大於母體大小，ValueError 會被引發。

在 3.9 版的變更: 新增 counts 參數。

在 3.11 版的變更: population 必須是一個序列。不再支援將 set 自動轉換為 list。

離散分布

以下函式產生離散分佈。

random.binomialvariate(n=1, p=0.5)

二項分佈 (Binomial distribution) [https://mathworld.wolfram.com/BinomialDistribution.html]。回傳 n 個獨立試驗的成功次數，每個試驗的成功機率為 p：

數學上等價於：

sum(random() < p for i in range(n))

試驗次數 n 應為非負整數。成功的機率 p 應在 0.0 <= p <= 1.0 之間。結果是 0 <= X <= n 範圍內的整數。

在 3.12 版被加入.

實數分布

以下函式產生特定的實數分佈。函式參數以分佈方程中的對應變數命名，如常見的數學實踐所示；這些方程式中的大多數都可以在任意統計文本中找到。

random.random()

回傳範圍 0.0 <= X < 1.0 中的下一個隨機浮點數

random.uniform(a, b)

回傳一個隨機浮點數 N，當 a <= b 時確保 N 為 a <= N <= b 、b < a 時確保 N 為 b <= N <= a。

終點值 b 可能包含在範圍內，也可能不包含在範圍內，取決於運算式 a + (b-a) * random() 中的浮點捨入。

random.triangular(low, high, mode)

回傳一個隨機浮點數 N，使得 low <= N <= high，並在這些邊界之間具有指定的 mode。low 和 high 邊界預設為零和一。mode 引數預設為邊界之間的中點，從而給出對稱分佈。

random.betavariate(alpha, beta)

Beta（貝它）分布。參數的條件為 alpha > 0 和 beta > 0。回傳值的範圍介於 0 和 1 之間。

random.expovariate(lambd=1.0)

指數分佈。lambd 為 1.0 除以所需的平均數。它應該不為零。（該參數將被稱為 "lambda"，但這是 Python 中的保留字）如果 lambd 為正，則回傳值的範圍從 0 到正無窮大；如果 lambd 為負，則回傳值的範圍從負無窮大到 0。

在 3.12 版的變更: 新增 lambd 的預設值。

random.gammavariate(alpha, beta)

Gamma（伽瑪）分佈。（不是 Gamma 函式！）。形狀 (shape) 和比例 (scale) 參數 alpha 和 beta 必須具有正值。（根據呼叫習慣不同，部分來源會將 'beta' 定義為比例的倒數）。

Probability distribution function（機率密度函式）是：

          x ** (alpha - 1) * math.exp(-x / beta)
pdf(x) =  --------------------------------------
            math.gamma(alpha) * beta ** alpha

random.gauss(mu=0.0, sigma=1.0)

常態分佈，也稱為高斯分佈。mu 是平均數，sigma 是標準差。這比下面定義的 normalvariate() 函式快一點。

多執行緒須注意：當兩個執行緒同時呼叫此函式時，它們可能會收到相同的傳回值。這可以透過三種方式避免。1）讓每個執行緒使用隨機數產生器的不同實例。2）在所有呼叫周圍加鎖。3）使用較慢但執行緒安全的 normalvariate() 函式代替。

在 3.11 版的變更: mu 和 sigma 現在有預設引數。

random.lognormvariate(mu, sigma)

對數常態分佈。如果你取此分佈的自然對數，你將獲得一個具有平均數 mu 和標準差 sigma 的常態分佈。mu 可以為任何值，並且 sigma 必須大於零。

random.normalvariate(mu=0.0, sigma=1.0)

常態分佈。mu 是平均數，sigma 是標準差。

在 3.11 版的變更: mu 和 sigma 現在有預設引數。

random.vonmisesvariate(mu, kappa)

mu 是平均角度，以 0 到 2*pi 之間的弧度表示，kappa 是濃度參數，必須大於或等於零。如果 kappa 等於零，則此分佈在 0 到 2*pi 的範圍內將減小為均勻的隨機角度。

random.paretovariate(alpha)

Pareto distribution（柏拉圖分佈）。alpha 是形狀參數。

random.weibullvariate(alpha, beta)

Weibull distribution（韋伯分佈）。alpha 是比例參數，beta 是形狀參數。

替代產生器

class random.Random([seed])

實現 random 模組使用的預設偽隨機數產生器的 class。

在 3.11 版的變更: 過去 seed 可以是任何可雜湊物件，但現在必須是以下類型之一：None、int、float、str、bytes、bytearray。

如果 Random 的子類別希望使用不同的基礎產生器，則應該覆寫以下方法：

seed(a=None, version=2)

在子類別中覆寫此方法以自訂 Random 實例的 seed() 行為。

getstate()

在子類別中覆寫此方法以自訂 Random 實例的 getstate() 行為。

setstate(state)

在子類別中覆寫此方法以自訂 Random 實例的 setstate() 行為。

random()

在子類別中覆寫此方法以自訂 Random 實例的 random() 行為。

或者，自訂產生器子類別還可以提供以下方法：

getrandbits(k)

在子類別中覆寫此方法以自訂 Random 實例的 getrandbits() 行為。

randbytes(n)

在子類別中覆寫此方法以自訂 Random 實例的 randbytes() 行為。

class random.SystemRandom([seed])

使用 os.urandom() 函式從作業系統提供的來源產生隨機數的 Class。並非在所有系統上都可用。不依賴於軟體狀態，並且序列不可復現。因此 seed() 方法沒有效果且被忽略。如果呼叫 getstate() 和 setstate() 方法會引發 NotImplementedError。

關於 Reproducibility（復現性）的注意事項

有時，能夠重現偽隨機數產生器給出的序列很有用。只要多執行緒未運行，透過重複使用種子值，同一序列就應該可以被復現。

大多數隨機 module 的演算法和 seed 設定函式在 Python 版本中可能會發生變化，但可以保證兩個方面不會改變：

如果增加了新的 seed 設定函式，則將提供向後相容的播種器 (seeder)。

當相容的播種器被賦予相同的種子時，產生器的 random() 方法將持續產生相同的序列。

範例

基礎範例：

>>> random()                          # 隨機浮點數：0.0 <= x < 1.0
0.37444887175646646

>>> uniform(2.5, 10.0)                # 隨機浮點數：2.5 <= x <= 10.0
3.1800146073117523

>>> expovariate(1 / 5)                # 到達間隔平均為 5 秒
5.148957571865031

>>> randrange(10)                     # 0 到 9（含）的整數
7\n

>>> randrange(0, 101, 2)              # 0 到 100（含）的偶數整數
26\n

>>> choice(['win', 'lose', 'draw'])   # 從序列中隨機選取單一元素
'draw'

>>> deck = 'ace two three four'.split()
>>> shuffle(deck)                     # 打亂串列
>>> deck
['four', 'two', 'ace', 'three']

>>> sample([10, 20, 30, 40, 50], k=4) # 四個無重置的樣本
[40, 10, 50, 30]

模擬：

>>> # 六次輪盤旋轉（有重置的加權抽樣）
>>> choices(['red', 'black', 'green'], [18, 18, 2], k=6)
['red', 'green', 'black', 'black', 'red', 'black']

>>> # 從一副 52 張撲克牌中無重置發 20 張牌
>>> # 並確定具有十點值的牌的比例：十、傑克、王后或國王
>>> deal = sample(['tens', 'low cards'], counts=[16, 36], k=20)
>>> deal.count('tens') / 20
0.15

>>> # 估計從 7 次旋轉中得到 5 次或更多正面的概率
>>> # 使用一枚 60% 概率為正面的偏幣
>>> sum(binomialvariate(n=7, p=0.6) >= 5 for i in range(10_000)) / 10_000
0.4169

>>> # 計算 5 個樣本的中位數位於中間兩個四分位數的概率
>>> def trial():
...     return 2_500 <= sorted(choices(range(10_000), k=5))[2] < 7_500
...
>>> sum(trial() for i in range(10_000)) / 10_000
0.7958

統計 bootstrapping（自助法） [https://en.wikipedia.org/wiki/Bootstrapping_(statistics)]的範例，使用有重置的重新取樣來估計樣本平均數的信賴區間：

# https://www.thoughtco.com/example-of-bootstrapping-3126155
from statistics import fmean as mean
from random import choices

data = [41, 50, 29, 37, 81, 30, 73, 63, 20, 35, 68, 22, 60, 31, 95]
means = sorted(mean(choices(data, k=len(data))) for i in range(100))
print(f'The sample mean of {mean(data):.1f} has a 90% confidence '
      f'interval from {means[5]:.1f} to {means[94]:.1f}')

重新取樣排列測試 [https://en.wikipedia.org/wiki/Resampling_(statistics)#Permutation_tests]的範例，來確定觀察到的藥物與安慰劑之間差異的統計學意義或 p 值 [https://en.wikipedia.org/wiki/P-value]：

# 範例來自 Dennis Shasha 和 Manda Wilson 的 "Statistics is Easy"
from statistics import fmean as mean
from random import shuffle

drug = [54, 73, 53, 70, 73, 68, 52, 65, 65]
placebo = [54, 51, 58, 44, 55, 52, 42, 47, 58, 46]
observed_diff = mean(drug) - mean(placebo)

n = 10_000
count = 0
combined = drug + placebo
for i in range(n):
    shuffle(combined)
    new_diff = mean(combined[:len(drug)]) - mean(combined[len(drug):])
    count += (new_diff >= observed_diff)

print(f'{n} 次標籤重新洗牌僅產生 {count} 個差異實例')
print(f'至少與觀察到的差異 {observed_diff:.1f} 一樣極端。')
print(f'單邊 p 值 {count / n:.4f} 使我們拒絕無效假設')
print(f'即藥物與安慰劑之間沒有差異。')

模擬多伺服器佇列 (queue) 的到達時間與服務交付：

from heapq import heapify, heapreplace
from random import expovariate, gauss
from statistics import mean, quantiles

average_arrival_interval = 5.6
average_service_time = 15.0
stdev_service_time = 3.5
num_servers = 3

waits = []
arrival_time = 0.0
servers = [0.0] * num_servers  # 每個伺服器可用的時間
heapify(servers)
for i in range(1_000_000):
    arrival_time += expovariate(1.0 / average_arrival_interval)
    next_server_available = servers[0]
    wait = max(0.0, next_server_available - arrival_time)
    waits.append(wait)
    service_duration = max(0.0, gauss(average_service_time, stdev_service_time))
    service_completed = arrival_time + wait + service_duration
    heapreplace(servers, service_completed)

print(f'平均等待時間：{mean(waits):.1f}   最大等待時間：{max(waits):.1f}')
print('四分位數：', [round(q, 1) for q in quantiles(waits)])

也參考

Statistics for Hackers [https://www.youtube.com/watch?v=Iq9DzN6mvYA] 是由 Jake Vanderplas [https://us.pycon.org/2016/speaker/profile/295/] 製作的教學影片，僅使用幾個基本概念（包括模擬、取樣、洗牌、交叉驗證）進行統計分析。

Economics Simulation [https://nbviewer.org/url/norvig.com/ipython/Economics.ipynb]是由 Peter Norvig [https://norvig.com/bio.html] 對市場進行的模擬，顯示了該模組提供的許多工具和分佈（高斯、均勻、樣本、 beta 變數、選擇，三角形、隨機數）的有效使用。

機率的具體介紹（使用Python） [https://nbviewer.org/url/norvig.com/ipython/Probability.ipynb]為 Peter Norvig [https://norvig.com/bio.html] 的教學課程，涵蓋了機率理論的基礎知識與如何模擬以及使用 Python 執行數據分析。

使用方案

這些使用方案展示了如何有效地從 itertools 模組的組合疊代器 (combinatoric iterators) 中進行隨機選擇：

import random

def random_product(*iterables, repeat=1):
    "Random selection from itertools.product(*iterables, repeat=repeat)"
    pools = tuple(map(tuple, iterables)) * repeat
    return tuple(map(random.choice, pools))

def random_permutation(iterable, r=None):
    "Random selection from itertools.permutations(iterable, r)"
    pool = tuple(iterable)
    r = len(pool) if r is None else r
    return tuple(random.sample(pool, r))

def random_combination(iterable, r):
    "Random selection from itertools.combinations(iterable, r)"
    pool = tuple(iterable)
    n = len(pool)
    indices = sorted(random.sample(range(n), r))
    return tuple(pool[i] for i in indices)

def random_combination_with_replacement(iterable, r):
    "Choose r elements with replacement.  Order the result to match the iterable."
    # Result will be in set(itertools.combinations_with_replacement(iterable, r)).
    pool = tuple(iterable)
    n = len(pool)
    indices = sorted(random.choices(range(n), k=r))
    return tuple(pool[i] for i in indices)

def random_derangement(iterable):
    "Choose a permutation where no element stays in its original position."
    seq = tuple(iterable)
    if len(seq) < 2:
        if not seq:
            return ()
        raise IndexError('No derangments to choose from')
    perm = list(range(len(seq)))
    start = tuple(perm)
    while True:
        random.shuffle(perm)
        if all(p != q for p, q in zip(start, perm)):
            return tuple([seq[i] for i in perm])

預設的 random() 回傳 0.0 ≤ x < 1.0 範圍內 2⁻⁵³ 的倍數。所有數字都是均勻分佈的，並且可以完全表示為 Python float。但是，該間隔中的許多其他可表示的 float 不是可能的選擇。 例如 0.05954861408025609 不是 2⁻⁵³ 的整數倍。

以下範例採用不同的方法。間隔中的所有 float 都是可能的選擇。尾數來自 2⁵² ≤ 尾數 < 2⁵³ 範圍內的整數均勻分佈。指數來自幾何分佈，其中小於 -53 的指數的出現頻率是下一個較大指數的一半。

from random import Random
from math import ldexp

class FullRandom(Random):

    def random(self):
        mantissa = 0x10_0000_0000_0000 | self.getrandbits(52)
        exponent = -53
        x = 0
        while not x:
            x = self.getrandbits(32)
            exponent += x.bit_length() - 32
        return ldexp(mantissa, exponent)

Class 中的所有實數分佈都將使用新方法：

>>> fr = FullRandom()
>>> fr.random()
0.05954861408025609
>>> fr.expovariate(0.25)
8.87925541791544

該範例在概念上等效於一種演算法，該演算法從 0.0 ≤ x < 1.0 範圍內 2⁻¹⁰⁷⁴ 的所有倍數中進行選擇。這些數字都是均勻分佈的，但大多數必須向下捨入到最接近的可表示的 Python float。（2⁻¹⁰⁷⁴ 是最小為正的非正規化 float，等於 math.ulp(0.0)）

也參考

產生偽隨機浮點值 [https://allendowney.com/research/rand/downey07randfloat.pdf] Allen B. Downey 的一篇論文描述了產生比通常由 random() 產生的 float 更 fine-grained（細粒的）的方法。

命令列用法

在 3.13 版被加入.

random 模組可以從命令列執行。

python -m random [-h] [-c CHOICE [CHOICE ...] | -i N | -f N] [input ...]

接受以下選項：

-h, --help

顯示幫助訊息並退出。

-c CHOICE [CHOICE ...]

--choice CHOICE [CHOICE ...]

列印一個隨機選擇，使用 choice()。

-i <N>

--integer <N>

列印 1 到 N（含）之間的隨機整數，使用 randint()。

-f <N>

--float <N>

列印 0 到 N（含）之間的隨機浮點數，使用 uniform()。

如果未給定選項，則輸出取決於輸入：

字串或多個：與 --choice 相同。

整數：與 --integer 相同。

浮點數：與 --float 相同。

命令列範例

以下是 random 命令列介面的一些範例：

$ # 隨機選擇一個
$ python -m random egg bacon sausage spam "Lobster Thermidor aux crevettes with a Mornay sauce"
Lobster Thermidor aux crevettes with a Mornay sauce

$ # 隨機整數
$ python -m random 6
6

$ # 隨機浮點數
$ python -m random 1.8
1.7080016272295635

$ # 使用明確的引數
$ python  -m random --choice egg bacon sausage spam "Lobster Thermidor aux crevettes with a Mornay sauce"
egg

$ python -m random --integer 6
3

$ python -m random --float 1.8
1.5666339105010318

$ python -m random --integer 6
5

$ python -m random --float 6
3.1942323316565915

statistics --- 數學統計函式

在 3.4 版被加入.

原始碼：Lib/statistics.py [https://github.com/python/cpython/tree/3.14/Lib/statistics.py]

這個模組提供計算數值 (Real-valued) 資料的數學統計函式。

這個模組並非旨在與 NumPy [https://numpy.org]、SciPy [https://scipy.org/] 等第三方函式庫，或者像 Minitab、SAS 和 Matlab 等專門設計給專業統計學家的高階統計軟體互相競爭。此模組的目標在於繪圖和科學計算。

除非特別註明，這些函數支援 int、float、Decimal 以及 Fraction。目前不支援其他型別（無論是否為數值型別）。含有混合型別的資料的集合亦是尚未定義，且取決於該型別的實作。若你的輸入資料含有混合型別，你可以考慮使用 map() 來確保結果是一致的，例如：map(float, input_data)。

有些資料集使用 NaN （非數）來表示缺漏的資料。由於 NaN 具有特殊的比較語義，在排序資料或是統計出現次數的統計函數中，會引發意料之外或是未定義的行為。受影響的函數包含 median()、median_low()、 median_high()、 median_grouped()、 mode()、 multimode() 以及 quantiles()。在呼叫這些函數之前，應該先移除 NaN 值：

>>> from statistics import median
>>> from math import isnan
>>> from itertools import filterfalse

>>> data = [20.7, float('NaN'),19.2, 18.3, float('NaN'), 14.4]
>>> sorted(data)  # This has surprising behavior
[20.7, nan, 14.4, 18.3, 19.2, nan]
>>> median(data)  # This result is unexpected
16.35

>>> sum(map(isnan, data))    # Number of missing values
2
>>> clean = list(filterfalse(isnan, data))  # Strip NaN values
>>> clean
[20.7, 19.2, 18.3, 14.4]
>>> sorted(clean)  # Sorting now works as expected
[14.4, 18.3, 19.2, 20.7]
>>> median(clean)       # This result is now well defined
18.75

平均值與中央位置量數

這些函式計算來自一個母體或樣本的平均值或代表值。

mean()

資料的算術平均數（平均值）。

fmean()

快速浮點數算數平均數，可調整權重。

geometric_mean()

資料的幾何平均數。

harmonic_mean()

資料的調和平均數。

kde()

Estimate the probability density distribution of the data.

kde_random()

Random sampling from the PDF generated by kde().

median()

資料的中位數（中間值）。

median_low()

資料中較小的中位數。

median_high()

資料中較大的中位數。

median_grouped()

分組資料的中位數（第 50 百分位數）。

mode()

離散 (discrete) 或名目 (nomial) 資料中的眾數（出現次數最多次的值），只回傳一個。

multimode()

離散或名目資料中的眾數（出現次數最多次的值）組成的 list。

quantiles()

將資料分成數個具有相等機率的區間，即分位數 (quantile)。

離度 (spread) 的測量

這些函式計算母體或樣本偏離平均值的程度。

pstdev()

資料的母體標準差。

pvariance()

資料的母體變異數。

stdev()

資料的樣本標準差。

variance()

資料的樣本變異數。

兩個輸入之間的關係統計

這些函式計算兩個輸入之間的關係統計數據。

covariance()

兩變數的樣本共變異數。

correlation()

Pearson 與 Spearman 相關係數 (correlation coefficient)。

linear_regression()

簡單線性迴歸的斜率和截距。

函式細節

註：這些函數並不要求輸入的資料必須排序過。為了閱讀方便，大部份的範例仍已排序過。

statistics.mean(data)

回傳 data 的樣本算數平均數，輸入可為一個 sequence 或者 iterable。

算數平均數為資料總和除以資料點的數目。他通常被稱為「平均值」，儘管它只是眾多不同的數學平均值之一。它是衡量資料集中位置的一種指標。

若 data 為空，則會引發 StatisticsError。

使用範例：

>>> mean([1, 2, 3, 4, 4])
2.8
>>> mean([-1.0, 2.5, 3.25, 5.75])
2.625

>>> from fractions import Fraction as F
>>> mean([F(3, 7), F(1, 21), F(5, 3), F(1, 3)])
Fraction(13, 21)

>>> from decimal import Decimal as D
>>> mean([D("0.5"), D("0.75"), D("0.625"), D("0.375")])
Decimal('0.5625')

備註

平均值強烈受到離群值 (outliers) [https://en.wikipedia.org/wiki/Outlier] 的影響，且不一定能當作這些資料點的典型範例。若要使用更穩健但效率較低的集中趨勢 (central tendency) [https://en.wikipedia.org/wiki/Central_tendency] 度量，請參考 median()。

樣本平均數提供了對真實母體平均數的不偏估計 (unbiased estimate)，所以從所有可能的樣本中取平均值時，mean(sample) 會收斂至整個母體的真實平均值。若 data 為整個母體而非單一樣本，則 mean(data) 等同於計算真實的母體平均數 μ。

statistics.fmean(data, weights=None)

將 data 轉換為浮點數並計算其算數平均數。

這個函式運算比 mean() 更快，並且它總是回傳一個 float。data 可以是一個 sequence 或者 iterable。如果輸入的資料為空，則引發 StatisticsError。

>>> fmean([3.5, 4.0, 5.25])
4.25

支援選擇性的加權。例如，一位教授以 20% 的比重計算小考分數，20% 的比重計算作業分數，30% 的比重計算期中考試分數，以及 30% 的比重計算期末考試分數：

>>> grades = [85, 92, 83, 91]
>>> weights = [0.20, 0.20, 0.30, 0.30]
>>> fmean(grades, weights)
87.6

如果有提供 weights，它必須與 data 長度相同，否則將引發 ValueError。

在 3.8 版被加入.

在 3.11 版的變更: 新增 weights 的支援。

statistics.geometric_mean(data)

將 data 轉換成浮點數並計算其幾何平均數。

幾何平均數使用數值的乘積（與之對照，算數平均數使用的是數值的和）來表示 data 的集中趨勢或典型值。

若輸入的資料集為空、包含零、包含負值，則引發 StatisticsError。data 可為 sequence 或者 iterable。

目前沒有特別為了精確結果而特別多下什麼工夫。（然而，未來或許會有。）

>>> round(geometric_mean([54, 24, 36]), 1)
36.0

在 3.8 版被加入.

statistics.harmonic_mean(data, weights=None)

回傳 data 的調和平均數。data 可為實數 (real-valued) sequence 或者 iterable。如果省略 weights 或者 weights 為 None，則假設各權重相等。

調和平均數是資料的倒數 (reciprocal) 經過 mean() 運算過後的倒數。例如，三個數 a，b 與 c 的調和平均數等於 3/(1/a + 1/b + 1/c)。若其中一個值為零，結果將為零。

調和平均數是一種平均數，是衡量資料中心位置的一種方法。它通常用於計算比率 (ratio) 或率 (rate) 的平均，例如速率（speed）。

假設一輛汽車以時速 40 公里的速率行駛 10 公里，然後再以時速 60 公里的速率行駛 10 公里，求汽車的平均速率？

>>> harmonic_mean([40, 60])
48.0

假設一輛汽車以時速 40 公里的速率行駛 5 公里，然後在交通順暢時，加速到時速 60 公里，以此速度行駛剩下的 30 公里。求汽車的平均速率？

>>> harmonic_mean([40, 60], weights=[5, 30])
56.0

若 data 為空、含有任何小於零的元素、或者加權總和不為正數，則引發 StatisticsError。

目前的演算法設計為，若在輸入當中遇到零，則會提前退出。這意味著後續的輸入並未進行有效性檢查。（這種行為在未來可能會改變。）

在 3.6 版被加入.

在 3.10 版的變更: 新增 weights 的支援。

statistics.kde(data, h, kernel='normal', *, cumulative=False)

Kernel Density Estimation (KDE) [https://www.itm-conferences.org/articles/itmconf/pdf/2018/08/itmconf_sam2018_00037.pdf]: Create a continuous probability density function or cumulative distribution function from discrete samples.

The basic idea is to smooth the data using a kernel function [https://en.wikipedia.org/wiki/Kernel_(statistics)]. to help draw inferences about a population from a sample.

The degree of smoothing is controlled by the scaling parameter h which is called the bandwidth. Smaller values emphasize local features while larger values give smoother results.

The kernel determines the relative weights of the sample data points. Generally, the choice of kernel shape does not matter as much as the more influential bandwidth smoothing parameter.

Kernels that give some weight to every sample point include normal (gauss), logistic, and sigmoid.

Kernels that only give weight to sample points within the bandwidth include rectangular (uniform), triangular, parabolic (epanechnikov), quartic (biweight), triweight, and cosine.

If cumulative is true, will return a cumulative distribution function.

若 data 為空，則引發 StatisticsError。

維基百科有一個範例 [https://en.wikipedia.org/wiki/Kernel_density_estimation#Example]，我們可以使用 kde() 來從一個小樣本生成並繪製估計的機率密度函數：

>>> sample = [-2.1, -1.3, -0.4, 1.9, 5.1, 6.2]
>>> f_hat = kde(sample, h=1.5)
>>> xarr = [i/100 for i in range(-750, 1100)]
>>> yarr = [f_hat(x) for x in xarr]

xarr 和 yarr 中的點可用於繪製 PDF 圖：

在 3.13 版被加入.

statistics.kde_random(data, h, kernel='normal', *, seed=None)

Return a function that makes a random selection from the estimated probability density function produced by kde(data, h, kernel).

Providing a seed allows reproducible selections. In the future, the values may change slightly as more accurate kernel inverse CDF estimates are implemented. The seed may be an integer, float, str, or bytes.

若 data 為空，則引發 StatisticsError。

Continuing the example for kde(), we can use kde_random() to generate new random selections from an estimated probability density function:

>>> data = [-2.1, -1.3, -0.4, 1.9, 5.1, 6.2]
>>> rand = kde_random(data, h=1.5, seed=8675309)
>>> new_selections = [rand() for i in range(10)]
>>> [round(x, 1) for x in new_selections]
[0.7, 6.2, 1.2, 6.9, 7.0, 1.8, 2.5, -0.5, -1.8, 5.6]

在 3.13 版被加入.

statistics.median(data)

使用常見的「中間兩數取平均」方法回傳數值資料的中位數 （中間值）。若 data 為空，則會引發 StatisticsError。data 可為一個 sequence 或者 iterable。

中位數是一種穩健的衡量資料中心位置的方法，較不易被離群值影響。當資料點數量為奇數時，會回傳中間的資料點：

>>> median([1, 3, 5])
3

當資料點數量為偶數時，中位數透過中間兩個值的平均數來插值計算：

>>> median([1, 3, 5, 7])
4.0

若你的資料為離散資料，並且你不介意中位數可能並非真實的資料點，那這函式適合你。

若你的資料為順序 (ordinal) 資料（支援排序操作）但並非數值型（不支援加法），可以考慮改用 median_low() 或是 median_high() 代替。

statistics.median_low(data)

回傳數值型資料的低中位數 (low median)。若 data 為空，則引發 StatisticsError。data 可為 sequence 或者 iterable。

低中位數一定會在原本的資料集當中。當資料點數量為奇數時，回傳中間值。當數量為偶數時，回傳兩個中間值當中較小的值。

>>> median_low([1, 3, 5])
3
>>> median_low([1, 3, 5, 7])
3

當你的資料為離散資料，且你希望中位數是實際的資料點而不是插值時，可以用低中位數。

statistics.median_high(data)

回傳數值型資料的高中位數 (high median)。若 data 為空，則引發 StatisticsError。data 可為 sequence 或者 iterable。

高中位數一定會在原本的資料集當中。當資料點數量為奇數時，回傳中間值。當數量為偶數時，回傳兩個中間值當中較大的值。

>>> median_high([1, 3, 5])
3
>>> median_high([1, 3, 5, 7])
5

當你的資料為離散資料，且你希望中位數是實際的資料點而不是插值時，可以用高中位數。

statistics.median_grouped(data, interval=1.0)

Estimates the median for numeric data that has been grouped or binned [https://en.wikipedia.org/wiki/Data_binning] around the midpoints of consecutive, fixed-width intervals.

The data can be any iterable of numeric data with each value being exactly the midpoint of a bin. At least one value must be present.

The interval is the width of each bin.

For example, demographic information may have been summarized into consecutive ten-year age groups with each group being represented by the 5-year midpoints of the intervals:

>>> from collections import Counter
>>> demographics = Counter({
...    25: 172,   # 20 to 30 years old
...    35: 484,   # 30 to 40 years old
...    45: 387,   # 40 to 50 years old
...    55:  22,   # 50 to 60 years old
...    65:   6,   # 60 to 70 years old
... })
...

The 50th percentile (median) is the 536th person out of the 1071 member cohort. That person is in the 30 to 40 year old age group.

The regular median() function would assume that everyone in the tricenarian age group was exactly 35 years old. A more tenable assumption is that the 484 members of that age group are evenly distributed between 30 and 40. For that, we use median_grouped():

>>> data = list(demographics.elements())
>>> median(data)
35
>>> round(median_grouped(data, interval=10), 1)
37.5

The caller is responsible for making sure the data points are separated by exact multiples of interval. This is essential for getting a correct result. The function does not check this precondition.

Inputs may be any numeric type that can be coerced to a float during the interpolation step.

statistics.mode(data)

回傳離散或名目 data 中出現次數最多次的值，只回傳一個。眾數（如果存在）是最典型的值，並用來衡量資料的中心位置。

若有多個出現次數相同的眾數，則回傳在 data 中最先出現的眾數。如果希望回傳其中最小或最大的眾數，可以使用 min(multimode(data)) 或 max(multimode(data))。如果輸入的 data 為空，則會引發 StatisticsError。

mode 假定為離散資料，並回傳單一的值。這也是一般學校教授的標準眾數定義：

>>> mode([1, 1, 2, 3, 3, 3, 3, 4])
3

眾數特別之處在於它是此套件中唯一也適用於名目（非數值型）資料的統計量：

>>> mode(["red", "blue", "blue", "red", "green", "red", "red"])
'red'

Only hashable inputs are supported. To handle type set, consider casting to frozenset. To handle type list, consider casting to tuple. For mixed or nested inputs, consider using this slower quadratic algorithm that only depends on equality tests: max(data, key=data.count).

在 3.8 版的變更: 現在，遇到資料中有多個眾數時，會回傳第一個遇到的眾數。在以前，當找到大於一個眾數時，會引發 StatisticsError。

statistics.multimode(data)

回傳一個 list，其組成為 data 中出現次數最多次的值，並按照它們在 data 中首次出現的順序排列。如果有多個眾數，將會回傳所有結果。若 data 為空，則回傳空的 list：

>>> multimode('aabbbbccddddeeffffgg')
['b', 'd', 'f']
>>> multimode('')
[]

在 3.8 版被加入.

statistics.pstdev(data, mu=None)

回傳母體標準差（即母體變異數的平方根）。有關引數以及其他細節，請參見 pvariance()。

>>> pstdev([1.5, 2.5, 2.5, 2.75, 3.25, 4.75])
0.986893273527251

statistics.pvariance(data, mu=None)

回傳 data 的母體變異數。data 可為非空實數 sequence 或者 iterable。變異數，或者以平均數為中心的二階動差，用於衡量資料的變異性（離度或分散程度）。變異數大表示資料分散，變異數小表示資料集中在平均數附近。

若有傳入選擇性的第二個引數 mu，該引數應該要是 data 的母體平均值 (population mean)。它也可以用於計算非以平均值為中心的第二動差。如果沒有傳入此引數或者引數為 None （預設值），則自動計算資料的算數平均數。

使用此函式來計算整個母體的變異數。如果要從樣本估算變異數，variance() 通常是較好的選擇。

若 data 為空，則引發 StatisticsError。

範例：

>>> data = [0.0, 0.25, 0.25, 1.25, 1.5, 1.75, 2.75, 3.25]
>>> pvariance(data)
1.25

如果已經計算出資料的平均值，你可以將其作為選擇性的第二個引數 mu 傳遞以避免重新計算：

>>> mu = mean(data)
>>> pvariance(data, mu)
1.25

支援小數 (decimal) 與分數 (fraction)：

>>> from decimal import Decimal as D
>>> pvariance([D("27.5"), D("30.25"), D("30.25"), D("34.5"), D("41.75")])
Decimal('24.815')

>>> from fractions import Fraction as F
>>> pvariance([F(1, 4), F(5, 4), F(1, 2)])
Fraction(13, 72)

備註

當在整個母體上呼叫此函式時，會回傳母體變異數 σ²。當在樣本上呼叫此函式時，會回傳有偏差的樣本變異數 s²，也就是具有 N 個自由度的變異數。

若你以某種方式知道真正的母體平均數 μ，你可以將一個已知的母體平均數作為第二個引數提供給此函式，用以計算樣本的變異數。只要資料點是母體的隨機樣本，結果將是母體變異數的不偏估計。

statistics.stdev(data, xbar=None)

回傳樣本標準差（即樣本變異數的平方根）。有關引數以及其他細節，請參見 variance()。

>>> stdev([1.5, 2.5, 2.5, 2.75, 3.25, 4.75])
1.0810874155219827

statistics.variance(data, xbar=None)

回傳 data 的樣本變異數。data 為兩個值以上的實數 iterable。變異數，或者以平均數為中心的二階動差，用於衡量資料的變異性（離度或分散程度）。變異數大表示資料分散，變異數小表示資料集中在平均數附近。

若有傳入選擇性的第二個引數 xbar，它應該是 data 的樣本平均值 (sample mean)。如果沒有傳入或者為 None （預設值），則自動計算資料的平均值。

當你的資料是來自母體的樣本時，請使用此函式。若要從整個母體計算變異數，請參見 pvariance()。

若 data 內少於兩個值，則引發 StatisticsError。

範例：

>>> data = [2.75, 1.75, 1.25, 0.25, 0.5, 1.25, 3.5]
>>> variance(data)
1.3720238095238095

如果已經計算出資料的樣本平均值，你可以將其作為選擇性的第二個引數 mu 傳遞以避免重新計算：

>>> m = mean(data)
>>> variance(data, m)
1.3720238095238095

此函式不會驗證你傳入的 xbar 是否為實際的平均數。傳入任意的 xbar 會導致無效或不可能的結果。

支援小數 (decimal) 與分數 (fraction)：

>>> from decimal import Decimal as D
>>> variance([D("27.5"), D("30.25"), D("30.25"), D("34.5"), D("41.75")])
Decimal('31.01875')

>>> from fractions import Fraction as F
>>> variance([F(1, 6), F(1, 2), F(5, 3)])
Fraction(67, 108)

備註

這是經過 Bessel 校正 (Bessel's correction) 後的樣本變異數 s² ，又稱為自由度為 N-1 的變異數。只要資料點具有代表性（例如：獨立且具有相同分布），結果應該會是對真實母體變異數的不偏估計。

若你剛好知道真正的母體平均數 μ，你應該將其作為 mu 參數傳入 pvariance() 函式來計算樣本變異數。

statistics.quantiles(data, *, n=4, method='exclusive')

將 data 分成 n 個具有相等機率的連續區間。回傳一個包含 n - 1 個用於切分各區間的分隔點的 list。

將 n 設為 4 以表示四分位數 (quartile) （預設值）。將 n 設置為 100 表示百分位數 (percentile)，這將給出 99 個分隔點將 data 分成 100 個大小相等的組。如果 n 不是至少為 1，則引發 StatisticsError。

data 可以是包含樣本資料的任何 iterable。為了取得有意義的結果，data 中的資料點數量應大於 n。如果連一個資料點都沒有，則引發 StatisticsError。

分隔點是從兩個最近的資料點線性內插值計算出來的。舉例來說，如果分隔點落在兩個樣本值 100 與 112 之間的距離三分之一處，則分隔點的值將為 104。

計算分位數的 method 可以根據 data 是否包含或排除來自母體的最小與最大可能的值而改變。

預設的 method 是 "exclusive"，用於從可能找到比樣本更極端的值的母體中抽樣的樣本資料。對於 m 個已排序的資料點，計算出低於 i-th 的部分為 i / (m + 1)。給定九個樣本資料，此方法將對資料排序且計算下列百分位數：10%、20%、30%、40%、50%、60%、70%、80%、90%。

若將 method 設為 "inclusive"，則用於描述母體或者已知包含母體中最極端值的樣本資料。在 data 中的最小值被視為第 0 百分位數，最大值為第 100 百分位數。對於 m 個已排序的資料點，計算出低於 i-th 的部分為 (i - 1) / (m - 1)。給定十一個個樣本資料，此方法將對資料排序且計算下列百分位數：0%、10%、20%、30%、40%、50%、60%、70%、80%、90%、100%。

# Decile cut points for empirically sampled data
>>> data = [105, 129, 87, 86, 111, 111, 89, 81, 108, 92, 110,
...         100, 75, 105, 103, 109, 76, 119, 99, 91, 103, 129,
...         106, 101, 84, 111, 74, 87, 86, 103, 103, 106, 86,
...         111, 75, 87, 102, 121, 111, 88, 89, 101, 106, 95,
...         103, 107, 101, 81, 109, 104]
>>> [round(q, 1) for q in quantiles(data, n=10)]
[81.0, 86.2, 89.0, 99.4, 102.5, 103.6, 106.0, 109.8, 111.0]

在 3.8 版被加入.

在 3.13 版的變更: No longer raises an exception for an input with only a single data point. This allows quantile estimates to be built up one sample point at a time becoming gradually more refined with each new data point.

statistics.covariance(x, y, /)

回傳兩輸入 x 與 y 的樣本共變異數 (sample covariance)。共變異數是衡量兩輸入的聯合變異性 (joint variability) 的指標。

兩輸入必須具有相同長度（至少兩個），否則會引發 StatisticsError。

範例：

>>> x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> y = [1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> covariance(x, y)
0.75
>>> z = [9, 8, 7, 6, 5, 4, 3, 2, 1]
>>> covariance(x, z)
-7.5
>>> covariance(z, x)
-7.5

在 3.10 版被加入.

statistics.correlation(x, y, /, *, method='linear')

回傳兩輸入的 Pearson 相關係數 (Pearson’s correlation coefficient) [https://en.wikipedia.org/wiki/Pearson_correlation_coefficient]。Pearson 相關係數 r 的值介於 -1 與 +1 之間。它衡量線性關係的強度與方向。

如果 method 為 "ranked"，則計算兩輸入的 Spearman 等級相關係數 (Spearman’s rank correlation coefficient) [https://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient]。資料將被取代為等級。平手的情況則取平均，令相同的值排名也相同。所得係數衡量單調關係 (monotonic relationship) 的強度。

Spearman 相關係數適用於順序型資料，或者不符合 Pearson 相關係數要求的線性比例關係的連續型 (continuous) 資料。

兩輸入必須具有相同長度（至少兩個），且不須為常數，否則會引發 StatisticsError。

以 Kepler 行星運動定律 [https://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion]為例：

>>> # Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and  Neptune
>>> orbital_period = [88, 225, 365, 687, 4331, 10_756, 30_687, 60_190]    # days
>>> dist_from_sun = [58, 108, 150, 228, 778, 1_400, 2_900, 4_500] # million km

>>> # Show that a perfect monotonic relationship exists
>>> correlation(orbital_period, dist_from_sun, method='ranked')
1.0

>>> # Observe that a linear relationship is imperfect
>>> round(correlation(orbital_period, dist_from_sun), 4)
0.9882

>>> # Demonstrate Kepler's third law: There is a linear correlation
>>> # between the square of the orbital period and the cube of the
>>> # distance from the sun.
>>> period_squared = [p * p for p in orbital_period]
>>> dist_cubed = [d * d * d for d in dist_from_sun]
>>> round(correlation(period_squared, dist_cubed), 4)
1.0

在 3.10 版被加入.

在 3.12 版的變更: 新增了對 Spearman 等級相關係數的支援。

statistics.linear_regression(x, y, /, *, proportional=False)

回傳使用普通最小平方法 (ordinary least square) 估計出的簡單線性迴歸 (simple linear regression) [https://en.wikipedia.org/wiki/Simple_linear_regression] 參數中的斜率 (slope) 與截距 (intercept)。簡單線性迴歸描述自變數 (independent variable) x 與應變數 (dependent variable) y 之間的關係，用以下的線性函式表示：

y = slope * x + intercept + noise

其中 slope 和 intercept 是被估計的迴歸參數，而 noise 表示由線性迴歸未解釋的資料變異性（它等於應變數的預測值與實際值之差）。

兩輸入必須具有相同長度（至少兩個），且自變數 x 不得為常數，否則會引發 StatisticsError。

舉例來說，我們可以使用 Monty Python 系列電影的上映日期 [https://en.wikipedia.org/wiki/Monty_Python#Films]來預測至 2019 年為止，假設他們保持固定的製作速度，應該會產生的 Monty Python 電影的累計數量。

>>> year = [1971, 1975, 1979, 1982, 1983]
>>> films_total = [1, 2, 3, 4, 5]
>>> slope, intercept = linear_regression(year, films_total)
>>> round(slope * 2019 + intercept)
16

若將 proportional 設為 True，則假設自變數 x 與應變數 y 是直接成比例的，資料座落在通過原點的一直線上。由於 intercept 始終為 0.0，因此線性函式可簡化如下：

y = slope * x + noise

繼續 correlation() 中的範例，我們看看基於主要行星的模型可以如何很好地預測矮行星的軌道距離：

>>> model = linear_regression(period_squared, dist_cubed, proportional=True)
>>> slope = model.slope

>>> # 矮行星：          冥王星、  鬩神星、  鳥神星、  妊神星、  穀神星
>>> orbital_periods = [90_560, 204_199, 111_845, 103_410, 1_680]  # 天數
>>> predicted_dist = [math.cbrt(slope * (p * p)) for p in orbital_periods]
>>> list(map(round, predicted_dist))
[5912, 10166, 6806, 6459, 414]

>>> [5_906, 10_152, 6_796, 6_450, 414]  # 以百萬公里為單位的實際距離
[5906, 10152, 6796, 6450, 414]

在 3.10 版被加入.

在 3.11 版的變更: 新增 proportional 的支援。

例外

定義了一個單一的例外：

exception statistics.StatisticsError

ValueError 的子類別，用於和統計相關的例外。

NormalDist 物件

NormalDist 是一種用於建立與操作隨機變數 (random variable) [http://www.stat.yale.edu/Courses/1997-98/101/ranvar.htm] 的常態分布的工具。它是一個將量測資料的平均數與標準差視為單一實體的類別。

常態分布源自於中央極限定理 (Central Limit Theorem) [https://en.wikipedia.org/wiki/Central_limit_theorem]，在統計學中有著廣泛的應用。

class statistics.NormalDist(mu=0.0, sigma=1.0)

此方法會回傳一個新 NormalDist 物件，其中 mu 代表算數平均數 [https://en.wikipedia.org/wiki/Arithmetic_mean]而 sigma 代表標準差 [https://en.wikipedia.org/wiki/Standard_deviation]。

若 sigma 為負值，則引發 StatisticsError。

mean

常態分布中的算數平均數 [https://en.wikipedia.org/wiki/Arithmetic_mean]唯讀屬性。

median

常態分布中的中位數 [https://en.wikipedia.org/wiki/Median]唯讀屬性。

mode

常態分布中的眾數 [https://en.wikipedia.org/wiki/Mode_(statistics)]唯讀屬性。

stdev

常態分布中的標準差 [https://en.wikipedia.org/wiki/Standard_deviation]唯讀屬性。

variance

常態分布中的變異數 [https://en.wikipedia.org/wiki/Variance]唯讀屬性。

classmethod from_samples(data)

利用 fmean() 與 stdev() 函式，估計 data 的 mu 與 sigma 參數，建立一個常態分布的實例。

data 可以是任何 iterable，並應包含可以轉換為 float 的值。若 data 沒有包含至少兩個以上的元素在內，則引發 StatisticsError，因為至少需要一個點來估計中央值且至少需要兩個點來估計分散情形。

samples(n, *, seed=None)

給定平均值與標準差，產生 n 個隨機樣本。回傳一個由 float 組成的 list。

若有給定 seed，則會建立一個以此為基礎的亂數產生器實例。這對於建立可重現的結果很有幫助，即使在多執行緒情境下也是如此。

在 3.13 版的變更.

Switched to a faster algorithm. To reproduce samples from previous versions, use random.seed() and random.gauss().

pdf(x)

利用機率密度函數 (probability density function, pdf) [https://en.wikipedia.org/wiki/Probability_density_function] 計算隨機變數 X 接近給定值 x 的相對概度 (relative likelihood)。數學上，它是比率 P(x <= X < x+dx) / dx 在 dx 趨近於零時的極限值。

相對概度是樣本出現在狹窄範圍的機率，除以該範圍的寬度（故稱為「密度」）計算而得。由於概度是相對於其它點，故其值可大於 1.0。

cdf(x)

利用累積分布函式 (cumulative distribution function, cdf) [https://en.wikipedia.org/wiki/Cumulative_distribution_function] 計算隨機變數 X 小於或等於 x 的機率。數學上，它記為 P(X <= x)。

inv_cdf(p)

計算反累計分布函式 (inverse cumulative distribution function)，也稱為分位數函式 (quantile function) [https://en.wikipedia.org/wiki/Quantile_function] 或者百分率點 (percent-point) [https://web.archive.org/web/20190203145224/https://www.statisticshowto.datasciencecentral.com/inverse-distribution-function/] 函式。數學上記為 x : P(X <= x) = p。

找出一個值 x，使得隨機變數 X 小於或等於該值的機率等於給定的機率 p。

overlap(other)

衡量兩常態分布之間的一致性。回傳一個介於 0.0 與 1.0 之間的值，表示兩機率密度函式的重疊區域 [https://www.rasch.org/rmt/rmt101r.htm]。

quantiles(n=4)

將常態分布分割成 n 個具有相等機率的連續區間。回傳一個 list，包含 (n-1) 個切割區間的分隔點。

將 n 設定為 4 表示四分位數（預設值）。將 n 設定為 10 表示十分位數。將 n 設定為 100 表示百分位數，這會產生 99 個分隔點，將常態分布切割成大小相等的群組。

zscore(x)

計算標準分數 (Standard Score) [https://www.statisticshowto.com/probability-and-statistics/z-score/]，用以描述在常態分布中，x 高出或低於平均數幾個標準差：(x - mean) / stdev。

在 3.9 版被加入.

NormalDist 的實例支援對常數的加法、減法、乘法與除法。這些操作用於平移與縮放。例如：

>>> temperature_february = NormalDist(5, 2.5)             # 攝氏
>>> temperature_february * (9/5) + 32                     # 華氏
NormalDist(mu=41.0, sigma=4.5)

不支援將常數除以 NormalDist 的實例，因為結果將不符合常態分布。

由於常態分布源自於自變數的加法效應 (additive effects)，因此可以將兩個獨立的常態分布隨機變數相加與相減 [https://en.wikipedia.org/wiki/Sum_of_normally_distributed_random_variables]，並且表示為 NormalDist 的實例。例如：

>>> birth_weights = NormalDist.from_samples([2.5, 3.1, 2.1, 2.4, 2.7, 3.5])
>>> drug_effects = NormalDist(0.4, 0.15)
>>> combined = birth_weights + drug_effects
>>> round(combined.mean, 1)
3.1
>>> round(combined.stdev, 1)
0.5

在 3.8 版被加入.

範例與錦囊妙計

經典機率問題

NormalDist 可以輕易地解決經典的機率問題。

例如，給定 SAT 測驗的歷史資料 [https://nces.ed.gov/programs/digest/d17/tables/dt17_226.40.asp]，顯示成績為平均 1060、標準差 195 的常態分布。我們要求出分數在 1100 與 1200 之間（四捨五入至最接近的整數）的學生的百分比：

>>> sat = NormalDist(1060, 195)
>>> fraction = sat.cdf(1200 + 0.5) - sat.cdf(1100 - 0.5)
>>> round(fraction * 100.0, 1)
18.4

找出 SAT 分數的四分位數 [https://en.wikipedia.org/wiki/Quartile]以及十分位數 [https://en.wikipedia.org/wiki/Decile]：

>>> list(map(round, sat.quantiles()))
[928, 1060, 1192]
>>> list(map(round, sat.quantiles(n=10)))
[810, 896, 958, 1011, 1060, 1109, 1162, 1224, 1310]

用於模擬的蒙地卡羅 (Monte Carlo) 輸入

欲估計一個不易透過解析方法求解的模型的分布，NormalDist 可以產生輸入樣本以進行蒙地卡羅模擬 [https://en.wikipedia.org/wiki/Monte_Carlo_method]：

>>> def model(x, y, z):
...     return (3*x + 7*x*y - 5*y) / (11 * z)
...
>>> n = 100_000
>>> X = NormalDist(10, 2.5).samples(n, seed=3652260728)
>>> Y = NormalDist(15, 1.75).samples(n, seed=4582495471)
>>> Z = NormalDist(50, 1.25).samples(n, seed=6582483453)
>>> quantiles(map(model, X, Y, Z))
[1.4591308524824727, 1.8035946855390597, 2.175091447274739]

近似二項分布

當樣本數量夠大，且試驗成功的機率接近 50%，可以使用常態分布來近似二項分布 (Binomial distributions) [https://mathworld.wolfram.com/BinomialDistribution.html]。

例如，一場有 750 位參加者的開源研討會中，有兩間可容納 500 人的會議室。一場是關於 Python 的講座，另一場則是關於 Ruby 的。在過去的會議中，有 65% 的參加者傾向參與 Python 講座。假設參與者的偏好沒有改變，那麼 Python 會議室未超過自身容量限制的機率是？

>>> n = 750             # Sample size
>>> p = 0.65            # Preference for Python
>>> q = 1.0 - p         # Preference for Ruby
>>> k = 500             # Room capacity

>>> # Approximation using the cumulative normal distribution
>>> from math import sqrt
>>> round(NormalDist(mu=n*p, sigma=sqrt(n*p*q)).cdf(k + 0.5), 4)
0.8402

>>> # Exact solution using the cumulative binomial distribution
>>> from math import comb, fsum
>>> round(fsum(comb(n, r) * p**r * q**(n-r) for r in range(k+1)), 4)
0.8402

>>> # Approximation using a simulation
>>> from random import seed, binomialvariate
>>> seed(8675309)
>>> mean(binomialvariate(n, p) <= k for i in range(10_000))
0.8406

單純貝氏分類器 (Naive bayesian classifier)

常態分布常在機器學習問題中出現。

維基百科有個 Naive Bayesian Classifier 的優良範例 [https://en.wikipedia.org/wiki/Naive_Bayes_classifier#Person_classification]。課題為從身高、體重與鞋子尺寸等符合常態分布的特徵量測值中判斷一個人的性別。

給定一組包含八個人的量測值的訓練資料集。假設這些量測值服從常態分布，我們可以利用 NormalDist 來總結資料：

>>> height_male = NormalDist.from_samples([6, 5.92, 5.58, 5.92])
>>> height_female = NormalDist.from_samples([5, 5.5, 5.42, 5.75])
>>> weight_male = NormalDist.from_samples([180, 190, 170, 165])
>>> weight_female = NormalDist.from_samples([100, 150, 130, 150])
>>> foot_size_male = NormalDist.from_samples([12, 11, 12, 10])
>>> foot_size_female = NormalDist.from_samples([6, 8, 7, 9])

接著，我們遇到一個新的人，他的特徵量測值已知，但性別未知：

>>> ht = 6.0        # height
>>> wt = 130        # weight
>>> fs = 8          # foot size

從可能為男性或女性的 50% 先驗機率 (prior probability) [https://en.wikipedia.org/wiki/Prior_probability] 為開端，我們將後驗機率 (posterior probability) 計算為先驗機率乘以給定性別下，各特徵量測值的概度乘積：

>>> prior_male = 0.5
>>> prior_female = 0.5
>>> posterior_male = (prior_male * height_male.pdf(ht) *
...                   weight_male.pdf(wt) * foot_size_male.pdf(fs))

>>> posterior_female = (prior_female * height_female.pdf(ht) *
...                     weight_female.pdf(wt) * foot_size_female.pdf(fs))

最終的預測結果將取決於最大的後驗機率。這被稱為最大後驗機率 (maximum a posteriori) [https://en.wikipedia.org/wiki/Maximum_a_posteriori_estimation] 或者 MAP：

>>> 'male' if posterior_male > posterior_female else 'female'
'female'

函式程式設計模組

本章節所描述的模組提供了支援函式程式設計風格的函式和類別，以及對可呼叫物件的一般操作。

本章包含下列的模組：

itertools --- 建立產生高效率迴圈之疊代器的函式

Itertool 函式

Itertools 應用技巧

functools --- 可呼叫物件上的高階函式與操作

partial 物件

operator --- 標準運算子替代函式

運算子與函式間的對映

原地 (in-place) 運算子

itertools --- 建立產生高效率迴圈之疊代器的函式

這個模組實作了許多 疊代器 (iterator) 構建塊 (building block)，其靈感來自 APL、Haskell 和 SML 的結構。每個構建塊都以適合 Python 的形式來重新設計。

這個模組標準化了快速且高效率利用記憶體的核心工具集，這些工具本身或組合使用都很有用。它們共同構成了一個「疊代器代數 (iterator algebra)」，使得在純 Python 中簡潔且高效地建構專用工具成為可能。

例如，SML 提供了一個造表工具：tabulate(f)，它產生一個序列 f(0), f(1), ...。在 Python 中，可以透過結合 map() 和 count() 組成 map(f, count()) 以達到同樣的效果。

無限疊代器：

疊代器

引數

結果

範例

count()

[start[, step]]

start, start+step, start+2*step, ...

count(10) → 10 11 12 13 14 ...

cycle()

p

p0, p1, ... plast, p0, p1, ...

cycle('ABCD') → A B C D A B C D ...

repeat()

elem [,n]

elem, elem, elem，... 重複無限次或 n 次

repeat(10, 3) → 10 10 10

在最短輸入序列 (shortest input sequence) 處終止的疊代器：

疊代器

引數

結果

範例

accumulate()

p [,func]

p0, p0+p1, p0+p1+p2, ...

accumulate([1,2,3,4,5]) → 1 3 6 10 15

batched()

p, n

(p0, p1, ..., p_n-1), ...

batched('ABCDEFG', n=3) → ABC DEF G

chain()

p, q, ...

p0, p1, ... plast, q0, q1, ...

chain('ABC', 'DEF') → A B C D E F

chain.from_iterable()

可疊代物件

p0, p1, ... plast, q0, q1, ...

chain.from_iterable(['ABC', 'DEF']) → A B C D E F

compress()

data, selectors

(d[0] if s[0]), (d[1] if s[1]), ...

compress('ABCDEF', [1,0,1,0,1,1]) → A C E F

dropwhile()

predicate, seq

seq[n], seq[n+1]，當 predicate 失敗時開始

dropwhile(lambda x: x<5, [1,4,6,3,8]) → 6 3 8

filterfalse()

predicate, seq

當 predicate(elem) 失敗時 seq 的元素

filterfalse(lambda x: x<5, [1,4,6,3,8]) → 6 8

groupby()

iterable[, key]

根據 key(v) 的值分組的子疊代器

groupby(['A','B','DEF'], len) → (1, A B) (3, DEF)

islice()

seq, [start,] stop [, step]

seq[start:stop:step] 的元素

islice('ABCDEFG', 2, None) → C D E F G

pairwise()

可疊代物件

(p[0], p[1]), (p[1], p[2])

pairwise('ABCDEFG') → AB BC CD DE EF FG

starmap()

func, seq

func(*seq[0]), func(*seq[1]), ...

starmap(pow, [(2,5), (3,2), (10,3)]) → 32 9 1000

takewhile()

predicate, seq

seq[0], seq[1]，直到 predicate 失敗

takewhile(lambda x: x<5, [1,4,6,3,8]) → 1 4

tee()

it, n

it1, it2, ... itn，將一個疊代器分成 n 個

tee('ABC', 2) → A B C, A B C

zip_longest()

p, q, ...

(p[0], q[0]), (p[1], q[1]), ...

zip_longest('ABCD', 'xy', fillvalue='-') → Ax By C- D-

組合疊代器：

疊代器

引數

結果

product()

p, q, ... [repeat=1]

笛卡爾乘積 (cartesian product)，相當於巢狀的 for 迴圈

permutations()

p[, r]

長度為 r 的元組，所有可能的定序，無重複元素

combinations()

p, r

長度為 r 的元組，按照排序過後的定序，無重複元素

combinations_with_replacement()

p, r

長度為 r 的元組，按照排序過後的定序，有重複元素

範例

結果

product('ABCD', repeat=2)

AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD

permutations('ABCD', 2)

AB AC AD BA BC BD CA CB CD DA DB DC

combinations('ABCD', 2)

AB AC AD BC BD CD

combinations_with_replacement('ABCD', 2)

AA AB AC AD BB BC BD CC CD DD

Itertool 函式

以下的函式都會建構並回傳疊代器。一些函式提供無限長度的串流 (stream)，因此應僅由截斷串流的函式或迴圈來存取它們。

itertools.accumulate(iterable[, function, *, initial=None])

建立一個回傳累積和的疊代器，或其他二進位函式的累積結果。

function 預設為加法。function 應接受兩個引數，即累積總和和來自 iterable 的值。

如果提供了 initial 值，則累積將從該值開始，並且輸出的元素數將比輸入的可疊代物件多一個。

大致等價於：

def accumulate(iterable, function=operator.add, *, initial=None):
    'Return running totals'
    # accumulate([1,2,3,4,5]) → 1 3 6 10 15
    # accumulate([1,2,3,4,5], initial=100) → 100 101 103 106 110 115
    # accumulate([1,2,3,4,5], operator.mul) → 1 2 6 24 120

    iterator = iter(iterable)
    total = initial
    if initial is None:
        try:
            total = next(iterator)
        except StopIteration:
            return

    yield total
    for element in iterator:
        total = function(total, element)
        yield total

function 引數可以被設定為 min() 以得到連續的最小值，設定為 max() 以得到連續的最大值，或者設定為 operator.mul() 以得到連續的乘積。也可以透過累積利息和付款來建立攤銷表 (Amortization tables) [https://www.ramseysolutions.com/real-estate/amortization-schedule] ：

>>> data = [3, 4, 6, 2, 1, 9, 0, 7, 5, 8]
>>> list(accumulate(data, max))              # 運行最大值
[3, 4, 6, 6, 6, 9, 9, 9, 9, 9]
>>> list(accumulate(data, operator.mul))     # 運行乘積
[3, 12, 72, 144, 144, 1296, 0, 0, 0, 0]

# 攤銷一筆 1000 的 5% 貸款，分 10 年、每年支付 90
>>> update = lambda balance, payment: round(balance * 1.05) - payment
>>> list(accumulate(repeat(90, 10), update, initial=1_000))
[1000, 960, 918, 874, 828, 779, 728, 674, 618, 559, 497]

可參見 functools.reduce()，其是個類似的函式，但僅回傳最終的累積值。

在 3.2 版被加入.

在 3.3 版的變更: 新增可選的 function 參數。

在 3.8 版的變更: 新增可選的 initial 參數。

itertools.batched(iterable, n, *, strict=False)

將來自 iterable 的資料分批為長度為 n 的元組。最後一個批次可能比 n 短。

如果 strict 為真，則當最後一個批次比 n 短時，會引發 ValueError。

對輸入的可疊代物件進行迴圈，並將資料累積到大小為 n 的元組中。輸入是惰性地被消耗 (consumed lazily) 的，會剛好足夠填充一批的資料。一旦批次填滿或輸入的可疊代物件耗盡，就會 yield 出結果：

>>> flattened_data = ['roses', 'red', 'violets', 'blue', 'sugar', 'sweet']
>>> unflattened = list(batched(flattened_data, 2))
>>> unflattened
[('roses', 'red'), ('violets', 'blue'), ('sugar', 'sweet')]

大致等價於：

def batched(iterable, n, *, strict=False):
    # batched('ABCDEFG', 3) → ABC DEF G
    if n < 1:
        raise ValueError('n must be at least one')
    iterator = iter(iterable)
    while batch := tuple(islice(iterator, n)):
        if strict and len(batch) != n:
            raise ValueError('batched(): incomplete batch')
        yield batch

在 3.12 版被加入.

在 3.13 版的變更: 新增 strict 選項。

itertools.chain(*iterables)

建立一個疊代器，從第一個可疊代物件回傳元素直到其耗盡，然後繼續處理下一個可疊代物件，直到所有可疊代物件都耗盡。這將多個資料來源結合為單一個疊代器。大致等價於：

def chain(*iterables):
    # chain('ABC', 'DEF') → A B C D E F
    for iterable in iterables:
        yield from iterable

classmethod chain.from_iterable(iterable)

chain() 的另一個建構函式。從單個可疊代的引數中得到鏈接的輸入，該引數是惰性計算的。大致等價於：

def from_iterable(iterables):
    # chain.from_iterable(['ABC', 'DEF']) → A B C D E F
    for iterable in iterables:
        yield from iterable

itertools.combinations(iterable, r)

從輸入 iterable 中回傳長度為 r 的元素的子序列。

輸出是 product() 的子序列，僅保留作為 iterable 子序列的條目。輸出的長度由 math.comb() 給定，當 0 ≤ r ≤ n 時，長度為 n! / r! / (n - r)!，當 r > n 時為零。

根據輸入值 iterable 的順序，組合的元組會按照字典順序輸出。如果輸入的 iterable 已經排序，則輸出的元組也將按排序的順序產生。

元素是根據它們的位置（而非值）來決定其唯一性。如果輸入的元素都是獨特的，則每個組合內將不會有重複的值。

大致等價於：

def combinations(iterable, r):
    # combinations('ABCD', 2) → AB AC AD BC BD CD
    # combinations(range(4), 3) → 012 013 023 123

    pool = tuple(iterable)
    n = len(pool)
    if r > n:
        return
    indices = list(range(r))

    yield tuple(pool[i] for i in indices)
    while True:
        for i in reversed(range(r)):
            if indices[i] != i + n - r:
                break
        else:
            return
        indices[i] += 1
        for j in range(i+1, r):
            indices[j] = indices[j-1] + 1
        yield tuple(pool[i] for i in indices)

itertools.combinations_with_replacement(iterable, r)

回傳來自輸入 iterable 的長度為 r 的子序列，且允許個別元素重複多次。

其輸出是一個 product() 的子序列，僅保留作為 iterable 子序列（可能有重複元素）的條目。當 n > 0 時，回傳的子序列數量為 (n + r - 1)! / r! / (n - 1)!。

根據輸入值 iterable 的順序，組合的元組會按照字典順序輸出。如果輸入的 iterable 已經排序，則輸出的元組也將按排序的順序產生。

元素是根據它們的位置（而非值）來決定其唯一性。如果輸入的元素都是獨特的，生成的組合也將是獨特的。

大致等價於：

def combinations_with_replacement(iterable, r):
    # combinations_with_replacement('ABC', 2) → AA AB AC BB BC CC

    pool = tuple(iterable)
    n = len(pool)
    if not n and r:
        return
    indices = [0] * r

    yield tuple(pool[i] for i in indices)
    while True:
        for i in reversed(range(r)):
            if indices[i] != n - 1:
                break
        else:
            return
        indices[i:] = [indices[i] + 1] * (r - i)
        yield tuple(pool[i] for i in indices)

在 3.1 版被加入.

itertools.compress(data, selectors)

建立一個疊代器，回傳 data 中對應 selectors 的元素為 true 的元素。當 data 或 selectors 可疊代物件耗盡時停止。大致等價於：

def compress(data, selectors):
    # compress('ABCDEF', [1,0,1,0,1,1]) → A C E F
    return (datum for datum, selector in zip(data, selectors) if selector)

在 3.1 版被加入.

itertools.count(start=0, step=1)

建立一個疊代器，回傳從 start 開始的等差的值。可以與 map() 一起使用來產生連續的資料點，或與 zip() 一起使用來增加序列號。大致等價於：

def count(start=0, step=1):
    # count(10) → 10 11 12 13 14 ...
    # count(2.5, 0.5) → 2.5 3.0 3.5 ...
    n = start
    while True:
        yield n
        n += step

當用浮點數計數時，將上述程式碼替換為乘法有時可以獲得更好的精確度，例如：(start + step * i for i in count())。

在 3.1 版的變更: 新增 step 引數並允許非整數引數。

itertools.cycle(iterable)

建立一個疊代器，回傳 iterable 中的元素並保存每個元素的副本。當可疊代物件耗盡時，從保存的副本中回傳元素。會無限次的重複。大致等價於：

def cycle(iterable):
    # cycle('ABCD') → A B C D A B C D A B C D ...

    saved = []
    for element in iterable:
        yield element
        saved.append(element)

    while saved:
        for element in saved:
            yield element

此 itertool 可能需要大量的輔助儲存空間（取決於可疊代物件的長度）。

itertools.dropwhile(predicate, iterable)

建立一個疊代器，在 predicate 為 true 時丟棄 iterable 中的元素，之後回傳每個元素。大致等價於：

def dropwhile(predicate, iterable):
    # dropwhile(lambda x: x<5, [1,4,6,3,8]) → 6 3 8

    iterator = iter(iterable)
    for x in iterator:
        if not predicate(x):
            yield x
            break

    for x in iterator:
        yield x

注意，在 predicate 首次變為 False 之前，這不會產生任何輸出，所以此 itertool 可能會有較長的啟動時間。

itertools.filterfalse(predicate, iterable)

建立一個疊代器，過濾 iterable 中的元素，僅回傳 predicate 為 False 值的元素。如果 predicate 是 None，則回傳為 False 的項目。大致等價於：

def filterfalse(predicate, iterable):
    # filterfalse(lambda x: x<5, [1,4,6,3,8]) → 6 8

    if predicate is None:
        predicate = bool

    for x in iterable:
        if not predicate(x):
            yield x

itertools.groupby(iterable, key=None)

建立一個疊代器，回傳 iterable 中連續的鍵和群組。key 是一個為每個元素計算鍵值的函式。如果其未指定或為 None，則 key 預設為一個識別性函式 (identity function)，並回傳未被更改的元素。一般來說，可疊代物件需要已經用相同的鍵函式進行排序。

groupby() 的操作類似於 Unix 中的 uniq 過濾器。每當鍵函式的值發生變化時，它會產生一個 break 或新的群組（這就是為什麼通常需要使用相同的鍵函式對資料進行排序）。這種行為不同於 SQL 的 GROUP BY，其無論輸入順序如何都會聚合相同的元素。

回傳的群組本身是一個與 groupby() 共享底層可疊代物件的疊代器。由於來源是共享的，當 groupby() 物件前進時，前一個群組將不再可見。因此，如果之後需要該資料，應將其儲存為串列：

groups = []
uniquekeys = []
data = sorted(data, key=keyfunc)
for k, g in groupby(data, keyfunc):
    groups.append(list(g))      # 將群組疊代器儲存為串列
    uniquekeys.append(k)

groupby() 大致等價於：

def groupby(iterable, key=None):
    # [k for k, g in groupby('AAAABBBCCDAABBB')] → A B C D A B
    # [list(g) for k, g in groupby('AAAABBBCCD')] → AAAA BBB CC D

    keyfunc = (lambda x: x) if key is None else key
    iterator = iter(iterable)
    exhausted = False

    def _grouper(target_key):
        nonlocal curr_value, curr_key, exhausted
        yield curr_value
        for curr_value in iterator:
            curr_key = keyfunc(curr_value)
            if curr_key != target_key:
                return
            yield curr_value
        exhausted = True

    try:
        curr_value = next(iterator)
    except StopIteration:
        return
    curr_key = keyfunc(curr_value)

    while not exhausted:
        target_key = curr_key
        curr_group = _grouper(target_key)
        yield curr_key, curr_group
        if curr_key == target_key:
            for _ in curr_group:
                pass

itertools.islice(iterable, stop)

itertools.islice(iterable, start, stop[, step])

建立一個疊代器，回傳從 iterable 中選取的元素。其作用類似於序列切片 (sequence slicing)，但不支援負數的 start、stop 或 step 的值。

如果 start 為零或 None，則從零開始疊代。否則在達到 start 之前，會跳過 iterable 中的元素。

如果 stop 為 None，則疊代將繼續前進直到輸入耗盡。如果指定了 stop，則在達到指定位置時停止。

如果 step 為 None，則步長 (step) 預設為一。元素會連續回傳，除非將 step 設定為大於一，這會導致一些項目被跳過。

大致等價於：

def islice(iterable, *args):
    # islice('ABCDEFG', 2) → A B
    # islice('ABCDEFG', 2, 4) → C D
    # islice('ABCDEFG', 2, None) → C D E F G
    # islice('ABCDEFG', 0, None, 2) → A C E G

    s = slice(*args)
    start = 0 if s.start is None else s.start
    stop = s.stop
    step = 1 if s.step is None else s.step
    if start < 0 or (stop is not None and stop < 0) or step <= 0:
        raise ValueError

    indices = count() if stop is None else range(max(start, stop))
    next_i = start
    for i, element in zip(indices, iterable):
        if i == next_i:
            yield element
            next_i += step

若輸入為疊代器，則完整耗盡 islice 會使輸入的疊代器向前移動 max(start, stop) 步，與 step 的值無關。

itertools.pairwise(iterable)

回傳從輸入的 iterable 中提取的連續重疊對。

輸出疊代器中的 2 元組數量將比輸入少一個。如果輸入的可疊代物件中的值少於兩個，則輸出將為空值。

大致等價於：

def pairwise(iterable):
    # pairwise('ABCDEFG') → AB BC CD DE EF FG

    iterator = iter(iterable)
    a = next(iterator, None)

    for b in iterator:
        yield a, b
        a = b

在 3.10 版被加入.

itertools.permutations(iterable, r=None)

回傳 iterable 中連續且長度為 r 的元素排列 [https://www.britannica.com/science/permutation] 。

如果未指定 r 或其值為 None，則 r 預設為 iterable 的長度，並產生所有可能的完整長度的排列。

輸出是 product() 的子序列，其中重複元素的條目已被濾除。輸出的長度由 math.perm() 給定，當 0 ≤ r ≤ n 時，長度為 n! / (n - r)!，當 r > n 時為零。

根據輸入值 iterable 的順序，排列的元組會按照字典順序輸出。如果輸入的 iterable 已排序，則輸出的元組也將按排序的順序產生。

元素是根據它們的位置（而非值）來決定其唯一性。如果輸入的元素都是獨特的，則排列中將不會有重複的值。

大致等價於：

def permutations(iterable, r=None):
    # permutations('ABCD', 2) → AB AC AD BA BC BD CA CB CD DA DB DC
    # permutations(range(3)) → 012 021 102 120 201 210

    pool = tuple(iterable)
    n = len(pool)
    r = n if r is None else r
    if r > n:
        return

    indices = list(range(n))
    cycles = list(range(n, n-r, -1))
    yield tuple(pool[i] for i in indices[:r])

    while n:
        for i in reversed(range(r)):
            cycles[i] -= 1
            if cycles[i] == 0:
                indices[i:] = indices[i+1:] + indices[i:i+1]
                cycles[i] = n - i
            else:
                j = cycles[i]
                indices[i], indices[-j] = indices[-j], indices[i]
                yield tuple(pool[i] for i in indices[:r])
                break
        else:
            return

itertools.product(*iterables, repeat=1)

輸入可疊代物的 笛卡爾乘積 [https://en.wikipedia.org/wiki/Cartesian_product]

大致等價於產生器運算式中的巢狀 for 迴圈。例如，product(A, B) 的回傳結果與 ((x,y) for x in A for y in B) 相同。

巢狀迴圈的循環類似於里程表，最右邊的元素在每次疊代時前進。這種模式會建立字典順序，因此如果輸入的 iterables 已排序，則輸出的乘積元組也將按排序的順序產生。

要計算可疊代物件自身的乘積，可以使用可選的 repeat 關鍵字引數來指定重複次數。例如，product(A, repeat=4) 與 product(A, A, A, A) 相同。

此函式大致等價於以下的程式碼，不同之處在於真正的實作不會在記憶體中建立中間結果：

def product(*iterables, repeat=1):
    # product('ABCD', 'xy') → Ax Ay Bx By Cx Cy Dx Dy
    # product(range(2), repeat=3) → 000 001 010 011 100 101 110 111

    if repeat < 0:
        raise ValueError('repeat argument cannot be negative')
    pools = [tuple(pool) for pool in iterables] * repeat

    result = [[]]
    for pool in pools:
        result = [x+[y] for x in result for y in pool]

    for prod in result:
        yield tuple(prod)

在 product() 執行之前，它會完全消耗輸入的 iterables，並將值的池 (pools of values) 保存在記憶體中以產生乘積。因此，它僅對有限的輸入有用。

itertools.repeat(object[, times])

建立一個疊代器，反覆回傳 object。除非指定了 times 引數，否則會執行無限次。

大致等價於：

def repeat(object, times=None):
    # repeat(10, 3) → 10 10 10
    if times is None:
        while True:
            yield object
    else:
        for i in range(times):
            yield object

repeat 的常見用途是為 map 或 zip 提供定值的串流：

>>> list(map(pow, range(10), repeat(2)))
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

itertools.starmap(function, iterable)

建立一個疊代器，使用從 iterable 取得的引數計算 function 。當引數參數已經被「預先壓縮 (pre-zipped)」成元組時，使用此方法代替 map()。

map() 和 starmap() 之間的區別類似於 function(a,b) 和 function(*c) 之間的區別。大致等價於：

def starmap(function, iterable):
    # starmap(pow, [(2,5), (3,2), (10,3)]) → 32 9 1000
    for args in iterable:
        yield function(*args)

itertools.takewhile(predicate, iterable)

建立一個疊代器，只在 predicate 為 true 時回傳 iterable 中的元素。大致等價於：

def takewhile(predicate, iterable):
    # takewhile(lambda x: x<5, [1,4,6,3,8]) → 1 4
    for x in iterable:
        if not predicate(x):
            break
        yield x

注意，第一個不符合條件判斷的元素將從輸入疊代器中被消耗，且無法再存取它。如果應用程式希望在 takewhile 耗盡後進一步消耗輸入疊代器，這可能會是個問題。為了解決這個問題，可以考慮使用 more-itertools 中的 before_and_after() [https://more-itertools.readthedocs.io/en/stable/api.html#more_itertools.before_and_after] 作為替代。

itertools.tee(iterable, n=2)

從一個 iterable 中回傳 n 個獨立的疊代器。

大致等價於：

def tee(iterable, n=2):
    if n < 0:
        raise ValueError
    if n == 0:
        return ()
    iterator = _tee(iterable)
    result = [iterator]
    for _ in range(n - 1):
        result.append(_tee(iterator))
    return tuple(result)

class _tee:

    def __init__(self, iterable):
        it = iter(iterable)
        if isinstance(it, _tee):
            self.iterator = it.iterator
            self.link = it.link
        else:
            self.iterator = it
            self.link = [None, None]

    def __iter__(self):
        return self

    def __next__(self):
        link = self.link
        if link[1] is None:
            link[0] = next(self.iterator)
            link[1] = [None, None]
        value, self.link = link
        return value

當輸入的 iterable 已經是一個 tee 疊代物件時，回傳的 tuple（元組）中所有成員都會被建立，就如同它們是由上游的 tee() 呼叫所產生的一樣。這個「展平步驟 (flattening step)」讓巢狀的 tee() 呼叫能共享相同的底層資料鏈，並以單一的更新步驟取代一連串的呼叫。

展平特性讓 tee 疊代器具備高效的預覽能力：

def lookahead(tee_iterator):
     "回傳下一個值，但不推進輸入"
     [forked_iterator] = tee(tee_iterator, 1)
     return next(forked_iterator)

>>> iterator = iter('abcdef')
>>> [iterator] = tee(iterator, 1)   # 使得輸入可預覽
>>> next(iterator)                  # 往前移動疊代器
'a'
>>> lookahead(iterator)             # 檢查下一個值
'b'
>>> next(iterator)                  # 繼續往前移動
'b'

tee 疊代器不是執行緒安全 (threadsafe) 的。當同時使用由同一個 tee() 呼叫所回傳的疊代器時，即使原始的 iterable 是執行緒安全的，也可能引發 RuntimeError。

此 itertool 可能需要大量的輔助儲存空間（取決於需要儲存多少臨時資料）。通常如果一個疊代器在另一個疊代器開始之前使用了大部分或全部的資料，使用 list() 會比 tee() 更快。

itertools.zip_longest(*iterables, fillvalue=None)

建立一個疊代器，聚合來自每個 iterables 中的元素。

如果 iterables 的長度不一，則使用 fillvalue 填充缺少的值。如果未指定，fillvalue 會預設為 None。

疊代將持續直到最長的可疊代物件耗盡為止。

大致等價於：

def zip_longest(*iterables, fillvalue=None):
    # zip_longest('ABCD', 'xy', fillvalue='-') → Ax By C- D-

    iterators = list(map(iter, iterables))
    num_active = len(iterators)
    if not num_active:
        return

    while True:
        values = []
        for i, iterator in enumerate(iterators):
            try:
                value = next(iterator)
            except StopIteration:
                num_active -= 1
                if not num_active:
                    return
                iterators[i] = repeat(fillvalue)
                value = fillvalue
            values.append(value)
        yield tuple(values)

如果其中一個 iterables 可能是無限的，那麼應該用別的可以限制呼叫次數的方法來包裝 zip_longest() 函式（例如 islice() 或 takewhile()）。

Itertools 應用技巧

此段落展示了使用現有的 itertools 作為構建塊來建立擴展工具集的應用技巧。

itertools 應用技巧的主要目的是教學。這些應用技巧展示了對單個工具進行思考的各種方式 —— 例如，chain.from_iterable 與攤平 (flattening) 的概念相關。這些應用技巧還提供了組合使用工具的想法 —— 例如，starmap() 和 repeat() 如何一起工作。另外還展示了將 itertools 與 operator 和 collections 模組一同使用以及與內建 itertools（如 map()、filter()、reversed() 和 enumerate()）一同使用的模式。

應用技巧的次要目的是作為 itertools 的孵化器。accumulate(), compress() 和 pairwise() itertools 最初都是作為應用技巧出現的。目前，sliding_window()、derangements() 和 sieve() 的應用技巧正在被測試，以確定它們是否有價值被收錄到內建的 itertools 中。

幾乎所有這些應用技巧以及許多其他應用技巧都可以從 Python Package Index 上的 more-itertools [https://pypi.org/project/more-itertools/] 專案中安裝：

python -m pip install more-itertools

許多應用技巧提供了與底層工具集相同的高性能。透過一次處理一個元素而不是將整個可疊代物件一次性引入記憶體，能保持優異的記憶體性能。以函式風格 (functional style) [https://www.cs.kent.ac.uk/people/staff/dat/miranda/whyfp90.pdf] 將工具連接在一起，能將程式碼的數量維持在較少的情況。透過優先使用「向量化 (vectorized)」的構建塊而不是使用會造成直譯器負擔的 for 迴圈和產生器，則能保持高速度。

from itertools import (accumulate, batched, chain, combinations, compress,
     count, cycle, filterfalse, groupby, islice, permutations, product,
     repeat, starmap, tee, zip_longest)
from collections import Counter, deque
from contextlib import suppress
from functools import reduce
from math import comb, isqrt, prod, sumprod
from operator import getitem, is_not, itemgetter, mul, neg

# ==== 基本單行函式 ====

def take(n, iterable):
    "回傳可疊代物件的前 n 個元素為串列。"
    return list(islice(iterable, n))

def prepend(value, iterable):
    "在可疊代物件開頭插入單一值。"
    # prepend(1, [2, 3, 4]) → 1 2 3 4
    return chain([value], iterable)

def tabulate(function, start=0):
    "回傳 function(0), function(1), ..."
    return map(function, count(start))

def repeatfunc(function, times=None, *args):
    "重複呼叫一個帶指定引數的函式。"
    if times is None:
        return starmap(function, repeat(args))
    return starmap(function, repeat(args, times))

def flatten(list_of_lists):
    "將巢狀結構攤平一層。"
    return chain.from_iterable(list_of_lists)

def ncycles(iterable, n):
    "回傳序列的元素重複 n 次。"
    return chain.from_iterable(repeat(tuple(iterable), n))

def loops(n):
    "執行 n 次的迴圈。類似 range(n) 但不建立整數序列。"
    # for _ in loops(100): ...
    return repeat(None, n)

def tail(n, iterable):
    "回傳一個疊代器，疊代最後 n 個元素。"
    # tail(3, 'ABCDEFG') → E F G
    return iter(deque(iterable, maxlen=n))

def consume(iterator, n=None):
    "將疊代器往前推進 n 步。如果 n 為 None，則完全消耗。"
    # 使用以 C 語言的速度消耗疊代器的函式。
    if n is None:
        deque(iterator, maxlen=0)
    else:
        next(islice(iterator, n, n), None)

def nth(iterable, n, default=None):
    "回傳第 n 個元素或預設值。"
    return next(islice(iterable, n, None), default)

def quantify(iterable, predicate=bool):
    "給定一個回傳 True 或 False 的判斷函式，計算為 True 的結果。"
    return sum(map(predicate, iterable))

def first_true(iterable, default=False, predicate=None):
    "回傳第一個為 true 的值，若無則回傳*預設值*。"
    # first_true([a, b, c], x) → a or b or c or x
    # first_true([a, b], x, f) → a if f(a) else b if f(b) else x
    return next(filter(predicate, iterable), default)

def all_equal(iterable, key=None):
    "回傳 True，如果所有元素兩兩相等。"
    # all_equal('4٤௪౪໔', key=int) → True
    return len(take(2, groupby(iterable, key))) <= 1

# ==== 資料管線 ====

def unique_justseen(iterable, key=None):
    "產生唯一的元素，並保留原始順序。只記住剛看見的元素。"
    # unique_justseen('AAAABBBCCDAABBB') → A B C D A B
    # unique_justseen('ABBcCAD', str.casefold) → A B c A D
    if key is None:
        return map(itemgetter(0), groupby(iterable))
    return map(next, map(itemgetter(1), groupby(iterable, key)))

def unique_everseen(iterable, key=None):
    "產生唯一的元素，並保留原始順序。記住所有曾見過的元素。"
    # unique_everseen('AAAABBBCCDAABBB') → A B C D
    # unique_everseen('ABBcCAD', str.casefold) → A B c D
    seen = set()
    if key is None:
        for element in filterfalse(seen.__contains__, iterable):
            seen.add(element)
            yield element
    else:
        for element in iterable:
            k = key(element)
            if k not in seen:
                seen.add(k)
                yield element

def unique(iterable, key=None, reverse=False):
   "產生排序後的不重複元素。支援不可雜湊的輸入。"
   # unique([[1, 2], [3, 4], [1, 2]]) → [1, 2] [3, 4]
   sequenced = sorted(iterable, key=key, reverse=reverse)
   return unique_justseen(sequenced, key=key)

def sliding_window(iterable, n):
    "將資料收集成重疊的固定長度區段或區塊。"
    # sliding_window('ABCDEFG', 3) → ABC BCD CDE DEF EFG
    iterator = iter(iterable)
    window = deque(islice(iterator, n - 1), maxlen=n)
    for x in iterator:
        window.append(x)
        yield tuple(window)

def grouper(iterable, n, *, incomplete='fill', fillvalue=None):
    "將資料收集成不重疊的固定長度區段或區塊。"
    # grouper('ABCDEFG', 3, fillvalue='x')       → ABC DEF Gxx
    # grouper('ABCDEFG', 3, incomplete='strict') → ABC DEF ValueError
    # grouper('ABCDEFG', 3, incomplete='ignore') → ABC DEF
    iterators = [iter(iterable)] * n
    match incomplete:
        case 'fill':
            return zip_longest(*iterators, fillvalue=fillvalue)
        case 'strict':
            return zip(*iterators, strict=True)
        case 'ignore':
            return zip(*iterators)
        case _:
            raise ValueError('Expected fill, strict, or ignore')

def roundrobin(*iterables):
    "以循環方式依序輸入可疊代物件，直到全部耗盡。"
    # roundrobin('ABC', 'D', 'EF') → A D E B F C
    # 演算法出自 George Sakkis
    iterators = map(iter, iterables)
    for num_active in range(len(iterables), 0, -1):
        iterators = cycle(islice(iterators, num_active))
        yield from map(next, iterators)

def subslices(seq):
    "回傳序列的所有連續非空子切片。"
    # subslices('ABCD') → A AB ABC ABCD B BC BCD C CD D
    slices = starmap(slice, combinations(range(len(seq) + 1), 2))
    return map(getitem, repeat(seq), slices)

def derangements(iterable, r=None):
    "產生長度為 r 且無固定點的排列。"
    # derangements('ABCD') → BADC BCDA BDAC CADB CDAB CDBA DABC DCAB DCBA
    # 演算法由 Stefan Pochmann 提供
    seq = tuple(iterable)
    pos = tuple(range(len(seq)))
    have_moved = map(map, repeat(is_not), repeat(pos), permutations(pos, r=r))
    valid_derangements = map(all, have_moved)
    return compress(permutations(seq, r=r), valid_derangements)

def iter_index(iterable, value, start=0, stop=None):
    "回傳在序列或可疊代物件中某值出現的索引位置。"
    # iter_index('AABCADEAF', 'A') → 0 1 4 7
    seq_index = getattr(iterable, 'index', None)
    if seq_index is None:
        iterator = islice(iterable, start, stop)
        for i, element in enumerate(iterator, start):
            if element is value or element == value:
                yield i
    else:
        stop = len(iterable) if stop is None else stop
        i = start
        with suppress(ValueError):
            while True:
                yield (i := seq_index(value, i, stop))
                i += 1

def iter_except(function, exception, first=None):
    "將一個 call-until-exception 介面轉換為疊代器介面。"
    # iter_except(d.popitem, KeyError) → 非阻塞的字典疊代器
    with suppress(exception):
        if first is not None:
            yield first()
        while True:
            yield function()

# ==== 數學運算 ====

def multinomial(*counts):
    "多重集合的不同排列數。"
    # Counter('abracadabra').values() → 5 2 2 1 1
    # multinomial(5, 2, 2, 1, 1) → 83160
    return prod(map(comb, accumulate(counts), counts))

def powerset(iterable):
    "可疊代物件的子序列，從最短到最長。"
    # powerset([1,2,3]) → () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))

def sum_of_squares(iterable):
    "將輸入值的平方加總。"
    # sum_of_squares([10, 20, 30]) → 1400
    return sumprod(*tee(iterable))

# ==== 矩陣運算 ====

def reshape(matrix, columns):
    "將二維矩陣重塑為指定的欄數。"
    # reshape([(0, 1), (2, 3), (4, 5)], 3) →  (0, 1, 2) (3, 4, 5)
    return batched(chain.from_iterable(matrix), columns, strict=True)

def transpose(matrix):
    "交換二維矩陣的列與欄。"
    # transpose([(1, 2, 3), (11, 22, 33)]) → (1, 11) (2, 22) (3, 33)
    return zip(*matrix, strict=True)

def matmul(m1, m2):
    "兩個矩陣相乘。"
    # matmul([(7, 5), (3, 5)], [(2, 5), (7, 9)]) → (49, 80) (41, 60)
    n = len(m2[0])
    return batched(starmap(sumprod, product(m1, transpose(m2))), n)

# ==== 多項式運算 ====

def convolve(signal, kernel):
    """兩個可疊代物件的離散線性卷積。
    等同於多項式乘法。

    卷積在數學上具有交換律；但輸入的處理方式不同。
    訊號是惰性消耗的，可以是無限的。
    核心在計算開始前會完全消耗。

    文章：https://betterexplained.com/articles/intuitive-convolution/
    影片：https://www.youtube.com/watch?v=KuXjwB4LzSA
    """
    # convolve([1, -1, -20], [1, -3]) → 1 -4 -17 60
    # convolve(data, [0.25, 0.25, 0.25, 0.25]) → 移動平均（模糊）
    # convolve(data, [1/2, 0, -1/2]) → 一階導數估計
    # convolve(data, [1, -2, 1]) → 二階導數估計
    kernel = tuple(kernel)[::-1]
    n = len(kernel)
    padded_signal = chain(repeat(0, n-1), signal, repeat(0, n-1))
    windowed_signal = sliding_window(padded_signal, n)
    return map(sumprod, repeat(kernel), windowed_signal)

def polynomial_from_roots(roots):
    """從根計算多項式的係數。

       (x - 5) (x + 4) (x - 3) 展開為：x³ -4x² -17x + 60
    """
    # polynomial_from_roots([5, -4, 3]) → [1, -4, -17, 60]
    factors = zip(repeat(1), map(neg, roots))
    return list(reduce(convolve, factors, [1]))

def polynomial_eval(coefficients, x):
    """在特定值計算多項式。

    比霍納法則具有更好的數值穩定性。
    """
    # 在 x = 5 計算 x³ -4x² -17x + 60
    # polynomial_eval([1, -4, -17, 60], x=5) → 0
    n = len(coefficients)
    if not n:
        return type(x)(0)
    powers = map(pow, repeat(x), reversed(range(n)))
    return sumprod(coefficients, powers)

def polynomial_derivative(coefficients):
    """計算多項式的一階導數。

       f(x)  =  x³ -4x² -17x + 60
       f'(x) = 3x² -8x  -17
    """
    # polynomial_derivative([1, -4, -17, 60]) → [3, -8, -17]
    n = len(coefficients)
    powers = reversed(range(1, n))
    return list(map(mul, coefficients, powers))

# ==== 數論 ====

def sieve(n):
    "小於 n 的質數。"
    # sieve(30) → 2 3 5 7 11 13 17 19 23 29
    if n > 2:
        yield 2
    data = bytearray((0, 1)) * (n // 2)
    for p in iter_index(data, 1, start=3, stop=isqrt(n) + 1):
        data[p*p : n : p+p] = bytes(len(range(p*p, n, p+p)))
    yield from iter_index(data, 1, start=3)

def factor(n):
    "n 的質因數。"
    # factor(99) → 3 3 11
    # factor(1_000_000_000_000_007) → 47 59 360620266859
    # factor(1_000_000_000_000_403) → 1000000000000403
    for prime in sieve(isqrt(n) + 1):
        while not n % prime:
            yield prime
            n //= prime
            if n == 1:
                return
    if n > 1:
        yield n

def is_prime(n):
    "如果 n 是質數則回傳 True。"
    # is_prime(1_000_000_000_000_403) → True
    return n > 1 and next(factor(n)) == n

def totient(n):
    "小於等於 n 且與 n 互質的自然數個數。"
    # https://mathworld.wolfram.com/TotientFunction.html
    # totient(12) → 4 因為 len([1, 5, 7, 11]) == 4
    for prime in set(factor(n)):
        n -= n // prime
    return n

functools --- 可呼叫物件上的高階函式與操作

原始碼：Lib/functools.py [https://github.com/python/cpython/tree/3.14/Lib/functools.py]

functools 模組用於高階函式：作用於或回傳其他函式的函式。一般來說，任何可呼叫物件都可以被視為用於此模組的函式。

functools 模組定義了以下函式：

@functools.cache(user_function)

簡單的輕量級無繫結函式快取 (Simple lightweight unbounded function cache)。有時稱之為 "memoize"（記憶化） [https://en.wikipedia.org/wiki/Memoization]。

和 lru_cache(maxsize=None) 回傳相同的值，為函式引數建立一個字典查找的薄包裝器。因為它永遠不需要丟棄舊值，所以這比有大小限制的 lru_cache() 更小、更快。

舉例來說：

@cache
def factorial(n):
    return n * factorial(n-1) if n else 1

>>> factorial(10)      # 沒有先前的快取結果，會進行 11 次遞迴呼叫
3628800
>>> factorial(5)       # 沒有新的呼叫，直接回傳被快取起來的結果
120
>>> factorial(12)      # 兩次新的遞迴呼叫，factorial(10) 有被快取起來
479001600

該快取是執行緒安全的 (threadsafe)，因此包裝的函式可以在多個執行緒中使用。這意味著底層資料結構在並行更新期間將保持連貫 (coherent)。

如果另一個執行緒在初始呼叫完成並快取之前進行額外的呼叫，則包裝的函式可能會被多次呼叫。

在 3.9 版被加入.

@functools.cached_property(func)

將類別的一個方法轉換為屬性 (property)，其值會計算一次，然後在實例的生命週期內快取為普通屬性。類似 property()，但增加了快取機制。對於除使用該裝飾器的屬性外實質上幾乎是不可變 (immutable) 的實例，針對其所需要繁重計算會很有用。

範例：

class DataSet:

    def __init__(self, sequence_of_numbers):
        self._data = tuple(sequence_of_numbers)

    @cached_property
    def stdev(self):
        return statistics.stdev(self._data)

cached_property() 的機制與 property() 有所不同。除非定義了 setter，否則常規屬性會阻止屬性的寫入。相反地，cached_property 則允許寫入。

cached_property 裝飾器僅在查找時且僅在同名屬性不存在時運行。當它運行時，cached_property 會寫入同名的屬性。後續屬性讀取和寫入優先於 cached_property 方法，並且它的工作方式與普通屬性類似。

可以透過刪除屬性來清除快取的值，這使得 cached_property 方法可以再次運行。

cached_property 無法防止多執行緒使用中可能出現的競爭條件 (race condition)。getter 函式可以在同一個實例上運行多次，最後一次運行會設定快取的值。所以快取的屬性最好是冪等的 (idempotent)，或者在一個實例上運行多次不會有害，就不會有問題。如果同步是必要的，請在裝飾的 getter 函式內部或在快取的屬性存取周圍實作必要的鎖。

請注意，此裝飾器會干擾 PEP 412 [https://peps.python.org/pep-0412/] 金鑰共用字典的操作。這意味著實例字典可能比平常佔用更多的空間。

此外，此裝飾器要求每個實例上的 __dict__ 屬性是可變對映 (mutable mapping)。這意味著它不適用於某些型別，例如元類別 (metaclass)（因為型別實例上的 __dict__ 屬性是類別命名空間的唯讀代理），以及那些指定 __slots__ 而不包含 __dict__ 的型別作為有定義的插槽之一（因為此種類別根本不提供 __dict__ 屬性）。

如果可變對映不可用或需要金鑰共享以節省空間，則也可以透過在 lru_cache() 之上堆疊 property() 來實作類似於 cached_property() 的效果。請參閱如何快取方法呼叫？以了解有關這與 cached_property() 間不同之處的更多詳細資訊。

在 3.8 版被加入.

在 3.12 版的變更: 在 Python 3.12 之前，cached_property 包含一個未以文件記錄的鎖，以確保在多執行緒使用中能保證 getter 函式對於每個實例只會執行一次。然而，鎖是針對每個屬性，而不是針對每個實例，這可能會導致無法被接受的嚴重鎖爭用 (lock contention)。在 Python 3.12+ 中，此鎖已被刪除。

functools.cmp_to_key(func)

將舊式比較函式轉換為鍵函式，能與接受鍵函式的工具一起使用（例如 sorted()、min()、max()、heapq.nlargest()、heapq.nsmallest()、itertools.groupby()）。此函式主要作為轉換工具，用於從有支援使用比較函式的 Python 2 轉換成的程式。

比較函式是任何能接受兩個引數、對它們進行比較，並回傳負數（小於）、零（相等）或正數（大於）的可呼叫物件。鍵函式是接受一個引數並回傳另一個用作排序鍵之值的可呼叫物件。

範例：

sorted(iterable, key=cmp_to_key(locale.strcoll))  # locale-aware sort order

有關排序範例和簡短的排序教學，請參閱排序技法。

在 3.2 版被加入.

@functools.lru_cache(user_function)

@functools.lru_cache(maxsize=128, typed=False)

以記憶化可呼叫物件來包裝函式的裝飾器，最多可省去 maxsize 個最近的呼叫。當使用相同引數定期呼叫繁重的或 I/O 密集的函式時，它可以節省時間。

該快取是執行緒安全的 (threadsafe)，因此包裝的函式可以在多個執行緒中使用。這意味著底層資料結構在並行更新期間將保持連貫 (coherent)。

如果另一個執行緒在初始呼叫完成並快取之前進行額外的呼叫，則包裝的函式可能會被多次呼叫。

由於字典用於快取結果，因此函式的位置引數和關鍵字引數必須是可雜湊的。

不同的引數模式可以被認為是具有不同快取條目的不同呼叫。例如，f(a=1, b=2) 和 f(b=2, a=1) 的關鍵字引數順序不同，並且可能有兩個不同的快取條目。

如果指定了 user_function，則它必須是個可呼叫物件。這使得 lru_cache 裝飾器能夠直接應用於使用者函式，將 maxsize 保留為其預設值 128：

@lru_cache
def count_vowels(sentence):
    return sum(sentence.count(vowel) for vowel in 'AEIOUaeiou')

如果 maxsize 設定為 None，則 LRU 功能將被停用，且快取可以無限制地成長。

如果 typed 設定為 true，不同型別的函式引數將會被單獨快取起來。如果 typed 為 false，則實作通常會將它們視為等效呼叫，並且僅快取單一結果。（某些型別，例如 str 和 int 可能會被單獨快取起來，即使 typed 為 false。）

請注意，型別特異性 (type specificity) 僅適用於函式的直接引數而不是其內容。純量 (scalar) 引數 Decimal(42) 和 Fraction(42) 被視為具有不同結果的不同呼叫。相反地，元組引數 ('answer', Decimal(42)) 和 ('answer', Fraction(42)) 被視為等效。

包裝的函式使用一個 cache_parameters() 函式來進行偵測，該函式回傳一個新的 dict 以顯示 maxsize 和 typed 的值。這僅能顯示資訊，改變其值不會有任何效果。

為了輔助測量快取的有效性並調整 maxsize 參數，包裝的函式使用了一個 cache_info() 函式來做檢測，該函式會回傳一個附名元組來顯示 hits、misses、maxsize 和 currsize。

裝飾器還提供了一個 cache_clear() 函式來清除或使快取失效。

原本的底層函式可以透過 __wrapped__ 屬性存取。這對於要自我檢查 (introspection)、繞過快取或使用不同的快取重新包裝函式時非常有用。

快取會保留對引數和回傳值的參照，直到快取過時 (age out) 或快取被清除為止。

如果方法被快取起來，則 self 實例引數將包含在快取中。請參閱如何快取方法呼叫？

當最近的呼叫是即將發生之呼叫的最佳預測因子時（例如新聞伺服器上最受歡迎的文章往往每天都會發生變化），LRU (least recently used) 快取 [https://en.wikipedia.org/wiki/Cache_replacement_policies#Least_Recently_Used_(LRU)]能發揮最好的效果。快取的大小限制可確保快取不會在長時間運行的行程（例如 Web 伺服器）上無限制地成長。

一般來說，僅當你想要重複使用先前計算的值時才應使用 LRU 快取。因此，快取具有 side-effects 的函式、需要在每次呼叫時建立不同可變物件的函式（例如產生器和非同步函式）或不純函式（impure function，例如 time() 或 random()）是沒有意義的。

靜態網頁內容的 LRU 快取範例：

@lru_cache(maxsize=32)
def get_pep(num):
    '取得 Python 改進提案的文字'
    resource = f'https://peps.python.org/pep-{num:04d}'
    try:
        with urllib.request.urlopen(resource) as s:
            return s.read()
    except urllib.error.HTTPError:
        return 'Not Found'

>>> for n in 8, 290, 308, 320, 8, 218, 320, 279, 289, 320, 9991:
...     pep = get_pep(n)
...     print(n, len(pep))

>>> get_pep.cache_info()
CacheInfo(hits=3, misses=8, maxsize=32, currsize=8)

使用快取來實作動態規劃 (dynamic programming) [https://en.wikipedia.org/wiki/Dynamic_programming] 技法以有效率地計算費波那契數 (Fibonacci numbers) [https://en.wikipedia.org/wiki/Fibonacci_number] 的範例：

@lru_cache(maxsize=None)
def fib(n):
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)

>>> [fib(n) for n in range(16)]
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610]

>>> fib.cache_info()
CacheInfo(hits=28, misses=16, maxsize=None, currsize=16)

在 3.2 版被加入.

在 3.3 版的變更: 新增 typed 選項。

在 3.8 版的變更: 新增 user_function 選項。

在 3.9 版的變更: 新增 cache_parameters() 函式。

@functools.total_ordering

給定一個定義一個或多個 rich comparison 排序方法的類別，該類別裝飾器會提供其餘部分。這簡化了指定所有可能的 rich comparison 操作所涉及的工作：

類別必須定義 __lt__()、__le__()、__gt__() 或 __ge__() 其中之一。此外，該類別應該提供 __eq__() 方法。

舉例來說：

@total_ordering
class Student:
    def _is_valid_operand(self, other):
        return (hasattr(other, "lastname") and
                hasattr(other, "firstname"))
    def __eq__(self, other):
        if not self._is_valid_operand(other):
            return NotImplemented
        return ((self.lastname.lower(), self.firstname.lower()) ==
                (other.lastname.lower(), other.firstname.lower()))
    def __lt__(self, other):
        if not self._is_valid_operand(other):
            return NotImplemented
        return ((self.lastname.lower(), self.firstname.lower()) <
                (other.lastname.lower(), other.firstname.lower()))

備註

雖然此裝飾器可以輕鬆建立能好好運作的完全有序型別 (totally ordered types)，但它的確以衍生比較方法的執行速度較慢和堆疊追蹤 (stack trace) 較複雜做為其代價。如果效能基準測試顯示這是給定應用程式的效能瓶頸，那麼實作全部六種 rich comparison 方法通常能輕鬆地提升速度。

備註

此裝飾器不會嘗試覆寫類別或其超類別 (superclass)中宣告的方法。這意味著如果超類別定義了比較運算子，total_ordering 將不會再次實作它，即使原始方法是抽象的。

在 3.2 版被加入.

在 3.4 版的變更: 現在支援從底層對於未識別型別的比較函式回傳 NotImplemented。

functools.Placeholder

A singleton object used as a sentinel to reserve a place for positional arguments when calling partial() and partialmethod().

在 3.14 版被加入.

functools.partial(func, /, *args, **keywords)

回傳一個新的 partial 物件，它在被呼叫時的行為類似於使用位置引數 args 和關鍵字引數 keywords 呼叫的 func。如果向呼叫提供更多引數，它們將被附加到 args。如果提供了額外的關鍵字引數，它們會擴充並覆寫 keywords。大致相當於：

def partial(func, /, *args, **keywords):
    def newfunc(*more_args, **more_keywords):
        return func(*args, *more_args, **(keywords | more_keywords))
    newfunc.func = func
    newfunc.args = args
    newfunc.keywords = keywords
    return newfunc

partial() 用於部分函式應用程序，它「凍結」函式引數和/或關鍵字的某些部分，從而產生具有簡化簽名的新物件。例如，partial() 可用來建立可呼叫函式，其行為類似於 int() 函式，其中 base 引數預設為 2：

>>> basetwo = partial(int, base=2)
>>> basetwo.__doc__ = 'Convert base 2 string to an int.'
>>> basetwo('10010')
18

If Placeholder sentinels are present in args, they will be filled first when partial() is called. This makes it possible to pre-fill any positional argument with a call to partial(); without Placeholder, only the chosen number of leading positional arguments can be pre-filled.

If any Placeholder sentinels are present, all must be filled at call time:

>>> say_to_world = partial(print, Placeholder, Placeholder, "world!")
>>> say_to_world('Hello', 'dear')
Hello dear world!

Calling say_to_world('Hello') raises a TypeError, because only one positional argument is provided, but there are two placeholders that must be filled in.

If partial() is applied to an existing partial() object, Placeholder sentinels of the input object are filled in with new positional arguments. A placeholder can be retained by inserting a new Placeholder sentinel to the place held by a previous Placeholder:

>>> from functools import partial, Placeholder as _
>>> remove = partial(str.replace, _, _, '')
>>> message = 'Hello, dear dear world!'
>>> remove(message, ' dear')
'Hello, world!'
>>> remove_dear = partial(remove, _, ' dear')
>>> remove_dear(message)
'Hello, world!'
>>> remove_first_dear = partial(remove_dear, _, 1)
>>> remove_first_dear(message)
'Hello, dear world!'

Placeholder cannot be passed to partial() as a keyword argument.

在 3.14 版的變更: Added support for Placeholder in positional arguments.

class functools.partialmethod(func, /, *args, **keywords)

回傳一個新的 partialmethod 描述器 (descriptor)，其行為類似於 partial，只不過它被設計為用於方法定義而不能直接呼叫。

func 必須是一個 descriptor 或可呼叫物件（兩者兼具的物件，就像普通函式一樣，會被當作描述器處理）。

當 func 是描述器時（例如普通的 Python 函式、classmethod()、staticmethod()、abstractmethod() 或 partialmethod 的另一個實例），對 __get__ 的呼叫將被委託 (delegated) 給底層描述器，且一個適當的 partial 物件會被作為結果回傳。

當 func 是非描述器可呼叫物件 (non-descriptor callable) 時，會動態建立適當的繫結方法 (bound method)。當被作為方法使用時，其行為類似於普通的 Python 函式：self 引數將作為第一個位置引數插入，甚至會在提供給 partialmethod 建構函式的 args 和 keywords 的前面。

範例：

>>> class Cell:
...     def __init__(self):
...         self._alive = False
...     @property
...     def alive(self):
...         return self._alive
...     def set_state(self, state):
...         self._alive = bool(state)
...     set_alive = partialmethod(set_state, True)
...     set_dead = partialmethod(set_state, False)
...
>>> c = Cell()
>>> c.alive
False
>>> c.set_alive()
>>> c.alive
True

在 3.4 版被加入.

functools.reduce(function, iterable, /[, initial])

從左到右，將兩個引數的 function 累加運用到 iterable 的項目上，從而將可疊代物件減少為單一值。例如，reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) 會計算出 ((((1+2)+3)+4)+5)。左邊的引數 x 是累積值，右邊的引數 y 是來自 iterable 的更新值。如果可選的 initial 存在，則在計算中會將其放置在可疊代物件的項目之前，並在可疊代物件為空時作為預設值。如果未給定 initial 且 iterable 僅包含一個項目，則回傳第一個項目。

大致相當於：

initial_missing = object()

def reduce(function, iterable, /, initial=initial_missing):
    it = iter(iterable)
    if initial is initial_missing:
        value = next(it)
    else:
        value = initial
    for element in it:
        value = function(value, element)
    return value

請參閱 itertools.accumulate() 以了解產生 (yield) 所有中間值 (intermediate value) 的疊代器。

在 3.14 版的變更: initial is now supported as a keyword argument.

@functools.singledispatch

將函式轉換為單一調度泛型函式。

若要定義泛型函式，請使用 @singledispatch 裝飾器對其裝飾。請注意，使用 @singledispatch 定義函式時，分派調度 (dispatch) 是發生在第一個引數的型別上：

>>> from functools import singledispatch
>>> @singledispatch
... def fun(arg, verbose=False):
...     if verbose:
...         print("Let me just say,", end=" ")
...     print(arg)

若要為函式新增過載實作，請使用泛型函式的 register() 屬性，該屬性可用作裝飾器。對於以型別來註釋的函式，裝飾器將自動推斷第一個引數的型別：

>>> @fun.register
... def _(arg: int, verbose=False):
...     if verbose:
...         print("Strength in numbers, eh?", end=" ")
...     print(arg)
...
>>> @fun.register
... def _(arg: list, verbose=False):
...     if verbose:
...         print("Enumerate this:")
...     for i, elem in enumerate(arg):
...         print(i, elem)

也可以使用 typing.Union：

>>> @fun.register
... def _(arg: int | float, verbose=False):
...     if verbose:
...         print("Strength in numbers, eh?", end=" ")
...     print(arg)
...
>>> from typing import Union
>>> @fun.register
... def _(arg: Union[list, set], verbose=False):
...     if verbose:
...         print("Enumerate this:")
...     for i, elem in enumerate(arg):
...         print(i, elem)
...

對於不使用型別註釋的程式碼，可以將適當的型別引數明確傳遞給裝飾器本身：

>>> @fun.register(complex)
... def _(arg, verbose=False):
...     if verbose:
...         print("Better than complicated.", end=" ")
...     print(arg.real, arg.imag)
...

For code that dispatches on a collections type (e.g., list), but wants to typehint the items of the collection (e.g., list[int]), the dispatch type should be passed explicitly to the decorator itself with the typehint going into the function definition:

>>> @fun.register(list)
... def _(arg: list[int], verbose=False):
...     if verbose:
...         print("Enumerate this:")
...     for i, elem in enumerate(arg):
...         print(i, elem)

備註

At runtime the function will dispatch on an instance of a list regardless of the type contained within the list i.e. [1,2,3] will be dispatched the same as ["foo", "bar", "baz"]. The annotation provided in this example is for static type checkers only and has no runtime impact.

若要啟用註冊 lambdas 和預先存在的函式，register() 屬性也能以函式形式使用：

>>> def nothing(arg, verbose=False):
...     print("Nothing.")
...
>>> fun.register(type(None), nothing)

register() 屬性回傳未加裝飾器的函式。這讓使得裝飾器堆疊 (decorator stacking)、pickling 以及為每個變體獨立建立單元測試成為可能：

>>> @fun.register(float)
... @fun.register(Decimal)
... def fun_num(arg, verbose=False):
...     if verbose:
...         print("Half of your number:", end=" ")
...     print(arg / 2)
...
>>> fun_num is fun
False

呼叫時，泛型函式會分派第一個引數的型別：

>>> fun("Hello, world.")
Hello, world.
>>> fun("test.", verbose=True)
Let me just say, test.
>>> fun(42, verbose=True)
Strength in numbers, eh? 42
>>> fun(['spam', 'spam', 'eggs', 'spam'], verbose=True)
Enumerate this:
0 spam
1 spam
2 eggs
3 spam
>>> fun(None)
Nothing.
>>> fun(1.23)
0.615

如果沒有為特定型別註冊實作，則使用其方法解析順序 (method resolution order) 來尋找更通用的實作。用 @singledispatch 裝飾的原始函式是為基底 object 型別註冊的，這意味著如果沒有找到更好的實作就會使用它。

如果一個實作有被註冊到一個抽象基底類別，則基底類別的虛擬子類別將被分派到該實作：

>>> from collections.abc import Mapping
>>> @fun.register
... def _(arg: Mapping, verbose=False):
...     if verbose:
...         print("Keys & Values")
...     for key, value in arg.items():
...         print(key, "=>", value)
...
>>> fun({"a": "b"})
a => b

若要檢查泛型函式將為給定型別選擇哪種實作，請使用 dispatch() 屬性：

>>> fun.dispatch(float)
<function fun_num at 0x1035a2840>
>>> fun.dispatch(dict)    # note: default implementation
<function fun at 0x103fe0000>

若要存取所有已註冊的實作，請使用唯讀 registry 屬性：

>>> fun.registry.keys()
dict_keys([<class 'NoneType'>, <class 'int'>, <class 'object'>,
          <class 'decimal.Decimal'>, <class 'list'>,
          <class 'float'>])
>>> fun.registry[float]
<function fun_num at 0x1035a2840>
>>> fun.registry[object]
<function fun at 0x103fe0000>

在 3.4 版被加入.

在 3.7 版的變更: register() 屬性現在支援使用型別註釋。

在 3.11 版的變更: register() 屬性現在支援使用 typing.Union 型別註釋。

class functools.singledispatchmethod(func)

將方法轉換為單一調度泛型函式。

若要定義泛型方法，請使用 @singledispatchmethod 裝飾器對其裝飾。請注意，使用 @singledispatchmethod 定義方法時，分派調度是發生在第一個非 self 或非 cls 引數的型別上：

class Negator:
    @singledispatchmethod
    def neg(self, arg):
        raise NotImplementedError("Cannot negate a")

    @neg.register
    def _(self, arg: int):
        return -arg

    @neg.register
    def _(self, arg: bool):
        return not arg

@singledispatchmethod 支援與其他裝飾器巢狀使用 (nesting)，例如 @classmethod。請注意，為了使 dispatcher.register 可用，singledispatchmethod 必須是最外面的裝飾器。以下範例是 Negator 類別，其 neg 方法繫結到該類別，而不是該類別的實例：

class Negator:
    @singledispatchmethod
    @classmethod
    def neg(cls, arg):
        raise NotImplementedError("Cannot negate a")

    @neg.register
    @classmethod
    def _(cls, arg: int):
        return -arg

    @neg.register
    @classmethod
    def _(cls, arg: bool):
        return not arg

相同的模式可用於其他類似的裝飾器：@staticmethod、@~abc.abstractmethod 等。

在 3.8 版被加入.

functools.update_wrapper(wrapper, wrapped, assigned=WRAPPER_ASSIGNMENTS, updated=WRAPPER_UPDATES)

更新 wrapper 函式，使其看起來像 wrapped 函式。可選引數是元組，用於指定原始函式的哪些屬性直接賦值給包裝函式上的匹配屬性，以及包裝函式的哪些屬性使用原始函式中的對應屬性進行更新。這些引數的預設值是模組層級的常數 WRAPPER_ASSIGNMENTS（它賦值給包裝函式的 __module__、__name__、__qualname__、__annotations__、__type_params__ 和 __doc__ 文件字串 (docstring））和 WRAPPER_UPDATES（更新包裝器函式的 __dict__，即實例字典）。

為了允許出於內省 (introspection) 和其他目的所對原始函式的存取（例如繞過快取裝飾器，如 lru_cache()），此函式會自動向包裝器新增 __wrapped__ 屬性，該包裝器參照被包裝的函式。

此函式的主要用途是在 decorator 函式中，它包裝函式並回傳包裝器。如果包裝器函式未更新，則回傳函式的元資料 (metadata) 將反映包裝器定義而非原始函式定義，這通常不太會有幫助。

update_wrapper() 可以與函式以外的可呼叫物件一起使用。被包裝的物件中缺少的 assigned 或 updated 中指定的任何屬性都將被忽略（即此函式不會嘗試在包裝器函式上設定它們）。如果包裝函式本身缺少 updated 中指定的任何屬性，仍然會引發 AttributeError。

在 3.2 版的變更: 現在會自動新增 __wrapped__ 屬性。現在預設會複製 __annotations__ 屬性。缺少的屬性不再觸發 AttributeError。

在 3.4 版的變更: __wrapped__ 屬性現在都會參照包裝函式，即便函式有定義 __wrapped__ 屬性。（參見 bpo-17482 [https://bugs.python.org/issue?@action=redirect&bpo=17482]）

在 3.12 版的變更: 現在預設會複製 __type_params__ 屬性。

@functools.wraps(wrapped, assigned=WRAPPER_ASSIGNMENTS, updated=WRAPPER_UPDATES)

這是一個方便的函式，用於在定義包裝器函式時呼叫 update_wrapper() 作為函式裝飾器。它相當於 partial(update_wrapper, wrapped=wrapped, assigned=assigned, updated=updated)。例如：

>>> from functools import wraps
>>> def my_decorator(f):
...     @wraps(f)
...     def wrapper(*args, **kwds):
...         print('Calling decorated function')
...         return f(*args, **kwds)
...     return wrapper
...
>>> @my_decorator
... def example():
...     """Docstring"""
...     print('Called example function')
...
>>> example()
Calling decorated function
Called example function
>>> example.__name__
'example'
>>> example.__doc__
'Docstring'

如果不使用這個裝飾器工廠 (decorator factory)，範例函式的名稱將會是 'wrapper'，並且原始 example() 的文件字串將會遺失。

partial 物件

partial 物件是由 partial() 所建立的可呼叫物件。它們有三個唯讀屬性：

partial.func

一個可呼叫的物件或函式。對 partial 物件的呼叫將被轉送到帶有新引數和關鍵字的 func。

partial.args

最左邊的位置引數將會被加入到提供給 partial 物件呼叫的位置引數的前面。

partial.keywords

呼叫 partial 物件時將提供的關鍵字引數。

partial 物件與函式物件類似，因為它們是可呼叫的、可弱參照的 (weak referencable) 且可以具有屬性的。但有一些重要的區別，例如，__name__ 和 __doc__ 屬性不會自動建立。

operator --- 標準運算子替代函式

原始碼：Lib/operator.py [https://github.com/python/cpython/tree/3.14/Lib/operator.py]

operator module（模組）提供了一套與 Python 原生運算子對應的高效率函式。例如，operator.add(x, y) 與表示式 x+y 相同。許多函式名與特殊方法名相同，只是沒有雙底線。為了向後相容，許多包含雙底線的函式被保留了下來，但為了易於表達，建議使用沒有雙底線的函式。

函式種類有物件的比較運算、邏輯運算、數學運算以及序列運算。

物件比較函式適用於所有物件，函式根據它們對應的 rich comparison 運算子命名：

operator.lt(a, b)

operator.le(a, b)

operator.eq(a, b)

operator.ne(a, b)

operator.ge(a, b)

operator.gt(a, b)

operator.__lt__(a, b)

operator.__le__(a, b)

operator.__eq__(a, b)

operator.__ne__(a, b)

operator.__ge__(a, b)

operator.__gt__(a, b)

在 a 和 b 之間進行 "rich comparison"。具體來說，lt(a, b) 與 a < b 相同，le(a, b) 與 a <= b 相同，eq(a, b) 與 a == b 相同，ne(a, b) 與 a != b 相同，gt(a, b) 與 a > b 相同，ge(a, b) 與 a >= b 相同。注意這些函式可以回傳任何值，無論它是否可當作 boolean（布林）值。關於 rich comparison 的更多資訊請參考 Comparisons。

邏輯運算通常也適用於所有物件，並且支援真值檢測、識別性測試和 boolean 運算：

operator.not_(obj)

operator.__not__(obj)

回傳 not obj 的結果。（請注意物件實例並沒有 __not__() method（方法）；只有直譯器核心定義此操作。結果會受 __bool__() 和 __len__() method 影響。）

operator.truth(obj)

如果 obj 為真值則回傳 True，否則回傳 False。這等價於使用 bool 建構函式。

operator.is_(a, b)

回傳 a is b。測試物件識別性。

operator.is_not(a, b)

回傳 a is not b。測試物件識別性。

operator.is_none(a)

回傳 a is None。測試物件識別性。

在 3.14 版被加入.

operator.is_not_none(a)

回傳 a is not None。測試物件識別性。

在 3.14 版被加入.

數學和位元運算的種類是最多的：

operator.abs(obj)

operator.__abs__(obj)

回傳 obj 的絕對值。

operator.add(a, b)

operator.__add__(a, b)

對於數字 a 和 b，回傳 a + b。

operator.and_(a, b)

operator.__and__(a, b)

回傳 x 和 y 位元運算與 (and) 的結果。

operator.floordiv(a, b)

operator.__floordiv__(a, b)

回傳 a // b。

operator.index(a)

operator.__index__(a)

回傳 a 轉換為整數的結果。等價於 a.__index__()。

在 3.10 版的變更: 結果總是 int 型別。在過去的版本中，結果可能為 int 子類別的實例。

operator.inv(obj)

operator.invert(obj)

operator.__inv__(obj)

operator.__invert__(obj)

回傳數字 obj 按位元取反 (inverse) 的結果。這等價於 ~obj。

operator.lshift(a, b)

operator.__lshift__(a, b)

回傳 a 左移 b 位的結果。

operator.mod(a, b)

operator.__mod__(a, b)

回傳 a % b。

operator.mul(a, b)

operator.__mul__(a, b)

對於數字 a 和 b，回傳 a * b。

operator.matmul(a, b)

operator.__matmul__(a, b)

回傳 a @ b。

在 3.5 版被加入.

operator.neg(obj)

operator.__neg__(obj)

回傳 obj 取負值的結果 (-obj)。

operator.or_(a, b)

operator.__or__(a, b)

回傳 a 和 b 按位元或 (or) 的結果。

operator.pos(obj)

operator.__pos__(obj)

回傳 obj 取正的結果 (+obj)。

operator.pow(a, b)

operator.__pow__(a, b)

對於數字 a 和 b，回傳 a ** b。

operator.rshift(a, b)

operator.__rshift__(a, b)

回傳 a 右移 b 位的結果。

operator.sub(a, b)

operator.__sub__(a, b)

回傳 a - b。

operator.truediv(a, b)

operator.__truediv__(a, b)

回傳 a / b，例如 2/3 將等於 .66 而不是 0。這也被稱為「真」除法。

operator.xor(a, b)

operator.__xor__(a, b)

回傳 a 和 b 按位元異或 (exclusive or) 的結果。

適用於序列的操作（其中一些也適用於對映 (mapping)），包括：

operator.concat(a, b)

operator.__concat__(a, b)

對於序列 a 和 b，回傳 a + b。

operator.contains(a, b)

operator.__contains__(a, b)

回傳 b in a 檢測的結果。請注意運算元是反序的。

operator.countOf(a, b)

回傳 b 在 a 中的出現次數。

operator.delitem(a, b)

operator.__delitem__(a, b)

移除 a 中索引為 b 的值。

operator.getitem(a, b)

operator.__getitem__(a, b)

回傳 a 中索引為 b 的值。

operator.indexOf(a, b)

回傳 b 在 a 中首次出現所在的索引。

operator.setitem(a, b, c)

operator.__setitem__(a, b, c)

將 a 中索引為 b 的值設為 c。

operator.length_hint(obj, default=0)

回傳物件 obj 的估計長度。首先嘗試回傳其實際長度，再使用 object.__length_hint__() 得出估計值，最後才是回傳預設值。

在 3.4 版被加入.

以下操作適用於可呼叫物件：

operator.call(obj, /, *args, **kwargs)

operator.__call__(obj, /, *args, **kwargs)

回傳 obj(*args, **kwargs)。

在 3.11 版被加入.

operator module 還定義了一些用於常規屬性和條目查詢的工具。這些工具適合用來編寫快速欄位提取器以作為 map()、sorted()、itertools.groupby() 或其他需要函式引數的函式之引數。

operator.attrgetter(attr)

operator.attrgetter(*attrs)

回傳一個可從運算元中取得 attr 的可呼叫 (callable) 物件。如果請求了一個以上的屬性，則回傳一個包含屬性的 tupple（元組）。屬性名稱還可包含點號。例如：

在 f = attrgetter('name') 之後，呼叫 f(b) 將回傳 b.name。

在 f = attrgetter('name', 'date') 之後，呼叫 f(b) 將回傳 (b.name, b.date)。

在 f = attrgetter('name.first', 'name.last') 之後，呼叫 f(b) 將回傳 (b.name.first, b.name.last)。

等價於：

def attrgetter(*items):
    if any(not isinstance(item, str) for item in items):
        raise TypeError('屬性名稱必須是一個字串')
    if len(items) == 1:
        attr = items[0]
        def g(obj):
            return resolve_attr(obj, attr)
    else:
        def g(obj):
            return tuple(resolve_attr(obj, attr) for attr in items)
    return g

def resolve_attr(obj, attr):
    for name in attr.split("."):
        obj = getattr(obj, name)
    return obj

operator.itemgetter(item)

operator.itemgetter(*items)

回傳一個使用運算元的 __getitem__() 方法從運算元中取得 item 的可呼叫物件。如果指定了多個條目，則回傳一個查詢值的 tupple。例如：

在 f = itemgetter(2) 之後，呼叫 f(r) 將回傳 r[2]。

在 g = itemgetter(2, 5, 3) 之後，呼叫 g(r) 將回傳 (r[2], r[5], r[3])。

等價於：

def itemgetter(*items):
    if len(items) == 1:
        item = items[0]
        def g(obj):
            return obj[item]
    else:
        def g(obj):
            return tuple(obj[item] for item in items)
    return g

傳入的條目可以為運算元的 __getitem__() 所接受的任何型別。dictionary（字典）接受任意可雜湊的值。list、tupple 和字串接受索引或切片：

>>> itemgetter(1)('ABCDEFG')
'B'
>>> itemgetter(1, 3, 5)('ABCDEFG')
('B', 'D', 'F')
>>> itemgetter(slice(2, None))('ABCDEFG')
'CDEFG'
>>> soldier = dict(rank='captain', name='dotterbart')
>>> itemgetter('rank')(soldier)
'captain'

使用 itemgetter() 從 tuple 中提取特定欄位的例子：

>>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)]
>>> getcount = itemgetter(1)
>>> list(map(getcount, inventory))
[3, 2, 5, 1]
>>> sorted(inventory, key=getcount)
[('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)]

operator.methodcaller(name, /, *args, **kwargs)

回傳一個在運算元上呼叫 name method 的可呼叫物件。如果給定額外的引數和/或關鍵字引數，它們也將被傳給該 method。例如：

在 f = methodcaller('name') 之後，呼叫 f(b) 將回傳 b.name()。

在 f = methodcaller('name', 'foo', bar=1) 之後，呼叫 f(b) 將回傳 b.name('foo', bar=1)。

等價於：

def methodcaller(name, /, *args, **kwargs):
    def caller(obj):
        return getattr(obj, name)(*args, **kwargs)
    return caller

運算子與函式間的對映

以下表格表示了抽象運算是如何對應於 Python 語法中的運算子和 operator module中的函式。

運算

語法

函式

加法

a + b

add(a, b)

字串串接

seq1 + seq2

concat(seq1, seq2)

包含性檢測

obj in seq

contains(seq, obj)

除法

a / b

truediv(a, b)

除法

a // b

floordiv(a, b)

按位元與 (And)

a & b

and_(a, b)

按位元互斥或 (Exclusive Or)

a ^ b

xor(a, b)

按位元取反 (Inversion)

~ a

invert(a)

按位元或 (Or)

a | b

or_(a, b)

取冪

a ** b

pow(a, b)

識別性

a is b

is_(a, b)

識別性

a is not b

is_not(a, b)

識別性

a is None

is_none(a)

識別性

a is not None

is_not_none(a)

索引賦值

obj[k] = v

setitem(obj, k, v)

索引刪除

del obj[k]

delitem(obj, k)

索引取值

obj[k]

getitem(obj, k)

左移

a << b

lshift(a, b)

模除 (Modulo)

a % b

mod(a, b)

乘法

a * b

mul(a, b)

矩陣乘法

a @ b

matmul(a, b)

反相（算術）

- a

neg(a)

反相（邏輯）

not a

not_(a)

正數

+ a

pos(a)

右移

a >> b

rshift(a, b)

切片賦值

seq[i:j] = values

setitem(seq, slice(i, j), values)

切片刪除

del seq[i:j]

delitem(seq, slice(i, j))

切片取值

seq[i:j]

getitem(seq, slice(i, j))

字串格式化

s % obj

mod(s, obj)

減法

a - b

sub(a, b)

真值檢測

obj

truth(obj)

比較大小

a < b

lt(a, b)

比較大小

a <= b

le(a, b)

相等性

a == b

eq(a, b)

不等性

a != b

ne(a, b)

比較大小

a >= b

ge(a, b)

比較大小

a > b

gt(a, b)

原地 (in-place) 運算子

許多運算都有「原地」版本。以下列出的是提供對原地運算子（與一般語法相比）更底層存取的函式，例如 statement x += y 相當於 x = operator.iadd(x, y)。換一種方式來講就是 z = operator.iadd(x, y) 等價於複合陳述式 z = x; z += y。

在這些例子中，請注意當呼叫一個原地方法時，運算和賦值是分成兩個步驟來執行的。下面列出的原地函式只執行第一步，即呼叫原地方法，第二步賦值則不加處理。

對於不可變 (immutable) 的目標例如字串、數字和 tupple，更新的值會被計算，但不會被再被賦值給輸入變數：

>>> a = 'hello'
>>> iadd(a, ' world')
'hello world'
>>> a
'hello'

對於可變 (mutable) 的目標例如 list 和 dictionary，原地方法將執行更新，因此不需要後續賦值操作：

>>> s = ['h', 'e', 'l', 'l', 'o']
>>> iadd(s, [' ', 'w', 'o', 'r', 'l', 'd'])
['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']
>>> s
['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']

operator.iadd(a, b)

operator.__iadd__(a, b)

a = iadd(a, b) 等價於 a += b。

operator.iand(a, b)

operator.__iand__(a, b)

a = iand(a, b) 等價於 a &= b。

operator.iconcat(a, b)

operator.__iconcat__(a, b)

a = iconcat(a, b) 等價於 a += b，其中 a 和 b 為序列。

operator.ifloordiv(a, b)

operator.__ifloordiv__(a, b)

a = ifloordiv(a, b) 等價於 a //= b。

operator.ilshift(a, b)

operator.__ilshift__(a, b)

a = ilshift(a, b) 等價於 a <<= b。

operator.imod(a, b)

operator.__imod__(a, b)

a = imod(a, b) 等價於 a %= b。

operator.imul(a, b)

operator.__imul__(a, b)

a = imul(a, b) 等價於 a *= b。

operator.imatmul(a, b)

operator.__imatmul__(a, b)

a = imatmul(a, b) 等價於 a @= b。

在 3.5 版被加入.

operator.ior(a, b)

operator.__ior__(a, b)

a = ior(a, b) 等價於 a |= b。

operator.ipow(a, b)

operator.__ipow__(a, b)

a = ipow(a, b) 等價於 a **= b。

operator.irshift(a, b)

operator.__irshift__(a, b)

a = irshift(a, b) 等價於 a >>= b。

operator.isub(a, b)

operator.__isub__(a, b)

a = isub(a, b) 等價於 a -= b。

operator.itruediv(a, b)

operator.__itruediv__(a, b)

a = itruediv(a, b) 等價於 a /= b。

operator.ixor(a, b)

operator.__ixor__(a, b)

a = ixor(a, b) 等價於 a ^= b。

檔案與目錄存取

本章中描述的 module（模組）用於處理硬碟檔案和目錄。例如，有一些 module 用於讀取檔案的屬性、以可攜 (portable) 方式操作路徑以及建立暫存檔。本章中的完整 module 清單是：

pathlib --- 物件導向檔案系統路徑

基本用法

例外

純路徑

通用屬性

運算子

對個別組成的存取

方法與屬性

實體路徑

剖析和產生 URI

擴展和解析路徑

查詢檔案類型和狀態

讀取和寫入檔案

讀取目錄

建立檔案和目錄

複製、移動和刪除

權限和所有權

模式語言 (pattern language)

與 glob 模組的比較

與 os 和 os.path 模組的比較

對應工具

Protocols

os.path --- 常見的路徑名操作

stat --- 直譯 stat() 的結果

filecmp --- 檔案與目錄比較

The dircmp class

tempfile --- 生成臨時檔案和目錄

範例

已棄用的函式和變數

glob --- Unix 風格的路徑名稱模式擴展

範例

fnmatch --- Unix 檔案名稱模式比對

linecache --- 隨機存取文字列

shutil — 高階檔案操作

目錄和檔案操作

Platform-dependent efficient copy operations

copytree 範例

rmtree 範例

Archiving operations

Archiving example

Archiving example with base_dir

Querying the size of the output terminal

也參考

Module os

作業系統介面，包括處理比 Python 檔案物件更低階檔案的函式。

Module io

Python 的內建 I/O 函式庫，包含抽象類別和一些具體類別 (concrete class)，如檔案 I/O。

內建函式 open()

使用 Python 打開檔案以進行讀寫檔案的標準方法。

pathlib --- 物件導向檔案系統路徑

在 3.4 版被加入.

原始碼：Lib/pathlib/ [https://github.com/python/cpython/tree/3.14/Lib/pathlib/]

此模組提供代表檔案系統路徑的類別，能適用不同作業系統的語意。路徑類別分成兩種，一種是純路徑 (pure paths)，提供沒有 I/O 的單純計算操作，另一種是實體路徑 (concrete paths)，繼承自純路徑但也提供 IO 操作。

如果你之前從未使用過此模組或不確定哪個類別適合你的任務，那你需要的最有可能是 Path。它針對程式執行所在的平台實例化一個實體路徑。

純路徑在某些特殊情境下是有用的，例如：

如果你想在 Unix 機器上處理 Windows 路徑（或反過來），你無法在 Unix 上實例化 WindowsPath，但你可以實例化 PureWindowsPath。

你想確保你的程式在操作路徑的時候不會真的存取到 OS。在這個情況下，實例化其中一種純路徑類別可能是有用的，因為它們不會有任何存取 OS 的操作。

也參考

PEP 428 [https://peps.python.org/pep-0428/]：pathlib 模組 -- 物件導向檔案系統路徑。

也參考

針對字串上的底層路徑操作，你也可以使用 os.path 模組。

基本用法

匯入主要類別：

>>> from pathlib import Path

列出子目錄：

>>> p = Path('.')
>>> [x for x in p.iterdir() if x.is_dir()]
[PosixPath('.hg'), PosixPath('docs'), PosixPath('dist'),
 PosixPath('__pycache__'), PosixPath('build')]

在目前目錄樹下列出 Python 原始碼檔案：

>>> list(p.glob('**/*.py'))
[PosixPath('test_pathlib.py'), PosixPath('setup.py'),
 PosixPath('pathlib.py'), PosixPath('docs/conf.py'),
 PosixPath('build/lib/pathlib.py')]

瀏覽目錄樹內部：

>>> p = Path('/etc')
>>> q = p / 'init.d' / 'reboot'
>>> q
PosixPath('/etc/init.d/reboot')
>>> q.resolve()
PosixPath('/etc/rc.d/init.d/halt')

查詢路徑屬性：

>>> q.exists()
True
>>> q.is_dir()
False

開啟檔案：

>>> with q.open() as f: f.readline()
...
'#!/bin/bash\n'

例外

exception pathlib.UnsupportedOperation

繼承自 NotImplementedError 的例外，當在路徑物件上呼叫不支援的操作時會被引發。

在 3.13 版被加入.

純路徑

純路徑物件提供處理路徑的操作，實際上不會存取檔案系統。有三種方式可以存取這些類別，我們也稱之為類型 (flavours)：

class pathlib.PurePath(*pathsegments)

一個通用的類別，表示系統的路徑類型（實例化時會建立一個 PurePosixPath 或 PureWindowsPath)：

>>> PurePath('setup.py')      # 執行在 Unix 機器上
PurePosixPath('setup.py')

pathsegments 中的每個元素可以是以下的其中一種：一個表示路徑片段的字串，或一個物件，它實作了 os.PathLike 介面且其中的 __fspath__() 方法會回傳字串，就像是另一個路徑物件：

>>> PurePath('foo', 'some/path', 'bar')
PurePosixPath('foo/some/path/bar')
>>> PurePath(Path('foo'), Path('bar'))
PurePosixPath('foo/bar')

當沒有給 pathsegments 的時候，會假設是目前的目錄：

>>> PurePath()
PurePosixPath('.')

如果一個片段是絕對路徑，則所有之前的片段會被忽略（類似 os.path.join())：

>>> PurePath('/etc', '/usr', 'lib64')
PurePosixPath('/usr/lib64')
>>> PureWindowsPath('c:/Windows', 'd:bar')
PureWindowsPath('d:bar')

在 Windows 系統上，當遇到具有根目錄的相對路徑片段（例如 r'\foo'）時，磁碟機 (drive) 部分不會被重置：

>>> PureWindowsPath('c:/Windows', '/Program Files')
PureWindowsPath('c:/Program Files')

不必要的斜線和單點會被合併，但雙點 ('..') 和前置的雙斜線 ('//') 不會被合併，因為這樣會因為各種原因改變路徑的意義（例如符號連結 (symbolic links)、UNC 路徑）：

>>> PurePath('foo//bar')
PurePosixPath('foo/bar')
>>> PurePath('//foo/bar')
PurePosixPath('//foo/bar')
>>> PurePath('foo/./bar')
PurePosixPath('foo/bar')
>>> PurePath('foo/../bar')
PurePosixPath('foo/../bar')

（一個使得 PurePosixPath('foo/../bar') 等同於 PurePosixPath('bar') 的單純方法，但如果 foo 是指到另一個目錄的符號連結，就會是錯誤的。）

純路徑物件實作了 os.PathLike 介面，使得它們可以在任何接受該介面的地方使用。

在 3.6 版的變更: 新增了對於 os.PathLike 介面的支援。

class pathlib.PurePosixPath(*pathsegments)

PurePath 的一個子類別，該路徑類型表示非 Windows 檔案系統的路徑：

>>> PurePosixPath('/etc/hosts')
PurePosixPath('/etc/hosts')

pathsegments 的指定方式與 PurePath 類似。

class pathlib.PureWindowsPath(*pathsegments)

PurePath 的一個子類別，該路徑類型表示 Windows 檔案系統的路徑，包括 UNC paths [https://en.wikipedia.org/wiki/Path_(computing)#UNC]：

>>> PureWindowsPath('c:/', 'Users', 'Ximénez')
PureWindowsPath('c:/Users/Ximénez')
>>> PureWindowsPath('//server/share/file')
PureWindowsPath('//server/share/file')

pathsegments 的指定方式與 PurePath 類似。

不論你使用的是什麼系統，你都可以實例化這些類別，因為它們不提供任何涉及系統呼叫的操作。

通用屬性

路徑物件是不可變 (immutable) 且可雜湊 (hashable) 的。相同類型的路徑物件可以被比較和排序。這些屬性遵守該類型的大小寫語意規則：

>>> PurePosixPath('foo') == PurePosixPath('FOO')
False
>>> PureWindowsPath('foo') == PureWindowsPath('FOO')
True
>>> PureWindowsPath('FOO') in { PureWindowsPath('foo') }
True
>>> PureWindowsPath('C:') < PureWindowsPath('d:')
True

不同類型的路徑物件在比較時視為不相等且無法被排序：

>>> PureWindowsPath('foo') == PurePosixPath('foo')
False
>>> PureWindowsPath('foo') < PurePosixPath('foo')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '<' not supported between instances of 'PureWindowsPath' and 'PurePosixPath'

運算子

斜線運算子 (slash operator) 用於建立子路徑，就像是 os.path.join() 函式一樣。如果引數是絕對路徑，則忽略前一個路徑。在 Windows 系統上，當引數是具有根目錄的相對路徑（例如，r'\foo'），磁碟機部分不會被重置：

>>> p = PurePath('/etc')
>>> p
PurePosixPath('/etc')
>>> p / 'init.d' / 'apache2'
PurePosixPath('/etc/init.d/apache2')
>>> q = PurePath('bin')
>>> '/usr' / q
PurePosixPath('/usr/bin')
>>> p / '/an_absolute_path'
PurePosixPath('/an_absolute_path')
>>> PureWindowsPath('c:/Windows', '/Program Files')
PureWindowsPath('c:/Program Files')

路徑物件可以被用在任何可以接受實作 os.PathLike 的物件的地方：

>>> import os
>>> p = PurePath('/etc')
>>> os.fspath(p)
'/etc'

路徑的字串表示是原始的檔案系統路徑本身（以原生的形式，例如在 Windows 下是反斜線），你可以將其傳入任何將檔案路徑當作字串傳入的函式：

>>> p = PurePath('/etc')
>>> str(p)
'/etc'
>>> p = PureWindowsPath('c:/Program Files')
>>> str(p)
'c:\\Program Files'

類似地，對路徑呼叫 bytes 會得到原始檔案系統路徑的 bytes 物件，就像使用 os.fsencode() 編碼過的一樣：

>>> bytes(p)
b'/etc'

備註

只建議在 Unix 下呼叫 bytes。在 Windows 裡，unicode 形式是檔案系統路徑的權威表示方式。

對個別組成的存取

可以使用下列屬性來存取路徑的個別「組成」(parts, components)：

PurePath.parts

一個可存取路徑的各組成的元組：

>>> p = PurePath('/usr/bin/python3')
>>> p.parts
('/', 'usr', 'bin', 'python3')

>>> p = PureWindowsPath('c:/Program Files/PSF')
>>> p.parts
('c:\\', 'Program Files', 'PSF')

（特別注意磁碟機跟本地根目錄是如何被重新組合成一個單一組成）

方法與屬性

純路徑提供以下方法與屬性：

PurePath.parser

用於底層路徑剖析和結合的 os.path 模組的實作：可能是 posixpath 或 ntpath。

在 3.13 版被加入.

PurePath.drive

若存在則為一個表示磁碟機字母 (drive letter) 或磁碟機名稱 (drive name) 的字串：

>>> PureWindowsPath('c:/Program Files/').drive
'c:'
>>> PureWindowsPath('/Program Files/').drive
''
>>> PurePosixPath('/etc').drive
''

UNC shares 也被視為磁碟機：

>>> PureWindowsPath('//host/share/foo.txt').drive
'\\\\host\\share'

PurePath.root

若存在則為一個表示（本地或全域）根目錄的字串：

>>> PureWindowsPath('c:/Program Files/').root
'\\'
>>> PureWindowsPath('c:Program Files/').root
''
>>> PurePosixPath('/etc').root
'/'

UNC shares 都會有一個根目錄：

>>> PureWindowsPath('//host/share').root
'\\'

如果路徑以超過兩個連續的斜線開頭，PurePosixPath 會合併它們：

>>> PurePosixPath('//etc').root
'//'
>>> PurePosixPath('///etc').root
'/'
>>> PurePosixPath('////etc').root
'/'

備註

此行為符合 The Open Group Base Specifications Issue 6，章節 4.11 路徑名稱解析 [https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap04.html#tag_04_11]：

「以兩個連續斜線開頭的路徑名稱可以根據實作定義的方式來解讀，儘管如此，開頭超過兩個斜線應該視為單一斜線。」

PurePath.anchor

磁碟機與根目錄的結合：

>>> PureWindowsPath('c:/Program Files/').anchor
'c:\\'
>>> PureWindowsPath('c:Program Files/').anchor
'c:'
>>> PurePosixPath('/etc').anchor
'/'
>>> PureWindowsPath('//host/share').anchor
'\\\\host\\share\\'

PurePath.parents

一個不可變的序列，為路徑邏輯上的祖先 (logical ancestors) 提供存取：

>>> p = PureWindowsPath('c:/foo/bar/setup.py')
>>> p.parents[0]
PureWindowsPath('c:/foo/bar')
>>> p.parents[1]
PureWindowsPath('c:/foo')
>>> p.parents[2]
PureWindowsPath('c:/')

在 3.10 版的變更: 父序列現在支援 slices 及負的索引值。

PurePath.parent

邏輯上的父路徑：

>>> p = PurePosixPath('/a/b/c/d')
>>> p.parent
PurePosixPath('/a/b/c')

你不能越過一個 anchor 或空路徑：

>>> p = PurePosixPath('/')
>>> p.parent
PurePosixPath('/')
>>> p = PurePosixPath('.')
>>> p.parent
PurePosixPath('.')

備註

這是一個純粹字句上的 (lexical) 運算，因此會有以下行為：

>>> p = PurePosixPath('foo/..')
>>> p.parent
PurePosixPath('foo')

如果你想要沿任意的檔案系統路徑往上走，建議要先呼叫 Path.resolve() 來解析符號連結 (symlink) 及去除其中的 ”..”。

PurePath.name

最後的路徑組成 (final path component) 的字串表示，不包含任何磁碟機或根目錄：

>>> PurePosixPath('my/library/setup.py').name
'setup.py'

UNC 磁碟機名稱並沒有算在內：

>>> PureWindowsPath('//some/share/setup.py').name
'setup.py'
>>> PureWindowsPath('//some/share').name
''

PurePath.suffix

以點分隔路徑的最後一個部分（如存在）：

>>> PurePosixPath('my/library/setup.py').suffix
'.py'
>>> PurePosixPath('my/library.tar.gz').suffix
'.gz'
>>> PurePosixPath('my/library').suffix
''

這通常被稱為檔案副檔名。

在 3.14 版的變更: A single dot (".") is considered a valid suffix.

PurePath.suffixes

一個路徑後綴 (suffix) 的串列，通常被稱為檔案副檔名：

>>> PurePosixPath('my/library.tar.gar').suffixes
['.tar', '.gar']
>>> PurePosixPath('my/library.tar.gz').suffixes
['.tar', '.gz']
>>> PurePosixPath('my/library').suffixes
[]

在 3.14 版的變更: A single dot (".") is considered a valid suffix.

PurePath.stem

最後的路徑組成，不包括後綴：

>>> PurePosixPath('my/library.tar.gz').stem
'library.tar'
>>> PurePosixPath('my/library.tar').stem
'library'
>>> PurePosixPath('my/library').stem
'library'

PurePath.as_posix()

回傳一個使用正斜線 (/) 的路徑的字串表示：

>>> p = PureWindowsPath('c:\\windows')
>>> str(p)
'c:\\windows'
>>> p.as_posix()
'c:/windows'

PurePath.is_absolute()

回傳一個路徑是否是絕對路徑。一個路徑被視為絕對路徑的條件是它同時有根目錄及（如果該系統類型允許的話）磁碟機：

>>> PurePosixPath('/a/b').is_absolute()
True
>>> PurePosixPath('a/b').is_absolute()
False

>>> PureWindowsPath('c:/a/b').is_absolute()
True
>>> PureWindowsPath('/a/b').is_absolute()
False
>>> PureWindowsPath('c:').is_absolute()
False
>>> PureWindowsPath('//some/share').is_absolute()
True

PurePath.is_relative_to(other)

回傳此路徑是否為 other 路徑的相對路徑。

>>> p = PurePath('/etc/passwd')
>>> p.is_relative_to('/etc')
True
>>> p.is_relative_to('/usr')
False

該方法是基於字串的；它既不存取檔案系統，也不特別處理 ".." 片段。以下程式碼是等效的：

>>> u = PurePath('/usr')
>>> u == p or u in p.parents
False

在 3.9 版被加入.

自從版本 3.12 後不推薦使用，已從版本 3.14 中移除。: 額外引數的傳入已棄用；如果有的話，它們會與 other 連接在一起。

PurePath.is_reserved()

對 PureWindowsPath 來說，當路徑在 Windows 下被視為保留的話會回傳 True，否則回傳 False。對 PurePosixPath 來說，總是回傳 False。

在 3.13 版的變更: Windows 路徑名稱中包含冒號或結尾為點或空格會被視為保留。UNC 路徑可能被視為保留。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: 此方法已被棄用；請使用 os.path.isreserved() 來檢測 Windows 上的保留路徑。

PurePath.joinpath(*pathsegments)

呼叫此方法會依序結合每個所給定的 pathsegments 到路徑上：

>>> PurePosixPath('/etc').joinpath('passwd')
PurePosixPath('/etc/passwd')
>>> PurePosixPath('/etc').joinpath(PurePosixPath('passwd'))
PurePosixPath('/etc/passwd')
>>> PurePosixPath('/etc').joinpath('init.d', 'apache2')
PurePosixPath('/etc/init.d/apache2')
>>> PureWindowsPath('c:').joinpath('/Program Files')
PureWindowsPath('c:/Program Files')

PurePath.full_match(pattern, *, case_sensitive=None)

將路徑與 glob 形式的模式 (glob-style pattern) 做比對。如果比對成功則回傳 True，否則回傳 False，例如：

>>> PurePath('a/b.py').full_match('a/*.py')
True
>>> PurePath('a/b.py').full_match('*.py')
False
>>> PurePath('/a/b/c.py').full_match('/a/**')
True
>>> PurePath('/a/b/c.py').full_match('**/*.py')
True

也參考

模式語言 (pattern language) 文件。

像其它方法一樣，是否區分大小寫會遵循平台的預設行為：

>>> PurePosixPath('b.py').full_match('*.PY')
False
>>> PureWindowsPath('b.py').full_match('*.PY')
True

將 case_sensitive 設定成 True 或 False 會覆蓋這個行為。

在 3.13 版被加入.

PurePath.match(pattern, *, case_sensitive=None)

將路徑與非遞迴 glob 形式的模式 (glob-style pattern) 做比對。如果比對成功則回傳 True，否則回傳 False。

此方法類似於 full_match()，但不允許空白模式（會引發 ValueError）、不支援遞迴萬用字元 "**"（它會像非遞迴的 "*" 一樣），且如果提供相對模式，則會從右邊進行比對：

>>> PurePath('a/b.py').match('*.py')
True
>>> PurePath('/a/b/c.py').match('b/*.py')
True
>>> PurePath('/a/b/c.py').match('a/*.py')
False

在 3.12 版的變更: pattern 參數接受類路徑物件。

在 3.12 版的變更: 新增 case_sensitive 參數。

PurePath.relative_to(other, walk_up=False)

計算這個路徑相對於 other 所表示路徑的版本。如果做不到會引發 ValueError：

>>> p = PurePosixPath('/etc/passwd')
>>> p.relative_to('/')
PurePosixPath('etc/passwd')
>>> p.relative_to('/etc')
PurePosixPath('passwd')
>>> p.relative_to('/usr')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pathlib.py", line 941, in relative_to
    raise ValueError(error_message.format(str(self), str(formatted)))
ValueError: '/etc/passwd' is not in the subpath of '/usr' OR one path is relative and the other is absolute.

當 walk_up 是 False（預設值），路徑必須以 other 為開始。當此引數是 True，可能會加入 .. 以組成相對路徑。在其他情況下，例如路徑參考到不同的磁碟機，則會引發 ValueError：

>>> p.relative_to('/usr', walk_up=True)
PurePosixPath('../etc/passwd')
>>> p.relative_to('foo', walk_up=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pathlib.py", line 941, in relative_to
    raise ValueError(error_message.format(str(self), str(formatted)))
ValueError: '/etc/passwd' is not on the same drive as 'foo' OR one path is relative and the other is absolute.

警告

這個函式是 PurePath 的一部分且可以在字串上運作。它不會檢查或存取實際的檔案架構。這會影響到 walk_up 選項，因為它假設路徑中沒有符號連結；如果需要解析符號連結的話可以先呼叫 resolve()。

在 3.12 版的變更: 加入 walk_up 參數（舊的行為和 walk_up=False 相同）。

自從版本 3.12 後不推薦使用，已從版本 3.14 中移除。: 額外位置引數的傳入已棄用；如果有的話，它們會與 other 連接在一起。

PurePath.with_name(name)

回傳一個修改 name 後的新路徑。如果原始路徑沒有名稱則引發 ValueError：

>>> p = PureWindowsPath('c:/Downloads/pathlib.tar.gz')
>>> p.with_name('setup.py')
PureWindowsPath('c:/Downloads/setup.py')
>>> p = PureWindowsPath('c:/')
>>> p.with_name('setup.py')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/cpython/default/Lib/pathlib.py", line 751, in with_name
    raise ValueError("%r has an empty name" % (self,))
ValueError: PureWindowsPath('c:/') has an empty name

PurePath.with_stem(stem)

回傳一個修改 stem 後的新路徑。如果原始路徑沒有名稱則引發 ValueError：

>>> p = PureWindowsPath('c:/Downloads/draft.txt')
>>> p.with_stem('final')
PureWindowsPath('c:/Downloads/final.txt')
>>> p = PureWindowsPath('c:/Downloads/pathlib.tar.gz')
>>> p.with_stem('lib')
PureWindowsPath('c:/Downloads/lib.gz')
>>> p = PureWindowsPath('c:/')
>>> p.with_stem('')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/cpython/default/Lib/pathlib.py", line 861, in with_stem
    return self.with_name(stem + self.suffix)
  File "/home/antoine/cpython/default/Lib/pathlib.py", line 851, in with_name
    raise ValueError("%r has an empty name" % (self,))
ValueError: PureWindowsPath('c:/') has an empty name

在 3.9 版被加入.

PurePath.with_suffix(suffix)

回傳一個修改 suffix 後的新路徑。如果原始路徑沒有後綴，新的 suffix 會附加在後面。如果 suffix 是一個空字串，原來的後綴會被移除：

>>> p = PureWindowsPath('c:/Downloads/pathlib.tar.gz')
>>> p.with_suffix('.bz2')
PureWindowsPath('c:/Downloads/pathlib.tar.bz2')
>>> p = PureWindowsPath('README')
>>> p.with_suffix('.txt')
PureWindowsPath('README.txt')
>>> p = PureWindowsPath('README.txt')
>>> p.with_suffix('')
PureWindowsPath('README')

在 3.14 版的變更: A single dot (".") is considered a valid suffix. In previous versions, ValueError is raised if a single dot is supplied.

PurePath.with_segments(*pathsegments)

透過結合給定的 pathsegments 建立一個相同型別的新路徑物件，當一個衍生路徑被建立的時候會呼叫這個方法，例如從 parent 和 relative_to() 建立衍生路徑。子類別可以覆寫此方法來傳遞資訊給衍生路徑，例如：

from pathlib import PurePosixPath

class MyPath(PurePosixPath):
    def __init__(self, *pathsegments, session_id):
        super().__init__(*pathsegments)
        self.session_id = session_id

    def with_segments(self, *pathsegments):
        return type(self)(*pathsegments, session_id=self.session_id)

etc = MyPath('/etc', session_id=42)
hosts = etc / 'hosts'
print(hosts.session_id)  # 42

在 3.12 版被加入.

實體路徑

實體路徑是純路徑類別的子類別。除了後者本來就有提供的操作，它們也提供方法可以對路徑物件做系統呼叫。有三種方式可以實例化實體路徑：

class pathlib.Path(*pathsegments)

PurePath 的子類別，此類別表示系統的路徑類型的實體路徑（實例化時會建立一個 PosixPath 或 WindowsPath）：

>>> Path('setup.py')
PosixPath('setup.py')

pathsegments 的指定方式與 PurePath 類似。

class pathlib.PosixPath(*pathsegments)

Path 和 PurePosixPath 的子類別，此類別表示實體非 Windows 檔案系統路徑：

>>> PosixPath('/etc/hosts')
PosixPath('/etc/hosts')

pathsegments 的指定方式與 PurePath 類似。

在 3.13 版的變更: 在 Windows 上會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

class pathlib.WindowsPath(*pathsegments)

Path 和 PureWindowsPath 的子類別，此類別表示實體 Windows 檔案系統路徑：

>>> WindowsPath('c:/', 'Users', 'Ximénez')
WindowsPath('c:/Users/Ximénez')

pathsegments 的指定方式與 PurePath 類似。

在 3.13 版的變更: 在非 Windows 平台上會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

你只能實例化對應你的系統的類別類型（允許在不相容的路徑類型上做系統呼叫可能在你的應用程式導致漏洞或故障）：

>>> import os
>>> os.name
'posix'
>>> Path('setup.py')
PosixPath('setup.py')
>>> PosixPath('setup.py')
PosixPath('setup.py')
>>> WindowsPath('setup.py')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pathlib.py", line 798, in __new__
    % (cls.__name__,))
UnsupportedOperation: cannot instantiate 'WindowsPath' on your system

有些實體路徑方法會在系統呼叫失敗（例如因為路徑不存在）時引發 OSError。

剖析和產生 URI

實體路徑物件可以從符合 RFC 8089 [https://datatracker.ietf.org/doc/html/rfc8089.html] 中的 'file' URI 建立，也可以以該形式來表示。

備註

檔案 URI 在跨不同檔案系統編碼的機器上是無法移植的。

classmethod Path.from_uri(uri)

從剖析 'file' URI 回傳新的路徑物件。例如：

>>> p = Path.from_uri('file:///etc/hosts')
PosixPath('/etc/hosts')

在 Windows 上，從 URI 可以剖析 DOS 裝置和 UNC 路徑：

>>> p = Path.from_uri('file:///c:/windows')
WindowsPath('c:/windows')
>>> p = Path.from_uri('file://server/share')
WindowsPath('//server/share')

支援多種變形：

>>> p = Path.from_uri('file:////server/share')
WindowsPath('//server/share')
>>> p = Path.from_uri('file://///server/share')
WindowsPath('//server/share')
>>> p = Path.from_uri('file:c:/windows')
WindowsPath('c:/windows')
>>> p = Path.from_uri('file:/c|/windows')
WindowsPath('c:/windows')

如果 URI 不是 file: 開頭，或是剖析後的路徑不是絕對路徑，則會引發 ValueError。

在 3.13 版被加入.

在 3.14 版的變更: The URL authority is discarded if it matches the local hostname. Otherwise, if the authority isn't empty or localhost, then on Windows a UNC path is returned (as before), and on other platforms a ValueError is raised.

Path.as_uri()

以 'file' URI 來表示路徑。如果路徑不是絕對的則會引發 ValueError。

>>> p = PosixPath('/etc/passwd')
>>> p.as_uri()
'file:///etc/passwd'
>>> p = WindowsPath('c:/Windows')
>>> p.as_uri()
'file:///c:/Windows'

自從版本 3.14 後不推薦使用，將會自版本 3.19 中移除。: Calling this method from PurePath rather than Path is possible but deprecated. The method's use of os.fsencode() makes it strictly impure.

擴展和解析路徑

classmethod Path.home()

回傳一個代表使用者家目錄的新的路徑物件（像以 ~ 構成的 os.path.expanduser() 的回傳一樣）。如果無法解析家目錄，會引發 RuntimeError。

>>> Path.home()
PosixPath('/home/antoine')

在 3.5 版被加入.

Path.expanduser()

回傳一個展開 ~ 和 ~user 構成的新路徑，像 os.path.expanduser() 回傳的一樣。如果無法解析家目錄，會引發 RuntimeError。

>>> p = PosixPath('~/films/Monty Python')
>>> p.expanduser()
PosixPath('/home/eric/films/Monty Python')

在 3.5 版被加入.

classmethod Path.cwd()

回傳一個代表目前目錄的新的路徑物件（像 os.getcwd() 回傳的一樣）：

>>> Path.cwd()
PosixPath('/home/antoine/pathlib')

Path.absolute()

將路徑轉換為絕對路徑，不進行標準化或解析符號連結。回傳一個新的路徑物件：

>>> p = Path('tests')
>>> p
PosixPath('tests')
>>> p.absolute()
PosixPath('/home/antoine/pathlib/tests')

Path.resolve(strict=False)

將路徑轉換為絕對路徑，解析所有符號連結。回傳一個新的路徑物件：

>>> p = Path()
>>> p
PosixPath('.')
>>> p.resolve()
PosixPath('/home/antoine/pathlib')

同時也會消除 ".." 的路徑組成（只有此方法這樣做）：

>>> p = Path('docs/../setup.py')
>>> p.resolve()
PosixPath('/home/antoine/pathlib/setup.py')

如果路徑不存在或遇到符號連結迴圈，且 strict 為 True，則引發 OSError。如果 strict 為 False，則將盡可能解析該路徑，並將任何剩餘部分追加到路徑中，而不檢查其是否存在。

在 3.6 版的變更: 新增 strict 參數（在 3.6 版本之前的行為是嚴格的）。

在 3.13 版的變更: 在嚴格模式下，符號連結迴圈會像其他錯誤一樣來處理：OSError 會被引發，而在非嚴格模式下，不會引發任何例外。在先前版本中，不管 strict 的值是什麼，都會引發 RuntimeError。

Path.readlink()

回傳符號連結指向的路徑（如 os.readlink() 的回傳值）：

>>> p = Path('mylink')
>>> p.symlink_to('setup.py')
>>> p.readlink()
PosixPath('setup.py')

在 3.9 版被加入.

在 3.13 版的變更: 如果 os.readlink() 不可用，會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

查詢檔案類型和狀態

在 3.8 版的變更: exists()、is_dir()、is_file()、is_mount()、is_symlink()、is_block_device()、is_char_device()、is_fifo()、is_socket() 遇到路徑包含 OS 層無法表示的字元時現在會回傳 False 而不是引發例外。

在 3.14 版的變更: The methods given above now return False instead of raising any OSError exception from the operating system. In previous versions, some kinds of OSError exception are raised, and others suppressed. The new behaviour is consistent with os.path.exists(), os.path.isdir(), etc. Use stat() to retrieve the file status without suppressing exceptions.

Path.stat(*, follow_symlinks=True)

回傳一個包含該路徑資訊的 os.stat_result 物件，像 os.stat() 一樣。每次呼叫此方法都會重新查詢結果。

此方法通常會跟隨 (follow) 符號連結；想要取得符號連結的資訊，可以加上引數 follow_symlinks=False 或使用 lstat()。

>>> p = Path('setup.py')
>>> p.stat().st_size
956
>>> p.stat().st_mtime
1327883547.852554

在 3.10 版的變更: 新增 follow_symlinks 參數。

Path.lstat()

類似 Path.stat()，但如果該路徑指向一個符號連結，則回傳符號連結的資訊而不是其指向的目標。

Path.exists(*, follow_symlinks=True)

Return True if the path points to an existing file or directory. False will be returned if the path is invalid, inaccessible or missing. Use Path.stat() to distinguish between these cases.

此方法通常會跟隨符號連結；如果想檢查符號連結是否存在，可以加上引數 follow_symlinks=False。

>>> Path('.').exists()
True
>>> Path('setup.py').exists()
True
>>> Path('/etc').exists()
True
>>> Path('nonexistentfile').exists()
False

在 3.12 版的變更: 新增 follow_symlinks 參數。

Path.is_file(*, follow_symlinks=True)

Return True if the path points to a regular file. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a regular file. Use Path.stat() to distinguish between these cases.

此方法通常會跟隨符號連結；如果想將符號連結除外，可以加上引數 follow_symlinks=False。

在 3.13 版的變更: 新增 follow_symlinks 參數。

Path.is_dir(*, follow_symlinks=True)

Return True if the path points to a directory. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a directory. Use Path.stat() to distinguish between these cases.

此方法通常會跟隨符號連結；如果想將對目錄的符號連結除外，可以加上引數 follow_symlinks=False。

在 3.13 版的變更: 新增 follow_symlinks 參數。

Path.is_symlink()

Return True if the path points to a symbolic link, even if that symlink is broken. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a symbolic link. Use Path.stat() to distinguish between these cases.

Path.is_junction()

如果該路徑指向一個連接點 (junction) 則回傳 True，對其他類型的檔案則回傳 False。目前只有 Windows 支援連接點。

在 3.12 版被加入.

Path.is_mount()

如果路徑是一個 mount point（一個檔案系統裡掛載不同檔案系統的存取點）則回傳 True。在 POSIX 上，此函式檢查 path 的父路徑 path/.. 是否和 path 在不同的裝置上，或者 path/.. 和 path 是否指向相同裝置的相同 i-node ── 這對於所有 Unix 和 POSIX 變體來說應該會偵測出掛載點。在 Windows 上，一個掛載點被視為一個根磁碟機字母（例如 c:\）、一個 UNC share（例如 \\server\share）或是掛載的檔案系統目錄。

在 3.7 版被加入.

在 3.12 版的變更: 加入對 Windows 的支援。

Path.is_socket()

Return True if the path points to a Unix socket. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a Unix socket. Use Path.stat() to distinguish between these cases.

Path.is_fifo()

Return True if the path points to a FIFO. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a FIFO. Use Path.stat() to distinguish between these cases.

Path.is_block_device()

Return True if the path points to a block device. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a block device. Use Path.stat() to distinguish between these cases.

Path.is_char_device()

Return True if the path points to a character device. False will be returned if the path is invalid, inaccessible or missing, or if it points to something other than a character device. Use Path.stat() to distinguish between these cases.

Path.samefile(other_path)

回傳此路徑是否指向與 other_path 相同的檔案，other_path 可以是路徑 (Path) 物件或字串。其語義類似於 os.path.samefile() 和 os.path.samestat()。

若任何一個檔案因為某些原因無法存取，則引發 OSError。

>>> p = Path('spam')
>>> q = Path('eggs')
>>> p.samefile(q)
False
>>> p.samefile('spam')
True

在 3.5 版被加入.

Path.info

A PathInfo object that supports querying file type information. The object exposes methods that cache their results, which can help reduce the number of system calls needed when switching on file type. For example:

>>> p = Path('src')
>>> if p.info.is_symlink():
...     print('symlink')
... elif p.info.is_dir():
...     print('directory')
... elif p.info.exists():
...     print('something else')
... else:
...     print('not found')
...
directory

If the path was generated from Path.iterdir() then this attribute is initialized with some information about the file type gleaned from scanning the parent directory. Merely accessing Path.info does not perform any filesystem queries.

To fetch up-to-date information, it's best to call Path.is_dir(), is_file() and is_symlink() rather than methods of this attribute. There is no way to reset the cache; instead you can create a new path object with an empty info cache via p = Path(p).

在 3.14 版被加入.

讀取和寫入檔案

Path.open(mode='r', buffering=-1, encoding=None, errors=None, newline=None)

開啟該路徑指向的檔案，像內建的 open() 函式做的一樣：

>>> p = Path('setup.py')
>>> with p.open() as f:
...     f.readline()
...
'#!/usr/bin/env python3\n'

Path.read_text(encoding=None, errors=None, newline=None)

將路徑指向的檔案的解碼內容以字串形式回傳：

>>> p = Path('my_text_file')
>>> p.write_text('Text file contents')
18
>>> p.read_text()
'Text file contents'

該檔案被打開並且隨後關閉。可選參數的含義與 open() 中的相同。

在 3.5 版被加入.

在 3.13 版的變更: 新增 newline 參數。

Path.read_bytes()

將路徑指向的檔案的二進位內容以一個位元組物件回傳：

>>> p = Path('my_binary_file')
>>> p.write_bytes(b'Binary file contents')
20
>>> p.read_bytes()
b'Binary file contents'

在 3.5 版被加入.

Path.write_text(data, encoding=None, errors=None, newline=None)

以文字模式開啟指向的檔案，將 data 寫到檔案，並關閉檔案:: ：

>>> p = Path('my_text_file')
>>> p.write_text('Text file contents')
18
>>> p.read_text()
'Text file contents'

一個名稱相同的已存在檔案會被覆寫。可選參數和 open() 的參數有相同意義。

在 3.5 版被加入.

在 3.10 版的變更: 新增 newline 參數。

Path.write_bytes(data)

以位元組模式開啟指向的檔案，將 data 寫到檔案，並關閉檔案:: ：

>>> p = Path('my_binary_file')
>>> p.write_bytes(b'Binary file contents')
20
>>> p.read_bytes()
b'Binary file contents'

一個名稱相同的已存在檔案會被覆寫。

在 3.5 版被加入.

讀取目錄

Path.iterdir()

當該路徑指向一個目錄，會 yield 目錄裡面的路徑物件：

>>> p = Path('docs')
>>> for child in p.iterdir(): child
...
PosixPath('docs/conf.py')
PosixPath('docs/_templates')
PosixPath('docs/make.bat')
PosixPath('docs/index.rst')
PosixPath('docs/_build')
PosixPath('docs/_static')
PosixPath('docs/Makefile')

子路徑會以任意順序被 yield，且不會包含特殊項目 '.' 和 '..'。如果一個檔案在建立這個疊代器之後加到該目錄或從目錄刪除，這個檔案的路徑物件是否會被包含是沒有明定的。

如果路徑不是目錄或無法存取，則會引發 OSError。

Path.glob(pattern, *, case_sensitive=None, recurse_symlinks=False)

在該路徑表示的目錄裡，以 glob 方式比對所給定的相對 pattern，並 yield 所有比對到的檔案（任意類型）：

>>> sorted(Path('.').glob('*.py'))
[PosixPath('pathlib.py'), PosixPath('setup.py'), PosixPath('test_pathlib.py')]
>>> sorted(Path('.').glob('*/*.py'))
[PosixPath('docs/conf.py')]
>>> sorted(Path('.').glob('**/*.py'))
[PosixPath('build/lib/pathlib.py'),
 PosixPath('docs/conf.py'),
 PosixPath('pathlib.py'),
 PosixPath('setup.py'),
 PosixPath('test_pathlib.py')]

備註

The paths are returned in no particular order. If you need a specific order, sort the results.

也參考

模式語言 (pattern language) 文件。

預設情況下，或者當 case_sensitive 僅限關鍵字引數被設定為 None 的時候，此方法會使用平台特定的大小寫規則來比對路徑；通常在 POSIX 上會區分大小寫，而在 Windows 上不區分大小寫。將 case_sensitive 設成 True 或 False 會覆寫這個行為。

預設情況下，或者當 recurse_symlinks 僅限關鍵字引數被設定為 False 的時候，此方法會跟隨符號連結，除非在擴展 "**" 萬用字元時。將 recurse_symlinks 設成 True 以總是跟隨符號連結。

引發一個附帶引數 self、pattern 的稽核事件 pathlib.Path.glob。

在 3.12 版的變更: 新增 case_sensitive 參數。

在 3.13 版的變更: 新增 recurse_symlinks 參數。

在 3.13 版的變更: pattern 參數接受類路徑物件。

在 3.13 版的變更: 從掃描檔案系統引發的任何 OSError 例外都會被抑制。在先前版本中，在許多情況下這種例外都會被抑制，但不是所有情況。

Path.rglob(pattern, *, case_sensitive=None, recurse_symlinks=False)

遞迴地 glob 給定的相對 pattern。這相當於在給定的相對 pattern 前面加上 "**/" 並呼叫 Path.glob()。

備註

The paths are returned in no particular order. If you need a specific order, sort the results.

也參考

模式語言 (pattern language) 和 Path.glob() 文件。

引發一個附帶引數 self、pattern 的稽核事件 pathlib.Path.rglob。

在 3.12 版的變更: 新增 case_sensitive 參數。

在 3.13 版的變更: 新增 recurse_symlinks 參數。

在 3.13 版的變更: pattern 參數接受類路徑物件。

Path.walk(top_down=True, on_error=None, follow_symlinks=False)

透過由上而下或由下而上地走訪目錄樹產生目錄樹裡的檔案名稱。

對每個以 self 為根且在目錄樹裡的目錄（包含 self 但不包含 '.' 和 '..' ），此方法會 yield 一個 (dirpath, dirnames, filenames) 的三元素元組。

dirpath 是一個目前走訪到的目錄的 Path，dirnames 是一個 dirpath 裡的子目錄名稱的字串串列（不包含 '.' 和 '..' ），而 filenames 是一個 dirpath 裡非目錄檔案名稱的字串串列。要取得在 dirpath 裡檔案或目錄的完整路徑（以 self 開頭），可以使用 dirpath / name。會根據檔案系統來決定串列是否有排序。

如果可選引數 top_down 是 true（預設值），一個目錄的三元素元組會在其任何子目錄的三元素元組之前產生（目錄是由上而下走訪）。如果 top_down 是 false，一個目錄的三元素元組會在其所有子目錄的三元素元組之後產生（目錄是由下而上走訪）。不論 top_down 的值是什麼，子目錄的串列會在走訪該目錄及其子目錄的三元素元組之前取得。

當 top_down 是 true，呼叫者可以原地 (in-place) 修改 dirnames 串列（例如使用 del 或切片賦值 (slice assignment)），且 Path.walk() 只會遞迴進名稱依然留在 dirnames 裡的子目錄。這可以用來修剪搜尋，或者強加特定順序的瀏覽，或者甚至在繼續 Path.walk() 之前，用來告訴 Path.walk() 關於呼叫者建立或重新命名的目錄。當 top_down 是 false 的時候，修改 dirnames 對 Path.walk() 的行為沒有影響，因為 dirnames 裡的目錄已經在 dirnames yield 給呼叫者之前被產生。

預設來自 os.scandir() 的錯誤會被忽略。如果指定了可選引數 on_error（它應該要是一個可呼叫物件），它會被以一個 OSError 實例為引數來呼叫。這個可呼叫物件可以處理錯誤以繼續走訪，或者再次引發錯誤來停止走訪。注意，檔案名稱可以從例外物件的 filename 屬性來取得。

預設 Path.walk() 不會跟隨符號連結，而是會把它們加到 filenames 串列。將 follow_symlinks 設定為 true 會解析符號連結，並將它們根據其指向的目標放在適當的 dirnames 和 filenames，而因此瀏覽到符號連結指向的目錄（在有支援符號連結的地方）。

備註

需要注意的是如果符號連結指向一個其本身的父目錄，則將 follow_symlinks 設定為 true 會導致無窮的遞迴。Path.walk() 不會紀錄其已經瀏覽過的目錄。

備註

Path.walk() 假設其走訪的目錄在執行過程中不會被修改。舉例來說，如果在 dirnames 裡的目錄已經被一個符號連結取代，且 follow_symlinks 是 false，Path.walk() 依然會試著往下進入它。為了防止這樣的行為，可以從 dirnames 適當地移除目錄。

備註

如果 follow_symlinks 是 false，和 os.walk() 行為不同的是 Path.walk() 會將指向目錄的符號連結放在 filenames 串列。

這個範例會顯示在每個目錄裡所有檔案使用的位元組數量，同時間忽略 __pycache__ 目錄：

from pathlib import Path
for root, dirs, files in Path("cpython/Lib/concurrent").walk(on_error=print):
  print(
      root,
      "consumes",
      sum((root / file).stat().st_size for file in files),
      "bytes in",
      len(files),
      "non-directory files"
  )
  if '__pycache__' in dirs:
        dirs.remove('__pycache__')

下一個範例是 shutil.rmtree() 的一個簡單的實作方式。由下而上走訪目錄樹是必要的，因為 rmdir() 不允許在目錄為空之前刪除它：

# 刪除可從 "top" 目錄到達的所有東西。
# 注意：這是危險的！例如，如果 top == Path('/')，
# 它可能會刪除你所有的檔案。
for root, dirs, files in top.walk(top_down=False):
    for name in files:
        (root / name).unlink()
    for name in dirs:
        (root / name).rmdir()

在 3.12 版被加入.

建立檔案和目錄

Path.touch(mode=0o666, exist_ok=True)

根據給定路徑來建立一個檔案。如果 mode 有給定，它會與行程的 umask 值結合，以確定檔案模式和存取旗標。當檔案已經存在時，若 exist_ok 為 true 則函式不會失敗（其變更時間會被更新為當下時間），否則會引發 FileExistsError。

也參考

open()、write_text() 和 write_bytes() 方法通常用於建立檔案。

Path.mkdir(mode=0o777, parents=False, exist_ok=False)

在給定路徑下建立一個新的目錄。如果有給 mode 則會結合行程 (process) 的 umask 值來決定檔案模式與存取旗標 (access flag)。如果路徑已經存在，會引發 FileExistsError。

如果 parents 是 true，則任何缺少的父路徑都會依需要被建立；它們不考慮 mode 而會以預設的權限來建立（模仿 POSIX 的 mkdir -p 指令）。

如果 parents 是 false（預設值），缺少的父路徑會引發 FileNotFoundError。

如果 exist_ok 是 false（預設值），則當目標目錄已經存在的話會引發 FileExistsError。

如果 exist_ok 是 true，只有當最後的路徑組成不是一個已存在的非目錄檔案，FileExistsError 例外會被忽略（與 POSIX 的 mkdir -p 指令行為相同）。

在 3.5 版的變更: 新增 exist_ok 參數。

Path.symlink_to(target, target_is_directory=False)

使這個路徑成為一個指向 target 的符號連結。

在 Windows 上，符號連結代表一個檔案或目錄，且不會隨著目標 (target) 動態改變。如果目標存在，則符號連結的類型會被建立來符合其目標。否則如果 target_is_directory 是 true，該符號連結會被建立成目錄，如果不是則建立成檔案（預設值）。在非 Windows 平台上，target_is_directory 會被忽略。

>>> p = Path('mylink')
>>> p.symlink_to('setup.py')
>>> p.resolve()
PosixPath('/home/antoine/pathlib/setup.py')
>>> p.stat().st_size
956
>>> p.lstat().st_size
8

備註

引數的順序 (link, target) 和 os.symlink() 相反。

在 3.13 版的變更: 如果 os.symlink() 不可用，會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

Path.hardlink_to(target)

使這個路徑成為與 target 相同檔案的一個硬連結 (hard link)。

備註

引數的順序 (link, target) 和 os.link() 相反。

在 3.10 版被加入.

在 3.13 版的變更: 如果 os.link() 不可用，會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

複製、移動和刪除

Path.copy(target, *, follow_symlinks=True, preserve_metadata=False)

將此檔案或目錄樹複製到給定的 target，並回傳一個指向 target 的新 Path 實例。

If the source is a file, the target will be replaced if it is an existing file. If the source is a symlink and follow_symlinks is true (the default), the symlink's target is copied. Otherwise, the symlink is recreated at the destination.

If preserve_metadata is false (the default), only directory structures and file data are guaranteed to be copied. Set preserve_metadata to true to ensure that file and directory permissions, flags, last access and modification times, and extended attributes are copied where supported. This argument has no effect when copying files on Windows (where metadata is always preserved).

備註

Where supported by the operating system and file system, this method performs a lightweight copy, where data blocks are only copied when modified. This is known as copy-on-write.

在 3.14 版被加入.

Path.copy_into(target_dir, *, follow_symlinks=True, preserve_metadata=False)

Copy this file or directory tree into the given target_dir, which should be an existing directory. Other arguments are handled identically to Path.copy(). Returns a new Path instance pointing to the copy.

在 3.14 版被加入.

Path.rename(target)

將此檔案或目錄重新命名為給定的 target ，並回傳一個新的 Path 實例指向該 target。在 Unix 系統上，若 target 存在且為一個檔案，若使用者有權限，則會在不顯示訊息的情況下進行取代。在 Windows 系統上，若 target 存在，則會引發 FileExistsError 錯誤。target 可以是字串或另一個路徑物件：

>>> p = Path('foo')
>>> p.open('w').write('some text')
9
>>> target = Path('bar')
>>> p.rename(target)
PosixPath('bar')
>>> target.open().read()
'some text'

目標路徑可以是絕對路徑或相對路徑。相對路徑會相對於目前的工作目錄進行解釋，而不是相對於 Path 物件所在的目錄。

此功能是使用 os.rename() 實現的，並提供相同的保證。

在 3.8 版的變更: 新增了回傳值，回傳新的 Path 實例。

Path.replace(target)

將此檔案或目錄重新命名為給定的 target，並回傳一個指向 target 的新 Path 實例。如果 target 指向一個現有的檔案或空目錄，它將被無條件地取代。

目標路徑可以是絕對路徑或相對路徑。相對路徑會相對於目前的工作目錄進行解釋，而不是相對於 Path 物件所在的目錄。

在 3.8 版的變更: 新增了回傳值，回傳新的 Path 實例。

Path.move(target)

將此檔案或目錄樹移動到給定的 target，並回傳一個指向 target 的新 Path 實例。

If the target doesn't exist it will be created. If both this path and the target are existing files, then the target is overwritten. If both paths point to the same file or directory, or the target is a non-empty directory, then OSError is raised.

If both paths are on the same filesystem, the move is performed with os.replace(). Otherwise, this path is copied (preserving metadata and symlinks) and then deleted.

在 3.14 版被加入.

Path.move_into(target_dir)

Move this file or directory tree into the given target_dir, which should be an existing directory. Returns a new Path instance pointing to the moved path.

在 3.14 版被加入.

Path.unlink(missing_ok=False)

移除這個檔案或符號連結。如果路徑指向目錄，請改用 Path.rmdir()。

如果 missing_ok 是 false（預設值），FileNotFoundError 會在路徑不存在時被引發。

如果 missing_ok 是 true，FileNotFoundError 例外會被忽略（行為與 POSIX rm -f 指令相同）。

在 3.8 版的變更: 新增 missing_ok 參數。

Path.rmdir()

移除此目錄。該目錄必須為空。

權限和所有權

Path.owner(*, follow_symlinks=True)

回傳擁有該檔案的用戶名稱。如果在系統資料庫中找不到該檔案的使用者識別字 (UID)，則會引發 KeyError。

此方法通常會跟隨符號連結；如果想取得符號連結的擁有者，可以加上引數 follow_symlinks=False。

在 3.13 版的變更: 如果 pwd 模組不可用，會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

在 3.13 版的變更: 新增 follow_symlinks 參數。

Path.group(*, follow_symlinks=True)

回傳擁有該檔案的群組名稱。如果在系統資料庫裡找不到檔案的群組識別字 (GID) 會引發 KeyError。

此方法通常會跟隨符號連結；如果想取得符號連結的群組，可以加上引數 follow_symlinks=False。

在 3.13 版的變更: 如果 grp 模組不可用，會引發 UnsupportedOperation。在先前版本中，則是引發 NotImplementedError。

在 3.13 版的變更: 新增 follow_symlinks 參數。

Path.chmod(mode, *, follow_symlinks=True)

修改檔案模式 (file mode) 與權限，像 os.chmod() 一樣。

此方法通常會跟隨符號連結。一些 Unix 類型支援修改符號連結本身的權限；在這些平台上你可以加上引數 follow_symlinks=False 或使用 lchmod()。

>>> p = Path('setup.py')
>>> p.stat().st_mode
33277
>>> p.chmod(0o444)
>>> p.stat().st_mode
33060

在 3.10 版的變更: 新增 follow_symlinks 參數。

Path.lchmod(mode)

類似 Path.chmod()，但如果該路徑指向一個符號連結，則符號連結的模式 (mode) 會被改變而不是其指向的目標。

模式語言 (pattern language)

以下的萬用字元在 full_match()、glob() 和 rglob() 的模式中被支援：

**（整個片段）

匹配任何數量的檔案或目錄片段，包括零個。

*（整個片段）

匹配一個檔案或目錄的片段。

*（片段的一部分）

匹配任意數量的非分隔字元，包括零個。

?

匹配一個非分隔字元。

[seq]

Matches one character in seq, where seq is a sequence of characters. Range expressions are supported; for example, [a-z] matches any lowercase ASCII letter. Multiple ranges can be combined: [a-zA-Z0-9_] matches any ASCII letter, digit, or underscore.

[!seq]

匹配一個不在 seq 中的字元，其中 seq 遵循上述相同的規則。

對於文本 (literal) 匹配，可以用方括號包裝元字元 (meta-characters)。例如，"[?]" 會匹配字元 "?"。

"**" 萬用字元讓它可以做遞迴 glob。例如：

模式

意涵

"**/*"

至少有一個片段的路徑。

"**/*.py"

最後一個片段以 ".py" 結尾的任何路徑。

"assets/**"

任何以 "assets/" 開頭的路徑。

"assets/**/*"

任何以 "assets/" 開頭的路徑，不包括 "assets/" 本身。

備註

Glob 使用 ** 萬用字元會訪問目錄樹中的每個目錄。對於大型的目錄樹，搜尋可能需要花費很長的時間。

在 3.13 版的變更: Glob 使用結尾為 ** 的模式會同時回傳檔案和目錄。在先前版本中，只會回傳目錄。

在 Path.glob() 和 rglob() 中，可以在模式後面加上斜線以只匹配目錄。

在 3.11 版的變更: Glob 使用以路徑名稱組成的分隔符號（sep 或 altsep）作結尾的模式則只會回傳目錄。

與 glob 模組的比較

Path.glob() 和 Path.rglob() 接受的模式和產生的結果與 glob 模組略有不同：

pathlib 中以點開頭的檔案並不特別。這和將 include_hidden=True 傳遞給 glob.glob() 相同。

** 模式組成在 pathlib 中總是遞迴的。這與將 recursive=True 傳遞給 glob.glob() 相同。

在 pathlib 中，** 模式組成預設不跟隨符號連結。這在 glob.glob() 中沒有等效的行為，但你可以將 recurse_symlinks=True 傳遞給 Path.glob() 以獲得相容的行為。

與所有 PurePath 和 Path 物件一樣，從 Path.glob() 和 Path.rglob() 回傳的值不包含結尾斜線。

pathlib 的 path.glob() 和 path.rglob() 回傳的值包含了 path 作為前綴，而 glob.glob(root_dir=path) 的結果則不會如此。

pathlib 的 path.glob() 和 path.rglob() 回傳的值可能包含 path 本身，例如當使用 "**" 做 glob 的時候，然而 glob.glob(root_dir=path) 的結果則永遠不會包含一個對應到 path 的空字串。

與 os 和 os.path 模組的比較

pathlib 使用 PurePath 和 Path 物件來實作路徑操作，因此它被稱為是物件導向的。另一方面，os 和 os.path 模組提供能夠與底層 str 和 bytes 物件互動的函式，這是一種更程序式的方法。有些使用者認為物件導向的風格更易讀。

os 和 os.path 中的許多函式支援 bytes 路徑和相對路徑的目錄描述器 (paths relative to directory descriptors)。這些功能在 pathlib 中不可用。

Python 的 str 和 bytes 型別，以及 os 和 os.path 模組的一些部分，是用 C 寫的且非常快速。pathlib 是用純 Python 寫的且通常比較慢，但很少會慢到足以產生影響。

pathlib 的路徑正規化略比 os.path 更武斷和一致。例如，儘管 os.path.abspath() 會從路徑中移除 ".." 片段，如果包含符號連結的話這可能會改變其意義，而 Path.absolute() 則會保留這些片段以增加安全性。

pathlib 的路徑正規化可能會使它不適合某些應用程式：

pathlib 將 Path("my_folder/") 正規化為 Path("my_folder")，這會在提供給各種作業系統 API 和命令列工具時改變路徑的意義。具體來說，缺少結尾分隔符號可能會允許該路徑被解析為檔案或目錄，而不只是目錄。

pathlib 將 Path("./my_program") 正規化為 Path("my_program")，這會在作為執行檔搜尋路徑使用時改變路徑的意義，例如在 shell 或在衍生 (spawn) 子行程時。具體來說，在路徑中缺少分隔符號可能會使其強制在 PATH 中尋找，而不是目前目錄。

因為這些差異，pathlib 不是 os.path 的直接替代品。

對應工具

以下是一張表格，對應許多 os 函式及其相符於 PurePath/Path 的項目。

os 和 os.path

pathlib

os.path.dirname()

PurePath.parent

os.path.basename()

PurePath.name

os.path.splitext()

PurePath.stem 和 PurePath.suffix

os.path.join()

PurePath.joinpath()

os.path.isabs()

PurePath.is_absolute()

os.path.relpath()

PurePath.relative_to() [1]

os.path.expanduser()

Path.expanduser() [2]

os.path.realpath()

Path.resolve()

os.path.abspath()

Path.absolute() [3]

os.path.exists()

Path.exists()

os.path.isfile()

Path.is_file()

os.path.isdir()

Path.is_dir()

os.path.islink()

Path.is_symlink()

os.path.isjunction()

Path.is_junction()

os.path.ismount()

Path.is_mount()

os.path.samefile()

Path.samefile()

os.getcwd()

Path.cwd()

os.stat()

Path.stat()

os.lstat()

Path.lstat()

os.listdir()

Path.iterdir()

os.walk()

Path.walk() [4]

os.mkdir()、os.makedirs()

Path.mkdir()

os.link()

Path.hardlink_to()

os.symlink()

Path.symlink_to()

os.readlink()

Path.readlink()

os.rename()

Path.rename()

os.replace()

Path.replace()

os.remove()、os.unlink()

Path.unlink()

os.rmdir()

Path.rmdir()

os.chmod()

Path.chmod()

os.lchmod()

Path.lchmod()

註腳

[1]

os.path.relpath() 會呼叫 abspath() 來將路徑變成絕對路徑並移除 ".." 部分，而 PurePath.relative_to() 是一個文本上的操作，當它輸入的錨點不同時（例如一個是絕對路徑，另一個則是相對路徑）會引發 ValueError。

[2]

os.path.expanduser() 會在無法解析家目錄時回傳原始路徑，而 Path.expanduser() 則會引發 RuntimeError。

[3]

os.path.abspath() 將 ".." 組成移除而不解析符號連結，這可能會改變路徑的意義，而 Path.absolute() 則會保留路徑中任何 ".." 組成。

[4]

當分類路徑成 dirnames 和 filenames 時 os.walk() 總是跟隨符號連結，而 Path.walk() 在 follow_symlinks 為 false（預設值）時，會將所有符號連結都分類為 filenames。

Protocols

The pathlib.types module provides types for static type checking.

在 3.14 版被加入.

class pathlib.types.PathInfo

A typing.Protocol describing the Path.info attribute. Implementations may return cached results from their methods.

exists(*, follow_symlinks=True)

如果路徑是個存在的檔案、目錄或任何其他類型的檔案則回傳 True，如果路徑不存在則回傳 False。

If follow_symlinks is False, return True for symlinks without checking if their targets exist.

is_dir(*, follow_symlinks=True)

Return True if the path is a directory, or a symbolic link pointing to a directory; return False if the path is (or points to) any other kind of file, or if it doesn't exist.

If follow_symlinks is False, return True only if the path is a directory (without following symlinks); return False if the path is any other kind of file, or if it doesn't exist.

is_file(*, follow_symlinks=True)

Return True if the path is a file, or a symbolic link pointing to a file; return False if the path is (or points to) a directory or other non-file, or if it doesn't exist.

If follow_symlinks is False, return True only if the path is a file (without following symlinks); return False if the path is a directory or other non-file, or if it doesn't exist.

is_symlink()

Return True if the path is a symbolic link (even if broken); return False if the path is a directory or any kind of file, or if it doesn't exist.

os.path --- 常見的路徑名操作

原始碼： Lib/genericpath.py [https://github.com/python/cpython/tree/3.14/Lib/genericpath.py]、Lib/posixpath.py [https://github.com/python/cpython/tree/3.14/Lib/posixpath.py] (用於 POSIX 系統) 和 Lib/ntpath.py [https://github.com/python/cpython/tree/3.14/Lib/ntpath.py] (用於 Windows).

該模組實現了一些有用的路徑名操作函式。若要讀取或寫入檔案，請參閱 open() 函式，要存取檔案系統，請參閱 os 模組。路徑參數可以以字串、位元組或任何依照 os.PathLike 協定實作的物件傳遞。

與 Unix shell 不同，Python 不會自動進行路徑展開 (path expansions)。當應用程式需要進行類似 shell 的路徑展開時，可以明確地叫用 expanduser() 和 expandvars() 等函式。（另請參閱 glob 模組。）

也參考

pathlib 模組提供了高階的路徑物件。

備註

所有這些函式都只接受位元組或字串物件作為參數。如果回傳的是路徑或檔案名稱，結果將是相同型別的物件。

備註

由於不同的作業系統具有不同的路徑命名慣例，在標準函式庫中的路徑模組有數個版本可供使用，而 os.path 模組都會是運行 Python 之作業系統所適用本地路徑。然而，如果你想要操作始終以某個不同於本機格式表示的路徑，你也可以引入並使用對應的模組。它們都具有相同的介面：

posixpath 用於 UNIX 形式的路徑

ntpath 用於 Windows 的路徑

在 3.8 版的變更: 對於包含有作業系統層級無法表示之字元或位元組的路徑，exists()、lexists()、isdir()、isfile()、islink() 和 ismount() 函式現在會回傳 False，而不是引發例外。

os.path.abspath(path)

回傳經正規化的絕對路徑名 path 。在大多數平台上，這等效於按照以下方式呼叫 normpath(join(os.getcwd(), path))。

也參考

os.path.join() 和 os.path.normpath()。

在 3.6 版的變更: 接受一個 path-like object。

os.path.basename(path, /)

回傳路徑名 path 的基底名稱。這是將 path 傳遞給函式 split() 後回傳結果中的第二個元素。請注意，此函式的結果與 Unix 的 basename 程式不同；對於 '/foo/bar/'，basename 回傳 'bar'，而 basename() 函式回傳空字串（''）。

在 3.6 版的變更: 接受一個 path-like object。

os.path.commonpath(paths)

回傳可疊代物件 paths 中每個路徑名稱的最長共同子路徑。如果 paths 同時包含絕對路徑名稱和相對路徑名稱、paths 位於不同的驅動機或 paths 為空，則引發 ValueError。與 commonprefix() 不同，此函式回傳的是有效路徑。

在 3.5 版被加入.

在 3.6 版的變更: 接受一個類路徑物件的序列。

在 3.13 版的變更: Any iterable can now be passed, rather than just sequences.

os.path.commonprefix(list, /)

回傳 list 中所有路徑的最長路徑前綴（逐字元比較）。如果 list 為空，則回傳空字串（''）。

備註

由於此函式是逐字元比較，因此可能會回傳無效的路徑。若要獲得有效的路徑，請參考 commonpath() 函式。

>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
'/usr/l'

>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
'/usr'

在 3.6 版的變更: 接受一個 path-like object。

os.path.dirname(path, /)

回傳路徑名 path 的目錄名稱。這是將 path 傳遞給函式 split() 後回傳之成對結果中的第一個元素。

在 3.6 版的變更: 接受一個 path-like object。

os.path.exists(path)

如果 path 是一個存在的路徑或一個開啟的檔案描述器則回傳 True。對於已損壞的符號連結則回傳 False。在某些平台上，即使 path 實際存在，如果未被授予執行 os.stat() 的權限，此函式仍可能回傳 False。

在 3.3 版的變更: 現在 path 可以是一個整數：如果它是一個開啟的檔案描述器，則回傳 True；否則回傳 False。

在 3.6 版的變更: 接受一個 path-like object。

os.path.lexists(path)

如果 path 是一個存在的路徑則回傳 True，對已損壞的符號連結也是。在缺乏 os.lstat() 的平台上，與 exists() 函式等效。

在 3.6 版的變更: 接受一個 path-like object。

os.path.expanduser(path)

在 Unix 和 Windows 上，將引數中以 ~ 或 ~user 開頭的部分替換為該 user 的家目錄。

在 Unix 上，如果環境變數 HOME 有被設置，則將初始的 ~ 替換為該變數的值；否則將使用內建模組 pwd 在密碼目錄中查找目前使用者的家目錄。對於初始的 ~user，直接在密碼目錄中查找該使用者的家目錄。

在 Windows 上，如果 USERPROFILE 有被設置，則使用該變數的值；否則將結合 HOMEPATH 和 HOMEDRIVE。對於初始的 ~user，會檢查目前使用者的家目錄的最後一個目錄元件是否與 USERNAME 相符，如果相符則替換它。

如果展開失敗或路徑不以波浪符號 (tilde) 開頭，則回傳原始路徑，不做任何變更。

在 3.6 版的變更: 接受一個 path-like object。

在 3.8 版的變更: 在 Windows 上不再使用 HOME 變數。

os.path.expandvars(path)

回傳已展開環境變數的引數。形如 $name 或 ${name} 的子字串會被替換為環境變數 name 的值。無效的變數名稱和對不存在變數的引用保持不變。

在 Windows 上，除了支援 $name 和 ${name} 形式的展開外，還支援 %name% 形式的展開。

在 3.6 版的變更: 接受一個 path-like object。

os.path.getatime(path, /)

回傳 path 的最後存取時間。回傳值是一個浮點數，表示自紀元（參見 time 模組）以來的秒數。如果檔案不存在或無法存取，則引發 OSError。

os.path.getmtime(path, /)

回傳 path 的最後修改時間。回傳值是一個浮點數，表示自紀元（參見 time 模組）以來的秒數。如果檔案不存在或無法存取，則引發 OSError。

在 3.6 版的變更: 接受一個 path-like object。

os.path.getctime(path, /)

回傳系統的 ctime。在某些系統（如 Unix）上，這是最後一次元數據 (metadata) 更改的時間，在其他系統（如 Windows）上則是 path 的建立時間。回傳值是一個浮點數，表示自紀元（參見 time 模組）以來的秒數。如果檔案不存在或無法存取），則引發 OSError。

在 3.6 版的變更: 接受一個 path-like object。

os.path.getsize(path, /)

回傳 path 的大小（以位元組為單位）。如果檔案不存在或無法存取，則引發 OSError。

在 3.6 版的變更: 接受一個 path-like object。

os.path.isabs(path, /)

如果 path 是絕對路徑名，則回傳 True。在 Unix 上，這表示它以斜線開頭；在 Windows 上，表示這是以兩個（反）斜線開頭或者以一個驅動機字母、冒號和（反）斜線開頭。

也參考

abspath()

在 3.6 版的變更: 接受一個 path-like object。

在 3.13 版的變更: On Windows, returns False if the given path starts with exactly one (back)slash.

os.path.isfile(path)

如果 path 是一個已存在的常規檔案，則回傳 True。這將跟隨符號連結，因此同一個路徑可以同時回傳 islink() 和 isfile() 的結果為真。

在 3.6 版的變更: 接受一個 path-like object。

os.path.isdir(path, /)

如果 path 是一個已存在的目錄，則回傳 True。這將跟隨符號連結，因此同一個路徑可以同時回傳 islink() 和 isdir() 的結果為真。

在 3.6 版的變更: 接受一個 path-like object。

os.path.isjunction(path)

如果 path 是指向已存在的目錄條目且為聯接點 (junction)，則回傳 True。如果目前平台不支援聯接點，則始終返回 False。

在 3.12 版被加入.

os.path.islink(path)

如果 path 是指向已存在的目錄項目且為符號連結，則回傳 True。如果 Python 執行時不支援符號連結，則始終回傳 False。

在 3.6 版的變更: 接受一個 path-like object。

os.path.ismount(path)

如果路徑名 path 是一個掛載點 (mount point)，則回傳 True：即在檔案系統中掛載了不同的檔案系統。在 POSIX 系統上，該函式檢查 path 的父目錄 path/.. 是否位於不同的設備上，或者 path/.. 和 path 是否指向同一設備上的相同 i-node --- 這應該能夠檢測出所有 Unix 和 POSIX 變體的掛載點。但無法可靠地檢測出相同檔案系統上的綁定掛載點 (bind mount)。在 Linux 系統上，即使它們不是掛載點，也會始終回傳 True 給 btrfs 子卷（subvolumes）。在 Windows 上，以驅動機字母開頭的根目錄和 UNC 共享路徑始終是掛載點，對於任何其他路徑，會呼叫 GetVolumePathName 函式來檢查它是否與輸入路徑不同。

在 3.4 版的變更: 新增在 Windows 上檢測非根目錄掛載點的支援。

在 3.6 版的變更: 接受一個 path-like object。

os.path.isdevdrive(path)

如果路徑名 path 位於 Windows Dev 驅動機上，則回傳 True。Dev 驅動機針對開發人員場景進行了最佳化，提供更快的讀寫檔案性能。建議將其用於原始程式碼、臨時建置目錄、封包快取和其他 I/O 密集型操作。

可能會對無效的路徑引發錯誤，例如，沒有可識別的驅動機的路徑，但在不支援 Dev 磁碟機的平台上回傳 False。請參閱 Windows 文件 [https://learn.microsoft.com/windows/dev-drive/]以了解有關啟用和建立 Dev 驅動機的資訊。

在 3.12 版被加入.

在 3.13 版的變更: The function is now available on all platforms, and will always return False on those that have no support for Dev Drives

os.path.isreserved(path)

Return True if path is a reserved pathname on the current system.

On Windows, reserved filenames include those that end with a space or dot; those that contain colons (i.e. file streams such as "name:stream"), wildcard characters (i.e. '*?"<>'), pipe, or ASCII control characters; as well as DOS device names such as "NUL", "CON", "CONIN$", "CONOUT$", "AUX", "PRN", "COM1", and "LPT1".

備註

This function approximates rules for reserved paths on most Windows systems. These rules change over time in various Windows releases. This function may be updated in future Python releases as changes to the rules become broadly available.

可用性: Windows.

在 3.13 版被加入.

os.path.join(path, /, *paths)

聰明地連接一個或多個路徑段。回傳值是 path 和 *paths 的所有成員的串聯，每個非空部分後面都有一個目錄分隔符號，除了最後一個部分。換句話說，如果最後一個部分為空或以分隔符號結尾，結果只會以分隔符號結尾。

If a segment is an absolute path (which on Windows requires both a drive and a root), then all previous segments are ignored and joining continues from the absolute path segment. On Linux, for example:

>>> os.path.join('/home/foo', 'bar')
'/home/foo/bar'
>>> os.path.join('/home/foo', '/home/bar')
'/home/bar'

在 Windows 上，當遇到根路徑段（例如，r'\foo'）時，驅動機不會被重置。如果一個段位於不同的驅動機上，或者是絕對路徑，則將忽略所有之前的段並重置驅動機。例如：

>>> os.path.join('c:\\', 'foo')
'c:\\foo'
>>> os.path.join('c:\\foo', 'd:\\bar')
'd:\\bar'

請注意，由於每個驅動機都有目前目錄，os.path.join("c:", "foo") 表示相對於驅動機 C: 的目前目錄的路徑（c:foo），而不是 c:\foo。

在 3.6 版的變更: path 和 paths 接受 path-like object 作為參數。

os.path.normcase(path, /)

將路徑名的大小寫規範化。在 Windows 上，將路徑名中的所有字元轉換為小寫，並將正斜線轉換為反斜線。在其他作業系統上，回傳原始路徑。

在 3.6 版的變更: 接受一個 path-like object。

os.path.normpath(path)

透過合併多餘的分隔符號和上層引用來標準化路徑名，使得 A//B、A/B/、A/./B 和 A/foo/../B 都變成 A/B。這種字串操作可能會改變包含符號連結的路徑的含義。在 Windows 上，它將正斜線轉換為反斜線。要標準化大小寫，請使用 normcase()。

備註

在 POSIX 系統中，根據 IEEE Std 1003.1 2013 版; 4.13 Pathname Resolution [https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13] 標準，如果一個路徑名恰好以兩個斜線開頭，則在前導字元後的第一個部分可能會以由實作品自行定義的方式解釋，雖然多於兩個前導字元應該被視為單個字元。

在 3.6 版的變更: 接受一個 path-like object。

os.path.realpath(path, /, *, strict=False)

回傳指定檔案名稱的規範路徑，會消除路徑中遇到的所有符號連結（如果作業系統支援）。在 Windows 上，此函式還會解析 MS-DOS（也稱為 8.3）樣式的名稱，例如 C:\\PROGRA~1 會被解析為 C:\\Program Files。

By default, the path is evaluated up to the first component that does not exist, is a symlink loop, or whose evaluation raises OSError. All such components are appended unchanged to the existing part of the path.

Some errors that are handled this way include "access denied", "not a directory", or "bad argument to internal function". Thus, the resulting path may be missing or inaccessible, may still contain links or loops, and may traverse non-directories.

This behavior can be modified by keyword arguments:

If strict is True, the first error encountered when evaluating the path is re-raised. In particular, FileNotFoundError is raised if path does not exist, or another OSError if it is otherwise inaccessible.

If strict is os.path.ALLOW_MISSING, errors other than FileNotFoundError are re-raised (as with strict=True). Thus, the returned path will not contain any symbolic links, but the named file and some of its parent directories may be missing.

備註

此函式模擬作業系統使路徑成為規範的過程，Windows 和 UNIX 之間在鏈接和後續路徑部份交互方式方面略有不同。

作業系統的 API 會根據需要自動使路徑正則，因此通常不需要呼叫此函式。

在 3.6 版的變更: 接受一個 path-like object。

在 3.8 版的變更: 在 Windows 上，現在會解析符號連結和連接點。

在 3.10 版的變更: 新增 strict 參數。

在 3.14 版的變更: The ALLOW_MISSING value for the strict parameter was added.

os.path.ALLOW_MISSING

Special value used for the strict argument in realpath().

在 3.14 版被加入.

os.path.relpath(path, start=os.curdir)

從目前目錄或可選的 start 目錄回傳到 path 的相對檔案路徑。這是一個路徑計算：不會存取檔案系統來確認 path 或 start 的存在或屬性。在 Windows 上，當 path 和 start 在不同的驅動機上時，會引發 ValueError。

start 的預設值為 os.curdir。

在 3.6 版的變更: 接受一個 path-like object。

os.path.samefile(path1, path2, /)

如果兩個路徑名引數指向同一個檔案或目錄，則回傳 True。這是透過設備編號和 i-node 編號來確定的，如果對任一路徑名的 os.stat() 呼叫失敗，則會引發異常。

在 3.2 版的變更: 新增對 Windows 的支援。

在 3.4 版的變更: 現在在 Windows 上使用與其他所有平台相同的實作方式。

在 3.6 版的變更: 接受一個 path-like object。

os.path.sameopenfile(fp1, fp2)

如果文件描述符 fp1 和 fp2 指向同一個檔案，則回傳 True。

在 3.2 版的變更: 新增對 Windows 的支援。

在 3.6 版的變更: 接受一個 path-like object。

os.path.samestat(stat1, stat2, /)

如果 stat 值組 stat1 和 stat2 指向同一個檔案，則回傳 True。這些結構可能由 os.fstat()、os.lstat() 或 os.stat() 回傳。此函式使用 samefile() 和 sameopenfile() 實現了底層比較。

在 3.4 版的變更: 新增對 Windows 的支援。

os.path.split(path, /)

將路徑名 path 拆分為 (head, tail) 一對，其中 tail 是最後一個路徑名部份，head 是在它之前的所有部分。tail 部分不會包含斜線；如果 path 以斜線結尾，則 tail 將為空。如果 path 中沒有斜線，則 head 將為空。如果 path 為空，則 head 和 tail 都為空。除非 head 是根目錄（僅有一個或多個斜線），否則從 head 中刪除尾部的斜線。在所有情況下，join(head, tail) 回傳指向與 path 相同位置的路徑（但字串可能不同）。另請參考函式 join()、dirname() 和 basename()。

在 3.6 版的變更: 接受一個 path-like object。

os.path.splitdrive(path, /)

將路徑名 path 拆分為 (drive, tail) 一對，其中 drive 是掛載點或空字串。在不使用驅動機規範的系統上，drive 將始終為空字串。在所有情況下，drive + tail 將與 path 相同。

在 Windows 上，將路徑名拆分為驅動機或 UNC 共享點以及相對路徑。

如果路徑包含驅動機字母，則 drive 將包含從頭到冒號（包括冒號）的所有內容：

>>> splitdrive("c:/dir")
("c:", "/dir")

如果路徑包含 UNC 路徑，則驅動機將包含主機名和共享名：

>>> splitdrive("//host/computer/dir")
("//host/computer", "/dir")

在 3.6 版的變更: 接受一個 path-like object。

os.path.splitroot(path, /)

將路徑名 path 拆分為一個 3 項值組 (drive, root, tail)，其中 drive 是設備名稱或掛載點，root 是驅動機後的分隔符字串，tail 是在根後的所有內容。這些項目中的任何一個都可能是空字串。在所有情況下，drive + root + tail 將與 path 相同。

在 POSIX 系統上，drive 始終為空。root 可能為空（如果 path 是相對路徑），一個斜線（如果 path 是絕對路徑），或者兩個斜線（根據 IEEE Std 1003.1-2017; 4.13 Pathname Resolution [https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13] 的實作定義）。例如：

>>> splitroot('/home/sam')
('', '/', 'home/sam')
>>> splitroot('//home/sam')
('', '//', 'home/sam')
>>> splitroot('///home/sam')
('', '/', '//home/sam')

在 Windows 上，drive 可能為空、驅動機名稱、UNC 共享或設備名稱。root 可能為空，斜線或反斜線。例如：

>>> splitroot('C:/Users/Sam')
('C:', '/', 'Users/Sam')
>>> splitroot('//Server/Share/Users/Sam')
('//Server/Share', '/', 'Users/Sam')

在 3.12 版被加入.

os.path.splitext(path, /)

將路徑名 path 拆分為一對 (root, ext)，使得 root + ext == path，且副檔名 ext 為空或以點開頭且最多包含一個點 (period)。

如果路徑不包含副檔名，則 ext 將為 ''：

>>> splitext('bar')
('bar', '')

如果路徑包含副檔名，則 ext 將設置為該副檔名，包括前導的點。請注意，前面的點將被忽略：

>>> splitext('foo.bar.exe')
('foo.bar', '.exe')
>>> splitext('/foo/bar.exe')
('/foo/bar', '.exe')

路徑的最後一個部份的前導點被認為是根的一部分：

>>> splitext('.cshrc')
('.cshrc', '')
>>> splitext('/foo/....jpg')
('/foo/....jpg', '')

在 3.6 版的變更: 接受一個 path-like object。

os.path.supports_unicode_filenames

如果可以使用任意的 Unicode 字串作為檔案名（在檔案系統所施加的限制範圍內），則回傳 True。

stat --- 直譯 stat() 的結果

原始碼：Lib/stat.py [https://github.com/python/cpython/tree/3.14/Lib/stat.py]

The stat module defines constants and functions for interpreting the results of os.stat(), os.fstat() and os.lstat() (if they exist). For complete details about the stat(), fstat() and lstat() calls, consult the documentation for your system.

在 3.4 版的變更: The stat module is backed by a C implementation.

stat 模組定義了以下函式，用於測試特定檔案類型：

stat.S_ISDIR(mode)

Return non-zero if the mode is from a directory.

stat.S_ISCHR(mode)

Return non-zero if the mode is from a character special device file.

stat.S_ISBLK(mode)

Return non-zero if the mode is from a block special device file.

stat.S_ISREG(mode)

Return non-zero if the mode is from a regular file.

stat.S_ISFIFO(mode)

Return non-zero if the mode is from a FIFO (named pipe).

stat.S_ISLNK(mode)

Return non-zero if the mode is from a symbolic link.

stat.S_ISSOCK(mode)

Return non-zero if the mode is from a socket.

stat.S_ISDOOR(mode)

Return non-zero if the mode is from a door.

在 3.4 版被加入.

stat.S_ISPORT(mode)

Return non-zero if the mode is from an event port.

在 3.4 版被加入.

stat.S_ISWHT(mode)

Return non-zero if the mode is from a whiteout.

在 3.4 版被加入.

Two additional functions are defined for more general manipulation of the file's mode:

stat.S_IMODE(mode)

Return the portion of the file's mode that can be set by os.chmod()---that is, the file's permission bits, plus the sticky bit, set-group-id, and set-user-id bits (on systems that support them).

stat.S_IFMT(mode)

Return the portion of the file's mode that describes the file type (used by the S_IS*() functions above).

Normally, you would use the os.path.is*() functions for testing the type of a file; the functions here are useful when you are doing multiple tests of the same file and wish to avoid the overhead of the stat() system call for each test. These are also useful when checking for information about a file that isn't handled by os.path, like the tests for block and character devices.

範例：

import os, sys
from stat import *

def walktree(top, callback):
    '''recursively descend the directory tree rooted at top,
       calling the callback function for each regular file'''

    for f in os.listdir(top):
        pathname = os.path.join(top, f)
        mode = os.lstat(pathname).st_mode
        if S_ISDIR(mode):
            # It's a directory, recurse into it
            walktree(pathname, callback)
        elif S_ISREG(mode):
            # It's a file, call the callback function
            callback(pathname)
        else:
            # Unknown file type, print a message
            print('Skipping %s' % pathname)

def visitfile(file):
    print('visiting', file)

if __name__ == '__main__':
    walktree(sys.argv[1], visitfile)

An additional utility function is provided to convert a file's mode in a human readable string:

stat.filemode(mode)

Convert a file's mode to a string of the form '-rwxrwxrwx'.

在 3.3 版被加入.

在 3.4 版的變更: The function supports S_IFDOOR, S_IFPORT and S_IFWHT.

All the variables below are simply symbolic indexes into the 10-tuple returned by os.stat(), os.fstat() or os.lstat().

stat.ST_MODE

Inode protection mode.

stat.ST_INO

Inode number.

stat.ST_DEV

Device inode resides on.

stat.ST_NLINK

Number of links to the inode.

stat.ST_UID

User id of the owner.

stat.ST_GID

Group id of the owner.

stat.ST_SIZE

Size in bytes of a plain file; amount of data waiting on some special files.

stat.ST_ATIME

Time of last access.

stat.ST_MTIME

Time of last modification.

stat.ST_CTIME

The "ctime" as reported by the operating system. On some systems (like Unix) is the time of the last metadata change, and, on others (like Windows), is the creation time (see platform documentation for details).

The interpretation of "file size" changes according to the file type. For plain files this is the size of the file in bytes. For FIFOs and sockets under most flavors of Unix (including Linux in particular), the "size" is the number of bytes waiting to be read at the time of the call to os.stat(), os.fstat(), or os.lstat(); this can sometimes be useful, especially for polling one of these special files after a non-blocking open. The meaning of the size field for other character and block devices varies more, depending on the implementation of the underlying system call.

The variables below define the flags used in the ST_MODE field.

Use of the functions above is more portable than use of the first set of flags:

stat.S_IFSOCK

Socket.

stat.S_IFLNK

Symbolic link.

stat.S_IFREG

Regular file.

stat.S_IFBLK

Block device.

stat.S_IFDIR

Directory.

stat.S_IFCHR

Character device.

stat.S_IFIFO

FIFO.

stat.S_IFDOOR

Door.

在 3.4 版被加入.

stat.S_IFPORT

Event port.

在 3.4 版被加入.

stat.S_IFWHT

Whiteout.

在 3.4 版被加入.

備註

S_IFDOOR, S_IFPORT or S_IFWHT are defined as 0 when the platform does not have support for the file types.

The following flags can also be used in the mode argument of os.chmod():

stat.S_ISUID

Set UID bit.

stat.S_ISGID

Set-group-ID bit. This bit has several special uses. For a directory it indicates that BSD semantics is to be used for that directory: files created there inherit their group ID from the directory, not from the effective group ID of the creating process, and directories created there will also get the S_ISGID bit set. For a file that does not have the group execution bit (S_IXGRP) set, the set-group-ID bit indicates mandatory file/record locking (see also S_ENFMT).

stat.S_ISVTX

Sticky bit. When this bit is set on a directory it means that a file in that directory can be renamed or deleted only by the owner of the file, by the owner of the directory, or by a privileged process.

stat.S_IRWXU

Mask for file owner permissions.

stat.S_IRUSR

Owner has read permission.

stat.S_IWUSR

Owner has write permission.

stat.S_IXUSR

Owner has execute permission.

stat.S_IRWXG

Mask for group permissions.

stat.S_IRGRP

Group has read permission.

stat.S_IWGRP

Group has write permission.

stat.S_IXGRP

Group has execute permission.

stat.S_IRWXO

Mask for permissions for others (not in group).

stat.S_IROTH

Others have read permission.

stat.S_IWOTH

Others have write permission.

stat.S_IXOTH

Others have execute permission.

stat.S_ENFMT

System V file locking enforcement. This flag is shared with S_ISGID: file/record locking is enforced on files that do not have the group execution bit (S_IXGRP) set.

stat.S_IREAD

Unix V7 synonym for S_IRUSR.

stat.S_IWRITE

Unix V7 synonym for S_IWUSR.

stat.S_IEXEC

Unix V7 synonym for S_IXUSR.

The following flags can be used in the flags argument of os.chflags():

stat.UF_SETTABLE

All user settable flags.

在 3.13 版被加入.

stat.UF_NODUMP

Do not dump the file.

stat.UF_IMMUTABLE

The file may not be changed.

stat.UF_APPEND

The file may only be appended to.

stat.UF_OPAQUE

The directory is opaque when viewed through a union stack.

stat.UF_NOUNLINK

The file may not be renamed or deleted.

stat.UF_COMPRESSED

The file is stored compressed (macOS 10.6+).

stat.UF_TRACKED

Used for handling document IDs (macOS)

在 3.13 版被加入.

stat.UF_DATAVAULT

The file needs an entitlement for reading or writing (macOS 10.13+)

在 3.13 版被加入.

stat.UF_HIDDEN

The file should not be displayed in a GUI (macOS 10.5+).

stat.SF_SETTABLE

All super-user changeable flags

在 3.13 版被加入.

stat.SF_SUPPORTED

All super-user supported flags

可用性: macOS

在 3.13 版被加入.

stat.SF_SYNTHETIC

All super-user read-only synthetic flags

可用性: macOS

在 3.13 版被加入.

stat.SF_ARCHIVED

The file may be archived.

stat.SF_IMMUTABLE

The file may not be changed.

stat.SF_APPEND

The file may only be appended to.

stat.SF_RESTRICTED

The file needs an entitlement to write to (macOS 10.13+)

在 3.13 版被加入.

stat.SF_NOUNLINK

The file may not be renamed or deleted.

stat.SF_SNAPSHOT

The file is a snapshot file.

stat.SF_FIRMLINK

The file is a firmlink (macOS 10.15+)

在 3.13 版被加入.

stat.SF_DATALESS

The file is a dataless object (macOS 10.15+)

在 3.13 版被加入.

See the *BSD or macOS systems man page chflags(2) [https://manpages.debian.org/chflags(2)] for more information.

On Windows, the following file attribute constants are available for use when testing bits in the st_file_attributes member returned by os.stat(). See the Windows API documentation [https://msdn.microsoft.com/en-us/library/windows/desktop/gg258117.aspx] for more detail on the meaning of these constants.

stat.FILE_ATTRIBUTE_ARCHIVE

stat.FILE_ATTRIBUTE_COMPRESSED

stat.FILE_ATTRIBUTE_DEVICE

stat.FILE_ATTRIBUTE_DIRECTORY

stat.FILE_ATTRIBUTE_ENCRYPTED

stat.FILE_ATTRIBUTE_HIDDEN

stat.FILE_ATTRIBUTE_INTEGRITY_STREAM

stat.FILE_ATTRIBUTE_NORMAL

stat.FILE_ATTRIBUTE_NOT_CONTENT_INDEXED

stat.FILE_ATTRIBUTE_NO_SCRUB_DATA

stat.FILE_ATTRIBUTE_OFFLINE

stat.FILE_ATTRIBUTE_READONLY

stat.FILE_ATTRIBUTE_REPARSE_POINT

stat.FILE_ATTRIBUTE_SPARSE_FILE

stat.FILE_ATTRIBUTE_SYSTEM

stat.FILE_ATTRIBUTE_TEMPORARY

stat.FILE_ATTRIBUTE_VIRTUAL

在 3.5 版被加入.

On Windows, the following constants are available for comparing against the st_reparse_tag member returned by os.lstat(). These are well-known constants, but are not an exhaustive list.

stat.IO_REPARSE_TAG_SYMLINK

stat.IO_REPARSE_TAG_MOUNT_POINT

stat.IO_REPARSE_TAG_APPEXECLINK

在 3.8 版被加入.

filecmp --- 檔案與目錄比較

原始碼：Lib/filecmp.py [https://github.com/python/cpython/tree/3.14/Lib/filecmp.py]

The filecmp module defines functions to compare files and directories, with various optional time/correctness trade-offs. For comparing files, see also the difflib module.

filecmp 模組定義了以下函式：

filecmp.cmp(f1, f2, shallow=True)

Compare the files named f1 and f2, returning True if they seem equal, False otherwise.

If shallow is true and the os.stat() signatures (file type, size, and modification time) of both files are identical, the files are taken to be equal.

Otherwise, the files are treated as different if their sizes or contents differ.

Note that no external programs are called from this function, giving it portability and efficiency.

This function uses a cache for past comparisons and the results, with cache entries invalidated if the os.stat() information for the file changes. The entire cache may be cleared using clear_cache().

filecmp.cmpfiles(dir1, dir2, common, shallow=True)

Compare the files in the two directories dir1 and dir2 whose names are given by common.

Returns three lists of file names: match, mismatch, errors. match contains the list of files that match, mismatch contains the names of those that don't, and errors lists the names of files which could not be compared. Files are listed in errors if they don't exist in one of the directories, the user lacks permission to read them or if the comparison could not be done for some other reason.

The shallow parameter has the same meaning and default value as for filecmp.cmp().

For example, cmpfiles('a', 'b', ['c', 'd/e']) will compare a/c with b/c and a/d/e with b/d/e. 'c' and 'd/e' will each be in one of the three returned lists.

filecmp.clear_cache()

Clear the filecmp cache. This may be useful if a file is compared so quickly after it is modified that it is within the mtime resolution of the underlying filesystem.

在 3.4 版被加入.

The dircmp class

class filecmp.dircmp(a, b, ignore=None, hide=None, *, shallow=True)

Construct a new directory comparison object, to compare the directories a and b. ignore is a list of names to ignore, and defaults to filecmp.DEFAULT_IGNORES. hide is a list of names to hide, and defaults to [os.curdir, os.pardir].

The dircmp class compares files by doing shallow comparisons as described for filecmp.cmp() by default using the shallow parameter.

在 3.13 版的變更: 新增了 shallow 參數。

The dircmp class provides the following methods:

report()

Print (to sys.stdout) a comparison between a and b.

report_partial_closure()

Print a comparison between a and b and common immediate subdirectories.

report_full_closure()

Print a comparison between a and b and common subdirectories (recursively).

The dircmp class offers a number of interesting attributes that may be used to get various bits of information about the directory trees being compared.

Note that via __getattr__() hooks, all attributes are computed lazily, so there is no speed penalty if only those attributes which are lightweight to compute are used.

left

The directory a.

right

The directory b.

left_list

Files and subdirectories in a, filtered by hide and ignore.

right_list

Files and subdirectories in b, filtered by hide and ignore.

common

Files and subdirectories in both a and b.

left_only

Files and subdirectories only in a.

right_only

Files and subdirectories only in b.

common_dirs

Subdirectories in both a and b.

common_files

Files in both a and b.

common_funny

Names in both a and b, such that the type differs between the directories, or names for which os.stat() reports an error.

same_files

Files which are identical in both a and b, using the class's file comparison operator.

diff_files

Files which are in both a and b, whose contents differ according to the class's file comparison operator.

funny_files

Files which are in both a and b, but could not be compared.

subdirs

A dictionary mapping names in common_dirs to dircmp instances (or MyDirCmp instances if this instance is of type MyDirCmp, a subclass of dircmp).

在 3.10 版的變更: Previously entries were always dircmp instances. Now entries are the same type as self, if self is a subclass of dircmp.

filecmp.DEFAULT_IGNORES

在 3.4 版被加入.

List of directories ignored by dircmp by default.

Here is a simplified example of using the subdirs attribute to search recursively through two directories to show common different files:

>>> from filecmp import dircmp
>>> def print_diff_files(dcmp):
...     for name in dcmp.diff_files:
...         print("diff_file %s found in %s and %s" % (name, dcmp.left,
...               dcmp.right))
...     for sub_dcmp in dcmp.subdirs.values():
...         print_diff_files(sub_dcmp)
...
>>> dcmp = dircmp('dir1', 'dir2')
>>> print_diff_files(dcmp)

tempfile --- 生成臨時檔案和目錄

原始碼：Lib/tempfile.py [https://github.com/python/cpython/tree/3.14/Lib/tempfile.py]

該 module（模組）用於建立臨時檔案和目錄，它可以在所有有支援的平臺上使用。TemporaryFile、NamedTemporaryFile、TemporaryDirectory 和 SpooledTemporaryFile 是有自動清除功能的高階介面，可作為情境管理器 (context manager) 使用。mkstemp() 和 mkdtemp() 是低階函式，使用完畢後需手動清理。

所有可被使用者呼叫的函式和建構函式都帶有可以設定臨時檔案和臨時目錄的路徑和名稱的引數。此 module 所使用的檔名為一個隨機字元組成的字串，這讓檔案可以更安全地在共享的臨時目錄中被建立。為了維持向後相容性，引數的順序會稍微奇怪，所以為了讓程式更容易被理解，建議使用關鍵字引數。

這個 module 定義了以下可供使用者呼叫的項目：

tempfile.TemporaryFile(mode='w+b', buffering=-1, encoding=None, newline=None, suffix=None, prefix=None, dir=None, *, errors=None)

回傳一個可當作臨時儲存區域的類檔案物件。建立該檔案使用了與 mkstemp() 相同的安全規則。它將在關閉（包括當物件被垃圾回收 (garbage collect) 時的隱式關閉）後立即銷毀。在 Unix 下，該檔案所在的目錄可能根本不被建立、或者在建立檔案後立即就被刪除，其他平臺不支援此功能；你的程式不應依賴使用此功能建立的臨時檔案名稱，因為它在檔案系統中的名稱有可能是不可見的。

生成的物件可以作為情境管理器使用（參見 範例）。完成情境或銷毀臨時檔案物件後，臨時檔案將從檔案系統中刪除。

mode 參數預設為 'w+b'，所以建立的檔案不用關閉就可以讀取或寫入。因為用的是二進位制模式，所以無論存的是什麼資料，它在所有平臺上的行為都一致。buffering、encoding、errors 和 newline 的含義與 open() 中的相同。

參數 dir、prefix 和 suffix 的含義和預設值都與它們在 mkstemp() 中的相同。

在 POSIX 平臺上，回傳物件是真實的檔案物件。在其他平臺上，它是一個 file-like object，它的 file 屬性為底層的真實檔案物件。

如果可用且可運作，則使用 os.O_TMPFILE 旗標（僅限於 Linux，需要 3.11 版本以上的核心）。

在不是 Posix 或 Cygwin 的平臺上，TemporaryFile 是 NamedTemporaryFile 的別名。

引發一個附帶引數 fullpath 的 tempfile.mkstemp 稽核事件。

在 3.5 版的變更: 如果可用，自此開始使用 os.O_TMPFILE 旗標。

在 3.8 版的變更: 新增 errors 參數。

tempfile.NamedTemporaryFile(mode='w+b', buffering=-1, encoding=None, newline=None, suffix=None, prefix=None, dir=None, delete=True, *, errors=None, delete_on_close=True)

此函式的操作與 TemporaryFile() 完全相同，但存在以下差異：

此函式回傳一個保證在檔案系統中具有可見名稱的檔案。

為了管理指定檔案，它使用 delete 和 delete_on_close 參數擴充 TemporaryFile() 來指定是否以及如何自動刪除指定檔案。

回傳的物件始終是一個類檔案物件，其 file 屬性是底層的真實檔案物件。這個類檔案物件可以在 with 陳述式中使用，就像普通檔案一樣。臨時檔案的名稱可以從回傳的類檔案物件的 name 屬性中取得。在 Unix 上則與 TemporaryFile() 不同，目錄條目不會在檔案建立後立即被取消鏈接 (unlink)。

如果 delete 為 true（預設值）並且 delete_on_close 為 true（預設值），則檔案在關閉後會立即被刪除。如果 delete 為 true 並且 delete_on_close 為 false，則僅在情境管理器退出時刪除檔案，或者在類檔案物件完結時刪除檔案。在這種情況下，並不總是保證能成功刪除（請參閱 object.__del__()）。如果 delete 為 false，則會忽略 delete_on_close 的值。

因此，要在關閉檔案後使用臨時檔案的名稱重新打開檔案，請確保在關閉時不刪除檔案（將 delete 參數設定為 false），或者如果臨時檔案是以 with 陳述式建立，要將 delete_on_close 參數設定為 false。建議使用後者，因為它有助於在情境管理器退出時自動清理臨時檔案。

在臨時檔案仍處於打開狀態時再次按其名稱打開它，其作用方式如下：

在 POSIX 上，檔案始終可以再次打開。

在 Windows 上，確保至少滿足以下條件之一：

delete 為 false

額外的 open 會共享刪除存取權限（例如，透過使用旗標 O_TEMPORARY 來呼叫 os.open()）

delete 為 true 但 delete_on_close 為 false。請注意，在這種情況下不共享刪除存取權限的其他 open（例如透過內建的 open() 建立）必須在退出情境管理器之前關閉，否則情境管理器上的 os.unlink() 呼叫退出將失敗並出現 PermissionError。

在 Windows 上，如果 delete_on_close 為 false，並且檔案是在使用者缺乏刪除存取權限的目錄中建立的，則情境管理器退出時的 os.unlink() 呼叫將失敗，並引發 PermissionError。當 delete_on_close 為 true 時，不會發生這種情況，因為刪除存取權限是由 open 來要求的，如果未授予存取權限則會立即失敗。

（僅）在 POSIX 上，因使用 SIGKILL 而被終止的行程無法自動刪除它建立的任何 NamedTemporaryFiles。

引發一個附帶引數 fullpath 的 tempfile.mkstemp 稽核事件。

在 3.8 版的變更: 新增 errors 參數。

在 3.12 版的變更: 新增 delete_on_close 參數。

class tempfile.SpooledTemporaryFile(max_size=0, mode='w+b', buffering=-1, encoding=None, newline=None, suffix=None, prefix=None, dir=None, *, errors=None)

此類別執行的操作與 TemporaryFile() 完全相同，但會將資料排存 (spool) 於在記憶體中，直到檔案大小超過 max_size，或檔案的 fileno() 方法被呼叫為止，此時資料會被寫入磁碟，並且之後的操作與 TemporaryFile() 相同。

rollover()

生成的檔案物件有一個額外的方法 rollover()，忽略檔案大小並立即將其寫入磁碟。

回傳的物件是 file-like object，它的 _file 屬性是 io.BytesIO 或 io.TextIOWrapper 物件（取決於指定的是二進位制模式還是文字模式）或真實的檔案物件（取決於是否已呼叫 rollover()）。file-like object 可以像普通檔案一樣在 with 陳述式中使用。

在 3.3 版的變更: 現在，檔案的截斷方法 (truncate method) 可接受一個 size 引數。

在 3.8 版的變更: 新增 errors 參數。

在 3.11 版的變更: 完全實作 io.BufferedIOBase 和 io.TextIOBase 抽象基底類別（取決於指定的是二進位還是文本 mode）。

class tempfile.TemporaryDirectory(suffix=None, prefix=None, dir=None, ignore_cleanup_errors=False, *, delete=True)

此類別會使用與 mkdtemp() 相同安全規則來建立一個臨時目錄。回傳物件可當作情境管理器使用（參見範例）。在完成情境或銷毀臨時目錄物件時，新建立的臨時目錄及其所有內容會從檔案系統中被移除。

name

可以從回傳物件的 name 屬性中找到的臨時目錄名稱。當回傳的物件用作情境管理器時，這個 name 會作為 with 陳述句中 as 子句的目標（如果有 as 的話）。

cleanup()

此目錄可透過呼叫 cleanup() 方法來顯式地清理。如果 ignore_cleanup_errors 為 true，則在顯式或隱式清理期間出現的未處理例外（例如在 Windows 上移除開啟的檔案而引發的 PermissionError）將被忽略，並且剩餘的可移除條目會「儘可能」地被刪除。在其他情況下，錯誤將在任何情境清理發生時被引發（cleanup() 呼叫、退出情境管理器、物件被作為垃圾回收或直譯器關閉等）。

delete 參數可以停用在退出情境時對目錄樹的清理，雖然停用情境管理器在退出情境時所採取的操作似乎不常見，但它在除錯期間或當你需要基於其他邏輯的清理行為時會非常有用。

引發一個附帶引數 fullpath 的 tempfile.mkdtemp 稽核事件。

在 3.2 版被加入.

在 3.10 版的變更: 新增 ignore_cleanup_errors 參數。

在 3.12 版的變更: 新增 delete 參數。

tempfile.mkstemp(suffix=None, prefix=None, dir=None, text=False)

盡可能以最安全的方式建立一個臨時檔案。假設所在平臺正確實作了 os.open() 的 os.O_EXCL 旗標，則建立檔案時不會有 race condition（競爭條件）的情況。該檔案只能由建立者讀寫，如果所在平臺用 permission bit（許可權位元）來表示檔案是否可執行，則沒有人有執行權。

檔案描述器不會被子行程繼承。

與 TemporaryFile() 不同，mkstemp() 使用者用完臨時檔案後需要自行將其刪除。

如果 suffix 不是 None 則檔名將以該後綴結尾，若為 None 則沒有後綴。mkstemp() 不會在檔名和後綴之間加點 (dot)，如果需要加一個點號，請將其放在 suffix 的開頭。

如果 prefix 不是 None 則檔名將以該字首開頭，若為 None 則使用預設前綴。預設前綴是 gettempprefix() 或 gettempprefixb() 函式的回傳值（自動呼叫合適的函式）。

如果 dir 不為 None 則在指定的目錄建立檔案，若為 None 則使用預設目錄。預設目錄是從一個相依於平臺的列表中選擇出來的，但是使用者可以設定 TMPDIR、TEMP 或 TMP 環境變數來設定目錄的位置。因此，不能保證生成的臨時檔案路徑是使用者友善的，比如透過 os.popen() 將路徑傳遞給外部命令時仍需要加引號 (quoting)。

如果 suffix、prefix 和 dir 中的任何一個不是 None，就要保證它們資料型別相同。如果它們是位元組串，則回傳名稱的型別就是位元組串而非字串。如果不想遵循預設行為但又想要回傳值是位元組串型別，請傳入 suffix=b''。

如果指定了 text 且為真值，檔案會以文字模式開啟。否則，檔案（預設）以二進位制模式開啟。

mkstemp() 回傳一個 tuple，tuple 中，第一個元素是一個作業系統層級 (OS-level) 控制代碼，指向一個開啟的檔案（如同 os.open() 的回傳值），第二元素是該檔案的絕對路徑。

引發一個附帶引數 fullpath 的 tempfile.mkstemp 稽核事件。

在 3.5 版的變更: 現在，suffix、prefix 和 dir 可以以位元組串型別按順序提供，以獲得位元組串型別的回傳值。在之前只允許使用字串。suffix 和 prefix 現在可以接受 None，並且預設為 None 以使用合適的預設值。

在 3.6 版的變更: dir 參數現在可接受一個類路徑物件 (path-like object)。

tempfile.mkdtemp(suffix=None, prefix=None, dir=None)

盡可能以最安全的方式建立一個臨時目錄，建立該目錄時不會有 race condition 的情況，該目錄只能由建立者讀取、寫入和搜尋。

mkdtemp() 的使用者用完臨時目錄後需要自行將其刪除。

引數 prefix、suffix 和 dir 的含義與它們在 mkstemp() 中相同。

mkdtemp() 回傳新目錄的絕對路徑名稱。

引發一個附帶引數 fullpath 的 tempfile.mkdtemp 稽核事件。

在 3.5 版的變更: 現在，suffix、prefix 和 dir 可以以位元組串型別按順序提供，以獲得位元組串型別的回傳值。在之前只允許使用字串。suffix 和 prefix 現在可以接受 None，並且預設為 None 以使用合適的預設值。

在 3.6 版的變更: dir 參數現在可接受一個類路徑物件 (path-like object)。

在 3.12 版的變更: mkdtemp() 現在都會回傳絕對路徑，即使 dir 是相對路徑。

tempfile.gettempdir()

回傳儲存臨時檔案的目錄名稱。這設定了此 module 所有函式 dir 引數的預設值。

Python 搜尋標準目錄列表來找到呼叫者可以在其中建立檔案的目錄。這個列表是：

TMPDIR 環境變數指向的目錄。

TEMP 環境變數指向的目錄。

TMP 環境變數指向的目錄。

與平臺相關的位置：

在 Windows 上，目錄依次為 C:\TEMP、C:\TMP、\TEMP 和 \TMP。

在所有其他平臺上，目錄依次為 /tmp、/var/tmp 和 /usr/tmp。

不得已時，使用目前工作目錄。

搜尋的結果會被 cache（快取）起來，請見下面 tempdir 的描述。

在 3.10 版的變更: 回傳一個字串。在之前的版本中它會回傳任意 tempdir 的值而不考慮它的型別，只要它不為 None。

tempfile.gettempdirb()

與 gettempdir() 相同，但回傳值為位元組串型別。

在 3.5 版被加入.

tempfile.gettempprefix()

回傳用於建立臨時檔案的檔名前綴，它不包含目錄部分。

tempfile.gettempprefixb()

與 gettempprefix() 相同，但回傳值為位元組串型別。

在 3.5 版被加入.

此 module 使用一個全域性變數來儲存由 gettempdir() 回傳的臨時檔案使用的目錄路徑。它可被直接設定以覆蓋選擇過程，但不建議這樣做。此 module 中的所有函式都接受一個 dir 引數，它可被用於指定目錄。這是個推薦的做法，它不會透過改變全域性 API 行為而對其他不預期此行為的程式造成影響。

tempfile.tempdir

當被設為 None 以外的值時，此變數會為此 module 所定義函式的引數 dir 定義預設值，包括確定其型別為位元組串還是字串。它不可以為 path-like object。

如果在呼叫除 gettempprefix() 外的上述任何函式時 tempdir 為 None (預設值) 則它會按照 gettempdir() 中所描述的演算法來初始化。

備註

請注意如果你將 tempdir 設為位元組串值，會有一個麻煩的副作用：mkstemp() 和 mkdtemp() 的全域性預設回傳型別會在沒有提供明顯字串型別的 prefix、suffix 或 dir 時被改為位元組串。請不要編寫預期此行為或依賴於此行為的程式。這個奇怪的行為是為了維持與以往實作版本的相容性。

範例

以下是 tempfile module 的一些常見用法範例：

>>> import tempfile

# 建立一個臨時檔案並寫入一些資料
>>> fp = tempfile.TemporaryFile()
>>> fp.write(b'Hello world!')
# read data from file
>>> fp.seek(0)
>>> fp.read()
b'Hello world!'
# 關閉檔案，檔案會被刪除
>>> fp.close()

# 使用情境管理器建立臨時檔案
>>> with tempfile.TemporaryFile() as fp:
...     fp.write(b'Hello world!')
...     fp.seek(0)
...     fp.read()
b'Hello world!'
>>>
# 檔案現在已關閉並刪除

# 使用情境管理器建立臨時檔案
# 關閉檔案，使用名稱再次開啟檔案
>>> with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
...     fp.write(b'Hello world!')
...     fp.close()
... # 檔案已被關閉，但未被刪除
... # 透過其名稱再次開啟檔案
...     with open(fp.name, mode='rb') as f:
...         f.read()
b'Hello world!'
>>>
# 現在檔案已被刪除

# 使用情境管理器建立臨時目錄
>>> with tempfile.TemporaryDirectory() as tmpdirname:
...     print('created temporary directory', tmpdirname)
>>>
# 目錄及其內容已被刪除

已棄用的函式和變數

在過去，建立臨時檔案首先使用 mktemp() 函式生成一個檔名，然後使用該檔名建立檔案。不幸的是這並不安全的，因為在呼叫 mktemp() 與隨後嘗試建立檔案之間的時間裡，其他程式可能會使用該名稱建立檔案。解決方案是將兩個步驟結合起來，並立即建立檔案。這個方案目前被 mkstemp() 和上述其他函式所採用。

tempfile.mktemp(suffix='', prefix='tmp', dir=None)

在 2.3 版之後被棄用: 使用 mkstemp() 代替。

回傳一個在呼叫本方法時不存在檔案的絕對路徑。引數 prefix、suffix 和 dir 與 mkstemp() 中所用的類似，除了在於不支援位元組串型別的檔名且不支援 suffix=None 和 prefix=None。

警告

使用此功能可能會在程式中引入安全漏洞。當你開始使用本方法回傳的檔案執行任何操作時，可能有人已經捷足先登了。mktemp() 的功能可以很輕鬆地用帶有 delete=False 參數的 NamedTemporaryFile() 代替：

>>> f = NamedTemporaryFile(delete=False)
>>> f.name
'/tmp/tmptjujjt'
>>> f.write(b"Hello World!\n")
13
>>> f.close()
>>> os.unlink(f.name)
>>> os.path.exists(f.name)
False

glob --- Unix 風格的路徑名稱模式擴展

原始碼：Lib/glob.py [https://github.com/python/cpython/tree/3.14/Lib/glob.py]

glob 模組使用類似於 Unix shell 的模式匹配規則來尋找路徑名稱。不會進行波浪號擴展 (tilde expansion) ，但 *、? 和使用 [] 表達的字元範圍將會被正確匹配。這是透過結合使用 os.scandir() 和 fnmatch.fnmatch() 函式來完成的，而沒有實際呼叫 subshell。

備註

路徑名稱不會以特定順序回傳。如果你需要特定的順序，請對結果進行排序。

以點 (.) 開頭的檔案只能與同樣以點開頭的模式匹配，這與 fnmatch.fnmatch() 或 pathlib.Path.glob() 不同。對於波浪號和 shell 變數擴展，請使用 os.path.expanduser() 和 os.path.expandvars()。

對於文本 (literal) 匹配，將元字元 (meta-character) 括在方括號中。例如，'[?]' 會匹配 '?' 字元。

glob 模組定義了以下函式：

glob.glob(pathname, *, root_dir=None, dir_fd=None, recursive=False, include_hidden=False)

回傳與 pathname 匹配、可能為空的路徑名稱 list，它必須是包含路徑規範的字串。 pathname 可以是絕對的（如 /usr/src/Python-1.5/Makefile）或相對的（如 ../../Tools/*/*.gif），並且可以包含 shell 樣式的通用字元 (wildcard)。已損壞的符號連接也會（如同在 shell）被包含在結果中。結果是否排序取決於檔案系統 (file system)。如果在呼叫此函式期間刪除或新增滿足條件的檔案，則結果不一定會包含該檔案的路徑名稱。

如果 root_dir 不是 None，它應該是一個指定搜尋根目錄的 path-like object。它在呼叫它之前更改目前目錄的影響與 glob() 相同。如果 pathname 是相對的，結果將包含相對於 root_dir 的路徑。

此函式可以支援以 dir_fd 參數使用相對目錄描述器的路徑。

如果 recursive 為真，模式 "**" 將匹配任何檔案、零個或多個目錄、子目錄和目錄的符號連結。如果模式後面有 os.sep 或 os.altsep 那麼檔案將不會被匹配。

如果 include_hidden 為真，"**" 模式將匹配被隱藏的目錄。

引發一個附帶引數 pathname、recursive 的稽核事件 glob.glob。

引發一個附帶引數 pathname、recursive、root_dir、dir_fd 的稽核事件 glob.glob/2。

備註

在大型目錄樹中使用 "**" 模式可能會消耗過多的時間。

備註

This function may return duplicate path names if pathname contains multiple "**" patterns and recursive is true.

在 3.5 版的變更: 支援以 "**" 使用遞迴 glob。

在 3.10 版的變更: 新增 root_dir 與 dir_fd 參數。

在 3.11 版的變更: 新增 include_hidden 參數。

glob.iglob(pathname, *, root_dir=None, dir_fd=None, recursive=False, include_hidden=False)

回傳一個會產生與 glob() 相同的值的 iterator ，而不是同時儲存全部的值。

引發一個附帶引數 pathname、recursive 的稽核事件 glob.glob。

引發一個附帶引數 pathname、recursive、root_dir、dir_fd 的稽核事件 glob.glob/2。

備註

This function may return duplicate path names if pathname contains multiple "**" patterns and recursive is true.

在 3.5 版的變更: 支援以 "**" 使用遞迴 glob。

在 3.10 版的變更: 新增 root_dir 與 dir_fd 參數。

在 3.11 版的變更: 新增 include_hidden 參數。

glob.escape(pathname)

跳脫 (escape) 所有特殊字元（'?'、'*' 和 '['）。如果你想匹配其中可能包含特殊字元的任意文本字串，這將會很有用。驅動器 (drive)/UNC 共享點 (sharepoints) 中的特殊字元不會被跳脫，例如在 Windows 上，escape('//?/c:/Quo vadis?.txt') 會回傳 '//?/c:/Quo vadis[?].txt'。

在 3.4 版被加入.

glob.translate(pathname, *, recursive=False, include_hidden=False, seps=None)

Convert the given path specification to a regular expression for use with re.match(). The path specification can contain shell-style wildcards.

舉例來說：

>>> import glob, re
>>>
>>> regex = glob.translate('**/*.txt', recursive=True, include_hidden=True)
>>> regex
'(?s:(?:.+/)?[^/]*\\.txt)\\z'
>>> reobj = re.compile(regex)
>>> reobj.match('foo/bar/baz.txt')
<re.Match object; span=(0, 15), match='foo/bar/baz.txt'>

Path separators and segments are meaningful to this function, unlike fnmatch.translate(). By default wildcards do not match path separators, and * pattern segments match precisely one path segment.

If recursive is true, the pattern segment "**" will match any number of path segments.

If include_hidden is true, wildcards can match path segments that start with a dot (.).

A sequence of path separators may be supplied to the seps argument. If not given, os.sep and altsep (if available) are used.

也參考

pathlib.PurePath.full_match() and pathlib.Path.glob() methods, which call this function to implement pattern matching and globbing.

在 3.13 版被加入.

範例

例如，在一個包含以下檔案的目錄：1.gif、2.txt、card.gif，和一個僅包含 3.txt 檔案的子目錄 sub，glob() 將產生以下結果。請注意路徑的任何前導部分是如何保留的。

>>> import glob
>>> glob.glob('./[0-9].*')
['./1.gif', './2.txt']
>>> glob.glob('*.gif')
['1.gif', 'card.gif']
>>> glob.glob('?.gif')
['1.gif']
>>> glob.glob('**/*.txt', recursive=True)
['2.txt', 'sub/3.txt']
>>> glob.glob('./**/', recursive=True)
['./', './sub/']

如果目錄包含以 . 開頭的檔案，則預設情況下不會去匹配到它們。例如，一個包含 card.gif 和 .card.gif 的目錄：

>>> import glob
>>> glob.glob('*.gif')
['card.gif']
>>> glob.glob('.c*')
['.card.gif']

也參考

fnmatch 模組提供了 shell 風格檔案名（不是路徑）的擴展

也參考

pathlib 模組提供高階路徑物件。

fnmatch --- Unix 檔案名稱模式比對

原始碼：Lib/fnmatch.py [https://github.com/python/cpython/tree/3.14/Lib/fnmatch.py]

This module provides support for Unix shell-style wildcards, which are not the same as regular expressions (which are documented in the re module). The special characters used in shell-style wildcards are:

Pattern

含義

*

matches everything

?

matches any single character

[seq]

matches any character in seq

[!seq]

matches any character not in seq

For a literal match, wrap the meta-characters in brackets. For example, '[?]' matches the character '?'.

Note that the filename separator ('/' on Unix) is not special to this module. See module glob for pathname expansion (glob uses filter() to match pathname segments). Similarly, filenames starting with a period are not special for this module, and are matched by the * and ? patterns.

Unless stated otherwise, "filename string" and "pattern string" either refer to str or ISO-8859-1 encoded bytes objects. Note that the functions documented below do not allow to mix a bytes pattern with a str filename, and vice-versa.

Finally, note that functools.lru_cache() with a maxsize of 32768 is used to cache the (typed) compiled regex patterns in the following functions: fnmatch(), fnmatchcase(), filter(), filterfalse().

fnmatch.fnmatch(name, pat)

Test whether the filename string name matches the pattern string pat, returning True or False. Both parameters are case-normalized using os.path.normcase(). fnmatchcase() can be used to perform a case-sensitive comparison, regardless of whether that's standard for the operating system.

This example will print all file names in the current directory with the extension .txt:

import fnmatch
import os

for file in os.listdir('.'):
    if fnmatch.fnmatch(file, '*.txt'):
        print(file)

fnmatch.fnmatchcase(name, pat)

Test whether the filename string name matches the pattern string pat, returning True or False; the comparison is case-sensitive and does not apply os.path.normcase().

fnmatch.filter(names, pat)

Construct a list from those elements of the iterable of filename strings names that match the pattern string pat. It is the same as [n for n in names if fnmatch(n, pat)], but implemented more efficiently.

fnmatch.filterfalse(names, pat)

Construct a list from those elements of the iterable of filename strings names that do not match the pattern string pat. It is the same as [n for n in names if not fnmatch(n, pat)], but implemented more efficiently.

在 3.14 版被加入.

fnmatch.translate(pat)

Return the shell-style pattern pat converted to a regular expression for using with re.match(). The pattern is expected to be a str.

範例：

>>> import fnmatch, re
>>>
>>> regex = fnmatch.translate('*.txt')
>>> regex
'(?s:.*\\.txt)\\z'
>>> reobj = re.compile(regex)
>>> reobj.match('foobar.txt')
<re.Match object; span=(0, 10), match='foobar.txt'>

也參考

glob 模組

Unix shell-style path expansion.

linecache --- 隨機存取文字列

原始碼：Lib/linecache.py [https://github.com/python/cpython/tree/3.14/Lib/linecache.py]

linecache 模組允許從 Python 原始碼檔案中取得任何一行。當嘗試在程式內部進行最佳化，會使用快取，這是從單一檔案讀取許多行的常見情況。 這被 traceback 模組用來擷取來自原始碼檔案的行，以包含在格式化的 traceback 中。

tokenize.open() 函式用來開啟檔案。這個函式使用 tokenize.detect_encoding() 來取得檔案的編碼；在沒有編碼標記的情況下，檔案編碼預設為 UTF-8。

linecache 模組定義了下列函式：

linecache.getline(filename, lineno, module_globals=None)

從名為 filename 的檔案中取得 lineno 行。這個函式不會產生例外 --- 它會在出錯時回傳 '' （找到的行會包含終止換行字元）。

如果 filename 表示一個凍結模組（以 '<frozen ' 開頭），且 module_globals 不是 None，則函式會嘗試從 module_globals['__file__'] 取得實際的檔案名稱。

如果找不到名為 filename 的檔案，函式會先檢查 module_globals 中是否有 PEP 302 [https://peps.python.org/pep-0302/] __loader__ 載入器。如果有這樣一個載入器，而且它定義了一個 get_source 方法，這之後它就會決定原始碼行（如果 get_source() 回傳 None，那麼就會回傳 ''）。最後，如果 filename 是相對的檔案名稱，則會相對於模組搜尋路徑 sys.path 中的項目進行搜尋。

在 3.14 版的變更: 凍結模組的支援 filename。

linecache.clearcache()

清除快取。如果你不再需要先前使用 getline() 讀取的檔案行數，請使用此函式。

linecache.checkcache(filename=None)

檢查快取是否有效。如果快取中的檔案可能已在磁碟上變更，而你需要更新的版本，請使用此功能。 如果省略 filename，則會檢查快取中的所有項目。

linecache.lazycache(filename, module_globals)

即使 module_globals 在稍後的呼叫中是 None ，也可以擷取非檔案型模組的足夠細節，以允許稍後透過 getline() 取得其行。這可以避免在真正需要某一行之前進行 I/O 操作，而不必無限期地帶著模組的全域變數。

在 3.5 版被加入.

範例：

>>> import linecache
>>> linecache.getline(linecache.__file__, 8)
'import sys\n'

shutil — 高階檔案操作

原始碼：Lib/shutil.py [https://github.com/python/cpython/tree/3.14/Lib/shutil.py]

The shutil module offers a number of high-level operations on files and collections of files. In particular, functions are provided which support file copying and removal. For operations on individual files, see also the os module.

警告

Even the higher-level file copying functions (shutil.copy(), shutil.copy2()) cannot copy all file metadata.

On POSIX platforms, this means that file owner and group are lost as well as ACLs. On Mac OS, the resource fork and other metadata are not used. This means that resources will be lost and file type and creator codes will not be correct. On Windows, file owners, ACLs and alternate data streams are not copied.

目錄和檔案操作

shutil.copyfileobj(fsrc, fdst[, length])

Copy the contents of the file-like object fsrc to the file-like object fdst. The integer length, if given, is the buffer size. In particular, a negative length value means to copy the data without looping over the source data in chunks; by default the data is read in chunks to avoid uncontrolled memory consumption. Note that if the current file position of the fsrc object is not 0, only the contents from the current file position to the end of the file will be copied.

copyfileobj() will not guarantee that the destination stream has been flushed on completion of the copy. If you want to read from the destination at the completion of the copy operation (for example, reading the contents of a temporary file that has been copied from a HTTP stream), you must ensure that you have called flush() or close() on the file-like object before attempting to read the destination file.

shutil.copyfile(src, dst, *, follow_symlinks=True)

Copy the contents (no metadata) of the file named src to a file named dst and return dst in the most efficient way possible. src and dst are path-like objects or path names given as strings.

dst must be the complete target file name; look at copy() for a copy that accepts a target directory path. If src and dst specify the same file, SameFileError is raised.

The destination location must be writable; otherwise, an OSError exception will be raised. If dst already exists, it will be replaced. Special files such as character or block devices and pipes cannot be copied with this function.

If follow_symlinks is false and src is a symbolic link, a new symbolic link will be created instead of copying the file src points to.

引發一個附帶引數 src、dst 的稽核事件 shutil.copyfile。

在 3.3 版的變更: IOError used to be raised instead of OSError. Added follow_symlinks argument. Now returns dst.

在 3.4 版的變更: Raise SameFileError instead of Error. Since the former is a subclass of the latter, this change is backward compatible.

在 3.8 版的變更: Platform-specific fast-copy syscalls may be used internally in order to copy the file more efficiently. See Platform-dependent efficient copy operations section.

exception shutil.SpecialFileError

This exception is raised when copyfile() or copytree() attempt to copy a named pipe.

在 2.7 版被加入.

exception shutil.SameFileError

This exception is raised if source and destination in copyfile() are the same file.

在 3.4 版被加入.

shutil.copymode(src, dst, *, follow_symlinks=True)

Copy the permission bits from src to dst. The file contents, owner, and group are unaffected. src and dst are path-like objects or path names given as strings. If follow_symlinks is false, and both src and dst are symbolic links, copymode() will attempt to modify the mode of dst itself (rather than the file it points to). This functionality is not available on every platform; please see copystat() for more information. If copymode() cannot modify symbolic links on the local platform, and it is asked to do so, it will do nothing and return.

引發一個附帶引數 src、dst 的稽核事件 shutil.copymode。

在 3.3 版的變更: 新增 follow_symlinks 引數。

shutil.copystat(src, dst, *, follow_symlinks=True)

Copy the permission bits, last access time, last modification time, and flags from src to dst. On Linux, copystat() also copies the "extended attributes" where possible. The file contents, owner, and group are unaffected. src and dst are path-like objects or path names given as strings.

If follow_symlinks is false, and src and dst both refer to symbolic links, copystat() will operate on the symbolic links themselves rather than the files the symbolic links refer to—reading the information from the src symbolic link, and writing the information to the dst symbolic link.

備註

Not all platforms provide the ability to examine and modify symbolic links. Python itself can tell you what functionality is locally available.

If os.chmod in os.supports_follow_symlinks is True, copystat() can modify the permission bits of a symbolic link.

If os.utime in os.supports_follow_symlinks is True, copystat() can modify the last access and modification times of a symbolic link.

If os.chflags in os.supports_follow_symlinks is True, copystat() can modify the flags of a symbolic link. (os.chflags is not available on all platforms.)

On platforms where some or all of this functionality is unavailable, when asked to modify a symbolic link, copystat() will copy everything it can. copystat() never returns failure.

更多資訊請見 os.supports_follow_symlinks。

引發一個附帶引數 src、dst 的稽核事件 shutil.copystat。

在 3.3 版的變更: Added follow_symlinks argument and support for Linux extended attributes.

shutil.copy(src, dst, *, follow_symlinks=True)

Copies the file src to the file or directory dst. src and dst should be path-like objects or strings. If dst specifies a directory, the file will be copied into dst using the base filename from src. If dst specifies a file that already exists, it will be replaced. Returns the path to the newly created file.

If follow_symlinks is false, and src is a symbolic link, dst will be created as a symbolic link. If follow_symlinks is true and src is a symbolic link, dst will be a copy of the file src refers to.

copy() copies the file data and the file's permission mode (see os.chmod()). Other metadata, like the file's creation and modification times, is not preserved. To preserve all file metadata from the original, use copy2() instead.

引發一個附帶引數 src、dst 的稽核事件 shutil.copyfile。

引發一個附帶引數 src、dst 的稽核事件 shutil.copymode。

在 3.3 版的變更: Added follow_symlinks argument. Now returns path to the newly created file.

在 3.8 版的變更: Platform-specific fast-copy syscalls may be used internally in order to copy the file more efficiently. See Platform-dependent efficient copy operations section.

shutil.copy2(src, dst, *, follow_symlinks=True)

Identical to copy() except that copy2() also attempts to preserve file metadata.

When follow_symlinks is false, and src is a symbolic link, copy2() attempts to copy all metadata from the src symbolic link to the newly created dst symbolic link. However, this functionality is not available on all platforms. On platforms where some or all of this functionality is unavailable, copy2() will preserve all the metadata it can; copy2() never raises an exception because it cannot preserve file metadata.

copy2() uses copystat() to copy the file metadata. Please see copystat() for more information about platform support for modifying symbolic link metadata.

引發一個附帶引數 src、dst 的稽核事件 shutil.copyfile。

引發一個附帶引數 src、dst 的稽核事件 shutil.copystat。

在 3.3 版的變更: Added follow_symlinks argument, try to copy extended file system attributes too (currently Linux only). Now returns path to the newly created file.

在 3.8 版的變更: Platform-specific fast-copy syscalls may be used internally in order to copy the file more efficiently. See Platform-dependent efficient copy operations section.

shutil.ignore_patterns(*patterns)

This factory function creates a function that can be used as a callable for copytree()'s ignore argument, ignoring files and directories that match one of the glob-style patterns provided. See the example below.

shutil.copytree(src, dst, symlinks=False, ignore=None, copy_function=copy2, ignore_dangling_symlinks=False, dirs_exist_ok=False)

Recursively copy an entire directory tree rooted at src to a directory named dst and return the destination directory. All intermediate directories needed to contain dst will also be created by default.

Permissions and times of directories are copied with copystat(), individual files are copied using copy2().

If symlinks is true, symbolic links in the source tree are represented as symbolic links in the new tree and the metadata of the original links will be copied as far as the platform allows; if false or omitted, the contents and metadata of the linked files are copied to the new tree.

When symlinks is false, if the file pointed to by the symlink doesn't exist, an exception will be added in the list of errors raised in an Error exception at the end of the copy process. You can set the optional ignore_dangling_symlinks flag to true if you want to silence this exception. Notice that this option has no effect on platforms that don't support os.symlink().

If ignore is given, it must be a callable that will receive as its arguments the directory being visited by copytree(), and a list of its contents, as returned by os.listdir(). Since copytree() is called recursively, the ignore callable will be called once for each directory that is copied. The callable must return a sequence of directory and file names relative to the current directory (i.e. a subset of the items in its second argument); these names will then be ignored in the copy process. ignore_patterns() can be used to create such a callable that ignores names based on glob-style patterns.

If exception(s) occur, an Error is raised with a list of reasons.

If copy_function is given, it must be a callable that will be used to copy each file. It will be called with the source path and the destination path as arguments. By default, copy2() is used, but any function that supports the same signature (like copy()) can be used.

If dirs_exist_ok is false (the default) and dst already exists, a FileExistsError is raised. If dirs_exist_ok is true, the copying operation will continue if it encounters existing directories, and files within the dst tree will be overwritten by corresponding files from the src tree.

引發一個附帶引數 src、dst 的稽核事件 shutil.copytree。

在 3.2 版的變更: Added the copy_function argument to be able to provide a custom copy function. Added the ignore_dangling_symlinks argument to silence dangling symlinks errors when symlinks is false.

在 3.3 版的變更: Copy metadata when symlinks is false. Now returns dst.

在 3.8 版的變更: Platform-specific fast-copy syscalls may be used internally in order to copy the file more efficiently. See Platform-dependent efficient copy operations section.

在 3.8 版的變更: 新增 dirs_exist_ok 參數。

shutil.rmtree(path, ignore_errors=False, onerror=None, *, onexc=None, dir_fd=None)

Delete an entire directory tree; path must point to a directory (but not a symbolic link to a directory). If ignore_errors is true, errors resulting from failed removals will be ignored; if false or omitted, such errors are handled by calling a handler specified by onexc or onerror or, if both are omitted, exceptions are propagated to the caller.

This function can support paths relative to directory descriptors.

備註

On platforms that support the necessary fd-based functions a symlink attack resistant version of rmtree() is used by default. On other platforms, the rmtree() implementation is susceptible to a symlink attack: given proper timing and circumstances, attackers can manipulate symlinks on the filesystem to delete files they wouldn't be able to access otherwise. Applications can use the rmtree.avoids_symlink_attacks function attribute to determine which case applies.

If onexc is provided, it must be a callable that accepts three parameters: function, path, and excinfo.

The first parameter, function, is the function which raised the exception; it depends on the platform and implementation. The second parameter, path, will be the path name passed to function. The third parameter, excinfo, is the exception that was raised. Exceptions raised by onexc will not be caught.

The deprecated onerror is similar to onexc, except that the third parameter it receives is the tuple returned from sys.exc_info().

也參考

rmtree 範例 for an example of handling the removal of a directory tree that contains read-only files.

引發一個附帶引數 path、dir_fd 的稽核事件 shutil.rmtree。

在 3.3 版的變更: Added a symlink attack resistant version that is used automatically if platform supports fd-based functions.

在 3.8 版的變更: On Windows, will no longer delete the contents of a directory junction before removing the junction.

在 3.11 版的變更: 新增 dir_fd 參數。

在 3.12 版的變更: 新增 onexc 參數並棄用 onerror。

在 3.13 版的變更: rmtree() now ignores FileNotFoundError exceptions for all but the top-level path. Exceptions other than OSError and subclasses of OSError are now always propagated to the caller.

rmtree.avoids_symlink_attacks

Indicates whether the current platform and implementation provides a symlink attack resistant version of rmtree(). Currently this is only true for platforms supporting fd-based directory access functions.

在 3.3 版被加入.

shutil.move(src, dst, copy_function=copy2)

Recursively move a file or directory (src) to another location and return the destination.

If dst is an existing directory or a symlink to a directory, then src is moved inside that directory. The destination path in that directory must not already exist.

If dst already exists but is not a directory, it may be overwritten depending on os.rename() semantics.

If the destination is on the current filesystem, then os.rename() is used. Otherwise, src is copied to the destination using copy_function and then removed. In case of symlinks, a new symlink pointing to the target of src will be created as the destination and src will be removed.

If copy_function is given, it must be a callable that takes two arguments, src and the destination, and will be used to copy src to the destination if os.rename() cannot be used. If the source is a directory, copytree() is called, passing it the copy_function. The default copy_function is copy2(). Using copy() as the copy_function allows the move to succeed when it is not possible to also copy the metadata, at the expense of not copying any of the metadata.

引發一個附帶引數 src、dst 的稽核事件 shutil.move。

在 3.3 版的變更: Added explicit symlink handling for foreign filesystems, thus adapting it to the behavior of GNU's mv. Now returns dst.

在 3.5 版的變更: 新增 copy_function 關鍵字引數。

在 3.8 版的變更: Platform-specific fast-copy syscalls may be used internally in order to copy the file more efficiently. See Platform-dependent efficient copy operations section.

在 3.9 版的變更: Accepts a path-like object for both src and dst.

shutil.disk_usage(path)

Return disk usage statistics about the given path as a named tuple with the attributes total, used and free, which are the amount of total, used and free space, in bytes. path may be a file or a directory.

備註

On Unix filesystems, path must point to a path within a mounted filesystem partition. On those platforms, CPython doesn't attempt to retrieve disk usage information from non-mounted filesystems.

在 3.3 版被加入.

在 3.8 版的變更: On Windows, path can now be a file or directory.

可用性: Unix, Windows.

shutil.chown(path, user=None, group=None, *, dir_fd=None, follow_symlinks=True)

Change owner user and/or group of the given path.

user can be a system user name or a uid; the same applies to group. At least one argument is required.

另請參閱 os.chown()，它是底層函式。

引發一個附帶引數 path、user、group 的稽核事件 shutil.chown。

可用性: Unix.

在 3.3 版被加入.

在 3.13 版的變更: 新增 dir_fd 和 follow_symlinks 參數。

shutil.which(cmd, mode=os.F_OK | os.X_OK, path=None)

Return the path to an executable which would be run if the given cmd was called. If no cmd would be called, return None.

mode is a permission mask passed to os.access(), by default determining if the file exists and is executable.

path is a "PATH string" specifying the directories to look in, delimited by os.pathsep. When no path is specified, the PATH environment variable is read from os.environ, falling back to os.defpath if it is not set.

If cmd contains a directory component, which() only checks the specified path directly and does not search the directories listed in path or in the system's PATH environment variable.

On Windows, the current directory is prepended to the path if mode does not include os.X_OK. When the mode does include os.X_OK, the Windows API NeedCurrentDirectoryForExePathW will be consulted to determine if the current directory should be prepended to path. To avoid consulting the current working directory for executables: set the environment variable NoDefaultCurrentDirectoryInExePath.

Also on Windows, the PATHEXT environment variable is used to resolve commands that may not already include an extension. For example, if you call shutil.which("python"), which() will search PATHEXT to know that it should look for python.exe within the path directories. For example, on Windows:

>>> shutil.which("python")
'C:\\Python33\\python.EXE'

This is also applied when cmd is a path that contains a directory component:

>>> shutil.which("C:\\Python33\\python")
'C:\\Python33\\python.EXE'

在 3.3 版被加入.

在 3.8 版的變更: The bytes type is now accepted. If cmd type is bytes, the result type is also bytes.

在 3.12 版的變更: On Windows, the current directory is no longer prepended to the search path if mode includes os.X_OK and WinAPI NeedCurrentDirectoryForExePathW(cmd) is false, else the current directory is prepended even if it is already in the search path; PATHEXT is used now even when cmd includes a directory component or ends with an extension that is in PATHEXT; and filenames that have no extension can now be found.

exception shutil.Error

This exception collects exceptions that are raised during a multi-file operation. For copytree(), the exception argument is a list of 3-tuples (srcname, dstname, exception).

Platform-dependent efficient copy operations

Starting from Python 3.8, all functions involving a file copy (copyfile(), copy(), copy2(), copytree(), and move()) may use platform-specific "fast-copy" syscalls in order to copy the file more efficiently (see bpo-33671 [https://bugs.python.org/issue?@action=redirect&bpo=33671]). "fast-copy" means that the copying operation occurs within the kernel, avoiding the use of userspace buffers in Python as in "outfd.write(infd.read())".

On macOS fcopyfile [http://www.manpagez.com/man/3/copyfile/] is used to copy the file content (not metadata).

Linux 上會使用 os.copy_file_range() 或 os.sendfile()。

Solaris 上會使用 os.sendfile()。

On Windows shutil.copyfile() uses a bigger default buffer size (1 MiB instead of 64 KiB) and a memoryview()-based variant of shutil.copyfileobj() is used.

If the fast-copy operation fails and no data was written in the destination file then shutil will silently fallback on using less efficient copyfileobj() function internally.

在 3.8 版的變更.

在 3.14 版的變更: Solaris now uses os.sendfile().

在 3.14 版的變更: Copy-on-write or server-side copy may be used internally via os.copy_file_range() on supported Linux filesystems.

copytree 範例

An example that uses the ignore_patterns() helper:

from shutil import copytree, ignore_patterns

copytree(source, destination, ignore=ignore_patterns('*.pyc', 'tmp*'))

This will copy everything except .pyc files and files or directories whose name starts with tmp.

Another example that uses the ignore argument to add a logging call:

from shutil import copytree
import logging

def _logpath(path, names):
    logging.info('Working in %s', path)
    return []   # 沒有東西被忽略

copytree(source, destination, ignore=_logpath)

rmtree 範例

This example shows how to remove a directory tree on Windows where some of the files have their read-only bit set. It uses the onexc callback to clear the readonly bit and reattempt the remove. Any subsequent failure will propagate.

import os, stat
import shutil

def remove_readonly(func, path, _):
    "Clear the readonly bit and reattempt the removal"
    os.chmod(path, stat.S_IWRITE)
    func(path)

shutil.rmtree(directory, onexc=remove_readonly)

Archiving operations

在 3.2 版被加入.

在 3.5 版的變更: 新增 xztar 格式的支援。

High-level utilities to create and read compressed and archived files are also provided. They rely on the zipfile and tarfile modules.

shutil.make_archive(base_name, format[, root_dir[, base_dir[, verbose[, dry_run[, owner[, group[, logger]]]]]]])

Create an archive file (such as zip or tar) and return its name.

base_name is the name of the file to create, including the path, minus any format-specific extension.

format is the archive format: one of "zip" (if the zlib module is available), "tar", "gztar" (if the zlib module is available), "bztar" (if the bz2 module is available), "xztar" (if the lzma module is available), or "zstdtar" (if the compression.zstd module is available).

root_dir is a directory that will be the root directory of the archive, all paths in the archive will be relative to it; for example, we typically chdir into root_dir before creating the archive.

base_dir is the directory where we start archiving from; i.e. base_dir will be the common prefix of all files and directories in the archive. base_dir must be given relative to root_dir. See Archiving example with base_dir for how to use base_dir and root_dir together.

root_dir and base_dir both default to the current directory.

If dry_run is true, no archive is created, but the operations that would be executed are logged to logger.

owner and group are used when creating a tar archive. By default, uses the current owner and group.

logger 必須是與 PEP 282 [https://peps.python.org/pep-0282/] 相容的物件，通常是 logging.Logger 的實例。

verbose 引數未被使用且已棄用。

引發一個附帶引數 base_name、format、root_dir、base_dir 的稽核事件 shutil.make_archive。

備註

This function is not thread-safe when custom archivers registered with register_archive_format() do not support the root_dir argument. In this case it temporarily changes the current working directory of the process to root_dir to perform archiving.

在 3.8 版的變更: The modern pax (POSIX.1-2001) format is now used instead of the legacy GNU format for archives created with format="tar".

在 3.10.6 版的變更: This function is now made thread-safe during creation of standard .zip and tar archives.

shutil.get_archive_formats()

Return a list of supported formats for archiving. Each element of the returned sequence is a tuple (name, description).

預設情況下 shutil 提供這些格式：

zip: ZIP file (if the zlib module is available).

tar: Uncompressed tar file. Uses POSIX.1-2001 pax format for new archives.

gztar: gzip'ed tar-file (if the zlib module is available).

bztar: bzip2'ed tar-file (if the bz2 module is available).

xztar: xz'ed tar-file (if the lzma module is available).

zstdtar: Zstandard compressed tar-file (if the compression.zstd module is available).

You can register new formats or provide your own archiver for any existing formats, by using register_archive_format().

shutil.register_archive_format(name, function[, extra_args[, description]])

Register an archiver for the format name.

function is the callable that will be used to unpack archives. The callable will receive the base_name of the file to create, followed by the base_dir (which defaults to os.curdir) to start archiving from. Further arguments are passed as keyword arguments: owner, group, dry_run and logger (as passed in make_archive()).

If function has the custom attribute function.supports_root_dir set to True, the root_dir argument is passed as a keyword argument. Otherwise the current working directory of the process is temporarily changed to root_dir before calling function. In this case make_archive() is not thread-safe.

If given, extra_args is a sequence of (name, value) pairs that will be used as extra keywords arguments when the archiver callable is used.

description is used by get_archive_formats() which returns the list of archivers. Defaults to an empty string.

在 3.12 版的變更: Added support for functions supporting the root_dir argument.

shutil.unregister_archive_format(name)

Remove the archive format name from the list of supported formats.

shutil.unpack_archive(filename[, extract_dir[, format[, filter]]])

Unpack an archive. filename is the full path of the archive.

extract_dir is the name of the target directory where the archive is unpacked. If not provided, the current working directory is used.

format is the archive format: one of "zip", "tar", "gztar", "bztar", "xztar", or "zstdtar". Or any other format registered with register_unpack_format(). If not provided, unpack_archive() will use the archive file name extension and see if an unpacker was registered for that extension. In case none is found, a ValueError is raised.

The keyword-only filter argument is passed to the underlying unpacking function. For zip files, filter is not accepted. For tar files, it is recommended to use 'data' (default since Python 3.14), unless using features specific to tar and UNIX-like filesystems. (See 解壓縮篩選器 for details.)

引發一個附帶引數 filename、extract_dir、format 的稽核事件 shutil.unpack_archive。

警告

Never extract archives from untrusted sources without prior inspection. It is possible that files are created outside of the path specified in the extract_dir argument, e.g. members that have absolute filenames starting with "/" or filenames with two dots "..".

Since Python 3.14, the defaults for both built-in formats (zip and tar files) will prevent the most dangerous of such security issues, but will not prevent all unintended behavior. Read the 進一步驗證的提示 section for tar-specific details.

在 3.7 版的變更: Accepts a path-like object for filename and extract_dir.

在 3.12 版的變更: 新增 filter 引數。

shutil.register_unpack_format(name, extensions, function[, extra_args[, description]])

Registers an unpack format. name is the name of the format and extensions is a list of extensions corresponding to the format, like .zip for Zip files.

function is the callable that will be used to unpack archives. The callable will receive:

the path of the archive, as a positional argument;

the directory the archive must be extracted to, as a positional argument;

possibly a filter keyword argument, if it was given to unpack_archive();

additional keyword arguments, specified by extra_args as a sequence of (name, value) tuples.

description can be provided to describe the format, and will be returned by the get_unpack_formats() function.

shutil.unregister_unpack_format(name)

Unregister an unpack format. name is the name of the format.

shutil.get_unpack_formats()

Return a list of all registered formats for unpacking. Each element of the returned sequence is a tuple (name, extensions, description).

預設情況下 shutil 提供這些格式：

zip: ZIP file (unpacking compressed files works only if the corresponding module is available).

tar: uncompressed tar file.

gztar: gzip'ed tar-file (if the zlib module is available).

bztar: bzip2'ed tar-file (if the bz2 module is available).

xztar: xz'ed tar-file (if the lzma module is available).

zstdtar: Zstandard compressed tar-file (if the compression.zstd module is available).

You can register new formats or provide your own unpacker for any existing formats, by using register_unpack_format().

Archiving example

In this example, we create a gzip'ed tar-file archive containing all files found in the .ssh directory of the user:

>>> from shutil import make_archive
>>> import os
>>> archive_name = os.path.expanduser(os.path.join('~', 'myarchive'))
>>> root_dir = os.path.expanduser(os.path.join('~', '.ssh'))
>>> make_archive(archive_name, 'gztar', root_dir)
'/Users/tarek/myarchive.tar.gz'

The resulting archive contains:

$ tar -tzvf /Users/tarek/myarchive.tar.gz
drwx------ tarek/staff       0 2010-02-01 16:23:40 ./
-rw-r--r-- tarek/staff     609 2008-06-09 13:26:54 ./authorized_keys
-rwxr-xr-x tarek/staff      65 2008-06-09 13:26:54 ./config
-rwx------ tarek/staff     668 2008-06-09 13:26:54 ./id_dsa
-rwxr-xr-x tarek/staff     609 2008-06-09 13:26:54 ./id_dsa.pub
-rw------- tarek/staff    1675 2008-06-09 13:26:54 ./id_rsa
-rw-r--r-- tarek/staff     397 2008-06-09 13:26:54 ./id_rsa.pub
-rw-r--r-- tarek/staff   37192 2010-02-06 18:23:10 ./known_hosts

Archiving example with base_dir

In this example, similar to the one above, we show how to use make_archive(), but this time with the usage of base_dir. We now have the following directory structure:

$ tree tmp
tmp
└── root
    └── structure
        ├── content
            └── please_add.txt
        └── do_not_add.txt

In the final archive, please_add.txt should be included, but do_not_add.txt should not. Therefore we use the following:

>>> from shutil import make_archive
>>> import os
>>> archive_name = os.path.expanduser(os.path.join('~', 'myarchive'))
>>> make_archive(
...     archive_name,
...     'tar',
...     root_dir='tmp/root',
...     base_dir='structure/content',
... )
'/Users/tarek/myarchive.tar'

Listing the files in the resulting archive gives us:

$ python -m tarfile -l /Users/tarek/myarchive.tar
structure/content/
structure/content/please_add.txt

Querying the size of the output terminal

shutil.get_terminal_size(fallback=(columns, lines))

Get the size of the terminal window.

For each of the two dimensions, the environment variable, COLUMNS and LINES respectively, is checked. If the variable is defined and the value is a positive integer, it is used.

When COLUMNS or LINES is not defined, which is the common case, the terminal connected to sys.__stdout__ is queried by invoking os.get_terminal_size().

If the terminal size cannot be successfully queried, either because the system doesn't support querying, or because we are not connected to a terminal, the value given in fallback parameter is used. fallback defaults to (80, 24) which is the default size used by many terminal emulators.

The value returned is a named tuple of type os.terminal_size.

See also: The Single UNIX Specification, Version 2, Other Environment Variables [https://pubs.opengroup.org/onlinepubs/7908799/xbd/envvar.html#tag_002_003].

在 3.3 版被加入.

在 3.11 版的變更: The fallback values are also used if os.get_terminal_size() returns zeroes.

資料持久性 (Data Persistence)

本章節所描述的模組支援將 Python 資料以持久形式儲存在磁碟上。pickle 和 marshal 模組可以將許多 Python 資料型別轉換為位元串流，然後再從位元串流重建物件。各種與 DBM 有關的模組支援一系列基於雜湊的檔案格式，用來儲存字串對字串的對映。

本章節所描述的模組列表為：

pickle --- Python 物件序列化

和其他 Python 模組的關係

和 marshal 的比較

和 json 的比較

資料串流格式

模組介面

哪些物件能或不能被封裝、拆封？

Pickling 類別實例

外部物件持久化

調度表

處裡紀錄大量狀態的物件

針對型別、函式或特定物件定製縮減函式

帶外（Out-of-band）資料緩衝區

供給者 API

消費者 API

範例

限制全域物件

效能

範例

命令列介面

copyreg --- 註冊 pickle 支援函式

範例

shelve --- Python object persistence

Restrictions

範例

marshal --- 內部 Python 物件序列化

dbm --- Unix "databases" 的介面

dbm.sqlite3 --- dbm 的 SQLite 後端

dbm.gnu --- GNU 資料庫管理器

dbm.ndbm --- 新資料庫管理器

dbm.dumb --- 可攜式 DBM 實作

sqlite3 --- SQLite 資料庫的 DB-API 2.0 介面

教學

Reference

Module functions

Module constants

Connection 物件

Cursor 物件

Row 物件

Blob 物件

PrepareProtocol 物件

例外

SQLite and Python types

Default adapters and converters (deprecated)

命令列介面

How-to guides

How to use placeholders to bind values in SQL queries

How to adapt custom Python types to SQLite values

How to write adaptable objects

How to register adapter callables

How to convert SQLite values to custom Python types

Adapter and converter recipes

How to use connection shortcut methods

How to use the connection context manager

How to work with SQLite URIs

How to create and use row factories

如何處理非 UTF-8 的文字編碼

解釋

Transaction control

Transaction control via the autocommit attribute

Transaction control via the isolation_level attribute

pickle --- Python 物件序列化

原始碼：Lib/pickle.py [https://github.com/python/cpython/tree/3.14/Lib/pickle.py]

pickle 模組實作的是一個在二進位層級上對 Python 物件進行序列化（serialize）或去序列化（de-serialize）。"Pickling" 用於專門指摘將一個 Python 物件轉換為一個二進位串流的過程，"unpickling" 則相反，指的是將一個（來自 binary file 或 bytes-like object 的）二進位串流轉換回 Python 物件的過程。Pickling（和 unpickling）的過程也可能被稱作 "serialization", "marshalling," [1] 或 "flattening"。不過，為了避免混淆，本文件將統一稱作封裝（pickling）、拆封（unpickling）。

警告

pickle 模組並不安全，切記只拆封你信任的資料。

pickle 封包是有可能被建立來在拆封的時候執行任意惡意程式碼的。絕對不要拆封任何你無法信任其來源、或可能被修改過的 pickle 封包。

建議你可以使用 hmac 模組來簽署這個封包，以確保其未被修改過。

如果你在處理不受信任的資料，其他比較安全的序列化格式（例如 json）可能會更適合。請參照 See 和 json 的比較 的說明。

和其他 Python 模組的關係

和 marshal 的比較

Python 有另一個比較原始的序列化模組叫 marshal，不過其設計目的是為了支援 Python 的預編譯功能 .pyc 的運作。總地來說，請盡可能地使用 pickle，沒事不要用 marshal。

pickle 和 marshal 有幾個明顯不同的地方：

marshal 無法序列化使用者自訂的類別和的實例。pickle 則可以讓使用者儲存並還原自訂的類別實例，前提是儲存時該類別的定義存在於與要被儲存的物件所在的模組中、且可以被引入（import）。

marshal 序列化格式無法保證能在不同版本的 Python 之間移植。因為其主要的作用是支援 .pyc 檔案的運作，Python 的實作人員會在需要時實作無法前向相容的序列化方式。但只要選擇了相容的 pickle 協定，且處理了 Python 2 和 Python 3 之間的資料類型差異，pickle 序列化協定能保證在不同 Python 版本間的相容性。

和 json 的比較

pickle 協定和 JSON (JavaScript Object Notation) [https://json.org] 有一些根本上的不同：

JSON 以文字形式作為序列化的輸出（輸出 unicode 文字，但大多數又會被編碼為 UTF-8），而 pickle 則是以二進位形式作為序列化的輸出；

JSON 是人類可讀的，而 pickle 則無法；

JSON 具有高互通性（interoperability）且在 Python 以外的環境也被大量利用，但 pickle 只能在 Python 內使用。

預設狀態下的 JSON 只能紀錄一小部份的 Python 內建型別，且無法紀錄自訂類別；但透過 Python 的自省措施，pickle 可以紀錄絕大多數的 Python 型別（其他比較複雜的狀況也可以透過實作 specific object APIs 來解決）；

去序列化不安全的 JSON 不會產生任意程式執行的風險，但去序列化不安全的 pickle 會。

也參考

json module: 是標準函式庫的一部分，可讓使用者進行 JSON 的序列化與去序列化。

資料串流格式

pickle 使用的資料格式是針對 Python 而設計的。好處是他不會受到外部標準（像是 JSON，無法紀錄指標共用）的限制；不過這也代表其他不是 Python 的程式可能無法重建 pickle 封裝的 Python 物件。

以預設設定來說，pickle 使用相對緊湊的二進位形式來儲存資料。如果你需要盡可能地縮小檔案大小，你可以壓縮封裝的資料。

pickletools 含有工具可分析 pickle 所產生的資料流。pickletools 的源始碼詳細地記載了所有 pickle 協定的操作碼（opcode）。

截至目前為止，共有六種不同版本的協定可用於封裝 pickle。數字越大版本代表你需要使用越新的 Python 版本來拆封相應的 pickle 封裝。

版本 0 的協定是最初「人類可讀」的版本，且可以向前支援早期版本的 Python。

版本 1 的協定使用舊的二進位格式，一樣能向前支援早期版本的 Python。

版本 2 的協定在 Python 2.3 中初次被引入。其可提供更高效率的 new-style classes 封裝過程。請參閱 PEP 307 [https://peps.python.org/pep-0307/] 以了解版本 2 帶來的改進。

版本 3 的協定在 Python 3.0 被新增。現在能支援封裝 bytes 的物件且無法被 2.x 版本的 Python 拆封。在 3.0～3.7 的 Python 預設使用 3 版協定。

版本 4 的協定在 Python 3.4 被新增。現在能支援超大物件的封裝、更多種型別的物件以及針對部份資料格式的儲存進行最佳化。從 Python 3.8 到 3.13，預設使用第 4 版協定。請參閱 PEP 3154 [https://peps.python.org/pep-3154/] 以了解第 4 版協定改進的細節。

版本 5 的協定在 Python 3.8 被新增。現在能支援帶外資料（Out-of-band data）並加速帶內資料的處理速度。自 3.14 起這是預設使用的協定。請參閱 PEP 574 [https://peps.python.org/pep-0574/] 以了解第 5 版協定改進的細節。

備註

資料序列化是一個比資料持久化更早出現的概念；雖然 pickle 可以讀寫檔案物件，但它並不處理命名持久物件的問題，也不處理對持久物件的並行存取、一個更棘手的問題。pickle 模組可以將複雜物件轉換成位元組串流，也可以將位元組串流轉換回具有相同原始內部結構的物件。對這些位元組串流最常見的處理方式是將它們寫入檔案中，但也可以將它們透過網路傳送或儲存在一個資料庫中。shelve 模組提供了一個簡單的介面來讓使用者在 DBM 風格的資料庫檔案中對物件進行封裝和拆封的操作。

模組介面

想要序列化一個物件，你只需要呼叫 dumps() 函式。而當你想要去序列化一個資料流時，你只需要呼叫 loads() 即可。不過，若你希望能各自對序列化和去序列化的過程中有更多的掌控度，你可以自訂一個 Pickler 或 Unpickler 物件。

pickle 模組提供以下常數：

pickle.HIGHEST_PROTOCOL

一個整數，表示可使用的最高協定版本。這個值可作為 protocol 的數值傳給 dump() 和 dumps() 函式以及 Pickler 建構式。

pickle.DEFAULT_PROTOCOL

一個整數，用於 pickle 的預設 協定版本。可能小於 HIGHEST_PROTOCOL。目前預設協定是 5，在 Python 3.8 中引入，與之前的版本不相容。此版本引入了對 out-of-band buffer 的支援，其中 PEP 3118 [https://peps.python.org/pep-3118/] 相容的資料可以與主要 pickle 串流分開傳輸。

在 3.0 版的變更: 預設協定版本為 3。

在 3.8 版的變更: 預設協定版本為 4。

在 3.14 版的變更: 預設協定是 5。

pickle 模組提供下列函式來簡化封裝的過程：

pickle.dump(obj, file, protocol=None, *, fix_imports=True, buffer_callback=None)

將被封裝成 pickle 形式的物件 obj 寫入到已開啟的file object file。這等效於Pickler(file, protocol).dump(obj)。

引數 file、protocol、fix_imports 和 buffer_callback 的意義與 Pickler 建構式中的相同。

在 3.8 版的變更: 新增 buffer_callback 引數。

pickle.dumps(obj, protocol=None, *, fix_imports=True, buffer_callback=None)

將被封裝為 pickle 形式的物件 obj 以 bytes 類別回傳，而非寫入進檔案。

引數 protocol、fix_imports 和 buffer_callback 的意義和 Pickler 建構式中的相同。

在 3.8 版的變更: 新增 buffer_callback 引數。

pickle.load(file, *, fix_imports=True, encoding='ASCII', errors='strict', buffers=None)

從已開啟的 檔案物件 file 中讀取已序列化的物件，並傳回其重建後的物件階層。這相當於呼叫 Unpickler(file).load()。

模組會自動偵測 pickle 封包所使用的協定版本，所以無須另外指定。超出 pickle 封包表示範圍的位元組將被忽略。

引數 file、fix_imports、encoding、errors、strict 和 buffers 的意義和 Unpickler 建構式中的相同。

在 3.8 版的變更: 新增 buffer 引數。

pickle.loads(data, /, *, fix_imports=True, encoding='ASCII', errors='strict', buffers=None)

回傳從 data 的 pickle 封包重建後的物件階層。data 必須是一個 bytes-like object。

模組會自動偵測 pickle 封包所使用的協定版本，所以無須另外指定。超出 pickle 封包表示範圍的位元組將被忽略。

引數 fix_imports、encoding、errors、strict 和 buffers 的意義與 Unpickler 建構式所用的相同。

在 3.8 版的變更: 新增 buffer 引數。

pickle 模組定義了以下三種例外：

exception pickle.PickleError

繼承 Exception 類別。一個在封裝或拆封時遭遇其他例外時通用的基底類別。

exception pickle.PicklingError

當 Pickler 遭遇無法封裝物件時會引發的例外。繼承 PickleError 類別。

請參閱 哪些物件能或不能被封裝、拆封？ 以了解哪些物件是可以被封裝的。

exception pickle.UnpicklingError

拆封物件時遇到問題（如資料毀損或違反安全性原則等）所引發的意外。繼承自 PickleError 類別。

拆封的時候還是可能會遭遇其他不在此列的例外（例如：AttributeError、EOFError、ImportError、或 IndexError），請注意。

引入模組 pickle 時會帶來三個類別：Pickler、Unpickler 和 PickleBuffer：

class pickle.Pickler(file, protocol=None, *, fix_imports=True, buffer_callback=None)

接受一個用以寫入 pickle 資料流的二進位檔案。

可選引數 protocol 接受整數，用來要求封裝器（pickler）使用指定的協定；支援從 0 版起到 HIGHEST_PROTOCOL 版的協定。如未指定，則預設為 DEFAULT_PROTOCOL。若指定了負數，則視為選擇 HIGHEST_PROTOCOL。

引數 file 必須支援可寫入單一位元組引數的 write() 方法。只要滿足此條件，傳入的物件可以是一個硬碟上二進位檔案、一個 io.BytesIO 實例或任何其他滿足這個介面要求的物件。

若 fix_imports 設為 true 且 protocol 版本小於 3，本模組會嘗試將 Python 3 的新模組名稱轉換為 Python 2 所支援的舊名，以讓 Python 2 能正確地讀取此資料流。

如果 buffer_callback 是 None（預設值），緩衝區的視圖會作為 pickle 封裝串流的一部分被序列化進 file 中。

如果 buffer_callback 不是 None，則它可以被多次呼叫並回傳一個緩衝區的視圖。如果回呼函式回傳一個假值（例如 None），則所給的緩衝區將被視為 帶外資料；否則，該緩衝區將被視為 pickle 串流的帶內資料被序列化。

如果 buffer_callback 不是 None 且 protocol 是 None 或小於 5 則會報錯。

在 3.8 版的變更: 新增 buffer_callback 引數。

dump(obj)

將已封裝（pickled）的 obj 寫入已在建構式中開啟的對應檔案。

persistent_id(obj)

預設不進行任何動作。這是一種抽象方法，用於讓後續繼承這個類別的物件可以覆寫本方法函式。

如果 persistent_id() 回傳 None，則 obj 會照一般的方式進行封裝（pickling）。若回傳其他值，則 Pickler 會將該值作為 obj 的永久識別碼回傳。此永久識別碼的意義應由 Unpickler.persistent_load() 定義。請注意 persistent_id() 回傳的值本身不能擁有自己的永久識別碼。

關於細節與用法範例請見 外部物件持久化。

在 3.13 版的變更: 在 C 的 Pickler 實作中的增加了這個方法的預設實作。

dispatch_table

封裝器（pickler）物件含有的的調度表是一個縮減函式（reduction function）的註冊表，可以使用 copyreg.pickle() 來宣告這類縮減函式。它是一個以類別為鍵、還原函式為值的映射表。縮減函式應準備接收一個對應類別的引數，並應遵循與 __reduce__() 方法相同的介面。

預設情況下，封裝器（pickler）物件不會有 dispatch_table 屬性，而是會使用由 copyreg 模組管理的全域調度表。不過，若要自訂某個封裝器（pickler）物件的序列化行為，可以將 dispatch_table 屬性設置為類字典物件。另外，如果 Pickler 的子類別具有 dispatch_table 屬性，那麼這個屬性將作為該子類別實例的預設調度表。

關於用法範例請見 調度表。

在 3.3 版被加入.

reducer_override(obj)

一個可以在 Pickler 子類別中被定義的縮減器（reducer）。這個方法的優先度高於任何其他 分派表 中的縮減器。他應該要有和 __reduce__() 方法相同的函式介面，且可以可選地回傳 NotImplemented 以後備（fallback）使用 分派表 中登錄的縮減方法來封裝 obj。

請查閱 針對型別、函式或特定物件定製縮減函式 來參考其他較詳細的範例。

在 3.8 版被加入.

fast

已棄用。如果設置為 true，將啟用快速模式。快速模式會停用備忘（memo），因此能透過不產生多餘的 PUT 操作碼（OpCode）來加速封裝過程。它不應被用於自我參照物件，否則將導致 Pickler 陷入無限遞迴。

使用 pickletools.optimize() 以獲得更緊湊的 pickle 輸出。

clear_memo()

Clears the pickler's "memo".

The memo is the data structure that remembers which objects the pickler has already seen, so that shared or recursive objects are pickled by reference and not by value. This method is useful when re-using picklers.

class pickle.Unpickler(file, *, fix_imports=True, encoding='ASCII', errors='strict', buffers=None)

這個物件接受一個二進位檔案 file 來從中讀取 pickle 資料流。

協定版本號會被自動偵測，所以不需要在這邊手動輸入。

參數 file 必須擁有三個方法，分別是接受整數作為引數的 read() 方法、接受緩衝區作為引數的 readinto() 方法以及不需要引數的 readline() 方法，如同在 io.BufferedIOBase 的介面一樣。因此，file 可以是一個以二進位讀取模式開啟的檔案、一個 io.BytesIO 物件、或任何符合此介面的自訂物件。

可選引數 fix_imports、encoding 和 errors 用來控制 Python 2 pickle 資料的相容性支援。如果 fix_imports 為 true，則 pickle 模組會嘗試將舊的 Python 2 模組名稱映射到 Python 3 中使用的新名稱。encoding 和 errors 告訴 pickle 模組如何解碼由 Python 2 pickle 封裝的 8 位元字串實例；encoding 和 errors 預設分別為 'ASCII' 和 'strict'。encoding 可以設定為 'bytes' 以將這些 8 位元字串實例讀為位元組物件。而由 Python 2 封裝的 NumPy 陣列、datetime、date 和 time 的實例則必須使用 encoding='latin1' 來拆封。

如果 buffers 是 None（預設值），那麼去序列化所需的所有資料都必須已經包含在 pickle 串流中。這意味著當初在建立對應的 Pickler 時（或在呼叫 dump() 或 dumps() 時）*buffer_callback* 引數必須為 None。

如果 buffers 不是 None，則其應該是一個可疊代物件，內含數個支援緩衝區的物件，並且每當 pickle 串流引用一個帶外緩衝區視圖時將會被照順序消耗。這些緩衝資料當初建立時應已按照順序給定於 Pickler 物件中的 buffer_callback。

在 3.8 版的變更: 新增 buffer 引數。

load()

開啟先前被傳入建構子的檔案，從中讀取一個被 pickle 封裝的物件，並回傳重建完成的物件階層。超過 pickle 表示範圍的位元組會被忽略。

persistent_load(pid)

預設會引發 UnpicklingError 例外。

若有定義，則 persistent_load() 將回傳符合持久化識別碼 pid 的物件。如果遭遇了無效的持久化識別碼，則會引發 UnpicklingError。

關於細節與用法範例請見 外部物件持久化。

在 3.13 版的變更: 在 C 的 Unpickler 實作中的增加了這個方法的預設實作。

find_class(module, name)

如有需要將引入 module，並從中回傳名為 name 的物件，這裡的 module 和 name 引數接受的輸入是 str 物件。注意，雖然名稱上看起來不像，但 find_class() 亦可被用於尋找其他函式。

子類別可以覆寫此方法以控制可以載入哪些類型的物件、以及如何載入它們，從而潛在地降低安全性風險。詳情請參考限制全域物件。

引發一個附帶引數 module、name 的稽核事件 pickle.find_class。

class pickle.PickleBuffer(buffer)

一個表示了含有可封裝資料緩衝區的包裝函式（wrapper function）。buffer 必須是一個 提供緩衝區 的物件，例如一個 類位元組物件 或 N 維陣列。

PickleBuffer 本身就是一個提供緩衝區的物件，所以是能夠將其提供給其它「預期收到含有緩衝物件的 API」的，比如 memoryview。

PickleBuffer 物件僅能由 5 版或以上的 pickle 協定進行封裝。該物件亦能被作為帶外資料來進行帶外資料序列化

在 3.8 版被加入.

raw()

回傳此緩衝區底層記憶體區域的 memoryview。被回傳的物件是一個（在 C 語言的 formatter 格式中）以 B (unsigned bytes) 二進位格式儲存、一維且列連續（C-contiguous）的 memoryview。如果緩衝區既不是列連續（C-contiguous）也不是行連續（Fortran-contiguous）的，則會引發 BufferError。

release()

釋放 PickleBuffer 物件現正曝光中的緩衝區。

哪些物件能或不能被封裝、拆封？

下列型別可以被封裝：

內建常數（None、True、False、Ellipsis 和 NotImplemented）；

整數、浮點數和複數；

字串、位元組物件、位元組陣列；

元組（tuple）、串列（list）、集合（set）和僅含有可封裝物件的字典；

在模組最表面的層級就能被存取的函式（內建或自訂的皆可，不過僅限使用 def 定義的函式，lambda 函式不適用）；

在模組最表面的層級就能被存取的類別；

實例，只要在呼叫了 __getstate__() 後其回傳值全都是可封裝物件。（詳情請參閱 Pickling 類別實例）。

嘗試封裝無法封裝的物件會引發 PicklingError 例外；注意當這種情況發生時，可能已經有未知數量的位元組已被寫入到檔案。嘗試封裝深度遞迴的資料結構可能會導致其超出最大遞迴深度，在這種情況下會引發 RecursionError 例外。你可以（小心地）使用 sys.setrecursionlimit() 來提高此上限。

請注意，函式（內建及自訂兩者皆是）是依據完整的 限定名稱 來封裝，而非依其值。[2] 這意味著封裝時只有函式名稱、所屬的模組和所屬的類別名稱會被封裝。函式本身的程式碼及其附帶的任何屬性均不會被封裝。因此，在拆封該物件的環境中，定義此函式的模組必須可被引入，且該模組必須包含具此命名之物件，否則將引發例外。 [3]

同樣情況，類別是依照其完整限定名稱來進行封裝，因此在進行拆封的環境中會具有同上的限制。類別中的程式碼或資料皆不會被封裝，因此在以下範例中，注意到類別屬性 attr 在拆封的環境中不會被還原:

class Foo:
    attr = 'A class attribute'

picklestring = pickle.dumps(Foo)

這些限制就是可封裝的函式和類別必須被定義在模組頂層的原因。

同樣地，當類別實例被封裝時，它所屬類別具有的程式碼和資料不會被一起封裝。只有實例資料本身會被封裝。這是有意而為的，因為如此你才可以在類別中修正錯誤或新增其他方法，且於此同時仍能夠載入使用較早期版本的類別所建立的物件實例。如果你預計將有長期存在的物件、且該物件將經歷許多版本的更替，你可以在物件中存放一個版本號，以便未來能透過 __setstate__() 方法來進行適當的版本轉換。

Pickling 類別實例

在這一個章節，我們會講述如何封裝或拆封一個物件實例的相關機制，以方便你進行自訂。

大部分的實例不需要額外的程式碼就已經是可封裝的了。在這樣的預設狀況中，pickle 模組透過自省機制來取得類別及其實例的屬性。當類別實例被拆封時，其 __init__() 方法通常不會被呼叫。預設行為首先會建立一個未初始化的實例，然後還原紀錄中的屬性。以下程式碼的實作展示了前述行為：

def save(obj):
    return (obj.__class__, obj.__dict__)

def restore(cls, attributes):
    obj = cls.__new__(cls)
    obj.__dict__.update(attributes)
    return obj

被封裝的目標類別可以提供一個或數個下列特殊方法來改變 pickle 的預設行為：

object.__getnewargs_ex__()

在第 2 版協定或更新的版本中，有實作 __getnewargs_ex__() 方法的類別，可以決定在拆封時要傳遞給 __new__() 方法的值。該方法必須回傳一個 (args, kwargs) 的組合，其中 args 是一個位置引數的元組（tuple），kwargs 是一個用於建構物件的命名引數字典。這些資訊將在拆封時傳遞給 __new__() 方法。

如果目標類別的方法 __new__() 需要僅限關鍵字的參數時，你應該實作此方法。否則，為了提高相容性，建議你改為實作 __getnewargs__()。

在 3.6 版的變更: 在第 2、3 版的協定中現在改為使用 __getnewargs_ex__()。

object.__getnewargs__()

此方法與 __getnewargs_ex__() 的目的一樣，但僅支援位置參數。它必須回傳一個由傳入引數所組成的元組（tuple）args，這些引數會在拆封時傳遞給 __new__() 方法。

當有定義 __getnewargs_ex__() 的時候便不會呼叫 __getnewargs__()。

在 3.6 版的變更: 在 Python 3.6 之前、版本 2 和版本 3 的協定中，會呼叫 __getnewargs__() 而非 __getnewargs_ex__()。

object.__getstate__()

目標類別可以透過覆寫方法 __getstate__() 進一步影響其實例被封裝的方式。封裝時，呼叫該方法所回傳的物件將作為該實例的內容被封裝、而非一個預設狀態。以下列出幾種預設狀態：

沒有 __dict__ 和 __slots__ 實例的類別，其預設狀態為 None。

有 __dict__ 實例、但沒有 __slots__ 實例的類別，其預設狀態為 self.__dict__。

有 __dict__ 和 __slots__ 實例的類別，其預設狀態是一個含有兩個字典的元組（tuple），該二字典分別為 self.__dict__ 本身，和紀錄欄位（slot）名稱和值對應關係的字典（只有含有值的欄位（slot）會被紀錄其中）。

沒有 __dict__ 但有 __slots__ 實例的類別，其預設狀態是一個二元組（tuple），元組中的第一個值是 None，第二個值則是紀錄欄位（slot）名稱和值對應關係的字典（與前一項提到的字典是同一個）。

在 3.11 版的變更: 在 object 類別中增加預設的 __getstate__() 實作。

object.__setstate__(state)

在拆封時，如果類別定義了 __setstate__()，則會使用拆封後的狀態呼叫它。在這種情況下，紀錄狀態的物件不需要是字典（dictionary）。否則，封裝時的狀態紀錄必須是一個字典，其紀錄的項目將被賦值給新實例的字典。

備註

如果 __reduce__() 在封裝時回傳了 None 狀態，則拆封時就不會去呼叫 __setstate__()。

參閱 處裡紀錄大量狀態的物件 以了解 __getstate__() 和 __setstate__() 的使用方法。

備註

在拆封時，某些方法如 __getattr__()、__getattribute__() 或 __setattr__() 可能會在建立實例時被呼叫。如果這些方法依賴了某些實例內部的不變性，則應實作 __new__() 以建立此不變性，因為在拆封實例時不會呼叫 __init__()。

如稍後所演示，pickle 並不直接使用上述方法。這些方法實際上是實作了 __reduce__() 特殊方法的拷貝協定（copy protocol）。拷貝協定提供了統一的介面，以檢索進行封裝及複製物件時所需的資料。 [4]

直接在類別中實作 __reduce__() 雖然功能強大但卻容易導致出錯。因此，設計類別者應盡可能使用高階介面（例如，__getnewargs_ex__()、__getstate__() 和 __setstate__()）。不過，我們也將展示一些特例狀況，在這些狀況中，使用 __reduce__() 可能是唯一的選擇、是更有效率的封裝方法或二者兼備。

object.__reduce__()

目前的介面定義如下。 __reduce__() 方法不接受引數，且應回傳一個字串或一個元組（元組一般而言是較佳的選擇；所回傳的物件通常稱為「縮減值」）。

如果回傳的是字串，該字串應被解讀為一個全域變數的名稱。它應是該物件相對其所在模組的本地名稱；pickle 模組會在模組命名空間中尋找，以確定該物件所在的模組。這種行為通常對於單例物件特別有用。

當回傳一個元組時，其長度必須介於兩至六項元素之間。可選項可以被省略，或者其值可以被設為 None。各項物件的語意依序為：

一個將會被呼叫來建立初始版本物件的可呼叫物件。

一個用於傳遞引數給前述物件的元組。如果前述物件不接受引數輸入，則你仍應在這裡給定一個空元組。

可選項。物件狀態。如前所述，會被傳遞給該物件的 __setstate__() 方法。如果該物件沒有實作此方法，則本值必須是一個字典，且其將會被新增到物件的 __dict__ 屬性中。

可選項。一個用來提供連續項目的疊代器（而非序列）。這些項目將個別透過 obj.append(item) 方法或成批次地透過 obj.extend(list_of_items) 方法被附加到物件中。主要用於串列（list）子類別，但只要其他類別具有相應的 append() 和 extend() 方法以及相同的函式簽章（signature）就也可以使用。 （是否會呼叫 append() 或 extend() 方法將取決於所選用的 pickle 協定版本以及要附加的項目數量，因此必須同時支援這兩種方法。）

可選項。一個產生連續鍵值對的疊代器（不是序列）。這些項目將以 obj[key] = value 方式被儲存到物件中。主要用於字典（dictionary）子類別，但只要有實現了 __setitem__() 的其他類別也可以使用。

可選項。一個具有 (obj, state) 函式簽章（signature）的可呼叫物件。該物件允許使用者以可編寫的邏輯，而不是物件 obj 預設的 __setstate__() 靜態方法去控制特定物件的狀態更新方式。如果這個物件不是 None，這個物件的呼叫優先權將優於物件 obj 的 __setstate__()。

在 3.8 版被加入: 加入第六個可選項（一個 (obj, state) 元組）。

object.__reduce_ex__(protocol)

另外，你也可以定義一個 __reduce_ex__() 方法。唯一的不同的地方是此方法只接受協定版本（整數）作為參數。當有定義本方法時，pickle 會優先呼叫它而不是 __reduce__() 。此外，呼叫 __reduce__() 時也會自動變成呼叫這個變體版本。此方法主要是為了向後相容的舊的 Python 版本而存在。

外部物件持久化

為了方便物件持久化，pickle 模組支援對被封裝資料串流以外的物件參照。被參照的物件是透過一個持久化 ID 來參照的，這個 ID 應該要是字母數字字元（alphanumeric）組成的字串（協定 0） [5] 或者是任意的物件（任何較新的協定）。

pickle 沒有定義要如何解決或分派這個持久化 ID 的問題；故其處理方式有賴使用者自行定義在封裝器（pickler）以及拆封器（unpickler）中。方法的名稱各自為 persistent_id() 和 persistent_load()。

要封裝具有外部持久化 ID 的物件，封裝器（pickler）必須擁有一個自訂的方法 persistent_id()，這個方法將接收一個物件作為參數，並回傳 None 或該物件的持久化 ID。當回傳 None 時，封裝器會正常地封裝該物件。當回傳一個持久化 ID 字串時，封裝器會封裝該物件並加上一個標記，讓拆封器（unpickler）能識別它是一個持久化 ID。

要拆封外部物件，拆封器（unpickler）必須有一個自訂的 persistent_load() 方法，該方法應接受一個持久化 ID 物件，並回傳相對應的物件。

以下是一個完整的範例，用以說明如何使用持久化 ID 來封裝具外部參照的物件。

# 展示如何使用持久化 ID 來封裝外部物件的簡單範例

import pickle
import sqlite3
from collections import namedtuple

# 代表資料庫中紀錄的一個簡易類別
MemoRecord = namedtuple("MemoRecord", "key, task")

class DBPickler(pickle.Pickler):

    def persistent_id(self, obj):
        # 我們派發出一個持久 ID，而不是像一般類別實例那樣封裝 MemoRecord。
        if isinstance(obj, MemoRecord):
            # 我們的持久 ID 就是一個元組，裡面包含一個標籤和一個鍵，指向資料庫中的特定紀錄。
            return ("MemoRecord", obj.key)
        else:
            # 如果 obj 沒有持久 ID，則回傳 None。這表示 obj 像平常那樣封裝即可。
            return None

class DBUnpickler(pickle.Unpickler):

    def __init__(self, file, connection):
        super().__init__(file)
        self.connection = connection

    def persistent_load(self, pid):
        # 每當遇到持久 ID 時，此方法都會被呼叫。
        # pid 是 DBPickler 所回傳的元組。
        cursor = self.connection.cursor()
        type_tag, key_id = pid
        if type_tag == "MemoRecord":
            # 從資料庫中抓取所引用的紀錄並回傳。
            cursor.execute("SELECT * FROM memos WHERE key=?", (str(key_id),))
            key, task = cursor.fetchone()
            return MemoRecord(key, task)
        else:
            # 如果無法回傳正確的物件，則必須引發錯誤。
            # 否則 unpickler 會誤認為 None 是持久 ID 所引用的物件。
            raise pickle.UnpicklingError("unsupported persistent object")

def main():
    import io
    import pprint

    # 初始化資料庫。
    conn = sqlite3.connect(":memory:")
    cursor = conn.cursor()
    cursor.execute("CREATE TABLE memos(key INTEGER PRIMARY KEY, task TEXT)")
    tasks = (
        'give food to fish',
        'prepare group meeting',
        'fight with a zebra',
        )
    for task in tasks:
        cursor.execute("INSERT INTO memos VALUES(NULL, ?)", (task,))

    # 抓取要封裝的紀錄。
    cursor.execute("SELECT * FROM memos")
    memos = [MemoRecord(key, task) for key, task in cursor]
    # 使用我們自訂的 DBPickler 來保存紀錄。
    file = io.BytesIO()
    DBPickler(file).dump(memos)

    print("被封裝的紀錄:")
    pprint.pprint(memos)

    # 更新一筆紀錄（測試用）。
    cursor.execute("UPDATE memos SET task='learn italian' WHERE key=1")

    # 從 pickle 資料流中載入紀錄。
    file.seek(0)
    memos = DBUnpickler(file, conn).load()

    print("已拆封的紀錄:")
    pprint.pprint(memos)

if __name__ == '__main__':
    main()

調度表

如果你希望在不干擾其他物件正常封裝的前提下建立一個針對特定物件的封裝器，你可建立一個有私密調度表的封裝器。

由 copyreg 模組管理的全域調度表可以 copyreg.dispatch_table 呼叫。你可以透過這個方式來基於原始 copyreg.dispatch_table 建立一個修改過的版本，作為你的專屬用途的調度表。

舉例來說：

f = io.BytesIO()
p = pickle.Pickler(f)
p.dispatch_table = copyreg.dispatch_table.copy()
p.dispatch_table[SomeClass] = reduce_SomeClass

建立了一個 pickle.Pickler，其中含有專門處裡 SomeClass 類別的專屬調度表。此外，你也可以寫作：:

class MyPickler(pickle.Pickler):
    dispatch_table = copyreg.dispatch_table.copy()
    dispatch_table[SomeClass] = reduce_SomeClass
f = io.BytesIO()
p = MyPickler(f)

這樣可產生相似的結果，唯一不同的是往後所有 MyPickler 預設都會使用這個專屬調度表。最後，如果將程式寫為：:

copyreg.pickle(SomeClass, reduce_SomeClass)
f = io.BytesIO()
p = pickle.Pickler(f)

則會改變 copyreg 模組內建、所有使用者共通的調度表。

處裡紀錄大量狀態的物件

以下的範例展示了如何修改針對特定類別封裝時的行為。下面的 TextReader 類別會開啟一個文字檔案，並在每次呼叫其 readline() 方法時返回目前行編號與該行內容。如果 TextReader 實例被封裝，所有除了檔案物件之外的屬性成員都會被保存。在該實例被拆封時，檔案將被重新開啟，並從上次的位置繼續讀取。這個行為的達成是透過 __setstate__() 和 __getstate__() 方法來實作的。:

class TextReader:
    """列出文字檔案中的行並對其進行編號。"""

    def __init__(self, filename):
        self.filename = filename
        self.file = open(filename)
        self.lineno = 0

    def readline(self):
        self.lineno += 1
        line = self.file.readline()
        if not line:
            return None
        if line.endswith('\n'):
            line = line[:-1]
        return "%i: %s" % (self.lineno, line)

    def __getstate__(self):
        # 從 self.__dict__ 中複製物件的狀態。包含了所有的實例屬性。
        # 使用 dict.copy() 方法以避免修改原始狀態。
        state = self.__dict__.copy()
        # 移除不可封裝的項目。
        del state['file']
        return state

    def __setstate__(self, state):
        # 恢復實例屬性（即 filename 和 lineno）。
        self.__dict__.update(state)
        # 恢復到先前開啟了檔案的狀態。為此，我們需要重新開啟它並一直讀取到行數編號相同。
        file = open(self.filename)
        for _ in range(self.lineno):
            file.readline()
        # 存檔。
        self.file = file

可以這樣實際使用：:

>>> reader = TextReader("hello.txt")
>>> reader.readline()
'1: Hello world!'
>>> reader.readline()
'2: I am line number two.'
>>> new_reader = pickle.loads(pickle.dumps(reader))
>>> new_reader.readline()
'3: Goodbye!'

針對型別、函式或特定物件定製縮減函式

在 3.8 版被加入.

有時候，dispatch_table 的彈性空間可能不夠。尤其當我們想要使用型別以外的方式來判斷如何使用自訂封裝、或者我們想要自訂特定函式和類別的封裝方法時。

如果是這樣的話，可以繼承 Pickler 類別並實作一個 reducer_override() 方法。此方法可以回傳任意的縮減元組（參閱 __reduce__()）、也可以回傳 NotImplemented 以使用後備的原始行為方案。

如果 dispatch_table 和 reducer_override() 都被定義了的話，reducer_override() 的優先度較高。

備註

出於效能考量，處裡以下物件可能不會呼叫 reducer_override()：None、True、False，以及 int、float、bytes、str、dict、set、frozenset、list 和 tuple 的實例。

以下是一個簡單的例子，我們示範如何允許封裝和重建給定的類別：:

import io
import pickle

class MyClass:
    my_attribute = 1

class MyPickler(pickle.Pickler):
    def reducer_override(self, obj):
        """MyClass 的自訂縮減函式。"""
        if getattr(obj, "__name__", None) == "MyClass":
            return type, (obj.__name__, obj.__bases__,
                          {'my_attribute': obj.my_attribute})
        else:
            # 遭遇其他物件，則使用一般的縮減方式
            return NotImplemented

f = io.BytesIO()
p = MyPickler(f)
p.dump(MyClass)

del MyClass

unpickled_class = pickle.loads(f.getvalue())

assert isinstance(unpickled_class, type)
assert unpickled_class.__name__ == "MyClass"
assert unpickled_class.my_attribute == 1

帶外（Out-of-band）資料緩衝區

在 3.8 版被加入.

pickle 模組會被用於用於傳輸龐大的資料。此時，將複製記憶體的次數降到最低以保持效能變得很重要。然而，pickle 模組的正常操作過程中，當它將物件的圖狀結構（graph-like structure）轉換為連續的位元組串流時，本質上就涉及將資料複製到封裝流以及從封裝流複製資料。

如果供給者（被傳遞物件的型別的實作）與消費者（資訊交換系統的實作）都支援由 pickle 協定 5 或更高版本提供的帶外傳輸功能，則可以避免此一先天限制。

供給者 API

要封裝的大型資料物件，則必須實作一個針對 5 版協定及以上的 __reduce_ex__() 方法，該方法應回傳一個 PickleBuffer 實例來處理任何大型資料（而非回傳如 bytes 物件）。

一個 PickleBuffer 物件指示了當下底層的緩衝區狀態適合進行帶外資料傳輸。這些物件仍然相容 pickle 模組的一般使用方式。消費者程式也可以選擇介入，指示 pickle 他們將自行處理這些緩衝區。

消費者 API

一個資訊交換系統可以決定要自行處裡序列化物件圖時產生的 PickleBuffer 物件。

傳送端需要傳遞一個呼叫緩衝區的回呼函式給 Pickler（或 dump() 或 dumps() 函式）的 buffer_callback 引數，使每次生成 PickleBuffer 時，該物件在處理物件圖時能被呼叫。除了一個簡易標記以外，由 buffer_callback 累積的緩衝區資料不會被複製到 pickle 串流中。

接收端需要傳遞一個緩衝區物件給 Unpickler（或 load() 或 loads() 函式）的 buffers 引數。該物件須是一個可疊代的（iterable）緩衝區（buffer）物件，其中包含傳遞給 buffer_callback 的緩衝區物件。這個可疊代物件的緩衝區順序應該與它們當初被封裝時傳遞給 buffer_callback 的順序相同。這些緩衝區將提供物件重建所需的資料，以使重建器能還原出那個當時產生了 PickleBuffer 的物件。

在傳送與接收端之間，通訊系統可以自由實作轉移帶外緩衝區資料的機制。該機制可能可以利用共用記憶體機制或根據資料類型特定的壓縮方式來最佳化執行速度。

範例

這一個簡單的範例展示了如何實作一個可以參與帶外緩衝區封裝的 bytearray 子類別：:

class ZeroCopyByteArray(bytearray):

    def __reduce_ex__(self, protocol):
        if protocol >= 5:
            return type(self)._reconstruct, (PickleBuffer(self),), None
        else:
            # PickleBuffer 在 pickle 協定 <= 4 時禁止使用。
            return type(self)._reconstruct, (bytearray(self),)

    @classmethod
    def _reconstruct(cls, obj):
        with memoryview(obj) as m:
            # 取得對原始緩衝區物件的控制
            obj = m.obj
            if type(obj) is cls:
                # 若原本的緩衝區物件是 ZeroCopyByteArray，則直接回傳。
                return obj
            else:
                return cls(obj)

如果型別正確，重建器（_reconstruct 類別方法）會回傳當時提供緩衝區的物件。這個簡易實作可以模擬一個無複製行為的重建器。

在使用端，我們可以用一般的方式封裝這些物件，當我們拆封時會得到一個原始物件的副本：:

b = ZeroCopyByteArray(b"abc")
data = pickle.dumps(b, protocol=5)
new_b = pickle.loads(data)
print(b == new_b)  # True
print(b is new_b)  # False: 曾進行過複製運算

但如果我們傳一個 buffer_callback 並在去序列化時正確回傳積累的緩衝資料，我們就能拿回原始的物件：:

b = ZeroCopyByteArray(b"abc")
buffers = []
data = pickle.dumps(b, protocol=5, buffer_callback=buffers.append)
new_b = pickle.loads(data, buffers=buffers)
print(b == new_b)  # True
print(b is new_b)  # True: 沒有進行過複製

此範例是因為受限於 bytearray 會自行分配記憶體：你無法建立以其他物件的記憶體為基礎的 bytearray 實例。不過第三方資料型別（如 NumPy 陣列）則可能沒有這個限制，而允許在不同程序或系統之間傳輸資料時使用零拷貝封裝（或儘可能地減少拷貝次數）。

也參考

PEP 574 [https://peps.python.org/pep-0574/] -- 第 5 版 Pickle 協定的帶外資料（out-of-band data）處裡

限制全域物件

預設情況下，拆封過程將會引入任何在 pickle 資料中找到的類別或函式。對於許多應用程式來說，這種行為是不可接受的，因為它讓拆封器能夠引入並執行任意程式碼。請參見以下 pickle 資料流在載入時的行為：:

>>> import pickle
>>> pickle.loads(b"cos\nsystem\n(S'echo hello world'\ntR.")
hello world
0

在這個例子中，拆封器會引入 os.system() 函式，然後執行命令「echo hello world」。雖然這個例子是無害的，但不難想像可以這個方式輕易執行任意可能對系統造成損害的命令。

基於以上原因，你可能會希望透過自訂 Unpickler.find_class() 來控制哪些是能夠被拆封的內容。與其名稱字面意義暗示的不同，實際上每當你請求一個全域物件（例如，類別或函式）時，就會呼叫 Unpickler.find_class()。因此，可以透過這個方法完全禁止全域物件或將其限制在安全的子集合。

以下是一個僅允許從 builtins 模組中載入少數安全類別的拆封器（unpickler）的例子：:

import builtins
import io
import pickle

safe_builtins = {
    'range',
    'complex',
    'set',
    'frozenset',
    'slice',
}

class RestrictedUnpickler(pickle.Unpickler):

    def find_class(self, module, name):
        # 只允許幾個內建的安全類別
        if module == "builtins" and name in safe_builtins:
            return getattr(builtins, name)
        # 完全禁止任何其他類別
        raise pickle.UnpicklingError("global '%s.%s' is forbidden" %
                                     (module, name))

def restricted_loads(s):
    """一個模擬 pickle.loads() 的輔助函式"""
    return RestrictedUnpickler(io.BytesIO(s)).load()

我們剛才實作的的拆封器範例正常運作的樣子：:

>>> restricted_loads(pickle.dumps([1, 2, range(15)]))
[1, 2, range(0, 15)]
>>> restricted_loads(b"cos\nsystem\n(S'echo hello world'\ntR.")
Traceback (most recent call last):
  ...
pickle.UnpicklingError: global 'os.system' is forbidden
>>> restricted_loads(b'cbuiltins\neval\n'
...                  b'(S\'getattr(__import__("os"), "system")'
...                  b'("echo hello world")\'\ntR.')
Traceback (most recent call last):
  ...
pickle.UnpicklingError: global 'builtins.eval' is forbidden

正如我們的範例所示，必須謹慎審視能被拆封的內容。因此，如果你的應用場景非常關心安全性，你可能需要考慮其他選擇，例如 xmlrpc.client 中的 marshalling API 或其他第三方解決方案。

效能

較近期的 pickle 協定版本（從 2 版協定開始）為多種常見功能和內建型別提供了高效率的二進位編碼。此外，pickle 模組還具備一個透明化的、以 C 語言編寫的最佳化工具。

範例

最簡單的使用方式，呼叫 dump() 和 load() 函式。:

import pickle

# 任意 pickle 支援的物件。
data = {
    'a': [1, 2.0, 3+4j],
    'b': ("string", b"byte string"),
    'c': {None, True, False}
}

with open('data.pickle', 'wb') as f:
    # 使用可用的最高協定來封裝 'data' 字典。
    pickle.dump(data, f, pickle.HIGHEST_PROTOCOL)

以下範例可以讀取前述程式所封裝的 pickle 資料。:

import pickle

with open('data.pickle', 'rb') as f:
    # 會自動檢測資料使用的協定版本，因此我們不需要手動指定。
    data = pickle.load(f)

命令列介面

The pickle module can be invoked as a script from the command line, it will display contents of the pickle files. However, when the pickle file that you want to examine comes from an untrusted source, -m pickletools is a safer option because it does not execute pickle bytecode, see pickletools CLI usage.

python -m pickle pickle_file [pickle_file ...]

接受以下選項：

pickle_file

A pickle file to read, or - to indicate reading from standard input.

也參考

copyreg 模組

註冊擴充型別的 Pickle 介面建構子。

pickletools 模組

用於分析或處裡被封裝資料的工具。

shelve 模組

索引式資料庫；使用 pickle 實作。

copy 模組

物件的淺層或深度拷貝。

marshal 模組

內建型別的高效能序列化。

註解

[1]

不要將此模組與 marshal 模組混淆

[2]

這就是為什麼 lambda 函式無法被封裝：所有 lambda 函式共享相同的名稱：<lambda>。

[3]

引發的例外應該是 ImportError 或 AttributeError，但也可能是其他例外。

[4]

copy 模組使用此協定進行淺層及深層複製操作。

[5]

協定 0 中限制僅能使用英文字母或數字字元來分配持久化 ID 是因為持久化 ID 是由換行符號所分隔的。因此，如果持久化 ID 中出現任何形式的換行字元，將導致封裝資料變得無法讀取。

copyreg --- 註冊 pickle 支援函式

原始碼：Lib/copyreg.py [https://github.com/python/cpython/tree/3.14/Lib/copyreg.py]

copyreg 模組提供了一種用以定義在 pickle 特定物件時使用之函式的方式。pickle 和 copy 模組在 pickle/copy 這些物件時使用這些函式。此模組提供有關非類別物件之建構函式的配置資訊。此類建構函式可以是工廠函式 (factory function) 或類別實例。

copyreg.constructor(object)

宣告 object 是一個有效的建構函式。如果 object 不可呼叫（因此不可作為有效的建構函式），則會引發 TypeError。

copyreg.pickle(type, function, constructor_ob=None)

宣告 function 應該用作 type 型別之物件的「歸約 ("reduction")」函式。function 必須回傳字串或包含 2 到 6 個元素的元組。有關 function 介面的更多詳細資訊，請參閱 dispatch_table。

constructor_ob 參數是一個遺留功能，現在已被忽略，但如果要傳遞它的話則必須是個可呼叫物件。

請注意，pickler 物件或 pickle.Pickler 子類別的 dispatch_table 屬性也可用於宣告歸約函式。

範例

下面範例展示如何註冊一個 pickle 函式以及如何使用它：

>>> import copyreg, copy, pickle
>>> class C:
...     def __init__(self, a):
...         self.a = a
...
>>> def pickle_c(c):
...     print("pickling a C instance...")
...     return C, (c.a,)
...
>>> copyreg.pickle(C, pickle_c)
>>> c = C(1)
>>> d = copy.copy(c)
pickling a C instance...
>>> p = pickle.dumps(c)
pickling a C instance...

shelve --- Python object persistence

原始碼：Lib/shelve.py [https://github.com/python/cpython/tree/3.14/Lib/shelve.py]

A "shelf" is a persistent, dictionary-like object. The difference with "dbm" databases is that the values (not the keys!) in a shelf can be essentially arbitrary Python objects --- anything that the pickle module can handle. This includes most class instances, recursive data types, and objects containing lots of shared sub-objects. The keys are ordinary strings.

shelve.open(filename, flag='c', protocol=None, writeback=False)

Open a persistent dictionary. The filename specified is the base filename for the underlying database. As a side-effect, an extension may be added to the filename and more than one file may be created. By default, the underlying database file is opened for reading and writing. The optional flag parameter has the same interpretation as the flag parameter of dbm.open().

By default, pickles created with pickle.DEFAULT_PROTOCOL are used to serialize values. The version of the pickle protocol can be specified with the protocol parameter.

Because of Python semantics, a shelf cannot know when a mutable persistent-dictionary entry is modified. By default modified objects are written only when assigned to the shelf (see 範例). If the optional writeback parameter is set to True, all entries accessed are also cached in memory, and written back on sync() and close(); this can make it handier to mutate mutable entries in the persistent dictionary, but, if many entries are accessed, it can consume vast amounts of memory for the cache, and it can make the close operation very slow since all accessed entries are written back (there is no way to determine which accessed entries are mutable, nor which ones were actually mutated).

在 3.10 版的變更: pickle.DEFAULT_PROTOCOL is now used as the default pickle protocol.

在 3.11 版的變更: Accepts path-like object for filename.

備註

Do not rely on the shelf being closed automatically; always call close() explicitly when you don't need it any more, or use shelve.open() as a context manager:

with shelve.open('spam') as db:
    db['eggs'] = 'eggs'

警告

Because the shelve module is backed by pickle, it is insecure to load a shelf from an untrusted source. Like with pickle, loading a shelf can execute arbitrary code.

Shelf objects support most of methods and operations supported by dictionaries (except copying, constructors and operators | and |=). This eases the transition from dictionary based scripts to those requiring persistent storage.

Two additional methods are supported:

Shelf.sync()

Write back all entries in the cache if the shelf was opened with writeback set to True. Also empty the cache and synchronize the persistent dictionary on disk, if feasible. This is called automatically when the shelf is closed with close().

Shelf.close()

Synchronize and close the persistent dict object. Operations on a closed shelf will fail with a ValueError.

也參考

Persistent dictionary recipe [https://code.activestate.com/recipes/576642-persistent-dict-with-multiple-standard-file-format/] with widely supported storage formats and having the speed of native dictionaries.

Restrictions

The choice of which database package will be used (such as dbm.ndbm or dbm.gnu) depends on which interface is available. Therefore it is not safe to open the database directly using dbm. The database is also (unfortunately) subject to the limitations of dbm, if it is used --- this means that (the pickled representation of) the objects stored in the database should be fairly small, and in rare cases key collisions may cause the database to refuse updates.

The shelve module does not support concurrent read/write access to shelved objects. (Multiple simultaneous read accesses are safe.) When a program has a shelf open for writing, no other program should have it open for reading or writing. Unix file locking can be used to solve this, but this differs across Unix versions and requires knowledge about the database implementation used.

On macOS dbm.ndbm can silently corrupt the database file on updates, which can cause hard crashes when trying to read from the database.

class shelve.Shelf(dict, protocol=None, writeback=False, keyencoding='utf-8')

A subclass of collections.abc.MutableMapping which stores pickled values in the dict object.

By default, pickles created with pickle.DEFAULT_PROTOCOL are used to serialize values. The version of the pickle protocol can be specified with the protocol parameter. See the pickle documentation for a discussion of the pickle protocols.

If the writeback parameter is True, the object will hold a cache of all entries accessed and write them back to the dict at sync and close times. This allows natural operations on mutable entries, but can consume much more memory and make sync and close take a long time.

The keyencoding parameter is the encoding used to encode keys before they are used with the underlying dict.

A Shelf object can also be used as a context manager, in which case it will be automatically closed when the with block ends.

在 3.2 版的變更: Added the keyencoding parameter; previously, keys were always encoded in UTF-8.

在 3.4 版的變更: 新增情境管理器的支援。

在 3.10 版的變更: pickle.DEFAULT_PROTOCOL is now used as the default pickle protocol.

class shelve.BsdDbShelf(dict, protocol=None, writeback=False, keyencoding='utf-8')

A subclass of Shelf which exposes first(), next(), previous(), last() and set_location() methods. These are available in the third-party bsddb module from pybsddb [https://www.jcea.es/programacion/pybsddb.htm] but not in other database modules. The dict object passed to the constructor must support those methods. This is generally accomplished by calling one of bsddb.hashopen(), bsddb.btopen() or bsddb.rnopen(). The optional protocol, writeback, and keyencoding parameters have the same interpretation as for the Shelf class.

class shelve.DbfilenameShelf(filename, flag='c', protocol=None, writeback=False)

A subclass of Shelf which accepts a filename instead of a dict-like object. The underlying file will be opened using dbm.open(). By default, the file will be created and opened for both read and write. The optional flag parameter has the same interpretation as for the open() function. The optional protocol and writeback parameters have the same interpretation as for the Shelf class.

範例

To summarize the interface (key is a string, data is an arbitrary object):

import shelve

d = shelve.open(filename)  # open -- file may get suffix added by low-level
                           # library

d[key] = data              # store data at key (overwrites old data if
                           # using an existing key)
data = d[key]              # retrieve a COPY of data at key (raise KeyError
                           # if no such key)
del d[key]                 # delete data stored at key (raises KeyError
                           # if no such key)

flag = key in d            # true if the key exists
klist = list(d.keys())     # a list of all existing keys (slow!)

# as d was opened WITHOUT writeback=True, beware:
d['xx'] = [0, 1, 2]        # this works as expected, but...
d['xx'].append(3)          # *this doesn't!* -- d['xx'] is STILL [0, 1, 2]!

# having opened d without writeback=True, you need to code carefully:
temp = d['xx']             # extracts the copy
temp.append(5)             # mutates the copy
d['xx'] = temp             # stores the copy right back, to persist it

# or, d=shelve.open(filename,writeback=True) would let you just code
# d['xx'].append(5) and have it work as expected, BUT it would also
# consume more memory and make the d.close() operation slower.

d.close()                  # close it

也參考

dbm 模組

Generic interface to dbm-style databases.

pickle 模組

shelve 使用的物件序列化。

marshal --- 內部 Python 物件序列化

此模組包含一個能以二進位制格式來讀寫 Python 值的函式。這種格式是 Python 專屬但獨立於機器架構的（例如，你可以在一臺 PC 上寫入某個 Python 值，再將檔案傳到一臺 Mac 上並在那裡讀取它）。這種格式的細節是有意地不在文件上說明的；它可能在不同 Python 版本中被改變（雖然這種情況極少發生）。[1]

這不是一個通用「持久性 (persistence)」模組。關於通用持久性以及透過 RPC 呼叫傳遞 Python 物件，請參閱 pickle 和 shelve 等模組。marshal 模組主要是為了支援用來讀寫 .pyc 檔案之 Python 模組的「偽編譯 (pseudo-compiled)」程式碼。因此，Python 維護者保留了在必要時以不向後相容的方式修改 marshal 格式的權利。程式碼物件的格式在不同 Python 版本間是不相容的，即使格式版本相同。在不正確的 Python 版本中反序列化程式碼物件會有未定義的行為。如果你要序列化和反序列化 Python 物件，請改用 pickle 模組 -- 其執行效率相當、有保證版本獨立性，且實質上 pickle 還支援比 marshal 更多樣的物件。

警告

marshal 模組對於錯誤或惡意構建的資料來說是不安全的。永遠不要 unmarshal 來自不受信任的或來源未經驗證的資料。

有些函式可以讀/寫檔案，還有些函式可以操作類位元組串物件 (bytes-like object)。

Not all Python object types are supported; in general, only objects whose value is independent from a particular invocation of Python can be written and read by this module. The following types are supported:

Numeric types: int, bool, float, complex.

Strings (str) and bytes. Bytes-like objects like bytearray are marshalled as bytes.

Containers: tuple, list, set, frozenset, and (since version 5), slice. It should be understood that these are supported only if the values contained therein are themselves supported. Recursive containers are supported since version 3.

The singletons None, Ellipsis and StopIteration.

code objects, if allow_code is true. See note above about version dependence.

在 3.4 版的變更:

Added format version 3, which supports marshalling recursive lists, sets and dictionaries.

Added format version 4, which supports efficient representations of short strings.

在 3.14 版的變更: Added format version 5, which allows marshalling slices.

這個模組定義了以下函式：

marshal.dump(value, file, version=version, /, *, allow_code=True)

將值寫入被開啟的檔案。值必須為受支援的型別，檔案必須為可寫入的 binary file。

如果值具有（或其所包含的物件具有）不支援的型別，則會引發 ValueError 例外 --- 但是垃圾資料 (garbage data) 也將寫入檔案，物件也無法正確地透過 load() 重新讀取。程式碼物件只有在 allow_code 為 true 時才會支援。

version 引數指明 dump 應該使用的資料格式（見下文）。

引發一個附帶引數 value 與 version 的稽核事件 (auditing event) marshal.dumps。

在 3.13 版的變更: 新增 allow_code 參數。

marshal.load(file, /, *, allow_code=True)

從開啟的檔案讀取一個值並回傳。如果讀不到有效的值（例如，由於資料為不同 Python 版本的不相容 marshal 格式），則會引發 EOFError、ValueError 或 TypeError。程式碼物件只有在 allow_code 為 true 時才會支援。檔案必須為可讀取的 binary file。

引發一個沒有附帶引數的稽核事件 marshal.load。

備註

如果透過 dump() marshal 了一個包含不支援型別的物件，load() 會將不可 marshal 的型別替換為 None。

在 3.10 版的變更: 使用此呼叫為每個程式碼物件引發一個 code.__new__ 稽核事件。現在它會為整個載入操作引發單個 marshal.load 事件。

在 3.13 版的變更: 新增 allow_code 參數。

marshal.dumps(value, version=version, /, *, allow_code=True)

回傳將透過 dump(value, file) 來被寫入一個檔案的位元組串物件，其值必須是有支援的型別，如果值（或其包含的任一物件）為不支援的型別則會引發 ValueError。程式碼物件只有在 allow_code 為 true 時才會支援。

version 引數指明 dumps 應當使用的資料型別（見下文）。

引發一個附帶引數 value 與 version 的稽核事件 (auditing event) marshal.dumps。

在 3.13 版的變更: 新增 allow_code 參數。

marshal.loads(bytes, /, *, allow_code=True)

將 bytes-like object 轉換為一個值。如果找不到有效的值，則會引發 EOFError、ValueError 或 TypeError。程式碼物件只有在 allow_code 為 true 時才會支援。輸入中額外的位元組串會被忽略。

引發一個附帶引數 bytes 的稽核事件 marshal.loads。

在 3.10 版的變更: 使用此呼叫為每個程式碼物件引發一個 code.__new__ 稽核事件。現在它會為整個載入操作引發單個 marshal.loads 事件。

在 3.13 版的變更: 新增 allow_code 參數。

此外，還定義了以下常數：

marshal.version

表示模組所使用的格式。第 0 版為歷史上第一版本；後續版本會新增功能。當引入新版本時，它通常會成為預設版本。

版本

Available since

New features

1

Python 2.4

共享駐留字串

2

Python 2.5

Binary representation of floats

3

Python 3.4

Support for object instancing and recursion

4

Python 3.4

Efficient representation of short strings

5

Python 3.14

Support for slice objects

註解

[1]

此模組的名稱來源於 Modula-3 (及其他語言) 的設計者所使用的術語，他們使用 "marshal" 來表示自包含 (self-contained) 形式資料的傳輸。嚴格來說，將資料從內部形式轉換為外部形式 (例如用於 RPC 緩衝區) 稱為 "marshal"，而其反向過程則稱為 "unmarshal"。

dbm --- Unix "databases" 的介面

原始碼：Lib/dbm/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/dbm/__init__.py]

dbm is a generic interface to variants of the DBM database:

dbm.sqlite3

dbm.gnu

dbm.ndbm

If none of these modules are installed, the slow-but-simple implementation in module dbm.dumb will be used. There is a third party interface [https://www.jcea.es/programacion/pybsddb.htm] to the Oracle Berkeley DB.

exception dbm.error

A tuple containing the exceptions that can be raised by each of the supported modules, with a unique exception also named dbm.error as the first item --- the latter is used when dbm.error is raised.

dbm.whichdb(filename)

This function attempts to guess which of the several simple database modules available --- dbm.sqlite3, dbm.gnu, dbm.ndbm, or dbm.dumb --- should be used to open a given file.

回傳以下其中一個值：

None if the file can't be opened because it's unreadable or doesn't exist

the empty string ('') if the file's format can't be guessed

a string containing the required module name, such as 'dbm.ndbm' or 'dbm.gnu'

在 3.11 版的變更: filename accepts a path-like object.

dbm.open(file, flag='r', mode=0o666)

Open a database and return the corresponding database object.

參數:

file (path-like object) --

要打開的資料庫檔案

If the database file already exists, the whichdb() function is used to determine its type and the appropriate module is used; if it does not exist, the first submodule listed above that can be imported is used.

flag (str) --

'r' (default): Open existing database for reading only.

'w': Open existing database for reading and writing.

'c': Open database for reading and writing, creating it if it doesn't exist.

'n': Always create a new, empty database, open for reading and writing.

mode (int) -- The Unix file access mode of the file (default: octal 0o666), used only when the database has to be created.

在 3.11 版的變更: file 接受一個類路徑物件。

The object returned by open() supports the basic functionality of mutable mappings; keys and their corresponding values can be stored, retrieved, and deleted, and iteration, the in operator and methods keys(), get(), setdefault() and clear() are available. The keys() method returns a list instead of a view object. The setdefault() method requires two arguments.

Key and values are always stored as bytes. This means that when strings are used they are implicitly converted to the default encoding before being stored.

These objects also support being used in a with statement, which will automatically close them when done.

在 3.2 版的變更: get() and setdefault() methods are now available for all dbm backends.

在 3.4 版的變更: Added native support for the context management protocol to the objects returned by open().

在 3.8 版的變更: Deleting a key from a read-only database raises a database module specific exception instead of KeyError.

在 3.13 版的變更: clear() 方法現在可用於所有 dbm 後端。

The following example records some hostnames and a corresponding title, and then prints out the contents of the database:

import dbm

# Open database, creating it if necessary.
with dbm.open('cache', 'c') as db:

    # Record some values
    db[b'hello'] = b'there'
    db['www.python.org'] = 'Python Website'
    db['www.cnn.com'] = 'Cable News Network'

    # Note that the keys are considered bytes now.
    assert db[b'www.python.org'] == b'Python Website'
    # Notice how the value is now in bytes.
    assert db['www.cnn.com'] == b'Cable News Network'

    # Often-used methods of the dict interface work too.
    print(db.get('python.org', b'not present'))

    # Storing a non-string key or value will raise an exception (most
    # likely a TypeError).
    db['www.yahoo.com'] = 4

# db is automatically closed when leaving the with statement.

也參考

shelve 模組

Persistence module which stores non-string data.

The individual submodules are described in the following sections.

dbm.sqlite3 --- dbm 的 SQLite 後端

在 3.13 版被加入.

原始碼：Lib/dbm/sqlite3.py [https://github.com/python/cpython/tree/3.14/Lib/dbm/sqlite3.py]

This module uses the standard library sqlite3 module to provide an SQLite backend for the dbm module. The files created by dbm.sqlite3 can thus be opened by sqlite3, or any other SQLite browser, including the SQLite CLI.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

dbm.sqlite3.open(filename, /, flag='r', mode=0o666)

打開一個 SQLite 資料庫。

參數:

filename (path-like object) -- 要打開的資料庫路徑

flag (str) --

'r' (default): Open existing database for reading only.

'w': Open existing database for reading and writing.

'c': Open database for reading and writing, creating it if it doesn't exist.

'n': Always create a new, empty database, open for reading and writing.

mode -- The Unix file access mode of the file (default: octal 0o666), used only when the database has to be created.

The returned database object behaves similar to a mutable mapping, but the keys() method returns a list, and the setdefault() method requires two arguments. It also supports a "closing" context manager via the with keyword.

也提供了以下方法：

sqlite3.close()

關閉 SQLite 資料庫。

dbm.gnu --- GNU 資料庫管理器

原始碼：Lib/dbm/gnu.py [https://github.com/python/cpython/tree/3.14/Lib/dbm/gnu.py]

The dbm.gnu module provides an interface to the GDBM library, similar to the dbm.ndbm module, but with additional functionality like crash tolerance.

備註

The file formats created by dbm.gnu and dbm.ndbm are incompatible and can not be used interchangeably.

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

exception dbm.gnu.error

Raised on dbm.gnu-specific errors, such as I/O errors. KeyError is raised for general mapping errors like specifying an incorrect key.

dbm.gnu.open_flags

A string of characters the flag parameter of open() supports.

dbm.gnu.open(filename, flag='r', mode=0o666, /)

打開一個 GDBM 資料庫，並回傳一個 gdbm 物件。

參數:

filename (path-like object) -- 要打開的資料庫檔案

flag (str) --

'r' (default): Open existing database for reading only.

'w': Open existing database for reading and writing.

'c': Open database for reading and writing, creating it if it doesn't exist.

'n': Always create a new, empty database, open for reading and writing.

The following additional characters may be appended to control how the database is opened:

'f': Open the database in fast mode. Writes to the database will not be synchronized.

's': Synchronized mode. Changes to the database will be written immediately to the file.

'u': 不要鎖住資料庫。

Not all flags are valid for all versions of GDBM. See the open_flags member for a list of supported flag characters.

mode (int) -- The Unix file access mode of the file (default: octal 0o666), used only when the database has to be created.

引發:

error -- 如果一個無效的 flag 引數被傳入。

在 3.11 版的變更: filename accepts a path-like object.

gdbm objects behave similar to mutable mappings, but methods items(), values(), pop(), popitem(), and update() are not supported, the keys() method returns a list, and the setdefault() method requires two arguments. It also supports a "closing" context manager via the with keyword.

在 3.2 版的變更: 新增了 get() 和 setdefault() 方法。

在 3.13 版的變更: 新增了 clear() 方法。

也提供了以下方法：

gdbm.close()

關閉 GDBM 資料庫。

gdbm.firstkey()

It's possible to loop over every key in the database using this method and the nextkey() method. The traversal is ordered by GDBM's internal hash values, and won't be sorted by the key values. This method returns the starting key.

gdbm.nextkey(key)

Returns the key that follows key in the traversal. The following code prints every key in the database db, without having to create a list in memory that contains them all:

k = db.firstkey()
while k is not None:
    print(k)
    k = db.nextkey(k)

gdbm.reorganize()

If you have carried out a lot of deletions and would like to shrink the space used by the GDBM file, this routine will reorganize the database. gdbm objects will not shorten the length of a database file except by using this reorganization; otherwise, deleted file space will be kept and reused as new (key, value) pairs are added.

gdbm.sync()

When the database has been opened in fast mode, this method forces any unwritten data to be written to the disk.

dbm.ndbm --- 新資料庫管理器

原始碼：Lib/dbm/ndbm.py [https://github.com/python/cpython/tree/3.14/Lib/dbm/ndbm.py]

The dbm.ndbm module provides an interface to the NDBM library. This module can be used with the "classic" NDBM interface or the GDBM compatibility interface.

備註

The file formats created by dbm.gnu and dbm.ndbm are incompatible and can not be used interchangeably.

警告

The NDBM library shipped as part of macOS has an undocumented limitation on the size of values, which can result in corrupted database files when storing values larger than this limit. Reading such corrupted files can result in a hard crash (segmentation fault).

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

exception dbm.ndbm.error

Raised on dbm.ndbm-specific errors, such as I/O errors. KeyError is raised for general mapping errors like specifying an incorrect key.

dbm.ndbm.library

Name of the NDBM implementation library used.

dbm.ndbm.open(filename, flag='r', mode=0o666, /)

Open an NDBM database and return an ndbm object.

參數:

filename (path-like object) -- The basename of the database file (without the .dir or .pag extensions).

flag (str) --

'r' (default): Open existing database for reading only.

'w': Open existing database for reading and writing.

'c': Open database for reading and writing, creating it if it doesn't exist.

'n': Always create a new, empty database, open for reading and writing.

mode (int) -- The Unix file access mode of the file (default: octal 0o666), used only when the database has to be created.

在 3.11 版的變更: Accepts path-like object for filename.

ndbm objects behave similar to mutable mappings, but methods items(), values(), pop(), popitem(), and update() are not supported, the keys() method returns a list, and the setdefault() method requires two arguments. It also supports a "closing" context manager via the with keyword.

在 3.2 版的變更: 新增了 get() 和 setdefault() 方法。

在 3.13 版的變更: 新增了 clear() 方法。

也提供了以下方法：

ndbm.close()

關閉 NDBM 資料庫。

dbm.dumb --- 可攜式 DBM 實作

原始碼：Lib/dbm/dumb.py [https://github.com/python/cpython/tree/3.14/Lib/dbm/dumb.py]

備註

The dbm.dumb module is intended as a last resort fallback for the dbm module when a more robust module is not available. The dbm.dumb module is not written for speed and is not nearly as heavily used as the other database modules.

The dbm.dumb module provides a persistent dict-like interface which is written entirely in Python. Unlike other dbm backends, such as dbm.gnu, no external library is required.

dbm.dumb 模組定義了以下項目：

exception dbm.dumb.error

Raised on dbm.dumb-specific errors, such as I/O errors. KeyError is raised for general mapping errors like specifying an incorrect key.

dbm.dumb.open(filename, flag='c', mode=0o666)

開啟一個 dbm.dumb 資料庫。

參數:

filename --

The basename of the database file (without extensions). A new database creates the following files:

filename.dat

filename.dir

flag (str) --

'r': Open existing database for reading only.

'w': Open existing database for reading and writing.

'c' (default): Open database for reading and writing, creating it if it doesn't exist.

'n': Always create a new, empty database, open for reading and writing.

mode (int) -- The Unix file access mode of the file (default: octal 0o666), used only when the database has to be created.

警告

It is possible to crash the Python interpreter when loading a database with a sufficiently large/complex entry due to stack depth limitations in Python's AST compiler.

在 3.5 版的變更: open() always creates a new database when flag is 'n'.

在 3.8 版的變更: A database opened read-only if flag is 'r'. A database is not created if it does not exist if flag is 'r' or 'w'.

在 3.11 版的變更: filename accepts a path-like object.

The returned database object behaves similar to a mutable mapping, but the keys() and items() methods return lists, and the setdefault() method requires two arguments. It also supports a "closing" context manager via the with keyword.

也提供了以下方法：

dumbdbm.close()

關閉資料庫。

dumbdbm.sync()

Synchronize the on-disk directory and data files. This method is called by the shelve.Shelf.sync() method.

sqlite3 --- SQLite 資料庫的 DB-API 2.0 介面

原始碼：Lib/sqlite3/ [https://github.com/python/cpython/tree/3.14/Lib/sqlite3/]

SQLite is a C library that provides a lightweight disk-based database that doesn't require a separate server process and allows accessing the database using a nonstandard variant of the SQL query language. Some applications can use SQLite for internal data storage. It's also possible to prototype an application using SQLite and then port the code to a larger database such as PostgreSQL or Oracle.

The sqlite3 module was written by Gerhard Häring. It provides an SQL interface compliant with the DB-API 2.0 specification described by PEP 249 [https://peps.python.org/pep-0249/], and requires the third-party SQLite [https://sqlite.org/] library.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

此文件包含四個主要章節：

教學 教導如何使用 sqlite3 模組。

Reference 描述此模組定義的類別與函式。

How-to guides 詳細說明如何處理特定工作。

解釋 深入提供交易 (transaction) 控制的背景。

也參考

https://www.sqlite.org

The SQLite web page; the documentation describes the syntax and the available data types for the supported SQL dialect.

https://www.w3schools.com/sql/

Tutorial, reference and examples for learning SQL syntax.

PEP 249 [https://peps.python.org/pep-0249/] - 資料庫 API 規格 2.0

PEP 由 Marc-André Lemburg 撰寫。

教學

In this tutorial, you will create a database of Monty Python movies using basic sqlite3 functionality. It assumes a fundamental understanding of database concepts, including cursors [https://en.wikipedia.org/wiki/Cursor_(databases)] and transactions [https://en.wikipedia.org/wiki/Database_transaction].

First, we need to create a new database and open a database connection to allow sqlite3 to work with it. Call sqlite3.connect() to create a connection to the database tutorial.db in the current working directory, implicitly creating it if it does not exist:

import sqlite3
con = sqlite3.connect("tutorial.db")

The returned Connection object con represents the connection to the on-disk database.

In order to execute SQL statements and fetch results from SQL queries, we will need to use a database cursor. Call con.cursor() to create the Cursor:

cur = con.cursor()

Now that we've got a database connection and a cursor, we can create a database table movie with columns for title, release year, and review score. For simplicity, we can just use column names in the table declaration -- thanks to the flexible typing [https://www.sqlite.org/flextypegood.html] feature of SQLite, specifying the data types is optional. Execute the CREATE TABLE statement by calling cur.execute(...):

cur.execute("CREATE TABLE movie(title, year, score)")

We can verify that the new table has been created by querying the sqlite_master table built-in to SQLite, which should now contain an entry for the movie table definition (see The Schema Table [https://www.sqlite.org/schematab.html] for details). Execute that query by calling cur.execute(...), assign the result to res, and call res.fetchone() to fetch the resulting row:

>>> res = cur.execute("SELECT name FROM sqlite_master")
>>> res.fetchone()
('movie',)

We can see that the table has been created, as the query returns a tuple containing the table's name. If we query sqlite_master for a non-existent table spam, res.fetchone() will return None:

>>> res = cur.execute("SELECT name FROM sqlite_master WHERE name='spam'")
>>> res.fetchone() is None
True

Now, add two rows of data supplied as SQL literals by executing an INSERT statement, once again by calling cur.execute(...):

cur.execute("""
    INSERT INTO movie VALUES
        ('Monty Python and the Holy Grail', 1975, 8.2),
        ('And Now for Something Completely Different', 1971, 7.5)
""")

The INSERT statement implicitly opens a transaction, which needs to be committed before changes are saved in the database (see Transaction control for details). Call con.commit() on the connection object to commit the transaction:

con.commit()

We can verify that the data was inserted correctly by executing a SELECT query. Use the now-familiar cur.execute(...) to assign the result to res, and call res.fetchall() to return all resulting rows:

>>> res = cur.execute("SELECT score FROM movie")
>>> res.fetchall()
[(8.2,), (7.5,)]

The result is a list of two tuples, one per row, each containing that row's score value.

Now, insert three more rows by calling cur.executemany(...):

data = [
    ("Monty Python Live at the Hollywood Bowl", 1982, 7.9),
    ("Monty Python's The Meaning of Life", 1983, 7.5),
    ("Monty Python's Life of Brian", 1979, 8.0),
]
cur.executemany("INSERT INTO movie VALUES(?, ?, ?)", data)
con.commit()  # Remember to commit the transaction after executing INSERT.

Notice that ? placeholders are used to bind data to the query. Always use placeholders instead of string formatting to bind Python values to SQL statements, to avoid SQL injection attacks [https://en.wikipedia.org/wiki/SQL_injection] (see How to use placeholders to bind values in SQL queries for more details).

We can verify that the new rows were inserted by executing a SELECT query, this time iterating over the results of the query:

>>> for row in cur.execute("SELECT year, title FROM movie ORDER BY year"):
...     print(row)
(1971, 'And Now for Something Completely Different')
(1975, 'Monty Python and the Holy Grail')
(1979, "Monty Python's Life of Brian")
(1982, 'Monty Python Live at the Hollywood Bowl')
(1983, "Monty Python's The Meaning of Life")

Each row is a two-item tuple of (year, title), matching the columns selected in the query.

Finally, verify that the database has been written to disk by calling con.close() to close the existing connection, opening a new one, creating a new cursor, then querying the database:

>>> con.close()
>>> new_con = sqlite3.connect("tutorial.db")
>>> new_cur = new_con.cursor()
>>> res = new_cur.execute("SELECT title, year FROM movie ORDER BY score DESC")
>>> title, year = res.fetchone()
>>> print(f'The highest scoring Monty Python movie is {title!r}, released in {year}')
The highest scoring Monty Python movie is 'Monty Python and the Holy Grail', released in 1975
>>> new_con.close()

You've now created an SQLite database using the sqlite3 module, inserted data and retrieved values from it in multiple ways.

也參考

進一步參考 How-to guides：

How to use placeholders to bind values in SQL queries

How to adapt custom Python types to SQLite values

How to convert SQLite values to custom Python types

How to use the connection context manager

How to create and use row factories

解釋 for in-depth background on transaction control.

Reference

Module functions

sqlite3.connect(database, timeout=5.0, detect_types=0, isolation_level='DEFERRED', check_same_thread=True, factory=sqlite3.Connection, cached_statements=128, uri=False, *, autocommit=sqlite3.LEGACY_TRANSACTION_CONTROL)

Open a connection to an SQLite database.

參數:

database (path-like object) -- The path to the database file to be opened. You can pass ":memory:" to create an SQLite database existing only in memory [https://sqlite.org/inmemorydb.html], and open a connection to it.

timeout (float) -- How many seconds the connection should wait before raising an OperationalError when a table is locked. If another connection opens a transaction to modify a table, that table will be locked until the transaction is committed. Default five seconds.

detect_types (int) -- Control whether and how data types not natively supported by SQLite are looked up to be converted to Python types, using the converters registered with register_converter(). Set it to any combination (using |, bitwise or) of PARSE_DECLTYPES and PARSE_COLNAMES to enable this. Column names takes precedence over declared types if both flags are set. By default (0), type detection is disabled.

isolation_level (str | None) -- Control legacy transaction handling behaviour. See Connection.isolation_level and Transaction control via the isolation_level attribute for more information. Can be "DEFERRED" (default), "EXCLUSIVE" or "IMMEDIATE"; or None to disable opening transactions implicitly. Has no effect unless Connection.autocommit is set to LEGACY_TRANSACTION_CONTROL (the default).

check_same_thread (bool) -- If True (default), ProgrammingError will be raised if the database connection is used by a thread other than the one that created it. If False, the connection may be accessed in multiple threads; write operations may need to be serialized by the user to avoid data corruption. See threadsafety for more information.

factory (Connection) -- A custom subclass of Connection to create the connection with, if not the default Connection class.

cached_statements (int) -- The number of statements that sqlite3 should internally cache for this connection, to avoid parsing overhead. By default, 128 statements.

uri (bool) -- If set to True, database is interpreted as a URI with a file path and an optional query string. The scheme part must be "file:", and the path can be relative or absolute. The query string allows passing parameters to SQLite, enabling various How to work with SQLite URIs.

autocommit (bool) -- Control PEP 249 [https://peps.python.org/pep-0249/] transaction handling behaviour. See Connection.autocommit and Transaction control via the autocommit attribute for more information. autocommit currently defaults to LEGACY_TRANSACTION_CONTROL. The default will change to False in a future Python release.

回傳型別:

Connection

引發一個附帶引數 database 的稽核事件 sqlite3.connect。

引發一個附帶引數 connection_handle 的稽核事件 sqlite3.connect/handle。

在 3.4 版的變更: 新增 uri 參數。

在 3.7 版的變更: database can now also be a path-like object, not only a string.

在 3.10 版的變更: 新增 sqlite3.connect/handle 稽核事件。

在 3.12 版的變更: 新增 autocommit 參數。

在 3.13 版的變更: Positional use of the parameters timeout, detect_types, isolation_level, check_same_thread, factory, cached_statements, and uri is deprecated. They will become keyword-only parameters in Python 3.15.

sqlite3.complete_statement(statement)

Return True if the string statement appears to contain one or more complete SQL statements. No syntactic verification or parsing of any kind is performed, other than checking that there are no unclosed string literals and the statement is terminated by a semicolon.

範例：

>>> sqlite3.complete_statement("SELECT foo FROM bar;")
True
>>> sqlite3.complete_statement("SELECT foo")
False

This function may be useful during command-line input to determine if the entered text seems to form a complete SQL statement, or if additional input is needed before calling execute().

See runsource() in Lib/sqlite3/__main__.py [https://github.com/python/cpython/tree/3.14/Lib/sqlite3/__main__.py] for real-world use.

sqlite3.enable_callback_tracebacks(flag, /)

Enable or disable callback tracebacks. By default you will not get any tracebacks in user-defined functions, aggregates, converters, authorizer callbacks etc. If you want to debug them, you can call this function with flag set to True. Afterwards, you will get tracebacks from callbacks on sys.stderr. Use False to disable the feature again.

備註

Errors in user-defined function callbacks are logged as unraisable exceptions. Use an unraisable hook handler for introspection of the failed callback.

sqlite3.register_adapter(type, adapter, /)

Register an adapter callable to adapt the Python type type into an SQLite type. The adapter is called with a Python object of type type as its sole argument, and must return a value of a type that SQLite natively understands.

sqlite3.register_converter(typename, converter, /)

Register the converter callable to convert SQLite objects of type typename into a Python object of a specific type. The converter is invoked for all SQLite values of type typename; it is passed a bytes object and should return an object of the desired Python type. Consult the parameter detect_types of connect() for information regarding how type detection works.

Note: typename and the name of the type in your query are matched case-insensitively.

Module constants

sqlite3.LEGACY_TRANSACTION_CONTROL

Set autocommit to this constant to select old style (pre-Python 3.12) transaction control behaviour. See Transaction control via the isolation_level attribute for more information.

sqlite3.PARSE_DECLTYPES

Pass this flag value to the detect_types parameter of connect() to look up a converter function using the declared types for each column. The types are declared when the database table is created. sqlite3 will look up a converter function using the first word of the declared type as the converter dictionary key. For example:

CREATE TABLE test(
   i integer primary key,  ! will look up a converter named "integer"
   p point,                ! will look up a converter named "point"
   n number(10)            ! will look up a converter named "number"
 )

This flag may be combined with PARSE_COLNAMES using the | (bitwise or) operator.

備註

Generated fields (for example MAX(p)) are returned as str. Use PARSE_COLNAMES to enforce types for such queries.

sqlite3.PARSE_COLNAMES

Pass this flag value to the detect_types parameter of connect() to look up a converter function by using the type name, parsed from the query column name, as the converter dictionary key. The query column name must be wrapped in double quotes (") and the type name must be wrapped in square brackets ([]).

SELECT MAX(p) as "p [point]" FROM test;  ! will look up converter "point"

This flag may be combined with PARSE_DECLTYPES using the | (bitwise or) operator.

sqlite3.SQLITE_OK

sqlite3.SQLITE_DENY

sqlite3.SQLITE_IGNORE

Flags that should be returned by the authorizer_callback callable passed to Connection.set_authorizer(), to indicate whether:

Access is allowed (SQLITE_OK),

The SQL statement should be aborted with an error (SQLITE_DENY)

The column should be treated as a NULL value (SQLITE_IGNORE)

sqlite3.apilevel

String constant stating the supported DB-API level. Required by the DB-API. Hard-coded to "2.0".

sqlite3.paramstyle

String constant stating the type of parameter marker formatting expected by the sqlite3 module. Required by the DB-API. Hard-coded to "qmark".

備註

The named DB-API parameter style is also supported.

sqlite3.sqlite_version

Version number of the runtime SQLite library as a string.

sqlite3.sqlite_version_info

Version number of the runtime SQLite library as a tuple of integers.

sqlite3.threadsafety

Integer constant required by the DB-API 2.0, stating the level of thread safety the sqlite3 module supports. This attribute is set based on the default threading mode [https://sqlite.org/threadsafe.html] the underlying SQLite library is compiled with. The SQLite threading modes are:

Single-thread: In this mode, all mutexes are disabled and SQLite is unsafe to use in more than a single thread at once.

Multi-thread: In this mode, SQLite can be safely used by multiple threads provided that no single database connection is used simultaneously in two or more threads.

Serialized: In serialized mode, SQLite can be safely used by multiple threads with no restriction.

The mappings from SQLite threading modes to DB-API 2.0 threadsafety levels are as follows:

SQLite 執行緒模式

執行緒安全 [https://peps.python.org/pep-0249/#threadsafety]

SQLITE_THREADSAFE [https://sqlite.org/compile.html#threadsafe]

DB-API 2.0 meaning

single-thread

0

0

Threads may not share the module

multi-thread

1

2

Threads may share the module, but not connections

serialized

3

1

Threads may share the module, connections and cursors

在 3.11 版的變更: Set threadsafety dynamically instead of hard-coding it to 1.

sqlite3.SQLITE_DBCONFIG_DEFENSIVE

sqlite3.SQLITE_DBCONFIG_DQS_DDL

sqlite3.SQLITE_DBCONFIG_DQS_DML

sqlite3.SQLITE_DBCONFIG_ENABLE_FKEY

sqlite3.SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER

sqlite3.SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION

sqlite3.SQLITE_DBCONFIG_ENABLE_QPSG

sqlite3.SQLITE_DBCONFIG_ENABLE_TRIGGER

sqlite3.SQLITE_DBCONFIG_ENABLE_VIEW

sqlite3.SQLITE_DBCONFIG_LEGACY_ALTER_TABLE

sqlite3.SQLITE_DBCONFIG_LEGACY_FILE_FORMAT

sqlite3.SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE

sqlite3.SQLITE_DBCONFIG_RESET_DATABASE

sqlite3.SQLITE_DBCONFIG_TRIGGER_EQP

sqlite3.SQLITE_DBCONFIG_TRUSTED_SCHEMA

sqlite3.SQLITE_DBCONFIG_WRITABLE_SCHEMA

These constants are used for the Connection.setconfig() and getconfig() methods.

The availability of these constants varies depending on the version of SQLite Python was compiled with.

在 3.12 版被加入.

也參考

https://www.sqlite.org/c3ref/c_dbconfig_defensive.html

SQLite docs: Database Connection Configuration Options

自從版本 3.12 後不推薦使用，已從版本 3.14 中移除。: The version and version_info constants.

Connection 物件

class sqlite3.Connection

Each open SQLite database is represented by a Connection object, which is created using sqlite3.connect(). Their main purpose is creating Cursor objects, and Transaction control.

也參考

How to use connection shortcut methods

How to use the connection context manager

在 3.13 版的變更: A ResourceWarning is emitted if close() is not called before a Connection object is deleted.

一個 SQLite 資料庫連線具有以下屬性和方法：

cursor(factory=Cursor)

Create and return a Cursor object. The cursor method accepts a single optional parameter factory. If supplied, this must be a callable returning an instance of Cursor or its subclasses.

blobopen(table, column, rowid, /, *, readonly=False, name='main')

Open a Blob handle to an existing BLOB.

參數:

table (str) -- The name of the table where the blob is located.

column (str) -- The name of the column where the blob is located.

rowid (int) -- The row id where the blob is located.

readonly (bool) -- Set to True if the blob should be opened without write permissions. Defaults to False.

name (str) -- The name of the database where the blob is located. Defaults to "main".

引發:

OperationalError -- When trying to open a blob in a WITHOUT ROWID table.

回傳型別:

Blob

備註

The blob size cannot be changed using the Blob class. Use the SQL function zeroblob to create a blob with a fixed size.

在 3.11 版被加入.

commit()

Commit any pending transaction to the database. If autocommit is True, or there is no open transaction, this method does nothing. If autocommit is False, a new transaction is implicitly opened if a pending transaction was committed by this method.

rollback()

Roll back to the start of any pending transaction. If autocommit is True, or there is no open transaction, this method does nothing. If autocommit is False, a new transaction is implicitly opened if a pending transaction was rolled back by this method.

close()

Close the database connection. If autocommit is False, any pending transaction is implicitly rolled back. If autocommit is True or LEGACY_TRANSACTION_CONTROL, no implicit transaction control is executed. Make sure to commit() before closing to avoid losing pending changes.

execute(sql, parameters=(), /)

Create a new Cursor object and call execute() on it with the given sql and parameters. Return the new cursor object.

executemany(sql, parameters, /)

Create a new Cursor object and call executemany() on it with the given sql and parameters. Return the new cursor object.

executescript(sql_script, /)

Create a new Cursor object and call executescript() on it with the given sql_script. Return the new cursor object.

create_function(name, narg, func, *, deterministic=False)

Create or remove a user-defined SQL function.

參數:

name (str) -- The name of the SQL function.

narg (int) -- The number of arguments the SQL function can accept. If -1, it may take any number of arguments.

func (callback | None) -- A callable that is called when the SQL function is invoked. The callable must return a type natively supported by SQLite. Set to None to remove an existing SQL function.

deterministic (bool) -- If True, the created SQL function is marked as deterministic [https://sqlite.org/deterministic.html], which allows SQLite to perform additional optimizations.

在 3.8 版的變更: 新增 deterministic 參數。

範例：

>>> import hashlib
>>> def md5sum(t):
...     return hashlib.md5(t).hexdigest()
>>> con = sqlite3.connect(":memory:")
>>> con.create_function("md5", 1, md5sum)
>>> for row in con.execute("SELECT md5(?)", (b"foo",)):
...     print(row)
('acbd18db4cc2f85cedef654fccc4a4d8',)
>>> con.close()

在 3.13 版的變更: Passing name, narg, and func as keyword arguments is deprecated. These parameters will become positional-only in Python 3.15.

create_aggregate(name, n_arg, aggregate_class)

Create or remove a user-defined SQL aggregate function.

參數:

name (str) -- The name of the SQL aggregate function.

n_arg (int) -- The number of arguments the SQL aggregate function can accept. If -1, it may take any number of arguments.

aggregate_class (class | None) --

A class must implement the following methods:

step(): Add a row to the aggregate.

finalize(): Return the final result of the aggregate as a type natively supported by SQLite.

The number of arguments that the step() method must accept is controlled by n_arg.

Set to None to remove an existing SQL aggregate function.

範例：

class MySum:
    def __init__(self):
        self.count = 0

    def step(self, value):
        self.count += value

    def finalize(self):
        return self.count

con = sqlite3.connect(":memory:")
con.create_aggregate("mysum", 1, MySum)
cur = con.execute("CREATE TABLE test(i)")
cur.execute("INSERT INTO test(i) VALUES(1)")
cur.execute("INSERT INTO test(i) VALUES(2)")
cur.execute("SELECT mysum(i) FROM test")
print(cur.fetchone()[0])

con.close()

在 3.13 版的變更: Passing name, n_arg, and aggregate_class as keyword arguments is deprecated. These parameters will become positional-only in Python 3.15.

create_window_function(name, num_params, aggregate_class, /)

Create or remove a user-defined aggregate window function.

參數:

name (str) -- The name of the SQL aggregate window function to create or remove.

num_params (int) -- The number of arguments the SQL aggregate window function can accept. If -1, it may take any number of arguments.

aggregate_class (class | None) --

A class that must implement the following methods:

step(): Add a row to the current window.

value(): Return the current value of the aggregate.

inverse(): Remove a row from the current window.

finalize(): Return the final result of the aggregate as a type natively supported by SQLite.

The number of arguments that the step() and value() methods must accept is controlled by num_params.

Set to None to remove an existing SQL aggregate window function.

引發:

NotSupportedError -- If used with a version of SQLite older than 3.25.0, which does not support aggregate window functions.

在 3.11 版被加入.

範例：

# Example taken from https://www.sqlite.org/windowfunctions.html#udfwinfunc
class WindowSumInt:
    def __init__(self):
        self.count = 0

    def step(self, value):
        """Add a row to the current window."""
        self.count += value

    def value(self):
        """Return the current value of the aggregate."""
        return self.count

    def inverse(self, value):
        """Remove a row from the current window."""
        self.count -= value

    def finalize(self):
        """Return the final value of the aggregate.

        Any clean-up actions should be placed here.
        """
        return self.count

con = sqlite3.connect(":memory:")
cur = con.execute("CREATE TABLE test(x, y)")
values = [
    ("a", 4),
    ("b", 5),
    ("c", 3),
    ("d", 8),
    ("e", 1),
]
cur.executemany("INSERT INTO test VALUES(?, ?)", values)
con.create_window_function("sumint", 1, WindowSumInt)
cur.execute("""
    SELECT x, sumint(y) OVER (
        ORDER BY x ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING
    ) AS sum_y
    FROM test ORDER BY x
""")
print(cur.fetchall())
con.close()

create_collation(name, callable, /)

Create a collation named name using the collating function callable. callable is passed two string arguments, and it should return an integer:

1 if the first is ordered higher than the second

-1 if the first is ordered lower than the second

0 if they are ordered equal

The following example shows a reverse sorting collation:

def collate_reverse(string1, string2):
    if string1 == string2:
        return 0
    elif string1 < string2:
        return 1
    else:
        return -1

con = sqlite3.connect(":memory:")
con.create_collation("reverse", collate_reverse)

cur = con.execute("CREATE TABLE test(x)")
cur.executemany("INSERT INTO test(x) VALUES(?)", [("a",), ("b",)])
cur.execute("SELECT x FROM test ORDER BY x COLLATE reverse")
for row in cur:
    print(row)
con.close()

Remove a collation function by setting callable to None.

在 3.11 版的變更: The collation name can contain any Unicode character. Earlier, only ASCII characters were allowed.

interrupt()

Call this method from a different thread to abort any queries that might be executing on the connection. Aborted queries will raise an OperationalError.

set_authorizer(authorizer_callback)

Register callable authorizer_callback to be invoked for each attempt to access a column of a table in the database. The callback should return one of SQLITE_OK, SQLITE_DENY, or SQLITE_IGNORE to signal how access to the column should be handled by the underlying SQLite library.

The first argument to the callback signifies what kind of operation is to be authorized. The second and third argument will be arguments or None depending on the first argument. The 4th argument is the name of the database ("main", "temp", etc.) if applicable. The 5th argument is the name of the inner-most trigger or view that is responsible for the access attempt or None if this access attempt is directly from input SQL code.

Please consult the SQLite documentation about the possible values for the first argument and the meaning of the second and third argument depending on the first one. All necessary constants are available in the sqlite3 module.

Passing None as authorizer_callback will disable the authorizer.

在 3.11 版的變更: 新增使用 None 來停用授權器的支援。

在 3.13 版的變更: Passing authorizer_callback as a keyword argument is deprecated. The parameter will become positional-only in Python 3.15.

set_progress_handler(progress_handler, n)

Register callable progress_handler to be invoked for every n instructions of the SQLite virtual machine. This is useful if you want to get called from SQLite during long-running operations, for example to update a GUI.

If you want to clear any previously installed progress handler, call the method with None for progress_handler.

Returning a non-zero value from the handler function will terminate the currently executing query and cause it to raise a DatabaseError exception.

在 3.13 版的變更: Passing progress_handler as a keyword argument is deprecated. The parameter will become positional-only in Python 3.15.

set_trace_callback(trace_callback)

Register callable trace_callback to be invoked for each SQL statement that is actually executed by the SQLite backend.

The only argument passed to the callback is the statement (as str) that is being executed. The return value of the callback is ignored. Note that the backend does not only run statements passed to the Cursor.execute() methods. Other sources include the transaction management of the sqlite3 module and the execution of triggers defined in the current database.

Passing None as trace_callback will disable the trace callback.

備註

Exceptions raised in the trace callback are not propagated. As a development and debugging aid, use enable_callback_tracebacks() to enable printing tracebacks from exceptions raised in the trace callback.

在 3.3 版被加入.

在 3.13 版的變更: Passing trace_callback as a keyword argument is deprecated. The parameter will become positional-only in Python 3.15.

enable_load_extension(enabled, /)

Enable the SQLite engine to load SQLite extensions from shared libraries if enabled is True; else, disallow loading SQLite extensions. SQLite extensions can define new functions, aggregates or whole new virtual table implementations. One well-known extension is the fulltext-search extension distributed with SQLite.

備註

The sqlite3 module is not built with loadable extension support by default, because some platforms (notably macOS) have SQLite libraries which are compiled without this feature. To get loadable extension support, you must pass the --enable-loadable-sqlite-extensions option to configure.

引發一個附帶引數 connection、enabled 的稽核事件 sqlite3.enable_load_extension。

在 3.2 版被加入.

在 3.10 版的變更: 加入 sqlite3.enable_load_extension 稽核事件。

con.enable_load_extension(True)

# Load the fulltext search extension
con.execute("select load_extension('./fts3.so')")

# alternatively you can load the extension using an API call:
# con.load_extension("./fts3.so")

# disable extension loading again
con.enable_load_extension(False)

# example from SQLite wiki
con.execute("CREATE VIRTUAL TABLE recipe USING fts3(name, ingredients)")
con.executescript("""
    INSERT INTO recipe (name, ingredients) VALUES('broccoli stew', 'broccoli peppers cheese tomatoes');
    INSERT INTO recipe (name, ingredients) VALUES('pumpkin stew', 'pumpkin onions garlic celery');
    INSERT INTO recipe (name, ingredients) VALUES('broccoli pie', 'broccoli cheese onions flour');
    INSERT INTO recipe (name, ingredients) VALUES('pumpkin pie', 'pumpkin sugar flour butter');
    """)
for row in con.execute("SELECT rowid, name, ingredients FROM recipe WHERE name MATCH 'pie'"):
    print(row)

load_extension(path, /, *, entrypoint=None)

Load an SQLite extension from a shared library. Enable extension loading with enable_load_extension() before calling this method.

參數:

path (str) -- The path to the SQLite extension.

entrypoint (str | None) -- Entry point name. If None (the default), SQLite will come up with an entry point name of its own; see the SQLite docs Loading an Extension [https://www.sqlite.org/loadext.html#loading_an_extension] for details.

引發一個附帶引數 connection、path 的稽核事件 sqlite3.load_extension。

在 3.2 版被加入.

在 3.10 版的變更: 加入 sqlite3.load_extension 稽核事件。

在 3.12 版的變更: 新增 entrypoint 參數。

iterdump(*, filter=None)

Return an iterator to dump the database as SQL source code. Useful when saving an in-memory database for later restoration. Similar to the .dump command in the sqlite3 shell.

參數:

filter (str | None) -- An optional LIKE pattern for database objects to dump, e.g. prefix_%. If None (the default), all database objects will be included.

範例：

# Convert file example.db to SQL dump file dump.sql
con = sqlite3.connect('example.db')
with open('dump.sql', 'w') as f:
    for line in con.iterdump():
        f.write('%s\n' % line)
con.close()

也參考

如何處理非 UTF-8 的文字編碼

在 3.13 版的變更: 新增 filter 參數。

backup(target, *, pages=-1, progress=None, name='main', sleep=0.250)

Create a backup of an SQLite database.

Works even if the database is being accessed by other clients or concurrently by the same connection.

參數:

target (Connection) -- The database connection to save the backup to.

pages (int) -- The number of pages to copy at a time. If equal to or less than 0, the entire database is copied in a single step. Defaults to -1.

progress (callback | None) -- If set to a callable, it is invoked with three integer arguments for every backup iteration: the status of the last iteration, the remaining number of pages still to be copied, and the total number of pages. Defaults to None.

name (str) -- The name of the database to back up. Either "main" (the default) for the main database, "temp" for the temporary database, or the name of a custom database as attached using the ATTACH DATABASE SQL statement.

sleep (float) -- The number of seconds to sleep between successive attempts to back up remaining pages.

Example 1, copy an existing database into another:

def progress(status, remaining, total):
    print(f'Copied {total-remaining} of {total} pages...')

src = sqlite3.connect('example.db')
dst = sqlite3.connect('backup.db')
with dst:
    src.backup(dst, pages=1, progress=progress)
dst.close()
src.close()

Example 2, copy an existing database into a transient copy:

src = sqlite3.connect('example.db')
dst = sqlite3.connect(':memory:')
src.backup(dst)
dst.close()
src.close()

在 3.7 版被加入.

也參考

如何處理非 UTF-8 的文字編碼

getlimit(category, /)

Get a connection runtime limit.

參數:

category (int) -- The SQLite limit category [https://www.sqlite.org/c3ref/c_limit_attached.html] to be queried.

回傳型別:

int

引發:

ProgrammingError -- If category is not recognised by the underlying SQLite library.

Example, query the maximum length of an SQL statement for Connection con (the default is 1000000000):

>>> con.getlimit(sqlite3.SQLITE_LIMIT_SQL_LENGTH)
1000000000

在 3.11 版被加入.

setlimit(category, limit, /)

Set a connection runtime limit. Attempts to increase a limit above its hard upper bound are silently truncated to the hard upper bound. Regardless of whether or not the limit was changed, the prior value of the limit is returned.

參數:

category (int) -- The SQLite limit category [https://www.sqlite.org/c3ref/c_limit_attached.html] to be set.

limit (int) -- The value of the new limit. If negative, the current limit is unchanged.

回傳型別:

int

引發:

ProgrammingError -- If category is not recognised by the underlying SQLite library.

Example, limit the number of attached databases to 1 for Connection con (the default limit is 10):

>>> con.setlimit(sqlite3.SQLITE_LIMIT_ATTACHED, 1)
10
>>> con.getlimit(sqlite3.SQLITE_LIMIT_ATTACHED)
1

在 3.11 版被加入.

getconfig(op, /)

Query a boolean connection configuration option.

參數:

op (int) -- A SQLITE_DBCONFIG code.

回傳型別:

bool

在 3.12 版被加入.

setconfig(op, enable=True, /)

Set a boolean connection configuration option.

參數:

op (int) -- A SQLITE_DBCONFIG code.

enable (bool) -- True if the configuration option should be enabled (default); False if it should be disabled.

在 3.12 版被加入.

serialize(*, name='main')

Serialize a database into a bytes object. For an ordinary on-disk database file, the serialization is just a copy of the disk file. For an in-memory database or a "temp" database, the serialization is the same sequence of bytes which would be written to disk if that database were backed up to disk.

參數:

name (str) -- The database name to be serialized. Defaults to "main".

回傳型別:

bytes

備註

This method is only available if the underlying SQLite library has the serialize API.

在 3.11 版被加入.

deserialize(data, /, *, name='main')

Deserialize a serialized database into a Connection. This method causes the database connection to disconnect from database name, and reopen name as an in-memory database based on the serialization contained in data.

參數:

data (bytes) -- A serialized database.

name (str) -- The database name to deserialize into. Defaults to "main".

引發:

OperationalError -- If the database connection is currently involved in a read transaction or a backup operation.

DatabaseError -- If data does not contain a valid SQLite database.

OverflowError -- If len(data) is larger than 2**63 - 1.

備註

This method is only available if the underlying SQLite library has the deserialize API.

在 3.11 版被加入.

autocommit

This attribute controls PEP 249 [https://peps.python.org/pep-0249/]-compliant transaction behaviour. autocommit has three allowed values:

False: Select PEP 249 [https://peps.python.org/pep-0249/]-compliant transaction behaviour, implying that sqlite3 ensures a transaction is always open. Use commit() and rollback() to close transactions.

This is the recommended value of autocommit.

True: Use SQLite's autocommit mode [https://www.sqlite.org/lang_transaction.html#implicit_versus_explicit_transactions]. commit() and rollback() have no effect in this mode.

LEGACY_TRANSACTION_CONTROL: Pre-Python 3.12 (non-PEP 249 [https://peps.python.org/pep-0249/]-compliant) transaction control. See isolation_level for more details.

This is currently the default value of autocommit.

Changing autocommit to False will open a new transaction, and changing it to True will commit any pending transaction.

更多詳情請見 Transaction control via the autocommit attribute。

備註

The isolation_level attribute has no effect unless autocommit is LEGACY_TRANSACTION_CONTROL.

在 3.12 版被加入.

in_transaction

This read-only attribute corresponds to the low-level SQLite autocommit mode [https://www.sqlite.org/lang_transaction.html#implicit_versus_explicit_transactions].

True if a transaction is active (there are uncommitted changes), False otherwise.

在 3.2 版被加入.

isolation_level

Controls the legacy transaction handling mode of sqlite3. If set to None, transactions are never implicitly opened. If set to one of "DEFERRED", "IMMEDIATE", or "EXCLUSIVE", corresponding to the underlying SQLite transaction behaviour [https://www.sqlite.org/lang_transaction.html#deferred_immediate_and_exclusive_transactions], implicit transaction management is performed.

If not overridden by the isolation_level parameter of connect(), the default is "", which is an alias for "DEFERRED".

備註

Using autocommit to control transaction handling is recommended over using isolation_level. isolation_level has no effect unless autocommit is set to LEGACY_TRANSACTION_CONTROL (the default).

row_factory

The initial row_factory for Cursor objects created from this connection. Assigning to this attribute does not affect the row_factory of existing cursors belonging to this connection, only new ones. Is None by default, meaning each row is returned as a tuple.

更多詳情請見 How to create and use row factories。

text_factory

A callable that accepts a bytes parameter and returns a text representation of it. The callable is invoked for SQLite values with the TEXT data type. By default, this attribute is set to str.

更多詳情請見 如何處理非 UTF-8 的文字編碼。

total_changes

Return the total number of database rows that have been modified, inserted, or deleted since the database connection was opened.

Cursor 物件

A Cursor object represents a database cursor [https://en.wikipedia.org/wiki/Cursor_(databases)] which is used to execute SQL statements, and manage the context of a fetch operation. Cursors are created using Connection.cursor(), or by using any of the connection shortcut methods.

Cursor objects are iterators, meaning that if you execute() a SELECT query, you can simply iterate over the cursor to fetch the resulting rows:

for row in cur.execute("SELECT t FROM data"):
    print(row)

class sqlite3.Cursor

Cursor 實例具有以下屬性和方法。

execute(sql, parameters=(), /)

Execute a single SQL statement, optionally binding Python values using placeholders.

參數:

sql (str) -- 單一個 SQL 陳述式。

parameters (dict | sequence) -- Python values to bind to placeholders in sql. A dict if named placeholders are used. A sequence if unnamed placeholders are used. See How to use placeholders to bind values in SQL queries.

引發:

ProgrammingError -- When sql contains more than one SQL statement. When named placeholders are used and parameters is a sequence instead of a dict.

If autocommit is LEGACY_TRANSACTION_CONTROL, isolation_level is not None, sql is an INSERT, UPDATE, DELETE, or REPLACE statement, and there is no open transaction, a transaction is implicitly opened before executing sql.

在 3.14 版的變更: ProgrammingError is emitted if named placeholders are used and parameters is a sequence instead of a dict.

Use executescript() to execute multiple SQL statements.

executemany(sql, parameters, /)

For every item in parameters, repeatedly execute the parameterized DML SQL statement sql.

Uses the same implicit transaction handling as execute().

參數:

sql (str) -- A single SQL DML statement.

parameters (iterable) -- An iterable of parameters to bind with the placeholders in sql. See How to use placeholders to bind values in SQL queries.

引發:

ProgrammingError -- When sql contains more than one SQL statement or is not a DML statement, When named placeholders are used and the items in parameters are sequences instead of dicts.

範例：

rows = [
    ("row1",),
    ("row2",),
]
# cur 是一個 sqlite3.Cursor 物件
cur.executemany("INSERT INTO data VALUES(?)", rows)

備註

Any resulting rows are discarded, including DML statements with RETURNING clauses [https://www.sqlite.org/lang_returning.html].

在 3.14 版的變更: ProgrammingError is emitted if named placeholders are used and the items in parameters are sequences instead of dicts.

executescript(sql_script, /)

Execute the SQL statements in sql_script. If the autocommit is LEGACY_TRANSACTION_CONTROL and there is a pending transaction, an implicit COMMIT statement is executed first. No other implicit transaction control is performed; any transaction control must be added to sql_script.

sql_script 必須是一個 string。

範例：

# cur 是一個 sqlite3.Cursor 物件
cur.executescript("""
    BEGIN;
    CREATE TABLE person(firstname, lastname, age);
    CREATE TABLE book(title, author, published);
    CREATE TABLE publisher(name, address);
    COMMIT;
""")

fetchone()

If row_factory is None, return the next row query result set as a tuple. Else, pass it to the row factory and return its result. Return None if no more data is available.

fetchmany(size=cursor.arraysize)

Return the next set of rows of a query result as a list. Return an empty list if no more rows are available.

The number of rows to fetch per call is specified by the size parameter. If size is not given, arraysize determines the number of rows to be fetched. If fewer than size rows are available, as many rows as are available are returned.

Note there are performance considerations involved with the size parameter. For optimal performance, it is usually best to use the arraysize attribute. If the size parameter is used, then it is best for it to retain the same value from one fetchmany() call to the next.

在 3.14.1 版的變更: Negative size values are rejected by raising ValueError.

fetchall()

Return all (remaining) rows of a query result as a list. Return an empty list if no rows are available. Note that the arraysize attribute can affect the performance of this operation.

close()

Close the cursor now (rather than whenever __del__ is called).

The cursor will be unusable from this point forward; a ProgrammingError exception will be raised if any operation is attempted with the cursor.

setinputsizes(sizes, /)

Required by the DB-API. Does nothing in sqlite3.

setoutputsize(size, column=None, /)

Required by the DB-API. Does nothing in sqlite3.

arraysize

Read/write attribute that controls the number of rows returned by fetchmany(). The default value is 1 which means a single row would be fetched per call.

在 3.14.1 版的變更: Negative values are rejected by raising ValueError.

connection

Read-only attribute that provides the SQLite database Connection belonging to the cursor. A Cursor object created by calling con.cursor() will have a connection attribute that refers to con:

>>> con = sqlite3.connect(":memory:")
>>> cur = con.cursor()
>>> cur.connection == con
True
>>> con.close()

description

Read-only attribute that provides the column names of the last query. To remain compatible with the Python DB API, it returns a 7-tuple for each column where the last six items of each tuple are None.

It is set for SELECT statements without any matching rows as well.

lastrowid

Read-only attribute that provides the row id of the last inserted row. It is only updated after successful INSERT or REPLACE statements using the execute() method. For other statements, after executemany() or executescript(), or if the insertion failed, the value of lastrowid is left unchanged. The initial value of lastrowid is None.

備註

Inserts into WITHOUT ROWID tables are not recorded.

在 3.6 版的變更: 新增 REPLACE 陳述式的支援。

rowcount

Read-only attribute that provides the number of modified rows for INSERT, UPDATE, DELETE, and REPLACE statements; is -1 for other statements, including CTE queries. It is only updated by the execute() and executemany() methods, after the statement has run to completion. This means that any resulting rows must be fetched in order for rowcount to be updated.

row_factory

Control how a row fetched from this Cursor is represented. If None, a row is represented as a tuple. Can be set to the included sqlite3.Row; or a callable that accepts two arguments, a Cursor object and the tuple of row values, and returns a custom object representing an SQLite row.

Defaults to what Connection.row_factory was set to when the Cursor was created. Assigning to this attribute does not affect Connection.row_factory of the parent connection.

更多詳情請見 How to create and use row factories。

Row 物件

class sqlite3.Row

A Row instance serves as a highly optimized row_factory for Connection objects. It supports iteration, equality testing, len(), and mapping access by column name and index.

Two Row objects compare equal if they have identical column names and values.

更多詳情請見 How to create and use row factories。

keys()

Return a list of column names as strings. Immediately after a query, it is the first member of each tuple in Cursor.description.

在 3.5 版的變更: 新增對切片的支援。

Blob 物件

class sqlite3.Blob

在 3.11 版被加入.

A Blob instance is a file-like object that can read and write data in an SQLite BLOB. Call len(blob) to get the size (number of bytes) of the blob. Use indices and slices for direct access to the blob data.

Use the Blob as a context manager to ensure that the blob handle is closed after use.

con = sqlite3.connect(":memory:")
con.execute("CREATE TABLE test(blob_col blob)")
con.execute("INSERT INTO test(blob_col) VALUES(zeroblob(13))")

# Write to our blob, using two write operations:
with con.blobopen("test", "blob_col", 1) as blob:
    blob.write(b"hello, ")
    blob.write(b"world.")
    # Modify the first and last bytes of our blob
    blob[0] = ord("H")
    blob[-1] = ord("!")

# Read the contents of our blob
with con.blobopen("test", "blob_col", 1) as blob:
    greeting = blob.read()

print(greeting)  # outputs "b'Hello, world!'"
con.close()

close()

Close the blob.

The blob will be unusable from this point onward. An Error (or subclass) exception will be raised if any further operation is attempted with the blob.

read(length=-1, /)

Read length bytes of data from the blob at the current offset position. If the end of the blob is reached, the data up to EOF will be returned. When length is not specified, or is negative, read() will read until the end of the blob.

write(data, /)

Write data to the blob at the current offset. This function cannot change the blob length. Writing beyond the end of the blob will raise ValueError.

tell()

Return the current access position of the blob.

seek(offset, origin=os.SEEK_SET, /)

Set the current access position of the blob to offset. The origin argument defaults to os.SEEK_SET (absolute blob positioning). Other values for origin are os.SEEK_CUR (seek relative to the current position) and os.SEEK_END (seek relative to the blob’s end).

PrepareProtocol 物件

class sqlite3.PrepareProtocol

The PrepareProtocol type's single purpose is to act as a PEP 246 [https://peps.python.org/pep-0246/] style adaption protocol for objects that can adapt themselves to native SQLite types.

例外

The exception hierarchy is defined by the DB-API 2.0 (PEP 249 [https://peps.python.org/pep-0249/]).

exception sqlite3.Warning

This exception is not currently raised by the sqlite3 module, but may be raised by applications using sqlite3, for example if a user-defined function truncates data while inserting. Warning is a subclass of Exception.

exception sqlite3.Error

The base class of the other exceptions in this module. Use this to catch all errors with one single except statement. Error is a subclass of Exception.

If the exception originated from within the SQLite library, the following two attributes are added to the exception:

sqlite_errorcode

The numeric error code from the SQLite API [https://sqlite.org/rescode.html]

在 3.11 版被加入.

sqlite_errorname

The symbolic name of the numeric error code from the SQLite API [https://sqlite.org/rescode.html]

在 3.11 版被加入.

exception sqlite3.InterfaceError

Exception raised for misuse of the low-level SQLite C API. In other words, if this exception is raised, it probably indicates a bug in the sqlite3 module. InterfaceError is a subclass of Error.

exception sqlite3.DatabaseError

Exception raised for errors that are related to the database. This serves as the base exception for several types of database errors. It is only raised implicitly through the specialised subclasses. DatabaseError is a subclass of Error.

exception sqlite3.DataError

Exception raised for errors caused by problems with the processed data, like numeric values out of range, and strings which are too long. DataError is a subclass of DatabaseError.

exception sqlite3.OperationalError

Exception raised for errors that are related to the database's operation, and not necessarily under the control of the programmer. For example, the database path is not found, or a transaction could not be processed. OperationalError is a subclass of DatabaseError.

exception sqlite3.IntegrityError

Exception raised when the relational integrity of the database is affected, e.g. a foreign key check fails. It is a subclass of DatabaseError.

exception sqlite3.InternalError

Exception raised when SQLite encounters an internal error. If this is raised, it may indicate that there is a problem with the runtime SQLite library. InternalError is a subclass of DatabaseError.

exception sqlite3.ProgrammingError

Exception raised for sqlite3 API programming errors, for example supplying the wrong number of bindings to a query, or trying to operate on a closed Connection. ProgrammingError is a subclass of DatabaseError.

exception sqlite3.NotSupportedError

Exception raised in case a method or database API is not supported by the underlying SQLite library. For example, setting deterministic to True in create_function(), if the underlying SQLite library does not support deterministic functions. NotSupportedError is a subclass of DatabaseError.

SQLite and Python types

SQLite natively supports the following types: NULL, INTEGER, REAL, TEXT, BLOB.

The following Python types can thus be sent to SQLite without any problem:

Python type

SQLite type

None

NULL

int

INTEGER

float

REAL

str

TEXT

bytes

BLOB

This is how SQLite types are converted to Python types by default:

SQLite type

Python type

NULL

None

INTEGER

int

REAL

float

TEXT

depends on text_factory, str by default

BLOB

bytes

The type system of the sqlite3 module is extensible in two ways: you can store additional Python types in an SQLite database via object adapters, and you can let the sqlite3 module convert SQLite types to Python types via converters.

Default adapters and converters (deprecated)

備註

The default adapters and converters are deprecated as of Python 3.12. Instead, use the Adapter and converter recipes and tailor them to your needs.

The deprecated default adapters and converters consist of:

An adapter for datetime.date objects to strings in ISO 8601 [https://en.wikipedia.org/wiki/ISO_8601] format.

An adapter for datetime.datetime objects to strings in ISO 8601 format.

A converter for declared "date" types to datetime.date objects.

A converter for declared "timestamp" types to datetime.datetime objects. Fractional parts will be truncated to 6 digits (microsecond precision).

備註

The default "timestamp" converter ignores UTC offsets in the database and always returns a naive datetime.datetime object. To preserve UTC offsets in timestamps, either leave converters disabled, or register an offset-aware converter with register_converter().

在 3.12 版之後被棄用.

命令列介面

The sqlite3 module can be invoked as a script, using the interpreter's -m switch, in order to provide a simple SQLite shell. The argument signature is as follows:

python -m sqlite3 [-h] [-v] [filename] [sql]

Type .quit or CTRL-D to exit the shell.

-h, --help

Print CLI help.

-v, --version

Print underlying SQLite library version.

在 3.12 版被加入.

How-to guides

How to use placeholders to bind values in SQL queries

SQL operations usually need to use values from Python variables. However, beware of using Python's string operations to assemble queries, as they are vulnerable to SQL injection attacks [https://en.wikipedia.org/wiki/SQL_injection]. For example, an attacker can simply close the single quote and inject OR TRUE to select all rows:

>>> # 千萬不要這樣做，這不安全！
>>> symbol = input()
' OR TRUE; --
>>> sql = "SELECT * FROM stocks WHERE symbol = '%s'" % symbol
>>> print(sql)
SELECT * FROM stocks WHERE symbol = '' OR TRUE; --'
>>> cur.execute(sql)

Instead, use the DB-API's parameter substitution. To insert a variable into a query string, use a placeholder in the string, and substitute the actual values into the query by providing them as a tuple of values to the second argument of the cursor's execute() method.

An SQL statement may use one of two kinds of placeholders: question marks (qmark style) or named placeholders (named style). For the qmark style, parameters must be a sequence whose length must match the number of placeholders, or a ProgrammingError is raised. For the named style, parameters must be an instance of a dict (or a subclass), which must contain keys for all named parameters; any extra items are ignored. Here's an example of both styles:

con = sqlite3.connect(":memory:")
cur = con.execute("CREATE TABLE lang(name, first_appeared)")

# This is the named style used with executemany():
data = (
    {"name": "C", "year": 1972},
    {"name": "Fortran", "year": 1957},
    {"name": "Python", "year": 1991},
    {"name": "Go", "year": 2009},
)
cur.executemany("INSERT INTO lang VALUES(:name, :year)", data)

# This is the qmark style used in a SELECT query:
params = (1972,)
cur.execute("SELECT * FROM lang WHERE first_appeared = ?", params)
print(cur.fetchall())
con.close()

備註

PEP 249 [https://peps.python.org/pep-0249/] numeric placeholders are not supported. If used, they will be interpreted as named placeholders.

How to adapt custom Python types to SQLite values

SQLite supports only a limited set of data types natively. To store custom Python types in SQLite databases, adapt them to one of the Python types SQLite natively understands.

There are two ways to adapt Python objects to SQLite types: letting your object adapt itself, or using an adapter callable. The latter will take precedence above the former. For a library that exports a custom type, it may make sense to enable that type to adapt itself. As an application developer, it may make more sense to take direct control by registering custom adapter functions.

How to write adaptable objects

Suppose we have a Point class that represents a pair of coordinates, x and y, in a Cartesian coordinate system. The coordinate pair will be stored as a text string in the database, using a semicolon to separate the coordinates. This can be implemented by adding a __conform__(self, protocol) method which returns the adapted value. The object passed to protocol will be of type PrepareProtocol.

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __conform__(self, protocol):
        if protocol is sqlite3.PrepareProtocol:
            return f"{self.x};{self.y}"

con = sqlite3.connect(":memory:")
cur = con.cursor()

cur.execute("SELECT ?", (Point(4.0, -3.2),))
print(cur.fetchone()[0])
con.close()

How to register adapter callables

The other possibility is to create a function that converts the Python object to an SQLite-compatible type. This function can then be registered using register_adapter().

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

def adapt_point(point):
    return f"{point.x};{point.y}"

sqlite3.register_adapter(Point, adapt_point)

con = sqlite3.connect(":memory:")
cur = con.cursor()

cur.execute("SELECT ?", (Point(1.0, 2.5),))
print(cur.fetchone()[0])
con.close()

How to convert SQLite values to custom Python types

Writing an adapter lets you convert from custom Python types to SQLite values. To be able to convert from SQLite values to custom Python types, we use converters.

Let's go back to the Point class. We stored the x and y coordinates separated via semicolons as strings in SQLite.

First, we'll define a converter function that accepts the string as a parameter and constructs a Point object from it.

備註

Converter functions are always passed a bytes object, no matter the underlying SQLite data type.

def convert_point(s):
    x, y = map(float, s.split(b";"))
    return Point(x, y)

We now need to tell sqlite3 when it should convert a given SQLite value. This is done when connecting to a database, using the detect_types parameter of connect(). There are three options:

Implicit: set detect_types to PARSE_DECLTYPES

Explicit: set detect_types to PARSE_COLNAMES

Both: set detect_types to sqlite3.PARSE_DECLTYPES | sqlite3.PARSE_COLNAMES. Column names take precedence over declared types.

The following example illustrates the implicit and explicit approaches:

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __repr__(self):
        return f"Point({self.x}, {self.y})"

def adapt_point(point):
    return f"{point.x};{point.y}"

def convert_point(s):
    x, y = list(map(float, s.split(b";")))
    return Point(x, y)

# Register the adapter and converter
sqlite3.register_adapter(Point, adapt_point)
sqlite3.register_converter("point", convert_point)

# 1) Parse using declared types
p = Point(4.0, -3.2)
con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_DECLTYPES)
cur = con.execute("CREATE TABLE test(p point)")

cur.execute("INSERT INTO test(p) VALUES(?)", (p,))
cur.execute("SELECT p FROM test")
print("with declared types:", cur.fetchone()[0])
cur.close()
con.close()

# 2) Parse using column names
con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_COLNAMES)
cur = con.execute("CREATE TABLE test(p)")

cur.execute("INSERT INTO test(p) VALUES(?)", (p,))
cur.execute('SELECT p AS "p [point]" FROM test')
print("with column names:", cur.fetchone()[0])
cur.close()
con.close()

Adapter and converter recipes

This section shows recipes for common adapters and converters.

import datetime
import sqlite3

def adapt_date_iso(val):
    """Adapt datetime.date to ISO 8601 date."""
    return val.isoformat()

def adapt_datetime_iso(val):
    """Adapt datetime.datetime to timezone-naive ISO 8601 date."""
    return val.replace(tzinfo=None).isoformat()

def adapt_datetime_epoch(val):
    """Adapt datetime.datetime to Unix timestamp."""
    return int(val.timestamp())

sqlite3.register_adapter(datetime.date, adapt_date_iso)
sqlite3.register_adapter(datetime.datetime, adapt_datetime_iso)
sqlite3.register_adapter(datetime.datetime, adapt_datetime_epoch)

def convert_date(val):
    """Convert ISO 8601 date to datetime.date object."""
    return datetime.date.fromisoformat(val.decode())

def convert_datetime(val):
    """Convert ISO 8601 datetime to datetime.datetime object."""
    return datetime.datetime.fromisoformat(val.decode())

def convert_timestamp(val):
    """Convert Unix epoch timestamp to datetime.datetime object."""
    return datetime.datetime.fromtimestamp(int(val))

sqlite3.register_converter("date", convert_date)
sqlite3.register_converter("datetime", convert_datetime)
sqlite3.register_converter("timestamp", convert_timestamp)

How to use connection shortcut methods

Using the execute(), executemany(), and executescript() methods of the Connection class, your code can be written more concisely because you don't have to create the (often superfluous) Cursor objects explicitly. Instead, the Cursor objects are created implicitly and these shortcut methods return the cursor objects. This way, you can execute a SELECT statement and iterate over it directly using only a single call on the Connection object.

# Create and fill the table.
con = sqlite3.connect(":memory:")
con.execute("CREATE TABLE lang(name, first_appeared)")
data = [
    ("C++", 1985),
    ("Objective-C", 1984),
]
con.executemany("INSERT INTO lang(name, first_appeared) VALUES(?, ?)", data)

# Print the table contents
for row in con.execute("SELECT name, first_appeared FROM lang"):
    print(row)

print("I just deleted", con.execute("DELETE FROM lang").rowcount, "rows")

# close() is not a shortcut method and it's not called automatically;
# the connection object should be closed manually
con.close()

How to use the connection context manager

A Connection object can be used as a context manager that automatically commits or rolls back open transactions when leaving the body of the context manager. If the body of the with statement finishes without exceptions, the transaction is committed. If this commit fails, or if the body of the with statement raises an uncaught exception, the transaction is rolled back. If autocommit is False, a new transaction is implicitly opened after committing or rolling back.

If there is no open transaction upon leaving the body of the with statement, or if autocommit is True, the context manager does nothing.

備註

The context manager neither implicitly opens a new transaction nor closes the connection. If you need a closing context manager, consider using contextlib.closing().

con = sqlite3.connect(":memory:")
con.execute("CREATE TABLE lang(id INTEGER PRIMARY KEY, name VARCHAR UNIQUE)")

# Successful, con.commit() is called automatically afterwards
with con:
    con.execute("INSERT INTO lang(name) VALUES(?)", ("Python",))

# con.rollback() is called after the with block finishes with an exception,
# the exception is still raised and must be caught
try:
    with con:
        con.execute("INSERT INTO lang(name) VALUES(?)", ("Python",))
except sqlite3.IntegrityError:
    print("couldn't add Python twice")

# Connection object used as context manager only commits or rollbacks transactions,
# so the connection object should be closed manually
con.close()

How to work with SQLite URIs

Some useful URI tricks include:

以唯讀模式開啟資料庫：

>>> con = sqlite3.connect("file:tutorial.db?mode=ro", uri=True)
>>> con.execute("CREATE TABLE readonly(data)")
Traceback (most recent call last):
OperationalError: attempt to write a readonly database
>>> con.close()

Do not implicitly create a new database file if it does not already exist; will raise OperationalError if unable to create a new file:

>>> con = sqlite3.connect("file:nosuchdb.db?mode=rw", uri=True)
Traceback (most recent call last):
OperationalError: unable to open database file

Create a shared named in-memory database:

db = "file:mem1?mode=memory&cache=shared"
con1 = sqlite3.connect(db, uri=True)
con2 = sqlite3.connect(db, uri=True)
with con1:
    con1.execute("CREATE TABLE shared(data)")
    con1.execute("INSERT INTO shared VALUES(28)")
res = con2.execute("SELECT data FROM shared")
assert res.fetchone() == (28,)

con1.close()
con2.close()

More information about this feature, including a list of parameters, can be found in the SQLite URI documentation [https://www.sqlite.org/uri.html].

How to create and use row factories

By default, sqlite3 represents each row as a tuple. If a tuple does not suit your needs, you can use the sqlite3.Row class or a custom row_factory.

While row_factory exists as an attribute both on the Cursor and the Connection, it is recommended to set Connection.row_factory, so all cursors created from the connection will use the same row factory.

Row provides indexed and case-insensitive named access to columns, with minimal memory overhead and performance impact over a tuple. To use Row as a row factory, assign it to the row_factory attribute:

>>> con = sqlite3.connect(":memory:")
>>> con.row_factory = sqlite3.Row

Queries now return Row objects:

>>> res = con.execute("SELECT 'Earth' AS name, 6378 AS radius")
>>> row = res.fetchone()
>>> row.keys()
['name', 'radius']
>>> row[0]         # Access by index.
'Earth'
>>> row["name"]    # Access by name.
'Earth'
>>> row["RADIUS"]  # Column names are case-insensitive.
6378
>>> con.close()

備註

The FROM clause can be omitted in the SELECT statement, as in the above example. In such cases, SQLite returns a single row with columns defined by expressions, e.g. literals, with the given aliases expr AS alias.

You can create a custom row_factory that returns each row as a dict, with column names mapped to values:

def dict_factory(cursor, row):
    fields = [column[0] for column in cursor.description]
    return {key: value for key, value in zip(fields, row)}

Using it, queries now return a dict instead of a tuple:

>>> con = sqlite3.connect(":memory:")
>>> con.row_factory = dict_factory
>>> for row in con.execute("SELECT 1 AS a, 2 AS b"):
...     print(row)
{'a': 1, 'b': 2}
>>> con.close()

The following row factory returns a named tuple:

from collections import namedtuple

def namedtuple_factory(cursor, row):
    fields = [column[0] for column in cursor.description]
    cls = namedtuple("Row", fields)
    return cls._make(row)

namedtuple_factory() 可以如下使用：

>>> con = sqlite3.connect(":memory:")
>>> con.row_factory = namedtuple_factory
>>> cur = con.execute("SELECT 1 AS a, 2 AS b")
>>> row = cur.fetchone()
>>> row
Row(a=1, b=2)
>>> row[0]  # Indexed access.
1
>>> row.b   # Attribute access.
2
>>> con.close()

With some adjustments, the above recipe can be adapted to use a dataclass, or any other custom class, instead of a namedtuple.

如何處理非 UTF-8 的文字編碼

By default, sqlite3 uses str to adapt SQLite values with the TEXT data type. This works well for UTF-8 encoded text, but it might fail for other encodings and invalid UTF-8. You can use a custom text_factory to handle such cases.

Because of SQLite's flexible typing [https://www.sqlite.org/flextypegood.html], it is not uncommon to encounter table columns with the TEXT data type containing non-UTF-8 encodings, or even arbitrary data. To demonstrate, let's assume we have a database with ISO-8859-2 (Latin-2) encoded text, for example a table of Czech-English dictionary entries. Assuming we now have a Connection instance con connected to this database, we can decode the Latin-2 encoded text using this text_factory:

con.text_factory = lambda data: str(data, encoding="latin2")

For invalid UTF-8 or arbitrary data in stored in TEXT table columns, you can use the following technique, borrowed from the Unicode HOWTO:

con.text_factory = lambda data: str(data, errors="surrogateescape")

備註

The sqlite3 module API does not support strings containing surrogates.

也參考

Unicode HOWTO

解釋

Transaction control

sqlite3 offers multiple methods of controlling whether, when and how database transactions are opened and closed. Transaction control via the autocommit attribute is recommended, while Transaction control via the isolation_level attribute retains the pre-Python 3.12 behaviour.

Transaction control via the autocommit attribute

The recommended way of controlling transaction behaviour is through the Connection.autocommit attribute, which should preferably be set using the autocommit parameter of connect().

It is suggested to set autocommit to False, which implies PEP 249 [https://peps.python.org/pep-0249/]-compliant transaction control. This means:

sqlite3 ensures that a transaction is always open, so connect(), Connection.commit(), and Connection.rollback() will implicitly open a new transaction (immediately after closing the pending one, for the latter two). sqlite3 uses BEGIN DEFERRED statements when opening transactions.

Transactions should be committed explicitly using commit().

Transactions should be rolled back explicitly using rollback().

An implicit rollback is performed if the database is close()-ed with pending changes.

Set autocommit to True to enable SQLite's autocommit mode [https://www.sqlite.org/lang_transaction.html#implicit_versus_explicit_transactions]. In this mode, Connection.commit() and Connection.rollback() have no effect. Note that SQLite's autocommit mode is distinct from the PEP 249 [https://peps.python.org/pep-0249/]-compliant Connection.autocommit attribute; use Connection.in_transaction to query the low-level SQLite autocommit mode.

Set autocommit to LEGACY_TRANSACTION_CONTROL to leave transaction control behaviour to the Connection.isolation_level attribute. See Transaction control via the isolation_level attribute for more information.

Transaction control via the isolation_level attribute

備註

The recommended way of controlling transactions is via the autocommit attribute. See Transaction control via the autocommit attribute.

If Connection.autocommit is set to LEGACY_TRANSACTION_CONTROL (the default), transaction behaviour is controlled using the Connection.isolation_level attribute. Otherwise, isolation_level has no effect.

If the connection attribute isolation_level is not None, new transactions are implicitly opened before execute() and executemany() executes INSERT, UPDATE, DELETE, or REPLACE statements; for other statements, no implicit transaction handling is performed. Use the commit() and rollback() methods to respectively commit and roll back pending transactions. You can choose the underlying SQLite transaction behaviour [https://www.sqlite.org/lang_transaction.html#deferred_immediate_and_exclusive_transactions] — that is, whether and what type of BEGIN statements sqlite3 implicitly executes – via the isolation_level attribute.

If isolation_level is set to None, no transactions are implicitly opened at all. This leaves the underlying SQLite library in autocommit mode [https://www.sqlite.org/lang_transaction.html#implicit_versus_explicit_transactions], but also allows the user to perform their own transaction handling using explicit SQL statements. The underlying SQLite library autocommit mode can be queried using the in_transaction attribute.

The executescript() method implicitly commits any pending transaction before execution of the given SQL script, regardless of the value of isolation_level.

在 3.6 版的變更: sqlite3 used to implicitly commit an open transaction before DDL statements. This is no longer the case.

在 3.12 版的變更: The recommended way of controlling transactions is now via the autocommit attribute.

資料壓縮與保存

本章中描述的模組支援使用 zlib、gzip、bzip2、lzma 和 zstd 演算法進行資料壓縮，以及建立 ZIP 和 tar 格式的存檔。另請參閱 shutil 模組提供的 Archiving operations。

compression 套件

compression.zstd --- 與 Zstandard 格式相容的壓縮

例外

Reading and writing compressed files

Compressing and decompressing data in memory

Zstandard 字典

Advanced parameter control

Miscellaneous

範例

zlib --- 相容於 gzip 的壓縮

gzip --- gzip 檔案的支援

用法範例

命令列介面

命令列選項

bz2 --- bzip2 壓縮的支援

(De)compression of files

Incremental (de)compression

One-shot (de)compression

用法範例

lzma --- 使用 LZMA 演算法進行壓縮

Reading and writing compressed files

Compressing and decompressing data in memory

Miscellaneous

Specifying custom filter chains

範例

zipfile --- 處理 ZIP 封存檔案

ZipFile 物件

Path 物件

PyZipFile 物件

ZipInfo 物件

命令列介面

命令列選項

解壓縮的陷阱

來自檔案本身

檔案系統限制

資源限制

中斷

解壓縮的預設行為

tarfile --- 讀取與寫入 tar 封存檔案

TarFile 物件

TarInfo 物件

解壓縮篩選器

預設具名篩選器

篩選器錯誤

進一步驗證的提示

支援舊版 Python

有狀態的解壓縮篩選器範例

命令列介面

命令列選項

範例

讀取範例

寫入範例

支援的 tar 格式

Unicode 議題

compression 套件

在 3.14 版被加入.

compression 套件包含了有多種不同壓縮演算法介面的標準壓縮模組。其中一些模組過去是以獨立模組的形式提供；為了相容性考量，這些模組將繼續以其原始名稱提供，並且不會在沒有經過棄用週期的情況下被移除。建議在可行的情況下盡量先使用 compression 中的模組。

compression.bz2 -- 重新匯出 bz2

compression.gzip -- 重新匯出 gzip

compression.lzma -- 重新匯出 lzma

compression.zlib -- 重新匯出 zlib

compression.zstd -- Zstandard 壓縮函式庫的包裝器

compression.zstd --- 與 Zstandard 格式相容的壓縮

在 3.14 版被加入.

原始碼：Lib/compression/zstd/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/compression/zstd/__init__.py]

This module provides classes and functions for compressing and decompressing data using the Zstandard (or zstd) compression algorithm. The zstd manual [https://facebook.github.io/zstd/doc/api_manual_latest.html] describes Zstandard as "a fast lossless compression algorithm, targeting real-time compression scenarios at zlib-level and better compression ratios." Also included is a file interface that supports reading and writing the contents of .zst files created by the zstd utility, as well as raw zstd compressed streams.

compression.zstd 模組包含：

The open() function and ZstdFile class for reading and writing compressed files.

The ZstdCompressor and ZstdDecompressor classes for incremental (de)compression.

The compress() and decompress() functions for one-shot (de)compression.

The train_dict() and finalize_dict() functions and the ZstdDict class to train and manage Zstandard dictionaries.

The CompressionParameter, DecompressionParameter, and Strategy classes for setting advanced (de)compression parameters.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

例外

exception compression.zstd.ZstdError

This exception is raised when an error occurs during compression or decompression, or while initializing the (de)compressor state.

Reading and writing compressed files

compression.zstd.open(file, /, mode='rb', *, level=None, options=None, zstd_dict=None, encoding=None, errors=None, newline=None)

Open a Zstandard-compressed file in binary or text mode, returning a file object.

The file argument can be either a file name (given as a str, bytes or path-like object), in which case the named file is opened, or it can be an existing file object to read from or write to.

The mode argument can be either 'rb' for reading (default), 'wb' for overwriting, 'ab' for appending, or 'xb' for exclusive creation. These can equivalently be given as 'r', 'w', 'a', and 'x' respectively. You may also open in text mode with 'rt', 'wt', 'at', and 'xt' respectively.

When reading, the options argument can be a dictionary providing advanced decompression parameters; see DecompressionParameter for detailed information about supported parameters. The zstd_dict argument is a ZstdDict instance to be used during decompression. When reading, if the level argument is not None, a TypeError will be raised.

When writing, the options argument can be a dictionary providing advanced compression parameters; see CompressionParameter for detailed information about supported parameters. The level argument is the compression level to use when writing compressed data. Only one of level or options may be non-None. The zstd_dict argument is a ZstdDict instance to be used during compression.

In binary mode, this function is equivalent to the ZstdFile constructor: ZstdFile(file, mode, ...). In this case, the encoding, errors, and newline parameters must not be provided.

In text mode, a ZstdFile object is created, and wrapped in an io.TextIOWrapper instance with the specified encoding, error handling behavior, and line endings.

class compression.zstd.ZstdFile(file, /, mode='rb', *, level=None, options=None, zstd_dict=None)

Open a Zstandard-compressed file in binary mode.

A ZstdFile can wrap an already-open file object, or operate directly on a named file. The file argument specifies either the file object to wrap, or the name of the file to open (as a str, bytes or path-like object). If wrapping an existing file object, the wrapped file will not be closed when the ZstdFile is closed.

The mode argument can be either 'rb' for reading (default), 'wb' for overwriting, 'xb' for exclusive creation, or 'ab' for appending. These can equivalently be given as 'r', 'w', 'x' and 'a' respectively.

If file is a file object (rather than an actual file name), a mode of 'w' does not truncate the file, and is instead equivalent to 'a'.

When reading, the options argument can be a dictionary providing advanced decompression parameters; see DecompressionParameter for detailed information about supported parameters. The zstd_dict argument is a ZstdDict instance to be used during decompression. When reading, if the level argument is not None, a TypeError will be raised.

When writing, the options argument can be a dictionary providing advanced compression parameters; see CompressionParameter for detailed information about supported parameters. The level argument is the compression level to use when writing compressed data. Only one of level or options may be passed. The zstd_dict argument is a ZstdDict instance to be used during compression.

ZstdFile supports all the members specified by io.BufferedIOBase, except for detach() and truncate(). Iteration and the with statement are supported.

The following method and attributes are also provided:

peek(size=-1)

Return buffered data without advancing the file position. At least one byte of data will be returned, unless EOF has been reached. The exact number of bytes returned is unspecified (the size argument is ignored).

備註

While calling peek() does not change the file position of the ZstdFile, it may change the position of the underlying file object (for example, if the ZstdFile was constructed by passing a file object for file).

mode

'rb' for reading and 'wb' for writing.

name

The name of the Zstandard file. Equivalent to the name attribute of the underlying file object.

Compressing and decompressing data in memory

compression.zstd.compress(data, level=None, options=None, zstd_dict=None)

Compress data (a bytes-like object), returning the compressed data as a bytes object.

The level argument is an integer controlling the level of compression. level is an alternative to setting CompressionParameter.compression_level in options. Use bounds() on compression_level to get the values that can be passed for level. If advanced compression options are needed, the level argument must be omitted and in the options dictionary the CompressionParameter.compression_level parameter should be set.

The options argument is a Python dictionary containing advanced compression parameters. The valid keys and values for compression parameters are documented as part of the CompressionParameter documentation.

The zstd_dict argument is an instance of ZstdDict containing trained data to improve compression efficiency. The function train_dict() can be used to generate a Zstandard dictionary.

compression.zstd.decompress(data, zstd_dict=None, options=None)

Decompress data (a bytes-like object), returning the uncompressed data as a bytes object.

The options argument is a Python dictionary containing advanced decompression parameters. The valid keys and values for compression parameters are documented as part of the DecompressionParameter documentation.

The zstd_dict argument is an instance of ZstdDict containing trained data used during compression. This must be the same Zstandard dictionary used during compression.

If data is the concatenation of multiple distinct compressed frames, decompress all of these frames, and return the concatenation of the results.

class compression.zstd.ZstdCompressor(level=None, options=None, zstd_dict=None)

Create a compressor object, which can be used to compress data incrementally.

For a more convenient way of compressing a single chunk of data, see the module-level function compress().

The level argument is an integer controlling the level of compression. level is an alternative to setting CompressionParameter.compression_level in options. Use bounds() on compression_level to get the values that can be passed for level. If advanced compression options are needed, the level argument must be omitted and in the options dictionary the CompressionParameter.compression_level parameter should be set.

The options argument is a Python dictionary containing advanced compression parameters. The valid keys and values for compression parameters are documented as part of the CompressionParameter documentation.

The zstd_dict argument is an optional instance of ZstdDict containing trained data to improve compression efficiency. The function train_dict() can be used to generate a Zstandard dictionary.

compress(data, mode=ZstdCompressor.CONTINUE)

Compress data (a bytes-like object), returning a bytes object with compressed data if possible, or otherwise an empty bytes object. Some of data may be buffered internally, for use in later calls to compress() and flush(). The returned data should be concatenated with the output of any previous calls to compress().

The mode argument is a ZstdCompressor attribute, either CONTINUE, FLUSH_BLOCK, or FLUSH_FRAME.

When all data has been provided to the compressor, call the flush() method to finish the compression process. If compress() is called with mode set to FLUSH_FRAME, flush() should not be called, as it would write out a new empty frame.

flush(mode=ZstdCompressor.FLUSH_FRAME)

Finish the compression process, returning a bytes object containing any data stored in the compressor's internal buffers.

The mode argument is a ZstdCompressor attribute, either FLUSH_BLOCK, or FLUSH_FRAME.

set_pledged_input_size(size)

Specify the amount of uncompressed data size that will be provided for the next frame. size will be written into the frame header of the next frame unless CompressionParameter.content_size_flag is False or 0. A size of 0 means that the frame is empty. If size is None, the frame header will omit the frame size. Frames that include the uncompressed data size require less memory to decompress, especially at higher compression levels.

If last_mode is not FLUSH_FRAME, a ValueError is raised as the compressor is not at the start of a frame. If the pledged size does not match the actual size of data provided to compress(), future calls to compress() or flush() may raise ZstdError and the last chunk of data may be lost.

After flush() or compress() are called with mode FLUSH_FRAME, the next frame will not include the frame size into the header unless set_pledged_input_size() is called again.

CONTINUE

Collect more data for compression, which may or may not generate output immediately. This mode optimizes the compression ratio by maximizing the amount of data per block and frame.

FLUSH_BLOCK

Complete and write a block to the data stream. The data returned so far can be immediately decompressed. Past data can still be referenced in future blocks generated by calls to compress(), improving compression.

FLUSH_FRAME

Complete and write out a frame. Future data provided to compress() will be written into a new frame and cannot reference past data.

last_mode

The last mode passed to either compress() or flush(). The value can be one of CONTINUE, FLUSH_BLOCK, or FLUSH_FRAME. The initial value is FLUSH_FRAME, signifying that the compressor is at the start of a new frame.

class compression.zstd.ZstdDecompressor(zstd_dict=None, options=None)

Create a decompressor object, which can be used to decompress data incrementally.

For a more convenient way of decompressing an entire compressed stream at once, see the module-level function decompress().

The options argument is a Python dictionary containing advanced decompression parameters. The valid keys and values for compression parameters are documented as part of the DecompressionParameter documentation.

The zstd_dict argument is an instance of ZstdDict containing trained data used during compression. This must be the same Zstandard dictionary used during compression.

備註

This class does not transparently handle inputs containing multiple compressed frames, unlike the decompress() function and ZstdFile class. To decompress a multi-frame input, you should use decompress(), ZstdFile if working with a file object, or multiple ZstdDecompressor instances.

decompress(data, max_length=-1)

Decompress data (a bytes-like object), returning uncompressed data as bytes. Some of data may be buffered internally, for use in later calls to decompress(). The returned data should be concatenated with the output of any previous calls to decompress().

If max_length is non-negative, the method returns at most max_length bytes of decompressed data. If this limit is reached and further output can be produced, the needs_input attribute will be set to False. In this case, the next call to decompress() may provide data as b'' to obtain more of the output.

If all of the input data was decompressed and returned (either because this was less than max_length bytes, or because max_length was negative), the needs_input attribute will be set to True.

Attempting to decompress data after the end of a frame will raise a ZstdError. Any data found after the end of the frame is ignored and saved in the unused_data attribute.

eof

True if the end-of-stream marker has been reached.

unused_data

Data found after the end of the compressed stream.

Before the end of the stream is reached, this will be b''.

needs_input

False if the decompress() method can provide more decompressed data before requiring new compressed input.

Zstandard 字典

compression.zstd.train_dict(samples, dict_size)

Train a Zstandard dictionary, returning a ZstdDict instance. Zstandard dictionaries enable more efficient compression of smaller sizes of data, which is traditionally difficult to compress due to less repetition. If you are compressing multiple similar groups of data (such as similar files), Zstandard dictionaries can improve compression ratios and speed significantly.

The samples argument (an iterable of bytes objects), is the population of samples used to train the Zstandard dictionary.

The dict_size argument, an integer, is the maximum size (in bytes) the Zstandard dictionary should be. The Zstandard documentation suggests an absolute maximum of no more than 100 KB, but the maximum can often be smaller depending on the data. Larger dictionaries generally slow down compression, but improve compression ratios. Smaller dictionaries lead to faster compression, but reduce the compression ratio.

compression.zstd.finalize_dict(zstd_dict, /, samples, dict_size, level)

An advanced function for converting a "raw content" Zstandard dictionary into a regular Zstandard dictionary. "Raw content" dictionaries are a sequence of bytes that do not need to follow the structure of a normal Zstandard dictionary.

The zstd_dict argument is a ZstdDict instance with the dict_content containing the raw dictionary contents.

The samples argument (an iterable of bytes objects), contains sample data for generating the Zstandard dictionary.

The dict_size argument, an integer, is the maximum size (in bytes) the Zstandard dictionary should be. See train_dict() for suggestions on the maximum dictionary size.

The level argument (an integer) is the compression level expected to be passed to the compressors using this dictionary. The dictionary information varies for each compression level, so tuning for the proper compression level can make compression more efficient.

class compression.zstd.ZstdDict(dict_content, /, *, is_raw=False)

A wrapper around Zstandard dictionaries. Dictionaries can be used to improve the compression of many small chunks of data. Use train_dict() if you need to train a new dictionary from sample data.

The dict_content argument (a bytes-like object), is the already trained dictionary information.

The is_raw argument, a boolean, is an advanced parameter controlling the meaning of dict_content. True means dict_content is a "raw content" dictionary, without any format restrictions. False means dict_content is an ordinary Zstandard dictionary, created from Zstandard functions, for example, train_dict() or the external zstd CLI.

When passing a ZstdDict to a function, the as_digested_dict and as_undigested_dict attributes can control how the dictionary is loaded by passing them as the zstd_dict argument, for example, compress(data, zstd_dict=zd.as_digested_dict). Digesting a dictionary is a costly operation that occurs when loading a Zstandard dictionary. When making multiple calls to compression or decompression, passing a digested dictionary will reduce the overhead of loading the dictionary.

Difference for compression

Digested dictionary

Undigested dictionary

Advanced parameters of the compressor which may be overridden by the dictionary's parameters

window_log, hash_log, chain_log, search_log, min_match, target_length, strategy, enable_long_distance_matching, ldm_hash_log, ldm_min_match, ldm_bucket_size_log, ldm_hash_rate_log, and some non-public parameters.

None

ZstdDict internally caches the dictionary

Yes. It's faster when loading a digested dictionary again with the same compression level.

No. If you wish to load an undigested dictionary multiple times, consider reusing a compressor object.

If passing a ZstdDict without any attribute, an undigested dictionary is passed by default when compressing and a digested dictionary is generated if necessary and passed by default when decompressing.

dict_content

The content of the Zstandard dictionary, a bytes object. It's the same as the dict_content argument in the __init__ method. It can be used with other programs, such as the zstd CLI program.

dict_id

Identifier of the Zstandard dictionary, a non-negative int value.

Non-zero means the dictionary is ordinary, created by Zstandard functions and following the Zstandard format.

0 means a "raw content" dictionary, free of any format restriction, used for advanced users.

備註

The meaning of 0 for ZstdDict.dict_id is different from the dictionary_id attribute to the get_frame_info() function.

as_digested_dict

Load as a digested dictionary.

as_undigested_dict

Load as an undigested dictionary.

Advanced parameter control

class compression.zstd.CompressionParameter

An IntEnum containing the advanced compression parameter keys that can be used when compressing data.

The bounds() method can be used on any attribute to get the valid values for that parameter.

Parameters are optional; any omitted parameter will have it's value selected automatically.

Example getting the lower and upper bound of compression_level:

lower, upper = CompressionParameter.compression_level.bounds()

Example setting the window_log to the maximum size:

_lower, upper = CompressionParameter.window_log.bounds()
options = {CompressionParameter.window_log: upper}
compress(b'venezuelan beaver cheese', options=options)

bounds()

Return the tuple of int bounds, (lower, upper), of a compression parameter. This method should be called on the attribute you wish to retrieve the bounds of. For example, to get the valid values for compression_level, one may check the result of CompressionParameter.compression_level.bounds().

Both the lower and upper bounds are inclusive.

compression_level

A high-level means of setting other compression parameters that affect the speed and ratio of compressing data.

Regular compression levels are greater than 0. Values greater than 20 are considered "ultra" compression and require more memory than other levels. Negative values can be used to trade off faster compression for worse compression ratios.

Setting the level to zero uses COMPRESSION_LEVEL_DEFAULT.

window_log

Maximum allowed back-reference distance the compressor can use when compressing data, expressed as power of two, 1 << window_log bytes. This parameter greatly influences the memory usage of compression. Higher values require more memory but gain better compression values.

A value of zero causes the value to be selected automatically.

hash_log

Size of the initial probe table, as a power of two. The resulting memory usage is 1 << (hash_log+2) bytes. Larger tables improve compression ratio of strategies <= dfast, and improve compression speed of strategies > dfast.

A value of zero causes the value to be selected automatically.

chain_log

Size of the multi-probe search table, as a power of two. The resulting memory usage is 1 << (chain_log+2) bytes. Larger tables result in better and slower compression. This parameter has no effect for the fast strategy. It's still useful when using dfast strategy, in which case it defines a secondary probe table.

A value of zero causes the value to be selected automatically.

search_log

Number of search attempts, as a power of two. More attempts result in better and slower compression. This parameter is useless for fast and dfast strategies.

A value of zero causes the value to be selected automatically.

min_match

Minimum size of searched matches. Larger values increase compression and decompression speed, but decrease ratio. Note that Zstandard can still find matches of smaller size, it just tweaks its search algorithm to look for this size and larger. For all strategies < btopt, the effective minimum is 4; for all strategies > fast, the effective maximum is 6.

A value of zero causes the value to be selected automatically.

target_length

The impact of this field depends on the selected Strategy.

For strategies btopt, btultra and btultra2, the value is the length of a match considered "good enough" to stop searching. Larger values make compression ratios better, but compresses slower.

For strategy fast, it is the distance between match sampling. Larger values make compression faster, but with a worse compression ratio.

A value of zero causes the value to be selected automatically.

strategy

The higher the value of selected strategy, the more complex the compression technique used by zstd, resulting in higher compression ratios but slower compression.

也參考

Strategy

enable_long_distance_matching

Long distance matching can be used to improve compression for large inputs by finding large matches at greater distances. It increases memory usage and window size.

True or 1 enable long distance matching while False or 0 disable it.

Enabling this parameter increases default window_log to 128 MiB except when expressly set to a different value. This setting is enabled by default if window_log >= 128 MiB and the compression strategy >= btopt (compression level 16+).

ldm_hash_log

Size of the table for long distance matching, as a power of two. Larger values increase memory usage and compression ratio, but decrease compression speed.

A value of zero causes the value to be selected automatically.

ldm_min_match

Minimum match size for long distance matcher. Larger or too small values can often decrease the compression ratio.

A value of zero causes the value to be selected automatically.

ldm_bucket_size_log

Log size of each bucket in the long distance matcher hash table for collision resolution. Larger values improve collision resolution but decrease compression speed.

A value of zero causes the value to be selected automatically.

ldm_hash_rate_log

Frequency of inserting/looking up entries into the long distance matcher hash table. Larger values improve compression speed. Deviating far from the default value will likely result in a compression ratio decrease.

A value of zero causes the value to be selected automatically.

content_size_flag

Write the size of the data to be compressed into the Zstandard frame header when known prior to compressing.

This flag only takes effect under the following scenarios:

Calling compress() for one-shot compression

Providing all of the data to be compressed in the frame in a single ZstdCompressor.compress() call, with the ZstdCompressor.FLUSH_FRAME mode.

Calling ZstdCompressor.set_pledged_input_size() with the exact amount of data that will be provided to the compressor prior to any calls to ZstdCompressor.compress() for the current frame. ZstdCompressor.set_pledged_input_size() must be called for each new frame.

All other compression calls may not write the size information into the frame header.

True or 1 enable the content size flag while False or 0 disable it.

checksum_flag

A four-byte checksum using XXHash64 of the uncompressed content is written at the end of each frame. Zstandard's decompression code verifies the checksum. If there is a mismatch a ZstdError exception is raised.

True or 1 enable checksum generation while False or 0 disable it.

dict_id_flag

When compressing with a ZstdDict, the dictionary's ID is written into the frame header.

True or 1 enable storing the dictionary ID while False or 0 disable it.

nb_workers

Select how many threads will be spawned to compress in parallel. When nb_workers > 0, enables multi-threaded compression, a value of 1 means "one-thread multi-threaded mode". More workers improve speed, but also increase memory usage and slightly reduce compression ratio.

A value of zero disables multi-threading.

job_size

Size of a compression job, in bytes. This value is enforced only when nb_workers >= 1. Each compression job is completed in parallel, so this value can indirectly impact the number of active threads.

A value of zero causes the value to be selected automatically.

overlap_log

Sets how much data is reloaded from previous jobs (threads) for new jobs to be used by the look behind window during compression. This value is only used when nb_workers >= 1. Acceptable values vary from 0 to 9.

0 means dynamically set the overlap amount

1 means no overlap

9 means use a full window size from the previous job

Each increment halves/doubles the overlap size. "8" means an overlap of window_size/2, "7" means an overlap of window_size/4, etc.

class compression.zstd.DecompressionParameter

An IntEnum containing the advanced decompression parameter keys that can be used when decompressing data. Parameters are optional; any omitted parameter will have it's value selected automatically.

The bounds() method can be used on any attribute to get the valid values for that parameter.

Example setting the window_log_max to the maximum size:

data = compress(b'Some very long buffer of bytes...')

_lower, upper = DecompressionParameter.window_log_max.bounds()

options = {DecompressionParameter.window_log_max: upper}
decompress(data, options=options)

bounds()

Return the tuple of int bounds, (lower, upper), of a decompression parameter. This method should be called on the attribute you wish to retrieve the bounds of.

Both the lower and upper bounds are inclusive.

window_log_max

The base-two logarithm of the maximum size of the window used during decompression. This can be useful to limit the amount of memory used when decompressing data. A larger maximum window size leads to faster decompression.

A value of zero causes the value to be selected automatically.

class compression.zstd.Strategy

An IntEnum containing strategies for compression. Higher-numbered strategies correspond to more complex and slower compression.

備註

The values of attributes of Strategy are not necessarily stable across zstd versions. Only the ordering of the attributes may be relied upon. The attributes are listed below in order.

The following strategies are available:

fast

dfast

greedy

lazy

lazy2

btlazy2

btopt

btultra

btultra2

Miscellaneous

compression.zstd.get_frame_info(frame_buffer)

Retrieve a FrameInfo object containing metadata about a Zstandard frame. Frames contain metadata related to the compressed data they hold.

class compression.zstd.FrameInfo

Metadata related to a Zstandard frame.

decompressed_size

The size of the decompressed contents of the frame.

dictionary_id

An integer representing the Zstandard dictionary ID needed for decompressing the frame. 0 means the dictionary ID was not recorded in the frame header. This may mean that a Zstandard dictionary is not needed, or that the ID of a required dictionary was not recorded.

compression.zstd.COMPRESSION_LEVEL_DEFAULT

The default compression level for Zstandard: 3.

compression.zstd.zstd_version_info

Version number of the runtime zstd library as a tuple of integers (major, minor, release).

範例

讀取壓縮檔案：

from compression import zstd

with zstd.open("file.zst") as f:
    file_content = f.read()

Creating a compressed file:

from compression import zstd

data = b"Insert Data Here"
with zstd.open("file.zst", "w") as f:
    f.write(data)

Compressing data in memory:

from compression import zstd

data_in = b"Insert Data Here"
data_out = zstd.compress(data_in)

Incremental compression:

from compression import zstd

comp = zstd.ZstdCompressor()
out1 = comp.compress(b"Some data\n")
out2 = comp.compress(b"Another piece of data\n")
out3 = comp.compress(b"Even more data\n")
out4 = comp.flush()
# Concatenate all the partial results:
result = b"".join([out1, out2, out3, out4])

Writing compressed data to an already-open file:

from compression import zstd

with open("myfile", "wb") as f:
    f.write(b"This data will not be compressed\n")
    with zstd.open(f, "w") as zstf:
        zstf.write(b"This *will* be compressed\n")
    f.write(b"Not compressed\n")

Creating a compressed file using compression parameters:

from compression import zstd

options = {
   zstd.CompressionParameter.checksum_flag: 1
}
with zstd.open("file.zst", "w", options=options) as f:
    f.write(b"Mind if I squeeze in?")

zlib --- 相容於 gzip 的壓縮

For applications that require data compression, the functions in this module allow compression and decompression, using the zlib library [https://www.zlib.net].

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

zlib 的函式有很多選項，且通常需要按特定順序使用。本文件並不打算解說所有選項排列組合的效果；相關官方資訊，請參閱 zlib 手冊 [https://www.zlib.net/manual.html]。

若要讀寫 .gz 文件，請參閱 gzip 模組。

該模組中可用的例外和函式是：

exception zlib.error

當壓縮和解壓縮發生錯誤時引發的例外。

zlib.adler32(data[, value])

計算 data 的 Adler-32 核對和 (checksum)。（Adler-32 核對和幾乎與 CRC32 一樣可靠，但計算速度更快。）結果是一個 unsigned（無符號的）32-bit 整數。如果有提供 value，則將其用作核對和的起始值，否則使用預設值 1。傳入 value 允許了於多個輸入的串聯 (concatenation) 上計算核對和。該演算法的加密強度不夠高，不該用於身份驗證 (authentication) 或數位簽章 (digital signature)。由於該演算法是為核對和演算法而設計的，它並不適合作為通用的雜湊演算法。

在 3.0 版的變更: 結果總是為 unsigned。

zlib.compress(data, /, level=Z_DEFAULT_COMPRESSION, wbits=MAX_WBITS)

壓縮 data 中的位元組，回傳一個包含壓縮資料的位元組物件。 level 是從 0 到 9 或 -1 的整數，控制了壓縮的級別；請見 Z_BEST_SPEED (1)、Z_BEST_COMPRESSION (9)、Z_NO_COMPRESSION (0)，以及預設值 Z_DEFAULT_COMPRESSION (-1) 以得到更多關於這些值的資訊。

wbits 引數控制了壓縮資料時所使用的歷史紀錄緩衝區 (history buffer) 大小（或「視窗大小」），以及輸出中是否包含標題和尾末 (trailer)。它可以採用多個值的範圍，預設為 15 (MAX_WBITS)：

+9 到 +15：視窗大小的以二為底的對數，因此範圍在 512 到 32768 之間。較大的值會產生更佳的壓縮，但會佔用更多的記憶體。生成輸出將包含特定於 zlib 的標頭和尾末。

−9 到 −15：使用 wbits 的絕對值作為視窗大小的對數，同時生成沒有標頭或尾末核對和的原始輸出串流。

+25 到 +31 = 16 +（9 到 15）：使用數值的最低 4 位元作為視窗大小的對數，同時在輸出中包含基本的 gzip 標頭和尾末核對和。

如果發生任何錯誤，則引發 error 例外。

在 3.6 版的變更: level 現在可以用作關鍵字參數。

在 3.11 版的變更: wbits 參數現在可用於設定視窗位元和壓縮型別。

zlib.compressobj(level=Z_DEFAULT_COMPRESSION, method=DEFLATED, wbits=MAX_WBITS, memLevel=DEF_MEM_LEVEL, strategy=Z_DEFAULT_STRATEGY[, zdict])

回傳一個壓縮物件，用於壓縮不能一次全部放入記憶體中的資料串流。

level is the compression level -- an integer from 0 to 9 or -1. See Z_BEST_SPEED (1), Z_BEST_COMPRESSION (9), Z_NO_COMPRESSION (0), and the default, Z_DEFAULT_COMPRESSION (-1) for more information about these values.

method 代表壓縮演算法。目前唯一支援的值是 DEFLATED。

wbits 參數控制歷史紀錄緩衝區的大小（或「視窗大小」），以及將使用的標頭和尾末格式。它與前面敘述的 compress() 具有相同的含義。

memLevel 引數控制用於內部壓縮狀態的記憶體大小。有效值範圍為 1 到 9。較高的值會使用更多的記憶體，但速度更快並產生更小的輸出。

strategy 被用於調整壓縮演算法。可用的值為 Z_DEFAULT_STRATEGY、Z_FILTERED、Z_HUFFMAN_ONLY、Z_RLE 和 Z_FIXED。

zdict 是事先定義好的的壓縮字典。這是一個位元組序列（例如一個 bytes 物件），其中包含預期在要壓縮的資料中頻繁出現的子序列。那些預期會最常見的子序列應該出現在字典的尾末。

在 3.3 版的變更: 新增 zdict 參數與支援關鍵字引數。

zlib.crc32(data[, value])

計算 data 的 CRC（Cyclic Redundancy Check，循環冗餘核對）核對和，結果會是一個 unsigned 32-bit 整數。如果 value 存在，則將其用作核對和的起始值，否則使用預設值 0。傳入 value 允許在多個輸入的串聯上計算核對和。該演算法的加密強度不夠高，不該用於身份驗證或數位簽章。由於該演算法是為核對和演算法而設計的，它並不適合作為通用的雜湊演算法。

在 3.0 版的變更: 結果總是為 unsigned。

zlib.decompress(data, /, wbits=MAX_WBITS, bufsize=DEF_BUF_SIZE)

解壓縮 data 中的位元組，回傳包含未壓縮資料的位元組物件。 wbits 參數依賴於 data 的格式，下面將進一步討論。如果有給定 bufsize，它會被用作輸出緩衝區的初始大小。如果發生任何錯誤，則引發 error 例外。

wbits 參數控制歷史紀錄緩衝區的大小（或「視窗大小」），以及期望的標頭和尾末格式。它類似於 compressobj() 的參數，但接受更多範圍的值：

+8 到 +15：視窗大小的以二為底的對數。輸入必須包括一個 zlib 標頭和尾末。

0：根據 zlib 標頭檔自動決定視窗大小。僅有在 zlib 1.2.3.5 或更新的版本支援。

−8 to −15：使用 wbits 的絕對值作為視窗大小的對數，輸入必須是沒有標頭或尾末的原始串流。

+24 到 +31 = 16 + （8 到 15）：取值的最低4位元作為視窗大小的對數，輸入必須包含 gzip 標頭和尾末。

+40 到 +47 = 32 + （8 到 15）：使用值的最低 4 位元作為視窗大小的對數，並自動接受 zlib 或 gzip 格式。

當解壓縮一個串流時，視窗大小不得小於最初用於壓縮串流的大小；使用太小的值可能會導致 error 例外。預設的 wbits 值對應於最大的視窗大小，並且需要包含 zlib 標頭和尾末。

bufsize 是用於保存解壓縮資料的緩衝區的初始大小。如果需要更多空間，緩衝區大小將根據需求來增加，因此你不需要讓該值完全剛好；調整它只會節省幾次對 malloc() 的呼叫。

在 3.6 版的變更: wbits 和 bufsize 可以用作關鍵字引數。

zlib.decompressobj(wbits=MAX_WBITS[, zdict])

回傳一個解壓縮物件，用於解壓縮不能一次全部放入記憶體的資料串流。

wbits 引數控制歷史紀錄緩衝區的大小（或「視窗大小」），以及期望的標頭和尾末格式。它與前面敘述的 decompress() 具有相同的含義。

zdict 參數指定是先定義好的壓縮字典。如果有提供，這必須與生成要解壓縮資料的壓縮器所使用的字典相同。

備註

如果 zdict 是一個可變物件 (mutable object)（例如一個 bytearray），你不能在呼叫 decompressobj() 和第一次呼叫解壓縮器的 decompress() 方法之間修改它的內容。

在 3.3 版的變更: 新增 zdict 參數。

壓縮物件支援以下方法：

Compress.compress(data)

壓縮 data，回傳一個位元組物件，其中至少包含 data 中部分資料的壓縮資料。此資料應串聯到任何先前呼叫 compress() 方法所產生的輸出。一些輸入可能會保存在內部緩衝區中以供後續處理。

Compress.flush([mode])

處理所有待處理的輸入，並回傳包含剩餘壓縮輸出的位元組物件。mode 可以從以下常數中選擇：Z_NO_FLUSH、Z_PARTIAL_FLUSH、Z_SYNC_FLUSH、Z_FULL_FLUSH、Z_BLOCK 或 Z_FINISH，預設為 Z_FINISH。除了 Z_FINISH 之外，所有常數都允許壓縮更多的資料位元組字串，而 Z_FINISH 會完成壓縮串流並同時防止壓縮更多資料。在 mode 設定為 Z_FINISH 的情況下呼叫 flush() 後，無法再次呼叫 compress() 方法；唯一可行的作法是刪除物件。

Compress.copy()

回傳壓縮物件的副本，這可用於有效壓縮一組共用初始前綴的資料。

在 3.8 版的變更: 於壓縮物件新增對 copy.copy() 和 copy.deepcopy() 的支援。

解壓縮物件支援以下方法和屬性：

Decompress.unused_data

一個位元組物件，它包含壓縮資料結束之後的任何位元組。也就是說，在包含壓縮資料的最後一個位元組可用之前，它會一直保持為 b""。如果整個位元組字串 (bytestring) 有包含壓縮資料，這會是 b""，也就是一個空位元組物件。

Decompress.unconsumed_tail

一個位元組物件，包含前一次 decompress() 的呼叫因超出了未壓縮資料緩衝區的限制而沒消耗掉的任何資料。 zlib 機制尚未看到此資料，因此你必須將其（和可能有和它串聯的其他資料）反饋給後續的 decompress() 方法呼叫以獲得正確的輸出。

Decompress.eof

一個布林值，代表是否已到達壓縮資料串流的尾末。

這使其能夠區分有正確建構的壓縮串流和不完整或被截斷的串流。

在 3.3 版被加入.

Decompress.decompress(data, max_length=0)

解壓縮 data 並回傳一個位元組物件，其包含與 string 中至少與部分資料相對應的未壓縮資料。此資料應串聯到任何先前呼叫 decompress() 方法所產生的輸出。一些輸入資料可能會保存在內部緩衝區中以供後續處理。

如果可選參數 max_length 不是零，則回傳值長度將不超過 max_length。這代表著並不是所有的已壓縮輸入都可以被處理；未使用的資料將被儲存在屬性 unconsumed_tail 中。如果要繼續解壓縮，則必須將此位元組字串傳遞給後續對 decompress() 的呼叫。如果 max_length 為零，則整個輸入會被解壓縮，並且 unconsumed_tail 為空。

在 3.6 版的變更: max_length 可以用作關鍵字引數。

Decompress.flush([length])

處理所有待處理的輸入，並回傳包含剩餘未壓縮輸出的位元組物件。呼叫 flush() 後，無法再次呼叫 decompress() 方法；唯一可行的方法是刪除該物件。

可選參數 length 設定了輸出緩衝區的初始大小。

Decompress.copy()

回傳解壓物件的副本，這可用於在資料串流中途保存解壓縮器的狀態，以便在未來某個時間點加速對串流的隨機搜尋 (random seek)。

在 3.8 版的變更: 於解壓縮物件新增對 copy.copy() 和 copy.deepcopy() 支援。

The following constants are available to configure compression and decompression behavior:

zlib.DEFLATED

The deflate compression method.

zlib.MAX_WBITS

The maximum window size, expressed as a power of 2. For example, if MAX_WBITS is 15 it results in a window size of 32 KiB.

zlib.DEF_MEM_LEVEL

壓縮物件的預設記憶體層級。

zlib.DEF_BUF_SIZE

解壓縮操作的預設緩衝區大小。

zlib.Z_NO_COMPRESSION

壓縮等級 0；不壓縮。

在 3.6 版被加入.

zlib.Z_BEST_SPEED

Compression level 1; fastest and produces the least compression.

zlib.Z_BEST_COMPRESSION

Compression level 9; slowest and produces the most compression.

zlib.Z_DEFAULT_COMPRESSION

Default compression level (-1); a compromise between speed and compression. Currently equivalent to compression level 6.

zlib.Z_DEFAULT_STRATEGY

Default compression strategy, for normal data.

zlib.Z_FILTERED

Compression strategy for data produced by a filter (or predictor).

zlib.Z_HUFFMAN_ONLY

Compression strategy that forces Huffman coding only.

zlib.Z_RLE

Compression strategy that limits match distances to one (run-length encoding).

This constant is only available if Python was compiled with zlib 1.2.0.1 or greater.

在 3.6 版被加入.

zlib.Z_FIXED

Compression strategy that prevents the use of dynamic Huffman codes.

This constant is only available if Python was compiled with zlib 1.2.2.2 or greater.

在 3.6 版被加入.

zlib.Z_NO_FLUSH

Flush mode 0. No special flushing behavior.

在 3.6 版被加入.

zlib.Z_PARTIAL_FLUSH

Flush mode 1. Flush as much output as possible.

zlib.Z_SYNC_FLUSH

Flush mode 2. All output is flushed and the output is aligned to a byte boundary.

zlib.Z_FULL_FLUSH

Flush mode 3. All output is flushed and the compression state is reset.

zlib.Z_FINISH

Flush mode 4. All pending input is processed, no more input is expected.

zlib.Z_BLOCK

Flush mode 5. A deflate block is completed and emitted.

This constant is only available if Python was compiled with zlib 1.2.2.2 or greater.

在 3.6 版被加入.

zlib.Z_TREES

Flush mode 6, for inflate operations. Instructs inflate to return when it gets to the next deflate block boundary.

This constant is only available if Python was compiled with zlib 1.2.3.4 or greater.

在 3.6 版被加入.

有關正在使用的 zlib 函式庫版本資訊可透過以下常數獲得：

zlib.ZLIB_VERSION

用於建置模組的 zlib 函式庫版本字串。這可能與實際在執行環境 (runtime) 使用的 zlib 函式庫不同，後者以 ZLIB_RUNTIME_VERSION 提供。

zlib.ZLIB_RUNTIME_VERSION

直譯器實際載入的 zlib 函式庫版本字串。

在 3.3 版被加入.

zlib.ZLIBNG_VERSION

The version string of the zlib-ng library that was used for building the module if zlib-ng was used. When present, the ZLIB_VERSION and ZLIB_RUNTIME_VERSION constants reflect the version of the zlib API provided by zlib-ng.

If zlib-ng was not used to build the module, this constant will be absent.

在 3.14 版被加入.

也參考

gzip 模組

讀寫 gzip 格式的檔案。

https://www.zlib.net

zlib 函式庫首頁。

https://www.zlib.net/manual.html

zlib 手冊解釋了函式庫中許多函式的語義和用法。

In case gzip (de)compression is a bottleneck, the python-isal [https://github.com/pycompression/python-isal] package speeds up (de)compression with a mostly compatible API.

gzip --- gzip 檔案的支援

原始碼：Lib/gzip.py [https://github.com/python/cpython/tree/3.14/Lib/gzip.py]

This module provides a simple interface to compress and decompress files just like the GNU programs gzip and gunzip would.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

The data compression is provided by the zlib module.

The gzip module provides the GzipFile class, as well as the open(), compress() and decompress() convenience functions. The GzipFile class reads and writes gzip-format files, automatically compressing or decompressing the data so that it looks like an ordinary file object.

Note that additional file formats which can be decompressed by the gzip and gunzip programs, such as those produced by compress and pack, are not supported by this module.

此模組定義了以下項目：

gzip.open(filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)

Open a gzip-compressed file in binary or text mode, returning a file object.

The filename argument can be an actual filename (a str or bytes object), or an existing file object to read from or write to.

The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', 'wb', 'x' or 'xb' for binary mode, or 'rt', 'at', 'wt', or 'xt' for text mode. The default is 'rb'.

The compresslevel argument is an integer from 0 to 9, as for the GzipFile constructor.

For binary mode, this function is equivalent to the GzipFile constructor: GzipFile(filename, mode, compresslevel). In this case, the encoding, errors and newline arguments must not be provided.

For text mode, a GzipFile object is created, and wrapped in an io.TextIOWrapper instance with the specified encoding, error handling behavior, and line ending(s).

在 3.3 版的變更: Added support for filename being a file object, support for text mode, and the encoding, errors and newline arguments.

在 3.4 版的變更: 新增 'x'、'xb' 和 'xt' 模式的支援。

在 3.6 版的變更: 接受類路徑物件。

exception gzip.BadGzipFile

An exception raised for invalid gzip files. It inherits from OSError. EOFError and zlib.error can also be raised for invalid gzip files.

在 3.8 版被加入.

class gzip.GzipFile(filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None)

Constructor for the GzipFile class, which simulates most of the methods of a file object, with the exception of the truncate() method. At least one of fileobj and filename must be given a non-trivial value.

The new class instance is based on fileobj, which can be a regular file, an io.BytesIO object, or any other object which simulates a file. It defaults to None, in which case filename is opened to provide a file object.

When fileobj is not None, the filename argument is only used to be included in the gzip file header, which may include the original filename of the uncompressed file. It defaults to the filename of fileobj, if discernible; otherwise, it defaults to the empty string, and in this case the original filename is not included in the header.

The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', 'wb', 'x', or 'xb', depending on whether the file will be read or written. The default is the mode of fileobj if discernible; otherwise, the default is 'rb'. In future Python releases the mode of fileobj will not be used. It is better to always specify mode for writing.

Note that the file is always opened in binary mode. To open a compressed file in text mode, use open() (or wrap your GzipFile with an io.TextIOWrapper).

The compresslevel argument is an integer from 0 to 9 controlling the level of compression; 1 is fastest and produces the least compression, and 9 is slowest and produces the most compression. 0 is no compression. The default is 9.

The optional mtime argument is the timestamp requested by gzip. The time is in Unix format, i.e., seconds since 00:00:00 UTC, January 1, 1970. If mtime is omitted or None, the current time is used. Use mtime = 0 to generate a compressed stream that does not depend on creation time.

See below for the mtime attribute that is set when decompressing.

Calling a GzipFile object's close() method does not close fileobj, since you might wish to append more material after the compressed data. This also allows you to pass an io.BytesIO object opened for writing as fileobj, and retrieve the resulting memory buffer using the io.BytesIO object's getvalue() method.

GzipFile supports the io.BufferedIOBase interface, including iteration and the with statement. Only the truncate() method isn't implemented.

GzipFile 也提供了以下的方法和屬性：

peek(n)

Read n uncompressed bytes without advancing the file position. The number of bytes returned may be more or less than requested.

備註

While calling peek() does not change the file position of the GzipFile, it may change the position of the underlying file object (e.g. if the GzipFile was constructed with the fileobj parameter).

在 3.2 版被加入.

mode

'rb' 用於讀取、'wb' 用於寫入。

在 3.13 版的變更: 在先前版本中它是整數 1 或 2。

mtime

When decompressing, this attribute is set to the last timestamp in the most recently read header. It is an integer, holding the number of seconds since the Unix epoch (00:00:00 UTC, January 1, 1970). The initial value before reading any headers is None.

name

The path to the gzip file on disk, as a str or bytes. Equivalent to the output of os.fspath() on the original input path, with no other normalization, resolution or expansion.

在 3.1 版的變更: Support for the with statement was added, along with the mtime constructor argument and mtime attribute.

在 3.2 版的變更: Support for zero-padded and unseekable files was added.

在 3.3 版的變更: io.BufferedIOBase.read1() 方法現在已有實作。

在 3.4 版的變更: 新增 'x' 和 'xb' 模式的支援。

在 3.5 版的變更: Added support for writing arbitrary bytes-like objects. The read() method now accepts an argument of None.

在 3.6 版的變更: 接受類路徑物件。

在 3.9 版之後被棄用: Opening GzipFile for writing without specifying the mode argument is deprecated.

在 3.12 版的變更: Remove the filename attribute, use the name attribute instead.

gzip.compress(data, compresslevel=9, *, mtime=0)

Compress the data, returning a bytes object containing the compressed data. compresslevel and mtime have the same meaning as in the GzipFile constructor above, but mtime defaults to 0 for reproducible output.

在 3.2 版被加入.

在 3.8 版的變更: Added the mtime parameter for reproducible output.

在 3.11 版的變更: Speed is improved by compressing all data at once instead of in a streamed fashion. Calls with mtime set to 0 are delegated to zlib.compress() for better speed. In this situation the output may contain a gzip header "OS" byte value other than 255 "unknown" as supplied by the underlying zlib implementation.

在 3.13 版的變更: The gzip header OS byte is guaranteed to be set to 255 when this function is used as was the case in 3.10 and earlier.

在 3.14 版的變更: The mtime parameter now defaults to 0 for reproducible output. For the previous behaviour of using the current time, pass None to mtime.

gzip.decompress(data)

Decompress the data, returning a bytes object containing the uncompressed data. This function is capable of decompressing multi-member gzip data (multiple gzip blocks concatenated together). When the data is certain to contain only one member the zlib.decompress() function with wbits set to 31 is faster.

在 3.2 版被加入.

在 3.11 版的變更: Speed is improved by decompressing members at once in memory instead of in a streamed fashion.

用法範例

如何讀取壓縮檔案的範例：

import gzip
with gzip.open('/home/joe/file.txt.gz', 'rb') as f:
    file_content = f.read()

如何建立一個壓縮的 GZIP 檔案的範例：

import gzip
content = b"Lots of content here"
with gzip.open('/home/joe/file.txt.gz', 'wb') as f:
    f.write(content)

如何壓縮一個已存在的檔案的範例：

import gzip
import shutil
with open('/home/joe/file.txt', 'rb') as f_in:
    with gzip.open('/home/joe/file.txt.gz', 'wb') as f_out:
        shutil.copyfileobj(f_in, f_out)

如何壓縮一個二進位字串的範例：

import gzip
s_in = b"Lots of content here"
s_out = gzip.compress(s_in)

也參考

zlib 模組

The basic data compression module needed to support the gzip file format.

In case gzip (de)compression is a bottleneck, the python-isal [https://github.com/pycompression/python-isal] package speeds up (de)compression with a mostly compatible API.

命令列介面

The gzip module provides a simple command line interface to compress or decompress files.

Once executed the gzip module keeps the input file(s).

在 3.8 版的變更: Add a new command line interface with a usage. By default, when you will execute the CLI, the default compression level is 6.

命令列選項

file

如果未指定 file，則從 sys.stdin 讀取。

--fast

Indicates the fastest compression method (less compression).

--best

Indicates the slowest compression method (best compression).

-d, --decompress

解壓縮指定的檔案。

-h, --help

顯示幫助訊息。

bz2 --- bzip2 壓縮的支援

原始碼：Lib/bz2.py [https://github.com/python/cpython/tree/3.14/Lib/bz2.py]

This module provides a comprehensive interface for compressing and decompressing data using the bzip2 compression algorithm.

bz2 模組包含：

The open() function and BZ2File class for reading and writing compressed files.

The BZ2Compressor and BZ2Decompressor classes for incremental (de)compression.

The compress() and decompress() functions for one-shot (de)compression.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

(De)compression of files

bz2.open(filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)

Open a bzip2-compressed file in binary or text mode, returning a file object.

As with the constructor for BZ2File, the filename argument can be an actual filename (a str or bytes object), or an existing file object to read from or write to.

The mode argument can be any of 'r', 'rb', 'w', 'wb', 'x', 'xb', 'a' or 'ab' for binary mode, or 'rt', 'wt', 'xt', or 'at' for text mode. The default is 'rb'.

The compresslevel argument is an integer from 1 to 9, as for the BZ2File constructor.

For binary mode, this function is equivalent to the BZ2File constructor: BZ2File(filename, mode, compresslevel=compresslevel). In this case, the encoding, errors and newline arguments must not be provided.

For text mode, a BZ2File object is created, and wrapped in an io.TextIOWrapper instance with the specified encoding, error handling behavior, and line ending(s).

在 3.3 版被加入.

在 3.4 版的變更: The 'x' (exclusive creation) mode was added.

在 3.6 版的變更: Accepts a path-like object.

class bz2.BZ2File(filename, mode='r', *, compresslevel=9)

Open a bzip2-compressed file in binary mode.

If filename is a str or bytes object, open the named file directly. Otherwise, filename should be a file object, which will be used to read or write the compressed data.

The mode argument can be either 'r' for reading (default), 'w' for overwriting, 'x' for exclusive creation, or 'a' for appending. These can equivalently be given as 'rb', 'wb', 'xb' and 'ab' respectively.

If filename is a file object (rather than an actual file name), a mode of 'w' does not truncate the file, and is instead equivalent to 'a'.

If mode is 'w' or 'a', compresslevel can be an integer between 1 and 9 specifying the level of compression: 1 produces the least compression, and 9 (default) produces the most compression.

If mode is 'r', the input file may be the concatenation of multiple compressed streams.

BZ2File provides all of the members specified by the io.BufferedIOBase, except for detach() and truncate(). Iteration and the with statement are supported.

BZ2File 也提供了以下方法和屬性：

peek([n])

Return buffered data without advancing the file position. At least one byte of data will be returned (unless at EOF). The exact number of bytes returned is unspecified.

備註

While calling peek() does not change the file position of the BZ2File, it may change the position of the underlying file object (e.g. if the BZ2File was constructed by passing a file object for filename).

在 3.3 版被加入.

fileno()

Return the file descriptor for the underlying file.

在 3.3 版被加入.

readable()

Return whether the file was opened for reading.

在 3.3 版被加入.

seekable()

Return whether the file supports seeking.

在 3.3 版被加入.

writable()

Return whether the file was opened for writing.

在 3.3 版被加入.

read1(size=-1)

Read up to size uncompressed bytes, while trying to avoid making multiple reads from the underlying stream. Reads up to a buffer's worth of data if size is negative.

Returns b'' if the file is at EOF.

在 3.3 版被加入.

readinto(b)

Read bytes into b.

Returns the number of bytes read (0 for EOF).

在 3.3 版被加入.

mode

'rb' for reading and 'wb' for writing.

在 3.13 版被加入.

name

The bzip2 file name. Equivalent to the name attribute of the underlying file object.

在 3.13 版被加入.

在 3.1 版的變更: Support for the with statement was added.

在 3.3 版的變更: Support was added for filename being a file object instead of an actual filename.

The 'a' (append) mode was added, along with support for reading multi-stream files.

在 3.4 版的變更: The 'x' (exclusive creation) mode was added.

在 3.5 版的變更: The read() method now accepts an argument of None.

在 3.6 版的變更: Accepts a path-like object.

在 3.9 版的變更: The buffering parameter has been removed. It was ignored and deprecated since Python 3.0. Pass an open file object to control how the file is opened.

The compresslevel parameter became keyword-only.

在 3.10 版的變更: This class is thread unsafe in the face of multiple simultaneous readers or writers, just like its equivalent classes in gzip and lzma have always been.

Incremental (de)compression

class bz2.BZ2Compressor(compresslevel=9)

Create a new compressor object. This object may be used to compress data incrementally. For one-shot compression, use the compress() function instead.

compresslevel, if given, must be an integer between 1 and 9. The default is 9.

compress(data)

Provide data to the compressor object. Returns a chunk of compressed data if possible, or an empty byte string otherwise.

When you have finished providing data to the compressor, call the flush() method to finish the compression process.

flush()

Finish the compression process. Returns the compressed data left in internal buffers.

The compressor object may not be used after this method has been called.

class bz2.BZ2Decompressor

Create a new decompressor object. This object may be used to decompress data incrementally. For one-shot compression, use the decompress() function instead.

備註

This class does not transparently handle inputs containing multiple compressed streams, unlike decompress() and BZ2File. If you need to decompress a multi-stream input with BZ2Decompressor, you must use a new decompressor for each stream.

decompress(data, max_length=-1)

Decompress data (a bytes-like object), returning uncompressed data as bytes. Some of data may be buffered internally, for use in later calls to decompress(). The returned data should be concatenated with the output of any previous calls to decompress().

If max_length is nonnegative, returns at most max_length bytes of decompressed data. If this limit is reached and further output can be produced, the needs_input attribute will be set to False. In this case, the next call to decompress() may provide data as b'' to obtain more of the output.

If all of the input data was decompressed and returned (either because this was less than max_length bytes, or because max_length was negative), the needs_input attribute will be set to True.

Attempting to decompress data after the end of stream is reached raises an EOFError. Any data found after the end of the stream is ignored and saved in the unused_data attribute.

在 3.5 版的變更: 新增 max_length 參數。

eof

True if the end-of-stream marker has been reached.

在 3.3 版被加入.

unused_data

Data found after the end of the compressed stream.

If this attribute is accessed before the end of the stream has been reached, its value will be b''.

needs_input

False if the decompress() method can provide more decompressed data before requiring new uncompressed input.

在 3.5 版被加入.

One-shot (de)compression

bz2.compress(data, compresslevel=9)

Compress data, a bytes-like object.

compresslevel, if given, must be an integer between 1 and 9. The default is 9.

For incremental compression, use a BZ2Compressor instead.

bz2.decompress(data)

Decompress data, a bytes-like object.

If data is the concatenation of multiple compressed streams, decompress all of the streams.

For incremental decompression, use a BZ2Decompressor instead.

在 3.3 版的變更: Support for multi-stream inputs was added.

用法範例

Below are some examples of typical usage of the bz2 module.

Using compress() and decompress() to demonstrate round-trip compression:

>>> import bz2
>>> data = b"""\
... Donec rhoncus quis sapien sit amet molestie. Fusce scelerisque vel augue
... nec ullamcorper. Nam rutrum pretium placerat. Aliquam vel tristique lorem,
... sit amet cursus ante. In interdum laoreet mi, sit amet ultrices purus
... pulvinar a. Nam gravida euismod magna, non varius justo tincidunt feugiat.
... Aliquam pharetra lacus non risus vehicula rutrum. Maecenas aliquam leo
... felis. Pellentesque semper nunc sit amet nibh ullamcorper, ac elementum
... dolor luctus. Curabitur lacinia mi ornare consectetur vestibulum."""
>>> c = bz2.compress(data)
>>> len(data) / len(c)  # Data compression ratio
1.513595166163142
>>> d = bz2.decompress(c)
>>> data == d  # Check equality to original object after round-trip
True

Using BZ2Compressor for incremental compression:

>>> import bz2
>>> def gen_data(chunks=10, chunksize=1000):
...     """Yield incremental blocks of chunksize bytes."""
...     for _ in range(chunks):
...         yield b"z" * chunksize
...
>>> comp = bz2.BZ2Compressor()
>>> out = b""
>>> for chunk in gen_data():
...     # Provide data to the compressor object
...     out = out + comp.compress(chunk)
...
>>> # Finish the compression process.  Call this once you have
>>> # finished providing data to the compressor.
>>> out = out + comp.flush()

The example above uses a very "nonrandom" stream of data (a stream of b"z" chunks). Random data tends to compress poorly, while ordered, repetitive data usually yields a high compression ratio.

Writing and reading a bzip2-compressed file in binary mode:

>>> import bz2
>>> data = b"""\
... Donec rhoncus quis sapien sit amet molestie. Fusce scelerisque vel augue
... nec ullamcorper. Nam rutrum pretium placerat. Aliquam vel tristique lorem,
... sit amet cursus ante. In interdum laoreet mi, sit amet ultrices purus
... pulvinar a. Nam gravida euismod magna, non varius justo tincidunt feugiat.
... Aliquam pharetra lacus non risus vehicula rutrum. Maecenas aliquam leo
... felis. Pellentesque semper nunc sit amet nibh ullamcorper, ac elementum
... dolor luctus. Curabitur lacinia mi ornare consectetur vestibulum."""
>>> with bz2.open("myfile.bz2", "wb") as f:
...     # Write compressed data to file
...     unused = f.write(data)
...
>>> with bz2.open("myfile.bz2", "rb") as f:
...     # Decompress data from file
...     content = f.read()
...
>>> content == data  # Check equality to original object after round-trip
True

lzma --- 使用 LZMA 演算法進行壓縮

在 3.3 版被加入.

原始碼：Lib/lzma.py [https://github.com/python/cpython/tree/3.14/Lib/lzma.py]

This module provides classes and convenience functions for compressing and decompressing data using the LZMA compression algorithm. Also included is a file interface supporting the .xz and legacy .lzma file formats used by the xz utility, as well as raw compressed streams.

The interface provided by this module is very similar to that of the bz2 module. Note that LZMAFile and bz2.BZ2File are not thread-safe, so if you need to use a single LZMAFile instance from multiple threads, it is necessary to protect it with a lock.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

exception lzma.LZMAError

This exception is raised when an error occurs during compression or decompression, or while initializing the compressor/decompressor state.

Reading and writing compressed files

lzma.open(filename, mode='rb', *, format=None, check=-1, preset=None, filters=None, encoding=None, errors=None, newline=None)

Open an LZMA-compressed file in binary or text mode, returning a file object.

The filename argument can be either an actual file name (given as a str, bytes or path-like object), in which case the named file is opened, or it can be an existing file object to read from or write to.

The mode argument can be any of "r", "rb", "w", "wb", "x", "xb", "a" or "ab" for binary mode, or "rt", "wt", "xt", or "at" for text mode. The default is "rb".

When opening a file for reading, the format and filters arguments have the same meanings as for LZMADecompressor. In this case, the check and preset arguments should not be used.

When opening a file for writing, the format, check, preset and filters arguments have the same meanings as for LZMACompressor.

For binary mode, this function is equivalent to the LZMAFile constructor: LZMAFile(filename, mode, ...). In this case, the encoding, errors and newline arguments must not be provided.

For text mode, a LZMAFile object is created, and wrapped in an io.TextIOWrapper instance with the specified encoding, error handling behavior, and line ending(s).

在 3.4 版的變更: 新增 "x"、"xb" 和 "xt" 模式的支援。

在 3.6 版的變更: Accepts a path-like object.

class lzma.LZMAFile(filename=None, mode='r', *, format=None, check=-1, preset=None, filters=None)

Open an LZMA-compressed file in binary mode.

An LZMAFile can wrap an already-open file object, or operate directly on a named file. The filename argument specifies either the file object to wrap, or the name of the file to open (as a str, bytes or path-like object). When wrapping an existing file object, the wrapped file will not be closed when the LZMAFile is closed.

The mode argument can be either "r" for reading (default), "w" for overwriting, "x" for exclusive creation, or "a" for appending. These can equivalently be given as "rb", "wb", "xb" and "ab" respectively.

If filename is a file object (rather than an actual file name), a mode of "w" does not truncate the file, and is instead equivalent to "a".

When opening a file for reading, the input file may be the concatenation of multiple separate compressed streams. These are transparently decoded as a single logical stream.

When opening a file for reading, the format and filters arguments have the same meanings as for LZMADecompressor. In this case, the check and preset arguments should not be used.

When opening a file for writing, the format, check, preset and filters arguments have the same meanings as for LZMACompressor.

LZMAFile supports all the members specified by io.BufferedIOBase, except for detach() and truncate(). Iteration and the with statement are supported.

The following method and attributes are also provided:

peek(size=-1)

Return buffered data without advancing the file position. At least one byte of data will be returned, unless EOF has been reached. The exact number of bytes returned is unspecified (the size argument is ignored).

備註

While calling peek() does not change the file position of the LZMAFile, it may change the position of the underlying file object (e.g. if the LZMAFile was constructed by passing a file object for filename).

mode

'rb' for reading and 'wb' for writing.

在 3.13 版被加入.

name

The lzma file name. Equivalent to the name attribute of the underlying file object.

在 3.13 版被加入.

在 3.4 版的變更: 新增 "x" 和 "xb" 模式的支援。

在 3.5 版的變更: The read() method now accepts an argument of None.

在 3.6 版的變更: Accepts a path-like object.

Compressing and decompressing data in memory

class lzma.LZMACompressor(format=FORMAT_XZ, check=-1, preset=None, filters=None)

Create a compressor object, which can be used to compress data incrementally.

For a more convenient way of compressing a single chunk of data, see compress().

The format argument specifies what container format should be used. Possible values are:

FORMAT_XZ: The .xz container format.

This is the default format.

FORMAT_ALONE: The legacy .lzma container format.

This format is more limited than .xz -- it does not support integrity checks or multiple filters.

FORMAT_RAW: A raw data stream, not using any container format.

This format specifier does not support integrity checks, and requires that you always specify a custom filter chain (for both compression and decompression). Additionally, data compressed in this manner cannot be decompressed using FORMAT_AUTO (see LZMADecompressor).

The check argument specifies the type of integrity check to include in the compressed data. This check is used when decompressing, to ensure that the data has not been corrupted. Possible values are:

CHECK_NONE: No integrity check. This is the default (and the only acceptable value) for FORMAT_ALONE and FORMAT_RAW.

CHECK_CRC32: 32-bit Cyclic Redundancy Check.

CHECK_CRC64: 64-bit Cyclic Redundancy Check. This is the default for FORMAT_XZ.

CHECK_SHA256: 256-bit Secure Hash Algorithm.

If the specified check is not supported, an LZMAError is raised.

The compression settings can be specified either as a preset compression level (with the preset argument), or in detail as a custom filter chain (with the filters argument).

The preset argument (if provided) should be an integer between 0 and 9 (inclusive), optionally OR-ed with the constant PRESET_EXTREME. If neither preset nor filters are given, the default behavior is to use PRESET_DEFAULT (preset level 6). Higher presets produce smaller output, but make the compression process slower.

備註

In addition to being more CPU-intensive, compression with higher presets also requires much more memory (and produces output that needs more memory to decompress). With preset 9 for example, the overhead for an LZMACompressor object can be as high as 800 MiB. For this reason, it is generally best to stick with the default preset.

The filters argument (if provided) should be a filter chain specifier. See Specifying custom filter chains for details.

compress(data)

Compress data (a bytes object), returning a bytes object containing compressed data for at least part of the input. Some of data may be buffered internally, for use in later calls to compress() and flush(). The returned data should be concatenated with the output of any previous calls to compress().

flush()

Finish the compression process, returning a bytes object containing any data stored in the compressor's internal buffers.

The compressor cannot be used after this method has been called.

class lzma.LZMADecompressor(format=FORMAT_AUTO, memlimit=None, filters=None)

Create a decompressor object, which can be used to decompress data incrementally.

For a more convenient way of decompressing an entire compressed stream at once, see decompress().

The format argument specifies the container format that should be used. The default is FORMAT_AUTO, which can decompress both .xz and .lzma files. Other possible values are FORMAT_XZ, FORMAT_ALONE, and FORMAT_RAW.

The memlimit argument specifies a limit (in bytes) on the amount of memory that the decompressor can use. When this argument is used, decompression will fail with an LZMAError if it is not possible to decompress the input within the given memory limit.

The filters argument specifies the filter chain that was used to create the stream being decompressed. This argument is required if format is FORMAT_RAW, but should not be used for other formats. See Specifying custom filter chains for more information about filter chains.

備註

This class does not transparently handle inputs containing multiple compressed streams, unlike decompress() and LZMAFile. To decompress a multi-stream input with LZMADecompressor, you must create a new decompressor for each stream.

decompress(data, max_length=-1)

Decompress data (a bytes-like object), returning uncompressed data as bytes. Some of data may be buffered internally, for use in later calls to decompress(). The returned data should be concatenated with the output of any previous calls to decompress().

If max_length is nonnegative, returns at most max_length bytes of decompressed data. If this limit is reached and further output can be produced, the needs_input attribute will be set to False. In this case, the next call to decompress() may provide data as b'' to obtain more of the output.

If all of the input data was decompressed and returned (either because this was less than max_length bytes, or because max_length was negative), the needs_input attribute will be set to True.

Attempting to decompress data after the end of stream is reached raises an EOFError. Any data found after the end of the stream is ignored and saved in the unused_data attribute.

在 3.5 版的變更: 新增 max_length 參數。

check

The ID of the integrity check used by the input stream. This may be CHECK_UNKNOWN until enough of the input has been decoded to determine what integrity check it uses.

eof

True if the end-of-stream marker has been reached.

unused_data

Data found after the end of the compressed stream.

Before the end of the stream is reached, this will be b"".

needs_input

False if the decompress() method can provide more decompressed data before requiring new uncompressed input.

在 3.5 版被加入.

lzma.compress(data, format=FORMAT_XZ, check=-1, preset=None, filters=None)

Compress data (a bytes object), returning the compressed data as a bytes object.

See LZMACompressor above for a description of the format, check, preset and filters arguments.

lzma.decompress(data, format=FORMAT_AUTO, memlimit=None, filters=None)

Decompress data (a bytes object), returning the uncompressed data as a bytes object.

If data is the concatenation of multiple distinct compressed streams, decompress all of these streams, and return the concatenation of the results.

See LZMADecompressor above for a description of the format, memlimit and filters arguments.

Miscellaneous

lzma.is_check_supported(check)

Return True if the given integrity check is supported on this system.

CHECK_NONE and CHECK_CRC32 are always supported. CHECK_CRC64 and CHECK_SHA256 may be unavailable if you are using a version of liblzma that was compiled with a limited feature set.

Specifying custom filter chains

A filter chain specifier is a sequence of dictionaries, where each dictionary contains the ID and options for a single filter. Each dictionary must contain the key "id", and may contain additional keys to specify filter-dependent options. Valid filter IDs are as follows:

Compression filters:

FILTER_LZMA1 (for use with FORMAT_ALONE)

FILTER_LZMA2 (for use with FORMAT_XZ and FORMAT_RAW)

Delta filter:

FILTER_DELTA

Branch-Call-Jump (BCJ) filters:

FILTER_X86

FILTER_IA64

FILTER_ARM

FILTER_ARMTHUMB

FILTER_POWERPC

FILTER_SPARC

A filter chain can consist of up to 4 filters, and cannot be empty. The last filter in the chain must be a compression filter, and any other filters must be delta or BCJ filters.

Compression filters support the following options (specified as additional entries in the dictionary representing the filter):

preset: A compression preset to use as a source of default values for options that are not specified explicitly.

dict_size: Dictionary size in bytes. This should be between 4 KiB and 1.5 GiB (inclusive).

lc: Number of literal context bits.

lp: Number of literal position bits. The sum lc + lp must be at most 4.

pb: Number of position bits; must be at most 4.

mode: MODE_FAST or MODE_NORMAL.

nice_len: What should be considered a "nice length" for a match. This should be 273 or less.

mf: What match finder to use -- MF_HC3, MF_HC4, MF_BT2, MF_BT3, or MF_BT4.

depth: Maximum search depth used by match finder. 0 (default) means to select automatically based on other filter options.

The delta filter stores the differences between bytes, producing more repetitive input for the compressor in certain circumstances. It supports one option, dist. This indicates the distance between bytes to be subtracted. The default is 1, i.e. take the differences between adjacent bytes.

The BCJ filters are intended to be applied to machine code. They convert relative branches, calls and jumps in the code to use absolute addressing, with the aim of increasing the redundancy that can be exploited by the compressor. These filters support one option, start_offset. This specifies the address that should be mapped to the beginning of the input data. The default is 0.

範例

Reading in a compressed file:

import lzma
with lzma.open("file.xz") as f:
    file_content = f.read()

Creating a compressed file:

import lzma
data = b"Insert Data Here"
with lzma.open("file.xz", "w") as f:
    f.write(data)

Compressing data in memory:

import lzma
data_in = b"Insert Data Here"
data_out = lzma.compress(data_in)

Incremental compression:

import lzma
lzc = lzma.LZMACompressor()
out1 = lzc.compress(b"Some data\n")
out2 = lzc.compress(b"Another piece of data\n")
out3 = lzc.compress(b"Even more data\n")
out4 = lzc.flush()
# Concatenate all the partial results:
result = b"".join([out1, out2, out3, out4])

Writing compressed data to an already-open file:

import lzma
with open("file.xz", "wb") as f:
    f.write(b"This data will not be compressed\n")
    with lzma.open(f, "w") as lzf:
        lzf.write(b"This *will* be compressed\n")
    f.write(b"Not compressed\n")

Creating a compressed file using a custom filter chain:

import lzma
my_filters = [
    {"id": lzma.FILTER_DELTA, "dist": 5},
    {"id": lzma.FILTER_LZMA2, "preset": 7 | lzma.PRESET_EXTREME},
]
with lzma.open("file.xz", "w", filters=my_filters) as f:
    f.write(b"blah blah blah")

zipfile --- 處理 ZIP 封存檔案

原始碼：Lib/zipfile/ [https://github.com/python/cpython/tree/3.14/Lib/zipfile/]

ZIP 檔案格式是一種常見的封存 (archive) 與壓縮標準。本模組提供了建立、讀取、寫入、附加與列出 ZIP 檔案的工具。任何對本模組的進階使用都將需要對 PKZIP Application Note [https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT] 中定義的格式有所理解。

本模組不處理多組件 (multipart) ZIP 檔案。它可以處理使用 ZIP64 擴充（即大於 4 GiB 的 ZIP 檔案）的 ZIP 檔案。它支援解密 ZIP 封存檔案中的加密檔案，但目前無法建立加密檔案。解密速度極慢，因為它是在原生 Python 中實作，而不是 C。

Handling compressed archives requires optional modules such as zlib, bz2, lzma, and compression.zstd. If any of them are missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

本模組定義了以下項目：

exception zipfile.BadZipFile

對於損壞的 ZIP 檔案所引發的錯誤。

在 3.2 版被加入.

exception zipfile.BadZipfile

BadZipFile 的別名，為了與舊版 Python 相容。

在 3.2 版之後被棄用.

exception zipfile.LargeZipFile

當 ZIP 檔案需要 ZIP64 功能但該功能未被啟用時所引發的錯誤。

class zipfile.ZipFile

用於讀取和寫入 ZIP 檔案的類別。有關建構函式的詳細資訊，請參閱 ZipFile 物件 章節。

class zipfile.Path

實作了 pathlib.Path 所提供介面子集的類別，包括完整的 importlib.resources.abc.Traversable 介面。

在 3.8 版被加入.

class zipfile.PyZipFile

用於建立包含 Python 函式庫的 ZIP 封存檔案的類別。

class zipfile.ZipInfo(filename='NoName', date_time=(1980, 1, 1, 0, 0, 0))

用於表示封存檔案中成員資訊的類別。此類別的實例由 ZipFile 物件的 getinfo() 和 infolist() 方法回傳。大多數 zipfile 模組的使用者不需要建立這些實例，而只需使用本模組所建立的。filename 應為封存成員的完整名稱，而 date_time 應為一個包含六個欄位的元組，用以描述檔案的最後修改時間；這些欄位在 ZipInfo 物件 章節中有所描述。

在 3.13 版的變更: 新增了一個公開的 compress_level 屬性，以公開先前受保護的 _compresslevel。為了向後相容，舊的受保護名稱仍可作為一個特性繼續運作。

_for_archive(archive)

Resolve the date_time, compression attributes, and external attributes to suitable defaults as used by ZipFile.writestr().

Returns self for chaining.

在 3.14 版被加入.

zipfile.is_zipfile(filename)

如果 filename 根據其魔術數字（magic number）是一個有效的 ZIP 檔案，則回傳 True，否則回傳 False。filename 也可以是一個檔案或類檔案物件。

在 3.1 版的變更: 支援檔案和類檔案物件。

zipfile.ZIP_STORED

用於未壓縮封存成員的數值常數。

zipfile.ZIP_DEFLATED

用於常用的 ZIP 壓縮方法的數值常數。這需要 zlib 模組。

zipfile.ZIP_BZIP2

用於 BZIP2 壓縮方法的數值常數。這需要 bz2 模組。

在 3.3 版被加入.

zipfile.ZIP_LZMA

用於 LZMA 壓縮方法的數值常數。這需要 lzma 模組。

在 3.3 版被加入.

zipfile.ZIP_ZSTANDARD

用於 Zstandard 壓縮方法的數值常數。這需要 compression.zstd 模組。

備註

In APPNOTE 6.3.7, the method ID 20 was assigned to Zstandard compression. This was changed in APPNOTE 6.3.8 to method ID 93 to avoid conflicts, with method ID 20 being deprecated. For compatibility, the zipfile module reads both method IDs but will only write data with method ID 93.

在 3.14 版被加入.

備註

ZIP 檔案格式規範自 2001 年起已包含對 bzip2 壓縮的支援、自 2006 年起支援 LZMA 壓縮、自 2020 年起支援 Zstandard 壓縮。然而某些工具（包括舊版的 Python）不支援這些壓縮方法，可能會完全拒絕處理該 ZIP 檔案，或無法解壓縮個別檔案。

也參考

PKZIP Application Note [https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT]

由 Phil Katz（該格式與所用演算法的創造者）所撰寫的關於 ZIP 檔案格式的文件。

Info-ZIP 首頁 [https://infozip.sourceforge.net/]

關於 Info-ZIP 專案的 ZIP 封存程式和開發函式庫的資訊。

ZipFile 物件

class zipfile.ZipFile(file, mode='r', compression=ZIP_STORED, allowZip64=True, compresslevel=None, *, strict_timestamps=True, metadata_encoding=None)

開啟一個 ZIP 檔案，其中 file 可以是一個檔案的路徑（一個字串）、一個類檔案物件或一個 path-like object。

mode 參數應為 'r' 來讀取一個現有檔案、'w' 來清空並寫入一個新檔案、'a' 來附加到一個現有檔案，或 'x' 來獨佔性地建立並寫入一個新檔案。如果 mode 為 'x' 且 file 指向一個現有檔案，將會引發 FileExistsError。如果 mode 為 'a' 且 file 指向一個現有的 ZIP 檔案，則會將額外的檔案加入其中。如果 file 並非指向一個 ZIP 檔案，則一個新的 ZIP 封存檔案會被附加到該檔案之後。這適用於將一個 ZIP 封存檔案附加到另一個檔案（例如 python.exe）。如果 mode 為 'a' 且檔案完全不存在，它會被建立。如果 mode 為 'r' 或 'a'，該檔案應為可定位的 (seekable)。

compression 是寫入封存檔案時要使用的 ZIP 壓縮方法，應為 ZIP_STORED、ZIP_DEFLATED、ZIP_BZIP2、ZIP_LZMA 或 ZIP_ZSTANDARD；無法識別的值將導致引發 NotImplementedError。如果指定了 ZIP_DEFLATED、ZIP_BZIP2、ZIP_LZMA 或 ZIP_ZSTANDARD，但對應的模組（zlib、bz2、lzma 或 compression.zstd）不可用，則會引發 RuntimeError。預設為 ZIP_STORED。

如果 allowZip64 為 True（預設值），當 zipfile 大於 4 GiB 時，zipfile 將會建立使用 ZIP64 擴充的 ZIP 檔案。如果為 false，當 ZIP 檔案需要 ZIP64 擴充時，zipfile 將會引發一個例外。

compresslevel 參數控制寫入檔案到封存時使用的壓縮層級。當使用 ZIP_STORED 或 ZIP_LZMA 時，它沒有效果。當使用 ZIP_DEFLATED 時，接受整數 0 到 9（更多資訊請參閱 zlib）。當使用 ZIP_BZIP2 時，接受整數 1 到 9（更多資訊請參閱 bz2）。當使用 ZIP_ZSTANDARD 時，通常接受整數 -131072 到 22（更多關於檢索有效值及其含義，請參閱 CompressionParameter.compression_level）。

strict_timestamps 引數，當設為 False 時，允許壓縮早於 1980-01-01 的檔案，代價是將時間戳記設為 1980-01-01。對於晚於 2107-12-31 的檔案，也會有類似的行為，時間戳記同樣會被設為極限值。

當 mode 為 'r' 時，metadata_encoding 可以設為一個編解碼器的名稱，該編解碼器將被用來解碼元資料，例如成員名稱和 ZIP 註解。

如果檔案以 'w'、'x' 或 'a' 模式建立，然後在沒有向封存檔案中加入任何檔案的情況下 關閉，則適用於空封存檔案的 ZIP 結構將被寫入檔案中。

ZipFile 也是一個情境管理器，因此支援 with 陳述式。在範例中，myzip 在 with 陳述式的程式碼區塊執行完畢後會被關閉 --- 即使發生例外也是如此：

with ZipFile('spam.zip', 'w') as myzip:
    myzip.write('eggs.txt')

備註

metadata_encoding 是 ZipFile 的一個實例範圍設定。無法以每個成員為基礎來設定此項。

此屬性是針對舊版實作的變通方法，這些實作會以目前區域編碼或頁碼（主要在 Windows 上）產生帶有名稱的封存檔案。根據 .ZIP 標準，元資料的編碼可以透過封存檔案標頭中的一個旗標指定為 IBM 頁碼（預設）或 UTF-8。該旗標的優先級高於 metadata_encoding，後者是 Python 特有的擴充。

在 3.2 版的變更: 新增 ZipFile 作為情境管理器使用的能力。

在 3.3 版的變更: 新增對於 bzip2 和 lzma 壓縮的支援。

在 3.4 版的變更: ZIP64 擴充預設為啟用。

在 3.5 版的變更: 新增了對寫入不可定位的 (unseekable) 串流的支援。新增了對 'x' 模式的支援。

在 3.6 版的變更: 先前，對於無法識別的壓縮值，會引發一個單純的 RuntimeError。

在 3.6.2 版的變更: file 參數接受一個 path-like object。

在 3.7 版的變更: 新增 compresslevel 參數。

在 3.8 版的變更: strict_timestamps 僅限關鍵字參數。

在 3.11 版的變更: 新增了在讀取 zipfile 目錄和檔案標頭中的元資料時，可指定成員名稱編碼的支援。

ZipFile.close()

關閉封存檔案。你必須在結束程式前呼叫 close()，否則必要的記錄將不會被寫入。

ZipFile.getinfo(name)

回傳一個帶有關於封存成員 name 資訊的 ZipInfo 物件。對一個目前不包含在封存檔案中的名稱呼叫 getinfo() 將會引發 KeyError。

ZipFile.infolist()

回傳一個串列，其中為每個封存成員包含一個 ZipInfo 物件。如果開啟的是一個現有的封存檔案，這些物件的順序與它們在磁碟上實際 ZIP 檔案中的條目順序相同。

ZipFile.namelist()

依名稱回傳封存成員的串列。

ZipFile.open(name, mode='r', pwd=None, *, force_zip64=False)

以二進位類檔案物件的形式存取封存檔案中的一個成員。name 可以是封存檔案內的檔案名稱，或是一個 ZipInfo 物件。mode 參數如果包含，則必須是 'r'（預設值）或 'w'。pwd 是用於解密加密 ZIP 檔案的密碼，為一個 bytes 物件。

open() 也是一個情境管理器，因此支援 with 陳述式：

with ZipFile('spam.zip') as myzip:
    with myzip.open('eggs.txt') as myfile:
        print(myfile.read())

在 mode 為 'r' 時，該類檔案物件（ZipExtFile）是唯讀的，並提供以下方法：read()、readline()、readlines()、seek()、tell()、__iter__()、__next__()。這些物件可以獨立於 ZipFile 運作。

在 mode='w' 時，會回傳一個可寫的檔案控點 (file handle)，它支援 write() 方法。當一個可寫的檔案控點開啟時，嘗試讀取或寫入 ZIP 檔案中的其他檔案將會引發 ValueError。

在這兩種情況下，該類檔案物件也具有 name 屬性，它相當於封存檔案內的檔案名稱，以及 mode 屬性，其值為 'rb' 或 'wb'，取決於輸入的模式。

寫入檔案時，如果檔案大小預先未知但可能超過 2 GiB，請傳入 force_zip64=True 以確保標頭格式能夠支援大檔案。如果檔案大小預先已知，請建構一個設定了 file_size 的 ZipInfo 物件，並將其用作 name 參數。

備註

open()、read() 和 extract() 方法可以接受一個檔名或一個 ZipInfo 物件。當你嘗試讀取一個包含重複名稱成員的 ZIP 檔案時，你會發現這很有用。

在 3.6 版的變更: 移除了對 mode='U' 的支援。請使用 io.TextIOWrapper 以 universal newlines 模式讀取壓縮的文字檔。

在 3.6 版的變更: ZipFile.open() 現在可以用於以 mode='w' 選項將檔案寫入封存檔案。

在 3.6 版的變更: 在一個已關閉的 ZipFile 上呼叫 open() 將會引發 ValueError。先前，會引發一個 RuntimeError。

在 3.13 版的變更: 為可寫的類檔案物件新增了 name 和 mode 屬性。可讀的類檔案物件的 mode 屬性值從 'r' 變更為 'rb'。

ZipFile.extract(member, path=None, pwd=None)

從封存檔案中解壓縮一個成員到目前工作目錄；member 必須是其完整名稱或一個 ZipInfo 物件。其檔案資訊會被盡可能精確地解壓縮。path 指定一個不同的目錄來解壓縮。member 可以是一個檔名或一個 ZipInfo 物件。pwd 是用於加密檔案的密碼，為一個 bytes 物件。

回傳建立的正規化路徑（一個目錄或新檔案）。

備註

如果成員檔名是絕對路徑，磁碟機/UNC 共享點和開頭的（反）斜線將被移除，例如：在 Unix 上 ///foo/bar 變成 foo/bar，在 Windows 上 C:\foo\bar 變成 foo\bar。並且成員檔名中所有的 ".." 元件將被移除，例如：../../foo../../ba..r 變成 foo../ba..r。在 Windows 上，非法字元（:、<、>、|、"、? 和 *）會被底線（_）取代。

在 3.6 版的變更: 在一個已關閉的 ZipFile 上呼叫 extract() 將會引發 ValueError。先前，會引發一個 RuntimeError。

在 3.6.2 版的變更: path 參數接受一個 path-like object。

ZipFile.extractall(path=None, members=None, pwd=None)

從封存檔案中解壓縮所有成員到目前工作目錄。path 指定一個不同的目錄來解壓縮。members 是可選的，且必須是 namelist() 回傳的串列的子集。pwd 是用於加密檔案的密碼，為一個 bytes 物件。

警告

絕不要在未經事先檢查的情況下，從不受信任的來源解壓縮封存檔案。檔案有可能被建立在 path 之外，例如，成員具有以 "/" 開頭的絕對檔名或帶有兩個點 ".." 的檔名。本模組會試圖防止這種情況。請參閱 extract() 的註解。

在 3.6 版的變更: 在一個已關閉的 ZipFile 上呼叫 extractall() 將會引發 ValueError。先前，會引發一個 RuntimeError。

在 3.6.2 版的變更: path 參數接受一個 path-like object。

ZipFile.printdir()

將封存檔案的內容目錄印出到 sys.stdout。

ZipFile.setpassword(pwd)

設定 pwd（一個 bytes 物件）為解壓縮加密檔案的預設密碼。

ZipFile.read(name, pwd=None)

回傳封存檔案中 name 檔案的位元組。name 是封存檔案中檔案的名稱，或是一個 ZipInfo 物件。封存檔案必須以讀取或附加模式開啟。pwd 是用於加密檔案的密碼，為一個 bytes 物件，如果指定，將會覆寫用 setpassword() 設定的預設密碼。在一個使用 ZIP_STORED、ZIP_DEFLATED、ZIP_BZIP2、ZIP_LZMA 或 ZIP_ZSTANDARD 以外壓縮方法的 ZipFile 上呼叫 read() 將會引發 NotImplementedError。如果對應的壓縮模組不可用，也會引發一個錯誤。

在 3.6 版的變更: 在一個已關閉的 ZipFile 上呼叫 read() 將會引發 ValueError。先前，會引發一個 RuntimeError。

ZipFile.testzip()

讀取封存檔案中的所有檔案，並檢查它們的 CRC 和檔案標頭。回傳第一個損壞檔案的名稱，否則回傳 None。

在 3.6 版的變更: 在一個已關閉的 ZipFile 上呼叫 testzip() 將會引發 ValueError。先前，會引發一個 RuntimeError。

ZipFile.write(filename, arcname=None, compress_type=None, compresslevel=None)

將名為 filename 的檔案寫入封存檔案，並給予它封存名稱 arcname（預設情況下，這將與 filename 相同，但不含磁碟機代號且移除了開頭的路徑分隔符）。如果給定，compress_type 將覆寫為建構函式中 compression 參數為新條目指定的值。同樣地，如果給定 compresslevel，它將覆寫建構函式。封存檔案必須以 'w'、'x' 或 'a' 模式開啟。

備註

ZIP 檔案標準在歷史上並未指定元資料編碼，但為了互通性 (interoperability) 強烈建議使用 CP437（原始的 IBM PC 編碼）。近期的版本允許（僅）使用 UTF-8。在本模組中，如果成員名稱包含任何非 ASCII 字元，將會自動使用 UTF-8 來寫入。無法以 ASCII 或 UTF-8 以外的任何編碼寫入成員名稱。

備註

封存名稱應相對於封存檔案的根目錄，也就是說，它們不應以路徑分隔符開頭。

備註

如果 arcname（或在未給定 arcname 時的 filename）包含一個空位元組，封存檔案中該檔案的名稱將在空位元組處被截斷。

備註

檔名中開頭的斜線可能導致在 Windows 系統上的某些 zip 程式中無法開啟該封存檔案。

在 3.6 版的變更: 在以 'r' 模式建立的 ZipFile 或一個已關閉的 ZipFile 上呼叫 write() 將會引發 ValueError。先前，會引發一個 RuntimeError。

ZipFile.writestr(zinfo_or_arcname, data, compress_type=None, compresslevel=None)

將一個檔案寫入封存檔案。內容為 data，它可以是一個 str 或一個 bytes 實例；如果它是一個 str，它會先被編碼為 UTF-8。zinfo_or_arcname 是它在封存檔案中將被賦予的檔案名稱，或是一個 ZipInfo 實例。如果它是一個實例，則至少必須給定檔名、日期和時間。如果它是一個名稱，則日期和時間被設為目前的日期和時間。封存檔案必須以 'w'、'x' 或 'a' 模式開啟。

如果給定，compress_type 將覆寫為建構函式中 compression 參數為新條目指定的值，或覆寫 zinfo_or_arcname（如果它是一個 ZipInfo 實例）中的值。同樣地，如果給定 compresslevel，它將覆寫建構函式。

備註

當傳遞一個 ZipInfo 實例作為 zinfo_or_arcname 參數時，所使用的壓縮方法將是給定的 ZipInfo 實例的 compress_type 成員中指定的方法。預設情況下，ZipInfo 建構函式將此成員設為 ZIP_STORED。

在 3.2 版的變更: compress_type 引數。

在 3.6 版的變更: 在以 'r' 模式建立的 ZipFile 或一個已關閉的 ZipFile 上呼叫 writestr() 將會引發 ValueError。先前，會引發一個 RuntimeError。

ZipFile.mkdir(zinfo_or_directory, mode=511)

在封存檔案內建立一個目錄。如果 zinfo_or_directory 是一個字串，則會在封存檔案內以 mode 引數中指定的模式建立一個目錄。然而，如果 zinfo_or_directory 是一個 ZipInfo 實例，則 mode 引數會被忽略。

封存檔案必須以 'w'、'x' 或 'a' 模式開啟。

在 3.11 版被加入.

以下資料屬性也可用：

ZipFile.filename

ZIP 檔案的名稱。

ZipFile.debug

要使用的偵錯輸出層級。可以從 0（預設，無輸出）設定到 3（最多輸出）。偵錯資訊會被寫入到 sys.stdout。

ZipFile.comment

與 ZIP 檔案關聯的註解，為一個 bytes 物件。如果為一個以 'w'、'x' 或 'a' 模式建立的 ZipFile 實例指派註解，其長度不應超過 65535 位元組。超過此長度的註解將被截斷。

Path 物件

class zipfile.Path(root, at='')

從一個 root zipfile（它可以是一個 ZipFile 實例或一個適合傳遞給 ZipFile 建構函式的 file）建構一個 Path 物件。

at 指定此 Path 在 zipfile 中的位置，例如 'dir/file.txt'、'dir/' 或 ''。預設為空字串，表示根目錄。

備註

Path 類別不會清理 ZIP 封存檔案內的檔名。與 ZipFile.extract() 和 ZipFile.extractall() 方法不同，呼叫者有責任驗證或清理檔名，以防止路徑遍歷漏洞（例如，包含 ".." 或絕對路徑的檔名）。在處理不受信任的封存檔案時，請考慮使用 os.path.abspath() 解析檔名，並使用 os.path.commonpath() 與目標目錄進行核對。

Path 物件公開了 pathlib.Path 物件的以下特性：

Path 物件可以使用 / 運算子或 joinpath 來遍歷。

Path.name

最後的路徑元件。

Path.open(mode='r', *, pwd, **)

在目前路徑上呼叫 ZipFile.open()。允許透過支援的模式 'r'、'w'、'rb'、'wb' 以讀取或寫入、文字或二進位模式開啟。當以文字模式開啟時，位置引數和關鍵字引數會被傳遞給 io.TextIOWrapper，否則會被忽略。pwd 是傳遞給 ZipFile.open() 的 pwd 參數。

在 3.9 版的變更: 新增了對 open 的文字和二進位模式的支援。預設模式現在是文字模式。

在 3.11.2 版的變更: encoding 參數可以作為位置引數提供，而不會導致 TypeError，就像在 3.9 中一樣。需要與未修補的 3.10 和 3.11 版本相容的程式碼，必須將所有 io.TextIOWrapper 引數，包括 encoding，作為關鍵字傳遞。

Path.iterdir()

列舉目前目錄的子項目。

Path.is_dir()

如果目前情境參照到一個目錄，則回傳 True。

Path.is_file()

如果目前情境參照到一個檔案，則回傳 True。

Path.is_symlink()

如果目前情境參照到一個符號連結，則回傳 True。

在 3.12 版被加入.

在 3.13 版的變更: 先前，is_symlink 會無條件地回傳 False。

Path.exists()

如果目前情境參照到 zip 檔案中的一個檔案或目錄，則回傳 True。

Path.suffix

最後一個元件中以點分隔的最後一部分（如果有的話）。這通常被稱為副檔名。

在 3.11 版被加入: 新增 Path.suffix 特性。

Path.stem

最後的路徑元件，不含其後綴。

在 3.11 版被加入: 新增 Path.stem 特性。

Path.suffixes

路徑的後綴串列，通常稱為副檔名。

在 3.11 版被加入: 新增 Path.suffixes 特性。

Path.read_text(*, **)

將目前檔案讀取為 unicode 文字。位置引數和關鍵字引數會被傳遞給 io.TextIOWrapper（但 buffer 會根據情境隱式處理）。

在 3.11.2 版的變更: encoding 參數可以作為位置引數提供，而不會導致 TypeError，就像在 3.9 中一樣。需要與未修補的 3.10 和 3.11 版本相容的程式碼，必須將所有 io.TextIOWrapper 引數，包括 encoding，作為關鍵字傳遞。

Path.read_bytes()

將目前檔案讀取為位元組。

Path.joinpath(*other)

回傳一個新的 Path 物件，並將每個 other 引數加入。以下是等效的：

>>> Path(...).joinpath('child').joinpath('grandchild')
>>> Path(...).joinpath('child', 'grandchild')
>>> Path(...) / 'child' / 'grandchild'

在 3.10 版的變更: 在 3.10 之前，joinpath 沒有文件記載，且只接受一個參數。

zipp [https://pypi.org/project/zipp/] 專案為舊版 Python 提供了最新的 path 物件功能的向後移植版本。使用 zipp.Path 來取代 zipfile.Path 以提早使用變更。

PyZipFile 物件

PyZipFile 建構函式接受與 ZipFile 建構函式相同的參數，以及一個額外的參數 optimize。

class zipfile.PyZipFile(file, mode='r', compression=ZIP_STORED, allowZip64=True, optimize=-1)

在 3.2 版的變更: 新增 optimize 參數。

在 3.4 版的變更: ZIP64 擴充預設為啟用。

實例除了 ZipFile 物件的方法之外，還有一個額外的方法：

writepy(pathname, basename='', filterfunc=None)

搜尋 *.py 檔案，並將對應的檔案加入封存檔案。

如果傳給 PyZipFile 的 optimize 參數未被給定或為 -1，則對應的檔案是一個 *.pyc 檔案，如有必要則進行編譯。

如果傳給 PyZipFile 的 optimize 參數為 0、1 或 2，則只有具有該最佳化層級（參閱 compile()）的檔案會被加入封存檔案，如有必要則進行編譯。

如果 pathname 是一個檔案，檔名必須以 .py 結尾，且只有（對應的 *.pyc）檔案會被加到頂層（沒有路徑資訊）。如果 pathname 是一個不以 .py 結尾的檔案，將會引發 RuntimeError。如果它是一個目錄，且該目錄不是一個套件目錄，則所有 *.pyc 檔案都會被加到頂層。如果該目錄是一個套件目錄，則所有 *.pyc 都會以檔案路徑的形式被加到套件名稱下，且如果任何子目錄是套件目錄，所有這些都會以排序後的順序遞迴地加入。

basename 僅供內部使用。

filterfunc，如果給定，必須是一個接受單一字串引數的函式。每個路徑（包括每個單獨的完整檔案路徑）在被加入封存檔案之前都會被傳遞給它。如果 filterfunc 回傳一個假值，該路徑將不會被加入，且如果它是一個目錄，其內容將被忽略。例如，如果我們的測試檔案要嘛在 test 目錄中，要嘛以字串 test_ 開頭，我們可以使用一個 filterfunc 來排除它們：

>>> zf = PyZipFile('myprog.zip')
>>> def notests(s):
...     fn = os.path.basename(s)
...     return (not (fn == 'test' or fn.startswith('test_')))
...
>>> zf.writepy('myprog', filterfunc=notests)

writepy() 方法會建立帶有如下檔名的封存檔案：

string.pyc                   # 頂層名稱
test/__init__.pyc            # 套件目錄
test/testall.pyc             # 模組 test.testall
test/bogus/__init__.pyc      # 子套件目錄
test/bogus/myfile.pyc        # 子模組 test.bogus.myfile

在 3.4 版的變更: 新增 filterfunc 參數。

在 3.6.2 版的變更: pathname 參數接受一個 path-like object。

在 3.7 版的變更: 遞迴會對目錄條目進行排序。

ZipInfo 物件

ZipInfo 類別的實例由 ZipFile 物件的 getinfo() 和 infolist() 方法回傳。每個物件儲存關於 ZIP 封存檔案單一成員的資訊。

有一個類別方法可以為檔案系統中的檔案建立一個 ZipInfo 實例：

classmethod ZipInfo.from_file(filename, arcname=None, *, strict_timestamps=True)

為檔案系統上的一個檔案建構一個 ZipInfo 實例，為將其加入 zip 檔案做準備。

filename 應為檔案系統上一個檔案或目錄的路徑。

如果指定了 arcname，它將被用作封存檔案內的名稱。如果未指定 arcname，名稱將與 filename 相同，但會移除任何磁碟機代號和開頭的路徑分隔符。

strict_timestamps 引數，當設為 False 時，允許壓縮早於 1980-01-01 的檔案，代價是將時間戳記設為 1980-01-01。對於晚於 2107-12-31 的檔案，也會有類似的行為，時間戳記同樣會被設為極限值。

在 3.6 版被加入.

在 3.6.2 版的變更: filename 參數接受一個 path-like object。

在 3.8 版的變更: 新增了 strict_timestamps 僅限關鍵字參數。

實例具有以下方法和屬性：

ZipInfo.is_dir()

如果此封存成員是一個目錄，則回傳 True。

這會使用條目的名稱：目錄應總是以 / 結尾。

在 3.6 版被加入.

ZipInfo.filename

封存檔案中檔案的名稱。

ZipInfo.date_time

封存成員的最後修改時間和日期。這是一個包含六個值的元組，代表 ZIP 檔案中中央目錄的「最後 [修改] 檔案時間」和「最後 [修改] 檔案日期」欄位。

該元組包含：

索引

值

0

年（>= 1980）

1

月（從 1 開始）

2

日（從 1 開始）

3

時（從 0 開始）

4

分（從 0 開始）

5

秒（從 0 開始）

備註

The ZIP format supports multiple timestamp fields in different locations (central directory, extra fields for NTFS/UNIX systems, etc.). This attribute specifically returns the timestamp from the central directory. The central directory timestamp format in ZIP files does not support timestamps before 1980. While some extra field formats (such as UNIX timestamps) can represent earlier dates, this attribute only returns the central directory timestamp.

The central directory timestamp is interpreted as representing local time, rather than UTC time, to match the behavior of other zip tools.

ZipInfo.compress_type

封存成員的壓縮型別。

ZipInfo.comment

個別封存成員的註解，為一個 bytes 物件。

ZipInfo.extra

擴充欄位資料。PKZIP Application Note [https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT] 包含一些關於此 bytes 物件中所含資料內部結構的註解。

ZipInfo.create_system

建立 ZIP 封存檔案的系統。

ZipInfo.create_version

建立 ZIP 封存檔案的 PKZIP 版本。

ZipInfo.extract_version

解壓縮封存檔案所需的 PKZIP 版本。

ZipInfo.reserved

必須為零。

ZipInfo.flag_bits

ZIP 旗標位元。

ZipInfo.volume

檔案標頭的磁碟空間編號。

ZipInfo.internal_attr

內部屬性。

ZipInfo.external_attr

外部檔案屬性。

ZipInfo.header_offset

到檔案標頭的位元組偏移量。

ZipInfo.CRC

未壓縮檔案的 CRC-32。

ZipInfo.compress_size

壓縮資料的大小。

ZipInfo.file_size

未壓縮檔案的大小。

命令列介面

zipfile 模組提供了一個簡單的命令列介面，用以與 ZIP 封存檔案互動。

如果你想建立一個新的 ZIP 封存檔案，請在 -c 選項後指定其名稱，然後列出應包含的檔名：

$ python -m zipfile -c monty.zip spam.txt eggs.txt

傳遞一個目錄也是可以的：

$ python -m zipfile -c monty.zip life-of-brian_1979/

如果你想將一個 ZIP 封存檔案解壓縮到指定的目錄，請使用 -e 選項：

$ python -m zipfile -e monty.zip target-dir/

要列出 ZIP 封存檔案中的檔案，請使用 -l 選項：

$ python -m zipfile -l monty.zip

命令列選項

-l <zipfile>

--list <zipfile>

列出 zipfile 中的檔案。

-c <zipfile> <source1> ... <sourceN>

--create <zipfile> <source1> ... <sourceN>

從來源檔案建立 zipfile。

-e <zipfile> <output_dir>

--extract <zipfile> <output_dir>

將 zipfile 解壓縮到目標目錄。

-t <zipfile>

--test <zipfile>

測試 zipfile 是否有效。

--metadata-encoding <encoding>

為 -l、-e 和 -t 指定成員名稱的編碼。

在 3.11 版被加入.

解壓縮的陷阱

zipfile 模組中的解壓縮可能會由於下面列出的一些陷阱而失敗。

來自檔案本身

解壓縮可能由於不正確的密碼 / CRC 校驗和 / ZIP 格式或不支援的壓縮方法 / 解密而失敗。

檔案系統限制

超出不同檔案系統的限制可能導致解壓縮失敗。例如目錄條目中允許的字元、檔名長度、路徑名長度、單一檔案的大小以及檔案數量等。

資源限制

記憶體或磁碟空間不足會導致解壓縮失敗。例如，解壓縮炸彈（又稱 ZIP bomb [https://en.wikipedia.org/wiki/Zip_bomb]）適用於 zipfile 函式庫，可能導致磁碟空間耗盡。

中斷

在解壓縮過程中斷，例如按下 control-C 或終止解壓縮過程，可能導致封存檔案解壓縮不完整。

解壓縮的預設行為

不了解預設的解壓縮行為可能導致非預期的解壓縮結果。例如，當兩次解壓縮同一個封存檔案時，它會不經詢問就覆寫檔案。

tarfile --- 讀取與寫入 tar 封存檔案

原始碼：Lib/tarfile.py [https://github.com/python/cpython/tree/3.14/Lib/tarfile.py]

tarfile 模組用於讀取與寫入 tar 封存檔案，包括使用 gzip、bz2 和 lzma 壓縮的檔案。使用 zipfile 模組來讀取或寫入 .zip 檔案，或使用 shutil 中的更高階函式。

一些事實和數據：

若相對應的模組可用，則可讀取與寫入 gzip、bz2、compression.zstd 和 lzma 壓縮的封存檔。

如果你的 CPython 副本中缺少這些選用模組 (optional modules)，請查閱你的發行者（即提供 Python 給你的人）的文件。如果你就是發行者，請參閱 可選模組的需求。

支援 POSIX.1-1988 (ustar) 格式的讀取與寫入。

支援 GNU tar 格式的讀取與寫入，包括 longname 和 longlink 擴充功能，以及所有 sparse 擴充功能變體的唯讀支援，包括還原稀疏檔案 (sparse files)。

支援 POSIX.1-2001 (pax) 格式的讀取與寫入。

處理目錄、一般檔案、硬連結 (hardlinks)、符號連結 (symbolic links)、fifos、字元裝置 (character devices) 和區塊裝置 (block devices)，並能夠取得與還原檔案資訊，如時間戳記、存取權限和擁有者。

在 3.3 版的變更: 新增對 lzma 壓縮的支援。

在 3.12 版的變更: 解壓縮封存檔時會使用篩選器 (filter)，你可以用它來限制一些意外或危險的功能，或是明確表示這些功能是你預期的，而且封存檔是完全可信任的。

在 3.14 版的變更: 將預設解壓縮篩選器設為 data，這會禁止一些危險的功能，例如指向絕對路徑或目的地之外路徑的連結。在此之前，篩選器策略等同於 fully_trusted。

在 3.14 版的變更: 新增對 Zstandard 壓縮的支援（使用 compression.zstd）。

tarfile.open(name=None, mode='r', fileobj=None, bufsize=10240, **kwargs)

回傳路徑名稱 name 的 TarFile 物件。關於 TarFile 物件與允許的關鍵字引數的詳細資訊，請參閱 TarFile 物件。

mode 必須是 'filemode[:compression]' 形式的字串，預設為 'r'。以下是所有可能的模式組合：

模式

操作

'r' 或 'r:*'

開啟以讀取，自動偵測壓縮格式（建議使用）。

'r:'

開啟以讀取未壓縮的檔案。

'r:gz'

開啟以讀取 gzip 壓縮的檔案。

'r:bz2'

開啟以讀取 bzip2 壓縮的檔案。

'r:xz'

開啟以讀取 lzma 壓縮的檔案。

'r:zst'

開啟以讀取 Zstandard 壓縮的檔案。

'x' 或 'x:'

建立一個不壓縮的 tarfile（獨佔模式）。如果檔案已存在，則引發 FileExistsError 例外。

'x:gz'

建立一個使用 gzip 壓縮的 tar 檔案。如果檔案已存在則引發 FileExistsError 例外。

'x:bz2'

建立一個使用 bzip2 壓縮的 tar 檔案。如果檔案已存在，則引發 FileExistsError 例外。

'x:xz'

建立一個使用 lzma 壓縮的 tar 檔案。如果檔案已存在，則引發 FileExistsError 例外。

'x:zst'

建立一個使用 Zstandard 壓縮的 tar 檔案。如果檔案已存在，則引發 FileExistsError 例外。

'a' 或 'a:'

開啟以附加內容且不使用壓縮。如果檔案不存在則建立它。

'w' 或 'w:'

開啟以寫入未壓縮的內容。

'w:gz'

開啟以進行 gzip 壓縮寫入。

'w:bz2'

開啟以進行 bzip2 壓縮寫入。

'w:xz'

開啟以進行 lzma 壓縮寫入。

'w:zst'

開啟以進行 Zstandard 壓縮寫入。

請注意 'a:gz'、'a:bz2' 或 'a:xz' 是不可能的。如果 mode 不適合開啟特定（壓縮）檔案以進行讀取，則會引發 ReadError。使用 mode 'r' 可避免此問題。如果不支援某個壓縮方法，則會引發 CompressionError。

如果指定了 fileobj，則它會被用作 name 以二進位模式開啟的檔案物件 的替代方案。它應該位於位置 0。

對於模式 'w:gz'、'x:gz'、'w|gz'、'w:bz2'、'x:bz2'、'w|bz2'，tarfile.open() 接受關鍵字引數 compresslevel（預設為 9）來指定檔案的壓縮等級。

對於模式 'w:xz'、'x:xz' 和 'w|xz'，tarfile.open() 接受關鍵字引數 preset 來指定檔案的壓縮等級。

對於模式 'w:zst'、'x:zst' 和 'w|zst'，tarfile.open() 接受關鍵字引數 level 來指定檔案的壓縮等級。也可以傳遞關鍵字引數 options，提供由 CompressionParameter 描述的進階 Zstandard 壓縮參數。可以傳遞關鍵字引數 zstd_dict 以提供 ZstdDict，這是一個用於改善較小資料量壓縮效果的 Zstandard 字典。

對於特殊用途，mode 有第二種格式：'filemode|[compression]'。tarfile.open() 會回傳一個 TarFile 物件，該物件將其資料作為區塊串流處理。不會對檔案進行隨機尋找。如果提供了 fileobj，它可以是任何具有 read() 或 write() 方法（取決於 mode）且能處理位元組的物件。bufsize 指定區塊大小，預設為 20 * 512 位元組。此變體可與 sys.stdin.buffer、socket 檔案物件 或磁帶裝置等結合使用。但是，這樣的 TarFile 物件受到限制，因為它不允許隨機存取，請參閱 範例。目前可能的模式：

模式

操作

'r|*'

開啟以讀取 tar 區塊的串流，自動偵測壓縮格式。

'r|'

開啟以讀取未壓縮的 tar 區塊串流。

'r|gz'

開啟以讀取 gzip 壓縮的串流。

'r|bz2'

開啟以讀取 bzip2 壓縮的串流。

'r|xz'

開啟以讀取 lzma 壓縮的串流。

'r|zst'

開啟以讀取 Zstandard 壓縮的串流。

'w|'

開啟以寫入未壓縮的串流。

'w|gz'

開啟以寫入 gzip 壓縮的串流。

'w|bz2'

開啟以寫入 bzip2 壓縮的串流。

'w|xz'

開啟以寫入 lzma 壓縮的串流。

'w|zst'

開啟以寫入 Zstandard 壓縮的串流。

在 3.5 版的變更: 新增了 'x'（獨佔建立）模式。

在 3.6 版的變更: name 參數接受類路徑物件。

在 3.12 版的變更: compresslevel 關鍵字引數也適用於串流。

在 3.14 版的變更: preset 關鍵字引數也適用於串流。

class tarfile.TarFile

用於讀取和寫入 tar 封存檔的類別。請勿直接使用此類別：請改用 tarfile.open()。請參閱 TarFile 物件。

tarfile.is_tarfile(name)

如果 name 是一個 tarfile 模組可以讀取的 tar 封存檔，則回傳 True。name 可以是 str、檔案或類檔案物件。

在 3.9 版的變更: 對檔案和類檔案物件的支援。

tarfile 模組定義了以下例外：

exception tarfile.TarError

所有 tarfile 例外的基底類別。

exception tarfile.ReadError

當開啟的 tar 封存檔無法被 tarfile 模組處理或以某種方式無效時引發。

exception tarfile.CompressionError

當壓縮方法不被支援或資料無法正確解碼時引發。

exception tarfile.StreamError

當遇到類似串流的 TarFile 物件的典型限制時引發。

exception tarfile.ExtractError

在使用 TarFile.extract() 時針對非致命錯誤引發，但僅限於 TarFile.errorlevel== 2 時。

exception tarfile.HeaderError

如果 TarInfo.frombuf() 得到的緩衝區無效，則引發此例外。

exception tarfile.FilterError

被篩選器拒絕的成員的基底類別。

tarinfo

篩選器拒絕解壓縮的成員資訊，以 TarInfo 表示。

exception tarfile.AbsolutePathError

當拒絕解壓縮具有絕對路徑的成員時引發。

exception tarfile.OutsideDestinationError

當拒絕解壓縮位於目的地目錄之外的成員時引發。

exception tarfile.SpecialFileError

當拒絕解壓縮特殊檔案（例如裝置或管道）時引發。

exception tarfile.AbsoluteLinkError

當拒絕解壓縮具有絕對路徑的符號連結時引發。

exception tarfile.LinkOutsideDestinationError

當拒絕解壓縮指向目的地目錄之外的符號連結時引發。

exception tarfile.LinkFallbackError

當透過解壓縮另一個封存檔成員來模擬連結（硬連結或符號連結）時，如果該成員會被篩選器位置拒絕，則引發此例外。用於拒絕替代成員的例外可作為 BaseException.__context__ 取得。

在 3.14 版被加入.

以下常數可在模組層級使用：

tarfile.ENCODING

預設字元編碼：在 Windows 上為 'utf-8'，否則為 sys.getfilesystemencoding() 回傳的值。

tarfile.REGTYPE

tarfile.AREGTYPE

一個普通檔案 type。

tarfile.LNKTYPE

一個連結（在 tar 檔案內）type。

tarfile.SYMTYPE

一個符號連結 type。

tarfile.CHRTYPE

一個字元特殊裝置 type。

tarfile.BLKTYPE

一個區塊特殊裝置 type。

tarfile.DIRTYPE

一個目錄 type。

tarfile.FIFOTYPE

一個 FIFO 特殊裝置 type。

tarfile.CONTTYPE

一個連續檔案 type。

tarfile.GNUTYPE_LONGNAME

一個 GNU tar longname type。

tarfile.GNUTYPE_LONGLINK

一個 GNU tar longlink type。

tarfile.GNUTYPE_SPARSE

一個 GNU tar 稀疏檔案 type。

以下每個常數定義了 tarfile 模組能夠建立的 tar 封存檔格式。詳細資訊請參閱 支援的 tar 格式 一節。

tarfile.USTAR_FORMAT

POSIX.1-1988 (ustar) 格式。

tarfile.GNU_FORMAT

GNU tar 格式。

tarfile.PAX_FORMAT

POSIX.1-2001 (pax) 格式。

tarfile.DEFAULT_FORMAT

建立封存檔的預設格式。目前為 PAX_FORMAT。

在 3.8 版的變更: 新封存檔的預設格式已從 GNU_FORMAT 變更為 PAX_FORMAT。

也參考

zipfile 模組

zipfile 標準模組的文件。

Archiving operations

標準 shutil 模組所提供的更高階封存功能的文件。

GNU tar 手冊，基本 Tar 格式 [https://www.gnu.org/software/tar/manual/html_node/Standard.html]

tar 封存檔案的文件，包括 GNU tar 擴充功能。

TarFile 物件

TarFile 物件提供一個 tar 封存檔的介面。tar 封存檔是一個區塊序列。一個封存檔成員（一個儲存的檔案）由一個標頭區塊和後續的資料區塊組成。可以在 tar 封存檔中多次儲存一個檔案。每個封存檔成員由一個 TarInfo 物件表示，詳細資訊請參閱 TarInfo 物件。

TarFile 物件可以在 with 陳述式中用作情境管理器。當區塊完成時，它會自動關閉。請注意，如果發生例外，以寫入方式開啟的封存檔將不會被最終化 (finalized)；只有內部使用的檔案物件會被關閉。使用案例請參閱 範例 一節。

在 3.2 版被加入: 新增對情境管理協定的支援。

class tarfile.TarFile(name=None, mode='r', fileobj=None, format=DEFAULT_FORMAT, tarinfo=TarInfo, dereference=False, ignore_zeros=False, encoding=ENCODING, errors='surrogateescape', pax_headers=None, debug=0, errorlevel=1, stream=False)

以下所有引數都是可選的，也可以作為實例屬性存取。

name 是封存檔的路徑名稱。name 可以是類路徑物件。如果提供了 fileobj 則可以省略它。在這種情況下，如果檔案物件的 name 屬性存在，則會使用該屬性。

mode 可以是 'r' 以從現有封存檔讀取、'a' 以附加資料到現有檔案、'w' 以建立新檔案覆蓋現有檔案，或 'x' 以僅在檔案不存在時建立新檔案。

如果提供了 fileobj，它會被用於讀取或寫入資料。如果可以確定，mode 會被 fileobj 的模式覆蓋。fileobj 將從位置 0 開始使用。

備註

當 TarFile 關閉時，fileobj 不會被關閉。

format 控制寫入時的封存檔格式。它必須是在模組層級定義的常數 USTAR_FORMAT、GNU_FORMAT 或 PAX_FORMAT 之一。讀取時，即使單一封存檔中存在不同格式，格式也會自動偵測。

tarinfo 引數可用於將預設的 TarInfo 類別替換為不同的類別。

如果 dereference 為 False，則將符號連結和硬連結新增到封存檔。如果為 True，則將目標檔案的內容新增到封存檔。這在不支援符號連結的系統上沒有效果。

如果 ignore_zeros 為 False，則將空區塊視為封存檔的結尾。如果為 True，則跳過空的（和無效的）區塊並嘗試取得盡可能多的成員。這僅對讀取串聯或損壞的封存檔有用。

debug 可設定從 0（無偵錯訊息）到 3（所有偵錯訊息）。訊息會寫入 sys.stderr。

errorlevel 控制如何處理解壓縮錯誤，請參閱對應的屬性。

encoding 和 errors 引數定義用於讀取或寫入封存檔的字元編碼以及如何處理轉換錯誤。預設設定適用於大多數使用者。深入資訊請參閱 Unicode 議題 一節。

pax_headers 引數是一個可選的字串字典，如果 format 為 PAX_FORMAT，則會作為 pax 全域標頭新增。

如果 stream 設為 True，則讀取封存檔時不會快取封存檔中關於檔案的資訊，從而節省記憶體。

在 3.2 版的變更: 使用 'surrogateescape' 作為 errors 引數的預設值。

在 3.5 版的變更: 新增了 'x'（獨佔建立）模式。

在 3.6 版的變更: name 參數接受類路徑物件。

在 3.13 版的變更: 新增 stream 參數。

classmethod TarFile.open(...)

替代建構函式。tarfile.open() 函式實際上是此類別方法的捷徑。

TarFile.getmember(name)

回傳成員 name 的 TarInfo 物件。如果在封存檔中找不到 name，則引發 KeyError。

備註

如果一個成員在封存檔中出現多次，則假定其最後一次出現是最新版本。

TarFile.getmembers()

以 TarInfo 物件串列的形式回傳封存檔的成員。串列的順序與封存檔中成員的順序相同。

TarFile.getnames()

以名稱串列的形式回傳成員。其順序與 getmembers() 回傳的串列順序相同。

TarFile.list(verbose=True, *, members=None)

將內容表印出到 sys.stdout。如果 verbose 為 False，則只印出成員的名稱。如果為 True，則產生類似於 ls -l 的輸出。如果提供了可選的 members，它必須是 getmembers() 回傳串列的子集合。

在 3.5 版的變更: 新增 members 參數。

TarFile.next()

當 TarFile 以讀取方式開啟時，以 TarInfo 物件的形式回傳封存檔的下一個成員。如果沒有更多成員可用，則回傳 None。

TarFile.extractall(path='.', members=None, *, numeric_owner=False, filter=None)

將所有成員從封存檔解壓縮到目前的工作目錄或目錄 path。如果提供了可選的 members，它必須是 getmembers() 回傳串列的子集合。目錄資訊（如擁有者、修改時間和權限）會在所有成員都被解壓縮後設定。這樣做是為了解決兩個問題：每次在目錄中建立檔案時，目錄的修改時間都會被重設。而且，如果目錄的權限不允許寫入，則無法將檔案解壓縮到其中。

如果 numeric_owner 為 True，則使用 tar 檔案中的 uid 和 gid 數字來設定解壓縮檔案的擁有者／群組。否則，使用 tar 檔案中的名稱值。

filter 引數指定在解壓縮之前如何修改或拒絕 members。詳細資訊請參閱 解壓縮篩選器。建議僅在需要特定 tar 功能時或作為 filter='data' 以支援預設安全性較低的 Python 版本（3.13 及更低版本）時明確設定此項。

警告

切勿在未事先檢查的情況下解壓縮來自不受信任來源的封存檔。

從 Python 3.14 開始，預設值（data）將防止最危險的安全問題。但是，它不會防止所有意外或不安全的行為。詳細資訊請閱讀 解壓縮篩選器 一節。

在 3.5 版的變更: 新增 numeric_owner 參數。

在 3.6 版的變更: path 參數接受類路徑物件。

在 3.12 版的變更: 新增 filter 參數。

在 3.14 版的變更: filter 參數現在預設為 'data'。

TarFile.extract(member, path='', set_attrs=True, *, numeric_owner=False, filter=None)

使用完整名稱將一個成員從封存檔解壓縮到目前的工作目錄。其檔案資訊會盡可能準確地解壓縮。member 可以是檔案名稱或 TarInfo 物件。你可以使用 path 指定不同的目錄。path 可以是類路徑物件。除非 set_attrs 為 false，否則會設定檔案屬性 (owner, mtime, mode)。

numeric_owner 和 filter 引數與 extractall() 相同。

備註

extract() 方法不處理多個解壓縮問題。在大多數情況下，你應該考慮使用 extractall() 方法。

警告

切勿在事先檢查之前從不受信任的來源解壓縮封存檔。詳細資訊請參閱 extractall() 的警告。

在 3.2 版的變更: 增加 set_attrs 參數。

在 3.5 版的變更: 新增 numeric_owner 參數。

在 3.6 版的變更: path 參數接受類路徑物件。

在 3.12 版的變更: 新增 filter 參數。

TarFile.extractfile(member)

以檔案物件的形式從封存檔解壓縮一個成員。member 可以是檔案名稱或 TarInfo 物件。如果 member 是一般檔案或連結，則回傳 io.BufferedReader 物件。對於所有其他現有成員，回傳 None。如果 member 未出現在封存檔中，則引發 KeyError。

在 3.3 版的變更: 回傳 io.BufferedReader 物件。

在 3.13 版的變更: 回傳的 io.BufferedReader 物件具有 mode 屬性，該屬性始終等於 'rb'。

TarFile.errorlevel: int

如果 errorlevel 為 0，則使用 TarFile.extract() 和 TarFile.extractall() 時會忽略錯誤。然而，當 debug 大於 0 時，它們會在偵錯輸出中顯示為錯誤訊息。如果為 1（預設值），所有致命錯誤都會以 OSError 或 FilterError 例外的形式引發。如果為 2，所有非致命錯誤也會以 TarError 例外的形式引發。

某些例外，例如由錯誤的引數型別或資料損壞引起的例外，總是會被引發。

自訂的解壓縮篩選器應該對致命錯誤引發 FilterError，對非致命錯誤引發 ExtractError。

請注意，當引發例外時，封存檔可能已部分解壓縮。清理是使用者的責任。

TarFile.extraction_filter

在 3.12 版被加入.

用作 extract() 和 extractall() 的 filter 引數預設的解壓縮篩選器。

此屬性可以是 None 或可呼叫物件。與 extract() 的 filter 引數不同，此屬性不允許使用字串名稱。

如果 extraction_filter 為 None（預設值），解壓縮方法將預設使用 data 篩選器。

此屬性可以在實例上設定或在子類別中覆寫。也可以在 TarFile 類別本身上設定它以設定全域預設值，儘管由於它會影響 tarfile 的所有使用，最佳做法是僅在頂層應用程式或 site 組態中這樣做。要以這種方式設定全域預設值，需要將篩選器函式包裝在 staticmethod() 中以防止注入 self 引數。

在 3.14 版的變更: 預設篩選器設為 data，這會禁止一些危險的功能，例如指向絕對路徑或目的地之外路徑的連結。在此之前，預設值等同於 fully_trusted。

TarFile.add(name, arcname=None, recursive=True, *, filter=None)

將檔案 name 新增到封存檔。name 可以是任何型別的檔案（目錄、FIFO、符號連結等）。如果提供了 arcname，則為封存檔中的檔案指定替代名稱。預設情況下，目錄會遞迴新增。這可以透過將 recursive 設為 False 來避免。遞迴以排序順序新增條目。如果提供了 filter，它應該是一個接受 TarInfo 物件引數並回傳變更後的 TarInfo 物件的函式。如果它回傳 None，則 TarInfo 物件將從封存檔中排除。範例請參閱 範例。

在 3.2 版的變更: 新增 filter 參數。

在 3.7 版的變更: 遞迴以排序後的順序新增條目。

TarFile.addfile(tarinfo, fileobj=None)

將 TarInfo 物件 tarinfo 新增到封存檔。如果 tarinfo 表示一個非零大小的一般檔案，fileobj 引數應該是二進位檔案，並從中讀取 tarinfo.size 位元組並新增到封存檔。你可以直接建立 TarInfo 物件，或使用 gettarinfo()。

在 3.13 版的變更: 對於非零大小的一般檔案，必須提供 fileobj。

TarFile.gettarinfo(name=None, arcname=None, fileobj=None)

從現有檔案的 os.stat() 或等效結果建立 TarInfo 物件。檔案可以由 name 命名，或指定為具有檔案描述符的檔案物件 fileobj。name 可以是類路徑物件。如果提供了 arcname，則為封存檔中的檔案指定替代名稱，否則，名稱取自 fileobj 的 name 屬性或 name 引數。名稱應該是文字字串。

在使用 addfile() 新增之前，你可以修改 TarInfo 的某些屬性。如果檔案物件不是位於檔案開頭的普通檔案物件，則可能需要修改諸如 size 之類的屬性。這種情況適用於 GzipFile 等物件。name 也可以被修改，在這種情況下 arcname 可以是一個虛設字串 (dummy string)。

在 3.6 版的變更: name 參數接受類路徑物件。

TarFile.close()

關閉 TarFile。在寫入模式下，會在封存檔末尾附加兩個結束零區塊。

TarFile.pax_headers: dict

包含 pax 全域標頭鍵值對的字典。

TarInfo 物件

TarInfo 物件表示 TarFile 中的一個成員。除了儲存檔案的所有必要屬性（如檔案型別、大小、時間、權限、擁有者等）之外，它還提供一些有用的方法來確定其型別。它不包含檔案的資料本身。

TarInfo 物件由 TarFile 的方法 getmember()、getmembers() 和 gettarinfo() 回傳。

修改由 getmember() 或 getmembers() 回傳的物件將影響封存檔上的所有後續操作。對於不希望出現這種情況的情況，你可以使用 copy.copy() 或呼叫 replace() 方法來一步建立修改後的副本。

可以將多個屬性設為 None 以表示一段中介資料 (metadata) 未被使用或未知。不同的 TarInfo 方法會以不同的方式處理 None：

extract() 或 extractall() 方法將忽略對應的中介資料，使其保持預設值。

addfile() 將失敗。

list() 將印出一個佔位字串 (placeholder string)。

class tarfile.TarInfo(name='')

建立 TarInfo 物件。

classmethod TarInfo.frombuf(buf, encoding, errors)

從字串緩衝區 buf 建立並回傳 TarInfo 物件。

如果緩衝區無效，則引發 HeaderError。

classmethod TarInfo.fromtarfile(tarfile)

從 TarFile 物件 tarfile 讀取下一個成員並將其作為 TarInfo 物件回傳。

TarInfo.tobuf(format=DEFAULT_FORMAT, encoding=ENCODING, errors='surrogateescape')

從 TarInfo 物件建立字串緩衝區。關於引數的資訊，請參閱 TarFile 類別的建構函式。

在 3.2 版的變更: 使用 'surrogateescape' 作為 errors 引數的預設值。

一個 TarInfo 物件具有以下公開資料屬性：

TarInfo.name: str

封存檔成員的名稱。

TarInfo.size: int

大小（以位元組為單位）。

TarInfo.mtime: int | float

自epoch 以來的最後修改時間（以秒為單位），如 os.stat_result.st_mtime。

在 3.12 版的變更: 對於 extract() 和 extractall()，可以設為 None，讓解壓縮跳過套用此屬性。

TarInfo.mode: int

權限位元 (permission bits)，如 os.chmod() 所用。

在 3.12 版的變更: 對於 extract() 和 extractall()，可以設為 None，讓解壓縮跳過套用此屬性。

TarInfo.type

檔案類型。type 通常是這些常數之一：REGTYPE、AREGTYPE、LNKTYPE、SYMTYPE、DIRTYPE、FIFOTYPE、CONTTYPE、CHRTYPE、BLKTYPE、GNUTYPE_SPARSE。要更方便地確定 TarInfo 物件的類型，請使用下面的 is*() 方法。

TarInfo.linkname: str

目標檔案名稱的名稱，僅存在於型別為 LNKTYPE 和 SYMTYPE 的 TarInfo 物件中。

對於符號連結（SYMTYPE），linkname 相對於包含連結的目錄。對於硬連結（LNKTYPE），linkname 相對於封存檔的根。

TarInfo.uid: int

最初儲存此成員的使用者的使用者 ID。

在 3.12 版的變更: 對於 extract() 和 extractall()，可以設為 None，讓解壓縮跳過套用此屬性。

TarInfo.gid: int

最初儲存此成員的使用者的群組 ID。

在 3.12 版的變更: 對於 extract() 和 extractall()，可以設為 None，讓解壓縮跳過套用此屬性。

TarInfo.uname: str

使用者名稱。

在 3.12 版的變更: 對於 extract() 和 extractall()，可以設為 None，讓解壓縮跳過套用此屬性。

TarInfo.gname: str

群組名稱。

在 3.12 版的變更: 對於 extract() 和 extractall()，可以設為 None，讓解壓縮跳過套用此屬性。

TarInfo.chksum: int

標頭校驗和 (checksum)。

TarInfo.devmajor: int

裝置主號碼。

TarInfo.devminor: int

裝置副號碼。

TarInfo.offset: int

tar 標頭從這裡開始。

TarInfo.offset_data: int

檔案的資料從這裡開始。

TarInfo.sparse

稀疏成員資訊。

TarInfo.pax_headers: dict

包含關聯的 pax 擴充標頭鍵值對的字典。

TarInfo.replace(name=..., mtime=..., mode=..., linkname=..., uid=..., gid=..., uname=..., gname=..., deep=True)

在 3.12 版被加入.

回傳具有給定屬性變更的 TarInfo 物件的新副本。例如，要回傳群組名稱設為 'staff' 的 TarInfo，請使用：

new_tarinfo = old_tarinfo.replace(gname='staff')

預設情況下，會進行深度複製。如果 deep 為 false，則複製為淺複製，即 pax_headers 和任何自訂屬性與原始 TarInfo 物件共用。

TarInfo 物件也提供一些方便的查詢方法：

TarInfo.isfile()

如果 TarInfo 物件是一般檔案，則回傳 True。

TarInfo.isreg()

與 isfile() 相同。

TarInfo.isdir()

如果它是一個目錄，則回傳 True。

TarInfo.issym()

如果它是一個符號連結，則回傳 True。

TarInfo.islnk()

如果它是一個硬連結，則回傳 True。

TarInfo.ischr()

如果它是一個字元裝置，則回傳 True。

TarInfo.isblk()

如果它是一個區塊裝置，則回傳 True。

TarInfo.isfifo()

如果它是一個 FIFO，則回傳 True。

TarInfo.isdev()

如果它是一個字元裝置、區塊裝置或 FIFO，則回傳 True。

解壓縮篩選器

在 3.12 版被加入.

tar 格式是為了捕捉 UNIX-like 檔案系統的所有細節而設計的，這使它非常強大。不幸的是，這些功能使得建立在解壓縮時具有非預期甚至可能是惡意影響的 tar 檔案變得很容易。例如，解壓縮 tar 檔案可以透過各種方式覆寫任意檔案（例如使用絕對路徑、.. 路徑元件，或影響後續成員的符號連結）。

在大多數情況下，不需要完整功能。因此，tarfile 支援解壓縮篩選器：一種限制功能的機制，從而減輕某些安全性問題。

警告

沒有任何可用的篩選器會阻擋所有危險的封存檔功能。永遠不要在沒有事先檢查的情況下從不受信任的來源解壓縮封存檔。另請參閱 進一步驗證的提示。

也參考

PEP 706 [https://peps.python.org/pep-0706/]

包含此設計背後的進一步動機和理由。

TarFile.extract() 或 extractall() 的 filter 引數可以是：

'fully_trusted' 字串：遵守封存檔中指定的所有中介資料。應在使用者完全信任封存檔或實作自己的複雜驗證時使用。

'tar' 字串：遵守大多數 tar 特定功能（即 UNIX-like 檔案系統的功能），但阻擋很可能令人驚訝或惡意的功能。詳見 tar_filter()。

'data' 字串：忽略或阻擋大多數 UNIX-like 檔案系統特定功能。用於解壓縮跨平台資料封存檔。詳見 data_filter()。

None（預設）：使用 TarFile.extraction_filter。

如果該值也是 None（預設值），則會使用 'data' 篩選器。

在 3.14 版的變更: 預設篩選器設為 data。在此之前，預設等同於 fully_trusted。

一個可呼叫物件，對於每個解壓縮的成員，會使用描述該成員的 TarInfo 和封存檔解壓縮目的地路徑來呼叫它（即所有成員使用相同的路徑）：

filter(member: TarInfo, path: str, /) -> TarInfo | None

此可呼叫物件在每個成員解壓縮之前被呼叫，因此可以考慮磁碟的目前狀態。它可以：

回傳一個 TarInfo 物件，該物件將用於替代封存檔中的中介資料，或

回傳 None，在此情況下該成員會被跳過，或

引發例外以中止操作或跳過該成員，取決於 errorlevel。請注意，當解壓縮被中止時，extractall() 可能會留下部分解壓縮的封存檔。它不會嘗試清理。

預設具名篩選器

預先定義的具名篩選器可作為函式使用，因此可以在自訂篩選器中重複使用：

tarfile.fully_trusted_filter(member, path)

回傳未經修改的 member。

這實作了 'fully_trusted' 篩選器。

tarfile.tar_filter(member, path)

實作 'tar' 篩選器。

從檔名中移除開頭的斜線（/ 和 os.sep）。

拒絕解壓縮具有絕對路徑的檔案（在移除斜線後名稱仍是絕對路徑的情況下，例如 Windows 上的 C:/foo）。這會引發 AbsolutePathError。

拒絕解壓縮其絕對路徑（在跟隨符號連結後）會位於目的地之外的檔案。這會引發 OutsideDestinationError。

清除高位模式位元 (setuid, setgid, sticky) 以及群組/其他人的寫入位元（S_IWGRP | S_IWOTH）。

回傳修改後的 TarInfo 成員。

tarfile.data_filter(member, path)

實作 'data' 篩選器。除了 tar_filter 的功能外，還包括：

使用 os.path.normpath() 正規化連結目標（TarInfo.linkname）。請注意，這會移除內部的 .. 元件，如果 TarInfo.linkname 中的路徑會遍歷符號連結，這可能會改變連結的意義。

拒絕解壓縮指向絕對路徑的連結（硬連結或軟連結），或指向目的地之外的連結。

這會引發 AbsoluteLinkError 或 LinkOutsideDestinationError。

請注意，即使在不支援符號連結的平台上，這類檔案也會被拒絕。

拒絕解壓縮裝置檔案（包括 pipe）。這會引發 SpecialFileError。

對於一般檔案，包括硬連結：

設定擁有者的讀取和寫入權限（S_IRUSR | S_IWUSR）。

如果擁有者沒有執行權限（S_IXUSR），則移除群組和其他人的執行權限（S_IXGRP | S_IXOTH）。

對於其他檔案（目錄），將 mode 設為 None，讓解壓縮方法跳過套用權限位元。

將使用者和群組資訊 (uid, gid, uname, gname) 設為 None，讓解壓縮方法跳過設定它們。

回傳修改後的 TarInfo 成員。

請注意，此篩選器並未阻擋所有危險的封存檔功能。詳細資訊請參閱 進一步驗證的提示。

在 3.14 版的變更: 連結目標現在會被正規化。

篩選器錯誤

當篩選器拒絕解壓縮檔案時，它會引發適當的例外，該例外是 FilterError 的子類別。如果 TarFile.errorlevel 為 1 或更高，這將中止解壓縮。使用 errorlevel=0 時，錯誤將被記錄並跳過該成員，但解壓縮將繼續進行。

進一步驗證的提示

即使使用 filter='data'，tarfile 也不適合在沒有事先檢查的情況下解壓縮不受信任的檔案。除了其他問題外，預先定義的篩選器不會防止阻斷服務攻擊。使用者應進行額外檢查。

以下是需要考慮的不完整清單：

解壓縮到新的臨時目錄以防止例如利用預先存在的連結，並使解壓縮失敗後更容易清理。

如果不需要符號連結功能，請禁止它。

處理不受信任的資料時，請使用外部（例如作業系統層級）的磁碟、記憶體和 CPU 使用量限制。

根據字元白名單檢查檔名（以過濾掉控制字元、易混淆字元、外部路徑分隔符號等）。

檢查檔名是否具有預期的副檔名（避免點擊時會執行的檔案，或像 Windows 特殊裝置名稱這樣的無副檔名檔案）。

限制解壓縮檔案的數量、解壓縮資料的總大小、檔名長度（包括符號連結長度）以及個別檔案的大小。

檢查在不區分大小寫的檔案系統上會被遮蔽的檔案。

另請注意：

Tar 檔案可能包含同一檔案的多個版本。較晚的版本預期會覆蓋較早的版本。此功能對於允許更新磁帶封存檔至關重要，但可能被惡意濫用。

tarfile 不會防止「即時」資料的問題，例如攻擊者在解壓縮（或封存）進行中時篡改目的地（或來源）目錄。

支援舊版 Python

解壓縮篩選器在 Python 3.12 中加入，但可能會作為安全性更新移植到較舊版本。要檢查此功能是否可用，請使用 hasattr(tarfile, 'data_filter') 而不是檢查 Python 版本。

以下範例顯示如何支援有此功能和沒有此功能的 Python 版本。請注意，設定 extraction_filter 會影響任何後續操作。

完全信任的封存檔：

my_tarfile.extraction_filter = (lambda member, path: member)
my_tarfile.extractall()

如果可用則使用 'data' 篩選器，但如果此功能不可用則使用後備的 Python 3.11 的行為（'fully_trusted'）：

my_tarfile.extraction_filter = getattr(tarfile, 'data_filter',
                                       (lambda member, path: member))
my_tarfile.extractall()

使用 'data' 篩選器；如果不可用則失敗：

my_tarfile.extractall(filter=tarfile.data_filter)

或：

my_tarfile.extraction_filter = tarfile.data_filter
my_tarfile.extractall()

使用 'data' 篩選器；如果不可用則警告：

if hasattr(tarfile, 'data_filter'):
    my_tarfile.extractall(filter='data')
else:
    # 當不再需要時移除它
    warn_the_user('Extracting may be unsafe; consider updating Python')
    my_tarfile.extractall()

有狀態的解壓縮篩選器範例

雖然 tarfile 的解壓縮方法接受一個簡單的 filter 可呼叫物件，但自訂篩選器可能是具有內部狀態的更複雜物件。將這些寫成情境管理器可能很有用，像這樣使用：

with StatefulFilter() as filter_func:
    tar.extractall(path, filter=filter_func)

例如，這樣的篩選器可以寫成：

class StatefulFilter:
    def __init__(self):
        self.file_count = 0

    def __enter__(self):
        return self

    def __call__(self, member, path):
        self.file_count += 1
        return member

    def __exit__(self, *exc_info):
        print(f'{self.file_count} files extracted')

命令列介面

在 3.4 版被加入.

tarfile 模組提供了簡單的命令列介面來與 tar 封存檔互動。

如果你要建立新的 tar 封存檔，請在 -c 選項後指定其名稱，然後列出應包含的檔案名稱：

$ python -m tarfile -c monty.tar  spam.txt eggs.txt

也可以傳遞目錄：

$ python -m tarfile -c monty.tar life-of-brian_1979/

如果你要將 tar 封存檔解壓縮到目前目錄，請使用 -e 選項：

$ python -m tarfile -e monty.tar

你也可以透過傳遞目錄名稱，將 tar 封存檔解壓縮到不同的目錄：

$ python -m tarfile -e monty.tar  other-dir/

若要列出 tar 封存檔中的檔案，請使用 -l 選項：

$ python -m tarfile -l monty.tar

命令列選項

-l <tarfile>

--list <tarfile>

列出 tarfile 中的檔案。

-c <tarfile> <source1> ... <sourceN>

--create <tarfile> <source1> ... <sourceN>

從來源檔案建立 tarfile。

-e <tarfile> [<output_dir>]

--extract <tarfile> [<output_dir>]

如果未指定 output_dir，則將 tarfile 解壓縮到目前目錄。

-t <tarfile>

--test <tarfile>

測試 tarfile 是否有效。

-v, --verbose

詳細輸出。

--filter <filtername>

為 --extract 指定 filter。詳見 解壓縮篩選器。僅接受字串名稱（即 fully_trusted、tar 和 data）。

範例

讀取範例

如何將整個 tar 封存檔解壓縮到目前的工作目錄：

import tarfile
tar = tarfile.open("sample.tar.gz")
tar.extractall(filter='data')
tar.close()

如何使用產生器函式而非串列，來以 TarFile.extractall() 解壓縮 tar 封存檔的子集：

import os
import tarfile

def py_files(members):
    for tarinfo in members:
        if os.path.splitext(tarinfo.name)[1] == ".py":
            yield tarinfo

tar = tarfile.open("sample.tar.gz")
tar.extractall(members=py_files(tar))
tar.close()

如何讀取 gzip 壓縮的 tar 封存檔並顯示部分成員資訊：

import tarfile
tar = tarfile.open("sample.tar.gz", "r:gz")
for tarinfo in tar:
    print(tarinfo.name, "is", tarinfo.size, "bytes in size and is ", end="")
    if tarinfo.isreg():
        print("a regular file.")
    elif tarinfo.isdir():
        print("a directory.")
    else:
        print("something else.")
tar.close()

寫入範例

如何從檔案名稱串列建立未壓縮的 tar 封存檔：

import tarfile
tar = tarfile.open("sample.tar", "w")
for name in ["foo", "bar", "quux"]:
    tar.add(name)
tar.close()

使用 with 陳述式的相同範例：

import tarfile
with tarfile.open("sample.tar", "w") as tar:
    for name in ["foo", "bar", "quux"]:
        tar.add(name)

如何在 TarFile.add() 的 fileobj 參數中使用 sys.stdout.buffer 建立封存檔並寫入標準輸出：

import sys
import tarfile
with tarfile.open("sample.tar.gz", "w|gz", fileobj=sys.stdout.buffer) as tar:
    for name in ["foo", "bar", "quux"]:
        tar.add(name)

如何在 TarFile.add() 中使用 filter 參數來建立封存檔並重設使用者資訊：

import tarfile
def reset(tarinfo):
    tarinfo.uid = tarinfo.gid = 0
    tarinfo.uname = tarinfo.gname = "root"
    return tarinfo
tar = tarfile.open("sample.tar.gz", "w:gz")
tar.add("foo", filter=reset)
tar.close()

支援的 tar 格式

使用 tarfile 模組可以建立三種 tar 格式：

POSIX.1-1988 ustar 格式（USTAR_FORMAT）。它支援最多 256 個字元的檔名和最多 100 個字元的連結名稱。檔案大小上限為 8 GiB。這是一種老舊且受限的格式，但廣受支援。

GNU tar 格式（GNU_FORMAT）。它支援長檔名和長連結名稱、超過 8 GiB 的檔案以及稀疏檔案。這是 GNU/Linux 系統上的實際標準。tarfile 完全支援 GNU tar 對長名稱的擴充，但稀疏檔案僅有唯讀支援。

POSIX.1-2001 pax 格式（PAX_FORMAT）。這是最靈活的格式，幾乎沒有任何限制。它支援長檔名和長連結名稱、大型檔案，並以可攜的方式儲存路徑名稱。現代的 tar 實作（包括 GNU tar、bsdtar/libarchive 和 star）都完全支援擴充的 pax 功能；某些舊的或未維護的函式庫可能不支援，但應將 pax 封存檔視為普遍支援的 ustar 格式。這是目前建立新封存檔的預設格式。

它透過額外的標頭擴充既有的 ustar 格式，以儲存無法以其他方式儲存的資訊。pax 標頭有兩種類型：擴充標頭（Extended headers）只影響緊接在後的檔案標頭，全域標頭（global headers）則對整個封存檔有效並影響所有後續檔案。為了可攜性，pax 標頭中的所有資料都使用 UTF-8 編碼。

還有一些 tar 格式的變體可以讀取，但無法建立：

古老的 V7 格式。這是 Unix 第七版的第一個 tar 格式，只能儲存一般檔案和目錄。名稱不得超過 100 個字元，且沒有使用者/群組名稱資訊。某些封存檔在欄位包含非 ASCII 字元時，標頭檢查碼會計算錯誤。

SunOS tar 擴充格式。此格式是 POSIX.1-2001 pax 格式的變體，但並不相容。

Unicode 議題

tar 格式最初是為了在磁帶機上進行備份而設計的，主要著重於保存檔案系統資訊。現今 tar 封存檔常用於檔案發布和透過網路交換封存檔。原始格式（也是所有其他格式的基礎）的一個問題是，它沒有支援不同字元編碼的概念。例如，在 UTF-8 系統上建立的普通 tar 封存檔，如果包含非 ASCII 字元，在 Latin-1 系統上就無法正確讀取。文字中介資料（如檔名、連結名稱、使用者/群組名稱）會顯示為損壞。不幸的是，無法自動偵測封存檔的編碼。pax 格式就是為了解決此問題而設計的。它使用通用字元編碼 UTF-8 來儲存非 ASCII 中介資料。

tarfile 中字元轉換的細節由 TarFile 類別的 encoding 和 errors 關鍵字引數控制。

encoding 定義封存檔中介資料所使用的字元編碼。預設值為 sys.getfilesystemencoding()，若無法取得則使用 'ascii' 作為備用。根據封存檔是讀取還是寫入，中介資料必須被解碼或編碼。如果 encoding 設定不當，此轉換可能會失敗。

errors 引數定義如何處理無法轉換的字元。可能的值列於 Error Handlers 一節。預設方案是 'surrogateescape'，這也是 Python 用於檔案系統呼叫的方案，參見 File Names, Command Line Arguments, and Environment Variables。

對於 PAX_FORMAT 封存檔（預設格式），通常不需要 encoding，因為所有中介資料都使用 UTF-8 儲存。encoding 只在少數情況下使用，例如解碼二進位 pax 標頭或儲存包含代理字元的字串時。

檔案格式

本章所描述的模組會剖析各種非標記類型語言且與電子郵件無關的雜項檔案格式。

csv --- CSV 檔案讀取及寫入

模組內容

Dialect 與格式參數

讀取器物件

寫入器物件

範例

configparser --- 設定檔剖析器

Quick Start

Supported Datatypes

Fallback Values

支援的 INI 檔案結構

Unnamed Sections

Interpolation of values

Mapping Protocol Access

Customizing Parser Behaviour

Legacy API Examples

ConfigParser 物件

RawConfigParser 物件

例外

tomllib --- 剖析 TOML 檔案

範例

轉換表

netrc --- netrc 檔案處理

netrc 物件

plistlib --- 產生和剖析 Apple .plist 檔案

範例

csv --- CSV 檔案讀取及寫入

原始碼：Lib/csv.py [https://github.com/python/cpython/tree/3.14/Lib/csv.py]

所謂的 CSV (Comma Separated Values) 檔案格式是試算表及資料庫中最常見的匯入、匯出檔案格式。在嘗試以 RFC 4180 [https://datatracker.ietf.org/doc/html/rfc4180.html] 中的標準化方式來描述格式之前，CSV 格式已經使用了許多年。由於缺少一個完善定義的標準，意味著各個不同的應用程式會在資料產生及銷毀時有微妙的差別。這些不同之處使得從不同資料來源處理 CSV 檔案時會非常擾人。儘管如此，雖然分隔符號和引號字元有所不同，整體的格式非常相似，可以寫個單一模組來高效率的操作這樣的資料，讓程式設計師可以隱藏讀取及寫入資料的細節。

csv 模組實作透過 class 去讀取、寫入 CSV 格式的表格資料。它讓程式設計師可以說出：「以 Excel 為首選並寫入該種格式的資料」或是「從 Excel 產生的檔案來讀取資料」，且無需知道這是 Excel 所使用的 CSV 格式等精確的細節。程式設計師也可以描述其他應用程式所理解的 CSV 格式或他們自行定義具有特殊意義的 CSV 格式。

csv 模組的 reader 及 writer 物件可以讀取及寫入序列。程式設計師也可以透過 DictReader 及 DictWriter class（類別）使用 dictionary （字典）讀取及寫入資料。

也參考

PEP 305 [https://peps.python.org/pep-0305/] - CSV 檔案 API

Python Enhancement Proposal (PEP) 所提出的 Python 附加功能。

模組內容

csv 模組定義了以下函式：

csv.reader(csvfile, /, dialect='excel', **fmtparams)

回傳一個讀取器物件 (reader object) 並處理在指定的 csvfile 中的每一行，csvfile 必須是字串的可疊代物件 (iterable of strings)，其中每個字串都要是讀取器所定義的 csv 格式，csvfile 通常是個類檔案物件或者 list。如果 csvfile 是個檔案物件，則需開啟時使用 newline=''。 [1] dialect 為一個可選填的參數，可以用為特定的 CSV dialect（方言） 定義一組參數。它可能為 Dialect 的一個子類別 (subclass) 的實例或是由 list_dialects() 函式回傳的多個字串中的其中之一。另一個可選填的關鍵字引數 fmtparams 可以在這個 dialect 中覆寫 (override) 個別的格式化參數 (formatting parameter)。關於 dialect 及格式化參數的完整說明，請見段落 Dialect 與格式參數。

從 CSV 檔案讀取的每一列會回傳為一個字串列表。除非格式選項 QUOTE_NONNUMERIC 有被指定（在這個情況之下，沒有引號的欄位都會被轉換成浮點數），否則不會進行自動資料型別轉換。

一個簡短的用法範例：

>>> import csv
>>> with open('eggs.csv', newline='') as csvfile:
...     spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
...     for row in spamreader:
...         print(', '.join(row))
Spam, Spam, Spam, Spam, Spam, Baked Beans
Spam, Lovely Spam, Wonderful Spam

csv.writer(csvfile, /, dialect='excel', **fmtparams)

回傳一個寫入器物件 (writer object)，其負責在給定的類檔案物件 (file-like object) 上將使用者的資料轉換為分隔字串 (delimited string)。csvfile 可以為具有 write() method 的任何物件。若 csvfile 為一個檔案物件，它應該使用 newline='' 開啟 [1] 。dialect 為一個可選填的參數，可以用為特定的 CSV dialect 定義一組參數。它可能為 Dialect 的一個子類別的實例或是由 list_dialects() 函式回傳的多個字串中的其中之一。另一個可選填的關鍵字引數 fmtparams 可以在這個 dialect 中覆寫個別的格式化參數。關於 dialect 及格式化參數的完整說明，請見段落 Dialect 與格式參數。為了更容易與有實作 DB API 的模組互相接合，None 值會被寫成空字串。雖然這不是一個可逆的變換，這使得dump （傾印） SQL NULL 資料值到 CSV 檔案上就無需讓 cursor.fetch* 呼叫回傳的資料進行預處理 (preprocessing)。其餘非字串的資料則會在寫入之前用 str() 函式進行字串化 (stringify)。

一個簡短的用法範例：

import csv
with open('eggs.csv', 'w', newline='') as csvfile:
    spamwriter = csv.writer(csvfile, delimiter=' ',
                            quotechar='|', quoting=csv.QUOTE_MINIMAL)
    spamwriter.writerow(['Spam'] * 5 + ['Baked Beans'])
    spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])

csv.register_dialect(name, /, dialect='excel', **fmtparams)

將 dialect 與 name 進行關聯 (associate)。name 必須為字串。這個 dialect 可以透過傳遞 Dialect 的子類別進行指定；或是關鍵字引數 fmtparams；或是以上兩者皆是，並透過關鍵字引數來覆寫 dialect 的參數。關於 dialect 及格式化參數的完整說明，請見段落 Dialect 與格式參數。

csv.unregister_dialect(name)

從 dialect 註冊表 (registry) 中，刪除與 name 關聯的 dialect。若 name 如果不是註冊的 dialect 名稱，則會產生一個 Error。

csv.get_dialect(name)

回傳一個與 name 關聯的 dialect。若 name 如果不是註冊的 dialect 名稱，則會產生一個 Error。這個函式會回傳一個 immutable （不可變物件） Dialect。

csv.list_dialects()

回傳所有已註冊的 dialect 名稱。

csv.field_size_limit()

csv.field_size_limit(new_limit)

回傳目前的剖析器 (parser) 允許的最大字串大小。如果 new_limit 被給定，則會變成新的最大字串大小。

csv 模組定義了下列的類別：

class csv.DictReader(f, fieldnames=None, restkey=None, restval=None, dialect='excel', *args, **kwds)

建立一個物件，其運作上就像一般的讀取器，但可以將每一列資訊 map （對映） 到 dict 中，可以透過選填的參數 fieldnames 設定 key。

參數 fieldnames 是一個 sequence。如果 fieldnames 被省略了，檔案 f 中第一列的值會被當作欄位標題，且於結果中會被省略。如果 fieldname 有提供，它們就會被使用，且第一列會被包含在結果中。不管欄位標題是如何決定的，dictionary 都會保留原始的排序。

如果一列資料中的欄位比欄位標題還多，其餘的資料及以 restkey （預設為 None）特指的欄位標題會放入列表當中並儲存。如果一個非空的 (non-blank) 列中的欄位比欄位標題還少，缺少的值則會填入 restval （預設為 None）的值。

所有其他選填的引數或關鍵字引數皆會傳遞至下層的 reader 實例。

如果傳遞至 fieldnames 的引數是個疊代器，則會被迫成為一個 list。

在 3.6 版的變更: 回傳的列已成為型別 OrderedDict。

在 3.8 版的變更: 回傳的列已成為型別 dict。

一個簡短的用法範例：

>>> import csv
>>> with open('names.csv', newline='') as csvfile:
...     reader = csv.DictReader(csvfile)
...     for row in reader:
...         print(row['first_name'], row['last_name'])
...
Eric Idle
John Cleese

>>> print(row)
{'first_name': 'John', 'last_name': 'Cleese'}

class csv.DictWriter(f, fieldnames, restval='', extrasaction='raise', dialect='excel', *args, **kwds)

建立一個物件，其運作上就像一般的寫入器，但可以將 dictionary map 到輸出的列上。參數 fieldnames 是一個鍵值的 sequence 且可以辨識 dictionary 中傳遞至 writerow() method 寫入至檔案 f 中的值。如果 dictionary 中缺少了 fieldnames 的鍵值，則會寫入選填的參數 restval 的值。如果傳遞至 writerow() method 的 dictionary 包含了一個 fieldnames 中不存在的鍵值，選填的參數 extrasaction 可以指出該執行的動作。如果它被設定為 'raise'，預設會觸發 ValueError。如果它被設定為 'ignore'，dictionary 中額外的值會被忽略。其他選填的引數或關鍵字引數皆會傳遞至下層的 writer 實例。

請記得這不像類別 DictReader，在類別 DictWriter 中，參數 fieldnames 並不是選填的。

如果傳遞至 fieldnames 的引數是個疊代器，則會被迫成為一個 list。

一個簡短的用法範例：

import csv

with open('names.csv', 'w', newline='') as csvfile:
    fieldnames = ['first_name', 'last_name']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

    writer.writeheader()
    writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})
    writer.writerow({'first_name': 'Lovely', 'last_name': 'Spam'})
    writer.writerow({'first_name': 'Wonderful', 'last_name': 'Spam'})

class csv.Dialect

類別 Dialect 是一個容器類別，其屬性 (attribute) 包含如何處理雙引號、空白、分隔符號等資訊。由於缺少一個嚴謹的 CSV 技術規範，不同的應用程式會產出有巧妙不同的 CSV 資料。Dialect 實例定義了 reader 以及 writer 的實例該如何表示。

所有可用的 Dialect 名稱會透過 list_dialects() 回傳，且它們可以透過特定 reader 及 writer 類別的初始器 (initializer, __init__) 函式進行註冊，就像這樣：

import csv

with open('students.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile, dialect='unix')

class csv.excel

類別 excel 定義了透過 Excel 產生的 CSV 檔案的慣用屬性。它被註冊的 dialect 名稱為 'excel'。

class csv.excel_tab

類別 excel_tab 定義了透過 Excel 產生並以 Tab 作為分隔的 CSV 檔案的慣用屬性。它被註冊的 dialect 名稱為 'excel-tab'。

class csv.unix_dialect

類別 unix_dialect 定義了透過 UNIX 系統產生的 CSV 檔案的慣用屬性，換句話說，使用 '\n' 作為換行符號且所有欄位都被引號包覆起來。它被註冊的 dialect 名稱為 'unix'。

在 3.2 版被加入.

class csv.Sniffer

類別 Sniffer 被用來推斷 CSV 檔案的格式。

類別 Sniffer 提供了兩個 method：

sniff(sample, delimiters=None)

分析給定的 sample 且回傳一個 Dialect 子類別，反應出找到的格式參數。如果給定選填的參數 delimiters，它會被解釋為一個字串且含有可能、有效的分隔字元。

has_header(sample)

如果第一列的文字顯示將作為一系列的欄位標題，會分析 sample 文字（假定他是 CSV 格式）並回傳 True。檢查每一欄時，會考慮是否滿足兩個關鍵標準其中之一，判斷 sample 是否包含標題：

第二列至第 n 列包含數字

第二列到第 n 列包含的字串中至少有一個值的長度與該行的假定標題的長度不同。

對標頭之後的二十一個列進行取樣；如果超過一半的行及列滿足條件，則回傳 True。

備註

此方法是一個粗略的啟發，可能會產生偽陽性及偽陰性 (false positives and negatives)。

一個 Sniffer 的使用範例：

with open('example.csv', newline='') as csvfile:
    dialect = csv.Sniffer().sniff(csvfile.read(1024))
    csvfile.seek(0)
    reader = csv.reader(csvfile, dialect)
    # ... 在這邊處理 CSV 檔案 ...

csv 模組定義了以下常數：

csv.QUOTE_ALL

引導 writer 物件引用所有欄位。

csv.QUOTE_MINIMAL

引導 writer 物件只引用包含特殊字元的欄位，例如：delimiter、quotechar、'\r'、'\n' 或是 lineterminator 的其他字元。

csv.QUOTE_NONNUMERIC

引導 writer 物件引用所有非數字的欄位。

引導 reader 物件轉換所有非引用的欄位為 float。

備註

Some numeric types, such as bool, Fraction, or IntEnum, have a string representation that cannot be converted to float. They cannot be read in the QUOTE_NONNUMERIC and QUOTE_STRINGS modes.

csv.QUOTE_NONE

引導 writer 物件不得引用欄位。當目前的 delimiter、quotechar、'\r'、'\n' 或是 lineterminator 的其他字元出現在輸出資料時，在他之前的字元是目前的 escapechar。如果沒有設定 escapechar，若遇到任何字元需要逸出，寫入器則會引發 Error。設定 quotechar 為 None 以防止逸出。

引導 reader 物件不對引號進行特別處理。

csv.QUOTE_NOTNULL

引導 writer 物件引用所有非 None 的欄位。這與 QUOTE_ALL 相似，除非如果欄位值為 None，該欄位則被寫成空（沒有引號）字串。

引導 reader 物件將空（沒有引號）欄位直譯 (interpret) 為 None，否則會和 QUOTE_ALL 有相同的表現方式。

在 3.12 版被加入.

csv.QUOTE_STRINGS

引導 writer 物件永遠在字串的欄位前後放置引號。這與 QUOTE_NONNUMERIC 相似，除非如果欄位值為 None，該欄位則被寫成空（沒有引號）字串。

引導 reader 物件將空（沒有引號）字串直譯為 None，否則會和 QUOTE_NONNUMERIC 有相同的表現方式。

在 3.12 版被加入.

csv 模組定義下列例外：

exception csv.Error

當偵測到錯誤時，任何函式都可以引發。

Dialect 與格式參數

為了讓指定輸入及輸出紀錄的格式更方便，特定的格式化參數會被組成 dialect。一個 dialect 是 Dialect class 的子類別，其包含多個描述 CSV 檔案格式的多個屬性。當建立 reader 或 writer 物件時，程式設計師可以指定一個字串或是一個 Dialect 的子類別作為 dialect 參數。此外，或是作為替代，在dialect參數中，程式設計師可以指定個別的格式化參數，其與 Dialect 類別定義的屬性具有相同的名字。

Dialect 支援下列屬性：

Dialect.delimiter

一個單一字元 (one-character) 的字串可已用來分割欄位。預設為 ','。

Dialect.doublequote

控制 quotechar 的實例何時出現在欄位之中，並讓它們自己被放在引號之內。當屬性為 True，字元會是雙引號。若為 False，在 quotechar 之前會先使用 escapechar 作為前綴字。預設為 True。

在輸出時，若 doublequote 是 False 且逸出字元沒有被設定，當一個引號在欄位中被發現時，Error 會被引發。

Dialect.escapechar

一個單一字元的字串，會被寫入器用來逸出需要逸出的字元：

the delimiter, the quotechar, '\r', '\n' and any of the characters in lineterminator are escaped if quoting is set to QUOTE_NONE;

the quotechar is escaped if doublequote is False;

escapechar 本身。

在讀取時，escapechar 會移除後面字元的任何特殊意義。預設為 None，表示禁止逸出。

在 3.11 版的變更: escapechar 為空是不被接受的。

Dialect.lineterminator

由 writer 產生被用來分行的字串。預設為 '\r\n'。

備註

reader 是 hard-coded 辨別 '\r' or '\n' 作為行尾 (end-of-line)，並忽略lineterminator。未來可能會改變這個行為。

Dialect.quotechar

一個單一字元的字串被用於引用包含特殊字元的欄位，像是 delimiter、quotechar 或是換行字元（'\r'、'\n' 或是 lineterminator 的任一字元）。預設為 '"'。如果 quoting 設定為 QUOTE_NONE，可以設定為 None 以防止逸出 '"'。

在 3.11 版的變更: quotechar 為空是不被允許的。

Dialect.quoting

控制 writer 何時產生引號，以及 reader 如何辨識引號。如 quotechar 不為 None，則可以使用任何 QUOTE_* 常數且預設為 QUOTE_MINIMAL。否則預設為 QUOTE_NONE。

Dialect.skipinitialspace

若為 True，在緊接著delimiter後的空格會被忽略。預設為 False。當結合 delimiter=' ' 與 skipinitialspace=True 時，不允許沒有引號的空欄位。

Dialect.strict

若為 True，若有錯誤的 CSV 輸入則會引發 Error。預設為 False。

讀取器物件

讀取器物件（reader() 函式回傳的 DictReader 實例與物件）有下列公開方法 (public method)：

csvreader.__next__()

回傳一個列表為讀入器的可疊代物件的下一列內容（若該物件是由 reader() 回傳）或是一個 dict（若為 DictReader 實例），會依據目前的 Dialect 進行剖析。通常會用 next(reader) 來進行呼叫。

讀取器物件有下列公開屬性 (public attributes)：

csvreader.dialect

dialect 的唯讀敘述，會被剖析器使用。

csvreader.line_num

來源疊代器所讀取的行數。這與回傳的紀錄數不同，因為可以進行跨行紀錄。

DictReader 物件有下列公開屬性：

DictReader.fieldnames

若在建立物件時沒有作為參數傳遞，這個屬性會在第一次存取之前或是第一筆資料被讀取之前進行初始化 (initialize)。

寫入器物件

writer 物件（writer() 函式回傳的 DictWriter 實例與物件）有下列公開方法。對於 writer 物件而言，一個列中必須為一個可疊代的字串或是數字；對於 DictWriter 物件而言，則必須為一個 dictionary ，且可以對應欄位標題至字串或數字（會先透過 str() 進行傳遞）。請注意，在寫入複數 (complex number) 時會用小括號 (parens) 包起來。這可能在其他程式讀取 CSV 檔案時導致某些問題（假設他們完全支援複雜數字）。

csvwriter.writerow(row, /)

將參數 row 寫入至寫入器的檔案物件中，並依照目前的 Dialect 進行格式化。回傳下層檔案物件 write 方法的回傳值。

在 3.5 版的變更: 新增對任意可疊代物件 (arbitrary iterables) 的支援。

csvwriter.writerows(rows, /)

將 rows 中所有元素（為上述的一個可疊代的 row 物件）寫入至寫入器的檔案物件中，並依照目前的 dialect 進行格式化。

寫入器物件有下列公開屬性：

csvwriter.dialect

dialect 的唯讀敘述，會被寫入器使用。

DictWriter 物件有下列公開方法：

DictWriter.writeheader()

將具欄位標題的一列（於建構函式 (constructor) 中指定的）寫入至寫入器的檔案物件中，並依照目前的 dialect 進行格式化。回傳內部呼叫 csvwriter.writerow() 的回傳值。

在 3.2 版被加入.

在 3.8 版的變更: writeheader() 現在也會回傳內部呼叫 csvwriter.writerow() 的回傳值。

範例

最簡單的讀取 CSV 檔案範例：

import csv
with open('some.csv', newline='') as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

讀取一個其他格式的檔案：

import csv
with open('passwd', newline='') as f:
    reader = csv.reader(f, delimiter=':', quoting=csv.QUOTE_NONE)
    for row in reader:
        print(row)

相對最簡單、可行的寫入範例為：

import csv
with open('some.csv', 'w', newline='') as f:
    writer = csv.writer(f)
    writer.writerows(someiterable)

當 open() 被使用於開啟並讀取一個 CSV 檔案，該檔案會預設使用系統預設的編碼格式（請見 locale.getencoding()），並解碼為 unicode。若要使用不同編碼格式進行檔案解碼，請使用 open 函式的 encoding 引數：

import csv
with open('some.csv', newline='', encoding='utf-8') as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

同理可以應用到使用不同編碼格式進行寫入：當開啟輸出檔案時，指定 encoding 引數。

註冊一個新的 dialect ：

import csv
csv.register_dialect('unixpwd', delimiter=':', quoting=csv.QUOTE_NONE)
with open('passwd', newline='') as f:
    reader = csv.reader(f, 'unixpwd')

稍微進階的讀取器用法 -- 擷取及回報錯誤：

import csv, sys
filename = 'some.csv'
with open(filename, newline='') as f:
    reader = csv.reader(f)
    try:
        for row in reader:
            print(row)
    except csv.Error as e:
        sys.exit(f'file {filename}, line {reader.line_num}: {e}')

而當模組無法直接支援剖析字串時，仍可以輕鬆的解決：

import csv
for row in csv.reader(['one,two,three']):
    print(row)

註解

[1] (1,2)

如果 newline='' 沒有被指定，則嵌入引號中的換行符號不會被正確直譯，使用 \r\n 行尾 (line ending) 的平台會寫入額外的 \r。自從 csv 模組有自己 (統一的) 換行處理方式，因此指定 newline='' 會永遠是安全的。

configparser --- 設定檔剖析器

原始碼：Lib/configparser.py [https://github.com/python/cpython/tree/3.14/Lib/configparser.py]

This module provides the ConfigParser class which implements a basic configuration language which provides a structure similar to what's found in Microsoft Windows INI files. You can use this to write Python programs which can be customized by end users easily.

備註

This library does not interpret or write the value-type prefixes used in the Windows Registry extended version of INI syntax.

也參考

tomllib 模組

TOML is a well-specified format for application configuration files. It is specifically designed to be an improved version of INI.

shlex 模組

Support for creating Unix shell-like mini-languages which can also be used for application configuration files.

json 模組

The json module implements a subset of JavaScript syntax which is sometimes used for configuration, but does not support comments.

Quick Start

Let's take a very basic configuration file that looks like this:

[DEFAULT]
ServerAliveInterval = 45
Compression = yes
CompressionLevel = 9
ForwardX11 = yes

[forge.example]
User = hg

[topsecret.server.example]
Port = 50022
ForwardX11 = no

The structure of INI files is described in the following section. Essentially, the file consists of sections, each of which contains keys with values. configparser classes can read and write such files. Let's start by creating the above configuration file programmatically.

>>> import configparser
>>> config = configparser.ConfigParser()
>>> config['DEFAULT'] = {'ServerAliveInterval': '45',
...                      'Compression': 'yes',
...                      'CompressionLevel': '9'}
>>> config['forge.example'] = {}
>>> config['forge.example']['User'] = 'hg'
>>> config['topsecret.server.example'] = {}
>>> topsecret = config['topsecret.server.example']
>>> topsecret['Port'] = '50022'     # mutates the parser
>>> topsecret['ForwardX11'] = 'no'  # same here
>>> config['DEFAULT']['ForwardX11'] = 'yes'
>>> with open('example.ini', 'w') as configfile:
...   config.write(configfile)
...

As you can see, we can treat a config parser much like a dictionary. There are differences, outlined later, but the behavior is very close to what you would expect from a dictionary.

Now that we have created and saved a configuration file, let's read it back and explore the data it holds.

>>> config = configparser.ConfigParser()
>>> config.sections()
[]
>>> config.read('example.ini')
['example.ini']
>>> config.sections()
['forge.example', 'topsecret.server.example']
>>> 'forge.example' in config
True
>>> 'python.org' in config
False
>>> config['forge.example']['User']
'hg'
>>> config['DEFAULT']['Compression']
'yes'
>>> topsecret = config['topsecret.server.example']
>>> topsecret['ForwardX11']
'no'
>>> topsecret['Port']
'50022'
>>> for key in config['forge.example']:
...     print(key)
user
compressionlevel
serveraliveinterval
compression
forwardx11
>>> config['forge.example']['ForwardX11']
'yes'

As we can see above, the API is pretty straightforward. The only bit of magic involves the DEFAULT section which provides default values for all other sections [1]. Note also that keys in sections are case-insensitive and stored in lowercase [1].

It is possible to read several configurations into a single ConfigParser, where the most recently added configuration has the highest priority. Any conflicting keys are taken from the more recent configuration while the previously existing keys are retained. The example below reads in an override.ini file, which will override any conflicting keys from the example.ini file.

[DEFAULT]
ServerAliveInterval = -1

>>> config_override = configparser.ConfigParser()
>>> config_override['DEFAULT'] = {'ServerAliveInterval': '-1'}
>>> with open('override.ini', 'w') as configfile:
...     config_override.write(configfile)
...
>>> config_override = configparser.ConfigParser()
>>> config_override.read(['example.ini', 'override.ini'])
['example.ini', 'override.ini']
>>> print(config_override.get('DEFAULT', 'ServerAliveInterval'))
-1

This behaviour is equivalent to a ConfigParser.read() call with several files passed to the filenames parameter.

Supported Datatypes

Config parsers do not guess datatypes of values in configuration files, always storing them internally as strings. This means that if you need other datatypes, you should convert on your own:

>>> int(topsecret['Port'])
50022
>>> float(topsecret['CompressionLevel'])
9.0

Since this task is so common, config parsers provide a range of handy getter methods to handle integers, floats and booleans. The last one is the most interesting because simply passing the value to bool() would do no good since bool('False') is still True. This is why config parsers also provide getboolean(). This method is case-insensitive and recognizes Boolean values from 'yes'/'no', 'on'/'off', 'true'/'false' and '1'/'0' [1]. For example:

>>> topsecret.getboolean('ForwardX11')
False
>>> config['forge.example'].getboolean('ForwardX11')
True
>>> config.getboolean('forge.example', 'Compression')
True

Apart from getboolean(), config parsers also provide equivalent getint() and getfloat() methods. You can register your own converters and customize the provided ones. [1]

Fallback Values

As with a dictionary, you can use a section's get() method to provide fallback values:

>>> topsecret.get('Port')
'50022'
>>> topsecret.get('CompressionLevel')
'9'
>>> topsecret.get('Cipher')
>>> topsecret.get('Cipher', '3des-cbc')
'3des-cbc'

Please note that default values have precedence over fallback values. For instance, in our example the 'CompressionLevel' key was specified only in the 'DEFAULT' section. If we try to get it from the section 'topsecret.server.example', we will always get the default, even if we specify a fallback:

>>> topsecret.get('CompressionLevel', '3')
'9'

One more thing to be aware of is that the parser-level get() method provides a custom, more complex interface, maintained for backwards compatibility. When using this method, a fallback value can be provided via the fallback keyword-only argument:

>>> config.get('forge.example', 'monster',
...            fallback='No such things as monsters')
'No such things as monsters'

The same fallback argument can be used with the getint(), getfloat() and getboolean() methods, for example:

>>> 'BatchMode' in topsecret
False
>>> topsecret.getboolean('BatchMode', fallback=True)
True
>>> config['DEFAULT']['BatchMode'] = 'no'
>>> topsecret.getboolean('BatchMode', fallback=True)
False

支援的 INI 檔案結構

A configuration file consists of sections, each led by a [section] header, followed by key/value entries separated by a specific string (= or : by default [1]). By default, section names are case sensitive but keys are not [1]. Leading and trailing whitespace is removed from keys and values. Values can be omitted if the parser is configured to allow it [1], in which case the key/value delimiter may also be left out. Values can also span multiple lines, as long as they are indented deeper than the first line of the value. Depending on the parser's mode, blank lines may be treated as parts of multiline values or ignored.

By default, a valid section name can be any string that does not contain '\n'. To change this, see ConfigParser.SECTCRE.

The first section name may be omitted if the parser is configured to allow an unnamed top level section with allow_unnamed_section=True. In this case, the keys/values may be retrieved by UNNAMED_SECTION as in config[UNNAMED_SECTION].

Configuration files may include comments, prefixed by specific characters (# and ; by default [1]). Comments may appear on their own on an otherwise empty line, possibly indented. [1]

舉例來說：

[Simple Values]
key=value
spaces in keys=allowed
spaces in values=allowed as well
spaces around the delimiter = obviously
you can also use : to delimit keys from values

[All Values Are Strings]
values like this: 1000000
or this: 3.14159265359
are they treated as numbers? : no
integers, floats and booleans are held as: strings
can use the API to get converted values directly: true

[Multiline Values]
chorus: I'm a lumberjack, and I'm okay
    I sleep all night and I work all day

[No Values]
key_without_value
empty string value here =

[You can use comments]
# like this
; or this

# By default only in an empty line.
# Inline comments can be harmful because they prevent users
# from using the delimiting characters as parts of values.
# That being said, this can be customized.

    [Sections Can Be Indented]
        can_values_be_as_well = True
        does_that_mean_anything_special = False
        purpose = formatting for readability
        multiline_values = are
            handled just fine as
            long as they are indented
            deeper than the first line
            of a value
        # Did I mention we can indent comments, too?

Unnamed Sections

The name of the first section (or unique) may be omitted and values retrieved by the UNNAMED_SECTION attribute.

>>> config = """
... option = value
...
... [  Section 2  ]
... another = val
... """
>>> unnamed = configparser.ConfigParser(allow_unnamed_section=True)
>>> unnamed.read_string(config)
>>> unnamed.get(configparser.UNNAMED_SECTION, 'option')
'value'

Interpolation of values

On top of the core functionality, ConfigParser supports interpolation. This means values can be preprocessed before returning them from get() calls.

class configparser.BasicInterpolation

The default implementation used by ConfigParser. It enables values to contain format strings which refer to other values in the same section, or values in the special default section [1]. Additional default values can be provided on initialization.

舉例來說：

[Paths]
home_dir: /Users
my_dir: %(home_dir)s/lumberjack
my_pictures: %(my_dir)s/Pictures

[Escape]
# use a %% to escape the % sign (% is the only character that needs to be escaped):
gain: 80%%

In the example above, ConfigParser with interpolation set to BasicInterpolation() would resolve %(home_dir)s to the value of home_dir (/Users in this case). %(my_dir)s in effect would resolve to /Users/lumberjack. All interpolations are done on demand so keys used in the chain of references do not have to be specified in any specific order in the configuration file.

With interpolation set to None, the parser would simply return %(my_dir)s/Pictures as the value of my_pictures and %(home_dir)s/lumberjack as the value of my_dir.

class configparser.ExtendedInterpolation

An alternative handler for interpolation which implements a more advanced syntax, used for instance in zc.buildout. Extended interpolation is using ${section:option} to denote a value from a foreign section. Interpolation can span multiple levels. For convenience, if the section: part is omitted, interpolation defaults to the current section (and possibly the default values from the special section).

For example, the configuration specified above with basic interpolation, would look like this with extended interpolation:

[Paths]
home_dir: /Users
my_dir: ${home_dir}/lumberjack
my_pictures: ${my_dir}/Pictures

[Escape]
# use a $$ to escape the $ sign ($ is the only character that needs to be escaped):
cost: $$80

Values from other sections can be fetched as well:

[Common]
home_dir: /Users
library_dir: /Library
system_dir: /System
macports_dir: /opt/local

[Frameworks]
Python: 3.2
path: ${Common:system_dir}/Library/Frameworks/

[Arthur]
nickname: Two Sheds
last_name: Jackson
my_dir: ${Common:home_dir}/twosheds
my_pictures: ${my_dir}/Pictures
python_dir: ${Frameworks:path}/Python/Versions/${Frameworks:Python}

Mapping Protocol Access

在 3.2 版被加入.

Mapping protocol access is a generic name for functionality that enables using custom objects as if they were dictionaries. In case of configparser, the mapping interface implementation is using the parser['section']['option'] notation.

parser['section'] in particular returns a proxy for the section's data in the parser. This means that the values are not copied but they are taken from the original parser on demand. What's even more important is that when values are changed on a section proxy, they are actually mutated in the original parser.

configparser objects behave as close to actual dictionaries as possible. The mapping interface is complete and adheres to the MutableMapping ABC. However, there are a few differences that should be taken into account:

By default, all keys in sections are accessible in a case-insensitive manner [1]. E.g. for option in parser["section"] yields only optionxform'ed option key names. This means lowercased keys by default. At the same time, for a section that holds the key 'a', both expressions return True:

"a" in parser["section"]
"A" in parser["section"]

All sections include DEFAULTSECT values as well which means that .clear() on a section may not leave the section visibly empty. This is because default values cannot be deleted from the section (because technically they are not there). If they are overridden in the section, deleting causes the default value to be visible again. Trying to delete a default value causes a KeyError.

DEFAULTSECT 不能從剖析器中移除：

嘗試刪除它會引發 ValueError，

parser.clear() 會保持它不變，

parser.popitem() 永遠不會回傳它。

parser.get(section, option, **kwargs) - the second argument is not a fallback value. Note however that the section-level get() methods are compatible both with the mapping protocol and the classic configparser API.

parser.items() is compatible with the mapping protocol (returns a list of section_name, section_proxy pairs including the DEFAULTSECT). However, this method can also be invoked with arguments: parser.items(section, raw, vars). The latter call returns a list of option, value pairs for a specified section, with all interpolations expanded (unless raw=True is provided).

The mapping protocol is implemented on top of the existing legacy API so that subclasses overriding the original interface still should have mappings working as expected.

Customizing Parser Behaviour

There are nearly as many INI format variants as there are applications using it. configparser goes a long way to provide support for the largest sensible set of INI styles available. The default functionality is mainly dictated by historical background and it's very likely that you will want to customize some of the features.

The most common way to change the way a specific config parser works is to use the __init__() options:

defaults, default value: None

This option accepts a dictionary of key-value pairs which will be initially put in the DEFAULT section. This makes for an elegant way to support concise configuration files that don't specify values which are the same as the documented default.

Hint: if you want to specify default values for a specific section, use read_dict() before you read the actual file.

dict_type, default value: dict

This option has a major impact on how the mapping protocol will behave and how the written configuration files look. With the standard dictionary, every section is stored in the order they were added to the parser. Same goes for options within sections.

An alternative dictionary type can be used for example to sort sections and options on write-back.

Please note: there are ways to add a set of key-value pairs in a single operation. When you use a regular dictionary in those operations, the order of the keys will be ordered. For example:

>>> parser = configparser.ConfigParser()
>>> parser.read_dict({'section1': {'key1': 'value1',
...                                'key2': 'value2',
...                                'key3': 'value3'},
...                   'section2': {'keyA': 'valueA',
...                                'keyB': 'valueB',
...                                'keyC': 'valueC'},
...                   'section3': {'foo': 'x',
...                                'bar': 'y',
...                                'baz': 'z'}
... })
>>> parser.sections()
['section1', 'section2', 'section3']
>>> [option for option in parser['section3']]
['foo', 'bar', 'baz']

allow_no_value, default value: False

Some configuration files are known to include settings without values, but which otherwise conform to the syntax supported by configparser. The allow_no_value parameter to the constructor can be used to indicate that such values should be accepted:

>>> import configparser

>>> sample_config = """
... [mysqld]
...   user = mysql
...   pid-file = /var/run/mysqld/mysqld.pid
...   skip-external-locking
...   old_passwords = 1
...   skip-bdb
...   # we don't need ACID today
...   skip-innodb
... """
>>> config = configparser.ConfigParser(allow_no_value=True)
>>> config.read_string(sample_config)

>>> # Settings with values are treated as before:
>>> config["mysqld"]["user"]
'mysql'

>>> # Settings without values provide None:
>>> config["mysqld"]["skip-bdb"]

>>> # Settings which aren't specified still raise an error:
>>> config["mysqld"]["does-not-exist"]
Traceback (most recent call last):
  ...
KeyError: 'does-not-exist'

delimiters, default value: ('=', ':')

Delimiters are substrings that delimit keys from values within a section. The first occurrence of a delimiting substring on a line is considered a delimiter. This means values (but not keys) can contain the delimiters.

See also the space_around_delimiters argument to ConfigParser.write().

comment_prefixes, default value: ('#', ';')

inline_comment_prefixes, default value: None

Comment prefixes are strings that indicate the start of a valid comment within a config file. comment_prefixes are used only on otherwise empty lines (optionally indented) whereas inline_comment_prefixes can be used after every valid value (e.g. section names, options and empty lines as well). By default inline comments are disabled and '#' and ';' are used as prefixes for whole line comments.

在 3.2 版的變更: In previous versions of configparser behaviour matched comment_prefixes=('#',';') and inline_comment_prefixes=(';',).

Please note that config parsers don't support escaping of comment prefixes so using inline_comment_prefixes may prevent users from specifying option values with characters used as comment prefixes. When in doubt, avoid setting inline_comment_prefixes. In any circumstances, the only way of storing comment prefix characters at the beginning of a line in multiline values is to interpolate the prefix, for example:

>>> from configparser import ConfigParser, ExtendedInterpolation
>>> parser = ConfigParser(interpolation=ExtendedInterpolation())
>>> # the default BasicInterpolation could be used as well
>>> parser.read_string("""
... [DEFAULT]
... hash = #
...
... [hashes]
... shebang =
...   ${hash}!/usr/bin/env python
...   ${hash} -*- coding: utf-8 -*-
...
... extensions =
...   enabled_extension
...   another_extension
...   #disabled_by_comment
...   yet_another_extension
...
... interpolation not necessary = if # is not at line start
... even in multiline values = line #1
...   line #2
...   line #3
... """)
>>> print(parser['hashes']['shebang'])

#!/usr/bin/env python
# -*- coding: utf-8 -*-
>>> print(parser['hashes']['extensions'])

enabled_extension
another_extension
yet_another_extension
>>> print(parser['hashes']['interpolation not necessary'])
if # is not at line start
>>> print(parser['hashes']['even in multiline values'])
line #1
line #2
line #3

strict, default value: True

When set to True, the parser will not allow for any section or option duplicates while reading from a single source (using read_file(), read_string() or read_dict()). It is recommended to use strict parsers in new applications.

在 3.2 版的變更: In previous versions of configparser behaviour matched strict=False.

empty_lines_in_values, default value: True

In config parsers, values can span multiple lines as long as they are indented more than the key that holds them. By default parsers also let empty lines to be parts of values. At the same time, keys can be arbitrarily indented themselves to improve readability. In consequence, when configuration files get big and complex, it is easy for the user to lose track of the file structure. Take for instance:

[Section]
key = multiline
  value with a gotcha

 this = is still a part of the multiline value of 'key'

This can be especially problematic for the user to see if she's using a proportional font to edit the file. That is why when your application does not need values with empty lines, you should consider disallowing them. This will make empty lines split keys every time. In the example above, it would produce two keys, key and this.

default_section, default value: configparser.DEFAULTSECT (that is: "DEFAULT")

The convention of allowing a special section of default values for other sections or interpolation purposes is a powerful concept of this library, letting users create complex declarative configurations. This section is normally called "DEFAULT" but this can be customized to point to any other valid section name. Some typical values include: "general" or "common". The name provided is used for recognizing default sections when reading from any source and is used when writing configuration back to a file. Its current value can be retrieved using the parser_instance.default_section attribute and may be modified at runtime (i.e. to convert files from one format to another).

interpolation, default value: configparser.BasicInterpolation

Interpolation behaviour may be customized by providing a custom handler through the interpolation argument. None can be used to turn off interpolation completely, ExtendedInterpolation() provides a more advanced variant inspired by zc.buildout. More on the subject in the dedicated documentation section. RawConfigParser has a default value of None.

converters, default value: not set

Config parsers provide option value getters that perform type conversion. By default getint(), getfloat(), and getboolean() are implemented. Should other getters be desirable, users may define them in a subclass or pass a dictionary where each key is a name of the converter and each value is a callable implementing said conversion. For instance, passing {'decimal': decimal.Decimal} would add getdecimal() on both the parser object and all section proxies. In other words, it will be possible to write both parser_instance.getdecimal('section', 'key', fallback=0) and parser_instance['section'].getdecimal('key', 0).

If the converter needs to access the state of the parser, it can be implemented as a method on a config parser subclass. If the name of this method starts with get, it will be available on all section proxies, in the dict-compatible form (see the getdecimal() example above).

More advanced customization may be achieved by overriding default values of these parser attributes. The defaults are defined on the classes, so they may be overridden by subclasses or by attribute assignment.

ConfigParser.BOOLEAN_STATES

By default when using getboolean(), config parsers consider the following values True: '1', 'yes', 'true', 'on' and the following values False: '0', 'no', 'false', 'off'. You can override this by specifying a custom dictionary of strings and their Boolean outcomes. For example:

>>> custom = configparser.ConfigParser()
>>> custom['section1'] = {'funky': 'nope'}
>>> custom['section1'].getboolean('funky')
Traceback (most recent call last):
...
ValueError: Not a boolean: nope
>>> custom.BOOLEAN_STATES = {'sure': True, 'nope': False}
>>> custom['section1'].getboolean('funky')
False

Other typical Boolean pairs include accept/reject or enabled/disabled.

ConfigParser.optionxform(option)

This method transforms option names on every read, get, or set operation. The default converts the name to lowercase. This also means that when a configuration file gets written, all keys will be lowercase. Override this method if that's unsuitable. For example:

>>> config = """
... [Section1]
... Key = Value
...
... [Section2]
... AnotherKey = Value
... """
>>> typical = configparser.ConfigParser()
>>> typical.read_string(config)
>>> list(typical['Section1'].keys())
['key']
>>> list(typical['Section2'].keys())
['anotherkey']
>>> custom = configparser.RawConfigParser()
>>> custom.optionxform = lambda option: option
>>> custom.read_string(config)
>>> list(custom['Section1'].keys())
['Key']
>>> list(custom['Section2'].keys())
['AnotherKey']

備註

The optionxform function transforms option names to a canonical form. This should be an idempotent function: if the name is already in canonical form, it should be returned unchanged.

ConfigParser.SECTCRE

A compiled regular expression used to parse section headers. The default matches [section] to the name "section". Whitespace is considered part of the section name, thus [  larch  ] will be read as a section of name "  larch  ". Override this attribute if that's unsuitable. For example:

>>> import re
>>> config = """
... [Section 1]
... option = value
...
... [  Section 2  ]
... another = val
... """
>>> typical = configparser.ConfigParser()
>>> typical.read_string(config)
>>> typical.sections()
['Section 1', '  Section 2  ']
>>> custom = configparser.ConfigParser()
>>> custom.SECTCRE = re.compile(r"\[ *(?P<header>[^]]+?) *\]")
>>> custom.read_string(config)
>>> custom.sections()
['Section 1', 'Section 2']

備註

While ConfigParser objects also use an OPTCRE attribute for recognizing option lines, it's not recommended to override it because that would interfere with constructor options allow_no_value and delimiters.

Legacy API Examples

Mainly because of backwards compatibility concerns, configparser provides also a legacy API with explicit get/set methods. While there are valid use cases for the methods outlined below, mapping protocol access is preferred for new projects. The legacy API is at times more advanced, low-level and downright counterintuitive.

An example of writing to a configuration file:

import configparser

config = configparser.RawConfigParser()

# Please note that using RawConfigParser's set functions, you can assign
# non-string values to keys internally, but will receive an error when
# attempting to write to a file or when you get it in non-raw mode. Setting
# values using the mapping protocol or ConfigParser's set() does not allow
# such assignments to take place.
config.add_section('Section1')
config.set('Section1', 'an_int', '15')
config.set('Section1', 'a_bool', 'true')
config.set('Section1', 'a_float', '3.1415')
config.set('Section1', 'baz', 'fun')
config.set('Section1', 'bar', 'Python')
config.set('Section1', 'foo', '%(bar)s is %(baz)s!')

# Writing our configuration file to 'example.cfg'
with open('example.cfg', 'w') as configfile:
    config.write(configfile)

An example of reading the configuration file again:

import configparser

config = configparser.RawConfigParser()
config.read('example.cfg')

# getfloat() raises an exception if the value is not a float
# getint() and getboolean() also do this for their respective types
a_float = config.getfloat('Section1', 'a_float')
an_int = config.getint('Section1', 'an_int')
print(a_float + an_int)

# Notice that the next output does not interpolate '%(bar)s' or '%(baz)s'.
# This is because we are using a RawConfigParser().
if config.getboolean('Section1', 'a_bool'):
    print(config.get('Section1', 'foo'))

To get interpolation, use ConfigParser:

import configparser

cfg = configparser.ConfigParser()
cfg.read('example.cfg')

# Set the optional *raw* argument of get() to True if you wish to disable
# interpolation in a single get operation.
print(cfg.get('Section1', 'foo', raw=False))  # -> "Python is fun!"
print(cfg.get('Section1', 'foo', raw=True))   # -> "%(bar)s is %(baz)s!"

# The optional *vars* argument is a dict with members that will take
# precedence in interpolation.
print(cfg.get('Section1', 'foo', vars={'bar': 'Documentation',
                                       'baz': 'evil'}))

# The optional *fallback* argument can be used to provide a fallback value
print(cfg.get('Section1', 'foo'))
      # -> "Python is fun!"

print(cfg.get('Section1', 'foo', fallback='Monty is not.'))
      # -> "Python is fun!"

print(cfg.get('Section1', 'monster', fallback='No such things as monsters.'))
      # -> "No such things as monsters."

# A bare print(cfg.get('Section1', 'monster')) would raise NoOptionError
# but we can also use:

print(cfg.get('Section1', 'monster', fallback=None))
      # -> None

Default values are available in both types of ConfigParsers. They are used in interpolation if an option used is not defined elsewhere.

import configparser

# New instance with 'bar' and 'baz' defaulting to 'Life' and 'hard' each
config = configparser.ConfigParser({'bar': 'Life', 'baz': 'hard'})
config.read('example.cfg')

print(config.get('Section1', 'foo'))     # -> "Python is fun!"
config.remove_option('Section1', 'bar')
config.remove_option('Section1', 'baz')
print(config.get('Section1', 'foo'))     # -> "Life is hard!"

ConfigParser 物件

class configparser.ConfigParser(defaults=None, dict_type=dict, allow_no_value=False, *, delimiters=('=', ':'), comment_prefixes=('#', ';'), inline_comment_prefixes=None, strict=True, empty_lines_in_values=True, default_section=configparser.DEFAULTSECT, interpolation=BasicInterpolation(), converters={}, allow_unnamed_section=False)

The main configuration parser. When defaults is given, it is initialized into the dictionary of intrinsic defaults. When dict_type is given, it will be used to create the dictionary objects for the list of sections, for the options within a section, and for the default values.

When delimiters is given, it is used as the set of substrings that divide keys from values. When comment_prefixes is given, it will be used as the set of substrings that prefix comments in otherwise empty lines. Comments can be indented. When inline_comment_prefixes is given, it will be used as the set of substrings that prefix comments in non-empty lines.

When strict is True (the default), the parser won't allow for any section or option duplicates while reading from a single source (file, string or dictionary), raising DuplicateSectionError or DuplicateOptionError. When empty_lines_in_values is False (default: True), each empty line marks the end of an option. Otherwise, internal empty lines of a multiline option are kept as part of the value. When allow_no_value is True (default: False), options without values are accepted; the value held for these is None and they are serialized without the trailing delimiter.

When default_section is given, it specifies the name for the special section holding default values for other sections and interpolation purposes (normally named "DEFAULT"). This value can be retrieved and changed at runtime using the default_section instance attribute. This won't re-evaluate an already parsed config file, but will be used when writing parsed settings to a new config file.

Interpolation behaviour may be customized by providing a custom handler through the interpolation argument. None can be used to turn off interpolation completely, ExtendedInterpolation() provides a more advanced variant inspired by zc.buildout. More on the subject in the dedicated documentation section.

All option names used in interpolation will be passed through the optionxform() method just like any other option name reference. For example, using the default implementation of optionxform() (which converts option names to lower case), the values foo %(bar)s and foo %(BAR)s are equivalent.

When converters is given, it should be a dictionary where each key represents the name of a type converter and each value is a callable implementing the conversion from string to the desired datatype. Every converter gets its own corresponding get*() method on the parser object and section proxies.

When allow_unnamed_section is True (default: False), the first section name can be omitted. See the "Unnamed Sections" section.

It is possible to read several configurations into a single ConfigParser, where the most recently added configuration has the highest priority. Any conflicting keys are taken from the more recent configuration while the previously existing keys are retained. The example below reads in an override.ini file, which will override any conflicting keys from the example.ini file.

[DEFAULT]
ServerAliveInterval = -1

>>> config_override = configparser.ConfigParser()
>>> config_override['DEFAULT'] = {'ServerAliveInterval': '-1'}
>>> with open('override.ini', 'w') as configfile:
...     config_override.write(configfile)
...
>>> config_override = configparser.ConfigParser()
>>> config_override.read(['example.ini', 'override.ini'])
['example.ini', 'override.ini']
>>> print(config_override.get('DEFAULT', 'ServerAliveInterval'))
-1

在 3.1 版的變更: 預設的 dict_type 是 collections.OrderedDict。

在 3.2 版的變更: allow_no_value, delimiters, comment_prefixes, strict, empty_lines_in_values, default_section and interpolation were added.

在 3.5 版的變更: 新增 converters 引數。

在 3.7 版的變更: The defaults argument is read with read_dict(), providing consistent behavior across the parser: non-string keys and values are implicitly converted to strings.

在 3.8 版的變更: The default dict_type is dict, since it now preserves insertion order.

在 3.13 版的變更: Raise a MultilineContinuationError when allow_no_value is True, and a key without a value is continued with an indented line.

在 3.13 版的變更: 新增 allow_unnamed_section 引數。

defaults()

回傳包含整個實例預設值的字典。

sections()

Return a list of the sections available; the default section is not included in the list.

add_section(section)

Add a section named section to the instance. If a section by the given name already exists, DuplicateSectionError is raised. If the default section name is passed, ValueError is raised. The name of the section must be a string; if not, TypeError is raised.

在 3.2 版的變更: Non-string section names raise TypeError.

has_section(section)

Indicates whether the named section is present in the configuration. The default section is not acknowledged.

options(section)

Return a list of options available in the specified section.

has_option(section, option)

If the given section exists, and contains the given option, return True; otherwise return False. If the specified section is None or an empty string, DEFAULT is assumed.

read(filenames, encoding=None)

Attempt to read and parse an iterable of filenames, returning a list of filenames which were successfully parsed.

If filenames is a string, a bytes object or a path-like object, it is treated as a single filename. If a file named in filenames cannot be opened, that file will be ignored. This is designed so that you can specify an iterable of potential configuration file locations (for example, the current directory, the user's home directory, and some system-wide directory), and all existing configuration files in the iterable will be read.

If none of the named files exist, the ConfigParser instance will contain an empty dataset. An application which requires initial values to be loaded from a file should load the required file or files using read_file() before calling read() for any optional files:

import configparser, os

config = configparser.ConfigParser()
config.read_file(open('defaults.cfg'))
config.read(['site.cfg', os.path.expanduser('~/.myapp.cfg')],
            encoding='cp1250')

在 3.2 版的變更: Added the encoding parameter. Previously, all files were read using the default encoding for open().

在 3.6.1 版的變更: The filenames parameter accepts a path-like object.

在 3.7 版的變更: The filenames parameter accepts a bytes object.

read_file(f, source=None)

Read and parse configuration data from f which must be an iterable yielding Unicode strings (for example files opened in text mode).

Optional argument source specifies the name of the file being read. If not given and f has a name attribute, that is used for source; the default is '<???>'.

在 3.2 版被加入: 取代 readfp()。

read_string(string, source='<string>')

Parse configuration data from a string.

Optional argument source specifies a context-specific name of the string passed. If not given, '<string>' is used. This should commonly be a filesystem path or a URL.

在 3.2 版被加入.

read_dict(dictionary, source='<dict>')

Load configuration from any object that provides a dict-like items() method. Keys are section names, values are dictionaries with keys and values that should be present in the section. If the used dictionary type preserves order, sections and their keys will be added in order. Values are automatically converted to strings.

Optional argument source specifies a context-specific name of the dictionary passed. If not given, <dict> is used.

This method can be used to copy state between parsers.

在 3.2 版被加入.

get(section, option, *, raw=False, vars=None[, fallback])

Get an option value for the named section. If vars is provided, it must be a dictionary. The option is looked up in vars (if provided), section, and in DEFAULTSECT in that order. If the key is not found and fallback is provided, it is used as a fallback value. None can be provided as a fallback value.

All the '%' interpolations are expanded in the return values, unless the raw argument is true. Values for interpolation keys are looked up in the same manner as the option.

在 3.2 版的變更: Arguments raw, vars and fallback are keyword only to protect users from trying to use the third argument as the fallback fallback (especially when using the mapping protocol).

getint(section, option, *, raw=False, vars=None[, fallback])

A convenience method which coerces the option in the specified section to an integer. See get() for explanation of raw, vars and fallback.

getfloat(section, option, *, raw=False, vars=None[, fallback])

A convenience method which coerces the option in the specified section to a floating-point number. See get() for explanation of raw, vars and fallback.

getboolean(section, option, *, raw=False, vars=None[, fallback])

A convenience method which coerces the option in the specified section to a Boolean value. Note that the accepted values for the option are '1', 'yes', 'true', and 'on', which cause this method to return True, and '0', 'no', 'false', and 'off', which cause it to return False. These string values are checked in a case-insensitive manner. Any other value will cause it to raise ValueError. See get() for explanation of raw, vars and fallback.

items(raw=False, vars=None)

items(section, raw=False, vars=None)

When section is not given, return a list of section_name, section_proxy pairs, including DEFAULTSECT.

Otherwise, return a list of name, value pairs for the options in the given section. Optional arguments have the same meaning as for the get() method.

在 3.8 版的變更: Items present in vars no longer appear in the result. The previous behaviour mixed actual parser options with variables provided for interpolation.

set(section, option, value)

If the given section exists, set the given option to the specified value; otherwise raise NoSectionError. option and value must be strings; if not, TypeError is raised.

write(fileobject, space_around_delimiters=True)

Write a representation of the configuration to the specified file object, which must be opened in text mode (accepting strings). This representation can be parsed by a future read() call. If space_around_delimiters is true, delimiters between keys and values are surrounded by spaces.

在 3.14 版的變更: Raises InvalidWriteError if this would write a representation which cannot be accurately parsed by a future read() call from this parser.

備註

Comments in the original configuration file are not preserved when writing the configuration back. What is considered a comment, depends on the given values for comment_prefix and inline_comment_prefix.

remove_option(section, option)

Remove the specified option from the specified section. If the section does not exist, raise NoSectionError. If the option existed to be removed, return True; otherwise return False.

remove_section(section)

Remove the specified section from the configuration. If the section in fact existed, return True. Otherwise return False.

optionxform(option)

Transforms the option name option as found in an input file or as passed in by client code to the form that should be used in the internal structures. The default implementation returns a lower-case version of option; subclasses may override this or client code can set an attribute of this name on instances to affect this behavior.

You don't need to subclass the parser to use this method, you can also set it on an instance, to a function that takes a string argument and returns a string. Setting it to str, for example, would make option names case sensitive:

cfgparser = ConfigParser()
cfgparser.optionxform = str

Note that when reading configuration files, whitespace around the option names is stripped before optionxform() is called.

configparser.UNNAMED_SECTION

A special object representing a section name used to reference the unnamed section (see Unnamed Sections).

configparser.MAX_INTERPOLATION_DEPTH

The maximum depth for recursive interpolation for get() when the raw parameter is false. This is relevant only when the default interpolation is used.

RawConfigParser 物件

class configparser.RawConfigParser(defaults=None, dict_type=dict, allow_no_value=False, *, delimiters=('=', ':'), comment_prefixes=('#', ';'), inline_comment_prefixes=None, strict=True, empty_lines_in_values=True, default_section=configparser.DEFAULTSECT, interpolation=BasicInterpolation(), converters={}, allow_unnamed_section=False)

Legacy variant of the ConfigParser. It has interpolation disabled by default and allows for non-string section names, option names, and values via its unsafe add_section and set methods, as well as the legacy defaults= keyword argument handling.

在 3.2 版的變更: allow_no_value, delimiters, comment_prefixes, strict, empty_lines_in_values, default_section and interpolation were added.

在 3.5 版的變更: 新增 converters 引數。

在 3.8 版的變更: The default dict_type is dict, since it now preserves insertion order.

在 3.13 版的變更: 新增 allow_unnamed_section 引數。

備註

Consider using ConfigParser instead which checks types of the values to be stored internally. If you don't want interpolation, you can use ConfigParser(interpolation=None).

add_section(section)

Add a section named section or UNNAMED_SECTION to the instance.

If the given section already exists, DuplicateSectionError is raised. If the default section name is passed, ValueError is raised. If UNNAMED_SECTION is passed and support is disabled, UnnamedSectionDisabledError is raised.

Type of section is not checked which lets users create non-string named sections. This behaviour is unsupported and may cause internal errors.

在 3.14 版的變更: 新增對 UNNAMED_SECTION 的支援。

set(section, option, value)

If the given section exists, set the given option to the specified value; otherwise raise NoSectionError. While it is possible to use RawConfigParser (or ConfigParser with raw parameters set to true) for internal storage of non-string values, full functionality (including interpolation and output to files) can only be achieved using string values.

This method lets users assign non-string values to keys internally. This behaviour is unsupported and will cause errors when attempting to write to a file or get it in non-raw mode. Use the mapping protocol API which does not allow such assignments to take place.

例外

exception configparser.Error

Base class for all other configparser exceptions.

exception configparser.NoSectionError

Exception raised when a specified section is not found.

exception configparser.DuplicateSectionError

Exception raised if add_section() is called with the name of a section that is already present or in strict parsers when a section if found more than once in a single input file, string or dictionary.

在 3.2 版的變更: Added the optional source and lineno attributes and parameters to __init__().

exception configparser.DuplicateOptionError

Exception raised by strict parsers if a single option appears twice during reading from a single file, string or dictionary. This catches misspellings and case sensitivity-related errors, e.g. a dictionary may have two keys representing the same case-insensitive configuration key.

exception configparser.NoOptionError

Exception raised when a specified option is not found in the specified section.

exception configparser.InterpolationError

Base class for exceptions raised when problems occur performing string interpolation.

exception configparser.InterpolationDepthError

Exception raised when string interpolation cannot be completed because the number of iterations exceeds MAX_INTERPOLATION_DEPTH. Subclass of InterpolationError.

exception configparser.InterpolationMissingOptionError

Exception raised when an option referenced from a value does not exist. Subclass of InterpolationError.

exception configparser.InterpolationSyntaxError

Exception raised when the source text into which substitutions are made does not conform to the required syntax. Subclass of InterpolationError.

exception configparser.MissingSectionHeaderError

Exception raised when attempting to parse a file which has no section headers.

exception configparser.ParsingError

Exception raised when errors occur attempting to parse a file.

在 3.12 版的變更: The filename attribute and __init__() constructor argument were removed. They have been available using the name source since 3.2.

exception configparser.MultilineContinuationError

Exception raised when a key without a corresponding value is continued with an indented line.

在 3.13 版被加入.

exception configparser.UnnamedSectionDisabledError

Exception raised when attempting to use the UNNAMED_SECTION without enabling it.

在 3.14 版被加入.

exception configparser.InvalidWriteError

Exception raised when an attempted ConfigParser.write() would not be parsed accurately with a future ConfigParser.read() call.

Ex: Writing a key beginning with the ConfigParser.SECTCRE pattern would parse as a section header when read. Attempting to write this will raise this exception.

在 3.14 版被加入.

註腳

[1] (1,2,3,4,5,6,7,8,9,10,11)

Config parsers allow for heavy customization. If you are interested in changing the behaviour outlined by the footnote reference, consult the Customizing Parser Behaviour section.

tomllib --- 剖析 TOML 檔案

在 3.11 版被加入.

原始碼：Lib/tomllib [https://github.com/python/cpython/tree/3.14/Lib/tomllib]

此模組提供了剖析 TOML 1.0.0 (Tom's Obvious Minimal Language, https://toml.io [https://toml.io/en/]) 的一個介面，此模組並不支援寫入 TOML。

也參考

Tomli-W 套件 [https://pypi.org/project/tomli-w/]是一個 TOML 編寫器，可以與此模組結合使用，以提供標準函式庫中 marshal 和 pickle 模組之使用者所熟悉的寫入 API。

也參考

TOML 工具套件 [https://pypi.org/project/tomlkit/]是一個保留風格且具有讀寫能力的 TOML 函式庫。若要編輯已存在的 TOML 文件，建議用它來替換此模組。

此模組定義了以下函式：

tomllib.load(fp, /, *, parse_float=float)

讀取一個 TOML 檔案。第一個引數應為一個可讀取的二進位檔案物件。回傳一個 dict。用這個轉換表將 TOML 型別轉換成 Python 的。

parse_float 會被呼叫於要解碼的每個 TOML 浮點數字串。預設情況下，這相當於 float(num_str)。若有使用另一種資料型別或剖析器的 TOML 浮點數（例如 decimal.Decimal），這就派得上用場。可呼叫物件不得回傳 dict 或 list，否則會引發 ValueError。

不合格的 TOML 文件會使得 TOMLDecodeError 被引發。

tomllib.loads(s, /, *, parse_float=float)

自一個 str 物件載入成 TOML。回傳一個 dict。用這個轉換表轉換 TOML 型別成 Python 的。parse_float 引數和 load() 中的相同。

不合格的 TOML 文件會使得 TOMLDecodeError 被引發。

以下為可用的例外：

exception tomllib.TOMLDecodeError(msg, doc, pos)

Subclass of ValueError with the following additional attributes:

msg

The unformatted error message.

doc

The TOML document being parsed.

pos

The index of doc where parsing failed.

lineno

The line corresponding to pos.

colno

The column corresponding to pos.

在 3.14 版的變更: Added the msg, doc and pos parameters. Added the msg, doc, pos, lineno and colno attributes.

在 3.14 版之後被棄用: 傳遞自由形式的位置引數已被棄用。

範例

剖析一個 TOML 檔案：

import tomllib

with open("pyproject.toml", "rb") as f:
    data = tomllib.load(f)

剖析一個 TOML 字串：

import tomllib

toml_str = """
python-version = "3.11.0"
python-implementation = "CPython"
"""

data = tomllib.loads(toml_str)

轉換表

TOML

Python

TOML 文件

dict

string

str

integer

int

float

float（可透過 parse_float 調整）

boolean

bool

偏移日期時間 (offset date-time)

datetime.datetime（設定 tzinfo 屬性為 datetime.timezone 的實例）

本地日期時間 (local date-time)

datetime.datetime（設定 tzinfo 為 None）

本地日期 (local date)

datetime.date

本地時間 (local time)

datetime.time

array

list

table

dict

行內表格 (inline table)

dict

表格陣列 (array of tables)

dict 串列 (list of dicts)

netrc --- netrc 檔案處理

原始碼：Lib/netrc.py [https://github.com/python/cpython/tree/3.14/Lib/netrc.py]

netrc 類別能夠剖析 (parse) 並封裝 (encapsulate) netrc 檔案格式，以供 Unix ftp 程式和其他 FTP 用戶端使用。

class netrc.netrc([file])

netrc 實例或其子類別實例能夠封裝來自 netrc 檔案的資料。可用初始化引數（如有給定）指定要剖析的檔案，如果未給定引數，則將讀取（由 os.path.expanduser() 指定的）使用者主目錄中的 .netrc 檔案，否則將引發 FileNotFoundError 例外。剖析錯誤會引發 NetrcParseError，其帶有包括檔案名稱、列號和終止 token 的診斷資訊。

如果在 POSIX 系統上未指定引數，且若檔案所有權或權限不安全（擁有者與運行該行程的使用者不同，或者可供任何其他使用者讀取或寫入），存有密碼的 .netrc 檔案將會引發 NetrcParseError。這實作了與 ftp 和其他使用 .netrc 程式等效的安全行為。這種安全檢查在不支援 os.getuid() 的平台上不可用。

在 3.4 版的變更: 新增了 POSIX 權限檢查。

在 3.7 版的變更: 當未傳遞 file 引數時，os.path.expanduser() 可用於查找 .netrc 檔案的位置。

在 3.10 版的變更: netrc 在使用特定語言環境編碼前會先嘗試 UTF-8 編碼。netrc 檔案中的條目就不再需要包含所有 token，缺少的 token 值被預設為空字串。現在所有 token 及其值都可以包含任意字元，例如空格和非 ASCII 字元。如果登入名稱為匿名，就不會觸發安全檢查。

exception netrc.NetrcParseError

當原始文本中遇到語法錯誤時，netrc 類別會引發例外。此例外的實例提供了三個有趣的屬性：

msg

錯誤的文字解釋。

filename

原始檔案的名稱。

lineno

發現錯誤的列號。

netrc 物件

netrc 實例具有以下方法：

netrc.authenticators(host)

回傳 host 身份驗證器的三元素 tuple (login, account, password)。如果 netrc 檔案不包含給定主機的條目，則回傳與 'default' 條目關聯的 tuple。如果並無匹配主機且預設條目也不可用則回傳 None。

netrc.__repr__()

將類別資料傾印 (dump) 為 netrc 檔案格式的字串。（這會將註解移除，並可能會對條目重新排序。）

netrc 的實例具有公開實例變數：

netrc.hosts

將主機名稱對映到 (login, account, password) tuple 的字典。'default' 條目（如存在）表示為該名稱對應到的偽主機 (pseudo-host)。

netrc.macros

巨集 (macro) 名稱與字串 list（串列）的對映字典。

plistlib --- 產生和剖析 Apple .plist 檔案

原始碼：Lib/plistlib.py [https://github.com/python/cpython/tree/3.14/Lib/plistlib.py]

This module provides an interface for reading and writing the "property list" files used by Apple, primarily on macOS and iOS. This module supports both binary and XML plist files.

The property list (.plist) file format is a simple serialization supporting basic object types, like dictionaries, lists, numbers and strings. Usually the top level object is a dictionary.

To write out and to parse a plist file, use the dump() and load() functions.

To work with plist data in bytes or string objects, use dumps() and loads().

Values can be strings, integers, floats, booleans, tuples, lists, dictionaries (but only with string keys), bytes, bytearray or datetime.datetime objects.

在 3.4 版的變更: New API, old API deprecated. Support for binary format plists added.

在 3.8 版的變更: Support added for reading and writing UID tokens in binary plists as used by NSKeyedArchiver and NSKeyedUnarchiver.

在 3.9 版的變更: Old API removed.

也參考

PList manual page [https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/PropertyLists/]

Apple's documentation of the file format.

此模組定義了以下函式：

plistlib.load(fp, *, fmt=None, dict_type=dict, aware_datetime=False)

Read a plist file. fp should be a readable and binary file object. Return the unpacked root object (which usually is a dictionary).

The fmt is the format of the file and the following values are valid:

None：自動偵測檔案格式

FMT_XML：XML 檔案格式

FMT_BINARY：二進位 plist 格式

The dict_type is the type used for dictionaries that are read from the plist file.

When aware_datetime is true, fields with type datetime.datetime will be created as aware object, with tzinfo as datetime.UTC.

XML data for the FMT_XML format is parsed using the Expat parser from xml.parsers.expat -- see its documentation for possible exceptions on ill-formed XML. Unknown elements will simply be ignored by the plist parser.

The parser raises InvalidFileException when the file cannot be parsed.

在 3.4 版被加入.

在 3.13 版的變更: 新增僅限關鍵字參數 aware_datetime。

plistlib.loads(data, *, fmt=None, dict_type=dict, aware_datetime=False)

Load a plist from a bytes or string object. See load() for an explanation of the keyword arguments.

在 3.4 版被加入.

在 3.13 版的變更: data 在 fmt 等於 FMT_XML 時可以是一個字串。

plistlib.dump(value, fp, *, fmt=FMT_XML, sort_keys=True, skipkeys=False, aware_datetime=False)

Write value to a plist file. fp should be a writable, binary file object.

The fmt argument specifies the format of the plist file and can be one of the following values:

FMT_XML: XML formatted plist file

FMT_BINARY: Binary formatted plist file

When sort_keys is true (the default) the keys for dictionaries will be written to the plist in sorted order, otherwise they will be written in the iteration order of the dictionary.

When skipkeys is false (the default) the function raises TypeError when a key of a dictionary is not a string, otherwise such keys are skipped.

When aware_datetime is true and any field with type datetime.datetime is set as an aware object, it will convert to UTC timezone before writing it.

A TypeError will be raised if the object is of an unsupported type or a container that contains objects of unsupported types.

An OverflowError will be raised for integer values that cannot be represented in (binary) plist files.

在 3.4 版被加入.

在 3.13 版的變更: 新增僅限關鍵字參數 aware_datetime。

plistlib.dumps(value, *, fmt=FMT_XML, sort_keys=True, skipkeys=False, aware_datetime=False)

Return value as a plist-formatted bytes object. See the documentation for dump() for an explanation of the keyword arguments of this function.

在 3.4 版被加入.

The following classes are available:

class plistlib.UID(data)

Wraps an int. This is used when reading or writing NSKeyedArchiver encoded data, which contains UID (see PList manual).

data

Int value of the UID. It must be in the range 0 <= data < 2**64.

在 3.8 版被加入.

以下常數可供使用：

plistlib.FMT_XML

The XML format for plist files.

在 3.4 版被加入.

plistlib.FMT_BINARY

The binary format for plist files

在 3.4 版被加入.

這個模組定義了以下例外：

exception plistlib.InvalidFileException

當檔案無法被剖析時引發。

在 3.4 版被加入.

範例

Generating a plist:

import datetime
import plistlib

pl = dict(
    aString = "Doodah",
    aList = ["A", "B", 12, 32.1, [1, 2, 3]],
    aFloat = 0.1,
    anInt = 728,
    aDict = dict(
        anotherString = "<hello & hi there!>",
        aThirdString = "M\xe4ssig, Ma\xdf",
        aTrueValue = True,
        aFalseValue = False,
    ),
    someData = b"<binary gunk>",
    someMoreData = b"<lots of binary gunk>" * 10,
    aDate = datetime.datetime.now()
)
print(plistlib.dumps(pl).decode())

Parsing a plist:

import plistlib

plist = b"""<plist version="1.0">
<dict>
    <key>foo</key>
    <string>bar</string>
</dict>
</plist>"""
pl = plistlib.loads(plist)
print(pl["foo"])

加密服務

本章所描述的模組實作了多種加密演算法。它們可以在安裝時選擇是否一同安裝。以下為概述：

hashlib --- 安全雜湊與訊息摘要

雜湊演算法

用法

建構函式

屬性

雜湊物件

SHAKE 可變長度摘要

檔案雜湊

密鑰的生成

BLAKE2

建立雜湊物件

常數

範例

簡單雜湊

使用不同的摘要大小

密鑰雜湊 (Keyed hashing)

隨機雜湊 (Randomized hashing)

個人化

樹狀模式

製作人員

hmac --- 基於金鑰雜湊的訊息驗證

secrets --- 產生用於管理機密的安全亂數

亂數

產生權杖（token）

權杖應當使用多少個位元組？

其他函式

應用技巧和典範實務（best practices）

hashlib --- 安全雜湊與訊息摘要

原始碼：Lib/hashlib.py [https://github.com/python/cpython/tree/3.14/Lib/hashlib.py]

該模組實作了許多不同雜湊演算法的通用介面，其中包括 FIPS 安全雜湊演算法 SHA1、SHA224、SHA256、SHA384、SHA512（定義於 FIPS 180-4 標準 [https://csrc.nist.gov/pubs/fips/180-4/upd1/final]）、SHA-3 系列（定義於 FIPS 202 標準 [https://csrc.nist.gov/pubs/fips/202/final]）以及遺留的 SHA1 演算法（先前為 FIPS 的一部分 [https://csrc.nist.gov/news/2023/decision-to-revise-fips-180-4]）和 MD5 演算法（定義於網際網路 RFC 1321 [https://datatracker.ietf.org/doc/html/rfc1321.html]）。

備註

如果你需要 adler32 或 crc32 雜湊函式，可以在 zlib 模組中找到它們。

雜湊演算法

每種種類的 hash 都有一個以其命名的建構函式方法。全部都會回傳具有相同簡單介面的雜湊物件。例如：可使用 sha256() 來建立 SHA-256 雜湊物件。現在你可以使用 update 方法向此物件提供類位元組物件 (bytes-like objects)（通常是 bytes）。在任何時候，你都可以使用 digest() 或 hexdigest() 方法來要求它提供迄今為止傳遞給它的資料串聯的摘要 (digest)。

為了允許多執行緒 (multithreading)，Python GIL 被釋放，同時在其建構函式或 .update 方法中計算一次提供超過 2047 位元組資料的雜湊值。

此模組中始終存在的雜湊演算法之建構函式有 sha1()、sha224()、sha256()、sha384()、sha512()、sha3_224()、sha3_256()、sha3_384()、sha3_512()、shake_128()、shake_256()、blake2b() 和 blake2s()。md5() 通常也可用，但如果你使用罕見的「符合 FIPS (FIPS compliant)」的 Python 建置版本，它可能不存在或者不被允許使用。以上會對應到 algorithms_guaranteed。

如果你的 Python 發行版的 hashlib 與提供其他演算法的 OpenSSL 版本鏈結，也可能有其他演算法可用。其他則不保證可用於在所有安裝上，並且只能以名稱來透過 new() 存取。請參閱 algorithms_available。

警告

某些演算法具有已知的雜湊碰撞 (hash collision) 弱點（包括 MD5 和 SHA1）。請參閱 Attacks on cryptographic hash algorithms [https://en.wikipedia.org/wiki/Cryptographic_hash_function#Attacks_on_cryptographic_hash_algorithms] 和本文件後面的也參考部分。

在 3.6 版被加入: 新增了 SHA3 (Keccak) 和 SHAKE 建構函式 sha3_224()、sha3_256()、sha3_384()、sha3_512()、shake_128()、shake_256()。也新增了 blake2b() 和 blake2s()。

在 3.9 版的變更: 所有 hashlib 建構函式都採用一個僅限關鍵字引數 (keyword-only argument) usedforsecurity，其預設值為 True。False 值則會允許在受限環境中使用不安全 (insecure) 和阻塞的 (blocked) 雜湊演算法。False 表示雜湊演算法未在安全情境中使用，例如作為一種非加密用途的單向壓縮函式。

在 3.9 版的變更: Hashlib 現在使用 OpenSSL 中的 SHA3 和 SHAKE（如果有提供的話）。

在 3.12 版的變更: 對於鏈結之 OpenSSL 未提供的任何 MD5、SHA1、SHA2 或 SHA3 演算法，我們會回退使用 HACL* 專案 [https://github.com/hacl-star/hacl-star]中經過驗證的實作。

用法

取得位元組字串 b"Nobody inspects the spammish repetition" 的摘要：

>>> import hashlib
>>> m = hashlib.sha256()
>>> m.update(b"Nobody inspects")
>>> m.update(b" the spammish repetition")
>>> m.digest()
b'\x03\x1e\xdd}Ae\x15\x93\xc5\xfe\\\x00o\xa5u+7\xfd\xdf\xf7\xbcN\x84:\xa6\xaf\x0c\x95\x0fK\x94\x06'
>>> m.hexdigest()
'031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'

更濃縮：

>>> hashlib.sha256(b"Nobody inspects the spammish repetition").hexdigest()
'031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'

建構函式

hashlib.new(name, [data, ]*, usedforsecurity=True)

是一個通用建構函式，它將目標演算法的字串 name 作為其第一個參數。它還允許使用者取得上面列出的雜湊值以及 OpenSSL 函式庫可能提供的任何其他演算法。

使用 new() 和演算法名稱：

>>> h = hashlib.new('sha256')
>>> h.update(b"Nobody inspects the spammish repetition")
>>> h.hexdigest()
'031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'

hashlib.md5([data, ]*, usedforsecurity=True)

hashlib.sha1([data, ]*, usedforsecurity=True)

hashlib.sha224([data, ]*, usedforsecurity=True)

hashlib.sha256([data, ]*, usedforsecurity=True)

hashlib.sha384([data, ]*, usedforsecurity=True)

hashlib.sha512([data, ]*, usedforsecurity=True)

hashlib.sha3_224([data, ]*, usedforsecurity=True)

hashlib.sha3_256([data, ]*, usedforsecurity=True)

hashlib.sha3_384([data, ]*, usedforsecurity=True)

hashlib.sha3_512([data, ]*, usedforsecurity=True)

諸如此類的附名建構函式比將演算法名稱傳遞給 new() 更快。

屬性

Hashlib 提供以下常數模組屬性：

hashlib.algorithms_guaranteed

包含所有平台上該模組保證支援的雜湊演算法名稱的集合。請注意，'md5' 有出現在此列表中，儘管有一些上游供應商提供了奇怪的「符合 FIPS (FIPS compliant)」的 Python 建置，並將其排除在外。

在 3.2 版被加入.

hashlib.algorithms_available

包含正在運行的 Python 直譯器中可用的雜湊演算法名稱的集合。這些名稱在傳遞給 new() 時將被識別。algorithms_guaranteed 都會是它的一個子集。相同的演算法可能會以不同的名稱多次出現在該集合中（多虧了 OpenSSL）。

在 3.2 版被加入.

雜湊物件

以下的值皆為建構函式回傳之雜湊物件的常數屬性：

hash.digest_size

生成雜湊的大小（以位元組為單位）。

hash.block_size

雜湊演算法的內部區塊大小（以位元組為單位）。

雜湊物件具有以下屬性：

hash.name

該雜湊的規範名稱，都會是小寫，且都會適合作為 new() 的參數以建立此型別的另一個雜湊。

在 3.4 版的變更: name 屬性自 CPython 誕生以來就存在於其中，但直到 Python 3.4 才正式確立，因此在某些平台上可能不存在。

雜湊物件具有以下方法：

hash.update(data)

使用類位元組物件來更新雜湊物件。重複呼叫相當於連接所有引數的單一呼叫：m.update(a); m.update(b) 等價於 m.update(a+b)。

hash.digest()

回傳目前有傳遞給 update() 方法的資料之摘要。這是一個大小為 digest_size 的位元組物件，它可能包含從 0 到 255 的整個範圍內的位元組。

hash.hexdigest()

與 digest() 類似，只不過摘要會是作為雙倍長度的字串物件回傳，僅包含十六進位數字。這可用於在電子郵件或其他非二進位環境中安全地交換值。

hash.copy()

回傳雜湊物件的副本（「複製 (clone)」），這可用於高效率地計算出共享同一初始子字串的資料之摘要。

SHAKE 可變長度摘要

hashlib.shake_128([data, ]*, usedforsecurity=True)

hashlib.shake_256([data, ]*, usedforsecurity=True)

shake_128() 和 shake_256() 演算法提供了可變長度摘要，其 length_in_bits//2 最高為 128 或 256 位元安全性。因此，他們的摘要方法會需要長度。最大長度不受 SHAKE 演算法限制。

shake.digest(length)

回傳目前有傳遞給 update() 方法的資料之摘要。這是一個大小為 length 的位元組物件，可能包含從 0 到 255 的整個範圍內的位元組。

shake.hexdigest(length)

與 digest() 類似，只不過摘要作為雙倍長度的字串物件回傳，僅包含十六進位數字。這可用於交換電子郵件或其他非二進位環境中的值。

範例：

>>> h = hashlib.shake_256(b'Nobody inspects the spammish repetition')
>>> h.hexdigest(20)
'44709d6fcb83d92a76dcb0b668c98e1b1d3dafe7'

檔案雜湊

hashlib 模組提供了一個輔助函式，用於對檔案或類檔案物件 (file-like object) 進行有效率的雜湊。

hashlib.file_digest(fileobj, digest, /)

回傳已用檔案物件內容更新的摘要物件。

fileobj 必須是以二進位模式讀取的類檔案物件。它接受來自內建 open() 的檔案物件、BytesIO 實例、來自 socket.socket.makefile() 的 SocketIO 物件等。fileobj 必須以阻塞模式開啟，否則可能會引發 BlockingIOError。

該函式可以繞過 Python 的 I/O 並直接使用 fileno() 中的檔案描述器 (file descriptor)。在此函式回傳或引發後，必須假定 fileobj 處於未知狀態 (unknown state)。由呼叫者決定是否關閉 fileobj。

digest 必須是名稱作為 str 的雜湊演算法、雜湊建構函式或會回傳雜湊物件的可呼叫函式。

範例：

>>> import io, hashlib, hmac
>>> with open("library/hashlib.rst", "rb") as f:
...     digest = hashlib.file_digest(f, "sha256")
...
>>> digest.hexdigest()
'...'

>>> buf = io.BytesIO(b"somedata")
>>> mac1 = hmac.HMAC(b"key", digestmod=hashlib.sha512)
>>> digest = hashlib.file_digest(buf, lambda: mac1)

>>> digest is mac1
True
>>> mac2 = hmac.HMAC(b"key", b"somedata", digestmod=hashlib.sha512)
>>> mac1.digest() == mac2.digest()
True

在 3.11 版被加入.

在 3.14 版的變更: Now raises a BlockingIOError if the file is opened in non-blocking mode. Previously, spurious null bytes were added to the digest.

密鑰的生成

密鑰生成 (key derivation) 和密鑰延伸 (key stretching) 演算法專為安全密碼雜湊而設計。像是 sha1(password) 這樣過於單純的演算法無法抵抗暴力攻擊。一個好的密碼雜湊函式必須是可調校的 (tunable)、緩慢的，並且有包含 salt（鹽） [https://zh.wikipedia.org/zh-tw/%E7%9B%90_(%E5%AF%86%E7%A0%81%E5%AD%A6)]。

hashlib.pbkdf2_hmac(hash_name, password, salt, iterations, dklen=None)

該函式提供基於密碼的 PKCS#5 密鑰生成函式 2。它使用 HMAC 作為偽隨機函式 (pseudorandom function)。

字串 hash_name 是 HMAC 的雜湊摘要演算法所需的名稱，例如 sha1 或 sha256。password 和 salt 被直譯為位元組緩衝區。應用程式和函式庫應為 password 設下合理的長度限制（例如 1024）。salt 應該是來自適當來源（例如 os.urandom()）且大約 16 或更多位元組。

應根據雜湊演算法和計算能力選擇 iterations 次數。截至 2022 年，建議進行數十萬次 SHA-256 疊代。有關為什麼以及如何選擇最適合你的應用程式的基本原理，請閱讀 NIST-SP-800-132 [https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf] 的 Appendix A.2.2。stackexchange pbkdf2 疊代問題 [https://security.stackexchange.com/questions/3959/recommended-of-iterations-when-using-pbkdf2-sha256/]上的答案有詳細解釋。

dklen 是生成的密鑰長度。如果 dklen 為 None，則會使用雜湊演算法 hash_name 的摘要大小，例如 SHA-512 為 64。

>>> from hashlib import pbkdf2_hmac
>>> our_app_iters = 500_000  # Application specific, read above.
>>> dk = pbkdf2_hmac('sha256', b'password', b'bad salt' * 2, our_app_iters)
>>> dk.hex()
'15530bba69924174860db778f2c6f8104d3aaf9d26241840c8c4a641c8d000a9'

僅當有使用 OpenSSL 編譯 Python 時該函式才可用。

在 3.4 版被加入.

在 3.12 版的變更: 該函式現在僅在有使用 OpenSSL 建置 Python 時可用。緩慢的純 Python 實作已被刪除。

hashlib.scrypt(password, *, salt, n, r, p, maxmem=0, dklen=64)

該函式提供（如 RFC 7914 [https://datatracker.ietf.org/doc/html/rfc7914.html] 中所定義的）scrypt 基於密碼的密鑰衍生函式。

password 和 salt 必須是類位元組物件。應用程式和函式庫應為 password 設下合理的長度限制（例如 1024）。salt 應該是來自適當來源（例如 os.urandom()）且大約 16 或更多位元組。

n 是 CPU/記憶體開銷係數、r 是區塊大小、p 為平行化係數、maxmem 為記憶體限制（OpenSSL 1.1.0 預設為 32 MiB）。dklen 是生成密鑰的長度。

在 3.6 版被加入.

BLAKE2

BLAKE2 [https://www.blake2.net] 是在 RFC 7693 [https://datatracker.ietf.org/doc/html/rfc7693.html] 中定義的加密雜湊函式，有兩種類型：

BLAKE2b，針對 64 位元平台進行了最佳化，可生成 1 到 64 位元組之間任意大小的摘要，

BLAKE2s，針對 8 至 32 位元平台進行了最佳化，可生成 1 至 32 位元組之間任意大小的摘要。

BLAKE2 支援密鑰模式 (keyed mode) （更快、更簡單的 HMAC [https://en.wikipedia.org/wiki/Hash-based_message_authentication_code] 替代品）、加鹽雜湊 (salted hashing)、個人化和樹狀雜湊。

該模組中的雜湊物件遵循標準函式庫的 hashlib 物件 API。

建立雜湊物件

新的雜湊物件是透過呼叫建構函式建立的：

hashlib.blake2b(data=b'', *, digest_size=64, key=b'', salt=b'', person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False, usedforsecurity=True)

hashlib.blake2s(data=b'', *, digest_size=32, key=b'', salt=b'', person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False, usedforsecurity=True)

這些函式回傳相應的雜湊物件以計算 BLAKE2b 或 BLAKE2s。他們可以選擇採用這些通用參數：

data：要雜湊的初始資料塊 (data chunk)，它必須是類位元組物件。它只能作為位置引數傳遞。

digest_size：輸出摘要的大小（以位元組為單位）。

key：用於密鑰雜湊的密鑰（BLAKE2b 最多 64 位元組、BLAKE2s 最多 32 位元組）。

salt：用於隨機雜湊的鹽（BLAKE2b 最多 16 個位元組、BLAKE2s 最多 8 個位元組）。

person：個人化字串（BLAKE2b 最多 16 個位元組、BLAKE2s 最多 8 個位元組）。

下表顯示了一般參數的限制（以位元組為單位）：

雜湊

digest_size

len(key)

len(salt)

len(person)

BLAKE2b

64

64

16

16

BLAKE2s

32

32

8

8

備註

BLAKE2 規範定義了鹽和個人化參數的恆定長度，但為了方便起見，此實作接受任意大小的位元組字串，最多可達指定長度。如果參數的長度小於指定的長度，則用零補滿，所以像是 b'salt 和 b'salt\x00 是相同的值。（但 key 的情況並非如此。）

這些大小可作為模組常數使用，如下所述。

建構函式還接受以下樹狀雜湊參數：

fanout：扇出（0 到 255，如果無限制則為 0、順序模式為 1）。

depth：樹的最大深度（1 到 255，如果無限制則為 255、順序模式為 1）。

leaf_size：葉的最大位元組長度（0 到 2**32-1，如果無限制或處於順序模式則為 0）。

node_offset：節點偏移量（BLAKE2b 為 0 到 2**64-1，BLAKE2s 為 0 到 2**48-1，0 表示第一個、最左邊、葉子或在順序模式下）。

node_depth：節點深度（0 到 255，葉為 0，或在順序模式下）。

inner_size：內部摘要大小（BLAKE2b 為 0 到 64，BLAKE2s 為 0 到 32，順序模式為 0）。

last_node：布林值，代表處理的節點是否為最後一個（False 代表順序模式）。

關於樹狀雜湊的綜合回顧，請參閱 BLAKE2 規範 [https://www.blake2.net/blake2_20130129.pdf]中的第 2.10 節。

常數

blake2b.SALT_SIZE

blake2s.SALT_SIZE

鹽長度（建構函式接受的最大長度）。

blake2b.PERSON_SIZE

blake2s.PERSON_SIZE

個人化字串長度（建構函式接受的最大長度）。

blake2b.MAX_KEY_SIZE

blake2s.MAX_KEY_SIZE

最大密鑰大小。

blake2b.MAX_DIGEST_SIZE

blake2s.MAX_DIGEST_SIZE

雜湊函式可以輸出的最大摘要大小。

範例

簡單雜湊

要計算某些資料的雜湊值，你應該首先透過呼叫適當的建構函式（blake2b() 或 blake2s()）以建構一個雜湊物件，然後透過於物件呼叫 update() 來以資料對它更新，最後透過呼叫 digest()（或對於十六進位編碼字串則為 hexdigest()）從物件中獲得摘要。

>>> from hashlib import blake2b
>>> h = blake2b()
>>> h.update(b'Hello world')
>>> h.hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'

作為一個快捷方式，你可以將要更新的第一個資料塊作為位置引數直接傳遞給建構函式：

>>> from hashlib import blake2b
>>> blake2b(b'Hello world').hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'

你可以根據需求來多次呼叫 hash.update() 以疊代更新雜湊：

>>> from hashlib import blake2b
>>> items = [b'Hello', b' ', b'world']
>>> h = blake2b()
>>> for item in items:
...     h.update(item)
...
>>> h.hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'

使用不同的摘要大小

BLAKE2 有可調整的摘要大小，BLAKE2b 最多為 64 位元組，BLAKE2s 最多為 32 位元組。例如，要在不改變輸出大小的情況下用 BLAKE2b 替換 SHA-1，我們可以指定 BLAKE2b 生成 20 位元組的摘要：

>>> from hashlib import blake2b
>>> h = blake2b(digest_size=20)
>>> h.update(b'Replacing SHA1 with the more secure function')
>>> h.hexdigest()
'd24f26cf8de66472d58d4e1b1774b4c9158b1f4c'
>>> h.digest_size
20
>>> len(h.digest())
20

具有不同摘要大小的雜湊物件具有完全不同的輸出（較短的雜湊值不是較長雜湊值的前綴）；即使輸出長度相同，BLAKE2b 和 BLAKE2s 也會產生不同的輸出：

>>> from hashlib import blake2b, blake2s
>>> blake2b(digest_size=10).hexdigest()
'6fa1d8fcfd719046d762'
>>> blake2b(digest_size=11).hexdigest()
'eb6ec15daf9546254f0809'
>>> blake2s(digest_size=10).hexdigest()
'1bf21a98c78a1c376ae9'
>>> blake2s(digest_size=11).hexdigest()
'567004bf96e4a25773ebf4'

密鑰雜湊 (Keyed hashing)

密鑰雜湊可用於身份驗證，作為基於雜湊的訊息驗證碼 (Hash-based message authentication code) [https://zh.wikipedia.org/zh-tw/HMAC] (HMAC) 的更快、更簡單的替代方案。由於繼承自 BLAKE 的不可微特性 (indifferentiability property)，BLAKE2 可以安全地用於 prefix-MAC 模式。

此範例示範了如何使用密鑰 b'pseudorandom key' 取得訊息 b'message data' 的（十六進位編碼）128 位元驗證碼：

>>> from hashlib import blake2b
>>> h = blake2b(key=b'pseudorandom key', digest_size=16)
>>> h.update(b'message data')
>>> h.hexdigest()
'3d363ff7401e02026f4a4687d4863ced'

舉一個實際的例子，網頁應用程式可以對發送給使用者的 cookie 進行對稱簽名 (symmetrically sign)，然後驗證它們以確保它們沒有被篡改：

>>> from hashlib import blake2b
>>> from hmac import compare_digest
>>>
>>> SECRET_KEY = b'pseudorandomly generated server secret key'
>>> AUTH_SIZE = 16
>>>
>>> def sign(cookie):
...     h = blake2b(digest_size=AUTH_SIZE, key=SECRET_KEY)
...     h.update(cookie)
...     return h.hexdigest().encode('utf-8')
>>>
>>> def verify(cookie, sig):
...     good_sig = sign(cookie)
...     return compare_digest(good_sig, sig)
>>>
>>> cookie = b'user-alice'
>>> sig = sign(cookie)
>>> print("{0},{1}".format(cookie.decode('utf-8'), sig))
user-alice,b'43b3c982cf697e0c5ab22172d1ca7421'
>>> verify(cookie, sig)
True
>>> verify(b'user-bob', sig)
False
>>> verify(cookie, b'0102030405060708090a0b0c0d0e0f00')
False

儘管有原生密鑰雜湊模式，BLAKE2 還是可以透過 hmac 模組用於建構 HMAC：

>>> import hmac, hashlib
>>> m = hmac.new(b'secret key', digestmod=hashlib.blake2s)
>>> m.update(b'message')
>>> m.hexdigest()
'e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142'

隨機雜湊 (Randomized hashing)

透過設定 salt 參數，使用者可以向雜湊函式引入隨機化。隨機雜湊在防止針對數位簽章中雜湊函式的碰撞攻擊 (collision attacks) 非常有用。

隨機雜湊是為這樣的情況而設計的：一方（訊息準備者）生成全部或部分訊息並由另一方（訊息簽名者）簽名。如果訊息準備者能夠發現加密雜湊函式發生碰撞（collision，即兩條訊息產生相同的雜湊值），那麼他們可能會準備有意義的訊息版本，該版本將產生相同的雜湊值和數位簽章，但結果不同（例如，將 $1,000,000 轉入賬戶，而不是 $10）。加密雜湊函式的設計以抗碰撞性為主要目標，但目前對加密雜湊函式攻擊的關注可能會導致給定的加密雜湊函式所提供的抗碰撞性低於預期。隨機雜湊透過降低準備者在數位簽章生成過程中生成最終產生相同雜湊值的兩個或多個訊息的可能性，為簽名者提供額外的保護 —— 即便嘗試去找到雜湊函式碰撞的發生是實際可行的。然而，若訊息的所有部分都是由簽名者所準備好的，使用隨機雜湊可能會降低數位簽章提供的安全性。

（NIST SP-800-106 「數位簽章的隨機雜湊 (Randomized Hashing for Digital Signatures)」 [https://csrc.nist.gov/pubs/sp/800/106/final]）

在 BLAKE2 中，鹽在初始化期間作為雜湊函式的一次性輸入被處理，而不是作為每個壓縮函式的輸入。

警告

使用 BLAKE2 或任何其他通用加密雜湊函式（例如 SHA-256）的加鹽雜湊 （或單純雜湊）不適合對密碼進行雜湊處理。有關更多資訊，請參閱 BLAKE2 FAQ [https://www.blake2.net/#qa] 。

>>> import os
>>> from hashlib import blake2b
>>> msg = b'some message'
>>> # Calculate the first hash with a random salt.
>>> salt1 = os.urandom(blake2b.SALT_SIZE)
>>> h1 = blake2b(salt=salt1)
>>> h1.update(msg)
>>> # Calculate the second hash with a different random salt.
>>> salt2 = os.urandom(blake2b.SALT_SIZE)
>>> h2 = blake2b(salt=salt2)
>>> h2.update(msg)
>>> # The digests are different.
>>> h1.digest() != h2.digest()
True

個人化

有時候強制雜湊函式為不同目的的相同輸入生成不同的摘要是很有用的。引用 Skein 雜湊函式的作者的話：

我們建議所有應用程式設計者認真考慮這樣做；我們已經看到許多協定，其中在協定的一個部分中計算的雜湊可以在完全不同的部分中使用，因為兩次雜湊計算是在相似或相關的資料上完成的，並且攻擊者可以強制應用程式將雜湊輸入設為相同的。對協定中使用的每個雜湊函式進行個人化可以立即阻止此類攻擊。

（Skein 雜湊函式系列 [https://www.schneier.com/wp-content/uploads/2016/02/skein.pdf]，第 21 頁）

BLAKE2 可以透過將位元組傳遞給 person 引數來做個人化：

>>> from hashlib import blake2b
>>> FILES_HASH_PERSON = b'MyApp Files Hash'
>>> BLOCK_HASH_PERSON = b'MyApp Block Hash'
>>> h = blake2b(digest_size=32, person=FILES_HASH_PERSON)
>>> h.update(b'the same content')
>>> h.hexdigest()
'20d9cd024d4fb086aae819a1432dd2466de12947831b75c5a30cf2676095d3b4'
>>> h = blake2b(digest_size=32, person=BLOCK_HASH_PERSON)
>>> h.update(b'the same content')
>>> h.hexdigest()
'cf68fb5761b9c44e7878bfb2c4c9aea52264a80b75005e65619778de59f383a3'

個人化與密鑰模式還可以一起用於從單個密鑰得出不同的密鑰。

>>> from hashlib import blake2s
>>> from base64 import b64decode, b64encode
>>> orig_key = b64decode(b'Rm5EPJai72qcK3RGBpW3vPNfZy5OZothY+kHY6h21KM=')
>>> enc_key = blake2s(key=orig_key, person=b'kEncrypt').digest()
>>> mac_key = blake2s(key=orig_key, person=b'kMAC').digest()
>>> print(b64encode(enc_key).decode('utf-8'))
rbPb15S/Z9t+agffno5wuhB77VbRi6F9Iv2qIxU7WHw=
>>> print(b64encode(mac_key).decode('utf-8'))
G9GtHFE1YluXY1zWPlYk1e/nWfu0WSEb0KRcjhDeP/o=

樹狀模式

下面是對具有兩個葉節點的最小樹進行雜湊處理的範例：

  10
 /  \
00  01

此範例使用 64-byte 內部摘要，並回傳 32-byte 最終摘要：

>>> from hashlib import blake2b
>>>
>>> FANOUT = 2
>>> DEPTH = 2
>>> LEAF_SIZE = 4096
>>> INNER_SIZE = 64
>>>
>>> buf = bytearray(6000)
>>>
>>> # Left leaf
... h00 = blake2b(buf[0:LEAF_SIZE], fanout=FANOUT, depth=DEPTH,
...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
...               node_offset=0, node_depth=0, last_node=False)
>>> # Right leaf
... h01 = blake2b(buf[LEAF_SIZE:], fanout=FANOUT, depth=DEPTH,
...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
...               node_offset=1, node_depth=0, last_node=True)
>>> # Root node
... h10 = blake2b(digest_size=32, fanout=FANOUT, depth=DEPTH,
...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
...               node_offset=0, node_depth=1, last_node=True)
>>> h10.update(h00.digest())
>>> h10.update(h01.digest())
>>> h10.hexdigest()
'3ad2a9b37c6070e374c7a8c508fe20ca86b6ed54e286e93a0318e95e881db5aa'

製作人員

BLAKE2 [https://www.blake2.net] 由 Jean-Philippe Aumasson、Samuel Neves、Zooko Wilcox-O'Hearn 和 Christian Winnerlein 設計，基於由 Jean-Philippe Aumasson、Luca Henzen、Willi Meier 和 Raphael C.-W. Phan 所建立的 SHA-3 [https://en.wikipedia.org/wiki/Secure_Hash_Algorithms] 最終版本 BLAKE [https://web.archive.org/web/20200918190133/https://131002.net/blake/]。

它使用 Daniel J. Bernstein 設計的 ChaCha [https://cr.yp.to/chacha.html] 密碼的核心演算法。

標準函式庫實作是基於 pyblake2 [https://pythonhosted.org/pyblake2/] 模組。它是由 Dmitry Chestnykh 在 Samuel Neves 的 C 版本實作為基礎所編寫的。該文件是由 Dmitry Chestnykh 編寫並從 pyblake2 [https://pythonhosted.org/pyblake2/] 複製過來的。

Christian Heimes 為 Python 重寫了部分 C 程式碼。

以下公開領域貢獻適用於 C 雜湊函式實作、擴充程式碼和此文件：

在法律允許的範圍內，作者已將該軟體的所有版權以及相關和鄰接權利奉獻給全球的公開領域。該軟體的發布沒有任何授權 (warranty)。

你應會隨本軟體一起收到一份 CC0 公眾領域貢獻宣告 (CC0 Public Domain Dedication) 的副本。如果沒有，請參閱 https://creativecommons.org/publicdomain/zero/1.0/ 。

以下人員根據創用 CC 通用公眾領域貢獻宣告 1.0 (Creative Commons Public Domain Dedication 1.0 Universal) 於專案和公開領域做出了開發或貢獻：

Alexandr Sokolovskiy

也參考

hmac 模組

使用雜湊生成訊息驗證程式碼的模組。

base64 模組

另一種在非二進位環境中編碼二進位雜湊的方法。

https://nvlpubs.nist.gov/nistpubs/fips/nist.fips.180-4.pdf

有關安全雜湊演算法的 FIPS 180-4 出版物。

https://csrc.nist.gov/pubs/fips/202/final

有關 SHA-3 標準的 FIPS 202 出版物。

https://www.blake2.net/

BLAKE2 官方網站。

https://en.wikipedia.org/wiki/Cryptographic_hash_function

包含有關哪些演算法存在已知問題以及這些問題對其使用意味著什麼資訊的維基百科文章。

https://www.ietf.org/rfc/rfc8018.txt

PKCS #5：基於密碼的加密規範版本 2.1

https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf

NIST（美國國家標準技術研究院）針對基於密碼的密鑰衍生的建議。

hmac --- 基於金鑰雜湊的訊息驗證

原始碼：Lib/hmac.py [https://github.com/python/cpython/tree/3.14/Lib/hmac.py]

此模組實作了 RFC 2014 [https://datatracker.ietf.org/doc/html/rfc2014.html] 所描述的 HMAC 演算法。此介面允許使用具有固定摘要 (digest) 長度的任意雜湊函式。要特別注意的是擴充輸出函式（如 SHAKE-128 或 SHAKE-256）不能與 HMAC 一起使用。

hmac.new(key, msg=None, digestmod)

回傳一個新的 hmac 物件。key 是一個指定密鑰的 bytes（位元組）或 bytearray 物件。如果提供了 msg，將會呼叫 update(msg) 方法。digestmod 為 HMAC 物件所用的摘要名稱、摘要建構函式 (constructor) 或模組。它可以是適用於 hashlib.new() 的任何名稱。儘管該引數的位置在後，但它卻是必須的。

在 3.4 版的變更: 參數 key 可以為 bytes 或 bytearray 物件。參數 msg 可以為 hashlib 所支援的任意型別。參數 digestmod 可以為雜湊演算法的名稱。

在 3.8 版的變更: digestmod 引數現在是必須的。請將其作為關鍵字引數傳入以避免當你沒有初始 msg 時導致的麻煩。

hmac.digest(key, msg, digest)

基於給定密鑰 key 和 digest 回傳 msg 的摘要。此函式等價於 HMAC(key, msg, digest).digest()，但使用了最佳化的 C 或 行內實作（inline implementation），對放入記憶體的訊息能處理得更快。參數 key、msg 和 digest 在 new() 中具有相同含義。

作為 CPython 的實現細節，C 的最佳化實作只有當 digest 為字串並且是一個 OpenSSL 所支援的摘要演算法的名稱時才會被使用。

在 3.7 版被加入.

class hmac.HMAC

HMAC 物件具有下列方法 (method)：

HMAC.update(msg)

用 msg 來更新 hmac 物件。重複呼叫相當於單次呼叫並傳入所有引數的拼接結果：m.update(a); m.update(b) 等價於 m.update(a + b)。

在 3.4 版的變更: 參數 msg 可以是 hashlib 所支援的任何型別。

HMAC.digest()

回傳目前已傳給 update() 方法的 bytes 摘要。這個 bytes 物件的長度會與傳給建構函式的摘要 digest_size 的長度相同。它可以包含 NUL bytes 以及 non-ASCII bytes。

警告

在一個例行的驗證事務運行期間，將 digest() 的輸出與外部提供的摘要進行比較時，建議使用 compare_digest() 函式而不是 == 運算子以減少被定時攻擊時的漏洞。

HMAC.hexdigest()

像是 digest() 但摘要的回傳形式為兩倍長度的字串，且此字串只包含十六進位數位。這可以被用於在電子郵件或其他非二進位制環境中安全地交換數據。

警告

在一個例行的驗證事務運行期間，將 hexdigest() 的輸出與外部提供的摘要進行比較時，建議使用 compare_digest() 函式而不是 == 運算子以減少被定時攻擊時的漏洞。

HMAC.copy()

回傳 hmac 物件的拷貝 ("clone")。這可以被用來有效率地計算那些共享相同初始子字串的字串的摘要。

一個 hash 物件具有以下屬性：

HMAC.digest_size

以 bytes 表示最終 HMAC 摘要的大小。

HMAC.block_size

以 bytes 表示雜湊演算法的內部區塊大小。

在 3.4 版被加入.

HMAC.name

HMAC 的正準名稱總是為小寫形式，例如 hmac-md5。

在 3.4 版被加入.

在 3.10 版的變更: 未寫入文件的屬性 HMAC.digest_cons，HMAC.inner 和 HMAC.outer 已被移除。

這個模組還提供了下列輔助函式：

hmac.compare_digest(a, b)

回傳 a == b。此函式使用一種經專門設計的方式透過避免基於內容的短路行為來防止定時分析，使得它適合處理密碼學。a 和 b 必須為相同的型別：可以是 str（僅限 ASCII，如 HMAC.hexdigest() 的回傳值），或者是 bytes-like object。

備註

如果 a 和 b 具有不同的長度，或者如果發生了錯誤，定時攻擊在理論上可以取得有關 a 和 b 的型別和長度的訊息 — 但不能取得他們的值。

在 3.3 版被加入.

在 3.10 版的變更: 此函式在可能的情況下會在內部使用 OpenSSL 的 CRYPTO_memcmp()。

也參考

hashlib 模組

Python 模組提供安全的雜湊函式。

secrets --- 產生用於管理機密的安全亂數

在 3.6 版被加入.

原始碼：Lib/secrets.py [https://github.com/python/cpython/tree/3.14/Lib/secrets.py]

secrets 模組可用於產生高加密強度的亂數，適合用來管理諸如密碼、帳號認證、安全性權杖（security tokens）這類資料，以及管理其他相關的機密資料。

尤其應優先使用 secrets 作為預設來替代 random 模組中的預設偽亂數產生器（pseudo-random number generator），該模組被設計用於建模和模擬，而非用於安全性和加密。

也參考

PEP 506 [https://peps.python.org/pep-0506/]

亂數

secrets 模組使你得以存取作業系統所提供安全性最高的亂數產生器。

class secrets.SystemRandom

一個用來產生亂數的類別，用的是作業系統提供的最高品質來源。 請參閱 random.SystemRandom 以取得更多細節。

secrets.choice(seq)

從一非空序列中，回傳一個隨機選取的元素。

secrets.randbelow(exclusive_upper_bound)

回傳一個 [0, exclusive_upper_bound) 範圍之內的隨機整數。

secrets.randbits(k)

回傳一個具 k 個隨機位元的非負整數。

產生權杖（token）

secrets 模組提供了一些產生安全性權杖的函式，適合用於諸如重設密碼、難以猜測的 URL，或類似的應用。

secrets.token_bytes([nbytes=None])

回傳一個隨機位元組字串，其中含有 nbytes 位元組的數字。 如果 nbytes 為 None 或未提供，則會使用一合理預設值。

>>> token_bytes(16)
b'\xebr\x17D*t\xae\xd4\xe3S\xb6\xe2\xebP1\x8b'

secrets.token_hex([nbytes=None])

回傳一以十六進位表示的隨機字串。 字串具有 nbytes 個隨機位元組，每個位元組會轉成兩個十六進位的數字。 如果 nbytes 為 None 或未提供，則會使用一個合理的預設值。

>>> token_hex(16)
'f9bf78b9a18ce6d46a0cd2b0b86df9da'

secrets.token_urlsafe([nbytes=None])

回傳一個 URL 安全的隨機文本字串，包含 nbytes 個隨機位元組。 文本將使用 Base64 編碼，因此平均來說每個位元組會對應到約 1.3 個字元。 如果 nbytes 為 None 或未提供，則會使用一個合理的預設值。

>>> token_urlsafe(16)
'Drmhze6EPcv0fN_81Bj-nA'

權杖應當使用多少個位元組？

為了在面對暴力攻擊 [https://en.wikipedia.org/wiki/Brute-force_attack]時能保證安全，權杖必須具有足夠的隨機性。 不幸的是，對隨機性是否足夠的標準，會隨著電腦越來越強大並能夠在更短時間內進行更多猜測而不斷提高。 在 2015 年時，人們認為 32 位元組（256 位元）的隨機性對於 secrets 模組所預期的一般使用場景來說是足夠的。

對於想自行管理權杖長度的使用者，你可以對各種 token_* 函式明白地指定 int 引數（argument）來指定權杖要使用的隨機性程度。 該引數以位元組數來表示要使用的隨機性程度。

否則，如未提供引數，或者如果引數為 None，則 token_* 函式則會使用一個合理的預設值。

備註

該預設值可能在任何時候被改變，包括在維護版本更新的時候。

其他函式

secrets.compare_digest(a, b)

如果字串或類位元組串物件 a 與 b 相等則回傳 True，否則回傳 False，以"恆定時間比較 (constant-time compare) "的處理方式可降低時序攻擊 [https://codahale.com/a-lesson-in-timing-attacks/]的風險。 請參閱 hmac.compare_digest() 以了解更多細節。

應用技巧和典範實務（best practices）

本節展示了一些使用 secrets 來管理基本安全等級的應用技巧和典範實務。

產生八個字元長的字母數字密碼：

import string
import secrets
alphabet = string.ascii_letters + string.digits
password = ''.join(secrets.choice(alphabet) for i in range(8))

備註

應用程式不能以可復原的格式儲存密碼 [https://cwe.mitre.org/data/definitions/257.html]，無論是用純文本還是經過加密。 它們應當先加鹽（salt），再使用高加密強度的單向（不可逆）雜湊函式來產生雜湊值。

產生十個字元長的字母數字密碼，其中包含至少一個小寫字母，至少一個大寫字母以及至少三個數字:

import string
import secrets
alphabet = string.ascii_letters + string.digits
while True:
    password = ''.join(secrets.choice(alphabet) for i in range(10))
    if (any(c.islower() for c in password)
            and any(c.isupper() for c in password)
            and sum(c.isdigit() for c in password) >= 3):
        break

產生 XKCD 風格的 passphrase [https://xkcd.com/936/]:

import secrets
# 在標準 Linux 系統上，使用一個方便的字典檔案。
# 其他平台可能需要提供自己的字詞列表。
with open('/usr/share/dict/words') as f:
    words = [word.strip() for word in f]
    password = ' '.join(secrets.choice(words) for i in range(4))

產生難以猜測的暫時性 URL，內含回復密碼時所用的一個安全性權杖：

import secrets
url = 'https://example.com/reset=' + secrets.token_urlsafe()

通用作業系統服務

此章節所描述的模組 (module) 提供了作業系統特性的使用介面，例如檔案與時鐘，（幾乎）在所有作業系統上皆能使用。這些介面通常是參考 Unix 或 C 的介面來實作，不過在其他大多數系統上也能使用。以下為概述：

os --- 各種作業系統介面

File Names, Command Line Arguments, and Environment Variables

Python UTF-8 模式

行程參數

File Object Creation

File Descriptor Operations

Querying the size of a terminal

Inheritance of File Descriptors

Files and Directories

計時器檔案描述器

Linux extended attributes

行程管理

排程器介面

Miscellaneous System Information

Random numbers

io — 處理資料串流的核心工具

總覽

文字 I/O

二進位 (Binary) I/O

原始 (Raw) I/O

文字編碼

選擇性加入的編碼警告

高階模組介面

類別階層

I/O 基礎類別

原始檔案 I/O

Buffered Streams

文字 I/O

Static Typing

Performance

二進位 (Binary) I/O

文字 I/O

Multi-threading

Reentrancy

time --- 時間存取與轉換

函式

時鐘 ID 常數

時區常數

logging --- Python 的日誌記錄工具

Logger 物件

Logging Levels

Handler Objects

Formatter Objects

Filter Objects

LogRecord 物件

LogRecord 屬性

LoggerAdapter 物件

執行緒安全

模組層級函式

模組層級屬性

Integration with the warnings module

logging.config --- 日誌記錄配置

Configuration functions

Security considerations

Configuration dictionary schema

Dictionary Schema Details

Incremental Configuration

Object connections

User-defined objects

Handler configuration order

Access to external objects

Access to internal objects

Import resolution and custom importers

Configuring QueueHandler and QueueListener

Configuration file format

logging.handlers --- 日誌紀錄處理器

StreamHandler

FileHandler

NullHandler

WatchedFileHandler

BaseRotatingHandler

RotatingFileHandler

TimedRotatingFileHandler

SocketHandler

DatagramHandler

SysLogHandler

NTEventLogHandler

SMTPHandler

MemoryHandler

HTTPHandler

QueueHandler

QueueListener

platform --- 對底層平臺識別資料的存取

跨平台

Java 平台

Windows 平台

macOS 平台

iOS 平台

Unix 平台

Linux 平台

Android 平台

命令列用法

errno --- 標準 errno 系統符號

ctypes --- 用於 Python 的外部函式庫

ctypes 教學

Loading dynamic link libraries

Accessing functions from loaded dlls

呼叫函式

Fundamental data types

Calling functions, continued

Calling variadic functions

Calling functions with your own custom data types

Specifying the required argument types (function prototypes)

Return types

Passing pointers (or: passing parameters by reference)

Structures and unions

Structure/union layout, alignment and byte order

Bit fields in structures and unions

Arrays

指標

Thread safety without the GIL

Type conversions

Incomplete Types

回呼函式

Accessing values exported from dlls

Surprises

Variable-sized data types

ctypes reference

Finding shared libraries

Listing loaded shared libraries

Loading shared libraries

Foreign functions

Function prototypes

Utility functions

Data types

Fundamental data types

Structured data types

Arrays and pointers

Exceptions

os --- 各種作業系統介面

原始碼：Lib/os.py [https://github.com/python/cpython/tree/3.14/Lib/os.py]

該模組提供了一種便利的方式來操作與作業系統相關的功能。如果你想讀取或寫入檔案，請參閱 open() ，如果你想操作檔案路徑，請參閱 os.path 模組，如果你想透過命令列查看所有檔案中的所有內容，請查看 fileinput 模組。要建立臨時檔案和目錄，請參閱 tempfile 模組，要操作高級檔案和目錄，請參閱 shutil 模組。

關於這些功能的可用性說明：

Python 所有內建作業系統相關的模組設計是這樣：只要有相同的函式可使用，就會使用相同的介面 （interface）。舉例來說，os.stat(path) 函式會以相同格式回傳關於 path 的統計資訊（這剛好來自於 POSIX 的介面。）。

對於特定的作業系統獨有的擴充功能也可以透過 os 取得，但使用它們的時候對於可移植性無疑會是個問題。

所有接受檔案路徑和檔案名稱的函式皆接受位元組 (bytes) 和字串物件 (string objects)，且如果回傳檔案路徑或檔案名稱，則會產出相同型別的物件。

在 VxWorks, 不支援 os.popen、os.fork、os.execv 和 os.spawn*p*。

在 WebAssembly 平台和 Android 與 iOS 上，大部分 os 模組無法使用或行為不同。與行程 (process)（例如 fork()、execve()）與資源（例如 nice()）相關的 API 不可使用。其他諸如 getuid() 和 getpid() 的相關 API 是 emulated 或 stubs。WebAssembly 平台也缺少訊號相關支援（例如 kill()、wait()）。

備註

在檔案名稱和路徑找不到或無效的時候，或引數型別正確但作業系統不接受的時候，在此模組中的所有的函式都會引發 OSError（或其子類別）。

exception os.error

內建例外 OSError 的別名。

os.name

The name of the operating system dependent module imported. The following names have currently been registered: 'posix', 'nt', 'java'.

也參考

sys.platform has a finer granularity. os.uname() gives system-dependent version information.

The platform module provides detailed checks for the system's identity.

File Names, Command Line Arguments, and Environment Variables

In Python, file names, command line arguments, and environment variables are represented using the string type. On some systems, decoding these strings to and from bytes is necessary before passing them to the operating system. Python uses the filesystem encoding and error handler to perform this conversion (see sys.getfilesystemencoding()).

The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read() function: see filesystem_encoding and filesystem_errors members of PyConfig.

在 3.1 版的變更: On some systems, conversion using the file system encoding may fail. In this case, Python uses the surrogateescape encoding error handler, which means that undecodable bytes are replaced by a Unicode character U+DCxx on decoding, and these are again translated to the original byte on encoding.

The file system encoding must guarantee to successfully decode all bytes below 128. If the file system encoding fails to provide this guarantee, API functions can raise UnicodeError.

另請參閱 locale encoding。

Python UTF-8 模式

在 3.7 版被加入: 更多資訊請見 PEP 540 [https://peps.python.org/pep-0540/]。

Python 在 UTF-8 模式下會忽略 locale encoding 並且強制使用 UTF-8 去編碼：

Use UTF-8 as the filesystem encoding.

sys.getfilesystemencoding() 回傳 'utf-8'。

locale.getpreferredencoding() 回傳 'utf-8'（do_setlocale 引數並無任何效果）。

sys.stdin, sys.stdout, and sys.stderr all use UTF-8 as their text encoding, with the surrogateescape error handler being enabled for sys.stdin and sys.stdout (sys.stderr continues to use backslashreplace as it does in the default locale-aware mode)

在 Unix 中，os.device_encoding() 回傳 'utf-8' 而非裝置編碼。

請注意，在 UTF-8 模式中，標準的串流設定會被 PYTHONIOENCODING 覆蓋（如同在預設在地化覺察 模式一樣）。

As a consequence of the changes in those lower level APIs, other higher level APIs also exhibit different default behaviours:

命令列引數、環境變數及檔案名稱會以 UTF-8 編碼形式來被解碼成文字。

os.fsdecode() 和 os.fsencode() 使用 UTF-8 編碼。

open(), io.open(), and codecs.open() use the UTF-8 encoding by default. However, they still use the strict error handler by default so that attempting to open a binary file in text mode is likely to raise an exception rather than producing nonsense data.

The Python UTF-8 Mode is enabled if the LC_CTYPE locale is C or POSIX at Python startup (see the PyConfig_Read() function).

It can be enabled or disabled using the -X utf8 command line option and the PYTHONUTF8 environment variable.

If the PYTHONUTF8 environment variable is not set at all, then the interpreter defaults to using the current locale settings, unless the current locale is identified as a legacy ASCII-based locale (as described for PYTHONCOERCECLOCALE), and locale coercion is either disabled or fails. In such legacy locales, the interpreter will default to enabling UTF-8 mode unless explicitly instructed not to do so.

The Python UTF-8 Mode can only be enabled at the Python startup. Its value can be read from sys.flags.utf8_mode.

See also the UTF-8 mode on Windows and the filesystem encoding and error handler.

也參考

PEP 686 [https://peps.python.org/pep-0686/]

Python 3.15 預設使用 Python UTF-8 模式

行程參數

These functions and data items provide information and operate on the current process and user.

os.ctermid()

Return the filename corresponding to the controlling terminal of the process.

可用性: Unix, not WASI.

os.environ

A mapping object where keys and values are strings that represent the process environment. For example, environ['HOME'] is the pathname of your home directory (on some platforms), and is equivalent to getenv("HOME") in C.

This mapping is captured the first time the os module is imported, typically during Python startup as part of processing site.py. Changes to the environment made after this time are not reflected in os.environ, except for changes made by modifying os.environ directly.

This mapping may be used to modify the environment as well as query the environment. putenv() will be called automatically when the mapping is modified.

On Unix, keys and values use sys.getfilesystemencoding() and 'surrogateescape' error handler. Use environb if you would like to use a different encoding.

On Windows, the keys are converted to uppercase. This also applies when getting, setting, or deleting an item. For example, environ['monty'] = 'python' maps the key 'MONTY' to the value 'python'.

備註

呼叫 putenv() 並不會改變 os.environ，所以建議直接修改 os.environ。

備註

On some platforms, including FreeBSD and macOS, setting environ may cause memory leaks. Refer to the system documentation for putenv().

You can delete items in this mapping to unset environment variables. unsetenv() will be called automatically when an item is deleted from os.environ, and when one of the pop() or clear() methods is called.

也參考

os.reload_environ() 函式。

在 3.9 版的變更: Updated to support PEP 584 [https://peps.python.org/pep-0584/]'s merge (|) and update (|=) operators.

os.environb

Bytes version of environ: a mapping object where both keys and values are bytes objects representing the process environment. environ and environb are synchronized (modifying environb updates environ, and vice versa).

environb is only available if supports_bytes_environ is True.

在 3.2 版被加入.

在 3.9 版的變更: Updated to support PEP 584 [https://peps.python.org/pep-0584/]'s merge (|) and update (|=) operators.

os.reload_environ()

The os.environ and os.environb mappings are a cache of environment variables at the time that Python started. As such, changes to the current process environment are not reflected if made outside Python, or by os.putenv() or os.unsetenv(). Use os.reload_environ() to update os.environ and os.environb with any such changes to the current process environment.

警告

This function is not thread-safe. Calling it while the environment is being modified in an other thread is an undefined behavior. Reading from os.environ or os.environb, or calling os.getenv() while reloading, may return an empty result.

在 3.14 版被加入.

os.chdir(path)

os.fchdir(fd)

os.getcwd()

These functions are described in Files and Directories.

os.fsencode(filename)

Encode path-like filename to the filesystem encoding and error handler; return bytes unchanged.

fsdecode() 是反函式。

在 3.2 版被加入.

在 3.6 版的變更: Support added to accept objects implementing the os.PathLike interface.

os.fsdecode(filename)

Decode the path-like filename from the filesystem encoding and error handler; return str unchanged.

fsencode() 是反函式。

在 3.2 版被加入.

在 3.6 版的變更: Support added to accept objects implementing the os.PathLike interface.

os.fspath(path)

Return the file system representation of the path.

If str or bytes is passed in, it is returned unchanged. Otherwise __fspath__() is called and its value is returned as long as it is a str or bytes object. In all other cases, TypeError is raised.

在 3.6 版被加入.

class os.PathLike

An abstract base class for objects representing a file system path, e.g. pathlib.PurePath.

在 3.6 版被加入.

abstractmethod __fspath__()

Return the file system path representation of the object.

The method should only return a str or bytes object, with the preference being for str.

os.getenv(key, default=None)

Return the value of the environment variable key as a string if it exists, or default if it doesn't. key is a string. Note that since getenv() uses os.environ, the mapping of getenv() is similarly also captured on import, and the function may not reflect future environment changes.

On Unix, keys and values are decoded with sys.getfilesystemencoding() and 'surrogateescape' error handler. Use os.getenvb() if you would like to use a different encoding.

可用性: Unix, Windows.

os.getenvb(key, default=None)

Return the value of the environment variable key as bytes if it exists, or default if it doesn't. key must be bytes. Note that since getenvb() uses os.environb, the mapping of getenvb() is similarly also captured on import, and the function may not reflect future environment changes.

getenvb() is only available if supports_bytes_environ is True.

可用性: Unix.

在 3.2 版被加入.

os.get_exec_path(env=None)

Returns the list of directories that will be searched for a named executable, similar to a shell, when launching a process. env, when specified, should be an environment variable dictionary to lookup the PATH in. By default, when env is None, environ is used.

在 3.2 版被加入.

os.getegid()

Return the effective group id of the current process. This corresponds to the "set id" bit on the file being executed in the current process.

可用性: Unix, not WASI.

os.geteuid()

Return the current process's effective user id.

可用性: Unix, not WASI.

os.getgid()

Return the real group id of the current process.

可用性: Unix.

The function is a stub on WASI, see WebAssembly 平台 for more information.

os.getgrouplist(user, group, /)

Return list of group ids that user belongs to. If group is not in the list, it is included; typically, group is specified as the group ID field from the password record for user, because that group ID will otherwise be potentially omitted.

可用性: Unix, not WASI.

在 3.3 版被加入.

os.getgroups()

Return list of supplemental group ids associated with the current process.

可用性: Unix, not WASI.

備註

On macOS, getgroups() behavior differs somewhat from other Unix platforms. If the Python interpreter was built with a deployment target of 10.5 or earlier, getgroups() returns the list of effective group ids associated with the current user process; this list is limited to a system-defined number of entries, typically 16, and may be modified by calls to setgroups() if suitably privileged. If built with a deployment target greater than 10.5, getgroups() returns the current group access list for the user associated with the effective user id of the process; the group access list may change over the lifetime of the process, it is not affected by calls to setgroups(), and its length is not limited to 16. The deployment target value, MACOSX_DEPLOYMENT_TARGET, can be obtained with sysconfig.get_config_var().

os.getlogin()

Return the name of the user logged in on the controlling terminal of the process. For most purposes, it is more useful to use getpass.getuser() since the latter checks the environment variables LOGNAME or USERNAME to find out who the user is, and falls back to pwd.getpwuid(os.getuid())[0] to get the login name of the current real user id.

可用性: Unix, Windows, not WASI.

os.getpgid(pid)

Return the process group id of the process with process id pid. If pid is 0, the process group id of the current process is returned.

可用性: Unix, not WASI.

os.getpgrp()

Return the id of the current process group.

可用性: Unix, not WASI.

os.getpid()

Return the current process id.

The function is a stub on WASI, see WebAssembly 平台 for more information.

os.getppid()

Return the parent's process id. When the parent process has exited, on Unix the id returned is the one of the init process (1), on Windows it is still the same id, which may be already reused by another process.

可用性: Unix, Windows, not WASI.

在 3.2 版的變更: 新增對 Windows 的支援。

os.getpriority(which, who)

Get program scheduling priority. The value which is one of PRIO_PROCESS, PRIO_PGRP, or PRIO_USER, and who is interpreted relative to which (a process identifier for PRIO_PROCESS, process group identifier for PRIO_PGRP, and a user ID for PRIO_USER). A zero value for who denotes (respectively) the calling process, the process group of the calling process, or the real user ID of the calling process.

可用性: Unix, not WASI.

在 3.3 版被加入.

os.PRIO_PROCESS

os.PRIO_PGRP

os.PRIO_USER

Parameters for the getpriority() and setpriority() functions.

可用性: Unix, not WASI.

在 3.3 版被加入.

os.PRIO_DARWIN_THREAD

os.PRIO_DARWIN_PROCESS

os.PRIO_DARWIN_BG

os.PRIO_DARWIN_NONUI

Parameters for the getpriority() and setpriority() functions.

可用性: macOS

在 3.12 版被加入.

os.getresuid()

Return a tuple (ruid, euid, suid) denoting the current process's real, effective, and saved user ids.

可用性: Unix, not WASI.

在 3.2 版被加入.

os.getresgid()

Return a tuple (rgid, egid, sgid) denoting the current process's real, effective, and saved group ids.

可用性: Unix, not WASI.

在 3.2 版被加入.

os.getuid()

Return the current process's real user id.

可用性: Unix.

The function is a stub on WASI, see WebAssembly 平台 for more information.

os.initgroups(username, gid, /)

Call the system initgroups() to initialize the group access list with all of the groups of which the specified username is a member, plus the specified group id.

可用性: Unix, not WASI, not Android.

在 3.2 版被加入.

os.putenv(key, value, /)

Set the environment variable named key to the string value. Such changes to the environment affect subprocesses started with os.system(), popen() or fork() and execv().

Assignments to items in os.environ are automatically translated into corresponding calls to putenv(); however, calls to putenv() don't update os.environ, so it is actually preferable to assign to items of os.environ. This also applies to getenv() and getenvb(), which respectively use os.environ and os.environb in their implementations.

也請見 os.reload_environ() 函式。

備註

On some platforms, including FreeBSD and macOS, setting environ may cause memory leaks. Refer to the system documentation for putenv().

引發一個附帶引數 key、value 的稽核事件 os.putenv。

在 3.9 版的變更: 此函式現在都會是可用的。

os.setegid(egid, /)

Set the current process's effective group id.

可用性: Unix, not WASI, not Android.

os.seteuid(euid, /)

Set the current process's effective user id.

可用性: Unix, not WASI, not Android.

os.setgid(gid, /)

Set the current process' group id.

可用性: Unix, not WASI, not Android.

os.setgroups(groups, /)

Set the list of supplemental group ids associated with the current process to groups. groups must be a sequence, and each element must be an integer identifying a group. This operation is typically available only to the superuser.

可用性: Unix, not WASI.

備註

On macOS, the length of groups may not exceed the system-defined maximum number of effective group ids, typically 16. See the documentation for getgroups() for cases where it may not return the same group list set by calling setgroups().

os.setns(fd, nstype=0)

Reassociate the current thread with a Linux namespace. See the setns(2) [https://manpages.debian.org/setns(2)] and namespaces(7) [https://manpages.debian.org/namespaces(7)] man pages for more details.

If fd refers to a /proc/pid/ns/ link, setns() reassociates the calling thread with the namespace associated with that link, and nstype may be set to one of the CLONE_NEW* constants to impose constraints on the operation (0 means no constraints).

Since Linux 5.8, fd may refer to a PID file descriptor obtained from pidfd_open(). In this case, setns() reassociates the calling thread into one or more of the same namespaces as the thread referred to by fd. This is subject to any constraints imposed by nstype, which is a bit mask combining one or more of the CLONE_NEW* constants, e.g. setns(fd, os.CLONE_NEWUTS | os.CLONE_NEWPID). The caller's memberships in unspecified namespaces are left unchanged.

fd can be any object with a fileno() method, or a raw file descriptor.

This example reassociates the thread with the init process's network namespace:

fd = os.open("/proc/1/ns/net", os.O_RDONLY)
os.setns(fd, os.CLONE_NEWNET)
os.close(fd)

可用性: Linux >= 3.0 with glibc >= 2.14.

在 3.12 版被加入.

也參考

unshare() 函式。

os.setpgrp()

Call the system call setpgrp() or setpgrp(0, 0) depending on which version is implemented (if any). See the Unix manual for the semantics.

可用性: Unix, not WASI.

os.setpgid(pid, pgrp, /)

Call the system call setpgid() to set the process group id of the process with id pid to the process group with id pgrp. See the Unix manual for the semantics.

可用性: Unix, not WASI.

os.setpriority(which, who, priority)

Set program scheduling priority. The value which is one of PRIO_PROCESS, PRIO_PGRP, or PRIO_USER, and who is interpreted relative to which (a process identifier for PRIO_PROCESS, process group identifier for PRIO_PGRP, and a user ID for PRIO_USER). A zero value for who denotes (respectively) the calling process, the process group of the calling process, or the real user ID of the calling process. priority is a value in the range -20 to 19. The default priority is 0; lower priorities cause more favorable scheduling.

可用性: Unix, not WASI.

在 3.3 版被加入.

os.setregid(rgid, egid, /)

Set the current process's real and effective group ids.

可用性: Unix, not WASI, not Android.

os.setresgid(rgid, egid, sgid, /)

Set the current process's real, effective, and saved group ids.

可用性: Unix, not WASI, not Android.

在 3.2 版被加入.

os.setresuid(ruid, euid, suid, /)

Set the current process's real, effective, and saved user ids.

可用性: Unix, not WASI, not Android.

在 3.2 版被加入.

os.setreuid(ruid, euid, /)

Set the current process's real and effective user ids.

可用性: Unix, not WASI, not Android.

os.getsid(pid, /)

Call the system call getsid(). See the Unix manual for the semantics.

可用性: Unix, not WASI.

os.setsid()

Call the system call setsid(). See the Unix manual for the semantics.

可用性: Unix, not WASI.

os.setuid(uid, /)

Set the current process's user id.

可用性: Unix, not WASI, not Android.

os.strerror(code, /)

Return the error message corresponding to the error code in code. On platforms where strerror() returns NULL when given an unknown error number, ValueError is raised.

os.supports_bytes_environ

True if the native OS type of the environment is bytes (eg. False on Windows).

在 3.2 版被加入.

os.umask(mask, /)

Set the current numeric umask and return the previous umask.

The function is a stub on WASI, see WebAssembly 平台 for more information.

os.uname()

Returns information identifying the current operating system. The return value is an object with five attributes:

sysname - 作業系統名稱

nodename - name of machine on network (implementation-defined)

release - operating system release

version - 作業系統版本

machine - hardware identifier

For backwards compatibility, this object is also iterable, behaving like a five-tuple containing sysname, nodename, release, version, and machine in that order.

Some systems truncate nodename to 8 characters or to the leading component; a better way to get the hostname is socket.gethostname() or even socket.gethostbyaddr(socket.gethostname()).

On macOS, iOS and Android, this returns the kernel name and version (i.e., 'Darwin' on macOS and iOS; 'Linux' on Android). platform.uname() can be used to get the user-facing operating system name and version on iOS and Android.

可用性: Unix.

在 3.3 版的變更: Return type changed from a tuple to a tuple-like object with named attributes.

os.unsetenv(key, /)

Unset (delete) the environment variable named key. Such changes to the environment affect subprocesses started with os.system(), popen() or fork() and execv().

Deletion of items in os.environ is automatically translated into a corresponding call to unsetenv(); however, calls to unsetenv() don't update os.environ, so it is actually preferable to delete items of os.environ.

也請見 os.reload_environ() 函式。

引發一個附帶引數 key 的稽核事件 os.unsetenv。

在 3.9 版的變更: The function is now always available and is also available on Windows.

os.unshare(flags)

Disassociate parts of the process execution context, and move them into a newly created namespace. See the unshare(2) [https://manpages.debian.org/unshare(2)] man page for more details. The flags argument is a bit mask, combining zero or more of the CLONE_* constants, that specifies which parts of the execution context should be unshared from their existing associations and moved to a new namespace. If the flags argument is 0, no changes are made to the calling process's execution context.

可用性: Linux >= 2.6.16.

在 3.12 版被加入.

也參考

setns() 函式。

Flags to the unshare() function, if the implementation supports them. See unshare(2) [https://manpages.debian.org/unshare(2)] in the Linux manual for their exact effect and availability.

os.CLONE_FILES

os.CLONE_FS

os.CLONE_NEWCGROUP

os.CLONE_NEWIPC

os.CLONE_NEWNET

os.CLONE_NEWNS

os.CLONE_NEWPID

os.CLONE_NEWTIME

os.CLONE_NEWUSER

os.CLONE_NEWUTS

os.CLONE_SIGHAND

os.CLONE_SYSVSEM

os.CLONE_THREAD

os.CLONE_VM

File Object Creation

These functions create new file objects. (See also open() for opening file descriptors.)

os.fdopen(fd, *args, **kwargs)

Return an open file object connected to the file descriptor fd. This is an alias of the open() built-in function and accepts the same arguments. The only difference is that the first argument of fdopen() must always be an integer.

File Descriptor Operations

These functions operate on I/O streams referenced using file descriptors.

File descriptors are small integers corresponding to a file that has been opened by the current process. For example, standard input is usually file descriptor 0, standard output is 1, and standard error is 2. Further files opened by a process will then be assigned 3, 4, 5, and so forth. The name "file descriptor" is slightly deceptive; on Unix platforms, sockets and pipes are also referenced by file descriptors.

The fileno() method can be used to obtain the file descriptor associated with a file object when required. Note that using the file descriptor directly will bypass the file object methods, ignoring aspects such as internal buffering of data.

os.close(fd)

Close file descriptor fd.

備註

This function is intended for low-level I/O and must be applied to a file descriptor as returned by os.open() or pipe(). To close a "file object" returned by the built-in function open() or by popen() or fdopen(), use its close() method.

os.closerange(fd_low, fd_high, /)

Close all file descriptors from fd_low (inclusive) to fd_high (exclusive), ignoring errors. Equivalent to (but much faster than):

for fd in range(fd_low, fd_high):
    try:
        os.close(fd)
    except OSError:
        pass

os.copy_file_range(src, dst, count, offset_src=None, offset_dst=None)

Copy count bytes from file descriptor src, starting from offset offset_src, to file descriptor dst, starting from offset offset_dst. If offset_src is None, then src is read from the current position; respectively for offset_dst.

In Linux kernel older than 5.3, the files pointed to by src and dst must reside in the same filesystem, otherwise an OSError is raised with errno set to errno.EXDEV.

This copy is done without the additional cost of transferring data from the kernel to user space and then back into the kernel. Additionally, some filesystems could implement extra optimizations, such as the use of reflinks (i.e., two or more inodes that share pointers to the same copy-on-write disk blocks; supported file systems include btrfs and XFS) and server-side copy (in the case of NFS).

The function copies bytes between two file descriptors. Text options, like the encoding and the line ending, are ignored.

The return value is the amount of bytes copied. This could be less than the amount requested.

備註

On Linux, os.copy_file_range() should not be used for copying a range of a pseudo file from a special filesystem like procfs and sysfs. It will always copy no bytes and return 0 as if the file was empty because of a known Linux kernel issue.

可用性: Linux >= 4.5 with glibc >= 2.27.

在 3.8 版被加入.

os.device_encoding(fd)

Return a string describing the encoding of the device associated with fd if it is connected to a terminal; else return None.

On Unix, if the Python UTF-8 Mode is enabled, return 'UTF-8' rather than the device encoding.

在 3.10 版的變更: On Unix, the function now implements the Python UTF-8 Mode.

os.dup(fd, /)

Return a duplicate of file descriptor fd. The new file descriptor is non-inheritable.

On Windows, when duplicating a standard stream (0: stdin, 1: stdout, 2: stderr), the new file descriptor is inheritable.

可用性: not WASI.

在 3.4 版的變更: The new file descriptor is now non-inheritable.

os.dup2(fd, fd2, inheritable=True)

Duplicate file descriptor fd to fd2, closing the latter first if necessary. Return fd2. The new file descriptor is inheritable by default or non-inheritable if inheritable is False.

可用性: not WASI.

在 3.4 版的變更: 新增可選用的參數 inheritable。

在 3.7 版的變更: Return fd2 on success. Previously, None was always returned.

os.fchmod(fd, mode)

Change the mode of the file given by fd to the numeric mode. See the docs for chmod() for possible values of mode. As of Python 3.3, this is equivalent to os.chmod(fd, mode).

引發一個附帶引數 path、mode、dir_fd 的稽核事件 os.chmod。

可用性: Unix, Windows.

The function is limited on WASI, see WebAssembly 平台 for more information.

在 3.13 版的變更: 新增對 Windows 的支援。

os.fchown(fd, uid, gid)

Change the owner and group id of the file given by fd to the numeric uid and gid. To leave one of the ids unchanged, set it to -1. See chown(). As of Python 3.3, this is equivalent to os.chown(fd, uid, gid).

引發一個附帶引數 path、uid、gid、dir_fd 的稽核事件 os.chown。

可用性: Unix.

The function is limited on WASI, see WebAssembly 平台 for more information.

os.fdatasync(fd)

Force write of file with filedescriptor fd to disk. Does not force update of metadata.

可用性: Unix.

備註

This function is not available on MacOS.

os.fpathconf(fd, name, /)

Return system configuration information relevant to an open file. name specifies the configuration value to retrieve; it may be a string which is the name of a defined system value; these names are specified in a number of standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define additional names as well. The names known to the host operating system are given in the pathconf_names dictionary. For configuration variables not included in that mapping, passing an integer for name is also accepted.

If name is a string and is not known, ValueError is raised. If a specific value for name is not supported by the host system, even if it is included in pathconf_names, an OSError is raised with errno.EINVAL for the error number.

As of Python 3.3, this is equivalent to os.pathconf(fd, name).

可用性: Unix.

os.fstat(fd)

Get the status of the file descriptor fd. Return a stat_result object.

As of Python 3.3, this is equivalent to os.stat(fd).

也參考

The stat() function.

os.fstatvfs(fd, /)

Return information about the filesystem containing the file associated with file descriptor fd, like statvfs(). As of Python 3.3, this is equivalent to os.statvfs(fd).

可用性: Unix.

os.fsync(fd)

Force write of file with filedescriptor fd to disk. On Unix, this calls the native fsync() function; on Windows, the MS _commit() function.

If you're starting with a buffered Python file object f, first do f.flush(), and then do os.fsync(f.fileno()), to ensure that all internal buffers associated with f are written to disk.

可用性: Unix, Windows.

os.ftruncate(fd, length, /)

Truncate the file corresponding to file descriptor fd, so that it is at most length bytes in size. As of Python 3.3, this is equivalent to os.truncate(fd, length).

引發一個附帶引數 fd、length 的稽核事件 os.truncate。

可用性: Unix, Windows.

在 3.5 版的變更: 新增對 Windows 的支援

os.get_blocking(fd, /)

Get the blocking mode of the file descriptor: False if the O_NONBLOCK flag is set, True if the flag is cleared.

另請參閱 set_blocking() 與 socket.socket.setblocking()。

可用性: Unix, Windows.

The function is limited on WASI, see WebAssembly 平台 for more information.

On Windows, this function is limited to pipes.

在 3.5 版被加入.

在 3.12 版的變更: 新增對 Windows 上的 pipe 支援。

os.grantpt(fd, /)

Grant access to the slave pseudo-terminal device associated with the master pseudo-terminal device to which the file descriptor fd refers. The file descriptor fd is not closed upon failure.

Calls the C standard library function grantpt().

可用性: Unix, not WASI.

在 3.13 版被加入.

os.isatty(fd, /)

Return True if the file descriptor fd is open and connected to a tty(-like) device, else False.

os.lockf(fd, cmd, len, /)

Apply, test or remove a POSIX lock on an open file descriptor. fd is an open file descriptor. cmd specifies the command to use - one of F_LOCK, F_TLOCK, F_ULOCK or F_TEST. len specifies the section of the file to lock.

引發一個附帶引數 fd、cmd、len 的稽核事件 os.lockf。

可用性: Unix.

在 3.3 版被加入.

os.F_LOCK

os.F_TLOCK

os.F_ULOCK

os.F_TEST

Flags that specify what action lockf() will take.

可用性: Unix.

在 3.3 版被加入.

os.login_tty(fd, /)

Prepare the tty of which fd is a file descriptor for a new login session. Make the calling process a session leader; make the tty the controlling tty, the stdin, the stdout, and the stderr of the calling process; close fd.

可用性: Unix, not WASI.

在 3.11 版被加入.

os.lseek(fd, pos, whence, /)

Set the current position of file descriptor fd to position pos, modified by whence, and return the new position in bytes relative to the start of the file. Valid values for whence are:

SEEK_SET or 0 -- set pos relative to the beginning of the file

SEEK_CUR or 1 -- set pos relative to the current file position

SEEK_END or 2 -- set pos relative to the end of the file

SEEK_HOLE -- set pos to the next data location, relative to pos

SEEK_DATA -- set pos to the next data hole, relative to pos

在 3.3 版的變更: Add support for SEEK_HOLE and SEEK_DATA.

os.SEEK_SET

os.SEEK_CUR

os.SEEK_END

Parameters to the lseek() function and the seek() method on file-like objects, for whence to adjust the file position indicator.

SEEK_SET

Adjust the file position relative to the beginning of the file.

SEEK_CUR

Adjust the file position relative to the current file position.

SEEK_END

Adjust the file position relative to the end of the file.

Their values are 0, 1, and 2, respectively.

os.SEEK_HOLE

os.SEEK_DATA

Parameters to the lseek() function and the seek() method on file-like objects, for seeking file data and holes on sparsely allocated files.

SEEK_DATA

Adjust the file offset to the next location containing data, relative to the seek position.

SEEK_HOLE

Adjust the file offset to the next location containing a hole, relative to the seek position. A hole is defined as a sequence of zeros.

備註

These operations only make sense for filesystems that support them.

可用性: Linux >= 3.1, macOS, Unix

在 3.3 版被加入.

os.open(path, flags, mode=0o777, *, dir_fd=None)

Open the file path and set various flags according to flags and possibly its mode according to mode. When computing mode, the current umask value is first masked out. Return the file descriptor for the newly opened file. The new file descriptor is non-inheritable.

For a description of the flag and mode values, see the C run-time documentation; flag constants (like O_RDONLY and O_WRONLY) are defined in the os module. In particular, on Windows adding O_BINARY is needed to open files in binary mode.

This function can support paths relative to directory descriptors with the dir_fd parameter.

引發一個附帶引數 path、mode、flags 的稽核事件 open。

在 3.4 版的變更: The new file descriptor is now non-inheritable.

備註

This function is intended for low-level I/O. For normal usage, use the built-in function open(), which returns a file object with read() and write() methods (and many more). To wrap a file descriptor in a file object, use fdopen().

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

在 3.6 版的變更: Accepts a path-like object.

The following constants are options for the flags parameter to the open() function. They can be combined using the bitwise OR operator |. Some of them are not available on all platforms. For descriptions of their availability and use, consult the open(2) [https://manpages.debian.org/open(2)] manual page on Unix or the MSDN [https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx] on Windows.

os.O_RDONLY

os.O_WRONLY

os.O_RDWR

os.O_APPEND

os.O_CREAT

os.O_EXCL

os.O_TRUNC

The above constants are available on Unix and Windows.

os.O_DSYNC

os.O_RSYNC

os.O_SYNC

os.O_NDELAY

os.O_NONBLOCK

os.O_NOCTTY

os.O_CLOEXEC

The above constants are only available on Unix.

在 3.3 版的變更: 新增 O_CLOEXEC 常數。

os.O_BINARY

os.O_NOINHERIT

os.O_SHORT_LIVED

os.O_TEMPORARY

os.O_RANDOM

os.O_SEQUENTIAL

os.O_TEXT

The above constants are only available on Windows.

os.O_EVTONLY

os.O_FSYNC

os.O_SYMLINK

os.O_NOFOLLOW_ANY

The above constants are only available on macOS.

在 3.10 版的變更: Add O_EVTONLY, O_FSYNC, O_SYMLINK and O_NOFOLLOW_ANY constants.

os.O_ASYNC

os.O_DIRECT

os.O_DIRECTORY

os.O_NOFOLLOW

os.O_NOATIME

os.O_PATH

os.O_TMPFILE

os.O_SHLOCK

os.O_EXLOCK

The above constants are extensions and not present if they are not defined by the C library.

在 3.4 版的變更: Add O_PATH on systems that support it. Add O_TMPFILE, only available on Linux Kernel 3.11 or newer.

os.openpty()

Open a new pseudo-terminal pair. Return a pair of file descriptors (master, slave) for the pty and the tty, respectively. The new file descriptors are non-inheritable. For a (slightly) more portable approach, use the pty module.

可用性: Unix, not WASI.

在 3.4 版的變更: The new file descriptors are now non-inheritable.

os.pipe()

Create a pipe. Return a pair of file descriptors (r, w) usable for reading and writing, respectively. The new file descriptor is non-inheritable.

可用性: Unix, Windows.

在 3.4 版的變更: The new file descriptors are now non-inheritable.

os.pipe2(flags, /)

Create a pipe with flags set atomically. flags can be constructed by ORing together one or more of these values: O_NONBLOCK, O_CLOEXEC. Return a pair of file descriptors (r, w) usable for reading and writing, respectively.

可用性: Unix, not WASI.

在 3.3 版被加入.

os.posix_fallocate(fd, offset, len, /)

Ensures that enough disk space is allocated for the file specified by fd starting from offset and continuing for len bytes.

可用性: Unix.

在 3.3 版被加入.

os.posix_fadvise(fd, offset, len, advice, /)

Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations. The advice applies to the region of the file specified by fd starting at offset and continuing for len bytes. advice is one of POSIX_FADV_NORMAL, POSIX_FADV_SEQUENTIAL, POSIX_FADV_RANDOM, POSIX_FADV_NOREUSE, POSIX_FADV_WILLNEED or POSIX_FADV_DONTNEED.

可用性: Unix.

在 3.3 版被加入.

os.POSIX_FADV_NORMAL

os.POSIX_FADV_SEQUENTIAL

os.POSIX_FADV_RANDOM

os.POSIX_FADV_NOREUSE

os.POSIX_FADV_WILLNEED

os.POSIX_FADV_DONTNEED

Flags that can be used in advice in posix_fadvise() that specify the access pattern that is likely to be used.

可用性: Unix.

在 3.3 版被加入.

os.pread(fd, n, offset, /)

Read at most n bytes from file descriptor fd at a position of offset, leaving the file offset unchanged.

Return a bytestring containing the bytes read. If the end of the file referred to by fd has been reached, an empty bytes object is returned.

可用性: Unix.

在 3.3 版被加入.

os.posix_openpt(oflag, /)

Open and return a file descriptor for a master pseudo-terminal device.

Calls the C standard library function posix_openpt(). The oflag argument is used to set file status flags and file access modes as specified in the manual page of posix_openpt() of your system.

The returned file descriptor is non-inheritable. If the value O_CLOEXEC is available on the system, it is added to oflag.

可用性: Unix, not WASI.

在 3.13 版被加入.

os.preadv(fd, buffers, offset, flags=0, /)

Read from a file descriptor fd at a position of offset into mutable bytes-like objects buffers, leaving the file offset unchanged. Transfer data into each buffer until it is full and then move on to the next buffer in the sequence to hold the rest of the data.

The flags argument contains a bitwise OR of zero or more of the following flags:

RWF_HIPRI

RWF_NOWAIT

Return the total number of bytes actually read which can be less than the total capacity of all the objects.

The operating system may set a limit (sysconf() value 'SC_IOV_MAX') on the number of buffers that can be used.

Combine the functionality of os.readv() and os.pread().

可用性: Linux >= 2.6.30, FreeBSD >= 6.0, OpenBSD >= 2.7, AIX >= 7.1.

Using flags requires Linux >= 4.6.

在 3.7 版被加入.

os.RWF_NOWAIT

Do not wait for data which is not immediately available. If this flag is specified, the system call will return instantly if it would have to read data from the backing storage or wait for a lock.

If some data was successfully read, it will return the number of bytes read. If no bytes were read, it will return -1 and set errno to errno.EAGAIN.

可用性: Linux >= 4.14.

在 3.7 版被加入.

os.RWF_HIPRI

High priority read/write. Allows block-based filesystems to use polling of the device, which provides lower latency, but may use additional resources.

Currently, on Linux, this feature is usable only on a file descriptor opened using the O_DIRECT flag.

可用性: Linux >= 4.6.

在 3.7 版被加入.

os.ptsname(fd, /)

Return the name of the slave pseudo-terminal device associated with the master pseudo-terminal device to which the file descriptor fd refers. The file descriptor fd is not closed upon failure.

Calls the reentrant C standard library function ptsname_r() if it is available; otherwise, the C standard library function ptsname(), which is not guaranteed to be thread-safe, is called.

可用性: Unix, not WASI.

在 3.13 版被加入.

os.pwrite(fd, str, offset, /)

Write the bytestring in str to file descriptor fd at position of offset, leaving the file offset unchanged.

Return the number of bytes actually written.

可用性: Unix.

在 3.3 版被加入.

os.pwritev(fd, buffers, offset, flags=0, /)

Write the buffers contents to file descriptor fd at an offset offset, leaving the file offset unchanged. buffers must be a sequence of bytes-like objects. Buffers are processed in array order. Entire contents of the first buffer is written before proceeding to the second, and so on.

The flags argument contains a bitwise OR of zero or more of the following flags:

RWF_DSYNC

RWF_SYNC

RWF_APPEND

Return the total number of bytes actually written.

The operating system may set a limit (sysconf() value 'SC_IOV_MAX') on the number of buffers that can be used.

Combine the functionality of os.writev() and os.pwrite().

可用性: Linux >= 2.6.30, FreeBSD >= 6.0, OpenBSD >= 2.7, AIX >= 7.1.

Using flags requires Linux >= 4.6.

在 3.7 版被加入.

os.RWF_DSYNC

Provide a per-write equivalent of the O_DSYNC os.open() flag. This flag effect applies only to the data range written by the system call.

可用性: Linux >= 4.7.

在 3.7 版被加入.

os.RWF_SYNC

Provide a per-write equivalent of the O_SYNC os.open() flag. This flag effect applies only to the data range written by the system call.

可用性: Linux >= 4.7.

在 3.7 版被加入.

os.RWF_APPEND

Provide a per-write equivalent of the O_APPEND os.open() flag. This flag is meaningful only for os.pwritev(), and its effect applies only to the data range written by the system call. The offset argument does not affect the write operation; the data is always appended to the end of the file. However, if the offset argument is -1, the current file offset is updated.

可用性: Linux >= 4.16.

在 3.10 版被加入.

os.read(fd, n, /)

Read at most n bytes from file descriptor fd.

Return a bytestring containing the bytes read. If the end of the file referred to by fd has been reached, an empty bytes object is returned.

備註

This function is intended for low-level I/O and must be applied to a file descriptor as returned by os.open() or pipe(). To read a "file object" returned by the built-in function open() or by popen() or fdopen(), or sys.stdin, use its read() or readline() methods.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

os.readinto(fd, buffer, /)

Read from a file descriptor fd into a mutable buffer object buffer.

The buffer should be mutable and bytes-like. On success, returns the number of bytes read. Less bytes may be read than the size of the buffer. The underlying system call will be retried when interrupted by a signal, unless the signal handler raises an exception. Other errors will not be retried and an error will be raised.

Returns 0 if fd is at end of file or if the provided buffer has length 0 (which can be used to check for errors without reading data). Never returns negative.

備註

This function is intended for low-level I/O and must be applied to a file descriptor as returned by os.open() or os.pipe(). To read a "file object" returned by the built-in function open(), or sys.stdin, use its member functions, for example io.BufferedIOBase.readinto(), io.BufferedIOBase.read(), or io.TextIOBase.read()

在 3.14 版被加入.

os.sendfile(out_fd, in_fd, offset, count)

os.sendfile(out_fd, in_fd, offset, count, headers=(), trailers=(), flags=0)

Copy count bytes from file descriptor in_fd to file descriptor out_fd starting at offset. Return the number of bytes sent. When EOF is reached return 0.

The first function notation is supported by all platforms that define sendfile().

On Linux, if offset is given as None, the bytes are read from the current position of in_fd and the position of in_fd is updated.

The second case may be used on macOS and FreeBSD where headers and trailers are arbitrary sequences of buffers that are written before and after the data from in_fd is written. It returns the same as the first case.

On macOS and FreeBSD, a value of 0 for count specifies to send until the end of in_fd is reached.

All platforms support sockets as out_fd file descriptor, and some platforms allow other types (e.g. regular file, pipe) as well.

Cross-platform applications should not use headers, trailers and flags arguments.

可用性: Unix, not WASI.

備註

For a higher-level wrapper of sendfile(), see socket.socket.sendfile().

在 3.3 版被加入.

在 3.9 版的變更: Parameters out and in was renamed to out_fd and in_fd.

os.SF_NODISKIO

os.SF_MNOWAIT

os.SF_SYNC

Parameters to the sendfile() function, if the implementation supports them.

可用性: Unix, not WASI.

在 3.3 版被加入.

os.SF_NOCACHE

Parameter to the sendfile() function, if the implementation supports it. The data won't be cached in the virtual memory and will be freed afterwards.

可用性: Unix, not WASI.

在 3.11 版被加入.

os.set_blocking(fd, blocking, /)

Set the blocking mode of the specified file descriptor. Set the O_NONBLOCK flag if blocking is False, clear the flag otherwise.

另請參閱 get_blocking() 與 socket.socket.setblocking()。

可用性: Unix, Windows.

The function is limited on WASI, see WebAssembly 平台 for more information.

On Windows, this function is limited to pipes.

在 3.5 版被加入.

在 3.12 版的變更: 新增對 Windows 上的 pipe 支援。

os.splice(src, dst, count, offset_src=None, offset_dst=None, flags=0)

Transfer count bytes from file descriptor src, starting from offset offset_src, to file descriptor dst, starting from offset offset_dst.

The splicing behaviour can be modified by specifying a flags value. Any of the following variables may used, combined using bitwise OR (the | operator):

If SPLICE_F_MOVE is specified, the kernel is asked to move pages instead of copying, but pages may still be copied if the kernel cannot move the pages from the pipe.

If SPLICE_F_NONBLOCK is specified, the kernel is asked to not block on I/O. This makes the splice pipe operations nonblocking, but splice may nevertheless block because the spliced file descriptors may block.

If SPLICE_F_MORE is specified, it hints to the kernel that more data will be coming in a subsequent splice.

At least one of the file descriptors must refer to a pipe. If offset_src is None, then src is read from the current position; respectively for offset_dst. The offset associated to the file descriptor that refers to a pipe must be None. The files pointed to by src and dst must reside in the same filesystem, otherwise an OSError is raised with errno set to errno.EXDEV.

This copy is done without the additional cost of transferring data from the kernel to user space and then back into the kernel. Additionally, some filesystems could implement extra optimizations. The copy is done as if both files are opened as binary.

Upon successful completion, returns the number of bytes spliced to or from the pipe. A return value of 0 means end of input. If src refers to a pipe, then this means that there was no data to transfer, and it would not make sense to block because there are no writers connected to the write end of the pipe.

也參考

splice(2) [https://manpages.debian.org/splice(2)] 使用手冊。

可用性: Linux >= 2.6.17 with glibc >= 2.5

在 3.10 版被加入.

os.SPLICE_F_MOVE

os.SPLICE_F_NONBLOCK

os.SPLICE_F_MORE

在 3.10 版被加入.

os.readv(fd, buffers, /)

Read from a file descriptor fd into a number of mutable bytes-like objects buffers. Transfer data into each buffer until it is full and then move on to the next buffer in the sequence to hold the rest of the data.

Return the total number of bytes actually read which can be less than the total capacity of all the objects.

The operating system may set a limit (sysconf() value 'SC_IOV_MAX') on the number of buffers that can be used.

可用性: Unix.

在 3.3 版被加入.

os.tcgetpgrp(fd, /)

Return the process group associated with the terminal given by fd (an open file descriptor as returned by os.open()).

可用性: Unix, not WASI.

os.tcsetpgrp(fd, pg, /)

Set the process group associated with the terminal given by fd (an open file descriptor as returned by os.open()) to pg.

可用性: Unix, not WASI.

os.ttyname(fd, /)

Return a string which specifies the terminal device associated with file descriptor fd. If fd is not associated with a terminal device, an exception is raised.

可用性: Unix.

os.unlockpt(fd, /)

Unlock the slave pseudo-terminal device associated with the master pseudo-terminal device to which the file descriptor fd refers. The file descriptor fd is not closed upon failure.

Calls the C standard library function unlockpt().

可用性: Unix, not WASI.

在 3.13 版被加入.

os.write(fd, str, /)

Write the bytestring in str to file descriptor fd.

Return the number of bytes actually written.

備註

This function is intended for low-level I/O and must be applied to a file descriptor as returned by os.open() or pipe(). To write a "file object" returned by the built-in function open() or by popen() or fdopen(), or sys.stdout or sys.stderr, use its write() method.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

os.writev(fd, buffers, /)

Write the contents of buffers to file descriptor fd. buffers must be a sequence of bytes-like objects. Buffers are processed in array order. Entire contents of the first buffer is written before proceeding to the second, and so on.

Returns the total number of bytes actually written.

The operating system may set a limit (sysconf() value 'SC_IOV_MAX') on the number of buffers that can be used.

可用性: Unix.

在 3.3 版被加入.

Querying the size of a terminal

在 3.3 版被加入.

os.get_terminal_size(fd=STDOUT_FILENO, /)

Return the size of the terminal window as (columns, lines), tuple of type terminal_size.

The optional argument fd (default STDOUT_FILENO, or standard output) specifies which file descriptor should be queried.

If the file descriptor is not connected to a terminal, an OSError is raised.

shutil.get_terminal_size() is the high-level function which should normally be used, os.get_terminal_size is the low-level implementation.

可用性: Unix, Windows.

class os.terminal_size

A subclass of tuple, holding (columns, lines) of the terminal window size.

columns

Width of the terminal window in characters.

lines

Height of the terminal window in characters.

Inheritance of File Descriptors

在 3.4 版被加入.

A file descriptor has an "inheritable" flag which indicates if the file descriptor can be inherited by child processes. Since Python 3.4, file descriptors created by Python are non-inheritable by default.

On UNIX, non-inheritable file descriptors are closed in child processes at the execution of a new program, other file descriptors are inherited. Note that non-inheritable file descriptors are still inherited by child processes on os.fork().

On Windows, non-inheritable handles and file descriptors are closed in child processes, except for standard streams (file descriptors 0, 1 and 2: stdin, stdout and stderr), which are always inherited. Using spawn* functions, all inheritable handles and all inheritable file descriptors are inherited. Using the subprocess module, all file descriptors except standard streams are closed, and inheritable handles are only inherited if the close_fds parameter is False.

On WebAssembly platforms, the file descriptor cannot be modified.

os.get_inheritable(fd, /)

Get the "inheritable" flag of the specified file descriptor (a boolean).

os.set_inheritable(fd, inheritable, /)

Set the "inheritable" flag of the specified file descriptor.

os.get_handle_inheritable(handle, /)

Get the "inheritable" flag of the specified handle (a boolean).

可用性: Windows.

os.set_handle_inheritable(handle, inheritable, /)

Set the "inheritable" flag of the specified handle.

可用性: Windows.

Files and Directories

On some Unix platforms, many of these functions support one or more of these features:

specifying a file descriptor: Normally the path argument provided to functions in the os module must be a string specifying a file path. However, some functions now alternatively accept an open file descriptor for their path argument. The function will then operate on the file referred to by the descriptor. For POSIX systems, Python will call the variant of the function prefixed with f (e.g. call fchdir instead of chdir).

You can check whether or not path can be specified as a file descriptor for a particular function on your platform using os.supports_fd. If this functionality is unavailable, using it will raise a NotImplementedError.

If the function also supports dir_fd or follow_symlinks arguments, it's an error to specify one of those when supplying path as a file descriptor.

paths relative to directory descriptors: If dir_fd is not None, it should be a file descriptor referring to a directory, and the path to operate on should be relative; path will then be relative to that directory. If the path is absolute, dir_fd is ignored. For POSIX systems, Python will call the variant of the function with an at suffix and possibly prefixed with f (e.g. call faccessat instead of access).

You can check whether or not dir_fd is supported for a particular function on your platform using os.supports_dir_fd. If it's unavailable, using it will raise a NotImplementedError.

not following symlinks: If follow_symlinks is False, and the last element of the path to operate on is a symbolic link, the function will operate on the symbolic link itself rather than the file pointed to by the link. For POSIX systems, Python will call the l... variant of the function.

You can check whether or not follow_symlinks is supported for a particular function on your platform using os.supports_follow_symlinks. If it's unavailable, using it will raise a NotImplementedError.

os.access(path, mode, *, dir_fd=None, effective_ids=False, follow_symlinks=True)

Use the real uid/gid to test for access to path. Note that most operations will use the effective uid/gid, therefore this routine can be used in a suid/sgid environment to test if the invoking user has the specified access to path. mode should be F_OK to test the existence of path, or it can be the inclusive OR of one or more of R_OK, W_OK, and X_OK to test permissions. Return True if access is allowed, False if not. See the Unix man page access(2) [https://manpages.debian.org/access(2)] for more information.

This function can support specifying paths relative to directory descriptors and not following symlinks.

If effective_ids is True, access() will perform its access checks using the effective uid/gid instead of the real uid/gid. effective_ids may not be supported on your platform; you can check whether or not it is available using os.supports_effective_ids. If it is unavailable, using it will raise a NotImplementedError.

備註

Using access() to check if a user is authorized to e.g. open a file before actually doing so using open() creates a security hole, because the user might exploit the short time interval between checking and opening the file to manipulate it. It's preferable to use EAFP techniques. For example:

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

is better written as:

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

備註

I/O operations may fail even when access() indicates that they would succeed, particularly for operations on network filesystems which may have permissions semantics beyond the usual POSIX permission-bit model.

在 3.3 版的變更: 新增 dir_fd、effective_ids 與 follow_symlinks 參數。

在 3.6 版的變更: Accepts a path-like object.

os.F_OK

os.R_OK

os.W_OK

os.X_OK

Values to pass as the mode parameter of access() to test the existence, readability, writability and executability of path, respectively.

os.chdir(path)

Change the current working directory to path.

This function can support specifying a file descriptor. The descriptor must refer to an opened directory, not an open file.

This function can raise OSError and subclasses such as FileNotFoundError, PermissionError, and NotADirectoryError.

引發一個附帶引數 path 的稽核事件 os.chdir。

在 3.3 版的變更: Added support for specifying path as a file descriptor on some platforms.

在 3.6 版的變更: Accepts a path-like object.

os.chflags(path, flags, *, follow_symlinks=True)

Set the flags of path to the numeric flags. flags may take a combination (bitwise OR) of the following values (as defined in the stat module):

stat.UF_NODUMP

stat.UF_IMMUTABLE

stat.UF_APPEND

stat.UF_OPAQUE

stat.UF_NOUNLINK

stat.UF_COMPRESSED

stat.UF_HIDDEN

stat.SF_ARCHIVED

stat.SF_IMMUTABLE

stat.SF_APPEND

stat.SF_NOUNLINK

stat.SF_SNAPSHOT

This function can support not following symlinks.

引發一個附帶引數 path、flags 的稽核事件 os.chflags。

可用性: Unix, not WASI.

在 3.3 版的變更: 新增 follow_symlinks 參數。

在 3.6 版的變更: Accepts a path-like object.

os.chmod(path, mode, *, dir_fd=None, follow_symlinks=True)

Change the mode of path to the numeric mode. mode may take one of the following values (as defined in the stat module) or bitwise ORed combinations of them:

stat.S_ISUID

stat.S_ISGID

stat.S_ENFMT

stat.S_ISVTX

stat.S_IREAD

stat.S_IWRITE

stat.S_IEXEC

stat.S_IRWXU

stat.S_IRUSR

stat.S_IWUSR

stat.S_IXUSR

stat.S_IRWXG

stat.S_IRGRP

stat.S_IWGRP

stat.S_IXGRP

stat.S_IRWXO

stat.S_IROTH

stat.S_IWOTH

stat.S_IXOTH

This function can support specifying a file descriptor, paths relative to directory descriptors and not following symlinks.

備註

Although Windows supports chmod(), you can only set the file's read-only flag with it (via the stat.S_IWRITE and stat.S_IREAD constants or a corresponding integer value). All other bits are ignored. The default value of follow_symlinks is False on Windows.

The function is limited on WASI, see WebAssembly 平台 for more information.

引發一個附帶引數 path、mode、dir_fd 的稽核事件 os.chmod。

在 3.3 版的變更: Added support for specifying path as an open file descriptor, and the dir_fd and follow_symlinks arguments.

在 3.6 版的變更: Accepts a path-like object.

在 3.13 版的變更: Added support for a file descriptor and the follow_symlinks argument on Windows.

os.chown(path, uid, gid, *, dir_fd=None, follow_symlinks=True)

Change the owner and group id of path to the numeric uid and gid. To leave one of the ids unchanged, set it to -1.

This function can support specifying a file descriptor, paths relative to directory descriptors and not following symlinks.

See shutil.chown() for a higher-level function that accepts names in addition to numeric ids.

引發一個附帶引數 path、uid、gid、dir_fd 的稽核事件 os.chown。

可用性: Unix.

The function is limited on WASI, see WebAssembly 平台 for more information.

在 3.3 版的變更: Added support for specifying path as an open file descriptor, and the dir_fd and follow_symlinks arguments.

在 3.6 版的變更: Supports a path-like object.

os.chroot(path)

Change the root directory of the current process to path.

可用性: Unix, not WASI, not Android.

在 3.6 版的變更: Accepts a path-like object.

os.fchdir(fd)

Change the current working directory to the directory represented by the file descriptor fd. The descriptor must refer to an opened directory, not an open file. As of Python 3.3, this is equivalent to os.chdir(fd).

引發一個附帶引數 path 的稽核事件 os.chdir。

可用性: Unix.

os.getcwd()

Return a string representing the current working directory.

os.getcwdb()

Return a bytestring representing the current working directory.

在 3.8 版的變更: The function now uses the UTF-8 encoding on Windows, rather than the ANSI code page: see PEP 529 [https://peps.python.org/pep-0529/] for the rationale. The function is no longer deprecated on Windows.

os.lchflags(path, flags)

Set the flags of path to the numeric flags, like chflags(), but do not follow symbolic links. As of Python 3.3, this is equivalent to os.chflags(path, flags, follow_symlinks=False).

引發一個附帶引數 path、flags 的稽核事件 os.chflags。

可用性: Unix, not WASI.

在 3.6 版的變更: Accepts a path-like object.

os.lchmod(path, mode)

Change the mode of path to the numeric mode. If path is a symlink, this affects the symlink rather than the target. See the docs for chmod() for possible values of mode. As of Python 3.3, this is equivalent to os.chmod(path, mode, follow_symlinks=False).

lchmod() is not part of POSIX, but Unix implementations may have it if changing the mode of symbolic links is supported.

引發一個附帶引數 path、mode、dir_fd 的稽核事件 os.chmod。

可用性: Unix, Windows, not Linux, FreeBSD >= 1.3, NetBSD >= 1.3, not OpenBSD

在 3.6 版的變更: Accepts a path-like object.

在 3.13 版的變更: 新增對 Windows 的支援。

os.lchown(path, uid, gid)

Change the owner and group id of path to the numeric uid and gid. This function will not follow symbolic links. As of Python 3.3, this is equivalent to os.chown(path, uid, gid, follow_symlinks=False).

引發一個附帶引數 path、uid、gid、dir_fd 的稽核事件 os.chown。

可用性: Unix.

在 3.6 版的變更: Accepts a path-like object.

os.link(src, dst, *, src_dir_fd=None, dst_dir_fd=None, follow_symlinks=True)

Create a hard link pointing to src named dst.

This function can support specifying src_dir_fd and/or dst_dir_fd to supply paths relative to directory descriptors, and not following symlinks. The default value of follow_symlinks is False on Windows.

引發一個附帶引數 src、dst、src_dir_fd、dst_dir_fd 的稽核事件 os.link。

可用性: Unix, Windows.

在 3.2 版的變更: 新支援 Windows。

在 3.3 版的變更: 新增 src_dir_fd、dst_dir_fd 與 follow_symlinks 參數。

在 3.6 版的變更: Accepts a path-like object for src and dst.

os.listdir(path='.')

Return a list containing the names of the entries in the directory given by path. The list is in arbitrary order, and does not include the special entries '.' and '..' even if they are present in the directory. If a file is removed from or added to the directory during the call of this function, whether a name for that file be included is unspecified.

path may be a path-like object. If path is of type bytes (directly or indirectly through the PathLike interface), the filenames returned will also be of type bytes; in all other circumstances, they will be of type str.

This function can also support specifying a file descriptor; the file descriptor must refer to a directory.

引發一個附帶引數 path 的稽核事件 os.listdir。

備註

To encode str filenames to bytes, use fsencode().

也參考

The scandir() function returns directory entries along with file attribute information, giving better performance for many common use cases.

在 3.2 版的變更: path 參數變為可選。

在 3.3 版的變更: Added support for specifying path as an open file descriptor.

在 3.6 版的變更: Accepts a path-like object.

os.listdrives()

Return a list containing the names of drives on a Windows system.

A drive name typically looks like 'C:\\'. Not every drive name will be associated with a volume, and some may be inaccessible for a variety of reasons, including permissions, network connectivity or missing media. This function does not test for access.

May raise OSError if an error occurs collecting the drive names.

引發一個不附帶引數的稽核事件 os.listdrives。

可用性: Windows

在 3.12 版被加入.

os.listmounts(volume)

Return a list containing the mount points for a volume on a Windows system.

volume must be represented as a GUID path, like those returned by os.listvolumes(). Volumes may be mounted in multiple locations or not at all. In the latter case, the list will be empty. Mount points that are not associated with a volume will not be returned by this function.

The mount points return by this function will be absolute paths, and may be longer than the drive name.

Raises OSError if the volume is not recognized or if an error occurs collecting the paths.

引發一個附帶引數 volume 的稽核事件 os.listmounts。

可用性: Windows

在 3.12 版被加入.

os.listvolumes()

Return a list containing the volumes in the system.

Volumes are typically represented as a GUID path that looks like \\?\Volume{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}\. Files can usually be accessed through a GUID path, permissions allowing. However, users are generally not familiar with them, and so the recommended use of this function is to retrieve mount points using os.listmounts().

May raise OSError if an error occurs collecting the volumes.

引發一個不附帶引數的稽核事件 os.listvolumes。

可用性: Windows

在 3.12 版被加入.

os.lstat(path, *, dir_fd=None)

Perform the equivalent of an lstat() system call on the given path. Similar to stat(), but does not follow symbolic links. Return a stat_result object.

On platforms that do not support symbolic links, this is an alias for stat().

As of Python 3.3, this is equivalent to os.stat(path, dir_fd=dir_fd, follow_symlinks=False).

This function can also support paths relative to directory descriptors.

也參考

The stat() function.

在 3.2 版的變更: Added support for Windows 6.0 (Vista) symbolic links.

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

在 3.8 版的變更: On Windows, now opens reparse points that represent another path (name surrogates), including symbolic links and directory junctions. Other kinds of reparse points are resolved by the operating system as for stat().

os.mkdir(path, mode=0o777, *, dir_fd=None)

Create a directory named path with numeric mode mode.

If the directory already exists, FileExistsError is raised. If a parent directory in the path does not exist, FileNotFoundError is raised.

On some systems, mode is ignored. Where it is used, the current umask value is first masked out. If bits other than the last 9 (i.e. the last 3 digits of the octal representation of the mode) are set, their meaning is platform-dependent. On some platforms, they are ignored and you should call chmod() explicitly to set them.

On Windows, a mode of 0o700 is specifically handled to apply access control to the new directory such that only the current user and administrators have access. Other values of mode are ignored.

This function can also support paths relative to directory descriptors.

It is also possible to create temporary directories; see the tempfile module's tempfile.mkdtemp() function.

引發一個附帶引數 path、mode、dir_fd 的稽核事件 os.mkdir。

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

在 3.13 版的變更: Windows now handles a mode of 0o700.

os.makedirs(name, mode=0o777, exist_ok=False)

Recursive directory creation function. Like mkdir(), but makes all intermediate-level directories needed to contain the leaf directory.

The mode parameter is passed to mkdir() for creating the leaf directory; see the mkdir() description for how it is interpreted. To set the file permission bits of any newly created parent directories you can set the umask before invoking makedirs(). The file permission bits of existing parent directories are not changed.

If exist_ok is False (the default), a FileExistsError is raised if the target directory already exists.

備註

makedirs() will become confused if the path elements to create include pardir (eg. ".." on UNIX systems).

This function handles UNC paths correctly.

引發一個附帶引數 path、mode、dir_fd 的稽核事件 os.mkdir。

在 3.2 版的變更: 新增 exist_ok 參數。

在 3.4.1 版的變更: Before Python 3.4.1, if exist_ok was True and the directory existed, makedirs() would still raise an error if mode did not match the mode of the existing directory. Since this behavior was impossible to implement safely, it was removed in Python 3.4.1. See bpo-21082 [https://bugs.python.org/issue?@action=redirect&bpo=21082].

在 3.6 版的變更: Accepts a path-like object.

在 3.7 版的變更: The mode argument no longer affects the file permission bits of newly created intermediate-level directories.

os.mkfifo(path, mode=0o666, *, dir_fd=None)

Create a FIFO (a named pipe) named path with numeric mode mode. The current umask value is first masked out from the mode.

This function can also support paths relative to directory descriptors.

FIFOs are pipes that can be accessed like regular files. FIFOs exist until they are deleted (for example with os.unlink()). Generally, FIFOs are used as rendezvous between "client" and "server" type processes: the server opens the FIFO for reading, and the client opens it for writing. Note that mkfifo() doesn't open the FIFO --- it just creates the rendezvous point.

可用性: Unix, not WASI.

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

os.mknod(path, mode=0o600, device=0, *, dir_fd=None)

Create a filesystem node (file, device special file or named pipe) named path. mode specifies both the permissions to use and the type of node to be created, being combined (bitwise OR) with one of stat.S_IFREG, stat.S_IFCHR, stat.S_IFBLK, and stat.S_IFIFO (those constants are available in stat). For stat.S_IFCHR and stat.S_IFBLK, device defines the newly created device special file (probably using os.makedev()), otherwise it is ignored.

This function can also support paths relative to directory descriptors.

可用性: Unix, not WASI.

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

os.major(device, /)

Extract the device major number from a raw device number (usually the st_dev or st_rdev field from stat).

os.minor(device, /)

Extract the device minor number from a raw device number (usually the st_dev or st_rdev field from stat).

os.makedev(major, minor, /)

Compose a raw device number from the major and minor device numbers.

os.pathconf(path, name)

Return system configuration information relevant to a named file. name specifies the configuration value to retrieve; it may be a string which is the name of a defined system value; these names are specified in a number of standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define additional names as well. The names known to the host operating system are given in the pathconf_names dictionary. For configuration variables not included in that mapping, passing an integer for name is also accepted.

If name is a string and is not known, ValueError is raised. If a specific value for name is not supported by the host system, even if it is included in pathconf_names, an OSError is raised with errno.EINVAL for the error number.

This function can support specifying a file descriptor.

可用性: Unix.

在 3.6 版的變更: Accepts a path-like object.

os.pathconf_names

Dictionary mapping names accepted by pathconf() and fpathconf() to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system.

可用性: Unix.

os.readlink(path, *, dir_fd=None)

Return a string representing the path to which the symbolic link points. The result may be either an absolute or relative pathname; if it is relative, it may be converted to an absolute pathname using os.path.join(os.path.dirname(path), result).

If the path is a string object (directly or indirectly through a PathLike interface), the result will also be a string object, and the call may raise a UnicodeDecodeError. If the path is a bytes object (direct or indirectly), the result will be a bytes object.

This function can also support paths relative to directory descriptors.

When trying to resolve a path that may contain links, use realpath() to properly handle recursion and platform differences.

可用性: Unix, Windows.

在 3.2 版的變更: Added support for Windows 6.0 (Vista) symbolic links.

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object on Unix.

在 3.8 版的變更: Accepts a path-like object and a bytes object on Windows.

Added support for directory junctions, and changed to return the substitution path (which typically includes \\?\ prefix) rather than the optional "print name" field that was previously returned.

os.remove(path, *, dir_fd=None)

Remove (delete) the file path. If path is a directory, an OSError is raised. Use rmdir() to remove directories. If the file does not exist, a FileNotFoundError is raised.

This function can support paths relative to directory descriptors.

On Windows, attempting to remove a file that is in use causes an exception to be raised; on Unix, the directory entry is removed but the storage allocated to the file is not made available until the original file is no longer in use.

This function is semantically identical to unlink().

引發一個附帶引數 path、dir_fd 的稽核事件 os.remove。

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

os.removedirs(name)

Remove directories recursively. Works like rmdir() except that, if the leaf directory is successfully removed, removedirs() tries to successively remove every parent directory mentioned in path until an error is raised (which is ignored, because it generally means that a parent directory is not empty). For example, os.removedirs('foo/bar/baz') will first remove the directory 'foo/bar/baz', and then remove 'foo/bar' and 'foo' if they are empty. Raises OSError if the leaf directory could not be successfully removed.

引發一個附帶引數 path、dir_fd 的稽核事件 os.remove。

在 3.6 版的變更: Accepts a path-like object.

os.rename(src, dst, *, src_dir_fd=None, dst_dir_fd=None)

Rename the file or directory src to dst. If dst exists, the operation will fail with an OSError subclass in a number of cases:

On Windows, if dst exists a FileExistsError is always raised. The operation may fail if src and dst are on different filesystems. Use shutil.move() to support moves to a different filesystem.

On Unix, if src is a file and dst is a directory or vice-versa, an IsADirectoryError or a NotADirectoryError will be raised respectively. If both are directories and dst is empty, dst will be silently replaced. If dst is a non-empty directory, an OSError is raised. If both are files, dst will be replaced silently if the user has permission. The operation may fail on some Unix flavors if src and dst are on different filesystems. If successful, the renaming will be an atomic operation (this is a POSIX requirement).

This function can support specifying src_dir_fd and/or dst_dir_fd to supply paths relative to directory descriptors.

If you want cross-platform overwriting of the destination, use replace().

引發一個附帶引數 src、dst、src_dir_fd、dst_dir_fd 的稽核事件 os.rename。

在 3.3 版的變更: 新增 src_dir_fd 與 dst_dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object for src and dst.

os.renames(old, new)

Recursive directory or file renaming function. Works like rename(), except creation of any intermediate directories needed to make the new pathname good is attempted first. After the rename, directories corresponding to rightmost path segments of the old name will be pruned away using removedirs().

備註

This function can fail with the new directory structure made if you lack permissions needed to remove the leaf directory or file.

引發一個附帶引數 src、dst、src_dir_fd、dst_dir_fd 的稽核事件 os.rename。

在 3.6 版的變更: Accepts a path-like object for old and new.

os.replace(src, dst, *, src_dir_fd=None, dst_dir_fd=None)

Rename the file or directory src to dst. If dst is a non-empty directory, OSError will be raised. If dst exists and is a file, it will be replaced silently if the user has permission. The operation may fail if src and dst are on different filesystems. If successful, the renaming will be an atomic operation (this is a POSIX requirement).

This function can support specifying src_dir_fd and/or dst_dir_fd to supply paths relative to directory descriptors.

引發一個附帶引數 src、dst、src_dir_fd、dst_dir_fd 的稽核事件 os.rename。

在 3.3 版被加入.

在 3.6 版的變更: Accepts a path-like object for src and dst.

os.rmdir(path, *, dir_fd=None)

Remove (delete) the directory path. If the directory does not exist or is not empty, a FileNotFoundError or an OSError is raised respectively. In order to remove whole directory trees, shutil.rmtree() can be used.

This function can support paths relative to directory descriptors.

引發一個附帶引數 path、dir_fd 的稽核事件 os.rmdir。

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

os.scandir(path='.')

Return an iterator of os.DirEntry objects corresponding to the entries in the directory given by path. The entries are yielded in arbitrary order, and the special entries '.' and '..' are not included. If a file is removed from or added to the directory after creating the iterator, whether an entry for that file be included is unspecified.

Using scandir() instead of listdir() can significantly increase the performance of code that also needs file type or file attribute information, because os.DirEntry objects expose this information if the operating system provides it when scanning a directory. All os.DirEntry methods may perform a system call, but is_dir() and is_file() usually only require a system call for symbolic links; os.DirEntry.stat() always requires a system call on Unix but only requires one for symbolic links on Windows.

path may be a path-like object. If path is of type bytes (directly or indirectly through the PathLike interface), the type of the name and path attributes of each os.DirEntry will be bytes; in all other circumstances, they will be of type str.

This function can also support specifying a file descriptor; the file descriptor must refer to a directory.

引發一個附帶引數 path 的稽核事件 os.scandir。

scandir() 疊代器支援 context manager 協定，並具有以下方法：

scandir.close()

Close the iterator and free acquired resources.

This is called automatically when the iterator is exhausted or garbage collected, or when an error happens during iterating. However it is advisable to call it explicitly or use the with statement.

在 3.6 版被加入.

The following example shows a simple use of scandir() to display all the files (excluding directories) in the given path that don't start with '.'. The entry.is_file() call will generally not make an additional system call:

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

備註

On Unix-based systems, scandir() uses the system's opendir() [https://pubs.opengroup.org/onlinepubs/009695399/functions/opendir.html] and readdir() [https://pubs.opengroup.org/onlinepubs/009695399/functions/readdir_r.html] functions. On Windows, it uses the Win32 FindFirstFileW [https://msdn.microsoft.com/en-us/library/windows/desktop/aa364418(v=vs.85).aspx] and FindNextFileW [https://msdn.microsoft.com/en-us/library/windows/desktop/aa364428(v=vs.85).aspx] functions.

在 3.5 版被加入.

在 3.6 版的變更: Added support for the context manager protocol and the close() method. If a scandir() iterator is neither exhausted nor explicitly closed a ResourceWarning will be emitted in its destructor.

The function accepts a path-like object.

在 3.7 版的變更: 新增對 Unix 上的檔案描述器的支援。

class os.DirEntry

Object yielded by scandir() to expose the file path and other file attributes of a directory entry.

scandir() will provide as much of this information as possible without making additional system calls. When a stat() or lstat() system call is made, the os.DirEntry object will cache the result.

os.DirEntry instances are not intended to be stored in long-lived data structures; if you know the file metadata has changed or if a long time has elapsed since calling scandir(), call os.stat(entry.path) to fetch up-to-date information.

Because the os.DirEntry methods can make operating system calls, they may also raise OSError. If you need very fine-grained control over errors, you can catch OSError when calling one of the os.DirEntry methods and handle as appropriate.

To be directly usable as a path-like object, os.DirEntry implements the PathLike interface.

Attributes and methods on a os.DirEntry instance are as follows:

name

The entry's base filename, relative to the scandir() path argument.

The name attribute will be bytes if the scandir() path argument is of type bytes and str otherwise. Use fsdecode() to decode byte filenames.

path

The entry's full path name: equivalent to os.path.join(scandir_path, entry.name) where scandir_path is the scandir() path argument. The path is only absolute if the scandir() path argument was absolute. If the scandir() path argument was a file descriptor, the path attribute is the same as the name attribute.

The path attribute will be bytes if the scandir() path argument is of type bytes and str otherwise. Use fsdecode() to decode byte filenames.

inode()

Return the inode number of the entry.

The result is cached on the os.DirEntry object. Use os.stat(entry.path, follow_symlinks=False).st_ino to fetch up-to-date information.

On the first, uncached call, a system call is required on Windows but not on Unix.

is_dir(*, follow_symlinks=True)

Return True if this entry is a directory or a symbolic link pointing to a directory; return False if the entry is or points to any other kind of file, or if it doesn't exist anymore.

If follow_symlinks is False, return True only if this entry is a directory (without following symlinks); return False if the entry is any other kind of file or if it doesn't exist anymore.

The result is cached on the os.DirEntry object, with a separate cache for follow_symlinks True and False. Call os.stat() along with stat.S_ISDIR() to fetch up-to-date information.

On the first, uncached call, no system call is required in most cases. Specifically, for non-symlinks, neither Windows or Unix require a system call, except on certain Unix file systems, such as network file systems, that return dirent.d_type == DT_UNKNOWN. If the entry is a symlink, a system call will be required to follow the symlink unless follow_symlinks is False.

This method can raise OSError, such as PermissionError, but FileNotFoundError is caught and not raised.

is_file(*, follow_symlinks=True)

Return True if this entry is a file or a symbolic link pointing to a file; return False if the entry is or points to a directory or other non-file entry, or if it doesn't exist anymore.

If follow_symlinks is False, return True only if this entry is a file (without following symlinks); return False if the entry is a directory or other non-file entry, or if it doesn't exist anymore.

The result is cached on the os.DirEntry object. Caching, system calls made, and exceptions raised are as per is_dir().

is_symlink()

Return True if this entry is a symbolic link (even if broken); return False if the entry points to a directory or any kind of file, or if it doesn't exist anymore.

The result is cached on the os.DirEntry object. Call os.path.islink() to fetch up-to-date information.

On the first, uncached call, no system call is required in most cases. Specifically, neither Windows or Unix require a system call, except on certain Unix file systems, such as network file systems, that return dirent.d_type == DT_UNKNOWN.

This method can raise OSError, such as PermissionError, but FileNotFoundError is caught and not raised.

is_junction()

Return True if this entry is a junction (even if broken); return False if the entry points to a regular directory, any kind of file, a symlink, or if it doesn't exist anymore.

The result is cached on the os.DirEntry object. Call os.path.isjunction() to fetch up-to-date information.

在 3.12 版被加入.

stat(*, follow_symlinks=True)

Return a stat_result object for this entry. This method follows symbolic links by default; to stat a symbolic link add the follow_symlinks=False argument.

On Unix, this method always requires a system call. On Windows, it only requires a system call if follow_symlinks is True and the entry is a reparse point (for example, a symbolic link or directory junction).

On Windows, the st_ino, st_dev and st_nlink attributes of the stat_result are always set to zero. Call os.stat() to get these attributes.

The result is cached on the os.DirEntry object, with a separate cache for follow_symlinks True and False. Call os.stat() to fetch up-to-date information.

Note that there is a nice correspondence between several attributes and methods of os.DirEntry and of pathlib.Path. In particular, the name attribute has the same meaning, as do the is_dir(), is_file(), is_symlink(), is_junction(), and stat() methods.

在 3.5 版被加入.

在 3.6 版的變更: Added support for the PathLike interface. Added support for bytes paths on Windows.

在 3.12 版的變更: The st_ctime attribute of a stat result is deprecated on Windows. The file creation time is properly available as st_birthtime, and in the future st_ctime may be changed to return zero or the metadata change time, if available.

os.stat(path, *, dir_fd=None, follow_symlinks=True)

Get the status of a file or a file descriptor. Perform the equivalent of a stat() system call on the given path. path may be specified as either a string or bytes -- directly or indirectly through the PathLike interface -- or as an open file descriptor. Return a stat_result object.

This function normally follows symlinks; to stat a symlink add the argument follow_symlinks=False, or use lstat().

This function can support specifying a file descriptor and not following symlinks.

On Windows, passing follow_symlinks=False will disable following all name-surrogate reparse points, which includes symlinks and directory junctions. Other types of reparse points that do not resemble links or that the operating system is unable to follow will be opened directly. When following a chain of multiple links, this may result in the original link being returned instead of the non-link that prevented full traversal. To obtain stat results for the final path in this case, use the os.path.realpath() function to resolve the path name as far as possible and call lstat() on the result. This does not apply to dangling symlinks or junction points, which will raise the usual exceptions.

範例：

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

也參考

fstat() 和 lstat() 函式。

在 3.3 版的變更: 新增 dir_fd 與 follow_symlinks 參數，指定一個檔案描述器而非路徑。

在 3.6 版的變更: Accepts a path-like object.

在 3.8 版的變更: On Windows, all reparse points that can be resolved by the operating system are now followed, and passing follow_symlinks=False disables following all name surrogate reparse points. If the operating system reaches a reparse point that it is not able to follow, stat now returns the information for the original path as if follow_symlinks=False had been specified instead of raising an error.

class os.stat_result

Object whose attributes correspond roughly to the members of the stat structure. It is used for the result of os.stat(), os.fstat() and os.lstat().

屬性：

st_mode

File mode: file type and file mode bits (permissions).

st_ino

Platform dependent, but if non-zero, uniquely identifies the file for a given value of st_dev. Typically:

the inode number on Unix,

the file index [https://msdn.microsoft.com/en-us/library/aa363788] on Windows

st_dev

Identifier of the device on which this file resides.

st_nlink

Number of hard links.

st_uid

User identifier of the file owner.

st_gid

Group identifier of the file owner.

st_size

Size of the file in bytes, if it is a regular file or a symbolic link. The size of a symbolic link is the length of the pathname it contains, without a terminating null byte.

Timestamps:

st_atime

Time of most recent access expressed in seconds.

st_mtime

Time of most recent content modification expressed in seconds.

st_ctime

Time of most recent metadata change expressed in seconds.

在 3.12 版的變更: st_ctime is deprecated on Windows. Use st_birthtime for the file creation time. In the future, st_ctime will contain the time of the most recent metadata change, as for other platforms.

st_atime_ns

Time of most recent access expressed in nanoseconds as an integer.

在 3.3 版被加入.

st_mtime_ns

Time of most recent content modification expressed in nanoseconds as an integer.

在 3.3 版被加入.

st_ctime_ns

Time of most recent metadata change expressed in nanoseconds as an integer.

在 3.3 版被加入.

在 3.12 版的變更: st_ctime_ns is deprecated on Windows. Use st_birthtime_ns for the file creation time. In the future, st_ctime will contain the time of the most recent metadata change, as for other platforms.

st_birthtime

Time of file creation expressed in seconds. This attribute is not always available, and may raise AttributeError.

在 3.12 版的變更: st_birthtime 現在在 Windows 上可用。

st_birthtime_ns

Time of file creation expressed in nanoseconds as an integer. This attribute is not always available, and may raise AttributeError.

在 3.12 版被加入.

備註

The exact meaning and resolution of the st_atime, st_mtime, st_ctime and st_birthtime attributes depend on the operating system and the file system. For example, on Windows systems using the FAT32 file systems, st_mtime has 2-second resolution, and st_atime has only 1-day resolution. See your operating system documentation for details.

Similarly, although st_atime_ns, st_mtime_ns, st_ctime_ns and st_birthtime_ns are always expressed in nanoseconds, many systems do not provide nanosecond precision. On systems that do provide nanosecond precision, the floating-point object used to store st_atime, st_mtime, st_ctime and st_birthtime cannot preserve all of it, and as such will be slightly inexact. If you need the exact timestamps you should always use st_atime_ns, st_mtime_ns, st_ctime_ns and st_birthtime_ns.

On some Unix systems (such as Linux), the following attributes may also be available:

st_blocks

Number of 512-byte blocks allocated for file. This may be smaller than st_size/512 when the file has holes.

st_blksize

"Preferred" blocksize for efficient file system I/O. Writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.

st_rdev

Type of device if an inode device.

st_flags

User defined flags for file.

On other Unix systems (such as FreeBSD), the following attributes may be available (but may be only filled out if root tries to use them):

st_gen

File generation number.

On Solaris and derivatives, the following attributes may also be available:

st_fstype

String that uniquely identifies the type of the filesystem that contains the file.

On macOS systems, the following attributes may also be available:

st_rsize

Real size of the file.

st_creator

Creator of the file.

st_type

File type.

On Windows systems, the following attributes are also available:

st_file_attributes

Windows file attributes: dwFileAttributes member of the BY_HANDLE_FILE_INFORMATION structure returned by GetFileInformationByHandle(). See the FILE_ATTRIBUTE_* <stat.FILE_ATTRIBUTE_ARCHIVE> constants in the stat module.

在 3.5 版被加入.

st_reparse_tag

When st_file_attributes has the FILE_ATTRIBUTE_REPARSE_POINT set, this field contains the tag identifying the type of reparse point. See the IO_REPARSE_TAG_* constants in the stat module.

The standard module stat defines functions and constants that are useful for extracting information from a stat structure. (On Windows, some items are filled with dummy values.)

For backward compatibility, a stat_result instance is also accessible as a tuple of at least 10 integers giving the most important (and portable) members of the stat structure, in the order st_mode, st_ino, st_dev, st_nlink, st_uid, st_gid, st_size, st_atime, st_mtime, st_ctime. More items may be added at the end by some implementations. For compatibility with older Python versions, accessing stat_result as a tuple always returns integers.

在 3.5 版的變更: Windows now returns the file index as st_ino when available.

在 3.7 版的變更: Added the st_fstype member to Solaris/derivatives.

在 3.8 版的變更: 在 Windows 上新增 st_reparse_tag 成員。

在 3.8 版的變更: On Windows, the st_mode member now identifies special files as S_IFCHR, S_IFIFO or S_IFBLK as appropriate.

在 3.12 版的變更: On Windows, st_ctime is deprecated. Eventually, it will contain the last metadata change time, for consistency with other platforms, but for now still contains creation time. Use st_birthtime for the creation time.

On Windows, st_ino may now be up to 128 bits, depending on the file system. Previously it would not be above 64 bits, and larger file identifiers would be arbitrarily packed.

On Windows, st_rdev no longer returns a value. Previously it would contain the same as st_dev, which was incorrect.

在 Windows 上新增 st_birthtime 成員。

os.statvfs(path)

Perform a statvfs() system call on the given path. The return value is an object whose attributes describe the filesystem on the given path, and correspond to the members of the statvfs structure, namely: f_bsize, f_frsize, f_blocks, f_bfree, f_bavail, f_files, f_ffree, f_favail, f_flag, f_namemax, f_fsid.

Two module-level constants are defined for the f_flag attribute's bit-flags: if ST_RDONLY is set, the filesystem is mounted read-only, and if ST_NOSUID is set, the semantics of setuid/setgid bits are disabled or not supported.

Additional module-level constants are defined for GNU/glibc based systems. These are ST_NODEV (disallow access to device special files), ST_NOEXEC (disallow program execution), ST_SYNCHRONOUS (writes are synced at once), ST_MANDLOCK (allow mandatory locks on an FS), ST_WRITE (write on file/directory/symlink), ST_APPEND (append-only file), ST_IMMUTABLE (immutable file), ST_NOATIME (do not update access times), ST_NODIRATIME (do not update directory access times), ST_RELATIME (update atime relative to mtime/ctime).

This function can support specifying a file descriptor.

可用性: Unix.

在 3.2 版的變更: 新增 ST_RDONLY 與 ST_NOSUID 常數。

在 3.3 版的變更: Added support for specifying path as an open file descriptor.

在 3.4 版的變更: The ST_NODEV, ST_NOEXEC, ST_SYNCHRONOUS, ST_MANDLOCK, ST_WRITE, ST_APPEND, ST_IMMUTABLE, ST_NOATIME, ST_NODIRATIME, and ST_RELATIME constants were added.

在 3.6 版的變更: Accepts a path-like object.

在 3.7 版的變更: 新增 f_fsid 屬性。

os.supports_dir_fd

A set object indicating which functions in the os module accept an open file descriptor for their dir_fd parameter. Different platforms provide different features, and the underlying functionality Python uses to implement the dir_fd parameter is not available on all platforms Python supports. For consistency's sake, functions that may support dir_fd always allow specifying the parameter, but will throw an exception if the functionality is used when it's not locally available. (Specifying None for dir_fd is always supported on all platforms.)

To check whether a particular function accepts an open file descriptor for its dir_fd parameter, use the in operator on supports_dir_fd. As an example, this expression evaluates to True if os.stat() accepts open file descriptors for dir_fd on the local platform:

os.stat in os.supports_dir_fd

Currently dir_fd parameters only work on Unix platforms; none of them work on Windows.

在 3.3 版被加入.

os.supports_effective_ids

A set object indicating whether os.access() permits specifying True for its effective_ids parameter on the local platform. (Specifying False for effective_ids is always supported on all platforms.) If the local platform supports it, the collection will contain os.access(); otherwise it will be empty.

This expression evaluates to True if os.access() supports effective_ids=True on the local platform:

os.access in os.supports_effective_ids

Currently effective_ids is only supported on Unix platforms; it does not work on Windows.

在 3.3 版被加入.

os.supports_fd

A set object indicating which functions in the os module permit specifying their path parameter as an open file descriptor on the local platform. Different platforms provide different features, and the underlying functionality Python uses to accept open file descriptors as path arguments is not available on all platforms Python supports.

To determine whether a particular function permits specifying an open file descriptor for its path parameter, use the in operator on supports_fd. As an example, this expression evaluates to True if os.chdir() accepts open file descriptors for path on your local platform:

os.chdir in os.supports_fd

在 3.3 版被加入.

os.supports_follow_symlinks

A set object indicating which functions in the os module accept False for their follow_symlinks parameter on the local platform. Different platforms provide different features, and the underlying functionality Python uses to implement follow_symlinks is not available on all platforms Python supports. For consistency's sake, functions that may support follow_symlinks always allow specifying the parameter, but will throw an exception if the functionality is used when it's not locally available. (Specifying True for follow_symlinks is always supported on all platforms.)

To check whether a particular function accepts False for its follow_symlinks parameter, use the in operator on supports_follow_symlinks. As an example, this expression evaluates to True if you may specify follow_symlinks=False when calling os.stat() on the local platform:

os.stat in os.supports_follow_symlinks

在 3.3 版被加入.

os.symlink(src, dst, target_is_directory=False, *, dir_fd=None)

Create a symbolic link pointing to src named dst.

The src parameter refers to the target of the link (the file or directory being linked to), and dst is the name of the link being created.

On Windows, a symlink represents either a file or a directory, and does not morph to the target dynamically. If the target is present, the type of the symlink will be created to match. Otherwise, the symlink will be created as a directory if target_is_directory is True or a file symlink (the default) otherwise. On non-Windows platforms, target_is_directory is ignored.

This function can support paths relative to directory descriptors.

備註

On newer versions of Windows 10, unprivileged accounts can create symlinks if Developer Mode is enabled. When Developer Mode is not available/enabled, the SeCreateSymbolicLinkPrivilege privilege is required, or the process must be run as an administrator.

OSError is raised when the function is called by an unprivileged user.

引發一個附帶引數 src、dst、dir_fd 的稽核事件 os.symlink。

可用性: Unix, Windows.

The function is limited on WASI, see WebAssembly 平台 for more information.

在 3.2 版的變更: Added support for Windows 6.0 (Vista) symbolic links.

在 3.3 版的變更: Added the dir_fd parameter, and now allow target_is_directory on non-Windows platforms.

在 3.6 版的變更: Accepts a path-like object for src and dst.

在 3.8 版的變更: Added support for unelevated symlinks on Windows with Developer Mode.

os.sync()

Force write of everything to disk.

可用性: Unix.

在 3.3 版被加入.

os.truncate(path, length)

Truncate the file corresponding to path, so that it is at most length bytes in size.

This function can support specifying a file descriptor.

引發一個附帶引數 path、length 的稽核事件 os.truncate。

可用性: Unix, Windows.

在 3.3 版被加入.

在 3.5 版的變更: 新增對 Windows 的支援

在 3.6 版的變更: Accepts a path-like object.

os.unlink(path, *, dir_fd=None)

Remove (delete) the file path. This function is semantically identical to remove(); the unlink name is its traditional Unix name. Please see the documentation for remove() for further information.

引發一個附帶引數 path、dir_fd 的稽核事件 os.remove。

在 3.3 版的變更: 新增 dir_fd 參數。

在 3.6 版的變更: Accepts a path-like object.

os.utime(path, times=None, *, [ns, ]dir_fd=None, follow_symlinks=True)

Set the access and modified times of the file specified by path.

utime() takes two optional parameters, times and ns. These specify the times set on path and are used as follows:

If ns is specified, it must be a 2-tuple of the form (atime_ns, mtime_ns) where each member is an int expressing nanoseconds.

If times is not None, it must be a 2-tuple of the form (atime, mtime) where each member is an int or float expressing seconds.

If times is None and ns is unspecified, this is equivalent to specifying ns=(atime_ns, mtime_ns) where both times are the current time.

It is an error to specify tuples for both times and ns.

Note that the exact times you set here may not be returned by a subsequent stat() call, depending on the resolution with which your operating system records access and modification times; see stat(). The best way to preserve exact times is to use the st_atime_ns and st_mtime_ns fields from the os.stat() result object with the ns parameter to utime().

This function can support specifying a file descriptor, paths relative to directory descriptors and not following symlinks.

引發一個附帶引數 path、times、ns、dir_fd 的稽核事件 os.utime。

在 3.3 版的變更: Added support for specifying path as an open file descriptor, and the dir_fd, follow_symlinks, and ns parameters.

在 3.6 版的變更: Accepts a path-like object.

os.walk(top, topdown=True, onerror=None, followlinks=False)

Generate the file names in a directory tree by walking the tree either top-down or bottom-up. For each directory in the tree rooted at directory top (including top itself), it yields a 3-tuple (dirpath, dirnames, filenames).

dirpath is a string, the path to the directory. dirnames is a list of the names of the subdirectories in dirpath (including symlinks to directories, and excluding '.' and '..'). filenames is a list of the names of the non-directory files in dirpath. Note that the names in the lists contain no path components. To get a full path (which begins with top) to a file or directory in dirpath, do os.path.join(dirpath, name). Whether or not the lists are sorted depends on the file system. If a file is removed from or added to the dirpath directory during generating the lists, whether a name for that file be included is unspecified.

If optional argument topdown is True or not specified, the triple for a directory is generated before the triples for any of its subdirectories (directories are generated top-down). If topdown is False, the triple for a directory is generated after the triples for all of its subdirectories (directories are generated bottom-up). No matter the value of topdown, the list of subdirectories is retrieved before the tuples for the directory and its subdirectories are generated.

When topdown is True, the caller can modify the dirnames list in-place (perhaps using del or slice assignment), and walk() will only recurse into the subdirectories whose names remain in dirnames; this can be used to prune the search, impose a specific order of visiting, or even to inform walk() about directories the caller creates or renames before it resumes walk() again. Modifying dirnames when topdown is False has no effect on the behavior of the walk, because in bottom-up mode the directories in dirnames are generated before dirpath itself is generated.

By default, errors from the scandir() call are ignored. If optional argument onerror is specified, it should be a function; it will be called with one argument, an OSError instance. It can report the error to continue with the walk, or raise the exception to abort the walk. Note that the filename is available as the filename attribute of the exception object.

By default, walk() will not walk down into symbolic links that resolve to directories. Set followlinks to True to visit directories pointed to by symlinks, on systems that support them.

備註

Be aware that setting followlinks to True can lead to infinite recursion if a link points to a parent directory of itself. walk() does not keep track of the directories it visited already.

備註

If you pass a relative pathname, don't change the current working directory between resumptions of walk(). walk() never changes the current directory, and assumes that its caller doesn't either.

This example displays the number of bytes taken by non-directory files in each directory under the starting directory, except that it doesn't look under any __pycache__ subdirectory:

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/xml'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if '__pycache__' in dirs:
        dirs.remove('__pycache__')  # don't visit __pycache__ directories

In the next example (simple implementation of shutil.rmtree()), walking the tree bottom-up is essential, rmdir() doesn't allow deleting a directory before the directory is empty:

# Delete everything reachable from the directory named in "top",
# assuming there are no symbolic links.
# CAUTION:  This is dangerous!  For example, if top == '/', it
# could delete all your disk files.
import os
for root, dirs, files in os.walk(top, topdown=False):
    for name in files:
        os.remove(os.path.join(root, name))
    for name in dirs:
        os.rmdir(os.path.join(root, name))
os.rmdir(top)

引發一個附帶引數 top、topdown、onerror、followlinks 的稽核事件 os.walk。

在 3.5 版的變更: This function now calls os.scandir() instead of os.listdir(), making it faster by reducing the number of calls to os.stat().

在 3.6 版的變更: Accepts a path-like object.

os.fwalk(top='.', topdown=True, onerror=None, *, follow_symlinks=False, dir_fd=None)

This behaves exactly like walk(), except that it yields a 4-tuple (dirpath, dirnames, filenames, dirfd), and it supports dir_fd.

dirpath, dirnames and filenames are identical to walk() output, and dirfd is a file descriptor referring to the directory dirpath.

This function always supports paths relative to directory descriptors and not following symlinks. Note however that, unlike other functions, the fwalk() default value for follow_symlinks is False.

備註

Since fwalk() yields file descriptors, those are only valid until the next iteration step, so you should duplicate them (e.g. with dup()) if you want to keep them longer.

This example displays the number of bytes taken by non-directory files in each directory under the starting directory, except that it doesn't look under any __pycache__ subdirectory:

import os
for root, dirs, files, rootfd in os.fwalk('python/Lib/xml'):
    print(root, "consumes", end=" ")
    print(sum([os.stat(name, dir_fd=rootfd).st_size for name in files]),
          end=" ")
    print("bytes in", len(files), "non-directory files")
    if '__pycache__' in dirs:
        dirs.remove('__pycache__')  # don't visit __pycache__ directories

In the next example, walking the tree bottom-up is essential: rmdir() doesn't allow deleting a directory before the directory is empty:

# Delete everything reachable from the directory named in "top",
# assuming there are no symbolic links.
# CAUTION:  This is dangerous!  For example, if top == '/', it
# could delete all your disk files.
import os
for root, dirs, files, rootfd in os.fwalk(top, topdown=False):
    for name in files:
        os.unlink(name, dir_fd=rootfd)
    for name in dirs:
        os.rmdir(name, dir_fd=rootfd)

引發一個附帶引數 top、topdown、onerror、follow_symlinks、dir_fd 的稽核事件 os.fwalk。

可用性: Unix.

在 3.3 版被加入.

在 3.6 版的變更: Accepts a path-like object.

在 3.7 版的變更: 新增對 bytes 路徑的支援。

os.memfd_create(name[, flags=os.MFD_CLOEXEC])

Create an anonymous file and return a file descriptor that refers to it. flags must be one of the os.MFD_* constants available on the system (or a bitwise ORed combination of them). By default, the new file descriptor is non-inheritable.

The name supplied in name is used as a filename and will be displayed as the target of the corresponding symbolic link in the directory /proc/self/fd/. The displayed name is always prefixed with memfd: and serves only for debugging purposes. Names do not affect the behavior of the file descriptor, and as such multiple files can have the same name without any side effects.

可用性: Linux >= 3.17 with glibc >= 2.27.

在 3.8 版被加入.

os.MFD_CLOEXEC

os.MFD_ALLOW_SEALING

os.MFD_HUGETLB

os.MFD_HUGE_SHIFT

os.MFD_HUGE_MASK

os.MFD_HUGE_64KB

os.MFD_HUGE_512KB

os.MFD_HUGE_1MB

os.MFD_HUGE_2MB

os.MFD_HUGE_8MB

os.MFD_HUGE_16MB

os.MFD_HUGE_32MB

os.MFD_HUGE_256MB

os.MFD_HUGE_512MB

os.MFD_HUGE_1GB

os.MFD_HUGE_2GB

os.MFD_HUGE_16GB

這些旗標可以傳給 memfd_create()。

可用性: Linux >= 3.17 with glibc >= 2.27

MFD_HUGE* 旗標僅在 Linux 4.14 以上可用。

在 3.8 版被加入.

os.eventfd(initval[, flags=os.EFD_CLOEXEC])

Create and return an event file descriptor. The file descriptors supports raw read() and write() with a buffer size of 8, select(), poll() and similar. See man page eventfd(2) [https://manpages.debian.org/eventfd(2)] for more information. By default, the new file descriptor is non-inheritable.

initval is the initial value of the event counter. The initial value must be a 32 bit unsigned integer. Please note that the initial value is limited to a 32 bit unsigned int although the event counter is an unsigned 64 bit integer with a maximum value of 2⁶⁴-2.

flags can be constructed from EFD_CLOEXEC, EFD_NONBLOCK, and EFD_SEMAPHORE.

If EFD_SEMAPHORE is specified and the event counter is non-zero, eventfd_read() returns 1 and decrements the counter by one.

If EFD_SEMAPHORE is not specified and the event counter is non-zero, eventfd_read() returns the current event counter value and resets the counter to zero.

If the event counter is zero and EFD_NONBLOCK is not specified, eventfd_read() blocks.

eventfd_write() increments the event counter. Write blocks if the write operation would increment the counter to a value larger than 2⁶⁴-2.

範例：

import os

# semaphore with start value '1'
fd = os.eventfd(1, os.EFD_SEMAPHORE | os.EFD_CLOEXEC)
try:
    # acquire semaphore
    v = os.eventfd_read(fd)
    try:
        do_work()
    finally:
        # release semaphore
        os.eventfd_write(fd, v)
finally:
    os.close(fd)

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.10 版被加入.

os.eventfd_read(fd)

Read value from an eventfd() file descriptor and return a 64 bit unsigned int. The function does not verify that fd is an eventfd().

可用性: Linux >= 2.6.27

在 3.10 版被加入.

os.eventfd_write(fd, value)

Add value to an eventfd() file descriptor. value must be a 64 bit unsigned int. The function does not verify that fd is an eventfd().

可用性: Linux >= 2.6.27

在 3.10 版被加入.

os.EFD_CLOEXEC

Set close-on-exec flag for new eventfd() file descriptor.

可用性: Linux >= 2.6.27

在 3.10 版被加入.

os.EFD_NONBLOCK

設定新的 eventfd() 檔案描述器的 O_NONBLOCK 狀態旗標。

可用性: Linux >= 2.6.27

在 3.10 版被加入.

os.EFD_SEMAPHORE

Provide semaphore-like semantics for reads from an eventfd() file descriptor. On read the internal counter is decremented by one.

可用性: Linux >= 2.6.30

在 3.10 版被加入.

計時器檔案描述器

在 3.13 版被加入.

These functions provide support for Linux's timer file descriptor API. Naturally, they are all only available on Linux.

os.timerfd_create(clockid, /, *, flags=0)

Create and return a timer file descriptor (timerfd).

The file descriptor returned by timerfd_create() supports:

read()

select()

poll()

The file descriptor's read() method can be called with a buffer size of 8. If the timer has already expired one or more times, read() returns the number of expirations with the host's endianness, which may be converted to an int by int.from_bytes(x, byteorder=sys.byteorder).

select() and poll() can be used to wait until timer expires and the file descriptor is readable.

clockid must be a valid clock ID, as defined in the time module:

time.CLOCK_REALTIME

time.CLOCK_MONOTONIC

time.CLOCK_BOOTTIME (Since Linux 3.15 for timerfd_create)

If clockid is time.CLOCK_REALTIME, a settable system-wide real-time clock is used. If system clock is changed, timer setting need to be updated. To cancel timer when system clock is changed, see TFD_TIMER_CANCEL_ON_SET.

If clockid is time.CLOCK_MONOTONIC, a non-settable monotonically increasing clock is used. Even if the system clock is changed, the timer setting will not be affected.

If clockid is time.CLOCK_BOOTTIME, same as time.CLOCK_MONOTONIC except it includes any time that the system is suspended.

The file descriptor's behaviour can be modified by specifying a flags value. Any of the following variables may used, combined using bitwise OR (the | operator):

TFD_NONBLOCK

TFD_CLOEXEC

If TFD_NONBLOCK is not set as a flag, read() blocks until the timer expires. If it is set as a flag, read() doesn't block, but If there hasn't been an expiration since the last call to read, read() raises OSError with errno is set to errno.EAGAIN.

TFD_CLOEXEC 總是由 Python 自動設定。

The file descriptor must be closed with os.close() when it is no longer needed, or else the file descriptor will be leaked.

也參考

timerfd_create(2) [https://manpages.debian.org/timerfd_create(2)] 使用手冊。

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.timerfd_settime(fd, /, *, flags=flags, initial=0.0, interval=0.0)

Alter a timer file descriptor's internal timer. This function operates the same interval timer as timerfd_settime_ns().

fd 必須是有效的計時器檔案描述器。

The timer's behaviour can be modified by specifying a flags value. Any of the following variables may used, combined using bitwise OR (the | operator):

TFD_TIMER_ABSTIME

TFD_TIMER_CANCEL_ON_SET

The timer is disabled by setting initial to zero (0). If initial is equal to or greater than zero, the timer is enabled. If initial is less than zero, it raises an OSError exception with errno set to errno.EINVAL

By default the timer will fire when initial seconds have elapsed. (If initial is zero, timer will fire immediately.)

However, if the TFD_TIMER_ABSTIME flag is set, the timer will fire when the timer's clock (set by clockid in timerfd_create()) reaches initial seconds.

The timer's interval is set by the interval float. If interval is zero, the timer only fires once, on the initial expiration. If interval is greater than zero, the timer fires every time interval seconds have elapsed since the previous expiration. If interval is less than zero, it raises OSError with errno set to errno.EINVAL

If the TFD_TIMER_CANCEL_ON_SET flag is set along with TFD_TIMER_ABSTIME and the clock for this timer is time.CLOCK_REALTIME, the timer is marked as cancelable if the real-time clock is changed discontinuously. Reading the descriptor is aborted with the error ECANCELED.

Linux manages system clock as UTC. A daylight-savings time transition is done by changing time offset only and doesn't cause discontinuous system clock change.

Discontinuous system clock change will be caused by the following events:

settimeofday

clock_settime

set the system date and time by date command

Return a two-item tuple of (next_expiration, interval) from the previous timer state, before this function executed.

也參考

timerfd_create(2) [https://manpages.debian.org/timerfd_create(2)], timerfd_settime(2) [https://manpages.debian.org/timerfd_settime(2)], settimeofday(2) [https://manpages.debian.org/settimeofday(2)], clock_settime(2) [https://manpages.debian.org/clock_settime(2)], and date(1) [https://manpages.debian.org/date(1)].

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.timerfd_settime_ns(fd, /, *, flags=0, initial=0, interval=0)

Similar to timerfd_settime(), but use time as nanoseconds. This function operates the same interval timer as timerfd_settime().

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.timerfd_gettime(fd, /)

Return a two-item tuple of floats (next_expiration, interval).

next_expiration denotes the relative time until next the timer next fires, regardless of if the TFD_TIMER_ABSTIME flag is set.

interval denotes the timer's interval. If zero, the timer will only fire once, after next_expiration seconds have elapsed.

也參考

timerfd_gettime(2) [https://manpages.debian.org/timerfd_gettime(2)]

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.timerfd_gettime_ns(fd, /)

Similar to timerfd_gettime(), but return time as nanoseconds.

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.TFD_NONBLOCK

A flag for the timerfd_create() function, which sets the O_NONBLOCK status flag for the new timer file descriptor. If TFD_NONBLOCK is not set as a flag, read() blocks.

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.TFD_CLOEXEC

A flag for the timerfd_create() function, If TFD_CLOEXEC is set as a flag, set close-on-exec flag for new file descriptor.

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.TFD_TIMER_ABSTIME

A flag for the timerfd_settime() and timerfd_settime_ns() functions. If this flag is set, initial is interpreted as an absolute value on the timer's clock (in UTC seconds or nanoseconds since the Unix Epoch).

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

os.TFD_TIMER_CANCEL_ON_SET

A flag for the timerfd_settime() and timerfd_settime_ns() functions along with TFD_TIMER_ABSTIME. The timer is cancelled when the time of the underlying clock changes discontinuously.

可用性: Linux >= 2.6.27 with glibc >= 2.8

在 3.13 版被加入.

Linux extended attributes

在 3.3 版被加入.

These functions are all available on Linux only.

os.getxattr(path, attribute, *, follow_symlinks=True)

Return the value of the extended filesystem attribute attribute for path. attribute can be bytes or str (directly or indirectly through the PathLike interface). If it is str, it is encoded with the filesystem encoding.

This function can support specifying a file descriptor and not following symlinks.

引發一個附帶引數 path、attribute 的稽核事件 os.getxattr。

在 3.6 版的變更: Accepts a path-like object for path and attribute.

os.listxattr(path=None, *, follow_symlinks=True)

Return a list of the extended filesystem attributes on path. The attributes in the list are represented as strings decoded with the filesystem encoding. If path is None, listxattr() will examine the current directory.

This function can support specifying a file descriptor and not following symlinks.

引發一個附帶引數 path 的稽核事件 os.listxattr。

在 3.6 版的變更: Accepts a path-like object.

os.removexattr(path, attribute, *, follow_symlinks=True)

Removes the extended filesystem attribute attribute from path. attribute should be bytes or str (directly or indirectly through the PathLike interface). If it is a string, it is encoded with the filesystem encoding and error handler.

This function can support specifying a file descriptor and not following symlinks.

引發一個附帶引數 path、attribute 的稽核事件 os.removexattr。

在 3.6 版的變更: Accepts a path-like object for path and attribute.

os.setxattr(path, attribute, value, flags=0, *, follow_symlinks=True)

Set the extended filesystem attribute attribute on path to value. attribute must be a bytes or str with no embedded NULs (directly or indirectly through the PathLike interface). If it is a str, it is encoded with the filesystem encoding and error handler. flags may be XATTR_REPLACE or XATTR_CREATE. If XATTR_REPLACE is given and the attribute does not exist, ENODATA will be raised. If XATTR_CREATE is given and the attribute already exists, the attribute will not be created and EEXISTS will be raised.

This function can support specifying a file descriptor and not following symlinks.

備註

A bug in Linux kernel versions less than 2.6.39 caused the flags argument to be ignored on some filesystems.

引發一個附帶引數 path、attribute、value、flags 的稽核事件 os.setxattr。

在 3.6 版的變更: Accepts a path-like object for path and attribute.

os.XATTR_SIZE_MAX

The maximum size the value of an extended attribute can be. Currently, this is 64 KiB on Linux.

os.XATTR_CREATE

This is a possible value for the flags argument in setxattr(). It indicates the operation must create an attribute.

os.XATTR_REPLACE

This is a possible value for the flags argument in setxattr(). It indicates the operation must replace an existing attribute.

行程管理

These functions may be used to create and manage processes.

The various exec* functions take a list of arguments for the new program loaded into the process. In each case, the first of these arguments is passed to the new program as its own name rather than as an argument a user may have typed on a command line. For the C programmer, this is the argv[0] passed to a program's main(). For example, os.execv('/bin/echo', ['foo', 'bar']) will only print bar on standard output; foo will seem to be ignored.

os.abort()

Generate a SIGABRT signal to the current process. On Unix, the default behavior is to produce a core dump; on Windows, the process immediately returns an exit code of 3. Be aware that calling this function will not call the Python signal handler registered for SIGABRT with signal.signal().

os.add_dll_directory(path)

Add a path to the DLL search path.

This search path is used when resolving dependencies for imported extension modules (the module itself is resolved through sys.path), and also by ctypes.

Remove the directory by calling close() on the returned object or using it in a with statement.

See the Microsoft documentation [https://msdn.microsoft.com/44228cf2-6306-466c-8f16-f513cd3ba8b5] for more information about how DLLs are loaded.

引發一個附帶引數 path 的稽核事件 os.add_dll_directory。

可用性: Windows.

在 3.8 版被加入: Previous versions of CPython would resolve DLLs using the default behavior for the current process. This led to inconsistencies, such as only sometimes searching PATH or the current working directory, and OS functions such as AddDllDirectory having no effect.

In 3.8, the two primary ways DLLs are loaded now explicitly override the process-wide behavior to ensure consistency. See the porting notes for information on updating libraries.

os.execl(path, arg0, arg1, ...)

os.execle(path, arg0, arg1, ..., env)

os.execlp(file, arg0, arg1, ...)

os.execlpe(file, arg0, arg1, ..., env)

os.execv(path, args)

os.execve(path, args, env)

os.execvp(file, args)

os.execvpe(file, args, env)

These functions all execute a new program, replacing the current process; they do not return. On Unix, the new executable is loaded into the current process, and will have the same process id as the caller. Errors will be reported as OSError exceptions.

The current process is replaced immediately. Open file objects and descriptors are not flushed, so if there may be data buffered on these open files, you should flush them using sys.stdout.flush() or os.fsync() before calling an exec* function.

The "l" and "v" variants of the exec* functions differ in how command-line arguments are passed. The "l" variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written; the individual parameters simply become additional parameters to the execl*() functions. The "v" variants are good when the number of parameters is variable, with the arguments being passed in a list or tuple as the args parameter. In either case, the arguments to the child process should start with the name of the command being run, but this is not enforced.

The variants which include a "p" near the end (execlp(), execlpe(), execvp(), and execvpe()) will use the PATH environment variable to locate the program file. When the environment is being replaced (using one of the exec*e variants, discussed in the next paragraph), the new environment is used as the source of the PATH variable. The other variants, execl(), execle(), execv(), and execve(), will not use the PATH variable to locate the executable; path must contain an appropriate absolute or relative path. Relative paths must include at least one slash, even on Windows, as plain names will not be resolved.

For execle(), execlpe(), execve(), and execvpe() (note that these all end in "e"), the env parameter must be a mapping which is used to define the environment variables for the new process (these are used instead of the current process' environment); the functions execl(), execlp(), execv(), and execvp() all cause the new process to inherit the environment of the current process.

For execve() on some platforms, path may also be specified as an open file descriptor. This functionality may not be supported on your platform; you can check whether or not it is available using os.supports_fd. If it is unavailable, using it will raise a NotImplementedError.

引發一個附帶引數 path、args、env 的稽核事件 os.exec。

可用性: Unix, Windows, not WASI, not Android, not iOS.

在 3.3 版的變更: Added support for specifying path as an open file descriptor for execve().

在 3.6 版的變更: Accepts a path-like object.

os._exit(n)

Exit the process with status n, without calling cleanup handlers, flushing stdio buffers, etc.

備註

The standard way to exit is sys.exit(n). _exit() should normally only be used in the child process after a fork().

The following exit codes are defined and can be used with _exit(), although they are not required. These are typically used for system programs written in Python, such as a mail server's external command delivery program.

備註

Some of these may not be available on all Unix platforms, since there is some variation. These constants are defined where they are defined by the underlying platform.

os.EX_OK

Exit code that means no error occurred. May be taken from the defined value of EXIT_SUCCESS on some platforms. Generally has a value of zero.

可用性: Unix, Windows.

os.EX_USAGE

Exit code that means the command was used incorrectly, such as when the wrong number of arguments are given.

可用性: Unix, not WASI.

os.EX_DATAERR

Exit code that means the input data was incorrect.

可用性: Unix, not WASI.

os.EX_NOINPUT

Exit code that means an input file did not exist or was not readable.

可用性: Unix, not WASI.

os.EX_NOUSER

Exit code that means a specified user did not exist.

可用性: Unix, not WASI.

os.EX_NOHOST

Exit code that means a specified host did not exist.

可用性: Unix, not WASI.

os.EX_UNAVAILABLE

Exit code that means that a required service is unavailable.

可用性: Unix, not WASI.

os.EX_SOFTWARE

Exit code that means an internal software error was detected.

可用性: Unix, not WASI.

os.EX_OSERR

Exit code that means an operating system error was detected, such as the inability to fork or create a pipe.

可用性: Unix, not WASI.

os.EX_OSFILE

Exit code that means some system file did not exist, could not be opened, or had some other kind of error.

可用性: Unix, not WASI.

os.EX_CANTCREAT

Exit code that means a user specified output file could not be created.

可用性: Unix, not WASI.

os.EX_IOERR

Exit code that means that an error occurred while doing I/O on some file.

可用性: Unix, not WASI.

os.EX_TEMPFAIL

Exit code that means a temporary failure occurred. This indicates something that may not really be an error, such as a network connection that couldn't be made during a retryable operation.

可用性: Unix, not WASI.

os.EX_PROTOCOL

Exit code that means that a protocol exchange was illegal, invalid, or not understood.

可用性: Unix, not WASI.

os.EX_NOPERM

Exit code that means that there were insufficient permissions to perform the operation (but not intended for file system problems).

可用性: Unix, not WASI.

os.EX_CONFIG

Exit code that means that some kind of configuration error occurred.

可用性: Unix, not WASI.

os.EX_NOTFOUND

Exit code that means something like "an entry was not found".

可用性: Unix, not WASI.

os.fork()

Fork a child process. Return 0 in the child and the child's process id in the parent. If an error occurs OSError is raised.

Note that some platforms including FreeBSD <= 6.3 and Cygwin have known issues when using fork() from a thread.

引發一個不附帶引數的稽核事件 os.fork。

警告

If you use TLS sockets in an application calling fork(), see the warning in the ssl documentation.

警告

On macOS the use of this function is unsafe when mixed with using higher-level system APIs, and that includes using urllib.request.

在 3.8 版的變更: Calling fork() in a subinterpreter is no longer supported (RuntimeError is raised).

在 3.12 版的變更: If Python is able to detect that your process has multiple threads, os.fork() now raises a DeprecationWarning.

We chose to surface this as a warning, when detectable, to better inform developers of a design problem that the POSIX platform specifically notes as not supported. Even in code that appears to work, it has never been safe to mix threading with os.fork() on POSIX platforms. The CPython runtime itself has always made API calls that are not safe for use in the child process when threads existed in the parent (such as malloc and free).

Users of macOS or users of libc or malloc implementations other than those typically found in glibc to date are among those already more likely to experience deadlocks running such code.

See this discussion on fork being incompatible with threads [https://discuss.python.org/t/33555] for technical details of why we're surfacing this longstanding platform compatibility problem to developers.

可用性: POSIX, not WASI, not Android, not iOS.

os.forkpty()

Fork a child process, using a new pseudo-terminal as the child's controlling terminal. Return a pair of (pid, fd), where pid is 0 in the child, the new child's process id in the parent, and fd is the file descriptor of the master end of the pseudo-terminal. For a more portable approach, use the pty module. If an error occurs OSError is raised.

引發一個不附帶引數的稽核事件 os.forkpty。

警告

On macOS the use of this function is unsafe when mixed with using higher-level system APIs, and that includes using urllib.request.

在 3.8 版的變更: Calling forkpty() in a subinterpreter is no longer supported (RuntimeError is raised).

在 3.12 版的變更: If Python is able to detect that your process has multiple threads, this now raises a DeprecationWarning. See the longer explanation on os.fork().

可用性: Unix, not WASI, not Android, not iOS.

os.kill(pid, sig, /)

Send signal sig to the process pid. Constants for the specific signals available on the host platform are defined in the signal module.

Windows: The signal.CTRL_C_EVENT and signal.CTRL_BREAK_EVENT signals are special signals which can only be sent to console processes which share a common console window, e.g., some subprocesses. Any other value for sig will cause the process to be unconditionally killed by the TerminateProcess API, and the exit code will be set to sig.

另請參閱 signal.pthread_kill()。

引發一個附帶引數 pid、sig 的稽核事件 os.kill。

可用性: Unix, Windows, not WASI, not iOS.

在 3.2 版的變更: 新支援 Windows。

os.killpg(pgid, sig, /)

Send the signal sig to the process group pgid.

引發一個附帶引數 pgid、sig 的稽核事件 os.killpg。

可用性: Unix, not WASI, not iOS.

os.nice(increment, /)

Add increment to the process's "niceness". Return the new niceness.

可用性: Unix, not WASI.

os.pidfd_open(pid, flags=0)

Return a file descriptor referring to the process pid with flags set. This descriptor can be used to perform process management without races and signals.

更多細節請見 pidfd_open(2) [https://manpages.debian.org/pidfd_open(2)] 使用手冊。

可用性: Linux >= 5.3, Android >= build-time API level 31

在 3.9 版被加入.

os.PIDFD_NONBLOCK

This flag indicates that the file descriptor will be non-blocking. If the process referred to by the file descriptor has not yet terminated, then an attempt to wait on the file descriptor using waitid(2) [https://manpages.debian.org/waitid(2)] will immediately return the error EAGAIN rather than blocking.

可用性: Linux >= 5.10

在 3.12 版被加入.

os.plock(op, /)

Lock program segments into memory. The value of op (defined in <sys/lock.h>) determines which segments are locked.

可用性: Unix, not WASI, not iOS.

os.popen(cmd, mode='r', buffering=-1)

Open a pipe to or from command cmd. The return value is an open file object connected to the pipe, which can be read or written depending on whether mode is 'r' (default) or 'w'. The buffering argument have the same meaning as the corresponding argument to the built-in open() function. The returned file object reads or writes text strings rather than bytes.

The close method returns None if the subprocess exited successfully, or the subprocess's return code if there was an error. On POSIX systems, if the return code is positive it represents the return value of the process left-shifted by one byte. If the return code is negative, the process was terminated by the signal given by the negated value of the return code. (For example, the return value might be - signal.SIGKILL if the subprocess was killed.) On Windows systems, the return value contains the signed integer return code from the child process.

On Unix, waitstatus_to_exitcode() can be used to convert the close method result (exit status) into an exit code if it is not None. On Windows, the close method result is directly the exit code (or None).

This is implemented using subprocess.Popen; see that class's documentation for more powerful ways to manage and communicate with subprocesses.

可用性: not WASI, not Android, not iOS.

備註

The Python UTF-8 Mode affects encodings used for cmd and pipe contents.

popen() is a simple wrapper around subprocess.Popen. Use subprocess.Popen or subprocess.run() to control options like encodings.

在 3.14 版之後被棄用: The function is soft deprecated and should no longer be used to write new code. The subprocess module is recommended instead.

os.posix_spawn(path, argv, env, *, file_actions=None, setpgroup=None, resetids=False, setsid=False, setsigmask=(), setsigdef=(), scheduler=None)

Wraps the posix_spawn() C library API for use from Python.

Most users should use subprocess.run() instead of posix_spawn().

The positional-only arguments path, args, and env are similar to execve(). env is allowed to be None, in which case current process' environment is used.

The path parameter is the path to the executable file. The path should contain a directory. Use posix_spawnp() to pass an executable file without directory.

The file_actions argument may be a sequence of tuples describing actions to take on specific file descriptors in the child process between the C library implementation's fork() and exec() steps. The first item in each tuple must be one of the three type indicator listed below describing the remaining tuple elements:

os.POSIX_SPAWN_OPEN

(os.POSIX_SPAWN_OPEN, fd, path, flags, mode)

Performs os.dup2(os.open(path, flags, mode), fd).

os.POSIX_SPAWN_CLOSE

(os.POSIX_SPAWN_CLOSE, fd)

Performs os.close(fd).

os.POSIX_SPAWN_DUP2

(os.POSIX_SPAWN_DUP2, fd, new_fd)

Performs os.dup2(fd, new_fd).

os.POSIX_SPAWN_CLOSEFROM

(os.POSIX_SPAWN_CLOSEFROM, fd)

Performs os.closerange(fd, INF).

These tuples correspond to the C library posix_spawn_file_actions_addopen(), posix_spawn_file_actions_addclose(), posix_spawn_file_actions_adddup2(), and posix_spawn_file_actions_addclosefrom_np() API calls used to prepare for the posix_spawn() call itself.

The setpgroup argument will set the process group of the child to the value specified. If the value specified is 0, the child's process group ID will be made the same as its process ID. If the value of setpgroup is not set, the child will inherit the parent's process group ID. This argument corresponds to the C library POSIX_SPAWN_SETPGROUP flag.

If the resetids argument is True it will reset the effective UID and GID of the child to the real UID and GID of the parent process. If the argument is False, then the child retains the effective UID and GID of the parent. In either case, if the set-user-ID and set-group-ID permission bits are enabled on the executable file, their effect will override the setting of the effective UID and GID. This argument corresponds to the C library POSIX_SPAWN_RESETIDS flag.

If the setsid argument is True, it will create a new session ID for posix_spawn. setsid requires POSIX_SPAWN_SETSID or POSIX_SPAWN_SETSID_NP flag. Otherwise, NotImplementedError is raised.

The setsigmask argument will set the signal mask to the signal set specified. If the parameter is not used, then the child inherits the parent's signal mask. This argument corresponds to the C library POSIX_SPAWN_SETSIGMASK flag.

The sigdef argument will reset the disposition of all signals in the set specified. This argument corresponds to the C library POSIX_SPAWN_SETSIGDEF flag.

The scheduler argument must be a tuple containing the (optional) scheduler policy and an instance of sched_param with the scheduler parameters. A value of None in the place of the scheduler policy indicates that is not being provided. This argument is a combination of the C library POSIX_SPAWN_SETSCHEDPARAM and POSIX_SPAWN_SETSCHEDULER flags.

引發一個附帶引數 path、argv、env 的稽核事件 os.posix_spawn。

在 3.8 版被加入.

在 3.13 版的變更: env parameter accepts None. os.POSIX_SPAWN_CLOSEFROM is available on platforms where posix_spawn_file_actions_addclosefrom_np() exists.

可用性: Unix, not WASI, not Android, not iOS.

os.posix_spawnp(path, argv, env, *, file_actions=None, setpgroup=None, resetids=False, setsid=False, setsigmask=(), setsigdef=(), scheduler=None)

Wraps the posix_spawnp() C library API for use from Python.

Similar to posix_spawn() except that the system searches for the executable file in the list of directories specified by the PATH environment variable (in the same way as for execvp(3)).

引發一個附帶引數 path、argv、env 的稽核事件 os.posix_spawn。

在 3.8 版被加入.

可用性: POSIX, not WASI, not Android, not iOS.

見 posix_spawn() 文件。

os.register_at_fork(*, before=None, after_in_parent=None, after_in_child=None)

Register callables to be executed when a new child process is forked using os.fork() or similar process cloning APIs. The parameters are optional and keyword-only. Each specifies a different call point.

before is a function called before forking a child process.

after_in_parent is a function called from the parent process after forking a child process.

after_in_child is a function called from the child process.

These calls are only made if control is expected to return to the Python interpreter. A typical subprocess launch will not trigger them as the child is not going to re-enter the interpreter.

Functions registered for execution before forking are called in reverse registration order. Functions registered for execution after forking (either in the parent or in the child) are called in registration order.

Note that fork() calls made by third-party C code may not call those functions, unless it explicitly calls PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

There is no way to unregister a function.

可用性: Unix, not WASI, not Android, not iOS.

在 3.7 版被加入.

os.spawnl(mode, path, ...)

os.spawnle(mode, path, ..., env)

os.spawnlp(mode, file, ...)

os.spawnlpe(mode, file, ..., env)

os.spawnv(mode, path, args)

os.spawnve(mode, path, args, env)

os.spawnvp(mode, file, args)

os.spawnvpe(mode, file, args, env)

Execute the program path in a new process.

(Note that the subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using these functions. Check especially the Replacing Older Functions with the subprocess Module section.)

If mode is P_NOWAIT, this function returns the process id of the new process; if mode is P_WAIT, returns the process's exit code if it exits normally, or -signal, where signal is the signal that killed the process. On Windows, the process id will actually be the process handle, so can be used with the waitpid() function.

Note on VxWorks, this function doesn't return -signal when the new process is killed. Instead it raises OSError exception.

The "l" and "v" variants of the spawn* functions differ in how command-line arguments are passed. The "l" variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written; the individual parameters simply become additional parameters to the spawnl*() functions. The "v" variants are good when the number of parameters is variable, with the arguments being passed in a list or tuple as the args parameter. In either case, the arguments to the child process must start with the name of the command being run.

The variants which include a second "p" near the end (spawnlp(), spawnlpe(), spawnvp(), and spawnvpe()) will use the PATH environment variable to locate the program file. When the environment is being replaced (using one of the spawn*e variants, discussed in the next paragraph), the new environment is used as the source of the PATH variable. The other variants, spawnl(), spawnle(), spawnv(), and spawnve(), will not use the PATH variable to locate the executable; path must contain an appropriate absolute or relative path.

For spawnle(), spawnlpe(), spawnve(), and spawnvpe() (note that these all end in "e"), the env parameter must be a mapping which is used to define the environment variables for the new process (they are used instead of the current process' environment); the functions spawnl(), spawnlp(), spawnv(), and spawnvp() all cause the new process to inherit the environment of the current process. Note that keys and values in the env dictionary must be strings; invalid keys or values will cause the function to fail, with a return value of 127.

As an example, the following calls to spawnlp() and spawnvpe() are equivalent:

import os
os.spawnlp(os.P_WAIT, 'cp', 'cp', 'index.html', '/dev/null')

L = ['cp', 'index.html', '/dev/null']
os.spawnvpe(os.P_WAIT, 'cp', L, os.environ)

引發一個附帶引數 mode、path、args、env 的稽核事件 os.spawn。

可用性: Unix, Windows, not WASI, not Android, not iOS.

spawnlp(), spawnlpe(), spawnvp() and spawnvpe() are not available on Windows. spawnle() and spawnve() are not thread-safe on Windows; we advise you to use the subprocess module instead.

在 3.6 版的變更: Accepts a path-like object.

在 3.14 版之後被棄用: These functions are soft deprecated and should no longer be used to write new code. The subprocess module is recommended instead.

os.P_NOWAIT

os.P_NOWAITO

Possible values for the mode parameter to the spawn* family of functions. If either of these values is given, the spawn* functions will return as soon as the new process has been created, with the process id as the return value.

可用性: Unix, Windows.

os.P_WAIT

Possible value for the mode parameter to the spawn* family of functions. If this is given as mode, the spawn* functions will not return until the new process has run to completion and will return the exit code of the process the run is successful, or -signal if a signal kills the process.

可用性: Unix, Windows.

os.P_DETACH

os.P_OVERLAY

Possible values for the mode parameter to the spawn* family of functions. These are less portable than those listed above. P_DETACH is similar to P_NOWAIT, but the new process is detached from the console of the calling process. If P_OVERLAY is used, the current process will be replaced; the spawn* function will not return.

可用性: Windows.

os.startfile(path[, operation][, arguments][, cwd][, show_cmd])

Start a file with its associated application.

When operation is not specified, this acts like double-clicking the file in Windows Explorer, or giving the file name as an argument to the start command from the interactive command shell: the file is opened with whatever application (if any) its extension is associated.

When another operation is given, it must be a "command verb" that specifies what should be done with the file. Common verbs documented by Microsoft are 'open', 'print' and 'edit' (to be used on files) as well as 'explore' and 'find' (to be used on directories).

When launching an application, specify arguments to be passed as a single string. This argument may have no effect when using this function to launch a document.

The default working directory is inherited, but may be overridden by the cwd argument. This should be an absolute path. A relative path will be resolved against this argument.

Use show_cmd to override the default window style. Whether this has any effect will depend on the application being launched. Values are integers as supported by the Win32 ShellExecute() function.

startfile() returns as soon as the associated application is launched. There is no option to wait for the application to close, and no way to retrieve the application's exit status. The path parameter is relative to the current directory or cwd. If you want to use an absolute path, make sure the first character is not a slash ('/') Use pathlib or the os.path.normpath() function to ensure that paths are properly encoded for Win32.

To reduce interpreter startup overhead, the Win32 ShellExecute() function is not resolved until this function is first called. If the function cannot be resolved, NotImplementedError will be raised.

引發一個附帶引數 path、operation 的稽核事件 os.startfile。

引發一個附帶引數 path、operation、arguments、cwd、show_cmd 的稽核事件 os.startfile/2。

可用性: Windows.

在 3.10 版的變更: Added the arguments, cwd and show_cmd arguments, and the os.startfile/2 audit event.

os.system(command)

Execute the command (a string) in a subshell. This is implemented by calling the Standard C function system(), and has the same limitations. Changes to sys.stdin, etc. are not reflected in the environment of the executed command. If command generates any output, it will be sent to the interpreter standard output stream. The C standard does not specify the meaning of the return value of the C function, so the return value of the Python function is system-dependent.

On Unix, the return value is the exit status of the process encoded in the format specified for wait().

On Windows, the return value is that returned by the system shell after running command. The shell is given by the Windows environment variable COMSPEC: it is usually cmd.exe, which returns the exit status of the command run; on systems using a non-native shell, consult your shell documentation.

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is recommended to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.

On Unix, waitstatus_to_exitcode() can be used to convert the result (exit status) into an exit code. On Windows, the result is directly the exit code.

引發一個附帶引數 command 的稽核事件 os.system。

可用性: Unix, Windows, not WASI, not Android, not iOS.

os.times()

Returns the current global process times. The return value is an object with five attributes:

user - 使用者時間

system - 系統時間

children_user - 所有子行程的使用者時間

children_system - 所有子行程的系統時間

elapsed - elapsed real time since a fixed point in the past

For backwards compatibility, this object also behaves like a five-tuple containing user, system, children_user, children_system, and elapsed in that order.

See the Unix manual page times(2) [https://manpages.debian.org/times(2)] and times(3) [https://man.freebsd.org/cgi/man.cgi?time(3)] manual page on Unix or the GetProcessTimes MSDN [https://docs.microsoft.com/windows/win32/api/processthreadsapi/nf-processthreadsapi-getprocesstimes] on Windows. On Windows, only user and system are known; the other attributes are zero.

可用性: Unix, Windows.

在 3.3 版的變更: Return type changed from a tuple to a tuple-like object with named attributes.

os.wait()

Wait for completion of a child process, and return a tuple containing its pid and exit status indication: a 16-bit number, whose low byte is the signal number that killed the process, and whose high byte is the exit status (if the signal number is zero); the high bit of the low byte is set if a core file was produced.

If there are no children that could be waited for, ChildProcessError is raised.

waitstatus_to_exitcode() can be used to convert the exit status into an exit code.

可用性: Unix, not WASI, not Android, not iOS.

也參考

The other wait*() functions documented below can be used to wait for the completion of a specific child process and have more options. waitpid() is the only one also available on Windows.

os.waitid(idtype, id, options, /)

Wait for the completion of a child process.

idtype can be P_PID, P_PGID, P_ALL, or (on Linux) P_PIDFD. The interpretation of id depends on it; see their individual descriptions.

options is an OR combination of flags. At least one of WEXITED, WSTOPPED or WCONTINUED is required; WNOHANG and WNOWAIT are additional optional flags.

The return value is an object representing the data contained in the siginfo_t structure with the following attributes:

si_pid (process ID)

si_uid (real user ID of the child)

si_signo (always SIGCHLD)

si_status (the exit status or signal number, depending on si_code)

si_code (see CLD_EXITED for possible values)

If WNOHANG is specified and there are no matching children in the requested state, None is returned. Otherwise, if there are no matching children that could be waited for, ChildProcessError is raised.

可用性: Unix, not WASI, not Android, not iOS.

在 3.3 版被加入.

在 3.13 版的變更: This function is now available on macOS as well.

os.waitpid(pid, options, /)

The details of this function differ on Unix and Windows.

On Unix: Wait for completion of a child process given by process id pid, and return a tuple containing its process id and exit status indication (encoded as for wait()). The semantics of the call are affected by the value of the integer options, which should be 0 for normal operation.

If pid is greater than 0, waitpid() requests status information for that specific process. If pid is 0, the request is for the status of any child in the process group of the current process. If pid is -1, the request pertains to any child of the current process. If pid is less than -1, status is requested for any process in the process group -pid (the absolute value of pid).

options is an OR combination of flags. If it contains WNOHANG and there are no matching children in the requested state, (0, 0) is returned. Otherwise, if there are no matching children that could be waited for, ChildProcessError is raised. Other options that can be used are WUNTRACED and WCONTINUED.

On Windows: Wait for completion of a process given by process handle pid, and return a tuple containing pid, and its exit status shifted left by 8 bits (shifting makes cross-platform use of the function easier). A pid less than or equal to 0 has no special meaning on Windows, and raises an exception. The value of integer options has no effect. pid can refer to any process whose id is known, not necessarily a child process. The spawn* functions called with P_NOWAIT return suitable process handles.

waitstatus_to_exitcode() can be used to convert the exit status into an exit code.

可用性: Unix, Windows, not WASI, not Android, not iOS.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

os.wait3(options)

Similar to waitpid(), except no process id argument is given and a 3-element tuple containing the child's process id, exit status indication, and resource usage information is returned. Refer to resource.getrusage() for details on resource usage information. The options argument is the same as that provided to waitpid() and wait4().

waitstatus_to_exitcode() can be used to convert the exit status into an exitcode.

可用性: Unix, not WASI, not Android, not iOS.

os.wait4(pid, options)

Similar to waitpid(), except a 3-element tuple, containing the child's process id, exit status indication, and resource usage information is returned. Refer to resource.getrusage() for details on resource usage information. The arguments to wait4() are the same as those provided to waitpid().

waitstatus_to_exitcode() can be used to convert the exit status into an exitcode.

可用性: Unix, not WASI, not Android, not iOS.

os.P_PID

os.P_PGID

os.P_ALL

os.P_PIDFD

These are the possible values for idtype in waitid(). They affect how id is interpreted:

P_PID - wait for the child whose PID is id.

P_PGID - wait for any child whose progress group ID is id.

P_ALL - wait for any child; id is ignored.

P_PIDFD - wait for the child identified by the file descriptor id (a process file descriptor created with pidfd_open()).

可用性: Unix, not WASI, not Android, not iOS.

備註

P_PIDFD is only available on Linux >= 5.4.

在 3.3 版被加入.

在 3.9 版被加入: The P_PIDFD constant.

os.WCONTINUED

This options flag for waitpid(), wait3(), wait4(), and waitid() causes child processes to be reported if they have been continued from a job control stop since they were last reported.

可用性: Unix, not WASI, not Android, not iOS.

os.WEXITED

This options flag for waitid() causes child processes that have terminated to be reported.

The other wait* functions always report children that have terminated, so this option is not available for them.

可用性: Unix, not WASI, not Android, not iOS.

在 3.3 版被加入.

os.WSTOPPED

This options flag for waitid() causes child processes that have been stopped by the delivery of a signal to be reported.

This option is not available for the other wait* functions.

可用性: Unix, not WASI, not Android, not iOS.

在 3.3 版被加入.

os.WUNTRACED

This options flag for waitpid(), wait3(), and wait4() causes child processes to also be reported if they have been stopped but their current state has not been reported since they were stopped.

This option is not available for waitid().

可用性: Unix, not WASI, not Android, not iOS.

os.WNOHANG

This options flag causes waitpid(), wait3(), wait4(), and waitid() to return right away if no child process status is available immediately.

可用性: Unix, not WASI, not Android, not iOS.

os.WNOWAIT

This options flag causes waitid() to leave the child in a waitable state, so that a later wait*() call can be used to retrieve the child status information again.

This option is not available for the other wait* functions.

可用性: Unix, not WASI, not Android, not iOS.

os.CLD_EXITED

os.CLD_KILLED

os.CLD_DUMPED

os.CLD_TRAPPED

os.CLD_STOPPED

os.CLD_CONTINUED

These are the possible values for si_code in the result returned by waitid().

可用性: Unix, not WASI, not Android, not iOS.

在 3.3 版被加入.

在 3.9 版的變更: 新增 CLD_KILLED 和 CLD_STOPPED 值。

os.waitstatus_to_exitcode(status)

Convert a wait status to an exit code.

在 Unix 上：

If the process exited normally (if WIFEXITED(status) is true), return the process exit status (return WEXITSTATUS(status)): result greater than or equal to 0.

If the process was terminated by a signal (if WIFSIGNALED(status) is true), return -signum where signum is the number of the signal that caused the process to terminate (return -WTERMSIG(status)): result less than 0.

否則，引發 ValueError。

On Windows, return status shifted right by 8 bits.

On Unix, if the process is being traced or if waitpid() was called with WUNTRACED option, the caller must first check if WIFSTOPPED(status) is true. This function must not be called if WIFSTOPPED(status) is true.

也參考

WIFEXITED(), WEXITSTATUS(), WIFSIGNALED(), WTERMSIG(), WIFSTOPPED(), WSTOPSIG() functions.

可用性: Unix, Windows, not WASI, not Android, not iOS.

在 3.9 版被加入.

The following functions take a process status code as returned by system(), wait(), or waitpid() as a parameter. They may be used to determine the disposition of a process.

os.WCOREDUMP(status, /)

Return True if a core dump was generated for the process, otherwise return False.

This function should be employed only if WIFSIGNALED() is true.

可用性: Unix, not WASI, not Android, not iOS.

os.WIFCONTINUED(status)

Return True if a stopped child has been resumed by delivery of SIGCONT (if the process has been continued from a job control stop), otherwise return False.

參閱 WCONTINUED 選項。

可用性: Unix, not WASI, not Android, not iOS.

os.WIFSTOPPED(status)

Return True if the process was stopped by delivery of a signal, otherwise return False.

WIFSTOPPED() only returns True if the waitpid() call was done using WUNTRACED option or when the process is being traced (see ptrace(2) [https://manpages.debian.org/ptrace(2)]).

可用性: Unix, not WASI, not Android, not iOS.

os.WIFSIGNALED(status)

Return True if the process was terminated by a signal, otherwise return False.

可用性: Unix, not WASI, not Android, not iOS.

os.WIFEXITED(status)

Return True if the process exited terminated normally, that is, by calling exit() or _exit(), or by returning from main(); otherwise return False.

可用性: Unix, not WASI, not Android, not iOS.

os.WEXITSTATUS(status)

Return the process exit status.

This function should be employed only if WIFEXITED() is true.

可用性: Unix, not WASI, not Android, not iOS.

os.WSTOPSIG(status)

Return the signal which caused the process to stop.

This function should be employed only if WIFSTOPPED() is true.

可用性: Unix, not WASI, not Android, not iOS.

os.WTERMSIG(status)

Return the number of the signal that caused the process to terminate.

This function should be employed only if WIFSIGNALED() is true.

可用性: Unix, not WASI, not Android, not iOS.

排程器介面

These functions control how a process is allocated CPU time by the operating system. They are only available on some Unix platforms. For more detailed information, consult your Unix manpages.

在 3.3 版被加入.

The following scheduling policies are exposed if they are supported by the operating system.

os.SCHED_OTHER

The default scheduling policy.

os.SCHED_BATCH

Scheduling policy for CPU-intensive processes that tries to preserve interactivity on the rest of the computer.

os.SCHED_DEADLINE

Scheduling policy for tasks with deadline constraints.

在 3.14 版被加入.

os.SCHED_IDLE

Scheduling policy for extremely low priority background tasks.

os.SCHED_NORMAL

SCHED_OTHER 的別名。

在 3.14 版被加入.

os.SCHED_SPORADIC

Scheduling policy for sporadic server programs.

os.SCHED_FIFO

先進先出排程策略。

os.SCHED_RR

輪轉排程策略。

os.SCHED_RESET_ON_FORK

This flag can be OR'ed with any other scheduling policy. When a process with this flag set forks, its child's scheduling policy and priority are reset to the default.

class os.sched_param(sched_priority)

This class represents tunable scheduling parameters used in sched_setparam(), sched_setscheduler(), and sched_getparam(). It is immutable.

At the moment, there is only one possible parameter:

sched_priority

The scheduling priority for a scheduling policy.

os.sched_get_priority_min(policy)

Get the minimum priority value for policy. policy is one of the scheduling policy constants above.

os.sched_get_priority_max(policy)

Get the maximum priority value for policy. policy is one of the scheduling policy constants above.

os.sched_setscheduler(pid, policy, param, /)

Set the scheduling policy for the process with PID pid. A pid of 0 means the calling process. policy is one of the scheduling policy constants above. param is a sched_param instance.

os.sched_getscheduler(pid, /)

Return the scheduling policy for the process with PID pid. A pid of 0 means the calling process. The result is one of the scheduling policy constants above.

os.sched_setparam(pid, param, /)

Set the scheduling parameters for the process with PID pid. A pid of 0 means the calling process. param is a sched_param instance.

os.sched_getparam(pid, /)

Return the scheduling parameters as a sched_param instance for the process with PID pid. A pid of 0 means the calling process.

os.sched_rr_get_interval(pid, /)

Return the round-robin quantum in seconds for the process with PID pid. A pid of 0 means the calling process.

os.sched_yield()

Voluntarily relinquish the CPU. See sched_yield(2) [https://manpages.debian.org/sched_yield(2)] for details.

os.sched_setaffinity(pid, mask, /)

Restrict the process with PID pid (or the current process if zero) to a set of CPUs. mask is an iterable of integers representing the set of CPUs to which the process should be restricted.

os.sched_getaffinity(pid, /)

Return the set of CPUs the process with PID pid is restricted to.

If pid is zero, return the set of CPUs the calling thread of the current process is restricted to.

也請見 process_cpu_count() 函式。

Miscellaneous System Information

os.confstr(name, /)

Return string-valued system configuration values. name specifies the configuration value to retrieve; it may be a string which is the name of a defined system value; these names are specified in a number of standards (POSIX, Unix 95, Unix 98, and others). Some platforms define additional names as well. The names known to the host operating system are given as the keys of the confstr_names dictionary. For configuration variables not included in that mapping, passing an integer for name is also accepted.

If the configuration value specified by name isn't defined, None is returned.

If name is a string and is not known, ValueError is raised. If a specific value for name is not supported by the host system, even if it is included in confstr_names, an OSError is raised with errno.EINVAL for the error number.

可用性: Unix.

os.confstr_names

Dictionary mapping names accepted by confstr() to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system.

可用性: Unix.

os.cpu_count()

Return the number of logical CPUs in the system. Returns None if undetermined.

The process_cpu_count() function can be used to get the number of logical CPUs usable by the calling thread of the current process.

在 3.4 版被加入.

在 3.13 版的變更: If -X cpu_count is given or PYTHON_CPU_COUNT is set, cpu_count() returns the override value n.

os.getloadavg()

Return the number of processes in the system run queue averaged over the last 1, 5, and 15 minutes or raises OSError if the load average was unobtainable.

可用性: Unix.

os.process_cpu_count()

Get the number of logical CPUs usable by the calling thread of the current process. Returns None if undetermined. It can be less than cpu_count() depending on the CPU affinity.

The cpu_count() function can be used to get the number of logical CPUs in the system.

If -X cpu_count is given or PYTHON_CPU_COUNT is set, process_cpu_count() returns the override value n.

也請見 sched_getaffinity() 函式。

在 3.13 版被加入.

os.sysconf(name, /)

Return integer-valued system configuration values. If the configuration value specified by name isn't defined, -1 is returned. The comments regarding the name parameter for confstr() apply here as well; the dictionary that provides information on the known names is given by sysconf_names.

可用性: Unix.

os.sysconf_names

Dictionary mapping names accepted by sysconf() to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system.

可用性: Unix.

在 3.11 版的變更: 新增 'SC_MINSIGSTKSZ' 名稱。

The following data values are used to support path manipulation operations. These are defined for all platforms.

Higher-level operations on pathnames are defined in the os.path module.

os.curdir

The constant string used by the operating system to refer to the current directory. This is '.' for Windows and POSIX. Also available via os.path.

os.pardir

The constant string used by the operating system to refer to the parent directory. This is '..' for Windows and POSIX. Also available via os.path.

os.sep

The character used by the operating system to separate pathname components. This is '/' for POSIX and '\\' for Windows. Note that knowing this is not sufficient to be able to parse or concatenate pathnames --- use os.path.split() and os.path.join() --- but it is occasionally useful. Also available via os.path.

os.altsep

An alternative character used by the operating system to separate pathname components, or None if only one separator character exists. This is set to '/' on Windows systems where sep is a backslash. Also available via os.path.

os.extsep

The character which separates the base filename from the extension; for example, the '.' in os.py. Also available via os.path.

os.pathsep

The character conventionally used by the operating system to separate search path components (as in PATH), such as ':' for POSIX or ';' for Windows. Also available via os.path.

os.defpath

The default search path used by exec*p* and spawn*p* if the environment doesn't have a 'PATH' key. Also available via os.path.

os.linesep

The string used to separate (or, rather, terminate) lines on the current platform. This may be a single character, such as '\n' for POSIX, or multiple characters, for example, '\r\n' for Windows. Do not use os.linesep as a line terminator when writing files opened in text mode (the default); use a single '\n' instead, on all platforms.

os.devnull

The file path of the null device. For example: '/dev/null' for POSIX, 'nul' for Windows. Also available via os.path.

os.RTLD_LAZY

os.RTLD_NOW

os.RTLD_GLOBAL

os.RTLD_LOCAL

os.RTLD_NODELETE

os.RTLD_NOLOAD

os.RTLD_DEEPBIND

Flags for use with the setdlopenflags() and getdlopenflags() functions. See the Unix manual page dlopen(3) [https://manpages.debian.org/dlopen(3)] for what the different flags mean.

在 3.3 版被加入.

Random numbers

os.getrandom(size, flags=0)

Get up to size random bytes. The function can return less bytes than requested.

These bytes can be used to seed user-space random number generators or for cryptographic purposes.

getrandom() relies on entropy gathered from device drivers and other sources of environmental noise. Unnecessarily reading large quantities of data will have a negative impact on other users of the /dev/random and /dev/urandom devices.

The flags argument is a bit mask that can contain zero or more of the following values ORed together: os.GRND_RANDOM and GRND_NONBLOCK.

See also the Linux getrandom() manual page [https://man7.org/linux/man-pages/man2/getrandom.2.html].

可用性: Linux >= 3.17.

在 3.6 版被加入.

os.urandom(size, /)

Return a bytestring of size random bytes suitable for cryptographic use.

This function returns random bytes from an OS-specific randomness source. The returned data should be unpredictable enough for cryptographic applications, though its exact quality depends on the OS implementation.

On Linux, if the getrandom() syscall is available, it is used in blocking mode: block until the system urandom entropy pool is initialized (128 bits of entropy are collected by the kernel). See the PEP 524 [https://peps.python.org/pep-0524/] for the rationale. On Linux, the getrandom() function can be used to get random bytes in non-blocking mode (using the GRND_NONBLOCK flag) or to poll until the system urandom entropy pool is initialized.

On a Unix-like system, random bytes are read from the /dev/urandom device. If the /dev/urandom device is not available or not readable, the NotImplementedError exception is raised.

On Windows, it will use BCryptGenRandom().

也參考

The secrets module provides higher level functions. For an easy-to-use interface to the random number generator provided by your platform, please see random.SystemRandom.

在 3.5 版的變更: On Linux 3.17 and newer, the getrandom() syscall is now used when available. On OpenBSD 5.6 and newer, the C getentropy() function is now used. These functions avoid the usage of an internal file descriptor.

在 3.5.2 版的變更: On Linux, if the getrandom() syscall blocks (the urandom entropy pool is not initialized yet), fall back on reading /dev/urandom.

在 3.6 版的變更: On Linux, getrandom() is now used in blocking mode to increase the security.

在 3.11 版的變更: On Windows, BCryptGenRandom() is used instead of CryptGenRandom() which is deprecated.

os.GRND_NONBLOCK

By default, when reading from /dev/random, getrandom() blocks if no random bytes are available, and when reading from /dev/urandom, it blocks if the entropy pool has not yet been initialized.

If the GRND_NONBLOCK flag is set, then getrandom() does not block in these cases, but instead immediately raises BlockingIOError.

在 3.6 版被加入.

os.GRND_RANDOM

If this bit is set, then random bytes are drawn from the /dev/random pool instead of the /dev/urandom pool.

在 3.6 版被加入.

io — 處理資料串流的核心工具

原始碼：Lib/io.py [https://github.com/python/cpython/tree/3.14/Lib/io.py]

總覽

io 模組替 Python 提供處理各種類型 IO 的主要工具。有三種主要的 IO 類型： 文字 I/O (text I/O)、二進位 I/O (binary I/O) 以及原始 I/O (raw I/O)。這些均為泛用 (generic) 類型，且每種類型都可以使用各式後端儲存 (backing store)。任一種屬於這些類型的具體物件稱為 file object。其它常見的名詞還有資料串流 (stream) 以及類檔案物件 (file-like objects)。

無論其類型為何，每個具體的資料串流物件也將具有各種能力：唯讀的、只接受寫入的、或者讀寫兼具的。它還允許任意的隨機存取（向前或向後尋找至任意位置），或者只能依順序存取（例如 socket 或 pipe 的情形下）。

所有的資料串流都會謹慎處理你所提供的資料的型別。舉例來說，提供一個 str 物件給二進位資料串流的 write() 方法將會引發 TypeError。同樣地，若提供一個 bytes 物件給文字資料串流的 write() 方法，也會引發同樣的錯誤。

在 3.3 版的變更: 原本會引發 IOError 的操作，現在將改成引發 OSError。因為 IOError 現在是 OSError 的別名。

文字 I/O

文字 I/O 要求和產出 str 物件。這意味著每當後端儲存為原生 bytes 時（例如在檔案的情形下），資料的編碼與解碼會以清楚易懂的方式進行，也可選擇同時轉換特定於平台的換行字元。

建立文字資料串流最簡單的方法是使用 open()，可選擇性地指定編碼：

f = open("myfile.txt", "r", encoding="utf-8")

記憶體內的文字資料串流也可以使用 StringIO 物件建立：

f = io.StringIO("some initial text data")

備註

When working with a non-blocking stream, be aware that read operations on text I/O objects might raise a BlockingIOError if the stream cannot perform the operation immediately.

文字資料串流 API 的詳細說明在 TextIOBase 文件當中。

二進位 (Binary) I/O

二進位 I/O（也稱為緩衝 I/O (buffered I/O)）要求的是類位元組物件 (bytes-like objects) 且產生 bytes 物件。不進行編碼、解碼或者換行字元轉換。這種類型的資料串流可用於各種非文字資料，以及需要手動控制對文字資料的處理時。

建立二進位資料串流最簡單的方法是使用 open()，並在 mode 字串中加入 'b'：

f = open("myfile.jpg", "rb")

記憶體內的二進位資料串流也可以透過 BytesIO 物件來建立：

f = io.BytesIO(b"some initial binary data: \x00\x01")

二進位資料串流 API 的詳細說明在 BufferedIOBase 文件當中。

其它函式庫模組可能提供額外的方法來建立文字或二進位資料串流。例如 socket.socket.makefile()。

原始 (Raw) I/O

原始 I/O（也稱為無緩衝 I/O (unbuffered I/O)）通常作為二進位以及文字資料串流的低階 building-block 使用；在使用者程式碼中直接操作原始資料串流很少有用。然而，你可以透過以無緩衝的二進位模式開啟一個檔案來建立一個原始資料串流：

f = open("myfile.jpg", "rb", buffering=0)

原始串流 API 在 RawIOBase 文件中有詳細描述。

文字編碼

TextIOWrapper 和 open() 預設編碼是根據區域設定的 (locale-specific) (locale.getencoding())。

然而，許多開發人員在開啟以 UTF-8 編碼的文字檔案（例如：JSON、TOML、Markdown等）時忘記指定編碼，因為多數 Unix 平台預設使用 UTF-8 區域設定。這會導致錯誤，因為對於大多數 Windows 使用者來說，預設地區編碼並非 UTF-8。舉例來說：

# May not work on Windows when non-ASCII characters in the file.
with open("README.md") as f:
    long_description = f.read()

因此，強烈建議在開啟文字檔案時，明確指定編碼。若你想使用 UTF-8 編碼，請傳入 encoding="utf-8"。若想使用目前的地區編碼，Python 3.10 以後的版本支援使用 encoding="locale"。

也參考

Python UTF-8 模式

在 Python UTF-8 模式下，可以將預設編碼從特定地區編碼改為 UTF-8。

PEP 686 [https://peps.python.org/pep-0686/]

Python 3.15 將預設使用 Python UTF-8 模式。

選擇性加入的編碼警告

在 3.10 版被加入: 更多資訊請見 PEP 597 [https://peps.python.org/pep-0597/]。

要找出哪些地方使用到預設的地區編碼，你可以啟用 -X warn_default_encoding 命令列選項，或者設定環境變數 PYTHONWARNDEFAULTENCODING。當使用到預設編碼時，會引發 EncodingWarning。

如果你正在提供一個使用 open() 或 TextIOWrapper 且傳遞 encoding=None 作為參數的 API，你可以使用 text_encoding()。如此一來如果 API 的呼叫方沒有傳遞 encoding，呼叫方就會發出一個 EncodingWarning。然而，對於新的 API，請考慮預設使用 UTF-8（即 encoding="utf-8"）。

高階模組介面

io.DEFAULT_BUFFER_SIZE

一個包含模組中緩衝 I/O 類別所使用的預設緩衝區大小的整數。若可能的話，open() 會使用檔案的 blksize （透過 os.stat() 取得）。

io.open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

這是內建函式 open() 的別名。

此函式會引發一個帶有引數 path、mode 以及 flags 的稽核事件 (auditing event) open。mode 與 flags 引數可能已經被修改或者從原始呼叫中被推斷出來。

io.open_code(path)

以 'rb' 模式開啟提供的檔案。此函式應用於意圖將內容視為可執行的程式碼的情況下。

path 應該要屬於 str 類別，且是個絕對路徑。

這個函式的行為可能會被之前對 PyFile_SetOpenCodeHook() 的呼叫覆寫。然而，假設 path 是個 str 且為絕對路徑，則 open_code(path) 總是與 open(path, 'rb') 有相同行為。覆寫這個行為是為了對檔案進行額外驗證或預處理。

在 3.8 版被加入.

io.text_encoding(encoding, stacklevel=2, /)

這是個輔助函式，適用於使用 open() 或 TextIOWrapper 且具有 encoding=None 參數的可呼叫物件。

若 encoding 不為 None，此函式將回傳 encoding。否則，將根據 UTF-8 Mode 回傳 "locale" 或 "utf-8"。

若 sys.flags.warn_default_encoding 為真，且 encoding 為 None，此函式會發出一個 EncodingWarning。stacklevel 指定警告在哪層發出。範例：

def read_text(path, encoding=None):
    encoding = io.text_encoding(encoding)  # stacklevel=2
    with open(path, encoding) as f:
        return f.read()

在此範例中，對於 read_text() 的呼叫方會引發一個 EncodingWarning。

更多資訊請見 文字編碼。

在 3.10 版被加入.

在 3.11 版的變更: 當 UTF-8 模式啟用且 encoding 為 None 時，text_encoding() 會回傳 "utf-8"。

exception io.BlockingIOError

這是內建的 BlockingIOError 例外的相容性別名。

exception io.UnsupportedOperation

當在資料串流上呼叫不支援的操作時，會引發繼承自 OSError 與 ValueError 的例外。

也參考

sys

包含標準的 IO 資料串流：sys.stdin、sys.stdout 以及 sys.stderr。

類別階層

I/O 串流的實作是由多個類別組合成的階層結構所構成。首先是 abstract base classes （抽象基底類別，ABCs），它們被用來規範各種不同類型的串流，接著具體類別會提供標準串流的實作。

備註

為了協助具體串流類別的實作，抽象基底類別提供了某些方法的預設實作。舉例來說，BufferedIOBase 提供未經最佳化的 readinto() 與 readline() 實作。

I/O 階層結構的最上層是抽象基底類別 IOBase。它定義了串流的基礎的介面。然而，請注意，讀取串流與寫入串流之間並沒有分離；若不支援給定的操作，實作是允許引發 UnsupportedOperation 例外的。

抽象基底類別 RawIOBase 繼承 IOBase。此類別處理對串流的位元組讀寫。FileIO 則繼承 RawIOBase 來提供一個介面以存取機器檔案系統內的檔案。

抽象基底類別 BufferedIOBase 繼承 IOBase。此類別緩衝原始二進位串流 (RawIOBase)。它的子類別 BufferedWriter、BufferedReader 與 BufferedRWPair 分別緩衝可寫、可讀、可讀也可寫的的原始二進位串流。類別 BufferedRandom 則提供一個對可搜尋串流 (seekable stream) 的緩衝介面。另一個類別 BufferedIOBase 的子類別 BytesIO，是一個記憶體內位元組串流。

抽象基底類別 TextIOBase 繼承 IOBase。此類別處理文本位元組串流，並處理字串的編碼和解碼。類別 TextIOWrapper 繼承自 TextIOBase，這是個對緩衝原始串流 (BufferedIOBase) 的緩衝文本介面。最後，StringIO 是個文字記憶體內串流。

引數名稱不是規範的一部份，只有 open() 的引數將作為關鍵字引數。

以下表格總結了 io 模組提供的抽象基底類別 (ABC)：

抽象基底類別 (ABC)

繼承

Stub 方法

Mixin 方法與屬性

IOBase

fileno、seek 和 truncate

close、closed、__enter__、__exit__、flush、isatty、__iter__、__next__、readable、readline、readlines、seekable、tell、writable 與 writelines

RawIOBase

IOBase

readinto 和 write

繼承自 IOBase 的方法，read 與 readall

BufferedIOBase

IOBase

detach、read、read1 和 write

繼承自 IOBase 的方法，readinto 與 readinto1

TextIOBase

IOBase

detach、read、readline 和 write

繼承自 IOBase 的方法，encoding、errors 與 newlines

I/O 基礎類別

class io.IOBase

所有 I/O 類別的抽象基礎類別。

為許多方法提供了空的抽象實作，衍生類別可以選擇性地覆寫這些方法；預設的實作代表一個無法讀取、寫入或搜尋的檔案。

即使 IOBase 因為實作的簽名差異巨大而沒有宣告 read() 或 write() 方法，實作與用戶端應把這些方法視為介面的一部份。此外，當呼叫不被它們支援的操作時，可能會引發 ValueError （或 UnsupportedOperation）例外。

The basic type used for binary data read from or written to a file is bytes. Other bytes-like objects are accepted as method arguments too. Text I/O classes work with str data.

請注意，在一個已經關閉的串流上呼叫任何方法（即使只是查詢）都是未定義的。在這種情況下，實作可能會引發 ValueError 例外。

IOBase (and its subclasses) supports the iterator protocol, meaning that an IOBase object can be iterated over yielding the lines in a stream. Lines are defined slightly differently depending on whether the stream is a binary stream (yielding bytes), or a text stream (yielding character strings). See readline() below.

IOBase 也是個情境管理器，因此支援 with 陳述式。在這個例子中，file 會在 with 陳述式執行完畢後關閉——即使發生了異常。

with open('spam.txt', 'w') as file:
    file.write('Spam and eggs!')

IOBase 提供這些資料屬性與方法：

close()

清除並關閉這個串流。若檔案已經關閉，則此方法沒有作用。一旦檔案被關閉，任何對檔案的操作（例如讀取或寫入）將引發 ValueError 異常。

為了方便起見，允許多次呼叫這個方法；然而，只有第一次呼叫會有效果。

closed

如果串流已關閉，則為 True。

fileno()

如果串流存在，則回傳其底層的檔案描述器（一個整數）。如果 IO 物件不使用檔案描述器，則會引發一個 OSError 例外。

flush()

如果適用，清空串流的寫入緩衝區。對於唯讀和非阻塞串流，此操作不會執行任何操作。

isatty()

如果串流是互動式的（即連接到終端機/tty 設備），則回傳 True。

readable()

如果串流可以被讀取，則回傳 True。如果是 False，read() 將會引發 OSError 例外。

readline(size=-1, /)

從串流讀取並回傳一行。如果指定了 size，則最多讀取 size 個位元組。

對於二進位檔案，行結束符總是 b'\n'；對於文字檔案，可以使用 open() 函式的 newline 引數來選擇識別的行結束符號。

readlines(hint=-1, /)

從串流讀取並回傳一個含有一或多行的 list。可以指定 hint 來控制讀取的行數：如果到目前為止所有行的總大小（以位元組/字元計）超過 hint，則不會再讀取更多行。

hint 值為 0 或更小，以及 None，都被視為沒有提供 hint。

請注意，已經可以使用 for line in file: ... 在檔案物件上進行疊代，而不一定需要呼叫 file.readlines()。

seek(offset, whence=os.SEEK_SET, /)

將串流位置改變到給定的位元組 offset，此位置是相對於由 whence 指示的位置解釋的，並回傳新的絕對位置。whence 的值可為：

os.SEEK_SET 或 0 -- 串流的起點（預設值）；offset 應為零或正數

os.SEEK_CUR 或 1 -- 目前串流位置；offset 可以是負數

os.SEEK_END 或 2 -- 串流的結尾；offset 通常是負數

在 3.1 版被加入: SEEK_* 常數。

在 3.3 版被加入: 某些作業系統可以支援額外的值，例如 os.SEEK_HOLE 或 os.SEEK_DATA。檔案的合法值取決於它是以文字模式還是二進位模式開啟。

seekable()

如果串流支援隨機存取，則回傳 True。如果是 False，則 seek()、tell() 和 truncate() 會引發 OSError。

tell()

回傳目前串流的位置。

truncate(size=None, /)

將串流的大小調整為指定的 size 位元組（如果沒有指定 size，則調整為目前位置）。目前串流位置不會改變。這種調整可以擴展或縮減目前檔案大小。在擴展的情況下，新檔案區域的內容取決於平台（在大多數系統上，額外的位元組會被填充為零）。回傳新的檔案大小。

在 3.5 版的變更: Windows 現在在擴展時會對檔案進行零填充 (zero-fill)。

writable()

如果串流支援寫入，則回傳 True。如果是 False，write() 和 truncate() 將會引發 OSError。

writelines(lines, /)

將一個包含每一行的 list 寫入串流。這不會新增行分隔符號，因此通常提供的每一行末尾都有一個行分隔符號。

__del__()

為物件銷毀做準備。IOBase 提供了這個方法的預設實作，該實作會呼叫實例的 close() 方法。

class io.RawIOBase

原始二進位串流的基底類別。它繼承自 IOBase。

原始二進位串流通常提供對底層作業系統設備或 API 的低階存取，並不嘗試將其封裝在高階基元 (primitive) 中（這項功能在緩衝二進位串流和文字串流中的更高階層級完成，後面的頁面會有描述）。

RawIOBase 除了 IOBase 的方法外，還提供以下這些方法：

read(size=-1, /)

從物件中讀取最多 size 個位元組並回傳。方便起見，如果 size 未指定或為 -1，則回傳直到檔案結尾 (EOF) 的所有位元組。否則，只會進行一次系統呼叫。如果作業系統呼叫回傳的位元組少於 size，則可能回傳少於 size 的位元組。

如果回傳了 0 位元組，且 size 不是 0，這表示檔案結尾 (end of file)。如果物件處於非阻塞模式且沒有可用的位元組，則回傳 None。

預設的實作會遵守 readall() 和 readinto() 的實作。

readall()

讀取並回傳串流中直到檔案結尾的所有位元組，必要時使用多次對串流的呼叫。

readinto(b, /)

將位元組讀入一個預先分配的、可寫的 bytes-like object （類位元組物件） b 中，並回傳讀取的位元組數量。例如，b 可能是一個 bytearray。如果物件處於非阻塞模式且沒有可用的位元組，則回傳 None。

write(b, /)

將給定的 bytes-like object （類位元組物件），b，寫入底層的原始串流，並回傳寫入的位元組大小。根據底層原始串流的具體情況，這可能少於 b 的位元組長度，尤其是當它處於非阻塞模式時。如果原始串流設置為非阻塞且無法立即寫入任何單一位元組，則回傳 None。呼叫者在此方法回傳後可以釋放或變更 b，因此實作應該只在方法呼叫期間存取 b。

class io.BufferedIOBase

支援某種緩衝的二進位串流的基底類別。它繼承自 IOBase。

與 RawIOBase 的主要差異在於，read()、readinto() 及 write() 方法將分別嘗試讀取所請求的盡可能多的輸入，或發出所有提供的資料。

In addition, if the underlying raw stream is in non-blocking mode, when the system returns would block write() will raise BlockingIOError with BlockingIOError.characters_written and read() will return data read so far or None if no data is available.

此外，read() 方法不存在一個遵從 readinto() 的預設實作。

一個典型的 BufferedIOBase 實作不應該繼承自一個 RawIOBase 的實作，而是應該改用包裝的方式，像 BufferedWriter 和 BufferedReader 那樣的作法。

BufferedIOBase 除了提供或覆寫來自 IOBase 的資料屬性和方法以外，還包含了這些：

raw

底層的原始串流（一個 RawIOBase 實例），BufferedIOBase 處理的對象。這不是 BufferedIOBase API 的一部分，且在某些實作可能不存在。

detach()

將底層的原始串流從緩衝區中分離出來，並回傳它。

在原始串流被分離後，緩衝區處於一個不可用的狀態。

某些緩衝區，如 BytesIO，沒有單一原始串流的概念可從此方法回傳。它們會引發 UnsupportedOperation。

在 3.1 版被加入.

read(size=-1, /)

讀取並回傳最多 size 個位元組。如果引數被省略、為 None 或為負值，將讀取盡可能最多的位元組。

Fewer bytes may be returned than requested. An empty bytes object is returned if the stream is already at EOF. More than one read may be made and calls may be retried if specific errors are encountered, see os.read() and PEP 475 [https://peps.python.org/pep-0475/] for more details. Less than size bytes being returned does not imply that EOF is imminent.

When reading as much as possible the default implementation will use raw.readall if available (which should implement RawIOBase.readall()), otherwise will read in a loop until read returns None, an empty bytes, or a non-retryable error. For most streams this is to EOF, but for non-blocking streams more data may become available.

備註

When the underlying raw stream is non-blocking, implementations may either raise BlockingIOError or return None if no data is available. io implementations return None.

read1(size=-1, /)

Read and return up to size bytes, calling readinto() which may retry if EINTR is encountered per PEP 475 [https://peps.python.org/pep-0475/]. If size is -1 or not provided, the implementation will choose an arbitrary value for size.

備註

When the underlying raw stream is non-blocking, implementations may either raise BlockingIOError or return None if no data is available. io implementations return None.

readinto(b, /)

讀取位元組到一個預先分配的、可寫的 bytes-like object b 當中，並回傳讀取的位元組數量。例如，b 可能是一個 bytearray。

類似於 read()，除非後者是互動式的，否則可能會對底層原始串流發出多次讀取。

如果底層原始串流處於非阻塞模式，且目前沒有可用資料，則會引發 BlockingIOError。

readinto1(b, /)

讀取位元組到一個預先分配的、可寫的 bytes-like object b 中，最多呼叫一次底層原始串流的 read() （或 readinto()）方法。此方法回傳讀取的位元組數量。

如果底層原始串流處於非阻塞模式，且目前沒有可用資料，則會引發 BlockingIOError。

在 3.5 版被加入.

write(b, /)

寫入給定的 bytes-like object，b，並回傳寫入的位元組數量（總是等於 b 的長度，以位元組計，因為如果寫入失敗將會引發 OSError）。根據實際的實作，這些位元組可能會立即寫入底層串流，或出於性能和延遲的緣故而被留在緩衝區當中。

當處於非阻塞模式時，如果需要將資料寫入原始串流，但它無法接受所有資料而不阻塞，則會引發 BlockingIOError。

呼叫者可以在此方法回傳後釋放或變更 b，因此實作應該僅在方法呼叫期間存取 b。

原始檔案 I/O

class io.FileIO(name, mode='r', closefd=True, opener=None)

一個代表包含位元組資料的 OS 層級檔案的原始二進制串流。它繼承自 RawIOBase。

name 可以是兩種事物之一：

代表將要打開的檔案路徑的一個字元串或 bytes 物件。在這種情況下，closefd 必須是 True （預設值），否則將引發錯誤。

an integer representing the number of an existing OS-level file descriptor to which the resulting FileIO object will give access. When the FileIO object is closed this fd will be closed as well, unless closefd is set to False.

The mode can be 'r', 'w', 'x' or 'a' for reading (default), writing, exclusive creation or appending. The file will be created if it doesn't exist when opened for writing or appending; it will be truncated when opened for writing. FileExistsError will be raised if it already exists when opened for creating. Opening a file for creating implies writing, so this mode behaves in a similar way to 'w'. Add a '+' to the mode to allow simultaneous reading and writing.

The read() (when called with a positive argument), readinto() and write() methods on this class will only make one system call.

A custom opener can be used by passing a callable as opener. The underlying file descriptor for the file object is then obtained by calling opener with (name, flags). opener must return an open file descriptor (passing os.open as opener results in functionality similar to passing None).

The newly created file is non-inheritable.

See the open() built-in function for examples on using the opener parameter.

在 3.3 版的變更: The opener parameter was added. The 'x' mode was added.

在 3.4 版的變更: The file is now non-inheritable.

FileIO provides these data attributes in addition to those from RawIOBase and IOBase:

mode

The mode as given in the constructor.

name

The file name. This is the file descriptor of the file when no name is given in the constructor.

Buffered Streams

Buffered I/O streams provide a higher-level interface to an I/O device than raw I/O does.

class io.BytesIO(initial_bytes=b'')

A binary stream using an in-memory bytes buffer. It inherits from BufferedIOBase. The buffer is discarded when the close() method is called.

The optional argument initial_bytes is a bytes-like object that contains initial data.

BytesIO provides or overrides these methods in addition to those from BufferedIOBase and IOBase:

getbuffer()

Return a readable and writable view over the contents of the buffer without copying them. Also, mutating the view will transparently update the contents of the buffer:

>>> b = io.BytesIO(b"abcdef")
>>> view = b.getbuffer()
>>> view[2:4] = b"56"
>>> b.getvalue()
b'ab56ef'

備註

As long as the view exists, the BytesIO object cannot be resized or closed.

在 3.2 版被加入.

getvalue()

Return bytes containing the entire contents of the buffer.

read1(size=-1, /)

In BytesIO, this is the same as read().

在 3.7 版的變更: The size argument is now optional.

readinto1(b, /)

In BytesIO, this is the same as readinto().

在 3.5 版被加入.

class io.BufferedReader(raw, buffer_size=DEFAULT_BUFFER_SIZE)

A buffered binary stream providing higher-level access to a readable, non seekable RawIOBase raw binary stream. It inherits from BufferedIOBase.

When reading data from this object, a larger amount of data may be requested from the underlying raw stream, and kept in an internal buffer. The buffered data can then be returned directly on subsequent reads.

The constructor creates a BufferedReader for the given readable raw stream and buffer_size. If buffer_size is omitted, DEFAULT_BUFFER_SIZE is used.

BufferedReader provides or overrides these methods in addition to those from BufferedIOBase and IOBase:

peek(size=0, /)

Return bytes from the stream without advancing the position. The number of bytes returned may be less or more than requested. If the underlying raw stream is non-blocking and the operation would block, returns empty bytes.

read(size=-1, /)

In BufferedReader this is the same as io.BufferedIOBase.read()

read1(size=-1, /)

In BufferedReader this is the same as io.BufferedIOBase.read1()

在 3.7 版的變更: The size argument is now optional.

class io.BufferedWriter(raw, buffer_size=DEFAULT_BUFFER_SIZE)

A buffered binary stream providing higher-level access to a writeable, non seekable RawIOBase raw binary stream. It inherits from BufferedIOBase.

When writing to this object, data is normally placed into an internal buffer. The buffer will be written out to the underlying RawIOBase object under various conditions, including:

when the buffer gets too small for all pending data;

when flush() is called;

when a seek() is requested (for BufferedRandom objects);

when the BufferedWriter object is closed or destroyed.

The constructor creates a BufferedWriter for the given writeable raw stream. If the buffer_size is not given, it defaults to DEFAULT_BUFFER_SIZE.

BufferedWriter provides or overrides these methods in addition to those from BufferedIOBase and IOBase:

flush()

Force bytes held in the buffer into the raw stream. A BlockingIOError should be raised if the raw stream blocks.

write(b, /)

Write the bytes-like object, b, and return the number of bytes written. When in non-blocking mode, a BlockingIOError with BlockingIOError.characters_written set is raised if the buffer needs to be written out but the raw stream blocks.

class io.BufferedRandom(raw, buffer_size=DEFAULT_BUFFER_SIZE)

A buffered binary stream providing higher-level access to a seekable RawIOBase raw binary stream. It inherits from BufferedReader and BufferedWriter.

The constructor creates a reader and writer for a seekable raw stream, given in the first argument. If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE.

BufferedRandom is capable of anything BufferedReader or BufferedWriter can do. In addition, seek() and tell() are guaranteed to be implemented.

class io.BufferedRWPair(reader, writer, buffer_size=DEFAULT_BUFFER_SIZE, /)

A buffered binary stream providing higher-level access to two non seekable RawIOBase raw binary streams---one readable, the other writeable. It inherits from BufferedIOBase.

reader and writer are RawIOBase objects that are readable and writeable respectively. If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE.

BufferedRWPair implements all of BufferedIOBase's methods except for detach(), which raises UnsupportedOperation.

警告

BufferedRWPair does not attempt to synchronize accesses to its underlying raw streams. You should not pass it the same object as reader and writer; use BufferedRandom instead.

文字 I/O

class io.TextIOBase

Base class for text streams. This class provides a character and line based interface to stream I/O. It inherits from IOBase.

TextIOBase provides or overrides these data attributes and methods in addition to those from IOBase:

encoding

The name of the encoding used to decode the stream's bytes into strings, and to encode strings into bytes.

errors

The error setting of the decoder or encoder.

newlines

A string, a tuple of strings, or None, indicating the newlines translated so far. Depending on the implementation and the initial constructor flags, this may not be available.

buffer

底層的二進位緩衝（一個 BufferedIOBase 或 RawIOBase 實例），為 TextIOBase 處理的對象。這不是 TextIOBase API 的一部分，且在某些實作可能不存在。

detach()

Separate the underlying binary buffer from the TextIOBase and return it.

After the underlying buffer has been detached, the TextIOBase is in an unusable state.

Some TextIOBase implementations, like StringIO, may not have the concept of an underlying buffer and calling this method will raise UnsupportedOperation.

在 3.1 版被加入.

read(size=-1, /)

Read and return at most size characters from the stream as a single str. If size is negative or None, reads until EOF.

readline(size=-1, /)

Read until newline or EOF and return a single str. If the stream is already at EOF, an empty string is returned.

If size is specified, at most size characters will be read.

seek(offset, whence=SEEK_SET, /)

Change the stream position to the given offset. Behaviour depends on the whence parameter. The default value for whence is SEEK_SET.

SEEK_SET or 0: seek from the start of the stream (the default); offset must either be a number returned by TextIOBase.tell(), or zero. Any other offset value produces undefined behaviour.

SEEK_CUR or 1: "seek" to the current position; offset must be zero, which is a no-operation (all other values are unsupported).

SEEK_END or 2: seek to the end of the stream; offset must be zero (all other values are unsupported).

Return the new absolute position as an opaque number.

在 3.1 版被加入: SEEK_* 常數。

tell()

Return the current stream position as an opaque number. The number does not usually represent a number of bytes in the underlying binary storage.

write(s, /)

Write the string s to the stream and return the number of characters written.

class io.TextIOWrapper(buffer, encoding=None, errors=None, newline=None, line_buffering=False, write_through=False)

A buffered text stream providing higher-level access to a BufferedIOBase buffered binary stream. It inherits from TextIOBase.

encoding gives the name of the encoding that the stream will be decoded or encoded with. In UTF-8 Mode, this defaults to UTF-8. Otherwise, it defaults to locale.getencoding(). encoding="locale" can be used to specify the current locale's encoding explicitly. See 文字編碼 for more information.

errors is an optional string that specifies how encoding and decoding errors are to be handled. Pass 'strict' to raise a ValueError exception if there is an encoding error (the default of None has the same effect), or pass 'ignore' to ignore errors. (Note that ignoring encoding errors can lead to data loss.) 'replace' causes a replacement marker (such as '?') to be inserted where there is malformed data. 'backslashreplace' causes malformed data to be replaced by a backslashed escape sequence. When writing, 'xmlcharrefreplace' (replace with the appropriate XML character reference) or 'namereplace' (replace with \N{...} escape sequences) can be used. Any other error handling name that has been registered with codecs.register_error() is also valid.

newline controls how line endings are handled. It can be None, '', '\n', '\r', and '\r\n'. It works as follows:

When reading input from the stream, if newline is None, universal newlines mode is enabled. Lines in the input can end in '\n', '\r', or '\r\n', and these are translated into '\n' before being returned to the caller. If newline is '', universal newlines mode is enabled, but line endings are returned to the caller untranslated. If newline has any of the other legal values, input lines are only terminated by the given string, and the line ending is returned to the caller untranslated.

When writing output to the stream, if newline is None, any '\n' characters written are translated to the system default line separator, os.linesep. If newline is '' or '\n', no translation takes place. If newline is any of the other legal values, any '\n' characters written are translated to the given string.

If line_buffering is True, flush() is implied when a call to write contains a newline character or a carriage return.

If write_through is True, calls to write() are guaranteed not to be buffered: any data written on the TextIOWrapper object is immediately handled to its underlying binary buffer.

在 3.3 版的變更: The write_through argument has been added.

在 3.3 版的變更: The default encoding is now locale.getpreferredencoding(False) instead of locale.getpreferredencoding(). Don't change temporary the locale encoding using locale.setlocale(), use the current locale encoding instead of the user preferred encoding.

在 3.10 版的變更: The encoding argument now supports the "locale" dummy encoding name.

備註

When the underlying raw stream is non-blocking, a BlockingIOError may be raised if a read operation cannot be completed immediately.

TextIOWrapper provides these data attributes and methods in addition to those from TextIOBase and IOBase:

line_buffering

Whether line buffering is enabled.

write_through

Whether writes are passed immediately to the underlying binary buffer.

在 3.7 版被加入.

reconfigure(*, encoding=None, errors=None, newline=None, line_buffering=None, write_through=None)

Reconfigure this text stream using new settings for encoding, errors, newline, line_buffering and write_through.

Parameters not specified keep current settings, except errors='strict' is used when encoding is specified but errors is not specified.

It is not possible to change the encoding or newline if some data has already been read from the stream. On the other hand, changing encoding after write is possible.

This method does an implicit stream flush before setting the new parameters.

在 3.7 版被加入.

在 3.11 版的變更: The method supports encoding="locale" option.

seek(cookie, whence=os.SEEK_SET, /)

Set the stream position. Return the new stream position as an int.

Four operations are supported, given by the following argument combinations:

seek(0, SEEK_SET): Rewind to the start of the stream.

seek(cookie, SEEK_SET): Restore a previous position; cookie must be a number returned by tell().

seek(0, SEEK_END): Fast-forward to the end of the stream.

seek(0, SEEK_CUR): Leave the current stream position unchanged.

Any other argument combinations are invalid, and may raise exceptions.

也參考

os.SEEK_SET、os.SEEK_CUR 以及 os.SEEK_END。

tell()

Return the stream position as an opaque number. The return value of tell() can be given as input to seek(), to restore a previous stream position.

class io.StringIO(initial_value='', newline='\n')

A text stream using an in-memory text buffer. It inherits from TextIOBase.

The text buffer is discarded when the close() method is called.

The initial value of the buffer can be set by providing initial_value. If newline translation is enabled, newlines will be encoded as if by write(). The stream is positioned at the start of the buffer which emulates opening an existing file in a w+ mode, making it ready for an immediate write from the beginning or for a write that would overwrite the initial value. To emulate opening a file in an a+ mode ready for appending, use f.seek(0, io.SEEK_END) to reposition the stream at the end of the buffer.

The newline argument works like that of TextIOWrapper, except that when writing output to the stream, if newline is None, newlines are written as \n on all platforms.

StringIO provides this method in addition to those from TextIOBase and IOBase:

getvalue()

Return a str containing the entire contents of the buffer. Newlines are decoded as if by read(), although the stream position is not changed.

使用範例：

import io

output = io.StringIO()
output.write('First line.\n')
print('Second line.', file=output)

# Retrieve file contents -- this will be
# 'First line.\nSecond line.\n'
contents = output.getvalue()

# Close object and discard memory buffer --
# .getvalue() will now raise an exception.
output.close()

class io.IncrementalNewlineDecoder

A helper codec that decodes newlines for universal newlines mode. It inherits from codecs.IncrementalDecoder.

Static Typing

The following protocols can be used for annotating function and method arguments for simple stream reading or writing operations. They are decorated with @typing.runtime_checkable.

class io.Reader[T]

Generic protocol for reading from a file or other input stream. T will usually be str or bytes, but can be any type that is read from the stream.

在 3.14 版被加入.

read()

read(size, /)

Read data from the input stream and return it. If size is specified, it should be an integer, and at most size items (bytes/characters) will be read.

例如：

def read_it(reader: Reader[str]):
    data = reader.read(11)
    assert isinstance(data, str)

class io.Writer[T]

Generic protocol for writing to a file or other output stream. T will usually be str or bytes, but can be any type that can be written to the stream.

在 3.14 版被加入.

write(data, /)

Write data to the output stream and return the number of items (bytes/characters) written.

例如：

def write_binary(writer: Writer[bytes]):
    writer.write(b"Hello world!\n")

See ABCs and Protocols for working with I/O for other I/O related protocols and classes that can be used for static type checking.

Performance

This section discusses the performance of the provided concrete I/O implementations.

二進位 (Binary) I/O

By reading and writing only large chunks of data even when the user asks for a single byte, buffered I/O hides any inefficiency in calling and executing the operating system's unbuffered I/O routines. The gain depends on the OS and the kind of I/O which is performed. For example, on some modern OSes such as Linux, unbuffered disk I/O can be as fast as buffered I/O. The bottom line, however, is that buffered I/O offers predictable performance regardless of the platform and the backing device. Therefore, it is almost always preferable to use buffered I/O rather than unbuffered I/O for binary data.

文字 I/O

Text I/O over a binary storage (such as a file) is significantly slower than binary I/O over the same storage, because it requires conversions between unicode and binary data using a character codec. This can become noticeable handling huge amounts of text data like large log files. Also, tell() and seek() are both quite slow due to the reconstruction algorithm used.

StringIO, however, is a native in-memory unicode container and will exhibit similar speed to BytesIO.

Multi-threading

FileIO objects are thread-safe to the extent that the operating system calls (such as read(2) [https://manpages.debian.org/read(2)] under Unix) they wrap are thread-safe too.

Binary buffered objects (instances of BufferedReader, BufferedWriter, BufferedRandom and BufferedRWPair) protect their internal structures using a lock; it is therefore safe to call them from multiple threads at once.

TextIOWrapper 物件不是執行緒安全的。

Reentrancy

Binary buffered objects (instances of BufferedReader, BufferedWriter, BufferedRandom and BufferedRWPair) are not reentrant. While reentrant calls will not happen in normal situations, they can arise from doing I/O in a signal handler. If a thread tries to re-enter a buffered object which it is already accessing, a RuntimeError is raised. Note this doesn't prohibit a different thread from entering the buffered object.

The above implicitly extends to text files, since the open() function will wrap a buffered object inside a TextIOWrapper. This includes standard streams and therefore affects the built-in print() function as well.

time --- 時間存取與轉換

這個模組提供了各種與時間相關的函式。若要查看相關功能，請參閱 datetime 和 calendar 模組。

雖然這個模組隨時可用，但並非所有函式在所有平台上都可用。這個模組中定義的大多數函式都會呼叫 C 語言平台的函式庫中具有相同名稱的函式。由於這些函式的語義因平台而異，所以偶爾查閱平台文件可能會有所幫助。

以下是對一些術語和慣例的說明。

epoch 是起始的時間點，即 time.gmtime(0) 的回傳值。在所有平台上，它是 1970 年 1 月 1 日，00:00:00（UTC）。

術語 seconds since the epoch（紀元秒數） 是指從 epoch（紀元）開始經過的總秒數，通常不包括 leap seconds [https://en.wikipedia.org/wiki/Leap_second]。在所有符合 POSIX 標準的平台上，leap seconds （閏秒）都不計入這個總數。

這個模組中的函式可能無法處理 epoch 之前或遙遠未來的日期和時間。未來的臨界點由 C 函式庫決定；對於 32 位元系統來說通常是在 2038 年。

函式 strptime() 在給定 %y 格式碼時可以剖析 (parse) 兩位數的年份。當剖析兩位數的年份時，它們會根據 POSIX 和 ISO C 標準進行轉換：69--99 的值對映到 1969--1999，0--68 的值對映到 2000--2068。

UTC is Coordinated Universal Time [https://en.wikipedia.org/wiki/Coordinated_Universal_Time] and superseded Greenwich Mean Time [https://en.wikipedia.org/wiki/Greenwich_Mean_Time] or GMT as the basis of international timekeeping. The acronym UTC is not a mistake but conforms to an earlier, language-agnostic naming scheme for time standards such as UT0, UT1, and UT2.

DST 是 Daylight Saving Time（日光節約時間），一年中的某些時段（通常）將會時區調整一小時。DST 的規則是根據當地法律決定的，且可能每年不同。C 函式庫有一個包含當地規則的表（通常會為了靈活性而從系統文件中讀取），在這方面是唯一的真正依據。

各種即時 (real-time) 函式的精確度可能低於其值或引數所表示的單位所建議的精確度。例如，在大多數 Unix 系統上，時鐘每秒只「跳」50 次或 100 次。

另一方面，time() 和 sleep() 的精確度比它們的在 Unix 的等效函式更高：時間以浮點數表示，time() 回傳最精確的可用時間（如果可以會使用 Unix 的 gettimeofday()），而 sleep() 可以接受帶有非零分數的時間（如果可以會使用 Unix 的 select() 來實作）。

由 gmtime()、localtime() 和 strptime() 回傳，並由 asctime()、mktime() 和 strftime() 接受的時間值，是一個 9 個整數的序列。gmtime()、localtime() 和 strptime() 的回傳值也為各個欄位提供屬性名稱。

關於這些物件的敘述請見 struct_time。

在 3.3 版的變更: 當平台支援對應的 struct tm 成員時，struct_time 型別被擴展以提供 tm_gmtoff 和 tm_zone 屬性。

在 3.6 版的變更: struct_time 的屬性 tm_gmtoff 和 tm_zone 現在在所有平台上都可用。

使用以下函式在時間表示之間進行轉換：

轉換來源

轉換目標

使用

紀元秒數

世界協調時間的 struct_time

gmtime()

紀元秒數

本地時間的 struct_time

localtime()

世界協調時間的 struct_time

紀元秒數

calendar.timegm()

本地時間的 struct_time

紀元秒數

mktime()

函式

time.asctime([t])

將由 gmtime() 或 localtime() 回傳的元組或 struct_time 表示的時間轉換為以下格式的字串：'Sun Jun 20 23:21:05 1993'。日期欄位為兩個字元長，如果日期是個位數，則用空格填充，例如：'Wed Jun  9 04:26:40 1993'。

如果沒有提供 t，則使用由 localtime() 回傳的目前時間。asctime() 不使用區域資訊。

備註

與同名的 C 函式不同，asctime() 不會添加結尾的換行字元。

time.pthread_getcpuclockid(thread_id)

為指定的 thread_id 回傳執行緒專用 CPU-time 時鐘的 clk_id。

使用 threading.get_ident() 或 threading.Thread 物件的 ident 屬性來取得適用於 thread_id 的值。

警告

傳遞無效或過期的 thread_id 可能會導致未定義的行為，例如分段錯誤 (segmentation fault)。

可用性: Unix

若需更多資訊，請參閱 pthread_getcpuclockid(3) [https://manpages.debian.org/pthread_getcpuclockid(3)] 的說明文件。

在 3.7 版被加入.

time.clock_getres(clk_id)

回傳指定時鐘 clk_id 的解析度（精確度）。有關 clk_id 可接受的值的串列，請參閱 時鐘 ID 常數。

可用性: Unix.

在 3.3 版被加入.

time.clock_gettime(clk_id) → float

回傳指定時鐘 clk_id 的時間。有關 clk_id 可接受的值的串列，請參閱 時鐘 ID 常數。

使用 clock_gettime_ns() 以避免 float 型別造成的精確度損失。

可用性: Unix.

在 3.3 版被加入.

time.clock_gettime_ns(clk_id) → int

類似於 clock_gettime()，但回傳以奈秒 (nanoseconds) 為單位的時間。

可用性: Unix.

在 3.7 版被加入.

time.clock_settime(clk_id, time: float)

設定指定時鐘 clk_id 的時間。目前，CLOCK_REALTIME 是 clk_id 唯一可以接受的值。

使用 clock_settime_ns() 以避免 float 型別造成的精確度損失。

可用性: Unix, not Android, not iOS.

在 3.3 版被加入.

time.clock_settime_ns(clk_id, time: int)

類似於 clock_settime()，但設定以奈秒為單位的時間。

可用性: Unix, not Android, not iOS.

在 3.7 版被加入.

time.ctime([secs])

將自 epoch 起以秒表示的時間轉換為表示當地時間且符合以下格式的字串：'Sun Jun 20 23:21:05 1993'。日期欄位為兩個字元長，如果日期是個位數，則用空格填充，例如：'Wed Jun  9 04:26:40 1993'。

如果未提供 secs 或其為 None，則使用由 time() 回傳的目前時間。ctime(secs) 等同於 asctime(localtime(secs))。ctime() 不使用區域資訊。

time.get_clock_info(name)

取得指定時鐘的資訊作為命名空間物件。支援的時鐘名稱及讀取他們的值的對應函式如下：

'monotonic'：time.monotonic()

'perf_counter'：time.perf_counter()

'process_time'：time.process_time()

'thread_time'：time.thread_time()

'time'：time.time()

其結果具有以下屬性：

adjustable: 如果時鐘可以設定為向前或向後跳轉時間則為 True，否則為 False。不指漸進式的 NTP 速率調整。

implementation: 用於取得時鐘的值的底層 C 函式名稱。有關可能的值，請參閱 時鐘 ID 常數。

monotonic: 如果時鐘不能倒轉，則為 True，否則為 False

resolution: 以秒 (float) 為單位的時鐘的解析度

在 3.3 版被加入.

time.gmtime([secs])

將自 epoch 起以秒表示的時間轉換為 UTC 中的 struct_time，其中 dst 旗標始終為零。如果未提供 secs 或其為 None，則使用由 time() 回傳的目前時間。忽略秒的分數部分。關於 struct_time 物件的描述，請參閱上文。此函式的反運算請參閱 calendar.timegm()。

time.localtime([secs])

類似於 gmtime()，但轉換為當地時間。如果未提供 secs 或其為 None，則使用由 time() 回傳的目前時間。當 DST 適用於給定時間時，dst 旗標會被設定為 1。

如果時間戳超出 C 平台的 localtime() 或 gmtime() 函式支援的範圍，localtime() 可能會引發 OverflowError；在 localtime() 或 gmtime() 失敗時，會引發 OSError。通常會把年份限制在 1970 年到 2038 年之間。

time.mktime(t)

這是 localtime() 的反函式。其引數是表示當地時間（不是 UTC）的 struct_time 或完整的 9 元組（因為需要 dst 旗標；如果 dst 為未知，則使用 -1 作為 dst 旗標）。它回傳一個浮點數，以與 time() 相容。如果輸入值不能表示為有效時間，將引發 OverflowError 或 ValueError（取決於無效值是被 Python 還是底層 C 函式庫捕獲）。它能生成時間的最早日期根據平台而有所不同。

time.monotonic() → float

回傳單調時鐘（monotonic clock，即不能倒轉的時鐘）的值（以帶有小數的秒數表示）。該時鐘不受系統時鐘更新的影響。回傳值的參考點沒有定義，因此只有兩次呼叫結果之間的差異才是有效的。

時鐘：

在 Windows 上，呼叫 QueryPerformanceCounter() 和 QueryPerformanceFrequency()。

在 macOS 上，呼叫 mach_absolute_time() 和 mach_timebase_info()。

在 HP-UX 上，呼叫 gethrtime()。

如果可以的話，呼叫 clock_gettime(CLOCK_HIGHRES)。

否則，呼叫 clock_gettime(CLOCK_MONOTONIC)。

使用 monotonic_ns() 以避免 float 型別造成的精確度損失。

在 3.3 版被加入.

在 3.5 版的變更: 此函式現在始終可用且時鐘對於所有行程都會是相同。

在 3.10 版的變更: 在 macOS 上，時鐘對於所有行程都會是相同。

time.monotonic_ns() → int

類似於 monotonic()，但回傳以奈秒為單位的時間。

在 3.7 版被加入.

time.perf_counter() → float

回傳性能計數器的值（以帶有小數的秒數表示），即具有最高可用解析度來測量短時間間隔的時鐘。它包括睡眠時經過的時間，且時鐘對於所有行程都會是相同。回傳值的參考點沒有定義，因此只有兩次呼叫結果之間的差異才是有效的。

在 CPython 上，使用與 time.monotonic() 相同的時鐘，且其為單調時鐘（即不能倒轉的時鐘）。

使用 perf_counter_ns() 以避免 float 型別造成的精確度損失。

在 3.3 版被加入.

在 3.10 版的變更: 在 Windows 上，時鐘對於所有行程都會是相同。

在 3.13 版的變更: 使用與 time.monotonic() 相同的時鐘。

time.perf_counter_ns() → int

類似於 perf_counter()，但回傳以奈秒為單位的時間。

在 3.7 版被加入.

time.process_time() → float

回傳目前行程的系統和用戶 CPU 時間之和（以帶有小數的秒數表示）。它不包括睡眠時經過的時間。根據定義，它涵蓋整個行程。回傳值的參考點沒有定義，因此只有兩次呼叫結果之間的差異才是有效的。

使用 process_time_ns() 以避免 float 型別造成的精確度損失。

在 3.3 版被加入.

time.process_time_ns() → int

類似於 process_time()，但回傳以奈秒為單位的時間。

在 3.7 版被加入.

time.sleep(secs)

在一個給定的秒數內暫停呼叫執行緒 (calling thread) 的執行。引數可以是浮點數，以表示更精確的睡眠時間。

如果睡眠被訊號中斷且訊號處理器未引發例外，則睡眠將以重新計算過的逾時 (timeout) 重新開始。

由於系統中其他活動的調度，暫停時間可能會比請求的時間長任意的量。

Windows 實作

在 Windows 上，如果 secs 為零，則執行緒將其剩餘的時間片段讓給任何準備運行的其他執行緒。如果沒有其他執行緒準備運行，該函式將立即回傳，而執行緒會繼續執行。在 Windows 10 及更新的版本中，此實作使用高解析度計時器 [https://learn.microsoft.com/windows/win32/api/synchapi/nf-synchapi-createwaitabletimerexw]，其解析度為 100 奈秒。如果 secs 為零，則使用 Sleep(0)。

Unix 實作

如果可以，使用 clock_nanosleep()（解析度：1 奈秒）；

或者使用 nanosleep()（解析度：1 奈秒）；

或使用 select()（解析度：1 微秒）。

備註

要模擬「無動作 (no-op)」，請使用 pass 而不是 time.sleep(0)。

To voluntarily relinquish the CPU, specify a real-time scheduling policy and use os.sched_yield() instead.

引發一個帶有引數 secs 的稽核事件 (auditing event) time.sleep。

在 3.5 版的變更: 即使睡眠被訊號中斷，此函式現在至少還是會睡眠 secs，除非訊號處理器引發例外（理由請參閱 PEP 475 [https://peps.python.org/pep-0475/]）。

在 3.11 版的變更: 在 Unix 上，如果可以的話現在會使用 clock_nanosleep() 和 nanosleep() 函式。在 Windows 上，現在使用可等待的計時器。

在 3.13 版的變更: 引發一個稽核事件。

time.strftime(format[, t])

將由 gmtime() 或 localtime() 回傳代表時間的一個元組或 struct_time 轉換為由 format 引數指定的字串。如果未提供 t，則使用由 localtime() 回傳的目前時間。format 必須是一個字串。如果 t 中的任何欄位超出允許範圍，將會引發 ValueError。

0 在時間元組中的任何位置都是合法引數；如果元組中出現常見的錯誤，該值將被強制更改為正確的值。

以下指令可以嵌入在 format 字串中。它們顯示時不帶可選的欄位寬度和精度規範，並在 strftime() 的結果中被標示的字元替換：

指令

意義

註解

%a

區域設定的週間日 (weekday) 縮寫名稱。

%A

區域設定的完整週間日名稱。

%b

區域設定的縮寫月份名稱。

%B

區域設定的完整月份名稱。

%c

區域設定的合適的日期和時間的表示法。

%d

月份中的日期，表示為十進位數 [01,31]。

%f

微秒，表示為十進位數

[000000,999999]。

(1)

%H

小時（24 小時制），表示為十進位數 [00,23]。

%I

小時（12 小時制），表示為十進位數 [01,12]。

%j

一年中的第幾天，表示為十進位數 [001,366]。

%m

月份，表示為十進位數 [01,12]。

%M

分鐘，表示為十進位數 [00,59]。

%p

區域設定中相當於 AM 或 PM 的表示。

(2)

%S

秒，表示為十進位數 [00,61]。

(3)

%U

一年中的週數（星期天作為一週的第一天），表示為十進位數 [00,53]。新的一年中，在第一個星期天之前的所有日子都被認定為第 0 週。

(4)

%u

一週中的日期（周一為 1；週日為 7），表示為十進位數 [1,7]。

%w

週間日，表示為十進位數 [0（星期天）,6]。

%W

一年中的週數（星期一作為一週的第一天），表示為十進位數 [00,53]。新的一年中，在第一個星期一之前的所有日子都被認定為第 0 週。

(4)

%x

區域設定的合適的日期表示法。

%X

區域設定的合適的時間表示法。

%y

去掉世紀的年份，表示為十進位數 [00,99]。

%Y

帶世紀的年份，表示為十進位數。

%z

時區偏移量，表示與 UTC/GMT 的正或負時間差，形式為 +HHMM 或 -HHMM，其中 H 代表十進位的小時數碼 (digits)，M 代表十進位的分鐘數碼 [-23:59, +23:59]。 [1]

%Z

時區名稱（如果不存在時區，則無字元）。已被棄用。 [1]

%G

ISO 8601 年（類似於 %Y，但遵循 ISO 8601 日曆年的規則）。年份從包含該日曆年第一個星期四的那一週開始。

%V

ISO 8601 週數（以十進位數表示 [01,53]）。年份的第一週是包含該年第一個星期四的那一週。每週從星期一開始。

%%

字面意義上的 '%' 字元。

註解：

%f 格式的指令僅適用於 strptime()，不適用於 strftime()。然而，在 datetime.datetime.strptime() 和 datetime.datetime.strftime() 其中的 %f 格式的指令適用於微秒。

當與 strptime() 函式一起使用時，%p 指令僅在使用 %I 指令剖析小時時影響輸出小時的欄位。

範圍確實是從 0 到 61；數值 60 在表示 leap seconds [https://en.wikipedia.org/wiki/Leap_second] 的時間戳中是有效的，而數值 61 是出於歷史因素而被支援。

當與 strptime() 函式一起使用時，%U 和 %W 僅在指定週間的某天和年份時用於計算中。

以下是一個範例，其為一種與 RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] 網際網路電子郵件標準中指定的日期格式兼容的格式。 [1]：

>>> from time import gmtime, strftime
>>> strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime())
'Thu, 28 Jun 2001 14:17:15 +0000'

某些平台可能支援額外的指令，但只有這裡列出的指令具有 ANSI C 標準化的意義。要查看你的平台上支援的完整格式碼集，請參閱 strftime(3) [https://manpages.debian.org/strftime(3)] 文件。

在某些平台上，可選的欄位寬度和精度規範可以以此順序緊跟在指令初始的 '%' 之後；這也是不可攜 (portable) 的。欄位寬度通常為 2，除了 %j 為 3。

time.strptime(string[, format])

根據格式剖析表示時間的字串。回傳值是 struct_time，如同由 gmtime() 或 localtime() 回傳的一樣。

format 參數使用與 strftime() 相同的指令；預設為 "%a %b %d %H:%M:%S %Y"，與 ctime() 回傳的格式匹配。如果 string 無法根據 format 解析，或剖析後有多餘的資料，將引發 ValueError。當無法推斷更精確的值時，用來填充任何缺失資料的預設值為 (1900, 1, 1, 0, 0, 0, 0, 1, -1)。string 和 format 都必須是字串。

例如：

>>> import time
>>> time.strptime("30 Nov 00", "%d %b %y")
time.struct_time(tm_year=2000, tm_mon=11, tm_mday=30, tm_hour=0, tm_min=0,
                 tm_sec=0, tm_wday=3, tm_yday=335, tm_isdst=-1)

對 %Z 指令的支援基於 tzname 中包含的值以及 daylight 是否為 true。因此，除了識別始終已知的 UTC 和 GMT（且被考慮為非日光節約時區）外，這是特定於平台的。

僅支援文件中指定的指令。由於 strftime() 是根據每個平台實作的，有時它可以提供比列出的還要更多的指令。但是 strptime() 與任何平台無關，因此不一定支援所有未記載為支援的指令。

class time.struct_time

由 gmtime()、localtime() 和 strptime() 回傳的時間值序列的型別。它是一個具有 named tuple 介面的物件：值可以透過索引和屬性名稱存取。包含以下值：

索引

屬性

值

0

tm_year

（例如 1993）

1

tm_mon

範圍 [1, 12]

2

tm_mday

範圍 [1, 31]

3

tm_hour

範圍 [0, 23]

4

tm_min

範圍 [0, 59]

5

tm_sec

範圍 [0, 61]；參見 strftime() 中的註釋 (2)

6

tm_wday

範圍 [0, 6]；星期一是 0

7

tm_yday

範圍 [1, 366]

8

tm_isdst

0、1 或 -1；見下文

N/A

tm_zone

時區名稱的縮寫

N/A

tm_gmtoff

UTC 向東的偏移量（以秒為單位）

請注意，與 C 結構不同，月份值的範圍是 [1, 12]，而不是 [0, 11]。

在呼叫 mktime() 時，當日光節約時間生效的時候，tm_isdst 可以設定為 1，不生效時設定為 0。值 -1 表示未知是否生效，通常結果會填入正確的狀態。

當一個長度不正確的元組被傳遞給預期得到 struct_time 的函式時，或者其中有元素型別錯誤時，將引發 TypeError。

time.time() → float

回傳自 epoch 起的時間（秒）至今的浮點數。對 leap seconds [https://en.wikipedia.org/wiki/Leap_second] 的處理是與平台有關的。在 Windows 和大多數 Unix 系統上，閏秒不計入自 epoch 起的秒數中。這通常被稱為 Unix 時間 [https://en.wikipedia.org/wiki/Unix_time]。

請注意，即使時間始終作為浮點數回傳，但並非所有系統都提供比 1 秒還更精確的時間。雖然此函式通常回傳非遞減的值，但如果在兩次呼叫之間系統時鐘被回調，則它可能回傳比之前呼叫更小的值。

由 time() 回傳的數字可以透過傳遞給 gmtime() 函式轉換為 UTC 內更常見的時間格式（即年、月、日、小時等）或透過傳遞給 localtime() 函式轉換為當地時間。在這兩種情況下都會回傳一個 struct_time 物件，從中可以作為屬性存取日曆日期的組成部分。

時鐘：

在 Windows 上，呼叫 GetSystemTimePreciseAsFileTime()。

如果可以的話，呼叫 clock_gettime(CLOCK_REALTIME)。

否則，呼叫 gettimeofday()。

使用 time_ns() 以避免 float 型別造成的精確度損失。

在 3.13 版的變更: 在 Windows 上，呼叫 GetSystemTimePreciseAsFileTime() 而不是 GetSystemTimeAsFileTime()。

time.time_ns() → int

類似於 time()，但回傳自 epoch 起的以奈秒為單位的整數。

在 3.7 版被加入.

time.thread_time() → float

回傳目前執行緒的系統和用戶 CPU 時間之和（以帶有小數的秒數表示）。它不包括睡眠期間經過的時間。根據定義，這是執行緒特定 (thread-specific) 的。回傳值的參照點未定義，因此只有同一執行緒中兩次呼叫結果之間的差異才是有效的。

使用 thread_time_ns() 以避免 float 型別造成的精確度損失。

可用性: Linux, Unix, Windows.

有支援 CLOCK_THREAD_CPUTIME_ID 的 Unix 系統。

在 3.7 版被加入.

time.thread_time_ns() → int

類似於 thread_time()，但回傳以奈秒為單位的時間。

在 3.7 版被加入.

time.tzset()

重置函式庫常式 (routine) 使用的時間轉換規則。環境變數 TZ 指定了這一過程的實施方式。它還會設定變數 tzname（來自 TZ 環境變數）、timezone（非日光節約時間的 UTC 以西的時間偏移，單位為秒）、altzone（日光節約時間的 UTC 以西的時間偏移，單位為秒）和 daylight（如果該時區沒有日光節約時間規則，則設定為 0；如果在過去、現在或未來的某個時間有日光節約時間規則，則設置為非零的值）。

可用性: Unix.

備註

雖然在許多情況下，更改 TZ 環境變數可能會在沒有呼叫 tzset() 的情況下影響 localtime() 等函式的輸出，但是這種行為是不該被依賴的。

TZ 環境變數不應包含空格字元。

TZ 環境變數的標準格式為（為了清楚表達，中間增加了空格字元）：

std offset [dst [offset [,start[/time], end[/time]]]]

其中各個組成部分為：

std 和 dst

三個或更多字母與數字 (alphanumerics) 組成的時區縮寫。這些縮寫會被傳播到 time.tzname 中。

offset

偏移量的格式為：± hh[:mm[:ss]]。這表示為達到 UTC 而增加到當地時間的值。如果以 '-' 開頭，則表示該時區位於本初子午線以東；否則，位於其西。如果 dst 之後沒有偏移量，則假定日光時間比標準時間快一小時。

start[/time], end[/time]

表示何時切換至日光節約時間及何時切換回來。開始和結束日期的格式如以下其一：

Jn

儒略日 (Julian day) n（1 <= n <= 365）。閏日不計算，因此在所有年份中，2 月 28 日是第 59 天，3 月 1 日是第 60 天。

n

從 0 開始的儒略日 (0 <= n <= 365)。閏日會計算，因此可以適用至 2 月 29 日。

Mm.n.d

一年中第 m 月的第 n 週的第 d 天（0 <= d <= 6，1 <= n <= 5，1 <= m <= 12，其中 n 為 5 表示「該月的最後一個第 d 天」，這可能出現在第四或第五週）。第 1 週是 d 天首次出現的那一週。第零天為星期天。

time 的格式與 offset 相同，但不允許出現前導符號（'-' 或 '+'）。如果未指定時間，則預設為 02:00:00。

>>> os.environ['TZ'] = 'EST+05EDT,M4.1.0,M10.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'02:07:36 05/08/03 EDT'
>>> os.environ['TZ'] = 'AEST-10AEDT-11,M10.5.0,M3.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'16:08:12 05/08/03 AEST'

在許多 Unix 系統（包括 *BSD、Linux、Solaris 和 Darwin）上，使用系統的 zoneinfo (tzfile(5) [https://manpages.debian.org/tzfile(5)]) 資料庫來指定時區規則會更加方便。要這樣做，請將 TZ 環境變數設定為所需時區資料檔案的路徑，相對於系統 'zoneinfo' 時區資料庫的根目錄，通常位於 /usr/share/zoneinfo。例如，'US/Eastern'、'Australia/Melbourne'、'Egypt' 或 'Europe/Amsterdam'。

>>> os.environ['TZ'] = 'US/Eastern'
>>> time.tzset()
>>> time.tzname
('EST', 'EDT')
>>> os.environ['TZ'] = 'Egypt'
>>> time.tzset()
>>> time.tzname
('EET', 'EEST')

時鐘 ID 常數

這些常數用作 clock_getres() 和 clock_gettime() 的參數。

time.CLOCK_BOOTTIME

與 CLOCK_MONOTONIC 基本相同，不同之處在於它還包括系統暫停的任何時間。

這允許應用程式取得一個能夠感知暫停的單調時鐘，而無需處理 CLOCK_REALTIME 的複雜情況，後者在使用 settimeofday() 或類似函式更改時間時可能會出現不連續的情況。

可用性: Linux >= 2.6.39.

在 3.7 版被加入.

time.CLOCK_HIGHRES

Solaris 作業系統具有 CLOCK_HIGHRES 計時器，它嘗試使用最佳的硬體資源，並可能提供接近奈秒的解析度。CLOCK_HIGHRES 是不可調整且高解析度的時鐘。

可用性: Solaris.

在 3.3 版被加入.

time.CLOCK_MONOTONIC

該時鐘無法被設定，其表示自某個未指定起點以來的單調時間。

可用性: Unix.

在 3.3 版被加入.

time.CLOCK_MONOTONIC_RAW

類似於 CLOCK_MONOTONIC，但提供對基於硬體的原始時間的存取，此時間不受 NTP 調整的影響。

可用性: Linux >= 2.6.28, macOS >= 10.12.

在 3.3 版被加入.

time.CLOCK_MONOTONIC_RAW_APPROX

類似於 CLOCK_MONOTONIC_RAW，但讀取的是系統在情境切換時快取的值，因此精準度較低。

可用性: macOS >= 10.12.

在 3.13 版被加入.

time.CLOCK_PROCESS_CPUTIME_ID

來自 CPU 的高解析度每個行程的計時器。

可用性: Unix.

在 3.3 版被加入.

time.CLOCK_PROF

來自 CPU 的高解析度每個行程的計時器。

可用性: FreeBSD, NetBSD >= 7, OpenBSD.

在 3.7 版被加入.

time.CLOCK_TAI

國際原子時間 [https://www.nist.gov/pml/time-and-frequency-division/how-utcnist-related-coordinated-universal-time-utc-international]

系統必須擁有目前的閏秒表才能給出正確答案。PTP 或 NTP 軟體可以維護閏秒表。

可用性: Linux.

在 3.9 版被加入.

time.CLOCK_THREAD_CPUTIME_ID

執行緒相關的 CPU 時間時鐘。

可用性: Unix.

在 3.3 版被加入.

time.CLOCK_UPTIME

表示系統運作且無暫停的絕對時間，提供包括絕對時間 (absolute) 和時間區間 (interval) 的精確的正常上線時間 (uptime) 測量。

可用性: FreeBSD, OpenBSD >= 5.5.

在 3.7 版被加入.

time.CLOCK_UPTIME_RAW

單調增量的時鐘，從某個任意點開始計時，不受頻率或時間調整影響，並且在系統休眠時不增量。

可用性: macOS >= 10.12.

在 3.8 版被加入.

time.CLOCK_UPTIME_RAW_APPROX

類似於 CLOCK_UPTIME_RAW，但該值在情境切換時由系統快取，因此精準度較低。

可用性: macOS >= 10.12.

在 3.13 版被加入.

以下常數是唯一可以傳遞給 clock_settime() 的參數。

time.CLOCK_REALTIME

即時時鐘。設定此時鐘需要適當的權限。時鐘對於所有行程都會是相同。

可用性: Unix.

在 3.3 版被加入.

時區常數

time.altzone

如果本地 DST 時區有被定義，則此值為本地 DST 時區相對於 UTC 以西的偏移量（以秒為單位）。若本地 DST 時區位於 UTC 以東（例如包括英國在內的西歐），則此值為負值。僅在 daylight 為非零時使用此值。詳情請參見下方註釋。

time.daylight

如果定義了 DST 時區，則為非零值。詳情請參見下方註釋。

time.timezone

本地（非 DST）時區相對於 UTC 以西的偏移量（以秒為單位），西歐大多數地區為負，美國為正，英國為零。詳情請參見下方註釋。

time.tzname

一個包含兩個字串的元組：第一個是本地非 DST 時區的名稱，第二個是本地 DST 時區的名稱。如果沒有定義 DST 時區，則不應使用第二個字串。詳情請參見下方註釋。

備註

對於上述時區常數（altzone、daylight、timezone 和 tzname），其值由模組載入時或 tzset() 最後一次被呼叫時的時區規則決定，且過去的時間可能會不準確。建議使用 localtime() 回傳的 tm_gmtoff 和 tm_zone 來取得時區資訊。

也參考

datetime 模組

更多物件導向的日期和時間介面。

locale 模組

國際化服務。區域設定會影響 strftime() 和 strptime() 中許多格式指定符號 (format specifiers) 的解譯。

calendar 模組

通用的日曆相關函式。timegm() 是本模組中 gmtime() 的反函式。

註腳

[1] (1,2,3)

現在 %Z 已被棄用，%z 藉由擴展為偏好的小時/分鐘偏移而逃離了被棄用的命運，但其並不是被所有 ANSI C 函式庫支援。此外，嚴格按照 1982 年的 RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] 標準，應該使用兩位數年份（%y 而不是 %Y），但實作中在 2000 年之前就已經轉向使用四位數年份。之後，RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] 被淘汰，四位數年份首先由 RFC 1123 [https://datatracker.ietf.org/doc/html/rfc1123.html] 推薦，然後由 RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html] 正式批准，並以 RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] 繼續此需求。

logging --- Python 的日誌記錄工具

原始碼：Lib/logging/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/logging/__init__.py]

Important

此頁面包含 API 參考訊息。有關教學流程和更進階的主題討論，請參閱

基礎教學

進階教學

日誌記錄手冊

這個模組定義了函式與類別 (class)，為應用程式和函式庫實作彈性的日誌管理系統。

由標準函式庫模組提供的日誌記錄 API 的主要好處是，所有的 Python 模組都能參與日誌記錄，因此你的應用程式日誌可以包含你自己的訊息，並與來自第三方模組的訊息整合在一起。

Here's a simple example of idiomatic usage:

# myapp.py
import logging
import mylib
logger = logging.getLogger(__name__)

def main():
    logging.basicConfig(filename='myapp.log', level=logging.INFO)
    logger.info('Started')
    mylib.do_something()
    logger.info('Finished')

if __name__ == '__main__':
    main()

# mylib.py
import logging
logger = logging.getLogger(__name__)

def do_something():
    logger.info('Doing something')

If you run myapp.py, you should see this in myapp.log:

INFO:__main__:Started
INFO:mylib:Doing something
INFO:__main__:Finished

The key feature of this idiomatic usage is that the majority of code is simply creating a module level logger with getLogger(__name__), and using that logger to do any needed logging. This is concise, while allowing downstream code fine-grained control if needed. Logged messages to the module-level logger get forwarded to handlers of loggers in higher-level modules, all the way up to the highest-level logger known as the root logger; this approach is known as hierarchical logging.

For logging to be useful, it needs to be configured: setting the levels and destinations for each logger, potentially changing how specific modules log, often based on command-line arguments or application configuration. In most cases, like the one above, only the root logger needs to be so configured, since all the lower level loggers at module level eventually forward their messages to its handlers. basicConfig() provides a quick way to configure the root logger that handles many use cases.

這個模組提供了很多的功能性以及彈性。如果你對於 logging 不熟悉，熟悉它最好的方法就是去看教學（請看右上方的連結）。

The basic classes defined by the module, together with their attributes and methods, are listed in the sections below.

Loggers expose the interface that application code directly uses.

Handlers send the log records (created by loggers) to the appropriate destination.

Filters provide a finer grained facility for determining which log records to output.

格式器指定日誌記錄在最終輸出中的佈局。

Logger 物件

Loggers have the following attributes and methods. Note that Loggers should NEVER be instantiated directly, but always through the module-level function logging.getLogger(name). Multiple calls to getLogger() with the same name will always return a reference to the same Logger object.

The name is potentially a period-separated hierarchical value, like foo.bar.baz (though it could also be just plain foo, for example). Loggers that are further down in the hierarchical list are children of loggers higher up in the list. For example, given a logger with a name of foo, loggers with names of foo.bar, foo.bar.baz, and foo.bam are all descendants of foo. In addition, all loggers are descendants of the root logger. The logger name hierarchy is analogous to the Python package hierarchy, and identical to it if you organise your loggers on a per-module basis using the recommended construction logging.getLogger(__name__). That's because in a module, __name__ is the module's name in the Python package namespace.

class logging.Logger

name

This is the logger's name, and is the value that was passed to getLogger() to obtain the logger.

備註

此屬性應被視為唯讀。

level

The threshold of this logger, as set by the setLevel() method.

備註

Do not set this attribute directly - always use setLevel(), which has checks for the level passed to it.

parent

The parent logger of this logger. It may change based on later instantiation of loggers which are higher up in the namespace hierarchy.

備註

This value should be treated as read-only.

propagate

如果此屬性評估為 true，則在此日誌紀錄器被記錄的事件會被傳到更高階（上代）日誌記錄器 的處理函式和所有附加在此日誌記錄器的任何處理器。訊息會直接傳到上代 loggers 的處理器 - 在問題中上代日誌記錄器的層級或是篩選器都不會被考慮。

If this evaluates to false, logging messages are not passed to the handlers of ancestor loggers.

Spelling it out with an example: If the propagate attribute of the logger named A.B.C evaluates to true, any event logged to A.B.C via a method call such as logging.getLogger('A.B.C').error(...) will [subject to passing that logger's level and filter settings] be passed in turn to any handlers attached to loggers named A.B, A and the root logger, after first being passed to any handlers attached to A.B.C. If any logger in the chain A.B.C, A.B, A has its propagate attribute set to false, then that is the last logger whose handlers are offered the event to handle, and propagation stops at that point.

此建構函式將該屬性設為 True。

備註

If you attach a handler to a logger and one or more of its ancestors, it may emit the same record multiple times. In general, you should not need to attach a handler to more than one logger - if you just attach it to the appropriate logger which is highest in the logger hierarchy, then it will see all events logged by all descendant loggers, provided that their propagate setting is left set to True. A common scenario is to attach handlers only to the root logger, and to let propagation take care of the rest.

handlers

The list of handlers directly attached to this logger instance.

備註

This attribute should be treated as read-only; it is normally changed via the addHandler() and removeHandler() methods, which use locks to ensure thread-safe operation.

disabled

This attribute disables handling of any events. It is set to False in the initializer, and only changed by logging configuration code.

備註

此屬性應被視為唯讀。

setLevel(level)

Sets the threshold for this logger to level. Logging messages which are less severe than level will be ignored; logging messages which have severity level or higher will be emitted by whichever handler or handlers service this logger, unless a handler's level has been set to a higher severity level than level.

當一個日誌記錄器被建立時，記錄層級會被設定成 NOTSET （當此日誌記錄器是根日誌記錄器，或是代表父日誌記錄器的非根日誌記錄器時，會使所有訊息被處理）。請注意根日誌記錄器會以記錄等級 WARNING 被建立。

The term 'delegation to the parent' means that if a logger has a level of NOTSET, its chain of ancestor loggers is traversed until either an ancestor with a level other than NOTSET is found, or the root is reached.

If an ancestor is found with a level other than NOTSET, then that ancestor's level is treated as the effective level of the logger where the ancestor search began, and is used to determine how a logging event is handled.

If the root is reached, and it has a level of NOTSET, then all messages will be processed. Otherwise, the root's level will be used as the effective level.

層級清單請見 Logging Levels。

在 3.2 版的變更: The level parameter now accepts a string representation of the level such as 'INFO' as an alternative to the integer constants such as INFO. Note, however, that levels are internally stored as integers, and methods such as e.g. getEffectiveLevel() and isEnabledFor() will return/expect to be passed integers.

isEnabledFor(level)

Indicates if a message of severity level would be processed by this logger. This method checks first the module-level level set by logging.disable(level) and then the logger's effective level as determined by getEffectiveLevel().

getEffectiveLevel()

Indicates the effective level for this logger. If a value other than NOTSET has been set using setLevel(), it is returned. Otherwise, the hierarchy is traversed towards the root until a value other than NOTSET is found, and that value is returned. The value returned is an integer, typically one of logging.DEBUG, logging.INFO etc.

getChild(suffix)

Returns a logger which is a descendant to this logger, as determined by the suffix. Thus, logging.getLogger('abc').getChild('def.ghi') would return the same logger as would be returned by logging.getLogger('abc.def.ghi'). This is a convenience method, useful when the parent logger is named using e.g. __name__ rather than a literal string.

在 3.2 版被加入.

getChildren()

Returns a set of loggers which are immediate children of this logger. So for example logging.getLogger().getChildren() might return a set containing loggers named foo and bar, but a logger named foo.bar wouldn't be included in the set. Likewise, logging.getLogger('foo').getChildren() might return a set including a logger named foo.bar, but it wouldn't include one named foo.bar.baz.

在 3.12 版被加入.

debug(msg, *args, **kwargs)

Logs a message with level DEBUG on this logger. The msg is the message format string, and the args are the arguments which are merged into msg using the string formatting operator. (Note that this means that you can use keywords in the format string, together with a single dictionary argument.) No % formatting operation is performed on msg when no args are supplied.

There are four keyword arguments in kwargs which are inspected: exc_info, stack_info, stacklevel and extra.

If exc_info does not evaluate as false, it causes exception information to be added to the logging message. If an exception tuple (in the format returned by sys.exc_info()) or an exception instance is provided, it is used; otherwise, sys.exc_info() is called to get the exception information.

The second optional keyword argument is stack_info, which defaults to False. If true, stack information is added to the logging message, including the actual logging call. Note that this is not the same stack information as that displayed through specifying exc_info: The former is stack frames from the bottom of the stack up to the logging call in the current thread, whereas the latter is information about stack frames which have been unwound, following an exception, while searching for exception handlers.

You can specify stack_info independently of exc_info, e.g. to just show how you got to a certain point in your code, even when no exceptions were raised. The stack frames are printed following a header line which says:

Stack (most recent call last):

This mimics the Traceback (most recent call last): which is used when displaying exception frames.

The third optional keyword argument is stacklevel, which defaults to 1. If greater than 1, the corresponding number of stack frames are skipped when computing the line number and function name set in the LogRecord created for the logging event. This can be used in logging helpers so that the function name, filename and line number recorded are not the information for the helper function/method, but rather its caller. The name of this parameter mirrors the equivalent one in the warnings module.

The fourth keyword argument is extra which can be used to pass a dictionary which is used to populate the __dict__ of the LogRecord created for the logging event with user-defined attributes. These custom attributes can then be used as you like. For example, they could be incorporated into logged messages. For example:

FORMAT = '%(asctime)s %(clientip)-15s %(user)-8s %(message)s'
logging.basicConfig(format=FORMAT)
d = {'clientip': '192.168.0.1', 'user': 'fbloggs'}
logger = logging.getLogger('tcpserver')
logger.warning('Protocol problem: %s', 'connection reset', extra=d)

would print something like

2006-02-08 22:20:02,165 192.168.0.1 fbloggs  Protocol problem: connection reset

The keys in the dictionary passed in extra should not clash with the keys used by the logging system. (See the section on LogRecord 屬性 for more information on which keys are used by the logging system.)

If you choose to use these attributes in logged messages, you need to exercise some care. In the above example, for instance, the Formatter has been set up with a format string which expects 'clientip' and 'user' in the attribute dictionary of the LogRecord. If these are missing, the message will not be logged because a string formatting exception will occur. So in this case, you always need to pass the extra dictionary with these keys.

While this might be annoying, this feature is intended for use in specialized circumstances, such as multi-threaded servers where the same code executes in many contexts, and interesting conditions which arise are dependent on this context (such as remote client IP address and authenticated user name, in the above example). In such circumstances, it is likely that specialized Formatters would be used with particular Handlers.

If no handler is attached to this logger (or any of its ancestors, taking into account the relevant Logger.propagate attributes), the message will be sent to the handler set on lastResort.

在 3.2 版的變更: 新增 stack_info 參數。

在 3.5 版的變更: The exc_info parameter can now accept exception instances.

在 3.8 版的變更: 新增 stacklevel 參數。

info(msg, *args, **kwargs)

Logs a message with level INFO on this logger. The arguments are interpreted as for debug().

warning(msg, *args, **kwargs)

在此記錄器上記錄一條層級為 WARNING 的訊息。這些引數被直譯的方式與 debug() 相同。

備註

There is an obsolete method warn which is functionally identical to warning. As warn is deprecated, please do not use it - use warning instead.

error(msg, *args, **kwargs)

Logs a message with level ERROR on this logger. The arguments are interpreted as for debug().

critical(msg, *args, **kwargs)

Logs a message with level CRITICAL on this logger. The arguments are interpreted as for debug().

log(level, msg, *args, **kwargs)

Logs a message with integer level level on this logger. The other arguments are interpreted as for debug().

exception(msg, *args, **kwargs)

Logs a message with level ERROR on this logger. The arguments are interpreted as for debug(). Exception info is added to the logging message. This method should only be called from an exception handler.

addFilter(filter)

在該 logger 內增加指定的 filter filter。

removeFilter(filter)

在該 logger 內移除指定的 filter filter。

filter(record)

Apply this logger's filters to the record and return True if the record is to be processed. The filters are consulted in turn, until one of them returns a false value. If none of them return a false value, the record will be processed (passed to handlers). If one returns a false value, no further processing of the record occurs.

addHandler(hdlr)

Adds the specified handler hdlr to this logger.

removeHandler(hdlr)

Removes the specified handler hdlr from this logger.

findCaller(stack_info=False, stacklevel=1)

Finds the caller's source filename and line number. Returns the filename, line number, function name and stack information as a 4-element tuple. The stack information is returned as None unless stack_info is True.

The stacklevel parameter is passed from code calling the debug() and other APIs. If greater than 1, the excess is used to skip stack frames before determining the values to be returned. This will generally be useful when calling logging APIs from helper/wrapper code, so that the information in the event log refers not to the helper/wrapper code, but to the code that calls it.

handle(record)

Handles a record by passing it to all handlers associated with this logger and its ancestors (until a false value of propagate is found). This method is used for unpickled records received from a socket, as well as those created locally. Logger-level filtering is applied using filter().

makeRecord(name, level, fn, lno, msg, args, exc_info, func=None, extra=None, sinfo=None)

This is a factory method which can be overridden in subclasses to create specialized LogRecord instances.

hasHandlers()

Checks to see if this logger has any handlers configured. This is done by looking for handlers in this logger and its parents in the logger hierarchy. Returns True if a handler was found, else False. The method stops searching up the hierarchy whenever a logger with the 'propagate' attribute set to false is found - that will be the last logger which is checked for the existence of handlers.

在 3.2 版被加入.

在 3.7 版的變更: Loggers can now be pickled and unpickled.

Logging Levels

The numeric values of logging levels are given in the following table. These are primarily of interest if you want to define your own levels, and need them to have specific values relative to the predefined levels. If you define a level with the same numeric value, it overwrites the predefined value; the predefined name is lost.

Level

Numeric value

What it means / When to use it

logging.NOTSET

0

When set on a logger, indicates that ancestor loggers are to be consulted to determine the effective level. If that still resolves to NOTSET, then all events are logged. When set on a handler, all events are handled.

logging.DEBUG

10

Detailed information, typically only of interest to a developer trying to diagnose a problem.

logging.INFO

20

Confirmation that things are working as expected.

logging.WARNING

30

An indication that something unexpected happened, or that a problem might occur in the near future (e.g. 'disk space low'). The software is still working as expected.

logging.ERROR

40

Due to a more serious problem, the software has not been able to perform some function.

logging.CRITICAL

50

A serious error, indicating that the program itself may be unable to continue running.

Handler Objects

Handlers have the following attributes and methods. Note that Handler is never instantiated directly; this class acts as a base for more useful subclasses. However, the __init__() method in subclasses needs to call Handler.__init__().

class logging.Handler

__init__(level=NOTSET)

Initializes the Handler instance by setting its level, setting the list of filters to the empty list and creating a lock (using createLock()) for serializing access to an I/O mechanism.

createLock()

Initializes a thread lock which can be used to serialize access to underlying I/O functionality which may not be threadsafe.

acquire()

Acquires the thread lock created with createLock().

release()

Releases the thread lock acquired with acquire().

setLevel(level)

Sets the threshold for this handler to level. Logging messages which are less severe than level will be ignored. When a handler is created, the level is set to NOTSET (which causes all messages to be processed).

層級清單請見 Logging Levels。

在 3.2 版的變更: The level parameter now accepts a string representation of the level such as 'INFO' as an alternative to the integer constants such as INFO.

setFormatter(fmt)

Sets the formatter for this handler to fmt. The fmt argument must be a Formatter instance or None.

addFilter(filter)

Adds the specified filter filter to this handler.

removeFilter(filter)

Removes the specified filter filter from this handler.

filter(record)

Apply this handler's filters to the record and return True if the record is to be processed. The filters are consulted in turn, until one of them returns a false value. If none of them return a false value, the record will be emitted. If one returns a false value, the handler will not emit the record.

flush()

Ensure all logging output has been flushed. This version does nothing and is intended to be implemented by subclasses.

close()

Tidy up any resources used by the handler. This version does no output but removes the handler from an internal map of handlers, which is used for handler lookup by name.

Subclasses should ensure that this gets called from overridden close() methods.

handle(record)

Conditionally emits the specified logging record, depending on filters which may have been added to the handler. Wraps the actual emission of the record with acquisition/release of the I/O thread lock.

handleError(record)

This method should be called from handlers when an exception is encountered during an emit() call. If the module-level attribute raiseExceptions is False, exceptions get silently ignored. This is what is mostly wanted for a logging system - most users will not care about errors in the logging system, they are more interested in application errors. You could, however, replace this with a custom handler if you wish. The specified record is the one which was being processed when the exception occurred. (The default value of raiseExceptions is True, as that is more useful during development).

format(record)

Do formatting for a record - if a formatter is set, use it. Otherwise, use the default formatter for the module.

emit(record)

Do whatever it takes to actually log the specified logging record. This version is intended to be implemented by subclasses and so raises a NotImplementedError.

警告

This method is called after a handler-level lock is acquired, which is released after this method returns. When you override this method, note that you should be careful when calling anything that invokes other parts of the logging API which might do locking, because that might result in a deadlock. Specifically:

Logging configuration APIs acquire the module-level lock, and then individual handler-level locks as those handlers are configured.

Many logging APIs lock the module-level lock. If such an API is called from this method, it could cause a deadlock if a configuration call is made on another thread, because that thread will try to acquire the module-level lock before the handler-level lock, whereas this thread tries to acquire the module-level lock after the handler-level lock (because in this method, the handler-level lock has already been acquired).

For a list of handlers included as standard, see logging.handlers.

Formatter Objects

class logging.Formatter(fmt=None, datefmt=None, style='%', validate=True, *, defaults=None)

Responsible for converting a LogRecord to an output string to be interpreted by a human or external system.

參數:

fmt (str) -- A format string in the given style for the logged output as a whole. The possible mapping keys are drawn from the LogRecord object's LogRecord 屬性. If not specified, '%(message)s' is used, which is just the logged message.

datefmt (str) -- A format string for the date/time portion of the logged output. If not specified, the default described in formatTime() is used.

style (str) -- Can be one of '%', '{' or '$' and determines how the format string will be merged with its data: using one of printf-style String Formatting (%), str.format() ({) or string.Template ($). This only applies to fmt (e.g. '%(message)s' versus '{message}'), not to the actual log messages passed to the logging methods. However, there are other ways to use {- and $-formatting for log messages.

validate (bool) -- If True (the default), incorrect or mismatched fmt and style will raise a ValueError; for example, logging.Formatter('%(asctime)s - %(message)s', style='{').

defaults (dict[str, Any]) -- A dictionary with default values to use in custom fields. For example, logging.Formatter('%(ip)s %(message)s', defaults={"ip": None})

在 3.2 版的變更: 新增 style 參數。

在 3.8 版的變更: 新增 validate 參數。

在 3.10 版的變更: 新增 defaults 參數。

format(record)

The record's attribute dictionary is used as the operand to a string formatting operation. Returns the resulting string. Before formatting the dictionary, a couple of preparatory steps are carried out. The message attribute of the record is computed using msg % args. If the formatting string contains '(asctime)', formatTime() is called to format the event time. If there is exception information, it is formatted using formatException() and appended to the message. Note that the formatted exception information is cached in attribute exc_text. This is useful because the exception information can be pickled and sent across the wire, but you should be careful if you have more than one Formatter subclass which customizes the formatting of exception information. In this case, you will have to clear the cached value (by setting the exc_text attribute to None) after a formatter has done its formatting, so that the next formatter to handle the event doesn't use the cached value, but recalculates it afresh.

If stack information is available, it's appended after the exception information, using formatStack() to transform it if necessary.

formatTime(record, datefmt=None)

This method should be called from format() by a formatter which wants to make use of a formatted time. This method can be overridden in formatters to provide for any specific requirement, but the basic behavior is as follows: if datefmt (a string) is specified, it is used with time.strftime() to format the creation time of the record. Otherwise, the format '%Y-%m-%d %H:%M:%S,uuu' is used, where the uuu part is a millisecond value and the other letters are as per the time.strftime() documentation. An example time in this format is 2003-01-23 00:29:50,411. The resulting string is returned.

This function uses a user-configurable function to convert the creation time to a tuple. By default, time.localtime() is used; to change this for a particular formatter instance, set the converter attribute to a function with the same signature as time.localtime() or time.gmtime(). To change it for all formatters, for example if you want all logging times to be shown in GMT, set the converter attribute in the Formatter class.

在 3.3 版的變更: Previously, the default format was hard-coded as in this example: 2010-09-06 22:38:15,292 where the part before the comma is handled by a strptime format string ('%Y-%m-%d %H:%M:%S'), and the part after the comma is a millisecond value. Because strptime does not have a format placeholder for milliseconds, the millisecond value is appended using another format string, '%s,%03d' --- and both of these format strings have been hardcoded into this method. With the change, these strings are defined as class-level attributes which can be overridden at the instance level when desired. The names of the attributes are default_time_format (for the strptime format string) and default_msec_format (for appending the millisecond value).

在 3.9 版的變更: The default_msec_format can be None.

formatException(exc_info)

Formats the specified exception information (a standard exception tuple as returned by sys.exc_info()) as a string. This default implementation just uses traceback.print_exception(). The resulting string is returned.

formatStack(stack_info)

Formats the specified stack information (a string as returned by traceback.print_stack(), but with the last newline removed) as a string. This default implementation just returns the input value.

class logging.BufferingFormatter(linefmt=None)

A base formatter class suitable for subclassing when you want to format a number of records. You can pass a Formatter instance which you want to use to format each line (that corresponds to a single record). If not specified, the default formatter (which just outputs the event message) is used as the line formatter.

formatHeader(records)

Return a header for a list of records. The base implementation just returns the empty string. You will need to override this method if you want specific behaviour, e.g. to show the count of records, a title or a separator line.

formatFooter(records)

Return a footer for a list of records. The base implementation just returns the empty string. You will need to override this method if you want specific behaviour, e.g. to show the count of records or a separator line.

format(records)

Return formatted text for a list of records. The base implementation just returns the empty string if there are no records; otherwise, it returns the concatenation of the header, each record formatted with the line formatter, and the footer.

Filter Objects

Filters can be used by Handlers and Loggers for more sophisticated filtering than is provided by levels. The base filter class only allows events which are below a certain point in the logger hierarchy. For example, a filter initialized with 'A.B' will allow events logged by loggers 'A.B', 'A.B.C', 'A.B.C.D', 'A.B.D' etc. but not 'A.BB', 'B.A.B' etc. If initialized with the empty string, all events are passed.

class logging.Filter(name='')

Returns an instance of the Filter class. If name is specified, it names a logger which, together with its children, will have its events allowed through the filter. If name is the empty string, allows every event.

filter(record)

Is the specified record to be logged? Returns false for no, true for yes. Filters can either modify log records in-place or return a completely different record instance which will replace the original log record in any future processing of the event.

Note that filters attached to handlers are consulted before an event is emitted by the handler, whereas filters attached to loggers are consulted whenever an event is logged (using debug(), info(), etc.), before sending an event to handlers. This means that events which have been generated by descendant loggers will not be filtered by a logger's filter setting, unless the filter has also been applied to those descendant loggers.

You don't actually need to subclass Filter: you can pass any instance which has a filter method with the same semantics.

在 3.2 版的變更: You don't need to create specialized Filter classes, or use other classes with a filter method: you can use a function (or other callable) as a filter. The filtering logic will check to see if the filter object has a filter attribute: if it does, it's assumed to be a Filter and its filter() method is called. Otherwise, it's assumed to be a callable and called with the record as the single parameter. The returned value should conform to that returned by filter().

在 3.12 版的變更: You can now return a LogRecord instance from filters to replace the log record rather than modifying it in place. This allows filters attached to a Handler to modify the log record before it is emitted, without having side effects on other handlers.

Although filters are used primarily to filter records based on more sophisticated criteria than levels, they get to see every record which is processed by the handler or logger they're attached to: this can be useful if you want to do things like counting how many records were processed by a particular logger or handler, or adding, changing or removing attributes in the LogRecord being processed. Obviously changing the LogRecord needs to be done with some care, but it does allow the injection of contextual information into logs (see Using Filters to impart contextual information).

LogRecord 物件

LogRecord instances are created automatically by the Logger every time something is logged, and can be created manually via makeLogRecord() (for example, from a pickled event received over the wire).

class logging.LogRecord(name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None)

Contains all the information pertinent to the event being logged.

The primary information is passed in msg and args, which are combined using msg % args to create the message attribute of the record.

參數:

name (str) -- The name of the logger used to log the event represented by this LogRecord. Note that the logger name in the LogRecord will always have this value, even though it may be emitted by a handler attached to a different (ancestor) logger.

level (int) -- The numeric level of the logging event (such as 10 for DEBUG, 20 for INFO, etc). Note that this is converted to two attributes of the LogRecord: levelno for the numeric value and levelname for the corresponding level name.

pathname (str) -- The full string path of the source file where the logging call was made.

lineno (int) -- The line number in the source file where the logging call was made.

msg (Any) -- The event description message, which can be a %-format string with placeholders for variable data, or an arbitrary object (see Using arbitrary objects as messages).

args (tuple | dict[str, Any]) -- Variable data to merge into the msg argument to obtain the event description.

exc_info (tuple[type[BaseException], BaseException, types.TracebackType] | None) -- An exception tuple with the current exception information, as returned by sys.exc_info(), or None if no exception information is available.

func (str | None) -- The name of the function or method from which the logging call was invoked.

sinfo (str | None) -- A text string representing stack information from the base of the stack in the current thread, up to the logging call.

getMessage()

Returns the message for this LogRecord instance after merging any user-supplied arguments with the message. If the user-supplied message argument to the logging call is not a string, str() is called on it to convert it to a string. This allows use of user-defined classes as messages, whose __str__ method can return the actual format string to be used.

在 3.2 版的變更: The creation of a LogRecord has been made more configurable by providing a factory which is used to create the record. The factory can be set using getLogRecordFactory() and setLogRecordFactory() (see this for the factory's signature).

This functionality can be used to inject your own values into a LogRecord at creation time. You can use the following pattern:

old_factory = logging.getLogRecordFactory()

def record_factory(*args, **kwargs):
    record = old_factory(*args, **kwargs)
    record.custom_attribute = 0xdecafbad
    return record

logging.setLogRecordFactory(record_factory)

With this pattern, multiple factories could be chained, and as long as they don't overwrite each other's attributes or unintentionally overwrite the standard attributes listed above, there should be no surprises.

LogRecord 屬性

The LogRecord has a number of attributes, most of which are derived from the parameters to the constructor. (Note that the names do not always correspond exactly between the LogRecord constructor parameters and the LogRecord attributes.) These attributes can be used to merge data from the record into the format string. The following table lists (in alphabetical order) the attribute names, their meanings and the corresponding placeholder in a %-style format string.

If you are using {}-formatting (str.format()), you can use {attrname} as the placeholder in the format string. If you are using $-formatting (string.Template), use the form ${attrname}. In both cases, of course, replace attrname with the actual attribute name you want to use.

In the case of {}-formatting, you can specify formatting flags by placing them after the attribute name, separated from it with a colon. For example: a placeholder of {msecs:03.0f} would format a millisecond value of 4 as 004. Refer to the str.format() documentation for full details on the options available to you.

屬性名稱

格式

描述

args

你不應該需要自己格式化它。

The tuple of arguments merged into msg to produce message, or a dict whose values are used for the merge (when there is only one argument, and it is a dictionary).

asctime

%(asctime)s

Human-readable time when the LogRecord was created. By default this is of the form '2003-07-08 16:49:45,896' (the numbers after the comma are millisecond portion of the time).

created

%(created)f

Time when the LogRecord was created (as returned by time.time_ns() / 1e9).

exc_info

你不應該需要自己格式化它。

Exception tuple (à la sys.exc_info) or, if no exception has occurred, None.

exc_text

你不應該需要自己格式化它。

Exception information formatted as a string. This is set when Formatter.format() is invoked, or None if no exception has occurred.

filename

%(filename)s

pathname 的檔案名稱部分。

funcName

%(funcName)s

Name of function containing the logging call.

levelname

%(levelname)s

Text logging level for the message ('DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL').

levelno

%(levelno)s

Numeric logging level for the message (DEBUG, INFO, WARNING, ERROR, CRITICAL).

lineno

%(lineno)d

Source line number where the logging call was issued (if available).

message

%(message)s

The logged message, computed as msg % args. This is set when Formatter.format() is invoked.

模組

%(module)s

模組（filename 的名稱部分）。

msecs

%(msecs)d

Millisecond portion of the time when the LogRecord was created.

msg

你不應該需要自己格式化它。

The format string passed in the original logging call. Merged with args to produce message, or an arbitrary object (see Using arbitrary objects as messages).

name

%(name)s

Name of the logger used to log the call.

pathname

%(pathname)s

Full pathname of the source file where the logging call was issued (if available).

process

%(process)d

行程 ID（如果可用）。

processName

%(processName)s

行程名稱（如果可用）。

relativeCreated

%(relativeCreated)d

Time in milliseconds when the LogRecord was created, relative to the time the logging module was loaded.

stack_info

你不應該需要自己格式化它。

Stack frame information (where available) from the bottom of the stack in the current thread, up to and including the stack frame of the logging call which resulted in the creation of this record.

thread

%(thread)d

執行緒 ID（如果可用）。

threadName

%(threadName)s

Thread name (if available).

taskName

%(taskName)s

asyncio.Task name (if available).

在 3.1 版的變更: 新增 processName。

在 3.12 版的變更: 新增 taskName。

LoggerAdapter 物件

LoggerAdapter instances are used to conveniently pass contextual information into logging calls. For a usage example, see the section on adding contextual information to your logging output.

class logging.LoggerAdapter(logger, extra=None, merge_extra=False)

Returns an instance of LoggerAdapter initialized with an underlying Logger instance, an optional dict-like object (extra), and an optional boolean (merge_extra) indicating whether or not the extra argument of individual log calls should be merged with the LoggerAdapter extra. The default behavior is to ignore the extra argument of individual log calls and only use the one of the LoggerAdapter instance

process(msg, kwargs)

Modifies the message and/or keyword arguments passed to a logging call in order to insert contextual information. This implementation takes the object passed as extra to the constructor and adds it to kwargs using key 'extra'. The return value is a (msg, kwargs) tuple which has the (possibly modified) versions of the arguments passed in.

manager

Delegates to the underlying manager on logger.

_log

Delegates to the underlying _log() method on logger.

In addition to the above, LoggerAdapter supports the following methods of Logger: debug(), info(), warning(), error(), exception(), critical(), log(), isEnabledFor(), getEffectiveLevel(), setLevel() and hasHandlers(). These methods have the same signatures as their counterparts in Logger, so you can use the two types of instances interchangeably.

在 3.2 版的變更: The isEnabledFor(), getEffectiveLevel(), setLevel() and hasHandlers() methods were added to LoggerAdapter. These methods delegate to the underlying logger.

在 3.6 版的變更: Attribute manager and method _log() were added, which delegate to the underlying logger and allow adapters to be nested.

在 3.10 版的變更: extra 引數現在是可選的。

在 3.13 版的變更: 新增 merge_extra 參數。

執行緒安全

The logging module is intended to be thread-safe without any special work needing to be done by its clients. It achieves this through using threading locks; there is one lock to serialize access to the module's shared data, and each handler also creates a lock to serialize access to its underlying I/O.

If you are implementing asynchronous signal handlers using the signal module, you may not be able to use logging from within such handlers. This is because lock implementations in the threading module are not always re-entrant, and so cannot be invoked from such signal handlers.

模組層級函式

In addition to the classes described above, there are a number of module-level functions.

logging.getLogger(name=None)

Return a logger with the specified name or, if name is None, return the root logger of the hierarchy. If specified, the name is typically a dot-separated hierarchical name like 'a', 'a.b' or 'a.b.c.d'. Choice of these names is entirely up to the developer who is using logging, though it is recommended that __name__ be used unless you have a specific reason for not doing that, as mentioned in Logger 物件.

All calls to this function with a given name return the same logger instance. This means that logger instances never need to be passed between different parts of an application.

logging.getLoggerClass()

Return either the standard Logger class, or the last class passed to setLoggerClass(). This function may be called from within a new class definition, to ensure that installing a customized Logger class will not undo customizations already applied by other code. For example:

class MyLogger(logging.getLoggerClass()):
    # ... 在這裡覆蓋其行為

logging.getLogRecordFactory()

Return a callable which is used to create a LogRecord.

在 3.2 版被加入: This function has been provided, along with setLogRecordFactory(), to allow developers more control over how the LogRecord representing a logging event is constructed.

See setLogRecordFactory() for more information about the how the factory is called.

logging.debug(msg, *args, **kwargs)

This is a convenience function that calls Logger.debug(), on the root logger. The handling of the arguments is in every way identical to what is described in that method.

The only difference is that if the root logger has no handlers, then basicConfig() is called, prior to calling debug on the root logger.

For very short scripts or quick demonstrations of logging facilities, debug and the other module-level functions may be convenient. However, most programs will want to carefully and explicitly control the logging configuration, and should therefore prefer creating a module-level logger and calling Logger.debug() (or other level-specific methods) on it, as described at the beginning of this documentation.

logging.info(msg, *args, **kwargs)

Logs a message with level INFO on the root logger. The arguments and behavior are otherwise the same as for debug().

logging.warning(msg, *args, **kwargs)

Logs a message with level WARNING on the root logger. The arguments and behavior are otherwise the same as for debug().

備註

There is an obsolete function warn which is functionally identical to warning. As warn is deprecated, please do not use it - use warning instead.

logging.error(msg, *args, **kwargs)

Logs a message with level ERROR on the root logger. The arguments and behavior are otherwise the same as for debug().

logging.critical(msg, *args, **kwargs)

Logs a message with level CRITICAL on the root logger. The arguments and behavior are otherwise the same as for debug().

logging.exception(msg, *args, **kwargs)

Logs a message with level ERROR on the root logger. The arguments and behavior are otherwise the same as for debug(). Exception info is added to the logging message. This function should only be called from an exception handler.

logging.log(level, msg, *args, **kwargs)

Logs a message with level level on the root logger. The arguments and behavior are otherwise the same as for debug().

logging.disable(level=CRITICAL)

Provides an overriding level level for all loggers which takes precedence over the logger's own level. When the need arises to temporarily throttle logging output down across the whole application, this function can be useful. Its effect is to disable all logging calls of severity level and below, so that if you call it with a value of INFO, then all INFO and DEBUG events would be discarded, whereas those of severity WARNING and above would be processed according to the logger's effective level. If logging.disable(logging.NOTSET) is called, it effectively removes this overriding level, so that logging output again depends on the effective levels of individual loggers.

Note that if you have defined any custom logging level higher than CRITICAL (this is not recommended), you won't be able to rely on the default value for the level parameter, but will have to explicitly supply a suitable value.

在 3.7 版的變更: The level parameter was defaulted to level CRITICAL. See bpo-28524 [https://bugs.python.org/issue?@action=redirect&bpo=28524] for more information about this change.

logging.addLevelName(level, levelName)

Associates level level with text levelName in an internal dictionary, which is used to map numeric levels to a textual representation, for example when a Formatter formats a message. This function can also be used to define your own levels. The only constraints are that all levels used must be registered using this function, levels should be positive integers and they should increase in increasing order of severity.

備註

If you are thinking of defining your own levels, please see the section on Custom Levels.

logging.getLevelNamesMapping()

Returns a mapping from level names to their corresponding logging levels. For example, the string "CRITICAL" maps to CRITICAL. The returned mapping is copied from an internal mapping on each call to this function.

在 3.11 版被加入.

logging.getLevelName(level)

Returns the textual or numeric representation of logging level level.

If level is one of the predefined levels CRITICAL, ERROR, WARNING, INFO or DEBUG then you get the corresponding string. If you have associated levels with names using addLevelName() then the name you have associated with level is returned. If a numeric value corresponding to one of the defined levels is passed in, the corresponding string representation is returned.

The level parameter also accepts a string representation of the level such as 'INFO'. In such cases, this functions returns the corresponding numeric value of the level.

If no matching numeric or string value is passed in, the string 'Level %s' % level is returned.

備註

Levels are internally integers (as they need to be compared in the logging logic). This function is used to convert between an integer level and the level name displayed in the formatted log output by means of the %(levelname)s format specifier (see LogRecord 屬性), and vice versa.

在 3.4 版的變更: In Python versions earlier than 3.4, this function could also be passed a text level, and would return the corresponding numeric value of the level. This undocumented behaviour was considered a mistake, and was removed in Python 3.4, but reinstated in 3.4.2 due to retain backward compatibility.

logging.getHandlerByName(name)

Returns a handler with the specified name, or None if there is no handler with that name.

在 3.12 版被加入.

logging.getHandlerNames()

Returns an immutable set of all known handler names.

在 3.12 版被加入.

logging.makeLogRecord(attrdict)

Creates and returns a new LogRecord instance whose attributes are defined by attrdict. This function is useful for taking a pickled LogRecord attribute dictionary, sent over a socket, and reconstituting it as a LogRecord instance at the receiving end.

logging.basicConfig(**kwargs)

Does basic configuration for the logging system by creating a StreamHandler with a default Formatter and adding it to the root logger. The functions debug(), info(), warning(), error() and critical() will call basicConfig() automatically if no handlers are defined for the root logger.

This function does nothing if the root logger already has handlers configured, unless the keyword argument force is set to True.

備註

This function should be called from the main thread before other threads are started. In versions of Python prior to 2.7.1 and 3.2, if this function is called from multiple threads, it is possible (in rare circumstances) that a handler will be added to the root logger more than once, leading to unexpected results such as messages being duplicated in the log.

支援以下的關鍵字引數。

格式

描述

filename

Specifies that a FileHandler be created, using the specified filename, rather than a StreamHandler.

filemode

If filename is specified, open the file in this mode. Defaults to 'a'.

format

Use the specified format string for the handler. Defaults to attributes levelname, name and message separated by colons.

datefmt

Use the specified date/time format, as accepted by time.strftime().

style

If format is specified, use this style for the format string. One of '%', '{' or '$' for printf-style, str.format() or string.Template respectively. Defaults to '%'.

level

Set the root logger level to the specified level.

stream

Use the specified stream to initialize the StreamHandler. Note that this argument is incompatible with filename - if both are present, a ValueError is raised.

handlers

If specified, this should be an iterable of already created handlers to add to the root logger. Any handlers which don't already have a formatter set will be assigned the default formatter created in this function. Note that this argument is incompatible with filename or stream - if both are present, a ValueError is raised.

force

If this keyword argument is specified as true, any existing handlers attached to the root logger are removed and closed, before carrying out the configuration as specified by the other arguments.

encoding

If this keyword argument is specified along with filename, its value is used when the FileHandler is created, and thus used when opening the output file.

errors

If this keyword argument is specified along with filename, its value is used when the FileHandler is created, and thus used when opening the output file. If not specified, the value 'backslashreplace' is used. Note that if None is specified, it will be passed as such to open(), which means that it will be treated the same as passing 'errors'.

在 3.2 版的變更: 新增 style 引數。

在 3.3 版的變更: The handlers argument was added. Additional checks were added to catch situations where incompatible arguments are specified (e.g. handlers together with stream or filename, or stream together with filename).

在 3.8 版的變更: 新增 force 引數。

在 3.9 版的變更: 新增 encoding 與 errors 引數。

logging.shutdown()

Informs the logging system to perform an orderly shutdown by flushing and closing all handlers. This should be called at application exit and no further use of the logging system should be made after this call.

When the logging module is imported, it registers this function as an exit handler (see atexit), so normally there's no need to do that manually.

logging.setLoggerClass(klass)

Tells the logging system to use the class klass when instantiating a logger. The class should define __init__() such that only a name argument is required, and the __init__() should call Logger.__init__(). This function is typically called before any loggers are instantiated by applications which need to use custom logger behavior. After this call, as at any other time, do not instantiate loggers directly using the subclass: continue to use the logging.getLogger() API to get your loggers.

logging.setLogRecordFactory(factory)

Set a callable which is used to create a LogRecord.

參數:

factory -- The factory callable to be used to instantiate a log record.

在 3.2 版被加入: This function has been provided, along with getLogRecordFactory(), to allow developers more control over how the LogRecord representing a logging event is constructed.

The factory has the following signature:

factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)

name:

The logger name.

level:

The logging level (numeric).

fn:

The full pathname of the file where the logging call was made.

lno:

The line number in the file where the logging call was made.

msg:

The logging message.

args:

The arguments for the logging message.

exc_info:

An exception tuple, or None.

func:

The name of the function or method which invoked the logging call.

sinfo:

A stack traceback such as is provided by traceback.print_stack(), showing the call hierarchy.

kwargs:

額外的關鍵字引數。

模組層級屬性

logging.lastResort

A "handler of last resort" is available through this attribute. This is a StreamHandler writing to sys.stderr with a level of WARNING, and is used to handle logging events in the absence of any logging configuration. The end result is to just print the message to sys.stderr. This replaces the earlier error message saying that "no handlers could be found for logger XYZ". If you need the earlier behaviour for some reason, lastResort can be set to None.

在 3.2 版被加入.

logging.raiseExceptions

Used to see if exceptions during handling should be propagated.

Default: True.

If raiseExceptions is False, exceptions get silently ignored. This is what is mostly wanted for a logging system - most users will not care about errors in the logging system, they are more interested in application errors.

Integration with the warnings module

The captureWarnings() function can be used to integrate logging with the warnings module.

logging.captureWarnings(capture)

This function is used to turn the capture of warnings by logging on and off.

If capture is True, warnings issued by the warnings module will be redirected to the logging system. Specifically, a warning will be formatted using warnings.formatwarning() and the resulting string logged to a logger named 'py.warnings' with a severity of WARNING.

If capture is False, the redirection of warnings to the logging system will stop, and warnings will be redirected to their original destinations (i.e. those in effect before captureWarnings(True) was called).

也參考

logging.config 模組

Configuration API for the logging module.

logging.handlers 模組

Useful handlers included with the logging module.

PEP 282 [https://peps.python.org/pep-0282/] - A Logging System

The proposal which described this feature for inclusion in the Python standard library.

Original Python logging package [https://old.red-dove.com/python_logging.html]

This is the original source for the logging package. The version of the package available from this site is suitable for use with Python 1.5.2, 2.1.x and 2.2.x, which do not include the logging package in the standard library.

logging.config --- 日誌記錄配置

原始碼：Lib/logging/config.py [https://github.com/python/cpython/tree/3.14/Lib/logging/config.py]

Important

This page contains only reference information. For tutorials, please see

基礎教學

進階教學

Logging Cookbook

This section describes the API for configuring the logging module.

Configuration functions

The following functions configure the logging module. They are located in the logging.config module. Their use is optional --- you can configure the logging module using these functions or by making calls to the main API (defined in logging itself) and defining handlers which are declared either in logging or logging.handlers.

logging.config.dictConfig(config)

Takes the logging configuration from a dictionary. The contents of this dictionary are described in Configuration dictionary schema below.

If an error is encountered during configuration, this function will raise a ValueError, TypeError, AttributeError or ImportError with a suitably descriptive message. The following is a (possibly incomplete) list of conditions which will raise an error:

A level which is not a string or which is a string not corresponding to an actual logging level.

A propagate value which is not a boolean.

An id which does not have a corresponding destination.

A non-existent handler id found during an incremental call.

An invalid logger name.

Inability to resolve to an internal or external object.

Parsing is performed by the DictConfigurator class, whose constructor is passed the dictionary used for configuration, and has a configure() method. The logging.config module has a callable attribute dictConfigClass which is initially set to DictConfigurator. You can replace the value of dictConfigClass with a suitable implementation of your own.

dictConfig() calls dictConfigClass passing the specified dictionary, and then calls the configure() method on the returned object to put the configuration into effect:

def dictConfig(config):
    dictConfigClass(config).configure()

For example, a subclass of DictConfigurator could call DictConfigurator.__init__() in its own __init__(), then set up custom prefixes which would be usable in the subsequent configure() call. dictConfigClass would be bound to this new subclass, and then dictConfig() could be called exactly as in the default, uncustomized state.

在 3.2 版被加入.

logging.config.fileConfig(fname, defaults=None, disable_existing_loggers=True, encoding=None)

Reads the logging configuration from a configparser-format file. The format of the file should be as described in Configuration file format. This function can be called several times from an application, allowing an end user to select from various pre-canned configurations (if the developer provides a mechanism to present the choices and load the chosen configuration).

It will raise FileNotFoundError if the file doesn't exist and RuntimeError if the file is invalid or empty.

參數:

fname -- A filename, or a file-like object, or an instance derived from RawConfigParser. If a RawConfigParser-derived instance is passed, it is used as is. Otherwise, a ConfigParser is instantiated, and the configuration read by it from the object passed in fname. If that has a readline() method, it is assumed to be a file-like object and read using read_file(); otherwise, it is assumed to be a filename and passed to read().

defaults -- Defaults to be passed to the ConfigParser can be specified in this argument.

disable_existing_loggers -- If specified as False, loggers which exist when this call is made are left enabled. The default is True because this enables old behaviour in a backward-compatible way. This behaviour is to disable any existing non-root loggers unless they or their ancestors are explicitly named in the logging configuration.

encoding -- The encoding used to open file when fname is filename.

在 3.4 版的變更: An instance of a subclass of RawConfigParser is now accepted as a value for fname. This facilitates:

Use of a configuration file where logging configuration is just part of the overall application configuration.

Use of a configuration read from a file, and then modified by the using application (e.g. based on command-line parameters or other aspects of the runtime environment) before being passed to fileConfig.

在 3.10 版的變更: 新增了 encoding 參數。

在 3.12 版的變更: An exception will be thrown if the provided file doesn't exist or is invalid or empty.

logging.config.listen(port=DEFAULT_LOGGING_CONFIG_PORT, verify=None)

Starts up a socket server on the specified port, and listens for new configurations. If no port is specified, the module's default DEFAULT_LOGGING_CONFIG_PORT is used. Logging configurations will be sent as a file suitable for processing by dictConfig() or fileConfig(). Returns a Thread instance on which you can call start() to start the server, and which you can join() when appropriate. To stop the server, call stopListening().

The verify argument, if specified, should be a callable which should verify whether bytes received across the socket are valid and should be processed. This could be done by encrypting and/or signing what is sent across the socket, such that the verify callable can perform signature verification and/or decryption. The verify callable is called with a single argument - the bytes received across the socket - and should return the bytes to be processed, or None to indicate that the bytes should be discarded. The returned bytes could be the same as the passed in bytes (e.g. when only verification is done), or they could be completely different (perhaps if decryption were performed).

To send a configuration to the socket, read in the configuration file and send it to the socket as a sequence of bytes preceded by a four-byte length string packed in binary using struct.pack('>L', n).

備註

Because portions of the configuration are passed through eval(), use of this function may open its users to a security risk. While the function only binds to a socket on localhost, and so does not accept connections from remote machines, there are scenarios where untrusted code could be run under the account of the process which calls listen(). Specifically, if the process calling listen() runs on a multi-user machine where users cannot trust each other, then a malicious user could arrange to run essentially arbitrary code in a victim user's process, simply by connecting to the victim's listen() socket and sending a configuration which runs whatever code the attacker wants to have executed in the victim's process. This is especially easy to do if the default port is used, but not hard even if a different port is used. To avoid the risk of this happening, use the verify argument to listen() to prevent unrecognised configurations from being applied.

在 3.4 版的變更: 新增 verify 引數。

備註

If you want to send configurations to the listener which don't disable existing loggers, you will need to use a JSON format for the configuration, which will use dictConfig() for configuration. This method allows you to specify disable_existing_loggers as False in the configuration you send.

logging.config.stopListening()

Stops the listening server which was created with a call to listen(). This is typically called before calling join() on the return value from listen().

Security considerations

The logging configuration functionality tries to offer convenience, and in part this is done by offering the ability to convert text in configuration files into Python objects used in logging configuration - for example, as described in User-defined objects. However, these same mechanisms (importing callables from user-defined modules and calling them with parameters from the configuration) could be used to invoke any code you like, and for this reason you should treat configuration files from untrusted sources with extreme caution and satisfy yourself that nothing bad can happen if you load them, before actually loading them.

Configuration dictionary schema

Describing a logging configuration requires listing the various objects to create and the connections between them; for example, you may create a handler named 'console' and then say that the logger named 'startup' will send its messages to the 'console' handler. These objects aren't limited to those provided by the logging module because you might write your own formatter or handler class. The parameters to these classes may also need to include external objects such as sys.stderr. The syntax for describing these objects and connections is defined in Object connections below.

Dictionary Schema Details

The dictionary passed to dictConfig() must contain the following keys:

version - to be set to an integer value representing the schema version. The only valid value at present is 1, but having this key allows the schema to evolve while still preserving backwards compatibility.

All other keys are optional, but if present they will be interpreted as described below. In all cases below where a 'configuring dict' is mentioned, it will be checked for the special '()' key to see if a custom instantiation is required. If so, the mechanism described in User-defined objects below is used to create an instance; otherwise, the context is used to determine what to instantiate.

formatters - the corresponding value will be a dict in which each key is a formatter id and each value is a dict describing how to configure the corresponding Formatter instance.

The configuring dict is searched for the following optional keys which correspond to the arguments passed to create a Formatter object:

format

datefmt

style

validate (自 3.8 版起)

defaults (自 3.12 版起)

An optional class key indicates the name of the formatter's class (as a dotted module and class name). The instantiation arguments are as for Formatter, thus this key is most useful for instantiating a customised subclass of Formatter. For example, the alternative class might present exception tracebacks in an expanded or condensed format. If your formatter requires different or extra configuration keys, you should use User-defined objects.

filters - the corresponding value will be a dict in which each key is a filter id and each value is a dict describing how to configure the corresponding Filter instance.

The configuring dict is searched for the key name (defaulting to the empty string) and this is used to construct a logging.Filter instance.

handlers - the corresponding value will be a dict in which each key is a handler id and each value is a dict describing how to configure the corresponding Handler instance.

The configuring dict is searched for the following keys:

class (mandatory). This is the fully qualified name of the handler class.

level (optional). The level of the handler.

formatter (optional). The id of the formatter for this handler.

filters (optional). A list of ids of the filters for this handler.

在 3.11 版的變更: filters can take filter instances in addition to ids.

All other keys are passed through as keyword arguments to the handler's constructor. For example, given the snippet:

handlers:
  console:
    class : logging.StreamHandler
    formatter: brief
    level   : INFO
    filters: [allow_foo]
    stream  : ext://sys.stdout
  file:
    class : logging.handlers.RotatingFileHandler
    formatter: precise
    filename: logconfig.log
    maxBytes: 1024
    backupCount: 3

the handler with id console is instantiated as a logging.StreamHandler, using sys.stdout as the underlying stream. The handler with id file is instantiated as a logging.handlers.RotatingFileHandler with the keyword arguments filename='logconfig.log', maxBytes=1024, backupCount=3.

loggers - the corresponding value will be a dict in which each key is a logger name and each value is a dict describing how to configure the corresponding Logger instance.

The configuring dict is searched for the following keys:

level (optional). The level of the logger.

propagate (optional). The propagation setting of the logger.

filters (optional). A list of ids of the filters for this logger.

在 3.11 版的變更: filters can take filter instances in addition to ids.

handlers (optional). A list of ids of the handlers for this logger.

The specified loggers will be configured according to the level, propagation, filters and handlers specified.

root - this will be the configuration for the root logger. Processing of the configuration will be as for any logger, except that the propagate setting will not be applicable.

incremental - whether the configuration is to be interpreted as incremental to the existing configuration. This value defaults to False, which means that the specified configuration replaces the existing configuration with the same semantics as used by the existing fileConfig() API.

If the specified value is True, the configuration is processed as described in the section on Incremental Configuration.

disable_existing_loggers - whether any existing non-root loggers are to be disabled. This setting mirrors the parameter of the same name in fileConfig(). If absent, this parameter defaults to True. This value is ignored if incremental is True.

Incremental Configuration

It is difficult to provide complete flexibility for incremental configuration. For example, because objects such as filters and formatters are anonymous, once a configuration is set up, it is not possible to refer to such anonymous objects when augmenting a configuration.

Furthermore, there is not a compelling case for arbitrarily altering the object graph of loggers, handlers, filters, formatters at run-time, once a configuration is set up; the verbosity of loggers and handlers can be controlled just by setting levels (and, in the case of loggers, propagation flags). Changing the object graph arbitrarily in a safe way is problematic in a multi-threaded environment; while not impossible, the benefits are not worth the complexity it adds to the implementation.

Thus, when the incremental key of a configuration dict is present and is True, the system will completely ignore any formatters and filters entries, and process only the level settings in the handlers entries, and the level and propagate settings in the loggers and root entries.

Using a value in the configuration dict lets configurations to be sent over the wire as pickled dicts to a socket listener. Thus, the logging verbosity of a long-running application can be altered over time with no need to stop and restart the application.

Object connections

The schema describes a set of logging objects - loggers, handlers, formatters, filters - which are connected to each other in an object graph. Thus, the schema needs to represent connections between the objects. For example, say that, once configured, a particular logger has attached to it a particular handler. For the purposes of this discussion, we can say that the logger represents the source, and the handler the destination, of a connection between the two. Of course in the configured objects this is represented by the logger holding a reference to the handler. In the configuration dict, this is done by giving each destination object an id which identifies it unambiguously, and then using the id in the source object's configuration to indicate that a connection exists between the source and the destination object with that id.

So, for example, consider the following YAML snippet:

formatters:
  brief:
    # configuration for formatter with id 'brief' goes here
  precise:
    # configuration for formatter with id 'precise' goes here
handlers:
  h1: #This is an id
   # configuration of handler with id 'h1' goes here
   formatter: brief
  h2: #This is another id
   # configuration of handler with id 'h2' goes here
   formatter: precise
loggers:
  foo.bar.baz:
    # other configuration for logger 'foo.bar.baz'
    handlers: [h1, h2]

(Note: YAML used here because it's a little more readable than the equivalent Python source form for the dictionary.)

The ids for loggers are the logger names which would be used programmatically to obtain a reference to those loggers, e.g. foo.bar.baz. The ids for Formatters and Filters can be any string value (such as brief, precise above) and they are transient, in that they are only meaningful for processing the configuration dictionary and used to determine connections between objects, and are not persisted anywhere when the configuration call is complete.

The above snippet indicates that logger named foo.bar.baz should have two handlers attached to it, which are described by the handler ids h1 and h2. The formatter for h1 is that described by id brief, and the formatter for h2 is that described by id precise.

User-defined objects

The schema supports user-defined objects for handlers, filters and formatters. (Loggers do not need to have different types for different instances, so there is no support in this configuration schema for user-defined logger classes.)

Objects to be configured are described by dictionaries which detail their configuration. In some places, the logging system will be able to infer from the context how an object is to be instantiated, but when a user-defined object is to be instantiated, the system will not know how to do this. In order to provide complete flexibility for user-defined object instantiation, the user needs to provide a 'factory' - a callable which is called with a configuration dictionary and which returns the instantiated object. This is signalled by an absolute import path to the factory being made available under the special key '()'. Here's a concrete example:

formatters:
  brief:
    format: '%(message)s'
  default:
    format: '%(asctime)s %(levelname)-8s %(name)-15s %(message)s'
    datefmt: '%Y-%m-%d %H:%M:%S'
  custom:
      (): my.package.customFormatterFactory
      bar: baz
      spam: 99.9
      answer: 42

The above YAML snippet defines three formatters. The first, with id brief, is a standard logging.Formatter instance with the specified format string. The second, with id default, has a longer format and also defines the time format explicitly, and will result in a logging.Formatter initialized with those two format strings. Shown in Python source form, the brief and default formatters have configuration sub-dictionaries:

{
  'format' : '%(message)s'
}

和：

{
  'format' : '%(asctime)s %(levelname)-8s %(name)-15s %(message)s',
  'datefmt' : '%Y-%m-%d %H:%M:%S'
}

respectively, and as these dictionaries do not contain the special key '()', the instantiation is inferred from the context: as a result, standard logging.Formatter instances are created. The configuration sub-dictionary for the third formatter, with id custom, is:

{
  '()' : 'my.package.customFormatterFactory',
  'bar' : 'baz',
  'spam' : 99.9,
  'answer' : 42
}

and this contains the special key '()', which means that user-defined instantiation is wanted. In this case, the specified factory callable will be used. If it is an actual callable it will be used directly - otherwise, if you specify a string (as in the example) the actual callable will be located using normal import mechanisms. The callable will be called with the remaining items in the configuration sub-dictionary as keyword arguments. In the above example, the formatter with id custom will be assumed to be returned by the call:

my.package.customFormatterFactory(bar='baz', spam=99.9, answer=42)

警告

The values for keys such as bar, spam and answer in the above example should not be configuration dictionaries or references such as cfg://foo or ext://bar, because they will not be processed by the configuration machinery, but passed to the callable as-is.

The key '()' has been used as the special key because it is not a valid keyword parameter name, and so will not clash with the names of the keyword arguments used in the call. The '()' also serves as a mnemonic that the corresponding value is a callable.

在 3.11 版的變更: The filters member of handlers and loggers can take filter instances in addition to ids.

You can also specify a special key '.' whose value is a mapping of attribute names to values. If found, the specified attributes will be set on the user-defined object before it is returned. Thus, with the following configuration:

{
  '()' : 'my.package.customFormatterFactory',
  'bar' : 'baz',
  'spam' : 99.9,
  'answer' : 42,
  '.' {
    'foo': 'bar',
    'baz': 'bozz'
  }
}

the returned formatter will have attribute foo set to 'bar' and attribute baz set to 'bozz'.

警告

The values for attributes such as foo and baz in the above example should not be configuration dictionaries or references such as cfg://foo or ext://bar, because they will not be processed by the configuration machinery, but set as attribute values as-is.

Handler configuration order

Handlers are configured in alphabetical order of their keys, and a configured handler replaces the configuration dictionary in (a working copy of) the handlers dictionary in the schema. If you use a construct such as cfg://handlers.foo, then initially handlers['foo'] points to the configuration dictionary for the handler named foo, and later (once that handler has been configured) it points to the configured handler instance. Thus, cfg://handlers.foo could resolve to either a dictionary or a handler instance. In general, it is wise to name handlers in a way such that dependent handlers are configured after any handlers they depend on; that allows something like cfg://handlers.foo to be used in configuring a handler that depends on handler foo. If that dependent handler were named bar, problems would result, because the configuration of bar would be attempted before that of foo, and foo would not yet have been configured. However, if the dependent handler were named foobar, it would be configured after foo, with the result that cfg://handlers.foo would resolve to configured handler foo, and not its configuration dictionary.

Access to external objects

There are times where a configuration needs to refer to objects external to the configuration, for example sys.stderr. If the configuration dict is constructed using Python code, this is straightforward, but a problem arises when the configuration is provided via a text file (e.g. JSON, YAML). In a text file, there is no standard way to distinguish sys.stderr from the literal string 'sys.stderr'. To facilitate this distinction, the configuration system looks for certain special prefixes in string values and treat them specially. For example, if the literal string 'ext://sys.stderr' is provided as a value in the configuration, then the ext:// will be stripped off and the remainder of the value processed using normal import mechanisms.

The handling of such prefixes is done in a way analogous to protocol handling: there is a generic mechanism to look for prefixes which match the regular expression ^(?P<prefix>[a-z]+)://(?P<suffix>.*)$ whereby, if the prefix is recognised, the suffix is processed in a prefix-dependent manner and the result of the processing replaces the string value. If the prefix is not recognised, then the string value will be left as-is.

Access to internal objects

As well as external objects, there is sometimes also a need to refer to objects in the configuration. This will be done implicitly by the configuration system for things that it knows about. For example, the string value 'DEBUG' for a level in a logger or handler will automatically be converted to the value logging.DEBUG, and the handlers, filters and formatter entries will take an object id and resolve to the appropriate destination object.

However, a more generic mechanism is needed for user-defined objects which are not known to the logging module. For example, consider logging.handlers.MemoryHandler, which takes a target argument which is another handler to delegate to. Since the system already knows about this class, then in the configuration, the given target just needs to be the object id of the relevant target handler, and the system will resolve to the handler from the id. If, however, a user defines a my.package.MyHandler which has an alternate handler, the configuration system would not know that the alternate referred to a handler. To cater for this, a generic resolution system allows the user to specify:

handlers:
  file:
    # configuration of file handler goes here

  custom:
    (): my.package.MyHandler
    alternate: cfg://handlers.file

The literal string 'cfg://handlers.file' will be resolved in an analogous way to strings with the ext:// prefix, but looking in the configuration itself rather than the import namespace. The mechanism allows access by dot or by index, in a similar way to that provided by str.format. Thus, given the following snippet:

handlers:
  email:
    class: logging.handlers.SMTPHandler
    mailhost: localhost
    fromaddr: my_app@domain.tld
    toaddrs:
      - support_team@domain.tld
      - dev_team@domain.tld
    subject: Houston, we have a problem.

in the configuration, the string 'cfg://handlers' would resolve to the dict with key handlers, the string 'cfg://handlers.email would resolve to the dict with key email in the handlers dict, and so on. The string 'cfg://handlers.email.toaddrs[1] would resolve to 'dev_team@domain.tld' and the string 'cfg://handlers.email.toaddrs[0]' would resolve to the value 'support_team@domain.tld'. The subject value could be accessed using either 'cfg://handlers.email.subject' or, equivalently, 'cfg://handlers.email[subject]'. The latter form only needs to be used if the key contains spaces or non-alphanumeric characters. Please note that the characters [ and ] are not allowed in the keys. If an index value consists only of decimal digits, access will be attempted using the corresponding integer value, falling back to the string value if needed.

Given a string cfg://handlers.myhandler.mykey.123, this will resolve to config_dict['handlers']['myhandler']['mykey']['123']. If the string is specified as cfg://handlers.myhandler.mykey[123], the system will attempt to retrieve the value from config_dict['handlers']['myhandler']['mykey'][123], and fall back to config_dict['handlers']['myhandler']['mykey']['123'] if that fails.

Import resolution and custom importers

Import resolution, by default, uses the builtin __import__() function to do its importing. You may want to replace this with your own importing mechanism: if so, you can replace the importer attribute of the DictConfigurator or its superclass, the BaseConfigurator class. However, you need to be careful because of the way functions are accessed from classes via descriptors. If you are using a Python callable to do your imports, and you want to define it at class level rather than instance level, you need to wrap it with staticmethod(). For example:

from importlib import import_module
from logging.config import BaseConfigurator

BaseConfigurator.importer = staticmethod(import_module)

You don't need to wrap with staticmethod() if you're setting the import callable on a configurator instance.

Configuring QueueHandler and QueueListener

If you want to configure a QueueHandler, noting that this is normally used in conjunction with a QueueListener, you can configure both together. After the configuration, the QueueListener instance will be available as the listener attribute of the created handler, and that in turn will be available to you using getHandlerByName() and passing the name you have used for the QueueHandler in your configuration. The dictionary schema for configuring the pair is shown in the example YAML snippet below.

handlers:
  qhand:
    class: logging.handlers.QueueHandler
    queue: my.module.queue_factory
    listener: my.package.CustomListener
    handlers:
      - hand_name_1
      - hand_name_2
      ...

The queue and listener keys are optional.

If the queue key is present, the corresponding value can be one of the following:

An object implementing the Queue.put_nowait and Queue.get public API. For instance, this may be an actual instance of queue.Queue or a subclass thereof, or a proxy obtained by multiprocessing.managers.SyncManager.Queue().

This is of course only possible if you are constructing or modifying the configuration dictionary in code.

A string that resolves to a callable which, when called with no arguments, returns the queue instance to use. That callable could be a queue.Queue subclass or a function which returns a suitable queue instance, such as my.module.queue_factory().

A dict with a '()' key which is constructed in the usual way as discussed in User-defined objects. The result of this construction should be a queue.Queue instance.

If the queue key is absent, a standard unbounded queue.Queue instance is created and used.

If the listener key is present, the corresponding value can be one of the following:

A subclass of logging.handlers.QueueListener. This is of course only possible if you are constructing or modifying the configuration dictionary in code.

A string which resolves to a class which is a subclass of QueueListener, such as 'my.package.CustomListener'.

A dict with a '()' key which is constructed in the usual way as discussed in User-defined objects. The result of this construction should be a callable with the same signature as the QueueListener initializer.

If the listener key is absent, logging.handlers.QueueListener is used.

The values under the handlers key are the names of other handlers in the configuration (not shown in the above snippet) which will be passed to the queue listener.

Any custom queue handler and listener classes will need to be defined with the same initialization signatures as QueueHandler and QueueListener.

在 3.12 版被加入.

Configuration file format

The configuration file format understood by fileConfig() is based on configparser functionality. The file must contain sections called [loggers], [handlers] and [formatters] which identify by name the entities of each type which are defined in the file. For each such entity, there is a separate section which identifies how that entity is configured. Thus, for a logger named log01 in the [loggers] section, the relevant configuration details are held in a section [logger_log01]. Similarly, a handler called hand01 in the [handlers] section will have its configuration held in a section called [handler_hand01], while a formatter called form01 in the [formatters] section will have its configuration specified in a section called [formatter_form01]. The root logger configuration must be specified in a section called [logger_root].

備註

The fileConfig() API is older than the dictConfig() API and does not provide functionality to cover certain aspects of logging. For example, you cannot configure Filter objects, which provide for filtering of messages beyond simple integer levels, using fileConfig(). If you need to have instances of Filter in your logging configuration, you will need to use dictConfig(). Note that future enhancements to configuration functionality will be added to dictConfig(), so it's worth considering transitioning to this newer API when it's convenient to do so.

Examples of these sections in the file are given below.

[loggers]
keys=root,log02,log03,log04,log05,log06,log07

[handlers]
keys=hand01,hand02,hand03,hand04,hand05,hand06,hand07,hand08,hand09

[formatters]
keys=form01,form02,form03,form04,form05,form06,form07,form08,form09

The root logger must specify a level and a list of handlers. An example of a root logger section is given below.

[logger_root]
level=NOTSET
handlers=hand01

The level entry can be one of DEBUG, INFO, WARNING, ERROR, CRITICAL or NOTSET. For the root logger only, NOTSET means that all messages will be logged. Level values are evaluated in the context of the logging package's namespace.

The handlers entry is a comma-separated list of handler names, which must appear in the [handlers] section. These names must appear in the [handlers] section and have corresponding sections in the configuration file.

For loggers other than the root logger, some additional information is required. This is illustrated by the following example.

[logger_parser]
level=DEBUG
handlers=hand01
propagate=1
qualname=compiler.parser

The level and handlers entries are interpreted as for the root logger, except that if a non-root logger's level is specified as NOTSET, the system consults loggers higher up the hierarchy to determine the effective level of the logger. The propagate entry is set to 1 to indicate that messages must propagate to handlers higher up the logger hierarchy from this logger, or 0 to indicate that messages are not propagated to handlers up the hierarchy. The qualname entry is the hierarchical channel name of the logger, that is to say the name used by the application to get the logger.

Sections which specify handler configuration are exemplified by the following.

[handler_hand01]
class=StreamHandler
level=NOTSET
formatter=form01
args=(sys.stdout,)

The class entry indicates the handler's class (as determined by eval() in the logging package's namespace). The level is interpreted as for loggers, and NOTSET is taken to mean 'log everything'.

The formatter entry indicates the key name of the formatter for this handler. If blank, a default formatter (logging._defaultFormatter) is used. If a name is specified, it must appear in the [formatters] section and have a corresponding section in the configuration file.

The args entry, when evaluated in the context of the logging package's namespace, is the list of arguments to the constructor for the handler class. Refer to the constructors for the relevant handlers, or to the examples below, to see how typical entries are constructed. If not provided, it defaults to ().

The optional kwargs entry, when evaluated in the context of the logging package's namespace, is the keyword argument dict to the constructor for the handler class. If not provided, it defaults to {}.

[handler_hand02]
class=FileHandler
level=DEBUG
formatter=form02
args=('python.log', 'w')

[handler_hand03]
class=handlers.SocketHandler
level=INFO
formatter=form03
args=('localhost', handlers.DEFAULT_TCP_LOGGING_PORT)

[handler_hand04]
class=handlers.DatagramHandler
level=WARN
formatter=form04
args=('localhost', handlers.DEFAULT_UDP_LOGGING_PORT)

[handler_hand05]
class=handlers.SysLogHandler
level=ERROR
formatter=form05
args=(('localhost', handlers.SYSLOG_UDP_PORT), handlers.SysLogHandler.LOG_USER)

[handler_hand06]
class=handlers.NTEventLogHandler
level=CRITICAL
formatter=form06
args=('Python Application', '', 'Application')

[handler_hand07]
class=handlers.SMTPHandler
level=WARN
formatter=form07
args=('localhost', 'from@abc', ['user1@abc', 'user2@xyz'], 'Logger Subject')
kwargs={'timeout': 10.0}

[handler_hand08]
class=handlers.MemoryHandler
level=NOTSET
formatter=form08
target=
args=(10, ERROR)

[handler_hand09]
class=handlers.HTTPHandler
level=NOTSET
formatter=form09
args=('localhost:9022', '/log', 'GET')
kwargs={'secure': True}

Sections which specify formatter configuration are typified by the following.

[formatter_form01]
format=F1 %(asctime)s %(levelname)s %(message)s %(customfield)s
datefmt=
style=%
validate=True
defaults={'customfield': 'defaultvalue'}
class=logging.Formatter

The arguments for the formatter configuration are the same as the keys in the dictionary schema formatters section.

The defaults entry, when evaluated in the context of the logging package's namespace, is a dictionary of default values for custom formatting fields. If not provided, it defaults to None.

備註

Due to the use of eval() as described above, there are potential security risks which result from using the listen() to send and receive configurations via sockets. The risks are limited to where multiple users with no mutual trust run code on the same machine; see the listen() documentation for more information.

也參考

logging 模組

API reference for the logging module.

logging.handlers 模組

Useful handlers included with the logging module.

logging.handlers --- 日誌紀錄處理器

原始碼：Lib/logging/handlers.py [https://github.com/python/cpython/tree/3.14/Lib/logging/handlers.py]

Important

This page contains only reference information. For tutorials, please see

基礎教學

進階教學

Logging Cookbook

The following useful handlers are provided in the package. Note that three of the handlers (StreamHandler, FileHandler and NullHandler) are actually defined in the logging module itself, but have been documented here along with the other handlers.

StreamHandler

The StreamHandler class, located in the core logging package, sends logging output to streams such as sys.stdout, sys.stderr or any file-like object (or, more precisely, any object which supports write() and flush() methods).

class logging.StreamHandler(stream=None)

Returns a new instance of the StreamHandler class. If stream is specified, the instance will use it for logging output; otherwise, sys.stderr will be used.

emit(record)

If a formatter is specified, it is used to format the record. The record is then written to the stream followed by terminator. If exception information is present, it is formatted using traceback.print_exception() and appended to the stream.

flush()

Flushes the stream by calling its flush() method. Note that the close() method is inherited from Handler and so does no output, so an explicit flush() call may be needed at times.

setStream(stream)

Sets the instance's stream to the specified value, if it is different. The old stream is flushed before the new stream is set.

參數:

stream -- The stream that the handler should use.

回傳:

the old stream, if the stream was changed, or None if it wasn't.

在 3.7 版被加入.

terminator

String used as the terminator when writing a formatted record to a stream. Default value is '\n'.

If you don't want a newline termination, you can set the handler instance's terminator attribute to the empty string.

In earlier versions, the terminator was hardcoded as '\n'.

在 3.2 版被加入.

FileHandler

The FileHandler class, located in the core logging package, sends logging output to a disk file. It inherits the output functionality from StreamHandler.

class logging.FileHandler(filename, mode='a', encoding=None, delay=False, errors=None)

Returns a new instance of the FileHandler class. The specified file is opened and used as the stream for logging. If mode is not specified, 'a' is used. If encoding is not None, it is used to open the file with that encoding. If delay is true, then file opening is deferred until the first call to emit(). By default, the file grows indefinitely. If errors is specified, it's used to determine how encoding errors are handled.

在 3.6 版的變更: As well as string values, Path objects are also accepted for the filename argument.

在 3.9 版的變更: 新增 errors 參數。

close()

關閉檔案。

emit(record)

Outputs the record to the file.

Note that if the file was closed due to logging shutdown at exit and the file mode is 'w', the record will not be emitted (see bpo-42378 [https://bugs.python.org/issue?@action=redirect&bpo=42378]).

NullHandler

在 3.1 版被加入.

The NullHandler class, located in the core logging package, does not do any formatting or output. It is essentially a 'no-op' handler for use by library developers.

class logging.NullHandler

Returns a new instance of the NullHandler class.

emit(record)

此方法不做任何事。

handle(record)

此方法不做任何事。

createLock()

This method returns None for the lock, since there is no underlying I/O to which access needs to be serialized.

See Configuring Logging for a Library for more information on how to use NullHandler.

WatchedFileHandler

The WatchedFileHandler class, located in the logging.handlers module, is a FileHandler which watches the file it is logging to. If the file changes, it is closed and reopened using the file name.

A file change can happen because of usage of programs such as newsyslog and logrotate which perform log file rotation. This handler, intended for use under Unix/Linux, watches the file to see if it has changed since the last emit. (A file is deemed to have changed if its device or inode have changed.) If the file has changed, the old file stream is closed, and the file opened to get a new stream.

This handler is not appropriate for use under Windows, because under Windows open log files cannot be moved or renamed - logging opens the files with exclusive locks - and so there is no need for such a handler. Furthermore, ST_INO is not supported under Windows; stat() always returns zero for this value.

class logging.handlers.WatchedFileHandler(filename, mode='a', encoding=None, delay=False, errors=None)

Returns a new instance of the WatchedFileHandler class. The specified file is opened and used as the stream for logging. If mode is not specified, 'a' is used. If encoding is not None, it is used to open the file with that encoding. If delay is true, then file opening is deferred until the first call to emit(). By default, the file grows indefinitely. If errors is provided, it determines how encoding errors are handled.

在 3.6 版的變更: As well as string values, Path objects are also accepted for the filename argument.

在 3.9 版的變更: 新增 errors 參數。

reopenIfNeeded()

Checks to see if the file has changed. If it has, the existing stream is flushed and closed and the file opened again, typically as a precursor to outputting the record to the file.

在 3.6 版被加入.

emit(record)

Outputs the record to the file, but first calls reopenIfNeeded() to reopen the file if it has changed.

BaseRotatingHandler

The BaseRotatingHandler class, located in the logging.handlers module, is the base class for the rotating file handlers, RotatingFileHandler and TimedRotatingFileHandler. You should not need to instantiate this class, but it has attributes and methods you may need to override.

class logging.handlers.BaseRotatingHandler(filename, mode, encoding=None, delay=False, errors=None)

The parameters are as for FileHandler. The attributes are:

namer

If this attribute is set to a callable, the rotation_filename() method delegates to this callable. The parameters passed to the callable are those passed to rotation_filename().

備註

The namer function is called quite a few times during rollover, so it should be as simple and as fast as possible. It should also return the same output every time for a given input, otherwise the rollover behaviour may not work as expected.

It's also worth noting that care should be taken when using a namer to preserve certain attributes in the filename which are used during rotation. For example, RotatingFileHandler expects to have a set of log files whose names contain successive integers, so that rotation works as expected, and TimedRotatingFileHandler deletes old log files (based on the backupCount parameter passed to the handler's initializer) by determining the oldest files to delete. For this to happen, the filenames should be sortable using the date/time portion of the filename, and a namer needs to respect this. (If a namer is wanted that doesn't respect this scheme, it will need to be used in a subclass of TimedRotatingFileHandler which overrides the getFilesToDelete() method to fit in with the custom naming scheme.)

在 3.3 版被加入.

rotator

If this attribute is set to a callable, the rotate() method delegates to this callable. The parameters passed to the callable are those passed to rotate().

在 3.3 版被加入.

rotation_filename(default_name)

Modify the filename of a log file when rotating.

This is provided so that a custom filename can be provided.

The default implementation calls the 'namer' attribute of the handler, if it's callable, passing the default name to it. If the attribute isn't callable (the default is None), the name is returned unchanged.

參數:

default_name -- The default name for the log file.

在 3.3 版被加入.

rotate(source, dest)

When rotating, rotate the current log.

The default implementation calls the 'rotator' attribute of the handler, if it's callable, passing the source and dest arguments to it. If the attribute isn't callable (the default is None), the source is simply renamed to the destination.

參數:

source -- The source filename. This is normally the base filename, e.g. 'test.log'.

dest -- The destination filename. This is normally what the source is rotated to, e.g. 'test.log.1'.

在 3.3 版被加入.

The reason the attributes exist is to save you having to subclass - you can use the same callables for instances of RotatingFileHandler and TimedRotatingFileHandler. If either the namer or rotator callable raises an exception, this will be handled in the same way as any other exception during an emit() call, i.e. via the handleError() method of the handler.

If you need to make more significant changes to rotation processing, you can override the methods.

For an example, see Using a rotator and namer to customize log rotation processing.

RotatingFileHandler

The RotatingFileHandler class, located in the logging.handlers module, supports rotation of disk log files.

class logging.handlers.RotatingFileHandler(filename, mode='a', maxBytes=0, backupCount=0, encoding=None, delay=False, errors=None)

Returns a new instance of the RotatingFileHandler class. The specified file is opened and used as the stream for logging. If mode is not specified, 'a' is used. If encoding is not None, it is used to open the file with that encoding. If delay is true, then file opening is deferred until the first call to emit(). By default, the file grows indefinitely. If errors is provided, it determines how encoding errors are handled.

You can use the maxBytes and backupCount values to allow the file to rollover at a predetermined size. When the size is about to be exceeded, the file is closed and a new file is silently opened for output. Rollover occurs whenever the current log file is nearly maxBytes in length; but if either of maxBytes or backupCount is zero, rollover never occurs, so you generally want to set backupCount to at least 1, and have a non-zero maxBytes. When backupCount is non-zero, the system will save old log files by appending the extensions '.1', '.2' etc., to the filename. For example, with a backupCount of 5 and a base file name of app.log, you would get app.log, app.log.1, app.log.2, up to app.log.5. The file being written to is always app.log. When this file is filled, it is closed and renamed to app.log.1, and if files app.log.1, app.log.2, etc. exist, then they are renamed to app.log.2, app.log.3 etc. respectively.

在 3.6 版的變更: As well as string values, Path objects are also accepted for the filename argument.

在 3.9 版的變更: 新增 errors 參數。

doRollover()

Does a rollover, as described above.

emit(record)

Outputs the record to the file, catering for rollover as described previously.

shouldRollover(record)

See if the supplied record would cause the file to exceed the configured size limit.

TimedRotatingFileHandler

The TimedRotatingFileHandler class, located in the logging.handlers module, supports rotation of disk log files at certain timed intervals.

class logging.handlers.TimedRotatingFileHandler(filename, when='h', interval=1, backupCount=0, encoding=None, delay=False, utc=False, atTime=None, errors=None)

Returns a new instance of the TimedRotatingFileHandler class. The specified file is opened and used as the stream for logging. On rotating it also sets the filename suffix. Rotating happens based on the product of when and interval.

You can use the when to specify the type of interval. The list of possible values is below. Note that they are not case sensitive.

Value

Type of interval

If/how atTime is used

'S'

Seconds

Ignored

'M'

Minutes

Ignored

'H'

Hours

Ignored

'D'

Days

Ignored

'W0'-'W6'

Weekday (0=Monday)

Used to compute initial rollover time

'midnight'

Roll over at midnight, if atTime not specified, else at time atTime

Used to compute initial rollover time

When using weekday-based rotation, specify 'W0' for Monday, 'W1' for Tuesday, and so on up to 'W6' for Sunday. In this case, the value passed for interval isn't used.

The system will save old log files by appending extensions to the filename. The extensions are date-and-time based, using the strftime format %Y-%m-%d_%H-%M-%S or a leading portion thereof, depending on the rollover interval.

When computing the next rollover time for the first time (when the handler is created), the last modification time of an existing log file, or else the current time, is used to compute when the next rotation will occur.

If the utc argument is true, times in UTC will be used; otherwise local time is used.

If backupCount is nonzero, at most backupCount files will be kept, and if more would be created when rollover occurs, the oldest one is deleted. The deletion logic uses the interval to determine which files to delete, so changing the interval may leave old files lying around.

If delay is true, then file opening is deferred until the first call to emit().

If atTime is not None, it must be a datetime.time instance which specifies the time of day when rollover occurs, for the cases where rollover is set to happen "at midnight" or "on a particular weekday". Note that in these cases, the atTime value is effectively used to compute the initial rollover, and subsequent rollovers would be calculated via the normal interval calculation.

If errors is specified, it's used to determine how encoding errors are handled.

備註

Calculation of the initial rollover time is done when the handler is initialised. Calculation of subsequent rollover times is done only when rollover occurs, and rollover occurs only when emitting output. If this is not kept in mind, it might lead to some confusion. For example, if an interval of "every minute" is set, that does not mean you will always see log files with times (in the filename) separated by a minute; if, during application execution, logging output is generated more frequently than once a minute, then you can expect to see log files with times separated by a minute. If, on the other hand, logging messages are only output once every five minutes (say), then there will be gaps in the file times corresponding to the minutes where no output (and hence no rollover) occurred.

在 3.4 版的變更: 新增 atTime 參數。

在 3.6 版的變更: As well as string values, Path objects are also accepted for the filename argument.

在 3.9 版的變更: 新增 errors 參數。

doRollover()

Does a rollover, as described above.

emit(record)

Outputs the record to the file, catering for rollover as described above.

getFilesToDelete()

Returns a list of filenames which should be deleted as part of rollover. These are the absolute paths of the oldest backup log files written by the handler.

shouldRollover(record)

See if enough time has passed for a rollover to occur and if it has, compute the next rollover time.

SocketHandler

The SocketHandler class, located in the logging.handlers module, sends logging output to a network socket. The base class uses a TCP socket.

class logging.handlers.SocketHandler(host, port)

Returns a new instance of the SocketHandler class intended to communicate with a remote machine whose address is given by host and port.

在 3.4 版的變更: If port is specified as None, a Unix domain socket is created using the value in host - otherwise, a TCP socket is created.

close()

關閉 socket。

emit()

Pickles the record's attribute dictionary and writes it to the socket in binary format. If there is an error with the socket, silently drops the packet. If the connection was previously lost, re-establishes the connection. To unpickle the record at the receiving end into a LogRecord, use the makeLogRecord() function.

handleError()

Handles an error which has occurred during emit(). The most likely cause is a lost connection. Closes the socket so that we can retry on the next event.

makeSocket()

This is a factory method which allows subclasses to define the precise type of socket they want. The default implementation creates a TCP socket (socket.SOCK_STREAM).

makePickle(record)

Pickles the record's attribute dictionary in binary format with a length prefix, and returns it ready for transmission across the socket. The details of this operation are equivalent to:

data = pickle.dumps(record_attr_dict, 1)
datalen = struct.pack('>L', len(data))
return datalen + data

Note that pickles aren't completely secure. If you are concerned about security, you may want to override this method to implement a more secure mechanism. For example, you can sign pickles using HMAC and then verify them on the receiving end, or alternatively you can disable unpickling of global objects on the receiving end.

send(packet)

Send a pickled byte-string packet to the socket. The format of the sent byte-string is as described in the documentation for makePickle().

This function allows for partial sends, which can happen when the network is busy.

createSocket()

Tries to create a socket; on failure, uses an exponential back-off algorithm. On initial failure, the handler will drop the message it was trying to send. When subsequent messages are handled by the same instance, it will not try connecting until some time has passed. The default parameters are such that the initial delay is one second, and if after that delay the connection still can't be made, the handler will double the delay each time up to a maximum of 30 seconds.

This behaviour is controlled by the following handler attributes:

retryStart (initial delay, defaulting to 1.0 seconds).

retryFactor (multiplier, defaulting to 2.0).

retryMax (maximum delay, defaulting to 30.0 seconds).

This means that if the remote listener starts up after the handler has been used, you could lose messages (since the handler won't even attempt a connection until the delay has elapsed, but just silently drop messages during the delay period).

DatagramHandler

The DatagramHandler class, located in the logging.handlers module, inherits from SocketHandler to support sending logging messages over UDP sockets.

class logging.handlers.DatagramHandler(host, port)

Returns a new instance of the DatagramHandler class intended to communicate with a remote machine whose address is given by host and port.

備註

As UDP is not a streaming protocol, there is no persistent connection between an instance of this handler and host. For this reason, when using a network socket, a DNS lookup might have to be made each time an event is logged, which can introduce some latency into the system. If this affects you, you can do a lookup yourself and initialize this handler using the looked-up IP address rather than the hostname.

在 3.4 版的變更: If port is specified as None, a Unix domain socket is created using the value in host - otherwise, a UDP socket is created.

emit()

Pickles the record's attribute dictionary and writes it to the socket in binary format. If there is an error with the socket, silently drops the packet. To unpickle the record at the receiving end into a LogRecord, use the makeLogRecord() function.

makeSocket()

The factory method of SocketHandler is here overridden to create a UDP socket (socket.SOCK_DGRAM).

send(s)

Send a pickled byte-string to a socket. The format of the sent byte-string is as described in the documentation for SocketHandler.makePickle().

SysLogHandler

The SysLogHandler class, located in the logging.handlers module, supports sending logging messages to a remote or local Unix syslog.

class logging.handlers.SysLogHandler(address=('localhost', SYSLOG_UDP_PORT), facility=LOG_USER, socktype=socket.SOCK_DGRAM, timeout=None)

Returns a new instance of the SysLogHandler class intended to communicate with a remote Unix machine whose address is given by address in the form of a (host, port) tuple. If address is not specified, ('localhost', 514) is used. The address is used to open a socket. An alternative to providing a (host, port) tuple is providing an address as a string, for example '/dev/log'. In this case, a Unix domain socket is used to send the message to the syslog. If facility is not specified, LOG_USER is used. The type of socket opened depends on the socktype argument, which defaults to socket.SOCK_DGRAM and thus opens a UDP socket. To open a TCP socket (for use with the newer syslog daemons such as rsyslog), specify a value of socket.SOCK_STREAM. If timeout is specified, it sets a timeout (in seconds) for the socket operations. This can help prevent the program from hanging indefinitely if the syslog server is unreachable. By default, timeout is None, meaning no timeout is applied.

Note that if your server is not listening on UDP port 514, SysLogHandler may appear not to work. In that case, check what address you should be using for a domain socket - it's system dependent. For example, on Linux it's usually '/dev/log' but on OS/X it's '/var/run/syslog'. You'll need to check your platform and use the appropriate address (you may need to do this check at runtime if your application needs to run on several platforms). On Windows, you pretty much have to use the UDP option.

備註

On macOS 12.x (Monterey), Apple has changed the behaviour of their syslog daemon - it no longer listens on a domain socket. Therefore, you cannot expect SysLogHandler to work on this system.

請見 gh-91070 [https://github.com/python/cpython/issues/91070] 以取得更多資訊。

在 3.2 版的變更: 新增 socktype。

在 3.14 版的變更: 新增 timeout。

close()

Closes the socket to the remote host.

createSocket()

Tries to create a socket and, if it's not a datagram socket, connect it to the other end. This method is called during handler initialization, but it's not regarded as an error if the other end isn't listening at this point - the method will be called again when emitting an event, if there is no socket at that point.

在 3.11 版被加入.

emit(record)

The record is formatted, and then sent to the syslog server. If exception information is present, it is not sent to the server.

在 3.2.1 版的變更: (See: bpo-12168 [https://bugs.python.org/issue?@action=redirect&bpo=12168].) In earlier versions, the message sent to the syslog daemons was always terminated with a NUL byte, because early versions of these daemons expected a NUL terminated message - even though it's not in the relevant specification (RFC 5424 [https://datatracker.ietf.org/doc/html/rfc5424.html]). More recent versions of these daemons don't expect the NUL byte but strip it off if it's there, and even more recent daemons (which adhere more closely to RFC 5424) pass the NUL byte on as part of the message.

To enable easier handling of syslog messages in the face of all these differing daemon behaviours, the appending of the NUL byte has been made configurable, through the use of a class-level attribute, append_nul. This defaults to True (preserving the existing behaviour) but can be set to False on a SysLogHandler instance in order for that instance to not append the NUL terminator.

在 3.3 版的變更: (See: bpo-12419 [https://bugs.python.org/issue?@action=redirect&bpo=12419].) In earlier versions, there was no facility for an "ident" or "tag" prefix to identify the source of the message. This can now be specified using a class-level attribute, defaulting to "" to preserve existing behaviour, but which can be overridden on a SysLogHandler instance in order for that instance to prepend the ident to every message handled. Note that the provided ident must be text, not bytes, and is prepended to the message exactly as is.

encodePriority(facility, priority)

Encodes the facility and priority into an integer. You can pass in strings or integers - if strings are passed, internal mapping dictionaries are used to convert them to integers.

The symbolic LOG_ values are defined in SysLogHandler and mirror the values defined in the sys/syslog.h header file.

Priorities

Name (string)

Symbolic value

alert

LOG_ALERT

crit 或 critical

LOG_CRIT

debug

LOG_DEBUG

emerg 或 panic

LOG_EMERG

err 或 error

LOG_ERR

info

LOG_INFO

notice

LOG_NOTICE

warn 或 warning

LOG_WARNING

Facilities

Name (string)

Symbolic value

auth

LOG_AUTH

authpriv

LOG_AUTHPRIV

cron

LOG_CRON

daemon

LOG_DAEMON

ftp

LOG_FTP

kern

LOG_KERN

lpr

LOG_LPR

mail

LOG_MAIL

news

LOG_NEWS

syslog

LOG_SYSLOG

user

LOG_USER

uucp

LOG_UUCP

local0

LOG_LOCAL0

local1

LOG_LOCAL1

local2

LOG_LOCAL2

local3

LOG_LOCAL3

local4

LOG_LOCAL4

local5

LOG_LOCAL5

local6

LOG_LOCAL6

local7

LOG_LOCAL7

mapPriority(levelname)

Maps a logging level name to a syslog priority name. You may need to override this if you are using custom levels, or if the default algorithm is not suitable for your needs. The default algorithm maps DEBUG, INFO, WARNING, ERROR and CRITICAL to the equivalent syslog names, and all other level names to 'warning'.

NTEventLogHandler

The NTEventLogHandler class, located in the logging.handlers module, supports sending logging messages to a local Windows NT, Windows 2000 or Windows XP event log. Before you can use it, you need Mark Hammond's Win32 extensions for Python installed.

class logging.handlers.NTEventLogHandler(appname, dllname=None, logtype='Application')

Returns a new instance of the NTEventLogHandler class. The appname is used to define the application name as it appears in the event log. An appropriate registry entry is created using this name. The dllname should give the fully qualified pathname of a .dll or .exe which contains message definitions to hold in the log (if not specified, 'win32service.pyd' is used - this is installed with the Win32 extensions and contains some basic placeholder message definitions. Note that use of these placeholders will make your event logs big, as the entire message source is held in the log. If you want slimmer logs, you have to pass in the name of your own .dll or .exe which contains the message definitions you want to use in the event log). The logtype is one of 'Application', 'System' or 'Security', and defaults to 'Application'.

close()

At this point, you can remove the application name from the registry as a source of event log entries. However, if you do this, you will not be able to see the events as you intended in the Event Log Viewer - it needs to be able to access the registry to get the .dll name. The current version does not do this.

emit(record)

Determines the message ID, event category and event type, and then logs the message in the NT event log.

getEventCategory(record)

Returns the event category for the record. Override this if you want to specify your own categories. This version returns 0.

getEventType(record)

Returns the event type for the record. Override this if you want to specify your own types. This version does a mapping using the handler's typemap attribute, which is set up in __init__() to a dictionary which contains mappings for DEBUG, INFO, WARNING, ERROR and CRITICAL. If you are using your own levels, you will either need to override this method or place a suitable dictionary in the handler's typemap attribute.

getMessageID(record)

Returns the message ID for the record. If you are using your own messages, you could do this by having the msg passed to the logger being an ID rather than a format string. Then, in here, you could use a dictionary lookup to get the message ID. This version returns 1, which is the base message ID in win32service.pyd.

SMTPHandler

The SMTPHandler class, located in the logging.handlers module, supports sending logging messages to an email address via SMTP.

class logging.handlers.SMTPHandler(mailhost, fromaddr, toaddrs, subject, credentials=None, secure=None, timeout=1.0)

Returns a new instance of the SMTPHandler class. The instance is initialized with the from and to addresses and subject line of the email. The toaddrs should be a list of strings. To specify a non-standard SMTP port, use the (host, port) tuple format for the mailhost argument. If you use a string, the standard SMTP port is used. If your SMTP server requires authentication, you can specify a (username, password) tuple for the credentials argument.

To specify the use of a secure protocol (TLS), pass in a tuple to the secure argument. This will only be used when authentication credentials are supplied. The tuple should be either an empty tuple, or a single-value tuple with the name of a keyfile, or a 2-value tuple with the names of the keyfile and certificate file. (This tuple is passed to the smtplib.SMTP.starttls() method.)

A timeout can be specified for communication with the SMTP server using the timeout argument.

在 3.3 版的變更: 新增 timeout 參數。

emit(record)

Formats the record and sends it to the specified addressees.

getSubject(record)

If you want to specify a subject line which is record-dependent, override this method.

MemoryHandler

The MemoryHandler class, located in the logging.handlers module, supports buffering of logging records in memory, periodically flushing them to a target handler. Flushing occurs whenever the buffer is full, or when an event of a certain severity or greater is seen.

MemoryHandler is a subclass of the more general BufferingHandler, which is an abstract class. This buffers logging records in memory. Whenever each record is added to the buffer, a check is made by calling shouldFlush() to see if the buffer should be flushed. If it should, then flush() is expected to do the flushing.

class logging.handlers.BufferingHandler(capacity)

Initializes the handler with a buffer of the specified capacity. Here, capacity means the number of logging records buffered.

emit(record)

Append the record to the buffer. If shouldFlush() returns true, call flush() to process the buffer.

flush()

For a BufferingHandler instance, flushing means that it sets the buffer to an empty list. This method can be overwritten to implement more useful flushing behavior.

shouldFlush(record)

Return True if the buffer is up to capacity. This method can be overridden to implement custom flushing strategies.

class logging.handlers.MemoryHandler(capacity, flushLevel=ERROR, target=None, flushOnClose=True)

Returns a new instance of the MemoryHandler class. The instance is initialized with a buffer size of capacity (number of records buffered). If flushLevel is not specified, ERROR is used. If no target is specified, the target will need to be set using setTarget() before this handler does anything useful. If flushOnClose is specified as False, then the buffer is not flushed when the handler is closed. If not specified or specified as True, the previous behaviour of flushing the buffer will occur when the handler is closed.

在 3.6 版的變更: 新增 flushOnClose 參數。

close()

Calls flush(), sets the target to None and clears the buffer.

flush()

For a MemoryHandler instance, flushing means just sending the buffered records to the target, if there is one. The buffer is also cleared when buffered records are sent to the target. Override if you want different behavior.

setTarget(target)

Sets the target handler for this handler.

shouldFlush(record)

Checks for buffer full or a record at the flushLevel or higher.

HTTPHandler

The HTTPHandler class, located in the logging.handlers module, supports sending logging messages to a web server, using either GET or POST semantics.

class logging.handlers.HTTPHandler(host, url, method='GET', secure=False, credentials=None, context=None)

Returns a new instance of the HTTPHandler class. The host can be of the form host:port, should you need to use a specific port number. If no method is specified, GET is used. If secure is true, a HTTPS connection will be used. The context parameter may be set to a ssl.SSLContext instance to configure the SSL settings used for the HTTPS connection. If credentials is specified, it should be a 2-tuple consisting of userid and password, which will be placed in a HTTP 'Authorization' header using Basic authentication. If you specify credentials, you should also specify secure=True so that your userid and password are not passed in cleartext across the wire.

在 3.5 版的變更: 新增 context 參數。

mapLogRecord(record)

Provides a dictionary, based on record, which is to be URL-encoded and sent to the web server. The default implementation just returns record.__dict__. This method can be overridden if e.g. only a subset of LogRecord is to be sent to the web server, or if more specific customization of what's sent to the server is required.

emit(record)

Sends the record to the web server as a URL-encoded dictionary. The mapLogRecord() method is used to convert the record to the dictionary to be sent.

備註

Since preparing a record for sending it to a web server is not the same as a generic formatting operation, using setFormatter() to specify a Formatter for a HTTPHandler has no effect. Instead of calling format(), this handler calls mapLogRecord() and then urllib.parse.urlencode() to encode the dictionary in a form suitable for sending to a web server.

QueueHandler

在 3.2 版被加入.

The QueueHandler class, located in the logging.handlers module, supports sending logging messages to a queue, such as those implemented in the queue or multiprocessing modules.

Along with the QueueListener class, QueueHandler can be used to let handlers do their work on a separate thread from the one which does the logging. This is important in web applications and also other service applications where threads servicing clients need to respond as quickly as possible, while any potentially slow operations (such as sending an email via SMTPHandler) are done on a separate thread.

class logging.handlers.QueueHandler(queue)

Returns a new instance of the QueueHandler class. The instance is initialized with the queue to send messages to. The queue can be any queue-like object; it's used as-is by the enqueue() method, which needs to know how to send messages to it. The queue is not required to have the task tracking API, which means that you can use SimpleQueue instances for queue.

備註

If you are using multiprocessing, you should avoid using SimpleQueue and instead use multiprocessing.Queue.

警告

The multiprocessing module uses an internal logger created and accessed via get_logger(). multiprocessing.Queue will log DEBUG level messages upon items being queued. If those log messages are processed by a QueueHandler using the same multiprocessing.Queue instance, it will cause a deadlock or infinite recursion.

emit(record)

Enqueues the result of preparing the LogRecord. Should an exception occur (e.g. because a bounded queue has filled up), the handleError() method is called to handle the error. This can result in the record silently being dropped (if logging.raiseExceptions is False) or a message printed to sys.stderr (if logging.raiseExceptions is True).

prepare(record)

Prepares a record for queuing. The object returned by this method is enqueued.

The base implementation formats the record to merge the message, arguments, exception and stack information, if present. It also removes unpickleable items from the record in-place. Specifically, it overwrites the record's msg and message attributes with the merged message (obtained by calling the handler's format() method), and sets the args, exc_info and exc_text attributes to None.

You might want to override this method if you want to convert the record to a dict or JSON string, or send a modified copy of the record while leaving the original intact.

備註

The base implementation formats the message with arguments, sets the message and msg attributes to the formatted message and sets the args and exc_text attributes to None to allow pickling and to prevent further attempts at formatting. This means that a handler on the QueueListener side won't have the information to do custom formatting, e.g. of exceptions. You may wish to subclass QueueHandler and override this method to e.g. avoid setting exc_text to None. Note that the message / msg / args changes are related to ensuring the record is pickleable, and you might or might not be able to avoid doing that depending on whether your args are pickleable. (Note that you may have to consider not only your own code but also code in any libraries that you use.)

enqueue(record)

Enqueues the record on the queue using put_nowait(); you may want to override this if you want to use blocking behaviour, or a timeout, or a customized queue implementation.

listener

When created via configuration using dictConfig(), this attribute will contain a QueueListener instance for use with this handler. Otherwise, it will be None.

在 3.12 版被加入.

QueueListener

在 3.2 版被加入.

The QueueListener class, located in the logging.handlers module, supports receiving logging messages from a queue, such as those implemented in the queue or multiprocessing modules. The messages are received from a queue in an internal thread and passed, on the same thread, to one or more handlers for processing. While QueueListener is not itself a handler, it is documented here because it works hand-in-hand with QueueHandler.

Along with the QueueHandler class, QueueListener can be used to let handlers do their work on a separate thread from the one which does the logging. This is important in web applications and also other service applications where threads servicing clients need to respond as quickly as possible, while any potentially slow operations (such as sending an email via SMTPHandler) are done on a separate thread.

class logging.handlers.QueueListener(queue, *handlers, respect_handler_level=False)

Returns a new instance of the QueueListener class. The instance is initialized with the queue to send messages to and a list of handlers which will handle entries placed on the queue. The queue can be any queue-like object; it's passed as-is to the dequeue() method, which needs to know how to get messages from it. The queue is not required to have the task tracking API (though it's used if available), which means that you can use SimpleQueue instances for queue.

備註

If you are using multiprocessing, you should avoid using SimpleQueue and instead use multiprocessing.Queue.

If respect_handler_level is True, a handler's level is respected (compared with the level for the message) when deciding whether to pass messages to that handler; otherwise, the behaviour is as in previous Python versions - to always pass each message to each handler.

在 3.5 版的變更: 新增 respect_handler_level 引數。

在 3.14 版的變更: QueueListener can now be used as a context manager via with. When entering the context, the listener is started. When exiting the context, the listener is stopped. __enter__() returns the QueueListener object.

dequeue(block)

Dequeues a record and return it, optionally blocking.

The base implementation uses get(). You may want to override this method if you want to use timeouts or work with custom queue implementations.

prepare(record)

Prepare a record for handling.

This implementation just returns the passed-in record. You may want to override this method if you need to do any custom marshalling or manipulation of the record before passing it to the handlers.

handle(record)

Handle a record.

This just loops through the handlers offering them the record to handle. The actual object passed to the handlers is that which is returned from prepare().

start()

Starts the listener.

This starts up a background thread to monitor the queue for LogRecords to process.

在 3.14 版的變更: Raises RuntimeError if called and the listener is already running.

stop()

Stops the listener.

This asks the thread to terminate, and then waits for it to do so. Note that if you don't call this before your application exits, there may be some records still left on the queue, which won't be processed.

enqueue_sentinel()

Writes a sentinel to the queue to tell the listener to quit. This implementation uses put_nowait(). You may want to override this method if you want to use timeouts or work with custom queue implementations.

在 3.3 版被加入.

也參考

logging 模組

API reference for the logging module.

logging.config 模組

Configuration API for the logging module.

platform --- 對底層平臺識別資料的存取

原始碼：Lib/platform.py [https://github.com/python/cpython/tree/3.14/Lib/platform.py]

備註

特定平臺清單為按字母順序排列，Linux 包括在 Unix 小節之中。

跨平台

platform.architecture(executable=sys.executable, bits='', linkage='')

查詢給定的可執行檔案（預設為 Python 直譯器二進位制檔案）來取得各種架構資訊。

回傳一個 tuple（元組） (bits, linkage)，其中包含可執行檔案所使用的位元架構和連結格式資訊。這兩個值均以字串形式回傳。

無法確定的值將回傳參數所給定之預先設置值。如果給定的位元為 ''，則會使用 sizeof(pointer)（或者當 Python 版本 < 1.5.2 時為 sizeof(long)）作為所支援指標大小的指示器 (indicator)。

此函式依賴於系統的 file 命令來執行實際的操作。這在幾乎所有 Unix 平臺和某些非 Unix 平臺上，只有當可執行檔案指向 Python 直譯器時才可使用。當以上要求不滿足時將會使用合理的預設值。

備註

在 macOS（也許還有其他平臺）上，可執行檔案可能是包含多種架構的通用檔案。

要取得目前直譯器的 "64 位元性 (64-bitness)"，更可靠的做法是查詢 sys.maxsize 屬性：

is_64bits = sys.maxsize > 2**32

platform.machine()

回傳機器種類，例如 'AMD64'。如果該值無法確定則會回傳一個空字串。

The output is platform-dependent and may differ in casing and naming conventions.

platform.node()

回傳電腦的網路名稱（可能不是完整名稱！）。如果該值無法確定則會回傳一個空字串。

platform.platform(aliased=False, terse=False)

會儘可能附帶有用資訊地回傳一個標識底層平臺的字串。

輸出應為人類易讀的 (human readable)，而非機器易剖析的 (machine parseable)。它在不同平臺上看起來可能不一致，這是有意為之的。

如果 aliased 為真值，此函式將使用各種不同於平臺通用名稱的別名來回報系統名稱，例如 SunOS 將被回報為 Solaris。system_alias() 函式被用於實作此功能。

將 terse 設為真值將導致此函式只回傳標識平臺所需的最小量資訊。

在 3.8 版的變更: 在 macOS 上，如果 mac_ver() 回傳的釋出版字串非空字串，此函式現在會使用它以取得 macOS 版本而非 darwin 版本。

platform.processor()

回傳（真實的）處理器名稱，例如 'amdk6'。

如果該值無法確定則將回傳空字串。請注意，許多平臺都不提供此資訊或是簡單地回傳與 machine() 相同的值。NetBSD 則會提供此資訊。

platform.python_build()

回傳一個 tuple (buildno, builddate)，表示字串形式的 Python 建置編號和日期。

platform.python_compiler()

回傳一個標識用於編譯 Python 的編譯器的字串。

platform.python_branch()

回傳一個標識 Python 實作 SCM 分支的字串。

platform.python_implementation()

回傳一個標識 Python 實作的字串。可能的回傳值有：'CPython'、'IronPython'、'Jython'、'PyPy'。

platform.python_revision()

回傳一個標識 Python 實作 SCM 修訂版的字串。

platform.python_version()

將 Python 版本以字串 'major.minor.patchlevel' 形式回傳。

請注意此回傳值不同於 Python sys.version，它總是會包括 patchlevel（預設為 '0'）。

platform.python_version_tuple()

將 Python 版本以字串 tuple (major, minor, patchlevel) 形式回傳。

請注意此回傳值不同於 Python sys.version，它總是會包括 patchlevel（預設為 '0'）。

platform.release()

回傳系統的釋出版本，例如 '2.2.0' 或 'NT'，如果該值無法確定則將回傳一個空字串。

platform.system()

回傳系統/OS 的名稱，例如 'Linux'、'Darwin'、'Java'、'Windows'。如果該值無法確定則回傳一個空字串。

On iOS and Android, this returns the user-facing OS name (i.e, 'iOS, 'iPadOS' or 'Android'). To obtain the kernel name ('Darwin' or 'Linux'), use os.uname().

platform.system_alias(system, release, version)

回傳做為某些系統所使用的常見行銷名稱之別名的 (system, release, version)。它還會在可能導致混淆的情況下對資訊進行一些重新排序。

platform.version()

回傳系統的釋出版本資訊，例如 '#3 on degas'。如果該值無法確定則將回傳一個空字串。

On iOS and Android, this is the user-facing OS version. To obtain the Darwin or Linux kernel version, use os.uname().

platform.uname()

具有高可攜性 (portable) 的 uname 介面。回傳包含六個屬性的 namedtuple()：system、node、release、version、machine 和 processor。

processor 會延遲解析，有需求時才會解析

注意：前兩個屬性名稱與 os.uname() 提供的名稱不同，它們分別命名為 sysname 和 nodename。

無法確定的條目會被設為 ''。

在 3.3 版的變更: 將結果從 tuple 改為 namedtuple()。

在 3.9 版的變更: processor 會延遲解析，並非立即解析。

platform.invalidate_caches()

Clear out the internal cache of information, such as the uname(). This is typically useful when the platform's node() is changed by an external process and one needs to retrieve the updated value.

在 3.14 版被加入.

Java 平台

platform.java_ver(release='', vendor='', vminfo=('', '', ''), osinfo=('', '', ''))

Jython 的版本介面。

回傳一個 tuple (release, vendor, vminfo, osinfo)，其中 vminfo 為 tuple (vm_name, vm_release, vm_vendor) 而 osinfo 為 tuple (os_name, os_version, os_arch)。無法確定的值將被設為由參數所給定的預設值（預設均為 ''）。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: It was largely untested, had a confusing API, and was only useful for Jython support.

Windows 平台

platform.win32_ver(release='', version='', csd='', ptype='')

從 Windows 登錄檔 (Window Registry) 取得額外的版本資訊並回傳一個 tuple (release, version, csd, ptype)，它代表 OS 發行版、版本號、CSD 級別 (service pack) 和 OS 類型（多個/單個處理器）。

一點提示：ptype 在單個處理器的 NT 機器上為 'Uniprocessor Free'，而在多個處理器的機器上為 'Multiprocessor Free'。'Free' 是指該 OS 版本沒有除錯程式。它也可能以 'Checked' 表示，代表該 OS 版本使用了除錯程式，即檢查引數、範圍等的程式。

platform.win32_edition()

回傳一個代表目前 Windows 版本的字串。可能的值包括但不限於 'Enterprise'、'IoTUAP'、'ServerStandard' 和 'nanoserver'。

在 3.8 版被加入.

platform.win32_is_iot()

如果 win32_edition() 回傳的 Windows 版本被識別為 IoT 版則回傳 True。

在 3.8 版被加入.

macOS 平台

platform.mac_ver(release='', versioninfo=('', '', ''), machine='')

取得 Mac OS 版本資訊並將其回傳為 tuple (release, versioninfo, machine)，其中 versioninfo 是一個 tuple (version, dev_stage, non_release_version)。

無法確定的條目會被設為 ''。所有 tuple 條目均為字串。

iOS 平台

platform.ios_ver(system='', release='', model='', is_simulator=False)

Get iOS version information and return it as a namedtuple() with the following attributes:

system 是 OS 名稱；可能是 'iOS' 或 'iPadOS'。

release is the iOS version number as a string (e.g., '17.2').

model is the device model identifier; this will be a string like 'iPhone13,2' for a physical device, or 'iPhone' on a simulator.

is_simulator is a boolean describing if the app is running on a simulator or a physical device.

無法確定的條目會被設定為以參數給定的預設值。

Unix 平台

platform.libc_ver(executable=sys.executable, lib='', version='', chunksize=16384)

嘗試確認可執行檔案（預設為 Python 直譯器）所連結到的 libc 版本。回傳一個字串 tuple (lib, version)，當查詢失敗時其預設值將被設為給定的參數值。

請注意，此函式對於不同 libc 版本如何為可執行檔案新增符號的方式有深層的關聯，可能僅適用於以 gcc 編譯出來的可執行檔案。

檔案會以 chunksize 位元組大小的分塊 (chunk) 來讀取和掃描。

Linux 平台

platform.freedesktop_os_release()

從 os-release 檔案取得作業系統標識，並將其作為一個字典回傳。os-release 檔案為 freedesktop.org 標準 [https://www.freedesktop.org/software/systemd/man/os-release.html]、並在大多數 Linux 發行版上可用。一個重要的例外是 Android 和基於 Android 的發行版。

當 /etc/os-release 與 /usr/lib/os-release 均無法被讀取時將引發 OSError 或其子類別。

成功時，該函式將回傳一個字典，其中鍵和值均為字串。值當中的特殊字元例如 " 和 $ 會被移除引號 (unquoted)。欄位 NAME、ID 和 PRETTY_NAME 總會按照標準來定義。所有其他欄位都是可選的。根據不同廠商可能會包括額外的欄位。

請注意 NAME、VERSION 和 VARIANT 等欄位是適用於向使用者展示的字串。程式應當使用 ID、ID_LIKE、VERSION_ID 或 VARIANT_ID 等欄位來標識 Linux 發行版。

範例：

def get_like_distro():
    info = platform.freedesktop_os_release()
    ids = [info["ID"]]
    if "ID_LIKE" in info:
        # ids are space separated and ordered by precedence
        ids.extend(info["ID_LIKE"].split())
    return ids

在 3.10 版被加入.

Android 平台

platform.android_ver(release='', api_level=0, manufacturer='', model='', device='', is_emulator=False)

Get Android device information. Returns a namedtuple() with the following attributes. Values which cannot be determined are set to the defaults given as parameters.

release - Android version, as a string (e.g. "14").

api_level - API level of the running device, as an integer (e.g. 34 for Android 14). To get the API level which Python was built against, see sys.getandroidapilevel().

manufacturer - Manufacturer name [https://developer.android.com/reference/android/os/Build#MANUFACTURER].

model - Model name [https://developer.android.com/reference/android/os/Build#MODEL] – typically the marketing name or model number.

device - Device name [https://developer.android.com/reference/android/os/Build#DEVICE] – typically the model number or a codename.

is_emulator - True if the device is an emulator; False if it's a physical device.

Google maintains a list of known model and device names [https://storage.googleapis.com/play_public/supported_devices.html].

在 3.13 版被加入.

命令列用法

platform can also be invoked directly using the -m switch of the interpreter:

python -m platform [--terse] [--nonaliased] [{nonaliased,terse} ...]

可接受以下選項：

--terse

Print terse information about the platform. This is equivalent to calling platform.platform() with the terse argument set to True.

--nonaliased

Print platform information without system/OS name aliasing. This is equivalent to calling platform.platform() with the aliased argument set to True.

You can also pass one or more positional arguments (terse, nonaliased) to explicitly control the output format. These behave similarly to their corresponding options.

errno --- 標準 errno 系統符號

This module makes available standard errno system symbols. The value of each symbol is the corresponding integer value. The names and descriptions are borrowed from linux/include/errno.h, which should be all-inclusive.

errno.errorcode

Dictionary providing a mapping from the errno value to the string name in the underlying system. For instance, errno.errorcode[errno.EPERM] maps to 'EPERM'.

To translate a numeric error code to an error message, use os.strerror().

Of the following list, symbols that are not used on the current platform are not defined by the module. The specific list of defined symbols is available as errno.errorcode.keys(). Symbols available can include:

errno.EPERM

Operation not permitted. This error is mapped to the exception PermissionError.

errno.ENOENT

No such file or directory. This error is mapped to the exception FileNotFoundError.

errno.ESRCH

No such process. This error is mapped to the exception ProcessLookupError.

errno.EINTR

Interrupted system call. This error is mapped to the exception InterruptedError.

errno.EIO

I/O error

errno.ENXIO

No such device or address

errno.E2BIG

Arg list too long

errno.ENOEXEC

Exec format error

errno.EBADF

Bad file number

errno.ECHILD

No child processes. This error is mapped to the exception ChildProcessError.

errno.EAGAIN

Try again. This error is mapped to the exception BlockingIOError.

errno.ENOMEM

Out of memory

errno.EACCES

Permission denied. This error is mapped to the exception PermissionError.

errno.EFAULT

Bad address

errno.ENOTBLK

Block device required

errno.EBUSY

Device or resource busy

errno.EEXIST

File exists. This error is mapped to the exception FileExistsError.

errno.EXDEV

Cross-device link

errno.ENODEV

No such device

errno.ENOTDIR

Not a directory. This error is mapped to the exception NotADirectoryError.

errno.EISDIR

Is a directory. This error is mapped to the exception IsADirectoryError.

errno.EINVAL

Invalid argument

errno.ENFILE

File table overflow

errno.EMFILE

Too many open files

errno.ENOTTY

Not a typewriter

errno.ETXTBSY

Text file busy

errno.EFBIG

File too large

errno.ENOSPC

No space left on device

errno.ESPIPE

Illegal seek

errno.EROFS

Read-only file system

errno.EMLINK

Too many links

errno.EPIPE

Broken pipe. This error is mapped to the exception BrokenPipeError.

errno.EDOM

Math argument out of domain of func

errno.ERANGE

Math result not representable

errno.EDEADLK

Resource deadlock would occur

errno.ENAMETOOLONG

File name too long

errno.ENOLCK

No record locks available

errno.ENOSYS

Function not implemented

errno.ENOTEMPTY

Directory not empty

errno.ELOOP

Too many symbolic links encountered

errno.EWOULDBLOCK

Operation would block. This error is mapped to the exception BlockingIOError.

errno.ENOMSG

No message of desired type

errno.EIDRM

Identifier removed

errno.ECHRNG

Channel number out of range

errno.EL2NSYNC

Level 2 not synchronized

errno.EL3HLT

Level 3 halted

errno.EL3RST

Level 3 reset

errno.ELNRNG

Link number out of range

errno.EUNATCH

Protocol driver not attached

errno.ENOCSI

No CSI structure available

errno.EL2HLT

Level 2 halted

errno.EBADE

Invalid exchange

errno.EBADR

Invalid request descriptor

errno.EXFULL

Exchange full

errno.ENOANO

No anode

errno.EBADRQC

Invalid request code

errno.EBADSLT

Invalid slot

errno.EDEADLOCK

File locking deadlock error

errno.EBFONT

Bad font file format

errno.ENOSTR

Device not a stream

errno.ENODATA

No data available

errno.ETIME

Timer expired

errno.ENOSR

Out of streams resources

errno.ENONET

Machine is not on the network

errno.ENOPKG

Package not installed

errno.EREMOTE

Object is remote

errno.ENOLINK

Link has been severed

errno.EADV

Advertise error

errno.ESRMNT

Srmount error

errno.ECOMM

Communication error on send

errno.EPROTO

Protocol error

errno.EMULTIHOP

Multihop attempted

errno.EDOTDOT

RFS specific error

errno.EBADMSG

Not a data message

errno.EOVERFLOW

Value too large for defined data type

errno.ENOTUNIQ

Name not unique on network

errno.EBADFD

File descriptor in bad state

errno.EREMCHG

Remote address changed

errno.ELIBACC

Can not access a needed shared library

errno.ELIBBAD

Accessing a corrupted shared library

errno.ELIBSCN

.lib section in a.out corrupted

errno.ELIBMAX

Attempting to link in too many shared libraries

errno.ELIBEXEC

Cannot exec a shared library directly

errno.EILSEQ

Illegal byte sequence

errno.ERESTART

Interrupted system call should be restarted

errno.ESTRPIPE

Streams pipe error

errno.EUSERS

使用者數量過多

errno.ENOTSOCK

Socket operation on non-socket

errno.EDESTADDRREQ

Destination address required

errno.EMSGSIZE

Message too long

errno.EPROTOTYPE

Protocol wrong type for socket

errno.ENOPROTOOPT

Protocol not available

errno.EPROTONOSUPPORT

Protocol not supported

errno.ESOCKTNOSUPPORT

Socket type not supported

errno.EOPNOTSUPP

Operation not supported on transport endpoint

errno.ENOTSUP

Operation not supported

在 3.2 版被加入.

errno.EPFNOSUPPORT

Protocol family not supported

errno.EAFNOSUPPORT

Address family not supported by protocol

errno.EADDRINUSE

Address already in use

errno.EADDRNOTAVAIL

Cannot assign requested address

errno.ENETDOWN

Network is down

errno.ENETUNREACH

Network is unreachable

errno.ENETRESET

Network dropped connection because of reset

errno.ECONNABORTED

Software caused connection abort. This error is mapped to the exception ConnectionAbortedError.

errno.ECONNRESET

Connection reset by peer. This error is mapped to the exception ConnectionResetError.

errno.ENOBUFS

No buffer space available

errno.EISCONN

Transport endpoint is already connected

errno.ENOTCONN

Transport endpoint is not connected

errno.ESHUTDOWN

Cannot send after transport endpoint shutdown. This error is mapped to the exception BrokenPipeError.

errno.ETOOMANYREFS

Too many references: cannot splice

errno.ETIMEDOUT

Connection timed out. This error is mapped to the exception TimeoutError.

errno.ECONNREFUSED

Connection refused. This error is mapped to the exception ConnectionRefusedError.

errno.EHOSTDOWN

Host is down

errno.EHOSTUNREACH

No route to host

errno.EHWPOISON

Memory page has hardware error.

在 3.14 版被加入.

errno.EALREADY

Operation already in progress. This error is mapped to the exception BlockingIOError.

errno.EINPROGRESS

Operation now in progress. This error is mapped to the exception BlockingIOError.

errno.ESTALE

Stale NFS file handle

errno.EUCLEAN

Structure needs cleaning

errno.ENOTNAM

Not a XENIX named type file

errno.ENAVAIL

No XENIX semaphores available

errno.EISNAM

Is a named type file

errno.EREMOTEIO

Remote I/O error

errno.EDQUOT

Quota exceeded

errno.EQFULL

Interface output queue is full

在 3.11 版被加入.

errno.ENOMEDIUM

No medium found

errno.EMEDIUMTYPE

Wrong medium type

errno.ENOKEY

Required key not available

errno.EKEYEXPIRED

Key has expired

errno.EKEYREVOKED

Key has been revoked

errno.EKEYREJECTED

Key was rejected by service

errno.ERFKILL

Operation not possible due to RF-kill

errno.ELOCKUNMAPPED

Locked lock was unmapped

errno.ENOTACTIVE

Facility is not active

errno.EAUTH

Authentication error

在 3.2 版被加入.

errno.EBADARCH

Bad CPU type in executable

在 3.2 版被加入.

errno.EBADEXEC

Bad executable (or shared library)

在 3.2 版被加入.

errno.EBADMACHO

Malformed Mach-o file

在 3.2 版被加入.

errno.EDEVERR

裝置錯誤

在 3.2 版被加入.

errno.EFTYPE

不適當的檔案類型或格式

在 3.2 版被加入.

errno.ENEEDAUTH

需要驗證器

在 3.2 版被加入.

errno.ENOATTR

找不到屬性

在 3.2 版被加入.

errno.ENOPOLICY

Policy not found

在 3.2 版被加入.

errno.EPROCLIM

行程數量過多

在 3.2 版被加入.

errno.EPROCUNAVAIL

Bad procedure for program

在 3.2 版被加入.

errno.EPROGMISMATCH

Program version wrong

在 3.2 版被加入.

errno.EPROGUNAVAIL

RPC prog. not avail

在 3.2 版被加入.

errno.EPWROFF

裝置電源關閉

在 3.2 版被加入.

errno.EBADRPC

RPC 結構不正確

在 3.2 版被加入.

errno.ERPCMISMATCH

RPC 版本錯誤

在 3.2 版被加入.

errno.ESHLIBVERS

共享函式庫版本不匹配

在 3.2 版被加入.

errno.ENOTCAPABLE

Capabilities insufficient. This error is mapped to the exception PermissionError.

可用性: WASI, FreeBSD

在 3.11.1 版被加入.

errno.ECANCELED

操作已取消

在 3.2 版被加入.

errno.EOWNERDEAD

擁有者過世

在 3.2 版被加入.

errno.ENOTRECOVERABLE

狀態無法恢復

在 3.2 版被加入.

ctypes --- 用於 Python 的外部函式庫

原始碼：Lib/ctypes [https://github.com/python/cpython/tree/3.14/Lib/ctypes]

ctypes is a foreign function library for Python. It provides C compatible data types, and allows calling functions in DLLs or shared libraries. It can be used to wrap these libraries in pure Python.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

ctypes 教學

Note: The code samples in this tutorial use doctest to make sure that they actually work. Since some code samples behave differently under Linux, Windows, or macOS, they contain doctest directives in comments.

Note: Some code samples reference the ctypes c_int type. On platforms where sizeof(long) == sizeof(int) it is an alias to c_long. So, you should not be confused if c_long is printed if you would expect c_int --- they are actually the same type.

Loading dynamic link libraries

ctypes exports the cdll, and on Windows windll and oledll objects, for loading dynamic link libraries.

You load libraries by accessing them as attributes of these objects. cdll loads libraries which export functions using the standard cdecl calling convention, while windll libraries call functions using the stdcall calling convention. oledll also uses the stdcall calling convention, and assumes the functions return a Windows HRESULT error code. The error code is used to automatically raise an OSError exception when the function call fails.

在 3.3 版的變更: Windows errors used to raise WindowsError, which is now an alias of OSError.

Here are some examples for Windows. Note that msvcrt is the MS standard C library containing most standard C functions, and uses the cdecl calling convention:

>>> from ctypes import *
>>> print(windll.kernel32)
<WinDLL 'kernel32', handle ... at ...>
>>> print(cdll.msvcrt)
<CDLL 'msvcrt', handle ... at ...>
>>> libc = cdll.msvcrt
>>>

Windows appends the usual .dll file suffix automatically.

備註

Accessing the standard C library through cdll.msvcrt will use an outdated version of the library that may be incompatible with the one being used by Python. Where possible, use native Python functionality, or else import and use the msvcrt module.

On Linux, it is required to specify the filename including the extension to load a library, so attribute access can not be used to load libraries. Either the LoadLibrary() method of the dll loaders should be used, or you should load the library by creating an instance of CDLL by calling the constructor:

>>> cdll.LoadLibrary("libc.so.6")
<CDLL 'libc.so.6', handle ... at ...>
>>> libc = CDLL("libc.so.6")
>>> libc
<CDLL 'libc.so.6', handle ... at ...>
>>>

Accessing functions from loaded dlls

Functions are accessed as attributes of dll objects:

>>> libc.printf
<_FuncPtr object at 0x...>
>>> print(windll.kernel32.GetModuleHandleA)
<_FuncPtr object at 0x...>
>>> print(windll.kernel32.MyOwnFunction)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ctypes.py", line 239, in __getattr__
    func = _StdcallFuncPtr(name, self)
AttributeError: function 'MyOwnFunction' not found
>>>

Note that win32 system dlls like kernel32 and user32 often export ANSI as well as UNICODE versions of a function. The UNICODE version is exported with a W appended to the name, while the ANSI version is exported with an A appended to the name. The win32 GetModuleHandle function, which returns a module handle for a given module name, has the following C prototype, and a macro is used to expose one of them as GetModuleHandle depending on whether UNICODE is defined or not:

/* ANSI 版本 */
HMODULE GetModuleHandleA(LPCSTR lpModuleName);
/* UNICODE 版本 */
HMODULE GetModuleHandleW(LPCWSTR lpModuleName);

windll does not try to select one of them by magic, you must access the version you need by specifying GetModuleHandleA or GetModuleHandleW explicitly, and then call it with bytes or string objects respectively.

Sometimes, dlls export functions with names which aren't valid Python identifiers, like "??2@YAPAXI@Z". In this case you have to use getattr() to retrieve the function:

>>> getattr(cdll.msvcrt, "??2@YAPAXI@Z")
<_FuncPtr object at 0x...>
>>>

On Windows, some dlls export functions not by name but by ordinal. These functions can be accessed by indexing the dll object with the ordinal number:

>>> cdll.kernel32[1]
<_FuncPtr object at 0x...>
>>> cdll.kernel32[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ctypes.py", line 310, in __getitem__
    func = _StdcallFuncPtr(name, self)
AttributeError: function ordinal 0 not found
>>>

呼叫函式

You can call these functions like any other Python callable. This example uses the rand() function, which takes no arguments and returns a pseudo-random integer:

>>> print(libc.rand())
1804289383

On Windows, you can call the GetModuleHandleA() function, which returns a win32 module handle (passing None as single argument to call it with a NULL pointer):

>>> print(hex(windll.kernel32.GetModuleHandleA(None)))
0x1d000000
>>>

ValueError is raised when you call an stdcall function with the cdecl calling convention, or vice versa:

>>> cdll.kernel32.GetModuleHandleA(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Procedure probably called with not enough arguments (4 bytes missing)
>>>

>>> windll.msvcrt.printf(b"spam")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Procedure probably called with too many arguments (4 bytes in excess)
>>>

To find out the correct calling convention you have to look into the C header file or the documentation for the function you want to call.

On Windows, ctypes uses win32 structured exception handling to prevent crashes from general protection faults when functions are called with invalid argument values:

>>> windll.kernel32.GetModuleHandleA(32)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: exception: access violation reading 0x00000020
>>>

There are, however, enough ways to crash Python with ctypes, so you should be careful anyway. The faulthandler module can be helpful in debugging crashes (e.g. from segmentation faults produced by erroneous C library calls).

None, integers, bytes objects and (unicode) strings are the only native Python objects that can directly be used as parameters in these function calls. None is passed as a C NULL pointer, bytes objects and strings are passed as pointer to the memory block that contains their data (char* or wchar_t*). Python integers are passed as the platform's default C int type, their value is masked to fit into the C type.

Before we move on calling functions with other parameter types, we have to learn more about ctypes data types.

Fundamental data types

ctypes defines a number of primitive C compatible data types:

ctypes 型別

C 型別

Python 型別

c_bool

_Bool

bool (1)

c_char

char

1-character bytes object

c_wchar

wchar_t

1-character string

c_byte

char

int

c_ubyte

unsigned char

int

c_short

short

int

c_ushort

unsigned short

int

c_int

int

int

c_int8

int8_t

int

c_int16

int16_t

int

c_int32

int32_t

int

c_int64

int64_t

int

c_uint

unsigned int

int

c_uint8

uint8_t

int

c_uint16

uint16_t

int

c_uint32

uint32_t

int

c_uint64

uint64_t

int

c_long

long

int

c_ulong

unsigned long

int

c_longlong

__int64 或 long long

int

c_ulonglong

unsigned __int64 或 unsigned long long

int

c_size_t

size_t

int

c_ssize_t

ssize_t 或 Py_ssize_t

int

c_time_t

time_t

int

c_float

float

float

c_double

double

float

c_longdouble

long double

float

c_char_p

char* (NUL terminated)

位元組物件或 None

c_wchar_p

wchar_t* (NUL terminated)

字串或 None

c_void_p

void*

int or None

The constructor accepts any object with a truth value.

Additionally, if IEC 60559 compatible complex arithmetic (Annex G) is supported in both C and libffi, the following complex types are available:

ctypes 型別

C 型別

Python 型別

c_float_complex

float complex

complex

c_double_complex

double complex

complex

c_longdouble_complex

long double complex

complex

All these types can be created by calling them with an optional initializer of the correct type and value:

>>> c_int()
c_long(0)
>>> c_wchar_p("Hello, World")
c_wchar_p(140018365411392)
>>> c_ushort(-3)
c_ushort(65533)
>>>

Since these types are mutable, their value can also be changed afterwards:

>>> i = c_int(42)
>>> print(i)
c_long(42)
>>> print(i.value)
42
>>> i.value = -99
>>> print(i.value)
-99
>>>

Assigning a new value to instances of the pointer types c_char_p, c_wchar_p, and c_void_p changes the memory location they point to, not the contents of the memory block (of course not, because Python string objects are immutable):

>>> s = "Hello, World"
>>> c_s = c_wchar_p(s)
>>> print(c_s)
c_wchar_p(139966785747344)
>>> print(c_s.value)
Hello World
>>> c_s.value = "Hi, there"
>>> print(c_s)              # 記憶體位置已改變
c_wchar_p(139966783348904)
>>> print(c_s.value)
Hi, there
>>> print(s)                # 第一個物件未改變
Hello, World
>>>

You should be careful, however, not to pass them to functions expecting pointers to mutable memory. If you need mutable memory blocks, ctypes has a create_string_buffer() function which creates these in various ways. The current memory block contents can be accessed (or changed) with the raw property; if you want to access it as NUL terminated string, use the value property:

>>> from ctypes import *
>>> p = create_string_buffer(3)            # create a 3 byte buffer, initialized to NUL bytes
>>> print(sizeof(p), repr(p.raw))
3 b'\x00\x00\x00'
>>> p = create_string_buffer(b"Hello")     # create a buffer containing a NUL terminated string
>>> print(sizeof(p), repr(p.raw))
6 b'Hello\x00'
>>> print(repr(p.value))
b'Hello'
>>> p = create_string_buffer(b"Hello", 10) # create a 10 byte buffer
>>> print(sizeof(p), repr(p.raw))
10 b'Hello\x00\x00\x00\x00\x00'
>>> p.value = b"Hi"
>>> print(sizeof(p), repr(p.raw))
10 b'Hi\x00lo\x00\x00\x00\x00\x00'
>>>

The create_string_buffer() function replaces the old c_buffer() function (which is still available as an alias). To create a mutable memory block containing unicode characters of the C type wchar_t, use the create_unicode_buffer() function.

Calling functions, continued

Note that printf prints to the real standard output channel, not to sys.stdout, so these examples will only work at the console prompt, not from within IDLE or PythonWin:

>>> printf = libc.printf
>>> printf(b"Hello, %s\n", b"World!")
Hello, World!
14
>>> printf(b"Hello, %S\n", "World!")
Hello, World!
14
>>> printf(b"%d bottles of beer\n", 42)
42 bottles of beer
19
>>> printf(b"%f bottles of beer\n", 42.5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ctypes.ArgumentError: argument 2: TypeError: Don't know how to convert parameter 2
>>>

As has been mentioned before, all Python types except integers, strings, and bytes objects have to be wrapped in their corresponding ctypes type, so that they can be converted to the required C data type:

>>> printf(b"An int %d, a double %f\n", 1234, c_double(3.14))
An int 1234, a double 3.140000
31
>>>

Calling variadic functions

On a lot of platforms calling variadic functions through ctypes is exactly the same as calling functions with a fixed number of parameters. On some platforms, and in particular ARM64 for Apple Platforms, the calling convention for variadic functions is different than that for regular functions.

On those platforms it is required to specify the argtypes attribute for the regular, non-variadic, function arguments:

libc.printf.argtypes = [ctypes.c_char_p]

Because specifying the attribute does not inhibit portability it is advised to always specify argtypes for all variadic functions.

Calling functions with your own custom data types

You can also customize ctypes argument conversion to allow instances of your own classes be used as function arguments. ctypes looks for an _as_parameter_ attribute and uses this as the function argument. The attribute must be an integer, string, bytes, a ctypes instance, or an object with an _as_parameter_ attribute:

>>> class Bottles:
...     def __init__(self, number):
...         self._as_parameter_ = number
...
>>> bottles = Bottles(42)
>>> printf(b"%d bottles of beer\n", bottles)
42 bottles of beer
19
>>>

If you don't want to store the instance's data in the _as_parameter_ instance variable, you could define a property which makes the attribute available on request.

Specifying the required argument types (function prototypes)

It is possible to specify the required argument types of functions exported from DLLs by setting the argtypes attribute.

argtypes must be a sequence of C data types (the printf() function is probably not a good example here, because it takes a variable number and different types of parameters depending on the format string, on the other hand this is quite handy to experiment with this feature):

>>> printf.argtypes = [c_char_p, c_char_p, c_int, c_double]
>>> printf(b"String '%s', Int %d, Double %f\n", b"Hi", 10, 2.2)
String 'Hi', Int 10, Double 2.200000
37
>>>

Specifying a format protects against incompatible argument types (just as a prototype for a C function), and tries to convert the arguments to valid types:

>>> printf(b"%d %d %d", 1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ctypes.ArgumentError: argument 2: TypeError: 'int' object cannot be interpreted as ctypes.c_char_p
>>> printf(b"%s %d %f\n", b"X", 2, 3)
X 2 3.000000
13
>>>

If you have defined your own classes which you pass to function calls, you have to implement a from_param() class method for them to be able to use them in the argtypes sequence. The from_param() class method receives the Python object passed to the function call, it should do a typecheck or whatever is needed to make sure this object is acceptable, and then return the object itself, its _as_parameter_ attribute, or whatever you want to pass as the C function argument in this case. Again, the result should be an integer, string, bytes, a ctypes instance, or an object with an _as_parameter_ attribute.

Return types

By default functions are assumed to return the C int type. Other return types can be specified by setting the restype attribute of the function object.

The C prototype of time() is time_t time(time_t *). Because time_t might be of a different type than the default return type int, you should specify the restype attribute:

>>> libc.time.restype = c_time_t

The argument types can be specified using argtypes:

>>> libc.time.argtypes = (POINTER(c_time_t),)

To call the function with a NULL pointer as first argument, use None:

>>> print(libc.time(None))
1150640792

Here is a more advanced example, it uses the strchr() function, which expects a string pointer and a char, and returns a pointer to a string:

>>> strchr = libc.strchr
>>> strchr(b"abcdef", ord("d"))
8059983
>>> strchr.restype = c_char_p    # c_char_p is a pointer to a string
>>> strchr(b"abcdef", ord("d"))
b'def'
>>> print(strchr(b"abcdef", ord("x")))
None
>>>

If you want to avoid the ord("x") calls above, you can set the argtypes attribute, and the second argument will be converted from a single character Python bytes object into a C char:

>>> strchr.restype = c_char_p
>>> strchr.argtypes = [c_char_p, c_char]
>>> strchr(b"abcdef", b"d")
b'def'
>>> strchr(b"abcdef", b"def")
Traceback (most recent call last):
ctypes.ArgumentError: argument 2: TypeError: one character bytes, bytearray or integer expected
>>> print(strchr(b"abcdef", b"x"))
None
>>> strchr(b"abcdef", b"d")
b'def'
>>>

You can also use a callable Python object (a function or a class for example) as the restype attribute, if the foreign function returns an integer. The callable will be called with the integer the C function returns, and the result of this call will be used as the result of your function call. This is useful to check for error return values and automatically raise an exception:

>>> GetModuleHandle = windll.kernel32.GetModuleHandleA
>>> def ValidHandle(value):
...     if value == 0:
...         raise WinError()
...     return value
...
>>>
>>> GetModuleHandle.restype = ValidHandle
>>> GetModuleHandle(None)
486539264
>>> GetModuleHandle("something silly")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in ValidHandle
OSError: [Errno 126] The specified module could not be found.
>>>

WinError is a function which will call Windows FormatMessage() api to get the string representation of an error code, and returns an exception. WinError takes an optional error code parameter, if no one is used, it calls GetLastError() to retrieve it.

Please note that a much more powerful error checking mechanism is available through the errcheck attribute; see the reference manual for details.

Passing pointers (or: passing parameters by reference)

Sometimes a C api function expects a pointer to a data type as parameter, probably to write into the corresponding location, or if the data is too large to be passed by value. This is also known as passing parameters by reference.

ctypes exports the byref() function which is used to pass parameters by reference. The same effect can be achieved with the pointer() function, although pointer() does a lot more work since it constructs a real pointer object, so it is faster to use byref() if you don't need the pointer object in Python itself:

>>> i = c_int()
>>> f = c_float()
>>> s = create_string_buffer(b'\000' * 32)
>>> print(i.value, f.value, repr(s.value))
0 0.0 b''
>>> libc.sscanf(b"1 3.14 Hello", b"%d %f %s",
...             byref(i), byref(f), s)
3
>>> print(i.value, f.value, repr(s.value))
1 3.1400001049 b'Hello'
>>>

Structures and unions

Structures and unions must derive from the Structure and Union base classes which are defined in the ctypes module. Each subclass must define a _fields_ attribute. _fields_ must be a list of 2-tuples, containing a field name and a field type.

The field type must be a ctypes type like c_int, or any other derived ctypes type: structure, union, array, pointer.

Here is a simple example of a POINT structure, which contains two integers named x and y, and also shows how to initialize a structure in the constructor:

>>> from ctypes import *
>>> class POINT(Structure):
...     _fields_ = [("x", c_int),
...                 ("y", c_int)]
...
>>> point = POINT(10, 20)
>>> print(point.x, point.y)
10 20
>>> point = POINT(y=5)
>>> print(point.x, point.y)
0 5
>>> POINT(1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: too many initializers
>>>

You can, however, build much more complicated structures. A structure can itself contain other structures by using a structure as a field type.

Here is a RECT structure which contains two POINTs named upperleft and lowerright:

>>> class RECT(Structure):
...     _fields_ = [("upperleft", POINT),
...                 ("lowerright", POINT)]
...
>>> rc = RECT(point)
>>> print(rc.upperleft.x, rc.upperleft.y)
0 5
>>> print(rc.lowerright.x, rc.lowerright.y)
0 0
>>>

Nested structures can also be initialized in the constructor in several ways:

>>> r = RECT(POINT(1, 2), POINT(3, 4))
>>> r = RECT((1, 2), (3, 4))

Field descriptors can be retrieved from the class, they are useful for debugging because they can provide useful information. See CField:

>>> POINT.x
<ctypes.CField 'x' type=c_int, ofs=0, size=4>
>>> POINT.y
<ctypes.CField 'y' type=c_int, ofs=4, size=4>
>>>

警告

ctypes does not support passing unions or structures with bit-fields to functions by value. While this may work on 32-bit x86, it's not guaranteed by the library to work in the general case. Unions and structures with bit-fields should always be passed to functions by pointer.

Structure/union layout, alignment and byte order

By default, Structure and Union fields are laid out in the same way the C compiler does it. It is possible to override this behavior entirely by specifying a _layout_ class attribute in the subclass definition; see the attribute documentation for details.

It is possible to specify the maximum alignment for the fields and/or for the structure itself by setting the class attributes _pack_ and/or _align_, respectively. See the attribute documentation for details.

ctypes uses the native byte order for Structures and Unions. To build structures with non-native byte order, you can use one of the BigEndianStructure, LittleEndianStructure, BigEndianUnion, and LittleEndianUnion base classes. These classes cannot contain pointer fields.

Bit fields in structures and unions

It is possible to create structures and unions containing bit fields. Bit fields are only possible for integer fields, the bit width is specified as the third item in the _fields_ tuples:

>>> class Int(Structure):
...     _fields_ = [("first_16", c_int, 16),
...                 ("second_16", c_int, 16)]
...
>>> print(Int.first_16)
<ctypes.CField 'first_16' type=c_int, ofs=0, bit_size=16, bit_offset=0>
>>> print(Int.second_16)
<ctypes.CField 'second_16' type=c_int, ofs=0, bit_size=16, bit_offset=16>

It is important to note that bit field allocation and layout in memory are not defined as a C standard; their implementation is compiler-specific. By default, Python will attempt to match the behavior of a "native" compiler for the current platform. See the _layout_ attribute for details on the default behavior and how to change it.

Arrays

Arrays are sequences, containing a fixed number of instances of the same type.

The recommended way to create array types is by multiplying a data type with a positive integer:

TenPointsArrayType = POINT * 10

Here is an example of a somewhat artificial data type, a structure containing 4 POINTs among other stuff:

>>> from ctypes import *
>>> class POINT(Structure):
...     _fields_ = ("x", c_int), ("y", c_int)
...
>>> class MyStruct(Structure):
...     _fields_ = [("a", c_int),
...                 ("b", c_float),
...                 ("point_array", POINT * 4)]
>>>
>>> print(len(MyStruct().point_array))
4
>>>

Instances are created in the usual way, by calling the class:

arr = TenPointsArrayType()
for pt in arr:
    print(pt.x, pt.y)

The above code print a series of 0 0 lines, because the array contents is initialized to zeros.

Initializers of the correct type can also be specified:

>>> from ctypes import *
>>> TenIntegers = c_int * 10
>>> ii = TenIntegers(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
>>> print(ii)
<c_long_Array_10 object at 0x...>
>>> for i in ii: print(i, end=" ")
...
1 2 3 4 5 6 7 8 9 10
>>>

指標

Pointer instances are created by calling the pointer() function on a ctypes type:

>>> from ctypes import *
>>> i = c_int(42)
>>> pi = pointer(i)
>>>

Pointer instances have a contents attribute which returns the object to which the pointer points, the i object above:

>>> pi.contents
c_long(42)
>>>

Note that ctypes does not have OOR (original object return), it constructs a new, equivalent object each time you retrieve an attribute:

>>> pi.contents is i
False
>>> pi.contents is pi.contents
False
>>>

Assigning another c_int instance to the pointer's contents attribute would cause the pointer to point to the memory location where this is stored:

>>> i = c_int(99)
>>> pi.contents = i
>>> pi.contents
c_long(99)
>>>

Pointer instances can also be indexed with integers:

>>> pi[0]
99
>>>

Assigning to an integer index changes the pointed to value:

>>> print(i)
c_long(99)
>>> pi[0] = 22
>>> print(i)
c_long(22)
>>>

It is also possible to use indexes different from 0, but you must know what you're doing, just as in C: You can access or change arbitrary memory locations. Generally you only use this feature if you receive a pointer from a C function, and you know that the pointer actually points to an array instead of a single item.

Behind the scenes, the pointer() function does more than simply create pointer instances, it has to create pointer types first. This is done with the POINTER() function, which accepts any ctypes type, and returns a new type:

>>> PI = POINTER(c_int)
>>> PI
<class 'ctypes.LP_c_long'>
>>> PI(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: expected c_long instead of int
>>> PI(c_int(42))
<ctypes.LP_c_long object at 0x...>
>>>

Calling the pointer type without an argument creates a NULL pointer. NULL pointers have a False boolean value:

>>> null_ptr = POINTER(c_int)()
>>> print(bool(null_ptr))
False
>>>

ctypes checks for NULL when dereferencing pointers (but dereferencing invalid non-NULL pointers would crash Python):

>>> null_ptr[0]
Traceback (most recent call last):
    ....
ValueError: NULL pointer access
>>>

>>> null_ptr[0] = 1234
Traceback (most recent call last):
    ....
ValueError: NULL pointer access
>>>

Thread safety without the GIL

From Python 3.13 onward, the GIL can be disabled on free threaded builds. In ctypes, reads and writes to a single object concurrently is safe, but not across multiple objects:

>>> number = c_int(42)
>>> pointer_a = pointer(number)
>>> pointer_b = pointer(number)

In the above, it's only safe for one object to read and write to the address at once if the GIL is disabled. So, pointer_a can be shared and written to across multiple threads, but only if pointer_b is not also attempting to do the same. If this is an issue, consider using a threading.Lock to synchronize access to memory:

>>> import threading
>>> lock = threading.Lock()
>>> # 執行緒 1
>>> with lock:
...    pointer_a.contents = 24
>>> # 執行緒 2
>>> with lock:
...    pointer_b.contents = 42

Type conversions

Usually, ctypes does strict type checking. This means, if you have POINTER(c_int) in the argtypes list of a function or as the type of a member field in a structure definition, only instances of exactly the same type are accepted. There are some exceptions to this rule, where ctypes accepts other objects. For example, you can pass compatible array instances instead of pointer types. So, for POINTER(c_int), ctypes accepts an array of c_int:

>>> class Bar(Structure):
...     _fields_ = [("count", c_int), ("values", POINTER(c_int))]
...
>>> bar = Bar()
>>> bar.values = (c_int * 3)(1, 2, 3)
>>> bar.count = 3
>>> for i in range(bar.count):
...     print(bar.values[i])
...
1
2
3
>>>

In addition, if a function argument is explicitly declared to be a pointer type (such as POINTER(c_int)) in argtypes, an object of the pointed type (c_int in this case) can be passed to the function. ctypes will apply the required byref() conversion in this case automatically.

To set a POINTER type field to NULL, you can assign None:

>>> bar.values = None
>>>

Sometimes you have instances of incompatible types. In C, you can cast one type into another type. ctypes provides a cast() function which can be used in the same way. The Bar structure defined above accepts POINTER(c_int) pointers or c_int arrays for its values field, but not instances of other types:

>>> bar.values = (c_byte * 4)()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: incompatible types, c_byte_Array_4 instance instead of LP_c_long instance
>>>

For these cases, the cast() function is handy.

The cast() function can be used to cast a ctypes instance into a pointer to a different ctypes data type. cast() takes two parameters, a ctypes object that is or can be converted to a pointer of some kind, and a ctypes pointer type. It returns an instance of the second argument, which references the same memory block as the first argument:

>>> a = (c_byte * 4)()
>>> cast(a, POINTER(c_int))
<ctypes.LP_c_long object at ...>
>>>

So, cast() can be used to assign to the values field of Bar the structure:

>>> bar = Bar()
>>> bar.values = cast((c_byte * 4)(), POINTER(c_int))
>>> print(bar.values[0])
0
>>>

Incomplete Types

Incomplete Types are structures, unions or arrays whose members are not yet specified. In C, they are specified by forward declarations, which are defined later:

struct cell; /* forward declaration */

struct cell {
    char *name;
    struct cell *next;
};

The straightforward translation into ctypes code would be this, but it does not work:

>>> class cell(Structure):
...     _fields_ = [("name", c_char_p),
...                 ("next", POINTER(cell))]
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in cell
NameError: name 'cell' is not defined
>>>

because the new class cell is not available in the class statement itself. In ctypes, we can define the cell class and set the _fields_ attribute later, after the class statement:

>>> from ctypes import *
>>> class cell(Structure):
...     pass
...
>>> cell._fields_ = [("name", c_char_p),
...                  ("next", POINTER(cell))]
>>>

Let's try it. We create two instances of cell, and let them point to each other, and finally follow the pointer chain a few times:

>>> c1 = cell()
>>> c1.name = b"foo"
>>> c2 = cell()
>>> c2.name = b"bar"
>>> c1.next = pointer(c2)
>>> c2.next = pointer(c1)
>>> p = c1
>>> for i in range(8):
...     print(p.name, end=" ")
...     p = p.next[0]
...
foo bar foo bar foo bar foo bar
>>>

回呼函式

ctypes allows creating C callable function pointers from Python callables. These are sometimes called callback functions.

First, you must create a class for the callback function. The class knows the calling convention, the return type, and the number and types of arguments this function will receive.

The CFUNCTYPE() factory function creates types for callback functions using the cdecl calling convention. On Windows, the WINFUNCTYPE() factory function creates types for callback functions using the stdcall calling convention.

Both of these factory functions are called with the result type as first argument, and the callback functions expected argument types as the remaining arguments.

I will present an example here which uses the standard C library's qsort() function, that is used to sort items with the help of a callback function. qsort() will be used to sort an array of integers:

>>> IntArray5 = c_int * 5
>>> ia = IntArray5(5, 1, 7, 33, 99)
>>> qsort = libc.qsort
>>> qsort.restype = None
>>>

qsort() must be called with a pointer to the data to sort, the number of items in the data array, the size of one item, and a pointer to the comparison function, the callback. The callback will then be called with two pointers to items, and it must return a negative integer if the first item is smaller than the second, a zero if they are equal, and a positive integer otherwise.

So our callback function receives pointers to integers, and must return an integer. First we create the type for the callback function:

>>> CMPFUNC = CFUNCTYPE(c_int, POINTER(c_int), POINTER(c_int))
>>>

To get started, here is a simple callback that shows the values it gets passed:

>>> def py_cmp_func(a, b):
...     print("py_cmp_func", a[0], b[0])
...     return 0
...
>>> cmp_func = CMPFUNC(py_cmp_func)
>>>

結果為：

>>> qsort(ia, len(ia), sizeof(c_int), cmp_func)
py_cmp_func 5 1
py_cmp_func 33 99
py_cmp_func 7 33
py_cmp_func 5 7
py_cmp_func 1 7
>>>

Now we can actually compare the two items and return a useful result:

>>> def py_cmp_func(a, b):
...     print("py_cmp_func", a[0], b[0])
...     return a[0] - b[0]
...
>>>
>>> qsort(ia, len(ia), sizeof(c_int), CMPFUNC(py_cmp_func))
py_cmp_func 5 1
py_cmp_func 33 99
py_cmp_func 7 33
py_cmp_func 1 7
py_cmp_func 5 7
>>>

As we can easily check, our array is sorted now:

>>> for i in ia: print(i, end=" ")
...
1 5 7 33 99
>>>

The function factories can be used as decorator factories, so we may as well write:

>>> @CFUNCTYPE(c_int, POINTER(c_int), POINTER(c_int))
... def py_cmp_func(a, b):
...     print("py_cmp_func", a[0], b[0])
...     return a[0] - b[0]
...
>>> qsort(ia, len(ia), sizeof(c_int), py_cmp_func)
py_cmp_func 5 1
py_cmp_func 33 99
py_cmp_func 7 33
py_cmp_func 1 7
py_cmp_func 5 7
>>>

備註

Make sure you keep references to CFUNCTYPE() objects as long as they are used from C code. ctypes doesn't, and if you don't, they may be garbage collected, crashing your program when a callback is made.

Also, note that if the callback function is called in a thread created outside of Python's control (e.g. by the foreign code that calls the callback), ctypes creates a new dummy Python thread on every invocation. This behavior is correct for most purposes, but it means that values stored with threading.local will not survive across different callbacks, even when those calls are made from the same C thread.

Accessing values exported from dlls

Some shared libraries not only export functions, they also export variables. An example in the Python library itself is the Py_Version, Python runtime version number encoded in a single constant integer.

ctypes can access values like this with the in_dll() class methods of the type. pythonapi is a predefined symbol giving access to the Python C api:

>>> version = ctypes.c_int.in_dll(ctypes.pythonapi, "Py_Version")
>>> print(hex(version.value))
0x30c00a0

An extended example which also demonstrates the use of pointers accesses the PyImport_FrozenModules pointer exported by Python.

Quoting the docs for that value:

This pointer is initialized to point to an array of _frozen records, terminated by one whose members are all NULL or zero. When a frozen module is imported, it is searched in this table. Third-party code could play tricks with this to provide a dynamically created collection of frozen modules.

So manipulating this pointer could even prove useful. To restrict the example size, we show only how this table can be read with ctypes:

>>> from ctypes import *
>>>
>>> class struct_frozen(Structure):
...     _fields_ = [("name", c_char_p),
...                 ("code", POINTER(c_ubyte)),
...                 ("size", c_int),
...                 ("get_code", POINTER(c_ubyte)),  # 函式指標
...                ]
...
>>>

We have defined the _frozen data type, so we can get the pointer to the table:

>>> FrozenTable = POINTER(struct_frozen)
>>> table = FrozenTable.in_dll(pythonapi, "_PyImport_FrozenBootstrap")
>>>

Since table is a pointer to the array of struct_frozen records, we can iterate over it, but we just have to make sure that our loop terminates, because pointers have no size. Sooner or later it would probably crash with an access violation or whatever, so it's better to break out of the loop when we hit the NULL entry:

>>> for item in table:
...     if item.name is None:
...         break
...     print(item.name.decode("ascii"), item.size)
...
_frozen_importlib 31764
_frozen_importlib_external 41499
zipimport 12345
>>>

The fact that standard Python has a frozen module and a frozen package (indicated by the negative size member) is not well known, it is only used for testing. Try it out with import __hello__ for example.

Surprises

There are some edges in ctypes where you might expect something other than what actually happens.

Consider the following example:

>>> from ctypes import *
>>> class POINT(Structure):
...     _fields_ = ("x", c_int), ("y", c_int)
...
>>> class RECT(Structure):
...     _fields_ = ("a", POINT), ("b", POINT)
...
>>> p1 = POINT(1, 2)
>>> p2 = POINT(3, 4)
>>> rc = RECT(p1, p2)
>>> print(rc.a.x, rc.a.y, rc.b.x, rc.b.y)
1 2 3 4
>>> # now swap the two points
>>> rc.a, rc.b = rc.b, rc.a
>>> print(rc.a.x, rc.a.y, rc.b.x, rc.b.y)
3 4 3 4
>>>

Hm. We certainly expected the last statement to print 3 4 1 2. What happened? Here are the steps of the rc.a, rc.b = rc.b, rc.a line above:

>>> temp0, temp1 = rc.b, rc.a
>>> rc.a = temp0
>>> rc.b = temp1
>>>

Note that temp0 and temp1 are objects still using the internal buffer of the rc object above. So executing rc.a = temp0 copies the buffer contents of temp0 into rc 's buffer. This, in turn, changes the contents of temp1. So, the last assignment rc.b = temp1, doesn't have the expected effect.

Keep in mind that retrieving sub-objects from Structure, Unions, and Arrays doesn't copy the sub-object, instead it retrieves a wrapper object accessing the root-object's underlying buffer.

Another example that may behave differently from what one would expect is this:

>>> s = c_char_p()
>>> s.value = b"abc def ghi"
>>> s.value
b'abc def ghi'
>>> s.value is s.value
False
>>>

備註

Objects instantiated from c_char_p can only have their value set to bytes or integers.

Why is it printing False? ctypes instances are objects containing a memory block plus some descriptors accessing the contents of the memory. Storing a Python object in the memory block does not store the object itself, instead the contents of the object is stored. Accessing the contents again constructs a new Python object each time!

Variable-sized data types

ctypes provides some support for variable-sized arrays and structures.

The resize() function can be used to resize the memory buffer of an existing ctypes object. The function takes the object as first argument, and the requested size in bytes as the second argument. The memory block cannot be made smaller than the natural memory block specified by the objects type, a ValueError is raised if this is tried:

>>> short_array = (c_short * 4)()
>>> print(sizeof(short_array))
8
>>> resize(short_array, 4)
Traceback (most recent call last):
    ...
ValueError: minimum size is 8
>>> resize(short_array, 32)
>>> sizeof(short_array)
32
>>> sizeof(type(short_array))
8
>>>

This is nice and fine, but how would one access the additional elements contained in this array? Since the type still only knows about 4 elements, we get errors accessing other elements:

>>> short_array[:]
[0, 0, 0, 0]
>>> short_array[7]
Traceback (most recent call last):
    ...
IndexError: invalid index
>>>

Another way to use variable-sized data types with ctypes is to use the dynamic nature of Python, and (re-)define the data type after the required size is already known, on a case by case basis.

ctypes reference

Finding shared libraries

When programming in a compiled language, shared libraries are accessed when compiling/linking a program, and when the program is run.

The purpose of the find_library() function is to locate a library in a way similar to what the compiler or runtime loader does (on platforms with several versions of a shared library the most recent should be loaded), while the ctypes library loaders act like when a program is run, and call the runtime loader directly.

The ctypes.util module provides a function which can help to determine the library to load.

ctypes.util.find_library(name)

Try to find a library and return a pathname. name is the library name without any prefix like lib, suffix like .so, .dylib or version number (this is the form used for the posix linker option -l). If no library can be found, returns None.

The exact functionality is system dependent.

On Linux, find_library() tries to run external programs (/sbin/ldconfig, gcc, objdump and ld) to find the library file. It returns the filename of the library file.

Note that if the output of these programs does not correspond to the dynamic linker used by Python, the result of this function may be misleading.

在 3.6 版的變更: On Linux, the value of the environment variable LD_LIBRARY_PATH is used when searching for libraries, if a library cannot be found by any other means.

以下是一些範例：

>>> from ctypes.util import find_library
>>> find_library("m")
'libm.so.6'
>>> find_library("c")
'libc.so.6'
>>> find_library("bz2")
'libbz2.so.1.0'
>>>

On macOS and Android, find_library() uses the system's standard naming schemes and paths to locate the library, and returns a full pathname if successful:

>>> from ctypes.util import find_library
>>> find_library("c")
'/usr/lib/libc.dylib'
>>> find_library("m")
'/usr/lib/libm.dylib'
>>> find_library("bz2")
'/usr/lib/libbz2.dylib'
>>> find_library("AGL")
'/System/Library/Frameworks/AGL.framework/AGL'
>>>

On Windows, find_library() searches along the system search path, and returns the full pathname, but since there is no predefined naming scheme a call like find_library("c") will fail and return None.

If wrapping a shared library with ctypes, it may be better to determine the shared library name at development time, and hardcode that into the wrapper module instead of using find_library() to locate the library at runtime.

Listing loaded shared libraries

When writing code that relies on code loaded from shared libraries, it can be useful to know which shared libraries have already been loaded into the current process.

The ctypes.util module provides the dllist() function, which calls the different APIs provided by the various platforms to help determine which shared libraries have already been loaded into the current process.

The exact output of this function will be system dependent. On most platforms, the first entry of this list represents the current process itself, which may be an empty string. For example, on glibc-based Linux, the return may look like:

>>> from ctypes.util import dllist
>>> dllist()
['', 'linux-vdso.so.1', '/lib/x86_64-linux-gnu/libm.so.6', '/lib/x86_64-linux-gnu/libc.so.6', ... ]

Loading shared libraries

There are several ways to load shared libraries into the Python process. One way is to instantiate one of the following classes:

class ctypes.CDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=None)

Instances of this class represent loaded shared libraries. Functions in these libraries use the standard C calling convention, and are assumed to return int.

On Windows creating a CDLL instance may fail even if the DLL name exists. When a dependent DLL of the loaded DLL is not found, a OSError error is raised with the message "[WinError 126] The specified module could not be found". This error message does not contain the name of the missing DLL because the Windows API does not return this information making this error hard to diagnose. To resolve this error and determine which DLL is not found, you need to find the list of dependent DLLs and determine which one is not found using Windows debugging and tracing tools.

在 3.12 版的變更: The name parameter can now be a path-like object.

也參考

Microsoft DUMPBIN tool [https://docs.microsoft.com/cpp/build/reference/dependents] -- A tool to find DLL dependents.

class ctypes.OleDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=None)

Instances of this class represent loaded shared libraries, functions in these libraries use the stdcall calling convention, and are assumed to return the windows specific HRESULT code. HRESULT values contain information specifying whether the function call failed or succeeded, together with additional error code. If the return value signals a failure, an OSError is automatically raised.

可用性: Windows

在 3.3 版的變更: WindowsError used to be raised, which is now an alias of OSError.

在 3.12 版的變更: The name parameter can now be a path-like object.

class ctypes.WinDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=None)

Instances of this class represent loaded shared libraries, functions in these libraries use the stdcall calling convention, and are assumed to return int by default.

可用性: Windows

在 3.12 版的變更: The name parameter can now be a path-like object.

The Python global interpreter lock is released before calling any function exported by these libraries, and reacquired afterwards.

class ctypes.PyDLL(name, mode=DEFAULT_MODE, handle=None)

Instances of this class behave like CDLL instances, except that the Python GIL is not released during the function call, and after the function execution the Python error flag is checked. If the error flag is set, a Python exception is raised.

Thus, this is only useful to call Python C api functions directly.

在 3.12 版的變更: The name parameter can now be a path-like object.

All these classes can be instantiated by calling them with at least one argument, the pathname of the shared library. If you have an existing handle to an already loaded shared library, it can be passed as the handle named parameter, otherwise the underlying platform's dlopen() or LoadLibrary() function is used to load the library into the process, and to get a handle to it.

The mode parameter can be used to specify how the library is loaded. For details, consult the dlopen(3) [https://manpages.debian.org/dlopen(3)] manpage. On Windows, mode is ignored. On posix systems, RTLD_NOW is always added, and is not configurable.

The use_errno parameter, when set to true, enables a ctypes mechanism that allows accessing the system errno error number in a safe way. ctypes maintains a thread-local copy of the system's errno variable; if you call foreign functions created with use_errno=True then the errno value before the function call is swapped with the ctypes private copy, the same happens immediately after the function call.

The function ctypes.get_errno() returns the value of the ctypes private copy, and the function ctypes.set_errno() changes the ctypes private copy to a new value and returns the former value.

The use_last_error parameter, when set to true, enables the same mechanism for the Windows error code which is managed by the GetLastError() and SetLastError() Windows API functions; ctypes.get_last_error() and ctypes.set_last_error() are used to request and change the ctypes private copy of the windows error code.

The winmode parameter is used on Windows to specify how the library is loaded (since mode is ignored). It takes any value that is valid for the Win32 API LoadLibraryEx flags parameter. When omitted, the default is to use the flags that result in the most secure DLL load, which avoids issues such as DLL hijacking. Passing the full path to the DLL is the safest way to ensure the correct library and dependencies are loaded.

在 3.8 版的變更: 新增 winmode 參數。

ctypes.RTLD_GLOBAL

Flag to use as mode parameter. On platforms where this flag is not available, it is defined as the integer zero.

ctypes.RTLD_LOCAL

Flag to use as mode parameter. On platforms where this is not available, it is the same as RTLD_GLOBAL.

ctypes.DEFAULT_MODE

The default mode which is used to load shared libraries. On OSX 10.3, this is RTLD_GLOBAL, otherwise it is the same as RTLD_LOCAL.

Instances of these classes have no public methods. Functions exported by the shared library can be accessed as attributes or by index. Please note that accessing the function through an attribute caches the result and therefore accessing it repeatedly returns the same object each time. On the other hand, accessing it through an index returns a new object each time:

>>> from ctypes import CDLL
>>> libc = CDLL("libc.so.6")  # 於 Linux
>>> libc.time == libc.time
True
>>> libc['time'] == libc['time']
False

The following public attributes are available, their name starts with an underscore to not clash with exported function names:

PyDLL._handle

The system handle used to access the library.

PyDLL._name

The name of the library passed in the constructor.

Shared libraries can also be loaded by using one of the prefabricated objects, which are instances of the LibraryLoader class, either by calling the LoadLibrary() method, or by retrieving the library as attribute of the loader instance.

class ctypes.LibraryLoader(dlltype)

Class which loads shared libraries. dlltype should be one of the CDLL, PyDLL, WinDLL, or OleDLL types.

__getattr__() has special behavior: It allows loading a shared library by accessing it as attribute of a library loader instance. The result is cached, so repeated attribute accesses return the same library each time.

LoadLibrary(name)

Load a shared library into the process and return it. This method always returns a new instance of the library.

These prefabricated library loaders are available:

ctypes.cdll

Creates CDLL instances.

ctypes.windll

Creates WinDLL instances.

可用性: Windows

ctypes.oledll

Creates OleDLL instances.

可用性: Windows

ctypes.pydll

Creates PyDLL instances.

For accessing the C Python api directly, a ready-to-use Python shared library object is available:

ctypes.pythonapi

An instance of PyDLL that exposes Python C API functions as attributes. Note that all these functions are assumed to return C int, which is of course not always the truth, so you have to assign the correct restype attribute to use these functions.

Loading a library through any of these objects raises an auditing event ctypes.dlopen with string argument name, the name used to load the library.

Accessing a function on a loaded library raises an auditing event ctypes.dlsym with arguments library (the library object) and name (the symbol's name as a string or integer).

In cases when only the library handle is available rather than the object, accessing a function raises an auditing event ctypes.dlsym/handle with arguments handle (the raw library handle) and name.

Foreign functions

As explained in the previous section, foreign functions can be accessed as attributes of loaded shared libraries. The function objects created in this way by default accept any number of arguments, accept any ctypes data instances as arguments, and return the default result type specified by the library loader.

They are instances of a private local class _FuncPtr (not exposed in ctypes) which inherits from the private _CFuncPtr class:

>>> import ctypes
>>> lib = ctypes.CDLL(None)
>>> issubclass(lib._FuncPtr, ctypes._CFuncPtr)
True
>>> lib._FuncPtr is ctypes._CFuncPtr
False

class ctypes._CFuncPtr

Base class for C callable foreign functions.

Instances of foreign functions are also C compatible data types; they represent C function pointers.

This behavior can be customized by assigning to special attributes of the foreign function object.

restype

Assign a ctypes type to specify the result type of the foreign function. Use None for void, a function not returning anything.

It is possible to assign a callable Python object that is not a ctypes type, in this case the function is assumed to return a C int, and the callable will be called with this integer, allowing further processing or error checking. Using this is deprecated, for more flexible post processing or error checking use a ctypes data type as restype and assign a callable to the errcheck attribute.

argtypes

Assign a tuple of ctypes types to specify the argument types that the function accepts. Functions using the stdcall calling convention can only be called with the same number of arguments as the length of this tuple; functions using the C calling convention accept additional, unspecified arguments as well.

When a foreign function is called, each actual argument is passed to the from_param() class method of the items in the argtypes tuple, this method allows adapting the actual argument to an object that the foreign function accepts. For example, a c_char_p item in the argtypes tuple will convert a string passed as argument into a bytes object using ctypes conversion rules.

New: It is now possible to put items in argtypes which are not ctypes types, but each item must have a from_param() method which returns a value usable as argument (integer, string, ctypes instance). This allows defining adapters that can adapt custom objects as function parameters.

errcheck

Assign a Python function or another callable to this attribute. The callable will be called with three or more arguments:

callable(result, func, arguments)

result is what the foreign function returns, as specified by the restype attribute.

func is the foreign function object itself, this allows reusing the same callable object to check or post process the results of several functions.

arguments is a tuple containing the parameters originally passed to the function call, this allows specializing the behavior on the arguments used.

The object that this function returns will be returned from the foreign function call, but it can also check the result value and raise an exception if the foreign function call failed.

On Windows, when a foreign function call raises a system exception (for example, due to an access violation), it will be captured and replaced with a suitable Python exception. Further, an auditing event ctypes.set_exception with argument code will be raised, allowing an audit hook to replace the exception with its own.

Some ways to invoke foreign function calls as well as some of the functions in this module may raise an auditing event ctypes.call_function with arguments function pointer and arguments.

Function prototypes

Foreign functions can also be created by instantiating function prototypes. Function prototypes are similar to function prototypes in C; they describe a function (return type, argument types, calling convention) without defining an implementation. The factory functions must be called with the desired result type and the argument types of the function, and can be used as decorator factories, and as such, be applied to functions through the @wrapper syntax. See 回呼函式 for examples.

ctypes.CFUNCTYPE(restype, *argtypes, use_errno=False, use_last_error=False)

The returned function prototype creates functions that use the standard C calling convention. The function will release the GIL during the call. If use_errno is set to true, the ctypes private copy of the system errno variable is exchanged with the real errno value before and after the call; use_last_error does the same for the Windows error code.

ctypes.WINFUNCTYPE(restype, *argtypes, use_errno=False, use_last_error=False)

The returned function prototype creates functions that use the stdcall calling convention. The function will release the GIL during the call. use_errno and use_last_error have the same meaning as above.

可用性: Windows

ctypes.PYFUNCTYPE(restype, *argtypes)

The returned function prototype creates functions that use the Python calling convention. The function will not release the GIL during the call.

Function prototypes created by these factory functions can be instantiated in different ways, depending on the type and number of the parameters in the call:

prototype(address)

Returns a foreign function at the specified address which must be an integer.

prototype(callable)

Create a C callable function (a callback function) from a Python callable.

prototype(func_spec[, paramflags])

Returns a foreign function exported by a shared library. func_spec must be a 2-tuple (name_or_ordinal, library). The first item is the name of the exported function as string, or the ordinal of the exported function as small integer. The second item is the shared library instance.

prototype(vtbl_index, name[, paramflags[, iid]])

Returns a foreign function that will call a COM method. vtbl_index is the index into the virtual function table, a small non-negative integer. name is name of the COM method. iid is an optional pointer to the interface identifier which is used in extended error reporting.

If iid is not specified, an OSError is raised if the COM method call fails. If iid is specified, a COMError is raised instead.

COM methods use a special calling convention: They require a pointer to the COM interface as first argument, in addition to those parameters that are specified in the argtypes tuple.

可用性: Windows

The optional paramflags parameter creates foreign function wrappers with much more functionality than the features described above.

paramflags must be a tuple of the same length as argtypes.

Each item in this tuple contains further information about a parameter, it must be a tuple containing one, two, or three items.

The first item is an integer containing a combination of direction flags for the parameter:

1

Specifies an input parameter to the function.

2

Output parameter. The foreign function fills in a value.

4

Input parameter which defaults to the integer zero.

The optional second item is the parameter name as string. If this is specified, the foreign function can be called with named parameters.

The optional third item is the default value for this parameter.

The following example demonstrates how to wrap the Windows MessageBoxW function so that it supports default parameters and named arguments. The C declaration from the windows header file is this:

WINUSERAPI int WINAPI
MessageBoxW(
    HWND hWnd,
    LPCWSTR lpText,
    LPCWSTR lpCaption,
    UINT uType);

Here is the wrapping with ctypes:

>>> from ctypes import c_int, WINFUNCTYPE, windll
>>> from ctypes.wintypes import HWND, LPCWSTR, UINT
>>> prototype = WINFUNCTYPE(c_int, HWND, LPCWSTR, LPCWSTR, UINT)
>>> paramflags = (1, "hwnd", 0), (1, "text", "Hi"), (1, "caption", "Hello from ctypes"), (1, "flags", 0)
>>> MessageBox = prototype(("MessageBoxW", windll.user32), paramflags)

The MessageBox foreign function can now be called in these ways:

>>> MessageBox()
>>> MessageBox(text="Spam, spam, spam")
>>> MessageBox(flags=2, text="foo bar")

A second example demonstrates output parameters. The win32 GetWindowRect function retrieves the dimensions of a specified window by copying them into RECT structure that the caller has to supply. Here is the C declaration:

WINUSERAPI BOOL WINAPI
GetWindowRect(
     HWND hWnd,
     LPRECT lpRect);

Here is the wrapping with ctypes:

>>> from ctypes import POINTER, WINFUNCTYPE, windll, WinError
>>> from ctypes.wintypes import BOOL, HWND, RECT
>>> prototype = WINFUNCTYPE(BOOL, HWND, POINTER(RECT))
>>> paramflags = (1, "hwnd"), (2, "lprect")
>>> GetWindowRect = prototype(("GetWindowRect", windll.user32), paramflags)
>>>

Functions with output parameters will automatically return the output parameter value if there is a single one, or a tuple containing the output parameter values when there are more than one, so the GetWindowRect function now returns a RECT instance, when called.

Output parameters can be combined with the errcheck protocol to do further output processing and error checking. The win32 GetWindowRect api function returns a BOOL to signal success or failure, so this function could do the error checking, and raises an exception when the api call failed:

>>> def errcheck(result, func, args):
...     if not result:
...         raise WinError()
...     return args
...
>>> GetWindowRect.errcheck = errcheck
>>>

If the errcheck function returns the argument tuple it receives unchanged, ctypes continues the normal processing it does on the output parameters. If you want to return a tuple of window coordinates instead of a RECT instance, you can retrieve the fields in the function and return them instead, the normal processing will no longer take place:

>>> def errcheck(result, func, args):
...     if not result:
...         raise WinError()
...     rc = args[1]
...     return rc.left, rc.top, rc.bottom, rc.right
...
>>> GetWindowRect.errcheck = errcheck
>>>

Utility functions

ctypes.addressof(obj)

Returns the address of the memory buffer as integer. obj must be an instance of a ctypes type.

引發一個附帶引數 obj 的稽核事件 ctypes.addressof。

ctypes.alignment(obj_or_type)

Returns the alignment requirements of a ctypes type. obj_or_type must be a ctypes type or instance.

ctypes.byref(obj[, offset])

Returns a light-weight pointer to obj, which must be an instance of a ctypes type. offset defaults to zero, and must be an integer that will be added to the internal pointer value.

byref(obj, offset) corresponds to this C code:

(((char *)&obj) + offset)

The returned object can only be used as a foreign function call parameter. It behaves similar to pointer(obj), but the construction is a lot faster.

ctypes.CopyComPointer(src, dst)

Copies a COM pointer from src to dst and returns the Windows specific HRESULT value.

If src is not NULL, its AddRef method is called, incrementing the reference count.

In contrast, the reference count of dst will not be decremented before assigning the new value. Unless dst is NULL, the caller is responsible for decrementing the reference count by calling its Release method when necessary.

可用性: Windows

在 3.14 版被加入.

ctypes.cast(obj, type)

This function is similar to the cast operator in C. It returns a new instance of type which points to the same memory block as obj. type must be a pointer type, and obj must be an object that can be interpreted as a pointer.

ctypes.create_string_buffer(init, size=None)

ctypes.create_string_buffer(size)

This function creates a mutable character buffer. The returned object is a ctypes array of c_char.

If size is given (and not None), it must be an int. It specifies the size of the returned array.

If the init argument is given, it must be bytes. It is used to initialize the array items. Bytes not initialized this way are set to zero (NUL).

If size is not given (or if it is None), the buffer is made one element larger than init, effectively adding a NUL terminator.

如果兩個引數皆有提供，size 不得小於 len(init)。

警告

If size is equal to len(init), a NUL terminator is not added. Do not treat such a buffer as a C string.

舉例來說：

>>> bytes(create_string_buffer(2))
b'\x00\x00'
>>> bytes(create_string_buffer(b'ab'))
b'ab\x00'
>>> bytes(create_string_buffer(b'ab', 2))
b'ab'
>>> bytes(create_string_buffer(b'ab', 4))
b'ab\x00\x00'
>>> bytes(create_string_buffer(b'abcdef', 2))
Traceback (most recent call last):
   ...
ValueError: byte string too long

引發一個附帶引數 init 與 size 的稽核事件 ctypes.create_string_buffer。

ctypes.create_unicode_buffer(init, size=None)

ctypes.create_unicode_buffer(size)

This function creates a mutable unicode character buffer. The returned object is a ctypes array of c_wchar.

The function takes the same arguments as create_string_buffer() except init must be a string and size counts c_wchar.

引發一個附帶引數 init 與 size 的稽核事件 ctypes.create_unicode_buffer。

ctypes.DllCanUnloadNow()

This function is a hook which allows implementing in-process COM servers with ctypes. It is called from the DllCanUnloadNow function that the _ctypes extension dll exports.

可用性: Windows

ctypes.DllGetClassObject()

This function is a hook which allows implementing in-process COM servers with ctypes. It is called from the DllGetClassObject function that the _ctypes extension dll exports.

可用性: Windows

ctypes.util.find_library(name)

Try to find a library and return a pathname. name is the library name without any prefix like lib, suffix like .so, .dylib or version number (this is the form used for the posix linker option -l). If no library can be found, returns None.

The exact functionality is system dependent.

See Finding shared libraries for complete documentation.

ctypes.util.find_msvcrt()

Returns the filename of the VC runtime library used by Python, and by the extension modules. If the name of the library cannot be determined, None is returned.

If you need to free memory, for example, allocated by an extension module with a call to the free(void *), it is important that you use the function in the same library that allocated the memory.

可用性: Windows

ctypes.util.dllist()

Try to provide a list of paths of the shared libraries loaded into the current process. These paths are not normalized or processed in any way. The function can raise OSError if the underlying platform APIs fail. The exact functionality is system dependent.

On most platforms, the first element of the list represents the current executable file. It may be an empty string.

可用性: Windows, macOS, iOS, glibc, BSD libc, musl

在 3.14 版被加入.

ctypes.FormatError([code])

Returns a textual description of the error code code. If no error code is specified, the last error code is used by calling the Windows API function GetLastError().

可用性: Windows

ctypes.GetLastError()

Returns the last error code set by Windows in the calling thread. This function calls the Windows GetLastError() function directly, it does not return the ctypes-private copy of the error code.

可用性: Windows

ctypes.get_errno()

Returns the current value of the ctypes-private copy of the system errno variable in the calling thread.

引發一個不附帶引數的稽核事件 ctypes.get_errno。

ctypes.get_last_error()

Returns the current value of the ctypes-private copy of the system LastError variable in the calling thread.

可用性: Windows

引發一個不附帶引數的稽核事件 ctypes.get_last_error。

ctypes.memmove(dst, src, count)

Same as the standard C memmove library function: copies count bytes from src to dst. dst and src must be integers or ctypes instances that can be converted to pointers.

ctypes.memset(dst, c, count)

Same as the standard C memset library function: fills the memory block at address dst with count bytes of value c. dst must be an integer specifying an address, or a ctypes instance.

ctypes.POINTER(type, /)

Create or return a ctypes pointer type. Pointer types are cached and reused internally, so calling this function repeatedly is cheap. type must be a ctypes type.

CPython 實作細節： The resulting pointer type is cached in the __pointer_type__ attribute of type. It is possible to set this attribute before the first call to POINTER in order to set a custom pointer type. However, doing this is discouraged: manually creating a suitable pointer type is difficult without relying on implementation details that may change in future Python versions.

ctypes.pointer(obj, /)

Create a new pointer instance, pointing to obj. The returned object is of the type POINTER(type(obj)).

Note: If you just want to pass a pointer to an object to a foreign function call, you should use byref(obj) which is much faster.

ctypes.resize(obj, size)

This function resizes the internal memory buffer of obj, which must be an instance of a ctypes type. It is not possible to make the buffer smaller than the native size of the objects type, as given by sizeof(type(obj)), but it is possible to enlarge the buffer.

ctypes.set_errno(value)

Set the current value of the ctypes-private copy of the system errno variable in the calling thread to value and return the previous value.

引發一個附帶引數 errno 的稽核事件 ctypes.set_errno。

ctypes.set_last_error(value)

Sets the current value of the ctypes-private copy of the system LastError variable in the calling thread to value and return the previous value.

可用性: Windows

引發一個附帶引數 error 的稽核事件 ctypes.set_last_error。

ctypes.sizeof(obj_or_type)

Returns the size in bytes of a ctypes type or instance memory buffer. Does the same as the C sizeof operator.

ctypes.string_at(ptr, size=-1)

Return the byte string at void *ptr. If size is specified, it is used as size, otherwise the string is assumed to be zero-terminated.

引發一個附帶引數 ptr、size 的稽核事件 ctypes.string_at。

ctypes.WinError(code=None, descr=None)

Creates an instance of OSError. If code is not specified, GetLastError() is called to determine the error code. If descr is not specified, FormatError() is called to get a textual description of the error.

可用性: Windows

在 3.3 版的變更: An instance of WindowsError used to be created, which is now an alias of OSError.

ctypes.wstring_at(ptr, size=-1)

Return the wide-character string at void *ptr. If size is specified, it is used as the number of characters of the string, otherwise the string is assumed to be zero-terminated.

引發一個附帶引數 ptr、size 的稽核事件 ctypes.wstring_at。

ctypes.memoryview_at(ptr, size, readonly=False)

Return a memoryview object of length size that references memory starting at void *ptr.

If readonly is true, the returned memoryview object can not be used to modify the underlying memory. (Changes made by other means will still be reflected in the returned object.)

This function is similar to string_at() with the key difference of not making a copy of the specified memory. It is a semantically equivalent (but more efficient) alternative to memoryview((c_byte * size).from_address(ptr)). (While from_address() only takes integers, ptr can also be given as a ctypes.POINTER or a byref() object.)

引發一個附帶引數 address、size 與 readonly 的稽核事件 ctypes.memoryview_at。

在 3.14 版被加入.

Data types

class ctypes._CData

This non-public class is the common base class of all ctypes data types. Among other things, all ctypes type instances contain a memory block that hold C compatible data; the address of the memory block is returned by the addressof() helper function. Another instance variable is exposed as _objects; this contains other Python objects that need to be kept alive in case the memory block contains pointers.

Common methods of ctypes data types, these are all class methods (to be exact, they are methods of the metaclass):

from_buffer(source[, offset])

This method returns a ctypes instance that shares the buffer of the source object. The source object must support the writeable buffer interface. The optional offset parameter specifies an offset into the source buffer in bytes; the default is zero. If the source buffer is not large enough a ValueError is raised.

引發一個附帶引數 pointer、size、offset 的稽核事件 ctypes.cdata/buffer。

from_buffer_copy(source[, offset])

This method creates a ctypes instance, copying the buffer from the source object buffer which must be readable. The optional offset parameter specifies an offset into the source buffer in bytes; the default is zero. If the source buffer is not large enough a ValueError is raised.

引發一個附帶引數 pointer、size、offset 的稽核事件 ctypes.cdata/buffer。

from_address(address)

This method returns a ctypes type instance using the memory specified by address which must be an integer.

This method, and others that indirectly call this method, raises an auditing event ctypes.cdata with argument address.

from_param(obj)

This method adapts obj to a ctypes type. It is called with the actual object used in a foreign function call when the type is present in the foreign function's argtypes tuple; it must return an object that can be used as a function call parameter.

All ctypes data types have a default implementation of this classmethod that normally returns obj if that is an instance of the type. Some types accept other objects as well.

in_dll(library, name)

This method returns a ctypes type instance exported by a shared library. name is the name of the symbol that exports the data, library is the loaded shared library.

Common class variables of ctypes data types:

__pointer_type__

The pointer type that was created by calling POINTER() for corresponding ctypes data type. If a pointer type was not yet created, the attribute is missing.

在 3.14 版被加入.

Common instance variables of ctypes data types:

_b_base_

Sometimes ctypes data instances do not own the memory block they contain, instead they share part of the memory block of a base object. The _b_base_ read-only member is the root ctypes object that owns the memory block.

_b_needsfree_

This read-only variable is true when the ctypes data instance has allocated the memory block itself, false otherwise.

_objects

This member is either None or a dictionary containing Python objects that need to be kept alive so that the memory block contents is kept valid. This object is only exposed for debugging; never modify the contents of this dictionary.

Fundamental data types

class ctypes._SimpleCData

This non-public class is the base class of all fundamental ctypes data types. It is mentioned here because it contains the common attributes of the fundamental ctypes data types. _SimpleCData is a subclass of _CData, so it inherits their methods and attributes. ctypes data types that are not and do not contain pointers can now be pickled.

Instances have a single attribute:

value

This attribute contains the actual value of the instance. For integer and pointer types, it is an integer, for character types, it is a single character bytes object or string, for character pointer types it is a Python bytes object or string.

When the value attribute is retrieved from a ctypes instance, usually a new object is returned each time. ctypes does not implement original object return, always a new object is constructed. The same is true for all other ctypes object instances.

Fundamental data types, when returned as foreign function call results, or, for example, by retrieving structure field members or array items, are transparently converted to native Python types. In other words, if a foreign function has a restype of c_char_p, you will always receive a Python bytes object, not a c_char_p instance.

Subclasses of fundamental data types do not inherit this behavior. So, if a foreign functions restype is a subclass of c_void_p, you will receive an instance of this subclass from the function call. Of course, you can get the value of the pointer by accessing the value attribute.

These are the fundamental ctypes data types:

class ctypes.c_byte

Represents the C signed char datatype, and interprets the value as small integer. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_char

Represents the C char datatype, and interprets the value as a single character. The constructor accepts an optional string initializer, the length of the string must be exactly one character.

class ctypes.c_char_p

Represents the C char* datatype when it points to a zero-terminated string. For a general character pointer that may also point to binary data, POINTER(c_char) must be used. The constructor accepts an integer address, or a bytes object.

class ctypes.c_double

Represents the C double datatype. The constructor accepts an optional float initializer.

class ctypes.c_longdouble

Represents the C long double datatype. The constructor accepts an optional float initializer. On platforms where sizeof(long double) == sizeof(double) it is an alias to c_double.

class ctypes.c_float

Represents the C float datatype. The constructor accepts an optional float initializer.

class ctypes.c_double_complex

Represents the C double complex datatype, if available. The constructor accepts an optional complex initializer.

在 3.14 版被加入.

class ctypes.c_float_complex

Represents the C float complex datatype, if available. The constructor accepts an optional complex initializer.

在 3.14 版被加入.

class ctypes.c_longdouble_complex

Represents the C long double complex datatype, if available. The constructor accepts an optional complex initializer.

在 3.14 版被加入.

class ctypes.c_int

Represents the C signed int datatype. The constructor accepts an optional integer initializer; no overflow checking is done. On platforms where sizeof(int) == sizeof(long) it is an alias to c_long.

class ctypes.c_int8

Represents the C 8-bit signed int datatype. It is an alias for c_byte.

class ctypes.c_int16

Represents the C 16-bit signed int datatype. Usually an alias for c_short.

class ctypes.c_int32

Represents the C 32-bit signed int datatype. Usually an alias for c_int.

class ctypes.c_int64

Represents the C 64-bit signed int datatype. Usually an alias for c_longlong.

class ctypes.c_long

Represents the C signed long datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_longlong

Represents the C signed long long datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_short

Represents the C signed short datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_size_t

Represents the C size_t datatype.

class ctypes.c_ssize_t

Represents the C ssize_t datatype.

在 3.2 版被加入.

class ctypes.c_time_t

Represents the C time_t datatype.

在 3.12 版被加入.

class ctypes.c_ubyte

Represents the C unsigned char datatype, it interprets the value as small integer. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_uint

Represents the C unsigned int datatype. The constructor accepts an optional integer initializer; no overflow checking is done. On platforms where sizeof(int) == sizeof(long) it is an alias for c_ulong.

class ctypes.c_uint8

Represents the C 8-bit unsigned int datatype. It is an alias for c_ubyte.

class ctypes.c_uint16

Represents the C 16-bit unsigned int datatype. Usually an alias for c_ushort.

class ctypes.c_uint32

Represents the C 32-bit unsigned int datatype. Usually an alias for c_uint.

class ctypes.c_uint64

Represents the C 64-bit unsigned int datatype. Usually an alias for c_ulonglong.

class ctypes.c_ulong

Represents the C unsigned long datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_ulonglong

Represents the C unsigned long long datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_ushort

Represents the C unsigned short datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class ctypes.c_void_p

Represents the C void* type. The value is represented as integer. The constructor accepts an optional integer initializer.

class ctypes.c_wchar

Represents the C wchar_t datatype, and interprets the value as a single character unicode string. The constructor accepts an optional string initializer, the length of the string must be exactly one character.

class ctypes.c_wchar_p

Represents the C wchar_t* datatype, which must be a pointer to a zero-terminated wide character string. The constructor accepts an integer address, or a string.

class ctypes.c_bool

Represent the C bool datatype (more accurately, _Bool from C99). Its value can be True or False, and the constructor accepts any object that has a truth value.

class ctypes.HRESULT

Represents a HRESULT value, which contains success or error information for a function or method call.

可用性: Windows

class ctypes.py_object

Represents the C PyObject* datatype. Calling this without an argument creates a NULL PyObject* pointer.

在 3.14 版的變更: py_object is now a generic type.

The ctypes.wintypes module provides quite some other Windows specific data types, for example HWND, WPARAM, or DWORD. Some useful structures like MSG or RECT are also defined.

Structured data types

class ctypes.Union(*args, **kw)

Abstract base class for unions in native byte order.

Unions share common attributes and behavior with structures; see Structure documentation for details.

class ctypes.BigEndianUnion(*args, **kw)

Abstract base class for unions in big endian byte order.

在 3.11 版被加入.

class ctypes.LittleEndianUnion(*args, **kw)

Abstract base class for unions in little endian byte order.

在 3.11 版被加入.

class ctypes.BigEndianStructure(*args, **kw)

Abstract base class for structures in big endian byte order.

class ctypes.LittleEndianStructure(*args, **kw)

Abstract base class for structures in little endian byte order.

Structures and unions with non-native byte order cannot contain pointer type fields, or any other data types containing pointer type fields.

class ctypes.Structure(*args, **kw)

Abstract base class for structures in native byte order.

Concrete structure and union types must be created by subclassing one of these types, and at least define a _fields_ class variable. ctypes will create descriptors which allow reading and writing the fields by direct attribute accesses. These are the

_fields_

A sequence defining the structure fields. The items must be 2-tuples or 3-tuples. The first item is the name of the field, the second item specifies the type of the field; it can be any ctypes data type.

For integer type fields like c_int, a third optional item can be given. It must be a small positive integer defining the bit width of the field.

Field names must be unique within one structure or union. This is not checked, only one field can be accessed when names are repeated.

It is possible to define the _fields_ class variable after the class statement that defines the Structure subclass, this allows creating data types that directly or indirectly reference themselves:

class List(Structure):
    pass
List._fields_ = [("pnext", POINTER(List)),
                 ...
                ]

The _fields_ class variable can only be set once. Later assignments will raise an AttributeError.

Additionally, the _fields_ class variable must be defined before the structure or union type is first used: an instance or subclass is created, sizeof() is called on it, and so on. Later assignments to _fields_ will raise an AttributeError. If _fields_ has not been set before such use, the structure or union will have no own fields, as if _fields_ was empty.

Sub-subclasses of structure types inherit the fields of the base class plus the _fields_ defined in the sub-subclass, if any.

_pack_

An optional small integer that allows overriding the alignment of structure fields in the instance.

This is only implemented for the MSVC-compatible memory layout (see _layout_).

Setting _pack_ to 0 is the same as not setting it at all. Otherwise, the value must be a positive power of two. The effect is equivalent to #pragma pack(N) in C, except ctypes may allow larger n than what the compiler accepts.

_pack_ must already be defined when _fields_ is assigned, otherwise it will have no effect.

自從版本 3.14 後不推薦使用，將會自版本 3.19 中移除。: For historical reasons, if _pack_ is non-zero, the MSVC-compatible layout will be used by default. On non-Windows platforms, this default is deprecated and is slated to become an error in Python 3.19. If it is intended, set _layout_ to 'ms' explicitly.

_align_

An optional small integer that allows increasing the alignment of the structure when being packed or unpacked to/from memory.

The value must not be negative. The effect is equivalent to __attribute__((aligned(N))) on GCC or #pragma align(N) on MSVC, except ctypes may allow values that the compiler would reject.

_align_ can only increase a structure's alignment requirements. Setting it to 0 or 1 has no effect.

Using values that are not powers of two is discouraged and may lead to surprising behavior.

_align_ must already be defined when _fields_ is assigned, otherwise it will have no effect.

在 3.13 版被加入.

_layout_

An optional string naming the struct/union layout. It can currently be set to:

"ms": the layout used by the Microsoft compiler (MSVC). On GCC and Clang, this layout can be selected with __attribute__((ms_struct)).

"gcc-sysv": the layout used by GCC with the System V or “SysV-like” data model, as used on Linux and macOS. With this layout, _pack_ must be unset or zero.

If not set explicitly, ctypes will use a default that matches the platform conventions. This default may change in future Python releases (for example, when a new platform gains official support, or when a difference between similar platforms is found). Currently the default will be:

On Windows: "ms"

When _pack_ is specified: "ms". (This is deprecated; see _pack_ documentation.)

Otherwise: "gcc-sysv"

_layout_ must already be defined when _fields_ is assigned, otherwise it will have no effect.

在 3.14 版被加入.

_anonymous_

An optional sequence that lists the names of unnamed (anonymous) fields. _anonymous_ must be already defined when _fields_ is assigned, otherwise it will have no effect.

The fields listed in this variable must be structure or union type fields. ctypes will create descriptors in the structure type that allows accessing the nested fields directly, without the need to create the structure or union field.

Here is an example type (Windows):

class _U(Union):
    _fields_ = [("lptdesc", POINTER(TYPEDESC)),
                ("lpadesc", POINTER(ARRAYDESC)),
                ("hreftype", HREFTYPE)]

class TYPEDESC(Structure):
    _anonymous_ = ("u",)
    _fields_ = [("u", _U),
                ("vt", VARTYPE)]

The TYPEDESC structure describes a COM data type, the vt field specifies which one of the union fields is valid. Since the u field is defined as anonymous field, it is now possible to access the members directly off the TYPEDESC instance. td.lptdesc and td.u.lptdesc are equivalent, but the former is faster since it does not need to create a temporary union instance:

td = TYPEDESC()
td.vt = VT_PTR
td.lptdesc = POINTER(some_type)
td.u.lptdesc = POINTER(some_type)

It is possible to define sub-subclasses of structures, they inherit the fields of the base class. If the subclass definition has a separate _fields_ variable, the fields specified in this are appended to the fields of the base class.

Structure and union constructors accept both positional and keyword arguments. Positional arguments are used to initialize member fields in the same order as they are appear in _fields_. Keyword arguments in the constructor are interpreted as attribute assignments, so they will initialize _fields_ with the same name, or create new attributes for names not present in _fields_.

class ctypes.CField(*args, **kw)

Descriptor for fields of a Structure and Union. For example:

>>> class Color(Structure):
...     _fields_ = (
...         ('red', c_uint8),
...         ('green', c_uint8),
...         ('blue', c_uint8),
...         ('intense', c_bool, 1),
...         ('blinking', c_bool, 1),
...    )
...
>>> Color.red
<ctypes.CField 'red' type=c_ubyte, ofs=0, size=1>
>>> Color.green.type
<class 'ctypes.c_ubyte'>
>>> Color.blue.byte_offset
2
>>> Color.intense
<ctypes.CField 'intense' type=c_bool, ofs=3, bit_size=1, bit_offset=0>
>>> Color.blinking.bit_offset
1

All attributes are read-only.

CField objects are created via _fields_; do not instantiate the class directly.

在 3.14 版被加入: Previously, descriptors only had offset and size attributes and a readable string representation; the CField class was not available directly.

name

Name of the field, as a string.

type

Type of the field, as a ctypes class.

offset

byte_offset

Offset of the field, in bytes.

For bitfields, this is the offset of the underlying byte-aligned storage unit; see bit_offset.

byte_size

Size of the field, in bytes.

For bitfields, this is the size of the underlying storage unit. Typically, it has the same size as the bitfield's type.

size

For non-bitfields, equivalent to byte_size.

For bitfields, this contains a backwards-compatible bit-packed value that combines bit_size and bit_offset. Prefer using the explicit attributes instead.

is_bitfield

True if this is a bitfield.

bit_offset

bit_size

The location of a bitfield within its storage unit, that is, within byte_size bytes of memory starting at byte_offset.

To get the field's value, read the storage unit as an integer, shift left by bit_offset and take the bit_size least significant bits.

For non-bitfields, bit_offset is zero and bit_size is equal to byte_size * 8.

is_anonymous

True if this field is anonymous, that is, it contains nested sub-fields that should be merged into a containing structure or union.

Arrays and pointers

class ctypes.Array(*args)

Abstract base class for arrays.

The recommended way to create concrete array types is by multiplying any ctypes data type with a non-negative integer. Alternatively, you can subclass this type and define _length_ and _type_ class variables. Array elements can be read and written using standard subscript and slice accesses; for slice reads, the resulting object is not itself an Array.

_length_

A positive integer specifying the number of elements in the array. Out-of-range subscripts result in an IndexError. Will be returned by len().

_type_

Specifies the type of each element in the array.

Array subclass constructors accept positional arguments, used to initialize the elements in order.

ctypes.ARRAY(type, length)

Create an array. Equivalent to type * length, where type is a ctypes data type and length an integer.

This function is soft deprecated in favor of multiplication. There are no plans to remove it.

class ctypes._Pointer

Private, abstract base class for pointers.

Concrete pointer types are created by calling POINTER() with the type that will be pointed to; this is done automatically by pointer().

If a pointer points to an array, its elements can be read and written using standard subscript and slice accesses. Pointer objects have no size, so len() will raise TypeError. Negative subscripts will read from the memory before the pointer (as in C), and out-of-range subscripts will probably crash with an access violation (if you're lucky).

_type_

Specifies the type pointed to.

contents

Returns the object to which to pointer points. Assigning to this attribute changes the pointer to point to the assigned object.

Exceptions

exception ctypes.ArgumentError

This exception is raised when a foreign function call cannot convert one of the passed arguments.

exception ctypes.COMError(hresult, text, details)

This exception is raised when a COM method call failed.

hresult

The integer value representing the error code.

text

The error message.

details

The 5-tuple (descr, source, helpfile, helpcontext, progid).

descr is the textual description. source is the language-dependent ProgID for the class or application that raised the error. helpfile is the path of the help file. helpcontext is the help context identifier. progid is the ProgID of the interface that defined the error.

可用性: Windows

在 3.14 版被加入.

命令列介面函式庫

本章節所描述的模組協助實作應用程式的命令列與終端介面。

以下為概覽：

argparse --- 命令列選項、引數和子命令的剖析器

optparse --- 命令列選項剖析器

getpass --- 可攜式密碼輸入工具

fileinput --- 逐列疊代多個輸入串流

curses --- 字元儲存格顯示的終端處理

curses.textpad --- Text input widget for curses programs

curses.ascii --- ASCII 字元的工具程式

curses.panel --- curses 的面板堆疊擴充

cmd --- 以列為導向的命令直譯器支援

argparse --- 命令列選項、引數和子命令的剖析器

在 3.2 版被加入.

原始碼：Lib/argparse.py [https://github.com/python/cpython/tree/3.14/Lib/argparse.py]

備註

While argparse is the default recommended standard library module for implementing basic command line applications, authors with more exacting requirements for exactly how their command line applications behave may find it doesn't provide the necessary level of control. Refer to 選擇一個命令列參數剖析函式庫 for alternatives to consider when argparse doesn't support behaviors that the application requires (such as entirely disabling support for interspersed options and positional arguments, or accepting option parameter values that start with - even when they correspond to another defined option).

教學

This page contains the API reference information. For a more gentle introduction to Python command-line parsing, have a look at the argparse tutorial.

The argparse module makes it easy to write user-friendly command-line interfaces. The program defines what arguments it requires, and argparse will figure out how to parse those out of sys.argv. The argparse module also automatically generates help and usage messages. The module will also issue errors when users give the program invalid arguments.

The argparse module's support for command-line interfaces is built around an instance of argparse.ArgumentParser. It is a container for argument specifications and has options that apply to the parser as whole:

parser = argparse.ArgumentParser(
                    prog='ProgramName',
                    description='What the program does',
                    epilog='Text at the bottom of help')

The ArgumentParser.add_argument() method attaches individual argument specifications to the parser. It supports positional arguments, options that accept values, and on/off flags:

parser.add_argument('filename')           # 位置引數
parser.add_argument('-c', '--count')      # 接收一個值的選項
parser.add_argument('-v', '--verbose',
                    action='store_true')  # 開關旗標

The ArgumentParser.parse_args() method runs the parser and places the extracted data in a argparse.Namespace object:

args = parser.parse_args()
print(args.filename, args.count, args.verbose)

備註

If you're looking for a guide about how to upgrade optparse code to argparse, see Upgrading Optparse Code.

ArgumentParser 物件

class argparse.ArgumentParser(prog=None, usage=None, description=None, epilog=None, parents=[], formatter_class=argparse.HelpFormatter, prefix_chars='-', fromfile_prefix_chars=None, argument_default=None, conflict_handler='error', add_help=True, allow_abbrev=True, exit_on_error=True, *, suggest_on_error=False, color=True)

Create a new ArgumentParser object. All parameters should be passed as keyword arguments. Each parameter has its own more detailed description below, but in short they are:

prog - 程式的名稱（預設值：從 __main__ 模組屬性和 sys.argv[0] 產生）

usage - 描述程式用法的字串（預設值：從新增到剖析器的引數產生）

description - 引數說明之前要顯示的文字（預設值：無文字）

epilog - 引數說明之後要顯示的文字（預設值：無文字）

parents - 一個 ArgumentParser 物件的串列，其引數也應該被包含

formatter_class - 用於自訂說明輸出的類別

prefix_chars - 前綴可選引數的字元集合（預設值：'-'）

fromfile_prefix_chars - The set of characters that prefix files from which additional arguments should be read (default: None)

argument_default - The global default value for arguments (default: None)

conflict_handler - The strategy for resolving conflicting optionals (usually unnecessary)

add_help - Add a -h/--help option to the parser (default: True)

allow_abbrev - Allows long options to be abbreviated if the abbreviation is unambiguous (default: True)

exit_on_error - Determines whether or not ArgumentParser exits with error info when an error occurs. (default: True)

suggest_on_error - Enables suggestions for mistyped argument choices and subparser names (default: False)

color - Allow color output (default: True)

在 3.5 版的變更: 新增 allow_abbrev 參數。

在 3.8 版的變更: In previous versions, allow_abbrev also disabled grouping of short flags such as -vv to mean -v -v.

在 3.9 版的變更: 新增 exit_on_error 參數。

在 3.14 版的變更: 新增 suggest_on_error 和 color 參數。

The following sections describe how each of these are used.

prog

By default, ArgumentParser calculates the name of the program to display in help messages depending on the way the Python interpreter was run:

The base name of sys.argv[0] if a file was passed as argument.

The Python interpreter name followed by sys.argv[0] if a directory or a zipfile was passed as argument.

The Python interpreter name followed by -m followed by the module or package name if the -m option was used.

This default is almost always desirable because it will make the help messages match the string that was used to invoke the program on the command line. However, to change this default behavior, another value can be supplied using the prog= argument to ArgumentParser:

>>> parser = argparse.ArgumentParser(prog='myprogram')
>>> parser.print_help()
usage: myprogram [-h]

options:
 -h, --help  show this help message and exit

Note that the program name, whether determined from sys.argv[0], from the __main__ module attributes or from the prog= argument, is available to help messages using the %(prog)s format specifier.

>>> parser = argparse.ArgumentParser(prog='myprogram')
>>> parser.add_argument('--foo', help='foo of the %(prog)s program')
>>> parser.print_help()
usage: myprogram [-h] [--foo FOO]

options:
 -h, --help  show this help message and exit
 --foo FOO   foo of the myprogram program

在 3.14 版的變更: The default prog value now reflects how __main__ was actually executed, rather than always being os.path.basename(sys.argv[0]).

usage

By default, ArgumentParser calculates the usage message from the arguments it contains. The default message can be overridden with the usage= keyword argument:

>>> parser = argparse.ArgumentParser(prog='PROG', usage='%(prog)s [options]')
>>> parser.add_argument('--foo', nargs='?', help='foo help')
>>> parser.add_argument('bar', nargs='+', help='bar help')
>>> parser.print_help()
usage: PROG [options]

positional arguments:
 bar          bar help

options:
 -h, --help   show this help message and exit
 --foo [FOO]  foo help

The %(prog)s format specifier is available to fill in the program name in your usage messages.

When a custom usage message is specified for the main parser, you may also want to consider passing the prog argument to add_subparsers() or the prog and the usage arguments to add_parser(), to ensure consistent command prefixes and usage information across subparsers.

description

Most calls to the ArgumentParser constructor will use the description= keyword argument. This argument gives a brief description of what the program does and how it works. In help messages, the description is displayed between the command-line usage string and the help messages for the various arguments.

By default, the description will be line-wrapped so that it fits within the given space. To change this behavior, see the formatter_class argument.

epilog

Some programs like to display additional description of the program after the description of the arguments. Such text can be specified using the epilog= argument to ArgumentParser:

>>> parser = argparse.ArgumentParser(
...     description='A foo that bars',
...     epilog="And that's how you'd foo a bar")
>>> parser.print_help()
usage: argparse.py [-h]

A foo that bars

options:
 -h, --help  show this help message and exit

And that's how you'd foo a bar

As with the description argument, the epilog= text is by default line-wrapped, but this behavior can be adjusted with the formatter_class argument to ArgumentParser.

parents

Sometimes, several parsers share a common set of arguments. Rather than repeating the definitions of these arguments, a single parser with all the shared arguments and passed to parents= argument to ArgumentParser can be used. The parents= argument takes a list of ArgumentParser objects, collects all the positional and optional actions from them, and adds these actions to the ArgumentParser object being constructed:

>>> parent_parser = argparse.ArgumentParser(add_help=False)
>>> parent_parser.add_argument('--parent', type=int)

>>> foo_parser = argparse.ArgumentParser(parents=[parent_parser])
>>> foo_parser.add_argument('foo')
>>> foo_parser.parse_args(['--parent', '2', 'XXX'])
Namespace(foo='XXX', parent=2)

>>> bar_parser = argparse.ArgumentParser(parents=[parent_parser])
>>> bar_parser.add_argument('--bar')
>>> bar_parser.parse_args(['--bar', 'YYY'])
Namespace(bar='YYY', parent=None)

Note that most parent parsers will specify add_help=False. Otherwise, the ArgumentParser will see two -h/--help options (one in the parent and one in the child) and raise an error.

備註

You must fully initialize the parsers before passing them via parents=. If you change the parent parsers after the child parser, those changes will not be reflected in the child.

formatter_class

ArgumentParser objects allow the help formatting to be customized by specifying an alternate formatting class. Currently, there are four such classes:

class argparse.RawDescriptionHelpFormatter

class argparse.RawTextHelpFormatter

class argparse.ArgumentDefaultsHelpFormatter

class argparse.MetavarTypeHelpFormatter

RawDescriptionHelpFormatter and RawTextHelpFormatter give more control over how textual descriptions are displayed. By default, ArgumentParser objects line-wrap the description and epilog texts in command-line help messages:

>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     description='''this description
...         was indented weird
...             but that is okay''',
...     epilog='''
...             likewise for this epilog whose whitespace will
...         be cleaned up and whose words will be wrapped
...         across a couple lines''')
>>> parser.print_help()
usage: PROG [-h]

this description was indented weird but that is okay

options:
 -h, --help  show this help message and exit

likewise for this epilog whose whitespace will be cleaned up and whose words
will be wrapped across a couple lines

Passing RawDescriptionHelpFormatter as formatter_class= indicates that description and epilog are already correctly formatted and should not be line-wrapped:

>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     formatter_class=argparse.RawDescriptionHelpFormatter,
...     description=textwrap.dedent('''\
...         Please do not mess up this text!
...         --------------------------------
...             I have indented it
...             exactly the way
...             I want it
...         '''))
>>> parser.print_help()
usage: PROG [-h]

Please do not mess up this text!
--------------------------------
   I have indented it
   exactly the way
   I want it

options:
 -h, --help  show this help message and exit

RawTextHelpFormatter maintains whitespace for all sorts of help text, including argument descriptions. However, multiple newlines are replaced with one. If you wish to preserve multiple blank lines, add spaces between the newlines.

ArgumentDefaultsHelpFormatter automatically adds information about default values to each of the argument help messages:

>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     formatter_class=argparse.ArgumentDefaultsHelpFormatter)
>>> parser.add_argument('--foo', type=int, default=42, help='FOO!')
>>> parser.add_argument('bar', nargs='*', default=[1, 2, 3], help='BAR!')
>>> parser.print_help()
usage: PROG [-h] [--foo FOO] [bar ...]

positional arguments:
 bar         BAR! (default: [1, 2, 3])

options:
 -h, --help  show this help message and exit
 --foo FOO   FOO! (default: 42)

MetavarTypeHelpFormatter uses the name of the type argument for each argument as the display name for its values (rather than using the dest as the regular formatter does):

>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     formatter_class=argparse.MetavarTypeHelpFormatter)
>>> parser.add_argument('--foo', type=int)
>>> parser.add_argument('bar', type=float)
>>> parser.print_help()
usage: PROG [-h] [--foo int] float

positional arguments:
  float

options:
  -h, --help  show this help message and exit
  --foo int

prefix_chars

Most command-line options will use - as the prefix, e.g. -f/--foo. Parsers that need to support different or additional prefix characters, e.g. for options like +f or /foo, may specify them using the prefix_chars= argument to the ArgumentParser constructor:

>>> parser = argparse.ArgumentParser(prog='PROG', prefix_chars='-+')
>>> parser.add_argument('+f')
>>> parser.add_argument('++bar')
>>> parser.parse_args('+f X ++bar Y'.split())
Namespace(bar='Y', f='X')

The prefix_chars= argument defaults to '-'. Supplying a set of characters that does not include - will cause -f/--foo options to be disallowed.

fromfile_prefix_chars

Sometimes, when dealing with a particularly long argument list, it may make sense to keep the list of arguments in a file rather than typing it out at the command line. If the fromfile_prefix_chars= argument is given to the ArgumentParser constructor, then arguments that start with any of the specified characters will be treated as files, and will be replaced by the arguments they contain. For example:

>>> with open('args.txt', 'w', encoding=sys.getfilesystemencoding()) as fp:
...     fp.write('-f\nbar')
...
>>> parser = argparse.ArgumentParser(fromfile_prefix_chars='@')
>>> parser.add_argument('-f')
>>> parser.parse_args(['-f', 'foo', '@args.txt'])
Namespace(f='bar')

Arguments read from a file must be one per line by default (but see also convert_arg_line_to_args()) and are treated as if they were in the same place as the original file referencing argument on the command line. So in the example above, the expression ['-f', 'foo', '@args.txt'] is considered equivalent to the expression ['-f', 'foo', '-f', 'bar'].

備註

Empty lines are treated as empty strings (''), which are allowed as values but not as arguments. Empty lines that are read as arguments will result in an "unrecognized arguments" error.

ArgumentParser uses filesystem encoding and error handler to read the file containing arguments.

The fromfile_prefix_chars= argument defaults to None, meaning that arguments will never be treated as file references.

在 3.12 版的變更: ArgumentParser changed encoding and errors to read arguments files from default (e.g. locale.getpreferredencoding(False) and "strict") to the filesystem encoding and error handler. Arguments file should be encoded in UTF-8 instead of ANSI Codepage on Windows.

argument_default

Generally, argument defaults are specified either by passing a default to add_argument() or by calling the set_defaults() methods with a specific set of name-value pairs. Sometimes however, it may be useful to specify a single parser-wide default for arguments. This can be accomplished by passing the argument_default= keyword argument to ArgumentParser. For example, to globally suppress attribute creation on parse_args() calls, we supply argument_default=SUPPRESS:

>>> parser = argparse.ArgumentParser(argument_default=argparse.SUPPRESS)
>>> parser.add_argument('--foo')
>>> parser.add_argument('bar', nargs='?')
>>> parser.parse_args(['--foo', '1', 'BAR'])
Namespace(bar='BAR', foo='1')
>>> parser.parse_args([])
Namespace()

allow_abbrev

Normally, when you pass an argument list to the parse_args() method of an ArgumentParser, it recognizes abbreviations of long options.

This feature can be disabled by setting allow_abbrev to False:

>>> parser = argparse.ArgumentParser(prog='PROG', allow_abbrev=False)
>>> parser.add_argument('--foobar', action='store_true')
>>> parser.add_argument('--foonley', action='store_false')
>>> parser.parse_args(['--foon'])
usage: PROG [-h] [--foobar] [--foonley]
PROG: error: unrecognized arguments: --foon

在 3.5 版被加入.

conflict_handler

ArgumentParser objects do not allow two actions with the same option string. By default, ArgumentParser objects raise an exception if an attempt is made to create an argument with an option string that is already in use:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-f', '--foo', help='old foo help')
>>> parser.add_argument('--foo', help='new foo help')
Traceback (most recent call last):
 ..
ArgumentError: argument --foo: conflicting option string(s): --foo

Sometimes (e.g. when using parents) it may be useful to simply override any older arguments with the same option string. To get this behavior, the value 'resolve' can be supplied to the conflict_handler= argument of ArgumentParser:

>>> parser = argparse.ArgumentParser(prog='PROG', conflict_handler='resolve')
>>> parser.add_argument('-f', '--foo', help='old foo help')
>>> parser.add_argument('--foo', help='new foo help')
>>> parser.print_help()
usage: PROG [-h] [-f FOO] [--foo FOO]

options:
 -h, --help  show this help message and exit
 -f FOO      old foo help
 --foo FOO   new foo help

Note that ArgumentParser objects only remove an action if all of its option strings are overridden. So, in the example above, the old -f/--foo action is retained as the -f action, because only the --foo option string was overridden.

add_help

By default, ArgumentParser objects add an option which simply displays the parser's help message. If -h or --help is supplied at the command line, the ArgumentParser help will be printed.

Occasionally, it may be useful to disable the addition of this help option. This can be achieved by passing False as the add_help= argument to ArgumentParser:

>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> parser.add_argument('--foo', help='foo help')
>>> parser.print_help()
usage: PROG [--foo FOO]

options:
 --foo FOO  foo help

The help option is typically -h/--help. The exception to this is if the prefix_chars= is specified and does not include -, in which case -h and --help are not valid options. In this case, the first character in prefix_chars is used to prefix the help options:

>>> parser = argparse.ArgumentParser(prog='PROG', prefix_chars='+/')
>>> parser.print_help()
usage: PROG [+h]

options:
  +h, ++help  show this help message and exit

exit_on_error

Normally, when you pass an invalid argument list to the parse_args() method of an ArgumentParser, it will print a message to sys.stderr and exit with a status code of 2.

If the user would like to catch errors manually, the feature can be enabled by setting exit_on_error to False:

>>> parser = argparse.ArgumentParser(exit_on_error=False)
>>> parser.add_argument('--integers', type=int)
_StoreAction(option_strings=['--integers'], dest='integers', nargs=None, const=None, default=None, type=<class 'int'>, choices=None, help=None, metavar=None)
>>> try:
...     parser.parse_args('--integers a'.split())
... except argparse.ArgumentError:
...     print('Catching an argumentError')
...
Catching an argumentError

在 3.9 版被加入.

suggest_on_error

By default, when a user passes an invalid argument choice or subparser name, ArgumentParser will exit with error info and list the permissible argument choices (if specified) or subparser names as part of the error message.

If the user would like to enable suggestions for mistyped argument choices and subparser names, the feature can be enabled by setting suggest_on_error to True. Note that this only applies for arguments when the choices specified are strings:

>>> parser = argparse.ArgumentParser(description='Process some integers.',
                                     suggest_on_error=True)
>>> parser.add_argument('--action', choices=['sum', 'max'])
>>> parser.add_argument('integers', metavar='N', type=int, nargs='+',
...                     help='an integer for the accumulator')
>>> parser.parse_args(['--action', 'sumn', 1, 2, 3])
tester.py: error: argument --action: invalid choice: 'sumn', maybe you meant 'sum'? (choose from 'sum', 'max')

If you're writing code that needs to be compatible with older Python versions and want to opportunistically use suggest_on_error when it's available, you can set it as an attribute after initializing the parser instead of using the keyword argument:

>>> parser = argparse.ArgumentParser(description='Process some integers.')
>>> parser.suggest_on_error = True

在 3.14 版被加入.

color

By default, the help message is printed in color using ANSI escape sequences [https://en.wikipedia.org/wiki/ANSI_escape_code]. If you want plain text help messages, you can disable this in your local environment, or in the argument parser itself by setting color to False:

>>> parser = argparse.ArgumentParser(description='Process some integers.',
...                                  color=False)
>>> parser.add_argument('--action', choices=['sum', 'max'])
>>> parser.add_argument('integers', metavar='N', type=int, nargs='+',
...                     help='an integer for the accumulator')
>>> parser.parse_args(['--help'])

Note that when color=True, colored output depends on both environment variables and terminal capabilities. However, if color=False, colored output is always disabled, even if environment variables like FORCE_COLOR are set.

備註

Error messages will include color codes when redirecting stderr to a file. To avoid this, set the NO_COLOR [https://no-color.org/] or PYTHON_COLORS environment variable (for example, NO_COLOR=1 python script.py 2> errors.txt).

在 3.14 版被加入.

add_argument() 方法

ArgumentParser.add_argument(name or flags..., *[, action][, nargs][, const][, default][, type][, choices][, required][, help][, metavar][, dest][, deprecated])

Define how a single command-line argument should be parsed. Each parameter has its own more detailed description below, but in short they are:

name or flags - Either a name or a list of option strings, e.g. 'foo' or '-f', '--foo'.

action - The basic type of action to be taken when this argument is encountered at the command line.

nargs - The number of command-line arguments that should be consumed.

const - A constant value required by some action and nargs selections.

default - The value produced if the argument is absent from the command line and if it is absent from the namespace object.

type - The type to which the command-line argument should be converted.

choices - A sequence of the allowable values for the argument.

required - Whether or not the command-line option may be omitted (optionals only).

help - A brief description of what the argument does.

metavar - A name for the argument in usage messages.

dest - The name of the attribute to be added to the object returned by parse_args().

deprecated - Whether or not use of the argument is deprecated.

The following sections describe how each of these are used.

name or flags

The add_argument() method must know whether an optional argument, like -f or --foo, or a positional argument, like a list of filenames, is expected. The first arguments passed to add_argument() must therefore be either a series of flags, or a simple argument name.

For example, an optional argument could be created like:

>>> parser.add_argument('-f', '--foo')

while a positional argument could be created like:

>>> parser.add_argument('bar')

When parse_args() is called, optional arguments will be identified by the - prefix, and the remaining arguments will be assumed to be positional:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-f', '--foo')
>>> parser.add_argument('bar')
>>> parser.parse_args(['BAR'])
Namespace(bar='BAR', foo=None)
>>> parser.parse_args(['BAR', '--foo', 'FOO'])
Namespace(bar='BAR', foo='FOO')
>>> parser.parse_args(['--foo', 'FOO'])
usage: PROG [-h] [-f FOO] bar
PROG: error: the following arguments are required: bar

By default, argparse automatically handles the internal naming and display names of arguments, simplifying the process without requiring additional configuration. As such, you do not need to specify the dest and metavar parameters. The dest parameter defaults to the argument name with underscores _ replacing hyphens - . The metavar parameter defaults to the upper-cased name. For example:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo-bar')
>>> parser.parse_args(['--foo-bar', 'FOO-BAR'])
Namespace(foo_bar='FOO-BAR')
>>> parser.print_help()
usage:  [-h] [--foo-bar FOO-BAR]

optional arguments:
 -h, --help  show this help message and exit
 --foo-bar FOO-BAR

action

ArgumentParser objects associate command-line arguments with actions. These actions can do just about anything with the command-line arguments associated with them, though most actions simply add an attribute to the object returned by parse_args(). The action keyword argument specifies how the command-line arguments should be handled. The supplied actions are:

'store' - This just stores the argument's value. This is the default action.

'store_const' - This stores the value specified by the const keyword argument; note that the const keyword argument defaults to None. The 'store_const' action is most commonly used with optional arguments that specify some sort of flag. For example:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_const', const=42)
>>> parser.parse_args(['--foo'])
Namespace(foo=42)

'store_true' and 'store_false' - These are special cases of 'store_const' that respectively store the values True and False with default values of False and True:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_true')
>>> parser.add_argument('--bar', action='store_false')
>>> parser.add_argument('--baz', action='store_false')
>>> parser.parse_args('--foo --bar'.split())
Namespace(foo=True, bar=False, baz=True)

'append' - This appends each argument value to a list. It is useful for allowing an option to be specified multiple times. If the default value is a non-empty list, the parsed value will start with the default list's elements and any values from the command line will be appended after those default values. Example usage:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='append', default=['0'])
>>> parser.parse_args('--foo 1 --foo 2'.split())
Namespace(foo=['0', '1', '2'])

'append_const' - This appends the value specified by the const keyword argument to a list; note that the const keyword argument defaults to None. The 'append_const' action is typically useful when multiple arguments need to store constants to the same list. For example:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--str', dest='types', action='append_const', const=str)
>>> parser.add_argument('--int', dest='types', action='append_const', const=int)
>>> parser.parse_args('--str --int'.split())
Namespace(types=[<class 'str'>, <class 'int'>])

'extend' - This appends each item from a multi-value argument to a list. The 'extend' action is typically used with the nargs keyword argument value '+' or '*'. Note that when nargs is None (the default) or '?', each character of the argument string will be appended to the list. Example usage:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument("--foo", action="extend", nargs="+", type=str)
>>> parser.parse_args(["--foo", "f1", "--foo", "f2", "f3", "f4"])
Namespace(foo=['f1', 'f2', 'f3', 'f4'])

在 3.8 版被加入.

'count' - This counts the number of times an argument occurs. For example, this is useful for increasing verbosity levels:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--verbose', '-v', action='count', default=0)
>>> parser.parse_args(['-vvv'])
Namespace(verbose=3)

Note, the default will be None unless explicitly set to 0.

'help' - This prints a complete help message for all the options in the current parser and then exits. By default a help action is automatically added to the parser. See ArgumentParser for details of how the output is created.

'version' - This expects a version= keyword argument in the add_argument() call, and prints version information and exits when invoked:

>>> import argparse
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--version', action='version', version='%(prog)s 2.0')
>>> parser.parse_args(['--version'])
PROG 2.0

你也可以傳遞一個 Action 子類別（例如 BooleanOptionalAction）或實作相同介面的其他物件。只有會消耗命令列引數的 action（例如 'store'、'append'、'extend' 或 nargs 不為零的自定義 action）可以被用於位置引數。

The recommended way to create a custom action is to extend Action, overriding the __call__() method and optionally the __init__() and format_usage() methods. You can also register custom actions using the register() method and reference them by their registered name.

自訂 action 的範例：

>>> class FooAction(argparse.Action):
...     def __init__(self, option_strings, dest, nargs=None, **kwargs):
...         if nargs is not None:
...             raise ValueError("nargs not allowed")
...         super().__init__(option_strings, dest, **kwargs)
...     def __call__(self, parser, namespace, values, option_string=None):
...         print('%r %r %r' % (namespace, values, option_string))
...         setattr(namespace, self.dest, values)
...
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action=FooAction)
>>> parser.add_argument('bar', action=FooAction)
>>> args = parser.parse_args('1 --foo 2'.split())
Namespace(bar=None, foo=None) '1' None
Namespace(bar='1', foo=None) '2' '--foo'
>>> args
Namespace(bar='1', foo='2')

更多詳情請見 Action。

nargs

ArgumentParser objects usually associate a single command-line argument with a single action to be taken. The nargs keyword argument associates a different number of command-line arguments with a single action. See also 指定不明確的引數. The supported values are:

N (an integer). N arguments from the command line will be gathered together into a list. For example:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs=2)
>>> parser.add_argument('bar', nargs=1)
>>> parser.parse_args('c --foo a b'.split())
Namespace(bar=['c'], foo=['a', 'b'])

Note that nargs=1 produces a list of one item. This is different from the default, in which the item is produced by itself.

'?'. One argument will be consumed from the command line if possible, and produced as a single item. If no command-line argument is present, the value from default will be produced. Note that for optional arguments, there is an additional case - the option string is present but not followed by a command-line argument. In this case the value from const will be produced. Some examples to illustrate this:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs='?', const='c', default='d')
>>> parser.add_argument('bar', nargs='?', default='d')
>>> parser.parse_args(['XX', '--foo', 'YY'])
Namespace(bar='XX', foo='YY')
>>> parser.parse_args(['XX', '--foo'])
Namespace(bar='XX', foo='c')
>>> parser.parse_args([])
Namespace(bar='d', foo='d')

One of the more common uses of nargs='?' is to allow optional input and output files:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('infile', nargs='?')
>>> parser.add_argument('outfile', nargs='?')
>>> parser.parse_args(['input.txt', 'output.txt'])
Namespace(infile='input.txt', outfile='output.txt')
>>> parser.parse_args(['input.txt'])
Namespace(infile='input.txt', outfile=None)
>>> parser.parse_args([])
Namespace(infile=None, outfile=None)

'*'. All command-line arguments present are gathered into a list. Note that it generally doesn't make much sense to have more than one positional argument with nargs='*', but multiple optional arguments with nargs='*' is possible. For example:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs='*')
>>> parser.add_argument('--bar', nargs='*')
>>> parser.add_argument('baz', nargs='*')
>>> parser.parse_args('a b --foo x y --bar 1 2'.split())
Namespace(bar=['1', '2'], baz=['a', 'b'], foo=['x', 'y'])

'+'. Just like '*', all command-line arguments present are gathered into a list. Additionally, an error message will be generated if there wasn't at least one command-line argument present. For example:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', nargs='+')
>>> parser.parse_args(['a', 'b'])
Namespace(foo=['a', 'b'])
>>> parser.parse_args([])
usage: PROG [-h] foo [foo ...]
PROG: error: the following arguments are required: foo

If the nargs keyword argument is not provided, the number of arguments consumed is determined by the action. Generally this means a single command-line argument will be consumed and a single item (not a list) will be produced. Actions that do not consume command-line arguments (e.g. 'store_const') set nargs=0.

const

The const argument of add_argument() is used to hold constant values that are not read from the command line but are required for the various ArgumentParser actions. The two most common uses of it are:

When add_argument() is called with action='store_const' or action='append_const'. These actions add the const value to one of the attributes of the object returned by parse_args(). See the action description for examples. If const is not provided to add_argument(), it will receive a default value of None.

When add_argument() is called with option strings (like -f or --foo) and nargs='?'. This creates an optional argument that can be followed by zero or one command-line arguments. When parsing the command line, if the option string is encountered with no command-line argument following it, the value from const will be used. See the nargs description for examples.

在 3.11 版的變更: const=None by default, including when action='append_const' or action='store_const'.

default

All optional arguments and some positional arguments may be omitted at the command line. The default keyword argument of add_argument(), whose value defaults to None, specifies what value should be used if the command-line argument is not present. For optional arguments, the default value is used when the option string was not present at the command line:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=42)
>>> parser.parse_args(['--foo', '2'])
Namespace(foo='2')
>>> parser.parse_args([])
Namespace(foo=42)

If the target namespace already has an attribute set, the action default will not overwrite it:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=42)
>>> parser.parse_args([], namespace=argparse.Namespace(foo=101))
Namespace(foo=101)

If the default value is a string, the parser parses the value as if it were a command-line argument. In particular, the parser applies any type conversion argument, if provided, before setting the attribute on the Namespace return value. Otherwise, the parser uses the value as is:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--length', default='10', type=int)
>>> parser.add_argument('--width', default=10.5, type=int)
>>> parser.parse_args()
Namespace(length=10, width=10.5)

For positional arguments with nargs equal to ? or *, the default value is used when no command-line argument was present:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', nargs='?', default=42)
>>> parser.parse_args(['a'])
Namespace(foo='a')
>>> parser.parse_args([])
Namespace(foo=42)

For required arguments, the default value is ignored. For example, this applies to positional arguments with nargs values other than ? or *, or optional arguments marked as required=True.

Providing default=argparse.SUPPRESS causes no attribute to be added if the command-line argument was not present:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=argparse.SUPPRESS)
>>> parser.parse_args([])
Namespace()
>>> parser.parse_args(['--foo', '1'])
Namespace(foo='1')

type

By default, the parser reads command-line arguments in as simple strings. However, quite often the command-line string should instead be interpreted as another type, such as a float or int. The type keyword for add_argument() allows any necessary type-checking and type conversions to be performed.

If the type keyword is used with the default keyword, the type converter is only applied if the default is a string.

The argument to type can be a callable that accepts a single string or the name of a registered type (see register()) If the function raises ArgumentTypeError, TypeError, or ValueError, the exception is caught and a nicely formatted error message is displayed. Other exception types are not handled.

Common built-in types and functions can be used as type converters:

import argparse
import pathlib

parser = argparse.ArgumentParser()
parser.add_argument('count', type=int)
parser.add_argument('distance', type=float)
parser.add_argument('street', type=ascii)
parser.add_argument('code_point', type=ord)
parser.add_argument('datapath', type=pathlib.Path)

User defined functions can be used as well:

>>> def hyphenated(string):
...     return '-'.join([word[:4] for word in string.casefold().split()])
...
>>> parser = argparse.ArgumentParser()
>>> _ = parser.add_argument('short_title', type=hyphenated)
>>> parser.parse_args(['"The Tale of Two Cities"'])
Namespace(short_title='"the-tale-of-two-citi')

The bool() function is not recommended as a type converter. All it does is convert empty strings to False and non-empty strings to True. This is usually not what is desired.

In general, the type keyword is a convenience that should only be used for simple conversions that can only raise one of the three supported exceptions. Anything with more interesting error-handling or resource management should be done downstream after the arguments are parsed.

For example, JSON or YAML conversions have complex error cases that require better reporting than can be given by the type keyword. A JSONDecodeError would not be well formatted and a FileNotFoundError exception would not be handled at all.

Even FileType has its limitations for use with the type keyword. If one argument uses FileType and then a subsequent argument fails, an error is reported but the file is not automatically closed. In this case, it would be better to wait until after the parser has run and then use the with-statement to manage the files.

For type checkers that simply check against a fixed set of values, consider using the choices keyword instead.

choices

Some command-line arguments should be selected from a restricted set of values. These can be handled by passing a sequence object as the choices keyword argument to add_argument(). When the command line is parsed, argument values will be checked, and an error message will be displayed if the argument was not one of the acceptable values:

>>> parser = argparse.ArgumentParser(prog='game.py')
>>> parser.add_argument('move', choices=['rock', 'paper', 'scissors'])
>>> parser.parse_args(['rock'])
Namespace(move='rock')
>>> parser.parse_args(['fire'])
usage: game.py [-h] {rock,paper,scissors}
game.py: error: argument move: invalid choice: 'fire' (choose from 'rock',
'paper', 'scissors')

Any sequence can be passed as the choices value, so list objects, tuple objects, and custom sequences are all supported.

Use of enum.Enum is not recommended because it is difficult to control its appearance in usage, help, and error messages.

Note that choices are checked after any type conversions have been performed, so objects in choices should match the type specified. This can make choices appear unfamiliar in usage, help, or error messages.

To keep choices user-friendly, consider a custom type wrapper that converts and formats values, or omit type and handle conversion in your application code.

Formatted choices override the default metavar which is normally derived from dest. This is usually what you want because the user never sees the dest parameter. If this display isn't desirable (perhaps because there are many choices), just specify an explicit metavar.

required

In general, the argparse module assumes that flags like -f and --bar indicate optional arguments, which can always be omitted at the command line. To make an option required, True can be specified for the required= keyword argument to add_argument():

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', required=True)
>>> parser.parse_args(['--foo', 'BAR'])
Namespace(foo='BAR')
>>> parser.parse_args([])
usage: [-h] --foo FOO
: error: the following arguments are required: --foo

As the example shows, if an option is marked as required, parse_args() will report an error if that option is not present at the command line.

備註

Required options are generally considered bad form because users expect options to be optional, and thus they should be avoided when possible.

help

The help value is a string containing a brief description of the argument. When a user requests help (usually by using -h or --help at the command line), these help descriptions will be displayed with each argument.

The help strings can include various format specifiers to avoid repetition of things like the program name or the argument default. The available specifiers include the program name, %(prog)s and most keyword arguments to add_argument(), e.g. %(default)s, %(type)s, etc.:

>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('bar', nargs='?', type=int, default=42,
...                     help='the bar to %(prog)s (default: %(default)s)')
>>> parser.print_help()
usage: frobble [-h] [bar]

positional arguments:
 bar     the bar to frobble (default: 42)

options:
 -h, --help  show this help message and exit

As the help string supports %-formatting, if you want a literal % to appear in the help string, you must escape it as %%.

argparse supports silencing the help entry for certain options, by setting the help value to argparse.SUPPRESS:

>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('--foo', help=argparse.SUPPRESS)
>>> parser.print_help()
usage: frobble [-h]

options:
  -h, --help  show this help message and exit

metavar

When ArgumentParser generates help messages, it needs some way to refer to each expected argument. By default, ArgumentParser objects use the dest value as the "name" of each object. By default, for positional argument actions, the dest value is used directly, and for optional argument actions, the dest value is uppercased. So, a single positional argument with dest='bar' will be referred to as bar. A single optional argument --foo that should be followed by a single command-line argument will be referred to as FOO. An example:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.add_argument('bar')
>>> parser.parse_args('X --foo Y'.split())
Namespace(bar='X', foo='Y')
>>> parser.print_help()
usage:  [-h] [--foo FOO] bar

positional arguments:
 bar

options:
 -h, --help  show this help message and exit
 --foo FOO

An alternative name can be specified with metavar:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', metavar='YYY')
>>> parser.add_argument('bar', metavar='XXX')
>>> parser.parse_args('X --foo Y'.split())
Namespace(bar='X', foo='Y')
>>> parser.print_help()
usage:  [-h] [--foo YYY] XXX

positional arguments:
 XXX

options:
 -h, --help  show this help message and exit
 --foo YYY

Note that metavar only changes the displayed name - the name of the attribute on the parse_args() object is still determined by the dest value.

Different values of nargs may cause the metavar to be used multiple times. Providing a tuple to metavar specifies a different display for each of the arguments:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x', nargs=2)
>>> parser.add_argument('--foo', nargs=2, metavar=('bar', 'baz'))
>>> parser.print_help()
usage: PROG [-h] [-x X X] [--foo bar baz]

options:
 -h, --help     show this help message and exit
 -x X X
 --foo bar baz

dest

Most ArgumentParser actions add some value as an attribute of the object returned by parse_args(). The name of this attribute is determined by the dest keyword argument of add_argument(). For positional argument actions, dest is normally supplied as the first argument to add_argument():

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('bar')
>>> parser.parse_args(['XXX'])
Namespace(bar='XXX')

For optional argument actions, the value of dest is normally inferred from the option strings. ArgumentParser generates the value of dest by taking the first long option string and stripping away the initial -- string. If no long option strings were supplied, dest will be derived from the first short option string by stripping the initial - character. Any internal - characters will be converted to _ characters to make sure the string is a valid attribute name. The examples below illustrate this behavior:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('-f', '--foo-bar', '--foo')
>>> parser.add_argument('-x', '-y')
>>> parser.parse_args('-f 1 -x 2'.split())
Namespace(foo_bar='1', x='2')
>>> parser.parse_args('--foo 1 -y 2'.split())
Namespace(foo_bar='1', x='2')

dest allows a custom attribute name to be provided:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', dest='bar')
>>> parser.parse_args('--foo XXX'.split())
Namespace(bar='XXX')

deprecated

During a project's lifetime, some arguments may need to be removed from the command line. Before removing them, you should inform your users that the arguments are deprecated and will be removed. The deprecated keyword argument of add_argument(), which defaults to False, specifies if the argument is deprecated and will be removed in the future. For arguments, if deprecated is True, then a warning will be printed to sys.stderr when the argument is used:

>>> import argparse
>>> parser = argparse.ArgumentParser(prog='snake.py')
>>> parser.add_argument('--legs', default=0, type=int, deprecated=True)
>>> parser.parse_args([])
Namespace(legs=0)
>>> parser.parse_args(['--legs', '4'])
snake.py: warning: option '--legs' is deprecated
Namespace(legs=4)

在 3.13 版被加入.

Action 類別

Action classes implement the Action API, a callable which returns a callable which processes arguments from the command-line. Any object which follows this API may be passed as the action parameter to add_argument().

class argparse.Action(option_strings, dest, nargs=None, const=None, default=None, type=None, choices=None, required=False, help=None, metavar=None)

Action objects are used by an ArgumentParser to represent the information needed to parse a single argument from one or more strings from the command line. The Action class must accept the two positional arguments plus any keyword arguments passed to ArgumentParser.add_argument() except for the action itself.

Instances of Action (or return value of any callable to the action parameter) should have attributes dest, option_strings, default, type, required, help, etc. defined. The easiest way to ensure these attributes are defined is to call Action.__init__().

__call__(parser, namespace, values, option_string=None)

Action instances should be callable, so subclasses must override the __call__() method, which should accept four parameters:

parser - The ArgumentParser object which contains this action.

namespace - The Namespace object that will be returned by parse_args(). Most actions add an attribute to this object using setattr().

values - The associated command-line arguments, with any type conversions applied. Type conversions are specified with the type keyword argument to add_argument().

option_string - The option string that was used to invoke this action. The option_string argument is optional, and will be absent if the action is associated with a positional argument.

The __call__() method may perform arbitrary actions, but will typically set attributes on the namespace based on dest and values.

format_usage()

Action subclasses can define a format_usage() method that takes no argument and return a string which will be used when printing the usage of the program. If such method is not provided, a sensible default will be used.

class argparse.BooleanOptionalAction

A subclass of Action for handling boolean flags with positive and negative options. Adding a single argument such as --foo automatically creates both --foo and --no-foo options, storing True and False respectively:

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action=argparse.BooleanOptionalAction)
>>> parser.parse_args(['--no-foo'])
Namespace(foo=False)

在 3.9 版被加入.

parse_args() 方法

ArgumentParser.parse_args(args=None, namespace=None)

Convert argument strings to objects and assign them as attributes of the namespace. Return the populated namespace.

Previous calls to add_argument() determine exactly what objects are created and how they are assigned. See the documentation for add_argument() for details.

args - List of strings to parse. The default is taken from sys.argv.

namespace - An object to take the attributes. The default is a new empty Namespace object.

Option value syntax

The parse_args() method supports several ways of specifying the value of an option (if it takes one). In the simplest case, the option and its value are passed as two separate arguments:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x')
>>> parser.add_argument('--foo')
>>> parser.parse_args(['-x', 'X'])
Namespace(foo=None, x='X')
>>> parser.parse_args(['--foo', 'FOO'])
Namespace(foo='FOO', x=None)

For long options (options with names longer than a single character), the option and value can also be passed as a single command-line argument, using = to separate them:

>>> parser.parse_args(['--foo=FOO'])
Namespace(foo='FOO', x=None)

For short options (options only one character long), the option and its value can be concatenated:

>>> parser.parse_args(['-xX'])
Namespace(foo=None, x='X')

Several short options can be joined together, using only a single - prefix, as long as only the last option (or none of them) requires a value:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x', action='store_true')
>>> parser.add_argument('-y', action='store_true')
>>> parser.add_argument('-z')
>>> parser.parse_args(['-xyzZ'])
Namespace(x=True, y=True, z='Z')

無效引數

While parsing the command line, parse_args() checks for a variety of errors, including ambiguous options, invalid types, invalid options, wrong number of positional arguments, etc. When it encounters such an error, it exits and prints the error along with a usage message:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', type=int)
>>> parser.add_argument('bar', nargs='?')

>>> # 無效型別
>>> parser.parse_args(['--foo', 'spam'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: argument --foo: invalid int value: 'spam'

>>> # 無效選項
>>> parser.parse_args(['--bar'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: no such option: --bar

>>> # 錯誤引數數量
>>> parser.parse_args(['spam', 'badger'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: extra arguments found: badger

包含 - 的引數

The parse_args() method attempts to give errors whenever the user has clearly made a mistake, but some situations are inherently ambiguous. For example, the command-line argument -1 could either be an attempt to specify an option or an attempt to provide a positional argument. The parse_args() method is cautious here: positional arguments may only begin with - if they look like negative numbers and there are no options in the parser that look like negative numbers:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x')
>>> parser.add_argument('foo', nargs='?')

>>> # no negative number options, so -1 is a positional argument
>>> parser.parse_args(['-x', '-1'])
Namespace(foo=None, x='-1')

>>> # no negative number options, so -1 and -5 are positional arguments
>>> parser.parse_args(['-x', '-1', '-5'])
Namespace(foo='-5', x='-1')

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-1', dest='one')
>>> parser.add_argument('foo', nargs='?')

>>> # negative number options present, so -1 is an option
>>> parser.parse_args(['-1', 'X'])
Namespace(foo=None, one='X')

>>> # negative number options present, so -2 is an option
>>> parser.parse_args(['-2'])
usage: PROG [-h] [-1 ONE] [foo]
PROG: error: no such option: -2

>>> # negative number options present, so both -1s are options
>>> parser.parse_args(['-1', '-1'])
usage: PROG [-h] [-1 ONE] [foo]
PROG: error: argument -1: expected one argument

If you have positional arguments that must begin with - and don't look like negative numbers, you can insert the pseudo-argument '--' which tells parse_args() that everything after that is a positional argument:

>>> parser.parse_args(['--', '-f'])
Namespace(foo='-f', one=None)

See also the argparse howto on ambiguous arguments for more details.

引數縮寫 (前綴匹配)

The parse_args() method by default allows long options to be abbreviated to a prefix, if the abbreviation is unambiguous (the prefix matches a unique option):

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-bacon')
>>> parser.add_argument('-badger')
>>> parser.parse_args('-bac MMM'.split())
Namespace(bacon='MMM', badger=None)
>>> parser.parse_args('-bad WOOD'.split())
Namespace(bacon=None, badger='WOOD')
>>> parser.parse_args('-ba BA'.split())
usage: PROG [-h] [-bacon BACON] [-badger BADGER]
PROG: error: ambiguous option: -ba could match -badger, -bacon

An error is produced for arguments that could produce more than one options. This feature can be disabled by setting allow_abbrev to False.

sys.argv 之外

Sometimes it may be useful to have an ArgumentParser parse arguments other than those of sys.argv. This can be accomplished by passing a list of strings to parse_args(). This is useful for testing at the interactive prompt:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument(
...     'integers', metavar='int', type=int, choices=range(10),
...     nargs='+', help='an integer in the range 0..9')
>>> parser.add_argument(
...     '--sum', dest='accumulate', action='store_const', const=sum,
...     default=max, help='sum the integers (default: find the max)')
>>> parser.parse_args(['1', '2', '3', '4'])
Namespace(accumulate=<built-in function max>, integers=[1, 2, 3, 4])
>>> parser.parse_args(['1', '2', '3', '4', '--sum'])
Namespace(accumulate=<built-in function sum>, integers=[1, 2, 3, 4])

命名空間物件

class argparse.Namespace

Simple class used by default by parse_args() to create an object holding attributes and return it.

This class is deliberately simple, just an object subclass with a readable string representation. If you prefer to have dict-like view of the attributes, you can use the standard Python idiom, vars():

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> args = parser.parse_args(['--foo', 'BAR'])
>>> vars(args)
{'foo': 'BAR'}

It may also be useful to have an ArgumentParser assign attributes to an already existing object, rather than a new Namespace object. This can be achieved by specifying the namespace= keyword argument:

>>> class C:
...     pass
...
>>> c = C()
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.parse_args(args=['--foo', 'BAR'], namespace=c)
>>> c.foo
'BAR'

Other utilities

子命令

ArgumentParser.add_subparsers(*[, title][, description][, prog][, parser_class][, action][, dest][, required][, help][, metavar])

Many programs split up their functionality into a number of subcommands, for example, the svn program can invoke subcommands like svn checkout, svn update, and svn commit. Splitting up functionality this way can be a particularly good idea when a program performs several different functions which require different kinds of command-line arguments. ArgumentParser supports the creation of such subcommands with the add_subparsers() method. The add_subparsers() method is normally called with no arguments and returns a special action object. This object has a single method, add_parser(), which takes a command name and any ArgumentParser constructor arguments, and returns an ArgumentParser object that can be modified as usual.

參數的解釋：

title - title for the sub-parser group in help output; by default "subcommands" if description is provided, otherwise uses title for positional arguments

description - description for the sub-parser group in help output, by default None

prog - usage information that will be displayed with subcommand help, by default the name of the program and any positional arguments before the subparser argument

parser_class - class which will be used to create sub-parser instances, by default the class of the current parser (e.g. ArgumentParser)

action - the basic type of action to be taken when this argument is encountered at the command line

dest - name of the attribute under which subcommand name will be stored; by default None and no value is stored

required - Whether or not a subcommand must be provided, by default False (added in 3.7)

help - help for sub-parser group in help output, by default None

metavar - string presenting available subcommands in help; by default it is None and presents subcommands in form {cmd1, cmd2, ..}

一些使用範例：

>>> # create the top-level parser
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', action='store_true', help='foo help')
>>> subparsers = parser.add_subparsers(help='subcommand help')
>>>
>>> # create the parser for the "a" command
>>> parser_a = subparsers.add_parser('a', help='a help')
>>> parser_a.add_argument('bar', type=int, help='bar help')
>>>
>>> # create the parser for the "b" command
>>> parser_b = subparsers.add_parser('b', help='b help')
>>> parser_b.add_argument('--baz', choices=('X', 'Y', 'Z'), help='baz help')
>>>
>>> # parse some argument lists
>>> parser.parse_args(['a', '12'])
Namespace(bar=12, foo=False)
>>> parser.parse_args(['--foo', 'b', '--baz', 'Z'])
Namespace(baz='Z', foo=True)

Note that the object returned by parse_args() will only contain attributes for the main parser and the subparser that was selected by the command line (and not any other subparsers). So in the example above, when the a command is specified, only the foo and bar attributes are present, and when the b command is specified, only the foo and baz attributes are present.

Similarly, when a help message is requested from a subparser, only the help for that particular parser will be printed. The help message will not include parent parser or sibling parser messages. (A help message for each subparser command, however, can be given by supplying the help= argument to add_parser() as above.)

>>> parser.parse_args(['--help'])
usage: PROG [-h] [--foo] {a,b} ...

positional arguments:
  {a,b}   subcommand help
    a     a help
    b     b help

options:
  -h, --help  show this help message and exit
  --foo   foo help

>>> parser.parse_args(['a', '--help'])
usage: PROG a [-h] bar

positional arguments:
  bar     bar help

options:
  -h, --help  show this help message and exit

>>> parser.parse_args(['b', '--help'])
usage: PROG b [-h] [--baz {X,Y,Z}]

options:
  -h, --help     show this help message and exit
  --baz {X,Y,Z}  baz help

The add_subparsers() method also supports title and description keyword arguments. When either is present, the subparser's commands will appear in their own group in the help output. For example:

>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(title='subcommands',
...                                    description='valid subcommands',
...                                    help='additional help')
>>> subparsers.add_parser('foo')
>>> subparsers.add_parser('bar')
>>> parser.parse_args(['-h'])
usage:  [-h] {foo,bar} ...

options:
  -h, --help  show this help message and exit

subcommands:
  valid subcommands

  {foo,bar}   additional help

Furthermore, add_parser() supports an additional aliases argument, which allows multiple strings to refer to the same subparser. This example, like svn, aliases co as a shorthand for checkout:

>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers()
>>> checkout = subparsers.add_parser('checkout', aliases=['co'])
>>> checkout.add_argument('foo')
>>> parser.parse_args(['co', 'bar'])
Namespace(foo='bar')

add_parser() supports also an additional deprecated argument, which allows to deprecate the subparser.

>>> import argparse
>>> parser = argparse.ArgumentParser(prog='chicken.py')
>>> subparsers = parser.add_subparsers()
>>> run = subparsers.add_parser('run')
>>> fly = subparsers.add_parser('fly', deprecated=True)
>>> parser.parse_args(['fly'])
chicken.py: warning: command 'fly' is deprecated
Namespace()

在 3.13 版被加入.

One particularly effective way of handling subcommands is to combine the use of the add_subparsers() method with calls to set_defaults() so that each subparser knows which Python function it should execute. For example:

>>> # subcommand functions
>>> def foo(args):
...     print(args.x * args.y)
...
>>> def bar(args):
...     print('((%s))' % args.z)
...
>>> # create the top-level parser
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(required=True)
>>>
>>> # create the parser for the "foo" command
>>> parser_foo = subparsers.add_parser('foo')
>>> parser_foo.add_argument('-x', type=int, default=1)
>>> parser_foo.add_argument('y', type=float)
>>> parser_foo.set_defaults(func=foo)
>>>
>>> # create the parser for the "bar" command
>>> parser_bar = subparsers.add_parser('bar')
>>> parser_bar.add_argument('z')
>>> parser_bar.set_defaults(func=bar)
>>>
>>> # parse the args and call whatever function was selected
>>> args = parser.parse_args('foo 1 -x 2'.split())
>>> args.func(args)
2.0
>>>
>>> # parse the args and call whatever function was selected
>>> args = parser.parse_args('bar XYZYX'.split())
>>> args.func(args)
((XYZYX))

This way, you can let parse_args() do the job of calling the appropriate function after argument parsing is complete. Associating functions with actions like this is typically the easiest way to handle the different actions for each of your subparsers. However, if it is necessary to check the name of the subparser that was invoked, the dest keyword argument to the add_subparsers() call will work:

>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(dest='subparser_name')
>>> subparser1 = subparsers.add_parser('1')
>>> subparser1.add_argument('-x')
>>> subparser2 = subparsers.add_parser('2')
>>> subparser2.add_argument('y')
>>> parser.parse_args(['2', 'frobble'])
Namespace(subparser_name='2', y='frobble')

在 3.7 版的變更: New required keyword-only parameter.

在 3.14 版的變更: Subparser's prog is no longer affected by a custom usage message in the main parser.

FileType 物件

class argparse.FileType(mode='r', bufsize=-1, encoding=None, errors=None)

The FileType factory creates objects that can be passed to the type argument of ArgumentParser.add_argument(). Arguments that have FileType objects as their type will open command-line arguments as files with the requested modes, buffer sizes, encodings and error handling (see the open() function for more details):

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--raw', type=argparse.FileType('wb', 0))
>>> parser.add_argument('out', type=argparse.FileType('w', encoding='UTF-8'))
>>> parser.parse_args(['--raw', 'raw.dat', 'file.txt'])
Namespace(out=<_io.TextIOWrapper name='file.txt' mode='w' encoding='UTF-8'>, raw=<_io.FileIO name='raw.dat' mode='wb'>)

FileType objects understand the pseudo-argument '-' and automatically convert this into sys.stdin for readable FileType objects and sys.stdout for writable FileType objects:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('infile', type=argparse.FileType('r'))
>>> parser.parse_args(['-'])
Namespace(infile=<_io.TextIOWrapper name='<stdin>' encoding='UTF-8'>)

備註

If one argument uses FileType and then a subsequent argument fails, an error is reported but the file is not automatically closed. This can also clobber the output files. In this case, it would be better to wait until after the parser has run and then use the with-statement to manage the files.

在 3.4 版的變更: 新增了 encodings 和 errors 參數。

在 3.14 版之後被棄用.

引數群組

ArgumentParser.add_argument_group(title=None, description=None, *[, argument_default][, conflict_handler])

By default, ArgumentParser groups command-line arguments into "positional arguments" and "options" when displaying help messages. When there is a better conceptual grouping of arguments than this default one, appropriate groups can be created using the add_argument_group() method:

>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> group = parser.add_argument_group('group')
>>> group.add_argument('--foo', help='foo help')
>>> group.add_argument('bar', help='bar help')
>>> parser.print_help()
usage: PROG [--foo FOO] bar

group:
  bar    bar help
  --foo FOO  foo help

The add_argument_group() method returns an argument group object which has an add_argument() method just like a regular ArgumentParser. When an argument is added to the group, the parser treats it just like a normal argument, but displays the argument in a separate group for help messages. The add_argument_group() method accepts title and description arguments which can be used to customize this display:

>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> group1 = parser.add_argument_group('group1', 'group1 description')
>>> group1.add_argument('foo', help='foo help')
>>> group2 = parser.add_argument_group('group2', 'group2 description')
>>> group2.add_argument('--bar', help='bar help')
>>> parser.print_help()
usage: PROG [--bar BAR] foo

group1:
  group1 description

  foo    foo help

group2:
  group2 description

  --bar BAR  bar help

The optional, keyword-only parameters argument_default and conflict_handler allow for finer-grained control of the behavior of the argument group. These parameters have the same meaning as in the ArgumentParser constructor, but apply specifically to the argument group rather than the entire parser.

Note that any arguments not in your user-defined groups will end up back in the usual "positional arguments" and "optional arguments" sections.

自從版本 3.11 後不推薦使用，已從版本 3.14 中移除。: Calling add_argument_group() on an argument group now raises an exception. This nesting was never supported, often failed to work correctly, and was unintentionally exposed through inheritance.

在 3.14 版之後被棄用: Passing prefix_chars to add_argument_group() is now deprecated.

Mutual exclusion

ArgumentParser.add_mutually_exclusive_group(required=False)

Create a mutually exclusive group. argparse will make sure that only one of the arguments in the mutually exclusive group was present on the command line:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_exclusive_group()
>>> group.add_argument('--foo', action='store_true')
>>> group.add_argument('--bar', action='store_false')
>>> parser.parse_args(['--foo'])
Namespace(bar=True, foo=True)
>>> parser.parse_args(['--bar'])
Namespace(bar=False, foo=False)
>>> parser.parse_args(['--foo', '--bar'])
usage: PROG [-h] [--foo | --bar]
PROG: error: argument --bar: not allowed with argument --foo

The add_mutually_exclusive_group() method also accepts a required argument, to indicate that at least one of the mutually exclusive arguments is required:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_exclusive_group(required=True)
>>> group.add_argument('--foo', action='store_true')
>>> group.add_argument('--bar', action='store_false')
>>> parser.parse_args([])
usage: PROG [-h] (--foo | --bar)
PROG: error: one of the arguments --foo --bar is required

Note that currently mutually exclusive argument groups do not support the title and description arguments of add_argument_group(). However, a mutually exclusive group can be added to an argument group that has a title and description. For example:

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_argument_group('Group title', 'Group description')
>>> exclusive_group = group.add_mutually_exclusive_group(required=True)
>>> exclusive_group.add_argument('--foo', help='foo help')
>>> exclusive_group.add_argument('--bar', help='bar help')
>>> parser.print_help()
usage: PROG [-h] (--foo FOO | --bar BAR)

options:
  -h, --help  show this help message and exit

Group title:
  Group description

  --foo FOO   foo help
  --bar BAR   bar help

自從版本 3.11 後不推薦使用，已從版本 3.14 中移除。: Calling add_argument_group() or add_mutually_exclusive_group() on a mutually exclusive group now raises an exception. This nesting was never supported, often failed to work correctly, and was unintentionally exposed through inheritance.

Parser defaults

ArgumentParser.set_defaults(**kwargs)

Most of the time, the attributes of the object returned by parse_args() will be fully determined by inspecting the command-line arguments and the argument actions. set_defaults() allows some additional attributes that are determined without any inspection of the command line to be added:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=int)
>>> parser.set_defaults(bar=42, baz='badger')
>>> parser.parse_args(['736'])
Namespace(bar=42, baz='badger', foo=736)

Note that defaults can be set at both the parser level using set_defaults() and at the argument level using add_argument(). If both are called for the same argument, the last default set for an argument is used:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default='bar')
>>> parser.set_defaults(foo='spam')
>>> parser.parse_args([])
Namespace(foo='spam')

Parser-level defaults can be particularly useful when working with multiple parsers. See the add_subparsers() method for an example of this type.

ArgumentParser.get_default(dest)

Get the default value for a namespace attribute, as set by either add_argument() or by set_defaults():

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default='badger')
>>> parser.get_default('foo')
'badger'

印出幫助訊息

In most typical applications, parse_args() will take care of formatting and printing any usage or error messages. However, several formatting methods are available:

ArgumentParser.print_usage(file=None)

Print a brief description of how the ArgumentParser should be invoked on the command line. If file is None, sys.stdout is assumed.

ArgumentParser.print_help(file=None)

Print a help message, including the program usage and information about the arguments registered with the ArgumentParser. If file is None, sys.stdout is assumed.

There are also variants of these methods that simply return a string instead of printing it:

ArgumentParser.format_usage()

Return a string containing a brief description of how the ArgumentParser should be invoked on the command line.

ArgumentParser.format_help()

Return a string containing a help message, including the program usage and information about the arguments registered with the ArgumentParser.

Partial parsing

ArgumentParser.parse_known_args(args=None, namespace=None)

Sometimes a script only needs to handle a specific set of command-line arguments, leaving any unrecognized arguments for another script or program. In these cases, the parse_known_args() method can be useful.

This method works similarly to parse_args(), but it does not raise an error for extra, unrecognized arguments. Instead, it parses the known arguments and returns a two item tuple that contains the populated namespace and the list of any unrecognized arguments.

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_true')
>>> parser.add_argument('bar')
>>> parser.parse_known_args(['--foo', '--badger', 'BAR', 'spam'])
(Namespace(bar='BAR', foo=True), ['--badger', 'spam'])

警告

Prefix matching rules apply to parse_known_args(). The parser may consume an option even if it's just a prefix of one of its known options, instead of leaving it in the remaining arguments list.

Customizing file parsing

ArgumentParser.convert_arg_line_to_args(arg_line)

Arguments that are read from a file (see the fromfile_prefix_chars keyword argument to the ArgumentParser constructor) are read one argument per line. convert_arg_line_to_args() can be overridden for fancier reading.

This method takes a single argument arg_line which is a string read from the argument file. It returns a list of arguments parsed from this string. The method is called once per line read from the argument file, in order.

A useful override of this method is one that treats each space-separated word as an argument. The following example demonstrates how to do this:

class MyArgumentParser(argparse.ArgumentParser):
    def convert_arg_line_to_args(self, arg_line):
        return arg_line.split()

Exiting methods

ArgumentParser.exit(status=0, message=None)

This method terminates the program, exiting with the specified status and, if given, it prints a message to sys.stderr before that. The user can override this method to handle these steps differently:

class ErrorCatchingArgumentParser(argparse.ArgumentParser):
    def exit(self, status=0, message=None):
        if status:
            raise Exception(f'Exiting because of an error: {message}')
        exit(status)

ArgumentParser.error(message)

This method prints a usage message, including the message, to sys.stderr and terminates the program with a status code of 2.

Intermixed parsing

ArgumentParser.parse_intermixed_args(args=None, namespace=None)

ArgumentParser.parse_known_intermixed_args(args=None, namespace=None)

A number of Unix commands allow the user to intermix optional arguments with positional arguments. The parse_intermixed_args() and parse_known_intermixed_args() methods support this parsing style.

These parsers do not support all the argparse features, and will raise exceptions if unsupported features are used. In particular, subparsers, and mutually exclusive groups that include both optionals and positionals are not supported.

The following example shows the difference between parse_known_args() and parse_intermixed_args(): the former returns ['2', '3'] as unparsed arguments, while the latter collects all the positionals into rest.

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.add_argument('cmd')
>>> parser.add_argument('rest', nargs='*', type=int)
>>> parser.parse_known_args('doit 1 --foo bar 2 3'.split())
(Namespace(cmd='doit', foo='bar', rest=[1]), ['2', '3'])
>>> parser.parse_intermixed_args('doit 1 --foo bar 2 3'.split())
Namespace(cmd='doit', foo='bar', rest=[1, 2, 3])

parse_known_intermixed_args() returns a two item tuple containing the populated namespace and the list of remaining argument strings. parse_intermixed_args() raises an error if there are any remaining unparsed argument strings.

在 3.7 版被加入.

Registering custom types or actions

ArgumentParser.register(registry_name, value, object)

Sometimes it's desirable to use a custom string in error messages to provide more user-friendly output. In these cases, register() can be used to register custom actions or types with a parser and allow you to reference the type by their registered name instead of their callable name.

The register() method accepts three arguments - a registry_name, specifying the internal registry where the object will be stored (e.g., action, type), value, which is the key under which the object will be registered, and object, the callable to be registered.

The following example shows how to register a custom type with a parser:

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.register('type', 'hexadecimal integer', lambda s: int(s, 16))
>>> parser.add_argument('--foo', type='hexadecimal integer')
_StoreAction(option_strings=['--foo'], dest='foo', nargs=None, const=None, default=None, type='hexadecimal integer', choices=None, required=False, help=None, metavar=None, deprecated=False)
>>> parser.parse_args(['--foo', '0xFA'])
Namespace(foo=250)
>>> parser.parse_args(['--foo', '1.2'])
usage: PROG [-h] [--foo FOO]
PROG: error: argument --foo: invalid 'hexadecimal integer' value: '1.2'

例外

exception argparse.ArgumentError

An error from creating or using an argument (optional or positional).

The string value of this exception is the message, augmented with information about the argument that caused it.

exception argparse.ArgumentTypeError

Raised when something goes wrong converting a command line string to a type.

Guides and Tutorials

Argparse 教學

將 optparse 程式碼遷移到 argparse

Argparse 教學

作者:

Tshepang Mbambo

本教學旨在簡要介紹 argparse 這個 Python 標準函式庫中推薦的命令列剖析模組。

備註

標準函式庫包含另外兩個與命令列參數處理直接相關的函式庫：較低階的 optparse 模組（可能需要更多程式碼來為給定應用程式設定，但也允許應用程式要求 argparse 不支援的行為），以及非常低階的 getopt（專門用作 C 程式設計師可用的 getopt() 函式系列的等價）。雖然這個指南並未直接涵蓋這些模組，但 argparse 的許多核心概念最初來自於 optparse，因此本教學的某些部分也適用於 optparse 使用者。

概念

讓我們透過使用 ls 指令來展示我們將在本介紹教學中探索的功能類型：

$ ls
cpython  devguide  prog.py  pypy  rm-unused-function.patch
$ ls pypy
ctypes_configure  demo  dotviewer  include  lib_pypy  lib-python ...
$ ls -l
total 20
drwxr-xr-x 19 wena wena 4096 Feb 18 18:51 cpython
drwxr-xr-x  4 wena wena 4096 Feb  8 12:04 devguide
-rwxr-xr-x  1 wena wena  535 Feb 19 00:05 prog.py
drwxr-xr-x 14 wena wena 4096 Feb  7 00:59 pypy
-rw-r--r--  1 wena wena  741 Feb 18 01:01 rm-unused-function.patch
$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
...

我們可以從這四個命令中學到一些概念：

ls 命令即便在沒有任何選項的情況下執行仍非常有用。它預設顯示目前目錄的內容。

如果我們想要看到比它預設提供更多的內容，我們也需要多告訴它一點。在本例中，我們希望它顯示不同的目錄 pypy，我們做的是指定所謂的位置引數。之所以如此命名是因為程式應該只根據該值在命令列中出現的位置來知道如何處理該值。這個概念與 cp 這樣的指令更相關，其最基本的用法是 cp SRC DEST。第一個是你想要複製的位置，第二個是你想要複製過去的位置。

現在假設我們想要改變程式的行為。在我們的範例中，我們顯示每個檔案的更多資訊，而不僅是顯示檔案名稱。在這種情況下，-l 被稱為可選引數。

這是幫助文字的片段。它非常有用，因為當你遇到以前從未使用過的程式時，只需閱讀其幫助文字即可了解它的工作原理。

基本用法

讓我們從一個非常簡單的例子開始，它（幾乎）什麼都不做：

import argparse
parser = argparse.ArgumentParser()
parser.parse_args()

程式碼執行結果如下：

$ python prog.py
$ python prog.py --help
usage: prog.py [-h]

options:
  -h, --help  show this help message and exit
$ python prog.py --verbose
usage: prog.py [-h]
prog.py: error: unrecognized arguments: --verbose
$ python prog.py foo
usage: prog.py [-h]
prog.py: error: unrecognized arguments: foo

這是發生的事情：

執行不帶任何選項的腳本不會在標準輸出中顯示任何內容。不太有用。

第二個開始能夠顯現 argparse 模組的有用之處。我們幾乎什麼也沒做，但我們已經收到了一個很好的幫助訊息。

--help 選項也可以縮寫為 -h，是我們能隨意獲得的唯一選項（即無需指定它）。指定任何其他內容都會導致錯誤。但即便如此，我們也還是輕鬆地獲得了有用的使用資訊。

位置引數的介紹

例如：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("echo")
args = parser.parse_args()
print(args.echo)

執行這段程式碼：

$ python prog.py
usage: prog.py [-h] echo
prog.py: error: the following arguments are required: echo
$ python prog.py --help
usage: prog.py [-h] echo

positional arguments:
  echo

options:
  -h, --help  show this help message and exit
$ python prog.py foo
foo

這是會發生的事情：

我們新增了 add_argument() 方法，我們用它來指定程式願意接受哪些命令列選項。在本例中，我將其命名為 echo，以便與其功能一致。

現在呼叫我們的程式時需要指定一個選項。

parse_args() 方法實際上從指定的選項中回傳一些資料，在本例中為 echo。

該變數是某種形式的「魔法」，argparse 可以自由執行（即無需指定該值儲存在哪個變數中）。你還會注意到，它的名稱與提供給方法 echo 的字串引數相符。

但請注意，儘管幫助顯示看起來不錯，但它目前還沒有發揮出應有的用處。例如，我們看到 echo 作為位置引數，但除了猜測或閱讀原始程式碼之外，我們不知道它的作用。那麼，我們來讓它變得更有用一點：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("echo", help="echo the string you use here")
args = parser.parse_args()
print(args.echo)

然後我們得到：

$ python prog.py -h
usage: prog.py [-h] echo

positional arguments:
  echo        echo the string you use here

options:
  -h, --help  show this help message and exit

現在來做一些更有用處的事情：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", help="display a square of a given number")
args = parser.parse_args()
print(args.square**2)

程式碼執行結果如下：

$ python prog.py 4
Traceback (most recent call last):
  File "prog.py", line 5, in <module>
    print(args.square**2)
TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'

進展不太順利。這是因為，除非我們另有說明，argparse 會將我們給它的選項視為字串。因此，讓我們告訴 argparse 將該輸入視為整數：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", help="display a square of a given number",
                    type=int)
args = parser.parse_args()
print(args.square**2)

程式碼執行結果如下：

$ python prog.py 4
16
$ python prog.py four
usage: prog.py [-h] square
prog.py: error: argument square: invalid int value: 'four'

順利進展。現在該程式甚至可以在繼續操作之前因錯誤的非法輸入而退出。

可選引數的介紹

到目前為止，我們一直在討論位置引數。我們來看看如何新增可選引數：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--verbosity", help="increase output verbosity")
args = parser.parse_args()
if args.verbosity:
    print("verbosity turned on")

接者是結果：

$ python prog.py --verbosity 1
verbosity turned on
$ python prog.py
$ python prog.py --help
usage: prog.py [-h] [--verbosity VERBOSITY]

options:
  -h, --help            show this help message and exit
  --verbosity VERBOSITY
                        increase output verbosity
$ python prog.py --verbosity
usage: prog.py [-h] [--verbosity VERBOSITY]
prog.py: error: argument --verbosity: expected one argument

這是發生的事情：

程式被編寫為在指定 --verbosity 時顯示一些內容，並在未指定時不顯示任何內容。

為了表示該選項實際上是可選的，沒使用它來執行程式並不會出現錯誤。請注意，預設情況下，如果未使用可選引數，則相關變數（在本例中為 args.verbosity）將被賦予 None 作為值，這就是它未能通過 if 陳述式真值測試的原因。

幫助訊息有點不同。

當使用 --verbosity 選項時必須要指定一些值，任何值都可以。

在上面的例子中，--verbosity 接受任意的整數，但對我們的程式來說只接受兩個輸入值， True 或 False。所以我們來修改一下程式碼使其符合：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--verbose", help="increase output verbosity",
                    action="store_true")
args = parser.parse_args()
if args.verbose:
    print("verbosity turned on")

接者是結果：

$ python prog.py --verbose
verbosity turned on
$ python prog.py --verbose 1
usage: prog.py [-h] [--verbose]
prog.py: error: unrecognized arguments: 1
$ python prog.py --help
usage: prog.py [-h] [--verbose]

options:
  -h, --help  show this help message and exit
  --verbose   increase output verbosity

這是發生的事情：

這個選項現在更像是一個旗標，而不是需要值的東西。我們甚至更改了選項的名稱以符合這個想法。請注意，我們現在指定一個新的關鍵字 action，並為其指定值 "store_true"。這意味著，如果指定了該選項，則將值 True 指派給 args.verbose。不指定它代表為 False。

當你指定一個值時，它會本著旗標的實際精神來抱怨。

請注意不同的幫助文字。

短選項

如果你熟悉命令列用法，你會注意到我尚未提及選項的簡短版本。這很簡單：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("-v", "--verbose", help="increase output verbosity",
                    action="store_true")
args = parser.parse_args()
if args.verbose:
    print("verbosity turned on")

而這為：

$ python prog.py -v
verbosity turned on
$ python prog.py --help
usage: prog.py [-h] [-v]

options:
  -h, --help     show this help message and exit
  -v, --verbose  increase output verbosity

請注意，新功能也反映在幫助文字中。

組合位置引數和可選引數

我們的程式的複雜性不斷增加：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbose", action="store_true",
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbose:
    print(f"the square of {args.square} equals {answer}")
else:
    print(answer)

然後現在的輸出結果：

$ python prog.py
usage: prog.py [-h] [-v] square
prog.py: error: the following arguments are required: square
$ python prog.py 4
16
$ python prog.py 4 --verbose
the square of 4 equals 16
$ python prog.py --verbose 4
the square of 4 equals 16

我們帶回了位置引數，因而被抱怨。

請注意，順序並不重要。

我們讓這個程式擁有多個訊息詳細級別 (verbosity) 之值的能力，並實際使用它們：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", type=int,
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print(f"the square of {args.square} equals {answer}")
elif args.verbosity == 1:
    print(f"{args.square}^2 == {answer}")
else:
    print(answer)

接者是結果：

$ python prog.py 4
16
$ python prog.py 4 -v
usage: prog.py [-h] [-v VERBOSITY] square
prog.py: error: argument -v/--verbosity: expected one argument
$ python prog.py 4 -v 1
4^2 == 16
$ python prog.py 4 -v 2
the square of 4 equals 16
$ python prog.py 4 -v 3
16

除了最後一個外都看起來正常，它透露了我們程式中的一個錯誤。我們可透過限制 --verbosity 選項可以接受的值來修復它：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", type=int, choices=[0, 1, 2],
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print(f"the square of {args.square} equals {answer}")
elif args.verbosity == 1:
    print(f"{args.square}^2 == {answer}")
else:
    print(answer)

接者是結果：

$ python prog.py 4 -v 3
usage: prog.py [-h] [-v {0,1,2}] square
prog.py: error: argument -v/--verbosity: invalid choice: 3 (choose from 0, 1, 2)
$ python prog.py 4 -h
usage: prog.py [-h] [-v {0,1,2}] square

positional arguments:
  square                display a square of a given number

options:
  -h, --help            show this help message and exit
  -v, --verbosity {0,1,2}
                        increase output verbosity

請注意，更改也會反映在錯誤訊息和幫助字串中。

現在，讓我們使用另一種常見方法來玩玩訊息詳細級別。它也與 CPython 執行檔處理其自身訊息詳細級別引數的方式相符（請見 python --help 的輸出）：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display the square of a given number")
parser.add_argument("-v", "--verbosity", action="count",
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print(f"the square of {args.square} equals {answer}")
elif args.verbosity == 1:
    print(f"{args.square}^2 == {answer}")
else:
    print(answer)

我們已經介紹過另一個操作 "count" 用來計算指定的選項出現的次數。

$ python prog.py 4
16
$ python prog.py 4 -v
4^2 == 16
$ python prog.py 4 -vv
the square of 4 equals 16
$ python prog.py 4 --verbosity --verbosity
the square of 4 equals 16
$ python prog.py 4 -v 1
usage: prog.py [-h] [-v] square
prog.py: error: unrecognized arguments: 1
$ python prog.py 4 -h
usage: prog.py [-h] [-v] square

positional arguments:
  square           display a square of a given number

options:
  -h, --help       show this help message and exit
  -v, --verbosity  increase output verbosity
$ python prog.py 4 -vvv
16

是的，現在它更像是我們上一版腳本中的旗標（類似於 action="store_true"），這應該可以解釋抱怨的原因。

它的行為也類似 "store_true" 操作。

現在這裡示範了 "count" 動作的作用。你可能以前見過這種用法。

如果你不指定 -v 旗標，則該旗標被視為具有 None 值。

正如預期的那樣，指定長形式旗標，我們應該得到相同的輸出。

遺憾的是，我們的幫助輸出對於我們腳本獲得的新功能並沒有提供太多資訊，但我們都可以透過改進腳本的文件來解決這個問題（例如：透過 help 關鍵字引數）。

最後的輸出透露了我們程式中的一個錯誤。

讓我們來解決問題：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", action="count",
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2

# bugfix: replace == with >=
if args.verbosity >= 2:
    print(f"the square of {args.square} equals {answer}")
elif args.verbosity >= 1:
    print(f"{args.square}^2 == {answer}")
else:
    print(answer)

這就是它給出的：

$ python prog.py 4 -vvv
the square of 4 equals 16
$ python prog.py 4 -vvvv
the square of 4 equals 16
$ python prog.py 4
Traceback (most recent call last):
  File "prog.py", line 11, in <module>
    if args.verbosity >= 2:
TypeError: '>=' not supported between instances of 'NoneType' and 'int'

第一次輸出順利進行，並修復了我們之前遇到的錯誤。也就是說，我們希望任何 >= 2 的值都盡可能詳細。

第三個輸出不太好。

我們來修復這個錯誤：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", action="count", default=0,
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity >= 2:
    print(f"the square of {args.square} equals {answer}")
elif args.verbosity >= 1:
    print(f"{args.square}^2 == {answer}")
else:
    print(answer)

我們剛剛引入了另一個關鍵字 default。我們將其設為 0，以便使其與其他 int 值進行比較。請記住，預設情況下，如果未指定可選引數，它將獲得 None 值，並且不能與 int 值進行比較（因此會出現 TypeError 例外）。

而且：

$ python prog.py 4
16

僅憑我們迄今為止所學到的知識就可以做到很多事情了，不過其實這樣只有學到一點皮毛而已。argparse 模組非常強大，在結束本教學之前我們會對它進行更多探索。

更進階一點

如果我們想擴充我們的小程式來執行其他次方的運算，而不僅是平方：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
parser.add_argument("-v", "--verbosity", action="count", default=0)
args = parser.parse_args()
answer = args.x**args.y
if args.verbosity >= 2:
    print(f"{args.x} to the power {args.y} equals {answer}")
elif args.verbosity >= 1:
    print(f"{args.x}^{args.y} == {answer}")
else:
    print(answer)

結果：

$ python prog.py
usage: prog.py [-h] [-v] x y
prog.py: error: the following arguments are required: x, y
$ python prog.py -h
usage: prog.py [-h] [-v] x y

positional arguments:
  x                the base
  y                the exponent

options:
  -h, --help       show this help message and exit
  -v, --verbosity
$ python prog.py 4 2 -v
4^2 == 16

請注意，到目前為止，我們一直在使用詳細級別來更改顯示的文字。以下範例使用詳細級別來顯示更多文字：

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
parser.add_argument("-v", "--verbosity", action="count", default=0)
args = parser.parse_args()
answer = args.x**args.y
if args.verbosity >= 2:
    print(f"Running '{__file__}'")
if args.verbosity >= 1:
    print(f"{args.x}^{args.y} == ", end="")
print(answer)

結果：

$ python prog.py 4 2
16
$ python prog.py 4 2 -v
4^2 == 16
$ python prog.py 4 2 -vv
Running 'prog.py'
4^2 == 16

指定不明確的引數

當決定一個引數是位置引數還是引數會有歧義，可以使用 -- 來告訴 parse_args() 之後的所有內容都是位置引數：

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-n', nargs='+')
>>> parser.add_argument('args', nargs='*')

>>> # ambiguous, so parse_args assumes it's an option
>>> parser.parse_args(['-f'])
usage: PROG [-h] [-n N [N ...]] [args ...]
PROG: error: unrecognized arguments: -f

>>> parser.parse_args(['--', '-f'])
Namespace(args=['-f'], n=None)

>>> # ambiguous, so the -n option greedily accepts arguments
>>> parser.parse_args(['-n', '1', '2', '3'])
Namespace(args=[], n=['1', '2', '3'])

>>> parser.parse_args(['-n', '1', '--', '2', '3'])
Namespace(args=['2', '3'], n=['1'])

相互衝突的選項

到目前為止，我們一直在使用 argparse.ArgumentParser 實例的兩種方法。讓我們介紹第三個，add_mutually_exclusive_group()，它允許我們指定彼此衝突的選項。我們還可以更改程式的其餘部分，以使得新功能更有意義：我們將引入 --quiet 選項，該選項與 --verbose 選項相反：

import argparse

parser = argparse.ArgumentParser()
group = parser.add_mutually_exclusive_group()
group.add_argument("-v", "--verbose", action="store_true")
group.add_argument("-q", "--quiet", action="store_true")
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
args = parser.parse_args()
answer = args.x**args.y

if args.quiet:
    print(answer)
elif args.verbose:
    print(f"{args.x} to the power {args.y} equals {answer}")
else:
    print(f"{args.x}^{args.y} == {answer}")

我們的程式現在更簡單了，我們因為功能展示失去了一些功能，但無論如何，以下這是輸出：

$ python prog.py 4 2
4^2 == 16
$ python prog.py 4 2 -q
16
$ python prog.py 4 2 -v
4 to the power 2 equals 16
$ python prog.py 4 2 -vq
usage: prog.py [-h] [-v | -q] x y
prog.py: error: argument -q/--quiet: not allowed with argument -v/--verbose
$ python prog.py 4 2 -v --quiet
usage: prog.py [-h] [-v | -q] x y
prog.py: error: argument -q/--quiet: not allowed with argument -v/--verbose

這應該很容易理解。我新增了最後一個輸出，以便看到所獲得的靈活性，即可以混合長形式與短形式選項。

在我們結束之前，你可能想告訴使用者你的程式的主要目的，以防他們不知道：

import argparse

parser = argparse.ArgumentParser(description="calculate X to the power of Y")
group = parser.add_mutually_exclusive_group()
group.add_argument("-v", "--verbose", action="store_true")
group.add_argument("-q", "--quiet", action="store_true")
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
args = parser.parse_args()
answer = args.x**args.y

if args.quiet:
    print(answer)
elif args.verbose:
    print(f"{args.x} to the power {args.y} equals {answer}")
else:
    print(f"{args.x}^{args.y} == {answer}")

請注意用法文字中的細微差別。注意 [-v | -q]，它告訴我們可以使用 -v 或 -q，但不能同時使用：

$ python prog.py --help
usage: prog.py [-h] [-v | -q] x y

calculate X to the power of Y

positional arguments:
  x              the base
  y              the exponent

options:
  -h, --help     show this help message and exit
  -v, --verbose
  -q, --quiet

如何翻譯 argparse 輸出

argparse 模組的輸出，例如幫助文字和錯誤訊息，都可以透過使用 gettext 模組進行翻譯。這允許應用程式能輕鬆在地化 argparse 生成的訊息。另請參閱 Internationalizing your programs and modules。

例如，在此 argparse 輸出中：

$ python prog.py --help
usage: prog.py [-h] [-v | -q] x y

calculate X to the power of Y

positional arguments:
  x              the base
  y              the exponent

options:
  -h, --help     show this help message and exit
  -v, --verbose
  -q, --quiet

字串 usage:、positional arguments:、options: 和 show this help message and exit 都是可被翻譯的。

為了翻譯這些字串，必須先將它們提取到 .po 檔案中。例如，使用 Babel [https://babel.pocoo.org/] 並執行下列命令：

$ pybabel extract -o messages.po /usr/lib/python3.12/argparse.py

此命令將從 argparse 模組中提取出所有可翻譯的字串，並將它們輸出到名為 messages.po 的檔案中。這個指令假設你的 Python 是安裝在 /usr/lib 中。

你可以使用以下腳本找到 argparse 模組在系統上的位置：

import argparse
print(argparse.__file__)

一旦翻譯了 .po 檔案中的訊息並使用 gettext 安裝了翻譯，argparse 將能夠顯示翻譯後的訊息。

若要在 argparse 輸出中翻譯你自己的字串，請使用 gettext。

自訂型別轉換器

The argparse module allows you to specify custom type converters for your command-line arguments. This allows you to modify user input before it's stored in the argparse.Namespace. This can be useful when you need to pre-process the input before it is used in your program.

When using a custom type converter, you can use any callable that takes a single string argument (the argument value) and returns the converted value. However, if you need to handle more complex scenarios, you can use a custom action class with the action parameter instead.

For example, let's say you want to handle arguments with different prefixes and process them accordingly:

import argparse

parser = argparse.ArgumentParser(prefix_chars='-+')

parser.add_argument('-a', metavar='<value>', action='append',
                    type=lambda x: ('-', x))
parser.add_argument('+a', metavar='<value>', action='append',
                    type=lambda x: ('+', x))

args = parser.parse_args()
print(args)

結果：

$ python prog.py -a value1 +a value2
Namespace(a=[('-', 'value1'), ('+', 'value2')])

在這個範例當中，我們：

Created a parser with custom prefix characters using the prefix_chars parameter.

Defined two arguments, -a and +a, which used the type parameter to create custom type converters to store the value in a tuple with the prefix.

Without the custom type converters, the arguments would have treated the -a and +a as the same argument, which would have been undesirable. By using custom type converters, we were able to differentiate between the two arguments.

結論

argparse 模組提供的功能比此篇內容的要多得多。它的文件非常詳細與透徹並有很多範例。讀完本教學後，你應該可以輕鬆消化它們，而不會感到不知所措。

將 optparse 程式碼遷移到 argparse

argparse 模組提供了一些高階功能，這些功能在 optparse 模組中並未原生提供，包括：

處理位置引數。

支援子命令。

允許替代選項前綴，如 + 和 /。

處理零或多個 (zero-or-more) 和一個或多個 (and one-or-more) 樣式的引數。

產生更多資訊的使用訊息。

為自訂 type 和 action 提供了一個更簡單的介面。

最初 argparse 模組試圖保持與 optparse 的相容性，但在基礎設計上的存在差異 -- 支援宣告式 (declarative) 命令列選項處理 (同時將位置引數處理留給應用程式的程式碼) 和在宣告式介面中支援命名選項 (named options) 和位置引數 -- 代表 API 隨著時間的推移已經與 optparse API 分歧。

如 選擇一個命令列參數剖析函式庫 中所述，目前使用 optparse 並對其運作方式滿意的應用程式可以繼續使用 optparse。

在決定是否遷移之前，應用程式開發人員應該先檢閱該段落中描述的內在行為差異清單，來決定是否值得遷移。

對於選擇從 optparse 遷移到 argparse 的應用程式，以下建議應會有所幫助：

將所有 optparse.OptionParser.add_option() 呼叫替換為 ArgumentParser.add_argument() 呼叫。

將 (options, args) = parser.parse_args() 替換為 args = parser.parse_args()，並為位置引數新增額外的 ArgumentParser.add_argument() 呼叫。請記住，以前稱為 options 的東西，在 argparse 情境中現在稱為 args。

使用 parse_intermixed_args() 來替換掉 optparse.OptionParser.disable_interspersed_args()，而不是使用 parse_args()。

將回呼動作和 callback_* 關鍵字引數替換為 type 或 action 引數。

將 type 關鍵字引數的字串名稱替換為相應的類型物件 (例如 int、float、complex 等)。

將 optparse.Values 替換為 Namespace，並將 optparse.OptionError 和 optparse.OptionValueError 替換為 ArgumentError。

將隱式引數的字串，如 %default 或 %prog 替換為使用字典來格式化字串的標準 Python 語法，即 %(default)s 和 %(prog)s。

將 OptionParser 建構函式的 version 引數替換為呼叫 parser.add_argument('--version', action='version', version='<the version>')。

optparse --- 命令列選項剖析器

原始碼：Lib/optparse.py [https://github.com/python/cpython/tree/3.14/Lib/optparse.py]

選擇一個命令列參數剖析函式庫

標準函式庫包含三個命令列引數剖析函式庫：

getopt: a module that closely mirrors the procedural C getopt API. Included in the standard library since before the initial Python 1.0 release.

optparse: a declarative replacement for getopt that provides equivalent functionality without requiring each application to implement its own procedural option parsing logic. Included in the standard library since the Python 2.3 release.

argparse: a more opinionated alternative to optparse that provides more functionality by default, at the expense of reduced application flexibility in controlling exactly how arguments are processed. Included in the standard library since the Python 2.7 and Python 3.2 releases.

In the absence of more specific argument parsing design constraints, argparse is the recommended choice for implementing command line applications, as it offers the highest level of baseline functionality with the least application level code.

getopt is retained almost entirely for backwards compatibility reasons. However, it also serves a niche use case as a tool for prototyping and testing command line argument handling in getopt-based C applications.

optparse should be considered as an alternative to argparse in the following cases:

an application is already using optparse and doesn't want to risk the subtle behavioural changes that may arise when migrating to argparse

the application requires additional control over the way options and positional parameters are interleaved on the command line (including the ability to disable the interleaving feature completely)

the application requires additional control over the incremental parsing of command line elements (while argparse does support this, the exact way it works in practice is undesirable for some use cases)

the application requires additional control over the handling of options which accept parameter values that may start with - (such as delegated options to be passed to invoked subprocesses)

the application requires some other command line parameter processing behavior which argparse does not support, but which can be implemented in terms of the lower level interface offered by optparse

These considerations also mean that optparse is likely to provide a better foundation for library authors writing third party command line argument processing libraries.

As a concrete example, consider the following two command line argument parsing configurations, the first using optparse, and the second using argparse:

import optparse

if __name__ == '__main__':
    parser = optparse.OptionParser()
    parser.add_option('-o', '--output')
    parser.add_option('-v', dest='verbose', action='store_true')
    opts, args = parser.parse_args()
    process(args, output=opts.output, verbose=opts.verbose)

import argparse

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('-o', '--output')
    parser.add_argument('-v', dest='verbose', action='store_true')
    parser.add_argument('rest', nargs='*')
    args = parser.parse_args()
    process(args.rest, output=args.output, verbose=args.verbose)

The most obvious difference is that in the optparse version, the non-option arguments are processed separately by the application after the option processing is complete. In the argparse version, positional arguments are declared and processed in the same way as the named options.

However, the argparse version will also handle some parameter combination differently from the way the optparse version would handle them. For example (amongst other differences):

supplying -o -v gives output="-v" and verbose=False when using optparse, but a usage error with argparse (complaining that no value has been supplied for -o/--output, since -v is interpreted as meaning the verbosity flag)

similarly, supplying -o -- gives output="--" and args=() when using optparse, but a usage error with argparse (also complaining that no value has been supplied for -o/--output, since -- is interpreted as terminating the option processing and treating all remaining values as positional arguments)

supplying -o=foo gives output="=foo" when using optparse, but gives output="foo" with argparse (since = is special cased as an alternative separator for option parameter values)

Whether these differing behaviors in the argparse version are considered desirable or a problem will depend on the specific command line application use case.

也參考

click [https://pypi.org/project/click/] is a third party argument processing library (originally based on optparse), which allows command line applications to be developed as a set of decorated command implementation functions.

Other third party libraries, such as typer [https://pypi.org/project/typer/] or msgspec-click [https://pypi.org/project/msgspec-click/], allow command line interfaces to be specified in ways that more effectively integrate with static checking of Python type annotations.

Introduction

optparse is a more convenient, flexible, and powerful library for parsing command-line options than the minimalist getopt module. optparse uses a more declarative style of command-line parsing: you create an instance of OptionParser, populate it with options, and parse the command line. optparse allows users to specify options in the conventional GNU/POSIX syntax, and additionally generates usage and help messages for you.

Here's an example of using optparse in a simple script:

from optparse import OptionParser
...
parser = OptionParser()
parser.add_option("-f", "--file", dest="filename",
                  help="write report to FILE", metavar="FILE")
parser.add_option("-q", "--quiet",
                  action="store_false", dest="verbose", default=True,
                  help="don't print status messages to stdout")

(options, args) = parser.parse_args()

With these few lines of code, users of your script can now do the "usual thing" on the command-line, for example:

<yourscript> --file=outfile -q

As it parses the command line, optparse sets attributes of the options object returned by parse_args() based on user-supplied command-line values. When parse_args() returns from parsing this command line, options.filename will be "outfile" and options.verbose will be False. optparse supports both long and short options, allows short options to be merged together, and allows options to be associated with their arguments in a variety of ways. Thus, the following command lines are all equivalent to the above example:

<yourscript> -f outfile --quiet
<yourscript> --quiet --file outfile
<yourscript> -q -foutfile
<yourscript> -qfoutfile

Additionally, users can run one of the following

<yourscript> -h
<yourscript> --help

and optparse will print out a brief summary of your script's options:

Usage: <yourscript> [options]

Options:
  -h, --help            show this help message and exit
  -f FILE, --file=FILE  write report to FILE
  -q, --quiet           don't print status messages to stdout

where the value of yourscript is determined at runtime (normally from sys.argv[0]).

背景

optparse was explicitly designed to encourage the creation of programs with straightforward command-line interfaces that follow the conventions established by the getopt() family of functions available to C developers. To that end, it supports only the most common command-line syntax and semantics conventionally used under Unix. If you are unfamiliar with these conventions, reading this section will allow you to acquaint yourself with them.

術語

引數

a string entered on the command-line, and passed by the shell to execl() or execv(). In Python, arguments are elements of sys.argv[1:] (sys.argv[0] is the name of the program being executed). Unix shells also use the term "word".

It is occasionally desirable to substitute an argument list other than sys.argv[1:], so you should read "argument" as "an element of sys.argv[1:], or of some other list provided as a substitute for sys.argv[1:]".

選項

an argument used to supply extra information to guide or customize the execution of a program. There are many different syntaxes for options; the traditional Unix syntax is a hyphen ("-") followed by a single letter, e.g. -x or -F. Also, traditional Unix syntax allows multiple options to be merged into a single argument, e.g. -x -F is equivalent to -xF. The GNU project introduced -- followed by a series of hyphen-separated words, e.g. --file or --dry-run. These are the only two option syntaxes provided by optparse.

Some other option syntaxes that the world has seen include:

a hyphen followed by a few letters, e.g. -pf (this is not the same as multiple options merged into a single argument)

a hyphen followed by a whole word, e.g. -file (this is technically equivalent to the previous syntax, but they aren't usually seen in the same program)

a plus sign followed by a single letter, or a few letters, or a word, e.g. +f, +rgb

a slash followed by a letter, or a few letters, or a word, e.g. /f, /file

These option syntaxes are not supported by optparse, and they never will be. This is deliberate: the first three are non-standard on any environment, and the last only makes sense if you're exclusively targeting Windows or certain legacy platforms (e.g. VMS, MS-DOS).

選項引數

an argument that follows an option, is closely associated with that option, and is consumed from the argument list when that option is. With optparse, option arguments may either be in a separate argument from their option:

-f foo
--file foo

or included in the same argument:

-ffoo
--file=foo

Typically, a given option either takes an argument or it doesn't. Lots of people want an "optional option arguments" feature, meaning that some options will take an argument if they see it, and won't if they don't. This is somewhat controversial, because it makes parsing ambiguous: if -a takes an optional argument and -b is another option entirely, how do we interpret -ab? Because of this ambiguity, optparse does not support this feature.

位置引數

something leftover in the argument list after options have been parsed, i.e. after options and their arguments have been parsed and removed from the argument list.

required option

an option that must be supplied on the command-line; note that the phrase "required option" is self-contradictory in English. optparse doesn't prevent you from implementing required options, but doesn't give you much help at it either.

For example, consider this hypothetical command-line:

prog -v --report report.txt foo bar

-v and --report are both options. Assuming that --report takes one argument, report.txt is an option argument. foo and bar are positional arguments.

What are options for?

Options are used to provide extra information to tune or customize the execution of a program. In case it wasn't clear, options are usually optional. A program should be able to run just fine with no options whatsoever. (Pick a random program from the Unix or GNU toolsets. Can it run without any options at all and still make sense? The main exceptions are find, tar, and dd---all of which are mutant oddballs that have been rightly criticized for their non-standard syntax and confusing interfaces.)

Lots of people want their programs to have "required options". Think about it. If it's required, then it's not optional! If there is a piece of information that your program absolutely requires in order to run successfully, that's what positional arguments are for.

As an example of good command-line interface design, consider the humble cp utility, for copying files. It doesn't make much sense to try to copy files without supplying a destination and at least one source. Hence, cp fails if you run it with no arguments. However, it has a flexible, useful syntax that does not require any options at all:

cp SOURCE DEST
cp SOURCE ... DEST-DIR

You can get pretty far with just that. Most cp implementations provide a bunch of options to tweak exactly how the files are copied: you can preserve mode and modification time, avoid following symlinks, ask before clobbering existing files, etc. But none of this distracts from the core mission of cp, which is to copy either one file to another, or several files to another directory.

What are positional arguments for?

Positional arguments are for those pieces of information that your program absolutely, positively requires to run.

A good user interface should have as few absolute requirements as possible. If your program requires 17 distinct pieces of information in order to run successfully, it doesn't much matter how you get that information from the user---most people will give up and walk away before they successfully run the program. This applies whether the user interface is a command-line, a configuration file, or a GUI: if you make that many demands on your users, most of them will simply give up.

In short, try to minimize the amount of information that users are absolutely required to supply---use sensible defaults whenever possible. Of course, you also want to make your programs reasonably flexible. That's what options are for. Again, it doesn't matter if they are entries in a config file, widgets in the "Preferences" dialog of a GUI, or command-line options---the more options you implement, the more flexible your program is, and the more complicated its implementation becomes. Too much flexibility has drawbacks as well, of course; too many options can overwhelm users and make your code much harder to maintain.

教學

While optparse is quite flexible and powerful, it's also straightforward to use in most cases. This section covers the code patterns that are common to any optparse-based program.

First, you need to import the OptionParser class; then, early in the main program, create an OptionParser instance:

from optparse import OptionParser
...
parser = OptionParser()

Then you can start defining options. The basic syntax is:

parser.add_option(opt_str, ...,
                  attr=value, ...)

Each option has one or more option strings, such as -f or --file, and several option attributes that tell optparse what to expect and what to do when it encounters that option on the command line.

Typically, each option will have one short option string and one long option string, e.g.:

parser.add_option("-f", "--file", ...)

You're free to define as many short option strings and as many long option strings as you like (including zero), as long as there is at least one option string overall.

The option strings passed to OptionParser.add_option() are effectively labels for the option defined by that call. For brevity, we will frequently refer to encountering an option on the command line; in reality, optparse encounters option strings and looks up options from them.

Once all of your options are defined, instruct optparse to parse your program's command line:

(options, args) = parser.parse_args()

(If you like, you can pass a custom argument list to parse_args(), but that's rarely necessary: by default it uses sys.argv[1:].)

parse_args() 回傳兩個值：

options, an object containing values for all of your options---e.g. if --file takes a single string argument, then options.file will be the filename supplied by the user, or None if the user did not supply that option

args, the list of positional arguments leftover after parsing options

This tutorial section only covers the four most important option attributes: action, type, dest (destination), and help. Of these, action is the most fundamental.

Understanding option actions

Actions tell optparse what to do when it encounters an option on the command line. There is a fixed set of actions hard-coded into optparse; adding new actions is an advanced topic covered in section Extending optparse. Most actions tell optparse to store a value in some variable---for example, take a string from the command line and store it in an attribute of options.

If you don't specify an option action, optparse defaults to store.

The store action

The most common option action is store, which tells optparse to take the next argument (or the remainder of the current argument), ensure that it is of the correct type, and store it to your chosen destination.

舉例來說：

parser.add_option("-f", "--file",
                  action="store", type="string", dest="filename")

Now let's make up a fake command line and ask optparse to parse it:

args = ["-f", "foo.txt"]
(options, args) = parser.parse_args(args)

When optparse sees the option string -f, it consumes the next argument, foo.txt, and stores it in options.filename. So, after this call to parse_args(), options.filename is "foo.txt".

Some other option types supported by optparse are int and float. Here's an option that expects an integer argument:

parser.add_option("-n", type="int", dest="num")

Note that this option has no long option string, which is perfectly acceptable. Also, there's no explicit action, since the default is store.

Let's parse another fake command-line. This time, we'll jam the option argument right up against the option: since -n42 (one argument) is equivalent to -n 42 (two arguments), the code

(options, args) = parser.parse_args(["-n42"])
print(options.num)

會印出 42。

If you don't specify a type, optparse assumes string. Combined with the fact that the default action is store, that means our first example can be a lot shorter:

parser.add_option("-f", "--file", dest="filename")

If you don't supply a destination, optparse figures out a sensible default from the option strings: if the first long option string is --foo-bar, then the default destination is foo_bar. If there are no long option strings, optparse looks at the first short option string: the default destination for -f is f.

optparse also includes the built-in complex type. Adding types is covered in section Extending optparse.

Handling boolean (flag) options

Flag options---set a variable to true or false when a particular option is seen---are quite common. optparse supports them with two separate actions, store_true and store_false. For example, you might have a verbose flag that is turned on with -v and off with -q:

parser.add_option("-v", action="store_true", dest="verbose")
parser.add_option("-q", action="store_false", dest="verbose")

Here we have two different options with the same destination, which is perfectly OK. (It just means you have to be a bit careful when setting default values---see below.)

When optparse encounters -v on the command line, it sets options.verbose to True; when it encounters -q, options.verbose is set to False.

Other actions

Some other actions supported by optparse are:

"store_const"

store a constant value, pre-set via Option.const

"append"

append this option's argument to a list

"count"

increment a counter by one

"callback"

call a specified function

These are covered in section Reference Guide, and section Option Callbacks.

預設值

All of the above examples involve setting some variable (the "destination") when certain command-line options are seen. What happens if those options are never seen? Since we didn't supply any defaults, they are all set to None. This is usually fine, but sometimes you want more control. optparse lets you supply a default value for each destination, which is assigned before the command line is parsed.

First, consider the verbose/quiet example. If we want optparse to set verbose to True unless -q is seen, then we can do this:

parser.add_option("-v", action="store_true", dest="verbose", default=True)
parser.add_option("-q", action="store_false", dest="verbose")

Since default values apply to the destination rather than to any particular option, and these two options happen to have the same destination, this is exactly equivalent:

parser.add_option("-v", action="store_true", dest="verbose")
parser.add_option("-q", action="store_false", dest="verbose", default=True)

Consider this:

parser.add_option("-v", action="store_true", dest="verbose", default=False)
parser.add_option("-q", action="store_false", dest="verbose", default=True)

Again, the default value for verbose will be True: the last default value supplied for any particular destination is the one that counts.

A clearer way to specify default values is the set_defaults() method of OptionParser, which you can call at any time before calling parse_args():

parser.set_defaults(verbose=True)
parser.add_option(...)
(options, args) = parser.parse_args()

As before, the last value specified for a given option destination is the one that counts. For clarity, try to use one method or the other of setting default values, not both.

Generating help

optparse's ability to generate help and usage text automatically is useful for creating user-friendly command-line interfaces. All you have to do is supply a help value for each option, and optionally a short usage message for your whole program. Here's an OptionParser populated with user-friendly (documented) options:

usage = "usage: %prog [options] arg1 arg2"
parser = OptionParser(usage=usage)
parser.add_option("-v", "--verbose",
                  action="store_true", dest="verbose", default=True,
                  help="make lots of noise [default]")
parser.add_option("-q", "--quiet",
                  action="store_false", dest="verbose",
                  help="be vewwy quiet (I'm hunting wabbits)")
parser.add_option("-f", "--filename",
                  metavar="FILE", help="write output to FILE")
parser.add_option("-m", "--mode",
                  default="intermediate",
                  help="interaction mode: novice, intermediate, "
                       "or expert [default: %default]")

If optparse encounters either -h or --help on the command-line, or if you just call parser.print_help(), it prints the following to standard output:

Usage: <yourscript> [options] arg1 arg2

Options:
  -h, --help            show this help message and exit
  -v, --verbose         make lots of noise [default]
  -q, --quiet           be vewwy quiet (I'm hunting wabbits)
  -f FILE, --filename=FILE
                        write output to FILE
  -m MODE, --mode=MODE  interaction mode: novice, intermediate, or
                        expert [default: intermediate]

(If the help output is triggered by a help option, optparse exits after printing the help text.)

There's a lot going on here to help optparse generate the best possible help message:

the script defines its own usage message:

usage = "usage: %prog [options] arg1 arg2"

optparse expands %prog in the usage string to the name of the current program, i.e. os.path.basename(sys.argv[0]). The expanded string is then printed before the detailed option help.

If you don't supply a usage string, optparse uses a bland but sensible default: "Usage: %prog [options]", which is fine if your script doesn't take any positional arguments.

every option defines a help string, and doesn't worry about line-wrapping---optparse takes care of wrapping lines and making the help output look good.

options that take a value indicate this fact in their automatically generated help message, e.g. for the "mode" option:

-m MODE, --mode=MODE

Here, "MODE" is called the meta-variable: it stands for the argument that the user is expected to supply to -m/--mode. By default, optparse converts the destination variable name to uppercase and uses that for the meta-variable. Sometimes, that's not what you want---for example, the --filename option explicitly sets metavar="FILE", resulting in this automatically generated option description:

-f FILE, --filename=FILE

This is important for more than just saving space, though: the manually written help text uses the meta-variable FILE to clue the user in that there's a connection between the semi-formal syntax -f FILE and the informal semantic description "write output to FILE". This is a simple but effective way to make your help text a lot clearer and more useful for end users.

options that have a default value can include %default in the help string---optparse will replace it with str() of the option's default value. If an option has no default value (or the default value is None), %default expands to none.

Grouping Options

When dealing with many options, it is convenient to group these options for better help output. An OptionParser can contain several option groups, each of which can contain several options.

An option group is obtained using the class OptionGroup:

class optparse.OptionGroup(parser, title, description=None)

where

parser is the OptionParser instance the group will be inserted in to

title is the group title

description, optional, is a long description of the group

OptionGroup inherits from OptionContainer (like OptionParser) and so the add_option() method can be used to add an option to the group.

Once all the options are declared, using the OptionParser method add_option_group() the group is added to the previously defined parser.

Continuing with the parser defined in the previous section, adding an OptionGroup to a parser is easy:

group = OptionGroup(parser, "Dangerous Options",
                    "Caution: use these options at your own risk.  "
                    "It is believed that some of them bite.")
group.add_option("-g", action="store_true", help="Group option.")
parser.add_option_group(group)

This would result in the following help output:

Usage: <yourscript> [options] arg1 arg2

Options:
  -h, --help            show this help message and exit
  -v, --verbose         make lots of noise [default]
  -q, --quiet           be vewwy quiet (I'm hunting wabbits)
  -f FILE, --filename=FILE
                        write output to FILE
  -m MODE, --mode=MODE  interaction mode: novice, intermediate, or
                        expert [default: intermediate]

  Dangerous Options:
    Caution: use these options at your own risk.  It is believed that some
    of them bite.

    -g                  Group option.

A bit more complete example might involve using more than one group: still extending the previous example:

group = OptionGroup(parser, "Dangerous Options",
                    "Caution: use these options at your own risk.  "
                    "It is believed that some of them bite.")
group.add_option("-g", action="store_true", help="Group option.")
parser.add_option_group(group)

group = OptionGroup(parser, "Debug Options")
group.add_option("-d", "--debug", action="store_true",
                 help="Print debug information")
group.add_option("-s", "--sql", action="store_true",
                 help="Print all SQL statements executed")
group.add_option("-e", action="store_true", help="Print every action done")
parser.add_option_group(group)

that results in the following output:

Usage: <yourscript> [options] arg1 arg2

Options:
  -h, --help            show this help message and exit
  -v, --verbose         make lots of noise [default]
  -q, --quiet           be vewwy quiet (I'm hunting wabbits)
  -f FILE, --filename=FILE
                        write output to FILE
  -m MODE, --mode=MODE  interaction mode: novice, intermediate, or expert
                        [default: intermediate]

  Dangerous Options:
    Caution: use these options at your own risk.  It is believed that some
    of them bite.

    -g                  Group option.

  Debug Options:
    -d, --debug         Print debug information
    -s, --sql           Print all SQL statements executed
    -e                  Print every action done

Another interesting method, in particular when working programmatically with option groups is:

OptionParser.get_option_group(opt_str)

Return the OptionGroup to which the short or long option string opt_str (e.g. '-o' or '--option') belongs. If there's no such OptionGroup, return None.

Printing a version string

Similar to the brief usage string, optparse can also print a version string for your program. You have to supply the string as the version argument to OptionParser:

parser = OptionParser(usage="%prog [-f] [-q]", version="%prog 1.0")

%prog is expanded just like it is in usage. Apart from that, version can contain anything you like. When you supply it, optparse automatically adds a --version option to your parser. If it encounters this option on the command line, it expands your version string (by replacing %prog), prints it to stdout, and exits.

For example, if your script is called /usr/bin/foo:

$ /usr/bin/foo --version
foo 1.0

The following two methods can be used to print and get the version string:

OptionParser.print_version(file=None)

Print the version message for the current program (self.version) to file (default stdout). As with print_usage(), any occurrence of %prog in self.version is replaced with the name of the current program. Does nothing if self.version is empty or undefined.

OptionParser.get_version()

Same as print_version() but returns the version string instead of printing it.

How optparse handles errors

There are two broad classes of errors that optparse has to worry about: programmer errors and user errors. Programmer errors are usually erroneous calls to OptionParser.add_option(), e.g. invalid option strings, unknown option attributes, missing option attributes, etc. These are dealt with in the usual way: raise an exception (either optparse.OptionError or TypeError) and let the program crash.

Handling user errors is much more important, since they are guaranteed to happen no matter how stable your code is. optparse can automatically detect some user errors, such as bad option arguments (passing -n 4x where -n takes an integer argument), missing arguments (-n at the end of the command line, where -n takes an argument of any type). Also, you can call OptionParser.error() to signal an application-defined error condition:

(options, args) = parser.parse_args()
...
if options.a and options.b:
    parser.error("options -a and -b are mutually exclusive")

In either case, optparse handles the error the same way: it prints the program's usage message and an error message to standard error and exits with error status 2.

Consider the first example above, where the user passes 4x to an option that takes an integer:

$ /usr/bin/foo -n 4x
Usage: foo [options]

foo: error: option -n: invalid integer value: '4x'

Or, where the user fails to pass a value at all:

$ /usr/bin/foo -n
Usage: foo [options]

foo: error: -n option requires an argument

optparse-generated error messages take care always to mention the option involved in the error; be sure to do the same when calling OptionParser.error() from your application code.

If optparse's default error-handling behaviour does not suit your needs, you'll need to subclass OptionParser and override its exit() and/or error() methods.

Putting it all together

Here's what optparse-based scripts usually look like:

from optparse import OptionParser
...
def main():
    usage = "usage: %prog [options] arg"
    parser = OptionParser(usage)
    parser.add_option("-f", "--file", dest="filename",
                      help="read data from FILENAME")
    parser.add_option("-v", "--verbose",
                      action="store_true", dest="verbose")
    parser.add_option("-q", "--quiet",
                      action="store_false", dest="verbose")
    ...
    (options, args) = parser.parse_args()
    if len(args) != 1:
        parser.error("incorrect number of arguments")
    if options.verbose:
        print("reading %s..." % options.filename)
    ...

if __name__ == "__main__":
    main()

Reference Guide

建立剖析器

The first step in using optparse is to create an OptionParser instance.

class optparse.OptionParser(...)

The OptionParser constructor has no required arguments, but a number of optional keyword arguments. You should always pass them as keyword arguments, i.e. do not rely on the order in which the arguments are declared.

usage（預設值："%prog [options]"）

The usage summary to print when your program is run incorrectly or with a help option. When optparse prints the usage string, it expands %prog to os.path.basename(sys.argv[0]) (or to prog if you passed that keyword argument). To suppress a usage message, pass the special value optparse.SUPPRESS_USAGE.

option_list（預設值：[]）

A list of Option objects to populate the parser with. The options in option_list are added after any options in standard_option_list (a class attribute that may be set by OptionParser subclasses), but before any version or help options. Deprecated; use add_option() after creating the parser instead.

option_class（預設值：optparse.Option）

在 add_option() 中新增選項時要使用的類別。

version（預設值：None）

A version string to print when the user supplies a version option. If you supply a true value for version, optparse automatically adds a version option with the single option string --version. The substring %prog is expanded the same as for usage.

conflict_handler（預設值："error"）

Specifies what to do when options with conflicting option strings are added to the parser; see section Conflicts between options.

description（預設值：None）

A paragraph of text giving a brief overview of your program. optparse reformats this paragraph to fit the current terminal width and prints it when the user requests help (after usage, but before the list of options).

formatter (default: a new IndentedHelpFormatter)

An instance of optparse.HelpFormatter that will be used for printing help text. optparse provides two concrete classes for this purpose: IndentedHelpFormatter and TitledHelpFormatter.

add_help_option（預設值：True）

If true, optparse will add a help option (with option strings -h and --help) to the parser.

prog

The string to use when expanding %prog in usage and version instead of os.path.basename(sys.argv[0]).

epilog（預設值：None）

A paragraph of help text to print after the option help.

Populating the parser

There are several ways to populate the parser with options. The preferred way is by using OptionParser.add_option(), as shown in section 教學. add_option() can be called in one of two ways:

pass it an Option instance (as returned by make_option())

pass it any combination of positional and keyword arguments that are acceptable to make_option() (i.e., to the Option constructor), and it will create the Option instance for you

The other alternative is to pass a list of pre-constructed Option instances to the OptionParser constructor, as in:

option_list = [
    make_option("-f", "--filename",
                action="store", type="string", dest="filename"),
    make_option("-q", "--quiet",
                action="store_false", dest="verbose"),
    ]
parser = OptionParser(option_list=option_list)

(make_option() is a factory function for creating Option instances; currently it is an alias for the Option constructor. A future version of optparse may split Option into several classes, and make_option() will pick the right class to instantiate. Do not instantiate Option directly.)

定義選項

Each Option instance represents a set of synonymous command-line option strings, e.g. -f and --file. You can specify any number of short or long option strings, but you must specify at least one overall option string.

The canonical way to create an Option instance is with the add_option() method of OptionParser.

OptionParser.add_option(option)

OptionParser.add_option(*opt_str, attr=value, ...)

To define an option with only a short option string:

parser.add_option("-f", attr=value, ...)

And to define an option with only a long option string:

parser.add_option("--foo", attr=value, ...)

The keyword arguments define attributes of the new Option object. The most important option attribute is action, and it largely determines which other attributes are relevant or required. If you pass irrelevant option attributes, or fail to pass required ones, optparse raises an OptionError exception explaining your mistake.

An option's action determines what optparse does when it encounters this option on the command-line. The standard option actions hard-coded into optparse are:

"store"

store this option's argument (default)

"store_const"

store a constant value, pre-set via Option.const

"store_true"

store True

"store_false"

store False

"append"

append this option's argument to a list

"append_const"

append a constant value to a list, pre-set via Option.const

"count"

increment a counter by one

"callback"

call a specified function

"help"

print a usage message including all options and the documentation for them

(If you don't supply an action, the default is "store". For this action, you may also supply type and dest option attributes; see 標準選項動作.)

As you can see, most actions involve storing or updating a value somewhere. optparse always creates a special object for this, conventionally called options, which is an instance of optparse.Values.

class optparse.Values

An object holding parsed argument names and values as attributes. Normally created by calling when calling OptionParser.parse_args(), and can be overridden by a custom subclass passed to the values argument of OptionParser.parse_args() (as described in 剖析引數).

Option arguments (and various other values) are stored as attributes of this object, according to the dest (destination) option attribute.

例如說，當你呼叫：

parser.parse_args()

one of the first things optparse does is create the options object:

options = Values()

If one of the options in this parser is defined with

parser.add_option("-f", "--file", action="store", type="string", dest="filename")

and the command-line being parsed includes any of the following:

-ffoo
-f foo
--file=foo
--file foo

then optparse, on seeing this option, will do the equivalent of

options.filename = "foo"

The type and dest option attributes are almost as important as action, but action is the only one that makes sense for all options.

選項屬性

class optparse.Option

A single command line argument, with various attributes passed by keyword to the constructor. Normally created with OptionParser.add_option() rather than directly, and can be overridden by a custom class via the option_class argument to OptionParser.

The following option attributes may be passed as keyword arguments to OptionParser.add_option(). If you pass an option attribute that is not relevant to a particular option, or fail to pass a required option attribute, optparse raises OptionError.

Option.action

（預設值： "store" ）

Determines optparse's behaviour when this option is seen on the command line; the available options are documented here.

Option.type

（預設值： "string" ）

The argument type expected by this option (e.g., "string" or "int"); the available option types are documented here.

Option.dest

(default: derived from option strings)

If the option's action implies writing or modifying a value somewhere, this tells optparse where to write it: dest names an attribute of the options object that optparse builds as it parses the command line.

Option.default

The value to use for this option's destination if the option is not seen on the command line. See also OptionParser.set_defaults().

Option.nargs

（預設值：1）

How many arguments of type type should be consumed when this option is seen. If > 1, optparse will store a tuple of values to dest.

Option.const

For actions that store a constant value, the constant value to store.

Option.choices

For options of type "choice", the list of strings the user may choose from.

Option.callback

For options with action "callback", the callable to call when this option is seen. See section Option Callbacks for detail on the arguments passed to the callable.

Option.callback_args

Option.callback_kwargs

Additional positional and keyword arguments to pass to callback after the four standard callback arguments.

Option.help

Help text to print for this option when listing all available options after the user supplies a help option (such as --help). If no help text is supplied, the option will be listed without help text. To hide this option, use the special value optparse.SUPPRESS_HELP.

Option.metavar

(default: derived from option strings)

Stand-in for the option argument(s) to use when printing help text. See section 教學 for an example.

標準選項動作

The various option actions all have slightly different requirements and effects. Most actions have several relevant option attributes which you may specify to guide optparse's behaviour; a few have required attributes, which you must specify for any option using that action.

"store" [relevant: type, dest, nargs, choices]

The option must be followed by an argument, which is converted to a value according to type and stored in dest. If nargs > 1, multiple arguments will be consumed from the command line; all will be converted according to type and stored to dest as a tuple. See the Standard option types section.

If choices is supplied (a list or tuple of strings), the type defaults to "choice".

如果沒有提供 type，它的預設值是 "string"。

If dest is not supplied, optparse derives a destination from the first long option string (e.g., --foo-bar implies foo_bar). If there are no long option strings, optparse derives a destination from the first short option string (e.g., -f implies f).

範例：

parser.add_option("-f")
parser.add_option("-p", type="float", nargs=3, dest="point")

As it parses the command line

-f foo.txt -p 1 -3.5 4 -fbar.txt

optparse 將會設定：

options.f = "foo.txt"
options.point = (1.0, -3.5, 4.0)
options.f = "bar.txt"

"store_const" [required: const; relevant: dest]

The value const is stored in dest.

範例：

parser.add_option("-q", "--quiet",
                  action="store_const", const=0, dest="verbose")
parser.add_option("-v", "--verbose",
                  action="store_const", const=1, dest="verbose")
parser.add_option("--noisy",
                  action="store_const", const=2, dest="verbose")

If --noisy is seen, optparse will set

options.verbose = 2

"store_true" [relevant: dest]

A special case of "store_const" that stores True to dest.

"store_false" [relevant: dest]

Like "store_true", but stores False.

範例：

parser.add_option("--clobber", action="store_true", dest="clobber")
parser.add_option("--no-clobber", action="store_false", dest="clobber")

"append" [relevant: type, dest, nargs, choices]

The option must be followed by an argument, which is appended to the list in dest. If no default value for dest is supplied, an empty list is automatically created when optparse first encounters this option on the command-line. If nargs > 1, multiple arguments are consumed, and a tuple of length nargs is appended to dest.

The defaults for type and dest are the same as for the "store" action.

範例：

parser.add_option("-t", "--tracks", action="append", type="int")

If -t3 is seen on the command-line, optparse does the equivalent of:

options.tracks = []
options.tracks.append(int("3"))

If, a little later on, --tracks=4 is seen, it does:

options.tracks.append(int("4"))

The append action calls the append method on the current value of the option. This means that any default value specified must have an append method. It also means that if the default value is non-empty, the default elements will be present in the parsed value for the option, with any values from the command line appended after those default values:

>>> parser.add_option("--files", action="append", default=['~/.mypkg/defaults'])
>>> opts, args = parser.parse_args(['--files', 'overrides.mypkg'])
>>> opts.files
['~/.mypkg/defaults', 'overrides.mypkg']

"append_const" [required: const; relevant: dest]

Like "store_const", but the value const is appended to dest; as with "append", dest defaults to None, and an empty list is automatically created the first time the option is encountered.

"count" [relevant: dest]

Increment the integer stored at dest. If no default value is supplied, dest is set to zero before being incremented the first time.

範例：

parser.add_option("-v", action="count", dest="verbosity")

The first time -v is seen on the command line, optparse does the equivalent of:

options.verbosity = 0
options.verbosity += 1

Every subsequent occurrence of -v results in

options.verbosity += 1

"callback" [required: callback; relevant: type, nargs, callback_args, callback_kwargs]

Call the function specified by callback, which is called as

func(option, opt_str, value, parser, *args, **kwargs)

更多細節請見 Option Callbacks。

"help"

Prints a complete help message for all the options in the current option parser. The help message is constructed from the usage string passed to OptionParser's constructor and the help string passed to every option.

If no help string is supplied for an option, it will still be listed in the help message. To omit an option entirely, use the special value optparse.SUPPRESS_HELP.

optparse automatically adds a help option to all OptionParsers, so you do not normally need to create one.

範例：

from optparse import OptionParser, SUPPRESS_HELP

# usually, a help option is added automatically, but that can
# be suppressed using the add_help_option argument
parser = OptionParser(add_help_option=False)

parser.add_option("-h", "--help", action="help")
parser.add_option("-v", action="store_true", dest="verbose",
                  help="Be moderately verbose")
parser.add_option("--file", dest="filename",
                  help="Input file to read data from")
parser.add_option("--secret", help=SUPPRESS_HELP)

If optparse sees either -h or --help on the command line, it will print something like the following help message to stdout (assuming sys.argv[0] is "foo.py"):

Usage: foo.py [options]

Options:
  -h, --help        Show this help message and exit
  -v                Be moderately verbose
  --file=FILENAME   Input file to read data from

After printing the help message, optparse terminates your process with sys.exit(0).

"version"

Prints the version number supplied to the OptionParser to stdout and exits. The version number is actually formatted and printed by the print_version() method of OptionParser. Generally only relevant if the version argument is supplied to the OptionParser constructor. As with help options, you will rarely create version options, since optparse automatically adds them when needed.

Standard option types

optparse has five built-in option types: "string", "int", "choice", "float" and "complex". If you need to add new option types, see section Extending optparse.

Arguments to string options are not checked or converted in any way: the text on the command line is stored in the destination (or passed to the callback) as-is.

Integer arguments (type "int") are parsed as follows:

if the number starts with 0x, it is parsed as a hexadecimal number

if the number starts with 0, it is parsed as an octal number

if the number starts with 0b, it is parsed as a binary number

otherwise, the number is parsed as a decimal number

The conversion is done by calling int() with the appropriate base (2, 8, 10, or 16). If this fails, so will optparse, although with a more useful error message.

"float" and "complex" option arguments are converted directly with float() and complex(), with similar error-handling.

"choice" options are a subtype of "string" options. The choices option attribute (a sequence of strings) defines the set of allowed option arguments. optparse.check_choice() compares user-supplied option arguments against this master list and raises OptionValueError if an invalid string is given.

剖析引數

The whole point of creating and populating an OptionParser is to call its parse_args() method.

OptionParser.parse_args(args=None, values=None)

Parse the command-line options found in args.

The input parameters are

args

the list of arguments to process (default: sys.argv[1:])

values

a Values object to store option arguments in (default: a new instance of Values) -- if you give an existing object, the option defaults will not be initialized on it

and the return value is a pair (options, args) where

options

the same object that was passed in as values, or the optparse.Values instance created by optparse

args

the leftover positional arguments after all options have been processed

The most common usage is to supply neither keyword argument. If you supply values, it will be modified with repeated setattr() calls (roughly one for every option argument stored to an option destination) and returned by parse_args().

If parse_args() encounters any errors in the argument list, it calls the OptionParser's error() method with an appropriate end-user error message. This ultimately terminates your process with an exit status of 2 (the traditional Unix exit status for command-line errors).

Querying and manipulating your option parser

The default behavior of the option parser can be customized slightly, and you can also poke around your option parser and see what's there. OptionParser provides several methods to help you out:

OptionParser.disable_interspersed_args()

Set parsing to stop on the first non-option. For example, if -a and -b are both simple options that take no arguments, optparse normally accepts this syntax:

prog -a arg1 -b arg2

and treats it as equivalent to

prog -a -b arg1 arg2

To disable this feature, call disable_interspersed_args(). This restores traditional Unix syntax, where option parsing stops with the first non-option argument.

Use this if you have a command processor which runs another command which has options of its own and you want to make sure these options don't get confused. For example, each command might have a different set of options.

OptionParser.enable_interspersed_args()

Set parsing to not stop on the first non-option, allowing interspersing switches with command arguments. This is the default behavior.

OptionParser.get_option(opt_str)

Returns the Option instance with the option string opt_str, or None if no options have that option string.

OptionParser.has_option(opt_str)

Return True if the OptionParser has an option with option string opt_str (e.g., -q or --verbose).

OptionParser.remove_option(opt_str)

If the OptionParser has an option corresponding to opt_str, that option is removed. If that option provided any other option strings, all of those option strings become invalid. If opt_str does not occur in any option belonging to this OptionParser, raises ValueError.

Conflicts between options

If you're not careful, it's easy to define options with conflicting option strings:

parser.add_option("-n", "--dry-run", ...)
...
parser.add_option("-n", "--noisy", ...)

(This is particularly true if you've defined your own OptionParser subclass with some standard options.)

Every time you add an option, optparse checks for conflicts with existing options. If it finds any, it invokes the current conflict-handling mechanism. You can set the conflict-handling mechanism either in the constructor:

parser = OptionParser(..., conflict_handler=handler)

or with a separate call:

parser.set_conflict_handler(handler)

The available conflict handlers are:

"error" (預設值)

assume option conflicts are a programming error and raise OptionConflictError

"resolve"

resolve option conflicts intelligently (see below)

As an example, let's define an OptionParser that resolves conflicts intelligently and add conflicting options to it:

parser = OptionParser(conflict_handler="resolve")
parser.add_option("-n", "--dry-run", ..., help="do no harm")
parser.add_option("-n", "--noisy", ..., help="be noisy")

At this point, optparse detects that a previously added option is already using the -n option string. Since conflict_handler is "resolve", it resolves the situation by removing -n from the earlier option's list of option strings. Now --dry-run is the only way for the user to activate that option. If the user asks for help, the help message will reflect that:

Options:
  --dry-run     do no harm
  ...
  -n, --noisy   be noisy

It's possible to whittle away the option strings for a previously added option until there are none left, and the user has no way of invoking that option from the command-line. In that case, optparse removes that option completely, so it doesn't show up in help text or anywhere else. Carrying on with our existing OptionParser:

parser.add_option("--dry-run", ..., help="new dry-run option")

At this point, the original -n/--dry-run option is no longer accessible, so optparse removes it, leaving this help text:

Options:
  ...
  -n, --noisy   be noisy
  --dry-run     new dry-run option

Cleanup

OptionParser instances have several cyclic references. This should not be a problem for Python's garbage collector, but you may wish to break the cyclic references explicitly by calling destroy() on your OptionParser once you are done with it. This is particularly useful in long-running applications where large object graphs are reachable from your OptionParser.

其他方法

OptionParser supports several other public methods:

OptionParser.set_usage(usage)

Set the usage string according to the rules described above for the usage constructor keyword argument. Passing None sets the default usage string; use optparse.SUPPRESS_USAGE to suppress a usage message.

OptionParser.print_usage(file=None)

Print the usage message for the current program (self.usage) to file (default stdout). Any occurrence of the string %prog in self.usage is replaced with the name of the current program. Does nothing if self.usage is empty or not defined.

OptionParser.get_usage()

Same as print_usage() but returns the usage string instead of printing it.

OptionParser.set_defaults(dest=value, ...)

Set default values for several option destinations at once. Using set_defaults() is the preferred way to set default values for options, since multiple options can share the same destination. For example, if several "mode" options all set the same destination, any one of them can set the default, and the last one wins:

parser.add_option("--advanced", action="store_const",
                  dest="mode", const="advanced",
                  default="novice")    # overridden below
parser.add_option("--novice", action="store_const",
                  dest="mode", const="novice",
                  default="advanced")  # overrides above setting

To avoid this confusion, use set_defaults():

parser.set_defaults(mode="advanced")
parser.add_option("--advanced", action="store_const",
                  dest="mode", const="advanced")
parser.add_option("--novice", action="store_const",
                  dest="mode", const="novice")

Option Callbacks

When optparse's built-in actions and types aren't quite enough for your needs, you have two choices: extend optparse or define a callback option. Extending optparse is more general, but overkill for a lot of simple cases. Quite often a simple callback is all you need.

There are two steps to defining a callback option:

define the option itself using the "callback" action

write the callback; this is a function (or method) that takes at least four arguments, as described below

Defining a callback option

As always, the easiest way to define a callback option is by using the OptionParser.add_option() method. Apart from action, the only option attribute you must specify is callback, the function to call:

parser.add_option("-c", action="callback", callback=my_callback)

callback is a function (or other callable object), so you must have already defined my_callback() when you create this callback option. In this simple case, optparse doesn't even know if -c takes any arguments, which usually means that the option takes no arguments---the mere presence of -c on the command-line is all it needs to know. In some circumstances, though, you might want your callback to consume an arbitrary number of command-line arguments. This is where writing callbacks gets tricky; it's covered later in this section.

optparse always passes four particular arguments to your callback, and it will only pass additional arguments if you specify them via callback_args and callback_kwargs. Thus, the minimal callback function signature is:

def my_callback(option, opt, value, parser):

The four arguments to a callback are described below.

There are several other option attributes that you can supply when you define a callback option:

type

has its usual meaning: as with the "store" or "append" actions, it instructs optparse to consume one argument and convert it to type. Rather than storing the converted value(s) anywhere, though, optparse passes it to your callback function.

nargs

also has its usual meaning: if it is supplied and > 1, optparse will consume nargs arguments, each of which must be convertible to type. It then passes a tuple of converted values to your callback.

callback_args

a tuple of extra positional arguments to pass to the callback

callback_kwargs

a dictionary of extra keyword arguments to pass to the callback

How callbacks are called

All callbacks are called as follows:

func(option, opt_str, value, parser, *args, **kwargs)

where

option

is the Option instance that's calling the callback

opt_str

is the option string seen on the command-line that's triggering the callback. (If an abbreviated long option was used, opt_str will be the full, canonical option string---e.g. if the user puts --foo on the command-line as an abbreviation for --foobar, then opt_str will be "--foobar".)

value

is the argument to this option seen on the command-line. optparse will only expect an argument if type is set; the type of value will be the type implied by the option's type. If type for this option is None (no argument expected), then value will be None. If nargs > 1, value will be a tuple of values of the appropriate type.

parser

is the OptionParser instance driving the whole thing, mainly useful because you can access some other interesting data through its instance attributes:

parser.largs

the current list of leftover arguments, ie. arguments that have been consumed but are neither options nor option arguments. Feel free to modify parser.largs, e.g. by adding more arguments to it. (This list will become args, the second return value of parse_args().)

parser.rargs

the current list of remaining arguments, ie. with opt_str and value (if applicable) removed, and only the arguments following them still there. Feel free to modify parser.rargs, e.g. by consuming more arguments.

parser.values

the object where option values are by default stored (an instance of optparse.OptionValues). This lets callbacks use the same mechanism as the rest of optparse for storing option values; you don't need to mess around with globals or closures. You can also access or modify the value(s) of any options already encountered on the command-line.

args

is a tuple of arbitrary positional arguments supplied via the callback_args option attribute.

kwargs

is a dictionary of arbitrary keyword arguments supplied via callback_kwargs.

Raising errors in a callback

The callback function should raise OptionValueError if there are any problems with the option or its argument(s). optparse catches this and terminates the program, printing the error message you supply to stderr. Your message should be clear, concise, accurate, and mention the option at fault. Otherwise, the user will have a hard time figuring out what they did wrong.

Callback example 1: trivial callback

Here's an example of a callback option that takes no arguments, and simply records that the option was seen:

def record_foo_seen(option, opt_str, value, parser):
    parser.values.saw_foo = True

parser.add_option("--foo", action="callback", callback=record_foo_seen)

Of course, you could do that with the "store_true" action.

Callback example 2: check option order

Here's a slightly more interesting example: record the fact that -a is seen, but blow up if it comes after -b in the command-line.

def check_order(option, opt_str, value, parser):
    if parser.values.b:
        raise OptionValueError("can't use -a after -b")
    parser.values.a = 1
...
parser.add_option("-a", action="callback", callback=check_order)
parser.add_option("-b", action="store_true", dest="b")

Callback example 3: check option order (generalized)

If you want to reuse this callback for several similar options (set a flag, but blow up if -b has already been seen), it needs a bit of work: the error message and the flag that it sets must be generalized.

def check_order(option, opt_str, value, parser):
    if parser.values.b:
        raise OptionValueError("can't use %s after -b" % opt_str)
    setattr(parser.values, option.dest, 1)
...
parser.add_option("-a", action="callback", callback=check_order, dest='a')
parser.add_option("-b", action="store_true", dest="b")
parser.add_option("-c", action="callback", callback=check_order, dest='c')

Callback example 4: check arbitrary condition

Of course, you could put any condition in there---you're not limited to checking the values of already-defined options. For example, if you have options that should not be called when the moon is full, all you have to do is this:

def check_moon(option, opt_str, value, parser):
    if is_moon_full():
        raise OptionValueError("%s option invalid when moon is full"
                               % opt_str)
    setattr(parser.values, option.dest, 1)
...
parser.add_option("--foo",
                  action="callback", callback=check_moon, dest="foo")

(The definition of is_moon_full() is left as an exercise for the reader.)

Callback example 5: fixed arguments

Things get slightly more interesting when you define callback options that take a fixed number of arguments. Specifying that a callback option takes arguments is similar to defining a "store" or "append" option: if you define type, then the option takes one argument that must be convertible to that type; if you further define nargs, then the option takes nargs arguments.

Here's an example that just emulates the standard "store" action:

def store_value(option, opt_str, value, parser):
    setattr(parser.values, option.dest, value)
...
parser.add_option("--foo",
                  action="callback", callback=store_value,
                  type="int", nargs=3, dest="foo")

Note that optparse takes care of consuming 3 arguments and converting them to integers for you; all you have to do is store them. (Or whatever; obviously you don't need a callback for this example.)

Callback example 6: variable arguments

Things get hairy when you want an option to take a variable number of arguments. For this case, you must write a callback, as optparse doesn't provide any built-in capabilities for it. And you have to deal with certain intricacies of conventional Unix command-line parsing that optparse normally handles for you. In particular, callbacks should implement the conventional rules for bare -- and - arguments:

either -- or - can be option arguments

bare -- (if not the argument to some option): halt command-line processing and discard the --

bare - (if not the argument to some option): halt command-line processing but keep the - (append it to parser.largs)

If you want an option that takes a variable number of arguments, there are several subtle, tricky issues to worry about. The exact implementation you choose will be based on which trade-offs you're willing to make for your application (which is why optparse doesn't support this sort of thing directly).

Nevertheless, here's a stab at a callback for an option with variable arguments:

def vararg_callback(option, opt_str, value, parser):
    assert value is None
    value = []

    def floatable(str):
        try:
            float(str)
            return True
        except ValueError:
            return False

    for arg in parser.rargs:
        # stop on --foo like options
        if arg[:2] == "--" and len(arg) > 2:
            break
        # stop on -a, but not on -3 or -3.0
        if arg[:1] == "-" and len(arg) > 1 and not floatable(arg):
            break
        value.append(arg)

    del parser.rargs[:len(value)]
    setattr(parser.values, option.dest, value)

...
parser.add_option("-c", "--callback", dest="vararg_attr",
                  action="callback", callback=vararg_callback)

Extending optparse

Since the two major controlling factors in how optparse interprets command-line options are the action and type of each option, the most likely direction of extension is to add new actions and new types.

Adding new types

To add new types, you need to define your own subclass of optparse's Option class. This class has a couple of attributes that define optparse's types: TYPES and TYPE_CHECKER.

Option.TYPES

A tuple of type names; in your subclass, simply define a new tuple TYPES that builds on the standard one.

Option.TYPE_CHECKER

A dictionary mapping type names to type-checking functions. A type-checking function has the following signature:

def check_mytype(option, opt, value)

where option is an Option instance, opt is an option string (e.g., -f), and value is the string from the command line that must be checked and converted to your desired type. check_mytype() should return an object of the hypothetical type mytype. The value returned by a type-checking function will wind up in the OptionValues instance returned by OptionParser.parse_args(), or be passed to a callback as the value parameter.

Your type-checking function should raise OptionValueError if it encounters any problems. OptionValueError takes a single string argument, which is passed as-is to OptionParser's error() method, which in turn prepends the program name and the string "error:" and prints everything to stderr before terminating the process.

Here's a silly example that demonstrates adding a "complex" option type to parse Python-style complex numbers on the command line. (This is even sillier than it used to be, because optparse 1.3 added built-in support for complex numbers, but never mind.)

First, the necessary imports:

from copy import copy
from optparse import Option, OptionValueError

You need to define your type-checker first, since it's referred to later (in the TYPE_CHECKER class attribute of your Option subclass):

def check_complex(option, opt, value):
    try:
        return complex(value)
    except ValueError:
        raise OptionValueError(
            "option %s: invalid complex value: %r" % (opt, value))

Finally, the Option subclass:

class MyOption (Option):
    TYPES = Option.TYPES + ("complex",)
    TYPE_CHECKER = copy(Option.TYPE_CHECKER)
    TYPE_CHECKER["complex"] = check_complex

(If we didn't make a copy() of Option.TYPE_CHECKER, we would end up modifying the TYPE_CHECKER attribute of optparse's Option class. This being Python, nothing stops you from doing that except good manners and common sense.)

That's it! Now you can write a script that uses the new option type just like any other optparse-based script, except you have to instruct your OptionParser to use MyOption instead of Option:

parser = OptionParser(option_class=MyOption)
parser.add_option("-c", type="complex")

Alternately, you can build your own option list and pass it to OptionParser; if you don't use add_option() in the above way, you don't need to tell OptionParser which option class to use:

option_list = [MyOption("-c", action="store", type="complex", dest="c")]
parser = OptionParser(option_list=option_list)

Adding new actions

Adding new actions is a bit trickier, because you have to understand that optparse has a couple of classifications for actions:

"store" actions

actions that result in optparse storing a value to an attribute of the current OptionValues instance; these options require a dest attribute to be supplied to the Option constructor.

"typed" actions

actions that take a value from the command line and expect it to be of a certain type; or rather, a string that can be converted to a certain type. These options require a type attribute to the Option constructor.

These are overlapping sets: some default "store" actions are "store", "store_const", "append", and "count", while the default "typed" actions are "store", "append", and "callback".

When you add an action, you need to categorize it by listing it in at least one of the following class attributes of Option (all are lists of strings):

Option.ACTIONS

All actions must be listed in ACTIONS.

Option.STORE_ACTIONS

"store" actions are additionally listed here.

Option.TYPED_ACTIONS

"typed" actions are additionally listed here.

Option.ALWAYS_TYPED_ACTIONS

Actions that always take a type (i.e. whose options always take a value) are additionally listed here. The only effect of this is that optparse assigns the default type, "string", to options with no explicit type whose action is listed in ALWAYS_TYPED_ACTIONS.

In order to actually implement your new action, you must override Option's take_action() method and add a case that recognizes your action.

For example, let's add an "extend" action. This is similar to the standard "append" action, but instead of taking a single value from the command-line and appending it to an existing list, "extend" will take multiple values in a single comma-delimited string, and extend an existing list with them. That is, if --names is an "extend" option of type "string", the command line

--names=foo,bar --names blah --names ding,dong

would result in a list

["foo", "bar", "blah", "ding", "dong"]

Again we define a subclass of Option:

class MyOption(Option):

    ACTIONS = Option.ACTIONS + ("extend",)
    STORE_ACTIONS = Option.STORE_ACTIONS + ("extend",)
    TYPED_ACTIONS = Option.TYPED_ACTIONS + ("extend",)
    ALWAYS_TYPED_ACTIONS = Option.ALWAYS_TYPED_ACTIONS + ("extend",)

    def take_action(self, action, dest, opt, value, values, parser):
        if action == "extend":
            lvalue = value.split(",")
            values.ensure_value(dest, []).extend(lvalue)
        else:
            Option.take_action(
                self, action, dest, opt, value, values, parser)

Features of note:

"extend" both expects a value on the command-line and stores that value somewhere, so it goes in both STORE_ACTIONS and TYPED_ACTIONS.

to ensure that optparse assigns the default type of "string" to "extend" actions, we put the "extend" action in ALWAYS_TYPED_ACTIONS as well.

MyOption.take_action() implements just this one new action, and passes control back to Option.take_action() for the standard optparse actions.

values is an instance of the optparse_parser.Values class, which provides the very useful ensure_value() method. ensure_value() is essentially getattr() with a safety valve; it is called as

values.ensure_value(attr, value)

If the attr attribute of values doesn't exist or is None, then ensure_value() first sets it to value, and then returns value. This is very handy for actions like "extend", "append", and "count", all of which accumulate data in a variable and expect that variable to be of a certain type (a list for the first two, an integer for the latter). Using ensure_value() means that scripts using your action don't have to worry about setting a default value for the option destinations in question; they can just leave the default as None and ensure_value() will take care of getting it right when it's needed.

例外

exception optparse.OptionError

Raised if an Option instance is created with invalid or inconsistent arguments.

exception optparse.OptionConflictError

Raised if conflicting options are added to an OptionParser.

exception optparse.OptionValueError

Raised if an invalid option value is encountered on the command line.

exception optparse.BadOptionError

Raised if an invalid option is passed on the command line.

exception optparse.AmbiguousOptionError

Raised if an ambiguous option is passed on the command line.

getpass --- 可攜式密碼輸入工具

原始碼：Lib/getpass.py [https://github.com/python/cpython/tree/3.14/Lib/getpass.py]

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

getpass 模組 (module) 提供了兩個函式：

getpass.getpass(prompt='Password: ', stream=None, *, echo_char=None)

提示使用者輸入一個密碼且不會有回音 (echo)。使用者會看到字串 prompt 作為提示，其預設值為 'Password: '。在 Unix 上，如有必要的話會使用替換錯誤處理函式 (replace error handler) 寫入到類檔案物件 (file-like object) stream中。stream 預設為主控終端機 (controlling terminal) (/dev/tty)，如果不可用則為 sys.stderr (此引數在 Windows 上會被忽略)。

The echo_char argument controls how user input is displayed while typing. If echo_char is None (default), input remains hidden. Otherwise, echo_char must be a single printable ASCII character and each typed character is replaced by it. For example, echo_char='*' will display asterisks instead of the actual input.

如果無回音輸入 (echo-free input) 無法使用則 getpass() 將回退為印出一條警告訊息到 stream，並從 sys.stdin 讀取且同時發出 GetPassWarning。

備註

如果你從 IDLE 內部呼叫 getpass，輸入可能會在你啟動 IDLE 的終端機中完成，而非在 IDLE 視窗中。

備註

On Unix systems, when echo_char is set, the terminal will be configured to operate in noncanonical mode [https://manpages.debian.org/termios(3)#Canonical_and_noncanonical_mode]. In particular, this means that line editing shortcuts such as Ctrl+U will not work and may insert unexpected characters into the input.

在 3.14 版的變更: Added the echo_char parameter for keyboard feedback.

exception getpass.GetPassWarning

當密碼輸入可能被回音時會發出的 UserWarning 子類別。

getpass.getuser()

回傳使用者的"登入名稱"。

此函式會按順序檢查環境變數 LOGNAME、USER、LNAME 和 USERNAME，並回傳其中第一個被設定成非空字串的值。如果均未設定，則在支援 pwd 模組的系統上將會回傳來自密碼資料庫的登入名稱，否則將引發一個 OSError 例外。

大部分情況下，此函式應該要比 os.getlogin() 優先使用。

在 3.13 版的變更: 在過去，除了 OSError 外還會引發各種例外。

fileinput --- 逐列疊代多個輸入串流

原始碼：Lib/fileinput.py [https://github.com/python/cpython/tree/3.14/Lib/fileinput.py]

This module implements a helper class and functions to quickly write a loop over standard input or a list of files. If you just want to read or write one file see open().

The typical use is:

import fileinput
for line in fileinput.input(encoding="utf-8"):
    process(line)

This iterates over the lines of all files listed in sys.argv[1:], defaulting to sys.stdin if the list is empty. If a filename is '-', it is also replaced by sys.stdin and the optional arguments mode and openhook are ignored. To specify an alternative list of filenames, pass it as the first argument to input(). A single file name is also allowed.

All files are opened in text mode by default, but you can override this by specifying the mode parameter in the call to input() or FileInput. If an I/O error occurs during opening or reading a file, OSError is raised.

在 3.3 版的變更: IOError 曾經被引發；現在它是一個 OSError 的別名。

If sys.stdin is used more than once, the second and further use will return no lines, except perhaps for interactive use, or if it has been explicitly reset (e.g. using sys.stdin.seek(0)).

Empty files are opened and immediately closed; the only time their presence in the list of filenames is noticeable at all is when the last file opened is empty.

Lines are returned with any newlines intact, which means that the last line in a file may not have one.

You can control how files are opened by providing an opening hook via the openhook parameter to fileinput.input() or FileInput(). The hook must be a function that takes two arguments, filename and mode, and returns an accordingly opened file-like object. If encoding and/or errors are specified, they will be passed to the hook as additional keyword arguments. This module provides a hook_compressed() to support compressed files.

The following function is the primary interface of this module:

fileinput.input(files=None, inplace=False, backup='', *, mode='r', openhook=None, encoding=None, errors=None)

Create an instance of the FileInput class. The instance will be used as global state for the functions of this module, and is also returned to use during iteration. The parameters to this function will be passed along to the constructor of the FileInput class.

The FileInput instance can be used as a context manager in the with statement. In this example, input is closed after the with statement is exited, even if an exception occurs:

with fileinput.input(files=('spam.txt', 'eggs.txt'), encoding="utf-8") as f:
    for line in f:
        process(line)

在 3.2 版的變更: Can be used as a context manager.

在 3.8 版的變更: The keyword parameters mode and openhook are now keyword-only.

在 3.10 版的變更: The keyword-only parameter encoding and errors are added.

The following functions use the global state created by fileinput.input(); if there is no active state, RuntimeError is raised.

fileinput.filename()

Return the name of the file currently being read. Before the first line has been read, returns None.

fileinput.fileno()

Return the integer "file descriptor" for the current file. When no file is opened (before the first line and between files), returns -1.

fileinput.lineno()

Return the cumulative line number of the line that has just been read. Before the first line has been read, returns 0. After the last line of the last file has been read, returns the line number of that line.

fileinput.filelineno()

Return the line number in the current file. Before the first line has been read, returns 0. After the last line of the last file has been read, returns the line number of that line within the file.

fileinput.isfirstline()

Return True if the line just read is the first line of its file, otherwise return False.

fileinput.isstdin()

Return True if the last line was read from sys.stdin, otherwise return False.

fileinput.nextfile()

Close the current file so that the next iteration will read the first line from the next file (if any); lines not read from the file will not count towards the cumulative line count. The filename is not changed until after the first line of the next file has been read. Before the first line has been read, this function has no effect; it cannot be used to skip the first file. After the last line of the last file has been read, this function has no effect.

fileinput.close()

Close the sequence.

The class which implements the sequence behavior provided by the module is available for subclassing as well:

class fileinput.FileInput(files=None, inplace=False, backup='', *, mode='r', openhook=None, encoding=None, errors=None)

Class FileInput is the implementation; its methods filename(), fileno(), lineno(), filelineno(), isfirstline(), isstdin(), nextfile() and close() correspond to the functions of the same name in the module. In addition it is iterable and has a readline() method which returns the next input line. The sequence must be accessed in strictly sequential order; random access and readline() cannot be mixed.

With mode you can specify which file mode will be passed to open(). It must be one of 'r' and 'rb'.

The openhook, when given, must be a function that takes two arguments, filename and mode, and returns an accordingly opened file-like object. You cannot use inplace and openhook together.

You can specify encoding and errors that is passed to open() or openhook.

A FileInput instance can be used as a context manager in the with statement. In this example, input is closed after the with statement is exited, even if an exception occurs:

with FileInput(files=('spam.txt', 'eggs.txt')) as input:
    process(input)

在 3.2 版的變更: Can be used as a context manager.

在 3.8 版的變更: The keyword parameter mode and openhook are now keyword-only.

在 3.10 版的變更: The keyword-only parameter encoding and errors are added.

在 3.11 版的變更: The 'rU' and 'U' modes and the __getitem__() method have been removed.

Optional in-place filtering: if the keyword argument inplace=True is passed to fileinput.input() or to the FileInput constructor, the file is moved to a backup file and standard output is directed to the input file (if a file of the same name as the backup file already exists, it will be replaced silently). This makes it possible to write a filter that rewrites its input file in place. If the backup parameter is given (typically as backup='.<some extension>'), it specifies the extension for the backup file, and the backup file remains around; by default, the extension is '.bak' and it is deleted when the output file is closed. In-place filtering is disabled when standard input is read.

The two following opening hooks are provided by this module:

fileinput.hook_compressed(filename, mode, *, encoding=None, errors=None)

Transparently opens files compressed with gzip and bzip2 (recognized by the extensions '.gz' and '.bz2') using the gzip and bz2 modules. If the filename extension is not '.gz' or '.bz2', the file is opened normally (ie, using open() without any decompression).

The encoding and errors values are passed to io.TextIOWrapper for compressed files and open for normal files.

Usage example: fi = fileinput.FileInput(openhook=fileinput.hook_compressed, encoding="utf-8")

在 3.10 版的變更: The keyword-only parameter encoding and errors are added.

fileinput.hook_encoded(encoding, errors=None)

Returns a hook which opens each file with open(), using the given encoding and errors to read the file.

Usage example: fi = fileinput.FileInput(openhook=fileinput.hook_encoded("utf-8", "surrogateescape"))

在 3.6 版的變更: 新增可選參數 errors。

在 3.10 版之後被棄用: This function is deprecated since fileinput.input() and FileInput now have encoding and errors parameters.

curses --- 字元儲存格顯示的終端處理

原始碼：Lib/curses [https://github.com/python/cpython/tree/3.14/Lib/curses]

The curses module provides an interface to the curses library, the de-facto standard for portable advanced terminal handling.

While curses is most widely used in the Unix environment, versions are available for Windows, DOS, and possibly other systems as well. This extension module is designed to match the API of ncurses, an open-source curses library hosted on Linux and the BSD variants of Unix.

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

備註

Whenever the documentation mentions a character it can be specified as an integer, a one-character Unicode string or a one-byte byte string.

Whenever the documentation mentions a character string it can be specified as a Unicode string or a byte string.

也參考

curses.ascii 模組

Utilities for working with ASCII characters, regardless of your locale settings.

curses.panel 模組

A panel stack extension that adds depth to curses windows.

curses.textpad 模組

Editable text widget for curses supporting Emacs-like bindings.

Curses Programming with Python

Tutorial material on using curses with Python, by Andrew Kuchling and Eric Raymond.

函式

curses 模組定義了以下例外：

exception curses.error

Exception raised when a curses library function returns an error.

備註

Whenever x or y arguments to a function or a method are optional, they default to the current cursor location. Whenever attr is optional, it defaults to A_NORMAL.

curses 模組定義了以下函式：

curses.assume_default_colors(fg, bg, /)

Allow use of default values for colors on terminals supporting this feature. Use this to support transparency in your application.

Assign terminal default foreground/background colors to color number -1. So init_pair(x, COLOR_RED, -1) will initialize pair x as red on default background and init_pair(x, -1, COLOR_BLUE) will initialize pair x as default foreground on blue.

Change the definition of the color-pair 0 to (fg, bg).

在 3.14 版被加入.

curses.baudrate()

Return the output speed of the terminal in bits per second. On software terminal emulators it will have a fixed high value. Included for historical reasons; in former times, it was used to write output loops for time delays and occasionally to change interfaces depending on the line speed.

curses.beep()

Emit a short attention sound.

curses.can_change_color()

Return True or False, depending on whether the programmer can change the colors displayed by the terminal.

curses.cbreak()

Enter cbreak mode. In cbreak mode (sometimes called "rare" mode) normal tty line buffering is turned off and characters are available to be read one by one. However, unlike raw mode, special characters (interrupt, quit, suspend, and flow control) retain their effects on the tty driver and calling program. Calling first raw() then cbreak() leaves the terminal in cbreak mode.

curses.color_content(color_number)

Return the intensity of the red, green, and blue (RGB) components in the color color_number, which must be between 0 and COLORS - 1. Return a 3-tuple, containing the R,G,B values for the given color, which will be between 0 (no component) and 1000 (maximum amount of component).

curses.color_pair(pair_number)

Return the attribute value for displaying text in the specified color pair. Only the first 256 color pairs are supported. This attribute value can be combined with A_STANDOUT, A_REVERSE, and the other A_* attributes. pair_number() is the counterpart to this function.

curses.curs_set(visibility)

Set the cursor state. visibility can be set to 0, 1, or 2, for invisible, normal, or very visible. If the terminal supports the visibility requested, return the previous cursor state; otherwise raise an exception. On many terminals, the "visible" mode is an underline cursor and the "very visible" mode is a block cursor.

curses.def_prog_mode()

Save the current terminal mode as the "program" mode, the mode when the running program is using curses. (Its counterpart is the "shell" mode, for when the program is not in curses.) Subsequent calls to reset_prog_mode() will restore this mode.

curses.def_shell_mode()

Save the current terminal mode as the "shell" mode, the mode when the running program is not using curses. (Its counterpart is the "program" mode, when the program is using curses capabilities.) Subsequent calls to reset_shell_mode() will restore this mode.

curses.delay_output(ms)

Insert an ms millisecond pause in output.

curses.doupdate()

Update the physical screen. The curses library keeps two data structures, one representing the current physical screen contents and a virtual screen representing the desired next state. The doupdate() ground updates the physical screen to match the virtual screen.

The virtual screen may be updated by a noutrefresh() call after write operations such as addstr() have been performed on a window. The normal refresh() call is simply noutrefresh() followed by doupdate(); if you have to update multiple windows, you can speed performance and perhaps reduce screen flicker by issuing noutrefresh() calls on all windows, followed by a single doupdate().

curses.echo()

Enter echo mode. In echo mode, each character input is echoed to the screen as it is entered.

curses.endwin()

De-initialize the library, and return terminal to normal status.

curses.erasechar()

Return the user's current erase character as a one-byte bytes object. Under Unix operating systems this is a property of the controlling tty of the curses program, and is not set by the curses library itself.

curses.filter()

The filter() routine, if used, must be called before initscr() is called. The effect is that, during those calls, LINES is set to 1; the capabilities clear, cup, cud, cud1, cuu1, cuu, vpa are disabled; and the home string is set to the value of cr. The effect is that the cursor is confined to the current line, and so are screen updates. This may be used for enabling character-at-a-time line editing without touching the rest of the screen.

curses.flash()

Flash the screen. That is, change it to reverse-video and then change it back in a short interval. Some people prefer such as 'visible bell' to the audible attention signal produced by beep().

curses.flushinp()

Flush all input buffers. This throws away any typeahead that has been typed by the user and has not yet been processed by the program.

curses.getmouse()

After getch() returns KEY_MOUSE to signal a mouse event, this method should be called to retrieve the queued mouse event, represented as a 5-tuple (id, x, y, z, bstate). id is an ID value used to distinguish multiple devices, and x, y, z are the event's coordinates. (z is currently unused.) bstate is an integer value whose bits will be set to indicate the type of event, and will be the bitwise OR of one or more of the following constants, where n is the button number from 1 to 5: BUTTONn_PRESSED, BUTTONn_RELEASED, BUTTONn_CLICKED, BUTTONn_DOUBLE_CLICKED, BUTTONn_TRIPLE_CLICKED, BUTTON_SHIFT, BUTTON_CTRL, BUTTON_ALT.

在 3.10 版的變更: The BUTTON5_* constants are now exposed if they are provided by the underlying curses library.

curses.getsyx()

Return the current coordinates of the virtual screen cursor as a tuple (y, x). If leaveok is currently True, then return (-1, -1).

curses.getwin(file)

Read window related data stored in the file by an earlier window.putwin() call. The routine then creates and initializes a new window using that data, returning the new window object.

curses.has_colors()

Return True if the terminal can display colors; otherwise, return False.

curses.has_extended_color_support()

Return True if the module supports extended colors; otherwise, return False. Extended color support allows more than 256 color pairs for terminals that support more than 16 colors (e.g. xterm-256color).

Extended color support requires ncurses version 6.1 or later.

在 3.10 版被加入.

curses.has_ic()

Return True if the terminal has insert- and delete-character capabilities. This function is included for historical reasons only, as all modern software terminal emulators have such capabilities.

curses.has_il()

Return True if the terminal has insert- and delete-line capabilities, or can simulate them using scrolling regions. This function is included for historical reasons only, as all modern software terminal emulators have such capabilities.

curses.has_key(ch)

Take a key value ch, and return True if the current terminal type recognizes a key with that value.

curses.halfdelay(tenths)

Used for half-delay mode, which is similar to cbreak mode in that characters typed by the user are immediately available to the program. However, after blocking for tenths tenths of seconds, raise an exception if nothing has been typed. The value of tenths must be a number between 1 and 255. Use nocbreak() to leave half-delay mode.

curses.init_color(color_number, r, g, b)

Change the definition of a color, taking the number of the color to be changed followed by three RGB values (for the amounts of red, green, and blue components). The value of color_number must be between 0 and COLORS - 1. Each of r, g, b, must be a value between 0 and 1000. When init_color() is used, all occurrences of that color on the screen immediately change to the new definition. This function is a no-op on most terminals; it is active only if can_change_color() returns True.

curses.init_pair(pair_number, fg, bg)

Change the definition of a color-pair. It takes three arguments: the number of the color-pair to be changed, the foreground color number, and the background color number. The value of pair_number must be between 1 and COLOR_PAIRS - 1 (the 0 color pair can only be changed by use_default_colors() and assume_default_colors()). The value of fg and bg arguments must be between 0 and COLORS - 1, or, after calling use_default_colors() or assume_default_colors(), -1. If the color-pair was previously initialized, the screen is refreshed and all occurrences of that color-pair are changed to the new definition.

curses.initscr()

Initialize the library. Return a window object which represents the whole screen.

備註

If there is an error opening the terminal, the underlying curses library may cause the interpreter to exit.

curses.is_term_resized(nlines, ncols)

Return True if resize_term() would modify the window structure, False otherwise.

curses.isendwin()

Return True if endwin() has been called (that is, the curses library has been deinitialized).

curses.keyname(k)

Return the name of the key numbered k as a bytes object. The name of a key generating printable ASCII character is the key's character. The name of a control-key combination is a two-byte bytes object consisting of a caret (b'^') followed by the corresponding printable ASCII character. The name of an alt-key combination (128--255) is a bytes object consisting of the prefix b'M-' followed by the name of the corresponding ASCII character.

curses.killchar()

Return the user's current line kill character as a one-byte bytes object. Under Unix operating systems this is a property of the controlling tty of the curses program, and is not set by the curses library itself.

curses.longname()

Return a bytes object containing the terminfo long name field describing the current terminal. The maximum length of a verbose description is 128 characters. It is defined only after the call to initscr().

curses.meta(flag)

If flag is True, allow 8-bit characters to be input. If flag is False, allow only 7-bit chars.

curses.mouseinterval(interval)

Set the maximum time in milliseconds that can elapse between press and release events in order for them to be recognized as a click, and return the previous interval value. The default value is 200 milliseconds, or one fifth of a second.

curses.mousemask(mousemask)

Set the mouse events to be reported, and return a tuple (availmask, oldmask). availmask indicates which of the specified mouse events can be reported; on complete failure it returns 0. oldmask is the previous value of the given window's mouse event mask. If this function is never called, no mouse events are ever reported.

curses.napms(ms)

Sleep for ms milliseconds.

curses.newpad(nlines, ncols)

Create and return a pointer to a new pad data structure with the given number of lines and columns. Return a pad as a window object.

A pad is like a window, except that it is not restricted by the screen size, and is not necessarily associated with a particular part of the screen. Pads can be used when a large window is needed, and only a part of the window will be on the screen at one time. Automatic refreshes of pads (such as from scrolling or echoing of input) do not occur. The refresh() and noutrefresh() methods of a pad require 6 arguments to specify the part of the pad to be displayed and the location on the screen to be used for the display. The arguments are pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol; the p arguments refer to the upper left corner of the pad region to be displayed and the s arguments define a clipping box on the screen within which the pad region is to be displayed.

curses.newwin(nlines, ncols)

curses.newwin(nlines, ncols, begin_y, begin_x)

Return a new window, whose left-upper corner is at (begin_y, begin_x), and whose height/width is nlines/ncols.

By default, the window will extend from the specified position to the lower right corner of the screen.

curses.nl()

Enter newline mode. This mode translates the return key into newline on input, and translates newline into return and line-feed on output. Newline mode is initially on.

curses.nocbreak()

Leave cbreak mode. Return to normal "cooked" mode with line buffering.

curses.noecho()

Leave echo mode. Echoing of input characters is turned off.

curses.nonl()

Leave newline mode. Disable translation of return into newline on input, and disable low-level translation of newline into newline/return on output (but this does not change the behavior of addch('\n'), which always does the equivalent of return and line feed on the virtual screen). With translation off, curses can sometimes speed up vertical motion a little; also, it will be able to detect the return key on input.

curses.noqiflush()

When the noqiflush() routine is used, normal flush of input and output queues associated with the INTR, QUIT and SUSP characters will not be done. You may want to call noqiflush() in a signal handler if you want output to continue as though the interrupt had not occurred, after the handler exits.

curses.noraw()

Leave raw mode. Return to normal "cooked" mode with line buffering.

curses.pair_content(pair_number)

Return a tuple (fg, bg) containing the colors for the requested color pair. The value of pair_number must be between 0 and COLOR_PAIRS - 1.

curses.pair_number(attr)

Return the number of the color-pair set by the attribute value attr. color_pair() is the counterpart to this function.

curses.putp(str)

Equivalent to tputs(str, 1, putchar); emit the value of a specified terminfo capability for the current terminal. Note that the output of putp() always goes to standard output.

curses.qiflush([flag])

If flag is False, the effect is the same as calling noqiflush(). If flag is True, or no argument is provided, the queues will be flushed when these control characters are read.

curses.raw()

Enter raw mode. In raw mode, normal line buffering and processing of interrupt, quit, suspend, and flow control keys are turned off; characters are presented to curses input functions one by one.

curses.reset_prog_mode()

Restore the terminal to "program" mode, as previously saved by def_prog_mode().

curses.reset_shell_mode()

Restore the terminal to "shell" mode, as previously saved by def_shell_mode().

curses.resetty()

Restore the state of the terminal modes to what it was at the last call to savetty().

curses.resize_term(nlines, ncols)

Backend function used by resizeterm(), performing most of the work; when resizing the windows, resize_term() blank-fills the areas that are extended. The calling application should fill in these areas with appropriate data. The resize_term() function attempts to resize all windows. However, due to the calling convention of pads, it is not possible to resize these without additional interaction with the application.

curses.resizeterm(nlines, ncols)

Resize the standard and current windows to the specified dimensions, and adjusts other bookkeeping data used by the curses library that record the window dimensions (in particular the SIGWINCH handler).

curses.savetty()

Save the current state of the terminal modes in a buffer, usable by resetty().

curses.get_escdelay()

Retrieves the value set by set_escdelay().

在 3.9 版被加入.

curses.set_escdelay(ms)

Sets the number of milliseconds to wait after reading an escape character, to distinguish between an individual escape character entered on the keyboard from escape sequences sent by cursor and function keys.

在 3.9 版被加入.

curses.get_tabsize()

Retrieves the value set by set_tabsize().

在 3.9 版被加入.

curses.set_tabsize(size)

Sets the number of columns used by the curses library when converting a tab character to spaces as it adds the tab to a window.

在 3.9 版被加入.

curses.setsyx(y, x)

Set the virtual screen cursor to y, x. If y and x are both -1, then leaveok is set True.

curses.setupterm(term=None, fd=-1)

Initialize the terminal. term is a string giving the terminal name, or None; if omitted or None, the value of the TERM environment variable will be used. fd is the file descriptor to which any initialization sequences will be sent; if not supplied or -1, the file descriptor for sys.stdout will be used.

curses.start_color()

Must be called if the programmer wants to use colors, and before any other color manipulation routine is called. It is good practice to call this routine right after initscr().

start_color() initializes eight basic colors (black, red, green, yellow, blue, magenta, cyan, and white), and two global variables in the curses module, COLORS and COLOR_PAIRS, containing the maximum number of colors and color-pairs the terminal can support. It also restores the colors on the terminal to the values they had when the terminal was just turned on.

curses.termattrs()

Return a logical OR of all video attributes supported by the terminal. This information is useful when a curses program needs complete control over the appearance of the screen.

curses.termname()

Return the value of the environment variable TERM, as a bytes object, truncated to 14 characters.

curses.tigetflag(capname)

Return the value of the Boolean capability corresponding to the terminfo capability name capname as an integer. Return the value -1 if capname is not a Boolean capability, or 0 if it is canceled or absent from the terminal description.

curses.tigetnum(capname)

Return the value of the numeric capability corresponding to the terminfo capability name capname as an integer. Return the value -2 if capname is not a numeric capability, or -1 if it is canceled or absent from the terminal description.

curses.tigetstr(capname)

Return the value of the string capability corresponding to the terminfo capability name capname as a bytes object. Return None if capname is not a terminfo "string capability", or is canceled or absent from the terminal description.

curses.tparm(str[, ...])

Instantiate the bytes object str with the supplied parameters, where str should be a parameterized string obtained from the terminfo database. E.g. tparm(tigetstr("cup"), 5, 3) could result in b'\033[6;4H', the exact result depending on terminal type.

curses.typeahead(fd)

Specify that the file descriptor fd be used for typeahead checking. If fd is -1, then no typeahead checking is done.

The curses library does "line-breakout optimization" by looking for typeahead periodically while updating the screen. If input is found, and it is coming from a tty, the current update is postponed until refresh or doupdate is called again, allowing faster response to commands typed in advance. This function allows specifying a different file descriptor for typeahead checking.

curses.unctrl(ch)

Return a bytes object which is a printable representation of the character ch. Control characters are represented as a caret followed by the character, for example as b'^C'. Printing characters are left as they are.

curses.ungetch(ch)

Push ch so the next getch() will return it.

備註

Only one ch can be pushed before getch() is called.

curses.update_lines_cols()

Update the LINES and COLS module variables. Useful for detecting manual screen resize.

在 3.5 版被加入.

curses.unget_wch(ch)

Push ch so the next get_wch() will return it.

備註

Only one ch can be pushed before get_wch() is called.

在 3.3 版被加入.

curses.ungetmouse(id, x, y, z, bstate)

Push a KEY_MOUSE event onto the input queue, associating the given state data with it.

curses.use_env(flag)

If used, this function should be called before initscr() or newterm are called. When flag is False, the values of lines and columns specified in the terminfo database will be used, even if environment variables LINES and COLUMNS (used by default) are set, or if curses is running in a window (in which case default behavior would be to use the window size if LINES and COLUMNS are not set).

curses.use_default_colors()

Equivalent to assume_default_colors(-1, -1).

curses.wrapper(func, /, *args, **kwargs)

Initialize curses and call another callable object, func, which should be the rest of your curses-using application. If the application raises an exception, this function will restore the terminal to a sane state before re-raising the exception and generating a traceback. The callable object func is then passed the main window 'stdscr' as its first argument, followed by any other arguments passed to wrapper(). Before calling func, wrapper() turns on cbreak mode, turns off echo, enables the terminal keypad, and initializes colors if the terminal has color support. On exit (whether normally or by exception) it restores cooked mode, turns on echo, and disables the terminal keypad.

Window Objects

class curses.window

Window objects, as returned by initscr() and newwin() above, have the following methods and attributes:

window.addch(ch[, attr])

window.addch(y, x, ch[, attr])

Paint character ch at (y, x) with attributes attr, overwriting any character previously painted at that location. By default, the character position and attributes are the current settings for the window object.

備註

Writing outside the window, subwindow, or pad raises a curses.error. Attempting to write to the lower right corner of a window, subwindow, or pad will cause an exception to be raised after the character is printed.

window.addnstr(str, n[, attr])

window.addnstr(y, x, str, n[, attr])

Paint at most n characters of the character string str at (y, x) with attributes attr, overwriting anything previously on the display.

window.addstr(str[, attr])

window.addstr(y, x, str[, attr])

Paint the character string str at (y, x) with attributes attr, overwriting anything previously on the display.

備註

Writing outside the window, subwindow, or pad raises curses.error. Attempting to write to the lower right corner of a window, subwindow, or pad will cause an exception to be raised after the string is printed.

A bug in ncurses [https://bugs.python.org/issue35924], the backend for this Python module, can cause SegFaults when resizing windows. This is fixed in ncurses-6.1-20190511. If you are stuck with an earlier ncurses, you can avoid triggering this if you do not call addstr() with a str that has embedded newlines. Instead, call addstr() separately for each line.

window.attroff(attr)

Remove attribute attr from the "background" set applied to all writes to the current window.

window.attron(attr)

Add attribute attr to the "background" set applied to all writes to the current window.

window.attrset(attr)

Set the "background" set of attributes to attr. This set is initially 0 (no attributes).

window.bkgd(ch[, attr])

Set the background property of the window to the character ch, with attributes attr. The change is then applied to every character position in that window:

The attribute of every character in the window is changed to the new background attribute.

Wherever the former background character appears, it is changed to the new background character.

window.bkgdset(ch[, attr])

Set the window's background. A window's background consists of a character and any combination of attributes. The attribute part of the background is combined (OR'ed) with all non-blank characters that are written into the window. Both the character and attribute parts of the background are combined with the blank characters. The background becomes a property of the character and moves with the character through any scrolling and insert/delete line/character operations.

window.border([ls[, rs[, ts[, bs[, tl[, tr[, bl[, br]]]]]]]])

Draw a border around the edges of the window. Each parameter specifies the character to use for a specific part of the border; see the table below for more details.

備註

A 0 value for any parameter will cause the default character to be used for that parameter. Keyword parameters can not be used. The defaults are listed in this table:

參數

描述

預設值

ls

Left side

ACS_VLINE

rs

Right side

ACS_VLINE

ts

Top

ACS_HLINE

bs

Bottom

ACS_HLINE

tl

Upper-left corner

ACS_ULCORNER

tr

Upper-right corner

ACS_URCORNER

bl

Bottom-left corner

ACS_LLCORNER

br

Bottom-right corner

ACS_LRCORNER

window.box([vertch, horch])

Similar to border(), but both ls and rs are vertch and both ts and bs are horch. The default corner characters are always used by this function.

window.chgat(attr)

window.chgat(num, attr)

window.chgat(y, x, attr)

window.chgat(y, x, num, attr)

Set the attributes of num characters at the current cursor position, or at position (y, x) if supplied. If num is not given or is -1, the attribute will be set on all the characters to the end of the line. This function moves cursor to position (y, x) if supplied. The changed line will be touched using the touchline() method so that the contents will be redisplayed by the next window refresh.

window.clear()

Like erase(), but also cause the whole window to be repainted upon next call to refresh().

window.clearok(flag)

If flag is True, the next call to refresh() will clear the window completely.

window.clrtobot()

Erase from cursor to the end of the window: all lines below the cursor are deleted, and then the equivalent of clrtoeol() is performed.

window.clrtoeol()

Erase from cursor to the end of the line.

window.cursyncup()

Update the current cursor position of all the ancestors of the window to reflect the current cursor position of the window.

window.delch([y, x])

Delete any character at (y, x).

window.deleteln()

Delete the line under the cursor. All following lines are moved up by one line.

window.derwin(begin_y, begin_x)

window.derwin(nlines, ncols, begin_y, begin_x)

An abbreviation for "derive window", derwin() is the same as calling subwin(), except that begin_y and begin_x are relative to the origin of the window, rather than relative to the entire screen. Return a window object for the derived window.

window.echochar(ch[, attr])

Add character ch with attribute attr, and immediately call refresh() on the window.

window.enclose(y, x)

Test whether the given pair of screen-relative character-cell coordinates are enclosed by the given window, returning True or False. It is useful for determining what subset of the screen windows enclose the location of a mouse event.

在 3.10 版的變更: Previously it returned 1 or 0 instead of True or False.

window.encoding

Encoding used to encode method arguments (Unicode strings and characters). The encoding attribute is inherited from the parent window when a subwindow is created, for example with window.subwin(). By default, current locale encoding is used (see locale.getencoding()).

在 3.3 版被加入.

window.erase()

清除視窗。

window.getbegyx()

回傳左上角的座標 (y, x)。

window.getbkgd()

回傳給定視窗目前的背景字元/屬性對。

window.getch([y, x])

Get a character. Note that the integer returned does not have to be in ASCII range: function keys, keypad keys and so on are represented by numbers higher than 255. In no-delay mode, return -1 if there is no input, otherwise wait until a key is pressed.

window.get_wch([y, x])

Get a wide character. Return a character for most keys, or an integer for function keys, keypad keys, and other special keys. In no-delay mode, raise an exception if there is no input.

在 3.3 版被加入.

window.getkey([y, x])

Get a character, returning a string instead of an integer, as getch() does. Function keys, keypad keys and other special keys return a multibyte string containing the key name. In no-delay mode, raise an exception if there is no input.

window.getmaxyx()

回傳視窗的高度和寬度的元組 (y, x)。

window.getparyx()

Return the beginning coordinates of this window relative to its parent window as a tuple (y, x). Return (-1, -1) if this window has no parent.

window.getstr()

window.getstr(n)

window.getstr(y, x)

window.getstr(y, x, n)

Read a bytes object from the user, with primitive line editing capacity. The maximum value for n is 2047.

在 3.14 版的變更: The maximum value for n was increased from 1023 to 2047.

window.getyx()

Return a tuple (y, x) of current cursor position relative to the window's upper-left corner.

window.hline(ch, n)

window.hline(y, x, ch, n)

Display a horizontal line starting at (y, x) with length n consisting of the character ch.

window.idcok(flag)

If flag is False, curses no longer considers using the hardware insert/delete character feature of the terminal; if flag is True, use of character insertion and deletion is enabled. When curses is first initialized, use of character insert/delete is enabled by default.

window.idlok(flag)

If flag is True, curses will try and use hardware line editing facilities. Otherwise, line insertion/deletion are disabled.

window.immedok(flag)

If flag is True, any change in the window image automatically causes the window to be refreshed; you no longer have to call refresh() yourself. However, it may degrade performance considerably, due to repeated calls to wrefresh. This option is disabled by default.

window.inch([y, x])

Return the character at the given position in the window. The bottom 8 bits are the character proper, and upper bits are the attributes.

window.insch(ch[, attr])

window.insch(y, x, ch[, attr])

Paint character ch at (y, x) with attributes attr, moving the line from position x right by one character.

window.insdelln(nlines)

Insert nlines lines into the specified window above the current line. The nlines bottom lines are lost. For negative nlines, delete nlines lines starting with the one under the cursor, and move the remaining lines up. The bottom nlines lines are cleared. The current cursor position remains the same.

window.insertln()

Insert a blank line under the cursor. All following lines are moved down by one line.

window.insnstr(str, n[, attr])

window.insnstr(y, x, str, n[, attr])

Insert a character string (as many characters as will fit on the line) before the character under the cursor, up to n characters. If n is zero or negative, the entire string is inserted. All characters to the right of the cursor are shifted right, with the rightmost characters on the line being lost. The cursor position does not change (after moving to y, x, if specified).

window.insstr(str[, attr])

window.insstr(y, x, str[, attr])

Insert a character string (as many characters as will fit on the line) before the character under the cursor. All characters to the right of the cursor are shifted right, with the rightmost characters on the line being lost. The cursor position does not change (after moving to y, x, if specified).

window.instr([n])

window.instr(y, x[, n])

Return a bytes object of characters, extracted from the window starting at the current cursor position, or at y, x if specified. Attributes are stripped from the characters. If n is specified, instr() returns a string at most n characters long (exclusive of the trailing NUL). The maximum value for n is 2047.

在 3.14 版的變更: The maximum value for n was increased from 1023 to 2047.

window.is_linetouched(line)

Return True if the specified line was modified since the last call to refresh(); otherwise return False. Raise a curses.error exception if line is not valid for the given window.

window.is_wintouched()

Return True if the specified window was modified since the last call to refresh(); otherwise return False.

window.keypad(flag)

If flag is True, escape sequences generated by some keys (keypad, function keys) will be interpreted by curses. If flag is False, escape sequences will be left as is in the input stream.

window.leaveok(flag)

If flag is True, cursor is left where it is on update, instead of being at "cursor position." This reduces cursor movement where possible. If possible the cursor will be made invisible.

If flag is False, cursor will always be at "cursor position" after an update.

window.move(new_y, new_x)

移動游標到 (new_y, new_x)。

window.mvderwin(y, x)

Move the window inside its parent window. The screen-relative parameters of the window are not changed. This routine is used to display different parts of the parent window at the same physical position on the screen.

window.mvwin(new_y, new_x)

Move the window so its upper-left corner is at (new_y, new_x).

window.nodelay(flag)

如果 flag 為 True，則 getch() 將為非阻塞的。

window.notimeout(flag)

If flag is True, escape sequences will not be timed out.

If flag is False, after a few milliseconds, an escape sequence will not be interpreted, and will be left in the input stream as is.

window.noutrefresh()

Mark for refresh but wait. This function updates the data structure representing the desired state of the window, but does not force an update of the physical screen. To accomplish that, call doupdate().

window.overlay(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

Overlay the window on top of destwin. The windows need not be the same size, only the overlapping region is copied. This copy is non-destructive, which means that the current background character does not overwrite the old contents of destwin.

To get fine-grained control over the copied region, the second form of overlay() can be used. sminrow and smincol are the upper-left coordinates of the source window, and the other variables mark a rectangle in the destination window.

window.overwrite(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

Overwrite the window on top of destwin. The windows need not be the same size, in which case only the overlapping region is copied. This copy is destructive, which means that the current background character overwrites the old contents of destwin.

To get fine-grained control over the copied region, the second form of overwrite() can be used. sminrow and smincol are the upper-left coordinates of the source window, the other variables mark a rectangle in the destination window.

window.putwin(file)

Write all data associated with the window into the provided file object. This information can be later retrieved using the getwin() function.

window.redrawln(beg, num)

Indicate that the num screen lines, starting at line beg, are corrupted and should be completely redrawn on the next refresh() call.

window.redrawwin()

Touch the entire window, causing it to be completely redrawn on the next refresh() call.

window.refresh([pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol])

Update the display immediately (sync actual screen with previous drawing/deleting methods).

The 6 optional arguments can only be specified when the window is a pad created with newpad(). The additional parameters are needed to indicate what part of the pad and screen are involved. pminrow and pmincol specify the upper left-hand corner of the rectangle to be displayed in the pad. sminrow, smincol, smaxrow, and smaxcol specify the edges of the rectangle to be displayed on the screen. The lower right-hand corner of the rectangle to be displayed in the pad is calculated from the screen coordinates, since the rectangles must be the same size. Both rectangles must be entirely contained within their respective structures. Negative values of pminrow, pmincol, sminrow, or smincol are treated as if they were zero.

window.resize(nlines, ncols)

Reallocate storage for a curses window to adjust its dimensions to the specified values. If either dimension is larger than the current values, the window's data is filled with blanks that have the current background rendition (as set by bkgdset()) merged into them.

window.scroll([lines=1])

Scroll the screen or scrolling region upward by lines lines.

window.scrollok(flag)

Control what happens when the cursor of a window is moved off the edge of the window or scrolling region, either as a result of a newline action on the bottom line, or typing the last character of the last line. If flag is False, the cursor is left on the bottom line. If flag is True, the window is scrolled up one line. Note that in order to get the physical scrolling effect on the terminal, it is also necessary to call idlok().

window.setscrreg(top, bottom)

Set the scrolling region from line top to line bottom. All scrolling actions will take place in this region.

window.standend()

Turn off the standout attribute. On some terminals this has the side effect of turning off all attributes.

window.standout()

Turn on attribute A_STANDOUT.

window.subpad(begin_y, begin_x)

window.subpad(nlines, ncols, begin_y, begin_x)

Return a sub-window, whose upper-left corner is at (begin_y, begin_x), and whose width/height is ncols/nlines.

window.subwin(begin_y, begin_x)

window.subwin(nlines, ncols, begin_y, begin_x)

Return a sub-window, whose upper-left corner is at (begin_y, begin_x), and whose width/height is ncols/nlines.

By default, the sub-window will extend from the specified position to the lower right corner of the window.

window.syncdown()

Touch each location in the window that has been touched in any of its ancestor windows. This routine is called by refresh(), so it should almost never be necessary to call it manually.

window.syncok(flag)

If flag is True, then syncup() is called automatically whenever there is a change in the window.

window.syncup()

Touch all locations in ancestors of the window that have been changed in the window.

window.timeout(delay)

Set blocking or non-blocking read behavior for the window. If delay is negative, blocking read is used (which will wait indefinitely for input). If delay is zero, then non-blocking read is used, and getch() will return -1 if no input is waiting. If delay is positive, then getch() will block for delay milliseconds, and return -1 if there is still no input at the end of that time.

window.touchline(start, count[, changed])

Pretend count lines have been changed, starting with line start. If changed is supplied, it specifies whether the affected lines are marked as having been changed (changed=True) or unchanged (changed=False).

window.touchwin()

Pretend the whole window has been changed, for purposes of drawing optimizations.

window.untouchwin()

Mark all lines in the window as unchanged since the last call to refresh().

window.vline(ch, n[, attr])

window.vline(y, x, ch, n[, attr])

Display a vertical line starting at (y, x) with length n consisting of the character ch with attributes attr.

Constants

curses 模組定義了以下資料成員：

curses.ERR

Some curses routines that return an integer, such as getch(), return ERR upon failure.

curses.OK

Some curses routines that return an integer, such as napms(), return OK upon success.

curses.version

A bytes object representing the current version of the module.

curses.ncurses_version

A named tuple containing the three components of the ncurses library version: major, minor, and patch. All values are integers. The components can also be accessed by name, so curses.ncurses_version[0] is equivalent to curses.ncurses_version.major and so on.

Availability: if the ncurses library is used.

在 3.8 版被加入.

curses.COLORS

The maximum number of colors the terminal can support. It is defined only after the call to start_color().

curses.COLOR_PAIRS

The maximum number of color pairs the terminal can support. It is defined only after the call to start_color().

curses.COLS

The width of the screen, i.e., the number of columns. It is defined only after the call to initscr(). Updated by update_lines_cols(), resizeterm() and resize_term().

curses.LINES

The height of the screen, i.e., the number of lines. It is defined only after the call to initscr(). Updated by update_lines_cols(), resizeterm() and resize_term().

Some constants are available to specify character cell attributes. The exact constants available are system dependent.

Attribute

含義

curses.A_ALTCHARSET

Alternate character set mode

curses.A_BLINK

Blink mode

curses.A_BOLD

Bold mode

curses.A_DIM

Dim mode

curses.A_INVIS

Invisible or blank mode

curses.A_ITALIC

Italic mode

curses.A_NORMAL

Normal attribute

curses.A_PROTECT

Protected mode

curses.A_REVERSE

Reverse background and foreground colors

curses.A_STANDOUT

Standout mode

curses.A_UNDERLINE

Underline mode

curses.A_HORIZONTAL

Horizontal highlight

curses.A_LEFT

Left highlight

curses.A_LOW

Low highlight

curses.A_RIGHT

Right highlight

curses.A_TOP

Top highlight

curses.A_VERTICAL

Vertical highlight

在 3.7 版被加入: 新增 A_ITALIC。

Several constants are available to extract corresponding attributes returned by some methods.

Bit-mask

含義

curses.A_ATTRIBUTES

Bit-mask to extract attributes

curses.A_CHARTEXT

Bit-mask to extract a character

curses.A_COLOR

Bit-mask to extract color-pair field information

Keys are referred to by integer constants with names starting with KEY_. The exact keycaps available are system dependent.

Key constant

Key

curses.KEY_MIN

Minimum key value

curses.KEY_BREAK

Break key (unreliable)

curses.KEY_DOWN

Down-arrow

curses.KEY_UP

Up-arrow

curses.KEY_LEFT

Left-arrow

curses.KEY_RIGHT

Right-arrow

curses.KEY_HOME

Home key (upward+left arrow)

curses.KEY_BACKSPACE

Backspace (unreliable)

curses.KEY_F0

Function keys. Up to 64 function keys are supported.

curses.KEY_Fn

Value of function key n

curses.KEY_DL

Delete line

curses.KEY_IL

Insert line

curses.KEY_DC

Delete character

curses.KEY_IC

Insert char or enter insert mode

curses.KEY_EIC

Exit insert char mode

curses.KEY_CLEAR

Clear screen

curses.KEY_EOS

Clear to end of screen

curses.KEY_EOL

Clear to end of line

curses.KEY_SF

Scroll 1 line forward

curses.KEY_SR

Scroll 1 line backward (reverse)

curses.KEY_NPAGE

Next page

curses.KEY_PPAGE

Previous page

curses.KEY_STAB

Set tab

curses.KEY_CTAB

Clear tab

curses.KEY_CATAB

Clear all tabs

curses.KEY_ENTER

Enter or send (unreliable)

curses.KEY_SRESET

Soft (partial) reset (unreliable)

curses.KEY_RESET

Reset or hard reset (unreliable)

curses.KEY_PRINT

Print

curses.KEY_LL

Home down or bottom (lower left)

curses.KEY_A1

Upper left of keypad

curses.KEY_A3

Upper right of keypad

curses.KEY_B2

Center of keypad

curses.KEY_C1

Lower left of keypad

curses.KEY_C3

Lower right of keypad

curses.KEY_BTAB

Back tab

curses.KEY_BEG

Beg (beginning)

curses.KEY_CANCEL

Cancel

curses.KEY_CLOSE

Close

curses.KEY_COMMAND

Cmd (command)

curses.KEY_COPY

Copy

curses.KEY_CREATE

Create

curses.KEY_END

End

curses.KEY_EXIT

Exit

curses.KEY_FIND

Find

curses.KEY_HELP

Help

curses.KEY_MARK

Mark

curses.KEY_MESSAGE

Message

curses.KEY_MOVE

Move

curses.KEY_NEXT

Next

curses.KEY_OPEN

Open

curses.KEY_OPTIONS

Options

curses.KEY_PREVIOUS

Prev (previous)

curses.KEY_REDO

Redo

curses.KEY_REFERENCE

Ref (reference)

curses.KEY_REFRESH

Refresh

curses.KEY_REPLACE

Replace

curses.KEY_RESTART

Restart

curses.KEY_RESUME

Resume

curses.KEY_SAVE

Save

curses.KEY_SBEG

Shifted Beg (beginning)

curses.KEY_SCANCEL

Shifted Cancel

curses.KEY_SCOMMAND

Shifted Command

curses.KEY_SCOPY

Shifted Copy

curses.KEY_SCREATE

Shifted Create

curses.KEY_SDC

Shifted Delete char

curses.KEY_SDL

Shifted Delete line

curses.KEY_SELECT

Select

curses.KEY_SEND

Shifted End

curses.KEY_SEOL

Shifted Clear line

curses.KEY_SEXIT

Shifted Exit

curses.KEY_SFIND

Shifted Find

curses.KEY_SHELP

Shifted Help

curses.KEY_SHOME

Shifted Home

curses.KEY_SIC

Shifted Input

curses.KEY_SLEFT

Shifted Left arrow

curses.KEY_SMESSAGE

Shifted Message

curses.KEY_SMOVE

Shifted Move

curses.KEY_SNEXT

Shifted Next

curses.KEY_SOPTIONS

Shifted Options

curses.KEY_SPREVIOUS

Shifted Prev

curses.KEY_SPRINT

Shifted Print

curses.KEY_SREDO

Shifted Redo

curses.KEY_SREPLACE

Shifted Replace

curses.KEY_SRIGHT

Shifted Right arrow

curses.KEY_SRSUME

Shifted Resume

curses.KEY_SSAVE

Shifted Save

curses.KEY_SSUSPEND

Shifted Suspend

curses.KEY_SUNDO

Shifted Undo

curses.KEY_SUSPEND

Suspend

curses.KEY_UNDO

Undo

curses.KEY_MOUSE

Mouse event has occurred

curses.KEY_RESIZE

Terminal resize event

curses.KEY_MAX

Maximum key value

On VT100s and their software emulations, such as X terminal emulators, there are normally at least four function keys (KEY_F1, KEY_F2, KEY_F3, KEY_F4) available, and the arrow keys mapped to KEY_UP, KEY_DOWN, KEY_LEFT and KEY_RIGHT in the obvious way. If your machine has a PC keyboard, it is safe to expect arrow keys and twelve function keys (older PC keyboards may have only ten function keys); also, the following keypad mappings are standard:

Keycap

Constant

Insert

KEY_IC

Delete

KEY_DC

Home

KEY_HOME

End

KEY_END

Page Up

KEY_PPAGE

Page Down

KEY_NPAGE

The following table lists characters from the alternate character set. These are inherited from the VT100 terminal, and will generally be available on software emulations such as X terminals. When there is no graphic available, curses falls back on a crude printable ASCII approximation.

備註

These are available only after initscr() has been called.

ACS code

含義

curses.ACS_BBSS

alternate name for upper right corner

curses.ACS_BLOCK

solid square block

curses.ACS_BOARD

board of squares

curses.ACS_BSBS

alternate name for horizontal line

curses.ACS_BSSB

alternate name for upper left corner

curses.ACS_BSSS

alternate name for top tee

curses.ACS_BTEE

bottom tee

curses.ACS_BULLET

bullet

curses.ACS_CKBOARD

checker board (stipple)

curses.ACS_DARROW

arrow pointing down

curses.ACS_DEGREE

degree symbol

curses.ACS_DIAMOND

diamond

curses.ACS_GEQUAL

greater-than-or-equal-to

curses.ACS_HLINE

horizontal line

curses.ACS_LANTERN

lantern symbol

curses.ACS_LARROW

left arrow

curses.ACS_LEQUAL

less-than-or-equal-to

curses.ACS_LLCORNER

lower left-hand corner

curses.ACS_LRCORNER

lower right-hand corner

curses.ACS_LTEE

left tee

curses.ACS_NEQUAL

not-equal sign

curses.ACS_PI

letter pi

curses.ACS_PLMINUS

plus-or-minus sign

curses.ACS_PLUS

big plus sign

curses.ACS_RARROW

right arrow

curses.ACS_RTEE

right tee

curses.ACS_S1

scan line 1

curses.ACS_S3

scan line 3

curses.ACS_S7

scan line 7

curses.ACS_S9

scan line 9

curses.ACS_SBBS

alternate name for lower right corner

curses.ACS_SBSB

alternate name for vertical line

curses.ACS_SBSS

alternate name for right tee

curses.ACS_SSBB

alternate name for lower left corner

curses.ACS_SSBS

alternate name for bottom tee

curses.ACS_SSSB

alternate name for left tee

curses.ACS_SSSS

alternate name for crossover or big plus

curses.ACS_STERLING

pound sterling

curses.ACS_TTEE

top tee

curses.ACS_UARROW

up arrow

curses.ACS_ULCORNER

upper left corner

curses.ACS_URCORNER

upper right corner

curses.ACS_VLINE

vertical line

The following table lists mouse button constants used by getmouse():

Mouse button constant

含義

curses.BUTTONn_PRESSED

Mouse button n pressed

curses.BUTTONn_RELEASED

Mouse button n released

curses.BUTTONn_CLICKED

Mouse button n clicked

curses.BUTTONn_DOUBLE_CLICKED

Mouse button n double clicked

curses.BUTTONn_TRIPLE_CLICKED

Mouse button n triple clicked

curses.BUTTON_SHIFT

Shift was down during button state change

curses.BUTTON_CTRL

Control was down during button state change

curses.BUTTON_ALT

Control was down during button state change

在 3.10 版的變更: The BUTTON5_* constants are now exposed if they are provided by the underlying curses library.

The following table lists the predefined colors:

Constant

顏色

curses.COLOR_BLACK

黑

curses.COLOR_BLUE

藍

curses.COLOR_CYAN

Cyan (light greenish blue)

curses.COLOR_GREEN

綠

curses.COLOR_MAGENTA

Magenta (purplish red)

curses.COLOR_RED

紅

curses.COLOR_WHITE

白

curses.COLOR_YELLOW

Yellow

curses.textpad --- Text input widget for curses programs

The curses.textpad module provides a Textbox class that handles elementary text editing in a curses window, supporting a set of keybindings resembling those of Emacs (thus, also of Netscape Navigator, BBedit 6.x, FrameMaker, and many other programs). The module also provides a rectangle-drawing function useful for framing text boxes or for other purposes.

curses.textpad 模組定義了以下函式：

curses.textpad.rectangle(win, uly, ulx, lry, lrx)

Draw a rectangle. The first argument must be a window object; the remaining arguments are coordinates relative to that window. The second and third arguments are the y and x coordinates of the upper left hand corner of the rectangle to be drawn; the fourth and fifth arguments are the y and x coordinates of the lower right hand corner. The rectangle will be drawn using VT100/IBM PC forms characters on terminals that make this possible (including xterm and most other software terminal emulators). Otherwise it will be drawn with ASCII dashes, vertical bars, and plus signs.

Textbox objects

You can instantiate a Textbox object as follows:

class curses.textpad.Textbox(win)

Return a textbox widget object. The win argument should be a curses window object in which the textbox is to be contained. The edit cursor of the textbox is initially located at the upper left hand corner of the containing window, with coordinates (0, 0). The instance's stripspaces flag is initially on.

Textbox objects have the following methods:

edit([validator])

This is the entry point you will normally use. It accepts editing keystrokes until one of the termination keystrokes is entered. If validator is supplied, it must be a function. It will be called for each keystroke entered with the keystroke as a parameter; command dispatch is done on the result. This method returns the window contents as a string; whether blanks in the window are included is affected by the stripspaces attribute.

do_command(ch)

Process a single command keystroke. Here are the supported special keystrokes:

Keystroke

Action

Control-A

Go to left edge of window.

Control-B

Cursor left, wrapping to previous line if appropriate.

Control-D

Delete character under cursor.

Control-E

Go to right edge (stripspaces off) or end of line (stripspaces on).

Control-F

Cursor right, wrapping to next line when appropriate.

Control-G

Terminate, returning the window contents.

Control-H

Delete character backward.

Control-J

Terminate if the window is 1 line, otherwise insert newline.

Control-K

If line is blank, delete it, otherwise clear to end of line.

Control-L

Refresh screen.

Control-N

Cursor down; move down one line.

Control-O

Insert a blank line at cursor location.

Control-P

Cursor up; move up one line.

Move operations do nothing if the cursor is at an edge where the movement is not possible. The following synonyms are supported where possible:

Constant

Keystroke

KEY_LEFT

Control-B

KEY_RIGHT

Control-F

KEY_UP

Control-P

KEY_DOWN

Control-N

KEY_BACKSPACE

Control-h

All other keystrokes are treated as a command to insert the given character and move right (with line wrapping).

gather()

Return the window contents as a string; whether blanks in the window are included is affected by the stripspaces member.

stripspaces

This attribute is a flag which controls the interpretation of blanks in the window. When it is on, trailing blanks on each line are ignored; any cursor motion that would land the cursor on a trailing blank goes to the end of that line instead, and trailing blanks are stripped when the window contents are gathered.

curses.ascii --- ASCII 字元的工具程式

原始碼：Lib/curses/ascii.py [https://github.com/python/cpython/tree/3.14/Lib/curses/ascii.py]

The curses.ascii module supplies name constants for ASCII characters and functions to test membership in various ASCII character classes. The constants supplied are names for control characters as follows:

名稱

含義

curses.ascii.NUL

curses.ascii.SOH

Start of heading, console interrupt

curses.ascii.STX

Start of text

curses.ascii.ETX

End of text

curses.ascii.EOT

End of transmission

curses.ascii.ENQ

Enquiry, goes with ACK flow control

curses.ascii.ACK

Acknowledgement

curses.ascii.BEL

Bell

curses.ascii.BS

Backspace

curses.ascii.TAB

Tab

curses.ascii.HT

Alias for TAB: "Horizontal tab"

curses.ascii.LF

Line feed

curses.ascii.NL

Alias for LF: "New line"

curses.ascii.VT

Vertical tab

curses.ascii.FF

Form feed

curses.ascii.CR

Carriage return

curses.ascii.SO

Shift-out, begin alternate character set

curses.ascii.SI

Shift-in, resume default character set

curses.ascii.DLE

Data-link escape

curses.ascii.DC1

XON, for flow control

curses.ascii.DC2

Device control 2, block-mode flow control

curses.ascii.DC3

XOFF, for flow control

curses.ascii.DC4

Device control 4

curses.ascii.NAK

Negative acknowledgement

curses.ascii.SYN

Synchronous idle

curses.ascii.ETB

End transmission block

curses.ascii.CAN

Cancel

curses.ascii.EM

End of medium

curses.ascii.SUB

Substitute

curses.ascii.ESC

Escape

curses.ascii.FS

File separator

curses.ascii.GS

Group separator

curses.ascii.RS

Record separator, block-mode terminator

curses.ascii.US

Unit separator

curses.ascii.SP

Space

curses.ascii.DEL

Delete

Note that many of these have little practical significance in modern usage. The mnemonics derive from teleprinter conventions that predate digital computers.

The module supplies the following functions, patterned on those in the standard C library:

curses.ascii.isalnum(c)

Checks for an ASCII alphanumeric character; it is equivalent to isalpha(c) or isdigit(c).

curses.ascii.isalpha(c)

Checks for an ASCII alphabetic character; it is equivalent to isupper(c) or islower(c).

curses.ascii.isascii(c)

Checks for a character value that fits in the 7-bit ASCII set.

curses.ascii.isblank(c)

Checks for an ASCII whitespace character; space or horizontal tab.

curses.ascii.iscntrl(c)

Checks for an ASCII control character (in the range 0x00 to 0x1f or 0x7f).

curses.ascii.isdigit(c)

Checks for an ASCII decimal digit, '0' through '9'. This is equivalent to c in string.digits.

curses.ascii.isgraph(c)

Checks for ASCII any printable character except space.

curses.ascii.islower(c)

Checks for an ASCII lower-case character.

curses.ascii.isprint(c)

Checks for any ASCII printable character including space.

curses.ascii.ispunct(c)

Checks for any printable ASCII character which is not a space or an alphanumeric character.

curses.ascii.isspace(c)

Checks for ASCII white-space characters; space, line feed, carriage return, form feed, horizontal tab, vertical tab.

curses.ascii.isupper(c)

Checks for an ASCII uppercase letter.

curses.ascii.isxdigit(c)

Checks for an ASCII hexadecimal digit. This is equivalent to c in string.hexdigits.

curses.ascii.isctrl(c)

Checks for an ASCII control character (ordinal values 0 to 31).

curses.ascii.ismeta(c)

Checks for a non-ASCII character (ordinal values 0x80 and above).

These functions accept either integers or single-character strings; when the argument is a string, it is first converted using the built-in function ord().

Note that all these functions check ordinal bit values derived from the character of the string you pass in; they do not actually know anything about the host machine's character encoding.

The following two functions take either a single-character string or integer byte value; they return a value of the same type.

curses.ascii.ascii(c)

Return the ASCII value corresponding to the low 7 bits of c.

curses.ascii.ctrl(c)

Return the control character corresponding to the given character (the character bit value is bitwise-anded with 0x1f).

curses.ascii.alt(c)

Return the 8-bit character corresponding to the given ASCII character (the character bit value is bitwise-ored with 0x80).

The following function takes either a single-character string or integer value; it returns a string.

curses.ascii.unctrl(c)

Return a string representation of the ASCII character c. If c is printable, this string is the character itself. If the character is a control character (0x00--0x1f) the string consists of a caret ('^') followed by the corresponding uppercase letter. If the character is an ASCII delete (0x7f) the string is '^?'. If the character has its meta bit (0x80) set, the meta bit is stripped, the preceding rules applied, and '!' prepended to the result.

curses.ascii.controlnames

A 33-element string array that contains the ASCII mnemonics for the thirty-two ASCII control characters from 0 (NUL) to 0x1f (US), in order, plus the mnemonic SP for the space character.

curses.panel --- curses 的面板堆疊擴充

Panels are windows with the added feature of depth, so they can be stacked on top of each other, and only the visible portions of each window will be displayed. Panels can be added, moved up or down in the stack, and removed.

函式

curses.panel 模組定義了以下函式：

curses.panel.bottom_panel()

Returns the bottom panel in the panel stack.

curses.panel.new_panel(win)

Returns a panel object, associating it with the given window win. Be aware that you need to keep the returned panel object referenced explicitly. If you don't, the panel object is garbage collected and removed from the panel stack.

curses.panel.top_panel()

Returns the top panel in the panel stack.

curses.panel.update_panels()

Updates the virtual screen after changes in the panel stack. This does not call curses.doupdate(), so you'll have to do this yourself.

Panel Objects

Panel objects, as returned by new_panel() above, are windows with a stacking order. There's always a window associated with a panel which determines the content, while the panel methods are responsible for the window's depth in the panel stack.

Panel objects have the following methods:

Panel.above()

Returns the panel above the current panel.

Panel.below()

Returns the panel below the current panel.

Panel.bottom()

Push the panel to the bottom of the stack.

Panel.hidden()

Returns True if the panel is hidden (not visible), False otherwise.

Panel.hide()

Hide the panel. This does not delete the object, it just makes the window on screen invisible.

Panel.move(y, x)

Move the panel to the screen coordinates (y, x).

Panel.replace(win)

Change the window associated with the panel to the window win.

Panel.set_userptr(obj)

Set the panel's user pointer to obj. This is used to associate an arbitrary piece of data with the panel, and can be any Python object.

Panel.show()

Display the panel (which might have been hidden).

Panel.top()

Push panel to the top of the stack.

Panel.userptr()

Returns the user pointer for the panel. This might be any Python object.

Panel.window()

Returns the window object associated with the panel.

cmd --- 以列為導向的命令直譯器支援

原始碼：Lib/cmd.py [https://github.com/python/cpython/tree/3.14/Lib/cmd.py]

Cmd 類別提供了一個簡單的架構，用於撰寫列導向的命令直譯器。這類直譯器常用於測試控制工具、管理工具以及日後將包裝於更高階介面的原型中。

class cmd.Cmd(completekey='tab', stdin=None, stdout=None)

Cmd 實例或其子類別實例是一種列導向的直譯器架構。通常沒有必要直接實例化 Cmd 本身；它更適合作為你自己定義的直譯器類別的父類別，讓你能繼承 Cmd 的方法，並封裝動作方法。

可選引數 completekey 是 readline 模組中用於自動完成的按鍵名稱；預設為 Tab。若 completekey 不為 None 且 readline 可用，則會自動啟用命令自動完成功能。

預設值 'tab' 會被特殊處理，使其在所有的 readline.backend 中皆代表 Tab 鍵。具體來說，若 readline.backend 為 editline，則 Cmd 會改用 '^I' 取代 'tab'。請注意，其他值不會有此處理方式，且可能僅能在特定的後端中適用。

可選引數 stdin 與 stdout 用來指定 Cmd 實例或其子類別實例所使用的輸入與輸出檔案物件。若未指定，預設為 sys.stdin 與 sys.stdout。

若你希望使用指定的 stdin，請務必將該實例的 use_rawinput 屬性設為 False，否則 stdin 會被忽略。

在 3.13 版的變更: 對於 editline，completekey='tab' 會被替換為 '^I'。

Cmd 物件

Cmd 實例具有以下方法：

Cmd.cmdloop(intro=None)

重複顯示提示字元、接收輸入、剖析接收到的輸入字串前綴，並派發給動作方法，將其餘部分作為引數傳遞給它們

此可選引數為橫幅或導言字串，會在首次顯示提示字元前輸出（此值會覆寫 intro 類別屬性）。

如果已載入 readline 模組，輸入將自動繼承類似 bash 的歷史紀錄編輯功能（例如 Control-P 可向上捲動至上一個命令，Control-N 向下捲動至下一個命令，Control-F 非破壞性地將游標向右移動，Control-B 非破壞性地將游標向左移動等）。

當輸入為檔案結尾（EOF）時，會傳回字串 'EOF'。

直譯器實例僅當存在 do_foo() 方法時，才會識別命令名稱 foo。作為特殊情況，以字元 '?' 開頭的列會被派發至 do_help() 方法；另一個特殊情況是，以字元 '!' 開頭的列會被派發至 do_shell() 方法（若該方法已定義）。

當 postcmd() 方法回傳真值時，此方法將會結束。傳遞給 postcmd() 的 stop 引數是該命令對應的 do_*() 方法的回傳值。

如果啟用了自動完成，命令的自動完成將會自動執行，而命令引數的自動完成則是透過呼叫 complete_foo() 方法並傳入 text、line、begidx 和 endidx 引數來處理。text 是要比對的字串前綴：所有回傳的符合項都必須以此字串開頭。line 是目前的輸入列（前置空白會被移除），begidx 和 endidx 則分別是前綴字串的起始與結束索引，可用來根據引數所在的位置提供不同的自動完成結果。

Cmd.do_help(arg)

所有 Cmd 的子類別都會繼承預先定義的 do_help() 方法。當此方法接收到引數 'bar' 時，會呼叫對應的 help_bar() 方法；若該方法不存在，則會列印 do_bar() 的說明字串（若有的話）。若未提供任何引數，do_help() 會列出所有可用的說明主題（也就是所有具有對應 help_*() 方法或有說明字串的命令），並且也會列出所有尚未記錄的命令。

Cmd.onecmd(str)

將引數視為在回應提示字元時所輸入的內容來直譯。這個方法可以被覆寫，但通常不需要這麼做；參見 precmd() 與 postcmd() 方法，它們提供實用的執行勾點（hook）。此方法的回傳值是一個旗標，用來指出是否應該停止直譯器對命令的直譯。若有對應 str 命令的 do_*() 方法，則會回傳該方法的回傳值；否則，回傳值將來自 default() 方法。

Cmd.emptyline()

在回應提示字元時輸入空白列，會呼叫此方法。若此方法未被覆寫，則會重復上一次輸入的非空命令。

Cmd.default(line)

當輸入列中的命令前綴無法辨識時，會呼叫此方法。若此方法未被覆寫，則會輸出並回傳錯誤訊息。

Cmd.completedefault(text, line, begidx, endidx)

當沒有對應特定命令的 complete_*() 方法時，會呼叫此方法以完成輸入列。預設會回傳空串列。

Cmd.columnize(list, displaywidth=80)

此方法用來將字串串列顯示為緊湊的欄集合。每一欄的寬度僅足以容納其內容，各欄之間以兩個空格分隔，以提高可讀性。

Cmd.precmd(line)

勾點方法會在直譯命令列 line 前執行，但會在提示字元產生並顯示後才觸發。這個方法在 Cmd 類別中為 stub，預期由子類別覆寫。回傳值會作為 onecmd() 方法所執行的命令；precmd() 的實作可以重寫該命令，或直接回傳未變更的 line。

Cmd.postcmd(stop, line)

勾點方法會在命令派發完成後執行。這個方法在 Cmd 類別中為 stub，預期由子類別覆寫。line 是剛剛執行的命令列，而 stop 是一個旗標，用來指出在呼叫 postcmd() 後是否應終止執行；該值即為 onecmd() 方法的回傳值。本方法的回傳值將會更新內部的 stop 旗標；若回傳 false，則會繼續進行直譯。

Cmd.preloop()

當 cmdloop() 被呼叫時，此勾點方法會執行一次。這個方法在 Cmd 類別中為 stub，預期由子類別覆寫。

Cmd.postloop()

當 cmdloop() 即將回傳時，此勾點方法會執行一次。這個方法在 Cmd 類別中為 stub，預期由子類別覆寫。

Cmd 子類別的實例包含一些公開的實例變數：

Cmd.prompt

用來請求輸入的提示字元。

Cmd.identchars

可作為命令前綴的字元字串

Cmd.lastcmd

最後一個遇到的非空命令前綴

Cmd.cmdqueue

排入佇列的輸入列串列。當 cmdloop() 需要新輸入時，會檢查 cmdqueue 串列；若不為空，其元素將依序處理，就如同它們是在提示字元中輸入的一樣。

Cmd.intro

作為簡介或橫幅的字串。可透過為 cmdloop() 方法提供引數來覆寫此內容。

Cmd.doc_header

若說明輸出包含已記錄命令的區段，則會顯示的標頭字串。

Cmd.misc_header

若說明輸出包含雜項說明主題的區段（也就是存在 help_*() 方法但沒有對應的 do_*() 方法），則會顯示的標頭字串。

Cmd.undoc_header

若說明輸出包含未記錄命令的區段（也就是存在 do_*() 方法但沒有對應的 help_*() 方法），則會顯示的標頭字串。

Cmd.ruler

用於在說明訊息的標頭下方繪製分隔線的字元。若為空，則不會繪製分隔線。預設為 '='。

Cmd.use_rawinput

一個旗標，預設為 true。若為 true，cmdloop() 會使用 input() 來顯示提示字元並讀取下一個命令；若為 false，則會改用 sys.stdout.write() 和 sys.stdin.readline()。（這表示在支援的系統中，透過 import readline module，直譯器將自動支援類似 Emacs 的列編輯與命令歷史快捷鍵。）

Cmd 範例

cmd module 主要用於建構自訂 shell，讓使用者能以互動方式操作程式。

本節將示範如何以 turtle module 中的幾個命令為基礎，建立一個簡單的 shell。

像是 forward() 這樣的基本 turtle 命令，可透過新增名為 do_forward() 的方法加入至 Cmd 子類別中。傳入的引數會轉換為數值，並傳送給 turtle 模組。該方法的說明字串會用於 shell 所提供的說明功能中。

此範例同時包含一個簡單的錄製與重播功能，其實作方式是透過 precmd() 方法，負責將輸入轉為小寫並寫入檔案。do_playback() 方法則會讀取該檔案，並將錄製的命令加入 cmdqueue 中以供立即重播:

import cmd, sys
from turtle import *

class TurtleShell(cmd.Cmd):
    intro = '歡迎來到 turtle shell。輸入 help 或 ? 來列出命令。\n'
    prompt = '(turtle) '
    file = None

    # ----- 基本烏龜命令 -----
    def do_forward(self, arg):
        '將烏龜向前移動指定的距離： FORWARD 10'
        forward(*parse(arg))
    def do_right(self, arg):
        '將烏龜右轉指定的角度： RIGHT 20'
        right(*parse(arg))
    def do_left(self, arg):
        '將烏龜左轉指定的角度： LEFT 90'
        left(*parse(arg))
    def do_goto(self, arg):
        '將烏龜移動到指定的絕對位置並改變方向。 GOTO 100 200'
        goto(*parse(arg))
    def do_home(self, arg):
        '將烏龜返回起始位置： HOME'
        home()
    def do_circle(self, arg):
        '畫出指定半徑、範圍和步數的圓： CIRCLE 50'
        circle(*parse(arg))
    def do_position(self, arg):
        '顯示目前烏龜位置： POSITION'
        print('目前位置是 %d %d\n' % position())
    def do_heading(self, arg):
        '顯示目前烏龜方向角度： HEADING'
        print('目前方向是 %d\n' % (heading(),))
    def do_color(self, arg):
        '設定顏色： COLOR BLUE'
        color(arg.lower())
    def do_undo(self, arg):
        '撤銷（重複）最後一次烏龜動作： UNDO'
    def do_reset(self, arg):
        '清除畫面並將烏龜返回到中心： RESET'
        reset()
    def do_bye(self, arg):
        '停止錄製、關閉烏龜視窗並退出： BYE'
        print('感謝使用 Turtle')
        self.close()
        bye()
        return True

    # ----- 錄製與重播 -----
    def do_record(self, arg):
        '將未來命令儲存至檔案： RECORD rose.cmd'
        self.file = open(arg, 'w')
    def do_playback(self, arg):
        '從檔案重播命令： PLAYBACK rose.cmd'
        self.close()
        with open(arg) as f:
            self.cmdqueue.extend(f.read().splitlines())
    def precmd(self, line):
        line = line.lower()
        if self.file and 'playback' not in line:
            print(line, file=self.file)
        return line
    def close(self):
        if self.file:
            self.file.close()
            self.file = None

def parse(arg):
    '將一串零個或多個數字轉換為引數 tuple'
    return tuple(map(int, arg.split()))

if __name__ == '__main__':
    TurtleShell().cmdloop()

以下是與 turtle shell 的一段範例互動，展示了說明功能、使用空白列重複執行命令，以及簡單的錄製與重播功能：

歡迎來到 turtle shell。輸入 help 或 ? 來列出命令。

(turtle) ?

已記錄的命令（輸入 help <主題>）：
========================================
bye     color    goto     home  playback  record  right
circle  forward  heading  left  position  reset   undo

(turtle) help forward
將烏龜向前移動指定的距離： FORWARD 10
(turtle) record spiral.cmd
(turtle) position
目前位置是 0 0

(turtle) heading
目前方向是 0

(turtle) reset
(turtle) circle 20
(turtle) right 30
(turtle) circle 40
(turtle) right 30
(turtle) circle 60
(turtle) right 30
(turtle) circle 80
(turtle) right 30
(turtle) circle 100
(turtle) right 30
(turtle) circle 120
(turtle) right 30
(turtle) circle 120
(turtle) heading
目前方向是 180

(turtle) forward 100
(turtle)
(turtle) right 90
(turtle) forward 100
(turtle)
(turtle) right 90
(turtle) forward 400
(turtle) right 90
(turtle) forward 500
(turtle) right 90
(turtle) forward 400
(turtle) right 90
(turtle) forward 300
(turtle) playback spiral.cmd
目前位置是 0 0

目前方向是 0

目前方向是 180

(turtle) bye
感謝使用 Turtle

並行執行 (Concurrent Execution)

本章節描述的模組在程式的並行執行上提供支援。選擇要使用哪一個工具則取決於是執行什麼樣的任務（CPU 密集或 IO 密集）與偏好的開發風格（事件驅動協作式多工處理或搶占式多工處理）。以下為此章節總覽：

threading --- 基於執行緒的平行性

Introduction

GIL and performance considerations

Reference

Thread-local data

Thread 物件

Lock 物件

RLock 物件

Condition objects

Semaphore 物件

Semaphore 範例

Event objects

Timer 物件

Barrier 物件

Using locks, conditions, and semaphores in the with statement

multiprocessing --- 以行程為基礎的平行性

簡介

Process 類別

Contexts and start methods

Exchanging objects between processes

Synchronization between processes

Sharing state between processes

Using a pool of workers

Reference

Global start method

Process 與例外

Pipes and Queues

Miscellaneous

Connection Objects

Synchronization primitives

共享的 ctypes 物件

multiprocessing.sharedctypes 模組

Managers

Customized managers

Using a remote manager

Proxy Objects

Cleanup

Process Pools

Listeners and Clients

Address Formats

Authentication keys

Logging

multiprocessing.dummy 模組

Programming guidelines

All start methods

The spawn and forkserver start methods

範例

multiprocessing.shared_memory --- 對於共享記憶體的跨行程直接存取

concurrent 套件

concurrent.futures --- 啟動平行任務

Executor 物件

ThreadPoolExecutor

ThreadPoolExecutor 範例

InterpreterPoolExecutor

ProcessPoolExecutor

ProcessPoolExecutor 範例

Future 物件

模組函式

例外類別

concurrent.interpreters --- 在同一個行程中使用多個直譯器

Key details

Introduction

Multiple Interpreters and Isolation

Running in an Interpreter

Concurrency and Parallelism

直譯器之間的溝通

"Sharing" Objects

Reference

Interpreter objects

例外

在直譯器之間溝通

基本用法

subprocess --- 子行程管理

Using the subprocess Module

Frequently Used Arguments

Popen Constructor

例外

安全性注意事項

Popen Objects

Windows Popen Helpers

Windows Constants

Older high-level API

Replacing Older Functions with the subprocess Module

Replacing /bin/sh shell command substitution

Replacing shell pipeline

取代 os.system()

Replacing the os.spawn family

取代 os.popen()

Legacy Shell Invocation Functions

註解

Timeout Behavior

Converting an argument sequence to a string on Windows

停用 posix_spawn()

sched --- 事件排程器

排程器物件

queue --- 同步佇列 (synchronized queue) 類別

佇列物件

Waiting for task completion

Terminating queues

SimpleQueue 物件

contextvars --- 情境變數

情境變數

手動情境管理

對 asyncio 的支援

以下是支援部份上述服務的模組：

_thread --- 低階執行緒 API

threading --- 基於執行緒的平行性

原始碼：Lib/threading.py [https://github.com/python/cpython/tree/3.14/Lib/threading.py]

This module constructs higher-level threading interfaces on top of the lower level _thread module.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

Introduction

The threading module provides a way to run multiple threads [https://en.wikipedia.org/wiki/Thread_(computing)] (smaller units of a process) concurrently within a single process. It allows for the creation and management of threads, making it possible to execute tasks in parallel, sharing memory space. Threads are particularly useful when tasks are I/O bound, such as file operations or making network requests, where much of the time is spent waiting for external resources.

A typical use case for threading includes managing a pool of worker threads that can process multiple tasks concurrently. Here's a basic example of creating and starting threads using Thread:

import threading
import time

def crawl(link, delay=3):
    print(f"crawl started for {link}")
    time.sleep(delay)  # Blocking I/O (simulating a network request)
    print(f"crawl ended for {link}")

links = [
    "https://python.org",
    "https://docs.python.org",
    "https://peps.python.org",
]

# Start threads for each link
threads = []
for link in links:
    # Using `args` to pass positional arguments and `kwargs` for keyword arguments
    t = threading.Thread(target=crawl, args=(link,), kwargs={"delay": 2})
    threads.append(t)

# Start each thread
for t in threads:
    t.start()

# Wait for all threads to finish
for t in threads:
    t.join()

在 3.7 版的變更: This module used to be optional, it is now always available.

也參考

concurrent.futures.ThreadPoolExecutor offers a higher level interface to push tasks to a background thread without blocking execution of the calling thread, while still being able to retrieve their results when needed.

queue provides a thread-safe interface for exchanging data between running threads.

asyncio offers an alternative approach to achieving task level concurrency without requiring the use of multiple operating system threads.

備註

In the Python 2.x series, this module contained camelCase names for some methods and functions. These are deprecated as of Python 3.10, but they are still supported for compatibility with Python 2.5 and lower.

CPython 實作細節： In CPython, due to the Global Interpreter Lock, only one thread can execute Python code at once (even though certain performance-oriented libraries might overcome this limitation). If you want your application to make better use of the computational resources of multi-core machines, you are advised to use multiprocessing or concurrent.futures.ProcessPoolExecutor. However, threading is still an appropriate model if you want to run multiple I/O-bound tasks simultaneously.

GIL and performance considerations

Unlike the multiprocessing module, which uses separate processes to bypass the global interpreter lock (GIL), the threading module operates within a single process, meaning that all threads share the same memory space. However, the GIL limits the performance gains of threading when it comes to CPU-bound tasks, as only one thread can execute Python bytecode at a time. Despite this, threads remain a useful tool for achieving concurrency in many scenarios.

As of Python 3.13, free-threaded builds can disable the GIL, enabling true parallel execution of threads, but this feature is not available by default (see PEP 703 [https://peps.python.org/pep-0703/]).

Reference

此模組定義了以下函式：

threading.active_count()

Return the number of Thread objects currently alive. The returned count is equal to the length of the list returned by enumerate().

The function activeCount is a deprecated alias for this function.

threading.current_thread()

Return the current Thread object, corresponding to the caller's thread of control. If the caller's thread of control was not created through the threading module, a dummy thread object with limited functionality is returned.

currentThread 函式是此函式的已棄用別名。

threading.excepthook(args, /)

處理由 Thread.run() 引發且未被捕捉到的例外。

args 引數有下列屬性：

exc_type：例外型別。

exc_value: Exception value, can be None.

exc_traceback: Exception traceback, can be None.

thread：引發例外的執行緒，可以是 None。

If exc_type is SystemExit, the exception is silently ignored. Otherwise, the exception is printed out on sys.stderr.

如果這個函式引發例外，則會呼叫 sys.excepthook() 來處理它。

threading.excepthook() can be overridden to control how uncaught exceptions raised by Thread.run() are handled.

Storing exc_value using a custom hook can create a reference cycle. It should be cleared explicitly to break the reference cycle when the exception is no longer needed.

Storing thread using a custom hook can resurrect it if it is set to an object which is being finalized. Avoid storing thread after the custom hook completes to avoid resurrecting objects.

也參考

sys.excepthook() 處理未被捕捉到的例外。

在 3.8 版被加入.

threading.__excepthook__

Holds the original value of threading.excepthook(). It is saved so that the original value can be restored in case they happen to get replaced with broken or alternative objects.

在 3.10 版被加入.

threading.get_ident()

Return the 'thread identifier' of the current thread. This is a nonzero integer. Its value has no direct meaning; it is intended as a magic cookie to be used e.g. to index a dictionary of thread-specific data. Thread identifiers may be recycled when a thread exits and another thread is created.

在 3.3 版被加入.

threading.get_native_id()

Return the native integral Thread ID of the current thread assigned by the kernel. This is a non-negative integer. Its value may be used to uniquely identify this particular thread system-wide (until the thread terminates, after which the value may be recycled by the OS).

可用性: Windows, FreeBSD, Linux, macOS, OpenBSD, NetBSD, AIX, DragonFlyBSD, GNU/kFreeBSD.

在 3.8 版被加入.

在 3.13 版的變更: 新增對 GNU/kFreeBSD 的支援。

threading.enumerate()

Return a list of all Thread objects currently active. The list includes daemonic threads and dummy thread objects created by current_thread(). It excludes terminated threads and threads that have not yet been started. However, the main thread is always part of the result, even when terminated.

threading.main_thread()

Return the main Thread object. In normal conditions, the main thread is the thread from which the Python interpreter was started.

在 3.4 版被加入.

threading.settrace(func)

Set a trace function for all threads started from the threading module. The func will be passed to sys.settrace() for each thread, before its run() method is called.

threading.settrace_all_threads(func)

Set a trace function for all threads started from the threading module and all Python threads that are currently executing.

The func will be passed to sys.settrace() for each thread, before its run() method is called.

在 3.12 版被加入.

threading.gettrace()

Get the trace function as set by settrace().

在 3.10 版被加入.

threading.setprofile(func)

Set a profile function for all threads started from the threading module. The func will be passed to sys.setprofile() for each thread, before its run() method is called.

threading.setprofile_all_threads(func)

Set a profile function for all threads started from the threading module and all Python threads that are currently executing.

The func will be passed to sys.setprofile() for each thread, before its run() method is called.

在 3.12 版被加入.

threading.getprofile()

取得由 setprofile() 設定的剖析函式。

在 3.10 版被加入.

threading.stack_size([size])

Return the thread stack size used when creating new threads. The optional size argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive integer value of at least 32,768 (32 KiB). If size is not specified, 0 is used. If changing the thread stack size is unsupported, a RuntimeError is raised. If the specified stack size is invalid, a ValueError is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient stack space for the interpreter itself. Note that some platforms may have particular restrictions on values for the stack size, such as requiring a minimum stack size > 32 KiB or requiring allocation in multiples of the system memory page size - platform documentation should be referred to for more information (4 KiB pages are common; using multiples of 4096 for the stack size is the suggested approach in the absence of more specific information).

可用性: Windows, pthreads.

Unix platforms with POSIX threads support.

此模組也定義了以下常數：

threading.TIMEOUT_MAX

The maximum value allowed for the timeout parameter of blocking functions (Lock.acquire(), RLock.acquire(), Condition.wait(), etc.). Specifying a timeout greater than this value will raise an OverflowError.

在 3.2 版被加入.

This module defines a number of classes, which are detailed in the sections below.

The design of this module is loosely based on Java's threading model. However, where Java makes locks and condition variables basic behavior of every object, they are separate objects in Python. Python's Thread class supports a subset of the behavior of Java's Thread class; currently, there are no priorities, no thread groups, and threads cannot be destroyed, stopped, suspended, resumed, or interrupted. The static methods of Java's Thread class, when implemented, are mapped to module-level functions.

All of the methods described below are executed atomically.

Thread-local data

Thread-local data is data whose values are thread specific. If you have data that you want to be local to a thread, create a local object and use its attributes:

>>> mydata = local()
>>> mydata.number = 42
>>> mydata.number
42

You can also access the local-object's dictionary:

>>> mydata.__dict__
{'number': 42}
>>> mydata.__dict__.setdefault('widgets', [])
[]
>>> mydata.widgets
[]

If we access the data in a different thread:

>>> log = []
>>> def f():
...     items = sorted(mydata.__dict__.items())
...     log.append(items)
...     mydata.number = 11
...     log.append(mydata.number)

>>> import threading
>>> thread = threading.Thread(target=f)
>>> thread.start()
>>> thread.join()
>>> log
[[], 11]

we get different data. Furthermore, changes made in the other thread don't affect data seen in this thread:

>>> mydata.number
42

Of course, values you get from a local object, including their __dict__ attribute, are for whatever thread was current at the time the attribute was read. For that reason, you generally don't want to save these values across threads, as they apply only to the thread they came from.

You can create custom local objects by subclassing the local class:

>>> class MyLocal(local):
...     number = 2
...     def __init__(self, /, **kw):
...         self.__dict__.update(kw)
...     def squared(self):
...         return self.number ** 2

This can be useful to support default values, methods and initialization. Note that if you define an __init__() method, it will be called each time the local object is used in a separate thread. This is necessary to initialize each thread's dictionary.

現在如果我們建立一個 local 物件：

>>> mydata = MyLocal(color='red')

會有一個預設的數字：

>>> mydata.number
2

和一個初始顏色：

>>> mydata.color
'red'
>>> del mydata.color

和一個操作資料的方法：

>>> mydata.squared()
4

As before, we can access the data in a separate thread:

>>> log = []
>>> thread = threading.Thread(target=f)
>>> thread.start()
>>> thread.join()
>>> log
[[('color', 'red')], 11]

without affecting this thread's data:

>>> mydata.number
2
>>> mydata.color
Traceback (most recent call last):
...
AttributeError: 'MyLocal' object has no attribute 'color'

Note that subclasses can define __slots__, but they are not thread local. They are shared across threads:

>>> class MyLocal(local):
...     __slots__ = 'number'

>>> mydata = MyLocal()
>>> mydata.number = 42
>>> mydata.color = 'red'

So, the separate thread:

>>> thread = threading.Thread(target=f)
>>> thread.start()
>>> thread.join()

affects what we see:

>>> mydata.number
11

class threading.local

A class that represents thread-local data.

Thread 物件

The Thread class represents an activity that is run in a separate thread of control. There are two ways to specify the activity: by passing a callable object to the constructor, or by overriding the run() method in a subclass. No other methods (except for the constructor) should be overridden in a subclass. In other words, only override the __init__() and run() methods of this class.

Once a thread object is created, its activity must be started by calling the thread's start() method. This invokes the run() method in a separate thread of control.

Once the thread's activity is started, the thread is considered 'alive'. It stops being alive when its run() method terminates -- either normally, or by raising an unhandled exception. The is_alive() method tests whether the thread is alive.

Other threads can call a thread's join() method. This blocks the calling thread until the thread whose join() method is called is terminated.

A thread has a name. The name can be passed to the constructor, and read or changed through the name attribute.

If the run() method raises an exception, threading.excepthook() is called to handle it. By default, threading.excepthook() ignores silently SystemExit.

A thread can be flagged as a "daemon thread". The significance of this flag is that the entire Python program exits when only daemon threads are left. The initial value is inherited from the creating thread. The flag can be set through the daemon property or the daemon constructor argument.

備註

Daemon threads are abruptly stopped at shutdown. Their resources (such as open files, database transactions, etc.) may not be released properly. If you want your threads to stop gracefully, make them non-daemonic and use a suitable signalling mechanism such as an Event.

There is a "main thread" object; this corresponds to the initial thread of control in the Python program. It is not a daemon thread.

There is the possibility that "dummy thread objects" are created. These are thread objects corresponding to "alien threads", which are threads of control started outside the threading module, such as directly from C code. Dummy thread objects have limited functionality; they are always considered alive and daemonic, and cannot be joined. They are never deleted, since it is impossible to detect the termination of alien threads.

class threading.Thread(group=None, target=None, name=None, args=(), kwargs={}, *, daemon=None, context=None)

This constructor should always be called with keyword arguments. Arguments are:

group should be None; reserved for future extension when a ThreadGroup class is implemented.

target is the callable object to be invoked by the run() method. Defaults to None, meaning nothing is called.

name is the thread name. By default, a unique name is constructed of the form "Thread-N" where N is a small decimal number, or "Thread-N (target)" where "target" is target.__name__ if the target argument is specified.

args is a list or tuple of arguments for the target invocation. Defaults to ().

kwargs is a dictionary of keyword arguments for the target invocation. Defaults to {}.

If not None, daemon explicitly sets whether the thread is daemonic. If None (the default), the daemonic property is inherited from the current thread.

context is the Context value to use when starting the thread. The default value is None which indicates that the sys.flags.thread_inherit_context flag controls the behaviour. If the flag is true, threads will start with a copy of the context of the caller of start(). If false, they will start with an empty context. To explicitly start with an empty context, pass a new instance of Context(). To explicitly start with a copy of the current context, pass the value from copy_context(). The flag defaults true on free-threaded builds and false otherwise.

If the subclass overrides the constructor, it must make sure to invoke the base class constructor (Thread.__init__()) before doing anything else to the thread.

在 3.3 版的變更: 新增 daemon 參數。

在 3.10 版的變更: Use the target name if name argument is omitted.

在 3.14 版的變更: 新增 context 參數。

start()

Start the thread's activity.

It must be called at most once per thread object. It arranges for the object's run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.

If supported, set the operating system thread name to threading.Thread.name. The name can be truncated depending on the operating system thread name limits.

在 3.14 版的變更: Set the operating system thread name.

run()

Method representing the thread's activity.

You may override this method in a subclass. The standard run() method invokes the callable object passed to the object's constructor as the target argument, if any, with positional and keyword arguments taken from the args and kwargs arguments, respectively.

Using list or tuple as the args argument which passed to the Thread could achieve the same effect.

舉例來說：

>>> from threading import Thread
>>> t = Thread(target=print, args=[1])
>>> t.run()
1
>>> t = Thread(target=print, args=(1,))
>>> t.run()
1

join(timeout=None)

Wait until the thread terminates. This blocks the calling thread until the thread whose join() method is called terminates -- either normally or through an unhandled exception -- or until the optional timeout occurs.

When the timeout argument is present and not None, it should be a floating-point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call is_alive() after join() to decide whether a timeout happened -- if the thread is still alive, the join() call timed out.

When the timeout argument is not present or None, the operation will block until the thread terminates.

A thread can be joined many times.

join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raise the same exception.

If an attempt is made to join a running daemonic thread in late stages of Python finalization join() raises a PythonFinalizationError.

在 3.14 版的變更: 可能引發 PythonFinalizationError。

name

A string used for identification purposes only. It has no semantics. Multiple threads may be given the same name. The initial name is set by the constructor.

On some platforms, the thread name is set at the operating system level when the thread starts, so that it is visible in task managers. This name may be truncated to fit in a system-specific limit (for example, 15 bytes on Linux or 63 bytes on macOS).

Changes to name are only reflected at the OS level when the currently running thread is renamed. (Setting the name attribute of a different thread only updates the Python Thread object.)

getName()

setName()

Deprecated getter/setter API for name; use it directly as a property instead.

在 3.10 版之後被棄用.

ident

The 'thread identifier' of this thread or None if the thread has not been started. This is a nonzero integer. See the get_ident() function. Thread identifiers may be recycled when a thread exits and another thread is created. The identifier is available even after the thread has exited.

native_id

The Thread ID (TID) of this thread, as assigned by the OS (kernel). This is a non-negative integer, or None if the thread has not been started. See the get_native_id() function. This value may be used to uniquely identify this particular thread system-wide (until the thread terminates, after which the value may be recycled by the OS).

備註

Similar to Process IDs, Thread IDs are only valid (guaranteed unique system-wide) from the time the thread is created until the thread has been terminated.

可用性: Windows, FreeBSD, Linux, macOS, OpenBSD, NetBSD, AIX, DragonFlyBSD.

在 3.8 版被加入.

is_alive()

Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. The module function enumerate() returns a list of all alive threads.

daemon

A boolean value indicating whether this thread is a daemon thread (True) or not (False). This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.

The entire Python program exits when no alive non-daemon threads are left.

isDaemon()

setDaemon()

Deprecated getter/setter API for daemon; use it directly as a property instead.

在 3.10 版之後被棄用.

Lock 物件

原始鎖 (primitive lock) 是一種同步原語 (synchronization primitive)，在鎖定時不屬於特定執行緒。在 Python 中，它是目前可用的最低階同步原語，直接由 _thread 擴充模組實作。

原始鎖會處於兩種狀態之一：「鎖定 (locked)」或「未鎖定 (unclocked)」，建立時會處於未鎖定狀態。它有兩個基本方法 acquire() 和 release()。當狀態為未鎖定時，acquire() 會將狀態變更為鎖定並立即回傳。當狀態被鎖定時，acquire() 會阻塞 (block)，直到另一個執行緒中對 release() 的呼叫將其更改為未鎖定狀態，然後 acquire() 呼叫會將其重置為鎖定並回傳。release() 方法只能在鎖定狀態下呼叫；它將狀態更改為未鎖定並立即回傳。如果嘗試釋放未鎖定的鎖，則會引發 RuntimeError。

鎖也支援情境管理協定。

當多個執行緒阻塞在 acquire() 中等待狀態轉變為未鎖定，此時若呼叫 release() 將狀態重置為未鎖定，則只會有一個執行緒繼續進行；哪一個等待執行緒會繼續進行是未定義的，並且可能因實作而異。

所有方法均以最小不可分割的操作方式 (atomically) 執行。

class threading.Lock

實作原始鎖物件的類別。一旦執行緒獲得了鎖，後續再嘗試獲得它就會被阻塞，直到鎖被釋放；任何執行緒都可以去釋放它。

在 3.13 版的變更: Lock 現在是一個類別。在早期的 Python 中，Lock 是一個會回傳底層私有鎖型別實例的工廠函式。

acquire(blocking=True, timeout=-1)

阻塞或非阻塞地取得鎖。

當以 blocking 引數設為 True（預設值）來叫用，將會阻塞直到鎖被解鎖，然後將其設為鎖定並回傳 True。

當以 blocking 引數設為 False 叫用則不會阻塞。如果 blocking 設定為 True 的呼叫會阻塞，則立即回傳 False；否則將鎖設為鎖定並回傳 True。

當使用設定為正值的浮點 timeout 引數進行叫用，只要持續無法取得鎖，最多會阻塞 timeout 指定的秒數。-1 的 timeout 引數代表指定為不會停止的等待。當 blocking 為 False 時禁止指定 timeout。

如果成功取得鎖，則回傳值為 True，否則回傳值為 False（例如像是 timeout 已逾期）。

在 3.2 版的變更: 新的 timeout 參數。

在 3.2 版的變更: 如果底層執行緒實作支援的話，鎖的取得現在可以被 POSIX 上的訊號中斷。

在 3.14 版的變更: Lock acquisition can now be interrupted by signals on Windows.

release()

釋放鎖。這可以從任何執行緒呼叫，而不是只有獲得鎖的執行緒。

當鎖被鎖定時，將其重置為未鎖定然後回傳。如果任何其他執行緒在等待鎖被解鎖時被阻塞，只允許其中一個執行緒繼續進行。

當在未鎖定的鎖上叫用時，會引發 RuntimeError

沒有回傳值。

locked()

如果有取得了鎖，則回傳 True。

RLock 物件

可重入鎖 (reentrant lock) 是一種同步原語，同一執行緒可以多次取得它。在內部，除了原始鎖使用的鎖定/未鎖定狀態之外，它還使用「所屬執行緒 (owning thread)」和「遞迴等級 (recursion level)」的概念。在鎖定狀態下，某個執行緒會擁有鎖；在未鎖定狀態下則沒有執行緒擁有它。

執行緒呼叫鎖的 acquire() 方法來鎖定它，並呼叫它的 release() 方法來解鎖它。

備註

可重入鎖支援情境管理協定，因此建議使用 with 而不是手動呼叫 acquire() 和 release() 來對程式碼區塊處理鎖的獲得和釋放。

RLock 的 acquire()/release() 呼叫成對組合可以嵌套使用，這與 Lock 的 acquire()/release() 不同。只有最後一個 release()（最外面一對的 release()）會將鎖重置為未鎖定狀態，並允許在 acquire() 中阻塞的另一個執行緒繼續進行。

acquire()/release() 必須成對使用：每次獲得都必須在已獲得鎖的執行緒中有一個釋放。如果鎖釋放的次數不能和取得的次數一樣的話，可能會導致死鎖 (deadlock)。

class threading.RLock

此類別實作了可重入鎖物件。可重入鎖必須由獲得它的執行緒釋放。一旦一個執行緒獲得了可重入鎖，同一個執行緒可以再次獲得它而不會阻塞；執行緒每次獲得它也都必須釋放它一次。

請注意，RLock 實際上是一個工廠函式，它會回傳平台有支援的特定 RLock 類別的最高效率版本的實例。

acquire(blocking=True, timeout=-1)

阻塞或非阻塞地取得鎖。

也參考

將 RLock 用作為情境管理器

若是使用場景合理，和手動呼叫 acquire() 和 release() 相比，會是更為推薦的使用方式。

當以 blocking 引數設為 True（預設值）來呼叫：

如果沒有執行緒擁有鎖，則獲得鎖並立即回傳。

如果另一個執行緒擁有鎖，則阻塞直到能夠取得鎖，或者達到 timeout（如果設定為正浮點值）。

如果同一個執行緒擁有鎖，則再次取得鎖，並立即回傳。這就是 Lock 和 RLock 之間的差別；Lock 處理方式與上一種情況相同，會阻塞直到能夠取得鎖。

當以 blocking 引數設為 False 來呼叫：

如果沒有執行緒擁有鎖，則獲得鎖並立即回傳。

如果另一個執行緒擁有該鎖，則立即回傳。

如果同一個執行緒擁有鎖，則再次取得鎖並立即回傳。

在所有情況下，如果執行緒能夠取得鎖則回傳 True。如果執行緒無法取得鎖（即沒有阻塞或已達超時限制）則回傳 False。

如果多次呼叫，又未能呼叫相同次數的 release()，則可能會導致死鎖。考慮將 RLock 作為情境管理器使用，而不是直接呼叫 acquire/release。

在 3.2 版的變更: 新的 timeout 參數。

release()

釋放鎖並減少遞迴等級。如果被減至零，則將鎖重置為未鎖定（不屬於任何執行緒），並且如果任何其他執行緒被阻塞以等待鎖變成未鎖定狀態，則僅允許其中一個執行緒繼續進行。如果遞減後遞迴等級仍然非零，則鎖會保持鎖定並由呼叫它的執行緒所擁有。

僅當呼叫的執行緒擁有鎖時才能呼叫此方法。如果在未取得鎖時呼叫此方法則會引發 RuntimeError。

沒有回傳值。

locked()

Return a boolean indicating whether this object is locked right now.

在 3.14 版被加入.

Condition objects

A condition variable is always associated with some kind of lock; this can be passed in or one will be created by default. Passing one in is useful when several condition variables must share the same lock. The lock is part of the condition object: you don't have to track it separately.

A condition variable obeys the context management protocol: using the with statement acquires the associated lock for the duration of the enclosed block. The acquire() and release() methods also call the corresponding methods of the associated lock.

Other methods must be called with the associated lock held. The wait() method releases the lock, and then blocks until another thread awakens it by calling notify() or notify_all(). Once awakened, wait() re-acquires the lock and returns. It is also possible to specify a timeout.

The notify() method wakes up one of the threads waiting for the condition variable, if any are waiting. The notify_all() method wakes up all threads waiting for the condition variable.

Note: the notify() and notify_all() methods don't release the lock; this means that the thread or threads awakened will not return from their wait() call immediately, but only when the thread that called notify() or notify_all() finally relinquishes ownership of the lock.

The typical programming style using condition variables uses the lock to synchronize access to some shared state; threads that are interested in a particular change of state call wait() repeatedly until they see the desired state, while threads that modify the state call notify() or notify_all() when they change the state in such a way that it could possibly be a desired state for one of the waiters. For example, the following code is a generic producer-consumer situation with unlimited buffer capacity:

# Consume one item
with cv:
    while not an_item_is_available():
        cv.wait()
    get_an_available_item()

# Produce one item
with cv:
    make_an_item_available()
    cv.notify()

The while loop checking for the application's condition is necessary because wait() can return after an arbitrary long time, and the condition which prompted the notify() call may no longer hold true. This is inherent to multi-threaded programming. The wait_for() method can be used to automate the condition checking, and eases the computation of timeouts:

# Consume an item
with cv:
    cv.wait_for(an_item_is_available)
    get_an_available_item()

To choose between notify() and notify_all(), consider whether one state change can be interesting for only one or several waiting threads. E.g. in a typical producer-consumer situation, adding one item to the buffer only needs to wake up one consumer thread.

class threading.Condition(lock=None)

This class implements condition variable objects. A condition variable allows one or more threads to wait until they are notified by another thread.

If the lock argument is given and not None, it must be a Lock or RLock object, and it is used as the underlying lock. Otherwise, a new RLock object is created and used as the underlying lock.

在 3.3 版的變更: changed from a factory function to a class.

acquire(*args)

Acquire the underlying lock. This method calls the corresponding method on the underlying lock; the return value is whatever that method returns.

release()

Release the underlying lock. This method calls the corresponding method on the underlying lock; there is no return value.

locked()

Return a boolean indicating whether this object is locked right now.

在 3.14 版被加入.

wait(timeout=None)

Wait until notified or until a timeout occurs. If the calling thread has not acquired the lock when this method is called, a RuntimeError is raised.

This method releases the underlying lock, and then blocks until it is awakened by a notify() or notify_all() call for the same condition variable in another thread, or until the optional timeout occurs. Once awakened or timed out, it re-acquires the lock and returns.

When the timeout argument is present and not None, it should be a floating-point number specifying a timeout for the operation in seconds (or fractions thereof).

When the underlying lock is an RLock, it is not released using its release() method, since this may not actually unlock the lock when it was acquired multiple times recursively. Instead, an internal interface of the RLock class is used, which really unlocks it even when it has been recursively acquired several times. Another internal interface is then used to restore the recursion level when the lock is reacquired.

The return value is True unless a given timeout expired, in which case it is False.

在 3.2 版的變更: 先前此方法總是回傳 None。

wait_for(predicate, timeout=None)

Wait until a condition evaluates to true. predicate should be a callable which result will be interpreted as a boolean value. A timeout may be provided giving the maximum time to wait.

This utility method may call wait() repeatedly until the predicate is satisfied, or until a timeout occurs. The return value is the last return value of the predicate and will evaluate to False if the method timed out.

Ignoring the timeout feature, calling this method is roughly equivalent to writing:

while not predicate():
    cv.wait()

Therefore, the same rules apply as with wait(): The lock must be held when called and is re-acquired on return. The predicate is evaluated with the lock held.

在 3.2 版被加入.

notify(n=1)

By default, wake up one thread waiting on this condition, if any. If the calling thread has not acquired the lock when this method is called, a RuntimeError is raised.

This method wakes up at most n of the threads waiting for the condition variable; it is a no-op if no threads are waiting.

The current implementation wakes up exactly n threads, if at least n threads are waiting. However, it's not safe to rely on this behavior. A future, optimized implementation may occasionally wake up more than n threads.

Note: an awakened thread does not actually return from its wait() call until it can reacquire the lock. Since notify() does not release the lock, its caller should.

notify_all()

Wake up all threads waiting on this condition. This method acts like notify(), but wakes up all waiting threads instead of one. If the calling thread has not acquired the lock when this method is called, a RuntimeError is raised.

The method notifyAll is a deprecated alias for this method.

Semaphore 物件

This is one of the oldest synchronization primitives in the history of computer science, invented by the early Dutch computer scientist Edsger W. Dijkstra (he used the names P() and V() instead of acquire() and release()).

A semaphore manages an internal counter which is decremented by each acquire() call and incremented by each release() call. The counter can never go below zero; when acquire() finds that it is zero, it blocks, waiting until some other thread calls release().

Semaphores also support the context management protocol.

class threading.Semaphore(value=1)

This class implements semaphore objects. A semaphore manages an atomic counter representing the number of release() calls minus the number of acquire() calls, plus an initial value. The acquire() method blocks if necessary until it can return without making the counter negative. If not given, value defaults to 1.

The optional argument gives the initial value for the internal counter; it defaults to 1. If the value given is less than 0, ValueError is raised.

在 3.3 版的變更: changed from a factory function to a class.

acquire(blocking=True, timeout=None)

Acquire a semaphore.

When invoked without arguments:

If the internal counter is larger than zero on entry, decrement it by one and return True immediately.

If the internal counter is zero on entry, block until awoken by a call to release(). Once awoken (and the counter is greater than 0), decrement the counter by 1 and return True. Exactly one thread will be awoken by each call to release(). The order in which threads are awoken should not be relied on.

When invoked with blocking set to False, do not block. If a call without an argument would block, return False immediately; otherwise, do the same thing as when called without arguments, and return True.

When invoked with a timeout other than None, it will block for at most timeout seconds. If acquire does not complete successfully in that interval, return False. Return True otherwise.

在 3.2 版的變更: 新的 timeout 參數。

release(n=1)

Release a semaphore, incrementing the internal counter by n. When it was zero on entry and other threads are waiting for it to become larger than zero again, wake up n of those threads.

在 3.9 版的變更: Added the n parameter to release multiple waiting threads at once.

class threading.BoundedSemaphore(value=1)

Class implementing bounded semaphore objects. A bounded semaphore checks to make sure its current value doesn't exceed its initial value. If it does, ValueError is raised. In most situations semaphores are used to guard resources with limited capacity. If the semaphore is released too many times it's a sign of a bug. If not given, value defaults to 1.

在 3.3 版的變更: changed from a factory function to a class.

Semaphore 範例

Semaphores are often used to guard resources with limited capacity, for example, a database server. In any situation where the size of the resource is fixed, you should use a bounded semaphore. Before spawning any worker threads, your main thread would initialize the semaphore:

maxconnections = 5
# ...
pool_sema = BoundedSemaphore(value=maxconnections)

Once spawned, worker threads call the semaphore's acquire and release methods when they need to connect to the server:

with pool_sema:
    conn = connectdb()
    try:
        # ... 使用該連線 ...
    finally:
        conn.close()

The use of a bounded semaphore reduces the chance that a programming error which causes the semaphore to be released more than it's acquired will go undetected.

Event objects

This is one of the simplest mechanisms for communication between threads: one thread signals an event and other threads wait for it.

An event object manages an internal flag that can be set to true with the set() method and reset to false with the clear() method. The wait() method blocks until the flag is true.

class threading.Event

Class implementing event objects. An event manages a flag that can be set to true with the set() method and reset to false with the clear() method. The wait() method blocks until the flag is true. The flag is initially false.

在 3.3 版的變更: changed from a factory function to a class.

is_set()

Return True if and only if the internal flag is true.

The method isSet is a deprecated alias for this method.

set()

Set the internal flag to true. All threads waiting for it to become true are awakened. Threads that call wait() once the flag is true will not block at all.

clear()

Reset the internal flag to false. Subsequently, threads calling wait() will block until set() is called to set the internal flag to true again.

wait(timeout=None)

Block as long as the internal flag is false and the timeout, if given, has not expired. The return value represents the reason that this blocking method returned; True if returning because the internal flag is set to true, or False if a timeout is given and the internal flag did not become true within the given wait time.

When the timeout argument is present and not None, it should be a floating-point number specifying a timeout for the operation in seconds, or fractions thereof.

在 3.1 版的變更: 先前此方法總是回傳 None。

Timer 物件

This class represents an action that should be run only after a certain amount of time has passed --- a timer. Timer is a subclass of Thread and as such also functions as an example of creating custom threads.

Timers are started, as with threads, by calling their Timer.start method. The timer can be stopped (before its action has begun) by calling the cancel() method. The interval the timer will wait before executing its action may not be exactly the same as the interval specified by the user.

舉例來說：

def hello():
    print("hello, world")

t = Timer(30.0, hello)
t.start()  # 30 秒後會印出 "hello, world"

class threading.Timer(interval, function, args=None, kwargs=None)

Create a timer that will run function with arguments args and keyword arguments kwargs, after interval seconds have passed. If args is None (the default) then an empty list will be used. If kwargs is None (the default) then an empty dict will be used.

在 3.3 版的變更: changed from a factory function to a class.

cancel()

Stop the timer, and cancel the execution of the timer's action. This will only work if the timer is still in its waiting stage.

Barrier 物件

在 3.2 版被加入.

This class provides a simple synchronization primitive for use by a fixed number of threads that need to wait for each other. Each of the threads tries to pass the barrier by calling the wait() method and will block until all of the threads have made their wait() calls. At this point, the threads are released simultaneously.

The barrier can be reused any number of times for the same number of threads.

As an example, here is a simple way to synchronize a client and server thread:

b = Barrier(2, timeout=5)

def server():
    start_server()
    b.wait()
    while True:
        connection = accept_connection()
        process_server_connection(connection)

def client():
    b.wait()
    while True:
        connection = make_connection()
        process_client_connection(connection)

class threading.Barrier(parties, action=None, timeout=None)

Create a barrier object for parties number of threads. An action, when provided, is a callable to be called by one of the threads when they are released. timeout is the default timeout value if none is specified for the wait() method.

wait(timeout=None)

Pass the barrier. When all the threads party to the barrier have called this function, they are all released simultaneously. If a timeout is provided, it is used in preference to any that was supplied to the class constructor.

The return value is an integer in the range 0 to parties -- 1, different for each thread. This can be used to select a thread to do some special housekeeping, e.g.:

i = barrier.wait()
if i == 0:
    # 只會有一個執行緒會印出這個
    print("passed the barrier")

If an action was provided to the constructor, one of the threads will have called it prior to being released. Should this call raise an error, the barrier is put into the broken state.

If the call times out, the barrier is put into the broken state.

This method may raise a BrokenBarrierError exception if the barrier is broken or reset while a thread is waiting.

reset()

Return the barrier to the default, empty state. Any threads waiting on it will receive the BrokenBarrierError exception.

Note that using this function may require some external synchronization if there are other threads whose state is unknown. If a barrier is broken it may be better to just leave it and create a new one.

abort()

Put the barrier into a broken state. This causes any active or future calls to wait() to fail with the BrokenBarrierError. Use this for example if one of the threads needs to abort, to avoid deadlocking the application.

It may be preferable to simply create the barrier with a sensible timeout value to automatically guard against one of the threads going awry.

parties

The number of threads required to pass the barrier.

n_waiting

The number of threads currently waiting in the barrier.

broken

A boolean that is True if the barrier is in the broken state.

exception threading.BrokenBarrierError

This exception, a subclass of RuntimeError, is raised when the Barrier object is reset or broken.

Using locks, conditions, and semaphores in the with statement

All of the objects provided by this module that have acquire and release methods can be used as context managers for a with statement. The acquire method will be called when the block is entered, and release will be called when the block is exited. Hence, the following snippet:

with some_lock:
    # 做某些事情...

is equivalent to:

some_lock.acquire()
try:
    # 做某些事情...
finally:
    some_lock.release()

Currently, Lock, RLock, Condition, Semaphore, and BoundedSemaphore objects may be used as with statement context managers.

multiprocessing --- 以行程為基礎的平行性

原始碼：Lib/multiprocessing/ [https://github.com/python/cpython/tree/3.14/Lib/multiprocessing/]

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

簡介

multiprocessing is a package that supports spawning processes using an API similar to the threading module. The multiprocessing package offers both local and remote concurrency, effectively side-stepping the Global Interpreter Lock by using subprocesses instead of threads. Due to this, the multiprocessing module allows the programmer to fully leverage multiple processors on a given machine. It runs on both POSIX and Windows.

The multiprocessing module also introduces the Pool object which offers a convenient means of parallelizing the execution of a function across multiple input values, distributing the input data across processes (data parallelism). The following example demonstrates the common practice of defining such functions in a module so that child processes can successfully import that module. This basic example of data parallelism using Pool,

from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(5) as p:
        print(p.map(f, [1, 2, 3]))

will print to standard output

[1, 4, 9]

The multiprocessing module also introduces APIs which do not have analogs in the threading module, like the ability to terminate, interrupt or kill a running process.

也參考

concurrent.futures.ProcessPoolExecutor offers a higher level interface to push tasks to a background process without blocking execution of the calling process. Compared to using the Pool interface directly, the concurrent.futures API more readily allows the submission of work to the underlying process pool to be separated from waiting for the results.

Process 類別

In multiprocessing, processes are spawned by creating a Process object and then calling its start() method. Process follows the API of threading.Thread. A trivial example of a multiprocess program is

from multiprocessing import Process

def f(name):
    print('hello', name)

if __name__ == '__main__':
    p = Process(target=f, args=('bob',))
    p.start()
    p.join()

To show the individual process IDs involved, here is an expanded example:

from multiprocessing import Process
import os

def info(title):
    print(title)
    print('module name:', __name__)
    print('parent process:', os.getppid())
    print('process id:', os.getpid())

def f(name):
    info('function f')
    print('hello', name)

if __name__ == '__main__':
    info('main line')
    p = Process(target=f, args=('bob',))
    p.start()
    p.join()

For an explanation of why the if __name__ == '__main__' part is necessary, see Programming guidelines.

The arguments to Process usually need to be unpickleable from within the child process. If you tried typing the above example directly into a REPL it could lead to an AttributeError in the child process trying to locate the f function in the __main__ module.

Contexts and start methods

Depending on the platform, multiprocessing supports three ways to start a process. These start methods are

spawn

The parent process starts a fresh Python interpreter process. The child process will only inherit those resources necessary to run the process object's run() method. In particular, unnecessary file descriptors and handles from the parent process will not be inherited. Starting a process using this method is rather slow compared to using fork or forkserver.

Available on POSIX and Windows platforms. The default on Windows and macOS.

fork

The parent process uses os.fork() to fork the Python interpreter. The child process, when it begins, is effectively identical to the parent process. All resources of the parent are inherited by the child process. Note that safely forking a multithreaded process is problematic.

Available on POSIX systems.

在 3.14 版的變更: This is no longer the default start method on any platform. Code that requires fork must explicitly specify that via get_context() or set_start_method().

在 3.12 版的變更: If Python is able to detect that your process has multiple threads, the os.fork() function that this start method calls internally will raise a DeprecationWarning. Use a different start method. See the os.fork() documentation for further explanation.

forkserver

When the program starts and selects the forkserver start method, a server process is spawned. From then on, whenever a new process is needed, the parent process connects to the server and requests that it fork a new process. The fork server process is single threaded unless system libraries or preloaded imports spawn threads as a side-effect so it is generally safe for it to use os.fork(). No unnecessary resources are inherited.

Available on POSIX platforms which support passing file descriptors over Unix pipes such as Linux. The default on those.

在 3.14 版的變更: This became the default start method on POSIX platforms.

在 3.4 版的變更: spawn added on all POSIX platforms, and forkserver added for some POSIX platforms. Child processes no longer inherit all of the parents inheritable handles on Windows.

在 3.8 版的變更: On macOS, the spawn start method is now the default. The fork start method should be considered unsafe as it can lead to crashes of the subprocess as macOS system libraries may start threads. See bpo-33725 [https://bugs.python.org/issue?@action=redirect&bpo=33725].

在 3.14 版的變更: On POSIX platforms the default start method was changed from fork to forkserver to retain the performance but avoid common multithreaded process incompatibilities. See gh-84559 [https://github.com/python/cpython/issues/84559].

On POSIX using the spawn or forkserver start methods will also start a resource tracker process which tracks the unlinked named system resources (such as named semaphores or SharedMemory objects) created by processes of the program. When all processes have exited the resource tracker unlinks any remaining tracked object. Usually there should be none, but if a process was killed by a signal there may be some "leaked" resources. (Neither leaked semaphores nor shared memory segments will be automatically unlinked until the next reboot. This is problematic for both objects because the system allows only a limited number of named semaphores, and shared memory segments occupy some space in the main memory.)

To select a start method you use the set_start_method() in the if __name__ == '__main__' clause of the main module. For example:

import multiprocessing as mp

def foo(q):
    q.put('hello')

if __name__ == '__main__':
    mp.set_start_method('spawn')
    q = mp.Queue()
    p = mp.Process(target=foo, args=(q,))
    p.start()
    print(q.get())
    p.join()

set_start_method() should not be used more than once in the program.

Alternatively, you can use get_context() to obtain a context object. Context objects have the same API as the multiprocessing module, and allow one to use multiple start methods in the same program.

import multiprocessing as mp

def foo(q):
    q.put('hello')

if __name__ == '__main__':
    ctx = mp.get_context('spawn')
    q = ctx.Queue()
    p = ctx.Process(target=foo, args=(q,))
    p.start()
    print(q.get())
    p.join()

Note that objects related to one context may not be compatible with processes for a different context. In particular, locks created using the fork context cannot be passed to processes started using the spawn or forkserver start methods.

Libraries using multiprocessing or ProcessPoolExecutor should be designed to allow their users to provide their own multiprocessing context. Using a specific context of your own within a library can lead to incompatibilities with the rest of the library user's application. Always document if your library requires a specific start method.

警告

The 'spawn' and 'forkserver' start methods generally cannot be used with "frozen" executables (i.e., binaries produced by packages like PyInstaller and cx_Freeze) on POSIX systems. The 'fork' start method may work if code does not use threads.

Exchanging objects between processes

multiprocessing supports two types of communication channel between processes:

Queues

The Queue class is a near clone of queue.Queue. For example:

from multiprocessing import Process, Queue

def f(q):
    q.put([42, None, 'hello'])

if __name__ == '__main__':
    q = Queue()
    p = Process(target=f, args=(q,))
    p.start()
    print(q.get())    # 印出 "[42, None, 'hello']"
    p.join()

Queues are thread and process safe. Any object put into a multiprocessing queue will be serialized.

Pipes

The Pipe() function returns a pair of connection objects connected by a pipe which by default is duplex (two-way). For example:

from multiprocessing import Process, Pipe

def f(conn):
    conn.send([42, None, 'hello'])
    conn.close()

if __name__ == '__main__':
    parent_conn, child_conn = Pipe()
    p = Process(target=f, args=(child_conn,))
    p.start()
    print(parent_conn.recv())   # 印出 "[42, None, 'hello']"
    p.join()

The two connection objects returned by Pipe() represent the two ends of the pipe. Each connection object has send() and recv() methods (among others). Note that data in a pipe may become corrupted if two processes (or threads) try to read from or write to the same end of the pipe at the same time. Of course there is no risk of corruption from processes using different ends of the pipe at the same time.

The send() method serializes the object and recv() re-creates the object.

Synchronization between processes

multiprocessing contains equivalents of all the synchronization primitives from threading. For instance one can use a lock to ensure that only one process prints to standard output at a time:

from multiprocessing import Process, Lock

def f(l, i):
    l.acquire()
    try:
        print('hello world', i)
    finally:
        l.release()

if __name__ == '__main__':
    lock = Lock()

    for num in range(10):
        Process(target=f, args=(lock, num)).start()

Without using the lock output from the different processes is liable to get all mixed up.

Sharing state between processes

As mentioned above, when doing concurrent programming it is usually best to avoid using shared state as far as possible. This is particularly true when using multiple processes.

However, if you really do need to use some shared data then multiprocessing provides a couple of ways of doing so.

Shared memory

Data can be stored in a shared memory map using Value or Array. For example, the following code

from multiprocessing import Process, Value, Array

def f(n, a):
    n.value = 3.1415927
    for i in range(len(a)):
        a[i] = -a[i]

if __name__ == '__main__':
    num = Value('d', 0.0)
    arr = Array('i', range(10))

    p = Process(target=f, args=(num, arr))
    p.start()
    p.join()

    print(num.value)
    print(arr[:])

will print

3.1415927
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]

The 'd' and 'i' arguments used when creating num and arr are typecodes of the kind used by the array module: 'd' indicates a double precision float and 'i' indicates a signed integer. These shared objects will be process and thread-safe.

For more flexibility in using shared memory one can use the multiprocessing.sharedctypes module which supports the creation of arbitrary ctypes objects allocated from shared memory.

Server process

A manager object returned by Manager() controls a server process which holds Python objects and allows other processes to manipulate them using proxies.

A manager returned by Manager() will support types list, dict, set, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Barrier, Queue, Value and Array. For example,

from multiprocessing import Process, Manager

def f(d, l, s):
    d[1] = '1'
    d['2'] = 2
    d[0.25] = None
    l.reverse()
    s.add('a')
    s.add('b')

if __name__ == '__main__':
    with Manager() as manager:
        d = manager.dict()
        l = manager.list(range(10))
        s = manager.set()

        p = Process(target=f, args=(d, l, s))
        p.start()
        p.join()

        print(d)
        print(l)
        print(s)

will print

{0.25: None, 1: '1', '2': 2}
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
{'a', 'b'}

Server process managers are more flexible than using shared memory objects because they can be made to support arbitrary object types. Also, a single manager can be shared by processes on different computers over a network. They are, however, slower than using shared memory.

Using a pool of workers

The Pool class represents a pool of worker processes. It has methods which allows tasks to be offloaded to the worker processes in a few different ways.

舉例來說：

from multiprocessing import Pool, TimeoutError
import time
import os

def f(x):
    return x*x

if __name__ == '__main__':
    # start 4 worker processes
    with Pool(processes=4) as pool:

        # print "[0, 1, 4,..., 81]"
        print(pool.map(f, range(10)))

        # print same numbers in arbitrary order
        for i in pool.imap_unordered(f, range(10)):
            print(i)

        # evaluate "f(20)" asynchronously
        res = pool.apply_async(f, (20,))      # runs in *only* one process
        print(res.get(timeout=1))             # prints "400"

        # evaluate "os.getpid()" asynchronously
        res = pool.apply_async(os.getpid, ()) # runs in *only* one process
        print(res.get(timeout=1))             # prints the PID of that process

        # launching multiple evaluations asynchronously *may* use more processes
        multiple_results = [pool.apply_async(os.getpid, ()) for i in range(4)]
        print([res.get(timeout=1) for res in multiple_results])

        # make a single worker sleep for 10 seconds
        res = pool.apply_async(time.sleep, (10,))
        try:
            print(res.get(timeout=1))
        except TimeoutError:
            print("We lacked patience and got a multiprocessing.TimeoutError")

        print("For the moment, the pool remains available for more work")

    # exiting the 'with'-block has stopped the pool
    print("Now the pool is closed and no longer available")

Note that the methods of a pool should only ever be used by the process which created it.

備註

Functionality within this package requires that the __main__ module be importable by the children. This is covered in Programming guidelines however it is worth pointing out here. This means that some examples, such as the multiprocessing.pool.Pool examples will not work in the interactive interpreter. For example:

>>> from multiprocessing import Pool
>>> p = Pool(5)
>>> def f(x):
...     return x*x
...
>>> with p:
...     p.map(f, [1,2,3])
Process PoolWorker-1:
Process PoolWorker-2:
Process PoolWorker-3:
Traceback (most recent call last):
Traceback (most recent call last):
Traceback (most recent call last):
AttributeError: Can't get attribute 'f' on <module '__main__' (<class '_frozen_importlib.BuiltinImporter'>)>
AttributeError: Can't get attribute 'f' on <module '__main__' (<class '_frozen_importlib.BuiltinImporter'>)>
AttributeError: Can't get attribute 'f' on <module '__main__' (<class '_frozen_importlib.BuiltinImporter'>)>

(If you try this it will actually output three full tracebacks interleaved in a semi-random fashion, and then you may have to stop the parent process somehow.)

Reference

The multiprocessing package mostly replicates the API of the threading module.

Global start method

Python supports several ways to create and initialize a process. The global start method sets the default mechanism for creating a process.

Several multiprocessing functions and methods that may also instantiate certain objects will implicitly set the global start method to the system's default, if it hasn’t been set already. The global start method can only be set once. If you need to change the start method from the system default, you must proactively set the global start method before calling functions or methods, or creating these objects.

Process 與例外

class multiprocessing.Process(group=None, target=None, name=None, args=(), kwargs={}, *, daemon=None)

Process objects represent activity that is run in a separate process. The Process class has equivalents of all the methods of threading.Thread.

The constructor should always be called with keyword arguments. group should always be None; it exists solely for compatibility with threading.Thread. target is the callable object to be invoked by the run() method. It defaults to None, meaning nothing is called. name is the process name (see name for more details). args is the argument tuple for the target invocation. kwargs is a dictionary of keyword arguments for the target invocation. If provided, the keyword-only daemon argument sets the process daemon flag to True or False. If None (the default), this flag will be inherited from the creating process.

By default, no arguments are passed to target. The args argument, which defaults to (), can be used to specify a list or tuple of the arguments to pass to target.

If a subclass overrides the constructor, it must make sure it invokes the base class constructor (super().__init__()) before doing anything else to the process.

備註

In general, all arguments to Process must be picklable. This is frequently observed when trying to create a Process or use a concurrent.futures.ProcessPoolExecutor from a REPL with a locally defined target function.

Passing a callable object defined in the current REPL session causes the child process to die via an uncaught AttributeError exception when starting as target must have been defined within an importable module in order to be loaded during unpickling.

Example of this uncatchable error from the child:

>>> import multiprocessing as mp
>>> def knigit():
...     print("Ni!")
...
>>> process = mp.Process(target=knigit)
>>> process.start()
>>> Traceback (most recent call last):
  File ".../multiprocessing/spawn.py", line ..., in spawn_main
  File ".../multiprocessing/spawn.py", line ..., in _main
AttributeError: module '__main__' has no attribute 'knigit'
>>> process
<SpawnProcess name='SpawnProcess-1' pid=379473 parent=378707 stopped exitcode=1>

See The spawn and forkserver start methods. While this restriction is not true if using the "fork" start method, as of Python 3.14 that is no longer the default on any platform. See Contexts and start methods. See also gh-132898 [https://github.com/python/cpython/issues/132898].

在 3.3 版的變更: 新增 daemon 參數。

run()

Method representing the process's activity.

You may override this method in a subclass. The standard run() method invokes the callable object passed to the object's constructor as the target argument, if any, with sequential and keyword arguments taken from the args and kwargs arguments, respectively.

Using a list or tuple as the args argument passed to Process achieves the same effect.

範例：

>>> from multiprocessing import Process
>>> p = Process(target=print, args=[1])
>>> p.run()
1
>>> p = Process(target=print, args=(1,))
>>> p.run()
1

start()

Start the process's activity.

This must be called at most once per process object. It arranges for the object's run() method to be invoked in a separate process.

join([timeout])

If the optional argument timeout is None (the default), the method blocks until the process whose join() method is called terminates. If timeout is a positive number, it blocks at most timeout seconds. Note that the method returns None if its process terminates or if the method times out. Check the process's exitcode to determine if it terminated.

A process can be joined many times.

A process cannot join itself because this would cause a deadlock. It is an error to attempt to join a process before it has been started.

name

The process's name. The name is a string used for identification purposes only. It has no semantics. Multiple processes may be given the same name.

The initial name is set by the constructor. If no explicit name is provided to the constructor, a name of the form 'Process-N₁:N₂:...:Nk' is constructed, where each Nk is the N-th child of its parent.

is_alive()

Return whether the process is alive.

Roughly, a process object is alive from the moment the start() method returns until the child process terminates.

daemon

The process's daemon flag, a Boolean value. This must be set before start() is called.

The initial value is inherited from the creating process.

When a process exits, it attempts to terminate all of its daemonic child processes.

Note that a daemonic process is not allowed to create child processes. Otherwise a daemonic process would leave its children orphaned if it gets terminated when its parent process exits. Additionally, these are not Unix daemons or services, they are normal processes that will be terminated (and not joined) if non-daemonic processes have exited.

In addition to the threading.Thread API, Process objects also support the following attributes and methods:

pid

Return the process ID. Before the process is spawned, this will be None.

exitcode

The child's exit code. This will be None if the process has not yet terminated.

If the child's run() method returned normally, the exit code will be 0. If it terminated via sys.exit() with an integer argument N, the exit code will be N.

If the child terminated due to an exception not caught within run(), the exit code will be 1. If it was terminated by signal N, the exit code will be the negative value -N.

authkey

The process's authentication key (a byte string).

When multiprocessing is initialized the main process is assigned a random string using os.urandom().

When a Process object is created, it will inherit the authentication key of its parent process, although this may be changed by setting authkey to another byte string.

參閱 Authentication keys。

sentinel

A numeric handle of a system object which will become "ready" when the process ends.

You can use this value if you want to wait on several events at once using multiprocessing.connection.wait(). Otherwise calling join() is simpler.

On Windows, this is an OS handle usable with the WaitForSingleObject and WaitForMultipleObjects family of API calls. On POSIX, this is a file descriptor usable with primitives from the select module.

在 3.3 版被加入.

interrupt()

Terminate the process. Works on POSIX using the SIGINT signal. Behavior on Windows is undefined.

By default, this terminates the child process by raising KeyboardInterrupt. This behavior can be altered by setting the respective signal handler in the child process signal.signal() for SIGINT.

Note: if the child process catches and discards KeyboardInterrupt, the process will not be terminated.

Note: the default behavior will also set exitcode to 1 as if an uncaught exception was raised in the child process. To have a different exitcode you may simply catch KeyboardInterrupt and call exit(your_code).

在 3.14 版被加入.

terminate()

Terminate the process. On POSIX this is done using the SIGTERM signal; on Windows TerminateProcess() is used. Note that exit handlers and finally clauses, etc., will not be executed.

Note that descendant processes of the process will not be terminated -- they will simply become orphaned.

警告

If this method is used when the associated process is using a pipe or queue then the pipe or queue is liable to become corrupted and may become unusable by other process. Similarly, if the process has acquired a lock or semaphore etc. then terminating it is liable to cause other processes to deadlock.

kill()

Same as terminate() but using the SIGKILL signal on POSIX.

在 3.7 版被加入.

close()

Close the Process object, releasing all resources associated with it. ValueError is raised if the underlying process is still running. Once close() returns successfully, most other methods and attributes of the Process object will raise ValueError.

在 3.7 版被加入.

Note that the start(), join(), is_alive(), terminate() and exitcode methods should only be called by the process that created the process object.

Example usage of some of the methods of Process:

>>> import multiprocessing, time, signal
>>> mp_context = multiprocessing.get_context('spawn')
>>> p = mp_context.Process(target=time.sleep, args=(1000,))
>>> print(p, p.is_alive())
<...Process ... initial> False
>>> p.start()
>>> print(p, p.is_alive())
<...Process ... started> True
>>> p.terminate()
>>> time.sleep(0.1)
>>> print(p, p.is_alive())
<...Process ... stopped exitcode=-SIGTERM> False
>>> p.exitcode == -signal.SIGTERM
True

exception multiprocessing.ProcessError

The base class of all multiprocessing exceptions.

exception multiprocessing.BufferTooShort

Exception raised by Connection.recv_bytes_into() when the supplied buffer object is too small for the message read.

If e is an instance of BufferTooShort then e.args[0] will give the message as a byte string.

exception multiprocessing.AuthenticationError

Raised when there is an authentication error.

exception multiprocessing.TimeoutError

Raised by methods with a timeout when the timeout expires.

Pipes and Queues

When using multiple processes, one generally uses message passing for communication between processes and avoids having to use any synchronization primitives like locks.

For passing messages one can use Pipe() (for a connection between two processes) or a queue (which allows multiple producers and consumers).

The Queue, SimpleQueue and JoinableQueue types are multi-producer, multi-consumer FIFO queues modelled on the queue.Queue class in the standard library. They differ in that Queue lacks the task_done() and join() methods introduced into Python 2.5's queue.Queue class.

If you use JoinableQueue then you must call JoinableQueue.task_done() for each task removed from the queue or else the semaphore used to count the number of unfinished tasks may eventually overflow, raising an exception.

One difference from other Python queue implementations, is that multiprocessing queues serializes all objects that are put into them using pickle. The object returned by the get method is a re-created object that does not share memory with the original object.

Note that one can also create a shared queue by using a manager object -- see Managers.

備註

multiprocessing uses the usual queue.Empty and queue.Full exceptions to signal a timeout. They are not available in the multiprocessing namespace so you need to import them from queue.

備註

When an object is put on a queue, the object is pickled and a background thread later flushes the pickled data to an underlying pipe. This has some consequences which are a little surprising, but should not cause any practical difficulties -- if they really bother you then you can instead use a queue created with a manager.

After putting an object on an empty queue there may be an infinitesimal delay before the queue's empty() method returns False and get_nowait() can return without raising queue.Empty.

If multiple processes are enqueuing objects, it is possible for the objects to be received at the other end out-of-order. However, objects enqueued by the same process will always be in the expected order with respect to each other.

警告

If a process is killed using Process.terminate() or os.kill() while it is trying to use a Queue, then the data in the queue is likely to become corrupted. This may cause any other process to get an exception when it tries to use the queue later on.

警告

As mentioned above, if a child process has put items on a queue (and it has not used JoinableQueue.cancel_join_thread), then that process will not terminate until all buffered items have been flushed to the pipe.

This means that if you try joining that process you may get a deadlock unless you are sure that all items which have been put on the queue have been consumed. Similarly, if the child process is non-daemonic then the parent process may hang on exit when it tries to join all its non-daemonic children.

Note that a queue created using a manager does not have this issue. See Programming guidelines.

For an example of the usage of queues for interprocess communication see 範例.

multiprocessing.Pipe(duplex=True)

Returns a pair (conn1, conn2) of Connection objects representing the ends of a pipe.

If duplex is True (the default) then the pipe is bidirectional. If duplex is False then the pipe is unidirectional: conn1 can only be used for receiving messages and conn2 can only be used for sending messages.

The send() method serializes the object using pickle and the recv() re-creates the object.

class multiprocessing.Queue([maxsize])

Returns a process shared queue implemented using a pipe and a few locks/semaphores. When a process first puts an item on the queue a feeder thread is started which transfers objects from a buffer into the pipe.

Instantiating this class may set the global start method. See Global start method for more details.

The usual queue.Empty and queue.Full exceptions from the standard library's queue module are raised to signal timeouts.

Queue implements all the methods of queue.Queue except for task_done() and join().

qsize()

Return the approximate size of the queue. Because of multithreading/multiprocessing semantics, this number is not reliable.

Note that this may raise NotImplementedError on platforms like macOS where sem_getvalue() is not implemented.

empty()

Return True if the queue is empty, False otherwise. Because of multithreading/multiprocessing semantics, this is not reliable.

May raise an OSError on closed queues. (not guaranteed)

full()

Return True if the queue is full, False otherwise. Because of multithreading/multiprocessing semantics, this is not reliable.

put(obj[, block[, timeout]])

Put obj into the queue. If the optional argument block is True (the default) and timeout is None (the default), block if necessary until a free slot is available. If timeout is a positive number, it blocks at most timeout seconds and raises the queue.Full exception if no free slot was available within that time. Otherwise (block is False), put an item on the queue if a free slot is immediately available, else raise the queue.Full exception (timeout is ignored in that case).

在 3.8 版的變更: If the queue is closed, ValueError is raised instead of AssertionError.

put_nowait(obj)

相當於 put(obj, False)。

get([block[, timeout]])

Remove and return an item from the queue. If optional args block is True (the default) and timeout is None (the default), block if necessary until an item is available. If timeout is a positive number, it blocks at most timeout seconds and raises the queue.Empty exception if no item was available within that time. Otherwise (block is False), return an item if one is immediately available, else raise the queue.Empty exception (timeout is ignored in that case).

在 3.8 版的變更: If the queue is closed, ValueError is raised instead of OSError.

get_nowait()

相當於 get(False)。

multiprocessing.Queue has a few additional methods not found in queue.Queue. These methods are usually unnecessary for most code:

close()

Close the queue: release internal resources.

A queue must not be used anymore after it is closed. For example, get(), put() and empty() methods must no longer be called.

The background thread will quit once it has flushed all buffered data to the pipe. This is called automatically when the queue is garbage collected.

join_thread()

Join the background thread. This can only be used after close() has been called. It blocks until the background thread exits, ensuring that all data in the buffer has been flushed to the pipe.

By default if a process is not the creator of the queue then on exit it will attempt to join the queue's background thread. The process can call cancel_join_thread() to make join_thread() do nothing.

cancel_join_thread()

Prevent join_thread() from blocking. In particular, this prevents the background thread from being joined automatically when the process exits -- see join_thread().

A better name for this method might be allow_exit_without_flush(). It is likely to cause enqueued data to be lost, and you almost certainly will not need to use it. It is really only there if you need the current process to exit immediately without waiting to flush enqueued data to the underlying pipe, and you don't care about lost data.

備註

This class's functionality requires a functioning shared semaphore implementation on the host operating system. Without one, the functionality in this class will be disabled, and attempts to instantiate a Queue will result in an ImportError. See bpo-3770 [https://bugs.python.org/issue?@action=redirect&bpo=3770] for additional information. The same holds true for any of the specialized queue types listed below.

class multiprocessing.SimpleQueue

It is a simplified Queue type, very close to a locked Pipe.

Instantiating this class may set the global start method. See Global start method for more details.

close()

Close the queue: release internal resources.

A queue must not be used anymore after it is closed. For example, get(), put() and empty() methods must no longer be called.

在 3.9 版被加入.

empty()

Return True if the queue is empty, False otherwise.

Always raises an OSError if the SimpleQueue is closed.

get()

Remove and return an item from the queue.

put(item)

Put item into the queue.

class multiprocessing.JoinableQueue([maxsize])

JoinableQueue, a Queue subclass, is a queue which additionally has task_done() and join() methods.

Instantiating this class may set the global start method. See Global start method for more details.

task_done()

Indicate that a formerly enqueued task is complete. Used by queue consumers. For each get() used to fetch a task, a subsequent call to task_done() tells the queue that the processing on the task is complete.

If a join() is currently blocking, it will resume when all items have been processed (meaning that a task_done() call was received for every item that had been put() into the queue).

Raises a ValueError if called more times than there were items placed in the queue.

join()

Block until all items in the queue have been gotten and processed.

The count of unfinished tasks goes up whenever an item is added to the queue. The count goes down whenever a consumer calls task_done() to indicate that the item was retrieved and all work on it is complete. When the count of unfinished tasks drops to zero, join() unblocks.

Miscellaneous

multiprocessing.active_children()

Return list of all live children of the current process.

Calling this has the side effect of "joining" any processes which have already finished.

multiprocessing.cpu_count()

Return the number of CPUs in the system.

This number is not equivalent to the number of CPUs the current process can use. The number of usable CPUs can be obtained with os.process_cpu_count() (or len(os.sched_getaffinity(0))).

When the number of CPUs cannot be determined a NotImplementedError is raised.

也參考

os.cpu_count() os.process_cpu_count()

在 3.13 版的變更: The return value can also be overridden using the -X cpu_count flag or PYTHON_CPU_COUNT as this is merely a wrapper around the os cpu count APIs.

multiprocessing.current_process()

Return the Process object corresponding to the current process.

An analogue of threading.current_thread().

multiprocessing.parent_process()

Return the Process object corresponding to the parent process of the current_process(). For the main process, parent_process will be None.

在 3.8 版被加入.

multiprocessing.freeze_support()

Add support for when a program which uses multiprocessing has been frozen to produce an executable. (Has been tested with py2exe, PyInstaller and cx_Freeze.)

One needs to call this function straight after the if __name__ == '__main__' line of the main module. For example:

from multiprocessing import Process, freeze_support

def f():
    print('hello world!')

if __name__ == '__main__':
    freeze_support()
    Process(target=f).start()

If the freeze_support() line is omitted then trying to run the frozen executable will raise RuntimeError.

Calling freeze_support() has no effect when the start method is not spawn. In addition, if the module is being run normally by the Python interpreter (the program has not been frozen), then freeze_support() has no effect.

multiprocessing.get_all_start_methods()

Returns a list of the supported start methods, the first of which is the default. The possible start methods are 'fork', 'spawn' and 'forkserver'. Not all platforms support all methods. See Contexts and start methods.

在 3.4 版被加入.

multiprocessing.get_context(method=None)

Return a context object which has the same attributes as the multiprocessing module.

If method is None then the default context is returned. Note that if the global start method has not been set, this will set it to the system default See Global start method for more details. Otherwise method should be 'fork', 'spawn', 'forkserver'. ValueError is raised if the specified start method is not available. See Contexts and start methods.

在 3.4 版被加入.

multiprocessing.get_start_method(allow_none=False)

Return the name of start method used for starting processes.

If the global start method is not set and allow_none is False, the global start method is set to the default, and its name is returned. See Global start method for more details.

The return value can be 'fork', 'spawn', 'forkserver' or None. See Contexts and start methods.

在 3.4 版被加入.

在 3.8 版的變更: On macOS, the spawn start method is now the default. The fork start method should be considered unsafe as it can lead to crashes of the subprocess. See bpo-33725 [https://bugs.python.org/issue?@action=redirect&bpo=33725].

multiprocessing.set_executable(executable)

Set the path of the Python interpreter to use when starting a child process. (By default sys.executable is used). Embedders will probably need to do some thing like

set_executable(os.path.join(sys.exec_prefix, 'pythonw.exe'))

before they can create child processes.

在 3.4 版的變更: Now supported on POSIX when the 'spawn' start method is used.

在 3.11 版的變更: 接受一個類路徑物件。

multiprocessing.set_forkserver_preload(module_names)

Set a list of module names for the forkserver main process to attempt to import so that their already imported state is inherited by forked processes. Any ImportError when doing so is silently ignored. This can be used as a performance enhancement to avoid repeated work in every process.

For this to work, it must be called before the forkserver process has been launched (before creating a Pool or starting a Process).

Only meaningful when using the 'forkserver' start method. See Contexts and start methods.

在 3.4 版被加入.

multiprocessing.set_start_method(method, force=False)

Set the method which should be used to start child processes. The method argument can be 'fork', 'spawn' or 'forkserver'. Raises RuntimeError if the start method has already been set and force is not True. If method is None and force is True then the start method is set to None. If method is None and force is False then the context is set to the default context.

Note that this should be called at most once, and it should be protected inside the if __name__ == '__main__' clause of the main module.

參閱 Contexts and start methods。

在 3.4 版被加入.

備註

multiprocessing contains no analogues of threading.active_count(), threading.enumerate(), threading.settrace(), threading.setprofile(), threading.Timer, or threading.local.

Connection Objects

Connection objects allow the sending and receiving of picklable objects or strings. They can be thought of as message oriented connected sockets.

Connection objects are usually created using Pipe -- see also Listeners and Clients.

class multiprocessing.connection.Connection

send(obj)

Send an object to the other end of the connection which should be read using recv().

The object must be picklable. Very large pickles (approximately 32 MiB+, though it depends on the OS) may raise a ValueError exception.

recv()

Return an object sent from the other end of the connection using send(). Blocks until there is something to receive. Raises EOFError if there is nothing left to receive and the other end was closed.

fileno()

Return the file descriptor or handle used by the connection.

close()

Close the connection.

This is called automatically when the connection is garbage collected.

poll([timeout])

Return whether there is any data available to be read.

If timeout is not specified then it will return immediately. If timeout is a number then this specifies the maximum time in seconds to block. If timeout is None then an infinite timeout is used.

Note that multiple connection objects may be polled at once by using multiprocessing.connection.wait().

send_bytes(buffer[, offset[, size]])

Send byte data from a bytes-like object as a complete message.

If offset is given then data is read from that position in buffer. If size is given then that many bytes will be read from buffer. Very large buffers (approximately 32 MiB+, though it depends on the OS) may raise a ValueError exception

recv_bytes([maxlength])

Return a complete message of byte data sent from the other end of the connection as a string. Blocks until there is something to receive. Raises EOFError if there is nothing left to receive and the other end has closed.

If maxlength is specified and the message is longer than maxlength then OSError is raised and the connection will no longer be readable.

在 3.3 版的變更: This function used to raise IOError, which is now an alias of OSError.

recv_bytes_into(buffer[, offset])

Read into buffer a complete message of byte data sent from the other end of the connection and return the number of bytes in the message. Blocks until there is something to receive. Raises EOFError if there is nothing left to receive and the other end was closed.

buffer must be a writable bytes-like object. If offset is given then the message will be written into the buffer from that position. Offset must be a non-negative integer less than the length of buffer (in bytes).

If the buffer is too short then a BufferTooShort exception is raised and the complete message is available as e.args[0] where e is the exception instance.

在 3.3 版的變更: Connection objects themselves can now be transferred between processes using Connection.send() and Connection.recv().

Connection objects also now support the context management protocol -- see 情境管理器型別. __enter__() returns the connection object, and __exit__() calls close().

舉例來說：

>>> from multiprocessing import Pipe
>>> a, b = Pipe()
>>> a.send([1, 'hello', None])
>>> b.recv()
[1, 'hello', None]
>>> b.send_bytes(b'thank you')
>>> a.recv_bytes()
b'thank you'
>>> import array
>>> arr1 = array.array('i', range(5))
>>> arr2 = array.array('i', [0] * 10)
>>> a.send_bytes(arr1)
>>> count = b.recv_bytes_into(arr2)
>>> assert count == len(arr1) * arr1.itemsize
>>> arr2
array('i', [0, 1, 2, 3, 4, 0, 0, 0, 0, 0])

警告

The Connection.recv() method automatically unpickles the data it receives, which can be a security risk unless you can trust the process which sent the message.

Therefore, unless the connection object was produced using Pipe() you should only use the recv() and send() methods after performing some sort of authentication. See Authentication keys.

警告

If a process is killed while it is trying to read or write to a pipe then the data in the pipe is likely to become corrupted, because it may become impossible to be sure where the message boundaries lie.

Synchronization primitives

Generally synchronization primitives are not as necessary in a multiprocess program as they are in a multithreaded program. See the documentation for threading module.

Note that one can also create synchronization primitives by using a manager object -- see Managers.

class multiprocessing.Barrier(parties[, action[, timeout]])

A barrier object: a clone of threading.Barrier.

Instantiating this class may set the global start method. See Global start method for more details.

在 3.3 版被加入.

class multiprocessing.BoundedSemaphore([value])

A bounded semaphore object: a close analog of threading.BoundedSemaphore.

Instantiating this class may set the global start method. See Global start method for more details.

A solitary difference from its close analog exists: its acquire method's first argument is named block, as is consistent with Lock.acquire().

locked()

Return a boolean indicating whether this object is locked right now.

在 3.14 版被加入.

備註

On macOS, this is indistinguishable from Semaphore because sem_getvalue() is not implemented on that platform.

class multiprocessing.Condition([lock])

A condition variable: an alias for threading.Condition.

If lock is specified then it should be a Lock or RLock object from multiprocessing.

Instantiating this class may set the global start method. See Global start method for more details.

在 3.3 版的變更: 新增 wait_for() 方法。

class multiprocessing.Event

A clone of threading.Event.

Instantiating this class may set the global start method. See Global start method for more details.

class multiprocessing.Lock

A non-recursive lock object: a close analog of threading.Lock. Once a process or thread has acquired a lock, subsequent attempts to acquire it from any process or thread will block until it is released; any process or thread may release it. The concepts and behaviors of threading.Lock as it applies to threads are replicated here in multiprocessing.Lock as it applies to either processes or threads, except as noted.

Note that Lock is actually a factory function which returns an instance of multiprocessing.synchronize.Lock initialized with a default context.

Instantiating this class may set the global start method. See Global start method for more details.

Lock supports the context manager protocol and thus may be used in with statements.

acquire(block=True, timeout=None)

Acquire a lock, blocking or non-blocking.

With the block argument set to True (the default), the method call will block until the lock is in an unlocked state, then set it to locked and return True. Note that the name of this first argument differs from that in threading.Lock.acquire().

With the block argument set to False, the method call does not block. If the lock is currently in a locked state, return False; otherwise set the lock to a locked state and return True.

When invoked with a positive, floating-point value for timeout, block for at most the number of seconds specified by timeout as long as the lock can not be acquired. Invocations with a negative value for timeout are equivalent to a timeout of zero. Invocations with a timeout value of None (the default) set the timeout period to infinite. Note that the treatment of negative or None values for timeout differs from the implemented behavior in threading.Lock.acquire(). The timeout argument has no practical implications if the block argument is set to False and is thus ignored. Returns True if the lock has been acquired or False if the timeout period has elapsed.

release()

Release a lock. This can be called from any process or thread, not only the process or thread which originally acquired the lock.

Behavior is the same as in threading.Lock.release() except that when invoked on an unlocked lock, a ValueError is raised.

locked()

Return a boolean indicating whether this object is locked right now.

在 3.14 版被加入.

class multiprocessing.RLock

A recursive lock object: a close analog of threading.RLock. A recursive lock must be released by the process or thread that acquired it. Once a process or thread has acquired a recursive lock, the same process or thread may acquire it again without blocking; that process or thread must release it once for each time it has been acquired.

Note that RLock is actually a factory function which returns an instance of multiprocessing.synchronize.RLock initialized with a default context.

Instantiating this class may set the global start method. See Global start method for more details.

RLock supports the context manager protocol and thus may be used in with statements.

acquire(block=True, timeout=None)

Acquire a lock, blocking or non-blocking.

When invoked with the block argument set to True, block until the lock is in an unlocked state (not owned by any process or thread) unless the lock is already owned by the current process or thread. The current process or thread then takes ownership of the lock (if it does not already have ownership) and the recursion level inside the lock increments by one, resulting in a return value of True. Note that there are several differences in this first argument's behavior compared to the implementation of threading.RLock.acquire(), starting with the name of the argument itself.

When invoked with the block argument set to False, do not block. If the lock has already been acquired (and thus is owned) by another process or thread, the current process or thread does not take ownership and the recursion level within the lock is not changed, resulting in a return value of False. If the lock is in an unlocked state, the current process or thread takes ownership and the recursion level is incremented, resulting in a return value of True.

Use and behaviors of the timeout argument are the same as in Lock.acquire(). Note that some of these behaviors of timeout differ from the implemented behaviors in threading.RLock.acquire().

release()

Release a lock, decrementing the recursion level. If after the decrement the recursion level is zero, reset the lock to unlocked (not owned by any process or thread) and if any other processes or threads are blocked waiting for the lock to become unlocked, allow exactly one of them to proceed. If after the decrement the recursion level is still nonzero, the lock remains locked and owned by the calling process or thread.

Only call this method when the calling process or thread owns the lock. An AssertionError is raised if this method is called by a process or thread other than the owner or if the lock is in an unlocked (unowned) state. Note that the type of exception raised in this situation differs from the implemented behavior in threading.RLock.release().

locked()

Return a boolean indicating whether this object is locked right now.

在 3.14 版被加入.

class multiprocessing.Semaphore([value])

A semaphore object: a close analog of threading.Semaphore.

Instantiating this class may set the global start method. See Global start method for more details.

A solitary difference from its close analog exists: its acquire method's first argument is named block, as is consistent with Lock.acquire().

get_value()

Return the current value of semaphore.

Note that this may raise NotImplementedError on platforms like macOS where sem_getvalue() is not implemented.

locked()

Return a boolean indicating whether this object is locked right now.

在 3.14 版被加入.

備註

On macOS, sem_timedwait is unsupported, so calling acquire() with a timeout will emulate that function's behavior using a sleeping loop.

備註

Some of this package's functionality requires a functioning shared semaphore implementation on the host operating system. Without one, the multiprocessing.synchronize module will be disabled, and attempts to import it will result in an ImportError. See bpo-3770 [https://bugs.python.org/issue?@action=redirect&bpo=3770] for additional information.

共享的 ctypes 物件

It is possible to create shared objects using shared memory which can be inherited by child processes.

multiprocessing.Value(typecode_or_type, *args, lock=True)

Return a ctypes object allocated from shared memory. By default the return value is actually a synchronized wrapper for the object. The object itself can be accessed via the value attribute of a Value.

typecode_or_type determines the type of the returned object: it is either a ctypes type or a one character typecode of the kind used by the array module. *args is passed on to the constructor for the type.

If lock is True (the default) then a new recursive lock object is created to synchronize access to the value. If lock is a Lock or RLock object then that will be used to synchronize access to the value. If lock is False then access to the returned object will not be automatically protected by a lock, so it will not necessarily be "process-safe".

Operations like += which involve a read and write are not atomic. So if, for instance, you want to atomically increment a shared value it is insufficient to just do

counter.value += 1

Assuming the associated lock is recursive (which it is by default) you can instead do

with counter.get_lock():
    counter.value += 1

Note that lock is a keyword-only argument.

multiprocessing.Array(typecode_or_type, size_or_initializer, *, lock=True)

Return a ctypes array allocated from shared memory. By default the return value is actually a synchronized wrapper for the array.

typecode_or_type determines the type of the elements of the returned array: it is either a ctypes type or a one character typecode of the kind used by the array module with the exception of 'w', which is not supported. In addition, the 'c' typecode is an alias for ctypes.c_char. If size_or_initializer is an integer, then it determines the length of the array, and the array will be initially zeroed. Otherwise, size_or_initializer is a sequence which is used to initialize the array and whose length determines the length of the array.

If lock is True (the default) then a new lock object is created to synchronize access to the value. If lock is a Lock or RLock object then that will be used to synchronize access to the value. If lock is False then access to the returned object will not be automatically protected by a lock, so it will not necessarily be "process-safe".

Note that lock is a keyword only argument.

Note that an array of ctypes.c_char has value and raw attributes which allow one to use it to store and retrieve strings.

multiprocessing.sharedctypes 模組

The multiprocessing.sharedctypes module provides functions for allocating ctypes objects from shared memory which can be inherited by child processes.

備註

Although it is possible to store a pointer in shared memory remember that this will refer to a location in the address space of a specific process. However, the pointer is quite likely to be invalid in the context of a second process and trying to dereference the pointer from the second process may cause a crash.

multiprocessing.sharedctypes.RawArray(typecode_or_type, size_or_initializer)

Return a ctypes array allocated from shared memory.

typecode_or_type determines the type of the elements of the returned array: it is either a ctypes type or a one character typecode of the kind used by the array module. If size_or_initializer is an integer then it determines the length of the array, and the array will be initially zeroed. Otherwise size_or_initializer is a sequence which is used to initialize the array and whose length determines the length of the array.

Note that setting and getting an element is potentially non-atomic -- use Array() instead to make sure that access is automatically synchronized using a lock.

multiprocessing.sharedctypes.RawValue(typecode_or_type, *args)

Return a ctypes object allocated from shared memory.

typecode_or_type determines the type of the returned object: it is either a ctypes type or a one character typecode of the kind used by the array module. *args is passed on to the constructor for the type.

Note that setting and getting the value is potentially non-atomic -- use Value() instead to make sure that access is automatically synchronized using a lock.

Note that an array of ctypes.c_char has value and raw attributes which allow one to use it to store and retrieve strings -- see documentation for ctypes.

multiprocessing.sharedctypes.Array(typecode_or_type, size_or_initializer, *, lock=True, ctx=None)

The same as RawArray() except that depending on the value of lock a process-safe synchronization wrapper may be returned instead of a raw ctypes array.

If lock is True (the default) then a new lock object is created to synchronize access to the value. If lock is a Lock or RLock object then that will be used to synchronize access to the value. If lock is False then access to the returned object will not be automatically protected by a lock, so it will not necessarily be "process-safe".

ctx is a context object, or None (use the current context). If None, calling this may set the global start method. See Global start method for more details.

Note that lock and ctx are keyword-only parameters.

multiprocessing.sharedctypes.Value(typecode_or_type, *args, lock=True, ctx=None)

The same as RawValue() except that depending on the value of lock a process-safe synchronization wrapper may be returned instead of a raw ctypes object.

If lock is True (the default) then a new lock object is created to synchronize access to the value. If lock is a Lock or RLock object then that will be used to synchronize access to the value. If lock is False then access to the returned object will not be automatically protected by a lock, so it will not necessarily be "process-safe".

ctx is a context object, or None (use the current context). If None, calling this may set the global start method. See Global start method for more details.

Note that lock and ctx are keyword-only parameters.

multiprocessing.sharedctypes.copy(obj)

Return a ctypes object allocated from shared memory which is a copy of the ctypes object obj.

multiprocessing.sharedctypes.synchronized(obj, lock=None, ctx=None)

Return a process-safe wrapper object for a ctypes object which uses lock to synchronize access. If lock is None (the default) then a multiprocessing.RLock object is created automatically.

ctx is a context object, or None (use the current context). If None, calling this may set the global start method. See Global start method for more details.

A synchronized wrapper will have two methods in addition to those of the object it wraps: get_obj() returns the wrapped object and get_lock() returns the lock object used for synchronization.

Note that accessing the ctypes object through the wrapper can be a lot slower than accessing the raw ctypes object.

在 3.5 版的變更: Synchronized objects support the context manager protocol.

The table below compares the syntax for creating shared ctypes objects from shared memory with the normal ctypes syntax. (In the table MyStruct is some subclass of ctypes.Structure.)

ctypes

sharedctypes using type

sharedctypes using typecode

c_double(2.4)

RawValue(c_double, 2.4)

RawValue('d', 2.4)

MyStruct(4, 6)

RawValue(MyStruct, 4, 6)

(c_short * 7)()

RawArray(c_short, 7)

RawArray('h', 7)

(c_int * 3)(9, 2, 8)

RawArray(c_int, (9, 2, 8))

RawArray('i', (9, 2, 8))

Below is an example where a number of ctypes objects are modified by a child process:

from multiprocessing import Process, Lock
from multiprocessing.sharedctypes import Value, Array
from ctypes import Structure, c_double

class Point(Structure):
    _fields_ = [('x', c_double), ('y', c_double)]

def modify(n, x, s, A):
    n.value **= 2
    x.value **= 2
    s.value = s.value.upper()
    for a in A:
        a.x **= 2
        a.y **= 2

if __name__ == '__main__':
    lock = Lock()

    n = Value('i', 7)
    x = Value(c_double, 1.0/3.0, lock=False)
    s = Array('c', b'hello world', lock=lock)
    A = Array(Point, [(1.875,-6.25), (-5.75,2.0), (2.375,9.5)], lock=lock)

    p = Process(target=modify, args=(n, x, s, A))
    p.start()
    p.join()

    print(n.value)
    print(x.value)
    print(s.value)
    print([(a.x, a.y) for a in A])

The results printed are

49
0.1111111111111111
HELLO WORLD
[(3.515625, 39.0625), (33.0625, 4.0), (5.640625, 90.25)]

Managers

Managers provide a way to create data which can be shared between different processes, including sharing over a network between processes running on different machines. A manager object controls a server process which manages shared objects. Other processes can access the shared objects by using proxies.

multiprocessing.Manager()

Returns a started SyncManager object which can be used for sharing objects between processes. The returned manager object corresponds to a spawned child process and has methods which will create shared objects and return corresponding proxies.

Manager processes will be shutdown as soon as they are garbage collected or their parent process exits. The manager classes are defined in the multiprocessing.managers module:

class multiprocessing.managers.BaseManager(address=None, authkey=None, serializer='pickle', ctx=None, *, shutdown_timeout=1.0)

建立一個 BaseManager 物件。

Once created one should call start() or get_server().serve_forever() to ensure that the manager object refers to a started manager process.

address is the address on which the manager process listens for new connections. If address is None then an arbitrary one is chosen.

authkey is the authentication key which will be used to check the validity of incoming connections to the server process. If authkey is None then current_process().authkey is used. Otherwise authkey is used and it must be a byte string.

serializer must be 'pickle' (use pickle serialization) or 'xmlrpclib' (use xmlrpc.client serialization).

ctx is a context object, or None (use the current context). If None, calling this may set the global start method. See Global start method for more details.

shutdown_timeout is a timeout in seconds used to wait until the process used by the manager completes in the shutdown() method. If the shutdown times out, the process is terminated. If terminating the process also times out, the process is killed.

在 3.11 版的變更: 新增 shutdown_timeout 參數。

start([initializer[, initargs]])

Start a subprocess to start the manager. If initializer is not None then the subprocess will call initializer(*initargs) when it starts.

get_server()

Returns a Server object which represents the actual server under the control of the Manager. The Server object supports the serve_forever() method:

>>> from multiprocessing.managers import BaseManager
>>> manager = BaseManager(address=('', 50000), authkey=b'abc')
>>> server = manager.get_server()
>>> server.serve_forever()

Server additionally has an address attribute.

connect()

Connect a local manager object to a remote manager process:

>>> from multiprocessing.managers import BaseManager
>>> m = BaseManager(address=('127.0.0.1', 50000), authkey=b'abc')
>>> m.connect()

shutdown()

Stop the process used by the manager. This is only available if start() has been used to start the server process.

This can be called multiple times.

register(typeid[, callable[, proxytype[, exposed[, method_to_typeid[, create_method]]]]])

A classmethod which can be used for registering a type or callable with the manager class.

typeid is a "type identifier" which is used to identify a particular type of shared object. This must be a string.

callable is a callable used for creating objects for this type identifier. If a manager instance will be connected to the server using the connect() method, or if the create_method argument is False then this can be left as None.

proxytype is a subclass of BaseProxy which is used to create proxies for shared objects with this typeid. If None then a proxy class is created automatically.

exposed is used to specify a sequence of method names which proxies for this typeid should be allowed to access using BaseProxy._callmethod(). (If exposed is None then proxytype._exposed_ is used instead if it exists.) In the case where no exposed list is specified, all "public methods" of the shared object will be accessible. (Here a "public method" means any attribute which has a __call__() method and whose name does not begin with '_'.)

method_to_typeid is a mapping used to specify the return type of those exposed methods which should return a proxy. It maps method names to typeid strings. (If method_to_typeid is None then proxytype._method_to_typeid_ is used instead if it exists.) If a method's name is not a key of this mapping or if the mapping is None then the object returned by the method will be copied by value.

create_method determines whether a method should be created with name typeid which can be used to tell the server process to create a new shared object and return a proxy for it. By default it is True.

BaseManager instances also have one read-only property:

address

The address used by the manager.

在 3.3 版的變更: Manager objects support the context management protocol -- see 情境管理器型別. __enter__() starts the server process (if it has not already started) and then returns the manager object. __exit__() calls shutdown().

In previous versions __enter__() did not start the manager's server process if it was not already started.

class multiprocessing.managers.SyncManager

A subclass of BaseManager which can be used for the synchronization of processes. Objects of this type are returned by multiprocessing.Manager().

Its methods create and return Proxy Objects for a number of commonly used data types to be synchronized across processes. This notably includes shared lists and dictionaries.

Barrier(parties[, action[, timeout]])

Create a shared threading.Barrier object and return a proxy for it.

在 3.3 版被加入.

BoundedSemaphore([value])

Create a shared threading.BoundedSemaphore object and return a proxy for it.

Condition([lock])

Create a shared threading.Condition object and return a proxy for it.

If lock is supplied then it should be a proxy for a threading.Lock or threading.RLock object.

在 3.3 版的變更: 新增 wait_for() 方法。

Event()

Create a shared threading.Event object and return a proxy for it.

Lock()

Create a shared threading.Lock object and return a proxy for it.

Namespace()

Create a shared Namespace object and return a proxy for it.

Queue([maxsize])

Create a shared queue.Queue object and return a proxy for it.

RLock()

Create a shared threading.RLock object and return a proxy for it.

Semaphore([value])

Create a shared threading.Semaphore object and return a proxy for it.

Array(typecode, sequence)

Create an array and return a proxy for it.

Value(typecode, value)

Create an object with a writable value attribute and return a proxy for it.

dict()

dict(mapping)

dict(sequence)

Create a shared dict object and return a proxy for it.

list()

list(sequence)

Create a shared list object and return a proxy for it.

set()

set(sequence)

set(mapping)

Create a shared set object and return a proxy for it.

在 3.14 版被加入: 已新增對 set 的支援。

在 3.6 版的變更: Shared objects are capable of being nested. For example, a shared container object such as a shared list can contain other shared objects which will all be managed and synchronized by the SyncManager.

class multiprocessing.managers.Namespace

A type that can register with SyncManager.

A namespace object has no public methods, but does have writable attributes. Its representation shows the values of its attributes.

However, when using a proxy for a namespace object, an attribute beginning with '_' will be an attribute of the proxy and not an attribute of the referent:

>>> mp_context = multiprocessing.get_context('spawn')
>>> manager = mp_context.Manager()
>>> Global = manager.Namespace()
>>> Global.x = 10
>>> Global.y = 'hello'
>>> Global._z = 12.3    # this is an attribute of the proxy
>>> print(Global)
Namespace(x=10, y='hello')

Customized managers

To create one's own manager, one creates a subclass of BaseManager and uses the register() classmethod to register new types or callables with the manager class. For example:

from multiprocessing.managers import BaseManager

class MathsClass:
    def add(self, x, y):
        return x + y
    def mul(self, x, y):
        return x * y

class MyManager(BaseManager):
    pass

MyManager.register('Maths', MathsClass)

if __name__ == '__main__':
    with MyManager() as manager:
        maths = manager.Maths()
        print(maths.add(4, 3))         # 印出 7
        print(maths.mul(7, 8))         # 印出 56

Using a remote manager

It is possible to run a manager server on one machine and have clients use it from other machines (assuming that the firewalls involved allow it).

Running the following commands creates a server for a single shared queue which remote clients can access:

>>> from multiprocessing.managers import BaseManager
>>> from queue import Queue
>>> queue = Queue()
>>> class QueueManager(BaseManager): pass
>>> QueueManager.register('get_queue', callable=lambda:queue)
>>> m = QueueManager(address=('', 50000), authkey=b'abracadabra')
>>> s = m.get_server()
>>> s.serve_forever()

One client can access the server as follows:

>>> from multiprocessing.managers import BaseManager
>>> class QueueManager(BaseManager): pass
>>> QueueManager.register('get_queue')
>>> m = QueueManager(address=('foo.bar.org', 50000), authkey=b'abracadabra')
>>> m.connect()
>>> queue = m.get_queue()
>>> queue.put('hello')

Another client can also use it:

>>> from multiprocessing.managers import BaseManager
>>> class QueueManager(BaseManager): pass
>>> QueueManager.register('get_queue')
>>> m = QueueManager(address=('foo.bar.org', 50000), authkey=b'abracadabra')
>>> m.connect()
>>> queue = m.get_queue()
>>> queue.get()
'hello'

Local processes can also access that queue, using the code from above on the client to access it remotely:

>>> from multiprocessing import Process, Queue
>>> from multiprocessing.managers import BaseManager
>>> class Worker(Process):
...     def __init__(self, q):
...         self.q = q
...         super().__init__()
...     def run(self):
...         self.q.put('local hello')
...
>>> queue = Queue()
>>> w = Worker(queue)
>>> w.start()
>>> class QueueManager(BaseManager): pass
...
>>> QueueManager.register('get_queue', callable=lambda: queue)
>>> m = QueueManager(address=('', 50000), authkey=b'abracadabra')
>>> s = m.get_server()
>>> s.serve_forever()

Proxy Objects

A proxy is an object which refers to a shared object which lives (presumably) in a different process. The shared object is said to be the referent of the proxy. Multiple proxy objects may have the same referent.

A proxy object has methods which invoke corresponding methods of its referent (although not every method of the referent will necessarily be available through the proxy). In this way, a proxy can be used just like its referent can:

>>> mp_context = multiprocessing.get_context('spawn')
>>> manager = mp_context.Manager()
>>> l = manager.list([i*i for i in range(10)])
>>> print(l)
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
>>> print(repr(l))
<ListProxy object, typeid 'list' at 0x...>
>>> l[4]
16
>>> l[2:5]
[4, 9, 16]

Notice that applying str() to a proxy will return the representation of the referent, whereas applying repr() will return the representation of the proxy.

An important feature of proxy objects is that they are picklable so they can be passed between processes. As such, a referent can contain Proxy Objects. This permits nesting of these managed lists, dicts, and other Proxy Objects:

>>> a = manager.list()
>>> b = manager.list()
>>> a.append(b)         # referent of a now contains referent of b
>>> print(a, b)
[<ListProxy object, typeid 'list' at ...>] []
>>> b.append('hello')
>>> print(a[0], b)
['hello'] ['hello']

Similarly, dict and list proxies may be nested inside one another:

>>> l_outer = manager.list([ manager.dict() for i in range(2) ])
>>> d_first_inner = l_outer[0]
>>> d_first_inner['a'] = 1
>>> d_first_inner['b'] = 2
>>> l_outer[1]['c'] = 3
>>> l_outer[1]['z'] = 26
>>> print(l_outer[0])
{'a': 1, 'b': 2}
>>> print(l_outer[1])
{'c': 3, 'z': 26}

If standard (non-proxy) list or dict objects are contained in a referent, modifications to those mutable values will not be propagated through the manager because the proxy has no way of knowing when the values contained within are modified. However, storing a value in a container proxy (which triggers a __setitem__ on the proxy object) does propagate through the manager and so to effectively modify such an item, one could re-assign the modified value to the container proxy:

# create a list proxy and append a mutable object (a dictionary)
lproxy = manager.list()
lproxy.append({})
# now mutate the dictionary
d = lproxy[0]
d['a'] = 1
d['b'] = 2
# at this point, the changes to d are not yet synced, but by
# updating the dictionary, the proxy is notified of the change
lproxy[0] = d

This approach is perhaps less convenient than employing nested Proxy Objects for most use cases but also demonstrates a level of control over the synchronization.

備註

The proxy types in multiprocessing do nothing to support comparisons by value. So, for instance, we have:

>>> manager.list([1,2,3]) == [1,2,3]
False

One should just use a copy of the referent instead when making comparisons.

class multiprocessing.managers.BaseProxy

Proxy objects are instances of subclasses of BaseProxy.

_callmethod(methodname[, args[, kwds]])

Call and return the result of a method of the proxy's referent.

If proxy is a proxy whose referent is obj then the expression

proxy._callmethod(methodname, args, kwds)

will evaluate the expression

getattr(obj, methodname)(*args, **kwds)

in the manager's process.

The returned value will be a copy of the result of the call or a proxy to a new shared object -- see documentation for the method_to_typeid argument of BaseManager.register().

If an exception is raised by the call, then is re-raised by _callmethod(). If some other exception is raised in the manager's process then this is converted into a RemoteError exception and is raised by _callmethod().

Note in particular that an exception will be raised if methodname has not been exposed.

An example of the usage of _callmethod():

>>> l = manager.list(range(10))
>>> l._callmethod('__len__')
10
>>> l._callmethod('__getitem__', (slice(2, 7),)) # 等價於 l[2:7]
[2, 3, 4, 5, 6]
>>> l._callmethod('__getitem__', (20,))          # 等價於 l[20]
Traceback (most recent call last):
...
IndexError: list index out of range

_getvalue()

Return a copy of the referent.

If the referent is unpicklable then this will raise an exception.

__repr__()

Return a representation of the proxy object.

__str__()

Return the representation of the referent.

Cleanup

A proxy object uses a weakref callback so that when it gets garbage collected it deregisters itself from the manager which owns its referent.

A shared object gets deleted from the manager process when there are no longer any proxies referring to it.

Process Pools

One can create a pool of processes which will carry out tasks submitted to it with the Pool class.

class multiprocessing.pool.Pool([processes[, initializer[, initargs[, maxtasksperchild[, context]]]]])

A process pool object which controls a pool of worker processes to which jobs can be submitted. It supports asynchronous results with timeouts and callbacks and has a parallel map implementation.

processes is the number of worker processes to use. If processes is None then the number returned by os.process_cpu_count() is used.

If initializer is not None then each worker process will call initializer(*initargs) when it starts.

maxtasksperchild is the number of tasks a worker process can complete before it will exit and be replaced with a fresh worker process, to enable unused resources to be freed. The default maxtasksperchild is None, which means worker processes will live as long as the pool.

context can be used to specify the context used for starting the worker processes. Usually a pool is created using the function multiprocessing.Pool() or the Pool() method of a context object. In both cases context is set appropriately. If None, calling this function will have the side effect of setting the current global start method if it has not been set already. See the get_context() function.

Note that the methods of the pool object should only be called by the process which created the pool.

警告

multiprocessing.pool objects have internal resources that need to be properly managed (like any other resource) by using the pool as a context manager or by calling close() and terminate() manually. Failure to do this can lead to the process hanging on finalization.

Note that it is not correct to rely on the garbage collector to destroy the pool as CPython does not assure that the finalizer of the pool will be called (see object.__del__() for more information).

在 3.2 版的變更: 新增 maxtasksperchild 參數。

在 3.4 版的變更: 新增 context 參數。

在 3.13 版的變更: processes uses os.process_cpu_count() by default, instead of os.cpu_count().

備註

Worker processes within a Pool typically live for the complete duration of the Pool's work queue. A frequent pattern found in other systems (such as Apache, mod_wsgi, etc) to free resources held by workers is to allow a worker within a pool to complete only a set amount of work before being exiting, being cleaned up and a new process spawned to replace the old one. The maxtasksperchild argument to the Pool exposes this ability to the end user.

apply(func[, args[, kwds]])

Call func with arguments args and keyword arguments kwds. It blocks until the result is ready. Given this blocks, apply_async() is better suited for performing work in parallel. Additionally, func is only executed in one of the workers of the pool.

apply_async(func[, args[, kwds[, callback[, error_callback]]]])

A variant of the apply() method which returns a AsyncResult object.

If callback is specified then it should be a callable which accepts a single argument. When the result becomes ready callback is applied to it, that is unless the call failed, in which case the error_callback is applied instead.

If error_callback is specified then it should be a callable which accepts a single argument. If the target function fails, then the error_callback is called with the exception instance.

Callbacks should complete immediately since otherwise the thread which handles the results will get blocked.

map(func, iterable[, chunksize])

A parallel equivalent of the map() built-in function (it supports only one iterable argument though, for multiple iterables see starmap()). It blocks until the result is ready.

This method chops the iterable into a number of chunks which it submits to the process pool as separate tasks. The (approximate) size of these chunks can be specified by setting chunksize to a positive integer.

Note that it may cause high memory usage for very long iterables. Consider using imap() or imap_unordered() with explicit chunksize option for better efficiency.

map_async(func, iterable[, chunksize[, callback[, error_callback]]])

A variant of the map() method which returns a AsyncResult object.

If callback is specified then it should be a callable which accepts a single argument. When the result becomes ready callback is applied to it, that is unless the call failed, in which case the error_callback is applied instead.

If error_callback is specified then it should be a callable which accepts a single argument. If the target function fails, then the error_callback is called with the exception instance.

Callbacks should complete immediately since otherwise the thread which handles the results will get blocked.

imap(func, iterable[, chunksize])

A lazier version of map().

The chunksize argument is the same as the one used by the map() method. For very long iterables using a large value for chunksize can make the job complete much faster than using the default value of 1.

Also if chunksize is 1 then the next() method of the iterator returned by the imap() method has an optional timeout parameter: next(timeout) will raise multiprocessing.TimeoutError if the result cannot be returned within timeout seconds.

imap_unordered(func, iterable[, chunksize])

The same as imap() except that the ordering of the results from the returned iterator should be considered arbitrary. (Only when there is only one worker process is the order guaranteed to be "correct".)

starmap(func, iterable[, chunksize])

Like map() except that the elements of the iterable are expected to be iterables that are unpacked as arguments.

Hence an iterable of [(1,2), (3, 4)] results in [func(1,2), func(3,4)].

在 3.3 版被加入.

starmap_async(func, iterable[, chunksize[, callback[, error_callback]]])

A combination of starmap() and map_async() that iterates over iterable of iterables and calls func with the iterables unpacked. Returns a result object.

在 3.3 版被加入.

close()

Prevents any more tasks from being submitted to the pool. Once all the tasks have been completed the worker processes will exit.

terminate()

Stops the worker processes immediately without completing outstanding work. When the pool object is garbage collected terminate() will be called immediately.

join()

Wait for the worker processes to exit. One must call close() or terminate() before using join().

在 3.3 版的變更: Pool objects now support the context management protocol -- see 情境管理器型別. __enter__() returns the pool object, and __exit__() calls terminate().

class multiprocessing.pool.AsyncResult

The class of the result returned by Pool.apply_async() and Pool.map_async().

get([timeout])

Return the result when it arrives. If timeout is not None and the result does not arrive within timeout seconds then multiprocessing.TimeoutError is raised. If the remote call raised an exception then that exception will be reraised by get().

wait([timeout])

Wait until the result is available or until timeout seconds pass.

ready()

Return whether the call has completed.

successful()

Return whether the call completed without raising an exception. Will raise ValueError if the result is not ready.

在 3.7 版的變更: If the result is not ready, ValueError is raised instead of AssertionError.

The following example demonstrates the use of a pool:

from multiprocessing import Pool
import time

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(processes=4) as pool:         # start 4 worker processes
        result = pool.apply_async(f, (10,)) # evaluate "f(10)" asynchronously in a single process
        print(result.get(timeout=1))        # prints "100" unless your computer is *very* slow

        print(pool.map(f, range(10)))       # prints "[0, 1, 4,..., 81]"

        it = pool.imap(f, range(10))
        print(next(it))                     # prints "0"
        print(next(it))                     # prints "1"
        print(it.next(timeout=1))           # prints "4" unless your computer is *very* slow

        result = pool.apply_async(time.sleep, (10,))
        print(result.get(timeout=1))        # raises multiprocessing.TimeoutError

Listeners and Clients

Usually message passing between processes is done using queues or by using Connection objects returned by Pipe().

However, the multiprocessing.connection module allows some extra flexibility. It basically gives a high level message oriented API for dealing with sockets or Windows named pipes. It also has support for digest authentication using the hmac module, and for polling multiple connections at the same time.

multiprocessing.connection.deliver_challenge(connection, authkey)

Send a randomly generated message to the other end of the connection and wait for a reply.

If the reply matches the digest of the message using authkey as the key then a welcome message is sent to the other end of the connection. Otherwise AuthenticationError is raised.

multiprocessing.connection.answer_challenge(connection, authkey)

Receive a message, calculate the digest of the message using authkey as the key, and then send the digest back.

If a welcome message is not received, then AuthenticationError is raised.

multiprocessing.connection.Client(address[, family[, authkey]])

Attempt to set up a connection to the listener which is using address address, returning a Connection.

The type of the connection is determined by family argument, but this can generally be omitted since it can usually be inferred from the format of address. (See Address Formats)

If authkey is given and not None, it should be a byte string and will be used as the secret key for an HMAC-based authentication challenge. No authentication is done if authkey is None. AuthenticationError is raised if authentication fails. See Authentication keys.

class multiprocessing.connection.Listener([address[, family[, backlog[, authkey]]]])

A wrapper for a bound socket or Windows named pipe which is 'listening' for connections.

address is the address to be used by the bound socket or named pipe of the listener object.

備註

If an address of '0.0.0.0' is used, the address will not be a connectable end point on Windows. If you require a connectable end-point, you should use '127.0.0.1'.

family is the type of socket (or named pipe) to use. This can be one of the strings 'AF_INET' (for a TCP socket), 'AF_UNIX' (for a Unix domain socket) or 'AF_PIPE' (for a Windows named pipe). Of these only the first is guaranteed to be available. If family is None then the family is inferred from the format of address. If address is also None then a default is chosen. This default is the family which is assumed to be the fastest available. See Address Formats. Note that if family is 'AF_UNIX' and address is None then the socket will be created in a private temporary directory created using tempfile.mkstemp().

If the listener object uses a socket then backlog (1 by default) is passed to the listen() method of the socket once it has been bound.

If authkey is given and not None, it should be a byte string and will be used as the secret key for an HMAC-based authentication challenge. No authentication is done if authkey is None. AuthenticationError is raised if authentication fails. See Authentication keys.

accept()

Accept a connection on the bound socket or named pipe of the listener object and return a Connection object. If authentication is attempted and fails, then AuthenticationError is raised.

close()

Close the bound socket or named pipe of the listener object. This is called automatically when the listener is garbage collected. However it is advisable to call it explicitly.

Listener objects have the following read-only properties:

address

The address which is being used by the Listener object.

last_accepted

The address from which the last accepted connection came. If this is unavailable then it is None.

在 3.3 版的變更: Listener objects now support the context management protocol -- see 情境管理器型別. __enter__() returns the listener object, and __exit__() calls close().

multiprocessing.connection.wait(object_list, timeout=None)

Wait till an object in object_list is ready. Returns the list of those objects in object_list which are ready. If timeout is a float then the call blocks for at most that many seconds. If timeout is None then it will block for an unlimited period. A negative timeout is equivalent to a zero timeout.

For both POSIX and Windows, an object can appear in object_list if it is

a readable Connection object;

a connected and readable socket.socket object; or

the sentinel attribute of a Process object.

A connection or socket object is ready when there is data available to be read from it, or the other end has been closed.

POSIX: wait(object_list, timeout) almost equivalent select.select(object_list, [], [], timeout). The difference is that, if select.select() is interrupted by a signal, it can raise OSError with an error number of EINTR, whereas wait() will not.

Windows: An item in object_list must either be an integer handle which is waitable (according to the definition used by the documentation of the Win32 function WaitForMultipleObjects()) or it can be an object with a fileno() method which returns a socket handle or pipe handle. (Note that pipe handles and socket handles are not waitable handles.)

在 3.3 版被加入.

Examples

The following server code creates a listener which uses 'secret password' as an authentication key. It then waits for a connection and sends some data to the client:

from multiprocessing.connection import Listener
from array import array

address = ('localhost', 6000)     # family is deduced to be 'AF_INET'

with Listener(address, authkey=b'secret password') as listener:
    with listener.accept() as conn:
        print('connection accepted from', listener.last_accepted)

        conn.send([2.25, None, 'junk', float])

        conn.send_bytes(b'hello')

        conn.send_bytes(array('i', [42, 1729]))

The following code connects to the server and receives some data from the server:

from multiprocessing.connection import Client
from array import array

address = ('localhost', 6000)

with Client(address, authkey=b'secret password') as conn:
    print(conn.recv())                  # => [2.25, None, 'junk', float]

    print(conn.recv_bytes())            # => 'hello'

    arr = array('i', [0, 0, 0, 0, 0])
    print(conn.recv_bytes_into(arr))    # => 8
    print(arr)                          # => array('i', [42, 1729, 0, 0, 0])

The following code uses wait() to wait for messages from multiple processes at once:

from multiprocessing import Process, Pipe, current_process
from multiprocessing.connection import wait

def foo(w):
    for i in range(10):
        w.send((i, current_process().name))
    w.close()

if __name__ == '__main__':
    readers = []

    for i in range(4):
        r, w = Pipe(duplex=False)
        readers.append(r)
        p = Process(target=foo, args=(w,))
        p.start()
        # We close the writable end of the pipe now to be sure that
        # p is the only process which owns a handle for it.  This
        # ensures that when p closes its handle for the writable end,
        # wait() will promptly report the readable end as being ready.
        w.close()

    while readers:
        for r in wait(readers):
            try:
                msg = r.recv()
            except EOFError:
                readers.remove(r)
            else:
                print(msg)

Address Formats

An 'AF_INET' address is a tuple of the form (hostname, port) where hostname is a string and port is an integer.

An 'AF_UNIX' address is a string representing a filename on the filesystem.

An 'AF_PIPE' address is a string of the form r'\\.\pipe\PipeName'. To use Client() to connect to a named pipe on a remote computer called ServerName one should use an address of the form r'\\ServerName\pipe\PipeName' instead.

Note that any string beginning with two backslashes is assumed by default to be an 'AF_PIPE' address rather than an 'AF_UNIX' address.

Authentication keys

When one uses Connection.recv, the data received is automatically unpickled. Unfortunately unpickling data from an untrusted source is a security risk. Therefore Listener and Client() use the hmac module to provide digest authentication.

An authentication key is a byte string which can be thought of as a password: once a connection is established both ends will demand proof that the other knows the authentication key. (Demonstrating that both ends are using the same key does not involve sending the key over the connection.)

If authentication is requested but no authentication key is specified then the return value of current_process().authkey is used (see Process). This value will be automatically inherited by any Process object that the current process creates. This means that (by default) all processes of a multi-process program will share a single authentication key which can be used when setting up connections between themselves.

Suitable authentication keys can also be generated by using os.urandom().

Logging

Some support for logging is available. Note, however, that the logging package does not use process shared locks so it is possible (depending on the handler type) for messages from different processes to get mixed up.

multiprocessing.get_logger()

Returns the logger used by multiprocessing. If necessary, a new one will be created.

When first created the logger has level logging.NOTSET and no default handler. Messages sent to this logger will not by default propagate to the root logger.

Note that on Windows child processes will only inherit the level of the parent process's logger -- any other customization of the logger will not be inherited.

multiprocessing.log_to_stderr(level=None)

This function performs a call to get_logger() but in addition to returning the logger created by get_logger, it adds a handler which sends output to sys.stderr using format '[%(levelname)s/%(processName)s] %(message)s'. You can modify levelname of the logger by passing a level argument.

Below is an example session with logging turned on:

>>> import multiprocessing, logging
>>> logger = multiprocessing.log_to_stderr()
>>> logger.setLevel(logging.INFO)
>>> logger.warning('doomed')
[WARNING/MainProcess] doomed
>>> m = multiprocessing.Manager()
[INFO/SyncManager-...] child process calling self.run()
[INFO/SyncManager-...] created temp directory /.../pymp-...
[INFO/SyncManager-...] manager serving at '/.../listener-...'
>>> del m
[INFO/MainProcess] sending shutdown message to manager
[INFO/SyncManager-...] manager exiting with exitcode 0

For a full table of logging levels, see the logging module.

multiprocessing.dummy 模組

multiprocessing.dummy replicates the API of multiprocessing but is no more than a wrapper around the threading module.

In particular, the Pool function provided by multiprocessing.dummy returns an instance of ThreadPool, which is a subclass of Pool that supports all the same method calls but uses a pool of worker threads rather than worker processes.

class multiprocessing.pool.ThreadPool([processes[, initializer[, initargs]]])

A thread pool object which controls a pool of worker threads to which jobs can be submitted. ThreadPool instances are fully interface compatible with Pool instances, and their resources must also be properly managed, either by using the pool as a context manager or by calling close() and terminate() manually.

processes is the number of worker threads to use. If processes is None then the number returned by os.process_cpu_count() is used.

If initializer is not None then each worker process will call initializer(*initargs) when it starts.

Unlike Pool, maxtasksperchild and context cannot be provided.

備註

A ThreadPool shares the same interface as Pool, which is designed around a pool of processes and predates the introduction of the concurrent.futures module. As such, it inherits some operations that don't make sense for a pool backed by threads, and it has its own type for representing the status of asynchronous jobs, AsyncResult, that is not understood by any other libraries.

Users should generally prefer to use concurrent.futures.ThreadPoolExecutor, which has a simpler interface that was designed around threads from the start, and which returns concurrent.futures.Future instances that are compatible with many other libraries, including asyncio.

Programming guidelines

There are certain guidelines and idioms which should be adhered to when using multiprocessing.

All start methods

The following applies to all start methods.

Avoid shared state

As far as possible one should try to avoid shifting large amounts of data between processes.

It is probably best to stick to using queues or pipes for communication between processes rather than using the lower level synchronization primitives.

Picklability

Ensure that the arguments to the methods of proxies are picklable.

Thread safety of proxies

Do not use a proxy object from more than one thread unless you protect it with a lock.

(There is never a problem with different processes using the same proxy.)

Joining zombie processes

On POSIX when a process finishes but has not been joined it becomes a zombie. There should never be very many because each time a new process starts (or active_children() is called) all completed processes which have not yet been joined will be joined. Also calling a finished process's Process.is_alive will join the process. Even so it is probably good practice to explicitly join all the processes that you start.

Better to inherit than pickle/unpickle

When using the spawn or forkserver start methods many types from multiprocessing need to be picklable so that child processes can use them. However, one should generally avoid sending shared objects to other processes using pipes or queues. Instead you should arrange the program so that a process which needs access to a shared resource created elsewhere can inherit it from an ancestor process.

Avoid terminating processes

Using the Process.terminate method to stop a process is liable to cause any shared resources (such as locks, semaphores, pipes and queues) currently being used by the process to become broken or unavailable to other processes.

Therefore it is probably best to only consider using Process.terminate on processes which never use any shared resources.

Joining processes that use queues

Bear in mind that a process that has put items in a queue will wait before terminating until all the buffered items are fed by the "feeder" thread to the underlying pipe. (The child process can call the Queue.cancel_join_thread method of the queue to avoid this behaviour.)

This means that whenever you use a queue you need to make sure that all items which have been put on the queue will eventually be removed before the process is joined. Otherwise you cannot be sure that processes which have put items on the queue will terminate. Remember also that non-daemonic processes will be joined automatically.

An example which will deadlock is the following:

from multiprocessing import Process, Queue

def f(q):
    q.put('X' * 1000000)

if __name__ == '__main__':
    queue = Queue()
    p = Process(target=f, args=(queue,))
    p.start()
    p.join()                    # this deadlocks
    obj = queue.get()

A fix here would be to swap the last two lines (or simply remove the p.join() line).

Explicitly pass resources to child processes

On POSIX using the fork start method, a child process can make use of a shared resource created in a parent process using a global resource. However, it is better to pass the object as an argument to the constructor for the child process.

Apart from making the code (potentially) compatible with Windows and the other start methods this also ensures that as long as the child process is still alive the object will not be garbage collected in the parent process. This might be important if some resource is freed when the object is garbage collected in the parent process.

So for instance

from multiprocessing import Process, Lock

def f():
    ... do something using "lock" ...

if __name__ == '__main__':
    lock = Lock()
    for i in range(10):
        Process(target=f).start()

should be rewritten as

from multiprocessing import Process, Lock

def f(l):
    ... do something using "l" ...

if __name__ == '__main__':
    lock = Lock()
    for i in range(10):
        Process(target=f, args=(lock,)).start()

Beware of replacing sys.stdin with a "file like object"

multiprocessing originally unconditionally called:

os.close(sys.stdin.fileno())

in the multiprocessing.Process._bootstrap() method --- this resulted in issues with processes-in-processes. This has been changed to:

sys.stdin.close()
sys.stdin = open(os.open(os.devnull, os.O_RDONLY), closefd=False)

Which solves the fundamental issue of processes colliding with each other resulting in a bad file descriptor error, but introduces a potential danger to applications which replace sys.stdin() with a "file-like object" with output buffering. This danger is that if multiple processes call close() on this file-like object, it could result in the same data being flushed to the object multiple times, resulting in corruption.

If you write a file-like object and implement your own caching, you can make it fork-safe by storing the pid whenever you append to the cache, and discarding the cache when the pid changes. For example:

@property
def cache(self):
    pid = os.getpid()
    if pid != self._pid:
        self._pid = pid
        self._cache = []
    return self._cache

For more information, see bpo-5155 [https://bugs.python.org/issue?@action=redirect&bpo=5155], bpo-5313 [https://bugs.python.org/issue?@action=redirect&bpo=5313] and bpo-5331 [https://bugs.python.org/issue?@action=redirect&bpo=5331]

The spawn and forkserver start methods

There are a few extra restrictions which don't apply to the fork start method.

More picklability

Ensure that all arguments to Process are picklable. Also, if you subclass Process.__init__, you must make sure that instances will be picklable when the Process.start method is called.

Global variables

Bear in mind that if code run in a child process tries to access a global variable, then the value it sees (if any) may not be the same as the value in the parent process at the time that Process.start was called.

However, global variables which are just module level constants cause no problems.

Safe importing of main module

Make sure that the main module can be safely imported by a new Python interpreter without causing unintended side effects (such as starting a new process).

For example, using the spawn or forkserver start method running the following module would fail with a RuntimeError:

from multiprocessing import Process

def foo():
    print('hello')

p = Process(target=foo)
p.start()

Instead one should protect the "entry point" of the program by using if __name__ == '__main__': as follows:

from multiprocessing import Process, freeze_support, set_start_method

def foo():
    print('hello')

if __name__ == '__main__':
    freeze_support()
    set_start_method('spawn')
    p = Process(target=foo)
    p.start()

(The freeze_support() line can be omitted if the program will be run normally instead of frozen.)

This allows the newly spawned Python interpreter to safely import the module and then run the module's foo() function.

Similar restrictions apply if a pool or manager is created in the main module.

範例

Demonstration of how to create and use customized managers and proxies:

from multiprocessing import freeze_support
from multiprocessing.managers import BaseManager, BaseProxy
import operator

##

class Foo:
    def f(self):
        print('you called Foo.f()')
    def g(self):
        print('you called Foo.g()')
    def _h(self):
        print('you called Foo._h()')

# A simple generator function
def baz():
    for i in range(10):
        yield i*i

# Proxy type for generator objects
class GeneratorProxy(BaseProxy):
    _exposed_ = ['__next__']
    def __iter__(self):
        return self
    def __next__(self):
        return self._callmethod('__next__')

# Function to return the operator module
def get_operator_module():
    return operator

##

class MyManager(BaseManager):
    pass

# register the Foo class; make `f()` and `g()` accessible via proxy
MyManager.register('Foo1', Foo)

# register the Foo class; make `g()` and `_h()` accessible via proxy
MyManager.register('Foo2', Foo, exposed=('g', '_h'))

# register the generator function baz; use `GeneratorProxy` to make proxies
MyManager.register('baz', baz, proxytype=GeneratorProxy)

# register get_operator_module(); make public functions accessible via proxy
MyManager.register('operator', get_operator_module)

##

def test():
    manager = MyManager()
    manager.start()

    print('-' * 20)

    f1 = manager.Foo1()
    f1.f()
    f1.g()
    assert not hasattr(f1, '_h')
    assert sorted(f1._exposed_) == sorted(['f', 'g'])

    print('-' * 20)

    f2 = manager.Foo2()
    f2.g()
    f2._h()
    assert not hasattr(f2, 'f')
    assert sorted(f2._exposed_) == sorted(['g', '_h'])

    print('-' * 20)

    it = manager.baz()
    for i in it:
        print('<%d>' % i, end=' ')
    print()

    print('-' * 20)

    op = manager.operator()
    print('op.add(23, 45) =', op.add(23, 45))
    print('op.pow(2, 94) =', op.pow(2, 94))
    print('op._exposed_ =', op._exposed_)

##

if __name__ == '__main__':
    freeze_support()
    test()

使用 Pool：

import multiprocessing
import time
import random
import sys

#
# Functions used by test code
#

def calculate(func, args):
    result = func(*args)
    return '%s says that %s%s = %s' % (
        multiprocessing.current_process().name,
        func.__name__, args, result
        )

def calculatestar(args):
    return calculate(*args)

def mul(a, b):
    time.sleep(0.5 * random.random())
    return a * b

def plus(a, b):
    time.sleep(0.5 * random.random())
    return a + b

def f(x):
    return 1.0 / (x - 5.0)

def pow3(x):
    return x ** 3

def noop(x):
    pass

#
# Test code
#

def test():
    PROCESSES = 4
    print('Creating pool with %d processes\n' % PROCESSES)

    with multiprocessing.Pool(PROCESSES) as pool:
        #
        # Tests
        #

        TASKS = [(mul, (i, 7)) for i in range(10)] + \
                [(plus, (i, 8)) for i in range(10)]

        results = [pool.apply_async(calculate, t) for t in TASKS]
        imap_it = pool.imap(calculatestar, TASKS)
        imap_unordered_it = pool.imap_unordered(calculatestar, TASKS)

        print('Ordered results using pool.apply_async():')
        for r in results:
            print('\t', r.get())
        print()

        print('Ordered results using pool.imap():')
        for x in imap_it:
            print('\t', x)
        print()

        print('Unordered results using pool.imap_unordered():')
        for x in imap_unordered_it:
            print('\t', x)
        print()

        print('Ordered results using pool.map() --- will block till complete:')
        for x in pool.map(calculatestar, TASKS):
            print('\t', x)
        print()

        #
        # Test error handling
        #

        print('Testing error handling:')

        try:
            print(pool.apply(f, (5,)))
        except ZeroDivisionError:
            print('\tGot ZeroDivisionError as expected from pool.apply()')
        else:
            raise AssertionError('expected ZeroDivisionError')

        try:
            print(pool.map(f, list(range(10))))
        except ZeroDivisionError:
            print('\tGot ZeroDivisionError as expected from pool.map()')
        else:
            raise AssertionError('expected ZeroDivisionError')

        try:
            print(list(pool.imap(f, list(range(10)))))
        except ZeroDivisionError:
            print('\tGot ZeroDivisionError as expected from list(pool.imap())')
        else:
            raise AssertionError('expected ZeroDivisionError')

        it = pool.imap(f, list(range(10)))
        for i in range(10):
            try:
                x = next(it)
            except ZeroDivisionError:
                if i == 5:
                    pass
            except StopIteration:
                break
            else:
                if i == 5:
                    raise AssertionError('expected ZeroDivisionError')

        assert i == 9
        print('\tGot ZeroDivisionError as expected from IMapIterator.next()')
        print()

        #
        # Testing timeouts
        #

        print('Testing ApplyResult.get() with timeout:', end=' ')
        res = pool.apply_async(calculate, TASKS[0])
        while 1:
            sys.stdout.flush()
            try:
                sys.stdout.write('\n\t%s' % res.get(0.02))
                break
            except multiprocessing.TimeoutError:
                sys.stdout.write('.')
        print()
        print()

        print('Testing IMapIterator.next() with timeout:', end=' ')
        it = pool.imap(calculatestar, TASKS)
        while 1:
            sys.stdout.flush()
            try:
                sys.stdout.write('\n\t%s' % it.next(0.02))
            except StopIteration:
                break
            except multiprocessing.TimeoutError:
                sys.stdout.write('.')
        print()
        print()

if __name__ == '__main__':
    multiprocessing.freeze_support()
    test()

An example showing how to use queues to feed tasks to a collection of worker processes and collect the results:

import time
import random

from multiprocessing import Process, Queue, current_process, freeze_support

#
# Function run by worker processes
#

def worker(input, output):
    for func, args in iter(input.get, 'STOP'):
        result = calculate(func, args)
        output.put(result)

#
# Function used to calculate result
#

def calculate(func, args):
    result = func(*args)
    return '%s says that %s%s = %s' % \
        (current_process().name, func.__name__, args, result)

#
# Functions referenced by tasks
#

def mul(a, b):
    time.sleep(0.5*random.random())
    return a * b

def plus(a, b):
    time.sleep(0.5*random.random())
    return a + b

#
#
#

def test():
    NUMBER_OF_PROCESSES = 4
    TASKS1 = [(mul, (i, 7)) for i in range(20)]
    TASKS2 = [(plus, (i, 8)) for i in range(10)]

    # Create queues
    task_queue = Queue()
    done_queue = Queue()

    # Submit tasks
    for task in TASKS1:
        task_queue.put(task)

    # Start worker processes
    for i in range(NUMBER_OF_PROCESSES):
        Process(target=worker, args=(task_queue, done_queue)).start()

    # Get and print results
    print('Unordered results:')
    for i in range(len(TASKS1)):
        print('\t', done_queue.get())

    # Add more tasks using `put()`
    for task in TASKS2:
        task_queue.put(task)

    # Get and print some more results
    for i in range(len(TASKS2)):
        print('\t', done_queue.get())

    # Tell child processes to stop
    for i in range(NUMBER_OF_PROCESSES):
        task_queue.put('STOP')

if __name__ == '__main__':
    freeze_support()
    test()

multiprocessing.shared_memory --- 對於共享記憶體的跨行程直接存取

原始碼：Lib/multiprocessing/shared_memory.py [https://github.com/python/cpython/tree/3.14/Lib/multiprocessing/shared_memory.py]

在 3.8 版被加入.

該模組提供了一個 SharedMemory 類別，用於分配和管理被多核心或對稱多處理器 (symmetric multiprocessor, SMP) 機器上的一個或多個行程存取的共享記憶體。為了協助共享記憶體的生命週期管理，特別是跨不同行程的管理，multiprocessing.managers 模組中還提供了一個 BaseManager 子類別 SharedMemoryManager。

在此模組中，共享記憶體是指「POSIX 風格」的共享記憶體區塊（儘管不一定如此明確實作），而不是指「分散式共享記憶體 (distributed shared memory)」。這種型別的共享記憶體允許不同的行程潛在地讀取和寫入揮發性記憶體 (volatile memory) 的公開（或共享）區域。通常行程只能存取自己的行程記憶體空間，但共享記憶體允許在行程之間共享資料，從而避免需要跨行程傳遞資料的情境。與透過硬碟或 socket 或其他需要序列化/還原序列化 (serialization/deserialization) 和複製資料的通訊方式以共享資料相比，直接透過記憶體共享資料可以提供顯著的性能優勢。

class multiprocessing.shared_memory.SharedMemory(name=None, create=False, size=0, *, track=True)

建立 SharedMemory 類別的實例，用於建立新的共享記憶體區塊或附加到現有的共享記憶體區塊。每個共享記憶體區塊都被分配了一個唯一的名稱。透過這種方式，一個行程可以建立具有特定名稱的共享記憶體區塊，而不同的行程可以使用該相同名稱附加到同一共享記憶體塊。

作為跨行程共享資料的資源，共享記憶體區塊的壽命可能比建立它們的原始行程還要長。當一個行程不再需要存取但其他行程可能仍需要的共享記憶體區塊時，應該呼叫 close() 方法。當任何行程不再需要共享記憶體區塊時，應呼叫 unlink() 方法以確保正確清理。

參數:

name (str | None) -- 所請求的共享記憶體的唯一名稱，指定為字串。建立新的共享記憶體區塊時，如果名稱提供為 None（預設值），則會生成一個新的名稱。

create (bool) -- 控制是否建立新的共享記憶體區塊 (True) 或附加現有的共享記憶體區塊 (False)。

size (int) -- 指定建立新共享記憶體區塊時請求的位元組數。由於某些平台會根據該平台的記憶體頁 (memory page) 大小來選擇分配記憶體區塊，因此共享記憶體區塊的確切大小可能大於或等於請求的大小。當附加到現有共享記憶體區塊時，size 參數將被忽略。

track (bool) -- When True, register the shared memory block with a resource tracker process on platforms where the OS does not do this automatically. The resource tracker ensures proper cleanup of the shared memory even if all other processes with access to the memory exit without doing so. Python processes created from a common ancestor using multiprocessing facilities share a single resource tracker process, and the lifetime of shared memory segments is handled automatically among these processes. Python processes created in any other way will receive their own resource tracker when accessing shared memory with track enabled. This will cause the shared memory to be deleted by the resource tracker of the first process that terminates. To avoid this issue, users of subprocess or standalone Python processes should set track to False when there is already another process in place that does the bookkeeping. track is ignored on Windows, which has its own tracking and automatically deletes shared memory when all handles to it have been closed.

在 3.13 版的變更: 新增 track 參數。

close()

Close the file descriptor/handle to the shared memory from this instance. close() should be called once access to the shared memory block from this instance is no longer needed. Depending on operating system, the underlying memory may or may not be freed even if all handles to it have been closed. To ensure proper cleanup, use the unlink() method.

unlink()

Delete the underlying shared memory block. This should be called only once per shared memory block regardless of the number of handles to it, even in other processes. unlink() and close() can be called in any order, but trying to access data inside a shared memory block after unlink() may result in memory access errors, depending on platform.

This method has no effect on Windows, where the only way to delete a shared memory block is to close all handles.

buf

共享記憶體區塊內容的記憶體視圖 (memoryview)。

name

對共享記憶體區塊之唯一名稱的唯讀存取。

size

對共享記憶體區塊大小（以位元組為單位）的唯讀存取。

以下範例示範了 SharedMemory 實例的低階使用方式：

>>> from multiprocessing import shared_memory
>>> shm_a = shared_memory.SharedMemory(create=True, size=10)
>>> type(shm_a.buf)
<class 'memoryview'>
>>> buffer = shm_a.buf
>>> len(buffer)
10
>>> buffer[:4] = bytearray([22, 33, 44, 55])  # Modify multiple at once
>>> buffer[4] = 100                           # Modify single byte at a time
>>> # Attach to an existing shared memory block
>>> shm_b = shared_memory.SharedMemory(shm_a.name)
>>> import array
>>> array.array('b', shm_b.buf[:5])  # Copy the data into a new array.array
array('b', [22, 33, 44, 55, 100])
>>> shm_b.buf[:5] = b'howdy'  # Modify via shm_b using bytes
>>> bytes(shm_a.buf[:5])      # Access via shm_a
b'howdy'
>>> shm_b.close()   # Close each SharedMemory instance
>>> shm_a.close()
>>> shm_a.unlink()  # Call unlink only once to release the shared memory

以下範例示範了 SharedMemory 類別與 NumPy 陣列 [https://numpy.org/]的實際用法：從兩個不同的 Python shell 存取相同的 numpy.ndarray：

>>> # In the first Python interactive shell
>>> import numpy as np
>>> a = np.array([1, 1, 2, 3, 5, 8])  # Start with an existing NumPy array
>>> from multiprocessing import shared_memory
>>> shm = shared_memory.SharedMemory(create=True, size=a.nbytes)
>>> # Now create a NumPy array backed by shared memory
>>> b = np.ndarray(a.shape, dtype=a.dtype, buffer=shm.buf)
>>> b[:] = a[:]  # Copy the original data into shared memory
>>> b
array([1, 1, 2, 3, 5, 8])
>>> type(b)
<class 'numpy.ndarray'>
>>> type(a)
<class 'numpy.ndarray'>
>>> shm.name  # We did not specify a name so one was chosen for us
'psm_21467_46075'

>>> # In either the same shell or a new Python shell on the same machine
>>> import numpy as np
>>> from multiprocessing import shared_memory
>>> # Attach to the existing shared memory block
>>> existing_shm = shared_memory.SharedMemory(name='psm_21467_46075')
>>> # Note that a.shape is (6,) and a.dtype is np.int64 in this example
>>> c = np.ndarray((6,), dtype=np.int64, buffer=existing_shm.buf)
>>> c
array([1, 1, 2, 3, 5, 8])
>>> c[-1] = 888
>>> c
array([  1,   1,   2,   3,   5, 888])

>>> # Back in the first Python interactive shell, b reflects this change
>>> b
array([  1,   1,   2,   3,   5, 888])

>>> # Clean up from within the second Python shell
>>> del c  # Unnecessary; merely emphasizing the array is no longer used
>>> existing_shm.close()

>>> # Clean up from within the first Python shell
>>> del b  # Unnecessary; merely emphasizing the array is no longer used
>>> shm.close()
>>> shm.unlink()  # Free and release the shared memory block at the very end

class multiprocessing.managers.SharedMemoryManager([address[, authkey]])

multiprocessing.managers.BaseManager 的子類別，可用於跨行程管理共享記憶體區塊。

在 SharedMemoryManager 實例上呼叫 start() 會啟動一個新行程。這個新行程的唯一目的是管理那些透過它建立出的所有共享記憶體區塊的生命週期。要觸發釋放該行程管理的所有共享記憶體區塊，請在實例上呼叫 shutdown()，這會觸發對該行程管理的所有 SharedMemory 物件的 unlink() 呼叫，然後再停止這個行程。透過 SharedMemoryManager 建立 SharedMemory 實例，我們無需手動追蹤和觸發共享記憶體資源的釋放。

此類別提供了用於建立和回傳 SharedMemory 實例以及建立由共享記憶體支援的類串列物件 (ShareableList) 的方法。

請參閱 BaseManager 了解繼承的 address 和 authkey 可選輸入引數的描述以及如何使用它們從其他行程連接到現有的 SharedMemoryManager 服務。

SharedMemory(size)

建立並回傳一個新的 SharedMemory 物件，該物件具有指定的 size（以位元組為單位）。

ShareableList(sequence)

建立並回傳一個新的 ShareableList 物件，該物件由輸入 sequence 中的值初始化。

以下範例示範了 SharedMemoryManager 的基本作用機制：

>>> from multiprocessing.managers import SharedMemoryManager
>>> smm = SharedMemoryManager()
>>> smm.start()  # Start the process that manages the shared memory blocks
>>> sl = smm.ShareableList(range(4))
>>> sl
ShareableList([0, 1, 2, 3], name='psm_6572_7512')
>>> raw_shm = smm.SharedMemory(size=128)
>>> another_sl = smm.ShareableList('alpha')
>>> another_sl
ShareableList(['a', 'l', 'p', 'h', 'a'], name='psm_6572_12221')
>>> smm.shutdown()  # Calls unlink() on sl, raw_shm, and another_sl

以下範例描述了一種可能更方便的模式，即透過 with 陳述式使用 SharedMemoryManager 物件，以確保所有共享記憶體區塊不再被需要後都被釋放：

>>> with SharedMemoryManager() as smm:
...     sl = smm.ShareableList(range(2000))
...     # Divide the work among two processes, storing partial results in sl
...     p1 = Process(target=do_work, args=(sl, 0, 1000))
...     p2 = Process(target=do_work, args=(sl, 1000, 2000))
...     p1.start()
...     p2.start()  # A multiprocessing.Pool might be more efficient
...     p1.join()
...     p2.join()   # Wait for all work to complete in both processes
...     total_result = sum(sl)  # Consolidate the partial results now in sl

在 with 陳述式中使用 SharedMemoryManager 時，當 with 陳述式的程式碼區塊執行完畢時，使用該管理器建立的共享記憶體區塊都會被釋放。

class multiprocessing.shared_memory.ShareableList(sequence=None, *, name=None)

提供一個類似 list 的可變物件，其中儲存的所有值都儲存在共享記憶體區塊中。這將可儲存值限制為以下內建資料型別：

int （有符號 64 位元）

float

bool

str （編碼為 UTF-8 時每個小於 10M 位元組）

bytes （每個小於 10M 位元組）

None

它也與內建 list 型別明顯不同，因為這些 list 不能更改其總長度（即沒有 append()、insert() 等）並且不支援透過切片動態建立新的 ShareableList 實例。

sequence 用於填充 (populate) 一個充滿值的新 ShareableList。設定為 None 以透過其唯一的共享記憶體名稱來附加到已經存在的 ShareableList。

如 SharedMemory 的定義中所述，name 是被請求之共享記憶體的唯一名稱。當附加到現有的 ShareableList 時，指定其共享記憶體區塊的唯一名稱，同時將 sequence 設定為 None。

備註

bytes 和 str 值存在一個已知問題。如果它們以 \x00 nul 位元組或字元結尾，那麼當透過索引從 ShareableList 中取得它們時，這些位元組或字元可能會被默默地剝離 (silently stripped)。這種 .rstrip(b'\x00') 行為被認為是一個錯誤，將來可能會消失。請參閱 gh-106939 [https://github.com/python/cpython/issues/106939]。

對於去除尾隨空值 (rstripping of trailing nulls) 會出問題的應用程式，變通解法 (workaround) 是始終無條件地在儲存時於此類值的末尾追加一個額外非 0 位元組，並在取得時也無條件地刪除它：

>>> from multiprocessing import shared_memory
>>> nul_bug_demo = shared_memory.ShareableList(['?\x00', b'\x03\x02\x01\x00\x00\x00'])
>>> nul_bug_demo[0]
'?'
>>> nul_bug_demo[1]
b'\x03\x02\x01'
>>> nul_bug_demo.shm.unlink()
>>> padded = shared_memory.ShareableList(['?\x00\x07', b'\x03\x02\x01\x00\x00\x00\x07'])
>>> padded[0][:-1]
'?\x00'
>>> padded[1][:-1]
b'\x03\x02\x01\x00\x00\x00'
>>> padded.shm.unlink()

count(value)

回傳 value 出現的次數。

index(value)

回傳 value 的第一個索引位置。如果 value 不存在，則引發 ValueError。

format

唯讀屬性，包含所有目前有儲存的值所使用的 struct 打包格式。

shm

儲存值的 SharedMemory 實例。

以下範例示範了 ShareableList 實例的基本用法：

>>> from multiprocessing import shared_memory
>>> a = shared_memory.ShareableList(['howdy', b'HoWdY', -273.154, 100, None, True, 42])
>>> [ type(entry) for entry in a ]
[<class 'str'>, <class 'bytes'>, <class 'float'>, <class 'int'>, <class 'NoneType'>, <class 'bool'>, <class 'int'>]
>>> a[2]
-273.154
>>> a[2] = -78.5
>>> a[2]
-78.5
>>> a[2] = 'dry ice'  # Changing data types is supported as well
>>> a[2]
'dry ice'
>>> a[2] = 'larger than previously allocated storage space'
Traceback (most recent call last):
  ...
ValueError: exceeds available storage for existing str
>>> a[2]
'dry ice'
>>> len(a)
7
>>> a.index(42)
6
>>> a.count(b'howdy')
0
>>> a.count(b'HoWdY')
1
>>> a.shm.close()
>>> a.shm.unlink()
>>> del a  # Use of a ShareableList after call to unlink() is unsupported

以下範例描述了一個、兩個或多個行程如何透過提供後面的共享記憶體區塊名稱來存取同一個 ShareableList：

>>> b = shared_memory.ShareableList(range(5))         # In a first process
>>> c = shared_memory.ShareableList(name=b.shm.name)  # In a second process
>>> c
ShareableList([0, 1, 2, 3, 4], name='...')
>>> c[-1] = -999
>>> b[-1]
-999
>>> b.shm.close()
>>> c.shm.close()
>>> c.shm.unlink()

以下範例示範了如果需要，可以對 ShareableList（和底層 SharedMemory）物件進行 pickle 和 unpickle。請注意，它仍然是相同的共享物件。發生這種情況是因為反序列化的物件具有相同的唯一名稱，並且只是附加到具有相同名稱的現有物件（如果該物件仍然存在）：

>>> import pickle
>>> from multiprocessing import shared_memory
>>> sl = shared_memory.ShareableList(range(10))
>>> list(sl)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> deserialized_sl = pickle.loads(pickle.dumps(sl))
>>> list(deserialized_sl)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> sl[0] = -1
>>> deserialized_sl[1] = -2
>>> list(sl)
[-1, -2, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(deserialized_sl)
[-1, -2, 2, 3, 4, 5, 6, 7, 8, 9]

>>> sl.shm.close()
>>> sl.shm.unlink()

concurrent 套件

此套件包含下列模組：

concurrent.futures -- 啟動平行任務

concurrent.interpreters -- 在同一行程中使用多個直譯器

concurrent.futures --- 啟動平行任務

在 3.2 版被加入.

原始碼：Lib/concurrent/futures/thread.py [https://github.com/python/cpython/tree/3.14/Lib/concurrent/futures/thread.py]、Lib/concurrent/futures/process.py [https://github.com/python/cpython/tree/3.14/Lib/concurrent/futures/process.py] 與 Lib/concurrent/futures/interpreter.py [https://github.com/python/cpython/tree/3.14/Lib/concurrent/futures/interpreter.py]

concurrent.futures 模組提供了一個高階介面來非同步地 (asynchronously) 執行可呼叫物件 (callable) 。

非同步執行可以透過 ThreadPoolExecutor 或 InterpreterPoolExecutor 來使用執行緒 (thread) 執行，或透過 ProcessPoolExecutor 來使用單獨行程 (process) 執行。兩者都實作了相同的介面，該介面由抽象的 Executor 類別定義。

concurrent.futures.Future must not be confused with asyncio.Future, which is designed for use with asyncio tasks and coroutines. See the asyncio's Future documentation for a detailed comparison of the two.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

Executor 物件

class concurrent.futures.Executor

提供非同步執行呼叫方法的抽象類別。不應直接使用它，而應透過其具體子類別來使用。

submit(fn, /, *args, **kwargs)

為可呼叫物件 fn 排程來以 fn(*args, **kwargs) 的形式執行並回傳一個表示可呼叫的執行的 Future 物件。

with ThreadPoolExecutor(max_workers=1) as executor:
    future = executor.submit(pow, 323, 1235)
    print(future.result())

map(fn, *iterables, timeout=None, chunksize=1, buffersize=None)

類似於 map(fn, *iterables)，除了：

The iterables are collected immediately rather than lazily, unless a buffersize is specified to limit the number of submitted tasks whose results have not yet been yielded. If the buffer is full, iteration over the iterables pauses until a result is yielded from the buffer.

fn 是非同步執行的，並且對 fn 的多次呼叫可以並行處理。

如果 __next__() 被呼叫，且在原先呼叫 Executor.map() 的 timeout 秒後結果仍不可用，回傳的疊代器就會引發 TimeoutError。timeout 可以是整數或浮點數。如果未指定 timeout 或為 None，則等待時間就不會有限制。

如果 fn 呼叫引發例外，則當從疊代器中檢索到它的值時將引發該例外。

使用 ProcessPoolExecutor 時，此方法將 iterables 分成許多分塊 (chunks)，並將其作為獨立的任務來提交給池 (pool)。可以透過將 chunksize 設定為正整數來指定這些分塊的（約略）大小。對於非常長的可疊代物件，chunksize 使用較大的值（與預設大小 1 相比）可以顯著提高性能。對於 ThreadPoolExecutor 和 InterpreterPoolExecutor，chunksize 無效。

在 3.5 版的變更: 新增 chunksize 參數。

在 3.14 版的變更: 新增 buffersize 參數。

shutdown(wait=True, *, cancel_futures=False)

向 executor 發出訊號 (signal)，表明它應該在目前未定 (pending) 的 future 完成執行時釋放它正在使用的任何資源。在關閉後呼叫 Executor.submit() 和 Executor.map() 將引發 RuntimeError。

如果 wait 為 True 則此方法將不會回傳，直到所有未定的 futures 完成執行並且與 executor 關聯的資源都被釋放。如果 wait 為 False 則此方法將立即回傳，並且當所有未定的 future 執行完畢時，與 executor 關聯的資源將被釋放。不管 wait 的值如何，整個 Python 程式都不會退出，直到所有未定的 futures 執行完畢。

如果 cancel_futures 為 True，此方法將取消 executor 尚未開始運行的所有未定 future。無論 cancel_futures 的值如何，任何已完成或正在運行的 future 都不會被取消。

如果 cancel_futures 和 wait 都為 True，則 executor 已開始運行的所有 future 將在此方法回傳之前完成。剩餘的 future 被取消。

如果使用 with 陳述式來將 executor 用作 context manager，那你就可以不用明確地呼叫此方法，這將會自己關閉 Executor（如同呼叫 Executor.shutdown() 時 wait 被設定為 True 般等待）：

import shutil
with ThreadPoolExecutor(max_workers=4) as e:
    e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
    e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
    e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
    e.submit(shutil.copy, 'src4.txt', 'dest4.txt')

在 3.9 版的變更: 新增 cancel_futures。

ThreadPoolExecutor

ThreadPoolExecutor 是一個 Executor 子類別，它使用執行緒池來非同步地執行呼叫。

當與 Future 關聯的可呼叫物件等待另一個 Future 的結果時，可能會發生死鎖 (deadlock)。例如：

import time
def wait_on_b():
    time.sleep(5)
    print(b.result())  # b 永遠不會完成，因為它正在等待 a。
    return 5

def wait_on_a():
    time.sleep(5)
    print(a.result())  # a 永遠不會完成，因為它正在等待 b。
    return 6

executor = ThreadPoolExecutor(max_workers=2)
a = executor.submit(wait_on_b)
b = executor.submit(wait_on_a)

和：

def wait_on_future():
    f = executor.submit(pow, 5, 2)
    # 這將永遠不會完成，因為只有一個工作執行緒且
    # 它正在執行這個函式。
    print(f.result())

executor = ThreadPoolExecutor(max_workers=1)
executor.submit(wait_on_future)

class concurrent.futures.ThreadPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=())

一個 Executor 子類別，它使用最多有 max_workers 個執行緒的池來非同步地執行呼叫。

所有排隊到 ThreadPoolExecutor 的執行緒都將在直譯器退出之前加入。請注意，執行此操作的退出處理程式會在任何使用 atexit 新增的退出處理程式之前執行。這意味著必須捕獲並處理主執行緒中的例外，以便向執行緒發出訊號來正常退出 (gracefully exit)。因此，建議不要將 ThreadPoolExecutor 用於長時間運行的任務。

initializer 是一個可選的可呼叫物件，在每個工作執行緒開始時呼叫； initargs 是傳遞給 initializer 的引數元組 (tuple)。如果 initializer 引發例外，所有目前未定的作業以及任何向池中提交 (submit) 更多作業的嘗試都將引發 BrokenThreadPool。

在 3.5 版的變更: 如果 max_workers 為 None 或未給定，它將預設為機器上的處理器數量乘以 5，這假定了 ThreadPoolExecutor 通常用於 I/O 重疊而非 CPU 密集的作業，並且 worker 的數量應該高於 ProcessPoolExecutor 的 worker 數量。

在 3.6 版的變更: 新增 thread_name_prefix 參數以允許使用者控制由池所建立的工作執行緒 (worker thread) 的 threading.Thread 名稱，以便於除錯。

在 3.7 版的變更: 新增 initializer 與 initargs 引數。

在 3.8 版的變更: max_workers 的預設值改為 min(32, os.cpu_count() + 4)。此預設值為 I/O 密集任務至少保留了 5 個 worker。它最多使用 32 個 CPU 核心來執行CPU 密集任務，以釋放 GIL。並且它避免了在多核機器上隱晦地使用非常大量的資源。

ThreadPoolExecutor 現在在啟動 max_workers 工作執行緒之前會重用 (reuse) 空閒的工作執行緒。

在 3.13 版的變更: max_workers 的預設值被改為 min(32, (os.process_cpu_count() or 1) + 4)。

ThreadPoolExecutor 範例

import concurrent.futures
import urllib.request

URLS = ['http://www.foxnews.com/',
        'http://www.cnn.com/',
        'http://europe.wsj.com/',
        'http://www.bbc.co.uk/',
        'http://nonexistent-subdomain.python.org/']

# Retrieve a single page and report the URL and contents
def load_url(url, timeout):
    with urllib.request.urlopen(url, timeout=timeout) as conn:
        return conn.read()

# We can use a with statement to ensure threads are cleaned up promptly
with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    # Start the load operations and mark each future with its URL
    future_to_url = {executor.submit(load_url, url, 60): url for url in URLS}
    for future in concurrent.futures.as_completed(future_to_url):
        url = future_to_url[future]
        try:
            data = future.result()
        except Exception as exc:
            print('%r generated an exception: %s' % (url, exc))
        else:
            print('%r page is %d bytes' % (url, len(data)))

InterpreterPoolExecutor

在 3.14 版被加入.

The InterpreterPoolExecutor class uses a pool of interpreters to execute calls asynchronously. It is a ThreadPoolExecutor subclass, which means each worker is running in its own thread. The difference here is that each worker has its own interpreter, and runs each task using that interpreter.

The biggest benefit to using interpreters instead of only threads is true multi-core parallelism. Each interpreter has its own Global Interpreter Lock, so code running in one interpreter can run on one CPU core, while code in another interpreter runs unblocked on a different core.

The tradeoff is that writing concurrent code for use with multiple interpreters can take extra effort. However, this is because it forces you to be deliberate about how and when interpreters interact, and to be explicit about what data is shared between interpreters. This results in several benefits that help balance the extra effort, including true multi-core parallelism, For example, code written this way can make it easier to reason about concurrency. Another major benefit is that you don't have to deal with several of the big pain points of using threads, like race conditions.

Each worker's interpreter is isolated from all the other interpreters. "Isolated" means each interpreter has its own runtime state and operates completely independently. For example, if you redirect sys.stdout in one interpreter, it will not be automatically redirected to any other interpreter. If you import a module in one interpreter, it is not automatically imported in any other. You would need to import the module separately in interpreter where you need it. In fact, each module imported in an interpreter is a completely separate object from the same module in a different interpreter, including sys, builtins, and even __main__.

Isolation means a mutable object, or other data, cannot be used by more than one interpreter at the same time. That effectively means interpreters cannot actually share such objects or data. Instead, each interpreter must have its own copy, and you will have to synchronize any changes between the copies manually. Immutable objects and data, like the builtin singletons, strings, and tuples of immutable objects, don't have these limitations.

Communicating and synchronizing between interpreters is most effectively done using dedicated tools, like those proposed in PEP 734 [https://peps.python.org/pep-0734/]. One less efficient alternative is to serialize with pickle and then send the bytes over a shared socket or pipe.

class concurrent.futures.InterpreterPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=())

A ThreadPoolExecutor subclass that executes calls asynchronously using a pool of at most max_workers threads. Each thread runs tasks in its own interpreter. The worker interpreters are isolated from each other, which means each has its own runtime state and that they can't share any mutable objects or other data. Each interpreter has its own Global Interpreter Lock, which means code run with this executor has true multi-core parallelism.

The optional initializer and initargs arguments have the same meaning as for ThreadPoolExecutor: the initializer is run when each worker is created, though in this case it is run in the worker's interpreter. The executor serializes the initializer and initargs using pickle when sending them to the worker's interpreter.

備註

The executor may replace uncaught exceptions from initializer with ExecutionFailed.

Other caveats from parent ThreadPoolExecutor apply here.

submit() and map() work like normal, except the worker serializes the callable and arguments using pickle when sending them to its interpreter. The worker likewise serializes the return value when sending it back.

When a worker's current task raises an uncaught exception, the worker always tries to preserve the exception as-is. If that is successful then it also sets the __cause__ to a corresponding ExecutionFailed instance, which contains a summary of the original exception. In the uncommon case that the worker is not able to preserve the original as-is then it directly preserves the corresponding ExecutionFailed instance instead.

ProcessPoolExecutor

ProcessPoolExecutor 類別是一個 Executor 的子類別，它使用行程池來非同步地執行呼叫。ProcessPoolExecutor 使用了 multiprocessing 模組，這允許它避開全域直譯器鎖 (Global Interpreter Lock)，但也意味著只能執行和回傳可被 pickle 的 (picklable) 物件。

__main__ 模組必須可以被工作子行程 (worker subprocess) 引入。這意味著 ProcessPoolExecutor 將無法在交互式直譯器 (interactive interpreter) 中工作。

從提交給 ProcessPoolExecutor 的可呼叫物件中呼叫 Executor 或 Future 方法將導致死鎖。

Note that the restrictions on functions and arguments needing to picklable as per multiprocessing.Process apply when using submit() and map() on a ProcessPoolExecutor. A function defined in a REPL or a lambda should not be expected to work.

class concurrent.futures.ProcessPoolExecutor(max_workers=None, mp_context=None, initializer=None, initargs=(), max_tasks_per_child=None)

一個 Executor 子類別，它使用了最多有 max_workers 個行程的池來非同步地執行呼叫。如果 max_workers 為 None 或未給定，它將被預設為 os.process_cpu_count()。如果 max_workers 小於或等於 0，則會引發 ValueError。在 Windows 上，max_workers 必須小於或等於 61。如果不是，則會引發 ValueError。如果 max_workers 為 None，則預設選擇最多為 61，即便有更多處理器可用。mp_context 可以是 multiprocessing 情境 (context) 或 None。它將用於啟動 worker。如果 mp_context 為 None 或未給定，則使用預設的 multiprocessing 情境。請見 Contexts and start methods。

initializer 是一個可選的可呼叫物件，在每個工作行程 (worker process) 開始時呼叫；initargs 是傳遞給 initializer 的引數元組。如果 initializer 引發例外，所有目前未定的作業以及任何向池中提交更多作業的嘗試都將引發 BrokenProcessPool。

max_tasks_per_child 是一個可選引數，它指定單個行程在退出並被新的工作行程替換之前可以執行的最大任務數。預設情況下 max_tasks_per_child 是 None，這意味著工作行程的生命週期將與池一樣長。當指定最大值時，在沒有 mp_context 參數的情況下，將預設使用 "spawn" 做為 multiprocessing 啟動方法。此功能與 "fork" 啟動方法不相容。

備註

Bugs have been reported when using the max_tasks_per_child feature that can result in the ProcessPoolExecutor hanging in some circumstances. Follow its eventual resolution in gh-115634 [https://github.com/python/cpython/issues/115634].

在 3.3 版的變更: 當其中一個工作行程突然終止時，現在會引發 BrokenProcessPool 錯誤。在過去，此行為是未定義的 (undefined)，但對 executor 或其 future 的操作經常會發生凍結或死鎖。

在 3.7 版的變更: 新增了 mp_context 引數以允許使用者控制由池所建立的工作行程的 start_method。

新增 initializer 與 initargs 引數。

在 3.11 版的變更: 新增了 max_tasks_per_child 引數以允許使用者控制池中 worker 的生命週期。

在 3.12 版的變更: 在 POSIX 系統上，如果你的應用程式有多個執行緒並且 multiprocessing 情境使用了 "fork" 啟動方法：內部呼叫以產生 worker 的 os.fork() 函式可能會引發 DeprecationWarning。傳遞一個 mp_context 以配置為使用不同的啟動方法。更多說明請參閱 os.fork() 文件。

在 3.13 版的變更: max_workers uses os.process_cpu_count() by default, instead of os.cpu_count().

在 3.14 版的變更: The default process start method (see Contexts and start methods) changed away from fork. If you require the fork start method for ProcessPoolExecutor you must explicitly pass mp_context=multiprocessing.get_context("fork").

terminate_workers()

Attempt to terminate all living worker processes immediately by calling Process.terminate on each of them. Internally, it will also call Executor.shutdown() to ensure that all other resources associated with the executor are freed.

After calling this method the caller should no longer submit tasks to the executor.

在 3.14 版被加入.

kill_workers()

Attempt to kill all living worker processes immediately by calling Process.kill on each of them. Internally, it will also call Executor.shutdown() to ensure that all other resources associated with the executor are freed.

After calling this method the caller should no longer submit tasks to the executor.

在 3.14 版被加入.

ProcessPoolExecutor 範例

import concurrent.futures
import math

PRIMES = [
    112272535095293,
    112582705942171,
    112272535095293,
    115280095190773,
    115797848077099,
    1099726899285419]

def is_prime(n):
    if n < 2:
        return False
    if n == 2:
        return True
    if n % 2 == 0:
        return False

    sqrt_n = int(math.floor(math.sqrt(n)))
    for i in range(3, sqrt_n + 1, 2):
        if n % i == 0:
            return False
    return True

def main():
    with concurrent.futures.ProcessPoolExecutor() as executor:
        for number, prime in zip(PRIMES, executor.map(is_prime, PRIMES)):
            print('%d is prime: %s' % (number, prime))

if __name__ == '__main__':
    main()

Future 物件

Future 類別封裝了可呼叫物件的非同步執行。Future 實例由 Executor.submit() 建立。

class concurrent.futures.Future

封裝可呼叫物件的非同步執行。Future 實例由 Executor.submit() 建立，且除測試外不應直接建立。

cancel()

嘗試取消呼叫。如果呼叫目前正在執行或已完成運行且無法取消，則該方法將回傳 False，否則呼叫將被取消並且該方法將回傳 True。

cancelled()

如果該呼叫成功被取消，則回傳 True。

running()

如果呼叫正在執行且無法取消，則回傳 True。

done()

如果呼叫成功被取消或結束運行，則回傳 True。

result(timeout=None)

回傳該呼叫回傳的值。如果呼叫尚未完成，則此方法將等待至多 timeout 秒。如果呼叫在 timeout 秒內未完成，則會引發 TimeoutError。timeout 可以是整數或浮點數。如果未指定 timeout 或為 None，則等待時間就不會有限制。

如果 future 在完成之前被取消，那麼 CancelledError 將被引發。

如果該呼叫引發了例外，此方法將引發相同的例外。

exception(timeout=None)

回傳該呼叫引發的例外。如果呼叫尚未完成，則此方法將等待至多 timeout 秒。如果呼叫在 timeout 秒內未完成，則會引發 TimeoutError。 timeout 可以是整數或浮點數。如果未指定 timeout 或為 None，則等待時間就不會有限制。

如果 future 在完成之前被取消，那麼 CancelledError 將被引發。

如果呼叫在沒有引發的情況下完成，則回傳 None。

add_done_callback(fn)

將可呼叫的 fn 附加到 future 上。當 future 被取消或完成運行時，fn 將被以 future 作為其唯一引數來呼叫。

新增的可呼叫物件按新增順序呼叫，並且始終在屬於新增它們的行程的執行緒中呼叫。如果可呼叫物件引發 Exception 子類別，它將被記錄 (log) 並忽略。如果可呼叫物件引發 BaseException 子類別，該行為未定義。

如果 future 已經完成或被取消，fn 將立即被呼叫。

以下 Future 方法旨在用於單元測試和 Executor 實作。

set_running_or_notify_cancel()

此方法只能在與 Future 關聯的工作被執行之前於 Executor 實作中呼叫，或者在單元測試中呼叫。

如果該方法回傳 False 則 Future 已被取消，即 Future.cancel() 被呼叫並回傳 True。任何等待 Future 完成的執行緒（即透過 as_completed() 或 wait()）將被喚醒。

如果該方法回傳 True 則代表 Future 未被取消並已進入運行狀態，意即呼叫 Future.running() 將回傳 True。

此方法只能呼叫一次，且不能在呼叫 Future.set_result() 或 Future.set_exception() 之後呼叫。

set_result(result)

將與 Future 關聯的工作結果設定為 result。

此方法只能在 Executor 實作中和單元測試中使用。

在 3.8 版的變更: 如果 Future 已經完成，此方法會引發 concurrent.futures.InvalidStateError。

set_exception(exception)

將與 Future 關聯的工作結果設定為 Exception exception。

此方法只能在 Executor 實作中和單元測試中使用。

在 3.8 版的變更: 如果 Future 已經完成，此方法會引發 concurrent.futures.InvalidStateError。

模組函式

concurrent.futures.wait(fs, timeout=None, return_when=ALL_COMPLETED)

等待 fs 給定的 Future 實例（可能由不同的 Executor 實例建立）完成。提供給 fs 的重複 future 將被刪除，並且只會回傳一次。回傳一個集合的附名二元組 (named 2-tuple of sets)。第一組名為 done，包含在等待完成之前完成的 future（已完成或被取消的 future）。第二組名為 not_done，包含未完成的 future（未定或運行中的 future）。

timeout 可用於控制回傳前等待的最大秒數。timeout 可以是整數或浮點數。如果未指定 timeout 或為 None，則等待時間就沒有限制。

return_when 表示此函式應回傳的時間。它必須是以下常數之一：

常數

描述

concurrent.futures.FIRST_COMPLETED

當任何 future 完成或被取消時，該函式就會回傳。

concurrent.futures.FIRST_EXCEPTION

該函式會在任何 future 透過引發例外而完結時回傳。如果 future 沒有引發例外，那麼它等同於 ALL_COMPLETED。

concurrent.futures.ALL_COMPLETED

當所有 future 都完成或被取消時，該函式才會回傳。

concurrent.futures.as_completed(fs, timeout=None)

回傳由 fs 給定的 Future 實例（可能由不同的 Executor 實例建立）的疊代器，它在完成時產生 future（已完成或被取消的 future）。fs 給定的任何重複的 future 將只被回傳一次。呼叫 as_completed() 之前完成的任何 future 將首先產生。如果 __next__() 被呼叫，並且在原先呼叫 as_completed() 的 timeout 秒後結果仍不可用，則回傳的疊代器會引發 TimeoutError。timeout 可以是整數或浮點數。如果未指定 timeout 或為 None，則等待時間就沒有限制。

也參考

PEP 3148 [https://peps.python.org/pep-3148/] -- futures - 非同步地執行運算

描述此功能並提出被包含於 Python 標準函式庫中的提案。

例外類別

exception concurrent.futures.CancelledError

當 future 被取消時引發。

exception concurrent.futures.TimeoutError

TimeoutError 的棄用別名，在 future 操作超過給定超時 (timeout) 時引發。

在 3.11 版的變更: 這個類別是 TimeoutError 的別名。

exception concurrent.futures.BrokenExecutor

衍生自 RuntimeError，當執行器因某種原因損壞時會引發此例外類別，並且不能用於提交或執行新任務。

在 3.7 版被加入.

exception concurrent.futures.InvalidStateError

目前狀態下不允許的 future 操作被執行時而引發。

在 3.8 版被加入.

exception concurrent.futures.thread.BrokenThreadPool

衍生自 BrokenExecutor，當 ThreadPoolExecutor 的其中一個 worker 初始化失敗時會引發此例外類別。

在 3.7 版被加入.

exception concurrent.futures.interpreter.BrokenInterpreterPool

衍生自 BrokenThreadPool，當 InterpreterPoolExecutor 的其中一個 worker 初始化失敗時會引發此例外類別。

在 3.14 版被加入.

exception concurrent.futures.process.BrokenProcessPool

衍生自 BrokenExecutor（以前為 RuntimeError），當 ProcessPoolExecutor 的其中一個 worker 以不乾淨的方式終止時將引發此例外類別（例如它是從外面被 kill 掉的）。

在 3.3 版被加入.

concurrent.interpreters --- 在同一個行程中使用多個直譯器

在 3.14 版被加入.

原始碼：Lib/concurrent/interpreters [https://github.com/python/cpython/tree/3.14/Lib/concurrent/interpreters]

The concurrent.interpreters module constructs higher-level interfaces on top of the lower level _interpreters module.

The module is primarily meant to provide a basic API for managing interpreters (AKA "subinterpreters") and running things in them. Running mostly involves switching to an interpreter (in the current thread) and calling a function in that execution context.

For concurrency, interpreters themselves (and this module) don't provide much more than isolation, which on its own isn't useful. Actual concurrency is available separately through threads See below

也參考

InterpreterPoolExecutor

Combines threads with interpreters in a familiar interface.

隔離擴充模組

How to update an extension module to support multiple interpreters.

PEP 554 [https://peps.python.org/pep-0554/]

PEP 734 [https://peps.python.org/pep-0734/]

PEP 684 [https://peps.python.org/pep-0684/]

可用性: not WASI.

This module does not work or is not available on WebAssembly. See WebAssembly 平台 for more information.

Key details

Before we dive in further, there are a small number of details to keep in mind about using multiple interpreters:

isolated, by default

no implicit threads

not all PyPI packages support use in multiple interpreters yet

Introduction

An "interpreter" is effectively the execution context of the Python runtime. It contains all of the state the runtime needs to execute a program. This includes things like the import state and builtins. (Each thread, even if there's only the main thread, has some extra runtime state, in addition to the current interpreter, related to the current exception and the bytecode eval loop.)

The concept and functionality of the interpreter have been a part of Python since version 2.2, but the feature was only available through the C-API and not well known, and the isolation was relatively incomplete until version 3.12.

Multiple Interpreters and Isolation

A Python implementation may support using multiple interpreters in the same process. CPython has this support. Each interpreter is effectively isolated from the others (with a limited number of carefully managed process-global exceptions to the rule).

That isolation is primarily useful as a strong separation between distinct logical components of a program, where you want to have careful control of how those components interact.

備註

Interpreters in the same process can technically never be strictly isolated from one another since there are few restrictions on memory access within the same process. The Python runtime makes a best effort at isolation but extension modules may easily violate that. Therefore, do not use multiple interpreters in security-sensitive situations, where they shouldn't have access to each other's data.

Running in an Interpreter

Running in a different interpreter involves switching to it in the current thread and then calling some function. The runtime will execute the function using the current interpreter's state. The concurrent.interpreters module provides a basic API for creating and managing interpreters, as well as the switch-and-call operation.

No other threads are automatically started for the operation. There is a helper for that though. There is another dedicated helper for calling the builtin exec() in an interpreter.

When exec() (or eval()) are called in an interpreter, they run using the interpreter's __main__ module as the "globals" namespace. The same is true for functions that aren't associated with any module. This is the same as how scripts invoked from the command-line run in the __main__ module.

Concurrency and Parallelism

As noted earlier, interpreters do not provide any concurrency on their own. They strictly represent the isolated execution context the runtime will use in the current thread. That isolation makes them similar to processes, but they still enjoy in-process efficiency, like threads.

All that said, interpreters do naturally support certain flavors of concurrency. There's a powerful side effect of that isolation. It enables a different approach to concurrency than you can take with async or threads. It's a similar concurrency model to CSP or the actor model, a model which is relatively easy to reason about.

You can take advantage of that concurrency model in a single thread, switching back and forth between interpreters, Stackless-style. However, this model is more useful when you combine interpreters with multiple threads. This mostly involves starting a new thread, where you switch to another interpreter and run what you want there.

Each actual thread in Python, even if you're only running in the main thread, has its own current execution context. Multiple threads can use the same interpreter or different ones.

At a high level, you can think of the combination of threads and interpreters as threads with opt-in sharing.

As a significant bonus, interpreters are sufficiently isolated that they do not share the GIL, which means combining threads with multiple interpreters enables full multi-core parallelism. (This has been the case since Python 3.12.)

直譯器之間的溝通

In practice, multiple interpreters are useful only if we have a way to communicate between them. This usually involves some form of message passing, but can even mean sharing data in some carefully managed way.

With this in mind, the concurrent.interpreters module provides a queue.Queue implementation, available through create_queue().

"Sharing" Objects

Any data actually shared between interpreters loses the thread-safety provided by the GIL. There are various options for dealing with this in extension modules. However, from Python code the lack of thread-safety means objects can't actually be shared, with a few exceptions. Instead, a copy must be created, which means mutable objects won't stay in sync.

By default, most objects are copied with pickle when they are passed to another interpreter. Nearly all of the immutable builtin objects are either directly shared or copied efficiently. For example:

None

bool（True 和 False）

bytes

str

int

float

tuple (of similarly supported objects)

There is a small number of Python types that actually share mutable data between interpreters:

memoryview

Queue

Reference

This module defines the following functions:

concurrent.interpreters.list_all()

Return a list of Interpreter objects, one for each existing interpreter.

concurrent.interpreters.get_current()

Return an Interpreter object for the currently running interpreter.

concurrent.interpreters.get_main()

Return an Interpreter object for the main interpreter. This is the interpreter the runtime created to run the REPL or the script given at the command-line. It is usually the only one.

concurrent.interpreters.create()

Initialize a new (idle) Python interpreter and return a Interpreter object for it.

concurrent.interpreters.create_queue()

Initialize a new cross-interpreter queue and return a Queue object for it.

Interpreter objects

class concurrent.interpreters.Interpreter(id)

A single interpreter in the current process.

Generally, Interpreter shouldn't be called directly. Instead, use create() or one of the other module functions.

id

(read-only)

The underlying interpreter's ID.

whence

(read-only)

A string describing where the interpreter came from.

is_running()

Return True if the interpreter is currently executing code in its __main__ module and False otherwise.

close()

Finalize and destroy the interpreter.

prepare_main(ns=None, **kwargs)

Bind objects in the interpreter's __main__ module.

Some objects are actually shared and some are copied efficiently, but most are copied via pickle. See "Sharing" Objects.

exec(code, /, dedent=True)

Run the given source code in the interpreter (in the current thread).

call(callable, /, *args, **kwargs)

Return the result of calling running the given function in the interpreter (in the current thread).

call_in_thread(callable, /, *args, **kwargs)

Run the given function in the interpreter (in a new thread).

例外

exception concurrent.interpreters.InterpreterError

This exception, a subclass of Exception, is raised when an interpreter-related error happens.

exception concurrent.interpreters.InterpreterNotFoundError

This exception, a subclass of InterpreterError, is raised when the targeted interpreter no longer exists.

exception concurrent.interpreters.ExecutionFailed

This exception, a subclass of InterpreterError, is raised when the running code raised an uncaught exception.

excinfo

A basic snapshot of the exception raised in the other interpreter.

exception concurrent.interpreters.NotShareableError

This exception, a subclass of TypeError, is raised when an object cannot be sent to another interpreter.

在直譯器之間溝通

class concurrent.interpreters.Queue(id)

A wrapper around a low-level, cross-interpreter queue, which implements the queue.Queue interface. The underlying queue can only be created through create_queue().

Some objects are actually shared and some are copied efficiently, but most are copied via pickle. See "Sharing" Objects.

id

(read-only)

The queue's ID.

exception concurrent.interpreters.QueueEmptyError

This exception, a subclass of queue.Empty, is raised from Queue.get() and Queue.get_nowait() when the queue is empty.

exception concurrent.interpreters.QueueFullError

This exception, a subclass of queue.Full, is raised from Queue.put() and Queue.put_nowait() when the queue is full.

基本用法

建立一個直譯器並在其中運行程式碼：

from concurrent import interpreters

interp = interpreters.create()

# Run in the current OS thread.

interp.exec('print("spam!")')

interp.exec("""if True:
    print('spam!')
    """)

from textwrap import dedent
interp.exec(dedent("""
    print('spam!')
    """))

def run(arg):
    return arg

res = interp.call(run, 'spam!')
print(res)

def run():
    print('spam!')

interp.call(run)

# Run in new OS thread.

t = interp.call_in_thread(run)
t.join()

subprocess --- 子行程管理

原始碼：Lib/subprocess.py [https://github.com/python/cpython/tree/3.14/Lib/subprocess.py]

The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several older modules and functions:

os.system
os.spawn*

Information about how the subprocess module can be used to replace these modules and functions can be found in the following sections.

也參考

PEP 324 [https://peps.python.org/pep-0324/] -- 提議 subprocess 模組的 PEP

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

Using the subprocess Module

The recommended approach to invoking subprocesses is to use the run() function for all use cases it can handle. For more advanced use cases, the underlying Popen interface can be used directly.

subprocess.run(args, *, stdin=None, input=None, stdout=None, stderr=None, capture_output=False, shell=False, cwd=None, timeout=None, check=False, encoding=None, errors=None, text=None, env=None, universal_newlines=None, **other_popen_kwargs)

Run the command described by args. Wait for command to complete, then return a CompletedProcess instance.

The arguments shown above are merely the most common ones, described below in Frequently Used Arguments (hence the use of keyword-only notation in the abbreviated signature). The full function signature is largely the same as that of the Popen constructor - most of the arguments to this function are passed through to that interface. (timeout, input, check, and capture_output are not.)

If capture_output is true, stdout and stderr will be captured. When used, the internal Popen object is automatically created with stdout and stderr both set to PIPE. The stdout and stderr arguments may not be supplied at the same time as capture_output. If you wish to capture and combine both streams into one, set stdout to PIPE and stderr to STDOUT, instead of using capture_output.

A timeout may be specified in seconds, it is internally passed on to Popen.communicate(). If the timeout expires, the child process will be killed and waited for. The TimeoutExpired exception will be re-raised after the child process has terminated. The initial process creation itself cannot be interrupted on many platform APIs so you are not guaranteed to see a timeout exception until at least after however long process creation takes.

The input argument is passed to Popen.communicate() and thus to the subprocess's stdin. If used it must be a byte sequence, or a string if encoding or errors is specified or text is true. When used, the internal Popen object is automatically created with stdin set to PIPE, and the stdin argument may not be used as well.

If check is true, and the process exits with a non-zero exit code, a CalledProcessError exception will be raised. Attributes of that exception hold the arguments, the exit code, and stdout and stderr if they were captured.

If encoding or errors are specified, or text is true, file objects for stdin, stdout and stderr are opened in text mode using the specified encoding and errors or the io.TextIOWrapper default. The universal_newlines argument is equivalent to text and is provided for backwards compatibility. By default, file objects are opened in binary mode.

If env is not None, it must be a mapping that defines the environment variables for the new process; these are used instead of the default behavior of inheriting the current process' environment. It is passed directly to Popen. This mapping can be str to str on any platform or bytes to bytes on POSIX platforms much like os.environ or os.environb.

範例：

>>> subprocess.run(["ls", "-l"])  # 不捕捉輸出
CompletedProcess(args=['ls', '-l'], returncode=0)

>>> subprocess.run("exit 1", shell=True, check=True)
Traceback (most recent call last):
  ...
subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1

>>> subprocess.run(["ls", "-l", "/dev/null"], capture_output=True)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n', stderr=b'')

在 3.5 版被加入.

在 3.6 版的變更: 新增 encoding 與 errors 參數。

在 3.7 版的變更: Added the text parameter, as a more understandable alias of universal_newlines. Added the capture_output parameter.

在 3.12 版的變更: Changed Windows shell search order for shell=True. The current directory and %PATH% are replaced with %COMSPEC% and %SystemRoot%\System32\cmd.exe. As a result, dropping a malicious program named cmd.exe into a current directory no longer works.

class subprocess.CompletedProcess

The return value from run(), representing a process that has finished.

args

The arguments used to launch the process. This may be a list or a string.

returncode

Exit status of the child process. Typically, an exit status of 0 indicates that it ran successfully.

A negative value -N indicates that the child was terminated by signal N (POSIX only).

stdout

Captured stdout from the child process. A bytes sequence, or a string if run() was called with an encoding, errors, or text=True. None if stdout was not captured.

If you ran the process with stderr=subprocess.STDOUT, stdout and stderr will be combined in this attribute, and stderr will be None.

stderr

Captured stderr from the child process. A bytes sequence, or a string if run() was called with an encoding, errors, or text=True. None if stderr was not captured.

check_returncode()

If returncode is non-zero, raise a CalledProcessError.

在 3.5 版被加入.

subprocess.DEVNULL

Special value that can be used as the stdin, stdout or stderr argument to Popen and indicates that the special file os.devnull will be used.

在 3.3 版被加入.

subprocess.PIPE

Special value that can be used as the stdin, stdout or stderr argument to Popen and indicates that a pipe to the standard stream should be opened. Most useful with Popen.communicate().

subprocess.STDOUT

Special value that can be used as the stderr argument to Popen and indicates that standard error should go into the same handle as standard output.

exception subprocess.SubprocessError

Base class for all other exceptions from this module.

在 3.3 版被加入.

exception subprocess.TimeoutExpired

Subclass of SubprocessError, raised when a timeout expires while waiting for a child process.

cmd

Command that was used to spawn the child process.

timeout

Timeout in seconds.

output

Output of the child process if it was captured by run() or check_output(). Otherwise, None. This is always bytes when any output was captured regardless of the text=True setting. It may remain None instead of b'' when no output was observed.

stdout

Alias for output, for symmetry with stderr.

stderr

Stderr output of the child process if it was captured by run(). Otherwise, None. This is always bytes when stderr output was captured regardless of the text=True setting. It may remain None instead of b'' when no stderr output was observed.

在 3.3 版被加入.

在 3.5 版的變更: stdout and stderr attributes added

exception subprocess.CalledProcessError

Subclass of SubprocessError, raised when a process run by check_call(), check_output(), or run() (with check=True) returns a non-zero exit status.

returncode

Exit status of the child process. If the process exited due to a signal, this will be the negative signal number.

cmd

Command that was used to spawn the child process.

output

Output of the child process if it was captured by run() or check_output(). Otherwise, None.

stdout

Alias for output, for symmetry with stderr.

stderr

Stderr output of the child process if it was captured by run(). Otherwise, None.

在 3.5 版的變更: stdout and stderr attributes added

Frequently Used Arguments

To support a wide variety of use cases, the Popen constructor (and the convenience functions) accept a large number of optional arguments. For most typical use cases, many of these arguments can be safely left at their default values. The arguments that are most commonly needed are:

args is required for all calls and should be a string, or a sequence of program arguments. Providing a sequence of arguments is generally preferred, as it allows the module to take care of any required escaping and quoting of arguments (e.g. to permit spaces in file names). If passing a single string, either shell must be True (see below) or else the string must simply name the program to be executed without specifying any arguments.

stdin, stdout and stderr specify the executed program's standard input, standard output and standard error file handles, respectively. Valid values are None, PIPE, DEVNULL, an existing file descriptor (a positive integer), and an existing file object with a valid file descriptor. With the default settings of None, no redirection will occur. PIPE indicates that a new pipe to the child should be created. DEVNULL indicates that the special file os.devnull will be used. Additionally, stderr can be STDOUT, which indicates that the stderr data from the child process should be captured into the same file handle as for stdout.

If encoding or errors are specified, or text (also known as universal_newlines) is true, the file objects stdin, stdout and stderr will be opened in text mode using the encoding and errors specified in the call or the defaults for io.TextIOWrapper.

For stdin, line ending characters '\n' in the input will be converted to the default line separator os.linesep. For stdout and stderr, all line endings in the output will be converted to '\n'. For more information see the documentation of the io.TextIOWrapper class when the newline argument to its constructor is None.

If text mode is not used, stdin, stdout and stderr will be opened as binary streams. No encoding or line ending conversion is performed.

在 3.6 版的變更: 新增 encoding 與 errors 參數。

在 3.7 版的變更: 新增 text 參數作為 universal_newlines 的別名。

備註

The newlines attribute of the file objects Popen.stdin, Popen.stdout and Popen.stderr are not updated by the Popen.communicate() method.

If shell is True, the specified command will be executed through the shell. This can be useful if you are using Python primarily for the enhanced control flow it offers over most system shells and still want convenient access to other shell features such as shell pipes, filename wildcards, environment variable expansion, and expansion of ~ to a user's home directory. However, note that Python itself offers implementations of many shell-like features (in particular, glob, fnmatch, os.walk(), os.path.expandvars(), os.path.expanduser(), and shutil).

在 3.3 版的變更: When universal_newlines is True, the class uses the encoding locale.getpreferredencoding(False) instead of locale.getpreferredencoding(). See the io.TextIOWrapper class for more information on this change.

備註

Read the Security Considerations section before using shell=True.

These options, along with all of the other options, are described in more detail in the Popen constructor documentation.

Popen Constructor

The underlying process creation and management in this module is handled by the Popen class. It offers a lot of flexibility so that developers are able to handle the less common cases not covered by the convenience functions.

class subprocess.Popen(args, bufsize=-1, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=True, shell=False, cwd=None, env=None, universal_newlines=None, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False, pass_fds=(), *, group=None, extra_groups=None, user=None, umask=-1, encoding=None, errors=None, text=None, pipesize=-1, process_group=None)

Execute a child program in a new process. On POSIX, the class uses os.execvpe()-like behavior to execute the child program. On Windows, the class uses the Windows CreateProcess() function. The arguments to Popen are as follows.

args should be a sequence of program arguments or else a single string or path-like object. By default, the program to execute is the first item in args if args is a sequence. If args is a string, the interpretation is platform-dependent and described below. See the shell and executable arguments for additional differences from the default behavior. Unless otherwise stated, it is recommended to pass args as a sequence.

警告

For maximum reliability, use a fully qualified path for the executable. To search for an unqualified name on PATH, use shutil.which(). On all platforms, passing sys.executable is the recommended way to launch the current Python interpreter again, and use the -m command-line format to launch an installed module.

Resolving the path of executable (or the first item of args) is platform dependent. For POSIX, see os.execvpe(), and note that when resolving or searching for the executable path, cwd overrides the current working directory and env can override the PATH environment variable. For Windows, see the documentation of the lpApplicationName and lpCommandLine parameters of WinAPI CreateProcess, and note that when resolving or searching for the executable path with shell=False, cwd does not override the current working directory and env cannot override the PATH environment variable. Using a full path avoids all of these variations.

An example of passing some arguments to an external program as a sequence is:

Popen(["/usr/bin/git", "commit", "-m", "Fixes a bug."])

On POSIX, if args is a string, the string is interpreted as the name or path of the program to execute. However, this can only be done if not passing arguments to the program.

備註

It may not be obvious how to break a shell command into a sequence of arguments, especially in complex cases. shlex.split() can illustrate how to determine the correct tokenization for args:

>>> import shlex, subprocess
>>> command_line = input()
/bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "echo '$MONEY'"
>>> args = shlex.split(command_line)
>>> print(args)
['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "echo '$MONEY'"]
>>> p = subprocess.Popen(args) # 成功！

Note in particular that options (such as -input) and arguments (such as eggs.txt) that are separated by whitespace in the shell go in separate list elements, while arguments that need quoting or backslash escaping when used in the shell (such as filenames containing spaces or the echo command shown above) are single list elements.

On Windows, if args is a sequence, it will be converted to a string in a manner described in Converting an argument sequence to a string on Windows. This is because the underlying CreateProcess() operates on strings.

在 3.6 版的變更: args parameter accepts a path-like object if shell is False and a sequence containing path-like objects on POSIX.

在 3.8 版的變更: args parameter accepts a path-like object if shell is False and a sequence containing bytes and path-like objects on Windows.

The shell argument (which defaults to False) specifies whether to use the shell as the program to execute. If shell is True, it is recommended to pass args as a string rather than as a sequence.

On POSIX with shell=True, the shell defaults to /bin/sh. If args is a string, the string specifies the command to execute through the shell. This means that the string must be formatted exactly as it would be when typed at the shell prompt. This includes, for example, quoting or backslash escaping filenames with spaces in them. If args is a sequence, the first item specifies the command string, and any additional items will be treated as additional arguments to the shell itself. That is to say, Popen does the equivalent of:

Popen(['/bin/sh', '-c', args[0], args[1], ...])

On Windows with shell=True, the COMSPEC environment variable specifies the default shell. The only time you need to specify shell=True on Windows is when the command you wish to execute is built into the shell (e.g. dir or copy). You do not need shell=True to run a batch file or console-based executable.

備註

Read the Security Considerations section before using shell=True.

bufsize will be supplied as the corresponding argument to the open() function when creating the stdin/stdout/stderr pipe file objects:

0 means unbuffered (read and write are one system call and can return short)

1 means line buffered (only usable if text=True or universal_newlines=True)

any other positive value means use a buffer of approximately that size

negative bufsize (the default) means the system default of io.DEFAULT_BUFFER_SIZE will be used.

在 3.3.1 版的變更: bufsize now defaults to -1 to enable buffering by default to match the behavior that most code expects. In versions prior to Python 3.2.4 and 3.3.1 it incorrectly defaulted to 0 which was unbuffered and allowed short reads. This was unintentional and did not match the behavior of Python 2 as most code expected.

The executable argument specifies a replacement program to execute. It is very seldom needed. When shell=False, executable replaces the program to execute specified by args. However, the original args is still passed to the program. Most programs treat the program specified by args as the command name, which can then be different from the program actually executed. On POSIX, the args name becomes the display name for the executable in utilities such as ps. If shell=True, on POSIX the executable argument specifies a replacement shell for the default /bin/sh.

在 3.6 版的變更: executable parameter accepts a path-like object on POSIX.

在 3.8 版的變更: executable parameter accepts a bytes and path-like object on Windows.

在 3.12 版的變更: Changed Windows shell search order for shell=True. The current directory and %PATH% are replaced with %COMSPEC% and %SystemRoot%\System32\cmd.exe. As a result, dropping a malicious program named cmd.exe into a current directory no longer works.

stdin, stdout and stderr specify the executed program's standard input, standard output and standard error file handles, respectively. Valid values are None, PIPE, DEVNULL, an existing file descriptor (a positive integer), and an existing file object with a valid file descriptor. With the default settings of None, no redirection will occur. PIPE indicates that a new pipe to the child should be created. DEVNULL indicates that the special file os.devnull will be used. Additionally, stderr can be STDOUT, which indicates that the stderr data from the applications should be captured into the same file handle as for stdout.

If preexec_fn is set to a callable object, this object will be called in the child process just before the child is executed. (POSIX only)

警告

The preexec_fn parameter is NOT SAFE to use in the presence of threads in your application. The child process could deadlock before exec is called.

備註

If you need to modify the environment for the child use the env parameter rather than doing it in a preexec_fn. The start_new_session and process_group parameters should take the place of code using preexec_fn to call os.setsid() or os.setpgid() in the child.

在 3.8 版的變更: The preexec_fn parameter is no longer supported in subinterpreters. The use of the parameter in a subinterpreter raises RuntimeError. The new restriction may affect applications that are deployed in mod_wsgi, uWSGI, and other embedded environments.

If close_fds is true, all file descriptors except 0, 1 and 2 will be closed before the child process is executed. Otherwise when close_fds is false, file descriptors obey their inheritable flag as described in Inheritance of File Descriptors.

On Windows, if close_fds is true then no handles will be inherited by the child process unless explicitly passed in the handle_list element of STARTUPINFO.lpAttributeList, or by standard handle redirection.

在 3.2 版的變更: The default for close_fds was changed from False to what is described above.

在 3.7 版的變更: On Windows the default for close_fds was changed from False to True when redirecting the standard handles. It's now possible to set close_fds to True when redirecting the standard handles.

pass_fds is an optional sequence of file descriptors to keep open between the parent and child. Providing any pass_fds forces close_fds to be True. (POSIX only)

在 3.2 版的變更: 新增 pass_fds 參數。

If cwd is not None, the function changes the working directory to cwd before executing the child. cwd can be a string, bytes or path-like object. On POSIX, the function looks for executable (or for the first item in args) relative to cwd if the executable path is a relative path.

在 3.6 版的變更: cwd 參數在 POSIX 上接受 path-like object。

在 3.7 版的變更: cwd 參數在 Windows 上接受 path-like object。

在 3.8 版的變更: cwd 參數在 Windows 上接受 bytes 物件。

If restore_signals is true (the default) all signals that Python has set to SIG_IGN are restored to SIG_DFL in the child process before the exec. Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals. (POSIX only)

在 3.2 版的變更: 新增 restore_signals。

If start_new_session is true the setsid() system call will be made in the child process prior to the execution of the subprocess.

可用性: POSIX

在 3.2 版的變更: 新增 start_new_session。

If process_group is a non-negative integer, the setpgid(0, value) system call will be made in the child process prior to the execution of the subprocess.

可用性: POSIX

在 3.11 版的變更: 新增 process_group。

If group is not None, the setregid() system call will be made in the child process prior to the execution of the subprocess. If the provided value is a string, it will be looked up via grp.getgrnam() and the value in gr_gid will be used. If the value is an integer, it will be passed verbatim. (POSIX only)

可用性: POSIX

在 3.9 版被加入.

If extra_groups is not None, the setgroups() system call will be made in the child process prior to the execution of the subprocess. Strings provided in extra_groups will be looked up via grp.getgrnam() and the values in gr_gid will be used. Integer values will be passed verbatim. (POSIX only)

可用性: POSIX

在 3.9 版被加入.

If user is not None, the setreuid() system call will be made in the child process prior to the execution of the subprocess. If the provided value is a string, it will be looked up via pwd.getpwnam() and the value in pw_uid will be used. If the value is an integer, it will be passed verbatim. (POSIX only)

可用性: POSIX

在 3.9 版被加入.

If umask is not negative, the umask() system call will be made in the child process prior to the execution of the subprocess.

可用性: POSIX

在 3.9 版被加入.

If env is not None, it must be a mapping that defines the environment variables for the new process; these are used instead of the default behavior of inheriting the current process' environment. This mapping can be str to str on any platform or bytes to bytes on POSIX platforms much like os.environ or os.environb.

備註

If specified, env must provide any variables required for the program to execute. On Windows, in order to run a side-by-side assembly [https://en.wikipedia.org/wiki/Side-by-Side_Assembly] the specified env must include a valid %SystemRoot%.

If encoding or errors are specified, or text is true, the file objects stdin, stdout and stderr are opened in text mode with the specified encoding and errors, as described above in Frequently Used Arguments. The universal_newlines argument is equivalent to text and is provided for backwards compatibility. By default, file objects are opened in binary mode.

在 3.6 版被加入: 新增 encoding 與 errors。

在 3.7 版被加入: text was added as a more readable alias for universal_newlines.

If given, startupinfo will be a STARTUPINFO object, which is passed to the underlying CreateProcess function.

If given, creationflags, can be one or more of the following flags:

CREATE_NEW_CONSOLE

CREATE_NEW_PROCESS_GROUP

ABOVE_NORMAL_PRIORITY_CLASS

BELOW_NORMAL_PRIORITY_CLASS

HIGH_PRIORITY_CLASS

IDLE_PRIORITY_CLASS

NORMAL_PRIORITY_CLASS

REALTIME_PRIORITY_CLASS

CREATE_NO_WINDOW

DETACHED_PROCESS

CREATE_DEFAULT_ERROR_MODE

CREATE_BREAKAWAY_FROM_JOB

pipesize can be used to change the size of the pipe when PIPE is used for stdin, stdout or stderr. The size of the pipe is only changed on platforms that support this (only Linux at this time of writing). Other platforms will ignore this parameter.

在 3.10 版的變更: 新增 pipesize 參數。

Popen objects are supported as context managers via the with statement: on exit, standard file descriptors are closed, and the process is waited for.

with Popen(["ifconfig"], stdout=PIPE) as proc:
    log.write(proc.stdout.read())

Popen and the other functions in this module that use it raise an auditing event subprocess.Popen with arguments executable, args, cwd, and env. The value for args may be a single string or a list of strings, depending on platform.

在 3.2 版的變更: 新增情境管理器的支援。

在 3.6 版的變更: Popen destructor now emits a ResourceWarning warning if the child process is still running.

在 3.8 版的變更: Popen can use os.posix_spawn() in some cases for better performance. On Windows Subsystem for Linux and QEMU User Emulation, Popen constructor using os.posix_spawn() no longer raise an exception on errors like missing program, but the child process fails with a non-zero returncode.

例外

Exceptions raised in the child process, before the new program has started to execute, will be re-raised in the parent.

The most common exception raised is OSError. This occurs, for example, when trying to execute a non-existent file. Applications should prepare for OSError exceptions. Note that, when shell=True, OSError will be raised by the child only if the selected shell itself was not found. To determine if the shell failed to find the requested application, it is necessary to check the return code or output from the subprocess.

A ValueError will be raised if Popen is called with invalid arguments.

check_call() and check_output() will raise CalledProcessError if the called process returns a non-zero return code.

All of the functions and methods that accept a timeout parameter, such as run() and Popen.communicate() will raise TimeoutExpired if the timeout expires before the process exits.

Exceptions defined in this module all inherit from SubprocessError.

在 3.3 版被加入: 新增 SubprocessError 基底類別。

安全性注意事項

Unlike some other popen functions, this library will not implicitly choose to call a system shell. This means that all characters, including shell metacharacters, can safely be passed to child processes. If the shell is invoked explicitly, via shell=True, it is the application's responsibility to ensure that all whitespace and metacharacters are quoted appropriately to avoid shell injection [https://en.wikipedia.org/wiki/Shell_injection#Shell_injection] vulnerabilities. On some platforms, it is possible to use shlex.quote() for this escaping.

On Windows, batch files (*.bat or *.cmd) may be launched by the operating system in a system shell regardless of the arguments passed to this library. This could result in arguments being parsed according to shell rules, but without any escaping added by Python. If you are intentionally launching a batch file with arguments from untrusted sources, consider passing shell=True to allow Python to escape special characters. See gh-114539 [https://github.com/python/cpython/issues/114539] for additional discussion.

Popen Objects

Instances of the Popen class have the following methods:

Popen.poll()

Check if child process has terminated. Set and return returncode attribute. Otherwise, returns None.

Popen.wait(timeout=None)

Wait for child process to terminate. Set and return returncode attribute.

If the process does not terminate after timeout seconds, raise a TimeoutExpired exception. It is safe to catch this exception and retry the wait.

備註

This will deadlock when using stdout=PIPE or stderr=PIPE and the child process generates enough output to a pipe such that it blocks waiting for the OS pipe buffer to accept more data. Use Popen.communicate() when using pipes to avoid that.

備註

When the timeout parameter is not None, then (on POSIX) the function is implemented using a busy loop (non-blocking call and short sleeps). Use the asyncio module for an asynchronous wait: see asyncio.create_subprocess_exec.

在 3.3 版的變更: 新增 timeout。

Popen.communicate(input=None, timeout=None)

Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate and set the returncode attribute. The optional input argument should be data to be sent to the child process, or None, if no data should be sent to the child. If streams were opened in text mode, input must be a string. Otherwise, it must be bytes.

communicate() returns a tuple (stdout_data, stderr_data). The data will be strings if streams were opened in text mode; otherwise, bytes.

Note that if you want to send data to the process's stdin, you need to create the Popen object with stdin=PIPE. Similarly, to get anything other than None in the result tuple, you need to give stdout=PIPE and/or stderr=PIPE too.

If the process does not terminate after timeout seconds, a TimeoutExpired exception will be raised. Catching this exception and retrying communication will not lose any output. Supplying input to a subsequent post-timeout communicate() call is in undefined behavior and may become an error in the future.

The child process is not killed if the timeout expires, so in order to cleanup properly a well-behaved application should kill the child process and finish communication:

proc = subprocess.Popen(...)
try:
    outs, errs = proc.communicate(timeout=15)
except TimeoutExpired:
    proc.kill()
    outs, errs = proc.communicate()

After a call to communicate() raises TimeoutExpired, do not call wait(). Use an additional communicate() call to finish handling pipes and populate the returncode attribute.

備註

The data read is buffered in memory, so do not use this method if the data size is large or unlimited.

在 3.3 版的變更: 新增 timeout。

Popen.send_signal(signal)

Sends the signal signal to the child.

Do nothing if the process completed.

備註

On Windows, SIGTERM is an alias for terminate(). CTRL_C_EVENT and CTRL_BREAK_EVENT can be sent to processes started with a creationflags parameter which includes CREATE_NEW_PROCESS_GROUP.

Popen.terminate()

Stop the child. On POSIX OSs the method sends SIGTERM to the child. On Windows the Win32 API function TerminateProcess() is called to stop the child.

Popen.kill()

Kills the child. On POSIX OSs the function sends SIGKILL to the child. On Windows kill() is an alias for terminate().

The following attributes are also set by the class for you to access. Reassigning them to new values is unsupported:

Popen.args

The args argument as it was passed to Popen -- a sequence of program arguments or else a single string.

在 3.3 版被加入.

Popen.stdin

If the stdin argument was PIPE, this attribute is a writeable stream object as returned by open(). If the encoding or errors arguments were specified or the text or universal_newlines argument was True, the stream is a text stream, otherwise it is a byte stream. If the stdin argument was not PIPE, this attribute is None.

Popen.stdout

If the stdout argument was PIPE, this attribute is a readable stream object as returned by open(). Reading from the stream provides output from the child process. If the encoding or errors arguments were specified or the text or universal_newlines argument was True, the stream is a text stream, otherwise it is a byte stream. If the stdout argument was not PIPE, this attribute is None.

Popen.stderr

If the stderr argument was PIPE, this attribute is a readable stream object as returned by open(). Reading from the stream provides error output from the child process. If the encoding or errors arguments were specified or the text or universal_newlines argument was True, the stream is a text stream, otherwise it is a byte stream. If the stderr argument was not PIPE, this attribute is None.

警告

Use communicate() rather than .stdin.write, .stdout.read or .stderr.read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.

Popen.pid

The process ID of the child process.

Note that if you set the shell argument to True, this is the process ID of the spawned shell.

Popen.returncode

The child return code. Initially None, returncode is set by a call to the poll(), wait(), or communicate() methods if they detect that the process has terminated.

A None value indicates that the process hadn't yet terminated at the time of the last method call.

A negative value -N indicates that the child was terminated by signal N (POSIX only).

Windows Popen Helpers

The STARTUPINFO class and following constants are only available on Windows.

class subprocess.STARTUPINFO(*, dwFlags=0, hStdInput=None, hStdOutput=None, hStdError=None, wShowWindow=0, lpAttributeList=None)

Partial support of the Windows STARTUPINFO [https://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx] structure is used for Popen creation. The following attributes can be set by passing them as keyword-only arguments.

在 3.7 版的變更: Keyword-only argument support was added.

dwFlags

A bit field that determines whether certain STARTUPINFO attributes are used when the process creates a window.

si = subprocess.STARTUPINFO()
si.dwFlags = subprocess.STARTF_USESTDHANDLES | subprocess.STARTF_USESHOWWINDOW

hStdInput

If dwFlags specifies STARTF_USESTDHANDLES, this attribute is the standard input handle for the process. If STARTF_USESTDHANDLES is not specified, the default for standard input is the keyboard buffer.

hStdOutput

If dwFlags specifies STARTF_USESTDHANDLES, this attribute is the standard output handle for the process. Otherwise, this attribute is ignored and the default for standard output is the console window's buffer.

hStdError

If dwFlags specifies STARTF_USESTDHANDLES, this attribute is the standard error handle for the process. Otherwise, this attribute is ignored and the default for standard error is the console window's buffer.

wShowWindow

If dwFlags specifies STARTF_USESHOWWINDOW, this attribute can be any of the values that can be specified in the nCmdShow parameter for the ShowWindow [https://msdn.microsoft.com/en-us/library/ms633548(v=vs.85).aspx] function, except for SW_SHOWDEFAULT. Otherwise, this attribute is ignored.

SW_HIDE is provided for this attribute. It is used when Popen is called with shell=True.

lpAttributeList

A dictionary of additional attributes for process creation as given in STARTUPINFOEX, see UpdateProcThreadAttribute [https://msdn.microsoft.com/en-us/library/windows/desktop/ms686880(v=vs.85).aspx].

Supported attributes:

handle_list

Sequence of handles that will be inherited. close_fds must be true if non-empty.

The handles must be temporarily made inheritable by os.set_handle_inheritable() when passed to the Popen constructor, else OSError will be raised with Windows error ERROR_INVALID_PARAMETER (87).

警告

In a multithreaded process, use caution to avoid leaking handles that are marked inheritable when combining this feature with concurrent calls to other process creation functions that inherit all handles such as os.system(). This also applies to standard handle redirection, which temporarily creates inheritable handles.

在 3.7 版被加入.

Windows Constants

The subprocess module exposes the following constants.

subprocess.STD_INPUT_HANDLE

The standard input device. Initially, this is the console input buffer, CONIN$.

subprocess.STD_OUTPUT_HANDLE

The standard output device. Initially, this is the active console screen buffer, CONOUT$.

subprocess.STD_ERROR_HANDLE

The standard error device. Initially, this is the active console screen buffer, CONOUT$.

subprocess.SW_HIDE

Hides the window. Another window will be activated.

subprocess.STARTF_USESTDHANDLES

Specifies that the STARTUPINFO.hStdInput, STARTUPINFO.hStdOutput, and STARTUPINFO.hStdError attributes contain additional information.

subprocess.STARTF_USESHOWWINDOW

Specifies that the STARTUPINFO.wShowWindow attribute contains additional information.

subprocess.STARTF_FORCEONFEEDBACK

A STARTUPINFO.dwFlags parameter to specify that the Working in Background mouse cursor will be displayed while a process is launching. This is the default behavior for GUI processes.

在 3.13 版被加入.

subprocess.STARTF_FORCEOFFFEEDBACK

A STARTUPINFO.dwFlags parameter to specify that the mouse cursor will not be changed when launching a process.

在 3.13 版被加入.

subprocess.CREATE_NEW_CONSOLE

The new process has a new console, instead of inheriting its parent's console (the default).

subprocess.CREATE_NEW_PROCESS_GROUP

A Popen creationflags parameter to specify that a new process group will be created. This flag is necessary for using os.kill() on the subprocess.

This flag is ignored if CREATE_NEW_CONSOLE is specified.

subprocess.ABOVE_NORMAL_PRIORITY_CLASS

A Popen creationflags parameter to specify that a new process will have an above average priority.

在 3.7 版被加入.

subprocess.BELOW_NORMAL_PRIORITY_CLASS

A Popen creationflags parameter to specify that a new process will have a below average priority.

在 3.7 版被加入.

subprocess.HIGH_PRIORITY_CLASS

A Popen creationflags parameter to specify that a new process will have a high priority.

在 3.7 版被加入.

subprocess.IDLE_PRIORITY_CLASS

A Popen creationflags parameter to specify that a new process will have an idle (lowest) priority.

在 3.7 版被加入.

subprocess.NORMAL_PRIORITY_CLASS

A Popen creationflags parameter to specify that a new process will have a normal priority. (default)

在 3.7 版被加入.

subprocess.REALTIME_PRIORITY_CLASS

A Popen creationflags parameter to specify that a new process will have realtime priority. You should almost never use REALTIME_PRIORITY_CLASS, because this interrupts system threads that manage mouse input, keyboard input, and background disk flushing. This class can be appropriate for applications that "talk" directly to hardware or that perform brief tasks that should have limited interruptions.

在 3.7 版被加入.

subprocess.CREATE_NO_WINDOW

A Popen creationflags parameter to specify that a new process will not create a window.

在 3.7 版被加入.

subprocess.DETACHED_PROCESS

A Popen creationflags parameter to specify that a new process will not inherit its parent's console. This value cannot be used with CREATE_NEW_CONSOLE.

在 3.7 版被加入.

subprocess.CREATE_DEFAULT_ERROR_MODE

A Popen creationflags parameter to specify that a new process does not inherit the error mode of the calling process. Instead, the new process gets the default error mode. This feature is particularly useful for multithreaded shell applications that run with hard errors disabled.

在 3.7 版被加入.

subprocess.CREATE_BREAKAWAY_FROM_JOB

A Popen creationflags parameter to specify that a new process is not associated with the job.

在 3.7 版被加入.

Older high-level API

Prior to Python 3.5, these three functions comprised the high level API to subprocess. You can now use run() in many cases, but lots of existing code calls these functions.

subprocess.call(args, *, stdin=None, stdout=None, stderr=None, shell=False, cwd=None, timeout=None, **other_popen_kwargs)

Run the command described by args. Wait for command to complete, then return the returncode attribute.

Code needing to capture stdout or stderr should use run() instead:

run(...).returncode

To suppress stdout or stderr, supply a value of DEVNULL.

The arguments shown above are merely some common ones. The full function signature is the same as that of the Popen constructor - this function passes all supplied arguments other than timeout directly through to that interface.

備註

Do not use stdout=PIPE or stderr=PIPE with this function. The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from.

在 3.3 版的變更: 新增 timeout。

在 3.12 版的變更: Changed Windows shell search order for shell=True. The current directory and %PATH% are replaced with %COMSPEC% and %SystemRoot%\System32\cmd.exe. As a result, dropping a malicious program named cmd.exe into a current directory no longer works.

subprocess.check_call(args, *, stdin=None, stdout=None, stderr=None, shell=False, cwd=None, timeout=None, **other_popen_kwargs)

Run command with arguments. Wait for command to complete. If the return code was zero then return, otherwise raise CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute. If check_call() was unable to start the process it will propagate the exception that was raised.

Code needing to capture stdout or stderr should use run() instead:

run(..., check=True)

To suppress stdout or stderr, supply a value of DEVNULL.

The arguments shown above are merely some common ones. The full function signature is the same as that of the Popen constructor - this function passes all supplied arguments other than timeout directly through to that interface.

備註

Do not use stdout=PIPE or stderr=PIPE with this function. The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from.

在 3.3 版的變更: 新增 timeout。

在 3.12 版的變更: Changed Windows shell search order for shell=True. The current directory and %PATH% are replaced with %COMSPEC% and %SystemRoot%\System32\cmd.exe. As a result, dropping a malicious program named cmd.exe into a current directory no longer works.

subprocess.check_output(args, *, stdin=None, stderr=None, shell=False, cwd=None, encoding=None, errors=None, universal_newlines=None, timeout=None, text=None, **other_popen_kwargs)

Run command with arguments and return its output.

If the return code was non-zero it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute and any output in the output attribute.

這等同於：

run(..., check=True, stdout=PIPE).stdout

The arguments shown above are merely some common ones. The full function signature is largely the same as that of run() - most arguments are passed directly through to that interface. One API deviation from run() behavior exists: passing input=None will behave the same as input=b'' (or input='', depending on other arguments) rather than using the parent's standard input file handle.

By default, this function will return the data as encoded bytes. The actual encoding of the output data may depend on the command being invoked, so the decoding to text will often need to be handled at the application level.

This behaviour may be overridden by setting text, encoding, errors, or universal_newlines to True as described in Frequently Used Arguments and run().

To also capture standard error in the result, use stderr=subprocess.STDOUT:

>>> subprocess.check_output(
...     "ls non_existent_file; exit 0",
...     stderr=subprocess.STDOUT,
...     shell=True)
'ls: non_existent_file: No such file or directory\n'

在 3.1 版被加入.

在 3.3 版的變更: 新增 timeout。

在 3.4 版的變更: 新增 input 關鍵字引數的支援。

在 3.6 版的變更: 新增 encoding 與 errors。細節請見 run()。

在 3.7 版被加入: text was added as a more readable alias for universal_newlines.

在 3.12 版的變更: Changed Windows shell search order for shell=True. The current directory and %PATH% are replaced with %COMSPEC% and %SystemRoot%\System32\cmd.exe. As a result, dropping a malicious program named cmd.exe into a current directory no longer works.

Replacing Older Functions with the subprocess Module

In this section, "a becomes b" means that b can be used as a replacement for a.

備註

All "a" functions in this section fail (more or less) silently if the executed program cannot be found; the "b" replacements raise OSError instead.

In addition, the replacements using check_output() will fail with a CalledProcessError if the requested operation produces a non-zero return code. The output is still available as the output attribute of the raised exception.

In the following examples, we assume that the relevant functions have already been imported from the subprocess module.

Replacing /bin/sh shell command substitution

output=$(mycmd myarg)

變成：

output = check_output(["mycmd", "myarg"])

Replacing shell pipeline

output=$(dmesg | grep hda)

變成：

p1 = Popen(["dmesg"], stdout=PIPE)
p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p2 exits.
output = p2.communicate()[0]

The p1.stdout.close() call after starting the p2 is important in order for p1 to receive a SIGPIPE if p2 exits before p1.

Alternatively, for trusted input, the shell's own pipeline support may still be used directly:

output=$(dmesg | grep hda)

變成：

output = check_output("dmesg | grep hda", shell=True)

取代 os.system()

sts = os.system("mycmd" + " myarg")
# 變成
retcode = call("mycmd" + " myarg", shell=True)

註解：

Calling the program through the shell is usually not required.

The call() return value is encoded differently to that of os.system().

The os.system() function ignores SIGINT and SIGQUIT signals while the command is running, but the caller must do this separately when using the subprocess module.

A more realistic example would look like this:

try:
    retcode = call("mycmd" + " myarg", shell=True)
    if retcode < 0:
        print("Child was terminated by signal", -retcode, file=sys.stderr)
    else:
        print("Child returned", retcode, file=sys.stderr)
except OSError as e:
    print("Execution failed:", e, file=sys.stderr)

Replacing the os.spawn family

P_NOWAIT 範例：

pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
==>
pid = Popen(["/bin/mycmd", "myarg"]).pid

P_WAIT 範例：

retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
==>
retcode = call(["/bin/mycmd", "myarg"])

向量範例：

os.spawnvp(os.P_NOWAIT, path, args)
==>
Popen([path] + args[1:])

環境範例：

os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
==>
Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})

取代 os.popen()

Return code handling translates as follows:

pipe = os.popen(cmd, 'w')
...
rc = pipe.close()
if rc is not None and rc >> 8:
    print("There were some errors")
==>
process = Popen(cmd, stdin=PIPE)
...
process.stdin.close()
if process.wait() != 0:
    print("There were some errors")

Legacy Shell Invocation Functions

This module also provides the following legacy functions from the 2.x commands module. These operations implicitly invoke the system shell and none of the guarantees described above regarding security and exception handling consistency are valid for these functions.

subprocess.getstatusoutput(cmd, *, encoding=None, errors=None)

Return (exitcode, output) of executing cmd in a shell.

Execute the string cmd in a shell with check_output() and return a 2-tuple (exitcode, output). encoding and errors are used to decode output; see the notes on Frequently Used Arguments for more details.

A trailing newline is stripped from the output. The exit code for the command can be interpreted as the return code of subprocess. Example:

>>> subprocess.getstatusoutput('ls /bin/ls')
(0, '/bin/ls')
>>> subprocess.getstatusoutput('cat /bin/junk')
(1, 'cat: /bin/junk: No such file or directory')
>>> subprocess.getstatusoutput('/bin/junk')
(127, 'sh: /bin/junk: not found')
>>> subprocess.getstatusoutput('/bin/kill $$')
(-15, '')

可用性: Unix, Windows.

在 3.3.4 版的變更: 新增對 Windows 的支援。

The function now returns (exitcode, output) instead of (status, output) as it did in Python 3.3.3 and earlier. exitcode has the same value as returncode.

在 3.11 版的變更: 新增 encoding 與 errors 參數。

subprocess.getoutput(cmd, *, encoding=None, errors=None)

Return output (stdout and stderr) of executing cmd in a shell.

Like getstatusoutput(), except the exit code is ignored and the return value is a string containing the command's output. Example:

>>> subprocess.getoutput('ls /bin/ls')
'/bin/ls'

可用性: Unix, Windows.

在 3.3.4 版的變更: 新增對 Windows 的支援

在 3.11 版的變更: 新增 encoding 與 errors 參數。

註解

Timeout Behavior

When using the timeout parameter in functions like run(), Popen.wait(), or Popen.communicate(), users should be aware of the following behaviors:

Process Creation Delay: The initial process creation itself cannot be interrupted on many platform APIs. This means that even when specifying a timeout, you are not guaranteed to see a timeout exception until at least after however long process creation takes.

Extremely Small Timeout Values: Setting very small timeout values (such as a few milliseconds) may result in almost immediate TimeoutExpired exceptions because process creation and system scheduling inherently require time.

Converting an argument sequence to a string on Windows

On Windows, an args sequence is converted to a string that can be parsed using the following rules (which correspond to the rules used by the MS C runtime):

Arguments are delimited by white space, which is either a space or a tab.

A string surrounded by double quotation marks is interpreted as a single argument, regardless of white space contained within. A quoted string can be embedded in an argument.

A double quotation mark preceded by a backslash is interpreted as a literal double quotation mark.

Backslashes are interpreted literally, unless they immediately precede a double quotation mark.

If backslashes immediately precede a double quotation mark, every pair of backslashes is interpreted as a literal backslash. If the number of backslashes is odd, the last backslash escapes the next double quotation mark as described in rule 3.

也參考

shlex

Module which provides function to parse and escape command lines.

停用 posix_spawn()

在 Linux 上，subprocess 在安全的情況下預設會在內部使用 vfork() 系統呼叫，而不是 fork()，這顯著地提高了性能。

subprocess._USE_POSIX_SPAWN = False  # 見 CPython 問題 gh-NNNNNN。

在任何 Python 版本上將這個設定為 false 都是安全的。當不受支援時，它對舊版本或沒有支援的新版本沒有影響。不要假設屬性可供讀取。儘管它的名稱是這樣，真實值並不表示將使用相應的函式，而只是表示可能會使用。

每當你需要使用這些私有開關以重現你所看到的問題時，請隨時提出問題 (file issues)。從程式碼中的註解連結到該問題。

在 3.8 版被加入: _USE_POSIX_SPAWN

sched --- 事件排程器

原始碼：Lib/sched.py [https://github.com/python/cpython/tree/3.14/Lib/sched.py]

sched 模組定義了一個有實作通用事件排程器的類別：

class sched.scheduler(timefunc=time.monotonic, delayfunc=time.sleep)

scheduler 類別定義了事件排程的泛用介面。它需要兩個函式來和「外部世界」作用 —— timefunc 應不帶引數地被呼叫，並回傳一個數字（為「時間」，可為任何單位）。delayfunc 函式應以一個引數呼叫，並與 timefunc 的輸出相容，且應延遲其指定的時間單位。每個事件運行後，也會以引數 0 呼叫 delayfunc，來使得其他執行緒有機會在多執行緒應用程式中運行。

在 3.3 版的變更: timefunc 和 delayfunc 參數是可選的。

在 3.3 版的變更: scheduler 類別可以安全地在多執行緒環境中使用。

範例：

>>> import sched, time
>>> s = sched.scheduler(time.time, time.sleep)
>>> def print_time(a='default'):
...     print("From print_time", time.time(), a)
...
>>> def print_some_times():
...     print(time.time())
...     s.enter(10, 1, print_time)
...     s.enter(5, 2, print_time, argument=('positional',))
...     # 儘管優先順序較高，但由於 enter() 是相對的，'keyword' 在 'positional' 之後運行
...     s.enter(5, 1, print_time, kwargs={'a': 'keyword'})
...     s.enterabs(1_650_000_000, 10, print_time, argument=("first enterabs",))
...     s.enterabs(1_650_000_000, 5, print_time, argument=("second enterabs",))
...     s.run()
...     print(time.time())
...
>>> print_some_times()
1652342830.3640375
From print_time 1652342830.3642538 second enterabs
From print_time 1652342830.3643398 first enterabs
From print_time 1652342835.3694863 positional
From print_time 1652342835.3696074 keyword
From print_time 1652342840.369612 default
1652342840.3697174

排程器物件

scheduler 實例具有以下方法和屬性：

scheduler.enterabs(time, priority, action, argument=(), kwargs={})

為一個新事件排程。time 引數應該是與傳遞給建構函式的 timefunc 函式回傳值相容的數字型別。安排在相同 time 的事件將按照其 priority 的順序執行。數字越小代表優先順序越高。

執行事件意味著執行 action(*argument, **kwargs)。argument 是一個包含 action 之位置引數的序列。kwargs 是一個字典，帶有 action 的關鍵字引數。

回傳值是一個事件，可用於後續取消該事件（請見 cancel()）。

在 3.3 版的變更: argument 參數是可選的。

在 3.3 版的變更: 新增 kwargs 參數。

scheduler.enter(delay, priority, action, argument=(), kwargs={})

為一個排程事件延期 delay 個時間單位。除了相對時間之外，其他引數、效果和回傳值皆與 enterabs() 的相同。

在 3.3 版的變更: argument 參數是可選的。

在 3.3 版的變更: 新增 kwargs 參數。

scheduler.cancel(event)

從佇列中刪除該事件。如果 event 不是目前佇列中的事件，此方法將引發 ValueError。

scheduler.empty()

如果事件佇列為空，則回傳 True。

scheduler.run(blocking=True)

運行所有已排程的事件。此方法將會等待（使用傳遞給建構函式的 delayfunc 函式）下一個事件，然後執行它，並依此類推，直到不再有排程好的事件。

如果 blocking 為 false，則執行最快到期的已排程事件（如存在），然後回傳排程器中下一個排程呼叫（如存在）的截止時間。

action 或 delayfunc 都可能引發例外。無論哪種情況，排程器都將保持一致的狀態並傳遞例外。如果是由 action 引發例外，則後續呼叫 run() 時將不會嘗試運行該事件。

如果一系列事件的運行時長比執行下一個事件前的可用時長 (available time) 更長，那麼排程器就單純會落後。不會有事件被丟棄；呼叫程式碼也要負責取消不再相關的事件。

在 3.3 版的變更: 新增 blocking 參數。

scheduler.queue

會按事件運行順序回傳即將發生的事件串列的唯讀屬性。每個事件都以附名元組 (named tuple) 表示，並包含以下欄位：時間、優先順序、動作 (action)、引數、kwargs。

queue --- 同步佇列 (synchronized queue) 類別

原始碼：Lib/queue.py [https://github.com/python/cpython/tree/3.14/Lib/queue.py]

queue module（模組）實作多生產者、多消費者佇列。在執行緒程式設計中，必須在多執行緒之間安全地交換資訊時，特別有用。此 module 中的 Queue class 實作所有必需的鎖定語義 (locking semantics)。

此 module 實作三種型別的佇列，它們僅在取出條目的順序上有所不同。在 FIFO 佇列中，先加入的任務是第一個被取出的。在 LIFO 佇列中，最近被加入的條目是第一個被取出的（像堆疊 (stack) 一樣操作）。使用優先佇列 (priority queue) 時，條目將保持排序狀態（使用 heapq module），並先取出最低值條目。

在內部，這三種型別的佇列使用鎖 (lock) 來暫時阻塞競爭執行緒；但是，它們並不是被設計來處理執行緒內的 reentrancy（可重入）。

此外，此 module 實作一個「簡單」的 FIFO 佇列型別 SimpleQueue，其特定的實作是以較少的功能為代價，來提供額外的保證。

queue module 定義了以下的 class 和例外：

class queue.Queue(maxsize=0)

FIFO 佇列的建構子 (constructor)。maxsize 是一個整數，用於設置佇列中可放置的項目數的上限。一旦達到此大小，插入將會阻塞，直到佇列中的項目被消耗。如果 maxsize 小於或等於零，則佇列大小為無限。

class queue.LifoQueue(maxsize=0)

LIFO 佇列的建構子。maxsize 是一個整數，用於設置佇列中可放置的項目數的上限。一旦達到此大小，插入將被鎖定，到佇列中的項目被消耗。如果 maxsize 小於或等於零，則佇列大小為無限。

class queue.PriorityQueue(maxsize=0)

優先佇列的建構子。maxsize 是一個整數，用於設置佇列中可放置的項目數的上限。一旦達到此大小，插入將被阻塞，直到佇列中的項目被消耗。如果 maxsize 小於或等於零，則佇列大小為無限。

最低值的條目會最先被取出（最低值的條目是被會 min(entries) 回傳的那一個）。條目的典型模式是格式為 (priority_number, data) 的 tuple（元組）。

如果 data 元素為不可比較的，則可以將資料包裝在一個 class 中，該 class 忽略資料項目並僅比較優先數：

from dataclasses import dataclass, field
from typing import Any

@dataclass(order=True)
class PrioritizedItem:
    priority: int
    item: Any=field(compare=False)

class queue.SimpleQueue

無界的 FIFO 佇列的建構子。簡單佇列缺少任務追蹤等進階功能。

在 3.7 版被加入.

exception queue.Empty

當對一個空的 Queue 物件呼叫非阻塞的 (non-blocking) get()（或 get_nowait()）將引發此例外。

exception queue.Full

當對一個已滿的 Queue 物件呼叫非阻塞的 put()（或 put_nowait()）將引發此例外。

exception queue.ShutDown

當對一個已關閉的 Queue 物件呼叫 put() 或 get() 時將引發此例外。

在 3.13 版被加入.

佇列物件

佇列物件（Queue、LifoQueue、PriorityQueue）提供下面描述的公用 method。

Queue.qsize()

回傳佇列的近似大小。注意，qsize() > 0 並不能保證後續的 get() 不會阻塞，qsize() < maxsize 也不會保證 put() 不會阻塞。

Queue.empty()

如果佇列為空，則回傳 True，否則回傳 False。如果 empty() 回傳 True，則不保證後續呼叫 put() 不會阻塞。同樣，如果 empty() 回傳 False，則不保證後續呼叫 get() 不會阻塞。

Queue.full()

如果佇列已滿，則回傳 True ，否則回傳 False。如果 full() 回傳 True，則不保證後續呼叫 get() 不會阻塞。同樣，如果 full() 回傳 False，則不保證後續呼叫 put() 不會阻塞。

Queue.put(item, block=True, timeout=None)

將 item 放入佇列中。如果可選的 args block 為 true、timeout 為 None（預設值），則在必要時阻塞，直到自由槽 (free slot) 可用。如果 timeout 為正數，則最多阻塞 timeout 秒，如果該時間內沒有可用的自由槽，則會引發 Full 例外。否則（block 為 false），如果自由槽立即可用，則將項目放在佇列中，否則引發 Full 例外（在這種情況下，timeout 將被忽略）。

如果佇列已被關閉，則引發 ShutDown。

Queue.put_nowait(item)

等效於 put(item, block=False)。

Queue.get(block=True, timeout=None)

從佇列中移除並回傳一個項目。如果可選的 args block 為 true，且 timeout 為 None（預設值），則在必要時阻塞，直到有可用的項目。如果 timeout 是正數，則最多會阻塞 timeout 秒，如果該時間內沒有可用的項目，則會引發 Empty 例外。否則（block 為 false），如果立即可用，則回傳一個項目，否則引發 Empty 例外（在這種情況下，timeout 將被忽略）。

在 POSIX 系統的 3.0 版之前，以及 Windows 的所有版本，如果 block 為 true 且 timeout 為 None，則此操作將在底層鎖上進入不間斷等待。這意味著不會發生例外，特別是 SIGINT（中斷訊號）不會觸發 KeyboardInterrupt。

如果佇列已被關閉且為空，或佇列已立即關閉，則引發 ShutDown。

Queue.get_nowait()

等效於 get(False)。

有兩個 method 可以支援追蹤放入佇列的任務是否已由常駐消費者執行緒 (daemon consumer threads) 完全處理。

Queue.task_done()

表示先前放入佇列的任務已完成。由佇列消費者執行緒使用。對於用來提取任務的每個 get()，隨後呼叫 task_done() 告訴佇列任務的處理已完成。

如果目前 join() 阻塞，它將會在所有項目都已處理完畢後恢復（代表對於以 put() 放進佇列的每個項目，都要收到 task_done() 的呼叫）。

如果呼叫次數超過佇列中放置的項目數量，則引發 ValueError。

Queue.join()

持續阻塞直到佇列中的所有項目都已被取得並處理完畢。

每當項目被加到佇列中時，未完成任務的計數都會增加。每當消費者執行緒呼叫 task_done() 以指示該項目已被取出並且對其的所有工作都已完成時，計數就會下降。當未完成任務的計數降至零時，join() 將停止阻塞。

Waiting for task completion

如何等待放入佇列的任務完成的範例：

import threading
import queue

q = queue.Queue()

def worker():
    while True:
        item = q.get()
        print(f'Working on {item}')
        print(f'Finished {item}')
        q.task_done()

# Turn-on the worker thread.
threading.Thread(target=worker, daemon=True).start()

# Send thirty task requests to the worker.
for item in range(30):
    q.put(item)

# Block until all tasks are done.
q.join()
print('All work completed')

Terminating queues

When no longer needed, Queue objects can be wound down until empty or terminated immediately with a hard shutdown.

Queue.shutdown(immediate=False)

Put a Queue instance into a shutdown mode.

The queue can no longer grow. Future calls to put() raise ShutDown. Currently blocked callers of put() will be unblocked and will raise ShutDown in the formerly blocked thread.

If immediate is false (the default), the queue can be wound down normally with get() calls to extract tasks that have already been loaded.

And if task_done() is called for each remaining task, a pending join() will be unblocked normally.

Once the queue is empty, future calls to get() will raise ShutDown.

If immediate is true, the queue is terminated immediately. The queue is drained to be completely empty and the count of unfinished tasks is reduced by the number of tasks drained. If unfinished tasks is zero, callers of join() are unblocked. Also, blocked callers of get() are unblocked and will raise ShutDown because the queue is empty.

Use caution when using join() with immediate set to true. This unblocks the join even when no work has been done on the tasks, violating the usual invariant for joining a queue.

在 3.13 版被加入.

SimpleQueue 物件

SimpleQueue 物件提供下面描述的公用 method。

SimpleQueue.qsize()

傳回佇列的近似大小。注意，qsize() > 0 並不能保證後續的 get() 不會阻塞。

SimpleQueue.empty()

如果佇列為空，則回傳 True，否則回傳 False。如果 empty() 回傳 False，則不保證後續呼叫 get() 不會阻塞。

SimpleQueue.put(item, block=True, timeout=None)

將 item 放入佇列中。此 method 從不阻塞，並且都會成功（除了潛在的低階錯誤，像是分配記憶體失敗）。可選的 args block 和 timeout 會被忽略，它們僅是為了與 Queue.put() 相容才存在。

此 method 有一個可重入 (reentrant) 的 C 實作。意思就是，一個 put() 或 get() 呼叫，可以被同一執行緒中的另一個 put() 呼叫中斷，而不會造成死鎖 (deadlock) 或損壞佇列中的內部狀態。這使得它適合在解構子 (destructor) 中使用，像是 __del__ method 或 weakref 回呼函式 (callback)。

SimpleQueue.put_nowait(item)

等效於 put(item, block=False)，用於與 Queue.put_nowait() 相容。

SimpleQueue.get(block=True, timeout=None)

從佇列中移除並回傳一個項目。如果可選的 args block 為 true，且 timeout 為 None（預設值），則在必要時阻塞，直到有可用的項目。如果 timeout 是正數，則最多會阻塞 timeout 秒，如果該時間內沒有可用的項目，則會引發 Empty 例外。否則（block 為 false），如果立即可用，則回傳一個項目，否則引發 Empty 例外（在這種情況下，timeout 將被忽略）。

SimpleQueue.get_nowait()

等效於 get(False)。

也參考

Class multiprocessing.Queue

用於多行程處理 (multi-processing)（而非多執行緒）情境 (context) 的佇列 class。

collections.deque 是無界佇列的替代實作，有快速且具原子性 (atomic) 的 append() 和 popleft() 操作，這些操作不需要鎖定，並且還支援索引。

contextvars --- 情境變數

本模組供 API 來管理、儲存及存取單一情境各自的狀態（context-local state）。 用 ContextVar 類別宣告和處理情境變數。 copy_context() 函式和 Context 類別應在非同步框架中管理目前的情境。

帶有狀態的 Context Manager 應該使用情境變數，而不是 threading.local()，才能防止它們的狀態在並行（concurrent）程式碼中使用時意外外溢並干擾到其他程式碼。

其他詳細資訊，請參閱 PEP 567 [https://peps.python.org/pep-0567/]。

在 3.7 版被加入.

情境變數

class contextvars.ContextVar(name[, *, default])

此類別用在宣告新的情境變數，例如：

var: ContextVar[int] = ContextVar('var', default=42)

必要參數 name 用於自我檢查（introspection）和除錯。

當在目前的情境中找不到變數的值時，ContextVar.get() 會回傳可選的僅限關鍵字參數 default。

重要：情境變數應該在最頂端的模組層級建立，絕對不要在閉包（closure）中建立。 Context 物件持有情境變數的強參照，這會阻止情境變數被正確地垃圾回收（garbage collected）。

name

這個變數的名稱。這是一個唯讀屬性。

在 3.7.1 版被加入.

get([default])

回傳目前情境的情境變數值。

如果在目前情境中沒有變數的值，此方法將：

回傳方法的 default 引數值（如果有的話）；否則

回傳情境變數的預設值（如果建立情境變數時有指定預設值的話）；否則

會引發一個 LookupError。

set(value)

在目前的情境中，呼叫以設定情境變數的新值。

value 屬必要引數，是情境變數的新值。

回傳一個 Token 物件，該物件可透過 ContextVar.reset() 方法，用來將變數還原到之前的值。

For convenience, the token object can be used as a context manager to avoid calling ContextVar.reset() manually:

var = ContextVar('var', default='default value')

with var.set('new value'):
    assert var.get() == 'new value'

assert var.get() == 'default value'

It is a shorthand for:

var = ContextVar('var', default='default value')

token = var.set('new value')
try:
    assert var.get() == 'new value'
finally:
    var.reset(token)

assert var.get() == 'default value'

在 3.14 版被加入: Added support for using tokens as context managers.

reset(token)

將情境變數重設為使用 ContextVar.set() 建立 token 前的值。

舉例來說：

var = ContextVar('var')

token = var.set('new value')
# 使用 'var' 的程式碼；var.get() 回傳 'new value'。
var.reset(token)

# 在重設呼叫之後，var 又沒有值了，所以
# var.get() 會引發 LookupError。

The same token cannot be used twice.

class contextvars.Token

Token objects are returned by the ContextVar.set() method. They can be passed to the ContextVar.reset() method to revert the value of the variable to what it was before the corresponding set. A single token cannot reset a context variable more than once.

Tokens support the context manager protocol to automatically reset context variables. See ContextVar.set().

在 3.14 版被加入: 新增對用作情境管理器的支援。

var

唯讀屬性。 指向建立 token 的 ContextVar 物件。

old_value

唯讀屬性。 值為變數在呼叫 ContextVar.set() 方法之前的值。如果變數在呼叫前沒有設定，則指向 Token.MISSING。

MISSING

由 Token.old_value 使用的標記物件。

手動情境管理

contextvars.copy_context()

回傳目前 Context 物件的複本（copy）。

以下程式碼片段會取得目前情境的複本，並顯示在其中設定的所有變數及其值：:

ctx: Context = copy_context()
print(list(ctx.items()))

這個函式具有 O(1) 的複雜度，也就是說，對於只有少許情境變數的情境和有大量情境變數的情境，速度都一樣快。

class contextvars.Context

ContextVars 到其值的映射。

Context() 會建立一個沒有值的空情境。要取得目前情境的複本，請使用 copy_context() 函式。

每個執行緒都有自己的 Context 物件中目前主控中的堆疊（stack）。current context 是目前執行緒堆疊頂端的 Context 物件。 堆疊中的所有 Context 物件都被視為已進入。

進入一個情境，可以藉由呼叫其 run() 方法來完成，此進入的動作會將一情境推到目前執行緒的情境堆疊的頂端，使該情境成為目前的情境。

如果你傳遞給 run() 方法的回呼函式（callback functions），該函式回傳之後，就會自動退出目前的情境，這會將目前的情境還原到進入情境之前的狀態，方法是將情境從情境堆疊的頂端彈出。

因為每個執行緒都有自己的情境堆疊，當值在不同的執行緒中被指定時， ContextVar 物件的行為與 threading.local() 相似。

嘗試進入已進入的情境，包括在其他執行緒中進入的情境，會引發 RuntimeError。

退出情境後，之後可以重新進入（從任何執行緒）。

任何透過 ContextVar.set() 方法對 ContextVar 值的改變都會記錄在目前的情境中。 ContextVar.get() 方法回傳與目前情境相關的值。 退出情境實際造成的效果會像是將其在進入情境時對情境變數所做的任何變一一彈出並還原（如果需要，可以透過重新進入情境來還原值）。

情境（Context）實作了 collections.abc.Mapping 介面。

run(callable, *args, **kwargs)

進入 Context，執行 callable(*args, **kwargs)，然後退出 Context。 回傳 callable 的回傳值，如果發生例外（exception），則傳播例外。

例如：

import contextvars

var = contextvars.ContextVar('var')
var.set('spam')
print(var.get())  # 'spam'

ctx = contextvars.copy_context()

def main():
    # 'var' 之前被設成 'spam'
    # 呼叫 'copy_context()' 和 'ctx.run(main)'，所以：
    print(var.get())  # 'spam'
    print(ctx[var])  # 'spam'

    var.set('ham')

    # 現在, 在把 'var' 的值設成 'ham' 後:
    print(var.get())  # 'ham'
    print(ctx[var])  # 'ham'

# 'main' 函式對 'var' 所做的任何變更都會
# 包含在 'ctx 裡：.
ctx.run(main)

# 'main()' 函式是在 'ctx' 情境中執行，
# 所以對 'var' 的變更會保存在 'ctx' 中：
print(ctx[var])  # 'ham'

# 但是，在 'ctx' 外, 'var' 的值仍然是 'spam':
print(var.get())  # 'spam'

copy()

回傳情境物件的淺層複本（shallow copy）。

var in context

如果情境裡面有 var 的值，則回傳 True，否則回傳 False。

context[var]

回傳 var ContextVar 變數的值。如果該變數並沒有在情境物件中設定，則會引發 KeyError 錯誤。

get(var[, default])

如果 var 的值在情境物件中，則回傳 var 的值。否則回傳 default。如果沒有 default 值，則回傳 None。

iter(context)

回傳儲存於情境物件中變數的疊代器。

len(proxy)

回傳情境物件中的變數個數。

keys()

回傳情境物件中所有變數的串列。

values()

回傳情境物件中所有變數的值的串列。

items()

回傳情境物件中所有變數與其值的 2-元組（2-tuples）的串列。

對 asyncio 的支援

asyncio 原生支援情境變數，不需任何額外設定。 舉例來說，以下是一個簡單的 echo 伺服器，使用情境變數讓遠端用戶端的位址在處理該用戶端的任務中可用：

import asyncio
import contextvars

client_addr_var = contextvars.ContextVar('client_addr')

def render_goodbye():
    # 即使不把目前處理中的用戶端（client）傳入此函式
    # 仍可取得其位址

    client_addr = client_addr_var.get()
    return f'Good bye, client @ {client_addr}\r\n'.encode()

async def handle_request(reader, writer):
    addr = writer.transport.get_extra_info('socket').getpeername()
    client_addr_var.set(addr)

    # 在任何我們呼叫的程式碼中，都可以
    # 呼叫 'client_addr_var.get()' 來取得用戶端的位址

    while True:
        line = await reader.readline()
        print(line)
        if not line.strip():
            break

    writer.write(b'HTTP/1.1 200 OK\r\n')  # status line
    writer.write(b'\r\n')  # headers
    writer.write(render_goodbye())  # body
    writer.close()

async def main():
    srv = await asyncio.start_server(
        handle_request, '127.0.0.1', 8081)

    async with srv:
        await srv.serve_forever()

asyncio.run(main())

# 你可以使用 telnet 或 curl 測試:
#     telnet 127.0.0.1 8081
#     curl 127.0.0.1:8081

_thread --- 低階執行緒 API

這個模組提供了與多個執行緒（也稱為:dfn:輕量級行程 或 :dfn: 任務）一起工作的低階原始物件 --- 多個控制執行緒分享其全域資料空間。為了處理同步問題，也提供了簡單的鎖 (lock) 機制（也稱為:dfn:互斥鎖 或 二進位號誌）。 threading 模組提供了一個建立在這個模組之上的更易於使用和高階的執行緒 API。

在 3.7 版的變更: 這個模組之前是可選擇性的，但現在已經是可用的。

這個模組定義了以下的常數和函式：

exception _thread.error

在執行緒相關的錯誤發生時引發。

在 3.3 版的變更: 現在是內建例外 RuntimeError 的別名。

_thread.LockType

這是鎖物件的型別。

_thread.start_new_thread(function, args[, kwargs])

開始一個新的執行緒並回傳其識別字 (identifier) 。該執行緒執行帶有引數列表 args（必須是一個 tuple（元組））的函式 function。可選的 kwargs 引數指定一個關鍵字引數的字典。

當函式回傳時，執行緒會靜默退出。

當函式因未處理的例外終止時，將呼叫 sys.unraisablehook() 來處理該例外。鉤子引數的 object 屬性是 function。預設情況下，會列印堆疊跟蹤，然後執行緒退出（但其他執行緒會繼續運行）。

當函式引發 SystemExit 例外時，它會被靜默忽略。

引發一個 稽核事件 _thread.start_new_thread，帶有引數 function、args 和 kwargs。

在 3.8 版的變更: 現在使用 sys.unraisablehook() 來處理未處理的例外。

_thread.interrupt_main(signum=signal.SIGINT, /)

模擬一個訊號到達主執行緒的效果。執行緒可以使用此函式來中斷主執行緒，但無法保證中斷會立即發生。

如果提供了 signum，則模擬指定的訊號編號。如果未提供 signum，則模擬 signal.SIGINT 訊號。

如果給定的訊號在 Python 中未被處理（即設置為 signal.SIG_DFL 或 signal.SIG_IGN），此函式不做任何操作。

在 3.10 版的變更: 新增了 signum 引數以自訂訊號編號。

備註

這並不會發出對應的訊號，而是安排呼叫相應的處理器（如果存在的話）。如果你想真正發出訊號，請使用 signal.raise_signal()。

_thread.exit()

引發 SystemExit 例外。當未捕獲時，將導致執行緒靜默退出。

_thread.allocate_lock()

回傳一個新的鎖物件。鎖物件的方法如下所述。初始狀況下鎖是解鎖狀態。

_thread.get_ident()

回傳目前執行緒的「執行緒識別字」。這是一個非零的整數。它的值沒有直接的含義；它被用作一個 magic cookie，例如用於索引特定於執行緒的資料的字典。當執行緒退出並建立另一個執行緒時，執行緒識別字可能會被重複使用。

_thread.get_native_id()

回傳由核心 (kernel) 分配的目前執行緒的原生整數執行緒 ID。這是一個非負整數。它的值可用於在整個系統中唯一標識此特定執行緒（直到執行緒終止後，該值可能被操作系統重新使用）。

可用性: Windows, FreeBSD, Linux, macOS, OpenBSD, NetBSD, AIX, DragonFlyBSD, GNU/kFreeBSD.

在 3.8 版被加入.

在 3.13 版的變更: 新增了對 GNU/kFreeBSD 的支援。

_thread.stack_size([size])

回傳在建立新執行緒時使用的執行緒堆疊大小。可選的 size 引數指定了隨後建立的執行緒要使用的堆疊大小，必須是 0（使用平台或配置的預設值）或至少 32,768（32 KiB）的正整數值。如果未指定 size，則使用 0。如果不支援更改執行緒堆疊大小，則會引發 RuntimeError 錯誤。如果指定的堆疊大小無效，則會引發 ValueError 錯誤，並且堆疊大小不會被修改。目前，32 KiB 是保證直譯器本身具有足夠堆疊空間所支援的最小堆疊大小值。請注意，某些平台對於堆疊大小的值可能有特定的限制，例如要求最小堆疊大小 > 32 KiB，或要求按系統記憶體頁面大小的倍數進行分配。應參考平台文件以取得更多訊息（4 KiB 頁面是比較普遍的；在缺乏更具體訊息的情況下，建議使用 4096 的倍數作為堆疊大小）。

可用性: Windows, pthreads.

Unix 平台上支援 POSIX 執行緒。

_thread.TIMEOUT_MAX

Lock.acquire 的 timeout 參數所允許的最大值。指定超過此值的 timeout 將引發 OverflowError 錯誤。

在 3.2 版被加入.

鎖物件具有以下方法：

lock.acquire(blocking=True, timeout=-1)

沒有任何可選引數時，此方法無條件地取得鎖，必要時會等待直到被另一個執行緒釋放（一次只能有一個執行緒取得鎖 --- 這正是鎖存在的原因）。

如果存在 blocking 引數，則根據其值執行操作：如果為 False，只有在可以立即獲取鎖而無需等待的情況下才取得鎖，而如果為 True，則像上面一樣無條件地取得鎖。

如果存在浮點數的 timeout 引數且為正值，則它指定了在回傳之前的最大等待時間（以秒為單位）。如果 timeout 引數為負值，則表示等待時間會無限期地等待。如果 blocking 為 False，則你無法指定 timeout。

如果成功取得鎖，回傳值為 True，否則為 False。

在 3.2 版的變更: 新增的 timeout 參數。

在 3.2 版的變更: 現在取得鎖的操作可以被 POSIX 訊號中斷。

在 3.14 版的變更: Lock acquires can now be interrupted by signals on Windows.

lock.release()

釋放鎖。鎖必須先前被取得，但不一定是由同一個執行緒取得的。

lock.locked()

回傳鎖的狀態：如果鎖已被某個執行緒取得，則回傳 True，否則回傳 False。

除了這些方法之外，鎖物件還可以透過 with 語句來使用，例如：

import _thread

a_lock = _thread.allocate_lock()

with a_lock:
    print("a_lock 在執行這裡時被鎖定")

注意事項：

中斷總會跳到主執行緒（該執行緒將接收 KeyboardInterrupt 例外。）

呼叫 sys.exit() 函式或引發 SystemExit 例外等同於呼叫 _thread.exit() 函式。

當主執行緒退出時，其他執行緒是否保留是由系統決定的。在大多數系統上，它們將被終止，而不會執行 try ... finally 子句或執行物件的解構函式。

網路與行程間通訊

本章所描述的模組提供了網路和行程間通訊的機制。

某些模組僅適用於同一台機器上的兩個行程，例如 signal 和 mmap。其他模組則支援網路通訊協定，可供兩個或多個行程跨機器進行通訊。

本章所述的模組列表如下：

asyncio --- 非同步 I/O

socket — 低階網路介面

ssl --- socket 物件的 TLS/SSL 包裝器

select --- 等待 I/O 完成

selectors --- 高階 I/O 多工

signal --- 設定非同步事件的處理函式

mmap --- 記憶體對映檔案的支援

asyncio --- 非同步 I/O

Hello World!

import asyncio

async def main():
    print('Hello ...')
    await asyncio.sleep(1)
    print('... World!')

asyncio.run(main())

asyncio 是讓使用者以 async/await 語法來編寫並行 (concurrent) 程式碼的函式庫 (library)。

asyncio 作為多個 Python 非同步框架的基礎，在高效能網路與網頁伺服器、資料庫連線函式庫、分散式任務佇列等服務都可以看得到它。

asyncio 往往是個建構 IO 密集型與高階層結構化網路程式碼的完美選擇。

也參考

asyncio 的概念性總覽

asyncio 的基本原理說明。

asyncio 提供了一系列高階 API：

並行地運行 Python 協程 (coroutine) 並擁有完整控制權；

執行網路 IO 與 IPC；

控制子行程 (subprocess)；

透過佇列 (queue) 分配任務；

同步並行程式碼；

此外，還有一些給函式庫與框架 (framework) 開發者的低階 API：

建立與管理 event loops（事件迴圈），它提供了能被用於網路、執行子行程、處理作業系統訊號等任務的非同步 API；

使用 transports（asyncio 底層傳輸相關類別）來實作高效能協定；

透過 async/await 語法來橋接基於回呼 (callback-based) 的函式庫與程式碼。

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

asyncio REPL

你能在 REPL 中對一個 asyncio 的並行情境 (context) 進行實驗：

$ python -m asyncio
asyncio REPL ...
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> await asyncio.sleep(10, result='hello')
'hello'

This REPL provides limited compatibility with PYTHON_BASIC_REPL. It is recommended that the default REPL is used for full functionality and the latest features.

產生一個 稽核事件 cpython.run_stdin 且沒有引數。

在 3.12.5 版的變更: (也包括 3.11.10、3.10.15、3.9.20 及 3.8.20）發出稽核事件。

在 3.13 版的變更: 可能的話使用 PyREPL，在這種情況下 PYTHONSTARTUP 也會被執行。發出稽核事件。

參閱

高階 API

Runners (執行器)

協程與任務

串流

同步化原始物件 (Synchronization Primitives)

子行程

佇列 (Queues)

例外

Call Graph Introspection

低階 API

事件迴圈

Futures

傳輸與協定

Policies

平臺支援

擴充

指南與教學

高階 API 索引

低階 API 索引

使用 asyncio 開發

備註

asyncio 的原始碼可以在 Lib/asyncio/ [https://github.com/python/cpython/tree/3.14/Lib/asyncio/] 中找到。

Runners (執行器)

原始碼：Lib/asyncio/runners.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/runners.py]

這個章節概述用於執行 asyncio 程式碼的高階 asyncio 原始物件。

他們是基於一個事件迴圈，目的是為了簡化常見且廣泛運用場景的非同步程式碼。

運行一個 asyncio 程式

Runner context manager

Handling Keyboard Interruption

運行一個 asyncio 程式

asyncio.run(coro, *, debug=None, loop_factory=None)

在 asyncio 事件迴圈中執行 coro 並回傳結果。

該引數可以是任何可等待物件 (awaitable object)。

這個函式負責運行被傳入的可等待物件、管理 asyncio 的事件迴圈、終結非同步產生器以及關閉執行器。

當另一個非同步事件迴圈在同一執行緒中執行時，無法呼叫此函式。

如果 debug 為 True，事件迴圈會以除錯模式執行。False 則會關閉除錯模式。None 則會優先使用除錯模式的全域設定。

如果 loop_factory 不為 None，它會被用於建立一個新的事件迴圈；否則會改用 asyncio.new_event_loop()。迴圈會在最後關閉。這個函式應該要作為asyncio 程式的主要進入點，且理想上僅會被呼叫一次。推薦使用 loop_factory 來設定事件迴圈時而不是使用 policies（政策）。傳遞 asyncio.EventLoop 可以讓 asyncio 在沒有政策系統的情況下運行。

The executor is given a timeout duration of 5 minutes to shutdown. If the executor hasn't finished within that duration, a warning is emitted and the executor is closed.

範例：

async def main():
    await asyncio.sleep(1)
    print('hello')

asyncio.run(main())

在 3.7 版被加入.

在 3.9 版的變更: Updated to use loop.shutdown_default_executor().

在 3.10 版的變更: debug is None by default to respect the global debug mode settings.

在 3.12 版的變更: 新增 loop_factory 參數。

在 3.14 版的變更: coro can be any awaitable object.

備註

The asyncio policy system is deprecated and will be removed in Python 3.16; from there on, an explicit loop_factory is needed to configure the event loop.

Runner context manager

class asyncio.Runner(*, debug=None, loop_factory=None)

A context manager that simplifies multiple async function calls in the same context.

Sometimes several top-level async functions should be called in the same event loop and contextvars.Context.

如果 debug 為 True，事件迴圈會以除錯模式執行。False 則會關閉除錯模式。None 則會優先使用除錯模式的全域設定。

loop_factory could be used for overriding the loop creation. It is the responsibility of the loop_factory to set the created loop as the current one. By default asyncio.new_event_loop() is used and set as current event loop with asyncio.set_event_loop() if loop_factory is None.

Basically, asyncio.run() example can be rewritten with the runner usage:

async def main():
    await asyncio.sleep(1)
    print('hello')

with asyncio.Runner() as runner:
    runner.run(main())

在 3.11 版被加入.

run(coro, *, context=None)

Execute coro in the embedded event loop.

該引數可以是任何可等待物件 (awaitable object)。

If the argument is a coroutine, it is wrapped in a Task.

An optional keyword-only context argument allows specifying a custom contextvars.Context for the code to run in. The runner's default context is used if context is None.

Returns the awaitable's result or raises an exception.

當另一個非同步事件迴圈在同一執行緒中執行時，無法呼叫此函式。

在 3.14 版的變更: coro can be any awaitable object.

close()

Close the runner.

Finalize asynchronous generators, shutdown default executor, close the event loop and release embedded contextvars.Context.

get_loop()

Return the event loop associated with the runner instance.

備註

Runner uses the lazy initialization strategy, its constructor doesn't initialize underlying low-level structures.

Embedded loop and context are created at the with body entering or the first call of run() or get_loop().

Handling Keyboard Interruption

在 3.11 版被加入.

When signal.SIGINT is raised by Ctrl-C, KeyboardInterrupt exception is raised in the main thread by default. However this doesn't work with asyncio because it can interrupt asyncio internals and can hang the program from exiting.

To mitigate this issue, asyncio handles signal.SIGINT as follows:

asyncio.Runner.run() installs a custom signal.SIGINT handler before any user code is executed and removes it when exiting from the function.

The Runner creates the main task for the passed coroutine for its execution.

When signal.SIGINT is raised by Ctrl-C, the custom signal handler cancels the main task by calling asyncio.Task.cancel() which raises asyncio.CancelledError inside the main task. This causes the Python stack to unwind, try/except and try/finally blocks can be used for resource cleanup. After the main task is cancelled, asyncio.Runner.run() raises KeyboardInterrupt.

A user could write a tight loop which cannot be interrupted by asyncio.Task.cancel(), in which case the second following Ctrl-C immediately raises the KeyboardInterrupt without cancelling the main task.

協程與任務

This section outlines high-level asyncio APIs to work with coroutines and Tasks.

協程

Awaitables

Creating Tasks

Task Cancellation

Task Groups

Sleeping

Running Tasks Concurrently

Eager Task Factory

Shielding From Cancellation

Timeouts

Waiting Primitives

Running in Threads

Scheduling From Other Threads

Introspection

Task 物件

協程

原始碼：Lib/asyncio/coroutines.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/coroutines.py]

Coroutines declared with the async/await syntax is the preferred way of writing asyncio applications. For example, the following snippet of code prints "hello", waits 1 second, and then prints "world":

>>> import asyncio

>>> async def main():
...     print('hello')
...     await asyncio.sleep(1)
...     print('world')

>>> asyncio.run(main())
hello
world

Note that simply calling a coroutine will not schedule it to be executed:

>>> main()
<coroutine object main at 0x1053bb7c8>

To actually run a coroutine, asyncio provides the following mechanisms:

The asyncio.run() function to run the top-level entry point "main()" function (see the above example.)

Awaiting on a coroutine. The following snippet of code will print "hello" after waiting for 1 second, and then print "world" after waiting for another 2 seconds:

import asyncio
import time

async def say_after(delay, what):
    await asyncio.sleep(delay)
    print(what)

async def main():
    print(f"started at {time.strftime('%X')}")

    await say_after(1, 'hello')
    await say_after(2, 'world')

    print(f"finished at {time.strftime('%X')}")

asyncio.run(main())

預期的輸出：

started at 17:13:52
hello
world
finished at 17:13:55

The asyncio.create_task() function to run coroutines concurrently as asyncio Tasks.

Let's modify the above example and run two say_after coroutines concurrently:

async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    print(f"started at {time.strftime('%X')}")

    # Wait until both tasks are completed (should take
    # around 2 seconds.)
    await task1
    await task2

    print(f"finished at {time.strftime('%X')}")

Note that expected output now shows that the snippet runs 1 second faster than before:

started at 17:14:32
hello
world
finished at 17:14:34

The asyncio.TaskGroup class provides a more modern alternative to create_task(). Using this API, the last example becomes:

async def main():
    async with asyncio.TaskGroup() as tg:
        task1 = tg.create_task(
            say_after(1, 'hello'))

        task2 = tg.create_task(
            say_after(2, 'world'))

        print(f"started at {time.strftime('%X')}")

    # The await is implicit when the context manager exits.

    print(f"finished at {time.strftime('%X')}")

The timing and output should be the same as for the previous version.

在 3.11 版被加入: asyncio.TaskGroup。

Awaitables

We say that an object is an awaitable object if it can be used in an await expression. Many asyncio APIs are designed to accept awaitables.

There are three main types of awaitable objects: coroutines, Tasks, and Futures.

協程

Python coroutines are awaitables and therefore can be awaited from other coroutines:

import asyncio

async def nested():
    return 42

async def main():
    # Nothing happens if we just call "nested()".
    # A coroutine object is created but not awaited,
    # so it *won't run at all*.
    nested()  # will raise a "RuntimeWarning".

    # Let's do it differently now and await it:
    print(await nested())  # will print "42".

asyncio.run(main())

重要

In this documentation the term "coroutine" can be used for two closely related concepts:

a coroutine function: an async def function;

a coroutine object: an object returned by calling a coroutine function.

Tasks

Tasks are used to schedule coroutines concurrently.

When a coroutine is wrapped into a Task with functions like asyncio.create_task() the coroutine is automatically scheduled to run soon:

import asyncio

async def nested():
    return 42

async def main():
    # Schedule nested() to run soon concurrently
    # with "main()".
    task = asyncio.create_task(nested())

    # "task" can now be used to cancel "nested()", or
    # can simply be awaited to wait until it is complete:
    await task

asyncio.run(main())

Futures

A Future is a special low-level awaitable object that represents an eventual result of an asynchronous operation.

When a Future object is awaited it means that the coroutine will wait until the Future is resolved in some other place.

Future objects in asyncio are needed to allow callback-based code to be used with async/await.

Normally there is no need to create Future objects at the application level code.

Future objects, sometimes exposed by libraries and some asyncio APIs, can be awaited:

async def main():
    await function_that_returns_a_future_object()

    # this is also valid:
    await asyncio.gather(
        function_that_returns_a_future_object(),
        some_python_coroutine()
    )

A good example of a low-level function that returns a Future object is loop.run_in_executor().

Creating Tasks

原始碼：Lib/asyncio/tasks.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/tasks.py]

asyncio.create_task(coro, *, name=None, context=None, eager_start=None, **kwargs)

Wrap the coro coroutine into a Task and schedule its execution. Return the Task object.

The full function signature is largely the same as that of the Task constructor (or factory) - all of the keyword arguments to this function are passed through to that interface.

An optional keyword-only context argument allows specifying a custom contextvars.Context for the coro to run in. The current context copy is created when no context is provided.

An optional keyword-only eager_start argument allows specifying if the task should execute eagerly during the call to create_task, or be scheduled later. If eager_start is not passed the mode set by loop.set_task_factory() will be used.

The task is executed in the loop returned by get_running_loop(), RuntimeError is raised if there is no running loop in current thread.

備註

asyncio.TaskGroup.create_task() is a new alternative leveraging structural concurrency; it allows for waiting for a group of related tasks with strong safety guarantees.

重要

Save a reference to the result of this function, to avoid a task disappearing mid-execution. The event loop only keeps weak references to tasks. A task that isn't referenced elsewhere may get garbage collected at any time, even before it's done. For reliable "fire-and-forget" background tasks, gather them in a collection:

background_tasks = set()

for i in range(10):
    task = asyncio.create_task(some_coro(param=i))

    # Add task to the set. This creates a strong reference.
    background_tasks.add(task)

    # To prevent keeping references to finished tasks forever,
    # make each task remove its own reference from the set after
    # completion:
    task.add_done_callback(background_tasks.discard)

在 3.7 版被加入.

在 3.8 版的變更: 新增 name 參數。

在 3.11 版的變更: 新增 context 參數。

在 3.14 版的變更: Added the eager_start parameter by passing on all kwargs.

Task Cancellation

Tasks can easily and safely be cancelled. When a task is cancelled, asyncio.CancelledError will be raised in the task at the next opportunity.

It is recommended that coroutines use try/finally blocks to robustly perform clean-up logic. In case asyncio.CancelledError is explicitly caught, it should generally be propagated when clean-up is complete. asyncio.CancelledError directly subclasses BaseException so most code will not need to be aware of it.

The asyncio components that enable structured concurrency, like asyncio.TaskGroup and asyncio.timeout(), are implemented using cancellation internally and might misbehave if a coroutine swallows asyncio.CancelledError. Similarly, user code should not generally call uncancel. However, in cases when suppressing asyncio.CancelledError is truly desired, it is necessary to also call uncancel() to completely remove the cancellation state.

Task Groups

Task groups combine a task creation API with a convenient and reliable way to wait for all tasks in the group to finish.

class asyncio.TaskGroup

An asynchronous context manager holding a group of tasks. Tasks can be added to the group using create_task(). All tasks are awaited when the context manager exits.

在 3.11 版被加入.

create_task(coro, *, name=None, context=None, eager_start=None, **kwargs)

Create a task in this task group. The signature matches that of asyncio.create_task(). If the task group is inactive (e.g. not yet entered, already finished, or in the process of shutting down), we will close the given coro.

在 3.13 版的變更: Close the given coroutine if the task group is not active.

在 3.14 版的變更: Passes on all kwargs to loop.create_task()

範例：

async def main():
    async with asyncio.TaskGroup() as tg:
        task1 = tg.create_task(some_coro(...))
        task2 = tg.create_task(another_coro(...))
    print(f"Both tasks have completed now: {task1.result()}, {task2.result()}")

The async with statement will wait for all tasks in the group to finish. While waiting, new tasks may still be added to the group (for example, by passing tg into one of the coroutines and calling tg.create_task() in that coroutine). Once the last task has finished and the async with block is exited, no new tasks may be added to the group.

The first time any of the tasks belonging to the group fails with an exception other than asyncio.CancelledError, the remaining tasks in the group are cancelled. No further tasks can then be added to the group. At this point, if the body of the async with statement is still active (i.e., __aexit__() hasn't been called yet), the task directly containing the async with statement is also cancelled. The resulting asyncio.CancelledError will interrupt an await, but it will not bubble out of the containing async with statement.

Once all tasks have finished, if any tasks have failed with an exception other than asyncio.CancelledError, those exceptions are combined in an ExceptionGroup or BaseExceptionGroup (as appropriate; see their documentation) which is then raised.

Two base exceptions are treated specially: If any task fails with KeyboardInterrupt or SystemExit, the task group still cancels the remaining tasks and waits for them, but then the initial KeyboardInterrupt or SystemExit is re-raised instead of ExceptionGroup or BaseExceptionGroup.

If the body of the async with statement exits with an exception (so __aexit__() is called with an exception set), this is treated the same as if one of the tasks failed: the remaining tasks are cancelled and then waited for, and non-cancellation exceptions are grouped into an exception group and raised. The exception passed into __aexit__(), unless it is asyncio.CancelledError, is also included in the exception group. The same special case is made for KeyboardInterrupt and SystemExit as in the previous paragraph.

Task groups are careful not to mix up the internal cancellation used to "wake up" their __aexit__() with cancellation requests for the task in which they are running made by other parties. In particular, when one task group is syntactically nested in another, and both experience an exception in one of their child tasks simultaneously, the inner task group will process its exceptions, and then the outer task group will receive another cancellation and process its own exceptions.

In the case where a task group is cancelled externally and also must raise an ExceptionGroup, it will call the parent task's cancel() method. This ensures that a asyncio.CancelledError will be raised at the next await, so the cancellation is not lost.

Task groups preserve the cancellation count reported by asyncio.Task.cancelling().

在 3.13 版的變更: Improved handling of simultaneous internal and external cancellations and correct preservation of cancellation counts.

Terminating a Task Group

While terminating a task group is not natively supported by the standard library, termination can be achieved by adding an exception-raising task to the task group and ignoring the raised exception:

import asyncio
from asyncio import TaskGroup

class TerminateTaskGroup(Exception):
    """Exception raised to terminate a task group."""

async def force_terminate_task_group():
    """Used to force termination of a task group."""
    raise TerminateTaskGroup()

async def job(task_id, sleep_time):
    print(f'Task {task_id}: start')
    await asyncio.sleep(sleep_time)
    print(f'Task {task_id}: done')

async def main():
    try:
        async with TaskGroup() as group:
            # spawn some tasks
            group.create_task(job(1, 0.5))
            group.create_task(job(2, 1.5))
            # sleep for 1 second
            await asyncio.sleep(1)
            # add an exception-raising task to force the group to terminate
            group.create_task(force_terminate_task_group())
    except* TerminateTaskGroup:
        pass

asyncio.run(main())

預期的輸出：

Task 1: start
Task 2: start
Task 1: done

Sleeping

async asyncio.sleep(delay, result=None)

Block for delay seconds.

If result is provided, it is returned to the caller when the coroutine completes.

sleep() always suspends the current task, allowing other tasks to run.

Setting the delay to 0 provides an optimized path to allow other tasks to run. This can be used by long-running functions to avoid blocking the event loop for the full duration of the function call.

Example of coroutine displaying the current date every second for 5 seconds:

import asyncio
import datetime

async def display_date():
    loop = asyncio.get_running_loop()
    end_time = loop.time() + 5.0
    while True:
        print(datetime.datetime.now())
        if (loop.time() + 1.0) >= end_time:
            break
        await asyncio.sleep(1)

asyncio.run(display_date())

在 3.10 版的變更: 移除 loop 參數。

在 3.13 版的變更: 如果 delay 是 nan，則引發 ValueError。

Running Tasks Concurrently

awaitable asyncio.gather(*aws, return_exceptions=False)

Run awaitable objects in the aws sequence concurrently.

If any awaitable in aws is a coroutine, it is automatically scheduled as a Task.

If all awaitables are completed successfully, the result is an aggregate list of returned values. The order of result values corresponds to the order of awaitables in aws.

If return_exceptions is False (default), the first raised exception is immediately propagated to the task that awaits on gather(). Other awaitables in the aws sequence won't be cancelled and will continue to run.

If return_exceptions is True, exceptions are treated the same as successful results, and aggregated in the result list.

If gather() is cancelled, all submitted awaitables (that have not completed yet) are also cancelled.

If any Task or Future from the aws sequence is cancelled, it is treated as if it raised CancelledError -- the gather() call is not cancelled in this case. This is to prevent the cancellation of one submitted Task/Future to cause other Tasks/Futures to be cancelled.

備註

A new alternative to create and run tasks concurrently and wait for their completion is asyncio.TaskGroup. TaskGroup provides stronger safety guarantees than gather for scheduling a nesting of subtasks: if a task (or a subtask, a task scheduled by a task) raises an exception, TaskGroup will, while gather will not, cancel the remaining scheduled tasks).

範例：

import asyncio

async def factorial(name, number):
    f = 1
    for i in range(2, number + 1):
        print(f"Task {name}: Compute factorial({number}), currently i={i}...")
        await asyncio.sleep(1)
        f *= i
    print(f"Task {name}: factorial({number}) = {f}")
    return f

async def main():
    # Schedule three calls *concurrently*:
    L = await asyncio.gather(
        factorial("A", 2),
        factorial("B", 3),
        factorial("C", 4),
    )
    print(L)

asyncio.run(main())

# Expected output:
#
#     Task A: Compute factorial(2), currently i=2...
#     Task B: Compute factorial(3), currently i=2...
#     Task C: Compute factorial(4), currently i=2...
#     Task A: factorial(2) = 2
#     Task B: Compute factorial(3), currently i=3...
#     Task C: Compute factorial(4), currently i=3...
#     Task B: factorial(3) = 6
#     Task C: Compute factorial(4), currently i=4...
#     Task C: factorial(4) = 24
#     [2, 6, 24]

備註

If return_exceptions is false, cancelling gather() after it has been marked done won't cancel any submitted awaitables. For instance, gather can be marked done after propagating an exception to the caller, therefore, calling gather.cancel() after catching an exception (raised by one of the awaitables) from gather won't cancel any other awaitables.

在 3.7 版的變更: If the gather itself is cancelled, the cancellation is propagated regardless of return_exceptions.

在 3.10 版的變更: 移除 loop 參數。

在 3.10 版之後被棄用: Deprecation warning is emitted if no positional arguments are provided or not all positional arguments are Future-like objects and there is no running event loop.

Eager Task Factory

asyncio.eager_task_factory(loop, coro, *, name=None, context=None)

A task factory for eager task execution.

When using this factory (via loop.set_task_factory(asyncio.eager_task_factory)), coroutines begin execution synchronously during Task construction. Tasks are only scheduled on the event loop if they block. This can be a performance improvement as the overhead of loop scheduling is avoided for coroutines that complete synchronously.

A common example where this is beneficial is coroutines which employ caching or memoization to avoid actual I/O when possible.

備註

Immediate execution of the coroutine is a semantic change. If the coroutine returns or raises, the task is never scheduled to the event loop. If the coroutine execution blocks, the task is scheduled to the event loop. This change may introduce behavior changes to existing applications. For example, the application's task execution order is likely to change.

在 3.12 版被加入.

asyncio.create_eager_task_factory(custom_task_constructor)

Create an eager task factory, similar to eager_task_factory(), using the provided custom_task_constructor when creating a new task instead of the default Task.

custom_task_constructor must be a callable with the signature matching the signature of Task.__init__. The callable must return a asyncio.Task-compatible object.

This function returns a callable intended to be used as a task factory of an event loop via loop.set_task_factory(factory)).

在 3.12 版被加入.

Shielding From Cancellation

awaitable asyncio.shield(aw)

Protect an awaitable object from being cancelled.

If aw is a coroutine it is automatically scheduled as a Task.

The statement:

task = asyncio.create_task(something())
res = await shield(task)

is equivalent to:

res = await something()

except that if the coroutine containing it is cancelled, the Task running in something() is not cancelled. From the point of view of something(), the cancellation did not happen. Although its caller is still cancelled, so the "await" expression still raises a CancelledError.

If something() is cancelled by other means (i.e. from within itself) that would also cancel shield().

If it is desired to completely ignore cancellation (not recommended) the shield() function should be combined with a try/except clause, as follows:

task = asyncio.create_task(something())
try:
    res = await shield(task)
except CancelledError:
    res = None

重要

Save a reference to tasks passed to this function, to avoid a task disappearing mid-execution. The event loop only keeps weak references to tasks. A task that isn't referenced elsewhere may get garbage collected at any time, even before it's done.

在 3.10 版的變更: 移除 loop 參數。

在 3.10 版之後被棄用: Deprecation warning is emitted if aw is not Future-like object and there is no running event loop.

Timeouts

asyncio.timeout(delay)

Return an asynchronous context manager that can be used to limit the amount of time spent waiting on something.

delay can either be None, or a float/int number of seconds to wait. If delay is None, no time limit will be applied; this can be useful if the delay is unknown when the context manager is created.

In either case, the context manager can be rescheduled after creation using Timeout.reschedule().

範例：

async def main():
    async with asyncio.timeout(10):
        await long_running_task()

If long_running_task takes more than 10 seconds to complete, the context manager will cancel the current task and handle the resulting asyncio.CancelledError internally, transforming it into a TimeoutError which can be caught and handled.

備註

The asyncio.timeout() context manager is what transforms the asyncio.CancelledError into a TimeoutError, which means the TimeoutError can only be caught outside of the context manager.

Example of catching TimeoutError:

async def main():
    try:
        async with asyncio.timeout(10):
            await long_running_task()
    except TimeoutError:
        print("The long operation timed out, but we've handled it.")

    print("This statement will run regardless.")

The context manager produced by asyncio.timeout() can be rescheduled to a different deadline and inspected.

class asyncio.Timeout(when)

An asynchronous context manager for cancelling overdue coroutines.

when should be an absolute time at which the context should time out, as measured by the event loop's clock:

If when is None, the timeout will never trigger.

If when < loop.time(), the timeout will trigger on the next iteration of the event loop.

when() → float | None

Return the current deadline, or None if the current deadline is not set.

reschedule(when: float | None)

Reschedule the timeout.

expired() → bool

Return whether the context manager has exceeded its deadline (expired).

範例：

async def main():
    try:
        # We do not know the timeout when starting, so we pass ``None``.
        async with asyncio.timeout(None) as cm:
            # We know the timeout now, so we reschedule it.
            new_deadline = get_running_loop().time() + 10
            cm.reschedule(new_deadline)

            await long_running_task()
    except TimeoutError:
        pass

    if cm.expired():
        print("Looks like we haven't finished on time.")

Timeout context managers can be safely nested.

在 3.11 版被加入.

asyncio.timeout_at(when)

Similar to asyncio.timeout(), except when is the absolute time to stop waiting, or None.

範例：

async def main():
    loop = get_running_loop()
    deadline = loop.time() + 20
    try:
        async with asyncio.timeout_at(deadline):
            await long_running_task()
    except TimeoutError:
        print("The long operation timed out, but we've handled it.")

    print("This statement will run regardless.")

在 3.11 版被加入.

async asyncio.wait_for(aw, timeout)

Wait for the aw awaitable to complete with a timeout.

If aw is a coroutine it is automatically scheduled as a Task.

timeout can either be None or a float or int number of seconds to wait for. If timeout is None, block until the future completes.

If a timeout occurs, it cancels the task and raises TimeoutError.

To avoid the task cancellation, wrap it in shield().

The function will wait until the future is actually cancelled, so the total wait time may exceed the timeout. If an exception happens during cancellation, it is propagated.

If the wait is cancelled, the future aw is also cancelled.

範例：

async def eternity():
    # Sleep for one hour
    await asyncio.sleep(3600)
    print('yay!')

async def main():
    # Wait for at most 1 second
    try:
        await asyncio.wait_for(eternity(), timeout=1.0)
    except TimeoutError:
        print('timeout!')

asyncio.run(main())

# Expected output:
#
#     timeout!

在 3.7 版的變更: When aw is cancelled due to a timeout, wait_for waits for aw to be cancelled. Previously, it raised TimeoutError immediately.

在 3.10 版的變更: 移除 loop 參數。

在 3.11 版的變更: 引發 TimeoutError 而不是 asyncio.TimeoutError。

Waiting Primitives

async asyncio.wait(aws, *, timeout=None, return_when=ALL_COMPLETED)

Run Future and Task instances in the aws iterable concurrently and block until the condition specified by return_when.

The aws iterable must not be empty.

Returns two sets of Tasks/Futures: (done, pending).

用法：

done, pending = await asyncio.wait(aws)

timeout (a float or int), if specified, can be used to control the maximum number of seconds to wait before returning.

Note that this function does not raise TimeoutError. Futures or Tasks that aren't done when the timeout occurs are simply returned in the second set.

return_when indicates when this function should return. It must be one of the following constants:

常數

描述

asyncio.FIRST_COMPLETED

The function will return when any future finishes or is cancelled.

asyncio.FIRST_EXCEPTION

The function will return when any future finishes by raising an exception. If no future raises an exception then it is equivalent to ALL_COMPLETED.

asyncio.ALL_COMPLETED

The function will return when all futures finish or are cancelled.

Unlike wait_for(), wait() does not cancel the futures when a timeout occurs.

在 3.10 版的變更: 移除 loop 參數。

在 3.11 版的變更: Passing coroutine objects to wait() directly is forbidden.

在 3.12 版的變更: Added support for generators yielding tasks.

asyncio.as_completed(aws, *, timeout=None)

Run awaitable objects in the aws iterable concurrently. The returned object can be iterated to obtain the results of the awaitables as they finish.

The object returned by as_completed() can be iterated as an asynchronous iterator or a plain iterator. When asynchronous iteration is used, the originally-supplied awaitables are yielded if they are tasks or futures. This makes it easy to correlate previously-scheduled tasks with their results. Example:

ipv4_connect = create_task(open_connection("127.0.0.1", 80))
ipv6_connect = create_task(open_connection("::1", 80))
tasks = [ipv4_connect, ipv6_connect]

async for earliest_connect in as_completed(tasks):
    # earliest_connect is done. The result can be obtained by
    # awaiting it or calling earliest_connect.result()
    reader, writer = await earliest_connect

    if earliest_connect is ipv6_connect:
        print("IPv6 connection established.")
    else:
        print("IPv4 connection established.")

During asynchronous iteration, implicitly-created tasks will be yielded for supplied awaitables that aren't tasks or futures.

When used as a plain iterator, each iteration yields a new coroutine that returns the result or raises the exception of the next completed awaitable. This pattern is compatible with Python versions older than 3.13:

ipv4_connect = create_task(open_connection("127.0.0.1", 80))
ipv6_connect = create_task(open_connection("::1", 80))
tasks = [ipv4_connect, ipv6_connect]

for next_connect in as_completed(tasks):
    # next_connect is not one of the original task objects. It must be
    # awaited to obtain the result value or raise the exception of the
    # awaitable that finishes next.
    reader, writer = await next_connect

A TimeoutError is raised if the timeout occurs before all awaitables are done. This is raised by the async for loop during asynchronous iteration or by the coroutines yielded during plain iteration.

在 3.10 版的變更: 移除 loop 參數。

在 3.10 版之後被棄用: Deprecation warning is emitted if not all awaitable objects in the aws iterable are Future-like objects and there is no running event loop.

在 3.12 版的變更: Added support for generators yielding tasks.

在 3.13 版的變更: The result can now be used as either an asynchronous iterator or as a plain iterator (previously it was only a plain iterator).

Running in Threads

async asyncio.to_thread(func, /, *args, **kwargs)

Asynchronously run function func in a separate thread.

Any *args and **kwargs supplied for this function are directly passed to func. Also, the current contextvars.Context is propagated, allowing context variables from the event loop thread to be accessed in the separate thread.

Return a coroutine that can be awaited to get the eventual result of func.

This coroutine function is primarily intended to be used for executing IO-bound functions/methods that would otherwise block the event loop if they were run in the main thread. For example:

def blocking_io():
    print(f"start blocking_io at {time.strftime('%X')}")
    # Note that time.sleep() can be replaced with any blocking
    # IO-bound operation, such as file operations.
    time.sleep(1)
    print(f"blocking_io complete at {time.strftime('%X')}")

async def main():
    print(f"started main at {time.strftime('%X')}")

    await asyncio.gather(
        asyncio.to_thread(blocking_io),
        asyncio.sleep(1))

    print(f"finished main at {time.strftime('%X')}")

asyncio.run(main())

# Expected output:
#
# started main at 19:50:53
# start blocking_io at 19:50:53
# blocking_io complete at 19:50:54
# finished main at 19:50:54

Directly calling blocking_io() in any coroutine would block the event loop for its duration, resulting in an additional 1 second of run time. Instead, by using asyncio.to_thread(), we can run it in a separate thread without blocking the event loop.

備註

Due to the GIL, asyncio.to_thread() can typically only be used to make IO-bound functions non-blocking. However, for extension modules that release the GIL or alternative Python implementations that don't have one, asyncio.to_thread() can also be used for CPU-bound functions.

在 3.9 版被加入.

Scheduling From Other Threads

asyncio.run_coroutine_threadsafe(coro, loop)

Submit a coroutine to the given event loop. Thread-safe.

Return a concurrent.futures.Future to wait for the result from another OS thread.

This function is meant to be called from a different OS thread than the one where the event loop is running. Example:

def in_thread(loop: asyncio.AbstractEventLoop) -> None:
    # Run some blocking IO
    pathlib.Path("example.txt").write_text("hello world", encoding="utf8")

    # Create a coroutine
    coro = asyncio.sleep(1, result=3)

    # Submit the coroutine to a given loop
    future = asyncio.run_coroutine_threadsafe(coro, loop)

    # Wait for the result with an optional timeout argument
    assert future.result(timeout=2) == 3

async def amain() -> None:
    # Get the running loop
    loop = asyncio.get_running_loop()

    # Run something in a thread
    await asyncio.to_thread(in_thread, loop)

It's also possible to run the other way around. Example:

@contextlib.contextmanager
def loop_in_thread() -> Generator[asyncio.AbstractEventLoop]:
    loop_fut = concurrent.futures.Future[asyncio.AbstractEventLoop]()
    stop_event = asyncio.Event()

    async def main() -> None:
        loop_fut.set_result(asyncio.get_running_loop())
        await stop_event.wait()

    with concurrent.futures.ThreadPoolExecutor(1) as tpe:
        complete_fut = tpe.submit(asyncio.run, main())
        for fut in concurrent.futures.as_completed((loop_fut, complete_fut)):
            if fut is loop_fut:
                loop = loop_fut.result()
                try:
                    yield loop
                finally:
                    loop.call_soon_threadsafe(stop_event.set)
            else:
                fut.result()

# Create a loop in another thread
with loop_in_thread() as loop:
    # Create a coroutine
    coro = asyncio.sleep(1, result=3)

    # Submit the coroutine to a given loop
    future = asyncio.run_coroutine_threadsafe(coro, loop)

    # Wait for the result with an optional timeout argument
    assert future.result(timeout=2) == 3

If an exception is raised in the coroutine, the returned Future will be notified. It can also be used to cancel the task in the event loop:

try:
    result = future.result(timeout)
except TimeoutError:
    print('The coroutine took too long, cancelling the task...')
    future.cancel()
except Exception as exc:
    print(f'The coroutine raised an exception: {exc!r}')
else:
    print(f'The coroutine returned: {result!r}')

See the concurrency and multithreading section of the documentation.

Unlike other asyncio functions this function requires the loop argument to be passed explicitly.

在 3.5.1 版被加入.

Introspection

asyncio.current_task(loop=None)

Return the currently running Task instance, or None if no task is running.

If loop is None get_running_loop() is used to get the current loop.

在 3.7 版被加入.

asyncio.all_tasks(loop=None)

Return a set of not yet finished Task objects run by the loop.

If loop is None, get_running_loop() is used for getting current loop.

在 3.7 版被加入.

asyncio.iscoroutine(obj)

Return True if obj is a coroutine object.

在 3.4 版被加入.

Task 物件

class asyncio.Task(coro, *, loop=None, name=None, context=None, eager_start=False)

A Future-like object that runs a Python coroutine. Not thread-safe.

Tasks are used to run coroutines in event loops. If a coroutine awaits on a Future, the Task suspends the execution of the coroutine and waits for the completion of the Future. When the Future is done, the execution of the wrapped coroutine resumes.

Event loops use cooperative scheduling: an event loop runs one Task at a time. While a Task awaits for the completion of a Future, the event loop runs other Tasks, callbacks, or performs IO operations.

Use the high-level asyncio.create_task() function to create Tasks, or the low-level loop.create_task() or ensure_future() functions. Manual instantiation of Tasks is discouraged.

To cancel a running Task use the cancel() method. Calling it will cause the Task to throw a CancelledError exception into the wrapped coroutine. If a coroutine is awaiting on a Future object during cancellation, the Future object will be cancelled.

cancelled() can be used to check if the Task was cancelled. The method returns True if the wrapped coroutine did not suppress the CancelledError exception and was actually cancelled.

asyncio.Task inherits from Future all of its APIs except Future.set_result() and Future.set_exception().

An optional keyword-only context argument allows specifying a custom contextvars.Context for the coro to run in. If no context is provided, the Task copies the current context and later runs its coroutine in the copied context.

An optional keyword-only eager_start argument allows eagerly starting the execution of the asyncio.Task at task creation time. If set to True and the event loop is running, the task will start executing the coroutine immediately, until the first time the coroutine blocks. If the coroutine returns or raises without blocking, the task will be finished eagerly and will skip scheduling to the event loop.

在 3.7 版的變更: 新增對 contextvars 模組的支援。

在 3.8 版的變更: 新增 name 參數。

在 3.10 版之後被棄用: Deprecation warning is emitted if loop is not specified and there is no running event loop.

在 3.11 版的變更: 新增 context 參數。

在 3.12 版的變更: 新增 eager_start 參數。

done()

Return True if the Task is done.

A Task is done when the wrapped coroutine either returned a value, raised an exception, or the Task was cancelled.

result()

Return the result of the Task.

If the Task is done, the result of the wrapped coroutine is returned (or if the coroutine raised an exception, that exception is re-raised.)

If the Task has been cancelled, this method raises a CancelledError exception.

If the Task's result isn't yet available, this method raises an InvalidStateError exception.

exception()

Return the exception of the Task.

If the wrapped coroutine raised an exception that exception is returned. If the wrapped coroutine returned normally this method returns None.

If the Task has been cancelled, this method raises a CancelledError exception.

If the Task isn't done yet, this method raises an InvalidStateError exception.

add_done_callback(callback, *, context=None)

Add a callback to be run when the Task is done.

This method should only be used in low-level callback-based code.

See the documentation of Future.add_done_callback() for more details.

remove_done_callback(callback)

Remove callback from the callbacks list.

This method should only be used in low-level callback-based code.

See the documentation of Future.remove_done_callback() for more details.

get_stack(*, limit=None)

Return the list of stack frames for this Task.

If the wrapped coroutine is not done, this returns the stack where it is suspended. If the coroutine has completed successfully or was cancelled, this returns an empty list. If the coroutine was terminated by an exception, this returns the list of traceback frames.

The frames are always ordered from oldest to newest.

Only one stack frame is returned for a suspended coroutine.

The optional limit argument sets the maximum number of frames to return; by default all available frames are returned. The ordering of the returned list differs depending on whether a stack or a traceback is returned: the newest frames of a stack are returned, but the oldest frames of a traceback are returned. (This matches the behavior of the traceback module.)

print_stack(*, limit=None, file=None)

Print the stack or traceback for this Task.

This produces output similar to that of the traceback module for the frames retrieved by get_stack().

The limit argument is passed to get_stack() directly.

The file argument is an I/O stream to which the output is written; by default output is written to sys.stdout.

get_coro()

Return the coroutine object wrapped by the Task.

備註

This will return None for Tasks which have already completed eagerly. See the Eager Task Factory.

在 3.8 版被加入.

在 3.12 版的變更: Newly added eager task execution means result may be None.

get_context()

Return the contextvars.Context object associated with the task.

在 3.12 版被加入.

get_name()

Return the name of the Task.

If no name has been explicitly assigned to the Task, the default asyncio Task implementation generates a default name during instantiation.

在 3.8 版被加入.

set_name(value)

Set the name of the Task.

The value argument can be any object, which is then converted to a string.

In the default Task implementation, the name will be visible in the repr() output of a task object.

在 3.8 版被加入.

cancel(msg=None)

Request the Task to be cancelled.

If the Task is already done or cancelled, return False, otherwise, return True.

The method arranges for a CancelledError exception to be thrown into the wrapped coroutine on the next cycle of the event loop.

The coroutine then has a chance to clean up or even deny the request by suppressing the exception with a try ... ... except CancelledError ... finally block. Therefore, unlike Future.cancel(), Task.cancel() does not guarantee that the Task will be cancelled, although suppressing cancellation completely is not common and is actively discouraged. Should the coroutine nevertheless decide to suppress the cancellation, it needs to call Task.uncancel() in addition to catching the exception.

在 3.9 版的變更: 新增 msg 參數。

在 3.11 版的變更: The msg parameter is propagated from cancelled task to its awaiter.

The following example illustrates how coroutines can intercept the cancellation request:

async def cancel_me():
    print('cancel_me(): before sleep')

    try:
        # Wait for 1 hour
        await asyncio.sleep(3600)
    except asyncio.CancelledError:
        print('cancel_me(): cancel sleep')
        raise
    finally:
        print('cancel_me(): after sleep')

async def main():
    # Create a "cancel_me" Task
    task = asyncio.create_task(cancel_me())

    # Wait for 1 second
    await asyncio.sleep(1)

    task.cancel()
    try:
        await task
    except asyncio.CancelledError:
        print("main(): cancel_me is cancelled now")

asyncio.run(main())

# Expected output:
#
#     cancel_me(): before sleep
#     cancel_me(): cancel sleep
#     cancel_me(): after sleep
#     main(): cancel_me is cancelled now

cancelled()

Return True if the Task is cancelled.

The Task is cancelled when the cancellation was requested with cancel() and the wrapped coroutine propagated the CancelledError exception thrown into it.

uncancel()

Decrement the count of cancellation requests to this Task.

Returns the remaining number of cancellation requests.

Note that once execution of a cancelled task completed, further calls to uncancel() are ineffective.

在 3.11 版被加入.

This method is used by asyncio's internals and isn't expected to be used by end-user code. In particular, if a Task gets successfully uncancelled, this allows for elements of structured concurrency like Task Groups and asyncio.timeout() to continue running, isolating cancellation to the respective structured block. For example:

async def make_request_with_timeout():
    try:
        async with asyncio.timeout(1):
            # Structured block affected by the timeout:
            await make_request()
            await make_another_request()
    except TimeoutError:
        log("There was a timeout")
    # Outer code not affected by the timeout:
    await unrelated_code()

While the block with make_request() and make_another_request() might get cancelled due to the timeout, unrelated_code() should continue running even in case of the timeout. This is implemented with uncancel(). TaskGroup context managers use uncancel() in a similar fashion.

If end-user code is, for some reason, suppressing cancellation by catching CancelledError, it needs to call this method to remove the cancellation state.

When this method decrements the cancellation count to zero, the method checks if a previous cancel() call had arranged for CancelledError to be thrown into the task. If it hasn't been thrown yet, that arrangement will be rescinded (by resetting the internal _must_cancel flag).

在 3.13 版的變更: Changed to rescind pending cancellation requests upon reaching zero.

cancelling()

Return the number of pending cancellation requests to this Task, i.e., the number of calls to cancel() less the number of uncancel() calls.

Note that if this number is greater than zero but the Task is still executing, cancelled() will still return False. This is because this number can be lowered by calling uncancel(), which can lead to the task not being cancelled after all if the cancellation requests go down to zero.

This method is used by asyncio's internals and isn't expected to be used by end-user code. See uncancel() for more details.

在 3.11 版被加入.

串流

原始碼：Lib/asyncio/streams.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/streams.py]

串流是支援 async/await (async/await-ready) 的高階原始物件 (high-level primitive)，用於處理網路連線。串流不需要使用回呼 (callback) 或低階協定和傳輸 (transport) 就能夠傳送和接收資料。

這是一個使用 asyncio 串流編寫的 TCP echo 用戶端範例：

import asyncio

async def tcp_echo_client(message):
    reader, writer = await asyncio.open_connection(
        '127.0.0.1', 8888)

    print(f'Send: {message!r}')
    writer.write(message.encode())
    await writer.drain()

    data = await reader.read(100)
    print(f'Received: {data.decode()!r}')

    print('Close the connection')
    writer.close()
    await writer.wait_closed()

asyncio.run(tcp_echo_client('Hello World!'))

另請參閱下方 Examples 段落。

串流函式

下面的高階 asyncio 函式可以用來建立和處理串流：

async asyncio.open_connection(host=None, port=None, *, limit=None, ssl=None, family=0, proto=0, flags=0, sock=None, local_addr=None, server_hostname=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None, happy_eyeballs_delay=None, interleave=None)

建立網路連線並回傳一對 (reader, writer) 物件。

回傳的 reader 和 writer 物件是 StreamReader 和 StreamWriter 類別的實例。

limit 指定了回傳的 StreamReader 實例所使用的緩衝區 (buffer) 大小限制。limit 預設為 64 KiB。

其餘的引數會直接傳遞到 loop.create_connection()。

備註

The sock argument transfers ownership of the socket to the StreamWriter created. To close the socket, call its close() method.

在 3.7 版的變更: 新增 ssl_handshake_timeout 參數。

在 3.8 版的變更: 新增 happy_eyeballs_delay 和 interleave 參數。

在 3.10 版的變更: 移除 loop 參數。

在 3.11 版的變更: 新增 ssl_shutdown_timeout 參數。

async asyncio.start_server(client_connected_cb, host=None, port=None, *, limit=None, family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE, sock=None, backlog=100, ssl=None, reuse_address=None, reuse_port=None, keep_alive=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None, start_serving=True)

啟動 socket 伺服器。

當一個新的用戶端連線被建立時，回呼函式 client_connected_cb 就會被呼叫。該函式會接收到一對引數 (reader, writer)，分別為 StreamReader 和 StreamWriter 的實例。

client_connected_cb 既可以是普通的可呼叫物件 (callable)，也可以是一個協程函式；如果它是一個協程函式，它將自動作為 Task 來被排程。

limit 指定了回傳的 StreamReader 實例所使用的緩衝區 (buffer) 大小限制。limit 預設為 64 KiB。

剩下的引數將會直接傳遞給 loop.create_server()。

備註

The sock argument transfers ownership of the socket to the server created. To close the socket, call the server's close() method.

在 3.7 版的變更: 新增 ssl_handshake_timeout 與 start_serving 參數。

在 3.10 版的變更: 移除 loop 參數。

在 3.11 版的變更: 新增 ssl_shutdown_timeout 參數。

在 3.13 版的變更: 新增 keep_alive 參數。

Unix Sockets

async asyncio.open_unix_connection(path=None, *, limit=None, ssl=None, sock=None, server_hostname=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None)

建立一個 Unix socket 連線並回傳一對 (reader, writer)。

與 open_connection() 相似，但是是操作 Unix sockets。

另請參閱 loop.create_unix_connection() 文件。

備註

The sock argument transfers ownership of the socket to the StreamWriter created. To close the socket, call its close() method.

可用性: Unix.

在 3.7 版的變更: 新增 ssl_handshake_timeout 參數。path 參數現在可以是個 path-like object

在 3.10 版的變更: 移除 loop 參數。

在 3.11 版的變更: 新增 ssl_shutdown_timeout 參數。

async asyncio.start_unix_server(client_connected_cb, path=None, *, limit=None, sock=None, backlog=100, ssl=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None, start_serving=True, cleanup_socket=True)

啟動一個 Unix socket 伺服器。

與 start_server() 相似，但會是操作 Unix sockets。

If cleanup_socket is true then the Unix socket will automatically be removed from the filesystem when the server is closed, unless the socket has been replaced after the server has been created.

另請參閱 loop.create_unix_server() 文件。

備註

The sock argument transfers ownership of the socket to the server created. To close the socket, call the server's close() method.

可用性: Unix.

在 3.7 版的變更: 新增 ssl_handshake_timeout 與 start_serving 參數。path 參數現在可以是個 path-like object。

在 3.10 版的變更: 移除 loop 參數。

在 3.11 版的變更: 新增 ssl_shutdown_timeout 參數。

在 3.13 版的變更: 新增 cleanup_socket 參數。

StreamReader

class asyncio.StreamReader

表示一個有提供 API 來從 IO 串流中讀取資料的 reader 物件。作為一個 asynchronous iterable，此物件支援 async for 陳述式。

不建議直接實例化 StreamReader 物件；使用 open_connection() 和 start_server() 會是較好的做法。

feed_eof()

Acknowledge the EOF.

async read(n=-1)

從串流中讀取至多 n 個位元組的資料。

如果沒有設定 n 或是被設為 -1，則會持續讀取直到 EOF，然後回傳所有讀取到的 bytes。讀取到 EOF 且內部緩衝區是空的，則回傳一個空的 bytes 物件。

如果 n 為 0，則立即回傳一個空的 bytes 物件。

If n is positive, return at most n available bytes as soon as at least 1 byte is available in the internal buffer. If EOF is received before any byte is read, return an empty bytes object.

async readline()

讀取一行，其中"行"指的是以 \n 結尾的位元組序列。

如果讀取到 EOF 而沒有找到 \n，該方法會回傳部分的已讀取資料。

如果讀取到 EOF 且內部緩衝區是空的，則回傳一個空的 bytes 物件。

async readexactly(n)

讀取剛好 n 個位元組。

如果在讀取完 n 個位元組之前讀取到 EOF，則會引發 IncompleteReadError。使用 IncompleteReadError.partial 屬性來取得串流結束前已讀取的部分資料。

async readuntil(separator=b'\n')

從串流中持續讀取資料直到出現 separator。

成功後，資料和 separator（分隔符號）會從內部緩衝區中刪除（或者說是被消費掉 (consumed)）。回傳的資料在末尾會有一個 separator。

如果讀取的資料量超過了設定的串流限制，將會引發 LimitOverrunError 例外，資料將被留在內部緩衝區中，並可以再次被讀取。

如果在完整的 separator 被找到之前就讀取到 EOF，則會引發 IncompleteReadError 例外，且內部緩衝區會被重置。IncompleteReadError.partial 屬性可能包含一部分的 separator。

The separator may also be a tuple of separators. In this case the return value will be the shortest possible that has any separator as the suffix. For the purposes of LimitOverrunError, the shortest possible separator is considered to be the one that matched.

在 3.5.2 版被加入.

在 3.13 版的變更: 現在 separator 參數可以是一個分隔符號的 tuple。

at_eof()

如果緩衝區是空的且 feed_eof() 曾被呼叫則回傳 True。

StreamWriter

class asyncio.StreamWriter

表示一個有提供 API 來將資料寫入 IO 串流的 writer 物件。

不建議直接實例化 StreamWriter 物件；使用 open_connection() 和 start_server() 會是較好的做法。

write(data)

此方法會嘗試立即將 data 寫入到底層的 socket。如果失敗，資料會被放到內部寫入緩衝中排隊等待 (queue)，直到它可被發送。

The data buffer should be a bytes, bytearray, or C-contiguous one-dimensional memoryview object.

此方法應當與 drain() 方法一起使用：

stream.write(data)
await stream.drain()

writelines(data)

此方法會立即嘗試將一個位元組 list（或任何可疊代物件 (iterable)）寫入到底層的 socket。如果失敗，資料會被放到內部寫入緩衝中排隊等待，直到它可被發送。

此方法應當與 drain() 方法一起使用：

stream.writelines(lines)
await stream.drain()

close()

此方法會關閉串流以及底層的 socket。

此方法應與 wait_closed() 方法一起使用，但並非強制：

stream.close()
await stream.wait_closed()

can_write_eof()

如果底層的傳輸支援 write_eof() 方法就回傳 True，否則回傳 False。

write_eof()

在已緩衝的寫入資料被清理 (flush) 後關閉串流的寫入端。

transport

回傳底層的 asyncio 傳輸。

get_extra_info(name, default=None)

存取可選的傳輸資訊；詳情請見 BaseTransport.get_extra_info()。

async drain()

等待直到可以繼續寫入到串流。範例：

writer.write(data)
await writer.drain()

這是一個與底層 IO 寫入緩衝區互動的流程控制方法。當緩衝區大小達到最高標記位 (high watermark) 時，drain() 會阻塞直到緩衝區大小減少至最低標記位 (low watermark) 以便繼續寫入。當沒有要等待的資料時，drain() 會立即回傳。

async start_tls(sslcontext, *, server_hostname=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None)

將現有的基於串流的連線升級到 TLS。

參數：

sslcontext：一個 SSLContext 的已配置實例。

server_hostname：設定或覆寫將會被目標伺服器憑證比對的主機名稱。

ssl_handshake_timeout is the time in seconds to wait for the TLS handshake to complete before aborting the connection. 60.0 seconds if None (default).

ssl_shutdown_timeout is the time in seconds to wait for the SSL shutdown to complete before aborting the connection. 30.0 seconds if None (default).

在 3.11 版被加入.

在 3.12 版的變更: 新增 ssl_shutdown_timeout 參數。

is_closing()

如果串流已被關閉或正在被關閉則回傳 True。

在 3.7 版被加入.

async wait_closed()

等待直到串流被關閉。

應當在 close() 之後才被呼叫，這會持續等待直到底層的連線被關閉，以確保在這之前（例如在程式退出前）所有資料都已經被清空

在 3.7 版被加入.

範例

使用串流的 TCP echo 用戶端

使用 asyncio.open_connection() 函式的 TCP echo 用戶端：

import asyncio

async def tcp_echo_client(message):
    reader, writer = await asyncio.open_connection(
        '127.0.0.1', 8888)

    print(f'Send: {message!r}')
    writer.write(message.encode())
    await writer.drain()

    data = await reader.read(100)
    print(f'Received: {data.decode()!r}')

    print('Close the connection')
    writer.close()
    await writer.wait_closed()

asyncio.run(tcp_echo_client('Hello World!'))

也參考

使用低階 loop.create_connection() 方法的 TCP echo 用戶端協定範例。

使用串流的 TCP echo 伺服器

TCP echo 伺服器使用 asyncio.start_server() 函式：

import asyncio

async def handle_echo(reader, writer):
    data = await reader.read(100)
    message = data.decode()
    addr = writer.get_extra_info('peername')

    print(f"Received {message!r} from {addr!r}")

    print(f"Send: {message!r}")
    writer.write(data)
    await writer.drain()

    print("Close the connection")
    writer.close()
    await writer.wait_closed()

async def main():
    server = await asyncio.start_server(
        handle_echo, '127.0.0.1', 8888)

    addrs = ', '.join(str(sock.getsockname()) for sock in server.sockets)
    print(f'Serving on {addrs}')

    async with server:
        await server.serve_forever()

asyncio.run(main())

也參考

使用 loop.create_server() 方法的 TCP echo 伺服器協定 範例。

取得 HTTP 標頭

查詢自命令列傳入之 URL 所帶有 HTTP 標頭的簡單範例：

import asyncio
import urllib.parse
import sys

async def print_http_headers(url):
    url = urllib.parse.urlsplit(url)
    if url.scheme == 'https':
        reader, writer = await asyncio.open_connection(
            url.hostname, 443, ssl=True)
    else:
        reader, writer = await asyncio.open_connection(
            url.hostname, 80)

    query = (
        f"HEAD {url.path or '/'} HTTP/1.0\r\n"
        f"Host: {url.hostname}\r\n"
        f"\r\n"
    )

    writer.write(query.encode('latin-1'))
    while True:
        line = await reader.readline()
        if not line:
            break

        line = line.decode('latin1').rstrip()
        if line:
            print(f'HTTP header> {line}')

    # Ignore the body, close the socket
    writer.close()
    await writer.wait_closed()

url = sys.argv[1]
asyncio.run(print_http_headers(url))

用法：

python example.py http://example.com/path/page.html

或使用 HTTPS：

python example.py https://example.com/path/page.html

註冊一個使用串流來等待資料的開放 socket

等待直到 socket 透過使用 open_connection() 函式接收到資料的協程：

import asyncio
import socket

async def wait_for_data():
    # Get a reference to the current event loop because
    # we want to access low-level APIs.
    loop = asyncio.get_running_loop()

    # Create a pair of connected sockets.
    rsock, wsock = socket.socketpair()

    # Register the open socket to wait for data.
    reader, writer = await asyncio.open_connection(sock=rsock)

    # Simulate the reception of data from the network
    loop.call_soon(wsock.send, 'abc'.encode())

    # Wait for data
    data = await reader.read(100)

    # Got data, we are done: close the socket
    print("Received:", data.decode())
    writer.close()
    await writer.wait_closed()

    # Close the second socket
    wsock.close()

asyncio.run(wait_for_data())

也參考

在註冊一個開啟的 socket 以等待有使用協定的資料範例中，有使用了低階協定以及 loop.create_connection() 方法。

在監視檔案描述器以讀取事件範例中，有使用低階的 loop.add_reader() 方法來監視檔案描述器。

同步化原始物件 (Synchronization Primitives)

原始碼：Lib/asyncio/locks.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/locks.py]

asyncio 的同步化原始物件被設計成和那些 threading 模組 (module) 中的同名物件相似，但有兩個重要的限制條件：

asyncio 原始物件並不支援執行緒安全 (thread-safe)，因此他們不可被用於 OS 執行緒同步化（請改用 threading）；

這些同步化原始物件的方法 (method) 並不接受 timeout 引數；要達成有超時 (timeout) 設定的操作請改用 asyncio.wait_for() 函式。

asyncio 有以下基礎同步化原始物件：

Lock

Event

Condition

Semaphore

BoundedSemaphore

Barrier

Lock

class asyncio.Lock

實作了一個給 asyncio 任務 (task) 用的互斥鎖 (mutex lock)。不支援執行緒安全。

一個 asyncio 的鎖可以用來確保一個共享資源的存取權被獨佔。

使用 Lock 的推薦方式是透過 async with 陳述式：

lock = asyncio.Lock()

# ... later
async with lock:
    # access shared state

這等價於：

lock = asyncio.Lock()

# ... later
await lock.acquire()
try:
    # access shared state
finally:
    lock.release()

在 3.10 版的變更: 移除 loop 參數。

async acquire()

獲得鎖。

此方法會持續等待直到鎖的狀態成為 unlocked，並將其設置為 locked 和回傳 True。

當多於一個的協程 (coroutine) 在 acquire() 中等待解鎖而被阻塞，最終只會有其中的一個被處理。

鎖的取得方式是公平的：被處理的協程會是最早開始等待解鎖的那一個。

release()

釋放鎖。

如果鎖的狀態為 locked 則將其重置為 unlocked 並回傳。

如果鎖的狀態為 unlocked 則 RuntimeError 會被引發。

locked()

如果鎖的狀態為 locked 則回傳 True。

Event

class asyncio.Event

一個事件 (event) 物件。不支援執行緒安全。

一個 asyncio 事件可以被用於通知多個有發生某些事件於其中的 asyncio 任務。

一個 Event 物件會管理一個內部旗標 (flag)，它可以透過 set() 方法來被設為 true 並透過 clear() 方法來重置為 false。wait() 方法會被阻塞 (block) 直到該旗標被設為 true。該旗標初始設置為 false。

在 3.10 版的變更: 移除 loop 參數。

範例：

async def waiter(event):
    print('waiting for it ...')
    await event.wait()
    print('... got it!')

async def main():
    # Create an Event object.
    event = asyncio.Event()

    # Spawn a Task to wait until 'event' is set.
    waiter_task = asyncio.create_task(waiter(event))

    # Sleep for 1 second and set the event.
    await asyncio.sleep(1)
    event.set()

    # Wait until the waiter task is finished.
    await waiter_task

asyncio.run(main())

async wait()

持續等待直到事件被設置。

如果事件有被設置則立刻回傳 True。否則持續阻塞直到另一個任務呼叫 set()。

set()

設置事件。

所有正在等待事件被設置的任務會立即被喚醒。

clear()

清除（還原）事件。

正透過 wait() 等待的後續 Tasks 現在會持續阻塞直到 set() 方法再次被呼叫。

is_set()

如果事件有被設置則回傳 True。

Condition

class asyncio.Condition(lock=None)

一個條件 (codition) 物件。不支援執行緒安全。

一個 asyncio 條件原始物件可以被任務用來等待某事件發生，並獲得一個共享資源的獨佔存取權。

本質上，一個 Condition 物件會結合 Event 和 Lock 的功能。多個 Condition 物件共享一個 Lock 是有可能發生的，這能夠協調關注同一共享資源的不同狀態以取得其獨佔存取權的多個任務。

可選的 lock 引數必須是一個 Lock 物件或者為 None。如為後者則一個新的 Lock 物件會被自動建立。

在 3.10 版的變更: 移除 loop 參數。

使用 Condition 的推薦方式是透過 async with 陳述式：

cond = asyncio.Condition()

# ... later
async with cond:
    await cond.wait()

這等價於：

cond = asyncio.Condition()

# ... later
await cond.acquire()
try:
    await cond.wait()
finally:
    cond.release()

async acquire()

取得底層的鎖。

此方法會持續等待直到底層的鎖為 unlocked，並將其設為 locked 並回傳 True。

notify(n=1)

喚醒至多 n 個正在等待此條件的任務（預設為 1），如果少於 n 個任務則全部被喚醒。

在此方法被呼叫前必須先獲得鎖，並在之後立刻將其釋放。如果呼叫於一個 unlocked 的鎖則 RuntimeError 錯誤會被引發。

locked()

如果已取得底層的鎖則回傳 True。

notify_all()

喚醒所有正在等待此條件的任務。

這個方法的行為就像 notify()，但會喚醒所有正在等待的任務。

在此方法被呼叫前必須先獲得鎖，並在之後立刻將其釋放。如果呼叫於一個 unlocked 的鎖則 RuntimeError 錯誤會被引發。

release()

釋放底層的鎖。

當叫用於一個未被解開的鎖之上時，會引發一個 RuntimeError。

async wait()

持續等待直到被通知 (notify)。

當此方法被呼叫時，如果呼叫它的任務還沒有取得鎖的話，RuntimeError 會被引發。

此方法會釋放底層的鎖，然後持續阻塞直到被 notify() 或 notify_all() 的呼叫所喚醒。一但被喚醒，Condition 會重新取得該鎖且此方法會回傳 True。

Note that a task may return from this call spuriously, which is why the caller should always re-check the state and be prepared to wait() again. For this reason, you may prefer to use wait_for() instead.

async wait_for(predicate)

持續等待直到謂語 (predicate) 成為 true。

謂語必須是一個結果可被直譯為一個 boolean 值的可呼叫物件 (callable)。此方法會重複地 wait() 直到謂語求值結果為 true。最終的值即為回傳值。

Semaphore

class asyncio.Semaphore(value=1)

一個旗號 (semaphore) 物件。不支援執行緒安全。

一個旗號物件會管理一個內部計數器，會在每次呼叫 acquire() 時減少一、每次呼叫 release() 時增加一。此計數器永遠不會少於零；當 acquire() 發現它是零時，它會持續阻塞並等待某任務呼叫 release()。

可選的 value 引數給定了內部計數器的初始值（預設為 1）。如給定的值少於 0 則 ValueError 會被引發。

在 3.10 版的變更: 移除 loop 參數。

使用 Semaphore 的推薦方式是透過 async with 陳述式：

sem = asyncio.Semaphore(10)

# ... later
async with sem:
    # work with shared resource

這等價於：

sem = asyncio.Semaphore(10)

# ... later
await sem.acquire()
try:
    # work with shared resource
finally:
    sem.release()

async acquire()

取得一個旗號。

如果內部計數器大於零，將其減一並立刻回傳 True。如果為零，則持續等待直到 release() 被呼叫，並回傳 True。

locked()

如果旗號無法立即被取得則回傳 True。

release()

釋放一個旗號，並為其內部的計數器數值增加一。可以把一個正在等待取得旗號的任務叫醒。

和 BoundedSemaphore 不同，Semaphore 允許 release() 的呼叫次數多於 acquire()。

BoundedSemaphore

class asyncio.BoundedSemaphore(value=1)

一個有界的旗號物件。不支援執行緒安全。

Bounded Semaphore 是 Semaphore 的另一版本，如果其內部的計數器數值增加至大於初始 value 值的話，ValueError 會在 release() 時被引發。

在 3.10 版的變更: 移除 loop 參數。

Barrier

class asyncio.Barrier(parties)

一個屏障 (barrier) 物件。不支援執行緒安全。

A barrier is a simple synchronization primitive that allows to block until parties number of tasks are waiting on it. Tasks can wait on the wait() method and would be blocked until the specified number of tasks end up waiting on wait(). At that point all of the waiting tasks would unblock simultaneously.

async with can be used as an alternative to awaiting on wait().

The barrier can be reused any number of times.

範例：

async def example_barrier():
   # barrier with 3 parties
   b = asyncio.Barrier(3)

   # create 2 new waiting tasks
   asyncio.create_task(b.wait())
   asyncio.create_task(b.wait())

   await asyncio.sleep(0)
   print(b)

   # The third .wait() call passes the barrier
   await b.wait()
   print(b)
   print("barrier passed")

   await asyncio.sleep(0)
   print(b)

asyncio.run(example_barrier())

Result of this example is:

<asyncio.locks.Barrier object at 0x... [filling, waiters:2/3]>
<asyncio.locks.Barrier object at 0x... [draining, waiters:0/3]>
barrier passed
<asyncio.locks.Barrier object at 0x... [filling, waiters:0/3]>

在 3.11 版被加入.

async wait()

Pass the barrier. When all the tasks party to the barrier have called this function, they are all unblocked simultaneously.

When a waiting or blocked task in the barrier is cancelled, this task exits the barrier which stays in the same state. If the state of the barrier is "filling", the number of waiting task decreases by 1.

The return value is an integer in the range of 0 to parties-1, different for each task. This can be used to select a task to do some special housekeeping, e.g.:

...
async with barrier as position:
   if position == 0:
      # Only one task prints this
      print('End of *draining phase*')

This method may raise a BrokenBarrierError exception if the barrier is broken or reset while a task is waiting. It could raise a CancelledError if a task is cancelled.

async reset()

Return the barrier to the default, empty state. Any tasks waiting on it will receive the BrokenBarrierError exception.

If a barrier is broken it may be better to just leave it and create a new one.

async abort()

Put the barrier into a broken state. This causes any active or future calls to wait() to fail with the BrokenBarrierError. Use this for example if one of the tasks needs to abort, to avoid infinite waiting tasks.

parties

The number of tasks required to pass the barrier.

n_waiting

The number of tasks currently waiting in the barrier while filling.

broken

A boolean that is True if the barrier is in the broken state.

exception asyncio.BrokenBarrierError

This exception, a subclass of RuntimeError, is raised when the Barrier object is reset or broken.

在 3.9 版的變更: 透過 await lock 或 yield from lock 和/或 with 陳述式 (with await lock, with (yield from lock)) 來取得鎖的方式已被移除。請改用 async with lock。

子行程

原始碼：Lib/asyncio/subprocess.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/subprocess.py]、Lib/asyncio/base_subprocess.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/base_subprocess.py]

This section describes high-level async/await asyncio APIs to create and manage subprocesses.

Here's an example of how asyncio can run a shell command and obtain its result:

import asyncio

async def run(cmd):
    proc = await asyncio.create_subprocess_shell(
        cmd,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE)

    stdout, stderr = await proc.communicate()

    print(f'[{cmd!r} exited with {proc.returncode}]')
    if stdout:
        print(f'[stdout]\n{stdout.decode()}')
    if stderr:
        print(f'[stderr]\n{stderr.decode()}')

asyncio.run(run('ls /zzz'))

會印出：

['ls /zzz' exited with 1]
[stderr]
ls: /zzz: No such file or directory

Because all asyncio subprocess functions are asynchronous and asyncio provides many tools to work with such functions, it is easy to execute and monitor multiple subprocesses in parallel. It is indeed trivial to modify the above example to run several commands simultaneously:

async def main():
    await asyncio.gather(
        run('ls /zzz'),
        run('sleep 1; echo "hello"'))

asyncio.run(main())

另請參閱Examples。

建立子行程

async asyncio.create_subprocess_exec(program, *args, stdin=None, stdout=None, stderr=None, limit=None, **kwds)

建立一個子行程。

The limit argument sets the buffer limit for StreamReader wrappers for stdout and stderr (if subprocess.PIPE is passed to stdout and stderr arguments).

回傳一個 Process 實例。

See the documentation of loop.subprocess_exec() for other parameters.

If the process object is garbage collected while the process is still running, the child process will be killed.

在 3.10 版的變更: 移除了 loop 參數。

async asyncio.create_subprocess_shell(cmd, stdin=None, stdout=None, stderr=None, limit=None, **kwds)

執行 cmd shell 命令。

The limit argument sets the buffer limit for StreamReader wrappers for stdout and stderr (if subprocess.PIPE is passed to stdout and stderr arguments).

回傳一個 Process 實例。

See the documentation of loop.subprocess_shell() for other parameters.

If the process object is garbage collected while the process is still running, the child process will be killed.

重要

It is the application's responsibility to ensure that all whitespace and special characters are quoted appropriately to avoid shell injection [https://en.wikipedia.org/wiki/Shell_injection#Shell_injection] vulnerabilities. The shlex.quote() function can be used to properly escape whitespace and special shell characters in strings that are going to be used to construct shell commands.

在 3.10 版的變更: 移除了 loop 參數。

備註

Subprocesses are available for Windows if a ProactorEventLoop is used. See Subprocess Support on Windows for details.

也參考

asyncio also has the following low-level APIs to work with subprocesses: loop.subprocess_exec(), loop.subprocess_shell(), loop.connect_read_pipe(), loop.connect_write_pipe(), as well as the Subprocess Transports and Subprocess Protocols.

常數

asyncio.subprocess.PIPE

Can be passed to the stdin, stdout or stderr parameters.

If PIPE is passed to stdin argument, the Process.stdin attribute will point to a StreamWriter instance.

If PIPE is passed to stdout or stderr arguments, the Process.stdout and Process.stderr attributes will point to StreamReader instances.

asyncio.subprocess.STDOUT

Special value that can be used as the stderr argument and indicates that standard error should be redirected into standard output.

asyncio.subprocess.DEVNULL

Special value that can be used as the stdin, stdout or stderr argument to process creation functions. It indicates that the special file os.devnull will be used for the corresponding subprocess stream.

與子行程互動

Both create_subprocess_exec() and create_subprocess_shell() functions return instances of the Process class. Process is a high-level wrapper that allows communicating with subprocesses and watching for their completion.

class asyncio.subprocess.Process

An object that wraps OS processes created by the create_subprocess_exec() and create_subprocess_shell() functions.

This class is designed to have a similar API to the subprocess.Popen class, but there are some notable differences:

unlike Popen, Process instances do not have an equivalent to the poll() method;

the communicate() and wait() methods don't have a timeout parameter: use the wait_for() function;

the Process.wait() method is asynchronous, whereas subprocess.Popen.wait() method is implemented as a blocking busy loop;

the universal_newlines parameter is not supported.

This class is not thread safe.

See also the Subprocess and Threads section.

async wait()

Wait for the child process to terminate.

Set and return the returncode attribute.

備註

This method can deadlock when using stdout=PIPE or stderr=PIPE and the child process generates so much output that it blocks waiting for the OS pipe buffer to accept more data. Use the communicate() method when using pipes to avoid this condition.

async communicate(input=None)

Interact with process:

send data to stdin (if input is not None);

關閉 stdin；

從 stdout 和 stderr 讀取資料，直到 EOF；

等待行程終止。

The optional input argument is the data (bytes object) that will be sent to the child process.

回傳一個 (stdout_data, stderr_data) 元組。

If either BrokenPipeError or ConnectionResetError exception is raised when writing input into stdin, the exception is ignored. This condition occurs when the process exits before all data are written into stdin.

If it is desired to send data to the process' stdin, the process needs to be created with stdin=PIPE. Similarly, to get anything other than None in the result tuple, the process has to be created with stdout=PIPE and/or stderr=PIPE arguments.

Note, that the data read is buffered in memory, so do not use this method if the data size is large or unlimited.

在 3.12 版的變更: stdin gets closed when input=None too.

send_signal(signal)

Sends the signal signal to the child process.

備註

On Windows, SIGTERM is an alias for terminate(). CTRL_C_EVENT and CTRL_BREAK_EVENT can be sent to processes started with a creationflags parameter which includes CREATE_NEW_PROCESS_GROUP.

terminate()

Stop the child process.

On POSIX systems this method sends SIGTERM to the child process.

On Windows the Win32 API function TerminateProcess() is called to stop the child process.

kill()

Kill the child process.

On POSIX systems this method sends SIGKILL to the child process.

On Windows this method is an alias for terminate().

stdin

Standard input stream (StreamWriter) or None if the process was created with stdin=None.

stdout

Standard output stream (StreamReader) or None if the process was created with stdout=None.

stderr

Standard error stream (StreamReader) or None if the process was created with stderr=None.

警告

Use the communicate() method rather than process.stdin.write(), await process.stdout.read() or await process.stderr.read(). This avoids deadlocks due to streams pausing reading or writing and blocking the child process.

pid

Process identification number (PID).

Note that for processes created by the create_subprocess_shell() function, this attribute is the PID of the spawned shell.

returncode

Return code of the process when it exits.

A None value indicates that the process has not terminated yet.

A negative value -N indicates that the child was terminated by signal N (POSIX only).

子行程與執行緒

Standard asyncio event loop supports running subprocesses from different threads by default.

On Windows subprocesses are provided by ProactorEventLoop only (default), SelectorEventLoop has no subprocess support.

Note that alternative event loop implementations might have own limitations; please refer to their documentation.

也參考

The Concurrency and multithreading in asyncio section.

範例

An example using the Process class to control a subprocess and the StreamReader class to read from its standard output.

The subprocess is created by the create_subprocess_exec() function:

import asyncio
import sys

async def get_date():
    code = 'import datetime; print(datetime.datetime.now())'

    # Create the subprocess; redirect the standard output
    # into a pipe.
    proc = await asyncio.create_subprocess_exec(
        sys.executable, '-c', code,
        stdout=asyncio.subprocess.PIPE)

    # Read one line of output.
    data = await proc.stdout.readline()
    line = data.decode('ascii').rstrip()

    # Wait for the subprocess exit.
    await proc.wait()
    return line

date = asyncio.run(get_date())
print(f"Current date: {date}")

See also the same example written using low-level APIs.

佇列 (Queues)

原始碼：Lib/asyncio/queues.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/queues.py]

asyncio 佇列被設計成與 queue 模組類似。儘管 asyncio 佇列不支援執行緒安全 (thread-safe)，但他們是被設計來專用於 async/await 程式。

注意 asyncio 的佇列沒有 timeout 參數；請使用 asyncio.wait_for() 函式來為佇列新增具有超時 (timeout) 設定的操作。

另請參閱下方 Examples。

Queue

class asyncio.Queue(maxsize=0)

先進先出 (FIFO) 佇列。

如果 maxsize 小於或等於零，則佇列大小是無限制的。如果是大於 0 的整數，則當佇列達到 maxsize 時，await put() 將會阻塞 (block)，直到某個元素被 get() 取出。

不像標準函式庫中執行緒類型的 queue，佇列的大小一直是已知的，可以透過呼叫 qsize() 方法回傳。

在 3.10 版的變更: 移除 loop 參數。

這個類別是不支援執行緒安全的。

maxsize

佇列中可存放的元素數量。

empty()

如果佇列為空則回傳 True，否則回傳 False。

full()

如果有 maxsize 個條目在佇列中，則回傳 True。

如果佇列用 maxsize=0 （預設）初始化，則 full() 永遠不會回傳 True。

async get()

從佇列中刪除並回傳一個元素。如果佇列為空，則持續等待直到佇列中有元素。

Raises QueueShutDown if the queue has been shut down and is empty, or if the queue has been shut down immediately.

get_nowait()

如果佇列內有值則立即回傳佇列中的元素，否則引發 QueueEmpty。

async join()

持續阻塞直到佇列中所有的元素都被接收和處理完畢。

當條目新增到佇列的時候，未完成任務的計數就會增加。每當一個消耗者 (consumer) 協程呼叫 task_done()，表示這個條目已經被取回且被它包含的所有工作都已完成，未完成任務計數就會減少。當未完成計數降到零的時候，join() 阻塞會被解除 (unblock)。

async put(item)

將一個元素放進佇列。如果佇列滿了，在新增元素之前，會持續等待直到有空閒插槽 (free slot) 能被使用。

如果佇列已經被關閉，則引發 QueueShutDown。

put_nowait(item)

不阻塞地將一個元素放入佇列。

如果沒有立即可用的空閒插槽，引發 QueueFull。

qsize()

回傳佇列中的元素數量。

shutdown(immediate=False)

Put a Queue instance into a shutdown mode.

The queue can no longer grow. Future calls to put() raise QueueShutDown. Currently blocked callers of put() will be unblocked and will raise QueueShutDown in the formerly awaiting task.

If immediate is false (the default), the queue can be wound down normally with get() calls to extract tasks that have already been loaded.

And if task_done() is called for each remaining task, a pending join() will be unblocked normally.

Once the queue is empty, future calls to get() will raise QueueShutDown.

If immediate is true, the queue is terminated immediately. The queue is drained to be completely empty and the count of unfinished tasks is reduced by the number of tasks drained. If unfinished tasks is zero, callers of join() are unblocked. Also, blocked callers of get() are unblocked and will raise QueueShutDown because the queue is empty.

Use caution when using join() with immediate set to true. This unblocks the join even when no work has been done on the tasks, violating the usual invariant for joining a queue.

在 3.13 版被加入.

task_done()

表示前面一個排隊的工作項目已經完成。

由佇列消耗者使用。對於每個用於取得一個工作項目的 get()，接續的 task_done() 呼叫會告訴佇列這個工作項目的處理已經完成。

如果 join() 目前正在阻塞，在所有項目都被處理後會解除阻塞（意味著每個以 put() 放進佇列的條目都會收到一個 task_done()）。

如果被呼叫的次數多於放入佇列中的項目數量，將引發 ValueError。

Priority Queue（優先佇列）

class asyncio.PriorityQueue

Queue 的變形；按優先順序取出條目 (最小的先取出)。

條目通常是 (priority_number, data) 形式的 tuple（元組）。

LIFO Queue

class asyncio.LifoQueue

Queue 的變形，先取出最近新增的條目（後進先出）。

例外

exception asyncio.QueueEmpty

當佇列為空的時候，呼叫 get_nowait() 方法會引發這個例外。

exception asyncio.QueueFull

當佇列中條目數量已經達到它的 maxsize 時，呼叫 put_nowait() 方法會引發這個例外。

exception asyncio.QueueShutDown

Exception raised when put() or get() is called on a queue which has been shut down.

在 3.13 版被加入.

範例

佇列能被用於多個並行任務的工作分配：

import asyncio
import random
import time

async def worker(name, queue):
    while True:
        # Get a "work item" out of the queue.
        sleep_for = await queue.get()

        # Sleep for the "sleep_for" seconds.
        await asyncio.sleep(sleep_for)

        # Notify the queue that the "work item" has been processed.
        queue.task_done()

        print(f'{name} has slept for {sleep_for:.2f} seconds')

async def main():
    # Create a queue that we will use to store our "workload".
    queue = asyncio.Queue()

    # Generate random timings and put them into the queue.
    total_sleep_time = 0
    for _ in range(20):
        sleep_for = random.uniform(0.05, 1.0)
        total_sleep_time += sleep_for
        queue.put_nowait(sleep_for)

    # Create three worker tasks to process the queue concurrently.
    tasks = []
    for i in range(3):
        task = asyncio.create_task(worker(f'worker-{i}', queue))
        tasks.append(task)

    # Wait until the queue is fully processed.
    started_at = time.monotonic()
    await queue.join()
    total_slept_for = time.monotonic() - started_at

    # Cancel our worker tasks.
    for task in tasks:
        task.cancel()
    # Wait until all worker tasks are cancelled.
    await asyncio.gather(*tasks, return_exceptions=True)

    print('====')
    print(f'3 workers slept in parallel for {total_slept_for:.2f} seconds')
    print(f'total expected sleep time: {total_sleep_time:.2f} seconds')

asyncio.run(main())

例外

原始碼：Lib/asyncio/exceptions.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/exceptions.py]

exception asyncio.TimeoutError

TimeoutError 的一個已被棄用的別名，當操作已超過規定的截止時間時被引發。

在 3.11 版的變更: 此 class 是 TimeoutError 的一個別名。

exception asyncio.CancelledError

該操作已被取消。

當 asyncio Task 被取消時，可以捕獲此例外以執行客製化操作。在幾乎所有情況下，該例外必須重新被引發。

在 3.8 版的變更: CancelledError 現在是 BaseException 而非 Exception 的子類別。

exception asyncio.InvalidStateError

Task 或 Future 的無效內部狀態。

可以在像是為已設定結果值的 Future 物件設定結果值的情況下引發。

exception asyncio.SendfileNotAvailableError

"sendfile" 系統呼叫不適用於給定的 socket 或檔案型別。

一個 RuntimeError 的子類別。

exception asyncio.IncompleteReadError

請求的讀取操作未全部完成。

由 asyncio 串流 APIs 引發。

此例外是 EOFError 的子類別。

expected

預期的位元組總數 (int)。

partial

串流結束之前讀取的 bytes 字串。

exception asyncio.LimitOverrunError

在查詢分隔符號 (separator) 時達到緩衝區 (buffer) 大小限制。

由 asyncio 串流 APIs 引發。

consumed

要消耗的位元組總數。

Call Graph Introspection

原始碼：Lib/asyncio/graph.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/graph.py]

asyncio has powerful runtime call graph introspection utilities to trace the entire call graph of a running coroutine or task, or a suspended future. These utilities and the underlying machinery can be used from within a Python program or by external profilers and debuggers.

在 3.14 版被加入.

asyncio.print_call_graph(future=None, /, *, file=None, depth=1, limit=None)

Print the async call graph for the current task or the provided Task or Future.

This function prints entries starting from the top frame and going down towards the invocation point.

The function receives an optional future argument. If not passed, the current running task will be used.

If the function is called on the current task, the optional keyword-only depth argument can be used to skip the specified number of frames from top of the stack.

If the optional keyword-only limit argument is provided, each call stack in the resulting graph is truncated to include at most abs(limit) entries. If limit is positive, the entries left are the closest to the invocation point. If limit is negative, the topmost entries are left. If limit is omitted or None, all entries are present. If limit is 0, the call stack is not printed at all, only "awaited by" information is printed.

If file is omitted or None, the function will print to sys.stdout.

範例：

以下 Python 程式碼：

import asyncio

async def test():
    asyncio.print_call_graph()

async def main():
    async with asyncio.TaskGroup() as g:
        g.create_task(test(), name='test')

asyncio.run(main())

會印出：

* Task(name='test', id=0x1039f0fe0)
+ Call stack:
|   File 't2.py', line 4, in async test()
+ Awaited by:
   * Task(name='Task-1', id=0x103a5e060)
      + Call stack:
      |   File 'taskgroups.py', line 107, in async TaskGroup.__aexit__()
      |   File 't2.py', line 7, in async main()

asyncio.format_call_graph(future=None, /, *, depth=1, limit=None)

Like print_call_graph(), but returns a string. If future is None and there's no current task, the function returns an empty string.

asyncio.capture_call_graph(future=None, /, *, depth=1, limit=None)

Capture the async call graph for the current task or the provided Task or Future.

The function receives an optional future argument. If not passed, the current running task will be used. If there's no current task, the function returns None.

If the function is called on the current task, the optional keyword-only depth argument can be used to skip the specified number of frames from top of the stack.

會回傳一個 FutureCallGraph 資料類別物件：

FutureCallGraph(future, call_stack, awaited_by)

Where future is a reference to a Future or a Task (or their subclasses.)

call_stack 是一個由 FrameCallGraphEntry 物件組成的元組。

awaited_by 是一個由 FutureCallGraph 物件組成的元組。

FrameCallGraphEntry(frame)

Where frame is a frame object of a regular Python function in the call stack.

低階工具函式

To introspect an async call graph asyncio requires cooperation from control flow structures, such as shield() or TaskGroup. Any time an intermediate Future object with low-level APIs like Future.add_done_callback() is involved, the following two functions should be used to inform asyncio about how exactly such intermediate future objects are connected with the tasks they wrap or control.

asyncio.future_add_to_awaited_by(future, waiter, /)

Record that future is awaited on by waiter.

Both future and waiter must be instances of Future or Task or their subclasses, otherwise the call would have no effect.

A call to future_add_to_awaited_by() must be followed by an eventual call to the future_discard_from_awaited_by() function with the same arguments.

asyncio.future_discard_from_awaited_by(future, waiter, /)

Record that future is no longer awaited on by waiter.

Both future and waiter must be instances of Future or Task or their subclasses, otherwise the call would have no effect.

事件迴圈

原始碼： Lib/asyncio/events.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/events.py]、Lib/asyncio/base_events.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/base_events.py]

前言

事件迴圈是每個 asyncio 應用程式的核心。事件迴圈執行非同步任務和回呼、執行網路 IO 操作並啟動子行程。

應用程式開發人員通常應使用高階的 asyncio 函式，例如 asyncio.run()，並且很少需要參照事件迴圈物件或呼叫其方法。本節主要針對那些需要更細粒度控制事件迴圈行為的低階程式碼、函式庫和框架的作者。

取得事件迴圈

以下的低階函式可用於取得、設置或建立事件迴圈：

asyncio.get_running_loop()

在目前作業系統執行緒中回傳正在運行的事件迴圈。

如果沒有運行的事件迴圈，則引發 RuntimeError。

此函式只能從協程或回呼函式中呼叫。

在 3.7 版被加入.

asyncio.get_event_loop()

取得目前的事件迴圈。

當從協程或回呼函式呼叫此函式（例如，使用 call_soon 或類似的 API 於排程呼叫），此函式將永遠回傳正在運行的事件迴圈。

如果沒有設定正在運行的事件迴圈，該函式將回傳 get_event_loop_policy().get_event_loop() 呼叫的結果。

由於此函式具有相當複雜的行為（尤其是在使用自訂事件迴圈策略時），在協程和回呼函式中，建議使用 get_running_loop() 函式，而不是 get_event_loop()。

如上所述，可以考慮使用高階的 asyncio.run() 函式，而不是使用這些較低階的函式手動建立和關閉事件迴圈。

在 3.14 版的變更: 如果沒有目前的事件迴圈，則引發 RuntimeError。

備註

The asyncio policy system is deprecated and will be removed in Python 3.16; from there on, this function will return the current running event loop if present else it will return the loop set by set_event_loop().

asyncio.set_event_loop(loop)

將 loop 設置為目前 OS 執行緒的目前事件迴圈。

asyncio.new_event_loop()

建立並回傳新的事件迴圈物件。

請注意 get_event_loop()、set_event_loop() 和 new_event_loop() 函式的行為可以透過設定自訂事件迴圈策略進行調整。

目錄

本頁文件包含以下章節：

事件迴圈方法章節是事件迴圈 API 們的參照文件；

回呼處理章節記錄了從排程方法（如 loop.call_soon() 和 loop.call_later()）回傳的 Handle 和 TimerHandle 實例；

Server 物件章節記錄了從事件迴圈方法（如 loop.create_server()）回傳的資料型別；

事件迴圈實作章節記錄了 SelectorEventLoop 和 ProactorEventLoop 類別；

範例章節展示了如何使用一些事件迴圈 API。

事件迴圈方法

事件迴圈提供以下低階 API：

啟動和停止迴圈

排程回呼函式

排程延遲的回呼函式

建立 Futures 和 Tasks

打開網路連線

建立網路伺服器

傳輸檔案

TLS 升級

監視檔案描述器

直接使用 socket 物件

DNS

使用管道

Unix 訊號

在執行緒池或行程池中執行程式碼

錯誤處理 API

啟用除錯模式

運行子行程

啟動和停止迴圈

loop.run_until_complete(future)

運行直到 future （一個 Future 實例）完成。

如果引數是協程物件，則它將被隱式排程為 asyncio.Task 運行。

回傳 Future 的結果或引發其例外。

loop.run_forever()

運行事件迴圈直到 stop() 被呼叫。

如果在呼叫 run_forever() 之前呼叫 stop()，則迴圈將使用超時為零的方式輪詢 I/O 選擇器，運行所有回應 I/O 事件（以及已經排程的事件）的回呼，然後退出。

如果在 run_forever() 運行時呼叫 stop()，則迴圈將運行目前批次的回呼函式，然後退出。請注意，由回呼函式排程的新回呼在此情況下不會運行；而是在下次呼叫 run_forever() 或 run_until_complete() 時運行。

loop.stop()

停止事件迴圈。

loop.is_running()

如果事件迴圈目前正在運行，則回傳 True。

loop.is_closed()

如果事件迴圈已關閉，則回傳 True。

loop.close()

關閉事件迴圈。

不得於迴圈運行中呼叫此函式。將丟棄任何待處理的回呼。

此方法清除所有佇列並關閉執行器，但不等待執行器完成。

此方法是冪等且不可逆的。在事件迴圈關閉後不應呼叫其他方法。

async loop.shutdown_asyncgens()

排程所有目前打開的非同步產生器物件使用 aclose() 呼叫來關閉。呼叫此方法後，如果疊代新的非同步產生器，事件迴圈將發出警告。應該使用此方法可靠地完成所有已排程的非同步產生器。

請注意，使用 asyncio.run() 時不需要呼叫此函式。

範例：

try:
    loop.run_forever()
finally:
    loop.run_until_complete(loop.shutdown_asyncgens())
    loop.close()

在 3.6 版被加入.

async loop.shutdown_default_executor(timeout=None)

排程預設執行器的關閉，並等待它加入 ThreadPoolExecutor 中的所有執行緒。一旦呼叫了此方法，使用預設執行器與 loop.run_in_executor() 將引發 RuntimeError。

timeout 參數指定執行器完成加入所需的時間（以 float 秒為單位）。預設情況下為 None，不會限制執行器所花費的時間。

如果達到 timeout，將發出 RuntimeWarning 警告，預設執行器將立即終止，不等待其執行緒完成加入。

備註

使用 asyncio.run() 時請勿呼叫此方法，因為後者會自動處理預設執行器的關閉。

在 3.9 版被加入.

在 3.12 版的變更: 加入 timeout 參數。

排程回呼函式

loop.call_soon(callback, *args, context=None)

在事件迴圈的下一次疊代中排程以 args 引數呼叫 callback callback。

回傳 asyncio.Handle 的實例，稍後可以用於取消回呼函式。

回呼函式按照其註冊的順序呼叫。每個回呼函式將被呼叫恰好一次。

選用的僅限關鍵字引數 context 指定了要給 callback 執行的自訂 contextvars.Context。當未提供 context 時，回呼函式使用目前情境。

與 call_soon_threadsafe() 不同，此方法不是執行緒安全的。

loop.call_soon_threadsafe(callback, *args, context=None)

這是 call_soon() 的執行緒安全變體。當從另一個執行緒排程回呼函式時，必須使用此函式，因為 call_soon() 不是執行緒安全的。

This function is safe to be called from a reentrant context or signal handler, however, it is not safe or fruitful to use the returned handle in such contexts.

如果在已關閉的迴圈上呼叫，則引發 RuntimeError。在主應用程式關閉時，這可能發生在次要執行緒上。

請參閱文件的並行和多執行緒部分。

在 3.7 版的變更: 新增了 context 僅限關鍵字參數。詳細資訊請參閱 PEP 567 [https://peps.python.org/pep-0567/]。

備註

大多數 asyncio 排程函式不允許傳遞關鍵字引數。要傳遞關鍵字引數，請使用 functools.partial()：

# 將會排程 "print("Hello", flush=True)"
loop.call_soon(
    functools.partial(print, "Hello", flush=True))

通常使用 partial 物件比使用 lambda 更方便，因為 asyncio 可以在除錯和錯誤訊息中更好地呈現 partial 物件。

排程延遲的回呼函式

事件迴圈提供為回呼函式排程在將來某個時間點才呼叫的機制。事件迴圈使用了單調時鐘來追蹤時間。

loop.call_later(delay, callback, *args, context=None)

排程 callback 在給定的 delay 秒數後呼叫（可以是整數或浮點數）。

回傳 asyncio.TimerHandle 的實例，可用於取消回呼函式。

callback 將只被呼叫恰好一次。如果有兩個回呼函式被排程在完全相同的時間，則其呼叫順序是不定的。

可選的位置引數 args 將在呼叫回呼函式時傳遞。如果要使用關鍵字引數呼叫回呼函數，請使用 functools.partial()。

可選的僅限關鍵字 context 引數允許為 callback 指定自訂的 contextvars.Context 以提供運行。當未提供 context 時，將使用目前情境。

備註

For performance, callbacks scheduled with loop.call_later() may run up to one clock-resolution early (see time.get_clock_info('monotonic').resolution).

在 3.7 版的變更: 新增了 context 僅限關鍵字參數。詳細資訊請參閱 PEP 567 [https://peps.python.org/pep-0567/]。

在 3.8 版的變更: 在 Python 3.7 及更早版本中，使用預設事件迴圈實作時，delay 不能超過一天。這在 Python 3.8 中已經修復。

loop.call_at(when, callback, *args, context=None)

排程 callback 在給定的絕對時間戳 when （整數或浮點數）處呼叫，使用與 loop.time() 相同的時間參照。

此方法的行為與 call_later() 相同。

回傳 asyncio.TimerHandle 的實例，可用於取消回呼函式。

備註

For performance, callbacks scheduled with loop.call_at() may run up to one clock-resolution early (see time.get_clock_info('monotonic').resolution).

在 3.7 版的變更: 新增了 context 僅限關鍵字參數。詳細資訊請參閱 PEP 567 [https://peps.python.org/pep-0567/]。

在 3.8 版的變更: 在 Python 3.7 及更早版本中，使用預設事件迴圈實作時，when 和目前時間之間的差值不能超過一天。這在 Python 3.8 中已經修復。

loop.time()

根據事件迴圈的內部單調時鐘，回傳目前時間，以 float 值表示。

備註

在 3.8 版的變更: 在 Python 3.7 及更早版本中，超時（相對 delay 或絕對 when）不應超過一天。這在 Python 3.8 中已經修復。

也參考

函式 asyncio.sleep()。

建立 Futures 和 Tasks

loop.create_future()

建立附加到事件迴圈的 asyncio.Future 物件。

這是在 asyncio 中建立 Futures 的首選方式。這允許第三方事件迴圈提供 Future 物件的替代實作（具有更好的性能或儀器計測表現）。

在 3.5.2 版被加入.

loop.create_task(coro, *, name=None, context=None, eager_start=None, **kwargs)

排程執行協程 coro。回傳 Task 物件。

第三方事件迴圈可以使用其自己的 Task 子類別以實現互操作性（interoperability）。在這種情況下，結果類型是 Task 的子類別。

The full function signature is largely the same as that of the Task constructor (or factory) - all of the keyword arguments to this function are passed through to that interface.

如果提供了 name 引數且不為 None，則將其設置為任務的名稱，使用 Task.set_name()。

可選的僅限關鍵字 context 引數允許為 coro 指定自訂的 contextvars.Context 以提供運行。當未提供 context 時，將建立目前情境的副本。

An optional keyword-only eager_start argument allows specifying if the task should execute eagerly during the call to create_task, or be scheduled later. If eager_start is not passed the mode set by loop.set_task_factory() will be used.

在 3.8 版的變更: 加入 name 參數。

在 3.11 版的變更: 加入 context 參數。

在 3.13.3 版的變更: Added kwargs which passes on arbitrary extra parameters, including name and context.

在 3.13.4 版的變更: Rolled back the change that passes on name and context (if it is None), while still passing on other arbitrary keyword arguments (to avoid breaking backwards compatibility with 3.13.3).

在 3.14 版的變更: All kwargs are now passed on. The eager_start parameter works with eager task factories.

loop.set_task_factory(factory)

設置將由 loop.create_task() 使用的任務工廠。

如果 factory 為 None，將設置預設的任務工廠。否則，factory 必須是一個具有匹配簽名 (loop, coro, **kwargs) 的 callable，其中 loop 是有效事件迴圈的參照、coro 是一個協程物件。該可呼叫物件必須傳遞所有 kwargs 並回傳一個與 asyncio.Task 相容的物件。

在 3.13.3 版的變更: Required that all kwargs are passed on to asyncio.Task.

在 3.13.4 版的變更: name is no longer passed to task factories. context is no longer passed to task factories if it is None.

在 3.14 版的變更: name and context are now unconditionally passed on to task factories again.

loop.get_task_factory()

回傳任務工廠，如果使用預設任務工廠則回傳 None。

打開網路連線

async loop.create_connection(protocol_factory, host=None, port=None, *, ssl=None, family=0, proto=0, flags=0, sock=None, local_addr=None, server_hostname=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None, happy_eyeballs_delay=None, interleave=None, all_errors=False)

打開以 host 和 port 指定之給定地址的串流傳輸連線。

根據 host（或提供的 family 引數）的情況，socket 家族可以是 AF_INET 或 AF_INET6。

Socket 類型將為 SOCK_STREAM。

protocol_factory 必須是一個回傳 asyncio protocol 實作的可呼叫函式。

此方法將嘗試在背景建立連線。成功時，它將回傳一對 (transport, protocol)。

底層操作的時間軸簡介如下：

建立連線並為其建立傳輸。

protocol_factory 在無引數的情況下被呼叫，並且預計回傳一個 協定 實例。

透過呼叫其 connection_made() 方法，將協定實例與傳輸連線在一起。

成功時回傳一個 (transport, protocol) 元組。

建立的傳輸是一個依賴實作的雙向串流。

其他引數：

若有給定 ssl 且非 false，將建立 SSL/TLS 傳輸（預設建立普通 TCP 傳輸）。如果 ssl 為 ssl.SSLContext 物件，則使用該情境來建立傳輸；如果 ssl 為 True，則使用 ssl.create_default_context() 回傳的預設情境。

也參考

SSL/TLS 安全考量

server_hostname 設置或覆蓋目標伺服器憑證將匹配的主機名稱。僅在 ssl 不為 None 時傳遞。預設情況下，將使用 host 引數的值。如果 host 為空，則沒有預設值，必須傳遞 server_hostname 的值。若 server_hostname 為空字串，將停用主機名稱匹配（這是一個嚴重的安全風險，可能導致中間人攻擊）。

family、proto、flags 是可選的位址家族、協定和旗標，用於傳遞至 getaddrinfo() 進行 host 解析。若有給定這些應該都是相應 socket 模組常數的整數。

若有給定，happy_eyeballs_delay 會啟用此連線的 Happy Eyeballs。它應該是一個浮點數，表示等待連線嘗試完成的秒數，然後在並行啟動下一次嘗試。這是 RFC 8305 [https://datatracker.ietf.org/doc/html/rfc8305.html] 中定義的「連線嘗試延遲」。RFC 建議的合理預設值為 0.25 秒（250 毫秒）。

interleave 控制主機名稱解析為多個 IP 位址時的地址重新排序。若為 0 或未指定，將不執行重排序，並按 getaddrinfo() 回傳的順序嘗試位址。如果指定正整數，則按地址家族交錯排列，給定的整數直譯為 RFC 8305 [https://datatracker.ietf.org/doc/html/rfc8305.html] 中定義的「首個地址家族計數」。如果未指定 happy_eyeballs_delay，則預設值為 0，如果指定則為 1。

若有給定 sock 則其應為已存在且已連線的 socket.socket 物件，可供傳輸使用。如果提供了 sock，則不應指定 host、port、family、proto、flags、happy_eyeballs_delay、interleave 和 local_addr 中的任何一項。

備註

引數 sock 將 socket 所有權轉移給所建立的傳輸 socket，請呼叫傳輸的 close() 方法。

若有給定 local_addr 則其為一個 (local_host, local_port) 元組，用於在本地綁定 socket。將使用 getaddrinfo() 查找 local_host 和 local_port，方式類似於 host 和 port。

ssl_handshake_timeout （對於 TLS 連線）是等待 TLS 交握的時間，以秒為單位，在那之前若未完成則會中斷連線。如果為 None （預設值），則會等待 60.0 秒。

ssl_shutdown_timeout 是等待 SSL 關閉完成以前中斷連線的時間，以秒為單位。如果為 None （預設值），則會等待 30.0 秒。

all_errors 決定在無法建立連線時會引發哪些例外。預設情況下，只會引發單一 Exception：如果只有一個例外或所有錯誤訊息相同，則引發第一個例外，否則引發包含所有錯誤訊息的單一 OSError。當 all_errors 為 True 時，將引發包含所有例外的 ExceptionGroup （即使只有一個例外）。

在 3.5 版的變更: 新增 ProactorEventLoop 中的 SSL/TLS 支援。

在 3.6 版的變更: 所有 TCP 連線都預設有 socket.TCP_NODELAY socket 選項。

在 3.7 版的變更: 增加 ssl_handshake_timeout 參數。

在 3.8 版的變更: 加入 happy_eyeballs_delay 和 interleave 參數。

Happy Eyeballs 演算法：雙協定堆疊主機 (Dual-Stack Hosts) 的成功。當伺服器的 IPv4 路徑和協定運作正常，但伺服器的 IPv6 路徑和協定不運作時，雙棧用戶端應用程式會比僅具 IPv4 的用戶端體驗到顯著的連線延遲。這是不希望的，因為這會導致雙棧用戶端的使用者體驗變差。本文件具體說明了減少此用戶可見延遲的演算法要求並提供了一種演算法。

更多資訊請見： https://datatracker.ietf.org/doc/html/rfc6555

在 3.11 版的變更: 增加 ssl_shutdown_timeout 參數。

在 3.12 版的變更: 已新增 all_errors。

也參考

函式 open_connection() 是高階的替代 API。它回傳一對 (StreamReader, StreamWriter) 可直接在 async/await 程式碼中使用。

async loop.create_datagram_endpoint(protocol_factory, local_addr=None, remote_addr=None, *, family=0, proto=0, flags=0, reuse_port=None, allow_broadcast=None, sock=None)

建立一個資料報連線。

Socket 家族可以是 AF_INET、AF_INET6 或 AF_UNIX，視乎 host（或提供的 family 引數）而定。

Socket 類型將為 SOCK_DGRAM。

protocol_factory 必須是可呼叫的函式，回傳 protocol 實作。

成功時回傳 (transport, protocol) 元組。

其他引數：

local_addr，如果提供，是一個 (local_host, local_port) 元組，用於在本地綁定 socket。local_host 和 local_port 使用 getaddrinfo() 來查找。

備註

On Windows, when using the proactor event loop with local_addr=None, an OSError with errno.WSAEINVAL will be raised when running it.

remote_addr，如果提供，是一個 (remote_host, remote_port) 元組，用於將 socket 連線到遠端位址。 remote_host 和 remote_port 使用 getaddrinfo() 來查找。

family、proto 和 flags 是用於傳遞給 getaddrinfo() 以解析 host 的可選地址家族、協定和旗標。如果提供，這些應該都是來自相應的 socket 模組常數的整數。

reuse_port 告訴核心允許將此端點綁定到與其他現有端點相同的埠，只要它們在建立時都設定了此旗標。此選項不受 Windows 和某些 Unix 系統支援。如果未定義 socket.SO_REUSEPORT 常數，則不支援此功能。

allow_broadcast 告訴核心允許此端點向廣播位址發送訊息。

sock 可以選擇性地指定，以使用預先存在且已連線的 socket.socket 物件供傳輸使用。如果指定，local_addr 和 remote_addr 應省略（必須是 None）。

備註

引數 sock 將 socket 所有權轉移給所建立的傳輸 socket，請呼叫傳輸的 close() 方法。

請參閱 UDP 回應用戶端協定 和 UDP 回應伺服器協定 範例。

在 3.4.4 版的變更: 新增 family、proto、flags、reuse_address、reuse_port、allow_broadcast 和 sock 參數。

在 3.8 版的變更: 新增對於 Windows 的支援。

在 3.8.1 版的變更: 不再支援 reuse_address 參數，因為使用 ~socket.SO_REUSEADDR 對於 UDP 存有重大的安全疑慮。明確傳遞 reuse_address=True 將引發例外。

當具有不同 UID 的多個行程使用 SO_REUSEADDR 將 socket 分配給相同的 UDP socket 地址時，傳入的封包可能會在 socket 之間隨機分佈。

對於有支援的平台，reuse_port 可以用作類似功能的替代方案。使用 reuse_port，將改為使用 ~socket.SO_REUSEPORT，該選項明確禁止具有不同 UID 的行程將 socket 分配給相同的 socket 地址。

在 3.11 版的變更: 自 Python 3.9.0、3.8.1、3.7.6 和 3.6.10 起，已完全移除 reuse_address 參數。

async loop.create_unix_connection(protocol_factory, path=None, *, ssl=None, sock=None, server_hostname=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None)

建立一個 Unix 連線。

Socket 家族將為 AF_UNIX；socket 類型將為 SOCK_STREAM。

成功時回傳 (transport, protocol) 元組。

path 是 Unix 域 socket 的名稱，除非指定 sock 參數，否則為必填。支援抽象 Unix sockets、str、bytes 和 Path 路徑。

有關此方法的引數資訊，請參閱 loop.create_connection() 方法的文件。

可用性: Unix.

在 3.7 版的變更: 新增 ssl_handshake_timeout 參數。path 參數現在可以是 path-like object。

在 3.11 版的變更: 增加 ssl_shutdown_timeout 參數。

建立網路伺服器

async loop.create_server(protocol_factory, host=None, port=None, *, family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE, sock=None, backlog=100, ssl=None, reuse_address=None, reuse_port=None, keep_alive=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None, start_serving=True)

建立一個 TCP 伺服器（socket 類型 SOCK_STREAM），監聽 host 位址的 port。

回傳一個 Server 物件。

引數：

protocol_factory 必須是可呼叫的函式，回傳 protocol 實作。

可以將 host 參數設為幾種類型，以確定伺服器將監聽的位置：

如果 host 是字串，則 TCP 伺服器綁定到由 host 指定的單個網路介面。

如果 host 是字串序列，則 TCP 伺服器綁定到序列指定的所有網路介面。

若 host 是空字串或 None，則所有介面都被假定並回傳多個 socket 的清單（可能一個用於 IPv4，另一個用於 IPv6）。

可以設定 port 參數以指定伺服器應該監聽的埠。如果是 0 或 None（預設值），將隨機選擇一個未使用的埠（請注意，如果 host 解析為多個網路介面，將為每個介面隨機選擇不同的隨機埠）。

family 可以設定為 socket.AF_INET 或 AF_INET6 以強制使用 IPv4 或 IPv6。如果未設定，family 將從主機名稱決定（預設為 AF_UNSPEC）。

flags 是 getaddrinfo() 的位元遮罩。

可以可選地指定 sock 以使用現有的 socket 物件。如果指定了，host 和 port 不能指定。

備註

sock 引數將 socket 的所有權轉移給建立的伺服器。要關閉 socket，請呼叫伺服器的 close() 方法。

backlog 是傳遞給 listen() 的最大佇列連線數（預設為 100）。

ssl 可以設定為 SSLContext 實例以在接受的連線上啟用 TLS。

reuse_address 告訴內核重用 TIME_WAIT 狀態下的本地 socket，而不等待其自然超時過期。如果未指定，在 Unix 上將自動設置為 True。

reuse_port 告訴內核允許此端點繫結到與其他現有端點繫結的相同埠，只要它們在建立時都設置了此旗標。此選項在旗標 Windows 上不受支援。

將 keep_alive 設為 True 透過啟用定期的訊息傳輸來保持連線活躍。

在 3.13 版的變更: 加入 keep_alive 參數。

（對於 TLS 伺服器）ssl_handshake_timeout 是在中斷連線之前等待 TLS 握手完成的時間（以秒為單位）。如果為 None（預設），則為 60.0 秒。

ssl_shutdown_timeout 是等待 SSL 關閉完成以前中斷連線的時間，以秒為單位。如果為 None （預設值），則會等待 30.0 秒。

將 start_serving 設置為 True（預設）將使建立的伺服器立即開始接受連接。當設置為 False 時，用戶應該等待 Server.start_serving() 或 Server.serve_forever() 來使伺服器開始接受連線。

在 3.5 版的變更: 新增 ProactorEventLoop 中的 SSL/TLS 支援。

在 3.5.1 版的變更: host 參數可以是字串序列。

在 3.6 版的變更: 新增 ssl_handshake_timeout 與 start_serving 參數。所有 TCP 連線都預設有 socket.TCP_NODELAY socket 選項。

在 3.11 版的變更: 增加 ssl_shutdown_timeout 參數。

也參考

start_server() 函式是一個更高階的替代 API，它回傳一對 StreamReader 和 StreamWriter，可以在 async/await 程式碼中使用。

async loop.create_unix_server(protocol_factory, path=None, *, sock=None, backlog=100, ssl=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None, start_serving=True, cleanup_socket=True)

類似 loop.create_server()，但適用於 AF_UNIX socket 家族。

path 是 Unix 域 socket 的名稱，除非提供了 sock 引數，否則必須給定。支援抽象 Unix sockets、str、bytes 和 Path 路徑。

如果 cleanup_socket 為真，則 Unix socket 將在伺服器關閉時自動從檔案系統中刪除，除非在建立伺服器後替換了 socket。

有關此方法的引數資訊，請參閱 loop.create_server() 方法的文件。

可用性: Unix.

在 3.7 版的變更: 新增 ssl_handshake_timeout 與 start_serving 參數。path 參數現在可為一個 Path 物件。

在 3.11 版的變更: 增加 ssl_shutdown_timeout 參數。

在 3.13 版的變更: 加入 cleanup_socket 參數。

async loop.connect_accepted_socket(protocol_factory, sock, *, ssl=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None)

將已接受的連線包裝成傳輸層/協定對。

此方法可以由在 asyncio 外接受連線但使用 asyncio 處理連線的伺服器使用。

參數：

protocol_factory 必須是可呼叫的函式，回傳 protocol 實作。

sock 是從 socket.accept 回傳的預先存在的 socket 物件。

備註

引數 sock 將 socket 所有權轉移給所建立的傳輸 socket，請呼叫傳輸的 close() 方法。

ssl 可以設置為 SSLContext 以在已接受的連線上啟用 SSL。

（對於 SSL 連線）ssl_handshake_timeout 是在中斷連線之前等待 SSL 握手完成的時間（以秒為單位）。如果為 None（預設），則為 60.0 秒。

ssl_shutdown_timeout 是等待 SSL 關閉完成以前中斷連線的時間，以秒為單位。如果為 None （預設值），則會等待 30.0 秒。

回傳 (transport, protocol) 對。

在 3.5.3 版被加入.

在 3.7 版的變更: 增加 ssl_handshake_timeout 參數。

在 3.11 版的變更: 增加 ssl_shutdown_timeout 參數。

傳輸檔案

async loop.sendfile(transport, file, offset=0, count=None, *, fallback=True)

透過 transport 發送 file。回傳發送的總位元組數。

如果可用，該方法使用高性能 os.sendfile()。

file 必須是以二進位模式打開的常規檔案物件。

offset 告訴從哪裡開始讀取檔案。如果指定了，count 是要傳輸的總位元組數，而不是發送檔案直到達到 EOF。即使此方法引發錯誤時，檔案位置也始終更新，可以使用 file.tell() 取得實際發送的位元組數。

將 fallback 設置為 True 會使 asyncio 在平台不支援 sendfile 系統呼叫時（例如 Windows 或 Unix 上的 SSL socket）手動讀取和發送檔案。

如果系統不支援 sendfile 系統呼叫且 fallback 為 False，則引發 SendfileNotAvailableError。

在 3.7 版被加入.

TLS 升級

async loop.start_tls(transport, protocol, sslcontext, *, server_side=False, server_hostname=None, ssl_handshake_timeout=None, ssl_shutdown_timeout=None)

將基於傳輸的現有連線升級到 TLS。

建立 TLS 編解碼器實例並在 transport 和 protocol 之間插入它。編解碼器既實作了對於 transport 的協定，也實作了對於 protocol 的傳輸。

回傳建立的雙介面實例。在 await 後，protocol 必須停止使用原始的 transport，僅與回傳的物件通信，因為編碼器快取了 protocol 端的資料，並且與 transport 間歇性地交換額外的 TLS session 封包。

在某些情況下（例如傳入的傳輸已經關閉），此函式可能回傳 None。

參數：

transport 和 protocol 實例，由像 create_server() 和 create_connection() 等方法回傳。

sslcontext：配置好的 SSLContext 實例。

當升級伺服器端連線時（像由 create_server() 建立的那樣）傳遞 True。

server_hostname：設置或覆蓋將用於匹配目標伺服器憑證的主機名。

ssl_handshake_timeout （對於 TLS 連線）是等待 TLS 交握的時間，以秒為單位，在那之前若未完成則會中斷連線。如果為 None （預設值），則會等待 60.0 秒。

ssl_shutdown_timeout 是等待 SSL 關閉完成以前中斷連線的時間，以秒為單位。如果為 None （預設值），則會等待 30.0 秒。

在 3.7 版被加入.

在 3.11 版的變更: 增加 ssl_shutdown_timeout 參數。

監視檔案描述器

loop.add_reader(fd, callback, *args)

開始監視 fd 檔案描述器的讀取可用性，一但 fd 可讀取，使用指定引數叫用 callback。

任何預先存在、為 fd 註冊的回呼函式將被取消並替換為 callback。

loop.remove_reader(fd)

停止監視 fd 檔案描述器的讀取可用性。如果 fd 之前正在監視讀取，則回傳 True。

loop.add_writer(fd, callback, *args)

開始監視 fd 檔案描述器的寫入可用性，一旦 fd 可寫入，使用指定引數叫用 callback。

任何預先存在、為 fd 註冊的回呼函式將被取消並替換為 callback。

使用 functools.partial() 向 callback 傳送關鍵字引數。

loop.remove_writer(fd)

停止監視 fd 檔案描述器的寫入可用性。如果 fd 之前正在監視寫入，則回傳 True。

另請參閱平台支援部分以了解這些方法的一些限制。

直接使用 socket 物件

一般情況下，使用基於傳輸的 API（如 loop.create_connection() 和 loop.create_server()）的協定實作比直接使用 socket 的實作更快。然而在某些情況下性能不是關鍵，直接使用 socket 物件更方便。

async loop.sock_recv(sock, nbytes)

從 sock 接收最多 nbytes。socket.recv() 的非同步版本。

將接收到的資料作為 bytes 物件回傳。

sock 必須是非阻塞 socket。

在 3.7 版的變更: 儘管此方法一直記錄為協程方法，但 Python 3.7 之前的版本回傳 Future。自 Python 3.7 起，這是 async def 方法。

async loop.sock_recv_into(sock, buf)

從 sock 接收資料到 buf 緩衝區。仿照阻塞 socket.recv_into() 方法。

回傳寫入緩衝區位元組的數目。

sock 必須是非阻塞 socket。

在 3.7 版被加入.

async loop.sock_recvfrom(sock, bufsize)

從 sock 接收最多 bufsize 大小的資料單元。socket.recvfrom() 的非同步版本。

回傳一個元組 (received data, remote address)。

sock 必須是非阻塞 socket。

在 3.11 版被加入.

async loop.sock_recvfrom_into(sock, buf, nbytes=0)

從 sock 接收最多 nbytes 大小的資料單元到 buf。socket.recvfrom_into() 的非同步版本。

回傳一個元組 (number of bytes received, remote address)。

sock 必須是非阻塞 socket。

在 3.11 版被加入.

async loop.sock_sendall(sock, data)

將 data 發送到 sock socket。socket.sendall() 的非同步版本。

此方法將繼續發送到 socket，直到 data 中的所有資料都已發送或發生錯誤。成功時回傳 None。錯誤時引發例外。此外，沒有辦法確定接收端成功處理了多少資料（如果有的話）。

sock 必須是非阻塞 socket。

在 3.7 版的變更: 儘管該方法一直被記錄為協程方法，但在 Python 3.7 之前它回傳 Future。從 Python 3.7 開始，這是一個 async def 方法。

async loop.sock_sendto(sock, data, address)

從 sock 向 address 發送一個資料單元。socket.sendto() 的非同步版本。

回傳發送的位元組數。

sock 必須是非阻塞 socket。

在 3.11 版被加入.

async loop.sock_connect(sock, address)

將 sock 連線到位於 address 的遠端 socket。

socket.connect() 的非同步版本。

sock 必須是非阻塞 socket。

在 3.5.2 版的變更: 不再需要解析 address。sock_connect 將嘗試透過呼叫 socket.inet_pton() 檢查 address 是否已解析。如果沒有，將使用 loop.getaddrinfo() 解析 address。

也參考

loop.create_connection() 和 asyncio.open_connection()。

async loop.sock_accept(sock)

接受一個連線。模擬阻塞的 socket.accept() 方法。

Socket 必須繫結到一個地址並偵聽連線。回傳值是一個 (conn, address) 對，其中 conn 是一個 新 socket 物件，可在連線上發送和接收資料，address 是連接另一端對應的 socket 地址。

sock 必須是非阻塞 socket。

在 3.7 版的變更: 儘管該方法一直被記錄為協程方法，但在 Python 3.7 之前它回傳 Future。從 Python 3.7 開始，這是一個 async def 方法。

也參考

loop.create_server() 和 start_server()。

async loop.sock_sendfile(sock, file, offset=0, count=None, *, fallback=True)

如果可行，使用高性能 os.sendfile 發送檔案。回傳發送的總位元組數。

socket.sendfile() 的非同步版本。

sock 必須是非阻塞的 socket.SOCK_STREAM socket。

file 必須是以二進位模式打開的常規檔案物件。

offset 告訴從哪裡開始讀取檔案。如果指定了，count 是要傳輸的總位元組數，而不是發送檔案直到達到 EOF。即使此方法引發錯誤時，檔案位置也始終更新，可以使用 file.tell() 取得實際發送的位元組數。

當設置為 True 時，fallback 使 asyncio 在平台不支援 sendfile 系統呼叫時（例如 Windows 或 Unix 上的 SSL socket）手動讀取和發送檔案。

如果系統不支援 sendfile 系統呼叫且 fallback 為 False，引發 SendfileNotAvailableError。

sock 必須是非阻塞 socket。

在 3.7 版被加入.

DNS

async loop.getaddrinfo(host, port, *, family=0, type=0, proto=0, flags=0)

socket.getaddrinfo() 的非同步版本。

async loop.getnameinfo(sockaddr, flags=0)

socket.getnameinfo() 的非同步版本。

備註

Both getaddrinfo and getnameinfo internally utilize their synchronous versions through the loop's default thread pool executor. When this executor is saturated, these methods may experience delays, which higher-level networking libraries may report as increased timeouts. To mitigate this, consider using a custom executor for other user tasks, or setting a default executor with a larger number of workers.

在 3.7 版的變更: getaddrinfo 和 getnameinfo 方法一直被記錄為回傳協程，但在 Python 3.7 之前它們實際上回傳 asyncio.Future 物件。從 Python 3.7 開始，兩個方法都是協程。

使用管道

async loop.connect_read_pipe(protocol_factory, pipe)

在事件迴圈中註冊 pipe 的讀取端。

protocol_factory 必須是一個回傳 asyncio protocol 實作的可呼叫函式。

pipe 是 類檔案物件。

回傳 (transport, protocol) 對，其中 transport 支援 ReadTransport 介面，protocol 是由 protocol_factory 實例化的物件。

使用 SelectorEventLoop 事件迴圈時，pipe 設置為非阻塞模式。

async loop.connect_write_pipe(protocol_factory, pipe)

在事件迴圈中註冊 pipe 的寫入端。

protocol_factory 必須是一個回傳 asyncio protocol 實作的可呼叫函式。

pipe 是 file-like object。

回傳 (transport, protocol) 對，其中 transport 支援 WriteTransport 介面，protocol 是由 protocol_factory 實例化的物件。

使用 SelectorEventLoop 事件迴圈時，pipe 設置為非阻塞模式。

備註

SelectorEventLoop 在 Windows 上不支援上述方法。對於 Windows 請使用 ProactorEventLoop。

也參考

loop.subprocess_exec() 和 loop.subprocess_shell() 方法。

Unix 訊號

loop.add_signal_handler(signum, callback, *args)

將 callback 設置為 signum 訊號的處理程式。

該回呼將由 loop 叫用，與該事件迴圈的其他排隊回呼和可運行的協程一起。與使用 signal.signal() 註冊的訊號處理程式不同，使用此函式註冊的回呼允許與事件迴圈進行互動。

如果訊號號無效或不可捕獲，引發 ValueError。如果設定處理程序有問題，拋出 RuntimeError。

使用 functools.partial() 向 callback 傳送關鍵字引數。

像 signal.signal() 一樣，此函式必須在主執行緒中叫用。

loop.remove_signal_handler(sig)

移除 sig 訊號的處理程式。

如果訊號處理程式被移除，回傳 True；如果給定訊號沒有設置處理程式，回傳 False。

可用性: Unix.

也參考

signal 模組。

在執行緒池或行程池中執行程式碼

awaitable loop.run_in_executor(executor, func, *args)

安排在指定的執行器中呼叫 func。

The executor argument should be an concurrent.futures.Executor instance. The default executor is used if executor is None. The default executor can be set by loop.set_default_executor(), otherwise, a concurrent.futures.ThreadPoolExecutor will be lazy-initialized and used by run_in_executor() if needed.

範例：

import asyncio
import concurrent.futures

def blocking_io():
    # File operations (such as logging) can block the
    # event loop: run them in a thread pool.
    with open('/dev/urandom', 'rb') as f:
        return f.read(100)

def cpu_bound():
    # CPU-bound operations will block the event loop:
    # in general it is preferable to run them in a
    # process pool.
    return sum(i * i for i in range(10 ** 7))

async def main():
    loop = asyncio.get_running_loop()

    ## Options:

    # 1. Run in the default loop's executor:
    result = await loop.run_in_executor(
        None, blocking_io)
    print('default thread pool', result)

    # 2. Run in a custom thread pool:
    with concurrent.futures.ThreadPoolExecutor() as pool:
        result = await loop.run_in_executor(
            pool, blocking_io)
        print('custom thread pool', result)

    # 3. Run in a custom process pool:
    with concurrent.futures.ProcessPoolExecutor() as pool:
        result = await loop.run_in_executor(
            pool, cpu_bound)
        print('custom process pool', result)

    # 4. Run in a custom interpreter pool:
    with concurrent.futures.InterpreterPoolExecutor() as pool:
        result = await loop.run_in_executor(
            pool, cpu_bound)
        print('custom interpreter pool', result)

if __name__ == '__main__':
    asyncio.run(main())

請注意，由於 multiprocessing（由 ProcessPoolExecutor 使用）的特殊性，選項 3 需要進入點保護（if __name__ == '__main__'）。請參閱主模組的安全引入。

此方法回傳 asyncio.Future 物件。

使用 functools.partial() 將來關鍵字引數傳遞給 func。

在 3.5.3 版的變更: loop.run_in_executor() 不再配置它建立的執行緒池執行器的 max_workers，而是讓執行緒池執行器（ThreadPoolExecutor）設定預設值。

loop.set_default_executor(executor)

將 executor 設置為 run_in_executor() 使用的預設執行器。executor 必須是 ThreadPoolExecutor（也包含 InterpreterPoolExecutor）的實例。

在 3.11 版的變更: executor 必須是 ThreadPoolExecutor 的實例。

錯誤處理 API

允許自訂事件迴圈中的例外處理方式。

loop.set_exception_handler(handler)

將 handler 設定為新的事件迴圈例外處理程式。

如果 handler 是 None，則將設置預設例外處理程式。否則，handler 必須是一個可呼叫物件，簽名匹配 (loop, context)，其中 loop 是參照活躍事件迴圈的，context 是包含例外詳細資訊的 dict 物件（有關情境的詳細資訊，請參閱 call_exception_handler() 文件）。

如果代表 Task 或 Handle 呼叫處理程式，它將在該任務或回呼處理程式的 contextvars.Context 中運行。

在 3.12 版的變更: 處理程式可能在引發例外的任務或處理程式的 Context 中被呼叫。

loop.get_exception_handler()

回傳目前的例外處理程式，如果未設置自訂例外處理程式，則回傳 None。

在 3.5.2 版被加入.

loop.default_exception_handler(context)

預設例外處理程式。

當發生例外且未設置例外處理程式時呼叫此函式。自訂例外處理程式可以呼叫此函式以轉由預設處理程式處理。

context 參數與 call_exception_handler() 中的意思相同。

loop.call_exception_handler(context)

呼叫目前事件迴圈例外處理程式。

context 是一個包含以下鍵的 dict 物件（未來的 Python 版本中可能會引入新的鍵）:

'message'：錯誤訊息；

'exception'（可選）：例外物件；

'future'（可選）： asyncio.Future 實例；

'task'（可選）： asyncio.Task 實例；

'handle'（可選）： asyncio.Handle 實例；

'protocol'（可選）： Protocol 實例；

'transport'（可選）： Transport 實例；

'socket'（可選）： socket.socket 實例；

'source_traceback' (optional): Traceback of the source;

'handle_traceback' (optional): Traceback of the handle;

'asyncgen'(可選)： 非同步產生器引發

例外。

備註

此方法不應在子類別事件迴圈中被覆寫。為了自訂例外處理，請使用 set_exception_handler() 方法。

啟用除錯模式

loop.get_debug()

取得事件迴圈的除錯模式（bool）。

如果環境變數 PYTHONASYNCIODEBUG 被設定為非空字串，則預設值為 True，否則為 False。

loop.set_debug(enabled: bool)

設定事件迴圈的除錯模式。

在 3.7 版的變更: 現在也可以使用新的 Python 開發模式 啟用除錯模式。

loop.slow_callback_duration

此屬性可用於設定被視為"慢"的最短執行時間（以秒為單位）。啟用偵錯模式後，"慢"回呼將被記錄。

預設值為 100 毫秒

也參考

asyncio 的除錯模式。

運行子行程

本小節描述的方法是低階的。在常規的 async/await 程式碼中，請考慮使用高階 asyncio.create_subprocess_shell() 和 asyncio.create_subprocess_exec() 輔助功能而不是。

備註

在 Windows 上，預設事件迴圈 ProactorEventLoop 支援子行程，而 SelectorEventLoop 不支援。詳細資訊請參見 Windows 上對於子行程的支援。

async loop.subprocess_exec(protocol_factory, *args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, **kwargs)

從 args 指定的一個或多個字串引數建立子行程。

args 必須是由以下項表示的字串串列：

str；

或 bytes，編碼為 檔案系統編碼。

第一個字串指定程序可執行檔案，其餘字串指定引數。字串引數一起組成程序的 argv。

這與標準函式庫 subprocess.Popen 類似，使用 shell=False 呼叫並將字串串列作為第一個引數傳遞；然而，Popen 接受單個字串串列引數，subprocess_exec 接受多個字串引數。

protocol_factory 必須是回傳 asyncio.SubprocessProtocol 子類別的可呼叫物件。

其他參數：

stdin 可以是以下任意一個：

類檔案物件

現有的檔案描述器（正整數），例如用 os.pipe() 建立的

subprocess.PIPE 常數（預設），它將建立一個新的管道並連線，

值 None 將使子行程從此行程繼承檔案描述器

subprocess.DEVNULL 常數，表示將使用特殊的 os.devnull 檔案

stdout 可以是以下任意一個：

類檔案物件

subprocess.PIPE 常數（預設），它將建立一個新的管道並連線，

值 None 將使子行程從此行程繼承檔案描述器

subprocess.DEVNULL 常數，表示將使用特殊的 os.devnull 檔案

stderr 可以是以下任意一個：

類檔案物件

subprocess.PIPE 常數（預設），它將建立一個新的管道並連線，

值 None 將使子行程從此行程繼承檔案描述器

subprocess.DEVNULL 常數，表示將使用特殊的 os.devnull 檔案

subprocess.STDOUT 常數，它將標準錯誤串流連線到行程的標準輸出串流

所有其他關鍵字引數都會傳遞給 subprocess.Popen 而不進行直譯，但 bufsize、universal_newlines、shell、text、encoding 和 errors 除外，這些不應該指定。

asyncio 子行程 API 不支援將串流解碼為文本。可以使用 bytes.decode() 將從串流回傳的位元組轉換為文本。

如果傳遞給 stdin、stdout 或 stderr 的類檔案物件表示管道，則該管道的另一端應該使用 connect_write_pipe() 或 connect_read_pipe() 註冊到事件迴圈中。

有關其他引數的文件，請參閱 subprocess.Popen 類別的建構函式。

回傳 (transport, protocol) 對，其中 transport 符合 asyncio.SubprocessTransport 基底類別，protocol 是由 protocol_factory 實例化的物件。

If the transport is closed or is garbage collected, the child process is killed if it is still running.

async loop.subprocess_shell(protocol_factory, cmd, *, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, **kwargs)

使用平台的 "shell" 語法從 cmd 建立子行程，cmd 可以是 str 或編碼為 檔案系統編碼 的 bytes 字串。

這類似於標準函式庫中的 subprocess.Popen 類別，使用 shell=True 呼叫。

protocol_factory 必須是回傳 SubprocessProtocol 子類別的可呼叫物件。

有關其餘引數的更多詳細資訊，請參閱 subprocess_exec()。

回傳一對 (transport, protocol)，其中 transport 符合 SubprocessTransport 基底類別，而 protocol 是由 protocol_factory 實例化的物件。

If the transport is closed or is garbage collected, the child process is killed if it is still running.

備註

由應用程式負責確保適當引用所有空白和特殊字元，以避免 shell 注入 [https://en.wikipedia.org/wiki/Shell_injection#Shell_injection]風險。可以使用 shlex.quote() 函式來正確跳脫用於構建 shell 命令的字串中的空白和特殊字元。

回呼處理

class asyncio.Handle

由 loop.call_soon() 和 loop.call_soon_threadsafe() 回傳的回呼包裝器。

get_context()

回傳與處理相關聯的 contextvars.Context 物件。

在 3.12 版被加入.

cancel()

取消回呼。如果回呼已被取消或執行，此方法將不起作用。

cancelled()

如果回呼已被取消，回傳 True。

在 3.7 版被加入.

class asyncio.TimerHandle

由 loop.call_later() 和 loop.call_at() 回傳的回呼包裝器。

這個類別是 Handle 的子類別。

when()

回傳預定的回呼時間，以 float 秒為單位。

時間是一個絕對的時間戳，使用與 loop.time() 相同的時間參照。

在 3.7 版被加入.

Server 物件

Server 物件是由 loop.create_server()、loop.create_unix_server()、start_server() 和 start_unix_server() 函式所建立。

請勿直接實例化 Server 類別。

class asyncio.Server

Server 物件是非同步情境管理器。當在 async with 陳述中使用時，可以保證在完成 async with 陳述時，Server 物件將會關閉並停止接受新的連線：

srv = await loop.create_server(...)

async with srv:
    # 一些程式碼

# 此時 srv 已關閉，不再接受新的連線。

在 3.7 版的變更: 自 Python 3.7 起，Server 物件是非同步情境管理器。

在 3.11 版的變更: 此類別在 Python 3.9.11、3.10.3 和 3.11 中以 asyncio.Server 的形式被公開。

close()

停止服務：關閉監聽的 sockets 並將 sockets 屬性設為 None。

代表現有傳入用戶端連線的 sockets 仍然保持開啟。

伺服器以非同步方式關閉；使用 wait_closed() 協程等待伺服器關閉（不再有活躍連線）。

close_clients()

關閉所有現有的傳入用戶端連線。

在所有關聯的傳輸上呼叫 close()。

close() should be called before close_clients() when closing the server to avoid races with new clients connecting.

在 3.13 版被加入.

abort_clients()

立即關閉所有現有的傳入用戶端連線，而不等待待定操作完成。

在所有關聯的傳輸上呼叫 abort()。

close() should be called before abort_clients() when closing the server to avoid races with new clients connecting.

在 3.13 版被加入.

get_loop()

回傳與伺服器物件關聯的事件迴圈。

在 3.7 版被加入.

async start_serving()

開始接受連線。

此方法是幂等的，因此可以在伺服器已經運行時呼叫。

start_serving 僅限關鍵字參數只能在 loop.create_server() 和 asyncio.start_server() 中使用，允許建立一個最初不接受連線的 Server 物件。在這種情況下，可以使用 Server.start_serving() 或 Server.serve_forever() 來使 Server 開始接受連線。

在 3.7 版被加入.

async serve_forever()

開始接受連線，直到協程被取消。取消 serve_forever 任務會導致伺服器關閉。

如果伺服器已經接受連線，則可以呼叫此方法。每個 Server 物件只能存在一個 serve_forever 任務。

範例：

async def client_connected(reader, writer):
    # 透過讀取器/寫入器串流
    # 與用戶端溝通。例如：
    await reader.readline()

async def main(host, port):
    srv = await asyncio.start_server(
        client_connected, host, port)
    await srv.serve_forever()

asyncio.run(main('127.0.0.1', 0))

在 3.7 版被加入.

is_serving()

如果伺服器正在接受新連線，則回傳 True。

在 3.7 版被加入.

async wait_closed()

等待 close() 方法完成且所有活動連線都已結束。

sockets

伺服器正在監聽的類似 socket 的物件串列，asyncio.trsock.TransportSocket。

在 3.7 版的變更: 在 Python 3.7 之前，Server.sockets 曾經直接回傳內部伺服器 sockets 的串列。在 3.7 中回傳了該串列的副本。

事件迴圈實作

asyncio 內附兩個不同的事件迴圈實作：SelectorEventLoop 和 ProactorEventLoop。

預設情況下，asyncio 被配置為要使用 EventLoop。

class asyncio.SelectorEventLoop

基於 selectors 模組的一個 AbstractEventLoop 子類別。

使用特定平台上最有效的 selector。也可以手動配置要使用的確切 selector 實作：

import asyncio
import selectors

async def main():
   ...

loop_factory = lambda: asyncio.SelectorEventLoop(selectors.SelectSelector())
asyncio.run(main(), loop_factory=loop_factory)

可用性: Unix, Windows.

class asyncio.ProactorEventLoop

用於 Windows 的 AbstractEventLoop 子類別，使用「I/O 完成埠 (IOCP, I/O Completion Ports)」。

可用性: Windows.

也參考

I/O 完成埠的 MSDN 文件 [https://learn.microsoft.com/windows/win32/fileio/i-o-completion-ports]。

class asyncio.EventLoop

An alias to the most efficient available subclass of AbstractEventLoop for the given platform.

在 Unix 上是 SelectorEventLoop 的別名，在 Windows 上是 ProactorEventLoop 的別名。

在 3.13 版被加入.

class asyncio.AbstractEventLoop

為符合 asyncio 標準的事件迴圈的抽象基礎類別。

事件迴圈方法 部分列出了替代 AbstractEventLoop 實作應該定義的所有方法。

範例

請注意，本節中的所有範例都 故意 展示如何使用低階事件迴圈 API，如 loop.run_forever() 和 loop.call_soon()。現代 asyncio 應用程式很少需要這種方式撰寫；請考慮使用高階的函式，如 asyncio.run()。

使用 call_soon() 的 Hello World 範例

使用 loop.call_soon() 方法排程回呼的範例。回呼會顯示 "Hello World"，然後停止事件迴圈：

import asyncio

def hello_world(loop):
    """列印 'Hello World' 並停止事件迴圈的回呼"""
    print('Hello World')
    loop.stop()

loop = asyncio.new_event_loop()

# 排程對 hello_world() 的呼叫
loop.call_soon(hello_world, loop)

# 阻塞呼叫被 loop.stop() 中斷
try:
    loop.run_forever()
finally:
    loop.close()

也參考

使用協程和 run() 函式建立的類似 Hello World 範例。

使用 call_later() 顯示目前日期

一個回呼的範例，每秒顯示目前日期。回呼使用 loop.call_later() 方法在 5 秒後重新排程自己，然後停止事件迴圈：

import asyncio
import datetime

def display_date(end_time, loop):
    print(datetime.datetime.now())
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, display_date, end_time, loop)
    else:
        loop.stop()

loop = asyncio.new_event_loop()

# 排程 display_date() 的第一次呼叫
end_time = loop.time() + 5.0
loop.call_soon(display_date, end_time, loop)

# 阻塞呼叫被 loop.stop() 中斷
try:
    loop.run_forever()
finally:
    loop.close()

也參考

使用協程和 run() 函式建立的類似 current date 範例。

監聽檔案描述器以進行讀取事件

使用 loop.add_reader() 方法等待檔案描述器接收到某些資料，然後關閉事件迴圈：

import asyncio
from socket import socketpair

# 建立一對連接的檔案描述器
rsock, wsock = socketpair()

loop = asyncio.new_event_loop()

def reader():
    data = rsock.recv(100)
    print("Received:", data.decode())

    # 我們完成了：註銷檔案描述器
    loop.remove_reader(rsock)

    # 停止事件迴圈
    loop.stop()

# 為讀取事件註冊檔案描述器
loop.add_reader(rsock, reader)

# 模擬從網路接收資料
loop.call_soon(wsock.send, 'abc'.encode())

try:
    # 運行事件迴圈
    loop.run_forever()
finally:
    # 我們完成了。關閉 socket 和事件迴圈。
    rsock.close()
    wsock.close()
    loop.close()

也參考

使用傳輸、協定和 loop.create_connection() 方法的類似 範例。

另一個使用高階 asyncio.open_connection() 函式和串流的類似 範例。

設定 SIGINT 和 SIGTERM 的訊號處理程式

（此 signals 範例僅在 Unix 上運作。）

使用 loop.add_signal_handler() 方法註冊訊號 SIGINT 和 SIGTERM 的處理程式：

import asyncio
import functools
import os
import signal

def ask_exit(signame, loop):
    print("got signal %s: exit" % signame)
    loop.stop()

async def main():
    loop = asyncio.get_running_loop()

    for signame in {'SIGINT', 'SIGTERM'}:
        loop.add_signal_handler(
            getattr(signal, signame),
            functools.partial(ask_exit, signame, loop))

    await asyncio.sleep(3600)

print("Event loop running for 1 hour, press Ctrl+C to interrupt.")
print(f"pid {os.getpid()}: send SIGINT or SIGTERM to exit.")

asyncio.run(main())

Futures

原始碼：Lib/asyncio/futures.py、source:`Lib/asyncio/base_futures.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/futures.py、source:`Lib/asyncio/base_futures.py]

Future 物件被用來連結低階回呼式程式和高階 async/await 程式。

Future 函式

asyncio.isfuture(obj)

如果 obj 為下面任意物件，回傳 True：

一個 asyncio.Future 的實例、

一個 asyncio.Task 的實例、

帶有 _asyncio_future_blocking 屬性的類 Future 物件 (Future-like object)。

在 3.5 版被加入.

asyncio.ensure_future(obj, *, loop=None)

回傳：

obj 引數會保持原樣，obj 須為 Future、Task 或類 Future 物件（可以用 isfuture() 來進行檢查。）

包裝 (wrap) 了 obj 的 Task 物件，如果 obj 是一個協程 (coroutine) (可以用 iscoroutine() 來進行檢查)；在此情況下該協程將透過 ensure_future() 來排程。

一個會等待 obj 的 Task 物件，obj 須為一個可等待物件（inspect.isawaitable() 用於測試。)

如果 obj 不是上述物件的話會引發一個 TypeError 例外。

重要

將參照 (reference) 儲存至此函式的結果，用以防止任務在執行中消失。

請見 create_task() 函式，它是建立新 Task 的推薦方法。或者使用 asyncio.TaskGroup，它會在內部保留對 Task 的參照。

在 3.5.1 版的變更: 這個函式接受任意 awaitable 物件。

在 3.10 版之後被棄用: 如果 obj 不是類 Future 物件且 loop 並未被指定，同時沒有正在執行的事件迴圈 (event loop)，則會發出棄用警告。

asyncio.wrap_future(future, *, loop=None)

將一個 concurrent.futures.Future 物件包裝到 asyncio.Future 物件中。

在 3.10 版之後被棄用: 如果 future 不是類 Future 物件且 loop 未被指定，同時沒有正在執行的事件迴圈，則會發出棄用警告。

Future 物件

class asyncio.Future(*, loop=None)

一個 Future 代表一個非同步運算的最終結果。並不支援執行緒安全 (thread-safe)。

Future 是一個 awaitable 物件。協程可以等待 Future 物件直到它們有結果或例外被設置、或者被取消。一個 Future 可被多次等待而結果都會是相同的。

Future 通常用於讓低階基於回呼的程式（例如在協定實作中使用 asyncio transports）能夠與高階 async/await 程式互動。

經驗法則為永遠不要在提供給使用者的 API 中公開 Future 物件，同時建議使用 loop.create_future() 來建立 Future 物件。如此一來，不同實作的事件迴圈可以注入自己最佳化實作的 Future 物件。

在 3.7 版的變更: 加入對 contextvars 模組的支援。

在 3.10 版之後被棄用: 如果未指定 loop 並且沒有正在執行的事件迴圈則會發出棄用警告。

result()

回傳 Future 的結果。

如果 Future 狀態為 done（完成），並擁有 set_result() 方法設定的一個結果，則回傳該結果之值。

如果 Future 狀態為 done，並擁有 set_exception() 方法設定的一個例外，那麼這個方法會引發該例外。

如果 Future 已被 cancelled（取消），此方法會引發一個 CancelledError 例外。

如果 Future 的結果還不可用，此方法會引發一個 InvalidStateError 例外。

set_result(result)

將 Future 標記為 done 並設定其結果。

如果 Future 已經 done 則引發一個 InvalidStateError 錯誤。

set_exception(exception)

將 Future 標記為 done 並設定一個例外。

如果 Future 已經 done 則引發一個 InvalidStateError 錯誤。

done()

如果 Future 已為 done 則回傳 True。

如果 Future 有被 cancelled、set_result() 有被呼叫來為其設定結果、或 set_exception() 有被呼叫為其設定例外，那麼它就是 done。

cancelled()

如果 Future 已經被 cancelled 則回傳 True。

這個方法通常在為 Future 設定結果或例外前用來確認它還沒被 cancelled：

if not fut.cancelled():
    fut.set_result(42)

add_done_callback(callback, *, context=None)

新增一個在 Future 為 done 時執行的回呼函式。

呼叫 callback 並附帶做為唯一引數的 Future 物件。

如果呼叫這個方法時 Future 已經為 done，回呼函式會被 loop.call_soon() 排程。

可選僅限關鍵字引數 context 用來指定一個讓 callback 執行於其中的客製化 contextvars.Context 物件。如果沒有提供 context，則使用目前情境。

可以用 functools.partial() 傳遞引數給回呼函式，例如：

# Call 'print("Future:", fut)' when "fut" is done.
fut.add_done_callback(
    functools.partial(print, "Future:"))

在 3.7 版的變更: 加入僅限關鍵字參數 context。更多細節請參閱 PEP 567 [https://peps.python.org/pep-0567/]。

remove_done_callback(callback)

從回呼列表中移除 callback。

回傳被移除的回呼函式數量，通常為 1，除非一個回呼函式被多次加入。

cancel(msg=None)

取消 Future 並為回呼函式排程。

如果 Future 已經是 done 或 cancelled，回傳 False。否則將 Future 狀態改為 cancelled 並在為回呼函式排程後回傳 True。

在 3.9 版的變更: 新增 msg 參數。

exception()

回傳被設定於此 Future 的例外。

只有 Future 在 done 時才回傳例外（如果沒有設定例外則回傳 None）。

如果 Future 已被 cancelled（取消），此方法會引發一個 CancelledError 例外。

如果 Future 還不為 done，此方法會引發一個 InvalidStateError 例外。

get_loop()

回傳已被 Future 物件繫結 (bind) 的事件迴圈。

在 3.7 版被加入.

這個例子建立一個 Future 物件，建立一個非同步 Task 並為其排程以設定 Future 結果，然後等待 Future 結果出現：

async def set_after(fut, delay, value):
    # Sleep for *delay* seconds.
    await asyncio.sleep(delay)

    # Set *value* as a result of *fut* Future.
    fut.set_result(value)

async def main():
    # Get the current event loop.
    loop = asyncio.get_running_loop()

    # Create a new Future object.
    fut = loop.create_future()

    # Run "set_after()" coroutine in a parallel Task.
    # We are using the low-level "loop.create_task()" API here because
    # we already have a reference to the event loop at hand.
    # Otherwise we could have just used "asyncio.create_task()".
    loop.create_task(
        set_after(fut, 1, '... world'))

    print('hello ...')

    # Wait until *fut* has a result (1 second) and print it.
    print(await fut)

asyncio.run(main())

重要

該 Future 物件是為了模仿 concurrent.futures.Future 而設計。主要差異包含：

與 asyncio 的 Future 不同，concurrent.futures.Future 實例不可被等待。

asyncio.Future.result() 和 asyncio.Future.exception() 不接受 timeout 引數。

Future 不為 done 時 asyncio.Future.result() 和 asyncio.Future.exception() 會引發一個 InvalidStateError 例外。

使用 asyncio.Future.add_done_callback() 註冊的回呼函式不會立即呼叫，而是被 loop.call_soon() 排程。

asyncio Future 不能與 concurrent.futures.wait() 和 concurrent.futures.as_completed() 函式相容。

asyncio.Future.cancel() 接受一個可選的 msg 引數，但 concurrent.futures.Future.cancel() 無此引數。

傳輸與協定

前言

Transports and Protocols are used by the low-level event loop APIs such as loop.create_connection(). They use callback-based programming style and enable high-performance implementations of network or IPC protocols (e.g. HTTP).

Essentially, transports and protocols should only be used in libraries and frameworks and never in high-level asyncio applications.

This documentation page covers both Transports and Protocols.

Introduction

At the highest level, the transport is concerned with how bytes are transmitted, while the protocol determines which bytes to transmit (and to some extent when).

A different way of saying the same thing: a transport is an abstraction for a socket (or similar I/O endpoint) while a protocol is an abstraction for an application, from the transport's point of view.

Yet another view is the transport and protocol interfaces together define an abstract interface for using network I/O and interprocess I/O.

There is always a 1:1 relationship between transport and protocol objects: the protocol calls transport methods to send data, while the transport calls protocol methods to pass it data that has been received.

Most of connection oriented event loop methods (such as loop.create_connection()) usually accept a protocol_factory argument used to create a Protocol object for an accepted connection, represented by a Transport object. Such methods usually return a tuple of (transport, protocol).

目錄

This documentation page contains the following sections:

The Transports section documents asyncio BaseTransport, ReadTransport, WriteTransport, Transport, DatagramTransport, and SubprocessTransport classes.

The Protocols section documents asyncio BaseProtocol, Protocol, BufferedProtocol, DatagramProtocol, and SubprocessProtocol classes.

The Examples section showcases how to work with transports, protocols, and low-level event loop APIs.

Transports

原始碼：Lib/asyncio/transports.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/transports.py]

Transports are classes provided by asyncio in order to abstract various kinds of communication channels.

Transport objects are always instantiated by an asyncio event loop.

asyncio implements transports for TCP, UDP, SSL, and subprocess pipes. The methods available on a transport depend on the transport's kind.

The transport classes are not thread safe.

Transports Hierarchy

class asyncio.BaseTransport

Base class for all transports. Contains methods that all asyncio transports share.

class asyncio.WriteTransport(BaseTransport)

A base transport for write-only connections.

Instances of the WriteTransport class are returned from the loop.connect_write_pipe() event loop method and are also used by subprocess-related methods like loop.subprocess_exec().

class asyncio.ReadTransport(BaseTransport)

A base transport for read-only connections.

Instances of the ReadTransport class are returned from the loop.connect_read_pipe() event loop method and are also used by subprocess-related methods like loop.subprocess_exec().

class asyncio.Transport(WriteTransport, ReadTransport)

Interface representing a bidirectional transport, such as a TCP connection.

The user does not instantiate a transport directly; they call a utility function, passing it a protocol factory and other information necessary to create the transport and protocol.

Instances of the Transport class are returned from or used by event loop methods like loop.create_connection(), loop.create_unix_connection(), loop.create_server(), loop.sendfile(), etc.

class asyncio.DatagramTransport(BaseTransport)

A transport for datagram (UDP) connections.

Instances of the DatagramTransport class are returned from the loop.create_datagram_endpoint() event loop method.

class asyncio.SubprocessTransport(BaseTransport)

An abstraction to represent a connection between a parent and its child OS process.

Instances of the SubprocessTransport class are returned from event loop methods loop.subprocess_shell() and loop.subprocess_exec().

Base Transport

BaseTransport.close()

Close the transport.

If the transport has a buffer for outgoing data, buffered data will be flushed asynchronously. No more data will be received. After all buffered data is flushed, the protocol's protocol.connection_lost() method will be called with None as its argument. The transport should not be used once it is closed.

BaseTransport.is_closing()

Return True if the transport is closing or is closed.

BaseTransport.get_extra_info(name, default=None)

Return information about the transport or underlying resources it uses.

name is a string representing the piece of transport-specific information to get.

default is the value to return if the information is not available, or if the transport does not support querying it with the given third-party event loop implementation or on the current platform.

For example, the following code attempts to get the underlying socket object of the transport:

sock = transport.get_extra_info('socket')
if sock is not None:
    print(sock.getsockopt(...))

Categories of information that can be queried on some transports:

socket:

'peername': the remote address to which the socket is connected, result of socket.socket.getpeername() (None on error)

'socket': socket.socket instance

'sockname': the socket's own address, result of socket.socket.getsockname()

SSL socket:

'compression': the compression algorithm being used as a string, or None if the connection isn't compressed; result of ssl.SSLSocket.compression()

'cipher': a three-value tuple containing the name of the cipher being used, the version of the SSL protocol that defines its use, and the number of secret bits being used; result of ssl.SSLSocket.cipher()

'peercert': peer certificate; result of ssl.SSLSocket.getpeercert()

'sslcontext': ssl.SSLContext instance

'ssl_object': ssl.SSLObject or ssl.SSLSocket instance

pipe:

'pipe': pipe object

subprocess:

'subprocess': subprocess.Popen instance

BaseTransport.set_protocol(protocol)

Set a new protocol.

Switching protocol should only be done when both protocols are documented to support the switch.

BaseTransport.get_protocol()

Return the current protocol.

Read-only Transports

ReadTransport.is_reading()

Return True if the transport is receiving new data.

在 3.7 版被加入.

ReadTransport.pause_reading()

Pause the receiving end of the transport. No data will be passed to the protocol's protocol.data_received() method until resume_reading() is called.

在 3.7 版的變更: The method is idempotent, i.e. it can be called when the transport is already paused or closed.

ReadTransport.resume_reading()

Resume the receiving end. The protocol's protocol.data_received() method will be called once again if some data is available for reading.

在 3.7 版的變更: The method is idempotent, i.e. it can be called when the transport is already reading.

Write-only Transports

WriteTransport.abort()

Close the transport immediately, without waiting for pending operations to complete. Buffered data will be lost. No more data will be received. The protocol's protocol.connection_lost() method will eventually be called with None as its argument.

WriteTransport.can_write_eof()

Return True if the transport supports write_eof(), False if not.

WriteTransport.get_write_buffer_size()

Return the current size of the output buffer used by the transport.

WriteTransport.get_write_buffer_limits()

Get the high and low watermarks for write flow control. Return a tuple (low, high) where low and high are positive number of bytes.

Use set_write_buffer_limits() to set the limits.

在 3.4.2 版被加入.

WriteTransport.set_write_buffer_limits(high=None, low=None)

Set the high and low watermarks for write flow control.

These two values (measured in number of bytes) control when the protocol's protocol.pause_writing() and protocol.resume_writing() methods are called. If specified, the low watermark must be less than or equal to the high watermark. Neither high nor low can be negative.

pause_writing() is called when the buffer size becomes greater than or equal to the high value. If writing has been paused, resume_writing() is called when the buffer size becomes less than or equal to the low value.

The defaults are implementation-specific. If only the high watermark is given, the low watermark defaults to an implementation-specific value less than or equal to the high watermark. Setting high to zero forces low to zero as well, and causes pause_writing() to be called whenever the buffer becomes non-empty. Setting low to zero causes resume_writing() to be called only once the buffer is empty. Use of zero for either limit is generally sub-optimal as it reduces opportunities for doing I/O and computation concurrently.

Use get_write_buffer_limits() to get the limits.

WriteTransport.write(data)

Write some data bytes to the transport.

This method does not block; it buffers the data and arranges for it to be sent out asynchronously.

WriteTransport.writelines(list_of_data)

Write a list (or any iterable) of data bytes to the transport. This is functionally equivalent to calling write() on each element yielded by the iterable, but may be implemented more efficiently.

WriteTransport.write_eof()

Close the write end of the transport after flushing all buffered data. Data may still be received.

This method can raise NotImplementedError if the transport (e.g. SSL) doesn't support half-closed connections.

Datagram Transports

DatagramTransport.sendto(data, addr=None)

Send the data bytes to the remote peer given by addr (a transport-dependent target address). If addr is None, the data is sent to the target address given on transport creation.

This method does not block; it buffers the data and arranges for it to be sent out asynchronously.

在 3.13 版的變更: This method can be called with an empty bytes object to send a zero-length datagram. The buffer size calculation used for flow control is also updated to account for the datagram header.

DatagramTransport.abort()

Close the transport immediately, without waiting for pending operations to complete. Buffered data will be lost. No more data will be received. The protocol's protocol.connection_lost() method will eventually be called with None as its argument.

Subprocess Transports

SubprocessTransport.get_pid()

Return the subprocess process id as an integer.

SubprocessTransport.get_pipe_transport(fd)

Return the transport for the communication pipe corresponding to the integer file descriptor fd:

0: writable streaming transport of the standard input (stdin), or None if the subprocess was not created with stdin=PIPE

1: readable streaming transport of the standard output (stdout), or None if the subprocess was not created with stdout=PIPE

2: readable streaming transport of the standard error (stderr), or None if the subprocess was not created with stderr=PIPE

other fd: None

SubprocessTransport.get_returncode()

Return the subprocess return code as an integer or None if it hasn't returned, which is similar to the subprocess.Popen.returncode attribute.

SubprocessTransport.kill()

Kill the subprocess.

On POSIX systems, the function sends SIGKILL to the subprocess. On Windows, this method is an alias for terminate().

另請參閱 subprocess.Popen.kill()。

SubprocessTransport.send_signal(signal)

Send the signal number to the subprocess, as in subprocess.Popen.send_signal().

SubprocessTransport.terminate()

Stop the subprocess.

On POSIX systems, this method sends SIGTERM to the subprocess. On Windows, the Windows API function TerminateProcess() is called to stop the subprocess.

另請參閱 subprocess.Popen.terminate()。

SubprocessTransport.close()

Kill the subprocess by calling the kill() method.

If the subprocess hasn't returned yet, and close transports of stdin, stdout, and stderr pipes.

Protocols

原始碼：Lib/asyncio/protocols.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/protocols.py]

asyncio provides a set of abstract base classes that should be used to implement network protocols. Those classes are meant to be used together with transports.

Subclasses of abstract base protocol classes may implement some or all methods. All these methods are callbacks: they are called by transports on certain events, for example when some data is received. A base protocol method should be called by the corresponding transport.

Base Protocols

class asyncio.BaseProtocol

Base protocol with methods that all protocols share.

class asyncio.Protocol(BaseProtocol)

The base class for implementing streaming protocols (TCP, Unix sockets, etc).

class asyncio.BufferedProtocol(BaseProtocol)

A base class for implementing streaming protocols with manual control of the receive buffer.

class asyncio.DatagramProtocol(BaseProtocol)

The base class for implementing datagram (UDP) protocols.

class asyncio.SubprocessProtocol(BaseProtocol)

The base class for implementing protocols communicating with child processes (unidirectional pipes).

Base Protocol

All asyncio protocols can implement Base Protocol callbacks.

Connection Callbacks

Connection callbacks are called on all protocols, exactly once per a successful connection. All other protocol callbacks can only be called between those two methods.

BaseProtocol.connection_made(transport)

Called when a connection is made.

The transport argument is the transport representing the connection. The protocol is responsible for storing the reference to its transport.

BaseProtocol.connection_lost(exc)

Called when the connection is lost or closed.

The argument is either an exception object or None. The latter means a regular EOF is received, or the connection was aborted or closed by this side of the connection.

Flow Control Callbacks

Flow control callbacks can be called by transports to pause or resume writing performed by the protocol.

See the documentation of the set_write_buffer_limits() method for more details.

BaseProtocol.pause_writing()

Called when the transport's buffer goes over the high watermark.

BaseProtocol.resume_writing()

Called when the transport's buffer drains below the low watermark.

If the buffer size equals the high watermark, pause_writing() is not called: the buffer size must go strictly over.

Conversely, resume_writing() is called when the buffer size is equal or lower than the low watermark. These end conditions are important to ensure that things go as expected when either mark is zero.

Streaming Protocols

Event methods, such as loop.create_server(), loop.create_unix_server(), loop.create_connection(), loop.create_unix_connection(), loop.connect_accepted_socket(), loop.connect_read_pipe(), and loop.connect_write_pipe() accept factories that return streaming protocols.

Protocol.data_received(data)

Called when some data is received. data is a non-empty bytes object containing the incoming data.

Whether the data is buffered, chunked or reassembled depends on the transport. In general, you shouldn't rely on specific semantics and instead make your parsing generic and flexible. However, data is always received in the correct order.

The method can be called an arbitrary number of times while a connection is open.

However, protocol.eof_received() is called at most once. Once eof_received() is called, data_received() is not called anymore.

Protocol.eof_received()

Called when the other end signals it won't send any more data (for example by calling transport.write_eof(), if the other end also uses asyncio).

This method may return a false value (including None), in which case the transport will close itself. Conversely, if this method returns a true value, the protocol used determines whether to close the transport. Since the default implementation returns None, it implicitly closes the connection.

Some transports, including SSL, don't support half-closed connections, in which case returning true from this method will result in the connection being closed.

State machine:

start -> connection_made
    [-> data_received]*
    [-> eof_received]?
-> connection_lost -> end

Buffered Streaming Protocols

在 3.7 版被加入.

Buffered Protocols can be used with any event loop method that supports Streaming Protocols.

BufferedProtocol implementations allow explicit manual allocation and control of the receive buffer. Event loops can then use the buffer provided by the protocol to avoid unnecessary data copies. This can result in noticeable performance improvement for protocols that receive big amounts of data. Sophisticated protocol implementations can significantly reduce the number of buffer allocations.

The following callbacks are called on BufferedProtocol instances:

BufferedProtocol.get_buffer(sizehint)

Called to allocate a new receive buffer.

sizehint is the recommended minimum size for the returned buffer. It is acceptable to return smaller or larger buffers than what sizehint suggests. When set to -1, the buffer size can be arbitrary. It is an error to return a buffer with a zero size.

get_buffer() must return an object implementing the buffer protocol.

BufferedProtocol.buffer_updated(nbytes)

Called when the buffer was updated with the received data.

nbytes is the total number of bytes that were written to the buffer.

BufferedProtocol.eof_received()

See the documentation of the protocol.eof_received() method.

get_buffer() can be called an arbitrary number of times during a connection. However, protocol.eof_received() is called at most once and, if called, get_buffer() and buffer_updated() won't be called after it.

State machine:

start -> connection_made
    [-> get_buffer
        [-> buffer_updated]?
    ]*
    [-> eof_received]?
-> connection_lost -> end

Datagram Protocols

Datagram Protocol instances should be constructed by protocol factories passed to the loop.create_datagram_endpoint() method.

DatagramProtocol.datagram_received(data, addr)

Called when a datagram is received. data is a bytes object containing the incoming data. addr is the address of the peer sending the data; the exact format depends on the transport.

DatagramProtocol.error_received(exc)

Called when a previous send or receive operation raises an OSError. exc is the OSError instance.

This method is called in rare conditions, when the transport (e.g. UDP) detects that a datagram could not be delivered to its recipient. In many conditions though, undeliverable datagrams will be silently dropped.

備註

On BSD systems (macOS, FreeBSD, etc.) flow control is not supported for datagram protocols, because there is no reliable way to detect send failures caused by writing too many packets.

The socket always appears 'ready' and excess packets are dropped. An OSError with errno set to errno.ENOBUFS may or may not be raised; if it is raised, it will be reported to DatagramProtocol.error_received() but otherwise ignored.

Subprocess Protocols

Subprocess Protocol instances should be constructed by protocol factories passed to the loop.subprocess_exec() and loop.subprocess_shell() methods.

SubprocessProtocol.pipe_data_received(fd, data)

Called when the child process writes data into its stdout or stderr pipe.

fd is the integer file descriptor of the pipe.

data is a non-empty bytes object containing the received data.

SubprocessProtocol.pipe_connection_lost(fd, exc)

Called when one of the pipes communicating with the child process is closed.

fd is the integer file descriptor that was closed.

SubprocessProtocol.process_exited()

Called when the child process has exited.

It can be called before pipe_data_received() and pipe_connection_lost() methods.

範例

TCP Echo Server

Create a TCP echo server using the loop.create_server() method, send back received data, and close the connection:

import asyncio

class EchoServerProtocol(asyncio.Protocol):
    def connection_made(self, transport):
        peername = transport.get_extra_info('peername')
        print('Connection from {}'.format(peername))
        self.transport = transport

    def data_received(self, data):
        message = data.decode()
        print('Data received: {!r}'.format(message))

        print('Send: {!r}'.format(message))
        self.transport.write(data)

        print('Close the client socket')
        self.transport.close()

async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    server = await loop.create_server(
        EchoServerProtocol,
        '127.0.0.1', 8888)

    async with server:
        await server.serve_forever()

asyncio.run(main())

也參考

The TCP echo server using streams example uses the high-level asyncio.start_server() function.

TCP Echo Client

A TCP echo client using the loop.create_connection() method, sends data, and waits until the connection is closed:

import asyncio

class EchoClientProtocol(asyncio.Protocol):
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost

    def connection_made(self, transport):
        transport.write(self.message.encode())
        print('Data sent: {!r}'.format(self.message))

    def data_received(self, data):
        print('Data received: {!r}'.format(data.decode()))

    def connection_lost(self, exc):
        print('The server closed the connection')
        self.on_con_lost.set_result(True)

async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    on_con_lost = loop.create_future()
    message = 'Hello World!'

    transport, protocol = await loop.create_connection(
        lambda: EchoClientProtocol(message, on_con_lost),
        '127.0.0.1', 8888)

    # Wait until the protocol signals that the connection
    # is lost and close the transport.
    try:
        await on_con_lost
    finally:
        transport.close()

asyncio.run(main())

也參考

The TCP echo client using streams example uses the high-level asyncio.open_connection() function.

UDP Echo Server

A UDP echo server, using the loop.create_datagram_endpoint() method, sends back received data:

import asyncio

class EchoServerProtocol:
    def connection_made(self, transport):
        self.transport = transport

    def datagram_received(self, data, addr):
        message = data.decode()
        print('Received %r from %s' % (message, addr))
        print('Send %r to %s' % (message, addr))
        self.transport.sendto(data, addr)

async def main():
    print("Starting UDP server")

    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    # One protocol instance will be created to serve all
    # client requests.
    transport, protocol = await loop.create_datagram_endpoint(
        EchoServerProtocol,
        local_addr=('127.0.0.1', 9999))

    try:
        await asyncio.sleep(3600)  # Serve for 1 hour.
    finally:
        transport.close()

asyncio.run(main())

UDP Echo Client

A UDP echo client, using the loop.create_datagram_endpoint() method, sends data and closes the transport when it receives the answer:

import asyncio

class EchoClientProtocol:
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost
        self.transport = None

    def connection_made(self, transport):
        self.transport = transport
        print('Send:', self.message)
        self.transport.sendto(self.message.encode())

    def datagram_received(self, data, addr):
        print("Received:", data.decode())

        print("Close the socket")
        self.transport.close()

    def error_received(self, exc):
        print('Error received:', exc)

    def connection_lost(self, exc):
        print("Connection closed")
        self.on_con_lost.set_result(True)

async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    on_con_lost = loop.create_future()
    message = "Hello World!"

    transport, protocol = await loop.create_datagram_endpoint(
        lambda: EchoClientProtocol(message, on_con_lost),
        remote_addr=('127.0.0.1', 9999))

    try:
        await on_con_lost
    finally:
        transport.close()

asyncio.run(main())

Connecting Existing Sockets

Wait until a socket receives data using the loop.create_connection() method with a protocol:

import asyncio
import socket

class MyProtocol(asyncio.Protocol):

    def __init__(self, on_con_lost):
        self.transport = None
        self.on_con_lost = on_con_lost

    def connection_made(self, transport):
        self.transport = transport

    def data_received(self, data):
        print("Received:", data.decode())

        # We are done: close the transport;
        # connection_lost() will be called automatically.
        self.transport.close()

    def connection_lost(self, exc):
        # The socket has been closed
        self.on_con_lost.set_result(True)

async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    on_con_lost = loop.create_future()

    # Create a pair of connected sockets
    rsock, wsock = socket.socketpair()

    # Register the socket to wait for data.
    transport, protocol = await loop.create_connection(
        lambda: MyProtocol(on_con_lost), sock=rsock)

    # Simulate the reception of data from the network.
    loop.call_soon(wsock.send, 'abc'.encode())

    try:
        await protocol.on_con_lost
    finally:
        transport.close()
        wsock.close()

asyncio.run(main())

也參考

The watch a file descriptor for read events example uses the low-level loop.add_reader() method to register an FD.

The register an open socket to wait for data using streams example uses high-level streams created by the open_connection() function in a coroutine.

loop.subprocess_exec() and SubprocessProtocol

An example of a subprocess protocol used to get the output of a subprocess and to wait for the subprocess exit.

The subprocess is created by the loop.subprocess_exec() method:

import asyncio
import sys

class DateProtocol(asyncio.SubprocessProtocol):
    def __init__(self, exit_future):
        self.exit_future = exit_future
        self.output = bytearray()
        self.pipe_closed = False
        self.exited = False

    def pipe_connection_lost(self, fd, exc):
        self.pipe_closed = True
        self.check_for_exit()

    def pipe_data_received(self, fd, data):
        self.output.extend(data)

    def process_exited(self):
        self.exited = True
        # process_exited() method can be called before
        # pipe_connection_lost() method: wait until both methods are
        # called.
        self.check_for_exit()

    def check_for_exit(self):
        if self.pipe_closed and self.exited:
            self.exit_future.set_result(True)

async def get_date():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    code = 'import datetime; print(datetime.datetime.now())'
    exit_future = asyncio.Future(loop=loop)

    # Create the subprocess controlled by DateProtocol;
    # redirect the standard output into a pipe.
    transport, protocol = await loop.subprocess_exec(
        lambda: DateProtocol(exit_future),
        sys.executable, '-c', code,
        stdin=None, stderr=None)

    # Wait for the subprocess exit using the process_exited()
    # method of the protocol.
    await exit_future

    # Close the stdout pipe.
    transport.close()

    # Read the output which was collected by the
    # pipe_data_received() method of the protocol.
    data = bytes(protocol.output)
    return data.decode('ascii').rstrip()

date = asyncio.run(get_date())
print(f"Current date: {date}")

See also the same example written using high-level APIs.

Policies

警告

Policies are deprecated and will be removed in Python 3.16. Users are encouraged to use the asyncio.run() function or the asyncio.Runner with loop_factory to use the desired loop implementation.

An event loop policy is a global object used to get and set the current event loop, as well as create new event loops. The default policy can be replaced with built-in alternatives to use different event loop implementations, or substituted by a custom policy that can override these behaviors.

The policy object gets and sets a separate event loop per context. This is per-thread by default, though custom policies could define context differently.

Custom event loop policies can control the behavior of get_event_loop(), set_event_loop(), and new_event_loop().

Policy objects should implement the APIs defined in the AbstractEventLoopPolicy abstract base class.

Getting and Setting the Policy

The following functions can be used to get and set the policy for the current process:

asyncio.get_event_loop_policy()

Return the current process-wide policy.

在 3.14 版之後被棄用: The get_event_loop_policy() function is deprecated and will be removed in Python 3.16.

asyncio.set_event_loop_policy(policy)

Set the current process-wide policy to policy.

If policy is set to None, the default policy is restored.

在 3.14 版之後被棄用: The set_event_loop_policy() function is deprecated and will be removed in Python 3.16.

Policy Objects

The abstract event loop policy base class is defined as follows:

class asyncio.AbstractEventLoopPolicy

An abstract base class for asyncio policies.

get_event_loop()

Get the event loop for the current context.

Return an event loop object implementing the AbstractEventLoop interface.

This method should never return None.

在 3.6 版的變更.

set_event_loop(loop)

Set the event loop for the current context to loop.

new_event_loop()

Create and return a new event loop object.

This method should never return None.

在 3.14 版之後被棄用: The AbstractEventLoopPolicy class is deprecated and will be removed in Python 3.16.

asyncio ships with the following built-in policies:

class asyncio.DefaultEventLoopPolicy

The default asyncio policy. Uses SelectorEventLoop on Unix and ProactorEventLoop on Windows.

There is no need to install the default policy manually. asyncio is configured to use the default policy automatically.

在 3.8 版的變更: On Windows, ProactorEventLoop is now used by default.

在 3.14 版的變更: The get_event_loop() method of the default asyncio policy now raises a RuntimeError if there is no set event loop.

在 3.14 版之後被棄用: The DefaultEventLoopPolicy class is deprecated and will be removed in Python 3.16.

class asyncio.WindowsSelectorEventLoopPolicy

An alternative event loop policy that uses the SelectorEventLoop event loop implementation.

可用性: Windows.

在 3.14 版之後被棄用: The WindowsSelectorEventLoopPolicy class is deprecated and will be removed in Python 3.16.

class asyncio.WindowsProactorEventLoopPolicy

An alternative event loop policy that uses the ProactorEventLoop event loop implementation.

可用性: Windows.

在 3.14 版之後被棄用: The WindowsProactorEventLoopPolicy class is deprecated and will be removed in Python 3.16.

Custom Policies

To implement a new event loop policy, it is recommended to subclass DefaultEventLoopPolicy and override the methods for which custom behavior is wanted, e.g.:

class MyEventLoopPolicy(asyncio.DefaultEventLoopPolicy):

    def get_event_loop(self):
        """Get the event loop.

        This may be None or an instance of EventLoop.
        """
        loop = super().get_event_loop()
        # Do something with loop ...
        return loop

asyncio.set_event_loop_policy(MyEventLoopPolicy())

平臺支援

asyncio module（模組）被設計為可攜的 (portable)，但由於平臺的底層架構和功能不同，在一些平臺上存在細微的差異和限制。

所有平台

loop.add_reader() 和 loop.add_writer() 不能用來監視檔案 I/O。

Windows

原始碼：Lib/asyncio/proactor_events.py、source:`Lib/asyncio/windows_events.py、source:`Lib/asyncio/windows_utils.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/proactor_events.py、source:`Lib/asyncio/windows_events.py、source:`Lib/asyncio/windows_utils.py]

在 3.8 版的變更: 在 Windows 上，現在 ProactorEventLoop 是預設的事件迴圈。

Windows 上的所有事件迴圈都不支援以下 method（方法）：

不支援 loop.create_unix_connection() 和 loop.create_unix_server()。socket.AF_UNIX socket 系列常數僅限於 Unix 上使用。

不支援 loop.add_signal_handler() 和 loop.remove_signal_handler()。

SelectorEventLoop 有以下限制：

SelectSelector 只被用於等待 socket 事件：它支援 socket 且最多支援 512 個 socket。

loop.add_reader() 和 loop.add_writer() 只接受 socket 處理函式（例如不支援 pipe 檔案描述器 (pipe file descriptor)）。

因為不支援 pipe，所以 loop.connect_read_pipe() 和 loop.connect_write_pipe() method 沒有被實作出來。

不支援子行程 (subprocess)，也就是說 loop.subprocess_exec() 和 loop.subprocess_shell() method 沒有被實作出來。

ProactorEventLoop 有以下限制：

不支援 loop.add_reader() 和 loop.add_writer() method。

Windows 上單調時鐘 (monotonic clock) 的解析度大約為 15.6 毫秒。最佳的解析度是 0.5 毫秒。解析度和硬體（HPET [https://zh.wikipedia.org/wiki/高精度事件計時器] 是否可用）與 Windows 的設定有關。

Windows 的子行程支援

在 Windows 上，預設的事件迴圈 ProactorEventLoop 支援子行程，而 SelectorEventLoop 則不支援。

macOS

完整支援現在普遍流行的 macOS 版本。

macOS <= 10.8

在 macOS 10.6、10.7 和 10.8 上，預設的事件迴圈是使用 selectors.KqueueSelector，在這些版本上它並不支援字元裝置 (character device)。可以手工設置 SelectorEventLoop 來使用 SelectSelector 或 PollSelector 以在這些舊版 macOS 上支援字元裝置。例如：

import asyncio
import selectors

selector = selectors.SelectSelector()
loop = asyncio.SelectorEventLoop(selector)
asyncio.set_event_loop(loop)

擴充

The main direction for asyncio extending is writing custom event loop classes. Asyncio has helpers that could be used to simplify this task.

備註

Third-parties should reuse existing asyncio code with caution, a new Python version is free to break backward compatibility in internal part of API.

Writing a Custom Event Loop

asyncio.AbstractEventLoop declares very many methods. Implementing all them from scratch is a tedious job.

A loop can get many common methods implementation for free by inheriting from asyncio.BaseEventLoop.

In turn, the successor should implement a bunch of private methods declared but not implemented in asyncio.BaseEventLoop.

For example, loop.create_connection() checks arguments, resolves DNS addresses, and calls loop._make_socket_transport() that should be implemented by inherited class. The _make_socket_transport() method is not documented and is considered as an internal API.

Future and Task private constructors

asyncio.Future and asyncio.Task should be never created directly, please use corresponding loop.create_future() and loop.create_task(), or asyncio.create_task() factories instead.

However, third-party event loops may reuse built-in future and task implementations for the sake of getting a complex and highly optimized code for free.

For this purpose the following, private constructors are listed:

Future.__init__(*, loop=None)

Create a built-in future instance.

loop is an optional event loop instance.

Task.__init__(coro, *, loop=None, name=None, context=None)

Create a built-in task instance.

loop is an optional event loop instance. The rest of arguments are described in loop.create_task() description.

在 3.11 版的變更: context argument is added.

Task lifetime support

A third party task implementation should call the following functions to keep a task visible by asyncio.all_tasks() and asyncio.current_task():

asyncio._register_task(task)

Register a new task as managed by asyncio.

Call the function from a task constructor.

asyncio._unregister_task(task)

Unregister a task from asyncio internal structures.

The function should be called when a task is about to finish.

asyncio._enter_task(loop, task)

Switch the current task to the task argument.

Call the function just before executing a portion of embedded coroutine (coroutine.send() or coroutine.throw()).

asyncio._leave_task(loop, task)

Switch the current task back from task to None.

Call the function just after coroutine.send() or coroutine.throw() execution.

高階 API 索引

這個頁面列出了所有能使用 async/wait 的高階 asyncio API。

任務 (Tasks)

用於執行非同步程式、建立 Task 物件、帶有超時 (timeout) 設定地等待多個事件的工具程式。

run()

建立事件迴圈 (event loop)、執行一個協程 (coroutine)、關閉事件迴圈。

Runner

A context manager that simplifies multiple async function calls.

Task

Task 物件。

TaskGroup

A context manager that holds a group of tasks. Provides a convenient and reliable way to wait for all tasks in the group to finish.

create_task()

啟動一個 asyncio 的 Task 物件，然後回傳它。

current_task()

回傳目前 Task 物件。

all_tasks()

回傳事件迴圈中所有未完成的 task 物件。

await sleep()

休眠數秒鐘。

await gather()

並行 (concurrent) 地執行事件的排程與等待。

await wait_for()

有超時設置的執行。

await shield()

防止被取消。

await wait()

監控完成情況。

timeout()

Run with a timeout. Useful in cases when wait_for is not suitable.

to_thread()

在不同的 OS 執行緒 (thread) 中非同步地執行一個函式。

run_coroutine_threadsafe()

從其他 OS 執行緒中為一個協程排程。

for in as_completed()

用 for 迴圈來監控完成情況。

範例

使用 asyncio.gather() 平行 (parallel) 執行。

使用 asyncio.wait_for() 強制設置超時。

取消任務。

使用 asyncio.sleep()。

請參閱 Tasks 文件頁面。

佇列 (Queues)

佇列應被用於為多個 asyncio Task 物件分配工作、實作 connection pools（連線池）以及 pub/sub（發行/訂閱）模式。

Queue

一個先進先出 (FIFO) 佇列。

PriorityQueue

一個優先佇列 (priority queue)。

LifoQueue

一個後進先出 (LIFO) 佇列。

範例

使用 asyncio.Queue 為多個 Task 分配工作。

請參閱佇列文件頁面。

子行程 (Subprocesses)

用於衍生（spawn）子行程和執行 shell 指令的工具程式。

await create_subprocess_exec()

建立一個子行程。

await create_subprocess_shell()

執行一個 shell 命令。

範例

執行一個 shell 指令。

請參閱子行程 APIs 相關文件。

串流 (Streams)

用於網路 IO 處理的高階 API。

await open_connection()

建立一個 TCP 連線。

await open_unix_connection()

建立一個 Unix socket 連線。

await start_server()

啟動一個 TCP 伺服器。

await start_unix_server()

啟動一個 Unix socket 伺服器。

StreamReader

接收網路資料的高階 async/await 物件。

StreamWriter

傳送網路資料的高階 async/await 物件。

範例

TCP 用戶端範例。

請參閱串流 APIs 文件。

同步化 (Synchronization)

類似執行緒且能被用於 Task 中的同步化原始物件 (primitive)。

Lock

一個互斥鎖 (mutex lock)。

Event

一個事件物件。

Condition

一個條件物件。

Semaphore

一個旗號 (semaphore) 物件。

BoundedSemaphore

一個有界的旗號物件。

Barrier

一個屏障物件。

範例

使用 asyncio.Event。

使用 asyncio.Barrier。

請參閱 asyncio 關於同步化原始物件的文件。

例外

asyncio.CancelledError

當一 Task 物件被取消時被引發。請參閱 Task.cancel()。

asyncio.BrokenBarrierError

當一 Barrier 物件損壞時被引發。請參閱 Barrier.wait()。

範例

在取消請求發生的程式中處理 CancelledError 例外。

請參閱 asyncio 專用例外完整列表。

低階 API 索引

本頁列出所有低階 asyncio APIs。

取得事件迴圈

asyncio.get_running_loop()

推薦使用於取得目前運行事件迴圈 (event loop) 的函式。

asyncio.get_event_loop()

獲得一個（正在運行的或透過目前 policy 建立的）事件迴圈實例。

asyncio.set_event_loop()

透過目前 policy 來設定目前事件迴圈。

asyncio.new_event_loop()

建立一個新的事件迴圈。

範例

使用 asyncio.get_running_loop()。

事件迴圈方法

也請查閱文件中關於事件迴圈方法的主要段落。

生命週期

loop.run_until_complete()

執行一個 Future/Task/awaitable（可等待物件）直到完成。

loop.run_forever()

持續運行事件迴圈。

loop.stop()

停止事件迴圈。

loop.close()

關閉事件迴圈。

loop.is_running()

如果事件迴圈正在執行則回傳 True。

loop.is_closed()

如果事件迴圈已經被關閉則回傳 True。

await loop.shutdown_asyncgens()

關閉非同步產生器 (asynchronous generators)。

除錯

loop.set_debug()

開啟或禁用除錯模式。

loop.get_debug()

取得目前除錯模式。

為回呼函式排程

loop.call_soon()

儘快呼叫回呼函式 (callback)。

loop.call_soon_threadsafe()

loop.call_soon() 方法之有支援執行緒安全 (thread-safe) 變體。

loop.call_later()

在給定時間之後呼叫回呼函式。

loop.call_at()

在給定時間當下呼叫回呼函式。

執行緒 (Thread)/直譯器 (Interpreter)/行程池 (Process Pool)

await loop.run_in_executor()

在 concurrent.futures 執行器 (excutor) 中執行一個 CPU 密集型 (CPU-bound) 或其它阻塞型式的函式。

loop.set_default_executor()

為 loop.run_in_executor() 設定預設執行器。

Tasks 與 Futures

loop.create_future()

建立一個 Future 物件。

loop.create_task()

像是 Task 一樣，為協程 (coroutine) 排程。

loop.set_task_factory()

設定被 loop.create_task() 用來建立 Tasks 的工廠函式 (factory)。

loop.get_task_factory()

取得被 loop.create_task() 用來建立 Tasks 的工廠函式。

DNS

await loop.getaddrinfo()

非同步版本的 socket.getaddrinfo()。

await loop.getnameinfo()

非同步版本的 socket.getnameinfo()。

網路和 IPC

await loop.create_connection()

開啟一個 TCP 連線。

await loop.create_server()

建立一個 TCP 伺服器。

await loop.create_unix_connection()

開啟一個 Unix socket 連線。

await loop.create_unix_server()

建立一個 Unix socket 伺服器。

await loop.connect_accepted_socket()

將 socket 包裝成 (transport, protocol)。

await loop.create_datagram_endpoint()

開啟一個資料單元 (datagram) (UDP) 連線。

await loop.sendfile()

透過傳輸通道傳送一個檔案。

await loop.start_tls()

將一個已存在的連線升級到 TLS。

await loop.connect_read_pipe()

將 pipe（管道）讀取端包裝成 (transport, protocol)。

await loop.connect_write_pipe()

將 pipe 寫入端包裝成 (transport, protocol)。

Sockets

await loop.sock_recv()

從 socket 接收資料。

await loop.sock_recv_into()

將從 socket 接收到的資料存放於一個緩衝區 (buffer) 中。

await loop.sock_recvfrom()

從 socket 接收一個資料單元。

await loop.sock_recvfrom_into()

將從 socket 接收到的資料單元存放於一個緩衝區中。

await loop.sock_sendall()

傳送資料到 socket。

await loop.sock_sendto()

透過 socket 將資料單元傳送至給定的地址。

await loop.sock_connect()

連接 socket。

await loop.sock_accept()

接受一個 socket 連線。

await loop.sock_sendfile()

透過 socket 傳送一個檔案。

loop.add_reader()

開始監控一個檔案描述器 (file descriptor) 的可讀取性。

loop.remove_reader()

停止監控一個檔案描述器的可讀取性。

loop.add_writer()

開始監控一個檔案描述器的可寫入性。

loop.remove_writer()

停止監控一個檔案描述器的可寫入性。

Unix 信號

loop.add_signal_handler()

為 signal 新增一個處理函式 (handler)。

loop.remove_signal_handler()

刪除 signal 的處理函式。

子行程

loop.subprocess_exec()

衍生 (spawn) 一個子行程 (subprocess)。

loop.subprocess_shell()

從 shell 指令衍生一個子行程。

錯誤處理

loop.call_exception_handler()

呼叫例外處理函式。

loop.set_exception_handler()

設定一個新的例外處理函式。

loop.get_exception_handler()

取得目前例外處理函式。

loop.default_exception_handler()

預設例外處理函式實作。

範例

使用 asyncio.new_event_loop() 和 loop.run_forever()。

使用 loop.call_later()。

使用 loop.create_connection() 以實作一個 echo 用戶端。

使用 loop.create_connection() 來連接 socket。

使用 add_reader() 監控 FD 的讀取事件。

使用 loop.add_signal_handler()。

使用 loop.add_signal_handler()。

傳輸

所有傳輸方式都有實作以下方法：

transport.close()

關閉傳輸。

transport.is_closing()

如果傳輸正在關閉或已經關閉則回傳 True。

transport.get_extra_info()

請求傳輸的相關資訊。

transport.set_protocol()

設定一個新協定。

transport.get_protocol()

回傳目前協定。

可以接收資料（TCP 和 Unix 連線、pipe 等）的傳輸。它由 loop.create_connection()、loop.create_unix_connection()、loop.connect_read_pipe() 等方法回傳：

讀取傳輸

transport.is_reading()

如果傳輸正在接收則回傳 True。

transport.pause_reading()

暫停接收。

transport.resume_reading()

繼續接收。

可以傳送資料（TCP 和 Unix 連線、pipe 等）的傳輸。它由 loop.create_connection()、loop.create_unix_connection()、loop.connect_write_pipe() 等方法回傳：

寫入傳輸

transport.write()

將資料寫入傳輸。

transport.writelines()

將緩衝區資料寫入傳輸。

transport.can_write_eof()

如果傳輸支援傳送 EOF 則回傳 True。

transport.write_eof()

在清除 (flush) 已緩衝的資料後關閉傳輸並傳送 EOF。

transport.abort()

立即關閉傳輸。

transport.get_write_buffer_size()

回傳目前輸出緩衝區的大小。

transport.get_write_buffer_limits()

回傳用於寫入流量控制 (write flow control) 的高低標記位 (high and low water marks)。

transport.set_write_buffer_limits()

為寫入流量控制設定高低標記位。

由 loop.create_datagram_endpoint() 回傳的傳輸：

資料單元傳輸

transport.sendto()

傳送資料到連線遠端。

transport.abort()

立即關閉傳輸。

基於子行程的低階傳輸抽象，它會由 loop.subprocess_exec() 和 loop.subprocess_shell() 所回傳：

子行程傳輸

transport.get_pid()

回傳子行程的行程 id。

transport.get_pipe_transport()

回傳被請求用於通訊 pipe （stdin、stdout 或 stderr）的傳輸。

transport.get_returncode()

回傳子行程的回傳代號 (return code)。

transport.kill()

殺死子行程。

transport.send_signal()

傳送一個訊號到子行程。

transport.terminate()

停止子行程。

transport.close()

殺死子行程並關閉所有 pipes。

協定

協定類別可以實作以下回呼方法：

callback connection_made()

在連線建立時被呼叫。

callback connection_lost()

在失去連線或連線關閉時被呼叫。

callback pause_writing()

在傳輸緩衝區超過高標記位時被呼叫。

callback resume_writing()

在傳輸緩衝區低於低標記位時被呼叫。

串流協定 (TCP, Unix socket, Pipes)

callback data_received()

在接收到資料時被呼叫。

callback eof_received()

在接收到 EOF 時被呼叫。

緩衝串流協定

callback get_buffer()

呼叫後會分配新的接收緩衝區。

callback buffer_updated()

在以接收到的資料更新緩衝區時被呼叫。

callback eof_received()

在接收到 EOF 時被呼叫。

資料單元協定

callback datagram_received()

在接收到資料單元時被呼叫。

callback error_received()

在前一個傳送或接收操作引發 OSError 時被呼叫。

子行程協定

callback pipe_data_received()

在子行程向 stdout 或 stderr pipe 寫入資料時被呼叫。

callback pipe_connection_lost()

在與子行程通訊的其中一個 pipes 關閉時被呼叫。

callback process_exited()

在子行程退出時呼叫。它可以在 pipe_data_received() 和 pipe_connection_lost() 方法之前呼叫。

事件迴圈 Policies

Policy 是改變 asyncio.get_event_loop() 這類函式行為的一個低階機制。更多細節請見 Policy 相關段落。

存取 Policy

asyncio.get_event_loop_policy()

回傳目前整個行程中的 Policy。

asyncio.set_event_loop_policy()

設定整個行程中的一個新 Policy。

AbstractEventLoopPolicy

Policy 物件的基礎類別。

使用 asyncio 開發

非同步程式設計 (asynchronous programming) 與傳統的"順序"程式設計 (sequential programming) 不同。

本頁列出常見的錯誤和陷阱，並解釋如何避免它們。

除錯模式

在預設情況下 asyncio 以正式生產模式 (production mode) 執行。為了讓開發更輕鬆，asyncio 還有一種除錯模式 (debug mode)。

有幾種方法可以啟用 asyncio 除錯模式：

將 PYTHONASYNCIODEBUG 環境變數設定為 1。

使用 Python 開發模式 (Development Mode)。

將 debug=True 傳遞給 asyncio.run()。

呼叫 loop.set_debug()。

除了啟用除錯模式外，還要考慮：

將 asyncio logger（日誌記錄器）的日誌級别設置為 logging.DEBUG，例如下面的程式片段可以在應用程式啟動時運行：

logging.basicConfig(level=logging.DEBUG)

配置 warnings 模組以顯示 ResourceWarning 警告。一種方法是使用 -W default 命令列選項。

啟用除錯模式時：

許多非執行緒安全 (non-threadsafe) 的 asyncio APIs（例如 loop.call_soon() 和 loop.call_at() 方法），如果從錯誤的執行緒呼叫就會引發例外。

如果執行一個 I/O 操作花費的時間太長，則將 I/O 選擇器 (selector) 的執行時間記錄到日誌中。

執行時間超過 100 毫秒的回呼 (callback) 將會被記錄於日誌。屬性 loop.slow_callback_duration 可用於設定以秒為單位的最小執行持續時間，超過這個值執行時間就會被視為"緩慢"。

並行性和多執行緒 (Concurrency and Multithreading)

事件迴圈在執行緒中運行（通常是主執行緒），並在其執行緒中執行所有回呼和 Tasks（任務）。當一個 Task 在事件迴圈中運行時，沒有其他 Task 可以在同一個執行緒中運行。當一個 Task 執行一個 await 運算式時，正在執行的 Task 會被暫停，而事件迴圈會執行下一個 Task。

要從不同的 OS 執行緒為一個 callback 排程，應該使用 loop.call_soon_threadsafe() 方法。例如：

loop.call_soon_threadsafe(callback, *args)

幾乎所有 asyncio 物件都不支援執行緒安全 (thread safe)，這通常不是問題，除非在 Task 或回呼函式之外有程式需要和它們一起運作。如果需要這樣的程式來呼叫低階 asyncio API，應該使用 loop.call_soon_threadsafe() 方法，例如：

loop.call_soon_threadsafe(fut.cancel)

要從不同的 OS 執行緒為一個協程物件排程，應該使用 run_coroutine_threadsafe() 函式。它會回傳一個 concurrent.futures.Future 以存取結果：

async def coro_func():
     return await asyncio.sleep(1, 42)

# Later in another OS thread:

future = asyncio.run_coroutine_threadsafe(coro_func(), loop)
# Wait for the result:
result = future.result()

為了能夠處理訊號，事件迴圈必須於主執行緒中運行。

loop.run_in_executor() 方法可以和 concurrent.futures.ThreadPoolExecutor 或 InterpreterPoolExecutor 一起使用，這能夠在作業系統上另一個不同的執行緒中執行阻塞程式，且避免阻塞執行事件迴圈的執行緒。

目前沒有什麼辦法能直接從另一個行程（例如透過 multiprocessing 啟動的程序）來為協程或回呼排程。事件迴圈方法小節列出了可以從 pipes（管道）讀取並監視 file descriptor（檔案描述器）而不會阻塞事件迴圈的 API。此外，asyncio 的子行程 API 提供了一種啟動行程並從事件迴圈與其通訊的辦法。最後，之前提到的 loop.run_in_executor() 方法也可和 concurrent.futures.ProcessPoolExecutor 搭配使用，以在另一個行程中執行程式。

執行阻塞的程式

不應該直接呼叫阻塞（CPU 密集型）程式。例如一個執行 1 秒 CPU 密集型計算的函式，那麼所有並行非同步 Tasks 和 IO 操作都會被延遲 1 秒。

一個 executor（執行器）可以被用來在不同的執行緒（包含不同直譯器）、或甚至不同的行程中執行任務，以避免事件迴圈阻塞了 OS 執行緒。詳情請見 loop.run_in_executor() 方法。

日誌記錄

asyncio 使用 logging 模組，所有日誌記錄都是透過 "asyncio" logger 執行的。

日誌級別被預設為 logging.INFO，它可以很容易地被調整：

logging.getLogger("asyncio").setLevel(logging.WARNING)

網路日誌記錄可能會阻塞事件迴圈。建議使用獨立的執行緒來處理日誌或使用非阻塞 IO，範例請參見 Dealing with handlers that block。

偵測從未被等待的 (never-awaited) 協程

當協程函式被呼叫而不是被等待時（即執行 coro() 而不是 await coro()）或者協程沒有透過 asyncio.create_task() 被排程，asyncio 將會發出 RuntimeWarning：

import asyncio

async def test():
    print("never scheduled")

async def main():
    test()

asyncio.run(main())

輸出：

test.py:7: RuntimeWarning: coroutine 'test' was never awaited
  test()

除錯模式中的輸出：

test.py:7: RuntimeWarning: coroutine 'test' was never awaited
Coroutine created at (most recent call last)
  File "../t.py", line 9, in <module>
    asyncio.run(main(), debug=True)

  < .. >

  File "../t.py", line 7, in main
    test()
  test()

常用的修復方法是去等待協程或者呼叫 asyncio.create_task() 函式：

async def main():
    await test()

偵測從未被取得的 (never-retrieved) 例外

如果呼叫 Future.set_exception()，但 Future 物件從未被等待，例外將無法被傳播 (propagate) 到使用者程式。在這種情況下，當 Future 物件被垃圾回收 (garbage collected) 時，asyncio 將發出一則日誌訊息。

未處理例外的例子：

import asyncio

async def bug():
    raise Exception("not consumed")

async def main():
    asyncio.create_task(bug())

asyncio.run(main())

輸出：

Task exception was never retrieved
future: <Task finished coro=<bug() done, defined at test.py:3>
  exception=Exception('not consumed')>

Traceback (most recent call last):
  File "test.py", line 4, in bug
    raise Exception("not consumed")
Exception: not consumed

啟用除錯模式以取得任務建立處的追蹤資訊 (traceback)：

asyncio.run(main(), debug=True)

除錯模式中的輸出：

Task exception was never retrieved
future: <Task finished coro=<bug() done, defined at test.py:3>
    exception=Exception('not consumed') created at asyncio/tasks.py:321>

source_traceback: Object created at (most recent call last):
  File "../t.py", line 9, in <module>
    asyncio.run(main(), debug=True)

< .. >

Traceback (most recent call last):
  File "../t.py", line 4, in bug
    raise Exception("not consumed")
Exception: not consumed

socket — 低階網路介面

原始碼：Lib/socket.py [https://github.com/python/cpython/tree/3.14/Lib/socket.py]

這個模組提供了操作 BSD socket 的介面。這在所有現代 Unix 系統、Windows、MacOS，以及一些其他平台上都可用。

備註

由於是呼叫作業系統的 socket API，某些行為可能會因平台而有所差異。

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

Python 的介面是將 Unix 的系統呼叫和 socket 函式庫介面直接轉換成 Python 的物件導向風格：socket() 函式會回傳一個 socket 物件，這個物件的方法實作了各種 socket 系統呼叫。與 C 語言介面相比，參數型別較為高階：就像 Python 文件操作中的 read() 和 write() 一樣，接收操作時會自動分配緩衝區，而發送操作時的緩衝區長度則是隱含的。

也參考

socketserver 模組

簡化編寫網路伺服器的類別。

ssl 模組

對 socket 物件的 TLS/SSL 的包裝器 (wrapper)。

Socket 系列家族

Depending on the system and the build options, various socket families are supported by this module.

The address format required by a particular socket object is automatically selected based on the address family specified when the socket object was created. Socket addresses are represented as follows:

The address of an AF_UNIX socket bound to a file system node is represented as a string, using the file system encoding and the 'surrogateescape' error handler (see PEP 383 [https://peps.python.org/pep-0383/]). An address in Linux's abstract namespace is returned as a bytes-like object with an initial null byte; note that sockets in this namespace can communicate with normal file system sockets, so programs intended to run on Linux may need to deal with both types of address. A string or bytes-like object can be used for either type of address when passing it as an argument.

在 3.3 版的變更: Previously, AF_UNIX socket paths were assumed to use UTF-8 encoding.

在 3.5 版的變更: Writable bytes-like object is now accepted.

A pair (host, port) is used for the AF_INET address family, where host is a string representing either a hostname in internet domain notation like 'daring.cwi.nl' or an IPv4 address like '100.50.200.5', and port is an integer.

For IPv4 addresses, two special forms are accepted instead of a host address: '' represents INADDR_ANY, which is used to bind to all interfaces, and the string '<broadcast>' represents INADDR_BROADCAST. This behavior is not compatible with IPv6, therefore, you may want to avoid these if you intend to support IPv6 with your Python programs.

For AF_INET6 address family, a four-tuple (host, port, flowinfo, scope_id) is used, where flowinfo and scope_id represent the sin6_flowinfo and sin6_scope_id members in struct sockaddr_in6 in C. For socket module methods, flowinfo and scope_id can be omitted just for backward compatibility. Note, however, omission of scope_id can cause problems in manipulating scoped IPv6 addresses.

在 3.7 版的變更: For multicast addresses (with scope_id meaningful) address may not contain %scope_id (or zone id) part. This information is superfluous and may be safely omitted (recommended).

AF_NETLINK socket 會以成對的 (pid, groups) 來表示。

Linux-only support for TIPC is available using the AF_TIPC address family. TIPC is an open, non-IP based networked protocol designed for use in clustered computer environments. Addresses are represented by a tuple, and the fields depend on the address type. The general tuple form is (addr_type, v1, v2, v3 [, scope]), where:

addr_type is one of TIPC_ADDR_NAMESEQ, TIPC_ADDR_NAME, or TIPC_ADDR_ID.

scope is one of TIPC_ZONE_SCOPE, TIPC_CLUSTER_SCOPE, and TIPC_NODE_SCOPE.

If addr_type is TIPC_ADDR_NAME, then v1 is the server type, v2 is the port identifier, and v3 should be 0.

If addr_type is TIPC_ADDR_NAMESEQ, then v1 is the server type, v2 is the lower port number, and v3 is the upper port number.

If addr_type is TIPC_ADDR_ID, then v1 is the node, v2 is the reference, and v3 should be set to 0.

A tuple (interface, ) is used for the AF_CAN address family, where interface is a string representing a network interface name like 'can0'. The network interface name '' can be used to receive packets from all network interfaces of this family.

CAN_ISOTP protocol require a tuple (interface, rx_addr, tx_addr) where both additional parameters are unsigned long integer that represent a CAN identifier (standard or extended).

CAN_J1939 protocol require a tuple (interface, name, pgn, addr) where additional parameters are 64-bit unsigned integer representing the ECU name, a 32-bit unsigned integer representing the Parameter Group Number (PGN), and an 8-bit integer representing the address.

A string or a tuple (id, unit) is used for the SYSPROTO_CONTROL protocol of the PF_SYSTEM family. The string is the name of a kernel control using a dynamically assigned ID. The tuple can be used if ID and unit number of the kernel control are known or if a registered ID is used.

在 3.3 版被加入.

AF_BLUETOOTH supports the following protocols and address formats:

BTPROTO_L2CAP accepts a tuple (bdaddr, psm[, cid[, bdaddr_type]]) where:

bdaddr 是一個指定藍牙位址的字串。

psm is an integer specifying the Protocol/Service Multiplexer.

cid is an optional integer specifying the Channel Identifier. If not given, defaults to zero.

bdaddr_type is an optional integer specifying the address type; one of BDADDR_BREDR (default), BDADDR_LE_PUBLIC, BDADDR_LE_RANDOM.

在 3.14 版的變更: 新增 cid 和 bdaddr_type 欄位。

BTPROTO_RFCOMM accepts (bdaddr, channel) where bdaddr is the Bluetooth address as a string and channel is an integer.

BTPROTO_HCI accepts a format that depends on your OS.

On Linux it accepts an integer device_id or a tuple (device_id, [channel]) where device_id specifies the number of the Bluetooth device, and channel is an optional integer specifying the HCI channel (HCI_CHANNEL_RAW by default).

On FreeBSD, NetBSD and DragonFly BSD it accepts bdaddr where bdaddr is the Bluetooth address as a string.

在 3.2 版的變更: 加入對 NetBSD 和 DragonFlyBSD 的支援。

在 3.13.3 版的變更: 新增對 FreeBSD 的支援。

在 3.14 版的變更: Added channel field. device_id not packed in a tuple is now accepted.

BTPROTO_SCO accepts bdaddr where bdaddr is the Bluetooth address as a string or a bytes object. (ex. '12:23:34:45:56:67' or b'12:23:34:45:56:67')

在 3.14 版的變更: 新增對 FreeBSD 的支援。

AF_ALG is a Linux-only socket based interface to Kernel cryptography. An algorithm socket is configured with a tuple of two to four elements (type, name [, feat [, mask]]), where:

type is the algorithm type as string, e.g. aead, hash, skcipher or rng.

name is the algorithm name and operation mode as string, e.g. sha256, hmac(sha256), cbc(aes) or drbg_nopr_ctr_aes256.

feat and mask are unsigned 32bit integers.

可用性: Linux >= 2.6.38.

Some algorithm types require more recent Kernels.

在 3.6 版被加入.

AF_VSOCK allows communication between virtual machines and their hosts. The sockets are represented as a (CID, port) tuple where the context ID or CID and port are integers.

可用性: Linux >= 3.9

請見 vsock(7) [https://manpages.debian.org/vsock(7)]

在 3.7 版被加入.

AF_PACKET is a low-level interface directly to network devices. The addresses are represented by the tuple (ifname, proto[, pkttype[, hatype[, addr]]]) where:

ifname - String specifying the device name.

proto - The Ethernet protocol number. May be ETH_P_ALL to capture all protocols, one of the ETHERTYPE_* constants or any other Ethernet protocol number.

pkttype - Optional integer specifying the packet type:

PACKET_HOST (the default) - Packet addressed to the local host.

PACKET_BROADCAST - Physical-layer broadcast packet.

PACKET_MULTICAST - Packet sent to a physical-layer multicast address.

PACKET_OTHERHOST - Packet to some other host that has been caught by a device driver in promiscuous mode.

PACKET_OUTGOING - Packet originating from the local host that is looped back to a packet socket.

hatype - Optional integer specifying the ARP hardware address type.

addr - Optional bytes-like object specifying the hardware physical address, whose interpretation depends on the device.

可用性: Linux >= 2.2.

AF_QIPCRTR is a Linux-only socket based interface for communicating with services running on co-processors in Qualcomm platforms. The address family is represented as a (node, port) tuple where the node and port are non-negative integers.

可用性: Linux >= 4.7.

在 3.8 版被加入.

IPPROTO_UDPLITE is a variant of UDP which allows you to specify what portion of a packet is covered with the checksum. It adds two socket options that you can change. self.setsockopt(IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, length) will change what portion of outgoing packets are covered by the checksum and self.setsockopt(IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV, length) will filter out packets which cover too little of their data. In both cases length should be in range(8, 2**16, 8).

Such a socket should be constructed with socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE) for IPv4 or socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDPLITE) for IPv6.

可用性: Linux >= 2.6.20, FreeBSD >= 10.1

在 3.9 版被加入.

AF_HYPERV is a Windows-only socket based interface for communicating with Hyper-V hosts and guests. The address family is represented as a (vm_id, service_id) tuple where the vm_id and service_id are UUID strings.

The vm_id is the virtual machine identifier or a set of known VMID values if the target is not a specific virtual machine. Known VMID constants defined on socket are:

HV_GUID_ZERO

HV_GUID_BROADCAST

HV_GUID_WILDCARD - Used to bind on itself and accept connections from all partitions.

HV_GUID_CHILDREN - Used to bind on itself and accept connection from child partitions.

HV_GUID_LOOPBACK - Used as a target to itself.

HV_GUID_PARENT - When used as a bind accepts connection from the parent partition. When used as an address target it will connect to the parent partition.

The service_id is the service identifier of the registered service.

在 3.12 版被加入.

If you use a hostname in the host portion of IPv4/v6 socket address, the program may show a nondeterministic behavior, as Python uses the first address returned from the DNS resolution. The socket address will be resolved differently into an actual IPv4/v6 address, depending on the results from DNS resolution and/or the host configuration. For deterministic behavior use a numeric address in host portion.

All errors raise exceptions. The normal exceptions for invalid argument types and out-of-memory conditions can be raised. Errors related to socket or address semantics raise OSError or one of its subclasses.

Non-blocking mode is supported through setblocking(). A generalization of this based on timeouts is supported through settimeout().

模組內容

The module socket exports the following elements.

例外

exception socket.error

一個已棄用的 OSError 的別名。

在 3.3 版的變更: Following PEP 3151 [https://peps.python.org/pep-3151/], this class was made an alias of OSError.

exception socket.herror

A subclass of OSError, this exception is raised for address-related errors, i.e. for functions that use h_errno in the POSIX C API, including gethostbyname_ex() and gethostbyaddr(). The accompanying value is a pair (h_errno, string) representing an error returned by a library call. h_errno is a numeric value, while string represents the description of h_errno, as returned by the hstrerror() C function.

在 3.3 版的變更: This class was made a subclass of OSError.

exception socket.gaierror

A subclass of OSError, this exception is raised for address-related errors by getaddrinfo() and getnameinfo(). The accompanying value is a pair (error, string) representing an error returned by a library call. string represents the description of error, as returned by the gai_strerror() C function. The numeric error value will match one of the EAI_* constants defined in this module.

在 3.3 版的變更: This class was made a subclass of OSError.

exception socket.timeout

A deprecated alias of TimeoutError.

A subclass of OSError, this exception is raised when a timeout occurs on a socket which has had timeouts enabled via a prior call to settimeout() (or implicitly through setdefaulttimeout()). The accompanying value is a string whose value is currently always "timed out".

在 3.3 版的變更: This class was made a subclass of OSError.

在 3.10 版的變更: This class was made an alias of TimeoutError.

常數

The AF_* and SOCK_* constants are now AddressFamily and SocketKind IntEnum collections.

在 3.4 版被加入.

socket.AF_UNIX

socket.AF_INET

socket.AF_INET6

These constants represent the address (and protocol) families, used for the first argument to socket(). If the AF_UNIX constant is not defined then this protocol is unsupported. More constants may be available depending on the system.

socket.AF_UNSPEC

AF_UNSPEC means that getaddrinfo() should return socket addresses for any address family (either IPv4, IPv6, or any other) that can be used.

socket.SOCK_STREAM

socket.SOCK_DGRAM

socket.SOCK_RAW

socket.SOCK_RDM

socket.SOCK_SEQPACKET

These constants represent the socket types, used for the second argument to socket(). More constants may be available depending on the system. (Only SOCK_STREAM and SOCK_DGRAM appear to be generally useful.)

socket.SOCK_CLOEXEC

socket.SOCK_NONBLOCK

These two constants, if defined, can be combined with the socket types and allow you to set some flags atomically (thus avoiding possible race conditions and the need for separate calls).

也參考

Secure File Descriptor Handling [https://udrepper.livejournal.com/20407.html] for a more thorough explanation.

可用性: Linux >= 2.6.27.

在 3.2 版被加入.

SO_*

socket.SOMAXCONN

MSG_*

SOL_*

SCM_*

IPPROTO_*

IPPORT_*

INADDR_*

IP_*

IPV6_*

EAI_*

AI_*

NI_*

TCP_*

Many constants of these forms, documented in the Unix documentation on sockets and/or the IP protocol, are also defined in the socket module. They are generally used in arguments to the setsockopt() and getsockopt() methods of socket objects. In most cases, only those symbols that are defined in the Unix header files are defined; for a few symbols, default values are provided.

在 3.6 版的變更: SO_DOMAIN, SO_PROTOCOL, SO_PEERSEC, SO_PASSSEC, TCP_USER_TIMEOUT, TCP_CONGESTION were added.

在 3.6.5 版的變更: Added support for TCP_FASTOPEN, TCP_KEEPCNT on Windows platforms when available.

在 3.7 版的變更: 新增 TCP_NOTSENT_LOWAT。

Added support for TCP_KEEPIDLE, TCP_KEEPINTVL on Windows platforms when available.

在 3.10 版的變更: IP_RECVTOS was added. Added TCP_KEEPALIVE. On MacOS this constant can be used in the same way that TCP_KEEPIDLE is used on Linux.

在 3.11 版的變更: Added TCP_CONNECTION_INFO. On MacOS this constant can be used in the same way that TCP_INFO is used on Linux and BSD.

在 3.12 版的變更: Added SO_RTABLE and SO_USER_COOKIE. On OpenBSD and FreeBSD respectively those constants can be used in the same way that SO_MARK is used on Linux. Also added missing TCP socket options from Linux: TCP_MD5SIG, TCP_THIN_LINEAR_TIMEOUTS, TCP_THIN_DUPACK, TCP_REPAIR, TCP_REPAIR_QUEUE, TCP_QUEUE_SEQ, TCP_REPAIR_OPTIONS, TCP_TIMESTAMP, TCP_CC_INFO, TCP_SAVE_SYN, TCP_SAVED_SYN, TCP_REPAIR_WINDOW, TCP_FASTOPEN_CONNECT, TCP_ULP, TCP_MD5SIG_EXT, TCP_FASTOPEN_KEY, TCP_FASTOPEN_NO_COOKIE, TCP_ZEROCOPY_RECEIVE, TCP_INQ, TCP_TX_DELAY. Added IP_PKTINFO, IP_UNBLOCK_SOURCE, IP_BLOCK_SOURCE, IP_ADD_SOURCE_MEMBERSHIP, IP_DROP_SOURCE_MEMBERSHIP.

在 3.13 版的變更: Added SO_BINDTOIFINDEX. On Linux this constant can be used in the same way that SO_BINDTODEVICE is used, but with the index of a network interface instead of its name.

在 3.14 版的變更: Added missing IP_FREEBIND, IP_RECVERR, IPV6_RECVERR, IP_RECVTTL, and IP_RECVORIGDSTADDR on Linux.

在 3.14 版的變更: Added support for TCP_QUICKACK on Windows platforms when available.

socket.AF_CAN

socket.PF_CAN

SOL_CAN_*

CAN_*

Many constants of these forms, documented in the Linux documentation, are also defined in the socket module.

可用性: Linux >= 2.6.25, NetBSD >= 8.

在 3.3 版被加入.

在 3.11 版的變更: 新增對 NetBSD 的支援。

在 3.14 版的變更: Restored missing CAN_RAW_ERR_FILTER on Linux.

socket.CAN_BCM

CAN_BCM_*

CAN_BCM, in the CAN protocol family, is the broadcast manager (BCM) protocol. Broadcast manager constants, documented in the Linux documentation, are also defined in the socket module.

可用性: Linux >= 2.6.25.

備註

The CAN_BCM_CAN_FD_FRAME flag is only available on Linux >= 4.8.

在 3.4 版被加入.

socket.CAN_RAW_FD_FRAMES

Enables CAN FD support in a CAN_RAW socket. This is disabled by default. This allows your application to send both CAN and CAN FD frames; however, you must accept both CAN and CAN FD frames when reading from the socket.

This constant is documented in the Linux documentation.

可用性: Linux >= 3.6.

在 3.5 版被加入.

socket.CAN_RAW_JOIN_FILTERS

Joins the applied CAN filters such that only CAN frames that match all given CAN filters are passed to user space.

This constant is documented in the Linux documentation.

可用性: Linux >= 4.1.

在 3.9 版被加入.

socket.CAN_ISOTP

CAN_ISOTP, in the CAN protocol family, is the ISO-TP (ISO 15765-2) protocol. ISO-TP constants, documented in the Linux documentation.

可用性: Linux >= 2.6.25.

在 3.7 版被加入.

socket.CAN_J1939

CAN_J1939, in the CAN protocol family, is the SAE J1939 protocol. J1939 constants, documented in the Linux documentation.

可用性: Linux >= 5.4.

在 3.9 版被加入.

socket.AF_DIVERT

socket.PF_DIVERT

These two constants, documented in the FreeBSD divert(4) manual page, are also defined in the socket module.

可用性: FreeBSD >= 14.0.

在 3.12 版被加入.

socket.AF_PACKET

socket.PF_PACKET

PACKET_*

Many constants of these forms, documented in the Linux documentation, are also defined in the socket module.

可用性: Linux >= 2.2.

socket.ETH_P_ALL

ETH_P_ALL can be used in the socket constructor as proto for the AF_PACKET family in order to capture every packet, regardless of protocol.

For more information, see the packet(7) [https://manpages.debian.org/packet(7)] manpage.

可用性: Linux.

在 3.12 版被加入.

socket.AF_RDS

socket.PF_RDS

socket.SOL_RDS

RDS_*

Many constants of these forms, documented in the Linux documentation, are also defined in the socket module.

可用性: Linux >= 2.6.30.

在 3.3 版被加入.

socket.SIO_RCVALL

socket.SIO_KEEPALIVE_VALS

socket.SIO_LOOPBACK_FAST_PATH

RCVALL_*

Constants for Windows' WSAIoctl(). The constants are used as arguments to the ioctl() method of socket objects.

在 3.6 版的變更: 加入 SIO_LOOPBACK_FAST_PATH。

TIPC_*

TIPC related constants, matching the ones exported by the C socket API. See the TIPC documentation for more information.

socket.AF_ALG

socket.SOL_ALG

ALG_*

Constants for Linux Kernel cryptography.

可用性: Linux >= 2.6.38.

在 3.6 版被加入.

socket.AF_VSOCK

socket.IOCTL_VM_SOCKETS_GET_LOCAL_CID

VMADDR*

SO_VM*

Constants for Linux host/guest communication.

可用性: Linux >= 4.8.

在 3.7 版被加入.

socket.AF_LINK

可用性: BSD, macOS.

在 3.4 版被加入.

socket.has_ipv6

This constant contains a boolean value which indicates if IPv6 is supported on this platform.

socket.AF_BLUETOOTH

socket.BTPROTO_L2CAP

socket.BTPROTO_RFCOMM

socket.BTPROTO_HCI

socket.BTPROTO_SCO

Integer constants for use with Bluetooth addresses.

socket.BDADDR_ANY

socket.BDADDR_LOCAL

These are string constants containing Bluetooth addresses with special meanings. For example, BDADDR_ANY can be used to indicate any address when specifying the binding socket with BTPROTO_RFCOMM.

socket.BDADDR_BREDR

socket.BDADDR_LE_PUBLIC

socket.BDADDR_LE_RANDOM

These constants describe the Bluetooth address type when binding or connecting a BTPROTO_L2CAP socket.

可用性: Linux, FreeBSD

在 3.14 版被加入.

socket.SOL_RFCOMM

socket.SOL_L2CAP

socket.SOL_HCI

socket.SOL_SCO

socket.SOL_BLUETOOTH

Used in the level argument to the setsockopt() and getsockopt() methods of Bluetooth socket objects.

SOL_BLUETOOTH is only available on Linux. Other constants are available if the corresponding protocol is supported.

SO_L2CAP_*

socket.L2CAP_LM

L2CAP_LM_*

SO_RFCOMM_*

RFCOMM_LM_*

SO_SCO_*

SO_BTH_*

BT_*

Used in the option name and value argument to the setsockopt() and getsockopt() methods of Bluetooth socket objects.

BT_* and L2CAP_LM are only available on Linux. SO_BTH_* are only available on Windows. Other constants may be available on Linux and various BSD platforms.

在 3.14 版被加入.

socket.HCI_FILTER

socket.HCI_TIME_STAMP

socket.HCI_DATA_DIR

socket.SO_HCI_EVT_FILTER

socket.SO_HCI_PKT_FILTER

Option names for use with BTPROTO_HCI. Availability and format of the option values depend on platform.

在 3.14 版的變更: Added SO_HCI_EVT_FILTER and SO_HCI_PKT_FILTER on NetBSD and DragonFly BSD. Added HCI_DATA_DIR on FreeBSD, NetBSD and DragonFly BSD.

socket.HCI_DEV_NONE

The device_id value used to create an HCI socket that isn't specific to a single Bluetooth adapter.

可用性: Linux

在 3.14 版被加入.

socket.HCI_CHANNEL_RAW

socket.HCI_CHANNEL_USER

socket.HCI_CHANNEL_MONITOR

socket.HCI_CHANNEL_CONTROL

socket.HCI_CHANNEL_LOGGING

Possible values for channel field in the BTPROTO_HCI address.

可用性: Linux

在 3.14 版被加入.

socket.AF_QIPCRTR

Constant for Qualcomm's IPC router protocol, used to communicate with service providing remote processors.

可用性: Linux >= 4.7.

socket.SCM_CREDS2

socket.LOCAL_CREDS

socket.LOCAL_CREDS_PERSISTENT

LOCAL_CREDS and LOCAL_CREDS_PERSISTENT can be used with SOCK_DGRAM, SOCK_STREAM sockets, equivalent to Linux/DragonFlyBSD SO_PASSCRED, while LOCAL_CREDS sends the credentials at first read, LOCAL_CREDS_PERSISTENT sends for each read, SCM_CREDS2 must be then used for the latter for the message type.

在 3.11 版被加入.

可用性: FreeBSD.

socket.SO_INCOMING_CPU

Constant to optimize CPU locality, to be used in conjunction with SO_REUSEPORT.

在 3.11 版被加入.

可用性: Linux >= 3.9

socket.SO_REUSEPORT_LB

Constant to enable duplicate address and port bindings with load balancing.

在 3.14 版被加入.

可用性: FreeBSD >= 12.0

socket.AF_HYPERV

socket.HV_PROTOCOL_RAW

socket.HVSOCKET_CONNECT_TIMEOUT

socket.HVSOCKET_CONNECT_TIMEOUT_MAX

socket.HVSOCKET_CONNECTED_SUSPEND

socket.HVSOCKET_ADDRESS_FLAG_PASSTHRU

socket.HV_GUID_ZERO

socket.HV_GUID_WILDCARD

socket.HV_GUID_BROADCAST

socket.HV_GUID_CHILDREN

socket.HV_GUID_LOOPBACK

socket.HV_GUID_PARENT

Constants for Windows Hyper-V sockets for host/guest communications.

可用性: Windows.

在 3.12 版被加入.

socket.ETHERTYPE_ARP

socket.ETHERTYPE_IP

socket.ETHERTYPE_IPV6

socket.ETHERTYPE_VLAN

IEEE 802.3 protocol number [https://www.iana.org/assignments/ieee-802-numbers/ieee-802-numbers.txt]. constants.

可用性: Linux, FreeBSD, macOS.

在 3.12 版被加入.

socket.SHUT_RD

socket.SHUT_WR

socket.SHUT_RDWR

These constants are used by the shutdown() method of socket objects.

可用性: not WASI.

函式

建立 sockets

The following functions all create socket objects.

class socket.socket(family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None)

Create a new socket using the given address family, socket type and protocol number. The address family should be AF_INET (the default), AF_INET6, AF_UNIX, AF_CAN, AF_PACKET, or AF_RDS. The socket type should be SOCK_STREAM (the default), SOCK_DGRAM, SOCK_RAW or perhaps one of the other SOCK_ constants. The protocol number is usually zero and may be omitted or in the case where the address family is AF_CAN the protocol should be one of CAN_RAW, CAN_BCM, CAN_ISOTP or CAN_J1939.

If fileno is specified, the values for family, type, and proto are auto-detected from the specified file descriptor. Auto-detection can be overruled by calling the function with explicit family, type, or proto arguments. This only affects how Python represents e.g. the return value of socket.getpeername() but not the actual OS resource. Unlike socket.fromfd(), fileno will return the same socket and not a duplicate. This may help close a detached socket using socket.close().

The newly created socket is non-inheritable.

引發一個附帶引數 self、family、type、protocol 的稽核事件 socket.__new__。

在 3.3 版的變更: The AF_CAN family was added. The AF_RDS family was added.

在 3.4 版的變更: 新增 CAN_BCM 協定。

在 3.4 版的變更: The returned socket is now non-inheritable.

在 3.7 版的變更: 新增 CAN_ISOTP 協定。

在 3.7 版的變更: When SOCK_NONBLOCK or SOCK_CLOEXEC bit flags are applied to type they are cleared, and socket.type will not reflect them. They are still passed to the underlying system socket() call. Therefore,

sock = socket.socket(
    socket.AF_INET,
    socket.SOCK_STREAM | socket.SOCK_NONBLOCK)

will still create a non-blocking socket on OSes that support SOCK_NONBLOCK, but sock.type will be set to socket.SOCK_STREAM.

在 3.9 版的變更: 新增 CAN_J1939 協定。

在 3.10 版的變更: 新增 IPPROTO_MPTCP 協定。

socket.socketpair([family[, type[, proto]]])

Build a pair of connected socket objects using the given address family, socket type, and protocol number. Address family, socket type, and protocol number are as for the socket() function above. The default family is AF_UNIX if defined on the platform; otherwise, the default is AF_INET.

The newly created sockets are non-inheritable.

在 3.2 版的變更: The returned socket objects now support the whole socket API, rather than a subset.

在 3.4 版的變更: The returned sockets are now non-inheritable.

在 3.5 版的變更: 新增對 Windows 的支援。

socket.create_connection(address, timeout=GLOBAL_DEFAULT, source_address=None, *, all_errors=False)

Connect to a TCP service listening on the internet address (a 2-tuple (host, port)), and return the socket object. This is a higher-level function than socket.connect(): if host is a non-numeric hostname, it will try to resolve it for both AF_INET and AF_INET6, and then try to connect to all possible addresses in turn until a connection succeeds. This makes it easy to write clients that are compatible to both IPv4 and IPv6.

Passing the optional timeout parameter will set the timeout on the socket instance before attempting to connect. If no timeout is supplied, the global default timeout setting returned by getdefaulttimeout() is used.

If supplied, source_address must be a 2-tuple (host, port) for the socket to bind to as its source address before connecting. If host or port are '' or 0 respectively the OS default behavior will be used.

When a connection cannot be created, an exception is raised. By default, it is the exception from the last address in the list. If all_errors is True, it is an ExceptionGroup containing the errors of all attempts.

在 3.2 版的變更: 新增 source_address。

在 3.11 版的變更: 新增 all_errors。

socket.create_server(address, *, family=AF_INET, backlog=None, reuse_port=False, dualstack_ipv6=False)

Convenience function which creates a TCP socket bound to address (a 2-tuple (host, port)) and returns the socket object.

family should be either AF_INET or AF_INET6. backlog is the queue size passed to socket.listen(); if not specified , a default reasonable value is chosen. reuse_port dictates whether to set the SO_REUSEPORT socket option.

If dualstack_ipv6 is true, family is AF_INET6 and the platform supports it the socket will be able to accept both IPv4 and IPv6 connections, else it will raise ValueError. Most POSIX platforms and Windows are supposed to support this functionality. When this functionality is enabled the address returned by socket.getpeername() when an IPv4 connection occurs will be an IPv6 address represented as an IPv4-mapped IPv6 address. If dualstack_ipv6 is false it will explicitly disable this functionality on platforms that enable it by default (e.g. Linux). This parameter can be used in conjunction with has_dualstack_ipv6():

import socket

addr = ("", 8080)  # all interfaces, port 8080
if socket.has_dualstack_ipv6():
    s = socket.create_server(addr, family=socket.AF_INET6, dualstack_ipv6=True)
else:
    s = socket.create_server(addr)

備註

On POSIX platforms the SO_REUSEADDR socket option is set in order to immediately reuse previous sockets which were bound on the same address and remained in TIME_WAIT state.

在 3.8 版被加入.

socket.has_dualstack_ipv6()

Return True if the platform supports creating a TCP socket which can handle both IPv4 and IPv6 connections.

在 3.8 版被加入.

socket.fromfd(fd, family, type, proto=0)

Duplicate the file descriptor fd (an integer as returned by a file object's fileno() method) and build a socket object from the result. Address family, socket type and protocol number are as for the socket() function above. The file descriptor should refer to a socket, but this is not checked --- subsequent operations on the object may fail if the file descriptor is invalid. This function is rarely needed, but can be used to get or set socket options on a socket passed to a program as standard input or output (such as a server started by the Unix inet daemon). The socket is assumed to be in blocking mode.

The newly created socket is non-inheritable.

在 3.4 版的變更: The returned socket is now non-inheritable.

socket.fromshare(data)

Instantiate a socket from data obtained from the socket.share() method. The socket is assumed to be in blocking mode.

可用性: Windows.

在 3.3 版被加入.

socket.SocketType

This is a Python type object that represents the socket object type. It is the same as type(socket(...)).

其他函式

The socket module also offers various network-related services:

socket.close(fd)

Close a socket file descriptor. This is like os.close(), but for sockets. On some platforms (most noticeable Windows) os.close() does not work for socket file descriptors.

在 3.7 版被加入.

socket.getaddrinfo(host, port, family=AF_UNSPEC, type=0, proto=0, flags=0)

This function wraps the C function getaddrinfo of the underlying system.

Translate the host/port argument into a sequence of 5-tuples that contain all the necessary arguments for creating a socket connected to that service. host is a domain name, a string representation of an IPv4/v6 address or None. port is a string service name such as 'http', a numeric port number or None. By passing None as the value of host and port, you can pass NULL to the underlying C API.

The family, type and proto arguments can be optionally specified in order to provide options and limit the list of addresses returned. Pass their default values (AF_UNSPEC, 0, and 0, respectively) to not limit the results. See the note below for details.

The flags argument can be one or several of the AI_* constants, and will influence how results are computed and returned. For example, AI_NUMERICHOST will disable domain name resolution and will raise an error if host is a domain name.

The function returns a list of 5-tuples with the following structure:

(family, type, proto, canonname, sockaddr)

In these tuples, family, type, proto are all integers and are meant to be passed to the socket() function. canonname will be a string representing the canonical name of the host if AI_CANONNAME is part of the flags argument; else canonname will be empty. sockaddr is a tuple describing a socket address, whose format depends on the returned family (a (address, port) 2-tuple for AF_INET, a (address, port, flowinfo, scope_id) 4-tuple for AF_INET6), and is meant to be passed to the socket.connect() method.

備註

If you intend to use results from getaddrinfo() to create a socket (rather than, for example, retrieve canonname), consider limiting the results by type (e.g. SOCK_STREAM or SOCK_DGRAM) and/or proto (e.g. IPPROTO_TCP or IPPROTO_UDP) that your application can handle.

The behavior with default values of family, type, proto and flags is system-specific.

Many systems (for example, most Linux configurations) will return a sorted list of all matching addresses. These addresses should generally be tried in order until a connection succeeds (possibly tried in parallel, for example, using a Happy Eyeballs [https://en.wikipedia.org/wiki/Happy_Eyeballs] algorithm). In these cases, limiting the type and/or proto can help eliminate unsuccessful or unusable connection attempts.

Some systems will, however, only return a single address. (For example, this was reported on Solaris and AIX configurations.) On these systems, limiting the type and/or proto helps ensure that this address is usable.

引發一個附帶引數 host、port、family、type、protocol 的稽核事件 socket.getaddrinfo。

The following example fetches address information for a hypothetical TCP connection to example.org on port 80 (results may differ on your system if IPv6 isn't enabled):

>>> socket.getaddrinfo("example.org", 80, proto=socket.IPPROTO_TCP)
[(socket.AF_INET6, socket.SOCK_STREAM,
 6, '', ('2606:2800:220:1:248:1893:25c8:1946', 80, 0, 0)),
 (socket.AF_INET, socket.SOCK_STREAM,
 6, '', ('93.184.216.34', 80))]

在 3.2 版的變更: parameters can now be passed using keyword arguments.

在 3.7 版的變更: for IPv6 multicast addresses, string representing an address will not contain %scope_id part.

socket.getfqdn([name])

Return a fully qualified domain name for name. If name is omitted or empty, it is interpreted as the local host. To find the fully qualified name, the hostname returned by gethostbyaddr() is checked, followed by aliases for the host, if available. The first name which includes a period is selected. In case no fully qualified domain name is available and name was provided, it is returned unchanged. If name was empty or equal to '0.0.0.0', the hostname from gethostname() is returned.

socket.gethostbyname(hostname)

Translate a host name to IPv4 address format. The IPv4 address is returned as a string, such as '100.50.200.5'. If the host name is an IPv4 address itself it is returned unchanged. See gethostbyname_ex() for a more complete interface. gethostbyname() does not support IPv6 name resolution, and getaddrinfo() should be used instead for IPv4/v6 dual stack support.

引發一個附帶引數 hostname 的稽核事件 socket.gethostbyname。

可用性: not WASI.

socket.gethostbyname_ex(hostname)

Translate a host name to IPv4 address format, extended interface. Return a 3-tuple (hostname, aliaslist, ipaddrlist) where hostname is the host's primary host name, aliaslist is a (possibly empty) list of alternative host names for the same address, and ipaddrlist is a list of IPv4 addresses for the same interface on the same host (often but not always a single address). gethostbyname_ex() does not support IPv6 name resolution, and getaddrinfo() should be used instead for IPv4/v6 dual stack support.

引發一個附帶引數 hostname 的稽核事件 socket.gethostbyname。

可用性: not WASI.

socket.gethostname()

Return a string containing the hostname of the machine where the Python interpreter is currently executing.

引發一個不附帶引數的稽核事件 socket.gethostname。

Note: gethostname() doesn't always return the fully qualified domain name; use getfqdn() for that.

可用性: not WASI.

socket.gethostbyaddr(ip_address)

Return a 3-tuple (hostname, aliaslist, ipaddrlist) where hostname is the primary host name responding to the given ip_address, aliaslist is a (possibly empty) list of alternative host names for the same address, and ipaddrlist is a list of IPv4/v6 addresses for the same interface on the same host (most likely containing only a single address). To find the fully qualified domain name, use the function getfqdn(). gethostbyaddr() supports both IPv4 and IPv6.

引發一個附帶引數 ip_address 的稽核事件 socket.gethostbyaddr。

可用性: not WASI.

socket.getnameinfo(sockaddr, flags)

Translate a socket address sockaddr into a 2-tuple (host, port). Depending on the settings of flags, the result can contain a fully qualified domain name or numeric address representation in host. Similarly, port can contain a string port name or a numeric port number.

For IPv6 addresses, %scope_id is appended to the host part if sockaddr contains meaningful scope_id. Usually this happens for multicast addresses.

For more information about flags you can consult getnameinfo(3) [https://manpages.debian.org/getnameinfo(3)].

引發一個附帶引數 sockaddr 的稽核事件 socket.getnameinfo。

可用性: not WASI.

socket.getprotobyname(protocolname)

Translate an internet protocol name (for example, 'icmp') to a constant suitable for passing as the (optional) third argument to the socket() function. This is usually only needed for sockets opened in "raw" mode (SOCK_RAW); for the normal socket modes, the correct protocol is chosen automatically if the protocol is omitted or zero.

可用性: not WASI.

socket.getservbyname(servicename[, protocolname])

Translate an internet service name and protocol name to a port number for that service. The optional protocol name, if given, should be 'tcp' or 'udp', otherwise any protocol will match.

引發一個附帶引數 sockaddr、protocolname 的稽核事件 socket.getservbyname。

可用性: not WASI.

socket.getservbyport(port[, protocolname])

Translate an internet port number and protocol name to a service name for that service. The optional protocol name, if given, should be 'tcp' or 'udp', otherwise any protocol will match.

引發一個附帶引數 port、protocolname 的稽核事件 socket.getservbyport。

可用性: not WASI.

socket.ntohl(x)

Convert 32-bit positive integers from network to host byte order. On machines where the host byte order is the same as network byte order, this is a no-op; otherwise, it performs a 4-byte swap operation.

socket.ntohs(x)

Convert 16-bit positive integers from network to host byte order. On machines where the host byte order is the same as network byte order, this is a no-op; otherwise, it performs a 2-byte swap operation.

在 3.10 版的變更: Raises OverflowError if x does not fit in a 16-bit unsigned integer.

socket.htonl(x)

Convert 32-bit positive integers from host to network byte order. On machines where the host byte order is the same as network byte order, this is a no-op; otherwise, it performs a 4-byte swap operation.

socket.htons(x)

Convert 16-bit positive integers from host to network byte order. On machines where the host byte order is the same as network byte order, this is a no-op; otherwise, it performs a 2-byte swap operation.

在 3.10 版的變更: Raises OverflowError if x does not fit in a 16-bit unsigned integer.

socket.inet_aton(ip_string)

Convert an IPv4 address from dotted-quad string format (for example, '123.45.67.89') to 32-bit packed binary format, as a bytes object four characters in length. This is useful when conversing with a program that uses the standard C library and needs objects of type in_addr, which is the C type for the 32-bit packed binary this function returns.

inet_aton() also accepts strings with less than three dots; see the Unix manual page inet(3) [https://manpages.debian.org/inet(3)] for details.

If the IPv4 address string passed to this function is invalid, OSError will be raised. Note that exactly what is valid depends on the underlying C implementation of inet_aton().

inet_aton() does not support IPv6, and inet_pton() should be used instead for IPv4/v6 dual stack support.

socket.inet_ntoa(packed_ip)

Convert a 32-bit packed IPv4 address (a bytes-like object four bytes in length) to its standard dotted-quad string representation (for example, '123.45.67.89'). This is useful when conversing with a program that uses the standard C library and needs objects of type in_addr, which is the C type for the 32-bit packed binary data this function takes as an argument.

If the byte sequence passed to this function is not exactly 4 bytes in length, OSError will be raised. inet_ntoa() does not support IPv6, and inet_ntop() should be used instead for IPv4/v6 dual stack support.

在 3.5 版的變更: Writable bytes-like object is now accepted.

socket.inet_pton(address_family, ip_string)

Convert an IP address from its family-specific string format to a packed, binary format. inet_pton() is useful when a library or network protocol calls for an object of type in_addr (similar to inet_aton()) or in6_addr.

Supported values for address_family are currently AF_INET and AF_INET6. If the IP address string ip_string is invalid, OSError will be raised. Note that exactly what is valid depends on both the value of address_family and the underlying implementation of inet_pton().

可用性: Unix, Windows.

在 3.4 版的變更: Windows support added

socket.inet_ntop(address_family, packed_ip)

Convert a packed IP address (a bytes-like object of some number of bytes) to its standard, family-specific string representation (for example, '7.10.0.5' or '5aef:2b::8'). inet_ntop() is useful when a library or network protocol returns an object of type in_addr (similar to inet_ntoa()) or in6_addr.

Supported values for address_family are currently AF_INET and AF_INET6. If the bytes object packed_ip is not the correct length for the specified address family, ValueError will be raised. OSError is raised for errors from the call to inet_ntop().

可用性: Unix, Windows.

在 3.4 版的變更: Windows support added

在 3.5 版的變更: Writable bytes-like object is now accepted.

socket.CMSG_LEN(length)

Return the total length, without trailing padding, of an ancillary data item with associated data of the given length. This value can often be used as the buffer size for recvmsg() to receive a single item of ancillary data, but RFC 3542 [https://datatracker.ietf.org/doc/html/rfc3542.html] requires portable applications to use CMSG_SPACE() and thus include space for padding, even when the item will be the last in the buffer. Raises OverflowError if length is outside the permissible range of values.

可用性: Unix, not WASI.

Most Unix platforms.

在 3.3 版被加入.

socket.CMSG_SPACE(length)

Return the buffer size needed for recvmsg() to receive an ancillary data item with associated data of the given length, along with any trailing padding. The buffer space needed to receive multiple items is the sum of the CMSG_SPACE() values for their associated data lengths. Raises OverflowError if length is outside the permissible range of values.

Note that some systems might support ancillary data without providing this function. Also note that setting the buffer size using the results of this function may not precisely limit the amount of ancillary data that can be received, since additional data may be able to fit into the padding area.

可用性: Unix, not WASI.

most Unix platforms.

在 3.3 版被加入.

socket.getdefaulttimeout()

Return the default timeout in seconds (float) for new socket objects. A value of None indicates that new socket objects have no timeout. When the socket module is first imported, the default is None.

socket.setdefaulttimeout(timeout)

Set the default timeout in seconds (float) for new socket objects. When the socket module is first imported, the default is None. See settimeout() for possible values and their respective meanings.

socket.sethostname(name)

Set the machine's hostname to name. This will raise an OSError if you don't have enough rights.

引發一個附帶引數 name 的稽核事件 socket.sethostname。

可用性: Unix, not Android.

在 3.3 版被加入.

socket.if_nameindex()

Return a list of network interface information (index int, name string) tuples. OSError if the system call fails.

可用性: Unix, Windows, not WASI.

在 3.3 版被加入.

在 3.8 版的變更: 增加對 Windows 的支援。

備註

On Windows network interfaces have different names in different contexts (all names are examples):

UUID: {FB605B73-AAC2-49A6-9A2F-25416AEA0573}

name: ethernet_32770

friendly name: vEthernet (nat)

description: Hyper-V Virtual Ethernet Adapter

This function returns names of the second form from the list, ethernet_32770 in this example case.

socket.if_nametoindex(if_name)

Return a network interface index number corresponding to an interface name. OSError if no interface with the given name exists.

可用性: Unix, Windows, not WASI.

在 3.3 版被加入.

在 3.8 版的變更: 增加對 Windows 的支援。

也參考

"Interface name" is a name as documented in if_nameindex().

socket.if_indextoname(if_index)

Return a network interface name corresponding to an interface index number. OSError if no interface with the given index exists.

可用性: Unix, Windows, not WASI.

在 3.3 版被加入.

在 3.8 版的變更: 增加對 Windows 的支援。

也參考

"Interface name" is a name as documented in if_nameindex().

socket.send_fds(sock, buffers, fds[, flags[, address]])

Send the list of file descriptors fds over an AF_UNIX socket sock. The fds parameter is a sequence of file descriptors. Consult sendmsg() for the documentation of these parameters.

可用性: Unix, not WASI.

Unix platforms supporting sendmsg() and SCM_RIGHTS mechanism.

在 3.9 版被加入.

socket.recv_fds(sock, bufsize, maxfds[, flags])

Receive up to maxfds file descriptors from an AF_UNIX socket sock. Return (msg, list(fds), flags, addr). Consult recvmsg() for the documentation of these parameters.

可用性: Unix, not WASI.

Unix platforms supporting recvmsg() and SCM_RIGHTS mechanism.

在 3.9 版被加入.

備註

Any truncated integers at the end of the list of file descriptors.

Socket 物件

Socket objects have the following methods. Except for makefile(), these correspond to Unix system calls applicable to sockets.

在 3.2 版的變更: Support for the context manager protocol was added. Exiting the context manager is equivalent to calling close().

socket.accept()

Accept a connection. The socket must be bound to an address and listening for connections. The return value is a pair (conn, address) where conn is a new socket object usable to send and receive data on the connection, and address is the address bound to the socket on the other end of the connection.

The newly created socket is non-inheritable.

在 3.4 版的變更: The socket is now non-inheritable.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.bind(address)

Bind the socket to address. The socket must not already be bound. (The format of address depends on the address family --- see above.)

引發一個附帶引數 self、address 的稽核事件 socket.bind。

可用性: not WASI.

socket.close()

Mark the socket closed. The underlying system resource (e.g. a file descriptor) is also closed when all file objects from makefile() are closed. Once that happens, all future operations on the socket object will fail. The remote end will receive no more data (after queued data is flushed).

Sockets are automatically closed when they are garbage-collected, but it is recommended to close() them explicitly, or to use a with statement around them.

在 3.6 版的變更: OSError is now raised if an error occurs when the underlying close() call is made.

備註

close() releases the resource associated with a connection but does not necessarily close the connection immediately. If you want to close the connection in a timely fashion, call shutdown() before close().

socket.connect(address)

Connect to a remote socket at address. (The format of address depends on the address family --- see above.)

If the connection is interrupted by a signal, the method waits until the connection completes, or raise a TimeoutError on timeout, if the signal handler doesn't raise an exception and the socket is blocking or has a timeout. For non-blocking sockets, the method raises an InterruptedError exception if the connection is interrupted by a signal (or the exception raised by the signal handler).

引發一個附帶引數 self、address 的稽核事件 socket.connect。

在 3.5 版的變更: The method now waits until the connection completes instead of raising an InterruptedError exception if the connection is interrupted by a signal, the signal handler doesn't raise an exception and the socket is blocking or has a timeout (see the PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

可用性: not WASI.

socket.connect_ex(address)

Like connect(address), but return an error indicator instead of raising an exception for errors returned by the C-level connect() call (other problems, such as "host not found," can still raise exceptions). The error indicator is 0 if the operation succeeded, otherwise the value of the errno variable. This is useful to support, for example, asynchronous connects.

引發一個附帶引數 self、address 的稽核事件 socket.connect。

可用性: not WASI.

socket.detach()

Put the socket object into closed state without actually closing the underlying file descriptor. The file descriptor is returned, and can be reused for other purposes.

在 3.2 版被加入.

socket.dup()

Duplicate the socket.

The newly created socket is non-inheritable.

在 3.4 版的變更: The socket is now non-inheritable.

可用性: not WASI.

socket.fileno()

Return the socket's file descriptor (a small integer), or -1 on failure. This is useful with select.select().

Under Windows the small integer returned by this method cannot be used where a file descriptor can be used (such as os.fdopen()). Unix does not have this limitation.

socket.get_inheritable()

Get the inheritable flag of the socket's file descriptor or socket's handle: True if the socket can be inherited in child processes, False if it cannot.

在 3.4 版被加入.

socket.getpeername()

Return the remote address to which the socket is connected. This is useful to find out the port number of a remote IPv4/v6 socket, for instance. (The format of the address returned depends on the address family --- see above.) On some systems this function is not supported.

socket.getsockname()

Return the socket's own address. This is useful to find out the port number of an IPv4/v6 socket, for instance. (The format of the address returned depends on the address family --- see above.)

socket.getsockopt(level, optname[, buflen])

Return the value of the given socket option (see the Unix man page getsockopt(2) [https://manpages.debian.org/getsockopt(2)]). The needed symbolic constants (SO_* etc.) are defined in this module. If buflen is absent, an integer option is assumed and its integer value is returned by the function. If buflen is present, it specifies the maximum length of the buffer used to receive the option in, and this buffer is returned as a bytes object. It is up to the caller to decode the contents of the buffer (see the optional built-in module struct for a way to decode C structures encoded as byte strings).

可用性: not WASI.

socket.getblocking()

Return True if socket is in blocking mode, False if in non-blocking.

這等同於檢查 socket.gettimeout() != 0。

在 3.7 版被加入.

socket.gettimeout()

Return the timeout in seconds (float) associated with socket operations, or None if no timeout is set. This reflects the last call to setblocking() or settimeout().

socket.ioctl(control, option)

The ioctl() method is a limited interface to the WSAIoctl system interface. Please refer to the Win32 documentation [https://msdn.microsoft.com/en-us/library/ms741621%28VS.85%29.aspx] for more information.

On other platforms, the generic fcntl.fcntl() and fcntl.ioctl() functions may be used; they accept a socket object as their first argument.

Currently only the following control codes are supported: SIO_RCVALL, SIO_KEEPALIVE_VALS, and SIO_LOOPBACK_FAST_PATH.

可用性: Windows

在 3.6 版的變更: 加入 SIO_LOOPBACK_FAST_PATH。

socket.listen([backlog])

Enable a server to accept connections. If backlog is specified, it must be at least 0 (if it is lower, it is set to 0); it specifies the number of unaccepted connections that the system will allow before refusing new connections. If not specified, a default reasonable value is chosen.

可用性: not WASI.

在 3.5 版的變更: The backlog parameter is now optional.

socket.makefile(mode='r', buffering=None, *, encoding=None, errors=None, newline=None)

Return a file object associated with the socket. The exact returned type depends on the arguments given to makefile(). These arguments are interpreted the same way as by the built-in open() function, except the only supported mode values are 'r' (default), 'w', 'b', or a combination of those.

The socket must be in blocking mode; it can have a timeout, but the file object's internal buffer may end up in an inconsistent state if a timeout occurs.

Closing the file object returned by makefile() won't close the original socket unless all other file objects have been closed and socket.close() has been called on the socket object.

備註

On Windows, the file-like object created by makefile() cannot be used where a file object with a file descriptor is expected, such as the stream arguments of subprocess.Popen().

socket.recv(bufsize[, flags])

Receive data from the socket. The return value is a bytes object representing the data received. The maximum amount of data to be received at once is specified by bufsize. A returned empty bytes object indicates that the client has disconnected. See the Unix manual page recv(2) [https://manpages.debian.org/recv(2)] for the meaning of the optional argument flags; it defaults to zero.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.recvfrom(bufsize[, flags])

Receive data from the socket. The return value is a pair (bytes, address) where bytes is a bytes object representing the data received and address is the address of the socket sending the data. See the Unix manual page recv(2) [https://manpages.debian.org/recv(2)] for the meaning of the optional argument flags; it defaults to zero. (The format of address depends on the address family --- see above.)

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

在 3.7 版的變更: For multicast IPv6 address, first item of address does not contain %scope_id part anymore. In order to get full IPv6 address use getnameinfo().

socket.recvmsg(bufsize[, ancbufsize[, flags]])

Receive normal data (up to bufsize bytes) and ancillary data from the socket. The ancbufsize argument sets the size in bytes of the internal buffer used to receive the ancillary data; it defaults to 0, meaning that no ancillary data will be received. Appropriate buffer sizes for ancillary data can be calculated using CMSG_SPACE() or CMSG_LEN(), and items which do not fit into the buffer might be truncated or discarded. The flags argument defaults to 0 and has the same meaning as for recv().

The return value is a 4-tuple: (data, ancdata, msg_flags, address). The data item is a bytes object holding the non-ancillary data received. The ancdata item is a list of zero or more tuples (cmsg_level, cmsg_type, cmsg_data) representing the ancillary data (control messages) received: cmsg_level and cmsg_type are integers specifying the protocol level and protocol-specific type respectively, and cmsg_data is a bytes object holding the associated data. The msg_flags item is the bitwise OR of various flags indicating conditions on the received message; see your system documentation for details. If the receiving socket is unconnected, address is the address of the sending socket, if available; otherwise, its value is unspecified.

On some systems, sendmsg() and recvmsg() can be used to pass file descriptors between processes over an AF_UNIX socket. When this facility is used (it is often restricted to SOCK_STREAM sockets), recvmsg() will return, in its ancillary data, items of the form (socket.SOL_SOCKET, socket.SCM_RIGHTS, fds), where fds is a bytes object representing the new file descriptors as a binary array of the native C int type. If recvmsg() raises an exception after the system call returns, it will first attempt to close any file descriptors received via this mechanism.

Some systems do not indicate the truncated length of ancillary data items which have been only partially received. If an item appears to extend beyond the end of the buffer, recvmsg() will issue a RuntimeWarning, and will return the part of it which is inside the buffer provided it has not been truncated before the start of its associated data.

On systems which support the SCM_RIGHTS mechanism, the following function will receive up to maxfds file descriptors, returning the message data and a list containing the descriptors (while ignoring unexpected conditions such as unrelated control messages being received). See also sendmsg().

import socket, array

def recv_fds(sock, msglen, maxfds):
    fds = array.array("i")   # Array of ints
    msg, ancdata, flags, addr = sock.recvmsg(msglen, socket.CMSG_LEN(maxfds * fds.itemsize))
    for cmsg_level, cmsg_type, cmsg_data in ancdata:
        if cmsg_level == socket.SOL_SOCKET and cmsg_type == socket.SCM_RIGHTS:
            # Append data, ignoring any truncated integers at the end.
            fds.frombytes(cmsg_data[:len(cmsg_data) - (len(cmsg_data) % fds.itemsize)])
    return msg, list(fds)

可用性: Unix.

Most Unix platforms.

在 3.3 版被加入.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.recvmsg_into(buffers[, ancbufsize[, flags]])

Receive normal data and ancillary data from the socket, behaving as recvmsg() would, but scatter the non-ancillary data into a series of buffers instead of returning a new bytes object. The buffers argument must be an iterable of objects that export writable buffers (e.g. bytearray objects); these will be filled with successive chunks of the non-ancillary data until it has all been written or there are no more buffers. The operating system may set a limit (sysconf() value SC_IOV_MAX) on the number of buffers that can be used. The ancbufsize and flags arguments have the same meaning as for recvmsg().

The return value is a 4-tuple: (nbytes, ancdata, msg_flags, address), where nbytes is the total number of bytes of non-ancillary data written into the buffers, and ancdata, msg_flags and address are the same as for recvmsg().

範例：

>>> import socket
>>> s1, s2 = socket.socketpair()
>>> b1 = bytearray(b'----')
>>> b2 = bytearray(b'0123456789')
>>> b3 = bytearray(b'--------------')
>>> s1.send(b'Mary had a little lamb')
22
>>> s2.recvmsg_into([b1, memoryview(b2)[2:9], b3])
(22, [], 0, None)
>>> [b1, b2, b3]
[bytearray(b'Mary'), bytearray(b'01 had a 9'), bytearray(b'little lamb---')]

可用性: Unix.

Most Unix platforms.

在 3.3 版被加入.

socket.recvfrom_into(buffer[, nbytes[, flags]])

Receive data from the socket, writing it into buffer instead of creating a new bytestring. The return value is a pair (nbytes, address) where nbytes is the number of bytes received and address is the address of the socket sending the data. See the Unix manual page recv(2) [https://manpages.debian.org/recv(2)] for the meaning of the optional argument flags; it defaults to zero. (The format of address depends on the address family --- see above.)

socket.recv_into(buffer[, nbytes[, flags]])

Receive up to nbytes bytes from the socket, storing the data into a buffer rather than creating a new bytestring. If nbytes is not specified (or 0), receive up to the size available in the given buffer. Returns the number of bytes received. See the Unix manual page recv(2) [https://manpages.debian.org/recv(2)] for the meaning of the optional argument flags; it defaults to zero.

socket.send(bytes[, flags])

Send data to the socket. The socket must be connected to a remote socket. The optional flags argument has the same meaning as for recv() above. Returns the number of bytes sent. Applications are responsible for checking that all data has been sent; if only some of the data was transmitted, the application needs to attempt delivery of the remaining data. For further information on this topic, consult the Socket 程式設計指南.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.sendall(bytes[, flags])

Send data to the socket. The socket must be connected to a remote socket. The optional flags argument has the same meaning as for recv() above. Unlike send(), this method continues to send data from bytes until either all data has been sent or an error occurs. None is returned on success. On error, an exception is raised, and there is no way to determine how much data, if any, was successfully sent.

在 3.5 版的變更: The socket timeout is no longer reset each time data is sent successfully. The socket timeout is now the maximum total duration to send all data.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.sendto(bytes, address)

socket.sendto(bytes, flags, address)

Send data to the socket. The socket should not be connected to a remote socket, since the destination socket is specified by address. The optional flags argument has the same meaning as for recv() above. Return the number of bytes sent. (The format of address depends on the address family --- see above.)

引發一個附帶引數 self、address 的稽核事件 socket.sendto。

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.sendmsg(buffers[, ancdata[, flags[, address]]])

Send normal and ancillary data to the socket, gathering the non-ancillary data from a series of buffers and concatenating it into a single message. The buffers argument specifies the non-ancillary data as an iterable of bytes-like objects (e.g. bytes objects); the operating system may set a limit (sysconf() value SC_IOV_MAX) on the number of buffers that can be used. The ancdata argument specifies the ancillary data (control messages) as an iterable of zero or more tuples (cmsg_level, cmsg_type, cmsg_data), where cmsg_level and cmsg_type are integers specifying the protocol level and protocol-specific type respectively, and cmsg_data is a bytes-like object holding the associated data. Note that some systems (in particular, systems without CMSG_SPACE()) might support sending only one control message per call. The flags argument defaults to 0 and has the same meaning as for send(). If address is supplied and not None, it sets a destination address for the message. The return value is the number of bytes of non-ancillary data sent.

The following function sends the list of file descriptors fds over an AF_UNIX socket, on systems which support the SCM_RIGHTS mechanism. See also recvmsg().

import socket, array

def send_fds(sock, msg, fds):
    return sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, array.array("i", fds))])

可用性: Unix, not WASI.

Most Unix platforms.

引發一個附帶引數 self、address 的稽核事件 socket.sendmsg。

在 3.3 版被加入.

在 3.5 版的變更: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale).

socket.sendmsg_afalg([msg, ]*, op[, iv[, assoclen[, flags]]])

Specialized version of sendmsg() for AF_ALG socket. Set mode, IV, AEAD associated data length and flags for AF_ALG socket.

可用性: Linux >= 2.6.38.

在 3.6 版被加入.

socket.sendfile(file, offset=0, count=None)

Send a file until EOF is reached by using high-performance os.sendfile and return the total number of bytes which were sent. file must be a regular file object opened in binary mode. If os.sendfile is not available (e.g. Windows) or file is not a regular file send() will be used instead. offset tells from where to start reading the file. If specified, count is the total number of bytes to transmit as opposed to sending the file until EOF is reached. File position is updated on return or also in case of error in which case file.tell() can be used to figure out the number of bytes which were sent. The socket must be of SOCK_STREAM type. Non-blocking sockets are not supported.

在 3.5 版被加入.

socket.set_inheritable(inheritable)

Set the inheritable flag of the socket's file descriptor or socket's handle.

在 3.4 版被加入.

socket.setblocking(flag)

Set blocking or non-blocking mode of the socket: if flag is false, the socket is set to non-blocking, else to blocking mode.

This method is a shorthand for certain settimeout() calls:

sock.setblocking(True) 等價於 sock.settimeout(None)

sock.setblocking(False) 等價於 sock.settimeout(0.0)

在 3.7 版的變更: The method no longer applies SOCK_NONBLOCK flag on socket.type.

socket.settimeout(value)

Set a timeout on blocking socket operations. The value argument can be a nonnegative floating-point number expressing seconds, or None. If a non-zero value is given, subsequent socket operations will raise a timeout exception if the timeout period value has elapsed before the operation has completed. If zero is given, the socket is put in non-blocking mode. If None is given, the socket is put in blocking mode.

For further information, please consult the notes on socket timeouts.

在 3.7 版的變更: The method no longer toggles SOCK_NONBLOCK flag on socket.type.

socket.setsockopt(level, optname, value: int | Buffer)

socket.setsockopt(level, optname, None, optlen: int)

Set the value of the given socket option (see the Unix manual page setsockopt(2) [https://manpages.debian.org/setsockopt(2)]). The needed symbolic constants are defined in this module (SO_* etc. <socket-unix-constants>). The value can be an integer, None or a bytes-like object representing a buffer. In the later case it is up to the caller to ensure that the bytestring contains the proper bits (see the optional built-in module struct for a way to encode C structures as bytestrings). When value is set to None, optlen argument is required. It's equivalent to call setsockopt() C function with optval=NULL and optlen=optlen.

在 3.5 版的變更: Writable bytes-like object is now accepted.

在 3.6 版的變更: setsockopt(level, optname, None, optlen: int) form added.

可用性: not WASI.

socket.shutdown(how)

Shut down one or both halves of the connection. If how is SHUT_RD, further receives are disallowed. If how is SHUT_WR, further sends are disallowed. If how is SHUT_RDWR, further sends and receives are disallowed.

可用性: not WASI.

socket.share(process_id)

Duplicate a socket and prepare it for sharing with a target process. The target process must be provided with process_id. The resulting bytes object can then be passed to the target process using some form of interprocess communication and the socket can be recreated there using fromshare(). Once this method has been called, it is safe to close the socket since the operating system has already duplicated it for the target process.

可用性: Windows.

在 3.3 版被加入.

Note that there are no methods read() or write(); use recv() and send() without flags argument instead.

Socket objects also have these (read-only) attributes that correspond to the values given to the socket constructor.

socket.family

The socket family.

socket.type

The socket type.

socket.proto

The socket protocol.

Notes on socket timeouts

A socket object can be in one of three modes: blocking, non-blocking, or timeout. Sockets are by default always created in blocking mode, but this can be changed by calling setdefaulttimeout().

In blocking mode, operations block until complete or the system returns an error (such as connection timed out).

In non-blocking mode, operations fail (with an error that is unfortunately system-dependent) if they cannot be completed immediately: functions from the select module can be used to know when and whether a socket is available for reading or writing.

In timeout mode, operations fail if they cannot be completed within the timeout specified for the socket (they raise a timeout exception) or if the system returns an error.

備註

At the operating system level, sockets in timeout mode are internally set in non-blocking mode. Also, the blocking and timeout modes are shared between file descriptors and socket objects that refer to the same network endpoint. This implementation detail can have visible consequences if e.g. you decide to use the fileno() of a socket.

Timeouts and the connect method

The connect() operation is also subject to the timeout setting, and in general it is recommended to call settimeout() before calling connect() or pass a timeout parameter to create_connection(). However, the system network stack may also return a connection timeout error of its own regardless of any Python socket timeout setting.

Timeouts and the accept method

If getdefaulttimeout() is not None, sockets returned by the accept() method inherit that timeout. Otherwise, the behaviour depends on settings of the listening socket:

if the listening socket is in blocking mode or in timeout mode, the socket returned by accept() is in blocking mode;

if the listening socket is in non-blocking mode, whether the socket returned by accept() is in blocking or non-blocking mode is operating system-dependent. If you want to ensure cross-platform behaviour, it is recommended you manually override this setting.

範例

Here are four minimal example programs using the TCP/IP protocol: a server that echoes all data that it receives back (servicing only one client), and a client using it. Note that a server must perform the sequence socket(), bind(), listen(), accept() (possibly repeating the accept() to service more than one client), while a client only needs the sequence socket(), connect(). Also note that the server does not sendall()/recv() on the socket it is listening on but on the new socket returned by accept().

前兩個範例只支援 IPv4：

# Echo server program
import socket

HOST = ''                 # Symbolic name meaning all available interfaces
PORT = 50007              # Arbitrary non-privileged port
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen(1)
    conn, addr = s.accept()
    with conn:
        print('Connected by', addr)
        while True:
            data = conn.recv(1024)
            if not data: break
            conn.sendall(data)

# Echo client program
import socket

HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((HOST, PORT))
    s.sendall(b'Hello, world')
    data = s.recv(1024)
print('Received', repr(data))

The next two examples are identical to the above two, but support both IPv4 and IPv6. The server side will listen to the first address family available (it should listen to both instead). On most of IPv6-ready systems, IPv6 will take precedence and the server may not accept IPv4 traffic. The client side will try to connect to all the addresses returned as a result of the name resolution, and sends traffic to the first one connected successfully.

# Echo server program
import socket
import sys

HOST = None               # Symbolic name meaning all available interfaces
PORT = 50007              # Arbitrary non-privileged port
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC,
                              socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
    af, socktype, proto, canonname, sa = res
    try:
        s = socket.socket(af, socktype, proto)
    except OSError as msg:
        s = None
        continue
    try:
        s.bind(sa)
        s.listen(1)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print('could not open socket')
    sys.exit(1)
conn, addr = s.accept()
with conn:
    print('Connected by', addr)
    while True:
        data = conn.recv(1024)
        if not data: break
        conn.send(data)

# Echo client program
import socket
import sys

HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM):
    af, socktype, proto, canonname, sa = res
    try:
        s = socket.socket(af, socktype, proto)
    except OSError as msg:
        s = None
        continue
    try:
        s.connect(sa)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print('could not open socket')
    sys.exit(1)
with s:
    s.sendall(b'Hello, world')
    data = s.recv(1024)
print('Received', repr(data))

The next example shows how to write a very simple network sniffer with raw sockets on Windows. The example requires administrator privileges to modify the interface:

import socket

# the public network interface
HOST = socket.gethostbyname(socket.gethostname())

# create a raw socket and bind it to the public interface
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP)
s.bind((HOST, 0))

# Include IP headers
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

# receive all packets
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)

# receive a packet
print(s.recvfrom(65565))

# disabled promiscuous mode
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)

The next example shows how to use the socket interface to communicate to a CAN network using the raw socket protocol. To use CAN with the broadcast manager protocol instead, open a socket with:

socket.socket(socket.AF_CAN, socket.SOCK_DGRAM, socket.CAN_BCM)

After binding (CAN_RAW) or connecting (CAN_BCM) the socket, you can use the socket.send() and socket.recv() operations (and their counterparts) on the socket object as usual.

This last example might require special privileges:

import socket
import struct

# CAN frame packing/unpacking (see 'struct can_frame' in <linux/can.h>)

can_frame_fmt = "=IB3x8s"
can_frame_size = struct.calcsize(can_frame_fmt)

def build_can_frame(can_id, data):
    can_dlc = len(data)
    data = data.ljust(8, b'\x00')
    return struct.pack(can_frame_fmt, can_id, can_dlc, data)

def dissect_can_frame(frame):
    can_id, can_dlc, data = struct.unpack(can_frame_fmt, frame)
    return (can_id, can_dlc, data[:can_dlc])

# create a raw socket and bind it to the 'vcan0' interface
s = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
s.bind(('vcan0',))

while True:
    cf, addr = s.recvfrom(can_frame_size)

    print('Received: can_id=%x, can_dlc=%x, data=%s' % dissect_can_frame(cf))

    try:
        s.send(cf)
    except OSError:
        print('Error sending CAN frame')

    try:
        s.send(build_can_frame(0x01, b'\x01\x02\x03'))
    except OSError:
        print('Error sending CAN frame')

Running an example several times with too small delay between executions, could lead to this error:

OSError: [Errno 98] Address already in use

This is because the previous execution has left the socket in a TIME_WAIT state, and can't be immediately reused.

There is a socket flag to set, in order to prevent this, socket.SO_REUSEADDR:

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))

the SO_REUSEADDR flag tells the kernel to reuse a local socket in TIME_WAIT state, without waiting for its natural timeout to expire.

也參考

For an introduction to socket programming (in C), see the following papers:

An Introductory 4.3BSD Interprocess Communication Tutorial, by Stuart Sechrest

An Advanced 4.3BSD Interprocess Communication Tutorial, by Samuel J. Leffler et al,

both in the UNIX Programmer's Manual, Supplementary Documents 1 (sections PS1:7 and PS1:8). The platform-specific reference material for the various socket-related system calls are also a valuable source of information on the details of socket semantics. For Unix, refer to the manual pages; for Windows, see the WinSock (or Winsock 2) specification. For IPv6-ready APIs, readers may want to refer to RFC 3493 [https://datatracker.ietf.org/doc/html/rfc3493.html] titled Basic Socket Interface Extensions for IPv6.

ssl --- socket 物件的 TLS/SSL 包裝器

原始碼：Lib/ssl.py [https://github.com/python/cpython/tree/3.14/Lib/ssl.py]

這個模組向用戶端及伺服器端提供了對於網路 socket 的傳輸層安全性協定（或稱為「安全通訊協定 (Secure Sockets Layer)」）加密及身分驗證功能。這個模組使用 OpenSSL 套件。

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

備註

由於呼叫了作業系統的 socket APIs，有些行為會根據平台而有所不同。OpenSSL 的安裝版本也會對模組的運作產生影響。例如，OpenSSL 版本 1.1.1 附帶 TLSv1.3。

警告

在使用此模組之前，請閱讀 Security considerations。如果不這樣做，可能會產生錯誤的安全性認知，因為 ssl 模組的預設設定未必適合你的應用程式。

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

這個章節記錄了 ssl 模組的物件及函式；關於 TSL、SSL、以及憑證的更多資訊，可以去參考此章節底部的「詳情」部分。

此模組提供了一個 ssl.SSLSocket 類別，它是從 socket.socket 衍生出來的，並且提供類似 socket 的包裝器，讓使用 SSL 進行資料傳輸時，可以進行資料的加密及解密。它也提供了一些額外的方法，如 getpeercert()，用於取得連結另一端的憑證；以及 cipher()，用於搜尋用於安全連接的加密方法 (cipher)；和 get_verified_chain()、get_unverified_chain() 能用於取得憑證鏈。

對於更複雜的應用程式，ssl.SSLContext 類別有助於管理設定及認證，然後可以透過 SSLContext.wrap_socket() 方法建立的 SSL socket 繼承這些設定和認證。

在 3.5.3 版的變更: 更新以支援與 OpenSSL 1.1.0 進行連結

在 3.6 版的變更: OpenSSL 0.9.8, 1.0.0 及 1.0.1 版本已被棄用且不再支援。在未來 ssl 模組將需要至少 OpenSSL 1.0.2 版本或 1.1.0 版本。

在 3.10 版的變更: PEP 644 [https://peps.python.org/pep-0644/] 已經被實作。ssl 模組需要 OpenSSL 1.1.1 以上的版本才能使用。

使用已經被棄用的常數或函式將會導致棄用警示。

函式、常數與例外

Socket 建立

SSLSocket 實例必須使用 SSLContext.wrap_socket() 方法來建立。輔助函式 create_default_context() 會回傳有安全預設設定的新語境 (context)。

使用預設語境及 IPv4/IPv6 雙協定堆疊的用戶端 socket 範例：

import socket
import ssl

hostname = 'www.python.org'
context = ssl.create_default_context()

with socket.create_connection((hostname, 443)) as sock:
    with context.wrap_socket(sock, server_hostname=hostname) as ssock:
        print(ssock.version())

使用自訂語境及 IPv4 的用戶端 socket範例：

hostname = 'www.python.org'
# PROTOCOL_TLS_CLIENT requires valid cert chain and hostname
context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
context.load_verify_locations('path/to/cabundle.pem')

with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
    with context.wrap_socket(sock, server_hostname=hostname) as ssock:
        print(ssock.version())

在本地 IPv4 上監聽伺服器 socket 的範例：

context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
context.load_cert_chain('/path/to/certchain.pem', '/path/to/private.key')

with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
    sock.bind(('127.0.0.1', 8443))
    sock.listen(5)
    with context.wrap_socket(sock, server_side=True) as ssock:
        conn, addr = ssock.accept()
        ...

語境建立

一個可以幫忙建立出 SSLContext 物件以用於一般目的的方便函式。

ssl.create_default_context(purpose=Purpose.SERVER_AUTH, *, cafile=None, capath=None, cadata=None)

回傳一個新的 SSLContext 物件，使用給定 purpose 的預設值。這些設定是由 ssl 選擇，通常比直接呼叫 SSLContext 有更高的安全性。

cafile, capath, cadata 是用來選擇用於憑證認證的 CA 憑證，就像 SSLContext.load_verify_locations() 一樣。如果三個值都是 None，此函式會自動選擇系統預設的 CA 憑證。

這些設定包含：PROTOCOL_TLS_CLIENT 或 PROTOCOL_TLS_SERVER、OP_NO_SSLv2、以及 OP_NO_SSLv3，使用高等加密套件但不包含 RC4 和未經身份驗證的加密套件。如果將 purpose 設定為 SERVER_AUTH，則會把 verify_mode 設為 CERT_REQUIRED 並使用設定的 CA 憑證(當 cafile、capath 或 cadata 其中一個值有被設定時) 或使用預設的 CA 憑證 SSLContext.load_default_certs() 。

當系統有支援 keylog_filename 並且有設定環境變數 SSLKEYLOGFILE 時 create_default_context() 會啟用密鑰日誌記錄 (logging)。

The default settings for this context include VERIFY_X509_PARTIAL_CHAIN and VERIFY_X509_STRICT. These make the underlying OpenSSL implementation behave more like a conforming implementation of RFC 5280 [https://datatracker.ietf.org/doc/html/rfc5280.html], in exchange for a small amount of incompatibility with older X.509 certificates.

備註

協定、選項、加密方式和其它設定可以在不捨棄舊值的情況下直接更改成新的值，這些值代表了在相容性和安全性之間取得的合理平衡。

如果你的應用程式需要特殊的設定，你應該要自行建立一個 SSLContext 並自行調整設定。

備註

如果你發現某些舊的用戶端或伺服器常適用此函式建立的 SSLContext 連線時，收到 "Protocol or cipher suite mismatch" 錯誤，這可能是因為他們的系統僅支援 SSL3.0，然而 SSL3.0 已被此函式用 OP_NO_SSLv3 排除。目前廣泛認為 SSL3.0 已經被完全破解 [https://en.wikipedia.org/wiki/POODLE]。如果你仍然希望在允許 SSL3.0 連線的情況下使用此函式，可以使用下面的方法：

ctx = ssl.create_default_context(Purpose.CLIENT_AUTH)
ctx.options &= ~ssl.OP_NO_SSLv3

備註

This context enables VERIFY_X509_STRICT by default, which may reject pre-RFC 5280 [https://datatracker.ietf.org/doc/html/rfc5280.html] or malformed certificates that the underlying OpenSSL implementation otherwise would accept. While disabling this is not recommended, you can do so using:

ctx = ssl.create_default_context()
ctx.verify_flags &= ~ssl.VERIFY_X509_STRICT

在 3.4 版被加入.

在 3.4.4 版的變更: 把 RC4 從預設加密方法字串中捨棄。

在 3.6 版的變更: 把 ChaCha20/Poly1305 加入預設加密方法字串。

把 3DES 從預設加密方法字串中捨棄。

在 3.8 版的變更: 增加了 SSLKEYLOGFILE 對密鑰日誌記錄 (logging) 的支援。

在 3.10 版的變更: 目前語境使用 PROTOCOL_TLS_CLIENT 協定或 PROTOCOL_TLS_SERVER 協定而非通用的 PROTOCOL_TLS。

在 3.13 版的變更: The context now uses VERIFY_X509_PARTIAL_CHAIN and VERIFY_X509_STRICT in its default verify flags.

例外

exception ssl.SSLError

引發由底層 SSL 實作（目前由 OpenSSL 函式庫提供）所引發的錯誤訊息。這表示在覆蓋底層網路連線的高階加密和身份驗證層中存在一些問題。這項錯誤是 OSError 的一個子型別。SSLError 實例的錯誤程式代碼和訊息是由 OpenSSL 函式庫提供。

在 3.3 版的變更: SSLError 曾經是 socket.error 的一個子型別。

library

一個字串符號 (string mnemonic)，用來指定發生錯誤的 OpenSSL 子模組，如：SSL、PEM 或 X509。可能值的範圍取決於 OpenSSL 的版本。

在 3.3 版被加入.

reason

一個字串符號，用來指定發生錯誤的原因，如：CERTIFICATE_VERIFY_FAILED。可能值的範圍取決於 OpenSSL 的版本。

在 3.3 版被加入.

exception ssl.SSLZeroReturnError

一個 SSLError 的子類別，當嘗試去讀寫已經被完全關閉的 SSL 連線時會被引發。請注意，這並不表示底層傳輸（例如 TCP）已經被關閉。

在 3.3 版被加入.

exception ssl.SSLWantReadError

一個 SSLError 的子類別，當嘗試去讀寫資料前，底層 TCP 傳輸需要先接收更多資料時會由非阻塞的 SSL socket 引發該錯誤。

在 3.3 版被加入.

exception ssl.SSLWantWriteError

一個 SSLError 的子類別，當嘗試去讀寫資料前，底層 TCP 傳輸需要先發送更多資料時會由非阻塞的 SSL socket 引發該錯誤。

在 3.3 版被加入.

exception ssl.SSLSyscallError

一個 SSLError 的子類別，當嘗試去操作 SSL socket 時有系統錯誤產生會引發此錯誤。不幸的是，目前沒有任何簡單的方法可以去檢查原本的的 errno 編號。

在 3.3 版被加入.

exception ssl.SSLEOFError

一個 SSLError 的子類別，當 SSL 連線被突然終止時會引發此錯誤。通常，當此錯誤發生時，你不該再去重新使用底層傳輸。

在 3.3 版被加入.

exception ssl.SSLCertVerificationError

當憑證驗證失敗時會引發的一個 SSLError 子類別。

在 3.7 版被加入.

verify_code

一個表示驗證錯誤的錯誤數值編號。

verify_message

一個人類可讀的驗證錯誤字串。

exception ssl.CertificateError

SSLCertVerificationError 的別名。

在 3.7 版的變更: 此例外現在是 SSLCertVerificationError 的別名。

隨機產生

ssl.RAND_bytes(num, /)

回傳 num 個加密性強的偽隨機位元組。如果 PRNG 未使用足夠的資料做為隨機種子 (seed) 或是目前的 RAND 方法不支援該操作則會導致 SSLError 錯誤。RAND_status() 函式可以用來檢查 PRNG 函式，而 RAND_add() 則可以用來為 PRNG 設定隨機種子。

在幾乎所有的應用程式中，os.urandom() 會是較好的選擇。

請閱讀維基百科的密碼學安全偽隨機數產生器 (CSPRNG) [https://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator]文章來了解密碼學安全偽隨機數產生器的需求。

在 3.3 版被加入.

ssl.RAND_status()

如果 SSL 偽隨機數產生器已經使用「足夠的」隨機性進行隨機種子生成，則回傳 True ，否則回傳 False。你可以使用 ssl.RAND_egd() 函式和 ssl.RAND_add() 函式來增加偽隨機數產生器的隨機性。

ssl.RAND_add(bytes, entropy, /)

將給定的 bytes 混進 SSL 隨機偽隨機數產生器中。 entropy 參數（float 值）是指字串中包含熵值的下限（因此你可以將其設為 0.0）。請參閱 RFC 1750 [https://datatracker.ietf.org/doc/html/rfc1750.html] 了解有關熵源的更多資訊。

在 3.5 版的變更: 可寫入的類位元組物件現在可被接受。

認證處理

ssl.cert_time_to_seconds(cert_time)

回傳自紀元以來的秒數，給定的 cert_time 字串表示憑證的 "notBefore" 或 "notAfter" 日期，字串採用 "%b %d %H:%M:%S %Y %Z" 格式（C 語言區域設定）。

以下是一個範例：

>>> import ssl
>>> timestamp = ssl.cert_time_to_seconds("Jan  5 09:34:43 2018 GMT")
>>> timestamp
1515144883
>>> from datetime import datetime
>>> print(datetime.utcfromtimestamp(timestamp))
2018-01-05 09:34:43

"notBefore" 或 "notAfter" 日期必須使用 GMT (RFC 5280 [https://datatracker.ietf.org/doc/html/rfc5280.html])。

在 3.5 版的變更: 將輸入的時間直譯為 UTC 時間，如輸入字串中指定的 'GMT' 時區。在之前是使用本地的時區。回傳一個整數（在輸入格式中不包括秒的小數部分）。

ssl.get_server_certificate(addr, ssl_version=PROTOCOL_TLS_CLIENT, ca_certs=None[, timeout])

輸入使用 SSL 保護的伺服器的地址 addr，輸入形式為一個 pair (hostname, port-number)，取得該伺服器的憑證，並以 PEM 編碼字串的形式回傳。如果指定了 ssl_version，則使用指定的 SSL 協定來嘗試與伺服器連線。如果指定 ca_certs，則它應該是一個包含根憑證列表的檔案，並與 SSLContext.load_verify_locations() 中的參數 cafile 所使用的格式相同。此呼叫將嘗試使用該組根憑證對伺服器憑證進行驗證，如果驗證失敗，呼叫將失敗。可以使用 timeout 參數指定超時時間。

在 3.3 版的變更: 此函式現在是與 IPv6 相容的。

在 3.5 版的變更: 預設的 ssl_version 已經從 PROTOCOL_SSLv3 改為 PROTOCOL_TLS，已確保與現今的伺服器有最大的相容性。

在 3.10 版的變更: 新增 timeout 參數。

ssl.DER_cert_to_PEM_cert(der_cert_bytes)

給定一個以 DER 編碼的位元組 blob 作為憑證，回傳以 PEM 編碼字串版本的相同憑證。

ssl.PEM_cert_to_DER_cert(pem_cert_string)

給定一個以 ASCII PEM 的字串作為憑證，回傳以 DER 編碼的位元組序列的相同憑證。

ssl.get_default_verify_paths()

回傳一個具有 OpenSSL 的預設 cafile 和 capath 路徑的附名元組。這些路徑與 SSLContext.set_default_verify_paths() 使用的相同。回傳值是一個 named tuple DefaultVerifyPaths：

cafile - 解析後的 cafile 路徑，如果檔案不存在則為 None，

capath - 解析後的 capath 路徑，如果目錄不存在則為 None，

openssl_cafile_env - 指向 cafile 的 OpenSSL 環境密鑰，

openssl_cafile - hard coded 的 cafile 路徑，

openssl_capath_env - 指向 capath 的 OpenSSL 環境密鑰，

openssl_capath - hard coded 的 capath 目錄路徑

在 3.4 版被加入.

ssl.enum_certificates(store_name)

從 Windows 的系統憑證儲存庫中搜尋憑證。store_name 可以是 CA、ROOT 或 MY 的其中一個。Windows 也可能會提供額外的憑證儲存庫。

此函式會回傳一個元組 (cert_bytes, encoding_type, trust) 串列。encoding_type 指定了 cert_bytes 的編碼格式。它可以是用來表示 X.509 ASN.1 資料的 x509_asn 或是用來表示 PKCS#7 ASN.1 資料的 pkcs_7_asn。Trust 透過一組 OIDS 來指定憑證的用途，或是如果憑證對所有用途都可以使用則回傳 True。

範例：

>>> ssl.enum_certificates("CA")
[(b'data...', 'x509_asn', {'1.3.6.1.5.5.7.3.1', '1.3.6.1.5.5.7.3.2'}),
 (b'data...', 'x509_asn', True)]

可用性: Windows.

在 3.4 版被加入.

ssl.enum_crls(store_name)

從 Windows 的系統憑證儲存庫中搜尋 CRLs。store_name 可以是 CA、ROOT 或 MY 的其中一個。Windows 也可能會提供額外的憑證儲存庫。

此函式會回傳一個元組 (cert_bytes, encoding_type, trust) 串列。encoding_type 指定了 cert_bytes 的編碼格式。它可以是用來表示 X.509 ASN.1 資料的 x509_asn 或是用來表示 PKCS#7 ASN.1 資料的 pkcs_7_asn。

可用性: Windows.

在 3.4 版被加入.

常數

所有的常數現在都是 enum.IntEnum 或 enum.IntFlag 的集合。

在 3.6 版被加入.

ssl.CERT_NONE

SSLContext.verify_mode 可能的值。除了 PROTOCOL_TLS_CLIENT 外，這是預設的模式。對於用戶端的 sockets，幾乎任何憑證都能被允許。驗證錯誤，像是不被信任或是過期的憑證，會被忽略並不會中止 TLS/SSL 握手。

在伺服器模式下，不會從用戶端請求任何憑證，所以用戶端不用發送任何用於用戶端憑證身分驗證的憑證。

參閱下方 Security considerations 的討論。

ssl.CERT_OPTIONAL

SSLContext.verify_mode 可能的值。在用戶端模式下，CERT_OPTIONAL 具有與 CERT_REQUIRED 相同的含意。對於客戶端 sockets 推薦改用 CERT_REQUIRED。

在伺服器模式下，客戶憑證請求會被發送給用戶端。用戶端可以選擇忽略請求或是選擇發送憑證來執行 TLS 用戶端憑證身分驗證。如果用戶端選擇發送憑證，則會對其進行驗證。任何驗證錯誤都會立刻終止 TLS 握手。

使用此設定需要將一組有效的 CA 憑證傳送給 SSLContext.load_verify_locations()。

ssl.CERT_REQUIRED

SSLContext.verify_mode 可能的值。在這個模式下，需要從 socket 連線的另一端取得憑證；如果未提供憑證或是驗證失敗，則將會導致 SSLError。此模式不能在用戶端模式下對憑證進行驗證，因為它無法去配對主機名稱。check_hostname 也必須被開起來來驗證憑證的真實性。PROTOCOL_TLS_CLIENT 會使用 CERT_REQUIRED 並預設開啟 check_hostname。

對於 socket 伺服器，此模式會提供強制的 TLS 用戶端憑證驗證。用戶端憑證請求會被發送給用戶端並且用戶端必須提供有效且被信任的憑證。

使用此設定需要將一組有效的 CA 憑證傳送給 SSLContext.load_verify_locations()。

class ssl.VerifyMode

enum.IntEnum 為 CERT_* 常數的一個集合。

在 3.6 版被加入.

ssl.VERIFY_DEFAULT

SSLContext.verify_flags 可能的值。在此模式下，不會檢查憑證吊銷列表 (CRLs)。預設的 OpenSSL 並不會請求及驗證 CRLs。

在 3.4 版被加入.

ssl.VERIFY_CRL_CHECK_LEAF

SSLContext.verify_flags 可能的值。在此模式下，只會檢查同等的憑證而不會去檢查中間的 CA 憑證。此模式需要提供由對等憑證發行者 (它的直接上級 CA) 的有效的 CRL 簽名。如果沒有用 SSLContext.load_verify_locations 載入適當的 CRL，則會驗證失敗。

在 3.4 版被加入.

ssl.VERIFY_CRL_CHECK_CHAIN

SSLContext.verify_flags 可能的值。在此模式下，會檢查對等憑證鍊中所有憑證的 CRLs。

在 3.4 版被加入.

ssl.VERIFY_X509_STRICT

SSLContext.verify_flags 可能的值，用來禁用已損壞的 X.509 憑證的解決方法。

在 3.4 版被加入.

ssl.VERIFY_ALLOW_PROXY_CERTS

SSLContext.verify_flags 可能的值，用來啟用憑證代理驗證。

在 3.10 版被加入.

ssl.VERIFY_X509_TRUSTED_FIRST

SSLContext.verify_flags 可能的值。它指示 OpenSSL 在構建信任鍊來驗證憑證時會優先使用被信任的憑證。此旗標預設開啟。

在 3.4.4 版被加入.

ssl.VERIFY_X509_PARTIAL_CHAIN

SSLContext.verify_flags 可能的值。它指示 OpenSSL 接受信任儲存中的中間 CAs 作為信任錨，就像自簽名的根 CA 憑證。這樣就能去信任中間 CA 所頒發的憑證，而不一定非要去信任其祖先的根 CA。

在 3.10 版被加入.

class ssl.VerifyFlags

enum.IntFlag 為 VERIFY_* 常數的其中一個集合。

在 3.6 版被加入.

ssl.PROTOCOL_TLS

選擇用戶端及伺服器均可以支援最高協定版本。儘管名稱只有 「TLS」，但實際上「SSL」和「TLS」均可以選擇。

在 3.6 版被加入.

在 3.10 版之後被棄用: TLS 的用戶端及伺服器端需要不同的預設值來實現安全通訊。通用的 TLS 協定常數已被廢除，並改用 PROTOCOL_TLS_CLIENT 和 PROTOCOL_TLS_SERVER。

ssl.PROTOCOL_TLS_CLIENT

自動協商用戶端和伺服器服務器都支援的最高協定版本，並配置用戶端語境連線。該協定預設啟用 CERT_REQUIRED 和 check_hostname。

在 3.6 版被加入.

ssl.PROTOCOL_TLS_SERVER

自動協商用戶端和伺服器都支援的最高協定版本，並配置用戶端語境連線。

在 3.6 版被加入.

ssl.PROTOCOL_SSLv23

PROTOCOL_TLS 的別名。

在 3.6 版之後被棄用: 請改用 PROTOCOL_TLS。

ssl.PROTOCOL_SSLv3

選擇第三版的 SSL 做為通道加密協定。

如果 OpenSSL 是用 no-ssl3 編譯的，則此項協定無法使用。

警告

第三版的 SSL 是不安全的，強烈建議不要使用。

在 3.6 版之後被棄用: OpenSSL 已經終止了所有特定版本的協定。請改用預設的 PROTOCOL_TLS_SERVER 協定或帶有 SSLContext.minimum_version 和 SSLContext.maximum_version 的 PROTOCOL_TLS_CLIENT。

ssl.PROTOCOL_TLSv1

選擇 1.0 版的 TLS 做為通道加密協定。

在 3.6 版之後被棄用: OpenSSL 已經將所有版本特定的協定棄用。

ssl.PROTOCOL_TLSv1_1

選擇 1.1 版的 TLS 做為通道加密協定。只有在 1.0.1 版本以上的 OpenSSL 才可以選用。

在 3.4 版被加入.

在 3.6 版之後被棄用: OpenSSL 已經將所有版本特定的協定棄用。

ssl.PROTOCOL_TLSv1_2

選擇 1.2 版的 TLS 做為通道加密協定。只有在 1.0.1 版本以上的 OpenSSL 才可以選用。

在 3.4 版被加入.

在 3.6 版之後被棄用: OpenSSL 已經將所有版本特定的協定棄用。

ssl.OP_ALL

啟用對 SSL 實作時所產生的各種錯誤的緩解措施。此選項預設被設定。它不一定設定與 OpenSSL 的 SSL_OP_ALL 常數相同的旗標。

在 3.2 版被加入.

ssl.OP_NO_SSLv2

防止 SSLv2 連線。此選項只可以跟 PROTOCOL_TLS 一起使用。它會防止同級 (peer)選用 SSLv2 做為協定版本。

在 3.2 版被加入.

在 3.6 版之後被棄用: SSLv2 已被棄用

ssl.OP_NO_SSLv3

防止 SSLv3 連線。此選項只可以跟 PROTOCOL_TLS 一起使用。它會防止同級選用 SSLv3 做為協定版本。

在 3.2 版被加入.

在 3.6 版之後被棄用: SSLv3 已被棄用

ssl.OP_NO_TLSv1

防止 TLSv1 連線。此選項只可以跟 PROTOCOL_TLS 一起使用。它會防止同級選用 TLSv1 做為協定版本。

在 3.2 版被加入.

在 3.7 版之後被棄用: 該選項自從 OpenSSL 1.1.0 以後已被棄用，請改用新的 SSLContext.minimum_version 及 SSLContext.maximum_version 代替。

ssl.OP_NO_TLSv1_1

防止 TLSv1.1 連線。此選項只可以跟 PROTOCOL_TLS 一起使用。它會防止同級選用 TLSv1.1 做為協定版本。只有 1.0.1 版後的 OpenSSL 版本才能使用。

在 3.4 版被加入.

在 3.7 版之後被棄用: 此選項自 OpenSSL 1.1.0 版已被棄用。

ssl.OP_NO_TLSv1_2

防止 TLSv1.2 連線。此選項只可以跟 PROTOCOL_TLS 一起使用。它會防止同級選用 TLSv1.2 做為協定版本。只有 1.0.1 版後的 OpenSSL 版本才能使用。

在 3.4 版被加入.

在 3.7 版之後被棄用: 此選項自 OpenSSL 1.1.0 版已被棄用。

ssl.OP_NO_TLSv1_3

防止 TLSv1.3 連線。此選項只可以跟 PROTOCOL_TLS 一起使用。它會防止同級選用 TLSv1.3 做為協定版本。TSL1.3 只適用於 1.1.1 版以後的 OpenSSL。當使用 Python 編譯舊版的 OpenSSL 時，該標志預設為 0。

在 3.6.3 版被加入.

在 3.7 版之後被棄用: 此選項自 OpenSSL 1.1.0 以後已被棄用。它被添加到 2.7.15 和 3.6.3 中，以向後相容 OpenSSL 1.0.2。

ssl.OP_NO_RENEGOTIATION

停用所有在 TLSv1.2 及更早版本的重協商 (renegotiation)。不發送 HelloRequest 訊息，並忽略透過 ClientHello 的重協商請求。

此選項僅適用於 OpenSSL 1.1.0h 及更新版本。

在 3.7 版被加入.

ssl.OP_CIPHER_SERVER_PREFERENCE

使用伺服器的加密方法名稱字串排序優先順序，而不是用戶端的。此選項並不會影響到用戶端及 SSLv2 伺服器的 sockets。

在 3.3 版被加入.

ssl.OP_SINGLE_DH_USE

防止對不同的 SSL 會談重複使用相同的 DH 密鑰。這會加強向前保密但需要更多的運算資源。此選項只適用於伺服器 sockets。

在 3.3 版被加入.

ssl.OP_SINGLE_ECDH_USE

防止對不同的 SSL 會談重複使用相同的 ECDH 密鑰。這會加強向前保密但需要更多的運算資源。此選項只適用於伺服器 sockets。

在 3.3 版被加入.

ssl.OP_ENABLE_MIDDLEBOX_COMPAT

在 TLS 1.3 握手中發送虛擬的變更加密方法規範 (CCS) 消息，以使 TLS 1.3 連接看起來更像 TLS 1.2 連線。

此選項僅適用於 OpenSSL 1.1.1 及更新版本。

在 3.8 版被加入.

ssl.OP_NO_COMPRESSION

在 SSL 通道上禁用壓縮。如果應用程序協定支援自己的壓縮方案，這會很有用。

在 3.3 版被加入.

class ssl.Options

enum.IntFlag 為 OP_* 常數中的一個集合。

ssl.OP_NO_TICKET

防止用戶端請求會談票據。

在 3.6 版被加入.

ssl.OP_IGNORE_UNEXPECTED_EOF

忽略意外關閉的 TLS 連線。

此選項僅適用於 OpenSSL 3.0.0 及更新版本。

在 3.10 版被加入.

ssl.OP_ENABLE_KTLS

允許使用 TLS 核心。要想受益於該功能，OpenSSL 必須編譯為支援該功能，並且想使用的加密套件及擴充套件也必須被該功能支援 (該功能所支援的列表可能會因平台及核心而有所差異)。

請注意當允許使用 TLS 核心時，一些加密操作將直接由核心執行而不是經由任何由可用的 OpenSSL 所提供的程序，而這可能並非你所想使用的，例如：當應用程式要求所有的加密操作由 FIPS 提供執行。

此選項僅適用於 OpenSSL 3.0.0 及更新版本。

在 3.12 版被加入.

ssl.OP_LEGACY_SERVER_CONNECT

只允許 OpenSSL 與未修補的伺服器進行遺留 (legacy) 不安全重協商。

在 3.12 版被加入.

ssl.HAS_ALPN

OpenSSL 函式庫是否內建支援 應用層協定協商 TLS 擴充套件，該擴充套件描述在 RFC 7301 [https://datatracker.ietf.org/doc/html/rfc7301.html] 中。

在 3.5 版被加入.

ssl.HAS_NEVER_CHECK_COMMON_NAME

OpenSSL 函式庫是否內建支援不檢查主題通用名稱及 SSLContext.hostname_checks_common_name 是否可寫。

在 3.7 版被加入.

ssl.HAS_ECDH

OpenSSL 函式庫是否內建支援基於橢圓曲線的 (Elliptic Curve-based) Diffie-Hellman 金鑰交換。此回傳值應該要為 true 除非發布者明確禁用此功能。

在 3.3 版被加入.

ssl.HAS_SNI

OpenSSL 函式庫是否內建支援 伺服器名稱提示 擴充套件 (在 RFC 6066 [https://datatracker.ietf.org/doc/html/rfc6066.html] 中定義)。

在 3.2 版被加入.

ssl.HAS_NPN

OpenSSL 函式庫是否內建支援 下一代協定協商 該功能在應用層協定協商 [https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation] 中有描述。當此值為 true 時，你可以使用 SSLContext.set_npn_protocols() 方法來公告你想支援的協定。

在 3.3 版被加入.

ssl.HAS_SSLv2

此 OpenSSL 函式庫是否內建支援 SSL 2.0 協定。

在 3.7 版被加入.

ssl.HAS_SSLv3

此 OpenSSL 函式庫是否內建支援 SSL 3.0 協定。

在 3.7 版被加入.

ssl.HAS_TLSv1

此 OpenSSL 函式庫是否內建支援 TLS 1.0 協定。

在 3.7 版被加入.

ssl.HAS_TLSv1_1

此 OpenSSL 函式庫是否內建支援 TLS 1.1 協定。

在 3.7 版被加入.

ssl.HAS_TLSv1_2

此 OpenSSL 函式庫是否內建支援 TLS 1.2 協定。

在 3.7 版被加入.

ssl.HAS_TLSv1_3

此 OpenSSL 函式庫是否內建支援 TLS 1.3 協定。

在 3.7 版被加入.

ssl.HAS_PSK

此 OpenSSL 函式庫是否內建支援 TLS-PSK。

在 3.13 版被加入.

ssl.HAS_PHA

此 OpenSSL 函式庫是否內建支援 TLS-PHA。

在 3.14 版被加入.

ssl.CHANNEL_BINDING_TYPES

支援的 TLS 通道綁定類型列表。列表中的字串可以作為 SSLSocket.get_channel_binding() 的參數。

在 3.3 版被加入.

ssl.OPENSSL_VERSION

直譯器所加載的 OpenSSL 函式庫的版本字串:

>>> ssl.OPENSSL_VERSION
'OpenSSL 1.0.2k  26 Jan 2017'

在 3.2 版被加入.

ssl.OPENSSL_VERSION_INFO

代表 OpenSSL 函式庫版本資訊的五個整數的元組：

>>> ssl.OPENSSL_VERSION_INFO
(1, 0, 2, 11, 15)

在 3.2 版被加入.

ssl.OPENSSL_VERSION_NUMBER

OpenSSL 函式庫的初始版本，以單一整數表示:

>>> ssl.OPENSSL_VERSION_NUMBER
268443839
>>> hex(ssl.OPENSSL_VERSION_NUMBER)
'0x100020bf'

在 3.2 版被加入.

ssl.ALERT_DESCRIPTION_HANDSHAKE_FAILURE

ssl.ALERT_DESCRIPTION_INTERNAL_ERROR

ALERT_DESCRIPTION_*

來自 RFC 5246 [https://datatracker.ietf.org/doc/html/rfc5246.html] 和其他文件的警報描述。IANA TLS Alert Registry [https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-6] 包含了此列表以及其含義定義所在的 RFC 的引用。

被用來做為 SSLContext.set_servername_callback() 中回呼函式的回傳值。

在 3.4 版被加入.

class ssl.AlertDescription

enum.IntEnum 為 ALERT_DESCRIPTION_* 常數中的一個集合。

在 3.6 版被加入.

Purpose.SERVER_AUTH

create_default_context() 和 SSLContext.load_default_certs() 的選項。此值表示該語境可能會用於驗證網頁伺服器 (因此它將用於建立用戶端 socket）。

在 3.4 版被加入.

Purpose.CLIENT_AUTH

create_default_context() 和 SSLContext.load_default_certs() 的選項。此值表示該語境可能會用於驗證網頁用戶端 (因此，它將用於建立伺服器端的 socket）。

在 3.4 版被加入.

class ssl.SSLErrorNumber

enum.IntEnum 為 SSL_ERROR_* 常數中的一個集合。

在 3.6 版被加入.

class ssl.TLSVersion

用於 SSLContext.maximum_version 和 SSLContext.minimum_version 的 SSL 和 TLS 版本 enum.IntEnum 集合。

在 3.7 版被加入.

TLSVersion.MINIMUM_SUPPORTED

TLSVersion.MAXIMUM_SUPPORTED

最低或最高支援的 SSL 或 TLS 版本。這些是特殊常數。它們的值並不反映可用的最低和最高 TLS/SSL 版本。

TLSVersion.SSLv3

TLSVersion.TLSv1

TLSVersion.TLSv1_1

TLSVersion.TLSv1_2

TLSVersion.TLSv1_3

SSL 3.0 到 TLS 1.3。

在 3.10 版之後被棄用: 除了 TLSVersion.TLSv1_2 和 TLSVersion.TLSv1_3 之外，所有的 TLSVersion 成員都已被棄用。

SSL Sockets

class ssl.SSLSocket(socket.socket)

SSL sockets 提供以下 Socket 物件 方法：

accept()

bind()

close()

connect()

detach()

fileno()

getpeername()、getsockname()

getsockopt()、setsockopt()

gettimeout()、settimeout()、setblocking()

listen()

makefile()

recv()、recv_into() （但不允許傳遞非零的 flags 引數）

send()、sendall() （同樣不允許傳遞非零的 flags 引數）

sendfile() （但 os.sendfile 只能用於純文本 sockets，其餘則會使用 send()）

shutdown()

然而，由於 SSL（和 TLS）協定在 TCP 之上有自己的框架，因此在某些方面，SSL sockets 的抽象可能會與普通作業系統級別的 sockets 規範有所不同。特別是請參閱關於 non-blocking sockets 的說明。

SSLSocket 的實例必須使用 SSLContext.wrap_socket() 方法建立。

在 3.5 版的變更: 新增 sendfile() 方法。

在 3.5 版的變更: shutdown() 不會在每次接收或發送位元組時重置 socket 超時時間。現在，socket 超時時間是關閉操作的最大總持續時間。

在 3.6 版之後被棄用: 直接建立 SSLSocket 實例的方式已被棄用，請使用 SSLContext.wrap_socket() 來包裝 socket。

在 3.7 版的變更: SSLSocket 實例必須使用 wrap_socket() 建立。在較早的版本中可以直接建立實例，但這從未被記錄或正式支援。

在 3.10 版的變更: Python 現在內部使用了 SSL_read_ex 和 SSL_write_ex 函式。這些函式支援讀取和寫入大於 2 GB 的資料。寫入零長度的資料不再會導致協定違規錯誤。

SSL sockets 還具有以下附加方法和屬性：

SSLSocket.read(len=1024, buffer=None)

從 SSL socket 讀取 len 位元組的資料，並將結果以 bytes 實例的形式回傳。如果指定了 buffer，則將資料讀入緩衝區，並回傳讀取的位元組。

如果 socket 是非阻塞的則會引發 SSLWantReadError 或 SSLWantWriteError 並且讀取操作將會被阻塞。

由於在任何時刻都可能發生重新協商，呼叫 read() 也可能觸發寫入操作。

在 3.5 版的變更: 當接收或發送位元組時，socket 的超時時間將不再重置。現在，socket 超時時間是讀取最多 len 位元組的總最大持續時間。

在 3.6 版之後被棄用: 請改用 recv() 來替換掉 read()。

SSLSocket.write(data)

將 data 寫入 SSL socket 並回傳寫入的位元組數量。data 引數必須是支援緩衝區介面的物件。

如果 socket 是非阻塞的則會引發 SSLWantReadError 或 SSLWantWriteError 並且寫入操作將會被阻塞。

由於在任何時刻都可能發生重新協商，呼叫 write() 也可能觸發讀取操作。

在 3.5 版的變更: 當接收或發送位元組時，socket 的超時時間將不再重置。現在，socket 超時時間是寫入 data 的總最大持續時間。

在 3.6 版之後被棄用: 請改用 send() 來替換掉 write()。

備註

read() 和 write() 方法為低階層的方法，負責讀取和寫入未加密的應用層資料，並將其加密/解密為加密的寫入層資料。這些方法需要一個已建立的 SSL 連接，即握手已完成，且未呼叫 SSLSocket.unwrap()。

通常你應該使用像 recv() 和 send() 這樣的 socket API 方法，而不是直接使用這些方法。

SSLSocket.do_handshake(block=False)

執行 SSL 設定握手。

If block is true and the timeout obtained by gettimeout() is zero, the socket is set in blocking mode until the handshake is performed.

在 3.4 版的變更: 當 socket 的 context 的 check_hostname 屬性質為 true 時，握手方法也會執行 match_hostname()。

在 3.5 版的變更: Socket 超時時間已經不會在每次接收或傳送位元組時重置。現在，超時時間是握手過程的最大總持續時間。

在 3.7 版的變更: 在握手過程中，OpenSSL 會去配對主機名稱或 IP 地址。已不再使用 match_hostname() 函式。如果 OpenSSL 拒絕某個主機名稱或 IP 地址，握手將會提前中止，並向對方發送 TLS 警報訊息。

SSLSocket.getpeercert(binary_form=False)

如果連線端沒有證書，則回傳 None。如果 SSL 握手尚未完成，則引發 ValueError。

如果 binary_form 參數為 False，且從對等 (peer) 接收到證書，則該方法回傳一個 dict 實例。如果證書未被驗證，則該字典為空。若證書已被驗證，則回傳的字典將包含數個鍵值，包括 subject (證書所簽發的對象) 和 issuer (簽發證書的主體)。如果證書中包含 Subject Alternative Name 擴充 (參考RFC 3280 [https://datatracker.ietf.org/doc/html/rfc3280.html])，字典中還會有一個 subjectAltName 鍵。

subject 和 issuer 欄位欄位是包含相對識別名稱 (relative distinguished names, RDNs) 序列的元組，這些 RDN 來自證書資料結構中的相應欄位。每個 RDN 都是一組名稱與值的對。以下是現實中的範例：

{'issuer': ((('countryName', 'IL'),),
            (('organizationName', 'StartCom Ltd.'),),
            (('organizationalUnitName',
              'Secure Digital Certificate Signing'),),
            (('commonName',
              'StartCom Class 2 Primary Intermediate Server CA'),)),
 'notAfter': 'Nov 22 08:15:19 2013 GMT',
 'notBefore': 'Nov 21 03:09:52 2011 GMT',
 'serialNumber': '95F0',
 'subject': ((('description', '571208-SLe257oHY9fVQ07Z'),),
             (('countryName', 'US'),),
             (('stateOrProvinceName', 'California'),),
             (('localityName', 'San Francisco'),),
             (('organizationName', 'Electronic Frontier Foundation, Inc.'),),
             (('commonName', '*.eff.org'),),
             (('emailAddress', 'hostmaster@eff.org'),)),
 'subjectAltName': (('DNS', '*.eff.org'), ('DNS', 'eff.org')),
 'version': 3}

如果 binary_form 參數設定為 True，且對等提供了證書，則該方法會以 DER 編碼形式 將整個證書以位元組序列形式回傳。如果對等未提供證書，則回傳 None。對等是否提供證書取決於 SSL socket 的腳色：

對於用戶端 SSL socket，伺服器將永遠提供證書，無論是否需要進行驗證；

對於伺服器 SSL socket，用戶端僅在伺服器要求時才會提供證書；因此，如果你使用的是 CERT_NONE (而非 CERT_OPTIONAL 或 CERT_REQUIRED)，則 getpeercert() 會回傳 None。

請見 SSLContext.check_hostname。

在 3.2 版的變更: The returned dictionary includes additional items such as issuer and notBefore.

在 3.4 版的變更: ValueError is raised when the handshake isn't done. The returned dictionary includes additional X509v3 extension items such as crlDistributionPoints, caIssuers and OCSP URIs.

在 3.9 版的變更: IPv6 address strings no longer have a trailing new line.

SSLSocket.get_verified_chain()

Returns verified certificate chain provided by the other end of the SSL channel as a list of DER-encoded bytes. If certificate verification was disabled method acts the same as get_unverified_chain().

在 3.13 版被加入.

SSLSocket.get_unverified_chain()

Returns raw certificate chain provided by the other end of the SSL channel as a list of DER-encoded bytes.

在 3.13 版被加入.

SSLSocket.cipher()

Returns a three-value tuple containing the name of the cipher being used, the version of the SSL protocol that defines its use, and the number of secret bits being used. If no connection has been established, returns None.

SSLSocket.shared_ciphers()

Return the list of ciphers available in both the client and server. Each entry of the returned list is a three-value tuple containing the name of the cipher, the version of the SSL protocol that defines its use, and the number of secret bits the cipher uses. shared_ciphers() returns None if no connection has been established or the socket is a client socket.

在 3.5 版被加入.

SSLSocket.compression()

Return the compression algorithm being used as a string, or None if the connection isn't compressed.

If the higher-level protocol supports its own compression mechanism, you can use OP_NO_COMPRESSION to disable SSL-level compression.

在 3.3 版被加入.

SSLSocket.get_channel_binding(cb_type='tls-unique')

Get channel binding data for current connection, as a bytes object. Returns None if not connected or the handshake has not been completed.

The cb_type parameter allow selection of the desired channel binding type. Valid channel binding types are listed in the CHANNEL_BINDING_TYPES list. Currently only the 'tls-unique' channel binding, defined by RFC 5929 [https://datatracker.ietf.org/doc/html/rfc5929.html], is supported. ValueError will be raised if an unsupported channel binding type is requested.

在 3.3 版被加入.

SSLSocket.selected_alpn_protocol()

Return the protocol that was selected during the TLS handshake. If SSLContext.set_alpn_protocols() was not called, if the other party does not support ALPN, if this socket does not support any of the client's proposed protocols, or if the handshake has not happened yet, None is returned.

在 3.5 版被加入.

SSLSocket.selected_npn_protocol()

Return the higher-level protocol that was selected during the TLS/SSL handshake. If SSLContext.set_npn_protocols() was not called, or if the other party does not support NPN, or if the handshake has not yet happened, this will return None.

在 3.3 版被加入.

在 3.10 版之後被棄用: NPN has been superseded by ALPN

SSLSocket.unwrap()

Performs the SSL shutdown handshake, which removes the TLS layer from the underlying socket, and returns the underlying socket object. This can be used to go from encrypted operation over a connection to unencrypted. The returned socket should always be used for further communication with the other side of the connection, rather than the original socket.

SSLSocket.verify_client_post_handshake()

Requests post-handshake authentication (PHA) from a TLS 1.3 client. PHA can only be initiated for a TLS 1.3 connection from a server-side socket, after the initial TLS handshake and with PHA enabled on both sides, see SSLContext.post_handshake_auth.

The method does not perform a cert exchange immediately. The server-side sends a CertificateRequest during the next write event and expects the client to respond with a certificate on the next read event.

If any precondition isn't met (e.g. not TLS 1.3, PHA not enabled), an SSLError is raised.

備註

Only available with OpenSSL 1.1.1 and TLS 1.3 enabled. Without TLS 1.3 support, the method raises NotImplementedError.

在 3.8 版被加入.

SSLSocket.version()

Return the actual SSL protocol version negotiated by the connection as a string, or None if no secure connection is established. As of this writing, possible return values include "SSLv2", "SSLv3", "TLSv1", "TLSv1.1" and "TLSv1.2". Recent OpenSSL versions may define more return values.

在 3.5 版被加入.

SSLSocket.pending()

Returns the number of already decrypted bytes available for read, pending on the connection.

SSLSocket.context

The SSLContext object this SSL socket is tied to.

在 3.2 版被加入.

SSLSocket.server_side

A boolean which is True for server-side sockets and False for client-side sockets.

在 3.2 版被加入.

SSLSocket.server_hostname

Hostname of the server: str type, or None for server-side socket or if the hostname was not specified in the constructor.

在 3.2 版被加入.

在 3.7 版的變更: The attribute is now always ASCII text. When server_hostname is an internationalized domain name (IDN), this attribute now stores the A-label form ("xn--pythn-mua.org"), rather than the U-label form ("pythön.org").

SSLSocket.session

The SSLSession for this SSL connection. The session is available for client and server side sockets after the TLS handshake has been performed. For client sockets the session can be set before do_handshake() has been called to reuse a session.

在 3.6 版被加入.

SSLSocket.session_reused

在 3.6 版被加入.

SSL Contexts

在 3.2 版被加入.

An SSL context holds various data longer-lived than single SSL connections, such as SSL configuration options, certificate(s) and private key(s). It also manages a cache of SSL sessions for server-side sockets, in order to speed up repeated connections from the same clients.

class ssl.SSLContext(protocol=None)

Create a new SSL context. You may pass protocol which must be one of the PROTOCOL_* constants defined in this module. The parameter specifies which version of the SSL protocol to use. Typically, the server chooses a particular protocol version, and the client must adapt to the server's choice. Most of the versions are not interoperable with the other versions. If not specified, the default is PROTOCOL_TLS; it provides the most compatibility with other versions.

Here's a table showing which versions in a client (down the side) can connect to which versions in a server (along the top):

client / server

SSLv2

SSLv3

TLS [3]

TLSv1

TLSv1.1

TLSv1.2

SSLv2

yes

no

no [1]

no

no

no

SSLv3

no

yes

no [2]

no

no

no

TLS (SSLv23) [3]

no [1]

no [2]

yes

yes

yes

yes

TLSv1

no

no

yes

yes

no

no

TLSv1.1

no

no

yes

no

yes

no

TLSv1.2

no

no

yes

no

no

yes

註腳

[1] (1,2)

SSLContext 預設會關閉 SSLv2 的 OP_NO_SSLv2。

[2] (1,2)

SSLContext 預設會關閉 SSLv3 的 OP_NO_SSLv3。

[3] (1,2)

TLS 1.3 protocol will be available with PROTOCOL_TLS in OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just TLS 1.3.

也參考

create_default_context() lets the ssl module choose security settings for a given purpose.

在 3.6 版的變更: The context is created with secure default values. The options OP_NO_COMPRESSION, OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE, OP_NO_SSLv2, and OP_NO_SSLv3 (except for PROTOCOL_SSLv3) are set by default. The initial cipher suite list contains only HIGH ciphers, no NULL ciphers and no MD5 ciphers.

在 3.10 版之後被棄用: SSLContext without protocol argument is deprecated. The context class will either require PROTOCOL_TLS_CLIENT or PROTOCOL_TLS_SERVER protocol in the future.

在 3.10 版的變更: The default cipher suites now include only secure AES and ChaCha20 ciphers with forward secrecy and security level 2. RSA and DH keys with less than 2048 bits and ECC keys with less than 224 bits are prohibited. PROTOCOL_TLS, PROTOCOL_TLS_CLIENT, and PROTOCOL_TLS_SERVER use TLS 1.2 as minimum TLS version.

備註

SSLContext only supports limited mutation once it has been used by a connection. Adding new certificates to the internal trust store is allowed, but changing ciphers, verification settings, or mTLS certificates may result in surprising behavior.

備註

SSLContext is designed to be shared and used by multiple connections. Thus, it is thread-safe as long as it is not reconfigured after being used by a connection.

SSLContext 物件具有以下方法和屬性：

SSLContext.cert_store_stats()

Get statistics about quantities of loaded X.509 certificates, count of X.509 certificates flagged as CA certificates and certificate revocation lists as dictionary.

Example for a context with one CA cert and one other cert:

>>> context.cert_store_stats()
{'crl': 0, 'x509_ca': 1, 'x509': 2}

在 3.4 版被加入.

SSLContext.load_cert_chain(certfile, keyfile=None, password=None)

Load a private key and the corresponding certificate. The certfile string must be the path to a single file in PEM format containing the certificate as well as any number of CA certificates needed to establish the certificate's authenticity. The keyfile string, if present, must point to a file containing the private key. Otherwise the private key will be taken from certfile as well. See the discussion of Certificates for more information on how the certificate is stored in the certfile.

The password argument may be a function to call to get the password for decrypting the private key. It will only be called if the private key is encrypted and a password is necessary. It will be called with no arguments, and it should return a string, bytes, or bytearray. If the return value is a string it will be encoded as UTF-8 before using it to decrypt the key. Alternatively a string, bytes, or bytearray value may be supplied directly as the password argument. It will be ignored if the private key is not encrypted and no password is needed.

If the password argument is not specified and a password is required, OpenSSL's built-in password prompting mechanism will be used to interactively prompt the user for a password.

An SSLError is raised if the private key doesn't match with the certificate.

在 3.3 版的變更: 新增可選引數 password。

SSLContext.load_default_certs(purpose=Purpose.SERVER_AUTH)

Load a set of default "certification authority" (CA) certificates from default locations. On Windows it loads CA certs from the CA and ROOT system stores. On all systems it calls SSLContext.set_default_verify_paths(). In the future the method may load CA certificates from other locations, too.

The purpose flag specifies what kind of CA certificates are loaded. The default settings Purpose.SERVER_AUTH loads certificates, that are flagged and trusted for TLS web server authentication (client side sockets). Purpose.CLIENT_AUTH loads CA certificates for client certificate verification on the server side.

在 3.4 版被加入.

SSLContext.load_verify_locations(cafile=None, capath=None, cadata=None)

Load a set of "certification authority" (CA) certificates used to validate other peers' certificates when verify_mode is other than CERT_NONE. At least one of cafile or capath must be specified.

This method can also load certification revocation lists (CRLs) in PEM or DER format. In order to make use of CRLs, SSLContext.verify_flags must be configured properly.

The cafile string, if present, is the path to a file of concatenated CA certificates in PEM format. See the discussion of Certificates for more information about how to arrange the certificates in this file.

The capath string, if present, is the path to a directory containing several CA certificates in PEM format, following an OpenSSL specific layout [https://docs.openssl.org/master/man3/SSL_CTX_load_verify_locations/].

The cadata object, if present, is either an ASCII string of one or more PEM-encoded certificates or a bytes-like object of DER-encoded certificates. Like with capath extra lines around PEM-encoded certificates are ignored but at least one certificate must be present.

在 3.4 版的變更: 新增可選引數 cadata

SSLContext.get_ca_certs(binary_form=False)

Get a list of loaded "certification authority" (CA) certificates. If the binary_form parameter is False each list entry is a dict like the output of SSLSocket.getpeercert(). Otherwise the method returns a list of DER-encoded certificates. The returned list does not contain certificates from capath unless a certificate was requested and loaded by a SSL connection.

備註

Certificates in a capath directory aren't loaded unless they have been used at least once.

在 3.4 版被加入.

SSLContext.get_ciphers()

Get a list of enabled ciphers. The list is in order of cipher priority. See SSLContext.set_ciphers().

範例：

>>> ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
>>> ctx.set_ciphers('ECDHE+AESGCM:!ECDSA')
>>> ctx.get_ciphers()
[{'aead': True,
  'alg_bits': 256,
  'auth': 'auth-rsa',
  'description': 'ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(256) Mac=AEAD',
  'digest': None,
  'id': 50380848,
  'kea': 'kx-ecdhe',
  'name': 'ECDHE-RSA-AES256-GCM-SHA384',
  'protocol': 'TLSv1.2',
  'strength_bits': 256,
  'symmetric': 'aes-256-gcm'},
 {'aead': True,
  'alg_bits': 128,
  'auth': 'auth-rsa',
  'description': 'ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(128) Mac=AEAD',
  'digest': None,
  'id': 50380847,
  'kea': 'kx-ecdhe',
  'name': 'ECDHE-RSA-AES128-GCM-SHA256',
  'protocol': 'TLSv1.2',
  'strength_bits': 128,
  'symmetric': 'aes-128-gcm'}]

在 3.6 版被加入.

SSLContext.set_default_verify_paths()

Load a set of default "certification authority" (CA) certificates from a filesystem path defined when building the OpenSSL library. Unfortunately, there's no easy way to know whether this method succeeds: no error is returned if no certificates are to be found. When the OpenSSL library is provided as part of the operating system, though, it is likely to be configured properly.

SSLContext.set_ciphers(ciphers, /)

Set the available ciphers for sockets created with this context. It should be a string in the OpenSSL cipher list format [https://docs.openssl.org/master/man1/ciphers/]. If no cipher can be selected (because compile-time options or other configuration forbids use of all the specified ciphers), an SSLError will be raised.

備註

when connected, the SSLSocket.cipher() method of SSL sockets will give the currently selected cipher.

TLS 1.3 cipher suites cannot be disabled with set_ciphers().

SSLContext.set_alpn_protocols(alpn_protocols)

Specify which protocols the socket should advertise during the SSL/TLS handshake. It should be a list of ASCII strings, like ['http/1.1', 'spdy/2'], ordered by preference. The selection of a protocol will happen during the handshake, and will play out according to RFC 7301 [https://datatracker.ietf.org/doc/html/rfc7301.html]. After a successful handshake, the SSLSocket.selected_alpn_protocol() method will return the agreed-upon protocol.

此方法會在 HAS_ALPN 為 False 時引發 NotImplementedError。

在 3.5 版被加入.

SSLContext.set_npn_protocols(npn_protocols)

Specify which protocols the socket should advertise during the SSL/TLS handshake. It should be a list of strings, like ['http/1.1', 'spdy/2'], ordered by preference. The selection of a protocol will happen during the handshake, and will play out according to the Application Layer Protocol Negotiation [https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation]. After a successful handshake, the SSLSocket.selected_npn_protocol() method will return the agreed-upon protocol.

此方法會在 HAS_NPN 為 False 時引發 NotImplementedError。

在 3.3 版被加入.

在 3.10 版之後被棄用: NPN has been superseded by ALPN

SSLContext.sni_callback

Register a callback function that will be called after the TLS Client Hello handshake message has been received by the SSL/TLS server when the TLS client specifies a server name indication. The server name indication mechanism is specified in RFC 6066 [https://datatracker.ietf.org/doc/html/rfc6066.html] section 3 - Server Name Indication.

Only one callback can be set per SSLContext. If sni_callback is set to None then the callback is disabled. Calling this function a subsequent time will disable the previously registered callback.

The callback function will be called with three arguments; the first being the ssl.SSLSocket, the second is a string that represents the server name that the client is intending to communicate (or None if the TLS Client Hello does not contain a server name) and the third argument is the original SSLContext. The server name argument is text. For internationalized domain name, the server name is an IDN A-label ("xn--pythn-mua.org").

A typical use of this callback is to change the ssl.SSLSocket's SSLSocket.context attribute to a new object of type SSLContext representing a certificate chain that matches the server name.

Due to the early negotiation phase of the TLS connection, only limited methods and attributes are usable like SSLSocket.selected_alpn_protocol() and SSLSocket.context. The SSLSocket.getpeercert(), SSLSocket.get_verified_chain(), SSLSocket.get_unverified_chain() SSLSocket.cipher() and SSLSocket.compression() methods require that the TLS connection has progressed beyond the TLS Client Hello and therefore will not return meaningful values nor can they be called safely.

The sni_callback function must return None to allow the TLS negotiation to continue. If a TLS failure is required, a constant ALERT_DESCRIPTION_* can be returned. Other return values will result in a TLS fatal error with ALERT_DESCRIPTION_INTERNAL_ERROR.

If an exception is raised from the sni_callback function the TLS connection will terminate with a fatal TLS alert message ALERT_DESCRIPTION_HANDSHAKE_FAILURE.

This method will raise NotImplementedError if the OpenSSL library had OPENSSL_NO_TLSEXT defined when it was built.

在 3.7 版被加入.

SSLContext.set_servername_callback(server_name_callback)

This is a legacy API retained for backwards compatibility. When possible, you should use sni_callback instead. The given server_name_callback is similar to sni_callback, except that when the server hostname is an IDN-encoded internationalized domain name, the server_name_callback receives a decoded U-label ("pythön.org").

If there is a decoding error on the server name, the TLS connection will terminate with an ALERT_DESCRIPTION_INTERNAL_ERROR fatal TLS alert message to the client.

在 3.4 版被加入.

SSLContext.load_dh_params(dhfile, /)

Load the key generation parameters for Diffie-Hellman (DH) key exchange. Using DH key exchange improves forward secrecy at the expense of computational resources (both on the server and on the client). The dhfile parameter should be the path to a file containing DH parameters in PEM format.

This setting doesn't apply to client sockets. You can also use the OP_SINGLE_DH_USE option to further improve security.

在 3.3 版被加入.

SSLContext.set_ecdh_curve(curve_name, /)

Set the curve name for Elliptic Curve-based Diffie-Hellman (ECDH) key exchange. ECDH is significantly faster than regular DH while arguably as secure. The curve_name parameter should be a string describing a well-known elliptic curve, for example prime256v1 for a widely supported curve.

This setting doesn't apply to client sockets. You can also use the OP_SINGLE_ECDH_USE option to further improve security.

此方法在 HAS_ECDH 為 False 時不可用。

在 3.3 版被加入.

也參考

SSL/TLS & Perfect Forward Secrecy [https://vincent.bernat.ch/en/blog/2011-ssl-perfect-forward-secrecy]

Vincent Bernat.

SSLContext.wrap_socket(sock, server_side=False, do_handshake_on_connect=True, suppress_ragged_eofs=True, server_hostname=None, session=None)

Wrap an existing Python socket sock and return an instance of SSLContext.sslsocket_class (default SSLSocket). The returned SSL socket is tied to the context, its settings and certificates. sock must be a SOCK_STREAM socket; other socket types are unsupported.

The parameter server_side is a boolean which identifies whether server-side or client-side behavior is desired from this socket.

For client-side sockets, the context construction is lazy; if the underlying socket isn't connected yet, the context construction will be performed after connect() is called on the socket. For server-side sockets, if the socket has no remote peer, it is assumed to be a listening socket, and the server-side SSL wrapping is automatically performed on client connections accepted via the accept() method. The method may raise SSLError.

On client connections, the optional parameter server_hostname specifies the hostname of the service which we are connecting to. This allows a single server to host multiple SSL-based services with distinct certificates, quite similarly to HTTP virtual hosts. Specifying server_hostname will raise a ValueError if server_side is true.

The parameter do_handshake_on_connect specifies whether to do the SSL handshake automatically after doing a socket.connect(), or whether the application program will call it explicitly, by invoking the SSLSocket.do_handshake() method. Calling SSLSocket.do_handshake() explicitly gives the program control over the blocking behavior of the socket I/O involved in the handshake.

The parameter suppress_ragged_eofs specifies how the SSLSocket.recv() method should signal unexpected EOF from the other end of the connection. If specified as True (the default), it returns a normal EOF (an empty bytes object) in response to unexpected EOF errors raised from the underlying socket; if False, it will raise the exceptions back to the caller.

session, see session.

To wrap an SSLSocket in another SSLSocket, use SSLContext.wrap_bio().

在 3.5 版的變更: Always allow a server_hostname to be passed, even if OpenSSL does not have SNI.

在 3.6 版的變更: 新增 session 引數。

在 3.7 版的變更: The method returns an instance of SSLContext.sslsocket_class instead of hard-coded SSLSocket.

SSLContext.sslsocket_class

The return type of SSLContext.wrap_socket(), defaults to SSLSocket. The attribute can be assigned to on instances of SSLContext in order to return a custom subclass of SSLSocket.

在 3.7 版被加入.

SSLContext.wrap_bio(incoming, outgoing, server_side=False, server_hostname=None, session=None)

Wrap the BIO objects incoming and outgoing and return an instance of SSLContext.sslobject_class (default SSLObject). The SSL routines will read input data from the incoming BIO and write data to the outgoing BIO.

The server_side, server_hostname and session parameters have the same meaning as in SSLContext.wrap_socket().

在 3.6 版的變更: 新增 session 引數。

在 3.7 版的變更: The method returns an instance of SSLContext.sslobject_class instead of hard-coded SSLObject.

SSLContext.sslobject_class

The return type of SSLContext.wrap_bio(), defaults to SSLObject. The attribute can be overridden on instance of class in order to return a custom subclass of SSLObject.

在 3.7 版被加入.

SSLContext.session_stats()

Get statistics about the SSL sessions created or managed by this context. A dictionary is returned which maps the names of each piece of information [https://docs.openssl.org/1.1.1/man3/SSL_CTX_sess_number/] to their numeric values. For example, here is the total number of hits and misses in the session cache since the context was created:

>>> stats = context.session_stats()
>>> stats['hits'], stats['misses']
(0, 0)

SSLContext.check_hostname

Whether to match the peer cert's hostname in SSLSocket.do_handshake(). The context's verify_mode must be set to CERT_OPTIONAL or CERT_REQUIRED, and you must pass server_hostname to wrap_socket() in order to match the hostname. Enabling hostname checking automatically sets verify_mode from CERT_NONE to CERT_REQUIRED. It cannot be set back to CERT_NONE as long as hostname checking is enabled. The PROTOCOL_TLS_CLIENT protocol enables hostname checking by default. With other protocols, hostname checking must be enabled explicitly.

範例：

import socket, ssl

context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
context.load_default_certs()

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ssl_sock = context.wrap_socket(s, server_hostname='www.verisign.com')
ssl_sock.connect(('www.verisign.com', 443))

在 3.4 版被加入.

在 3.7 版的變更: verify_mode is now automatically changed to CERT_REQUIRED when hostname checking is enabled and verify_mode is CERT_NONE. Previously the same operation would have failed with a ValueError.

SSLContext.keylog_filename

Write TLS keys to a keylog file, whenever key material is generated or received. The keylog file is designed for debugging purposes only. The file format is specified by NSS and used by many traffic analyzers such as Wireshark. The log file is opened in append-only mode. Writes are synchronized between threads, but not between processes.

在 3.8 版被加入.

SSLContext.maximum_version

A TLSVersion enum member representing the highest supported TLS version. The value defaults to TLSVersion.MAXIMUM_SUPPORTED. The attribute is read-only for protocols other than PROTOCOL_TLS, PROTOCOL_TLS_CLIENT, and PROTOCOL_TLS_SERVER.

The attributes maximum_version, minimum_version and SSLContext.options all affect the supported SSL and TLS versions of the context. The implementation does not prevent invalid combination. For example a context with OP_NO_TLSv1_2 in options and maximum_version set to TLSVersion.TLSv1_2 will not be able to establish a TLS 1.2 connection.

在 3.7 版被加入.

SSLContext.minimum_version

Like SSLContext.maximum_version except it is the lowest supported version or TLSVersion.MINIMUM_SUPPORTED.

在 3.7 版被加入.

SSLContext.num_tickets

Control the number of TLS 1.3 session tickets of a PROTOCOL_TLS_SERVER context. The setting has no impact on TLS 1.0 to 1.2 connections.

在 3.8 版被加入.

SSLContext.options

An integer representing the set of SSL options enabled on this context. The default value is OP_ALL, but you can specify other options such as OP_NO_SSLv2 by ORing them together.

在 3.6 版的變更: SSLContext.options 會回傳 Options 旗標：

>>> ssl.create_default_context().options
<Options.OP_ALL|OP_NO_SSLv3|OP_NO_SSLv2|OP_NO_COMPRESSION: 2197947391>

在 3.7 版之後被棄用: All OP_NO_SSL* and OP_NO_TLS* options have been deprecated since Python 3.7. Use SSLContext.minimum_version and SSLContext.maximum_version instead.

SSLContext.post_handshake_auth

Enable TLS 1.3 post-handshake client authentication. Post-handshake auth is disabled by default and a server can only request a TLS client certificate during the initial handshake. When enabled, a server may request a TLS client certificate at any time after the handshake.

When enabled on client-side sockets, the client signals the server that it supports post-handshake authentication.

When enabled on server-side sockets, SSLContext.verify_mode must be set to CERT_OPTIONAL or CERT_REQUIRED, too. The actual client cert exchange is delayed until SSLSocket.verify_client_post_handshake() is called and some I/O is performed.

在 3.8 版被加入.

SSLContext.protocol

The protocol version chosen when constructing the context. This attribute is read-only.

SSLContext.hostname_checks_common_name

Whether check_hostname falls back to verify the cert's subject common name in the absence of a subject alternative name extension (default: true).

在 3.7 版被加入.

在 3.10 版的變更: The flag had no effect with OpenSSL before version 1.1.1l. Python 3.8.9, 3.9.3, and 3.10 include workarounds for previous versions.

SSLContext.security_level

An integer representing the security level [https://docs.openssl.org/master/man3/SSL_CTX_get_security_level/] for the context. This attribute is read-only.

在 3.10 版被加入.

SSLContext.verify_flags

The flags for certificate verification operations. You can set flags like VERIFY_CRL_CHECK_LEAF by ORing them together. By default OpenSSL does neither require nor verify certificate revocation lists (CRLs).

在 3.4 版被加入.

在 3.6 版的變更: SSLContext.verify_flags 會回傳 VerifyFlags 旗標：

>>> ssl.create_default_context().verify_flags
<VerifyFlags.VERIFY_X509_TRUSTED_FIRST: 32768>

SSLContext.verify_mode

Whether to try to verify other peers' certificates and how to behave if verification fails. This attribute must be one of CERT_NONE, CERT_OPTIONAL or CERT_REQUIRED.

在 3.6 版的變更: SSLContext.verify_mode 會回傳 VerifyMode 列舉：

>>> ssl.create_default_context().verify_mode
<VerifyMode.CERT_REQUIRED: 2>

SSLContext.set_psk_client_callback(callback)

Enables TLS-PSK (pre-shared key) authentication on a client-side connection.

In general, certificate based authentication should be preferred over this method.

The parameter callback is a callable object with the signature: def callback(hint: str | None) -> tuple[str | None, bytes]. The hint parameter is an optional identity hint sent by the server. The return value is a tuple in the form (client-identity, psk). Client-identity is an optional string which may be used by the server to select a corresponding PSK for the client. The string must be less than or equal to 256 octets when UTF-8 encoded. PSK is a bytes-like object representing the pre-shared key. Return a zero length PSK to reject the connection.

Setting callback to None removes any existing callback.

備註

使用 TLS 1.3 時：

hint 參數始終為 None。

client-identity must be a non-empty string.

範例用法：

context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
context.check_hostname = False
context.verify_mode = ssl.CERT_NONE
context.maximum_version = ssl.TLSVersion.TLSv1_2
context.set_ciphers('PSK')

# A simple lambda:
psk = bytes.fromhex('c0ffee')
context.set_psk_client_callback(lambda hint: (None, psk))

# A table using the hint from the server:
psk_table = { 'ServerId_1': bytes.fromhex('c0ffee'),
              'ServerId_2': bytes.fromhex('facade')
}
def callback(hint):
    return 'ClientId_1', psk_table.get(hint, b'')
context.set_psk_client_callback(callback)

This method will raise NotImplementedError if HAS_PSK is False.

在 3.13 版被加入.

SSLContext.set_psk_server_callback(callback, identity_hint=None)

Enables TLS-PSK (pre-shared key) authentication on a server-side connection.

In general, certificate based authentication should be preferred over this method.

The parameter callback is a callable object with the signature: def callback(identity: str | None) -> bytes. The identity parameter is an optional identity sent by the client which can be used to select a corresponding PSK. The return value is a bytes-like object representing the pre-shared key. Return a zero length PSK to reject the connection.

Setting callback to None removes any existing callback.

The parameter identity_hint is an optional identity hint string sent to the client. The string must be less than or equal to 256 octets when UTF-8 encoded.

備註

When using TLS 1.3 the identity_hint parameter is not sent to the client.

範例用法：

context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
context.maximum_version = ssl.TLSVersion.TLSv1_2
context.set_ciphers('PSK')

# A simple lambda:
psk = bytes.fromhex('c0ffee')
context.set_psk_server_callback(lambda identity: psk)

# A table using the identity of the client:
psk_table = { 'ClientId_1': bytes.fromhex('c0ffee'),
              'ClientId_2': bytes.fromhex('facade')
}
def callback(identity):
    return psk_table.get(identity, b'')
context.set_psk_server_callback(callback, 'ServerId_1')

This method will raise NotImplementedError if HAS_PSK is False.

在 3.13 版被加入.

Certificates

Certificates in general are part of a public-key / private-key system. In this system, each principal, (which may be a machine, or a person, or an organization) is assigned a unique two-part encryption key. One part of the key is public, and is called the public key; the other part is kept secret, and is called the private key. The two parts are related, in that if you encrypt a message with one of the parts, you can decrypt it with the other part, and only with the other part.

A certificate contains information about two principals. It contains the name of a subject, and the subject's public key. It also contains a statement by a second principal, the issuer, that the subject is who they claim to be, and that this is indeed the subject's public key. The issuer's statement is signed with the issuer's private key, which only the issuer knows. However, anyone can verify the issuer's statement by finding the issuer's public key, decrypting the statement with it, and comparing it to the other information in the certificate. The certificate also contains information about the time period over which it is valid. This is expressed as two fields, called "notBefore" and "notAfter".

In the Python use of certificates, a client or server can use a certificate to prove who they are. The other side of a network connection can also be required to produce a certificate, and that certificate can be validated to the satisfaction of the client or server that requires such validation. The connection attempt can be set to raise an exception if the validation fails. Validation is done automatically, by the underlying OpenSSL framework; the application need not concern itself with its mechanics. But the application does usually need to provide sets of certificates to allow this process to take place.

Python uses files to contain certificates. They should be formatted as "PEM" (see RFC 1422 [https://datatracker.ietf.org/doc/html/rfc1422.html]), which is a base-64 encoded form wrapped with a header line and a footer line:

-----BEGIN CERTIFICATE-----
... (certificate in base64 PEM encoding) ...
-----END CERTIFICATE-----

Certificate chains

The Python files which contain certificates can contain a sequence of certificates, sometimes called a certificate chain. This chain should start with the specific certificate for the principal who "is" the client or server, and then the certificate for the issuer of that certificate, and then the certificate for the issuer of that certificate, and so on up the chain till you get to a certificate which is self-signed, that is, a certificate which has the same subject and issuer, sometimes called a root certificate. The certificates should just be concatenated together in the certificate file. For example, suppose we had a three certificate chain, from our server certificate to the certificate of the certification authority that signed our server certificate, to the root certificate of the agency which issued the certification authority's certificate:

-----BEGIN CERTIFICATE-----
... (certificate for your server)...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
... (the certificate for the CA)...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
... (the root certificate for the CA's issuer)...
-----END CERTIFICATE-----

CA certificates

If you are going to require validation of the other side of the connection's certificate, you need to provide a "CA certs" file, filled with the certificate chains for each issuer you are willing to trust. Again, this file just contains these chains concatenated together. For validation, Python will use the first chain it finds in the file which matches. The platform's certificates file can be used by calling SSLContext.load_default_certs(), this is done automatically with create_default_context().

Combined key and certificate

Often the private key is stored in the same file as the certificate; in this case, only the certfile parameter to SSLContext.load_cert_chain() needs to be passed. If the private key is stored with the certificate, it should come before the first certificate in the certificate chain:

-----BEGIN RSA PRIVATE KEY-----
... (private key in base64 encoding) ...
-----END RSA PRIVATE KEY-----
-----BEGIN CERTIFICATE-----
... (certificate in base64 PEM encoding) ...
-----END CERTIFICATE-----

Self-signed certificates

If you are going to create a server that provides SSL-encrypted connection services, you will need to acquire a certificate for that service. There are many ways of acquiring appropriate certificates, such as buying one from a certification authority. Another common practice is to generate a self-signed certificate. The simplest way to do this is with the OpenSSL package, using something like the following:

% openssl req -new -x509 -days 365 -nodes -out cert.pem -keyout cert.pem
Generating a 1024 bit RSA private key
.......++++++
.............................++++++
writing new private key to 'cert.pem'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:MyState
Locality Name (eg, city) []:Some City
Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Organization, Inc.
Organizational Unit Name (eg, section) []:My Group
Common Name (eg, YOUR name) []:myserver.mygroup.myorganization.com
Email Address []:ops@myserver.mygroup.myorganization.com
%

The disadvantage of a self-signed certificate is that it is its own root certificate, and no one else will have it in their cache of known (and trusted) root certificates.

範例

Testing for SSL support

To test for the presence of SSL support in a Python installation, user code should use the following idiom:

try:
    import ssl
except ImportError:
    pass
else:
    ...  # do something that requires SSL support

Client-side operation

This example creates a SSL context with the recommended security settings for client sockets, including automatic certificate verification:

>>> context = ssl.create_default_context()

If you prefer to tune security settings yourself, you might create a context from scratch (but beware that you might not get the settings right):

>>> context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
>>> context.load_verify_locations("/etc/ssl/certs/ca-bundle.crt")

(this snippet assumes your operating system places a bundle of all CA certificates in /etc/ssl/certs/ca-bundle.crt; if not, you'll get an error and have to adjust the location)

The PROTOCOL_TLS_CLIENT protocol configures the context for cert validation and hostname verification. verify_mode is set to CERT_REQUIRED and check_hostname is set to True. All other protocols create SSL contexts with insecure defaults.

When you use the context to connect to a server, CERT_REQUIRED and check_hostname validate the server certificate: it ensures that the server certificate was signed with one of the CA certificates, checks the signature for correctness, and verifies other properties like validity and identity of the hostname:

>>> conn = context.wrap_socket(socket.socket(socket.AF_INET),
...                            server_hostname="www.python.org")
>>> conn.connect(("www.python.org", 443))

You may then fetch the certificate:

>>> cert = conn.getpeercert()

Visual inspection shows that the certificate does identify the desired service (that is, the HTTPS host www.python.org):

>>> pprint.pprint(cert)
{'OCSP': ('http://ocsp.digicert.com',),
 'caIssuers': ('http://cacerts.digicert.com/DigiCertSHA2ExtendedValidationServerCA.crt',),
 'crlDistributionPoints': ('http://crl3.digicert.com/sha2-ev-server-g1.crl',
                           'http://crl4.digicert.com/sha2-ev-server-g1.crl'),
 'issuer': ((('countryName', 'US'),),
            (('organizationName', 'DigiCert Inc'),),
            (('organizationalUnitName', 'www.digicert.com'),),
            (('commonName', 'DigiCert SHA2 Extended Validation Server CA'),)),
 'notAfter': 'Sep  9 12:00:00 2016 GMT',
 'notBefore': 'Sep  5 00:00:00 2014 GMT',
 'serialNumber': '01BB6F00122B177F36CAB49CEA8B6B26',
 'subject': ((('businessCategory', 'Private Organization'),),
             (('1.3.6.1.4.1.311.60.2.1.3', 'US'),),
             (('1.3.6.1.4.1.311.60.2.1.2', 'Delaware'),),
             (('serialNumber', '3359300'),),
             (('streetAddress', '16 Allen Rd'),),
             (('postalCode', '03894-4801'),),
             (('countryName', 'US'),),
             (('stateOrProvinceName', 'NH'),),
             (('localityName', 'Wolfeboro'),),
             (('organizationName', 'Python Software Foundation'),),
             (('commonName', 'www.python.org'),)),
 'subjectAltName': (('DNS', 'www.python.org'),
                    ('DNS', 'python.org'),
                    ('DNS', 'pypi.org'),
                    ('DNS', 'docs.python.org'),
                    ('DNS', 'testpypi.org'),
                    ('DNS', 'bugs.python.org'),
                    ('DNS', 'wiki.python.org'),
                    ('DNS', 'hg.python.org'),
                    ('DNS', 'mail.python.org'),
                    ('DNS', 'packaging.python.org'),
                    ('DNS', 'pythonhosted.org'),
                    ('DNS', 'www.pythonhosted.org'),
                    ('DNS', 'test.pythonhosted.org'),
                    ('DNS', 'us.pycon.org'),
                    ('DNS', 'id.python.org')),
 'version': 3}

Now the SSL channel is established and the certificate verified, you can proceed to talk with the server:

>>> conn.sendall(b"HEAD / HTTP/1.0\r\nHost: linuxfr.org\r\n\r\n")
>>> pprint.pprint(conn.recv(1024).split(b"\r\n"))
[b'HTTP/1.1 200 OK',
 b'Date: Sat, 18 Oct 2014 18:27:20 GMT',
 b'Server: nginx',
 b'Content-Type: text/html; charset=utf-8',
 b'X-Frame-Options: SAMEORIGIN',
 b'Content-Length: 45679',
 b'Accept-Ranges: bytes',
 b'Via: 1.1 varnish',
 b'Age: 2188',
 b'X-Served-By: cache-lcy1134-LCY',
 b'X-Cache: HIT',
 b'X-Cache-Hits: 11',
 b'Vary: Cookie',
 b'Strict-Transport-Security: max-age=63072000; includeSubDomains',
 b'Connection: close',
 b'',
 b'']

參閱下方 Security considerations 的討論。

伺服器端操作

For server operation, typically you'll need to have a server certificate, and private key, each in a file. You'll first create a context holding the key and the certificate, so that clients can check your authenticity. Then you'll open a socket, bind it to a port, call listen() on it, and start waiting for clients to connect:

import socket, ssl

context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
context.load_cert_chain(certfile="mycertfile", keyfile="mykeyfile")

bindsocket = socket.socket()
bindsocket.bind(('myaddr.example.com', 10023))
bindsocket.listen(5)

When a client connects, you'll call accept() on the socket to get the new socket from the other end, and use the context's SSLContext.wrap_socket() method to create a server-side SSL socket for the connection:

while True:
    newsocket, fromaddr = bindsocket.accept()
    connstream = context.wrap_socket(newsocket, server_side=True)
    try:
        deal_with_client(connstream)
    finally:
        connstream.shutdown(socket.SHUT_RDWR)
        connstream.close()

Then you'll read data from the connstream and do something with it till you are finished with the client (or the client is finished with you):

def deal_with_client(connstream):
    data = connstream.recv(1024)
    # empty data means the client is finished with us
    while data:
        if not do_something(connstream, data):
            # we'll assume do_something returns False
            # when we're finished with client
            break
        data = connstream.recv(1024)
    # finished with client

And go back to listening for new client connections (of course, a real server would probably handle each client connection in a separate thread, or put the sockets in non-blocking mode and use an event loop).

Notes on non-blocking sockets

SSL sockets behave slightly different than regular sockets in non-blocking mode. When working with non-blocking sockets, there are thus several things you need to be aware of:

Most SSLSocket methods will raise either SSLWantWriteError or SSLWantReadError instead of BlockingIOError if an I/O operation would block. SSLWantReadError will be raised if a read operation on the underlying socket is necessary, and SSLWantWriteError for a write operation on the underlying socket. Note that attempts to write to an SSL socket may require reading from the underlying socket first, and attempts to read from the SSL socket may require a prior write to the underlying socket.

在 3.5 版的變更: In earlier Python versions, the SSLSocket.send() method returned zero instead of raising SSLWantWriteError or SSLWantReadError.

Calling select() tells you that the OS-level socket can be read from (or written to), but it does not imply that there is sufficient data at the upper SSL layer. For example, only part of an SSL frame might have arrived. Therefore, you must be ready to handle SSLSocket.recv() and SSLSocket.send() failures, and retry after another call to select().

Conversely, since the SSL layer has its own framing, a SSL socket may still have data available for reading without select() being aware of it. Therefore, you should first call SSLSocket.recv() to drain any potentially available data, and then only block on a select() call if still necessary.

(of course, similar provisions apply when using other primitives such as poll(), or those in the selectors module)

The SSL handshake itself will be non-blocking: the SSLSocket.do_handshake() method has to be retried until it returns successfully. Here is a synopsis using select() to wait for the socket's readiness:

while True:
    try:
        sock.do_handshake()
        break
    except ssl.SSLWantReadError:
        select.select([sock], [], [])
    except ssl.SSLWantWriteError:
        select.select([], [sock], [])

也參考

The asyncio module supports non-blocking SSL sockets and provides a higher level Streams API. It polls for events using the selectors module and handles SSLWantWriteError, SSLWantReadError and BlockingIOError exceptions. It runs the SSL handshake asynchronously as well.

記憶體 BIO 支援

在 3.5 版被加入.

Ever since the SSL module was introduced in Python 2.6, the SSLSocket class has provided two related but distinct areas of functionality:

SSL protocol handling

Network IO

The network IO API is identical to that provided by socket.socket, from which SSLSocket also inherits. This allows an SSL socket to be used as a drop-in replacement for a regular socket, making it very easy to add SSL support to an existing application.

Combining SSL protocol handling and network IO usually works well, but there are some cases where it doesn't. An example is async IO frameworks that want to use a different IO multiplexing model than the "select/poll on a file descriptor" (readiness based) model that is assumed by socket.socket and by the internal OpenSSL socket IO routines. This is mostly relevant for platforms like Windows where this model is not efficient. For this purpose, a reduced scope variant of SSLSocket called SSLObject is provided.

class ssl.SSLObject

A reduced-scope variant of SSLSocket representing an SSL protocol instance that does not contain any network IO methods. This class is typically used by framework authors that want to implement asynchronous IO for SSL through memory buffers.

This class implements an interface on top of a low-level SSL object as implemented by OpenSSL. This object captures the state of an SSL connection but does not provide any network IO itself. IO needs to be performed through separate "BIO" objects which are OpenSSL's IO abstraction layer.

This class has no public constructor. An SSLObject instance must be created using the wrap_bio() method. This method will create the SSLObject instance and bind it to a pair of BIOs. The incoming BIO is used to pass data from Python to the SSL protocol instance, while the outgoing BIO is used to pass data the other way around.

The following methods are available:

context

server_side

server_hostname

session

session_reused

read()

write()

getpeercert()

get_verified_chain()

get_unverified_chain()

selected_alpn_protocol()

selected_npn_protocol()

cipher()

shared_ciphers()

compression()

pending()

do_handshake()

verify_client_post_handshake()

unwrap()

get_channel_binding()

version()

When compared to SSLSocket, this object lacks the following features:

Any form of network IO; recv() and send() read and write only to the underlying MemoryBIO buffers.

There is no do_handshake_on_connect machinery. You must always manually call do_handshake() to start the handshake.

There is no handling of suppress_ragged_eofs. All end-of-file conditions that are in violation of the protocol are reported via the SSLEOFError exception.

The method unwrap() call does not return anything, unlike for an SSL socket where it returns the underlying socket.

The server_name_callback callback passed to SSLContext.set_servername_callback() will get an SSLObject instance instead of a SSLSocket instance as its first parameter.

Some notes related to the use of SSLObject:

All IO on an SSLObject is non-blocking. This means that for example read() will raise an SSLWantReadError if it needs more data than the incoming BIO has available.

在 3.7 版的變更: SSLObject instances must be created with wrap_bio(). In earlier versions, it was possible to create instances directly. This was never documented or officially supported.

An SSLObject communicates with the outside world using memory buffers. The class MemoryBIO provides a memory buffer that can be used for this purpose. It wraps an OpenSSL memory BIO (Basic IO) object:

class ssl.MemoryBIO

A memory buffer that can be used to pass data between Python and an SSL protocol instance.

pending

Return the number of bytes currently in the memory buffer.

eof

A boolean indicating whether the memory BIO is current at the end-of-file position.

read(n=-1, /)

Read up to n bytes from the memory buffer. If n is not specified or negative, all bytes are returned.

write(buf, /)

Write the bytes from buf to the memory BIO. The buf argument must be an object supporting the buffer protocol.

The return value is the number of bytes written, which is always equal to the length of buf.

write_eof()

Write an EOF marker to the memory BIO. After this method has been called, it is illegal to call write(). The attribute eof will become true after all data currently in the buffer has been read.

SSL session

在 3.6 版被加入.

class ssl.SSLSession

Session object used by session.

id

time

timeout

ticket_lifetime_hint

has_ticket

Security considerations

Best defaults

For client use, if you don't have any special requirements for your security policy, it is highly recommended that you use the create_default_context() function to create your SSL context. It will load the system's trusted CA certificates, enable certificate validation and hostname checking, and try to choose reasonably secure protocol and cipher settings.

For example, here is how you would use the smtplib.SMTP class to create a trusted, secure connection to a SMTP server:

>>> import ssl, smtplib
>>> smtp = smtplib.SMTP("mail.python.org", port=587)
>>> context = ssl.create_default_context()
>>> smtp.starttls(context=context)
(220, b'2.0.0 Ready to start TLS')

If a client certificate is needed for the connection, it can be added with SSLContext.load_cert_chain().

By contrast, if you create the SSL context by calling the SSLContext constructor yourself, it will not have certificate validation nor hostname checking enabled by default. If you do so, please read the paragraphs below to achieve a good security level.

手動設定

驗證憑證

When calling the SSLContext constructor directly, CERT_NONE is the default. Since it does not authenticate the other peer, it can be insecure, especially in client mode where most of the time you would like to ensure the authenticity of the server you're talking to. Therefore, when in client mode, it is highly recommended to use CERT_REQUIRED. However, it is in itself not sufficient; you also have to check that the server certificate, which can be obtained by calling SSLSocket.getpeercert(), matches the desired service. For many protocols and applications, the service can be identified by the hostname. This common check is automatically performed when SSLContext.check_hostname is enabled.

在 3.7 版的變更: Hostname matchings is now performed by OpenSSL. Python no longer uses match_hostname().

In server mode, if you want to authenticate your clients using the SSL layer (rather than using a higher-level authentication mechanism), you'll also have to specify CERT_REQUIRED and similarly check the client certificate.

協定版本

SSL versions 2 and 3 are considered insecure and are therefore dangerous to use. If you want maximum compatibility between clients and servers, it is recommended to use PROTOCOL_TLS_CLIENT or PROTOCOL_TLS_SERVER as the protocol version. SSLv2 and SSLv3 are disabled by default.

>>> client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
>>> client_context.minimum_version = ssl.TLSVersion.TLSv1_3
>>> client_context.maximum_version = ssl.TLSVersion.TLSv1_3

The SSL context created above will only allow TLSv1.3 and later (if supported by your system) connections to a server. PROTOCOL_TLS_CLIENT implies certificate validation and hostname checks by default. You have to load certificates into the context.

Cipher selection

If you have advanced security requirements, fine-tuning of the ciphers enabled when negotiating a SSL session is possible through the SSLContext.set_ciphers() method. Starting from Python 3.2.3, the ssl module disables certain weak ciphers by default, but you may want to further restrict the cipher choice. Be sure to read OpenSSL's documentation about the cipher list format [https://docs.openssl.org/1.1.1/man1/ciphers/#cipher-list-format]. If you want to check which ciphers are enabled by a given cipher list, use SSLContext.get_ciphers() or the openssl ciphers command on your system.

Multi-processing

If using this module as part of a multi-processed application (using, for example the multiprocessing or concurrent.futures modules), be aware that OpenSSL's internal random number generator does not properly handle forked processes. Applications must change the PRNG state of the parent process if they use any SSL feature with os.fork(). Any successful call of RAND_add() or RAND_bytes() is sufficient.

TLS 1.3

在 3.7 版被加入.

The TLS 1.3 protocol behaves slightly differently than previous version of TLS/SSL. Some new TLS 1.3 features are not yet available.

TLS 1.3 uses a disjunct set of cipher suites. All AES-GCM and ChaCha20 cipher suites are enabled by default. The method SSLContext.set_ciphers() cannot enable or disable any TLS 1.3 ciphers yet, but SSLContext.get_ciphers() returns them.

Session tickets are no longer sent as part of the initial handshake and are handled differently. SSLSocket.session and SSLSession are not compatible with TLS 1.3.

Client-side certificates are also no longer verified during the initial handshake. A server can request a certificate at any time. Clients process certificate requests while they send or receive application data from the server.

TLS 1.3 features like early data, deferred TLS client cert request, signature algorithm configuration, and rekeying are not supported yet.

也參考

socket.socket 類別

底層 socket 類別的文件

SSL/TLS Strong Encryption: An Introduction [https://httpd.apache.org/docs/trunk/en/ssl/ssl_intro.html]

Apache HTTP Server 文件的介紹

RFC 1422: Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management [https://datatracker.ietf.org/doc/html/rfc1422.html]

Steve Kent

RFC 4086: Randomness Requirements for Security [https://datatracker.ietf.org/doc/html/rfc4086.html]

Donald E. Eastlake, Jeffrey I. Schiller, Steve Crocker

RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile [https://datatracker.ietf.org/doc/html/rfc5280.html]

David Cooper et al.

RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2 [https://datatracker.ietf.org/doc/html/rfc5246.html]

Tim Dierks 與 Eric Rescorla.

RFC 6066: Transport Layer Security (TLS) Extensions [https://datatracker.ietf.org/doc/html/rfc6066.html]

Donald E. Eastlake

IANA TLS: Transport Layer Security (TLS) Parameters [https://www.iana.org/assignments/tls-parameters/tls-parameters.xml]

IANA

RFC 7525: Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) [https://datatracker.ietf.org/doc/html/rfc7525.html]

IETF

Mozilla's Server Side TLS recommendations [https://wiki.mozilla.org/Security/Server_Side_TLS]

Mozilla

select --- 等待 I/O 完成

This module provides access to the select() and poll() functions available in most operating systems, devpoll() available on Solaris and derivatives, epoll() available on Linux 2.5+ and kqueue() available on most BSD. Note that on Windows, it only works for sockets; on other operating systems, it also works for other file types (in particular, on Unix, it works on pipes). It cannot be used on regular files to determine whether a file has grown since it was last read.

備註

The selectors module allows high-level and efficient I/O multiplexing, built upon the select module primitives. Users are encouraged to use the selectors module instead, unless they want precise control over the OS-level primitives used.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

The module defines the following:

exception select.error

A deprecated alias of OSError.

在 3.3 版的變更: Following PEP 3151 [https://peps.python.org/pep-3151/], this class was made an alias of OSError.

select.devpoll()

(Only supported on Solaris and derivatives.) Returns a /dev/poll polling object; see section /dev/poll Polling Objects below for the methods supported by devpoll objects.

devpoll() objects are linked to the number of file descriptors allowed at the time of instantiation. If your program reduces this value, devpoll() will fail. If your program increases this value, devpoll() may return an incomplete list of active file descriptors.

The new file descriptor is non-inheritable.

在 3.3 版被加入.

在 3.4 版的變更: The new file descriptor is now non-inheritable.

select.epoll(sizehint=-1, flags=0)

(Only supported on Linux 2.5.44 and newer.) Return an edge polling object, which can be used as Edge or Level Triggered interface for I/O events.

sizehint informs epoll about the expected number of events to be registered. It must be positive, or -1 to use the default. It is only used on older systems where epoll_create1() is not available; otherwise it has no effect (though its value is still checked).

flags is deprecated and completely ignored. However, when supplied, its value must be 0 or select.EPOLL_CLOEXEC, otherwise OSError is raised.

See the Edge and Level Trigger Polling (epoll) Objects section below for the methods supported by epolling objects.

epoll objects support the context management protocol: when used in a with statement, the new file descriptor is automatically closed at the end of the block.

The new file descriptor is non-inheritable.

在 3.3 版的變更: 新增 flags 參數。

在 3.4 版的變更: Support for the with statement was added. The new file descriptor is now non-inheritable.

在 3.4 版之後被棄用: The flags parameter. select.EPOLL_CLOEXEC is used by default now. Use os.set_inheritable() to make the file descriptor inheritable.

select.poll()

(Not supported by all operating systems.) Returns a polling object, which supports registering and unregistering file descriptors, and then polling them for I/O events; see section Polling Objects below for the methods supported by polling objects.

select.kqueue()

(Only supported on BSD.) Returns a kernel queue object; see section Kqueue Objects below for the methods supported by kqueue objects.

The new file descriptor is non-inheritable.

在 3.4 版的變更: The new file descriptor is now non-inheritable.

select.kevent(ident, filter=KQ_FILTER_READ, flags=KQ_EV_ADD, fflags=0, data=0, udata=0)

(Only supported on BSD.) Returns a kernel event object; see section Kevent Objects below for the methods supported by kevent objects.

select.select(rlist, wlist, xlist, timeout=None)

This is a straightforward interface to the Unix select() system call. The first three arguments are iterables of 'waitable objects': either integers representing file descriptors or objects with a parameterless method named fileno() returning such an integer:

rlist: wait until ready for reading

wlist: wait until ready for writing

xlist: wait for an "exceptional condition" (see the manual page for what your system considers such a condition)

Empty iterables are allowed, but acceptance of three empty iterables is platform-dependent. (It is known to work on Unix but not on Windows.) The optional timeout argument specifies a time-out as a floating-point number in seconds. When the timeout argument is omitted or None, the function blocks until at least one file descriptor is ready. A time-out value of zero specifies a poll and never blocks.

The return value is a triple of lists of objects that are ready: subsets of the first three arguments. When the time-out is reached without a file descriptor becoming ready, three empty lists are returned.

Among the acceptable object types in the iterables are Python file objects (e.g. sys.stdin, or objects returned by open() or os.popen()), socket objects returned by socket.socket(). You may also define a wrapper class yourself, as long as it has an appropriate fileno() method (that really returns a file descriptor, not just a random integer).

備註

File objects on Windows are not acceptable, but sockets are. On Windows, the underlying select() function is provided by the WinSock library, and does not handle file descriptors that don't originate from WinSock.

在 3.5 版的變更: The function is now retried with a recomputed timeout when interrupted by a signal, except if the signal handler raises an exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale), instead of raising InterruptedError.

select.PIPE_BUF

The minimum number of bytes which can be written without blocking to a pipe when the pipe has been reported as ready for writing by select(), poll() or another interface in this module. This doesn't apply to other kind of file-like objects such as sockets.

This value is guaranteed by POSIX to be at least 512.

可用性: Unix

在 3.2 版被加入.

/dev/poll Polling Objects

Solaris and derivatives have /dev/poll. While select() is O(highest file descriptor) and poll() is O(number of file descriptors), /dev/poll is O(active file descriptors).

/dev/poll behaviour is very close to the standard poll() object.

devpoll.close()

Close the file descriptor of the polling object.

在 3.4 版被加入.

devpoll.closed

True if the polling object is closed.

在 3.4 版被加入.

devpoll.fileno()

Return the file descriptor number of the polling object.

在 3.4 版被加入.

devpoll.register(fd[, eventmask])

Register a file descriptor with the polling object. Future calls to the poll() method will then check whether the file descriptor has any pending I/O events. fd can be either an integer, or an object with a fileno() method that returns an integer. File objects implement fileno(), so they can also be used as the argument.

eventmask is an optional bitmask describing the type of events you want to check for. The constants are the same that with poll() object. The default value is a combination of the constants POLLIN, POLLPRI, and POLLOUT.

警告

Registering a file descriptor that's already registered is not an error, but the result is undefined. The appropriate action is to unregister or modify it first. This is an important difference compared with poll().

devpoll.modify(fd[, eventmask])

This method does an unregister() followed by a register(). It is (a bit) more efficient that doing the same explicitly.

devpoll.unregister(fd)

Remove a file descriptor being tracked by a polling object. Just like the register() method, fd can be an integer or an object with a fileno() method that returns an integer.

Attempting to remove a file descriptor that was never registered is safely ignored.

devpoll.poll([timeout])

Polls the set of registered file descriptors, and returns a possibly empty list containing (fd, event) 2-tuples for the descriptors that have events or errors to report. fd is the file descriptor, and event is a bitmask with bits set for the reported events for that descriptor --- POLLIN for waiting input, POLLOUT to indicate that the descriptor can be written to, and so forth. An empty list indicates that the call timed out and no file descriptors had any events to report. If timeout is given, it specifies the length of time in milliseconds which the system will wait for events before returning. If timeout is omitted, -1, or None, the call will block until there is an event for this poll object.

在 3.5 版的變更: The function is now retried with a recomputed timeout when interrupted by a signal, except if the signal handler raises an exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale), instead of raising InterruptedError.

Edge and Level Trigger Polling (epoll) Objects

https://linux.die.net/man/4/epoll

eventmask

常數

含義

EPOLLIN

Available for read

EPOLLOUT

Available for write

EPOLLPRI

Urgent data for read

EPOLLERR

Error condition happened on the assoc. fd

EPOLLHUP

Hang up happened on the assoc. fd

EPOLLET

Set Edge Trigger behavior, the default is Level Trigger behavior

EPOLLONESHOT

Set one-shot behavior. After one event is pulled out, the fd is internally disabled

EPOLLEXCLUSIVE

Wake only one epoll object when the associated fd has an event. The default (if this flag is not set) is to wake all epoll objects polling on a fd.

EPOLLRDHUP

Stream socket peer closed connection or shut down writing half of connection.

EPOLLRDNORM

等價於 EPOLLIN

EPOLLRDBAND

Priority data band can be read.

EPOLLWRNORM

等價於 EPOLLOUT

EPOLLWRBAND

Priority data may be written.

EPOLLMSG

Ignored.

EPOLLWAKEUP

Prevents sleep during event waiting.

在 3.6 版被加入: EPOLLEXCLUSIVE was added. It's only supported by Linux Kernel 4.5 or later.

在 3.14 版被加入: EPOLLWAKEUP was added. It's only supported by Linux Kernel 3.5 or later.

epoll.close()

Close the control file descriptor of the epoll object.

epoll.closed

True if the epoll object is closed.

epoll.fileno()

Return the file descriptor number of the control fd.

epoll.fromfd(fd)

Create an epoll object from a given file descriptor.

epoll.register(fd[, eventmask])

Register a fd descriptor with the epoll object.

epoll.modify(fd, eventmask)

Modify a registered file descriptor.

epoll.unregister(fd)

Remove a registered file descriptor from the epoll object.

在 3.9 版的變更: The method no longer ignores the EBADF error.

epoll.poll(timeout=None, maxevents=-1)

Wait for events. timeout in seconds (float)

在 3.5 版的變更: The function is now retried with a recomputed timeout when interrupted by a signal, except if the signal handler raises an exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale), instead of raising InterruptedError.

Polling Objects

The poll() system call, supported on most Unix systems, provides better scalability for network servers that service many, many clients at the same time. poll() scales better because the system call only requires listing the file descriptors of interest, while select() builds a bitmap, turns on bits for the fds of interest, and then afterward the whole bitmap has to be linearly scanned again. select() is O(highest file descriptor), while poll() is O(number of file descriptors).

poll.register(fd[, eventmask])

Register a file descriptor with the polling object. Future calls to the poll() method will then check whether the file descriptor has any pending I/O events. fd can be either an integer, or an object with a fileno() method that returns an integer. File objects implement fileno(), so they can also be used as the argument.

eventmask is an optional bitmask describing the type of events you want to check for, and can be a combination of the constants POLLIN, POLLPRI, and POLLOUT, described in the table below. If not specified, the default value used will check for all 3 types of events.

常數

含義

POLLIN

There is data to read

POLLPRI

There is urgent data to read

POLLOUT

Ready for output: writing will not block

POLLERR

Error condition of some sort

POLLHUP

Hung up

POLLRDHUP

Stream socket peer closed connection, or shut down writing half of connection

POLLNVAL

Invalid request: descriptor not open

Registering a file descriptor that's already registered is not an error, and has the same effect as registering the descriptor exactly once.

poll.modify(fd, eventmask)

Modifies an already registered fd. This has the same effect as register(fd, eventmask). Attempting to modify a file descriptor that was never registered causes an OSError exception with errno ENOENT to be raised.

poll.unregister(fd)

Remove a file descriptor being tracked by a polling object. Just like the register() method, fd can be an integer or an object with a fileno() method that returns an integer.

Attempting to remove a file descriptor that was never registered causes a KeyError exception to be raised.

poll.poll([timeout])

Polls the set of registered file descriptors, and returns a possibly empty list containing (fd, event) 2-tuples for the descriptors that have events or errors to report. fd is the file descriptor, and event is a bitmask with bits set for the reported events for that descriptor --- POLLIN for waiting input, POLLOUT to indicate that the descriptor can be written to, and so forth. An empty list indicates that the call timed out and no file descriptors had any events to report. If timeout is given, it specifies the length of time in milliseconds which the system will wait for events before returning. If timeout is omitted, negative, or None, the call will block until there is an event for this poll object.

在 3.5 版的變更: The function is now retried with a recomputed timeout when interrupted by a signal, except if the signal handler raises an exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale), instead of raising InterruptedError.

Kqueue Objects

kqueue.close()

Close the control file descriptor of the kqueue object.

kqueue.closed

True if the kqueue object is closed.

kqueue.fileno()

Return the file descriptor number of the control fd.

kqueue.fromfd(fd)

Create a kqueue object from a given file descriptor.

kqueue.control(changelist, max_events[, timeout]) → eventlist

Low level interface to kevent

changelist must be an iterable of kevent objects or None

max_events must be 0 or a positive integer

timeout in seconds (floats possible); the default is None, to wait forever

在 3.5 版的變更: The function is now retried with a recomputed timeout when interrupted by a signal, except if the signal handler raises an exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale), instead of raising InterruptedError.

Kevent Objects

https://man.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2

kevent.ident

Value used to identify the event. The interpretation depends on the filter but it's usually the file descriptor. In the constructor ident can either be an int or an object with a fileno() method. kevent stores the integer internally.

kevent.filter

Name of the kernel filter.

常數

含義

KQ_FILTER_READ

Takes a descriptor and returns whenever there is data available to read

KQ_FILTER_WRITE

Takes a descriptor and returns whenever there is data available to write

KQ_FILTER_AIO

AIO requests

KQ_FILTER_VNODE

Returns when one or more of the requested events watched in fflag occurs

KQ_FILTER_PROC

Watch for events on a process id

KQ_FILTER_NETDEV

Watch for events on a network device [not available on macOS]

KQ_FILTER_SIGNAL

Returns whenever the watched signal is delivered to the process

KQ_FILTER_TIMER

Establishes an arbitrary timer

kevent.flags

Filter action.

常數

含義

KQ_EV_ADD

Adds or modifies an event

KQ_EV_DELETE

Removes an event from the queue

KQ_EV_ENABLE

Permitscontrol() to returns the event

KQ_EV_DISABLE

Disablesevent

KQ_EV_ONESHOT

Removes event after first occurrence

KQ_EV_CLEAR

Reset the state after an event is retrieved

KQ_EV_SYSFLAGS

internal event

KQ_EV_FLAG1

internal event

KQ_EV_EOF

Filter specific EOF condition

KQ_EV_ERROR

See return values

kevent.fflags

Filter specific flags.

KQ_FILTER_READ 和 KQ_FILTER_WRITE 篩選旗標：

常數

含義

KQ_NOTE_LOWAT

low water mark of a socket buffer

KQ_FILTER_VNODE 篩選旗標：

常數

含義

KQ_NOTE_DELETE

unlink() was called

KQ_NOTE_WRITE

a write occurred

KQ_NOTE_EXTEND

the file was extended

KQ_NOTE_ATTRIB

an attribute was changed

KQ_NOTE_LINK

the link count has changed

KQ_NOTE_RENAME

the file was renamed

KQ_NOTE_REVOKE

access to the file was revoked

KQ_FILTER_PROC 篩選旗標：

常數

含義

KQ_NOTE_EXIT

the process has exited

KQ_NOTE_FORK

the process has called fork()

KQ_NOTE_EXEC

the process has executed a new process

KQ_NOTE_PCTRLMASK

internal filter flag

KQ_NOTE_PDATAMASK

internal filter flag

KQ_NOTE_TRACK

follow a process across fork()

KQ_NOTE_CHILD

returned on the child process for NOTE_TRACK

KQ_NOTE_TRACKERR

unable to attach to a child

KQ_FILTER_NETDEV 篩選旗標（macOS 上不可用）：

常數

含義

KQ_NOTE_LINKUP

link is up

KQ_NOTE_LINKDOWN

link is down

KQ_NOTE_LINKINV

link state is invalid

kevent.data

Filter specific data.

kevent.udata

User defined value.

selectors --- 高階 I/O 多工

在 3.4 版被加入.

原始碼：Lib/selectors.py [https://github.com/python/cpython/tree/3.14/Lib/selectors.py]

簡介

This module allows high-level and efficient I/O multiplexing, built upon the select module primitives. Users are encouraged to use this module instead, unless they want precise control over the OS-level primitives used.

It defines a BaseSelector abstract base class, along with several concrete implementations (KqueueSelector, EpollSelector...), that can be used to wait for I/O readiness notification on multiple file objects. In the following, "file object" refers to any object with a fileno() method, or a raw file descriptor. See file object.

DefaultSelector is an alias to the most efficient implementation available on the current platform: this should be the default choice for most users.

備註

The type of file objects supported depends on the platform: on Windows, sockets are supported, but not pipes, whereas on Unix, both are supported (some other types may be supported as well, such as fifos or special file devices).

也參考

select

Low-level I/O multiplexing module.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

Classes

Classes hierarchy:

BaseSelector
+-- SelectSelector
+-- PollSelector
+-- EpollSelector
+-- DevpollSelector
+-- KqueueSelector

In the following, events is a bitwise mask indicating which I/O events should be waited for on a given file object. It can be a combination of the modules constants below:

常數

含義

selectors.EVENT_READ

Available for read

selectors.EVENT_WRITE

Available for write

class selectors.SelectorKey

A SelectorKey is a namedtuple used to associate a file object to its underlying file descriptor, selected event mask and attached data. It is returned by several BaseSelector methods.

fileobj

File object registered.

fd

Underlying file descriptor.

events

Events that must be waited for on this file object.

data

Optional opaque data associated to this file object: for example, this could be used to store a per-client session ID.

class selectors.BaseSelector

A BaseSelector is used to wait for I/O event readiness on multiple file objects. It supports file stream registration, unregistration, and a method to wait for I/O events on those streams, with an optional timeout. It's an abstract base class, so cannot be instantiated. Use DefaultSelector instead, or one of SelectSelector, KqueueSelector etc. if you want to specifically use an implementation, and your platform supports it. BaseSelector and its concrete implementations support the context manager protocol.

abstractmethod register(fileobj, events, data=None)

Register a file object for selection, monitoring it for I/O events.

fileobj is the file object to monitor. It may either be an integer file descriptor or an object with a fileno() method. events is a bitwise mask of events to monitor. data is an opaque object.

This returns a new SelectorKey instance, or raises a ValueError in case of invalid event mask or file descriptor, or KeyError if the file object is already registered.

abstractmethod unregister(fileobj)

Unregister a file object from selection, removing it from monitoring. A file object shall be unregistered prior to being closed.

fileobj must be a file object previously registered.

This returns the associated SelectorKey instance, or raises a KeyError if fileobj is not registered. It will raise ValueError if fileobj is invalid (e.g. it has no fileno() method or its fileno() method has an invalid return value).

modify(fileobj, events, data=None)

Change a registered file object's monitored events or attached data.

This is equivalent to BaseSelector.unregister(fileobj) followed by BaseSelector.register(fileobj, events, data), except that it can be implemented more efficiently.

This returns a new SelectorKey instance, or raises a ValueError in case of invalid event mask or file descriptor, or KeyError if the file object is not registered.

abstractmethod select(timeout=None)

Wait until some registered file objects become ready, or the timeout expires.

If timeout > 0, this specifies the maximum wait time, in seconds. If timeout <= 0, the call won't block, and will report the currently ready file objects. If timeout is None, the call will block until a monitored file object becomes ready.

This returns a list of (key, events) tuples, one for each ready file object.

key is the SelectorKey instance corresponding to a ready file object. events is a bitmask of events ready on this file object.

備註

This method can return before any file object becomes ready or the timeout has elapsed if the current process receives a signal: in this case, an empty list will be returned.

在 3.5 版的變更: The selector is now retried with a recomputed timeout when interrupted by a signal if the signal handler did not raise an exception (see PEP 475 [https://peps.python.org/pep-0475/] for the rationale), instead of returning an empty list of events before the timeout.

close()

Close the selector.

This must be called to make sure that any underlying resource is freed. The selector shall not be used once it has been closed.

get_key(fileobj)

Return the key associated with a registered file object.

This returns the SelectorKey instance associated to this file object, or raises KeyError if the file object is not registered.

abstractmethod get_map()

Return a mapping of file objects to selector keys.

This returns a Mapping instance mapping registered file objects to their associated SelectorKey instance.

class selectors.DefaultSelector

The default selector class, using the most efficient implementation available on the current platform. This should be the default choice for most users.

class selectors.SelectSelector

基於 select.select() 的選擇器。

class selectors.PollSelector

基於 select.poll() 的選擇器。

class selectors.EpollSelector

基於 select.epoll() 的選擇器。

fileno()

This returns the file descriptor used by the underlying select.epoll() object.

class selectors.DevpollSelector

基於 select.devpoll() 的選擇器。

fileno()

This returns the file descriptor used by the underlying select.devpoll() object.

在 3.5 版被加入.

class selectors.KqueueSelector

基於 select.kqueue() 的選擇器。

fileno()

This returns the file descriptor used by the underlying select.kqueue() object.

範例

Here is a simple echo server implementation:

import selectors
import socket

sel = selectors.DefaultSelector()

def accept(sock, mask):
    conn, addr = sock.accept()  # Should be ready
    print('accepted', conn, 'from', addr)
    conn.setblocking(False)
    sel.register(conn, selectors.EVENT_READ, read)

def read(conn, mask):
    data = conn.recv(1000)  # Should be ready
    if data:
        print('echoing', repr(data), 'to', conn)
        conn.send(data)  # Hope it won't block
    else:
        print('closing', conn)
        sel.unregister(conn)
        conn.close()

sock = socket.socket()
sock.bind(('localhost', 1234))
sock.listen(100)
sock.setblocking(False)
sel.register(sock, selectors.EVENT_READ, accept)

while True:
    events = sel.select()
    for key, mask in events:
        callback = key.data
        callback(key.fileobj, mask)

signal --- 設定非同步事件的處理函式

原始碼：Lib/signal.py [https://github.com/python/cpython/tree/3.14/Lib/signal.py]

本模組提供於 Python 中使用訊號處理程式的機制。

一般規則

signal.signal() 函式允許定義自訂的處理程式，會在收到訊號時執行。我們安裝了少數的預設處理程式：SIGPIPE 會被忽略 (所以管道和 socket 上的寫入錯誤可以當作一般的 Python 例外報告)，而 SIGINT（如果父行程沒有改變它的話）會被轉換成 KeyboardInterrupt 例外。

特定訊號的處理程式一旦被設定，就會一直被安裝，直到被明確地重設為止 (不管底層的實作為何，Python 皆模擬出 BSD 風格的介面)，但 SIGCHLD 的處理程式除外，它會跟隨底層的實作。

在 WebAssembly 平台上，訊號是模擬出來的，故行為不同。有幾個函式和訊號在這些平台上是不可用的。

Python 訊號處理程式的執行

Python 訊號處理程式不會在低階（C 語言）訊號處理程式中執行。相反地，低階訊號處理程式會設定一個旗標，告訴虛擬機在稍後執行相對應的 Python 訊號處理程式（例如在下一個 bytecode 指令）。這會有一些後果：

捕捉像 SIGFPE 或 SIGSEGV 這類由 C 程式碼中無效操作所引起的同步錯誤是沒有意義的。Python 將從訊號處理程式中回傳到 C 程式碼，而 C 程式碼很可能再次引發相同的訊號，導致 Python 明顯假當機 (hang)。從 Python 3.3 開始，你可以使用 faulthandler 模組來報告同步錯誤。

純粹以 C 實作的長時間計算（例如在大量文字上的正規表示式比對）可能會不間斷地運行任意長度的時間而不考慮收到的任何訊號。當計算完成時，Python 訊號處理程式會被呼叫。

如果處理程式引發例外，就會在主執行緒中「憑空」產生例外。請參閱下面的說明。

訊號和執行緒

Python 訊號處理程式總是在主直譯器的主 Python 執行緒中執行，即使訊號是在另一個執行緒中接收到的。這意味著訊號不能用來做為執行緒間通訊的方式。你可以使用 threading 模組的同步原語 (synchronization primitive) 來代替。

此外，只有主直譯器的主執行緒才被允許設定新的訊號處理程式。

模組內容

在 3.5 版的變更: 下面列出的訊號 (SIG*)、處理器（SIG_DFL、SIG_IGN）和訊號遮罩 (sigmask)（SIG_BLOCK、SIG_UNBLOCK、SIG_SETMASK）的相關常數被轉換成 enums（Signals、Handlers 和 Sigmasks）。getsignal()、pthread_sigmask()、sigpending() 和 sigwait() 函式會回傳可被人類閱讀的枚舉作為 Signals 物件。

訊號模組定義了三個枚舉：

class signal.Signals

SIG* 常數和 CTRL_* 常數的 enum.IntEnum 集合。

在 3.5 版被加入.

class signal.Handlers

SIG_DFL 和 SIG_IGN 常數的 enum.IntEnum 集合。

在 3.5 版被加入.

class signal.Sigmasks

SIG_BLOCK、SIG_UNBLOCK 和 SIG_SETMASK 常數的 enum.IntEnum 集合。

可用性: Unix.

更多資訊請見 sigprocmask(2) [https://manpages.debian.org/sigprocmask(2)] 與 pthread_sigmask(3) [https://manpages.debian.org/pthread_sigmask(3)] 線上手冊。

在 3.5 版被加入.

在 signal 模組中定義的變數有：

signal.SIG_DFL

這是兩種標準訊號處理選項之一；它會簡單地執行訊號的預設功能。例如，在大多數系統上，SIGQUIT 的預設動作是轉儲 (dump) 核心並退出，而 SIGCHLD 的預設動作是直接忽略。

signal.SIG_IGN

這是另一個標準的訊號處理程式，會直接忽略給定的訊號。

signal.SIGABRT

來自 abort(3) [https://manpages.debian.org/abort(3)] 的中止訊號。

signal.SIGALRM

來自 alarm(2) [https://manpages.debian.org/alarm(2)] 的計時器訊號。

可用性: Unix.

signal.SIGBREAK

從鍵盤中斷 (CTRL + BREAK)。

可用性: Windows.

signal.SIGBUS

匯流排錯誤（記憶體存取不良）。

可用性: Unix.

signal.SIGCHLD

子行程停止或終止。

可用性: Unix.

signal.SIGCLD

SIGCHLD 的別名。

可用性: not macOS.

signal.SIGCONT

如果目前行程是被停止的，則繼續運行

可用性: Unix.

signal.SIGFPE

浮點運算例外。例如除以零。

也參考

ZeroDivisionError 會在除法或模運算 (modulo operation) 的第二個引數為零時引發。

signal.SIGHUP

偵測到控制終端機掛斷 (hangup) 或控制行程死亡。

可用性: Unix.

signal.SIGILL

非法指令。

signal.SIGINT

從鍵盤中斷 (CTRL + C)。

預設動作是引發 KeyboardInterrupt。

signal.SIGKILL

殺死訊號。

它無法被捕捉、阻擋或忽略。

可用性: Unix.

signal.SIGPIPE

管道中斷 (broken pipe)：寫到沒有讀取器 (reader) 的管道。

預設動作是忽略訊號。

可用性: Unix.

signal.SIGPROF

Profiling timer expired.

可用性: Unix.

signal.SIGQUIT

Terminal quit signal.

可用性: Unix.

signal.SIGSEGV

記憶體區段錯誤 (segmentation fault)：無效記憶體參照。

signal.SIGSTOP

停止執行（無法被捕捉或忽略）。

signal.SIGSTKFLT

輔助處理器 (coprocessor) 上的堆疊錯誤 (stack fault)。Linux 核心不會引發此訊號：它只能在使用者空間 (user space) 中引發。

可用性: Linux.

在訊號可用的架構上。請參閱 signal(7) [https://manpages.debian.org/signal(7)] 線上手冊以取得更多資訊。

在 3.11 版被加入.

signal.SIGTERM

終止訊號。

signal.SIGUSR1

使用者定義訊號 1。

可用性: Unix.

signal.SIGUSR2

使用者定義訊號 2。

可用性: Unix.

signal.SIGVTALRM

Virtual timer expired.

可用性: Unix.

signal.SIGWINCH

視窗調整大小訊號。

可用性: Unix.

signal.SIGXCPU

CPU time limit exceeded.

可用性: Unix.

SIG*

所有的訊號編號都是以符號定義的。例如，掛斷訊號被定義為 signal.SIGHUP；變數名稱與 C 程式中使用的名稱相同，可在 <signal.h> 中找到。Unix 線上手冊 'signal' 列出了現有的訊號（在某些系統上是 signal(2) [https://manpages.debian.org/signal(2)]，在其他系統上是在 signal(7) [https://manpages.debian.org/signal(7)] 中）。請注意，並非所有系統都會定義同一套訊號名稱；只有那些由系統所定義的名稱才會由這個模組定義。

signal.CTRL_C_EVENT

與 Ctrl+C 擊鍵 (keystroke) 事件相對應的訊號。此訊號只能與 os.kill() 搭配使用。

可用性: Windows.

在 3.2 版被加入.

signal.CTRL_BREAK_EVENT

與 Ctrl+Break 擊鍵事件相對應的訊號。此訊號只能與 os.kill() 搭配使用。

可用性: Windows.

在 3.2 版被加入.

signal.NSIG

比最高編號訊號的編號多一。使用 valid_signals() 來取得有效的訊號編號。

signal.ITIMER_REAL

即時減少間隔計時器 (interval timer)，並在到期時送出 SIGALRM。

signal.ITIMER_VIRTUAL

僅在執行行程時遞減間隔計時器，並在到期時傳送 SIGVTALRM。

signal.ITIMER_PROF

當行程執行或系統代表行程執行時，都會減少間隔計時器。與 ITIMER_VIRTUAL 配合，這個計時器通常用來分析 (profile) 應用程式在使用者空間與核心空間 (kernel space) 所花費的時間。SIGPROF 會在到期時傳送。

signal.SIG_BLOCK

pthread_sigmask() 的 how 參數的可能值，表示訊號將被阻檔。

在 3.3 版被加入.

signal.SIG_UNBLOCK

pthread_sigmask() 的 how 參數的可能值，表示訊號將被解除阻檔。

在 3.3 版被加入.

signal.SIG_SETMASK

pthread_sigmask() 的 how 參數的可能值，表示訊號遮罩 (signal mask) 要被取代。

在 3.3 版被加入.

signal 模組定義了一個例外：

exception signal.ItimerError

當 setitimer() 或 getitimer() 底層實作發生錯誤時引發訊號。如果傳給 setitimer() 的是無效的間隔計時器或負數時間，則預期會發生此錯誤。這個錯誤是 OSError 的子型別。

在 3.3 版被加入: 此錯誤過去是 IOError 的子型別，現在是 OSError 的別名。

signal 模組定義了下列函式：

signal.alarm(time)

如果 time 非零，則此函式會要求在 time 秒後傳送 SIGALRM 訊號給該行程。任何先前排程 (scheduled) 的警報都會被取消（任何時候都只能排程一個警報）。回傳值是先前設定的警報原本再等多久就會被傳送的秒數。如果 time 為零，則不會去排程任何警報，且已排程的警報會被取消。如果回傳值為零，則代表目前未排程任何警報。

可用性: Unix.

更多資訊請見 alarm(2) [https://manpages.debian.org/alarm(2)] 線上手冊。

signal.getsignal(signalnum)

回傳訊號 signalnum 的目前訊號處理程式。回傳值可以是一個可呼叫的 Python 物件，或是特殊值 signal.SIG_IGN、signal.SIG_DFL 或 None 之一。這裡的 signal.SIG_IGN 表示訊號先前被忽略，signal.SIG_DFL 表示訊號先前使用預設的處理方式，而 None 表示先前的訊號處理程式並未從 Python 安裝。

signal.strsignal(signalnum)

回傳訊號 signalnum 的描述，例如 SIGINT 的 "Interrupt"。如果 signalnum 沒有描述，則回傳 None。如果 signalnum 無效則會引發 ValueError。

在 3.8 版被加入.

signal.valid_signals()

回傳此平台上的有效訊號編號集合。如果某些訊號被系統保留作為內部使用，則此值可能小於 range(1, NSIG)。

在 3.8 版被加入.

signal.pause()

使行程休眠，直到接收到訊號；然後呼叫適當的處理程式。不會回傳任何東西。

可用性: Unix.

更多資訊請見 signal(2) [https://manpages.debian.org/signal(2)] 線上手冊。

也請見 sigwait()、sigwaitinfo()、sigtimedwait() 和 sigpending()。

signal.raise_signal(signum)

傳送訊號至呼叫的行程。不會回傳任何東西。

在 3.8 版被加入.

signal.pidfd_send_signal(pidfd, sig, siginfo=None, flags=0)

傳送訊號 sig 到檔案描述器 pidfd 所指的行程。Python 目前不支援 siginfo 參數；它必須是 None。flags 引數是提供給未來的擴充；目前沒有定義旗標值。

更多資訊請見 pidfd_send_signal(2) [https://manpages.debian.org/pidfd_send_signal(2)] 線上手冊。

可用性: Linux >= 5.1, Android >= build-time API level 31

在 3.9 版被加入.

signal.pthread_kill(thread_id, signalnum)

將訊號 signalnum 傳送給與呼叫者在同一行程中的另一個執行緒 thread_id。目標執行緒能執行任何程式碼（無論為 Python 與否）。但是，如果目標執行緒正執行 Python 直譯器，Python 訊號處理程式將會由主直譯器的主執行緒來執行。因此，向特定 Python 執行緒發送訊號的唯一意義是強制執行中的系統呼叫以 InterruptedError 方式失敗。

使用 threading.get_ident() 或 threading.Thread 物件的 ident 屬性來取得 thread_id 的適當值。

如果 signalnum 為 0，則不會傳送訊號，但仍會執行錯誤檢查；這可用來檢查目標執行緒是否仍在執行。

引發一個附帶引數 thread_id、signalnum 的稽核事件 signal.pthread_kill。

可用性: Unix.

更多資訊請見 pthread_kill(3) [https://manpages.debian.org/pthread_kill(3)] 線上手冊。

另請參閱 os.kill()。

在 3.3 版被加入.

signal.pthread_sigmask(how, mask)

擷取和/或變更呼叫執行緒的訊號遮罩。訊號遮罩是目前阻擋呼叫者傳送的訊號集合。將舊的訊號遮罩作為一組訊號集合回傳。

呼叫的行為取決於 how 的值，如下所示。

SIG_BLOCK：被阻檔的訊號集合是目前訊號集合與 mask 引數的聯集。

SIG_UNBLOCK：將 mask 中的訊號從目前阻檔的訊號集合中移除。嘗試為未被阻檔的訊號解除阻檔是允許的。

SIG_SETMASK：將被阻檔的訊號集合設定為 mask 引數。

mask 是一組訊號編號（例如 {signal.SIGINT, signal.SIGTERM}）的集合。使用 valid_signals() 來取得包含所有訊號的完整遮罩。

例如，signal.pthread_sigmask(signal.SIG_BLOCK, []) 會讀取呼叫執行緒的訊號遮罩。

SIGKILL 和 SIGSTOP 不能被阻檔。

可用性: Unix.

更多資訊請見 sigprocmask(2) [https://manpages.debian.org/sigprocmask(2)] 與 pthread_sigmask(3) [https://manpages.debian.org/pthread_sigmask(3)] 線上手冊。

另請參閱 pause()、sigpending() 與 sigwait()。

在 3.3 版被加入.

signal.setitimer(which, seconds, interval=0.0)

設定由 which 指定的間隔計時器（signal.ITIMER_REAL、signal.ITIMER_VIRTUAL 或 signal.ITIMER_PROF 之一）並在*seconds*（接受浮點數，與 alarm() 不同）之後啟動，在之後的每 interval 秒啟動一次（如果 interval 非零）。which 指定的間隔計時器可透過將 seconds 設定為零來清除它。

當間隔計時器啟動時，一個訊號會被傳送給行程。傳送的訊號取決於使用的計時器；signal.ITIMER_REAL 會傳送 SIGALRM，signal.ITIMER_VIRTUAL 會傳送 SIGVTALRM，而 signal.ITIMER_PROF 會傳送 SIGPROF。

舊值會以一個元組回傳：(delay, interval)。

嘗試傳入無效的間隔計時器會導致 ItimerError。

可用性: Unix.

signal.getitimer(which)

回傳由 which 指定之間隔計時器的目前值。

可用性: Unix.

signal.set_wakeup_fd(fd, *, warn_on_full_buffer=True)

設定喚醒檔案描述器為 fd。當接收到其處理程式已有被註冊的訊號時，訊號編號會以單一位元組寫入 fd。如果你沒有為你在意的訊號註冊處理程式，就不會寫入到喚醒 fd。這可被函式庫用來喚醒輪詢 (wakeup a poll) 或 select 呼叫，讓訊號得以完全處理。

回傳舊的喚醒 fd（如果檔案描述器喚醒未啟用，則回傳 -1）。如果 fd 為 -1，則會停用檔案描述器喚醒。如果不是 -1，fd 必須是非阻塞的。在再次呼叫輪詢或 select 之前，由函式庫來決定是否移除 fd 中的任何位元組。

當啟用執行緒時，這個函式只能從主直譯器的主執行緒來呼叫；嘗試從其他執行緒呼叫它將會引發 ValueError 例外。

使用這個函式有兩種常見的方式。在這兩種方法中，當訊號抵達時，你都要使用 fd 來喚醒，但它們的不同之處在於如何判斷哪個或哪些訊號有抵達。

在第一種方法中，我們從 fd 的緩衝區中讀取資料，而位元組值則提供訊號編號。這個方法很簡單，但在少數情況下可能會遇到問題：一般來說，fd 的緩衝區空間有限，如果太多訊號來得太快，那麼緩衝區可能會滿，而有些訊號可能會遺失。如果你使用這種方法，那麼你應該設定 warn_on_full_buffer=True，這至少會在訊號丟失時將警告印出到 stderr。

在第二種方法中，我們只會將喚醒 fd 用於喚醒，而忽略實際的位元組值。在這種情況下，我們只在乎 fd 的緩衝區是空或非空；即便緩衝區滿了也不代表有問題。如果你使用這種方法，那麼你應該設定 warn_on_full_buffer=False，這樣你的使用者就不會被虛假的警告訊息所混淆。

在 3.5 版的變更: 在 Windows 上，此功能現在也支援 socket 處理程式。

在 3.7 版的變更: 新增 warn_on_full_buffer 參數。

signal.siginterrupt(signalnum, flag)

改變系統呼叫重新啟動的行為：如果 flag 是 False，系統呼叫會在被訊號 signalnum 中斷時重新啟動，否則系統呼叫會被中斷。不會回傳任何東西。

可用性: Unix.

更多資訊請見 siginterrupt(3) [https://manpages.debian.org/siginterrupt(3)] 線上手冊。

請注意，使用 signal() 安裝訊號處理程式，會透過隱式呼叫 siginterrupt() 來將重新啟動的行為重設為可中斷，且指定訊號的 flag 值為 true。

signal.signal(signalnum, handler)

將訊號 signalnum 的處理程式設定為函式 handler。handler 可以是帶兩個引數的可呼叫 Python 物件（見下面），或是特殊值 signal.SIG_IGN 或 signal.SIG_DFL 之一。先前的訊號處理程式將會被回傳（請參閱上面 getsignal() 的說明）。（更多資訊請參閱 Unix 線上手冊 signal(2) [https://manpages.debian.org/signal(2)]）。

當啟用執行緒時，這個函式只能從主直譯器的主執行緒來呼叫；嘗試從其他執行緒呼叫它將會引發 ValueError 例外。

handler 被呼叫時有兩個引數：訊號編號和目前的堆疊 frame（None 或一個 frame 物件；關於 frame 物件的描述，請參閱型別階層中的描述或 inspect 模組中的屬性描述）。

在 Windows 上，signal() 只能在使用 SIGABRT、SIGFPE、SIGILL、SIGINT、SIGSEGV、SIGTERM 或 SIGBREAK 時呼叫。在其他情況下會引發 ValueError。請注意，並非所有系統都定義相同的訊號名稱；如果訊號名稱沒有被定義為 SIG* 模組層級常數，則會引發 AttributeError 錯誤。

signal.sigpending()

檢查待傳送至呼叫執行緒的訊號集合（即阻檔時已被提出的訊號）。回傳待定訊號的集合。

可用性: Unix.

更多資訊請見 sigpending(2) [https://manpages.debian.org/sigpending(2)] 線上手冊。

另請參閱 pause()、pthread_sigmask() 與 sigwait()。

在 3.3 版被加入.

signal.sigwait(sigset)

暫停呼叫執行緒的執行，直到送出訊號集合 sigset 中指定的一個訊號。函式接受訊號（將其從待定訊號清單中移除），並回傳訊號編號。

可用性: Unix.

更多資訊請見 sigwait(3) [https://manpages.debian.org/sigwait(3)] 線上手冊。

另也請見 pause()、pthread_sigmask()、sigpending()、sigwaitinfo() 和 sigtimedwait()。

在 3.3 版被加入.

signal.sigwaitinfo(sigset)

暫停呼叫執行緒的執行，直到送出訊號集合 sigset 中指定的一個訊號。該函式接受訊號，並將其從待定訊號清單中移除。如果 sigset 中的一個訊號已經是呼叫執行緒的待定訊號，函式會立即回傳該訊號的相關資訊。對於已傳送的訊號，訊號處理程式不會被呼叫。如果被不在 sigset 中的訊號中斷，函式會引發 InterruptedError。

回傳值是一個物件，代表 siginfo_t 結構所包含的資料，即 si_signo、si_code、si_errno、si_pid、si_uid、si_status、si_band。

可用性: Unix.

更多資訊請見 sigwaitinfo(2) [https://manpages.debian.org/sigwaitinfo(2)] 線上手冊。

另請參閱 pause()、sigwait() 與 sigtimedwait()。

在 3.3 版被加入.

在 3.5 版的變更: 現在如果被不在 sigset 中的訊號中斷，且訊號處理程式沒有引發例外，則會重試函式（理由請參閱 PEP 475 [https://peps.python.org/pep-0475/]）。

signal.sigtimedwait(sigset, timeout)

類似 sigwaitinfo()，但需要額外的 timeout 引數指定逾時時間。如果 timeout 指定為 0，會執行輪詢。如果發生逾時則會回傳 None。

可用性: Unix.

更多資訊請見 sigtimedwait(2) [https://manpages.debian.org/sigtimedwait(2)] 線上手冊。

另請參閱 pause()、sigwait() 與 sigwaitinfo()。

在 3.3 版被加入.

在 3.5 版的變更: 現在如果被不在 sigset 中的訊號中斷，且訊號處理程式沒有引發例外，則會使用重新計算的 timeout 重試函式（理由請參閱 PEP 475 [https://peps.python.org/pep-0475/]）。

範例

這是一個最小範例程式。它使用 alarm() 函式來限制等待開啟檔案的時間；如果檔案是用於可能未開啟的序列裝置，這會很有用，因為這通常會導致 os.open() 無限期地被擱置。解決方法是在開啟檔案前設定一個 5 秒的警報；如果操作時間過長，警報訊號就會被送出，而處理程式會產生例外。

import signal, os

def handler(signum, frame):
    signame = signal.Signals(signum).name
    print(f'Signal handler called with signal {signame} ({signum})')
    raise OSError("Couldn't open device!")

# 設定訊號處理程式與五秒警報
signal.signal(signal.SIGALRM, handler)
signal.alarm(5)

# 這個 open() 可能無限期地被擱置
fd = os.open('/dev/ttyS0', os.O_RDWR)

signal.alarm(0)          # 停用警報

關於 SIGPIPE 的說明

將程式的輸出管道化到 head(1) [https://manpages.debian.org/head(1)] 之類的工具，會在你的行程的標準輸出接收器提早關閉時，導致 SIGPIPE 訊號傳送給你的行程。這會導致類似 BrokenPipeError: [Errno 32] Broken pipe 的例外。要處理這種情況，請將你的進入點包裝成如下的樣子來捕捉這個例外：

import os
import sys

def main():
    try:
        # 模擬大量輸出（你的程式取代此迴圈）
        for x in range(10000):
            print("y")
        # 在這裡清除輸出以強制 SIGPIPE 在這個 try 區塊
        # 中被觸發
        sys.stdout.flush()
    except BrokenPipeError:
        # Python 在退出時清除標準串流；為剩下的輸出重新導向
        # 至 devnull 來避免關閉時的 BrokenPipeError
        devnull = os.open(os.devnull, os.O_WRONLY)
        os.dup2(devnull, sys.stdout.fileno())
        sys.exit(1)  # Python 在 EPIPE 時以錯誤碼 1 退出

if __name__ == '__main__':
    main()

不要為了避免 BrokenPipeError 而將 SIGPIPE 之處置 (disposition) 設定為 SIG_DFL。這樣做會導致你的程式在寫入任何 socket 連線時被中斷而意外退出。

訊號處理程式與例外的說明

如果訊號處理程式產生例外，例外會傳送到主執行緒並可能在任何 bytecode 指令之後發生。最值得注意的是，KeyboardInterrupt 可能在執行過程中的任何時候出現。大多數 Python 程式碼，包括標準函式庫，都無法避免這種情況，因此 KeyboardInterrupt（或任何其他由訊號處理程式產生的例外）可能會在罕見的情況下使程式處於預期之外的狀態。

為了說明這個問題，請參考以下程式碼：

class SpamContext:
    def __init__(self):
        self.lock = threading.Lock()

    def __enter__(self):
        # 如果 KeyboardInterrupt 在此發生則一切正常
        self.lock.acquire()
        # 如果 KeyboardInterrupt 在此發生，__exit__ 將不會被呼叫
        ...
        # KeyboardInterrupt 可能在函式回傳之前發生

    def __exit__(self, exc_type, exc_val, exc_tb):
        ...
        self.lock.release()

對許多程式來說，尤其是那些只想在 KeyboardInterrupt 時退出的程式，這並不是問題，但是對於複雜或需要高可靠性的應用程式來說，應該避免從訊號處理程式產生例外。它們也應該避免將捕獲 KeyboardInterrupt 作為一種優雅關閉 (gracefully shutting down) 的方式。相反地，它們應該安裝自己的 SIGINT 處理程式。以下是 HTTP 伺服器避免 KeyboardInterrupt 的範例：

import signal
import socket
from selectors import DefaultSelector, EVENT_READ
from http.server import HTTPServer, SimpleHTTPRequestHandler

interrupt_read, interrupt_write = socket.socketpair()

def handler(signum, frame):
    print('Signal handler called with signal', signum)
    interrupt_write.send(b'\0')
signal.signal(signal.SIGINT, handler)

def serve_forever(httpd):
    sel = DefaultSelector()
    sel.register(interrupt_read, EVENT_READ)
    sel.register(httpd, EVENT_READ)

    while True:
        for key, _ in sel.select():
            if key.fileobj == interrupt_read:
                interrupt_read.recv(1)
                return
            if key.fileobj == httpd:
                httpd.handle_request()

print("Serving on port 8000")
httpd = HTTPServer(('', 8000), SimpleHTTPRequestHandler)
serve_forever(httpd)
print("Shutdown...")

mmap --- 記憶體對映檔案的支援

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

記憶體對映檔案物件 (memory-mapped file objects) 的行為類似於 bytearray 和檔案物件。你可以在大多數預期使用 bytearray 的地方使用 mmap 物件；例如，你可以使用 re 模組來搜尋記憶體對映檔案的內容。你也可以透過 obj[index] = 97 來變更單一位元組，或透過賦值給切片來變更子序列：obj[i1:i2] = b'...'。你也可以從目前的檔案位置開始讀寫資料，並使用 seek() 在檔案中移動到不同的位置。

記憶體對映檔案是由 mmap 建構函式所建立，在 Unix 和 Windows 上的用法不同。無論哪種情況，你都必須提供一個以變更模式開啟之檔案的檔案描述器。如果你想要對映現有的 Python 檔案物件，請使用其 fileno() 方法來取得 fileno 參數的正確值。或者你也可以使用 os.open() 函式來開啟檔案，它會直接回傳檔案描述器（檔案在使用完畢後仍需要關閉）。

備註

如果你想要為可寫入的緩衝檔案建立記憶體對映，應該先 flush() 該檔案。這是為了確保對緩衝區的區域修改確實可供對映使用。

對於 Unix 和 Windows 版本的建構函式，access 都可以指定為可選的關鍵字參數。access 接受四個值之一：ACCESS_READ、ACCESS_WRITE 或 ACCESS_COPY 分別用於指定唯讀、直寫 (write-through) 或寫入時複製 (copy-on-write) 記憶體，或 ACCESS_DEFAULT 以遵從 prot。access 在 Unix 和 Windows 上都可以使用。如果未指定 access，Windows 的 mmap 會回傳直寫對映。三種存取類型的初始記憶體值都是取自指定的檔案。對 ACCESS_READ 記憶體對映進行賦值會引發 TypeError 例外。對 ACCESS_WRITE 記憶體對映進行賦值會同時影響記憶體和底層檔案。對 ACCESS_COPY 記憶體對映進行賦值會影響記憶體，但不會改變底層檔案。

在 3.7 版的變更: 新增 ACCESS_DEFAULT 常數。

要對映匿名記憶體，應將 -1 與長度一起作為 fileno 傳入。

class mmap.mmap(fileno, length, tagname=None, access=ACCESS_DEFAULT, offset=0)

（Windows 版本） 從檔案控制代碼 (file handle) fileno 指定的檔案來對映 length 個位元組，並建立一個 mmap 物件。如果 length 大於檔案目前的大小，檔案會被擴充為能夠包含 length 個位元組。如果 length 為 0，對映的最大長度就是檔案目前的大小，但如果檔案為空，Windows 會引發例外（因無法在 Windows 上建立空白的對映）。

若有指定 tagname 且不為 None，則其為給定對映的標籤名稱字串。Windows 允許你對同一個檔案設定許多不同的對映。如果你指定了一個現有標籤名稱，該標籤就會被開啟，否則會建立一個具有此名稱的新標籤。如果省略此參數或為 None，對映會在沒有名稱的情況下建立。避免使用 tagname 參數將有助於保持你的程式碼在 Unix 和 Windows 之間的可移植性。

offset 可以指定為非負整數偏移量。mmap 的參照會是相對於從檔案開頭算起之偏移量。offset 預設為 0。offset 必須是 ALLOCATIONGRANULARITY 的倍數。

引發一個附帶引數 fileno、length、access、offset 的稽核事件 mmap.__new__。

class mmap.mmap(fileno, length, flags=MAP_SHARED, prot=PROT_WRITE | PROT_READ, access=ACCESS_DEFAULT, offset=0, *, trackfd=True)

（Unix 版本） 從檔案描述器 fileno 指定的檔案對映 length 個位元組，並回傳一個 mmap 物件。如果 length 為 0，對映的最大長度將是呼叫 mmap 時檔案的目前大小。

flags 指定對映的性質。MAP_PRIVATE 會建立私有的寫入時複製對映，因此對 mmap 物件內容的變更將僅限於此行程，而 MAP_SHARED 會建立與所有其他對映相同檔案區域之行程共享的對映。預設值為 MAP_SHARED。某些系統有額外的可用旗標，完整列表請參閱 MAP_* 常數。

prot 若有指定，則會給予所需的記憶體保護；最常用的兩個值是 PROT_READ 和 PROT_WRITE，用於指定分頁可以被讀取或寫入。prot 預設為 PROT_READ | PROT_WRITE。

access 可以作為可選的關鍵字參數來指定，以代替 flags 和 prot。同時指定 flags、prot 和 access 會產生錯誤。關於如何使用此參數的資訊，請參閱上面 access 的說明。

offset 可以指定為非負整數偏移量。mmap 的參照將相對於從檔案開頭算起的偏移量。offset 預設為 0。offset 必須是 ALLOCATIONGRANULARITY 的倍數，且在 Unix 系統上等於 PAGESIZE。

如果 trackfd 為 False，由 fileno 指定的檔案描述器將不會被複製，且產生的 mmap 物件將不會與對映的底層檔案關聯。這意味著 size() 和 resize() 方法會失敗。此模式對於限制開啟的檔案描述器數量很有用。

為了確保建立的記憶體對映有效，在 macOS 上由描述器 fileno 指定的檔案會在內部自動與實體備份儲存同步。

在 3.13 版的變更: 新增 trackfd 參數。

這個範例示範了使用 mmap 的簡單方式：

import mmap

# 寫入一個簡單的範例檔案
with open("hello.txt", "wb") as f:
    f.write(b"Hello Python!\n")

with open("hello.txt", "r+b") as f:
    # 對映檔案到記憶體，size 0 表示整個檔案
    mm = mmap.mmap(f.fileno(), 0)
    # 透過標準檔案方法讀取內容
    print(mm.readline())  # 印出 b"Hello Python!\n"
    # 透過切片標記法讀取內容
    print(mm[:5])  # 印出 b"Hello"
    # 使用切片標記法更新內容；
    # 注意新內容必須有相同的大小
    mm[6:] = b" world!\n"
    # ... 然後再次使用標準檔案方法讀取
    mm.seek(0)
    print(mm.readline())  # 印出 b"Hello  world!\n"
    # 關閉對映
    mm.close()

mmap 也可以在 with 陳述式中作為情境管理器使用：

import mmap

with mmap.mmap(-1, 13) as mm:
    mm.write(b"Hello world!")

在 3.2 版被加入: 情境管理器的支援。

下一個範例展示了如何建立匿名對映並在父行程與子行程之間交換資料：

import mmap
import os

mm = mmap.mmap(-1, 13)
mm.write(b"Hello world!")

pid = os.fork()

if pid == 0:  # 在子行程中
    mm.seek(0)
    print(mm.readline())

    mm.close()

引發一個附帶引數 fileno、length、access、offset 的稽核事件 mmap.__new__。

記憶體對映檔案物件支援以下方法：

close()

關閉 mmap。後續對物件其他方法的呼叫將導致 ValueError 例外被引發。這不會關閉已開啟的檔案。

closed

若檔案已關閉則回傳 True。

在 3.2 版被加入.

find(sub[, start[, end]])

回傳物件中找到子序列 sub 的最小索引，使得 sub 包含在範圍 [start, end] 中。可選引數 start 和 end 的直譯方式與切片標記法相同。失敗時回傳 -1。

在 3.5 版的變更: 現在接受可寫入的類位元組物件。

flush()

flush(offset, size, /)

將對檔案之記憶體內副本 (in-memory copy) 所做的變更給排清 (flush) 回磁碟。若不使用此呼叫，則無法保證在物件被銷毀之前變更會被寫回。如果指定了 offset 和 size，則只有給定位元組範圍的變更會被排清到磁碟；否則會排清整個對映範圍。offset 必須是 PAGESIZE 或 ALLOCATIONGRANULARITY 的倍數。

回傳 None 表示成功。呼叫失敗時會引發例外。

在 3.8 版的變更: 以前在 Windows 上成功時會回傳非零值，錯誤時回傳零。在 Unix 上成功時回傳零值，錯誤時引發例外。

madvise(option[, start[, length]])

向核心 (kernel) 發送關於從 start 開始並延伸 length 個位元組之記憶體區域的建議 option。option 必須是系統上可用的 MADV_* 常數 之一。如果省略 start 和 length，則會涵蓋整個對映。在某些系統（包括 Linux）上，start 必須是 PAGESIZE 的倍數。

可用性：具有 madvise() 系統呼叫的系統。

在 3.8 版被加入.

move(dest, src, count)

將從偏移量 src 開始的 count 個位元組複製到目的地索引 dest。如果 mmap 是以 ACCESS_READ 建立的，則對 move 的呼叫會引發 TypeError 例外。

read([n])

回傳一個從目前檔案位置開始、包含最多 n 個位元組的 bytes。如果引數被省略、為 None 或為負數，則回傳從目前檔案位置到對映結尾的所有位元組。檔案位置會被更新為指向回傳的位元組之後。

在 3.3 版的變更: 引數可以省略或為 None。

read_byte()

以整數形式回傳目前檔案位置的位元組，並將檔案位置前進 1。

readline()

回傳從目前檔案位置開始到下一個換行符號的單一行。檔案位置會被更新為指向回傳的位元組之後。

resize(newsize)

調整對映和底層檔案（如果有的話）的大小。

調整以 access 為 ACCESS_READ 或 ACCESS_COPY 建立的對映大小會引發 TypeError 例外。調整以 trackfd 設定為 False 建立的對映大小會引發 ValueError 例外。

在 Windows 上：如果有其他對映指向同一個具名檔案，調整對映大小會引發 OSError。調整匿名對映（即指向分頁檔案）的大小會靜默地建立一個新對映，並將原始資料複製到新大小的長度。

在 3.11 版的變更: 當持有另一個對映時嘗試調整大小會正確失敗；在 Windows 上允許對匿名對映調整大小

rfind(sub[, start[, end]])

回傳物件中找到子序列 sub 的最大索引，使得 sub 包含在範圍 [start, end] 中。可選引數 start 和 end 的直譯方式與切片標記法相同。失敗時回傳 -1。

在 3.5 版的變更: 現在接受可寫入的類位元組物件。

seek(pos[, whence])

設定檔案的目前位置。whence 引數是可選的，預設為 os.SEEK_SET 或 0（絕對檔案定位）；其他值為 os.SEEK_CUR 或 1（相對於目前位置的定位）和 os.SEEK_END 或 2（相對於檔案結尾的定位）。

在 3.13 版的變更: 回傳新的絕對位置而非 None。

seekable()

回傳檔案是否支援定位 (seeking)，回傳值永遠為 True。

在 3.13 版被加入.

size()

回傳檔案的長度，該長度可以大於記憶體對映區域的大小。

tell()

回傳檔案指標的目前位置。

write(bytes)

將 bytes 中的位元組寫入檔案指標目前位置的記憶體，並回傳寫入的位元組數（絕不會少於 len(bytes)，因為如果寫入失敗，會引發 ValueError）。檔案位置會被更新為指向寫入的位元組之後。如果 mmap 是以 ACCESS_READ 建立的，則對其寫入會引發 TypeError 例外。

在 3.5 版的變更: 現在接受可寫入的類位元組物件。

在 3.6 版的變更: 現在會回傳寫入的位元組數。

write_byte(byte)

將整數 byte 寫入檔案指標目前位置的記憶體；檔案位置會前進 1。如果 mmap 是以 ACCESS_READ 建立的，則對其寫入會引發 TypeError 例外。

MADV_* 常數

mmap.MADV_NORMAL

mmap.MADV_RANDOM

mmap.MADV_SEQUENTIAL

mmap.MADV_WILLNEED

mmap.MADV_DONTNEED

mmap.MADV_REMOVE

mmap.MADV_DONTFORK

mmap.MADV_DOFORK

mmap.MADV_HWPOISON

mmap.MADV_MERGEABLE

mmap.MADV_UNMERGEABLE

mmap.MADV_SOFT_OFFLINE

mmap.MADV_HUGEPAGE

mmap.MADV_NOHUGEPAGE

mmap.MADV_DONTDUMP

mmap.MADV_DODUMP

mmap.MADV_FREE

mmap.MADV_NOSYNC

mmap.MADV_AUTOSYNC

mmap.MADV_NOCORE

mmap.MADV_CORE

mmap.MADV_PROTECT

mmap.MADV_FREE_REUSABLE

mmap.MADV_FREE_REUSE

這些選項可以傳遞給 mmap.madvise()。並非每個選項都會出現在每個系統上。

可用性：具有 madvise() 系統呼叫的系統。

在 3.8 版被加入.

MAP_* 常數

mmap.MAP_SHARED

mmap.MAP_PRIVATE

mmap.MAP_32BIT

mmap.MAP_ALIGNED_SUPER

mmap.MAP_ANON

mmap.MAP_ANONYMOUS

mmap.MAP_CONCEAL

mmap.MAP_DENYWRITE

mmap.MAP_EXECUTABLE

mmap.MAP_HASSEMAPHORE

mmap.MAP_JIT

mmap.MAP_NOCACHE

mmap.MAP_NOEXTEND

mmap.MAP_NORESERVE

mmap.MAP_POPULATE

mmap.MAP_RESILIENT_CODESIGN

mmap.MAP_RESILIENT_MEDIA

mmap.MAP_STACK

mmap.MAP_TPRO

mmap.MAP_TRANSLATED_ALLOW_EXECUTE

mmap.MAP_UNIX03

這些是可以傳遞給 mmap.mmap() 的各種旗標。MAP_ALIGNED_SUPER 僅在 FreeBSD 上可用，而 MAP_CONCEAL 僅在 OpenBSD 上可用。請注意，某些選項可能不會出現在某些系統上。

在 3.10 版的變更: 新增 MAP_POPULATE 常數。

在 3.11 版被加入: 新增 MAP_STACK 常數。

在 3.12 版被加入: 新增 MAP_ALIGNED_SUPER 和 MAP_CONCEAL 常數。

在 3.13 版被加入: 新增 MAP_32BIT、MAP_HASSEMAPHORE、MAP_JIT、MAP_NOCACHE、MAP_NOEXTEND、MAP_NORESERVE、MAP_RESILIENT_CODESIGN、MAP_RESILIENT_MEDIA、MAP_TPRO、MAP_TRANSLATED_ALLOW_EXECUTE 和 MAP_UNIX03 常數。

網際網路資料處理

本章描述了支援網際網路上處理常用資料格式的模組。

email --- 郵件和 MIME 處理套件

email.message：表示電子郵件訊息

email.parser：剖析電子郵件訊息

FeedParser API

Parser API

Additional notes

email.generator：產生 MIME 文件

email.policy: Policy Objects

email.errors：例外和缺陷類別

email.headerregistry：自訂標頭物件

email.contentmanager：管理 MIME 內容

Content Manager Instances

email：範例

email.message.Message: Representing an email message using the compat32 API

email.mime：從頭開始建立電子郵件和 MIME 物件

email.header：國際化標頭

email.charset：字元集合的表示

email.encoders：編碼器

email.utils：雜項工具

email.iterators：疊代器

json --- JSON 編碼器與解碼器

基本用法

編碼器與解碼器

例外

合規性與互通性（Interoperability）

字元編碼格式

正負無限與非數值

物件內重複的名稱

位於頂層的非物件及非列表值

實作限制

命令列介面

命令列選項

mailbox --- 以各種格式操作郵件信箱

Mailbox 物件

Mailbox 物件

mbox 物件

MH 物件

Babyl 物件

MMDF 物件

Message 物件

MaildirMessage 物件

mboxMessage 物件

MHMessage 物件

BabylMessage 物件

MMDFMessage 物件

例外

範例

mimetypes --- 將檔案名稱對映到 MIME 類型

MimeTypes 物件

命令列用法

Command-line example

base64 --- Base16、Base32、Base64、Base85 資料編碼

RFC 4648 編碼

Base85 編碼

舊版介面

安全性注意事項

binascii --- 在二進位制和 ASCII 之間轉換

quopri --- 編碼和解碼 MIME 可列印字元資料

email --- 郵件和 MIME 處理套件

原始碼：Lib/email/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/email/__init__.py]

The email package is a library for managing email messages. It is specifically not designed to do any sending of email messages to SMTP (RFC 2821 [https://datatracker.ietf.org/doc/html/rfc2821.html]), NNTP, or other servers; those are functions of modules such as smtplib. The email package attempts to be as RFC-compliant as possible, supporting RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] and RFC 6532 [https://datatracker.ietf.org/doc/html/rfc6532.html], as well as such MIME-related RFCs as RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html], RFC 2046 [https://datatracker.ietf.org/doc/html/rfc2046.html], RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html], RFC 2183 [https://datatracker.ietf.org/doc/html/rfc2183.html], and RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html].

The overall structure of the email package can be divided into three major components, plus a fourth component that controls the behavior of the other components.

The central component of the package is an "object model" that represents email messages. An application interacts with the package primarily through the object model interface defined in the message sub-module. The application can use this API to ask questions about an existing email, to construct a new email, or to add or remove email subcomponents that themselves use the same object model interface. That is, following the nature of email messages and their MIME subcomponents, the email object model is a tree structure of objects that all provide the EmailMessage API.

The other two major components of the package are the parser and the generator. The parser takes the serialized version of an email message (a stream of bytes) and converts it into a tree of EmailMessage objects. The generator takes an EmailMessage and turns it back into a serialized byte stream. (The parser and generator also handle streams of text characters, but this usage is discouraged as it is too easy to end up with messages that are not valid in one way or another.)

The control component is the policy module. Every EmailMessage, every generator, and every parser has an associated policy object that controls its behavior. Usually an application only needs to specify the policy when an EmailMessage is created, either by directly instantiating an EmailMessage to create a new email, or by parsing an input stream using a parser. But the policy can be changed when the message is serialized using a generator. This allows, for example, a generic email message to be parsed from disk, but to serialize it using standard SMTP settings when sending it to an email server.

The email package does its best to hide the details of the various governing RFCs from the application. Conceptually the application should be able to treat the email message as a structured tree of unicode text and binary attachments, without having to worry about how these are represented when serialized. In practice, however, it is often necessary to be aware of at least some of the rules governing MIME messages and their structure, specifically the names and nature of the MIME "content types" and how they identify multipart documents. For the most part this knowledge should only be required for more complex applications, and even then it should only be the high level structure in question, and not the details of how those structures are represented. Since MIME content types are used widely in modern internet software (not just email), this will be a familiar concept to many programmers.

The following sections describe the functionality of the email package. We start with the message object model, which is the primary interface an application will use, and follow that with the parser and generator components. Then we cover the policy controls, which completes the treatment of the main components of the library.

The next three sections cover the exceptions the package may raise and the defects (non-compliance with the RFCs) that the parser may detect. Then we cover the headerregistry and the contentmanager sub-components, which provide tools for doing more detailed manipulation of headers and payloads, respectively. Both of these components contain features relevant to consuming and producing non-trivial messages, but also document their extensibility APIs, which will be of interest to advanced applications.

Following those is a set of examples of using the fundamental parts of the APIs covered in the preceding sections.

The foregoing represent the modern (unicode friendly) API of the email package. The remaining sections, starting with the Message class, cover the legacy compat32 API that deals much more directly with the details of how email messages are represented. The compat32 API does not hide the details of the RFCs from the application, but for applications that need to operate at that level, they can be useful tools. This documentation is also relevant for applications that are still using the compat32 API for backward compatibility reasons.

在 3.6 版的變更: Docs reorganized and rewritten to promote the new EmailMessage/EmailPolicy API.

Contents of the email package documentation:

email.message：表示電子郵件訊息

email.parser：剖析電子郵件訊息

FeedParser API

Parser API

Additional notes

email.generator：產生 MIME 文件

email.policy: Policy Objects

email.errors：例外和缺陷類別

email.headerregistry：自訂標頭物件

email.contentmanager：管理 MIME 內容

Content Manager Instances

email：範例

Legacy API:

email.message.Message: Representing an email message using the compat32 API

email.mime：從頭開始建立電子郵件和 MIME 物件

email.header：國際化標頭

email.charset：字元集合的表示

email.encoders：編碼器

email.utils：雜項工具

email.iterators：疊代器

也參考

smtplib 模組

SMTP (Simple Mail Transport Protocol) client

poplib 模組

POP (Post Office Protocol) client

imaplib 模組

IMAP (Internet Message Access Protocol) client

mailbox 模組

Tools for creating, reading, and managing collections of messages on disk using a variety standard formats.

email.message：表示電子郵件訊息

原始碼：Lib/email/message.py [https://github.com/python/cpython/tree/3.14/Lib/email/message.py]

在 3.6 版被加入: [1]

The central class in the email package is the EmailMessage class, imported from the email.message module. It is the base class for the email object model. EmailMessage provides the core functionality for setting and querying header fields, for accessing message bodies, and for creating or modifying structured messages.

An email message consists of headers and a payload (which is also referred to as the content). Headers are RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] or RFC 6532 [https://datatracker.ietf.org/doc/html/rfc6532.html] style field names and values, where the field name and value are separated by a colon. The colon is not part of either the field name or the field value. The payload may be a simple text message, or a binary object, or a structured sequence of sub-messages each with their own set of headers and their own payload. The latter type of payload is indicated by the message having a MIME type such as multipart/* or message/rfc822.

The conceptual model provided by an EmailMessage object is that of an ordered dictionary of headers coupled with a payload that represents the RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] body of the message, which might be a list of sub-EmailMessage objects. In addition to the normal dictionary methods for accessing the header names and values, there are methods for accessing specialized information from the headers (for example the MIME content type), for operating on the payload, for generating a serialized version of the message, and for recursively walking over the object tree.

The EmailMessage dictionary-like interface is indexed by the header names, which must be ASCII values. The values of the dictionary are strings with some extra methods. Headers are stored and returned in case-preserving form, but field names are matched case-insensitively. The keys are ordered, but unlike a real dict, there can be duplicates. Additional methods are provided for working with headers that have duplicate keys.

The payload is either a string or bytes object, in the case of simple message objects, or a list of EmailMessage objects, for MIME container documents such as multipart/* and message/rfc822 message objects.

class email.message.EmailMessage(policy=default)

If policy is specified use the rules it specifies to update and serialize the representation of the message. If policy is not set, use the default policy, which follows the rules of the email RFCs except for line endings (instead of the RFC mandated \r\n, it uses the Python standard \n line endings). For more information see the policy documentation. [2]

as_string(unixfrom=False, maxheaderlen=None, policy=None)

Return the entire message flattened as a string. When optional unixfrom is true, the envelope header is included in the returned string. unixfrom defaults to False. For backward compatibility with the base Message class maxheaderlen is accepted, but defaults to None, which means that by default the line length is controlled by the max_line_length of the policy. The policy argument may be used to override the default policy obtained from the message instance. This can be used to control some of the formatting produced by the method, since the specified policy will be passed to the Generator.

Flattening the message may trigger changes to the EmailMessage if defaults need to be filled in to complete the transformation to a string (for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not be the most useful way to serialize messages in your application, especially if you are dealing with multiple messages. See email.generator.Generator for a more flexible API for serializing messages. Note also that this method is restricted to producing messages serialized as "7 bit clean" when utf8 is False, which is the default.

在 3.6 版的變更: the default behavior when maxheaderlen is not specified was changed from defaulting to 0 to defaulting to the value of max_line_length from the policy.

__str__()

Equivalent to as_string(policy=self.policy.clone(utf8=True)). Allows str(msg) to produce a string containing the serialized message in a readable format.

在 3.4 版的變更: the method was changed to use utf8=True, thus producing an RFC 6531 [https://datatracker.ietf.org/doc/html/rfc6531.html]-like message representation, instead of being a direct alias for as_string().

as_bytes(unixfrom=False, policy=None)

Return the entire message flattened as a bytes object. When optional unixfrom is true, the envelope header is included in the returned string. unixfrom defaults to False. The policy argument may be used to override the default policy obtained from the message instance. This can be used to control some of the formatting produced by the method, since the specified policy will be passed to the BytesGenerator.

Flattening the message may trigger changes to the EmailMessage if defaults need to be filled in to complete the transformation to a string (for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not be the most useful way to serialize messages in your application, especially if you are dealing with multiple messages. See email.generator.BytesGenerator for a more flexible API for serializing messages.

__bytes__()

Equivalent to as_bytes(). Allows bytes(msg) to produce a bytes object containing the serialized message.

is_multipart()

Return True if the message's payload is a list of sub-EmailMessage objects, otherwise return False. When is_multipart() returns False, the payload should be a string object (which might be a CTE encoded binary payload). Note that is_multipart() returning True does not necessarily mean that "msg.get_content_maintype() == 'multipart'" will return the True. For example, is_multipart will return True when the EmailMessage is of type message/rfc822.

set_unixfrom(unixfrom)

Set the message's envelope header to unixfrom, which should be a string. (See mboxMessage for a brief description of this header.)

get_unixfrom()

Return the message's envelope header. Defaults to None if the envelope header was never set.

The following methods implement the mapping-like interface for accessing the message's headers. Note that there are some semantic differences between these methods and a normal mapping (i.e. dictionary) interface. For example, in a dictionary there are no duplicate keys, but here there may be duplicate message headers. Also, in dictionaries there is no guaranteed order to the keys returned by keys(), but in an EmailMessage object, headers are always returned in the order they appeared in the original message, or in which they were added to the message later. Any header deleted and then re-added is always appended to the end of the header list.

These semantic differences are intentional and are biased toward convenience in the most common use cases.

Note that in all cases, any envelope header present in the message is not included in the mapping interface.

__len__()

Return the total number of headers, including duplicates.

__contains__(name)

Return True if the message object has a field named name. Matching is done without regard to case and name does not include the trailing colon. Used for the in operator. For example:

if 'message-id' in myMessage:
   print('Message-ID:', myMessage['message-id'])

__getitem__(name)

Return the value of the named header field. name does not include the colon field separator. If the header is missing, None is returned; a KeyError is never raised.

Note that if the named field appears more than once in the message's headers, exactly which of those field values will be returned is undefined. Use the get_all() method to get the values of all the extant headers named name.

Using the standard (non-compat32) policies, the returned value is an instance of a subclass of email.headerregistry.BaseHeader.

__setitem__(name, val)

Add a header to the message with field name name and value val. The field is appended to the end of the message's existing headers.

Note that this does not overwrite or delete any existing header with the same name. If you want to ensure that the new header is the only one present in the message with field name name, delete the field first, e.g.:

del msg['subject']
msg['subject'] = 'Python roolz!'

If the policy defines certain headers to be unique (as the standard policies do), this method may raise a ValueError when an attempt is made to assign a value to such a header when one already exists. This behavior is intentional for consistency's sake, but do not depend on it as we may choose to make such assignments do an automatic deletion of the existing header in the future.

__delitem__(name)

Delete all occurrences of the field with name name from the message's headers. No exception is raised if the named field isn't present in the headers.

keys()

Return a list of all the message's header field names.

values()

Return a list of all the message's field values.

items()

Return a list of 2-tuples containing all the message's field headers and values.

get(name, failobj=None)

Return the value of the named header field. This is identical to __getitem__() except that optional failobj is returned if the named header is missing (failobj defaults to None).

Here are some additional useful header related methods:

get_all(name, failobj=None)

Return a list of all the values for the field named name. If there are no such named headers in the message, failobj is returned (defaults to None).

add_header(_name, _value, **_params)

Extended header setting. This method is similar to __setitem__() except that additional header parameters can be provided as keyword arguments. _name is the header field to add and _value is the primary value for the header.

For each item in the keyword argument dictionary _params, the key is taken as the parameter name, with underscores converted to dashes (since dashes are illegal in Python identifiers). Normally, the parameter will be added as key="value" unless the value is None, in which case only the key will be added.

If the value contains non-ASCII characters, the charset and language may be explicitly controlled by specifying the value as a three tuple in the format (CHARSET, LANGUAGE, VALUE), where CHARSET is a string naming the charset to be used to encode the value, LANGUAGE can usually be set to None or the empty string (see RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] for other possibilities), and VALUE is the string value containing non-ASCII code points. If a three tuple is not passed and the value contains non-ASCII characters, it is automatically encoded in RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] format using a CHARSET of utf-8 and a LANGUAGE of None.

以下是個範例：

msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')

This will add a header that looks like

Content-Disposition: attachment; filename="bud.gif"

An example of the extended interface with non-ASCII characters:

msg.add_header('Content-Disposition', 'attachment',
               filename=('iso-8859-1', '', 'Fußballer.ppt'))

replace_header(_name, _value)

Replace a header. Replace the first header found in the message that matches _name, retaining header order and field name case of the original header. If no matching header is found, raise a KeyError.

get_content_type()

Return the message's content type, coerced to lower case of the form maintype/subtype. If there is no Content-Type header in the message return the value returned by get_default_type(). If the Content-Type header is invalid, return text/plain.

(According to RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html], messages always have a default type, get_content_type() will always return a value. RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] defines a message's default type to be text/plain unless it appears inside a multipart/digest container, in which case it would be message/rfc822. If the Content-Type header has an invalid type specification, RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] mandates that the default type be text/plain.)

get_content_maintype()

Return the message's main content type. This is the maintype part of the string returned by get_content_type().

get_content_subtype()

Return the message's sub-content type. This is the subtype part of the string returned by get_content_type().

get_default_type()

Return the default content type. Most messages have a default content type of text/plain, except for messages that are subparts of multipart/digest containers. Such subparts have a default content type of message/rfc822.

set_default_type(ctype)

Set the default content type. ctype should either be text/plain or message/rfc822, although this is not enforced. The default content type is not stored in the Content-Type header, so it only affects the return value of the get_content_type methods when no Content-Type header is present in the message.

set_param(param, value, header='Content-Type', requote=True, charset=None, language='', replace=False)

Set a parameter in the Content-Type header. If the parameter already exists in the header, replace its value with value. When header is Content-Type (the default) and the header does not yet exist in the message, add it, set its value to text/plain, and append the new parameter value. Optional header specifies an alternative header to Content-Type.

If the value contains non-ASCII characters, the charset and language may be explicitly specified using the optional charset and language parameters. Optional language specifies the RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] language, defaulting to the empty string. Both charset and language should be strings. The default is to use the utf8 charset and None for the language.

If replace is False (the default) the header is moved to the end of the list of headers. If replace is True, the header will be updated in place.

Use of the requote parameter with EmailMessage objects is deprecated.

Note that existing parameter values of headers may be accessed through the params attribute of the header value (for example, msg['Content-Type'].params['charset']).

在 3.4 版的變更: 新增 replace 關鍵字。

del_param(param, header='content-type', requote=True)

Remove the given parameter completely from the Content-Type header. The header will be re-written in place without the parameter or its value. Optional header specifies an alternative to Content-Type.

Use of the requote parameter with EmailMessage objects is deprecated.

get_filename(failobj=None)

Return the value of the filename parameter of the Content-Disposition header of the message. If the header does not have a filename parameter, this method falls back to looking for the name parameter on the Content-Type header. If neither is found, or the header is missing, then failobj is returned. The returned string will always be unquoted as per email.utils.unquote().

get_boundary(failobj=None)

Return the value of the boundary parameter of the Content-Type header of the message, or failobj if either the header is missing, or has no boundary parameter. The returned string will always be unquoted as per email.utils.unquote().

set_boundary(boundary)

Set the boundary parameter of the Content-Type header to boundary. set_boundary() will always quote boundary if necessary. A HeaderParseError is raised if the message object has no Content-Type header.

Note that using this method is subtly different from deleting the old Content-Type header and adding a new one with the new boundary via add_header(), because set_boundary() preserves the order of the Content-Type header in the list of headers.

get_content_charset(failobj=None)

Return the charset parameter of the Content-Type header, coerced to lower case. If there is no Content-Type header, or if that header has no charset parameter, failobj is returned.

get_charsets(failobj=None)

Return a list containing the character set names in the message. If the message is a multipart, then the list will contain one element for each subpart in the payload, otherwise, it will be a list of length 1.

Each item in the list will be a string which is the value of the charset parameter in the Content-Type header for the represented subpart. If the subpart has no Content-Type header, no charset parameter, or is not of the text main MIME type, then that item in the returned list will be failobj.

is_attachment()

Return True if there is a Content-Disposition header and its (case insensitive) value is attachment, False otherwise.

在 3.4.2 版的變更: is_attachment is now a method instead of a property, for consistency with is_multipart().

get_content_disposition()

Return the lowercased value (without parameters) of the message's Content-Disposition header if it has one, or None. The possible values for this method are inline, attachment or None if the message follows RFC 2183 [https://datatracker.ietf.org/doc/html/rfc2183.html].

在 3.5 版被加入.

The following methods relate to interrogating and manipulating the content (payload) of the message.

walk()

The walk() method is an all-purpose generator which can be used to iterate over all the parts and subparts of a message object tree, in depth-first traversal order. You will typically use walk() as the iterator in a for loop; each iteration returns the next subpart.

Here's an example that prints the MIME type of every part of a multipart message structure:

>>> for part in msg.walk():
...     print(part.get_content_type())
multipart/report
text/plain
message/delivery-status
text/plain
text/plain
message/rfc822
text/plain

walk iterates over the subparts of any part where is_multipart() returns True, even though msg.get_content_maintype() == 'multipart' may return False. We can see this in our example by making use of the _structure debug helper function:

>>> from email.iterators import _structure
>>> for part in msg.walk():
...     print(part.get_content_maintype() == 'multipart',
...           part.is_multipart())
True True
False False
False True
False False
False False
False True
False False
>>> _structure(msg)
multipart/report
    text/plain
    message/delivery-status
        text/plain
        text/plain
    message/rfc822
        text/plain

Here the message parts are not multiparts, but they do contain subparts. is_multipart() returns True and walk descends into the subparts.

get_body(preferencelist=('related', 'html', 'plain'))

Return the MIME part that is the best candidate to be the "body" of the message.

preferencelist must be a sequence of strings from the set related, html, and plain, and indicates the order of preference for the content type of the part returned.

Start looking for candidate matches with the object on which the get_body method is called.

If related is not included in preferencelist, consider the root part (or subpart of the root part) of any related encountered as a candidate if the (sub-)part matches a preference.

When encountering a multipart/related, check the start parameter and if a part with a matching Content-ID is found, consider only it when looking for candidate matches. Otherwise consider only the first (default root) part of the multipart/related.

If a part has a Content-Disposition header, only consider the part a candidate match if the value of the header is inline.

If none of the candidates matches any of the preferences in preferencelist, return None.

Notes: (1) For most applications the only preferencelist combinations that really make sense are ('plain',), ('html', 'plain'), and the default ('related', 'html', 'plain'). (2) Because matching starts with the object on which get_body is called, calling get_body on a multipart/related will return the object itself unless preferencelist has a non-default value. (3) Messages (or message parts) that do not specify a Content-Type or whose Content-Type header is invalid will be treated as if they are of type text/plain, which may occasionally cause get_body to return unexpected results.

iter_attachments()

Return an iterator over all of the immediate sub-parts of the message that are not candidate "body" parts. That is, skip the first occurrence of each of text/plain, text/html, multipart/related, or multipart/alternative (unless they are explicitly marked as attachments via Content-Disposition: attachment), and return all remaining parts. When applied directly to a multipart/related, return an iterator over the all the related parts except the root part (ie: the part pointed to by the start parameter, or the first part if there is no start parameter or the start parameter doesn't match the Content-ID of any of the parts). When applied directly to a multipart/alternative or a non-multipart, return an empty iterator.

iter_parts()

Return an iterator over all of the immediate sub-parts of the message, which will be empty for a non-multipart. (See also walk().)

get_content(*args, content_manager=None, **kw)

Call the get_content() method of the content_manager, passing self as the message object, and passing along any other arguments or keywords as additional arguments. If content_manager is not specified, use the content_manager specified by the current policy.

set_content(*args, content_manager=None, **kw)

Call the set_content() method of the content_manager, passing self as the message object, and passing along any other arguments or keywords as additional arguments. If content_manager is not specified, use the content_manager specified by the current policy.

make_related(boundary=None)

Convert a non-multipart message into a multipart/related message, moving any existing Content- headers and payload into a (new) first part of the multipart. If boundary is specified, use it as the boundary string in the multipart, otherwise leave the boundary to be automatically created when it is needed (for example, when the message is serialized).

make_alternative(boundary=None)

Convert a non-multipart or a multipart/related into a multipart/alternative, moving any existing Content- headers and payload into a (new) first part of the multipart. If boundary is specified, use it as the boundary string in the multipart, otherwise leave the boundary to be automatically created when it is needed (for example, when the message is serialized).

make_mixed(boundary=None)

Convert a non-multipart, a multipart/related, or a multipart-alternative into a multipart/mixed, moving any existing Content- headers and payload into a (new) first part of the multipart. If boundary is specified, use it as the boundary string in the multipart, otherwise leave the boundary to be automatically created when it is needed (for example, when the message is serialized).

add_related(*args, content_manager=None, **kw)

If the message is a multipart/related, create a new message object, pass all of the arguments to its set_content() method, and attach() it to the multipart. If the message is a non-multipart, call make_related() and then proceed as above. If the message is any other type of multipart, raise a TypeError. If content_manager is not specified, use the content_manager specified by the current policy. If the added part has no Content-Disposition header, add one with the value inline.

add_alternative(*args, content_manager=None, **kw)

If the message is a multipart/alternative, create a new message object, pass all of the arguments to its set_content() method, and attach() it to the multipart. If the message is a non-multipart or multipart/related, call make_alternative() and then proceed as above. If the message is any other type of multipart, raise a TypeError. If content_manager is not specified, use the content_manager specified by the current policy.

add_attachment(*args, content_manager=None, **kw)

If the message is a multipart/mixed, create a new message object, pass all of the arguments to its set_content() method, and attach() it to the multipart. If the message is a non-multipart, multipart/related, or multipart/alternative, call make_mixed() and then proceed as above. If content_manager is not specified, use the content_manager specified by the current policy. If the added part has no Content-Disposition header, add one with the value attachment. This method can be used both for explicit attachments (Content-Disposition: attachment) and inline attachments (Content-Disposition: inline), by passing appropriate options to the content_manager.

clear()

Remove the payload and all of the headers.

clear_content()

Remove the payload and all of the !Content- headers, leaving all other headers intact and in their original order.

EmailMessage objects have the following instance attributes:

preamble

The format of a MIME document allows for some text between the blank line following the headers, and the first multipart boundary string. Normally, this text is never visible in a MIME-aware mail reader because it falls outside the standard MIME armor. However, when viewing the raw text of the message, or when viewing the message in a non-MIME aware reader, this text can become visible.

The preamble attribute contains this leading extra-armor text for MIME documents. When the Parser discovers some text after the headers but before the first boundary string, it assigns this text to the message's preamble attribute. When the Generator is writing out the plain text representation of a MIME message, and it finds the message has a preamble attribute, it will write this text in the area between the headers and the first boundary. See email.parser and email.generator for details.

Note that if the message object has no preamble, the preamble attribute will be None.

epilogue

The epilogue attribute acts the same way as the preamble attribute, except that it contains text that appears between the last boundary and the end of the message. As with the preamble, if there is no epilog text this attribute will be None.

defects

The defects attribute contains a list of all the problems found when parsing this message. See email.errors for a detailed description of the possible parsing defects.

class email.message.MIMEPart(policy=default)

This class represents a subpart of a MIME message. It is identical to EmailMessage, except that no MIME-Version headers are added when set_content() is called, since sub-parts do not need their own MIME-Version headers.

註解

[1]

Originally added in 3.4 as a provisional module. Docs for legacy message class moved to email.message.Message: Representing an email message using the compat32 API.

[2]

The EmailMessage class requires a policy that provides a content_manager attribute for content management methods like set_content() and get_content() to work. The legacy compat32 policy does not support these methods and should not be used with EmailMessage.

email.parser：剖析電子郵件訊息

原始碼：Lib/email/parser.py [https://github.com/python/cpython/tree/3.14/Lib/email/parser.py]

Message object structures can be created in one of two ways: they can be created from whole cloth by creating an EmailMessage object, adding headers using the dictionary interface, and adding payload(s) using set_content() and related methods, or they can be created by parsing a serialized representation of the email message.

The email package provides a standard parser that understands most email document structures, including MIME documents. You can pass the parser a bytes, string or file object, and the parser will return to you the root EmailMessage instance of the object structure. For simple, non-MIME messages the payload of this root object will likely be a string containing the text of the message. For MIME messages, the root object will return True from its is_multipart() method, and the subparts can be accessed via the payload manipulation methods, such as get_body(), iter_parts(), and walk().

There are actually two parser interfaces available for use, the Parser API and the incremental FeedParser API. The Parser API is most useful if you have the entire text of the message in memory, or if the entire message lives in a file on the file system. FeedParser is more appropriate when you are reading the message from a stream which might block waiting for more input (such as reading an email message from a socket). The FeedParser can consume and parse the message incrementally, and only returns the root object when you close the parser.

Note that the parser can be extended in limited ways, and of course you can implement your own parser completely from scratch. All of the logic that connects the email package's bundled parser and the EmailMessage class is embodied in the Policy class, so a custom parser can create message object trees any way it finds necessary by implementing custom versions of the appropriate Policy methods.

FeedParser API

The BytesFeedParser, imported from the email.feedparser module, provides an API that is conducive to incremental parsing of email messages, such as would be necessary when reading the text of an email message from a source that can block (such as a socket). The BytesFeedParser can of course be used to parse an email message fully contained in a bytes-like object, string, or file, but the BytesParser API may be more convenient for such use cases. The semantics and results of the two parser APIs are identical.

The BytesFeedParser's API is simple; you create an instance, feed it a bunch of bytes until there's no more to feed it, then close the parser to retrieve the root message object. The BytesFeedParser is extremely accurate when parsing standards-compliant messages, and it does a very good job of parsing non-compliant messages, providing information about how a message was deemed broken. It will populate a message object's defects attribute with a list of any problems it found in a message. See the email.errors module for the list of defects that it can find.

Here is the API for the BytesFeedParser:

class email.parser.BytesFeedParser(_factory=None, *, policy=policy.compat32)

Create a BytesFeedParser instance. Optional _factory is a no-argument callable; if not specified use the message_factory from the policy. Call _factory whenever a new message object is needed.

If policy is specified use the rules it specifies to update the representation of the message. If policy is not set, use the compat32 policy, which maintains backward compatibility with the Python 3.2 version of the email package and provides Message as the default factory. All other policies provide EmailMessage as the default _factory. For more information on what else policy controls, see the policy documentation.

Note: The policy keyword should always be specified; The default will change to email.policy.default in a future version of Python.

在 3.2 版被加入.

在 3.3 版的變更: 新增 policy 關鍵字。

在 3.6 版的變更: _factory defaults to the policy message_factory.

feed(data)

Feed the parser some more data. data should be a bytes-like object containing one or more lines. The lines can be partial and the parser will stitch such partial lines together properly. The lines can have any of the three common line endings: carriage return, newline, or carriage return and newline (they can even be mixed).

close()

Complete the parsing of all previously fed data and return the root message object. It is undefined what happens if feed() is called after this method has been called.

class email.parser.FeedParser(_factory=None, *, policy=policy.compat32)

Works like BytesFeedParser except that the input to the feed() method must be a string. This is of limited utility, since the only way for such a message to be valid is for it to contain only ASCII text or, if utf8 is True, no binary attachments.

在 3.3 版的變更: 新增 policy 關鍵字。

Parser API

The BytesParser class, imported from the email.parser module, provides an API that can be used to parse a message when the complete contents of the message are available in a bytes-like object or file. The email.parser module also provides Parser for parsing strings, and header-only parsers, BytesHeaderParser and HeaderParser, which can be used if you're only interested in the headers of the message. BytesHeaderParser and HeaderParser can be much faster in these situations, since they do not attempt to parse the message body, instead setting the payload to the raw body.

class email.parser.BytesParser(_class=None, *, policy=policy.compat32)

Create a BytesParser instance. The _class and policy arguments have the same meaning and semantics as the _factory and policy arguments of BytesFeedParser.

Note: The policy keyword should always be specified; The default will change to email.policy.default in a future version of Python.

在 3.3 版的變更: Removed the strict argument that was deprecated in 2.4. Added the policy keyword.

在 3.6 版的變更: _class defaults to the policy message_factory.

parse(fp, headersonly=False)

Read all the data from the binary file-like object fp, parse the resulting bytes, and return the message object. fp must support both the readline() and the read() methods.

The bytes contained in fp must be formatted as a block of RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] (or, if utf8 is True, RFC 6532 [https://datatracker.ietf.org/doc/html/rfc6532.html]) style headers and header continuation lines, optionally preceded by an envelope header. The header block is terminated either by the end of the data or by a blank line. Following the header block is the body of the message (which may contain MIME-encoded subparts, including subparts with a Content-Transfer-Encoding of 8bit).

Optional headersonly is a flag specifying whether to stop parsing after reading the headers or not. The default is False, meaning it parses the entire contents of the file.

parsebytes(bytes, headersonly=False)

Similar to the parse() method, except it takes a bytes-like object instead of a file-like object. Calling this method on a bytes-like object is equivalent to wrapping bytes in a BytesIO instance first and calling parse().

Optional headersonly is as with the parse() method.

在 3.2 版被加入.

class email.parser.BytesHeaderParser(_class=None, *, policy=policy.compat32)

Exactly like BytesParser, except that headersonly defaults to True.

在 3.3 版被加入.

class email.parser.Parser(_class=None, *, policy=policy.compat32)

This class is parallel to BytesParser, but handles string input.

在 3.3 版的變更: Removed the strict argument. Added the policy keyword.

在 3.6 版的變更: _class defaults to the policy message_factory.

parse(fp, headersonly=False)

Read all the data from the text-mode file-like object fp, parse the resulting text, and return the root message object. fp must support both the readline() and the read() methods on file-like objects.

Other than the text mode requirement, this method operates like BytesParser.parse().

parsestr(text, headersonly=False)

Similar to the parse() method, except it takes a string object instead of a file-like object. Calling this method on a string is equivalent to wrapping text in a StringIO instance first and calling parse().

Optional headersonly is as with the parse() method.

class email.parser.HeaderParser(_class=None, *, policy=policy.compat32)

Exactly like Parser, except that headersonly defaults to True.

Since creating a message object structure from a string or a file object is such a common task, four functions are provided as a convenience. They are available in the top-level email package namespace.

email.message_from_bytes(s, _class=None, *, policy=policy.compat32)

Return a message object structure from a bytes-like object. This is equivalent to BytesParser().parsebytes(s). Optional _class and policy are interpreted as with the BytesParser class constructor.

在 3.2 版被加入.

在 3.3 版的變更: Removed the strict argument. Added the policy keyword.

email.message_from_binary_file(fp, _class=None, *, policy=policy.compat32)

Return a message object structure tree from an open binary file object. This is equivalent to BytesParser().parse(fp). _class and policy are interpreted as with the BytesParser class constructor.

在 3.2 版被加入.

在 3.3 版的變更: Removed the strict argument. Added the policy keyword.

email.message_from_string(s, _class=None, *, policy=policy.compat32)

Return a message object structure from a string. This is equivalent to Parser().parsestr(s). _class and policy are interpreted as with the Parser class constructor.

在 3.3 版的變更: Removed the strict argument. Added the policy keyword.

email.message_from_file(fp, _class=None, *, policy=policy.compat32)

Return a message object structure tree from an open file object. This is equivalent to Parser().parse(fp). _class and policy are interpreted as with the Parser class constructor.

在 3.3 版的變更: Removed the strict argument. Added the policy keyword.

在 3.6 版的變更: _class defaults to the policy message_factory.

Here's an example of how you might use message_from_bytes() at an interactive Python prompt:

>>> import email
>>> msg = email.message_from_bytes(myBytes)

Additional notes

Here are some notes on the parsing semantics:

Most non-multipart type messages are parsed as a single message object with a string payload. These objects will return False for is_multipart(), and iter_parts() will yield an empty list.

All multipart type messages will be parsed as a container message object with a list of sub-message objects for their payload. The outer container message will return True for is_multipart(), and iter_parts() will yield a list of subparts.

Most messages with a content type of message/* (such as message/delivery-status and message/rfc822) will also be parsed as container object containing a list payload of length 1. Their is_multipart() method will return True. The single element yielded by iter_parts() will be a sub-message object.

Some non-standards-compliant messages may not be internally consistent about their multipart-edness. Such messages may have a Content-Type header of type multipart, but their is_multipart() method may return False. If such messages were parsed with the FeedParser, they will have an instance of the MultipartInvariantViolationDefect class in their defects attribute list. See email.errors for details.

email.generator：產生 MIME 文件

原始碼：Lib/email/generator.py [https://github.com/python/cpython/tree/3.14/Lib/email/generator.py]

One of the most common tasks is to generate the flat (serialized) version of the email message represented by a message object structure. You will need to do this if you want to send your message via smtplib.SMTP.sendmail(), or print the message on the console. Taking a message object structure and producing a serialized representation is the job of the generator classes.

As with the email.parser module, you aren't limited to the functionality of the bundled generator; you could write one from scratch yourself. However the bundled generator knows how to generate most email in a standards-compliant way, should handle MIME and non-MIME email messages just fine, and is designed so that the bytes-oriented parsing and generation operations are inverses, assuming the same non-transforming policy is used for both. That is, parsing the serialized byte stream via the BytesParser class and then regenerating the serialized byte stream using BytesGenerator should produce output identical to the input [1]. (On the other hand, using the generator on an EmailMessage constructed by program may result in changes to the EmailMessage object as defaults are filled in.)

The Generator class can be used to flatten a message into a text (as opposed to binary) serialized representation, but since Unicode cannot represent binary data directly, the message is of necessity transformed into something that contains only ASCII characters, using the standard email RFC Content Transfer Encoding techniques for encoding email messages for transport over channels that are not "8 bit clean".

To accommodate reproducible processing of SMIME-signed messages Generator disables header folding for message parts of type multipart/signed and all subparts.

class email.generator.BytesGenerator(outfp, mangle_from_=None, maxheaderlen=None, *, policy=None)

Return a BytesGenerator object that will write any message provided to the flatten() method, or any surrogateescape encoded text provided to the write() method, to the file-like object outfp. outfp must support a write method that accepts binary data.

If optional mangle_from_ is True, put a > character in front of any line in the body that starts with the exact string "From ", that is From followed by a space at the beginning of a line. mangle_from_ defaults to the value of the mangle_from_ setting of the policy (which is True for the compat32 policy and False for all others). mangle_from_ is intended for use when messages are stored in Unix mbox format (see mailbox and WHY THE CONTENT-LENGTH FORMAT IS BAD [https://www.jwz.org/doc/content-length.html]).

If maxheaderlen is not None, refold any header lines that are longer than maxheaderlen, or if 0, do not rewrap any headers. If manheaderlen is None (the default), wrap headers and other message lines according to the policy settings.

If policy is specified, use that policy to control message generation. If policy is None (the default), use the policy associated with the Message or EmailMessage object passed to flatten to control the message generation. See email.policy for details on what policy controls.

在 3.2 版被加入.

在 3.3 版的變更: 新增關鍵字 policy。

在 3.6 版的變更: The default behavior of the mangle_from_ and maxheaderlen parameters is to follow the policy.

flatten(msg, unixfrom=False, linesep=None)

Print the textual representation of the message object structure rooted at msg to the output file specified when the BytesGenerator instance was created.

If the policy option cte_type is 8bit (the default), copy any headers in the original parsed message that have not been modified to the output with any bytes with the high bit set reproduced as in the original, and preserve the non-ASCII Content-Transfer-Encoding of any body parts that have them. If cte_type is 7bit, convert the bytes with the high bit set as needed using an ASCII-compatible Content-Transfer-Encoding. That is, transform parts with non-ASCII Content-Transfer-Encoding (Content-Transfer-Encoding: 8bit) to an ASCII compatible Content-Transfer-Encoding, and encode RFC-invalid non-ASCII bytes in headers using the MIME unknown-8bit character set, thus rendering them RFC-compliant.

If unixfrom is True, print the envelope header delimiter used by the Unix mailbox format (see mailbox) before the first of the RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] headers of the root message object. If the root object has no envelope header, craft a standard one. The default is False. Note that for subparts, no envelope header is ever printed.

If linesep is not None, use it as the separator character between all the lines of the flattened message. If linesep is None (the default), use the value specified in the policy.

clone(fp)

Return an independent clone of this BytesGenerator instance with the exact same option settings, and fp as the new outfp.

write(s)

Encode s using the ASCII codec and the surrogateescape error handler, and pass it to the write method of the outfp passed to the BytesGenerator's constructor.

As a convenience, EmailMessage provides the methods as_bytes() and bytes(aMessage) (a.k.a. __bytes__()), which simplify the generation of a serialized binary representation of a message object. For more detail, see email.message.

Because strings cannot represent binary data, the Generator class must convert any binary data in any message it flattens to an ASCII compatible format, by converting them to an ASCII compatible Content-Transfer_Encoding. Using the terminology of the email RFCs, you can think of this as Generator serializing to an I/O stream that is not "8 bit clean". In other words, most applications will want to be using BytesGenerator, and not Generator.

class email.generator.Generator(outfp, mangle_from_=None, maxheaderlen=None, *, policy=None)

Return a Generator object that will write any message provided to the flatten() method, or any text provided to the write() method, to the file-like object outfp. outfp must support a write method that accepts string data.

If optional mangle_from_ is True, put a > character in front of any line in the body that starts with the exact string "From ", that is From followed by a space at the beginning of a line. mangle_from_ defaults to the value of the mangle_from_ setting of the policy (which is True for the compat32 policy and False for all others). mangle_from_ is intended for use when messages are stored in Unix mbox format (see mailbox and WHY THE CONTENT-LENGTH FORMAT IS BAD [https://www.jwz.org/doc/content-length.html]).

If maxheaderlen is not None, refold any header lines that are longer than maxheaderlen, or if 0, do not rewrap any headers. If manheaderlen is None (the default), wrap headers and other message lines according to the policy settings.

If policy is specified, use that policy to control message generation. If policy is None (the default), use the policy associated with the Message or EmailMessage object passed to flatten to control the message generation. See email.policy for details on what policy controls.

在 3.3 版的變更: 新增關鍵字 policy。

在 3.6 版的變更: The default behavior of the mangle_from_ and maxheaderlen parameters is to follow the policy.

flatten(msg, unixfrom=False, linesep=None)

Print the textual representation of the message object structure rooted at msg to the output file specified when the Generator instance was created.

If the policy option cte_type is 8bit, generate the message as if the option were set to 7bit. (This is required because strings cannot represent non-ASCII bytes.) Convert any bytes with the high bit set as needed using an ASCII-compatible Content-Transfer-Encoding. That is, transform parts with non-ASCII Content-Transfer-Encoding (Content-Transfer-Encoding: 8bit) to an ASCII compatible Content-Transfer-Encoding, and encode RFC-invalid non-ASCII bytes in headers using the MIME unknown-8bit character set, thus rendering them RFC-compliant.

If unixfrom is True, print the envelope header delimiter used by the Unix mailbox format (see mailbox) before the first of the RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] headers of the root message object. If the root object has no envelope header, craft a standard one. The default is False. Note that for subparts, no envelope header is ever printed.

If linesep is not None, use it as the separator character between all the lines of the flattened message. If linesep is None (the default), use the value specified in the policy.

在 3.2 版的變更: Added support for re-encoding 8bit message bodies, and the linesep argument.

clone(fp)

Return an independent clone of this Generator instance with the exact same options, and fp as the new outfp.

write(s)

Write s to the write method of the outfp passed to the Generator's constructor. This provides just enough file-like API for Generator instances to be used in the print() function.

As a convenience, EmailMessage provides the methods as_string() and str(aMessage) (a.k.a. __str__()), which simplify the generation of a formatted string representation of a message object. For more detail, see email.message.

The email.generator module also provides a derived class, DecodedGenerator, which is like the Generator base class, except that non-text parts are not serialized, but are instead represented in the output stream by a string derived from a template filled in with information about the part.

class email.generator.DecodedGenerator(outfp, mangle_from_=None, maxheaderlen=None, fmt=None, *, policy=None)

Act like Generator, except that for any subpart of the message passed to Generator.flatten(), if the subpart is of main type text, print the decoded payload of the subpart, and if the main type is not text, instead of printing it fill in the string fmt using information from the part and print the resulting filled-in string.

To fill in fmt, execute fmt % part_info, where part_info is a dictionary composed of the following keys and values:

type -- Full MIME type of the non-text part

maintype -- Main MIME type of the non-text part

subtype -- Sub-MIME type of the non-text part

filename -- Filename of the non-text part

description -- Description associated with the non-text part

encoding -- Content transfer encoding of the non-text part

If fmt is None, use the following default fmt:

"[Non-text (%(type)s) part of message omitted, filename %(filename)s]"

Optional _mangle_from_ and maxheaderlen are as with the Generator base class.

註解

[1]

This statement assumes that you use the appropriate setting for unixfrom, and that there are no email.policy settings calling for automatic adjustments (for example, refold_source must be none, which is not the default). It is also not 100% true, since if the message does not conform to the RFC standards occasionally information about the exact original text is lost during parsing error recovery. It is a goal to fix these latter edge cases when possible.

email.policy: Policy Objects

在 3.3 版被加入.

原始碼：Lib/email/policy.py [https://github.com/python/cpython/tree/3.14/Lib/email/policy.py]

The email package's prime focus is the handling of email messages as described by the various email and MIME RFCs. However, the general format of email messages (a block of header fields each consisting of a name followed by a colon followed by a value, the whole block followed by a blank line and an arbitrary 'body'), is a format that has found utility outside of the realm of email. Some of these uses conform fairly closely to the main email RFCs, some do not. Even when working with email, there are times when it is desirable to break strict compliance with the RFCs, such as generating emails that interoperate with email servers that do not themselves follow the standards, or that implement extensions you want to use in ways that violate the standards.

Policy objects give the email package the flexibility to handle all these disparate use cases.

A Policy object encapsulates a set of attributes and methods that control the behavior of various components of the email package during use. Policy instances can be passed to various classes and methods in the email package to alter the default behavior. The settable values and their defaults are described below.

There is a default policy used by all classes in the email package. For all of the parser classes and the related convenience functions, and for the Message class, this is the Compat32 policy, via its corresponding pre-defined instance compat32. This policy provides for complete backward compatibility (in some cases, including bug compatibility) with the pre-Python3.3 version of the email package.

This default value for the policy keyword to EmailMessage is the EmailPolicy policy, via its pre-defined instance default.

When a Message or EmailMessage object is created, it acquires a policy. If the message is created by a parser, a policy passed to the parser will be the policy used by the message it creates. If the message is created by the program, then the policy can be specified when it is created. When a message is passed to a generator, the generator uses the policy from the message by default, but you can also pass a specific policy to the generator that will override the one stored on the message object.

The default value for the policy keyword for the email.parser classes and the parser convenience functions will be changing in a future version of Python. Therefore you should always specify explicitly which policy you want to use when calling any of the classes and functions described in the parser module.

The first part of this documentation covers the features of Policy, an abstract base class that defines the features that are common to all policy objects, including compat32. This includes certain hook methods that are called internally by the email package, which a custom policy could override to obtain different behavior. The second part describes the concrete classes EmailPolicy and Compat32, which implement the hooks that provide the standard behavior and the backward compatible behavior and features, respectively.

Policy instances are immutable, but they can be cloned, accepting the same keyword arguments as the class constructor and returning a new Policy instance that is a copy of the original but with the specified attributes values changed.

As an example, the following code could be used to read an email message from a file on disk and pass it to the system sendmail program on a Unix system:

>>> from email import message_from_binary_file
>>> from email.generator import BytesGenerator
>>> from email import policy
>>> from subprocess import Popen, PIPE
>>> with open('mymsg.txt', 'rb') as f:
...     msg = message_from_binary_file(f, policy=policy.default)
...
>>> p = Popen(['sendmail', msg['To'].addresses[0]], stdin=PIPE)
>>> g = BytesGenerator(p.stdin, policy=msg.policy.clone(linesep='\r\n'))
>>> g.flatten(msg)
>>> p.stdin.close()
>>> rc = p.wait()

Here we are telling BytesGenerator to use the RFC correct line separator characters when creating the binary string to feed into sendmail's stdin, where the default policy would use \n line separators.

Some email package methods accept a policy keyword argument, allowing the policy to be overridden for that method. For example, the following code uses the as_bytes() method of the msg object from the previous example and writes the message to a file using the native line separators for the platform on which it is running:

>>> import os
>>> with open('converted.txt', 'wb') as f:
...     f.write(msg.as_bytes(policy=msg.policy.clone(linesep=os.linesep)))
17

Policy objects can also be combined using the addition operator, producing a policy object whose settings are a combination of the non-default values of the summed objects:

>>> compat_SMTP = policy.compat32.clone(linesep='\r\n')
>>> compat_strict = policy.compat32.clone(raise_on_defect=True)
>>> compat_strict_SMTP = compat_SMTP + compat_strict

This operation is not commutative; that is, the order in which the objects are added matters. To illustrate:

>>> policy100 = policy.compat32.clone(max_line_length=100)
>>> policy80 = policy.compat32.clone(max_line_length=80)
>>> apolicy = policy100 + policy80
>>> apolicy.max_line_length
80
>>> apolicy = policy80 + policy100
>>> apolicy.max_line_length
100

class email.policy.Policy(**kw)

This is the abstract base class for all policy classes. It provides default implementations for a couple of trivial methods, as well as the implementation of the immutability property, the clone() method, and the constructor semantics.

The constructor of a policy class can be passed various keyword arguments. The arguments that may be specified are any non-method properties on this class, plus any additional non-method properties on the concrete class. A value specified in the constructor will override the default value for the corresponding attribute.

This class defines the following properties, and thus values for the following may be passed in the constructor of any policy class:

max_line_length

The maximum length of any line in the serialized output, not counting the end of line character(s). Default is 78, per RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html]. A value of 0 or None indicates that no line wrapping should be done at all.

linesep

The string to be used to terminate lines in serialized output. The default is \n because that's the internal end-of-line discipline used by Python, though \r\n is required by the RFCs.

cte_type

Controls the type of Content Transfer Encodings that may be or are required to be used. The possible values are:

7bit

all data must be "7 bit clean" (ASCII-only). This means that where necessary data will be encoded using either quoted-printable or base64 encoding.

8bit

data is not constrained to be 7 bit clean. Data in headers is still required to be ASCII-only and so will be encoded (see fold_binary() and utf8 below for exceptions), but body parts may use the 8bit CTE.

A cte_type value of 8bit only works with BytesGenerator, not Generator, because strings cannot contain binary data. If a Generator is operating under a policy that specifies cte_type=8bit, it will act as if cte_type is 7bit.

raise_on_defect

If True, any defects encountered will be raised as errors. If False (the default), defects will be passed to the register_defect() method.

mangle_from_

If True, lines starting with "From " in the body are escaped by putting a > in front of them. This parameter is used when the message is being serialized by a generator. Default: False.

在 3.5 版被加入.

message_factory

A factory function for constructing a new empty message object. Used by the parser when building messages. Defaults to None, in which case Message is used.

在 3.6 版被加入.

verify_generated_headers

If True (the default), the generator will raise HeaderWriteError instead of writing a header that is improperly folded or delimited, such that it would be parsed as multiple headers or joined with adjacent data. Such headers can be generated by custom header classes or bugs in the email module.

As it's a security feature, this defaults to True even in the Compat32 policy. For backwards compatible, but unsafe, behavior, it must be set to False explicitly.

在 3.13 版被加入.

The following Policy method is intended to be called by code using the email library to create policy instances with custom settings:

clone(**kw)

Return a new Policy instance whose attributes have the same values as the current instance, except where those attributes are given new values by the keyword arguments.

The remaining Policy methods are called by the email package code, and are not intended to be called by an application using the email package. A custom policy must implement all of these methods.

handle_defect(obj, defect)

Handle a defect found on obj. When the email package calls this method, defect will always be a subclass of MessageDefect.

The default implementation checks the raise_on_defect flag. If it is True, defect is raised as an exception. If it is False (the default), obj and defect are passed to register_defect().

register_defect(obj, defect)

Register a defect on obj. In the email package, defect will always be a subclass of MessageDefect.

The default implementation calls the append method of the defects attribute of obj. When the email package calls handle_defect, obj will normally have a defects attribute that has an append method. Custom object types used with the email package (for example, custom Message objects) should also provide such an attribute, otherwise defects in parsed messages will raise unexpected errors.

header_max_count(name)

Return the maximum allowed number of headers named name.

Called when a header is added to an EmailMessage or Message object. If the returned value is not 0 or None, and there are already a number of headers with the name name greater than or equal to the value returned, a ValueError is raised.

Because the default behavior of Message.__setitem__ is to append the value to the list of headers, it is easy to create duplicate headers without realizing it. This method allows certain headers to be limited in the number of instances of that header that may be added to a Message programmatically. (The limit is not observed by the parser, which will faithfully produce as many headers as exist in the message being parsed.)

The default implementation returns None for all header names.

header_source_parse(sourcelines)

The email package calls this method with a list of strings, each string ending with the line separation characters found in the source being parsed. The first line includes the field header name and separator. All whitespace in the source is preserved. The method should return the (name, value) tuple that is to be stored in the Message to represent the parsed header.

If an implementation wishes to retain compatibility with the existing email package policies, name should be the case preserved name (all characters up to the ':' separator), while value should be the unfolded value (all line separator characters removed, but whitespace kept intact), stripped of leading whitespace.

sourcelines may contain surrogateescaped binary data.

There is no default implementation

header_store_parse(name, value)

The email package calls this method with the name and value provided by the application program when the application program is modifying a Message programmatically (as opposed to a Message created by a parser). The method should return the (name, value) tuple that is to be stored in the Message to represent the header.

If an implementation wishes to retain compatibility with the existing email package policies, the name and value should be strings or string subclasses that do not change the content of the passed in arguments.

There is no default implementation

header_fetch_parse(name, value)

The email package calls this method with the name and value currently stored in the Message when that header is requested by the application program, and whatever the method returns is what is passed back to the application as the value of the header being retrieved. Note that there may be more than one header with the same name stored in the Message; the method is passed the specific name and value of the header destined to be returned to the application.

value may contain surrogateescaped binary data. There should be no surrogateescaped binary data in the value returned by the method.

There is no default implementation

fold(name, value)

The email package calls this method with the name and value currently stored in the Message for a given header. The method should return a string that represents that header "folded" correctly (according to the policy settings) by composing the name with the value and inserting linesep characters at the appropriate places. See RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] for a discussion of the rules for folding email headers.

value may contain surrogateescaped binary data. There should be no surrogateescaped binary data in the string returned by the method.

fold_binary(name, value)

The same as fold(), except that the returned value should be a bytes object rather than a string.

value may contain surrogateescaped binary data. These could be converted back into binary data in the returned bytes object.

class email.policy.EmailPolicy(**kw)

This concrete Policy provides behavior that is intended to be fully compliant with the current email RFCs. These include (but are not limited to) RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html], RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html], and the current MIME RFCs.

This policy adds new header parsing and folding algorithms. Instead of simple strings, headers are str subclasses with attributes that depend on the type of the field. The parsing and folding algorithm fully implement RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] and RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html].

The default value for the message_factory attribute is EmailMessage.

In addition to the settable attributes listed above that apply to all policies, this policy adds the following additional attributes:

在 3.6 版被加入: [1]

utf8

If False, follow RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html], supporting non-ASCII characters in headers by encoding them as "encoded words". If True, follow RFC 6532 [https://datatracker.ietf.org/doc/html/rfc6532.html] and use utf-8 encoding for headers. Messages formatted in this way may be passed to SMTP servers that support the SMTPUTF8 extension (RFC 6531 [https://datatracker.ietf.org/doc/html/rfc6531.html]).

refold_source

If the value for a header in the Message object originated from a parser (as opposed to being set by a program), this attribute indicates whether or not a generator should refold that value when transforming the message back into serialized form. The possible values are:

none

all source values use original folding

long

source values that have any line that is longer than max_line_length will be refolded

all

all values are refolded.

預設為 long。

header_factory

A callable that takes two arguments, name and value, where name is a header field name and value is an unfolded header field value, and returns a string subclass that represents that header. A default header_factory (see headerregistry) is provided that supports custom parsing for the various address and date RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] header field types, and the major MIME header field stypes. Support for additional custom parsing will be added in the future.

content_manager

An object with at least two methods: get_content and set_content. When the get_content() or set_content() method of an EmailMessage object is called, it calls the corresponding method of this object, passing it the message object as its first argument, and any arguments or keywords that were passed to it as additional arguments. By default content_manager is set to raw_data_manager.

在 3.4 版被加入.

The class provides the following concrete implementations of the abstract methods of Policy:

header_max_count(name)

Returns the value of the max_count attribute of the specialized class used to represent the header with the given name.

header_source_parse(sourcelines)

The name is parsed as everything up to the ':' and returned unmodified. The value is determined by stripping leading whitespace off the remainder of the first line, joining all subsequent lines together, and stripping any trailing carriage return or linefeed characters.

header_store_parse(name, value)

The name is returned unchanged. If the input value has a name attribute and it matches name ignoring case, the value is returned unchanged. Otherwise the name and value are passed to header_factory, and the resulting header object is returned as the value. In this case a ValueError is raised if the input value contains CR or LF characters.

header_fetch_parse(name, value)

If the value has a name attribute, it is returned to unmodified. Otherwise the name, and the value with any CR or LF characters removed, are passed to the header_factory, and the resulting header object is returned. Any surrogateescaped bytes get turned into the unicode unknown-character glyph.

fold(name, value)

Header folding is controlled by the refold_source policy setting. A value is considered to be a 'source value' if and only if it does not have a name attribute (having a name attribute means it is a header object of some sort). If a source value needs to be refolded according to the policy, it is converted into a header object by passing the name and the value with any CR and LF characters removed to the header_factory. Folding of a header object is done by calling its fold method with the current policy.

Source values are split into lines using splitlines(). If the value is not to be refolded, the lines are rejoined using the linesep from the policy and returned. The exception is lines containing non-ascii binary data. In that case the value is refolded regardless of the refold_source setting, which causes the binary data to be CTE encoded using the unknown-8bit charset.

fold_binary(name, value)

The same as fold() if cte_type is 7bit, except that the returned value is bytes.

If cte_type is 8bit, non-ASCII binary data is converted back into bytes. Headers with binary data are not refolded, regardless of the refold_header setting, since there is no way to know whether the binary data consists of single byte characters or multibyte characters.

The following instances of EmailPolicy provide defaults suitable for specific application domains. Note that in the future the behavior of these instances (in particular the HTTP instance) may be adjusted to conform even more closely to the RFCs relevant to their domains.

email.policy.default

An instance of EmailPolicy with all defaults unchanged. This policy uses the standard Python \n line endings rather than the RFC-correct \r\n.

email.policy.SMTP

Suitable for serializing messages in conformance with the email RFCs. Like default, but with linesep set to \r\n, which is RFC compliant.

email.policy.SMTPUTF8

The same as SMTP except that utf8 is True. Useful for serializing messages to a message store without using encoded words in the headers. Should only be used for SMTP transmission if the sender or recipient addresses have non-ASCII characters (the smtplib.SMTP.send_message() method handles this automatically).

email.policy.HTTP

Suitable for serializing headers with for use in HTTP traffic. Like SMTP except that max_line_length is set to None (unlimited).

email.policy.strict

Convenience instance. The same as default except that raise_on_defect is set to True. This allows any policy to be made strict by writing:

somepolicy + policy.strict

With all of these EmailPolicies, the effective API of the email package is changed from the Python 3.2 API in the following ways:

Setting a header on a Message results in that header being parsed and a header object created.

Fetching a header value from a Message results in that header being parsed and a header object created and returned.

Any header object, or any header that is refolded due to the policy settings, is folded using an algorithm that fully implements the RFC folding algorithms, including knowing where encoded words are required and allowed.

From the application view, this means that any header obtained through the EmailMessage is a header object with extra attributes, whose string value is the fully decoded unicode value of the header. Likewise, a header may be assigned a new value, or a new header created, using a unicode string, and the policy will take care of converting the unicode string into the correct RFC encoded form.

The header objects and their attributes are described in headerregistry.

class email.policy.Compat32(**kw)

This concrete Policy is the backward compatibility policy. It replicates the behavior of the email package in Python 3.2. The policy module also defines an instance of this class, compat32, that is used as the default policy. Thus the default behavior of the email package is to maintain compatibility with Python 3.2.

The following attributes have values that are different from the Policy default:

mangle_from_

預設值為 True。

The class provides the following concrete implementations of the abstract methods of Policy:

header_source_parse(sourcelines)

The name is parsed as everything up to the ':' and returned unmodified. The value is determined by stripping leading whitespace off the remainder of the first line, joining all subsequent lines together, and stripping any trailing carriage return or linefeed characters.

header_store_parse(name, value)

名稱和值會原封不動地回傳。

header_fetch_parse(name, value)

If the value contains binary data, it is converted into a Header object using the unknown-8bit charset. Otherwise it is returned unmodified.

fold(name, value)

Headers are folded using the Header folding algorithm, which preserves existing line breaks in the value, and wraps each resulting line to the max_line_length. Non-ASCII binary data are CTE encoded using the unknown-8bit charset.

fold_binary(name, value)

Headers are folded using the Header folding algorithm, which preserves existing line breaks in the value, and wraps each resulting line to the max_line_length. If cte_type is 7bit, non-ascii binary data is CTE encoded using the unknown-8bit charset. Otherwise the original source header is used, with its existing line breaks and any (RFC invalid) binary data it may contain.

email.policy.compat32

An instance of Compat32, providing backward compatibility with the behavior of the email package in Python 3.2.

備註

The compat32 policy should not be used as a policy for EmailMessage objects, and should only be used to serialize messages that were created using the compat32 policy.

註解

[1]

Originally added in 3.3 as a provisional feature.

email.errors：例外和缺陷類別

原始碼：Lib/email/errors.py [https://github.com/python/cpython/tree/3.14/Lib/email/errors.py]

The following exception classes are defined in the email.errors module:

exception email.errors.MessageError

This is the base class for all exceptions that the email package can raise. It is derived from the standard Exception class and defines no additional methods.

exception email.errors.MessageParseError

This is the base class for exceptions raised by the Parser class. It is derived from MessageError. This class is also used internally by the parser used by headerregistry.

exception email.errors.HeaderParseError

Raised under some error conditions when parsing the RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] headers of a message, this class is derived from MessageParseError. The set_boundary() method will raise this error if the content type is unknown when the method is called. Header may raise this error for certain base64 decoding errors, and when an attempt is made to create a header that appears to contain an embedded header (that is, there is what is supposed to be a continuation line that has no leading whitespace and looks like a header).

exception email.errors.BoundaryError

Deprecated and no longer used.

exception email.errors.MultipartConversionError

Raised if the attach() method is called on an instance of a class derived from MIMENonMultipart (e.g. MIMEImage). MultipartConversionError multiply inherits from MessageError and the built-in TypeError.

exception email.errors.HeaderWriteError

Raised when an error occurs when the generator outputs headers.

exception email.errors.MessageDefect

This is the base class for all defects found when parsing email messages. It is derived from ValueError.

exception email.errors.HeaderDefect

This is the base class for all defects found when parsing email headers. It is derived from MessageDefect.

Here is the list of the defects that the FeedParser can find while parsing messages. Note that the defects are added to the message where the problem was found, so for example, if a message nested inside a multipart/alternative had a malformed header, that nested message object would have a defect, but the containing messages would not.

All defect classes are subclassed from email.errors.MessageDefect.

exception email.errors.NoBoundaryInMultipartDefect

A message claimed to be a multipart, but had no boundary parameter.

exception email.errors.StartBoundaryNotFoundDefect

The start boundary claimed in the Content-Type header was never found.

exception email.errors.CloseBoundaryNotFoundDefect

A start boundary was found, but no corresponding close boundary was ever found.

在 3.3 版被加入.

exception email.errors.FirstHeaderLineIsContinuationDefect

The message had a continuation line as its first header line.

exception email.errors.MisplacedEnvelopeHeaderDefect

A "Unix From" header was found in the middle of a header block.

exception email.errors.MissingHeaderBodySeparatorDefect

A line was found while parsing headers that had no leading white space but contained no ':'. Parsing continues assuming that the line represents the first line of the body.

在 3.3 版被加入.

exception email.errors.MalformedHeaderDefect

A header was found that was missing a colon, or was otherwise malformed.

在 3.3 版之後被棄用: This defect has not been used for several Python versions.

exception email.errors.MultipartInvariantViolationDefect

A message claimed to be a multipart, but no subparts were found. Note that when a message has this defect, its is_multipart() method may return False even though its content type claims to be multipart.

exception email.errors.InvalidBase64PaddingDefect

When decoding a block of base64 encoded bytes, the padding was not correct. Enough padding is added to perform the decode, but the resulting decoded bytes may be invalid.

exception email.errors.InvalidBase64CharactersDefect

When decoding a block of base64 encoded bytes, characters outside the base64 alphabet were encountered. The characters are ignored, but the resulting decoded bytes may be invalid.

exception email.errors.InvalidBase64LengthDefect

When decoding a block of base64 encoded bytes, the number of non-padding base64 characters was invalid (1 more than a multiple of 4). The encoded block was kept as-is.

exception email.errors.InvalidDateDefect

When decoding an invalid or unparsable date field. The original value is kept as-is.

email.headerregistry：自訂標頭物件

原始碼：Lib/email/headerregistry.py [https://github.com/python/cpython/tree/3.14/Lib/email/headerregistry.py]

在 3.6 版被加入: [1]

Headers are represented by customized subclasses of str. The particular class used to represent a given header is determined by the header_factory of the policy in effect when the headers are created. This section documents the particular header_factory implemented by the email package for handling RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] compliant email messages, which not only provides customized header objects for various header types, but also provides an extension mechanism for applications to add their own custom header types.

When using any of the policy objects derived from EmailPolicy, all headers are produced by HeaderRegistry and have BaseHeader as their last base class. Each header class has an additional base class that is determined by the type of the header. For example, many headers have the class UnstructuredHeader as their other base class. The specialized second class for a header is determined by the name of the header, using a lookup table stored in the HeaderRegistry. All of this is managed transparently for the typical application program, but interfaces are provided for modifying the default behavior for use by more complex applications.

The sections below first document the header base classes and their attributes, followed by the API for modifying the behavior of HeaderRegistry, and finally the support classes used to represent the data parsed from structured headers.

class email.headerregistry.BaseHeader(name, value)

name and value are passed to BaseHeader from the header_factory call. The string value of any header object is the value fully decoded to unicode.

這個基底類別定義了以下唯讀屬性：

name

The name of the header (the portion of the field before the ':'). This is exactly the value passed in the header_factory call for name; that is, case is preserved.

defects

A tuple of HeaderDefect instances reporting any RFC compliance problems found during parsing. The email package tries to be complete about detecting compliance issues. See the errors module for a discussion of the types of defects that may be reported.

max_count

The maximum number of headers of this type that can have the same name. A value of None means unlimited. The BaseHeader value for this attribute is None; it is expected that specialized header classes will override this value as needed.

BaseHeader also provides the following method, which is called by the email library code and should not in general be called by application programs:

fold(*, policy)

Return a string containing linesep characters as required to correctly fold the header according to policy. A cte_type of 8bit will be treated as if it were 7bit, since headers may not contain arbitrary binary data. If utf8 is False, non-ASCII data will be RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] encoded.

BaseHeader by itself cannot be used to create a header object. It defines a protocol that each specialized header cooperates with in order to produce the header object. Specifically, BaseHeader requires that the specialized class provide a classmethod() named parse. This method is called as follows:

parse(string, kwds)

kwds is a dictionary containing one pre-initialized key, defects. defects is an empty list. The parse method should append any detected defects to this list. On return, the kwds dictionary must contain values for at least the keys decoded and defects. decoded should be the string value for the header (that is, the header value fully decoded to unicode). The parse method should assume that string may contain content-transfer-encoded parts, but should correctly handle all valid unicode characters as well so that it can parse un-encoded header values.

BaseHeader's __new__ then creates the header instance, and calls its init method. The specialized class only needs to provide an init method if it wishes to set additional attributes beyond those provided by BaseHeader itself. Such an init method should look like this:

def init(self, /, *args, **kw):
    self._myattr = kw.pop('myattr')
    super().init(*args, **kw)

That is, anything extra that the specialized class puts in to the kwds dictionary should be removed and handled, and the remaining contents of kw (and args) passed to the BaseHeader init method.

class email.headerregistry.UnstructuredHeader

An "unstructured" header is the default type of header in RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html]. Any header that does not have a specified syntax is treated as unstructured. The classic example of an unstructured header is the Subject header.

In RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html], an unstructured header is a run of arbitrary text in the ASCII character set. RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html], however, has an RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] compatible mechanism for encoding non-ASCII text as ASCII characters within a header value. When a value containing encoded words is passed to the constructor, the UnstructuredHeader parser converts such encoded words into unicode, following the RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] rules for unstructured text. The parser uses heuristics to attempt to decode certain non-compliant encoded words. Defects are registered in such cases, as well as defects for issues such as invalid characters within the encoded words or the non-encoded text.

This header type provides no additional attributes.

class email.headerregistry.DateHeader

RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] specifies a very specific format for dates within email headers. The DateHeader parser recognizes that date format, as well as recognizing a number of variant forms that are sometimes found "in the wild".

This header type provides the following additional attributes:

datetime

If the header value can be recognized as a valid date of one form or another, this attribute will contain a datetime instance representing that date. If the timezone of the input date is specified as -0000 (indicating it is in UTC but contains no information about the source timezone), then datetime will be a naive datetime. If a specific timezone offset is found (including +0000), then datetime will contain an aware datetime that uses datetime.timezone to record the timezone offset.

The decoded value of the header is determined by formatting the datetime according to the RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] rules; that is, it is set to:

email.utils.format_datetime(self.datetime)

When creating a DateHeader, value may be datetime instance. This means, for example, that the following code is valid and does what one would expect:

msg['Date'] = datetime(2011, 7, 15, 21)

Because this is a naive datetime it will be interpreted as a UTC timestamp, and the resulting value will have a timezone of -0000. Much more useful is to use the localtime() function from the utils module:

msg['Date'] = utils.localtime()

This example sets the date header to the current time and date using the current timezone offset.

class email.headerregistry.AddressHeader

Address headers are one of the most complex structured header types. The AddressHeader class provides a generic interface to any address header.

This header type provides the following additional attributes:

groups

A tuple of Group objects encoding the addresses and groups found in the header value. Addresses that are not part of a group are represented in this list as single-address Groups whose display_name is None.

addresses

A tuple of Address objects encoding all of the individual addresses from the header value. If the header value contains any groups, the individual addresses from the group are included in the list at the point where the group occurs in the value (that is, the list of addresses is "flattened" into a one dimensional list).

The decoded value of the header will have all encoded words decoded to unicode. idna encoded domain names are also decoded to unicode. The decoded value is set by joining the str value of the elements of the groups attribute with ', '.

A list of Address and Group objects in any combination may be used to set the value of an address header. Group objects whose display_name is None will be interpreted as single addresses, which allows an address list to be copied with groups intact by using the list obtained from the groups attribute of the source header.

class email.headerregistry.SingleAddressHeader

A subclass of AddressHeader that adds one additional attribute:

address

The single address encoded by the header value. If the header value actually contains more than one address (which would be a violation of the RFC under the default policy), accessing this attribute will result in a ValueError.

Many of the above classes also have a Unique variant (for example, UniqueUnstructuredHeader). The only difference is that in the Unique variant, max_count is set to 1.

class email.headerregistry.MIMEVersionHeader

There is really only one valid value for the MIME-Version header, and that is 1.0. For future proofing, this header class supports other valid version numbers. If a version number has a valid value per RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html], then the header object will have non-None values for the following attributes:

version

The version number as a string, with any whitespace and/or comments removed.

major

The major version number as an integer

minor

The minor version number as an integer

class email.headerregistry.ParameterizedMIMEHeader

MIME headers all start with the prefix 'Content-'. Each specific header has a certain value, described under the class for that header. Some can also take a list of supplemental parameters, which have a common format. This class serves as a base for all the MIME headers that take parameters.

params

A dictionary mapping parameter names to parameter values.

class email.headerregistry.ContentTypeHeader

A ParameterizedMIMEHeader class that handles the Content-Type header.

content_type

The content type string, in the form maintype/subtype.

maintype

subtype

class email.headerregistry.ContentDispositionHeader

A ParameterizedMIMEHeader class that handles the Content-Disposition header.

content_disposition

inline and attachment are the only valid values in common use.

class email.headerregistry.ContentTransferEncodingHeader

Handles the Content-Transfer-Encoding header.

cte

Valid values are 7bit, 8bit, base64, and quoted-printable. See RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] for more information.

class email.headerregistry.HeaderRegistry(base_class=BaseHeader, default_class=UnstructuredHeader, use_default_map=True)

This is the factory used by EmailPolicy by default. HeaderRegistry builds the class used to create a header instance dynamically, using base_class and a specialized class retrieved from a registry that it holds. When a given header name does not appear in the registry, the class specified by default_class is used as the specialized class. When use_default_map is True (the default), the standard mapping of header names to classes is copied in to the registry during initialization. base_class is always the last class in the generated class's __bases__ list.

The default mappings are:

subject:

UniqueUnstructuredHeader

date:

UniqueDateHeader

resent-date:

DateHeader

orig-date:

UniqueDateHeader

sender:

UniqueSingleAddressHeader

resent-sender:

SingleAddressHeader

to:

UniqueAddressHeader

resent-to:

AddressHeader

cc:

UniqueAddressHeader

resent-cc:

AddressHeader

bcc:

UniqueAddressHeader

resent-bcc:

AddressHeader

from:

UniqueAddressHeader

resent-from:

AddressHeader

reply-to:

UniqueAddressHeader

mime-version:

MIMEVersionHeader

content-type:

ContentTypeHeader

content-disposition:

ContentDispositionHeader

content-transfer-encoding:

ContentTransferEncodingHeader

message-id:

MessageIDHeader

HeaderRegistry 有以下方法：

map_to_type(self, name, cls)

name is the name of the header to be mapped. It will be converted to lower case in the registry. cls is the specialized class to be used, along with base_class, to create the class used to instantiate headers that match name.

__getitem__(name)

Construct and return a class to handle creating a name header.

__call__(name, value)

Retrieves the specialized header associated with name from the registry (using default_class if name does not appear in the registry) and composes it with base_class to produce a class, calls the constructed class's constructor, passing it the same argument list, and finally returns the class instance created thereby.

The following classes are the classes used to represent data parsed from structured headers and can, in general, be used by an application program to construct structured values to assign to specific headers.

class email.headerregistry.Address(display_name='', username='', domain='', addr_spec=None)

The class used to represent an email address. The general form of an address is:

[display_name] <username@domain>

或是：

username@domain

where each part must conform to specific syntax rules spelled out in RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html].

As a convenience addr_spec can be specified instead of username and domain, in which case username and domain will be parsed from the addr_spec. An addr_spec must be a properly RFC quoted string; if it is not Address will raise an error. Unicode characters are allowed and will be property encoded when serialized. However, per the RFCs, unicode is not allowed in the username portion of the address.

display_name

The display name portion of the address, if any, with all quoting removed. If the address does not have a display name, this attribute will be an empty string.

username

The username portion of the address, with all quoting removed.

domain

The domain portion of the address.

addr_spec

The username@domain portion of the address, correctly quoted for use as a bare address (the second form shown above). This attribute is not mutable.

__str__()

The str value of the object is the address quoted according to RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] rules, but with no Content Transfer Encoding of any non-ASCII characters.

To support SMTP (RFC 5321 [https://datatracker.ietf.org/doc/html/rfc5321.html]), Address handles one special case: if username and domain are both the empty string (or None), then the string value of the Address is <>.

class email.headerregistry.Group(display_name=None, addresses=None)

The class used to represent an address group. The general form of an address group is:

display_name: [address-list];

As a convenience for processing lists of addresses that consist of a mixture of groups and single addresses, a Group may also be used to represent single addresses that are not part of a group by setting display_name to None and providing a list of the single address as addresses.

display_name

The display_name of the group. If it is None and there is exactly one Address in addresses, then the Group represents a single address that is not in a group.

addresses

A possibly empty tuple of Address objects representing the addresses in the group.

__str__()

The str value of a Group is formatted according to RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html], but with no Content Transfer Encoding of any non-ASCII characters. If display_name is none and there is a single Address in the addresses list, the str value will be the same as the str of that single Address.

註解

[1]

Originally added in 3.3 as a provisional module

email.contentmanager：管理 MIME 內容

原始碼：Lib/email/contentmanager.py [https://github.com/python/cpython/tree/3.14/Lib/email/contentmanager.py]

在 3.6 版被加入: [1]

class email.contentmanager.ContentManager

Base class for content managers. Provides the standard registry mechanisms to register converters between MIME content and other representations, as well as the get_content and set_content dispatch methods.

get_content(msg, *args, **kw)

Look up a handler function based on the mimetype of msg (see next paragraph), call it, passing through all arguments, and return the result of the call. The expectation is that the handler will extract the payload from msg and return an object that encodes information about the extracted data.

To find the handler, look for the following keys in the registry, stopping with the first one found:

the string representing the full MIME type (maintype/subtype)

the string representing the maintype

the empty string

If none of these keys produce a handler, raise a KeyError for the full MIME type.

set_content(msg, obj, *args, **kw)

If the maintype is multipart, raise a TypeError; otherwise look up a handler function based on the type of obj (see next paragraph), call clear_content() on the msg, and call the handler function, passing through all arguments. The expectation is that the handler will transform and store obj into msg, possibly making other changes to msg as well, such as adding various MIME headers to encode information needed to interpret the stored data.

To find the handler, obtain the type of obj (typ = type(obj)), and look for the following keys in the registry, stopping with the first one found:

the type itself (typ)

the type's fully qualified name (typ.__module__ + '.' + typ.__qualname__).

the type's qualname (typ.__qualname__)

the type's name (typ.__name__).

If none of the above match, repeat all of the checks above for each of the types in the MRO (typ.__mro__). Finally, if no other key yields a handler, check for a handler for the key None. If there is no handler for None, raise a KeyError for the fully qualified name of the type.

Also add a MIME-Version header if one is not present (see also MIMEPart).

add_get_handler(key, handler)

Record the function handler as the handler for key. For the possible values of key, see get_content().

add_set_handler(typekey, handler)

Record handler as the function to call when an object of a type matching typekey is passed to set_content(). For the possible values of typekey, see set_content().

Content Manager Instances

Currently the email package provides only one concrete content manager, raw_data_manager, although more may be added in the future. raw_data_manager is the content_manager provided by EmailPolicy and its derivatives.

email.contentmanager.raw_data_manager

This content manager provides only a minimum interface beyond that provided by Message itself: it deals only with text, raw byte strings, and Message objects. Nevertheless, it provides significant advantages compared to the base API: get_content on a text part will return a unicode string without the application needing to manually decode it, set_content provides a rich set of options for controlling the headers added to a part and controlling the content transfer encoding, and it enables the use of the various add_ methods, thereby simplifying the creation of multipart messages.

email.contentmanager.get_content(msg, errors='replace')

Return the payload of the part as either a string (for text parts), an EmailMessage object (for message/rfc822 parts), or a bytes object (for all other non-multipart types). Raise a KeyError if called on a multipart. If the part is a text part and errors is specified, use it as the error handler when decoding the payload to unicode. The default error handler is replace.

email.contentmanager.set_content(msg, <'str'>, subtype="plain", charset='utf-8', cte=None, disposition=None, filename=None, cid=None, params=None, headers=None)

email.contentmanager.set_content(msg, <'bytes'>, maintype, subtype, cte="base64", disposition=None, filename=None, cid=None, params=None, headers=None)

email.contentmanager.set_content(msg, <'EmailMessage'>, cte=None, disposition=None, filename=None, cid=None, params=None, headers=None)

Add headers and payload to msg:

Add a Content-Type header with a maintype/subtype value.

For str, set the MIME maintype to text, and set the subtype to subtype if it is specified, or plain if it is not.

For bytes, use the specified maintype and subtype, or raise a TypeError if they are not specified.

For EmailMessage objects, set the maintype to message, and set the subtype to subtype if it is specified or rfc822 if it is not. If subtype is partial, raise an error (bytes objects must be used to construct message/partial parts).

If charset is provided (which is valid only for str), encode the string to bytes using the specified character set. The default is utf-8. If the specified charset is a known alias for a standard MIME charset name, use the standard charset instead.

If cte is set, encode the payload using the specified content transfer encoding, and set the Content-Transfer-Encoding header to that value. Possible values for cte are quoted-printable, base64, 7bit, 8bit, and binary. If the input cannot be encoded in the specified encoding (for example, specifying a cte of 7bit for an input that contains non-ASCII values), raise a ValueError.

For str objects, if cte is not set use heuristics to determine the most compact encoding. Prior to encoding, str.splitlines() is used to normalize all line boundaries, ensuring that each line of the payload is terminated by the current policy's linesep property (even if the original string did not end with one).

For bytes objects, cte is taken to be base64 if not set, and the aforementioned newline translation is not performed.

For EmailMessage, per RFC 2046 [https://datatracker.ietf.org/doc/html/rfc2046.html], raise an error if a cte of quoted-printable or base64 is requested for subtype rfc822, and for any cte other than 7bit for subtype external-body. For message/rfc822, use 8bit if cte is not specified. For all other values of subtype, use 7bit.

備註

A cte of binary does not actually work correctly yet. The EmailMessage object as modified by set_content is correct, but BytesGenerator does not serialize it correctly.

If disposition is set, use it as the value of the Content-Disposition header. If not specified, and filename is specified, add the header with the value attachment. If disposition is not specified and filename is also not specified, do not add the header. The only valid values for disposition are attachment and inline.

If filename is specified, use it as the value of the filename parameter of the Content-Disposition header.

If cid is specified, add a Content-ID header with cid as its value.

If params is specified, iterate its items method and use the resulting (key, value) pairs to set additional parameters on the Content-Type header.

If headers is specified and is a list of strings of the form headername: headervalue or a list of header objects (distinguished from strings by having a name attribute), add the headers to msg.

註解

[1]

Originally added in 3.4 as a provisional module

email：範例

Here are a few examples of how to use the email package to read, write, and send simple email messages, as well as more complex MIME messages.

First, let's see how to create and send a simple text message (both the text content and the addresses may contain unicode characters):

# Import smtplib for the actual sending function
import smtplib

# Import the email modules we'll need
from email.message import EmailMessage

# Open the plain text file whose name is in textfile for reading.
with open(textfile) as fp:
    # Create a text/plain message
    msg = EmailMessage()
    msg.set_content(fp.read())

# me == the sender's email address
# you == the recipient's email address
msg['Subject'] = f'The contents of {textfile}'
msg['From'] = me
msg['To'] = you

# Send the message via our own SMTP server.
s = smtplib.SMTP('localhost')
s.send_message(msg)
s.quit()

Parsing RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] headers can easily be done by the using the classes from the parser module:

# Import the email modules we'll need
#from email.parser import BytesParser
from email.parser import Parser
from email.policy import default

# If the e-mail headers are in a file, uncomment these two lines:
# with open(messagefile, 'rb') as fp:
#     headers = BytesParser(policy=default).parse(fp)

#  Or for parsing headers in a string (this is an uncommon operation), use:
headers = Parser(policy=default).parsestr(
        'From: Foo Bar <user@example.com>\n'
        'To: <someone_else@example.com>\n'
        'Subject: Test message\n'
        '\n'
        'Body would go here\n')

#  Now the header items can be accessed as a dictionary:
print('To: {}'.format(headers['to']))
print('From: {}'.format(headers['from']))
print('Subject: {}'.format(headers['subject']))

# You can also access the parts of the addresses:
print('Recipient username: {}'.format(headers['to'].addresses[0].username))
print('Sender name: {}'.format(headers['from'].addresses[0].display_name))

Here's an example of how to send a MIME message containing a bunch of family pictures that may be residing in a directory:

# Import smtplib for the actual sending function.
import smtplib

# Here are the email package modules we'll need.
from email.message import EmailMessage

# Create the container email message.
msg = EmailMessage()
msg['Subject'] = 'Our family reunion'
# me == the sender's email address
# family = the list of all recipients' email addresses
msg['From'] = me
msg['To'] = ', '.join(family)
msg.preamble = 'You will not see this in a MIME-aware mail reader.\n'

# Open the files in binary mode.  You can also omit the subtype
# if you want MIMEImage to guess it.
for file in pngfiles:
    with open(file, 'rb') as fp:
        img_data = fp.read()
    msg.add_attachment(img_data, maintype='image',
                                 subtype='png')

# Send the email via our own SMTP server.
with smtplib.SMTP('localhost') as s:
    s.send_message(msg)

Here's an example of how to send the entire contents of a directory as an email message: [1]

#!/usr/bin/env python3

"""Send the contents of a directory as a MIME message."""

import os
import smtplib
# For guessing MIME type based on file name extension
import mimetypes

from argparse import ArgumentParser

from email.message import EmailMessage
from email.policy import SMTP

def main():
    parser = ArgumentParser(description="""\
Send the contents of a directory as a MIME message.
Unless the -o option is given, the email is sent by forwarding to your local
SMTP server, which then does the normal delivery process.  Your local machine
must be running an SMTP server.
""")
    parser.add_argument('-d', '--directory',
                        help="""Mail the contents of the specified directory,
                        otherwise use the current directory.  Only the regular
                        files in the directory are sent, and we don't recurse to
                        subdirectories.""")
    parser.add_argument('-o', '--output',
                        metavar='FILE',
                        help="""Print the composed message to FILE instead of
                        sending the message to the SMTP server.""")
    parser.add_argument('-s', '--sender', required=True,
                        help='The value of the From: header (required)')
    parser.add_argument('-r', '--recipient', required=True,
                        action='append', metavar='RECIPIENT',
                        default=[], dest='recipients',
                        help='A To: header value (at least one required)')
    args = parser.parse_args()
    directory = args.directory
    if not directory:
        directory = '.'
    # Create the message
    msg = EmailMessage()
    msg['Subject'] = f'Contents of directory {os.path.abspath(directory)}'
    msg['To'] = ', '.join(args.recipients)
    msg['From'] = args.sender
    msg.preamble = 'You will not see this in a MIME-aware mail reader.\n'

    for filename in os.listdir(directory):
        path = os.path.join(directory, filename)
        if not os.path.isfile(path):
            continue
        # Guess the content type based on the file's extension.  Encoding
        # will be ignored, although we should check for simple things like
        # gzip'd or compressed files.
        ctype, encoding = mimetypes.guess_file_type(path)
        if ctype is None or encoding is not None:
            # No guess could be made, or the file is encoded (compressed), so
            # use a generic bag-of-bits type.
            ctype = 'application/octet-stream'
        maintype, subtype = ctype.split('/', 1)
        with open(path, 'rb') as fp:
            msg.add_attachment(fp.read(),
                               maintype=maintype,
                               subtype=subtype,
                               filename=filename)
    # Now send or store the message
    if args.output:
        with open(args.output, 'wb') as fp:
            fp.write(msg.as_bytes(policy=SMTP))
    else:
        with smtplib.SMTP('localhost') as s:
            s.send_message(msg)

if __name__ == '__main__':
    main()

Here's an example of how to unpack a MIME message like the one above, into a directory of files:

#!/usr/bin/env python3

"""Unpack a MIME message into a directory of files."""

import os
import email
import mimetypes

from email.policy import default

from argparse import ArgumentParser

def main():
    parser = ArgumentParser(description="""\
Unpack a MIME message into a directory of files.
""")
    parser.add_argument('-d', '--directory', required=True,
                        help="""Unpack the MIME message into the named
                        directory, which will be created if it doesn't already
                        exist.""")
    parser.add_argument('msgfile')
    args = parser.parse_args()

    with open(args.msgfile, 'rb') as fp:
        msg = email.message_from_binary_file(fp, policy=default)

    try:
        os.mkdir(args.directory)
    except FileExistsError:
        pass

    counter = 1
    for part in msg.walk():
        # multipart/* are just containers
        if part.get_content_maintype() == 'multipart':
            continue
        # Applications should really sanitize the given filename so that an
        # email message can't be used to overwrite important files
        filename = part.get_filename()
        if not filename:
            ext = mimetypes.guess_extension(part.get_content_type())
            if not ext:
                # Use a generic bag-of-bits extension
                ext = '.bin'
            filename = f'part-{counter:03d}{ext}'
        counter += 1
        with open(os.path.join(args.directory, filename), 'wb') as fp:
            fp.write(part.get_payload(decode=True))

if __name__ == '__main__':
    main()

Here's an example of how to create an HTML message with an alternative plain text version. To make things a bit more interesting, we include a related image in the html part, and we save a copy of what we are going to send to disk, as well as sending it.

#!/usr/bin/env python3

import smtplib

from email.message import EmailMessage
from email.headerregistry import Address
from email.utils import make_msgid

# Create the base text message.
msg = EmailMessage()
msg['Subject'] = "Pourquoi pas des asperges pour ce midi ?"
msg['From'] = Address("Pepé Le Pew", "pepe", "example.com")
msg['To'] = (Address("Penelope Pussycat", "penelope", "example.com"),
             Address("Fabrette Pussycat", "fabrette", "example.com"))
msg.set_content("""\
Salut!

Cette recette [1] sera sûrement un très bon repas.

[1] http://www.yummly.com/recipe/Roasted-Asparagus-Epicurious-203718

--Pepé
""")

# Add the html version.  This converts the message into a multipart/alternative
# container, with the original text message as the first part and the new html
# message as the second part.
asparagus_cid = make_msgid()
msg.add_alternative("""\
<html>
  <head></head>
  <body>
    <p>Salut!</p>
    <p>Cette
        <a href="http://www.yummly.com/recipe/Roasted-Asparagus-Epicurious-203718">
            recette
        </a> sera sûrement un très bon repas.
    </p>
    <img src="cid:{asparagus_cid}">
  </body>
</html>
""".format(asparagus_cid=asparagus_cid[1:-1]), subtype='html')
# note that we needed to peel the <> off the msgid for use in the html.

# Now add the related image to the html part.
with open("roasted-asparagus.jpg", 'rb') as img:
    msg.get_payload()[1].add_related(img.read(), 'image', 'jpeg',
                                     cid=asparagus_cid)

# Make a local copy of what we are going to send.
with open('outgoing.msg', 'wb') as f:
    f.write(bytes(msg))

# Send the message via local SMTP server.
with smtplib.SMTP('localhost') as s:
    s.send_message(msg)

If we were sent the message from the last example, here is one way we could process it:

import os
import sys
import tempfile
import mimetypes
import webbrowser

# Import the email modules we'll need
from email import policy
from email.parser import BytesParser

def magic_html_parser(html_text, partfiles):
    """Return safety-sanitized html linked to partfiles.

    Rewrite the href="cid:...." attributes to point to the filenames in partfiles.
    Though not trivial, this should be possible using html.parser.
    """
    raise NotImplementedError("Add the magic needed")

# In a real program you'd get the filename from the arguments.
with open('outgoing.msg', 'rb') as fp:
    msg = BytesParser(policy=policy.default).parse(fp)

# Now the header items can be accessed as a dictionary, and any non-ASCII will
# be converted to unicode:
print('To:', msg['to'])
print('From:', msg['from'])
print('Subject:', msg['subject'])

# If we want to print a preview of the message content, we can extract whatever
# the least formatted payload is and print the first three lines.  Of course,
# if the message has no plain text part printing the first three lines of html
# is probably useless, but this is just a conceptual example.
simplest = msg.get_body(preferencelist=('plain', 'html'))
print()
print(''.join(simplest.get_content().splitlines(keepends=True)[:3]))

ans = input("View full message?")
if ans.lower()[0] == 'n':
    sys.exit()

# We can extract the richest alternative in order to display it:
richest = msg.get_body()
partfiles = {}
if richest['content-type'].maintype == 'text':
    if richest['content-type'].subtype == 'plain':
        for line in richest.get_content().splitlines():
            print(line)
        sys.exit()
    elif richest['content-type'].subtype == 'html':
        body = richest
    else:
        print("Don't know how to display {}".format(richest.get_content_type()))
        sys.exit()
elif richest['content-type'].content_type == 'multipart/related':
    body = richest.get_body(preferencelist=('html'))
    for part in richest.iter_attachments():
        fn = part.get_filename()
        if fn:
            extension = os.path.splitext(part.get_filename())[1]
        else:
            extension = mimetypes.guess_extension(part.get_content_type())
        with tempfile.NamedTemporaryFile(suffix=extension, delete=False) as f:
            f.write(part.get_content())
            # again strip the <> to go from email form of cid to html form.
            partfiles[part['content-id'][1:-1]] = f.name
else:
    print("Don't know how to display {}".format(richest.get_content_type()))
    sys.exit()
with tempfile.NamedTemporaryFile(mode='w', delete=False) as f:
    f.write(magic_html_parser(body.get_content(), partfiles))
webbrowser.open(f.name)
os.remove(f.name)
for fn in partfiles.values():
    os.remove(fn)

# Of course, there are lots of email messages that could break this simple
# minded program, but it will handle the most common ones.

Up to the prompt, the output from the above is:

To: Penelope Pussycat <penelope@example.com>, Fabrette Pussycat <fabrette@example.com>
From: Pepé Le Pew <pepe@example.com>
Subject: Pourquoi pas des asperges pour ce midi ?

Salut!

Cette recette [1] sera sûrement un très bon repas.

註解

[1]

Thanks to Matthew Dixon Cowles for the original inspiration and examples.

email.message.Message: Representing an email message using the compat32 API

The Message class is very similar to the EmailMessage class, without the methods added by that class, and with the default behavior of certain other methods being slightly different. We also document here some methods that, while supported by the EmailMessage class, are not recommended unless you are dealing with legacy code.

The philosophy and structure of the two classes is otherwise the same.

This document describes the behavior under the default (for Message) policy Compat32. If you are going to use another policy, you should be using the EmailMessage class instead.

An email message consists of headers and a payload. Headers must be RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] style names and values, where the field name and value are separated by a colon. The colon is not part of either the field name or the field value. The payload may be a simple text message, or a binary object, or a structured sequence of sub-messages each with their own set of headers and their own payload. The latter type of payload is indicated by the message having a MIME type such as multipart/* or message/rfc822.

The conceptual model provided by a Message object is that of an ordered dictionary of headers with additional methods for accessing both specialized information from the headers, for accessing the payload, for generating a serialized version of the message, and for recursively walking over the object tree. Note that duplicate headers are supported but special methods must be used to access them.

The Message pseudo-dictionary is indexed by the header names, which must be ASCII values. The values of the dictionary are strings that are supposed to contain only ASCII characters; there is some special handling for non-ASCII input, but it doesn't always produce the correct results. Headers are stored and returned in case-preserving form, but field names are matched case-insensitively. There may also be a single envelope header, also known as the Unix-From header or the From_ header. The payload is either a string or bytes, in the case of simple message objects, or a list of Message objects, for MIME container documents (e.g. multipart/* and message/rfc822).

Here are the methods of the Message class:

class email.message.Message(policy=compat32)

If policy is specified (it must be an instance of a policy class) use the rules it specifies to update and serialize the representation of the message. If policy is not set, use the compat32 policy, which maintains backward compatibility with the Python 3.2 version of the email package. For more information see the policy documentation.

在 3.3 版的變更: 新增 policy 關鍵字引數。

as_string(unixfrom=False, maxheaderlen=0, policy=None)

Return the entire message flattened as a string. When optional unixfrom is true, the envelope header is included in the returned string. unixfrom defaults to False. For backward compatibility reasons, maxheaderlen defaults to 0, so if you want a different value you must override it explicitly (the value specified for max_line_length in the policy will be ignored by this method). The policy argument may be used to override the default policy obtained from the message instance. This can be used to control some of the formatting produced by the method, since the specified policy will be passed to the Generator.

Flattening the message may trigger changes to the Message if defaults need to be filled in to complete the transformation to a string (for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not always format the message the way you want. For example, by default it does not do the mangling of lines that begin with From that is required by the Unix mbox format. For more flexibility, instantiate a Generator instance and use its flatten() method directly. For example:

from io import StringIO
from email.generator import Generator
fp = StringIO()
g = Generator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()

If the message object contains binary data that is not encoded according to RFC standards, the non-compliant data will be replaced by unicode "unknown character" code points. (See also as_bytes() and BytesGenerator.)

在 3.4 版的變更: 新增 policy 關鍵字引數。

__str__()

Equivalent to as_string(). Allows str(msg) to produce a string containing the formatted message.

as_bytes(unixfrom=False, policy=None)

Return the entire message flattened as a bytes object. When optional unixfrom is true, the envelope header is included in the returned string. unixfrom defaults to False. The policy argument may be used to override the default policy obtained from the message instance. This can be used to control some of the formatting produced by the method, since the specified policy will be passed to the BytesGenerator.

Flattening the message may trigger changes to the Message if defaults need to be filled in to complete the transformation to a string (for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not always format the message the way you want. For example, by default it does not do the mangling of lines that begin with From that is required by the Unix mbox format. For more flexibility, instantiate a BytesGenerator instance and use its flatten() method directly. For example:

from io import BytesIO
from email.generator import BytesGenerator
fp = BytesIO()
g = BytesGenerator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()

在 3.4 版被加入.

__bytes__()

Equivalent to as_bytes(). Allows bytes(msg) to produce a bytes object containing the formatted message.

在 3.4 版被加入.

is_multipart()

Return True if the message's payload is a list of sub-Message objects, otherwise return False. When is_multipart() returns False, the payload should be a string object (which might be a CTE encoded binary payload). (Note that is_multipart() returning True does not necessarily mean that "msg.get_content_maintype() == 'multipart'" will return the True. For example, is_multipart will return True when the Message is of type message/rfc822.)

set_unixfrom(unixfrom)

Set the message's envelope header to unixfrom, which should be a string.

get_unixfrom()

Return the message's envelope header. Defaults to None if the envelope header was never set.

attach(payload)

Add the given payload to the current payload, which must be None or a list of Message objects before the call. After the call, the payload will always be a list of Message objects. If you want to set the payload to a scalar object (e.g. a string), use set_payload() instead.

This is a legacy method. On the EmailMessage class its functionality is replaced by set_content() and the related make and add methods.

get_payload(i=None, decode=False)

Return the current payload, which will be a list of Message objects when is_multipart() is True, or a string when is_multipart() is False. If the payload is a list and you mutate the list object, you modify the message's payload in place.

With optional argument i, get_payload() will return the i-th element of the payload, counting from zero, if is_multipart() is True. An IndexError will be raised if i is less than 0 or greater than or equal to the number of items in the payload. If the payload is a string (i.e. is_multipart() is False) and i is given, a TypeError is raised.

Optional decode is a flag indicating whether the payload should be decoded or not, according to the Content-Transfer-Encoding header. When True and the message is not a multipart, the payload will be decoded if this header's value is quoted-printable or base64. If some other encoding is used, or Content-Transfer-Encoding header is missing, the payload is returned as-is (undecoded). In all cases the returned value is binary data. If the message is a multipart and the decode flag is True, then None is returned. If the payload is base64 and it was not perfectly formed (missing padding, characters outside the base64 alphabet), then an appropriate defect will be added to the message's defect property (InvalidBase64PaddingDefect or InvalidBase64CharactersDefect, respectively).

When decode is False (the default) the body is returned as a string without decoding the Content-Transfer-Encoding. However, for a Content-Transfer-Encoding of 8bit, an attempt is made to decode the original bytes using the charset specified by the Content-Type header, using the replace error handler. If no charset is specified, or if the charset given is not recognized by the email package, the body is decoded using the default ASCII charset.

This is a legacy method. On the EmailMessage class its functionality is replaced by get_content() and iter_parts().

set_payload(payload, charset=None)

Set the entire message object's payload to payload. It is the client's responsibility to ensure the payload invariants. Optional charset sets the message's default character set; see set_charset() for details.

This is a legacy method. On the EmailMessage class its functionality is replaced by set_content().

set_charset(charset)

Set the character set of the payload to charset, which can either be a Charset instance (see email.charset), a string naming a character set, or None. If it is a string, it will be converted to a Charset instance. If charset is None, the charset parameter will be removed from the Content-Type header (the message will not be otherwise modified). Anything else will generate a TypeError.

If there is no existing MIME-Version header one will be added. If there is no existing Content-Type header, one will be added with a value of text/plain. Whether the Content-Type header already exists or not, its charset parameter will be set to charset.output_charset. If charset.input_charset and charset.output_charset differ, the payload will be re-encoded to the output_charset. If there is no existing Content-Transfer-Encoding header, then the payload will be transfer-encoded, if needed, using the specified Charset, and a header with the appropriate value will be added. If a Content-Transfer-Encoding header already exists, the payload is assumed to already be correctly encoded using that Content-Transfer-Encoding and is not modified.

This is a legacy method. On the EmailMessage class its functionality is replaced by the charset parameter of the email.message.EmailMessage.set_content() method.

get_charset()

Return the Charset instance associated with the message's payload.

This is a legacy method. On the EmailMessage class it always returns None.

The following methods implement a mapping-like interface for accessing the message's RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html] headers. Note that there are some semantic differences between these methods and a normal mapping (i.e. dictionary) interface. For example, in a dictionary there are no duplicate keys, but here there may be duplicate message headers. Also, in dictionaries there is no guaranteed order to the keys returned by keys(), but in a Message object, headers are always returned in the order they appeared in the original message, or were added to the message later. Any header deleted and then re-added are always appended to the end of the header list.

These semantic differences are intentional and are biased toward maximal convenience.

Note that in all cases, any envelope header present in the message is not included in the mapping interface.

In a model generated from bytes, any header values that (in contravention of the RFCs) contain non-ASCII bytes will, when retrieved through this interface, be represented as Header objects with a charset of unknown-8bit.

__len__()

Return the total number of headers, including duplicates.

__contains__(name)

Return True if the message object has a field named name. Matching is done case-insensitively and name should not include the trailing colon. Used for the in operator, e.g.:

if 'message-id' in myMessage:
   print('Message-ID:', myMessage['message-id'])

__getitem__(name)

Return the value of the named header field. name should not include the colon field separator. If the header is missing, None is returned; a KeyError is never raised.

Note that if the named field appears more than once in the message's headers, exactly which of those field values will be returned is undefined. Use the get_all() method to get the values of all the extant named headers.

__setitem__(name, val)

Add a header to the message with field name name and value val. The field is appended to the end of the message's existing fields.

Note that this does not overwrite or delete any existing header with the same name. If you want to ensure that the new header is the only one present in the message with field name name, delete the field first, e.g.:

del msg['subject']
msg['subject'] = 'Python roolz!'

__delitem__(name)

Delete all occurrences of the field with name name from the message's headers. No exception is raised if the named field isn't present in the headers.

keys()

Return a list of all the message's header field names.

values()

Return a list of all the message's field values.

items()

Return a list of 2-tuples containing all the message's field headers and values.

get(name, failobj=None)

Return the value of the named header field. This is identical to __getitem__() except that optional failobj is returned if the named header is missing (defaults to None).

Here are some additional useful methods:

get_all(name, failobj=None)

Return a list of all the values for the field named name. If there are no such named headers in the message, failobj is returned (defaults to None).

add_header(_name, _value, **_params)

Extended header setting. This method is similar to __setitem__() except that additional header parameters can be provided as keyword arguments. _name is the header field to add and _value is the primary value for the header.

For each item in the keyword argument dictionary _params, the key is taken as the parameter name, with underscores converted to dashes (since dashes are illegal in Python identifiers). Normally, the parameter will be added as key="value" unless the value is None, in which case only the key will be added. If the value contains non-ASCII characters, it can be specified as a three tuple in the format (CHARSET, LANGUAGE, VALUE), where CHARSET is a string naming the charset to be used to encode the value, LANGUAGE can usually be set to None or the empty string (see RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] for other possibilities), and VALUE is the string value containing non-ASCII code points. If a three tuple is not passed and the value contains non-ASCII characters, it is automatically encoded in RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] format using a CHARSET of utf-8 and a LANGUAGE of None.

以下是個範例：

msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')

This will add a header that looks like

Content-Disposition: attachment; filename="bud.gif"

An example with non-ASCII characters:

msg.add_header('Content-Disposition', 'attachment',
               filename=('iso-8859-1', '', 'Fußballer.ppt'))

Which produces

Content-Disposition: attachment; filename*="iso-8859-1''Fu%DFballer.ppt"

replace_header(_name, _value)

Replace a header. Replace the first header found in the message that matches _name, retaining header order and field name case. If no matching header was found, a KeyError is raised.

get_content_type()

Return the message's content type. The returned string is coerced to lower case of the form maintype/subtype. If there was no Content-Type header in the message the default type as given by get_default_type() will be returned. Since according to RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html], messages always have a default type, get_content_type() will always return a value.

RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] defines a message's default type to be text/plain unless it appears inside a multipart/digest container, in which case it would be message/rfc822. If the Content-Type header has an invalid type specification, RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] mandates that the default type be text/plain.

get_content_maintype()

Return the message's main content type. This is the maintype part of the string returned by get_content_type().

get_content_subtype()

Return the message's sub-content type. This is the subtype part of the string returned by get_content_type().

get_default_type()

Return the default content type. Most messages have a default content type of text/plain, except for messages that are subparts of multipart/digest containers. Such subparts have a default content type of message/rfc822.

set_default_type(ctype)

Set the default content type. ctype should either be text/plain or message/rfc822, although this is not enforced. The default content type is not stored in the Content-Type header.

get_params(failobj=None, header='content-type', unquote=True)

Return the message's Content-Type parameters, as a list. The elements of the returned list are 2-tuples of key/value pairs, as split on the '=' sign. The left hand side of the '=' is the key, while the right hand side is the value. If there is no '=' sign in the parameter the value is the empty string, otherwise the value is as described in get_param() and is unquoted if optional unquote is True (the default).

Optional failobj is the object to return if there is no Content-Type header. Optional header is the header to search instead of Content-Type.

This is a legacy method. On the EmailMessage class its functionality is replaced by the params property of the individual header objects returned by the header access methods.

get_param(param, failobj=None, header='content-type', unquote=True)

Return the value of the Content-Type header's parameter param as a string. If the message has no Content-Type header or if there is no such parameter, then failobj is returned (defaults to None).

Optional header if given, specifies the message header to use instead of Content-Type.

Parameter keys are always compared case insensitively. The return value can either be a string, or a 3-tuple if the parameter was RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] encoded. When it's a 3-tuple, the elements of the value are of the form (CHARSET, LANGUAGE, VALUE). Note that both CHARSET and LANGUAGE can be None, in which case you should consider VALUE to be encoded in the us-ascii charset. You can usually ignore LANGUAGE.

If your application doesn't care whether the parameter was encoded as in RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html], you can collapse the parameter value by calling email.utils.collapse_rfc2231_value(), passing in the return value from get_param(). This will return a suitably decoded Unicode string when the value is a tuple, or the original string unquoted if it isn't. For example:

rawparam = msg.get_param('foo')
param = email.utils.collapse_rfc2231_value(rawparam)

In any case, the parameter value (either the returned string, or the VALUE item in the 3-tuple) is always unquoted, unless unquote is set to False.

This is a legacy method. On the EmailMessage class its functionality is replaced by the params property of the individual header objects returned by the header access methods.

set_param(param, value, header='Content-Type', requote=True, charset=None, language='', replace=False)

Set a parameter in the Content-Type header. If the parameter already exists in the header, its value will be replaced with value. If the Content-Type header as not yet been defined for this message, it will be set to text/plain and the new parameter value will be appended as per RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html].

Optional header specifies an alternative header to Content-Type, and all parameters will be quoted as necessary unless optional requote is False (the default is True).

If optional charset is specified, the parameter will be encoded according to RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html]. Optional language specifies the RFC 2231 language, defaulting to the empty string. Both charset and language should be strings.

If replace is False (the default) the header is moved to the end of the list of headers. If replace is True, the header will be updated in place.

在 3.4 版的變更: 新增 replace 關鍵字。

del_param(param, header='content-type', requote=True)

Remove the given parameter completely from the Content-Type header. The header will be re-written in place without the parameter or its value. All values will be quoted as necessary unless requote is False (the default is True). Optional header specifies an alternative to Content-Type.

set_type(type, header='Content-Type', requote=True)

Set the main type and subtype for the Content-Type header. type must be a string in the form maintype/subtype, otherwise a ValueError is raised.

This method replaces the Content-Type header, keeping all the parameters in place. If requote is False, this leaves the existing header's quoting as is, otherwise the parameters will be quoted (the default).

An alternative header can be specified in the header argument. When the Content-Type header is set a MIME-Version header is also added.

This is a legacy method. On the EmailMessage class its functionality is replaced by the make_ and add_ methods.

get_filename(failobj=None)

Return the value of the filename parameter of the Content-Disposition header of the message. If the header does not have a filename parameter, this method falls back to looking for the name parameter on the Content-Type header. If neither is found, or the header is missing, then failobj is returned. The returned string will always be unquoted as per email.utils.unquote().

get_boundary(failobj=None)

Return the value of the boundary parameter of the Content-Type header of the message, or failobj if either the header is missing, or has no boundary parameter. The returned string will always be unquoted as per email.utils.unquote().

set_boundary(boundary)

Set the boundary parameter of the Content-Type header to boundary. set_boundary() will always quote boundary if necessary. A HeaderParseError is raised if the message object has no Content-Type header.

Note that using this method is subtly different than deleting the old Content-Type header and adding a new one with the new boundary via add_header(), because set_boundary() preserves the order of the Content-Type header in the list of headers. However, it does not preserve any continuation lines which may have been present in the original Content-Type header.

get_content_charset(failobj=None)

Return the charset parameter of the Content-Type header, coerced to lower case. If there is no Content-Type header, or if that header has no charset parameter, failobj is returned.

Note that this method differs from get_charset() which returns the Charset instance for the default encoding of the message body.

get_charsets(failobj=None)

Return a list containing the character set names in the message. If the message is a multipart, then the list will contain one element for each subpart in the payload, otherwise, it will be a list of length 1.

Each item in the list will be a string which is the value of the charset parameter in the Content-Type header for the represented subpart. However, if the subpart has no Content-Type header, no charset parameter, or is not of the text main MIME type, then that item in the returned list will be failobj.

get_content_disposition()

Return the lowercased value (without parameters) of the message's Content-Disposition header if it has one, or None. The possible values for this method are inline, attachment or None if the message follows RFC 2183 [https://datatracker.ietf.org/doc/html/rfc2183.html].

在 3.5 版被加入.

walk()

The walk() method is an all-purpose generator which can be used to iterate over all the parts and subparts of a message object tree, in depth-first traversal order. You will typically use walk() as the iterator in a for loop; each iteration returns the next subpart.

Here's an example that prints the MIME type of every part of a multipart message structure:

>>> for part in msg.walk():
...     print(part.get_content_type())
multipart/report
text/plain
message/delivery-status
text/plain
text/plain
message/rfc822
text/plain

walk iterates over the subparts of any part where is_multipart() returns True, even though msg.get_content_maintype() == 'multipart' may return False. We can see this in our example by making use of the _structure debug helper function:

>>> for part in msg.walk():
...     print(part.get_content_maintype() == 'multipart',
...           part.is_multipart())
True True
False False
False True
False False
False False
False True
False False
>>> _structure(msg)
multipart/report
    text/plain
    message/delivery-status
        text/plain
        text/plain
    message/rfc822
        text/plain

Here the message parts are not multiparts, but they do contain subparts. is_multipart() returns True and walk descends into the subparts.

Message objects can also optionally contain two instance attributes, which can be used when generating the plain text of a MIME message.

preamble

The format of a MIME document allows for some text between the blank line following the headers, and the first multipart boundary string. Normally, this text is never visible in a MIME-aware mail reader because it falls outside the standard MIME armor. However, when viewing the raw text of the message, or when viewing the message in a non-MIME aware reader, this text can become visible.

The preamble attribute contains this leading extra-armor text for MIME documents. When the Parser discovers some text after the headers but before the first boundary string, it assigns this text to the message's preamble attribute. When the Generator is writing out the plain text representation of a MIME message, and it finds the message has a preamble attribute, it will write this text in the area between the headers and the first boundary. See email.parser and email.generator for details.

Note that if the message object has no preamble, the preamble attribute will be None.

epilogue

The epilogue attribute acts the same way as the preamble attribute, except that it contains text that appears between the last boundary and the end of the message.

You do not need to set the epilogue to the empty string in order for the Generator to print a newline at the end of the file.

defects

The defects attribute contains a list of all the problems found when parsing this message. See email.errors for a detailed description of the possible parsing defects.

email.mime：從頭開始建立電子郵件和 MIME 物件

原始碼：Lib/email/mime/ [https://github.com/python/cpython/tree/3.14/Lib/email/mime/]

This module is part of the legacy (Compat32) email API. Its functionality is partially replaced by the contentmanager in the new API, but in certain applications these classes may still be useful, even in non-legacy code.

Ordinarily, you get a message object structure by passing a file or some text to a parser, which parses the text and returns the root message object. However you can also build a complete message structure from scratch, or even individual Message objects by hand. In fact, you can also take an existing structure and add new Message objects, move them around, etc. This makes a very convenient interface for slicing-and-dicing MIME messages.

You can create a new object structure by creating Message instances, adding attachments and all the appropriate headers manually. For MIME messages though, the email package provides some convenient subclasses to make things easier.

Here are the classes:

class email.mime.base.MIMEBase(_maintype, _subtype, *, policy=compat32, **_params)

模組：email.mime.base

This is the base class for all the MIME-specific subclasses of Message. Ordinarily you won't create instances specifically of MIMEBase, although you could. MIMEBase is provided primarily as a convenient base class for more specific MIME-aware subclasses.

_maintype is the Content-Type major type (e.g. text or image), and _subtype is the Content-Type minor type (e.g. plain or gif). _params is a parameter key/value dictionary and is passed directly to Message.add_header.

If policy is specified, (defaults to the compat32 policy) it will be passed to Message.

The MIMEBase class always adds a Content-Type header (based on _maintype, _subtype, and _params), and a MIME-Version header (always set to 1.0).

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

class email.mime.nonmultipart.MIMENonMultipart

模組：email.mime.nonmultipart

A subclass of MIMEBase, this is an intermediate base class for MIME messages that are not multipart. The primary purpose of this class is to prevent the use of the attach() method, which only makes sense for multipart messages. If attach() is called, a MultipartConversionError exception is raised.

class email.mime.multipart.MIMEMultipart(_subtype='mixed', boundary=None, _subparts=None, *, policy=compat32, **_params)

模組：email.mime.multipart

A subclass of MIMEBase, this is an intermediate base class for MIME messages that are multipart. Optional _subtype defaults to mixed, but can be used to specify the subtype of the message. A Content-Type header of multipart/_subtype will be added to the message object. A MIME-Version header will also be added.

Optional boundary is the multipart boundary string. When None (the default), the boundary is calculated when needed (for example, when the message is serialized).

_subparts is a sequence of initial subparts for the payload. It must be possible to convert this sequence to a list. You can always attach new subparts to the message by using the Message.attach method.

Optional policy argument defaults to compat32.

Additional parameters for the Content-Type header are taken from the keyword arguments, or passed into the _params argument, which is a keyword dictionary.

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

class email.mime.application.MIMEApplication(_data, _subtype='octet-stream', _encoder=email.encoders.encode_base64, *, policy=compat32, **_params)

模組：email.mime.application

A subclass of MIMENonMultipart, the MIMEApplication class is used to represent MIME message objects of major type application. _data contains the bytes for the raw application data. Optional _subtype specifies the MIME subtype and defaults to octet-stream.

Optional _encoder is a callable (i.e. function) which will perform the actual encoding of the data for transport. This callable takes one argument, which is the MIMEApplication instance. It should use get_payload() and set_payload() to change the payload to encoded form. It should also add any Content-Transfer-Encoding or other headers to the message object as necessary. The default encoding is base64. See the email.encoders module for a list of the built-in encoders.

Optional policy argument defaults to compat32.

_params are passed straight through to the base class constructor.

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

class email.mime.audio.MIMEAudio(_audiodata, _subtype=None, _encoder=email.encoders.encode_base64, *, policy=compat32, **_params)

模組：email.mime.audio

A subclass of MIMENonMultipart, the MIMEAudio class is used to create MIME message objects of major type audio. _audiodata contains the bytes for the raw audio data. If this data can be decoded as au, wav, aiff, or aifc, then the subtype will be automatically included in the Content-Type header. Otherwise you can explicitly specify the audio subtype via the _subtype argument. If the minor type could not be guessed and _subtype was not given, then TypeError is raised.

Optional _encoder is a callable (i.e. function) which will perform the actual encoding of the audio data for transport. This callable takes one argument, which is the MIMEAudio instance. It should use get_payload() and set_payload() to change the payload to encoded form. It should also add any Content-Transfer-Encoding or other headers to the message object as necessary. The default encoding is base64. See the email.encoders module for a list of the built-in encoders.

Optional policy argument defaults to compat32.

_params are passed straight through to the base class constructor.

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

class email.mime.image.MIMEImage(_imagedata, _subtype=None, _encoder=email.encoders.encode_base64, *, policy=compat32, **_params)

模組：email.mime.image

A subclass of MIMENonMultipart, the MIMEImage class is used to create MIME message objects of major type image. _imagedata contains the bytes for the raw image data. If this data type can be detected (jpeg, png, gif, tiff, rgb, pbm, pgm, ppm, rast, xbm, bmp, webp, and exr attempted), then the subtype will be automatically included in the Content-Type header. Otherwise you can explicitly specify the image subtype via the _subtype argument. If the minor type could not be guessed and _subtype was not given, then TypeError is raised.

Optional _encoder is a callable (i.e. function) which will perform the actual encoding of the image data for transport. This callable takes one argument, which is the MIMEImage instance. It should use get_payload() and set_payload() to change the payload to encoded form. It should also add any Content-Transfer-Encoding or other headers to the message object as necessary. The default encoding is base64. See the email.encoders module for a list of the built-in encoders.

Optional policy argument defaults to compat32.

_params are passed straight through to the MIMEBase constructor.

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

class email.mime.message.MIMEMessage(_msg, _subtype='rfc822', *, policy=compat32)

模組：email.mime.message

A subclass of MIMENonMultipart, the MIMEMessage class is used to create MIME objects of main type message. _msg is used as the payload, and must be an instance of class Message (or a subclass thereof), otherwise a TypeError is raised.

Optional _subtype sets the subtype of the message; it defaults to rfc822.

Optional policy argument defaults to compat32.

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

class email.mime.text.MIMEText(_text, _subtype='plain', _charset=None, *, policy=compat32)

模組：email.mime.text

A subclass of MIMENonMultipart, the MIMEText class is used to create MIME objects of major type text. _text is the string for the payload. _subtype is the minor type and defaults to plain. _charset is the character set of the text and is passed as an argument to the MIMENonMultipart constructor; it defaults to us-ascii if the string contains only ascii code points, and utf-8 otherwise. The _charset parameter accepts either a string or a Charset instance.

Unless the _charset argument is explicitly set to None, the MIMEText object created will have both a Content-Type header with a charset parameter, and a Content-Transfer-Encoding header. This means that a subsequent set_payload call will not result in an encoded payload, even if a charset is passed in the set_payload command. You can "reset" this behavior by deleting the Content-Transfer-Encoding header, after which a set_payload call will automatically encode the new payload (and add a new Content-Transfer-Encoding header).

Optional policy argument defaults to compat32.

在 3.5 版的變更: _charset also accepts Charset instances.

在 3.6 版的變更: 新增僅限關鍵字參數 policy。

email.header：國際化標頭

原始碼：Lib/email/header.py [https://github.com/python/cpython/tree/3.14/Lib/email/header.py]

This module is part of the legacy (Compat32) email API. In the current API encoding and decoding of headers is handled transparently by the dictionary-like API of the EmailMessage class. In addition to uses in legacy code, this module can be useful in applications that need to completely control the character sets used when encoding headers.

The remaining text in this section is the original documentation of the module.

RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html] is the base standard that describes the format of email messages. It derives from the older RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] standard which came into widespread use at a time when most email was composed of ASCII characters only. RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html] is a specification written assuming email contains only 7-bit ASCII characters.

Of course, as email has been deployed worldwide, it has become internationalized, such that language specific character sets can now be used in email messages. The base standard still requires email messages to be transferred using only 7-bit ASCII characters, so a slew of RFCs have been written describing how to encode email containing non-ASCII characters into RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html]-compliant format. These RFCs include RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html], RFC 2046 [https://datatracker.ietf.org/doc/html/rfc2046.html], RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html], and RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html]. The email package supports these standards in its email.header and email.charset modules.

If you want to include non-ASCII characters in your email headers, say in the Subject or To fields, you should use the Header class and assign the field in the Message object to an instance of Header instead of using a string for the header value. Import the Header class from the email.header module. For example:

>>> from email.message import Message
>>> from email.header import Header
>>> msg = Message()
>>> h = Header('p\xf6stal', 'iso-8859-1')
>>> msg['Subject'] = h
>>> msg.as_string()
'Subject: =?iso-8859-1?q?p=F6stal?=\n\n'

Notice here how we wanted the Subject field to contain a non-ASCII character? We did this by creating a Header instance and passing in the character set that the byte string was encoded in. When the subsequent Message instance was flattened, the Subject field was properly RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] encoded. MIME-aware mail readers would show this header using the embedded ISO-8859-1 character.

Here is the Header class description:

class email.header.Header(s=None, charset=None, maxlinelen=None, header_name=None, continuation_ws=' ', errors='strict')

Create a MIME-compliant header that can contain strings in different character sets.

Optional s is the initial header value. If None (the default), the initial header value is not set. You can later append to the header with append() method calls. s may be an instance of bytes or str, but see the append() documentation for semantics.

Optional charset serves two purposes: it has the same meaning as the charset argument to the append() method. It also sets the default character set for all subsequent append() calls that omit the charset argument. If charset is not provided in the constructor (the default), the us-ascii character set is used both as s's initial charset and as the default for subsequent append() calls.

The maximum line length can be specified explicitly via maxlinelen. For splitting the first line to a shorter value (to account for the field header which isn't included in s, e.g. Subject) pass in the name of the field in header_name. The default maxlinelen is 78, and the default value for header_name is None, meaning it is not taken into account for the first line of a long, split header.

Optional continuation_ws must be RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html]-compliant folding whitespace, and is usually either a space or a hard tab character. This character will be prepended to continuation lines. continuation_ws defaults to a single space character.

Optional errors is passed straight through to the append() method.

append(s, charset=None, errors='strict')

Append the string s to the MIME header.

Optional charset, if given, should be a Charset instance (see email.charset) or the name of a character set, which will be converted to a Charset instance. A value of None (the default) means that the charset given in the constructor is used.

s may be an instance of bytes or str. If it is an instance of bytes, then charset is the encoding of that byte string, and a UnicodeError will be raised if the string cannot be decoded with that character set.

If s is an instance of str, then charset is a hint specifying the character set of the characters in the string.

In either case, when producing an RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html]-compliant header using RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] rules, the string will be encoded using the output codec of the charset. If the string cannot be encoded using the output codec, a UnicodeError will be raised.

Optional errors is passed as the errors argument to the decode call if s is a byte string.

encode(splitchars=';, \t', maxlinelen=None, linesep='\n')

Encode a message header into an RFC-compliant format, possibly wrapping long lines and encapsulating non-ASCII parts in base64 or quoted-printable encodings.

Optional splitchars is a string containing characters which should be given extra weight by the splitting algorithm during normal header wrapping. This is in very rough support of RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html]'s 'higher level syntactic breaks': split points preceded by a splitchar are preferred during line splitting, with the characters preferred in the order in which they appear in the string. Space and tab may be included in the string to indicate whether preference should be given to one over the other as a split point when other split chars do not appear in the line being split. Splitchars does not affect RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] encoded lines.

maxlinelen, if given, overrides the instance's value for the maximum line length.

linesep specifies the characters used to separate the lines of the folded header. It defaults to the most useful value for Python application code (\n), but \r\n can be specified in order to produce headers with RFC-compliant line separators.

在 3.2 版的變更: 新增引數 linesep。

The Header class also provides a number of methods to support standard operators and built-in functions.

__str__()

Returns an approximation of the Header as a string, using an unlimited line length. All pieces are converted to unicode using the specified encoding and joined together appropriately. Any pieces with a charset of 'unknown-8bit' are decoded as ASCII using the 'replace' error handler.

在 3.2 版的變更: Added handling for the 'unknown-8bit' charset.

__eq__(other)

This method allows you to compare two Header instances for equality.

__ne__(other)

This method allows you to compare two Header instances for inequality.

The email.header module also provides the following convenient functions.

email.header.decode_header(header)

Decode a message header value without converting the character set. The header value is in header.

For historical reasons, this function may return either:

A list of pairs containing each of the decoded parts of the header, (decoded_bytes, charset), where decoded_bytes is always an instance of bytes, and charset is either:

A lower case string containing the name of the character set specified.

None for non-encoded parts of the header.

A list of length 1 containing a pair (string, None), where string is always an instance of str.

An email.errors.HeaderParseError may be raised when certain decoding errors occur (e.g. a base64 decoding exception).

以下為範例：

>>> from email.header import decode_header
>>> decode_header('=?iso-8859-1?q?p=F6stal?=')
[(b'p\xf6stal', 'iso-8859-1')]
>>> decode_header('unencoded_string')
[('unencoded_string', None)]
>>> decode_header('bar =?utf-8?B?ZsOzbw==?=')
[(b'bar ', None), (b'f\xc3\xb3o', 'utf-8')]

備註

This function exists for backwards compatibility only. For new code, we recommend using email.headerregistry.HeaderRegistry.

email.header.make_header(decoded_seq, maxlinelen=None, header_name=None, continuation_ws=' ')

Create a Header instance from a sequence of pairs as returned by decode_header().

decode_header() takes a header value string and returns a sequence of pairs of the format (decoded_string, charset) where charset is the name of the character set.

This function takes one of those sequence of pairs and returns a Header instance. Optional maxlinelen, header_name, and continuation_ws are as in the Header constructor.

備註

This function exists for backwards compatibility only, and is not recommended for use in new code.

email.charset：字元集合的表示

原始碼：Lib/email/charset.py [https://github.com/python/cpython/tree/3.14/Lib/email/charset.py]

此模組是舊版 (Compat32) email API的其中一部份，在新版的 API 只有使用別名表。

此章節的其餘內容是模組的原始說明文件

此模組提供一個類別 Charset 來表示電子郵件訊息中的字元集合和字元集合轉換，也包含字元集合登錄檔 (registry) 和其他許多運用此登錄檔的便捷方法。Charset 的實例被 email 套件中其他數個模組所使用。

從 email.charset 模組中引入此類別

class email.charset.Charset(input_charset=DEFAULT_CHARSET)

將字元集合對映到其電子郵件特性 (properties)。

此類別提供有關於電子郵件對特定字元集合的規範資訊。考慮到適用之編解碼器 (codec) 的可用性，它還提供了在字元集合之間進行轉換的便利例行操作 (routine)。給定一個字元集合，它將盡量提供有關如何以符合 RFC (RFC-compliant) 的方式在電子郵件訊息中使用該字元集合的資訊。

在電子郵件標頭 (header) 或內文 (body) 用特定字元集合時必須使用可列印字元編碼 (quoted-printable) 或 base64 來編碼。特定字元集合不允許出現在電子郵件中、必須被徹底轉換。

可選的 input_charset 描述如下；input_charset 會被強制轉換 (coerced) 為小寫。經過別名標準化 (alias normalize) 後，會進到字元集合登錄檔 (registry) 去查詢此字元集合使用的標頭編碼、內文編碼以及輸出轉換編解碼器。舉例來說，如果 input_charset 是 iso-8859-1，標頭跟內文會以可列印字元編碼並且不需要輸出轉換編解碼器。如果 input_charset 是 euc-jp，標頭則會被編碼成 base64、內文不會被編碼，但輸出文字則會從 euc-jp 字元集合被轉換成 iso-2022-jp 字元集合。

Charset 實例有以下資料屬性：

input_charset

指定的初始字元集合。通用別名會被轉換成它們的官方電子郵件名稱（例如：latin_1 會被轉換成 iso-8859-1）。預設為 7 位元 us-ascii。

header_encoding

如果字元集合在被用於電子郵件標頭前必須被編碼的話，這個屬性會被設為 charset.QP（表示可列印字元編碼）、charset.BASE64（表示 base64 編碼格式）或是 charset.SHORTEST 表示最短的 QP 或是 base64 編碼格式。不然這個屬性會是 None。

body_encoding

與 header_encoding 相同，但表示郵件訊息內文的編碼，與上述的標頭編碼有可能不同。charset.SHORTEST 是不允許於 body_encoding 使用的。

output_charset

部分的字元集合在用於電子郵件的標頭或內文前必須先被轉換。如果 input_charset 是這些字元集合的其中之一，這個屬性將會包含輸出時轉換成的字元集合名稱。不然這個屬性則為 None。

input_codec

用於將 input_charset 轉換成 Unicode 的 Python 編解碼器的名稱。如果不需要轉換編解碼器，這個屬性為 None。

output_codec

用於將 Unicode 轉換成 output_charset 的 Python 編解碼器名稱。如果不需要轉換編解碼器，這個屬性將會與 input_codec 有相同的值。

Charset 實例還有以下方法：

get_body_encoding()

回傳用於內文編碼的內容傳輸編碼 (content transfer encoding)。

這可以是字串 quoted-printable 或 base64，具體取決於所使用的編碼，或者它也可以是一個函式，在這種情況下，你應該使用單個引數呼叫該函式，即正被編碼的 Message 物件。然後函式應將 Content-Transfer-Encoding 標頭本身設定為任何適當的值。

如果 body_encoding 為 QP 則回傳字串 quoted-printable，如果 body_encoding 為 BASE64 則回傳字串 base64，否則回傳字串 7bit 。

get_output_charset()

回傳輸出字元集合。

如果不為 None 則這會是 output_charset 屬性，否則它是 input_charset。

header_encode(string)

對字串 string 進行標頭編碼 (header-encode)。

編碼類型（base64 或可列印字元編碼）將基於 header_encoding 屬性。

header_encode_lines(string, maxlengths)

透過先將 string 轉換為位元組來對它進行標頭編碼。

這與 header_encode() 類似，只不過字串不會超過由引數 maxlengths 給定的最大列長度 (maximum line length)，該引數必須是個疊代器：從此疊代器回傳的每個元素將提供下一個最大列長度。

body_encode(string)

對字串 string 進行內文編碼 (body-encode)。

編碼類型（base64 或可列印字元編碼）將基於 body_encoding 屬性。

Charset 類別也提供了許多支援標準操作和內建函式的方法。

__str__()

回傳強制轉換 input_charset 為小寫後的字串。__repr__() 是 __str__() 的別名。

__eq__(other)

此方法讓你比較兩個 Charset 實例的相等性。

__ne__(other)

此方法讓你比較兩個 Charset 實例的不相等性。

email.charset 模組還提供以下函式，用於將項目新增至全域字元集合、別名和編解碼器登錄檔中：

email.charset.add_charset(charset, header_enc=None, body_enc=None, output_charset=None)

將字元特性 (properties) 新增至全域登錄檔。

charset 是輸入的字元集合，且必須是字元集合的規範名稱 (canonical name)。

可選的 header_enc 和 body_enc 為 charset.QP（表示可列印字元編碼）、charset.BASE64（表示 base64 編碼）、charset.SHORTEST（表示最短的 base64 或可列印字元編碼）或 None（表示無編碼）。SHORTEST 僅在用於 header_enc 時有效。預設為 None，表示無編碼。

可選的 output_charset 是輸出應採用的字元集合。當呼叫 Charset.convert() 方法時，將從輸入字元集合轉換為 Unicode，再轉換為輸出字元集合。預設是以與輸入相同的字元集合輸出。

input_charset 和 output_charset 都必須在模組的字元集合到編解碼器對映 (character set-to-codec mapping) 中具有 Unicode 編解碼器項目；使用 add_codec() 來新增模組未知的編解碼器。有關更多資訊請參閱 codecs 模組的文件。

全域字元集合登錄檔保存在模組全域字典 CHARSETS 中。

email.charset.add_alias(alias, canonical)

新增字元集合別名。alias 是別名，例如 latin-1。canonical 是字元集合的規範名稱，例如 iso-8859-1。

全域字元集合別名登錄檔保存在模組全域字典 ALIASES 中。

email.charset.add_codec(charset, codecname)

新增一個編解碼器，將給定字元集合中的字元與 Unicode 進行對映。

charset 是字元集合的規範名稱。codecname 是 Python 編解碼器的名稱，適用於 str 的 encode() 方法的第二個引數。

email.encoders：編碼器

原始碼：Lib/email/encoders.py [https://github.com/python/cpython/tree/3.14/Lib/email/encoders.py]

此模組是舊版 (Compat32) 電子郵件 API 的一部分。在新 API 中，此功能由 set_content() 方法的 cte 參數提供。

此模組在 Python 3 中已棄用。不應明確呼叫此處提供的函式，因為 MIMEText 類別使用在該類別的實例化過程中傳遞的 _subtype 和 _charset 值來設定內容類型 (content type) 和 CTE 標頭。

本節中的其餘文字是該模組的原始文件。

從零開始建立 Message 物件時，你通常需要對負載 (payload) 進行編碼，以便透過相容的郵件伺服器進行傳輸。對於包含二進位資料的 image/* 和 text/* 類型的訊息尤其如此。

email 套件在其 encoders 模組中提供了一些方便的編碼器。這些編碼器實際上由 MIMEAudio 和 MIMEImage 類別建構函式使用來提供預設編碼。所有編碼器函式都只接受一個引數，也就是要編碼的訊息物件。他們通常會提取負載、對其進行編碼，然後將負載重設為新編碼的值。他們也應適當地設定 Content-Transfer-Encoding 標頭。

請注意，這些函式對於多部分訊息 (multipart message) 沒有意義。它們必須應用於各個子部分，如果傳遞類型為多部分訊息，則會引發 TypeError。

以下是提供的編碼函式：

email.encoders.encode_quopri(msg)

將負載編碼為可列印字元 (quoted-printable) 形式，並將 Content-Transfer-Encoding 標頭設定為 quoted-printable [1]。當大部分負載是正常的可列印資料，但包含一些不可列印的字元時，這是一種很好的編碼。

email.encoders.encode_base64(msg)

將負載編碼為 base64 形式，並將 Content-Transfer-Encoding 標頭設定為 base64。當大部分負載是不可列印資料時，這是一種很好的編碼，因為它是比可列印字元更緊湊的形式。Base64 編碼的缺點是它使文字無法讓人類可讀。

email.encoders.encode_7or8bit(msg)

這實際上並沒有修改訊息的負載，但它確實根據負載資料將 Content-Transfer-Encoding 標頭設定為適當的 7bit 或 8bit。

email.encoders.encode_noop(msg)

這沒有任何作用；它甚至沒有設定 Content-Transfer-Encoding 標頭。

註腳

[1]

請注意，使用 encode_quopri() 進行編碼也會對資料中的所有定位字元 (tab) 和空格字元進行編碼。

email.utils：雜項工具

原始碼：Lib/email/utils.py [https://github.com/python/cpython/tree/3.14/Lib/email/utils.py]

There are a couple of useful utilities provided in the email.utils module:

email.utils.localtime(dt=None)

Return local time as an aware datetime object. If called without arguments, return current time. Otherwise dt argument should be a datetime instance, and it is converted to the local time zone according to the system time zone database. If dt is naive (that is, dt.tzinfo is None), it is assumed to be in local time.

在 3.3 版被加入.

自從版本 3.12 後不推薦使用，已從版本 3.14 中移除。: The isdst parameter.

email.utils.make_msgid(idstring=None, domain=None)

Returns a string suitable for an RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html]-compliant Message-ID header. Optional idstring if given, is a string used to strengthen the uniqueness of the message id. Optional domain if given provides the portion of the msgid after the '@'. The default is the local hostname. It is not normally necessary to override this default, but may be useful certain cases, such as a constructing distributed system that uses a consistent domain name across multiple hosts.

在 3.2 版的變更: 新增 domain 關鍵字。

The remaining functions are part of the legacy (Compat32) email API. There is no need to directly use these with the new API, since the parsing and formatting they provide is done automatically by the header parsing machinery of the new API.

email.utils.quote(str)

Return a new string with backslashes in str replaced by two backslashes, and double quotes replaced by backslash-double quote.

email.utils.unquote(str)

Return a new string which is an unquoted version of str. If str ends and begins with double quotes, they are stripped off. Likewise if str ends and begins with angle brackets, they are stripped off.

email.utils.parseaddr(address, *, strict=True)

Parse address -- which should be the value of some address-containing field such as To or Cc -- into its constituent realname and email address parts. Returns a tuple of that information, unless the parse fails, in which case a 2-tuple of ('', '') is returned.

If strict is true, use a strict parser which rejects malformed inputs.

在 3.13 版的變更: Add strict optional parameter and reject malformed inputs by default.

email.utils.formataddr(pair, charset='utf-8')

The inverse of parseaddr(), this takes a 2-tuple of the form (realname, email_address) and returns the string value suitable for a To or Cc header. If the first element of pair is false, then the second element is returned unmodified.

Optional charset is the character set that will be used in the RFC 2047 [https://datatracker.ietf.org/doc/html/rfc2047.html] encoding of the realname if the realname contains non-ASCII characters. Can be an instance of str or a Charset. Defaults to utf-8.

在 3.3 版的變更: 新增 charset 選項。

email.utils.getaddresses(fieldvalues, *, strict=True)

This method returns a list of 2-tuples of the form returned by parseaddr(). fieldvalues is a sequence of header field values as might be returned by Message.get_all.

If strict is true, use a strict parser which rejects malformed inputs.

Here's a simple example that gets all the recipients of a message:

from email.utils import getaddresses

tos = msg.get_all('to', [])
ccs = msg.get_all('cc', [])
resent_tos = msg.get_all('resent-to', [])
resent_ccs = msg.get_all('resent-cc', [])
all_recipients = getaddresses(tos + ccs + resent_tos + resent_ccs)

在 3.13 版的變更: Add strict optional parameter and reject malformed inputs by default.

email.utils.parsedate(date)

Attempts to parse a date according to the rules in RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html]. however, some mailers don't follow that format as specified, so parsedate() tries to guess correctly in such cases. date is a string containing an RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html] date, such as "Mon, 20 Nov 1995 19:12:08 -0500". If it succeeds in parsing the date, parsedate() returns a 9-tuple that can be passed directly to time.mktime(); otherwise None will be returned. Note that indexes 6, 7, and 8 of the result tuple are not usable.

email.utils.parsedate_tz(date)

Performs the same function as parsedate(), but returns either None or a 10-tuple; the first 9 elements make up a tuple that can be passed directly to time.mktime(), and the tenth is the offset of the date's timezone from UTC (which is the official term for Greenwich Mean Time) [1]. If the input string has no timezone, the last element of the tuple returned is 0, which represents UTC. Note that indexes 6, 7, and 8 of the result tuple are not usable.

email.utils.parsedate_to_datetime(date)

The inverse of format_datetime(). Performs the same function as parsedate(), but on success returns a datetime; otherwise ValueError is raised if date contains an invalid value such as an hour greater than 23 or a timezone offset not between -24 and 24 hours. If the input date has a timezone of -0000, the datetime will be a naive datetime, and if the date is conforming to the RFCs it will represent a time in UTC but with no indication of the actual source timezone of the message the date comes from. If the input date has any other valid timezone offset, the datetime will be an aware datetime with the corresponding a timezone tzinfo.

在 3.3 版被加入.

email.utils.mktime_tz(tuple)

Turn a 10-tuple as returned by parsedate_tz() into a UTC timestamp (seconds since the Epoch). If the timezone item in the tuple is None, assume local time.

email.utils.formatdate(timeval=None, localtime=False, usegmt=False)

Returns a date string as per RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html], e.g.:

Fri, 09 Nov 2001 01:08:47 -0000

Optional timeval if given is a floating-point time value as accepted by time.gmtime() and time.localtime(), otherwise the current time is used.

Optional localtime is a flag that when True, interprets timeval, and returns a date relative to the local timezone instead of UTC, properly taking daylight savings time into account. The default is False meaning UTC is used.

Optional usegmt is a flag that when True, outputs a date string with the timezone as an ascii string GMT, rather than a numeric -0000. This is needed for some protocols (such as HTTP). This only applies when localtime is False. The default is False.

email.utils.format_datetime(dt, usegmt=False)

Like formatdate, but the input is a datetime instance. If it is a naive datetime, it is assumed to be "UTC with no information about the source timezone", and the conventional -0000 is used for the timezone. If it is an aware datetime, then the numeric timezone offset is used. If it is an aware timezone with offset zero, then usegmt may be set to True, in which case the string GMT is used instead of the numeric timezone offset. This provides a way to generate standards conformant HTTP date headers.

在 3.3 版被加入.

email.utils.decode_rfc2231(s)

Decode the string s according to RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html].

email.utils.encode_rfc2231(s, charset=None, language=None)

Encode the string s according to RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html]. Optional charset and language, if given is the character set name and language name to use. If neither is given, s is returned as-is. If charset is given but language is not, the string is encoded using the empty string for language.

email.utils.collapse_rfc2231_value(value, errors='replace', fallback_charset='us-ascii')

When a header parameter is encoded in RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] format, Message.get_param may return a 3-tuple containing the character set, language, and value. collapse_rfc2231_value() turns this into a unicode string. Optional errors is passed to the errors argument of str's encode() method; it defaults to 'replace'. Optional fallback_charset specifies the character set to use if the one in the RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html] header is not known by Python; it defaults to 'us-ascii'.

For convenience, if the value passed to collapse_rfc2231_value() is not a tuple, it should be a string and it is returned unquoted.

email.utils.decode_params(params)

Decode parameters list according to RFC 2231 [https://datatracker.ietf.org/doc/html/rfc2231.html]. params is a sequence of 2-tuples containing elements of the form (content-type, string-value).

註解

[1]

Note that the sign of the timezone offset is the opposite of the sign of the time.timezone variable for the same timezone; the latter variable follows the POSIX standard while this module follows RFC 2822 [https://datatracker.ietf.org/doc/html/rfc2822.html].

email.iterators：疊代器

原始碼：Lib/email/iterators.py [https://github.com/python/cpython/tree/3.14/Lib/email/iterators.py]

Iterating over a message object tree is fairly easy with the Message.walk method. The email.iterators module provides some useful higher level iterations over message object trees.

email.iterators.body_line_iterator(msg, decode=False)

This iterates over all the payloads in all the subparts of msg, returning the string payloads line-by-line. It skips over all the subpart headers, and it skips over any subpart with a payload that isn't a Python string. This is somewhat equivalent to reading the flat text representation of the message from a file using readline(), skipping over all the intervening headers.

Optional decode is passed through to Message.get_payload.

email.iterators.typed_subpart_iterator(msg, maintype='text', subtype=None)

This iterates over all the subparts of msg, returning only those subparts that match the MIME type specified by maintype and subtype.

Note that subtype is optional; if omitted, then subpart MIME type matching is done only with the main type. maintype is optional too; it defaults to text.

Thus, by default typed_subpart_iterator() returns each subpart that has a MIME type of text/*.

The following function has been added as a useful debugging tool. It should not be considered part of the supported public interface for the package.

email.iterators._structure(msg, fp=None, level=0, include_default=False)

Prints an indented representation of the content types of the message object structure. For example:

>>> msg = email.message_from_file(somefile)
>>> _structure(msg)
multipart/mixed
    text/plain
    text/plain
    multipart/digest
        message/rfc822
            text/plain
        message/rfc822
            text/plain
        message/rfc822
            text/plain
        message/rfc822
            text/plain
        message/rfc822
            text/plain
    text/plain

Optional fp is a file-like object to print the output to. It must be suitable for Python's print() function. level is used internally. include_default, if true, prints the default type as well.

json --- JSON 編碼器與解碼器

原始碼：Lib/json/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/json/__init__.py]

JSON (JavaScript Object Notation) [https://json.org] 是一個輕量化的資料交換格式，在 RFC 7159 [https://datatracker.ietf.org/doc/html/rfc7159.html]（其廢棄了 RFC 4627 [https://datatracker.ietf.org/doc/html/rfc4627.html]）及 ECMA-404 [https://ecma-international.org/publications-and-standards/standards/ecma-404/] 裡面有詳細說明，它啟發自 JavaScript [https://en.wikipedia.org/wiki/JavaScript] 的物件字面語法 (object literal syntax)（雖然它並不是 JavaScript 的嚴格子集 [1]）。

備註

The term "object" in the context of JSON processing in Python can be ambiguous. All values in Python are objects. In JSON, an object refers to any data wrapped in curly braces, similar to a Python dictionary.

警告

當剖析無法信任來源的 JSON 資料時要小心。一段惡意的 JSON 字串可能會導致解碼器耗費大量 CPU 與記憶體資源。建議限制剖析資料的大小。

此模組為習慣標準函式庫 marshal 與 pickle 模組的使用者提供熟悉的 API。

對基本 Python 物件階層進行編碼：

>>> import json
>>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
'["foo", {"bar": ["baz", null, 1.0, 2]}]'
>>> print(json.dumps("\"foo\bar"))
"\"foo\bar"
>>> print(json.dumps('\u1234'))
"\u1234"
>>> print(json.dumps('\\'))
"\\"
>>> print(json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True))
{"a": 0, "b": 0, "c": 0}
>>> from io import StringIO
>>> io = StringIO()
>>> json.dump(['streaming API'], io)
>>> io.getvalue()
'["streaming API"]'

改用緊湊型編碼方式：

>>> import json
>>> json.dumps([1, 2, 3, {'4': 5, '6': 7}], separators=(',', ':'))
'[1,2,3,{"4":5,"6":7}]'

美化輸出：

>>> import json
>>> print(json.dumps({'6': 7, '4': 5}, sort_keys=True, indent=4))
{
    "4": 5,
    "6": 7
}

自訂 JSON 物件編碼方式：

>>> import json
>>> def custom_json(obj):
...     if isinstance(obj, complex):
...         return {'__complex__': True, 'real': obj.real, 'imag': obj.imag}
...     raise TypeError(f'Cannot serialize object of {type(obj)}')
...
>>> json.dumps(1 + 2j, default=custom_json)
'{"__complex__": true, "real": 1.0, "imag": 2.0}'

JSON 解碼：

>>> import json
>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]')
['foo', {'bar': ['baz', None, 1.0, 2]}]
>>> json.loads('"\\"foo\\bar"')
'"foo\x08ar'
>>> from io import StringIO
>>> io = StringIO('["streaming API"]')
>>> json.load(io)
['streaming API']

自訂 JSON 物件解碼方式：

>>> import json
>>> def as_complex(dct):
...     if '__complex__' in dct:
...         return complex(dct['real'], dct['imag'])
...     return dct
...
>>> json.loads('{"__complex__": true, "real": 1, "imag": 2}',
...     object_hook=as_complex)
(1+2j)
>>> import decimal
>>> json.loads('1.1', parse_float=decimal.Decimal)
Decimal('1.1')

繼承 JSONEncoder 類別並自行擴充額外的編碼方法：

>>> import json
>>> class ComplexEncoder(json.JSONEncoder):
...     def default(self, obj):
...         if isinstance(obj, complex):
...             return [obj.real, obj.imag]
...         # Let the base class default method raise the TypeError
...         return super().default(obj)
...
>>> json.dumps(2 + 1j, cls=ComplexEncoder)
'[2.0, 1.0]'
>>> ComplexEncoder().encode(2 + 1j)
'[2.0, 1.0]'
>>> list(ComplexEncoder().iterencode(2 + 1j))
['[2.0', ', 1.0', ']']

在 shell 使用 json 來驗證和美化印出：

$ echo '{"json":"obj"}' | python -m json
{
    "json": "obj"
}
$ echo '{1.2:3.4}' | python -m json
Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

更詳盡的文件請見 命令列介面。

備註

JSON 語法是 YAML [https://yaml.org/] 1.2 語法的一種子集合。所以如果使用預設的設定的話（準確來說，使用預設的 separators 分隔符設定的話），這個模組的輸出也符合 YAML 1.0 和 1.1 的子集合規範。因此你也可以利用這個模組來當作 YAML 的序列化工具（serializer）。

備註

這個模組的編、解碼器預設會保存輸入與輸出資料的順序關係，除非一開始的輸入本身就是無序的。

基本用法

json.dump(obj, fp, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)

參考這個 Python-to-JSON 轉換表將 obj 序列化為符合 JSON 格式的串流，並寫入到 fp （一個支援 .write() 方法的 file-like object）

備註

與 pickle 和 marshal 不同，JSON 不具有二進位分框（binary framed）的協定，因此嘗試重複呼叫 dump() 來序列化多個物件到同一個 fp 裡將導致無效的 JSON 檔案。

參數:

obj (object) -- 要被序列化的 Python 物件。

fp (file-like object) -- The file-like object obj will be serialized to. The json module always produces str objects, not bytes objects, therefore fp.write() must support str input.

skipkeys (bool) -- If True, keys that are not of a basic type (str, int, float, bool, None) will be skipped instead of raising a TypeError. Default False.

ensure_ascii (bool) -- If True (the default), the output is guaranteed to have all incoming non-ASCII and non-printable characters escaped. If False, all characters will be outputted as-is, except for the characters that must be escaped: quotation mark, reverse solidus, and the control characters U+0000 through U+001F.

check_circular (bool) -- 如為 False，則針對不同容器型別的循環參照 (circular reference) 檢查將會被跳過，若有循環參照則最後將引發 RecursionError（或其他更糟的錯誤）。預設為 True。

allow_nan (bool) -- 如為 False，則序列化不符合嚴格 JSON 規範的超出範圍 float 值 (nan, inf, -inf) 會引發 ValueError。如為 True（預設值），則將使用它們的 JavaScript 等效表示 (NaN, Infinity, -Infinity)。

cls (a JSONEncoder subclass) -- If set, a custom JSON encoder with the default() method overridden, for serializing into custom datatypes. If None (the default), JSONEncoder is used.

indent (int | str | None) -- If a positive integer or string, JSON array elements and object members will be pretty-printed with that indent level. A positive integer indents that many spaces per level; a string (such as "\t") is used to indent each level. If zero, negative, or "" (the empty string), only newlines are inserted. If None (the default), the most compact representation is used.

separators (tuple | None) -- 一個二元組：(item_separator, key_separator)。如為 None（預設值）則 separators 被預設為 (', ', ': ')，否則預設為 (',', ': ')。想要獲得最緊湊的 JSON 表示形式，你可以指定 (',', ':') 來消除空格。

default (callable | None) -- A function that is called for objects that can't otherwise be serialized. It should return a JSON encodable version of the object or raise a TypeError. If None (the default), TypeError is raised.

sort_keys (bool) -- If True, dictionaries will be outputted sorted by key. Default False.

在 3.2 版的變更: 除了整數之外，indent 還允許使用字串作為輸入。

在 3.4 版的變更: 如果 indent 不是 None，則使用 (',', ': ') 作為預設值

在 3.6 版的變更: 所有可選參數現在都是僅限關鍵字參數了。

json.dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)

使用此轉換表來將 obj 序列化為 JSON 格式 str。這個引數的作用與 dump() 中的同名引數意義相同。

備註

JSON 鍵/值對中的鍵始終為 str 型別。當字典被轉換為 JSON 時，字典的所有鍵值資料型別都會被強制轉換為字串。因此，如果將字典先轉換為 JSON 格式然後再轉換回字典，則該字典可能不等於原始字典。也就是說，如果字典 x 含有非字串鍵值，則 loads(dumps(x)) != x。

json.load(fp, *, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)

使用此 JSON-to-Python 轉換表將 fp 解碼為 Python 物件。

參數:

fp (file-like object) -- A .read()-supporting text file or binary file containing the JSON document to be deserialized.

cls (a JSONDecoder subclass) -- If set, a custom JSON decoder. Additional keyword arguments to load() will be passed to the constructor of cls. If None (the default), JSONDecoder is used.

object_hook (callable | None) -- 如果有設定，會用解碼後的 JSON 物件字面值的結果（一個 dict）來呼叫此函式。此函式的回傳值將用來取代 dict。此功能可用於實作自訂解碼器，例如 JSON-RPC [https://www.jsonrpc.org] 類別提示。預設為 None。

object_pairs_hook (callable | None) -- 如果有設定，會用任何 JSON 物件字面值以有序對串列解碼的結果來呼叫此函式。此函式的回傳值將用來取代 dict。此功能可用於實作自訂解碼器。如果也設定了 object_hook，以 object_pairs_hook 優先。預設為 None。

parse_float (callable | None) -- 如果有設定，會用每個要被解碼的 JSON 浮點數字串來呼叫此函式。如果為 None（預設值），則等同於 float(num_str)。此功能可用於將 JSON 浮點數剖析為自訂資料型別，例如 decimal.Decimal。

parse_int (callable | None) -- 如果有設定，會用每個要被解碼的 JSON 整數字串來呼叫此函式。如果為 None（預設值），則等同於 int(num_str)。此功能可用於將 JSON 整數剖析為自訂資料型別，例如 float。

parse_constant (callable | None) -- 如果有設定，會用以下字串之一來呼叫此函式：'-Infinity'、'Infinity' 或 'NaN'。此功能可用於在遇到無效的 JSON 數字時引發例外。預設為 None。

引發:

JSONDecodeError -- 當被去序列化的資料不是有效的 JSON 文件時。

UnicodeDecodeError -- 當被去序列化的資料不包含 UTF-8、UTF-16 或 UTF-32 編碼資料時。

在 3.1 版的變更:

新增可選的 object_pairs_hook 參數。

遭遇 'null'、'true' 或 'false' 時不再以 parse_constant 給定的函式來處理了。

在 3.6 版的變更:

所有可選參數現在都是僅限關鍵字參數了。

現在，fp 可以是一個二進位檔案，前提是其編碼格式為 UTF-8、UTF-16 或 UTF-32。

在 3.11 版的變更: 預設 parse_int 使用的 int() 函式現在有限制整數字串的長度上限了，限制由直譯器的整數字串轉換長度限制機制來達成，這能防止阻斷服務攻擊 (Denial of Service attacks)。

json.loads(s, *, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)

與 load() 相同，但不是類檔案物件，而是使用轉換表將 s（一個包含 JSON 文件的 str、bytes 或 bytearray 實例）去序列化為 Python 物件。

在 3.6 版的變更: 現在，s 可以是一個二進位檔案如 bytes 或 bytearray，前提是其編碼格式為 UTF-8、UTF-16 或 UTF-32。

在 3.9 版的變更: 刪除關鍵字引數 encoding。

編碼器與解碼器

class json.JSONDecoder(*, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None)

簡易 JSON 解碼器

預設將執行下列資料型別轉換：

JSON

Python

object

dict

array

list

string

str

number (整數)

int

number (實數)

float

true

True

false

False

null

None

雖然 NaN、Infinity 和 -Infinity 並不符合 JSON 規範，但解碼器依然能正確地將其轉換到相應的 Python float 值。

object_hook 是一個可選函式，其接受一個解碼後的 JSON 物件作為輸入，並使用其回傳值來取代原先的 dict。這個功能可用於提供自訂的去序列化（例如支援 JSON-RPC [https://www.jsonrpc.org] 類別提示）。

object_pairs_hook is an optional function that will be called with the result of every JSON object decoded with an ordered list of pairs. The return value of object_pairs_hook will be used instead of the dict. This feature can be used to implement custom decoders. If object_hook is also defined, the object_pairs_hook takes priority.

在 3.1 版的變更: 新增對於 object_pairs_hook 的支援。

parse_float 為可選函式，每個要被解碼的 JSON 浮點數字串都會改用這個參數給定的函式來進行解碼。預設情況這等效於 float(num_str)。這個參數可用於將 JSON 中的浮點數解碼或剖析為另一種資料型別（例如 decimal.Decimal）。

parse_int 為可選函式，當解碼 JSON 整數字串時會被呼叫。預設情況等效於 int(num_str)。這個參數可用於將 JSON 中的整數解碼或剖析為另一種資料型別（例如 float）。

parse_constant 為可選函式，在解碼時若遭遇字串 '-Infinity'、'Infinity' 或 'NaN' 其中之一則會改用這個參數給定的函式來進行解碼。這也可用於使解碼過程中遇到無效的 JSON 數字時引發一個例外。

如果 strict 被設為 false（預設值為 True），那麼字串中將允許控制字元。此語境中的控制字元指的是 ASCII 字元編碼在 0～31 範圍內的字元，包括 '\t'``（tab）、'n'、'r'`` 和 '\0'。

如果被去序列化（deserialized）的資料不符合 JSON 格式，將會引發 JSONDecodeError 例外。

在 3.6 版的變更: 所有參數現在都是僅限關鍵字參數了。

decode(s)

回傳用 Python 型式表達的 s （一個含有 JSON 文件的 str 實例）。

若給定的輸入不符合 JSON 格式會引發 JSONDecodeError 例外。

raw_decode(s)

將 s （一個開頭部分含有合格 JSON 文件的 str） 解碼，並將 JSON 文件結束點的索引值（index）和解碼結果合併為一個二元組（2-tuple）後回傳。

這個方法可以用來解碼尾段可能帶有 JSON 以外資料的文字。

class json.JSONEncoder(*, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, sort_keys=False, indent=None, separators=None, default=None)

可擴充的 Python 資料結構 JSON 編碼器。

預設可支援下列物件及型別：

Python

JSON

dict

object

list, tuple

array

str

string

int、float 或可作為整數或浮點數運算的衍生列舉（int- or float-derived Enums）

number

True

true

False

false

None

null

在 3.4 版的變更: 增加對整數（int）、浮點數（float）或可作為整數或浮點數運算的衍生列舉（int- or float-derived Enums）類別的支援性。

若要擴充此功能來識別其他物件，請繼承並實作一個 default() 方法。此方法應回傳一個可序列化的 o 物件，否則此方法應呼叫父類別的 JSONEncoder.default 方法（以引發 TypeError 例外）。

若 skipkeys 為 false（預設值），則當在編碼不是 str、int、float、bool 或 None 的鍵值時，將引發 TypeError。如果 skipkeys 為 true，這些項目將直接被跳過。

如果 ensure_ascii 為 true（預設值），則輸出將保證所有非 ASCII 和非可列印字元都會被跳脫。如果 ensure_ascii 為 false，則所有字元都將按原樣輸出，唯有必須跳脫的字元例外：引號、反斜線，以及控制字元 U+0000 到 U+001F。

如果 check_circular 為 true（預設值），則會在編碼期間檢查串列（list）、字典（dict）和自訂編碼物件的循環參照，以防止無限遞迴（一個會導致 RecursionError 例外的問題）。否則不會進行此類檢查。

如果 allow_nan 為 true（預設值），則 NaN、Infinity 和 -Infinity 將按照原樣進行編碼。請記得此行為不符合標準 JSON 規範，但的確與大多數基於 JavaScript 的編碼器和解碼器一致。否則若設為 false，嘗試對這些浮點數進行編碼將引發 ValueError 例外。

如果 sort_keys 為 true（預設值：False），則 dictionary（字典）的輸出將按鍵值排序。這項功能可確保 JSON 序列化的結果能被互相比較，能讓日常的回歸測試檢查變得方便一些。

如果 indent 是非負整數或字串，則 JSON 陣列元素和物件成員將使用該縮排等級進行格式美化。縮排等級 0、負數或 "" 只會插入換行符號。None（預設值）等於是選擇最緊湊的表示法。使用正整數縮排可以在每層縮排數量相同的空格。如果 indent 是一個字串（例如 "\t"），則該字串用於縮排每個層級。

在 3.2 版的變更: 除了整數之外，indent 還允許使用字串作為輸入。

如果有指定本引數內容，separators 應該是一個 (item_separator, key_separator) 二元組。如果 indent 為 None 則預設為 (', ', ': ')，否則預設為 (',', ': ')。想要獲得最緊湊的 JSON 表示形式，你可以改成指定 (',', ':') 來消除空格。

在 3.4 版的變更: 如果 indent 不是 None，則使用 (',', ': ') 作為預設值

如果有指定本參數，default 會是一個遭遇無法序列化的物件時會被呼叫的函式。它應該回傳該物件的 JSON 可編碼版本或引發 TypeError。如果未指定，則會直接引發 TypeError。

在 3.6 版的變更: 所有參數現在都是僅限關鍵字參數了。

default(o)

在任意一個子類別裡實作這個方法時須讓其回傳一個可序列化的物件 o ，或呼叫原始的實作以引發 TypeError 例外。

舉例來說，想要讓編碼器支援任意疊代器（iterator），你可以實作這樣子的 default()：

def default(self, o):
   try:
       iterable = iter(o)
   except TypeError:
       pass
   else:
       return list(iterable)
   # 讓基底類別的預設方法引發 TypeError
   return super().default(o)

encode(o)

回傳一個 Python 資料結構物件 o 的 JSON 的字串表示。例如：

>>> json.JSONEncoder().encode({"foo": ["bar", "baz"]})
'{"foo": ["bar", "baz"]}'

iterencode(o)

將物件 o 編碼，並將結果統整為一個能依序產生（yield）各結果字串的物件。如下例：

for chunk in json.JSONEncoder().iterencode(bigobject):
    mysocket.write(chunk)

例外

exception json.JSONDecodeError(msg, doc, pos)

ValueError 的子類別具有下列額外屬性：

msg

未受格式化的錯誤訊息。

doc

正在被剖析的 JSON 文件。

pos

doc 剖析失敗處的起始點的索引值。

lineno

pos 所在的列（line）數。

colno

pos 所在的行（column）數。

在 3.5 版被加入.

合規性與互通性（Interoperability）

JSON 格式是由 RFC 7159 [https://datatracker.ietf.org/doc/html/rfc7159.html] 和 ECMA-404 [https://ecma-international.org/publications-and-standards/standards/ecma-404/] 規範的。本節詳細說明了本模組對 RFC 的遵循程度。簡單起見，JSONEncoder 和 JSONDecoder 子類別以及未明確提及的參數將不予討論。

這個模組的部份實作並未非常嚴格地遵循 RFC 規範。準確來說，下列實際實作符合 JavaScript 語法格式，但並不符合 JSON 格式：

無限（Infinite）和非數字（NaN）值會被接受。

同一個物件內可以有重複的名稱，但只有最後一個同名物件是有效的。

不過 RFC 准許遵循 RFC 的剖析器接受不合規的文字輸入，所以技術上來說若以預設設定運作，本模組的去序列化器（deserializer）是符合 RFC 規範的。

字元編碼格式

RFC 要求 JSON 必須以 UTF-8、UTF-16 或 UTF-32 格式編碼。並推薦以 UTF-8 編碼以達成最佳的互通性。

RFC 准許但並不強制編碼器預設要設定 ensure_ascii=True，因此跳脫輸出使得結果字串只包含可列印的 ASCII 字元。

除了 ensure_ascii 選項參數之外，本模組嚴格遵循 Python 物件與 Unicode strings 之間的轉換規範，因此並不另外處理字元編碼的問題。

RFC 禁止在文件的開頭加上端序記號（Byte Order Mark），因此本模組的序列化器（serializer）也不會在輸出中加入端序記號。RFC 允許但不強制 JSON 去序列化器（deserializer）忽略文件初始的端序記號，因此本模組的去序列化器將在遭遇位於文件開頭的端序記號時引發 ValueError 例外。

RFC 並未明確禁止 JSON 文件包含無法對應有效 Unicode 字元的位元組序列（例如未配對的 UTF-16 代理對（surrogate pairs）），但這個特性的確可能會引起相容性問題。預設情況下，當原始輸入的 str 中存在此類序列時，該模組將接受並輸出這些序列的編碼位置（code points）。

正負無限與非數值

RFC 不允許表現無限大或非數值（NaN）。但預設情況下，這個模組仍接受並輸出 Infinity、-Infinity 和 NaN，如同它們是有效的 JSON 數值字面值：

>>> # Neither of these calls raises an exception, but the results are not valid JSON
>>> json.dumps(float('-inf'))
'-Infinity'
>>> json.dumps(float('nan'))
'NaN'
>>> # Same when deserializing
>>> json.loads('-Infinity')
-inf
>>> json.loads('NaN')
nan

在序列化器中，allow_nan 參數可以改變這個行為。在去序列化器中，parse_constant 參數可以改變這個行為。

物件內重複的名稱

RFC 規範僅表明 JSON 物件中的名字應該是唯一的，但沒有強制要求如何處理重複的名字。預設情況下，本模組不會因此引發例外；相反的，它會忽略該名字的所有重複鍵值對，並只保留最後一個：

>>> weird_json = '{"x": 1, "x": 2, "x": 3}'
>>> json.loads(weird_json)
{'x': 3}

object_pairs_hook 參數可以改變這個行為。

位於頂層的非物件及非列表值

由已廢棄的 RFC 4627 [https://datatracker.ietf.org/doc/html/rfc4627.html] 所規範的舊版 JSON 要求 JSON 文字的頂層值必須是 JSON 物件或陣列（Python dict 或 list），而且不能是 JSON 的 null、boolean、數字或字串值。 RFC 7159 [https://datatracker.ietf.org/doc/html/rfc7159.html] 移除了這個限制，而本模組的序列化器或去串列化器中未曾實施過該限制。

如果想要最大限度地保留互通性，你可能還是會想要自行施加這個限制。

實作限制

某些 JSON 去序列化器的實作可能會造成下列限制：

JSON 文件長度上限

JSON 物件或陣列的最大巢狀層數（level of nesting）限制

數字的精準度或範圍

JSON 字串長度上限

本模組除了 Python 資料型別本身或 Python 直譯器本身的限制以外，不會設定任何此類限制。

將資料序列化為 JSON 時，要注意可能會使用該 JSON 輸出的應用程式中的相關限制。特別要注意的是，JSON 數字常會被去序列化為 IEEE 754 雙精度浮點數（double），並因而受到其表示範圍和精度限制的影響。這在序列化極大的 Python int 數值、或是序列化特殊數字型別的實例時（例如 decimal.Decimal）尤其重要。

命令列介面

原始碼：Lib/json/tool.py [https://github.com/python/cpython/tree/3.14/Lib/json/tool.py]

The json module can be invoked as a script via python -m json to validate and pretty-print JSON objects. The json.tool submodule implements this interface.

如果沒有指定可選引數 infile 和 outfile ，則 sys.stdin 和 sys.stdout 將各自做為輸入和輸出的預設值。

$ echo '{"json": "obj"}' | python -m json
{
    "json": "obj"
}
$ echo '{1.2:3.4}' | python -m json
Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

在 3.5 版的變更: 現在開始輸出和輸入的資料順序會是相同的。傳入 --sort-keys 引數以按照鍵值的字母順序對輸出進行排序。

在 3.14 版的變更: The json module may now be directly executed as python -m json. For backwards compatibility, invoking the CLI as python -m json.tool remains supported.

命令列選項

infile

將被用於校驗或美化呈現的 JSON 文件：

$ python -m json mp_films.json
[
    {
        "title": "And Now for Something Completely Different",
        "year": 1971
    },
    {
        "title": "Monty Python and the Holy Grail",
        "year": 1975
    }
]

如果沒有指定 infile 則會從 sys.stdin 讀取輸入。

outfile

將 infile 的結果寫入到給定的 outfile。若未提供則寫入到 sys.stdout。

--sort-keys

按照鍵值的字母順序對輸出字典進行排序。

在 3.5 版被加入.

--no-ensure-ascii

關閉非 ASCII 字元的自動跳脫功能。詳情請參照 json.dumps()。

在 3.9 版被加入.

--json-lines

將每一行輸入都單獨輸出為一個 JSON 物件。

在 3.8 版被加入.

--indent, --tab, --no-indent, --compact

互斥的空白字元控制選項。

在 3.9 版被加入.

-h, --help

顯示說明訊息。

註解

[1]

如 RFC 7159 更正 [https://www.rfc-editor.org/errata_search.php?rfc=7159] 所述，JSON 允許字串中出現 U+2028（列分隔符）和 U+2029（段落分隔符）字元，而 JavaScript（截至 ECMAScript 5.1 版）則不允許。

mailbox --- 以各種格式操作郵件信箱

原始碼：Lib/mailbox.py [https://github.com/python/cpython/tree/3.14/Lib/mailbox.py]

This module defines two classes, Mailbox and Message, for accessing and manipulating on-disk mailboxes and the messages they contain. Mailbox offers a dictionary-like mapping from keys to messages. Message extends the email.message module's Message class with format-specific state and behavior. Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.

也參考

email 模組

Represent and manipulate messages.

Mailbox 物件

class mailbox.Mailbox

A mailbox, which may be inspected and modified.

The Mailbox class defines an interface and is not intended to be instantiated. Instead, format-specific subclasses should inherit from Mailbox and your code should instantiate a particular subclass.

The Mailbox interface is dictionary-like, with small keys corresponding to messages. Keys are issued by the Mailbox instance with which they will be used and are only meaningful to that Mailbox instance. A key continues to identify a message even if the corresponding message is modified, such as by replacing it with another message.

Messages may be added to a Mailbox instance using the set-like method add() and removed using a del statement or the set-like methods remove() and discard().

Mailbox interface semantics differ from dictionary semantics in some noteworthy ways. Each time a message is requested, a new representation (typically a Message instance) is generated based upon the current state of the mailbox. Similarly, when a message is added to a Mailbox instance, the provided message representation's contents are copied. In neither case is a reference to the message representation kept by the Mailbox instance.

The default Mailbox iterator iterates over message representations, not keys as the default dictionary iterator does. Moreover, modification of a mailbox during iteration is safe and well-defined. Messages added to the mailbox after an iterator is created will not be seen by the iterator. Messages removed from the mailbox before the iterator yields them will be silently skipped, though using a key from an iterator may result in a KeyError exception if the corresponding message is subsequently removed.

警告

Be very cautious when modifying mailboxes that might be simultaneously changed by some other process. The safest mailbox format to use for such tasks is Maildir; try to avoid using single-file formats such as mbox for concurrent writing. If you're modifying a mailbox, you must lock it by calling the lock() and unlock() methods before reading any messages in the file or making any changes by adding or deleting a message. Failing to lock the mailbox runs the risk of losing messages or corrupting the entire mailbox.

Mailbox instances have the following methods:

add(message)

Add message to the mailbox and return the key that has been assigned to it.

Parameter message may be a Message instance, an email.message.Message instance, a string, a byte string, or a file-like object (which should be open in binary mode). If message is an instance of the appropriate format-specific Message subclass (e.g., if it's an mboxMessage instance and this is an mbox instance), its format-specific information is used. Otherwise, reasonable defaults for format-specific information are used.

在 3.2 版的變更: Support for binary input was added.

remove(key)

__delitem__(key)

discard(key)

Delete the message corresponding to key from the mailbox.

If no such message exists, a KeyError exception is raised if the method was called as remove() or __delitem__() but no exception is raised if the method was called as discard(). The behavior of discard() may be preferred if the underlying mailbox format supports concurrent modification by other processes.

__setitem__(key, message)

Replace the message corresponding to key with message. Raise a KeyError exception if no message already corresponds to key.

As with add(), parameter message may be a Message instance, an email.message.Message instance, a string, a byte string, or a file-like object (which should be open in binary mode). If message is an instance of the appropriate format-specific Message subclass (e.g., if it's an mboxMessage instance and this is an mbox instance), its format-specific information is used. Otherwise, the format-specific information of the message that currently corresponds to key is left unchanged.

iterkeys()

Return an iterator over all keys

keys()

The same as iterkeys(), except that a list is returned rather than an iterator

itervalues()

__iter__()

Return an iterator over representations of all messages. The messages are represented as instances of the appropriate format-specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized.

備註

The behavior of __iter__() is unlike that of dictionaries, which iterate over keys.

values()

The same as itervalues(), except that a list is returned rather than an iterator

iteritems()

Return an iterator over (key, message) pairs, where key is a key and message is a message representation. The messages are represented as instances of the appropriate format-specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized.

items()

The same as iteritems(), except that a list of pairs is returned rather than an iterator of pairs.

get(key, default=None)

__getitem__(key)

Return a representation of the message corresponding to key. If no such message exists, default is returned if the method was called as get() and a KeyError exception is raised if the method was called as __getitem__(). The message is represented as an instance of the appropriate format-specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized.

get_message(key)

Return a representation of the message corresponding to key as an instance of the appropriate format-specific Message subclass, or raise a KeyError exception if no such message exists.

get_bytes(key)

Return a byte representation of the message corresponding to key, or raise a KeyError exception if no such message exists.

在 3.2 版被加入.

get_string(key)

Return a string representation of the message corresponding to key, or raise a KeyError exception if no such message exists. The message is processed through email.message.Message to convert it to a 7bit clean representation.

get_file(key)

Return a file-like representation of the message corresponding to key, or raise a KeyError exception if no such message exists. The file-like object behaves as if open in binary mode. This file should be closed once it is no longer needed.

在 3.2 版的變更: The file object really is a binary file; previously it was incorrectly returned in text mode. Also, the file-like object now supports the context manager protocol: you can use a with statement to automatically close it.

備註

Unlike other representations of messages, file-like representations are not necessarily independent of the Mailbox instance that created them or of the underlying mailbox. More specific documentation is provided by each subclass.

__contains__(key)

Return True if key corresponds to a message, False otherwise.

__len__()

Return a count of messages in the mailbox.

clear()

Delete all messages from the mailbox.

pop(key, default=None)

Return a representation of the message corresponding to key and delete the message. If no such message exists, return default. The message is represented as an instance of the appropriate format-specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized.

popitem()

Return an arbitrary (key, message) pair, where key is a key and message is a message representation, and delete the corresponding message. If the mailbox is empty, raise a KeyError exception. The message is represented as an instance of the appropriate format-specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized.

update(arg)

Parameter arg should be a key-to-message mapping or an iterable of (key, message) pairs. Updates the mailbox so that, for each given key and message, the message corresponding to key is set to message as if by using __setitem__(). As with __setitem__(), each key must already correspond to a message in the mailbox or else a KeyError exception will be raised, so in general it is incorrect for arg to be a Mailbox instance.

備註

Unlike with dictionaries, keyword arguments are not supported.

flush()

Write any pending changes to the filesystem. For some Mailbox subclasses, changes are always written immediately and flush() does nothing, but you should still make a habit of calling this method.

lock()

Acquire an exclusive advisory lock on the mailbox so that other processes know not to modify it. An ExternalClashError is raised if the lock is not available. The particular locking mechanisms used depend upon the mailbox format. You should always lock the mailbox before making any modifications to its contents.

unlock()

Release the lock on the mailbox, if any.

close()

Flush the mailbox, unlock it if necessary, and close any open files. For some Mailbox subclasses, this method does nothing.

Mailbox 物件

class mailbox.Maildir(dirname, factory=None, create=True)

A subclass of Mailbox for mailboxes in Maildir format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, MaildirMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

If create is True and the dirname path exists, it will be treated as an existing maildir without attempting to verify its directory layout.

It is for historical reasons that dirname is named as such rather than path.

Maildir is a directory-based mailbox format invented for the qmail mail transfer agent and now widely supported by other programs. Messages in a Maildir mailbox are stored in separate files within a common directory structure. This design allows Maildir mailboxes to be accessed and modified by multiple unrelated programs without data corruption, so file locking is unnecessary.

Maildir mailboxes contain three subdirectories, namely: tmp, new, and cur. Messages are created momentarily in the tmp subdirectory and then moved to the new subdirectory to finalize delivery. A mail user agent may subsequently move the message to the cur subdirectory and store information about the state of the message in a special "info" section appended to its file name.

Folders of the style introduced by the Courier mail transfer agent are also supported. Any subdirectory of the main mailbox is considered a folder if '.' is the first character in its name. Folder names are represented by Maildir without the leading '.'. Each folder is itself a Maildir mailbox but should not contain other folders. Instead, a logical nesting is indicated using '.' to delimit levels, e.g., "Archived.2005.07".

colon

The Maildir specification requires the use of a colon (':') in certain message file names. However, some operating systems do not permit this character in file names, If you wish to use a Maildir-like format on such an operating system, you should specify another character to use instead. The exclamation point ('!') is a popular choice. For example:

import mailbox
mailbox.Maildir.colon = '!'

The colon attribute may also be set on a per-instance basis.

在 3.13 版的變更: Maildir now ignores files with a leading dot.

Maildir instances have all of the methods of Mailbox in addition to the following:

list_folders()

Return a list of the names of all folders.

get_folder(folder)

Return a Maildir instance representing the folder whose name is folder. A NoSuchMailboxError exception is raised if the folder does not exist.

add_folder(folder)

Create a folder whose name is folder and return a Maildir instance representing it.

remove_folder(folder)

Delete the folder whose name is folder. If the folder contains any messages, a NotEmptyError exception will be raised and the folder will not be deleted.

clean()

Delete temporary files from the mailbox that have not been accessed in the last 36 hours. The Maildir specification says that mail-reading programs should do this occasionally.

get_flags(key)

Return as a string the flags that are set on the message corresponding to key. This is the same as get_message(key).get_flags() but much faster, because it does not open the message file. Use this method when iterating over the keys to determine which messages are interesting to get.

If you do have a MaildirMessage object, use its get_flags() method instead, because changes made by the message's set_flags(), add_flag() and remove_flag() methods are not reflected here until the mailbox's __setitem__() method is called.

在 3.13 版被加入.

set_flags(key, flags)

On the message corresponding to key, set the flags specified by flags and unset all others. Calling some_mailbox.set_flags(key, flags) is similar to

one_message = some_mailbox.get_message(key)
one_message.set_flags(flags)
some_mailbox[key] = one_message

but faster, because it does not open the message file.

If you do have a MaildirMessage object, use its set_flags() method instead, because changes made with this mailbox method will not be visible to the message object's method, get_flags().

在 3.13 版被加入.

add_flag(key, flag)

On the message corresponding to key, set the flags specified by flag without changing other flags. To add more than one flag at a time, flag may be a string of more than one character.

Considerations for using this method versus the message object's add_flag() method are similar to those for set_flags(); see the discussion there.

在 3.13 版被加入.

remove_flag(key, flag)

On the message corresponding to key, unset the flags specified by flag without changing other flags. To remove more than one flag at a time, flag may be a string of more than one character.

Considerations for using this method versus the message object's remove_flag() method are similar to those for set_flags(); see the discussion there.

在 3.13 版被加入.

get_info(key)

Return a string containing the info for the message corresponding to key. This is the same as get_message(key).get_info() but much faster, because it does not open the message file. Use this method when iterating over the keys to determine which messages are interesting to get.

If you do have a MaildirMessage object, use its get_info() method instead, because changes made by the message's set_info() method are not reflected here until the mailbox's __setitem__() method is called.

在 3.13 版被加入.

set_info(key, info)

Set the info of the message corresponding to key to info. Calling some_mailbox.set_info(key, flags) is similar to

one_message = some_mailbox.get_message(key)
one_message.set_info(info)
some_mailbox[key] = one_message

but faster, because it does not open the message file.

If you do have a MaildirMessage object, use its set_info() method instead, because changes made with this mailbox method will not be visible to the message object's method, get_info().

在 3.13 版被加入.

Some Mailbox methods implemented by Maildir deserve special remarks:

add(message)

__setitem__(key, message)

update(arg)

警告

These methods generate unique file names based upon the current process ID. When using multiple threads, undetected name clashes may occur and cause corruption of the mailbox unless threads are coordinated to avoid using these methods to manipulate the same mailbox simultaneously.

flush()

All changes to Maildir mailboxes are immediately applied, so this method does nothing.

lock()

unlock()

Maildir mailboxes do not support (or require) locking, so these methods do nothing.

close()

Maildir instances do not keep any open files and the underlying mailboxes do not support locking, so this method does nothing.

get_file(key)

Depending upon the host platform, it may not be possible to modify or remove the underlying message while the returned file remains open.

也參考

maildir man page from Courier [https://www.courier-mta.org/maildir.html]

A specification of the format. Describes a common extension for supporting folders.

Using maildir format [https://cr.yp.to/proto/maildir.html]

Notes on Maildir by its inventor. Includes an updated name-creation scheme and details on "info" semantics.

mbox 物件

class mailbox.mbox(path, factory=None, create=True)

A subclass of Mailbox for mailboxes in mbox format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, mboxMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

The mbox format is the classic format for storing mail on Unix systems. All messages in an mbox mailbox are stored in a single file with the beginning of each message indicated by a line whose first five characters are "From ".

Several variations of the mbox format exist to address perceived shortcomings in the original. In the interest of compatibility, mbox implements the original format, which is sometimes referred to as mboxo. This means that the Content-Length header, if present, is ignored and that any occurrences of "From " at the beginning of a line in a message body are transformed to ">From " when storing the message, although occurrences of ">From " are not transformed to "From " when reading the message.

Some Mailbox methods implemented by mbox deserve special remarks:

get_bytes(key, from_=False)

Note: This method has an extra parameter (from_) compared with other classes. The first line of an mbox file entry is the Unix "From " line. If from_ is False, the first line of the file is dropped.

get_file(key, from_=False)

Using the file after calling flush() or close() on the mbox instance may yield unpredictable results or raise an exception.

Note: This method has an extra parameter (from_) compared with other classes. The first line of an mbox file entry is the Unix "From " line. If from_ is False, the first line of the file is dropped.

get_string(key, from_=False)

Note: This method has an extra parameter (from_) compared with other classes. The first line of an mbox file entry is the Unix "From " line. If from_ is False, the first line of the file is dropped.

lock()

unlock()

Three locking mechanisms are used---dot locking and, if available, the flock() and lockf() system calls.

也參考

mbox man page from tin [http://www.tin.org/bin/man.cgi?section=5&topic=mbox]

A specification of the format, with details on locking.

Configuring Netscape Mail on Unix: Why The Content-Length Format is Bad [https://www.jwz.org/doc/content-length.html]

An argument for using the original mbox format rather than a variation.

"mbox" is a family of several mutually incompatible mailbox formats [https://www.loc.gov/preservation/digital/formats/fdd/fdd000383.shtml]

A history of mbox variations.

MH 物件

class mailbox.MH(path, factory=None, create=True)

A subclass of Mailbox for mailboxes in MH format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, MHMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

MH is a directory-based mailbox format invented for the MH Message Handling System, a mail user agent. Each message in an MH mailbox resides in its own file. An MH mailbox may contain other MH mailboxes (called folders) in addition to messages. Folders may be nested indefinitely. MH mailboxes also support sequences, which are named lists used to logically group messages without moving them to sub-folders. Sequences are defined in a file called .mh_sequences in each folder.

The MH class manipulates MH mailboxes, but it does not attempt to emulate all of mh's behaviors. In particular, it does not modify and is not affected by the context or .mh_profile files that are used by mh to store its state and configuration.

MH instances have all of the methods of Mailbox in addition to the following:

在 3.13 版的變更: Supported folders that don't contain a .mh_sequences file.

list_folders()

Return a list of the names of all folders.

get_folder(folder)

Return an MH instance representing the folder whose name is folder. A NoSuchMailboxError exception is raised if the folder does not exist.

add_folder(folder)

Create a folder whose name is folder and return an MH instance representing it.

remove_folder(folder)

Delete the folder whose name is folder. If the folder contains any messages, a NotEmptyError exception will be raised and the folder will not be deleted.

get_sequences()

Return a dictionary of sequence names mapped to key lists. If there are no sequences, the empty dictionary is returned.

set_sequences(sequences)

Re-define the sequences that exist in the mailbox based upon sequences, a dictionary of names mapped to key lists, like returned by get_sequences().

pack()

Rename messages in the mailbox as necessary to eliminate gaps in numbering. Entries in the sequences list are updated correspondingly.

備註

Already-issued keys are invalidated by this operation and should not be subsequently used.

Some Mailbox methods implemented by MH deserve special remarks:

remove(key)

__delitem__(key)

discard(key)

These methods immediately delete the message. The MH convention of marking a message for deletion by prepending a comma to its name is not used.

lock()

unlock()

Three locking mechanisms are used---dot locking and, if available, the flock() and lockf() system calls. For MH mailboxes, locking the mailbox means locking the .mh_sequences file and, only for the duration of any operations that affect them, locking individual message files.

get_file(key)

Depending upon the host platform, it may not be possible to remove the underlying message while the returned file remains open.

flush()

All changes to MH mailboxes are immediately applied, so this method does nothing.

close()

MH instances do not keep any open files, so this method is equivalent to unlock().

也參考

nmh - Message Handling System [https://www.nongnu.org/nmh/]

Home page of nmh, an updated version of the original mh.

MH & nmh: Email for Users & Programmers [https://rand-mh.sourceforge.io/book/]

A GPL-licensed book on mh and nmh, with some information on the mailbox format.

Babyl 物件

class mailbox.Babyl(path, factory=None, create=True)

A subclass of Mailbox for mailboxes in Babyl format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, BabylMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

Babyl is a single-file mailbox format used by the Rmail mail user agent included with Emacs. The beginning of a message is indicated by a line containing the two characters Control-Underscore ('\037') and Control-L ('\014'). The end of a message is indicated by the start of the next message or, in the case of the last message, a line containing a Control-Underscore ('\037') character.

Messages in a Babyl mailbox have two sets of headers, original headers and so-called visible headers. Visible headers are typically a subset of the original headers that have been reformatted or abridged to be more attractive. Each message in a Babyl mailbox also has an accompanying list of labels, or short strings that record extra information about the message, and a list of all user-defined labels found in the mailbox is kept in the Babyl options section.

Babyl instances have all of the methods of Mailbox in addition to the following:

get_labels()

Return a list of the names of all user-defined labels used in the mailbox.

備註

The actual messages are inspected to determine which labels exist in the mailbox rather than consulting the list of labels in the Babyl options section, but the Babyl section is updated whenever the mailbox is modified.

Some Mailbox methods implemented by Babyl deserve special remarks:

get_file(key)

In Babyl mailboxes, the headers of a message are not stored contiguously with the body of the message. To generate a file-like representation, the headers and body are copied together into an io.BytesIO instance, which has an API identical to that of a file. As a result, the file-like object is truly independent of the underlying mailbox but does not save memory compared to a string representation.

lock()

unlock()

Three locking mechanisms are used---dot locking and, if available, the flock() and lockf() system calls.

也參考

Format of Version 5 Babyl Files [https://quimby.gnus.org/notes/BABYL]

A specification of the Babyl format.

Reading Mail with Rmail [https://www.gnu.org/software/emacs/manual/html_node/emacs/Rmail.html]

The Rmail manual, with some information on Babyl semantics.

MMDF 物件

class mailbox.MMDF(path, factory=None, create=True)

A subclass of Mailbox for mailboxes in MMDF format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, MMDFMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

MMDF is a single-file mailbox format invented for the Multichannel Memorandum Distribution Facility, a mail transfer agent. Each message is in the same form as an mbox message but is bracketed before and after by lines containing four Control-A ('\001') characters. As with the mbox format, the beginning of each message is indicated by a line whose first five characters are "From ", but additional occurrences of "From " are not transformed to ">From " when storing messages because the extra message separator lines prevent mistaking such occurrences for the starts of subsequent messages.

Some Mailbox methods implemented by MMDF deserve special remarks:

get_bytes(key, from_=False)

Note: This method has an extra parameter (from_) compared with other classes. The first line of an mbox file entry is the Unix "From " line. If from_ is False, the first line of the file is dropped.

get_file(key, from_=False)

Using the file after calling flush() or close() on the MMDF instance may yield unpredictable results or raise an exception.

Note: This method has an extra parameter (from_) compared with other classes. The first line of an mbox file entry is the Unix "From " line. If from_ is False, the first line of the file is dropped.

lock()

unlock()

Three locking mechanisms are used---dot locking and, if available, the flock() and lockf() system calls.

也參考

mmdf man page from tin [http://www.tin.org/bin/man.cgi?section=5&topic=mmdf]

A specification of MMDF format from the documentation of tin, a newsreader.

MMDF [https://en.wikipedia.org/wiki/MMDF]

A Wikipedia article describing the Multichannel Memorandum Distribution Facility.

Message 物件

class mailbox.Message(message=None)

A subclass of the email.message module's Message. Subclasses of mailbox.Message add mailbox-format-specific state and behavior.

If message is omitted, the new instance is created in a default, empty state. If message is an email.message.Message instance, its contents are copied; furthermore, any format-specific information is converted insofar as possible if message is a Message instance. If message is a string, a byte string, or a file, it should contain an RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html]-compliant message, which is read and parsed. Files should be open in binary mode, but text mode files are accepted for backward compatibility.

The format-specific state and behaviors offered by subclasses vary, but in general it is only the properties that are not specific to a particular mailbox that are supported (although presumably the properties are specific to a particular mailbox format). For example, file offsets for single-file mailbox formats and file names for directory-based mailbox formats are not retained, because they are only applicable to the original mailbox. But state such as whether a message has been read by the user or marked as important is retained, because it applies to the message itself.

There is no requirement that Message instances be used to represent messages retrieved using Mailbox instances. In some situations, the time and memory required to generate Message representations might not be acceptable. For such situations, Mailbox instances also offer string and file-like representations, and a custom message factory may be specified when a Mailbox instance is initialized.

MaildirMessage 物件

class mailbox.MaildirMessage(message=None)

A message with Maildir-specific behaviors. Parameter message has the same meaning as with the Message constructor.

Typically, a mail user agent application moves all of the messages in the new subdirectory to the cur subdirectory after the first time the user opens and closes the mailbox, recording that the messages are old whether or not they've actually been read. Each message in cur has an "info" section added to its file name to store information about its state. (Some mail readers may also add an "info" section to messages in new.) The "info" section may take one of two forms: it may contain "2," followed by a list of standardized flags (e.g., "2,FR") or it may contain "1," followed by so-called experimental information. Standard flags for Maildir messages are as follows:

旗標

含義

解釋

D

草稿

編輯中

F

已標記

標記為重要

P

Passed

Forwarded, resent, or bounced

R

已回覆

Replied to

S

已查看

Read

T

Trashed

Marked for subsequent deletion

MaildirMessage 實例提供以下方法：

get_subdir()

Return either "new" (if the message should be stored in the new subdirectory) or "cur" (if the message should be stored in the cur subdirectory).

備註

A message is typically moved from new to cur after its mailbox has been accessed, whether or not the message has been read. A message msg has been read if "S" in msg.get_flags() is True.

set_subdir(subdir)

Set the subdirectory the message should be stored in. Parameter subdir must be either "new" or "cur".

get_flags()

Return a string specifying the flags that are currently set. If the message complies with the standard Maildir format, the result is the concatenation in alphabetical order of zero or one occurrence of each of 'D', 'F', 'P', 'R', 'S', and 'T'. The empty string is returned if no flags are set or if "info" contains experimental semantics.

set_flags(flags)

Set the flags specified by flags and unset all others.

add_flag(flag)

Set the flag(s) specified by flag without changing other flags. To add more than one flag at a time, flag may be a string of more than one character. The current "info" is overwritten whether or not it contains experimental information rather than flags.

remove_flag(flag)

Unset the flag(s) specified by flag without changing other flags. To remove more than one flag at a time, flag maybe a string of more than one character. If "info" contains experimental information rather than flags, the current "info" is not modified.

get_date()

Return the delivery date of the message as a floating-point number representing seconds since the epoch.

set_date(date)

Set the delivery date of the message to date, a floating-point number representing seconds since the epoch.

get_info()

Return a string containing the "info" for a message. This is useful for accessing and modifying "info" that is experimental (i.e., not a list of flags).

set_info(info)

Set "info" to info, which should be a string.

When a MaildirMessage instance is created based upon an mboxMessage or MMDFMessage instance, the Status and X-Status headers are omitted and the following conversions take place:

Resulting state

mboxMessage 或 MMDFMessage 狀態

"cur" 子目錄

O 旗標

F 旗標

F 旗標

R 旗標

A 旗標

S 旗標

R 旗標

T 旗標

D 旗標

When a MaildirMessage instance is created based upon an MHMessage instance, the following conversions take place:

Resulting state

MHMessage 狀態

"cur" 子目錄

"unseen" 序列

"cur" 子目錄和 S 旗標

沒有 "unseen" 序列

F 旗標

"flagged" 序列

R 旗標

"replied" 序列

When a MaildirMessage instance is created based upon a BabylMessage instance, the following conversions take place:

Resulting state

BabylMessage 狀態

"cur" 子目錄

"unseen" 標籤

"cur" 子目錄和 S 旗標

沒有 "unseen" 標籤

P 旗標

"forwarded" 或 "resent" 標籤

R 旗標

"answered" 標籤

T 旗標

"deleted" 標籤

mboxMessage 物件

class mailbox.mboxMessage(message=None)

A message with mbox-specific behaviors. Parameter message has the same meaning as with the Message constructor.

Messages in an mbox mailbox are stored together in a single file. The sender's envelope address and the time of delivery are typically stored in a line beginning with "From " that is used to indicate the start of a message, though there is considerable variation in the exact format of this data among mbox implementations. Flags that indicate the state of the message, such as whether it has been read or marked as important, are typically stored in Status and X-Status headers.

Conventional flags for mbox messages are as follows:

旗標

含義

解釋

R

Read

Read

O

Old

Previously detected by MUA

D

Deleted

Marked for subsequent deletion

F

已標記

標記為重要

A

Answered

Replied to

The "R" and "O" flags are stored in the Status header, and the "D", "F", and "A" flags are stored in the X-Status header. The flags and headers typically appear in the order mentioned.

mboxMessage 實例提供以下方法：

get_from()

Return a string representing the "From " line that marks the start of the message in an mbox mailbox. The leading "From " and the trailing newline are excluded.

set_from(from_, time_=None)

Set the "From " line to from_, which should be specified without a leading "From " or trailing newline. For convenience, time_ may be specified and will be formatted appropriately and appended to from_. If time_ is specified, it should be a time.struct_time instance, a tuple suitable for passing to time.strftime(), or True (to use time.gmtime()).

get_flags()

Return a string specifying the flags that are currently set. If the message complies with the conventional format, the result is the concatenation in the following order of zero or one occurrence of each of 'R', 'O', 'D', 'F', and 'A'.

set_flags(flags)

Set the flags specified by flags and unset all others. Parameter flags should be the concatenation in any order of zero or more occurrences of each of 'R', 'O', 'D', 'F', and 'A'.

add_flag(flag)

Set the flag(s) specified by flag without changing other flags. To add more than one flag at a time, flag may be a string of more than one character.

remove_flag(flag)

Unset the flag(s) specified by flag without changing other flags. To remove more than one flag at a time, flag maybe a string of more than one character.

When an mboxMessage instance is created based upon a MaildirMessage instance, a "From " line is generated based upon the MaildirMessage instance's delivery date, and the following conversions take place:

Resulting state

MaildirMessage 狀態

R 旗標

S 旗標

O 旗標

"cur" 子目錄

D 旗標

T 旗標

F 旗標

F 旗標

A 旗標

R 旗標

When an mboxMessage instance is created based upon an MHMessage instance, the following conversions take place:

Resulting state

MHMessage 狀態

R 旗標和 O 旗標

沒有 "unseen" 序列

O 旗標

"unseen" 序列

F 旗標

"flagged" 序列

A 旗標

"replied" 序列

When an mboxMessage instance is created based upon a BabylMessage instance, the following conversions take place:

Resulting state

BabylMessage 狀態

R 旗標和 O 旗標

沒有 "unseen" 標籤

O 旗標

"unseen" 標籤

D 旗標

"deleted" 標籤

A 旗標

"answered" 標籤

When a mboxMessage instance is created based upon an MMDFMessage instance, the "From " line is copied and all flags directly correspond:

Resulting state

MMDFMessage 狀態

R 旗標

R 旗標

O 旗標

O 旗標

D 旗標

D 旗標

F 旗標

F 旗標

A 旗標

A 旗標

MHMessage 物件

class mailbox.MHMessage(message=None)

A message with MH-specific behaviors. Parameter message has the same meaning as with the Message constructor.

MH messages do not support marks or flags in the traditional sense, but they do support sequences, which are logical groupings of arbitrary messages. Some mail reading programs (although not the standard mh and nmh) use sequences in much the same way flags are used with other formats, as follows:

Sequence

解釋

unseen

Not read, but previously detected by MUA

replied

Replied to

flagged

標記為重要

MHMessage 實例提供以下方法：

get_sequences()

Return a list of the names of sequences that include this message.

set_sequences(sequences)

Set the list of sequences that include this message.

add_sequence(sequence)

Add sequence to the list of sequences that include this message.

remove_sequence(sequence)

Remove sequence from the list of sequences that include this message.

When an MHMessage instance is created based upon a MaildirMessage instance, the following conversions take place:

Resulting state

MaildirMessage 狀態

"unseen" 序列

無 S 旗標

"replied" 序列

R 旗標

"flagged" 序列

F 旗標

When an MHMessage instance is created based upon an mboxMessage or MMDFMessage instance, the Status and X-Status headers are omitted and the following conversions take place:

Resulting state

mboxMessage 或 MMDFMessage 狀態

"unseen" 序列

無 R 旗標

"replied" 序列

A 旗標

"flagged" 序列

F 旗標

When an MHMessage instance is created based upon a BabylMessage instance, the following conversions take place:

Resulting state

BabylMessage 狀態

"unseen" 序列

"unseen" 標籤

"replied" 序列

"answered" 標籤

BabylMessage 物件

class mailbox.BabylMessage(message=None)

A message with Babyl-specific behaviors. Parameter message has the same meaning as with the Message constructor.

Certain message labels, called attributes, are defined by convention to have special meanings. The attributes are as follows:

Label

解釋

unseen

Not read, but previously detected by MUA

deleted

Marked for subsequent deletion

filed

Copied to another file or mailbox

answered

Replied to

forwarded

Forwarded

edited

Modified by the user

resent

Resent

By default, Rmail displays only visible headers. The BabylMessage class, though, uses the original headers because they are more complete. Visible headers may be accessed explicitly if desired.

BabylMessage 實例提供以下方法：

get_labels()

Return a list of labels on the message.

set_labels(labels)

Set the list of labels on the message to labels.

add_label(label)

Add label to the list of labels on the message.

remove_label(label)

Remove label from the list of labels on the message.

get_visible()

Return a Message instance whose headers are the message's visible headers and whose body is empty.

set_visible(visible)

Set the message's visible headers to be the same as the headers in message. Parameter visible should be a Message instance, an email.message.Message instance, a string, or a file-like object (which should be open in text mode).

update_visible()

When a BabylMessage instance's original headers are modified, the visible headers are not automatically modified to correspond. This method updates the visible headers as follows: each visible header with a corresponding original header is set to the value of the original header, each visible header without a corresponding original header is removed, and any of Date, From, Reply-To, To, CC, and Subject that are present in the original headers but not the visible headers are added to the visible headers.

When a BabylMessage instance is created based upon a MaildirMessage instance, the following conversions take place:

Resulting state

MaildirMessage 狀態

"unseen" 標籤

無 S 旗標

"deleted" 標籤

T 旗標

"answered" 標籤

R 旗標

"forwarded" 標籤

P 旗標

When a BabylMessage instance is created based upon an mboxMessage or MMDFMessage instance, the Status and X-Status headers are omitted and the following conversions take place:

Resulting state

mboxMessage 或 MMDFMessage 狀態

"unseen" 標籤

無 R 旗標

"deleted" 標籤

D 旗標

"answered" 標籤

A 旗標

When a BabylMessage instance is created based upon an MHMessage instance, the following conversions take place:

Resulting state

MHMessage 狀態

"unseen" 標籤

"unseen" 序列

"answered" 標籤

"replied" 序列

MMDFMessage 物件

class mailbox.MMDFMessage(message=None)

A message with MMDF-specific behaviors. Parameter message has the same meaning as with the Message constructor.

As with message in an mbox mailbox, MMDF messages are stored with the sender's address and the delivery date in an initial line beginning with "From ". Likewise, flags that indicate the state of the message are typically stored in Status and X-Status headers.

Conventional flags for MMDF messages are identical to those of mbox message and are as follows:

旗標

含義

解釋

R

Read

Read

O

Old

Previously detected by MUA

D

Deleted

Marked for subsequent deletion

F

已標記

標記為重要

A

Answered

Replied to

The "R" and "O" flags are stored in the Status header, and the "D", "F", and "A" flags are stored in the X-Status header. The flags and headers typically appear in the order mentioned.

MMDFMessage instances offer the following methods, which are identical to those offered by mboxMessage:

get_from()

Return a string representing the "From " line that marks the start of the message in an mbox mailbox. The leading "From " and the trailing newline are excluded.

set_from(from_, time_=None)

Set the "From " line to from_, which should be specified without a leading "From " or trailing newline. For convenience, time_ may be specified and will be formatted appropriately and appended to from_. If time_ is specified, it should be a time.struct_time instance, a tuple suitable for passing to time.strftime(), or True (to use time.gmtime()).

get_flags()

Return a string specifying the flags that are currently set. If the message complies with the conventional format, the result is the concatenation in the following order of zero or one occurrence of each of 'R', 'O', 'D', 'F', and 'A'.

set_flags(flags)

Set the flags specified by flags and unset all others. Parameter flags should be the concatenation in any order of zero or more occurrences of each of 'R', 'O', 'D', 'F', and 'A'.

add_flag(flag)

Set the flag(s) specified by flag without changing other flags. To add more than one flag at a time, flag may be a string of more than one character.

remove_flag(flag)

Unset the flag(s) specified by flag without changing other flags. To remove more than one flag at a time, flag maybe a string of more than one character.

When an MMDFMessage instance is created based upon a MaildirMessage instance, a "From " line is generated based upon the MaildirMessage instance's delivery date, and the following conversions take place:

Resulting state

MaildirMessage 狀態

R 旗標

S 旗標

O 旗標

"cur" 子目錄

D 旗標

T 旗標

F 旗標

F 旗標

A 旗標

R 旗標

When an MMDFMessage instance is created based upon an MHMessage instance, the following conversions take place:

Resulting state

MHMessage 狀態

R 旗標和 O 旗標

沒有 "unseen" 序列

O 旗標

"unseen" 序列

F 旗標

"flagged" 序列

A 旗標

"replied" 序列

When an MMDFMessage instance is created based upon a BabylMessage instance, the following conversions take place:

Resulting state

BabylMessage 狀態

R 旗標和 O 旗標

沒有 "unseen" 標籤

O 旗標

"unseen" 標籤

D 旗標

"deleted" 標籤

A 旗標

"answered" 標籤

When an MMDFMessage instance is created based upon an mboxMessage instance, the "From " line is copied and all flags directly correspond:

Resulting state

mboxMessage 狀態

R 旗標

R 旗標

O 旗標

O 旗標

D 旗標

D 旗標

F 旗標

F 旗標

A 旗標

A 旗標

例外

The following exception classes are defined in the mailbox module:

exception mailbox.Error

The based class for all other module-specific exceptions.

exception mailbox.NoSuchMailboxError

Raised when a mailbox is expected but is not found, such as when instantiating a Mailbox subclass with a path that does not exist (and with the create parameter set to False), or when opening a folder that does not exist.

exception mailbox.NotEmptyError

Raised when a mailbox is not empty but is expected to be, such as when deleting a folder that contains messages.

exception mailbox.ExternalClashError

Raised when some mailbox-related condition beyond the control of the program causes it to be unable to proceed, such as when failing to acquire a lock that another program already holds a lock, or when a uniquely generated file name already exists.

exception mailbox.FormatError

Raised when the data in a file cannot be parsed, such as when an MH instance attempts to read a corrupted .mh_sequences file.

範例

A simple example of printing the subjects of all messages in a mailbox that seem interesting:

import mailbox
for message in mailbox.mbox('~/mbox'):
    subject = message['subject']       # 可能為 None.
    if subject and 'python' in subject.lower():
        print(subject)

To copy all mail from a Babyl mailbox to an MH mailbox, converting all of the format-specific information that can be converted:

import mailbox
destination = mailbox.MH('~/Mail')
destination.lock()
for message in mailbox.Babyl('~/RMAIL'):
    destination.add(mailbox.MHMessage(message))
destination.flush()
destination.unlock()

This example sorts mail from several mailing lists into different mailboxes, being careful to avoid mail corruption due to concurrent modification by other programs, mail loss due to interruption of the program, or premature termination due to malformed messages in the mailbox:

import mailbox
import email.errors

list_names = ('python-list', 'python-dev', 'python-bugs')

boxes = {name: mailbox.mbox('~/email/%s' % name) for name in list_names}
inbox = mailbox.Maildir('~/Maildir', factory=None)

for key in inbox.iterkeys():
    try:
        message = inbox[key]
    except email.errors.MessageParseError:
        continue                # The message is malformed. Just leave it.

    for name in list_names:
        list_id = message['list-id']
        if list_id and name in list_id:
            # Get mailbox to use
            box = boxes[name]

            # Write copy to disk before removing original.
            # If there's a crash, you might duplicate a message, but
            # that's better than losing a message completely.
            box.lock()
            box.add(message)
            box.flush()
            box.unlock()

            # Remove original message
            inbox.lock()
            inbox.discard(key)
            inbox.flush()
            inbox.unlock()
            break               # Found destination, so stop looking.

for box in boxes.itervalues():
    box.close()

mimetypes --- 將檔案名稱對映到 MIME 類型

原始碼：Lib/mimetypes.py [https://github.com/python/cpython/tree/3.14/Lib/mimetypes.py]

The mimetypes module converts between a filename or URL and the MIME type associated with the filename extension. Conversions are provided from filename to MIME type and from MIME type to filename extension; encodings are not supported for the latter conversion.

The module provides one class and a number of convenience functions. The functions are the normal interface to this module, but some applications may be interested in the class as well.

The functions described below provide the primary interface for this module. If the module has not been initialized, they will call init() if they rely on the information init() sets up.

mimetypes.guess_type(url, strict=True)

Guess the type of a file based on its filename, path or URL, given by url. URL can be a string or a path-like object.

The return value is a tuple (type, encoding) where type is None if the type can't be guessed (missing or unknown suffix) or a string of the form 'type/subtype', usable for a MIME content-type header.

encoding is None for no encoding or the name of the program used to encode (e.g. compress or gzip). The encoding is suitable for use as a Content-Encoding header, not as a Content-Transfer-Encoding header. The mappings are table driven. Encoding suffixes are case sensitive; type suffixes are first tried case sensitively, then case insensitively.

The optional strict argument is a flag specifying whether the list of known MIME types is limited to only the official types registered with IANA [https://www.iana.org/assignments/media-types/media-types.xhtml]. However, the behavior of this module also depends on the underlying operating system. Only file types recognized by the OS or explicitly registered with Python's internal database can be identified. When strict is True (the default), only the IANA types are supported; when strict is False, some additional non-standard but commonly used MIME types are also recognized.

在 3.8 版的變更: 新增 url 做為 path-like object 的支援。

在 3.13 版之後被棄用: Passing a file path instead of URL is soft deprecated. Use guess_file_type() for this.

mimetypes.guess_file_type(path, *, strict=True)

Guess the type of a file based on its path, given by path. Similar to the guess_type() function, but accepts a path instead of URL. Path can be a string, a bytes object or a path-like object.

在 3.13 版被加入.

mimetypes.guess_all_extensions(type, strict=True)

Guess the extensions for a file based on its MIME type, given by type. The return value is a list of strings giving all possible filename extensions, including the leading dot ('.'). The extensions are not guaranteed to have been associated with any particular data stream, but would be mapped to the MIME type type by guess_type() and guess_file_type().

The optional strict argument has the same meaning as with the guess_type() function.

mimetypes.guess_extension(type, strict=True)

Guess the extension for a file based on its MIME type, given by type. The return value is a string giving a filename extension, including the leading dot ('.'). The extension is not guaranteed to have been associated with any particular data stream, but would be mapped to the MIME type type by guess_type() and guess_file_type(). If no extension can be guessed for type, None is returned.

The optional strict argument has the same meaning as with the guess_type() function.

Some additional functions and data items are available for controlling the behavior of the module.

mimetypes.init(files=None)

Initialize the internal data structures. If given, files must be a sequence of file names which should be used to augment the default type map. If omitted, the file names to use are taken from knownfiles; on Windows, the current registry settings are loaded. Each file named in files or knownfiles takes precedence over those named before it. Calling init() repeatedly is allowed.

Specifying an empty list for files will prevent the system defaults from being applied: only the well-known values will be present from a built-in list.

If files is None the internal data structure is completely rebuilt to its initial default value. This is a stable operation and will produce the same results when called multiple times.

在 3.2 版的變更: 先前 Windows 登錄設定會被忽略。

mimetypes.read_mime_types(filename)

Load the type map given in the file filename, if it exists. The type map is returned as a dictionary mapping filename extensions, including the leading dot ('.'), to strings of the form 'type/subtype'. If the file filename does not exist or cannot be read, None is returned.

mimetypes.add_type(type, ext, strict=True)

Add a mapping from the MIME type type to the extension ext. When the extension is already known, the new type will replace the old one. When the type is already known the extension will be added to the list of known extensions.

When strict is True (the default), the mapping will be added to the official MIME types, otherwise to the non-standard ones.

mimetypes.inited

Flag indicating whether or not the global data structures have been initialized. This is set to True by init().

mimetypes.knownfiles

List of type map file names commonly installed. These files are typically named mime.types and are installed in different locations by different packages.

mimetypes.suffix_map

Dictionary mapping suffixes to suffixes. This is used to allow recognition of encoded files for which the encoding and the type are indicated by the same extension. For example, the .tgz extension is mapped to .tar.gz to allow the encoding and type to be recognized separately.

mimetypes.encodings_map

Dictionary mapping filename extensions to encoding types.

mimetypes.types_map

Dictionary mapping filename extensions to MIME types.

mimetypes.common_types

Dictionary mapping filename extensions to non-standard, but commonly found MIME types.

模組的使用範例：

>>> import mimetypes
>>> mimetypes.init()
>>> mimetypes.knownfiles
['/etc/mime.types', '/etc/httpd/mime.types', ... ]
>>> mimetypes.suffix_map['.tgz']
'.tar.gz'
>>> mimetypes.encodings_map['.gz']
'gzip'
>>> mimetypes.types_map['.tgz']
'application/x-tar-gz'

MimeTypes 物件

The MimeTypes class may be useful for applications which may want more than one MIME-type database; it provides an interface similar to the one of the mimetypes module.

class mimetypes.MimeTypes(filenames=(), strict=True)

This class represents a MIME-types database. By default, it provides access to the same database as the rest of this module. The initial database is a copy of that provided by the module, and may be extended by loading additional mime.types-style files into the database using the read() or readfp() methods. The mapping dictionaries may also be cleared before loading additional data if the default data is not desired.

The optional filenames parameter can be used to cause additional files to be loaded "on top" of the default database.

suffix_map

Dictionary mapping suffixes to suffixes. This is used to allow recognition of encoded files for which the encoding and the type are indicated by the same extension. For example, the .tgz extension is mapped to .tar.gz to allow the encoding and type to be recognized separately. This is initially a copy of the global suffix_map defined in the module.

encodings_map

Dictionary mapping filename extensions to encoding types. This is initially a copy of the global encodings_map defined in the module.

types_map

Tuple containing two dictionaries, mapping filename extensions to MIME types: the first dictionary is for the non-standards types and the second one is for the standard types. They are initialized by common_types and types_map.

types_map_inv

Tuple containing two dictionaries, mapping MIME types to a list of filename extensions: the first dictionary is for the non-standards types and the second one is for the standard types. They are initialized by common_types and types_map.

guess_extension(type, strict=True)

Similar to the guess_extension() function, using the tables stored as part of the object.

guess_type(url, strict=True)

Similar to the guess_type() function, using the tables stored as part of the object.

guess_file_type(path, *, strict=True)

Similar to the guess_file_type() function, using the tables stored as part of the object.

在 3.13 版被加入.

guess_all_extensions(type, strict=True)

Similar to the guess_all_extensions() function, using the tables stored as part of the object.

read(filename, strict=True)

Load MIME information from a file named filename. This uses readfp() to parse the file.

If strict is True, information will be added to list of standard types, else to the list of non-standard types.

readfp(fp, strict=True)

Load MIME type information from an open file fp. The file must have the format of the standard mime.types files.

If strict is True, information will be added to the list of standard types, else to the list of non-standard types.

read_windows_registry(strict=True)

Load MIME type information from the Windows registry.

可用性: Windows.

If strict is True, information will be added to the list of standard types, else to the list of non-standard types.

在 3.2 版被加入.

add_type(type, ext, strict=True)

Add a mapping from the MIME type type to the extension ext. Valid extensions start with a '.' or are empty. When the extension is already known, the new type will replace the old one. When the type is already known the extension will be added to the list of known extensions.

When strict is True (the default), the mapping will be added to the official MIME types, otherwise to the non-standard ones.

自從版本 3.14 後不推薦使用，將會自版本 3.16 中移除。: Invalid, undotted extensions will raise a ValueError in Python 3.16.

命令列用法

The mimetypes module can be executed as a script from the command line.

python -m mimetypes [-h] [-e] [-l] type [type ...]

The following options are accepted:

-h

--help

Show the help message and exit.

-e

--extension

Guess extension instead of type.

-l

--lenient

Additionally search for some common, but non-standard types.

By default the script converts MIME types to file extensions. However, if --extension is specified, it converts file extensions to MIME types.

For each type entry, the script writes a line into the standard output stream. If an unknown type occurs, it writes an error message into the standard error stream and exits with the return code 1.

Command-line example

Here are some examples of typical usage of the mimetypes command-line interface:

$ # get a MIME type by a file name
$ python -m mimetypes filename.png
type: image/png encoding: None

$ # get a MIME type by a URL
$ python -m mimetypes https://example.com/filename.txt
type: text/plain encoding: None

$ # get a complex MIME type
$ python -m mimetypes filename.tar.gz
type: application/x-tar encoding: gzip

$ # get a MIME type for a rare file extension
$ python -m mimetypes filename.pict
error: unknown extension of filename.pict

$ # now look in the extended database built into Python
$ python -m mimetypes --lenient filename.pict
type: image/pict encoding: None

$ # get a file extension by a MIME type
$ python -m mimetypes --extension text/javascript
.js

$ # get a file extension by a rare MIME type
$ python -m mimetypes --extension text/xul
error: unknown type text/xul

$ # now look in the extended database again
$ python -m mimetypes --extension --lenient text/xul
.xul

$ # try to feed an unknown file extension
$ python -m mimetypes filename.sh filename.nc filename.xxx filename.txt
type: application/x-sh encoding: None
type: application/x-netcdf encoding: None
error: unknown extension of filename.xxx

$ # try to feed an unknown MIME type
$ python -m mimetypes --extension audio/aac audio/opus audio/future audio/x-wav
.aac
.opus
error: unknown type audio/future

base64 --- Base16、Base32、Base64、Base85 資料編碼

原始碼： Lib/base64.py [https://github.com/python/cpython/tree/3.14/Lib/base64.py]

這個模組提供將二進位資料編碼成可顯示 ASCII 字元以及解碼回原始資料的功能。這包括了 RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html] 中指定的編碼（Base64、Base32 和 Base16）和非標準的 Base85 編碼。

該模組提供了兩個介面。新介面支援將類位元組物件 編碼成 ASCII bytes，並將包含 ASCII 的類位元組物件或字串解碼為 bytes。支援 RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html] 中定義的兩種 base-64 字母表（常見和 URL 安全 (URL-safe) 及檔案系統安全 (filesystem-safe) 字母表）。

舊版介面不支援從字串解碼，但它提供對檔案物件進行編碼和解碼的函式。它僅支援 Base64 標準字母表，並且按照 RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] 每 76 個字元添加換行字元。請注意，如果你需要 RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] 的支援，你可能會需要 email 函式庫。

在 3.3 版的變更: 新介面的解碼功能現在接受 ASCII-only 的 Unicode 字串。

在 3.4 版的變更: 任何類位元組物件現在被該模組中的所有編碼和解碼函式接受。新增了對 Ascii85/Base85 的支援。

RFC 4648 編碼

RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html] 編碼適合對二進位資料進行編碼來使得電子郵件、URL 或是 HTTP POST 內容等傳輸管道能夠安全地傳遞資料。

base64.b64encode(s, altchars=None)

使用 Base64 對類位元組物件 s 進行編碼並回傳編碼過的 bytes。

可選的 altchars 必須是一個長度為 2 的類位元組物件，用來指定替代的字母表，以替換 + 和 / 字元。這使得應用程式可以生成對 URL 或檔案系統安全的 Base64 字串。預設值為 None，即使用標準的 Base64 字母表。

如果 altchars 的長度不是 2，可以斷言或引發 ValueError。如果 altchars 不是類位元組物件，則會引發 TypeError。

base64.b64decode(s, altchars=None, validate=False)

將經過 Base64 編碼的類位元組物件或 ASCII 字串 s 解碼，並回傳解碼後的 bytes。

可選的 altchars 必須是長度為 2 的類位元組物件或 ASCII 字串，用於指定替代字母表，取代 + 和 / 字元。

如果 s 填充 (pad) 不正確，將引發 binascii.Error 例外。

如果 validate 為 False（預設值），在 padding check（填充檢查）之前，不屬於標準 base-64 字母表和替代字母表的字元將被丟棄。如果 validate 為 True，輸入中的這些非字母表字元將導致引發 binascii.Error。

有關嚴格的 base64 檢查的更多資訊，請參閱 binascii.a2b_base64()。

如果 altchars 的長度不是 2，可能會斷言或引發 ValueError。

base64.standard_b64encode(s)

使用標準 Base64 字母表對類位元組物件 s 進行編碼，並回傳編碼後的 bytes。

base64.standard_b64decode(s)

使用標準 Base64 字母表對類位元組物件或 ASCII 字串 s 進行解碼，並回傳解碼後的 bytes。

base64.urlsafe_b64encode(s)

使用 URL 安全和檔案系統安全的字母表對類位元組物件 s 進行編碼，該字母表將標準 Base64 字母表中的 + 替換為 -，/ 替換為 _，並回傳編碼後的 bytes。結果仍可能包含 =。

base64.urlsafe_b64decode(s)

使用 URL 安全和檔案系統安全字母表對類位元組物件或 ASCII 字串 s 進行解碼，該字母表將標準 Base64 字母表中的 + 替換為 -，/ 替換為 _，並回傳解碼後的 bytes。

base64.b32encode(s)

使用 Base32 對類位元組物件 s 進行編碼，並回傳編碼後的 bytes。

base64.b32decode(s, casefold=False, map01=None)

解碼經過 Base32 編碼的類位元組物件或 ASCII 字串 s，並回傳解碼後的 bytes。

可選的 casefold 是一個是否接受小寫字母表作為輸入的旗標。出於安全性考量，預設值為 False。

RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html] 允許將數字 0 選擇性地對應對映為字母 O，並且允許將數字 1 選擇性地對映為字母 I 或字母 L。當可選的引數 map01 不為 None 時，指定數字 1 應該對映為哪個字母（當 map01 不為 None 時，數字 0 總是對映為字母 O）。出於安全性考量，預設值為 None，因此不允許在輸入中使用數字 0 和 1。

如果 s 的填充不正確或輸入中存在非字母表字元，將引發 binascii.Error。

base64.b32hexencode(s)

類似於 b32encode()，但使用在 RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html] 中定義的擴展十六進位字母表 (Extended Hex Alphabet)。

在 3.10 版被加入.

base64.b32hexdecode(s, casefold=False)

類似於 b32decode()，但使用在 RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html] 中定義的擴展十六進位字母表。

這個版本不允許將數字 0 對映為字母 O ，以及將數字 1 對映為字母 I 或字母 L，所有這些字元都包含在擴展十六進位字母表中，並且不能互換使用。

在 3.10 版被加入.

base64.b16encode(s)

使用 Base16 對類位元組物件 s 進行編碼，並回傳編碼後的 bytes。

base64.b16decode(s, casefold=False)

解碼經過 Base16 編碼的類位元組物件或 ASCII 字串 s，並回傳解碼後的 bytes。

可選的 casefold 是一個是否接受小寫字母表作為輸入的旗標。出於安全性考量，預設值為 False。

如果 s 的填充不正確或輸入中存在非字母表字元，將引發 binascii.Error。

Base85 編碼

Base85 encoding is not formally specified but rather a de facto standard, thus different systems perform the encoding differently.

The a85encode() and b85encode() functions in this module are two implementations of the de facto standard. You should call the function with the Base85 implementation used by the software you intend to work with.

The two functions present in this module differ in how they handle the following:

Whether to include enclosing <~ and ~> markers

Whether to include newline characters

The set of ASCII characters used for encoding

Handling of null bytes

Refer to the documentation of the individual functions for more information.

base64.a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False)

使用 Ascii85 對類位元組物件 b 進行編碼，並回傳編碼後的 bytes。

foldspaces 是一個可選的旗標，它使用特殊的短序列 'y' 來替代連續的 4 個空格 (ASCII 0x20)，這是由 'btoa' 支援的功能。這個特性不被「標準」的 Ascii85 編碼所支援。

wrapcol 控制輸出是否應該包含換行字元 (b'\n') 。如果這個值不為零，每行輸出的長度將不超過這個字元長度（不包含後面的換行符號）。

pad 控制是否在編碼之前將輸入填充為 4 的倍數。請注意，btoa 實作始終會填充。

adobe 控制編碼的位元組序列前後是否加上 <~ 和 ~>，這是 Adobe 實作中使用的。

在 3.4 版被加入.

base64.a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\x0b')

解碼經過 Ascii85 編碼的類位元組物件或 ASCII 字串 b，並回傳解碼後的 bytes。

foldspaces 是一個旗標，指定是否應該將短序列 'y' 視為 4 個連續的空格 (ASCII 0x20) 的簡寫。這個功能不受「標準」Ascii85 編碼的支援。

adobe 控制輸入序列是否符合 Adobe Ascii85 格式（即前後加上 <~ 和 ~>）。

ignorechars should be a byte string containing characters to ignore from the input. This should only contain whitespace characters, and by default contains all whitespace characters in ASCII.

在 3.4 版被加入.

base64.b85encode(b, pad=False)

使用 Base85（例如，git 風格的二進位差異 (binary diff)）對類位元組物件 b 進行編碼，並回傳編碼後的 bytes。

如果 pad 為 true，則在編碼之前，輸入將使用 b'\0' 進行填充，以使其長度為 4 的倍數。

在 3.4 版被加入.

base64.b85decode(b)

解碼經過 base85 編碼的類位元組物件或 ASCII 字串 b，並回傳解碼後的 bytes。必要時會隱式移除填充。

在 3.4 版被加入.

base64.z85encode(s)

使用 Z85（如用於 ZeroMQ）對類位元組物件 s 進行編碼，並回傳編碼後的 bytes。有關更多資訊，請參閱 Z85 規格 [https://rfc.zeromq.org/spec/32/]。

在 3.13 版被加入.

base64.z85decode(s)

解碼經 Z85 編碼的類位元組物件或 ASCII 字串 s，並回傳解碼後的 bytes。有關更多資訊，請參閱 Z85 規格 [https://rfc.zeromq.org/spec/32/]。

在 3.13 版被加入.

舊版介面

base64.decode(input, output)

解碼二進位檔案 input 的內容，並將結果的二進位資料寫入 output 檔案。 input 和 output 必須是檔案物件。input 將被讀取，直到 input.readline() 回傳一個空的 bytes 物件為止。

base64.decodebytes(s)

解碼必須包含一行或多行的 base64 編碼資料類位元組物件 s，並回傳解碼後的 bytes。

在 3.1 版被加入.

base64.encode(input, output)

編碼二進位檔案 input 的內容，並將結果的 base64 編碼資料寫入 output 檔案。input 和 output 必須是檔案物件。input 將被讀取，直到 input.read() 回傳一個空的 bytes 物件為止。encode() 會在輸出的每 76 個位元組之後插入一個換行字元 (b'\n')，並確保輸出始終以換行字元結尾，符合 RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] (MIME) 的規定。

base64.encodebytes(s)

對包含任意二進位資料的類位元組物件 s 進行編碼，並回傳包含 base64 編碼資料 bytes，在每 76 個輸出位元組後插入換行字元 (b'\n') ，並確保有尾隨換行字元，符合 RFC 2045 [https://datatracker.ietf.org/doc/html/rfc2045.html] (MIME) 的規定。

在 3.1 版被加入.

模組的一個範例用法：

>>> import base64
>>> encoded = base64.b64encode(b'data to be encoded')
>>> encoded
b'ZGF0YSB0byBiZSBlbmNvZGVk'
>>> data = base64.b64decode(encoded)
>>> data
b'data to be encoded'

安全性注意事項

RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html]（第 12 節）中添加了一個新的安全性考量部分；建議對部署到正式環境的任何程式碼進行安全性部分的審查。

也參考

binascii 模組

支援模組中包含 ASCII 到二進位 (ASCII-to-binary) 和二進位到 ASCII (binary-to-ASCII) 的轉換功能。

RFC 1521 [https://datatracker.ietf.org/doc/html/rfc1521.html] - MIME（多用途網際網路郵件擴展）第一部分：指定和描述網際網路主體格式的機制。

第 5.2 節，"Base64 Content-Transfer-Encoding"，提供了 base64 編碼的定義。

binascii --- 在二進位制和 ASCII 之間轉換

The binascii module contains a number of methods to convert between binary and various ASCII-encoded binary representations. Normally, you will not use these functions directly but use wrapper modules like base64 instead. The binascii module contains low-level functions written in C for greater speed that are used by the higher-level modules.

備註

a2b_* functions accept Unicode strings containing only ASCII characters. Other functions only accept bytes-like objects (such as bytes, bytearray and other objects that support the buffer protocol).

在 3.3 版的變更: ASCII-only unicode strings are now accepted by the a2b_* functions.

binascii 模組定義了以下函式：

binascii.a2b_uu(string)

Convert a single line of uuencoded data back to binary and return the binary data. Lines normally contain 45 (binary) bytes, except for the last line. Line data may be followed by whitespace.

binascii.b2a_uu(data, *, backtick=False)

Convert binary data to a line of ASCII characters, the return value is the converted line, including a newline char. The length of data should be at most 45. If backtick is true, zeros are represented by '`' instead of spaces.

在 3.7 版的變更: 新增 backtick 參數。

binascii.a2b_base64(string, /, *, strict_mode=False)

Convert a block of base64 data back to binary and return the binary data. More than one line may be passed at a time.

If strict_mode is true, only valid base64 data will be converted. Invalid base64 data will raise binascii.Error.

Valid base64:

Conforms to RFC 3548 [https://datatracker.ietf.org/doc/html/rfc3548.html].

Contains only characters from the base64 alphabet.

Contains no excess data after padding (including excess padding, newlines, etc.).

Does not start with a padding.

在 3.11 版的變更: 新增 strict_mode 參數。

binascii.b2a_base64(data, *, newline=True)

Convert binary data to a line of ASCII characters in base64 coding. The return value is the converted line, including a newline char if newline is true. The output of this function conforms to RFC 3548 [https://datatracker.ietf.org/doc/html/rfc3548.html].

在 3.6 版的變更: 新增 newline 參數。

binascii.a2b_qp(data, header=False)

Convert a block of quoted-printable data back to binary and return the binary data. More than one line may be passed at a time. If the optional argument header is present and true, underscores will be decoded as spaces.

binascii.b2a_qp(data, quotetabs=False, istext=True, header=False)

Convert binary data to a line(s) of ASCII characters in quoted-printable encoding. The return value is the converted line(s). If the optional argument quotetabs is present and true, all tabs and spaces will be encoded. If the optional argument istext is present and true, newlines are not encoded but trailing whitespace will be encoded. If the optional argument header is present and true, spaces will be encoded as underscores per RFC 1522 [https://datatracker.ietf.org/doc/html/rfc1522.html]. If the optional argument header is present and false, newline characters will be encoded as well; otherwise linefeed conversion might corrupt the binary data stream.

binascii.crc_hqx(data, value)

Compute a 16-bit CRC value of data, starting with value as the initial CRC, and return the result. This uses the CRC-CCITT polynomial x¹⁶ + x¹² + x⁵ + 1, often represented as 0x1021. This CRC is used in the binhex4 format.

binascii.crc32(data[, value])

Compute CRC-32, the unsigned 32-bit checksum of data, starting with an initial CRC of value. The default initial CRC is zero. The algorithm is consistent with the ZIP file checksum. Since the algorithm is designed for use as a checksum algorithm, it is not suitable for use as a general hash algorithm. Use as follows:

print(binascii.crc32(b"hello world"))
# Or, in two pieces:
crc = binascii.crc32(b"hello")
crc = binascii.crc32(b" world", crc)
print('crc32 = {:#010x}'.format(crc))

在 3.0 版的變更: The result is always unsigned.

binascii.b2a_hex(data[, sep[, bytes_per_sep=1]])

binascii.hexlify(data[, sep[, bytes_per_sep=1]])

Return the hexadecimal representation of the binary data. Every byte of data is converted into the corresponding 2-digit hex representation. The returned bytes object is therefore twice as long as the length of data.

Similar functionality (but returning a text string) is also conveniently accessible using the bytes.hex() method.

If sep is specified, it must be a single character str or bytes object. It will be inserted in the output after every bytes_per_sep input bytes. Separator placement is counted from the right end of the output by default, if you wish to count from the left, supply a negative bytes_per_sep value.

>>> import binascii
>>> binascii.b2a_hex(b'\xb9\x01\xef')
b'b901ef'
>>> binascii.hexlify(b'\xb9\x01\xef', '-')
b'b9-01-ef'
>>> binascii.b2a_hex(b'\xb9\x01\xef', b'_', 2)
b'b9_01ef'
>>> binascii.b2a_hex(b'\xb9\x01\xef', b' ', -2)
b'b901 ef'

在 3.8 版的變更: 新增 sep 與 bytes_per_sep 參數。

binascii.a2b_hex(hexstr)

binascii.unhexlify(hexstr)

Return the binary data represented by the hexadecimal string hexstr. This function is the inverse of b2a_hex(). hexstr must contain an even number of hexadecimal digits (which can be upper or lower case), otherwise an Error exception is raised.

Similar functionality (accepting only text string arguments, but more liberal towards whitespace) is also accessible using the bytes.fromhex() class method.

exception binascii.Error

Exception raised on errors. These are usually programming errors.

exception binascii.Incomplete

Exception raised on incomplete data. These are usually not programming errors, but may be handled by reading a little more data and trying again.

也參考

base64 模組

Support for RFC compliant base64-style encoding in base 16, 32, 64, and 85.

quopri 模組

Support for quoted-printable encoding used in MIME email messages.

quopri --- 編碼和解碼 MIME 可列印字元資料

原始碼：Lib/quopri.py [https://github.com/python/cpython/tree/3.14/Lib/quopri.py]

該模組根據 RFC 1521 [https://datatracker.ietf.org/doc/html/rfc1521.html]：「MIME（多功能網際網路郵件擴充）第一部分：指定和描述網際網路訊息正文格式的機制」中的定義來執行可列印字元 (quoted-printable) 傳輸編碼和解碼。可列印字元編碼是為不可列印字元相對較少的資料而設計的；如果存在許多此類字元（例如發送圖形檔案時），則透過 base64 模組提供的 Base64 編碼方案會更加簡潔。

quopri.decode(input, output, header=False)

解碼 input 檔案的內容並將解碼後的二進位資料寫入 output 檔案。 input 和 output 必須是二進位檔案物件。如果可選參數 header 存在且為 true，則底線將被解碼為空格。這用於解碼如 RFC 1522 [https://datatracker.ietf.org/doc/html/rfc1522.html]：「MIME（多功能網際網路郵件擴充）第二部分：非 ASCII 文字的訊息標頭擴充」中所述的 "Q" 編碼標頭。

quopri.encode(input, output, quotetabs, header=False)

對 input 檔案的內容進行編碼，並將生成的可列印字元資料寫入 output 檔案。 input 和 output 必須是二進位檔案物件。 quotetabs，一個非可選旗標，控制是否對嵌入的空格和製表符號 (tab) 進行編碼；當為 true 時，它將對此類嵌入的空白進行編碼，當為 false 時，它將不對它們進行編碼。請注意，出現在列尾的空格和製表符號都會按照 RFC 1521 [https://datatracker.ietf.org/doc/html/rfc1521.html] 進行編碼。 header 是一個旗標，用於控制空格是否按照 RFC 1522 [https://datatracker.ietf.org/doc/html/rfc1522.html] 編碼為底線。

quopri.decodestring(s, header=False)

與 decode() 類似，不同之處在於它接受來源的 bytes 並回傳相應的已解碼 bytes。

quopri.encodestring(s, quotetabs=False, header=False)

與 encode() 類似，不同之處在於它接受來源的 bytes 並回傳相應的已編碼 bytes。預設情況下，它向 encode() 函式的 quotetabs 參數發送一個 False 值。

也參考

base64 模組

對 MIME Base64 資料進行編碼和解碼

結構化標記處理工具

Python 支援多種模組來處理各種形式的結構化資料標記。這包括用於處理標準通用標記語言 (SGML, Standard Generalized Markup Language) 和超文本標記語言 (HTML, Hypertext Markup Language) 的模組，以及用於處理可擴展標記語言 (XML, Extensible Markup Language) 的幾個介面。

html --- 超文本標記語言 (HTML) 支援

html.parser --- 簡單的 HTML 和 XHTML 剖析器

HTML 剖析器應用程式範例

HTMLParser 方法

範例

html.entities --- HTML 一般實體的定義

XML 處理模組

XML 安全性

xml.etree.cElementTree --- ElementTree XML API

教學

XML tree and elements

剖析 XML

Pull API for non-blocking parsing

Finding interesting elements

改動 XML 檔案

建立 XML 文件

Parsing XML with Namespaces

XPath 支援

範例

支援的 XPath 語法

Reference

函式

XInclude support

範例

Reference

函式

Element 物件

ElementTree 物件

QName 物件

TreeBuilder 物件

XMLParser 物件

XMLPullParser 物件

例外

xml.dom --- Document 物件模型 API

模組內容

Objects in the DOM

DOMImplementation 物件

Node Objects

NodeList 物件

DocumentType 物件

Document Objects

Element Objects

Attr Objects

NamedNodeMap 物件

Comment Objects

Text and CDATASection Objects

ProcessingInstruction 物件

例外

Conformance

Type Mapping

Accessor Methods

xml.dom.minidom --- 最小的 DOM 實作

DOM 物件

DOM 範例

minidom 和 DOM 標準

xml.dom.pulldom --- 支援建置部分 DOM 樹

DOMEventStream 物件

xml.sax --- SAX2 剖析器支援

SAXException 物件

xml.sax.handler --- SAX 處理函式的基本類別

ContentHandler 物件

DTDHandler 物件

EntityResolver 物件

ErrorHandler 物件

LexicalHandler 物件

xml.sax.saxutils --- SAX 工具程式

xml.sax.xmlreader --- XML 剖析器的介面

XMLReader 物件

IncrementalParser 物件

Locator Objects

InputSource 物件

The Attributes Interface

The AttributesNS Interface

xml.parsers.expat --- 使用 Expat 進行快速 XML 剖析

XMLParser 物件

ExpatError 例外

範例

Content Model Descriptions

Expat 錯誤常數

html --- 超文本標記語言 (HTML) 支援

原始碼：Lib/html/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/html/__init__.py]

此模組定義了操作 HTML 的工具。

html.escape(s, quote=True)

將字串 s 中的 &、< 和 > 字元轉換為在 HTML 中安全的序列 (sequence)。如果你需要在 HTML 中顯示可能包含這些字元的文字，可以使用這個函式。如果選擇性的旗標 quote 為 true（預設），則 (") 與 (') 字元也會被轉換；這樣能包含在 HTML 中，被引號分隔的屬性值，如 <a href="..."> 。如果 quote 設為 false，則 (") 與 (') 字元不會被轉換。

在 3.2 版被加入.

html.unescape(s)

將字串 s 中所有附名 (named) 且為數值的 (numeric) 字元參照（如： &gt;、 &#62;、&#x3e; ）轉換為對應的 Unicode 字元。此函式針對有效及無效的字元參照，皆使用 HTML 5 標準所定義的規則，以及 HTML 5 附名字元參照清單 。

在 3.4 版被加入.

html 套件中的子模組為：

html.parser -- 帶有寬鬆剖析模式的 HTML/XHTML 剖析器

html.entities -- HTML 實體的定義

html.parser --- 簡單的 HTML 和 XHTML 剖析器

原始碼：Lib/html/parser.py [https://github.com/python/cpython/tree/3.14/Lib/html/parser.py]

該模組定義了一個類別 HTMLParser，是剖析 (parse) HTML（HyperText Mark-up Language、超文本標記語言）和 XHTML 格式文本檔案的基礎。

class html.parser.HTMLParser(*, convert_charrefs=True, scripting=False)

建立一個能夠剖析無效標記的剖析器實例。

如果 convert_charrefs 為 true （預設值），所有字元參照 (reference)（元素中的參照除外，像是 script 和 style ）將自動轉換為相應的 Unicode 字元。

If scripting is false (the default), the content of the noscript element is parsed normally; if it's true, it's returned as is without being parsed.

HTMLParser 實例被提供 HTML 資料，並在遇到開始標籤、結束標籤、文本、註解和其他標記元素時呼叫處理程式 (handler) 方法。使用者應該繼承 HTMLParser 並覆蓋其方法以實作所需的行為。

此剖析器不檢查結束標籤是否與開始標籤匹配，也不會為透過結束外部元素來隱晦地被結束的元素呼叫結束標籤處理程式。

在 3.4 版的變更: 新增關鍵字引數 convert_charrefs。

在 3.5 版的變更: 引數 convert_charrefs 的預設值現在是 True。

在 3.14.1 版的變更: 新增了 scripting 參數。

HTML 剖析器應用程式範例

以下的基礎範例是一個簡單的 HTML 剖析器，它使用 HTMLParser 類別，當遇到開始標籤、結束標籤和資料時將它們印出：

from html.parser import HTMLParser

class MyHTMLParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print("Encountered a start tag:", tag)

    def handle_endtag(self, tag):
        print("Encountered an end tag :", tag)

    def handle_data(self, data):
        print("Encountered some data  :", data)

parser = MyHTMLParser()
parser.feed('<html><head><title>Test</title></head>'
            '<body><h1>Parse me!</h1></body></html>')

輸出將是：

Encountered a start tag: html
Encountered a start tag: head
Encountered a start tag: title
Encountered some data  : Test
Encountered an end tag : title
Encountered an end tag : head
Encountered a start tag: body
Encountered a start tag: h1
Encountered some data  : Parse me!
Encountered an end tag : h1
Encountered an end tag : body
Encountered an end tag : html

HTMLParser 方法

HTMLParser 實例具有以下方法：

HTMLParser.feed(data)

向剖析器提供一些文本。只要它由完整的元素組成，它就會被處理；不完整的資料會被緩衝，直到輸入更多資料或呼叫 close()。 data 必須是 str。

HTMLParser.close()

強制處理所有緩衝資料，如同它後面跟有文件結束標籤一樣。此方法可能有被衍生類別重新定義，以在輸入末尾定義額外的處理，但重新定義的版本仍應要呼叫 HTMLParser 基底類別方法 close()。

HTMLParser.reset()

重置實例。丟棄所有未處理的資料。這在實例化時被會隱晦地呼叫。

HTMLParser.getpos()

回傳目前列號 (line number) 和偏移量 (offset)。

HTMLParser.get_starttag_text()

回傳最近開啟 (open) 的開始標籤的文本。這對於結構化處理通常不必要，但在處理「已部署」的 HTML 或以最少的更改重新生成輸入（可以保留屬性之間的空白等）時可能很有用。

當遇到資料或標記元素時將呼叫以下方法，並且它們應在子類別中被覆蓋。基底類別實作什麼都不做（除了 handle_startendtag()）：

HTMLParser.handle_starttag(tag, attrs)

呼叫此方法來處理元素的開始標籤（例如 <div id="main">）。

tag 引數是轉換為小寫的標籤名稱。 attrs 引數是一個 (name, value) 對的列表，包含在標籤的 <> 括號內找到的屬性。 name 將被轉成小寫，value 中的引號會被刪除，字元和實體參照也會被替換。

例如，對於標籤 <A HREF="https://www.cwi.nl/">，這個方法會以 handle_starttag('a', [('href', 'https://www.cwi.nl/')]) 的形式被呼叫。

在屬性值中來自 html.entities 的所有實體參照都會被替換。

HTMLParser.handle_endtag(tag)

呼叫此方法來處理元素的結束標籤（例如 </div>）。

tag 引數是轉換為小寫的標籤名稱。

HTMLParser.handle_startendtag(tag, attrs)

與 handle_starttag() 類似，但在剖析器遇到 XHTML 樣式的空標籤 (<img ... />) 時呼叫。這個方法可能被需要這個特定詞彙資訊 (lexical information) 的子類別覆蓋；預設實作只是呼叫 handle_starttag() 和 handle_endtag()。

HTMLParser.handle_data(data)

呼叫此方法來處理任意資料（例如文本節點與像是 script 和 style 元素的內容）。

HTMLParser.handle_entityref(name)

呼叫此方法來處理形式為 &name; （例如 &gt;）的附名字元參照，其中 name 是一般實體參照（例如 'gt'）。此方法只有在 convert_charrefs 為 false 時才會被呼叫。

HTMLParser.handle_charref(name)

呼叫此方法來處理 &#NNN; 和 &#xNNN; 形式的十進位和十六進位數字字元參照。例如，&gt; 的十進位等效為 &#62;，而十六進位為 &#x3E;；在這種情況下，該方法將收到 '62' 或 'x3E'。此方法只有在 convert_charrefs 為 false 時才會被呼叫。

HTMLParser.handle_comment(data)

當遇到註解時呼叫此方法（例如 <!--comment-->）。

舉例來說，註解 <!-- comment --> 會使得此方法被以引數 ' comment ' 來呼叫。

Internet Explorer 條件式註解（conditional comments, condcoms）的內容也會被發送到這個方法，故以 <!--[if IE 9]>IE9-specific content<![endif]--> 為例，這個方法將會收到 '[if IE 9]>IE9-specific content<![endif]'。

HTMLParser.handle_decl(decl)

呼叫此方法來處理 HTML 文件類型聲明 (doctype declaration)（例如 <!DOCTYPE html>）。

decl 參數將是 <!...> 標記內聲明部分的全部內容（例如 'DOCTYPE html'）。

HTMLParser.handle_pi(data)

遇到處理指示 (processing instruction) 時會呼叫的方法。 data 參數將包含整個處理指示。例如，對於處理指示 <?proc color='red'>，這個方法將以 handle_pi("proc color='red'") 形式被呼叫。它旨在被衍生類別覆蓋；基底類別實作中什麼都不做。

備註

HTMLParser 類別使用 SGML 語法規則來處理指示。使用有 ? 跟隨在後面的 XHTML 處理指示將導致 ? 被包含在 data 中。

HTMLParser.unknown_decl(data)

當剖析器讀取無法識別的聲明時會呼叫此方法。

data 參數將是 <![...]> 標記內聲明的全部內容。有時被衍生類別被覆蓋會是好用的。在基底類別實作中什麼都不做。

範例

以下類別實作了一個剖析器，將用於解說更多範例：

from html.parser import HTMLParser
from html.entities import name2codepoint

class MyHTMLParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print("Start tag:", tag)
        for attr in attrs:
            print("     attr:", attr)

    def handle_endtag(self, tag):
        print("End tag  :", tag)

    def handle_data(self, data):
        print("Data     :", data)

    def handle_comment(self, data):
        print("Comment  :", data)

    def handle_entityref(self, name):
        c = chr(name2codepoint[name])
        print("Named ent:", c)

    def handle_charref(self, name):
        if name.startswith('x'):
            c = chr(int(name[1:], 16))
        else:
            c = chr(int(name))
        print("Num ent  :", c)

    def handle_decl(self, data):
        print("Decl     :", data)

parser = MyHTMLParser()

剖析文件類型：

>>> parser.feed('<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" '
...             '"http://www.w3.org/TR/html4/strict.dtd">')
Decl     : DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"

剖析一個具有一些屬性和標題的元素：

>>> parser.feed('<img src="python-logo.png" alt="The Python logo">')
Start tag: img
     attr: ('src', 'python-logo.png')
     attr: ('alt', 'The Python logo')
>>>
>>> parser.feed('<h1>Python</h1>')
Start tag: h1
Data     : Python
End tag  : h1

像是 script 和 style 這類元素的內容將按原樣回傳，無需進一步的剖析：

>>> parser.feed('<style type="text/css">#python { color: green }</style>')
Start tag: style
     attr: ('type', 'text/css')
Data     : #python { color: green }
End tag  : style

>>> parser.feed('<script type="text/javascript">'
...             'alert("<strong>hello! &#9786;</strong>");</script>')
Start tag: script
     attr: ('type', 'text/javascript')
Data     : alert("<strong>hello! &#9786;</strong>");
End tag  : script

剖析註解：

>>> parser.feed('<!--a comment-->'
...             '<!--[if IE 9]>IE-specific content<![endif]-->')
Comment  : a comment
Comment  : [if IE 9]>IE-specific content<![endif]

剖析附名 (named) 且為數值的 (numeric) 字元參照，並將它們轉換為正確的字元（注意：這 3 個參照都等同於 '>'）：

>>> parser = MyHTMLParser()
>>> parser.feed('&gt;&#62;&#x3E;')
Data     : >>>

>>> parser = MyHTMLParser(convert_charrefs=False)
>>> parser.feed('&gt;&#62;&#x3E;')
Named ent: >
Num ent  : >
Num ent  : >

將不完整的區塊提供給 feed() 是可行的，但是如果 convert_charrefs 為 false，handle_data() 可能會被呼叫多次：

>>> for chunk in ['<sp', 'an>buff', 'ered', ' text</s', 'pan>']:
...     parser.feed(chunk)
...
Start tag: span
Data     : buff
Data     : ered
Data     :  text
End tag  : span

也能夠剖析無效的 HTML（例如未加引號的屬性）：

>>> parser.feed('<p><a class=link href=#main>tag soup</p ></a>')
Start tag: p
Start tag: a
     attr: ('class', 'link')
     attr: ('href', '#main')
Data     : tag soup
End tag  : p
End tag  : a

html.entities --- HTML 一般實體的定義

原始碼：Lib/html/entities.py [https://github.com/python/cpython/tree/3.14/Lib/html/entities.py]

該 module（模組）定義了四個字典：html5、name2codepoint、codepoint2name 以及 entitydefs。

html.entities.html5

將 HTML5 命名字元引用 [1] 對映到同等 Unicode 字元的字典，例如 html5['gt;'] == '>'。請注意，後面的的分號包含在名稱中（例如 'gt;'），但有些名稱即使沒有分號也會被此標準接受：在這種情況下，名稱可帶有或不帶有 ';'。請見 html.unescape()。

在 3.3 版被加入.

html.entities.entitydefs

將 XHTML 1.0 實體定義對映到 ISO Latin-1 中的替換文字的字典。

html.entities.name2codepoint

將 HTML4 實體名稱對映到 Unicode 程式點的字典。

html.entities.codepoint2name

將 Unicode 程式點對映到 HTML4 實體名稱的字典。

註解

[1]

請見 https://html.spec.whatwg.org/multipage/named-characters.html#named-character-references

XML 處理模組

原始碼：Lib/xml/ [https://github.com/python/cpython/tree/3.14/Lib/xml/]

Python 處理 XML 的介面被歸類於 xml 套件中。

備註

如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

請務必注意 xml 套件中的模組要求至少有一個可用的 SAX 相容 XML 剖析器。Expat 剖析器包含在 Python 中，所以總是可以使用 xml.parsers.expat 模組。

xml.dom 和 xml.sax 套件的文件為 DOM 和 SAX 介面的 Python 繫結的定義。

以下是 XML 處理子模組：

xml.etree.ElementTree：ElementTree API，一個簡單且輕量級的 XML 處理器

xml.dom：DOM API 定義

xml.dom.minidom：最小的 DOM 實作

xml.dom.pulldom：支援建置部分 DOM 樹

xml.sax：SAX2 基底類別和便利函式

xml.parsers.expat：Expat 剖析器繫結

XML 安全性

攻擊者可以濫用 XML 功能來執行阻斷服務攻擊 (denial of service attack)、存取本地檔案、生成與其他機器的網路連接或繞過防火牆，無論由攻擊者控制的 XML 是在 Python 中還是其他地方被剖析。

The built-in XML parsers of Python rely on the library libexpat [https://github.com/libexpat/libexpat], commonly called Expat, for parsing XML.

By default, Expat itself does not access local files or create network connections.

Expat versions lower than 2.7.2 may be vulnerable to the "billion laughs", "quadratic blowup" and "large tokens" vulnerabilities, or to disproportional use of dynamic memory. Python bundles a copy of Expat, and whether Python uses the bundled or a system-wide Expat, depends on how the Python interpreter has been configured in your environment. Python may be vulnerable if it uses such older versions of Expat. Check pyexpat.EXPAT_VERSION.

xmlrpc 容易受到「解壓縮炸彈」攻擊。

十億笑聲 / 指數實體擴展

十億笑聲 [https://en.wikipedia.org/wiki/Billion_laughs]攻擊（也稱為指數實體擴展 (exponential entity expansion)）使用多層巢狀實體。每個實體多次引用另一個實體，最終的實體定義包含一個小字串。指數擴展會產生數 GB 的文本，並消耗大量記憶體和 CPU 時間。

二次爆炸實體擴展

二次爆炸攻擊類似於十億笑聲 [https://en.wikipedia.org/wiki/Billion_laughs]攻擊；它也濫用實體擴展。它不是巢狀實體，而是一遍又一遍地重複一個具有幾千個字元的大型實體。該攻擊不如指數擴展那麼有效率，但它不會觸發那些用來防止深度巢狀實體的剖析器對策。

解壓縮炸彈 (decompression bomb)

解壓縮炸彈（又名 ZIP bomb [https://en.wikipedia.org/wiki/Zip_bomb]）適用於所有可以剖析壓縮 XML 串流（例如 gzip 壓縮的 HTTP 串流或 LZMA 壓縮檔案）的 XML 函式庫。對於攻擊者來說，它可以將傳輸的資料量減少三個或更多數量級。

大型 token

Expat 需要重新剖析未完成的 token；如果沒有 Expat 2.6.0 中引入的保護，這可能會導致二次 runtime 而導致剖析 XML 的應用程式出現阻斷服務。此問題記錄於 CVE 2023-52425 [https://www.cve.org/CVERecord?id=CVE-2023-52425]。

xml.etree.cElementTree --- ElementTree XML API

原始碼：Lib/xml/etree/ElementTree.py [https://github.com/python/cpython/tree/3.14/Lib/xml/etree/ElementTree.py]

The xml.etree.ElementTree module implements a simple and efficient API for parsing and creating XML data.

在 3.3 版的變更: This module will use a fast implementation whenever available.

在 3.3 版之後被棄用: xml.etree.cElementTree 模組已被棄用。

備註

如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

教學

This is a short tutorial for using xml.etree.ElementTree (ET in short). The goal is to demonstrate some of the building blocks and basic concepts of the module.

XML tree and elements

XML is an inherently hierarchical data format, and the most natural way to represent it is with a tree. ET has two classes for this purpose - ElementTree represents the whole XML document as a tree, and Element represents a single node in this tree. Interactions with the whole document (reading and writing to/from files) are usually done on the ElementTree level. Interactions with a single XML element and its sub-elements are done on the Element level.

剖析 XML

We'll be using the fictive country_data.xml XML document as the sample data for this section:

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank>1</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank>4</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank>68</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>

We can import this data by reading from a file:

import xml.etree.ElementTree as ET
tree = ET.parse('country_data.xml')
root = tree.getroot()

Or directly from a string:

root = ET.fromstring(country_data_as_string)

fromstring() parses XML from a string directly into an Element, which is the root element of the parsed tree. Other parsing functions may create an ElementTree. Check the documentation to be sure.

As an Element, root has a tag and a dictionary of attributes:

>>> root.tag
'data'
>>> root.attrib
{}

It also has children nodes over which we can iterate:

>>> for child in root:
...     print(child.tag, child.attrib)
...
country {'name': 'Liechtenstein'}
country {'name': 'Singapore'}
country {'name': 'Panama'}

Children are nested, and we can access specific child nodes by index:

>>> root[0][1].text
'2008'

備註

Not all elements of the XML input will end up as elements of the parsed tree. Currently, this module skips over any XML comments, processing instructions, and document type declarations in the input. Nevertheless, trees built using this module's API rather than parsing from XML text can have comments and processing instructions in them; they will be included when generating XML output. A document type declaration may be accessed by passing a custom TreeBuilder instance to the XMLParser constructor.

Pull API for non-blocking parsing

Most parsing functions provided by this module require the whole document to be read at once before returning any result. It is possible to use an XMLParser and feed data into it incrementally, but it is a push API that calls methods on a callback target, which is too low-level and inconvenient for most needs. Sometimes what the user really wants is to be able to parse XML incrementally, without blocking operations, while enjoying the convenience of fully constructed Element objects.

The most powerful tool for doing this is XMLPullParser. It does not require a blocking read to obtain the XML data, and is instead fed with data incrementally with XMLPullParser.feed() calls. To get the parsed XML elements, call XMLPullParser.read_events(). Here is an example:

>>> parser = ET.XMLPullParser(['start', 'end'])
>>> parser.feed('<mytag>sometext')
>>> list(parser.read_events())
[('start', <Element 'mytag' at 0x7fa66db2be58>)]
>>> parser.feed(' more text</mytag>')
>>> for event, elem in parser.read_events():
...     print(event)
...     print(elem.tag, 'text=', elem.text)
...
end
mytag text= sometext more text

The obvious use case is applications that operate in a non-blocking fashion where the XML data is being received from a socket or read incrementally from some storage device. In such cases, blocking reads are unacceptable.

Because it's so flexible, XMLPullParser can be inconvenient to use for simpler use-cases. If you don't mind your application blocking on reading XML data but would still like to have incremental parsing capabilities, take a look at iterparse(). It can be useful when you're reading a large XML document and don't want to hold it wholly in memory.

Where immediate feedback through events is wanted, calling method XMLPullParser.flush() can help reduce delay; please make sure to study the related security notes.

Finding interesting elements

Element has some useful methods that help iterate recursively over all the sub-tree below it (its children, their children, and so on). For example, Element.iter():

>>> for neighbor in root.iter('neighbor'):
...     print(neighbor.attrib)
...
{'name': 'Austria', 'direction': 'E'}
{'name': 'Switzerland', 'direction': 'W'}
{'name': 'Malaysia', 'direction': 'N'}
{'name': 'Costa Rica', 'direction': 'W'}
{'name': 'Colombia', 'direction': 'E'}

Element.findall() finds only elements with a tag which are direct children of the current element. Element.find() finds the first child with a particular tag, and Element.text accesses the element's text content. Element.get() accesses the element's attributes:

>>> for country in root.findall('country'):
...     rank = country.find('rank').text
...     name = country.get('name')
...     print(name, rank)
...
Liechtenstein 1
Singapore 4
Panama 68

More sophisticated specification of which elements to look for is possible by using XPath.

改動 XML 檔案

ElementTree provides a simple way to build XML documents and write them to files. The ElementTree.write() method serves this purpose.

Once created, an Element object may be manipulated by directly changing its fields (such as Element.text), adding and modifying attributes (Element.set() method), as well as adding new children (for example with Element.append()).

Let's say we want to add one to each country's rank, and add an updated attribute to the rank element:

>>> for rank in root.iter('rank'):
...     new_rank = int(rank.text) + 1
...     rank.text = str(new_rank)
...     rank.set('updated', 'yes')
...
>>> tree.write('output.xml')

XML 現在看起來像這樣：

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank updated="yes">69</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>

We can remove elements using Element.remove(). Let's say we want to remove all countries with a rank higher than 50:

>>> for country in root.findall('country'):
...     # 使用 root.findall() 來避免在遍歷時移除
...     rank = int(country.find('rank').text)
...     if rank > 50:
...         root.remove(country)
...
>>> tree.write('output.xml')

Note that concurrent modification while iterating can lead to problems, just like when iterating and modifying Python lists or dicts. Therefore, the example first collects all matching elements with root.findall(), and only then iterates over the list of matches.

XML 現在看起來像這樣：

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
</data>

建立 XML 文件

The SubElement() function also provides a convenient way to create new sub-elements for a given element:

>>> a = ET.Element('a')
>>> b = ET.SubElement(a, 'b')
>>> c = ET.SubElement(a, 'c')
>>> d = ET.SubElement(c, 'd')
>>> ET.dump(a)
<a><b /><c><d /></c></a>

Parsing XML with Namespaces

If the XML input has namespaces [https://en.wikipedia.org/wiki/XML_namespace], tags and attributes with prefixes in the form prefix:sometag get expanded to {uri}sometag where the prefix is replaced by the full URI. Also, if there is a default namespace [https://www.w3.org/TR/xml-names/#defaulting], that full URI gets prepended to all of the non-prefixed tags.

Here is an XML example that incorporates two namespaces, one with the prefix "fictional" and the other serving as the default namespace:

<?xml version="1.0"?>
<actors xmlns:fictional="http://characters.example.com"
        xmlns="http://people.example.com">
    <actor>
        <name>John Cleese</name>
        <fictional:character>Lancelot</fictional:character>
        <fictional:character>Archie Leach</fictional:character>
    </actor>
    <actor>
        <name>Eric Idle</name>
        <fictional:character>Sir Robin</fictional:character>
        <fictional:character>Gunther</fictional:character>
        <fictional:character>Commander Clement</fictional:character>
    </actor>
</actors>

One way to search and explore this XML example is to manually add the URI to every tag or attribute in the xpath of a find() or findall():

root = fromstring(xml_text)
for actor in root.findall('{http://people.example.com}actor'):
    name = actor.find('{http://people.example.com}name')
    print(name.text)
    for char in actor.findall('{http://characters.example.com}character'):
        print(' |-->', char.text)

A better way to search the namespaced XML example is to create a dictionary with your own prefixes and use those in the search functions:

ns = {'real_person': 'http://people.example.com',
      'role': 'http://characters.example.com'}

for actor in root.findall('real_person:actor', ns):
    name = actor.find('real_person:name', ns)
    print(name.text)
    for char in actor.findall('role:character', ns):
        print(' |-->', char.text)

These two approaches both output:

John Cleese
 |--> Lancelot
 |--> Archie Leach
Eric Idle
 |--> Sir Robin
 |--> Gunther
 |--> Commander Clement

XPath 支援

This module provides limited support for XPath expressions [https://www.w3.org/TR/xpath] for locating elements in a tree. The goal is to support a small subset of the abbreviated syntax; a full XPath engine is outside the scope of the module.

範例

Here's an example that demonstrates some of the XPath capabilities of the module. We'll be using the countrydata XML document from the Parsing XML section:

import xml.etree.ElementTree as ET

root = ET.fromstring(countrydata)

# Top-level elements
root.findall(".")

# All 'neighbor' grand-children of 'country' children of the top-level
# elements
root.findall("./country/neighbor")

# Nodes with name='Singapore' that have a 'year' child
root.findall(".//year/..[@name='Singapore']")

# 'year' nodes that are children of nodes with name='Singapore'
root.findall(".//*[@name='Singapore']/year")

# All 'neighbor' nodes that are the second child of their parent
root.findall(".//neighbor[2]")

For XML with namespaces, use the usual qualified {namespace}tag notation:

# All dublin-core "title" tags in the document
root.findall(".//{http://purl.org/dc/elements/1.1/}title")

支援的 XPath 語法

語法

意義

tag

Selects all child elements with the given tag. For example, spam selects all child elements named spam, and spam/egg selects all grandchildren named egg in all children named spam. {namespace}* selects all tags in the given namespace, {*}spam selects tags named spam in any (or no) namespace, and {}* only selects tags that are not in a namespace.

在 3.8 版的變更: 新增對星號萬用字元的支援。

*

Selects all child elements, including comments and processing instructions. For example, */egg selects all grandchildren named egg.

.

Selects the current node. This is mostly useful at the beginning of the path, to indicate that it's a relative path.

//

Selects all subelements, on all levels beneath the current element. For example, .//egg selects all egg elements in the entire tree.

..

Selects the parent element. Returns None if the path attempts to reach the ancestors of the start element (the element find was called on).

[@attrib]

選擇所有具有給定屬性的元素。

[@attrib='value']

Selects all elements for which the given attribute has the given value. The value cannot contain quotes.

[@attrib!='value']

Selects all elements for which the given attribute does not have the given value. The value cannot contain quotes.

在 3.10 版被加入.

[tag]

Selects all elements that have a child named tag. Only immediate children are supported.

[.='text']

Selects all elements whose complete text content, including descendants, equals the given text.

在 3.7 版被加入.

[.!='text']

Selects all elements whose complete text content, including descendants, does not equal the given text.

在 3.10 版被加入.

[tag='text']

Selects all elements that have a child named tag whose complete text content, including descendants, equals the given text.

[tag!='text']

Selects all elements that have a child named tag whose complete text content, including descendants, does not equal the given text.

在 3.10 版被加入.

[position]

Selects all elements that are located at the given position. The position can be either an integer (1 is the first position), the expression last() (for the last position), or a position relative to the last position (e.g. last()-1).

Predicates (expressions within square brackets) must be preceded by a tag name, an asterisk, or another predicate. position predicates must be preceded by a tag name.

Reference

函式

xml.etree.ElementTree.canonicalize(xml_data=None, *, out=None, from_file=None, **options)

C14N 2.0 [https://www.w3.org/TR/xml-c14n2/] transformation function.

Canonicalization is a way to normalise XML output in a way that allows byte-by-byte comparisons and digital signatures. It reduces the freedom that XML serializers have and instead generates a more constrained XML representation. The main restrictions regard the placement of namespace declarations, the ordering of attributes, and ignorable whitespace.

This function takes an XML data string (xml_data) or a file path or file-like object (from_file) as input, converts it to the canonical form, and writes it out using the out file(-like) object, if provided, or returns it as a text string if not. The output file receives text, not bytes. It should therefore be opened in text mode with utf-8 encoding.

Typical uses:

xml_data = "<root>...</root>"
print(canonicalize(xml_data))

with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file:
    canonicalize(xml_data, out=out_file)

with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file:
    canonicalize(from_file="inputfile.xml", out=out_file)

The configuration options are as follows:

with_comments: set to true to include comments (default: false)

strip_text: set to true to strip whitespace before and after text content

(default: false)

rewrite_prefixes: set to true to replace namespace prefixes by "n{number}"

(default: false)

qname_aware_tags: a set of qname aware tag names in which prefixes

should be replaced in text content (default: empty)

qname_aware_attrs: a set of qname aware attribute names in which prefixes

should be replaced in text content (default: empty)

exclude_attrs: a set of attribute names that should not be serialised

exclude_tags: a set of tag names that should not be serialised

In the option list above, "a set" refers to any collection or iterable of strings, no ordering is expected.

在 3.8 版被加入.

xml.etree.ElementTree.Comment(text=None)

Comment element factory. This factory function creates a special element that will be serialized as an XML comment by the standard serializer. The comment string can be either a bytestring or a Unicode string. text is a string containing the comment string. Returns an element instance representing a comment.

Note that XMLParser skips over comments in the input instead of creating comment objects for them. An ElementTree will only contain comment nodes if they have been inserted into to the tree using one of the Element methods.

xml.etree.ElementTree.dump(elem)

Writes an element tree or element structure to sys.stdout. This function should be used for debugging only.

The exact output format is implementation dependent. In this version, it's written as an ordinary XML file.

elem is an element tree or an individual element.

在 3.8 版的變更: The dump() function now preserves the attribute order specified by the user.

xml.etree.ElementTree.fromstring(text, parser=None)

Parses an XML section from a string constant. Same as XML(). text is a string containing XML data. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns an Element instance.

xml.etree.ElementTree.fromstringlist(sequence, parser=None)

Parses an XML document from a sequence of string fragments. sequence is a list or other sequence containing XML data fragments. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns an Element instance.

在 3.2 版被加入.

xml.etree.ElementTree.indent(tree, space='  ', level=0)

Appends whitespace to the subtree to indent the tree visually. This can be used to generate pretty-printed XML output. tree can be an Element or ElementTree. space is the whitespace string that will be inserted for each indentation level, two space characters by default. For indenting partial subtrees inside of an already indented tree, pass the initial indentation level as level.

在 3.9 版被加入.

xml.etree.ElementTree.iselement(element)

Check if an object appears to be a valid element object. element is an element instance. Return True if this is an element object.

xml.etree.ElementTree.iterparse(source, events=None, parser=None)

Parses an XML section into an element tree incrementally, and reports what's going on to the user. source is a filename or file object containing XML data. events is a sequence of events to report back. The supported events are the strings "start", "end", "comment", "pi", "start-ns" and "end-ns" (the "ns" events are used to get detailed namespace information). If events is omitted, only "end" events are reported. parser is an optional parser instance. If not given, the standard XMLParser parser is used. parser must be a subclass of XMLParser and can only use the default TreeBuilder as a target. Returns an iterator providing (event, elem) pairs; it has a root attribute that references the root element of the resulting XML tree once source is fully read. The iterator has the close() method that closes the internal file object if source is a filename.

Note that while iterparse() builds the tree incrementally, it issues blocking reads on source (or the file it names). As such, it's unsuitable for applications where blocking reads can't be made. For fully non-blocking parsing, see XMLPullParser.

備註

iterparse() only guarantees that it has seen the ">" character of a starting tag when it emits a "start" event, so the attributes are defined, but the contents of the text and tail attributes are undefined at that point. The same applies to the element children; they may or may not be present.

If you need a fully populated element, look for "end" events instead.

在 3.4 版之後被棄用: parser 引數。

在 3.8 版的變更: 新增 context 與 check_hostname 事件。

在 3.13 版的變更: 新增 close() 方法。

xml.etree.ElementTree.parse(source, parser=None)

Parses an XML section into an element tree. source is a filename or file object containing XML data. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns an ElementTree instance.

xml.etree.ElementTree.ProcessingInstruction(target, text=None)

PI element factory. This factory function creates a special element that will be serialized as an XML processing instruction. target is a string containing the PI target. text is a string containing the PI contents, if given. Returns an element instance, representing a processing instruction.

Note that XMLParser skips over processing instructions in the input instead of creating PI objects for them. An ElementTree will only contain processing instruction nodes if they have been inserted into to the tree using one of the Element methods.

xml.etree.ElementTree.register_namespace(prefix, uri)

Registers a namespace prefix. The registry is global, and any existing mapping for either the given prefix or the namespace URI will be removed. prefix is a namespace prefix. uri is a namespace uri. Tags and attributes in this namespace will be serialized with the given prefix, if at all possible.

在 3.2 版被加入.

xml.etree.ElementTree.SubElement(parent, tag, attrib={}, **extra)

Subelement factory. This function creates an element instance, and appends it to an existing element.

The element name, attribute names, and attribute values can be either bytestrings or Unicode strings. parent is the parent element. tag is the subelement name. attrib is an optional dictionary, containing element attributes. extra contains additional attributes, given as keyword arguments. Returns an element instance.

xml.etree.ElementTree.tostring(element, encoding='us-ascii', method='xml', *, xml_declaration=None, default_namespace=None, short_empty_elements=True)

Generates a string representation of an XML element, including all subelements. element is an Element instance. encoding [1] is the output encoding (default is US-ASCII). Use encoding="unicode" to generate a Unicode string (otherwise, a bytestring is generated). method is either "xml", "html" or "text" (default is "xml"). xml_declaration, default_namespace and short_empty_elements has the same meaning as in ElementTree.write(). Returns an (optionally) encoded string containing the XML data.

在 3.4 版的變更: 新增 short_empty_elements 參數。

在 3.8 版的變更: 新增 xml_declaration 與 default_namespace 參數。

在 3.8 版的變更: The tostring() function now preserves the attribute order specified by the user.

xml.etree.ElementTree.tostringlist(element, encoding='us-ascii', method='xml', *, xml_declaration=None, default_namespace=None, short_empty_elements=True)

Generates a string representation of an XML element, including all subelements. element is an Element instance. encoding [1] is the output encoding (default is US-ASCII). Use encoding="unicode" to generate a Unicode string (otherwise, a bytestring is generated). method is either "xml", "html" or "text" (default is "xml"). xml_declaration, default_namespace and short_empty_elements has the same meaning as in ElementTree.write(). Returns a list of (optionally) encoded strings containing the XML data. It does not guarantee any specific sequence, except that b"".join(tostringlist(element)) == tostring(element).

在 3.2 版被加入.

在 3.4 版的變更: 新增 short_empty_elements 參數。

在 3.8 版的變更: 新增 xml_declaration 與 default_namespace 參數。

在 3.8 版的變更: The tostringlist() function now preserves the attribute order specified by the user.

xml.etree.ElementTree.XML(text, parser=None)

Parses an XML section from a string constant. This function can be used to embed "XML literals" in Python code. text is a string containing XML data. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns an Element instance.

xml.etree.ElementTree.XMLID(text, parser=None)

Parses an XML section from a string constant, and also returns a dictionary which maps from element id:s to elements. text is a string containing XML data. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns a tuple containing an Element instance and a dictionary.

XInclude support

This module provides limited support for XInclude directives [https://www.w3.org/TR/xinclude/], via the xml.etree.ElementInclude helper module. This module can be used to insert subtrees and text strings into element trees, based on information in the tree.

範例

Here's an example that demonstrates use of the XInclude module. To include an XML document in the current document, use the {http://www.w3.org/2001/XInclude}include element and set the parse attribute to "xml", and use the href attribute to specify the document to include.

<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  <xi:include href="source.xml" parse="xml" />
</document>

By default, the href attribute is treated as a file name. You can use custom loaders to override this behaviour. Also note that the standard helper does not support XPointer syntax.

To process this file, load it as usual, and pass the root element to the xml.etree.ElementTree module:

from xml.etree import ElementTree, ElementInclude

tree = ElementTree.parse("document.xml")
root = tree.getroot()

ElementInclude.include(root)

The ElementInclude module replaces the {http://www.w3.org/2001/XInclude}include element with the root element from the source.xml document. The result might look something like this:

<document xmlns:xi="http://www.w3.org/2001/XInclude">
  <para>This is a paragraph.</para>
</document>

If the parse attribute is omitted, it defaults to "xml". The href attribute is required.

To include a text document, use the {http://www.w3.org/2001/XInclude}include element, and set the parse attribute to "text":

<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  Copyright (c) <xi:include href="year.txt" parse="text" />.
</document>

The result might look something like:

<document xmlns:xi="http://www.w3.org/2001/XInclude">
  Copyright (c) 2003.
</document>

Reference

函式

xml.etree.ElementInclude.default_loader(href, parse, encoding=None)

Default loader. This default loader reads an included resource from disk. href is a URL. parse is for parse mode either "xml" or "text". encoding is an optional text encoding. If not given, encoding is utf-8. Returns the expanded resource. If the parse mode is "xml", this is an Element instance. If the parse mode is "text", this is a string. If the loader fails, it can return None or raise an exception.

xml.etree.ElementInclude.include(elem, loader=None, base_url=None, max_depth=6)

This function expands XInclude directives in-place in tree pointed by elem. elem is either the root Element or an ElementTree instance to find such element. loader is an optional resource loader. If omitted, it defaults to default_loader(). If given, it should be a callable that implements the same interface as default_loader(). base_url is base URL of the original file, to resolve relative include file references. max_depth is the maximum number of recursive inclusions. Limited to reduce the risk of malicious content explosion. Pass None to disable the limitation.

在 3.9 版的變更: 新增 base_url 與 max_depth 參數。

Element 物件

class xml.etree.ElementTree.Element(tag, attrib={}, **extra)

Element class. This class defines the Element interface, and provides a reference implementation of this interface.

The element name, attribute names, and attribute values can be either bytestrings or Unicode strings. tag is the element name. attrib is an optional dictionary, containing element attributes. extra contains additional attributes, given as keyword arguments.

tag

A string identifying what kind of data this element represents (the element type, in other words).

text

tail

These attributes can be used to hold additional data associated with the element. Their values are usually strings but may be any application-specific object. If the element is created from an XML file, the text attribute holds either the text between the element's start tag and its first child or end tag, or None, and the tail attribute holds either the text between the element's end tag and the next tag, or None. For the XML data

<a><b>1<c>2<d/>3</c></b>4</a>

the a element has None for both text and tail attributes, the b element has text "1" and tail "4", the c element has text "2" and tail None, and the d element has text None and tail "3".

To collect the inner text of an element, see itertext(), for example "".join(element.itertext()).

Applications may store arbitrary objects in these attributes.

attrib

A dictionary containing the element's attributes. Note that while the attrib value is always a real mutable Python dictionary, an ElementTree implementation may choose to use another internal representation, and create the dictionary only if someone asks for it. To take advantage of such implementations, use the dictionary methods below whenever possible.

The following dictionary-like methods work on the element attributes.

clear()

Resets an element. This function removes all subelements, clears all attributes, and sets the text and tail attributes to None.

get(key, default=None)

Gets the element attribute named key.

Returns the attribute value, or default if the attribute was not found.

items()

Returns the element attributes as a sequence of (name, value) pairs. The attributes are returned in an arbitrary order.

keys()

Returns the elements attribute names as a list. The names are returned in an arbitrary order.

set(key, value)

Set the attribute key on the element to value.

The following methods work on the element's children (subelements).

append(subelement)

Adds the element subelement to the end of this element's internal list of subelements. Raises TypeError if subelement is not an Element.

extend(subelements)

Appends subelements from an iterable of elements. Raises TypeError if a subelement is not an Element.

在 3.2 版被加入.

find(match, namespaces=None)

Finds the first subelement matching match. match may be a tag name or a path. Returns an element instance or None. namespaces is an optional mapping from namespace prefix to full name. Pass '' as prefix to move all unprefixed tag names in the expression into the given namespace.

findall(match, namespaces=None)

Finds all matching subelements, by tag name or path. Returns a list containing all matching elements in document order. namespaces is an optional mapping from namespace prefix to full name. Pass '' as prefix to move all unprefixed tag names in the expression into the given namespace.

findtext(match, default=None, namespaces=None)

Finds text for the first subelement matching match. match may be a tag name or a path. Returns the text content of the first matching element, or default if no element was found. Note that if the matching element has no text content an empty string is returned. namespaces is an optional mapping from namespace prefix to full name. Pass '' as prefix to move all unprefixed tag names in the expression into the given namespace.

insert(index, subelement)

Inserts subelement at the given position in this element. Raises TypeError if subelement is not an Element.

iter(tag=None)

Creates a tree iterator with the current element as the root. The iterator iterates over this element and all elements below it, in document (depth first) order. If tag is not None or '*', only elements whose tag equals tag are returned from the iterator. If the tree structure is modified during iteration, the result is undefined.

在 3.2 版被加入.

iterfind(match, namespaces=None)

Finds all matching subelements, by tag name or path. Returns an iterable yielding all matching elements in document order. namespaces is an optional mapping from namespace prefix to full name.

在 3.2 版被加入.

itertext()

Creates a text iterator. The iterator loops over this element and all subelements, in document order, and returns all inner text.

在 3.2 版被加入.

makeelement(tag, attrib)

Creates a new element object of the same type as this element. Do not call this method, use the SubElement() factory function instead.

remove(subelement)

Removes subelement from the element. Unlike the find* methods this method compares elements based on the instance identity, not on tag value or contents.

Element objects also support the following sequence type methods for working with subelements: __delitem__(), __getitem__(), __setitem__(), __len__().

Caution: Elements with no subelements will test as False. In a future release of Python, all elements will test as True regardless of whether subelements exist. Instead, prefer explicit len(elem) or elem is not None tests.:

element = root.find('foo')

if not element:  # careful!
    print("element not found, or element has no subelements")

if element is None:
    print("element not found")

在 3.12 版的變更: Testing the truth value of an Element emits DeprecationWarning.

Prior to Python 3.8, the serialisation order of the XML attributes of elements was artificially made predictable by sorting the attributes by their name. Based on the now guaranteed ordering of dicts, this arbitrary reordering was removed in Python 3.8 to preserve the order in which attributes were originally parsed or created by user code.

In general, user code should try not to depend on a specific ordering of attributes, given that the XML Information Set [https://www.w3.org/TR/xml-infoset/] explicitly excludes the attribute order from conveying information. Code should be prepared to deal with any ordering on input. In cases where deterministic XML output is required, e.g. for cryptographic signing or test data sets, canonical serialisation is available with the canonicalize() function.

In cases where canonical output is not applicable but a specific attribute order is still desirable on output, code should aim for creating the attributes directly in the desired order, to avoid perceptual mismatches for readers of the code. In cases where this is difficult to achieve, a recipe like the following can be applied prior to serialisation to enforce an order independently from the Element creation:

def reorder_attributes(root):
    for el in root.iter():
        attrib = el.attrib
        if len(attrib) > 1:
            # 調整屬性順序，例如排序
            attribs = sorted(attrib.items())
            attrib.clear()
            attrib.update(attribs)

ElementTree 物件

class xml.etree.ElementTree.ElementTree(element=None, file=None)

ElementTree wrapper class. This class represents an entire element hierarchy, and adds some extra support for serialization to and from standard XML.

element is the root element. The tree is initialized with the contents of the XML file if given.

_setroot(element)

Replaces the root element for this tree. This discards the current contents of the tree, and replaces it with the given element. Use with care. element is an element instance.

find(match, namespaces=None)

Same as Element.find(), starting at the root of the tree.

findall(match, namespaces=None)

Same as Element.findall(), starting at the root of the tree.

findtext(match, default=None, namespaces=None)

Same as Element.findtext(), starting at the root of the tree.

getroot()

Returns the root element for this tree.

iter(tag=None)

Creates and returns a tree iterator for the root element. The iterator loops over all elements in this tree, in section order. tag is the tag to look for (default is to return all elements).

iterfind(match, namespaces=None)

Same as Element.iterfind(), starting at the root of the tree.

在 3.2 版被加入.

parse(source, parser=None)

Loads an external XML section into this element tree. source is a file name or file object. parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns the section root element.

write(file, encoding='us-ascii', xml_declaration=None, default_namespace=None, method='xml', *, short_empty_elements=True)

Writes the element tree to a file, as XML. file is a file name, or a file object opened for writing. encoding [1] is the output encoding (default is US-ASCII). xml_declaration controls if an XML declaration should be added to the file. Use False for never, True for always, None for only if not US-ASCII or UTF-8 or Unicode (default is None). default_namespace sets the default XML namespace (for "xmlns"). method is either "xml", "html" or "text" (default is "xml"). The keyword-only short_empty_elements parameter controls the formatting of elements that contain no content. If True (the default), they are emitted as a single self-closed tag, otherwise they are emitted as a pair of start/end tags.

The output is either a string (str) or binary (bytes). This is controlled by the encoding argument. If encoding is "unicode", the output is a string; otherwise, it's binary. Note that this may conflict with the type of file if it's an open file object; make sure you do not try to write a string to a binary stream and vice versa.

在 3.4 版的變更: 新增 short_empty_elements 參數。

在 3.8 版的變更: The write() method now preserves the attribute order specified by the user.

This is the XML file that is going to be manipulated:

<html>
    <head>
        <title>Example page</title>
    </head>
    <body>
        <p>Moved to <a href="http://example.org/">example.org</a>
        or <a href="http://example.com/">example.com</a>.</p>
    </body>
</html>

Example of changing the attribute "target" of every link in first paragraph:

>>> from xml.etree.ElementTree import ElementTree
>>> tree = ElementTree()
>>> tree.parse("index.xhtml")
<Element 'html' at 0xb77e6fac>
>>> p = tree.find("body/p")     # Finds first occurrence of tag p in body
>>> p
<Element 'p' at 0xb77ec26c>
>>> links = list(p.iter("a"))   # Returns list of all links
>>> links
[<Element 'a' at 0xb77ec2ac>, <Element 'a' at 0xb77ec1cc>]
>>> for i in links:             # Iterates through all found links
...     i.attrib["target"] = "blank"
...
>>> tree.write("output.xhtml")

QName 物件

class xml.etree.ElementTree.QName(text_or_uri, tag=None)

QName wrapper. This can be used to wrap a QName attribute value, in order to get proper namespace handling on output. text_or_uri is a string containing the QName value, in the form {uri}local, or, if the tag argument is given, the URI part of a QName. If tag is given, the first argument is interpreted as a URI, and this argument is interpreted as a local name. QName instances are opaque.

TreeBuilder 物件

class xml.etree.ElementTree.TreeBuilder(element_factory=None, *, comment_factory=None, pi_factory=None, insert_comments=False, insert_pis=False)

Generic element structure builder. This builder converts a sequence of start, data, end, comment and pi method calls to a well-formed element structure. You can use this class to build an element structure using a custom XML parser, or a parser for some other XML-like format.

element_factory, when given, must be a callable accepting two positional arguments: a tag and a dict of attributes. It is expected to return a new element instance.

The comment_factory and pi_factory functions, when given, should behave like the Comment() and ProcessingInstruction() functions to create comments and processing instructions. When not given, the default factories will be used. When insert_comments and/or insert_pis is true, comments/pis will be inserted into the tree if they appear within the root element (but not outside of it).

close()

Flushes the builder buffers, and returns the toplevel document element. Returns an Element instance.

data(data)

Adds text to the current element. data is a string. This should be either a bytestring, or a Unicode string.

end(tag)

Closes the current element. tag is the element name. Returns the closed element.

start(tag, attrs)

Opens a new element. tag is the element name. attrs is a dictionary containing element attributes. Returns the opened element.

comment(text)

Creates a comment with the given text. If insert_comments is true, this will also add it to the tree.

在 3.8 版被加入.

pi(target, text)

Creates a process instruction with the given target name and text. If insert_pis is true, this will also add it to the tree.

在 3.8 版被加入.

In addition, a custom TreeBuilder object can provide the following methods:

doctype(name, pubid, system)

Handles a doctype declaration. name is the doctype name. pubid is the public identifier. system is the system identifier. This method does not exist on the default TreeBuilder class.

在 3.2 版被加入.

start_ns(prefix, uri)

Is called whenever the parser encounters a new namespace declaration, before the start() callback for the opening element that defines it. prefix is '' for the default namespace and the declared namespace prefix name otherwise. uri is the namespace URI.

在 3.8 版被加入.

end_ns(prefix)

Is called after the end() callback of an element that declared a namespace prefix mapping, with the name of the prefix that went out of scope.

在 3.8 版被加入.

class xml.etree.ElementTree.C14NWriterTarget(write, *, with_comments=False, strip_text=False, rewrite_prefixes=False, qname_aware_tags=None, qname_aware_attrs=None, exclude_attrs=None, exclude_tags=None)

A C14N 2.0 [https://www.w3.org/TR/xml-c14n2/] writer. Arguments are the same as for the canonicalize() function. This class does not build a tree but translates the callback events directly into a serialised form using the write function.

在 3.8 版被加入.

XMLParser 物件

class xml.etree.ElementTree.XMLParser(*, target=None, encoding=None)

This class is the low-level building block of the module. It uses xml.parsers.expat for efficient, event-based parsing of XML. It can be fed XML data incrementally with the feed() method, and parsing events are translated to a push API - by invoking callbacks on the target object. If target is omitted, the standard TreeBuilder is used. If encoding [1] is given, the value overrides the encoding specified in the XML file.

在 3.8 版的變更: Parameters are now keyword-only. The html argument is no longer supported.

close()

Finishes feeding data to the parser. Returns the result of calling the close() method of the target passed during construction; by default, this is the toplevel document element.

feed(data)

Feeds data to the parser. data is encoded data.

flush()

Triggers parsing of any previously fed unparsed data, which can be used to ensure more immediate feedback, in particular with Expat >=2.6.0. The implementation of flush() temporarily disables reparse deferral with Expat (if currently enabled) and triggers a reparse. Disabling reparse deferral has security consequences; please see xml.parsers.expat.xmlparser.SetReparseDeferralEnabled() for details.

Note that flush() has been backported to some prior releases of CPython as a security fix. Check for availability of flush() using hasattr() if used in code running across a variety of Python versions.

在 3.13 版被加入.

XMLParser.feed() calls target's start(tag, attrs_dict) method for each opening tag, its end(tag) method for each closing tag, and data is processed by method data(data). For further supported callback methods, see the TreeBuilder class. XMLParser.close() calls target's method close(). XMLParser can be used not only for building a tree structure. This is an example of counting the maximum depth of an XML file:

>>> from xml.etree.ElementTree import XMLParser
>>> class MaxDepth:                     # The target object of the parser
...     maxDepth = 0
...     depth = 0
...     def start(self, tag, attrib):   # Called for each opening tag.
...         self.depth += 1
...         if self.depth > self.maxDepth:
...             self.maxDepth = self.depth
...     def end(self, tag):             # Called for each closing tag.
...         self.depth -= 1
...     def data(self, data):
...         pass            # We do not need to do anything with data.
...     def close(self):    # Called when all data has been parsed.
...         return self.maxDepth
...
>>> target = MaxDepth()
>>> parser = XMLParser(target=target)
>>> exampleXml = """
... <a>
...   <b>
...   </b>
...   <b>
...     <c>
...       <d>
...       </d>
...     </c>
...   </b>
... </a>"""
>>> parser.feed(exampleXml)
>>> parser.close()
4

XMLPullParser 物件

class xml.etree.ElementTree.XMLPullParser(events=None)

A pull parser suitable for non-blocking applications. Its input-side API is similar to that of XMLParser, but instead of pushing calls to a callback target, XMLPullParser collects an internal list of parsing events and lets the user read from it. events is a sequence of events to report back. The supported events are the strings "start", "end", "comment", "pi", "start-ns" and "end-ns" (the "ns" events are used to get detailed namespace information). If events is omitted, only "end" events are reported.

feed(data)

將給定的位元組資料饋送給剖析器。

flush()

Triggers parsing of any previously fed unparsed data, which can be used to ensure more immediate feedback, in particular with Expat >=2.6.0. The implementation of flush() temporarily disables reparse deferral with Expat (if currently enabled) and triggers a reparse. Disabling reparse deferral has security consequences; please see xml.parsers.expat.xmlparser.SetReparseDeferralEnabled() for details.

Note that flush() has been backported to some prior releases of CPython as a security fix. Check for availability of flush() using hasattr() if used in code running across a variety of Python versions.

在 3.13 版被加入.

close()

Signal the parser that the data stream is terminated. Unlike XMLParser.close(), this method always returns None. Any events not yet retrieved when the parser is closed can still be read with read_events().

read_events()

Return an iterator over the events which have been encountered in the data fed to the parser. The iterator yields (event, elem) pairs, where event is a string representing the type of event (e.g. "end") and elem is the encountered Element object, or other context value as follows.

start、end：目前的 Element。

comment, pi: the current comment / processing instruction

start-ns: a tuple (prefix, uri) naming the declared namespace mapping.

end-ns: None (this may change in a future version)

Events provided in a previous call to read_events() will not be yielded again. Events are consumed from the internal queue only when they are retrieved from the iterator, so multiple readers iterating in parallel over iterators obtained from read_events() will have unpredictable results.

備註

XMLPullParser only guarantees that it has seen the ">" character of a starting tag when it emits a "start" event, so the attributes are defined, but the contents of the text and tail attributes are undefined at that point. The same applies to the element children; they may or may not be present.

If you need a fully populated element, look for "end" events instead.

在 3.4 版被加入.

在 3.8 版的變更: 新增 context 與 check_hostname 事件。

例外

class xml.etree.ElementTree.ParseError

XML parse error, raised by the various parsing methods in this module when parsing fails. The string representation of an instance of this exception will contain a user-friendly error message. In addition, it will have the following attributes available:

code

A numeric error code from the expat parser. See the documentation of xml.parsers.expat for the list of error codes and their meanings.

position

A tuple of line, column numbers, specifying where the error occurred.

註解

[1] (1,2,3,4)

The encoding string included in XML output should conform to the appropriate standards. For example, "UTF-8" is valid, but "UTF8" is not. See https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl and https://www.iana.org/assignments/character-sets/character-sets.xhtml.

xml.dom --- Document 物件模型 API

原始碼：Lib/xml/dom/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/xml/dom/__init__.py]

The Document Object Model, or "DOM," is a cross-language API from the World Wide Web Consortium (W3C) for accessing and modifying XML documents. A DOM implementation presents an XML document as a tree structure, or allows client code to build such a structure from scratch. It then gives access to the structure through a set of objects which provided well-known interfaces.

The DOM is extremely useful for random-access applications. SAX only allows you a view of one bit of the document at a time. If you are looking at one SAX element, you have no access to another. If you are looking at a text node, you have no access to a containing element. When you write a SAX application, you need to keep track of your program's position in the document somewhere in your own code. SAX does not do it for you. Also, if you need to look ahead in the XML document, you are just out of luck.

Some applications are simply impossible in an event driven model with no access to a tree. Of course you could build some sort of tree yourself in SAX events, but the DOM allows you to avoid writing that code. The DOM is a standard tree representation for XML data.

The Document Object Model is being defined by the W3C in stages, or "levels" in their terminology. The Python mapping of the API is substantially based on the DOM Level 2 recommendation.

DOM applications typically start by parsing some XML into a DOM. How this is accomplished is not covered at all by DOM Level 1, and Level 2 provides only limited improvements: There is a DOMImplementation object class which provides access to Document creation methods, but no way to access an XML reader/parser/Document builder in an implementation-independent way. There is also no well-defined way to access these methods without an existing Document object. In Python, each DOM implementation will provide a function getDOMImplementation(). DOM Level 3 adds a Load/Store specification, which defines an interface to the reader, but this is not yet available in the Python standard library.

Once you have a DOM document object, you can access the parts of your XML document through its properties and methods. These properties are defined in the DOM specification; this portion of the reference manual describes the interpretation of the specification in Python.

The specification provided by the W3C defines the DOM API for Java, ECMAScript, and OMG IDL. The Python mapping defined here is based in large part on the IDL version of the specification, but strict compliance is not required (though implementations are free to support the strict mapping from IDL). See section Conformance for a detailed discussion of mapping requirements.

也參考

Document Object Model (DOM) Level 2 Specification [https://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/]

The W3C recommendation upon which the Python DOM API is based.

Document Object Model (DOM) Level 1 Specification [https://www.w3.org/TR/REC-DOM-Level-1/]

The W3C recommendation for the DOM supported by xml.dom.minidom.

Python Language Mapping Specification [https://www.omg.org/spec/PYTH/1.2/PDF]

This specifies the mapping from OMG IDL to Python.

模組內容

The xml.dom contains the following functions:

xml.dom.registerDOMImplementation(name, factory)

Register the factory function with the name name. The factory function should return an object which implements the DOMImplementation interface. The factory function can return the same object every time, or a new one for each call, as appropriate for the specific implementation (e.g. if that implementation supports some customization).

xml.dom.getDOMImplementation(name=None, features=())

Return a suitable DOM implementation. The name is either well-known, the module name of a DOM implementation, or None. If it is not None, imports the corresponding module and returns a DOMImplementation object if the import succeeds. If no name is given, and if the environment variable PYTHON_DOM is set, this variable is used to find the implementation.

If name is not given, this examines the available implementations to find one with the required feature set. If no implementation can be found, raise an ImportError. The features list must be a sequence of (feature, version) pairs which are passed to the hasFeature() method on available DOMImplementation objects.

Some convenience constants are also provided:

xml.dom.EMPTY_NAMESPACE

The value used to indicate that no namespace is associated with a node in the DOM. This is typically found as the namespaceURI of a node, or used as the namespaceURI parameter to a namespaces-specific method.

xml.dom.XML_NAMESPACE

The namespace URI associated with the reserved prefix xml, as defined by Namespaces in XML [https://www.w3.org/TR/REC-xml-names/] (section 4).

xml.dom.XMLNS_NAMESPACE

The namespace URI for namespace declarations, as defined by Document Object Model (DOM) Level 2 Core Specification [https://www.w3.org/TR/DOM-Level-2-Core/core.html] (section 1.1.8).

xml.dom.XHTML_NAMESPACE

The URI of the XHTML namespace as defined by XHTML 1.0: The Extensible HyperText Markup Language [https://www.w3.org/TR/xhtml1/] (section 3.1.1).

In addition, xml.dom contains a base Node class and the DOM exception classes. The Node class provided by this module does not implement any of the methods or attributes defined by the DOM specification; concrete DOM implementations must provide those. The Node class provided as part of this module does provide the constants used for the nodeType attribute on concrete Node objects; they are located within the class rather than at the module level to conform with the DOM specifications.

Objects in the DOM

The definitive documentation for the DOM is the DOM specification from the W3C.

Note that DOM attributes may also be manipulated as nodes instead of as simple strings. It is fairly rare that you must do this, however, so this usage is not yet documented.

Interface

Section

Purpose

DOMImplementation

DOMImplementation 物件

Interface to the underlying implementation.

Node

Node Objects

Base interface for most objects in a document.

NodeList

NodeList 物件

Interface for a sequence of nodes.

DocumentType

DocumentType 物件

Information about the declarations needed to process a document.

Document

Document Objects

Object which represents an entire document.

Element

Element Objects

Element nodes in the document hierarchy.

Attr

Attr Objects

Attribute value nodes on element nodes.

Comment

Comment Objects

Representation of comments in the source document.

Text

Text and CDATASection Objects

Nodes containing textual content from the document.

ProcessingInstruction

ProcessingInstruction 物件

Processing instruction representation.

An additional section describes the exceptions defined for working with the DOM in Python.

DOMImplementation 物件

The DOMImplementation interface provides a way for applications to determine the availability of particular features in the DOM they are using. DOM Level 2 added the ability to create new Document and DocumentType objects using the DOMImplementation as well.

DOMImplementation.hasFeature(feature, version)

Return True if the feature identified by the pair of strings feature and version is implemented.

DOMImplementation.createDocument(namespaceUri, qualifiedName, doctype)

Return a new Document object (the root of the DOM), with a child Element object having the given namespaceUri and qualifiedName. The doctype must be a DocumentType object created by createDocumentType(), or None. In the Python DOM API, the first two arguments can also be None in order to indicate that no Element child is to be created.

DOMImplementation.createDocumentType(qualifiedName, publicId, systemId)

Return a new DocumentType object that encapsulates the given qualifiedName, publicId, and systemId strings, representing the information contained in an XML document type declaration.

Node Objects

All of the components of an XML document are subclasses of Node.

Node.nodeType

An integer representing the node type. Symbolic constants for the types are on the Node object: ELEMENT_NODE, ATTRIBUTE_NODE, TEXT_NODE, CDATA_SECTION_NODE, ENTITY_NODE, PROCESSING_INSTRUCTION_NODE, COMMENT_NODE, DOCUMENT_NODE, DOCUMENT_TYPE_NODE, NOTATION_NODE. This is a read-only attribute.

Node.parentNode

The parent of the current node, or None for the document node. The value is always a Node object or None. For Element nodes, this will be the parent element, except for the root element, in which case it will be the Document object. For Attr nodes, this is always None. This is a read-only attribute.

Node.attributes

A NamedNodeMap of attribute objects. Only elements have actual values for this; others provide None for this attribute. This is a read-only attribute.

Node.previousSibling

The node that immediately precedes this one with the same parent. For instance the element with an end-tag that comes just before the self element's start-tag. Of course, XML documents are made up of more than just elements so the previous sibling could be text, a comment, or something else. If this node is the first child of the parent, this attribute will be None. This is a read-only attribute.

Node.nextSibling

The node that immediately follows this one with the same parent. See also previousSibling. If this is the last child of the parent, this attribute will be None. This is a read-only attribute.

Node.childNodes

A list of nodes contained within this node. This is a read-only attribute.

Node.firstChild

The first child of the node, if there are any, or None. This is a read-only attribute.

Node.lastChild

The last child of the node, if there are any, or None. This is a read-only attribute.

Node.localName

The part of the tagName following the colon if there is one, else the entire tagName. The value is a string.

Node.prefix

The part of the tagName preceding the colon if there is one, else the empty string. The value is a string, or None.

Node.namespaceURI

The namespace associated with the element name. This will be a string or None. This is a read-only attribute.

Node.nodeName

This has a different meaning for each node type; see the DOM specification for details. You can always get the information you would get here from another property such as the tagName property for elements or the name property for attributes. For all node types, the value of this attribute will be either a string or None. This is a read-only attribute.

Node.nodeValue

This has a different meaning for each node type; see the DOM specification for details. The situation is similar to that with nodeName. The value is a string or None.

Node.hasAttributes()

Return True if the node has any attributes.

Node.hasChildNodes()

Return True if the node has any child nodes.

Node.isSameNode(other)

Return True if other refers to the same node as this node. This is especially useful for DOM implementations which use any sort of proxy architecture (because more than one object can refer to the same node).

備註

This is based on a proposed DOM Level 3 API which is still in the "working draft" stage, but this particular interface appears uncontroversial. Changes from the W3C will not necessarily affect this method in the Python DOM interface (though any new W3C API for this would also be supported).

Node.appendChild(newChild)

Add a new child node to this node at the end of the list of children, returning newChild. If the node was already in the tree, it is removed first.

Node.insertBefore(newChild, refChild)

Insert a new child node before an existing child. It must be the case that refChild is a child of this node; if not, ValueError is raised. newChild is returned. If refChild is None, it inserts newChild at the end of the children's list.

Node.removeChild(oldChild)

Remove a child node. oldChild must be a child of this node; if not, ValueError is raised. oldChild is returned on success. If oldChild will not be used further, its unlink() method should be called.

Node.replaceChild(newChild, oldChild)

Replace an existing node with a new node. It must be the case that oldChild is a child of this node; if not, ValueError is raised.

Node.normalize()

Join adjacent text nodes so that all stretches of text are stored as single Text instances. This simplifies processing text from a DOM tree for many applications.

Node.cloneNode(deep)

Clone this node. Setting deep means to clone all child nodes as well. This returns the clone.

NodeList 物件

A NodeList represents a sequence of nodes. These objects are used in two ways in the DOM Core recommendation: an Element object provides one as its list of child nodes, and the getElementsByTagName() and getElementsByTagNameNS() methods of Node return objects with this interface to represent query results.

The DOM Level 2 recommendation defines one method and one attribute for these objects:

NodeList.item(i)

Return the i'th item from the sequence, if there is one, or None. The index i is not allowed to be less than zero or greater than or equal to the length of the sequence.

NodeList.length

The number of nodes in the sequence.

In addition, the Python DOM interface requires that some additional support is provided to allow NodeList objects to be used as Python sequences. All NodeList implementations must include support for __len__() and __getitem__(); this allows iteration over the NodeList in for statements and proper support for the len() built-in function.

If a DOM implementation supports modification of the document, the NodeList implementation must also support the __setitem__() and __delitem__() methods.

DocumentType 物件

Information about the notations and entities declared by a document (including the external subset if the parser uses it and can provide the information) is available from a DocumentType object. The DocumentType for a document is available from the Document object's doctype attribute; if there is no DOCTYPE declaration for the document, the document's doctype attribute will be set to None instead of an instance of this interface.

DocumentType is a specialization of Node, and adds the following attributes:

DocumentType.publicId

The public identifier for the external subset of the document type definition. This will be a string or None.

DocumentType.systemId

The system identifier for the external subset of the document type definition. This will be a URI as a string, or None.

DocumentType.internalSubset

A string giving the complete internal subset from the document. This does not include the brackets which enclose the subset. If the document has no internal subset, this should be None.

DocumentType.name

The name of the root element as given in the DOCTYPE declaration, if present.

DocumentType.entities

This is a NamedNodeMap giving the definitions of external entities. For entity names defined more than once, only the first definition is provided (others are ignored as required by the XML recommendation). This may be None if the information is not provided by the parser, or if no entities are defined.

DocumentType.notations

This is a NamedNodeMap giving the definitions of notations. For notation names defined more than once, only the first definition is provided (others are ignored as required by the XML recommendation). This may be None if the information is not provided by the parser, or if no notations are defined.

Document Objects

A Document represents an entire XML document, including its constituent elements, attributes, processing instructions, comments etc. Remember that it inherits properties from Node.

Document.documentElement

The one and only root element of the document.

Document.createElement(tagName)

Create and return a new element node. The element is not inserted into the document when it is created. You need to explicitly insert it with one of the other methods such as insertBefore() or appendChild().

Document.createElementNS(namespaceURI, tagName)

Create and return a new element with a namespace. The tagName may have a prefix. The element is not inserted into the document when it is created. You need to explicitly insert it with one of the other methods such as insertBefore() or appendChild().

Document.createTextNode(data)

Create and return a text node containing the data passed as a parameter. As with the other creation methods, this one does not insert the node into the tree.

Document.createComment(data)

Create and return a comment node containing the data passed as a parameter. As with the other creation methods, this one does not insert the node into the tree.

Document.createProcessingInstruction(target, data)

Create and return a processing instruction node containing the target and data passed as parameters. As with the other creation methods, this one does not insert the node into the tree.

Document.createAttribute(name)

Create and return an attribute node. This method does not associate the attribute node with any particular element. You must use setAttributeNode() on the appropriate Element object to use the newly created attribute instance.

Document.createAttributeNS(namespaceURI, qualifiedName)

Create and return an attribute node with a namespace. The tagName may have a prefix. This method does not associate the attribute node with any particular element. You must use setAttributeNode() on the appropriate Element object to use the newly created attribute instance.

Document.getElementsByTagName(tagName)

Search for all descendants (direct children, children's children, etc.) with a particular element type name.

Document.getElementsByTagNameNS(namespaceURI, localName)

Search for all descendants (direct children, children's children, etc.) with a particular namespace URI and localname. The localname is the part of the namespace after the prefix.

Element Objects

Element is a subclass of Node, so inherits all the attributes of that class.

Element.tagName

The element type name. In a namespace-using document it may have colons in it. The value is a string.

Element.getElementsByTagName(tagName)

Same as equivalent method in the Document class.

Element.getElementsByTagNameNS(namespaceURI, localName)

Same as equivalent method in the Document class.

Element.hasAttribute(name)

Return True if the element has an attribute named by name.

Element.hasAttributeNS(namespaceURI, localName)

Return True if the element has an attribute named by namespaceURI and localName.

Element.getAttribute(name)

Return the value of the attribute named by name as a string. If no such attribute exists, an empty string is returned, as if the attribute had no value.

Element.getAttributeNode(attrname)

Return the Attr node for the attribute named by attrname.

Element.getAttributeNS(namespaceURI, localName)

Return the value of the attribute named by namespaceURI and localName as a string. If no such attribute exists, an empty string is returned, as if the attribute had no value.

Element.getAttributeNodeNS(namespaceURI, localName)

Return an attribute value as a node, given a namespaceURI and localName.

Element.removeAttribute(name)

Remove an attribute by name. If there is no matching attribute, a NotFoundErr is raised.

Element.removeAttributeNode(oldAttr)

Remove and return oldAttr from the attribute list, if present. If oldAttr is not present, NotFoundErr is raised.

Element.removeAttributeNS(namespaceURI, localName)

Remove an attribute by name. Note that it uses a localName, not a qname. No exception is raised if there is no matching attribute.

Element.setAttribute(name, value)

Set an attribute value from a string.

Element.setAttributeNode(newAttr)

Add a new attribute node to the element, replacing an existing attribute if necessary if the name attribute matches. If a replacement occurs, the old attribute node will be returned. If newAttr is already in use, InuseAttributeErr will be raised.

Element.setAttributeNodeNS(newAttr)

Add a new attribute node to the element, replacing an existing attribute if necessary if the namespaceURI and localName attributes match. If a replacement occurs, the old attribute node will be returned. If newAttr is already in use, InuseAttributeErr will be raised.

Element.setAttributeNS(namespaceURI, qname, value)

Set an attribute value from a string, given a namespaceURI and a qname. Note that a qname is the whole attribute name. This is different than above.

Attr Objects

Attr inherits from Node, so inherits all its attributes.

Attr.name

The attribute name. In a namespace-using document it may include a colon.

Attr.localName

The part of the name following the colon if there is one, else the entire name. This is a read-only attribute.

Attr.prefix

The part of the name preceding the colon if there is one, else the empty string.

Attr.value

The text value of the attribute. This is a synonym for the nodeValue attribute.

NamedNodeMap 物件

NamedNodeMap does not inherit from Node.

NamedNodeMap.length

The length of the attribute list.

NamedNodeMap.item(index)

Return an attribute with a particular index. The order you get the attributes in is arbitrary but will be consistent for the life of a DOM. Each item is an attribute node. Get its value with the value attribute.

There are also experimental methods that give this class more mapping behavior. You can use them or you can use the standardized getAttribute*() family of methods on the Element objects.

Comment Objects

Comment represents a comment in the XML document. It is a subclass of Node, but cannot have child nodes.

Comment.data

The content of the comment as a string. The attribute contains all characters between the leading <!-- and trailing -->, but does not include them.

Text and CDATASection Objects

The Text interface represents text in the XML document. If the parser and DOM implementation support the DOM's XML extension, portions of the text enclosed in CDATA marked sections are stored in CDATASection objects. These two interfaces are identical, but provide different values for the nodeType attribute.

These interfaces extend the Node interface. They cannot have child nodes.

Text.data

The content of the text node as a string.

備註

The use of a CDATASection node does not indicate that the node represents a complete CDATA marked section, only that the content of the node was part of a CDATA section. A single CDATA section may be represented by more than one node in the document tree. There is no way to determine whether two adjacent CDATASection nodes represent different CDATA marked sections.

ProcessingInstruction 物件

Represents a processing instruction in the XML document; this inherits from the Node interface and cannot have child nodes.

ProcessingInstruction.target

The content of the processing instruction up to the first whitespace character. This is a read-only attribute.

ProcessingInstruction.data

The content of the processing instruction following the first whitespace character.

例外

The DOM Level 2 recommendation defines a single exception, DOMException, and a number of constants that allow applications to determine what sort of error occurred. DOMException instances carry a code attribute that provides the appropriate value for the specific exception.

The Python DOM interface provides the constants, but also expands the set of exceptions so that a specific exception exists for each of the exception codes defined by the DOM. The implementations must raise the appropriate specific exception, each of which carries the appropriate value for the code attribute.

exception xml.dom.DOMException

Base exception class used for all specific DOM exceptions. This exception class cannot be directly instantiated.

exception xml.dom.DomstringSizeErr

Raised when a specified range of text does not fit into a string. This is not known to be used in the Python DOM implementations, but may be received from DOM implementations not written in Python.

exception xml.dom.HierarchyRequestErr

Raised when an attempt is made to insert a node where the node type is not allowed.

exception xml.dom.IndexSizeErr

Raised when an index or size parameter to a method is negative or exceeds the allowed values.

exception xml.dom.InuseAttributeErr

Raised when an attempt is made to insert an Attr node that is already present elsewhere in the document.

exception xml.dom.InvalidAccessErr

Raised if a parameter or an operation is not supported on the underlying object.

exception xml.dom.InvalidCharacterErr

This exception is raised when a string parameter contains a character that is not permitted in the context it's being used in by the XML 1.0 recommendation. For example, attempting to create an Element node with a space in the element type name will cause this error to be raised.

exception xml.dom.InvalidModificationErr

Raised when an attempt is made to modify the type of a node.

exception xml.dom.InvalidStateErr

Raised when an attempt is made to use an object that is not defined or is no longer usable.

exception xml.dom.NamespaceErr

If an attempt is made to change any object in a way that is not permitted with regard to the Namespaces in XML [https://www.w3.org/TR/REC-xml-names/] recommendation, this exception is raised.

exception xml.dom.NotFoundErr

Exception when a node does not exist in the referenced context. For example, NamedNodeMap.removeNamedItem() will raise this if the node passed in does not exist in the map.

exception xml.dom.NotSupportedErr

Raised when the implementation does not support the requested type of object or operation.

exception xml.dom.NoDataAllowedErr

This is raised if data is specified for a node which does not support data.

exception xml.dom.NoModificationAllowedErr

Raised on attempts to modify an object where modifications are not allowed (such as for read-only nodes).

exception xml.dom.SyntaxErr

Raised when an invalid or illegal string is specified.

exception xml.dom.WrongDocumentErr

Raised when a node is inserted in a different document than it currently belongs to, and the implementation does not support migrating the node from one document to the other.

The exception codes defined in the DOM recommendation map to the exceptions described above according to this table:

常數

例外

DOMSTRING_SIZE_ERR

DomstringSizeErr

HIERARCHY_REQUEST_ERR

HierarchyRequestErr

INDEX_SIZE_ERR

IndexSizeErr

INUSE_ATTRIBUTE_ERR

InuseAttributeErr

INVALID_ACCESS_ERR

InvalidAccessErr

INVALID_CHARACTER_ERR

InvalidCharacterErr

INVALID_MODIFICATION_ERR

InvalidModificationErr

INVALID_STATE_ERR

InvalidStateErr

NAMESPACE_ERR

NamespaceErr

NOT_FOUND_ERR

NotFoundErr

NOT_SUPPORTED_ERR

NotSupportedErr

NO_DATA_ALLOWED_ERR

NoDataAllowedErr

NO_MODIFICATION_ALLOWED_ERR

NoModificationAllowedErr

SYNTAX_ERR

SyntaxErr

WRONG_DOCUMENT_ERR

WrongDocumentErr

Conformance

This section describes the conformance requirements and relationships between the Python DOM API, the W3C DOM recommendations, and the OMG IDL mapping for Python.

Type Mapping

The IDL types used in the DOM specification are mapped to Python types according to the following table.

IDL Type

Python Type

boolean

bool 或 int

int

int

long int

int

unsigned int

int

DOMString

str 或 bytes

null

None

Accessor Methods

The mapping from OMG IDL to Python defines accessor functions for IDL attribute declarations in much the way the Java mapping does. Mapping the IDL declarations

readonly attribute string someValue;
         attribute string anotherValue;

yields three accessor functions: a "get" method for someValue (_get_someValue()), and "get" and "set" methods for anotherValue (_get_anotherValue() and _set_anotherValue()). The mapping, in particular, does not require that the IDL attributes are accessible as normal Python attributes: object.someValue is not required to work, and may raise an AttributeError.

The Python DOM API, however, does require that normal attribute access work. This means that the typical surrogates generated by Python IDL compilers are not likely to work, and wrapper objects may be needed on the client if the DOM objects are accessed via CORBA. While this does require some additional consideration for CORBA DOM clients, the implementers with experience using DOM over CORBA from Python do not consider this a problem. Attributes that are declared readonly may not restrict write access in all DOM implementations.

In the Python DOM API, accessor functions are not required. If provided, they should take the form defined by the Python IDL mapping, but these methods are considered unnecessary since the attributes are accessible directly from Python. "Set" accessors should never be provided for readonly attributes.

The IDL definitions do not fully embody the requirements of the W3C DOM API, such as the notion of certain objects, such as the return value of getElementsByTagName(), being "live". The Python DOM API does not require implementations to enforce such requirements.

xml.dom.minidom --- 最小的 DOM 實作

原始碼：Lib/xml/dom/minidom.py [https://github.com/python/cpython/tree/3.14/Lib/xml/dom/minidom.py]

xml.dom.minidom is a minimal implementation of the Document Object Model interface, with an API similar to that in other languages. It is intended to be simpler than the full DOM and also significantly smaller. Users who are not already proficient with the DOM should consider using the xml.etree.ElementTree module for their XML processing instead.

備註

如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

DOM applications typically start by parsing some XML into a DOM. With xml.dom.minidom, this is done through the parse functions:

from xml.dom.minidom import parse, parseString

dom1 = parse('c:\\temp\\mydata.xml')  # 以檔名來剖析 XML 檔案

datasource = open('c:\\temp\\mydata.xml')
dom2 = parse(datasource)  # 剖析開啟的檔案

dom3 = parseString('<myxml>Some data<empty/> some more data</myxml>')

parse() 函式可以接受一個檔案名稱或開啟的檔案物件。

xml.dom.minidom.parse(filename_or_file, parser=None, bufsize=None)

Return a Document from the given input. filename_or_file may be either a file name, or a file-like object. parser, if given, must be a SAX2 parser object. This function will change the document handler of the parser and activate namespace support; other parser configuration (like setting an entity resolver) must have been done in advance.

如果你有一個字串中的 XML，你可以使用 parseString() 函式來代替：

xml.dom.minidom.parseString(string, parser=None)

Return a Document that represents the string. This method creates an io.StringIO object for the string and passes that on to parse().

這兩個函式都會回傳一個 Document 物件，表示文件的內容。

What the parse() and parseString() functions do is connect an XML parser with a "DOM builder" that can accept parse events from any SAX parser and convert them into a DOM tree. The name of the functions are perhaps misleading, but are easy to grasp when learning the interfaces. The parsing of the document will be completed before these functions return; it's simply that these functions do not provide a parser implementation themselves.

You can also create a Document by calling a method on a "DOM Implementation" object. You can get this object either by calling the getDOMImplementation() function in the xml.dom package or the xml.dom.minidom module. Once you have a Document, you can add child nodes to it to populate the DOM:

from xml.dom.minidom import getDOMImplementation

impl = getDOMImplementation()

newdoc = impl.createDocument(None, "some_tag", None)
top_element = newdoc.documentElement
text = newdoc.createTextNode('Some textual content.')
top_element.appendChild(text)

Once you have a DOM document object, you can access the parts of your XML document through its properties and methods. These properties are defined in the DOM specification. The main property of the document object is the documentElement property. It gives you the main element in the XML document: the one that holds all others. Here is an example program:

dom3 = parseString("<myxml>Some data</myxml>")
assert dom3.documentElement.tagName == "myxml"

When you are finished with a DOM tree, you may optionally call the unlink() method to encourage early cleanup of the now-unneeded objects. unlink() is an xml.dom.minidom-specific extension to the DOM API that renders the node and its descendants essentially useless. Otherwise, Python's garbage collector will eventually take care of the objects in the tree.

也參考

Document Object Model (DOM) Level 1 Specification [https://www.w3.org/TR/REC-DOM-Level-1/]

W3C 對 xml.dom.minidom DOM 支援 的建議。

DOM 物件

The definition of the DOM API for Python is given as part of the xml.dom module documentation. This section lists the differences between the API and xml.dom.minidom.

Node.unlink()

Break internal references within the DOM so that it will be garbage collected on versions of Python without cyclic GC. Even when cyclic GC is available, using this can make large amounts of memory available sooner, so calling this on DOM objects as soon as they are no longer needed is good practice. This only needs to be called on the Document object, but may be called on child nodes to discard children of that node.

You can avoid calling this method explicitly by using the with statement. The following code will automatically unlink dom when the with block is exited:

with xml.dom.minidom.parse(datasource) as dom:
    ... # 使用 dom。

Node.writexml(writer, indent='', addindent='', newl='', encoding=None, standalone=None)

Write XML to the writer object. The writer receives texts but not bytes as input, it should have a write() method which matches that of the file object interface. The indent parameter is the indentation of the current node. The addindent parameter is the incremental indentation to use for subnodes of the current one. The newl parameter specifies the string to use to terminate newlines.

For the Document node, an additional keyword argument encoding can be used to specify the encoding field of the XML header.

Similarly, explicitly stating the standalone argument causes the standalone document declarations to be added to the prologue of the XML document. If the value is set to True, standalone="yes" is added, otherwise it is set to "no". Not stating the argument will omit the declaration from the document.

在 3.8 版的變更: The writexml() method now preserves the attribute order specified by the user.

在 3.9 版的變更: 新增 standalone 參數。

Node.toxml(encoding=None, standalone=None)

Return a string or byte string containing the XML represented by the DOM node.

With an explicit encoding [1] argument, the result is a byte string in the specified encoding. With no encoding argument, the result is a Unicode string, and the XML declaration in the resulting string does not specify an encoding. Encoding this string in an encoding other than UTF-8 is likely incorrect, since UTF-8 is the default encoding of XML.

The standalone argument behaves exactly as in writexml().

在 3.8 版的變更: 現在 toxml() 方法會保留使用者指定的屬性順序。

在 3.9 版的變更: 新增 standalone 參數。

Node.toprettyxml(indent='\t', newl='\n', encoding=None, standalone=None)

Return a pretty-printed version of the document. indent specifies the indentation string and defaults to a tabulator; newl specifies the string emitted at the end of each line and defaults to \n.

The encoding argument behaves like the corresponding argument of toxml().

The standalone argument behaves exactly as in writexml().

在 3.8 版的變更: The toprettyxml() method now preserves the attribute order specified by the user.

在 3.9 版的變更: 新增 standalone 參數。

DOM 範例

This example program is a fairly realistic example of a simple program. In this particular case, we do not take much advantage of the flexibility of the DOM.

import xml.dom.minidom

document = """\
<slideshow>
<title>Demo slideshow</title>
<slide><title>Slide title</title>
<point>This is a demo</point>
<point>Of a program for processing slides</point>
</slide>

<slide><title>Another demo slide</title>
<point>It is important</point>
<point>To have more than</point>
<point>one slide</point>
</slide>
</slideshow>
"""

dom = xml.dom.minidom.parseString(document)

def getText(nodelist):
    rc = []
    for node in nodelist:
        if node.nodeType == node.TEXT_NODE:
            rc.append(node.data)
    return ''.join(rc)

def handleSlideshow(slideshow):
    print("<html>")
    handleSlideshowTitle(slideshow.getElementsByTagName("title")[0])
    slides = slideshow.getElementsByTagName("slide")
    handleToc(slides)
    handleSlides(slides)
    print("</html>")

def handleSlides(slides):
    for slide in slides:
        handleSlide(slide)

def handleSlide(slide):
    handleSlideTitle(slide.getElementsByTagName("title")[0])
    handlePoints(slide.getElementsByTagName("point"))

def handleSlideshowTitle(title):
    print(f"<title>{getText(title.childNodes)}</title>")

def handleSlideTitle(title):
    print(f"<h2>{getText(title.childNodes)}</h2>")

def handlePoints(points):
    print("<ul>")
    for point in points:
        handlePoint(point)
    print("</ul>")

def handlePoint(point):
    print(f"<li>{getText(point.childNodes)}</li>")

def handleToc(slides):
    for slide in slides:
        title = slide.getElementsByTagName("title")[0]
        print(f"<p>{getText(title.childNodes)}</p>")

handleSlideshow(dom)

minidom 和 DOM 標準

The xml.dom.minidom module is essentially a DOM 1.0-compatible DOM with some DOM 2 features (primarily namespace features).

Usage of the DOM interface in Python is straight-forward. The following mapping rules apply:

Interfaces are accessed through instance objects. Applications should not instantiate the classes themselves; they should use the creator functions available on the Document object. Derived interfaces support all operations (and attributes) from the base interfaces, plus any new operations.

Operations are used as methods. Since the DOM uses only in parameters, the arguments are passed in normal order (from left to right). There are no optional arguments. void operations return None.

IDL attributes map to instance attributes. For compatibility with the OMG IDL language mapping for Python, an attribute foo can also be accessed through accessor methods _get_foo() and _set_foo(). readonly attributes must not be changed; this is not enforced at runtime.

The types short int, unsigned int, unsigned long long, and boolean all map to Python integer objects.

The type DOMString maps to Python strings. xml.dom.minidom supports either bytes or strings, but will normally produce strings. Values of type DOMString may also be None where allowed to have the IDL null value by the DOM specification from the W3C.

const declarations map to variables in their respective scope (e.g. xml.dom.minidom.Node.PROCESSING_INSTRUCTION_NODE); they must not be changed.

DOMException is currently not supported in xml.dom.minidom. Instead, xml.dom.minidom uses standard Python exceptions such as TypeError and AttributeError.

NodeList objects are implemented using Python's built-in list type. These objects provide the interface defined in the DOM specification, but with earlier versions of Python they do not support the official API. They are, however, much more "Pythonic" than the interface defined in the W3C recommendations.

The following interfaces have no implementation in xml.dom.minidom:

DOMTimeStamp

EntityReference

Most of these reflect information in the XML document that is not of general utility to most DOM users.

註腳

[1]

The encoding name included in the XML output should conform to the appropriate standards. For example, "UTF-8" is valid, but "UTF8" is not valid in an XML document's declaration, even though Python accepts it as an encoding name. See https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl and https://www.iana.org/assignments/character-sets/character-sets.xhtml.

xml.dom.pulldom --- 支援建置部分 DOM 樹

原始碼：Lib/xml/dom/pulldom.py [https://github.com/python/cpython/tree/3.14/Lib/xml/dom/pulldom.py]

The xml.dom.pulldom module provides a "pull parser" which can also be asked to produce DOM-accessible fragments of the document where necessary. The basic concept involves pulling "events" from a stream of incoming XML and processing them. In contrast to SAX which also employs an event-driven processing model together with callbacks, the user of a pull parser is responsible for explicitly pulling events from the stream, looping over those events until either processing is finished or an error condition occurs.

備註

如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

在 3.7.1 版的變更: The SAX parser no longer processes general external entities by default to increase security by default. To enable processing of external entities, pass a custom parser instance in:

from xml.dom.pulldom import parse
from xml.sax import make_parser
from xml.sax.handler import feature_external_ges

parser = make_parser()
parser.setFeature(feature_external_ges, True)
parse(filename, parser=parser)

範例：

from xml.dom import pulldom

doc = pulldom.parse('sales_items.xml')
for event, node in doc:
    if event == pulldom.START_ELEMENT and node.tagName == 'item':
        if int(node.getAttribute('price')) > 50:
            doc.expandNode(node)
            print(node.toxml())

event 是一個常數，可以是以下其中一個：

START_ELEMENT

END_ELEMENT

COMMENT

START_DOCUMENT

END_DOCUMENT

CHARACTERS

PROCESSING_INSTRUCTION

IGNORABLE_WHITESPACE

node is an object of type xml.dom.minidom.Document, xml.dom.minidom.Element or xml.dom.minidom.Text.

Since the document is treated as a "flat" stream of events, the document "tree" is implicitly traversed and the desired elements are found regardless of their depth in the tree. In other words, one does not need to consider hierarchical issues such as recursive searching of the document nodes, although if the context of elements were important, one would either need to maintain some context-related state (i.e. remembering where one is in the document at any given point) or to make use of the DOMEventStream.expandNode() method and switch to DOM-related processing.

class xml.dom.pulldom.PullDOM(documentFactory=None)

xml.sax.handler.ContentHandler 的子類別。

class xml.dom.pulldom.SAX2DOM(documentFactory=None)

xml.sax.handler.ContentHandler 的子類別。

xml.dom.pulldom.parse(stream_or_string, parser=None, bufsize=None)

Return a DOMEventStream from the given input. stream_or_string may be either a file name, or a file-like object. parser, if given, must be an XMLReader object. This function will change the document handler of the parser and activate namespace support; other parser configuration (like setting an entity resolver) must have been done in advance.

If you have XML in a string, you can use the parseString() function instead:

xml.dom.pulldom.parseString(string, parser=None)

回傳一個表示 (Unicode) string 的 DOMEventStream。

xml.dom.pulldom.default_bufsize

Default value for the bufsize parameter to parse().

The value of this variable can be changed before calling parse() and the new value will take effect.

DOMEventStream 物件

class xml.dom.pulldom.DOMEventStream(stream, parser, bufsize)

在 3.11 版的變更: 已移除對 __getitem__() 方法的支援。

getEvent()

Return a tuple containing event and the current node as xml.dom.minidom.Document if event equals START_DOCUMENT, xml.dom.minidom.Element if event equals START_ELEMENT or END_ELEMENT or xml.dom.minidom.Text if event equals CHARACTERS. The current node does not contain information about its children, unless expandNode() is called.

expandNode(node)

展開 node 的所有子節點到 node。範例：

from xml.dom import pulldom

xml = '<html><title>Foo</title> <p>Some text <div>and more</div></p> </html>'
doc = pulldom.parseString(xml)
for event, node in doc:
    if event == pulldom.START_ELEMENT and node.tagName == 'p':
        # 以下陳述式只會印出 '<p/>'
        print(node.toxml())
        doc.expandNode(node)
        # 以下陳述式會印出包含所有子節點的節點 '<p>Some text <div>and more</div></p>'
        print(node.toxml())

reset()

xml.sax --- SAX2 剖析器支援

原始碼：Lib/xml/sax/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/xml/sax/__init__.py]

The xml.sax package provides a number of modules which implement the Simple API for XML (SAX) interface for Python. The package itself provides the SAX exceptions and the convenience functions which will be most used by users of the SAX API.

備註

如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

在 3.7.1 版的變更: The SAX parser no longer processes general external entities by default to increase security. Before, the parser created network connections to fetch remote files or loaded local files from the file system for DTD and entities. The feature can be enabled again with method setFeature() on the parser object and argument feature_external_ges.

The convenience functions are:

xml.sax.make_parser(parser_list=[])

Create and return a SAX XMLReader object. The first parser found will be used. If parser_list is provided, it must be an iterable of strings which name modules that have a function named create_parser(). Modules listed in parser_list will be used before modules in the default list of parsers.

在 3.8 版的變更: The parser_list argument can be any iterable, not just a list.

xml.sax.parse(filename_or_stream, handler, error_handler=handler.ErrorHandler())

Create a SAX parser and use it to parse a document. The document, passed in as filename_or_stream, can be a filename or a file object. The handler parameter needs to be a SAX ContentHandler instance. If error_handler is given, it must be a SAX ErrorHandler instance; if omitted, SAXParseException will be raised on all errors. There is no return value; all work must be done by the handler passed in.

xml.sax.parseString(string, handler, error_handler=handler.ErrorHandler())

Similar to parse(), but parses from a buffer string received as a parameter. string must be a str instance or a bytes-like object.

在 3.5 版的變更: 新增 str 實例的支援。

A typical SAX application uses three kinds of objects: readers, handlers and input sources. "Reader" in this context is another term for parser, i.e. some piece of code that reads the bytes or characters from the input source, and produces a sequence of events. The events then get distributed to the handler objects, i.e. the reader invokes a method on the handler. A SAX application must therefore obtain a reader object, create or open the input sources, create the handlers, and connect these objects all together. As the final step of preparation, the reader is called to parse the input. During parsing, methods on the handler objects are called based on structural and syntactic events from the input data.

For these objects, only the interfaces are relevant; they are normally not instantiated by the application itself. Since Python does not have an explicit notion of interface, they are formally introduced as classes, but applications may use implementations which do not inherit from the provided classes. The InputSource, Locator, Attributes, AttributesNS, and XMLReader interfaces are defined in the module xml.sax.xmlreader. The handler interfaces are defined in xml.sax.handler. For convenience, InputSource (which is often instantiated directly) and the handler classes are also available from xml.sax. These interfaces are described below.

In addition to these classes, xml.sax provides the following exception classes.

exception xml.sax.SAXException(msg, exception=None)

Encapsulate an XML error or warning. This class can contain basic error or warning information from either the XML parser or the application: it can be subclassed to provide additional functionality or to add localization. Note that although the handlers defined in the ErrorHandler interface receive instances of this exception, it is not required to actually raise the exception --- it is also useful as a container for information.

When instantiated, msg should be a human-readable description of the error. The optional exception parameter, if given, should be None or an exception that was caught by the parsing code and is being passed along as information.

This is the base class for the other SAX exception classes.

exception xml.sax.SAXParseException(msg, exception, locator)

Subclass of SAXException raised on parse errors. Instances of this class are passed to the methods of the SAX ErrorHandler interface to provide information about the parse error. This class supports the SAX Locator interface as well as the SAXException interface.

exception xml.sax.SAXNotRecognizedException(msg, exception=None)

Subclass of SAXException raised when a SAX XMLReader is confronted with an unrecognized feature or property. SAX applications and extensions may use this class for similar purposes.

exception xml.sax.SAXNotSupportedException(msg, exception=None)

Subclass of SAXException raised when a SAX XMLReader is asked to enable a feature that is not supported, or to set a property to a value that the implementation does not support. SAX applications and extensions may use this class for similar purposes.

也參考

SAX: The Simple API for XML [http://www.saxproject.org/]

This site is the focal point for the definition of the SAX API. It provides a Java implementation and online documentation. Links to implementations and historical information are also available.

xml.sax.handler 模組

Definitions of the interfaces for application-provided objects.

xml.sax.saxutils 模組

Convenience functions for use in SAX applications.

xml.sax.xmlreader 模組

Definitions of the interfaces for parser-provided objects.

SAXException 物件

The SAXException exception class supports the following methods:

SAXException.getMessage()

Return a human-readable message describing the error condition.

SAXException.getException()

Return an encapsulated exception object, or None.

xml.sax.handler --- SAX 處理函式的基本類別

原始碼：Lib/xml/sax/handler.py [https://github.com/python/cpython/tree/3.14/Lib/xml/sax/handler.py]

The SAX API defines five kinds of handlers: content handlers, DTD handlers, error handlers, entity resolvers and lexical handlers. Applications normally only need to implement those interfaces whose events they are interested in; they can implement the interfaces in a single object or in multiple objects. Handler implementations should inherit from the base classes provided in the module xml.sax.handler, so that all methods get default implementations.

class xml.sax.handler.ContentHandler

This is the main callback interface in SAX, and the one most important to applications. The order of events in this interface mirrors the order of the information in the document.

class xml.sax.handler.DTDHandler

Handle DTD events.

This interface specifies only those DTD events required for basic parsing (unparsed entities and attributes).

class xml.sax.handler.EntityResolver

Basic interface for resolving entities. If you create an object implementing this interface, then register the object with your Parser, the parser will call the method in your object to resolve all external entities.

class xml.sax.handler.ErrorHandler

Interface used by the parser to present error and warning messages to the application. The methods of this object control whether errors are immediately converted to exceptions or are handled in some other way.

class xml.sax.handler.LexicalHandler

Interface used by the parser to represent low frequency events which may not be of interest to many applications.

In addition to these classes, xml.sax.handler provides symbolic constants for the feature and property names.

xml.sax.handler.feature_namespaces

value: "http://xml.org/sax/features/namespaces"

true: Perform Namespace processing.

false: Optionally do not perform Namespace processing (implies namespace-prefixes; default).

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.feature_namespace_prefixes

value: "http://xml.org/sax/features/namespace-prefixes"

true: Report the original prefixed names and attributes used for Namespace declarations.

false: Do not report attributes used for Namespace declarations, and optionally do not report original prefixed names (default).

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.feature_string_interning

value: "http://xml.org/sax/features/string-interning"

true: All element names, prefixes, attribute names, Namespace URIs, and local names are interned using the built-in intern function.

false: Names are not necessarily interned, although they may be (default).

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.feature_validation

value: "http://xml.org/sax/features/validation"

true: Report all validation errors (implies external-general-entities and external-parameter-entities).

false: Do not report validation errors.

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.feature_external_ges

警告

Enabling opens a vulnerability to external entity attacks [https://en.wikipedia.org/wiki/XML_external_entity_attack] if the parser is used with user-provided XML content. Please reflect on your threat model [https://en.wikipedia.org/wiki/Threat_model] before enabling this feature.

value: "http://xml.org/sax/features/external-general-entities"

true: Include all external general (text) entities.

false: Do not include external general entities.

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.feature_external_pes

value: "http://xml.org/sax/features/external-parameter-entities"

true: Include all external parameter entities, including the external DTD subset.

false: Do not include any external parameter entities, even the external DTD subset.

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.all_features

List of all features.

xml.sax.handler.property_lexical_handler

value: "http://xml.org/sax/properties/lexical-handler"

data type: xml.sax.handler.LexicalHandler (not supported in Python 2)

description: An optional extension handler for lexical events like comments.

access: read/write

xml.sax.handler.property_declaration_handler

value: "http://xml.org/sax/properties/declaration-handler"

data type: xml.sax.sax2lib.DeclHandler (not supported in Python 2)

description: An optional extension handler for DTD-related events other than notations and unparsed entities.

access: read/write

xml.sax.handler.property_dom_node

value: "http://xml.org/sax/properties/dom-node"

data type: org.w3c.dom.Node (not supported in Python 2)

description: When parsing, the current DOM node being visited if this is a DOM iterator; when not parsing, the root DOM node for iteration.

access: (parsing) read-only; (not parsing) read/write

xml.sax.handler.property_xml_string

value: "http://xml.org/sax/properties/xml-string"

data type: Bytes

description: The literal string of characters that was the source for the current event.

access: read-only

xml.sax.handler.all_properties

List of all known property names.

ContentHandler 物件

Users are expected to subclass ContentHandler to support their application. The following methods are called by the parser on the appropriate events in the input document:

ContentHandler.setDocumentLocator(locator)

Called by the parser to give the application a locator for locating the origin of document events.

SAX parsers are strongly encouraged (though not absolutely required) to supply a locator: if it does so, it must supply the locator to the application by invoking this method before invoking any of the other methods in the DocumentHandler interface.

The locator allows the application to determine the end position of any document-related event, even if the parser is not reporting an error. Typically, the application will use this information for reporting its own errors (such as character content that does not match an application's business rules). The information returned by the locator is probably not sufficient for use with a search engine.

Note that the locator will return correct information only during the invocation of the events in this interface. The application should not attempt to use it at any other time.

ContentHandler.startDocument()

Receive notification of the beginning of a document.

The SAX parser will invoke this method only once, before any other methods in this interface or in DTDHandler (except for setDocumentLocator()).

ContentHandler.endDocument()

Receive notification of the end of a document.

The SAX parser will invoke this method only once, and it will be the last method invoked during the parse. The parser shall not invoke this method until it has either abandoned parsing (because of an unrecoverable error) or reached the end of input.

ContentHandler.startPrefixMapping(prefix, uri)

Begin the scope of a prefix-URI Namespace mapping.

The information from this event is not necessary for normal Namespace processing: the SAX XML reader will automatically replace prefixes for element and attribute names when the feature_namespaces feature is enabled (the default).

There are cases, however, when applications need to use prefixes in character data or in attribute values, where they cannot safely be expanded automatically; the startPrefixMapping() and endPrefixMapping() events supply the information to the application to expand prefixes in those contexts itself, if necessary.

Note that startPrefixMapping() and endPrefixMapping() events are not guaranteed to be properly nested relative to each-other: all startPrefixMapping() events will occur before the corresponding startElement() event, and all endPrefixMapping() events will occur after the corresponding endElement() event, but their order is not guaranteed.

ContentHandler.endPrefixMapping(prefix)

End the scope of a prefix-URI mapping.

See startPrefixMapping() for details. This event will always occur after the corresponding endElement() event, but the order of endPrefixMapping() events is not otherwise guaranteed.

ContentHandler.startElement(name, attrs)

Signals the start of an element in non-namespace mode.

The name parameter contains the raw XML 1.0 name of the element type as a string and the attrs parameter holds an object of the Attributes interface containing the attributes of the element. The object passed as attrs may be re-used by the parser; holding on to a reference to it is not a reliable way to keep a copy of the attributes. To keep a copy of the attributes, use the copy() method of the attrs object.

ContentHandler.endElement(name)

Signals the end of an element in non-namespace mode.

The name parameter contains the name of the element type, just as with the startElement() event.

ContentHandler.startElementNS(name, qname, attrs)

Signals the start of an element in namespace mode.

The name parameter contains the name of the element type as a (uri, localname) tuple, the qname parameter contains the raw XML 1.0 name used in the source document, and the attrs parameter holds an instance of the AttributesNS interface containing the attributes of the element. If no namespace is associated with the element, the uri component of name will be None. The object passed as attrs may be re-used by the parser; holding on to a reference to it is not a reliable way to keep a copy of the attributes. To keep a copy of the attributes, use the copy() method of the attrs object.

Parsers may set the qname parameter to None, unless the feature_namespace_prefixes feature is activated.

ContentHandler.endElementNS(name, qname)

Signals the end of an element in namespace mode.

The name parameter contains the name of the element type, just as with the startElementNS() method, likewise the qname parameter.

ContentHandler.characters(content)

Receive notification of character data.

The Parser will call this method to report each chunk of character data. SAX parsers may return all contiguous character data in a single chunk, or they may split it into several chunks; however, all of the characters in any single event must come from the same external entity so that the Locator provides useful information.

content may be a string or bytes instance; the expat reader module always produces strings.

備註

The earlier SAX 1 interface provided by the Python XML Special Interest Group used a more Java-like interface for this method. Since most parsers used from Python did not take advantage of the older interface, the simpler signature was chosen to replace it. To convert old code to the new interface, use content instead of slicing content with the old offset and length parameters.

ContentHandler.ignorableWhitespace(whitespace)

Receive notification of ignorable whitespace in element content.

Validating Parsers must use this method to report each chunk of ignorable whitespace (see the W3C XML 1.0 recommendation, section 2.10): non-validating parsers may also use this method if they are capable of parsing and using content models.

SAX parsers may return all contiguous whitespace in a single chunk, or they may split it into several chunks; however, all of the characters in any single event must come from the same external entity, so that the Locator provides useful information.

ContentHandler.processingInstruction(target, data)

Receive notification of a processing instruction.

The Parser will invoke this method once for each processing instruction found: note that processing instructions may occur before or after the main document element.

A SAX parser should never report an XML declaration (XML 1.0, section 2.8) or a text declaration (XML 1.0, section 4.3.1) using this method.

ContentHandler.skippedEntity(name)

Receive notification of a skipped entity.

The Parser will invoke this method once for each entity skipped. Non-validating processors may skip entities if they have not seen the declarations (because, for example, the entity was declared in an external DTD subset). All processors may skip external entities, depending on the values of the feature_external_ges and the feature_external_pes properties.

DTDHandler 物件

DTDHandler instances provide the following methods:

DTDHandler.notationDecl(name, publicId, systemId)

Handle a notation declaration event.

DTDHandler.unparsedEntityDecl(name, publicId, systemId, ndata)

Handle an unparsed entity declaration event.

EntityResolver 物件

EntityResolver.resolveEntity(publicId, systemId)

Resolve the system identifier of an entity and return either the system identifier to read from as a string, or an InputSource to read from. The default implementation returns systemId.

ErrorHandler 物件

Objects with this interface are used to receive error and warning information from the XMLReader. If you create an object that implements this interface, then register the object with your XMLReader, the parser will call the methods in your object to report all warnings and errors. There are three levels of errors available: warnings, (possibly) recoverable errors, and unrecoverable errors. All methods take a SAXParseException as the only parameter. Errors and warnings may be converted to an exception by raising the passed-in exception object.

ErrorHandler.error(exception)

Called when the parser encounters a recoverable error. If this method does not raise an exception, parsing may continue, but further document information should not be expected by the application. Allowing the parser to continue may allow additional errors to be discovered in the input document.

ErrorHandler.fatalError(exception)

Called when the parser encounters an error it cannot recover from; parsing is expected to terminate when this method returns.

ErrorHandler.warning(exception)

Called when the parser presents minor warning information to the application. Parsing is expected to continue when this method returns, and document information will continue to be passed to the application. Raising an exception in this method will cause parsing to end.

LexicalHandler 物件

Optional SAX2 handler for lexical events.

This handler is used to obtain lexical information about an XML document. Lexical information includes information describing the document encoding used and XML comments embedded in the document, as well as section boundaries for the DTD and for any CDATA sections. The lexical handlers are used in the same manner as content handlers.

Set the LexicalHandler of an XMLReader by using the setProperty method with the property identifier 'http://xml.org/sax/properties/lexical-handler'.

LexicalHandler.comment(content)

Reports a comment anywhere in the document (including the DTD and outside the document element).

LexicalHandler.startDTD(name, public_id, system_id)

Reports the start of the DTD declarations if the document has an associated DTD.

LexicalHandler.endDTD()

Reports the end of DTD declaration.

LexicalHandler.startCDATA()

Reports the start of a CDATA marked section.

The contents of the CDATA marked section will be reported through the characters handler.

LexicalHandler.endCDATA()

Reports the end of a CDATA marked section.

xml.sax.saxutils --- SAX 工具程式

原始碼：Lib/xml/sax/saxutils.py [https://github.com/python/cpython/tree/3.14/Lib/xml/sax/saxutils.py]

模組 xml.sax.saxutils 包含了許多在建立 SAX 應用程式時非常有用的類別和函式，這些類別和函式可以直接使用，也可以作為基底類別。

xml.sax.saxutils.escape(data, entities={})

在資料字串中跳脫 '&'、'<' 及 '>'。

你可以透過傳入字典作為可選的 entities 參數，來跳脫其他資料字串。鍵和值都必須是字串；每個鍵都會被對應的值取代。即使提供 entities，'&'、'<' 和 '>' 字元始終會被跳脫。

備註

這個函式只能用來跳脫 XML 中無法直接使用的字元。請勿將此函式用作一般的字串轉換函式。

xml.sax.saxutils.unescape(data, entities={})

取消跳脫資料字串中的 '&amp;'、'&lt;' 和 '&gt;'。

你可以透過傳入字典作為可選的 entities 參數，來取消其他字串的資料。鍵和值都必須是字串；每個鍵都會被對應的值取代。即使提供了 entities，'&amp;'、'&lt;’ 和 ‘&gt;' 總是會取消跳脫。

xml.sax.saxutils.quoteattr(data, entities={})

類似於 escape()，但也準備 data 作為屬性值。quoteattr() 會根據 data 的內容選擇引號字元，嘗試避免在字串中編碼任何引號字元。如果 data 中已經有單引號和雙引號字元，雙引號字元將被編碼，而 data 將被雙引號包覆。結果字串可直接用作屬性值：

>>> print("<element attr=%s>" % quoteattr("ab ' cd \" ef"))
<element attr="ab ' cd &quot; ef">

當使用參考具體語法為 HTML 或任何 SGML 產生屬性值時，此功能非常有用。

class xml.sax.saxutils.XMLGenerator(out=None, encoding='iso-8859-1', short_empty_elements=False)

這個類別透過將 SAX 事件寫回 XML 文件來實作 ContentHandler 介面。換句話說，使用 XMLGenerator 作為內容處理器將會重現被剖析的原始文件。out 應該是類檔案物件，預設為 sys.stdout。encoding 是輸出串流的編碼，預設為 'iso-8859-1'。short_empty_elements 控制不包含內容的元素的格式：如果設定為 False（預設值），它們會以一對開始/結束（start/end）標籤的形式輸出；如果設定為 True，它們會以單一自封（self-closed）標籤的形式輸出。

在 3.2 版的變更: 新增 short_empty_elements 參數。

class xml.sax.saxutils.XMLFilterBase(base)

這個類別的設計是在 XMLReader 與用戶端應用程式的事件處理程式之間。預設情況下，它什麼都不做，只是將要求傳送到閱讀器，並將事件未經修改地傳送到處理程式，但子類別可以覆寫特定的方法，以在傳送它們的時候修改事件串流或配置請求。

xml.sax.saxutils.prepare_input_source(source, base='')

這個函式接收一個輸入來源和一個可選的基底 URL，並回傳一個完全解析的 InputSource 物件，以準備讀取。輸入來源可以是字串、類檔案物件或 InputSource 物件；剖析器會使用這個函式來實作它們的 parse() 方法的多型 source 引數。

xml.sax.xmlreader --- XML 剖析器的介面

原始碼：Lib/xml/sax/xmlreader.py [https://github.com/python/cpython/tree/3.14/Lib/xml/sax/xmlreader.py]

SAX parsers implement the XMLReader interface. They are implemented in a Python module, which must provide a function create_parser(). This function is invoked by xml.sax.make_parser() with no arguments to create a new parser object.

class xml.sax.xmlreader.XMLReader

Base class which can be inherited by SAX parsers.

class xml.sax.xmlreader.IncrementalParser

In some cases, it is desirable not to parse an input source at once, but to feed chunks of the document as they get available. Note that the reader will normally not read the entire file, but read it in chunks as well; still parse() won't return until the entire document is processed. So these interfaces should be used if the blocking behaviour of parse() is not desirable.

When the parser is instantiated it is ready to begin accepting data from the feed method immediately. After parsing has been finished with a call to close the reset method must be called to make the parser ready to accept new data, either from feed or using the parse method.

Note that these methods must not be called during parsing, that is, after parse has been called and before it returns.

By default, the class also implements the parse method of the XMLReader interface using the feed, close and reset methods of the IncrementalParser interface as a convenience to SAX 2.0 driver writers.

class xml.sax.xmlreader.Locator

Interface for associating a SAX event with a document location. A locator object will return valid results only during calls to DocumentHandler methods; at any other time, the results are unpredictable. If information is not available, methods may return None.

class xml.sax.xmlreader.InputSource(system_id=None)

Encapsulation of the information needed by the XMLReader to read entities.

This class may include information about the public identifier, system identifier, byte stream (possibly with character encoding information) and/or the character stream of an entity.

Applications will create objects of this class for use in the XMLReader.parse() method and for returning from EntityResolver.resolveEntity.

An InputSource belongs to the application, the XMLReader is not allowed to modify InputSource objects passed to it from the application, although it may make copies and modify those.

class xml.sax.xmlreader.AttributesImpl(attrs)

This is an implementation of the Attributes interface (see section The Attributes Interface). This is a dictionary-like object which represents the element attributes in a startElement() call. In addition to the most useful dictionary operations, it supports a number of other methods as described by the interface. Objects of this class should be instantiated by readers; attrs must be a dictionary-like object containing a mapping from attribute names to attribute values.

class xml.sax.xmlreader.AttributesNSImpl(attrs, qnames)

Namespace-aware variant of AttributesImpl, which will be passed to startElementNS(). It is derived from AttributesImpl, but understands attribute names as two-tuples of namespaceURI and localname. In addition, it provides a number of methods expecting qualified names as they appear in the original document. This class implements the AttributesNS interface (see section The AttributesNS Interface).

XMLReader 物件

The XMLReader interface supports the following methods:

XMLReader.parse(source)

Process an input source, producing SAX events. The source object can be a system identifier (a string identifying the input source -- typically a file name or a URL), a pathlib.Path or path-like object, or an InputSource object. When parse() returns, the input is completely processed, and the parser object can be discarded or reset.

在 3.5 版的變更: 新增對字元串流的支援。

在 3.8 版的變更: 新增對類路徑物件的支援。

XMLReader.getContentHandler()

Return the current ContentHandler.

XMLReader.setContentHandler(handler)

Set the current ContentHandler. If no ContentHandler is set, content events will be discarded.

XMLReader.getDTDHandler()

Return the current DTDHandler.

XMLReader.setDTDHandler(handler)

Set the current DTDHandler. If no DTDHandler is set, DTD events will be discarded.

XMLReader.getEntityResolver()

Return the current EntityResolver.

XMLReader.setEntityResolver(handler)

Set the current EntityResolver. If no EntityResolver is set, attempts to resolve an external entity will result in opening the system identifier for the entity, and fail if it is not available.

XMLReader.getErrorHandler()

Return the current ErrorHandler.

XMLReader.setErrorHandler(handler)

Set the current error handler. If no ErrorHandler is set, errors will be raised as exceptions, and warnings will be printed.

XMLReader.setLocale(locale)

Allow an application to set the locale for errors and warnings.

SAX parsers are not required to provide localization for errors and warnings; if they cannot support the requested locale, however, they must raise a SAX exception. Applications may request a locale change in the middle of a parse.

XMLReader.getFeature(featurename)

Return the current setting for feature featurename. If the feature is not recognized, SAXNotRecognizedException is raised. The well-known featurenames are listed in the module xml.sax.handler.

XMLReader.setFeature(featurename, value)

Set the featurename to value. If the feature is not recognized, SAXNotRecognizedException is raised. If the feature or its setting is not supported by the parser, SAXNotSupportedException is raised.

XMLReader.getProperty(propertyname)

Return the current setting for property propertyname. If the property is not recognized, a SAXNotRecognizedException is raised. The well-known propertynames are listed in the module xml.sax.handler.

XMLReader.setProperty(propertyname, value)

Set the propertyname to value. If the property is not recognized, SAXNotRecognizedException is raised. If the property or its setting is not supported by the parser, SAXNotSupportedException is raised.

IncrementalParser 物件

Instances of IncrementalParser offer the following additional methods:

IncrementalParser.feed(data)

Process a chunk of data.

IncrementalParser.close()

Assume the end of the document. That will check well-formedness conditions that can be checked only at the end, invoke handlers, and may clean up resources allocated during parsing.

IncrementalParser.reset()

This method is called after close has been called to reset the parser so that it is ready to parse new documents. The results of calling parse or feed after close without calling reset are undefined.

Locator Objects

Instances of Locator provide these methods:

Locator.getColumnNumber()

Return the column number where the current event begins.

Locator.getLineNumber()

Return the line number where the current event begins.

Locator.getPublicId()

Return the public identifier for the current event.

Locator.getSystemId()

Return the system identifier for the current event.

InputSource 物件

InputSource.setPublicId(id)

Sets the public identifier of this InputSource.

InputSource.getPublicId()

Returns the public identifier of this InputSource.

InputSource.setSystemId(id)

Sets the system identifier of this InputSource.

InputSource.getSystemId()

Returns the system identifier of this InputSource.

InputSource.setEncoding(encoding)

Sets the character encoding of this InputSource.

The encoding must be a string acceptable for an XML encoding declaration (see section 4.3.3 of the XML recommendation).

The encoding attribute of the InputSource is ignored if the InputSource also contains a character stream.

InputSource.getEncoding()

Get the character encoding of this InputSource.

InputSource.setByteStream(bytefile)

Set the byte stream (a binary file) for this input source.

The SAX parser will ignore this if there is also a character stream specified, but it will use a byte stream in preference to opening a URI connection itself.

If the application knows the character encoding of the byte stream, it should set it with the setEncoding method.

InputSource.getByteStream()

Get the byte stream for this input source.

The getEncoding method will return the character encoding for this byte stream, or None if unknown.

InputSource.setCharacterStream(charfile)

Set the character stream (a text file) for this input source.

If there is a character stream specified, the SAX parser will ignore any byte stream and will not attempt to open a URI connection to the system identifier.

InputSource.getCharacterStream()

Get the character stream for this input source.

The Attributes Interface

Attributes objects implement a portion of the mapping protocol, including the methods copy(), get(), __contains__(), items(), keys(), and values(). The following methods are also provided:

Attributes.getLength()

Return the number of attributes.

Attributes.getNames()

Return the names of the attributes.

Attributes.getType(name)

Returns the type of the attribute name, which is normally 'CDATA'.

Attributes.getValue(name)

Return the value of attribute name.

The AttributesNS Interface

This interface is a subtype of the Attributes interface (see section The Attributes Interface). All methods supported by that interface are also available on AttributesNS objects.

The following methods are also available:

AttributesNS.getValueByQName(name)

Return the value for a qualified name.

AttributesNS.getNameByQName(name)

Return the (namespace, localname) pair for a qualified name.

AttributesNS.getQNameByName(name)

Return the qualified name for a (namespace, localname) pair.

AttributesNS.getQNames()

Return the qualified names of all attributes.

xml.parsers.expat --- 使用 Expat 進行快速 XML 剖析

備註

如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

The xml.parsers.expat module is a Python interface to the Expat non-validating XML parser. The module provides a single extension type, xmlparser, that represents the current state of an XML parser. After an xmlparser object has been created, various attributes of the object can be set to handler functions. When an XML document is then fed to the parser, the handler functions are called for the character data and markup in the XML document.

This module uses the pyexpat module to provide access to the Expat parser. Direct use of the pyexpat module is deprecated.

這個模組提供一個例外和一個型別物件：

exception xml.parsers.expat.ExpatError

The exception raised when Expat reports an error. See section ExpatError 例外 for more information on interpreting Expat errors.

exception xml.parsers.expat.error

ExpatError 的別名。

xml.parsers.expat.XMLParserType

The type of the return values from the ParserCreate() function.

xml.parsers.expat 模組包含兩個函式：

xml.parsers.expat.ErrorString(errno)

回傳一個給定錯誤編號 errno 的解釋字串。

xml.parsers.expat.ParserCreate(encoding=None, namespace_separator=None)

Creates and returns a new xmlparser object. encoding, if specified, must be a string naming the encoding used by the XML data. Expat doesn't support as many encodings as Python does, and its repertoire of encodings can't be extended; it supports UTF-8, UTF-16, ISO-8859-1 (Latin1), and ASCII. If encoding [1] is given it will override the implicit or explicit encoding of the document.

Parsers created through ParserCreate() are called "root" parsers, in the sense that they do not have any parent parser attached. Non-root parsers are created by parser.ExternalEntityParserCreate.

Expat can optionally do XML namespace processing for you, enabled by providing a value for namespace_separator. The value must be a one-character string; a ValueError will be raised if the string has an illegal length (None is considered the same as omission). When namespace processing is enabled, element type names and attribute names that belong to a namespace will be expanded. The element name passed to the element handlers StartElementHandler and EndElementHandler will be the concatenation of the namespace URI, the namespace separator character, and the local part of the name. If the namespace separator is a zero byte (chr(0)) then the namespace URI and the local part will be concatenated without any separator.

For example, if namespace_separator is set to a space character (' ') and the following document is parsed:

<?xml version="1.0"?>
<root xmlns    = "http://default-namespace.org/"
      xmlns:py = "http://www.python.org/ns/">
  <py:elem1 />
  <elem2 xmlns="" />
</root>

StartElementHandler 將會收到每個元素的以下字串：

http://default-namespace.org/ root
http://www.python.org/ns/ elem1
elem2

Due to limitations in the Expat library used by pyexpat, the xmlparser instance returned can only be used to parse a single XML document. Call ParserCreate for each document to provide unique parser instances.

也參考

Expat XML 剖析器 [http://www.libexpat.org/]

Expat 專案的首頁。

XMLParser 物件

xmlparser 物件擁有以下方法：

xmlparser.Parse(data[, isfinal])

Parses the contents of the string data, calling the appropriate handler functions to process the parsed data. isfinal must be true on the final call to this method; it allows the parsing of a single file in fragments, not the submission of multiple files. data can be the empty string at any time.

xmlparser.ParseFile(file)

Parse XML data reading from the object file. file only needs to provide the read(nbytes) method, returning the empty string when there's no more data.

xmlparser.SetBase(base)

Sets the base to be used for resolving relative URIs in system identifiers in declarations. Resolving relative identifiers is left to the application: this value will be passed through as the base argument to the ExternalEntityRefHandler(), NotationDeclHandler(), and UnparsedEntityDeclHandler() functions.

xmlparser.GetBase()

Returns a string containing the base set by a previous call to SetBase(), or None if SetBase() hasn't been called.

xmlparser.GetInputContext()

Returns the input data that generated the current event as a string. The data is in the encoding of the entity which contains the text. When called while an event handler is not active, the return value is None.

xmlparser.ExternalEntityParserCreate(context[, encoding])

Create a "child" parser which can be used to parse an external parsed entity referred to by content parsed by the parent parser. The context parameter should be the string passed to the ExternalEntityRefHandler() handler function, described below. The child parser is created with the ordered_attributes and specified_attributes set to the values of this parser.

xmlparser.SetParamEntityParsing(flag)

Control parsing of parameter entities (including the external DTD subset). Possible flag values are XML_PARAM_ENTITY_PARSING_NEVER, XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE and XML_PARAM_ENTITY_PARSING_ALWAYS. Return true if setting the flag was successful.

xmlparser.UseForeignDTD([flag])

Calling this with a true value for flag (the default) will cause Expat to call the ExternalEntityRefHandler with None for all arguments to allow an alternate DTD to be loaded. If the document does not contain a document type declaration, the ExternalEntityRefHandler will still be called, but the StartDoctypeDeclHandler and EndDoctypeDeclHandler will not be called.

Passing a false value for flag will cancel a previous call that passed a true value, but otherwise has no effect.

This method can only be called before the Parse() or ParseFile() methods are called; calling it after either of those have been called causes ExpatError to be raised with the code attribute set to errors.codes[errors.XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING].

xmlparser.SetReparseDeferralEnabled(enabled)

警告

Calling SetReparseDeferralEnabled(False) has security implications, as detailed below; please make sure to understand these consequences prior to using the SetReparseDeferralEnabled method.

Expat 2.6.0 introduced a security mechanism called "reparse deferral" where instead of causing denial of service through quadratic runtime from reparsing large tokens, reparsing of unfinished tokens is now delayed by default until a sufficient amount of input is reached. Due to this delay, registered handlers may — depending of the sizing of input chunks pushed to Expat — no longer be called right after pushing new input to the parser. Where immediate feedback and taking over responsibility of protecting against denial of service from large tokens are both wanted, calling SetReparseDeferralEnabled(False) disables reparse deferral for the current Expat parser instance, temporarily or altogether. Calling SetReparseDeferralEnabled(True) allows re-enabling reparse deferral.

Note that SetReparseDeferralEnabled() has been backported to some prior releases of CPython as a security fix. Check for availability of SetReparseDeferralEnabled() using hasattr() if used in code running across a variety of Python versions.

在 3.13 版被加入.

xmlparser.GetReparseDeferralEnabled()

Returns whether reparse deferral is currently enabled for the given Expat parser instance.

在 3.13 版被加入.

xmlparser 物件擁有以下方法來減輕一些常見的 XML 漏洞。

xmlparser.SetAllocTrackerActivationThreshold(threshold, /)

Sets the number of allocated bytes of dynamic memory needed to activate protection against disproportionate use of RAM.

By default, parser objects have an allocation activation threshold of 64 MiB, or equivalently 67,108,864 bytes.

An ExpatError is raised if this method is called on a non-root parser. The corresponding lineno and offset should not be used as they may have no special meaning.

在 3.14.1 版被加入.

xmlparser.SetAllocTrackerMaximumAmplification(max_factor, /)

Sets the maximum amplification factor between direct input and bytes of dynamic memory allocated.

The amplification factor is calculated as allocated / direct while parsing, where direct is the number of bytes read from the primary document in parsing and allocated is the number of bytes of dynamic memory allocated in the parser hierarchy.

The max_factor value must be a non-NaN float value greater than or equal to 1.0. Amplification factors greater than 100.0 can be observed near the start of parsing even with benign files in practice. In particular, the activation threshold should be carefully chosen to avoid false positives.

By default, parser objects have a maximum amplification factor of 100.0.

An ExpatError is raised if this method is called on a non-root parser or if max_factor is outside the valid range. The corresponding lineno and offset should not be used as they may have no special meaning.

備註

The maximum amplification factor is only considered if the threshold that can be adjusted by SetAllocTrackerActivationThreshold() is exceeded.

在 3.14.1 版被加入.

xmlparser 物件擁有以下屬性：

xmlparser.buffer_size

The size of the buffer used when buffer_text is true. A new buffer size can be set by assigning a new integer value to this attribute. When the size is changed, the buffer will be flushed.

xmlparser.buffer_text

Setting this to true causes the xmlparser object to buffer textual content returned by Expat to avoid multiple calls to the CharacterDataHandler() callback whenever possible. This can improve performance substantially since Expat normally breaks character data into chunks at every line ending. This attribute is false by default, and may be changed at any time. Note that when it is false, data that does not contain newlines may be chunked too.

xmlparser.buffer_used

If buffer_text is enabled, the number of bytes stored in the buffer. These bytes represent UTF-8 encoded text. This attribute has no meaningful interpretation when buffer_text is false.

xmlparser.ordered_attributes

Setting this attribute to a non-zero integer causes the attributes to be reported as a list rather than a dictionary. The attributes are presented in the order found in the document text. For each attribute, two list entries are presented: the attribute name and the attribute value. (Older versions of this module also used this format.) By default, this attribute is false; it may be changed at any time.

xmlparser.specified_attributes

If set to a non-zero integer, the parser will report only those attributes which were specified in the document instance and not those which were derived from attribute declarations. Applications which set this need to be especially careful to use what additional information is available from the declarations as needed to comply with the standards for the behavior of XML processors. By default, this attribute is false; it may be changed at any time.

The following attributes contain values relating to the most recent error encountered by an xmlparser object, and will only have correct values once a call to Parse() or ParseFile() has raised an xml.parsers.expat.ExpatError exception.

xmlparser.ErrorByteIndex

Byte index at which an error occurred.

xmlparser.ErrorCode

Numeric code specifying the problem. This value can be passed to the ErrorString() function, or compared to one of the constants defined in the errors object.

xmlparser.ErrorColumnNumber

Column number at which an error occurred.

xmlparser.ErrorLineNumber

Line number at which an error occurred.

The following attributes contain values relating to the current parse location in an xmlparser object. During a callback reporting a parse event they indicate the location of the first of the sequence of characters that generated the event. When called outside of a callback, the position indicated will be just past the last parse event (regardless of whether there was an associated callback).

xmlparser.CurrentByteIndex

Current byte index in the parser input.

xmlparser.CurrentColumnNumber

Current column number in the parser input.

xmlparser.CurrentLineNumber

Current line number in the parser input.

Here is the list of handlers that can be set. To set a handler on an xmlparser object o, use o.handlername = func. handlername must be taken from the following list, and func must be a callable object accepting the correct number of arguments. The arguments are all strings, unless otherwise stated.

xmlparser.XmlDeclHandler(version, encoding, standalone)

Called when the XML declaration is parsed. The XML declaration is the (optional) declaration of the applicable version of the XML recommendation, the encoding of the document text, and an optional "standalone" declaration. version and encoding will be strings, and standalone will be 1 if the document is declared standalone, 0 if it is declared not to be standalone, or -1 if the standalone clause was omitted. This is only available with Expat version 1.95.0 or newer.

xmlparser.StartDoctypeDeclHandler(doctypeName, systemId, publicId, has_internal_subset)

Called when Expat begins parsing the document type declaration (<!DOCTYPE ...). The doctypeName is provided exactly as presented. The systemId and publicId parameters give the system and public identifiers if specified, or None if omitted. has_internal_subset will be true if the document contains and internal document declaration subset. This requires Expat version 1.2 or newer.

xmlparser.EndDoctypeDeclHandler()

Called when Expat is done parsing the document type declaration. This requires Expat version 1.2 or newer.

xmlparser.ElementDeclHandler(name, model)

Called once for each element type declaration. name is the name of the element type, and model is a representation of the content model.

xmlparser.AttlistDeclHandler(elname, attname, type, default, required)

Called for each declared attribute for an element type. If an attribute list declaration declares three attributes, this handler is called three times, once for each attribute. elname is the name of the element to which the declaration applies and attname is the name of the attribute declared. The attribute type is a string passed as type; the possible values are 'CDATA', 'ID', 'IDREF', ... default gives the default value for the attribute used when the attribute is not specified by the document instance, or None if there is no default value (#IMPLIED values). If the attribute is required to be given in the document instance, required will be true. This requires Expat version 1.95.0 or newer.

xmlparser.StartElementHandler(name, attributes)

Called for the start of every element. name is a string containing the element name, and attributes is the element attributes. If ordered_attributes is true, this is a list (see ordered_attributes for a full description). Otherwise it's a dictionary mapping names to values.

xmlparser.EndElementHandler(name)

Called for the end of every element.

xmlparser.ProcessingInstructionHandler(target, data)

Called for every processing instruction.

xmlparser.CharacterDataHandler(data)

Called for character data. This will be called for normal character data, CDATA marked content, and ignorable whitespace. Applications which must distinguish these cases can use the StartCdataSectionHandler, EndCdataSectionHandler, and ElementDeclHandler callbacks to collect the required information. Note that the character data may be chunked even if it is short and so you may receive more than one call to CharacterDataHandler(). Set the buffer_text instance attribute to True to avoid that.

xmlparser.UnparsedEntityDeclHandler(entityName, base, systemId, publicId, notationName)

Called for unparsed (NDATA) entity declarations. This is only present for version 1.2 of the Expat library; for more recent versions, use EntityDeclHandler instead. (The underlying function in the Expat library has been declared obsolete.)

xmlparser.EntityDeclHandler(entityName, is_parameter_entity, value, base, systemId, publicId, notationName)

Called for all entity declarations. For parameter and internal entities, value will be a string giving the declared contents of the entity; this will be None for external entities. The notationName parameter will be None for parsed entities, and the name of the notation for unparsed entities. is_parameter_entity will be true if the entity is a parameter entity or false for general entities (most applications only need to be concerned with general entities). This is only available starting with version 1.95.0 of the Expat library.

xmlparser.NotationDeclHandler(notationName, base, systemId, publicId)

Called for notation declarations. notationName, base, and systemId, and publicId are strings if given. If the public identifier is omitted, publicId will be None.

xmlparser.StartNamespaceDeclHandler(prefix, uri)

Called when an element contains a namespace declaration. Namespace declarations are processed before the StartElementHandler is called for the element on which declarations are placed.

xmlparser.EndNamespaceDeclHandler(prefix)

Called when the closing tag is reached for an element that contained a namespace declaration. This is called once for each namespace declaration on the element in the reverse of the order for which the StartNamespaceDeclHandler was called to indicate the start of each namespace declaration's scope. Calls to this handler are made after the corresponding EndElementHandler for the end of the element.

xmlparser.CommentHandler(data)

Called for comments. data is the text of the comment, excluding the leading '<!--' and trailing '-->'.

xmlparser.StartCdataSectionHandler()

Called at the start of a CDATA section. This and EndCdataSectionHandler are needed to be able to identify the syntactical start and end for CDATA sections.

xmlparser.EndCdataSectionHandler()

在 CDATA 區塊結束時呼叫。

xmlparser.DefaultHandler(data)

Called for any characters in the XML document for which no applicable handler has been specified. This means characters that are part of a construct which could be reported, but for which no handler has been supplied.

xmlparser.DefaultHandlerExpand(data)

This is the same as the DefaultHandler(), but doesn't inhibit expansion of internal entities. The entity reference will not be passed to the default handler.

xmlparser.NotStandaloneHandler()

Called if the XML document hasn't been declared as being a standalone document. This happens when there is an external subset or a reference to a parameter entity, but the XML declaration does not set standalone to yes in an XML declaration. If this handler returns 0, then the parser will raise an XML_ERROR_NOT_STANDALONE error. If this handler is not set, no exception is raised by the parser for this condition.

xmlparser.ExternalEntityRefHandler(context, base, systemId, publicId)

警告

Implementing a handler that accesses local files and/or the network may create a vulnerability to external entity attacks [https://en.wikipedia.org/wiki/XML_external_entity_attack] if xmlparser is used with user-provided XML content. Please reflect on your threat model [https://en.wikipedia.org/wiki/Threat_model] before implementing this handler.

Called for references to external entities. base is the current base, as set by a previous call to SetBase(). The public and system identifiers, systemId and publicId, are strings if given; if the public identifier is not given, publicId will be None. The context value is opaque and should only be used as described below.

For external entities to be parsed, this handler must be implemented. It is responsible for creating the sub-parser using ExternalEntityParserCreate(context), initializing it with the appropriate callbacks, and parsing the entity. This handler should return an integer; if it returns 0, the parser will raise an XML_ERROR_EXTERNAL_ENTITY_HANDLING error, otherwise parsing will continue.

If this handler is not provided, external entities are reported by the DefaultHandler callback, if provided.

ExpatError 例外

ExpatError exceptions have a number of interesting attributes:

ExpatError.code

Expat's internal error number for the specific error. The errors.messages dictionary maps these error numbers to Expat's error messages. For example:

from xml.parsers.expat import ParserCreate, ExpatError, errors

p = ParserCreate()
try:
    p.Parse(some_xml_document)
except ExpatError as err:
    print("Error:", errors.messages[err.code])

The errors module also provides error message constants and a dictionary codes mapping these messages back to the error codes, see below.

ExpatError.lineno

Line number on which the error was detected. The first line is numbered 1.

ExpatError.offset

Character offset into the line where the error occurred. The first column is numbered 0.

範例

The following program defines three handlers that just print out their arguments.

import xml.parsers.expat

# 3 handler functions
def start_element(name, attrs):
    print('Start element:', name, attrs)
def end_element(name):
    print('End element:', name)
def char_data(data):
    print('Character data:', repr(data))

p = xml.parsers.expat.ParserCreate()

p.StartElementHandler = start_element
p.EndElementHandler = end_element
p.CharacterDataHandler = char_data

p.Parse("""<?xml version="1.0"?>
<parent id="top"><child1 name="paul">Text goes here</child1>
<child2 name="fred">More text</child2>
</parent>""", 1)

這個程式的輸出是：

Start element: parent {'id': 'top'}
Start element: child1 {'name': 'paul'}
Character data: 'Text goes here'
End element: child1
Character data: '\n'
Start element: child2 {'name': 'fred'}
Character data: 'More text'
End element: child2
Character data: '\n'
End element: parent

Content Model Descriptions

Content models are described using nested tuples. Each tuple contains four values: the type, the quantifier, the name, and a tuple of children. Children are simply additional content model descriptions.

The values of the first two fields are constants defined in the xml.parsers.expat.model module. These constants can be collected in two groups: the model type group and the quantifier group.

The constants in the model type group are:

xml.parsers.expat.model.XML_CTYPE_ANY

The element named by the model name was declared to have a content model of ANY.

xml.parsers.expat.model.XML_CTYPE_CHOICE

The named element allows a choice from a number of options; this is used for content models such as (A | B | C).

xml.parsers.expat.model.XML_CTYPE_EMPTY

Elements which are declared to be EMPTY have this model type.

xml.parsers.expat.model.XML_CTYPE_MIXED

xml.parsers.expat.model.XML_CTYPE_NAME

xml.parsers.expat.model.XML_CTYPE_SEQ

Models which represent a series of models which follow one after the other are indicated with this model type. This is used for models such as (A, B, C).

The constants in the quantifier group are:

xml.parsers.expat.model.XML_CQUANT_NONE

No modifier is given, so it can appear exactly once, as for A.

xml.parsers.expat.model.XML_CQUANT_OPT

The model is optional: it can appear once or not at all, as for A?.

xml.parsers.expat.model.XML_CQUANT_PLUS

The model must occur one or more times (like A+).

xml.parsers.expat.model.XML_CQUANT_REP

The model must occur zero or more times, as for A*.

Expat 錯誤常數

The following constants are provided in the xml.parsers.expat.errors module. These constants are useful in interpreting some of the attributes of the ExpatError exception objects raised when an error has occurred. Since for backwards compatibility reasons, the constants' value is the error message and not the numeric error code, you do this by comparing its code attribute with errors.codes[errors.XML_ERROR_CONSTANT_NAME].

errors 模組有以下屬性：

xml.parsers.expat.errors.codes

A dictionary mapping string descriptions to their error codes.

在 3.2 版被加入.

xml.parsers.expat.errors.messages

A dictionary mapping numeric error codes to their string descriptions.

在 3.2 版被加入.

xml.parsers.expat.errors.XML_ERROR_ASYNC_ENTITY

xml.parsers.expat.errors.XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF

An entity reference in an attribute value referred to an external entity instead of an internal entity.

xml.parsers.expat.errors.XML_ERROR_BAD_CHAR_REF

A character reference referred to a character which is illegal in XML (for example, character 0, or '&#0;').

xml.parsers.expat.errors.XML_ERROR_BINARY_ENTITY_REF

An entity reference referred to an entity which was declared with a notation, so cannot be parsed.

xml.parsers.expat.errors.XML_ERROR_DUPLICATE_ATTRIBUTE

An attribute was used more than once in a start tag.

xml.parsers.expat.errors.XML_ERROR_INCORRECT_ENCODING

xml.parsers.expat.errors.XML_ERROR_INVALID_TOKEN

Raised when an input byte could not properly be assigned to a character; for example, a NUL byte (value 0) in a UTF-8 input stream.

xml.parsers.expat.errors.XML_ERROR_JUNK_AFTER_DOC_ELEMENT

Something other than whitespace occurred after the document element.

xml.parsers.expat.errors.XML_ERROR_MISPLACED_XML_PI

An XML declaration was found somewhere other than the start of the input data.

xml.parsers.expat.errors.XML_ERROR_NO_ELEMENTS

The document contains no elements (XML requires all documents to contain exactly one top-level element)..

xml.parsers.expat.errors.XML_ERROR_NO_MEMORY

Expat was not able to allocate memory internally.

xml.parsers.expat.errors.XML_ERROR_PARAM_ENTITY_REF

A parameter entity reference was found where it was not allowed.

xml.parsers.expat.errors.XML_ERROR_PARTIAL_CHAR

An incomplete character was found in the input.

xml.parsers.expat.errors.XML_ERROR_RECURSIVE_ENTITY_REF

An entity reference contained another reference to the same entity; possibly via a different name, and possibly indirectly.

xml.parsers.expat.errors.XML_ERROR_SYNTAX

Some unspecified syntax error was encountered.

xml.parsers.expat.errors.XML_ERROR_TAG_MISMATCH

An end tag did not match the innermost open start tag.

xml.parsers.expat.errors.XML_ERROR_UNCLOSED_TOKEN

Some token (such as a start tag) was not closed before the end of the stream or the next token was encountered.

xml.parsers.expat.errors.XML_ERROR_UNDEFINED_ENTITY

A reference was made to an entity which was not defined.

xml.parsers.expat.errors.XML_ERROR_UNKNOWN_ENCODING

The document encoding is not supported by Expat.

xml.parsers.expat.errors.XML_ERROR_UNCLOSED_CDATA_SECTION

以 CDATA 標記的區塊未被關閉。

xml.parsers.expat.errors.XML_ERROR_EXTERNAL_ENTITY_HANDLING

xml.parsers.expat.errors.XML_ERROR_NOT_STANDALONE

The parser determined that the document was not "standalone" though it declared itself to be in the XML declaration, and the NotStandaloneHandler was set and returned 0.

xml.parsers.expat.errors.XML_ERROR_UNEXPECTED_STATE

xml.parsers.expat.errors.XML_ERROR_ENTITY_DECLARED_IN_PE

xml.parsers.expat.errors.XML_ERROR_FEATURE_REQUIRES_XML_DTD

An operation was requested that requires DTD support to be compiled in, but Expat was configured without DTD support. This should never be reported by a standard build of the xml.parsers.expat module.

xml.parsers.expat.errors.XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING

A behavioral change was requested after parsing started that can only be changed before parsing has started. This is (currently) only raised by UseForeignDTD().

xml.parsers.expat.errors.XML_ERROR_UNBOUND_PREFIX

An undeclared prefix was found when namespace processing was enabled.

xml.parsers.expat.errors.XML_ERROR_UNDECLARING_PREFIX

The document attempted to remove the namespace declaration associated with a prefix.

xml.parsers.expat.errors.XML_ERROR_INCOMPLETE_PE

A parameter entity contained incomplete markup.

xml.parsers.expat.errors.XML_ERROR_XML_DECL

The document contained no document element at all.

xml.parsers.expat.errors.XML_ERROR_TEXT_DECL

There was an error parsing a text declaration in an external entity.

xml.parsers.expat.errors.XML_ERROR_PUBLICID

Characters were found in the public id that are not allowed.

xml.parsers.expat.errors.XML_ERROR_SUSPENDED

The requested operation was made on a suspended parser, but isn't allowed. This includes attempts to provide additional input or to stop the parser.

xml.parsers.expat.errors.XML_ERROR_NOT_SUSPENDED

An attempt to resume the parser was made when the parser had not been suspended.

xml.parsers.expat.errors.XML_ERROR_ABORTED

This should not be reported to Python applications.

xml.parsers.expat.errors.XML_ERROR_FINISHED

The requested operation was made on a parser which was finished parsing input, but isn't allowed. This includes attempts to provide additional input or to stop the parser.

xml.parsers.expat.errors.XML_ERROR_SUSPEND_PE

xml.parsers.expat.errors.XML_ERROR_RESERVED_PREFIX_XML

An attempt was made to undeclare reserved namespace prefix xml or to bind it to another namespace URI.

xml.parsers.expat.errors.XML_ERROR_RESERVED_PREFIX_XMLNS

An attempt was made to declare or undeclare reserved namespace prefix xmlns.

xml.parsers.expat.errors.XML_ERROR_RESERVED_NAMESPACE_URI

An attempt was made to bind the URI of one the reserved namespace prefixes xml and xmlns to another namespace prefix.

xml.parsers.expat.errors.XML_ERROR_INVALID_ARGUMENT

This should not be reported to Python applications.

xml.parsers.expat.errors.XML_ERROR_NO_BUFFER

This should not be reported to Python applications.

xml.parsers.expat.errors.XML_ERROR_AMPLIFICATION_LIMIT_BREACH

The limit on input amplification factor (from DTD and entities) has been breached.

xml.parsers.expat.errors.XML_ERROR_NOT_STARTED

The parser was tried to be stopped or suspended before it started.

在 3.14 版被加入.

註腳

[1]

The encoding string included in XML output should conform to the appropriate standards. For example, "UTF-8" is valid, but "UTF8" is not. See https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl and https://www.iana.org/assignments/character-sets/character-sets.xhtml.

網路協定 (Internet protocols) 及支援

這個章節講述的模組實作了網路協定及相關技術的支援；他們全都是用 Python 實作的。這裡的大多數模組都需要相依於系統的模組 socket，目前普遍的平台都支援該模組。 以下為概述：

webbrowser --- 方便的網頁瀏覽器控制器

命令列介面

瀏覽器控制器物件

wsgiref --- WSGI 工具與參考實作

wsgiref.util -- WSGI 環境工具

wsgiref.headers -- WSGI 回應標頭工具

wsgiref.simple_server -- 一個簡單的 WSGI HTTP 伺服器

wsgiref.validate --- WSGI 符合性檢查

wsgiref.handlers -- 伺服器 / 閘道基本類別

wsgiref.types -- 用於靜態型別檢查的 WSGI 型別

範例

urllib --- URL 處理模組

urllib.request --- 用來開啟 URLs 的可擴充函式庫

Request 物件

OpenerDirector 物件

BaseHandler 物件

HTTPRedirectHandler 物件

HTTPCookieProcessor 物件

ProxyHandler 物件

HTTPPasswordMgr 物件

HTTPPasswordMgrWithPriorAuth 物件

AbstractBasicAuthHandler 物件

HTTPBasicAuthHandler 物件

ProxyBasicAuthHandler 物件

AbstractDigestAuthHandler 物件

HTTPDigestAuthHandler 物件

ProxyDigestAuthHandler 物件

HTTPHandler 物件

HTTPSHandler 物件

FileHandler 物件

DataHandler 物件

FTPHandler 物件

CacheFTPHandler 物件

UnknownHandler 物件

HTTPErrorProcessor 物件

範例

遺留介面

urllib.request 限制

urllib.response --- Response classes used by urllib

urllib.parse --- 將 URL 剖析成元件

URL Parsing

URL parsing security

Parsing ASCII Encoded Bytes

Structured Parse Results

URL Quoting

urllib.error --- urllib.request 引發的例外類別

urllib.robotparser --- robots.txt 的剖析器

http --- HTTP 模組

HTTP 狀態碼

HTTP 狀態分類

HTTP 方法

http.client --- HTTP 協定用戶端

HTTPConnection 物件

HTTPResponse 物件

範例

HTTPMessage 物件

ftplib --- FTP 協定用戶端

參考

FTP 物件

FTP_TLS 物件

模組變數

poplib --- POP3 協定用戶端

POP3 物件

POP3 範例

imaplib --- IMAP4 協定用戶端

IMAP4 物件

IMAP4 範例

smtplib --- SMTP 協定用戶端

SMTP 物件

SMTP 範例

uuid --- RFC 9562 定義的 UUID 物件

命令列的用法

範例

命令列的範例

socketserver --- 用於網路伺服器的框架

Server Creation Notes

Server Objects

Request Handler Objects

範例

socketserver.TCPServer 範例

socketserver.UDPServer 範例

Asynchronous Mixins

http.server — HTTP 伺服器

命令列介面

安全性注意事項

http.cookies --- HTTP 狀態管理

Cookie 物件

Morsel 物件

範例

http.cookiejar --- HTTP 用戶端的 Cookie 處理

CookieJar 與 FileCookieJar 物件

FileCookieJar 子類別及與網頁瀏覽器的合作

CookiePolicy 物件

DefaultCookiePolicy 物件

Cookie 物件

範例

xmlrpc --- XMLRPC 伺服器與用戶模組

xmlrpc.client --- XML-RPC 用戶端存取

ServerProxy 物件

日期時間物件

Binary Objects

Fault Objects

ProtocolError 物件

MultiCall 物件

便捷的函式

Example of Client Usage

Example of Client and Server Usage

xmlrpc.server --- 基本 XML-RPC 伺服器

SimpleXMLRPCServer 物件

SimpleXMLRPCServer 範例

CGIXMLRPCRequestHandler

記錄 XMLRPC 伺服器

DocXMLRPCServer 物件

DocCGIXMLRPCRequestHandler

ipaddress --- IPv4/IPv6 操作函式庫

Convenience factory functions

IP Addresses

Address objects

Conversion to Strings and Integers

運算子

比較運算子

算術運算子

IP Network definitions

Prefix, net mask and host mask

Network objects

運算子

Logical operators

疊代

Networks as containers of addresses

Interface objects

運算子

Logical operators

Other Module Level Functions

Custom Exceptions

webbrowser --- 方便的網頁瀏覽器控制器

原始碼：Lib/webbrowser.py [https://github.com/python/cpython/tree/3.14/Lib/webbrowser.py]

webbrowser 模組提供了一個高階介面，允許向使用者顯示基於網頁的文件。在大多數情況下，只需從此模組呼叫 open() 函式即可完成正確的操作。

在 Unix 下，X11 下首選圖形瀏覽器，但如果圖形瀏覽器不可用或 X11 顯示不可用，則將使用文字模式瀏覽器。如果使用文字模式瀏覽器，則呼叫程序將會阻塞 (block)，直到使用者退出瀏覽器。

如果環境變數 BROWSER 存在，它會被直譯為以 os.pathsep 分隔的瀏覽器串列，以在平台預設值之前嘗試。當串列部分的值包含字串 %s 時，它會被直譯為字面瀏覽器命令列，並使用引數 URL 替換 %s；如果值是指向已註冊瀏覽器之一的單個字，則此瀏覽器會被新增到搜尋串列的前面；如果該部分不包含 %s，則它僅被直譯為要啟動的瀏覽器的名稱。 [1]

在 3.14 版的變更: The BROWSER variable can now also be used to reorder the list of platform defaults. This is particularly useful on macOS where the platform defaults do not refer to command-line tools on PATH.

對於非 Unix 平台，或當 Unix 上有可用的遠端瀏覽器時，控制行程不會等待使用者以完成瀏覽器，而是允許遠端瀏覽器在顯示器上維護自己的視窗。如果遠端瀏覽器在 Unix 上不可用，控制行程將啟動新的瀏覽器並等待。

在 iOS 上，BROWSER 環境變數以及控制自動引發 (autoraise)、瀏覽器設定和新分頁/視窗建立的任何引數都將被忽略。網頁將始終在使用者偏好的瀏覽器中的新分頁中開啟，並將瀏覽器帶到前台。在 iOS 上使用 webbrowser 模組需要 ctypes 模組。如果 ctypes 不可用，則呼叫 open() 將會失敗。

命令列介面

腳本 webbrowser 可以用作模組的命令列介面。它接受 URL 作為引數。它接受以下可選參數：

-n, --new-window

如果可能的話會在新的瀏覽器視窗中開啟 URL。

-t, --new-tab

會在新的瀏覽器分頁 ("tab") 中開啟 URL。

這些選項自然是相互排斥的。用法範例如下：

python -m webbrowser -t "https://www.python.org"

可用性: not WASI, not Android.

以下例外有被定義於該模組：

exception webbrowser.Error

當瀏覽器控制項發生錯誤時引發例外。

以下函式有被定義於該模組：

webbrowser.open(url, new=0, autoraise=True)

使用預設瀏覽器顯示 url。如果 new 為 0，則盡可能在同一瀏覽器視窗中開啟 url。如果 new 為 1，則盡可能開啟一個新的瀏覽器視窗。如果 new 為 2，則盡可能開啟一個新的瀏覽器分頁 ("tab")。如果 autoraise 為 True，則盡可能提升視窗（請注意，無論此變數的設定如何，許多視窗管理器下都會發生這種情況）。

如果瀏覽器成功啟動則回傳 True，否則回傳 False。

請注意，在某些平台上，嘗試使用此函式開啟檔案名稱可能能夠運作並啟動作業系統的關聯程式。然而這既不支援也不可移植。

引發一個附帶引數 url 的稽核事件 webbrowser.open。

webbrowser.open_new(url)

盡可能在預設瀏覽器的新視窗中開啟 url，否則在唯一的瀏覽器視窗中開啟 url。

如果瀏覽器成功啟動則回傳 True，否則回傳 False。

webbrowser.open_new_tab(url)

盡可能在預設瀏覽器的新分頁 ("tab") 中開啟 url，否則相當於 open_new()。

如果瀏覽器成功啟動則回傳 True，否則回傳 False。

webbrowser.get(using=None)

回傳瀏覽器類型使用（以引數 using 給定）的控制器物件。如果 using 為 None，則回傳適合呼叫者環境的預設瀏覽器控制器。

webbrowser.register(name, constructor, instance=None, *, preferred=False)

註冊瀏覽器類型名稱（以引數 name 給定）。一旦註冊了瀏覽器類型，get() 函式就可以回傳該瀏覽器類型的控制器。如果沒有提供 instance 或為 None，則會在需要時不帶參數地呼叫 constructor 來建立實例。如果提供了 instance，constructor 將永遠不會被呼叫，並且可能為 None。

將 preferred 設為 True 會使該瀏覽器成為不帶引數的 get() 呼叫的偏好結果。否則只有當你計劃設定 BROWSER 變數或使用與你宣告的處理程序名稱相符的非空引數呼叫 get() 時，此入口點才會有用。

在 3.7 版的變更: 新增了 preferred 僅限關鍵字參數。

預先定義了多種瀏覽器類型。此表給出了可以傳遞給 get() 函式的類型名稱以及控制器類別的相應實例化方式，這些都定義於此模組中。

類型名稱

類別名稱

註解

'mozilla'

Mozilla('mozilla')

'firefox'

Mozilla('mozilla')

'epiphany'

Epiphany('epiphany')

'kfmclient'

Konqueror()

(1)

'konqueror'

Konqueror()

(1)

'kfm'

Konqueror()

(1)

'opera'

Opera()

'links'

GenericBrowser('links')

'elinks'

Elinks('elinks')

'lynx'

GenericBrowser('lynx')

'w3m'

GenericBrowser('w3m')

'windows-default'

WindowsDefault

(2)

'macosx'

MacOSXOSAScript('default')

(3)

'safari'

MacOSXOSAScript('safari')

(3)

'google-chrome'

Chrome('google-chrome')

'chrome'

Chrome('chrome')

'chromium'

Chromium('chromium')

'chromium-browser'

Chromium('chromium-browser')

'iosbrowser'

IOSBrowser

(4)

註解：

"Konqueror" 是 Unix 的 KDE 桌面環境的檔案管理器，只有在 KDE 運作時才有意義。最好能有某種可靠的 KDE 檢測方法；僅有 KDEDIR 變數是不夠的。另請注意，即使在 KDE 2 中使用 konqueror 命令時，也會使用 "kfm" 名稱 --- 該實作會選擇執行 Konqueror 的最佳策略。

僅在 Windows 平台上。

僅在 macOS 上。

僅在 iOS 上。

在 3.2 版被加入: 新增了 MacOSXOSAScript 類別並於 Mac 上使用，而非使用先前的 MacOSX 類別。這增加了對開啟目前未設定為作業系統預設之瀏覽器的支援。

在 3.3 版被加入: 新增了對 Chrome/Chromium 的支援。

在 3.12 版的變更: 對多個過時瀏覽器的支援已被刪除。已刪除的瀏覽器包括 Grail、Mosaic、Netscape、Galeon、Skipstone、Iceape 和 Firefox 35 及以下版本。

在 3.13 版的變更: 新增了對 iOS 的支援。

以下是一些簡單範例：

url = 'https://docs.python.org/'

# 如果瀏覽器視窗已打開，則在新分頁中開啟 URL。
webbrowser.open_new_tab(url)

# 在新視窗中開啟 URL，如果可能的話提升視窗。
webbrowser.open_new(url)

瀏覽器控制器物件

瀏覽器控制器提供了 name 屬性和以下三個與模組層級便利函式相同的方法：

controller.name

瀏覽器的系統相依名稱 (system-dependent name)。

controller.open(url, new=0, autoraise=True)

使用此控制器處理的瀏覽器顯示 url。如果 new 為 1，則盡可能開啟一個新的瀏覽器視窗。如果 new 為 2，則盡可能開啟一個新的瀏覽器分頁 ("tab")。

controller.open_new(url)

盡可能在此控制器處理的瀏覽器的新視窗中開啟 url，否則在唯一的瀏覽器視窗中開啟 url。別名為 open_new()。

controller.open_new_tab(url)

盡可能在此控制器處理的瀏覽器的新分頁 ("tab") 中開啟 url，否則相當於 open_new()。

註腳

[1]

此處命名的無完整路徑可執行檔將在 PATH 環境變數中給定的目錄中被搜尋。

wsgiref --- WSGI 工具與參考實作

原始碼：Lib/wsgiref [https://github.com/python/cpython/tree/3.14/Lib/wsgiref]

網頁伺服器閘道介面 (WSGI) 是一個標準介面，用於連接網頁伺服器軟體與使用 Python 撰寫的網頁應用程式，擁有一個標準介面使得支援 WSGI 的應用程式可以與多個不同的網頁伺服器運行。

只有網頁伺服器與程式框架的作者需要瞭解 WSGI 設計的每個細節與邊角案例，你並不需要為了安裝 WSGI 應用程式或是使用現有框架撰寫網頁應用程式而必須理解每個細節。

wsgiref 是 WSGI 規格的參考實作，可用於新增 WSGI 來支援網頁伺服器或框架，它提供操作 WSGI 環境變數以及回應標頭的工具，用於實作 WSGI 伺服器的基本類別，提供用於示範 HTTP 伺服器的 WSGI 應用程式、靜態型別檢查、以及驗證 WSGI 伺服器與應用程式是否符合 WSGI 規格的驗證工具 (PEP 3333 [https://peps.python.org/pep-3333/])。

參閱 wsgi.readthedocs.io [https://wsgi.readthedocs.io/] 更多 WSGI 相關資訊，以及教學連結與其他資源。

wsgiref.util -- WSGI 環境工具

這個模組提供許多用於處理 WSGI 環境運作的功能。WSGI 環境是一個包含 HTTP 請求變數的字典，如 PEP 3333 [https://peps.python.org/pep-3333/] 所述。所有接受 environ 的參數的函式都需要提供符合 WSGI 標準的字典；請參閱 PEP 3333 [https://peps.python.org/pep-3333/] 取得詳細規格，以及 WSGIEnvironment 取得可用於使用型別註釋的型別別名。

wsgiref.util.guess_scheme(environ)

透過檢查 environ 字典中的 HTTPS 環境變數，回傳 wsgi.url_scheme 應該是 "http" 或 "https" 的猜測。回傳值為一個字串。

當建立一個包裝 CGI 或類似 FastCGI 的 CGI-like 協定閘道時，此函式非常有用。例如 FastCGI，通常提供這類協定的伺服器在透過 SSL 接收到請求時會包含 "1"，"yes"，或 "on" 的 HTTPS 變數，因此，如果找到這樣的值，此函式回傳 "https"，否則回傳 "http"。

wsgiref.util.request_uri(environ, include_query=True)

根據 PEP 3333 [https://peps.python.org/pep-3333/] 中 "URL Reconstruction" 章節所找到的演算法，回傳完整的請求 URI，可選擇性的包含查詢字串，如果 include_query 設為 false，查詢字串不會被包含在結果的 URI 中。

wsgiref.util.application_uri(environ)

類似於 request_uri()，但忽略 PATH_INFO 和 QUERY_STRING 變數。結果是請求地址的應用程式物件的的基本 URI。

wsgiref.util.shift_path_info(environ)

將單一名稱從 PATH_INFO 移到 SCRIPT_NAME 並回傳該名稱。environ 字典會在適當時機被 modified；如果你需要保留原始完好無損的 PATH_INFO 或 SCRIPT_NAME 請使用副本。

如果在 PATH_INFO 中沒有剩餘的路徑片段，則回傳 None。

通常，此程式用於處理請求 URI 的每一部分路徑，例如將路徑視為一系列的字典鍵此程式會修改傳入的環境，使其適用於呼叫位於目標 URI 的 WSGI 應用程式。例如，如果在 /foo 上有一個 WSGI 應用程式且請求 URI 路徑為 /foo/bar/baz，並且位於 /foo 的 WSGI 應用程式呼叫 shift_path_info()，它將接收字串 "bar"，而環境將被更新為適用於傳遞給位於 /foo/bar 的 WSGI 應用程式。換句話說，SCRIPT_NAME 將從 /foo 變更為 /foo/bar，而 PATH_INFO 將從 /bar/baz 變更為 /baz。

當 PATH_INFO 只是一個 "/" 時， 此程式會回傳一個空字串，並在 SCRIPT_NAME 後添加尾部斜號，即使空路徑片段通常是被忽略的，而且 SCRIPT_NAME 通常不會以斜號結尾。這是刻意行為，以確保應用程式在使用這個程式進行物件遍歷時可以區分結尾為 /x 和結尾為 /x/ 的 URIs。

wsgiref.util.setup_testing_defaults(environ)

為測試目的，以簡單的預設值更新 environ 。

這個程式新增 WSGI 所需的各種參數，包括 HTTP_HOST、SERVER_NAME、SERVER_PORT、REQUEST_METHOD、SCRIPT_NAME、PATH_INFO，以及所有 PEP 3333 [https://peps.python.org/pep-3333/] 定義的 wsgi.* 變數，它只提供預設值，並且不會取代現有的這些變數設定。

這個程式目的為了讓 WSGI 伺服器和應用程式的單元測試更容易建置虛擬環境。實際的 WSGI 伺服器或應用程式不應該使用它，因為所產生的數據是假的！

Example usage (see also demo_app() for another example):

from wsgiref.util import setup_testing_defaults
from wsgiref.simple_server import make_server

# A relatively simple WSGI application. It's going to print out the
# environment dictionary after being updated by setup_testing_defaults
def simple_app(environ, start_response):
    setup_testing_defaults(environ)

    status = '200 OK'
    headers = [('Content-type', 'text/plain; charset=utf-8')]

    start_response(status, headers)

    ret = [("%s: %s\n" % (key, value)).encode("utf-8")
           for key, value in environ.items()]
    return ret

with make_server('', 8000, simple_app) as httpd:
    print("Serving on port 8000...")
    httpd.serve_forever()

除了上述的環境功能外，wsgiref.util 模組還提供以下各類工具：

wsgiref.util.is_hop_by_hop(header_name)

如果 'header_name' 是根據 RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html] 所定義的 HTTP/1.1 "Hop-by-Hop" 標頭，則回傳 True。

class wsgiref.util.FileWrapper(filelike, blksize=8192)

wsgiref.types.FileWrapper 協定的具體實作，用於將類檔案物件轉換為 iterator。產生的物件是 iterable。當物件進行疊代時，將可選的 blksize 引數重複傳遞給 filelike 物件的 read() 方法來獲得將產生（yield）的位元組字串。當 read() 回傳一個空位元組字串，代表疊代已結束且無法回復。

如果 filelike 有 close() 方法，則回傳的物件也會具有 close() 方法，並在呼叫時叫用 filelike 物件的 close() 方法。

用法範例：

from io import StringIO
from wsgiref.util import FileWrapper

# We're using a StringIO-buffer for as the file-like object
filelike = StringIO("This is an example file-like object"*10)
wrapper = FileWrapper(filelike, blksize=5)

for chunk in wrapper:
    print(chunk)

在 3.11 版的變更: 已移除對 __getitem__() 方法的支援。

wsgiref.headers -- WSGI 回應標頭工具

這個模組提供單一類別 Headers，用於使用類似對映的介面方便地操作 WSGI 回應標頭。

class wsgiref.headers.Headers([headers])

建立一個類似對映物件並包裝 headers，並且必須是符合 PEP 3333 [https://peps.python.org/pep-3333/] 描述的 name/value 元組的標頭串列。headers 的預設值是一個空串列。

Headers 物件支援典型對映操作包括 __getitem__()、get()、__setitem__()、setdefault()、__delitem__() 以及 __contains__()。對於這些方法中的每一個，鍵是標頭名稱（以不區分大小寫方式處理），而值則是與該標頭名稱關聯的第一個值。設定標頭會刪除該標頭的所有現有值，然後將新值添加到包裝的標頭串列末尾。標頭的現有順序通常保持不變，新標頭會添加到包裝串列的末尾。

不同於字典，當你嘗試取得或刪除包裝的標頭串列不存在的鍵，Headers 物件不會引發例外錯誤。取得不存在的標頭只會回傳 None，而刪除不存在的標頭則不會有任何效果。

Headers 物件還支援 keys()、values()、和 items() 方法。由 keys() 和 items() 回傳的串列在存在多值標頭時可能會包含相同的鍵。Headers 物件的 len() 與 items() 的長度相同，也與包裝標頭串列的長度相同。實際上，items() 方法只是回傳包裝的標頭串列的副本。

對 Headers 物件呼叫 bytes() 會回傳適合作為 HTTP 傳輸回應標頭的格式化的位元組字串。每個標頭都與其值一起置於一行上，由冒號與空格分隔。每行以回車（carriage return）和換行（line feed）結束，而該位元組字串則以空行結束。

除了對映介面和格式化功能外，Headers 物件還具有以下查詢及附加多值標頭的以及附加 MIME 參數標頭的方法：

get_all(name)

回傳指定標頭的所有值的串列。

回傳的串列按照它們在在原始的標頭串列出現的順序或是被添加到此實例的順序進行排序，並且可能包含重複的內容。任何被刪除並重新插入的欄位都會被添加到標頭串列的末尾。如果不存在指定名稱的欄位，則回傳空串列。

add_header(name, value, **_params)

添加一個（可能是多值的）標頭，可透過關鍵字引數來指定選擇性的 MIME 參數。

name 是要添加的標頭欄位。關鍵字引數可使於設定標頭欄位的 MIME 參數。每一個參數必須是字串或是 None。由於破折號在 Python 識別符中是非法的，但是許多 MIME 參數名稱包含破折號，因此參數名稱的底線會轉換成破折號。如果參數值是字串，則以 name="value" 的形式添加到標頭值參數中。如果它是 None，則僅添加參數名稱。（這使用於沒有值的 MIME 參數）使用範例：

h.add_header('content-disposition', 'attachment', filename='bud.gif')

上述操作將添加看起來像這樣的標頭：

Content-Disposition: attachment; filename="bud.gif"

在 3.5 版的變更: headers 參數是可選的。

wsgiref.simple_server -- 一個簡單的 WSGI HTTP 伺服器

這個模組實作一個簡單的的 HTTP 伺服器（基於 http.server）用於提供 WSGI 應用程式。每個伺服器執行個體在特定的主機與埠提供單一的 WSGI 應用程式。如果你想要在單一主機與埠上提供多個應用程式，你應該建立一個 WSGI 應用程式以剖析 PATH_INFO 去選擇為每個請求叫用哪個應用程式。（例如，使用來自 wsgiref.util 的 shift_path_info() 函式。）

wsgiref.simple_server.make_server(host, port, app, server_class=WSGIServer, handler_class=WSGIRequestHandler)

建立一個新的 WSGI 伺服器監聽 host 和 port，接受 app 的連線。回傳值是提供 server_class 的實例，並將使用指定的 handler_class 處理請求。app 必須是一個 WSGI 應用程式物件，如 PEP 3333 [https://peps.python.org/pep-3333/] 所定義。

用法範例：

from wsgiref.simple_server import make_server, demo_app

with make_server('', 8000, demo_app) as httpd:
    print("Serving HTTP on port 8000...")

    # Respond to requests until process is killed
    httpd.serve_forever()

    # Alternative: serve one request, then exit
    httpd.handle_request()

wsgiref.simple_server.demo_app(environ, start_response)

這個函式是一個簡單但完整的 WSGI 應用程式，它回傳一個包含訊息 "Hello world!" 和在 environ 參數中提供的鍵值對串列的文字頁面。這對於驗證 WSGI 伺服器（例如 wsgiref.simple_server）是否能正確執行簡單的 WSGI 應用程式非常有用。

The start_response callable should follow the StartResponse protocol.

class wsgiref.simple_server.WSGIServer(server_address, RequestHandlerClass)

建立一個 WSGIServer 實例。server_address 應該是一個 (host, port) 元組，而 RequestHandlerClass 應該是 http.server.BaseHTTPRequestHandler 的子類別，將用於處理請求。

通常你不需要呼叫這個建構函式（constructor），因為 make_server() 函式可以為你處理所有細節。

WSGIServer 是 http.server.HTTPServer 的子類別，因此它的所有方法（例如 serve_forever() 和 handle_request()）都可用。WSGIServer 也提供這些特定於 WSGI 的方法：

set_app(application)

將可呼叫的 application 設定為接收請求的 WSGI 應用程式。

get_app()

回傳目前設定應用程式的可呼叫物件。

然而，通常情況下你不需要去使用這些額外方法，因為 set_app() 通常會被 make_server() 呼叫而 get_app() 主要存在於請求處理程式（handler）實例的好處上。

class wsgiref.simple_server.WSGIRequestHandler(request, client_address, server)

為給定的 request（即一個 socket）、client_address（一個 (host,port) 位元組）、server (WSGIServer 實例) 建立一個 HTTP 處理程式（handler）。

你不需要直接建立這個類別的實例；它們會在需要時由 WSGIServer 物件自動建立。不過，你可以建立這個類別的子類別並將其作為 handler_class 提供給 make_server() 函式。一些可能相關的方法可以在子類別中進行覆寫：

get_environ()

唯一個請求回傳一個 WSGIEnvironment 字典。預設的實作會複製 WSGIServer 物件的 base_environ 字典屬性的內容以及添加從 HTTP 請求中衍生的各種標頭。每次呼叫這個方法都應該回傳一個包含所有如 PEP 3333 [https://peps.python.org/pep-3333/] 所指定的相關 CGI 環境變數的新字典。

get_stderr()

回傳的物件應該被用作 wsgi.errors 串流。預設實作只會回傳 sys.stderr。

handle()

處理 HTTP 請求。預設實作會使用 wsgiref.handlers 類別來建立處置程式（handler）實例來實作實際 WSGI 應用程式介面。

wsgiref.validate --- WSGI 符合性檢查

當建立新的 WSGI 應用程式物件、框架、伺服器、或是中介軟體（middleware）時，使用 wsgiref.validate 來驗證新程式碼的符合性可能會很有用。這個模組提供一個函式用於建立 WSGI 應用程式物件，並用於驗證 WSGI 伺服器或是閘道與 WSGI 應用程式物件之間的通訊，以檢查雙方協定的符合性。

請注意這個工具並不保證完全符合 PEP 3333 [https://peps.python.org/pep-3333/]；這個模組中的錯誤不一定代表不存在錯誤。但是，如果如果這個模組產生錯誤，那麼幾乎可以確定伺服器或應用程式不是 100% 符合標準。

這個模組基於 Ian Bicking 的 "Python Paste" 函式庫的 paste.lint 模組。

wsgiref.validate.validator(application)

包裝 application 並回傳一個新的 WSGI 應用程式物件。回傳的應用程式將轉發所有請求給原始的 application，並檢查 application 和呼叫它的伺服器是否符合 WSGI 規範和 RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html]。

任何在 AssertionError 中偵測不符合結果都會發起例外；但請注意，如何處理這些錯誤取決於伺服器。例如，基於 wsgiref.handlers 的 wsgiref.simple_server 以及其他伺服器（未覆蓋錯誤處理方法以執行其他操作的伺服器）將僅輸出一條錯誤訊息，指示發生錯誤，並將回溯訊息輸出到 sys.stderr 或是其他錯誤串流。

這個包裝器也可以使用 warnings 模組生成輸出去指示一些可能有疑慮但實際上可能不會被 PEP 3333 [https://peps.python.org/pep-3333/] 禁止的行為。除非使用 Python 命令列選項或 warnings API，抑制了這些警告，否則這類警告將被寫入到 sys.stderr（not wsgi.errors，除非它們碰巧是相同的物件）。

用法範例：

from wsgiref.validate import validator
from wsgiref.simple_server import make_server

# Our callable object which is intentionally not compliant to the
# standard, so the validator is going to break
def simple_app(environ, start_response):
    status = '200 OK'  # HTTP Status
    headers = [('Content-type', 'text/plain')]  # HTTP Headers
    start_response(status, headers)

    # This is going to break because we need to return a list, and
    # the validator is going to inform us
    return b"Hello World"

# This is the application wrapped in a validator
validator_app = validator(simple_app)

with make_server('', 8000, validator_app) as httpd:
    print("Listening on port 8000....")
    httpd.serve_forever()

wsgiref.handlers -- 伺服器 / 閘道基本類別

這個模組提供實作 WSGI 伺服器和閘道的基礎處理程式（handler）類別。這些基底類別處理程式大部分與 WSGI 應用程式通訊的工作，只要它們被提供 CGI-like 環境，以及輸入、輸出和錯誤串流。

class wsgiref.handlers.CGIHandler

這是基於 CGI 的呼叫方式並透過 sys.stdin、sys.stdout、sys.stderr 和 os.environ。當你擁有一個 WSGI 應用程式並希望將其作為 CGI 腳本運行時是很有用的。只需叫用 CGIHandler().run(app)，其中 app 是你希望叫用的 WSGI 應用程式物件。

這個類別是 BaseCGIHandler 的子類別將 wsgi.run_once 設置為 true，wsgi.multithread 設置為 false，並將 wsgi.multiprocess 設置為 true，並且始終使用 sys 和 os 來取得所需的 CGI 串流以及環境。

class wsgiref.handlers.IISCGIHandler

這是用於在 Microsoft 的 IIS 網頁伺服器上部署時使用的 CGIHandler 的一個專門替代選擇，無需設置 config 的 allowPathInfo 選項（IIS>=7），或 metabase 的 allowPathInfoForScriptMappings 選項（IIS<7）。

預設情況下，IIS 提供的 PATH_INFO 會在前面複製 SCRIPT_NAME，對於希望實作路由的 WSGI 應用程式造成問題。這個處理程式（handler）會移除任何這樣的重複路徑。

IIS 可以配置去傳遞正確的 PATH_INFO，但這會導致 PATH_TRANSLATED 是錯誤的問題。幸運的是這個變數很少被使用並且不受 WSGI 保證。然而，在 IIS<7 上，這個設置只能在虛擬主機層級進行，影響所有其他腳本的對映，其中許多在暴露 PATH_TRANSLATED 問題時會中斷。由於這個原因幾乎從不會使用修復的 IIS<7（即使是 IIS7 也很少使用它，因為它仍然沒有相應的 UI）。

CGI 程式碼無法知道是否已設置該選項，因此提供了一個獨立的處理程式（handler）類別。它的使用方式與 CGIHandler 相同，即透過呼叫 IISCGIHandler().run(app) 來使用，其中 app 是你希望叫用的 WSGI 應用程式物件。

在 3.2 版被加入.

class wsgiref.handlers.BaseCGIHandler(stdin, stdout, stderr, environ, multithread=True, multiprocess=False)

類似於 CGIHandler，但不是使用 sys 和 os 模組，而是明確指定 CGI 環境與 I/O 串流。multithread 和 multiprocess 值用於設置由處理程式（handler）實例運行的任何應用程式的旗標。

這個類別是專門為除了 HTTP "origin servers" 以外的軟體一起使用的 SimpleHandler 的子類別。如果你正在撰寫一個使用 Status: 標頭來發送 HTTP 狀態的閘道協定實作（例如 CGI、FastCGI、SCGI 等），你可能會想要子類化這個類別來替代 SimpleHandler。

class wsgiref.handlers.SimpleHandler(stdin, stdout, stderr, environ, multithread=True, multiprocess=False)

類似於 BaseCGIHandler，但是被設計使用在 HTTP origin 伺服器。如果你正在撰寫 HTTP 伺服器的實作，你可能會想要子類別化這個類別來替代 BaseCGIHandler。

這個類別是 BaseHandler 的子類別。它透過建構函式去覆寫 __init__()、get_stdin()、get_stderr()、add_cgi_vars()、_write()、和 _flush() 方法來明確提供設置環境與串流。提供的環境與串流被儲存在 stdin、stdout、stderr、和 environ 環境中。

stdout 的 write() 方法應該完整地寫入每個塊（chunk），像是 io.BufferedIOBase。

class wsgiref.handlers.BaseHandler

這是一個運行 WSGI 應用程式的抽象基底類別。每個實例將處理單個 HTTP 請求，儘管原則上你可以建立一個可重用於多個請求的子類別。

BaseHandler 實例只有一個供外部使用的方法：

run(app)

運行指定 WSGI 應用程式，app。

此方法在運行應用程式的過程中叫用了所有其他 BaseHandler 的方法，因此這些方法主要存在是為了允許自訂整個過程。

以下方法必須在子類別中覆寫：

_write(data)

緩衝要傳送給用戶端的位元組 data。如果這個方法實際上傳送了數據也是可以的；當底層系統實際具有這種區分時，BaseHandler 為了更好的效能進而分離寫入和刷新操作。

_flush()

強制將緩衝數據傳送到用戶端。如果這是一個無操作（no-op）的方法（即，如果 _write() 實際上發送了數據），那麼是可以的。

get_stdin()

回傳一個與 InputStream 相容的物件並適用於用作目前正在處理請求的 wsgi.input。

get_stderr()

回傳一個與 ErrorStream 相容的物件並適用於用作目前正在處理請求的 wsgi.errors。

add_cgi_vars()

將目前請求的 CGI 變數插入到 environ 屬性中。

以下是你可能希望覆寫的其他方法和屬性。這個列表只是一個摘要，然而，不包括可以被覆寫的每個方法。在嘗試建立自訂的 BaseHandler 子類別之前，你應該參考文件說明和原始碼以獲得更多資訊。

用於自訂 WSGI 環境的屬性和方法：

wsgi_multithread

用於 wsgi.multithread 環境變數的值。在 BaseHandler 中預設為 true，但在其他子類別中可能有不同的預設值（或由建構函式設置）。

wsgi_multiprocess

用於 wsgi.multiprocess 環境變數的值。在 BaseHandler 中預設為 true，但在其他子類別中可能有不同的預設值（或由建構函式設置）。

wsgi_run_once

用於 wsgi.run_once 環境變數的值。在 BaseHandler 中預設為 false，但 CGIHandler 預設將其設置為 true。

os_environ

預設環境變數包含在每一個請求的 WSGI 環境中。預設情況下，這是在載入 wsgiref.handlers 時的 os.environ 副本，但子類別可以在類別或實例層級建立自己的副本。注意字典應該被視為唯讀，因為預設值在多個類別與實例中共享。

server_software

如果設置 origin_server 屬性，則此屬性的值將用於設置預設的 SERVER_SOFTWARE WSGI 環境變數，並且還將用於設置 HTTP 回應中的預設 Server: 標頭。對於不是 HTTP origin 伺服器的處置程式（例如 BaseCGIHandler 和 CGIHandler），此屬性將被忽略。

在 3.3 版的變更: 將術語 "Python" 替換為特定實作的術語，如 "CPython"、"Jython" 等。

get_scheme()

回傳用於目前請求的 URL scheme。預設的實作使用 wsgiref.util 中的 guess_scheme() 函式去猜測 scheme 是 "http" 或是 "https"，基於目前請求的 environ 變數。

setup_environ()

將 environ 屬性設置為完全填充的 WSGI 環境。預設的實作使用上述所有方法和屬性，以及 get_stdin()、get_stderr() 和 add_cgi_vars() 方法以及 wsgi_file_wrapper 屬性。如果不呈現它也會插入一個 SERVER_SOFTWARE 關鍵字，只要 origin_server 屬性是一個 true 值並且 server_software 屬性被設置。

用於自訂例外處理的屬性和方法：

log_exception(exc_info)

將 exc_info 元組記錄到伺服器日誌中。exc_info 是一個 (type, value, traceback) 元組。預設實作只是將追蹤資訊寫入到請求的 wsgi.errors 串流中並刷新它。子類別可以覆蓋此方法以更改格式或重新定向輸出，將追蹤資訊發送給管理員，或執行其他被認為合適的操作。

traceback_limit

預設的 log_exception() 方法追蹤輸出中包含的最大幀數 。如果為 None，則包含所有幀。

error_output(environ, start_response)

這個方法是一個為使用者去產生錯誤頁面的 WSGI 應用程式。只有在標頭傳送給用戶端前如果發生錯誤才會被叫用。

此方法使用 sys.exception() 存取目前的錯誤，當呼叫它（如 PEP 3333 [https://peps.python.org/pep-3333/] 的 "Error Handling" 部分所描述）時應該傳遞資訊給 start_response。特別是 start_response 可呼叫物件應該遵循 StartResponse 協定。

預設的實作只是使用 error_status、error_headers 和 error_body 屬性產生輸出頁面。子類別可以覆蓋此方法以生成更動態的錯誤輸出。

然而，從安全的角度並不建議向任何普通使用者顯示診斷資訊；理想情況下，你應該需要採取特殊措施才能啟用診斷輸出，這就是預設實作不包括任何診斷資訊的原因。

error_status

用於錯誤回應的 HTTP 狀態。這應該是一個按照 PEP 3333 [https://peps.python.org/pep-3333/] 定義的狀態字串；預設為 500 狀態碼和訊息。

error_headers

用於錯誤回應的 HTTP 標頭。這應該是一個 WSGI 回應標頭的串列（(name, value) 元組），如 PEP 3333 [https://peps.python.org/pep-3333/] 中所描述。預設串列只設置內容種類為 text/plain。

error_body

錯誤回應的主體。這應該是一個 HTTP 回應內容的位元組字串。預設為純文字 "A server error occurred. Please contact the administrator."

用於 PEP 3333 [https://peps.python.org/pep-3333/] 中的 "Optional Platform-Specific File Handling" 功能的方法和屬性：

wsgi_file_wrapper

一個 wsgi.file_wrapper 工廠函式（factory），與 wsgiref.types.FileWrapper 相容，或者為 None。這個屬性的預設值是 wsgiref.util.FileWrapper 類別。

sendfile()

覆蓋以實作特定平台的檔案傳輸。只有當應用程式的回傳值是由 wsgi_file_wrapper 屬性指定的類別實例時才會呼叫此方法。如果它能夠成功傳輸檔案應該回傳一個 true 值，以便不執行預設的傳輸程式碼。該方法的預設實作只回傳一個 false 值。

其他方法和屬性：

origin_server

這個屬性應該被設置為 true 值，如果處理程式（handler）的 _write() 和 _flush() 被用於直接與用戶端通訊，而不是透過 CGI-like 的閘道協定希望 HTTP 狀態在特殊的 Status: 標頭中。

這個屬性在 BaseHandler 預設值為 true，但是在 BaseCGIHandler 和 CGIHandler 為 false。

http_version

如果 origin_server 為 true，則此字串屬性用於設定傳送給用戶端的回應的 HTTP 版本。預設為 "1.0"。

wsgiref.handlers.read_environ()

從 os.environ 轉碼 CGI 變數到 PEP 3333 [https://peps.python.org/pep-3333/] 中的 "bytes in unicode" 字串，並回傳一個新字典。這個函式被 CGIHandler 和 IISCGIHandler 使用來直接替代 os.environ，在所有平台和使用 Python 3 的網頁伺服器上不一定符合 WSGI 標準，具體來說，在 OS 的實際環境是 Unicode（例如 Windows）的情況下，或者在環境是位元組的情況下，但 Python 用於解碼它的系統編碼不是 ISO-8859-1 （例如使用 UTF-8 的 Unix 系統）。

如果你自己正在實作 CGI-based 處理程式（handler），你可能想要使用這個函式來替換單純直接從 os.environ 中複製值。

在 3.2 版被加入.

wsgiref.types -- 用於靜態型別檢查的 WSGI 型別

這個模組提供在 PEP 3333 [https://peps.python.org/pep-3333/] 中所描述的各種用於靜態型別檢查的型別。

在 3.11 版被加入.

class wsgiref.types.StartResponse

一個描述 start_response() [https://peps.python.org/pep-3333/#the-start-response-callable] 可呼叫物件的 typing.Protocol (PEP 3333 [https://peps.python.org/pep-3333/])。

wsgiref.types.WSGIEnvironment

一個描述 WSGI 環境字典的型別別名。

wsgiref.types.WSGIApplication

一個描述 WSGI 應用程式可呼叫物件的型別別名。

class wsgiref.types.InputStream

一個描述 WSGI 輸入串流 [https://peps.python.org/pep-3333/#input-and-error-streams]的 typing.Protocol。

class wsgiref.types.ErrorStream

一個描述 WSGI 錯誤串流 [https://peps.python.org/pep-3333/#input-and-error-streams]的 typing.Protocol。

class wsgiref.types.FileWrapper

一個描述檔案包裝器 [https://peps.python.org/pep-3333/#optional-platform-specific-file-handling]的 typing.Protocol。請參閱 wsgiref.util.FileWrapper 來瞭解此協定的具體實作。

範例

This is a working "Hello World" WSGI application, where the start_response callable should follow the StartResponse protocol:

"""
Every WSGI application must have an application object - a callable
object that accepts two arguments. For that purpose, we're going to
use a function (note that you're not limited to a function, you can
use a class for example). The first argument passed to the function
is a dictionary containing CGI-style environment variables and the
second variable is the callable object.
"""
from wsgiref.simple_server import make_server

def hello_world_app(environ, start_response):
    status = "200 OK"  # HTTP Status
    headers = [("Content-type", "text/plain; charset=utf-8")]  # HTTP Headers
    start_response(status, headers)

    # The returned object is going to be printed
    return [b"Hello World"]

with make_server("", 8000, hello_world_app) as httpd:
    print("Serving on port 8000...")

    # Serve until process is killed
    httpd.serve_forever()

提供目前目錄的 WSGI 應用程式範例，並接受命令列上的可選目錄和埠號（預設：8000）：

"""
Small wsgiref based web server. Takes a path to serve from and an
optional port number (defaults to 8000), then tries to serve files.
MIME types are guessed from the file names, 404 errors are raised
if the file is not found.
"""
import mimetypes
import os
import sys
from wsgiref import simple_server, util

def app(environ, respond):
    # Get the file name and MIME type
    fn = os.path.join(path, environ["PATH_INFO"][1:])
    if "." not in fn.split(os.path.sep)[-1]:
        fn = os.path.join(fn, "index.html")
    mime_type = mimetypes.guess_file_type(fn)[0]

    # Return 200 OK if file exists, otherwise 404 Not Found
    if os.path.exists(fn):
        respond("200 OK", [("Content-Type", mime_type)])
        return util.FileWrapper(open(fn, "rb"))
    else:
        respond("404 Not Found", [("Content-Type", "text/plain")])
        return [b"not found"]

if __name__ == "__main__":
    # Get the path and port from command-line arguments
    path = sys.argv[1] if len(sys.argv) > 1 else os.getcwd()
    port = int(sys.argv[2]) if len(sys.argv) > 2 else 8000

    # Make and start the server until control-c
    httpd = simple_server.make_server("", port, app)
    print(f"Serving {path} on port {port}, control-C to stop")
    try:
        httpd.serve_forever()
    except KeyboardInterrupt:
        print("Shutting down.")
        httpd.server_close()

urllib --- URL 處理模組

原始碼：Lib/urllib/ [https://github.com/python/cpython/tree/3.14/Lib/urllib/]

urllib 是一個蒐集了許多處理 URLs 的 module（模組）的 package（套件）：

urllib.request 用來開啟和讀取 URLs

urllib.error 包含了 urllib.request 所引發的例外

urllib.parse 用來剖析 URLs

urllib.robotparser 用來剖析 robots.txt 檔案

urllib.request --- 用來開啟 URLs 的可擴充函式庫

原始碼：Lib/urllib/request.py [https://github.com/python/cpython/tree/3.14/Lib/urllib/request.py]

urllib.request module（模組）定義了一些函式與 class（類別）用以開啟 URLs（大部分是 HTTP），並處理各式複雜情況如：basic 驗證與 digest 驗證、重新導向、cookies。

也參考

有關於更高階的 HTTP 用戶端介面，推薦使用 Requests 套件 [https://requests.readthedocs.io/en/master/]。

警告

On macOS it is unsafe to use this module in programs using os.fork() because the getproxies() implementation for macOS uses a higher-level system API. Set the environment variable no_proxy to * to avoid this problem (e.g. os.environ["no_proxy"] = "*").

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

urllib.request module 定義下列函式：

urllib.request.urlopen(url, data=None, [timeout, ]*, context=None)

打開 url，其值可以是一個包含有效且適當編碼 URL 的字串或是一個 Request 物件。

data 必須是一個包含傳送給伺服器額外資料的物件，若不需要傳送額外資料則指定為 None。更多細節請見 Request。

urllib.request module 使用 HTTP/1.1 並包含 Connection:close header（標頭）在其 HTTP 請求中。

透過選擇性參數 timeout 來指定 blocking operations（阻塞性操作，如：嘗試連接）的 timeout（超時時間），以秒為單位。若沒有指定值，則會使用全域預設超時時間設定。實際上，此參數僅作用於 HTTP、HTTPS 以及 FTP 的連接。

若 context 有被指定時，它必須是一個 ssl.SSLContext 的實例並描述著各種 SSL 選項。更多細節請見 HTTPSConnection。

這個函式總是回傳一個可作為 context manager 使用的物件，並有著特性 (property) url、headers 與 status。欲知更多這些特性細節請參見 urllib.response.addinfourl。

對於 HTTP 與 HTTPS 的 URLs，這個函式回傳一個稍有不同的 http.client.HTTPResponse 物件。除了上述提到的三個方法外，另有 msg 屬性並有著與 reason 相同的資訊 --- 由伺服器回傳的原因敘述 (reason phrase)，而不是在 HTTPResponse 文件中提到的回應 headers。

對於 FTP、檔案及資料的 URLs，這個函式會回傳一個 urllib.response.addinfourl 物件。

當遇到協定上的錯誤時會引發 URLError。

請注意若沒有 handler 處理請求時，None 值將會被回傳。（即使有預設的全域類別 OpenerDirector 使用 UnknownHandler 來確保這種情況不會發生）

另外，若有偵測到代理服務的設定（例如當 *_proxy 環境變數像是：:envvar:!http_proxy` 有被設置時），ProxyHandler 會被預設使用以確保請求有透過代理服務來處理。

Python 2.6 或更早版本的遺留函式 urllib.urlopen 已經不再被維護；新函式 urllib.request.urlopen() 對應到舊函式 urllib2.urlopen。有關代理服務的處理，以往是透過傳遞 dictionary（字典）參數給 urllib.urlopen 來取得的，現在則可以透過 ProxyHandler 物件來取得。

預設的 opener 會觸發一個 auditing event urllib.Request 與其從請求物件中所獲得的引數 fullurl、data、headers、method。

在 3.2 版的變更: 新增 cafile 與 capath。

HTTPS 虛擬主機 (virtual hosts) 現已支援，只要 ssl.HAS_SNI 的值為 true。

data 可以是一個可疊代物件。

在 3.3 版的變更: cadefault 被新增。

在 3.4.3 版的變更: context 被新增。

在 3.10 版的變更: 當 context 沒有被指定時，HTTPS 連線現在會傳送一個帶有協定指示器 http/1.1 的 ALPN 擴充 (extension)。自訂的 context 應該利用 set_alpn_protocols() 來自行設定 ALPN 協定。

在 3.13 版的變更: Remove cafile, capath and cadefault parameters: use the context parameter instead.

urllib.request.install_opener(opener)

安裝一個 OpenerDirector 實例作為預設的全域 opener。僅在當你想要讓 urlopen 使用該 opener 時安裝一個 opener，否則的話應直接呼叫 OpenerDirector.open() 而非 urlopen()。程式碼不會檢查 class 是否真的為 OpenerDirector，而是任何具有正確介面的 class 都能適用。

urllib.request.build_opener([handler, ...])

回傳一個 OpenerDirector 實例，以給定的順序把 handlers 串接起來。handlers 可以是 BaseHandler 的實例，亦或是 BaseHandler 的 subclasses（這個情況下必須有不帶參數的建構函式能夠被呼叫）。以下 classes 的實例順位會在 handlers 之前，除非 handlers 已經包含它們，是它們的實例，或是它們的 subclasses：ProxyHandler（如果代理服務設定被偵測到）、UnknownHandler、HTTPHandler、HTTPDefaultErrorHandler、HTTPRedirectHandler、FTPHandler、FileHandler、HTTPErrorProcessor。

如果 Python 安裝時已帶有 SSL 支援（如果 ssl module 能夠被 import），則 HTTPSHandler 也在上述 class 之中。

一個 BaseHandler 的 subclass 可能透過改變其 handler_order 屬性來調整它在 handlers list 中的位置。

urllib.request.pathname2url(path, *, add_scheme=False)

Convert the given local path to a file: URL. This function uses quote() function to encode the path.

If add_scheme is false (the default), the return value omits the file: scheme prefix. Set add_scheme to true to return a complete URL.

This example shows the function being used on Windows:

>>> from urllib.request import pathname2url
>>> path = 'C:\\Program Files'
>>> pathname2url(path, add_scheme=True)
'file:///C:/Program%20Files'

在 3.14 版的變更: Windows drive letters are no longer converted to uppercase, and : characters not following a drive letter no longer cause an OSError exception to be raised on Windows.

在 3.14 版的變更: Paths beginning with a slash are converted to URLs with authority sections. For example, the path /etc/hosts is converted to the URL ///etc/hosts.

在 3.14 版的變更: 新增 add_scheme 參數。

urllib.request.url2pathname(url, *, require_scheme=False, resolve_host=False)

Convert the given file: URL to a local path. This function uses unquote() to decode the URL.

If require_scheme is false (the default), the given value should omit a file: scheme prefix. If require_scheme is set to true, the given value should include the prefix; a URLError is raised if it doesn't.

The URL authority is discarded if it is empty, localhost, or the local hostname. Otherwise, if resolve_host is set to true, the authority is resolved using socket.gethostbyname() and discarded if it matches a local IP address (as per RFC 8089 §3 [https://datatracker.ietf.org/doc/html/rfc8089.html#section-3]). If the authority is still unhandled, then on Windows a UNC path is returned, and on other platforms a URLError is raised.

This example shows the function being used on Windows:

>>> from urllib.request import url2pathname
>>> url = 'file:///C:/Program%20Files'
>>> url2pathname(url, require_scheme=True)
'C:\\Program Files'

在 3.14 版的變更: Windows drive letters are no longer converted to uppercase, and : characters not following a drive letter no longer cause an OSError exception to be raised on Windows.

在 3.14 版的變更: The URL authority is discarded if it matches the local hostname. Otherwise, if the authority isn't empty or localhost, then on Windows a UNC path is returned (as before), and on other platforms a URLError is raised.

在 3.14 版的變更: The URL query and fragment components are discarded if present.

在 3.14 版的變更: The require_scheme and resolve_host parameters were added.

urllib.request.getproxies()

這個輔助函式 (helper function) 回傳一個代理伺服器 URL mappings（對映）的 dictionary。在所有的作業系統中，它首先掃描環境中有著 <scheme>_proxy 名稱的變數（忽略大小寫的），如果找不到的話就會在 macOS 中的系統設定 (System Configuration) 或是 Windows 系統中的 Windows Systems Registry 尋找代理服務設定。如果大小寫的環境變數同時存在且值有不同，小寫的環境變數會被選用。

備註

如果環境變數 REQUEST_METHOD 有被設置（通常這代表著你的 script 是運行在一個共用閘道介面 (CGI) 環境中），那麼環境變數 HTTP_PROXY （大寫的 _PROXY）將被忽略。這是因為變數可以透過使用 "Proxy:" HTTP header 被注入。如果需要在共用閘道介面環境中使用 HTTP 代理服務，可以明確使用 ProxyHandler，亦或是確認變數名稱是小寫的（或至少 _proxy 後綴是小寫的）。

提供了以下的 classes：

class urllib.request.Request(url, data=None, headers={}, origin_req_host=None, unverifiable=False, method=None)

這個 class 是一個 URL 請求的抽象 class。

url 是一個包含有效且適當編碼的 URL 字串。

data 必須是一個包含要送到伺服器的附加資料的物件，若不需帶附加資料則其值應為 None。目前 HTTP 請求是唯一有使用 data 參數的，其支援的物件型別包含位元組、類檔案物件 (file-like objects)、以及可疊代的類位元組串物件 (bytes-like objects)。如果沒有提供 Content-Length 及 Transfer-Encoding headers 欄位，HTTPHandler 將會根據 data 的型別設置這些 header。Content-Length 會被用來傳送位元組串物件，而 RFC 7230 [https://datatracker.ietf.org/doc/html/rfc7230.html] 章節 3.3.1 所定義的 Transfer-Encoding: chunked 則會被用來傳送檔案或是其它可疊代物件 (iterables)。

對於一個 HTTP POST 請求方法，data 應為一個標準 application/x-www-form-urlencoded 格式的 buffer。urllib.parse.urlencode() 方法接受一個 mapping 或是 sequence（序列）的 2-tuples，並回傳一個對應格式的 ASCII 字串。在被作為 data 參數前它應該被編碼成位元組串。

headers 必須是一個 dictionary，並會被視為如同每對 key 和 value 作為引數來呼叫 add_header()。經常用於「偽裝」 User-Agent header 的值，這個 header 是用來讓一個瀏覽器向伺服器表明自己的身分 --- 有些 HTTP 伺服器僅允許來自普通瀏覽器的請求，而不接受來自程式腳本的請求。例如，Mozilla Firefox 會將 header 的值設為 "Mozilla/5.0 (X11; U; Linux i686) Gecko/20071127 Firefox/2.0.0.11"，而 urllib 的值則是 "Python-urllib/2.6"（在 Python 2.6 上）。所有 header 的鍵都會以 camel case（駝峰式大小寫）來傳送。

當有給定 data 引數時，一個適當的 Content-Type header 應該被設置。如果這個 header 沒有被提供且 data 也不為 None 時，預設值 Content-Type: application/x-www-form-urlencoded 會被新增至請求中。

接下來的兩個引數的介紹提供給那些有興趣正確處理第三方 HTTP cookies 的使用者：

origin_req_host 應為原始傳輸互動的請求主機 (request-host)，如同在 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 中的定義。預設值為 http.cookiejar.request_host(self)。這是使用者發起的原始請求的主機名稱或是 IP 位址。例如當請求是要求一個 HTML 文件中的一個影像，則這個屬性應為請求包含影像頁面的請求主機。

unverifiable 應該標示一個請求是否是無法驗證的，如同在 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 中的定義。其預設值為 False。一個無法驗證的請求是指使用者沒有機會去批准請求的 URL，例如一個對於 HTML 文件中的影像所做的請求，而使用者沒有機會去批准是否能自動擷取影像，則這個值應該為 true。

method 應為一個標示 HTTP 請求方法的字串（例如：'HEAD'）。如果有提供值，則會被存在 method 屬性中且被 get_method() 所使用。當 data 是 None 時，其預設值為 'GET'，否則預設值為 'POST'。Subclasses 可以透過設置其 method 屬性來設定不一樣的預設請求方法。

備註

如果資料物件無法重複提供其內容（例如一個檔案或是只能產生一次內容的可疊代物件）且請求因為 HTTP 重導向 (redirects) 或是 HTTP 驗證 (authentication) 而被重新嘗試傳送，則該請求不會正常運作。data 會接在 headers 之後被送至 HTTP 伺服器。此函式庫沒有支援 100-continue expectation。

在 3.3 版的變更: 新增 Request.method 引數到 Request class。

在 3.4 版的變更: 能夠在 class 中設置預設的 Request.method。

在 3.6 版的變更: 如果 Content-Length 尚未被提供且 data 既不是 None 也不是一個位元組串物件，則不會觸發錯誤，並 fall back（後備）使用分塊傳輸編碼 (chunked transfer encoding)。

class urllib.request.OpenerDirector

The OpenerDirector class opens URLs via BaseHandlers chained together. It manages the chaining of handlers, and recovery from errors.

class urllib.request.BaseHandler

This is the base class for all registered handlers --- and handles only the simple mechanics of registration.

class urllib.request.HTTPDefaultErrorHandler

A class which defines a default handler for HTTP error responses; all responses are turned into HTTPError exceptions.

class urllib.request.HTTPRedirectHandler

用於處理重新導向的類別。

class urllib.request.HTTPCookieProcessor(cookiejar=None)

用於處理 HTTP Cookie 的類別。

class urllib.request.ProxyHandler(proxies=None)

Cause requests to go through a proxy. If proxies is given, it must be a dictionary mapping protocol names to URLs of proxies. The default is to read the list of proxies from the environment variables <protocol>_proxy. If no proxy environment variables are set, then in a Windows environment proxy settings are obtained from the registry's Internet Settings section, and in a macOS environment proxy information is retrieved from the System Configuration Framework.

To disable autodetected proxy pass an empty dictionary.

The no_proxy environment variable can be used to specify hosts which shouldn't be reached via proxy; if set, it should be a comma-separated list of hostname suffixes, optionally with :port appended, for example cern.ch,ncsa.uiuc.edu,some.host:8080.

備註

HTTP_PROXY will be ignored if a variable REQUEST_METHOD is set; see the documentation on getproxies().

class urllib.request.HTTPPasswordMgr

Keep a database of (realm, uri) -> (user, password) mappings.

class urllib.request.HTTPPasswordMgrWithDefaultRealm

Keep a database of (realm, uri) -> (user, password) mappings. A realm of None is considered a catch-all realm, which is searched if no other realm fits.

class urllib.request.HTTPPasswordMgrWithPriorAuth

A variant of HTTPPasswordMgrWithDefaultRealm that also has a database of uri -> is_authenticated mappings. Can be used by a BasicAuth handler to determine when to send authentication credentials immediately instead of waiting for a 401 response first.

在 3.5 版被加入.

class urllib.request.AbstractBasicAuthHandler(password_mgr=None)

This is a mixin class that helps with HTTP authentication, both to the remote host and to a proxy. password_mgr, if given, should be something that is compatible with HTTPPasswordMgr; refer to section HTTPPasswordMgr 物件 for information on the interface that must be supported. If passwd_mgr also provides is_authenticated and update_authenticated methods (see HTTPPasswordMgrWithPriorAuth 物件), then the handler will use the is_authenticated result for a given URI to determine whether or not to send authentication credentials with the request. If is_authenticated returns True for the URI, credentials are sent. If is_authenticated is False, credentials are not sent, and then if a 401 response is received the request is re-sent with the authentication credentials. If authentication succeeds, update_authenticated is called to set is_authenticated True for the URI, so that subsequent requests to the URI or any of its super-URIs will automatically include the authentication credentials.

在 3.5 版被加入: 新增 is_authenticated 的支援。

class urllib.request.HTTPBasicAuthHandler(password_mgr=None)

Handle authentication with the remote host. password_mgr, if given, should be something that is compatible with HTTPPasswordMgr; refer to section HTTPPasswordMgr 物件 for information on the interface that must be supported. HTTPBasicAuthHandler will raise a ValueError when presented with a wrong Authentication scheme.

class urllib.request.ProxyBasicAuthHandler(password_mgr=None)

Handle authentication with the proxy. password_mgr, if given, should be something that is compatible with HTTPPasswordMgr; refer to section HTTPPasswordMgr 物件 for information on the interface that must be supported.

class urllib.request.AbstractDigestAuthHandler(password_mgr=None)

This is a mixin class that helps with HTTP authentication, both to the remote host and to a proxy. password_mgr, if given, should be something that is compatible with HTTPPasswordMgr; refer to section HTTPPasswordMgr 物件 for information on the interface that must be supported.

在 3.14 版的變更: Added support for HTTP digest authentication algorithm SHA-256.

class urllib.request.HTTPDigestAuthHandler(password_mgr=None)

Handle authentication with the remote host. password_mgr, if given, should be something that is compatible with HTTPPasswordMgr; refer to section HTTPPasswordMgr 物件 for information on the interface that must be supported. When both Digest Authentication Handler and Basic Authentication Handler are both added, Digest Authentication is always tried first. If the Digest Authentication returns a 40x response again, it is sent to Basic Authentication handler to Handle. This Handler method will raise a ValueError when presented with an authentication scheme other than Digest or Basic.

在 3.3 版的變更: 針對不支援的驗證方案 (Authentication Scheme) 引發 ValueError。

class urllib.request.ProxyDigestAuthHandler(password_mgr=None)

Handle authentication with the proxy. password_mgr, if given, should be something that is compatible with HTTPPasswordMgr; refer to section HTTPPasswordMgr 物件 for information on the interface that must be supported.

class urllib.request.HTTPHandler

用於處理開啟 HTTP URL 的類別。

class urllib.request.HTTPSHandler(debuglevel=0, context=None, check_hostname=None)

A class to handle opening of HTTPS URLs. context and check_hostname have the same meaning as in http.client.HTTPSConnection.

在 3.2 版的變更: 新增 context 與 check_hostname。

class urllib.request.FileHandler

Open local files.

class urllib.request.DataHandler

Open data URLs.

在 3.4 版被加入.

class urllib.request.FTPHandler

打開 FTP URLs。

class urllib.request.CacheFTPHandler

Open FTP URLs, keeping a cache of open FTP connections to minimize delays.

class urllib.request.UnknownHandler

A catch-all class to handle unknown URLs.

class urllib.request.HTTPErrorProcessor

Process HTTP error responses.

Request 物件

The following methods describe Request's public interface, and so all may be overridden in subclasses. It also defines several public attributes that can be used by clients to inspect the parsed request.

Request.full_url

The original URL passed to the constructor.

在 3.4 版的變更.

Request.full_url is a property with setter, getter and a deleter. Getting full_url returns the original request URL with the fragment, if it was present.

Request.type

The URI scheme.

Request.host

The URI authority, typically a host, but may also contain a port separated by a colon.

Request.origin_req_host

The original host for the request, without port.

Request.selector

The URI path. If the Request uses a proxy, then selector will be the full URL that is passed to the proxy.

Request.data

The entity body for the request, or None if not specified.

在 3.4 版的變更: Changing value of Request.data now deletes "Content-Length" header if it was previously set or calculated.

Request.unverifiable

boolean, indicates whether the request is unverifiable as defined by RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html].

Request.method

The HTTP request method to use. By default its value is None, which means that get_method() will do its normal computation of the method to be used. Its value can be set (thus overriding the default computation in get_method()) either by providing a default value by setting it at the class level in a Request subclass, or by passing a value in to the Request constructor via the method argument.

在 3.3 版被加入.

在 3.4 版的變更: A default value can now be set in subclasses; previously it could only be set via the constructor argument.

Request.get_method()

Return a string indicating the HTTP request method. If Request.method is not None, return its value, otherwise return 'GET' if Request.data is None, or 'POST' if it's not. This is only meaningful for HTTP requests.

在 3.3 版的變更: get_method now looks at the value of Request.method.

Request.add_header(key, val)

Add another header to the request. Headers are currently ignored by all handlers except HTTP handlers, where they are added to the list of headers sent to the server. Note that there cannot be more than one header with the same name, and later calls will overwrite previous calls in case the key collides. Currently, this is no loss of HTTP functionality, since all headers which have meaning when used more than once have a (header-specific) way of gaining the same functionality using only one header. Note that headers added using this method are also added to redirected requests.

Request.add_unredirected_header(key, header)

Add a header that will not be added to a redirected request.

Request.has_header(header)

Return whether the instance has the named header (checks both regular and unredirected).

Request.remove_header(header)

Remove named header from the request instance (both from regular and unredirected headers).

在 3.4 版被加入.

Request.get_full_url()

Return the URL given in the constructor.

在 3.4 版的變更.

回傳 Request.full_url

Request.set_proxy(host, type)

Prepare the request by connecting to a proxy server. The host and type will replace those of the instance, and the instance's selector will be the original URL given in the constructor.

Request.get_header(header_name, default=None)

Return the value of the given header. If the header is not present, return the default value.

Request.header_items()

Return a list of tuples (header_name, header_value) of the Request headers.

在 3.4 版的變更: The request methods add_data, has_data, get_data, get_type, get_host, get_selector, get_origin_req_host and is_unverifiable that were deprecated since 3.3 have been removed.

OpenerDirector 物件

OpenerDirector 物件有以下的方法：

OpenerDirector.add_handler(handler)

handler should be an instance of BaseHandler. The following methods are searched, and added to the possible chains (note that HTTP errors are a special case). Note that, in the following, protocol should be replaced with the actual protocol to handle, for example http_response() would be the HTTP protocol response handler. Also type should be replaced with the actual HTTP code, for example http_error_404() would handle HTTP 404 errors.

<protocol>_open() --- signal that the handler knows how to open protocol URLs.

更多資訊請見 BaseHandler.<protocol>_open()。

http_error_<type>() --- signal that the handler knows how to handle HTTP errors with HTTP error code type.

更多資訊請見 BaseHandler.http_error_<nnn>()。

<protocol>_error() --- signal that the handler knows how to handle errors from (non-http) protocol.

<protocol>_request() --- signal that the handler knows how to pre-process protocol requests.

更多資訊請見 BaseHandler.<protocol>_request()。

<protocol>_response() --- signal that the handler knows how to post-process protocol responses.

更多資訊請見 BaseHandler.<protocol>_response()。

OpenerDirector.open(url, data=None[, timeout])

Open the given url (which can be a request object or a string), optionally passing the given data. Arguments, return values and exceptions raised are the same as those of urlopen() (which simply calls the open() method on the currently installed global OpenerDirector). The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt (if not specified, the global default timeout setting will be used). The timeout feature actually works only for HTTP, HTTPS and FTP connections.

OpenerDirector.error(proto, *args)

Handle an error of the given protocol. This will call the registered error handlers for the given protocol with the given arguments (which are protocol specific). The HTTP protocol is a special case which uses the HTTP response code to determine the specific error handler; refer to the http_error_<type>() methods of the handler classes.

Return values and exceptions raised are the same as those of urlopen().

OpenerDirector objects open URLs in three stages:

The order in which these methods are called within each stage is determined by sorting the handler instances.

Every handler with a method named like <protocol>_request() has that method called to pre-process the request.

Handlers with a method named like <protocol>_open() are called to handle the request. This stage ends when a handler either returns a non-None value (ie. a response), or raises an exception (usually URLError). Exceptions are allowed to propagate.

In fact, the above algorithm is first tried for methods named default_open(). If all such methods return None, the algorithm is repeated for methods named like <protocol>_open(). If all such methods return None, the algorithm is repeated for methods named unknown_open().

Note that the implementation of these methods may involve calls of the parent OpenerDirector instance's open() and error() methods.

Every handler with a method named like <protocol>_response() has that method called to post-process the response.

BaseHandler 物件

BaseHandler objects provide a couple of methods that are directly useful, and others that are meant to be used by derived classes. These are intended for direct use:

BaseHandler.add_parent(director)

Add a director as parent.

BaseHandler.close()

Remove any parents.

The following attribute and methods should only be used by classes derived from BaseHandler.

備註

The convention has been adopted that subclasses defining <protocol>_request() or <protocol>_response() methods are named *Processor; all others are named *Handler.

BaseHandler.parent

A valid OpenerDirector, which can be used to open using a different protocol, or handle errors.

BaseHandler.default_open(req)

This method is not defined in BaseHandler, but subclasses should define it if they want to catch all URLs.

This method, if implemented, will be called by the parent OpenerDirector. It should return a file-like object as described in the return value of the open() method of OpenerDirector, or None. It should raise URLError, unless a truly exceptional thing happens (for example, MemoryError should not be mapped to URLError).

This method will be called before any protocol-specific open method.

BaseHandler.<protocol>_open(req)

This method is not defined in BaseHandler, but subclasses should define it if they want to handle URLs with the given protocol.

This method, if defined, will be called by the parent OpenerDirector. Return values should be the same as for default_open().

BaseHandler.unknown_open(req)

This method is not defined in BaseHandler, but subclasses should define it if they want to catch all URLs with no specific registered handler to open it.

This method, if implemented, will be called by the parent OpenerDirector. Return values should be the same as for default_open().

BaseHandler.http_error_default(req, fp, code, msg, hdrs)

This method is not defined in BaseHandler, but subclasses should override it if they intend to provide a catch-all for otherwise unhandled HTTP errors. It will be called automatically by the OpenerDirector getting the error, and should not normally be called in other circumstances.

OpenerDirector 會以五個位置引數呼叫此方法：

一個 Request 物件

一個類檔案物件，包含 HTTP 錯誤主體，

HTTP 錯誤的三位數代號字串，

HTTP 錯誤代號的使用者可見解釋字串，以及

HTTP 錯誤的標頭，為一個對映物件。

Return values and exceptions raised should be the same as those of urlopen().

BaseHandler.http_error_<nnn>(req, fp, code, msg, hdrs)

nnn should be a three-digit HTTP error code. This method is also not defined in BaseHandler, but will be called, if it exists, on an instance of a subclass, when an HTTP error with code nnn occurs.

Subclasses should override this method to handle specific HTTP errors.

Arguments, return values and exceptions raised should be the same as for http_error_default().

BaseHandler.<protocol>_request(req)

This method is not defined in BaseHandler, but subclasses should define it if they want to pre-process requests of the given protocol.

This method, if defined, will be called by the parent OpenerDirector. req will be a Request object. The return value should be a Request object.

BaseHandler.<protocol>_response(req, response)

This method is not defined in BaseHandler, but subclasses should define it if they want to post-process responses of the given protocol.

This method, if defined, will be called by the parent OpenerDirector. req will be a Request object. response will be an object implementing the same interface as the return value of urlopen(). The return value should implement the same interface as the return value of urlopen().

HTTPRedirectHandler 物件

備註

Some HTTP redirections require action from this module's client code. If this is the case, HTTPError is raised. See RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html] for details of the precise meanings of the various redirection codes.

An HTTPError exception raised as a security consideration if the HTTPRedirectHandler is presented with a redirected URL which is not an HTTP, HTTPS or FTP URL.

HTTPRedirectHandler.redirect_request(req, fp, code, msg, hdrs, newurl)

Return a Request or None in response to a redirect. This is called by the default implementations of the http_error_30*() methods when a redirection is received from the server. If a redirection should take place, return a new Request to allow http_error_30*() to perform the redirect to newurl. Otherwise, raise HTTPError if no other handler should try to handle this URL, or return None if you can't but another handler might.

備註

The default implementation of this method does not strictly follow RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html], which says that 301 and 302 responses to POST requests must not be automatically redirected without confirmation by the user. In reality, browsers do allow automatic redirection of these responses, changing the POST to a GET, and the default implementation reproduces this behavior.

HTTPRedirectHandler.http_error_301(req, fp, code, msg, hdrs)

Redirect to the Location: or URI: URL. This method is called by the parent OpenerDirector when getting an HTTP 'moved permanently' response.

HTTPRedirectHandler.http_error_302(req, fp, code, msg, hdrs)

The same as http_error_301(), but called for the 'found' response.

HTTPRedirectHandler.http_error_303(req, fp, code, msg, hdrs)

The same as http_error_301(), but called for the 'see other' response.

HTTPRedirectHandler.http_error_307(req, fp, code, msg, hdrs)

The same as http_error_301(), but called for the 'temporary redirect' response. It does not allow changing the request method from POST to GET.

HTTPRedirectHandler.http_error_308(req, fp, code, msg, hdrs)

The same as http_error_301(), but called for the 'permanent redirect' response. It does not allow changing the request method from POST to GET.

在 3.11 版被加入.

HTTPCookieProcessor 物件

HTTPCookieProcessor 實例有一個屬性：

HTTPCookieProcessor.cookiejar

存放 cookies 的 http.cookiejar.CookieJar。

ProxyHandler 物件

ProxyHandler.<protocol>_open(request)

The ProxyHandler will have a method <protocol>_open() for every protocol which has a proxy in the proxies dictionary given in the constructor. The method will modify requests to go through the proxy, by calling request.set_proxy(), and call the next handler in the chain to actually execute the protocol.

HTTPPasswordMgr 物件

These methods are available on HTTPPasswordMgr and HTTPPasswordMgrWithDefaultRealm objects.

HTTPPasswordMgr.add_password(realm, uri, user, passwd)

uri can be either a single URI, or a sequence of URIs. realm, user and passwd must be strings. This causes (user, passwd) to be used as authentication tokens when authentication for realm and a super-URI of any of the given URIs is given.

HTTPPasswordMgr.find_user_password(realm, authuri)

Get user/password for given realm and URI, if any. This method will return (None, None) if there is no matching user/password.

For HTTPPasswordMgrWithDefaultRealm objects, the realm None will be searched if the given realm has no matching user/password.

HTTPPasswordMgrWithPriorAuth 物件

This password manager extends HTTPPasswordMgrWithDefaultRealm to support tracking URIs for which authentication credentials should always be sent.

HTTPPasswordMgrWithPriorAuth.add_password(realm, uri, user, passwd, is_authenticated=False)

realm, uri, user, passwd are as for HTTPPasswordMgr.add_password(). is_authenticated sets the initial value of the is_authenticated flag for the given URI or list of URIs. If is_authenticated is specified as True, realm is ignored.

HTTPPasswordMgrWithPriorAuth.find_user_password(realm, authuri)

Same as for HTTPPasswordMgrWithDefaultRealm objects

HTTPPasswordMgrWithPriorAuth.update_authenticated(self, uri, is_authenticated=False)

Update the is_authenticated flag for the given uri or list of URIs.

HTTPPasswordMgrWithPriorAuth.is_authenticated(self, authuri)

Returns the current state of the is_authenticated flag for the given URI.

AbstractBasicAuthHandler 物件

AbstractBasicAuthHandler.http_error_auth_reqed(authreq, host, req, headers)

Handle an authentication request by getting a user/password pair, and re-trying the request. authreq should be the name of the header where the information about the realm is included in the request, host specifies the URL and path to authenticate for, req should be the (failed) Request object, and headers should be the error headers.

host is either an authority (e.g. "python.org") or a URL containing an authority component (e.g. "http://python.org/"). In either case, the authority must not contain a userinfo component (so, "python.org" and "python.org:80" are fine, "joe:password@python.org" is not).

HTTPBasicAuthHandler 物件

HTTPBasicAuthHandler.http_error_401(req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.

ProxyBasicAuthHandler 物件

ProxyBasicAuthHandler.http_error_407(req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.

AbstractDigestAuthHandler 物件

AbstractDigestAuthHandler.http_error_auth_reqed(authreq, host, req, headers)

authreq should be the name of the header where the information about the realm is included in the request, host should be the host to authenticate to, req should be the (failed) Request object, and headers should be the error headers.

HTTPDigestAuthHandler 物件

HTTPDigestAuthHandler.http_error_401(req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.

ProxyDigestAuthHandler 物件

ProxyDigestAuthHandler.http_error_407(req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.

HTTPHandler 物件

HTTPHandler.http_open(req)

Send an HTTP request, which can be either GET or POST, depending on req.data.

HTTPSHandler 物件

HTTPSHandler.https_open(req)

Send an HTTPS request, which can be either GET or POST, depending on req.data.

FileHandler 物件

FileHandler.file_open(req)

Open the file locally, if there is no host name, or the host name is 'localhost'.

在 3.2 版的變更: This method is applicable only for local hostnames. When a remote hostname is given, a URLError is raised.

DataHandler 物件

DataHandler.data_open(req)

Read a data URL. This kind of URL contains the content encoded in the URL itself. The data URL syntax is specified in RFC 2397 [https://datatracker.ietf.org/doc/html/rfc2397.html]. This implementation ignores white spaces in base64 encoded data URLs so the URL may be wrapped in whatever source file it comes from. But even though some browsers don't mind about a missing padding at the end of a base64 encoded data URL, this implementation will raise a ValueError in that case.

FTPHandler 物件

FTPHandler.ftp_open(req)

Open the FTP file indicated by req. The login is always done with empty username and password.

CacheFTPHandler 物件

CacheFTPHandler objects are FTPHandler objects with the following additional methods:

CacheFTPHandler.setTimeout(t)

Set timeout of connections to t seconds.

CacheFTPHandler.setMaxConns(m)

Set maximum number of cached connections to m.

UnknownHandler 物件

UnknownHandler.unknown_open()

Raise a URLError exception.

HTTPErrorProcessor 物件

HTTPErrorProcessor.http_response(request, response)

Process HTTP error responses.

For 200 error codes, the response object is returned immediately.

For non-200 error codes, this simply passes the job on to the http_error_<type>() handler methods, via OpenerDirector.error(). Eventually, HTTPDefaultErrorHandler will raise an HTTPError if no other handler handles the error.

HTTPErrorProcessor.https_response(request, response)

Process HTTPS error responses.

The behavior is same as http_response().

範例

In addition to the examples below, more examples are given in 如何使用 urllib 套件取得網路資源.

This example gets the python.org main page and displays the first 300 bytes of it:

>>> import urllib.request
>>> with urllib.request.urlopen('http://www.python.org/') as f:
...     print(f.read(300))
...
b'<!doctype html>\n<!--[if lt IE 7]>   <html class="no-js ie6 lt-ie7 lt-ie8 lt-ie9">   <![endif]-->\n<!--[if IE 7]>      <html class="no-js ie7 lt-ie8 lt-ie9">          <![endif]-->\n<!--[if IE 8]>      <html class="no-js ie8 lt-ie9">

Note that urlopen returns a bytes object. This is because there is no way for urlopen to automatically determine the encoding of the byte stream it receives from the HTTP server. In general, a program will decode the returned bytes object to string once it determines or guesses the appropriate encoding.

The following HTML spec document, https://html.spec.whatwg.org/#charset, lists the various ways in which an HTML or an XML document could have specified its encoding information.

For additional information, see the W3C document: https://www.w3.org/International/questions/qa-html-encoding-declarations.

As the python.org website uses utf-8 encoding as specified in its meta tag, we will use the same for decoding the bytes object:

>>> with urllib.request.urlopen('http://www.python.org/') as f:
...     print(f.read(100).decode('utf-8'))
...
<!doctype html>
<!--[if lt IE 7]>   <html class="no-js ie6 lt-ie7 lt-ie8 lt-ie9">   <![endif]-->
<!-

It is also possible to achieve the same result without using the context manager approach:

>>> import urllib.request
>>> f = urllib.request.urlopen('http://www.python.org/')
>>> try:
...     print(f.read(100).decode('utf-8'))
... finally:
...     f.close()
...
<!doctype html>
<!--[if lt IE 7]>   <html class="no-js ie6 lt-ie7 lt-ie8 lt-ie9">   <![endif]-->
<!--

In the following example, we are sending a data-stream to the stdin of a CGI and reading the data it returns to us. Note that this example will only work when the Python installation supports SSL.

>>> import urllib.request
>>> req = urllib.request.Request(url='https://localhost/cgi-bin/test.cgi',
...                       data=b'This data is passed to stdin of the CGI')
>>> with urllib.request.urlopen(req) as f:
...     print(f.read().decode('utf-8'))
...
Got Data: "This data is passed to stdin of the CGI"

The code for the sample CGI used in the above example is:

#!/usr/bin/env python
import sys
data = sys.stdin.read()
print('Content-type: text/plain\n\nGot Data: "%s"' % data)

Here is an example of doing a PUT request using Request:

import urllib.request
DATA = b'some data'
req = urllib.request.Request(url='http://localhost:8080', data=DATA, method='PUT')
with urllib.request.urlopen(req) as f:
    pass
print(f.status)
print(f.reason)

使用基本 HTTP 認證：

import urllib.request
# Create an OpenerDirector with support for Basic HTTP Authentication...
auth_handler = urllib.request.HTTPBasicAuthHandler()
auth_handler.add_password(realm='PDQ Application',
                          uri='https://mahler:8092/site-updates.py',
                          user='klem',
                          passwd='kadidd!ehopper')
opener = urllib.request.build_opener(auth_handler)
# ...and install it globally so it can be used with urlopen.
urllib.request.install_opener(opener)
with urllib.request.urlopen('http://www.example.com/login.html') as f:
    print(f.read().decode('utf-8'))

build_opener() provides many handlers by default, including a ProxyHandler. By default, ProxyHandler uses the environment variables named <scheme>_proxy, where <scheme> is the URL scheme involved. For example, the http_proxy environment variable is read to obtain the HTTP proxy's URL.

This example replaces the default ProxyHandler with one that uses programmatically supplied proxy URLs, and adds proxy authorization support with ProxyBasicAuthHandler.

proxy_handler = urllib.request.ProxyHandler({'http': 'http://www.example.com:3128/'})
proxy_auth_handler = urllib.request.ProxyBasicAuthHandler()
proxy_auth_handler.add_password('realm', 'host', 'username', 'password')

opener = urllib.request.build_opener(proxy_handler, proxy_auth_handler)
# 這次我們直接使用它而不安裝 OpenerDirector:
with opener.open('http://www.example.com/login.html') as f:
   print(f.read().decode('utf-8'))

添加 HTTP 標頭：

使用 Request 建構函式的 headers 引數，或：

import urllib.request
req = urllib.request.Request('http://www.example.com/')
req.add_header('Referer', 'http://www.python.org/')
# 自訂預設的使用者代理標頭值：
req.add_header('User-Agent', 'urllib-example/0.1 (Contact: . . .)')
with urllib.request.urlopen(req) as f:
    print(f.read().decode('utf-8'))

OpenerDirector automatically adds a User-Agent header to every Request. To change this:

import urllib.request
opener = urllib.request.build_opener()
opener.addheaders = [('User-agent', 'Mozilla/5.0')]
with opener.open('http://www.example.com/') as f:
   print(f.read().decode('utf-8'))

Also, remember that a few standard headers (Content-Length, Content-Type and Host) are added when the Request is passed to urlopen() (or OpenerDirector.open()).

Here is an example session that uses the GET method to retrieve a URL containing parameters:

>>> import urllib.request
>>> import urllib.parse
>>> params = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
>>> url = "http://www.musi-cal.com/cgi-bin/query?%s" % params
>>> with urllib.request.urlopen(url) as f:
...     print(f.read().decode('utf-8'))
...

The following example uses the POST method instead. Note that params output from urlencode is encoded to bytes before it is sent to urlopen as data:

>>> import urllib.request
>>> import urllib.parse
>>> data = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
>>> data = data.encode('ascii')
>>> with urllib.request.urlopen("http://requestb.in/xrbl82xr", data) as f:
...     print(f.read().decode('utf-8'))
...

The following example uses an explicitly specified HTTP proxy, overriding environment settings:

>>> import urllib.request
>>> proxies = {'http': 'http://proxy.example.com:8080/'}
>>> opener = urllib.request.build_opener(urllib.request.ProxyHandler(proxies))
>>> with opener.open("http://www.python.org") as f:
...     f.read().decode('utf-8')
...

The following example uses no proxies at all, overriding environment settings:

>>> import urllib.request
>>> opener = urllib.request.build_opener(urllib.request.ProxyHandler({}}))
>>> with opener.open("http://www.python.org/") as f:
...     f.read().decode('utf-8')
...

遺留介面

The following functions and classes are ported from the Python 2 module urllib (as opposed to urllib2). They might become deprecated at some point in the future.

urllib.request.urlretrieve(url, filename=None, reporthook=None, data=None)

Copy a network object denoted by a URL to a local file. If the URL points to a local file, the object will not be copied unless filename is supplied. Return a tuple (filename, headers) where filename is the local file name under which the object can be found, and headers is whatever the info() method of the object returned by urlopen() returned (for a remote object). Exceptions are the same as for urlopen().

The second argument, if present, specifies the file location to copy to (if absent, the location will be a tempfile with a generated name). The third argument, if present, is a callable that will be called once on establishment of the network connection and once after each block read thereafter. The callable will be passed three arguments; a count of blocks transferred so far, a block size in bytes, and the total size of the file. The third argument may be -1 on older FTP servers which do not return a file size in response to a retrieval request.

The following example illustrates the most common usage scenario:

>>> import urllib.request
>>> local_filename, headers = urllib.request.urlretrieve('http://python.org/')
>>> html = open(local_filename)
>>> html.close()

If the url uses the http: scheme identifier, the optional data argument may be given to specify a POST request (normally the request type is GET). The data argument must be a bytes object in standard application/x-www-form-urlencoded format; see the urllib.parse.urlencode() function.

urlretrieve() will raise ContentTooShortError when it detects that the amount of data available was less than the expected amount (which is the size reported by a Content-Length header). This can occur, for example, when the download is interrupted.

The Content-Length is treated as a lower bound: if there's more data to read, urlretrieve reads more data, but if less data is available, it raises the exception.

You can still retrieve the downloaded data in this case, it is stored in the content attribute of the exception instance.

If no Content-Length header was supplied, urlretrieve can not check the size of the data it has downloaded, and just returns it. In this case you just have to assume that the download was successful.

urllib.request.urlcleanup()

Cleans up temporary files that may have been left behind by previous calls to urlretrieve().

urllib.request 限制

Currently, only the following protocols are supported: HTTP (versions 0.9 and 1.0), FTP, local files, and data URLs.

在 3.4 版的變更: Added support for data URLs.

The caching feature of urlretrieve() has been disabled until someone finds the time to hack proper processing of Expiration time headers.

There should be a function to query whether a particular URL is in the cache.

For backward compatibility, if a URL appears to point to a local file but the file can't be opened, the URL is re-interpreted using the FTP protocol. This can sometimes cause confusing error messages.

The urlopen() and urlretrieve() functions can cause arbitrarily long delays while waiting for a network connection to be set up. This means that it is difficult to build an interactive web client using these functions without using threads.

The data returned by urlopen() or urlretrieve() is the raw data returned by the server. This may be binary data (such as an image), plain text or (for example) HTML. The HTTP protocol provides type information in the reply header, which can be inspected by looking at the Content-Type header. If the returned data is HTML, you can use the module html.parser to parse it.

The code handling the FTP protocol cannot differentiate between a file and a directory. This can lead to unexpected behavior when attempting to read a URL that points to a file that is not accessible. If the URL ends in a /, it is assumed to refer to a directory and will be handled accordingly. But if an attempt to read a file leads to a 550 error (meaning the URL cannot be found or is not accessible, often for permission reasons), then the path is treated as a directory in order to handle the case when a directory is specified by a URL but the trailing / has been left off. This can cause misleading results when you try to fetch a file whose read permissions make it inaccessible; the FTP code will try to read it, fail with a 550 error, and then perform a directory listing for the unreadable file. If fine-grained control is needed, consider using the ftplib module.

urllib.response --- Response classes used by urllib

The urllib.response module defines functions and classes which define a minimal file-like interface, including read() and readline(). Functions defined by this module are used internally by the urllib.request module. The typical response object is a urllib.response.addinfourl instance:

class urllib.response.addinfourl

url

URL of the resource retrieved, commonly used to determine if a redirect was followed.

headers

Returns the headers of the response in the form of an EmailMessage instance.

status

在 3.9 版被加入.

伺服器回傳的狀態碼。

geturl()

在 3.9 版之後被棄用: 已被 url 取代而棄用。

info()

在 3.9 版之後被棄用: 已被 headers 取代而棄用。

code

在 3.9 版之後被棄用: 已被 status 取代而棄用。

getcode()

在 3.9 版之後被棄用: 已被 status 取代而棄用。

urllib.parse --- 將 URL 剖析成元件

原始碼：Lib/urllib/parse.py [https://github.com/python/cpython/tree/3.14/Lib/urllib/parse.py]

This module defines a standard interface to break Uniform Resource Locator (URL) strings up in components (addressing scheme, network location, path etc.), to combine the components back into a URL string, and to convert a "relative URL" to an absolute URL given a "base URL."

The module has been designed to match the internet RFC on Relative Uniform Resource Locators. It supports the following URL schemes: file, ftp, gopher, hdl, http, https, imap, itms-services, mailto, mms, news, nntp, prospero, rsync, rtsp, rtsps, rtspu, sftp, shttp, sip, sips, snews, svn, svn+ssh, telnet, wais, ws, wss.

CPython 實作細節： The inclusion of the itms-services URL scheme can prevent an app from passing Apple's App Store review process for the macOS and iOS App Stores. Handling for the itms-services scheme is always removed on iOS; on macOS, it may be removed if CPython has been built with the --with-app-store-compliance option.

The urllib.parse module defines functions that fall into two broad categories: URL parsing and URL quoting. These are covered in detail in the following sections.

This module's functions use the deprecated term netloc (or net_loc), which was introduced in RFC 1808 [https://datatracker.ietf.org/doc/html/rfc1808.html]. However, this term has been obsoleted by RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html], which introduced the term authority as its replacement. The use of netloc is continued for backward compatibility.

URL Parsing

The URL parsing functions focus on splitting a URL string into its components, or on combining URL components into a URL string.

urllib.parse.urlparse(urlstring, scheme='', allow_fragments=True)

Parse a URL into six components, returning a 6-item named tuple. This corresponds to the general structure of a URL: scheme://netloc/path;parameters?query#fragment. Each tuple item is a string, possibly empty. The components are not broken up into smaller parts (for example, the network location is a single string), and % escapes are not expanded. The delimiters as shown above are not part of the result, except for a leading slash in the path component, which is retained if present. For example:

>>> from urllib.parse import urlparse
>>> urlparse("scheme://netloc/path;parameters?query#fragment")
ParseResult(scheme='scheme', netloc='netloc', path='/path;parameters', params='',
            query='query', fragment='fragment')
>>> o = urlparse("http://docs.python.org:80/3/library/urllib.parse.html?"
...              "highlight=params#url-parsing")
>>> o
ParseResult(scheme='http', netloc='docs.python.org:80',
            path='/3/library/urllib.parse.html', params='',
            query='highlight=params', fragment='url-parsing')
>>> o.scheme
'http'
>>> o.netloc
'docs.python.org:80'
>>> o.hostname
'docs.python.org'
>>> o.port
80
>>> o._replace(fragment="").geturl()
'http://docs.python.org:80/3/library/urllib.parse.html?highlight=params'

Following the syntax specifications in RFC 1808 [https://datatracker.ietf.org/doc/html/rfc1808.html], urlparse recognizes a netloc only if it is properly introduced by '//'. Otherwise the input is presumed to be a relative URL and thus to start with a path component.

>>> from urllib.parse import urlparse
>>> urlparse('//www.cwi.nl:80/%7Eguido/Python.html')
ParseResult(scheme='', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='', query='', fragment='')
>>> urlparse('www.cwi.nl/%7Eguido/Python.html')
ParseResult(scheme='', netloc='', path='www.cwi.nl/%7Eguido/Python.html',
            params='', query='', fragment='')
>>> urlparse('help/Python.html')
ParseResult(scheme='', netloc='', path='help/Python.html', params='',
            query='', fragment='')

The scheme argument gives the default addressing scheme, to be used only if the URL does not specify one. It should be the same type (text or bytes) as urlstring, except that the default value '' is always allowed, and is automatically converted to b'' if appropriate.

If the allow_fragments argument is false, fragment identifiers are not recognized. Instead, they are parsed as part of the path, parameters or query component, and fragment is set to the empty string in the return value.

The return value is a named tuple, which means that its items can be accessed by index or as named attributes, which are:

屬性

Index

Value

Value if not present

scheme

0

URL scheme specifier

scheme parameter

netloc

1

Network location part

empty string

path

2

Hierarchical path

empty string

params

3

Parameters for last path element

empty string

query

4

Query component

empty string

fragment

5

Fragment identifier

empty string

username

User name

None

password

Password

None

hostname

Host name (lower case)

None

port

Port number as integer, if present

None

Reading the port attribute will raise a ValueError if an invalid port is specified in the URL. See section Structured Parse Results for more information on the result object.

Unmatched square brackets in the netloc attribute will raise a ValueError.

Characters in the netloc attribute that decompose under NFKC normalization (as used by the IDNA encoding) into any of /, ?, #, @, or : will raise a ValueError. If the URL is decomposed before parsing, no error will be raised.

As is the case with all named tuples, the subclass has a few additional methods and attributes that are particularly useful. One such method is _replace(). The _replace() method will return a new ParseResult object replacing specified fields with new values.

>>> from urllib.parse import urlparse
>>> u = urlparse('//www.cwi.nl:80/%7Eguido/Python.html')
>>> u
ParseResult(scheme='', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='', query='', fragment='')
>>> u._replace(scheme='http')
ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='', query='', fragment='')

警告

urlparse() does not perform validation. See URL parsing security for details.

在 3.2 版的變更: 新增剖析 IPv6 URL 的能力。

在 3.3 版的變更: The fragment is now parsed for all URL schemes (unless allow_fragments is false), in accordance with RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html]. Previously, an allowlist of schemes that support fragments existed.

在 3.6 版的變更: Out-of-range port numbers now raise ValueError, instead of returning None.

在 3.8 版的變更: Characters that affect netloc parsing under NFKC normalization will now raise ValueError.

urllib.parse.parse_qs(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None, separator='&')

Parse a query string given as a string argument (data of type application/x-www-form-urlencoded). Data are returned as a dictionary. The dictionary keys are the unique query variable names and the values are lists of values for each name.

The optional argument keep_blank_values is a flag indicating whether blank values in percent-encoded queries should be treated as blank strings. A true value indicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included.

The optional argument strict_parsing is a flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception.

The optional encoding and errors parameters specify how to decode percent-encoded sequences into Unicode characters, as accepted by the bytes.decode() method.

The optional argument max_num_fields is the maximum number of fields to read. If set, then throws a ValueError if there are more than max_num_fields fields read.

The optional argument separator is the symbol to use for separating the query arguments. It defaults to &.

Use the urllib.parse.urlencode() function (with the doseq parameter set to True) to convert such dictionaries into query strings.

在 3.2 版的變更: 新增 encoding 和 errors 參數。

在 3.8 版的變更: 新增 max_num_fields 參數。

在 3.10 版的變更: Added separator parameter with the default value of &. Python versions earlier than Python 3.10 allowed using both ; and & as query parameter separator. This has been changed to allow only a single separator key, with & as the default separator.

在 3.14 版之後被棄用: Accepting objects with false values (like 0 and []) except empty strings and byte-like objects and None is now deprecated.

urllib.parse.parse_qsl(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None, separator='&')

Parse a query string given as a string argument (data of type application/x-www-form-urlencoded). Data are returned as a list of name, value pairs.

The optional argument keep_blank_values is a flag indicating whether blank values in percent-encoded queries should be treated as blank strings. A true value indicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included.

The optional argument strict_parsing is a flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception.

The optional encoding and errors parameters specify how to decode percent-encoded sequences into Unicode characters, as accepted by the bytes.decode() method.

The optional argument max_num_fields is the maximum number of fields to read. If set, then throws a ValueError if there are more than max_num_fields fields read.

The optional argument separator is the symbol to use for separating the query arguments. It defaults to &.

Use the urllib.parse.urlencode() function to convert such lists of pairs into query strings.

在 3.2 版的變更: 新增 encoding 和 errors 參數。

在 3.8 版的變更: 新增 max_num_fields 參數。

在 3.10 版的變更: Added separator parameter with the default value of &. Python versions earlier than Python 3.10 allowed using both ; and & as query parameter separator. This has been changed to allow only a single separator key, with & as the default separator.

urllib.parse.urlunparse(parts)

Construct a URL from a tuple as returned by urlparse(). The parts argument can be any six-item iterable. This may result in a slightly different, but equivalent URL, if the URL that was parsed originally had unnecessary delimiters (for example, a ? with an empty query; the RFC states that these are equivalent).

urllib.parse.urlsplit(urlstring, scheme='', allow_fragments=True)

This is similar to urlparse(), but does not split the params from the URL. This should generally be used instead of urlparse() if the more recent URL syntax allowing parameters to be applied to each segment of the path portion of the URL (see RFC 2396 [https://datatracker.ietf.org/doc/html/rfc2396.html]) is wanted. A separate function is needed to separate the path segments and parameters. This function returns a 5-item named tuple:

(addressing scheme, network location, path, query, fragment identifier).

The return value is a named tuple, its items can be accessed by index or as named attributes:

屬性

Index

Value

Value if not present

scheme

0

URL scheme specifier

scheme parameter

netloc

1

Network location part

empty string

path

2

Hierarchical path

empty string

query

3

Query component

empty string

fragment

4

Fragment identifier

empty string

username

User name

None

password

Password

None

hostname

Host name (lower case)

None

port

Port number as integer, if present

None

Reading the port attribute will raise a ValueError if an invalid port is specified in the URL. See section Structured Parse Results for more information on the result object.

Unmatched square brackets in the netloc attribute will raise a ValueError.

Characters in the netloc attribute that decompose under NFKC normalization (as used by the IDNA encoding) into any of /, ?, #, @, or : will raise a ValueError. If the URL is decomposed before parsing, no error will be raised.

Following some of the WHATWG spec [https://url.spec.whatwg.org/#concept-basic-url-parser] that updates RFC 3986, leading C0 control and space characters are stripped from the URL. \n, \r and tab \t characters are removed from the URL at any position.

警告

urlsplit() does not perform validation. See URL parsing security for details.

在 3.6 版的變更: Out-of-range port numbers now raise ValueError, instead of returning None.

在 3.8 版的變更: Characters that affect netloc parsing under NFKC normalization will now raise ValueError.

在 3.10 版的變更: ASCII newline and tab characters are stripped from the URL.

在 3.12 版的變更: Leading WHATWG C0 control and space characters are stripped from the URL.

urllib.parse.urlunsplit(parts)

Combine the elements of a tuple as returned by urlsplit() into a complete URL as a string. The parts argument can be any five-item iterable. This may result in a slightly different, but equivalent URL, if the URL that was parsed originally had unnecessary delimiters (for example, a ? with an empty query; the RFC states that these are equivalent).

urllib.parse.urljoin(base, url, allow_fragments=True)

Construct a full ("absolute") URL by combining a "base URL" (base) with another URL (url). Informally, this uses components of the base URL, in particular the addressing scheme, the network location and (part of) the path, to provide missing components in the relative URL. For example:

>>> from urllib.parse import urljoin
>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html', 'FAQ.html')
'http://www.cwi.nl/%7Eguido/FAQ.html'

The allow_fragments argument has the same meaning and default as for urlparse().

備註

If url is an absolute URL (that is, it starts with // or scheme://), the url's hostname and/or scheme will be present in the result. For example:

>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html',
...         '//www.python.org/%7Eguido')
'http://www.python.org/%7Eguido'

If you do not want that behavior, preprocess the url with urlsplit() and urlunsplit(), removing possible scheme and netloc parts.

警告

Because an absolute URL may be passed as the url parameter, it is generally not secure to use urljoin with an attacker-controlled url. For example in, urljoin("https://website.com/users/", username), if username can contain an absolute URL, the result of urljoin will be the absolute URL.

在 3.5 版的變更: Behavior updated to match the semantics defined in RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html].

urllib.parse.urldefrag(url)

If url contains a fragment identifier, return a modified version of url with no fragment identifier, and the fragment identifier as a separate string. If there is no fragment identifier in url, return url unmodified and an empty string.

The return value is a named tuple, its items can be accessed by index or as named attributes:

屬性

Index

Value

Value if not present

url

0

URL with no fragment

empty string

fragment

1

Fragment identifier

empty string

See section Structured Parse Results for more information on the result object.

在 3.2 版的變更: Result is a structured object rather than a simple 2-tuple.

urllib.parse.unwrap(url)

Extract the url from a wrapped URL (that is, a string formatted as <URL:scheme://host/path>, <scheme://host/path>, URL:scheme://host/path or scheme://host/path). If url is not a wrapped URL, it is returned without changes.

URL parsing security

The urlsplit() and urlparse() APIs do not perform validation of inputs. They may not raise errors on inputs that other applications consider invalid. They may also succeed on some inputs that might not be considered URLs elsewhere. Their purpose is for practical functionality rather than purity.

Instead of raising an exception on unusual input, they may instead return some component parts as empty strings. Or components may contain more than perhaps they should.

We recommend that users of these APIs where the values may be used anywhere with security implications code defensively. Do some verification within your code before trusting a returned component part. Does that scheme make sense? Is that a sensible path? Is there anything strange about that hostname? etc.

What constitutes a URL is not universally well defined. Different applications have different needs and desired constraints. For instance the living WHATWG spec [https://url.spec.whatwg.org/#concept-basic-url-parser] describes what user facing web clients such as a web browser require. While RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html] is more general. These functions incorporate some aspects of both, but cannot be claimed compliant with either. The APIs and existing user code with expectations on specific behaviors predate both standards leading us to be very cautious about making API behavior changes.

Parsing ASCII Encoded Bytes

The URL parsing functions were originally designed to operate on character strings only. In practice, it is useful to be able to manipulate properly quoted and encoded URLs as sequences of ASCII bytes. Accordingly, the URL parsing functions in this module all operate on bytes and bytearray objects in addition to str objects.

If str data is passed in, the result will also contain only str data. If bytes or bytearray data is passed in, the result will contain only bytes data.

Attempting to mix str data with bytes or bytearray in a single function call will result in a TypeError being raised, while attempting to pass in non-ASCII byte values will trigger UnicodeDecodeError.

To support easier conversion of result objects between str and bytes, all return values from URL parsing functions provide either an encode() method (when the result contains str data) or a decode() method (when the result contains bytes data). The signatures of these methods match those of the corresponding str and bytes methods (except that the default encoding is 'ascii' rather than 'utf-8'). Each produces a value of a corresponding type that contains either bytes data (for encode() methods) or str data (for decode() methods).

Applications that need to operate on potentially improperly quoted URLs that may contain non-ASCII data will need to do their own decoding from bytes to characters before invoking the URL parsing methods.

The behaviour described in this section applies only to the URL parsing functions. The URL quoting functions use their own rules when producing or consuming byte sequences as detailed in the documentation of the individual URL quoting functions.

在 3.2 版的變更: URL parsing functions now accept ASCII encoded byte sequences

Structured Parse Results

The result objects from the urlparse(), urlsplit() and urldefrag() functions are subclasses of the tuple type. These subclasses add the attributes listed in the documentation for those functions, the encoding and decoding support described in the previous section, as well as an additional method:

urllib.parse.SplitResult.geturl()

Return the re-combined version of the original URL as a string. This may differ from the original URL in that the scheme may be normalized to lower case and empty components may be dropped. Specifically, empty parameters, queries, and fragment identifiers will be removed.

For urldefrag() results, only empty fragment identifiers will be removed. For urlsplit() and urlparse() results, all noted changes will be made to the URL returned by this method.

The result of this method remains unchanged if passed back through the original parsing function:

>>> from urllib.parse import urlsplit
>>> url = 'HTTP://www.Python.org/doc/#'
>>> r1 = urlsplit(url)
>>> r1.geturl()
'http://www.Python.org/doc/'
>>> r2 = urlsplit(r1.geturl())
>>> r2.geturl()
'http://www.Python.org/doc/'

The following classes provide the implementations of the structured parse results when operating on str objects:

class urllib.parse.DefragResult(url, fragment)

Concrete class for urldefrag() results containing str data. The encode() method returns a DefragResultBytes instance.

在 3.2 版被加入.

class urllib.parse.ParseResult(scheme, netloc, path, params, query, fragment)

Concrete class for urlparse() results containing str data. The encode() method returns a ParseResultBytes instance.

class urllib.parse.SplitResult(scheme, netloc, path, query, fragment)

Concrete class for urlsplit() results containing str data. The encode() method returns a SplitResultBytes instance.

The following classes provide the implementations of the parse results when operating on bytes or bytearray objects:

class urllib.parse.DefragResultBytes(url, fragment)

Concrete class for urldefrag() results containing bytes data. The decode() method returns a DefragResult instance.

在 3.2 版被加入.

class urllib.parse.ParseResultBytes(scheme, netloc, path, params, query, fragment)

Concrete class for urlparse() results containing bytes data. The decode() method returns a ParseResult instance.

在 3.2 版被加入.

class urllib.parse.SplitResultBytes(scheme, netloc, path, query, fragment)

Concrete class for urlsplit() results containing bytes data. The decode() method returns a SplitResult instance.

在 3.2 版被加入.

URL Quoting

The URL quoting functions focus on taking program data and making it safe for use as URL components by quoting special characters and appropriately encoding non-ASCII text. They also support reversing these operations to recreate the original data from the contents of a URL component if that task isn't already covered by the URL parsing functions above.

urllib.parse.quote(string, safe='/', encoding=None, errors=None)

Replace special characters in string using the %xx escape. Letters, digits, and the characters '_.-~' are never quoted. By default, this function is intended for quoting the path section of a URL. The optional safe parameter specifies additional ASCII characters that should not be quoted --- its default value is '/'.

string may be either a str or a bytes object.

在 3.7 版的變更: Moved from RFC 2396 [https://datatracker.ietf.org/doc/html/rfc2396.html] to RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html] for quoting URL strings. "~" is now included in the set of unreserved characters.

The optional encoding and errors parameters specify how to deal with non-ASCII characters, as accepted by the str.encode() method. encoding defaults to 'utf-8'. errors defaults to 'strict', meaning unsupported characters raise a UnicodeEncodeError. encoding and errors must not be supplied if string is a bytes, or a TypeError is raised.

Note that quote(string, safe, encoding, errors) is equivalent to quote_from_bytes(string.encode(encoding, errors), safe).

Example: quote('/El Niño/') yields '/El%20Ni%C3%B1o/'.

urllib.parse.quote_plus(string, safe='', encoding=None, errors=None)

Like quote(), but also replace spaces with plus signs, as required for quoting HTML form values when building up a query string to go into a URL. Plus signs in the original string are escaped unless they are included in safe. It also does not have safe default to '/'.

Example: quote_plus('/El Niño/') yields '%2FEl+Ni%C3%B1o%2F'.

urllib.parse.quote_from_bytes(bytes, safe='/')

Like quote(), but accepts a bytes object rather than a str, and does not perform string-to-bytes encoding.

Example: quote_from_bytes(b'a&\xef') yields 'a%26%EF'.

urllib.parse.unquote(string, encoding='utf-8', errors='replace')

Replace %xx escapes with their single-character equivalent. The optional encoding and errors parameters specify how to decode percent-encoded sequences into Unicode characters, as accepted by the bytes.decode() method.

string may be either a str or a bytes object.

encoding defaults to 'utf-8'. errors defaults to 'replace', meaning invalid sequences are replaced by a placeholder character.

Example: unquote('/El%20Ni%C3%B1o/') yields '/El Niño/'.

在 3.9 版的變更: string parameter supports bytes and str objects (previously only str).

urllib.parse.unquote_plus(string, encoding='utf-8', errors='replace')

Like unquote(), but also replace plus signs with spaces, as required for unquoting HTML form values.

string must be a str.

Example: unquote_plus('/El+Ni%C3%B1o/') yields '/El Niño/'.

urllib.parse.unquote_to_bytes(string)

Replace %xx escapes with their single-octet equivalent, and return a bytes object.

string may be either a str or a bytes object.

If it is a str, unescaped non-ASCII characters in string are encoded into UTF-8 bytes.

Example: unquote_to_bytes('a%26%EF') yields b'a&\xef'.

urllib.parse.urlencode(query, doseq=False, safe='', encoding=None, errors=None, quote_via=quote_plus)

Convert a mapping object or a sequence of two-element tuples, which may contain str or bytes objects, to a percent-encoded ASCII text string. If the resultant string is to be used as a data for POST operation with the urlopen() function, then it should be encoded to bytes, otherwise it would result in a TypeError.

The resulting string is a series of key=value pairs separated by '&' characters, where both key and value are quoted using the quote_via function. By default, quote_plus() is used to quote the values, which means spaces are quoted as a '+' character and '/' characters are encoded as %2F, which follows the standard for GET requests (application/x-www-form-urlencoded). An alternate function that can be passed as quote_via is quote(), which will encode spaces as %20 and not encode '/' characters. For maximum control of what is quoted, use quote and specify a value for safe.

When a sequence of two-element tuples is used as the query argument, the first element of each tuple is a key and the second is a value. The value element in itself can be a sequence and in that case, if the optional parameter doseq evaluates to True, individual key=value pairs separated by '&' are generated for each element of the value sequence for the key. The order of parameters in the encoded string will match the order of parameter tuples in the sequence.

The safe, encoding, and errors parameters are passed down to quote_via (the encoding and errors parameters are only passed when a query element is a str).

To reverse this encoding process, parse_qs() and parse_qsl() are provided in this module to parse query strings into Python data structures.

Refer to urllib examples to find out how the urllib.parse.urlencode() method can be used for generating the query string of a URL or data for a POST request.

在 3.2 版的變更: query supports bytes and string objects.

在 3.5 版的變更: 新增 quote_via 參數。

在 3.14 版之後被棄用: Accepting objects with false values (like 0 and []) except empty strings and byte-like objects and None is now deprecated.

也參考

WHATWG [https://url.spec.whatwg.org/] - URL Living standard

Working Group for the URL Standard that defines URLs, domains, IP addresses, the application/x-www-form-urlencoded format, and their API.

RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html] - 統一資源識別碼

This is the current standard (STD66). Any changes to urllib.parse module should conform to this. Certain deviations could be observed, which are mostly for backward compatibility purposes and for certain de-facto parsing requirements as commonly observed in major browsers.

RFC 2732 [https://datatracker.ietf.org/doc/html/rfc2732.html] - Format for Literal IPv6 Addresses in URL's.

This specifies the parsing requirements of IPv6 URLs.

RFC 2396 [https://datatracker.ietf.org/doc/html/rfc2396.html] - 統一資源識別碼 (URI)：通用語法

Document describing the generic syntactic requirements for both Uniform Resource Names (URNs) and Uniform Resource Locators (URLs).

RFC 2368 [https://datatracker.ietf.org/doc/html/rfc2368.html] - The mailto URL scheme.

Parsing requirements for mailto URL schemes.

RFC 1808 [https://datatracker.ietf.org/doc/html/rfc1808.html] - 相對的統一資源定位器 (Relative Uniform Resource Locators)

This Request For Comments includes the rules for joining an absolute and a relative URL, including a fair number of "Abnormal Examples" which govern the treatment of border cases.

RFC 1738 [https://datatracker.ietf.org/doc/html/rfc1738.html] - 統一資源定位器 (URL, Uniform Resource Locators)

This specifies the formal syntax and semantics of absolute URLs.

urllib.error --- urllib.request 引發的例外類別

原始碼：Lib/urllib/error.py [https://github.com/python/cpython/tree/3.14/Lib/urllib/error.py]

urllib.error module（模組）為 urllib.request 所引發的例外定義了例外 (exception) 類別。基礎例外類別是 URLError。

下列例外會被 urllib.error 適時引發：

exception urllib.error.URLError

處理程式 (handler) 在遇到問題時會引發此例外（或其衍生例外）。它是 OSError 的一個子類別。

reason

此錯誤的原因。它可以是一個訊息字串或另一個例外實例。

在 3.3 版的變更: URLError 過去是 IOError 的子類別，但現在為 OSError 的別名。

exception urllib.error.HTTPError(url, code, msg, hdrs, fp)

雖然是一個例外（URLError 的一個子類別），HTTPError 也可以作為一個非例外的類檔案回傳值（與 urlopen() 所回傳的物件相同）。這適用於處理特殊 HTTP 錯誤，例如為請求認證。

url

包含請求 URL。filename 屬性的別名。

code

一個 HTTP 狀態碼，具體定義見 RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html]。這個數值會對應到存放在 http.server.BaseHTTPRequestHandler.responses 程式碼 dictionary 中的某個值。

reason

這通常是一個解釋本次錯誤原因的字串。為 msg 屬性的別名。

headers

導致 HTTPError 的特定 HTTP 請求的 HTTP 回應 header。為 hdrs 屬性的別名。

在 3.4 版被加入.

fp

一個類檔案物件，可以從中讀取 HTTP 錯誤主體 (body)。

exception urllib.error.ContentTooShortError(msg, content)

此例外會在 urlretrieve() 函式檢查到已下載的資料量小於期待的資料量（由 Content-Length header 給定）時被引發。

content

已下載（可能已被截斷）的資料。

urllib.robotparser --- robots.txt 的剖析器

原始碼：Lib/urllib/robotparser.py [https://github.com/python/cpython/tree/3.14/Lib/urllib/robotparser.py]

此模組 (module) 提供了一個單獨的類別 (class) RobotFileParser，它可以知道某個特定 user agent（使用者代理）是否能在有發布 robots.txt 文件的網站 fetch（擷取）特定 URL。有關 robots.txt 文件結構的更多細節，請參閱 http://www.robotstxt.org/orig.html。

class urllib.robotparser.RobotFileParser(url='')

此類別提供了一些方法可以讀取、剖析和回答關於 url 上的 robots.txt 文件的問題。

set_url(url)

設置指向 robots.txt 文件的 URL。

read()

讀取 robots.txt URL 並將其輸入到剖析器。

parse(lines)

剖析 lines 引數。

can_fetch(useragent, url)

根據從 robots.txt 文件中剖析出的規則，如果 useragent 被允許 fetch url 的話，則回傳 True。

mtime()

回傳最近一次 fetch robots.txt 文件的時間。這適用於需要定期檢查 robots.txt 文件更新情況的長時間運行網頁爬蟲。

modified()

將最近一次 fetch robots.txt 文件的時間設置為目前時間。

crawl_delay(useragent)

針對指定的 useragent 從 robots.txt 回傳 Crawl-delay 參數的值。如果此參數不存在、不適用於指定的 useragent ，或是此參數在 robots.txt 中所指的條目含有無效語法，則回傳 None。

在 3.6 版被加入.

request_rate(useragent)

以 named tuple RequestRate(requests, seconds) 的形式從 robots.txt 回傳 Request-rate 參數的內容。如果此參數不存在、不適用於指定的 useragent ，或是此參數在 robots.txt 中所指的條目含有無效語法，則回傳 None。

在 3.6 版被加入.

site_maps()

以 list() 的形式從 robots.txt 回傳 Sitemap 參數的內容。如果此參數不存在或此參數在 robots.txt 中所指的條目含有無效語法，則回傳 None。

在 3.8 版被加入.

下面的範例展示了 RobotFileParser 類別的基本用法：

>>> import urllib.robotparser
>>> rp = urllib.robotparser.RobotFileParser()
>>> rp.set_url("http://www.musi-cal.com/robots.txt")
>>> rp.read()
>>> rrate = rp.request_rate("*")
>>> rrate.requests
3
>>> rrate.seconds
20
>>> rp.crawl_delay("*")
6
>>> rp.can_fetch("*", "http://www.musi-cal.com/cgi-bin/search?city=San+Francisco")
False
>>> rp.can_fetch("*", "http://www.musi-cal.com/")
True

http --- HTTP 模組

原始碼：Lib/http/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/http/__init__.py]

http 是一個收集了多個用於處理超文本傳輸協定 (HyperText Transfer Protocol) 之模組 (module) 的套件：

http.client 是一個低階的 HTTP 協定用戶端；對於高階的 URL 存取請使用 urllib.request

http.server 包含基於 socketserver 的基本 HTTP 伺服器類別

http.cookies 包含透過 cookies 實作狀態管理的工具程式 (utilities)

http.cookiejar 提供了 cookies 的持續留存 (persistence)

The http module also defines the following enums that help you work with http related code:

class http.HTTPStatus

在 3.5 版被加入.

enum.IntEnum 的子類別，它定義了一組 HTTP 狀態碼、原理短語 (reason phrase) 以及英文長描述。

用法：

>>> from http import HTTPStatus
>>> HTTPStatus.OK
HTTPStatus.OK
>>> HTTPStatus.OK == 200
True
>>> HTTPStatus.OK.value
200
>>> HTTPStatus.OK.phrase
'OK'
>>> HTTPStatus.OK.description
'Request fulfilled, document follows'
>>> list(HTTPStatus)
[HTTPStatus.CONTINUE, HTTPStatus.SWITCHING_PROTOCOLS, ...]

HTTP 狀態碼

http.HTTPStatus 當中，已支援並且有於 IANA 註冊的狀態碼 [https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml]有：

狀態碼

列舉名稱

詳情

100

CONTINUE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.2.1

101

SWITCHING_PROTOCOLS

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.2.2

102

PROCESSING

WebDAV RFC 2518 [https://datatracker.ietf.org/doc/html/rfc2518.html]，10.1 節

103

EARLY_HINTS

用於指定提示 (Indicating Hints) RFC 8297 [https://datatracker.ietf.org/doc/html/rfc8297.html] 的 HTTP 狀態碼

200

OK

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.1

201

CREATED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.2

202

ACCEPTED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.3

203

NON_AUTHORITATIVE_INFORMATION

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.4

204

NO_CONTENT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.5

205

RESET_CONTENT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.6

206

PARTIAL_CONTENT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.3.7

207

MULTI_STATUS

WebDAV RFC 4918 [https://datatracker.ietf.org/doc/html/rfc4918.html]，11.1 節

208

ALREADY_REPORTED

WebDAV 繫結擴充 (Binding Extensions) RFC 5842 [https://datatracker.ietf.org/doc/html/rfc5842.html]，7.1 節（實驗性）

226

IM_USED

HTTP 中的差分編碼 RFC 3229 [https://datatracker.ietf.org/doc/html/rfc3229.html]，10.4.1 節

300

MULTIPLE_CHOICES

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.1

301

MOVED_PERMANENTLY

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.2

302

FOUND

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.3

303

SEE_OTHER

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.4

304

NOT_MODIFIED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.5

305

USE_PROXY

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.6

307

TEMPORARY_REDIRECT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.8

308

PERMANENT_REDIRECT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.4.9

400

BAD_REQUEST

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.1

401

UNAUTHORIZED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.2

402

PAYMENT_REQUIRED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.3

403

FORBIDDEN

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.4

404

NOT_FOUND

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.5

405

METHOD_NOT_ALLOWED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.6

406

NOT_ACCEPTABLE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.7

407

PROXY_AUTHENTICATION_REQUIRED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.8

408

REQUEST_TIMEOUT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.9

409

CONFLICT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.10

410

GONE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.11

411

LENGTH_REQUIRED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.12

412

PRECONDITION_FAILED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.13

413

CONTENT_TOO_LARGE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.14

414

URI_TOO_LONG

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.15

415

UNSUPPORTED_MEDIA_TYPE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.16

416

RANGE_NOT_SATISFIABLE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.17

417

EXPECTATION_FAILED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.18

418

IM_A_TEAPOT

HTCPCP/1.0 RFC 2324 [https://datatracker.ietf.org/doc/html/rfc2324.html]，Section 2.3.2

421

MISDIRECTED_REQUEST

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.20

422

UNPROCESSABLE_CONTENT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.21

423

LOCKED

WebDAV RFC 4918 [https://datatracker.ietf.org/doc/html/rfc4918.html]，11.3 節

424

FAILED_DEPENDENCY

WebDAV RFC 4918 [https://datatracker.ietf.org/doc/html/rfc4918.html]，11.4 節

425

TOO_EARLY

使用 HTTP 中的早期資料 RFC 8470 [https://datatracker.ietf.org/doc/html/rfc8470.html]

426

UPGRADE_REQUIRED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.5.22

428

PRECONDITION_REQUIRED

額外的 HTTP 狀態碼 RFC 6585 [https://datatracker.ietf.org/doc/html/rfc6585.html]

429

TOO_MANY_REQUESTS

額外的 HTTP 狀態碼 RFC 6585 [https://datatracker.ietf.org/doc/html/rfc6585.html]

431

REQUEST_HEADER_FIELDS_TOO_LARGE

額外的 HTTP 狀態碼 RFC 6585 [https://datatracker.ietf.org/doc/html/rfc6585.html]

451

UNAVAILABLE_FOR_LEGAL_REASONS

一個用來回報合法性障礙 (Legal Obstacles) 的 HTTP 狀態碼 RFC 7725 [https://datatracker.ietf.org/doc/html/rfc7725.html]

500

INTERNAL_SERVER_ERROR

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.6.1

501

NOT_IMPLEMENTED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.6.2

502

BAD_GATEWAY

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.6.3

503

SERVICE_UNAVAILABLE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.6.4

504

GATEWAY_TIMEOUT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.6.5

505

HTTP_VERSION_NOT_SUPPORTED

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15.6.6

506

VARIANT_ALSO_NEGOTIATES

HTTP 中的透明內容協商 (Transparent Content Negotiation) RFC 2295 [https://datatracker.ietf.org/doc/html/rfc2295.html]，8.1 節（實驗性）

507

INSUFFICIENT_STORAGE

WebDAV RFC 4918 [https://datatracker.ietf.org/doc/html/rfc4918.html]，11.5 節

508

LOOP_DETECTED

WebDAV 繫結擴充 RFC 5842 [https://datatracker.ietf.org/doc/html/rfc5842.html]，7.2 節（實驗性）

510

NOT_EXTENDED

一個 HTTP 擴充框架 RFC 2774 [https://datatracker.ietf.org/doc/html/rfc2774.html]，7 節（實驗性）

511

NETWORK_AUTHENTICATION_REQUIRED

額外的 HTTP 狀態碼 RFC 6585 [https://datatracker.ietf.org/doc/html/rfc6585.html]，6 節

為了向後相容性，列舉值也以常數形式出現在 http.client 模組中。列舉名稱等於常數名稱（例如 http.HTTPStatus.OK 也可以是 http.client.OK）。

在 3.7 版的變更: 新增 421 MISDIRECTED_REQUEST 狀態碼。

在 3.8 版被加入: 新增 451 UNAVAILABLE_FOR_LEGAL_REASONS 狀態碼。

在 3.9 版被加入: 新增 103 EARLY_HINTS、418 IM_A_TEAPOT 與 425 TOO_EARLY 狀態碼。

在 3.13 版的變更: Implemented RFC9110 naming for status constants. Old constant names are preserved for backwards compatibility: 413 REQUEST_ENTITY_TOO_LARGE, 414 REQUEST_URI_TOO_LONG, 416 REQUESTED_RANGE_NOT_SATISFIABLE and 422 UNPROCESSABLE_ENTITY.

HTTP 狀態分類

在 3.12 版被加入.

The enum values have several properties to indicate the HTTP status category:

Property

Indicates that

詳情

is_informational

100 <= status <= 199

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15

is_success

200 <= status <= 299

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15

is_redirection

300 <= status <= 399

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15

is_client_error

400 <= status <= 499

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15

is_server_error

500 <= status <= 599

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 15

用法：

>>> from http import HTTPStatus
>>> HTTPStatus.OK.is_success
True
>>> HTTPStatus.OK.is_client_error
False

class http.HTTPMethod

在 3.11 版被加入.

enum.StrEnum 的子類別，它定義了一組 HTTP 方法以及英文描述。

用法：

>>> from http import HTTPMethod
>>>
>>> HTTPMethod.GET
<HTTPMethod.GET>
>>> HTTPMethod.GET == 'GET'
True
>>> HTTPMethod.GET.value
'GET'
>>> HTTPMethod.GET.description
'Retrieve the target.'
>>> list(HTTPMethod)
[<HTTPMethod.CONNECT>,
 <HTTPMethod.DELETE>,
 <HTTPMethod.GET>,
 <HTTPMethod.HEAD>,
 <HTTPMethod.OPTIONS>,
 <HTTPMethod.PATCH>,
 <HTTPMethod.POST>,
 <HTTPMethod.PUT>,
 <HTTPMethod.TRACE>]

HTTP 方法

http.HTTPMethod 當中，已支援並且有於 IANA 註冊的狀態碼 [https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml]有：

方法

列舉名稱

詳情

GET

GET

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.1

HEAD

HEAD

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.2

POST

POST

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.3

PUT

PUT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.4

DELETE

DELETE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.5

CONNECT

CONNECT

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.6

OPTIONS

OPTIONS

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.7

TRACE

TRACE

HTTP Semantics RFC 9110 [https://datatracker.ietf.org/doc/html/rfc9110.html], Section 9.3.8

PATCH

PATCH

HTTP/1.1 RFC 5789 [https://datatracker.ietf.org/doc/html/rfc5789.html]

http.client --- HTTP 協定用戶端

原始碼：Lib/http/client.py [https://github.com/python/cpython/tree/3.14/Lib/http/client.py]

This module defines classes that implement the client side of the HTTP and HTTPS protocols. It is normally not used directly --- the module urllib.request uses it to handle URLs that use HTTP and HTTPS.

也參考

The Requests package [https://requests.readthedocs.io/en/latest/] is recommended for a higher-level HTTP client interface.

備註

HTTPS support is only available if Python was compiled with SSL support (through the ssl module).

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

The module provides the following classes:

class http.client.HTTPConnection(host, port=None, [timeout, ]source_address=None, blocksize=8192)

An HTTPConnection instance represents one transaction with an HTTP server. It should be instantiated by passing it a host and optional port number. If no port number is passed, the port is extracted from the host string if it has the form host:port, else the default HTTP port (80) is used. If the optional timeout parameter is given, blocking operations (like connection attempts) will timeout after that many seconds (if it is not given, the global default timeout setting is used). The optional source_address parameter may be a tuple of a (host, port) to use as the source address the HTTP connection is made from. The optional blocksize parameter sets the buffer size in bytes for sending a file-like message body.

For example, the following calls all create instances that connect to the server at the same host and port:

>>> h1 = http.client.HTTPConnection('www.python.org')
>>> h2 = http.client.HTTPConnection('www.python.org:80')
>>> h3 = http.client.HTTPConnection('www.python.org', 80)
>>> h4 = http.client.HTTPConnection('www.python.org', 80, timeout=10)

在 3.2 版的變更: 新增 source_address。

在 3.4 版的變更: The strict parameter was removed. HTTP 0.9-style "Simple Responses" are no longer supported.

在 3.7 版的變更: 新增 blocksize 參數。

class http.client.HTTPSConnection(host, port=None, *, [timeout, ]source_address=None, context=None, blocksize=8192)

A subclass of HTTPConnection that uses SSL for communication with secure servers. Default port is 443. If context is specified, it must be a ssl.SSLContext instance describing the various SSL options.

Please read Security considerations for more information on best practices.

在 3.2 版的變更: 新增 source_address、context 與 check_hostname。

在 3.2 版的變更: This class now supports HTTPS virtual hosts if possible (that is, if ssl.HAS_SNI is true).

在 3.4 版的變更: The strict parameter was removed. HTTP 0.9-style "Simple Responses" are no longer supported.

在 3.4.3 版的變更: This class now performs all the necessary certificate and hostname checks by default. To revert to the previous, unverified, behavior ssl._create_unverified_context() can be passed to the context parameter.

在 3.8 版的變更: This class now enables TLS 1.3 ssl.SSLContext.post_handshake_auth for the default context or when cert_file is passed with a custom context.

在 3.10 版的變更: This class now sends an ALPN extension with protocol indicator http/1.1 when no context is given. Custom context should set ALPN protocols with set_alpn_protocols().

在 3.12 版的變更: The deprecated key_file, cert_file and check_hostname parameters have been removed.

class http.client.HTTPResponse(sock, debuglevel=0, method=None, url=None)

Class whose instances are returned upon successful connection. Not instantiated directly by user.

在 3.4 版的變更: The strict parameter was removed. HTTP 0.9 style "Simple Responses" are no longer supported.

This module provides the following function:

http.client.parse_headers(fp)

Parse the headers from a file pointer fp representing a HTTP request/response. The file has to be a BufferedIOBase reader (i.e. not text) and must provide a valid RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] style header.

This function returns an instance of http.client.HTTPMessage that holds the header fields, but no payload (the same as HTTPResponse.msg and http.server.BaseHTTPRequestHandler.headers). After returning, the file pointer fp is ready to read the HTTP body.

備註

parse_headers() does not parse the start-line of a HTTP message; it only parses the Name: value lines. The file has to be ready to read these field lines, so the first line should already be consumed before calling the function.

The following exceptions are raised as appropriate:

exception http.client.HTTPException

The base class of the other exceptions in this module. It is a subclass of Exception.

exception http.client.NotConnected

HTTPException 的子類別。

exception http.client.InvalidURL

A subclass of HTTPException, raised if a port is given and is either non-numeric or empty.

exception http.client.UnknownProtocol

HTTPException 的子類別。

exception http.client.UnknownTransferEncoding

HTTPException 的子類別。

exception http.client.UnimplementedFileMode

HTTPException 的子類別。

exception http.client.IncompleteRead

HTTPException 的子類別。

exception http.client.ImproperConnectionState

HTTPException 的子類別。

exception http.client.CannotSendRequest

A subclass of ImproperConnectionState.

exception http.client.CannotSendHeader

A subclass of ImproperConnectionState.

exception http.client.ResponseNotReady

A subclass of ImproperConnectionState.

exception http.client.BadStatusLine

A subclass of HTTPException. Raised if a server responds with a HTTP status code that we don't understand.

exception http.client.LineTooLong

A subclass of HTTPException. Raised if an excessively long line is received in the HTTP protocol from the server.

exception http.client.RemoteDisconnected

A subclass of ConnectionResetError and BadStatusLine. Raised by HTTPConnection.getresponse() when the attempt to read the response results in no data read from the connection, indicating that the remote end has closed the connection.

在 3.5 版被加入: Previously, BadStatusLine('') was raised.

The constants defined in this module are:

http.client.HTTP_PORT

The default port for the HTTP protocol (always 80).

http.client.HTTPS_PORT

The default port for the HTTPS protocol (always 443).

http.client.responses

This dictionary maps the HTTP 1.1 status codes to the W3C names.

Example: http.client.responses[http.client.NOT_FOUND] is 'Not Found'.

See HTTP 狀態碼 for a list of HTTP status codes that are available in this module as constants.

HTTPConnection 物件

HTTPConnection instances have the following methods:

HTTPConnection.request(method, url, body=None, headers={}, *, encode_chunked=False)

This will send a request to the server using the HTTP request method method and the request URI url. The provided url must be an absolute path to conform with RFC 2616 §5.1.2 [https://datatracker.ietf.org/doc/html/rfc2616.html#section-5.1.2] (unless connecting to an HTTP proxy server or using the OPTIONS or CONNECT methods).

If body is specified, the specified data is sent after the headers are finished. It may be a str, a bytes-like object, an open file object, or an iterable of bytes. If body is a string, it is encoded as ISO-8859-1, the default for HTTP. If it is a bytes-like object, the bytes are sent as is. If it is a file object, the contents of the file is sent; this file object should support at least the read() method. If the file object is an instance of io.TextIOBase, the data returned by the read() method will be encoded as ISO-8859-1, otherwise the data returned by read() is sent as is. If body is an iterable, the elements of the iterable are sent as is until the iterable is exhausted.

The headers argument should be a mapping of extra HTTP headers to send with the request. A Host header [https://datatracker.ietf.org/doc/html/rfc2616.html#section-14.23] must be provided to conform with RFC 2616 §5.1.2 [https://datatracker.ietf.org/doc/html/rfc2616.html#section-5.1.2] (unless connecting to an HTTP proxy server or using the OPTIONS or CONNECT methods).

If headers contains neither Content-Length nor Transfer-Encoding, but there is a request body, one of those header fields will be added automatically. If body is None, the Content-Length header is set to 0 for methods that expect a body (PUT, POST, and PATCH). If body is a string or a bytes-like object that is not also a file, the Content-Length header is set to its length. Any other type of body (files and iterables in general) will be chunk-encoded, and the Transfer-Encoding header will automatically be set instead of Content-Length.

The encode_chunked argument is only relevant if Transfer-Encoding is specified in headers. If encode_chunked is False, the HTTPConnection object assumes that all encoding is handled by the calling code. If it is True, the body will be chunk-encoded.

For example, to perform a GET request to https://docs.python.org/3/:

>>> import http.client
>>> host = "docs.python.org"
>>> conn = http.client.HTTPSConnection(host)
>>> conn.request("GET", "/3/", headers={"Host": host})
>>> response = conn.getresponse()
>>> print(response.status, response.reason)
200 OK

備註

Chunked transfer encoding has been added to the HTTP protocol version 1.1. Unless the HTTP server is known to handle HTTP 1.1, the caller must either specify the Content-Length, or must pass a str or bytes-like object that is not also a file as the body representation.

備註

Note that you must have read the whole response or call close() if getresponse() raised an non-ConnectionError exception before you can send a new request to the server.

在 3.2 版的變更: body can now be an iterable.

在 3.6 版的變更: If neither Content-Length nor Transfer-Encoding are set in headers, file and iterable body objects are now chunk-encoded. The encode_chunked argument was added. No attempt is made to determine the Content-Length for file objects.

HTTPConnection.getresponse()

Should be called after a request is sent to get the response from the server. Returns an HTTPResponse instance.

在 3.5 版的變更: If a ConnectionError or subclass is raised, the HTTPConnection object will be ready to reconnect when a new request is sent.

Note that this does not apply to OSErrors raised by the underlying socket. Instead the caller is responsible to call close() on the existing connection.

HTTPConnection.set_debuglevel(level)

Set the debugging level. The default debug level is 0, meaning no debugging output is printed. Any value greater than 0 will cause all currently defined debug output to be printed to stdout. The debuglevel is passed to any new HTTPResponse objects that are created.

在 3.1 版被加入.

HTTPConnection.set_tunnel(host, port=None, headers=None)

Set the host and the port for HTTP Connect Tunnelling. This allows running the connection through a proxy server.

The host and port arguments specify the endpoint of the tunneled connection (i.e. the address included in the CONNECT request, not the address of the proxy server).

The headers argument should be a mapping of extra HTTP headers to send with the CONNECT request.

As HTTP/1.1 is used for HTTP CONNECT tunnelling request, as per the RFC [https://datatracker.ietf.org/doc/html/rfc7231#section-4.3.6], a HTTP Host: header must be provided, matching the authority-form of the request target provided as the destination for the CONNECT request. If a HTTP Host: header is not provided via the headers argument, one is generated and transmitted automatically.

For example, to tunnel through a HTTPS proxy server running locally on port 8080, we would pass the address of the proxy to the HTTPSConnection constructor, and the address of the host that we eventually want to reach to the set_tunnel() method:

>>> import http.client
>>> conn = http.client.HTTPSConnection("localhost", 8080)
>>> conn.set_tunnel("www.python.org")
>>> conn.request("HEAD","/index.html")

在 3.2 版被加入.

在 3.12 版的變更: HTTP CONNECT tunnelling requests use protocol HTTP/1.1, upgraded from protocol HTTP/1.0. Host: HTTP headers are mandatory for HTTP/1.1, so one will be automatically generated and transmitted if not provided in the headers argument.

HTTPConnection.get_proxy_response_headers()

Returns a dictionary with the headers of the response received from the proxy server to the CONNECT request.

If the CONNECT request was not sent, the method returns None.

在 3.12 版被加入.

HTTPConnection.connect()

Connect to the server specified when the object was created. By default, this is called automatically when making a request if the client does not already have a connection.

引發一個附帶引數 self、host、port 的稽核事件 http.client.connect。

HTTPConnection.close()

Close the connection to the server.

HTTPConnection.blocksize

Buffer size in bytes for sending a file-like message body.

在 3.7 版被加入.

As an alternative to using the request() method described above, you can also send your request step by step, by using the four functions below.

HTTPConnection.putrequest(method, url, skip_host=False, skip_accept_encoding=False)

This should be the first call after the connection to the server has been made. It sends a line to the server consisting of the method string, the url string, and the HTTP version (HTTP/1.1). To disable automatic sending of Host: or Accept-Encoding: headers (for example to accept additional content encodings), specify skip_host or skip_accept_encoding with non-False values.

HTTPConnection.putheader(header, argument[, ...])

Send an RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html]-style header to the server. It sends a line to the server consisting of the header, a colon and a space, and the first argument. If more arguments are given, continuation lines are sent, each consisting of a tab and an argument.

HTTPConnection.endheaders(message_body=None, *, encode_chunked=False)

Send a blank line to the server, signalling the end of the headers. The optional message_body argument can be used to pass a message body associated with the request.

If encode_chunked is True, the result of each iteration of message_body will be chunk-encoded as specified in RFC 7230 [https://datatracker.ietf.org/doc/html/rfc7230.html], Section 3.3.1. How the data is encoded is dependent on the type of message_body. If message_body implements the buffer interface the encoding will result in a single chunk. If message_body is a collections.abc.Iterable, each iteration of message_body will result in a chunk. If message_body is a file object, each call to .read() will result in a chunk. The method automatically signals the end of the chunk-encoded data immediately after message_body.

備註

Due to the chunked encoding specification, empty chunks yielded by an iterator body will be ignored by the chunk-encoder. This is to avoid premature termination of the read of the request by the target server due to malformed encoding.

在 3.6 版的變更: Added chunked encoding support and the encode_chunked parameter.

HTTPConnection.send(data)

Send data to the server. This should be used directly only after the endheaders() method has been called and before getresponse() is called.

引發一個附帶引數 self、data 的稽核事件 http.client.send。

HTTPResponse 物件

An HTTPResponse instance wraps the HTTP response from the server. It provides access to the request headers and the entity body. The response is an iterable object and can be used in a with statement.

在 3.5 版的變更: The io.BufferedIOBase interface is now implemented and all of its reader operations are supported.

HTTPResponse.read([amt])

Reads and returns the response body, or up to the next amt bytes.

HTTPResponse.readinto(b)

Reads up to the next len(b) bytes of the response body into the buffer b. Returns the number of bytes read.

在 3.3 版被加入.

HTTPResponse.getheader(name, default=None)

Return the value of the header name, or default if there is no header matching name. If there is more than one header with the name name, return all of the values joined by ', '. If default is any iterable other than a single string, its elements are similarly returned joined by commas.

HTTPResponse.getheaders()

Return a list of (header, value) tuples.

HTTPResponse.fileno()

Return the fileno of the underlying socket.

HTTPResponse.msg

A http.client.HTTPMessage instance containing the response headers. http.client.HTTPMessage is a subclass of email.message.Message.

HTTPResponse.version

HTTP protocol version used by server. 10 for HTTP/1.0, 11 for HTTP/1.1.

HTTPResponse.url

URL of the resource retrieved, commonly used to determine if a redirect was followed.

HTTPResponse.headers

Headers of the response in the form of an email.message.EmailMessage instance.

HTTPResponse.status

Status code returned by server.

HTTPResponse.reason

Reason phrase returned by server.

HTTPResponse.debuglevel

A debugging hook. If debuglevel is greater than zero, messages will be printed to stdout as the response is read and parsed.

HTTPResponse.closed

Is True if the stream is closed.

HTTPResponse.geturl()

在 3.9 版之後被棄用: Deprecated in favor of url.

HTTPResponse.info()

在 3.9 版之後被棄用: Deprecated in favor of headers.

HTTPResponse.getcode()

在 3.9 版之後被棄用: Deprecated in favor of status.

範例

Here is an example session that uses the GET method:

>>> import http.client
>>> conn = http.client.HTTPSConnection("www.python.org")
>>> conn.request("GET", "/")
>>> r1 = conn.getresponse()
>>> print(r1.status, r1.reason)
200 OK
>>> data1 = r1.read()  # This will return entire content.
>>> # The following example demonstrates reading data in chunks.
>>> conn.request("GET", "/")
>>> r1 = conn.getresponse()
>>> while chunk := r1.read(200):
...     print(repr(chunk))
b'<!doctype html>\n<!--[if"...
...
>>> # Example of an invalid request
>>> conn = http.client.HTTPSConnection("docs.python.org")
>>> conn.request("GET", "/parrot.spam")
>>> r2 = conn.getresponse()
>>> print(r2.status, r2.reason)
404 Not Found
>>> data2 = r2.read()
>>> conn.close()

Here is an example session that uses the HEAD method. Note that the HEAD method never returns any data.

>>> import http.client
>>> conn = http.client.HTTPSConnection("www.python.org")
>>> conn.request("HEAD", "/")
>>> res = conn.getresponse()
>>> print(res.status, res.reason)
200 OK
>>> data = res.read()
>>> print(len(data))
0
>>> data == b''
True

Here is an example session that uses the POST method:

>>> import http.client, urllib.parse
>>> params = urllib.parse.urlencode({'@number': 12524, '@type': 'issue', '@action': 'show'})
>>> headers = {"Content-type": "application/x-www-form-urlencoded",
...            "Accept": "text/plain"}
>>> conn = http.client.HTTPConnection("bugs.python.org")
>>> conn.request("POST", "", params, headers)
>>> response = conn.getresponse()
>>> print(response.status, response.reason)
302 Found
>>> data = response.read()
>>> data
b'Redirecting to <a href="https://bugs.python.org/issue12524">https://bugs.python.org/issue12524</a>'
>>> conn.close()

Client side HTTP PUT requests are very similar to POST requests. The difference lies only on the server side where HTTP servers will allow resources to be created via PUT requests. It should be noted that custom HTTP methods are also handled in urllib.request.Request by setting the appropriate method attribute. Here is an example session that uses the PUT method:

>>> # This creates an HTTP request
>>> # with the content of BODY as the enclosed representation
>>> # for the resource http://localhost:8080/file
...
>>> import http.client
>>> BODY = "***filecontents***"
>>> conn = http.client.HTTPConnection("localhost", 8080)
>>> conn.request("PUT", "/file", BODY)
>>> response = conn.getresponse()
>>> print(response.status, response.reason)
200, OK

HTTPMessage 物件

class http.client.HTTPMessage(email.message.Message)

An http.client.HTTPMessage instance holds the headers from an HTTP response. It is implemented using the email.message.Message class.

ftplib --- FTP 協定用戶端

原始碼：Lib/ftplib.py [https://github.com/python/cpython/tree/3.14/Lib/ftplib.py]

這個模組定義了 FTP 類別和一些相關的項目。FTP 類別實作了 FTP 協定的用戶端。你可以使用它來編寫能夠執行各種 FTP 自動作業的 Python 程式，例如鏡像 (mirror) 其他 FTP 伺服器。urllib.request 模組也使用它來處理使用 FTP 的 URL。有關 FTP（檔案傳輸協定）的更多資訊，請參閱 RFC 959 [https://datatracker.ietf.org/doc/html/rfc959.html]。

預設編碼是 UTF-8，遵循 RFC 2640 [https://datatracker.ietf.org/doc/html/rfc2640.html]。

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

這是一個使用 ftplib 模組的會話範例：

>>> from ftplib import FTP
>>> ftp = FTP('ftp.us.debian.org')  # connect to host, default port
>>> ftp.login()                     # user anonymous, passwd anonymous@
'230 Login successful.'
>>> ftp.cwd('debian')               # change into "debian" directory
'250 Directory successfully changed.'
>>> ftp.retrlines('LIST')           # list directory contents
-rw-rw-r--    1 1176     1176         1063 Jun 15 10:18 README
...
drwxr-sr-x    5 1176     1176         4096 Dec 19  2000 pool
drwxr-sr-x    4 1176     1176         4096 Nov 17  2008 project
drwxr-xr-x    3 1176     1176         4096 Oct 10  2012 tools
'226 Directory send OK.'
>>> with open('README', 'wb') as fp:
>>>     ftp.retrbinary('RETR README', fp.write)
'226 Transfer complete.'
>>> ftp.quit()
'221 Goodbye.'

參考

FTP 物件

class ftplib.FTP(host='', user='', passwd='', acct='', timeout=None, source_address=None, *, encoding='utf-8')

回傳一個新的 FTP 類別實例。

參數:

host (str) -- 要連接的主機名稱。如果有給定，connect(host) 會由建構函式來隱式地呼叫。

user (str) -- The username to log in with (default: 'anonymous'). 如果有給定，login(host, passwd, acct) 會由建構函式來隱式地呼叫。

passwd (str) -- The password to use when logging in. If not given, and if passwd is the empty string or "-", a password will be automatically generated.

acct (str) -- Account information to be used for the ACCT FTP command. Few systems implement this. See RFC-959 [https://datatracker.ietf.org/doc/html/rfc959.html] for more details.

timeout (float | None) -- 如 connect() 的阻塞操作的超時設定，以秒為單位（預設：使用全域預設超時設定）。

source_address (tuple | None) -- A 2-tuple (host, port) for the socket to bind to as its source address before connecting.

encoding (str) -- The encoding for directories and filenames (default: 'utf-8').

FTP 類別支援 with 陳述式，例如：

>>> from ftplib import FTP
>>> with FTP("ftp1.at.proftpd.org") as ftp:
...     ftp.login()
...     ftp.dir()
...
'230 Anonymous login ok, restrictions apply.'
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 .
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 ..
dr-xr-xr-x   5 ftp      ftp          4096 May  6 10:43 CentOS
dr-xr-xr-x   3 ftp      ftp            18 Jul 10  2008 Fedora
>>>

在 3.2 版的變更: 新增了對 with 陳述式的支援。

在 3.3 版的變更: 新增 source_address 參數。

在 3.9 版的變更: 如果 timeout 參數設定為零，它將引發 ValueError 以防止建立非阻塞 socket。新增了 encoding 參數，預設值從 Latin-1 更改為 UTF-8 以遵循 RFC 2640 [https://datatracker.ietf.org/doc/html/rfc2640.html]。

FTP 的多個可用方法大致有分為兩個方向：一種用於處理文本檔案 (text files)，另一種用於二進位檔案 (binary files)。這些以在文本檔案的 lines 或二進位檔案的 binary 前使用的命令命名。

FTP 實例具有以下方法：

set_debuglevel(level)

將實例的偵錯級別設定為一個 int，這控制印出的偵錯訊息輸出量。

0（預設值）：不產生偵錯輸出。

1：會產生適量的偵錯輸出，通常是每個請求輸出一行。

2 或更高的值：會產生最大量的偵錯輸出，以日誌紀錄下控制連線發送和接收的每個步驟。

connect(host='', port=0, timeout=None, source_address=None)

連線到給定的主機 (host) 和連接埠 (port)。每個實例只應呼叫此函式一次；如果在建立 FTP 實例時有給定 host 引數，則不應呼叫它。所有其他的 FTP 方法只能在成功建立連線後使用。

參數:

host (str) -- 要連接的主機。

port (int) -- 要連接的 TCP 連接埠（預設值：21，由 FTP 協定規範指定）。很少需要指定不同的連接埠號碼。

timeout (float | None) -- 連線嘗試的超時設定，以秒為單位（預設：全域預設超時設定）。

source_address (tuple | None) -- A 2-tuple (host, port) for the socket to bind to as its source address before connecting.

引發一個附帶引數 self、host、port 的稽核事件 ftplib.connect。

在 3.3 版的變更: 新增 source_address 參數。

getwelcome()

回傳伺服器為回應初始連線而發送的歡迎訊息。（此訊息有時會包含與使用者相關的免責聲明或幫助資訊。）

login(user='anonymous', passwd='', acct='')

在以連線的伺服器上登入。在建立連線後，每個實例只應呼叫此函式一次；如果在建立 FTP 實例時有給定 host 和 user 引數，則不應呼叫它。大多數 FTP 命令僅在用戶端登錄後才允許使用

參數:

user (str) -- The username to log in with (default: 'anonymous').

passwd (str) -- The password to use when logging in. If not given, and if passwd is the empty string or "-", a password will be automatically generated.

acct (str) -- Account information to be used for the ACCT FTP command. Few systems implement this. See RFC-959 [https://datatracker.ietf.org/doc/html/rfc959.html] for more details.

abort()

中止正在進行的檔案傳輸。使用它並不是都會成功，但值得一試。

sendcmd(cmd)

向伺服器發送一個簡單的命令字串並回傳回應字串。

引發一個附帶引數 self、cmd 的稽核事件 ftplib.sendcmd。

voidcmd(cmd)

向伺服器發送一個簡單的命令字串並處理回應。如果收到代表成功的回應狀態碼（範圍為 200--299 的狀態碼），則回傳回應字串，否則引發 error_reply。

引發一個附帶引數 self、cmd 的稽核事件 ftplib.sendcmd。

retrbinary(cmd, callback, blocksize=8192, rest=None)

以二進位傳輸模式 (binary transfer mode) 取得檔案。

參數:

cmd (str) -- 一個正確的 RETR 指令："RETR filename"。

callback (callable) -- 為接收到的每個資料區塊呼叫的單一參數可呼叫物件，其單一引數是以 bytes 為形式的資料。

blocksize (int) -- 在執行實際傳輸時所建立的低階 socket 物件上讀取的最大分塊 (chunk) 大小。這也對應於將傳遞給 callback 的最大資料大小。預設為 8192。

rest (int) -- 一個要發送到伺服器的 REST 命令。參見 transfercmd() 方法之 rest 參數的文件。

retrlines(cmd, callback=None)

在初始化時以 encoding 參數指定的編碼來取得檔案或目錄列表。 cmd 要是一個正確的 RETR 命令（見 retrbinary()）或者一個像 LIST 或 NLST 的命令（通常只是字串 'LIST' )。 LIST 會取得檔案列表和這些檔案的相關資訊。 NLST 取得檔案名稱列表。會為每一行以一個字串引數呼叫 callback 函式，其引數包含已經刪除尾隨 CRLF 的一行。預設的 callback 會將各行印出到 sys.stdout。

set_pasv(val)

如果 val 為真，則啟用「被動」模式，否則禁用被動模式。被動模式預設開啟。

storbinary(cmd, fp, blocksize=8192, callback=None, rest=None)

以二進位傳輸模式儲存檔案。

參數:

cmd (str) -- 一個正確的 STOR 指令："STOR filename"。

fp (file object) -- 一個檔案物件（以二進位模式開啟），在大小為 blocksize 的區塊中使用其 read() 方法讀取直到 EOF 來提供要儲存的資料。

blocksize (int) -- 讀取區塊大小。預設為 8192。

callback (callable) -- 為發送的每個資料區塊來呼叫的單一參數可呼叫物件，其單一引數是以 bytes 為形式的資料。

rest (int) -- 一個要發送到伺服器的 REST 命令。參見 transfercmd() 方法之 rest 參數的文件。

在 3.2 版的變更: 新增 rest 參數。

storlines(cmd, fp, callback=None)

以行模式 (line mode) 儲存檔案。 cmd 應是一個正確的 STOR 命令（參見 storbinary()）。使用其 readline() 方法從檔案物件 fp （以二進位模式打開）讀取各行、直到 EOF，以提供要儲存的資料。 callback 是可選的單參數可呼叫物件，於發送後以各行進行呼叫。

transfercmd(cmd, rest=None)

透過資料連線啟動傳輸。如果傳輸為主動 (active) 模式，則發送 EPRT 或 PORT 命令和 cmd 指定的傳輸命令，並接受連線。如果伺服器是被動 (passive) 模式，則發送 EPSV 或 PASV 命令、連線、並啟動傳輸命令。無論哪種方式，都是回傳連線的 socket。

如果有給定可選的 rest，一個 REST 命令會被發送到伺服器，並以 rest 作為引數。rest 通常是請求檔案的一個位元組偏移量 (byte offset)，告訴伺服器以請求的偏移量重新開始發送檔案的位元組，並跳過初始位元組。但是請注意，transfercmd() 方法將 rest 轉換為帶有初始化時指定的 encoding 參數的字串，但不會對字串的內容執行檢查。如果伺服器無法識別 REST 命令，則會引發 error_reply 例外。如果發生這種情況，只需在沒有 rest 引數的情況下呼叫 transfercmd()。

ntransfercmd(cmd, rest=None)

類似於 transfercmd()，但回傳一個帶有資料連線和資料預期大小的元組。如果無法計算預期大小，則回傳 None。 cmd 和 rest 與 transfercmd() 中的含義相同。

mlsd(path='', facts=[])

使用 MLSD 命令 (RFC 3659 [https://datatracker.ietf.org/doc/html/rfc3659.html]) 列出標準格式的目錄。如果省略 path 則假定為作用於目前目錄。facts 是表示所需資訊類型的字串列表（例如 ["type", "size", "perm"] ）。會回傳一個產生器物件，為每個在路徑中找到的檔案生成一個包含兩個元素的元組，第一個元素是檔案名稱，第二個元素是包含有關檔案名稱 facts的字典。該字典的內容可能受 facts 引數限制，但不保證伺服器會回傳所有請求的 facts。

在 3.3 版被加入.

nlst(argument[, ...])

回傳由 NLST 命令回傳的檔案名稱列表。可選的 argument 是要列出的目錄（預設為目前伺服器目錄）。多個引數可用於將非標準選項傳遞給 NLST 命令。

備註

如果你的伺服器支援該命令，mlsd() 會提供更好的 API。

dir(argument[, ...])

生成由 LIST 命令回傳的目錄列表，並將其印出到標準輸出 (standard output)。可選的 argument 是要列出的目錄（預設為目前伺服器目錄）。有多個引數可用於將非標準選項傳遞給 LIST 命令。如果最後一個引數是一個函式，它被用作 retrlines() 的 callback 函式；預設印出到 sys.stdout。此方法回傳 None。

備註

如果你的伺服器支援該命令，mlsd() 會提供更好的 API。

rename(fromname, toname)

將伺服器上的檔案 fromname 重新命名為 toname。

delete(filename)

從伺服器中刪除名為 filename 的檔案。如果成功，回傳回應的文字，否則引發 error_perm 權限錯誤或在其他錯誤發生時引發 error_reply。

cwd(pathname)

設定伺服器上的目前目錄。

mkd(pathname)

在伺服器上建立一個新目錄。

pwd()

回傳伺服器上目前目錄的路徑名。

rmd(dirname)

刪除伺服器上名為 dirname 的目錄。

size(filename)

請求伺服器上名為 filename 的檔案的大小。成功時，檔案的大小作為整數回傳，否則回傳 None。請注意，SIZE 命令不是標準化的，但被許多常見的伺服器實作支援。

quit()

向伺服器發送 QUIT 命令並關閉連線。這是關閉連線的「禮貌」方式，但如果伺服器對 QUIT 命令作出錯誤回應，它可能會引發例外。這意味著呼叫 close() 方法使 FTP 實例無法用於後續呼叫（見下文）。

close()

單方面關閉連線。這不應該使用於已經關閉的連線，例如在成功呼叫 quit() 之後。呼叫後就不應該再次使用 FTP 實例（在呼叫 close() 或 quit() 後，你不能透過發出另一個 login() 方法重新打開連線）。

FTP_TLS 物件

class ftplib.FTP_TLS(host='', user='', passwd='', acct='', *, context=None, timeout=None, source_address=None, encoding='utf-8')

An FTP subclass which adds TLS support to FTP as described in RFC 4217 [https://datatracker.ietf.org/doc/html/rfc4217.html]. Connect to port 21 implicitly securing the FTP control connection before authenticating.

備註

The user must explicitly secure the data connection by calling the prot_p() method.

參數:

host (str) -- 要連接的主機名稱。如果有給定，connect(host) 會由建構函式來隱式地呼叫。

user (str) -- The username to log in with (default: 'anonymous'). 如果有給定，login(host, passwd, acct) 會由建構函式來隱式地呼叫。

passwd (str) -- The password to use when logging in. If not given, and if passwd is the empty string or "-", a password will be automatically generated.

acct (str) -- Account information to be used for the ACCT FTP command. Few systems implement this. See RFC-959 [https://datatracker.ietf.org/doc/html/rfc959.html] for more details.

context (ssl.SSLContext) -- An SSL context object which allows bundling SSL configuration options, certificates and private keys into a single, potentially long-lived, structure. Please read Security considerations for best practices.

timeout (float | None) -- 如 connect() 的阻塞操作的超時設定，以秒為單位（預設：使用全域預設超時設定）。

source_address (tuple | None) -- A 2-tuple (host, port) for the socket to bind to as its source address before connecting.

encoding (str) -- The encoding for directories and filenames (default: 'utf-8').

在 3.2 版被加入.

在 3.3 版的變更: 新增 source_address 參數。

在 3.4 版的變更: 該類別現在支援使用 ssl.SSLContext.check_hostname 和 Server Name Indication 進行主機名 (hostname) 檢查（參見 ssl.HAS_SNI）。

在 3.9 版的變更: 如果 timeout 參數設定為零，它將引發 ValueError 以防止建立非阻塞 socket。新增了 encoding 參數，預設值從 Latin-1 更改為 UTF-8 以遵循 RFC 2640 [https://datatracker.ietf.org/doc/html/rfc2640.html]。

在 3.12 版的變更: 已棄用的 keyfile 和 certfile 參數已被移除。

這是一個使用 FTP_TLS 類別的範例會話：

>>> ftps = FTP_TLS('ftp.pureftpd.org')
>>> ftps.login()
'230 Anonymous user logged in'
>>> ftps.prot_p()
'200 Data protection level set to "private"'
>>> ftps.nlst()
['6jack', 'OpenBSD', 'antilink', 'blogbench', 'bsdcam', 'clockspeed', 'djbdns-jedi', 'docs', 'eaccelerator-jedi', 'favicon.ico', 'francotone', 'fugu', 'ignore', 'libpuzzle', 'metalog', 'minidentd', 'misc', 'mysql-udf-global-user-variables', 'php-jenkins-hash', 'php-skein-hash', 'php-webdav', 'phpaudit', 'phpbench', 'pincaster', 'ping', 'posto', 'pub', 'public', 'public_keys', 'pure-ftpd', 'qscan', 'qtc', 'sharedance', 'skycache', 'sound', 'tmp', 'ucarp']

FTP_TLS 類別繼承自 FTP，並另外定義了這些的方法與屬性：

ssl_version

要使用的 SSL 版本（預設為 ssl.PROTOCOL_SSLv23）。

auth()

根據 ssl_version 屬性中指定的內容，使用 TLS 或 SSL 設定安全控制連線。

在 3.4 版的變更: 該方法現在支援使用 ssl.SSLContext.check_hostname 和 Server Name Indication 進行主機名檢查（參見 ssl.HAS_SNI）。

ccc()

將控制通道恢復為純文本。這對於利用知道如何在不打開固定連接埠的情況下使用非安全 (non-secure) FTP 以處理 NAT 的防火牆很有用。

在 3.3 版被加入.

prot_p()

設定安全資料連線。

prot_c()

設定明文資料 (clear text data) 連線。

模組變數

exception ftplib.error_reply

伺服器收到意外回覆時所引發的例外。

exception ftplib.error_temp

當收到表示暫時錯誤的錯誤碼（400--499 範圍內的回應狀態碼）時引發的例外。

exception ftplib.error_perm

當收到表示永久錯誤的錯誤碼（500--599 範圍內的回應狀態碼）時引發的例外。

exception ftplib.error_proto

當從伺服器收到不符合檔案傳輸協定回應規範的回覆時引發例外，即 1--5 範圍內的數字開頭。

ftplib.all_errors

FTP 實例方法由於 FTP 連線問題（相對於呼叫者的程式錯誤）而可能引發的所有例外集合（元組形式）。該集合包括上面列出的四個例外以及 OSError 和 EOFError。

也參考

netrc 模組

.netrc 檔案格式的剖析器。.netrc 檔案通常被 FTP 用戶端用來在提示使用者之前載入使用者身份驗證資訊。

poplib --- POP3 協定用戶端

原始碼：Lib/poplib.py [https://github.com/python/cpython/tree/3.14/Lib/poplib.py]

This module defines a class, POP3, which encapsulates a connection to a POP3 server and implements the protocol as defined in RFC 1939 [https://datatracker.ietf.org/doc/html/rfc1939.html]. The POP3 class supports both the minimal and optional command sets from RFC 1939 [https://datatracker.ietf.org/doc/html/rfc1939.html]. The POP3 class also supports the STLS command introduced in RFC 2595 [https://datatracker.ietf.org/doc/html/rfc2595.html] to enable encrypted communication on an already established connection.

Additionally, this module provides a class POP3_SSL, which provides support for connecting to POP3 servers that use SSL as an underlying protocol layer.

Note that POP3, though widely supported, is obsolescent. The implementation quality of POP3 servers varies widely, and too many are quite poor. If your mailserver supports IMAP, you would be better off using the imaplib.IMAP4 class, as IMAP servers tend to be better implemented.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

The poplib module provides two classes:

class poplib.POP3(host, port=POP3_PORT[, timeout])

This class implements the actual POP3 protocol. The connection is created when the instance is initialized. If port is omitted, the standard POP3 port (110) is used. The optional timeout parameter specifies a timeout in seconds for the connection attempt (if not specified, the global default timeout setting will be used).

引發一個附帶引數 self、host、port 的稽核事件 poplib.connect。

引發一個附帶引數 self、line 的稽核事件 poplib.putline。其中 line 為即將傳送給遠端的位元組。

在 3.9 版的變更: If the timeout parameter is set to be zero, it will raise a ValueError to prevent the creation of a non-blocking socket.

class poplib.POP3_SSL(host, port=POP3_SSL_PORT, *, timeout=None, context=None)

This is a subclass of POP3 that connects to the server over an SSL encrypted socket. If port is not specified, 995, the standard POP3-over-SSL port is used. timeout works as in the POP3 constructor. context is an optional ssl.SSLContext object which allows bundling SSL configuration options, certificates and private keys into a single (potentially long-lived) structure. Please read Security considerations for best practices.

引發一個附帶引數 self、host、port 的稽核事件 poplib.connect。

引發一個附帶引數 self、line 的稽核事件 poplib.putline。其中 line 為即將傳送給遠端的位元組。

在 3.2 版的變更: 新增 context 參數。

在 3.4 版的變更: The class now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

在 3.9 版的變更: If the timeout parameter is set to be zero, it will raise a ValueError to prevent the creation of a non-blocking socket.

在 3.12 版的變更: The deprecated keyfile and certfile parameters have been removed.

One exception is defined as an attribute of the poplib module:

exception poplib.error_proto

Exception raised on any errors from this module (errors from socket module are not caught). The reason for the exception is passed to the constructor as a string.

也參考

imaplib 模組

The standard Python IMAP module.

關於 Fetchmail 的常見問題 [http://www.catb.org/~esr/fetchmail/fetchmail-FAQ.html]

The FAQ for the fetchmail POP/IMAP client collects information on POP3 server variations and RFC noncompliance that may be useful if you need to write an application based on the POP protocol.

POP3 物件

All POP3 commands are represented by methods of the same name, in lowercase; most return the response text sent by the server.

POP3 實例擁有以下方法：

POP3.set_debuglevel(level)

Set the instance's debugging level. This controls the amount of debugging output printed. The default, 0, produces no debugging output. A value of 1 produces a moderate amount of debugging output, generally a single line per request. A value of 2 or higher produces the maximum amount of debugging output, logging each line sent and received on the control connection.

POP3.getwelcome()

回傳 POP3 伺服器傳送的歡迎字串。

POP3.capa()

Query the server's capabilities as specified in RFC 2449 [https://datatracker.ietf.org/doc/html/rfc2449.html]. Returns a dictionary in the form {'name': ['param'...]}.

在 3.4 版被加入.

POP3.user(username)

Send user command, response should indicate that a password is required.

POP3.pass_(password)

Send password, response includes message count and mailbox size. Note: the mailbox on the server is locked until quit() is called.

POP3.apop(user, secret)

Use the more secure APOP authentication to log into the POP3 server.

POP3.rpop(user)

Use RPOP authentication (similar to UNIX r-commands) to log into POP3 server.

POP3.stat()

Get mailbox status. The result is a tuple of 2 integers: (message count, mailbox size).

POP3.list([which])

Request message list, result is in the form (response, ['mesg_num octets', ...], octets). If which is set, it is the message to list.

POP3.retr(which)

Retrieve whole message number which, and set its seen flag. Result is in form (response, ['line', ...], octets).

POP3.dele(which)

Flag message number which for deletion. On most servers deletions are not actually performed until QUIT (the major exception is Eudora QPOP, which deliberately violates the RFCs by doing pending deletes on any disconnect).

POP3.rset()

Remove any deletion marks for the mailbox.

POP3.noop()

Do nothing. Might be used as a keep-alive.

POP3.quit()

Signoff: commit changes, unlock mailbox, drop connection.

POP3.top(which, howmuch)

Retrieves the message header plus howmuch lines of the message after the header of message number which. Result is in form (response, ['line', ...], octets).

The POP3 TOP command this method uses, unlike the RETR command, doesn't set the message's seen flag; unfortunately, TOP is poorly specified in the RFCs and is frequently broken in off-brand servers. Test this method by hand against the POP3 servers you will use before trusting it.

POP3.uidl(which=None)

Return message digest (unique id) list. If which is specified, result contains the unique id for that message in the form 'response mesgnum uid, otherwise result is list (response, ['mesgnum uid', ...], octets).

POP3.utf8()

Try to switch to UTF-8 mode. Returns the server response if successful, raises error_proto if not. Specified in RFC 6856 [https://datatracker.ietf.org/doc/html/rfc6856.html].

在 3.5 版被加入.

POP3.stls(context=None)

Start a TLS session on the active connection as specified in RFC 2595 [https://datatracker.ietf.org/doc/html/rfc2595.html]. This is only allowed before user authentication

context parameter is a ssl.SSLContext object which allows bundling SSL configuration options, certificates and private keys into a single (potentially long-lived) structure. Please read Security considerations for best practices.

This method supports hostname checking via ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

在 3.4 版被加入.

Instances of POP3_SSL have no additional methods. The interface of this subclass is identical to its parent.

POP3 範例

Here is a minimal example (without error checking) that opens a mailbox and retrieves and prints all messages:

import getpass, poplib

M = poplib.POP3('localhost')
M.user(getpass.getuser())
M.pass_(getpass.getpass())
numMessages = len(M.list()[1])
for i in range(numMessages):
    for j in M.retr(i+1)[1]:
        print(j)

At the end of the module, there is a test section that contains a more extensive example of usage.

imaplib --- IMAP4 協定用戶端

原始碼：Lib/imaplib.py [https://github.com/python/cpython/tree/3.14/Lib/imaplib.py]

This module defines three classes, IMAP4, IMAP4_SSL and IMAP4_stream, which encapsulate a connection to an IMAP4 server and implement a large subset of the IMAP4rev1 client protocol as defined in RFC 2060 [https://datatracker.ietf.org/doc/html/rfc2060.html]. It is backward compatible with IMAP4 (RFC 1730 [https://datatracker.ietf.org/doc/html/rfc1730.html]) servers, but note that the STATUS command is not supported in IMAP4.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

Three classes are provided by the imaplib module, IMAP4 is the base class:

class imaplib.IMAP4(host='', port=IMAP4_PORT, timeout=None)

This class implements the actual IMAP4 protocol. The connection is created and protocol version (IMAP4 or IMAP4rev1) is determined when the instance is initialized. If host is not specified, '' (the local host) is used. If port is omitted, the standard IMAP4 port (143) is used. The optional timeout parameter specifies a timeout in seconds for the connection attempt. If timeout is not given or is None, the global default socket timeout is used.

The IMAP4 class supports the with statement. When used like this, the IMAP4 LOGOUT command is issued automatically when the with statement exits. E.g.:

>>> from imaplib import IMAP4
>>> with IMAP4("domain.org") as M:
...     M.noop()
...
('OK', [b'Nothing Accomplished. d25if65hy903weo.87'])

在 3.5 版的變更: 新增對 with 陳述式的支援。

在 3.9 版的變更: 新增 timeout 選用參數。

Three exceptions are defined as attributes of the IMAP4 class:

exception IMAP4.error

Exception raised on any errors. The reason for the exception is passed to the constructor as a string.

exception IMAP4.abort

IMAP4 server errors cause this exception to be raised. This is a sub-class of IMAP4.error. Note that closing the instance and instantiating a new one will usually allow recovery from this exception.

exception IMAP4.readonly

This exception is raised when a writable mailbox has its status changed by the server. This is a sub-class of IMAP4.error. Some other client now has write permission, and the mailbox will need to be re-opened to re-obtain write permission.

There's also a subclass for secure connections:

class imaplib.IMAP4_SSL(host='', port=IMAP4_SSL_PORT, *, ssl_context=None, timeout=None)

This is a subclass derived from IMAP4 that connects over an SSL encrypted socket (to use this class you need a socket module that was compiled with SSL support). If host is not specified, '' (the local host) is used. If port is omitted, the standard IMAP4-over-SSL port (993) is used. ssl_context is a ssl.SSLContext object which allows bundling SSL configuration options, certificates and private keys into a single (potentially long-lived) structure. Please read Security considerations for best practices.

The optional timeout parameter specifies a timeout in seconds for the connection attempt. If timeout is not given or is None, the global default socket timeout is used.

在 3.3 版的變更: 新增 ssl_context 參數。

在 3.4 版的變更: The class now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

在 3.9 版的變更: 新增 timeout 選用參數。

在 3.12 版的變更: The deprecated keyfile and certfile parameters have been removed.

The second subclass allows for connections created by a child process:

class imaplib.IMAP4_stream(command)

This is a subclass derived from IMAP4 that connects to the stdin/stdout file descriptors created by passing command to subprocess.Popen().

The following utility functions are defined:

imaplib.Internaldate2tuple(datestr)

Parse an IMAP4 INTERNALDATE string and return corresponding local time. The return value is a time.struct_time tuple or None if the string has wrong format.

imaplib.Int2AP(num)

Converts an integer into a bytes representation using characters from the set [A .. P].

imaplib.ParseFlags(flagstr)

Converts an IMAP4 FLAGS response to a tuple of individual flags.

imaplib.Time2Internaldate(date_time)

Convert date_time to an IMAP4 INTERNALDATE representation. The return value is a string in the form: "DD-Mmm-YYYY HH:MM:SS +HHMM" (including double-quotes). The date_time argument can be a number (int or float) representing seconds since epoch (as returned by time.time()), a 9-tuple representing local time an instance of time.struct_time (as returned by time.localtime()), an aware instance of datetime.datetime, or a double-quoted string. In the last case, it is assumed to already be in the correct format.

Note that IMAP4 message numbers change as the mailbox changes; in particular, after an EXPUNGE command performs deletions the remaining messages are renumbered. So it is highly advisable to use UIDs instead, with the UID command.

At the end of the module, there is a test section that contains a more extensive example of usage.

也參考

Documents describing the protocol, sources for servers implementing it, by the University of Washington's IMAP Information Center can all be found at (Source Code) https://github.com/uw-imap/imap (Not Maintained).

IMAP4 物件

All IMAP4rev1 commands are represented by methods of the same name, either uppercase or lowercase.

All arguments to commands are converted to strings, except for AUTHENTICATE, and the last argument to APPEND which is passed as an IMAP4 literal. If necessary (the string contains IMAP4 protocol-sensitive characters and isn't enclosed with either parentheses or double quotes) each string is quoted. However, the password argument to the LOGIN command is always quoted. If you want to avoid having an argument string quoted (eg: the flags argument to STORE) then enclose the string in parentheses (eg: r'(\Deleted)').

Most commands return a tuple: (type, [data, ...]) where type is usually 'OK' or 'NO', and data is either the text from the command response, or mandated results from the command. Each data is either a bytes, or a tuple. If a tuple, then the first part is the header of the response, and the second part contains the data (ie: 'literal' value).

The message_set options to commands below is a string specifying one or more messages to be acted upon. It may be a simple message number ('1'), a range of message numbers ('2:4'), or a group of non-contiguous ranges separated by commas ('1:3,6:9'). A range can contain an asterisk to indicate an infinite upper bound ('3:*').

IMAP4 實例擁有以下方法：

IMAP4.append(mailbox, flags, date_time, message)

Append message to named mailbox.

IMAP4.authenticate(mechanism, authobject)

Authenticate command --- requires response processing.

mechanism specifies which authentication mechanism is to be used - it should appear in the instance variable capabilities in the form AUTH=mechanism.

authobject must be a callable object:

data = authobject(response)

It will be called to process server continuation responses; the response argument it is passed will be bytes. It should return bytes data that will be base64 encoded and sent to the server. It should return None if the client abort response * should be sent instead.

在 3.5 版的變更: string usernames and passwords are now encoded to utf-8 instead of being limited to ASCII.

IMAP4.check()

Checkpoint mailbox on server.

IMAP4.close()

Close currently selected mailbox. Deleted messages are removed from writable mailbox. This is the recommended command before LOGOUT.

IMAP4.copy(message_set, new_mailbox)

Copy message_set messages onto end of new_mailbox.

IMAP4.create(mailbox)

Create new mailbox named mailbox.

IMAP4.delete(mailbox)

Delete old mailbox named mailbox.

IMAP4.deleteacl(mailbox, who)

Delete the ACLs (remove any rights) set for who on mailbox.

IMAP4.enable(capability)

Enable capability (see RFC 5161 [https://datatracker.ietf.org/doc/html/rfc5161.html]). Most capabilities do not need to be enabled. Currently only the UTF8=ACCEPT capability is supported (see RFC 6855 [https://datatracker.ietf.org/doc/html/rfc6855.html]).

在 3.5 版被加入: The enable() method itself, and RFC 6855 [https://datatracker.ietf.org/doc/html/rfc6855.html] support.

IMAP4.expunge()

Permanently remove deleted items from selected mailbox. Generates an EXPUNGE response for each deleted message. Returned data contains a list of EXPUNGE message numbers in order received.

IMAP4.fetch(message_set, message_parts)

Fetch (parts of) messages. message_parts should be a string of message part names enclosed within parentheses, eg: "(UID BODY[TEXT])". Returned data are tuples of message part envelope and data.

IMAP4.getacl(mailbox)

Get the ACLs for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.getannotation(mailbox, entry, attribute)

Retrieve the specified ANNOTATIONs for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.getquota(root)

Get the quota root's resource usage and limits. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

IMAP4.getquotaroot(mailbox)

Get the list of quota roots for the named mailbox. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

IMAP4.idle(duration=None)

Return an Idler: an iterable context manager implementing the IMAP4 IDLE command as defined in RFC 2177 [https://datatracker.ietf.org/doc/html/rfc2177.html].

The returned object sends the IDLE command when activated by the with statement, produces IMAP untagged responses via the iterator protocol, and sends DONE upon context exit.

All untagged responses that arrive after sending the IDLE command (including any that arrive before the server acknowledges the command) will be available via iteration. Any leftover responses (those not iterated in the with context) can be retrieved in the usual way after IDLE ends, using IMAP4.response().

Responses are represented as (type, [data, ...]) tuples, as described in IMAP4 Objects.

The duration argument sets a maximum duration (in seconds) to keep idling, after which any ongoing iteration will stop. It can be an int or float, or None for no time limit. Callers wishing to avoid inactivity timeouts on servers that impose them should keep this at most 29 minutes (1740 seconds). Requires a socket connection; duration must be None on IMAP4_stream connections.

>>> with M.idle(duration=29 * 60) as idler:
...     for typ, data in idler:
...         print(typ, data)
...
EXISTS [b'1']
RECENT [b'1']

Idler.burst(interval=0.1)

Yield a burst of responses no more than interval seconds apart (expressed as an int or float).

This generator is an alternative to iterating one response at a time, intended to aid in efficient batch processing. It retrieves the next response along with any immediately available subsequent responses. (For example, a rapid series of EXPUNGE responses after a bulk delete.)

Requires a socket connection; does not work on IMAP4_stream connections.

>>> with M.idle() as idler:
...     # get a response and any others following by < 0.1 seconds
...     batch = list(idler.burst())
...     print(f'processing {len(batch)} responses...')
...     print(batch)
...
processing 3 responses...
[('EXPUNGE', [b'2']), ('EXPUNGE', [b'1']), ('RECENT', [b'0'])]

小訣竅

The IDLE context's maximum duration, as passed to IMAP4.idle(), is respected when waiting for the first response in a burst. Therefore, an expired Idler will cause this generator to return immediately without producing anything. Callers should consider this if using it in a loop.

備註

The iterator returned by IMAP4.idle() is usable only within a with statement. Before or after that context, unsolicited responses are collected internally whenever a command finishes, and can be retrieved with IMAP4.response().

備註

The Idler class name and structure are internal interfaces, subject to change. Calling code can rely on its context management, iteration, and public method to remain stable, but should not subclass, instantiate, compare, or otherwise directly reference the class.

在 3.14 版被加入.

IMAP4.list([directory[, pattern]])

List mailbox names in directory matching pattern. directory defaults to the top-level mail folder, and pattern defaults to match anything. Returned data contains a list of LIST responses.

IMAP4.login(user, password)

Identify the client using a plaintext password. The password will be quoted.

IMAP4.login_cram_md5(user, password)

Force use of CRAM-MD5 authentication when identifying the client to protect the password. Will only work if the server CAPABILITY response includes the phrase AUTH=CRAM-MD5.

在 3.14 版的變更: An IMAP4.error is raised if MD5 support is not available.

IMAP4.logout()

Shutdown connection to server. Returns server BYE response.

在 3.8 版的變更: The method no longer ignores silently arbitrary exceptions.

IMAP4.lsub(directory='""', pattern='*')

List subscribed mailbox names in directory matching pattern. directory defaults to the top level directory and pattern defaults to match any mailbox. Returned data are tuples of message part envelope and data.

IMAP4.myrights(mailbox)

Show my ACLs for a mailbox (i.e. the rights that I have on mailbox).

IMAP4.namespace()

Returns IMAP namespaces as defined in RFC 2342 [https://datatracker.ietf.org/doc/html/rfc2342.html].

IMAP4.noop()

Send NOOP to server.

IMAP4.open(host, port, timeout=None)

Opens socket to port at host. The optional timeout parameter specifies a timeout in seconds for the connection attempt. If timeout is not given or is None, the global default socket timeout is used. Also note that if the timeout parameter is set to be zero, it will raise a ValueError to reject creating a non-blocking socket. This method is implicitly called by the IMAP4 constructor. The connection objects established by this method will be used in the IMAP4.read(), IMAP4.readline(), IMAP4.send(), and IMAP4.shutdown() methods. You may override this method.

引發一個附帶引數 self、host、port 的稽核事件 imaplib.open。

在 3.9 版的變更: 新增 timeout 參數。

IMAP4.partial(message_num, message_part, start, length)

Fetch truncated part of a message. Returned data is a tuple of message part envelope and data.

IMAP4.proxyauth(user)

Assume authentication as user. Allows an authorised administrator to proxy into any user's mailbox.

IMAP4.read(size)

Reads size bytes from the remote server. You may override this method.

IMAP4.readline()

Reads one line from the remote server. You may override this method.

IMAP4.recent()

Prompt server for an update. Returned data is None if no new messages, else value of RECENT response.

IMAP4.rename(oldmailbox, newmailbox)

Rename mailbox named oldmailbox to newmailbox.

IMAP4.response(code)

Return data for response code if received, or None. Returns the given code, instead of the usual type.

IMAP4.search(charset, criterion[, ...])

Search mailbox for matching messages. charset may be None, in which case no CHARSET will be specified in the request to the server. The IMAP protocol requires that at least one criterion be specified; an exception will be raised when the server returns an error. charset must be None if the UTF8=ACCEPT capability was enabled using the enable() command.

範例：

# M is a connected IMAP4 instance...
typ, msgnums = M.search(None, 'FROM', '"LDJ"')

# or:
typ, msgnums = M.search(None, '(FROM "LDJ")')

IMAP4.select(mailbox='INBOX', readonly=False)

Select a mailbox. Returned data is the count of messages in mailbox (EXISTS response). The default mailbox is 'INBOX'. If the readonly flag is set, modifications to the mailbox are not allowed.

IMAP4.send(data)

Sends data to the remote server. You may override this method.

引發一個附帶引數 self、data 的稽核事件 imaplib.send。

IMAP4.setacl(mailbox, who, what)

Set an ACL for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.setannotation(mailbox, entry, attribute[, ...])

Set ANNOTATIONs for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.setquota(root, limits)

Set the quota root's resource limits. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

IMAP4.shutdown()

Close connection established in open. This method is implicitly called by IMAP4.logout(). You may override this method.

IMAP4.socket()

Returns socket instance used to connect to server.

IMAP4.sort(sort_criteria, charset, search_criterion[, ...])

The sort command is a variant of search with sorting semantics for the results. Returned data contains a space separated list of matching message numbers.

Sort has two arguments before the search_criterion argument(s); a parenthesized list of sort_criteria, and the searching charset. Note that unlike search, the searching charset argument is mandatory. There is also a uid sort command which corresponds to sort the way that uid search corresponds to search. The sort command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria. It then returns the numbers of matching messages.

This is an IMAP4rev1 extension command.

IMAP4.starttls(ssl_context=None)

Send a STARTTLS command. The ssl_context argument is optional and should be a ssl.SSLContext object. This will enable encryption on the IMAP connection. Please read Security considerations for best practices.

在 3.2 版被加入.

在 3.4 版的變更: The method now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

IMAP4.status(mailbox, names)

Request named status conditions for mailbox.

IMAP4.store(message_set, command, flag_list)

Alters flag dispositions for messages in mailbox. command is specified by section 6.4.6 of RFC 2060 [https://datatracker.ietf.org/doc/html/rfc2060.html] as being one of "FLAGS", "+FLAGS", or "-FLAGS", optionally with a suffix of ".SILENT".

For example, to set the delete flag on all messages:

typ, data = M.search(None, 'ALL')
for num in data[0].split():
   M.store(num, '+FLAGS', '\\Deleted')
M.expunge()

備註

Creating flags containing ']' (for example: "[test]") violates RFC 3501 [https://datatracker.ietf.org/doc/html/rfc3501.html] (the IMAP protocol). However, imaplib has historically allowed creation of such tags, and popular IMAP servers, such as Gmail, accept and produce such flags. There are non-Python programs which also create such tags. Although it is an RFC violation and IMAP clients and servers are supposed to be strict, imaplib still continues to allow such tags to be created for backward compatibility reasons, and as of Python 3.6, handles them if they are sent from the server, since this improves real-world compatibility.

IMAP4.subscribe(mailbox)

Subscribe to new mailbox.

IMAP4.thread(threading_algorithm, charset, search_criterion[, ...])

The thread command is a variant of search with threading semantics for the results. Returned data contains a space separated list of thread members.

Thread members consist of zero or more messages numbers, delimited by spaces, indicating successive parent and child.

Thread has two arguments before the search_criterion argument(s); a threading_algorithm, and the searching charset. Note that unlike search, the searching charset argument is mandatory. There is also a uid thread command which corresponds to thread the way that uid search corresponds to search. The thread command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria. It then returns the matching messages threaded according to the specified threading algorithm.

This is an IMAP4rev1 extension command.

IMAP4.uid(command, arg[, ...])

Execute command args with messages identified by UID, rather than message number. Returns response appropriate to command. At least one argument must be supplied; if none are provided, the server will return an error and an exception will be raised.

IMAP4.unsubscribe(mailbox)

Unsubscribe from old mailbox.

IMAP4.unselect()

imaplib.IMAP4.unselect() frees server's resources associated with the selected mailbox and returns the server to the authenticated state. This command performs the same actions as imaplib.IMAP4.close(), except that no messages are permanently removed from the currently selected mailbox.

在 3.9 版被加入.

IMAP4.xatom(name[, ...])

Allow simple extension commands notified by server in CAPABILITY response.

The following attributes are defined on instances of IMAP4:

IMAP4.PROTOCOL_VERSION

The most recent supported protocol in the CAPABILITY response from the server.

IMAP4.debug

Integer value to control debugging output. The initialize value is taken from the module variable Debug. Values greater than three trace each command.

IMAP4.utf8_enabled

Boolean value that is normally False, but is set to True if an enable() command is successfully issued for the UTF8=ACCEPT capability.

在 3.5 版被加入.

IMAP4 範例

Here is a minimal example (without error checking) that opens a mailbox and retrieves and prints all messages:

import getpass, imaplib

M = imaplib.IMAP4(host='example.org')
M.login(getpass.getuser(), getpass.getpass())
M.select()
typ, data = M.search(None, 'ALL')
for num in data[0].split():
    typ, data = M.fetch(num, '(RFC822)')
    print('Message %s\n%s\n' % (num, data[0][1]))
M.close()
M.logout()

smtplib --- SMTP 協定用戶端

原始碼：Lib/smtplib.py [https://github.com/python/cpython/tree/3.14/Lib/smtplib.py]

The smtplib module defines an SMTP client session object that can be used to send mail to any internet machine with an SMTP or ESMTP listener daemon. For details of SMTP and ESMTP operation, consult RFC 821 [https://datatracker.ietf.org/doc/html/rfc821.html] (Simple Mail Transfer Protocol) and RFC 1869 [https://datatracker.ietf.org/doc/html/rfc1869.html] (SMTP Service Extensions).

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

class smtplib.SMTP(host='', port=0, local_hostname=None, [timeout, ]source_address=None)

An SMTP instance encapsulates an SMTP connection. It has methods that support a full repertoire of SMTP and ESMTP operations. If the optional host and port parameters are given, the SMTP connect() method is called with those parameters during initialization. If specified, local_hostname is used as the FQDN of the local host in the HELO/EHLO command. Otherwise, the local hostname is found using socket.getfqdn(). If the connect() call returns anything other than a success code, an SMTPConnectError is raised. The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt (if not specified, the global default timeout setting will be used). If the timeout expires, TimeoutError is raised. The optional source_address parameter allows binding to some specific source address in a machine with multiple network interfaces, and/or to some specific source TCP port. It takes a 2-tuple (host, port), for the socket to bind to as its source address before connecting. If omitted (or if host or port are '' and/or 0 respectively) the OS default behavior will be used.

For normal use, you should only require the initialization/connect, sendmail(), and SMTP.quit() methods. An example is included below.

The SMTP class supports the with statement. When used like this, the SMTP QUIT command is issued automatically when the with statement exits. E.g.:

>>> from smtplib import SMTP
>>> with SMTP("domain.org") as smtp:
...     smtp.noop()
...
(250, b'Ok')
>>>

所有指令都會引發一個附帶引數 self、data 的稽核事件 smtplib.SMTP.send，其中 data 為即將傳送至遠端的位元組。

在 3.3 版的變更: 新增對 with 陳述式的支援。

在 3.3 版的變更: 新增 source_address 引數。

在 3.5 版被加入: The SMTPUTF8 extension (RFC 6531 [https://datatracker.ietf.org/doc/html/rfc6531.html]) is now supported.

在 3.9 版的變更: If the timeout parameter is set to be zero, it will raise a ValueError to prevent the creation of a non-blocking socket.

class smtplib.SMTP_SSL(host='', port=0, local_hostname=None, *, [timeout, ]context=None, source_address=None)

An SMTP_SSL instance behaves exactly the same as instances of SMTP. SMTP_SSL should be used for situations where SSL is required from the beginning of the connection and using starttls() is not appropriate. If host is not specified, the local host is used. If port is zero, the standard SMTP-over-SSL port (465) is used. The optional arguments local_hostname, timeout and source_address have the same meaning as they do in the SMTP class. context, also optional, can contain a SSLContext and allows configuring various aspects of the secure connection. Please read Security considerations for best practices.

在 3.3 版的變更: 新增 context。

在 3.3 版的變更: 新增 source_address 引數。

在 3.4 版的變更: The class now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

在 3.9 版的變更: If the timeout parameter is set to be zero, it will raise a ValueError to prevent the creation of a non-blocking socket

在 3.12 版的變更: The deprecated keyfile and certfile parameters have been removed.

class smtplib.LMTP(host='', port=LMTP_PORT, local_hostname=None, source_address=None[, timeout])

The LMTP protocol, which is very similar to ESMTP, is heavily based on the standard SMTP client. It's common to use Unix sockets for LMTP, so our connect() method must support that as well as a regular host:port server. The optional arguments local_hostname and source_address have the same meaning as they do in the SMTP class. To specify a Unix socket, you must use an absolute path for host, starting with a '/'.

Authentication is supported, using the regular SMTP mechanism. When using a Unix socket, LMTP generally don't support or require any authentication, but your mileage might vary.

在 3.9 版的變更: 新增 timeout 選用參數。

A nice selection of exceptions is defined as well:

exception smtplib.SMTPException

Subclass of OSError that is the base exception class for all the other exceptions provided by this module.

在 3.4 版的變更: SMTPException became subclass of OSError

exception smtplib.SMTPServerDisconnected

This exception is raised when the server unexpectedly disconnects, or when an attempt is made to use the SMTP instance before connecting it to a server.

exception smtplib.SMTPResponseException

Base class for all exceptions that include an SMTP error code. These exceptions are generated in some instances when the SMTP server returns an error code.

smtp_code

The error code.

smtp_error

The error message.

exception smtplib.SMTPSenderRefused

Sender address refused. In addition to the attributes set by on all SMTPResponseException exceptions, this sets 'sender' to the string that the SMTP server refused.

exception smtplib.SMTPRecipientsRefused

All recipient addresses refused.

recipients

A dictionary of exactly the same sort as returned by SMTP.sendmail() containing the errors for each recipient.

exception smtplib.SMTPDataError

The SMTP server refused to accept the message data.

exception smtplib.SMTPConnectError

Error occurred during establishment of a connection with the server.

exception smtplib.SMTPHeloError

The server refused our HELO message.

exception smtplib.SMTPNotSupportedError

The command or option attempted is not supported by the server.

在 3.5 版被加入.

exception smtplib.SMTPAuthenticationError

SMTP authentication went wrong. Most probably the server didn't accept the username/password combination provided.

也參考

RFC 821 [https://datatracker.ietf.org/doc/html/rfc821.html] - 簡易郵件傳輸協定

Protocol definition for SMTP. This document covers the model, operating procedure, and protocol details for SMTP.

RFC 1869 [https://datatracker.ietf.org/doc/html/rfc1869.html] - SMTP Service Extensions

Definition of the ESMTP extensions for SMTP. This describes a framework for extending SMTP with new commands, supporting dynamic discovery of the commands provided by the server, and defines a few additional commands.

SMTP 物件

SMTP 實例擁有以下方法：

SMTP.set_debuglevel(level)

Set the debug output level. A value of 1 or True for level results in debug messages for connection and for all messages sent to and received from the server. A value of 2 for level results in these messages being timestamped.

在 3.5 版的變更: 新增 debuglevel 2。

SMTP.docmd(cmd, args='')

Send a command cmd to the server. The optional argument args is simply concatenated to the command, separated by a space.

This returns a 2-tuple composed of a numeric response code and the actual response line (multiline responses are joined into one long line.)

In normal operation it should not be necessary to call this method explicitly. It is used to implement other methods and may be useful for testing private extensions.

If the connection to the server is lost while waiting for the reply, SMTPServerDisconnected will be raised.

SMTP.connect(host='localhost', port=0)

Connect to a host on a given port. The defaults are to connect to the local host at the standard SMTP port (25). If the hostname ends with a colon (':') followed by a number, that suffix will be stripped off and the number interpreted as the port number to use. This method is automatically invoked by the constructor if a host is specified during instantiation. Returns a 2-tuple of the response code and message sent by the server in its connection response.

引發一個附帶引數 self、host、port 的稽核事件 smtplib.connect。

SMTP.helo(name='')

Identify yourself to the SMTP server using HELO. The hostname argument defaults to the fully qualified domain name of the local host. The message returned by the server is stored as the helo_resp attribute of the object.

In normal operation it should not be necessary to call this method explicitly. It will be implicitly called by the sendmail() when necessary.

SMTP.ehlo(name='')

Identify yourself to an ESMTP server using EHLO. The hostname argument defaults to the fully qualified domain name of the local host. Examine the response for ESMTP option and store them for use by has_extn(). Also sets several informational attributes: the message returned by the server is stored as the ehlo_resp attribute, does_esmtp is set to True or False depending on whether the server supports ESMTP, and esmtp_features will be a dictionary containing the names of the SMTP service extensions this server supports, and their parameters (if any).

Unless you wish to use has_extn() before sending mail, it should not be necessary to call this method explicitly. It will be implicitly called by sendmail() when necessary.

SMTP.ehlo_or_helo_if_needed()

This method calls ehlo() and/or helo() if there has been no previous EHLO or HELO command this session. It tries ESMTP EHLO first.

SMTPHeloError

The server didn't reply properly to the HELO greeting.

SMTP.has_extn(name)

Return True if name is in the set of SMTP service extensions returned by the server, False otherwise. Case is ignored.

SMTP.verify(address)

Check the validity of an address on this server using SMTP VRFY. Returns a tuple consisting of code 250 and a full RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] address (including human name) if the user address is valid. Otherwise returns an SMTP error code of 400 or greater and an error string.

備註

Many sites disable SMTP VRFY in order to foil spammers.

SMTP.login(user, password, *, initial_response_ok=True)

Log in on an SMTP server that requires authentication. The arguments are the username and the password to authenticate with. If there has been no previous EHLO or HELO command this session, this method tries ESMTP EHLO first. This method will return normally if the authentication was successful, or may raise the following exceptions:

SMTPHeloError

The server didn't reply properly to the HELO greeting.

SMTPAuthenticationError

The server didn't accept the username/password combination.

SMTPNotSupportedError

The AUTH command is not supported by the server.

SMTPException

No suitable authentication method was found.

Each of the authentication methods supported by smtplib are tried in turn if they are advertised as supported by the server. See auth() for a list of supported authentication methods. initial_response_ok is passed through to auth().

Optional keyword argument initial_response_ok specifies whether, for authentication methods that support it, an "initial response" as specified in RFC 4954 [https://datatracker.ietf.org/doc/html/rfc4954.html] can be sent along with the AUTH command, rather than requiring a challenge/response.

在 3.5 版的變更: SMTPNotSupportedError may be raised, and the initial_response_ok parameter was added.

SMTP.auth(mechanism, authobject, *, initial_response_ok=True)

Issue an SMTP AUTH command for the specified authentication mechanism, and handle the challenge response via authobject.

mechanism specifies which authentication mechanism is to be used as argument to the AUTH command; the valid values are those listed in the auth element of esmtp_features.

authobject must be a callable object taking an optional single argument:

data = authobject(challenge=None)

If optional keyword argument initial_response_ok is true, authobject() will be called first with no argument. It can return the RFC 4954 [https://datatracker.ietf.org/doc/html/rfc4954.html] "initial response" ASCII str which will be encoded and sent with the AUTH command as below. If the authobject() does not support an initial response (e.g. because it requires a challenge), it should return None when called with challenge=None. If initial_response_ok is false, then authobject() will not be called first with None.

If the initial response check returns None, or if initial_response_ok is false, authobject() will be called to process the server's challenge response; the challenge argument it is passed will be a bytes. It should return ASCII str data that will be base64 encoded and sent to the server.

The SMTP class provides authobjects for the CRAM-MD5, PLAIN, and LOGIN mechanisms; they are named SMTP.auth_cram_md5, SMTP.auth_plain, and SMTP.auth_login respectively. They all require that the user and password properties of the SMTP instance are set to appropriate values.

User code does not normally need to call auth directly, but can instead call the login() method, which will try each of the above mechanisms in turn, in the order listed. auth is exposed to facilitate the implementation of authentication methods not (or not yet) supported directly by smtplib.

在 3.5 版被加入.

SMTP.starttls(*, context=None)

Put the SMTP connection in TLS (Transport Layer Security) mode. All SMTP commands that follow will be encrypted. You should then call ehlo() again.

If keyfile and certfile are provided, they are used to create an ssl.SSLContext.

Optional context parameter is an ssl.SSLContext object; This is an alternative to using a keyfile and a certfile and if specified both keyfile and certfile should be None.

If there has been no previous EHLO or HELO command this session, this method tries ESMTP EHLO first.

在 3.12 版的變更: The deprecated keyfile and certfile parameters have been removed.

SMTPHeloError

The server didn't reply properly to the HELO greeting.

SMTPNotSupportedError

The server does not support the STARTTLS extension.

RuntimeError

SSL/TLS support is not available to your Python interpreter.

在 3.3 版的變更: 新增 context。

在 3.4 版的變更: The method now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indicator (see HAS_SNI).

在 3.5 版的變更: The error raised for lack of STARTTLS support is now the SMTPNotSupportedError subclass instead of the base SMTPException.

SMTP.sendmail(from_addr, to_addrs, msg, mail_options=(), rcpt_options=())

Send mail. The required arguments are an RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] from-address string, a list of RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] to-address strings (a bare string will be treated as a list with 1 address), and a message string. The caller may pass a list of ESMTP options (such as "8bitmime") to be used in MAIL FROM commands as mail_options. ESMTP options (such as DSN commands) that should be used with all RCPT commands can be passed as rcpt_options. Each option should be passed as a string containing the full text of the option, including any potential key (for instance, "NOTIFY=SUCCESS,FAILURE"). (If you need to use different ESMTP options to different recipients you have to use the low-level methods such as mail(), rcpt() and data() to send the message.)

備註

The from_addr and to_addrs parameters are used to construct the message envelope used by the transport agents. sendmail does not modify the message headers in any way.

msg may be a string containing characters in the ASCII range, or a byte string. A string is encoded to bytes using the ascii codec, and lone \r and \n characters are converted to \r\n characters. A byte string is not modified.

If there has been no previous EHLO or HELO command this session, this method tries ESMTP EHLO first. If the server does ESMTP, message size and each of the specified options will be passed to it (if the option is in the feature set the server advertises). If EHLO fails, HELO will be tried and ESMTP options suppressed.

This method will return normally if the mail is accepted for at least one recipient. Otherwise it will raise an exception. That is, if this method does not raise an exception, then someone should get your mail. If this method does not raise an exception, it returns a dictionary, with one entry for each recipient that was refused. Each entry contains a tuple of the SMTP error code and the accompanying error message sent by the server.

If SMTPUTF8 is included in mail_options, and the server supports it, from_addr and to_addrs may contain non-ASCII characters.

This method may raise the following exceptions:

SMTPRecipientsRefused

All recipients were refused. Nobody got the mail.

SMTPHeloError

The server didn't reply properly to the HELO greeting.

SMTPSenderRefused

The server didn't accept the from_addr.

SMTPDataError

The server replied with an unexpected error code (other than a refusal of a recipient).

SMTPNotSupportedError

SMTPUTF8 was given in the mail_options but is not supported by the server.

Unless otherwise noted, the connection will be open even after an exception is raised.

在 3.2 版的變更: msg may be a byte string.

在 3.5 版的變更: SMTPUTF8 support added, and SMTPNotSupportedError may be raised if SMTPUTF8 is specified but the server does not support it.

SMTP.send_message(msg, from_addr=None, to_addrs=None, mail_options=(), rcpt_options=())

This is a convenience method for calling sendmail() with the message represented by an email.message.Message object. The arguments have the same meaning as for sendmail(), except that msg is a Message object.

If from_addr is None or to_addrs is None, send_message fills those arguments with addresses extracted from the headers of msg as specified in RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html]: from_addr is set to the Sender field if it is present, and otherwise to the From field. to_addrs combines the values (if any) of the To, Cc, and Bcc fields from msg. If exactly one set of Resent-* headers appear in the message, the regular headers are ignored and the Resent-* headers are used instead. If the message contains more than one set of Resent-* headers, a ValueError is raised, since there is no way to unambiguously detect the most recent set of Resent- headers.

send_message serializes msg using BytesGenerator with \r\n as the linesep, and calls sendmail() to transmit the resulting message. Regardless of the values of from_addr and to_addrs, send_message does not transmit any Bcc or Resent-Bcc headers that may appear in msg. If any of the addresses in from_addr and to_addrs contain non-ASCII characters and the server does not advertise SMTPUTF8 support, an SMTPNotSupportedError is raised. Otherwise the Message is serialized with a clone of its policy with the utf8 attribute set to True, and SMTPUTF8 and BODY=8BITMIME are added to mail_options.

在 3.2 版被加入.

在 3.5 版被加入: Support for internationalized addresses (SMTPUTF8).

SMTP.quit()

Terminate the SMTP session and close the connection. Return the result of the SMTP QUIT command.

Low-level methods corresponding to the standard SMTP/ESMTP commands HELP, RSET, NOOP, MAIL, RCPT, and DATA are also supported. Normally these do not need to be called directly, so they are not documented here. For details, consult the module code.

此外，SMTP 實例擁有以下屬性：

SMTP.helo_resp

The response to the HELO command, see helo().

SMTP.ehlo_resp

The response to the EHLO command, see ehlo().

SMTP.does_esmtp

A boolean value indicating whether the server supports ESMTP, see ehlo().

SMTP.esmtp_features

A dictionary of the names of SMTP service extensions supported by the server, see ehlo().

SMTP 範例

This example prompts the user for addresses needed in the message envelope ('To' and 'From' addresses), and the message to be delivered. Note that the headers to be included with the message must be included in the message as entered; this example doesn't do any processing of the RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html] headers. In particular, the 'To' and 'From' addresses must be included in the message headers explicitly:

import smtplib

def prompt(title):
    return input(title).strip()

from_addr = prompt("From: ")
to_addrs  = prompt("To: ").split()
print("Enter message, end with ^D (Unix) or ^Z (Windows):")

# Add the From: and To: headers at the start!
lines = [f"From: {from_addr}", f"To: {', '.join(to_addrs)}", ""]
while True:
    try:
        line = input()
    except EOFError:
        break
    else:
        lines.append(line)

msg = "\r\n".join(lines)
print("Message length is", len(msg))

server = smtplib.SMTP("localhost")
server.set_debuglevel(1)
server.sendmail(from_addr, to_addrs, msg)
server.quit()

備註

In general, you will want to use the email package's features to construct an email message, which you can then send via send_message(); see email：範例.

uuid --- RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html] 定義的 UUID 物件

原始碼：Lib/uuid.py [https://github.com/python/cpython/tree/3.14/Lib/uuid.py]

This module provides immutable UUID objects (the UUID class) and functions for generating UUIDs corresponding to a specific UUID version as specified in RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html] (which supersedes RFC 4122 [https://datatracker.ietf.org/doc/html/rfc4122.html]), for example, uuid1() for UUID version 1, uuid3() for UUID version 3, and so on. Note that UUID version 2 is deliberately omitted as it is outside the scope of the RFC.

如果你只需要一個唯一的 ID，你應該呼叫 uuid1() 或 uuid4()。需要注意的是，uuid1() 可能會危害隱私，因為它會建立一個包含了電腦網路位址的 UUID。而 uuid4() 則會建立一個隨機的 UUID。

根據底層平台的支援情況，uuid1() 可能會也可能不會回傳一個「安全的」UUID。安全的 UUID 是使用同步方法生成的，以確保不會有兩個行程取得到相同的 UUID。所有 UUID 的實例都有一個 is_safe 屬性，該屬性使用下面這個列舉來傳遞有關 UUID 安全性的任何資訊：

class uuid.SafeUUID

在 3.7 版被加入.

safe

該 UUID 是由平台以多行程安全的 (multiprocessing-safe) 方式生成的。

unsafe

該 UUID 不是以多行程安全的方式生成的。

unknown

該平台不提供 UUID 是否為安全生成的資訊。

class uuid.UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=SafeUUID.unknown)

從以下其中一種引數來建立 UUID：由 32 個十六進位的數字組成的字串、以大端順序 (big-endian) 排列的 16 個位元組組成的字串作為 bytes 引數、以小端順序 (little-endian) 排列的 16 個位元組組成的字串作為 bytes_le 引數、由 6 個整數（32 位元的 time_low、16 位元的 time_mid、16 位元的 time_hi_version、8 位元的 clock_seq_hi_variant、8 位元的 clock_seq_low、48 位元的 node）組成的元組 (tuple) 作為 fields 引數，或者是單一的 128 位元整數作為 int 引數。當給定由十六進位的數字組成的字串時，大括號、連字符號和 URN 前綴都是可以選用的。例如，以下這些運算式都會產生相同的 UUID：

UUID('{12345678-1234-5678-1234-567812345678}')
UUID('12345678123456781234567812345678')
UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
UUID(bytes=b'\x12\x34\x56\x78'*4)
UUID(bytes_le=b'\x78\x56\x34\x12\x34\x12\x78\x56' +
              b'\x12\x34\x56\x78\x12\x34\x56\x78')
UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
UUID(int=0x12345678123456781234567812345678)

必須正好給定其中一個引數 hex、bytes、bytes_le、fields 或 int。version 引數是選用的；如果給定了該引數，生成的 UUID 將根據 RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html] 設置其變體 (variant) 和版本號，覆蓋掉給定的 hex、bytes、bytes_le、fields 或 int 中的位元。

UUID 物件之間的比較是透過比較它們的 UUID.int 屬性。與非 UUID 的物件進行比較會引發 TypeError。

str(uuid) 會回傳一個像是 12345678-1234-5678-1234-567812345678 形式的字串，其中 32 個十六進位的數字代表 UUID。

UUID 實例有以下唯讀的屬性：

UUID.bytes

UUID 以 16 位元組的字串表示（包含 6 個整數欄位，按照大端位元組順序排列）。

UUID.bytes_le

UUID 以 16 位元組的字串表示（其中 time_low、time_mid 和 time_hi_version 按照小端位元組順序排列）。

UUID.fields

UUID 以 6 個整數欄位所組成的元組表示，也可以看作有 6 個個別屬性和 2 個衍生屬性：

欄位

意義

UUID.time_low

UUID 的前 32 位元。只與版本 1 有關。

UUID.time_mid

UUID 接下來的 16 位元。只與版本 1 有關。

UUID.time_hi_version

UUID 接下來的 16 位元。只與版本 1 有關。

UUID.clock_seq_hi_variant

UUID 接下來的 8 位元。只與版本 1 和 6 有關。

UUID.clock_seq_low

UUID 接下來的 8 位元。只與版本 1 和 6 有關。

UUID.node

UUID 最後的 48 位元。只與版本 1 有關。

UUID.time

The 60-bit timestamp as a count of 100-nanosecond intervals since Gregorian epoch (1582-10-15 00:00:00) for versions 1 and 6, or the 48-bit timestamp in milliseconds since Unix epoch (1970-01-01 00:00:00) for version 7.

UUID.clock_seq

14 位元的序列號。只與版本 1 和 6 有關。

UUID.hex

UUID 以 32 個小寫十六進位字元組成的字串表示。

UUID.int

UUID 以 128 位元的整數表示。

UUID.urn

UUID 以 RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html] 中指定的 URN 形式表示。

UUID.variant

UUID 的變體，決定 UUID 內部的佈局 (layout)，是 RESERVED_NCS、RFC_4122、RESERVED_MICROSOFT 或 RESERVED_FUTURE 其中一個常數。

UUID.version

UUID 的版本號（1 到 8，只有當變體是 RFC_4122 時才有意義）。

在 3.14 版的變更: 新增了 UUID 版本 6、7 和 8。

UUID.is_safe

SafeUUID 的列舉，表示平台是否以多行程安全的方式產生 UUID。

在 3.7 版被加入.

uuid 模組定義了以下函式：

uuid.getnode()

取得 48 位元正整數形式的硬體位址。第一次執行時，有可能會啟動一個獨立的程式，這也許會相當耗時。如果所有取得硬體位址的嘗試都失敗，我們會根據 RFC 4122 [https://datatracker.ietf.org/doc/html/rfc4122.html] 中的建議，使用一個 48 位元的隨機數，其中群播位元 (multicast bit)（第一個八位元組的最低有效位）設置為 1。「硬體位址」指的是網路介面 (network interface) 的 MAC 位址。在具有多個網路介面的機器上，將優先選擇通用管理 (universally administered) 的 MAC 位址（即第一個八位元組的第二個最低有效位是 未設置的），而不是本地管理 (locally administered) 的 MAC 位址，除此之外不保證任何選擇的順序。

在 3.7 版的變更: 通用管理的 MAC 位址優於本地管理的 MAC 位址，因為前者保證是全球唯一的，而後者不是。

uuid.uuid1(node=None, clock_seq=None)

Generate a UUID from a host ID, sequence number, and the current time according to RFC 9562, §5.1 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.1].

When node is not specified, getnode() is used to obtain the hardware address as a 48-bit positive integer. When a sequence number clock_seq is not specified, a pseudo-random 14-bit positive integer is generated.

If node or clock_seq exceed their expected bit count, only their least significant bits are kept.

uuid.uuid3(namespace, name)

根據 RFC 9562, §5.3 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.3]，基於命名空間識別碼 (namespace identifier)（一個 UUID）和名稱（一個 bytes 物件或使用 UTF-8 編碼的字串）的 MD5 hash 來生成 UUID。

uuid.uuid4()

Generate a random UUID in a cryptographically-secure method according to RFC 9562, §5.4 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.4].

uuid.uuid5(namespace, name)

根據 RFC 9562, §5.5 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.5]，基於命名空間識別碼（一個 UUID）和名稱（一個 bytes 物件或使用 UTF-8 編碼的字串）的 SHA-1 hash 來生成 UUID。

uuid.uuid6(node=None, clock_seq=None)

Generate a UUID from a sequence number and the current time according to RFC 9562, §5.6 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.6].

This is an alternative to uuid1() to improve database locality.

When node is not specified, getnode() is used to obtain the hardware address as a 48-bit positive integer. When a sequence number clock_seq is not specified, a pseudo-random 14-bit positive integer is generated.

If node or clock_seq exceed their expected bit count, only their least significant bits are kept.

在 3.14 版被加入.

uuid.uuid7()

Generate a time-based UUID according to RFC 9562, §5.7 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.7].

For portability across platforms lacking sub-millisecond precision, UUIDs produced by this function embed a 48-bit timestamp and use a 42-bit counter to guarantee monotonicity within a millisecond.

在 3.14 版被加入.

uuid.uuid8(a=None, b=None, c=None)

Generate a pseudo-random UUID according to RFC 9562, §5.8 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.8].

When specified, the parameters a, b and c are expected to be positive integers of 48, 12 and 62 bits respectively. If they exceed their expected bit count, only their least significant bits are kept; non-specified arguments are substituted for a pseudo-random integer of appropriate size.

By default, a, b and c are not generated by a cryptographically secure pseudo-random number generator (CSPRNG). Use uuid4() when a UUID needs to be used in a security-sensitive context.

在 3.14 版被加入.

uuid 模組為 uuid3() 或 uuid5() 定義了以下的命名空間識別碼。

uuid.NAMESPACE_DNS

當指定這個命名空間時，name 字串是一個完整網域名稱 (fully qualified domain name)。

uuid.NAMESPACE_URL

當指定這個命名空間時，name 字串是一個 URL。

uuid.NAMESPACE_OID

當指定這個命名空間時，name 字串是一個 ISO OID。

uuid.NAMESPACE_X500

當指定這個命名空間時，name 字串是以 DER 或文字輸出格式表示的 X.500 DN。

uuid 模組為 variant 屬性的可能值定義了以下常數：

uuid.RESERVED_NCS

保留供 NCS 相容性使用。

uuid.RFC_4122

Specifies the UUID layout given in RFC 4122 [https://datatracker.ietf.org/doc/html/rfc4122.html]. This constant is kept for backward compatibility even though RFC 4122 [https://datatracker.ietf.org/doc/html/rfc4122.html] has been superseded by RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html].

uuid.RESERVED_MICROSOFT

保留供 Microsoft 相容性使用。

uuid.RESERVED_FUTURE

保留供未來定義使用。

uuid 模組定義了特殊的 Nil 和 Max UUID 值：

uuid.NIL

A special form of UUID that is specified to have all 128 bits set to zero according to RFC 9562, §5.9 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.9].

在 3.14 版被加入.

uuid.MAX

A special form of UUID that is specified to have all 128 bits set to one according to RFC 9562, §5.10 [https://datatracker.ietf.org/doc/html/rfc9562.html#section-5.10].

在 3.14 版被加入.

也參考

RFC 9562 [https://datatracker.ietf.org/doc/html/rfc9562.html] - 通用唯一辨識碼 (UUID, Universally Unique IDentifier) 的 URN 命名空間

這個規範定義了 UUID 的統一資源名稱 (Uniform Resource Name) 命名空間、UUID 的內部格式和生成 UUID 的方法。

命令列的用法

在 3.12 版被加入.

uuid 模組可以在命令列下作為腳本來執行。

python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n NAMESPACE] [-N NAME]

可以接受以下選項：

-h, --help

顯示幫助訊息並退出。

-u <uuid>

--uuid <uuid>

指定要用來生成 UUID 的函式名稱。預設使用 uuid4()。

在 3.14 版的變更: Allow generating UUID versions 6, 7 and 8.

-n <namespace>

--namespace <namespace>

該命名空間是一個 UUID 或 @ns，其中 ns 是指知名預定義 UUID 的命名空間名稱，例如 @dns、@url、@oid 和 @x500。 只有 uuid3() / uuid5() 函式會需要。

-N <name>

--name <name>

用於生成 uuid 的名稱。只有 uuid3() / uuid5() 函式會需要。

-C <num>

--count <num>

生成 num 個新 UUID。

在 3.14 版被加入.

範例

以下是一些 uuid 模組的典型使用範例：

>>> import uuid

>>> # make a UUID based on the host ID and current time
>>> uuid.uuid1()
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

>>> # make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

>>> # make a random UUID
>>> uuid.uuid4()
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

>>> # make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

>>> # make a UUID from a string of hex digits (braces and hyphens ignored)
>>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')

>>> # convert a UUID to a string of hex digits in standard form
>>> str(x)
'00010203-0405-0607-0809-0a0b0c0d0e0f'

>>> # get the raw 16 bytes of the UUID
>>> x.bytes
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'

>>> # make a UUID from a 16-byte string
>>> uuid.UUID(bytes=x.bytes)
UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')

>>> # get the Nil UUID
>>> uuid.NIL
UUID('00000000-0000-0000-0000-000000000000')

>>> # get the Max UUID
>>> uuid.MAX
UUID('ffffffff-ffff-ffff-ffff-ffffffffffff')

>>> # same as UUIDv1 but with fields reordered to improve DB locality
>>> uuid.uuid6()
UUID('1f0799c0-98b9-62db-92c6-a0d365b91053')

>>> # get UUIDv7 creation (local) time as a timestamp in milliseconds
>>> u = uuid.uuid7()
>>> u.time
1743936859822

>>> # get UUIDv7 creation (local) time as a datetime object
>>> import datetime as dt
>>> dt.datetime.fromtimestamp(u.time / 1000)
datetime.datetime(...)

>>> # make a UUID with custom blocks
>>> uuid.uuid8(0x12345678, 0x9abcdef0, 0x11223344)
UUID('00001234-5678-8ef0-8000-000011223344')

命令列的範例

以下是一些 uuid 命令列介面的典型使用範例：

# 生成一個隨機的 UUID - 預設使用 uuid4()
$ python -m uuid

# 使用 uuid1() 生成一組 UUID
$ python -m uuid -u uuid1

# 使用 uuid5 生成一組 UUID
$ python -m uuid -u uuid5 -n @url -N example.com

# 生成 42 個隨機 UUID
$ python -m uuid -C 42

socketserver --- 用於網路伺服器的框架

原始碼：Lib/socketserver.py [https://github.com/python/cpython/tree/3.14/Lib/socketserver.py]

The socketserver module simplifies the task of writing network servers.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

There are four basic concrete server classes:

class socketserver.TCPServer(server_address, RequestHandlerClass, bind_and_activate=True)

This uses the internet TCP protocol, which provides for continuous streams of data between the client and server. If bind_and_activate is true, the constructor automatically attempts to invoke server_bind() and server_activate(). The other parameters are passed to the BaseServer base class.

class socketserver.UDPServer(server_address, RequestHandlerClass, bind_and_activate=True)

This uses datagrams, which are discrete packets of information that may arrive out of order or be lost while in transit. The parameters are the same as for TCPServer.

class socketserver.UnixStreamServer(server_address, RequestHandlerClass, bind_and_activate=True)

class socketserver.UnixDatagramServer(server_address, RequestHandlerClass, bind_and_activate=True)

These more infrequently used classes are similar to the TCP and UDP classes, but use Unix domain sockets; they're not available on non-Unix platforms. The parameters are the same as for TCPServer.

These four classes process requests synchronously; each request must be completed before the next request can be started. This isn't suitable if each request takes a long time to complete, because it requires a lot of computation, or because it returns a lot of data which the client is slow to process. The solution is to create a separate process or thread to handle each request; the ForkingMixIn and ThreadingMixIn mix-in classes can be used to support asynchronous behaviour.

Creating a server requires several steps. First, you must create a request handler class by subclassing the BaseRequestHandler class and overriding its handle() method; this method will process incoming requests. Second, you must instantiate one of the server classes, passing it the server's address and the request handler class. It is recommended to use the server in a with statement. Then call the handle_request() or serve_forever() method of the server object to process one or many requests. Finally, call server_close() to close the socket (unless you used a with statement).

When inheriting from ThreadingMixIn for threaded connection behavior, you should explicitly declare how you want your threads to behave on an abrupt shutdown. The ThreadingMixIn class defines an attribute daemon_threads, which indicates whether or not the server should wait for thread termination. You should set the flag explicitly if you would like threads to behave autonomously; the default is False, meaning that Python will not exit until all threads created by ThreadingMixIn have exited.

Server classes have the same external methods and attributes, no matter what network protocol they use.

Server Creation Notes

There are five classes in an inheritance diagram, four of which represent synchronous servers of four types:

+------------+
| BaseServer |
+------------+
      |
      v
+-----------+        +------------------+
| TCPServer |------->| UnixStreamServer |
+-----------+        +------------------+
      |
      v
+-----------+        +--------------------+
| UDPServer |------->| UnixDatagramServer |
+-----------+        +--------------------+

Note that UnixDatagramServer derives from UDPServer, not from UnixStreamServer --- the only difference between an IP and a Unix server is the address family.

class socketserver.ForkingMixIn

class socketserver.ThreadingMixIn

Forking and threading versions of each type of server can be created using these mix-in classes. For instance, ThreadingUDPServer is created as follows:

class ThreadingUDPServer(ThreadingMixIn, UDPServer):
    pass

The mix-in class comes first, since it overrides a method defined in UDPServer. Setting the various attributes also changes the behavior of the underlying server mechanism.

ForkingMixIn and the Forking classes mentioned below are only available on POSIX platforms that support fork().

block_on_close

ForkingMixIn.server_close waits until all child processes complete, except if block_on_close attribute is False.

ThreadingMixIn.server_close waits until all non-daemon threads complete, except if block_on_close attribute is False.

max_children

Specify how many child processes will exist to handle requests at a time for ForkingMixIn. If the limit is reached, new requests will wait until one child process has finished.

daemon_threads

For ThreadingMixIn use daemonic threads by setting ThreadingMixIn.daemon_threads to True to not wait until threads complete.

在 3.7 版的變更: ForkingMixIn.server_close and ThreadingMixIn.server_close now waits until all child processes and non-daemonic threads complete. Add a new ForkingMixIn.block_on_close class attribute to opt-in for the pre-3.7 behaviour.

class socketserver.ForkingTCPServer

class socketserver.ForkingUDPServer

class socketserver.ThreadingTCPServer

class socketserver.ThreadingUDPServer

class socketserver.ForkingUnixStreamServer

class socketserver.ForkingUnixDatagramServer

class socketserver.ThreadingUnixStreamServer

class socketserver.ThreadingUnixDatagramServer

These classes are pre-defined using the mix-in classes.

在 3.12 版被加入: The ForkingUnixStreamServer and ForkingUnixDatagramServer classes were added.

To implement a service, you must derive a class from BaseRequestHandler and redefine its handle() method. You can then run various versions of the service by combining one of the server classes with your request handler class. The request handler class must be different for datagram or stream services. This can be hidden by using the handler subclasses StreamRequestHandler or DatagramRequestHandler.

Of course, you still have to use your head! For instance, it makes no sense to use a forking server if the service contains state in memory that can be modified by different requests, since the modifications in the child process would never reach the initial state kept in the parent process and passed to each child. In this case, you can use a threading server, but you will probably have to use locks to protect the integrity of the shared data.

On the other hand, if you are building an HTTP server where all data is stored externally (for instance, in the file system), a synchronous class will essentially render the service "deaf" while one request is being handled -- which may be for a very long time if a client is slow to receive all the data it has requested. Here a threading or forking server is appropriate.

In some cases, it may be appropriate to process part of a request synchronously, but to finish processing in a forked child depending on the request data. This can be implemented by using a synchronous server and doing an explicit fork in the request handler class handle() method.

Another approach to handling multiple simultaneous requests in an environment that supports neither threads nor fork() (or where these are too expensive or inappropriate for the service) is to maintain an explicit table of partially finished requests and to use selectors to decide which request to work on next (or whether to handle a new incoming request). This is particularly important for stream services where each client can potentially be connected for a long time (if threads or subprocesses cannot be used).

Server Objects

class socketserver.BaseServer(server_address, RequestHandlerClass)

This is the superclass of all Server objects in the module. It defines the interface, given below, but does not implement most of the methods, which is done in subclasses. The two parameters are stored in the respective server_address and RequestHandlerClass attributes.

fileno()

Return an integer file descriptor for the socket on which the server is listening. This function is most commonly passed to selectors, to allow monitoring multiple servers in the same process.

handle_request()

Process a single request. This function calls the following methods in order: get_request(), verify_request(), and process_request(). If the user-provided handle() method of the handler class raises an exception, the server's handle_error() method will be called. If no request is received within timeout seconds, handle_timeout() will be called and handle_request() will return.

serve_forever(poll_interval=0.5)

Handle requests until an explicit shutdown() request. Poll for shutdown every poll_interval seconds. Ignores the timeout attribute. It also calls service_actions(), which may be used by a subclass or mixin to provide actions specific to a given service. For example, the ForkingMixIn class uses service_actions() to clean up zombie child processes.

在 3.3 版的變更: Added service_actions call to the serve_forever method.

service_actions()

This is called in the serve_forever() loop. This method can be overridden by subclasses or mixin classes to perform actions specific to a given service, such as cleanup actions.

在 3.3 版被加入.

shutdown()

Tell the serve_forever() loop to stop and wait until it does. shutdown() must be called while serve_forever() is running in a different thread otherwise it will deadlock.

server_close()

Clean up the server. May be overridden.

address_family

The family of protocols to which the server's socket belongs. Common examples are socket.AF_INET, socket.AF_INET6, and socket.AF_UNIX. Subclass the TCP or UDP server classes in this module with class attribute address_family = AF_INET6 set if you want IPv6 server classes.

RequestHandlerClass

The user-provided request handler class; an instance of this class is created for each request.

server_address

The address on which the server is listening. The format of addresses varies depending on the protocol family; see the documentation for the socket module for details. For internet protocols, this is a tuple containing a string giving the address, and an integer port number: ('127.0.0.1', 80), for example.

socket

The socket object on which the server will listen for incoming requests.

The server classes support the following class variables:

allow_reuse_address

Whether the server will allow the reuse of an address. This defaults to False, and can be set in subclasses to change the policy.

request_queue_size

The size of the request queue. If it takes a long time to process a single request, any requests that arrive while the server is busy are placed into a queue, up to request_queue_size requests. Once the queue is full, further requests from clients will get a "Connection denied" error. The default value is usually 5, but this can be overridden by subclasses.

socket_type

The type of socket used by the server; socket.SOCK_STREAM and socket.SOCK_DGRAM are two common values.

timeout

Timeout duration, measured in seconds, or None if no timeout is desired. If handle_request() receives no incoming requests within the timeout period, the handle_timeout() method is called.

There are various server methods that can be overridden by subclasses of base server classes like TCPServer; these methods aren't useful to external users of the server object.

finish_request(request, client_address)

Actually processes the request by instantiating RequestHandlerClass and calling its handle() method.

get_request()

Must accept a request from the socket, and return a 2-tuple containing the new socket object to be used to communicate with the client, and the client's address.

handle_error(request, client_address)

This function is called if the handle() method of a RequestHandlerClass instance raises an exception. The default action is to print the traceback to standard error and continue handling further requests.

在 3.6 版的變更: Now only called for exceptions derived from the Exception class.

handle_timeout()

This function is called when the timeout attribute has been set to a value other than None and the timeout period has passed with no requests being received. The default action for forking servers is to collect the status of any child processes that have exited, while in threading servers this method does nothing.

process_request(request, client_address)

Calls finish_request() to create an instance of the RequestHandlerClass. If desired, this function can create a new process or thread to handle the request; the ForkingMixIn and ThreadingMixIn classes do this.

server_activate()

Called by the server's constructor to activate the server. The default behavior for a TCP server just invokes listen() on the server's socket. May be overridden.

server_bind()

Called by the server's constructor to bind the socket to the desired address. May be overridden.

verify_request(request, client_address)

Must return a Boolean value; if the value is True, the request will be processed, and if it's False, the request will be denied. This function can be overridden to implement access controls for a server. The default implementation always returns True.

在 3.6 版的變更: Support for the context manager protocol was added. Exiting the context manager is equivalent to calling server_close().

Request Handler Objects

class socketserver.BaseRequestHandler

This is the superclass of all request handler objects. It defines the interface, given below. A concrete request handler subclass must define a new handle() method, and can override any of the other methods. A new instance of the subclass is created for each request.

setup()

Called before the handle() method to perform any initialization actions required. The default implementation does nothing.

handle()

This function must do all the work required to service a request. The default implementation does nothing. Several instance attributes are available to it; the request is available as request; the client address as client_address; and the server instance as server, in case it needs access to per-server information.

The type of request is different for datagram or stream services. For stream services, request is a socket object; for datagram services, request is a pair of string and socket.

finish()

Called after the handle() method to perform any clean-up actions required. The default implementation does nothing. If setup() raises an exception, this function will not be called.

request

The new socket.socket object to be used to communicate with the client.

client_address

Client address returned by BaseServer.get_request().

server

BaseServer object used for handling the request.

class socketserver.StreamRequestHandler

class socketserver.DatagramRequestHandler

These BaseRequestHandler subclasses override the setup() and finish() methods, and provide rfile and wfile attributes.

rfile

A file object from which receives the request is read. Support the io.BufferedIOBase readable interface.

wfile

A file object to which the reply is written. Support the io.BufferedIOBase writable interface

在 3.6 版的變更: wfile also supports the io.BufferedIOBase writable interface.

範例

socketserver.TCPServer 範例

This is the server side:

import socketserver

class MyTCPHandler(socketserver.BaseRequestHandler):
    """
    The request handler class for our server.

    It is instantiated once per connection to the server, and must
    override the handle() method to implement communication to the
    client.
    """

    def handle(self):
        # self.request is the TCP socket connected to the client
        pieces = [b'']
        total = 0
        while b'\n' not in pieces[-1] and total < 10_000:
            pieces.append(self.request.recv(2000))
            total += len(pieces[-1])
        self.data = b''.join(pieces)
        print(f"Received from {self.client_address[0]}:")
        print(self.data.decode("utf-8"))
        # just send back the same data, but upper-cased
        self.request.sendall(self.data.upper())
        # after we return, the socket will be closed.

if __name__ == "__main__":
    HOST, PORT = "localhost", 9999

    # Create the server, binding to localhost on port 9999
    with socketserver.TCPServer((HOST, PORT), MyTCPHandler) as server:
        # Activate the server; this will keep running until you
        # interrupt the program with Ctrl-C
        server.serve_forever()

An alternative request handler class that makes use of streams (file-like objects that simplify communication by providing the standard file interface):

class MyTCPHandler(socketserver.StreamRequestHandler):

    def handle(self):
        # self.rfile is a file-like object created by the handler.
        # We can now use e.g. readline() instead of raw recv() calls.
        # We limit ourselves to 10000 bytes to avoid abuse by the sender.
        self.data = self.rfile.readline(10000).rstrip()
        print(f"{self.client_address[0]} wrote:")
        print(self.data.decode("utf-8"))
        # Likewise, self.wfile is a file-like object used to write back
        # to the client
        self.wfile.write(self.data.upper())

The difference is that the readline() call in the second handler will call recv() multiple times until it encounters a newline character, while the first handler had to use a recv() loop to accumulate data until a newline itself. If it had just used a single recv() without the loop it would just have returned what has been received so far from the client. TCP is stream based: data arrives in the order it was sent, but there is no correlation between client send() or sendall() calls and the number of recv() calls on the server required to receive it.

This is the client side:

import socket
import sys

HOST, PORT = "localhost", 9999
data = " ".join(sys.argv[1:])

# Create a socket (SOCK_STREAM means a TCP socket)
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
    # Connect to server and send data
    sock.connect((HOST, PORT))
    sock.sendall(bytes(data, "utf-8"))
    sock.sendall(b"\n")

    # Receive data from the server and shut down
    received = str(sock.recv(1024), "utf-8")

print("Sent:    ", data)
print("Received:", received)

The output of the example should look something like this:

Server:

$ python TCPServer.py
127.0.0.1 wrote:
b'hello world with TCP'
127.0.0.1 wrote:
b'python is nice'

Client:

$ python TCPClient.py hello world with TCP
Sent:     hello world with TCP
Received: HELLO WORLD WITH TCP
$ python TCPClient.py python is nice
Sent:     python is nice
Received: PYTHON IS NICE

socketserver.UDPServer 範例

This is the server side:

import socketserver

class MyUDPHandler(socketserver.BaseRequestHandler):
    """
    This class works similar to the TCP handler class, except that
    self.request consists of a pair of data and client socket, and since
    there is no connection the client address must be given explicitly
    when sending data back via sendto().
    """

    def handle(self):
        data = self.request[0].strip()
        socket = self.request[1]
        print(f"{self.client_address[0]} wrote:")
        print(data)
        socket.sendto(data.upper(), self.client_address)

if __name__ == "__main__":
    HOST, PORT = "localhost", 9999
    with socketserver.UDPServer((HOST, PORT), MyUDPHandler) as server:
        server.serve_forever()

This is the client side:

import socket
import sys

HOST, PORT = "localhost", 9999
data = " ".join(sys.argv[1:])

# SOCK_DGRAM is the socket type to use for UDP sockets
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# As you can see, there is no connect() call; UDP has no connections.
# Instead, data is directly sent to the recipient via sendto().
sock.sendto(bytes(data + "\n", "utf-8"), (HOST, PORT))
received = str(sock.recv(1024), "utf-8")

print("Sent:    ", data)
print("Received:", received)

The output of the example should look exactly like for the TCP server example.

Asynchronous Mixins

To build asynchronous handlers, use the ThreadingMixIn and ForkingMixIn classes.

An example for the ThreadingMixIn class:

import socket
import threading
import socketserver

class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler):

    def handle(self):
        data = str(self.request.recv(1024), 'ascii')
        cur_thread = threading.current_thread()
        response = bytes("{}: {}".format(cur_thread.name, data), 'ascii')
        self.request.sendall(response)

class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer):
    pass

def client(ip, port, message):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
        sock.connect((ip, port))
        sock.sendall(bytes(message, 'ascii'))
        response = str(sock.recv(1024), 'ascii')
        print("Received: {}".format(response))

if __name__ == "__main__":
    # Port 0 means to select an arbitrary unused port
    HOST, PORT = "localhost", 0

    server = ThreadedTCPServer((HOST, PORT), ThreadedTCPRequestHandler)
    with server:
        ip, port = server.server_address

        # Start a thread with the server -- that thread will then start one
        # more thread for each request
        server_thread = threading.Thread(target=server.serve_forever)
        # Exit the server thread when the main thread terminates
        server_thread.daemon = True
        server_thread.start()
        print("Server loop running in thread:", server_thread.name)

        client(ip, port, "Hello World 1")
        client(ip, port, "Hello World 2")
        client(ip, port, "Hello World 3")

        server.shutdown()

The output of the example should look something like this:

$ python ThreadedTCPServer.py
Server loop running in thread: Thread-1
Received: Thread-2: Hello World 1
Received: Thread-3: Hello World 2
Received: Thread-4: Hello World 3

The ForkingMixIn class is used in the same way, except that the server will spawn a new process for each request. Available only on POSIX platforms that support fork().

http.server — HTTP 伺服器

原始碼：Lib/http/server.py [https://github.com/python/cpython/tree/3.14/Lib/http/server.py]

此模組定義了用於實作 HTTP 伺服器的類別。

警告

http.server is not recommended for production. It only implements basic security checks.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

One class, HTTPServer, is a socketserver.TCPServer subclass. It creates and listens at the HTTP socket, dispatching the requests to a handler. Code to create and run the server looks like this:

def run(server_class=HTTPServer, handler_class=BaseHTTPRequestHandler):
    server_address = ('', 8000)
    httpd = server_class(server_address, handler_class)
    httpd.serve_forever()

class http.server.HTTPServer(server_address, RequestHandlerClass)

This class builds on the TCPServer class by storing the server address as instance variables named server_name and server_port. The server is accessible by the handler, typically through the handler's server instance variable.

class http.server.ThreadingHTTPServer(server_address, RequestHandlerClass)

This class is identical to HTTPServer but uses threads to handle requests by using the ThreadingMixIn. This is useful to handle web browsers pre-opening sockets, on which HTTPServer would wait indefinitely.

在 3.7 版被加入.

class http.server.HTTPSServer(server_address, RequestHandlerClass, bind_and_activate=True, *, certfile, keyfile=None, password=None, alpn_protocols=None)

Subclass of HTTPServer with a wrapped socket using the ssl module. If the ssl module is not available, instantiating a HTTPSServer object fails with a RuntimeError.

The certfile argument is the path to the SSL certificate chain file, and the keyfile is the path to file containing the private key.

A password can be specified for files protected and wrapped with PKCS#8, but beware that this could possibly expose hardcoded passwords in clear.

也參考

See ssl.SSLContext.load_cert_chain() for additional information on the accepted values for certfile, keyfile and password.

When specified, the alpn_protocols argument must be a sequence of strings specifying the "Application-Layer Protocol Negotiation" (ALPN) protocols supported by the server. ALPN allows the server and the client to negotiate the application protocol during the TLS handshake.

By default, it is set to ["http/1.1"], meaning the server supports HTTP/1.1.

在 3.14 版被加入.

class http.server.ThreadingHTTPSServer(server_address, RequestHandlerClass, bind_and_activate=True, *, certfile, keyfile=None, password=None, alpn_protocols=None)

This class is identical to HTTPSServer but uses threads to handle requests by inheriting from ThreadingMixIn. This is analogous to ThreadingHTTPServer only using HTTPSServer.

在 3.14 版被加入.

The HTTPServer, ThreadingHTTPServer, HTTPSServer and ThreadingHTTPSServer must be given a RequestHandlerClass on instantiation, of which this module provides three different variants:

class http.server.BaseHTTPRequestHandler(request, client_address, server)

This class is used to handle the HTTP requests that arrive at the server. By itself, it cannot respond to any actual HTTP requests; it must be subclassed to handle each request method (e.g. GET or POST). BaseHTTPRequestHandler provides a number of class and instance variables, and methods for use by subclasses.

The handler will parse the request and the headers, then call a method specific to the request type. The method name is constructed from the request. For example, for the request method SPAM, the do_SPAM() method will be called with no arguments. All of the relevant information is stored in instance variables of the handler. Subclasses should not need to override or extend the __init__() method.

BaseHTTPRequestHandler 有以下實例變數：

client_address

Contains a tuple of the form (host, port) referring to the client's address.

server

Contains the server instance.

close_connection

Boolean that should be set before handle_one_request() returns, indicating if another request may be expected, or if the connection should be shut down.

requestline

Contains the string representation of the HTTP request line. The terminating CRLF is stripped. This attribute should be set by handle_one_request(). If no valid request line was processed, it should be set to the empty string.

command

Contains the command (request type). For example, 'GET'.

path

Contains the request path. If query component of the URL is present, then path includes the query. Using the terminology of RFC 3986 [https://datatracker.ietf.org/doc/html/rfc3986.html], path here includes hier-part and the query.

request_version

Contains the version string from the request. For example, 'HTTP/1.0'.

headers

Holds an instance of the class specified by the MessageClass class variable. This instance parses and manages the headers in the HTTP request. The parse_headers() function from http.client is used to parse the headers and it requires that the HTTP request provide a valid RFC 5322 [https://datatracker.ietf.org/doc/html/rfc5322.html] style header.

rfile

An io.BufferedIOBase input stream, ready to read from the start of the optional input data.

wfile

Contains the output stream for writing a response back to the client. Proper adherence to the HTTP protocol must be used when writing to this stream in order to achieve successful interoperation with HTTP clients.

在 3.6 版的變更: This is an io.BufferedIOBase stream.

BaseHTTPRequestHandler 擁有以下屬性：

server_version

Specifies the server software version. You may want to override this. The format is multiple whitespace-separated strings, where each string is of the form name[/version]. For example, 'BaseHTTP/0.2'.

sys_version

Contains the Python system version, in a form usable by the version_string method and the server_version class variable. For example, 'Python/1.4'.

error_message_format

Specifies a format string that should be used by send_error() method for building an error response to the client. The string is filled by default with variables from responses based on the status code that passed to send_error().

error_content_type

Specifies the Content-Type HTTP header of error responses sent to the client. The default value is 'text/html'.

protocol_version

Specifies the HTTP version to which the server is conformant. It is sent in responses to let the client know the server's communication capabilities for future requests. If set to 'HTTP/1.1', the server will permit HTTP persistent connections; however, your server must then include an accurate Content-Length header (using send_header()) in all of its responses to clients. For backwards compatibility, the setting defaults to 'HTTP/1.0'.

MessageClass

Specifies an email.message.Message-like class to parse HTTP headers. Typically, this is not overridden, and it defaults to http.client.HTTPMessage.

responses

This attribute contains a mapping of error code integers to two-element tuples containing a short and long message. For example, {code: (shortmessage, longmessage)}. The shortmessage is usually used as the message key in an error response, and longmessage as the explain key. It is used by send_response_only() and send_error() methods.

BaseHTTPRequestHandler 實例擁有以下方法：

handle()

Calls handle_one_request() once (or, if persistent connections are enabled, multiple times) to handle incoming HTTP requests. You should never need to override it; instead, implement appropriate do_*() methods.

handle_one_request()

This method will parse and dispatch the request to the appropriate do_*() method. You should never need to override it.

handle_expect_100()

When an HTTP/1.1 conformant server receives an Expect: 100-continue request header it responds back with a 100 Continue followed by 200 OK headers. This method can be overridden to raise an error if the server does not want the client to continue. For e.g. server can choose to send 417 Expectation Failed as a response header and return False.

在 3.2 版被加入.

send_error(code, message=None, explain=None)

Sends and logs a complete error reply to the client. The numeric code specifies the HTTP error code, with message as an optional, short, human readable description of the error. The explain argument can be used to provide more detailed information about the error; it will be formatted using the error_message_format attribute and emitted, after a complete set of headers, as the response body. The responses attribute holds the default values for message and explain that will be used if no value is provided; for unknown codes the default value for both is the string ???. The body will be empty if the method is HEAD or the response code is one of the following: 1xx, 204 No Content, 205 Reset Content, 304 Not Modified.

在 3.4 版的變更: The error response includes a Content-Length header. Added the explain argument.

send_response(code, message=None)

Adds a response header to the headers buffer and logs the accepted request. The HTTP response line is written to the internal buffer, followed by Server and Date headers. The values for these two headers are picked up from the version_string() and date_time_string() methods, respectively. If the server does not intend to send any other headers using the send_header() method, then send_response() should be followed by an end_headers() call.

在 3.3 版的變更: Headers are stored to an internal buffer and end_headers() needs to be called explicitly.

send_header(keyword, value)

Adds the HTTP header to an internal buffer which will be written to the output stream when either end_headers() or flush_headers() is invoked. keyword should specify the header keyword, with value specifying its value. Note that, after the send_header calls are done, end_headers() MUST BE called in order to complete the operation.

在 3.2 版的變更: Headers are stored in an internal buffer.

send_response_only(code, message=None)

Sends the response header only, used for the purposes when 100 Continue response is sent by the server to the client. The headers not buffered and sent directly the output stream.If the message is not specified, the HTTP message corresponding the response code is sent.

在 3.2 版被加入.

end_headers()

Adds a blank line (indicating the end of the HTTP headers in the response) to the headers buffer and calls flush_headers().

在 3.2 版的變更: The buffered headers are written to the output stream.

flush_headers()

Finally send the headers to the output stream and flush the internal headers buffer.

在 3.3 版被加入.

log_request(code='-', size='-')

Logs an accepted (successful) request. code should specify the numeric HTTP code associated with the response. If a size of the response is available, then it should be passed as the size parameter.

log_error(...)

Logs an error when a request cannot be fulfilled. By default, it passes the message to log_message(), so it takes the same arguments (format and additional values).

log_message(format, ...)

Logs an arbitrary message to sys.stderr. This is typically overridden to create custom error logging mechanisms. The format argument is a standard printf-style format string, where the additional arguments to log_message() are applied as inputs to the formatting. The client ip address and current date and time are prefixed to every message logged.

version_string()

Returns the server software's version string. This is a combination of the server_version and sys_version attributes.

date_time_string(timestamp=None)

Returns the date and time given by timestamp (which must be None or in the format returned by time.time()), formatted for a message header. If timestamp is omitted, it uses the current date and time.

The result looks like 'Sun, 06 Nov 1994 08:49:37 GMT'.

log_date_time_string()

Returns the current date and time, formatted for logging.

address_string()

Returns the client address.

在 3.3 版的變更: Previously, a name lookup was performed. To avoid name resolution delays, it now always returns the IP address.

class http.server.SimpleHTTPRequestHandler(request, client_address, server, directory=None)

This class serves files from the directory directory and below, or the current directory if directory is not provided, directly mapping the directory structure to HTTP requests.

在 3.7 版的變更: 新增 directory 參數。

在 3.9 版的變更: The directory parameter accepts a path-like object.

A lot of the work, such as parsing the request, is done by the base class BaseHTTPRequestHandler. This class implements the do_GET() and do_HEAD() functions.

The following are defined as class-level attributes of SimpleHTTPRequestHandler:

server_version

This will be "SimpleHTTP/" + __version__, where __version__ is defined at the module level.

extensions_map

A dictionary mapping suffixes into MIME types, contains custom overrides for the default system mappings. The mapping is used case-insensitively, and so should contain only lower-cased keys.

在 3.9 版的變更: This dictionary is no longer filled with the default system mappings, but only contains overrides.

SimpleHTTPRequestHandler 類別定義了以下方法：

do_HEAD()

This method serves the 'HEAD' request type: it sends the headers it would send for the equivalent GET request. See the do_GET() method for a more complete explanation of the possible headers.

do_GET()

The request is mapped to a local file by interpreting the request as a path relative to the current working directory.

If the request was mapped to a directory, the directory is checked for a file named index.html or index.htm (in that order). If found, the file's contents are returned; otherwise a directory listing is generated by calling the list_directory() method. This method uses os.listdir() to scan the directory, and returns a 404 error response if the listdir() fails.

If the request was mapped to a file, it is opened. Any OSError exception in opening the requested file is mapped to a 404, 'File not found' error. If there was an 'If-Modified-Since' header in the request, and the file was not modified after this time, a 304, 'Not Modified' response is sent. Otherwise, the content type is guessed by calling the guess_type() method, which in turn uses the extensions_map variable, and the file contents are returned.

A 'Content-type:' header with the guessed content type is output, followed by a 'Content-Length:' header with the file's size and a 'Last-Modified:' header with the file's modification time.

Then follows a blank line signifying the end of the headers, and then the contents of the file are output.

For example usage, see the implementation of the test function in Lib/http/server.py [https://github.com/python/cpython/tree/3.14/Lib/http/server.py].

在 3.7 版的變更: Support of the 'If-Modified-Since' header.

The SimpleHTTPRequestHandler class can be used in the following manner in order to create a very basic webserver serving files relative to the current directory:

import http.server
import socketserver

PORT = 8000

Handler = http.server.SimpleHTTPRequestHandler

with socketserver.TCPServer(("", PORT), Handler) as httpd:
    print("serving at port", PORT)
    httpd.serve_forever()

SimpleHTTPRequestHandler can also be subclassed to enhance behavior, such as using different index file names by overriding the class attribute index_pages.

class http.server.CGIHTTPRequestHandler(request, client_address, server)

This class is used to serve either files or output of CGI scripts from the current directory and below. Note that mapping HTTP hierarchic structure to local directory structure is exactly as in SimpleHTTPRequestHandler.

備註

CGI scripts run by the CGIHTTPRequestHandler class cannot execute redirects (HTTP code 302), because code 200 (script output follows) is sent prior to execution of the CGI script. This pre-empts the status code.

The class will however, run the CGI script, instead of serving it as a file, if it guesses it to be a CGI script. Only directory-based CGI are used --- the other common server configuration is to treat special extensions as denoting CGI scripts.

The do_GET() and do_HEAD() functions are modified to run CGI scripts and serve the output, instead of serving files, if the request leads to somewhere below the cgi_directories path.

CGIHTTPRequestHandler 類別定義了以下資料成員：

cgi_directories

This defaults to ['/cgi-bin', '/htbin'] and describes directories to treat as containing CGI scripts.

CGIHTTPRequestHandler 類別定義了以下方法：

do_POST()

This method serves the 'POST' request type, only allowed for CGI scripts. Error 501, "Can only POST to CGI scripts", is output when trying to POST to a non-CGI url.

Note that CGI scripts will be run with UID of user nobody, for security reasons. Problems with the CGI script will be translated to error 403.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: CGIHTTPRequestHandler is being removed in 3.15. CGI has not been considered a good way to do things for well over a decade. This code has been unmaintained for a while now and sees very little practical use. Retaining it could lead to further security considerations.

命令列介面

http.server can also be invoked directly using the -m switch of the interpreter. The following example illustrates how to serve files relative to the current directory:

python -m http.server [OPTIONS] [port]

可接受以下選項：

port

The server listens to port 8000 by default. The default can be overridden by passing the desired port number as an argument:

python -m http.server 9000

-b, --bind <address>

Specifies a specific address to which it should bind. Both IPv4 and IPv6 addresses are supported. By default, the server binds itself to all interfaces. For example, the following command causes the server to bind to localhost only:

python -m http.server --bind 127.0.0.1

在 3.4 版被加入.

在 3.8 版的變更: 於 --bind 選項中支援 IPv6。

-d, --directory <dir>

Specifies a directory to which it should serve the files. By default, the server uses the current directory. For example, the following command uses a specific directory:

python -m http.server --directory /tmp/

在 3.7 版被加入.

-p, --protocol <version>

Specifies the HTTP version to which the server is conformant. By default, the server is conformant to HTTP/1.0. For example, the following command runs an HTTP/1.1 conformant server:

python -m http.server --protocol HTTP/1.1

在 3.11 版被加入.

--cgi

CGIHTTPRequestHandler can be enabled in the command line by passing the --cgi option:

python -m http.server --cgi

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: http.server command line --cgi support is being removed because CGIHTTPRequestHandler is being removed.

警告

CGIHTTPRequestHandler and the --cgi command-line option are not intended for use by untrusted clients and may be vulnerable to exploitation. Always use within a secure environment.

--tls-cert

Specifies a TLS certificate chain for HTTPS connections:

python -m http.server --tls-cert fullchain.pem

在 3.14 版被加入.

--tls-key

Specifies a private key file for HTTPS connections.

This option requires --tls-cert to be specified.

在 3.14 版被加入.

--tls-password-file

Specifies the password file for password-protected private keys:

python -m http.server \
       --tls-cert cert.pem \
       --tls-key key.pem \
       --tls-password-file password.txt

This option requires --tls-cert` to be specified.

在 3.14 版被加入.

安全性注意事項

SimpleHTTPRequestHandler will follow symbolic links when handling requests, this makes it possible for files outside of the specified directory to be served.

Earlier versions of Python did not scrub control characters from the log messages emitted to stderr from python -m http.server or the default BaseHTTPRequestHandler .log_message implementation. This could allow remote clients connecting to your server to send nefarious control codes to your terminal.

在 3.12 版的變更: Control characters are scrubbed in stderr logs.

http.cookies --- HTTP 狀態管理

原始碼：Lib/http/cookies.py [https://github.com/python/cpython/tree/3.14/Lib/http/cookies.py]

http.cookies 模組定義了 cookie 概念的抽象化的類別，cookie 是一種 HTTP 狀態管理機制。它支援簡單的純字串 cookie，也提供了將任何可序列化的資料型別作為 cookie 值的抽象化。

此模組原先嚴格遵循了 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 和 RFC 2068 [https://datatracker.ietf.org/doc/html/rfc2068.html] 規範所描述的剖析規則。自從發現 MSIE 3.0x 並不遵循這些規範所描述的字元規則，許多目前的瀏覽器和伺服器也在處理 cookie 時放寬了剖析規則。因此，此模組現在使用的剖析規則比之前的更為寬鬆。

字元集 string.ascii_letters、string.digits 和 !#$%&'*+-.^_`|~ 表示此模組在 cookie 名稱 (key) 中允許的合法字元集合。

在 3.3 版的變更: 允許 ':' 作為有效的 cookie 名稱字元。

備註

當遇到無效的 cookie 時，會引發 CookieError，因此如果你的 cookie 資料來自瀏覽器，在剖析時你應該總是為無效資料作準備並捕捉 CookieError。

exception http.cookies.CookieError

因為不符合 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 而引發的例外：不正確的屬性、不正確的 Set-Cookie 標頭等。

class http.cookies.BaseCookie([input])

這個類別是一個類似字典的物件，其中的鍵是字串，而值則是 Morsel 實例。請注意，當設定鍵的值時，值會先被轉換為一個包含該鍵和值的 Morsel。

如果有給定 input，它會被傳遞給 load() 方法。

class http.cookies.SimpleCookie([input])

這個類別繼承自 BaseCookie 並覆寫了 value_decode() 和 value_encode()。SimpleCookie 支援字串作為 cookie 值。當設定值時，SimpleCookie 會呼叫內建的 str() 來將值轉換為字串。從 HTTP 接收的值會保持為字串。

也參考

http.cookiejar 模組

用於網路用戶端的 HTTP cookie 處理。http.cookiejar 和 http.cookies 模組互不相依。

RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] - HTTP 狀態管理機制

這是此模組實作的狀態管理規範。

Cookie 物件

BaseCookie.value_decode(val)

從字串表示回傳 (real_value, coded_value) 的元組。real_value 可以是任何型別。此方法在 BaseCookie 中不做解碼 --- 它存在以便可以被覆寫。

BaseCookie.value_encode(val)

回傳一個元組 (real_value, coded_value)。val 可以是任何型別，但 coded_value 總是會被轉換為字串。此方法在 BaseCookie 中不做編碼 --- 它存在以便可以被覆寫。

一般來說，value_encode() 和 value_decode() 應該在 value_decode 的範圍內是互逆的 (inverse)。

BaseCookie.output(attrs=None, header='Set-Cookie:', sep='\r\n')

回傳一個適合作為 HTTP 標頭來傳送的字串表示。attrs 和 header 會傳送給每個 Morsel 的 output() 方法。sep 用來連接標頭，預設為 '\r\n' (CRLF) 的組合。

BaseCookie.js_output(attrs=None)

回傳一個可嵌入的 JavaScript 片段，如果在支援 JavaScript 的瀏覽器上執行，它的行為會與 HTTP 標頭被傳送的情況相同。

attrs 的意義與 output() 裡的相同。

BaseCookie.load(rawdata)

如果 rawdata 是字串，會將其作為 HTTP_COOKIE 剖析，並將在其中找到的值當作 Morsel 新增。如果它是一個字典，則等同於：

for k, v in rawdata.items():
    cookie[k] = v

Morsel 物件

class http.cookies.Morsel

抽象化一個鍵 / 值對，它有一些 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 屬性。

Morsel 是一種類似字典的物件，其鍵的集合是固定的 --- 有效的 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 屬性，它們是：

expires

path

comment

domain

max-age

secure

version

httponly

samesite

partitioned

屬性 httponly 指定 cookie 僅在 HTTP 請求中傳輸，而不可透過 JavaScript 存取。這是為了減輕某些形式的跨網站腳本攻擊。

samesite 屬性控制瀏覽器要在何時將 cookie 與跨網站請求一起傳送，這有助於減輕 CSRF 攻擊。有效值為 "Strict"（僅在同站請求時傳送）、"Lax"（同站請求和頂層導航時傳送）和 "None"（同站請求和跨站請求時傳送）。使用 "None" 時，必須同時設定 "secure" 屬性，這是現代瀏覽器的要求。

屬性 partitioned 向 user agent（使用者代理）表明這些跨網站 cookie 應該只能在與首次設定 cookie 時相同的頂層情境中使用。要讓 user agent 接受此設定，你必須同時設定 Secure。

此外，建議在設定 partitioned（分區）cookie 時使用 __Host 前綴，使其綁定到主機名稱而非可註冊網域。請閱讀 CHIPS (Cookies Having Independent Partitioned State) [https://github.com/privacycg/CHIPS/blob/main/README.md] 以取得完整細節和範例。

鍵不區分大小寫，其預設值為 ''。

在 3.5 版的變更: __eq__() 現在會考慮 key 和 value。

在 3.7 版的變更: 屬性 key、value 和 coded_value 是唯讀的。請使用 set() 來設定它們。

在 3.8 版的變更: 新增對 samesite 屬性的支援。

在 3.14 版的變更: 新增對 partitioned 屬性的支援。

Morsel.value

cookie 的值。

Morsel.coded_value

cookie 的編碼值 --- 這是應該被傳送的值。

Morsel.key

cookie 的名稱。

Morsel.set(key, value, coded_value)

設定 key、value 和 coded_value 屬性。

Morsel.isReservedKey(K)

K 是否為 Morsel 的鍵集合中的成員。

Morsel.output(attrs=None, header='Set-Cookie:')

回傳適合作為 HTTP 標頭傳送的 Morsel 的字串表示。預設會包含所有屬性，除非有給定 attrs，在此情況下，它應該是一個要使用的屬性的串列。預設的 header 是 "Set-Cookie:"。

Morsel.js_output(attrs=None)

回傳一個可嵌入的 JavaScript 片段，如果在支援 JavaScript 的瀏覽器上執行，它的行為會與 HTTP 標頭被傳送的情況相同。

attrs 的意義與 output() 裡的相同。

Morsel.OutputString(attrs=None)

回傳表示 Morsel 的字串，不包含周圍任何的 HTTP 或 JavaScript。

attrs 的意義與 output() 裡的相同。

Morsel.update(values)

更新 Morsel 字典中的值為 values 字典中的值。如果 values 字典中的任何鍵不是有效的 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 屬性則引發錯誤。

在 3.5 版的變更: 對於無效的鍵會引發錯誤。

Morsel.copy(value)

回傳 Morsel 物件的淺層複製。

在 3.5 版的變更: 回傳 Morsel 物件而不是字典。

Morsel.setdefault(key, value=None)

如果鍵不是一個有效的 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 屬性會引發錯誤，否則行為與 dict.setdefault() 相同。

範例

以下範例示範如何使用 http.cookies 模組。

>>> from http import cookies
>>> C = cookies.SimpleCookie()
>>> C["fig"] = "newton"
>>> C["sugar"] = "wafer"
>>> print(C) # generate HTTP headers
Set-Cookie: fig=newton
Set-Cookie: sugar=wafer
>>> print(C.output()) # same thing
Set-Cookie: fig=newton
Set-Cookie: sugar=wafer
>>> C = cookies.SimpleCookie()
>>> C["rocky"] = "road"
>>> C["rocky"]["path"] = "/cookie"
>>> print(C.output(header="Cookie:"))
Cookie: rocky=road; Path=/cookie
>>> print(C.output(attrs=[], header="Cookie:"))
Cookie: rocky=road
>>> C = cookies.SimpleCookie()
>>> C.load("chips=ahoy; vienna=finger") # load from a string (HTTP header)
>>> print(C)
Set-Cookie: chips=ahoy
Set-Cookie: vienna=finger
>>> C = cookies.SimpleCookie()
>>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=;";')
>>> print(C)
Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=;"
>>> C = cookies.SimpleCookie()
>>> C["oreo"] = "doublestuff"
>>> C["oreo"]["path"] = "/"
>>> print(C)
Set-Cookie: oreo=doublestuff; Path=/
>>> C = cookies.SimpleCookie()
>>> C["twix"] = "none for you"
>>> C["twix"].value
'none for you'
>>> C = cookies.SimpleCookie()
>>> C["number"] = 7 # equivalent to C["number"] = str(7)
>>> C["string"] = "seven"
>>> C["number"].value
'7'
>>> C["string"].value
'seven'
>>> print(C)
Set-Cookie: number=7
Set-Cookie: string=seven

http.cookiejar --- HTTP 用戶端的 Cookie 處理

原始碼：Lib/http/cookiejar.py [https://github.com/python/cpython/tree/3.14/Lib/http/cookiejar.py]

http.cookiejar 模組定義了自動處理 HTTP cookie 的類別。當需要存取小量資料 —— cookies —— 的網站時會非常有用。這些資料會依據網頁伺服器的 HTTP 回應來設置於用戶端機器，並在之後的請求中被回傳到伺服器。

一般的 Netscape cookie 協定和 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 定義的 cookie 協定都會被處理。RFC 2965 的處理預設是關閉的。RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] cookie 會被剖析為 Netscape cookie，然後根據有生效的「策略」來被看作為 Netscape 或 RFC 2965 cookie。http.cookiejar 會嘗試遵循實際上的 Netscape cookie 協定（與原始的 Netscape 規格中的協定有很大的不同），包括 RFC 2965 所引進的 max-age 和 port cookie 屬性。

備註

在 Set-Cookie 和 Set-Cookie2 標頭中出現的各種命名參數（例如 domain 和 expires）通常被稱為 attributes。為了與 Python 的屬性分別開，這個模組的說明檔案改用 cookie-attribute 來稱呼。

模組定義了以下例外：

exception http.cookiejar.LoadError

當從檔案載入 cookies 失敗時，FileCookieJar 的實例會引發這個例外。LoadError 是 OSError 的子類別。

在 3.3 版的變更: LoadError 以前是 IOError 的子型別，現在是 OSError 的別名。

這個模組提供了以下類別：

class http.cookiejar.CookieJar(policy=None)

policy 是實作了 CookiePolicy 介面的一個物件。

CookieJar 類別會儲存 HTTP cookies。它會從 HTTP 請求中抽取出 cookies，並在 HTTP 回應中將它們回傳。CookieJar 實例會在必要時自動使包含的 cookies 過期。它的子類別也負責從檔案或資料庫中儲存和擷取 cookies。

class http.cookiejar.FileCookieJar(filename=None, delayload=None, policy=None)

policy 是實作了 CookiePolicy 介面的一個物件。至於其他引數，請參閱對應屬性的說明文件。

一個可以從磁碟上的檔案載入 Cookie，也可以儲存 Cookie 到磁碟上檔案的 CookieJar。在 load() 或 revert() 方法被呼叫之前，Cookie 並不會從指定的檔案載入。這個類別的子類別有記載於 FileCookieJar 子類別及與網頁瀏覽器的合作 章節。

這個類別不應該直接初始化 - 請使用下面的子類別代替。

在 3.8 版的變更: filename 參數支援傳入一個 path-like object。

class http.cookiejar.CookiePolicy

此類別負責決定是否應從伺服器接受 / 回傳每個 cookie。

class http.cookiejar.DefaultCookiePolicy(blocked_domains=None, allowed_domains=None, netscape=True, rfc2965=False, rfc2109_as_netscape=None, hide_cookie2=False, strict_domain=False, strict_rfc2965_unverifiable=True, strict_ns_unverifiable=False, strict_ns_domain=DefaultCookiePolicy.DomainLiberal, strict_ns_set_initial_dollar=False, strict_ns_set_path=False, secure_protocols=('https', 'wss'))

建構函式引數只能以關鍵字引數的形式傳送。blocked_domains 是我們從不接受 cookies 或回傳 cookies 的網域名稱序列。allowed_domains 如果不是 None，這是我們接受並回傳 cookies 的唯一網域名稱序列。 secure_protocols 是可以加入安全 cookies 的通訊協定序列。預設情況下，https 和 wss（安全 websocket）會被視為安全通訊協定。所有其他引數請參閱 CookiePolicy 及 DefaultCookiePolicy 物件的說明文件。

DefaultCookiePolicy 實作了 Netscape 和 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] cookies 的標準接受/拒絕規則。預設情況下，RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] cookies（即在 Set-Cookie 標頭中接收到的版本 cookie-attribute 為 1 的 cookies）會根據 RFC 2965 規則處理。 但是，如果 RFC 2965 處理被關閉，或者 rfc2109_as_netscape 是 True，RFC 2109 cookie 會被 CookieJar 實例「降級 」為 Netscape cookie，方法是將 Cookie 實例的 version 屬性設為 0。DefaultCookiePolicy 也提供了一些參數來允許對策略進行一些微調。

class http.cookiejar.Cookie

這個類別代表 Netscape、RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] 和 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] cookies。 我們不希望 http.cookiejar 的使用者建立自己的 Cookie 實例。 如有必要，請在 CookieJar 實例上呼叫 make_cookies()。

也參考

urllib.request 模組

URL 打開時會自動處理 cookie。

http.cookies 模組

HTTP cookie 類別，主要用於伺服器端程式碼。 http.cookiejar 和 http.cookies 模組不互相依賴。

https://curl.se/rfc/cookie_spec.html

原始 Netscape cookie 協定的規範。雖然這仍是主流協定，但所有主要瀏覽器（以及 http.cookiejar）實作的「Netscape cookie 協定」與 cookie_spec.html 中實作的協定只有一點相似之處。

RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] - HTTP 狀態管理機制

被 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 所取代，會使用 Set-Cookie 設定 version=1。

RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] - HTTP 狀態管理機制

有錯誤修正的 Netscape 通訊協定。使用 Set-Cookie2 取代 Set-Cookie。未被廣泛使用。

https://kristol.org/cookie/errata.html

未完成的 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 勘誤表。

RFC 2964 [https://datatracker.ietf.org/doc/html/rfc2964.html] - HTTP 狀態管理使用方法

CookieJar 與 FileCookieJar 物件

CookieJar 物件支援 iterator 協定來遍歷包含的 Cookie 物件。

CookieJar 擁有以下方法：

CookieJar.add_cookie_header(request)

將正確的 Cookie 標頭加入 request。

如果策略允許（即 CookieJar 的 CookiePolicy 實例的 rfc2965 和 hide_cookie2 屬性分別為 true 和 false），Cookie2 標頭也會在適當的時候加入。

如 urllib.request 文件所述，request 物件（通常是 urllib.request.Request 的實例）必須支援 get_full_url()、has_header()、get_header()、header_items()、add_unredirected_header() 方法與 host、type、unverifiable、origin_req_host 屬性。

在 3.3 版的變更: request 物件需要 origin_req_host 屬性。已移除對已廢棄方法 get_origin_req_host() 的依賴。

CookieJar.extract_cookies(response, request)

在策略允許的情況下，從 HTTP response 抽取出 cookies 並儲存到 CookieJar 中。

CookieJar 會在 response 引數中尋找允許的 Set-Cookie 和 Set-Cookie2 標頭，並視情況儲存 cookies（需經 CookiePolicy.set_ok() 方法的檢測）。

response 物件（通常是呼叫 urllib.request.urlopen() 的結果或類似的東西）應該支援 info() 方法，它會回傳一個 email.message.Message 的實例。

如 urllib.request 的檔案所說，request 物件（通常是 urllib.request.Request 的實例）必須支援 get_full_url() 方法以及 host、unverifiable 和 origin_req_host 等屬性，該請求被用於設置 cookie-attributes 的預設值並檢查 cookie 是否允許被設置。

在 3.3 版的變更: request 物件需要 origin_req_host 屬性。已移除對已廢棄方法 get_origin_req_host() 的依賴。

CookieJar.set_policy(policy)

設定要使用的 CookiePolicy 實例。

CookieJar.make_cookies(response, request)

回傳從 response 物件抽取出的 Cookie 物件序列。

有關 response 和 request 引數所需的介面，請參閱 extract_cookies() 的說明檔案。

CookieJar.set_cookie_if_ok(cookie, request)

如果策略允許這麼做，設定 Cookie。

CookieJar.set_cookie(cookie)

設定一個 Cookie，不經過策略檢查。

CookieJar.clear([domain[, path[, name]]])

清除一些 cookies。

如果不帶引數地叫用，則清除所有 cookies。如果給定單一引數，則只移除屬於該 domain 的 cookies。如果給定兩個引數，則會移除屬於指定 domain 和 URL path 的 cookie。 如果給定三個引數，則會移除指定 domain、path 和 name 的 cookie。

如果沒有符合的 cookie 存在，則引發 KeyError。

CookieJar.clear_session_cookies()

刪除所有 session cookies。

刪除所有包含有 true discard 屬性的 cookie (通常是因為它們沒有 max-age 或 expires cookie 屬性，或有明確的 discard cookie 屬性)。 對於互動式瀏覽器，工作階段的結束通常對應於關閉瀏覽器視窗。

請注意 save() 方法無論如何都不會儲存 session cookies，除非你透過傳入 true ignore_discard 引數來要求。

FileCookieJar 實例有下列附加方法：

FileCookieJar.save(filename=None, ignore_discard=False, ignore_expires=False)

將 cookies 儲存到檔案中。

這個基底類別會產生 NotImplementedError。子類別可以不實作此方法。

filename 是儲存 cookies 的檔案名稱。 如果 filename 未指定，則會使用 self.filename (其預設值是傳給建構函式的值（如果有）)；如果 self.filename 是 None，則會產生 ValueError。

ignore_discard: 即使設定為捨棄的 cookies 也會儲存。ignore_expires: 保存過期的 cookie

如果檔案已經存在，則會被覆寫，因此會抹除其中包含的所有 cookies。 儲存的 cookies 可以稍後使用 load() 或 revert() 方法還原。

FileCookieJar.load(filename=None, ignore_discard=False, ignore_expires=False)

從檔案中載入 cookies。

舊的 cookies 會被保留，除非被新載入的 cookies 覆蓋。

引數與 save() 相同。

被命名的檔案必須是類別所能正確剖析的格式，否則會產生 LoadError。此外，OSError 可能會被引發，例如檔案不存在時。

在 3.3 版的變更: 以前會引發 IOError，現在它是 OSError 的別名。

FileCookieJar.revert(filename=None, ignore_discard=False, ignore_expires=False)

清除所有 cookies， 並從儲存的檔案重新載入 cookies。

revert() 可以產生與 load() 相同的例外。如果失敗，物件的狀態不會被改變。

FileCookieJar 實例擁有以下公開屬性：

FileCookieJar.filename

保存 cookie 的預設檔案的檔案名稱。 此屬性可以被指定。

FileCookieJar.delayload

若為 true，則從硬盤惰性地載入 cookies。 此屬性不應被指定。 這只是一個提示，因為這只會影響效能，不會影響行為 (除非磁碟上的 cookies 正在改變)。一個 CookieJar 物件可以忽略它。 沒有一個包含在標準函式庫中的 FileCookieJar 類別會惰性地載入 cookies。

FileCookieJar 子類別及與網頁瀏覽器的合作

以下 CookieJar 子類別提供用於讀取和寫入。

class http.cookiejar.MozillaCookieJar(filename=None, delayload=None, policy=None)

一個能夠以 Mozilla cookies.txt 檔案格式（該格式也被 curl 和 Lynx 以及 Netscape 瀏覽器所使用）從磁碟載入和儲存 cookie 的 FileCookieJar。

備註

這會遺失關於 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] cookie 的訊息，以及較新或非標準 cookie 屬性（例如 port）的訊息。

警告

如果 Cookie 遺失或損壞會造成不便，請在儲存之前先備份 Cookie（有些微妙的情況可能會導致檔案在載入/儲存往返過程中發生輕微變化）。

另外請注意，在 Mozilla 執行時儲存的 cookies 會被 Mozilla 刪除。

class http.cookiejar.LWPCookieJar(filename=None, delayload=None, policy=None)

一個 FileCookieJar 可以從 libwww-perl 函式庫的 Set-Cookie3 檔案格式載入 cookies 並儲存 cookies 到磁碟。如果你想要將 cookie 儲存在人類可讀的檔案中，這是很方便的。

在 3.8 版的變更: filename 參數支援傳入一個 path-like object。

CookiePolicy 物件

實作 CookiePolicy 介面的物件有以下方法：

CookiePolicy.set_ok(cookie, request)

回傳值表示的是否接受伺服器 cookie 的布林值。

cookie 是一個 Cookie 實例。 request 是一個實作了 CookieJar.extract_cookies() 文件所定義的介面的物件。

CookiePolicy.return_ok(cookie, request)

回傳布林值，表示 cookie 是否應回傳伺服器。

cookie 是一個 Cookie 實例。 request 是一個實作了 CookieJar.add_cookie_header() 文件所定義的介面的物件。

CookiePolicy.domain_return_ok(domain, request)

在給定 cookie 網域如果不應回傳 cookie，則回傳 False。

此方法為一種最佳化。它消除了檢查每個具有特定網域的 cookie 的需要（這可能需要讀取許多檔案）。從 domain_return_ok() 和 path_return_ok() 回傳 true 會把所有的工作留給 return_ok()。

如果 domain_return_ok() 對 cookie 網域回傳 true，path_return_ok() 就會被用來呼叫 cookie 路徑。否則 path_return_ok() 和 return_ok() 永遠不會被呼叫。如果 path_return_ok() 回傳 true，則會呼叫 return_ok() 附帶的 Cookie 物件本身以進行全面檢查。否則，return_ok() 將永遠不會被呼叫。

請注意，domain_return_ok() 是針對每個 cookie 網域來呼叫的，而不只是針對 request 網域。 例如，如果請求網域是 "www.example.com" ，這個函式可能會同時被 ".example.com" 和 "www.example.com" 呼叫。 同樣的道理也適用於 path_return_ok()。

request 引數與 return_ok() 的說明文件相同。

CookiePolicy.path_return_ok(path, request)

給定 cookie 路徑如不應該回傳 cookie，則回傳 False 。

關於 domain_return_ok() 請見文件。

除了實作上述方法外， CookiePolicy 介面的實作也必須提供下列屬性，指出應該使用哪些通訊協定，以及如何使用。所有這些屬性都可以被指定。

CookiePolicy.netscape

實作 Netscape 協定。

CookiePolicy.rfc2965

實作 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 協定。

CookiePolicy.hide_cookie2

不要在請求中加入 Cookie2 標頭（這個標頭的存在向伺服器表明我們能夠正確剖析 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] cookie）。

以 DefaultCookiePolicy 為子類別定義 CookiePolicy 類別，並覆寫其中的一些或全部方法是最有用的。CookiePolicy 本身可以用做 '無策略'，允許設定和接收任何和所有的 cookies (這不太可能有用)。

DefaultCookiePolicy 物件

執行接受和回傳 cookie 的標準規則。

同時支援 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 和 Netscape cookies。 RFC 2965 的處理預設為關閉。

提供你自己的策略的最簡單方法是覆寫此類別，並在你覆寫的實作中呼叫其方法，然後再加入你自己的額外檢查：

import http.cookiejar
class MyCookiePolicy(http.cookiejar.DefaultCookiePolicy):
    def set_ok(self, cookie, request):
        if not http.cookiejar.DefaultCookiePolicy.set_ok(self, cookie, request):
            return False
        if i_dont_want_to_store_this_cookie(cookie):
            return False
        return True

除了實作 CookiePolicy 介面所需的功能外，這個類別還允許你阻止或允許網域名稱設定和接收 cookies。 還有調整嚴格度的控制選項，可讓你稍微收緊相對寬鬆的 Netscape 通訊協定（代價是阻擋一些良性 cookies）。

提供網域阻止清單和允許清單（預設都關閉）。只有不在阻止清單中和在允許清單中（如果允許清單是有效的）的網域才參與 cookie 設定和回傳。使用 blocked_domains 構造函式引數，以及 blocked_domains() 和 set_blocked_domains() 方法（以及 allowed_domains 的相應引數和方法）。如果你設定了允許清單，你可以透過設定為 None 來再次關閉它。

封鎖或允許清單中不以點開頭的網域必須與 cookie 網域相等才能匹配。 例如，"example.com" 會與封鎖清單項目 "example.com" 匹配，但 "www.example.com" 則不會。 以點開頭的網域也會與更特定的網域相匹配。例如，"www.example.com" 和 "www.coyote.example.com" 都匹配 ".example.com"（但 "example.com" 本身不匹配）。 IP 位址是例外，它們必須完全匹配。例如，如果 blocked_domains 包含 "192.168.1.2" 和 ".168.1.2"，則 192.168.1.2 會被封鎖，但 193.168.1.2 則不會。

DefaultCookiePolicy 實作了下列附加方法：

DefaultCookiePolicy.blocked_domains()

回傳被阻止網域的序列（以元組形式）。

DefaultCookiePolicy.set_blocked_domains(blocked_domains)

設定阻止網域的順序。

DefaultCookiePolicy.is_blocked(domain)

如果 domain 在設定或接收 cookies 的阻止列表上，則回傳 True。

DefaultCookiePolicy.allowed_domains()

回傳 None，或允許網域的序列（以元組形式）。

DefaultCookiePolicy.set_allowed_domains(allowed_domains)

設定允許網域的序列，或 None。

DefaultCookiePolicy.is_not_allowed(domain)

如果 domain 不在設定或接收 cookies 的允許清單上，則回傳 True。

DefaultCookiePolicy 實例有以下屬性，這些屬性都是由同名的建構函式引數初始化，而且都可以被指定。

DefaultCookiePolicy.rfc2109_as_netscape

如果為 true，請求 CookieJar 實例透過設定 Cookie 實例的版本屬性為 0，將 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] cookies (即在 Set-Cookie 標頭中收到的、版本 cookie 屬性為 1 的 cookies) 降級為 Netscape cookies。 預設值是 None，在這種情況下，如果且僅如果 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 處理被關閉，RFC 2109 cookies 才會被降級。 因此，RFC 2109 cookie 在預設情況下被降級。

一般的調整嚴格度的控制選項：

DefaultCookiePolicy.strict_domain

不允許網站設定具有國家代碼頂層域名的兩層域名，如 .co.uk、.gov.uk、.co.nz 等。 這遠遠不夠完美，也不能保證一定有效！

RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 通訊協定調整嚴格度的控制選項：

DefaultCookiePolicy.strict_rfc2965_unverifiable

遵循針對不可驗證事務（transaction）的 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 規則（不可驗證事務通常是由重定向或請求發佈在其它網站的圖片導致的）。 如果該屬性為假值，則永遠不會基於可驗證性而阻止 cookie

Netscape 通訊協定調整嚴格度的控制選項：

DefaultCookiePolicy.strict_ns_unverifiable

即便是對 Netscape cookie 也要應用 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 規則。

DefaultCookiePolicy.strict_ns_domain

指明針對 Netscape cookie 的網域匹配規則的嚴格程度。 可接受的值見下文。

DefaultCookiePolicy.strict_ns_set_initial_dollar

忽略 Set-Cookie: 標頭中名稱以 '$' 開頭的 cookies。

DefaultCookiePolicy.strict_ns_set_path

不允許設置路徑與請求 URL 路徑不匹配的 cookie。

strict_ns_domain 是一系列旗標。它的值由將旗標按位元或組成（例如，DomainStrictNoDots|DomainStrictNonDomain 表示兩個旗標都被設定）。

DefaultCookiePolicy.DomainStrictNoDots

設定 cookie 時，「host 前綴」不得包含點（例如，www.foo.bar.com 不能為 .bar.com 設定 cookie，因為 www.foo 包含一個點）。

DefaultCookiePolicy.DomainStrictNonDomain

未明確指定 domain cookie-attribute 的 Cookie 只能回傳給與設定 Cookie 的網域相同的網域（例如，spam.example.com 將不會回傳來自 example.com 但沒有 domain cookie-attribute 的 Cookie）。

DefaultCookiePolicy.DomainRFC2965Match

設定 cookie 時，需要完整的 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 網域匹配。

為了方便起見，以下屬性是上述旗標最有用的組合：

DefaultCookiePolicy.DomainLiberal

等於 0（即關閉上述所有 Netscape 網域嚴格度旗標）。

DefaultCookiePolicy.DomainStrict

等價於 DomainStrictNoDots|DomainStrictNonDomain。

Cookie 物件

Cookie 實例的 Python 屬性大致對應於各種 cookie 標準中指定的標準 cookie 屬性。 這個對應關係不是一一對應的，因為有複雜的規則來指定預設值，因為 max-age 和 expires cookie 屬性包含相等的訊息，也因為 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] cookie 可能會被 http.cookiejar 從版本 1「降級」到版本 0 (Netscape) cookie。

除了在 CookiePolicy 方法中的罕見情況外，不應該對這些屬性進行指定。 這個類別不會強制執行內部一致性，所以如果你這麼做，你應該要知道你在做什麼。

Cookie.version

整數或 None。 Netscape cookie 的 version 為 0。 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] 和 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] cookie 的 version cookie 屬性為 1。但是，請注意 http.cookiejar 可能會將 RFC 2109 cookie 「降級」 為 Netscape cookie，在這種情況下 version 為 0。

Cookie.name

Cookie 名稱（字串）。

Cookie.value

Cookie 值（字串），或 None。

Cookie.port

代表一個連接埠或一組連接埠的字串 (例如「80」，或「880,8080」)，或 None。

Cookie.domain

Cookie 網域（字串）。

Cookie.path

Cookie 路徑（字串，例如 '/acme/rocket_launchers'）。

Cookie.secure

如果 cookie 只能透過安全連線回傳，則為 True。

Cookie.expires

自 epoch 起計算的整數到期時間，以秒為單位，或 None。另請參閱 is_expired() 方法。

Cookie.discard

如果這是 session cookie，即為 True。

Cookie.comment

來自伺服器解釋此 cookie 功能的字串註解，或 None。

Cookie.comment_url

鏈接到來自伺服器的解釋此 cookie 功能的註釋的 URL，或者為 None。

Cookie.rfc2109

True 如果這個 cookie 是以 RFC 2109 [https://datatracker.ietf.org/doc/html/rfc2109.html] cookie 的形式收到的 (即這個 cookie 是在 Set-Cookie 標頭中收到的，而且在那個標頭中的 Version cookie-attribute 的值是 1)。 提供這個屬性的原因是 http.cookiejar 可能會將 RFC 2109 cookie 「降級」 為 Netscape cookie，在這種情況下 version 的值是 0。

Cookie.port_specified

如果伺服器顯式地指定了一個連接埠或一組連接埠（在 Set-Cookie / Set-Cookie2 標頭中)。

Cookie.domain_specified

如果伺服器明確指定網域，則為 True。

Cookie.domain_initial_dot

如果伺服器明確指定的網域以點 ('.') 開頭，則為 True。

Cookies 可能具有額外的非標準 cookie 屬性。你可以使用下列方法存取這些屬性：

Cookie.has_nonstandard_attr(name)

如果 cookie 具有指定的 cookie 屬性，則回傳 True 。

Cookie.get_nonstandard_attr(name, default=None)

如果 cookie 具有指定的 cookie 屬性，則回傳其值。否則，回傳 default。

Cookie.set_nonstandard_attr(name, value)

設定指定 cookie 屬性的值。

Cookie 類別也定義了以下方法：

Cookie.is_expired(now=None)

如果 cookie 已經超過伺服器要求的過期時間，則回傳 True 。 如果給定了 now （以自紀元起的秒數為單位），則會回傳 cookie 是否已在指定時間過期。

範例

第一個範例展示了 http.cookiejar: 最常見的用法：

import http.cookiejar, urllib.request
cj = http.cookiejar.CookieJar()
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")

本範例說明如何使用你的 Netscape、Mozilla 或 Lynx cookies 打開 URL (假設 Unix/Netscape 會慣用 cookies 檔案的位置)：

import os, http.cookiejar, urllib.request
cj = http.cookiejar.MozillaCookieJar()
cj.load(os.path.join(os.path.expanduser("~"), ".netscape", "cookies.txt"))
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")

下一個範例說明 DefaultCookiePolicy 的使用。開啟 RFC 2965 [https://datatracker.ietf.org/doc/html/rfc2965.html] cookies，在設定和回傳 Netscape cookies 時對網域更嚴格，並阻止某些網域設定 cookies 或讓其回傳：

import urllib.request
from http.cookiejar import CookieJar, DefaultCookiePolicy
policy = DefaultCookiePolicy(
    rfc2965=True, strict_ns_domain=Policy.DomainStrict,
    blocked_domains=["ads.net", ".ads.net"])
cj = CookieJar(policy)
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")

xmlrpc --- XMLRPC 伺服器與用戶模組

XML-RPC 是一種遠端程序呼叫 (Remote Procedure Call) 方法，它使用透過 HTTP 傳輸（transport）的 XML 來做傳遞。有了它，用戶端可以在遠端伺服器上呼叫帶有參數的方法（伺服器以 URI 命名）並取得結構化的資料。

xmlrpc 是一個集合了 XML-RPC 伺服器與用戶端模組實作的套件。這些模組是：

xmlrpc.client

xmlrpc.server

xmlrpc.client --- XML-RPC 用戶端存取

原始碼：Lib/xmlrpc/client.py [https://github.com/python/cpython/tree/3.14/Lib/xmlrpc/client.py]

XML-RPC is a Remote Procedure Call method that uses XML passed via HTTP(S) as a transport. With it, a client can call methods with parameters on a remote server (the server is named by a URI) and get back structured data. This module supports writing XML-RPC client code; it handles all the details of translating between conformable Python objects and XML on the wire.

警告

The xmlrpc.client module is not secure against maliciously constructed data. If you need to parse untrusted or unauthenticated data, see XML 安全性.

在 3.5 版的變更: For HTTPS URIs, xmlrpc.client now performs all the necessary certificate and hostname checks by default.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

class xmlrpc.client.ServerProxy(uri, transport=None, encoding=None, verbose=False, allow_none=False, use_datetime=False, use_builtin_types=False, *, headers=(), context=None)

A ServerProxy instance is an object that manages communication with a remote XML-RPC server. The required first argument is a URI (Uniform Resource Indicator), and will normally be the URL of the server. The optional second argument is a transport factory instance; by default it is an internal SafeTransport instance for https: URLs and an internal HTTP Transport instance otherwise. The optional third argument is an encoding, by default UTF-8. The optional fourth argument is a debugging flag.

The following parameters govern the use of the returned proxy instance. If allow_none is true, the Python constant None will be translated into XML; the default behaviour is for None to raise a TypeError. This is a commonly used extension to the XML-RPC specification, but isn't supported by all clients and servers; see http://ontosys.com/xml-rpc/extensions.php [https://web.archive.org/web/20130120074804/http://ontosys.com/xml-rpc/extensions.php] for a description. The use_builtin_types flag can be used to cause date/time values to be presented as datetime.datetime objects and binary data to be presented as bytes objects; this flag is false by default. datetime.datetime, bytes and bytearray objects may be passed to calls. The headers parameter is an optional sequence of HTTP headers to send with each request, expressed as a sequence of 2-tuples representing the header name and value. (e.g. [('Header-Name', 'value')]). If an HTTPS URL is provided, context may be ssl.SSLContext and configures the SSL settings of the underlying HTTPS connection. The obsolete use_datetime flag is similar to use_builtin_types but it applies only to date/time values.

在 3.3 版的變更: 新增 use_builtin_types 旗標。

在 3.8 版的變更: 新增 headers 參數。

Both the HTTP and HTTPS transports support the URL syntax extension for HTTP Basic Authentication: http://user:pass@host:port/path. The user:pass portion will be base64-encoded as an HTTP 'Authorization' header, and sent to the remote server as part of the connection process when invoking an XML-RPC method. You only need to use this if the remote server requires a Basic Authentication user and password.

The returned instance is a proxy object with methods that can be used to invoke corresponding RPC calls on the remote server. If the remote server supports the introspection API, the proxy can also be used to query the remote server for the methods it supports (service discovery) and fetch other server-associated metadata.

Types that are conformable (e.g. that can be marshalled through XML), include the following (and except where noted, they are unmarshalled as the same Python type):

XML-RPC type

Python type

boolean

bool

int、i1、i2、i4、i8 或 biginteger

int in range from -2147483648 to 2147483647. Values get the <int> tag.

double 或 float

float. Values get the <double> tag.

string

str

array

list or tuple containing conformable elements. Arrays are returned as lists.

struct

dict. Keys must be strings, values may be any conformable type. Objects of user-defined classes can be passed in; only their __dict__ attribute is transmitted.

dateTime.iso8601

DateTime or datetime.datetime. Returned type depends on values of use_builtin_types and use_datetime flags.

base64

Binary, bytes or bytearray. Returned type depends on the value of the use_builtin_types flag.

nil

The None constant. Passing is allowed only if allow_none is true.

bigdecimal

decimal.Decimal. Returned type only.

This is the full set of data types supported by XML-RPC. Method calls may also raise a special Fault instance, used to signal XML-RPC server errors, or ProtocolError used to signal an error in the HTTP/HTTPS transport layer. Both Fault and ProtocolError derive from a base class called Error. Note that the xmlrpc client module currently does not marshal instances of subclasses of built-in types.

When passing strings, characters special to XML such as <, >, and & will be automatically escaped. However, it's the caller's responsibility to ensure that the string is free of characters that aren't allowed in XML, such as the control characters with ASCII values between 0 and 31 (except, of course, tab, newline and carriage return); failing to do this will result in an XML-RPC request that isn't well-formed XML. If you have to pass arbitrary bytes via XML-RPC, use bytes or bytearray classes or the Binary wrapper class described below.

Server is retained as an alias for ServerProxy for backwards compatibility. New code should use ServerProxy.

在 3.5 版的變更: 加入 context 引數。

在 3.6 版的變更: Added support of type tags with prefixes (e.g. ex:nil). Added support of unmarshalling additional types used by Apache XML-RPC implementation for numerics: i1, i2, i8, biginteger, float and bigdecimal. See https://ws.apache.org/xmlrpc/types.html for a description.

也參考

XML-RPC HOWTO [https://tldp.org/HOWTO/XML-RPC-HOWTO/index.html]

A good description of XML-RPC operation and client software in several languages. Contains pretty much everything an XML-RPC client developer needs to know.

XML-RPC Introspection [https://xmlrpc-c.sourceforge.io/introspection.html]

Describes the XML-RPC protocol extension for introspection.

XML-RPC Specification [http://xmlrpc.scripting.com/spec.html]

The official specification.

ServerProxy 物件

A ServerProxy instance has a method corresponding to each remote procedure call accepted by the XML-RPC server. Calling the method performs an RPC, dispatched by both name and argument signature (e.g. the same method name can be overloaded with multiple argument signatures). The RPC finishes by returning a value, which may be either returned data in a conformant type or a Fault or ProtocolError object indicating an error.

Servers that support the XML introspection API support some common methods grouped under the reserved system attribute:

ServerProxy.system.listMethods()

This method returns a list of strings, one for each (non-system) method supported by the XML-RPC server.

ServerProxy.system.methodSignature(name)

This method takes one parameter, the name of a method implemented by the XML-RPC server. It returns an array of possible signatures for this method. A signature is an array of types. The first of these types is the return type of the method, the rest are parameters.

Because multiple signatures (ie. overloading) is permitted, this method returns a list of signatures rather than a singleton.

Signatures themselves are restricted to the top level parameters expected by a method. For instance if a method expects one array of structs as a parameter, and it returns a string, its signature is simply "string, array". If it expects three integers and returns a string, its signature is "string, int, int, int".

If no signature is defined for the method, a non-array value is returned. In Python this means that the type of the returned value will be something other than list.

ServerProxy.system.methodHelp(name)

This method takes one parameter, the name of a method implemented by the XML-RPC server. It returns a documentation string describing the use of that method. If no such string is available, an empty string is returned. The documentation string may contain HTML markup.

在 3.5 版的變更: Instances of ServerProxy support the context manager protocol for closing the underlying transport.

A working example follows. The server code:

from xmlrpc.server import SimpleXMLRPCServer

def is_even(n):
    return n % 2 == 0

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(is_even, "is_even")
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client

with xmlrpc.client.ServerProxy("http://localhost:8000/") as proxy:
    print("3 is even: %s" % str(proxy.is_even(3)))
    print("100 is even: %s" % str(proxy.is_even(100)))

日期時間物件

class xmlrpc.client.DateTime

This class may be initialized with seconds since the epoch, a time tuple, an ISO 8601 time/date string, or a datetime.datetime instance. It has the following methods, supported mainly for internal use by the marshalling/unmarshalling code:

decode(string)

Accept a string as the instance's new time value.

encode(out)

Write the XML-RPC encoding of this DateTime item to the out stream object.

It also supports certain of Python's built-in operators through rich comparison and __repr__() methods.

A working example follows. The server code:

import datetime
from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client

def today():
    today = datetime.datetime.today()
    return xmlrpc.client.DateTime(today)

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(today, "today")
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client
import datetime

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")

today = proxy.today()
# 將 ISO8601 字串轉換成 datetime 物件
converted = datetime.datetime.strptime(today.value, "%Y%m%dT%H:%M:%S")
print("Today: %s" % converted.strftime("%d.%m.%Y, %H:%M"))

Binary Objects

class xmlrpc.client.Binary

This class may be initialized from bytes data (which may include NULs). The primary access to the content of a Binary object is provided by an attribute:

data

The binary data encapsulated by the Binary instance. The data is provided as a bytes object.

Binary objects have the following methods, supported mainly for internal use by the marshalling/unmarshalling code:

decode(bytes)

Accept a base64 bytes object and decode it as the instance's new data.

encode(out)

Write the XML-RPC base 64 encoding of this binary item to the out stream object.

The encoded data will have newlines every 76 characters as per RFC 2045 section 6.8 [https://datatracker.ietf.org/doc/html/rfc2045.html#section-6.8], which was the de facto standard base64 specification when the XML-RPC spec was written.

It also supports certain of Python's built-in operators through __eq__() and __ne__() methods.

Example usage of the binary objects. We're going to transfer an image over XMLRPC:

from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client

def python_logo():
    with open("python_logo.jpg", "rb") as handle:
        return xmlrpc.client.Binary(handle.read())

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(python_logo, 'python_logo')

server.serve_forever()

The client gets the image and saves it to a file:

import xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
with open("fetched_python_logo.jpg", "wb") as handle:
    handle.write(proxy.python_logo().data)

Fault Objects

class xmlrpc.client.Fault

A Fault object encapsulates the content of an XML-RPC fault tag. Fault objects have the following attributes:

faultCode

An int indicating the fault type.

faultString

A string containing a diagnostic message associated with the fault.

In the following example we're going to intentionally cause a Fault by returning a complex type object. The server code:

from xmlrpc.server import SimpleXMLRPCServer

# A marshalling error is going to occur because we're returning a
# complex number
def add(x, y):
    return x+y+0j

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(add, 'add')

server.serve_forever()

The client code for the preceding server:

import xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
try:
    proxy.add(2, 5)
except xmlrpc.client.Fault as err:
    print("A fault occurred")
    print("Fault code: %d" % err.faultCode)
    print("Fault string: %s" % err.faultString)

ProtocolError 物件

class xmlrpc.client.ProtocolError

A ProtocolError object describes a protocol error in the underlying transport layer (such as a 404 'not found' error if the server named by the URI does not exist). It has the following attributes:

url

The URI or URL that triggered the error.

errcode

The error code.

errmsg

The error message or diagnostic string.

headers

A dict containing the headers of the HTTP/HTTPS request that triggered the error.

In the following example we're going to intentionally cause a ProtocolError by providing an invalid URI:

import xmlrpc.client

# create a ServerProxy with a URI that doesn't respond to XMLRPC requests
proxy = xmlrpc.client.ServerProxy("http://google.com/")

try:
    proxy.some_method()
except xmlrpc.client.ProtocolError as err:
    print("A protocol error occurred")
    print("URL: %s" % err.url)
    print("HTTP/HTTPS headers: %s" % err.headers)
    print("Error code: %d" % err.errcode)
    print("Error message: %s" % err.errmsg)

MultiCall 物件

The MultiCall object provides a way to encapsulate multiple calls to a remote server into a single request [1].

class xmlrpc.client.MultiCall(server)

Create an object used to boxcar method calls. server is the eventual target of the call. Calls can be made to the result object, but they will immediately return None, and only store the call name and parameters in the MultiCall object. Calling the object itself causes all stored calls to be transmitted as a single system.multicall request. The result of this call is a generator; iterating over this generator yields the individual results.

A usage example of this class follows. The server code:

from xmlrpc.server import SimpleXMLRPCServer

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

def multiply(x, y):
    return x * y

def divide(x, y):
    return x // y

# A simple server with simple arithmetic functions
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_multicall_functions()
server.register_function(add, 'add')
server.register_function(subtract, 'subtract')
server.register_function(multiply, 'multiply')
server.register_function(divide, 'divide')
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
multicall = xmlrpc.client.MultiCall(proxy)
multicall.add(7, 3)
multicall.subtract(7, 3)
multicall.multiply(7, 3)
multicall.divide(7, 3)
result = multicall()

print("7+3=%d, 7-3=%d, 7*3=%d, 7//3=%d" % tuple(result))

便捷的函式

xmlrpc.client.dumps(params, methodname=None, methodresponse=None, encoding=None, allow_none=False)

Convert params into an XML-RPC request, or into a response if methodresponse is true. params can be either a tuple of arguments or an instance of the Fault exception class. If methodresponse is true, only a single value can be returned, meaning that params must be of length 1. encoding, if supplied, is the encoding to use in the generated XML; the default is UTF-8. Python's None value cannot be used in standard XML-RPC; to allow using it via an extension, provide a true value for allow_none.

xmlrpc.client.loads(data, use_datetime=False, use_builtin_types=False)

Convert an XML-RPC request or response into Python objects, a (params, methodname). params is a tuple of argument; methodname is a string, or None if no method name is present in the packet. If the XML-RPC packet represents a fault condition, this function will raise a Fault exception. The use_builtin_types flag can be used to cause date/time values to be presented as datetime.datetime objects and binary data to be presented as bytes objects; this flag is false by default.

The obsolete use_datetime flag is similar to use_builtin_types but it applies only to date/time values.

在 3.3 版的變更: 新增 use_builtin_types 旗標。

Example of Client Usage

# simple test program (from the XML-RPC specification)
from xmlrpc.client import ServerProxy, Error

# server = ServerProxy("http://localhost:8000") # local server
with ServerProxy("http://betty.userland.com") as proxy:

    print(proxy)

    try:
        print(proxy.examples.getStateName(41))
    except Error as v:
        print("ERROR", v)

To access an XML-RPC server through a HTTP proxy, you need to define a custom transport. The following example shows how:

import http.client
import xmlrpc.client

class ProxiedTransport(xmlrpc.client.Transport):

    def set_proxy(self, host, port=None, headers=None):
        self.proxy = host, port
        self.proxy_headers = headers

    def make_connection(self, host):
        connection = http.client.HTTPConnection(*self.proxy)
        connection.set_tunnel(host, headers=self.proxy_headers)
        self._connection = host, connection
        return connection

transport = ProxiedTransport()
transport.set_proxy('proxy-server', 8080)
server = xmlrpc.client.ServerProxy('http://betty.userland.com', transport=transport)
print(server.examples.getStateName(41))

Example of Client and Server Usage

See SimpleXMLRPCServer 範例.

註腳

[1]

This approach has been first presented in a discussion on xmlrpc.com [https://web.archive.org/web/20060624230303/http://www.xmlrpc.com/discuss/msgReader$1208?mode=topic].

xmlrpc.server --- 基本 XML-RPC 伺服器

原始碼：Lib/xmlrpc/server.py [https://github.com/python/cpython/tree/3.14/Lib/xmlrpc/server.py]

xmlrpc.server 模組為以 Python 撰寫的 XML-RPC 伺服器提供了基本的伺服器框架。伺服器可以是獨立執行的（使用 SimpleXMLRPCServer），或嵌入在 CGI 環境中（使用 CGIXMLRPCRequestHandler）。

警告

xmlrpc.server 模組對於惡意建構的資料並不安全。如果你需要剖析不受信任或未經驗證的資料，請參閱 XML 安全性。

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

class xmlrpc.server.SimpleXMLRPCServer(addr, requestHandler=SimpleXMLRPCRequestHandler, logRequests=True, allow_none=False, encoding=None, bind_and_activate=True, use_builtin_types=False)

建立一個新的伺服器實例。此類別提供了可被 XML-RPC 協定呼叫之函式的註冊方法。requestHandler 參數應該是請求處理器實例的工廠（factory）；它預設為 SimpleXMLRPCRequestHandler。addr 和 requestHandler 參數會傳遞給 socketserver.TCPServer 建構函式。如果 logRequests 為 true（預設值），請求會被記錄；將此參數設定為 false 將關閉記錄。allow_none 和 encoding 參數會傳遞給 xmlrpc.client 並控制從伺服器回傳的 XML-RPC 回應。bind_and_activate 參數控制建構函式是否立即呼叫 server_bind() 和 server_activate()；它預設為 true。將其設定為 false 允許程式碼在位址被綁定之前操作 allow_reuse_address 類別變數。use_builtin_types 參數會傳遞給 loads() 函式，並控制在接收到日期/時間值或二進位資料時要處理哪些型別；它預設為 false。

在 3.3 版的變更: 新增 use_builtin_types 旗標。

class xmlrpc.server.CGIXMLRPCRequestHandler(allow_none=False, encoding=None, use_builtin_types=False)

建立一個新的實例以在 CGI 環境中處理 XML-RPC 請求。allow_none 和 encoding 參數會傳遞給 xmlrpc.client 並控制從伺服器回傳的 XML-RPC 回應。use_builtin_types 參數會傳遞給 loads() 函式，並控制在接收到日期/時間值或二進位資料時要處理哪些型別；它預設為 false。

在 3.3 版的變更: 新增 use_builtin_types 旗標。

class xmlrpc.server.SimpleXMLRPCRequestHandler

建立一個新的請求處理器實例。此請求處理器支援 POST 請求，並修改日誌記錄功能以遵守 SimpleXMLRPCServer 建構函式的 logRequests 參數。

SimpleXMLRPCServer 物件

SimpleXMLRPCServer 類別是基於 socketserver.TCPServer 的，並提供了建立簡單、獨立 XML-RPC 伺服器的方式。

SimpleXMLRPCServer.register_function(function=None, name=None)

註冊一個可以回應 XML-RPC 請求的函式。如果有給定 name，它將成為與 function 關聯的方法名稱，否則將使用 function.__name__。name 是一個字串，可以包含在 Python 識別符中不合法的字元，包括句點字元。

此方法也可以用作裝飾器。當用作裝飾器時，name 只能作為關鍵字引數給定，以在 name 下註冊 function。如果沒有給定 name，將使用 function.__name__。

在 3.7 版的變更: register_function() 也可被當作裝飾器使用。

SimpleXMLRPCServer.register_instance(instance, allow_dotted_names=False)

註冊一個物件，用於公開尚未使用 register_function() 註冊的方法名稱。如果 instance 包含 _dispatch() 方法，它會被呼叫並傳入請求的方法名稱和來自請求的參數。其 API 為 def _dispatch(self, method, params)（注意 params 不代表可變引數列表）。如果它呼叫底層函式來執行其任務，該函式會以 func(*params) 的方式被呼叫，展開參數列表。來自 _dispatch() 的回傳值會作為結果回傳給用戶端。如果 instance 沒有 _dispatch() 方法，則會搜尋與請求方法名稱匹配的屬性。

如果可選的 allow_dotted_names 引數為 true 且實例沒有 _dispatch() 方法，那麼如果請求的方法名稱包含句點，方法名稱的每個組成部分會被單獨搜尋，從而執行簡單的階層式搜尋。從此搜尋中找到的值會以來自請求的參數被呼叫，並將回傳值傳回給用戶端。

警告

啟用 allow_dotted_names 選項允許入侵者存取你模組的全域變數，並可能允許入侵者在你的機器上執行任意程式碼。請在安全、封閉的網路上才使用此選項。

SimpleXMLRPCServer.register_introspection_functions()

註冊 XML-RPC 自我檢查函式 (introspection functions) system.listMethods、system.methodHelp 和 system.methodSignature。

SimpleXMLRPCServer.register_multicall_functions()

註冊 XML-RPC 多重呼叫函式 (multicall function) system.multicall。

SimpleXMLRPCRequestHandler.rpc_paths

一個屬性值，必須是一個元組，列出接收 XML-RPC 請求的 URL 的有效路徑部分。發布到其他路徑的請求將導致 404 "no such page" HTTP 錯誤。如果此元組為空，所有路徑都將被視為有效。預設值為 ('/', '/RPC2')。

SimpleXMLRPCServer 範例

伺服器程式碼：

from xmlrpc.server import SimpleXMLRPCServer
from xmlrpc.server import SimpleXMLRPCRequestHandler

# 限制為特定路徑。
class RequestHandler(SimpleXMLRPCRequestHandler):
    rpc_paths = ('/RPC2',)

# 建立伺服器
with SimpleXMLRPCServer(('localhost', 8000),
                        requestHandler=RequestHandler) as server:
    server.register_introspection_functions()

    # 註冊 pow() 函式；這將使用 pow.__name__ 的值作為名稱，即 'pow'。
    server.register_function(pow)

    # 以不同的名稱註冊函式
    def adder_function(x, y):
        return x + y
    server.register_function(adder_function, 'add')

    # 註冊一個實例；該實例的所有方法都會被發布為 XML-RPC 方法（在此例中僅 'mul'）。
    class MyFuncs:
        def mul(self, x, y):
            return x * y

    server.register_instance(MyFuncs())

    # 執行伺服器的主迴圈
    server.serve_forever()

以下用戶端程式碼將呼叫前述伺服器提供的方法：

import xmlrpc.client

s = xmlrpc.client.ServerProxy('http://localhost:8000')
print(s.pow(2,3))  # 回傳 2**3 = 8
print(s.add(2,3))  # 回傳 5
print(s.mul(5,2))  # 回傳 5*2 = 10

# 印出可用方法列表
print(s.system.listMethods())

register_function() 也可以用作裝飾器。前述的伺服器範例可以用裝飾器方式註冊函式：

from xmlrpc.server import SimpleXMLRPCServer
from xmlrpc.server import SimpleXMLRPCRequestHandler

class RequestHandler(SimpleXMLRPCRequestHandler):
    rpc_paths = ('/RPC2',)

with SimpleXMLRPCServer(('localhost', 8000),
                        requestHandler=RequestHandler) as server:
    server.register_introspection_functions()

    # 註冊 pow() 函式；這將使用 pow.__name__ 的值作為名稱，即 'pow'。
    server.register_function(pow)

    # 使用 register_function 作為裝飾器以不同的名稱註冊函式。
    # *name* 只能作為關鍵字引數給定。
    @server.register_function(name='add')
    def adder_function(x, y):
        return x + y

    # 以 function.__name__ 註冊函式。
    @server.register_function
    def mul(x, y):
        return x * y

    server.serve_forever()

以下包含在 Lib/xmlrpc/server.py 模組中的範例展示了一個允許點分隔名稱並註冊多重呼叫函式的伺服器。

警告

啟用 allow_dotted_names 選項來允許入侵者存取你模組的全域變數，並可能允許入侵者在你的機器上執行任意程式碼。請在安全、封閉的網路中才使用此範例。

import datetime

class ExampleService:
    def getData(self):
        return '42'

    class currentTime:
        @staticmethod
        def getCurrentTime():
            return datetime.datetime.now()

with SimpleXMLRPCServer(("localhost", 8000)) as server:
    server.register_function(pow)
    server.register_function(lambda x,y: x+y, 'add')
    server.register_instance(ExampleService(), allow_dotted_names=True)
    server.register_multicall_functions()
    print('Serving XML-RPC on localhost port 8000')
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        print("\nKeyboard interrupt received, exiting.")
        sys.exit(0)

此 ExampleService 示範可以從命令列觸發：

python -m xmlrpc.server

與上述伺服器互動的用戶端被包含在 Lib/xmlrpc/client.py 中：

server = ServerProxy("http://localhost:8000")

try:
    print(server.currentTime.getCurrentTime())
except Error as v:
    print("ERROR", v)

multi = MultiCall(server)
multi.getData()
multi.pow(2,9)
multi.add(1,2)
try:
    for response in multi():
        print(response)
except Error as v:
    print("ERROR", v)

與示範 XMLRPC 伺服器互動的此用戶端可以如下呼叫：

python -m xmlrpc.client

CGIXMLRPCRequestHandler

CGIXMLRPCRequestHandler 類別可用於處理發送到 Python CGI 指令稿的 XML-RPC 請求。

CGIXMLRPCRequestHandler.register_function(function=None, name=None)

註冊一個可以回應 XML-RPC 請求的函式。如果有給定 name，它將成為與 function 關聯的方法名稱，否則將使用 function.__name__。name 是一個字串，可以包含在 Python 識別符中不合法的字元，包括句點字元。

此方法也可以用作裝飾器。當用作裝飾器時，name 只能作為關鍵字引數給定，以在 name 下註冊 function。如果沒有給定 name，將使用 function.__name__。

在 3.7 版的變更: register_function() 也可被當作裝飾器使用。

CGIXMLRPCRequestHandler.register_instance(instance)

註冊一個物件，用於公開尚未使用 register_function() 註冊的方法名稱。如果實例包含 _dispatch() 方法，它會以請求的方法名稱和來自請求的參數來被呼叫；回傳值會作為結果回傳給用戶端。如果實例沒有 _dispatch() 方法，則會搜尋與請求方法名稱匹配的屬性；如果請求的方法名稱包含句點，方法名稱的每個組成部分會被單獨搜尋，從而執行簡單的階層式搜尋。從此搜尋中找到的值會以來自請求的參數被呼叫，並將回傳值傳回給用戶端。

CGIXMLRPCRequestHandler.register_introspection_functions()

註冊 XML-RPC 自我檢查函式 system.listMethods、system.methodHelp 和 system.methodSignature。

CGIXMLRPCRequestHandler.register_multicall_functions()

註冊 XML-RPC 多重呼叫函式 system.multicall。

CGIXMLRPCRequestHandler.handle_request(request_text=None)

處理 XML-RPC 請求。如果給定 request_text，它應該是 HTTP 伺服器提供的 POST 資料，否則將使用 stdin 的內容。

範例：

class MyFuncs:
    def mul(self, x, y):
        return x * y

handler = CGIXMLRPCRequestHandler()
handler.register_function(pow)
handler.register_function(lambda x,y: x+y, 'add')
handler.register_introspection_functions()
handler.register_instance(MyFuncs())
handler.handle_request()

記錄 XMLRPC 伺服器

這些類別擴充了上述類別，來為 HTTP GET 請求於回應中提供 HTML 文件。伺服器可以是獨立執行的（使用 DocXMLRPCServer），或嵌入在 CGI 環境中（使用 DocCGIXMLRPCRequestHandler）。

class xmlrpc.server.DocXMLRPCServer(addr, requestHandler=DocXMLRPCRequestHandler, logRequests=True, allow_none=False, encoding=None, bind_and_activate=True, use_builtin_types=True)

建立一個新的伺服器實例。所有參數的意義與 SimpleXMLRPCServer 相同；requestHandler 預設為 DocXMLRPCRequestHandler。

在 3.3 版的變更: 新增 use_builtin_types 旗標。

class xmlrpc.server.DocCGIXMLRPCRequestHandler

建立一個新的實例以在 CGI 環境中處理 XML-RPC 請求。

class xmlrpc.server.DocXMLRPCRequestHandler

建立一個新的請求處理器實例。此請求處理器支援 XML-RPC POST 請求、文件 GET 請求，並修改日誌記錄功能以遵守 DocXMLRPCServer 建構函式的 logRequests 參數。

DocXMLRPCServer 物件

DocXMLRPCServer 類別衍生自 SimpleXMLRPCServer，並提供了建立自我記錄 (self-documenting) 的獨立 XML-RPC 伺服器的方式。HTTP POST 請求會被作為 XML-RPC 方法呼叫來處理。HTTP GET 請求會透過產生 pydoc 風格的 HTML 文件來處理。這允許伺服器提供自己的網頁文件。

DocXMLRPCServer.set_server_title(server_title)

設定在產生的 HTML 文件中使用的標題。此標題將用於 HTML "title" 元素內。

DocXMLRPCServer.set_server_name(server_name)

設定在產生的 HTML 文件中使用的名稱。此名稱將顯示在產生的文件頂部的 "h1" 元素內。

DocXMLRPCServer.set_server_documentation(server_documentation)

設定在產生的 HTML 文件中使用的描述。此描述將作為一個段落顯示在文件中伺服器名稱的下方。

DocCGIXMLRPCRequestHandler

DocCGIXMLRPCRequestHandler 類別衍生自 CGIXMLRPCRequestHandler，並提供了建立自我記錄的 XML-RPC CGI 指令稿的方法。HTTP POST 請求會被作為 XML-RPC 方法呼叫來處理。HTTP GET 請求會透過產生 pydoc 風格的 HTML 文件來處理。這允許伺服器提供自己的網頁文件。

DocCGIXMLRPCRequestHandler.set_server_title(server_title)

設定在產生的 HTML 文件中使用的標題。此標題將用於 HTML "title" 元素內。

DocCGIXMLRPCRequestHandler.set_server_name(server_name)

設定在產生的 HTML 文件中使用的名稱。此名稱將顯示在產生的文件頂部的 "h1" 元素內。

DocCGIXMLRPCRequestHandler.set_server_documentation(server_documentation)

設定在產生的 HTML 文件中使用的描述。此描述將作為一個段落顯示在文件中伺服器名稱的下方。

ipaddress --- IPv4/IPv6 操作函式庫

原始碼：Lib/ipaddress.py [https://github.com/python/cpython/tree/3.14/Lib/ipaddress.py]

ipaddress provides the capabilities to create, manipulate and operate on IPv4 and IPv6 addresses and networks.

The functions and classes in this module make it straightforward to handle various tasks related to IP addresses, including checking whether or not two hosts are on the same subnet, iterating over all hosts in a particular subnet, checking whether or not a string represents a valid IP address or network definition, and so on.

This is the full module API reference—for an overview and introduction, see ipaddress 模組介紹.

在 3.3 版被加入.

Convenience factory functions

The ipaddress module provides factory functions to conveniently create IP addresses, networks and interfaces:

ipaddress.ip_address(address)

Return an IPv4Address or IPv6Address object depending on the IP address passed as argument. Either IPv4 or IPv6 addresses may be supplied; integers less than 2**32 will be considered to be IPv4 by default. A ValueError is raised if address does not represent a valid IPv4 or IPv6 address.

>>> ipaddress.ip_address('192.168.0.1')
IPv4Address('192.168.0.1')
>>> ipaddress.ip_address('2001:db8::')
IPv6Address('2001:db8::')

ipaddress.ip_network(address, strict=True)

Return an IPv4Network or IPv6Network object depending on the IP address passed as argument. address is a string or integer representing the IP network. Either IPv4 or IPv6 networks may be supplied; integers less than 2**32 will be considered to be IPv4 by default. strict is passed to IPv4Network or IPv6Network constructor. A ValueError is raised if address does not represent a valid IPv4 or IPv6 address, or if the network has host bits set.

>>> ipaddress.ip_network('192.168.0.0/28')
IPv4Network('192.168.0.0/28')

ipaddress.ip_interface(address)

Return an IPv4Interface or IPv6Interface object depending on the IP address passed as argument. address is a string or integer representing the IP address. Either IPv4 or IPv6 addresses may be supplied; integers less than 2**32 will be considered to be IPv4 by default. A ValueError is raised if address does not represent a valid IPv4 or IPv6 address.

One downside of these convenience functions is that the need to handle both IPv4 and IPv6 formats means that error messages provide minimal information on the precise error, as the functions don't know whether the IPv4 or IPv6 format was intended. More detailed error reporting can be obtained by calling the appropriate version specific class constructors directly.

IP Addresses

Address objects

The IPv4Address and IPv6Address objects share a lot of common attributes. Some attributes that are only meaningful for IPv6 addresses are also implemented by IPv4Address objects, in order to make it easier to write code that handles both IP versions correctly. Address objects are hashable, so they can be used as keys in dictionaries.

class ipaddress.IPv4Address(address)

Construct an IPv4 address. An AddressValueError is raised if address is not a valid IPv4 address.

The following constitutes a valid IPv4 address:

A string in decimal-dot notation, consisting of four decimal integers in the inclusive range 0--255, separated by dots (e.g. 192.168.0.1). Each integer represents an octet (byte) in the address. Leading zeroes are not tolerated to prevent confusion with octal notation.

一個可以放入 32 位元的整數。

An integer packed into a bytes object of length 4 (most significant octet first).

>>> ipaddress.IPv4Address('192.168.0.1')
IPv4Address('192.168.0.1')
>>> ipaddress.IPv4Address(3232235521)
IPv4Address('192.168.0.1')
>>> ipaddress.IPv4Address(b'\xC0\xA8\x00\x01')
IPv4Address('192.168.0.1')

在 3.8 版的變更: Leading zeros are tolerated, even in ambiguous cases that look like octal notation.

在 3.9.5 版的變更: Leading zeros are no longer tolerated and are treated as an error. IPv4 address strings are now parsed as strict as glibc inet_pton().

version

The appropriate version number: 4 for IPv4, 6 for IPv6.

在 3.14 版的變更: Made available on the class.

max_prefixlen

The total number of bits in the address representation for this version: 32 for IPv4, 128 for IPv6.

The prefix defines the number of leading bits in an address that are compared to determine whether or not an address is part of a network.

在 3.14 版的變更: Made available on the class.

compressed

exploded

The string representation in dotted decimal notation. Leading zeroes are never included in the representation.

As IPv4 does not define a shorthand notation for addresses with octets set to zero, these two attributes are always the same as str(addr) for IPv4 addresses. Exposing these attributes makes it easier to write display code that can handle both IPv4 and IPv6 addresses.

packed

The binary representation of this address - a bytes object of the appropriate length (most significant octet first). This is 4 bytes for IPv4 and 16 bytes for IPv6.

reverse_pointer

The name of the reverse DNS PTR record for the IP address, e.g.:

>>> ipaddress.ip_address("127.0.0.1").reverse_pointer
'1.0.0.127.in-addr.arpa'
>>> ipaddress.ip_address("2001:db8::1").reverse_pointer
'1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa'

This is the name that could be used for performing a PTR lookup, not the resolved hostname itself.

在 3.5 版被加入.

is_multicast

True if the address is reserved for multicast use. See RFC 3171 [https://datatracker.ietf.org/doc/html/rfc3171.html] (for IPv4) or RFC 2373 [https://datatracker.ietf.org/doc/html/rfc2373.html] (for IPv6).

is_private

True if the address is defined as not globally reachable by iana-ipv4-special-registry [https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml] (for IPv4) or iana-ipv6-special-registry [https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml] (for IPv6) with the following exceptions:

is_private is False for the shared address space (100.64.0.0/10)

For IPv4-mapped IPv6-addresses the is_private value is determined by the semantics of the underlying IPv4 addresses and the following condition holds (see IPv6Address.ipv4_mapped):

address.is_private == address.ipv4_mapped.is_private

is_private has value opposite to is_global, except for the shared address space (100.64.0.0/10 range) where they are both False.

在 3.13 版的變更: Fixed some false positives and false negatives.

192.0.0.0/24 is considered private with the exception of 192.0.0.9/32 and 192.0.0.10/32 (previously: only the 192.0.0.0/29 sub-range was considered private).

64:ff9b:1::/48 被視為私有。

2002::/16 被視為私有。

There are exceptions within 2001::/23 (otherwise considered private): 2001:1::1/128, 2001:1::2/128, 2001:3::/32, 2001:4:112::/48, 2001:20::/28, 2001:30::/28. The exceptions are not considered private.

is_global

True if the address is defined as globally reachable by iana-ipv4-special-registry [https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml] (for IPv4) or iana-ipv6-special-registry [https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml] (for IPv6) with the following exception:

For IPv4-mapped IPv6-addresses the is_private value is determined by the semantics of the underlying IPv4 addresses and the following condition holds (see IPv6Address.ipv4_mapped):

address.is_global == address.ipv4_mapped.is_global

is_global has value opposite to is_private, except for the shared address space (100.64.0.0/10 range) where they are both False.

在 3.4 版被加入.

在 3.13 版的變更: Fixed some false positives and false negatives, see is_private for details.

is_unspecified

True if the address is unspecified. See RFC 5735 [https://datatracker.ietf.org/doc/html/rfc5735.html] (for IPv4) or RFC 2373 [https://datatracker.ietf.org/doc/html/rfc2373.html] (for IPv6).

is_reserved

True if the address is noted as reserved by the IETF. For IPv4, this is only 240.0.0.0/4, the Reserved address block. For IPv6, this is all addresses allocated [https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml] as Reserved by IETF for future use.

備註

For IPv4, is_reserved is not related to the address block value of the Reserved-by-Protocol column in iana-ipv4-special-registry [https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml].

警示

For IPv6, fec0::/10 a former Site-Local scoped address prefix is currently excluded from that list (see is_site_local & RFC 3879 [https://datatracker.ietf.org/doc/html/rfc3879.html]).

is_loopback

True if this is a loopback address. See RFC 3330 [https://datatracker.ietf.org/doc/html/rfc3330.html] (for IPv4) or RFC 2373 [https://datatracker.ietf.org/doc/html/rfc2373.html] (for IPv6).

is_link_local

True if the address is reserved for link-local usage. See RFC 3927 [https://datatracker.ietf.org/doc/html/rfc3927.html].

ipv6_mapped

IPv4Address object representing the IPv4-mapped IPv6 address. See RFC 4291 [https://datatracker.ietf.org/doc/html/rfc4291.html].

在 3.13 版被加入.

IPv4Address.__format__(fmt)

Returns a string representation of the IP address, controlled by an explicit format string. fmt can be one of the following: 's', the default option, equivalent to str(), 'b' for a zero-padded binary string, 'X' or 'x' for an uppercase or lowercase hexadecimal representation, or 'n', which is equivalent to 'b' for IPv4 addresses and 'x' for IPv6. For binary and hexadecimal representations, the form specifier '#' and the grouping option '_' are available. __format__ is used by format, str.format and f-strings.

>>> format(ipaddress.IPv4Address('192.168.0.1'))
'192.168.0.1'
>>> '{:#b}'.format(ipaddress.IPv4Address('192.168.0.1'))
'0b11000000101010000000000000000001'
>>> f'{ipaddress.IPv6Address("2001:db8::1000"):s}'
'2001:db8::1000'
>>> format(ipaddress.IPv6Address('2001:db8::1000'), '_X')
'2001_0DB8_0000_0000_0000_0000_0000_1000'
>>> '{:#_n}'.format(ipaddress.IPv6Address('2001:db8::1000'))
'0x2001_0db8_0000_0000_0000_0000_0000_1000'

在 3.9 版被加入.

class ipaddress.IPv6Address(address)

Construct an IPv6 address. An AddressValueError is raised if address is not a valid IPv6 address.

The following constitutes a valid IPv6 address:

A string consisting of eight groups of four hexadecimal digits, each group representing 16 bits. The groups are separated by colons. This describes an exploded (longhand) notation. The string can also be compressed (shorthand notation) by various means. See RFC 4291 [https://datatracker.ietf.org/doc/html/rfc4291.html] for details. For example, "0000:0000:0000:0000:0000:0abc:0007:0def" can be compressed to "::abc:7:def".

Optionally, the string may also have a scope zone ID, expressed with a suffix %scope_id. If present, the scope ID must be non-empty, and may not contain %. See RFC 4007 [https://datatracker.ietf.org/doc/html/rfc4007.html] for details. For example, fe80::1234%1 might identify address fe80::1234 on the first link of the node.

一個可以放入 128 位元的整數。

An integer packed into a bytes object of length 16, big-endian.

>>> ipaddress.IPv6Address('2001:db8::1000')
IPv6Address('2001:db8::1000')
>>> ipaddress.IPv6Address('ff02::5678%1')
IPv6Address('ff02::5678%1')

compressed

The short form of the address representation, with leading zeroes in groups omitted and the longest sequence of groups consisting entirely of zeroes collapsed to a single empty group.

This is also the value returned by str(addr) for IPv6 addresses.

exploded

The long form of the address representation, with all leading zeroes and groups consisting entirely of zeroes included.

For the following attributes and methods, see the corresponding documentation of the IPv4Address class:

packed

reverse_pointer

version

max_prefixlen

is_multicast

is_private

is_global

在 3.4 版被加入.

is_unspecified

is_reserved

is_loopback

is_link_local

is_site_local

True if the address is reserved for site-local usage. Note that the site-local address space has been deprecated by RFC 3879 [https://datatracker.ietf.org/doc/html/rfc3879.html]. Use is_private to test if this address is in the space of unique local addresses as defined by RFC 4193 [https://datatracker.ietf.org/doc/html/rfc4193.html].

ipv4_mapped

For addresses that appear to be IPv4 mapped addresses (starting with ::FFFF/96), this property will report the embedded IPv4 address. For any other address, this property will be None.

scope_id

For scoped addresses as defined by RFC 4007 [https://datatracker.ietf.org/doc/html/rfc4007.html], this property identifies the particular zone of the address's scope that the address belongs to, as a string. When no scope zone is specified, this property will be None.

sixtofour

For addresses that appear to be 6to4 addresses (starting with 2002::/16) as defined by RFC 3056 [https://datatracker.ietf.org/doc/html/rfc3056.html], this property will report the embedded IPv4 address. For any other address, this property will be None.

teredo

For addresses that appear to be Teredo addresses (starting with 2001::/32) as defined by RFC 4380 [https://datatracker.ietf.org/doc/html/rfc4380.html], this property will report the embedded (server, client) IP address pair. For any other address, this property will be None.

IPv6Address.__format__(fmt)

Refer to the corresponding method documentation in IPv4Address.

在 3.9 版被加入.

Conversion to Strings and Integers

To interoperate with networking interfaces such as the socket module, addresses must be converted to strings or integers. This is handled using the str() and int() builtin functions:

>>> str(ipaddress.IPv4Address('192.168.0.1'))
'192.168.0.1'
>>> int(ipaddress.IPv4Address('192.168.0.1'))
3232235521
>>> str(ipaddress.IPv6Address('::1'))
'::1'
>>> int(ipaddress.IPv6Address('::1'))
1

Note that IPv6 scoped addresses are converted to integers without scope zone ID.

運算子

Address objects support some operators. Unless stated otherwise, operators can only be applied between compatible objects (i.e. IPv4 with IPv4, IPv6 with IPv6).

比較運算子

Address objects can be compared with the usual set of comparison operators. Same IPv6 addresses with different scope zone IDs are not equal. Some examples:

>>> IPv4Address('127.0.0.2') > IPv4Address('127.0.0.1')
True
>>> IPv4Address('127.0.0.2') == IPv4Address('127.0.0.1')
False
>>> IPv4Address('127.0.0.2') != IPv4Address('127.0.0.1')
True
>>> IPv6Address('fe80::1234') == IPv6Address('fe80::1234%1')
False
>>> IPv6Address('fe80::1234%1') != IPv6Address('fe80::1234%2')
True

算術運算子

Integers can be added to or subtracted from address objects. Some examples:

>>> IPv4Address('127.0.0.2') + 3
IPv4Address('127.0.0.5')
>>> IPv4Address('127.0.0.2') - 3
IPv4Address('126.255.255.255')
>>> IPv4Address('255.255.255.255') + 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ipaddress.AddressValueError: 4294967296 (>= 2**32) is not permitted as an IPv4 address

IP Network definitions

The IPv4Network and IPv6Network objects provide a mechanism for defining and inspecting IP network definitions. A network definition consists of a mask and a network address, and as such defines a range of IP addresses that equal the network address when masked (binary AND) with the mask. For example, a network definition with the mask 255.255.255.0 and the network address 192.168.1.0 consists of IP addresses in the inclusive range 192.168.1.0 to 192.168.1.255.

Prefix, net mask and host mask

There are several equivalent ways to specify IP network masks. A prefix /<nbits> is a notation that denotes how many high-order bits are set in the network mask. A net mask is an IP address with some number of high-order bits set. Thus the prefix /24 is equivalent to the net mask 255.255.255.0 in IPv4, or ffff:ff00:: in IPv6. In addition, a host mask is the logical inverse of a net mask, and is sometimes used (for example in Cisco access control lists) to denote a network mask. The host mask equivalent to /24 in IPv4 is 0.0.0.255.

Network objects

All attributes implemented by address objects are implemented by network objects as well. In addition, network objects implement additional attributes. All of these are common between IPv4Network and IPv6Network, so to avoid duplication they are only documented for IPv4Network. Network objects are hashable, so they can be used as keys in dictionaries.

class ipaddress.IPv4Network(address, strict=True)

Construct an IPv4 network definition. address can be one of the following:

A string consisting of an IP address and an optional mask, separated by a slash (/). The IP address is the network address, and the mask can be either a single number, which means it's a prefix, or a string representation of an IPv4 address. If it's the latter, the mask is interpreted as a net mask if it starts with a non-zero field, or as a host mask if it starts with a zero field, with the single exception of an all-zero mask which is treated as a net mask. If no mask is provided, it's considered to be /32.

For example, the following address specifications are equivalent: 192.168.1.0/24, 192.168.1.0/255.255.255.0 and 192.168.1.0/0.0.0.255.

An integer that fits into 32 bits. This is equivalent to a single-address network, with the network address being address and the mask being /32.

An integer packed into a bytes object of length 4, big-endian. The interpretation is similar to an integer address.

A two-tuple of an address description and a netmask, where the address description is either a string, a 32-bits integer, a 4-bytes packed integer, or an existing IPv4Address object; and the netmask is either an integer representing the prefix length (e.g. 24) or a string representing the prefix mask (e.g. 255.255.255.0).

An AddressValueError is raised if address is not a valid IPv4 address. A NetmaskValueError is raised if the mask is not valid for an IPv4 address.

If strict is True and host bits are set in the supplied address, then ValueError is raised. Otherwise, the host bits are masked out to determine the appropriate network address.

Unless stated otherwise, all network methods accepting other network/address objects will raise TypeError if the argument's IP version is incompatible to self.

在 3.5 版的變更: Added the two-tuple form for the address constructor parameter.

version

max_prefixlen

Refer to the corresponding attribute documentation in IPv4Address.

is_multicast

is_private

is_unspecified

is_reserved

is_loopback

is_link_local

These attributes are true for the network as a whole if they are true for both the network address and the broadcast address.

network_address

The network address for the network. The network address and the prefix length together uniquely define a network.

broadcast_address

The broadcast address for the network. Packets sent to the broadcast address should be received by every host on the network.

hostmask

The host mask, as an IPv4Address object.

netmask

The net mask, as an IPv4Address object.

with_prefixlen

compressed

exploded

A string representation of the network, with the mask in prefix notation.

with_prefixlen and compressed are always the same as str(network). exploded uses the exploded form the network address.

with_netmask

A string representation of the network, with the mask in net mask notation.

with_hostmask

A string representation of the network, with the mask in host mask notation.

num_addresses

The total number of addresses in the network.

prefixlen

Length of the network prefix, in bits.

hosts()

Returns an iterator over the usable hosts in the network. The usable hosts are all the IP addresses that belong to the network, except the network address itself and the network broadcast address. For networks with a mask length of 31, the network address and network broadcast address are also included in the result. Networks with a mask of 32 will return a list containing the single host address.

>>> list(ip_network('192.0.2.0/29').hosts())
[IPv4Address('192.0.2.1'), IPv4Address('192.0.2.2'),
 IPv4Address('192.0.2.3'), IPv4Address('192.0.2.4'),
 IPv4Address('192.0.2.5'), IPv4Address('192.0.2.6')]
>>> list(ip_network('192.0.2.0/31').hosts())
[IPv4Address('192.0.2.0'), IPv4Address('192.0.2.1')]
>>> list(ip_network('192.0.2.1/32').hosts())
[IPv4Address('192.0.2.1')]

overlaps(other)

True if this network is partly or wholly contained in other or other is wholly contained in this network.

address_exclude(network)

Computes the network definitions resulting from removing the given network from this one. Returns an iterator of network objects. Raises ValueError if network is not completely contained in this network.

>>> n1 = ip_network('192.0.2.0/28')
>>> n2 = ip_network('192.0.2.1/32')
>>> list(n1.address_exclude(n2))
[IPv4Network('192.0.2.8/29'), IPv4Network('192.0.2.4/30'),
 IPv4Network('192.0.2.2/31'), IPv4Network('192.0.2.0/32')]

subnets(prefixlen_diff=1, new_prefix=None)

The subnets that join to make the current network definition, depending on the argument values. prefixlen_diff is the amount our prefix length should be increased by. new_prefix is the desired new prefix of the subnets; it must be larger than our prefix. One and only one of prefixlen_diff and new_prefix must be set. Returns an iterator of network objects.

>>> list(ip_network('192.0.2.0/24').subnets())
[IPv4Network('192.0.2.0/25'), IPv4Network('192.0.2.128/25')]
>>> list(ip_network('192.0.2.0/24').subnets(prefixlen_diff=2))
[IPv4Network('192.0.2.0/26'), IPv4Network('192.0.2.64/26'),
 IPv4Network('192.0.2.128/26'), IPv4Network('192.0.2.192/26')]
>>> list(ip_network('192.0.2.0/24').subnets(new_prefix=26))
[IPv4Network('192.0.2.0/26'), IPv4Network('192.0.2.64/26'),
 IPv4Network('192.0.2.128/26'), IPv4Network('192.0.2.192/26')]
>>> list(ip_network('192.0.2.0/24').subnets(new_prefix=23))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    raise ValueError('new prefix must be longer')
ValueError: new prefix must be longer
>>> list(ip_network('192.0.2.0/24').subnets(new_prefix=25))
[IPv4Network('192.0.2.0/25'), IPv4Network('192.0.2.128/25')]

supernet(prefixlen_diff=1, new_prefix=None)

The supernet containing this network definition, depending on the argument values. prefixlen_diff is the amount our prefix length should be decreased by. new_prefix is the desired new prefix of the supernet; it must be smaller than our prefix. One and only one of prefixlen_diff and new_prefix must be set. Returns a single network object.

>>> ip_network('192.0.2.0/24').supernet()
IPv4Network('192.0.2.0/23')
>>> ip_network('192.0.2.0/24').supernet(prefixlen_diff=2)
IPv4Network('192.0.0.0/22')
>>> ip_network('192.0.2.0/24').supernet(new_prefix=20)
IPv4Network('192.0.0.0/20')

subnet_of(other)

Return True if this network is a subnet of other.

>>> a = ip_network('192.168.1.0/24')
>>> b = ip_network('192.168.1.128/30')
>>> b.subnet_of(a)
True

在 3.7 版被加入.

supernet_of(other)

Return True if this network is a supernet of other.

>>> a = ip_network('192.168.1.0/24')
>>> b = ip_network('192.168.1.128/30')
>>> a.supernet_of(b)
True

在 3.7 版被加入.

compare_networks(other)

Compare this network to other. In this comparison only the network addresses are considered; host bits aren't. Returns either -1, 0 or 1.

>>> ip_network('192.0.2.1/32').compare_networks(ip_network('192.0.2.2/32'))
-1
>>> ip_network('192.0.2.1/32').compare_networks(ip_network('192.0.2.0/32'))
1
>>> ip_network('192.0.2.1/32').compare_networks(ip_network('192.0.2.1/32'))
0

在 3.7 版之後被棄用: It uses the same ordering and comparison algorithm as "<", "==", and ">"

class ipaddress.IPv6Network(address, strict=True)

Construct an IPv6 network definition. address can be one of the following:

A string consisting of an IP address and an optional prefix length, separated by a slash (/). The IP address is the network address, and the prefix length must be a single number, the prefix. If no prefix length is provided, it's considered to be /128.

Note that currently expanded netmasks are not supported. That means 2001:db00::0/24 is a valid argument while 2001:db00::0/ffff:ff00:: is not.

An integer that fits into 128 bits. This is equivalent to a single-address network, with the network address being address and the mask being /128.

An integer packed into a bytes object of length 16, big-endian. The interpretation is similar to an integer address.

A two-tuple of an address description and a netmask, where the address description is either a string, a 128-bits integer, a 16-bytes packed integer, or an existing IPv6Address object; and the netmask is an integer representing the prefix length.

An AddressValueError is raised if address is not a valid IPv6 address. A NetmaskValueError is raised if the mask is not valid for an IPv6 address.

If strict is True and host bits are set in the supplied address, then ValueError is raised. Otherwise, the host bits are masked out to determine the appropriate network address.

在 3.5 版的變更: Added the two-tuple form for the address constructor parameter.

version

max_prefixlen

is_multicast

is_private

is_unspecified

is_reserved

is_loopback

is_link_local

network_address

broadcast_address

hostmask

netmask

with_prefixlen

compressed

exploded

with_netmask

with_hostmask

num_addresses

prefixlen

hosts()

Returns an iterator over the usable hosts in the network. The usable hosts are all the IP addresses that belong to the network, except the Subnet-Router anycast address. For networks with a mask length of 127, the Subnet-Router anycast address is also included in the result. Networks with a mask of 128 will return a list containing the single host address.

overlaps(other)

address_exclude(network)

subnets(prefixlen_diff=1, new_prefix=None)

supernet(prefixlen_diff=1, new_prefix=None)

subnet_of(other)

supernet_of(other)

compare_networks(other)

Refer to the corresponding attribute documentation in IPv4Network.

is_site_local

This attribute is true for the network as a whole if it is true for both the network address and the broadcast address.

運算子

Network objects support some operators. Unless stated otherwise, operators can only be applied between compatible objects (i.e. IPv4 with IPv4, IPv6 with IPv6).

Logical operators

Network objects can be compared with the usual set of logical operators. Network objects are ordered first by network address, then by net mask.

疊代

Network objects can be iterated to list all the addresses belonging to the network. For iteration, all hosts are returned, including unusable hosts (for usable hosts, use the hosts() method). An example:

>>> for addr in IPv4Network('192.0.2.0/28'):
...     addr
...
IPv4Address('192.0.2.0')
IPv4Address('192.0.2.1')
IPv4Address('192.0.2.2')
IPv4Address('192.0.2.3')
IPv4Address('192.0.2.4')
IPv4Address('192.0.2.5')
IPv4Address('192.0.2.6')
IPv4Address('192.0.2.7')
IPv4Address('192.0.2.8')
IPv4Address('192.0.2.9')
IPv4Address('192.0.2.10')
IPv4Address('192.0.2.11')
IPv4Address('192.0.2.12')
IPv4Address('192.0.2.13')
IPv4Address('192.0.2.14')
IPv4Address('192.0.2.15')

Networks as containers of addresses

Network objects can act as containers of addresses. Some examples:

>>> IPv4Network('192.0.2.0/28')[0]
IPv4Address('192.0.2.0')
>>> IPv4Network('192.0.2.0/28')[15]
IPv4Address('192.0.2.15')
>>> IPv4Address('192.0.2.6') in IPv4Network('192.0.2.0/28')
True
>>> IPv4Address('192.0.3.6') in IPv4Network('192.0.2.0/28')
False

Interface objects

Interface objects are hashable, so they can be used as keys in dictionaries.

class ipaddress.IPv4Interface(address)

Construct an IPv4 interface. The meaning of address is as in the constructor of IPv4Network, except that arbitrary host addresses are always accepted.

IPv4Interface is a subclass of IPv4Address, so it inherits all the attributes from that class. In addition, the following attributes are available:

ip

The address (IPv4Address) without network information.

>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.ip
IPv4Address('192.0.2.5')

network

The network (IPv4Network) this interface belongs to.

>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.network
IPv4Network('192.0.2.0/24')

with_prefixlen

A string representation of the interface with the mask in prefix notation.

>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.with_prefixlen
'192.0.2.5/24'

with_netmask

A string representation of the interface with the network as a net mask.

>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.with_netmask
'192.0.2.5/255.255.255.0'

with_hostmask

A string representation of the interface with the network as a host mask.

>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.with_hostmask
'192.0.2.5/0.0.0.255'

class ipaddress.IPv6Interface(address)

Construct an IPv6 interface. The meaning of address is as in the constructor of IPv6Network, except that arbitrary host addresses are always accepted.

IPv6Interface is a subclass of IPv6Address, so it inherits all the attributes from that class. In addition, the following attributes are available:

ip

network

with_prefixlen

with_netmask

with_hostmask

Refer to the corresponding attribute documentation in IPv4Interface.

運算子

Interface objects support some operators. Unless stated otherwise, operators can only be applied between compatible objects (i.e. IPv4 with IPv4, IPv6 with IPv6).

Logical operators

Interface objects can be compared with the usual set of logical operators.

For equality comparison (== and !=), both the IP address and network must be the same for the objects to be equal. An interface will not compare equal to any address or network object.

For ordering (<, >, etc) the rules are different. Interface and address objects with the same IP version can be compared, and the address objects will always sort before the interface objects. Two interface objects are first compared by their networks and, if those are the same, then by their IP addresses.

Other Module Level Functions

The module also provides the following module level functions:

ipaddress.v4_int_to_packed(address)

Represent an address as 4 packed bytes in network (big-endian) order. address is an integer representation of an IPv4 IP address. A ValueError is raised if the integer is negative or too large to be an IPv4 IP address.

>>> ipaddress.ip_address(3221225985)
IPv4Address('192.0.2.1')
>>> ipaddress.v4_int_to_packed(3221225985)
b'\xc0\x00\x02\x01'

ipaddress.v6_int_to_packed(address)

Represent an address as 16 packed bytes in network (big-endian) order. address is an integer representation of an IPv6 IP address. A ValueError is raised if the integer is negative or too large to be an IPv6 IP address.

ipaddress.summarize_address_range(first, last)

Return an iterator of the summarized network range given the first and last IP addresses. first is the first IPv4Address or IPv6Address in the range and last is the last IPv4Address or IPv6Address in the range. A TypeError is raised if first or last are not IP addresses or are not of the same version. A ValueError is raised if last is not greater than first or if first address version is not 4 or 6.

>>> [ipaddr for ipaddr in ipaddress.summarize_address_range(
...    ipaddress.IPv4Address('192.0.2.0'),
...    ipaddress.IPv4Address('192.0.2.130'))]
[IPv4Network('192.0.2.0/25'), IPv4Network('192.0.2.128/31'), IPv4Network('192.0.2.130/32')]

ipaddress.collapse_addresses(addresses)

Return an iterator of the collapsed IPv4Network or IPv6Network objects. addresses is an iterable of IPv4Network or IPv6Network objects. A TypeError is raised if addresses contains mixed version objects.

>>> [ipaddr for ipaddr in
... ipaddress.collapse_addresses([ipaddress.IPv4Network('192.0.2.0/25'),
... ipaddress.IPv4Network('192.0.2.128/25')])]
[IPv4Network('192.0.2.0/24')]

ipaddress.get_mixed_type_key(obj)

Return a key suitable for sorting between networks and addresses. Address and Network objects are not sortable by default; they're fundamentally different, so the expression:

IPv4Address('192.0.2.0') <= IPv4Network('192.0.2.0/24')

doesn't make sense. There are some times however, where you may wish to have ipaddress sort these anyway. If you need to do this, you can use this function as the key argument to sorted().

obj is either a network or address object.

Custom Exceptions

To support more specific error reporting from class constructors, the module defines the following exceptions:

exception ipaddress.AddressValueError(ValueError)

Any value error related to the address.

exception ipaddress.NetmaskValueError(ValueError)

Any value error related to the net mask.

多媒體服務

此章節所描述的模組 (module) 實作了多種在多媒體服務中相當有用的演算法和介面，並可在安裝時決定是否要使用它們。以下為綜述：

wave --- 讀寫 WAV 檔案

Wave_read 物件

Wave_write 物件

colorsys --- 顏色系統間的轉換

wave --- 讀寫 WAV 檔案

原始碼：Lib/wave.py [https://github.com/python/cpython/tree/3.14/Lib/wave.py]

wave 模組為波形音訊檔案格式「WAVE」（或稱「WAV」）提供了便捷的介面。僅支援未壓縮的 PCM 編碼波形檔。

在 3.12 版的變更: 增加了標頭 WAVE_FORMAT_EXTENSIBLE 的支援，要求的擴展格式為 KSDATAFORMAT_SUBTYPE_PCM。

wave 模組定義了以下的函式和例外:

wave.open(file, mode=None)

如果 file 是一個字串，會打開對應名稱的檔案，否則會以類檔案物件處理。mode 可以是：

'rb'

唯讀模式。

'wb'

唯寫模式。

請注意，不支援同時讀寫 WAV 檔案。

mode 設定為 'rb' 時，會回傳一個 Wave_read 物件，mode 設定為 'wb' 時，則回傳一個 Wave_write 物件。如果省略 mode，並且將類檔案 (file-like) 物件作為 file 參數傳遞，則 file.mode 會是 mode 的預設值。

如果你傳遞一個類檔案物件，當呼叫其 close() 方法時，wave 物件不會自動關閉該物件；關閉檔案物件的責任會在呼叫者上。

open() 函式可以在 with 陳述式中使用。當 with 區塊完成時，會呼叫 Wave_read.close() 或是 Wave_write.close() 方法。

在 3.4 版的變更: 增加對不可搜尋 (unseekable) 檔案的支援。

exception wave.Error

當不符合 WAV 格式或無法操作時會引發錯誤。

Wave_read 物件

class wave.Wave_read

讀取一個 WAV 檔案。

由 open() 回傳的 Wave_read 物件具有以下方法：

close()

關閉 wave 開啟的串流並使該實例無法使用。當物件回收時自動呼叫。

getnchannels()

回傳音訊聲道的數量（單聲道為 1，立體聲為 2）。

getsampwidth()

回傳以位元組表示的取樣寬度 (sample width)。

getframerate()

回傳取樣率。

getnframes()

回傳音訊幀數。

getcomptype()

回傳壓縮類型（僅支援 'NONE' 類型）。

getcompname()

getcomptype() 的人類可讀的版本。通常使用 'not compressed' 代替 'NONE'。

getparams()

回傳一個 namedtuple() (nchannels, sampwidth, framerate, nframes, comptype, compname)，等同於 get*() 方法的輸出。

readframes(n)

讀取並回傳以 bytes 物件表示的最多 n 個音訊幀。

rewind()

重置檔案指標至音訊流的開頭。

以下兩個方法是為了與舊的 aifc 模組保持相容性，並不執行任何操作。

getmarkers()

回傳 None。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: 該方法是為了保持與 aifc 模組相容性而留存，此模組已於 Python 3.13 中刪除。

getmark(id)

引發錯誤。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: 該方法是為了保持與 aifc 模組相容性而留存，此模組已於 Python 3.13 中刪除。

以下兩個方法所定義的「位置」，在它們之間是相容的，但其他情況下則取決於具體實作方式。

setpos(pos)

將檔案指標設定為指定的位置。

tell()

回傳目前的檔案指標位置。

Wave_write 物件

class wave.Wave_write

寫入一個 WAV 檔案。

Wave_write 物件，由 open() 回傳。

對於可搜尋 (seekable) 的輸出串流，wave 標頭將自動更新，以反映實際寫入的幀數。對於不可搜尋的串流，當寫入第一個幀資料時，nframes 的值必須是準確的。要取得準確的 nframes 值，可以透過呼叫 setnframes() 或 setparams() 方法，並在呼叫 close() 之前設定將寫入的幀數量，然後使用 writeframesraw() 方法寫入幀資料；或者透過呼叫 writeframes() 方法一次性寫入所有的幀資料。在後一種情況下，writeframes() 方法將計算資料中的幀數量，並在寫入幀資料之前相應地設定 nframes 的值。

在 3.4 版的變更: 增加對不可搜尋 (unseekable) 檔案的支援。

Wave_write 物件具有以下方法：

close()

確保 nframes 正確，如果該檔案是由 wave 開啟的，則關閉該檔案。此方法在物件回收時被呼叫。如果輸出串流不可搜尋且 nframes 不符合實際寫入的幀數，則會引發例外。

setnchannels(n)

設定音訊的通道數量。

setsampwidth(n)

設定取樣寬度為 n 個位元組。

setframerate(n)

設定取樣頻率為 n。

在 3.2 版的變更: 此方法的非整數輸入會被將四捨五入到最接近的整數。

setnframes(n)

設定幀數為 n。如果實際寫入的幀數不同，則稍後將進行更改（如果輸出串流不可搜尋，則此嘗試將引發錯誤）。

setcomptype(type, name)

設定壓縮類型和描述。目前只支援壓縮類型為 NONE，表示無壓縮。

setparams(tuple)

這個 tuple 應該是 (nchannels, sampwidth, framerate, nframes, comptype, compname)，值需要是符合 set*() 方法的參數。設定所有參數。

tell()

回傳檔案中的指標位置，其指標位置含意與 Wave_read.tell() 和 Wave_read.setpos() 是一致的。

writeframesraw(data)

寫入音訊幀，不修正 nframes。

在 3.4 版的變更: 現在可接受任何 bytes-like object。

writeframes(data)

寫入音訊幀並確保 nframes 正確。如果輸出串流不可搜尋，並且在寫入 data 後已寫入的總幀數與先前設定的 nframes 值不符，則會引發錯誤。

在 3.4 版的變更: 現在可接受任何 bytes-like object。

注意在呼叫 writeframes() 或 writeframesraw() 之後設置任何參數都是無效的，任何嘗試這樣做的操作都會引發 wave.Error。

colorsys --- 顏色系統間的轉換

原始碼：Lib/colorsys.py [https://github.com/python/cpython/tree/3.14/Lib/colorsys.py]

colorsys 模組 (module) 定義了電腦顯示器所用的 RGB （紅綠藍）色彩空間與三種其他色彩座標系統：YIQ、HLS (色相、亮度、飽和度) 和 HSV (色相、 飽和度、 明度) 所表示的顏色值之間的雙向轉換。所有這些色彩空間的座標都使用浮點數值 (floating-point) 來表示。在 YIQ 空間中，Y 座標值為 0 和 1 之間，而 I 和 Q 座標均可以為正數或負數。在所有其他空間中，座標值均為 0 和 1 之間。

也參考

有關色彩空間的更多資訊請見 https://poynton.ca/ColorFAQ.html 和 https://www.cambridgeincolour.com/tutorials/color-spaces.htm。

colorsys 模組定義了以下函式：

colorsys.rgb_to_yiq(r, g, b)

將顏色自 RGB 座標轉換至 YIQ 座標。

colorsys.yiq_to_rgb(y, i, q)

將顏色自 YIQ 座標轉換至 RGB 座標。

colorsys.rgb_to_hls(r, g, b)

將顏色自 RGB 座標轉換至 HLS 座標。

colorsys.hls_to_rgb(h, l, s)

將顏色自 HLS 座標轉換至 RGB 座標。

colorsys.rgb_to_hsv(r, g, b)

將顏色自 RGB 座標轉換至 HSV 座標。

colorsys.hsv_to_rgb(h, s, v)

將顏色自 HSV 座標轉換至 RGB 座標。

範例：

>>> import colorsys
>>> colorsys.rgb_to_hsv(0.2, 0.4, 0.4)
(0.5, 0.5, 0.4)
>>> colorsys.hsv_to_rgb(0.5, 0.5, 0.4)
(0.2, 0.4, 0.4)

國際化

本章所描述的模組透過提供用於程式訊息中語言的選擇機制或是調整輸出以符合當地慣例，來幫助你編寫不依賴語言和地區設定的軟體

本章節所描述的模組列表為：

gettext --- 多語言國際化服務

GNU gettext API

Class-based API

The NullTranslations class

The GNUTranslations class

Solaris message catalog support

The Catalog constructor

Internationalizing your programs and modules

Localizing your module

Localizing your application

Changing languages on the fly

Deferred translations

致謝

locale --- 國際化服務

Background, details, hints, tips and caveats

Locale names

For extension writers and programs that embed Python

Access to message catalogs

gettext --- 多語言國際化服務

原始碼：Lib/gettext.py [https://github.com/python/cpython/tree/3.14/Lib/gettext.py]

The gettext module provides internationalization (I18N) and localization (L10N) services for your Python modules and applications. It supports both the GNU gettext message catalog API and a higher level, class-based API that may be more appropriate for Python files. The interface described below allows you to write your module and application messages in one natural language, and provide a catalog of translated messages for running under different natural languages.

Some hints on localizing your Python modules and applications are also given.

GNU gettext API

The gettext module defines the following API, which is very similar to the GNU gettext API. If you use this API you will affect the translation of your entire application globally. Often this is what you want if your application is monolingual, with the choice of language dependent on the locale of your user. If you are localizing a Python module, or if your application needs to switch languages on the fly, you probably want to use the class-based API instead.

gettext.bindtextdomain(domain, localedir=None)

Bind the domain to the locale directory localedir. More concretely, gettext will look for binary .mo files for the given domain using the path (on Unix): localedir/language/LC_MESSAGES/domain.mo, where language is searched for in the environment variables LANGUAGE, LC_ALL, LC_MESSAGES, and LANG respectively.

If localedir is omitted or None, then the current binding for domain is returned. [1]

gettext.textdomain(domain=None)

Change or query the current global domain. If domain is None, then the current global domain is returned, otherwise the global domain is set to domain, which is returned.

gettext.gettext(message)

Return the localized translation of message, based on the current global domain, language, and locale directory. This function is usually aliased as _() in the local namespace (see examples below).

gettext.dgettext(domain, message)

Like gettext(), but look the message up in the specified domain.

gettext.ngettext(singular, plural, n)

Like gettext(), but consider plural forms. If a translation is found, apply the plural formula to n, and return the resulting message (some languages have more than two plural forms). If no translation is found, return singular if n is 1; return plural otherwise.

The Plural formula is taken from the catalog header. It is a C or Python expression that has a free variable n; the expression evaluates to the index of the plural in the catalog. See the GNU gettext documentation [https://www.gnu.org/software/gettext/manual/gettext.html] for the precise syntax to be used in .po files and the formulas for a variety of languages.

gettext.dngettext(domain, singular, plural, n)

Like ngettext(), but look the message up in the specified domain.

gettext.pgettext(context, message)

gettext.dpgettext(domain, context, message)

gettext.npgettext(context, singular, plural, n)

gettext.dnpgettext(domain, context, singular, plural, n)

Similar to the corresponding functions without the p in the prefix (that is, gettext(), dgettext(), ngettext(), dngettext()), but the translation is restricted to the given message context.

在 3.8 版被加入.

Note that GNU gettext also defines a dcgettext() method, but this was deemed not useful and so it is currently unimplemented.

Here's an example of typical usage for this API:

import gettext
gettext.bindtextdomain('myapplication', '/path/to/my/language/directory')
gettext.textdomain('myapplication')
_ = gettext.gettext
# ...
print(_('This is a translatable string.'))

Class-based API

The class-based API of the gettext module gives you more flexibility and greater convenience than the GNU gettext API. It is the recommended way of localizing your Python applications and modules. gettext defines a GNUTranslations class which implements the parsing of GNU .mo format files, and has methods for returning strings. Instances of this class can also install themselves in the built-in namespace as the function _().

gettext.find(domain, localedir=None, languages=None, all=False)

This function implements the standard .mo file search algorithm. It takes a domain, identical to what textdomain() takes. Optional localedir is as in bindtextdomain(). Optional languages is a list of strings, where each string is a language code.

If localedir is not given, then the default system locale directory is used. [2] If languages is not given, then the following environment variables are searched: LANGUAGE, LC_ALL, LC_MESSAGES, and LANG. The first one returning a non-empty value is used for the languages variable. The environment variables should contain a colon separated list of languages, which will be split on the colon to produce the expected list of language code strings.

find() then expands and normalizes the languages, and then iterates through them, searching for an existing file built of these components:

localedir/language/LC_MESSAGES/domain.mo

The first such file name that exists is returned by find(). If no such file is found, then None is returned. If all is given, it returns a list of all file names, in the order in which they appear in the languages list or the environment variables.

gettext.translation(domain, localedir=None, languages=None, class_=None, fallback=False)

Return a *Translations instance based on the domain, localedir, and languages, which are first passed to find() to get a list of the associated .mo file paths. Instances with identical .mo file names are cached. The actual class instantiated is class_ if provided, otherwise GNUTranslations. The class's constructor must take a single file object argument.

If multiple files are found, later files are used as fallbacks for earlier ones. To allow setting the fallback, copy.copy() is used to clone each translation object from the cache; the actual instance data is still shared with the cache.

If no .mo file is found, this function raises OSError if fallback is false (which is the default), and returns a NullTranslations instance if fallback is true.

在 3.3 版的變更: IOError 曾經被引發，現在它是一個 OSError 的別名。

在 3.11 版的變更: codeset 參數被移除。

gettext.install(domain, localedir=None, *, names=None)

This installs the function _() in Python's builtins namespace, based on domain and localedir which are passed to the function translation().

For the names parameter, please see the description of the translation object's install() method.

As seen below, you usually mark the strings in your application that are candidates for translation, by wrapping them in a call to the _() function, like this:

print(_('This string will be translated.'))

For convenience, you want the _() function to be installed in Python's builtins namespace, so it is easily accessible in all modules of your application.

在 3.11 版的變更: names is now a keyword-only parameter.

The NullTranslations class

Translation classes are what actually implement the translation of original source file message strings to translated message strings. The base class used by all translation classes is NullTranslations; this provides the basic interface you can use to write your own specialized translation classes. Here are the methods of NullTranslations:

class gettext.NullTranslations(fp=None)

Takes an optional file object fp, which is ignored by the base class. Initializes "protected" instance variables _info and _charset which are set by derived classes, as well as _fallback, which is set through add_fallback(). It then calls self._parse(fp) if fp is not None.

_parse(fp)

No-op in the base class, this method takes file object fp, and reads the data from the file, initializing its message catalog. If you have an unsupported message catalog file format, you should override this method to parse your format.

add_fallback(fallback)

Add fallback as the fallback object for the current translation object. A translation object should consult the fallback if it cannot provide a translation for a given message.

gettext(message)

If a fallback has been set, forward gettext() to the fallback. Otherwise, return message. Overridden in derived classes.

ngettext(singular, plural, n)

If a fallback has been set, forward ngettext() to the fallback. Otherwise, return singular if n is 1; return plural otherwise. Overridden in derived classes.

pgettext(context, message)

If a fallback has been set, forward pgettext() to the fallback. Otherwise, return the translated message. Overridden in derived classes.

在 3.8 版被加入.

npgettext(context, singular, plural, n)

If a fallback has been set, forward npgettext() to the fallback. Otherwise, return the translated message. Overridden in derived classes.

在 3.8 版被加入.

info()

Return a dictionary containing the metadata found in the message catalog file.

charset()

Return the encoding of the message catalog file.

install(names=None)

This method installs gettext() into the built-in namespace, binding it to _.

If the names parameter is given, it must be a sequence containing the names of functions you want to install in the builtins namespace in addition to _(). Supported names are 'gettext', 'ngettext', 'pgettext', and 'npgettext'.

Note that this is only one way, albeit the most convenient way, to make the _() function available to your application. Because it affects the entire application globally, and specifically the built-in namespace, localized modules should never install _(). Instead, they should use this code to make _() available to their module:

import gettext
t = gettext.translation('mymodule', ...)
_ = t.gettext

This puts _() only in the module's global namespace and so only affects calls within this module.

在 3.8 版的變更: 新增 'pgettext' 與 'npgettext'。

The GNUTranslations class

The gettext module provides one additional class derived from NullTranslations: GNUTranslations. This class overrides _parse() to enable reading GNU gettext format .mo files in both big-endian and little-endian format.

GNUTranslations parses optional metadata out of the translation catalog. It is convention with GNU gettext to include metadata as the translation for the empty string. This metadata is in RFC 822 [https://datatracker.ietf.org/doc/html/rfc822.html]-style key: value pairs, and should contain the Project-Id-Version key. If the key Content-Type is found, then the charset property is used to initialize the "protected" _charset instance variable, defaulting to None if not found. If the charset encoding is specified, then all message ids and message strings read from the catalog are converted to Unicode using this encoding, else ASCII is assumed.

Since message ids are read as Unicode strings too, all *gettext() methods will assume message ids as Unicode strings, not byte strings.

The entire set of key/value pairs are placed into a dictionary and set as the "protected" _info instance variable.

If the .mo file's magic number is invalid, the major version number is unexpected, or if other problems occur while reading the file, instantiating a GNUTranslations class can raise OSError.

class gettext.GNUTranslations

The following methods are overridden from the base class implementation:

gettext(message)

Look up the message id in the catalog and return the corresponding message string, as a Unicode string. If there is no entry in the catalog for the message id, and a fallback has been set, the look up is forwarded to the fallback's gettext() method. Otherwise, the message id is returned.

ngettext(singular, plural, n)

Do a plural-forms lookup of a message id. singular is used as the message id for purposes of lookup in the catalog, while n is used to determine which plural form to use. The returned message string is a Unicode string.

If the message id is not found in the catalog, and a fallback is specified, the request is forwarded to the fallback's ngettext() method. Otherwise, when n is 1 singular is returned, and plural is returned in all other cases.

以下是個範例：

n = len(os.listdir('.'))
cat = GNUTranslations(somefile)
message = cat.ngettext(
    'There is %(num)d file in this directory',
    'There are %(num)d files in this directory',
    n) % {'num': n}

pgettext(context, message)

Look up the context and message id in the catalog and return the corresponding message string, as a Unicode string. If there is no entry in the catalog for the message id and context, and a fallback has been set, the look up is forwarded to the fallback's pgettext() method. Otherwise, the message id is returned.

在 3.8 版被加入.

npgettext(context, singular, plural, n)

Do a plural-forms lookup of a message id. singular is used as the message id for purposes of lookup in the catalog, while n is used to determine which plural form to use.

If the message id for context is not found in the catalog, and a fallback is specified, the request is forwarded to the fallback's npgettext() method. Otherwise, when n is 1 singular is returned, and plural is returned in all other cases.

在 3.8 版被加入.

Solaris message catalog support

The Solaris operating system defines its own binary .mo file format, but since no documentation can be found on this format, it is not supported at this time.

The Catalog constructor

GNOME uses a version of the gettext module by James Henstridge, but this version has a slightly different API. Its documented usage was:

import gettext
cat = gettext.Catalog(domain, localedir)
_ = cat.gettext
print(_('hello world'))

For compatibility with this older module, the function Catalog() is an alias for the translation() function described above.

One difference between this module and Henstridge's: his catalog objects supported access through a mapping API, but this appears to be unused and so is not currently supported.

Internationalizing your programs and modules

Internationalization (I18N) refers to the operation by which a program is made aware of multiple languages. Localization (L10N) refers to the adaptation of your program, once internationalized, to the local language and cultural habits. In order to provide multilingual messages for your Python programs, you need to take the following steps:

prepare your program or module by specially marking translatable strings

run a suite of tools over your marked files to generate raw messages catalogs

create language-specific translations of the message catalogs

use the gettext module so that message strings are properly translated

In order to prepare your code for I18N, you need to look at all the strings in your files. Any string that needs to be translated should be marked by wrapping it in _('...') --- that is, a call to the function _. For example:

filename = 'mylog.txt'
message = _('writing a log message')
with open(filename, 'w') as fp:
    fp.write(message)

In this example, the string 'writing a log message' is marked as a candidate for translation, while the strings 'mylog.txt' and 'w' are not.

There are a few tools to extract the strings meant for translation. The original GNU gettext only supported C or C++ source code but its extended version xgettext scans code written in a number of languages, including Python, to find strings marked as translatable. Babel [https://babel.pocoo.org/] is a Python internationalization library that includes a pybabel script to extract and compile message catalogs. François Pinard's program called xpot does a similar job and is available as part of his po-utils package [https://github.com/pinard/po-utils].

(Python also includes pure-Python versions of these programs, called pygettext.py and msgfmt.py; some Python distributions will install them for you. pygettext.py is similar to xgettext, but only understands Python source code and cannot handle other programming languages such as C or C++. pygettext.py supports a command-line interface similar to xgettext; for details on its use, run pygettext.py --help. msgfmt.py is binary compatible with GNU msgfmt. With these two programs, you may not need the GNU gettext package to internationalize your Python applications.)

xgettext, pygettext, and similar tools generate .po files that are message catalogs. They are structured human-readable files that contain every marked string in the source code, along with a placeholder for the translated versions of these strings.

Copies of these .po files are then handed over to the individual human translators who write translations for every supported natural language. They send back the completed language-specific versions as a <language-name>.po file that's compiled into a machine-readable .mo binary catalog file using the msgfmt program. The .mo files are used by the gettext module for the actual translation processing at run-time.

How you use the gettext module in your code depends on whether you are internationalizing a single module or your entire application. The next two sections will discuss each case.

Localizing your module

If you are localizing your module, you must take care not to make global changes, e.g. to the built-in namespace. You should not use the GNU gettext API but instead the class-based API.

Let's say your module is called "spam" and the module's various natural language translation .mo files reside in /usr/share/locale in GNU gettext format. Here's what you would put at the top of your module:

import gettext
t = gettext.translation('spam', '/usr/share/locale')
_ = t.gettext

Localizing your application

If you are localizing your application, you can install the _() function globally into the built-in namespace, usually in the main driver file of your application. This will let all your application-specific files just use _('...') without having to explicitly install it in each file.

In the simple case then, you need only add the following bit of code to the main driver file of your application:

import gettext
gettext.install('myapplication')

If you need to set the locale directory, you can pass it into the install() function:

import gettext
gettext.install('myapplication', '/usr/share/locale')

Changing languages on the fly

If your program needs to support many languages at the same time, you may want to create multiple translation instances and then switch between them explicitly, like so:

import gettext

lang1 = gettext.translation('myapplication', languages=['en'])
lang2 = gettext.translation('myapplication', languages=['fr'])
lang3 = gettext.translation('myapplication', languages=['de'])

# start by using language1
lang1.install()

# ... time goes by, user selects language 2
lang2.install()

# ... more time goes by, user selects language 3
lang3.install()

Deferred translations

In most coding situations, strings are translated where they are coded. Occasionally however, you need to mark strings for translation, but defer actual translation until later. A classic example is:

animals = ['mollusk',
           'albatross',
           'rat',
           'penguin',
           'python', ]
# ...
for a in animals:
    print(a)

Here, you want to mark the strings in the animals list as being translatable, but you don't actually want to translate them until they are printed.

Here is one way you can handle this situation:

def _(message): return message

animals = [_('mollusk'),
           _('albatross'),
           _('rat'),
           _('penguin'),
           _('python'), ]

del _

# ...
for a in animals:
    print(_(a))

This works because the dummy definition of _() simply returns the string unchanged. And this dummy definition will temporarily override any definition of _() in the built-in namespace (until the del command). Take care, though if you have a previous definition of _() in the local namespace.

Note that the second use of _() will not identify "a" as being translatable to the gettext program, because the parameter is not a string literal.

Another way to handle this is with the following example:

def N_(message): return message

animals = [N_('mollusk'),
           N_('albatross'),
           N_('rat'),
           N_('penguin'),
           N_('python'), ]

# ...
for a in animals:
    print(_(a))

In this case, you are marking translatable strings with the function N_(), which won't conflict with any definition of _(). However, you will need to teach your message extraction program to look for translatable strings marked with N_(). xgettext, pygettext, pybabel extract, and xpot all support this through the use of the -k command-line switch. The choice of N_() here is totally arbitrary; it could have just as easily been MarkThisStringForTranslation().

致謝

The following people contributed code, feedback, design suggestions, previous implementations, and valuable experience to the creation of this module:

Peter Funk

James Henstridge

Juan David Ibáñez Palomar

Marc-André Lemburg

Martin von Löwis

François Pinard

Barry Warsaw

Gustavo Niemeyer

註解

[1]

The default locale directory is system dependent; for example, on Red Hat Linux it is /usr/share/locale, but on Solaris it is /usr/lib/locale. The gettext module does not try to support these system dependent defaults; instead its default is sys.base_prefix/share/locale (see sys.base_prefix). For this reason, it is always best to call bindtextdomain() with an explicit absolute path at the start of your application.

[2]

請見上方 bindtextdomain() 之註解。

locale --- 國際化服務

原始碼：Lib/locale.py [https://github.com/python/cpython/tree/3.14/Lib/locale.py]

The locale module opens access to the POSIX locale database and functionality. The POSIX locale mechanism allows programmers to deal with certain cultural issues in an application, without requiring the programmer to know all the specifics of each country where the software is executed.

The locale module is implemented on top of the _locale module, which in turn uses an ANSI C locale implementation if available.

The locale module defines the following exception and functions:

exception locale.Error

Exception raised when the locale passed to setlocale() is not recognized.

locale.setlocale(category, locale=None)

If locale is given and not None, setlocale() modifies the locale setting for the category. The available categories are listed in the data description below. locale may be a string, or a pair, language code and encoding. An empty string specifies the user's default settings. If the modification of the locale fails, the exception Error is raised. If successful, the new locale setting is returned.

If locale is a pair, it is converted to a locale name using the locale aliasing engine. The language code has the same format as a locale name, but without encoding and @-modifier. The language code and encoding can be None.

If locale is omitted or None, the current setting for category is returned.

範例：

>>> import locale
>>> loc = locale.setlocale(locale.LC_ALL)  # get current locale
# use German locale; name and availability varies with platform
>>> locale.setlocale(locale.LC_ALL, 'de_DE.UTF-8')
>>> locale.strcoll('f\xe4n', 'foo')  # compare a string containing an umlaut
>>> locale.setlocale(locale.LC_ALL, '')   # use user's preferred locale
>>> locale.setlocale(locale.LC_ALL, 'C')  # use default (C) locale
>>> locale.setlocale(locale.LC_ALL, loc)  # restore saved locale

setlocale() is not thread-safe on most systems. Applications typically start with a call of:

import locale
locale.setlocale(locale.LC_ALL, '')

This sets the locale for all categories to the user's default setting (typically specified in the LANG environment variable). If the locale is not changed thereafter, using multithreading should not cause problems.

locale.localeconv()

Returns the database of the local conventions as a dictionary. This dictionary has the following strings as keys:

分類

Key

含義

LC_NUMERIC

'decimal_point'

Decimal point character.

'grouping'

Sequence of numbers specifying which relative positions the 'thousands_sep' is expected. If the sequence is terminated with CHAR_MAX, no further grouping is performed. If the sequence terminates with a 0, the last group size is repeatedly used.

'thousands_sep'

Character used between groups.

LC_MONETARY

'int_curr_symbol'

International currency symbol.

'currency_symbol'

Local currency symbol.

'p_cs_precedes/n_cs_precedes'

Whether the currency symbol precedes the value (for positive resp. negative values).

'p_sep_by_space/n_sep_by_space'

Whether the currency symbol is separated from the value by a space (for positive resp. negative values).

'mon_decimal_point'

Decimal point used for monetary values.

'frac_digits'

Number of fractional digits used in local formatting of monetary values.

'int_frac_digits'

Number of fractional digits used in international formatting of monetary values.

'mon_thousands_sep'

Group separator used for monetary values.

'mon_grouping'

Equivalent to 'grouping', used for monetary values.

'positive_sign'

Symbol used to annotate a positive monetary value.

'negative_sign'

Symbol used to annotate a negative monetary value.

'p_sign_posn/n_sign_posn'

The position of the sign (for positive resp. negative values), see below.

All numeric values can be set to CHAR_MAX to indicate that there is no value specified in this locale.

The possible values for 'p_sign_posn' and 'n_sign_posn' are given below.

Value

Explanation

0

Currency and value are surrounded by parentheses.

1

The sign should precede the value and currency symbol.

2

The sign should follow the value and currency symbol.

3

The sign should immediately precede the value.

4

The sign should immediately follow the value.

CHAR_MAX

Nothing is specified in this locale.

The function temporarily sets the LC_CTYPE locale to the LC_NUMERIC locale or the LC_MONETARY locale if locales are different and numeric or monetary strings are non-ASCII. This temporary change affects other threads.

在 3.7 版的變更: The function now temporarily sets the LC_CTYPE locale to the LC_NUMERIC locale in some cases.

locale.nl_langinfo(option)

Return some locale-specific information as a string. This function is not available on all systems, and the set of possible options might also vary across platforms. The possible argument values are numbers, for which symbolic constants are available in the locale module.

The nl_langinfo() function accepts one of the following keys. Most descriptions are taken from the corresponding description in the GNU C library.

locale.CODESET

Get a string with the name of the character encoding used in the selected locale.

locale.D_T_FMT

Get a string that can be used as a format string for time.strftime() to represent date and time in a locale-specific way.

locale.D_FMT

Get a string that can be used as a format string for time.strftime() to represent a date in a locale-specific way.

locale.T_FMT

Get a string that can be used as a format string for time.strftime() to represent a time in a locale-specific way.

locale.T_FMT_AMPM

Get a format string for time.strftime() to represent time in the am/pm format.

locale.DAY_1

locale.DAY_2

locale.DAY_3

locale.DAY_4

locale.DAY_5

locale.DAY_6

locale.DAY_7

Get the name of the n-th day of the week.

備註

This follows the US convention of DAY_1 being Sunday, not the international convention (ISO 8601) that Monday is the first day of the week.

locale.ABDAY_1

locale.ABDAY_2

locale.ABDAY_3

locale.ABDAY_4

locale.ABDAY_5

locale.ABDAY_6

locale.ABDAY_7

Get the abbreviated name of the n-th day of the week.

locale.MON_1

locale.MON_2

locale.MON_3

locale.MON_4

locale.MON_5

locale.MON_6

locale.MON_7

locale.MON_8

locale.MON_9

locale.MON_10

locale.MON_11

locale.MON_12

Get the name of the n-th month.

locale.ABMON_1

locale.ABMON_2

locale.ABMON_3

locale.ABMON_4

locale.ABMON_5

locale.ABMON_6

locale.ABMON_7

locale.ABMON_8

locale.ABMON_9

locale.ABMON_10

locale.ABMON_11

locale.ABMON_12

Get the abbreviated name of the n-th month.

locale.RADIXCHAR

Get the radix character (decimal dot, decimal comma, etc.).

locale.THOUSEP

Get the separator character for thousands (groups of three digits).

locale.YESEXPR

Get a regular expression that can be used with the regex function to recognize a positive response to a yes/no question.

locale.NOEXPR

Get a regular expression that can be used with the regex(3) function to recognize a negative response to a yes/no question.

備註

The regular expressions for YESEXPR and NOEXPR use syntax suitable for the regex function from the C library, which might differ from the syntax used in re.

locale.CRNCYSTR

Get the currency symbol, preceded by "-" if the symbol should appear before the value, "+" if the symbol should appear after the value, or "." if the symbol should replace the radix character.

locale.ERA

Get a string which describes how years are counted and displayed for each era in a locale.

Most locales do not define this value. An example of a locale which does define this value is the Japanese one. In Japan, the traditional representation of dates includes the name of the era corresponding to the then-emperor's reign.

Normally it should not be necessary to use this value directly. Specifying the E modifier in their format strings causes the time.strftime() function to use this information. The format of the returned string is specified in The Open Group Base Specifications Issue 8, paragraph 7.3.5.2 LC_TIME C-Language Access [https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap07.html#tag_07_03_05_02].

locale.ERA_D_T_FMT

Get a format string for time.strftime() to represent date and time in a locale-specific era-based way.

locale.ERA_D_FMT

Get a format string for time.strftime() to represent a date in a locale-specific era-based way.

locale.ERA_T_FMT

Get a format string for time.strftime() to represent a time in a locale-specific era-based way.

locale.ALT_DIGITS

Get a string consisting of up to 100 semicolon-separated symbols used to represent the values 0 to 99 in a locale-specific way. In most locales this is an empty string.

The function temporarily sets the LC_CTYPE locale to the locale of the category that determines the requested value (LC_TIME, LC_NUMERIC, LC_MONETARY or LC_MESSAGES) if locales are different and the resulting string is non-ASCII. This temporary change affects other threads.

在 3.14 版的變更: The function now temporarily sets the LC_CTYPE locale in some cases.

locale.getdefaultlocale([envvars])

Tries to determine the default locale settings and returns them as a tuple of the form (language code, encoding).

According to POSIX, a program which has not called setlocale(LC_ALL, '') runs using the portable 'C' locale. Calling setlocale(LC_ALL, '') lets it use the default locale as defined by the LANG variable. Since we do not want to interfere with the current locale setting we thus emulate the behavior in the way described above.

To maintain compatibility with other platforms, not only the LANG variable is tested, but a list of variables given as envvars parameter. The first found to be defined will be used. envvars defaults to the search path used in GNU gettext; it must always contain the variable name 'LANG'. The GNU gettext search path contains 'LC_ALL', 'LC_CTYPE', 'LANG' and 'LANGUAGE', in that order.

The language code has the same format as a locale name, but without encoding and @-modifier. The language code and encoding may be None if their values cannot be determined. The "C" locale is represented as (None, None).

自從版本 3.11 後不推薦使用，將會自版本 3.15 中移除。.

locale.getlocale(category=LC_CTYPE)

Returns the current setting for the given locale category as a tuple containing the language code and encoding. category may be one of the LC_* values except LC_ALL. It defaults to LC_CTYPE.

The language code has the same format as a locale name, but without encoding and @-modifier. The language code and encoding may be None if their values cannot be determined. The "C" locale is represented as (None, None).

locale.getpreferredencoding(do_setlocale=True)

Return the locale encoding used for text data, according to user preferences. User preferences are expressed differently on different systems, and might not be available programmatically on some systems, so this function only returns a guess.

On some systems, it is necessary to invoke setlocale() to obtain the user preferences, so this function is not thread-safe. If invoking setlocale is not necessary or desired, do_setlocale should be set to False.

On Android or if the Python UTF-8 Mode is enabled, always return 'utf-8', the locale encoding and the do_setlocale argument are ignored.

The Python preinitialization configures the LC_CTYPE locale. See also the filesystem encoding and error handler.

在 3.7 版的變更: The function now always returns "utf-8" on Android or if the Python UTF-8 Mode is enabled.

locale.getencoding()

Get the current locale encoding:

On Android and VxWorks, return "utf-8".

On Unix, return the encoding of the current LC_CTYPE locale. Return "utf-8" if nl_langinfo(CODESET) returns an empty string: for example, if the current LC_CTYPE locale is not supported.

On Windows, return the ANSI code page.

The Python preinitialization configures the LC_CTYPE locale. See also the filesystem encoding and error handler.

This function is similar to getpreferredencoding(False) except this function ignores the Python UTF-8 Mode.

在 3.11 版被加入.

locale.normalize(localename)

Returns a normalized locale code for the given locale name. The returned locale code is formatted for use with setlocale(). If normalization fails, the original name is returned unchanged.

If the given encoding is not known, the function defaults to the default encoding for the locale code just like setlocale().

locale.strcoll(string1, string2)

Compares two strings according to the current LC_COLLATE setting. As any other compare function, returns a negative, or a positive value, or 0, depending on whether string1 collates before or after string2 or is equal to it.

locale.strxfrm(string)

Transforms a string to one that can be used in locale-aware comparisons. For example, strxfrm(s1) < strxfrm(s2) is equivalent to strcoll(s1, s2) < 0. This function can be used when the same string is compared repeatedly, e.g. when collating a sequence of strings.

locale.format_string(format, val, grouping=False, monetary=False)

Formats a number val according to the current LC_NUMERIC setting. The format follows the conventions of the % operator. For floating-point values, the decimal point is modified if appropriate. If grouping is True, also takes the grouping into account.

If monetary is true, the conversion uses monetary thousands separator and grouping strings.

Processes formatting specifiers as in format % val, but takes the current locale settings into account.

在 3.7 版的變更: 新增了 monetary 關鍵字參數。

locale.currency(val, symbol=True, grouping=False, international=False)

Formats a number val according to the current LC_MONETARY settings.

The returned string includes the currency symbol if symbol is true, which is the default. If grouping is True (which is not the default), grouping is done with the value. If international is True (which is not the default), the international currency symbol is used.

備註

This function will not work with the 'C' locale, so you have to set a locale via setlocale() first.

locale.str(float)

Formats a floating-point number using the same format as the built-in function str(float), but takes the decimal point into account.

locale.delocalize(string)

Converts a string into a normalized number string, following the LC_NUMERIC settings.

在 3.5 版被加入.

locale.localize(string, grouping=False, monetary=False)

Converts a normalized number string into a formatted string following the LC_NUMERIC settings.

在 3.10 版被加入.

locale.atof(string, func=float)

Converts a string to a number, following the LC_NUMERIC settings, by calling func on the result of calling delocalize() on string.

locale.atoi(string)

Converts a string to an integer, following the LC_NUMERIC conventions.

locale.LC_CTYPE

Locale category for the character type functions. Most importantly, this category defines the text encoding, i.e. how bytes are interpreted as Unicode codepoints. See PEP 538 [https://peps.python.org/pep-0538/] and PEP 540 [https://peps.python.org/pep-0540/] for how this variable might be automatically coerced to C.UTF-8 to avoid issues created by invalid settings in containers or incompatible settings passed over remote SSH connections.

Python doesn't internally use locale-dependent character transformation functions from ctype.h. Instead, pyctype.h provides locale-independent equivalents like Py_TOLOWER.

locale.LC_COLLATE

Locale category for sorting strings. The functions strcoll() and strxfrm() of the locale module are affected.

locale.LC_TIME

Locale category for the formatting of time. The function time.strftime() follows these conventions.

locale.LC_MONETARY

Locale category for formatting of monetary values. The available options are available from the localeconv() function.

locale.LC_MESSAGES

Locale category for message display. Python currently does not support application specific locale-aware messages. Messages displayed by the operating system, like those returned by os.strerror() might be affected by this category.

This value may not be available on operating systems not conforming to the POSIX standard, most notably Windows.

locale.LC_NUMERIC

Locale category for formatting numbers. The functions format_string(), atoi(), atof() and str() of the locale module are affected by that category. All other numeric formatting operations are not affected.

locale.LC_ALL

Combination of all locale settings. If this flag is used when the locale is changed, setting the locale for all categories is attempted. If that fails for any category, no category is changed at all. When the locale is retrieved using this flag, a string indicating the setting for all categories is returned. This string can be later used to restore the settings.

locale.CHAR_MAX

This is a symbolic constant used for different values returned by localeconv().

Background, details, hints, tips and caveats

The C standard defines the locale as a program-wide property that may be relatively expensive to change. On top of that, some implementations are broken in such a way that frequent locale changes may cause core dumps. This makes the locale somewhat painful to use correctly.

Initially, when a program is started, the locale is the C locale, no matter what the user's preferred locale is. There is one exception: the LC_CTYPE category is changed at startup to set the current locale encoding to the user's preferred locale encoding. The program must explicitly say that it wants the user's preferred locale settings for other categories by calling setlocale(LC_ALL, '').

It is generally a bad idea to call setlocale() in some library routine, since as a side effect it affects the entire program. Saving and restoring it is almost as bad: it is expensive and affects other threads that happen to run before the settings have been restored.

If, when coding a module for general use, you need a locale independent version of an operation that is affected by the locale (such as certain formats used with time.strftime()), you will have to find a way to do it without using the standard library routine. Even better is convincing yourself that using locale settings is okay. Only as a last resort should you document that your module is not compatible with non-C locale settings.

The only way to perform numeric operations according to the locale is to use the special functions defined by this module: atof(), atoi(), format_string(), str().

There is no way to perform case conversions and character classifications according to the locale. For (Unicode) text strings these are done according to the character value only, while for byte strings, the conversions and classifications are done according to the ASCII value of the byte, and bytes whose high bit is set (i.e., non-ASCII bytes) are never converted or considered part of a character class such as letter or whitespace.

Locale names

The format of the locale name is platform dependent, and the set of supported locales can depend on the system configuration.

On Posix platforms, it usually has the format [1]:

  language ["_" territory] ["." charset] ["@" modifier]

where language is a two- or three-letter language code from ISO 639 [https://www.iso.org/iso-639-language-code], territory is a two-letter country or region code from ISO 3166 [https://www.iso.org/iso-3166-country-codes.html], charset is a locale encoding, and modifier is a script name, a language subtag, a sort order identifier, or other locale modifier (for example, "latin", "valencia", "stroke" and "euro").

On Windows, several formats are supported. [2] [3] A subset of IETF BCP 47 [https://www.rfc-editor.org/info/bcp47] tags:

  language ["-" script] ["-" territory] ["." charset]
  language ["-" script] "-" territory "-" modifier

where language and territory have the same meaning as in Posix, script is a four-letter script code from ISO 15924 [https://www.unicode.org/iso15924/], and modifier is a language subtag, a sort order identifier or custom modifier (for example, "valencia", "stroke" or "x-python"). Both hyphen ('-') and underscore ('_') separators are supported. Only UTF-8 encoding is allowed for BCP 47 tags.

Windows also supports locale names in the format:

  language ["_" territory] ["." charset]

where language and territory are full names, such as "English" and "United States", and charset is either a code page number (for example, "1252") or UTF-8. Only the underscore separator is supported in this format.

The "C" locale is supported on all platforms.

[1]

IEEE Std 1003.1-2024; 8.2 Internationalization Variables [https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap08.html#tag_08_02]

[2]

UCRT Locale names, Languages, and Country/Region strings [https://learn.microsoft.com/en-us/cpp/c-runtime-library/locale-names-languages-and-country-region-strings]

[3]

Locale Names [https://learn.microsoft.com/en-us/windows/win32/intl/locale-names]

For extension writers and programs that embed Python

Extension modules should never call setlocale(), except to find out what the current locale is. But since the return value can only be used portably to restore it, that is not very useful (except perhaps to find out whether or not the locale is C).

When Python code uses the locale module to change the locale, this also affects the embedding application. If the embedding application doesn't want this to happen, it should remove the _locale extension module (which does all the work) from the table of built-in modules in the config.c file, and make sure that the _locale module is not accessible as a shared library.

Access to message catalogs

locale.gettext(msg)

locale.dgettext(domain, msg)

locale.dcgettext(domain, msg, category)

locale.textdomain(domain)

locale.bindtextdomain(domain, dir)

locale.bind_textdomain_codeset(domain, codeset)

The locale module exposes the C library's gettext interface on systems that provide this interface. It consists of the functions gettext(), dgettext(), dcgettext(), textdomain(), bindtextdomain(), and bind_textdomain_codeset(). These are similar to the same functions in the gettext module, but use the C library's binary format for message catalogs, and the C library's search algorithms for locating message catalogs.

Python applications should normally find no need to invoke these functions, and should use gettext instead. A known exception to this rule are applications that link with additional C libraries which internally invoke C functions gettext or dcgettext. For these applications, it may be necessary to bind the text domain, so that the libraries can properly locate their message catalogs.

以 Tk 打造圖形使用者介面 (Graphical User Interfaces)

Tk/Tcl 長期以來一直是 Python 不可或缺的一部分。它提供了一個強大且獨立於平台的視窗工具包，可供使用 tkinter 套件及其擴充套件 tkinter.ttk 模組的 Python 開發者使用。

tkinter 套件是 Tcl/Tk 之上的一個輕薄物件導向層。要使用 tkinter，你不需要編寫 Tcl 程式，但會需要查閱 Tk 文件和部份 Tcl 文件。tkinter 是一組將 Tk 小工具 (widget) 實作為 Python 類別的包裝器。

tkinter 的主要優點是速度快，而且通常與 Python 捆綁 (bundle) 在一起。儘管其標準文件不是很完整，但還是有些不錯的材料，包括：參考資料、教學、書籍等。tkinter 曾因其過時的外觀而眾所皆知，但這在 Tk 8.5 中得到了極大的改進。此外，還有許多其他你可能會感興趣的 GUI 函式庫。Python wiki 列出了幾個替代的 GUI 框架和工具 [https://wiki.python.org/moin/GuiProgramming]。

tkinter --- Tcl/Tk 的 Python 介面

架構

Tkinter 模組

Tkinter 應急指南

一個 Hello World 程式

重要的 Tk 概念

了解 Tkinter 如何包裝 Tcl/Tk

我該如何...？哪個選項可以...？

瀏覽 Tcl/Tk 參考手冊

執行緒模型

實用參考

設定選項

Packer 佈局管理器

Packer 選項

耦合元件變數

視窗管理器

Tk 選項資料型別

繫結與事件

index 參數

圖片

檔案處理常式

tkinter.colorchooser --- 顏色選擇對話框

tkinter.font --- Tkinter 字型包裝器

Tkinter 對話框

tkinter.simpledialog --- 標準 Tkinter 輸入對話框

tkinter.filedialog --- 檔案選擇對話框

Native Load/Save Dialogs

tkinter.commondialog --- Dialog window templates

tkinter.messagebox --- Tkinter 訊息提示

tkinter.scrolledtext --- 捲動文字小工具

tkinter.dnd --- 拖放支援

tkinter.ttk --- Tk 主題化小工具

使用 Ttk

Ttk Widgets

Widget

標準選項

Scrollable Widget Options

Label Options

相容性選項

Widget States

ttk.Widget

Combobox

選項

Virtual events

ttk.Combobox

Spinbox

選項

Virtual events

ttk.Spinbox

Notebook

選項

Tab Options

Tab Identifiers

虛擬事件

ttk.Notebook

Progressbar

選項

ttk.Progressbar

Separator

選項

Sizegrip

Platform-specific notes

Bugs

Treeview

選項

Item Options

Tag Options

Column Identifiers

虛擬事件

ttk.Treeview

Ttk Styling

Layouts

IDLE --- Python 編輯器與 shell

目錄

File menu (Shell and Editor)

Edit menu (Shell and Editor)

Format menu (Editor window only)

Run menu (Editor window only)

Shell menu (Shell window only)

Debug menu (Shell window only)

Options menu (Shell and Editor)

Window menu (Shell and Editor)

Help menu (Shell and Editor)

Context menus

Editing and Navigation

Editor windows

Key bindings

Automatic indentation

Search and Replace

Completions

Calltips

Format block

Code Context

Shell window

Text colors

Startup and Code Execution

命令列用法

Startup failure

Running user code

User output in Shell

Developing tkinter applications

Running without a subprocess

Help and Preferences

Help sources

設定偏好

macOS 上的 IDLE

Extensions

idlelib --- implementation of IDLE application

turtle --- 龜圖學 (Turtle graphics)

介紹

Get started

教學

啟動一個烏龜環境

基本繪圖

Pen control

The turtle's position

Making algorithmic patterns

How to...

Get started as quickly as possible

Automatically begin and end filling

Use the turtle module namespace

Use turtle graphics in a script

Use object-oriented turtle graphics

Turtle graphics reference

Turtle methods

Methods of TurtleScreen/Screen

Methods of RawTurtle/Turtle and corresponding functions

Turtle motion

Tell Turtle's state

Settings for measurement

Pen control

Drawing state

Color control

Filling

More drawing control

Turtle state

Visibility

Appearance

Using events

Special Turtle methods

Compound shapes

Methods of TurtleScreen/Screen and corresponding functions

Window control

Animation control

Using screen events

Input methods

Settings and special methods

Methods specific to Screen, not inherited from TurtleScreen

Public classes

解釋

Help and configuration

How to use help

Translation of docstrings into different languages

How to configure Screen and Turtles

turtledemo --- Demo scripts

自 Python 2.6 以來的變更

自 Python 3.0 以來的變更

tkinter --- Tcl/Tk 的 Python 介面

原始碼：Lib/tkinter/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/__init__.py]

tkinter 套件（「Tk 介面」）是 Tcl/Tk GUI 工具集的標準 Python 介面。Tk 和 tkinter 在大多數 Unix 平台（包含 macOS）以及 Windows 系統上都可以使用。

從命令列執行 python -m tkinter 應該會開啟一個展示簡單 Tk 介面的視窗，讓你知道 tkinter 已正確安裝在你的系統上，並且也會顯示已安裝的 Tcl/Tk 版本，這樣你就可以閱讀該版本專屬的 Tcl/Tk 文件。

Tkinter 支援一系列的 Tcl/Tk 版本，這些版本可以是有或沒有執行緒支援的建構版本。官方的 Python 二進位發行版捆綁了有執行緒支援的 Tcl/Tk 8.6。關於支援版本的更多資訊，請參閱 _tkinter 模組的原始碼。

Tkinter 並非一個輕薄的包裝器，而是加入了相當多自身的邏輯，使其體驗更具 Python 風格（pythonic）。本文件將著重於這些新增和變更，對於未變更的細節，則會引導讀者參閱官方的 Tcl/Tk 文件。

備註

Tcl/Tk 8.5（2007）引入了一套現代化的主題式使用者介面元件，以及一個用以操作它們的新 API。新舊 API 目前都還能使用。你在網路上找到的大多數文件仍使用舊版 API，而且可能已經嚴重過時。

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

也參考

TkDocs [https://tkdocs.com/]

關於使用 Tkinter 建立使用者介面的詳盡教學。內容解釋了關鍵概念，並使用現代 API 來說明建議的方法。

Tkinter 8.5 reference: a GUI for Python [https://www.tkdocs.com/shipman/]

Tkinter 8.5 的參考文件，詳細說明了可用的類別、方法和選項。

Tcl/Tk 相關資源：

Tk 指令 [https://www.tcl.tk/man/tcl8.6/TkCmd/contents.htm]

Tkinter 所使用的每個底層 Tcl/Tk 指令的綜合參考資料。

Tcl/Tk 首頁 [https://www.tcl.tk]

額外的文件，以及連至 Tcl/Tk 核心開發的連結。

書籍：

Modern Tkinter for Busy Python Developers [https://tkdocs.com/book.html]

由 Mark Roseman 所著。（ISBN 978-1999149567）

Python GUI programming with Tkinter [https://www.packtpub.com/en-us/product/python-gui-programming-with-tkinter-9781788835886]

由 Alan D. Moore 所著。（ISBN 978-1788835886）

Programming Python [https://learning-python.com/about-pp4e.html]

由 Mark Lutz 所著；對 Tkinter 有極佳的涵蓋。（ISBN 978-0596158101）

Tcl and the Tk Toolkit (2nd edition) [https://www.amazon.com/exec/obidos/ASIN/032133633X]

由 Tcl/Tk 發明者 John Ousterhout 與 Ken Jones 所著；不包含 Tkinter。（ISBN 978-0321336330）

架構

Tcl/Tk 並非單一函式庫，而是由幾個不同的模組所組成，每個模組都有獨立的功能和官方文件。Python 的二進位發行版也隨附了一個附加模組。

Tcl

Tcl 是一個動態直譯的程式語言，就像 Python 一樣。雖然它可以作為通用程式語言獨立使用，但它最常被嵌入到 C 應用程式中，作為腳本引擎或 Tk 工具集的介面。Tcl 函式庫有一個 C 介面，可用於建立和管理一個或多個 Tcl 直譯器的實例，在這些實例中執行 Tcl 指令和腳本，並新增以 Tcl 或 C 實作的自訂指令。每個直譯器都有一個事件佇列，並有設施可以向其傳送事件並加以處理。與 Python 不同，Tcl 的執行模型是圍繞著協同多工（cooperative multitasking）設計的，而 Tkinter 則彌合了這種差異（詳情請參閱 Threading model）。

Tk

Tk 是一個以 C 實作的 Tcl 套件 [https://wiki.tcl-lang.org/37432]，它新增了自訂指令來建立和操作 GUI 元件。每個 Tk 物件都嵌入了自己載入 Tk 的 Tcl 直譯器實例。Tk 的元件非常可自訂，但代價是外觀較為過時。Tk 使用 Tcl 的事件佇列來產生和處理 GUI 事件。

Ttk

主題式 Tk（Ttk）是較新的一族 Tk 元件，相較於許多傳統的 Tk 元件，它在不同平台上提供了更好的外觀。從 Tk 8.5 版開始，Ttk 作為 Tk 的一部分發行。Python 的繫結（bindings）則在一個獨立的模組 tkinter.ttk 中提供。

在內部，Tk 和 Ttk 使用底層作業系統的設施，即 Unix/X11 上的 Xlib、macOS 上的 Cocoa、Windows 上的 GDI。

當你的 Python 應用程式使用 Tkinter 中的類別（例如，建立一個元件）時，tkinter 模組會先組合一個 Tcl/Tk 指令字串。它將該 Tcl 指令字串傳遞給一個內部的 _tkinter 二進位模組，後者再呼叫 Tcl 直譯器來對其進行計算。Tcl 直譯器接著會呼叫 Tk 和/或 Ttk 套件，而這些套件又會再呼叫 Xlib、Cocoa 或 GDI。

Tkinter 模組

對 Tkinter 的支援分散在數個模組中。大多數應用程式將需要主要的 tkinter 模組，以及 tkinter.ttk 模組，後者提供了現代主題式元件集和 API：

from tkinter import *
from tkinter import ttk

class tkinter.Tk(screenName=None, baseName=None, className='Tk', useTk=True, sync=False, use=None)

建構一個頂層 Tk 元件，它通常是應用程式的主視窗，並為此元件初始化一個 Tcl 直譯器。每個實例都有其自己關聯的 Tcl 直譯器。

Tk 類別通常使用所有預設值來實例化。然而，目前可辨識下列關鍵字引數：

screenName

當給定（作為字串）時，設定 DISPLAY 環境變數。（僅限 X11）

baseName

設定檔的名稱。預設情況下，baseName 是從程式名稱（sys.argv[0]）衍生而來。

className

元件類別的名稱。用作設定檔，也用作呼叫 Tcl 時的名稱（interp 中的 argv0）。

useTk

若為 True，則初始化 Tk 子系統。tkinter.Tcl() 函式會將此設定為 False。

sync

若為 True，則同步執行所有 X 伺服器指令，以便立即回報錯誤。可用於偵錯。（僅限 X11）

use

指定要嵌入應用程式的視窗 id，而不是將其建立為獨立的頂層視窗。id 必須以與頂層元件的 -use 選項值相同的方式指定（也就是說，其形式類似 winfo_id() 回傳的形式）。

請注意，在某些平台上，只有當 id 指向一個已啟用 -container 選項的 Tk 框架或頂層視窗時，此功能才能正常運作。

Tk 會讀取名為 .className.tcl 和 .baseName.tcl 的設定檔，並在 Tcl 直譯器中進行直譯，並對 .className.py 和 .baseName.py 的內容呼叫 exec()。設定檔的路徑是 HOME 環境變數，如果未定義，則是 os.curdir。

tk

透過實例化 Tk 建立的 Tk 應用程式物件。這提供了對 Tcl 直譯器的存取。每個附加到同一個 Tk 實例的元件，其 tk 屬性都具有相同的值。

master

包含此元件的元件物件。對於 Tk，master 是 None，因為它是主視窗。master 和 parent 這兩個術語很相似，有時會作為引數名稱互換使用；然而，呼叫 winfo_parent() 會回傳元件名稱的字串，而 master 則回傳物件。parent/child 反映了樹狀關係，而 master （或 container）/content 反映了容器結構。

children

此元件的直接子代，形式為一個 dict，其中鍵為子元件的名稱，值為子實例物件。

tkinter.Tcl(screenName=None, baseName=None, className='Tk', useTk=False)

Tcl() 函式是一個工廠函式，它建立的物件與 Tk 類別建立的物件非常相似，只是它不會初始化 Tk 子系統。這在驅動 Tcl 直譯器時最為有用，尤其是在不希望建立額外頂層視窗的環境中，或者在無法建立的環境中（例如沒有 X 伺服器的 Unix/Linux 系統）。由 Tcl() 物件建立的物件可以透過呼叫其 loadtk() 方法來建立一個頂層視窗（並初始化 Tk 子系統）。

提供 Tk 支援的模組包括：

tkinter

主要的 Tkinter 模組。

tkinter.colorchooser

讓使用者選擇顏色的對話方塊。

tkinter.commondialog

此處列出的其他模組中定義的對話方塊的基底類別。

tkinter.filedialog

讓使用者指定要開啟或儲存的檔案的通用對話方塊。

tkinter.font

協助處理字型的工具程式。

tkinter.messagebox

存取標準的 Tk 對話方塊。

tkinter.scrolledtext

內建垂直捲軸的文字元件。

tkinter.simpledialog

基本的對話方塊和便利函式。

tkinter.ttk

在 Tk 8.5 中引入的主題式元件集，為主 tkinter 模組中的許多傳統元件提供了現代化的替代方案。

額外模組：

_tkinter

一個包含 Tcl/Tk 低階介面的二進位模組。它由主 tkinter 模組自動引入，應用程式開發者不應直接使用它。它通常是一個共享函式庫（或 DLL），但在某些情況下可能會與 Python 直譯器靜態連結。

idlelib

Python 的整合開發與學習環境（IDLE）。基於 tkinter。

tkinter.constants

在將各種參數傳遞給 Tkinter 呼叫時，可用於替代字串的符號常數。由主 tkinter 模組自動引入。

tkinter.dnd

（實驗性）對 tkinter 的拖放支援。當它被 Tk DND 取代時，將會被棄用。

turtle

在 Tk 視窗中的海龜繪圖。

Tkinter 應急指南

本節並非旨在成為 Tk 或 Tkinter 的詳盡教學。為此，請參閱前面提到的外部資源之一。相反地，本節提供了一個快速導覽，介紹 Tkinter 應用程式的外觀、識別基礎的 Tk 概念，並解釋 Tkinter 包裝器的結構。

本節的其餘部分將幫助你識別在 Tkinter 應用程式中所需的類別、方法和選項，以及在哪裡可以找到關於它們的更詳細文件，包括在官方的 Tcl/Tk 參考手冊中。

一個 Hello World 程式

我們將從一個 Tkinter 的 "Hello World" 應用程式開始。這不是我們能寫出的最小程式，但足以說明一些你需要知道的關鍵概念。

from tkinter import *
from tkinter import ttk
root = Tk()
frm = ttk.Frame(root, padding=10)
frm.grid()
ttk.Label(frm, text="Hello World!").grid(column=0, row=0)
ttk.Button(frm, text="Quit", command=root.destroy).grid(column=1, row=0)
root.mainloop()

在引入之後，下一行建立了一個 Tk 類別的實例，它會初始化 Tk 並建立其關聯的 Tcl 直譯器。它還會建立一個頂層視窗，稱為根視窗，作為應用程式的主視窗。

接下來的一行建立了一個框架元件，在本例中，它將包含我們接下來要建立的一個標籤和一個按鈕。該框架被放置在根視窗內。

下一行建立了一個包含靜態文字字串的標籤元件。grid() 方法用於指定標籤在其包含的框架元件中的相對佈局（位置），類似於 HTML 中表格的運作方式。

然後建立一個按鈕元件，並放置在標籤的右側。當按下時，它將呼叫根視窗的 destroy() 方法。

最後，mainloop() 方法將所有內容顯示在螢幕上，並回應使用者輸入，直到程式終止。

重要的 Tk 概念

即使是這個簡單的程式也說明了以下關鍵的 Tk 概念：

元件（widgets）

一個 Tkinter 使用者介面是由個別的元件所組成。每個元件都表示為一個 Python 物件，從 ttk.Frame、ttk.Label 和 ttk.Button 等類別實例化而來。

元件階層（widget hierarchy）

元件被安排在一個階層中。標籤和按鈕被包含在一個框架內，而框架又被包含在根視窗內。在建立每個子元件時，其父元件會作為第一個引數傳遞給元件的建構函式。

設定選項（configuration options）

元件具有設定選項，可以修改其外觀和行為，例如在標籤或按鈕中顯示的文字。不同類別的元件會有不同的選項集。

佈局管理（geometry management）

元件在建立時不會自動新增到使用者介面中。像 grid 這樣的佈局管理器（geometry manager）會控制它們在使用者介面中的放置位置。

事件迴圈（event loop）

Tkinter 只有在主動執行事件迴圈時，才會對使用者輸入、程式的變更，甚至螢幕刷新做出反應。如果你的程式沒有執行事件迴圈，你的使用者介面將不會更新。

了解 Tkinter 如何包裝 Tcl/Tk

當你的應用程式使用 Tkinter 的類別和方法時，Tkinter 內部正在組合代表 Tcl/Tk 指令的字串，並在附加到你應用程式 Tk 實例的 Tcl 直譯器中執行這些指令。

無論是試圖瀏覽參考文件、尋找正確的方法或選項、改寫一些現有程式碼，還是偵錯你的 Tkinter 應用程式，在某些時候，了解那些底層 Tcl/Tk 指令的樣貌會很有幫助。

為了說明，以下是上面 Tkinter 腳本主要部分的 Tcl/Tk 對等程式碼。

ttk::frame .frm -padding 10
grid .frm
grid [ttk::label .frm.lbl -text "Hello World!"] -column 0 -row 0
grid [ttk::button .frm.btn -text "Quit" -command "destroy ."] -column 1 -row 0

Tcl 的語法類似於許多 shell 語言，第一個字是要執行的指令，後面跟著該指令的引數，以空格分隔。在不深入太多細節的情況下，請注意以下幾點：

用於建立元件的指令（如 ttk::frame）對應於 Tkinter 中的元件類別。

Tcl 元件選項（如 -text）對應於 Tkinter 中的關鍵字引數。

在 Tcl 中，元件是透過路徑名稱（如 .frm.btn）來參照，而 Tkinter 不使用名稱，而是使用物件參照。

元件在元件階層中的位置被編碼在其（階層式）路徑名稱中，該路徑名稱使用 .（點）作為路徑分隔符。根視窗的路徑名稱就是 .（點）。在 Tkinter 中，階層不是由路徑名稱定義的，而是在建立每個子元件時指定父元件來定義的。

在 Tcl 中實作為獨立指令的操作（如 grid 或 destroy），在 Tkinter 中則表示為元件物件上的方法。正如你稍後會看到的，在其他時候，Tcl 使用的看起來像是對元件物件的方法呼叫，這更接近 Tkinter 中的用法。

我該如何...？哪個選項可以...？

如果你不確定如何在 Tkinter 中做某件事，並且無法立即在你正在使用的教學或參考文件中找到它，這裡有一些可能有幫助的策略。

首先，請記住，個別元件的運作細節可能會因 Tkinter 和 Tcl/Tk 的不同版本而異。如果你正在搜尋文件，請確保它對應於你系統上安裝的 Python 和 Tcl/Tk 版本。

在搜尋如何使用 API 時，知道你正在使用的類別、選項或方法的確切名稱會很有幫助。自省（Introspection），無論是在互動式 Python shell 中還是使用 print()，都可以幫助你識別所需內容。

要找出任何元件上有哪些可用的設定選項，請呼叫其 configure() 方法，該方法會回傳一個字典，其中包含有關每個物件的各種資訊，包括其預設值和目前值。使用 keys() 僅取得每個選項的名稱。

btn = ttk.Button(frm, ...)
print(btn.configure().keys())

由於大多數元件有許多共通的設定選項，找出特定於某個元件類別的選項會很有用。將選項串列與像框架這樣較簡單的元件的選項串列進行比較，是做到這一點的一種方法。

print(set(btn.configure().keys()) - set(frm.configure().keys()))

同樣地，你可以使用標準的 dir() 函式來尋找元件物件可用的方法。如果你試一下，你會看到有超過 200 個常見的元件方法，所以再次強調，識別特定於某個元件類別的方法是很有幫助的。

print(dir(btn))
print(set(dir(btn)) - set(dir(frm)))

瀏覽 Tcl/Tk 參考手冊

如前所述，官方的 Tk 指令 [https://www.tcl.tk/man/tcl8.6/TkCmd/contents.htm] 參考手冊（man pages）通常是對元件上特定操作作用的最準確描述。即使你知道所需選項或方法的名稱，你可能仍有幾個地方需要查看。

雖然 Tkinter 中的所有操作都實作為對元件物件的方法呼叫，但你已經看到許多 Tcl/Tk 操作顯示為指令，這些指令將元件路徑名稱作為其第一個參數，後面跟著可選的參數，例如：

destroy .
grid .frm.btn -column 0 -row 0

然而，其他的看起來更像是對元件物件呼叫的方法（事實上，當你在 Tcl/Tk 中建立一個元件時，它會建立一個以元件路徑名稱為名的 Tcl 指令，該指令的第一個參數是要呼叫的方法名稱）。

.frm.btn invoke
.frm.lbl configure -text "Goodbye"

在官方的 Tcl/Tk 參考文件中，你會在特定元件的 man page 上找到大多數看起來像方法呼叫的操作（例如，你可以在 ttk::button [https://www.tcl.tk/man/tcl8.6/TkCmd/ttk_button.htm] man page 上找到 invoke() 方法），而將元件作為參數的函式通常有自己的 man page（例如 grid [https://www.tcl.tk/man/tcl8.6/TkCmd/grid.htm]）。

你可以在 options [https://www.tcl.tk/man/tcl8.6/TkCmd/options.htm] 或 ttk::widget [https://www.tcl.tk/man/tcl8.6/TkCmd/ttk_widget.htm] man page 中找到許多常見的選項和方法，而其他的則在特定元件類別的 man page 中找到。

你還會發現許多 Tkinter 方法有複合名稱，例如 winfo_x()、winfo_height()、winfo_viewable()。你可以在 winfo [https://www.tcl.tk/man/tcl8.6/TkCmd/winfo.htm] man page 中找到所有這些文件的說明。

備註

有點令人困惑的是，所有 Tkinter 元件上還有一些方法，它們實際上並不是對該元件進行操作，而是在全域範圍內操作，獨立於任何元件。例如存取剪貼簿或系統鈴聲的方法。（它們恰好被實作為所有 Tkinter 元件都繼承的基底 Widget 類別中的方法）。

執行緒模型

Python 和 Tcl/Tk 有非常不同的執行緒模型，tkinter 試圖彌合這種差異。如果你使用執行緒，你可能需要意識到這一點。

一個 Python 直譯器可能有多個與之關聯的執行緒。在 Tcl 中，可以建立多個執行緒，但每個執行緒都有一個獨立的 Tcl 直譯器實例與之關聯。執行緒也可以建立多個直譯器實例，但每個直譯器實例只能由建立它的那個執行緒使用。

由 tkinter 建立的每個 Tk 物件都包含一個 Tcl 直譯器。它還會追蹤是哪個執行緒建立了該直譯器。可以從任何 Python 執行緒呼叫 tkinter。在內部，如果呼叫來自建立 Tk 物件的執行緒以外的執行緒，則會將一個事件發佈到直譯器的事件佇列中，執行後，結果會回傳給呼叫的 Python 執行緒。

Tcl/Tk 應用程式通常是事件驅動的，這意味著在初始化之後，直譯器會執行一個事件迴圈（即 Tk.mainloop()）並回應事件。因為它是單執行緒的，事件處理常式必須快速回應，否則它們會阻塞其他事件的處理。為避免這種情況，任何長時間執行的計算都不應在事件處理常式中執行，而是使用計時器將其分解成更小的部分，或在另一個執行緒中執行。這與許多 GUI 工具集不同，在那些工具集中，GUI 在一個與所有應用程式碼（包括事件處理常式）完全分離的執行緒中執行。

如果 Tcl 直譯器沒有在執行事件迴圈和處理事件，那麼從執行 Tcl 直譯器的執行緒以外的執行緒發出的任何 tkinter 呼叫都將失敗。

存在一些特殊情況：

Tcl/Tk 函式庫可以被建構成不具備執行緒感知能力。在這種情況下，tkinter 會從原始的 Python 執行緒呼叫該函式庫，即使這與建立 Tcl 直譯器的執行緒不同。一個全域鎖確保一次只發生一個呼叫。

雖然 tkinter 允許你建立多個 Tk 物件的實例（每個都有自己的直譯器），但屬於同一個執行緒的所有直譯器共享一個共同的事件佇列，這很快就會變得混亂。在實務上，不要一次建立多個 Tk 的實例。否則，最好在不同的執行緒中建立它們，並確保你正在執行一個具備執行緒感知能力的 Tcl/Tk 建構版本。

阻塞事件處理常式並不是防止 Tcl 直譯器重新進入事件迴圈的唯一方法。甚至可以執行多個巢狀的事件迴圈或完全放棄事件迴圈。如果你在事件或執行緒方面做任何複雜的操作，請注意這些可能性。

目前有少數幾個 tkinter 函式只有在從建立 Tcl 直譯器的執行緒中呼叫時才能正常運作。

實用參考

設定選項

選項控制著諸如元件的顏色和邊框寬度等。選項可以透過三種方式設定：

在物件建立時，使用關鍵字引數

fred = Button(self, fg="red", bg="blue")

在物件建立後，將選項名稱視為字典索引

fred["fg"] = "red"
fred["bg"] = "blue"

在物件建立後，使用 config() 方法更新多個屬性

fred.config(fg="red", bg="blue")

有關給定選項及其行為的完整解釋，請參閱相關元件的 Tk man pages。

請注意，man pages 為每個元件列出了「標準選項」和「元件特定選項」。前者是許多元件共有的選項串列，後者是該特定元件特有的選項。標準選項記錄在 options(3) [https://manpages.debian.org/options(3)] man page 中。

本文件中未對標準選項和元件特定選項進行區分。某些選項不適用於某些類型的元件。給定元件是否回應特定選項取決於該元件的類別；按鈕有 command 選項，標籤則沒有。

給定元件支援的選項列在該元件的 man page 中，或者可以在 runtime 透過不帶引數呼叫 config() 方法，或對該元件呼叫 keys() 方法來查詢。這些呼叫的回傳值是一個字典，其鍵是選項名稱的字串（例如 'relief'），其值是 5-tuples。

某些選項，如 bg，是具有長名稱的常見選項的同義詞（bg 是 "background" 的簡寫）。將簡寫選項的名稱傳遞給 config() 方法將回傳一個 2-tuple，而不是 5-tuple。回傳的 2-tuple 將包含同義詞的名稱和「真實」選項（例如 ('bg', 'background')）。

索引

含義

範例

0

選項名稱

'relief'

1

用於資料庫查詢的選項名稱

'relief'

2

用於資料庫查詢的選項類別

'Relief'

3

預設值

'raised'

4

目前值

'groove'

範例：

>>> print(fred.config())
{'relief': ('relief', 'relief', 'Relief', 'raised', 'groove')}

當然，印出的字典將包含所有可用的選項及其值。這僅作為一個範例。

Packer 佈局管理器

packer 是 Tk 的佈局管理（geometry manager）機制之一。佈局管理器（geometry manager）用於指定元件在其容器內的相對位置。與較為繁瑣的 placer（較不常用，我們在此不予介紹）相比，packer 採用定性的關係規範——上方、左方、填滿等——並為你計算出確切的放置座標。

任何 master 元件的大小由其內部的「content 元件」的大小決定。packer 用於控制 content 元件在被 packed 的容器內部出現的位置。你可以將元件 pack 到框架中，再將框架 pack 到其他框架中，以達到你想要的佈局。此外，一旦 packed，佈局會動態調整以適應設定的增量變更。

請注意，元件在透過佈局管理器（geometry manager）指定其佈局（geometry）之前是不會出現的。一個常見的早期錯誤是忽略了佈局（geometry）指定，然後在元件被建立但沒有任何東西出現時感到驚訝。一個元件只有在例如 packer 的 pack() 方法被應用於其上之後才會出現。

pack() 方法可以與關鍵字選項/值對一起呼叫，以控制元件在其容器中出現的位置，以及當主應用程式視窗調整大小時它的行為方式。以下是一些範例：

fred.pack()                     # 預設為 side = "top"
fred.pack(side="left")
fred.pack(expand=1)

Packer 選項

有關 packer 及其可接受選項的更詳盡資訊，請參閱 man pages 和 John Ousterhout 書中的第 183 頁。

anchor

錨點類型。表示 packer 將每個內容放置在其區域中的位置。

expand

布林值，0 或 1。

fill

合法值：'x'、'y'、'both'、'none'。

ipadx 和 ipady

一個距離 —— 指定內容每一側的內部填充。

padx 和 pady

一個距離 —— 指定內容每一側的外部填充。

side

合法值為：'left'、'right'、'top'、'bottom'。

耦合元件變數

某些元件（如文字輸入元件）的目前值設定可以透過使用特殊選項直接連接到應用程式變數。這些選項是 variable、textvariable、onvalue、offvalue 和 value。這種連接是雙向的：如果變數因任何原因發生變化，與之連接的元件將會更新以反映新值。

不幸的是，在 tkinter 的目前實作中，無法透過 variable 或 textvariable 選項將任意的 Python 變數傳遞給元件。唯一適用此功能的變數類型是從 tkinter 中定義的一個名為 Variable 的類別繼承的子類別變數。

已經定義了許多有用的 Variable 子類別：StringVar、IntVar、DoubleVar 和 BooleanVar。要讀取此類變數的目前值，請對其呼叫 get() 方法，要更改其值，則呼叫 set() 方法。如果你遵循此協定，元件將始終追蹤變數的值，無需你進一步干預。

舉例來說：

import tkinter as tk

class App(tk.Frame):
    def __init__(self, master):
        super().__init__(master)
        self.pack()

        self.entrythingy = tk.Entry()
        self.entrythingy.pack()

        # 建立應用程式變數。
        self.contents = tk.StringVar()
        # 將其設定為某個值。
        self.contents.set("this is a variable")
        # 告訴 entry 元件監視此變數。
        self.entrythingy["textvariable"] = self.contents

        # 為使用者按下 return 鍵定義一個回呼。
        # 它會印出變數的目前值。
        self.entrythingy.bind('<Key-Return>',
                             self.print_contents)

    def print_contents(self, event):
        print("Hi. The current entry content is:",
              self.contents.get())

root = tk.Tk()
myapp = App(root)
myapp.mainloop()

視窗管理器

在 Tk 中，有一個工具指令 wm，用於與視窗管理器互動。wm 指令的選項允許你控制標題、位置、圖示點陣圖等。在 tkinter 中，這些指令已實作為 Wm 類別上的方法。頂層元件是 Wm 類別的子類別，因此可以直接呼叫 Wm 方法。

要取得包含給定元件的頂層視窗，你通常可以直接參照該元件的 master。當然，如果該元件被 packed 在一個框架內，master 將不代表一個頂層視窗。要取得包含任意元件的頂層視窗，你可以呼叫 _root() 方法。此方法以底線開頭，表示此函式是實作的一部分，而不是 Tk 功能的介面。

以下是一些常見用法範例：

import tkinter as tk

class App(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()

# 建立應用程式
myapp = App()

#
# 以下是對視窗管理器類別的方法呼叫
#
myapp.master.title("My Do-Nothing Application")
myapp.master.maxsize(1000, 400)

# 啟動程式
myapp.mainloop()

Tk 選項資料型別

anchor

合法值為羅盤方位點："n"、"ne"、"e"、"se"、"s"、"sw"、"w"、"nw"，以及 "center"。

bitmap

有八個內建的、命名的點陣圖：'error'、'gray25'、'gray50'、'hourglass'、'info'、'questhead'、'question'、'warning'。要指定一個 X 點陣圖檔名，請給出檔案的完整路徑，並在前面加上一個 @，例如 "@/usr/contrib/bitmap/gumby.bit"。

boolean

你可以傳遞整數 0 或 1，或字串 "yes" 或 "no"。

callback

這是任何不帶引數的 Python 函式。例如：

def print_it():
    print("hi there")
fred["command"] = print_it

color

顏色可以以 rgb.txt 檔案中的 X 顏色名稱給出，或以表示 RGB 值的字串給出，範圍可以是 4 位元："#RGB"、8 位元："#RRGGBB"、12 位元："#RRRGGGBBB" 或 16 位元："#RRRRGGGGBBBB"，其中 R、G、B 在此代表任何合法的十六進位數字。詳情請參閱 Ousterhout 書中的第 160 頁。

cursor

可以使用 cursorfont.h 中的標準 X 游標名稱，無需 XC_ 前綴。例如，要取得手形游標（XC_hand2），請使用字串 "hand2"。你也可以指定自己的點陣圖和遮罩檔案。請參閱 Ousterhout 書中的第 179 頁。

distance

螢幕距離可以以像素或絕對距離指定。像素以數字給出，絕對距離以字串給出，尾隨字元表示單位：c 代表公分，i 代表英寸，m 代表毫米，p 代表印刷的點。例如，3.5 英寸表示為 "3.5i"。

font

Tk 使用串列字型名稱格式，例如 {courier 10 bold}。帶有正數的字型大小以點為單位；帶有負數的大小以像素為單位。

geometry

這是一個 widthxheight 形式的字串，其中 width 和 height 對於大多數元件是以像素為單位（對於顯示文字的元件則以字元為單位）。例如：fred["geometry"] = "200x100"。

justify

合法值為字串："left"、"center" 和 "right"。

region

這是一個由四個以空格分隔的元素組成的字串，每個元素都是一個合法的距離（見上文）。例如："2 3 4 5"、"3i 2i 4.5i 2i" 和 "3c 2c 4c 10.43c" 都是合法的區域。

relief

決定元件的邊框樣式。合法值為："raised"、"sunken"、"flat"、"groove" 和 "ridge"。

scrollcommand

這幾乎總是某個捲軸元件的 set() 方法，但也可以是任何接受單一引數的元件方法。

wrap

必須是以下之一："none"、"char" 或 "word"。

繫結與事件

來自元件指令的 bind 方法允許你監視某些事件，並在該事件類型發生時觸發一個回呼函式。bind 方法的形式是：

def bind(self, sequence, func, add=''):

其中：

sequence

是一個表示目標事件類型的字串。（詳情請參閱 bind(3tk) [https://manpages.debian.org/bind(3tk)] man page，以及 John Ousterhout 的書 Tcl and the Tk Toolkit (2nd edition) 的第 201 頁）。

func

是一個 Python 函式，接受一個引數，在事件發生時被呼叫。一個 Event 實例將作為引數傳遞。（以這種方式部署的函式通常稱為回呼。）

add

是可選的，可以是 '' 或 '+'。傳遞一個空字串表示此繫結將取代與此事件關聯的任何其他繫結。傳遞一個 '+' 意味著此函式將被新增到繫結到此事件類型的函式串列中。

舉例來說：

def turn_red(self, event):
    event.widget["activeforeground"] = "red"

self.button.bind("<Enter>", self.turn_red)

請注意在 turn_red() 回呼中如何存取事件的 widget 欄位。此欄位包含捕獲 X 事件的元件。下表列出了你可以存取的其他事件欄位，以及它們在 Tk 中的表示方式，這在參閱 Tk man pages 時可能很有用。

Tk

Tkinter 事件欄位

Tk

Tkinter 事件欄位

%f

focus

%A

char

%h

height

%E

send_event

%k

keycode

%K

keysym

%s

state

%N

keysym_num

%t

time

%T

type

%w

width

%W

widget

%x

x

%X

x_root

%y

y

%Y

y_root

index 參數

許多元件需要傳遞 "index" 參數。這些參數用於指向 Text 元件中的特定位置、Entry 元件中的特定字元，或 Menu 元件中的特定選單項目。

Entry 元件索引（index、view index 等）

Entry 元件具有參照所顯示文字中字元位置的選項。你可以使用這些 tkinter 函式來存取文字元件中的這些特殊點：

Text 元件索引

Text 元件的索引表示法非常豐富，在 Tk man pages 中有最好的描述。

選單索引（menu.invoke()、menu.entryconfig() 等）

選單的某些選項和方法會操作特定的選單項目。每當選項或參數需要選單索引時，你可以傳入：

一個整數，它參照元件中項目的數字位置，從頂部開始計數，從 0 開始；

字串 "active"，它參照目前在游標下的選單位置；

字串 "last"，它參照最後一個選單項目；

一個以 @ 為前綴的整數，如 @6，其中該整數被解釋為選單座標系統中的 y 像素座標；

字串 "none"，表示完全沒有選單項目，最常用於 menu.activate() 以停用所有項目，最後，

一個文字字串，它會與從選單頂部掃描到底部的選單項目標籤進行模式匹配。請注意，此索引類型在所有其他類型之後考慮，這意味著標籤為 last、active 或 none 的選單項目的匹配可能會被解釋為上述的字面值。

圖片

可以透過 tkinter.Image 的相應子類別來建立不同格式的圖片：

BitmapImage 用於 XBM 格式的圖片。

PhotoImage 用於 PGM、PPM、GIF 和 PNG 格式的圖片。後者從 Tk 8.6 開始支援。

任一類型的圖片都是透過 file 或 data 選項建立的（也有其他選項可用）。

在 3.13 版的變更: 新增了 PhotoImage 方法 copy_replace()，用於將一個區域從一個圖片複製到另一個圖片，可能帶有像素縮放和/或子採樣。將 from_coords 參數新增到 PhotoImage 方法 copy()、zoom() 和 subsample()。將 zoom 和 subsample 參數新增到 PhotoImage 方法 copy()。

然後，圖片物件可以在任何支援 image 選項的元件（例如標籤、按鈕、選單）中使用。在這些情況下，Tk 將不會保留對圖片的參照。當對圖片物件的最後一個 Python 參照被刪除時，圖片資料也會被刪除，Tk 將在使用該圖片的任何地方顯示一個空框。

也參考

Pillow [https://python-pillow.org/] 套件新增了對 BMP、JPEG、TIFF 和 WebP 等格式的支援。

檔案處理常式

Tk 允許你註冊和取消註冊一個回呼函式，當檔案描述器上可以進行 I/O 時，該函式將從 Tk 主迴圈中被呼叫。每個檔案描述器只能註冊一個處理常式。範例程式碼：

import tkinter
widget = tkinter.Tk()
mask = tkinter.READABLE | tkinter.WRITABLE
widget.tk.createfilehandler(file, mask, callback)
...
widget.tk.deletefilehandler(file)

此功能在 Windows 上不可用。

由於你不知道有多少位元組可供讀取，你可能不想使用 BufferedIOBase 或 TextIOBase 的 read() 或 readline() 方法，因為這些方法會堅持讀取預定義數量的位元組。對於 sockets（通訊端），recv() 或 recvfrom() 方法可以正常運作；對於其他檔案，請使用原始讀取或 os.read(file.fileno(), maxbytecount)。

Widget.tk.createfilehandler(file, mask, func)

註冊檔案處理常式回呼函式 func。file 引數可以是一個具有 fileno() 方法的物件（例如檔案或 socket（通訊端）物件），或是一個整數檔案描述器。mask 引數是下面三個常數中任意一個的 OR 組合。回呼函式被呼叫的方式如下：

callback(file, mask)

Widget.tk.deletefilehandler(file)

取消註冊檔案處理常式。

_tkinter.READABLE

_tkinter.WRITABLE

_tkinter.EXCEPTION

用於 mask 引數的常數。

tkinter.colorchooser --- 顏色選擇對話框

原始碼：Lib/tkinter/colorchooser.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/colorchooser.py]

tkinter.colorchooser 模組提供類別 Chooser 當作與原生顏色選擇器對話框的介面。Chooser 實作了一個顏色選擇的互動視窗。類別 Chooser 繼承了類別 Dialog。

class tkinter.colorchooser.Chooser(master=None, **options)

tkinter.colorchooser.askcolor(color=None, **options)

建立一個顏色選擇對話框。一旦呼叫這個方法便會顯示視窗，等待使用者做出選擇後，回傳選擇的顏色（或者是 None）給呼叫者。

也參考

tkinter.commondialog 模組

Tkinter 標準對話框模組

tkinter.font --- Tkinter 字型包裝器

原始碼：Lib/tkinter/font.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/font.py]

tkinter.font 模組提供類別 Font，可以建立及使用已命名的字型。

不同的字重 (font weights) 以及傾斜 (slant) 是：

tkinter.font.NORMAL

tkinter.font.BOLD

tkinter.font.ITALIC

tkinter.font.ROMAN

class tkinter.font.Font(root=None, font=None, name=None, exists=False, **options)

類別 Font 代表一個已命名字型。Font 實例會被賦予一個的名字，也可以特指他們的字型家族 (font family)、字級 (size)、以及外觀設定。已命名字型是 Tk 建立及辨識字型為單一物件的方式，而不是每次出現時特指字型的屬性。

引數：

font - 字型指定符號元組 (family, size, options)

name - 獨特字型名稱

exists - 如果存在的話，指向現有的已命名字型

額外的關鍵字選項（若已指定 font 則會忽略）：

family - 字型家族，例如：Courier、Times

size - 字級

如果 size 是正數則會直譯成以點 (point) 為單位的字級。

如果 size 是負數則會變成絕對值

以像素 (pixel) 為單位的字級。

weight - 強調字型，例如：NORMAL（標準體）、BOLD（粗體）

slant - 例如：ROMAN（正體）、ITALIC（斜體）

underline - 字型加上底線（0 - 無底線、 1 - 加上底線）

overstrike - 字型加上刪除線（0 - 無刪除線、 1 - 加上刪除線）

actual(option=None, displayof=None)

回傳字型的屬性。

cget(option)

取得字型的其中一個屬性。

config(**options)

修改字體的多個屬性。

copy()

回傳目前字體的新實例。

measure(text, displayof=None)

回傳目前字型被格式化時，在特定顯示區域中文字所用的空間。若顯示區域沒有被指定，則會假定主程式視窗為顯示區域。

metrics(*options, **kw)

回傳字型特定的資料。其選項包含：

ascent - 基準線以及最高點的距離

在字型中的一個字母可以佔用的空間

descent - 基準線以及最低點的距離

在字型中的一個字母可以佔用的空間

linespace - 最小所需的垂直間距

在字型中的任兩個字母之間，確保跨行時不會有垂直重疊。

fixed - 若字型為等寬 (fixed-width) 的則為 1，否則為 0

tkinter.font.families(root=None, displayof=None)

回傳不同的字型家族。

tkinter.font.names(root=None)

回傳已定義字型的名字。

tkinter.font.nametofont(name, root=None)

回傳一個 Font，代表一個 tk 已命名字型。

在 3.10 版的變更: 新增 root 參數。

Tkinter 對話框

tkinter.simpledialog --- 標準 Tkinter 輸入對話框

原始碼：Lib/tkinter/simpledialog.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/simpledialog.py]

The tkinter.simpledialog module contains convenience classes and functions for creating simple modal dialogs to get a value from the user.

tkinter.simpledialog.askfloat(title, prompt, **kw)

tkinter.simpledialog.askinteger(title, prompt, **kw)

tkinter.simpledialog.askstring(title, prompt, **kw)

The above three functions provide dialogs that prompt the user to enter a value of the desired type.

class tkinter.simpledialog.Dialog(parent, title=None)

The base class for custom dialogs.

body(master)

Override to construct the dialog's interface and return the widget that should have initial focus.

buttonbox()

Default behaviour adds OK and Cancel buttons. Override for custom button layouts.

tkinter.filedialog --- 檔案選擇對話框

原始碼：Lib/tkinter/filedialog.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/filedialog.py]

The tkinter.filedialog module provides classes and factory functions for creating file/directory selection windows.

Native Load/Save Dialogs

The following classes and functions provide file dialog windows that combine a native look-and-feel with configuration options to customize behaviour. The following keyword arguments are applicable to the classes and functions listed below:

parent - the window to place the dialog on top of

title - the title of the window

initialdir - the directory that the dialog starts in

initialfile - the file selected upon opening of the dialog

filetypes - a sequence of (label, pattern) tuples, '*' wildcard is allowed

defaultextension - default extension to append to file (save dialogs)

multiple - when true, selection of multiple items is allowed

Static factory functions

The below functions when called create a modal, native look-and-feel dialog, wait for the user's selection, then return the selected value(s) or None to the caller.

tkinter.filedialog.askopenfile(mode='r', **options)

tkinter.filedialog.askopenfiles(mode='r', **options)

The above two functions create an Open dialog and return the opened file object(s) in read-only mode.

tkinter.filedialog.asksaveasfile(mode='w', **options)

Create a SaveAs dialog and return a file object opened in write-only mode.

tkinter.filedialog.askopenfilename(**options)

tkinter.filedialog.askopenfilenames(**options)

The above two functions create an Open dialog and return the selected filename(s) that correspond to existing file(s).

tkinter.filedialog.asksaveasfilename(**options)

Create a SaveAs dialog and return the selected filename.

tkinter.filedialog.askdirectory(**options)

Prompt user to select a directory.

Additional keyword option:

mustexist - determines if selection must be an existing directory.

class tkinter.filedialog.Open(master=None, **options)

class tkinter.filedialog.SaveAs(master=None, **options)

The above two classes provide native dialog windows for saving and loading files.

Convenience classes

The below classes are used for creating file/directory windows from scratch. These do not emulate the native look-and-feel of the platform.

class tkinter.filedialog.Directory(master=None, **options)

Create a dialog prompting the user to select a directory.

備註

The FileDialog class should be subclassed for custom event handling and behaviour.

class tkinter.filedialog.FileDialog(master, title=None)

Create a basic file selection dialog.

cancel_command(event=None)

Trigger the termination of the dialog window.

dirs_double_event(event)

Event handler for double-click event on directory.

dirs_select_event(event)

Event handler for click event on directory.

files_double_event(event)

Event handler for double-click event on file.

files_select_event(event)

Event handler for single-click event on file.

filter_command(event=None)

Filter the files by directory.

get_filter()

Retrieve the file filter currently in use.

get_selection()

Retrieve the currently selected item.

go(dir_or_file=os.curdir, pattern='*', default='', key=None)

Render dialog and start event loop.

ok_event(event)

Exit dialog returning current selection.

quit(how=None)

Exit dialog returning filename, if any.

set_filter(dir, pat)

Set the file filter.

set_selection(file)

Update the current file selection to file.

class tkinter.filedialog.LoadFileDialog(master, title=None)

A subclass of FileDialog that creates a dialog window for selecting an existing file.

ok_command()

Test that a file is provided and that the selection indicates an already existing file.

class tkinter.filedialog.SaveFileDialog(master, title=None)

A subclass of FileDialog that creates a dialog window for selecting a destination file.

ok_command()

Test whether or not the selection points to a valid file that is not a directory. Confirmation is required if an already existing file is selected.

tkinter.commondialog --- Dialog window templates

原始碼：Lib/tkinter/commondialog.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/commondialog.py]

The tkinter.commondialog module provides the Dialog class that is the base class for dialogs defined in other supporting modules.

class tkinter.commondialog.Dialog(master=None, **options)

show(**options)

Render the Dialog window.

也參考

tkinter.messagebox 模組、讀寫檔案

tkinter.messagebox --- Tkinter 訊息提示

原始碼：Lib/tkinter/messagebox.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/messagebox.py]

tkinter.messagebox 模組提供了模板基底類別以及各種常用配置的便捷方法。訊息框 (message box) 是互動視窗 (modal)，會基於使用者的選擇回傳（True、False、None、OK、CANCEL、YES、NO）的子集。常見的訊息框樣式 (style) 和版面配置 (layout) 包括但不限於：

class tkinter.messagebox.Message(master=None, **options)

建立一個訊息視窗，其中包含應用程式指定的訊息、一個圖示和一組按鈕。訊息視窗中的每個按鈕都有唯一的符號名稱作為識別（請參考 type 選項）。

支援以下選項：

command

指定當使用者關閉對話框 (dialog) 時要呼叫的函式。使用者按一下以關閉對話框的按鈕的名稱作為引數傳遞。此選項僅適用於 macOS。

default

給出此訊息視窗的預設按鈕的符號名稱（OK、CANCEL 等）。如果未指定此選項，則對話框中的第一個按鈕將成為預設按鈕。

detail

透過 message 選項指定將輔助訊息給主訊息。訊息詳細資訊將顯示在主要訊息下方，並且在作業系統支援的情況下，將以比主要訊息更不強調的字體顯示。

icon

指定要顯示的圖示。如果未指定此選項，則會顯示 INFO 圖示。

message

指定要在此訊息框中顯示的訊息。預設值為空字串。

parent

使指定視窗成為訊息框的邏輯父視窗 (logical parent window)。訊息框顯示在其父視窗的頂部。

title

指定顯示為訊息框標題的字串。此選項在 macOS 上被忽略，其平台指南禁止在此類對話方塊上使用標題。

type

安排一組需顯示的預先定義的按鈕組合。

show(**options)

顯示訊息視窗並等待使用者選擇其中一個按鈕。然後回傳所選按鈕的符號名稱。關鍵字引數可以覆寫建構函式中指定的選項。

資訊訊息框

tkinter.messagebox.showinfo(title=None, message=None, **options)

建立並顯示具有指定標題和訊息的資訊訊息框。

警告訊息框

tkinter.messagebox.showwarning(title=None, message=None, **options)

建立並顯示具有指定標題和訊息的警告訊息框。

tkinter.messagebox.showerror(title=None, message=None, **options)

建立並顯示具有指定標題和訊息的錯誤訊息框。

問題留言框

tkinter.messagebox.askquestion(title=None, message=None, *, type=YESNO, **options)

問一個問題。預設顯示按鈕 YES 和 NO。回傳所選按鈕的符號名稱。

tkinter.messagebox.askokcancel(title=None, message=None, **options)

詢問操作是否應該繼續。顯示按鈕 OK 和 CANCEL。如果答案正確則傳回 True，否則回傳 False。

tkinter.messagebox.askretrycancel(title=None, message=None, **options)

詢問是否應重試操作。顯示按鈕 RETRY 和 CANCEL。如果答案為是，則回傳 True，否則回傳 False。

tkinter.messagebox.askyesno(title=None, message=None, **options)

問一個問題。顯示按鈕 YES 和 NO。如果答案為是，則回傳 True，否則回傳 False。

tkinter.messagebox.askyesnocancel(title=None, message=None, **options)

問一個問題。顯示按鈕 YES、NO 和 CANCEL。如果答案為是，則回傳 True；如果取消則回傳 None，否則回傳 False。

按鈕的符號名稱：

tkinter.messagebox.ABORT = 'abort'

tkinter.messagebox.RETRY = 'retry'

tkinter.messagebox.IGNORE = 'ignore'

tkinter.messagebox.OK = 'ok'

tkinter.messagebox.CANCEL = 'cancel'

tkinter.messagebox.YES = 'yes'

tkinter.messagebox.NO = 'no'

預先定義的按鈕組合：

tkinter.messagebox.ABORTRETRYIGNORE = 'abortretryignore'

顯示三個按鈕，其符號名稱為 ABORT、RETRY 和 IGNORE。

tkinter.messagebox.OK = 'ok'

顯示一個按鈕，其符號名稱為 OK。

tkinter.messagebox.OKCANCEL = 'okcancel'

顯示兩個按鈕，其符號名稱為 OK 和 CANCEL。

tkinter.messagebox.RETRYCANCEL = 'retrycancel'

顯示兩個按鈕，其符號名稱為 RETRY 和 CANCEL。

tkinter.messagebox.YESNO = 'yesno'

顯示兩個按鈕，其符號名稱為 YES 和 NO。

tkinter.messagebox.YESNOCANCEL = 'yesnocancel'

顯示三個按鈕，其符號名稱為 YES、NO 和 CANCEL。

圖示圖像：

tkinter.messagebox.ERROR = 'error'

tkinter.messagebox.INFO = 'info'

tkinter.messagebox.QUESTION = 'question'

tkinter.messagebox.WARNING = 'warning'

tkinter.scrolledtext --- 捲動文字小工具

原始碼：Lib/tkinter/scrolledtext.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/scrolledtext.py]

The tkinter.scrolledtext module provides a class of the same name which implements a basic text widget which has a vertical scroll bar configured to do the "right thing." Using the ScrolledText class is a lot easier than setting up a text widget and scroll bar directly.

The text widget and scrollbar are packed together in a Frame, and the methods of the Grid and Pack geometry managers are acquired from the Frame object. This allows the ScrolledText widget to be used directly to achieve most normal geometry management behavior.

Should more specific control be necessary, the following attributes are available:

class tkinter.scrolledtext.ScrolledText(master=None, **kw)

frame

The frame which surrounds the text and scroll bar widgets.

vbar

The scroll bar widget.

tkinter.dnd --- 拖放支援

原始碼：Lib/tkinter/dnd.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/dnd.py]

備註

這是一個實驗性的功能，並將在被 Tk DND 取代時棄用。

tkinter.dnd 模組為單一應用程式內、同一個視窗內或視窗之間的物件提供拖放支援。要讓一個物件可以被拖動，你必須為它建立一個事件繫結來啟動拖放過程。你通常會將一個 ButtonPress 事件繫結到你所寫的回呼函式（請參閱 繫結與事件）。該函式應該呼叫 dnd_start()，其中 'source' 是要被拖動的物件，而 'event' 是觸發呼叫的事件（你的回呼函式的引數）。

目標物件的選擇過程如下：

由上而下搜尋滑鼠下方的區域以尋找目標元件（widget）

目標元件應該要有一個可呼叫的 dnd_accept 屬性（attribute）

如果 dnd_accept 不存在或回傳 None，搜尋會移至父元件

如果找不到目標元件，則目標物件為 None

呼叫 <old_target>.dnd_leave(source, event)

呼叫 <new_target>.dnd_enter(source, event)

呼叫 <target>.dnd_commit(source, event) 以通知放下動作

呼叫 <source>.dnd_end(target, event) 以表示拖放結束

class tkinter.dnd.DndHandler(source, event)

DndHandler 類別處理拖放事件，它會追蹤事件元件的根上的 Motion 和 ButtonRelease 事件。

cancel(event=None)

取消拖放過程。

finish(event, commit=0)

執行拖放結束函式。

on_motion(event)

在拖動過程中檢查滑鼠下方的區域以尋找目標物件。

on_release(event)

當釋放模式被觸發時，發出拖動結束的訊號。

tkinter.dnd.dnd_start(source, event)

用於拖放過程的工廠函式。

也參考

繫結與事件

tkinter.ttk --- Tk 主題化小工具

原始碼：Lib/tkinter/ttk.py [https://github.com/python/cpython/tree/3.14/Lib/tkinter/ttk.py]

The tkinter.ttk module provides access to the Tk themed widget set, introduced in Tk 8.5. It provides additional benefits including anti-aliased font rendering under X11 and window transparency (requiring a composition window manager on X11).

The basic idea for tkinter.ttk is to separate, to the extent possible, the code implementing a widget's behavior from the code implementing its appearance.

也參考

Tk Widget Styling Support [https://core.tcl.tk/tips/doc/trunk/tip/48.md]

A document introducing theming support for Tk

使用 Ttk

To start using Ttk, import its module:

from tkinter import ttk

To override the basic Tk widgets, the import should follow the Tk import:

from tkinter import *
from tkinter.ttk import *

That code causes several tkinter.ttk widgets (Button, Checkbutton, Entry, Frame, Label, LabelFrame, Menubutton, PanedWindow, Radiobutton, Scale and Scrollbar) to automatically replace the Tk widgets.

This has the direct benefit of using the new widgets which gives a better look and feel across platforms; however, the replacement widgets are not completely compatible. The main difference is that widget options such as "fg", "bg" and others related to widget styling are no longer present in Ttk widgets. Instead, use the ttk.Style class for improved styling effects.

也參考

Converting existing applications to use Tile widgets [https://tktable.sourceforge.net/tile/doc/converting.txt]

A monograph (using Tcl terminology) about differences typically encountered when moving applications to use the new widgets.

Ttk Widgets

Ttk comes with 18 widgets, twelve of which already existed in tkinter: Button, Checkbutton, Entry, Frame, Label, LabelFrame, Menubutton, PanedWindow, Radiobutton, Scale, Scrollbar, and Spinbox. The other six are new: Combobox, Notebook, Progressbar, Separator, Sizegrip and Treeview. And all them are subclasses of Widget.

Using the Ttk widgets gives the application an improved look and feel. As discussed above, there are differences in how the styling is coded.

Tk code:

l1 = tkinter.Label(text="Test", fg="black", bg="white")
l2 = tkinter.Label(text="Test", fg="black", bg="white")

Ttk code:

style = ttk.Style()
style.configure("BW.TLabel", foreground="black", background="white")

l1 = ttk.Label(text="Test", style="BW.TLabel")
l2 = ttk.Label(text="Test", style="BW.TLabel")

For more information about TtkStyling, see the Style class documentation.

Widget

ttk.Widget defines standard options and methods supported by Tk themed widgets and is not supposed to be directly instantiated.

標準選項

All the ttk Widgets accept the following options:

選項

描述

class

Specifies the window class. The class is used when querying the option database for the window's other options, to determine the default bindtags for the window, and to select the widget's default layout and style. This option is read-only, and may only be specified when the window is created.

cursor

Specifies the mouse cursor to be used for the widget. If set to the empty string (the default), the cursor is inherited for the parent widget.

takefocus

Determines whether the window accepts the focus during keyboard traversal. 0, 1 or an empty string is returned. If 0 is returned, it means that the window should be skipped entirely during keyboard traversal. If 1, it means that the window should receive the input focus as long as it is viewable. And an empty string means that the traversal scripts make the decision about whether or not to focus on the window.

style

May be used to specify a custom widget style.

Scrollable Widget Options

The following options are supported by widgets that are controlled by a scrollbar.

選項

描述

xscrollcommand

Used to communicate with horizontal scrollbars.

When the view in the widget's window change, the widget will generate a Tcl command based on the scrollcommand.

Usually this option consists of the method Scrollbar.set() of some scrollbar. This will cause the scrollbar to be updated whenever the view in the window changes.

yscrollcommand

Used to communicate with vertical scrollbars. For some more information, see above.

Label Options

The following options are supported by labels, buttons and other button-like widgets.

選項

描述

text

Specifies a text string to be displayed inside the widget.

textvariable

Specifies a name whose value will be used in place of the text option resource.

underline

If set, specifies the index (0-based) of a character to underline in the text string. The underline character is used for mnemonic activation.

image

Specifies an image to display. This is a list of 1 or more elements. The first element is the default image name. The rest of the list if a sequence of statespec/value pairs as defined by Style.map(), specifying different images to use when the widget is in a particular state or a combination of states. All images in the list should have the same size.

compound

Specifies how to display the image relative to the text, in the case both text and images options are present. Valid values are:

text: display text only

image: display image only

top, bottom, left, right: display image above, below, left of, or right of the text, respectively.

none: the default. display the image if present, otherwise the text.

width

If greater than zero, specifies how much space, in character widths, to allocate for the text label, if less than zero, specifies a minimum width. If zero or unspecified, the natural width of the text label is used.

相容性選項

選項

描述

state

May be set to "normal" or "disabled" to control the "disabled" state bit. This is a write-only option: setting it changes the widget state, but the Widget.state() method does not affect this option.

Widget States

The widget state is a bitmap of independent state flags.

旗標

描述

active

The mouse cursor is over the widget and pressing a mouse button will cause some action to occur

disabled

Widget is disabled under program control

focus

Widget has keyboard focus

pressed

Widget is being pressed

selected

"On", "true", or "current" for things like Checkbuttons and radiobuttons

background

Windows and Mac have a notion of an "active" or foreground window. The background state is set for widgets in a background window, and cleared for those in the foreground window

readonly

Widget should not allow user modification

alternate

A widget-specific alternate display format

invalid

The widget's value is invalid

A state specification is a sequence of state names, optionally prefixed with an exclamation point indicating that the bit is off.

ttk.Widget

Besides the methods described below, the ttk.Widget supports the methods tkinter.Widget.cget() and tkinter.Widget.configure().

class tkinter.ttk.Widget

identify(x, y)

Returns the name of the element at position x y, or the empty string if the point does not lie within any element.

x and y are pixel coordinates relative to the widget.

instate(statespec, callback=None, *args, **kw)

Test the widget's state. If a callback is not specified, returns True if the widget state matches statespec and False otherwise. If callback is specified then it is called with args if widget state matches statespec.

state(statespec=None)

Modify or inquire widget state. If statespec is specified, sets the widget state according to it and return a new statespec indicating which flags were changed. If statespec is not specified, returns the currently enabled state flags.

statespec will usually be a list or a tuple.

Combobox

The ttk.Combobox widget combines a text field with a pop-down list of values. This widget is a subclass of Entry.

Besides the methods inherited from Widget: Widget.cget(), Widget.configure(), Widget.identify(), Widget.instate() and Widget.state(), and the following inherited from Entry: Entry.bbox(), Entry.delete(), Entry.icursor(), Entry.index(), Entry.insert(), Entry.selection(), Entry.xview(), it has some other methods, described at ttk.Combobox.

選項

This widget accepts the following specific options:

選項

描述

exportselection

Boolean value. If set, the widget selection is linked to the Window Manager selection (which can be returned by invoking Misc.selection_get, for example).

justify

Specifies how the text is aligned within the widget. One of "left", "center", or "right".

height

Specifies the height of the pop-down listbox, in rows.

postcommand

A script (possibly registered with Misc.register) that is called immediately before displaying the values. It may specify which values to display.

state

One of "normal", "readonly", or "disabled". In the "readonly" state, the value may not be edited directly, and the user can only selection of the values from the dropdown list. In the "normal" state, the text field is directly editable. In the "disabled" state, no interaction is possible.

textvariable

Specifies a name whose value is linked to the widget value. Whenever the value associated with that name changes, the widget value is updated, and vice versa. See tkinter.StringVar.

values

Specifies the list of values to display in the drop-down listbox.

width

Specifies an integer value indicating the desired width of the entry window, in average-size characters of the widget's font.

Virtual events

The combobox widgets generates a <<ComboboxSelected>> virtual event when the user selects an element from the list of values.

ttk.Combobox

class tkinter.ttk.Combobox

current(newindex=None)

If newindex is specified, sets the combobox value to the element position newindex. Otherwise, returns the index of the current value or -1 if the current value is not in the values list.

get()

Returns the current value of the combobox.

set(value)

Sets the value of the combobox to value.

Spinbox

The ttk.Spinbox widget is a ttk.Entry enhanced with increment and decrement arrows. It can be used for numbers or lists of string values. This widget is a subclass of Entry.

Besides the methods inherited from Widget: Widget.cget(), Widget.configure(), Widget.identify(), Widget.instate() and Widget.state(), and the following inherited from Entry: Entry.bbox(), Entry.delete(), Entry.icursor(), Entry.index(), Entry.insert(), Entry.xview(), it has some other methods, described at ttk.Spinbox.

選項

This widget accepts the following specific options:

選項

描述

from

Float value. If set, this is the minimum value to which the decrement button will decrement. Must be spelled as from_ when used as an argument, since from is a Python keyword.

to

Float value. If set, this is the maximum value to which the increment button will increment.

increment

Float value. Specifies the amount which the increment/decrement buttons change the value. Defaults to 1.0.

values

Sequence of string or float values. If specified, the increment/decrement buttons will cycle through the items in this sequence rather than incrementing or decrementing numbers.

wrap

Boolean value. If True, increment and decrement buttons will cycle from the to value to the from value or the from value to the to value, respectively.

format

String value. This specifies the format of numbers set by the increment/decrement buttons. It must be in the form "%W.Pf", where W is the padded width of the value, P is the precision, and '%' and 'f' are literal.

command

Python callable. Will be called with no arguments whenever either of the increment or decrement buttons are pressed.

Virtual events

The spinbox widget generates an <<Increment>> virtual event when the user presses <Up>, and a <<Decrement>> virtual event when the user presses <Down>.

ttk.Spinbox

class tkinter.ttk.Spinbox

get()

Returns the current value of the spinbox.

set(value)

Sets the value of the spinbox to value.

Notebook

Ttk Notebook widget manages a collection of windows and displays a single one at a time. Each child window is associated with a tab, which the user may select to change the currently displayed window.

選項

This widget accepts the following specific options:

選項

描述

height

If present and greater than zero, specifies the desired height of the pane area (not including internal padding or tabs). Otherwise, the maximum height of all panes is used.

padding

Specifies the amount of extra space to add around the outside of the notebook. The padding is a list up to four length specifications left top right bottom. If fewer than four elements are specified, bottom defaults to top, right defaults to left, and top defaults to left.

width

If present and greater than zero, specified the desired width of the pane area (not including internal padding). Otherwise, the maximum width of all panes is used.

Tab Options

There are also specific options for tabs:

選項

描述

state

Either "normal", "disabled" or "hidden". If "disabled", then the tab is not selectable. If "hidden", then the tab is not shown.

sticky

Specifies how the child window is positioned within the pane area. Value is a string containing zero or more of the characters "n", "s", "e" or "w". Each letter refers to a side (north, south, east or west) that the child window will stick to, as per the grid() geometry manager.

padding

Specifies the amount of extra space to add between the notebook and this pane. Syntax is the same as for the option padding used by this widget.

text

Specifies a text to be displayed in the tab.

image

Specifies an image to display in the tab. See the option image described in Widget.

compound

Specifies how to display the image relative to the text, in the case both options text and image are present. See Label Options for legal values.

underline

Specifies the index (0-based) of a character to underline in the text string. The underlined character is used for mnemonic activation if Notebook.enable_traversal() is called.

Tab Identifiers

The tab_id present in several methods of ttk.Notebook may take any of the following forms:

An integer between zero and the number of tabs

The name of a child window

A positional specification of the form "@x,y", which identifies the tab

The literal string "current", which identifies the currently selected tab

The literal string "end", which returns the number of tabs (only valid for Notebook.index())

虛擬事件

This widget generates a <<NotebookTabChanged>> virtual event after a new tab is selected.

ttk.Notebook

class tkinter.ttk.Notebook

add(child, **kw)

Adds a new tab to the notebook.

If window is currently managed by the notebook but hidden, it is restored to its previous position.

可用的選項清單請見 Tab Options。

forget(tab_id)

Removes the tab specified by tab_id, unmaps and unmanages the associated window.

hide(tab_id)

Hides the tab specified by tab_id.

The tab will not be displayed, but the associated window remains managed by the notebook and its configuration remembered. Hidden tabs may be restored with the add() command.

identify(x, y)

Returns the name of the tab element at position x, y, or the empty string if none.

index(tab_id)

Returns the numeric index of the tab specified by tab_id, or the total number of tabs if tab_id is the string "end".

insert(pos, child, **kw)

Inserts a pane at the specified position.

pos is either the string "end", an integer index, or the name of a managed child. If child is already managed by the notebook, moves it to the specified position.

可用的選項清單請見 Tab Options。

select(tab_id=None)

Selects the specified tab_id.

The associated child window will be displayed, and the previously selected window (if different) is unmapped. If tab_id is omitted, returns the widget name of the currently selected pane.

tab(tab_id, option=None, **kw)

Query or modify the options of the specific tab_id.

If kw is not given, returns a dictionary of the tab option values. If option is specified, returns the value of that option. Otherwise, sets the options to the corresponding values.

tabs()

Returns a list of windows managed by the notebook.

enable_traversal()

Enable keyboard traversal for a toplevel window containing this notebook.

This will extend the bindings for the toplevel window containing the notebook as follows:

Control-Tab: selects the tab following the currently selected one.

Shift-Control-Tab: selects the tab preceding the currently selected one.

Alt-K: where K is the mnemonic (underlined) character of any tab, will select that tab.

Multiple notebooks in a single toplevel may be enabled for traversal, including nested notebooks. However, notebook traversal only works properly if all panes have the notebook they are in as master.

Progressbar

The ttk.Progressbar widget shows the status of a long-running operation. It can operate in two modes: 1) the determinate mode which shows the amount completed relative to the total amount of work to be done and 2) the indeterminate mode which provides an animated display to let the user know that work is progressing.

選項

This widget accepts the following specific options:

選項

描述

orient

One of "horizontal" or "vertical". Specifies the orientation of the progress bar.

length

Specifies the length of the long axis of the progress bar (width if horizontal, height if vertical).

mode

"determinate" 與 "indeterminate" 其中之一

maximum

A number specifying the maximum value. Defaults to 100.

value

The current value of the progress bar. In "determinate" mode, this represents the amount of work completed. In "indeterminate" mode, it is interpreted as modulo maximum; that is, the progress bar completes one "cycle" when its value increases by maximum.

variable

A name which is linked to the option value. If specified, the value of the progress bar is automatically set to the value of this name whenever the latter is modified.

phase

Read-only option. The widget periodically increments the value of this option whenever its value is greater than 0 and, in determinate mode, less than maximum. This option may be used by the current theme to provide additional animation effects.

ttk.Progressbar

class tkinter.ttk.Progressbar

start(interval=None)

Begin autoincrement mode: schedules a recurring timer event that calls Progressbar.step() every interval milliseconds. If omitted, interval defaults to 50 milliseconds.

step(amount=None)

Increments the progress bar's value by amount.

amount defaults to 1.0 if omitted.

stop()

Stop autoincrement mode: cancels any recurring timer event initiated by Progressbar.start() for this progress bar.

Separator

The ttk.Separator widget displays a horizontal or vertical separator bar.

It has no other methods besides the ones inherited from ttk.Widget.

選項

This widget accepts the following specific option:

選項

描述

orient

One of "horizontal" or "vertical". Specifies the orientation of the separator.

Sizegrip

The ttk.Sizegrip widget (also known as a grow box) allows the user to resize the containing toplevel window by pressing and dragging the grip.

This widget has neither specific options nor specific methods, besides the ones inherited from ttk.Widget.

Platform-specific notes

On macOS, toplevel windows automatically include a built-in size grip by default. Adding a Sizegrip is harmless, since the built-in grip will just mask the widget.

Bugs

If the containing toplevel's position was specified relative to the right or bottom of the screen (e.g. ....), the Sizegrip widget will not resize the window.

This widget supports only "southeast" resizing.

Treeview

The ttk.Treeview widget displays a hierarchical collection of items. Each item has a textual label, an optional image, and an optional list of data values. The data values are displayed in successive columns after the tree label.

The order in which data values are displayed may be controlled by setting the widget option displaycolumns. The tree widget can also display column headings. Columns may be accessed by number or symbolic names listed in the widget option columns. See Column Identifiers.

Each item is identified by a unique name. The widget will generate item IDs if they are not supplied by the caller. There is a distinguished root item, named {}. The root item itself is not displayed; its children appear at the top level of the hierarchy.

Each item also has a list of tags, which can be used to associate event bindings with individual items and control the appearance of the item.

The Treeview widget supports horizontal and vertical scrolling, according to the options described in Scrollable Widget Options and the methods Treeview.xview() and Treeview.yview().

選項

This widget accepts the following specific options:

選項

描述

columns

A list of column identifiers, specifying the number of columns and their names.

displaycolumns

A list of column identifiers (either symbolic or integer indices) specifying which data columns are displayed and the order in which they appear, or the string "#all".

height

Specifies the number of rows which should be visible. Note: the requested width is determined from the sum of the column widths.

padding

Specifies the internal padding for the widget. The padding is a list of up to four length specifications.

selectmode

Controls how the built-in class bindings manage the selection. One of "extended", "browse" or "none". If set to "extended" (the default), multiple items may be selected. If "browse", only a single item will be selected at a time. If "none", the selection will not be changed.

Note that the application code and tag bindings can set the selection however they wish, regardless of the value of this option.

show

A list containing zero or more of the following values, specifying which elements of the tree to display.

tree: display tree labels in column #0.

headings: display the heading row.

The default is "tree headings", i.e., show all elements.

Note: Column #0 always refers to the tree column, even if show="tree" is not specified.

Item Options

The following item options may be specified for items in the insert and item widget commands.

選項

描述

text

The textual label to display for the item.

image

A Tk Image, displayed to the left of the label.

values

The list of values associated with the item.

Each item should have the same number of values as the widget option columns. If there are fewer values than columns, the remaining values are assumed empty. If there are more values than columns, the extra values are ignored.

open

True/False value indicating whether the item's children should be displayed or hidden.

tags

A list of tags associated with this item.

Tag Options

The following options may be specified on tags:

選項

描述

foreground

Specifies the text foreground color.

background

Specifies the cell or item background color.

font

Specifies the font to use when drawing text.

image

Specifies the item image, in case the item's image option is empty.

Column Identifiers

Column identifiers take any of the following forms:

A symbolic name from the list of columns option.

An integer n, specifying the nth data column.

A string of the form #n, where n is an integer, specifying the nth display column.

註解：

Item's option values may be displayed in a different order than the order in which they are stored.

Column #0 always refers to the tree column, even if show="tree" is not specified.

A data column number is an index into an item's option values list; a display column number is the column number in the tree where the values are displayed. Tree labels are displayed in column #0. If option displaycolumns is not set, then data column n is displayed in column #n+1. Again, column #0 always refers to the tree column.

虛擬事件

The Treeview widget generates the following virtual events.

事件

描述

<<TreeviewSelect>>

Generated whenever the selection changes.

<<TreeviewOpen>>

Generated just before settings the focus item to open=True.

<<TreeviewClose>>

Generated just after setting the focus item to open=False.

The Treeview.focus() and Treeview.selection() methods can be used to determine the affected item or items.

ttk.Treeview

class tkinter.ttk.Treeview

bbox(item, column=None)

Returns the bounding box (relative to the treeview widget's window) of the specified item in the form (x, y, width, height).

If column is specified, returns the bounding box of that cell. If the item is not visible (i.e., if it is a descendant of a closed item or is scrolled offscreen), returns an empty string.

get_children(item=None)

Returns the list of children belonging to item.

If item is not specified, returns root children.

set_children(item, *newchildren)

Replaces item's child with newchildren.

Children present in item that are not present in newchildren are detached from the tree. No items in newchildren may be an ancestor of item. Note that not specifying newchildren results in detaching item's children.

column(column, option=None, **kw)

Query or modify the options for the specified column.

If kw is not given, returns a dict of the column option values. If option is specified then the value for that option is returned. Otherwise, sets the options to the corresponding values.

有效的選項/值為：

id

回傳欄位名稱。這是唯讀選項。

anchor: One of the standard Tk anchor values.

Specifies how the text in this column should be aligned with respect to the cell.

minwidth: width

The minimum width of the column in pixels. The treeview widget will not make the column any smaller than specified by this option when the widget is resized or the user drags a column.

stretch: True/False

Specifies whether the column's width should be adjusted when the widget is resized.

width: width

The width of the column in pixels.

To configure the tree column, call this with column = "#0"

delete(*items)

Delete all specified items and all their descendants.

The root item may not be deleted.

detach(*items)

Unlinks all of the specified items from the tree.

The items and all of their descendants are still present, and may be reinserted at another point in the tree, but will not be displayed.

The root item may not be detached.

exists(item)

Returns True if the specified item is present in the tree.

focus(item=None)

If item is specified, sets the focus item to item. Otherwise, returns the current focus item, or '' if there is none.

heading(column, option=None, **kw)

Query or modify the heading options for the specified column.

If kw is not given, returns a dict of the heading option values. If option is specified then the value for that option is returned. Otherwise, sets the options to the corresponding values.

有效的選項/值為：

text: text

The text to display in the column heading.

image: imageName

Specifies an image to display to the right of the column heading.

anchor: anchor

Specifies how the heading text should be aligned. One of the standard Tk anchor values.

command: callback

A callback to be invoked when the heading label is pressed.

To configure the tree column heading, call this with column = "#0".

identify(component, x, y)

Returns a description of the specified component under the point given by x and y, or the empty string if no such component is present at that position.

identify_row(y)

Returns the item ID of the item at position y.

identify_column(x)

Returns the data column identifier of the cell at position x.

The tree column has ID #0.

identify_region(x, y)

Returns one of:

region

meaning

heading

Tree heading area.

separator

Space between two columns headings.

tree

The tree area.

cell

A data cell.

Availability: Tk 8.6.

identify_element(x, y)

Returns the element at position x, y.

Availability: Tk 8.6.

index(item)

Returns the integer index of item within its parent's list of children.

insert(parent, index, iid=None, **kw)

Creates a new item and returns the item identifier of the newly created item.

parent is the item ID of the parent item, or the empty string to create a new top-level item. index is an integer, or the value "end", specifying where in the list of parent's children to insert the new item. If index is less than or equal to zero, the new node is inserted at the beginning; if index is greater than or equal to the current number of children, it is inserted at the end. If iid is specified, it is used as the item identifier; iid must not already exist in the tree. Otherwise, a new unique identifier is generated.

可用的選項清單請見 Item Options。

item(item, option=None, **kw)

Query or modify the options for the specified item.

If no options are given, a dict with options/values for the item is returned. If option is specified then the value for that option is returned. Otherwise, sets the options to the corresponding values as given by kw.

move(item, parent, index)

Moves item to position index in parent's list of children.

It is illegal to move an item under one of its descendants. If index is less than or equal to zero, item is moved to the beginning; if greater than or equal to the number of children, it is moved to the end. If item was detached it is reattached.

next(item)

Returns the identifier of item's next sibling, or '' if item is the last child of its parent.

parent(item)

Returns the ID of the parent of item, or '' if item is at the top level of the hierarchy.

prev(item)

Returns the identifier of item's previous sibling, or '' if item is the first child of its parent.

reattach(item, parent, index)

一個 Treeview.move() 的別名。

see(item)

確保 item 是可見的。

Sets all of item's ancestors open option to True, and scrolls the widget if necessary so that item is within the visible portion of the tree.

selection()

Returns a tuple of selected items.

在 3.8 版的變更: selection() no longer takes arguments. For changing the selection state use the following selection methods.

selection_set(*items)

items becomes the new selection.

在 3.6 版的變更: items can be passed as separate arguments, not just as a single tuple.

selection_add(*items)

將 items 加入選擇。

在 3.6 版的變更: items can be passed as separate arguments, not just as a single tuple.

selection_remove(*items)

從選擇中移除 items。

在 3.6 版的變更: items can be passed as separate arguments, not just as a single tuple.

selection_toggle(*items)

Toggle the selection state of each item in items.

在 3.6 版的變更: items can be passed as separate arguments, not just as a single tuple.

set(item, column=None, value=None)

With one argument, returns a dictionary of column/value pairs for the specified item. With two arguments, returns the current value of the specified column. With three arguments, sets the value of given column in given item to the specified value.

tag_bind(tagname, sequence=None, callback=None)

Bind a callback for the given event sequence to the tag tagname. When an event is delivered to an item, the callbacks for each of the item's tags option are called.

tag_configure(tagname, option=None, **kw)

Query or modify the options for the specified tagname.

If kw is not given, returns a dict of the option settings for tagname. If option is specified, returns the value for that option for the specified tagname. Otherwise, sets the options to the corresponding values for the given tagname.

tag_has(tagname, item=None)

If item is specified, returns 1 or 0 depending on whether the specified item has the given tagname. Otherwise, returns a list of all items that have the specified tag.

Availability: Tk 8.6

xview(*args)

Query or modify horizontal position of the treeview.

yview(*args)

Query or modify vertical position of the treeview.

Ttk Styling

Each widget in ttk is assigned a style, which specifies the set of elements making up the widget and how they are arranged, along with dynamic and default settings for element options. By default the style name is the same as the widget's class name, but it may be overridden by the widget's style option. If you don't know the class name of a widget, use the method Misc.winfo_class() (somewidget.winfo_class()).

也參考

Tcl'2004 conference presentation [https://tktable.sourceforge.net/tile/tile-tcl2004.pdf]

This document explains how the theme engine works

class tkinter.ttk.Style

This class is used to manipulate the style database.

configure(style, query_opt=None, **kw)

Query or set the default value of the specified option(s) in style.

Each key in kw is an option and each value is a string identifying the value for that option.

For example, to change every default button to be a flat button with some padding and a different background color:

from tkinter import ttk
import tkinter

root = tkinter.Tk()

ttk.Style().configure("TButton", padding=6, relief="flat",
   background="#ccc")

btn = ttk.Button(text="Sample")
btn.pack()

root.mainloop()

map(style, query_opt=None, **kw)

Query or sets dynamic values of the specified option(s) in style.

Each key in kw is an option and each value should be a list or a tuple (usually) containing statespecs grouped in tuples, lists, or some other preference. A statespec is a compound of one or more states and then a value.

An example may make it more understandable:

import tkinter
from tkinter import ttk

root = tkinter.Tk()

style = ttk.Style()
style.map("C.TButton",
    foreground=[('pressed', 'red'), ('active', 'blue')],
    background=[('pressed', '!disabled', 'black'), ('active', 'white')]
    )

colored_btn = ttk.Button(text="Test", style="C.TButton").pack()

root.mainloop()

Note that the order of the (states, value) sequences for an option does matter, if the order is changed to [('active', 'blue'), ('pressed', 'red')] in the foreground option, for example, the result would be a blue foreground when the widget were in active or pressed states.

lookup(style, option, state=None, default=None)

Returns the value specified for option in style.

If state is specified, it is expected to be a sequence of one or more states. If the default argument is set, it is used as a fallback value in case no specification for option is found.

To check what font a Button uses by default:

from tkinter import ttk

print(ttk.Style().lookup("TButton", "font"))

layout(style, layoutspec=None)

Define the widget layout for given style. If layoutspec is omitted, return the layout specification for given style.

layoutspec, if specified, is expected to be a list or some other sequence type (excluding strings), where each item should be a tuple and the first item is the layout name and the second item should have the format described in Layouts.

To understand the format, see the following example (it is not intended to do anything useful):

from tkinter import ttk
import tkinter

root = tkinter.Tk()

style = ttk.Style()
style.layout("TMenubutton", [
   ("Menubutton.background", None),
   ("Menubutton.button", {"children":
       [("Menubutton.focus", {"children":
           [("Menubutton.padding", {"children":
               [("Menubutton.label", {"side": "left", "expand": 1})]
           })]
       })]
   }),
])

mbtn = ttk.Menubutton(text='Text')
mbtn.pack()
root.mainloop()

element_create(elementname, etype, *args, **kw)

Create a new element in the current theme, of the given etype which is expected to be either "image", "from" or "vsapi". The latter is only available in Tk 8.6 on Windows.

If "image" is used, args should contain the default image name followed by statespec/value pairs (this is the imagespec), and kw may have the following options:

border=padding

padding is a list of up to four integers, specifying the left, top, right, and bottom borders, respectively.

height=height

Specifies a minimum height for the element. If less than zero, the base image's height is used as a default.

padding=padding

Specifies the element's interior padding. Defaults to border's value if not specified.

sticky=spec

Specifies how the image is placed within the final parcel. spec contains zero or more characters "n", "s", "w", or "e".

width=width

Specifies a minimum width for the element. If less than zero, the base image's width is used as a default.

範例：

img1 = tkinter.PhotoImage(master=root, file='button.png')
img1 = tkinter.PhotoImage(master=root, file='button-pressed.png')
img1 = tkinter.PhotoImage(master=root, file='button-active.png')
style = ttk.Style(root)
style.element_create('Button.button', 'image',
                     img1, ('pressed', img2), ('active', img3),
                     border=(2, 4), sticky='we')

If "from" is used as the value of etype, element_create() will clone an existing element. args is expected to contain a themename, from which the element will be cloned, and optionally an element to clone from. If this element to clone from is not specified, an empty element will be used. kw is discarded.

範例：

style = ttk.Style(root)
style.element_create('plain.background', 'from', 'default')

If "vsapi" is used as the value of etype, element_create() will create a new element in the current theme whose visual appearance is drawn using the Microsoft Visual Styles API which is responsible for the themed styles on Windows XP and Vista. args is expected to contain the Visual Styles class and part as given in the Microsoft documentation followed by an optional sequence of tuples of ttk states and the corresponding Visual Styles API state value. kw may have the following options:

padding=padding

Specify the element's interior padding. padding is a list of up to four integers specifying the left, top, right and bottom padding quantities respectively. If fewer than four elements are specified, bottom defaults to top, right defaults to left, and top defaults to left. In other words, a list of three numbers specify the left, vertical, and right padding; a list of two numbers specify the horizontal and the vertical padding; a single number specifies the same padding all the way around the widget. This option may not be mixed with any other options.

margins=padding

Specifies the elements exterior padding. padding is a list of up to four integers specifying the left, top, right and bottom padding quantities respectively. This option may not be mixed with any other options.

width=width

Specifies the width for the element. If this option is set then the Visual Styles API will not be queried for the recommended size or the part. If this option is set then height should also be set. The width and height options cannot be mixed with the padding or margins options.

height=height

Specifies the height of the element. See the comments for width.

範例：

style = ttk.Style(root)
style.element_create('pin', 'vsapi', 'EXPLORERBAR', 3, [
                     ('pressed', '!selected', 3),
                     ('active', '!selected', 2),
                     ('pressed', 'selected', 6),
                     ('active', 'selected', 5),
                     ('selected', 4),
                     ('', 1)])
style.layout('Explorer.Pin',
             [('Explorer.Pin.pin', {'sticky': 'news'})])
pin = ttk.Checkbutton(style='Explorer.Pin')
pin.pack(expand=True, fill='both')

在 3.13 版的變更: Added support of the "vsapi" element factory.

element_names()

Returns the list of elements defined in the current theme.

element_options(elementname)

Returns the list of elementname's options.

theme_create(themename, parent=None, settings=None)

Create a new theme.

It is an error if themename already exists. If parent is specified, the new theme will inherit styles, elements and layouts from the parent theme. If settings are present they are expected to have the same syntax used for theme_settings().

theme_settings(themename, settings)

Temporarily sets the current theme to themename, apply specified settings and then restore the previous theme.

Each key in settings is a style and each value may contain the keys 'configure', 'map', 'layout' and 'element create' and they are expected to have the same format as specified by the methods Style.configure(), Style.map(), Style.layout() and Style.element_create() respectively.

As an example, let's change the Combobox for the default theme a bit:

from tkinter import ttk
import tkinter

root = tkinter.Tk()

style = ttk.Style()
style.theme_settings("default", {
   "TCombobox": {
       "configure": {"padding": 5},
       "map": {
           "background": [("active", "green2"),
                          ("!disabled", "green4")],
           "fieldbackground": [("!disabled", "green3")],
           "foreground": [("focus", "OliveDrab1"),
                          ("!disabled", "OliveDrab2")]
       }
   }
})

combo = ttk.Combobox().pack()

root.mainloop()

theme_names()

回傳所有已知的主題。

theme_use(themename=None)

If themename is not given, returns the theme in use. Otherwise, sets the current theme to themename, refreshes all widgets and emits a <<ThemeChanged>> event.

Layouts

A layout can be just None, if it takes no options, or a dict of options specifying how to arrange the element. The layout mechanism uses a simplified version of the pack geometry manager: given an initial cavity, each element is allocated a parcel.

有效的選項/值為：

side: whichside

Specifies which side of the cavity to place the element; one of top, right, bottom or left. If omitted, the element occupies the entire cavity.

sticky: nswe

Specifies where the element is placed inside its allocated parcel.

unit：0 或 1

If set to 1, causes the element and all of its descendants to be treated as a single element for the purposes of Widget.identify() et al. It's used for things like scrollbar thumbs with grips.

children: [sublayout... ]

Specifies a list of elements to place inside the element. Each element is a tuple (or other sequence type) where the first item is the layout name, and the other is a Layout.

IDLE --- Python 編輯器與 shell

原始碼：Lib/idlelib/ [https://github.com/python/cpython/tree/3.14/Lib/idlelib/]

IDLE 是 Python 的整合開發與學習環境 (Integrated Development and Learning Environment)。

IDLE 具有以下功能：

跨平台：在 Windows、Unix 和 macOS 上的運作大致相同

Python shell window（互動式直譯器）提供有色彩的程式碼輸入、輸出和錯誤訊息

多視窗文字編輯器，具有多次復原、Python 語法上色、智慧縮排、呼叫提示、自動完成等功能

能在任何視窗中搜尋、編輯器視窗中取代文字，以及搜尋多個檔案 (grep)

具有持久性斷點、能夠逐步執行和檢視全域和區域命名空間的除錯器

設定、瀏覽器和其他對話框

The IDLE application is implemented in the idlelib package.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

目錄

IDLE has two main window types, the Shell window and the Editor window. It is possible to have multiple editor windows simultaneously. On Windows and Linux, each has its own top menu. Each menu documented below indicates which window type it is associated with.

Output windows, such as used for Edit => Find in Files, are a subtype of editor window. They currently have the same top menu but a different default title and context menu.

On macOS, there is one application menu. It dynamically changes according to the window currently selected. It has an IDLE menu, and some entries described below are moved around to conform to Apple guidelines.

File menu (Shell and Editor)

新增檔案

Create a new file editing window.

Open...

Open an existing file with an Open dialog.

Open Module...

Open an existing module (searches sys.path).

Recent Files

Open a list of recent files. Click one to open it.

Module Browser

Show functions, classes, and methods in the current Editor file in a tree structure. In the shell, open a module first.

Path Browser

Show sys.path directories, modules, functions, classes and methods in a tree structure.

Save

Save the current window to the associated file, if there is one. Windows that have been changed since being opened or last saved have a * before and after the window title. If there is no associated file, do Save As instead.

Save As...

Save the current window with a Save As dialog. The file saved becomes the new associated file for the window. (If your file manager is set to hide extensions, the current extension will be omitted in the file name box. If the new filename has no '.', '.py' and '.txt' will be added for Python and text files, except that on macOS Aqua,'.py' is added for all files.)

Save Copy As...

Save the current window to different file without changing the associated file. (See Save As note above about filename extensions.)

Print Window

Print the current window to the default printer.

Close Window

Close the current window (if an unsaved editor, ask to save; if an unsaved Shell, ask to quit execution). Calling exit() or close() in the Shell window also closes Shell. If this is the only window, also exit IDLE.

離開 IDLE

Close all windows and quit IDLE (ask to save unsaved edit windows).

Edit menu (Shell and Editor)

Undo

Undo the last change to the current window. A maximum of 1000 changes may be undone.

Redo

Redo the last undone change to the current window.

Select All（選擇全部）

Select the entire contents of the current window.

Cut（剪下）

Copy selection into the system-wide clipboard; then delete the selection.

Copy（複製）

Copy selection into the system-wide clipboard.

Paste（貼上）

Insert contents of the system-wide clipboard into the current window.

The clipboard functions are also available in context menus.

Find...

Open a search dialog with many options

Find Again

Repeat the last search, if there is one.

Find Selection

Search for the currently selected string, if there is one.

Find in Files...

Open a file search dialog. Put results in a new output window.

Replace...

Open a search-and-replace dialog.

Go to Line

Move the cursor to the beginning of the line requested and make that line visible. A request past the end of the file goes to the end. Clear any selection and update the line and column status.

Show Completions

Open a scrollable list allowing selection of existing names. See Completions in the Editing and Navigation section below.

Expand Word

Expand a prefix you have typed to match a full word in the same window; repeat to get a different expansion.

Show Call Tip

After an unclosed parenthesis for a function, open a small window with function parameter hints. See Calltips in the Editing and Navigation section below.

Show Surrounding Parens

Highlight the surrounding parenthesis.

Format menu (Editor window only)

Format Paragraph

Rewrap the text block containing the text insert cursor. Avoid code lines. See Format block in the Editing and Navigation section below.

Indent Region

Shift selected lines right by the indent width (default 4 spaces).

Dedent Region

Shift selected lines left by the indent width (default 4 spaces).

Comment Out Region

Insert ## in front of selected lines.

Uncomment Region

Remove leading # or ## from selected lines.

Tabify Region

Turn leading stretches of spaces into tabs. (Note: We recommend using 4 space blocks to indent Python code.)

Untabify Region

Turn all tabs into the correct number of spaces.

Toggle Tabs

Open a dialog to switch between indenting with spaces and tabs.

New Indent Width

Open a dialog to change indent width. The accepted default by the Python community is 4 spaces.

Strip Trailing Whitespace

Remove trailing space and other whitespace characters after the last non-whitespace character of a line by applying str.rstrip() to each line, including lines within multiline strings. Except for Shell windows, remove extra newlines at the end of the file.

Run menu (Editor window only)

Run Module

Do Check Module. If no error, restart the shell to clean the environment, then execute the module. Output is displayed in the Shell window. Note that output requires use of print or write. When execution is complete, the Shell retains focus and displays a prompt. At this point, one may interactively explore the result of execution. This is similar to executing a file with python -i file at a command line.

Run... Customized

Same as Run Module, but run the module with customized settings. Command Line Arguments extend sys.argv as if passed on a command line. The module can be run in the Shell without restarting.

Check Module

Check the syntax of the module currently open in the Editor window. If the module has not been saved IDLE will either prompt the user to save or autosave, as selected in the General tab of the Idle Settings dialog. If there is a syntax error, the approximate location is indicated in the Editor window.

Python Shell

Open or wake up the Python Shell window.

Shell menu (Shell window only)

View Last Restart

Scroll the shell window to the last Shell restart.

Restart Shell

Restart the shell to clean the environment and reset display and exception handling.

Previous History

Cycle through earlier commands in history which match the current entry.

Next History

Cycle through later commands in history which match the current entry.

Interrupt Execution

Stop a running program.

Debug menu (Shell window only)

Go to File/Line

Look on the current line. with the cursor, and the line above for a filename and line number. If found, open the file if not already open, and show the line. Use this to view source lines referenced in an exception traceback and lines found by Find in Files. Also available in the context menu of the Shell window and Output windows.

Debugger (toggle)

When activated, code entered in the Shell or run from an Editor will run under the debugger. In the Editor, breakpoints can be set with the context menu. This feature is still incomplete and somewhat experimental.

Stack Viewer

Show the stack traceback of the last exception in a tree widget, with access to locals and globals.

Auto-open Stack Viewer

Toggle automatically opening the stack viewer on an unhandled exception.

Options menu (Shell and Editor)

Configure IDLE

Open a configuration dialog and change preferences for the following: fonts, indentation, keybindings, text color themes, startup windows and size, additional help sources, and extensions. On macOS, open the configuration dialog by selecting Preferences in the application menu. For more details, see Setting preferences under Help and preferences.

Most configuration options apply to all windows or all future windows. The option items below only apply to the active window.

Show/Hide Code Context (Editor Window only)

Open a pane at the top of the edit window which shows the block context of the code which has scrolled above the top of the window. See Code Context in the Editing and Navigation section below.

Show/Hide Line Numbers (Editor Window only)

Open a column to the left of the edit window which shows the number of each line of text. The default is off, which may be changed in the preferences (see Setting preferences).

Zoom/Restore Height

Toggles the window between normal size and maximum height. The initial size defaults to 40 lines by 80 chars unless changed on the General tab of the Configure IDLE dialog. The maximum height for a screen is determined by momentarily maximizing a window the first time one is zoomed on the screen. Changing screen settings may invalidate the saved height. This toggle has no effect when a window is maximized.

Window menu (Shell and Editor)

Lists the names of all open windows; select one to bring it to the foreground (deiconifying it if necessary).

Help menu (Shell and Editor)

關於 IDLE

Display version, copyright, license, credits, and more.

IDLE Help

Display this IDLE document, detailing the menu options, basic editing and navigation, and other tips.

Python 文件

Access local Python documentation, if installed, or start a web browser and open docs.python.org showing the latest Python documentation.

Turtle Demo

Run the turtledemo module with example Python code and turtle drawings.

Additional help sources may be added here with the Configure IDLE dialog under the General tab. See the Help sources subsection below for more on Help menu choices.

Context menus

Open a context menu by right-clicking in a window (Control-click on macOS). Context menus have the standard clipboard functions also on the Edit menu.

Cut（剪下）

Copy selection into the system-wide clipboard; then delete the selection.

Copy（複製）

Copy selection into the system-wide clipboard.

Paste（貼上）

Insert contents of the system-wide clipboard into the current window.

Editor windows also have breakpoint functions. Lines with a breakpoint set are specially marked. Breakpoints only have an effect when running under the debugger. Breakpoints for a file are saved in the user's .idlerc directory.

Set Breakpoint

Set a breakpoint on the current line.

Clear Breakpoint

Clear the breakpoint on that line.

Shell and Output windows also have the following.

Go to file/line

Same as in Debug menu.

The Shell window also has an output squeezing facility explained in the Python Shell window subsection below.

Squeeze

If the cursor is over an output line, squeeze all the output between the code above and the prompt below down to a 'Squeezed text' label.

Editing and Navigation

Editor windows

IDLE may open editor windows when it starts, depending on settings and how you start IDLE. Thereafter, use the File menu. There can be only one open editor window for a given file.

The title bar contains the name of the file, the full path, and the version of Python and IDLE running the window. The status bar contains the line number ('Ln') and column number ('Col'). Line numbers start with 1; column numbers with 0.

IDLE assumes that files with a known .py* extension contain Python code and that other files do not. Run Python code with the Run menu.

Key bindings

The IDLE insertion cursor is a thin vertical bar between character positions. When characters are entered, the insertion cursor and everything to its right moves right one character and the new character is entered in the new space.

Several non-character keys move the cursor and possibly delete characters. Deletion does not puts text on the clipboard, but IDLE has an undo list. Wherever this doc discusses keys, 'C' refers to the Control key on Windows and Unix and the Command key on macOS. (And all such discussions assume that the keys have not been re-bound to something else.)

Arrow keys move the cursor one character or line.

C-LeftArrow and C-RightArrow moves left or right one word.

Home and End go to the beginning or end of the line.

Page Up and Page Down go up or down one screen.

C-Home and C-End go to beginning or end of the file.

Backspace and Del (or C-d) delete the previous or next character.

C-Backspace and C-Del delete one word left or right.

C-k deletes ('kills') everything to the right.

Standard keybindings (like C-c to copy and C-v to paste) may work. Keybindings are selected in the Configure IDLE dialog.

Automatic indentation

After a block-opening statement, the next line is indented by 4 spaces (in the Python Shell window by one tab). After certain keywords (break, return etc.) the next line is dedented. In leading indentation, Backspace deletes up to 4 spaces if they are there. Tab inserts spaces (in the Python Shell window one tab), number depends on Indent width. Currently, tabs are restricted to four spaces due to Tcl/Tk limitations.

See also the indent/dedent region commands on the Format menu.

Search and Replace

Any selection becomes a search target. However, only selections within a line work because searches are only performed within lines with the terminal newline removed. If [x] Regular expression is checked, the target is interpreted according to the Python re module.

Completions

Completions are supplied, when requested and available, for module names, attributes of classes or functions, or filenames. Each request method displays a completion box with existing names. (See tab completions below for an exception.) For any box, change the name being completed and the item highlighted in the box by typing and deleting characters; by hitting Up, Down, PageUp, PageDown, Home, and End keys; and by a single click within the box. Close the box with Escape, Enter, and double Tab keys or clicks outside the box. A double click within the box selects and closes.

One way to open a box is to type a key character and wait for a predefined interval. This defaults to 2 seconds; customize it in the settings dialog. (To prevent auto popups, set the delay to a large number of milliseconds, such as 100000000.) For imported module names or class or function attributes, type '.'. For filenames in the root directory, type os.sep or os.altsep immediately after an opening quote. (On Windows, one can specify a drive first.) Move into subdirectories by typing a directory name and a separator.

Instead of waiting, or after a box is closed, open a completion box immediately with Show Completions on the Edit menu. The default hot key is C-space. If one types a prefix for the desired name before opening the box, the first match or near miss is made visible. The result is the same as if one enters a prefix after the box is displayed. Show Completions after a quote completes filenames in the current directory instead of a root directory.

Hitting Tab after a prefix usually has the same effect as Show Completions. (With no prefix, it indents.) However, if there is only one match to the prefix, that match is immediately added to the editor text without opening a box.

Invoking 'Show Completions', or hitting Tab after a prefix, outside of a string and without a preceding '.' opens a box with keywords, builtin names, and available module-level names.

When editing code in an editor (as oppose to Shell), increase the available module-level names by running your code and not restarting the Shell thereafter. This is especially useful after adding imports at the top of a file. This also increases possible attribute completions.

Completion boxes initially exclude names beginning with '_' or, for modules, not included in '__all__'. The hidden names can be accessed by typing '_' after '.', either before or after the box is opened.

Calltips

A calltip is shown automatically when one types ( after the name of an accessible function. A function name expression may include dots and subscripts. A calltip remains until it is clicked, the cursor is moved out of the argument area, or ) is typed. Whenever the cursor is in the argument part of a definition, select Edit and "Show Call Tip" on the menu or enter its shortcut to display a calltip.

The calltip consists of the function's signature and docstring up to the latter's first blank line or the fifth non-blank line. (Some builtin functions lack an accessible signature.) A '/' or '*' in the signature indicates that the preceding or following arguments are passed by position or name (keyword) only. Details are subject to change.

In Shell, the accessible functions depends on what modules have been imported into the user process, including those imported by Idle itself, and which definitions have been run, all since the last restart.

For example, restart the Shell and enter itertools.count(. A calltip appears because Idle imports itertools into the user process for its own use. (This could change.) Enter turtle.write( and nothing appears. Idle does not itself import turtle. The menu entry and shortcut also do nothing. Enter import turtle. Thereafter, turtle.write( will display a calltip.

In an editor, import statements have no effect until one runs the file. One might want to run a file after writing import statements, after adding function definitions, or after opening an existing file.

Format block

Reformat Paragraph rewraps a block ('paragraph') of contiguous equally indented non-blank comments, a similar block of text within a multiline string, or a selected subset of either. If needed, add a blank line to separate string from code. Partial lines in a selection expand to complete lines. The resulting lines have the same indent as before but have maximum total length of N columns (characters). Change the default N of 72 on the Window tab of IDLE Settings.

Code Context

Within an editor window containing Python code, code context can be toggled in order to show or hide a pane at the top of the window. When shown, this pane freezes the opening lines for block code, such as those beginning with class, def, or if keywords, that would have otherwise scrolled out of view. The size of the pane will be expanded and contracted as needed to show the all current levels of context, up to the maximum number of lines defined in the Configure IDLE dialog (which defaults to 15). If there are no current context lines and the feature is toggled on, a single blank line will display. Clicking on a line in the context pane will move that line to the top of the editor.

The text and background colors for the context pane can be configured under the Highlights tab in the Configure IDLE dialog.

Shell window

In IDLE's Shell, enter, edit, and recall complete statements. (Most consoles and terminals only work with a single physical line at a time).

Submit a single-line statement for execution by hitting Return with the cursor anywhere on the line. If a line is extended with Backslash (\), the cursor must be on the last physical line. Submit a multi-line compound statement by entering a blank line after the statement.

When one pastes code into Shell, it is not compiled and possibly executed until one hits Return, as specified above. One may edit pasted code first. If one pastes more than one statement into Shell, the result will be a SyntaxError when multiple statements are compiled as if they were one.

Lines containing RESTART mean that the user execution process has been re-started. This occurs when the user execution process has crashed, when one requests a restart on the Shell menu, or when one runs code in an editor window.

The editing features described in previous subsections work when entering code interactively. IDLE's Shell window also responds to the following:

C-c attempts to interrupt statement execution (but may fail).

C-d closes Shell if typed at a >>> prompt.

Alt-p and Alt-n (C-p and C-n on macOS) retrieve to the current prompt the previous or next previously entered statement that matches anything already typed.

Return while the cursor is on any previous statement appends the latter to anything already typed at the prompt.

Text colors

Idle defaults to black on white text, but colors text with special meanings. For the shell, these are shell output, shell error, user output, and user error. For Python code, at the shell prompt or in an editor, these are keywords, builtin class and function names, names following class and def, strings, and comments. For any text window, these are the cursor (when present), found text (when possible), and selected text.

IDLE also highlights the soft keywords match, case, and _ in pattern-matching statements. However, this highlighting is not perfect and will be incorrect in some rare cases, including some _-s in case patterns.

Text coloring is done in the background, so uncolorized text is occasionally visible. To change the color scheme, use the Configure IDLE dialog Highlighting tab. The marking of debugger breakpoint lines in the editor and text in popups and dialogs is not user-configurable.

Startup and Code Execution

Upon startup with the -s option, IDLE will execute the file referenced by the environment variables IDLESTARTUP or PYTHONSTARTUP. IDLE first checks for IDLESTARTUP; if IDLESTARTUP is present the file referenced is run. If IDLESTARTUP is not present, IDLE checks for PYTHONSTARTUP. Files referenced by these environment variables are convenient places to store functions that are used frequently from the IDLE shell, or for executing import statements to import common modules.

In addition, Tk also loads a startup file if it is present. Note that the Tk file is loaded unconditionally. This additional file is .Idle.py and is looked for in the user's home directory. Statements in this file will be executed in the Tk namespace, so this file is not useful for importing functions to be used from IDLE's Python shell.

命令列用法

IDLE can be invoked from the command line with various options. The general syntax is:

python -m idlelib [options] [file ...]

The following options are available:

-c <command>

Run the specified Python command in the shell window. For example, pass -c "print('Hello, World!')". On Windows, the outer quotes must be double quotes as shown.

-d

Enable the debugger and open the shell window.

-e

Open an editor window.

-h

Print a help message with legal combinations of options and exit.

-i

Open a shell window.

-r <file>

Run the specified file in the shell window.

-s

Run the startup file (as defined by the environment variables IDLESTARTUP or PYTHONSTARTUP) before opening the shell window.

-t <title>

Set the title of the shell window.

-

Read and execute standard input in the shell window. This option must be the last one before any arguments.

If arguments are provided:

If -, -c, or -r is used, all arguments are placed in sys.argv[1:], and sys.argv[0] is set to '', '-c', or '-r' respectively. No editor window is opened, even if that is the default set in the Options dialog.

Otherwise, arguments are treated as files to be opened for editing, and sys.argv reflects the arguments passed to IDLE itself.

Startup failure

IDLE uses a socket to communicate between the IDLE GUI process and the user code execution process. A connection must be established whenever the Shell starts or restarts. (The latter is indicated by a divider line that says 'RESTART'). If the user process fails to connect to the GUI process, it usually displays a Tk error box with a 'cannot connect' message that directs the user here. It then exits.

One specific connection failure on Unix systems results from misconfigured masquerading rules somewhere in a system's network setup. When IDLE is started from a terminal, one will see a message starting with ** Invalid host:. The valid value is 127.0.0.1 (idlelib.rpc.LOCALHOST). One can diagnose with tcpconnect -irv 127.0.0.1 6543 in one terminal window and tcplisten <same args> in another.

A common cause of failure is a user-written file with the same name as a standard library module, such as random.py and tkinter.py. When such a file is located in the same directory as a file that is about to be run, IDLE cannot import the stdlib file. The current fix is to rename the user file.

Though less common than in the past, an antivirus or firewall program may stop the connection. If the program cannot be taught to allow the connection, then it must be turned off for IDLE to work. It is safe to allow this internal connection because no data is visible on external ports. A similar problem is a network mis-configuration that blocks connections.

Python installation issues occasionally stop IDLE: multiple versions can clash, or a single installation might need admin access. If one undo the clash, or cannot or does not want to run as admin, it might be easiest to completely remove Python and start over.

A zombie pythonw.exe process could be a problem. On Windows, use Task Manager to check for one and stop it if there is. Sometimes a restart initiated by a program crash or Keyboard Interrupt (control-C) may fail to connect. Dismissing the error box or using Restart Shell on the Shell menu may fix a temporary problem.

When IDLE first starts, it attempts to read user configuration files in ~/.idlerc/ (~ is one's home directory). If there is a problem, an error message should be displayed. Leaving aside random disk glitches, this can be prevented by never editing the files by hand. Instead, use the configuration dialog, under Options. Once there is an error in a user configuration file, the best solution may be to delete it and start over with the settings dialog.

If IDLE quits with no message, and it was not started from a console, try starting it from a console or terminal (python -m idlelib) and see if this results in an error message.

On Unix-based systems with tcl/tk older than 8.6.11 (see About IDLE) certain characters of certain fonts can cause a tk failure with a message to the terminal. This can happen either if one starts IDLE to edit a file with such a character or later when entering such a character. If one cannot upgrade tcl/tk, then re-configure IDLE to use a font that works better.

Running user code

With rare exceptions, the result of executing Python code with IDLE is intended to be the same as executing the same code by the default method, directly with Python in a text-mode system console or terminal window. However, the different interface and operation occasionally affect visible results. For instance, sys.modules starts with more entries, and threading.active_count() returns 2 instead of 1.

By default, IDLE runs user code in a separate OS process rather than in the user interface process that runs the shell and editor. In the execution process, it replaces sys.stdin, sys.stdout, and sys.stderr with objects that get input from and send output to the Shell window. The original values stored in sys.__stdin__, sys.__stdout__, and sys.__stderr__ are not touched, but may be None.

Sending print output from one process to a text widget in another is slower than printing to a system terminal in the same process. This has the most effect when printing multiple arguments, as the string for each argument, each separator, the newline are sent separately. For development, this is usually not a problem, but if one wants to print faster in IDLE, format and join together everything one wants displayed together and then print a single string. Both format strings and str.join() can help combine fields and lines.

IDLE's standard stream replacements are not inherited by subprocesses created in the execution process, whether directly by user code or by modules such as multiprocessing. If such subprocess use input from sys.stdin or print or write to sys.stdout or sys.stderr, IDLE should be started in a command line window. (On Windows, use python or py rather than pythonw or pyw.) The secondary subprocess will then be attached to that window for input and output.

If sys is reset by user code, such as with importlib.reload(sys), IDLE's changes are lost and input from the keyboard and output to the screen will not work correctly.

When Shell has the focus, it controls the keyboard and screen. This is normally transparent, but functions that directly access the keyboard and screen will not work. These include system-specific functions that determine whether a key has been pressed and if so, which.

The IDLE code running in the execution process adds frames to the call stack that would not be there otherwise. IDLE wraps sys.getrecursionlimit and sys.setrecursionlimit to reduce the effect of the additional stack frames.

When user code raises SystemExit either directly or by calling sys.exit, IDLE returns to a Shell prompt instead of exiting.

User output in Shell

When a program outputs text, the result is determined by the corresponding output device. When IDLE executes user code, sys.stdout and sys.stderr are connected to the display area of IDLE's Shell. Some of its features are inherited from the underlying Tk Text widget. Others are programmed additions. Where it matters, Shell is designed for development rather than production runs.

For instance, Shell never throws away output. A program that sends unlimited output to Shell will eventually fill memory, resulting in a memory error. In contrast, some system text windows only keep the last n lines of output. A Windows console, for instance, keeps a user-settable 1 to 9999 lines, with 300 the default.

A Tk Text widget, and hence IDLE's Shell, displays characters (codepoints) in the BMP (Basic Multilingual Plane) subset of Unicode. Which characters are displayed with a proper glyph and which with a replacement box depends on the operating system and installed fonts. Tab characters cause the following text to begin after the next tab stop. (They occur every 8 'characters'). Newline characters cause following text to appear on a new line. Other control characters are ignored or displayed as a space, box, or something else, depending on the operating system and font. (Moving the text cursor through such output with arrow keys may exhibit some surprising spacing behavior.)

>>> s = 'a\tb\a<\x02><\r>\bc\nd'  # Enter 22 chars.
>>> len(s)
14
>>> s  # Display repr(s)
'a\tb\x07<\x02><\r>\x08c\nd'
>>> print(s, end='')  # Display s as is.
# Result varies by OS and font.  Try it.

The repr function is used for interactive echo of expression values. It returns an altered version of the input string in which control codes, some BMP codepoints, and all non-BMP codepoints are replaced with escape codes. As demonstrated above, it allows one to identify the characters in a string, regardless of how they are displayed.

Normal and error output are generally kept separate (on separate lines) from code input and each other. They each get different highlight colors.

For SyntaxError tracebacks, the normal '^' marking where the error was detected is replaced by coloring the text with an error highlight. When code run from a file causes other exceptions, one may right click on a traceback line to jump to the corresponding line in an IDLE editor. The file will be opened if necessary.

Shell has a special facility for squeezing output lines down to a 'Squeezed text' label. This is done automatically for output over N lines (N = 50 by default). N can be changed in the PyShell section of the General page of the Settings dialog. Output with fewer lines can be squeezed by right clicking on the output. This can be useful lines long enough to slow down scrolling.

Squeezed output is expanded in place by double-clicking the label. It can also be sent to the clipboard or a separate view window by right-clicking the label.

Developing tkinter applications

IDLE is intentionally different from standard Python in order to facilitate development of tkinter programs. Enter import tkinter as tk; root = tk.Tk() in standard Python and nothing appears. Enter the same in IDLE and a tk window appears. In standard Python, one must also enter root.update() to see the window. IDLE does the equivalent in the background, about 20 times a second, which is about every 50 milliseconds. Next enter b = tk.Button(root, text='button'); b.pack(). Again, nothing visibly changes in standard Python until one enters root.update().

Most tkinter programs run root.mainloop(), which usually does not return until the tk app is destroyed. If the program is run with python -i or from an IDLE editor, a >>> shell prompt does not appear until mainloop() returns, at which time there is nothing left to interact with.

When running a tkinter program from an IDLE editor, one can comment out the mainloop call. One then gets a shell prompt immediately and can interact with the live application. One just has to remember to re-enable the mainloop call when running in standard Python.

Running without a subprocess

By default, IDLE executes user code in a separate subprocess via a socket, which uses the internal loopback interface. This connection is not externally visible and no data is sent to or received from the internet. If firewall software complains anyway, you can ignore it.

If the attempt to make the socket connection fails, Idle will notify you. Such failures are sometimes transient, but if persistent, the problem may be either a firewall blocking the connection or misconfiguration of a particular system. Until the problem is fixed, one can run Idle with the -n command line switch.

If IDLE is started with the -n command line switch it will run in a single process and will not create the subprocess which runs the RPC Python execution server. This can be useful if Python cannot create the subprocess or the RPC socket interface on your platform. However, in this mode user code is not isolated from IDLE itself. Also, the environment is not restarted when Run/Run Module (F5) is selected. If your code has been modified, you must reload() the affected modules and re-import any specific items (e.g. from foo import baz) if the changes are to take effect. For these reasons, it is preferable to run IDLE with the default subprocess if at all possible.

在 3.4 版之後被棄用.

Help and Preferences

Help sources

Help menu entry "IDLE Help" displays a formatted html version of the IDLE chapter of the Library Reference. The result, in a read-only tkinter text window, is close to what one sees in a web browser. Navigate through the text with a mousewheel, the scrollbar, or up and down arrow keys held down. Or click the TOC (Table of Contents) button and select a section header in the opened box.

Help menu entry "Python Docs" opens the extensive sources of help, including tutorials, available at docs.python.org/x.y, where 'x.y' is the currently running Python version. If your system has an off-line copy of the docs (this may be an installation option), that will be opened instead.

Selected URLs can be added or removed from the help menu at any time using the General tab of the Configure IDLE dialog.

設定偏好

The font preferences, highlighting, keys, and general preferences can be changed via Configure IDLE on the Option menu. Non-default user settings are saved in a .idlerc directory in the user's home directory. Problems caused by bad user configuration files are solved by editing or deleting one or more of the files in .idlerc.

On the Font tab, see the text sample for the effect of font face and size on multiple characters in multiple languages. Edit the sample to add other characters of personal interest. Use the sample to select monospaced fonts. If particular characters have problems in Shell or an editor, add them to the top of the sample and try changing first size and then font.

On the Highlights and Keys tab, select a built-in or custom color theme and key set. To use a newer built-in color theme or key set with older IDLEs, save it as a new custom theme or key set and it well be accessible to older IDLEs.

macOS 上的 IDLE

Under System Preferences: Dock, one can set "Prefer tabs when opening documents" to "Always". This setting is not compatible with the tk/tkinter GUI framework used by IDLE, and it breaks a few IDLE features.

Extensions

IDLE contains an extension facility. Preferences for extensions can be changed with the Extensions tab of the preferences dialog. See the beginning of config-extensions.def in the idlelib directory for further information. The only current default extension is zzdummy, an example also used for testing.

idlelib --- implementation of IDLE application

原始碼：Lib/idlelib/ [https://github.com/python/cpython/tree/3.14/Lib/idlelib/]

The Lib/idlelib package implements the IDLE application. See the rest of this page for how to use IDLE.

The files in idlelib are described in idlelib/README.txt. Access it either in idlelib or click Help => About IDLE on the IDLE menu. This file also maps IDLE menu items to the code that implements the item. Except for files listed under 'Startup', the idlelib code is 'private' in sense that feature changes can be backported (see PEP 434 [https://peps.python.org/pep-0434/]).

turtle --- 龜圖學 (Turtle graphics)

原始碼：Lib/turtle.py [https://github.com/python/cpython/tree/3.14/Lib/turtle.py]

介紹

龜圖學是由 Wally Feurzeig，Seymour Papert 與 Cynthia Solomon 於 1967 年開發的，一個 以 Logo 程式語言撰寫的廣受歡迎的幾何繪圖工具 [https://en.wikipedia.org/wiki/Turtle_(robot)]。

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

Get started

Imagine a robotic turtle starting at (0, 0) in the x-y plane. After an import turtle, give it the command turtle.forward(15), and it moves (on-screen!) 15 pixels in the direction it is facing, drawing a line as it moves. Give it the command turtle.right(25), and it rotates in-place 25 degrees clockwise.

Turtle star

龜可以使用重複簡單動作之程式來畫出複雜的形狀。

In Python, turtle graphics provides a representation of a physical "turtle" (a little robot with a pen) that draws on a sheet of paper on the floor.

It's an effective and well-proven way for learners to encounter programming concepts and interaction with software, as it provides instant, visible feedback. It also provides convenient access to graphical output in general.

Turtle drawing was originally created as an educational tool, to be used by teachers in the classroom. For the programmer who needs to produce some graphical output it can be a way to do that without the overhead of introducing more complex or external libraries into their work.

教學

New users should start here. In this tutorial we'll explore some of the basics of turtle drawing.

啟動一個烏龜環境

在 Python shell 中，引入 turtle 模組中所有物件：

from turtle import *

If you run into a No module named '_tkinter' error, you'll have to install the Tk interface package on your system.

基本繪圖

Send the turtle forward 100 steps:

forward(100)

You should see (most likely, in a new window on your display) a line drawn by the turtle, heading East. Change the direction of the turtle, so that it turns 120 degrees left (anti-clockwise):

left(120)

Let's continue by drawing a triangle:

forward(100)
left(120)
forward(100)

Notice how the turtle, represented by an arrow, points in different directions as you steer it.

Experiment with those commands, and also with backward() and right().

Pen control

Try changing the color - for example, color('blue') - and width of the line - for example, width(3) - and then drawing again.

You can also move the turtle around without drawing, by lifting up the pen: up() before moving. To start drawing again, use down().

The turtle's position

Send your turtle back to its starting-point (useful if it has disappeared off-screen):

home()

The home position is at the center of the turtle's screen. If you ever need to know them, get the turtle's x-y coordinates with:

pos()

Home is at (0, 0).

And after a while, it will probably help to clear the window so we can start anew:

clearscreen()

Making algorithmic patterns

Using loops, it's possible to build up geometric patterns:

for steps in range(100):
    for c in ('blue', 'red', 'green'):
        color(c)
        forward(steps)
        right(30)

- which of course, are limited only by the imagination!

Let's draw the star shape at the top of this page. We want red lines, filled in with yellow:

color('red')
fillcolor('yellow')

Just as up() and down() determine whether lines will be drawn, filling can be turned on and off:

begin_fill()

Next we'll create a loop:

while True:
    forward(200)
    left(170)
    if abs(pos()) < 1:
        break

abs(pos()) < 1 is a good way to know when the turtle is back at its home position.

Finally, complete the filling:

end_fill()

(Note that filling only actually takes place when you give the end_fill() command.)

How to...

This section covers some typical turtle use-cases and approaches.

Get started as quickly as possible

One of the joys of turtle graphics is the immediate, visual feedback that's available from simple commands - it's an excellent way to introduce children to programming ideas, with a minimum of overhead (not just children, of course).

The turtle module makes this possible by exposing all its basic functionality as functions, available with from turtle import *. The turtle graphics tutorial covers this approach.

It's worth noting that many of the turtle commands also have even more terse equivalents, such as fd() for forward(). These are especially useful when working with learners for whom typing is not a skill.

You'll need to have the Tk interface package installed on your system for turtle graphics to work. Be warned that this is not always straightforward, so check this in advance if you're planning to use turtle graphics with a learner.

Automatically begin and end filling

Starting with Python 3.14, you can use the fill() context manager instead of begin_fill() and end_fill() to automatically begin and end fill. Here is an example:

with fill():
    for i in range(4):
        forward(100)
        right(90)

forward(200)

The code above is equivalent to:

begin_fill()
for i in range(4):
    forward(100)
    right(90)
end_fill()

forward(200)

Use the turtle module namespace

Using from turtle import * is convenient - but be warned that it imports a rather large collection of objects, and if you're doing anything but turtle graphics you run the risk of a name conflict (this becomes even more an issue if you're using turtle graphics in a script where other modules might be imported).

The solution is to use import turtle - fd() becomes turtle.fd(), width() becomes turtle.width() and so on. (If typing "turtle" over and over again becomes tedious, use for example import turtle as t instead.)

Use turtle graphics in a script

It's recommended to use the turtle module namespace as described immediately above, for example:

import turtle as t
from random import random

for i in range(100):
    steps = int(random() * 100)
    angle = int(random() * 360)
    t.right(angle)
    t.fd(steps)

Another step is also required though - as soon as the script ends, Python will also close the turtle's window. Add:

t.mainloop()

to the end of the script. The script will now wait to be dismissed and will not exit until it is terminated, for example by closing the turtle graphics window.

Use object-oriented turtle graphics

也參考

Explanation of the object-oriented interface

Other than for very basic introductory purposes, or for trying things out as quickly as possible, it's more usual and much more powerful to use the object-oriented approach to turtle graphics. For example, this allows multiple turtles on screen at once.

In this approach, the various turtle commands are methods of objects (mostly of Turtle objects). You can use the object-oriented approach in the shell, but it would be more typical in a Python script.

The example above then becomes:

from turtle import Turtle
from random import random

t = Turtle()
for i in range(100):
    steps = int(random() * 100)
    angle = int(random() * 360)
    t.right(angle)
    t.fd(steps)

t.screen.mainloop()

Note the last line. t.screen is an instance of the Screen that a Turtle instance exists on; it's created automatically along with the turtle.

The turtle's screen can be customised, for example:

t.screen.title('Object-oriented turtle demo')
t.screen.bgcolor("orange")

Turtle graphics reference

備註

In the following documentation the argument list for functions is given. Methods, of course, have the additional first argument self which is omitted here.

Turtle methods

Turtle motion

Move and draw

forward() | fd()

backward() | bk() | back()

right() | rt()

left() | lt()

goto() | setpos() | setposition()

teleport()

setx()

sety()

setheading() | seth()

home()

circle()

dot()

stamp()

clearstamp()

clearstamps()

undo()

speed()

Tell Turtle's state

position() | pos()

towards()

xcor()

ycor()

heading()

distance()

Setting and measurement

degrees()

radians()

Pen control

Drawing state

pendown() | pd() | down()

penup() | pu() | up()

pensize() | width()

pen()

isdown()

Color control

color()

pencolor()

fillcolor()

Filling

filling()

fill()

begin_fill()

end_fill()

More drawing control

reset()

clear()

write()

Turtle state

Visibility

showturtle() | st()

hideturtle() | ht()

isvisible()

Appearance

shape()

resizemode()

shapesize() | turtlesize()

shearfactor()

tiltangle()

tilt()

shapetransform()

get_shapepoly()

Using events

onclick()

onrelease()

ondrag()

Special Turtle methods

poly()

begin_poly()

end_poly()

get_poly()

clone()

getturtle() | getpen()

getscreen()

setundobuffer()

undobufferentries()

Methods of TurtleScreen/Screen

Window control

bgcolor()

bgpic()

clearscreen()

resetscreen()

screensize()

setworldcoordinates()

Animation control

no_animation()

delay()

tracer()

update()

Using screen events

listen()

onkey() | onkeyrelease()

onkeypress()

onclick() | onscreenclick()

ontimer()

mainloop() | done()

Settings and special methods

mode()

colormode()

getcanvas()

getshapes()

register_shape() | addshape()

turtles()

window_height()

window_width()

Input methods

textinput()

numinput()

Methods specific to Screen

bye()

exitonclick()

save()

setup()

title()

Methods of RawTurtle/Turtle and corresponding functions

Most of the examples in this section refer to a Turtle instance called turtle.

Turtle motion

turtle.forward(distance)

turtle.fd(distance)

參數:

distance -- a number (integer or float)

Move the turtle forward by the specified distance, in the direction the turtle is headed.

>>> turtle.position()
(0.00,0.00)
>>> turtle.forward(25)
>>> turtle.position()
(25.00,0.00)
>>> turtle.forward(-75)
>>> turtle.position()
(-50.00,0.00)

turtle.back(distance)

turtle.bk(distance)

turtle.backward(distance)

參數:

distance -- a number

Move the turtle backward by distance, opposite to the direction the turtle is headed. Do not change the turtle's heading.

>>> turtle.position()
(0.00,0.00)
>>> turtle.backward(30)
>>> turtle.position()
(-30.00,0.00)

turtle.right(angle)

turtle.rt(angle)

參數:

angle -- a number (integer or float)

Turn turtle right by angle units. (Units are by default degrees, but can be set via the degrees() and radians() functions.) Angle orientation depends on the turtle mode, see mode().

>>> turtle.heading()
22.0
>>> turtle.right(45)
>>> turtle.heading()
337.0

turtle.left(angle)

turtle.lt(angle)

參數:

angle -- a number (integer or float)

Turn turtle left by angle units. (Units are by default degrees, but can be set via the degrees() and radians() functions.) Angle orientation depends on the turtle mode, see mode().

>>> turtle.heading()
22.0
>>> turtle.left(45)
>>> turtle.heading()
67.0

turtle.goto(x, y=None)

turtle.setpos(x, y=None)

turtle.setposition(x, y=None)

參數:

x -- a number or a pair/vector of numbers

y -- a number or None

If y is None, x must be a pair of coordinates or a Vec2D (e.g. as returned by pos()).

Move turtle to an absolute position. If the pen is down, draw line. Do not change the turtle's orientation.

>>> tp = turtle.pos()
>>> tp
(0.00,0.00)
>>> turtle.setpos(60,30)
>>> turtle.pos()
(60.00,30.00)
>>> turtle.setpos((20,80))
>>> turtle.pos()
(20.00,80.00)
>>> turtle.setpos(tp)
>>> turtle.pos()
(0.00,0.00)

turtle.teleport(x, y=None, *, fill_gap=False)

參數:

x -- a number or None

y -- a number or None

fill_gap -- a boolean

Move turtle to an absolute position. Unlike goto(x, y), a line will not be drawn. The turtle's orientation does not change. If currently filling, the polygon(s) teleported from will be filled after leaving, and filling will begin again after teleporting. This can be disabled with fill_gap=True, which makes the imaginary line traveled during teleporting act as a fill barrier like in goto(x, y).

>>> tp = turtle.pos()
>>> tp
(0.00,0.00)
>>> turtle.teleport(60)
>>> turtle.pos()
(60.00,0.00)
>>> turtle.teleport(y=10)
>>> turtle.pos()
(60.00,10.00)
>>> turtle.teleport(20, 30)
>>> turtle.pos()
(20.00,30.00)

在 3.12 版被加入.

turtle.setx(x)

參數:

x -- a number (integer or float)

Set the turtle's first coordinate to x, leave second coordinate unchanged.

>>> turtle.position()
(0.00,240.00)
>>> turtle.setx(10)
>>> turtle.position()
(10.00,240.00)

turtle.sety(y)

參數:

y -- a number (integer or float)

Set the turtle's second coordinate to y, leave first coordinate unchanged.

>>> turtle.position()
(0.00,40.00)
>>> turtle.sety(-10)
>>> turtle.position()
(0.00,-10.00)

turtle.setheading(to_angle)

turtle.seth(to_angle)

參數:

to_angle -- a number (integer or float)

Set the orientation of the turtle to to_angle. Here are some common directions in degrees:

standard mode

logo mode

0 - east

0 - north

90 - north

90 - east

180 - west

180 - south

270 - south

270 - west

>>> turtle.setheading(90)
>>> turtle.heading()
90.0

turtle.home()

Move turtle to the origin -- coordinates (0,0) -- and set its heading to its start-orientation (which depends on the mode, see mode()).

>>> turtle.heading()
90.0
>>> turtle.position()
(0.00,-10.00)
>>> turtle.home()
>>> turtle.position()
(0.00,0.00)
>>> turtle.heading()
0.0

turtle.circle(radius, extent=None, steps=None)

參數:

radius -- a number

extent -- a number (or None)

steps -- an integer (or None)

Draw a circle with given radius. The center is radius units left of the turtle; extent -- an angle -- determines which part of the circle is drawn. If extent is not given, draw the entire circle. If extent is not a full circle, one endpoint of the arc is the current pen position. Draw the arc in counterclockwise direction if radius is positive, otherwise in clockwise direction. Finally the direction of the turtle is changed by the amount of extent.

As the circle is approximated by an inscribed regular polygon, steps determines the number of steps to use. If not given, it will be calculated automatically. May be used to draw regular polygons.

>>> turtle.home()
>>> turtle.position()
(0.00,0.00)
>>> turtle.heading()
0.0
>>> turtle.circle(50)
>>> turtle.position()
(-0.00,0.00)
>>> turtle.heading()
0.0
>>> turtle.circle(120, 180)  # draw a semicircle
>>> turtle.position()
(0.00,240.00)
>>> turtle.heading()
180.0

turtle.dot()

turtle.dot(size)

turtle.dot(color, /)

turtle.dot(size, color, /)

turtle.dot(size, r, g, b, /)

參數:

size -- an integer >= 1 (if given)

color -- a colorstring or a numeric color tuple

Draw a circular dot with diameter size, using color. If size is not given, the maximum of pensize+4 and 2*pensize is used.

>>> turtle.home()
>>> turtle.dot()
>>> turtle.fd(50); turtle.dot(20, "blue"); turtle.fd(50)
>>> turtle.position()
(100.00,-0.00)
>>> turtle.heading()
0.0

turtle.stamp()

Stamp a copy of the turtle shape onto the canvas at the current turtle position. Return a stamp_id for that stamp, which can be used to delete it by calling clearstamp(stamp_id).

>>> turtle.color("blue")
>>> stamp_id = turtle.stamp()
>>> turtle.fd(50)

turtle.clearstamp(stampid)

參數:

stampid -- an integer, must be return value of previous stamp() call

Delete stamp with given stampid.

>>> turtle.position()
(150.00,-0.00)
>>> turtle.color("blue")
>>> astamp = turtle.stamp()
>>> turtle.fd(50)
>>> turtle.position()
(200.00,-0.00)
>>> turtle.clearstamp(astamp)
>>> turtle.position()
(200.00,-0.00)

turtle.clearstamps(n=None)

參數:

n -- an integer (or None)

Delete all or first/last n of turtle's stamps. If n is None, delete all stamps, if n > 0 delete first n stamps, else if n < 0 delete last n stamps.

>>> for i in range(8):
...     unused_stamp_id = turtle.stamp()
...     turtle.fd(30)
>>> turtle.clearstamps(2)
>>> turtle.clearstamps(-2)
>>> turtle.clearstamps()

turtle.undo()

Undo (repeatedly) the last turtle action(s). Number of available undo actions is determined by the size of the undobuffer.

>>> for i in range(4):
...     turtle.fd(50); turtle.lt(80)
...
>>> for i in range(8):
...     turtle.undo()

turtle.speed(speed=None)

參數:

speed -- an integer in the range 0..10 or a speedstring (see below)

Set the turtle's speed to an integer value in the range 0..10. If no argument is given, return current speed.

If input is a number greater than 10 or smaller than 0.5, speed is set to 0. Speedstrings are mapped to speedvalues as follows:

"fastest": 0

"fast": 10

"normal": 6

"slow": 3

"slowest": 1

Speeds from 1 to 10 enforce increasingly faster animation of line drawing and turtle turning.

Attention: speed = 0 means that no animation takes place. forward/back makes turtle jump and likewise left/right make the turtle turn instantly.

>>> turtle.speed()
3
>>> turtle.speed('normal')
>>> turtle.speed()
6
>>> turtle.speed(9)
>>> turtle.speed()
9

Tell Turtle's state

turtle.position()

turtle.pos()

Return the turtle's current location (x,y) (as a Vec2D vector).

>>> turtle.pos()
(440.00,-0.00)

turtle.towards(x, y=None)

參數:

x -- a number or a pair/vector of numbers or a turtle instance

y -- a number if x is a number, else None

Return the angle between the line from turtle position to position specified by (x,y), the vector or the other turtle. This depends on the turtle's start orientation which depends on the mode - "standard"/"world" or "logo".

>>> turtle.goto(10, 10)
>>> turtle.towards(0,0)
225.0

turtle.xcor()

Return the turtle's x coordinate.

>>> turtle.home()
>>> turtle.left(50)
>>> turtle.forward(100)
>>> turtle.pos()
(64.28,76.60)
>>> print(round(turtle.xcor(), 5))
64.27876

turtle.ycor()

Return the turtle's y coordinate.

>>> turtle.home()
>>> turtle.left(60)
>>> turtle.forward(100)
>>> print(turtle.pos())
(50.00,86.60)
>>> print(round(turtle.ycor(), 5))
86.60254

turtle.heading()

Return the turtle's current heading (value depends on the turtle mode, see mode()).

>>> turtle.home()
>>> turtle.left(67)
>>> turtle.heading()
67.0

turtle.distance(x, y=None)

參數:

x -- a number or a pair/vector of numbers or a turtle instance

y -- a number if x is a number, else None

Return the distance from the turtle to (x,y), the given vector, or the given other turtle, in turtle step units.

>>> turtle.home()
>>> turtle.distance(30,40)
50.0
>>> turtle.distance((30,40))
50.0
>>> joe = Turtle()
>>> joe.forward(77)
>>> turtle.distance(joe)
77.0

Settings for measurement

turtle.degrees(fullcircle=360.0)

參數:

fullcircle -- a number

Set angle measurement units, i.e. set number of "degrees" for a full circle. Default value is 360 degrees.

>>> turtle.home()
>>> turtle.left(90)
>>> turtle.heading()
90.0

>>> # Change angle measurement unit to grad (also known as gon,
>>> # grade, or gradian and equals 1/100-th of the right angle.)
>>> turtle.degrees(400.0)
>>> turtle.heading()
100.0
>>> turtle.degrees(360)
>>> turtle.heading()
90.0

turtle.radians()

Set the angle measurement units to radians. Equivalent to degrees(2*math.pi).

>>> turtle.home()
>>> turtle.left(90)
>>> turtle.heading()
90.0
>>> turtle.radians()
>>> turtle.heading()
1.5707963267948966

Pen control

Drawing state

turtle.pendown()

turtle.pd()

turtle.down()

Pull the pen down -- drawing when moving.

turtle.penup()

turtle.pu()

turtle.up()

Pull the pen up -- no drawing when moving.

turtle.pensize(width=None)

turtle.width(width=None)

參數:

width -- a positive number

Set the line thickness to width or return it. If resizemode is set to "auto" and turtleshape is a polygon, that polygon is drawn with the same line thickness. If no argument is given, the current pensize is returned.

>>> turtle.pensize()
1
>>> turtle.pensize(10)   # from here on lines of width 10 are drawn

turtle.pen(pen=None, **pendict)

參數:

pen -- a dictionary with some or all of the below listed keys

pendict -- one or more keyword-arguments with the below listed keys as keywords

Return or set the pen's attributes in a "pen-dictionary" with the following key/value pairs:

"shown": True/False

"pendown": True/False

"pencolor": color-string or color-tuple

"fillcolor": color-string or color-tuple

"pensize": positive number

"speed": number in range 0..10

"resizemode": "auto" or "user" or "noresize"

"stretchfactor": (positive number, positive number)

"outline": positive number

"tilt": number

This dictionary can be used as argument for a subsequent call to pen() to restore the former pen-state. Moreover one or more of these attributes can be provided as keyword-arguments. This can be used to set several pen attributes in one statement.

>>> turtle.pen(fillcolor="black", pencolor="red", pensize=10)
>>> sorted(turtle.pen().items())
[('fillcolor', 'black'), ('outline', 1), ('pencolor', 'red'),
 ('pendown', True), ('pensize', 10), ('resizemode', 'noresize'),
 ('shearfactor', 0.0), ('shown', True), ('speed', 9),
 ('stretchfactor', (1.0, 1.0)), ('tilt', 0.0)]
>>> penstate=turtle.pen()
>>> turtle.color("yellow", "")
>>> turtle.penup()
>>> sorted(turtle.pen().items())[:3]
[('fillcolor', ''), ('outline', 1), ('pencolor', 'yellow')]
>>> turtle.pen(penstate, fillcolor="green")
>>> sorted(turtle.pen().items())[:3]
[('fillcolor', 'green'), ('outline', 1), ('pencolor', 'red')]

turtle.isdown()

Return True if pen is down, False if it's up.

>>> turtle.penup()
>>> turtle.isdown()
False
>>> turtle.pendown()
>>> turtle.isdown()
True

Color control

turtle.pencolor()

turtle.pencolor(color, /)

turtle.pencolor(r, g, b, /)

Return or set the pencolor.

Four input formats are allowed:

pencolor()

Return the current pencolor as color specification string or as a tuple (see example). May be used as input to another color/pencolor/fillcolor/bgcolor call.

pencolor(colorstring)

Set pencolor to colorstring, which is a Tk color specification string, such as "red", "yellow", or "#33cc8c".

pencolor((r, g, b))

Set pencolor to the RGB color represented by the tuple of r, g, and b. Each of r, g, and b must be in the range 0..colormode, where colormode is either 1.0 or 255 (see colormode()).

pencolor(r, g, b)

Set pencolor to the RGB color represented by r, g, and b. Each of r, g, and b must be in the range 0..colormode.

If turtleshape is a polygon, the outline of that polygon is drawn with the newly set pencolor.

>>> colormode()
1.0
>>> turtle.pencolor()
'red'
>>> turtle.pencolor("brown")
>>> turtle.pencolor()
'brown'
>>> tup = (0.2, 0.8, 0.55)
>>> turtle.pencolor(tup)
>>> turtle.pencolor()
(0.2, 0.8, 0.5490196078431373)
>>> colormode(255)
>>> turtle.pencolor()
(51.0, 204.0, 140.0)
>>> turtle.pencolor('#32c18f')
>>> turtle.pencolor()
(50.0, 193.0, 143.0)

turtle.fillcolor()

turtle.fillcolor(color, /)

turtle.fillcolor(r, g, b, /)

Return or set the fillcolor.

Four input formats are allowed:

fillcolor()

Return the current fillcolor as color specification string, possibly in tuple format (see example). May be used as input to another color/pencolor/fillcolor/bgcolor call.

fillcolor(colorstring)

Set fillcolor to colorstring, which is a Tk color specification string, such as "red", "yellow", or "#33cc8c".

fillcolor((r, g, b))

Set fillcolor to the RGB color represented by the tuple of r, g, and b. Each of r, g, and b must be in the range 0..colormode, where colormode is either 1.0 or 255 (see colormode()).

fillcolor(r, g, b)

Set fillcolor to the RGB color represented by r, g, and b. Each of r, g, and b must be in the range 0..colormode.

If turtleshape is a polygon, the interior of that polygon is drawn with the newly set fillcolor.

>>> turtle.fillcolor("violet")
>>> turtle.fillcolor()
'violet'
>>> turtle.pencolor()
(50.0, 193.0, 143.0)
>>> turtle.fillcolor((50, 193, 143))  # 為整數而非浮點數
>>> turtle.fillcolor()
(50.0, 193.0, 143.0)
>>> turtle.fillcolor('#ffffff')
>>> turtle.fillcolor()
(255.0, 255.0, 255.0)

turtle.color()

turtle.color(color, /)

turtle.color(r, g, b, /)

turtle.color(pencolor, fillcolor, /)

Return or set pencolor and fillcolor.

Several input formats are allowed. They use 0 to 3 arguments as follows:

color()

Return the current pencolor and the current fillcolor as a pair of color specification strings or tuples as returned by pencolor() and fillcolor().

color(colorstring), color((r,g,b)), color(r,g,b)

Inputs as in pencolor(), set both, fillcolor and pencolor, to the given value.

color(colorstring1, colorstring2), color((r1,g1,b1), (r2,g2,b2))

Equivalent to pencolor(colorstring1) and fillcolor(colorstring2) and analogously if the other input format is used.

If turtleshape is a polygon, outline and interior of that polygon is drawn with the newly set colors.

>>> turtle.color("red", "green")
>>> turtle.color()
('red', 'green')
>>> color("#285078", "#a0c8f0")
>>> color()
((40.0, 80.0, 120.0), (160.0, 200.0, 240.0))

See also: Screen method colormode().

Filling

turtle.filling()

Return fillstate (True if filling, False else).

>>> turtle.begin_fill()
>>> if turtle.filling():
...    turtle.pensize(5)
... else:
...    turtle.pensize(3)

turtle.fill()

Fill the shape drawn in the with turtle.fill(): block.

>>> turtle.color("black", "red")
>>> with turtle.fill():
...     turtle.circle(80)

Using fill() is equivalent to adding the begin_fill() before the fill-block and end_fill() after the fill-block:

>>> turtle.color("black", "red")
>>> turtle.begin_fill()
>>> turtle.circle(80)
>>> turtle.end_fill()

在 3.14 版被加入.

turtle.begin_fill()

To be called just before drawing a shape to be filled.

turtle.end_fill()

Fill the shape drawn after the last call to begin_fill().

Whether or not overlap regions for self-intersecting polygons or multiple shapes are filled depends on the operating system graphics, type of overlap, and number of overlaps. For example, the Turtle star above may be either all yellow or have some white regions.

>>> turtle.color("black", "red")
>>> turtle.begin_fill()
>>> turtle.circle(80)
>>> turtle.end_fill()

More drawing control

turtle.reset()

Delete the turtle's drawings from the screen, re-center the turtle and set variables to the default values.

>>> turtle.goto(0,-22)
>>> turtle.left(100)
>>> turtle.position()
(0.00,-22.00)
>>> turtle.heading()
100.0
>>> turtle.reset()
>>> turtle.position()
(0.00,0.00)
>>> turtle.heading()
0.0

turtle.clear()

Delete the turtle's drawings from the screen. Do not move turtle. State and position of the turtle as well as drawings of other turtles are not affected.

turtle.write(arg, move=False, align='left', font=('Arial', 8, 'normal'))

參數:

arg -- object to be written to the TurtleScreen

move -- True/False

align -- one of the strings "left", "center" or right"

font -- a triple (fontname, fontsize, fonttype)

Write text - the string representation of arg - at the current turtle position according to align ("left", "center" or "right") and with the given font. If move is true, the pen is moved to the bottom-right corner of the text. By default, move is False.

>>> turtle.write("Home = ", True, align="center")
>>> turtle.write((0,0), True)

Turtle state

Visibility

turtle.hideturtle()

turtle.ht()

Make the turtle invisible. It's a good idea to do this while you're in the middle of doing some complex drawing, because hiding the turtle speeds up the drawing observably.

>>> turtle.hideturtle()

turtle.showturtle()

turtle.st()

Make the turtle visible.

>>> turtle.showturtle()

turtle.isvisible()

Return True if the Turtle is shown, False if it's hidden.

>>> turtle.hideturtle()
>>> turtle.isvisible()
False
>>> turtle.showturtle()
>>> turtle.isvisible()
True

Appearance

turtle.shape(name=None)

參數:

name -- a string which is a valid shapename

Set turtle shape to shape with given name or, if name is not given, return name of current shape. Shape with name must exist in the TurtleScreen's shape dictionary. Initially there are the following polygon shapes: "arrow", "turtle", "circle", "square", "triangle", "classic". To learn about how to deal with shapes see Screen method register_shape().

>>> turtle.shape()
'classic'
>>> turtle.shape("turtle")
>>> turtle.shape()
'turtle'

turtle.resizemode(rmode=None)

參數:

rmode -- one of the strings "auto", "user", "noresize"

Set resizemode to one of the values: "auto", "user", "noresize". If rmode is not given, return current resizemode. Different resizemodes have the following effects:

"auto": adapts the appearance of the turtle corresponding to the value of pensize.

"user": adapts the appearance of the turtle according to the values of stretchfactor and outlinewidth (outline), which are set by shapesize().

"noresize": no adaption of the turtle's appearance takes place.

resizemode("user") is called by shapesize() when used with arguments.

>>> turtle.resizemode()
'noresize'
>>> turtle.resizemode("auto")
>>> turtle.resizemode()
'auto'

turtle.shapesize(stretch_wid=None, stretch_len=None, outline=None)

turtle.turtlesize(stretch_wid=None, stretch_len=None, outline=None)

參數:

stretch_wid -- positive number

stretch_len -- positive number

outline -- positive number

Return or set the pen's attributes x/y-stretchfactors and/or outline. Set resizemode to "user". If and only if resizemode is set to "user", the turtle will be displayed stretched according to its stretchfactors: stretch_wid is stretchfactor perpendicular to its orientation, stretch_len is stretchfactor in direction of its orientation, outline determines the width of the shape's outline.

>>> turtle.shapesize()
(1.0, 1.0, 1)
>>> turtle.resizemode("user")
>>> turtle.shapesize(5, 5, 12)
>>> turtle.shapesize()
(5, 5, 12)
>>> turtle.shapesize(outline=8)
>>> turtle.shapesize()
(5, 5, 8)

turtle.shearfactor(shear=None)

參數:

shear -- number (optional)

Set or return the current shearfactor. Shear the turtleshape according to the given shearfactor shear, which is the tangent of the shear angle. Do not change the turtle's heading (direction of movement). If shear is not given: return the current shearfactor, i. e. the tangent of the shear angle, by which lines parallel to the heading of the turtle are sheared.

>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.shearfactor(0.5)
>>> turtle.shearfactor()
0.5

turtle.tilt(angle)

參數:

angle -- a number

Rotate the turtleshape by angle from its current tilt-angle, but do not change the turtle's heading (direction of movement).

>>> turtle.reset()
>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.tilt(30)
>>> turtle.fd(50)
>>> turtle.tilt(30)
>>> turtle.fd(50)

turtle.tiltangle(angle=None)

參數:

angle -- a number (optional)

Set or return the current tilt-angle. If angle is given, rotate the turtleshape to point in the direction specified by angle, regardless of its current tilt-angle. Do not change the turtle's heading (direction of movement). If angle is not given: return the current tilt-angle, i. e. the angle between the orientation of the turtleshape and the heading of the turtle (its direction of movement).

>>> turtle.reset()
>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.tilt(45)
>>> turtle.tiltangle()
45.0

turtle.shapetransform(t11=None, t12=None, t21=None, t22=None)

參數:

t11 -- a number (optional)

t12 -- a number (optional)

t21 -- a number (optional)

t12 -- a number (optional)

Set or return the current transformation matrix of the turtle shape.

If none of the matrix elements are given, return the transformation matrix as a tuple of 4 elements. Otherwise set the given elements and transform the turtleshape according to the matrix consisting of first row t11, t12 and second row t21, t22. The determinant t11 * t22 - t12 * t21 must not be zero, otherwise an error is raised. Modify stretchfactor, shearfactor and tiltangle according to the given matrix.

>>> turtle = Turtle()
>>> turtle.shape("square")
>>> turtle.shapesize(4,2)
>>> turtle.shearfactor(-0.5)
>>> turtle.shapetransform()
(4.0, -1.0, -0.0, 2.0)

turtle.get_shapepoly()

Return the current shape polygon as tuple of coordinate pairs. This can be used to define a new shape or components of a compound shape.

>>> turtle.shape("square")
>>> turtle.shapetransform(4, -1, 0, 2)
>>> turtle.get_shapepoly()
((50, -20), (30, 20), (-50, 20), (-30, -20))

Using events

turtle.onclick(fun, btn=1, add=None)

參數:

fun -- a function with two arguments which will be called with the coordinates of the clicked point on the canvas

btn -- number of the mouse-button, defaults to 1 (left mouse button)

add -- True or False -- if True, a new binding will be added, otherwise it will replace a former binding

Bind fun to mouse-click events on this turtle. If fun is None, existing bindings are removed. Example for the anonymous turtle, i.e. the procedural way:

>>> def turn(x, y):
...     left(180)
...
>>> onclick(turn)  # Now clicking into the turtle will turn it.
>>> onclick(None)  # event-binding will be removed

turtle.onrelease(fun, btn=1, add=None)

參數:

fun -- a function with two arguments which will be called with the coordinates of the clicked point on the canvas

btn -- number of the mouse-button, defaults to 1 (left mouse button)

add -- True or False -- if True, a new binding will be added, otherwise it will replace a former binding

Bind fun to mouse-button-release events on this turtle. If fun is None, existing bindings are removed.

>>> class MyTurtle(Turtle):
...     def glow(self,x,y):
...         self.fillcolor("red")
...     def unglow(self,x,y):
...         self.fillcolor("")
...
>>> turtle = MyTurtle()
>>> turtle.onclick(turtle.glow)     # clicking on turtle turns fillcolor red,
>>> turtle.onrelease(turtle.unglow) # releasing turns it to transparent.

turtle.ondrag(fun, btn=1, add=None)

參數:

fun -- a function with two arguments which will be called with the coordinates of the clicked point on the canvas

btn -- number of the mouse-button, defaults to 1 (left mouse button)

add -- True or False -- if True, a new binding will be added, otherwise it will replace a former binding

Bind fun to mouse-move events on this turtle. If fun is None, existing bindings are removed.

Remark: Every sequence of mouse-move-events on a turtle is preceded by a mouse-click event on that turtle.

>>> turtle.ondrag(turtle.goto)

Subsequently, clicking and dragging the Turtle will move it across the screen thereby producing handdrawings (if pen is down).

Special Turtle methods

turtle.poly()

Record the vertices of a polygon drawn in the with turtle.poly(): block. The first and last vertices will be connected.

>>> with turtle.poly():
...     turtle.forward(100)
...     turtle.right(60)
...     turtle.forward(100)

在 3.14 版被加入.

turtle.begin_poly()

Start recording the vertices of a polygon. Current turtle position is first vertex of polygon.

turtle.end_poly()

Stop recording the vertices of a polygon. Current turtle position is last vertex of polygon. This will be connected with the first vertex.

turtle.get_poly()

Return the last recorded polygon.

>>> turtle.home()
>>> turtle.begin_poly()
>>> turtle.fd(100)
>>> turtle.left(20)
>>> turtle.fd(30)
>>> turtle.left(60)
>>> turtle.fd(50)
>>> turtle.end_poly()
>>> p = turtle.get_poly()
>>> register_shape("myFavouriteShape", p)

turtle.clone()

Create and return a clone of the turtle with same position, heading and turtle properties.

>>> mick = Turtle()
>>> joe = mick.clone()

turtle.getturtle()

turtle.getpen()

Return the Turtle object itself. Only reasonable use: as a function to return the "anonymous turtle":

>>> pet = getturtle()
>>> pet.fd(50)
>>> pet
<turtle.Turtle object at 0x...>

turtle.getscreen()

Return the TurtleScreen object the turtle is drawing on. TurtleScreen methods can then be called for that object.

>>> ts = turtle.getscreen()
>>> ts
<turtle._Screen object at 0x...>
>>> ts.bgcolor("pink")

turtle.setundobuffer(size)

參數:

size -- 一個整數或 None

Set or disable undobuffer. If size is an integer, an empty undobuffer of given size is installed. size gives the maximum number of turtle actions that can be undone by the undo() method/function. If size is None, the undobuffer is disabled.

>>> turtle.setundobuffer(42)

turtle.undobufferentries()

Return number of entries in the undobuffer.

>>> while undobufferentries():
...     undo()

Compound shapes

To use compound turtle shapes, which consist of several polygons of different color, you must use the helper class Shape explicitly as described below:

Create an empty Shape object of type "compound".

Add as many components to this object as desired, using the addcomponent() method.

舉例來說：

>>> s = Shape("compound")
>>> poly1 = ((0,0),(10,-5),(0,10),(-10,-5))
>>> s.addcomponent(poly1, "red", "blue")
>>> poly2 = ((0,0),(10,-5),(-10,-5))
>>> s.addcomponent(poly2, "blue", "red")

Now add the Shape to the Screen's shapelist and use it:

>>> register_shape("myshape", s)
>>> shape("myshape")

備註

The Shape class is used internally by the register_shape() method in different ways. The application programmer has to deal with the Shape class only when using compound shapes like shown above!

Methods of TurtleScreen/Screen and corresponding functions

Most of the examples in this section refer to a TurtleScreen instance called screen.

Window control

turtle.bgcolor()

turtle.bgcolor(color, /)

turtle.bgcolor(r, g, b, /)

Return or set the background color of the TurtleScreen.

Four input formats are allowed:

bgcolor()

Return the current background color as color specification string or as a tuple (see example). May be used as input to another color/pencolor/fillcolor/bgcolor call.

bgcolor(colorstring)

Set the background color to colorstring, which is a Tk color specification string, such as "red", "yellow", or "#33cc8c".

bgcolor((r, g, b))

Set the background color to the RGB color represented by the tuple of r, g, and b. Each of r, g, and b must be in the range 0..colormode, where colormode is either 1.0 or 255 (see colormode()).

bgcolor(r, g, b)

Set the background color to the RGB color represented by r, g, and b. Each of r, g, and b must be in the range 0..colormode.

>>> screen.bgcolor("orange")
>>> screen.bgcolor()
'orange'
>>> screen.bgcolor("#800080")
>>> screen.bgcolor()
(128.0, 0.0, 128.0)

turtle.bgpic(picname=None)

參數:

picname -- a string, name of an image file (PNG, GIF, PGM, and PPM) or "nopic", or None

Set background image or return name of current backgroundimage. If picname is a filename, set the corresponding image as background. If picname is "nopic", delete background image, if present. If picname is None, return the filename of the current backgroundimage.

>>> screen.bgpic()
'nopic'
>>> screen.bgpic("landscape.gif")
>>> screen.bgpic()
"landscape.gif"

turtle.clear()

備註

This TurtleScreen method is available as a global function only under the name clearscreen. The global function clear is a different one derived from the Turtle method clear.

turtle.clearscreen()

Delete all drawings and all turtles from the TurtleScreen. Reset the now empty TurtleScreen to its initial state: white background, no background image, no event bindings and tracing on.

turtle.reset()

備註

This TurtleScreen method is available as a global function only under the name resetscreen. The global function reset is another one derived from the Turtle method reset.

turtle.resetscreen()

Reset all Turtles on the Screen to their initial state.

turtle.screensize(canvwidth=None, canvheight=None, bg=None)

參數:

canvwidth -- positive integer, new width of canvas in pixels

canvheight -- positive integer, new height of canvas in pixels

bg -- colorstring or color-tuple, new background color

If no arguments are given, return current (canvaswidth, canvasheight). Else resize the canvas the turtles are drawing on. Do not alter the drawing window. To observe hidden parts of the canvas, use the scrollbars. With this method, one can make visible those parts of a drawing which were outside the canvas before.

>>> screen.screensize()
(400, 300)
>>> screen.screensize(2000,1500)
>>> screen.screensize()
(2000, 1500)

e.g. to search for an erroneously escaped turtle ;-)

turtle.setworldcoordinates(llx, lly, urx, ury)

參數:

llx -- a number, x-coordinate of lower left corner of canvas

lly -- a number, y-coordinate of lower left corner of canvas

urx -- a number, x-coordinate of upper right corner of canvas

ury -- a number, y-coordinate of upper right corner of canvas

Set up user-defined coordinate system and switch to mode "world" if necessary. This performs a screen.reset(). If mode "world" is already active, all drawings are redrawn according to the new coordinates.

ATTENTION: in user-defined coordinate systems angles may appear distorted.

>>> screen.reset()
>>> screen.setworldcoordinates(-50,-7.5,50,7.5)
>>> for _ in range(72):
...     left(10)
...
>>> for _ in range(8):
...     left(45); fd(2)   # 一個一般的八邊形

Animation control

turtle.no_animation()

Temporarily disable turtle animation. The code written inside the no_animation block will not be animated; once the code block is exited, the drawing will appear.

>>> with screen.no_animation():
...     for dist in range(2, 400, 2):
...         fd(dist)
...         rt(90)

在 3.14 版被加入.

turtle.delay(delay=None)

參數:

delay -- 正整數

Set or return the drawing delay in milliseconds. (This is approximately the time interval between two consecutive canvas updates.) The longer the drawing delay, the slower the animation.

可選引數：

>>> screen.delay()
10
>>> screen.delay(5)
>>> screen.delay()
5

turtle.tracer(n=None, delay=None)

參數:

n -- 非負整數

delay -- 非負整數

Turn turtle animation on/off and set delay for update drawings. If n is given, only each n-th regular screen update is really performed. (Can be used to accelerate the drawing of complex graphics.) When called without arguments, returns the currently stored value of n. Second argument sets delay value (see delay()).

>>> screen.tracer(8, 25)
>>> dist = 2
>>> for i in range(200):
...     fd(dist)
...     rt(90)
...     dist += 2

turtle.update()

Perform a TurtleScreen update. To be used when tracer is turned off.

另請參閱 RawTurtle/Turtle 的 speed() 方法。

Using screen events

turtle.listen(xdummy=None, ydummy=None)

Set focus on TurtleScreen (in order to collect key-events). Dummy arguments are provided in order to be able to pass listen() to the onclick method.

turtle.onkey(fun, key)

turtle.onkeyrelease(fun, key)

參數:

fun -- a function with no arguments or None

key -- a string: key (e.g. "a") or key-symbol (e.g. "space")

Bind fun to key-release event of key. If fun is None, event bindings are removed. Remark: in order to be able to register key-events, TurtleScreen must have the focus. (See method listen().)

>>> def f():
...     fd(50)
...     lt(60)
...
>>> screen.onkey(f, "Up")
>>> screen.listen()

turtle.onkeypress(fun, key=None)

參數:

fun -- a function with no arguments or None

key -- a string: key (e.g. "a") or key-symbol (e.g. "space")

Bind fun to key-press event of key if key is given, or to any key-press-event if no key is given. Remark: in order to be able to register key-events, TurtleScreen must have focus. (See method listen().)

>>> def f():
...     fd(50)
...
>>> screen.onkey(f, "Up")
>>> screen.listen()

turtle.onclick(fun, btn=1, add=None)

turtle.onscreenclick(fun, btn=1, add=None)

參數:

fun -- a function with two arguments which will be called with the coordinates of the clicked point on the canvas

btn -- number of the mouse-button, defaults to 1 (left mouse button)

add -- True or False -- if True, a new binding will be added, otherwise it will replace a former binding

Bind fun to mouse-click events on this screen. If fun is None, existing bindings are removed.

Example for a TurtleScreen instance named screen and a Turtle instance named turtle:

>>> screen.onclick(turtle.goto) # Subsequently clicking into the TurtleScreen will
>>>                             # make the turtle move to the clicked point.
>>> screen.onclick(None)        # remove event binding again

備註

This TurtleScreen method is available as a global function only under the name onscreenclick. The global function onclick is another one derived from the Turtle method onclick.

turtle.ontimer(fun, t=0)

參數:

fun -- a function with no arguments

t -- a number >= 0

Install a timer that calls fun after t milliseconds.

>>> running = True
>>> def f():
...     if running:
...         fd(50)
...         lt(60)
...         screen.ontimer(f, 250)
>>> f()   ### makes the turtle march around
>>> running = False

turtle.mainloop()

turtle.done()

Starts event loop - calling Tkinter's mainloop function. Must be the last statement in a turtle graphics program. Must not be used if a script is run from within IDLE in -n mode (No subprocess) - for interactive use of turtle graphics.

>>> screen.mainloop()

Input methods

turtle.textinput(title, prompt)

參數:

title -- string（字串）

prompt -- string（字串）

Pop up a dialog window for input of a string. Parameter title is the title of the dialog window, prompt is a text mostly describing what information to input. Return the string input. If the dialog is canceled, return None.

>>> screen.textinput("NIM", "Name of first player:")

turtle.numinput(title, prompt, default=None, minval=None, maxval=None)

參數:

title -- string（字串）

prompt -- string（字串）

default -- number (optional)

minval -- number (optional)

maxval -- number (optional)

Pop up a dialog window for input of a number. title is the title of the dialog window, prompt is a text mostly describing what numerical information to input. default: default value, minval: minimum value for input, maxval: maximum value for input. The number input must be in the range minval .. maxval if these are given. If not, a hint is issued and the dialog remains open for correction. Return the number input. If the dialog is canceled, return None.

>>> screen.numinput("Poker", "Your stakes:", 1000, minval=10, maxval=10000)

Settings and special methods

turtle.mode(mode=None)

參數:

mode -- one of the strings "standard", "logo" or "world"

Set turtle mode ("standard", "logo" or "world") and perform reset. If mode is not given, current mode is returned.

Mode "standard" is compatible with old turtle. Mode "logo" is compatible with most Logo turtle graphics. Mode "world" uses user-defined "world coordinates". Attention: in this mode angles appear distorted if x/y unit-ratio doesn't equal 1.

Mode

Initial turtle heading

positive angles

"standard"

to the right (east)

counterclockwise

"logo"

upward (north)

clockwise

>>> mode("logo")   # resets turtle heading to north
>>> mode()
'logo'

turtle.colormode(cmode=None)

參數:

cmode -- one of the values 1.0 or 255

Return the colormode or set it to 1.0 or 255. Subsequently r, g, b values of color triples have to be in the range 0..*cmode*.

>>> screen.colormode(1)
>>> turtle.pencolor(240, 160, 80)
Traceback (most recent call last):
     ...
TurtleGraphicsError: bad color sequence: (240, 160, 80)
>>> screen.colormode()
1.0
>>> screen.colormode(255)
>>> screen.colormode()
255
>>> turtle.pencolor(240,160,80)

turtle.getcanvas()

Return the Canvas of this TurtleScreen. Useful for insiders who know what to do with a Tkinter Canvas.

>>> cv = screen.getcanvas()
>>> cv
<turtle.ScrolledCanvas object ...>

turtle.getshapes()

Return a list of names of all currently available turtle shapes.

>>> screen.getshapes()
['arrow', 'blank', 'circle', ..., 'turtle']

turtle.register_shape(name, shape=None)

turtle.addshape(name, shape=None)

There are four different ways to call this function:

name is the name of an image file (PNG, GIF, PGM, and PPM) and shape is None: Install the corresponding image shape.

>>> screen.register_shape("turtle.gif")

備註

Image shapes do not rotate when turning the turtle, so they do not display the heading of the turtle!

name is an arbitrary string and shape is the name of an image file (PNG, GIF, PGM, and PPM): Install the corresponding image shape.

>>> screen.register_shape("turtle", "turtle.gif")

備註

Image shapes do not rotate when turning the turtle, so they do not display the heading of the turtle!

name is an arbitrary string and shape is a tuple of pairs of coordinates: Install the corresponding polygon shape.

>>> screen.register_shape("triangle", ((5,-3), (0,5), (-5,-3)))

name is an arbitrary string and shape is a (compound) Shape object: Install the corresponding compound shape.

Add a turtle shape to TurtleScreen's shapelist. Only thusly registered shapes can be used by issuing the command shape(shapename).

在 3.14 版的變更: Added support for PNG, PGM, and PPM image formats. Both a shape name and an image file name can be specified.

turtle.turtles()

Return the list of turtles on the screen.

>>> for turtle in screen.turtles():
...     turtle.color("red")

turtle.window_height()

Return the height of the turtle window.

>>> screen.window_height()
480

turtle.window_width()

Return the width of the turtle window.

>>> screen.window_width()
640

Methods specific to Screen, not inherited from TurtleScreen

turtle.bye()

Shut the turtlegraphics window.

turtle.exitonclick()

Bind bye() method to mouse clicks on the Screen.

If the value "using_IDLE" in the configuration dictionary is False (default value), also enter mainloop. Remark: If IDLE with the -n switch (no subprocess) is used, this value should be set to True in turtle.cfg. In this case IDLE's own mainloop is active also for the client script.

turtle.save(filename, overwrite=False)

Save the current turtle drawing (and turtles) as a PostScript file.

參數:

filename -- the path of the saved PostScript file

overwrite -- if False and there already exists a file with the given filename, then the function will raise a FileExistsError. If it is True, the file will be overwritten.

>>> screen.save("my_drawing.ps")
>>> screen.save("my_drawing.ps", overwrite=True)

在 3.14 版被加入.

turtle.setup(width=_CFG['width'], height=_CFG['height'], startx=_CFG['leftright'], starty=_CFG['topbottom'])

Set the size and position of the main window. Default values of arguments are stored in the configuration dictionary and can be changed via a turtle.cfg file.

參數:

width -- if an integer, a size in pixels, if a float, a fraction of the screen; default is 50% of screen

height -- if an integer, the height in pixels, if a float, a fraction of the screen; default is 75% of screen

startx -- if positive, starting position in pixels from the left edge of the screen, if negative from the right edge, if None, center window horizontally

starty -- if positive, starting position in pixels from the top edge of the screen, if negative from the bottom edge, if None, center window vertically

>>> screen.setup (width=200, height=200, startx=0, starty=0)
>>>              # sets window to 200x200 pixels, in upper left of screen
>>> screen.setup(width=.75, height=0.5, startx=None, starty=None)
>>>              # sets window to 75% of screen by 50% of screen and centers

turtle.title(titlestring)

參數:

titlestring -- a string that is shown in the titlebar of the turtle graphics window

Set title of turtle window to titlestring.

>>> screen.title("Welcome to the turtle zoo!")

Public classes

class turtle.RawTurtle(canvas)

class turtle.RawPen(canvas)

參數:

canvas -- a tkinter.Canvas, a ScrolledCanvas or a TurtleScreen

Create a turtle. The turtle has all methods described above as "methods of Turtle/RawTurtle".

class turtle.Turtle

Subclass of RawTurtle, has the same interface but draws on a default Screen object created automatically when needed for the first time.

class turtle.TurtleScreen(cv)

參數:

cv -- 一個 tkinter.Canvas

Provides screen oriented methods like bgcolor() etc. that are described above.

class turtle.Screen

Subclass of TurtleScreen, with four methods added.

class turtle.ScrolledCanvas(master)

參數:

master -- some Tkinter widget to contain the ScrolledCanvas, i.e. a Tkinter-canvas with scrollbars added

Used by class Screen, which thus automatically provides a ScrolledCanvas as playground for the turtles.

class turtle.Shape(type_, data)

參數:

type_ -- one of the strings "polygon", "image", "compound"

Data structure modeling shapes. The pair (type_, data) must follow this specification:

type_

data

"polygon"

a polygon-tuple, i.e. a tuple of pairs of coordinates

"image"

an image (in this form only used internally!)

"compound"

None (a compound shape has to be constructed using the addcomponent() method)

addcomponent(poly, fill, outline=None)

參數:

poly -- a polygon, i.e. a tuple of pairs of numbers

fill -- a color the poly will be filled with

outline -- a color for the poly's outline (if given)

例如：

>>> poly = ((0,0),(10,-5),(0,10),(-10,-5))
>>> s = Shape("compound")
>>> s.addcomponent(poly, "red", "blue")
>>> # ... add more components and then use register_shape()

請見Compound shapes。

class turtle.Vec2D(x, y)

A two-dimensional vector class, used as a helper class for implementing turtle graphics. May be useful for turtle graphics programs too. Derived from tuple, so a vector is a tuple!

Provides (for a, b vectors, k number):

a + b 向量加法

a - b 向量減法

a * b 內積

k * a and a * k multiplication with scalar

abs(a) a 的絕對值

a.rotate(angle) 旋轉

解釋

A turtle object draws on a screen object, and there a number of key classes in the turtle object-oriented interface that can be used to create them and relate them to each other.

A Turtle instance will automatically create a Screen instance if one is not already present.

Turtle is a subclass of RawTurtle, which doesn't automatically create a drawing surface - a canvas will need to be provided or created for it. The canvas can be a tkinter.Canvas, ScrolledCanvas or TurtleScreen.

TurtleScreen is the basic drawing surface for a turtle. Screen is a subclass of TurtleScreen, and includes some additional methods for managing its appearance (including size and title) and behaviour. TurtleScreen's constructor needs a tkinter.Canvas or a ScrolledCanvas as an argument.

The functional interface for turtle graphics uses the various methods of Turtle and TurtleScreen/Screen. Behind the scenes, a screen object is automatically created whenever a function derived from a Screen method is called. Similarly, a turtle object is automatically created whenever any of the functions derived from a Turtle method is called.

To use multiple turtles on a screen, the object-oriented interface must be used.

Help and configuration

How to use help

The public methods of the Screen and Turtle classes are documented extensively via docstrings. So these can be used as online-help via the Python help facilities:

When using IDLE, tooltips show the signatures and first lines of the docstrings of typed in function-/method calls.

Calling help() on methods or functions displays the docstrings:

>>> help(Screen.bgcolor)
Help on method bgcolor in module turtle:

bgcolor(self, *args) unbound turtle.Screen method
    Set or return backgroundcolor of the TurtleScreen.

    Arguments (if given): a color string or three numbers
    in the range 0..colormode or a 3-tuple of such numbers.

    >>> screen.bgcolor("orange")
    >>> screen.bgcolor()
    "orange"
    >>> screen.bgcolor(0.5,0,0.5)
    >>> screen.bgcolor()
    "#800080"

>>> help(Turtle.penup)
Help on method penup in module turtle:

penup(self) unbound turtle.Turtle method
    Pull the pen up -- no drawing when moving.

    Aliases: penup | pu | up

    No argument

    >>> turtle.penup()

The docstrings of the functions which are derived from methods have a modified form:

>>> help(bgcolor)
Help on function bgcolor in module turtle:

bgcolor(*args)
    Set or return backgroundcolor of the TurtleScreen.

    Arguments (if given): a color string or three numbers
    in the range 0..colormode or a 3-tuple of such numbers.

    Example::

      >>> bgcolor("orange")
      >>> bgcolor()
      "orange"
      >>> bgcolor(0.5,0,0.5)
      >>> bgcolor()
      "#800080"

>>> help(penup)
Help on function penup in module turtle:

penup()
    Pull the pen up -- no drawing when moving.

    Aliases: penup | pu | up

    No argument

    Example:
    >>> penup()

These modified docstrings are created automatically together with the function definitions that are derived from the methods at import time.

Translation of docstrings into different languages

There is a utility to create a dictionary the keys of which are the method names and the values of which are the docstrings of the public methods of the classes Screen and Turtle.

turtle.write_docstringdict(filename='turtle_docstringdict')

參數:

filename -- a string, used as filename

Create and write docstring-dictionary to a Python script with the given filename. This function has to be called explicitly (it is not used by the turtle graphics classes). The docstring dictionary will be written to the Python script filename.py. It is intended to serve as a template for translation of the docstrings into different languages.

If you (or your students) want to use turtle with online help in your native language, you have to translate the docstrings and save the resulting file as e.g. turtle_docstringdict_german.py.

If you have an appropriate entry in your turtle.cfg file this dictionary will be read in at import time and will replace the original English docstrings.

At the time of this writing there are docstring dictionaries in German and in Italian. (Requests please to glingl@aon.at.)

How to configure Screen and Turtles

The built-in default configuration mimics the appearance and behaviour of the old turtle module in order to retain best possible compatibility with it.

If you want to use a different configuration which better reflects the features of this module or which better fits to your needs, e.g. for use in a classroom, you can prepare a configuration file turtle.cfg which will be read at import time and modify the configuration according to its settings.

The built in configuration would correspond to the following turtle.cfg:

width = 0.5
height = 0.75
leftright = None
topbottom = None
canvwidth = 400
canvheight = 300
mode = standard
colormode = 1.0
delay = 10
undobuffersize = 1000
shape = classic
pencolor = black
fillcolor = black
resizemode = noresize
visible = True
language = english
exampleturtle = turtle
examplescreen = screen
title = Python Turtle Graphics
using_IDLE = False

Short explanation of selected entries:

The first four lines correspond to the arguments of the Screen.setup method.

Line 5 and 6 correspond to the arguments of the method Screen.screensize.

shape can be any of the built-in shapes, e.g: arrow, turtle, etc. For more info try help(shape).

If you want to use no fill color (i.e. make the turtle transparent), you have to write fillcolor = "" (but all nonempty strings must not have quotes in the cfg file).

If you want to reflect the turtle its state, you have to use resizemode = auto.

If you set e.g. language = italian the docstringdict turtle_docstringdict_italian.py will be loaded at import time (if present on the import path, e.g. in the same directory as turtle).

The entries exampleturtle and examplescreen define the names of these objects as they occur in the docstrings. The transformation of method-docstrings to function-docstrings will delete these names from the docstrings.

using_IDLE: Set this to True if you regularly work with IDLE and its -n switch ("no subprocess"). This will prevent exitonclick() to enter the mainloop.

There can be a turtle.cfg file in the directory where turtle is stored and an additional one in the current working directory. The latter will override the settings of the first one.

The Lib/turtledemo directory contains a turtle.cfg file. You can study it as an example and see its effects when running the demos (preferably not from within the demo-viewer).

turtledemo --- Demo scripts

The turtledemo package includes a set of demo scripts. These scripts can be run and viewed using the supplied demo viewer as follows:

python -m turtledemo

Alternatively, you can run the demo scripts individually. For example,

python -m turtledemo.bytedesign

turtledemo 套件目錄包含：

A demo viewer __main__.py which can be used to view the sourcecode of the scripts and run them at the same time.

Multiple scripts demonstrating different features of the turtle module. Examples can be accessed via the Examples menu. They can also be run standalone.

A turtle.cfg file which serves as an example of how to write and use such files.

The demo scripts are:

Name

描述

Features

bytedesign

complex classical turtle graphics pattern

tracer()、delay()、update()

chaos

graphs Verhulst dynamics, shows that computer's computations can generate results sometimes against the common sense expectations

world coordinates

clock

analog clock showing time of your computer

turtles as clock's hands, ontimer()

colormixer

experiment with r, g, b

ondrag()

forest

3 breadth-first trees

randomization

fractalcurves

Hilbert & Koch curves

recursion

lindenmayer

ethnomathematics (indian kolams)

L-System

minimal_hanoi

河內塔

Rectangular Turtles as Hanoi discs (shape(), shapesize())

nim

play the classical nim game with three heaps of sticks against the computer.

turtles as nimsticks, event driven (mouse, keyboard)

paint

super minimalistic drawing program

onclick()

peace

elementary

turtle: appearance and animation

penrose

aperiodic tiling with kites and darts

stamp()

planet_and_moon

simulation of gravitational system

compound shapes, Vec2D

rosette

a pattern from the wikipedia article on turtle graphics

clone()、undo()

round_dance

dancing turtles rotating pairwise in opposite direction

compound shapes, clone() shapesize(), tilt(), get_shapepoly(), update()

sorting_animate

visual demonstration of different sorting methods

simple alignment, randomization

tree

a (graphical) breadth first tree (using generators)

clone()

two_canvases

simple design

turtles on two canvases

yinyang

another elementary example

circle()

Have fun!

自 Python 2.6 以來的變更

The methods Turtle.tracer, Turtle.window_width and Turtle.window_height have been eliminated. Methods with these names and functionality are now available only as methods of Screen. The functions derived from these remain available. (In fact already in Python 2.6 these methods were merely duplications of the corresponding TurtleScreen/Screen methods.)

The method Turtle.fill() has been eliminated. The behaviour of begin_fill() and end_fill() have changed slightly: now every filling process must be completed with an end_fill() call.

A method Turtle.filling has been added. It returns a boolean value: True if a filling process is under way, False otherwise. This behaviour corresponds to a fill() call without arguments in Python 2.6.

自 Python 3.0 以來的變更

The Turtle methods shearfactor(), shapetransform() and get_shapepoly() have been added. Thus the full range of regular linear transforms is now available for transforming turtle shapes. tiltangle() has been enhanced in functionality: it now can be used to get or set the tilt angle.

The Screen method onkeypress() has been added as a complement to onkey(). As the latter binds actions to the key release event, an alias: onkeyrelease() was also added for it.

The method Screen.mainloop has been added, so there is no longer a need to use the standalone mainloop() function when working with Screen and Turtle objects.

Two input methods have been added: Screen.textinput and Screen.numinput. These pop up input dialogs and return strings and numbers respectively.

開發工具

本章所描述的模組可以幫助你編寫軟體。例如 pydoc 模組可以根據模組的內容生成文件；doctest 和 unittest 模組則包含編寫單元測試的框架，這些測試程式碼會自動執行並驗證輸出結果是否正確。

本章節所描述的模組列表為：

typing --- 支援型別提示

Python 型別系統的技術規範

型別別名

NewType

註釋 callable 物件

泛型

註釋元組 (tuple)

類別物件的型別

Annotating generators and coroutines

使用者定義泛型型別

Any 型別

標稱 (nominal) 子型別 vs 結構子型別

模組內容

特別型別原語 (primitive)

特別型別

特別型式

Building generic types and type aliases

Other special directives

協定

ABCs and Protocols for working with I/O

函式與裝飾器

Introspection helpers

常數

棄用的別名

內建型別的別名

collections 中型別的別名

Aliases to other concrete types

collections.abc 中容器 ABC 的別名

collections.abc 中非同步 ABC 的別名

Aliases to other ABCs in collections.abc

contextlib ABC 的別名

主要功能的棄用時程表

pydoc --- 文件產生器與線上幫助系統

Python 開發模式

Python 開發模式的影響

ResourceWarning 範例

檔案描述器的錯誤範例

doctest --- 測試互動式 Python 範例

Simple Usage: Checking Examples in Docstrings

Simple Usage: Checking Examples in a Text File

命令列用法

運作方式

Which Docstrings Are Examined?

How are Docstring Examples Recognized?

What's the Execution Context?

What About Exceptions?

可選旗標

Directives

警告

基礎 API

Unittest API

Advanced API

DocTest 物件

Example 物件

DocTestFinder 物件

DocTestParser 物件

TestResults 物件

DocTestRunner 物件

OutputChecker 物件

偵錯

Soapbox

unittest --- 單元測試框架

簡單範例

命令列介面

命令列模式選項

Test Discovery（測試探索）

Organizing test code

Re-using old test code

Skipping tests and expected failures

Distinguishing test iterations using subtests

類別與函式

Test cases

Grouping tests

Loading and running tests

load_tests 協定

Class and Module Fixtures

setUpClass 和 tearDownClass

setUpModule 和 tearDownModule

Signal Handling

unittest.mock — mock 物件函式庫

快速導引

Mock 類別

呼叫

刪除屬性

Mock 名稱與名稱屬性

如同屬性一般附加 mock

Patchers

patch

patch.object

patch.dict

patch.multiple

patch 方法：啟動與停止

patch 內建函式

TEST_PREFIX

巢狀使用 Patch 裝飾器

該 patch 何處

Patch 描述器與代理物件 (Proxy Objects)

MagicMock 以及魔術方法支援

Mock 魔術方法

Magic Mock

輔助函式

sentinel（哨兵）

DEFAULT

call

create_autospec

ANY

FILTER_DIR

mock_open

Autospeccing（自動規格）

密封 mock

side_effect、return_value 和 wraps 的優先順序

unittest.mock --- 入門指南

使用 Mock 的方式

使用 Mock 來 patching 方法

對物件的方法呼叫使用 mock

Mock 類別

命名你的 mock

追蹤所有呼叫

設定回傳值和屬性

透過 mock 引發例外

Side effect 函式以及可疊代物件

Mock 非同步可疊代物件

Mock 非同步情境管理器

從現有物件建立 mock

使用 side_effect 回傳各別檔案內容

Patch 裝飾器

更多範例

Mock 鍊接呼叫

部分 mocking

Mock 產生器方法

對每個測試方法應用相同的 patch

Mock Unbound Methods （未繫結方法）

使用 mock 檢查多個呼叫

應對可變引數

巢狀使用 Patch

使用 MagicMock 來 mock 字典

Mock 子類別及其屬性

使用 patch.dict 來 mock import

追蹤呼叫順序與更簡潔的呼叫斷言

更複雜的引數匹配

test --- Python 的回歸測試 (regression tests) 套件

撰寫 test 套件的單元測試

使用命令列介面執行測試

test.support --- Python 測試套件的工具

test.support.socket_helper --- 用於 socket 測試的工具

test.support.script_helper --- 用於 Python 執行測試的工具

test.support.bytecode_helper --- 用於測試位元組碼能正確產生的支援工具

test.support.threading_helper --- Utilities for threading tests

test.support.os_helper --- 用於 os 測試的工具

test.support.import_helper --- 用於 import 測試的工具

test.support.warnings_helper --- 用於 warnings 測試的工具

typing --- 支援型別提示

在 3.5 版被加入.

原始碼：Lib/typing.py [https://github.com/python/cpython/tree/3.14/Lib/typing.py]

備註

Python runtime 不強制要求函式與變數的型別註釋。他們可以被第三方工具使用，如：型別檢查器、IDE、linter 等。

此模組提供 runtime 型別提示支援。

動腦筋思考下面的函式：

def surface_area_of_cube(edge_length: float) -> str:
    return f"The surface area of the cube is {6 * edge_length ** 2}."

函式 surface_area_of_cube 需要一個引數且預期是一個 float 的實例，如 edge_length: float 所指出的型別提示。這個函式預期會回傳一個 str 的實例，如 -> str 所指出的提示。

儘管型別提示可以是簡單類別，像是 float 或 str，他們也可以變得更為複雜。模組 typing 提供一組更高階的型別提示詞彙。

新功能會頻繁的新增至 typing 模組中。typing_extensions [https://pypi.org/project/typing_extensions/] 套件為這些新功能提供了 backport（向後移植的）版本，提供給舊版本的 Python 使用。

也參考

型別小抄 (Typing cheat sheet) [https://mypy.readthedocs.io/en/stable/cheat_sheet_py3.html]

型別提示的快速預覽（發布於 mypy 的文件中）

mypy 文件 [https://mypy.readthedocs.io/en/stable/index.html]的 型別系統參考資料 (Type System Reference) 章節

Python 的加註型別系統是基於 PEPs 進行標準化，所以這個參照 (reference) 應該在多數 Python 型別檢查器中廣為使用。（某些部分依然是特定給 mypy 使用。）

Python 的靜態型別 (Static Typing) [https://typing.python.org/en/latest/]

由社群編寫的跨平台型別檢查器文件 (type-checker-agnostic) 詳細描述加註型別系統的功能、實用的加註型別衍伸工具、以及加註型別的最佳實踐 (best practice)。

Python 型別系統的技術規範

關於 Python 型別系統標準的 (canonical)、最新的技術規範可以在Python 型別系統的技術規範 [https://typing.python.org/en/latest/spec/index.html]找到。

型別別名

一個型別別名被定義來使用 type 陳述式，其建立了 TypeAliasType 的實例。在這個範例中，Vector 及 list[float] 會被當作和靜態型別檢查器一樣同等對待：

type Vector = list[float]

def scale(scalar: float, vector: Vector) -> Vector:
    return [scalar * num for num in vector]

# passes type checking; a list of floats qualifies as a Vector.
new_vector = scale(2.0, [1.0, -4.2, 5.4])

型別別名對於簡化複雜的型別簽名 (complex type signature) 非常好用。舉例來說：

from collections.abc import Sequence

type ConnectionOptions = dict[str, str]
type Address = tuple[str, int]
type Server = tuple[Address, ConnectionOptions]

def broadcast_message(message: str, servers: Sequence[Server]) -> None:
    ...

# The static type checker will treat the previous type signature as
# being exactly equivalent to this one.
def broadcast_message(
    message: str,
    servers: Sequence[tuple[tuple[str, int], dict[str, str]]]
) -> None:
    ...

type 陳述式是 Python 3.12 的新功能。為了向後相容性，型別別名可以透過簡單的賦值來建立：

Vector = list[float]

或是用 TypeAlias 標記，讓它明確的表示這是一個型別別名，而非一般的變數賦值：

from typing import TypeAlias

Vector: TypeAlias = list[float]

NewType

使用 NewType 輔助工具 (helper) 建立獨特型別：

from typing import NewType

UserId = NewType('UserId', int)
some_id = UserId(524313)

若它是原本型別的子類別，靜態型別檢查器會將其視為一個新的型別。這對於幫助擷取邏輯性錯誤非常有用：

def get_user_name(user_id: UserId) -> str:
    ...

# passes type checking
user_a = get_user_name(UserId(42351))

# fails type checking; an int is not a UserId
user_b = get_user_name(-1)

你依然可以在對於型別 UserId 的變數中執行所有 int 的操作。這讓你可以在預期接受 int 的地方傳遞一個 UserId，還能預防你意外使用無效的方法建立一個 UserId：

# 'output' is of type 'int', not 'UserId'
output = UserId(23413) + UserId(54341)

注意這只會透過靜態型別檢查器強制檢查。在 runtime 中，陳述式 (statement) Derived = NewType('Derived', Base) 會使 Derived 成為一個 callable（可呼叫物件），會立即回傳任何你傳遞的引數。這意味著 expression （運算式）Derived(some_value) 不會建立一個新的類別或過度引入原有的函式呼叫。

更精確地說，expression some_value is Derived(some_value) 在 runtime 永遠為 true。

這會無法建立一個 Derived 的子型別：

from typing import NewType

UserId = NewType('UserId', int)

# Fails at runtime and does not pass type checking
class AdminUserId(UserId): pass

無論如何，這有辦法基於 '衍生的' NewType 建立一個 NewType：

from typing import NewType

UserId = NewType('UserId', int)

ProUserId = NewType('ProUserId', UserId)

以及針對 ProUserId 的型別檢查會如期運作。

更多細節請見 PEP 484 [https://peps.python.org/pep-0484/]。

備註

請記得使用型別別名是宣告兩種型別是互相相等的。使用 type Alias = Original 則會讓靜態型別檢查器在任何情況之下將 Alias 視為與 Original 完全相等。這當你想把複雜的型別簽名進行簡化時，非常好用。

相反的，NewType 宣告一個型別會是另外一種型別的子類別。使用 Derived = NewType('Derived', Original) 會使靜態型別檢查器將 Derived 視為 Original 的子類別，也意味著一個型別為 Original 的值，不能被使用在任何預期接收到型別 Derived 的值的區域。這當你想用最小的 runtime 成本預防邏輯性錯誤而言，非常有用。

在 3.5.2 版被加入.

在 3.10 版的變更: 現在的 NewType 比起一個函式更像一個類別。因此，比起一般的函式，呼叫 NewType 需要額外的 runtime 成本。

在 3.11 版的變更: 呼叫 NewType 的效能已經恢復與 Python 3.9 相同的水準。

註釋 callable 物件

函式，或者是其他 callable 物件，可以使用 collections.abc.Callable 或以棄用的 typing.Callable 進行註釋。 Callable[[int], str] 象徵為一個函式，可以接受一個型別為 int 的引數，並回傳一個 str。

舉例來說：

from collections.abc import Callable, Awaitable

def feeder(get_next_item: Callable[[], str]) -> None:
    ...  # 主體

def async_query(on_success: Callable[[int], None],
                on_error: Callable[[int, Exception], None]) -> None:
    ...  # 主體

async def on_update(value: str) -> None:
    ...  # 主體

callback: Callable[[str], Awaitable[None]] = on_update

使用下標語法 (subscription syntax) 時，必須使用到兩個值，分別為引述串列以及回傳類別。引數串列必須為一個型別串列：ParamSpec、Concatenate 或是一個刪節號 (ellipsis, ...)。回傳類別必為一個單一類別。

若刪節號字面值 ... 被當作引數串列給定，其指出一個具任何、任意參數列表的 callable 會被接受：

def concat(x: str, y: str) -> str:
    return x + y

x: Callable[..., str]
x = str     # OK
x = concat  # 也 OK

Callable 不如有可變數量引數的函式、overloaded functions、或是僅限關鍵字參數的函式，可以表示複雜簽名。然而，這些簽名可以透過定義一個具有 __call__() 方法的 Protocol 類別進行表示：

from collections.abc import Iterable
from typing import Protocol

class Combiner(Protocol):
    def __call__(self, *vals: bytes, maxlen: int | None = None) -> list[bytes]: ...

def batch_proc(data: Iterable[bytes], cb_results: Combiner) -> bytes:
    for item in data:
        ...

def good_cb(*vals: bytes, maxlen: int | None = None) -> list[bytes]:
    ...
def bad_cb(*vals: bytes, maxitems: int | None) -> list[bytes]:
    ...

batch_proc([], good_cb)  # OK
batch_proc([], bad_cb)   # Error! Argument 2 has incompatible type because of
                         # different name and kind in the callback

Callable 物件可以取用其他 callable 當作引數使用，可以透過 ParamSpec 指出他們的參數型別是個別獨立的。另外，如果這個 callable 從其他 callable 新增或刪除引數時，將會使用到 Concatenate 運算子。他們可以分別採用 Callable[ParamSpecVariable, ReturnType] 以及 Callable[Concatenate[Arg1Type, Arg2Type, ..., ParamSpecVariable], ReturnType] 的形式。

在 3.10 版的變更: Callable 現已支援 ParamSpec 以及 Concatenate。請參閱 PEP 612 [https://peps.python.org/pep-0612/] 閱讀詳細內容。

也參考

ParamSpec 以及 Concatenate 的文件中，提供範例如何在 Callable 中使用。

泛型

因為關於物件的型別資訊留存在容器之內，且無法使用通用的方式進行靜態推論 (statically inferred)，許多標準函式庫的容器類別支援以下標來表示容器內預期的元素。

from collections.abc import Mapping, Sequence

class Employee: ...

# Sequence[Employee] indicates that all elements in the sequence
# must be instances of "Employee".
# Mapping[str, str] indicates that all keys and all values in the mapping
# must be strings.
def notify_by_email(employees: Sequence[Employee],
                    overrides: Mapping[str, str]) -> None: ...

泛型函式及類別可以使用型別參數語法 (type parameter syntax) 進行參數化 (parameterize) ：

from collections.abc import Sequence

def first[T](l: Sequence[T]) -> T:  # Function is generic over the TypeVar "T"
    return l[0]

或是直接使用 TypeVar 工廠 (factory)：

from collections.abc import Sequence
from typing import TypeVar

U = TypeVar('U')                  # Declare type variable "U"

def second(l: Sequence[U]) -> U:  # Function is generic over the TypeVar "U"
    return l[1]

在 3.12 版的變更: 在 Python 3.12 中，泛型的語法支援是全新功能。

註釋元組 (tuple)

在 Python 大多數的容器當中，加註型別系統認為容器內的所有元素會是相同型別。舉例來說：

from collections.abc import Mapping

# Type checker will infer that all elements in ``x`` are meant to be ints
x: list[int] = []

# Type checker error: ``list`` only accepts a single type argument:
y: list[int, str] = [1, 'foo']

# Type checker will infer that all keys in ``z`` are meant to be strings,
# and that all values in ``z`` are meant to be either strings or ints
z: Mapping[str, str | int] = {}

list 只接受一個型別引數，所以型別檢查器可能在上述 y 賦值 (assignment) 觸發錯誤。類似的範例，Mapping 只接受兩個型別引數：第一個引數指出 keys（鍵）的型別；第二個引數指出 values（值）的型別。

然而，與其他多數的 Python 容器不同，在慣用的 (idiomatic) Python 程式碼中，元組可以擁有不完全相同型別的元素是相當常見的。為此，元組在 Python 的加註型別系統中是個特例 (special-cased)。tuple 接受任何數量的型別引數：

# OK: ``x`` is assigned to a tuple of length 1 where the sole element is an int
x: tuple[int] = (5,)

# OK: ``y`` is assigned to a tuple of length 2;
# element 1 is an int, element 2 is a str
y: tuple[int, str] = (5, "foo")

# Error: the type annotation indicates a tuple of length 1,
# but ``z`` has been assigned to a tuple of length 3
z: tuple[int] = (1, 2, 3)

為了標示一個元組可以為任意長度，且所有元素皆是相同型別 T，請使用 刪節號字面值 (literal ellipsis) ...：tuple[T, ...]。為了標示一個空元組，請使用 tuple[()]。單純使用 tuple 作為註釋會與使用 tuple[Any, ...] 相等：

x: tuple[int, ...] = (1, 2)
# These reassignments are OK: ``tuple[int, ...]`` indicates x can be of any length
x = (1, 2, 3)
x = ()
# This reassignment is an error: all elements in ``x`` must be ints
x = ("foo", "bar")

# ``y`` can only ever be assigned to an empty tuple
y: tuple[()] = ()

z: tuple = ("foo", "bar")
# These reassignments are OK: plain ``tuple`` is equivalent to ``tuple[Any, ...]``
z = (1, 2, 3)
z = ()

類別物件的型別

一個變數被註釋為 C 可以接受一個型別為 C 的值。相對的，一個變數備註解為 type[C] （或已棄用的 typing.Type[C]）可以接受本身為該類別的值 -- 具體來說，他可能會接受 C 的類別物件。舉例來說：

a = 3         # Has type ``int``
b = int       # Has type ``type[int]``
c = type(a)   # Also has type ``type[int]``

請記得 type[C] 是共變 (covariant) 的：

class User: ...
class ProUser(User): ...
class TeamUser(User): ...

def make_new_user(user_class: type[User]) -> User:
    # ...
    return user_class()

make_new_user(User)      # OK
make_new_user(ProUser)   # Also OK: ``type[ProUser]`` is a subtype of ``type[User]``
make_new_user(TeamUser)  # Still fine
make_new_user(User())    # Error: expected ``type[User]`` but got ``User``
make_new_user(int)       # Error: ``type[int]`` is not a subtype of ``type[User]``

type 僅有的合法參數是類別、Any、型別變數以及這些型別任意組合成的聯集。舉例來說：

def new_non_team_user(user_class: type[BasicUser | ProUser]): ...

new_non_team_user(BasicUser)  # OK
new_non_team_user(ProUser)    # OK
new_non_team_user(TeamUser)   # Error: ``type[TeamUser]`` is not a subtype
                              # of ``type[BasicUser | ProUser]``
new_non_team_user(User)       # Also an error

type[Any] 等價於 type ，其為 Python metaclass 階層結構 (hierachy)。

Annotating generators and coroutines

A generator can be annotated using the generic type Generator[YieldType, SendType, ReturnType]. For example:

def echo_round() -> Generator[int, float, str]:
    sent = yield 0
    while sent >= 0:
        sent = yield round(sent)
    return 'Done'

Note that unlike many other generic classes in the standard library, the SendType of Generator behaves contravariantly, not covariantly or invariantly.

The SendType and ReturnType parameters default to None:

def infinite_stream(start: int) -> Generator[int]:
    while True:
        yield start
        start += 1

It is also possible to set these types explicitly:

def infinite_stream(start: int) -> Generator[int, None, None]:
    while True:
        yield start
        start += 1

Simple generators that only ever yield values can also be annotated as having a return type of either Iterable[YieldType] or Iterator[YieldType]:

def infinite_stream(start: int) -> Iterator[int]:
    while True:
        yield start
        start += 1

Async generators are handled in a similar fashion, but don't expect a ReturnType type argument (AsyncGenerator[YieldType, SendType]). The SendType argument defaults to None, so the following definitions are equivalent:

async def infinite_stream(start: int) -> AsyncGenerator[int]:
    while True:
        yield start
        start = await increment(start)

async def infinite_stream(start: int) -> AsyncGenerator[int, None]:
    while True:
        yield start
        start = await increment(start)

As in the synchronous case, AsyncIterable[YieldType] and AsyncIterator[YieldType] are available as well:

async def infinite_stream(start: int) -> AsyncIterator[int]:
    while True:
        yield start
        start = await increment(start)

Coroutines can be annotated using Coroutine[YieldType, SendType, ReturnType]. Generic arguments correspond to those of Generator, for example:

from collections.abc import Coroutine
c: Coroutine[list[str], str, int]  # Some coroutine defined elsewhere
x = c.send('hi')                   # Inferred type of 'x' is list[str]
async def bar() -> None:
    y = await c                    # Inferred type of 'y' is int

使用者定義泛型型別

一個使用者定義的類別可以被定義成一個泛型類別。

from logging import Logger

class LoggedVar[T]:
    def __init__(self, value: T, name: str, logger: Logger) -> None:
        self.name = name
        self.logger = logger
        self.value = value

    def set(self, new: T) -> None:
        self.log('Set ' + repr(self.value))
        self.value = new

    def get(self) -> T:
        self.log('Get ' + repr(self.value))
        return self.value

    def log(self, message: str) -> None:
        self.logger.info('%s: %s', self.name, message)

這個語法指出類別 LoggedVar 透過一個單一的 型別變數 T 進行參數化 (parameterised)。這使得 T 在類別中有效的成為型別。

泛型類別隱性繼承了 Generic。為了相容 Python 3.11 及更早版本，也可以明確的繼承 Generic 並指出是一個泛型類別：

from typing import TypeVar, Generic

T = TypeVar('T')

class LoggedVar(Generic[T]):
    ...

泛型類別有 __class_getitem__() 方法，其意味著可以在 runtime 進行參數化（如下述的 LoggedVar[int]）：

from collections.abc import Iterable

def zero_all_vars(vars: Iterable[LoggedVar[int]]) -> None:
    for var in vars:
        var.set(0)

一個泛型型別可以有任意數量的型別變數。所有種類的 TypeVar 都可以作為泛型型別的參數：

from typing import TypeVar, Generic, Sequence

class WeirdTrio[T, B: Sequence[bytes], S: (int, str)]:
    ...

OldT = TypeVar('OldT', contravariant=True)
OldB = TypeVar('OldB', bound=Sequence[bytes], covariant=True)
OldS = TypeVar('OldS', int, str)

class OldWeirdTrio(Generic[OldT, OldB, OldS]):
    ...

Generic 的每個型別變數引數必不相同。因此以下是無效的：

from typing import TypeVar, Generic
...

class Pair[M, M]:  # SyntaxError
    ...

T = TypeVar('T')

class Pair(Generic[T, T]):   # INVALID
    ...

泛型類別亦可以繼承其他類別：

from collections.abc import Sized

class LinkedList[T](Sized):
    ...

當繼承泛型類別時，部份的型別參數可固定：

from collections.abc import Mapping

class MyDict[T](Mapping[str, T]):
    ...

在這種情況下 MyDict 有一個單一的參數 T。

若使用泛型類別卻沒有特指型別參數，則會將每個位置視為 Any。在下列的範例中 MyIterable 不是泛型，但隱性繼承了 Iterable[Any]：

from collections.abc import Iterable

class MyIterable(Iterable): # Same as Iterable[Any]
    ...

使用者定義的泛型型別別名也有支援。例如：

from collections.abc import Iterable

type Response[S] = Iterable[S] | int

# Return type here is same as Iterable[str] | int
def response(query: str) -> Response[str]:
    ...

type Vec[T] = Iterable[tuple[T, T]]

def inproduct[T: (int, float, complex)](v: Vec[T]) -> T: # Same as Iterable[tuple[T, T]]
    return sum(x*y for x, y in v)

為了向後相容性，泛型型別別名可以透過簡單的賦值來建立：

from collections.abc import Iterable
from typing import TypeVar

S = TypeVar("S")
Response = Iterable[S] | int

在 3.7 版的變更: Generic 不再是一個自訂的 metaclass。

在 3.12 版的變更: 在版本 3.12 新增了泛型及型別別名的語法支援。在之前的版本中，泛型類別必須顯性繼承 Generic 或是包含一個型別變數在基底類別 (base) 當中。

使用者定義的參數運算式 (parameter expression) 泛型一樣有支援，透過 [**P] 格式的參數規格變數來進行表示。對於上述作為參數規格變數的型別變數，將持續被 typing 模組視為一個特定的型別變數。對此，其中一個例外是一個型別列表可以替代 ParamSpec：

>>> class Z[T, **P]: ...  # T 為 TypeVar；P 為 ParamSpec
...
>>> Z[int, [dict, float]]
__main__.Z[int, [dict, float]]

具有 ParamSpec 的泛型類別可以透過顯性繼承 Generic 進行建立。在這種情況下，不需要使用 **：

from typing import ParamSpec, Generic

P = ParamSpec('P')

class Z(Generic[P]):
    ...

另外一個 TypeVar 以及 ParamSpec 之間的差異是，基於美觀因素，只有一個參數規格變數的泛型可以接受如 X[[Type1, Type2, ...]] 以及 X[Type1, Type2, ...] 的參數列表。在內部中，後者會被轉換為前者，所以在下方的範例中為相等的：

>>> class X[**P]: ...
...
>>> X[int, str]
__main__.X[[int, str]]
>>> X[[int, str]]
__main__.X[[int, str]]

請記得，具有 ParamSpec 的泛型在某些情況下替換之後可能不會有正確的 __parameters__，因為參數規格主要還是用於靜態型別檢查。

在 3.10 版的變更: Generic 現在可以透過參數運算式來進行參數化。詳細內容請見 ParamSpec 以及 PEP 612 [https://peps.python.org/pep-0612/]。

一個使用者定義的泛型類別可以將 ABC 作為他們的基底類別，且不會有 metaclass 衝突。泛型的 metaclass 則不支援。參數化泛型的輸出將被存為快取，而在 typing 模組中多數的型別皆為 hashable 且可以比較相等性。

Any 型別

Any 是一種特別的型別。一個靜態型別檢查器會將每個型別視為可相容於 Any 且 Any 也可以相容於每個型別。

這意味著如果在一個為 Any 的值上執行任何操作或呼叫方法是可行的，且可以賦值給任意變數：

from typing import Any

a: Any = None
a = []          # OK
a = 2           # OK

s: str = ''
s = a           # OK

def foo(item: Any) -> int:
    # Passes type checking; 'item' could be any type,
    # and that type might have a 'bar' method
    item.bar()
    ...

請注意，當賦予型別為 Any 的值更精確的型別時，將不會執行任何型別檢查。舉例來說，靜態型別檢查器不會在 runtime 中，將 a 賦值給 s 的情況下回報錯誤，儘管 s 是被宣告為型別 str 卻接收到 int 的值！

另外，所有缺少回傳型別或參數型別的函式將會隱性預設為 Any：

def legacy_parser(text):
    ...
    return data

# A static type checker will treat the above
# as having the same signature as:
def legacy_parser(text: Any) -> Any:
    ...
    return data

當你需要混和動態及靜態的型別程式碼，這個行為允許 Any 被當作一個緊急出口 (escape hatch)使用。

Any 的行為對比 object 的行為。與 Any 相似，所有的型別會作為 object 的子型別。然而，不像 Any，反之不亦然：object 並不是一個其他型別的子型別。

這意味著當一個值的型別為 object 時，型別檢查器會拒絕幾乎所有的操作，並將賦予這個值到一個特定型別變數（或是當作回傳值使用）視為一個型別錯誤。舉例來說：

def hash_a(item: object) -> int:
    # Fails type checking; an object does not have a 'magic' method.
    item.magic()
    ...

def hash_b(item: Any) -> int:
    # Passes type checking
    item.magic()
    ...

# Passes type checking, since ints and strs are subclasses of object
hash_a(42)
hash_a("foo")

# Passes type checking, since Any is compatible with all types
hash_b(42)
hash_b("foo")

使用 object ，將指出在型別安全 (typesafe) 的習慣之下一個值可以為任意型別。使用 Any，將指出這個值是個動態型別。

標稱 (nominal) 子型別 vs 結構子型別

最初 PEP 484 [https://peps.python.org/pep-0484/] 定義 Python 靜態型別系統使用標稱子型別。這意味著只有 A 為 B 的子類別時，A 才被允許使用在預期是類別 B 出現的地方。

這個需求之前也被運用在抽象基底類別，例如 Iterable。這種方式的問題在於，一個類別需要顯式的標記來支援他們，這並不符合 Python 風格，也不像一個常見的慣用動態型別 Python 程式碼。舉例來說，下列程式碼符合 PEP 484 [https://peps.python.org/pep-0484/]：

from collections.abc import Sized, Iterable, Iterator

class Bucket(Sized, Iterable[int]):
    ...
    def __len__(self) -> int: ...
    def __iter__(self) -> Iterator[int]: ...

PEP 544 [https://peps.python.org/pep-0544/] 可以透過使用上方的程式碼，且在類別定義時不用顯式基底類別解決這個問題，讓 Bucket 被靜態型別檢查器隱性認為是 Sized 以及 Iterable[int] 兩者的子型別。這就是眾所周知的結構子型別（或是靜態鴨子型別）：

from collections.abc import Iterator, Iterable

class Bucket:  # 注意：沒有基底類別
    ...
    def __len__(self) -> int: ...
    def __iter__(self) -> Iterator[int]: ...

def collect(items: Iterable[int]) -> int: ...
result = collect(Bucket())  # Passes type check

而且，基於一個特別的型別 Protocol 建立子型別時，使用者可以定義新的協定並充份發揮結構子型別的優勢（請見下方範例）。

模組內容

模組 typing 定義了下列的類別、函式以及裝飾器。

特別型別原語 (primitive)

特別型別

這些可以在註釋中做為型別。他們並不支援 [] 的下標使用。

typing.Any

特別型別，指出一個不受約束 (unconstrained) 的型別。

所有型別皆與 Any 相容。

Any 相容於所有型別。

在 3.11 版的變更: Any 可以作為一個基礎類別。這對於在任何地方使用鴨子型別或是高度動態的型別，避免型別檢查器的錯誤是非常有用的。

typing.AnyStr

一個不受約束的型別變數。

定義：

AnyStr = TypeVar('AnyStr', str, bytes)

AnyStr 是對於函式有用的，他可以接受 str 或 bytes 引數但不可以將此兩種混合。

舉例來說：

def concat(a: AnyStr, b: AnyStr) -> AnyStr:
    return a + b

concat("foo", "bar")    # OK, output has type 'str'
concat(b"foo", b"bar")  # OK, output has type 'bytes'
concat("foo", b"bar")   # Error, cannot mix str and bytes

請注意，儘管他的名稱相近，AnyStr 與 Any 型別無關，更不代表是「任何字串」的意思。尤其，AnyStr 與 str | bytes 兩者不同且具有不同的使用情境：

# Invalid use of AnyStr:
# The type variable is used only once in the function signature,
# so cannot be "solved" by the type checker
def greet_bad(cond: bool) -> AnyStr:
    return "hi there!" if cond else b"greetings!"

# The better way of annotating this function:
def greet_proper(cond: bool) -> str | bytes:
    return "hi there!" if cond else b"greetings!"

自從版本 3.13 後不推薦使用，將會自版本 3.18 中移除。: Deprecated in favor of the new type parameter syntax. Use class A[T: (str, bytes)]: ... instead of importing AnyStr. See PEP 695 [https://peps.python.org/pep-0695/] for more details.

In Python 3.16, AnyStr will be removed from typing.__all__, and deprecation warnings will be emitted at runtime when it is accessed or imported from typing. AnyStr will be removed from typing in Python 3.18.

typing.LiteralString

特別型別，只包含文本字串。

任何文本字串都相容於 LiteralString，對於另一個 LiteralString 亦是如此。然而，若是一個型別僅為 str 的物件則不相容。一個字串若是透過組合多個 LiteralString 型別的物件建立，則此字串也可以視為 LiteralString。

舉例來說：

def run_query(sql: LiteralString) -> None:
    ...

def caller(arbitrary_string: str, literal_string: LiteralString) -> None:
    run_query("SELECT * FROM students")  # OK
    run_query(literal_string)  # OK
    run_query("SELECT * FROM " + literal_string)  # OK
    run_query(arbitrary_string)  # 型別檢查錯誤
    run_query(  # 型別檢查錯誤
        f"SELECT * FROM students WHERE name = {arbitrary_string}"
    )

LiteralString 對於敏感的 API 來說是有用的，其中任意的使用者產生的字串可能會產生問題。舉例來說，上面兩個案例中產生的型別檢查器錯誤是脆弱的且容易受到 SQL 注入攻擊。

更多細節請見 PEP 675 [https://peps.python.org/pep-0675/]。

在 3.11 版被加入.

typing.Never

typing.NoReturn

Never 和 NoReturn 表示底部型別 (bottom type) [https://en.wikipedia.org/wiki/Bottom_type]，為一個沒有任何成員的型別。

它們可以被用來代表一個不會回傳的函式，像是 sys.exit()：

from typing import Never  # 或 NoReturn

def stop() -> Never:
    raise RuntimeError('no way')

或被用來定義一個不應被呼叫的函式，因為不會有有效的引數，、像是 assert_never()：

from typing import Never  # or NoReturn

def never_call_me(arg: Never) -> None:
    pass

def int_or_str(arg: int | str) -> None:
    never_call_me(arg)  # type checker error
    match arg:
        case int():
            print("It's an int")
        case str():
            print("It's a str")
        case _:
            never_call_me(arg)  # OK, arg is of type Never (or NoReturn)

Never 以及 NoReturn 在型別系統中具有相同的意義且靜態型別檢查器會將兩者視為相等。

在 3.6.2 版被加入: 新增 NoReturn。

在 3.11 版被加入: 新增 Never。

typing.Self

特別型別，用來表示目前類別之內 (enclosed class)。

舉例來說：

from typing import Self, reveal_type

class Foo:
    def return_self(self) -> Self:
        ...
        return self

class SubclassOfFoo(Foo): pass

reveal_type(Foo().return_self())  # Revealed type is "Foo"
reveal_type(SubclassOfFoo().return_self())  # Revealed type is "SubclassOfFoo"

這個註釋在語意上相等於下列內容，且形式更為簡潔：

from typing import TypeVar

Self = TypeVar("Self", bound="Foo")

class Foo:
    def return_self(self: Self) -> Self:
        ...
        return self

一般來說，如果某個東西回傳 self 如上方的範例所示，你則應該使用 Self 做為回傳值的註釋。若 Foo.return_self 被註釋為回傳 "Foo"，則型別檢查器應該推論這個從 SubclassOfFoo.return_self 回傳的物件為 Foo 型別，而並非回傳 SubclassOfFoo 型別。

其他常見的使用案例包含：

classmethod 被用來作為替代的建構函式 (constructor) 並回傳 cls 參數的實例。

註釋一個回傳自己的 __enter__() 方法。

當類別被子類別化時，若方法不保證回傳一個子類別的實例，你不應該使用 Self 作為回傳註釋：

class Eggs:
    # Self would be an incorrect return annotation here,
    # as the object returned is always an instance of Eggs,
    # even in subclasses
    def returns_eggs(self) -> "Eggs":
        return Eggs()

更多細節請見 PEP 673 [https://peps.python.org/pep-0673/]。

在 3.11 版被加入.

typing.TypeAlias

做為明確宣告一個型別別名 的特別註釋。

舉例來說：

from typing import TypeAlias

Factors: TypeAlias = list[int]

TypeAlias 在舊的 Python 版本中特別有用，其註釋別名可以用來進行傳遞參照 (forward reference)，因為對於型別檢查器來說，分辨這些別名與一般的變數賦值相當困難：

from typing import Generic, TypeAlias, TypeVar

T = TypeVar("T")

# "Box" does not exist yet,
# so we have to use quotes for the forward reference on Python <3.12.
# Using ``TypeAlias`` tells the type checker that this is a type alias declaration,
# not a variable assignment to a string.
BoxOfStrings: TypeAlias = "Box[str]"

class Box(Generic[T]):
    @classmethod
    def make_box_of_strings(cls) -> BoxOfStrings: ...

更多細節請見 PEP 613 [https://peps.python.org/pep-0613/]。

在 3.10 版被加入.

在 3.12 版之後被棄用: TypeAlias 被棄用，請改用 type 陳述式來建立 TypeAliasType 的實例，其自然可以支援傳遞參照的使用。請注意，雖然 TypeAlias 以及 TypeAliasType 提供相似的用途且具有相似的名稱，他們是不同的，且後者不是前者的型別。現在還沒有移除 TypeAlias 的計畫，但鼓勵使用者們遷移 (migrate) 至 type 陳述式。

特別型式

這些在註釋中可以當作型別使用。他們全都支援 [] 的下標使用，但每個都具有獨特的語法。

class typing.Union

聯集型別；Union[X, Y] 與 X | Y 是相等的，且都意味著 X 或 Y 兩者其一。

為了定義聯集，例如可以使用 Union[int, str] 或是使用簡寫 (shorthand) int | str。使用這種簡寫是非常推薦的。詳細請看：

引數必須為型別且必須有至少一個。

聯集中的聯集會是扁平化的 (flattened)，舉例來說：

Union[Union[int, str], float] == Union[int, str, float]

However, this does not apply to unions referenced through a type alias, to avoid forcing evaluation of the underlying TypeAliasType:

type A = Union[int, str]
Union[A, float] != Union[int, str, float]

單一引數的聯集會消失不見，舉例來說：

Union[int] == int  # 實際上建構函式會回傳 int

多餘的引數會被略過，舉例來說：

Union[int, str, int] == Union[int, str] == int | str

當比較聯集時，引數的順序會被忽略，舉例來說：

Union[int, str] == Union[str, int]

你不能建立 Union 的子類別或是實例。

你不能寫成 Union[X][Y]。

在 3.7 版的變更: 請勿在 runtime 中將顯性子類別從聯集中移除。

在 3.10 版的變更: 現在可以將聯集寫成 X | Y。請見聯集型別運算式。

在 3.14 版的變更: types.UnionType is now an alias for Union, and both Union[int, str] and int | str create instances of the same class. To check whether an object is a Union at runtime, use isinstance(obj, Union). For compatibility with earlier versions of Python, use get_origin(obj) is typing.Union or get_origin(obj) is types.UnionType.

typing.Optional

Optional[X] 與 X | None 是相等的（或是 Union[X, None]）。

請注意，這與具有預設值的選擇性引數 (optional argument) 不是相同的概念。一個具有預設值的選擇性引數的型別註釋中不具有 Optional 限定符 (qualifier)，單純的因為它就是選擇性的。舉例來說：

def foo(arg: int = 0) -> None:
    ...

另一方面，如果一個顯性的值 None 是被允許的，不論引數是不是選擇性的，Optional 都適用。舉例來說：

def foo(arg: Optional[int] = None) -> None:
    ...

在 3.10 版的變更: 現在可以將 Optional 寫成 X | None。請見聯集型別運算式。

typing.Concatenate

用於註釋高階函式的特別型式。

Concatenate 可以被用在可呼叫物件與 ParamSpec 的接合 (conjunction) 並註釋一個高階的 Callable 物件可以新增、移除、轉換另一個 Callable 物件的參數。使用方法是依照這個格式 Concatenate[Arg1Type, Arg2Type, ..., ParamSpecVariable]。Concatenate 目前只在 Callable 物件中第一個引數使用時有效。Concatenate 的最後一個參數必須為一個 ParamSpec 或是刪節號 (...)。

舉例來說，註釋一個為裝飾過後的函式提供 threading.Lock 的裝飾器 with_lock，Concatenate 可以用於指出 with_lock 預期一個 Callable 物件，該物件可以接受 Lock 作為第一引數，並回傳一個具有不同型別簽名 Callable 物件。在這種情況下，ParamSpec 指出回傳的 Callable 物件的參數型別會依賴傳遞的 Callable 物件的參數型別：

from collections.abc import Callable
from threading import Lock
from typing import Concatenate

# Use this lock to ensure that only one thread is executing a function
# at any time.
my_lock = Lock()

def with_lock[**P, R](f: Callable[Concatenate[Lock, P], R]) -> Callable[P, R]:
    '''A type-safe decorator which provides a lock.'''
    def inner(*args: P.args, **kwargs: P.kwargs) -> R:
        # Provide the lock as the first argument.
        return f(my_lock, *args, **kwargs)
    return inner

@with_lock
def sum_threadsafe(lock: Lock, numbers: list[float]) -> float:
    '''Add a list of numbers together in a thread-safe manner.'''
    with lock:
        return sum(numbers)

# We don't need to pass in the lock ourselves thanks to the decorator.
sum_threadsafe([1.1, 2.2, 3.3])

在 3.10 版被加入.

也參考

PEP 612 [https://peps.python.org/pep-0612/] -- 參數技術規範變數

ParamSpec

註釋 callable 物件

typing.Literal

特殊型別格式，用於定義「文本型別 (literal type)」。

Literal 可以用於型別檢查器並指出註釋物件具有一個與提供的文本相同的值。

舉例來說：

def validate_simple(data: Any) -> Literal[True]:  # 永遠回傳 True
    ...

type Mode = Literal['r', 'rb', 'w', 'wb']
def open_helper(file: str, mode: Mode) -> str:
    ...

open_helper('/some/path', 'r')      # 通過型別檢查
open_helper('/other/path', 'typo')  # 型別檢查器中的錯誤

Literal[...] 不可以進行子類別化。在 runtime 之中，任意的值是允許作為 Literal[...] 的型別引數，但型別檢查器可能會加強限制。更多有關文本型別的詳細資訊請看 PEP 586 [https://peps.python.org/pep-0586/]。

其他細節：

引數必須為文本值且必須有至少一個。

巢狀的 Literal 會是扁平化的 (flattened)，舉例來說：

assert Literal[Literal[1, 2], 3] == Literal[1, 2, 3]

However, this does not apply to Literal types referenced through a type alias, to avoid forcing evaluation of the underlying TypeAliasType:

type A = Literal[1, 2]
assert Literal[A, 3] != Literal[1, 2, 3]

多餘的引數會被略過，舉例來說：

assert Literal[1, 2, 1] == Literal[1, 2]

當比較文本時，引數的順序會被忽略，舉例來說：

assert Literal[1, 2] == Literal[2, 1]

你不能建立 Literal 的子類別或是實例。

你不能寫成 Literal[X][Y]。

在 3.8 版被加入.

在 3.9.1 版的變更: Literal 現在可以刪除重複 (de-deplicate) 的參數。Literal 物件的相等性比較不再依照相依性排序。Literal 物件現在會在相等性比較期間，若任一個其中的參數無法 hashable 時，則會引發一個 TypeError 例外。

typing.ClassVar

特殊型別建構，用來標記類別變數。

如同在 PEP 526 [https://peps.python.org/pep-0526/] 中的介紹，一個變數註解被包裝在 ClassVar 中時，會指出一個給定的屬性 (attribute) 意圖被當作類別變數使用，且不該被設定成該類別的實例。使用方法如下：

class Starship:
    stats: ClassVar[dict[str, int]] = {} # 類別變數
    damage: int = 10                     # 實例變數

ClassVar 只接受型別請不得使用下標。

ClassVar 並不代表該類別本身，而且不應該和 isinstance() 或是 issubclass() 一起使用。ClassVar 不會改變 Python runtime 的行為，但它可以被第三方的型別檢查器使用。舉例來說，一個型別檢查器可能會標記下方的程式碼為一個錯誤：

enterprise_d = Starship(3000)
enterprise_d.stats = {} # Error, setting class variable on instance
Starship.stats = {}     # This is OK

在 3.5.3 版被加入.

在 3.13 版的變更: ClassVar can now be nested in Final and vice versa.

typing.Final

特殊型別建構，用來指出給型別檢查器的最終名稱。

最終名稱不可以在任何作用域 (scope) 中重新賦值。在類別作用域中宣告的最終名稱，不得在子類別中進行覆寫 (override)。

舉例來說：

MAX_SIZE: Final = 9000
MAX_SIZE += 1  # Error reported by type checker

class Connection:
    TIMEOUT: Final[int] = 10

class FastConnector(Connection):
    TIMEOUT = 1  # Error reported by type checker

這些屬性 (property) 不會在 runtime 時進行檢查。更多詳細資訊請看 PEP 591 [https://peps.python.org/pep-0591/]。

在 3.8 版被加入.

在 3.13 版的變更: Final can now be nested in ClassVar and vice versa.

typing.Required

特殊型別建構，用來標記一個 TypedDict 鍵值是必須的。

主要用於 total=False 的 TypedDict。更多細節請見 TypedDict 與 PEP 655 [https://peps.python.org/pep-0655/]。

在 3.11 版被加入.

typing.NotRequired

特殊型別建構，用來標記一個 TypedDict 鍵值是可能消失的。

更多細節請見 TypedDict 與 PEP 655 [https://peps.python.org/pep-0655/]。

在 3.11 版被加入.

typing.ReadOnly

特殊型別建構，用來標記一個 TypedDict 的項目是唯讀的。

舉例來說：

class Movie(TypedDict):
   title: ReadOnly[str]
   year: int

def mutate_movie(m: Movie) -> None:
   m["year"] = 1999  # allowed
   m["title"] = "The Matrix"  # 型別檢查器錯誤

這些屬性 (property) 不會在 runtime 時進行檢查。

更多細節請見 TypedDict 與 PEP 705 [https://peps.python.org/pep-0705/]。

在 3.13 版被加入.

typing.Annotated

Special typing form to add context-specific metadata to an annotation.

Add metadata x to a given type T by using the annotation Annotated[T, x]. Metadata added using Annotated can be used by static analysis tools or at runtime. At runtime, the metadata is stored in a __metadata__ attribute.

If a library or tool encounters an annotation Annotated[T, x] and has no special logic for the metadata, it should ignore the metadata and simply treat the annotation as T. As such, Annotated can be useful for code that wants to use annotations for purposes outside Python's static typing system.

Using Annotated[T, x] as an annotation still allows for static typechecking of T, as type checkers will simply ignore the metadata x. In this way, Annotated differs from the @no_type_check decorator, which can also be used for adding annotations outside the scope of the typing system, but completely disables typechecking for a function or class.

The responsibility of how to interpret the metadata lies with the tool or library encountering an Annotated annotation. A tool or library encountering an Annotated type can scan through the metadata elements to determine if they are of interest (e.g., using isinstance()).

Annotated[<type>, <metadata>]

Here is an example of how you might use Annotated to add metadata to type annotations if you were doing range analysis:

@dataclass
class ValueRange:
    lo: int
    hi: int

T1 = Annotated[int, ValueRange(-10, 5)]
T2 = Annotated[T1, ValueRange(-20, 3)]

The first argument to Annotated must be a valid type. Multiple metadata elements can be supplied as Annotated supports variadic arguments. The order of the metadata elements is preserved and matters for equality checks:

@dataclass
class ctype:
     kind: str

a1 = Annotated[int, ValueRange(3, 10), ctype("char")]
a2 = Annotated[int, ctype("char"), ValueRange(3, 10)]

assert a1 != a2  # 順序是有意義的

It is up to the tool consuming the annotations to decide whether the client is allowed to add multiple metadata elements to one annotation and how to merge those annotations.

Nested Annotated types are flattened. The order of the metadata elements starts with the innermost annotation:

assert Annotated[Annotated[int, ValueRange(3, 10)], ctype("char")] == Annotated[
    int, ValueRange(3, 10), ctype("char")
]

However, this does not apply to Annotated types referenced through a type alias, to avoid forcing evaluation of the underlying TypeAliasType:

type From3To10[T] = Annotated[T, ValueRange(3, 10)]
assert Annotated[From3To10[int], ctype("char")] != Annotated[
   int, ValueRange(3, 10), ctype("char")
]

Duplicated metadata elements are not removed:

assert Annotated[int, ValueRange(3, 10)] != Annotated[
    int, ValueRange(3, 10), ValueRange(3, 10)
]

Annotated can be used with nested and generic aliases:

@dataclass
class MaxLen:
    value: int

type Vec[T] = Annotated[list[tuple[T, T]], MaxLen(10)]

# When used in a type annotation, a type checker will treat "V" the same as
# ``Annotated[list[tuple[int, int]], MaxLen(10)]``:
type V = Vec[int]

Annotated cannot be used with an unpacked TypeVarTuple:

type Variadic[*Ts] = Annotated[*Ts, Ann1] = Annotated[T1, T2, T3, ..., Ann1]  # 無效

where T1, T2, ... are TypeVars. This is invalid as only one type should be passed to Annotated.

By default, get_type_hints() strips the metadata from annotations. Pass include_extras=True to have the metadata preserved:

>>> from typing import Annotated, get_type_hints
>>> def func(x: Annotated[int, "metadata"]) -> None: pass
...
>>> get_type_hints(func)
{'x': <class 'int'>, 'return': <class 'NoneType'>}
>>> get_type_hints(func, include_extras=True)
{'x': typing.Annotated[int, 'metadata'], 'return': <class 'NoneType'>}

At runtime, the metadata associated with an Annotated type can be retrieved via the __metadata__ attribute:

>>> from typing import Annotated
>>> X = Annotated[int, "very", "important", "metadata"]
>>> X
typing.Annotated[int, 'very', 'important', 'metadata']
>>> X.__metadata__
('very', 'important', 'metadata')

If you want to retrieve the original type wrapped by Annotated, use the __origin__ attribute:

>>> from typing import Annotated, get_origin
>>> Password = Annotated[str, "secret"]
>>> Password.__origin__
<class 'str'>

Note that using get_origin() will return Annotated itself:

>>> get_origin(Password)
typing.Annotated

也參考

PEP 593 [https://peps.python.org/pep-0593/] - Flexible function and variable annotations

The PEP introducing Annotated to the standard library.

在 3.9 版被加入.

typing.TypeIs

Special typing construct for marking user-defined type predicate functions.

TypeIs can be used to annotate the return type of a user-defined type predicate function. TypeIs only accepts a single type argument. At runtime, functions marked this way should return a boolean and take at least one positional argument.

TypeIs aims to benefit type narrowing -- a technique used by static type checkers to determine a more precise type of an expression within a program's code flow. Usually type narrowing is done by analyzing conditional code flow and applying the narrowing to a block of code. The conditional expression here is sometimes referred to as a "type predicate":

def is_str(val: str | float):
    # "isinstance" type predicate
    if isinstance(val, str):
        # Type of ``val`` is narrowed to ``str``
        ...
    else:
        # Else, type of ``val`` is narrowed to ``float``.
        ...

Sometimes it would be convenient to use a user-defined boolean function as a type predicate. Such a function should use TypeIs[...] or TypeGuard as its return type to alert static type checkers to this intention. TypeIs usually has more intuitive behavior than TypeGuard, but it cannot be used when the input and output types are incompatible (e.g., list[object] to list[int]) or when the function does not return True for all instances of the narrowed type.

Using -> TypeIs[NarrowedType] tells the static type checker that for a given function:

回傳值是一個布林值。

If the return value is True, the type of its argument is the intersection of the argument's original type and NarrowedType.

If the return value is False, the type of its argument is narrowed to exclude NarrowedType.

舉例來說：

from typing import assert_type, final, TypeIs

class Parent: pass
class Child(Parent): pass
@final
class Unrelated: pass

def is_parent(val: object) -> TypeIs[Parent]:
    return isinstance(val, Parent)

def run(arg: Child | Unrelated):
    if is_parent(arg):
        # Type of ``arg`` is narrowed to the intersection
        # of ``Parent`` and ``Child``, which is equivalent to
        # ``Child``.
        assert_type(arg, Child)
    else:
        # Type of ``arg`` is narrowed to exclude ``Parent``,
        # so only ``Unrelated`` is left.
        assert_type(arg, Unrelated)

The type inside TypeIs must be consistent with the type of the function's argument; if it is not, static type checkers will raise an error. An incorrectly written TypeIs function can lead to unsound behavior in the type system; it is the user's responsibility to write such functions in a type-safe manner.

If a TypeIs function is a class or instance method, then the type in TypeIs maps to the type of the second parameter (after cls or self).

In short, the form def foo(arg: TypeA) -> TypeIs[TypeB]: ..., means that if foo(arg) returns True, then arg is an instance of TypeB, and if it returns False, it is not an instance of TypeB.

TypeIs also works with type variables. For more information, see PEP 742 [https://peps.python.org/pep-0742/] (Narrowing types with TypeIs).

在 3.13 版被加入.

typing.TypeGuard

Special typing construct for marking user-defined type predicate functions.

Type predicate functions are user-defined functions that return whether their argument is an instance of a particular type. TypeGuard works similarly to TypeIs, but has subtly different effects on type checking behavior (see below).

Using -> TypeGuard tells the static type checker that for a given function:

回傳值是一個布林值。

If the return value is True, the type of its argument is the type inside TypeGuard.

TypeGuard also works with type variables. See PEP 647 [https://peps.python.org/pep-0647/] for more details.

舉例來說：

def is_str_list(val: list[object]) -> TypeGuard[list[str]]:
    '''Determines whether all objects in the list are strings'''
    return all(isinstance(x, str) for x in val)

def func1(val: list[object]):
    if is_str_list(val):
        # Type of ``val`` is narrowed to ``list[str]``.
        print(" ".join(val))
    else:
        # Type of ``val`` remains as ``list[object]``.
        print("Not a list of strings!")

TypeIs 和 TypeGuard 在以下幾個方面有所不同：

TypeIs requires the narrowed type to be a subtype of the input type, while TypeGuard does not. The main reason is to allow for things like narrowing list[object] to list[str] even though the latter is not a subtype of the former, since list is invariant.

When a TypeGuard function returns True, type checkers narrow the type of the variable to exactly the TypeGuard type. When a TypeIs function returns True, type checkers can infer a more precise type combining the previously known type of the variable with the TypeIs type. (Technically, this is known as an intersection type.)

When a TypeGuard function returns False, type checkers cannot narrow the type of the variable at all. When a TypeIs function returns False, type checkers can narrow the type of the variable to exclude the TypeIs type.

在 3.10 版被加入.

typing.Unpack

Typing operator to conceptually mark an object as having been unpacked.

For example, using the unpack operator * on a type variable tuple is equivalent to using Unpack to mark the type variable tuple as having been unpacked:

Ts = TypeVarTuple('Ts')
tup: tuple[*Ts]
# Effectively does:
tup: tuple[Unpack[Ts]]

In fact, Unpack can be used interchangeably with * in the context of typing.TypeVarTuple and builtins.tuple types. You might see Unpack being used explicitly in older versions of Python, where * couldn't be used in certain places:

# In older versions of Python, TypeVarTuple and Unpack
# are located in the `typing_extensions` backports package.
from typing_extensions import TypeVarTuple, Unpack

Ts = TypeVarTuple('Ts')
tup: tuple[*Ts]         # Syntax error on Python <= 3.10!
tup: tuple[Unpack[Ts]]  # Semantically equivalent, and backwards-compatible

Unpack can also be used along with typing.TypedDict for typing **kwargs in a function signature:

from typing import TypedDict, Unpack

class Movie(TypedDict):
    name: str
    year: int

# This function expects two keyword arguments - `name` of type `str`
# and `year` of type `int`.
def foo(**kwargs: Unpack[Movie]): ...

See PEP 692 [https://peps.python.org/pep-0692/] for more details on using Unpack for **kwargs typing.

在 3.11 版被加入.

Building generic types and type aliases

The following classes should not be used directly as annotations. Their intended purpose is to be building blocks for creating generic types and type aliases.

These objects can be created through special syntax (type parameter lists and the type statement). For compatibility with Python 3.11 and earlier, they can also be created without the dedicated syntax, as documented below.

class typing.Generic

Abstract base class for generic types.

A generic type is typically declared by adding a list of type parameters after the class name:

class Mapping[KT, VT]:
    def __getitem__(self, key: KT) -> VT:
        ...
        # Etc.

Such a class implicitly inherits from Generic. The runtime semantics of this syntax are discussed in the Language Reference.

This class can then be used as follows:

def lookup_name[X, Y](mapping: Mapping[X, Y], key: X, default: Y) -> Y:
    try:
        return mapping[key]
    except KeyError:
        return default

Here the brackets after the function name indicate a generic function.

For backwards compatibility, generic classes can also be declared by explicitly inheriting from Generic. In this case, the type parameters must be declared separately:

KT = TypeVar('KT')
VT = TypeVar('VT')

class Mapping(Generic[KT, VT]):
    def __getitem__(self, key: KT) -> VT:
        ...
        # Etc.

class typing.TypeVar(name, *constraints, bound=None, covariant=False, contravariant=False, infer_variance=False, default=typing.NoDefault)

Type variable.

The preferred way to construct a type variable is via the dedicated syntax for generic functions, generic classes, and generic type aliases:

class Sequence[T]:  # T 是一個 TypeVar
    ...

This syntax can also be used to create bounded and constrained type variables:

class StrSequence[S: str]:  # S is a TypeVar with a `str` upper bound;
    ...                     # we can say that S is "bounded by `str`"

class StrOrBytesSequence[A: (str, bytes)]:  # A is a TypeVar constrained to str or bytes
    ...

However, if desired, reusable type variables can also be constructed manually, like so:

T = TypeVar('T')  # 可以是任何東西
S = TypeVar('S', bound=str)  # 可以是任何 str 的子型別
A = TypeVar('A', str, bytes)  # 必須是 str 或 bytes

Type variables exist primarily for the benefit of static type checkers. They serve as the parameters for generic types as well as for generic function and type alias definitions. See Generic for more information on generic types. Generic functions work as follows:

def repeat[T](x: T, n: int) -> Sequence[T]:
    """Return a list containing n references to x."""
    return [x]*n

def print_capitalized[S: str](x: S) -> S:
    """Print x capitalized, and return x."""
    print(x.capitalize())
    return x

def concatenate[A: (str, bytes)](x: A, y: A) -> A:
    """Add two strings or bytes objects together."""
    return x + y

Note that type variables can be bounded, constrained, or neither, but cannot be both bounded and constrained.

The variance of type variables is inferred by type checkers when they are created through the type parameter syntax or when infer_variance=True is passed. Manually created type variables may be explicitly marked covariant or contravariant by passing covariant=True or contravariant=True. By default, manually created type variables are invariant. See PEP 484 [https://peps.python.org/pep-0484/] and PEP 695 [https://peps.python.org/pep-0695/] for more details.

Bounded type variables and constrained type variables have different semantics in several important ways. Using a bounded type variable means that the TypeVar will be solved using the most specific type possible:

x = print_capitalized('a string')
reveal_type(x)  # revealed type is str

class StringSubclass(str):
    pass

y = print_capitalized(StringSubclass('another string'))
reveal_type(y)  # revealed type is StringSubclass

z = print_capitalized(45)  # error: int is not a subtype of str

The upper bound of a type variable can be a concrete type, abstract type (ABC or Protocol), or even a union of types:

# Can be anything with an __abs__ method
def print_abs[T: SupportsAbs](arg: T) -> None:
    print("Absolute value:", abs(arg))

U = TypeVar('U', bound=str|bytes)  # Can be any subtype of the union str|bytes
V = TypeVar('V', bound=SupportsAbs)  # Can be anything with an __abs__ method

Using a constrained type variable, however, means that the TypeVar can only ever be solved as being exactly one of the constraints given:

a = concatenate('one', 'two')
reveal_type(a)  # revealed type is str

b = concatenate(StringSubclass('one'), StringSubclass('two'))
reveal_type(b)  # revealed type is str, despite StringSubclass being passed in

c = concatenate('one', b'two')  # error: type variable 'A' can be either str or bytes in a function call, but not both

在 runtime isinstance(x, T) 會引發 TypeError。

__name__

The name of the type variable.

__covariant__

Whether the type var has been explicitly marked as covariant.

__contravariant__

Whether the type var has been explicitly marked as contravariant.

__infer_variance__

Whether the type variable's variance should be inferred by type checkers.

在 3.12 版被加入.

__bound__

The upper bound of the type variable, if any.

在 3.12 版的變更: For type variables created through type parameter syntax, the bound is evaluated only when the attribute is accessed, not when the type variable is created (see Lazy evaluation).

evaluate_bound()

An evaluate function corresponding to the __bound__ attribute. When called directly, this method supports only the VALUE format, which is equivalent to accessing the __bound__ attribute directly, but the method object can be passed to annotationlib.call_evaluate_function() to evaluate the value in a different format.

在 3.14 版被加入.

__constraints__

A tuple containing the constraints of the type variable, if any.

在 3.12 版的變更: For type variables created through type parameter syntax, the constraints are evaluated only when the attribute is accessed, not when the type variable is created (see Lazy evaluation).

evaluate_constraints()

An evaluate function corresponding to the __constraints__ attribute. When called directly, this method supports only the VALUE format, which is equivalent to accessing the __constraints__ attribute directly, but the method object can be passed to annotationlib.call_evaluate_function() to evaluate the value in a different format.

在 3.14 版被加入.

__default__

The default value of the type variable, or typing.NoDefault if it has no default.

在 3.13 版被加入.

evaluate_default()

An evaluate function corresponding to the __default__ attribute. When called directly, this method supports only the VALUE format, which is equivalent to accessing the __default__ attribute directly, but the method object can be passed to annotationlib.call_evaluate_function() to evaluate the value in a different format.

在 3.14 版被加入.

has_default()

Return whether or not the type variable has a default value. This is equivalent to checking whether __default__ is not the typing.NoDefault singleton, except that it does not force evaluation of the lazily evaluated default value.

在 3.13 版被加入.

在 3.12 版的變更: Type variables can now be declared using the type parameter syntax introduced by PEP 695 [https://peps.python.org/pep-0695/]. The infer_variance parameter was added.

在 3.13 版的變更: 新增對預設值的支援。

class typing.TypeVarTuple(name, *, default=typing.NoDefault)

Type variable tuple. A specialized form of type variable that enables variadic generics.

Type variable tuples can be declared in type parameter lists using a single asterisk (*) before the name:

def move_first_element_to_last[T, *Ts](tup: tuple[T, *Ts]) -> tuple[*Ts, T]:
    return (*tup[1:], tup[0])

Or by explicitly invoking the TypeVarTuple constructor:

T = TypeVar("T")
Ts = TypeVarTuple("Ts")

def move_first_element_to_last(tup: tuple[T, *Ts]) -> tuple[*Ts, T]:
    return (*tup[1:], tup[0])

A normal type variable enables parameterization with a single type. A type variable tuple, in contrast, allows parameterization with an arbitrary number of types by acting like an arbitrary number of type variables wrapped in a tuple. For example:

# T is bound to int, Ts is bound to ()
# Return value is (1,), which has type tuple[int]
move_first_element_to_last(tup=(1,))

# T is bound to int, Ts is bound to (str,)
# Return value is ('spam', 1), which has type tuple[str, int]
move_first_element_to_last(tup=(1, 'spam'))

# T is bound to int, Ts is bound to (str, float)
# Return value is ('spam', 3.0, 1), which has type tuple[str, float, int]
move_first_element_to_last(tup=(1, 'spam', 3.0))

# This fails to type check (and fails at runtime)
# because tuple[()] is not compatible with tuple[T, *Ts]
# (at least one element is required)
move_first_element_to_last(tup=())

Note the use of the unpacking operator * in tuple[T, *Ts]. Conceptually, you can think of Ts as a tuple of type variables (T1, T2, ...). tuple[T, *Ts] would then become tuple[T, *(T1, T2, ...)], which is equivalent to tuple[T, T1, T2, ...]. (Note that in older versions of Python, you might see this written using Unpack instead, as Unpack[Ts].)

Type variable tuples must always be unpacked. This helps distinguish type variable tuples from normal type variables:

x: Ts          # 無效
x: tuple[Ts]   # 無效
x: tuple[*Ts]  # 正確的做法

Type variable tuples can be used in the same contexts as normal type variables. For example, in class definitions, arguments, and return types:

class Array[*Shape]:
    def __getitem__(self, key: tuple[*Shape]) -> float: ...
    def __abs__(self) -> "Array[*Shape]": ...
    def get_shape(self) -> tuple[*Shape]: ...

Type variable tuples can be happily combined with normal type variables:

class Array[DType, *Shape]:  # This is fine
    pass

class Array2[*Shape, DType]:  # This would also be fine
    pass

class Height: ...
class Width: ...

float_array_1d: Array[float, Height] = Array()     # Totally fine
int_array_2d: Array[int, Height, Width] = Array()  # Yup, fine too

However, note that at most one type variable tuple may appear in a single list of type arguments or type parameters:

x: tuple[*Ts, *Ts]            # 無效
class Array[*Shape, *Shape]:  # 無效
    pass

Finally, an unpacked type variable tuple can be used as the type annotation of *args:

def call_soon[*Ts](
    callback: Callable[[*Ts], None],
    *args: *Ts
) -> None:
    ...
    callback(*args)

In contrast to non-unpacked annotations of *args - e.g. *args: int, which would specify that all arguments are int - *args: *Ts enables reference to the types of the individual arguments in *args. Here, this allows us to ensure the types of the *args passed to call_soon match the types of the (positional) arguments of callback.

See PEP 646 [https://peps.python.org/pep-0646/] for more details on type variable tuples.

__name__

The name of the type variable tuple.

__default__

The default value of the type variable tuple, or typing.NoDefault if it has no default.

在 3.13 版被加入.

evaluate_default()

An evaluate function corresponding to the __default__ attribute. When called directly, this method supports only the VALUE format, which is equivalent to accessing the __default__ attribute directly, but the method object can be passed to annotationlib.call_evaluate_function() to evaluate the value in a different format.

在 3.14 版被加入.

has_default()

Return whether or not the type variable tuple has a default value. This is equivalent to checking whether __default__ is not the typing.NoDefault singleton, except that it does not force evaluation of the lazily evaluated default value.

在 3.13 版被加入.

在 3.11 版被加入.

在 3.12 版的變更: Type variable tuples can now be declared using the type parameter syntax introduced by PEP 695 [https://peps.python.org/pep-0695/].

在 3.13 版的變更: 新增對預設值的支援。

class typing.ParamSpec(name, *, bound=None, covariant=False, contravariant=False, default=typing.NoDefault)

Parameter specification variable. A specialized version of type variables.

In type parameter lists, parameter specifications can be declared with two asterisks (**):

type IntFunc[**P] = Callable[P, int]

For compatibility with Python 3.11 and earlier, ParamSpec objects can also be created as follows:

P = ParamSpec('P')

Parameter specification variables exist primarily for the benefit of static type checkers. They are used to forward the parameter types of one callable to another callable -- a pattern commonly found in higher order functions and decorators. They are only valid when used in Concatenate, or as the first argument to Callable, or as parameters for user-defined Generics. See Generic for more information on generic types.

For example, to add basic logging to a function, one can create a decorator add_logging to log function calls. The parameter specification variable tells the type checker that the callable passed into the decorator and the new callable returned by it have inter-dependent type parameters:

from collections.abc import Callable
import logging

def add_logging[T, **P](f: Callable[P, T]) -> Callable[P, T]:
    '''A type-safe decorator to add logging to a function.'''
    def inner(*args: P.args, **kwargs: P.kwargs) -> T:
        logging.info(f'{f.__name__} was called')
        return f(*args, **kwargs)
    return inner

@add_logging
def add_two(x: float, y: float) -> float:
    '''Add two numbers together.'''
    return x + y

Without ParamSpec, the simplest way to annotate this previously was to use a TypeVar with upper bound Callable[..., Any]. However this causes two problems:

The type checker can't type check the inner function because *args and **kwargs have to be typed Any.

cast() may be required in the body of the add_logging decorator when returning the inner function, or the static type checker must be told to ignore the return inner.

args

kwargs

Since ParamSpec captures both positional and keyword parameters, P.args and P.kwargs can be used to split a ParamSpec into its components. P.args represents the tuple of positional parameters in a given call and should only be used to annotate *args. P.kwargs represents the mapping of keyword parameters to their values in a given call, and should be only be used to annotate **kwargs. Both attributes require the annotated parameter to be in scope. At runtime, P.args and P.kwargs are instances respectively of ParamSpecArgs and ParamSpecKwargs.

__name__

The name of the parameter specification.

__default__

The default value of the parameter specification, or typing.NoDefault if it has no default.

在 3.13 版被加入.

evaluate_default()

An evaluate function corresponding to the __default__ attribute. When called directly, this method supports only the VALUE format, which is equivalent to accessing the __default__ attribute directly, but the method object can be passed to annotationlib.call_evaluate_function() to evaluate the value in a different format.

在 3.14 版被加入.

has_default()

Return whether or not the parameter specification has a default value. This is equivalent to checking whether __default__ is not the typing.NoDefault singleton, except that it does not force evaluation of the lazily evaluated default value.

在 3.13 版被加入.

Parameter specification variables created with covariant=True or contravariant=True can be used to declare covariant or contravariant generic types. The bound argument is also accepted, similar to TypeVar. However the actual semantics of these keywords are yet to be decided.

在 3.10 版被加入.

在 3.12 版的變更: Parameter specifications can now be declared using the type parameter syntax introduced by PEP 695 [https://peps.python.org/pep-0695/].

在 3.13 版的變更: 新增對預設值的支援。

備註

Only parameter specification variables defined in global scope can be pickled.

也參考

PEP 612 [https://peps.python.org/pep-0612/] -- 參數技術規範變數

Concatenate

註釋 callable 物件

typing.ParamSpecArgs

typing.ParamSpecKwargs

Arguments and keyword arguments attributes of a ParamSpec. The P.args attribute of a ParamSpec is an instance of ParamSpecArgs, and P.kwargs is an instance of ParamSpecKwargs. They are intended for runtime introspection and have no special meaning to static type checkers.

Calling get_origin() on either of these objects will return the original ParamSpec:

>>> from typing import ParamSpec, get_origin
>>> P = ParamSpec("P")
>>> get_origin(P.args) is P
True
>>> get_origin(P.kwargs) is P
True

在 3.10 版被加入.

class typing.TypeAliasType(name, value, *, type_params=())

The type of type aliases created through the type statement.

舉例來說：

>>> type Alias = int
>>> type(Alias)
<class 'typing.TypeAliasType'>

在 3.12 版被加入.

__name__

The name of the type alias:

>>> type Alias = int
>>> Alias.__name__
'Alias'

__module__

The name of the module in which the type alias was defined:

>>> type Alias = int
>>> Alias.__module__
'__main__'

__type_params__

The type parameters of the type alias, or an empty tuple if the alias is not generic:

>>> type ListOrSet[T] = list[T] | set[T]
>>> ListOrSet.__type_params__
(T,)
>>> type NotGeneric = int
>>> NotGeneric.__type_params__
()

__value__

The type alias's value. This is lazily evaluated, so names used in the definition of the alias are not resolved until the __value__ attribute is accessed:

>>> type Mutually = Recursive
>>> type Recursive = Mutually
>>> Mutually
Mutually
>>> Recursive
Recursive
>>> Mutually.__value__
Recursive
>>> Recursive.__value__
Mutually

evaluate_value()

An evaluate function corresponding to the __value__ attribute. When called directly, this method supports only the VALUE format, which is equivalent to accessing the __value__ attribute directly, but the method object can be passed to annotationlib.call_evaluate_function() to evaluate the value in a different format:

>>> type Alias = undefined
>>> Alias.__value__
Traceback (most recent call last):
...
NameError: name 'undefined' is not defined
>>> from annotationlib import Format, call_evaluate_function
>>> Alias.evaluate_value(Format.VALUE)
Traceback (most recent call last):
...
NameError: name 'undefined' is not defined
>>> call_evaluate_function(Alias.evaluate_value, Format.FORWARDREF)
ForwardRef('undefined')

在 3.14 版被加入.

Unpacking

Type aliases support star unpacking using the *Alias syntax. This is equivalent to using Unpack[Alias] directly:

>>> type Alias = tuple[int, str]
>>> type Unpacked = tuple[bool, *Alias]
>>> Unpacked.__value__
tuple[bool, typing.Unpack[Alias]]

在 3.14 版被加入.

Other special directives

These functions and classes should not be used directly as annotations. Their intended purpose is to be building blocks for creating and declaring types.

class typing.NamedTuple

Typed version of collections.namedtuple().

用法：

class Employee(NamedTuple):
    name: str
    id: int

這等價於：

Employee = collections.namedtuple('Employee', ['name', 'id'])

To give a field a default value, you can assign to it in the class body:

class Employee(NamedTuple):
    name: str
    id: int = 3

employee = Employee('Guido')
assert employee.id == 3

Fields with a default value must come after any fields without a default.

The resulting class has an extra attribute __annotations__ giving a dict that maps the field names to the field types. (The field names are in the _fields attribute and the default values are in the _field_defaults attribute, both of which are part of the namedtuple() API.)

NamedTuple subclasses can also have docstrings and methods:

class Employee(NamedTuple):
    """Represents an employee."""
    name: str
    id: int = 3

    def __repr__(self) -> str:
        return f'<Employee {self.name}, id={self.id}>'

NamedTuple subclasses can be generic:

class Group[T](NamedTuple):
    key: T
    group: list[T]

Backward-compatible usage:

# For creating a generic NamedTuple on Python 3.11
T = TypeVar("T")

class Group(NamedTuple, Generic[T]):
    key: T
    group: list[T]

# A functional syntax is also supported
Employee = NamedTuple('Employee', [('name', str), ('id', int)])

在 3.6 版的變更: Added support for PEP 526 [https://peps.python.org/pep-0526/] variable annotation syntax.

在 3.6.1 版的變更: Added support for default values, methods, and docstrings.

在 3.8 版的變更: The _field_types and __annotations__ attributes are now regular dictionaries instead of instances of OrderedDict.

在 3.9 版的變更: Removed the _field_types attribute in favor of the more standard __annotations__ attribute which has the same information.

在 3.9 版的變更: NamedTuple is now a function rather than a class. It can still be used as a class base, as described above.

在 3.11 版的變更: Added support for generic namedtuples.

在 3.14 版的變更: Using super() (and the __class__ closure variable) in methods of NamedTuple subclasses is unsupported and causes a TypeError.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: The undocumented keyword argument syntax for creating NamedTuple classes (NT = NamedTuple("NT", x=int)) is deprecated, and will be disallowed in 3.15. Use the class-based syntax or the functional syntax instead.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: When using the functional syntax to create a NamedTuple class, failing to pass a value to the 'fields' parameter (NT = NamedTuple("NT")) is deprecated. Passing None to the 'fields' parameter (NT = NamedTuple("NT", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use class NT(NamedTuple): pass or NT = NamedTuple("NT", []).

class typing.NewType(name, tp)

Helper class to create low-overhead distinct types.

A NewType is considered a distinct type by a typechecker. At runtime, however, calling a NewType returns its argument unchanged.

用法：

UserId = NewType('UserId', int)  # Declare the NewType "UserId"
first_user = UserId(1)  # "UserId" returns the argument unchanged at runtime

__module__

The name of the module in which the new type is defined.

__name__

The name of the new type.

__supertype__

The type that the new type is based on.

在 3.5.2 版被加入.

在 3.10 版的變更: NewType is now a class rather than a function.

class typing.Protocol(Generic)

Base class for protocol classes.

Protocol classes are defined like this:

class Proto(Protocol):
    def meth(self) -> int:
        ...

Such classes are primarily used with static type checkers that recognize structural subtyping (static duck-typing), for example:

class C:
    def meth(self) -> int:
        return 0

def func(x: Proto) -> int:
    return x.meth()

func(C())  # Passes static type check

See PEP 544 [https://peps.python.org/pep-0544/] for more details. Protocol classes decorated with runtime_checkable() (described later) act as simple-minded runtime protocols that check only the presence of given attributes, ignoring their type signatures. Protocol classes without this decorator cannot be used as the second argument to isinstance() or issubclass().

Protocol classes can be generic, for example:

class GenProto[T](Protocol):
    def meth(self) -> T:
        ...

In code that needs to be compatible with Python 3.11 or older, generic Protocols can be written as follows:

T = TypeVar("T")

class GenProto(Protocol[T]):
    def meth(self) -> T:
        ...

在 3.8 版被加入.

@typing.runtime_checkable

Mark a protocol class as a runtime protocol.

Such a protocol can be used with isinstance() and issubclass(). This allows a simple-minded structural check, very similar to "one trick ponies" in collections.abc such as Iterable. For example:

@runtime_checkable
class Closable(Protocol):
    def close(self): ...

assert isinstance(open('/some/file'), Closable)

@runtime_checkable
class Named(Protocol):
    name: str

import threading
assert isinstance(threading.Thread(name='Bob'), Named)

This decorator raises TypeError when applied to a non-protocol class.

備註

runtime_checkable() will check only the presence of the required methods or attributes, not their type signatures or types. For example, ssl.SSLObject is a class, therefore it passes an issubclass() check against Callable. However, the ssl.SSLObject.__init__ method exists only to raise a TypeError with a more informative message, therefore making it impossible to call (instantiate) ssl.SSLObject.

備註

An isinstance() check against a runtime-checkable protocol can be surprisingly slow compared to an isinstance() check against a non-protocol class. Consider using alternative idioms such as hasattr() calls for structural checks in performance-sensitive code.

在 3.8 版被加入.

在 3.12 版的變更: The internal implementation of isinstance() checks against runtime-checkable protocols now uses inspect.getattr_static() to look up attributes (previously, hasattr() was used). As a result, some objects which used to be considered instances of a runtime-checkable protocol may no longer be considered instances of that protocol on Python 3.12+, and vice versa. Most users are unlikely to be affected by this change.

在 3.12 版的變更: The members of a runtime-checkable protocol are now considered "frozen" at runtime as soon as the class has been created. Monkey-patching attributes onto a runtime-checkable protocol will still work, but will have no impact on isinstance() checks comparing objects to the protocol. See What's new in Python 3.12 for more details.

class typing.TypedDict(dict)

Special construct to add type hints to a dictionary. At runtime "TypedDict instances" are simply dicts.

TypedDict declares a dictionary type that expects all of its instances to have a certain set of keys, where each key is associated with a value of a consistent type. This expectation is not checked at runtime but is only enforced by type checkers. Usage:

class Point2D(TypedDict):
    x: int
    y: int
    label: str

a: Point2D = {'x': 1, 'y': 2, 'label': 'good'}  # OK
b: Point2D = {'z': 3, 'label': 'bad'}           # Fails type check

assert Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first')

An alternative way to create a TypedDict is by using function-call syntax. The second argument must be a literal dict:

Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})

This functional syntax allows defining keys which are not valid identifiers, for example because they are keywords or contain hyphens, or when key names must not be mangled like regular private names:

# raises SyntaxError
class Point2D(TypedDict):
    in: int  # 'in' is a keyword
    x-y: int  # name with hyphens

class Definition(TypedDict):
    __schema: str  # mangled to `_Definition__schema`

# OK, functional syntax
Point2D = TypedDict('Point2D', {'in': int, 'x-y': int})
Definition = TypedDict('Definition', {'__schema': str})  # not mangled

By default, all keys must be present in a TypedDict. It is possible to mark individual keys as non-required using NotRequired:

class Point2D(TypedDict):
    x: int
    y: int
    label: NotRequired[str]

# 替代語法
Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': NotRequired[str]})

This means that a Point2D TypedDict can have the label key omitted.

It is also possible to mark all keys as non-required by default by specifying a totality of False:

class Point2D(TypedDict, total=False):
    x: int
    y: int

# 替代語法
Point2D = TypedDict('Point2D', {'x': int, 'y': int}, total=False)

This means that a Point2D TypedDict can have any of the keys omitted. A type checker is only expected to support a literal False or True as the value of the total argument. True is the default, and makes all items defined in the class body required.

Individual keys of a total=False TypedDict can be marked as required using Required:

class Point2D(TypedDict, total=False):
    x: Required[int]
    y: Required[int]
    label: str

# 替代語法
Point2D = TypedDict('Point2D', {
    'x': Required[int],
    'y': Required[int],
    'label': str
}, total=False)

It is possible for a TypedDict type to inherit from one or more other TypedDict types using the class-based syntax. Usage:

class Point3D(Point2D):
    z: int

Point3D has three items: x, y and z. It is equivalent to this definition:

class Point3D(TypedDict):
    x: int
    y: int
    z: int

A TypedDict cannot inherit from a non-TypedDict class, except for Generic. For example:

class X(TypedDict):
    x: int

class Y(TypedDict):
    y: int

class Z(object): pass  # 一個非 TypedDict 的類別

class XY(X, Y): pass  # OK

class XZ(X, Z): pass  # 引發 TypeError

A TypedDict can be generic:

class Group[T](TypedDict):
    key: T
    group: list[T]

To create a generic TypedDict that is compatible with Python 3.11 or lower, inherit from Generic explicitly:

T = TypeVar("T")

class Group(TypedDict, Generic[T]):
    key: T
    group: list[T]

A TypedDict can be introspected via annotations dicts (see 註釋 (annotation) 最佳實踐 for more information on annotations best practices), __total__, __required_keys__, and __optional_keys__.

__total__

Point2D.__total__ gives the value of the total argument. Example:

>>> from typing import TypedDict
>>> class Point2D(TypedDict): pass
>>> Point2D.__total__
True
>>> class Point2D(TypedDict, total=False): pass
>>> Point2D.__total__
False
>>> class Point3D(Point2D): pass
>>> Point3D.__total__
True

This attribute reflects only the value of the total argument to the current TypedDict class, not whether the class is semantically total. For example, a TypedDict with __total__ set to True may have keys marked with NotRequired, or it may inherit from another TypedDict with total=False. Therefore, it is generally better to use __required_keys__ and __optional_keys__ for introspection.

__required_keys__

在 3.9 版被加入.

__optional_keys__

Point2D.__required_keys__ and Point2D.__optional_keys__ return frozenset objects containing required and non-required keys, respectively.

Keys marked with Required will always appear in __required_keys__ and keys marked with NotRequired will always appear in __optional_keys__.

For backwards compatibility with Python 3.10 and below, it is also possible to use inheritance to declare both required and non-required keys in the same TypedDict . This is done by declaring a TypedDict with one value for the total argument and then inheriting from it in another TypedDict with a different value for total:

>>> class Point2D(TypedDict, total=False):
...     x: int
...     y: int
...
>>> class Point3D(Point2D):
...     z: int
...
>>> Point3D.__required_keys__ == frozenset({'z'})
True
>>> Point3D.__optional_keys__ == frozenset({'x', 'y'})
True

在 3.9 版被加入.

備註

If from __future__ import annotations is used or if annotations are given as strings, annotations are not evaluated when the TypedDict is defined. Therefore, the runtime introspection that __required_keys__ and __optional_keys__ rely on may not work properly, and the values of the attributes may be incorrect.

Support for ReadOnly is reflected in the following attributes:

__readonly_keys__

A frozenset containing the names of all read-only keys. Keys are read-only if they carry the ReadOnly qualifier.

在 3.13 版被加入.

__mutable_keys__

A frozenset containing the names of all mutable keys. Keys are mutable if they do not carry the ReadOnly qualifier.

在 3.13 版被加入.

See the TypedDict [https://typing.python.org/en/latest/spec/typeddict.html#typeddict] section in the typing documentation for more examples and detailed rules.

在 3.8 版被加入.

在 3.9 版的變更: TypedDict is now a function rather than a class. It can still be used as a class base, as described above.

在 3.11 版的變更: Added support for marking individual keys as Required or NotRequired. See PEP 655 [https://peps.python.org/pep-0655/].

在 3.11 版的變更: Added support for generic TypedDicts.

在 3.13 版的變更: Removed support for the keyword-argument method of creating TypedDicts.

在 3.13 版的變更: Support for the ReadOnly qualifier was added.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: When using the functional syntax to create a TypedDict class, failing to pass a value to the 'fields' parameter (TD = TypedDict("TD")) is deprecated. Passing None to the 'fields' parameter (TD = TypedDict("TD", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a TypedDict class with 0 fields, use class TD(TypedDict): pass or TD = TypedDict("TD", {}).

協定

The following protocols are provided by the typing module. All are decorated with @runtime_checkable.

class typing.SupportsAbs

An ABC with one abstract method __abs__ that is covariant in its return type.

class typing.SupportsBytes

一個有抽象方法 __bytes__ 的 ABC。

class typing.SupportsComplex

一個有抽象方法 __complex__ 的 ABC。

class typing.SupportsFloat

一個有抽象方法 __float__ 的 ABC。

class typing.SupportsIndex

一個有抽象方法 __index__ 的 ABC。

在 3.8 版被加入.

class typing.SupportsInt

一個有抽象方法 __int__ 的 ABC。

class typing.SupportsRound

An ABC with one abstract method __round__ that is covariant in its return type.

ABCs and Protocols for working with I/O

class typing.IO[AnyStr]

class typing.TextIO

class typing.BinaryIO

Generic class IO[AnyStr] and its subclasses TextIO(IO[str]) and BinaryIO(IO[bytes]) represent the types of I/O streams such as returned by open(). Please note that these classes are not protocols, and their interface is fairly broad.

The protocols io.Reader and io.Writer offer a simpler alternative for argument types, when only the read() or write() methods are accessed, respectively:

def read_and_write(reader: Reader[str], writer: Writer[bytes]):
    data = reader.read()
    writer.write(data.encode())

Also consider using collections.abc.Iterable for iterating over the lines of an input stream:

def read_config(stream: Iterable[str]):
    for line in stream:
        ...

函式與裝飾器

typing.cast(typ, val)

Cast a value to a type.

This returns the value unchanged. To the type checker this signals that the return value has the designated type, but at runtime we intentionally don't check anything (we want this to be as fast as possible).

typing.assert_type(val, typ, /)

Ask a static type checker to confirm that val has an inferred type of typ.

At runtime this does nothing: it returns the first argument unchanged with no checks or side effects, no matter the actual type of the argument.

When a static type checker encounters a call to assert_type(), it emits an error if the value is not of the specified type:

def greet(name: str) -> None:
    assert_type(name, str)  # OK，推斷出的 `name` 型別是 `str`
    assert_type(name, int)  # 型別檢查器錯誤

This function is useful for ensuring the type checker's understanding of a script is in line with the developer's intentions:

def complex_function(arg: object):
    # Do some complex type-narrowing logic,
    # after which we hope the inferred type will be `int`
    ...
    # Test whether the type checker correctly understands our function
    assert_type(arg, int)

在 3.11 版被加入.

typing.assert_never(arg, /)

Ask a static type checker to confirm that a line of code is unreachable.

舉例來說：

def int_or_str(arg: int | str) -> None:
    match arg:
        case int():
            print("It's an int")
        case str():
            print("It's a str")
        case _ as unreachable:
            assert_never(unreachable)

Here, the annotations allow the type checker to infer that the last case can never execute, because arg is either an int or a str, and both options are covered by earlier cases.

If a type checker finds that a call to assert_never() is reachable, it will emit an error. For example, if the type annotation for arg was instead int | str | float, the type checker would emit an error pointing out that unreachable is of type float. For a call to assert_never to pass type checking, the inferred type of the argument passed in must be the bottom type, Never, and nothing else.

At runtime, this throws an exception when called.

也參考

Unreachable Code and Exhaustiveness Checking [https://typing.python.org/en/latest/guides/unreachable.html] has more information about exhaustiveness checking with static typing.

在 3.11 版被加入.

typing.reveal_type(obj, /)

Ask a static type checker to reveal the inferred type of an expression.

When a static type checker encounters a call to this function, it emits a diagnostic with the inferred type of the argument. For example:

x: int = 1
reveal_type(x)  # Revealed type is "builtins.int"

This can be useful when you want to debug how your type checker handles a particular piece of code.

At runtime, this function prints the runtime type of its argument to sys.stderr and returns the argument unchanged (allowing the call to be used within an expression):

x = reveal_type(1)  # 印出 "Runtime type is int"
print(x)  # 印出 "1"

Note that the runtime type may be different from (more or less specific than) the type statically inferred by a type checker.

Most type checkers support reveal_type() anywhere, even if the name is not imported from typing. Importing the name from typing, however, allows your code to run without runtime errors and communicates intent more clearly.

在 3.11 版被加入.

@typing.dataclass_transform(*, eq_default=True, order_default=False, kw_only_default=False, frozen_default=False, field_specifiers=(), **kwargs)

Decorator to mark an object as providing dataclass-like behavior.

dataclass_transform may be used to decorate a class, metaclass, or a function that is itself a decorator. The presence of @dataclass_transform() tells a static type checker that the decorated object performs runtime "magic" that transforms a class in a similar way to @dataclasses.dataclass.

Example usage with a decorator function:

@dataclass_transform()
def create_model[T](cls: type[T]) -> type[T]:
    ...
    return cls

@create_model
class CustomerModel:
    id: int
    name: str

On a base class:

@dataclass_transform()
class ModelBase: ...

class CustomerModel(ModelBase):
    id: int
    name: str

On a metaclass:

@dataclass_transform()
class ModelMeta(type): ...

class ModelBase(metaclass=ModelMeta): ...

class CustomerModel(ModelBase):
    id: int
    name: str

The CustomerModel classes defined above will be treated by type checkers similarly to classes created with @dataclasses.dataclass. For example, type checkers will assume these classes have __init__ methods that accept id and name.

The decorated class, metaclass, or function may accept the following bool arguments which type checkers will assume have the same effect as they would have on the @dataclasses.dataclass decorator: init, eq, order, unsafe_hash, frozen, match_args, kw_only, and slots. It must be possible for the value of these arguments (True or False) to be statically evaluated.

The arguments to the dataclass_transform decorator can be used to customize the default behaviors of the decorated class, metaclass, or function:

參數:

eq_default (bool) -- Indicates whether the eq parameter is assumed to be True or False if it is omitted by the caller. Defaults to True.

order_default (bool) -- Indicates whether the order parameter is assumed to be True or False if it is omitted by the caller. Defaults to False.

kw_only_default (bool) -- Indicates whether the kw_only parameter is assumed to be True or False if it is omitted by the caller. Defaults to False.

frozen_default (bool) --

Indicates whether the frozen parameter is assumed to be True or False if it is omitted by the caller. Defaults to False.

在 3.12 版被加入.

field_specifiers (tuple[Callable[..., Any], ...]) -- Specifies a static list of supported classes or functions that describe fields, similar to dataclasses.field(). Defaults to ().

**kwargs (Any) -- Arbitrary other keyword arguments are accepted in order to allow for possible future extensions.

Type checkers recognize the following optional parameters on field specifiers:

Recognised parameters for field specifiers

Parameter name

Description

init

Indicates whether the field should be included in the synthesized __init__ method. If unspecified, init defaults to True.

default

Provides the default value for the field.

default_factory

Provides a runtime callback that returns the default value for the field. If neither default nor default_factory are specified, the field is assumed to have no default value and must be provided a value when the class is instantiated.

factory

An alias for the default_factory parameter on field specifiers.

kw_only

Indicates whether the field should be marked as keyword-only. If True, the field will be keyword-only. If False, it will not be keyword-only. If unspecified, the value of the kw_only parameter on the object decorated with dataclass_transform will be used, or if that is unspecified, the value of kw_only_default on dataclass_transform will be used.

alias

Provides an alternative name for the field. This alternative name is used in the synthesized __init__ method.

At runtime, this decorator records its arguments in the __dataclass_transform__ attribute on the decorated object. It has no other runtime effect.

更多細節請見 PEP 681 [https://peps.python.org/pep-0681/]。

在 3.11 版被加入.

@typing.overload

Decorator for creating overloaded functions and methods.

The @overload decorator allows describing functions and methods that support multiple different combinations of argument types. A series of @overload-decorated definitions must be followed by exactly one non-@overload-decorated definition (for the same function/method).

@overload-decorated definitions are for the benefit of the type checker only, since they will be overwritten by the non-@overload-decorated definition. The non-@overload-decorated definition, meanwhile, will be used at runtime but should be ignored by a type checker. At runtime, calling an @overload-decorated function directly will raise NotImplementedError.

An example of overload that gives a more precise type than can be expressed using a union or a type variable:

@overload
def process(response: None) -> None:
    ...
@overload
def process(response: int) -> tuple[int, str]:
    ...
@overload
def process(response: bytes) -> str:
    ...
def process(response):
    ...  # 實際的實作在這邊

See PEP 484 [https://peps.python.org/pep-0484/] for more details and comparison with other typing semantics.

在 3.11 版的變更: Overloaded functions can now be introspected at runtime using get_overloads().

typing.get_overloads(func)

Return a sequence of @overload-decorated definitions for func.

func is the function object for the implementation of the overloaded function. For example, given the definition of process in the documentation for @overload, get_overloads(process) will return a sequence of three function objects for the three defined overloads. If called on a function with no overloads, get_overloads() returns an empty sequence.

get_overloads() can be used for introspecting an overloaded function at runtime.

在 3.11 版被加入.

typing.clear_overloads()

Clear all registered overloads in the internal registry.

This can be used to reclaim the memory used by the registry.

在 3.11 版被加入.

@typing.final

Decorator to indicate final methods and final classes.

Decorating a method with @final indicates to a type checker that the method cannot be overridden in a subclass. Decorating a class with @final indicates that it cannot be subclassed.

舉例來說：

class Base:
    @final
    def done(self) -> None:
        ...
class Sub(Base):
    def done(self) -> None:  # 型別檢查器回報的錯誤
        ...

@final
class Leaf:
    ...
class Other(Leaf):  # 型別檢查器回報的錯誤
    ...

這些屬性 (property) 不會在 runtime 時進行檢查。更多詳細資訊請看 PEP 591 [https://peps.python.org/pep-0591/]。

在 3.8 版被加入.

在 3.11 版的變更: The decorator will now attempt to set a __final__ attribute to True on the decorated object. Thus, a check like if getattr(obj, "__final__", False) can be used at runtime to determine whether an object obj has been marked as final. If the decorated object does not support setting attributes, the decorator returns the object unchanged without raising an exception.

@typing.no_type_check

Decorator to indicate that annotations are not type hints.

This works as a class or function decorator. With a class, it applies recursively to all methods and classes defined in that class (but not to methods defined in its superclasses or subclasses). Type checkers will ignore all annotations in a function or class with this decorator.

@no_type_check mutates the decorated object in place.

@typing.no_type_check_decorator

Decorator to give another decorator the no_type_check() effect.

This wraps the decorator with something that wraps the decorated function in no_type_check().

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: No type checker ever added support for @no_type_check_decorator. It is therefore deprecated, and will be removed in Python 3.15.

@typing.override

Decorator to indicate that a method in a subclass is intended to override a method or attribute in a superclass.

Type checkers should emit an error if a method decorated with @override does not, in fact, override anything. This helps prevent bugs that may occur when a base class is changed without an equivalent change to a child class.

舉例來說：

class Base:
    def log_status(self) -> None:
        ...

class Sub(Base):
    @override
    def log_status(self) -> None:  # Okay: overrides Base.log_status
        ...

    @override
    def done(self) -> None:  # Error reported by type checker
        ...

There is no runtime checking of this property.

The decorator will attempt to set an __override__ attribute to True on the decorated object. Thus, a check like if getattr(obj, "__override__", False) can be used at runtime to determine whether an object obj has been marked as an override. If the decorated object does not support setting attributes, the decorator returns the object unchanged without raising an exception.

更多細節請見 PEP 698 [https://peps.python.org/pep-0698/]。

在 3.12 版被加入.

@typing.type_check_only

Decorator to mark a class or function as unavailable at runtime.

This decorator is itself not available at runtime. It is mainly intended to mark classes that are defined in type stub files if an implementation returns an instance of a private class:

@type_check_only
class Response:  # private or not available at runtime
    code: int
    def get_header(self, name: str) -> str: ...

def fetch_response() -> Response: ...

Note that returning instances of private classes is not recommended. It is usually preferable to make such classes public.

Introspection helpers

typing.get_type_hints(obj, globalns=None, localns=None, include_extras=False)

Return a dictionary containing type hints for a function, method, module or class object.

This is often the same as obj.__annotations__, but this function makes the following changes to the annotations dictionary:

Forward references encoded as string literals or ForwardRef objects are handled by evaluating them in globalns, localns, and (where applicable) obj's type parameter namespace. If globalns or localns is not given, appropriate namespace dictionaries are inferred from obj.

None is replaced with types.NoneType.

If @no_type_check has been applied to obj, an empty dictionary is returned.

If obj is a class C, the function returns a dictionary that merges annotations from C's base classes with those on C directly. This is done by traversing C.__mro__ and iteratively combining __annotations__ dictionaries. Annotations on classes appearing earlier in the method resolution order always take precedence over annotations on classes appearing later in the method resolution order.

The function recursively replaces all occurrences of Annotated[T, ...], Required[T], NotRequired[T], and ReadOnly[T] with T, unless include_extras is set to True (see Annotated for more information).

See also annotationlib.get_annotations(), a lower-level function that returns annotations more directly.

警示

This function may execute arbitrary code contained in annotations. See Security implications of introspecting annotations for more information.

備註

If any forward references in the annotations of obj are not resolvable or are not valid Python code, this function will raise an exception such as NameError. For example, this can happen with imported type aliases that include forward references, or with names imported under if TYPE_CHECKING.

在 3.9 版的變更: 新增 include_extras 參數（如 PEP 593 [https://peps.python.org/pep-0593/] 中所述）。更多資訊請見 Annotated 的文件。

在 3.11 版的變更: Previously, Optional[t] was added for function and method annotations if a default value equal to None was set. Now the annotation is returned unchanged.

typing.get_origin(tp)

Get the unsubscripted version of a type: for a typing object of the form X[Y, Z, ...] return X.

If X is a typing-module alias for a builtin or collections class, it will be normalized to the original class. If X is an instance of ParamSpecArgs or ParamSpecKwargs, return the underlying ParamSpec. Return None for unsupported objects.

舉例：

assert get_origin(str) is None
assert get_origin(Dict[str, int]) is dict
assert get_origin(Union[int, str]) is Union
assert get_origin(Annotated[str, "metadata"]) is Annotated
P = ParamSpec('P')
assert get_origin(P.args) is P
assert get_origin(P.kwargs) is P

在 3.8 版被加入.

typing.get_args(tp)

Get type arguments with all substitutions performed: for a typing object of the form X[Y, Z, ...] return (Y, Z, ...).

If X is a union or Literal contained in another generic type, the order of (Y, Z, ...) may be different from the order of the original arguments [Y, Z, ...] due to type caching. Return () for unsupported objects.

舉例：

assert get_args(int) == ()
assert get_args(Dict[int, str]) == (int, str)
assert get_args(Union[int, str]) == (int, str)

在 3.8 版被加入.

typing.get_protocol_members(tp)

Return the set of members defined in a Protocol.

>>> from typing import Protocol, get_protocol_members
>>> class P(Protocol):
...     def a(self) -> str: ...
...     b: int
>>> get_protocol_members(P) == frozenset({'a', 'b'})
True

Raise TypeError for arguments that are not Protocols.

在 3.13 版被加入.

typing.is_protocol(tp)

確定一個型別是否 Protocol。

舉例來說：

class P(Protocol):
    def a(self) -> str: ...
    b: int

is_protocol(P)    # => True
is_protocol(int)  # => False

在 3.13 版被加入.

typing.is_typeddict(tp)

Check if a type is a TypedDict.

舉例來說：

class Film(TypedDict):
    title: str
    year: int

assert is_typeddict(Film)
assert not is_typeddict(list | str)

# TypedDict is a factory for creating typed dicts,
# not a typed dict itself
assert not is_typeddict(TypedDict)

在 3.10 版被加入.

class typing.ForwardRef

Class used for internal typing representation of string forward references.

For example, List["SomeClass"] is implicitly transformed into List[ForwardRef("SomeClass")]. ForwardRef should not be instantiated by a user, but may be used by introspection tools.

備註

PEP 585 [https://peps.python.org/pep-0585/] generic types such as list["SomeClass"] will not be implicitly transformed into list[ForwardRef("SomeClass")] and thus will not automatically resolve to list[SomeClass].

在 3.7.4 版被加入.

在 3.14 版的變更: This is now an alias for annotationlib.ForwardRef. Several undocumented behaviors of this class have been changed; for example, after a ForwardRef has been evaluated, the evaluated value is no longer cached.

typing.evaluate_forward_ref(forward_ref, *, owner=None, globals=None, locals=None, type_params=None, format=annotationlib.Format.VALUE)

Evaluate an annotationlib.ForwardRef as a type hint.

This is similar to calling annotationlib.ForwardRef.evaluate(), but unlike that method, evaluate_forward_ref() also recursively evaluates forward references nested within the type hint.

See the documentation for annotationlib.ForwardRef.evaluate() for the meaning of the owner, globals, locals, type_params, and format parameters.

警示

This function may execute arbitrary code contained in annotations. See Security implications of introspecting annotations for more information.

在 3.14 版被加入.

typing.NoDefault

A sentinel object used to indicate that a type parameter has no default value. For example:

>>> T = TypeVar("T")
>>> T.__default__ is typing.NoDefault
True
>>> S = TypeVar("S", default=None)
>>> S.__default__ is None
True

在 3.13 版被加入.

常數

typing.TYPE_CHECKING

A special constant that is assumed to be True by 3rd party static type checkers. It's False at runtime.

A module which is expensive to import, and which only contain types used for typing annotations, can be safely imported inside an if TYPE_CHECKING: block. This prevents the module from actually being imported at runtime; annotations aren't eagerly evaluated (see PEP 649 [https://peps.python.org/pep-0649/]) so using undefined symbols in annotations is harmless--as long as you don't later examine them. Your static type analysis tool will set TYPE_CHECKING to True during static type analysis, which means the module will be imported and the types will be checked properly during such analysis.

用法：

if TYPE_CHECKING:
    import expensive_mod

def fun(arg: expensive_mod.SomeType) -> None:
    local_var: expensive_mod.AnotherType = other_fun()

If you occasionally need to examine type annotations at runtime which may contain undefined symbols, use annotationlib.get_annotations() with a format parameter of annotationlib.Format.STRING or annotationlib.Format.FORWARDREF to safely retrieve the annotations without raising NameError.

在 3.5.2 版被加入.

棄用的別名

This module defines several deprecated aliases to pre-existing standard library classes. These were originally included in the typing module in order to support parameterizing these generic classes using []. However, the aliases became redundant in Python 3.9 when the corresponding pre-existing classes were enhanced to support [] (see PEP 585 [https://peps.python.org/pep-0585/]).

The redundant types are deprecated as of Python 3.9. However, while the aliases may be removed at some point, removal of these aliases is not currently planned. As such, no deprecation warnings are currently issued by the interpreter for these aliases.

If at some point it is decided to remove these deprecated aliases, a deprecation warning will be issued by the interpreter for at least two releases prior to removal. The aliases are guaranteed to remain in the typing module without deprecation warnings until at least Python 3.14.

Type checkers are encouraged to flag uses of the deprecated types if the program they are checking targets a minimum Python version of 3.9 or newer.

內建型別的別名

class typing.Dict(dict, MutableMapping[KT, VT])

棄用 dict 的別名。

Note that to annotate arguments, it is preferred to use an abstract collection type such as Mapping rather than to use dict or typing.Dict.

在 3.9 版之後被棄用: builtins.dict now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.List(list, MutableSequence[T])

棄用 list 的別名。

Note that to annotate arguments, it is preferred to use an abstract collection type such as Sequence or Iterable rather than to use list or typing.List.

在 3.9 版之後被棄用: builtins.list now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Set(set, MutableSet[T])

棄用 builtins.set 的別名。

Note that to annotate arguments, it is preferred to use an abstract collection type such as collections.abc.Set rather than to use set or typing.Set.

在 3.9 版之後被棄用: builtins.set now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.FrozenSet(frozenset, AbstractSet[T_co])

棄用 builtins.frozenset 的別名。

在 3.9 版之後被棄用: builtins.frozenset now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

typing.Tuple

棄用 tuple 的別名。

tuple and Tuple are special-cased in the type system; see 註釋元組 (tuple) for more details.

在 3.9 版之後被棄用: builtins.tuple now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Type(Generic[CT_co])

棄用 type 的別名。

See 類別物件的型別 for details on using type or typing.Type in type annotations.

在 3.5.2 版被加入.

在 3.9 版之後被棄用: builtins.type now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

collections 中型別的別名

class typing.DefaultDict(collections.defaultdict, MutableMapping[KT, VT])

棄用 collections.defaultdict 的別名。

在 3.5.2 版被加入.

在 3.9 版之後被棄用: collections.defaultdict now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.OrderedDict(collections.OrderedDict, MutableMapping[KT, VT])

棄用 collections.OrderedDict 的別名。

在 3.7.2 版被加入.

在 3.9 版之後被棄用: collections.OrderedDict now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.ChainMap(collections.ChainMap, MutableMapping[KT, VT])

棄用 collections.ChainMap 的別名。

在 3.6.1 版被加入.

在 3.9 版之後被棄用: collections.ChainMap now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Counter(collections.Counter, Dict[T, int])

棄用 collections.Counter 的別名。

在 3.6.1 版被加入.

在 3.9 版之後被棄用: collections.Counter now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Deque(deque, MutableSequence[T])

棄用 collections.deque 的別名。

在 3.6.1 版被加入.

在 3.9 版之後被棄用: collections.deque now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

Aliases to other concrete types

class typing.Pattern

class typing.Match

Deprecated aliases corresponding to the return types from re.compile() and re.match().

These types (and the corresponding functions) are generic over AnyStr. Pattern can be specialised as Pattern[str] or Pattern[bytes]; Match can be specialised as Match[str] or Match[bytes].

在 3.9 版之後被棄用: Classes Pattern and Match from re now support []. See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Text

棄用 str 的別名。

Text is provided to supply a forward compatible path for Python 2 code: in Python 2, Text is an alias for unicode.

Use Text to indicate that a value must contain a unicode string in a manner that is compatible with both Python 2 and Python 3:

def add_unicode_checkmark(text: Text) -> Text:
    return text + u' \u2713'

在 3.5.2 版被加入.

在 3.11 版之後被棄用: Python 2 is no longer supported, and most type checkers also no longer support type checking Python 2 code. Removal of the alias is not currently planned, but users are encouraged to use str instead of Text.

collections.abc 中容器 ABC 的別名

class typing.AbstractSet(Collection[T_co])

棄用 collections.abc.Set 的別名。

在 3.9 版之後被棄用: collections.abc.Set now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.ByteString(Sequence[int])

棄用 collections.abc.ByteString 的別名。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。

自從版本 3.9 後不推薦使用，將會自版本 3.17 中移除。.

class typing.Collection(Sized, Iterable[T_co], Container[T_co])

棄用 collections.abc.Collection 的別名。

在 3.6 版被加入.

在 3.9 版之後被棄用: collections.abc.Collection now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Container(Generic[T_co])

棄用 collections.abc.Container 的別名。

在 3.9 版之後被棄用: collections.abc.Container now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.ItemsView(MappingView, AbstractSet[tuple[KT_co, VT_co]])

棄用 collections.abc.ItemsView 的別名。

在 3.9 版之後被棄用: collections.abc.ItemsView now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.KeysView(MappingView, AbstractSet[KT_co])

棄用 collections.abc.KeysView 的別名。

在 3.9 版之後被棄用: collections.abc.KeysView now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Mapping(Collection[KT], Generic[KT, VT_co])

棄用 collections.abc.Mapping 的別名。

在 3.9 版之後被棄用: collections.abc.Mapping now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.MappingView(Sized)

棄用 collections.abc.MappingView 的別名。

在 3.9 版之後被棄用: collections.abc.MappingView now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.MutableMapping(Mapping[KT, VT])

棄用 collections.abc.MutableMapping 的別名。

在 3.9 版之後被棄用: collections.abc.MutableMapping now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.MutableSequence(Sequence[T])

棄用 collections.abc.MutableSequence 的別名。

在 3.9 版之後被棄用: collections.abc.MutableSequence now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.MutableSet(AbstractSet[T])

棄用 collections.abc.MutableSet 的別名。

在 3.9 版之後被棄用: collections.abc.MutableSet now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Sequence(Reversible[T_co], Collection[T_co])

棄用 collections.abc.Sequence 的別名。

在 3.9 版之後被棄用: collections.abc.Sequence now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.ValuesView(MappingView, Collection[_VT_co])

棄用 collections.abc.ValuesView 的別名。

在 3.9 版之後被棄用: collections.abc.ValuesView now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

collections.abc 中非同步 ABC 的別名

class typing.Coroutine(Awaitable[ReturnType], Generic[YieldType, SendType, ReturnType])

棄用 collections.abc.Coroutine 的別名。

See Annotating generators and coroutines for details on using collections.abc.Coroutine and typing.Coroutine in type annotations.

在 3.5.3 版被加入.

在 3.9 版之後被棄用: collections.abc.Coroutine now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.AsyncGenerator(AsyncIterator[YieldType], Generic[YieldType, SendType])

棄用 collections.abc.AsyncGenerator 的別名。

See Annotating generators and coroutines for details on using collections.abc.AsyncGenerator and typing.AsyncGenerator in type annotations.

在 3.6.1 版被加入.

在 3.9 版之後被棄用: collections.abc.AsyncGenerator now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

在 3.13 版的變更: SendType 參數現在有預設值。

class typing.AsyncIterable(Generic[T_co])

棄用 collections.abc.AsyncIterable 的別名。

在 3.5.2 版被加入.

在 3.9 版之後被棄用: collections.abc.AsyncIterable now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.AsyncIterator(AsyncIterable[T_co])

棄用 collections.abc.AsyncIterator 的別名。

在 3.5.2 版被加入.

在 3.9 版之後被棄用: collections.abc.AsyncIterator now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Awaitable(Generic[T_co])

棄用 collections.abc.Awaitable 的別名。

在 3.5.2 版被加入.

在 3.9 版之後被棄用: collections.abc.Awaitable now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

Aliases to other ABCs in collections.abc

class typing.Iterable(Generic[T_co])

棄用 collections.abc.Iterable 的別名。

在 3.9 版之後被棄用: collections.abc.Iterable now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Iterator(Iterable[T_co])

棄用 collections.abc.Iterator 的別名。

在 3.9 版之後被棄用: collections.abc.Iterator now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

typing.Callable

棄用 collections.abc.Callable 的別名。

See 註釋 callable 物件 for details on how to use collections.abc.Callable and typing.Callable in type annotations.

在 3.9 版之後被棄用: collections.abc.Callable now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

在 3.10 版的變更: Callable 現已支援 ParamSpec 以及 Concatenate。請參閱 PEP 612 [https://peps.python.org/pep-0612/] 閱讀詳細內容。

class typing.Generator(Iterator[YieldType], Generic[YieldType, SendType, ReturnType])

棄用 collections.abc.Generator 的別名。

See Annotating generators and coroutines for details on using collections.abc.Generator and typing.Generator in type annotations.

在 3.9 版之後被棄用: collections.abc.Generator now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

在 3.13 版的變更: Default values for the send and return types were added.

class typing.Hashable

棄用 collections.abc.Hashable 的別名。

在 3.12 版之後被棄用: 改為直接使用 collections.abc.Hashable。

class typing.Reversible(Iterable[T_co])

棄用 collections.abc.Reversible 的別名。

在 3.9 版之後被棄用: collections.abc.Reversible now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

class typing.Sized

棄用 collections.abc.Sized 的別名。

在 3.12 版之後被棄用: 改為直接使用 collections.abc.Sized。

contextlib ABC 的別名

class typing.ContextManager(Generic[T_co, ExitT_co])

Deprecated alias to contextlib.AbstractContextManager.

The first type parameter, T_co, represents the type returned by the __enter__() method. The optional second type parameter, ExitT_co, which defaults to bool | None, represents the type returned by the __exit__() method.

在 3.5.4 版被加入.

在 3.9 版之後被棄用: contextlib.AbstractContextManager now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

在 3.13 版的變更: Added the optional second type parameter, ExitT_co.

class typing.AsyncContextManager(Generic[T_co, AExitT_co])

Deprecated alias to contextlib.AbstractAsyncContextManager.

The first type parameter, T_co, represents the type returned by the __aenter__() method. The optional second type parameter, AExitT_co, which defaults to bool | None, represents the type returned by the __aexit__() method.

在 3.6.2 版被加入.

在 3.9 版之後被棄用: contextlib.AbstractAsyncContextManager now supports subscripting ([]). See PEP 585 [https://peps.python.org/pep-0585/] and 泛型別名型別.

在 3.13 版的變更: Added the optional second type parameter, AExitT_co.

主要功能的棄用時程表

Certain features in typing are deprecated and may be removed in a future version of Python. The following table summarizes major deprecations for your convenience. This is subject to change, and not all deprecations are listed.

Feature

棄用於

Projected removal

PEP/issue

typing versions of standard collections

3.9

Undecided (see 棄用的別名 for more information)

PEP 585 [https://peps.python.org/pep-0585/]

typing.ByteString

3.9

3.17

gh-91896 [https://github.com/python/cpython/issues/91896]

typing.Text

3.11

Undecided

gh-92332 [https://github.com/python/cpython/issues/92332]

typing.Hashable 和 typing.Sized

3.12

Undecided

gh-94309 [https://github.com/python/cpython/issues/94309]

typing.TypeAlias

3.12

Undecided

PEP 695 [https://peps.python.org/pep-0695/]

@typing.no_type_check_decorator

3.13

3.15

gh-106309 [https://github.com/python/cpython/issues/106309]

typing.AnyStr

3.13

3.18

gh-105578 [https://github.com/python/cpython/issues/105578]

pydoc --- 文件產生器與線上幫助系統

原始碼：Lib/pydoc.py [https://github.com/python/cpython/tree/3.14/Lib/pydoc.py]

pydoc 模組會自動從 Python 模組產生文件。文件可以以文字頁面的形式呈現在主控台上、提供給網頁瀏覽器，或儲存為 HTML 檔案。

對於模組、類別、函式和方法，所顯示的文件是從物件的說明字串（也就是物件的 __doc__ 屬性）以及遞迴地從其可文件化成員的說明字串所取得。如果沒有說明字串，pydoc 會嘗試從原始碼檔案中，類別、函式或方法定義正上方的註解區塊，或從模組的頂部取得描述（參見 inspect.getcomments()）。

內建函式 help() 會在互動式直譯器中呼叫線上幫助系統，它會使用 pydoc 在主控台上以文字形式產生文件。同樣的文字文件也可以在 Python 直譯器外部檢視，方法是在作業系統的命令提示字元中，將 pydoc 當作腳本執行。例如，執行：

python -m pydoc sys

在 shell 提示字元下，將會顯示 sys 模組的文件，其風格類似於 Unix man 命令所顯示的使用手冊。pydoc 的引數可以是函式、模組或套件的名稱，或是一個指向模組中或套件中模組內的類別、方法或函式的點號參照 (dotted reference)。如果 pydoc 的引數看起來像一個路徑（也就是說，它包含你作業系統的路徑分隔符，例如 Unix 中的斜線），並且指向一個已存在的 Python 原始碼檔案，那麼就會為該檔案產生文件。

備註

為了找到物件及其文件，pydoc 會引入要文件化的模組。因此，任何在模組層級的程式碼都會在那個時候被執行。使用 if __name__ == '__main__': 的防護措施，可以確保程式碼只在檔案作為腳本被呼叫時執行，而不會在被引入時就執行。

當在主控台印出輸出內容時，pydoc 會嘗試將輸出內容做分頁以便於閱讀。如果 MANPAGER 或 PAGER 環境變數其中之一被設定，pydoc 將會使用其值作為分頁程式。當兩者都被設定時，會使用 MANPAGER。

在引數前指定一個 -w 旗標，將會使 HTML 文件被寫入目前目錄的一個檔案中，而不是在主控台上顯示文字。

在引數前指定一個 -k 旗標，將會搜尋所有可用模組的摘要行 (synopsis lines)，尋找作為引數給出的關鍵字，其方式同樣類似於 Unix 的 man 命令。一個模組的摘要行是其說明字串的第一行。

你也可以使用 pydoc 在本機上啟動一個 HTTP 伺服器，它會向來訪的網頁瀏覽器提供文件。python -m pydoc -p 1234 將會在 1234 埠啟動一個 HTTP 伺服器，讓你可以用你偏好的網頁瀏覽器在 http://localhost:1234/ 瀏覽文件。指定 0 作為通訊埠編號將會選擇一個任意未使用的通訊埠。

python -m pydoc -n <hostname> 將會啟動伺服器並在給定的主機名稱上監聽。預設的主機名稱是 'localhost'，但如果你希望伺服器能被其他機器連線，你可能會想改變伺服器回應的主機名稱。在開發期間，如果你想在容器內執行 pydoc，這點特別有用。

python -m pydoc -b 將會啟動伺服器，並額外開啟一個網頁瀏覽器到模組索引頁面。每個提供的頁面頂部都有一個導覽列，你可以在那裡 Get（取得）個別項目的幫助、Search（搜尋）所有在其摘要行中包含關鍵字的模組，以及前往 Module index（模組索引）、Topics（主題）和 Keywords（關鍵字）頁面。

當 pydoc 產生文件時，它會使用目前的環境和路徑來定位模組。因此，呼叫 pydoc spam 所產生的文件，會完全對應到你啟動 Python 直譯器並輸入 import spam 時所取得的模組版本。

核心模組的文件被假定存放在 https://docs.python.org/X.Y/library/，其中 X 和 Y 是 Python 直譯器的主版本號和次版本號。這可以透過將 PYTHONDOCS 環境變數設定為不同的 URL 或包含函式庫參考使用手冊的本機目錄來覆寫。

在 3.2 版的變更: 新增 -b 選項。

在 3.3 版的變更: 移除 -g 命令列選項。

在 3.4 版的變更: pydoc 現在使用 inspect.signature() 而不是 inspect.getfullargspec() 來從可呼叫物件中提取簽章資訊。

在 3.7 版的變更: 新增 -n 選項。

Python 開發模式

在 3.7 版被加入.

Python 開發模式引入了額外的 runtime 檢查，預設啟用這些檢查的成本太高。如果程式碼正確，它不應比預設值更詳細；僅當偵測到問題時才會發出新警告。

可以使用 -X dev 命令列選項或將 PYTHONDEVMODE 環境變數設為 1 來啟用它。

另請參閱 Python 除錯建置。

Python 開發模式的影響

啟用 Python 開發模式類似以下指令，但具有如下所述的附加效果：

PYTHONMALLOC=debug PYTHONASYNCIODEBUG=1 python -W default -X faulthandler

Python 開發模式的效果：

新增 default 警告過濾器。以下警告會被顯示：

DeprecationWarning

ImportWarning

PendingDeprecationWarning

ResourceWarning

一般來說，上述警告會被預設的警告過濾器給過濾掉。

它的行為就像使用 -W default 命令列選項一樣。

使用 -W error 命令列選項或將 PYTHONWARNINGS 環境變數設為 error 會將警告視為錯誤。

在記憶體分配器上安裝除錯 hook（掛鉤）以檢查：

緩衝區下溢 (underflow)

緩衝區溢位 (overflow)

記憶體分配器 API 違規

GIL 的不安全使用

請參閱 PyMem_SetupDebugHooks() C 函式。

它的行為就好像是將 PYTHONMALLOC 環境變數設定為 debug 一樣。

若要啟用 Python 開發模式而不在記憶體分配器上安裝偵錯 hook，請將 PYTHONMALLOC 環境變數設為 default。

在 Python 啟動時呼叫 faulthandler.enable() 來為 SIGSEGV、SIGFPE、SIGABRT、SIGBUS 和 SIGILL 訊號安裝處理函式以在當機時傾印 (dump) Python 回溯 (traceback)。

它的行為就像使用 -X faulthandler 命令列選項或將 PYTHONFAULTHANDLER 環境變數設定為 1。

啟用 asyncio 除錯模式。例如 asyncio 會檢查未被等待的 (not awaited) 協程並記錄 (log) 它們。

它的行為就像將 PYTHONASYNCIODEBUG 環境變數設定為 1 一樣。

檢查字串編碼和解碼操作的 encoding 和 errors 引數。例如：open()、str.encode() 和 bytes.decode()。

預設情況下，為了獲得最佳效能，僅在第一個編碼/解碼錯誤時檢查 errors 引數，並且有時會因為是空字串而忽略 encoding 引數。

io.IOBase 解構函式會記錄 close() 例外。

將 sys.flags 的 dev_mode 屬性設為 True。

Python 開發模式預設不會啟用 tracemalloc 模組，因為（效能和記憶體的）開銷太大。啟用 tracemalloc 模組可提供有關某些錯誤來源的附加資訊。例如 ResourceWarning 記錄了分配資源之處的回溯、緩衝區溢位錯誤記錄了分配記憶體區塊的回溯。

Python 開發模式不會防止 -O 命令列選項刪除 assert 陳述式，也不會防止將 __debug__ 設定為 False。

Python 開發模式只能在 Python 啟動時啟用。它的值可以從 sys.flags.dev_mode 讀取。

在 3.8 版的變更: io.IOBase 解構函式現在會記錄 close() 例外。

在 3.9 版的變更: 現在會為字串編碼和解碼操作檢查 encoding 和 errors 引數。

ResourceWarning 範例

計算命令列中指定的文字檔案列數的腳本範例：

import sys

def main():
    fp = open(sys.argv[1])
    nlines = len(fp.readlines())
    print(nlines)
    # The file is closed implicitly

if __name__ == "__main__":
    main()

該腳本不會明確關閉檔案。預設情況下，Python 不會發出任何警告。使用 README.txt 的範例，該檔案有 269 列：

$ python script.py README.txt
269

啟用 Python 開發模式會顯示 ResourceWarning 警告：

$ python -X dev script.py README.txt
269
script.py:10: ResourceWarning: unclosed file <_io.TextIOWrapper name='README.rst' mode='r' encoding='UTF-8'>
  main()
ResourceWarning: Enable tracemalloc to get the object allocation traceback

此外，啟用 tracemalloc 會顯示檔案被開啟的那一列：

$ python -X dev -X tracemalloc=5 script.py README.rst
269
script.py:10: ResourceWarning: unclosed file <_io.TextIOWrapper name='README.rst' mode='r' encoding='UTF-8'>
  main()
Object allocated at (most recent call last):
  File "script.py", lineno 10
    main()
  File "script.py", lineno 4
    fp = open(sys.argv[1])

修復方法是明確關閉該檔案。以下是使用情境管理器的範例：

def main():
    # 在退出 with 區塊時明確關閉檔案
    with open(sys.argv[1]) as fp:
        nlines = len(fp.readlines())
    print(nlines)

不明確關閉資源可能會使資源開啟的時間比預期的長得多；它可能會在退出 Python 時導致嚴重問題。在 CPython 中很糟糕，但在 PyPy 中更糟。明確關閉資源使應用程式更具確定性和可靠性。

檔案描述器的錯誤範例

顯示自身第一列的腳本：

import os

def main():
    fp = open(__file__)
    firstline = fp.readline()
    print(firstline.rstrip())
    os.close(fp.fileno())
    # 檔案是隱式關閉的

main()

預設情況下，Python 不會發出任何警告：

$ python script.py
import os

Python 開發模式在最終化 (finalize) 檔案物件時顯示 ResourceWarning 並記錄 "Bad file descriptor" 錯誤：

$ python -X dev script.py
import os
script.py:10: ResourceWarning: unclosed file <_io.TextIOWrapper name='script.py' mode='r' encoding='UTF-8'>
  main()
ResourceWarning: Enable tracemalloc to get the object allocation traceback
Exception ignored in: <_io.TextIOWrapper name='script.py' mode='r' encoding='UTF-8'>
Traceback (most recent call last):
  File "script.py", line 10, in <module>
    main()
OSError: [Errno 9] Bad file descriptor

os.close(fp.fileno()) 會關閉檔案描述器。當檔案物件最終化函式 (finalizer) 嘗試再次關閉檔案描述器時，它會失敗並出現 Bad file descriptor 錯誤。檔案描述器只能關閉一次。在最壞的情況下，將它關閉兩次可能會導致崩潰 (crash)（相關範例請參閱 bpo-18748 [https://bugs.python.org/issue?@action=redirect&bpo=18748]）。

修復方法是刪除 os.close(fp.fileno()) 那列，或使用 closefd=False 開啟檔案。

doctest --- 測試互動式 Python 範例

原始碼：Lib/doctest.py [https://github.com/python/cpython/tree/3.14/Lib/doctest.py]

The doctest module searches for pieces of text that look like interactive Python sessions, and then executes those sessions to verify that they work exactly as shown. There are several common ways to use doctest:

To check that a module's docstrings are up-to-date by verifying that all interactive examples still work as documented.

透過驗證測試檔案或測試物件中的互動式範例是否按預期運作來執行迴歸測試。

To write tutorial documentation for a package, liberally illustrated with input-output examples. Depending on whether the examples or the expository text are emphasized, this has the flavor of "literate testing" or "executable documentation".

Here's a complete but small example module:

"""
This is the "example" module.

The example module supplies one function, factorial().  For example,

>>> factorial(5)
120
"""

def factorial(n):
    """Return the factorial of n, an exact integer >= 0.

    >>> [factorial(n) for n in range(6)]
    [1, 1, 2, 6, 24, 120]
    >>> factorial(30)
    265252859812191058636308480000000
    >>> factorial(-1)
    Traceback (most recent call last):
        ...
    ValueError: n must be >= 0

    Factorials of floats are OK, but the float must be an exact integer:
    >>> factorial(30.1)
    Traceback (most recent call last):
        ...
    ValueError: n must be exact integer
    >>> factorial(30.0)
    265252859812191058636308480000000

    It must also not be ridiculously large:
    >>> factorial(1e100)
    Traceback (most recent call last):
        ...
    OverflowError: n too large
    """

    import math
    if not n >= 0:
        raise ValueError("n must be >= 0")
    if math.floor(n) != n:
        raise ValueError("n must be exact integer")
    if n+1 == n:  # catch a value like 1e300
        raise OverflowError("n too large")
    result = 1
    factor = 2
    while factor <= n:
        result *= factor
        factor += 1
    return result

if __name__ == "__main__":
    import doctest
    doctest.testmod()

If you run example.py directly from the command line, doctest works its magic:

$ python example.py
$

There's no output! That's normal, and it means all the examples worked. Pass -v to the script, and doctest prints a detailed log of what it's trying, and prints a summary at the end:

$ python example.py -v
Trying:
    factorial(5)
Expecting:
    120
ok
Trying:
    [factorial(n) for n in range(6)]
Expecting:
    [1, 1, 2, 6, 24, 120]
ok

And so on, eventually ending with:

Trying:
    factorial(1e100)
Expecting:
    Traceback (most recent call last):
        ...
    OverflowError: n too large
ok
2 items passed all tests:
   1 test in __main__
   6 tests in __main__.factorial
7 tests in 2 items.
7 passed.
Test passed.
$

That's all you need to know to start making productive use of doctest! Jump in. The following sections provide full details. Note that there are many examples of doctests in the standard Python test suite and libraries. Especially useful examples can be found in the standard test file Lib/test/test_doctest/test_doctest.py.

在 3.13 版被加入: Output is colorized by default and can be controlled using environment variables.

Simple Usage: Checking Examples in Docstrings

The simplest way to start using doctest (but not necessarily the way you'll continue to do it) is to end each module M with:

if __name__ == "__main__":
    import doctest
    doctest.testmod()

doctest then examines docstrings in module M.

Running the module as a script causes the examples in the docstrings to get executed and verified:

python M.py

This won't display anything unless an example fails, in which case the failing example(s) and the cause(s) of the failure(s) are printed to stdout, and the final line of output is ***Test Failed*** N failures., where N is the number of examples that failed.

Run it with the -v switch instead:

python M.py -v

and a detailed report of all examples tried is printed to standard output, along with assorted summaries at the end.

You can force verbose mode by passing verbose=True to testmod(), or prohibit it by passing verbose=False. In either of those cases, sys.argv is not examined by testmod() (so passing -v or not has no effect).

There is also a command line shortcut for running testmod(), see section 命令列用法.

For more information on testmod(), see section 基礎 API.

Simple Usage: Checking Examples in a Text File

Another simple application of doctest is testing interactive examples in a text file. This can be done with the testfile() function:

import doctest
doctest.testfile("example.txt")

That short script executes and verifies any interactive Python examples contained in the file example.txt. The file content is treated as if it were a single giant docstring; the file doesn't need to contain a Python program! For example, perhaps example.txt contains this:

The ``example`` module
======================

Using ``factorial``
-------------------

This is an example text file in reStructuredText format.  First import
``factorial`` from the ``example`` module:

    >>> from example import factorial

Now use it:

    >>> factorial(6)
    120

Running doctest.testfile("example.txt") then finds the error in this documentation:

File "./example.txt", line 14, in example.txt
Failed example:
    factorial(6)
Expected:
    120
Got:
    720

As with testmod(), testfile() won't display anything unless an example fails. If an example does fail, then the failing example(s) and the cause(s) of the failure(s) are printed to stdout, using the same format as testmod().

By default, testfile() looks for files in the calling module's directory. See section 基礎 API for a description of the optional arguments that can be used to tell it to look for files in other locations.

Like testmod(), testfile()'s verbosity can be set with the -v command-line switch or with the optional keyword argument verbose.

There is also a command line shortcut for running testfile(), see section 命令列用法.

For more information on testfile(), see section 基礎 API.

命令列用法

可以從命令列以腳本方式叫用 doctest 模組：

python -m doctest [-v] [-o OPTION] [-f] file [file ...]

-v, --verbose

Detailed report of all examples tried is printed to standard output, along with assorted summaries at the end:

python -m doctest -v example.py

This will import example.py as a standalone module and run testmod() on it. Note that this may not work correctly if the file is part of a package and imports other submodules from that package.

If the file name does not end with .py, doctest infers that it must be run with testfile() instead:

python -m doctest -v example.txt

-o, --option <option>

Option flags control various aspects of doctest's behavior, see section 可選旗標.

在 3.4 版被加入.

-f, --fail-fast

This is shorthand for -o FAIL_FAST.

在 3.4 版被加入.

運作方式

This section examines in detail how doctest works: which docstrings it looks at, how it finds interactive examples, what execution context it uses, how it handles exceptions, and how option flags can be used to control its behavior. This is the information that you need to know to write doctest examples; for information about actually running doctest on these examples, see the following sections.

Which Docstrings Are Examined?

The module docstring, and all function, class and method docstrings are searched. Objects imported into the module are not searched.

In addition, there are cases when you want tests to be part of a module but not part of the help text, which requires that the tests not be included in the docstring. Doctest looks for a module-level variable called __test__ and uses it to locate other tests. If M.__test__ exists, it must be a dict, and each entry maps a (string) name to a function object, class object, or string. Function and class object docstrings found from M.__test__ are searched, and strings are treated as if they were docstrings. In output, a key K in M.__test__ appears with name M.__test__.K.

For example, place this block of code at the top of example.py:

__test__ = {
    'numbers': """
>>> factorial(6)
720

>>> [factorial(n) for n in range(6)]
[1, 1, 2, 6, 24, 120]
"""
}

The value of example.__test__["numbers"] will be treated as a docstring and all the tests inside it will be run. It is important to note that the value can be mapped to a function, class object, or module; if so, doctest searches them recursively for docstrings, which are then scanned for tests.

Any classes found are recursively searched similarly, to test docstrings in their contained methods and nested classes.

備註

doctest can only automatically discover classes and functions that are defined at the module level or inside other classes.

Since nested classes and functions only exist when an outer function is called, they cannot be discovered. Define them outside to make them visible.

How are Docstring Examples Recognized?

In most cases a copy-and-paste of an interactive console session works fine, but doctest isn't trying to do an exact emulation of any specific Python shell.

>>> # 註解會被忽略
>>> x = 12
>>> x
12
>>> if x == 13:
...     print("yes")
... else:
...     print("no")
...     print("NO")
...     print("NO!!!")
...
no
NO
NO!!!
>>>

Any expected output must immediately follow the final '>>> ' or '... ' line containing the code, and the expected output (if any) extends to the next '>>> ' or all-whitespace line.

The fine print:

Expected output cannot contain an all-whitespace line, since such a line is taken to signal the end of expected output. If expected output does contain a blank line, put <BLANKLINE> in your doctest example each place a blank line is expected.

All hard tab characters are expanded to spaces, using 8-column tab stops. Tabs in output generated by the tested code are not modified. Because any hard tabs in the sample output are expanded, this means that if the code output includes hard tabs, the only way the doctest can pass is if the NORMALIZE_WHITESPACE option or directive is in effect. Alternatively, the test can be rewritten to capture the output and compare it to an expected value as part of the test. This handling of tabs in the source was arrived at through trial and error, and has proven to be the least error prone way of handling them. It is possible to use a different algorithm for handling tabs by writing a custom DocTestParser class.

Output to stdout is captured, but not output to stderr (exception tracebacks are captured via a different means).

If you continue a line via backslashing in an interactive session, or for any other reason use a backslash, you should use a raw docstring, which will preserve your backslashes exactly as you type them:

>>> def f(x):
...     r'''Backslashes in a raw docstring: m\n'''
...
>>> print(f.__doc__)
Backslashes in a raw docstring: m\n

Otherwise, the backslash will be interpreted as part of the string. For example, the \n above would be interpreted as a newline character. Alternatively, you can double each backslash in the doctest version (and not use a raw string):

>>> def f(x):
...     '''Backslashes in a raw docstring: m\\n'''
...
>>> print(f.__doc__)
Backslashes in a raw docstring: m\n

The starting column doesn't matter:

>>> assert "Easy!"
      >>> import math
          >>> math.floor(1.9)
          1

and as many leading whitespace characters are stripped from the expected output as appeared in the initial '>>> ' line that started the example.

What's the Execution Context?

By default, each time doctest finds a docstring to test, it uses a shallow copy of M's globals, so that running tests doesn't change the module's real globals, and so that one test in M can't leave behind crumbs that accidentally allow another test to work. This means examples can freely use any names defined at top-level in M, and names defined earlier in the docstring being run. Examples cannot see names defined in other docstrings.

You can force use of your own dict as the execution context by passing globs=your_dict to testmod() or testfile() instead.

What About Exceptions?

No problem, provided that the traceback is the only output produced by the example: just paste in the traceback. [1] Since tracebacks contain details that are likely to change rapidly (for example, exact file paths and line numbers), this is one case where doctest works hard to be flexible in what it accepts.

簡單範例：

>>> [1, 2, 3].remove(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list

That doctest succeeds if ValueError is raised, with the list.remove(x): x not in list detail as shown.

The expected output for an exception must start with a traceback header, which may be either of the following two lines, indented the same as the first line of the example:

Traceback (most recent call last):
Traceback (innermost last):

The traceback header is followed by an optional traceback stack, whose contents are ignored by doctest. The traceback stack is typically omitted, or copied verbatim from an interactive session.

The traceback stack is followed by the most interesting part: the line(s) containing the exception type and detail. This is usually the last line of a traceback, but can extend across multiple lines if the exception has a multi-line detail:

>>> raise ValueError('multi\n    line\ndetail')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: multi
    line
detail

The last three lines (starting with ValueError) are compared against the exception's type and detail, and the rest are ignored.

Best practice is to omit the traceback stack, unless it adds significant documentation value to the example. So the last example is probably better as:

>>> raise ValueError('multi\n    line\ndetail')
Traceback (most recent call last):
    ...
ValueError: multi
    line
detail

Note that tracebacks are treated very specially. In particular, in the rewritten example, the use of ... is independent of doctest's ELLIPSIS option. The ellipsis in that example could be left out, or could just as well be three (or three hundred) commas or digits, or an indented transcript of a Monty Python skit.

Some details you should read once, but won't need to remember:

Doctest can't guess whether your expected output came from an exception traceback or from ordinary printing. So, e.g., an example that expects ValueError: 42 is prime will pass whether ValueError is actually raised or if the example merely prints that traceback text. In practice, ordinary output rarely begins with a traceback header line, so this doesn't create real problems.

Each line of the traceback stack (if present) must be indented further than the first line of the example, or start with a non-alphanumeric character. The first line following the traceback header indented the same and starting with an alphanumeric is taken to be the start of the exception detail. Of course this does the right thing for genuine tracebacks.

When the IGNORE_EXCEPTION_DETAIL doctest option is specified, everything following the leftmost colon and any module information in the exception name is ignored.

The interactive shell omits the traceback header line for some SyntaxErrors. But doctest uses the traceback header line to distinguish exceptions from non-exceptions. So in the rare case where you need to test a SyntaxError that omits the traceback header, you will need to manually add the traceback header line to your test example.

For some exceptions, Python displays the position of the error using ^ markers and tildes:

>>> 1 + None
  File "<stdin>", line 1
    1 + None
    ~~^~~~~~
TypeError: unsupported operand type(s) for +: 'int' and 'NoneType'

Since the lines showing the position of the error come before the exception type and detail, they are not checked by doctest. For example, the following test would pass, even though it puts the ^ marker in the wrong location:

>>> 1 + None
  File "<stdin>", line 1
    1 + None
    ^~~~~~~~
TypeError: unsupported operand type(s) for +: 'int' and 'NoneType'

可選旗標

A number of option flags control various aspects of doctest's behavior. Symbolic names for the flags are supplied as module constants, which can be bitwise ORed together and passed to various functions. The names can also be used in doctest directives, and may be passed to the doctest command line interface via the -o option.

The first group of options define test semantics, controlling aspects of how doctest decides whether actual output matches an example's expected output:

doctest.DONT_ACCEPT_TRUE_FOR_1

By default, if an expected output block contains just 1, an actual output block containing just 1 or just True is considered to be a match, and similarly for 0 versus False. When DONT_ACCEPT_TRUE_FOR_1 is specified, neither substitution is allowed. The default behavior caters to that Python changed the return type of many functions from integer to boolean; doctests expecting "little integer" output still work in these cases. This option will probably go away, but not for several years.

doctest.DONT_ACCEPT_BLANKLINE

By default, if an expected output block contains a line containing only the string <BLANKLINE>, then that line will match a blank line in the actual output. Because a genuinely blank line delimits the expected output, this is the only way to communicate that a blank line is expected. When DONT_ACCEPT_BLANKLINE is specified, this substitution is not allowed.

doctest.NORMALIZE_WHITESPACE

When specified, all sequences of whitespace (blanks and newlines) are treated as equal. Any sequence of whitespace within the expected output will match any sequence of whitespace within the actual output. By default, whitespace must match exactly. NORMALIZE_WHITESPACE is especially useful when a line of expected output is very long, and you want to wrap it across multiple lines in your source.

doctest.ELLIPSIS

When specified, an ellipsis marker (...) in the expected output can match any substring in the actual output. This includes substrings that span line boundaries, and empty substrings, so it's best to keep usage of this simple. Complicated uses can lead to the same kinds of "oops, it matched too much!" surprises that .* is prone to in regular expressions.

doctest.IGNORE_EXCEPTION_DETAIL

When specified, doctests expecting exceptions pass so long as an exception of the expected type is raised, even if the details (message and fully qualified exception name) don't match.

For example, an example expecting ValueError: 42 will pass if the actual exception raised is ValueError: 3*14, but will fail if, say, a TypeError is raised instead. It will also ignore any fully qualified name included before the exception class, which can vary between implementations and versions of Python and the code/libraries in use. Hence, all three of these variations will work with the flag specified:

>>> raise Exception('message')
Traceback (most recent call last):
Exception: message

>>> raise Exception('message')
Traceback (most recent call last):
builtins.Exception: message

>>> raise Exception('message')
Traceback (most recent call last):
__main__.Exception: message

Note that ELLIPSIS can also be used to ignore the details of the exception message, but such a test may still fail based on whether the module name is present or matches exactly.

在 3.2 版的變更: IGNORE_EXCEPTION_DETAIL now also ignores any information relating to the module containing the exception under test.

doctest.SKIP

When specified, do not run the example at all. This can be useful in contexts where doctest examples serve as both documentation and test cases, and an example should be included for documentation purposes, but should not be checked. E.g., the example's output might be random; or the example might depend on resources which would be unavailable to the test driver.

The SKIP flag can also be used for temporarily "commenting out" examples.

doctest.COMPARISON_FLAGS

A bitmask or'ing together all the comparison flags above.

The second group of options controls how test failures are reported:

doctest.REPORT_UDIFF

When specified, failures that involve multi-line expected and actual outputs are displayed using a unified diff.

doctest.REPORT_CDIFF

When specified, failures that involve multi-line expected and actual outputs will be displayed using a context diff.

doctest.REPORT_NDIFF

When specified, differences are computed by difflib.Differ, using the same algorithm as the popular ndiff.py utility. This is the only method that marks differences within lines as well as across lines. For example, if a line of expected output contains digit 1 where actual output contains letter l, a line is inserted with a caret marking the mismatching column positions.

doctest.REPORT_ONLY_FIRST_FAILURE

When specified, display the first failing example in each doctest, but suppress output for all remaining examples. This will prevent doctest from reporting correct examples that break because of earlier failures; but it might also hide incorrect examples that fail independently of the first failure. When REPORT_ONLY_FIRST_FAILURE is specified, the remaining examples are still run, and still count towards the total number of failures reported; only the output is suppressed.

doctest.FAIL_FAST

When specified, exit after the first failing example and don't attempt to run the remaining examples. Thus, the number of failures reported will be at most 1. This flag may be useful during debugging, since examples after the first failure won't even produce debugging output.

doctest.REPORTING_FLAGS

A bitmask or'ing together all the reporting flags above.

There is also a way to register new option flag names, though this isn't useful unless you intend to extend doctest internals via subclassing:

doctest.register_optionflag(name)

Create a new option flag with a given name, and return the new flag's integer value. register_optionflag() can be used when subclassing OutputChecker or DocTestRunner to create new options that are supported by your subclasses. register_optionflag() should always be called using the following idiom:

MY_FLAG = register_optionflag('MY_FLAG')

Directives

Doctest directives may be used to modify the option flags for an individual example. Doctest directives are special Python comments following an example's source code:

directive:             "#" "doctest:" directive_options
directive_options:     directive_option ("," directive_option)*
directive_option:      on_or_off directive_option_name
on_or_off:             "+" | "-"
directive_option_name: "DONT_ACCEPT_BLANKLINE" | "NORMALIZE_WHITESPACE" | ...

Whitespace is not allowed between the + or - and the directive option name. The directive option name can be any of the option flag names explained above.

An example's doctest directives modify doctest's behavior for that single example. Use + to enable the named behavior, or - to disable it.

舉例來說，這個測試會通過：

>>> print(list(range(20)))  # doctest: +NORMALIZE_WHITESPACE
[0,   1,  2,  3,  4,  5,  6,  7,  8,  9,
10,  11, 12, 13, 14, 15, 16, 17, 18, 19]

Without the directive it would fail, both because the actual output doesn't have two blanks before the single-digit list elements, and because the actual output is on a single line. This test also passes, and also requires a directive to do so:

>>> print(list(range(20)))  # doctest: +ELLIPSIS
[0, 1, ..., 18, 19]

Multiple directives can be used on a single physical line, separated by commas:

>>> print(list(range(20)))  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
[0,    1, ...,   18,    19]

If multiple directive comments are used for a single example, then they are combined:

>>> print(list(range(20)))  # doctest: +ELLIPSIS
...                         # doctest: +NORMALIZE_WHITESPACE
[0,    1, ...,   18,    19]

As the previous example shows, you can add ... lines to your example containing only directives. This can be useful when an example is too long for a directive to comfortably fit on the same line:

>>> print(list(range(5)) + list(range(10, 20)) + list(range(30, 40)))
... # doctest: +ELLIPSIS
[0, ..., 4, 10, ..., 19, 30, ..., 39]

Note that since all options are disabled by default, and directives apply only to the example they appear in, enabling options (via + in a directive) is usually the only meaningful choice. However, option flags can also be passed to functions that run doctests, establishing different defaults. In such cases, disabling an option via - in a directive can be useful.

警告

doctest is serious about requiring exact matches in expected output. If even a single character doesn't match, the test fails. This will probably surprise you a few times, as you learn exactly what Python does and doesn't guarantee about output. For example, when printing a set, Python doesn't guarantee that the element is printed in any particular order, so a test like

>>> foo()
{"spam", "eggs"}

is vulnerable! One workaround is to do

>>> foo() == {"spam", "eggs"}
True

instead. Another is to do

>>> d = sorted(foo())
>>> d
['eggs', 'spam']

There are others, but you get the idea.

Another bad idea is to print things that embed an object address, like

>>> id(1.0)  # certain to fail some of the time
7948648
>>> class C: pass
>>> C()  # the default repr() for instances embeds an address
<C object at 0x00AC18F0>

The ELLIPSIS directive gives a nice approach for the last example:

>>> C()  # doctest: +ELLIPSIS
<C object at 0x...>

Floating-point numbers are also subject to small output variations across platforms, because Python defers to the platform C library for some floating-point calculations, and C libraries vary widely in quality here.

>>> 1000**0.1  # 有風險
1.9952623149688797
>>> round(1000**0.1, 9) # 更安全
1.995262315
>>> print(f'{1000**0.1:.4f}') # 更加安全
1.9953

Numbers of the form I/2.**J are safe across all platforms, and I often contrive doctest examples to produce numbers of that form:

>>> 3./4  # utterly safe
0.75

Simple fractions are also easier for people to understand, and that makes for better documentation.

基礎 API

The functions testmod() and testfile() provide a simple interface to doctest that should be sufficient for most basic uses. For a less formal introduction to these two functions, see sections Simple Usage: Checking Examples in Docstrings and Simple Usage: Checking Examples in a Text File.

doctest.testfile(filename, module_relative=True, name=None, package=None, globs=None, verbose=None, report=True, optionflags=0, extraglobs=None, raise_on_error=False, parser=DocTestParser(), encoding=None)

All arguments except filename are optional, and should be specified in keyword form.

Test examples in the file named filename. Return (failure_count, test_count).

Optional argument module_relative specifies how the filename should be interpreted:

If module_relative is True (the default), then filename specifies an OS-independent module-relative path. By default, this path is relative to the calling module's directory; but if the package argument is specified, then it is relative to that package. To ensure OS-independence, filename should use / characters to separate path segments, and may not be an absolute path (i.e., it may not begin with /).

If module_relative is False, then filename specifies an OS-specific path. The path may be absolute or relative; relative paths are resolved with respect to the current working directory.

Optional argument name gives the name of the test; by default, or if None, os.path.basename(filename) is used.

Optional argument package is a Python package or the name of a Python package whose directory should be used as the base directory for a module-relative filename. If no package is specified, then the calling module's directory is used as the base directory for module-relative filenames. It is an error to specify package if module_relative is False.

Optional argument globs gives a dict to be used as the globals when executing examples. A new shallow copy of this dict is created for the doctest, so its examples start with a clean slate. By default, or if None, a new empty dict is used.

Optional argument extraglobs gives a dict merged into the globals used to execute examples. This works like dict.update(): if globs and extraglobs have a common key, the associated value in extraglobs appears in the combined dict. By default, or if None, no extra globals are used. This is an advanced feature that allows parameterization of doctests. For example, a doctest can be written for a base class, using a generic name for the class, then reused to test any number of subclasses by passing an extraglobs dict mapping the generic name to the subclass to be tested.

Optional argument verbose prints lots of stuff if true, and prints only failures if false; by default, or if None, it's true if and only if '-v' is in sys.argv.

Optional argument report prints a summary at the end when true, else prints nothing at the end. In verbose mode, the summary is detailed, else the summary is very brief (in fact, empty if all tests passed).

Optional argument optionflags (default value 0) takes the bitwise OR of option flags. See section 可選旗標.

Optional argument raise_on_error defaults to false. If true, an exception is raised upon the first failure or unexpected exception in an example. This allows failures to be post-mortem debugged. Default behavior is to continue running examples.

Optional argument parser specifies a DocTestParser (or subclass) that should be used to extract tests from the files. It defaults to a normal parser (i.e., DocTestParser()).

Optional argument encoding specifies an encoding that should be used to convert the file to unicode.

doctest.testmod(m=None, name=None, globs=None, verbose=None, report=True, optionflags=0, extraglobs=None, raise_on_error=False, exclude_empty=False)

All arguments are optional, and all except for m should be specified in keyword form.

Test examples in docstrings in functions and classes reachable from module m (or module __main__ if m is not supplied or is None), starting with m.__doc__.

Also test examples reachable from dict m.__test__, if it exists. m.__test__ maps names (strings) to functions, classes and strings; function and class docstrings are searched for examples; strings are searched directly, as if they were docstrings.

Only docstrings attached to objects belonging to module m are searched.

回傳 (failure_count, test_count)。

Optional argument name gives the name of the module; by default, or if None, m.__name__ is used.

Optional argument exclude_empty defaults to false. If true, objects for which no doctests are found are excluded from consideration. The default is a backward compatibility hack, so that code still using doctest.master.summarize in conjunction with testmod() continues to get output for objects with no tests. The exclude_empty argument to the newer DocTestFinder constructor defaults to true.

Optional arguments extraglobs, verbose, report, optionflags, raise_on_error, and globs are the same as for function testfile() above, except that globs defaults to m.__dict__.

doctest.run_docstring_examples(f, globs, verbose=False, name='NoName', compileflags=None, optionflags=0)

Test examples associated with object f; for example, f may be a string, a module, a function, or a class object.

A shallow copy of dictionary argument globs is used for the execution context.

Optional argument name is used in failure messages, and defaults to "NoName".

If optional argument verbose is true, output is generated even if there are no failures. By default, output is generated only in case of an example failure.

Optional argument compileflags gives the set of flags that should be used by the Python compiler when running the examples. By default, or if None, flags are deduced corresponding to the set of future features found in globs.

Optional argument optionflags works as for function testfile() above.

Unittest API

As your collection of doctest'ed modules grows, you'll want a way to run all their doctests systematically. doctest provides two functions that can be used to create unittest test suites from modules and text files containing doctests. To integrate with unittest test discovery, include a load_tests function in your test module:

import unittest
import doctest
import my_module_with_doctests

def load_tests(loader, tests, ignore):
    tests.addTests(doctest.DocTestSuite(my_module_with_doctests))
    return tests

There are two main functions for creating unittest.TestSuite instances from text files and modules with doctests:

doctest.DocFileSuite(*paths, module_relative=True, package=None, setUp=None, tearDown=None, globs=None, optionflags=0, parser=DocTestParser(), encoding=None)

Convert doctest tests from one or more text files to a unittest.TestSuite.

The returned unittest.TestSuite is to be run by the unittest framework and runs the interactive examples in each file. If an example in any file fails, then the synthesized unit test fails, and a failureException exception is raised showing the name of the file containing the test and a (sometimes approximate) line number. If all the examples in a file are skipped, then the synthesized unit test is also marked as skipped.

Pass one or more paths (as strings) to text files to be examined.

Options may be provided as keyword arguments:

Optional argument module_relative specifies how the filenames in paths should be interpreted:

If module_relative is True (the default), then each filename in paths specifies an OS-independent module-relative path. By default, this path is relative to the calling module's directory; but if the package argument is specified, then it is relative to that package. To ensure OS-independence, each filename should use / characters to separate path segments, and may not be an absolute path (i.e., it may not begin with /).

If module_relative is False, then each filename in paths specifies an OS-specific path. The path may be absolute or relative; relative paths are resolved with respect to the current working directory.

Optional argument package is a Python package or the name of a Python package whose directory should be used as the base directory for module-relative filenames in paths. If no package is specified, then the calling module's directory is used as the base directory for module-relative filenames. It is an error to specify package if module_relative is False.

Optional argument setUp specifies a set-up function for the test suite. This is called before running the tests in each file. The setUp function will be passed a DocTest object. The setUp function can access the test globals as the globs attribute of the test passed.

Optional argument tearDown specifies a tear-down function for the test suite. This is called after running the tests in each file. The tearDown function will be passed a DocTest object. The tearDown function can access the test globals as the globs attribute of the test passed.

Optional argument globs is a dictionary containing the initial global variables for the tests. A new copy of this dictionary is created for each test. By default, globs is a new empty dictionary.

Optional argument optionflags specifies the default doctest options for the tests, created by or-ing together individual option flags. See section 可選旗標. See function set_unittest_reportflags() below for a better way to set reporting options.

Optional argument parser specifies a DocTestParser (or subclass) that should be used to extract tests from the files. It defaults to a normal parser (i.e., DocTestParser()).

Optional argument encoding specifies an encoding that should be used to convert the file to unicode.

The global __file__ is added to the globals provided to doctests loaded from a text file using DocFileSuite().

doctest.DocTestSuite(module=None, globs=None, extraglobs=None, test_finder=None, setUp=None, tearDown=None, optionflags=0, checker=None)

Convert doctest tests for a module to a unittest.TestSuite.

The returned unittest.TestSuite is to be run by the unittest framework and runs each doctest in the module. Each docstring is run as a separate unit test. If any of the doctests fail, then the synthesized unit test fails, and a unittest.TestCase.failureException exception is raised showing the name of the file containing the test and a (sometimes approximate) line number. If all the examples in a docstring are skipped, then the

Optional argument module provides the module to be tested. It can be a module object or a (possibly dotted) module name. If not specified, the module calling this function is used.

Optional argument globs is a dictionary containing the initial global variables for the tests. A new copy of this dictionary is created for each test. By default, globs is the module's __dict__.

Optional argument extraglobs specifies an extra set of global variables, which is merged into globs. By default, no extra globals are used.

Optional argument test_finder is the DocTestFinder object (or a drop-in replacement) that is used to extract doctests from the module.

Optional arguments setUp, tearDown, and optionflags are the same as for function DocFileSuite() above, but they are called for each docstring.

This function uses the same search technique as testmod().

在 3.5 版的變更: DocTestSuite() returns an empty unittest.TestSuite if module contains no docstrings instead of raising ValueError.

Under the covers, DocTestSuite() creates a unittest.TestSuite out of doctest.DocTestCase instances, and DocTestCase is a subclass of unittest.TestCase. DocTestCase isn't documented here (it's an internal detail), but studying its code can answer questions about the exact details of unittest integration.

Similarly, DocFileSuite() creates a unittest.TestSuite out of doctest.DocFileCase instances, and DocFileCase is a subclass of DocTestCase.

So both ways of creating a unittest.TestSuite run instances of DocTestCase. This is important for a subtle reason: when you run doctest functions yourself, you can control the doctest options in use directly, by passing option flags to doctest functions. However, if you're writing a unittest framework, unittest ultimately controls when and how tests get run. The framework author typically wants to control doctest reporting options (perhaps, e.g., specified by command line options), but there's no way to pass options through unittest to doctest test runners.

For this reason, doctest also supports a notion of doctest reporting flags specific to unittest support, via this function:

doctest.set_unittest_reportflags(flags)

Set the doctest reporting flags to use.

Argument flags takes the bitwise OR of option flags. See section 可選旗標. Only "reporting flags" can be used.

This is a module-global setting, and affects all future doctests run by module unittest: the runTest() method of DocTestCase looks at the option flags specified for the test case when the DocTestCase instance was constructed. If no reporting flags were specified (which is the typical and expected case), doctest's unittest reporting flags are bitwise ORed into the option flags, and the option flags so augmented are passed to the DocTestRunner instance created to run the doctest. If any reporting flags were specified when the DocTestCase instance was constructed, doctest's unittest reporting flags are ignored.

The value of the unittest reporting flags in effect before the function was called is returned by the function.

Advanced API

The basic API is a simple wrapper that's intended to make doctest easy to use. It is fairly flexible, and should meet most users' needs; however, if you require more fine-grained control over testing, or wish to extend doctest's capabilities, then you should use the advanced API.

The advanced API revolves around two container classes, which are used to store the interactive examples extracted from doctest cases:

Example: A single Python statement, paired with its expected output.

DocTest: A collection of Examples, typically extracted from a single docstring or text file.

Additional processing classes are defined to find, parse, and run, and check doctest examples:

DocTestFinder: Finds all docstrings in a given module, and uses a DocTestParser to create a DocTest from every docstring that contains interactive examples.

DocTestParser: Creates a DocTest object from a string (such as an object's docstring).

DocTestRunner: Executes the examples in a DocTest, and uses an OutputChecker to verify their output.

OutputChecker: Compares the actual output from a doctest example with the expected output, and decides whether they match.

The relationships among these processing classes are summarized in the following diagram:

                            list of:
+------+                   +---------+
|module| --DocTestFinder-> | DocTest | --DocTestRunner-> results
+------+    |        ^     +---------+     |       ^    (printed)
            |        |     | Example |     |       |
            v        |     |   ...   |     v       |
           DocTestParser   | Example |   OutputChecker
                           +---------+

DocTest 物件

class doctest.DocTest(examples, globs, name, filename, lineno, docstring)

A collection of doctest examples that should be run in a single namespace. The constructor arguments are used to initialize the attributes of the same names.

DocTest defines the following attributes. They are initialized by the constructor, and should not be modified directly.

examples

A list of Example objects encoding the individual interactive Python examples that should be run by this test.

globs

The namespace (aka globals) that the examples should be run in. This is a dictionary mapping names to values. Any changes to the namespace made by the examples (such as binding new variables) will be reflected in globs after the test is run.

name

A string name identifying the DocTest. Typically, this is the name of the object or file that the test was extracted from.

filename

The name of the file that this DocTest was extracted from; or None if the filename is unknown, or if the DocTest was not extracted from a file.

lineno

The line number within filename where this DocTest begins, or None if the line number is unavailable. This line number is zero-based with respect to the beginning of the file.

docstring

The string that the test was extracted from, or None if the string is unavailable, or if the test was not extracted from a string.

Example 物件

class doctest.Example(source, want, exc_msg=None, lineno=0, indent=0, options=None)

A single interactive example, consisting of a Python statement and its expected output. The constructor arguments are used to initialize the attributes of the same names.

Example defines the following attributes. They are initialized by the constructor, and should not be modified directly.

source

A string containing the example's source code. This source code consists of a single Python statement, and always ends with a newline; the constructor adds a newline when necessary.

want

The expected output from running the example's source code (either from stdout, or a traceback in case of exception). want ends with a newline unless no output is expected, in which case it's an empty string. The constructor adds a newline when necessary.

exc_msg

The exception message generated by the example, if the example is expected to generate an exception; or None if it is not expected to generate an exception. This exception message is compared against the return value of traceback.format_exception_only(). exc_msg ends with a newline unless it's None. The constructor adds a newline if needed.

lineno

The line number within the string containing this example where the example begins. This line number is zero-based with respect to the beginning of the containing string.

indent

The example's indentation in the containing string, i.e., the number of space characters that precede the example's first prompt.

options

A dictionary mapping from option flags to True or False, which is used to override default options for this example. Any option flags not contained in this dictionary are left at their default value (as specified by the DocTestRunner's optionflags). By default, no options are set.

DocTestFinder 物件

class doctest.DocTestFinder(verbose=False, parser=DocTestParser(), recurse=True, exclude_empty=True)

A processing class used to extract the DocTests that are relevant to a given object, from its docstring and the docstrings of its contained objects. DocTests can be extracted from modules, classes, functions, methods, staticmethods, classmethods, and properties.

The optional argument verbose can be used to display the objects searched by the finder. It defaults to False (no output).

The optional argument parser specifies the DocTestParser object (or a drop-in replacement) that is used to extract doctests from docstrings.

If the optional argument recurse is false, then DocTestFinder.find() will only examine the given object, and not any contained objects.

If the optional argument exclude_empty is false, then DocTestFinder.find() will include tests for objects with empty docstrings.

DocTestFinder 定義了以下方法：

find(obj[, name][, module][, globs][, extraglobs])

Return a list of the DocTests that are defined by obj's docstring, or by any of its contained objects' docstrings.

The optional argument name specifies the object's name; this name will be used to construct names for the returned DocTests. If name is not specified, then obj.__name__ is used.

The optional parameter module is the module that contains the given object. If the module is not specified or is None, then the test finder will attempt to automatically determine the correct module. The object's module is used:

As a default namespace, if globs is not specified.

To prevent the DocTestFinder from extracting DocTests from objects that are imported from other modules. (Contained objects with modules other than module are ignored.)

To find the name of the file containing the object.

To help find the line number of the object within its file.

If module is False, no attempt to find the module will be made. This is obscure, of use mostly in testing doctest itself: if module is False, or is None but cannot be found automatically, then all objects are considered to belong to the (non-existent) module, so all contained objects will (recursively) be searched for doctests.

The globals for each DocTest is formed by combining globs and extraglobs (bindings in extraglobs override bindings in globs). A new shallow copy of the globals dictionary is created for each DocTest. If globs is not specified, then it defaults to the module's __dict__, if specified, or {} otherwise. If extraglobs is not specified, then it defaults to {}.

DocTestParser 物件

class doctest.DocTestParser

A processing class used to extract interactive examples from a string, and use them to create a DocTest object.

DocTestParser 定義了以下方法：

get_doctest(string, globs, name, filename, lineno)

Extract all doctest examples from the given string, and collect them into a DocTest object.

globs, name, filename, and lineno are attributes for the new DocTest object. See the documentation for DocTest for more information.

get_examples(string, name='<string>')

Extract all doctest examples from the given string, and return them as a list of Example objects. Line numbers are 0-based. The optional argument name is a name identifying this string, and is only used for error messages.

parse(string, name='<string>')

Divide the given string into examples and intervening text, and return them as a list of alternating Examples and strings. Line numbers for the Examples are 0-based. The optional argument name is a name identifying this string, and is only used for error messages.

TestResults 物件

class doctest.TestResults(failed, attempted)

failed

失敗的測試數量。

attempted

嘗試的測試數量。

skipped

跳過的測試數量。

在 3.13 版被加入.

DocTestRunner 物件

class doctest.DocTestRunner(checker=None, verbose=None, optionflags=0)

A processing class used to execute and verify the interactive examples in a DocTest.

The comparison between expected outputs and actual outputs is done by an OutputChecker. This comparison may be customized with a number of option flags; see section 可選旗標 for more information. If the option flags are insufficient, then the comparison may also be customized by passing a subclass of OutputChecker to the constructor.

The test runner's display output can be controlled in two ways. First, an output function can be passed to run(); this function will be called with strings that should be displayed. It defaults to sys.stdout.write. If capturing the output is not sufficient, then the display output can be also customized by subclassing DocTestRunner, and overriding the methods report_start(), report_success(), report_unexpected_exception(), and report_failure().

The optional keyword argument checker specifies the OutputChecker object (or drop-in replacement) that should be used to compare the expected outputs to the actual outputs of doctest examples.

The optional keyword argument verbose controls the DocTestRunner's verbosity. If verbose is True, then information is printed about each example, as it is run. If verbose is False, then only failures are printed. If verbose is unspecified, or None, then verbose output is used iff the command-line switch -v is used.

The optional keyword argument optionflags can be used to control how the test runner compares expected output to actual output, and how it displays failures. For more information, see section 可選旗標.

The test runner accumulates statistics. The aggregated number of attempted, failed and skipped examples is also available via the tries, failures and skips attributes. The run() and summarize() methods return a TestResults instance.

DocTestRunner 定義了以下方法：

report_start(out, test, example)

Report that the test runner is about to process the given example. This method is provided to allow subclasses of DocTestRunner to customize their output; it should not be called directly.

example is the example about to be processed. test is the test containing example. out is the output function that was passed to DocTestRunner.run().

report_success(out, test, example, got)

Report that the given example ran successfully. This method is provided to allow subclasses of DocTestRunner to customize their output; it should not be called directly.

example is the example about to be processed. got is the actual output from the example. test is the test containing example. out is the output function that was passed to DocTestRunner.run().

report_failure(out, test, example, got)

Report that the given example failed. This method is provided to allow subclasses of DocTestRunner to customize their output; it should not be called directly.

example is the example about to be processed. got is the actual output from the example. test is the test containing example. out is the output function that was passed to DocTestRunner.run().

report_unexpected_exception(out, test, example, exc_info)

Report that the given example raised an unexpected exception. This method is provided to allow subclasses of DocTestRunner to customize their output; it should not be called directly.

example is the example about to be processed. exc_info is a tuple containing information about the unexpected exception (as returned by sys.exc_info()). test is the test containing example. out is the output function that was passed to DocTestRunner.run().

run(test, compileflags=None, out=None, clear_globs=True)

Run the examples in test (a DocTest object), and display the results using the writer function out. Return a TestResults instance.

The examples are run in the namespace test.globs. If clear_globs is true (the default), then this namespace will be cleared after the test runs, to help with garbage collection. If you would like to examine the namespace after the test completes, then use clear_globs=False.

compileflags gives the set of flags that should be used by the Python compiler when running the examples. If not specified, then it will default to the set of future-import flags that apply to globs.

The output of each example is checked using the DocTestRunner's output checker, and the results are formatted by the DocTestRunner.report_*() methods.

summarize(verbose=None)

Print a summary of all the test cases that have been run by this DocTestRunner, and return a TestResults instance.

The optional verbose argument controls how detailed the summary is. If the verbosity is not specified, then the DocTestRunner's verbosity is used.

DocTestParser 有以下屬性：

tries

嘗試的範例數量。

failures

失敗的範例數量。

skips

跳過的範例數量。

在 3.13 版被加入.

OutputChecker 物件

class doctest.OutputChecker

A class used to check the whether the actual output from a doctest example matches the expected output. OutputChecker defines two methods: check_output(), which compares a given pair of outputs, and returns True if they match; and output_difference(), which returns a string describing the differences between two outputs.

OutputChecker 定義了以下方法：

check_output(want, got, optionflags)

Return True iff the actual output from an example (got) matches the expected output (want). These strings are always considered to match if they are identical; but depending on what option flags the test runner is using, several non-exact match types are also possible. See section 可選旗標 for more information about option flags.

output_difference(example, got, optionflags)

Return a string describing the differences between the expected output for a given example (example) and the actual output (got). optionflags is the set of option flags used to compare want and got.

偵錯

Doctest 提供了幾種偵錯 doctest 範例的機制：

Several functions convert doctests to executable Python programs, which can be run under the Python debugger, pdb.

The DebugRunner class is a subclass of DocTestRunner that raises an exception for the first failing example, containing information about that example. This information can be used to perform post-mortem debugging on the example.

The unittest cases generated by DocTestSuite() support the debug() method defined by unittest.TestCase.

You can add a call to pdb.set_trace() in a doctest example, and you'll drop into the Python debugger when that line is executed. Then you can inspect current values of variables, and so on. For example, suppose a.py contains just this module docstring:

"""
>>> def f(x):
...     g(x*2)
>>> def g(x):
...     print(x+3)
...     import pdb; pdb.set_trace()
>>> f(3)
9
"""

Then an interactive Python session may look like this:

>>> import a, doctest
>>> doctest.testmod(a)
--Return--
> <doctest a[1]>(3)g()->None
-> import pdb; pdb.set_trace()
(Pdb) list
  1     def g(x):
  2         print(x+3)
  3  ->     import pdb; pdb.set_trace()
[EOF]
(Pdb) p x
6
(Pdb) step
--Return--
> <doctest a[0]>(2)f()->None
-> g(x*2)
(Pdb) list
  1     def f(x):
  2  ->     g(x*2)
[EOF]
(Pdb) p x
3
(Pdb) step
--Return--
> <doctest a[2]>(1)?()->None
-> f(3)
(Pdb) cont
(0, 3)
>>>

Functions that convert doctests to Python code, and possibly run the synthesized code under the debugger:

doctest.script_from_examples(s)

Convert text with examples to a script.

Argument s is a string containing doctest examples. The string is converted to a Python script, where doctest examples in s are converted to regular code, and everything else is converted to Python comments. The generated script is returned as a string. For example,

import doctest
print(doctest.script_from_examples(r"""
    Set x and y to 1 and 2.
    >>> x, y = 1, 2

    Print their sum:
    >>> print(x+y)
    3
"""))

displays:

# Set x and y to 1 and 2.
x, y = 1, 2
#
# Print their sum:
print(x+y)
# Expected:
## 3

This function is used internally by other functions (see below), but can also be useful when you want to transform an interactive Python session into a Python script.

doctest.testsource(module, name)

Convert the doctest for an object to a script.

Argument module is a module object, or dotted name of a module, containing the object whose doctests are of interest. Argument name is the name (within the module) of the object with the doctests of interest. The result is a string, containing the object's docstring converted to a Python script, as described for script_from_examples() above. For example, if module a.py contains a top-level function f(), then

import a, doctest
print(doctest.testsource(a, "a.f"))

prints a script version of function f()'s docstring, with doctests converted to code, and the rest placed in comments.

doctest.debug(module, name, pm=False)

Debug the doctests for an object.

The module and name arguments are the same as for function testsource() above. The synthesized Python script for the named object's docstring is written to a temporary file, and then that file is run under the control of the Python debugger, pdb.

A shallow copy of module.__dict__ is used for both local and global execution context.

Optional argument pm controls whether post-mortem debugging is used. If pm has a true value, the script file is run directly, and the debugger gets involved only if the script terminates via raising an unhandled exception. If it does, then post-mortem debugging is invoked, via pdb.post_mortem(), passing the traceback object from the unhandled exception. If pm is not specified, or is false, the script is run under the debugger from the start, via passing an appropriate exec() call to pdb.run().

doctest.debug_src(src, pm=False, globs=None)

Debug the doctests in a string.

This is like function debug() above, except that a string containing doctest examples is specified directly, via the src argument.

Optional argument pm has the same meaning as in function debug() above.

Optional argument globs gives a dictionary to use as both local and global execution context. If not specified, or None, an empty dictionary is used. If specified, a shallow copy of the dictionary is used.

The DebugRunner class, and the special exceptions it may raise, are of most interest to testing framework authors, and will only be sketched here. See the source code, and especially DebugRunner's docstring (which is a doctest!) for more details:

class doctest.DebugRunner(checker=None, verbose=None, optionflags=0)

A subclass of DocTestRunner that raises an exception as soon as a failure is encountered. If an unexpected exception occurs, an UnexpectedException exception is raised, containing the test, the example, and the original exception. If the output doesn't match, then a DocTestFailure exception is raised, containing the test, the example, and the actual output.

For information about the constructor parameters and methods, see the documentation for DocTestRunner in section Advanced API.

There are two exceptions that may be raised by DebugRunner instances:

exception doctest.DocTestFailure(test, example, got)

An exception raised by DocTestRunner to signal that a doctest example's actual output did not match its expected output. The constructor arguments are used to initialize the attributes of the same names.

DocTestFailure 定義了以下屬性：

DocTestFailure.test

The DocTest object that was being run when the example failed.

DocTestFailure.example

The Example that failed.

DocTestFailure.got

The example's actual output.

exception doctest.UnexpectedException(test, example, exc_info)

An exception raised by DocTestRunner to signal that a doctest example raised an unexpected exception. The constructor arguments are used to initialize the attributes of the same names.

UnexpectedException 定義了以下屬性：

UnexpectedException.test

The DocTest object that was being run when the example failed.

UnexpectedException.example

The Example that failed.

UnexpectedException.exc_info

A tuple containing information about the unexpected exception, as returned by sys.exc_info().

Soapbox

As mentioned in the introduction, doctest has grown to have three primary uses:

Checking examples in docstrings.

回歸測試。

Executable documentation / literate testing.

These uses have different requirements, and it is important to distinguish them. In particular, filling your docstrings with obscure test cases makes for bad documentation.

When writing a docstring, choose docstring examples with care. There's an art to this that needs to be learned---it may not be natural at first. Examples should add genuine value to the documentation. A good example can often be worth many words. If done with care, the examples will be invaluable for your users, and will pay back the time it takes to collect them many times over as the years go by and things change. I'm still amazed at how often one of my doctest examples stops working after a "harmless" change.

Doctest also makes an excellent tool for regression testing, especially if you don't skimp on explanatory text. By interleaving prose and examples, it becomes much easier to keep track of what's actually being tested, and why. When a test fails, good prose can make it much easier to figure out what the problem is, and how it should be fixed. It's true that you could write extensive comments in code-based testing, but few programmers do. Many have found that using doctest approaches instead leads to much clearer tests. Perhaps this is simply because doctest makes writing prose a little easier than writing code, while writing comments in code is a little harder. I think it goes deeper than just that: the natural attitude when writing a doctest-based test is that you want to explain the fine points of your software, and illustrate them with examples. This in turn naturally leads to test files that start with the simplest features, and logically progress to complications and edge cases. A coherent narrative is the result, instead of a collection of isolated functions that test isolated bits of functionality seemingly at random. It's a different attitude, and produces different results, blurring the distinction between testing and explaining.

Regression testing is best confined to dedicated objects or files. There are several options for organizing tests:

Write text files containing test cases as interactive examples, and test the files using testfile() or DocFileSuite(). This is recommended, although is easiest to do for new projects, designed from the start to use doctest.

Define functions named _regrtest_topic that consist of single docstrings, containing test cases for the named topics. These functions can be included in the same file as the module, or separated out into a separate test file.

Define a __test__ dictionary mapping from regression test topics to docstrings containing test cases.

When you have placed your tests in a module, the module can itself be the test runner. When a test fails, you can arrange for your test runner to re-run only the failing doctest while you debug the problem. Here is a minimal example of such a test runner:

if __name__ == '__main__':
    import doctest
    flags = doctest.REPORT_NDIFF|doctest.FAIL_FAST
    if len(sys.argv) > 1:
        name = sys.argv[1]
        if name in globals():
            obj = globals()[name]
        else:
            obj = __test__[name]
        doctest.run_docstring_examples(obj, globals(), name=name,
                                       optionflags=flags)
    else:
        fail, total = doctest.testmod(optionflags=flags)
        print(f"{fail} failures out of {total} tests")

註腳

[1]

Examples containing both expected output and an exception are not supported. Trying to guess where one ends and the other begins is too error-prone, and that also makes for a confusing test.

unittest --- 單元測試框架

原始碼：Lib/unittest/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/unittest/__init__.py]

（假如你已經熟悉相關基礎的測試概念，你可能會希望跳過以下段落，直接參考 assert 方法清單。）

unittest 原生的單元測試框架最初由 JUnit 開發，和其他程式語言相似有主要的單元測試框架。支援自動化測試，對測試分享安裝與關閉程式碼，集合所有匯總的測試，並且獨立各個測試報告框架。

unittest 用來作為實現支援一些重要的物件導向方法的概念：

test fixture

一個 test fixture 代表執行一個或多個測試所需要的準備，以及其他相關清理操作，例如可以是建立臨時性的或是代理用 (proxy) 資料庫、目錄、或是啟動一個伺服器程序。

test case（測試用例）

一個 test case 是一個獨立的單元測試。這是用來確認一個特定設定的輸入的特殊回饋。 unittest 提供一個基礎類別，類別 TestCase，可以用來建立一個新的測試條例。

test suite（測試套件）

test suite 是一個搜集測試條例，測試套件，或是兩者皆有。它需要一起被執行並用來匯總測試。

test runner（測試執行器）

test runner 是一個編排測試執行與提供結果給使用者的一個元件。執行器可以使用圖形化介面，文字介面或是回傳一個特別值用來標示出執行測試的結果。

也參考

doctest 模組

另一個執行測試的模組，但使用不一樣的測試方法與規範。

Simple Smalltalk Testing: With Patterns [https://web.archive.org/web/20150315073817/http://www.xprogramming.com/testfram.htm]

Kent Beck 的原始論文討論使用 unittest 這樣模式的測試框架。

pytest [https://docs.pytest.org/]

第三方的單元測試框架，但在撰寫測試時使用更輕量的語法。例如： assert func(10) == 42。

The Python Testing Tools Taxonomy [https://wiki.python.org/moin/PythonTestingToolsTaxonomy]

一份詳細的 Python 測試工具列表，包含 functional testing 框架和mock object 函式庫。

Testing in Python Mailing List [http://lists.idyll.org/listinfo/testing-in-python]

一個專門興趣的群組用來討論 Python 中的測試方式與測試工具。

The script Tools/unittestgui/unittestgui.py in the Python source distribution is a GUI tool for test discovery and execution. This is intended largely for ease of use for those new to unit testing. For production environments it is recommended that tests be driven by a continuous integration system such as Buildbot [https://buildbot.net/], Jenkins [https://www.jenkins.io/], GitHub Actions [https://github.com/features/actions], or AppVeyor [https://www.appveyor.com/].

簡單範例

unittest 模組提供一系列豐富的工具用來建構與執行測試。本節將展示這一系列工具中一部份，它們已能滿足大部份使用者需求。

這是一段簡短的腳本用來測試 3 個字串方法：

import unittest

class TestStringMethods(unittest.TestCase):

    def test_upper(self):
        self.assertEqual('foo'.upper(), 'FOO')

    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())

    def test_split(self):
        s = 'hello world'
        self.assertEqual(s.split(), ['hello', 'world'])
        # check that s.split fails when the separator is not a string
        with self.assertRaises(TypeError):
            s.split(2)

if __name__ == '__main__':
    unittest.main()

測試用例 (test case) 可以透過繼承 unittest.TestCase 類別來建立。這裡定義了三個獨立的物件方法，名稱皆以 test 開頭。這樣的命名方式能告知 test runner 哪些物件方法為定義的測試。

每個測試的關鍵為呼叫 assertEqual() 來確認是否為期望的結果； assertTrue() 或是 assertFalse() 用來驗證一個條件式； assertRaises() 用來驗證是否觸發一個特定的 exception。使用這些物件方法來取代 assert 陳述句，將能使 test runner 收集所有的測試結果並產生一個報表。

The setUp() and tearDown() methods allow you to define instructions that will be executed before and after each test method. They are covered in more detail in the section Organizing test code.

最後將顯示一個簡單的方法去執行測試 unittest.main() 提供一個命令列介面測試腳本。當透過命令列執行，輸出結果將會像是：

...
----------------------------------------------------------------------
Ran 3 tests in 0.000s

OK

在測試時加入 -v 選項將指示 unittest.main() 提高 verbosity 層級，產生以下的輸出：

test_isupper (__main__.TestStringMethods.test_isupper) ... ok
test_split (__main__.TestStringMethods.test_split) ... ok
test_upper (__main__.TestStringMethods.test_upper) ... ok

----------------------------------------------------------------------
Ran 3 tests in 0.001s

OK

以上的例子顯示大多數使用 unittest 特徵足以滿足大多數日常測試的需求。接下來第一部分文件的剩餘部分將繼續探索完整特徵設定。

在 3.11 版的變更: The behavior of returning a value from a test method (other than the default None value), is now deprecated.

命令列介面

單元測試模組可以透過命令列執行測試模組，物件甚至個別的測試方法：

python -m unittest test_module1 test_module2
python -m unittest test_module.TestClass
python -m unittest test_module.TestClass.test_method

你可以透過一個串列與任何模組名稱的組合，完全符合類別與方法的名稱。

測試模組可以根據檔案路徑指定：

python -m unittest tests/test_something.py

這允許你使用 shell 檔案名稱補完功能 (filename completion) 來指定測試模組。給定的檔案路徑必須亦能被當作模組 import。此路徑轉換為模組名稱的方式為移除 '.py' 並將路徑分隔符 (path separator) 轉換成 '.'。 假如你的測試檔案無法被 import 成模組，你應該直接執行該測試檔案。

透過增加 -v 的旗標數，可以在你執行測試時得到更多細節（更高的 verbosity）：

python -m unittest -v test_module

若執行時不代任何引數，將執行 Test Discovery（測試探索）：

python -m unittest

列出所有命令列選項：

python -m unittest -h

在 3.2 版的變更: 在早期的版本可以個別執行測試方法和不需要模組或是類別。

在 3.14 版被加入: Output is colorized by default and can be controlled using environment variables.

命令列模式選項

unittest 支援以下命令列選項：

-b, --buffer

Standard output 與 standard error stream 將在測試執行被緩衝 (buffer)。這些輸出在測試透過時被丟棄。若是測試錯誤或失則，這些輸出將會正常地被印出，並且被加入至錯誤訊息中。

-c, --catch

Control-C 測試執行過程中等待正確的測試結果並回報目前為止所有的測試結果。第二個 Control-C 拋出一般例外 KeyboardInterrupt。

參照 Signal Handling 針對函式提供的功能。

-f, --failfast

在第一次錯誤或是失敗停止執行測試。

-k

Only run test methods and classes that match the pattern or substring. This option may be used multiple times, in which case all test cases that match any of the given patterns are included.

Patterns that contain a wildcard character (*) are matched against the test name using fnmatch.fnmatchcase(); otherwise simple case-sensitive substring matching is used.

Patterns are matched against the fully qualified test method name as imported by the test loader.

For example, -k foo matches foo_tests.SomeTest.test_something, bar_tests.SomeTest.test_foo, but not bar_tests.FooTest.test_something.

--locals

透過 traceback 顯示本地變數。

--durations N

Show the N slowest test cases (N=0 for all).

在 3.2 版被加入: 增加命令列模式選項 -b 、 -c 與 -f。

在 3.5 版被加入: 命令列選項 --locals。

在 3.7 版被加入: 命令列選項 -k。

在 3.12 版被加入: 命令列選項 --durations。

對執行所有的專案或是一個子集合測試，命令列模式可以可以被用來做測試探索。

Test Discovery（測試探索）

在 3.2 版被加入.

單元測試支援簡單的 test discovery（測試探索）。為了相容於測試探索，所有的測試檔案都要是模組或是套件，並能從專案的最上層目錄中 import（代表它們的檔案名稱必須是有效的 identifiers）。

Test discovery（測試探索）實作在 TestLoader.discover()，但也可以被用於命令列模式。基本的命令列模式用法如下：

cd project_directory
python -m unittest discover

備註

python -m unittest 作為捷徑，其功能相當於 python -m unittest discover。假如你想傳遞引數至探索測試的話，一定要明確地加入 discover 子指令。

discover 子命令有以下幾個選項：

-v, --verbose

詳細 (verbose) 輸出

-s, --start-directory directory

開始尋找的資料夾（預設為 .）

-p, --pattern pattern

匹配測試檔案的模式（預設為 test*.py）

-t, --top-level-directory directory

專案的最高階層目錄（預設為開始的資料夾）

-s, -p, 和 -t 選項依照傳遞位置作為引數排序順序。以下兩個命令列被視為等價：

python -m unittest discover -s project_directory -p "*_test.py"
python -m unittest discover project_directory "*_test.py"

As well as being a path it is possible to pass a package name, for example myproject.subpackage.test, as the start directory. The package name you supply will then be imported and its location on the filesystem will be used as the start directory.

警示

Test discovery loads tests by importing them. Once test discovery has found all the test files from the start directory you specify it turns the paths into package names to import. For example foo/bar/baz.py will be imported as foo.bar.baz.

If you have a package installed globally and attempt test discovery on a different copy of the package then the import could happen from the wrong place. If this happens test discovery will warn you and exit.

If you supply the start directory as a package name rather than a path to a directory then discover assumes that whichever location it imports from is the location you intended, so you will not get the warning.

Test modules and packages can customize test loading and discovery by through the load_tests protocol.

在 3.4 版的變更: Test discovery supports namespace packages.

在 3.11 版的變更: Test discovery dropped the namespace packages support. It has been broken since Python 3.7. Start directory and its subdirectories containing tests must be regular package that have __init__.py file.

If the start directory is the dotted name of the package, the ancestor packages can be namespace packages.

在 3.14 版的變更: Test discovery supports namespace package as start directory again. To avoid scanning directories unrelated to Python, tests are not searched in subdirectories that do not contain __init__.py.

Organizing test code

The basic building blocks of unit testing are test cases --- single scenarios that must be set up and checked for correctness. In unittest, test cases are represented by unittest.TestCase instances. To make your own test cases you must write subclasses of TestCase or use FunctionTestCase.

The testing code of a TestCase instance should be entirely self contained, such that it can be run either in isolation or in arbitrary combination with any number of other test cases.

The simplest TestCase subclass will simply implement a test method (i.e. a method whose name starts with test) in order to perform specific testing code:

import unittest

class DefaultWidgetSizeTestCase(unittest.TestCase):
    def test_default_widget_size(self):
        widget = Widget('The widget')
        self.assertEqual(widget.size(), (50, 50))

Note that in order to test something, we use one of the assert* methods provided by the TestCase base class. If the test fails, an exception will be raised with an explanatory message, and unittest will identify the test case as a failure. Any other exceptions will be treated as errors.

Tests can be numerous, and their set-up can be repetitive. Luckily, we can factor out set-up code by implementing a method called setUp(), which the testing framework will automatically call for every single test we run:

import unittest

class WidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')

    def test_default_widget_size(self):
        self.assertEqual(self.widget.size(), (50,50),
                         'incorrect default size')

    def test_widget_resize(self):
        self.widget.resize(100,150)
        self.assertEqual(self.widget.size(), (100,150),
                         'wrong size after resize')

備註

The order in which the various tests will be run is determined by sorting the test method names with respect to the built-in ordering for strings.

If the setUp() method raises an exception while the test is running, the framework will consider the test to have suffered an error, and the test method will not be executed.

Similarly, we can provide a tearDown() method that tidies up after the test method has been run:

import unittest

class WidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')

    def tearDown(self):
        self.widget.dispose()

If setUp() succeeded, tearDown() will be run whether the test method succeeded or not.

Such a working environment for the testing code is called a test fixture. A new TestCase instance is created as a unique test fixture used to execute each individual test method. Thus setUp(), tearDown(), and TestCase.__init__() will be called once per test.

It is recommended that you use TestCase implementations to group tests together according to the features they test. unittest provides a mechanism for this: the test suite, represented by unittest's TestSuite class. In most cases, calling unittest.main() will do the right thing and collect all the module's test cases for you and execute them.

However, should you want to customize the building of your test suite, you can do it yourself:

def suite():
    suite = unittest.TestSuite()
    suite.addTest(WidgetTestCase('test_default_widget_size'))
    suite.addTest(WidgetTestCase('test_widget_resize'))
    return suite

if __name__ == '__main__':
    runner = unittest.TextTestRunner()
    runner.run(suite())

You can place the definitions of test cases and test suites in the same modules as the code they are to test (such as widget.py), but there are several advantages to placing the test code in a separate module, such as test_widget.py:

The test module can be run standalone from the command line.

The test code can more easily be separated from shipped code.

There is less temptation to change test code to fit the code it tests without a good reason.

Test code should be modified much less frequently than the code it tests.

Tested code can be refactored more easily.

Tests for modules written in C must be in separate modules anyway, so why not be consistent?

If the testing strategy changes, there is no need to change the source code.

Re-using old test code

Some users will find that they have existing test code that they would like to run from unittest, without converting every old test function to a TestCase subclass.

For this reason, unittest provides a FunctionTestCase class. This subclass of TestCase can be used to wrap an existing test function. Set-up and tear-down functions can also be provided.

Given the following test function:

def testSomething():
    something = makeSomething()
    assert something.name is not None
    # ...

one can create an equivalent test case instance as follows, with optional set-up and tear-down methods:

testcase = unittest.FunctionTestCase(testSomething,
                                     setUp=makeSomethingDB,
                                     tearDown=deleteSomethingDB)

備註

Even though FunctionTestCase can be used to quickly convert an existing test base over to a unittest-based system, this approach is not recommended. Taking the time to set up proper TestCase subclasses will make future test refactorings infinitely easier.

In some cases, the existing tests may have been written using the doctest module. If so, doctest provides a DocTestSuite class that can automatically build unittest.TestSuite instances from the existing doctest-based tests.

Skipping tests and expected failures

在 3.1 版被加入.

Unittest supports skipping individual test methods and even whole classes of tests. In addition, it supports marking a test as an "expected failure," a test that is broken and will fail, but shouldn't be counted as a failure on a TestResult.

Skipping a test is simply a matter of using the skip() decorator or one of its conditional variants, calling TestCase.skipTest() within a setUp() or test method, or raising SkipTest directly.

Basic skipping looks like this:

class MyTestCase(unittest.TestCase):

    @unittest.skip("demonstrating skipping")
    def test_nothing(self):
        self.fail("shouldn't happen")

    @unittest.skipIf(mylib.__version__ < (1, 3),
                     "not supported in this library version")
    def test_format(self):
        # Tests that work for only a certain version of the library.
        pass

    @unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
    def test_windows_support(self):
        # windows specific testing code
        pass

    def test_maybe_skipped(self):
        if not external_resource_available():
            self.skipTest("external resource not available")
        # test code that depends on the external resource
        pass

This is the output of running the example above in verbose mode:

test_format (__main__.MyTestCase.test_format) ... skipped 'not supported in this library version'
test_nothing (__main__.MyTestCase.test_nothing) ... skipped 'demonstrating skipping'
test_maybe_skipped (__main__.MyTestCase.test_maybe_skipped) ... skipped 'external resource not available'
test_windows_support (__main__.MyTestCase.test_windows_support) ... skipped 'requires Windows'

----------------------------------------------------------------------
Ran 4 tests in 0.005s

OK (skipped=4)

Classes can be skipped just like methods:

@unittest.skip("showing class skipping")
class MySkippedTestCase(unittest.TestCase):
    def test_not_run(self):
        pass

TestCase.setUp() can also skip the test. This is useful when a resource that needs to be set up is not available.

Expected failures use the expectedFailure() decorator.

class ExpectedFailureTestCase(unittest.TestCase):
    @unittest.expectedFailure
    def test_fail(self):
        self.assertEqual(1, 0, "broken")

It's easy to roll your own skipping decorators by making a decorator that calls skip() on the test when it wants it to be skipped. This decorator skips the test unless the passed object has a certain attribute:

def skipUnlessHasattr(obj, attr):
    if hasattr(obj, attr):
        return lambda func: func
    return unittest.skip("{!r} doesn't have {!r}".format(obj, attr))

The following decorators and exception implement test skipping and expected failures:

@unittest.skip(reason)

Unconditionally skip the decorated test. reason should describe why the test is being skipped.

@unittest.skipIf(condition, reason)

Skip the decorated test if condition is true.

@unittest.skipUnless(condition, reason)

Skip the decorated test unless condition is true.

@unittest.expectedFailure

Mark the test as an expected failure or error. If the test fails or errors in the test function itself (rather than in one of the test fixture methods) then it will be considered a success. If the test passes, it will be considered a failure.

exception unittest.SkipTest(reason)

This exception is raised to skip a test.

Usually you can use TestCase.skipTest() or one of the skipping decorators instead of raising this directly.

Skipped tests will not have setUp() or tearDown() run around them. Skipped classes will not have setUpClass() or tearDownClass() run. Skipped modules will not have setUpModule() or tearDownModule() run.

Distinguishing test iterations using subtests

在 3.4 版被加入.

When there are very small differences among your tests, for instance some parameters, unittest allows you to distinguish them inside the body of a test method using the subTest() context manager.

舉例來說，以下測試：

class NumbersTest(unittest.TestCase):

    def test_even(self):
        """
        Test that numbers between 0 and 5 are all even.
        """
        for i in range(0, 6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)

會有以下輸出：

======================================================================
FAIL: test_even (__main__.NumbersTest.test_even) (i=1)
Test that numbers between 0 and 5 are all even.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 11, in test_even
    self.assertEqual(i % 2, 0)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1 != 0

======================================================================
FAIL: test_even (__main__.NumbersTest.test_even) (i=3)
Test that numbers between 0 and 5 are all even.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 11, in test_even
    self.assertEqual(i % 2, 0)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1 != 0

======================================================================
FAIL: test_even (__main__.NumbersTest.test_even) (i=5)
Test that numbers between 0 and 5 are all even.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 11, in test_even
    self.assertEqual(i % 2, 0)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1 != 0

Without using a subtest, execution would stop after the first failure, and the error would be less easy to diagnose because the value of i wouldn't be displayed:

======================================================================
FAIL: test_even (__main__.NumbersTest.test_even)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 32, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0

類別與函式

This section describes in depth the API of unittest.

Test cases

class unittest.TestCase(methodName='runTest')

Instances of the TestCase class represent the logical test units in the unittest universe. This class is intended to be used as a base class, with specific tests being implemented by concrete subclasses. This class implements the interface needed by the test runner to allow it to drive the tests, and methods that the test code can use to check for and report various kinds of failure.

Each instance of TestCase will run a single base method: the method named methodName. In most uses of TestCase, you will neither change the methodName nor reimplement the default runTest() method.

在 3.2 版的變更: TestCase can be instantiated successfully without providing a methodName. This makes it easier to experiment with TestCase from the interactive interpreter.

TestCase instances provide three groups of methods: one group used to run the test, another used by the test implementation to check conditions and report failures, and some inquiry methods allowing information about the test itself to be gathered.

Methods in the first group (running the test) are:

setUp()

Method called to prepare the test fixture. This is called immediately before calling the test method; other than AssertionError or SkipTest, any exception raised by this method will be considered an error rather than a test failure. The default implementation does nothing.

tearDown()

Method called immediately after the test method has been called and the result recorded. This is called even if the test method raised an exception, so the implementation in subclasses may need to be particularly careful about checking internal state. Any exception, other than AssertionError or SkipTest, raised by this method will be considered an additional error rather than a test failure (thus increasing the total number of reported errors). This method will only be called if the setUp() succeeds, regardless of the outcome of the test method. The default implementation does nothing.

setUpClass()

A class method called before tests in an individual class are run. setUpClass is called with the class as the only argument and must be decorated as a classmethod():

@classmethod
def setUpClass(cls):
    ...

更多細節請見 Class and Module Fixtures。

在 3.2 版被加入.

tearDownClass()

A class method called after tests in an individual class have run. tearDownClass is called with the class as the only argument and must be decorated as a classmethod():

@classmethod
def tearDownClass(cls):
    ...

更多細節請見 Class and Module Fixtures。

在 3.2 版被加入.

run(result=None)

Run the test, collecting the result into the TestResult object passed as result. If result is omitted or None, a temporary result object is created (by calling the defaultTestResult() method) and used. The result object is returned to run()'s caller.

The same effect may be had by simply calling the TestCase instance.

在 3.3 版的變更: Previous versions of run did not return the result. Neither did calling an instance.

skipTest(reason)

Calling this during a test method or setUp() skips the current test. See Skipping tests and expected failures for more information.

在 3.1 版被加入.

subTest(msg=None, **params)

Return a context manager which executes the enclosed code block as a subtest. msg and params are optional, arbitrary values which are displayed whenever a subtest fails, allowing you to identify them clearly.

A test case can contain any number of subtest declarations, and they can be arbitrarily nested.

更多資訊請見 Distinguishing test iterations using subtests。

在 3.4 版被加入.

debug()

Run the test without collecting the result. This allows exceptions raised by the test to be propagated to the caller, and can be used to support running tests under a debugger.

The TestCase class provides several assert methods to check for and report failures. The following table lists the most commonly used methods (see the tables below for more assert methods):

方法

Checks that

New in

assertEqual(a, b)

a == b

assertNotEqual(a, b)

a != b

assertTrue(x)

bool(x) is True

assertFalse(x)

bool(x) is False

assertIs(a, b)

a is b

3.1

assertIsNot(a, b)

a is not b

3.1

assertIsNone(x)

x is None

3.1

assertIsNotNone(x)

x is not None

3.1

assertIn(a, b)

a in b

3.1

assertNotIn(a, b)

a not in b

3.1

assertIsInstance(a, b)

isinstance(a, b)

3.2

assertNotIsInstance(a, b)

not isinstance(a, b)

3.2

assertIsSubclass(a, b)

issubclass(a, b)

3.14

assertNotIsSubclass(a, b)

not issubclass(a, b)

3.14

All the assert methods accept a msg argument that, if specified, is used as the error message on failure (see also longMessage). Note that the msg keyword argument can be passed to assertRaises(), assertRaisesRegex(), assertWarns(), assertWarnsRegex() only when they are used as a context manager.

assertEqual(first, second, msg=None)

Test that first and second are equal. If the values do not compare equal, the test will fail.

In addition, if first and second are the exact same type and one of list, tuple, dict, set, frozenset or str or any type that a subclass registers with addTypeEqualityFunc() the type-specific equality function will be called in order to generate a more useful default error message (see also the list of type-specific methods).

在 3.1 版的變更: Added the automatic calling of type-specific equality function.

在 3.2 版的變更: assertMultiLineEqual() added as the default type equality function for comparing strings.

assertNotEqual(first, second, msg=None)

Test that first and second are not equal. If the values do compare equal, the test will fail.

assertTrue(expr, msg=None)

assertFalse(expr, msg=None)

Test that expr is true (or false).

Note that this is equivalent to bool(expr) is True and not to expr is True (use assertIs(expr, True) for the latter). This method should also be avoided when more specific methods are available (e.g. assertEqual(a, b) instead of assertTrue(a == b)), because they provide a better error message in case of failure.

assertIs(first, second, msg=None)

assertIsNot(first, second, msg=None)

Test that first and second are (or are not) the same object.

在 3.1 版被加入.

assertIsNone(expr, msg=None)

assertIsNotNone(expr, msg=None)

Test that expr is (or is not) None.

在 3.1 版被加入.

assertIn(member, container, msg=None)

assertNotIn(member, container, msg=None)

Test that member is (or is not) in container.

在 3.1 版被加入.

assertIsInstance(obj, cls, msg=None)

assertNotIsInstance(obj, cls, msg=None)

Test that obj is (or is not) an instance of cls (which can be a class or a tuple of classes, as supported by isinstance()). To check for the exact type, use assertIs(type(obj), cls).

在 3.2 版被加入.

assertIsSubclass(cls, superclass, msg=None)

assertNotIsSubclass(cls, superclass, msg=None)

Test that cls is (or is not) a subclass of superclass (which can be a class or a tuple of classes, as supported by issubclass()). To check for the exact type, use assertIs(cls, superclass).

在 3.14 版被加入.

It is also possible to check the production of exceptions, warnings, and log messages using the following methods:

方法

Checks that

New in

assertRaises(exc, fun, *args, **kwds)

fun(*args, **kwds) 會引發 exc

assertRaisesRegex(exc, r, fun, *args, **kwds)

fun(*args, **kwds) raises exc and the message matches regex r

3.1

assertWarns(warn, fun, *args, **kwds)

fun(*args, **kwds) 會引發 warn

3.2

assertWarnsRegex(warn, r, fun, *args, **kwds)

fun(*args, **kwds) raises warn and the message matches regex r

3.2

assertLogs(logger, level)

The with block logs on logger with minimum level

3.4

assertNoLogs(logger, level)

The with block does not log on

logger with minimum level

3.10

assertRaises(exception, callable, *args, **kwds)

assertRaises(exception, *, msg=None)

Test that an exception is raised when callable is called with any positional or keyword arguments that are also passed to assertRaises(). The test passes if exception is raised, is an error if another exception is raised, or fails if no exception is raised. To catch any of a group of exceptions, a tuple containing the exception classes may be passed as exception.

If only the exception and possibly the msg arguments are given, return a context manager so that the code under test can be written inline rather than as a function:

with self.assertRaises(SomeException):
    do_something()

When used as a context manager, assertRaises() accepts the additional keyword argument msg.

The context manager will store the caught exception object in its exception attribute. This can be useful if the intention is to perform additional checks on the exception raised:

with self.assertRaises(SomeException) as cm:
    do_something()

the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)

在 3.1 版的變更: 新增 assertRaises() 可作為情境管理器使用的能力。

在 3.2 版的變更: 新增 exception 屬性。

在 3.3 版的變更: 新增作為情境管理器使用時的 msg 引數。

assertRaisesRegex(exception, regex, callable, *args, **kwds)

assertRaisesRegex(exception, regex, *, msg=None)

Like assertRaises() but also tests that regex matches on the string representation of the raised exception. regex may be a regular expression object or a string containing a regular expression suitable for use by re.search(). Examples:

self.assertRaisesRegex(ValueError, "invalid literal for.*XYZ'$",
                       int, 'XYZ')

或是：

with self.assertRaisesRegex(ValueError, 'literal'):
   int('XYZ')

在 3.1 版被加入: 以 assertRaisesRegexp 為名新增。

在 3.2 版的變更: 重新命名為 assertRaisesRegex()。

在 3.3 版的變更: 新增作為情境管理器使用時的 msg 引數。

assertWarns(warning, callable, *args, **kwds)

assertWarns(warning, *, msg=None)

Test that a warning is triggered when callable is called with any positional or keyword arguments that are also passed to assertWarns(). The test passes if warning is triggered and fails if it isn't. Any exception is an error. To catch any of a group of warnings, a tuple containing the warning classes may be passed as warnings.

If only the warning and possibly the msg arguments are given, return a context manager so that the code under test can be written inline rather than as a function:

with self.assertWarns(SomeWarning):
    do_something()

When used as a context manager, assertWarns() accepts the additional keyword argument msg.

The context manager will store the caught warning object in its warning attribute, and the source line which triggered the warnings in the filename and lineno attributes. This can be useful if the intention is to perform additional checks on the warning caught:

with self.assertWarns(SomeWarning) as cm:
    do_something()

self.assertIn('myfile.py', cm.filename)
self.assertEqual(320, cm.lineno)

This method works regardless of the warning filters in place when it is called.

在 3.2 版被加入.

在 3.3 版的變更: 新增作為情境管理器使用時的 msg 引數。

assertWarnsRegex(warning, regex, callable, *args, **kwds)

assertWarnsRegex(warning, regex, *, msg=None)

Like assertWarns() but also tests that regex matches on the message of the triggered warning. regex may be a regular expression object or a string containing a regular expression suitable for use by re.search(). Example:

self.assertWarnsRegex(DeprecationWarning,
                      r'legacy_function\(\) is deprecated',
                      legacy_function, 'XYZ')

或是：

with self.assertWarnsRegex(RuntimeWarning, 'unsafe frobnicating'):
    frobnicate('/etc/passwd')

在 3.2 版被加入.

在 3.3 版的變更: 新增作為情境管理器使用時的 msg 引數。

assertLogs(logger=None, level=None)

A context manager to test that at least one message is logged on the logger or one of its children, with at least the given level.

If given, logger should be a logging.Logger object or a str giving the name of a logger. The default is the root logger, which will catch all messages that were not blocked by a non-propagating descendent logger.

If given, level should be either a numeric logging level or its string equivalent (for example either "ERROR" or logging.ERROR). The default is logging.INFO.

The test passes if at least one message emitted inside the with block matches the logger and level conditions, otherwise it fails.

The object returned by the context manager is a recording helper which keeps tracks of the matching log messages. It has two attributes:

records

A list of logging.LogRecord objects of the matching log messages.

output

A list of str objects with the formatted output of matching messages.

範例：

with self.assertLogs('foo', level='INFO') as cm:
    logging.getLogger('foo').info('first message')
    logging.getLogger('foo.bar').error('second message')
self.assertEqual(cm.output, ['INFO:foo:first message',
                             'ERROR:foo.bar:second message'])

在 3.4 版被加入.

assertNoLogs(logger=None, level=None)

A context manager to test that no messages are logged on the logger or one of its children, with at least the given level.

If given, logger should be a logging.Logger object or a str giving the name of a logger. The default is the root logger, which will catch all messages.

If given, level should be either a numeric logging level or its string equivalent (for example either "ERROR" or logging.ERROR). The default is logging.INFO.

Unlike assertLogs(), nothing will be returned by the context manager.

在 3.10 版被加入.

There are also other methods used to perform more specific checks, such as:

方法

Checks that

New in

assertAlmostEqual(a, b)

round(a-b, 7) == 0

assertNotAlmostEqual(a, b)

round(a-b, 7) != 0

assertGreater(a, b)

a > b

3.1

assertGreaterEqual(a, b)

a >= b

3.1

assertLess(a, b)

a < b

3.1

assertLessEqual(a, b)

a <= b

3.1

assertRegex(s, r)

r.search(s)

3.1

assertNotRegex(s, r)

not r.search(s)

3.2

assertCountEqual(a, b)

a and b have the same elements in the same number, regardless of their order.

3.2

assertStartsWith(a, b)

a.startswith(b)

3.14

assertNotStartsWith(a, b)

not a.startswith(b)

3.14

assertEndsWith(a, b)

a.endswith(b)

3.14

assertNotEndsWith(a, b)

not a.endswith(b)

3.14

assertHasAttr(a, b)

hastattr(a, b)

3.14

assertNotHasAttr(a, b)

not hastattr(a, b)

3.14

assertAlmostEqual(first, second, places=7, msg=None, delta=None)

assertNotAlmostEqual(first, second, places=7, msg=None, delta=None)

Test that first and second are approximately (or not approximately) equal by computing the difference, rounding to the given number of decimal places (default 7), and comparing to zero. Note that these methods round the values to the given number of decimal places (i.e. like the round() function) and not significant digits.

If delta is supplied instead of places then the difference between first and second must be less or equal to (or greater than) delta.

Supplying both delta and places raises a TypeError.

在 3.2 版的變更: assertAlmostEqual() automatically considers almost equal objects that compare equal. assertNotAlmostEqual() automatically fails if the objects compare equal. Added the delta keyword argument.

assertGreater(first, second, msg=None)

assertGreaterEqual(first, second, msg=None)

assertLess(first, second, msg=None)

assertLessEqual(first, second, msg=None)

Test that first is respectively >, >=, < or <= than second depending on the method name. If not, the test will fail:

>>> self.assertGreaterEqual(3, 4)
AssertionError: "3" unexpectedly not greater than or equal to "4"

在 3.1 版被加入.

assertRegex(text, regex, msg=None)

assertNotRegex(text, regex, msg=None)

Test that a regex search matches (or does not match) text. In case of failure, the error message will include the pattern and the text (or the pattern and the part of text that unexpectedly matched). regex may be a regular expression object or a string containing a regular expression suitable for use by re.search().

在 3.1 版被加入: 以 assertRegexpMatches 為名新增。

在 3.2 版的變更: assertRegexpMatches() 方法已重新命名為 assertRegex()。

在 3.2 版被加入: assertNotRegex()。

assertCountEqual(first, second, msg=None)

Test that sequence first contains the same elements as second, regardless of their order. When they don't, an error message listing the differences between the sequences will be generated.

Duplicate elements are not ignored when comparing first and second. It verifies whether each element has the same count in both sequences. Equivalent to: assertEqual(Counter(list(first)), Counter(list(second))) but works with sequences of unhashable objects as well.

在 3.2 版被加入.

assertStartsWith(s, prefix, msg=None)

assertNotStartsWith(s, prefix, msg=None)

Test that the Unicode or byte string s starts (or does not start) with a prefix. prefix can also be a tuple of strings to try.

在 3.14 版被加入.

assertEndsWith(s, suffix, msg=None)

assertNotEndsWith(s, suffix, msg=None)

Test that the Unicode or byte string s ends (or does not end) with a suffix. suffix can also be a tuple of strings to try.

在 3.14 版被加入.

assertHasAttr(obj, name, msg=None)

assertNotHasAttr(obj, name, msg=None)

Test that the object obj has (or has not) an attribute name.

在 3.14 版被加入.

The assertEqual() method dispatches the equality check for objects of the same type to different type-specific methods. These methods are already implemented for most of the built-in types, but it's also possible to register new methods using addTypeEqualityFunc():

addTypeEqualityFunc(typeobj, function)

Registers a type-specific method called by assertEqual() to check if two objects of exactly the same typeobj (not subclasses) compare equal. function must take two positional arguments and a third msg=None keyword argument just as assertEqual() does. It must raise self.failureException(msg) when inequality between the first two parameters is detected -- possibly providing useful information and explaining the inequalities in details in the error message.

在 3.1 版被加入.

The list of type-specific methods automatically used by assertEqual() are summarized in the following table. Note that it's usually not necessary to invoke these methods directly.

方法

Used to compare

New in

assertMultiLineEqual(a, b)

字串

3.1

assertSequenceEqual(a, b)

序列

3.1

assertListEqual(a, b)

串列

3.1

assertTupleEqual(a, b)

元組

3.1

assertSetEqual(a, b)

集合或凍結集合

3.1

assertDictEqual(a, b)

字典

3.1

assertMultiLineEqual(first, second, msg=None)

Test that the multiline string first is equal to the string second. When not equal a diff of the two strings highlighting the differences will be included in the error message. This method is used by default when comparing strings with assertEqual().

在 3.1 版被加入.

assertSequenceEqual(first, second, msg=None, seq_type=None)

Tests that two sequences are equal. If a seq_type is supplied, both first and second must be instances of seq_type or a failure will be raised. If the sequences are different an error message is constructed that shows the difference between the two.

This method is not called directly by assertEqual(), but it's used to implement assertListEqual() and assertTupleEqual().

在 3.1 版被加入.

assertListEqual(first, second, msg=None)

assertTupleEqual(first, second, msg=None)

Tests that two lists or tuples are equal. If not, an error message is constructed that shows only the differences between the two. An error is also raised if either of the parameters are of the wrong type. These methods are used by default when comparing lists or tuples with assertEqual().

在 3.1 版被加入.

assertSetEqual(first, second, msg=None)

Tests that two sets are equal. If not, an error message is constructed that lists the differences between the sets. This method is used by default when comparing sets or frozensets with assertEqual().

Fails if either of first or second does not have a difference() method.

在 3.1 版被加入.

assertDictEqual(first, second, msg=None)

Test that two dictionaries are equal. If not, an error message is constructed that shows the differences in the dictionaries. This method will be used by default to compare dictionaries in calls to assertEqual().

在 3.1 版被加入.

Finally the TestCase provides the following methods and attributes:

fail(msg=None)

Signals a test failure unconditionally, with msg or None for the error message.

failureException

This class attribute gives the exception raised by the test method. If a test framework needs to use a specialized exception, possibly to carry additional information, it must subclass this exception in order to "play fair" with the framework. The initial value of this attribute is AssertionError.

longMessage

This class attribute determines what happens when a custom failure message is passed as the msg argument to an assertXYY call that fails. True is the default value. In this case, the custom message is appended to the end of the standard failure message. When set to False, the custom message replaces the standard message.

The class setting can be overridden in individual test methods by assigning an instance attribute, self.longMessage, to True or False before calling the assert methods.

The class setting gets reset before each test call.

在 3.1 版被加入.

maxDiff

This attribute controls the maximum length of diffs output by assert methods that report diffs on failure. It defaults to 80*8 characters. Assert methods affected by this attribute are assertSequenceEqual() (including all the sequence comparison methods that delegate to it), assertDictEqual() and assertMultiLineEqual().

Setting maxDiff to None means that there is no maximum length of diffs.

在 3.2 版被加入.

Testing frameworks can use the following methods to collect information on the test:

countTestCases()

Return the number of tests represented by this test object. For TestCase instances, this will always be 1.

defaultTestResult()

Return an instance of the test result class that should be used for this test case class (if no other result instance is provided to the run() method).

For TestCase instances, this will always be an instance of TestResult; subclasses of TestCase should override this as necessary.

id()

Return a string identifying the specific test case. This is usually the full name of the test method, including the module and class name.

shortDescription()

Returns a description of the test, or None if no description has been provided. The default implementation of this method returns the first line of the test method's docstring, if available, or None.

在 3.1 版的變更: In 3.1 this was changed to add the test name to the short description even in the presence of a docstring. This caused compatibility issues with unittest extensions and adding the test name was moved to the TextTestResult in Python 3.2.

addCleanup(function, /, *args, **kwargs)

Add a function to be called after tearDown() to cleanup resources used during the test. Functions will be called in reverse order to the order they are added (LIFO). They are called with any arguments and keyword arguments passed into addCleanup() when they are added.

If setUp() fails, meaning that tearDown() is not called, then any cleanup functions added will still be called.

在 3.1 版被加入.

enterContext(cm)

Enter the supplied context manager. If successful, also add its __exit__() method as a cleanup function by addCleanup() and return the result of the __enter__() method.

在 3.11 版被加入.

doCleanups()

This method is called unconditionally after tearDown(), or after setUp() if setUp() raises an exception.

It is responsible for calling all the cleanup functions added by addCleanup(). If you need cleanup functions to be called prior to tearDown() then you can call doCleanups() yourself.

doCleanups() pops methods off the stack of cleanup functions one at a time, so it can be called at any time.

在 3.1 版被加入.

classmethod addClassCleanup(function, /, *args, **kwargs)

Add a function to be called after tearDownClass() to cleanup resources used during the test class. Functions will be called in reverse order to the order they are added (LIFO). They are called with any arguments and keyword arguments passed into addClassCleanup() when they are added.

If setUpClass() fails, meaning that tearDownClass() is not called, then any cleanup functions added will still be called.

在 3.8 版被加入.

classmethod enterClassContext(cm)

Enter the supplied context manager. If successful, also add its __exit__() method as a cleanup function by addClassCleanup() and return the result of the __enter__() method.

在 3.11 版被加入.

classmethod doClassCleanups()

This method is called unconditionally after tearDownClass(), or after setUpClass() if setUpClass() raises an exception.

It is responsible for calling all the cleanup functions added by addClassCleanup(). If you need cleanup functions to be called prior to tearDownClass() then you can call doClassCleanups() yourself.

doClassCleanups() pops methods off the stack of cleanup functions one at a time, so it can be called at any time.

在 3.8 版被加入.

class unittest.IsolatedAsyncioTestCase(methodName='runTest')

This class provides an API similar to TestCase and also accepts coroutines as test functions.

在 3.8 版被加入.

loop_factory

The loop_factory passed to asyncio.Runner. Override in subclasses with asyncio.EventLoop to avoid using the asyncio policy system.

在 3.13 版被加入.

async asyncSetUp()

Method called to prepare the test fixture. This is called after TestCase.setUp(). This is called immediately before calling the test method; other than AssertionError or SkipTest, any exception raised by this method will be considered an error rather than a test failure. The default implementation does nothing.

async asyncTearDown()

Method called immediately after the test method has been called and the result recorded. This is called before tearDown(). This is called even if the test method raised an exception, so the implementation in subclasses may need to be particularly careful about checking internal state. Any exception, other than AssertionError or SkipTest, raised by this method will be considered an additional error rather than a test failure (thus increasing the total number of reported errors). This method will only be called if the asyncSetUp() succeeds, regardless of the outcome of the test method. The default implementation does nothing.

addAsyncCleanup(function, /, *args, **kwargs)

This method accepts a coroutine that can be used as a cleanup function.

async enterAsyncContext(cm)

Enter the supplied asynchronous context manager. If successful, also add its __aexit__() method as a cleanup function by addAsyncCleanup() and return the result of the __aenter__() method.

在 3.11 版被加入.

run(result=None)

Sets up a new event loop to run the test, collecting the result into the TestResult object passed as result. If result is omitted or None, a temporary result object is created (by calling the defaultTestResult() method) and used. The result object is returned to run()'s caller. At the end of the test all the tasks in the event loop are cancelled.

An example illustrating the order:

from unittest import IsolatedAsyncioTestCase

events = []

class Test(IsolatedAsyncioTestCase):

    def setUp(self):
        events.append("setUp")

    async def asyncSetUp(self):
        self._async_connection = await AsyncConnection()
        events.append("asyncSetUp")

    async def test_response(self):
        events.append("test_response")
        response = await self._async_connection.get("https://example.com")
        self.assertEqual(response.status_code, 200)
        self.addAsyncCleanup(self.on_cleanup)

    def tearDown(self):
        events.append("tearDown")

    async def asyncTearDown(self):
        await self._async_connection.close()
        events.append("asyncTearDown")

    async def on_cleanup(self):
        events.append("cleanup")

if __name__ == "__main__":
    unittest.main()

After running the test, events would contain ["setUp", "asyncSetUp", "test_response", "asyncTearDown", "tearDown", "cleanup"].

class unittest.FunctionTestCase(testFunc, setUp=None, tearDown=None, description=None)

This class implements the portion of the TestCase interface which allows the test runner to drive the test, but does not provide the methods which test code can use to check and report errors. This is used to create test cases using legacy test code, allowing it to be integrated into a unittest-based test framework.

Grouping tests

class unittest.TestSuite(tests=())

This class represents an aggregation of individual test cases and test suites. The class presents the interface needed by the test runner to allow it to be run as any other test case. Running a TestSuite instance is the same as iterating over the suite, running each test individually.

If tests is given, it must be an iterable of individual test cases or other test suites that will be used to build the suite initially. Additional methods are provided to add test cases and suites to the collection later on.

TestSuite objects behave much like TestCase objects, except they do not actually implement a test. Instead, they are used to aggregate tests into groups of tests that should be run together. Some additional methods are available to add tests to TestSuite instances:

addTest(test)

Add a TestCase or TestSuite to the suite.

addTests(tests)

Add all the tests from an iterable of TestCase and TestSuite instances to this test suite.

This is equivalent to iterating over tests, calling addTest() for each element.

TestSuite shares the following methods with TestCase:

run(result)

Run the tests associated with this suite, collecting the result into the test result object passed as result. Note that unlike TestCase.run(), TestSuite.run() requires the result object to be passed in.

debug()

Run the tests associated with this suite without collecting the result. This allows exceptions raised by the test to be propagated to the caller and can be used to support running tests under a debugger.

countTestCases()

Return the number of tests represented by this test object, including all individual tests and sub-suites.

__iter__()

Tests grouped by a TestSuite are always accessed by iteration. Subclasses can lazily provide tests by overriding __iter__(). Note that this method may be called several times on a single suite (for example when counting tests or comparing for equality) so the tests returned by repeated iterations before TestSuite.run() must be the same for each call iteration. After TestSuite.run(), callers should not rely on the tests returned by this method unless the caller uses a subclass that overrides TestSuite._removeTestAtIndex() to preserve test references.

在 3.2 版的變更: In earlier versions the TestSuite accessed tests directly rather than through iteration, so overriding __iter__() wasn't sufficient for providing tests.

在 3.4 版的變更: In earlier versions the TestSuite held references to each TestCase after TestSuite.run(). Subclasses can restore that behavior by overriding TestSuite._removeTestAtIndex().

In the typical usage of a TestSuite object, the run() method is invoked by a TestRunner rather than by the end-user test harness.

Loading and running tests

class unittest.TestLoader

The TestLoader class is used to create test suites from classes and modules. Normally, there is no need to create an instance of this class; the unittest module provides an instance that can be shared as unittest.defaultTestLoader. Using a subclass or instance, however, allows customization of some configurable properties.

TestLoader objects have the following attributes:

errors

A list of the non-fatal errors encountered while loading tests. Not reset by the loader at any point. Fatal errors are signalled by the relevant method raising an exception to the caller. Non-fatal errors are also indicated by a synthetic test that will raise the original error when run.

在 3.5 版被加入.

TestLoader objects have the following methods:

loadTestsFromTestCase(testCaseClass)

Return a suite of all test cases contained in the TestCase-derived testCaseClass.

A test case instance is created for each method named by getTestCaseNames(). By default these are the method names beginning with test. If getTestCaseNames() returns no methods, but the runTest() method is implemented, a single test case is created for that method instead.

loadTestsFromModule(module, *, pattern=None)

Return a suite of all test cases contained in the given module. This method searches module for classes derived from TestCase and creates an instance of the class for each test method defined for the class.

備註

While using a hierarchy of TestCase-derived classes can be convenient in sharing fixtures and helper functions, defining test methods on base classes that are not intended to be instantiated directly does not play well with this method. Doing so, however, can be useful when the fixtures are different and defined in subclasses.

If a module provides a load_tests function it will be called to load the tests. This allows modules to customize test loading. This is the load_tests protocol. The pattern argument is passed as the third argument to load_tests.

在 3.2 版的變更: Support for load_tests added.

在 3.5 版的變更: Support for a keyword-only argument pattern has been added.

在 3.12 版的變更: The undocumented and unofficial use_load_tests parameter has been removed.

loadTestsFromName(name, module=None)

Return a suite of all test cases given a string specifier.

The specifier name is a "dotted name" that may resolve either to a module, a test case class, a test method within a test case class, a TestSuite instance, or a callable object which returns a TestCase or TestSuite instance. These checks are applied in the order listed here; that is, a method on a possible test case class will be picked up as "a test method within a test case class", rather than "a callable object".

For example, if you have a module SampleTests containing a TestCase-derived class SampleTestCase with three test methods (test_one(), test_two(), and test_three()), the specifier 'SampleTests.SampleTestCase' would cause this method to return a suite which will run all three test methods. Using the specifier 'SampleTests.SampleTestCase.test_two' would cause it to return a test suite which will run only the test_two() test method. The specifier can refer to modules and packages which have not been imported; they will be imported as a side-effect.

The method optionally resolves name relative to the given module.

在 3.5 版的變更: If an ImportError or AttributeError occurs while traversing name then a synthetic test that raises that error when run will be returned. These errors are included in the errors accumulated by self.errors.

loadTestsFromNames(names, module=None)

Similar to loadTestsFromName(), but takes a sequence of names rather than a single name. The return value is a test suite which supports all the tests defined for each name.

getTestCaseNames(testCaseClass)

Return a sorted sequence of method names found within testCaseClass; this should be a subclass of TestCase.

discover(start_dir, pattern='test*.py', top_level_dir=None)

Find all the test modules by recursing into subdirectories from the specified start directory, and return a TestSuite object containing them. Only test files that match pattern will be loaded. (Using shell style pattern matching.) Only module names that are importable (i.e. are valid Python identifiers) will be loaded.

All test modules must be importable from the top level of the project. If the start directory is not the top level directory then top_level_dir must be specified separately.

If importing a module fails, for example due to a syntax error, then this will be recorded as a single error and discovery will continue. If the import failure is due to SkipTest being raised, it will be recorded as a skip instead of an error.

If a package (a directory containing a file named __init__.py) is found, the package will be checked for a load_tests function. If this exists then it will be called package.load_tests(loader, tests, pattern). Test discovery takes care to ensure that a package is only checked for tests once during an invocation, even if the load_tests function itself calls loader.discover.

If load_tests exists then discovery does not recurse into the package, load_tests is responsible for loading all tests in the package.

The pattern is deliberately not stored as a loader attribute so that packages can continue discovery themselves.

top_level_dir is stored internally, and used as a default to any nested calls to discover(). That is, if a package's load_tests calls loader.discover(), it does not need to pass this argument.

start_dir can be a dotted module name as well as a directory.

在 3.2 版被加入.

在 3.4 版的變更: Modules that raise SkipTest on import are recorded as skips, not errors.

start_dir can be a namespace packages.

Paths are sorted before being imported so that execution order is the same even if the underlying file system's ordering is not dependent on file name.

在 3.5 版的變更: Found packages are now checked for load_tests regardless of whether their path matches pattern, because it is impossible for a package name to match the default pattern.

在 3.11 版的變更: start_dir can not be a namespace packages. It has been broken since Python 3.7, and Python 3.11 officially removes it.

在 3.13 版的變更: top_level_dir is only stored for the duration of discover call.

在 3.14 版的變更: start_dir can once again be a namespace package.

The following attributes of a TestLoader can be configured either by subclassing or assignment on an instance:

testMethodPrefix

String giving the prefix of method names which will be interpreted as test methods. The default value is 'test'.

This affects getTestCaseNames() and all the loadTestsFrom* methods.

sortTestMethodsUsing

Function to be used to compare method names when sorting them in getTestCaseNames() and all the loadTestsFrom* methods.

suiteClass

Callable object that constructs a test suite from a list of tests. No methods on the resulting object are needed. The default value is the TestSuite class.

This affects all the loadTestsFrom* methods.

testNamePatterns

List of Unix shell-style wildcard test name patterns that test methods have to match to be included in test suites (see -k option).

If this attribute is not None (the default), all test methods to be included in test suites must match one of the patterns in this list. Note that matches are always performed using fnmatch.fnmatchcase(), so unlike patterns passed to the -k option, simple substring patterns will have to be converted using * wildcards.

This affects all the loadTestsFrom* methods.

在 3.7 版被加入.

class unittest.TestResult

This class is used to compile information about which tests have succeeded and which have failed.

A TestResult object stores the results of a set of tests. The TestCase and TestSuite classes ensure that results are properly recorded; test authors do not need to worry about recording the outcome of tests.

Testing frameworks built on top of unittest may want access to the TestResult object generated by running a set of tests for reporting purposes; a TestResult instance is returned by the TestRunner.run() method for this purpose.

TestResult instances have the following attributes that will be of interest when inspecting the results of running a set of tests:

errors

A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents a test which raised an unexpected exception.

failures

A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents a test where a failure was explicitly signalled using the assert* methods.

skipped

A list containing 2-tuples of TestCase instances and strings holding the reason for skipping the test.

在 3.1 版被加入.

expectedFailures

A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents an expected failure or error of the test case.

unexpectedSuccesses

A list containing TestCase instances that were marked as expected failures, but succeeded.

collectedDurations

A list containing 2-tuples of test case names and floats representing the elapsed time of each test which was run.

在 3.12 版被加入.

shouldStop

Set to True when the execution of tests should stop by stop().

testsRun

The total number of tests run so far.

buffer

If set to true, sys.stdout and sys.stderr will be buffered in between startTest() and stopTest() being called. Collected output will only be echoed onto the real sys.stdout and sys.stderr if the test fails or errors. Any output is also attached to the failure / error message.

在 3.2 版被加入.

failfast

If set to true stop() will be called on the first failure or error, halting the test run.

在 3.2 版被加入.

tb_locals

If set to true then local variables will be shown in tracebacks.

在 3.5 版被加入.

wasSuccessful()

Return True if all tests run so far have passed, otherwise returns False.

在 3.4 版的變更: Returns False if there were any unexpectedSuccesses from tests marked with the expectedFailure() decorator.

stop()

This method can be called to signal that the set of tests being run should be aborted by setting the shouldStop attribute to True. TestRunner objects should respect this flag and return without running any additional tests.

For example, this feature is used by the TextTestRunner class to stop the test framework when the user signals an interrupt from the keyboard. Interactive tools which provide TestRunner implementations can use this in a similar manner.

The following methods of the TestResult class are used to maintain the internal data structures, and may be extended in subclasses to support additional reporting requirements. This is particularly useful in building tools which support interactive reporting while tests are being run.

startTest(test)

Called when the test case test is about to be run.

stopTest(test)

Called after the test case test has been executed, regardless of the outcome.

startTestRun()

Called once before any tests are executed.

在 3.1 版被加入.

stopTestRun()

Called once after all tests are executed.

在 3.1 版被加入.

addError(test, err)

Called when the test case test raises an unexpected exception. err is a tuple of the form returned by sys.exc_info(): (type, value, traceback).

The default implementation appends a tuple (test, formatted_err) to the instance's errors attribute, where formatted_err is a formatted traceback derived from err.

addFailure(test, err)

Called when the test case test signals a failure. err is a tuple of the form returned by sys.exc_info(): (type, value, traceback).

The default implementation appends a tuple (test, formatted_err) to the instance's failures attribute, where formatted_err is a formatted traceback derived from err.

addSuccess(test)

Called when the test case test succeeds.

The default implementation does nothing.

addSkip(test, reason)

Called when the test case test is skipped. reason is the reason the test gave for skipping.

The default implementation appends a tuple (test, reason) to the instance's skipped attribute.

addExpectedFailure(test, err)

Called when the test case test fails or errors, but was marked with the expectedFailure() decorator.

The default implementation appends a tuple (test, formatted_err) to the instance's expectedFailures attribute, where formatted_err is a formatted traceback derived from err.

addUnexpectedSuccess(test)

Called when the test case test was marked with the expectedFailure() decorator, but succeeded.

The default implementation appends the test to the instance's unexpectedSuccesses attribute.

addSubTest(test, subtest, outcome)

Called when a subtest finishes. test is the test case corresponding to the test method. subtest is a custom TestCase instance describing the subtest.

If outcome is None, the subtest succeeded. Otherwise, it failed with an exception where outcome is a tuple of the form returned by sys.exc_info(): (type, value, traceback).

The default implementation does nothing when the outcome is a success, and records subtest failures as normal failures.

在 3.4 版被加入.

addDuration(test, elapsed)

Called when the test case finishes. elapsed is the time represented in seconds, and it includes the execution of cleanup functions.

在 3.12 版被加入.

class unittest.TextTestResult(stream, descriptions, verbosity, *, durations=None)

A concrete implementation of TestResult used by the TextTestRunner. Subclasses should accept **kwargs to ensure compatibility as the interface changes.

在 3.2 版被加入.

在 3.12 版的變更: 新增 durations 關鍵字參數。

unittest.defaultTestLoader

Instance of the TestLoader class intended to be shared. If no customization of the TestLoader is needed, this instance can be used instead of repeatedly creating new instances.

class unittest.TextTestRunner(stream=None, descriptions=True, verbosity=1, failfast=False, buffer=False, resultclass=None, warnings=None, *, tb_locals=False, durations=None)

A basic test runner implementation that outputs results to a stream. If stream is None, the default, sys.stderr is used as the output stream. This class has a few configurable parameters, but is essentially very simple. Graphical applications which run test suites should provide alternate implementations. Such implementations should accept **kwargs as the interface to construct runners changes when features are added to unittest.

By default this runner shows DeprecationWarning, PendingDeprecationWarning, ResourceWarning and ImportWarning even if they are ignored by default. This behavior can be overridden using Python's -Wd or -Wa options (see Warning control) and leaving warnings to None.

在 3.2 版的變更: 新增 warnings 參數。

在 3.2 版的變更: The default stream is set to sys.stderr at instantiation time rather than import time.

在 3.5 版的變更: 新增 tb_locals 參數。

在 3.12 版的變更: 新增 durations 參數。

_makeResult()

This method returns the instance of TestResult used by run(). It is not intended to be called directly, but can be overridden in subclasses to provide a custom TestResult.

_makeResult() instantiates the class or callable passed in the TextTestRunner constructor as the resultclass argument. It defaults to TextTestResult if no resultclass is provided. The result class is instantiated with the following arguments:

stream, descriptions, verbosity

run(test)

This method is the main public interface to the TextTestRunner. This method takes a TestSuite or TestCase instance. A TestResult is created by calling _makeResult() and the test(s) are run and the results printed to stdout.

unittest.main(module='__main__', defaultTest=None, argv=None, testRunner=None, testLoader=unittest.defaultTestLoader, exit=True, verbosity=1, failfast=None, catchbreak=None, buffer=None, warnings=None)

A command-line program that loads a set of tests from module and runs them; this is primarily for making test modules conveniently executable. The simplest use for this function is to include the following line at the end of a test script:

if __name__ == '__main__':
    unittest.main()

You can run tests with more detailed information by passing in the verbosity argument:

if __name__ == '__main__':
    unittest.main(verbosity=2)

The defaultTest argument is either the name of a single test or an iterable of test names to run if no test names are specified via argv. If not specified or None and no test names are provided via argv, all tests found in module are run.

The argv argument can be a list of options passed to the program, with the first element being the program name. If not specified or None, the values of sys.argv are used.

The testRunner argument can either be a test runner class or an already created instance of it. By default main calls sys.exit() with an exit code indicating success (0) or failure (1) of the tests run. An exit code of 5 indicates that no tests were run or skipped.

The testLoader argument has to be a TestLoader instance, and defaults to defaultTestLoader.

main supports being used from the interactive interpreter by passing in the argument exit=False. This displays the result on standard output without calling sys.exit():

>>> from unittest import main
>>> main(module='test_module', exit=False)

The failfast, catchbreak and buffer parameters have the same effect as the same-name command-line options.

The warnings argument specifies the warning filter that should be used while running the tests. If it's not specified, it will remain None if a -W option is passed to python (see Warning control), otherwise it will be set to 'default'.

Calling main returns an object with the result attribute that contains the result of the tests run as a unittest.TestResult.

在 3.1 版的變更: 新增 exit 參數。

在 3.2 版的變更: The verbosity, failfast, catchbreak, buffer and warnings parameters were added.

在 3.4 版的變更: The defaultTest parameter was changed to also accept an iterable of test names.

load_tests 協定

在 3.2 版被加入.

Modules or packages can customize how tests are loaded from them during normal test runs or test discovery by implementing a function called load_tests.

If a test module defines load_tests it will be called by TestLoader.loadTestsFromModule() with the following arguments:

load_tests(loader, standard_tests, pattern)

where pattern is passed straight through from loadTestsFromModule. It defaults to None.

它應該回傳一個 TestSuite。

loader is the instance of TestLoader doing the loading. standard_tests are the tests that would be loaded by default from the module. It is common for test modules to only want to add or remove tests from the standard set of tests. The third argument is used when loading packages as part of test discovery.

A typical load_tests function that loads tests from a specific set of TestCase classes may look like:

test_cases = (TestCase1, TestCase2, TestCase3)

def load_tests(loader, tests, pattern):
    suite = TestSuite()
    for test_class in test_cases:
        tests = loader.loadTestsFromTestCase(test_class)
        suite.addTests(tests)
    return suite

If discovery is started in a directory containing a package, either from the command line or by calling TestLoader.discover(), then the package __init__.py will be checked for load_tests. If that function does not exist, discovery will recurse into the package as though it were just another directory. Otherwise, discovery of the package's tests will be left up to load_tests which is called with the following arguments:

load_tests(loader, standard_tests, pattern)

This should return a TestSuite representing all the tests from the package. (standard_tests will only contain tests collected from __init__.py.)

Because the pattern is passed into load_tests the package is free to continue (and potentially modify) test discovery. A 'do nothing' load_tests function for a test package would look like:

def load_tests(loader, standard_tests, pattern):
    # top level directory cached on loader instance
    this_dir = os.path.dirname(__file__)
    package_tests = loader.discover(start_dir=this_dir, pattern=pattern)
    standard_tests.addTests(package_tests)
    return standard_tests

在 3.5 版的變更: Discovery no longer checks package names for matching pattern due to the impossibility of package names matching the default pattern.

Class and Module Fixtures

Class and module level fixtures are implemented in TestSuite. When the test suite encounters a test from a new class then tearDownClass() from the previous class (if there is one) is called, followed by setUpClass() from the new class.

Similarly if a test is from a different module from the previous test then tearDownModule from the previous module is run, followed by setUpModule from the new module.

After all the tests have run the final tearDownClass and tearDownModule are run.

Note that shared fixtures do not play well with [potential] features like test parallelization and they break test isolation. They should be used with care.

The default ordering of tests created by the unittest test loaders is to group all tests from the same modules and classes together. This will lead to setUpClass / setUpModule (etc) being called exactly once per class and module. If you randomize the order, so that tests from different modules and classes are adjacent to each other, then these shared fixture functions may be called multiple times in a single test run.

Shared fixtures are not intended to work with suites with non-standard ordering. A BaseTestSuite still exists for frameworks that don't want to support shared fixtures.

If there are any exceptions raised during one of the shared fixture functions the test is reported as an error. Because there is no corresponding test instance an _ErrorHolder object (that has the same interface as a TestCase) is created to represent the error. If you are just using the standard unittest test runner then this detail doesn't matter, but if you are a framework author it may be relevant.

setUpClass 和 tearDownClass

These must be implemented as class methods:

import unittest

class Test(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        cls._connection = createExpensiveConnectionObject()

    @classmethod
    def tearDownClass(cls):
        cls._connection.destroy()

If you want the setUpClass and tearDownClass on base classes called then you must call up to them yourself. The implementations in TestCase are empty.

If an exception is raised during a setUpClass then the tests in the class are not run and the tearDownClass is not run. Skipped classes will not have setUpClass or tearDownClass run. If the exception is a SkipTest exception then the class will be reported as having been skipped instead of as an error.

setUpModule 和 tearDownModule

These should be implemented as functions:

def setUpModule():
    createConnection()

def tearDownModule():
    closeConnection()

If an exception is raised in a setUpModule then none of the tests in the module will be run and the tearDownModule will not be run. If the exception is a SkipTest exception then the module will be reported as having been skipped instead of as an error.

To add cleanup code that must be run even in the case of an exception, use addModuleCleanup:

unittest.addModuleCleanup(function, /, *args, **kwargs)

Add a function to be called after tearDownModule() to cleanup resources used during the test class. Functions will be called in reverse order to the order they are added (LIFO). They are called with any arguments and keyword arguments passed into addModuleCleanup() when they are added.

If setUpModule() fails, meaning that tearDownModule() is not called, then any cleanup functions added will still be called.

在 3.8 版被加入.

unittest.enterModuleContext(cm)

Enter the supplied context manager. If successful, also add its __exit__() method as a cleanup function by addModuleCleanup() and return the result of the __enter__() method.

在 3.11 版被加入.

unittest.doModuleCleanups()

This function is called unconditionally after tearDownModule(), or after setUpModule() if setUpModule() raises an exception.

It is responsible for calling all the cleanup functions added by addModuleCleanup(). If you need cleanup functions to be called prior to tearDownModule() then you can call doModuleCleanups() yourself.

doModuleCleanups() pops methods off the stack of cleanup functions one at a time, so it can be called at any time.

在 3.8 版被加入.

Signal Handling

在 3.2 版被加入.

The -c/--catch command-line option to unittest, along with the catchbreak parameter to unittest.main(), provide more friendly handling of control-C during a test run. With catch break behavior enabled control-C will allow the currently running test to complete, and the test run will then end and report all the results so far. A second control-c will raise a KeyboardInterrupt in the usual way.

The control-c handling signal handler attempts to remain compatible with code or tests that install their own signal.SIGINT handler. If the unittest handler is called but isn't the installed signal.SIGINT handler, i.e. it has been replaced by the system under test and delegated to, then it calls the default handler. This will normally be the expected behavior by code that replaces an installed handler and delegates to it. For individual tests that need unittest control-c handling disabled the removeHandler() decorator can be used.

There are a few utility functions for framework authors to enable control-c handling functionality within test frameworks.

unittest.installHandler()

Install the control-c handler. When a signal.SIGINT is received (usually in response to the user pressing control-c) all registered results have stop() called.

unittest.registerResult(result)

Register a TestResult object for control-c handling. Registering a result stores a weak reference to it, so it doesn't prevent the result from being garbage collected.

Registering a TestResult object has no side-effects if control-c handling is not enabled, so test frameworks can unconditionally register all results they create independently of whether or not handling is enabled.

unittest.removeResult(result)

Remove a registered result. Once a result has been removed then stop() will no longer be called on that result object in response to a control-c.

unittest.removeHandler(function=None)

When called without arguments this function removes the control-c handler if it has been installed. This function can also be used as a test decorator to temporarily remove the handler while the test is being executed:

@unittest.removeHandler
def test_signal_handling(self):
    ...

unittest.mock — mock 物件函式庫

在 3.3 版被加入.

原始碼：Lib/unittest/mock.py [https://github.com/python/cpython/tree/3.14/Lib/unittest/mock.py]

unittest.mock 在 Python 中是一個用於進行測試的函式庫。 它允許你用 mock 物件在測試中替換部分系統，並判定它們是如何被使用的。

unittest.mock 提供了一個以 Mock 為核心的類別，去除在測試中建立大量 stubs 的需求。 在執行動作之後，你可以判定哪些 method （方法）／屬性被使用，以及有哪些引數被呼叫。 你還可以用常規的方式指定回傳值與設定所需的屬性。

此外，mock 還提供了一個 patch() 裝飾器，用於 patching 測試範圍內對 module（模組）以及 class（類別）級別的屬性，以及用於建立唯一物件的 sentinel。有關如何使用 Mock、MagicMock 和 patch() 的一些範例，請參閱快速導引。

Mock 被設計用於與 unittest 一起使用，並且基於 「action（操作） -> assertion（判定）」 模式，而不是許多 mocking 框架使用的 「record（記錄） -> replay（重播）」 模式。

對於早期版本的 Python，有一個 backport（向後移植的）unittest.mock 可以使用，可從 PyPI 下載 mock [https://pypi.org/project/mock/]。

快速導引

Mock 和 MagicMock 物件在你存取它們時建立所有屬性和 method（方法），並儲存它們如何被使用的詳細訊息。你可以配置它們，以指定回傳值或限制可用的屬性，然後對它們的使用方式做出判定：

>>> from unittest.mock import MagicMock
>>> thing = ProductionClass()
>>> thing.method = MagicMock(return_value=3)
>>> thing.method(3, 4, 5, key='value')
3
>>> thing.method.assert_called_with(3, 4, 5, key='value')

side_effect 允許你執行 side effects，包含在 mock 被呼叫時引發例外：

>>> from unittest.mock import Mock
>>> mock = Mock(side_effect=KeyError('foo'))
>>> mock()
Traceback (most recent call last):
 ...
KeyError: 'foo'

>>> values = {'a': 1, 'b': 2, 'c': 3}
>>> def side_effect(arg):
...     return values[arg]
...
>>> mock.side_effect = side_effect
>>> mock('a'), mock('b'), mock('c')
(1, 2, 3)
>>> mock.side_effect = [5, 4, 3, 2, 1]
>>> mock(), mock(), mock()
(5, 4, 3)

Mock 有許多其他方法可以讓你配置與控制它的行為。例如，spec 引數可以配置 mock ，讓其從另一個物件取得規格。嘗試讀取 mock 中不存在於規格中的屬性或方法將會失敗，並出現 AttributeError。

patch() 裝飾器／情境管理器可以在測試中簡單的 mock 模組中的類別或物件。被指定的物件在測試期間會被替換為 mock（或其他物件），並在測試結束時恢復：

>>> from unittest.mock import patch
>>> @patch('module.ClassName2')
... @patch('module.ClassName1')
... def test(MockClass1, MockClass2):
...     module.ClassName1()
...     module.ClassName2()
...     assert MockClass1 is module.ClassName1
...     assert MockClass2 is module.ClassName2
...     assert MockClass1.called
...     assert MockClass2.called
...
>>> test()

備註

當你巢狀使用 patch 裝飾器時，mock 傳遞到被裝飾函式的順序會跟其被應用的順序相同（一般 Python 應用裝飾器的順序）。這意味著由下而上，因此在上面的範例中，module.ClassName1 的 mock 會先被傳入。

使用 patch() 時，需注意的是你得在被查找物件的命名空間中（in the namespace where they are looked up）patch 物件。這通常很直接，但若需要快速導引，請參閱該 patch 何處。

裝飾器 patch() 也可以在 with 陳述式中被用來作為情境管理器：

>>> with patch.object(ProductionClass, 'method', return_value=None) as mock_method:
...     thing = ProductionClass()
...     thing.method(1, 2, 3)
...
>>> mock_method.assert_called_once_with(1, 2, 3)

也有 patch.dict()，用於在測試範圍中設定 dictionary（字典）內的值，並在測試結束時將其恢復為原始狀態：

>>> foo = {'key': 'value'}
>>> original = foo.copy()
>>> with patch.dict(foo, {'newkey': 'newvalue'}, clear=True):
...     assert foo == {'newkey': 'newvalue'}
...
>>> assert foo == original

Mock 支援對 Python 的魔術方法的 mocking。最簡單使用魔術方法的方式是使用 MagicMock 類別。它允許你執行以下操作：

>>> mock = MagicMock()
>>> mock.__str__.return_value = 'foobarbaz'
>>> str(mock)
'foobarbaz'
>>> mock.__str__.assert_called_with()

Mock 允許你將函式（或其他 Mock 實例）分配給魔術方法，並且它們將被適當地呼叫。MagicMock 類別是一個 Mock 的變體，它為你預先建好了所有魔術方法（好吧，所有有用的方法）。

以下是在一般 Mock 類別中使用魔術方法的範例：

>>> mock = Mock()
>>> mock.__str__ = Mock(return_value='wheeeeee')
>>> str(mock)
'wheeeeee'

為了確保測試中的 mock 物件與它們要替換的物件具有相同的 api，你可以使用自動規格。自動規格（auto-speccing）可以透過 patch 的 autospec 引數或 create_autospec() 函式來完成。自動規格建立的 mock 物件與它們要替換的物件具有相同的屬性和方法，並且任何函式和方法（包括建構函式）都具有與真實物件相同的呼叫簽名（call signature）。

這可以確保如果使用方法錯誤，你的 mock 會跟實際程式碼以相同的方式失敗：

>>> from unittest.mock import create_autospec
>>> def function(a, b, c):
...     pass
...
>>> mock_function = create_autospec(function, return_value='fishy')
>>> mock_function(1, 2, 3)
'fishy'
>>> mock_function.assert_called_once_with(1, 2, 3)
>>> mock_function('wrong arguments')
Traceback (most recent call last):
 ...
TypeError: missing a required argument: 'b'

create_autospec() 也可以用在類別上，它複製了 __init__ 方法的簽名，它也可以用在可呼叫物件上，其複製了 __call__ 方法的簽名。

Mock 類別

Mock 是一個彈性的的 mock 物件，旨在代替程式碼中 stubs 和 test doubles （測試替身）的使用。Mock 是可呼叫的，並在你存取它們時將屬性建立為新的 mock [1]。存取相同的屬性將永遠回傳相同的 mock。Mock 記錄了你如何使用它們，允許你判定你的程式碼對 mock 的行為。

MagicMock 是 Mock 的子類別，其中所有魔術方法均已預先建立並可供使用。也有不可呼叫的變體，在你 mock 無法呼叫的物件時很有用：NonCallableMock 和 NonCallableMagicMock

patch() 裝飾器可以輕鬆地用 Mock 物件臨時替換特定模組中的類別。預設情況下，patch() 會為你建立一個 MagicMock。你可以使用 patch() 的 new_callable 引數指定 Mock 的替代類別。

class unittest.mock.Mock(spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, **kwargs)

建立一個新的 Mock 物件。Mock 接受數個可選的引數來指定 Mock 物件的行為：

spec：這可以是字串的 list（串列），也可以是充當 mock 物件規格的現有物件（類別或實例）。如果傳入一個物件，則透過對該物件呼叫 dir 來形成字串的串列（不包括不支援的魔術屬性和方法）。存取不在此串列中的任何屬性都會引發 AttributeError。

如果 spec 是一個物件（而不是一個字串的串列），那麼 __class__ 會回傳 spec 物件的類別。這允許 mocks 通過 isinstance() 測試。

spec_set：spec 的一個更嚴格的變體。如果使用 spec_set，在 mock 上嘗試 set 或取得不在傳遞給 spec_set 的物件上的屬性將會引發 AttributeError。

side_effect：每當呼叫 Mock 時要呼叫的函式，參見 side_effect 屬性，用於引發例外或動態變更回傳值。該函式使用與 mock 相同的引數呼叫，且除非它回傳 DEFAULT，否則此函式的回傳值將用作回傳值。

side_effect 也可以是一個例外的類別或實例。在這種情況下，當呼叫 mock 時，該例外將被引發。

如果 side_effect 是一個可疊代物件，那麼對 mock 的每次呼叫將回傳可疊代物件中的下一個值。

side_effect 可以透過將其設置為 None 來清除。

return_value：當呼叫 mock 時回傳的值。預設情況下，這是一個新的 Mock（在首次存取時建立）。參見 return_value 屬性。

unsafe：預設情況下，存取任何以 assert、assret、asert、aseert 或 assrt 開頭的屬性將引發 AttributeError。如果傳遞 unsafe=True，將會允許存取這些屬性。

在 3.5 版被加入.

wraps：被 mock 物件包裝的項目。如果 wraps 不是 None，那麼呼叫 Mock 將透過被包裝的物件（回傳真實結果）。存取 mock 的屬性將會回傳一個 Mock 物件，該物件包裝了被包裝物件的對應屬性（因此嘗試存取不存在的屬性將引發 AttributeError）。

如果 mock 已經明確設定了 return_value，那麼呼叫並不會被傳遞到被包裝的物件，而是回傳已設定好的 return_value。

name：如果 mock 有一個名稱，那麼它會被用於 mock 的 repr。這對於除錯很有用。此名稱將被傳播到子 mocks。

Mocks 還可以使用任意的關鍵字引數進行呼叫。這些關鍵字引數將在建立 mock 之後用於設定 mock 的屬性。欲知更多，請參見 configure_mock() 方法。

assert_called()

確認 mock 至少被呼叫一次。

>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called()

在 3.6 版被加入.

assert_called_once()

確認 mock 只被呼叫一次。

>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_once()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_once()
Traceback (most recent call last):
...
AssertionError: Expected 'method' to have been called once. Called 2 times.
Calls: [call(), call()].

在 3.6 版被加入.

assert_called_with(*args, **kwargs)

這個方法是一個便利的方式，用來斷言最後一次呼叫是以特定方式進行的：

>>> mock = Mock()
>>> mock.method(1, 2, 3, test='wow')
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_with(1, 2, 3, test='wow')

assert_called_once_with(*args, **kwargs)

確認 mock 只被呼叫一次，且該次呼叫使用了指定的引數。

>>> mock = Mock(return_value=None)
>>> mock('foo', bar='baz')
>>> mock.assert_called_once_with('foo', bar='baz')
>>> mock('other', bar='values')
>>> mock.assert_called_once_with('other', bar='values')
Traceback (most recent call last):
  ...
AssertionError: Expected 'mock' to be called once. Called 2 times.
Calls: [call('foo', bar='baz'), call('other', bar='values')].

assert_any_call(*args, **kwargs)

斷言 mock 已經被使用指定的引數呼叫。

這個斷言在 mock 曾經被呼叫過時通過，不同於 assert_called_with() 和 assert_called_once_with()，他們針對的是最近的一次的呼叫，而且對於 assert_called_once_with()，最近一次的呼叫還必須也是唯一一次的呼叫。

>>> mock = Mock(return_value=None)
>>> mock(1, 2, arg='thing')
>>> mock('some', 'thing', 'else')
>>> mock.assert_any_call(1, 2, arg='thing')

assert_has_calls(calls, any_order=False)

斷言 mock 已經使用指定的呼叫方式來呼叫。此斷言會檢查 mock_calls 串列中的呼叫。

如果 any_order 為 false，那麼這些呼叫必須按照順序。在指定的呼叫之前或之後可以有額外的呼叫。

如果 any_order 為 true，那麼這些呼叫可以以任何順序出現，但它們必須全部出現在 mock_calls 中。

>>> mock = Mock(return_value=None)
>>> mock(1)
>>> mock(2)
>>> mock(3)
>>> mock(4)
>>> calls = [call(2), call(3)]
>>> mock.assert_has_calls(calls)
>>> calls = [call(4), call(2), call(3)]
>>> mock.assert_has_calls(calls, any_order=True)

assert_not_called()

斷言 mock 從未被呼叫。

>>> m = Mock()
>>> m.hello.assert_not_called()
>>> obj = m.hello()
>>> m.hello.assert_not_called()
Traceback (most recent call last):
  ...
AssertionError: Expected 'hello' to not have been called. Called 1 times.
Calls: [call()].

在 3.5 版被加入.

reset_mock(*, return_value=False, side_effect=False)

reset_mock 方法重置 mock 物件上的所有呼叫屬性：

>>> mock = Mock(return_value=None)
>>> mock('hello')
>>> mock.called
True
>>> mock.reset_mock()
>>> mock.called
False

This can be useful where you want to make a series of assertions that reuse the same object.

return_value parameter when set to True resets return_value:

>>> mock = Mock(return_value=5)
>>> mock('hello')
5
>>> mock.reset_mock(return_value=True)
>>> mock('hello')
<Mock name='mock()' id='...'>

side_effect parameter when set to True resets side_effect:

>>> mock = Mock(side_effect=ValueError)
>>> mock('hello')
Traceback (most recent call last):
  ...
ValueError
>>> mock.reset_mock(side_effect=True)
>>> mock('hello')
<Mock name='mock()' id='...'>

Note that reset_mock() doesn't clear the return_value, side_effect or any child attributes you have set using normal assignment by default.

Child mocks are reset as well.

在 3.6 版的變更: reset_mock 函式新增了兩個僅限關鍵字引數 (keyword-only arguments)。

mock_add_spec(spec, spec_set=False)

向 mock 增加一個規格 (spec)。spec 可以是一個物件或一個字串串列 (list of strings)。只有在 spec 上的屬性才能作為 mock 的屬性被取得。

如果 spec_set 為 true，那麼只能設定在規格中的屬性。

attach_mock(mock, attribute)

將一個 mock 作為這個 Mock 的屬性附加，取代它的名稱和上代 (parent)。對附加的 mock 的呼叫將被記錄在這個 Mock 的 method_calls 和 mock_calls 屬性中。

configure_mock(**kwargs)

透過關鍵字引數在 mock 上設定屬性。

可以在使用 method（方法）呼叫時，使用標準點記法 (dot notation) 並將字典拆開，為 child mock 設定屬性、回傳值和 side effects：

>>> mock = Mock()
>>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> mock.configure_mock(**attrs)
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
  ...
KeyError

同樣的事情可以在 mock 的建構函式呼叫中實現：

>>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> mock = Mock(some_attribute='eggs', **attrs)
>>> mock.some_attribute
'eggs'
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
  ...
KeyError

configure_mock() 的存在是為了在 mock 被建立後更容易進行組態設定。

__dir__()

Mock 物件限制了 dir(some_mock) 僅顯示有用的結果。對於具有 spec 的 mock，這包含所有被允許的 mock 屬性。

請參閱 FILTER_DIR 以了解這種過濾行為的作用，以及如何關閉它。

_get_child_mock(**kw)

建立為了得到屬性和回傳值的 child mock。預設情況下，child mock 將與其上代是相同的型別。Mock 的子類別可能會想要置換此行為，以自訂 child mock 的建立方式。

對於不可呼叫的 mock，將使用可呼叫的變體，而不是任何的自訂子類別。

called

一個 boolean（布林），表述 mock 物件是否已經被呼叫：

>>> mock = Mock(return_value=None)
>>> mock.called
False
>>> mock()
>>> mock.called
True

call_count

一個整數，告訴你 mock 物件被呼叫的次數：

>>> mock = Mock(return_value=None)
>>> mock.call_count
0
>>> mock()
>>> mock()
>>> mock.call_count
2

return_value

設定此值以配置呼叫 mock 時回傳的值：

>>> mock = Mock()
>>> mock.return_value = 'fish'
>>> mock()
'fish'

預設的回傳值是一個 mock 物件，你也可以按照正常的方式配置它：

>>> mock = Mock()
>>> mock.return_value.attribute = sentinel.Attribute
>>> mock.return_value()
<Mock name='mock()()' id='...'>
>>> mock.return_value.assert_called_with()

return_value 也可以在建構函式中設定：

>>> mock = Mock(return_value=3)
>>> mock.return_value
3
>>> mock()
3

side_effect

這可以是一個在呼叫 mock 時要呼叫的函式、一個可疊代物件，或者要引發的例外（類別或實例）。

如果你傳遞一個函式，它將被呼叫，其引數與 mock 相同，且除非該函式回傳 DEFAULT 單例 (singleton)，否則對 mock 的呼叫將回傳函式回傳的任何值。如果函式回傳 DEFAULT，那麼 mock 將回傳其正常的回傳值（從 return_value 得到）。

如果你傳遞一個可疊代物件，它將被用於檢索一個疊代器，該疊代器必須在每次呼叫時產出 (yield) 一個值。這個值可以是要引發的例外實例，或者是對 mock 呼叫時要回傳的值（處理 DEFAULT 的方式與函式的狀況相同）。

以下是一個引發例外的 mock 的範例（用於測試 API 的例外處理）：

>>> mock = Mock()
>>> mock.side_effect = Exception('Boom!')
>>> mock()
Traceback (most recent call last):
  ...
Exception: Boom!

使用 side_effect 回傳一連串值的範例：

>>> mock = Mock()
>>> mock.side_effect = [3, 2, 1]
>>> mock(), mock(), mock()
(3, 2, 1)

使用可被呼叫物件的範例：

>>> mock = Mock(return_value=3)
>>> def side_effect(*args, **kwargs):
...     return DEFAULT
...
>>> mock.side_effect = side_effect
>>> mock()
3

side_effect 可以在建構函式中設定。以下是一個範例，它將 mock 被呼叫時給的值加一並回傳：

>>> side_effect = lambda value: value + 1
>>> mock = Mock(side_effect=side_effect)
>>> mock(3)
4
>>> mock(-8)
-7

將 side_effect 設定為 None 可以清除它：

>>> m = Mock(side_effect=KeyError, return_value=3)
>>> m()
Traceback (most recent call last):
 ...
KeyError
>>> m.side_effect = None
>>> m()
3

call_args

這會是 None（如果 mock 尚未被呼叫），或是 mock 上次被呼叫時使用的引數。這將以元組的形式呈現：第一個成員 (member)，其可以透過 args 屬性存取，是 mock 被呼叫時傳遞的所有位置引數（或一個空元組）。第二個成員，其可以透過 kwargs 屬性存取，是所有關鍵字引數（或一個空字典）。

>>> mock = Mock(return_value=None)
>>> print(mock.call_args)
None
>>> mock()
>>> mock.call_args
call()
>>> mock.call_args == ()
True
>>> mock(3, 4)
>>> mock.call_args
call(3, 4)
>>> mock.call_args == ((3, 4),)
True
>>> mock.call_args.args
(3, 4)
>>> mock.call_args.kwargs
{}
>>> mock(3, 4, 5, key='fish', next='w00t!')
>>> mock.call_args
call(3, 4, 5, key='fish', next='w00t!')
>>> mock.call_args.args
(3, 4, 5)
>>> mock.call_args.kwargs
{'key': 'fish', 'next': 'w00t!'}

call_args，以及串列 call_args_list、method_calls 和 mock_calls 的成員都是 call 物件。這些都是元組，因此可以解包以取得各個引數並進行更複雜的斷言。參見 calls as tuples。

在 3.8 版的變更: 新增 args 與 kwargs 特性。

call_args_list

這是按順序列出所有呼叫 mock 物件的串列（因此串列的長度表示它被呼叫的次數）。在任何呼叫發生之前，它會是一個空的串列。 call 物件可用於方便地建構呼叫的串列，以便與 call_args_list 進行比較。

>>> mock = Mock(return_value=None)
>>> mock()
>>> mock(3, 4)
>>> mock(key='fish', next='w00t!')
>>> mock.call_args_list
[call(), call(3, 4), call(key='fish', next='w00t!')]
>>> expected = [(), ((3, 4),), ({'key': 'fish', 'next': 'w00t!'},)]
>>> mock.call_args_list == expected
True

call_args_list 的成員都是 call 物件。這些物件可以被拆包為元組，以取得各個引數。參見 calls as tuples。

method_calls

除了追蹤對自身的呼叫之外，mock 還會追蹤對方法和屬性的呼叫，以及它們（這些方法和屬性）的方法和屬性：

>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.property.method.attribute()
<Mock name='mock.property.method.attribute()' id='...'>
>>> mock.method_calls
[call.method(), call.property.method.attribute()]

method_calls 的成員都是 call 物件。這些物件可以拆包為元組，以取得各個引數。參見 calls as tuples。

mock_calls

mock_calls 記錄了 所有 對 mock 物件的呼叫，包含其方法、魔術方法以及回傳值 mock。

>>> mock = MagicMock()
>>> result = mock(1, 2, 3)
>>> mock.first(a=3)
<MagicMock name='mock.first()' id='...'>
>>> mock.second()
<MagicMock name='mock.second()' id='...'>
>>> int(mock)
1
>>> result(1)
<MagicMock name='mock()()' id='...'>
>>> expected = [call(1, 2, 3), call.first(a=3), call.second(),
... call.__int__(), call()(1)]
>>> mock.mock_calls == expected
True

mock_calls 的成員都是 call 物件。這些物件可以拆包為元組，以取得各個引數。參見 calls as tuples。

備註

mock_calls 記錄的方式意味著在進行巢狀呼叫時，上代 (ancestor) 呼叫的參數不會被記錄，因此在比較時它們將始終相等：

>>> mock = MagicMock()
>>> mock.top(a=3).bottom()
<MagicMock name='mock.top().bottom()' id='...'>
>>> mock.mock_calls
[call.top(a=3), call.top().bottom()]
>>> mock.mock_calls[-1] == call.top(a=-1).bottom()
True

__class__

通常，物件的 __class__ 屬性會回傳它的型別。但對於擁有 spec 的 mock 物件，__class__ 會回傳 spec 的類別。這允許 mock 物件透過對它們所替代或偽裝的物件進行的 isinstance() 測試：

>>> mock = Mock(spec=3)
>>> isinstance(mock, int)
True

__class__ 可以被指定，這允許 mock 通過 isinstance() 檢查，而不需要強制使用 spec：

>>> mock = Mock()
>>> mock.__class__ = dict
>>> isinstance(mock, dict)
True

class unittest.mock.NonCallableMock(spec=None, wraps=None, name=None, spec_set=None, **kwargs)

Mock 的一個不可呼叫版本。建構函式參數的意義與 Mock 相同，其例外為 return_value 和 side_effect 在不可呼叫的 mock 上無意義。

使用類別或實例作為 spec 或 spec_set 的 mock 物件能夠通過 isinstance() 測試：

>>> mock = Mock(spec=SomeClass)
>>> isinstance(mock, SomeClass)
True
>>> mock = Mock(spec_set=SomeClass())
>>> isinstance(mock, SomeClass)
True

Mock 類別支援 mock 魔術方法。細節請參考魔術方法。

Mock類別和 patch() 裝飾器於組態時接受任意的關鍵字引數。對於 patch() 裝飾器，這些關鍵字會傳遞給正在建立 mock 的建構函式。這些關鍵字引數用於配置 mock 的屬性：

>>> m = MagicMock(attribute=3, other='fish')
>>> m.attribute
3
>>> m.other
'fish'

Child mock 的回傳值和 side effect 可以使用使用點記法進行設置。由於你無法直接在呼叫中使用帶有點 (.) 的名稱，因此你必須建立一個字典並使用 ** 解包：

>>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> mock = Mock(some_attribute='eggs', **attrs)
>>> mock.some_attribute
'eggs'
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
  ...
KeyError

在匹配對 mock 的呼叫時，使用 spec（或 spec_set）建立的可呼叫 mock 將會內省 (introspect) 規格物件的簽名 (signature)。因此，它可以匹配實際呼叫的引數，無論它們是按位置傳遞還是按名稱傳遞：

>>> def f(a, b, c): pass
...
>>> mock = Mock(spec=f)
>>> mock(1, 2, c=3)
<Mock name='mock()' id='140161580456576'>
>>> mock.assert_called_with(1, 2, 3)
>>> mock.assert_called_with(a=1, b=2, c=3)

這適用於 assert_called_with()、assert_called_once_with()、assert_has_calls() 和 assert_any_call()。在使用 Autospeccing（自動規格） 時，它還適用於 mock 物件的方法呼叫。

在 3.4 版的變更: 對於已經設置了規格（spec）和自動規格（autospec）的 mock 物件，新增簽名內省功能。

class unittest.mock.PropertyMock(*args, **kwargs)

一個理應在類別上當成 property 或其他 descriptor 的 mock。PropertyMock 提供了 __get__() 和 __set__() 方法，因此你可以在它被提取時指定回傳值。

從物件中提取 PropertyMock 實例會不帶任何引數呼叫 mock。設定它則會用設定的值來呼叫 mock：

>>> class Foo:
...     @property
...     def foo(self):
...         return 'something'
...     @foo.setter
...     def foo(self, value):
...         pass
...
>>> with patch('__main__.Foo.foo', new_callable=PropertyMock) as mock_foo:
...     mock_foo.return_value = 'mockity-mock'
...     this_foo = Foo()
...     print(this_foo.foo)
...     this_foo.foo = 6
...
mockity-mock
>>> mock_foo.mock_calls
[call(), call(6)]

由於 mock 屬性的儲存方式，你無法直接將 PropertyMock 附加到 mock 物件。但是你可以將其附加到 mock 型別的物件：

>>> m = MagicMock()
>>> p = PropertyMock(return_value=3)
>>> type(m).foo = p
>>> m.foo
3
>>> p.assert_called_once_with()

警示

If an AttributeError is raised by PropertyMock, it will be interpreted as a missing descriptor and __getattr__() will be called on the parent mock:

>>> m = MagicMock()
>>> no_attribute = PropertyMock(side_effect=AttributeError)
>>> type(m).my_property = no_attribute
>>> m.my_property
<MagicMock name='mock.my_property' id='140165240345424'>

詳情請見 __getattr__()。

class unittest.mock.AsyncMock(spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, **kwargs)

MagicMock 的非同步版本。AsyncMock 物件的表現將被視為非同步函式，並且呼叫的結果是一個可等待物件。

>>> mock = AsyncMock()
>>> inspect.iscoroutinefunction(mock)
True
>>> inspect.isawaitable(mock())
True

mock() 的結果是一個非同步函式，在它被等待後將具有 side_effect 或 return_value 的結果：

如果 side_effect 是一個函式，非同步函式將回傳該函式的結果，

如果 side_effect 是一個例外，則非同步函式將引發該例外，

如果 side_effect 是一個可疊代物件，非同步函式將回傳可疊代物件的下一個值，但如果結果序列耗盡，將立即引發 StopAsyncIteration，

如果 side_effect 沒有被定義，非同步函式將回傳由 return_value 定義的值，因此在預設情況下，非同步函式回傳一個新的 AsyncMock 物件。

將 Mock 或 MagicMock 的 spec 設定為非同步函式將導致在呼叫後回傳一個協程物件。

>>> async def async_func(): pass
...
>>> mock = MagicMock(async_func)
>>> mock
<MagicMock spec='function' id='...'>
>>> mock()
<coroutine object AsyncMockMixin._mock_call at ...>

將 Mock、MagicMock 或 AsyncMock 的 spec 設定為具有同步和非同步函式的類別，會自動檢測同步函式並將其設定為 MagicMock（如果上代 mock 為 AsyncMock 或 MagicMock）或 Mock（如果上代 mock 為 Mock）。所有非同步函式將被設定為 AsyncMock。

>>> class ExampleClass:
...     def sync_foo():
...         pass
...     async def async_foo():
...         pass
...
>>> a_mock = AsyncMock(ExampleClass)
>>> a_mock.sync_foo
<MagicMock name='mock.sync_foo' id='...'>
>>> a_mock.async_foo
<AsyncMock name='mock.async_foo' id='...'>
>>> mock = Mock(ExampleClass)
>>> mock.sync_foo
<Mock name='mock.sync_foo' id='...'>
>>> mock.async_foo
<AsyncMock name='mock.async_foo' id='...'>

在 3.8 版被加入.

assert_awaited()

斷言 mock 至少被等待過一次。請注意這與物件是否被呼叫是分開的，await 關鍵字必須被使用：

>>> mock = AsyncMock()
>>> async def main(coroutine_mock):
...     await coroutine_mock
...
>>> coroutine_mock = mock()
>>> mock.called
True
>>> mock.assert_awaited()
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited.
>>> asyncio.run(main(coroutine_mock))
>>> mock.assert_awaited()

assert_awaited_once()

斷言 mock 正好被等待了一次。

>>> mock = AsyncMock()
>>> async def main():
...     await mock()
...
>>> asyncio.run(main())
>>> mock.assert_awaited_once()
>>> asyncio.run(main())
>>> mock.assert_awaited_once()
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited once. Awaited 2 times.

assert_awaited_with(*args, **kwargs)

斷言最後一次等待使用了指定的引數。

>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_with('foo', bar='bar')
>>> mock.assert_awaited_with('other')
Traceback (most recent call last):
...
AssertionError: expected await not found.
Expected: mock('other')
Actual: mock('foo', bar='bar')

assert_awaited_once_with(*args, **kwargs)

斷言 mock 只被等待了一次並使用了指定的引數。

>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_once_with('foo', bar='bar')
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_once_with('foo', bar='bar')
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited once. Awaited 2 times.

assert_any_await(*args, **kwargs)

斷言 mock 曾經被使用指定的引數等待過。

>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> asyncio.run(main('hello'))
>>> mock.assert_any_await('foo', bar='bar')
>>> mock.assert_any_await('other')
Traceback (most recent call last):
...
AssertionError: mock('other') await not found

assert_has_awaits(calls, any_order=False)

斷言 mock 已被使用指定的呼叫進行等待。await_args_list 串列將被檢查以確認等待的內容。

如果 any_order 為 false，則等待必須按照順序。指定的等待之前或之後可以有額外的呼叫。

如果 any_order 為 true，則等待可以以任何順序出現，但它們必須全部出現在 await_args_list 中。

>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> calls = [call("foo"), call("bar")]
>>> mock.assert_has_awaits(calls)
Traceback (most recent call last):
...
AssertionError: Awaits not found.
Expected: [call('foo'), call('bar')]
Actual: []
>>> asyncio.run(main('foo'))
>>> asyncio.run(main('bar'))
>>> mock.assert_has_awaits(calls)

assert_not_awaited()

斷言 mock 從未被等待。

>>> mock = AsyncMock()
>>> mock.assert_not_awaited()

reset_mock(*args, **kwargs)

參見 Mock.reset_mock()。同時將 await_count 設定為 0，await_args 設定為 None，並清除 await_args_list。

await_count

一個整數，用來記錄 mock 物件已被等待的次數。

>>> mock = AsyncMock()
>>> async def main():
...     await mock()
...
>>> asyncio.run(main())
>>> mock.await_count
1
>>> asyncio.run(main())
>>> mock.await_count
2

await_args

這可能是 None（如果 mock 尚未被等待），或者是上次等待 mock 時使用的引數。與 Mock.call_args 的功能相同。

>>> mock = AsyncMock()
>>> async def main(*args):
...     await mock(*args)
...
>>> mock.await_args
>>> asyncio.run(main('foo'))
>>> mock.await_args
call('foo')
>>> asyncio.run(main('bar'))
>>> mock.await_args
call('bar')

await_args_list

這是一個按照順序記錄 mock 物件所有等待的串列（因此串列的長度表示該物件已被等待的次數）。在進行任何等待之前，此串列為空。

>>> mock = AsyncMock()
>>> async def main(*args):
...     await mock(*args)
...
>>> mock.await_args_list
[]
>>> asyncio.run(main('foo'))
>>> mock.await_args_list
[call('foo')]
>>> asyncio.run(main('bar'))
>>> mock.await_args_list
[call('foo'), call('bar')]

class unittest.mock.ThreadingMock(spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, *, timeout=UNSET, **kwargs)

A version of MagicMock for multithreading tests. The ThreadingMock object provides extra methods to wait for a call to be invoked, rather than assert on it immediately.

The default timeout is specified by the timeout argument, or if unset by the ThreadingMock.DEFAULT_TIMEOUT attribute, which defaults to blocking (None).

You can configure the global default timeout by setting ThreadingMock.DEFAULT_TIMEOUT.

wait_until_called(*, timeout=UNSET)

等待直到 mock 被呼叫。

If a timeout was passed at the creation of the mock or if a timeout argument is passed to this function, the function raises an AssertionError if the call is not performed in time.

>>> mock = ThreadingMock()
>>> thread = threading.Thread(target=mock)
>>> thread.start()
>>> mock.wait_until_called(timeout=1)
>>> thread.join()

wait_until_any_call_with(*args, **kwargs)

等到直到 mock 被以特定引數呼叫。

If a timeout was passed at the creation of the mock the function raises an AssertionError if the call is not performed in time.

>>> mock = ThreadingMock()
>>> thread = threading.Thread(target=mock, args=("arg1", "arg2",), kwargs={"arg": "thing"})
>>> thread.start()
>>> mock.wait_until_any_call_with("arg1", "arg2", arg="thing")
>>> thread.join()

DEFAULT_TIMEOUT

Global default timeout in seconds to create instances of ThreadingMock.

在 3.13 版被加入.

呼叫

Mock 物件可被呼叫。呼叫將回傳設定為 return_value 屬性的值。預設的回傳值是一個新的 Mock 物件；它會在第一次存取回傳值時（無論是顯式存取還是透過呼叫 Mock）被建立，但是這個回傳值會被儲存，之後每次都回傳同一個值。

對物件的呼叫會被記錄在如 call_args 和 call_args_list 等屬性中。

如果 side_effect 被設定，那麼在呼叫被記錄後它才會被呼叫，所以如果 side_effect 引發例外，呼叫仍然會被記錄。

呼叫 mock 時引發例外的最簡單方式是將 side_effect 設定為例外類別或實例：

>>> m = MagicMock(side_effect=IndexError)
>>> m(1, 2, 3)
Traceback (most recent call last):
  ...
IndexError
>>> m.mock_calls
[call(1, 2, 3)]
>>> m.side_effect = KeyError('Bang!')
>>> m('two', 'three', 'four')
Traceback (most recent call last):
  ...
KeyError: 'Bang!'
>>> m.mock_calls
[call(1, 2, 3), call('two', 'three', 'four')]

如果 side_effect 是一個函式，則該函式回傳的東西就是對 mock 的呼叫所回傳的值。side_effect 函式會使用與 mock 相同的引數被呼叫。這讓你可以根據輸入動態地變更呼叫的回傳值：

>>> def side_effect(value):
...     return value + 1
...
>>> m = MagicMock(side_effect=side_effect)
>>> m(1)
2
>>> m(2)
3
>>> m.mock_calls
[call(1), call(2)]

如果你希望 mock 仍然回傳預設的回傳值（一個新的 mock），或者是任何已設定的回傳值，有兩種方法可以實現。從 side_effect 內部回傳 return_value，或回傳 DEFAULT：

>>> m = MagicMock()
>>> def side_effect(*args, **kwargs):
...     return m.return_value
...
>>> m.side_effect = side_effect
>>> m.return_value = 3
>>> m()
3
>>> def side_effect(*args, **kwargs):
...     return DEFAULT
...
>>> m.side_effect = side_effect
>>> m()
3

要刪除 side_effect，並恢復預設行為，將 side_effect 設為 None：

>>> m = MagicMock(return_value=6)
>>> def side_effect(*args, **kwargs):
...     return 3
...
>>> m.side_effect = side_effect
>>> m()
3
>>> m.side_effect = None
>>> m()
6

side_effect 也可以是任何可疊代的物件。對 mock 的重複呼叫將從可疊代物件中回傳值（直到疊代物件耗盡並引發 StopIteration 為止）：

>>> m = MagicMock(side_effect=[1, 2, 3])
>>> m()
1
>>> m()
2
>>> m()
3
>>> m()
Traceback (most recent call last):
  ...
StopIteration

如果可疊代物件中的任何成員是例外，則它們將被引發而不是被回傳：

>>> iterable = (33, ValueError, 66)
>>> m = MagicMock(side_effect=iterable)
>>> m()
33
>>> m()
Traceback (most recent call last):
 ...
ValueError
>>> m()
66

刪除屬性

Mock 物件會在需要時建立屬性。這使得它們可以假裝成任何種類的物件。

你可能希望一個 mock 物件在 hasattr() 呼叫時回傳 False，或者在屬性被提取時引發 AttributeError。你可以透過將物件提供為 mock 的 spec 來實現這一點，但這並不總是那麼好用。

你可以透過刪除屬性來「阻擋」它們。一旦刪除，再次存取該屬性將會引發 AttributeError。

>>> mock = MagicMock()
>>> hasattr(mock, 'm')
True
>>> del mock.m
>>> hasattr(mock, 'm')
False
>>> del mock.f
>>> mock.f
Traceback (most recent call last):
    ...
AttributeError: f

Mock 名稱與名稱屬性

由於 "name" 是傳遞給 Mock 建構函式的引數，如果你想讓你的 mock 物件擁有 "name" 屬性，你不能在建立時直接傳遞它。有兩種替代方法。其中一個選擇是使用 configure_mock()：

>>> mock = MagicMock()
>>> mock.configure_mock(name='my_name')
>>> mock.name
'my_name'

更簡單的方法是在 mock 建立後直接設定 "name" 屬性：

>>> mock = MagicMock()
>>> mock.name = "foo"

如同屬性一般附加 mock

當你將一個 mock 附加為另一個 mock 的屬性（或作為回傳值），它將成為該 mock 的「子代 (child)」。對子代的呼叫將被記錄在上代的 method_calls 和 mock_calls 屬性中。這對於配置子代並將它們附加到上代，或將 mock 附加到記錄所有對子代的呼叫的上代並允許你對 mock 間的呼叫順序進行斷言非常有用：

>>> parent = MagicMock()
>>> child1 = MagicMock(return_value=None)
>>> child2 = MagicMock(return_value=None)
>>> parent.child1 = child1
>>> parent.child2 = child2
>>> child1(1)
>>> child2(2)
>>> parent.mock_calls
[call.child1(1), call.child2(2)]

如果 mock 有 name 引數，則上述規則會有例外。這使你可以防止「親屬關係 (parenting)」的建立，假設因為某些原因你不希望這種狀況發生。

>>> mock = MagicMock()
>>> not_a_child = MagicMock(name='not-a-child')
>>> mock.attribute = not_a_child
>>> mock.attribute()
<MagicMock name='not-a-child()' id='...'>
>>> mock.mock_calls
[]

由 patch() 為你建立的 mock 會自動被賦予名稱。若要將具有名稱的 mock 附加到上代，你可以使用 attach_mock() 方法：

>>> thing1 = object()
>>> thing2 = object()
>>> parent = MagicMock()
>>> with patch('__main__.thing1', return_value=None) as child1:
...     with patch('__main__.thing2', return_value=None) as child2:
...         parent.attach_mock(child1, 'child1')
...         parent.attach_mock(child2, 'child2')
...         child1('one')
...         child2('two')
...
>>> parent.mock_calls
[call.child1('one'), call.child2('two')]

[1]

唯一的例外是魔術方法和屬性（具有前後雙底線）。Mock 不會建立這些，而是會引發 AttributeError。這是因為直譯器通常會隱式地要求這些方法，在期望得到一個魔術方法卻獲得一個新的 Mock 物件時，會讓直譯器非常困惑。如果你需要魔術方法的支援，請參閱魔術方法。

Patchers

patch 裝飾器僅用於在裝飾的函式範圍內對物件進行 patch。它們會自動為你處理 patch 的中止，即使有異常被引發也是如此。所有這些函式也可以在 with 陳述式中使用，或者作為類別裝飾器使用。

patch

備註

關鍵是要在正確的命名空間進行 patch。請參閱 where to patch 一節。

unittest.mock.patch(target, new=DEFAULT, spec=None, create=False, spec_set=None, autospec=None, new_callable=None, **kwargs)

patch() 充當函式裝飾器、類別裝飾器或情境管理器。在函式或 with 陳述式的內部，目標會被 patch 成一個新的物件。當函式或 with 陳述式結束時，patch 就會被解除。

如果 new 被省略，則如果被 patch 的物件是非同步函式，目標會被替換為 AsyncMock，反之則替換為 MagicMock。如果 patch() 做為裝飾器使用且省略了 new，則所建立的 mock 會作為額外的引數傳遞給被裝飾的函式。如果 patch() 作為情境管理器使用，則所建立的 mock 將由情境管理器回傳。

target 應該是以 'package.module.ClassName' 形式出現的字串。target 會被引入並用 new 物件替換指定的物件，因此 target 必須可從你呼叫 patch() 的環境中引入。target 在執行被裝飾的函式時被引入，而不是在裝飾器作用時 (decoration time)。

spec 和 spec_set 關鍵字引數會傳遞給 MagicMock，如果 patch 正在為你建立一個。

此外，你還可以傳遞 spec=True 或 spec_set=True，這將導致 patch 將被 mock 的物件作為 spec/spec_set 物件傳遞。

new_callable 允許你指定一個不同的類別或可呼叫的物件，用於被呼叫並建立 new 物件。預設情況下，對於非同步函式使用 AsyncMock，而對於其他情況則使用 MagicMock。

spec 的一種更強大的形式是 autospec。如果你設定 autospec=True，則該 mock 將使用被替換物件的規格來建立。該 mock 的所有屬性也將具有被替換物件的對應屬性的規格。被 mock 的方法和函式將檢查其引數，如果呼叫時引數與規格不符（被使用錯誤的簽名 (signature) 呼叫），將引發 TypeError。對於替換類別的 mock，它們的回傳值（即 'instance'）將具有與類別相同的規格。請參閱 create_autospec() 函式和 Autospeccing（自動規格）。

你可以用 autospec=some_object 替代 autospec=True，以使用任意物件作為規格，而不是被替換的物件。

預設情況下，patch() 將無法取代不存在的屬性。如果你傳入 create=True，且屬性不存在，則當被 patch 的函式被呼叫時，patch 將為你建立該屬性，並在被 patch 的函式結束後再次刪除它。這對於撰寫針對你的生產程式碼在執行環境建立的屬性的測試時非常有用。此功能預設為關閉，因為這可能會相當危險。開啟這個功能後，你可以對於實際上不存在的 API 撰寫會通過的測試！

備註

在 3.5 版的變更: 如果你正在 patch 模組中的內建函式，那麼你不需要傳遞 create=True，它預設會被加入。

patch 可以做為 TestCase 類別的裝飾器使用。它透過裝飾類別中的每個測試方法來運作。當你的測試方法共享一組常見的 patch 時，這會減少繁冗的代碼。patch() 透過搜尋以 patch.TEST_PREFIX 開頭的方法名來尋找測試。預設情況下會是 'test'，這與 unittest 尋找測試的方式相匹配。你可以通過設定 patch.TEST_PREFIX 來指定別的前綴。

透過 with 陳述式，Patch 可以做為情境管理器使用。patch 適用於 with 陳述式之後的縮排區塊。如果你使用 "as"，則被 patch 的物件將被綁定到 "as" 後面的名稱；如果 patch() 正在為你建立一個 mock 物件，這會非常有用。

patch() 接受任意的關鍵字引數。如果被 patch 的物件是非同步的，這些將會被傳遞給 AsyncMock，如果是同步的則會傳遞給 MagicMock，或如果指定了 new_callable，則傳遞給它。

patch.dict(...)、patch.multiple(...) 和 patch.object(...) 可用於其餘的使用情境。

patch() 作為函式裝飾器，為你建立 mock 並將其傳遞給被裝飾的函式：

>>> @patch('__main__.SomeClass')
... def function(normal_argument, mock_class):
...     print(mock_class is SomeClass)
...
>>> function(None)
True

Patch 一個類別會以 MagicMock 實例取代該類別。如果該類別在被測試的程式碼中實例化，那麼它將是會被使用的 mock 的 return_value。

如果該類別被實例化多次，你可以使用 side_effect 來每次回傳一個新的 mock。 或者你可以將 return_value 設定成你想要的任何值。

若要配置被 patch 的類別的實例方法的回傳值，你必須在 return_value 上進行配置。例如：

>>> class Class:
...     def method(self):
...         pass
...
>>> with patch('__main__.Class') as MockClass:
...     instance = MockClass.return_value
...     instance.method.return_value = 'foo'
...     assert Class() is instance
...     assert Class().method() == 'foo'
...

如果你使用 spec 或 spec_set 且 patch() 正在取代一個類別，那麼被建立的 mock 的回傳值將具有相同的規格。：

>>> Original = Class
>>> patcher = patch('__main__.Class', spec=True)
>>> MockClass = patcher.start()
>>> instance = MockClass()
>>> assert isinstance(instance, Original)
>>> patcher.stop()

當你想要為被建立的 mock 使用一個替代的類別取代預設的 MagicMock 時，new_callable 引數非常有用。例如，如果你想要一個 NonCallableMock 被使用：

>>> thing = object()
>>> with patch('__main__.thing', new_callable=NonCallableMock) as mock_thing:
...     assert thing is mock_thing
...     thing()
...
Traceback (most recent call last):
  ...
TypeError: 'NonCallableMock' object is not callable

另一個用法是用一個 io.StringIO 實例替換一個物件：

>>> from io import StringIO
>>> def foo():
...     print('Something')
...
>>> @patch('sys.stdout', new_callable=StringIO)
... def test(mock_stdout):
...     foo()
...     assert mock_stdout.getvalue() == 'Something\n'
...
>>> test()

當 patch() 為你建立 mock 時，通常你需要做的第一件事就是配置 mock。其中一些配置可以在對 patch 的呼叫中完成。你傳遞到呼叫中的任何關鍵字都將用於在被建立的 mock 上設定屬性：

>>> patcher = patch('__main__.thing', first='one', second='two')
>>> mock_thing = patcher.start()
>>> mock_thing.first
'one'
>>> mock_thing.second
'two'

除了被建立的 mock 上的屬性外，還可以配置 child mock 的 return_value 和 side_effect。它們在語法上不能直接作為關鍵字引數傳入，但是以它們作為鍵的字典仍然可以使用 ** 擴充為一個 patch() 呼叫：

>>> config = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> patcher = patch('__main__.thing', **config)
>>> mock_thing = patcher.start()
>>> mock_thing.method()
3
>>> mock_thing.other()
Traceback (most recent call last):
  ...
KeyError

預設情況下，嘗試 patch 模組中不存在的函式（或類別中的方法或屬性）將會失敗，並引發 AttributeError：

>>> @patch('sys.non_existing_attribute', 42)
... def test():
...     assert sys.non_existing_attribute == 42
...
>>> test()
Traceback (most recent call last):
  ...
AttributeError: <module 'sys' (built-in)> does not have the attribute 'non_existing_attribute'

但是在對 patch() 的呼叫中增加 create=True 將使前面的範例按照預期運作：

>>> @patch('sys.non_existing_attribute', 42, create=True)
... def test(mock_stdout):
...     assert sys.non_existing_attribute == 42
...
>>> test()

在 3.8 版的變更: 如果目標是一個非同步函式，patch() 現在會回傳一個 AsyncMock。

patch.object

patch.object(target, attribute, new=DEFAULT, spec=None, create=False, spec_set=None, autospec=None, new_callable=None, **kwargs)

使用一個 mock 物件 patch 一個物件（目標）上的命名成員（屬性）。

patch.object() 可以做為裝飾器、類別裝飾器或情境管理器使用。引數 new、spec、create、spec_set、autospec 和 new_callable 與在 patch() 中的引數具有相同的意義。與 patch() 一樣，patch.object() 接受任意關鍵字引數來配置它所建立的 mock 物件。

當作為類別裝飾器使用時，patch.object() 會遵循 patch.TEST_PREFIX 來選擇要包裝的方法。

你可以使用三個引數或兩個引數來呼叫 patch.object()。三個引數的形式接受要被 patch 的物件、屬性名稱和要替換掉屬性的物件。

當使用兩個引數的形式呼叫時，你會省略要替換的物件，一個 mock 會為你建立並將其作為額外的引數傳遞給被裝飾的函式：

>>> @patch.object(SomeClass, 'class_method')
... def test(mock_method):
...     SomeClass.class_method(3)
...     mock_method.assert_called_with(3)
...
>>> test()

spec、create 和 patch.object() 的其他引數與在 patch() 中的引數具有相同的意義。

patch.dict

patch.dict(in_dict, values=(), clear=False, **kwargs)

Patch 字典或類字典的物件，並在測試後將字典回復到其原本的狀態，其中回復的字典是測試前字典的複本。

in_dict 可以是一個字典或一個類對映的容器。如果它是一個對映，那麼它至少必須支援取得、設定、刪除項目以及對鍵的疊代。

in_dict 也可以是指定字典名稱的字串，然後透過 import 來取得該字典。

values 可以是要設定的值的字典。values 也可以是 (key, value) 對 (pairs) 的可疊代物件。

如果 clear 為 true，則在設定新值之前字典將被清除。

也可以使用任意關鍵字引數呼叫 patch.dict() 以在字典中設定值。

在 3.8 版的變更: patch.dict() 現在在做為情境管理器使用時回傳被 patch 的字典。

patch.dict() 可以做為情境管理器、裝飾器或類別裝飾器使用：

>>> foo = {}
>>> @patch.dict(foo, {'newkey': 'newvalue'})
... def test():
...     assert foo == {'newkey': 'newvalue'}
...
>>> test()
>>> assert foo == {}

當作為類別裝飾器使用時，patch.dict() 會遵循 patch.TEST_PREFIX（預設為 'test'）來選擇要包裝的方法：

>>> import os
>>> import unittest
>>> from unittest.mock import patch
>>> @patch.dict('os.environ', {'newkey': 'newvalue'})
... class TestSample(unittest.TestCase):
...     def test_sample(self):
...         self.assertEqual(os.environ['newkey'], 'newvalue')

如果你想在測試中使用不同的前綴，你可以透過設定 patch.TEST_PREFIX 來告知 patcher 使用不同的前綴。請參閱 TEST_PREFIX 以得知如何修改前綴的更多內容。

patch.dict() 可用於在字典中新增成員，或單純地讓測試更改字典，並確保在測試結束時將字典回復原狀。

>>> foo = {}
>>> with patch.dict(foo, {'newkey': 'newvalue'}) as patched_foo:
...     assert foo == {'newkey': 'newvalue'}
...     assert patched_foo == {'newkey': 'newvalue'}
...     # You can add, update or delete keys of foo (or patched_foo, it's the same dict)
...     patched_foo['spam'] = 'eggs'
...
>>> assert foo == {}
>>> assert patched_foo == {}

>>> import os
>>> with patch.dict('os.environ', {'newkey': 'newvalue'}):
...     print(os.environ['newkey'])
...
newvalue
>>> assert 'newkey' not in os.environ

可以在 patch.dict() 呼叫中使用關鍵字來設定字典中的值：

>>> mymodule = MagicMock()
>>> mymodule.function.return_value = 'fish'
>>> with patch.dict('sys.modules', mymodule=mymodule):
...     import mymodule
...     mymodule.function('some', 'args')
...
'fish'

patch.dict() 可以與實際上不是字典的類字典物件一起使用。最低限度它們必須支援項目的取得、設定、刪除以及疊代或隸屬資格檢測。這對應到魔術方法中的 __getitem__()、__setitem__()、__delitem__() 以及 __iter__() 或 __contains__()。

>>> class Container:
...     def __init__(self):
...         self.values = {}
...     def __getitem__(self, name):
...         return self.values[name]
...     def __setitem__(self, name, value):
...         self.values[name] = value
...     def __delitem__(self, name):
...         del self.values[name]
...     def __iter__(self):
...         return iter(self.values)
...
>>> thing = Container()
>>> thing['one'] = 1
>>> with patch.dict(thing, one=2, two=3):
...     assert thing['one'] == 2
...     assert thing['two'] == 3
...
>>> assert thing['one'] == 1
>>> assert list(thing) == ['one']

patch.multiple

patch.multiple(target, spec=None, create=False, spec_set=None, autospec=None, new_callable=None, **kwargs)

在一次呼叫中執行多個 patch。它接受被 patch 的物件（作為物件或透過 import 取得物件的字串）和 patch 的關鍵字引數：

with patch.multiple(settings, FIRST_PATCH='one', SECOND_PATCH='two'):
    ...

如果你想要 patch.multiple() 為你建立 mock，請使用 DEFAULT 作為值。在這種情況下，被建立的 mock 會透過關鍵字傳遞到被裝飾的函式中，並且當 patch.multiple() 作為情境管理器時會回傳字典。

patch.multiple() 可以做為裝飾器、類別裝飾器或情境管理器使用。引數 spec、spec_set、create、autospec 和 new_callable 與在 patch() 中的引數具有相同的意義。這些引數將應用於由 patch.multiple() 完成的所有 patch。

當作為類別裝飾器使用時，patch.multiple() 遵循 patch.TEST_PREFIX 來選擇要包裝的方法。

如果你想要 patch.multiple() 為你建立 mock，那麼你可以使用 DEFAULT 作為值。如果你使用 patch.multiple() 作為裝飾器，那麼被建立的 mock 將透過關鍵字傳遞到被裝飾的函式中。：

>>> thing = object()
>>> other = object()

>>> @patch.multiple('__main__', thing=DEFAULT, other=DEFAULT)
... def test_function(thing, other):
...     assert isinstance(thing, MagicMock)
...     assert isinstance(other, MagicMock)
...
>>> test_function()

patch.multiple() 可以與其他 patch 裝飾器巢狀使用，但需要將透過關鍵字傳遞的引數放在 patch() 建立的任何標準引數之後：

>>> @patch('sys.exit')
... @patch.multiple('__main__', thing=DEFAULT, other=DEFAULT)
... def test_function(mock_exit, other, thing):
...     assert 'other' in repr(other)
...     assert 'thing' in repr(thing)
...     assert 'exit' in repr(mock_exit)
...
>>> test_function()

如果 patch.multiple() 作為情境管理器使用，則情境管理器回傳的值是一個字典，其中被建立的 mock 會按名稱作為其鍵值：

>>> with patch.multiple('__main__', thing=DEFAULT, other=DEFAULT) as values:
...     assert 'other' in repr(values['other'])
...     assert 'thing' in repr(values['thing'])
...     assert values['thing'] is thing
...     assert values['other'] is other
...

patch 方法：啟動與停止

所有的 patcher 都有 start() 與 stop() 方法。這使得在 setUp 方法中進行 patch 或在你想要在沒有巢狀使用裝飾器或 with 陳述式的情況下進行多個 patch 時變得更簡單。

要使用它們，請像平常一樣呼叫 patch()、patch.object() 或 patch.dict() ，並保留對回傳的 patcher 物件的參照。之後你就可以呼叫 start() 將 patch 準備就緒，並呼叫 stop() 來取消 patch。

如果你使用 patch() 為你建立 mock，那麼它將透過呼叫 patcher.start 回傳。：

>>> patcher = patch('package.module.ClassName')
>>> from package import module
>>> original = module.ClassName
>>> new_mock = patcher.start()
>>> assert module.ClassName is not original
>>> assert module.ClassName is new_mock
>>> patcher.stop()
>>> assert module.ClassName is original
>>> assert module.ClassName is not new_mock

一個典型的用法是在一個 TestCase 的 setUp 方法中執行多個 patch：

>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         self.patcher1 = patch('package.module.Class1')
...         self.patcher2 = patch('package.module.Class2')
...         self.MockClass1 = self.patcher1.start()
...         self.MockClass2 = self.patcher2.start()
...
...     def tearDown(self):
...         self.patcher1.stop()
...         self.patcher2.stop()
...
...     def test_something(self):
...         assert package.module.Class1 is self.MockClass1
...         assert package.module.Class2 is self.MockClass2
...
>>> MyTest('test_something').run()

警示

如果你使用這個技巧，你必須確保透過呼叫 stop 來 "取消" patch。這可能會比你想像的還要複雜一點，因為如果有例外在 setUp 中被引發，則 tearDown 就不會被呼叫。unittest.TestCase.addCleanup() 會讓這稍微簡單一點：

>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         patcher = patch('package.module.Class')
...         self.MockClass = patcher.start()
...         self.addCleanup(patcher.stop)
...
...     def test_something(self):
...         assert package.module.Class is self.MockClass
...

作為額外的好處，你不再需要保留對 patcher 物件的參照。

也可以使用 patch.stopall() 來停止所有已啟動的 patch。

patch.stopall()

停止所有運作的 patch。只停止以 start 啟動的 patch。

patch 內建函式

你可以 patch 模組內的任何內建函式。以下範例 patch 內建函式 ord()：

>>> @patch('__main__.ord')
... def test(mock_ord):
...     mock_ord.return_value = 101
...     print(ord('c'))
...
>>> test()
101

TEST_PREFIX

所有 patcher 都可以作為類別裝飾器使用。以這種方式使用時，它們包裝了類別上的每個測試方法。Patcher 將 'test' 開頭的方法認定為測試方法。這與 unittest.TestLoader 預設尋找測試方法的方式相同。

你可能會想為你的測試使用不同的前綴。你可以透過設定 patch.TEST_PREFIX 來告知 patcher 使用不同的前綴：

>>> patch.TEST_PREFIX = 'foo'
>>> value = 3
>>>
>>> @patch('__main__.value', 'not three')
... class Thing:
...     def foo_one(self):
...         print(value)
...     def foo_two(self):
...         print(value)
...
>>>
>>> Thing().foo_one()
not three
>>> Thing().foo_two()
not three
>>> value
3

巢狀使用 Patch 裝飾器

如果你想執行多個 patch，那麼你可以簡單地堆疊裝飾器。

你可以使用這個模式來堆疊多個 patch 裝飾器：

>>> @patch.object(SomeClass, 'class_method')
... @patch.object(SomeClass, 'static_method')
... def test(mock1, mock2):
...     assert SomeClass.static_method is mock1
...     assert SomeClass.class_method is mock2
...     SomeClass.static_method('foo')
...     SomeClass.class_method('bar')
...     return mock1, mock2
...
>>> mock1, mock2 = test()
>>> mock1.assert_called_once_with('foo')
>>> mock2.assert_called_once_with('bar')

請注意，裝飾器是從底部向上應用的。這是 Python 應用裝飾器的標準方式。被建立的 mock 傳遞到測試函式中的順序與此順序相同。

該 patch 何處

patch() 的工作原理是（暫時）將 name 指向的物件變更為另一個物件。可以有許多 name 指向任何單一物件，因此為了使 patch 起作用，你必須確保你 patch 了被測試系統使用的 name。

基本原則是在物件被查找的位置進行 patch，該位置不一定與其被定義的位置相同。幾個範例將有助於闡明這一點。

想像一下，我們想要測試一個專案，其結構如下：

a.py
    -> Defines SomeClass

b.py
    -> from a import SomeClass
    -> some_function instantiates SomeClass

現在我們想要測試 some_function，但我們想使用 patch() mock SomeClass。問題是，當我們 import 模組 b 時（我們必須這樣做），它會從模組 a import SomeClass。如果我們使用 patch() 來 mock a.SomeClass，那麼它對我們的測試就不會有任何影響；模組 b 已經有了一個真實的 SomeClass 的參照 ，看起來我們的 patch 並沒有任何效果。

關鍵是在使用（或查找它）的地方 patch SomeClass。在這個情況下，some_function 實際上會在我們 import 它的模組 b 中查找 SomeClass。這裡的 patch 應該長得像這樣：

@patch('b.SomeClass')

然而，考慮另一種情況，其中模組 b 並不是使用 from a import SomeClass，而是 import a，然後 some_function 使用 a.SomeClass。這兩種 import 形式都很常見。在這種情況下，我們想要 patch 的類別正在其模組中被查找，因此我們必須 patch a.SomeClass：

@patch('a.SomeClass')

Patch 描述器與代理物件 (Proxy Objects)

patch 和 patch.object 都正確地 patch 和還原描述器：類別方法、靜態方法以及屬性。你應該在 類別 而不是實例上 patch 它們。它們還可以使用代理屬性存取的一些物件，例如 django 設定物件 [https://web.archive.org/web/20200603181648/http://www.voidspace.org.uk/python/weblog/arch_d7_2010_12_04.shtml#e1198]。

MagicMock 以及魔術方法支援

Mock 魔術方法

Mock 支援 mock Python 協定方法，其也被稱作 "魔術方法"。這允許 mock 物件替換容器或實作 Python 協定的其他物件。

由於魔術方法被查找的方式與一般的方法 [2] 不同，因此專門實作了此支援方式。這代表著僅有特定的魔術方法被此方式支援。現在已支援清單中已經幾乎包含了所有魔術方法。如果你需要 mock 任何魔術方法而其尚未被支援，請讓我們知道。

你可以透過將你感興趣的方法設定為函式或 mock 實例來 mock 魔術方法。如果你使用函式，那麼它必須將 self 作為第一個引數 [3]。

>>> def __str__(self):
...     return 'fooble'
...
>>> mock = Mock()
>>> mock.__str__ = __str__
>>> str(mock)
'fooble'

>>> mock = Mock()
>>> mock.__str__ = Mock()
>>> mock.__str__.return_value = 'fooble'
>>> str(mock)
'fooble'

>>> mock = Mock()
>>> mock.__iter__ = Mock(return_value=iter([]))
>>> list(mock)
[]

一個用法是在 with 陳述式中 mock 作為情境管理器使用的物件：

>>> mock = Mock()
>>> mock.__enter__ = Mock(return_value='foo')
>>> mock.__exit__ = Mock(return_value=False)
>>> with mock as m:
...     assert m == 'foo'
...
>>> mock.__enter__.assert_called_with()
>>> mock.__exit__.assert_called_with(None, None, None)

對魔術方法的呼叫並不會出現在 method_calls 中，它們會被記錄在 mock_calls 內。

備註

如果你使用spec關鍵字引數來建立一個 mock，則嘗試設定規格中未包含的魔術方法將引發一個 AttributeError。

已支援的魔術方法的完整列表是：

__hash__、__sizeof__、 __repr__ 和 __str__

__dir__、 __format__ 和 __subclasses__

__round__、__floor__、__trunc__ 和 __ceil__

比較方法：__lt__、__gt__、__le__、__ge__、__eq__ 和 __ne__

容器方法：__getitem__、__setitem__、__delitem__、__contains__、__len__、__iter__、__reversed__ 和 __missing__

情境管理器：__enter__、__exit__、__aenter__ 和 __aexit__

一元數值方法：__neg__、__pos__ 和 __invert__

數值方法（包括右側 (right hand) 和原地 (in-place) 變體）：__add__、__sub__、__mul__、__matmul__、__truediv__、__floordiv__、__mod__、__divmod__、__lshift__、__rshift__、__and__、__xor__、__or__ 和 __pow__

數值轉換方法：__complex__、__int__、__float__ 和 __index__

描述器方法：__get__、__set__ 和 __delete__

Pickling：__reduce__、__reduce_ex__、__getinitargs__、__getnewargs__、__getstate__ 和 __setstate__

檔案系統路徑表示法：__fspath__

非同步疊代方法：__aiter__ 和 __anext__

在 3.8 版的變更: 新增對於 os.PathLike.__fspath__() 的支援。

在 3.8 版的變更: 新增對於 __aenter__、__aexit__、__aiter__ 和 __anext__ 的支援。

以下方法存在，但「不」被支援，因為它們在被 mock 使用時，會無法動態設定，或可能導致問題：

__getattr__、__setattr__、__init__ 和 __new__

__prepare__、__instancecheck__、__subclasscheck__、__del__

Magic Mock

MagicMock 有兩個變體：MagicMock 和 NonCallableMagicMock。

class unittest.mock.MagicMock(*args, **kw)

MagicMock 是 Mock 的子類別，其預設具有大多數魔術方法的實作。你可以使用 MagicMock，而無需自行配置魔術方法。

建構函式參數的意義與 Mock 中的參數相同。

如果你使用 spec 或 spec_set 引數，那麼只有規格中存在的魔術方法會被建立。

class unittest.mock.NonCallableMagicMock(*args, **kw)

MagicMock 的不可呼叫版本。

建構函式參數的意義與 MagicMock 中的參數相同，但 return_value 和 side_effect 除外，它們對不可呼叫的 mock 來說沒有任何意義。

魔術方法是使用 MagicMock 物件設定的，因此你可以配置它們並以一般的方法來使用它們：

>>> mock = MagicMock()
>>> mock[3] = 'fish'
>>> mock.__setitem__.assert_called_with(3, 'fish')
>>> mock.__getitem__.return_value = 'result'
>>> mock[2]
'result'

預設情況下，許多協定方法都需要回傳特定種類的物件。這些方法預先配置了預設回傳值，因此如果你對回傳值不感興趣，則無需執行任何操作即可使用它們。如果你想更改預設值，你仍然可以手動設定回傳值。

方法及其預設值：

__lt__：NotImplemented

__gt__：NotImplemented

__le__：NotImplemented

__ge__：NotImplemented

__int__：1

__contains__：False

__len__：0

__iter__：iter([])

__exit__：False

__aexit__：False

__complex__：1j

__float__：1.0

__bool__：True

__index__：1

__hash__：mock 的預設雜湊

__str__：mock 的預設字串

__sizeof__：mock 的預設 sizeof

舉例來說：

>>> mock = MagicMock()
>>> int(mock)
1
>>> len(mock)
0
>>> list(mock)
[]
>>> object() in mock
False

__eq__() 和 __ne__() 這兩個相等的方法是特別的。它們使用 side_effect 屬性對識別性 (identity) 進行預設的相等比較，除非你變更它們的回傳值以回傳其他內容：

>>> MagicMock() == 3
False
>>> MagicMock() != 3
True
>>> mock = MagicMock()
>>> mock.__eq__.return_value = True
>>> mock == 3
True

MagicMock.__iter__() 的回傳值可以是任何可疊代物件，且不需是一個疊代器：

>>> mock = MagicMock()
>>> mock.__iter__.return_value = ['a', 'b', 'c']
>>> list(mock)
['a', 'b', 'c']
>>> list(mock)
['a', 'b', 'c']

如果回傳值是一個疊代器，那麼對其進行一次疊代將消耗它，並且後續疊代將產生一個空串列：

>>> mock.__iter__.return_value = iter(['a', 'b', 'c'])
>>> list(mock)
['a', 'b', 'c']
>>> list(mock)
[]

MagicMock 配置了所有支援的魔術方法，除了一些少見和過時的方法。如果你想要，你仍然可以設定這些魔術方法。

MagicMock 中支援但預設未設置的魔術方法包含：

__subclasses__

__dir__

__format__

__get__、__set__ 和 __delete__

__reversed__ 和 __missing__

__reduce__、__reduce_ex__、__getinitargs__、__getnewargs__、__getstate__ 和 __setstate__

__getformat__

[2]

魔術方法應該在類別而不是實例上被查找。不同版本的 Python 對於這條規則的適用並不一致。支援的協定方法應適用於所有支援的 Python 版本。

[3]

該函式基本上與類別掛鉤，但每個 Mock 實例都與其他實例保持隔離。

輔助函式

sentinel（哨兵）

unittest.mock.sentinel

哨兵物件提供了一種為你的測試提供獨特物件的便利方式。

當你使用名稱存取屬性時，屬性會根據需要被建立。存取相同的屬性將始終回傳相同的物件。回傳的物件會具有合適的 repr，讓測試失敗的訊息是可閱讀的。

在 3.7 版的變更: 哨兵屬性現在當被複製或序列化時會保留其識別性。

在測試時，有時你需要測試特定物件是否作為引數被傳遞給另一個方法或回傳。建立命名的哨兵物件來測試這一點是常見的。sentinel 提供了一種此類建立和測試物件識別性的便利方式。

在這個例子中，我們 monkey patch method 以回傳 sentinel.some_object：

>>> real = ProductionClass()
>>> real.method = Mock(name="method")
>>> real.method.return_value = sentinel.some_object
>>> result = real.method()
>>> assert result is sentinel.some_object
>>> result
sentinel.some_object

DEFAULT

unittest.mock.DEFAULT

DEFAULT 物件是一個預先建立的哨兵（實際上是 sentinel.DEFAULT）。它可以被 side_effect 函式使用來表示正常的回傳值應該被使用。

call

unittest.mock.call(*args, **kwargs)

與 call_args、call_args_list、mock_calls 和 method_calls 相比，call() 是一個用於進行更簡單的斷言的輔助物件。call() 也可以與 assert_has_calls() 一起使用。

>>> m = MagicMock(return_value=None)
>>> m(1, 2, a='foo', b='bar')
>>> m()
>>> m.call_args_list == [call(1, 2, a='foo', b='bar'), call()]
True

call.call_list()

對於表示多個呼叫的 call 物件，call_list() 回傳所有中間呼叫以及最終呼叫的串列。

call_list 在對「鍊接呼叫 (chained calls)」進行斷言時特別有用。鍊接呼叫是在單行程式碼進行的多次呼叫。這會導致 mock 上的 mock_calls 中出現多個項目。手動建構呼叫序列會相當單調乏味。

call_list() 可以從同一個鍊接呼叫建構呼叫序列：

>>> m = MagicMock()
>>> m(1).method(arg='foo').other('bar')(2.0)
<MagicMock name='mock().method().other()()' id='...'>
>>> kall = call(1).method(arg='foo').other('bar')(2.0)
>>> kall.call_list()
[call(1),
 call().method(arg='foo'),
 call().method().other('bar'),
 call().method().other()(2.0)]
>>> m.mock_calls == kall.call_list()
True

取決於它的建構方式，一個 call 物件會是（位置引數, 關鍵字引數）的元組，或是 (名稱, 位置引數, 關鍵字引數) 的元組。當你自己建構它們時，這並不是那麼有趣，但是 Mock.call_args、Mock.call_args_list 和 Mock.mock_calls 屬性中的 call 物件可以被內省以取得它們包含的各個引數。

Mock.call_args 和 Mock.call_args_list 中的 call 物件是（位置引數, 關鍵字引數）的二元組，而 Mock.mock_calls 中的 call 物件以及你自己建立的 call 物件是（名稱, 位置引數, 關鍵字引數）的三元組。

你可以利用它們作為元組的特性來提取單個引數，以進行更複雜的內省和斷言。位置引數是一個元組（如果沒有位置引數則為空元組），關鍵字引數是一個字典：

>>> m = MagicMock(return_value=None)
>>> m(1, 2, 3, arg='one', arg2='two')
>>> kall = m.call_args
>>> kall.args
(1, 2, 3)
>>> kall.kwargs
{'arg': 'one', 'arg2': 'two'}
>>> kall.args is kall[0]
True
>>> kall.kwargs is kall[1]
True

>>> m = MagicMock()
>>> m.foo(4, 5, 6, arg='two', arg2='three')
<MagicMock name='mock.foo()' id='...'>
>>> kall = m.mock_calls[0]
>>> name, args, kwargs = kall
>>> name
'foo'
>>> args
(4, 5, 6)
>>> kwargs
{'arg': 'two', 'arg2': 'three'}
>>> name is m.mock_calls[0][0]
True

create_autospec

unittest.mock.create_autospec(spec, spec_set=False, instance=False, **kwargs)

使用另一個物件作為規格建立一個 mock 物件。Mock 上的屬性將使用 spec 物件上的對應屬性作為其規格。

被 mock 的函式或方法將檢查其引數，以確保他們被使用正確的簽名來呼叫。

如果 spec_set 為 True，則嘗試設定規格物件上不存在的屬性將引發 AttributeError。

如果一個類別作為規格使用，則 mock（該類別的實例）的回傳值將具有相同的規格。你可以透過傳遞 instance=True 來使用一個類別作為一個實例物件的規格。只有當 mock 的實例是可呼叫物件時，回傳的 mock 才會是可呼叫物件。

create_autospec() 也接受任意的關鍵字引數，這些引數會傳遞給已建立的 mock 的建構函式。

請參閱 Autospeccing（自動規格） 以得知如何以 create_autospec() 使用自動規格以及如何在 patch() 中使用 autospec 引數的範例。

在 3.8 版的變更: 如果目標是一個非同步函式，create_autospec() 現在會回傳一個 AsyncMock。

ANY

unittest.mock.ANY

有時你可能需要對 mock 的呼叫中的某些引數進行斷言，但你不在意其他的某些引數，或想將它們單獨從 call_args 中取出並進行更加複雜的斷言。

要忽略某些引數，你可以傳入對所有物件來說都相等的物件。那麼無論傳入什麼內容，對 assert_called_with() 和 assert_called_once_with() 的呼叫都會成功。

>>> mock = Mock(return_value=None)
>>> mock('foo', bar=object())
>>> mock.assert_called_once_with('foo', bar=ANY)

ANY 也可以用來與呼叫串列進行比較，例如 mock_calls：

>>> m = MagicMock(return_value=None)
>>> m(1)
>>> m(1, 2)
>>> m(object())
>>> m.mock_calls == [call(1), call(1, 2), ANY]
True

ANY 不只能與呼叫物件比較，其也可以在測試斷言中使用：

class TestStringMethods(unittest.TestCase):

    def test_split(self):
        s = 'hello world'
        self.assertEqual(s.split(), ['hello', ANY])

FILTER_DIR

unittest.mock.FILTER_DIR

FILTER_DIR 是一個模組級別的變數，用於控制 mock 物件回應 dir() 的方式。其預設值為 True，它使用以下描述的過濾方式來只顯示有用的成員。如果你不喜歡這個過濾方式，或由於診斷意圖而需要將其關閉，請設定 mock.FILTER_DIR = False。

當過濾方式開啟時，dir(some_mock) 僅會顯示有用的屬性，並將包括通常不會顯示的任何動態建立的屬性。如果 mock 是使用 spec（或 autospec）來建立的，那麼源頭的所有屬性都會顯示，即使它們尚未被存取：

>>> dir(Mock())
['assert_any_call',
 'assert_called',
 'assert_called_once',
 'assert_called_once_with',
 'assert_called_with',
 'assert_has_calls',
 'assert_not_called',
 'attach_mock',
 ...
>>> from urllib import request
>>> dir(Mock(spec=request))
['AbstractBasicAuthHandler',
 'AbstractDigestAuthHandler',
 'AbstractHTTPHandler',
 'BaseHandler',
 ...

許多不是很有用的（對 Mock 來說是私有的，而不是被 mock 的東西）底線和雙底線前綴屬性已從在 Mock 上呼叫 dir() 的結果中濾除。如果你不喜歡這種特性，可以透過設定模組級別開關 FILTER_DIR 來將其關閉：

>>> from unittest import mock
>>> mock.FILTER_DIR = False
>>> dir(mock.Mock())
['_NonCallableMock__get_return_value',
 '_NonCallableMock__get_side_effect',
 '_NonCallableMock__return_value_doc',
 '_NonCallableMock__set_return_value',
 '_NonCallableMock__set_side_effect',
 '__call__',
 '__class__',
 ...

或者，你可以只使用 vars(my_mock)（實例成員）和 dir(type(my_mock))（型別成員）來略過過濾，而不考慮 FILTER_DIR。

mock_open

unittest.mock.mock_open(mock=None, read_data=None)

用於建立取代 open() 用途的 mock 的輔助函式。它適用於直接呼叫或用作情境管理器的 open()。

mock 引數是要配置的 mock 物件。如果其為 None（預設值），那麼就會為你建立一個 MagicMock，其 API 限制在標準檔案處理上可用的方法或屬性。

read_data 是檔案處理方法 read()、readline() 和 readlines() 的回傳字串。對這些方法的呼叫將從 read_data 取得資料，直到資料耗盡。對這些方法的 mock 非常單純：每次呼叫 mock 時，read_data 都會倒回到起點。如果你需要對提供給測試程式碼的資料進行更多控制，你會需要自行客製化這個 mock。如果這樣還不夠，PyPI [https://pypi.org] 上的其中一個記憶體內檔案系統 (in-memory filesystem) 套件可以提供用於測試的真實檔案系統。

在 3.4 版的變更: 新增對 readline() 和 readlines() 的支援。read() 的 mock 更改為消耗 read_data 而不是在每次呼叫時回傳它。

在 3.5 版的變更: 現在，每次呼叫 mock 時都會重置 read_data。

在 3.8 版的變更: 新增 __iter__() 到實作中，以便使疊代（例如在 for 迴圈中）正確地消耗 read_data。

使用 open() 作為情境管理器是確保檔案處理正確關閉的好方式，且這種方式正在變得普遍：

with open('/some/path', 'w') as f:
    f.write('something')

問題是，即使你 mock 了對 open() 的呼叫，它也是作為情境管理器使用的回傳物件（且其 __enter__() 和 __exit__() 已被呼叫）。

使用 MagicMock mock 情境管理器相當常見並且精細，因此輔助函式就非常有用：

>>> m = mock_open()
>>> with patch('__main__.open', m):
...     with open('foo', 'w') as h:
...         h.write('some stuff')
...
>>> m.mock_calls
[call('foo', 'w'),
 call().__enter__(),
 call().write('some stuff'),
 call().__exit__(None, None, None)]
>>> m.assert_called_once_with('foo', 'w')
>>> handle = m()
>>> handle.write.assert_called_once_with('some stuff')

以及讀取檔案：

>>> with patch('__main__.open', mock_open(read_data='bibble')) as m:
...     with open('foo') as h:
...         result = h.read()
...
>>> m.assert_called_once_with('foo')
>>> assert result == 'bibble'

Autospeccing（自動規格）

自動規格以 mock 現有的 spec 功能作為基礎。它將 mock 的 api 限制為原始物件（規格）的 api，但它是遞迴的（惰性 (lazily) 實現），因此 mock 的屬性僅具有與規格的屬性相同的 api。此外，被 mock 的函式/方法具有與原始的函式/方法相同的呼叫簽名，因此如果它們被不正確地呼叫，就會引發 TypeError。

在解釋自動規格如何運作之前，我們先解釋為什麼需要它。

Mock 是一個非常強大且靈活的物件，但它有一個常見的 mock 缺陷。如果你重構某些程式碼或重新命名成員等，則任何仍然使用舊 api 但使用 mock 而非真實物件的程式碼測試仍然會通過。這意味著即使你的程式碼壞了，但測試仍可以全部通過。

在 3.5 版的變更: 在 3.5 之前，當測試應該引發錯誤時，斷言單字中存在拼字錯誤的測驗會默默地通過。你仍可以透過將 unsafe=True 傳遞給 Mock 來實作此行為。

謹記這是你需要有整合測試和單元測試的另一個原因。單獨測試所有內容都很好，但如果你不測試你的單元是如何「連接在一起」的，那麼測試還是有機會發現很多錯誤。

unittest.mock 已經提供了一個功能來幫助解決這個問題，其稱為 speccing。如果你使用類別或實例作為 mock 的 spec，那麼你在 mock 上只能存取真實類別中存在的屬性：

>>> from urllib import request
>>> mock = Mock(spec=request.Request)
>>> mock.assret_called_with  # Intentional typo!
Traceback (most recent call last):
 ...
AttributeError: Mock object has no attribute 'assret_called_with'

該規格僅適用於 mock 本身，因此在 mock 上的任何方法仍然有相同的問題：

>>> mock.header_items()
<mock.Mock object at 0x...>
>>> mock.header_items.assret_called_with()  # 故意的錯字！

自動規格解決了這個問題。你可以將 autospec=True 傳遞給 patch() / patch.object() 或使用 create_autospec() 函式建立帶有規格的 mock。如果你對 patch() 使用 autospec=True 引數，則被取代的物件將作為規格物件使用。因為規格是「惰性」完成的（規格是在 mock 被存取時作為屬性被建立的），所以你可以將它與非常複雜或深度巢狀使用的物件（例如連續引用的模組）一起使用，而不會過於影響性能。

這是一個正在使用的例子：

>>> from urllib import request
>>> patcher = patch('__main__.request', autospec=True)
>>> mock_request = patcher.start()
>>> request is mock_request
True
>>> mock_request.Request
<MagicMock name='request.Request' spec='Request' id='...'>

你可以看到 request.Request 有一個規格。request.Request 在建構函式中接受兩個引數（其中之一是 self）。如果我們錯誤地呼叫它，會發生以下情況：

>>> req = request.Request()
Traceback (most recent call last):
 ...
TypeError: <lambda>() takes at least 2 arguments (1 given)

此規格也適用於實例化的類別（即有規格的 mock 的回傳值）：

>>> req = request.Request('foo')
>>> req
<NonCallableMagicMock name='request.Request()' spec='Request' id='...'>

Request 物件不是可呼叫物件，因此實例化我們 mock out 的 request.Request 的回傳值是不可呼叫的 mock。規格到位後，斷言中的任何拼字錯誤都會引發正確的錯誤：

>>> req.add_header('spam', 'eggs')
<MagicMock name='request.Request().add_header()' id='...'>
>>> req.add_header.assret_called_with  # Intentional typo!
Traceback (most recent call last):
 ...
AttributeError: Mock object has no attribute 'assret_called_with'
>>> req.add_header.assert_called_with('spam', 'eggs')

在許多情況下，你只需要將 autospec=True 新增至現有的 patch() 呼叫中，然後就可以防止因拼字錯誤和 api 變更而導致的錯誤。

除了透過 patch() 使用 autospec 之外，還有一個 create_autospec() 用於直接建立有自動規格的 mock：

>>> from urllib import request
>>> mock_request = create_autospec(request)
>>> mock_request.Request('foo', 'bar')
<NonCallableMagicMock name='mock.Request()' spec='Request' id='...'>

然而，這並非完全沒有限制，這就是為什麼它不是預設的行為。為了理解規格物件上有哪些可用屬性，autospec 必須內省（存取屬性）規格。當你遍歷 mock 上的屬性時，原始物件的對應遍歷正在默默發生。如果你的規格物件具有可以觸發程式碼執行的屬性或描述器，那麼你可能無法使用 autospec。換句話說，設計你的物件讓內省是安全的 [4] 會比較好。

一個更嚴重的問題是，在 __init__() 方法中建立實例屬性是常見的，而其根本不存在於類別中。autospec 無法知道任何動態建立的屬性，並將 api 限制為可見的屬性。：

>>> class Something:
...   def __init__(self):
...     self.a = 33
...
>>> with patch('__main__.Something', autospec=True):
...   thing = Something()
...   thing.a
...
Traceback (most recent call last):
  ...
AttributeError: Mock object has no attribute 'a'

有幾種不同的方法可以解決這個問題。最簡單但可能有點煩人的方法是在建立後簡單地在 mock 上設定所需的屬性。因為雖然 autospec 不允許你取得規格中不存在的屬性，但是它不會阻止你設定它們：

>>> with patch('__main__.Something', autospec=True):
...   thing = Something()
...   thing.a = 33
...

spec 和 autospec 有一個更激進的版本，它會確實地阻止你設定不存在的屬性。如果你想確保你的程式碼僅能設定有效的屬性，那麼這會很有用，但顯然它也順便阻止了這個特殊情況：

>>> with patch('__main__.Something', autospec=True, spec_set=True):
...   thing = Something()
...   thing.a = 33
...
Traceback (most recent call last):
 ...
AttributeError: Mock object has no attribute 'a'

解決問題的最佳方法可能是新增類別屬性作為在 __init__() 中初始化的實例成員的預設值。請注意，如果你僅在 __init__() 中設定預設屬性，那麼透過類別屬性（當然在實例之間共用）提供它們也會更快。例如：

class Something:
    a = 33

這就帶來了另一個問題。為稍後將成為不同型別的物件的成員提供預設值 None 是相對常見的。None 作為規格是無用的，因為它不允許你存取其上的任何屬性或方法。由於 None 作為規格永遠不會有用，並且可能表示通常屬於其他型別的成員，因此自動規格不會對設定為 None 的成員使用規格。這些會只是普通的 mock（通常是 MagicMocks）：

>>> class Something:
...     member = None
...
>>> mock = create_autospec(Something)
>>> mock.member.foo.bar.baz()
<MagicMock name='mock.member.foo.bar.baz()' id='...'>

如果修改正式生產 (production) 類別以新增預設值不符合你的喜好，那麼還有更多選擇。其中之一就是簡單地使用實例作為規格而不是使用類別。另一種是建立一個正式生產類別的子類別，並將預設值新增至子類別中，而不影響正式生產類別。這兩個都需要你使用替代物件作為規格。值得慶幸的是 patch() 支援這一點 - 你可以簡單地將替代物件作為 autospec 引數傳遞：

>>> class Something:
...   def __init__(self):
...     self.a = 33
...
>>> class SomethingForTest(Something):
...   a = 33
...
>>> p = patch('__main__.Something', autospec=SomethingForTest)
>>> mock = p.start()
>>> mock.a
<NonCallableMagicMock name='Something.a' spec='int' id='...'>

[4]

這只適用於類別或已經實例化的物件。呼叫一個被 mock 的類別來建立一個 mock 實例不會建立真的實例。它僅查找屬性及對 dir() 的呼叫。

密封 mock

unittest.mock.seal(mock)

當存取被密封的 mock 的屬性或其任何已經遞迴 mock 的屬性時，seal 將停用 mock 的自動建立。

如果將具有名稱或規格的 mock 實例指派給屬性，則不會出現在密封鏈中。這表示可藉由固定 mock 物件的一部分來防止密封。：

>>> mock = Mock()
>>> mock.submock.attribute1 = 2
>>> mock.not_submock = mock.Mock(name="sample_name")
>>> seal(mock)
>>> mock.new_attribute  # This will raise AttributeError.
>>> mock.submock.attribute2  # This will raise AttributeError.
>>> mock.not_submock.attribute2  # This won't raise.

在 3.7 版被加入.

side_effect、return_value 和 wraps 的優先順序

它們的優先順序是：

side_effect

return_value

wraps

如果這三個都有設定，mock 將會回傳來自 side_effect 的值，並忽略 return_value 和被包裝物件。如果設定了任兩項，則優先順序較高的一項將回傳該值。無論先設定哪個順序，優先順序都保持不變。

>>> from unittest.mock import Mock
>>> class Order:
...     @staticmethod
...     def get_value():
...         return "third"
...
>>> order_mock = Mock(spec=Order, wraps=Order)
>>> order_mock.get_value.side_effect = ["first"]
>>> order_mock.get_value.return_value = "second"
>>> order_mock.get_value()
'first'

由於 None 是 side_effect 的預設值，如果將其值重新賦值回為 None，則會檢查 return_value 和被包裝物件之間的優先順序，忽略 side_effect。

>>> order_mock.get_value.side_effect = None
>>> order_mock.get_value()
'second'

如果 side_effect 回傳的值是 DEFAULT，它將被忽略，並且優先順序被移動到後面一個以獲得要回傳的值。

>>> from unittest.mock import DEFAULT
>>> order_mock.get_value.side_effect = [DEFAULT]
>>> order_mock.get_value()
'second'

當 Mock 包裝一個物件時，return_value 的預設值將為 DEFAULT。

>>> order_mock = Mock(spec=Order, wraps=Order)
>>> order_mock.return_value
sentinel.DEFAULT
>>> order_mock.get_value.return_value
sentinel.DEFAULT

優先順序將忽略該值，並將移動到最後一個，即被包裝物件。

當對被包裝物件進行真正的呼叫時，建立此 mock 的實例將回傳該類別的真實實例。必須傳遞被包裝物件所需的位置引數（如果存在）。

>>> order_mock_instance = order_mock()
>>> isinstance(order_mock_instance, Order)
True
>>> order_mock_instance.get_value()
'third'

>>> order_mock.get_value.return_value = DEFAULT
>>> order_mock.get_value()
'third'

>>> order_mock.get_value.return_value = "second"
>>> order_mock.get_value()
'second'

但如果你為其賦予 None 則不會被忽略，因為它是明確賦值。因此，優先順序不會移至被包裝物件。

>>> order_mock.get_value.return_value = None
>>> order_mock.get_value() is None
True

即使你在初始化 mock 時同時設定所有三個，優先順序也保持不變：

>>> order_mock = Mock(spec=Order, wraps=Order,
...                   **{"get_value.side_effect": ["first"],
...                      "get_value.return_value": "second"}
...                   )
...
>>> order_mock.get_value()
'first'
>>> order_mock.get_value.side_effect = None
>>> order_mock.get_value()
'second'
>>> order_mock.get_value.return_value = DEFAULT
>>> order_mock.get_value()
'third'

如果 side_effect 已耗盡，則優先順序將不會使值由後面取得。相反地這會引發 StopIteration 例外。

>>> order_mock = Mock(spec=Order, wraps=Order)
>>> order_mock.get_value.side_effect = ["first side effect value",
...                                     "another side effect value"]
>>> order_mock.get_value.return_value = "second"

>>> order_mock.get_value()
'first side effect value'
>>> order_mock.get_value()
'another side effect value'

>>> order_mock.get_value()
Traceback (most recent call last):
 ...
StopIteration

unittest.mock --- 入門指南

在 3.3 版被加入.

使用 Mock 的方式

使用 Mock 來 patching 方法

Mock 物件的常見用法包含：

Patching 方法

記錄在物件上的方法呼叫

你可能會想要取代一個物件上的方法，以便檢查系統的另一部分是否使用正確的引數呼叫它：

>>> real = SomeClass()
>>> real.method = MagicMock(name='method')
>>> real.method(3, 4, 5, key='value')
<MagicMock name='method()' id='...'>

一旦我們的 mock 已經被使用（例如在這個範例中的 real.method），它就有了方法和屬性，允許你對其使用方式進行斷言 (assertions)。

備註

在大多數的範例中，Mock 和 MagicMock 類別是可以互換的。不過由於 MagicMock 是功能更強大的類別，因此通常它是一個更好的選擇。

一旦 mock 被呼叫，它的 called 屬性將被設定為 True。更重要的是，我們可以使用 assert_called_with() 或 assert_called_once_with() 方法來檢查它是否被使用正確的引數來呼叫。

這個範例測試呼叫 ProductionClass().method 是否導致對 something 方法的呼叫：

>>> class ProductionClass:
...     def method(self):
...         self.something(1, 2, 3)
...     def something(self, a, b, c):
...         pass
...
>>> real = ProductionClass()
>>> real.something = MagicMock()
>>> real.method()
>>> real.something.assert_called_once_with(1, 2, 3)

對物件的方法呼叫使用 mock

在上一個範例中，我們直接對物件上的方法進行 patch，以檢查它是否被正確呼叫。另一個常見的用法是將一個物件傳遞給一個方法（或受測系統的某一部分），然後檢查它是否以正確的方式被使用。

下面是一個單純的 ProductionClass，含有一個 closer 方法。如果它被傳入一個物件，它就會呼叫此物件中的 close。

>>> class ProductionClass:
...     def closer(self, something):
...         something.close()
...

因此，為了對此進行測試，我們需要傳遞一個具有 close 方法的物件，並檢查它是否被正確的呼叫。

>>> real = ProductionClass()
>>> mock = Mock()
>>> real.closer(mock)
>>> mock.close.assert_called_with()

我們不必做任何額外的事情來為 mock 提供 'close' 方法，存取 close 會建立它。因此，如果 'close' 並未被呼叫過，在測試中存取 'close' 就會建立它，但 assert_called_with() 就會引發一個失敗的例外。

Mock 類別

一個常見的使用案例是在測試的時候 mock 被程式碼實例化的類別。當你 patch 一個類別時，該類別就會被替換為 mock。實例是透過呼叫類別建立的。這代表你可以透過查看被 mock 的類別的回傳值來存取「mock 實例」。

在下面的範例中，我們有一個函式 some_function，它實例化 Foo 並呼叫它的方法。對 patch() 的呼叫將類別 Foo 替換為一個 mock。Foo 實例是呼叫 mock 的結果，因此它是透過修改 mock return_value 來配置的。：

>>> def some_function():
...     instance = module.Foo()
...     return instance.method()
...
>>> with patch('module.Foo') as mock:
...     instance = mock.return_value
...     instance.method.return_value = 'the result'
...     result = some_function()
...     assert result == 'the result'

命名你的 mock

為你的 mock 命名可能會很有用。這個名稱會顯示在 mock 的 repr 中，且當 mock 出現在測試的失敗訊息中時，名稱會很有幫助。該名稱也會傳播到 mock 的屬性或方法：

>>> mock = MagicMock(name='foo')
>>> mock
<MagicMock name='foo' id='...'>
>>> mock.method
<MagicMock name='foo.method' id='...'>

追蹤所有呼叫

通常你會想要追蹤對一個方法的多個呼叫。mock_calls 屬性記錄對 mock 的子屬性以及其子屬性的所有呼叫。

>>> mock = MagicMock()
>>> mock.method()
<MagicMock name='mock.method()' id='...'>
>>> mock.attribute.method(10, x=53)
<MagicMock name='mock.attribute.method()' id='...'>
>>> mock.mock_calls
[call.method(), call.attribute.method(10, x=53)]

如果你對 mock_calls 做出斷言並且有任何不預期的方法被呼叫，則斷言將失敗。這很有用，因為除了斷言你期望的呼叫已經進行之外，你還可以檢查它們是否按正確的順序進行，並且沒有多餘的呼叫：

你可以使用 call 物件來建構串列以與 mock_calls 進行比較：

>>> expected = [call.method(), call.attribute.method(10, x=53)]
>>> mock.mock_calls == expected
True

然而，回傳 mock 的呼叫的參數不會被記錄，這代表在巢狀呼叫中，無法追蹤用於建立上代的參數 important 的值：

>>> m = Mock()
>>> m.factory(important=True).deliver()
<Mock name='mock.factory().deliver()' id='...'>
>>> m.mock_calls[-1] == call.factory(important=False).deliver()
True

設定回傳值和屬性

在 mock 物件上設定回傳值非常簡單：

>>> mock = Mock()
>>> mock.return_value = 3
>>> mock()
3

當然，你可以對 mock 上的方法執行相同的操作：

>>> mock = Mock()
>>> mock.method.return_value = 3
>>> mock.method()
3

回傳值也可以在建構函式中設定：

>>> mock = Mock(return_value=3)
>>> mock()
3

如果你需要在 mock 上進行屬性設置，只需執行以下操作：

>>> mock = Mock()
>>> mock.x = 3
>>> mock.x
3

有時你想要 mock 更複雜的情況，例如 mock.connection.cursor().execute("SELECT 1")。如果我們希望此呼叫回傳一個串列，那麼我們就必須配置巢狀呼叫的結果。

如下所示，我們可以使用 call 在「鍊接呼叫 (chained call)」中建構呼叫的集合，以便在之後輕鬆的進行斷言：

>>> mock = Mock()
>>> cursor = mock.connection.cursor.return_value
>>> cursor.execute.return_value = ['foo']
>>> mock.connection.cursor().execute("SELECT 1")
['foo']
>>> expected = call.connection.cursor().execute("SELECT 1").call_list()
>>> mock.mock_calls
[call.connection.cursor(), call.connection.cursor().execute('SELECT 1')]
>>> mock.mock_calls == expected
True

正是對 .call_list() 的呼叫將我們的呼叫物件轉換為代表鍊接呼叫的呼叫串列。

透過 mock 引發例外

一個有用的屬性是 side_effect。如果將其設定為例外類別或實例，則當 mock 被呼叫時將引發例外。

>>> mock = Mock(side_effect=Exception('Boom!'))
>>> mock()
Traceback (most recent call last):
  ...
Exception: Boom!

Side effect 函式以及可疊代物件

side_effect 也可以設定為函式或可疊代物件。side_effect 作為可疊代物件的使用案例是：當你的 mock 將會被多次呼叫，且你希望每次呼叫回傳不同的值。當你將 side_effect 設定為可疊代物件時，對 mock 的每次呼叫都會傳回可疊代物件中的下一個值：

>>> mock = MagicMock(side_effect=[4, 5, 6])
>>> mock()
4
>>> mock()
5
>>> mock()
6

對於更進階的使用案例，例如根據 mock 被呼叫的內容動態變更回傳值，可以將 side_effect 設成一個函式。該函式會使用與 mock 相同的引數被呼叫。函式回傳的內容就會是呼叫回傳的內容：

>>> vals = {(1, 2): 1, (2, 3): 2}
>>> def side_effect(*args):
...     return vals[args]
...
>>> mock = MagicMock(side_effect=side_effect)
>>> mock(1, 2)
1
>>> mock(2, 3)
2

Mock 非同步可疊代物件

從 Python 3.8 開始，AsyncMock 和 MagicMock 支援透過 __aiter__ 來 mock Asynchronous Iterators。__aiter__ 的 return_value 屬性可用來設定用於疊代的回傳值。

>>> mock = MagicMock()  # AsyncMock also works here
>>> mock.__aiter__.return_value = [1, 2, 3]
>>> async def main():
...     return [i async for i in mock]
...
>>> asyncio.run(main())
[1, 2, 3]

Mock 非同步情境管理器

從 Python 3.8 開始，AsyncMock 和 MagicMock 支援透過 __aenter__ 和 __aexit__ 來 mock Asynchronous Context Managers。預設情況下，__aenter__ 和 __aexit__ 是回傳非同步函式的 AsyncMock 實例。

>>> class AsyncContextManager:
...     async def __aenter__(self):
...         return self
...     async def __aexit__(self, exc_type, exc, tb):
...         pass
...
>>> mock_instance = MagicMock(AsyncContextManager())  # AsyncMock also works here
>>> async def main():
...     async with mock_instance as result:
...         pass
...
>>> asyncio.run(main())
>>> mock_instance.__aenter__.assert_awaited_once()
>>> mock_instance.__aexit__.assert_awaited_once()

從現有物件建立 mock

過度使用 mock 的一個問題是，它將你的測試與 mock 的實作結合在一起，而不是與真實的程式碼結合。假設你有一個實作 some_method 的類別，在另一個類別的測試中，你提供了一個 mock 的物件，其也提供了 some_method。如果之後你重構第一個類別，使其不再具有 some_method - 那麼即使你的程式碼已經損壞，你的測試也將繼續通過！

Mock 允許你使用 spec 關鍵字引數提供一個物件作為 mock 的規格。對 mock 存取規格物件上不存在的方法或屬性將立即引發一個屬性錯誤。如果你更改規格的實作，那麼使用該類別的測試將立即失敗，而無需在這些測試中實例化該類別。

>>> mock = Mock(spec=SomeClass)
>>> mock.old_method()
Traceback (most recent call last):
   ...
AttributeError: Mock object has no attribute 'old_method'. Did you mean: 'class_method'?

使用規格還可以更聰明地匹配對 mock 的呼叫，無論引數是作為位置引數還是命名引數傳遞：

>>> def f(a, b, c): pass
...
>>> mock = Mock(spec=f)
>>> mock(1, 2, 3)
<Mock name='mock()' id='140161580456576'>
>>> mock.assert_called_with(a=1, b=2, c=3)

如果你希望這種更聰明的匹配也可以應用於 mock 上的方法呼叫，你可以使用自動規格。

如果你想要一種更強大的規格形式來防止設定任意屬性以及取得它們，那麼你可以使用 spec_set 而不是 spec。

使用 side_effect 回傳各別檔案內容

mock_open() 是用於 patch open() 方法。side_effect 可以用來在每次呼叫回傳一個新的 mock 物件。這可以用於回傳儲存在字典中的各別檔案的不同內容：

DEFAULT = "default"
data_dict = {"file1": "data1",
             "file2": "data2"}

def open_side_effect(name):
    return mock_open(read_data=data_dict.get(name, DEFAULT))()

with patch("builtins.open", side_effect=open_side_effect):
    with open("file1") as file1:
        assert file1.read() == "data1"

    with open("file2") as file2:
        assert file2.read() == "data2"

    with open("file3") as file2:
        assert file2.read() == "default"

Patch 裝飾器

備註

使用 patch() 時，需注意的是你得在被查找物件的命名空間中（in the namespace where they are looked up）patch 物件。這通常很直接，但若需要快速導引，請參閱該 patch 何處。

測試中的常見需求是 patch 類別屬性或模組屬性，例如 patch 一個內建函式（built-in）或 patch 模組中的類別以測試它是否已實例化。模組和類別實際上是全域的，因此在測試後必須撤銷它們的 patch，否則 patch 將延續到其他測試中並導致難以診斷問題。

mock 為此提供了三個方便的裝飾器：patch()、patch.object() 和 patch.dict()。patch 接受單一字串，格式為 package.module.Class.attribute，用來指定要 patch 的屬性。同時它也可以接受你想要替換的屬性（或類別或其他）的值。patch.object 接受一個物件和你想要 patch 的屬性的名稱，同時也可以接受要 patch 的值。

patch.object：

>>> original = SomeClass.attribute
>>> @patch.object(SomeClass, 'attribute', sentinel.attribute)
... def test():
...     assert SomeClass.attribute == sentinel.attribute
...
>>> test()
>>> assert SomeClass.attribute == original

>>> @patch('package.module.attribute', sentinel.attribute)
... def test():
...     from package.module import attribute
...     assert attribute is sentinel.attribute
...
>>> test()

如果你要 patch 一個模組（包括 builtins），請使用 patch() 而非 patch.object()：

>>> mock = MagicMock(return_value=sentinel.file_handle)
>>> with patch('builtins.open', mock):
...     handle = open('filename', 'r')
...
>>> mock.assert_called_with('filename', 'r')
>>> assert handle == sentinel.file_handle, "incorrect file handle returned"

如有需要，模組名稱可以含有 .，形式為 package.module：

>>> @patch('package.module.ClassName.attribute', sentinel.attribute)
... def test():
...     from package.module import ClassName
...     assert ClassName.attribute == sentinel.attribute
...
>>> test()

一個好的模式是實際裝飾測試方法本身：

>>> class MyTest(unittest.TestCase):
...     @patch.object(SomeClass, 'attribute', sentinel.attribute)
...     def test_something(self):
...         self.assertEqual(SomeClass.attribute, sentinel.attribute)
...
>>> original = SomeClass.attribute
>>> MyTest('test_something').test_something()
>>> assert SomeClass.attribute == original

如果你想使用一個 mock 進行 patch，你可以使用僅帶有一個引數的 patch()（或帶有兩個引數的 patch.object()）。Mock 將被建立並被傳遞到測試函式 / 方法中：

>>> class MyTest(unittest.TestCase):
...     @patch.object(SomeClass, 'static_method')
...     def test_something(self, mock_method):
...         SomeClass.static_method()
...         mock_method.assert_called_with()
...
>>> MyTest('test_something').test_something()

你可以使用這個模式堆疊多個 patch 裝飾器：

>>> class MyTest(unittest.TestCase):
...     @patch('package.module.ClassName1')
...     @patch('package.module.ClassName2')
...     def test_something(self, MockClass2, MockClass1):
...         self.assertIs(package.module.ClassName1, MockClass1)
...         self.assertIs(package.module.ClassName2, MockClass2)
...
>>> MyTest('test_something').test_something()

當你巢狀使用 patch 裝飾器時，mock 傳遞到被裝飾函式的順序會跟其被應用的順序相同（一般 Python 應用裝飾器的順序）。這意味著由下而上，因此在上面的範例中，module.ClassName2 的 mock 會先被傳入。

也有 patch.dict()，用於在測試範圍中設定字典內的值，並在測試結束時將其恢復為原始狀態：

>>> foo = {'key': 'value'}
>>> original = foo.copy()
>>> with patch.dict(foo, {'newkey': 'newvalue'}, clear=True):
...     assert foo == {'newkey': 'newvalue'}
...
>>> assert foo == original

patch、patch.object 和 patch.dict 都可以用來作為情境管理器。

當你使用 patch() 為你建立一個 mock 時，你可以使用 with 陳述式的 "as" 形式來取得 mock 的參照：

>>> class ProductionClass:
...     def method(self):
...         pass
...
>>> with patch.object(ProductionClass, 'method') as mock_method:
...     mock_method.return_value = None
...     real = ProductionClass()
...     real.method(1, 2, 3)
...
>>> mock_method.assert_called_with(1, 2, 3)

另外，patch、patch.object 和 patch.dict 也可以用來作為類別裝飾器。以這種方式使用時，與將裝飾器單獨應用於每個名稱以 "test" 開頭的方法相同。

更多範例

以下是一些更進階一點的情境的範例。

Mock 鍊接呼叫

一旦你了解了 return_value 屬性，mock 鍊接呼叫其實就很簡單了。當一個 mock 第一次被呼叫，或者你在它被呼叫之前取得其 return_value 時，一個新的 Mock 就會被建立。

這代表你可以透過查問 return_value mock 來了解一個對被 mock 的物件的呼叫回傳的物件是如何被使用的：

>>> mock = Mock()
>>> mock().foo(a=2, b=3)
<Mock name='mock().foo()' id='...'>
>>> mock.return_value.foo.assert_called_with(a=2, b=3)

這裡只需一個簡單的步驟即可進行配置並對鍊接呼叫進行斷言。當然，另一種選擇是先以更容易被測試的方式撰寫程式碼...

所以，假設我們有一些程式碼，看起來大概像這樣：

>>> class Something:
...     def __init__(self):
...         self.backend = BackendProvider()
...     def method(self):
...         response = self.backend.get_endpoint('foobar').create_call('spam', 'eggs').start_call()
...         # more code

假設 BackendProvider 已經經過充分測試，那麼我們該如何測試 method()？具體來說，我們要測試程式碼部分 # more code 是否以正確的方式使用 response 物件。

由於此呼叫鍊是從實例屬性進行的，因此我們可以在 Something 實例上 monkey patch backend 屬性。在這種特定的情況下，我們只對最終呼叫 start_call 的回傳值感興趣，因此我們不需要做太多配置。我們假設它傳回的物件是類檔案物件 (file-like)，因此我們會確保我們的 response 物件使用內建的 open() 作為其 spec。

為此，我們建立一個 mock 實例作為我們的 mock backend，並為其建立一個 mock response 物件。要將 response 設定為最後的 start_call 的回傳值，我們可以這樣做：

mock_backend.get_endpoint.return_value.create_call.return_value.start_call.return_value = mock_response

我們可以使用 configure_mock() 方法來以稍微好一點的方式為我們直接設定回傳值：

>>> something = Something()
>>> mock_response = Mock(spec=open)
>>> mock_backend = Mock()
>>> config = {'get_endpoint.return_value.create_call.return_value.start_call.return_value': mock_response}
>>> mock_backend.configure_mock(**config)

有了這些，我們就可以原地 (in place) monkey patch "mock backend"，並且可以進行真正的呼叫：

>>> something.backend = mock_backend
>>> something.method()

藉由使用 mock_calls，我們可以使用單一一個斷言來檢查鍊接呼叫。一個鍊接呼叫是一行程式碼中的多個呼叫，因此 mock_calls 中會有多個項目。我們可以使用 call.call_list() 來為我們建立這個呼叫串列：

>>> chained = call.get_endpoint('foobar').create_call('spam', 'eggs').start_call()
>>> call_list = chained.call_list()
>>> assert mock_backend.mock_calls == call_list

部分 mocking

對於某些測試，你可能會想 mock 對 datetime.date.today() 的呼叫以回傳一個已知日期，但不想阻止測試中的程式碼建立新的日期物件。不幸的是 datetime.date 是用 C 語言寫的，所以們我不能 monkey patch 靜態的 datetime.date.today() 方法。

然而你可以使用一個 mock 有效地包裝日期類別，同時將對建構函式的呼叫傳遞給真實的類別（並回傳真實的實例）。

這裡使用 patch 裝飾器 來 mock 被測模組中的 date 類別。然後，mock 日期類別上的 side_effect 屬性會被設定為回傳真實日期的 lambda 函式。當 mock 日期類別被呼叫時，將透過 side_effect 建構並回傳真實日期。：

>>> from datetime import date
>>> with patch('mymodule.date') as mock_date:
...     mock_date.today.return_value = date(2010, 10, 8)
...     mock_date.side_effect = lambda *args, **kw: date(*args, **kw)
...
...     assert mymodule.date.today() == date(2010, 10, 8)
...     assert mymodule.date(2009, 6, 8) == date(2009, 6, 8)

注意，我們沒有全域 patch datetime.date，而是在使用它的模組中 patch date。請參閱 該 patch 何處。

當 date.today() 被呼叫時，一個已知日期會被回傳，但對 date(...) 建構函式的呼叫仍然會回傳正常日期。如果不這樣使用，你可能會發現自己必須使用與被測程式碼完全相同的演算法來計算預期結果，這是一個典型的測試的反面模式 (anti-pattern)。

對日期建構函式的呼叫被記錄在 mock_date 屬性（call_count 及其相關屬性）中，這對你的測試也可能有用處。

處理 mock 日期或其他內建類別的另一種方法在 這個 blog [https://williambert.online/2011/07/how-to-unit-testing-in-django-with-mocking-and-patching/] 中討論。

Mock 產生器方法

Python 產生器是一個函式或方法，它使用 yield 陳述式在疊代 [1] 時回傳一系列的值。

產生器方法 / 函式會被呼叫以回傳產生器物件。之後此產生器會進行疊代。疊代的協定方法是 __iter__()，所以我們可以使用 MagicMock 來 mock 它。

下面是一個範例類別，其包含實作產生器的一個 "iter" 方法：

>>> class Foo:
...     def iter(self):
...         for i in [1, 2, 3]:
...             yield i
...
>>> foo = Foo()
>>> list(foo.iter())
[1, 2, 3]

我們該如何 mock 這個類別，特別是它的 "iter" 方法呢？

要配置從疊代回傳的值（隱含在對 list 的呼叫中），我們需要配置呼叫 foo.iter() 所回傳的物件。

>>> mock_foo = MagicMock()
>>> mock_foo.iter.return_value = iter([1, 2, 3])
>>> list(mock_foo.iter())
[1, 2, 3]

[1]

還有關於產生器運算式及產生器的更多 進階用法 [http://www.dabeaz.com/coroutines/index.html] ，但我們在這裡不考慮它們。一個關於產生器及其強大功能的優良說明是：Generator Tricks for Systems Programmers [http://www.dabeaz.com/generators/]。

對每個測試方法應用相同的 patch

如果你希望 patch 能用在多個測試方法上，顯而易見的方式是將 patch 裝飾器應用於每個方法。這感覺是不必要的重複行為，因此你可以使用 patch()（及其他 patch 的變體）作為類別裝飾器。這會將 patch 應用在該類別的所有測試方法上。測試方法由名稱以 test 開頭來識別：

>>> @patch('mymodule.SomeClass')
... class MyTest(unittest.TestCase):
...
...     def test_one(self, MockSomeClass):
...         self.assertIs(mymodule.SomeClass, MockSomeClass)
...
...     def test_two(self, MockSomeClass):
...         self.assertIs(mymodule.SomeClass, MockSomeClass)
...
...     def not_a_test(self):
...         return 'something'
...
>>> MyTest('test_one').test_one()
>>> MyTest('test_two').test_two()
>>> MyTest('test_two').not_a_test()
'something'

管理 patch 的另一種方式是使用 patch 方法：啟動與停止。這允許你將 patch 移到你的 setUp 與 tearDown 方法中。：

>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         self.patcher = patch('mymodule.foo')
...         self.mock_foo = self.patcher.start()
...
...     def test_foo(self):
...         self.assertIs(mymodule.foo, self.mock_foo)
...
...     def tearDown(self):
...         self.patcher.stop()
...
>>> MyTest('test_foo').run()

如果你使用這個技巧，你必須確保透過呼叫 stop 來 "取消" patch。這可能會比你想像的還要複雜一點，因為如果有例外在 setUp 中被引發，則 tearDown 就不會被呼叫。unittest.TestCase.addCleanup() 會讓這稍微簡單一點：

>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         patcher = patch('mymodule.foo')
...         self.addCleanup(patcher.stop)
...         self.mock_foo = patcher.start()
...
...     def test_foo(self):
...         self.assertIs(mymodule.foo, self.mock_foo)
...
>>> MyTest('test_foo').run()

Mock Unbound Methods （未繫結方法）

有時候測試會需要 patch 一個未繫結方法，即為 patch 類別上的方法而不是實例上的方法。為了斷言哪些物件正在呼叫這個特定方法，你需要將 self 作為第一個引數傳入。問題是你無法為此使用 mock 進行 patch，因為就算你用一個 mock 替換未繫結方法，從實例取得它時它也不會成為一個繫結方法，因此 self 並不會被傳遞。解決方法是使用真實的函式來 patch 未繫結方法。patch() 裝飾器使得用 mock 來 patch out 方法是如此的簡單，以至於建立一個真正的函式相對變得很麻煩。

如果你將 autospec=True 傳遞給 patch，那麼它會使用真的函式物件來進行 patch。此函式物件與它所替換的函式物件具有相同的簽名，但實際上委託給 mock。你仍然會以與之前完全相同的方式自動建立 mock。但這意味著，如果你使用它來 patch 類別上的未繫結方法，則從實例取得的 mock 函式將轉換為繫結方法。self 會作為其第一個引數傳入，而這正是我們需要的：

>>> class Foo:
...   def foo(self):
...     pass
...
>>> with patch.object(Foo, 'foo', autospec=True) as mock_foo:
...   mock_foo.return_value = 'foo'
...   foo = Foo()
...   foo.foo()
...
'foo'
>>> mock_foo.assert_called_once_with(foo)

如果我們不使用 autospec=True，那麼未繫結方法將使用一個 Mock 實例 patch out，並且不被使用 self 進行呼叫。

使用 mock 檢查多個呼叫

mock 有很好的 API，用於對 mock 物件的使用方式做出斷言。

>>> mock = Mock()
>>> mock.foo_bar.return_value = None
>>> mock.foo_bar('baz', spam='eggs')
>>> mock.foo_bar.assert_called_with('baz', spam='eggs')

如果你的 mock 只被呼叫一次，你可以使用 assert_called_once_with() 方法，其也斷言 call_count 是1。

>>> mock.foo_bar.assert_called_once_with('baz', spam='eggs')
>>> mock.foo_bar()
>>> mock.foo_bar.assert_called_once_with('baz', spam='eggs')
Traceback (most recent call last):
    ...
AssertionError: Expected 'foo_bar' to be called once. Called 2 times.
Calls: [call('baz', spam='eggs'), call()].

assert_called_with 和 assert_called_once_with 都對最近一次的呼叫做出斷言。如果你的 mock 將被多次呼叫，並且你想要對所有這些呼叫進行斷言，你可以使用 call_args_list：

>>> mock = Mock(return_value=None)
>>> mock(1, 2, 3)
>>> mock(4, 5, 6)
>>> mock()
>>> mock.call_args_list
[call(1, 2, 3), call(4, 5, 6), call()]

call 輔助函式可以輕鬆地對這些呼叫做出斷言。你可以建立預期呼叫的清單並將其與 call_args_list 進行比較。這看起來與 call_args_list 的 repr 非常相似：

>>> expected = [call(1, 2, 3), call(4, 5, 6), call()]
>>> mock.call_args_list == expected
True

應對可變引數

另一種情況很少見，但可能會困擾你，那就是當你的 mock 被使用可變引數呼叫。call_args 和 call_args_list 儲存對引數的參照。如果引數被測試中的程式碼改變，那麼你將無法再對 mock 被呼叫時的值進行斷言。

這是一些秀出問題的程式碼範例。 想像 'mymodule' 中定義以下函式：

def frob(val):
    pass

def grob(val):
    "First frob and then clear val"
    frob(val)
    val.clear()

當我們嘗試測試 grob 使用正確的引數呼叫 frob 時，看看會發生什麼：

>>> with patch('mymodule.frob') as mock_frob:
...     val = {6}
...     mymodule.grob(val)
...
>>> val
set()
>>> mock_frob.assert_called_with({6})
Traceback (most recent call last):
    ...
AssertionError: Expected: (({6},), {})
Called with: ((set(),), {})

一種可能是讓 mock 複製你傳入的引數。如果你進行的斷言依賴於物件識別性來確定相等性，這就可能導致問題。

以下是一種使用 side_effect 功能的解法。如果你為 mock 提供一個 side_effect 函式，則 side_effect 將被使用與 mock 相同的引數呼叫。這使我們有機會複製引數並將其儲存以供之後的斷言。在這個範例中，我們使用另一個 mock 來儲存引數，以便我們可以使用 mock 方法來執行斷言。同樣的，有一個輔助函式為我們設定了這些。：

>>> from copy import deepcopy
>>> from unittest.mock import Mock, patch, DEFAULT
>>> def copy_call_args(mock):
...     new_mock = Mock()
...     def side_effect(*args, **kwargs):
...         args = deepcopy(args)
...         kwargs = deepcopy(kwargs)
...         new_mock(*args, **kwargs)
...         return DEFAULT
...     mock.side_effect = side_effect
...     return new_mock
...
>>> with patch('mymodule.frob') as mock_frob:
...     new_mock = copy_call_args(mock_frob)
...     val = {6}
...     mymodule.grob(val)
...
>>> new_mock.assert_called_with({6})
>>> new_mock.call_args
call({6})

copy_call_args 與將要被呼叫的 mock 一起被呼叫。它回傳一個我們會對其進行斷言的新的 mock。side_effect 函式建立引數們的副本，並用該副本呼叫我們的 new_mock。

備註

如果你的 mock 只會被使用一次，則有一種更簡單的方法可以在呼叫引數時檢查它們。你可以簡單地在 side_effect 函式內進行檢查。

>>> def side_effect(arg):
...     assert arg == {6}
...
>>> mock = Mock(side_effect=side_effect)
>>> mock({6})
>>> mock(set())
Traceback (most recent call last):
    ...
AssertionError

另一種方法是建立 Mock 或 MagicMock 的子類別來複製（使用 copy.deepcopy()）引數。這是一個實作的例子：

>>> from copy import deepcopy
>>> class CopyingMock(MagicMock):
...     def __call__(self, /, *args, **kwargs):
...         args = deepcopy(args)
...         kwargs = deepcopy(kwargs)
...         return super().__call__(*args, **kwargs)
...
>>> c = CopyingMock(return_value=None)
>>> arg = set()
>>> c(arg)
>>> arg.add(1)
>>> c.assert_called_with(set())
>>> c.assert_called_with(arg)
Traceback (most recent call last):
    ...
AssertionError: expected call not found.
Expected: mock({1})
Actual: mock(set())
>>> c.foo
<CopyingMock name='mock.foo' id='...'>

當你將 Mock 或 MagicMock 子類別化時，所有屬性會被動態建立，且 return_value 會自動使用你的子類別。這代表著 CopyingMock 的所有子代 (child) 也會具有 CopyingMock 型別。

巢狀使用 Patch

將 patch 作為情境管理器使用很好，但是如果你使用複數個 patch，你最終可能會得到巢狀的 with 陳述式，並且越來越向右縮排：

>>> class MyTest(unittest.TestCase):
...
...     def test_foo(self):
...         with patch('mymodule.Foo') as mock_foo:
...             with patch('mymodule.Bar') as mock_bar:
...                 with patch('mymodule.Spam') as mock_spam:
...                     assert mymodule.Foo is mock_foo
...                     assert mymodule.Bar is mock_bar
...                     assert mymodule.Spam is mock_spam
...
>>> original = mymodule.Foo
>>> MyTest('test_foo').test_foo()
>>> assert mymodule.Foo is original

我們可以使用 unittest 的 cleanup 函式以及 patch 方法：啟動與停止 來達到相同的效果，而不會出現因巢狀導致的縮排。一個簡單的輔助方法 create_patch 會將 patch 放置到位並為我們回傳被建立的 mock：

>>> class MyTest(unittest.TestCase):
...
...     def create_patch(self, name):
...         patcher = patch(name)
...         thing = patcher.start()
...         self.addCleanup(patcher.stop)
...         return thing
...
...     def test_foo(self):
...         mock_foo = self.create_patch('mymodule.Foo')
...         mock_bar = self.create_patch('mymodule.Bar')
...         mock_spam = self.create_patch('mymodule.Spam')
...
...         assert mymodule.Foo is mock_foo
...         assert mymodule.Bar is mock_bar
...         assert mymodule.Spam is mock_spam
...
>>> original = mymodule.Foo
>>> MyTest('test_foo').run()
>>> assert mymodule.Foo is original

使用 MagicMock 來 mock 字典

你可能會想要 mock 字典或其他容器物件，記錄對它的所有存取，同時讓它仍然像字典一樣運作。

我們可以使用 MagicMock 來做到這一點，它的行為會與字典一致，並使用 side_effect 將字典存取委託給我們控制下的真實底層字典。

當 MagicMock 的 __getitem__() 和 __setitem__() 方法被呼叫時（一般的字典存取）， side_effect 會被使用鍵 (key) 來呼叫 （在 __setitem__ 的情況也會使用值 (value)）。我們也可以控制回傳的內容。

使用 MagicMock 後，我們可以使用諸如 call_args_list 之類的屬性來斷言字典被使用的方式：

>>> my_dict = {'a': 1, 'b': 2, 'c': 3}
>>> def getitem(name):
...      return my_dict[name]
...
>>> def setitem(name, val):
...     my_dict[name] = val
...
>>> mock = MagicMock()
>>> mock.__getitem__.side_effect = getitem
>>> mock.__setitem__.side_effect = setitem

備註

不使用 MagicMock 的替代方案是使用 Mock 並且只提供你特別想要的魔術方法：

>>> mock = Mock()
>>> mock.__getitem__ = Mock(side_effect=getitem)
>>> mock.__setitem__ = Mock(side_effect=setitem)

第三個選擇是使用 MagicMock，但傳入 dict 作為 spec （或 spec_set）引數，以使被建立的 MagicMock 僅具有字典可用的魔術方法：

>>> mock = MagicMock(spec_set=dict)
>>> mock.__getitem__.side_effect = getitem
>>> mock.__setitem__.side_effect = setitem

有了這些 side effect 函式，mock 會像一般的字典一樣運作，但會記錄存取。如果你嘗試存取不存在的鍵，它甚至會引發一個 KeyError。

>>> mock['a']
1
>>> mock['c']
3
>>> mock['d']
Traceback (most recent call last):
    ...
KeyError: 'd'
>>> mock['b'] = 'fish'
>>> mock['d'] = 'eggs'
>>> mock['b']
'fish'
>>> mock['d']
'eggs'

在上述方式被使用後，你就可以使用普通的 mock 方法和屬性對存取進行斷言：

>>> mock.__getitem__.call_args_list
[call('a'), call('c'), call('d'), call('b'), call('d')]
>>> mock.__setitem__.call_args_list
[call('b', 'fish'), call('d', 'eggs')]
>>> my_dict
{'a': 1, 'b': 'fish', 'c': 3, 'd': 'eggs'}

Mock 子類別及其屬性

你會想子類別化 Mock 的原因可能有很多種。其中之一是增加輔助方法。以下是一個有點笨的例子：

>>> class MyMock(MagicMock):
...     def has_been_called(self):
...         return self.called
...
>>> mymock = MyMock(return_value=None)
>>> mymock
<MyMock id='...'>
>>> mymock.has_been_called()
False
>>> mymock()
>>> mymock.has_been_called()
True

Mock 實例的標準行為是屬性 mock 和回傳值 mock 會與存取它們的 mock 具有相同的型別。這確保了 Mock 屬性是 Mocks，MagicMock 屬性是 MagicMocks [2]。因此，如果你要子類別化以新增輔助方法，那麼它們也可用於子類別實例的屬性 mock 和回傳值 mock。

>>> mymock.foo
<MyMock name='mock.foo' id='...'>
>>> mymock.foo.has_been_called()
False
>>> mymock.foo()
<MyMock name='mock.foo()' id='...'>
>>> mymock.foo.has_been_called()
True

有時候這很不方便。例如，有一個使用者 [https://code.google.com/archive/p/mock/issues/105]正在子類別化 mock 以建立 Twisted adaptor [https://twisted.org/documents/11.0.0/api/twisted.python.components.html]。將其應用於屬性實際上會導致錯誤。

Mock （及其各種形式）使用名為 _get_child_mock 的方法來為屬性和回傳值建立這些 "子 mock"。你可以透過置換此方法來防止你的子類別被用為屬性。其簽名是取用任意的關鍵字引數（**kwargs），然後將其傳遞給 mock 建構函式：

>>> class Subclass(MagicMock):
...     def _get_child_mock(self, /, **kwargs):
...         return MagicMock(**kwargs)
...
>>> mymock = Subclass()
>>> mymock.foo
<MagicMock name='mock.foo' id='...'>
>>> assert isinstance(mymock, Subclass)
>>> assert not isinstance(mymock.foo, Subclass)
>>> assert not isinstance(mymock(), Subclass)

[2]

此規則的例外是非可呼叫物件的 mock。屬性使用可呼叫物件的變體，否則非可呼叫物件的 mock 無法具有可呼叫的方法。

使用 patch.dict 來 mock import

可能會讓 mock 很困難的一種情況是在函式內部進行區域 import。這些狀況會更難進行 mock，因為它們沒有使用我們可以 patch out 的模組命名空間中的物件。

一般來說，我們應該避免區域 import 的發生。有時這樣做是為了防止循環相依 (circular dependencies)，為此通常有更好的方式來解決問題（例如重構程式碼）或透過延遲 import 來防止「前期成本 (up front costs)」。這也可以透過比無條件的區域 import 更好的方式來解決（例如將模組儲存為類別或模組屬性，並且僅在第一次使用時進行 import）。

除此之外，還有一種方法可以使用 mock 來影響 import 的結果。Import 會從 sys.modules 字典中取得一個物件。請注意，它會取得一個物件，而該物件不需要是一個模組。初次 import 模組會導致模組物件被放入 sys.modules 中，因此通常當你 import 某些東西時，你會得到一個模組。但並非一定要如此。

這代表你可以使用 patch.dict() 來暫時在 sys.modules 中原地放置 mock。在這個 patch 作用時的任何 import 都會取得這個 mock。當 patch 完成時（被裝飾的函式結束、with 陳述式主體完成或 patcher.stop() 被呼叫），那麼之前在 sys.modules 中的任何內容都會被安全地復原。

下面是一個 mock out 'fooble' 模組的例子。

>>> import sys
>>> mock = Mock()
>>> with patch.dict('sys.modules', {'fooble': mock}):
...    import fooble
...    fooble.blob()
...
<Mock name='mock.blob()' id='...'>
>>> assert 'fooble' not in sys.modules
>>> mock.blob.assert_called_once_with()

如你所見，import fooble 成功了，但在離開之後，sys.modules 中就沒有 'fooble' 了。

這也適用於 from module import name 形式：

>>> mock = Mock()
>>> with patch.dict('sys.modules', {'fooble': mock}):
...    from fooble import blob
...    blob.blip()
...
<Mock name='mock.blob.blip()' id='...'>
>>> mock.blob.blip.assert_called_once_with()

透過稍微多一點的處理，你也可以 mock 套件的引入：

>>> mock = Mock()
>>> modules = {'package': mock, 'package.module': mock.module}
>>> with patch.dict('sys.modules', modules):
...    from package.module import fooble
...    fooble()
...
<Mock name='mock.module.fooble()' id='...'>
>>> mock.module.fooble.assert_called_once_with()

追蹤呼叫順序與更簡潔的呼叫斷言

Mock 類別可以讓你透過 method_calls 屬性追蹤 mock 物件上方法呼叫的順序。這不會讓你可以追蹤不同的 mock 物件之間的呼叫順序，然而我們可以使用 mock_calls 來達到相同的效果。

因為 mock 會在 mock_calls 中追蹤對子 mock 的呼叫，且存取 mock 的任意屬性會建立一個子 mock，所以我們可以從父 mock 建立不同的 mock。之後對這些子 mock 的呼叫將依序全部記錄在父 mock 的 mock_calls 中：

>>> manager = Mock()
>>> mock_foo = manager.foo
>>> mock_bar = manager.bar

>>> mock_foo.something()
<Mock name='mock.foo.something()' id='...'>
>>> mock_bar.other.thing()
<Mock name='mock.bar.other.thing()' id='...'>

>>> manager.mock_calls
[call.foo.something(), call.bar.other.thing()]

之後我們可以透過與管理器 (manager) mock 上的 mock_calls 屬性進行比較來斷言呼叫及其順序：

>>> expected_calls = [call.foo.something(), call.bar.other.thing()]
>>> manager.mock_calls == expected_calls
True

如果 patch 正在被建立並放置為你的 mock，那麼你可以使用 attach_mock() 方法將它們附加到管理器 mock。附加之後，呼叫將被記錄在管理器的 mock_calls 中。：

>>> manager = MagicMock()
>>> with patch('mymodule.Class1') as MockClass1:
...     with patch('mymodule.Class2') as MockClass2:
...         manager.attach_mock(MockClass1, 'MockClass1')
...         manager.attach_mock(MockClass2, 'MockClass2')
...         MockClass1().foo()
...         MockClass2().bar()
<MagicMock name='mock.MockClass1().foo()' id='...'>
<MagicMock name='mock.MockClass2().bar()' id='...'>
>>> manager.mock_calls
[call.MockClass1(),
call.MockClass1().foo(),
call.MockClass2(),
call.MockClass2().bar()]

如果進行了多次呼叫，但你只對其中特定呼叫的序列感興趣，則可以使用 assert_has_calls() 方法。這需要一個呼叫串列（使用 call 物件建構）。如果該呼叫序列位於 mock_calls 中，則斷言成功。

>>> m = MagicMock()
>>> m().foo().bar().baz()
<MagicMock name='mock().foo().bar().baz()' id='...'>
>>> m.one().two().three()
<MagicMock name='mock.one().two().three()' id='...'>
>>> calls = call.one().two().three().call_list()
>>> m.assert_has_calls(calls)

儘管鍊接呼叫 m.one().two().three() 並不是對 mock 進行的唯一呼叫，斷言仍會成功。

有時可能會對一個 mock 進行多次呼叫，而你只對斷言其中某些呼叫感興趣。你甚至可能不關心順序。在這種情況下，你可以將 any_order=True 傳遞給 assert_has_calls：

>>> m = MagicMock()
>>> m(1), m.two(2, 3), m.seven(7), m.fifty('50')
(...)
>>> calls = [call.fifty('50'), call(1), call.seven(7)]
>>> m.assert_has_calls(calls, any_order=True)

更複雜的引數匹配

使用與 ANY 相同的基本概念，我們可以實作匹配器 (matcher)，對用來作為 mock 引數的物件進行更複雜的斷言。

假設我們預期某個物件會被傳進 mock，預設情況下，該 mock 會根據物件識別性進行相等比較（對使用者定義類別的 Python 預設行為）。要使用 assert_called_with()，我們需要傳入完全相同的物件。如果我們只對該物件的某些屬性感興趣，那麼我們可以建立一個匹配器來為我們檢查這些屬性。

你可以在這個範例中看到對 assert_called_with 的一個「標準」呼叫是不夠的：

>>> class Foo:
...     def __init__(self, a, b):
...         self.a, self.b = a, b
...
>>> mock = Mock(return_value=None)
>>> mock(Foo(1, 2))
>>> mock.assert_called_with(Foo(1, 2))
Traceback (most recent call last):
    ...
AssertionError: expected call not found.
Expected: mock(<__main__.Foo object at 0x...>)
Actual: mock(<__main__.Foo object at 0x...>)

對我們的 Foo 類別的比較函式看起來可能會像這樣：

>>> def compare(self, other):
...     if not type(self) == type(other):
...         return False
...     if self.a != other.a:
...         return False
...     if self.b != other.b:
...         return False
...     return True
...

而可以使用像這樣的比較函式進行其相等性運算的匹配器物件會長得像這樣：

>>> class Matcher:
...     def __init__(self, compare, some_obj):
...         self.compare = compare
...         self.some_obj = some_obj
...     def __eq__(self, other):
...         return self.compare(self.some_obj, other)
...

把這些都放在一起：

>>> match_foo = Matcher(compare, Foo(1, 2))
>>> mock.assert_called_with(match_foo)

Matcher 是用我們想要比較的 Foo 物件和比較函式實例化的。在 assert_called_with 中，Matcher 相等方法將被呼叫，它將呼叫 mock 時傳入的物件與我們建立匹配器時傳入的物件進行比較。如果它們匹配，則 assert_called_with 會通過，如果它們不匹配，則會引發 AssertionError：

>>> match_wrong = Matcher(compare, Foo(3, 4))
>>> mock.assert_called_with(match_wrong)
Traceback (most recent call last):
    ...
AssertionError: Expected: ((<Matcher object at 0x...>,), {})
Called with: ((<Foo object at 0x...>,), {})

透過一些調整，你可以讓比較函式直接引發 AssertionError 並提供更有用的失敗訊息。

從版本 1.5 開始，Python 測試函式庫 PyHamcrest [https://pyhamcrest.readthedocs.io/] 以其相等匹配器的形式，提供了類似的功能，在這裡可能是有用的 (hamcrest.library.integration.match_equality [https://pyhamcrest.readthedocs.io/en/release-1.8/integration/#module-hamcrest.library.integration.match_equality])。

test --- Python 的回歸測試 (regression tests) 套件

備註

The test package is meant for internal use by Python only. It is documented for the benefit of the core developers of Python. Any use of this package outside of Python's standard library is discouraged as code mentioned here can change or be removed without notice between releases of Python.

The test package contains all regression tests for Python as well as the modules test.support and test.regrtest. test.support is used to enhance your tests while test.regrtest drives the testing suite.

Each module in the test package whose name starts with test_ is a testing suite for a specific module or feature. All new tests should be written using the unittest or doctest module. Some older tests are written using a "traditional" testing style that compares output printed to sys.stdout; this style of test is considered deprecated.

也參考

unittest 模組

撰寫 PyUnit 回歸測試。

doctest 模組

鑲嵌在文件字串中的測試。

撰寫 test 套件的單元測試

It is preferred that tests that use the unittest module follow a few guidelines. One is to name the test module by starting it with test_ and end it with the name of the module being tested. The test methods in the test module should start with test_ and end with a description of what the method is testing. This is needed so that the methods are recognized by the test driver as test methods. Also, no documentation string for the method should be included. A comment (such as # Tests function returns only True or False) should be used to provide documentation for test methods. This is done because documentation strings get printed out if they exist and thus what test is being run is not stated.

A basic boilerplate is often used:

import unittest
from test import support

class MyTestCase1(unittest.TestCase):

    # Only use setUp() and tearDown() if necessary

    def setUp(self):
        ... code to execute in preparation for tests ...

    def tearDown(self):
        ... code to execute to clean up after tests ...

    def test_feature_one(self):
        # Test feature one.
        ... testing code ...

    def test_feature_two(self):
        # Test feature two.
        ... testing code ...

    ... more test methods ...

class MyTestCase2(unittest.TestCase):
    ... same structure as MyTestCase1 ...

... more test classes ...

if __name__ == '__main__':
    unittest.main()

This code pattern allows the testing suite to be run by test.regrtest, on its own as a script that supports the unittest CLI, or via the python -m unittest CLI.

The goal for regression testing is to try to break code. This leads to a few guidelines to be followed:

The testing suite should exercise all classes, functions, and constants. This includes not just the external API that is to be presented to the outside world but also "private" code.

Whitebox testing (examining the code being tested when the tests are being written) is preferred. Blackbox testing (testing only the published user interface) is not complete enough to make sure all boundary and edge cases are tested.

Make sure all possible values are tested including invalid ones. This makes sure that not only all valid values are acceptable but also that improper values are handled correctly.

Exhaust as many code paths as possible. Test where branching occurs and thus tailor input to make sure as many different paths through the code are taken.

Add an explicit test for any bugs discovered for the tested code. This will make sure that the error does not crop up again if the code is changed in the future.

Make sure to clean up after your tests (such as close and remove all temporary files).

If a test is dependent on a specific condition of the operating system then verify the condition already exists before attempting the test.

Import as few modules as possible and do it as soon as possible. This minimizes external dependencies of tests and also minimizes possible anomalous behavior from side-effects of importing a module.

Try to maximize code reuse. On occasion, tests will vary by something as small as what type of input is used. Minimize code duplication by subclassing a basic test class with a class that specifies the input:

class TestFuncAcceptsSequencesMixin:

    func = mySuperWhammyFunction

    def test_func(self):
        self.func(self.arg)

class AcceptLists(TestFuncAcceptsSequencesMixin, unittest.TestCase):
    arg = [1, 2, 3]

class AcceptStrings(TestFuncAcceptsSequencesMixin, unittest.TestCase):
    arg = 'abc'

class AcceptTuples(TestFuncAcceptsSequencesMixin, unittest.TestCase):
    arg = (1, 2, 3)

When using this pattern, remember that all classes that inherit from unittest.TestCase are run as tests. The TestFuncAcceptsSequencesMixin class in the example above does not have any data and so can't be run by itself, thus it does not inherit from unittest.TestCase.

也參考

測試驅動開發

由 Kent Beck 所著，關於先寫測試再寫程式的書籍。

使用命令列介面執行測試

The test package can be run as a script to drive Python's regression test suite, thanks to the -m option: python -m test. Under the hood, it uses test.regrtest; the call python -m test.regrtest used in previous Python versions still works. Running the script by itself automatically starts running all regression tests in the test package. It does this by finding all modules in the package whose name starts with test_, importing them, and executing the function test_main() if present or loading the tests via unittest.TestLoader.loadTestsFromModule if test_main does not exist. The names of tests to execute may also be passed to the script. Specifying a single regression test (python -m test test_spam) will minimize output and only print whether the test passed or failed.

Running test directly allows what resources are available for tests to use to be set. You do this by using the -u command-line option. Specifying all as the value for the -u option enables all possible resources: python -m test -uall. If all but one resource is desired (a more common case), a comma-separated list of resources that are not desired may be listed after all. The command python -m test -uall,-audio,-largefile will run test with all resources except the audio and largefile resources. For a list of all resources and more command-line options, run python -m test -h.

Some other ways to execute the regression tests depend on what platform the tests are being executed on. On Unix, you can run make test at the top-level directory where Python was built. On Windows, executing rt.bat from your PCbuild directory will run all regression tests.

在 3.14 版被加入: Output is colorized by default and can be controlled using environment variables.

test.support --- Python 測試套件的工具

test.support 模組提供 Python 回歸測試套件的支援。

備註

test.support is not a public module. It is documented here to help Python developers write tests. The API of this module is subject to change without backwards compatibility concerns between releases.

此模組定義了以下例外：

exception test.support.TestFailed

Exception to be raised when a test fails. This is deprecated in favor of unittest-based tests and unittest.TestCase's assertion methods.

exception test.support.ResourceDenied

Subclass of unittest.SkipTest. Raised when a resource (such as a network connection) is not available. Raised by the requires() function.

test.support 模組定義了以下常數：

test.support.verbose

True when verbose output is enabled. Should be checked when more detailed information is desired about a running test. verbose is set by test.regrtest.

test.support.is_jython

如果執行的直譯器是 Jython，則為 True。

test.support.is_android

如果 sys.platform 是 android 則為 True。

test.support.is_emscripten

如果 sys.platform 是 emscripten 則為 True。

test.support.is_wasi

如果 sys.platform 是 wasi 則為 True。

test.support.is_apple_mobile

如果 sys.platform 是 ios、tvos 或 watchos 則為 True。

test.support.is_apple

True if sys.platform is darwin or is_apple_mobile is True.

test.support.unix_shell

Path for shell if not on Windows; otherwise None.

test.support.LOOPBACK_TIMEOUT

Timeout in seconds for tests using a network server listening on the network local loopback interface like 127.0.0.1.

The timeout is long enough to prevent test failure: it takes into account that the client and the server can run in different threads or even different processes.

The timeout should be long enough for connect(), recv() and send() methods of socket.socket.

預設值為 5 秒。

另請參閱 INTERNET_TIMEOUT。

test.support.INTERNET_TIMEOUT

Timeout in seconds for network requests going to the internet.

The timeout is short enough to prevent a test to wait for too long if the internet request is blocked for whatever reason.

Usually, a timeout using INTERNET_TIMEOUT should not mark a test as failed, but skip the test instead: see transient_internet().

預設值為 1 分鐘。

另請參閱 LOOPBACK_TIMEOUT。

test.support.SHORT_TIMEOUT

Timeout in seconds to mark a test as failed if the test takes "too long".

The timeout value depends on the regrtest --timeout command line option.

If a test using SHORT_TIMEOUT starts to fail randomly on slow buildbots, use LONG_TIMEOUT instead.

預設值為 30 秒。

test.support.LONG_TIMEOUT

Timeout in seconds to detect when a test hangs.

It is long enough to reduce the risk of test failure on the slowest Python buildbots. It should not be used to mark a test as failed if the test takes "too long". The timeout value depends on the regrtest --timeout command line option.

預設值為 5 分鐘。

請參閱 LOOPBACK_TIMEOUT、INTERNET_TIMEOUT 和 SHORT_TIMEOUT。

test.support.PGO

Set when tests can be skipped when they are not useful for PGO.

test.support.PIPE_MAX_SIZE

A constant that is likely larger than the underlying OS pipe buffer size, to make writes blocking.

test.support.Py_DEBUG

True if Python was built with the Py_DEBUG macro defined, that is, if Python was built in debug mode.

在 3.12 版被加入.

test.support.SOCK_MAX_SIZE

A constant that is likely larger than the underlying OS socket buffer size, to make writes blocking.

test.support.TEST_SUPPORT_DIR

設定為包含 test.support 的頂層目錄。

test.support.TEST_HOME_DIR

設定為測試套件的頂層目錄。

test.support.TEST_DATA_DIR

設定為測試套件中的 data 目錄。

test.support.MAX_Py_ssize_t

設定為 sys.maxsize 以進行大記憶體測試。

test.support.max_memuse

Set by set_memlimit() as the memory limit for big memory tests. Limited by MAX_Py_ssize_t.

test.support.real_max_memuse

Set by set_memlimit() as the memory limit for big memory tests. Not limited by MAX_Py_ssize_t.

test.support.MISSING_C_DOCSTRINGS

Set to True if Python is built without docstrings (the WITH_DOC_STRINGS macro is not defined). See the configure --without-doc-strings option.

另請參閱 HAVE_DOCSTRINGS 變數。

test.support.HAVE_DOCSTRINGS

Set to True if function docstrings are available. See the python -OO option, which strips docstrings of functions implemented in Python.

請參閱 MISSING_C_DOCSTRINGS 變數。

test.support.TEST_HTTP_URL

Define the URL of a dedicated HTTP server for the network tests.

test.support.ALWAYS_EQ

Object that is equal to anything. Used to test mixed type comparison.

test.support.NEVER_EQ

Object that is not equal to anything (even to ALWAYS_EQ). Used to test mixed type comparison.

test.support.LARGEST

Object that is greater than anything (except itself). Used to test mixed type comparison.

test.support.SMALLEST

Object that is less than anything (except itself). Used to test mixed type comparison.

test.support 模組定義了以下函式：

test.support.busy_retry(timeout, err_msg=None, /, *, error=True)

執行迴圈主體直到 break 停止迴圈。

After timeout seconds, raise an AssertionError if error is true, or just stop the loop if error is false.

範例：

for _ in support.busy_retry(support.SHORT_TIMEOUT):
    if check():
        break

error=False 用法範例：

for _ in support.busy_retry(support.SHORT_TIMEOUT, error=False):
    if check():
        break
else:
    raise RuntimeError('my custom error')

test.support.sleeping_retry(timeout, err_msg=None, /, *, init_delay=0.010, max_delay=1.0, error=True)

Wait strategy that applies exponential backoff.

Run the loop body until break stops the loop. Sleep at each loop iteration, but not at the first iteration. The sleep delay is doubled at each iteration (up to max_delay seconds).

請見 busy_retry() 文件以瞭解參數用法。

在 SHORT_TIMEOUT 秒後引發例外的範例：

for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
    if check():
        break

error=False 用法範例：

for _ in support.sleeping_retry(support.SHORT_TIMEOUT, error=False):
    if check():
        break
else:
    raise RuntimeError('my custom error')

test.support.is_resource_enabled(resource)

Return True if resource is enabled and available. The list of available resources is only set when test.regrtest is executing the tests.

test.support.get_resource_value(resource)

Return the value specified for resource (as -u resource=value). Return None if resource is disabled or no value is specified.

test.support.python_is_optimized()

如果 Python 不是使用 -O0 或 -Og 建置則回傳 True。

test.support.with_pymalloc()

回傳 _testcapi.WITH_PYMALLOC。

test.support.requires(resource, msg=None)

Raise ResourceDenied if resource is not available. msg is the argument to ResourceDenied if it is raised. Always returns True if called by a function whose __name__ is '__main__'. Used when tests are executed by test.regrtest.

test.support.sortdict(dict)

Return a repr of dict with keys sorted.

test.support.findfile(filename, subdir=None)

Return the path to the file named filename. If no match is found filename is returned. This does not equal a failure since it could be the path to the file.

Setting subdir indicates a relative path to use to find the file rather than looking directly in the path directories.

test.support.get_pagesize()

Get size of a page in bytes.

在 3.12 版被加入.

test.support.setswitchinterval(interval)

Set the sys.setswitchinterval() to the given interval. Defines a minimum interval for Android systems to prevent the system from hanging.

test.support.check_impl_detail(**guards)

Use this check to guard CPython's implementation-specific tests or to run them only on the implementations guarded by the arguments. This function returns True or False depending on the host platform. Example usage:

check_impl_detail()               # Only on CPython (default).
check_impl_detail(jython=True)    # Only on Jython.
check_impl_detail(cpython=False)  # Everywhere except CPython.

test.support.set_memlimit(limit)

Set the values for max_memuse and real_max_memuse for big memory tests.

test.support.record_original_stdout(stdout)

Store the value from stdout. It is meant to hold the stdout at the time the regrtest began.

test.support.get_original_stdout()

Return the original stdout set by record_original_stdout() or sys.stdout if it's not set.

test.support.args_from_interpreter_flags()

Return a list of command line arguments reproducing the current settings in sys.flags and sys.warnoptions.

test.support.optim_args_from_interpreter_flags()

Return a list of command line arguments reproducing the current optimization settings in sys.flags.

test.support.captured_stdin()

test.support.captured_stdout()

test.support.captured_stderr()

A context managers that temporarily replaces the named stream with io.StringIO object.

使用輸出串流的範例：

with captured_stdout() as stdout, captured_stderr() as stderr:
    print("hello")
    print("error", file=sys.stderr)
assert stdout.getvalue() == "hello\n"
assert stderr.getvalue() == "error\n"

使用輸入串流的範例：

with captured_stdin() as stdin:
    stdin.write('hello\n')
    stdin.seek(0)
    # call test code that consumes from sys.stdin
    captured = input()
self.assertEqual(captured, "hello")

test.support.disable_faulthandler()

A context manager that temporary disables faulthandler.

test.support.gc_collect()

Force as many objects as possible to be collected. This is needed because timely deallocation is not guaranteed by the garbage collector. This means that __del__ methods may be called later than expected and weakrefs may remain alive for longer than expected.

test.support.disable_gc()

A context manager that disables the garbage collector on entry. On exit, the garbage collector is restored to its prior state.

test.support.swap_attr(obj, attr, new_val)

Context manager to swap out an attribute with a new object.

用法：

with swap_attr(obj, "attr", 5):
    ...

This will set obj.attr to 5 for the duration of the with block, restoring the old value at the end of the block. If attr doesn't exist on obj, it will be created and then deleted at the end of the block.

The old value (or None if it doesn't exist) will be assigned to the target of the "as" clause, if there is one.

test.support.swap_item(obj, attr, new_val)

Context manager to swap out an item with a new object.

用法：

with swap_item(obj, "item", 5):
    ...

This will set obj["item"] to 5 for the duration of the with block, restoring the old value at the end of the block. If item doesn't exist on obj, it will be created and then deleted at the end of the block.

The old value (or None if it doesn't exist) will be assigned to the target of the "as" clause, if there is one.

test.support.flush_std_streams()

Call the flush() method on sys.stdout and then on sys.stderr. It can be used to make sure that the logs order is consistent before writing into stderr.

在 3.11 版被加入.

test.support.print_warning(msg)

Print a warning into sys.__stderr__. Format the message as: f"Warning -- {msg}". If msg is made of multiple lines, add "Warning -- " prefix to each line.

在 3.9 版被加入.

test.support.wait_process(pid, *, exitcode, timeout=None)

Wait until process pid completes and check that the process exit code is exitcode.

如果行程退出代號不等於 exitcode 則引發 AssertionError。

If the process runs longer than timeout seconds (SHORT_TIMEOUT by default), kill the process and raise an AssertionError. The timeout feature is not available on Windows.

在 3.9 版被加入.

test.support.calcobjsize(fmt)

Return the size of the PyObject whose structure members are defined by fmt. The returned value includes the size of the Python object header and alignment.

test.support.calcvobjsize(fmt)

Return the size of the PyVarObject whose structure members are defined by fmt. The returned value includes the size of the Python object header and alignment.

test.support.checksizeof(test, o, size)

For testcase test, assert that the sys.getsizeof for o plus the GC header size equals size.

@test.support.anticipate_failure(condition)

A decorator to conditionally mark tests with unittest.expectedFailure(). Any use of this decorator should have an associated comment identifying the relevant tracker issue.

test.support.system_must_validate_cert(f)

A decorator that skips the decorated test on TLS certification validation failures.

@test.support.run_with_locale(catstr, *locales)

A decorator for running a function in a different locale, correctly resetting it after it has finished. catstr is the locale category as a string (for example "LC_ALL"). The locales passed will be tried sequentially, and the first valid locale will be used.

@test.support.run_with_tz(tz)

A decorator for running a function in a specific timezone, correctly resetting it after it has finished.

@test.support.requires_freebsd_version(*min_version)

Decorator for the minimum version when running test on FreeBSD. If the FreeBSD version is less than the minimum, the test is skipped.

@test.support.requires_linux_version(*min_version)

Decorator for the minimum version when running test on Linux. If the Linux version is less than the minimum, the test is skipped.

@test.support.requires_mac_version(*min_version)

Decorator for the minimum version when running test on macOS. If the macOS version is less than the minimum, the test is skipped.

@test.support.requires_gil_enabled

Decorator for skipping tests on the free-threaded build. If the GIL is disabled, the test is skipped.

@test.support.requires_IEEE_754

Decorator for skipping tests on non-IEEE 754 platforms.

@test.support.requires_zlib

如果 zlib 不存在則跳過測試的裝飾器。

@test.support.requires_gzip

如果 gzip 不存在則跳過測試的裝飾器。

@test.support.requires_bz2

如果 bz2 不存在則跳過測試的裝飾器。

@test.support.requires_lzma

如果 lzma 不存在則跳過測試的裝飾器。

@test.support.requires_resource(resource)

如果 resource 不可用則跳過測試的裝飾器。

@test.support.requires_docstrings

Decorator for only running the test if HAVE_DOCSTRINGS.

@test.support.requires_limited_api

Decorator for only running the test if Limited C API is available.

@test.support.cpython_only

Decorator for tests only applicable to CPython.

@test.support.impl_detail(msg=None, **guards)

Decorator for invoking check_impl_detail() on guards. If that returns False, then uses msg as the reason for skipping the test.

@test.support.thread_unsafe(reason=None)

Decorator for marking tests as thread-unsafe. This test always runs in one thread even when invoked with --parallel-threads.

@test.support.no_tracing

Decorator to temporarily turn off tracing for the duration of the test.

@test.support.refcount_test

Decorator for tests which involve reference counting. The decorator does not run the test if it is not run by CPython. Any trace function is unset for the duration of the test to prevent unexpected refcounts caused by the trace function.

@test.support.bigmemtest(size, memuse, dry_run=True)

大記憶體測試的裝飾器。

size is a requested size for the test (in arbitrary, test-interpreted units.) memuse is the number of bytes per unit for the test, or a good estimate of it. For example, a test that needs two byte buffers, of 4 GiB each, could be decorated with @bigmemtest(size=_4G, memuse=2).

The size argument is normally passed to the decorated test method as an extra argument. If dry_run is True, the value passed to the test method may be less than the requested value. If dry_run is False, it means the test doesn't support dummy runs when -M is not specified.

@test.support.bigaddrspacetest

Decorator for tests that fill the address space.

test.support.linked_to_musl()

Return False if there is no evidence the interpreter was compiled with musl, otherwise return a version triple, either (0, 0, 0) if the version is unknown, or the actual version if it is known. Intended for use in skip decorators. emscripten and wasi are assumed to be compiled with musl; otherwise platform.libc_ver is checked.

test.support.check_syntax_error(testcase, statement, errtext='', *, lineno=None, offset=None)

Test for syntax errors in statement by attempting to compile statement. testcase is the unittest instance for the test. errtext is the regular expression which should match the string representation of the raised SyntaxError. If lineno is not None, compares to the line of the exception. If offset is not None, compares to the offset of the exception.

test.support.open_urlresource(url, *args, **kw)

Open url. If open fails, raises TestFailed.

test.support.reap_children()

Use this at the end of test_main whenever sub-processes are started. This will help ensure that no extra children (zombies) stick around to hog resources and create problems when looking for refleaks.

test.support.get_attribute(obj, name)

Get an attribute, raising unittest.SkipTest if AttributeError is raised.

test.support.catch_unraisable_exception()

Context manager catching unraisable exception using sys.unraisablehook().

Storing the exception value (cm.unraisable.exc_value) creates a reference cycle. The reference cycle is broken explicitly when the context manager exits.

Storing the object (cm.unraisable.object) can resurrect it if it is set to an object which is being finalized. Exiting the context manager clears the stored object.

用法：

with support.catch_unraisable_exception() as cm:
    # code creating an "unraisable exception"
    ...

    # check the unraisable exception: use cm.unraisable
    ...

# cm.unraisable attribute no longer exists at this point
# (to break a reference cycle)

在 3.8 版被加入.

test.support.load_package_tests(pkg_dir, loader, standard_tests, pattern)

Generic implementation of the unittest load_tests protocol for use in test packages. pkg_dir is the root directory of the package; loader, standard_tests, and pattern are the arguments expected by load_tests. In simple cases, the test package's __init__.py can be the following:

import os
from test.support import load_package_tests

def load_tests(*args):
    return load_package_tests(os.path.dirname(__file__), *args)

test.support.detect_api_mismatch(ref_api, other_api, *, ignore=())

Returns the set of attributes, functions or methods of ref_api not found on other_api, except for a defined list of items to be ignored in this check specified in ignore.

這預設會跳過以 '_' 開頭的私有屬性，但會包含所有魔術方法，即以 '__' 開頭和結尾的方法。

在 3.5 版被加入.

test.support.patch(test_instance, object_to_patch, attr_name, new_value)

Override object_to_patch.attr_name with new_value. Also add cleanup procedure to test_instance to restore object_to_patch for attr_name. The attr_name should be a valid attribute for object_to_patch.

test.support.run_in_subinterp(code)

Run code in subinterpreter. Raise unittest.SkipTest if tracemalloc is enabled.

test.support.check_free_after_iterating(test, iter, cls, args=())

Assert instances of cls are deallocated after iterating.

test.support.missing_compiler_executable(cmd_names=[])

Check for the existence of the compiler executables whose names are listed in cmd_names or all the compiler executables when cmd_names is empty and return the first missing executable or None when none is found missing.

test.support.check__all__(test_case, module, name_of_module=None, extra=(), not_exported=())

Assert that the __all__ variable of module contains all public names.

The module's public names (its API) are detected automatically based on whether they match the public name convention and were defined in module.

The name_of_module argument can specify (as a string or tuple thereof) what module(s) an API could be defined in order to be detected as a public API. One case for this is when module imports part of its public API from other modules, possibly a C backend (like csv and its _csv).

The extra argument can be a set of names that wouldn't otherwise be automatically detected as "public", like objects without a proper __module__ attribute. If provided, it will be added to the automatically detected ones.

The not_exported argument can be a set of names that must not be treated as part of the public API even though their names indicate otherwise.

用法範例：

import bar
import foo
import unittest
from test import support

class MiscTestCase(unittest.TestCase):
    def test__all__(self):
        support.check__all__(self, foo)

class OtherTestCase(unittest.TestCase):
    def test__all__(self):
        extra = {'BAR_CONST', 'FOO_CONST'}
        not_exported = {'baz'}  # Undocumented name.
        # bar imports part of its API from _bar.
        support.check__all__(self, bar, ('bar', '_bar'),
                             extra=extra, not_exported=not_exported)

在 3.6 版被加入.

test.support.skip_if_broken_multiprocessing_synchronize()

Skip tests if the multiprocessing.synchronize module is missing, if there is no available semaphore implementation, or if creating a lock raises an OSError.

在 3.10 版被加入.

test.support.check_disallow_instantiation(test_case, tp, *args, **kwds)

Assert that type tp cannot be instantiated using args and kwds.

在 3.10 版被加入.

test.support.adjust_int_max_str_digits(max_digits)

This function returns a context manager that will change the global sys.set_int_max_str_digits() setting for the duration of the context to allow execution of test code that needs a different limit on the number of digits when converting between an integer and string.

在 3.11 版被加入.

test.support 模組定義了以下類別：

class test.support.SuppressCrashReport

A context manager used to try to prevent crash dialog popups on tests that are expected to crash a subprocess.

On Windows, it disables Windows Error Reporting dialogs using SetErrorMode [https://msdn.microsoft.com/en-us/library/windows/desktop/ms680621.aspx].

On UNIX, resource.setrlimit() is used to set resource.RLIMIT_CORE's soft limit to 0 to prevent coredump file creation.

在兩個平台上，舊值會被 __exit__() 還原。

class test.support.SaveSignals

Class to save and restore signal handlers registered by the Python signal handler.

save(self)

Save the signal handlers to a dictionary mapping signal numbers to the current signal handler.

restore(self)

Set the signal numbers from the save() dictionary to the saved handler.

class test.support.Matcher

matches(self, d, **kwargs)

Try to match a single dict with the supplied arguments.

match_value(self, k, dv, v)

Try to match a single stored value (dv) with a supplied value (v).

test.support.socket_helper --- 用於 socket 測試的工具

The test.support.socket_helper module provides support for socket tests.

在 3.9 版被加入.

test.support.socket_helper.IPV6_ENABLED

Set to True if IPv6 is enabled on this host, False otherwise.

test.support.socket_helper.find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM)

Returns an unused port that should be suitable for binding. This is achieved by creating a temporary socket with the same family and type as the sock parameter (default is AF_INET, SOCK_STREAM), and binding it to the specified host address (defaults to 0.0.0.0) with the port set to 0, eliciting an unused ephemeral port from the OS. The temporary socket is then closed and deleted, and the ephemeral port is returned.

Either this method or bind_port() should be used for any tests where a server socket needs to be bound to a particular port for the duration of the test. Which one to use depends on whether the calling code is creating a Python socket, or if an unused port needs to be provided in a constructor or passed to an external program (i.e. the -accept argument to openssl's s_server mode). Always prefer bind_port() over find_unused_port() where possible. Using a hard coded port is discouraged since it can make multiple instances of the test impossible to run simultaneously, which is a problem for buildbots.

test.support.socket_helper.bind_port(sock, host=HOST)

Bind the socket to a free port and return the port number. Relies on ephemeral ports in order to ensure we are using an unbound port. This is important as many tests may be running simultaneously, especially in a buildbot environment. This method raises an exception if the sock.family is AF_INET and sock.type is SOCK_STREAM, and the socket has SO_REUSEADDR or SO_REUSEPORT set on it. Tests should never set these socket options for TCP/IP sockets. The only case for setting these options is testing multicasting via multiple UDP sockets.

Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e. on Windows), it will be set on the socket. This will prevent anyone else from binding to our host/port for the duration of the test.

test.support.socket_helper.bind_unix_socket(sock, addr)

Bind a Unix socket, raising unittest.SkipTest if PermissionError is raised.

@test.support.socket_helper.skip_unless_bind_unix_socket

A decorator for running tests that require a functional bind() for Unix sockets.

test.support.socket_helper.transient_internet(resource_name, *, timeout=30.0, errnos=())

A context manager that raises ResourceDenied when various issues with the internet connection manifest themselves as exceptions.

test.support.script_helper --- 用於 Python 執行測試的工具

test.support.script_helper 模組提供 Python 的腳本執行測試的支援。

test.support.script_helper.interpreter_requires_environment()

Return True if sys.executable interpreter requires environment variables in order to be able to run at all.

This is designed to be used with @unittest.skipIf() to annotate tests that need to use an assert_python*() function to launch an isolated mode (-I) or no environment mode (-E) sub-interpreter process.

A normal build & test does not run into this situation but it can happen when trying to run the standard library test suite from an interpreter that doesn't have an obvious home with Python's current home finding logic.

Setting PYTHONHOME is one way to get most of the testsuite to run in that situation. PYTHONPATH or PYTHONUSERSITE are other common environment variables that might impact whether or not the interpreter can start.

test.support.script_helper.run_python_until_end(*args, **env_vars)

Set up the environment based on env_vars for running the interpreter in a subprocess. The values can include __isolated, __cleanenv, __cwd, and TERM.

在 3.9 版的變更: 此函式不再從 stderr 中移除空白。

test.support.script_helper.assert_python_ok(*args, **env_vars)

Assert that running the interpreter with args and optional environment variables env_vars succeeds (rc == 0) and return a (return code, stdout, stderr) tuple.

If the __cleanenv keyword-only parameter is set, env_vars is used as a fresh environment.

Python is started in isolated mode (command line option -I), except if the __isolated keyword-only parameter is set to False.

在 3.9 版的變更: 此函式不再從 stderr 中移除空白。

test.support.script_helper.assert_python_failure(*args, **env_vars)

Assert that running the interpreter with args and optional environment variables env_vars fails (rc != 0) and return a (return code, stdout, stderr) tuple.

更多選項請見 assert_python_ok()。

在 3.9 版的變更: 此函式不再從 stderr 中移除空白。

test.support.script_helper.spawn_python(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kw)

Run a Python subprocess with the given arguments.

kw is extra keyword args to pass to subprocess.Popen(). Returns a subprocess.Popen object.

test.support.script_helper.kill_python(p)

Run the given subprocess.Popen process until completion and return stdout.

test.support.script_helper.make_script(script_dir, script_basename, source, omit_suffix=False)

Create script containing source in path script_dir and script_basename. If omit_suffix is False, append .py to the name. Return the full script path.

test.support.script_helper.make_zip_script(zip_dir, zip_basename, script_name, name_in_zip=None)

Create zip file at zip_dir and zip_basename with extension zip which contains the files in script_name. name_in_zip is the archive name. Return a tuple containing (full path, full path of archive name).

test.support.script_helper.make_pkg(pkg_dir, init_source='')

Create a directory named pkg_dir containing an __init__ file with init_source as its contents.

test.support.script_helper.make_zip_pkg(zip_dir, zip_basename, pkg_name, script_basename, source, depth=1, compiled=False)

Create a zip package directory with a path of zip_dir and zip_basename containing an empty __init__ file and a file script_basename containing the source. If compiled is True, both source files will be compiled and added to the zip package. Return a tuple of the full zip path and the archive name for the zip file.

test.support.bytecode_helper --- 用於測試位元組碼能正確產生的支援工具

test.support.bytecode_helper 模組提供測試和檢查位元組碼產生的支援。

在 3.9 版被加入.

此模組定義了以下類別：

class test.support.bytecode_helper.BytecodeTestCase(unittest.TestCase)

This class has custom assertion methods for inspecting bytecode.

BytecodeTestCase.get_disassembly_as_string(co)

Return the disassembly of co as string.

BytecodeTestCase.assertInBytecode(x, opname, argval=_UNSPECIFIED)

Return instr if opname is found, otherwise throws AssertionError.

BytecodeTestCase.assertNotInBytecode(x, opname, argval=_UNSPECIFIED)

Throws AssertionError if opname is found.

test.support.threading_helper --- Utilities for threading tests

The test.support.threading_helper module provides support for threading tests.

在 3.10 版被加入.

test.support.threading_helper.join_thread(thread, timeout=None)

Join a thread within timeout. Raise an AssertionError if thread is still alive after timeout seconds.

@test.support.threading_helper.reap_threads

Decorator to ensure the threads are cleaned up even if the test fails.

test.support.threading_helper.start_threads(threads, unlock=None)

Context manager to start threads, which is a sequence of threads. unlock is a function called after the threads are started, even if an exception was raised; an example would be threading.Event.set(). start_threads will attempt to join the started threads upon exit.

test.support.threading_helper.threading_cleanup(*original_values)

Cleanup up threads not specified in original_values. Designed to emit a warning if a test leaves running threads in the background.

test.support.threading_helper.threading_setup()

Return current thread count and copy of dangling threads.

test.support.threading_helper.wait_threads_exit(timeout=None)

Context manager to wait until all threads created in the with statement exit.

test.support.threading_helper.catch_threading_exception()

Context manager catching threading.Thread exception using threading.excepthook().

當捕捉到例外時會設定的屬性：

exc_type

exc_value

exc_traceback

thread

參閱 threading.excepthook() 文件。

這些屬性會在離開情境管理器時被刪除。

用法：

with threading_helper.catch_threading_exception() as cm:
    # code spawning a thread which raises an exception
    ...

    # check the thread exception, use cm attributes:
    # exc_type, exc_value, exc_traceback, thread
    ...

# exc_type, exc_value, exc_traceback, thread attributes of cm no longer
# exists at this point
# (to avoid reference cycles)

在 3.8 版被加入.

test.support.threading_helper.run_concurrently(worker_func, nthreads, args=(), kwargs={})

Run the worker function concurrently in multiple threads. Re-raises an exception if any thread raises one, after all threads have finished.

test.support.os_helper --- 用於 os 測試的工具

test.support.os_helper 模組提供 os 測試的支援。

在 3.10 版被加入.

test.support.os_helper.FS_NONASCII

A non-ASCII character encodable by os.fsencode().

test.support.os_helper.SAVEDCWD

設定為 os.getcwd()。

test.support.os_helper.TESTFN

Set to a name that is safe to use as the name of a temporary file. Any temporary file that is created should be closed and unlinked (removed).

test.support.os_helper.TESTFN_NONASCII

Set to a filename containing the FS_NONASCII character, if it exists. This guarantees that if the filename exists, it can be encoded and decoded with the default filesystem encoding. This allows tests that require a non-ASCII filename to be easily skipped on platforms where they can't work.

test.support.os_helper.TESTFN_UNENCODABLE

Set to a filename (str type) that should not be able to be encoded by file system encoding in strict mode. It may be None if it's not possible to generate such a filename.

test.support.os_helper.TESTFN_UNDECODABLE

Set to a filename (bytes type) that should not be able to be decoded by file system encoding in strict mode. It may be None if it's not possible to generate such a filename.

test.support.os_helper.TESTFN_UNICODE

Set to a non-ASCII name for a temporary file.

class test.support.os_helper.EnvironmentVarGuard

Class used to temporarily set or unset environment variables. Instances can be used as a context manager and have a complete dictionary interface for querying/modifying the underlying os.environ. After exit from the context manager all changes to environment variables done through this instance will be rolled back.

在 3.1 版的變更: 新增字典介面。

class test.support.os_helper.FakePath(path)

Simple path-like object. It implements the __fspath__() method which just returns the path argument. If path is an exception, it will be raised in __fspath__().

EnvironmentVarGuard.set(envvar, value)

Temporarily set the environment variable envvar to the value of value.

EnvironmentVarGuard.unset(envvar, *others)

暫時取消一個或多個環境變數。

在 3.14 版的變更: 可以取消多於一個環境變數。

test.support.os_helper.can_symlink()

如果作業系統支援符號連結則回傳 True，否則回傳 False。

test.support.os_helper.can_xattr()

如果作業系統支援 xattr 則回傳 True，否則回傳 False。

test.support.os_helper.change_cwd(path, quiet=False)

A context manager that temporarily changes the current working directory to path and yields the directory.

If quiet is False, the context manager raises an exception on error. Otherwise, it issues only a warning and keeps the current working directory the same.

test.support.os_helper.create_empty_file(filename)

Create an empty file with filename. If it already exists, truncate it.

test.support.os_helper.fd_count()

Count the number of open file descriptors.

test.support.os_helper.fs_is_case_insensitive(directory)

Return True if the file system for directory is case-insensitive.

test.support.os_helper.make_bad_fd()

Create an invalid file descriptor by opening and closing a temporary file, and returning its descriptor.

test.support.os_helper.rmdir(filename)

Call os.rmdir() on filename. On Windows platforms, this is wrapped with a wait loop that checks for the existence of the file, which is needed due to antivirus programs that can hold files open and prevent deletion.

test.support.os_helper.rmtree(path)

Call shutil.rmtree() on path or call os.lstat() and os.rmdir() to remove a path and its contents. As with rmdir(), on Windows platforms this is wrapped with a wait loop that checks for the existence of the files.

@test.support.os_helper.skip_unless_symlink

A decorator for running tests that require support for symbolic links.

@test.support.os_helper.skip_unless_xattr

A decorator for running tests that require support for xattr.

test.support.os_helper.temp_cwd(name='tempcwd', quiet=False)

A context manager that temporarily creates a new directory and changes the current working directory (CWD).

The context manager creates a temporary directory in the current directory with name name before temporarily changing the current working directory. If name is None, the temporary directory is created using tempfile.mkdtemp().

If quiet is False and it is not possible to create or change the CWD, an error is raised. Otherwise, only a warning is raised and the original CWD is used.

test.support.os_helper.temp_dir(path=None, quiet=False)

A context manager that creates a temporary directory at path and yields the directory.

If path is None, the temporary directory is created using tempfile.mkdtemp(). If quiet is False, the context manager raises an exception on error. Otherwise, if path is specified and cannot be created, only a warning is issued.

test.support.os_helper.temp_umask(umask)

A context manager that temporarily sets the process umask.

test.support.os_helper.unlink(filename)

Call os.unlink() on filename. As with rmdir(), on Windows platforms, this is wrapped with a wait loop that checks for the existence of the file.

test.support.import_helper --- 用於 import 測試的工具

test.support.import_helper 模組提供 import 測試的支援。

在 3.10 版被加入.

test.support.import_helper.forget(module_name)

Remove the module named module_name from sys.modules and delete any byte-compiled files of the module.

test.support.import_helper.import_fresh_module(name, fresh=(), blocked=(), deprecated=False)

This function imports and returns a fresh copy of the named Python module by removing the named module from sys.modules before doing the import. Note that unlike reload(), the original module is not affected by this operation.

fresh is an iterable of additional module names that are also removed from the sys.modules cache before doing the import.

blocked is an iterable of module names that are replaced with None in the module cache during the import to ensure that attempts to import them raise ImportError.

The named module and any modules named in the fresh and blocked parameters are saved before starting the import and then reinserted into sys.modules when the fresh import is complete.

Module and package deprecation messages are suppressed during this import if deprecated is True.

如果無法引入指定的模組則此函式會引發 ImportError。

用法範例：

# Get copies of the warnings module for testing without affecting the
# version being used by the rest of the test suite. One copy uses the
# C implementation, the other is forced to use the pure Python fallback
# implementation
py_warnings = import_fresh_module('warnings', blocked=['_warnings'])
c_warnings = import_fresh_module('warnings', fresh=['_warnings'])

在 3.1 版被加入.

test.support.import_helper.import_module(name, deprecated=False, *, required_on=())

This function imports and returns the named module. Unlike a normal import, this function raises unittest.SkipTest if the module cannot be imported.

Module and package deprecation messages are suppressed during this import if deprecated is True. If a module is required on a platform but optional for others, set required_on to an iterable of platform prefixes which will be compared against sys.platform.

在 3.1 版被加入.

test.support.import_helper.modules_setup()

回傳 sys.modules 的複本。

test.support.import_helper.modules_cleanup(oldmodules)

Remove modules except for oldmodules and encodings in order to preserve internal cache.

test.support.import_helper.unload(name)

從 sys.modules 中刪除 name。

test.support.import_helper.make_legacy_pyc(source)

Move a PEP 3147 [https://peps.python.org/pep-3147/]/PEP 488 [https://peps.python.org/pep-0488/] pyc file to its legacy pyc location and return the file system path to the legacy pyc file. The source value is the file system path to the source file. It does not need to exist, however the PEP 3147/488 pyc file must exist.

class test.support.import_helper.CleanImport(*module_names)

A context manager to force import to return a new module reference. This is useful for testing module-level behaviors, such as the emission of a DeprecationWarning on import. Example usage:

with CleanImport('foo'):
    importlib.import_module('foo')  # New reference.

class test.support.import_helper.DirsOnSysPath(*paths)

A context manager to temporarily add directories to sys.path.

This makes a copy of sys.path, appends any directories given as positional arguments, then reverts sys.path to the copied settings when the context ends.

Note that all sys.path modifications in the body of the context manager, including replacement of the object, will be reverted at the end of the block.

test.support.warnings_helper --- 用於 warnings 測試的工具

test.support.warnings_helper 模組提供 warnings 測試的支援。

在 3.10 版被加入.

test.support.warnings_helper.ignore_warnings(*, category)

Suppress warnings that are instances of category, which must be Warning or a subclass. Roughly equivalent to warnings.catch_warnings() with warnings.simplefilter('ignore', category=category). For example:

@warning_helper.ignore_warnings(category=DeprecationWarning)
def test_suppress_warning():
    # do something

在 3.8 版被加入.

test.support.warnings_helper.check_no_resource_warning(testcase)

Context manager to check that no ResourceWarning was raised. You must remove the object which may emit ResourceWarning before the end of the context manager.

test.support.warnings_helper.check_syntax_warning(testcase, statement, errtext='', *, lineno=1, offset=None)

Test for syntax warning in statement by attempting to compile statement. Test also that the SyntaxWarning is emitted only once, and that it will be converted to a SyntaxError when turned into error. testcase is the unittest instance for the test. errtext is the regular expression which should match the string representation of the emitted SyntaxWarning and raised SyntaxError. If lineno is not None, compares to the line of the warning and exception. If offset is not None, compares to the offset of the exception.

在 3.8 版被加入.

test.support.warnings_helper.check_warnings(*filters, quiet=True)

A convenience wrapper for warnings.catch_warnings() that makes it easier to test that a warning was correctly raised. It is approximately equivalent to calling warnings.catch_warnings(record=True) with warnings.simplefilter() set to always and with the option to automatically validate the results that are recorded.

check_warnings accepts 2-tuples of the form ("message regexp", WarningCategory) as positional arguments. If one or more filters are provided, or if the optional keyword argument quiet is False, it checks to make sure the warnings are as expected: each specified filter must match at least one of the warnings raised by the enclosed code or the test fails, and if any warnings are raised that do not match any of the specified filters the test fails. To disable the first of these checks, set quiet to True.

如果沒有指定引數，預設為：

check_warnings(("", Warning), quiet=True)

In this case all warnings are caught and no errors are raised.

On entry to the context manager, a WarningRecorder instance is returned. The underlying warnings list from catch_warnings() is available via the recorder object's warnings attribute. As a convenience, the attributes of the object representing the most recent warning can also be accessed directly through the recorder object (see example below). If no warning has been raised, then any of the attributes that would otherwise be expected on an object representing a warning will return None.

The recorder object also has a reset() method, which clears the warnings list.

The context manager is designed to be used like this:

with check_warnings(("assertion is always true", SyntaxWarning),
                    ("", UserWarning)):
    exec('assert(False, "Hey!")')
    warnings.warn(UserWarning("Hide me!"))

In this case if either warning was not raised, or some other warning was raised, check_warnings() would raise an error.

When a test needs to look more deeply into the warnings, rather than just checking whether or not they occurred, code like this can be used:

with check_warnings(quiet=True) as w:
    warnings.warn("foo")
    assert str(w.args[0]) == "foo"
    warnings.warn("bar")
    assert str(w.args[0]) == "bar"
    assert str(w.warnings[0].args[0]) == "foo"
    assert str(w.warnings[1].args[0]) == "bar"
    w.reset()
    assert len(w.warnings) == 0

Here all warnings will be caught, and the test code tests the captured warnings directly.

在 3.2 版的變更: 新的可選引數 filters 和 quiet。

class test.support.warnings_helper.WarningsRecorder

Class used to record warnings for unit tests. See documentation of check_warnings() above for more details.

除錯與效能分析

這些函式庫幫助你進行 Python 程式開發：除錯器允許你在程式碼中單步 (step) 執行、分析堆疊框 (stack frames) 以及設置中斷點 (breakpoints) 等，效能分析工具執行程式碼並提供關於執行時間的詳細分析，讓你找到程式中的瓶頸 (bottlenecks)。事件稽核 (auditing events) 提供執行時期行為的可見性，否則的話可能需要更侵入性的除錯或修補。

稽核事件表

bdb --- 偵錯器框架

faulthandler --- 傾印 Python 回溯

Dumping the traceback

Dumping the C stack

C Stack Compatibility

Fault handler state

Dumping the tracebacks after a timeout

Dumping the traceback on a user signal

Issue with file descriptors

範例

pdb --- Python 偵錯器

命令列介面

Debugger commands

Python 的分析器

分析器簡介

Instant User's Manual

profile 與 cProfile 模組參考文件

Stats 類別

What Is Deterministic Profiling?

限制

校正

Using a custom timer

timeit --- 測量小量程式片段的執行時間

基礎範例

Python 介面

命令列介面

範例

trace --- 追蹤或追查 Python 陳述式執行

命令列用法

主要選項

修飾子（Modifier）

篩選子（Filter）

程式介面

tracemalloc --- 追蹤記憶體配置

範例

Display the top 10

Compute differences

Get the traceback of a memory block

Pretty top

Record the current and peak size of all traced memory blocks

API

函式

DomainFilter

Filter

Frame

Snapshot

Statistic

StatisticDiff

Trace

Traceback

稽核事件表

這張表包含了所有在 CPython 運行環境 (runtime) 與標準函式庫對於 sys.audit() 或 PySys_Audit() 的呼叫所觸發的事件。這些呼叫是在 3.8 或更新的版本中被新增（請見 PEP 578 [https://peps.python.org/pep-0578/]）。

請參考 sys.addaudithook() 及 PySys_AddAuditHook() 來了解如何處理這些事件。

這張表是從 CPython 文件產生的，可能不包含其它實作所觸發的事件。請參考你的運行環境 (runtime) 特定文件來了解實際會觸發的事件。

Audit event

Arguments

References

_thread.start_new_thread

function, args, kwargs

[1]

array.__new__

typecode, initializer

[1]

builtins.breakpoint

breakpointhook

[1]

builtins.id

id

[1]

builtins.input

prompt

[1]

builtins.input/result

result

[1]

code.__new__

code, filename, name, argcount, posonlyargcount, kwonlyargcount, nlocals, stacksize, flags

[1]

compile

source, filename

[1]

cpython.PyConfig_Set

name, value

[1]

cpython.PyInterpreterState_Clear

[1]

cpython.PyInterpreterState_New

[1]

cpython._PySys_ClearAuditHooks

[1]

cpython.remote_debugger_script

script_path

[1]

cpython.run_command

command

[1]

cpython.run_file

filename

[1]

cpython.run_interactivehook

hook

[1]

cpython.run_module

module-name

[1]

cpython.run_startup

filename

[1]

cpython.run_stdin

[1][2][3]

ctypes.addressof

obj

[1]

ctypes.call_function

func_pointer, arguments

[1]

ctypes.cdata

address

[1]

ctypes.cdata/buffer

pointer, size, offset

[1][2]

ctypes.create_string_buffer

init, size

[1]

ctypes.create_unicode_buffer

init, size

[1]

ctypes.dlopen

name

[1]

ctypes.dlsym

library, name

[1]

ctypes.dlsym/handle

handle, name

[1]

ctypes.get_errno

[1]

ctypes.get_last_error

[1]

ctypes.memoryview_at

address, size, readonly

[1]

ctypes.set_errno

errno

[1]

ctypes.set_exception

code

[1]

ctypes.set_last_error

error

[1]

ctypes.string_at

ptr, size

[1]

ctypes.wstring_at

ptr, size

[1]

ensurepip.bootstrap

root

[1]

exec

code_object

[1][2]

fcntl.fcntl

fd, cmd, arg

[1]

fcntl.flock

fd, operation

[1]

fcntl.ioctl

fd, request, arg

[1]

fcntl.lockf

fd, cmd, len, start, whence

[1]

ftplib.connect

self, host, port

[1]

ftplib.sendcmd

self, cmd

[1][2]

function.__new__

code

[1]

gc.get_objects

generation

[1]

gc.get_referents

objs

[1]

gc.get_referrers

objs

[1]

glob.glob

pathname, recursive

[1][2]

glob.glob/2

pathname, recursive, root_dir, dir_fd

[1][2]

http.client.connect

self, host, port

[1]

http.client.send

self, data

[1]

imaplib.open

self, host, port

[1]

imaplib.send

self, data

[1]

import

module, filename, sys.path, sys.meta_path, sys.path_hooks

[1]

marshal.dumps

value, version

[1]

marshal.load

[1]

marshal.loads

bytes

[1]

mmap.__new__

fileno, length, access, offset

[1]

msvcrt.get_osfhandle

fd

[1]

msvcrt.locking

fd, mode, nbytes

[1]

msvcrt.open_osfhandle

handle, flags

[1]

object.__delattr__

obj, name

[1]

object.__getattr__

obj, name

[1]

object.__setattr__

obj, name, value

[1]

open

path, mode, flags

[1][2][3]

os.add_dll_directory

path

[1]

os.chdir

path

[1][2]

os.chflags

path, flags

[1][2]

os.chmod

path, mode, dir_fd

[1][2][3]

os.chown

path, uid, gid, dir_fd

[1][2][3]

os.exec

path, args, env

[1]

os.fork

[1]

os.forkpty

[1]

os.fwalk

top, topdown, onerror, follow_symlinks, dir_fd

[1]

os.getxattr

path, attribute

[1]

os.kill

pid, sig

[1]

os.killpg

pgid, sig

[1]

os.link

src, dst, src_dir_fd, dst_dir_fd

[1]

os.listdir

path

[1]

os.listdrives

[1]

os.listmounts

volume

[1]

os.listvolumes

[1]

os.listxattr

path

[1]

os.lockf

fd, cmd, len

[1]

os.mkdir

path, mode, dir_fd

[1][2]

os.posix_spawn

path, argv, env

[1][2]

os.putenv

key, value

[1]

os.remove

path, dir_fd

[1][2][3]

os.removexattr

path, attribute

[1]

os.rename

src, dst, src_dir_fd, dst_dir_fd

[1][2][3]

os.rmdir

path, dir_fd

[1]

os.scandir

path

[1]

os.setxattr

path, attribute, value, flags

[1]

os.spawn

mode, path, args, env

[1]

os.startfile

path, operation

[1]

os.startfile/2

path, operation, arguments, cwd, show_cmd

[1]

os.symlink

src, dst, dir_fd

[1]

os.system

command

[1]

os.truncate

fd, length

[1][2]

os.unsetenv

key

[1]

os.utime

path, times, ns, dir_fd

[1]

os.walk

top, topdown, onerror, followlinks

[1]

pathlib.Path.glob

self, pattern

[1]

pathlib.Path.rglob

self, pattern

[1]

pdb.Pdb

[1]

pickle.find_class

module, name

[1]

poplib.connect

self, host, port

[1][2]

poplib.putline

self, line

[1][2]

pty.spawn

argv

[1]

resource.prlimit

pid, resource, limits

[1]

resource.setrlimit

resource, limits

[1]

setopencodehook

[1]

shutil.chown

path, user, group

[1]

shutil.copyfile

src, dst

[1][2][3]

shutil.copymode

src, dst

[1][2]

shutil.copystat

src, dst

[1][2]

shutil.copytree

src, dst

[1]

shutil.make_archive

base_name, format, root_dir, base_dir

[1]

shutil.move

src, dst

[1]

shutil.rmtree

path, dir_fd

[1]

shutil.unpack_archive

filename, extract_dir, format

[1]

signal.pthread_kill

thread_id, signalnum

[1]

smtplib.connect

self, host, port

[1]

smtplib.send

self, data

[1]

socket.__new__

self, family, type, protocol

[1]

socket.bind

self, address

[1]

socket.connect

self, address

[1][2]

socket.getaddrinfo

host, port, family, type, protocol

[1]

socket.gethostbyaddr

ip_address

[1]

socket.gethostbyname

hostname

[1][2]

socket.gethostname

[1]

socket.getnameinfo

sockaddr

[1]

socket.getservbyname

servicename, protocolname

[1]

socket.getservbyport

port, protocolname

[1]

socket.sendmsg

self, address

[1]

socket.sendto

self, address

[1]

socket.sethostname

name

[1]

sqlite3.connect

database

[1]

sqlite3.connect/handle

connection_handle

[1]

sqlite3.enable_load_extension

connection, enabled

[1]

sqlite3.load_extension

connection, path

[1]

subprocess.Popen

executable, args, cwd, env

[1]

sys._current_exceptions

[1]

sys._current_frames

[1]

sys._getframe

frame

[1]

sys._getframemodulename

depth

[1]

sys.addaudithook

[1][2]

sys.excepthook

hook, type, value, traceback

[1]

sys.monitoring.register_callback

func

[1]

sys.remote_exec

pid

[1]

sys.set_asyncgen_hooks_finalizer

[1]

sys.set_asyncgen_hooks_firstiter

[1]

sys.setprofile

[1]

sys.settrace

[1]

sys.unraisablehook

hook, unraisable

[1]

syslog.closelog

[1]

syslog.openlog

ident, logoption, facility

[1]

syslog.setlogmask

maskpri

[1]

syslog.syslog

priority, message

[1]

tempfile.mkdtemp

fullpath

[1][2]

tempfile.mkstemp

fullpath

[1][2][3]

time.sleep

secs

[1]

urllib.Request

fullurl, data, headers, method

[1]

webbrowser.open

url

[1]

winreg.ConnectRegistry

computer_name, key

[1]

winreg.CreateKey

key, sub_key, access

[1][2]

winreg.DeleteKey

key, sub_key, access

[1][2]

winreg.DeleteValue

key, value

[1]

winreg.DisableReflectionKey

key

[1]

winreg.EnableReflectionKey

key

[1]

winreg.EnumKey

key, index

[1]

winreg.EnumValue

key, index

[1]

winreg.ExpandEnvironmentStrings

str

[1]

winreg.LoadKey

key, sub_key, file_name

[1]

winreg.OpenKey

key, sub_key, access

[1]

winreg.OpenKey/result

key

[1][2][3]

winreg.PyHKEY.Detach

key

[1]

winreg.QueryInfoKey

key

[1]

winreg.QueryReflectionKey

key

[1]

winreg.QueryValue

key, sub_key, value_name

[1][2]

winreg.SaveKey

key, file_name

[1]

winreg.SetValue

key, sub_key, type, value

[1][2]

下列事件是內部觸發的，與任何 CPython 的公開 API 並無關係：

稽核事件

引數

_winapi.CreateFile

file_name, desired_access, share_mode, creation_disposition, flags_and_attributes

_winapi.CreateJunction

src_path, dst_path

_winapi.CreateNamedPipe

name, open_mode, pipe_mode

_winapi.CreatePipe

_winapi.CreateProcess

application_name, command_line, current_directory

_winapi.OpenProcess

process_id, desired_access

_winapi.TerminateProcess

handle, exit_code

_posixsubprocess.fork_exec

exec_list, args, env

ctypes.PyObj_FromPtr

obj

在 3.14 版被加入: 內部稽核事件 _posixsubprocess.fork_exec。

bdb --- 偵錯器框架

原始碼：Lib/bdb.py [https://github.com/python/cpython/tree/3.14/Lib/bdb.py]

The bdb module handles basic debugger functions, like setting breakpoints or managing execution via the debugger.

有定義以下例外：

exception bdb.BdbQuit

由 Bdb 類別所引發的例外，用來退出偵錯器。

bdb 模組也定義了兩個類別：

class bdb.Breakpoint(self, file, line, temporary=False, cond=None, funcname=None)

This class implements temporary breakpoints, ignore counts, disabling and (re-)enabling, and conditionals.

Breakpoints are indexed by number through a list called bpbynumber and by (file, line) pairs through bplist. The former points to a single instance of class Breakpoint. The latter points to a list of such instances since there may be more than one breakpoint per line.

When creating a breakpoint, its associated file name should be in canonical form. If a funcname is defined, a breakpoint hit will be counted when the first line of that function is executed. A conditional breakpoint always counts a hit.

Breakpoint 實例有以下方法：

deleteMe()

Delete the breakpoint from the list associated to a file/line. If it is the last breakpoint in that position, it also deletes the entry for the file/line.

enable()

Mark the breakpoint as enabled.

disable()

Mark the breakpoint as disabled.

bpformat()

Return a string with all the information about the breakpoint, nicely formatted:

Breakpoint number.

Temporary status (del or keep).

File/line position.

Break condition.

Number of times to ignore.

Number of times hit.

在 3.2 版被加入.

bpprint(out=None)

Print the output of bpformat() to the file out, or if it is None, to standard output.

Breakpoint 實例有以下屬性：

file

Breakpoint 的檔案名稱。

line

Line number of the Breakpoint within file.

temporary

True if a Breakpoint at (file, line) is temporary.

cond

Condition for evaluating a Breakpoint at (file, line).

funcname

Function name that defines whether a Breakpoint is hit upon entering the function.

enabled

如 Breakpoint 有被啟用則為 True。

bpbynumber

Numeric index for a single instance of a Breakpoint.

bplist

Dictionary of Breakpoint instances indexed by (file, line) tuples.

ignore

Number of times to ignore a Breakpoint.

hits

Count of the number of times a Breakpoint has been hit.

class bdb.Bdb(skip=None, backend='settrace')

The Bdb class acts as a generic Python debugger base class.

This class takes care of the details of the trace facility; a derived class should implement user interaction. The standard debugger class (pdb.Pdb) is an example.

The skip argument, if given, must be an iterable of glob-style module name patterns. The debugger will not step into frames that originate in a module that matches one of these patterns. Whether a frame is considered to originate in a certain module is determined by the __name__ in the frame globals.

The backend argument specifies the backend to use for Bdb. It can be either 'settrace' or 'monitoring'. 'settrace' uses sys.settrace() which has the best backward compatibility. The 'monitoring' backend uses the new sys.monitoring that was introduced in Python 3.12, which can be much more efficient because it can disable unused events. We are trying to keep the exact interfaces for both backends, but there are some differences. The debugger developers are encouraged to use the 'monitoring' backend to achieve better performance.

在 3.1 版的變更: 新增 skip 引數。

在 3.14 版的變更: 新增 backend 參數。

The following methods of Bdb normally don't need to be overridden.

canonic(filename)

Return canonical form of filename.

For real file names, the canonical form is an operating-system-dependent, case-normalized absolute path. A filename with angle brackets, such as "<stdin>" generated in interactive mode, is returned unchanged.

start_trace(self)

Start tracing. For 'settrace' backend, this method is equivalent to sys.settrace(self.trace_dispatch)

在 3.14 版被加入.

stop_trace(self)

Stop tracing. For 'settrace' backend, this method is equivalent to sys.settrace(None)

在 3.14 版被加入.

reset()

Set the botframe, stopframe, returnframe and quitting attributes with values ready to start debugging.

trace_dispatch(frame, event, arg)

This function is installed as the trace function of debugged frames. Its return value is the new trace function (in most cases, that is, itself).

The default implementation decides how to dispatch a frame, depending on the type of event (passed as a string) that is about to be executed. event can be one of the following:

"line": A new line of code is going to be executed.

"call": A function is about to be called, or another code block entered.

"return": A function or other code block is about to return.

"exception": An exception has occurred.

"c_call": A C function is about to be called.

"c_return": A C function has returned.

"c_exception": A C function has raised an exception.

For the Python events, specialized functions (see below) are called. For the C events, no action is taken.

The arg parameter depends on the previous event.

See the documentation for sys.settrace() for more information on the trace function. For more information on code and frame objects, refer to 標準型別階層.

dispatch_line(frame)

If the debugger should stop on the current line, invoke the user_line() method (which should be overridden in subclasses). Raise a BdbQuit exception if the quitting flag is set (which can be set from user_line()). Return a reference to the trace_dispatch() method for further tracing in that scope.

dispatch_call(frame, arg)

If the debugger should stop on this function call, invoke the user_call() method (which should be overridden in subclasses). Raise a BdbQuit exception if the quitting flag is set (which can be set from user_call()). Return a reference to the trace_dispatch() method for further tracing in that scope.

dispatch_return(frame, arg)

If the debugger should stop on this function return, invoke the user_return() method (which should be overridden in subclasses). Raise a BdbQuit exception if the quitting flag is set (which can be set from user_return()). Return a reference to the trace_dispatch() method for further tracing in that scope.

dispatch_exception(frame, arg)

If the debugger should stop at this exception, invokes the user_exception() method (which should be overridden in subclasses). Raise a BdbQuit exception if the quitting flag is set (which can be set from user_exception()). Return a reference to the trace_dispatch() method for further tracing in that scope.

Normally derived classes don't override the following methods, but they may if they want to redefine the definition of stopping and breakpoints.

is_skipped_module(module_name)

Return True if module_name matches any skip pattern.

stop_here(frame)

Return True if frame is below the starting frame in the stack.

break_here(frame)

Return True if there is an effective breakpoint for this line.

Check whether a line or function breakpoint exists and is in effect. Delete temporary breakpoints based on information from effective().

break_anywhere(frame)

Return True if any breakpoint exists for frame's filename.

Derived classes should override these methods to gain control over debugger operation.

user_call(frame, argument_list)

Called from dispatch_call() if a break might stop inside the called function.

argument_list is not used anymore and will always be None. The argument is kept for backwards compatibility.

user_line(frame)

Called from dispatch_line() when either stop_here() or break_here() returns True.

user_return(frame, return_value)

Called from dispatch_return() when stop_here() returns True.

user_exception(frame, exc_info)

Called from dispatch_exception() when stop_here() returns True.

do_clear(arg)

Handle how a breakpoint must be removed when it is a temporary one.

This method must be implemented by derived classes.

Derived classes and clients can call the following methods to affect the stepping state.

set_step()

Stop after one line of code.

set_next(frame)

Stop on the next line in or below the given frame.

set_return(frame)

Stop when returning from the given frame.

set_until(frame, lineno=None)

Stop when the line with the lineno greater than the current one is reached or when returning from current frame.

set_trace([frame])

Start debugging from frame. If frame is not specified, debugging starts from caller's frame.

在 3.13 版的變更: set_trace() will enter the debugger immediately, rather than on the next line of code to be executed.

set_continue()

Stop only at breakpoints or when finished. If there are no breakpoints, set the system trace function to None.

set_quit()

Set the quitting attribute to True. This raises BdbQuit in the next call to one of the dispatch_*() methods.

Derived classes and clients can call the following methods to manipulate breakpoints. These methods return a string containing an error message if something went wrong, or None if all is well.

set_break(filename, lineno, temporary=False, cond=None, funcname=None)

Set a new breakpoint. If the lineno line doesn't exist for the filename passed as argument, return an error message. The filename should be in canonical form, as described in the canonic() method.

clear_break(filename, lineno)

Delete the breakpoints in filename and lineno. If none were set, return an error message.

clear_bpbynumber(arg)

Delete the breakpoint which has the index arg in the Breakpoint.bpbynumber. If arg is not numeric or out of range, return an error message.

clear_all_file_breaks(filename)

Delete all breakpoints in filename. If none were set, return an error message.

clear_all_breaks()

Delete all existing breakpoints. If none were set, return an error message.

get_bpbynumber(arg)

Return a breakpoint specified by the given number. If arg is a string, it will be converted to a number. If arg is a non-numeric string, if the given breakpoint never existed or has been deleted, a ValueError is raised.

在 3.2 版被加入.

get_break(filename, lineno)

Return True if there is a breakpoint for lineno in filename.

get_breaks(filename, lineno)

Return all breakpoints for lineno in filename, or an empty list if none are set.

get_file_breaks(filename)

Return all breakpoints in filename, or an empty list if none are set.

get_all_breaks()

Return all breakpoints that are set.

Derived classes and clients can call the following methods to disable and restart events to achieve better performance. These methods only work when using the 'monitoring' backend.

disable_current_event()

Disable the current event until the next time restart_events() is called. This is helpful when the debugger is not interested in the current line.

在 3.14 版被加入.

restart_events()

Restart all the disabled events. This function is automatically called in dispatch_* methods after user_* methods are called. If the dispatch_* methods are not overridden, the disabled events will be restarted after each user interaction.

在 3.14 版被加入.

Derived classes and clients can call the following methods to get a data structure representing a stack trace.

get_stack(f, t)

Return a list of (frame, lineno) tuples in a stack trace, and a size.

The most recently called frame is last in the list. The size is the number of frames below the frame where the debugger was invoked.

format_stack_entry(frame_lineno, lprefix=': ')

Return a string with information about a stack entry, which is a (frame, lineno) tuple. The return string contains:

The canonical filename which contains the frame.

函式名稱或 "<lambda>"。

輸入引數。

回傳值。

The line of code (if it exists).

The following two methods can be called by clients to use a debugger to debug a statement, given as a string.

run(cmd, globals=None, locals=None)

Debug a statement executed via the exec() function. globals defaults to __main__.__dict__, locals defaults to globals.

runeval(expr, globals=None, locals=None)

Debug an expression executed via the eval() function. globals and locals have the same meaning as in run().

runctx(cmd, globals, locals)

For backwards compatibility. Calls the run() method.

runcall(func, /, *args, **kwds)

Debug a single function call, and return its result.

最後，這個模組定義了以下函式：

bdb.checkfuncname(b, frame)

Return True if we should break here, depending on the way the Breakpoint b was set.

If it was set via line number, it checks if b.line is the same as the one in frame. If the breakpoint was set via function name, we have to check we are in the right frame (the right function) and if we are on its first executable line.

bdb.effective(file, line, frame)

Return (active breakpoint, delete temporary flag) or (None, None) as the breakpoint to act upon.

The active breakpoint is the first entry in bplist for the (file, line) (which must exist) that is enabled, for which checkfuncname() is true, and that has neither a false condition nor positive ignore count. The flag, meaning that a temporary breakpoint should be deleted, is False only when the cond cannot be evaluated (in which case, ignore count is ignored).

If no such entry exists, then (None, None) is returned.

bdb.set_trace()

Start debugging with a Bdb instance from caller's frame.

faulthandler --- 傾印 Python 回溯

在 3.3 版被加入.

This module contains functions to dump Python tracebacks explicitly, on a fault, after a timeout, or on a user signal. Call faulthandler.enable() to install fault handlers for the SIGSEGV, SIGFPE, SIGABRT, SIGBUS, and SIGILL signals. You can also enable them at startup by setting the PYTHONFAULTHANDLER environment variable or by using the -X faulthandler command line option.

The fault handler is compatible with system fault handlers like Apport or the Windows fault handler. The module uses an alternative stack for signal handlers if the sigaltstack() function is available. This allows it to dump the traceback even on a stack overflow.

The fault handler is called on catastrophic cases and therefore can only use signal-safe functions (e.g. it cannot allocate memory on the heap). Because of this limitation traceback dumping is minimal compared to normal Python tracebacks:

Only ASCII is supported. The backslashreplace error handler is used on encoding.

每個字串限制為 500 個字元。

Only the filename, the function name and the line number are displayed. (no source code)

It is limited to 100 frames and 100 threads.

The order is reversed: the most recent call is shown first.

By default, the Python traceback is written to sys.stderr. To see tracebacks, applications must be run in the terminal. A log file can alternatively be passed to faulthandler.enable().

The module is implemented in C, so tracebacks can be dumped on a crash or when Python is deadlocked.

The Python Development Mode calls faulthandler.enable() at Python startup.

也參考

pdb 模組

Interactive source code debugger for Python programs.

traceback 模組

Standard interface to extract, format and print stack traces of Python programs.

Dumping the traceback

faulthandler.dump_traceback(file=sys.stderr, all_threads=True)

Dump the tracebacks of all threads into file. If all_threads is False, dump only the current thread.

也參考

traceback.print_tb(), which can be used to print a traceback object.

在 3.5 版的變更: 新增傳遞檔案描述器給此函式的支援。

Dumping the C stack

在 3.14 版被加入.

faulthandler.dump_c_stack(file=sys.stderr)

Dump the C stack trace of the current thread into file.

If the Python build does not support it or the operating system does not provide a stack trace, then this prints an error in place of a dumped C stack.

C Stack Compatibility

If the system does not support the C-level backtrace(3) [https://manpages.debian.org/backtrace(3)] or dladdr1(3) [https://manpages.debian.org/dladdr1(3)], then C stack dumps will not work. An error will be printed instead of the stack.

Additionally, some compilers do not support CPython's implementation of C stack dumps. As a result, a different error may be printed instead of the stack, even if the operating system supports dumping stacks.

備註

Dumping C stacks can be arbitrarily slow, depending on the DWARF level of the binaries in the call stack.

Fault handler state

faulthandler.enable(file=sys.stderr, all_threads=True, c_stack=True)

Enable the fault handler: install handlers for the SIGSEGV, SIGFPE, SIGABRT, SIGBUS and SIGILL signals to dump the Python traceback. If all_threads is True, produce tracebacks for every running thread. Otherwise, dump only the current thread.

The file must be kept open until the fault handler is disabled: see issue with file descriptors.

If c_stack is True, then the C stack trace is printed after the Python traceback, unless the system does not support it. See dump_c_stack() for more information on compatibility.

在 3.5 版的變更: 新增傳遞檔案描述器給此函式的支援。

在 3.6 版的變更: On Windows, a handler for Windows exception is also installed.

在 3.10 版的變更: The dump now mentions if a garbage collector collection is running if all_threads is true.

在 3.14 版的變更: Only the current thread is dumped if the GIL is disabled to prevent the risk of data races.

在 3.14 版的變更: The dump now displays the C stack trace if c_stack is true.

faulthandler.disable()

Disable the fault handler: uninstall the signal handlers installed by enable().

faulthandler.is_enabled()

Check if the fault handler is enabled.

Dumping the tracebacks after a timeout

faulthandler.dump_traceback_later(timeout, repeat=False, file=sys.stderr, exit=False)

Dump the tracebacks of all threads, after a timeout of timeout seconds, or every timeout seconds if repeat is True. If exit is True, call _exit() with status=1 after dumping the tracebacks. (Note _exit() exits the process immediately, which means it doesn't do any cleanup like flushing file buffers.) If the function is called twice, the new call replaces previous parameters and resets the timeout. The timer has a sub-second resolution.

The file must be kept open until the traceback is dumped or cancel_dump_traceback_later() is called: see issue with file descriptors.

This function is implemented using a watchdog thread.

在 3.5 版的變更: 新增傳遞檔案描述器給此函式的支援。

在 3.7 版的變更: This function is now always available.

faulthandler.cancel_dump_traceback_later()

Cancel the last call to dump_traceback_later().

Dumping the traceback on a user signal

faulthandler.register(signum, file=sys.stderr, all_threads=True, chain=False)

Register a user signal: install a handler for the signum signal to dump the traceback of all threads, or of the current thread if all_threads is False, into file. Call the previous handler if chain is True.

The file must be kept open until the signal is unregistered by unregister(): see issue with file descriptors.

Not available on Windows.

在 3.5 版的變更: 新增傳遞檔案描述器給此函式的支援。

faulthandler.unregister(signum)

Unregister a user signal: uninstall the handler of the signum signal installed by register(). Return True if the signal was registered, False otherwise.

Not available on Windows.

Issue with file descriptors

enable(), dump_traceback_later() and register() keep the file descriptor of their file argument. If the file is closed and its file descriptor is reused by a new file, or if os.dup2() is used to replace the file descriptor, the traceback will be written into a different file. Call these functions again each time that the file is replaced.

範例

Example of a segmentation fault on Linux with and without enabling the fault handler:

$ python -c "import ctypes; ctypes.string_at(0)"
Segmentation fault

$ python -q -X faulthandler
>>> import ctypes
>>> ctypes.string_at(0)
Fatal Python error: Segmentation fault

Current thread 0x00007fb899f39700 (most recent call first):
  File "/opt/python/Lib/ctypes/__init__.py", line 486 in string_at
  File "<stdin>", line 1 in <module>

Current thread's C stack trace (most recent call first):
  Binary file "/opt/python/python", at _Py_DumpStack+0x42 [0x5b27f7d7147e]
  Binary file "/opt/python/python", at +0x32dcbd [0x5b27f7d85cbd]
  Binary file "/opt/python/python", at +0x32df8a [0x5b27f7d85f8a]
  Binary file "/usr/lib/libc.so.6", at +0x3def0 [0x77b73226bef0]
  Binary file "/usr/lib/libc.so.6", at +0x17ef9c [0x77b7323acf9c]
  Binary file "/opt/python/build/lib.linux-x86_64-3.14/_ctypes.cpython-314d-x86_64-linux-gnu.so", at +0xcdf6 [0x77b7315dddf6]
  Binary file "/usr/lib/libffi.so.8", at +0x7976 [0x77b73158f976]
  Binary file "/usr/lib/libffi.so.8", at +0x413c [0x77b73158c13c]
  Binary file "/usr/lib/libffi.so.8", at ffi_call+0x12e [0x77b73158ef0e]
  Binary file "/opt/python/build/lib.linux-x86_64-3.14/_ctypes.cpython-314d-x86_64-linux-gnu.so", at +0x15a33 [0x77b7315e6a33]
  Binary file "/opt/python/build/lib.linux-x86_64-3.14/_ctypes.cpython-314d-x86_64-linux-gnu.so", at +0x164fa [0x77b7315e74fa]
  Binary file "/opt/python/build/lib.linux-x86_64-3.14/_ctypes.cpython-314d-x86_64-linux-gnu.so", at +0xc624 [0x77b7315dd624]
  Binary file "/opt/python/python", at _PyObject_MakeTpCall+0xce [0x5b27f7b73883]
  Binary file "/opt/python/python", at +0x11bab6 [0x5b27f7b73ab6]
  Binary file "/opt/python/python", at PyObject_Vectorcall+0x23 [0x5b27f7b73b04]
  Binary file "/opt/python/python", at _PyEval_EvalFrameDefault+0x490c [0x5b27f7cbb302]
  Binary file "/opt/python/python", at +0x2818e6 [0x5b27f7cd98e6]
  Binary file "/opt/python/python", at +0x281aab [0x5b27f7cd9aab]
  Binary file "/opt/python/python", at PyEval_EvalCode+0xc5 [0x5b27f7cd9ba3]
  Binary file "/opt/python/python", at +0x255957 [0x5b27f7cad957]
  Binary file "/opt/python/python", at +0x255ab4 [0x5b27f7cadab4]
  Binary file "/opt/python/python", at _PyEval_EvalFrameDefault+0x6c3e [0x5b27f7cbd634]
  Binary file "/opt/python/python", at +0x2818e6 [0x5b27f7cd98e6]
  Binary file "/opt/python/python", at +0x281aab [0x5b27f7cd9aab]
  Binary file "/opt/python/python", at +0x11b6e1 [0x5b27f7b736e1]
  Binary file "/opt/python/python", at +0x11d348 [0x5b27f7b75348]
  Binary file "/opt/python/python", at +0x11d626 [0x5b27f7b75626]
  Binary file "/opt/python/python", at PyObject_Call+0x20 [0x5b27f7b7565e]
  Binary file "/opt/python/python", at +0x32a67a [0x5b27f7d8267a]
  Binary file "/opt/python/python", at +0x32a7f8 [0x5b27f7d827f8]
  Binary file "/opt/python/python", at +0x32ac1b [0x5b27f7d82c1b]
  Binary file "/opt/python/python", at Py_RunMain+0x31 [0x5b27f7d82ebe]
  <truncated rest of calls>
Segmentation fault

pdb --- Python 偵錯器

原始碼：Lib/pdb.py [https://github.com/python/cpython/tree/3.14/Lib/pdb.py]

pdb 模組定義了一個 Python 程式的互動式原始碼偵錯器。它支援在原始碼列層級 (source line level) 設定（條件式的）斷點 (breakpoint) 和單步執行、檢視 stack frame（堆疊框）、列出原始碼、以及在任何 stack frame 情境 (context) 中為任意 Python 程式碼求值 (evaluation)。它還支援事後偵錯 (post-mortem debugging)，並可以在程式控制下呼叫。

偵錯器是可擴充的 —— 偵錯器實際被定義為 Pdb 類別。該類別目前沒有文件，但可以很容易地透過閱讀原始碼來理解它。擴充套件介面使用了 bdb 和 cmd 模組。

也參考

faulthandler 模組

用於在出現故障時、超時 (timeout) 後或於接收到使用者訊號時，顯式地轉儲 (dump) Python 回溯 (traceback)。

traceback 模組

用於提取、格式化和印出 Python 程式 stack trace（堆疊追蹤）的標準介面。

自一個執行中程式切入偵錯器的典型用法為插入：

import pdb; pdb.set_trace()

或：

breakpoint()

到你想切入偵錯器的位置，然後執行程式，就可以單步執行上述陳述式之後的程式碼，並可以使用 continue 命令來離開偵錯器、繼續執行。

在 3.7 版的變更: 當使用預設值呼叫時，可以使用內建的 breakpoint() 來取代 import pdb; pdb.set_trace()。

def double(x):
   breakpoint()
   return x * 2
val = 3
print(f"{val} * 2 is {double(val)}")

偵錯器的提示字元是 (Pdb)，這表示你處於偵錯模式：

> ...(2)double()
-> breakpoint()
(Pdb) p x
3
(Pdb) continue
3 * 2 is 6

在 3.3 版的變更: 透過 readline 模組達成的 tab 補全可用於補全本模組的命令和命令的引數，例如會提供目前的全域和區域名稱以作為 p 命令的引數。

命令列介面

你還可以從命令列叫用 pdb 來偵錯其他腳本。例如：

python -m pdb [-c command] (-m module | -p pid | pyfile) [args ...]

當作為模組叫用時，如果被偵錯的程序不正常地退出，pdb 將自動進入事後偵錯。事後偵錯後（或程式正常退出後），pdb 將重新啟動程式。自動重新啟動會保留 pdb 的狀態（例如斷點），並且在大多數情況下比在程式退出時退出偵錯器更有用。

-c, --command <command>

就像在 .pdbrc 檔案中給定的那樣來執行命令；請參閱偵錯器命令。

在 3.2 版的變更: 新增了 -c 選項。

-m <module>

以類似於 python -m 的方式來執行模組。與腳本一樣，偵錯器將在模組的第一列之前暫停執行。

在 3.7 版的變更: 新增了 -m 選項。

-p, --pid <pid>

Attach to the process with the specified PID.

在 3.14 版被加入.

To attach to a running Python process for remote debugging, use the -p or --pid option with the target process's PID:

python -m pdb -p 1234

備註

Attaching to a process that is blocked in a system call or waiting for I/O will only work once the next bytecode instruction is executed or when the process receives a signal.

在偵錯器控制下執行陳述式的典型用法是：

>>> import pdb
>>> def f(x):
...     print(1 / x)
>>> pdb.run("f(2)")
> <string>(1)<module>()
(Pdb) continue
0.5
>>>

檢查一個損壞程式的典型用法：

>>> import pdb
>>> def f(x):
...     print(1 / x)
...
>>> f(0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in f
ZeroDivisionError: division by zero
>>> pdb.pm()
> <stdin>(2)f()
(Pdb) p x
0
(Pdb)

在 3.13 版的變更: PEP 667 [https://peps.python.org/pep-0667/] 的實作意味著透過 pdb 進行的名稱賦予 (name assignments) 會立即影響有效作用域，即使在最佳化作用域內運作也是如此。

本模組定義了下列函式，每個函式進入偵錯器的方式略有不同：

pdb.run(statement, globals=None, locals=None)

在偵錯器控制下執行 statement（以字串或程式碼物件形式給定）。偵錯提示字元會在執行任何程式碼前出現；你可以設定斷點並輸入 continue，或也可以使用 step 或 next 逐步執行陳述式（這些命令在下面都有說明）。可選引數 globals 和 locals 指定程式碼執行的環境；預設使用 __main__ 模組的字典。（請參閱內建函式 exec() 或 eval() 的說明。）

pdb.runeval(expression, globals=None, locals=None)

在偵錯器控制下為 expression 求值（以字串或程式碼物件形式給定）。當 runeval() 回傳時，它回傳 expression 的值。除此之外，該函式與 run() 類似。

pdb.runcall(function, *args, **kwds)

使用給定的引數呼叫 function（只可以是函式或方法物件，不能是字串）。runcall() 回傳的是所呼叫函式的回傳值。偵錯器提示字元將在進入函式後立即出現。

pdb.set_trace(*, header=None, commands=None)

在呼叫此函式的 stack frame 進入偵錯器。用於在程式中給定之處寫死 (hard-code) 一個斷點，即便該程式碼不在偵錯狀態（如斷言失敗時）。如有給定 header，它將在偵錯正要開始前被印出到控制台。如果給定了 commands 引數，它會是在偵錯器啟動時要執行的命令清單。

在 3.7 版的變更: 僅限關鍵字引數 header。

在 3.13 版的變更: set_trace() 將立即進入偵錯器，而不是在下一列要執行的程式碼中。

在 3.14 版被加入: commands 引數。

awaitable pdb.set_trace_async(*, header=None, commands=None)

async version of set_trace(). This function should be used inside an async function with await.

async def f():
    await pdb.set_trace_async()

await statements are supported if the debugger is invoked by this function.

在 3.14 版被加入.

pdb.post_mortem(t=None)

進入所給定例外或回溯物件的事後偵錯。如果沒有給定，預設使用目前正在處理的例外，或如果沒有例外則會引發 ValueError。

在 3.13 版的變更: 新增對例外物件的支援。

pdb.pm()

進入在 sys.last_exc 中發現的例外的事後偵錯。

pdb.set_default_backend(backend)

There are two supported backends for pdb: 'settrace' and 'monitoring'. See bdb.Bdb for details. The user can set the default backend to use if none is specified when instantiating Pdb. If no backend is specified, the default is 'settrace'.

備註

breakpoint() and set_trace() will not be affected by this function. They always use 'monitoring' backend.

在 3.14 版被加入.

pdb.get_default_backend()

Returns the default backend for pdb.

在 3.14 版被加入.

run* 函式和 set_trace() 都是別名，用於實例化 (instantiate) Pdb 類別並呼叫同名方法。如果要使用更多功能，則必須自己執行以下操作：

class pdb.Pdb(completekey='tab', stdin=None, stdout=None, skip=None, nosigint=False, readrc=True, mode=None, backend=None, colorize=False)

Pdb 是偵錯器類別。

completekey、stdin 與 stdout 引數會被傳到底層的 cmd.Cmd 類別；請於該文件閱讀相關敘述。

如果給定 skip 引數，則它必須是一個給出 glob 樣式之模組名稱的疊代器。如果遇到匹配這些樣式的模組，偵錯器將不會進入來自該模組的 frame。 [1]

預設情況下，當你發出 continue 命令時，Pdb 會為 SIGINT 訊號（即使用者在控制台上按下 Ctrl-C 時會發送的訊號）設定一個處理程式 (handler)，這允許你透過按下 Ctrl-C 再次切入偵錯器。如果你希望 Pdb 不影響到 SIGINT 處理程式，請將 nosigint 設定為 true。

readrc 引數預設為 true，它控制 Pdb 是否從檔案系統載入 .pdbrc 檔案。

The mode argument specifies how the debugger was invoked. It impacts the workings of some debugger commands. Valid values are 'inline' (used by the breakpoint() builtin), 'cli' (used by the command line invocation) or None (for backwards compatible behaviour, as before the mode argument was added).

The backend argument specifies the backend to use for the debugger. If None is passed, the default backend will be used. See set_default_backend(). Otherwise the supported backends are 'settrace' and 'monitoring'.

The colorize argument, if set to True, will enable colorized output in the debugger, if color is supported. This will highlight source code displayed in pdb.

啟用追蹤 (tracing) 且帶有 skip 引數的呼叫示範：

import pdb; pdb.Pdb(skip=['django.*']).set_trace()

不帶引數地引發一個稽核事件 (auditing event) pdb.Pdb。

在 3.1 版的變更: 新增了 skip 參數。

在 3.2 版的變更: 新增了 nosigint 參數。以前 SIGINT 處理程式從未被 Pdb 設定過。

在 3.6 版的變更: readrc 引數。

在 3.14 版被加入: 新增了 mode 引數。

在 3.14 版被加入: 新增了 backend 引數。

在 3.14 版被加入: 新增了 colorize 引數。

在 3.14 版的變更: Inline breakpoints like breakpoint() or pdb.set_trace() will always stop the program at calling frame, ignoring the skip pattern (if any).

run(statement, globals=None, locals=None)

runeval(expression, globals=None, locals=None)

runcall(function, *args, **kwds)

set_trace()

請見上面關於這些函式的文件說明。

Debugger commands

下方列出的是偵錯器能認得的命令。如下所示，大多數命令可以縮寫為一個或兩個字母。如 h(elp) 表示可以輸入 h 或 help 來輸入幫助命令（但不能輸入 he 或 hel，也不能是 H 或 Help 或 HELP）。命令的引數必須用空格（空格符 (spaces) 或製表符 (tabs)）分隔。在命令語法中，可選引數被括在方括號 ([]) 中；使用時請勿輸入方括號。命令語法中的選擇項由豎線 (|) 分隔。

輸入一個空白列 (blank line) 將重複上次輸入的命令。例外：如果上一個命令是 list 命令，則會列出接下來的 11 列。

偵錯器無法識別的命令將被認為是 Python 陳述式，並以正在偵錯的程式之情境來執行。Python 陳述式也可以用驚嘆號 (!) 作為前綴，這是檢視正在偵錯之程式的強大方法，甚至可以修改變數或呼叫函式。當此類陳述式發生例外，將印出例外名稱，但偵錯器的狀態不會改變。

在 3.13 版的變更: 現在可以正確辨識並執行前綴為 pdb 命令的運算式/陳述式。

偵錯器有支援設定別名。別名可以有參數，使得偵錯器對被檢查的情境有一定程度的適應性。

在一列中可以輸入多個以 ;; 分隔的命令。（不能使用單個 ;，因為它用於分隔傳遞給 Python 剖析器一列中的多個命令。）切分命令沒運用什麼高深的方式；輸入總是在第一處 ;; 被切分開，即使它位於引號內的字串之中。對於具有雙分號字串的一個變通解法，是使用隱式字串連接 ';'';' 或 ";"";"。

要設定臨時全域變數，請使用便利變數 (convenience variable)。便利變數是名稱以 $ 開頭的變數。例如 $foo = 1 會設定一個全域變數 $foo，你可以在偵錯器會話 (debugger session) 中使用它。當程式恢復執行時，便利變數將被清除，因此與使用 foo = 1 等普通變數相比，它不太會去干擾你的程式。

共有四個預先設定的便利變數：

$_frame：目前正在偵錯的 frame

$_retval：frame 回傳時的回傳值

$_exception：frame 引發例外時的例外

$_asynctask: the asyncio task if pdb stops in an async function

在 3.12 版被加入: 新增了便利變數功能。

在 3.14 版被加入: 新增了 $_asynctask 便利變數。

如果 .pdbrc 檔案存在於使用者的家目錄或目前目錄中，則會使用 'utf-8' 編碼讀取並執行該檔案，就像在偵錯器提示字元下鍵入該檔案一樣，除了空列和以 # 開頭的列會被忽略之外。這對於別名設定特別有用。如果兩個檔案都存在，則先讀取家目錄中的檔案，且定義於其中的別名可以被本地檔案覆蓋。

在 3.2 版的變更: .pdbrc 現在可以包含繼續偵錯的命令，如 continue 或 next。以前檔案中的這些命令是無效的。

在 3.11 版的變更: .pdbrc 現在使用 'utf-8' 編碼讀取。以前它是使用系統區域設定編碼讀取的。

h(elp) [command]

如不帶引數，印出可用的命令列表。引數為 command 時，印出有關該命令的幫助訊息，help pdb 會顯示完整文件（即 pdb 模組的說明字串 (docstring)）。由於 command 引數必須是一個識別字 (identifier)，若要取得 ! 命令的幫助訊息則必須輸入 help exec。

w(here) [count]

印出 stack trace，最新的 frame 會位於底部。如果 count 為 0，則印出目前的 frame 條目。如果 count 為負數，印出最舊的 count 個 frame。如果 count 為正數，印出最新的 count 個 frame。箭頭（>）表示目前的 frame，它也決定了大多數命令的情境。

在 3.14 版的變更: count argument is added.

d(own) [count]

在 stack trace 中，將目前 frame 向下移動 count 級（預設為 1 級，移往較新的 frame）。

u(p) [count]

在 stack trace 中，將目前 frame 向上移動 count 級（預設為 1 級，移向較舊的 frame）。

b(reak) [([filename:]lineno | function) [, condition]]

如帶有 lineno 引數，則在目前檔案中的 lineno 列處設定中斷。列號可以以 filename 和冒號為前綴，以指定另一個檔案（可能是尚未載入的檔案）中的斷點。該檔案會在 sys.path 上搜尋。可接受的 filename 形式為 /abspath/to/file.py、relpath/file.py、module 和 package.module。

如帶有 function 引數，在該函式內的第一個可執行陳述式處設定中斷。function 可以是任何其求值結果為目前命名空間中函式的運算式。

如果第二個引數存在，它是一個運算式，在斷點生效前其必須求值為 true

如果不帶引數執行會列出所有斷點資訊，包括每個斷點、命中該斷點的次數、目前的忽略次數以及關聯的條件（如存在）。

每個斷點都有賦予一個編號，所有其他斷點命令都參照該編號。

tbreak [([filename:]lineno | function) [, condition]]

臨時斷點，在第一次遇見時會自動被刪除。它的引數與 break 相同。

cl(ear) [filename:lineno | bpnumber ...]

如帶有 filename:lineno 引數，則清除此列上的所有斷點。如果引數是空格分隔的斷點編號列表，則清除這些斷點。如果不帶引數則清除所有斷點（但會先提示確認）。

disable bpnumber [bpnumber ...]

停用斷點，斷點以空格分隔的斷點編號列表來給定。停用斷點表示它不會導致程式停止執行，但是與清除斷點不同，停用的斷點將保留在斷點列表中並且可以（重新）啟用。

enable bpnumber [bpnumber ...]

啟用指定的斷點。

ignore bpnumber [count]

為給定的斷點編號設定忽略計數。如果省略 count 則忽略計數設定為 0。當忽略計數為 0 時，斷點將變為有效狀態。當非 0 時，每次到達斷點，且斷點沒有被禁用，且任何關聯的條件被求值為 true，則 count 就會遞減。

condition bpnumber [condition]

為斷點設定一個新 condition，為一個運算式，且其求值結果為 true 時斷點才會起作用。如果沒有給定 condition，則刪除任何現有條件，也就是不為斷點設定條件。

commands [bpnumber]

為編號是 bpnumber 的斷點指定一系列命令。命令內容出現在後續的幾列中。輸入僅包含 end 的一列來結束命令列表。例如：

(Pdb) commands 1
(com) p some_variable
(com) end
(Pdb)

要刪除斷點上的所有命令，請輸入 commands 並立即以 end 結尾，也就是不指定任何命令。

不帶有 bpnumber 引數則 commands 會關聯到上一個設定的斷點。

可以使用斷點命令來重新啟動程式，只需使用 continue 或 step 命令，或其他可以繼續執行程式的命令。

如果指定了某個繼續執行程式的命令（目前包括 continue、step、next、return、until、jump、quit 及它們的縮寫）將終止命令列表（就像該命令後馬上跟著 end）。因為在任何時候繼續執行下去（即使是簡單的 next 或 step），都可能會遇到另一個斷點，該斷點可能具有自己的命令列表，這會導致無法確定要執行哪個列表。

If the list of commands contains the silent command, or a command that resumes execution, then the breakpoint message containing information about the frame is not displayed.

在 3.14 版的變更: Frame information will not be displayed if a command that resumes execution is present in the command list.

s(tep)

執行目前列，在第一個可以停止的位置（在被呼叫的函式內部或在目前函式的下一列）停止。

n(ext)

繼續執行，直至執行到目前函式的下一列或者目前函式回傳為止。（next 和 step 之間的區別在於 step 會在被呼叫函式的內部停止、而 next（幾乎）全速執行被呼叫的函式，並僅在目前函式的下一列停止。）

unt(il) [lineno]

如果不帶引數則繼續執行，直到列號比目前的列大時停止。

如帶有 lineno 則繼續執行，直到到達列號大於或等於 lineno 的那一列。在這兩種情況下，目前 frame 回傳時也會停止。

在 3.2 版的變更: 允許明確給定一個列號。

r(eturn)

繼續執行，直到目前的函式回傳。

c(ont(inue))

繼續執行，除非遇到斷點才停下來。

j(ump) lineno

設定即將執行的下一列，僅可用於堆疊中最底部的 frame。這讓你可以跳回去並再次執行程式碼，或者往前跳以跳過不想執行的程式碼。

需要注意的是，不是所有的跳轉都是被允許的 -- 例如不能跳轉到 for 迴圈的中間或跳出 finally 子句。

l(ist) [first[, last]]

列出目前檔案的原始碼。如果不帶引數，則列出目前列周圍的 11 列，或繼續先前的列表操作。如果用 . 作為引數，則列出目前列周圍的 11 列。如果帶有一個引數，則列出那一列周圍的 11 列。如果帶有兩個引數，則列出給定範圍中的程式碼；如果第二個引數小於第一個引數，則將其直譯為要列出的列數。

目前 frame 中的目前列會用 -> 標記出來。如果正在偵錯一個例外，且引發或傳遞該例外的那一列不是目前列，則會用 >> 來標記該列。

在 3.2 版的變更: 新增了 >> 標記。

ll | longlist

列出目前函式或 frame 的所有原始碼。相關列的標記方式與 list 相同。

在 3.2 版被加入.

a(rgs)

印出目前函式的引數及它們目前的值。

p expression

在目前情境中為 expression 求值並印出其值。

備註

也可以使用 print()，但它不是一個偵錯器命令 --- 它會執行 Python print() 函式。

pp expression

與 p 命令類似，除了 expression 的值是使用 pprint 模組美化後印出來的。

whatis expression

印出 expression 的型別。

source expression

嘗試取得 expression 的原始碼並顯示它。

在 3.2 版被加入.

display [expression]

每次在目前 frame 中停止執行時，顯示 expression 的值（如果有變更）。

如果不帶有 expression，則列出目前 frame 的所有運算式。

備註

display 會對 expression 求值並將結果與之前 expression 的求值結果進行比較，因此當結果可變時，display 可能無法取得其變更。

範例如下：

lst = []
breakpoint()
pass
lst.append(1)
print(lst)

display 不會意識到 lst 已更改，因為其求值結果在比較之前已被 lst.append(1) 原地 (in place) 修改：

> example.py(3)<module>()
-> pass
(Pdb) display lst
display lst: []
(Pdb) n
> example.py(4)<module>()
-> lst.append(1)
(Pdb) n
> example.py(5)<module>()
-> print(lst)
(Pdb)

你可以運用複製機制的一些技巧來使其能夠運作：

> example.py(3)<module>()
-> pass
(Pdb) display lst[:]
display lst[:]: []
(Pdb) n
> example.py(4)<module>()
-> lst.append(1)
(Pdb) n
> example.py(5)<module>()
-> print(lst)
display lst[:]: [1]  [old: []]
(Pdb)

在 3.2 版被加入.

undisplay [expression]

不再顯示目前 frame 中的 expression。如果不帶有 expression，則清除目前 frame 的所有顯示運算式。

在 3.2 版被加入.

interact

在從目前作用域的區域和全域命名空間初始化的新全域命名空間中啟動互動式直譯器（使用 code 模組）。可使用 exit() 或 quit() 退出直譯器並回到偵錯器。

備註

由於 interact 為程式碼執行建立了一個新的專用命名空間，因此變數的賦值不會影響原始命名空間，但是對任何被參照的可變物件的修改將像往常一樣反映在原始命名空間中。

在 3.2 版被加入.

在 3.13 版的變更: exit() 和 quit() 可用來退出 interact 命令。

在 3.13 版的變更: interact 將其輸出導向到偵錯器的輸出通道 (output channel)，而不是 sys.stderr。

alias [name [command]]

建立一個名為 name 的別名，用於執行 command。command 不得用引號包起來。可被替換的參數要用 %1、%2、 ... 和 %9 標示，而 %* 則被所有參數替換。如果省略 command，則顯示 name 的目前別名。如果未給定引數，則列出所有別名。

巢狀別名是允許的，且可包含能在 pdb 提示字元下合法輸入的任何內容。請注意，內部 pdb 命令可以被別名所覆蓋。這樣的命令在別名被移除前都將被隱藏。別名會遞迴地應用到命令列的第一個單詞；該列內的其他單詞則不會受影響。

作為範例，這裡列出了兩個有用的別名（特別是放在 .pdbrc 檔案中時）：

# 印出實例變數（用法如 "pi classInst"）
alias pi for k in %1.__dict__.keys(): print(f"%1.{k} = {%1.__dict__[k]}")
# 印出 self 中的實例變數
alias ps pi self

unalias name

刪除指定的別名 name。

! statement

在目前 stack frame 的情境中執行（單列）statement。除非陳述式的第一個單詞類似於偵錯器命令，否則可以省略驚嘆號，例如：

(Pdb) ! n=42
(Pdb)

要設定全域變數，你可以在同一列的賦值命令前面加上 global 陳述式，例如：

(Pdb) global list_options; list_options = ['-l']
(Pdb)

run [args ...]

restart [args ...]

重新啟動已偵錯完畢的 Python 程式。如果提供了 args，它將以 shlex 分割，並將結果用作新的 sys.argv。歷史記錄、斷點、操作和偵錯器選項均會被保留。restart 是 run 的別名。

在 3.14 版的變更: run and restart commands are disabled when the debugger is invoked in 'inline' mode.

q(uit)

離開偵錯器，執行中的程式會被中止。輸入檔案結尾 (end-of-file) 相當於 quit。

A confirmation prompt will be shown if the debugger is invoked in 'inline' mode. Either y, Y, <Enter> or EOF will confirm the quit.

在 3.14 版的變更: A confirmation prompt will be shown if the debugger is invoked in 'inline' mode. After the confirmation, the debugger will call sys.exit() immediately, instead of raising bdb.BdbQuit in the next trace event.

debug code

進入一個遞迴偵錯器，逐步執行 code（這是要在目前環境中執行的任意運算式或陳述式）。

retval

印出目前函式最後一次回傳的回傳值。

exceptions [excnumber]

列出鏈接例外 (chained exceptions)，或在其間跳轉。

當使用 pdb.pm() 或 Pdb.post_mortem(...) 於鏈接例外而不是回溯時，它允許使用者在鏈接例外之間移動，使用 exceptions 命令以列出例外，並使用 exceptions <number> 切換到該例外。

範例如下：

def out():
    try:
        middle()
    except Exception as e:
        raise ValueError("reraise middle() error") from e

def middle():
    try:
        return inner(0)
    except Exception as e:
        raise ValueError("Middle fail")

def inner(x):
    1 / x

 out()

呼叫 pdb.pm() 將允許在例外之間移動：

> example.py(5)out()
-> raise ValueError("reraise middle() error") from e

(Pdb) exceptions
  0 ZeroDivisionError('division by zero')
  1 ValueError('Middle fail')
> 2 ValueError('reraise middle() error')

(Pdb) exceptions 0
> example.py(16)inner()
-> 1 / x

(Pdb) up
> example.py(10)middle()
-> return inner(0)

在 3.13 版被加入.

註腳

[1]

一個 frame 是否會被認為源自特定模組是由該 frame 全域性變數中的 __name__ 來決定的。

Python 的分析器

原始碼：Lib/profile.py [https://github.com/python/cpython/tree/3.14/Lib/profile.py] 與 Lib/pstats.py [https://github.com/python/cpython/tree/3.14/Lib/pstats.py]

分析器簡介

cProfile and profile provide deterministic profiling of Python programs. A profile is a set of statistics that describes how often and for how long various parts of the program executed. These statistics can be formatted into reports via the pstats module.

The Python standard library provides two different implementations of the same profiling interface:

cProfile is recommended for most users; it's a C extension with reasonable overhead that makes it suitable for profiling long-running programs. Based on lsprof, contributed by Brett Rosen and Ted Czotter.

profile, a pure Python module whose interface is imitated by cProfile, but which adds significant overhead to profiled programs. If you're trying to extend the profiler in some way, the task might be easier with this module. Originally designed and written by Jim Roskind.

備註

The profiler modules are designed to provide an execution profile for a given program, not for benchmarking purposes (for that, there is timeit for reasonably accurate results). This particularly applies to benchmarking Python code against C code: the profilers introduce overhead for Python code, but not for C-level functions, and so the C code would seem faster than any Python one.

Instant User's Manual

This section is provided for users that "don't want to read the manual." It provides a very brief overview, and allows a user to rapidly perform profiling on an existing application.

To profile a function that takes a single argument, you can do:

import cProfile
import re
cProfile.run('re.compile("foo|bar")')

(Use profile instead of cProfile if the latter is not available on your system.)

The above action would run re.compile() and print profile results like the following:

      214 function calls (207 primitive calls) in 0.002 seconds

Ordered by: cumulative time

ncalls  tottime  percall  cumtime  percall filename:lineno(function)
     1    0.000    0.000    0.002    0.002 {built-in method builtins.exec}
     1    0.000    0.000    0.001    0.001 <string>:1(<module>)
     1    0.000    0.000    0.001    0.001 __init__.py:250(compile)
     1    0.000    0.000    0.001    0.001 __init__.py:289(_compile)
     1    0.000    0.000    0.000    0.000 _compiler.py:759(compile)
     1    0.000    0.000    0.000    0.000 _parser.py:937(parse)
     1    0.000    0.000    0.000    0.000 _compiler.py:598(_code)
     1    0.000    0.000    0.000    0.000 _parser.py:435(_parse_sub)

The first line indicates that 214 calls were monitored. Of those calls, 207 were primitive, meaning that the call was not induced via recursion. The next line: Ordered by: cumulative time indicates the output is sorted by the cumtime values. The column headings include:

ncalls

for the number of calls.

tottime

for the total time spent in the given function (and excluding time made in calls to sub-functions)

percall

is the quotient of tottime divided by ncalls

cumtime

is the cumulative time spent in this and all subfunctions (from invocation till exit). This figure is accurate even for recursive functions.

percall

is the quotient of cumtime divided by primitive calls

filename:lineno(function)

provides the respective data of each function

When there are two numbers in the first column (for example 3/1), it means that the function recursed. The second value is the number of primitive calls and the former is the total number of calls. Note that when the function does not recurse, these two values are the same, and only the single figure is printed.

Instead of printing the output at the end of the profile run, you can save the results to a file by specifying a filename to the run() function:

import cProfile
import re
cProfile.run('re.compile("foo|bar")', 'restats')

The pstats.Stats class reads profile results from a file and formats them in various ways.

The files cProfile and profile can also be invoked as a script to profile another script. For example:

python -m cProfile [-o output_file] [-s sort_order] (-m module | myscript.py)

-o <output_file>

Writes the profile results to a file instead of to stdout.

-s <sort_order>

Specifies one of the sort_stats() sort values to sort the output by. This only applies when -o is not supplied.

-m <module>

Specifies that a module is being profiled instead of a script.

在 3.7 版被加入: 新增 -m 選項到 cProfile。

在 3.8 版被加入: 新增 -m 選項到 profile。

The pstats module's Stats class has a variety of methods for manipulating and printing the data saved into a profile results file:

import pstats
from pstats import SortKey
p = pstats.Stats('restats')
p.strip_dirs().sort_stats(-1).print_stats()

The strip_dirs() method removed the extraneous path from all the module names. The sort_stats() method sorted all the entries according to the standard module/line/name string that is printed. The print_stats() method printed out all the statistics. You might try the following sort calls:

p.sort_stats(SortKey.NAME)
p.print_stats()

The first call will actually sort the list by function name, and the second call will print out the statistics. The following are some interesting calls to experiment with:

p.sort_stats(SortKey.CUMULATIVE).print_stats(10)

This sorts the profile by cumulative time in a function, and then only prints the ten most significant lines. If you want to understand what algorithms are taking time, the above line is what you would use.

If you were looking to see what functions were looping a lot, and taking a lot of time, you would do:

p.sort_stats(SortKey.TIME).print_stats(10)

to sort according to time spent within each function, and then print the statistics for the top ten functions.

You might also try:

p.sort_stats(SortKey.FILENAME).print_stats('__init__')

This will sort all the statistics by file name, and then print out statistics for only the class init methods (since they are spelled with __init__ in them). As one final example, you could try:

p.sort_stats(SortKey.TIME, SortKey.CUMULATIVE).print_stats(.5, 'init')

This line sorts statistics with a primary key of time, and a secondary key of cumulative time, and then prints out some of the statistics. To be specific, the list is first culled down to 50% (re: .5) of its original size, then only lines containing init are maintained, and that sub-sub-list is printed.

If you wondered what functions called the above functions, you could now (p is still sorted according to the last criteria) do:

p.print_callers(.5, 'init')

and you would get a list of callers for each of the listed functions.

If you want more functionality, you're going to have to read the manual, or guess what the following functions do:

p.print_callees()
p.add('restats')

Invoked as a script, the pstats module is a statistics browser for reading and examining profile dumps. It has a simple line-oriented interface (implemented using cmd) and interactive help.

profile 與 cProfile 模組參考文件

Both the profile and cProfile modules provide the following functions:

profile.run(command, filename=None, sort=-1)

This function takes a single argument that can be passed to the exec() function, and an optional file name. In all cases this routine executes:

exec(command, __main__.__dict__, __main__.__dict__)

and gathers profiling statistics from the execution. If no file name is present, then this function automatically creates a Stats instance and prints a simple profiling report. If the sort value is specified, it is passed to this Stats instance to control how the results are sorted.

profile.runctx(command, globals, locals, filename=None, sort=-1)

This function is similar to run(), with added arguments to supply the globals and locals mappings for the command string. This routine executes:

exec(command, globals, locals)

and gathers profiling statistics as in the run() function above.

class profile.Profile(timer=None, timeunit=0.0, subcalls=True, builtins=True)

This class is normally only used if more precise control over profiling is needed than what the cProfile.run() function provides.

A custom timer can be supplied for measuring how long code takes to run via the timer argument. This must be a function that returns a single number representing the current time. If the number is an integer, the timeunit specifies a multiplier that specifies the duration of each unit of time. For example, if the timer returns times measured in thousands of seconds, the time unit would be .001.

Directly using the Profile class allows formatting profile results without writing the profile data to a file:

import cProfile, pstats, io
from pstats import SortKey
pr = cProfile.Profile()
pr.enable()
# ... do something ...
pr.disable()
s = io.StringIO()
sortby = SortKey.CUMULATIVE
ps = pstats.Stats(pr, stream=s).sort_stats(sortby)
ps.print_stats()
print(s.getvalue())

The Profile class can also be used as a context manager (supported only in cProfile module. see 情境管理器型別):

import cProfile

with cProfile.Profile() as pr:
    # ... do something ...

    pr.print_stats()

在 3.8 版的變更: 新增情境管理器的支援。

enable()

Start collecting profiling data. Only in cProfile.

disable()

Stop collecting profiling data. Only in cProfile.

create_stats()

Stop collecting profiling data and record the results internally as the current profile.

print_stats(sort=-1)

Create a Stats object based on the current profile and print the results to stdout.

The sort parameter specifies the sorting order of the displayed statistics. It accepts a single key or a tuple of keys to enable multi-level sorting, as in Stats.sort_stats.

在 3.13 版被加入: print_stats() now accepts a tuple of keys.

dump_stats(filename)

Write the results of the current profile to filename.

run(cmd)

Profile the cmd via exec().

runctx(cmd, globals, locals)

Profile the cmd via exec() with the specified global and local environment.

runcall(func, /, *args, **kwargs)

Profile func(*args, **kwargs)

Note that profiling will only work if the called command/function actually returns. If the interpreter is terminated (e.g. via a sys.exit() call during the called command/function execution) no profiling results will be printed.

Stats 類別

Analysis of the profiler data is done using the Stats class.

class pstats.Stats(*filenames or profile, stream=sys.stdout)

This class constructor creates an instance of a "statistics object" from a filename (or list of filenames) or from a Profile instance. Output will be printed to the stream specified by stream.

The file selected by the above constructor must have been created by the corresponding version of profile or cProfile. To be specific, there is no file compatibility guaranteed with future versions of this profiler, and there is no compatibility with files produced by other profilers, or the same profiler run on a different operating system. If several files are provided, all the statistics for identical functions will be coalesced, so that an overall view of several processes can be considered in a single report. If additional files need to be combined with data in an existing Stats object, the add() method can be used.

Instead of reading the profile data from a file, a cProfile.Profile or profile.Profile object can be used as the profile data source.

Stats 物件有以下方法：

strip_dirs()

This method for the Stats class removes all leading path information from file names. It is very useful in reducing the size of the printout to fit within (close to) 80 columns. This method modifies the object, and the stripped information is lost. After performing a strip operation, the object is considered to have its entries in a "random" order, as it was just after object initialization and loading. If strip_dirs() causes two function names to be indistinguishable (they are on the same line of the same filename, and have the same function name), then the statistics for these two entries are accumulated into a single entry.

add(*filenames)

This method of the Stats class accumulates additional profiling information into the current profiling object. Its arguments should refer to filenames created by the corresponding version of profile.run() or cProfile.run(). Statistics for identically named (re: file, line, name) functions are automatically accumulated into single function statistics.

dump_stats(filename)

Save the data loaded into the Stats object to a file named filename. The file is created if it does not exist, and is overwritten if it already exists. This is equivalent to the method of the same name on the profile.Profile and cProfile.Profile classes.

sort_stats(*keys)

This method modifies the Stats object by sorting it according to the supplied criteria. The argument can be either a string or a SortKey enum identifying the basis of a sort (example: 'time', 'name', SortKey.TIME or SortKey.NAME). The SortKey enums argument have advantage over the string argument in that it is more robust and less error prone.

When more than one key is provided, then additional keys are used as secondary criteria when there is equality in all keys selected before them. For example, sort_stats(SortKey.NAME, SortKey.FILE) will sort all the entries according to their function name, and resolve all ties (identical function names) by sorting by file name.

For the string argument, abbreviations can be used for any key names, as long as the abbreviation is unambiguous.

The following are the valid string and SortKey:

Valid String Arg

Valid enum Arg

含義

'calls'

SortKey.CALLS

call count

'cumulative'

SortKey.CUMULATIVE

cumulative time

'cumtime'

N/A

cumulative time

'file'

N/A

file name（檔案名稱）

'filename'

SortKey.FILENAME

file name（檔案名稱）

'module'

N/A

file name（檔案名稱）

'ncalls'

N/A

call count

'pcalls'

SortKey.PCALLS

primitive call count

'line'

SortKey.LINE

列號

'name'

SortKey.NAME

function name

'nfl'

SortKey.NFL

name/file/line

'stdname'

SortKey.STDNAME

standard name

'time'

SortKey.TIME

internal time

'tottime'

N/A

internal time

Note that all sorts on statistics are in descending order (placing most time consuming items first), where as name, file, and line number searches are in ascending order (alphabetical). The subtle distinction between SortKey.NFL and SortKey.STDNAME is that the standard name is a sort of the name as printed, which means that the embedded line numbers get compared in an odd way. For example, lines 3, 20, and 40 would (if the file names were the same) appear in the string order 20, 3 and 40. In contrast, SortKey.NFL does a numeric compare of the line numbers. In fact, sort_stats(SortKey.NFL) is the same as sort_stats(SortKey.NAME, SortKey.FILENAME, SortKey.LINE).

For backward-compatibility reasons, the numeric arguments -1, 0, 1, and 2 are permitted. They are interpreted as 'stdname', 'calls', 'time', and 'cumulative' respectively. If this old style format (numeric) is used, only one sort key (the numeric key) will be used, and additional arguments will be silently ignored.

在 3.7 版被加入: Added the SortKey enum.

reverse_order()

This method for the Stats class reverses the ordering of the basic list within the object. Note that by default ascending vs descending order is properly selected based on the sort key of choice.

print_stats(*restrictions)

This method for the Stats class prints out a report as described in the profile.run() definition.

The order of the printing is based on the last sort_stats() operation done on the object (subject to caveats in add() and strip_dirs()).

The arguments provided (if any) can be used to limit the list down to the significant entries. Initially, the list is taken to be the complete set of profiled functions. Each restriction is either an integer (to select a count of lines), or a decimal fraction between 0.0 and 1.0 inclusive (to select a percentage of lines), or a string that will be interpreted as a regular expression (to pattern match the standard name that is printed). If several restrictions are provided, then they are applied sequentially. For example:

print_stats(.1, 'foo:')

would first limit the printing to first 10% of list, and then only print functions that were part of filename .*foo:. In contrast, the command:

print_stats('foo:', .1)

would limit the list to all functions having file names .*foo:, and then proceed to only print the first 10% of them.

print_callers(*restrictions)

This method for the Stats class prints a list of all functions that called each function in the profiled database. The ordering is identical to that provided by print_stats(), and the definition of the restricting argument is also identical. Each caller is reported on its own line. The format differs slightly depending on the profiler that produced the stats:

With profile, a number is shown in parentheses after each caller to show how many times this specific call was made. For convenience, a second non-parenthesized number repeats the cumulative time spent in the function at the right.

With cProfile, each caller is preceded by three numbers: the number of times this specific call was made, and the total and cumulative times spent in the current function while it was invoked by this specific caller.

print_callees(*restrictions)

This method for the Stats class prints a list of all function that were called by the indicated function. Aside from this reversal of direction of calls (re: called vs was called by), the arguments and ordering are identical to the print_callers() method.

get_stats_profile()

This method returns an instance of StatsProfile, which contains a mapping of function names to instances of FunctionProfile. Each FunctionProfile instance holds information related to the function's profile such as how long the function took to run, how many times it was called, etc...

在 3.9 版被加入: Added the following dataclasses: StatsProfile, FunctionProfile. Added the following function: get_stats_profile.

What Is Deterministic Profiling?

Deterministic profiling is meant to reflect the fact that all function call, function return, and exception events are monitored, and precise timings are made for the intervals between these events (during which time the user's code is executing). In contrast, statistical profiling (which is not done by this module) randomly samples the effective instruction pointer, and deduces where time is being spent. The latter technique traditionally involves less overhead (as the code does not need to be instrumented), but provides only relative indications of where time is being spent.

In Python, since there is an interpreter active during execution, the presence of instrumented code is not required in order to do deterministic profiling. Python automatically provides a hook (optional callback) for each event. In addition, the interpreted nature of Python tends to add so much overhead to execution, that deterministic profiling tends to only add small processing overhead in typical applications. The result is that deterministic profiling is not that expensive, yet provides extensive run time statistics about the execution of a Python program.

Call count statistics can be used to identify bugs in code (surprising counts), and to identify possible inline-expansion points (high call counts). Internal time statistics can be used to identify "hot loops" that should be carefully optimized. Cumulative time statistics should be used to identify high level errors in the selection of algorithms. Note that the unusual handling of cumulative times in this profiler allows statistics for recursive implementations of algorithms to be directly compared to iterative implementations.

限制

One limitation has to do with accuracy of timing information. There is a fundamental problem with deterministic profilers involving accuracy. The most obvious restriction is that the underlying "clock" is only ticking at a rate (typically) of about .001 seconds. Hence no measurements will be more accurate than the underlying clock. If enough measurements are taken, then the "error" will tend to average out. Unfortunately, removing this first error induces a second source of error.

The second problem is that it "takes a while" from when an event is dispatched until the profiler's call to get the time actually gets the state of the clock. Similarly, there is a certain lag when exiting the profiler event handler from the time that the clock's value was obtained (and then squirreled away), until the user's code is once again executing. As a result, functions that are called many times, or call many functions, will typically accumulate this error. The error that accumulates in this fashion is typically less than the accuracy of the clock (less than one clock tick), but it can accumulate and become very significant.

The problem is more important with profile than with the lower-overhead cProfile. For this reason, profile provides a means of calibrating itself for a given platform so that this error can be probabilistically (on the average) removed. After the profiler is calibrated, it will be more accurate (in a least square sense), but it will sometimes produce negative numbers (when call counts are exceptionally low, and the gods of probability work against you :-). ) Do not be alarmed by negative numbers in the profile. They should only appear if you have calibrated your profiler, and the results are actually better than without calibration.

校正

The profiler of the profile module subtracts a constant from each event handling time to compensate for the overhead of calling the time function, and socking away the results. By default, the constant is 0. The following procedure can be used to obtain a better constant for a given platform (see 限制).

import profile
pr = profile.Profile()
for i in range(5):
    print(pr.calibrate(10000))

The method executes the number of Python calls given by the argument, directly and again under the profiler, measuring the time for both. It then computes the hidden overhead per profiler event, and returns that as a float. For example, on a 1.8Ghz Intel Core i5 running macOS, and using Python's time.process_time() as the timer, the magical number is about 4.04e-6.

The object of this exercise is to get a fairly consistent result. If your computer is very fast, or your timer function has poor resolution, you might have to pass 100000, or even 1000000, to get consistent results.

When you have a consistent answer, there are three ways you can use it:

import profile

# 1. Apply computed bias to all Profile instances created hereafter.
profile.Profile.bias = your_computed_bias

# 2. Apply computed bias to a specific Profile instance.
pr = profile.Profile()
pr.bias = your_computed_bias

# 3. Specify computed bias in instance constructor.
pr = profile.Profile(bias=your_computed_bias)

If you have a choice, you are better off choosing a smaller constant, and then your results will "less often" show up as negative in profile statistics.

Using a custom timer

If you want to change how current time is determined (for example, to force use of wall-clock time or elapsed process time), pass the timing function you want to the Profile class constructor:

pr = profile.Profile(your_time_func)

The resulting profiler will then call your_time_func. Depending on whether you are using profile.Profile or cProfile.Profile, your_time_func's return value will be interpreted differently:

profile.Profile

your_time_func should return a single number, or a list of numbers whose sum is the current time (like what os.times() returns). If the function returns a single time number, or the list of returned numbers has length 2, then you will get an especially fast version of the dispatch routine.

Be warned that you should calibrate the profiler class for the timer function that you choose (see 校正). For most machines, a timer that returns a lone integer value will provide the best results in terms of low overhead during profiling. (os.times() is pretty bad, as it returns a tuple of floating-point values). If you want to substitute a better timer in the cleanest fashion, derive a class and hardwire a replacement dispatch method that best handles your timer call, along with the appropriate calibration constant.

cProfile.Profile

your_time_func should return a single number. If it returns integers, you can also invoke the class constructor with a second argument specifying the real duration of one unit of time. For example, if your_integer_time_func returns times measured in thousands of seconds, you would construct the Profile instance as follows:

pr = cProfile.Profile(your_integer_time_func, 0.001)

As the cProfile.Profile class cannot be calibrated, custom timer functions should be used with care and should be as fast as possible. For the best results with a custom timer, it might be necessary to hard-code it in the C source of the internal _lsprof module.

Python 3.3 adds several new functions in time that can be used to make precise measurements of process or wall-clock time. For example, see time.perf_counter().

timeit --- 測量小量程式片段的執行時間

原始碼：Lib/timeit.py [https://github.com/python/cpython/tree/3.14/Lib/timeit.py]

該模組提供了一種對少量 Python 程式碼進行計時的簡單方法。它有一個命令列介面和一個可呼叫介面，它避免了許多測量執行時間的常見陷阱。另請參閱由 O'Reilly 出版的 Python 錦囊妙計 (Python Cookbook) 第二版中 Tim Peters 所寫的「演算法」章節的介紹。

基礎範例

以下範例展示了如何使用命令列介面來比較三個不同的運算式：

$ python -m timeit "'-'.join(str(n) for n in range(100))"
10000 loops, best of 5: 30.2 usec per loop
$ python -m timeit "'-'.join([str(n) for n in range(100)])"
10000 loops, best of 5: 27.5 usec per loop
$ python -m timeit "'-'.join(map(str, range(100)))"
10000 loops, best of 5: 23.2 usec per loop

這可以透過 Python 介面來實現：

>>> import timeit
>>> timeit.timeit('"-".join(str(n) for n in range(100))', number=10000)
0.3018611848820001
>>> timeit.timeit('"-".join([str(n) for n in range(100)])', number=10000)
0.2727368790656328
>>> timeit.timeit('"-".join(map(str, range(100)))', number=10000)
0.23702679807320237

也可以在 Python 介面傳遞可呼叫物件：

>>> timeit.timeit(lambda: "-".join(map(str, range(100))), number=10000)
0.19665591977536678

但請注意，僅當使用命令列介面時 timeit() 才會自動確定重複次數。在範例章節中有更進階的範例。

Python 介面

該模組定義了三個便利函式和一個公開類別：

timeit.timeit(stmt='pass', setup='pass', timer=<default timer>, number=1000000, globals=None)

使用給定的陳述式、setup 程式碼和 timer 函式建立一個 Timer 實例，並執行其 timeit() 方法 number 次。可選的 globals 引數指定會在其中執行程式碼的命名空間。

在 3.5 版的變更: 新增 globals 選用參數。

timeit.repeat(stmt='pass', setup='pass', timer=<default timer>, repeat=5, number=1000000, globals=None)

使用給定的陳述式、setup 程式碼和 timer 函式建立一個 Timer 實例，並使用給定的 repeat 計數和 number 來運行其 repeat() 方法。可選的 globals 引數指定會在其中執行程式碼的命名空間。

在 3.5 版的變更: 新增 globals 選用參數。

在 3.7 版的變更: repeat 的預設值從 3 更改為 5。

timeit.default_timer()

預設計時器始終為 time.perf_counter()，會回傳浮點秒數。另一種方法是 time.perf_counter_ns，會回傳整數奈秒。

在 3.3 版的變更: time.perf_counter() 現在是預設計時器。

class timeit.Timer(stmt='pass', setup='pass', timer=<timer function>, globals=None)

用於計時小程式碼片段執行速度的類別。

建構函式接受一個要計時的陳述式、一個用於設定的附加陳述式和一個計時器函式。兩個陳述式都預設為 'pass'；計時器函式會與平台相依（請參閱模組文件字串 (doc string)）。stmt 和 setup 還可以包含由 ; 或換行符號分隔的多個陳述式，只要它們不包含多行字串文字即可。預設情況下，該陳述式將在 timeit 的命名空間內執行；可以透過將命名空間傳遞給 globals 來控制此行為。

要測量第一個陳述式的執行時間，請使用 timeit() 方法。repeat() 和 autorange() 方法是多次呼叫 timeit() 的便捷方法。

setup 的執行時間不包含在總體運行計時中。

stmt 和 setup 參數還可以接受無需引數即可呼叫的物件。這會把對它們的呼叫嵌入到計時器函式中，然後由 timeit() 去執行。請注意，在這種情況下，因有額外的函式呼叫，時間開銷 (timing overhead) 會稍大一些。

在 3.5 版的變更: 新增 globals 選用參數。

timeit(number=1000000)

主陳述式執行 number 次的時間。這將執行一次設定陳述式，然後回傳多次執行主陳述式所需的時間。預設計時器以浮點形式回傳秒數，引數是迴圈的次數，預設為一百萬次。要使用的主陳述式、設定陳述式和計時器函式會被傳遞給建構函式。

備註

預設情況下 timeit() 在計時期間會暫時關閉垃圾回收。這種方法的優點是它使獨立時序更具可比較性，缺點是 GC 可能是被測函式性能的重要組成部分。如果是這樣，可以將 GC 作為 setup 字串中的第一個陳述式以重新啟用。例如：

timeit.Timer('for i in range(10): oct(i)', 'gc.enable()').timeit()

autorange(callback=None)

自動決定呼叫 timeit() 次數。

這是一個便捷函式，它重複呼叫 timeit() 以使得總時間 >= 0.2 秒，再回傳最終結果（迴圈數、該迴圈數所花費的時間）。它以 1、2、5、10、20、50... 的順序遞增數字來呼叫 timeit() 直到所用時間至少為 0.2 秒。

如果有給定 callback 且不是 None，則每次試驗後都會使用兩個引數來呼叫它：callback(number, time_taken)。

在 3.6 版被加入.

repeat(repeat=5, number=1000000)

呼叫 timeit() 數次。

這是一個方便的函式，它會重複呼叫 timeit() 並回傳結果列表。第一個引數指定呼叫 timeit() 的次數，第二個引數指定 timeit() 的 number 引數。

備註

人們很容易根據結果向量來計算出平均值和標準差並將其作為依歸，然而這並不是很有用。在典型情況下，最低值給出了機器運行給定程式碼片段的速度的下限；結果向量中較高的值通常不是由 Python 速度的變化所引起，而是由干擾計時精度的其他行程造成的。因此，結果中的 min() 可能是你應該感興趣的唯一數字。在解讀該數據後，你應該查看整個向量並以常識判讀而非單純仰賴統計資訊。

在 3.7 版的變更: repeat 的預設值從 3 更改為 5。

print_exc(file=None)

從計時程式碼印出回溯 (traceback) 的輔助函式。

典型用法：

t = Timer(...)       # 在 try/except 之外
try:
    t.timeit(...)    # 或 t.repeat(...)
except Exception:
    t.print_exc()

相對於標準回溯的優點是，已編譯模板中的原始程式碼會被顯示出來。可選的 file 引數指定回溯的發送位置；它預設為 sys.stderr。

命令列介面

當從命令列作為程式呼叫時，請使用以下形式：

python -m timeit [-n N] [-r N] [-u U] [-s S] [-p] [-v] [-h] [statement ...]

其中之以下選項：

-n N, --number=N

執行 'statement' 多少次

-r N, --repeat=N

計時器重複多少次（預設 5）

-s S, --setup=S

會在一開始執行一次的陳述式（預設為 pass）

-p, --process

若要測量行程時間 (process time) 而非掛鐘時間 (wallclock time)，請使用 time.process_time() 而不是預設的 time.perf_counter()

在 3.3 版被加入.

-u, --unit=U

指定定時器輸出的時間單位；可以選擇 nsec、usec、msec 或 sec

在 3.5 版被加入.

-v, --verbose

印出原始計時結果；重複執行以獲得更高的數字精度

-h, --help

印出一條簡短的使用訊息並退出

可以透過將每一列陳述式指定為單獨引數來給定多列陳述式；可透過將引數括在引號中並使用前導空格以實現縮進列 (indented lines)。多個 -s 選項的作用類似。

如果沒有給定 -n，則透過嘗試從序列 1, 2, 5, 10, 20, 50, ... 中增加數字來計算合適的迴圈次數，直到總時間至少為 0.2 秒。

default_timer() 測量可能會受到同一台機器上運行的其他程式的影響，因此，當需要精確計時時，最好的做法是重複計時幾次並使用最佳時間。-r 選項對此很有用；在大多數情況下，預設的重複 5 次可能就足夠了。你可以使用 time.process_time() 來測量 CPU 時間。

備註

執行 pass 陳述式會產生一定的基本開銷。這裡的程式碼並不試圖隱藏它，但你應該意識到它的存在。可以透過不帶引數呼叫程式來測量這個基本開銷，且不同 Python 版本之間的基本開銷可能有所不同。

範例

可以提供一個僅會在開始時執行一次的設定陳述式：

$ python -m timeit -s "text = 'sample string'; char = 'g'" "char in text"
5000000 loops, best of 5: 0.0877 usec per loop
$ python -m timeit -s "text = 'sample string'; char = 'g'" "text.find(char)"
1000000 loops, best of 5: 0.342 usec per loop

輸出中包含三個欄位。迴圈計數，它告訴你每次計時迴圈內重複運行陳述式主體的次數。重複計數（「最好的 5 次」）告訴你計時迴圈重複了多少次。以及最後陳述式主體在計時迴圈的最佳的幾次重複執行內平均花費的時間。也就是說，最快的幾次重複執行所花費的總時間除以迴圈計數。

>>> import timeit
>>> timeit.timeit('char in text', setup='text = "sample string"; char = "g"')
0.41440500499993504
>>> timeit.timeit('text.find(char)', setup='text = "sample string"; char = "g"')
1.7246671520006203

同樣可以使用 Timer 類別及其方法來完成：

>>> import timeit
>>> t = timeit.Timer('char in text', setup='text = "sample string"; char = "g"')
>>> t.timeit()
0.3955516149999312
>>> t.repeat()
[0.40183617287970225, 0.37027556854118704, 0.38344867356679524, 0.3712595970846668, 0.37866875250654886]

以下範例展示如何對包含多行的運算式進行計時。這裡我們使用 hasattr() 與 try/except 來測試缺失和存在之物件屬性並比較其花費 (cost)：

$ python -m timeit "try:" "  str.__bool__" "except AttributeError:" "  pass"
20000 loops, best of 5: 15.7 usec per loop
$ python -m timeit "if hasattr(str, '__bool__'): pass"
50000 loops, best of 5: 4.26 usec per loop

$ python -m timeit "try:" "  int.__bool__" "except AttributeError:" "  pass"
200000 loops, best of 5: 1.43 usec per loop
$ python -m timeit "if hasattr(int, '__bool__'): pass"
100000 loops, best of 5: 2.23 usec per loop

>>> import timeit
>>> # attribute is missing
>>> s = """\
... try:
...     str.__bool__
... except AttributeError:
...     pass
... """
>>> timeit.timeit(stmt=s, number=100000)
0.9138244460009446
>>> s = "if hasattr(str, '__bool__'): pass"
>>> timeit.timeit(stmt=s, number=100000)
0.5829014980008651
>>>
>>> # attribute is present
>>> s = """\
... try:
...     int.__bool__
... except AttributeError:
...     pass
... """
>>> timeit.timeit(stmt=s, number=100000)
0.04215312199994514
>>> s = "if hasattr(int, '__bool__'): pass"
>>> timeit.timeit(stmt=s, number=100000)
0.08588060699912603

要讓 timeit 模組存取你定義的函式，你可以傳遞一個包含 import 陳述式的 setup 參數：

def test():
    """一個笨笨的測試函式"""
    L = [i for i in range(100)]

if __name__ == '__main__':
    import timeit
    print(timeit.timeit("test()", setup="from __main__ import test"))

另一種選擇是將 globals() 傳遞給 globals 參數，這將導致程式碼在目前的全域命名空間中執行，這比單獨指定 import 更方便：

def f(x):
    return x**2
def g(x):
    return x**4
def h(x):
    return x**8

import timeit
print(timeit.timeit('[func(42) for func in (f,g,h)]', globals=globals()))

trace --- 追蹤或追查 Python 陳述式執行

原始碼：Lib/trace.py [https://github.com/python/cpython/tree/3.14/Lib/trace.py]

trace 模組可用來追蹤程式執行過程、產生帶註解的陳述式涵蓋範圍清單、輸出呼叫者／被呼叫者的關係，以及在程式執行期間被執行的函式串列。它可以在其他程式中使用，也可以從命令列啟動。

也參考

Coverage.py [https://coverage.readthedocs.io/]

一款受歡迎的第三方涵蓋範圍工具，提供 HTML 輸出與分支涵蓋等進階功能。

命令列用法

trace 模組可從命令列執行，用法可以非常簡單，如：:

python -m trace --count -C . somefile.py ...

上述命令會執行 somefile.py，並將產生執行期間所引入的所有 Python 模組的帶註解串列，輸出至目前目錄。

--help

顯示用法並結束程式。

--version

顯示模組版本並結束程式。

在 3.8 版被加入: 新增 --module 選項，允許執行可執行模組。

主要選項

執行 trace 時，至少必須指定以下選項之一。--listfuncs 選項與 --trace 及 --count 選項互斥。當提供 --listfuncs 時，將不接受 --count 或 --trace，反之亦然。

-c, --count

在程式執行結束時產生一組帶註解串列檔案，顯示每個陳述式被執行的次數。參見下方的 --coverdir、--file 及 --no-report。

-t, --trace

執行時即時顯示每一行。

-l, --listfuncs

顯示程式執行過程中被呼叫的函式。

-r, --report

從先前使用 --count 與 --file 選項執行過的程式生成帶註解的串列，不會執行任何程式碼。

-T, --trackcalls

顯示程式執行時產生的呼叫關係。

修飾子（Modifier）

-f, --file=<file>

指定用來累積多次追蹤結果的檔案之名稱。應與 --count 選項搭配使用。

-C, --coverdir=<dir>

報告檔案的輸出目錄。package.module 的涵蓋範圍報告將寫入檔案：dir/package/module.cover。

-m, --missing

在產生帶註解的串列時，使用 >>>>>> 標記未被執行的程式碼行。

-s, --summary

使用 --count 或 --report 時，會將每個處理過的檔案摘要輸出至 stdout。

-R, --no-report

不產生帶註解的串列。若你打算多次使用 --count 執行程式，並在最後再統一產生串列，這會很有幫助。

-g, --timing

在每一行前加上自程式啟動以來的經過時間。僅在追蹤時使用。

篩選子（Filter）

這些選項可以重複使用多次。

--ignore-module=<mod>

忽略所指定的模組名稱及其子模組（若為套件）。引數可以是以逗號分隔的名稱串列。

--ignore-dir=<dir>

忽略指定目錄及其子目錄中的所有模組與套件。引數可以是以 os.pathsep 分隔的目錄串列。

程式介面

class trace.Trace(count=1, trace=1, countfuncs=0, countcallers=0, ignoremods=(), ignoredirs=(), infile=None, outfile=None, timing=False)

建立一個物件以追蹤單一陳述式或運算式的執行。所有參數皆為可選的。count 啟用行數統計，trace 啟用逐行追蹤執行，countfuncs 可列出執行期間呼叫的函式，countcallers 追蹤呼叫關係，ignoremods 是要忽略的模組或套件名稱串列，ignoredirs 是其模組或套件應被忽略的目錄串列，infile 是讀取儲存計數資料的檔案名稱，outfile 是要寫入更新後計數資料的檔案名稱，timing 則會顯示自開始追蹤以來的時間戳記。

run(cmd)

執行命令，並依目前追蹤參數收集執行統計資料。cmd 必須是可傳入 exec() 的字串或程式碼物件。

runctx(cmd, globals=None, locals=None)

在指定的全域與區域命名空間中，根據目前的追蹤參數執行命令並收集統計資料。若未指定，globals 與 locals 預設為空字典。

runfunc(func, /, *args, **kwds)

在目前的追蹤參數下，使用 Trace 物件控制呼叫 func，並傳入指定的引數。

results()

回傳一個 CoverageResults 物件，包含指定 Trace 實例中所有先前對 run、runctx 與 runfunc 呼叫的累積結果。不會重設累積的追蹤結果。

class trace.CoverageResults

一個用來儲存涵蓋範圍結果的容器，由 Trace.results() 建立。不應由使用者直接建立。

update(other)

合併來自另一個 CoverageResults 物件的資料。

write_results(show_missing=True, summary=False, coverdir=None, *, ignore_missing_files=False)

寫入涵蓋範圍結果。將 show_missing 設為真可顯示未被執行的程式碼行；將 summary 設為真則會在輸出中加入每個模組的涵蓋範圍摘要。coverdir 指定輸出涵蓋範圍結果檔案的目錄，若為 None，則每個原始檔案的結果會輸出至其所在目錄中。

若 ignore_missing_files 為 True，則會忽略那些已不存在的檔案的涵蓋範圍資料，不會顯示任何錯誤。否則，缺少的檔案將會引發 FileNotFoundError。

在 3.13 版的變更: 新增 ignore_missing_files 參數。

以下是一個簡單範例，展示如何使用程式介面：

import sys
import trace

# 建立一個 Trace 物件，指定要忽略的目錄，
# 並設定是否進行追蹤、行數統計或兩者皆做。
tracer = trace.Trace(
    ignoredirs=[sys.prefix, sys.exec_prefix],
    trace=0,
    count=1)

# 使用該 tracer 執行新的命令
tracer.run('main()')

# 建立報告，將輸出放在目前目錄中
r = tracer.results()
r.write_results(show_missing=True, coverdir=".")

tracemalloc --- 追蹤記憶體配置

在 3.4 版被加入.

原始碼：Lib/tracemalloc.py [https://github.com/python/cpython/tree/3.14/Lib/tracemalloc.py]

The tracemalloc module is a debug tool to trace memory blocks allocated by Python. It provides the following information:

Traceback where an object was allocated

Statistics on allocated memory blocks per filename and per line number: total size, number and average size of allocated memory blocks

Compute the differences between two snapshots to detect memory leaks

To trace most memory blocks allocated by Python, the module should be started as early as possible by setting the PYTHONTRACEMALLOC environment variable to 1, or by using -X tracemalloc command line option. The tracemalloc.start() function can be called at runtime to start tracing Python memory allocations.

By default, a trace of an allocated memory block only stores the most recent frame (1 frame). To store 25 frames at startup: set the PYTHONTRACEMALLOC environment variable to 25, or use the -X tracemalloc=25 command line option.

範例

Display the top 10

Display the 10 files allocating the most memory:

import tracemalloc

tracemalloc.start()

# ... run your application ...

snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('lineno')

print("[ Top 10 ]")
for stat in top_stats[:10]:
    print(stat)

Example of output of the Python test suite:

[ Top 10 ]
<frozen importlib._bootstrap>:716: size=4855 KiB, count=39328, average=126 B
<frozen importlib._bootstrap>:284: size=521 KiB, count=3199, average=167 B
/usr/lib/python3.4/collections/__init__.py:368: size=244 KiB, count=2315, average=108 B
/usr/lib/python3.4/unittest/case.py:381: size=185 KiB, count=779, average=243 B
/usr/lib/python3.4/unittest/case.py:402: size=154 KiB, count=378, average=416 B
/usr/lib/python3.4/abc.py:133: size=88.7 KiB, count=347, average=262 B
<frozen importlib._bootstrap>:1446: size=70.4 KiB, count=911, average=79 B
<frozen importlib._bootstrap>:1454: size=52.0 KiB, count=25, average=2131 B
<string>:5: size=49.7 KiB, count=148, average=344 B
/usr/lib/python3.4/sysconfig.py:411: size=48.0 KiB, count=1, average=48.0 KiB

We can see that Python loaded 4855 KiB data (bytecode and constants) from modules and that the collections module allocated 244 KiB to build namedtuple types.

更多選項請見 Snapshot.statistics()。

Compute differences

Take two snapshots and display the differences:

import tracemalloc
tracemalloc.start()
# ... start your application ...

snapshot1 = tracemalloc.take_snapshot()
# ... call the function leaking memory ...
snapshot2 = tracemalloc.take_snapshot()

top_stats = snapshot2.compare_to(snapshot1, 'lineno')

print("[ Top 10 differences ]")
for stat in top_stats[:10]:
    print(stat)

Example of output before/after running some tests of the Python test suite:

[ Top 10 differences ]
<frozen importlib._bootstrap>:716: size=8173 KiB (+4428 KiB), count=71332 (+39369), average=117 B
/usr/lib/python3.4/linecache.py:127: size=940 KiB (+940 KiB), count=8106 (+8106), average=119 B
/usr/lib/python3.4/unittest/case.py:571: size=298 KiB (+298 KiB), count=589 (+589), average=519 B
<frozen importlib._bootstrap>:284: size=1005 KiB (+166 KiB), count=7423 (+1526), average=139 B
/usr/lib/python3.4/mimetypes.py:217: size=112 KiB (+112 KiB), count=1334 (+1334), average=86 B
/usr/lib/python3.4/http/server.py:848: size=96.0 KiB (+96.0 KiB), count=1 (+1), average=96.0 KiB
/usr/lib/python3.4/inspect.py:1465: size=83.5 KiB (+83.5 KiB), count=109 (+109), average=784 B
/usr/lib/python3.4/unittest/mock.py:491: size=77.7 KiB (+77.7 KiB), count=143 (+143), average=557 B
/usr/lib/python3.4/urllib/parse.py:476: size=71.8 KiB (+71.8 KiB), count=969 (+969), average=76 B
/usr/lib/python3.4/contextlib.py:38: size=67.2 KiB (+67.2 KiB), count=126 (+126), average=546 B

We can see that Python has loaded 8173 KiB of module data (bytecode and constants), and that this is 4428 KiB more than had been loaded before the tests, when the previous snapshot was taken. Similarly, the linecache module has cached 940 KiB of Python source code to format tracebacks, all of it since the previous snapshot.

If the system has little free memory, snapshots can be written on disk using the Snapshot.dump() method to analyze the snapshot offline. Then use the Snapshot.load() method reload the snapshot.

Get the traceback of a memory block

Code to display the traceback of the biggest memory block:

import tracemalloc

# Store 25 frames
tracemalloc.start(25)

# ... run your application ...

snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('traceback')

# pick the biggest memory block
stat = top_stats[0]
print("%s memory blocks: %.1f KiB" % (stat.count, stat.size / 1024))
for line in stat.traceback.format():
    print(line)

Example of output of the Python test suite (traceback limited to 25 frames):

903 memory blocks: 870.1 KiB
  File "<frozen importlib._bootstrap>", line 716
  File "<frozen importlib._bootstrap>", line 1036
  File "<frozen importlib._bootstrap>", line 934
  File "<frozen importlib._bootstrap>", line 1068
  File "<frozen importlib._bootstrap>", line 619
  File "<frozen importlib._bootstrap>", line 1581
  File "<frozen importlib._bootstrap>", line 1614
  File "/usr/lib/python3.4/doctest.py", line 101
    import pdb
  File "<frozen importlib._bootstrap>", line 284
  File "<frozen importlib._bootstrap>", line 938
  File "<frozen importlib._bootstrap>", line 1068
  File "<frozen importlib._bootstrap>", line 619
  File "<frozen importlib._bootstrap>", line 1581
  File "<frozen importlib._bootstrap>", line 1614
  File "/usr/lib/python3.4/test/support/__init__.py", line 1728
    import doctest
  File "/usr/lib/python3.4/test/test_pickletools.py", line 21
    support.run_doctest(pickletools)
  File "/usr/lib/python3.4/test/regrtest.py", line 1276
    test_runner()
  File "/usr/lib/python3.4/test/regrtest.py", line 976
    display_failure=not verbose)
  File "/usr/lib/python3.4/test/regrtest.py", line 761
    match_tests=ns.match_tests)
  File "/usr/lib/python3.4/test/regrtest.py", line 1563
    main()
  File "/usr/lib/python3.4/test/__main__.py", line 3
    regrtest.main_in_temp_cwd()
  File "/usr/lib/python3.4/runpy.py", line 73
    exec(code, run_globals)
  File "/usr/lib/python3.4/runpy.py", line 160
    "__main__", fname, loader, pkg_name)

We can see that the most memory was allocated in the importlib module to load data (bytecode and constants) from modules: 870.1 KiB. The traceback is where the importlib loaded data most recently: on the import pdb line of the doctest module. The traceback may change if a new module is loaded.

Pretty top

Code to display the 10 lines allocating the most memory with a pretty output, ignoring <frozen importlib._bootstrap> and <unknown> files:

import linecache
import os
import tracemalloc

def display_top(snapshot, key_type='lineno', limit=10):
    snapshot = snapshot.filter_traces((
        tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
        tracemalloc.Filter(False, "<unknown>"),
    ))
    top_stats = snapshot.statistics(key_type)

    print("Top %s lines" % limit)
    for index, stat in enumerate(top_stats[:limit], 1):
        frame = stat.traceback[0]
        print("#%s: %s:%s: %.1f KiB"
              % (index, frame.filename, frame.lineno, stat.size / 1024))
        line = linecache.getline(frame.filename, frame.lineno).strip()
        if line:
            print('    %s' % line)

    other = top_stats[limit:]
    if other:
        size = sum(stat.size for stat in other)
        print("%s other: %.1f KiB" % (len(other), size / 1024))
    total = sum(stat.size for stat in top_stats)
    print("Total allocated size: %.1f KiB" % (total / 1024))

tracemalloc.start()

# ... run your application ...

snapshot = tracemalloc.take_snapshot()
display_top(snapshot)

Example of output of the Python test suite:

Top 10 lines
#1: Lib/base64.py:414: 419.8 KiB
    _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
#2: Lib/base64.py:306: 419.8 KiB
    _a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
#3: collections/__init__.py:368: 293.6 KiB
    exec(class_definition, namespace)
#4: Lib/abc.py:133: 115.2 KiB
    cls = super().__new__(mcls, name, bases, namespace)
#5: unittest/case.py:574: 103.1 KiB
    testMethod()
#6: Lib/linecache.py:127: 95.4 KiB
    lines = fp.readlines()
#7: urllib/parse.py:476: 71.8 KiB
    for a in _hexdig for b in _hexdig}
#8: <string>:5: 62.0 KiB
#9: Lib/_weakrefset.py:37: 60.0 KiB
    self.data = set()
#10: Lib/base64.py:142: 59.8 KiB
    _b32tab2 = [a + b for a in _b32tab for b in _b32tab]
6220 other: 3602.8 KiB
Total allocated size: 5303.1 KiB

更多選項請見 Snapshot.statistics()。

Record the current and peak size of all traced memory blocks

The following code computes two sums like 0 + 1 + 2 + ... inefficiently, by creating a list of those numbers. This list consumes a lot of memory temporarily. We can use get_traced_memory() and reset_peak() to observe the small memory usage after the sum is computed as well as the peak memory usage during the computations:

import tracemalloc

tracemalloc.start()

# Example code: compute a sum with a large temporary list
large_sum = sum(list(range(100000)))

first_size, first_peak = tracemalloc.get_traced_memory()

tracemalloc.reset_peak()

# Example code: compute a sum with a small temporary list
small_sum = sum(list(range(1000)))

second_size, second_peak = tracemalloc.get_traced_memory()

print(f"{first_size=}, {first_peak=}")
print(f"{second_size=}, {second_peak=}")

輸出：

first_size=664, first_peak=3592984
second_size=804, second_peak=29704

Using reset_peak() ensured we could accurately record the peak during the computation of small_sum, even though it is much smaller than the overall peak size of memory blocks since the start() call. Without the call to reset_peak(), second_peak would still be the peak from the computation large_sum (that is, equal to first_peak). In this case, both peaks are much higher than the final memory usage, and which suggests we could optimise (by removing the unnecessary call to list, and writing sum(range(...))).

API

函式

tracemalloc.clear_traces()

Clear traces of memory blocks allocated by Python.

另請參閱 stop()。

tracemalloc.get_object_traceback(obj)

Get the traceback where the Python object obj was allocated. Return a Traceback instance, or None if the tracemalloc module is not tracing memory allocations or did not trace the allocation of the object.

另請參閱 gc.get_referrers() 與 sys.getsizeof() 函式。

tracemalloc.get_traceback_limit()

Get the maximum number of frames stored in the traceback of a trace.

The tracemalloc module must be tracing memory allocations to get the limit, otherwise an exception is raised.

The limit is set by the start() function.

tracemalloc.get_traced_memory()

Get the current size and peak size of memory blocks traced by the tracemalloc module as a tuple: (current: int, peak: int).

tracemalloc.reset_peak()

Set the peak size of memory blocks traced by the tracemalloc module to the current size.

Do nothing if the tracemalloc module is not tracing memory allocations.

This function only modifies the recorded peak size, and does not modify or clear any traces, unlike clear_traces(). Snapshots taken with take_snapshot() before a call to reset_peak() can be meaningfully compared to snapshots taken after the call.

另請參閱 get_traced_memory()。

在 3.9 版被加入.

tracemalloc.get_tracemalloc_memory()

Get the memory usage in bytes of the tracemalloc module used to store traces of memory blocks. Return an int.

tracemalloc.is_tracing()

True if the tracemalloc module is tracing Python memory allocations, False otherwise.

另請參閱 start() 與 stop() 函式。

tracemalloc.start(nframe: int = 1)

Start tracing Python memory allocations: install hooks on Python memory allocators. Collected tracebacks of traces will be limited to nframe frames. By default, a trace of a memory block only stores the most recent frame: the limit is 1. nframe must be greater or equal to 1.

You can still read the original number of total frames that composed the traceback by looking at the Traceback.total_nframe attribute.

Storing more than 1 frame is only useful to compute statistics grouped by 'traceback' or to compute cumulative statistics: see the Snapshot.compare_to() and Snapshot.statistics() methods.

Storing more frames increases the memory and CPU overhead of the tracemalloc module. Use the get_tracemalloc_memory() function to measure how much memory is used by the tracemalloc module.

The PYTHONTRACEMALLOC environment variable (PYTHONTRACEMALLOC=NFRAME) and the -X tracemalloc=NFRAME command line option can be used to start tracing at startup.

See also stop(), is_tracing() and get_traceback_limit() functions.

tracemalloc.stop()

Stop tracing Python memory allocations: uninstall hooks on Python memory allocators. Also clears all previously collected traces of memory blocks allocated by Python.

Call take_snapshot() function to take a snapshot of traces before clearing them.

See also start(), is_tracing() and clear_traces() functions.

tracemalloc.take_snapshot()

Take a snapshot of traces of memory blocks allocated by Python. Return a new Snapshot instance.

The snapshot does not include memory blocks allocated before the tracemalloc module started to trace memory allocations.

Tracebacks of traces are limited to get_traceback_limit() frames. Use the nframe parameter of the start() function to store more frames.

The tracemalloc module must be tracing memory allocations to take a snapshot, see the start() function.

另請參閱 get_object_traceback() 函式。

DomainFilter

class tracemalloc.DomainFilter(inclusive: bool, domain: int)

Filter traces of memory blocks by their address space (domain).

在 3.6 版被加入.

inclusive

If inclusive is True (include), match memory blocks allocated in the address space domain.

If inclusive is False (exclude), match memory blocks not allocated in the address space domain.

domain

Address space of a memory block (int). Read-only property.

Filter

class tracemalloc.Filter(inclusive: bool, filename_pattern: str, lineno: int = None, all_frames: bool = False, domain: int = None)

Filter on traces of memory blocks.

See the fnmatch.fnmatch() function for the syntax of filename_pattern. The '.pyc' file extension is replaced with '.py'.

範例：

Filter(True, subprocess.__file__) only includes traces of the subprocess module

Filter(False, tracemalloc.__file__) excludes traces of the tracemalloc module

Filter(False, "<unknown>") excludes empty tracebacks

在 3.5 版的變更: The '.pyo' file extension is no longer replaced with '.py'.

在 3.6 版的變更: 新增 domain 屬性。

domain

Address space of a memory block (int or None).

tracemalloc uses the domain 0 to trace memory allocations made by Python. C extensions can use other domains to trace other resources.

inclusive

If inclusive is True (include), only match memory blocks allocated in a file with a name matching filename_pattern at line number lineno.

If inclusive is False (exclude), ignore memory blocks allocated in a file with a name matching filename_pattern at line number lineno.

lineno

Line number (int) of the filter. If lineno is None, the filter matches any line number.

filename_pattern

Filename pattern of the filter (str). Read-only property.

all_frames

If all_frames is True, all frames of the traceback are checked. If all_frames is False, only the most recent frame is checked.

This attribute has no effect if the traceback limit is 1. See the get_traceback_limit() function and Snapshot.traceback_limit attribute.

Frame

class tracemalloc.Frame

Frame of a traceback.

The Traceback class is a sequence of Frame instances.

filename

Filename (str).

lineno

Line number (int).

Snapshot

class tracemalloc.Snapshot

Snapshot of traces of memory blocks allocated by Python.

The take_snapshot() function creates a snapshot instance.

compare_to(old_snapshot: Snapshot, key_type: str, cumulative: bool = False)

Compute the differences with an old snapshot. Get statistics as a sorted list of StatisticDiff instances grouped by key_type.

See the Snapshot.statistics() method for key_type and cumulative parameters.

The result is sorted from the biggest to the smallest by: absolute value of StatisticDiff.size_diff, StatisticDiff.size, absolute value of StatisticDiff.count_diff, Statistic.count and then by StatisticDiff.traceback.

dump(filename)

Write the snapshot into a file.

Use load() to reload the snapshot.

filter_traces(filters)

Create a new Snapshot instance with a filtered traces sequence, filters is a list of DomainFilter and Filter instances. If filters is an empty list, return a new Snapshot instance with a copy of the traces.

All inclusive filters are applied at once, a trace is ignored if no inclusive filters match it. A trace is ignored if at least one exclusive filter matches it.

在 3.6 版的變更: DomainFilter 實例現在也被接受於 filters 中。

classmethod load(filename)

Load a snapshot from a file.

另請參閱 dump()。

statistics(key_type: str, cumulative: bool = False)

Get statistics as a sorted list of Statistic instances grouped by key_type:

key_type

描述

'filename'

filename

'lineno'

filename and line number

'traceback'

traceback

If cumulative is True, cumulate size and count of memory blocks of all frames of the traceback of a trace, not only the most recent frame. The cumulative mode can only be used with key_type equals to 'filename' and 'lineno'.

The result is sorted from the biggest to the smallest by: Statistic.size, Statistic.count and then by Statistic.traceback.

traceback_limit

Maximum number of frames stored in the traceback of traces: result of the get_traceback_limit() when the snapshot was taken.

traces

Traces of all memory blocks allocated by Python: sequence of Trace instances.

The sequence has an undefined order. Use the Snapshot.statistics() method to get a sorted list of statistics.

Statistic

class tracemalloc.Statistic

Statistic on memory allocations.

Snapshot.statistics() returns a list of Statistic instances.

另請參閱 StatisticDiff 類別。

count

Number of memory blocks (int).

size

Total size of memory blocks in bytes (int).

traceback

Traceback where the memory block was allocated, Traceback instance.

StatisticDiff

class tracemalloc.StatisticDiff

Statistic difference on memory allocations between an old and a new Snapshot instance.

Snapshot.compare_to() returns a list of StatisticDiff instances. See also the Statistic class.

count

Number of memory blocks in the new snapshot (int): 0 if the memory blocks have been released in the new snapshot.

count_diff

Difference of number of memory blocks between the old and the new snapshots (int): 0 if the memory blocks have been allocated in the new snapshot.

size

Total size of memory blocks in bytes in the new snapshot (int): 0 if the memory blocks have been released in the new snapshot.

size_diff

Difference of total size of memory blocks in bytes between the old and the new snapshots (int): 0 if the memory blocks have been allocated in the new snapshot.

traceback

Traceback where the memory blocks were allocated, Traceback instance.

Trace

class tracemalloc.Trace

Trace of a memory block.

The Snapshot.traces attribute is a sequence of Trace instances.

在 3.6 版的變更: 新增 domain 屬性。

domain

Address space of a memory block (int). Read-only property.

tracemalloc uses the domain 0 to trace memory allocations made by Python. C extensions can use other domains to trace other resources.

size

Size of the memory block in bytes (int).

traceback

Traceback where the memory block was allocated, Traceback instance.

Traceback

class tracemalloc.Traceback

Sequence of Frame instances sorted from the oldest frame to the most recent frame.

A traceback contains at least 1 frame. If the tracemalloc module failed to get a frame, the filename "<unknown>" at line number 0 is used.

When a snapshot is taken, tracebacks of traces are limited to get_traceback_limit() frames. See the take_snapshot() function. The original number of frames of the traceback is stored in the Traceback.total_nframe attribute. That allows to know if a traceback has been truncated by the traceback limit.

The Trace.traceback attribute is an instance of Traceback instance.

在 3.7 版的變更: Frames are now sorted from the oldest to the most recent, instead of most recent to oldest.

total_nframe

Total number of frames that composed the traceback before truncation. This attribute can be set to None if the information is not available.

在 3.9 版的變更: 新增 Traceback.total_nframe 屬性。

format(limit=None, most_recent_first=False)

Format the traceback as a list of lines. Use the linecache module to retrieve lines from the source code. If limit is set, format the limit most recent frames if limit is positive. Otherwise, format the abs(limit) oldest frames. If most_recent_first is True, the order of the formatted frames is reversed, returning the most recent frame first instead of last.

Similar to the traceback.format_tb() function, except that format() does not include newlines.

範例：

print("Traceback (most recent call first):")
for line in traceback:
    print(line)

輸出：

Traceback (most recent call first):
  File "test.py", line 9
    obj = Object()
  File "test.py", line 12
    tb = tracemalloc.get_object_traceback(f())

軟體封裝與發布

這些函式庫可以幫助你發布和安裝 Python 軟體。雖然這些模組設計是為了與 Python 套件索引 (Python Package Index) [https://pypi.org] 結合使用，但它們也可以搭配本地索引伺服器，甚至可以在沒有任何索引伺服器的情況下使用。

ensurepip --- pip 安裝器的初始建置 (bootstrapping)

命令列介面

模組 API

venv --- 建立虛擬環境

建立虛擬環境

虛擬環境如何運作

API

一個擴展 EnvBuilder 的範例

zipapp —-- 管理可執行的 Python zip 封存檔案

基本範例

命令列介面

Python API

範例

指定直譯器

使用 zipapp 建立獨立應用程式

注意事項

Python Zip 應用程式封存檔案格式

ensurepip --- pip 安裝器的初始建置 (bootstrapping)

在 3.4 版被加入.

原始碼：Lib/ensurepip [https://github.com/python/cpython/tree/3.14/Lib/ensurepip]

ensurepip 套件 (package) 為既有的 Python 安裝或虛擬環境提供 pip 安裝器初始建置 (bootstrapping) 的支援。這個初始建置的方式應證了事實 —— pip 是有其獨立發布週期的專案，且其最新可用穩定的版本，會與 CPython 直譯器 (interpreter) 之維護和功能發布綁定。

大多數情況下，Python 的終端使用者不需要直接叫用此模組（因為 pip 預設應為初始建置），但若安裝 Python 時 pip 被省略（或建立一虛擬環境時），又或是 pip 被明確解除安裝時，則此模組的初始建置仍有可能用上。

備註

此模組不會存取網路。所有需要用來初始建置 pip 的元件都已包含在套件之內。

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see 可選模組的需求.

也參考

安裝 Python 模組

對於終端使用者安裝 Python 套件的指引

PEP 453 [https://peps.python.org/pep-0453/]: 在 Python 安裝中的 pip 明確初始建置

此模組的最初設計理念與規範。

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

命令列介面

使用直譯器 (interpreter) 的 -m 來叫用命令列介面

最簡單可行的呼叫：

python -m ensurepip

若 pip 未安裝，此呼叫會將其安裝；否則甚麼也不做。可透過傳入 --upgrade 參數來確保 pip 的安裝版本至少為目前 ensurepip 中最新可用的版本：

python -m ensurepip --upgrade

預設上，pip 會被安裝至目前虛擬環境（若已啟動虛擬環境）或系統端的套件（若沒有啟動的虛擬環境）。安裝位置可透過兩個額外的命令列選項來控制：

--root <dir>

安裝 pip 到給定的根目錄 (root directory) 的相對路徑，而不是目前虛擬環境（若存在）的根目錄，或目前 Python 安裝版所預設的根目錄。

--user

安裝 pip 到使用者端的套件目錄，而不是全域安裝到目前的 Python 安裝版（此選項不允許在一啟動的虛擬環境中使用）。

預設會安裝 pipX 和 pipX.Y 腳本（X.Y 代表用來叫用 ensurepip 的 Python 之版本）。安裝的腳本可透過兩個額外的命令列選項來控制：

--altinstall

若要求一個替代安裝版，則不會安裝 pipX 腳本。

--default-pip

若要求安裝「預設 pip」，則會安裝 pip 腳本，及 2 個常規腳本。

提供兩種指令選項將會導致例外 (exception) 。

模組 API

ensurepip 開放了兩個用於編寫程式的函式：

ensurepip.version()

回傳一個字串，用以標明初始建置時，安裝的 pip 的可行版本號。

ensurepip.bootstrap(root=None, upgrade=False, user=False, altinstall=False, default_pip=False, verbosity=0)

在目前或指定的環境之中建立 pip。

root 指定一個替代的根目錄，作為安裝的相對路徑。若 root 為 None，則安裝使用目前環境的預設安裝位置。

upgrade 指出是否要將一個既有的較早版本的 pip 升級至可用的新版。

user 指出是否要使用使用者的安裝方案而不是全域安裝。

預設會安裝 pipX 和 pipX.Y 腳本（X.Y 代表 Python 的目前版本）。

如果啟用了 altinstall，則不會安裝 pipX。

如果啟用了 default_pip，則會安裝 pip，以及 2 個常規腳本。

同時啟用 altinstall 跟 default_pip，將會觸發 ValueError。

verbosity 用來控制初始建置操作內，對於 sys.stdout 的輸出等級。

引發一個附帶引數 root 的稽核事件 ensurepip.bootstrap。

備註

初始建置的過程對於 sys.path 及 os.environ 均有副作用。改為在一子行程 (subprocess) 呼叫命令列介面可避免這些副作用。

備註

初始建置的過程也許會安裝 pip 所需要的額外的模組，但其他軟體不應該假設這些相依 (dependency) 總是預設存在（因為這些相依很可能會在未來版本的 pip 中被移除）。

venv --- 建立虛擬環境

在 3.3 版被加入.

原始碼：Lib/venv/ [https://github.com/python/cpython/tree/3.14/Lib/venv/]

venv 模組支援建立輕量級的「虛擬環境」，每個虛擬環境都有獨立安裝在其 site 目錄中的一組 Python 套件。虛擬環境是建立在既有的 Python 安裝上（稱為該虛擬環境的「基底」Python）之上，預設會與基底環境中的套件隔離，使得僅能存取明確安裝在虛擬環境中的套件。更多資訊請參閱 虛擬環境 以及 site 的虛擬環境文件。

在使用虛擬環境中時，像 pip [https://pypi.org/project/pip/] 這樣的常用安裝工具會自動將 Python 套件安裝至虛擬環境中，而不需要額外指定。

虛擬環境是（主要的特性）：

用來包含特定的 Python 直譯器、函式庫與二進位檔案，以支援某個專案（函式庫或應用程式）。預設情況下，這些內容會與其他虛擬環境中的軟體以及作業系統中安裝的 Python 直譯器與函式庫隔離。

被包含在一個目錄中，通常命名為專案目錄下的 .venv 或 venv，也可能是在用來管理多個虛擬環境的容器目錄中，例如 ~/.virtualenvs。

不應提交至 Git 等版本控制系統。

被視為可拋棄的資源——應能簡單地刪除並從頭重新建立。請勿將任何專案程式碼放置於虛擬環境中。

不應移動或複製——若需在其他位置使用，應重新建立相同的虛擬環境。

更多關於 Python 虛擬環境的背景資訊請見 PEP 405 [https://peps.python.org/pep-0405/]。

也參考

Python 套件指南：建立與使用虛擬環境 [https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#create-and-use-virtual-environments]

可用性: not Android, not iOS, not WASI.

此模組在行動平台或 WebAssembly 平台上不支援。

建立虛擬環境

虛擬環境是透過執行 venv 模組來建立：

python -m venv /path/to/new/virtual/environment

執行此命令會建立目標目錄（同時也會建立任何還不存在的父目錄）並在目錄中放置一個名為 pyvenv.cfg 的檔案，其中包含一個指向執行該命令的 Python 安裝路徑的 home 鍵。它同時會建立一個 bin （在 Windows 上為 Scripts）子目錄，其中包含一個 Python 二進位檔案的副本/符號連結（根據建立環境時使用的平台或引數而定）。此外，它還會建立一個 lib/pythonX.Y/site-packages 子目錄（在 Windows 上為 Lib\site-packages）。如果指定的目錄已存在，則將重新使用該目錄。

在 3.5 版的變更: 目前建議使用 venv 來建立虛擬環境。

自從版本 3.6 後不推薦使用，已從版本 3.8 中移除。: pyvenv 是在 Python 3.3 和 3.4 中建立虛擬環境的推薦工具，但在 Python 3.5 中已被直接執行 venv 所取代。

在 Windows 上，執行以下命令以使用 venv：

PS> python -m venv C:\path\to\new\virtual\environment

如果使用 -h 選項執行該命令，將會顯示可用的選項：

usage: venv [-h] [--system-site-packages] [--symlinks | --copies] [--clear]
            [--upgrade] [--without-pip] [--prompt PROMPT] [--upgrade-deps]
            [--without-scm-ignore-files]
            ENV_DIR [ENV_DIR ...]

Creates virtual Python environments in one or more target directories.

Once an environment has been created, you may wish to activate it, e.g. by
sourcing an activate script in its bin directory.

ENV_DIR

A required argument specifying the directory to create the environment in.

--system-site-packages

Give the virtual environment access to the system site-packages directory.

--symlinks

Try to use symlinks rather than copies, when symlinks are not the default for the platform.

--copies

Try to use copies rather than symlinks, even when symlinks are the default for the platform.

--clear

Delete the contents of the environment directory if it already exists, before environment creation.

--upgrade

Upgrade the environment directory to use this version of Python, assuming Python has been upgraded in-place.

--without-pip

Skips installing or upgrading pip in the virtual environment (pip is bootstrapped by default).

--prompt <PROMPT>

Provides an alternative prompt prefix for this environment.

--upgrade-deps

Upgrade core dependencies (pip) to the latest version in PyPI.

--without-scm-ignore-files

Skips adding SCM ignore files to the environment directory (Git is supported by default).

在 3.4 版的變更: 預設會安裝 pip，並新增了 --without-pip 和 --copies 選項

在 3.4 版的變更: 在較早的版本中，如果目標目錄已存在，除非提供了 --clear 或 --upgrade 選項，否則會引發錯誤。

在 3.9 版的變更: 新增 --upgrade-deps 選項以將 pip 和 setuptools 升級至 PyPI 上的最新版本

在 3.12 版的變更: setuptools 不再是 venv 的核心相依套件。

在 3.13 版的變更: 新增 --without-scm-ignore-files 選項

在 3.13 版的變更: venv 現在預設會為 Git 建立 .gitignore 檔案。

備註

雖然在 Windows 上支援符號連結，但並不建議使用。特別需要注意的是，在檔案總管中按兩下 python.exe 會急切地解析符號連結並忽略虛擬環境。

備註

在 Microsoft Windows 上，可能需要透過設置使用者的執行策略來啟用 Activate.ps1 腳本。你可以發出以下 PowerShell 命令來執行此操作：

PS C:\> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

有關更多資訊，請參閱關於執行策略 [https://go.microsoft.com/fwlink/?LinkID=135170]。

被建立的 pyvenv.cfg 檔案還包括了 include-system-site-packages 的鍵，如果使用 venv 執行時帶有 --system-site-packages 選項，則設置為 true，否則設置為 false。

除非 --without-pip 選項被提供，否則將叫用 ensurepip 來啟動 pip 到虛擬環境中。

可以向 venv 提供多個路徑，這樣每個提供的路徑都將根據給定的選項建立一個相同的虛擬環境。

虛擬環境如何運作

當 Python 直譯器跑在虛擬環境時，sys.prefix 和 sys.exec_prefix 會指向虛擬環境的目錄，而 sys.base_prefix 和 sys.base_exec_prefix 會指向建立虛擬環境的基礎 Python 的目錄。檢查 sys.prefix != sys.base_prefix 就可以確定目前的直譯器是否跑在虛擬環境中。

虛擬環境可以透過位於二進位檔案目錄中的腳本「啟用」（在 POSIX 上為 bin；在 Windows 上為 Scripts）這會將該目錄加入到你的 PATH，當你運行 python 時就會叫用該環境的直譯器並且執行已安裝的腳本，而不需要使用完整的路徑。啟動腳本的方式因平台而異（<venv> 需要替換成包含虛擬環境的目錄路徑）

平台

Shell

啟動虛擬環境的指令

POSIX

bash/zsh

$ source <venv>/bin/activate

fish

$ source <venv>/bin/activate.fish

csh/tcsh

$ source <venv>/bin/activate.csh

pwsh

$ <venv>/bin/Activate.ps1

Windows

cmd.exe

C:\> <venv>\Scripts\activate.bat

PowerShell

PS C:\> <venv>\Scripts\Activate.ps1

在 3.4 版被加入: fish 和 csh 啟動腳本。

在 3.8 版被加入: PowerShell 的啟動腳本安裝在 POSIX 上支援 PowerShell Core。

你不用特別開啟虛擬環境，你可以在呼叫 Python 時指定該環境下 Python 直譯器的完整路徑。此外，所有安裝在環境裡的腳本都應該都可以在未啟用虛擬環境的情況下運行。

為了實現這一點，安裝在虛擬環境中的腳本會有一個 "shebang" 列，此列指向該環境的 Python 直譯器 #!/<path-to-venv>/bin/python。這代表無論 PATH 的值為何，該腳本都會在直譯器上運行。在 Windows 上，如果你安裝了 Python 安裝管理員，則支援 "shebang" 列處理。因此，在 Windows 檔案總管（Windows Explorer）中雙擊已安裝的腳本，應該可以在沒有啟用環境或將其加入 PATH 的情況下正確地運行。

當虛擬環境被啟用時，VIRTUAL_ENV 環境變數會被設置為該環境的路徑。由於不需要明確啟用虛擬環境才能使用它。因此，無法依賴 VIRTUAL_ENV 來判斷是否正在使用虛擬環境。

警告

因為安裝在環境中的腳本不應該預期該環境已經被啟動，所以它們的 shebang 列會包含環境直譯器的絕對路徑。因此，在一般情況下，環境本質上是不可攜帶的。你應該使用一個簡單的方法來重新建立一個環境（例如：如果你有一個名為 requirements.txt 的需求檔案，你可以使用環境的 pip install -r requirements.txt 來安裝環境所需的所有套件）。如果出於某種原因，你需要將環境移至新位置，你應該在所需位置重新建立它，並刪除舊位置的環境。如果你移動環境是因為移動了其父目錄，你應該在新位置重新建立環境。否則，安裝在該環境中的軟體可能無法正常運作。

你可以在 shell 輸入 deactivate 來關閉虛擬環境。具體的使用方式因平台而異，是內部實作的細節（通常會使用腳本或是 shell 函式）

API

上述提到的高階 method（方法）透過簡單的 API 使用， 為第三方虛擬環境建立者提供可以依據他們需求來建立環境的客製化機制： EnvBuilder class。

class venv.EnvBuilder(system_site_packages=False, clear=False, symlinks=False, upgrade=False, with_pip=False, prompt=None, upgrade_deps=False, *, scm_ignore_files=frozenset())

進行實例化時，class EnvBuilder 接受下列的關鍵字引數：

system_site_packages -- 為一個 boolean （布林值），並表明系統的 Python site-packages 是否可以在環境中可用（預設為 False ）。

clear -- 為一個 boolean，如果為 true，則在建立環境之前，刪除目標目錄內所有存在的內容。

symlinks -- 為一個 boolean，並表明是否嘗試與 Python 二進位檔案建立符號連結而不是複製該檔案。

upgrade -- 為一個 boolean，若為 true，則會在執行 Python 時為現有的環境進行升級。目的是讓 Python 可以升級到位（預設為 False）。

with_pip -- 為一個 boolean，若為 true，則確保 pip 有安裝至虛擬環境之中。當有 --default-pip 的選項時，會使用 ensurepip。

prompt -- 為一個 String（字串），該字串會在虛擬環境啟動時被使用。（預設為 None，代表該環境的目錄名稱會被使用）倘若出現特殊字串 "." ，則目前目錄的 basename 會做為提示路徑使用。

upgrade_deps -- 更新基礎 venv 模組至 PyPI 的最新版本

scm_ignore_files——根據可疊代物件中指定的來源控制管理（SCM），建立對應的忽略檔。支援情況取決於是否有名為 create_{scm}_ignore_file 的方法。預設唯一支援的值是 "git"，透過 create_git_ignore_file() 方法提供支援。

在 3.4 版的變更: 新增 with_pip 參數

在 3.6 版的變更: 新增 prompt 參數

在 3.9 版的變更: 新增 upgrade_deps 參數

在 3.13 版的變更: 新增 scm_ignore_files 參數

EnvBuilder 可以被用作為基底類別。

create(env_dir)

透過指定將會容納虛擬環境的目標目錄來建立一個虛擬環境（絕對路徑或相對路徑到該目錄），也就是在該目錄中容納虛擬環境。create method 將會在指定的目錄下建立環境，或是觸發適當的例外。

EnvBuilder class 的 create method 會闡述可用的 Hooks 以客製化 subclass （子類別）:

def create(self, env_dir):
    """
    在目標目錄中建立一個虛擬化的 Python 環境。
    env_dir 是要建立虛擬環境的目標目錄。
    """
    env_dir = os.path.abspath(env_dir)
    context = self.ensure_directories(env_dir)
    self.create_configuration(context)
    self.setup_python(context)
    self.setup_scripts(context)
    self.post_setup(context)

每個 methods ensure_directories()、create_configuration()、setup_python()、setup_scripts() 及 post_setup() 都可以被覆寫。

ensure_directories(env_dir)

建立還不存在的環境目錄及必要的子目錄，並回傳一個情境物件（context object）。這個情境物件只是一個屬性 (例如：路徑) 的所有者，可被其他 method 使用。如果 EnvBuilder 已被建立且帶有 clear=True 的引數，該環境目錄下的內容將被清空，以及所有必要的子目錄將被重新建立。

回傳的情境物件（context object）其型別會是 types.SimpleNamespace，並包含以下屬性：

env_dir —— 虛擬環境的位置。用於啟用腳本中的 __VENV_DIR__（參見 install_scripts()）。

env_name —— 虛擬環境的名稱。用於啟用腳本中的 __VENV_NAME__（參見 install_scripts()）。

prompt —— 啟用腳本所使用的提示字元。用於啟用腳本中的 __VENV_PROMPT__（參見 install_scripts()）。

executable —— 虛擬環境所使用的底層 Python 執行檔。在從其他虛擬環境建立虛擬環境的情況下，也會一併考慮該情境。

inc_path —— 虛擬環境的 include 路徑。

lib_path —— 虛擬環境的 purelib 路徑。

bin_path —— 虛擬環境的腳本路徑。

bin_name —— 相對於虛擬環境位置的腳本路徑名稱。用於啟用腳本中的 __VENV_BIN_NAME__（參見 install_scripts()）。

env_exe —— 虛擬環境中 Python 直譯器的名稱。用於啟用腳本中的 __VENV_PYTHON__（參見 install_scripts()）。

env_exec_cmd —— Python 直譯器名稱，會將檔案系統重新導向後納入考慮。可用於在虛擬環境中執行 Python。

在 3.11 版的變更: venv 使用 sysconfig 安裝配置方案 來建構所建立目錄的路徑。

在 3.12 版的變更: lib_path 屬性已新增至情境中，且情境物件已加入文件說明。

create_configuration(context)

在環境中建立 pyvenv.cfg 設定檔。

setup_python(context)

在環境中建立 Python 執行檔的複本或符號連結。在 POSIX 系統上，若使用了特定的 python3.x 執行檔，將建立指向該執行檔的 python 與 python3 符號連結（除非這些名稱的檔案已存在）。

setup_scripts(context)

將符合平台的啟用腳本安裝到虛擬環境中。

upgrade_dependencies(context)

更新虛擬環境中的核心 venv 相依套件（目前為 pip [https://pypi.org/project/pip/]）。此動作會透過執行虛擬環境中的 pip 執行檔來完成。

在 3.9 版被加入.

在 3.12 版的變更: setuptools [https://pypi.org/project/setuptools/] 不再是核心 venv 的相依項目。

post_setup(context)

此佔位方法在虛擬環境中預先安裝套件，或執行其他建立後的動作，可由第三方實作覆寫。

install_scripts(context, path)

此方法可由子類別中的 setup_scripts() 或 post_setup() 呼叫，協助將自訂腳本安裝到虛擬環境中。

path 是一個目錄的路徑，該目錄應包含子目錄 common、posix 和 nt；每個子目錄中都包含指向環境中 bin 目錄的腳本。在執行部分佔位符文字替換後，將會複製 common 及與 os.name 對應的目錄的內容：

__VENV_DIR__ 會被替換為環境目錄的絕對路徑。

__VENV_NAME__ 會被替換為環境的名稱（即該環境目錄路徑的最後一段）。

__VENV_PROMPT__ 會被替換為提示字元（即以括號包裹的環境名稱，並附帶一個空格）。

__VENV_BIN_NAME__ 會被替換為 bin 目錄的名稱（可能是 bin 或 Scripts）。

__VENV_PYTHON__ 會被替換為環境中 Python 執行檔的絕對路徑。

允許這些目錄存在（例如當更新既有環境時）。

create_git_ignore_file(context)

在虛擬環境中建立一個 .gitignore 檔案，讓 Git 原始碼控管工具忽略整個目錄。

在 3.13 版被加入.

在 3.7.2 版的變更: Windows 現在使用重新導向腳本來處理 python[w].exe，而不再複製實際的二進位檔。在 3.7.2 中，只有當從原始碼樹中建構時，setup_python() 才會執行操作。

在 3.7.3 版的變更: Windows會在 setup_python() 中複製重新導向腳本，而非在 setup_scripts() 中進行。這在 3.7.2 中並非如此。若使用符號連結，則會連結至原始的可執行檔。

也有一個方便的模組層級的函式：

venv.create(env_dir, system_site_packages=False, clear=False, symlinks=False, with_pip=False, prompt=None, upgrade_deps=False, *, scm_ignore_files=frozenset())

使用提供的關鍵字引數建立一個 EnvBuilder，並以 env_dir 作為引數呼叫其 create() 方法。

在 3.3 版被加入.

在 3.4 版的變更: 新增 with_pip 參數

在 3.6 版的變更: 新增 prompt 參數

在 3.9 版的變更: 新增 upgrade_deps 參數

在 3.13 版的變更: 新增 scm_ignore_files 參數

一個擴展 EnvBuilder 的範例

以下的腳本展示了如何透過實作子類別來擴充 EnvBuilder，並在建立的虛擬環境中安裝 setuptools 與 pip：

import os
import os.path
from subprocess import Popen, PIPE
import sys
from threading import Thread
from urllib.parse import urlparse
from urllib.request import urlretrieve
import venv

class ExtendedEnvBuilder(venv.EnvBuilder):
    """
    此建構子會安裝 setuptools 和 pip，使你能夠使用 pip 或
    easy_install 安裝其他套件到建立的虛擬環境中。

    :param nodist: 若為 true，則不會安裝 setuptools 和 pip 至
                   所建立的虛擬環境中。
    :param nopip: 若為 true，則不會安裝 pip 至所建立的
                  虛擬環境中。
    :param progress: 若安裝了 setuptools 或 pip，可透過傳入 progress
                     可呼叫物件來監控安裝進度。若有指定，該可呼叫物件會接收兩個引數：
                     一個表示進度的字串，以及一個表示該字串來源的情境。
                     context 引數可能有三種值：
                     'main' 表示該呼叫來自 virtualize() 本身，
                     'stdout' 與 'stderr' 則分別表示從子行程輸出資料串流中
                     讀取的輸出內容，該子行程用於安裝應用程式。

                     若未指定可呼叫物件，則預設的進度資訊會輸出至 sys.stderr。
    """

    def __init__(self, *args, **kwargs):
        self.nodist = kwargs.pop('nodist', False)
        self.nopip = kwargs.pop('nopip', False)
        self.progress = kwargs.pop('progress', None)
        self.verbose = kwargs.pop('verbose', False)
        super().__init__(*args, **kwargs)

    def post_setup(self, context):
        """
        設定在建立虛擬環境時需預先安裝的套件。

        :param context: 處理中的虛擬環境建立請求所需的資訊。
        """
        os.environ['VIRTUAL_ENV'] = context.env_dir
        if not self.nodist:
            self.install_setuptools(context)
       # 沒有 setuptools 就無法安裝 pip
        if not self.nopip and not self.nodist:
            self.install_pip(context)

    def reader(self, stream, context):
        """
        從子行程的輸出串流中讀取每一列，並將其傳遞給進度回呼函式（若有指定），或將進度資訊寫入 sys.stderr。
        """
        progress = self.progress
        while True:
            s = stream.readline()
            if not s:
                break
            if progress is not None:
                progress(s, context)
            else:
                if not self.verbose:
                    sys.stderr.write('.')
                else:
                    sys.stderr.write(s.decode('utf-8'))
                sys.stderr.flush()
        stream.close()

    def install_script(self, context, name, url):
        _, _, path, _, _, _ = urlparse(url)
        fn = os.path.split(path)[-1]
        binpath = context.bin_path
        distpath = os.path.join(binpath, fn)
        # 將腳本下載到虛擬環境的執行檔資料夾中
        urlretrieve(url, distpath)
        progress = self.progress
        if self.verbose:
            term = '\n'
        else:
            term = ''
        if progress is not None:
            progress('Installing %s ...%s' % (name, term), 'main')
        else:
            sys.stderr.write('Installing %s ...%s' % (name, term))
            sys.stderr.flush()
        # 安裝到虛擬環境中
        args = [context.env_exe, fn]
        p = Popen(args, stdout=PIPE, stderr=PIPE, cwd=binpath)
        t1 = Thread(target=self.reader, args=(p.stdout, 'stdout'))
        t1.start()
        t2 = Thread(target=self.reader, args=(p.stderr, 'stderr'))
        t2.start()
        p.wait()
        t1.join()
        t2.join()
        if progress is not None:
            progress('done.', 'main')
        else:
            sys.stderr.write('done.\n')
        # 清理——不再需要
        os.unlink(distpath)

    def install_setuptools(self, context):
        """
        Install setuptools in the virtual environment.

        :param context: The information for the virtual environment
                        creation request being processed.
        """
        url = "https://bootstrap.pypa.io/ez_setup.py"
        self.install_script(context, 'setuptools', url)
        # 清除已下載的 setuptools 檔案
        pred = lambda o: o.startswith('setuptools-') and o.endswith('.tar.gz')
        files = filter(pred, os.listdir(context.bin_path))
        for f in files:
            f = os.path.join(context.bin_path, f)
            os.unlink(f)

    def install_pip(self, context):
        """
        在虛擬環境中安裝 pip。

        :param context: 處理中的虛擬環境建立請求相關資訊。
        """
        url = 'https://bootstrap.pypa.io/get-pip.py'
        self.install_script(context, 'pip', url)

def main(args=None):
    import argparse

    parser = argparse.ArgumentParser(prog=__name__,
                                     description='Creates virtual Python '
                                                 'environments in one or '
                                                 'more target '
                                                 'directories.')
    parser.add_argument('dirs', metavar='ENV_DIR', nargs='+',
                        help='A directory in which to create the '
                             'virtual environment.')
    parser.add_argument('--no-setuptools', default=False,
                        action='store_true', dest='nodist',
                        help="Don't install setuptools or pip in the "
                             "virtual environment.")
    parser.add_argument('--no-pip', default=False,
                        action='store_true', dest='nopip',
                        help="Don't install pip in the virtual "
                             "environment.")
    parser.add_argument('--system-site-packages', default=False,
                        action='store_true', dest='system_site',
                        help='Give the virtual environment access to the '
                             'system site-packages dir.')
    if os.name == 'nt':
        use_symlinks = False
    else:
        use_symlinks = True
    parser.add_argument('--symlinks', default=use_symlinks,
                        action='store_true', dest='symlinks',
                        help='Try to use symlinks rather than copies, '
                             'when symlinks are not the default for '
                             'the platform.')
    parser.add_argument('--clear', default=False, action='store_true',
                        dest='clear', help='Delete the contents of the '
                                           'virtual environment '
                                           'directory if it already '
                                           'exists, before virtual '
                                           'environment creation.')
    parser.add_argument('--upgrade', default=False, action='store_true',
                        dest='upgrade', help='Upgrade the virtual '
                                             'environment directory to '
                                             'use this version of '
                                             'Python, assuming Python '
                                             'has been upgraded '
                                             'in-place.')
    parser.add_argument('--verbose', default=False, action='store_true',
                        dest='verbose', help='Display the output '
                                             'from the scripts which '
                                             'install setuptools and pip.')
    options = parser.parse_args(args)
    if options.upgrade and options.clear:
        raise ValueError('you cannot supply --upgrade and --clear together.')
    builder = ExtendedEnvBuilder(system_site_packages=options.system_site,
                                   clear=options.clear,
                                   symlinks=options.symlinks,
                                   upgrade=options.upgrade,
                                   nodist=options.nodist,
                                   nopip=options.nopip,
                                   verbose=options.verbose)
    for d in options.dirs:
        builder.create(d)

if __name__ == '__main__':
    rc = 1
    try:
        main()
        rc = 0
    except Exception as e:
        print('Error: %s' % e, file=sys.stderr)
    sys.exit(rc)

此腳本也可從線上 [https://gist.github.com/vsajip/4673395]下載。

zipapp —-- 管理可執行的 Python zip 封存檔案

在 3.5 版被加入.

原始碼：Lib/zipapp.py [https://github.com/python/cpython/tree/3.14/Lib/zipapp.py]

本模組提供工具來建立包含 Python 程式碼的 zip 檔案，這些檔案可以 直接由 Python 直譯器執行。此模組同時提供了 zipapp 命令列介面 和 zipapp Python API。

基本範例

以下範例展示了如何使用 zipapp 命令列介面，從一個包含 Python 程式碼的目錄中建立一個可執行的封存檔案。執行時，該封存檔案將會執行封存檔案中 myapp 模組的 main 函式。

$ python -m zipapp myapp -m "myapp:main"
$ python myapp.pyz
<output from myapp>

命令列介面

當從命令列作為程式呼叫時，會使用以下格式：

$ python -m zipapp source [options]

如果 source 是一個目錄，這將會從 source 的內容建立一個封存檔案。如果 source 是一個檔案，它應該是一個封存檔案，並且它將被複製到目標封存檔案（或者如果指定了 --info 選項，將會顯示其 shebang 行的內容）。

可使用以下選項：

-o <output>, --output=<output>

將輸出寫入名為 output 的檔案。如果未指定此選項，輸出檔名將與輸入 source 相同，並加上 .pyz 副檔名。如果給定了明確的檔名，則會直接使用它（因此如果需要，應包含 .pyz 副檔名）。

如果 source 是一個封存檔案，則必須指定輸出檔名（且在這種情況下，output 不得與 source 相同）。

-p <interpreter>, --python=<interpreter>

在封存檔案中加入一行 #!，指定 interpreter 作為要執行的命令。此外，在 POSIX 上，使封存檔案成為可執行檔。預設是不寫入 #! 行，也不讓檔案成為可執行檔。

-m <mainfn>, --main=<mainfn>

在封存檔案中寫入一個執行 mainfn 的 __main__.py 檔案。mainfn 引數應為 "pkg.mod:fn" 的形式，其中 "pkg.mod" 是封存檔案中的一個套件/模組，而 "fn" 是給定模組中的一個可呼叫物件。__main__.py 檔案將會執行該可呼叫物件。

複製封存檔案時，不可指定 --main。

-c, --compress

使用 deflate 方法壓縮檔案，以減少輸出檔案的大小。預設情況下，檔案在封存檔案中是不壓縮儲存的。

複製封存檔案時，--compress 沒有作用。

在 3.7 版被加入.

--info

顯示嵌入在封存檔案中的直譯器，以供診斷之用。在這種情況下，任何其他選項都會被忽略，且 SOURCE 必須是一個封存檔案，而不是一個目錄。

-h, --help

印出簡短的使用訊息並退出。

Python API

此模組定義了兩個便利的函式：

zipapp.create_archive(source, target=None, interpreter=None, main=None, filter=None, compressed=False)

從 source 建立一個應用程式封存檔案。source 可以是以下任何一種：

一個目錄的名稱，或是一個指向目錄的 類路徑物件，在這種情況下，將會從該目錄的內容建立一個新的應用程式封存檔案。

一個現有應用程式封存檔案的名稱，或是一個指向該檔案的 類路徑物件，在這種情況下，該檔案會被複製到目標（並修改它以反映為 interpreter 引數所給定的值）。如果需要，檔名應包含 .pyz 副檔名。

一個以位元組模式開啟以供讀取的檔案物件。該檔案的內容應該是一個應用程式封存檔案，並且檔案物件被假定位於封存檔案的開頭。

target 引數決定了產生的封存檔案將被寫入何處：

如果它是一個檔案的名稱，或是一個 類路徑物件，封存檔案將被寫入該檔案。

如果它是一個開啟的檔案物件，封存檔案將被寫入該檔案物件，該物件必須以位元組模式開啟以供寫入。

如果省略了 target（或為 None），則 source 必須是一個目錄，而 target 將是一個與 source 同名的檔案，並加上 .pyz 副檔名。

interpreter 引數指定了將用來執行封存檔案的 Python 直譯器名稱。它會作為「shebang」行寫入封存檔案的開頭。在 POSIX 上，這將由作業系統解讀，而在 Windows 上，它將由 Python 啟動器處理。省略 interpreter 將導致不寫入 shebang 行。如果指定了直譯器，且 target 是一個檔名，則目標檔案的可執行位元將被設定。

main 引數指定了一個可呼叫物件的名稱，它將被用作封存檔案的主程式。只有當 source 是一個目錄，且該 source 尚未包含 __main__.py 檔案時，才能指定此引數。main 引數應採用「pkg.module:callable」的形式，封存檔案將透過引入「pkg.module」並執行給定的無引數可呼叫物件來執行。如果 source 是一個目錄且不包含 __main__.py 檔案，則省略 main 會導致錯誤，因為這樣產生的封存檔案將無法執行。

可選的 filter 引數指定了一個回呼函式，該函式會被傳入一個 Path 物件，代表要加入的檔案路徑（相對於 source 目錄）。如果要加入該檔案，它應該回傳 True。

可選的 compressed 引數決定檔案是否被壓縮。如果設定為 True，封存檔案中的檔案將使用 deflate 方法進行壓縮；否則，檔案將不壓縮儲存。複製現有封存檔案時，此引數無效。

如果為 source 或 target 指定了檔案物件，呼叫者有責任在呼叫 create_archive 後將其關閉。

複製現有封存檔案時，提供的檔案物件只需要 read 和 readline，或 write 方法。從目錄建立封存檔案時，如果 target 是一個檔案物件，它將被傳遞給 zipfile.ZipFile 類別，並且必須提供該類別所需的方法。

在 3.7 版的變更: 新增 filter 與 compressed 參數。

zipapp.get_interpreter(archive)

回傳封存檔案開頭 #! 行中指定的直譯器。如果沒有 #! 行，則回傳 None。archive 引數可以是一個檔名或一個以位元組模式開啟以供讀取的類檔案物件。它被假定位於封存檔案的開頭。

範例

將一個目錄打包成一個封存檔案，並執行它。

$ python -m zipapp myapp
$ python myapp.pyz
<output from myapp>

使用 create_archive() 函式也可以達到同樣的效果：

>>> import zipapp
>>> zipapp.create_archive('myapp', 'myapp.pyz')

要讓應用程式在 POSIX 上可以直接執行，請指定要使用的直譯器。

$ python -m zipapp myapp -p "/usr/bin/env python"
$ ./myapp.pyz
<output from myapp>

要替換現有封存檔案上的 shebang 行，請使用 create_archive() 函式建立一個修改過的封存檔案：

>>> import zipapp
>>> zipapp.create_archive('old_archive.pyz', 'new_archive.pyz', '/usr/bin/python3')

要原地 (in place) 更新檔案，請使用 BytesIO 物件在記憶體中進行替換，然後再覆寫來源檔案。請注意，原地覆寫檔案存在風險，錯誤可能導致原始檔案遺失。這段程式碼沒有防範此類錯誤，但生產環境的程式碼應作此類防護。此外，此方法只有在封存檔案能容納於記憶體中時才有效：

>>> import zipapp
>>> import io
>>> temp = io.BytesIO()
>>> zipapp.create_archive('myapp.pyz', temp, '/usr/bin/python2')
>>> with open('myapp.pyz', 'wb') as f:
>>>     f.write(temp.getvalue())

指定直譯器

請注意，如果你指定了一個直譯器然後分發你的應用程式封存檔案，你需要確保所使用的直譯器是可攜的。Windows 的 Python 啟動器支援大多數常見形式的 POSIX #! 行，但還有其他問題需要考慮：

如果你使用「/usr/bin/env python」（或「python」命令的其他形式，例如「/usr/bin/python」），你需要考慮到你的使用者可能將 Python 2 或 Python 3 作為預設版本，並編寫你的程式碼使其能在兩個版本下運作。

如果你使用一個明確的版本，例如「/usr/bin/env python3」，你的應用程式將無法為沒有該版本的使用者運作。（如果你尚未讓你的程式碼與 Python 2 相容，這可能正是你想要的）。

沒有辦法說「python X.Y 或更新版本」，所以要小心使用像「/usr/bin/env python3.4」這樣的確切版本，因為舉例來說，你將需要為 Python 3.5 的使用者更改你的 shebang 行。

通常，你應該使用「/usr/bin/env python2」或「/usr/bin/env python3」，這取決於你的程式碼是為 Python 2 還是 Python 3 編寫的。

使用 zipapp 建立獨立應用程式

使用 zipapp 模組，可以建立獨立的 Python 程式，這些程式可以分發給終端使用者，他們只需要在他們的系統上安裝合適版本的 Python。實現這一點的關鍵是將應用程式的所有依賴項與應用程式程式碼一起打包到封存檔案中。

建立獨立封存檔案的步驟如下：

像平常一樣在一個目錄中建立你的應用程式，這樣你就有一個 myapp 目錄，其中包含一個 __main__.py 檔案和任何支援的應用程式程式碼。

使用 pip 將你應用程式的所有依賴項安裝到 myapp 目錄中：

$ python -m pip install -r requirements.txt --target myapp

（這假設你的專案需求在一個 requirements.txt 檔案中——如果沒有，你可以在 pip 命令列上手動列出依賴項）。

使用以下命令打包應用程式：

$ python -m zipapp -p "interpreter" myapp

這將產生一個獨立的可執行檔，可以在任何有適當直譯器的機器上執行。詳情請參閱 指定直譯器。它可以作為單一檔案交付給使用者。

在 Unix 上，myapp.pyz 檔案本身就是可執行的。如果你偏好一個「普通」的命令名稱，可以重新命名檔案以移除 .pyz 副檔名。在 Windows 上，myapp.pyz[w] 檔案是可執行的，因為 Python 直譯器在安裝時會註冊 .pyz 和 .pyzw 副檔名。

注意事項

如果你的應用程式依賴於一個包含 C 擴充的套件，該套件無法從 zip 檔案中執行（這是一個作業系統的限制，因為可執行程式碼必須存在於檔案系統中，作業系統的載入器才能載入它）。在這種情況下，你可以從 zipfile 中排除該依賴項，並要求你的使用者安裝它，或者將它與你的 zipfile 一起發布，並在你的 __main__.py 中加入程式碼，將包含解壓縮後模組的目錄加入到 sys.path 中。在這種情況下，你需要確保為你的目標架構提供適當的二進位檔案（並可能在 runtime 根據使用者的機器選擇正確的版本加入到 sys.path 中）。

Python Zip 應用程式封存檔案格式

自 2.6 版以來，Python 就能夠執行包含 __main__.py 檔案的 zip 檔案。為了能被 Python 執行，一個應用程式封存檔案只需要是一個標準的 zip 檔案，其中包含一個 __main__.py 檔案，該檔案將作為應用程式的進入點執行。如同任何 Python 腳本一樣，腳本的父目錄（在此情況下是 zip 檔案）將被放置在 sys.path 上，因此可以從 zip 檔案中引入更多的模組。

zip 檔案格式允許在 zip 檔案前附加任意資料。zip 應用程式格式利用此功能在檔案前附加一個標準的 POSIX「shebang」行（#!/path/to/interpreter）。

因此，Python zip 應用程式格式的正式定義如下：

一個可選的 shebang 行，包含字元 b'#!'，後跟一個直譯器名稱，然後是一個換行符（b'\n'）。直譯器名稱可以是任何作業系統「shebang」處理或 Windows 上的 Python 啟動器可接受的內容。在 Windows 上，直譯器應以 UTF-8 編碼，在 POSIX 上應以 sys.getfilesystemencoding() 編碼。

由 zipfile 模組產生的標準 zipfile 資料。zipfile 內容*必須*包含一個名為 __main__.py 的檔案（該檔案必須位於 zipfile 的「根目錄」中——即，它不能在子目錄中）。zipfile 資料可以被壓縮或不壓縮。

如果應用程式封存檔案有 shebang 行，它在 POSIX 系統上可能會設定可執行位元，以允許其直接執行。

沒有要求必須使用此模組中的工具來建立應用程式封存檔案——此模組是一個便利工具，但以任何方式建立的符合上述格式的封存檔案對 Python 都是可接受的。

Python Runtime 服務

本章節所描述的模組提供了與 Python 直譯器及其與環境互動相關的廣泛服務。以下是概觀：

sys --- 系統特定的參數與函式

sys.monitoring --- 執行事件監控

工具識別器

註冊和使用工具

事件

區域事件

已棄用的事件

附屬事件 (ancillary events)

其他事件

STOP_ITERATION 事件

開啟和關閉事件

全域設定事件

各別程式碼物件事件

停用事件

註冊回呼函式

回呼函式引數

sysconfig --- 提供 Python 設定資訊的存取

Configuration variables

Installation paths

User scheme

posix_user

nt_user

osx_framework_user

Home scheme

posix_home

Prefix scheme

posix_prefix

nt

安裝路徑函式

其他函式

命令列用法

builtins --- 內建物件

__main__ --- 頂層程式碼環境

__name__ == '__main__'

什麼是「頂層程式碼環境」？

慣用 (Idiomatic) 用法

打包時須考慮的事情

Python 套件中的 __main__.py

慣用 (Idiomatic) 用法

import __main__

warnings --- 警告控制

警告類別

警告過濾器

重複警告的抑制標準

描述警告過濾器

預設警告過濾器

覆寫預設過濾器

暫時抑制警告

測試警告

為新版相依套件更新程式碼

可用的函式

可用的情境管理器

情境管理器的並行安全性

dataclasses --- Data Classes

模組內容

Post-init processing

類別變數

Init-only variables

凍結實例

繼承

Re-ordering of keyword-only parameters in __init__()

預設工廠函式

可變預設值

Descriptor-typed fields

contextlib --- with 陳述式工具程式

Utilities

Examples and Recipes

Supporting a variable number of context managers

Catching exceptions from __enter__ methods

Cleaning up in an __enter__ implementation

Replacing any use of try-finally and flag variables

Using a context manager as a function decorator

Single use, reusable and reentrant context managers

Reentrant context managers

Reusable context managers

abc --- 抽象基底類別

atexit --- 退出處理函式

atexit 範例

traceback --- 列印或取得堆疊回溯 (stack traceback)

Module-Level Functions

TracebackException 物件

StackSummary 物件

FrameSummary 物件

Examples of Using the Module-Level Functions

TracebackException 的使用範例

__future__ --- Future 陳述式定義

模組內容

gc --- 垃圾回收器介面 (Garbage Collector interface)

inspect --- 檢視活動物件

Types and members

取得原始碼

Introspecting callables with the Signature object

類別與函式

直譯器堆疊

Fetching attributes statically

Current State of Generators, Coroutines, and Asynchronous Generators

Code Objects Bit Flags

Buffer flags

命令列介面

annotationlib --- 用於自我檢查註釋的功能

Annotation semantics

Classes

Functions

Recipes

Using annotations in a metaclass

STRING 格式的限制

FORWARDREF 格式的限制

Security implications of introspecting annotations

site --- Site-specific configuration hook

sitecustomize

usercustomize

Readline configuration

模組內容

命令列介面

也參考

請參閱 concurrent.interpreters 模組，它同樣揭露了核心的 runtime 功能。

sys --- 系統特定的參數與函式

This module provides access to some variables used or maintained by the interpreter and to functions that interact strongly with the interpreter. It is always available. Unless explicitly noted otherwise, all variables are read-only.

sys.abiflags

On POSIX systems where Python was built with the standard configure script, this contains the ABI flags as specified by PEP 3149 [https://peps.python.org/pep-3149/].

在 3.2 版被加入.

在 3.8 版的變更: Default flags became an empty string (m flag for pymalloc has been removed).

可用性: Unix.

sys.addaudithook(hook)

Append the callable hook to the list of active auditing hooks for the current (sub)interpreter.

When an auditing event is raised through the sys.audit() function, each hook will be called in the order it was added with the event name and the tuple of arguments. Native hooks added by PySys_AddAuditHook() are called first, followed by hooks added in the current (sub)interpreter. Hooks can then log the event, raise an exception to abort the operation, or terminate the process entirely.

Note that audit hooks are primarily for collecting information about internal or otherwise unobservable actions, whether by Python or libraries written in Python. They are not suitable for implementing a "sandbox". In particular, malicious code can trivially disable or bypass hooks added using this function. At a minimum, any security-sensitive hooks must be added using the C API PySys_AddAuditHook() before initialising the runtime, and any modules allowing arbitrary memory modification (such as ctypes) should be completely removed or closely monitored.

呼叫 sys.addaudithook() 本身會引發一個不帶任何引數、名為 sys.addaudithook 的稽核事件。如果任何現有的 hook 引發從 RuntimeError 衍生的例外，則不會添加新的 hook 並抑制異常。因此，除非呼叫者控制所有已存在的 hook，他們不能假設他們的 hook 已被添加。

所有會被 CPython 所引發的事件請參考稽核事件總表、設計相關討論請見 PEP 578 [https://peps.python.org/pep-0578/]。

在 3.8 版被加入.

在 3.8.1 版的變更: Exceptions derived from Exception but not RuntimeError are no longer suppressed.

CPython 實作細節： When tracing is enabled (see settrace()), Python hooks are only traced if the callable has a __cantrace__ member that is set to a true value. Otherwise, trace functions will skip the hook.

sys.argv

The list of command line arguments passed to a Python script. argv[0] is the script name (it is operating system dependent whether this is a full pathname or not). If the command was executed using the -c command line option to the interpreter, argv[0] is set to the string '-c'. If no script name was passed to the Python interpreter, argv[0] is the empty string.

To loop over the standard input, or the list of files given on the command line, see the fileinput module.

另請參閱 sys.orig_argv。

備註

On Unix, command line arguments are passed by bytes from OS. Python decodes them with filesystem encoding and "surrogateescape" error handler. When you need original bytes, you can get it by [os.fsencode(arg) for arg in sys.argv].

sys.audit(event, *args)

Raise an auditing event and trigger any active auditing hooks. event is a string identifying the event, and args may contain optional arguments with more information about the event. The number and types of arguments for a given event are considered a public and stable API and should not be modified between releases.

舉例來說，一個名為 os.chdir 的稽核事件擁有一個引數 path，其內容為所要求的新工作目錄。

sys.audit() will call the existing auditing hooks, passing the event name and arguments, and will re-raise the first exception from any hook. In general, if an exception is raised, it should not be handled and the process should be terminated as quickly as possible. This allows hook implementations to decide how to respond to particular events: they can merely log the event or abort the operation by raising an exception.

Hooks are added using the sys.addaudithook() or PySys_AddAuditHook() functions.

The native equivalent of this function is PySys_Audit(). Using the native function is preferred when possible.

所有會被 CPython 所引發的事件請參考稽核事件總表。

在 3.8 版被加入.

sys.base_exec_prefix

Equivalent to exec_prefix, but referring to the base Python installation.

When running under 虛擬環境, exec_prefix gets overwritten to the virtual environment prefix. base_exec_prefix, conversely, does not change, and always points to the base Python installation. Refer to 虛擬環境 for more information.

在 3.3 版被加入.

sys.base_prefix

Equivalent to prefix, but referring to the base Python installation.

When running under virtual environment, prefix gets overwritten to the virtual environment prefix. base_prefix, conversely, does not change, and always points to the base Python installation. Refer to 虛擬環境 for more information.

在 3.3 版被加入.

sys.byteorder

An indicator of the native byte order. This will have the value 'big' on big-endian (most-significant byte first) platforms, and 'little' on little-endian (least-significant byte first) platforms.

sys.builtin_module_names

A tuple of strings containing the names of all modules that are compiled into this Python interpreter. (This information is not available in any other way --- modules.keys() only lists the imported modules.)

另請參閱 sys.stdlib_module_names 清單。

sys.call_tracing(func, args)

Call func(*args), while tracing is enabled. The tracing state is saved, and restored afterwards. This is intended to be called from a debugger from a checkpoint, to recursively debug or profile some other code.

Tracing is suspended while calling a tracing function set by settrace() or setprofile() to avoid infinite recursion. call_tracing() enables explicit recursion of the tracing function.

sys.copyright

A string containing the copyright pertaining to the Python interpreter.

sys._clear_type_cache()

Clear the internal type cache. The type cache is used to speed up attribute and method lookups. Use the function only to drop unnecessary references during reference leak debugging.

This function should be used for internal and specialized purposes only.

在 3.13 版之後被棄用: Use the more general _clear_internal_caches() function instead.

sys._clear_internal_caches()

Clear all internal performance-related caches. Use this function only to release unnecessary references and memory blocks when hunting for leaks.

在 3.13 版被加入.

sys._current_frames()

Return a dictionary mapping each thread's identifier to the topmost stack frame currently active in that thread at the time the function is called. Note that functions in the traceback module can build the call stack given such a frame.

This is most useful for debugging deadlock: this function does not require the deadlocked threads' cooperation, and such threads' call stacks are frozen for as long as they remain deadlocked. The frame returned for a non-deadlocked thread may bear no relationship to that thread's current activity by the time calling code examines the frame.

This function should be used for internal and specialized purposes only.

引發一個不附帶引數的稽核事件 sys._current_frames。

sys._current_exceptions()

Return a dictionary mapping each thread's identifier to the topmost exception currently active in that thread at the time the function is called. If a thread is not currently handling an exception, it is not included in the result dictionary.

This is most useful for statistical profiling.

This function should be used for internal and specialized purposes only.

引發一個不附帶引數的稽核事件 sys._current_exceptions。

在 3.12 版的變更: Each value in the dictionary is now a single exception instance, rather than a 3-tuple as returned from sys.exc_info().

sys.breakpointhook()

This hook function is called by built-in breakpoint(). By default, it drops you into the pdb debugger, but it can be set to any other function so that you can choose which debugger gets used.

The signature of this function is dependent on what it calls. For example, the default binding (e.g. pdb.set_trace()) expects no arguments, but you might bind it to a function that expects additional arguments (positional and/or keyword). The built-in breakpoint() function passes its *args and **kws straight through. Whatever breakpointhooks() returns is returned from breakpoint().

The default implementation first consults the environment variable PYTHONBREAKPOINT. If that is set to "0" then this function returns immediately; i.e. it is a no-op. If the environment variable is not set, or is set to the empty string, pdb.set_trace() is called. Otherwise this variable should name a function to run, using Python's dotted-import nomenclature, e.g. package.subpackage.module.function. In this case, package.subpackage.module would be imported and the resulting module must have a callable named function(). This is run, passing in *args and **kws, and whatever function() returns, sys.breakpointhook() returns to the built-in breakpoint() function.

Note that if anything goes wrong while importing the callable named by PYTHONBREAKPOINT, a RuntimeWarning is reported and the breakpoint is ignored.

Also note that if sys.breakpointhook() is overridden programmatically, PYTHONBREAKPOINT is not consulted.

在 3.7 版被加入.

sys._debugmallocstats()

Print low-level information to stderr about the state of CPython's memory allocator.

If Python is built in debug mode (configure --with-pydebug option), it also performs some expensive internal consistency checks.

在 3.3 版被加入.

CPython 實作細節： This function is specific to CPython. The exact output format is not defined here, and may change.

sys.dllhandle

Integer specifying the handle of the Python DLL.

可用性: Windows.

sys.displayhook(value)

If value is not None, this function prints repr(value) to sys.stdout, and saves value in builtins._. If repr(value) is not encodable to sys.stdout.encoding with sys.stdout.errors error handler (which is probably 'strict'), encode it to sys.stdout.encoding with 'backslashreplace' error handler.

sys.displayhook is called on the result of evaluating an expression entered in an interactive Python session. The display of these values can be customized by assigning another one-argument function to sys.displayhook.

Pseudo-code:

def displayhook(value):
    if value is None:
        return
    # Set '_' to None to avoid recursion
    builtins._ = None
    text = repr(value)
    try:
        sys.stdout.write(text)
    except UnicodeEncodeError:
        bytes = text.encode(sys.stdout.encoding, 'backslashreplace')
        if hasattr(sys.stdout, 'buffer'):
            sys.stdout.buffer.write(bytes)
        else:
            text = bytes.decode(sys.stdout.encoding, 'strict')
            sys.stdout.write(text)
    sys.stdout.write("\n")
    builtins._ = value

在 3.2 版的變更: Use 'backslashreplace' error handler on UnicodeEncodeError.

sys.dont_write_bytecode

If this is true, Python won't try to write .pyc files on the import of source modules. This value is initially set to True or False depending on the -B command line option and the PYTHONDONTWRITEBYTECODE environment variable, but you can set it yourself to control bytecode file generation.

sys._emscripten_info

A named tuple holding information about the environment on the wasm32-emscripten platform. The named tuple is provisional and may change in the future.

_emscripten_info.emscripten_version

Emscripten version as tuple of ints (major, minor, micro), e.g. (3, 1, 8).

_emscripten_info.runtime

運行環境字串，例如瀏覽器使用者代理 (browser user agent) 'Node.js v14.18.2' 或 'UNKNOWN'。

_emscripten_info.pthreads

True if Python is compiled with Emscripten pthreads support.

_emscripten_info.shared_memory

True if Python is compiled with shared memory support.

可用性: Emscripten.

在 3.11 版被加入.

sys.pycache_prefix

If this is set (not None), Python will write bytecode-cache .pyc files to (and read them from) a parallel directory tree rooted at this directory, rather than from __pycache__ directories in the source code tree. Any __pycache__ directories in the source code tree will be ignored and new .pyc files written within the pycache prefix. Thus if you use compileall as a pre-build step, you must ensure you run it with the same pycache prefix (if any) that you will use at runtime.

A relative path is interpreted relative to the current working directory.

This value is initially set based on the value of the -X pycache_prefix=PATH command-line option or the PYTHONPYCACHEPREFIX environment variable (command-line takes precedence). If neither are set, it is None.

在 3.8 版被加入.

sys.excepthook(type, value, traceback)

This function prints out a given traceback and exception to sys.stderr.

When an exception other than SystemExit is raised and uncaught, the interpreter calls sys.excepthook with three arguments, the exception class, exception instance, and a traceback object. In an interactive session this happens just before control is returned to the prompt; in a Python program this happens just before the program exits. The handling of such top-level exceptions can be customized by assigning another three-argument function to sys.excepthook.

Raise an auditing event sys.excepthook with arguments hook, type, value, traceback when an uncaught exception occurs. If no hook has been set, hook may be None. If any hook raises an exception derived from RuntimeError the call to the hook will be suppressed. Otherwise, the audit hook exception will be reported as unraisable and sys.excepthook will be called.

也參考

The sys.unraisablehook() function handles unraisable exceptions and the threading.excepthook() function handles exception raised by threading.Thread.run().

sys.__breakpointhook__

sys.__displayhook__

sys.__excepthook__

sys.__unraisablehook__

These objects contain the original values of breakpointhook, displayhook, excepthook, and unraisablehook at the start of the program. They are saved so that breakpointhook, displayhook and excepthook, unraisablehook can be restored in case they happen to get replaced with broken or alternative objects.

在 3.7 版被加入: __breakpointhook__

在 3.8 版被加入: __unraisablehook__

sys.exception()

This function, when called while an exception handler is executing (such as an except or except* clause), returns the exception instance that was caught by this handler. When exception handlers are nested within one another, only the exception handled by the innermost handler is accessible.

If no exception handler is executing, this function returns None.

在 3.11 版被加入.

sys.exc_info()

This function returns the old-style representation of the handled exception. If an exception e is currently handled (so exception() would return e), exc_info() returns the tuple (type(e), e, e.__traceback__). That is, a tuple containing the type of the exception (a subclass of BaseException), the exception itself, and a traceback object which typically encapsulates the call stack at the point where the exception last occurred.

If no exception is being handled anywhere on the stack, this function return a tuple containing three None values.

在 3.11 版的變更: The type and traceback fields are now derived from the value (the exception instance), so when an exception is modified while it is being handled, the changes are reflected in the results of subsequent calls to exc_info().

sys.exec_prefix

A string giving the site-specific directory prefix where the platform-dependent Python files are installed; by default, this is also '/usr/local'. This can be set at build time with the --exec-prefix argument to the configure script. Specifically, all configuration files (e.g. the pyconfig.h header file) are installed in the directory exec_prefix/lib/pythonX.Y/config, and shared library modules are installed in exec_prefix/lib/pythonX.Y/lib-dynload, where X.Y is the version number of Python, for example 3.2.

備註

If a virtual environment is in effect, this exec_prefix will point to the virtual environment. The value for the Python installation will still be available, via base_exec_prefix. Refer to 虛擬環境 for more information.

在 3.14 版的變更: When running under a virtual environment, prefix and exec_prefix are now set to the virtual environment prefix by the path initialization, instead of site. This means that prefix and exec_prefix always point to the virtual environment, even when site is disabled (-S).

sys.executable

A string giving the absolute path of the executable binary for the Python interpreter, on systems where this makes sense. If Python is unable to retrieve the real path to its executable, sys.executable will be an empty string or None.

sys.exit([arg])

Raise a SystemExit exception, signaling an intention to exit the interpreter.

The optional argument arg can be an integer giving the exit status (defaulting to zero), or another type of object. If it is an integer, zero is considered "successful termination" and any nonzero value is considered "abnormal termination" by shells and the like. Most systems require it to be in the range 0--127, and produce undefined results otherwise. Some systems have a convention for assigning specific meanings to specific exit codes, but these are generally underdeveloped; Unix programs generally use 2 for command line syntax errors and 1 for all other kind of errors. If another type of object is passed, None is equivalent to passing zero, and any other object is printed to stderr and results in an exit code of 1. In particular, sys.exit("some error message") is a quick way to exit a program when an error occurs.

Since exit() ultimately "only" raises an exception, it will only exit the process when called from the main thread, and the exception is not intercepted. Cleanup actions specified by finally clauses of try statements are honored, and it is possible to intercept the exit attempt at an outer level.

在 3.6 版的變更: If an error occurs in the cleanup after the Python interpreter has caught SystemExit (such as an error flushing buffered data in the standard streams), the exit status is changed to 120.

sys.flags

The named tuple flags exposes the status of command line flags. Flags should only be accessed only by name and not by index. The attributes are read only.

flags.debug

-d

flags.inspect

-i

flags.interactive

-i

flags.isolated

-I

flags.optimize

-O 或 -OO

flags.dont_write_bytecode

-B

flags.no_user_site

-s

flags.no_site

-S

flags.ignore_environment

-E

flags.verbose

-v

flags.bytes_warning

-b

flags.quiet

-q

flags.hash_randomization

-R

flags.dev_mode

-X dev （Python 開發模式）

flags.utf8_mode

-X utf8

flags.safe_path

-P

flags.int_max_str_digits

-X int_max_str_digits (integer string conversion length limitation)

flags.warn_default_encoding

-X warn_default_encoding

flags.gil

-X gil 和 PYTHON_GIL

flags.thread_inherit_context

-X thread_inherit_context and PYTHON_THREAD_INHERIT_CONTEXT

flags.context_aware_warnings

-X context_aware_warnings and PYTHON_CONTEXT_AWARE_WARNINGS

在 3.2 版的變更: 新增 quiet 屬性，用於新的 -q 旗標。

在 3.2.3 版被加入: hash_randomization 屬性。

在 3.3 版的變更: 移除過時的 division_warning 屬性。

在 3.4 版的變更: 新增 isolated 屬性，用於 -I isolated 旗標。

在 3.7 版的變更: Added the dev_mode attribute for the new Python Development Mode and the utf8_mode attribute for the new -X utf8 flag.

在 3.10 版的變更: 新增 warn_default_encoding 屬性，用於 -X warn_default_encoding 旗標。

在 3.11 版的變更: 新增 safe_path 屬性，用於 -P 選項。

在 3.11 版的變更: 新增 int_max_str_digits 屬性。

在 3.13 版的變更: 新增 gil 屬性。

在 3.14 版的變更: 新增 thread_inherit_context 屬性。

在 3.14 版的變更: 新增 context_aware_warnings 屬性。

sys.float_info

A named tuple holding information about the float type. It contains low level information about the precision and internal representation. The values correspond to the various floating-point constants defined in the standard header file float.h for the 'C' programming language; see section 5.2.4.2.2 of the 1999 ISO/IEC C standard [C99], 'Characteristics of floating types', for details.

Attributes of the float_info named tuple

屬性

float.h macro

解釋

float_info.epsilon

DBL_EPSILON

difference between 1.0 and the least value greater than 1.0 that is representable as a float.

另請參閱 math.ulp()。

float_info.dig

DBL_DIG

The maximum number of decimal digits that can be faithfully represented in a float; see below.

float_info.mant_dig

DBL_MANT_DIG

Float precision: the number of base-radix digits in the significand of a float.

float_info.max

DBL_MAX

The maximum representable positive finite float.

float_info.max_exp

DBL_MAX_EXP

The maximum integer e such that radix**(e-1) is a representable finite float.

float_info.max_10_exp

DBL_MAX_10_EXP

The maximum integer e such that 10**e is in the range of representable finite floats.

float_info.min

DBL_MIN

The minimum representable positive normalized float.

Use math.ulp(0.0) to get the smallest positive denormalized representable float.

float_info.min_exp

DBL_MIN_EXP

The minimum integer e such that radix**(e-1) is a normalized float.

float_info.min_10_exp

DBL_MIN_10_EXP

The minimum integer e such that 10**e is a normalized float.

float_info.radix

FLT_RADIX

The radix of exponent representation.

float_info.rounds

FLT_ROUNDS

An integer representing the rounding mode for floating-point arithmetic. This reflects the value of the system FLT_ROUNDS macro at interpreter startup time:

-1: indeterminable

0: toward zero

1: to nearest

2: toward positive infinity

3: toward negative infinity

All other values for FLT_ROUNDS characterize implementation-defined rounding behavior.

The attribute sys.float_info.dig needs further explanation. If s is any string representing a decimal number with at most sys.float_info.dig significant digits, then converting s to a float and back again will recover a string representing the same decimal value:

>>> import sys
>>> sys.float_info.dig
15
>>> s = '3.14159265358979'    # decimal string with 15 significant digits
>>> format(float(s), '.15g')  # convert to float and back -> same value
'3.14159265358979'

But for strings with more than sys.float_info.dig significant digits, this isn't always true:

>>> s = '9876543211234567'    # 16 significant digits is too many!
>>> format(float(s), '.16g')  # conversion changes value
'9876543211234568'

sys.float_repr_style

A string indicating how the repr() function behaves for floats. If the string has value 'short' then for a finite float x, repr(x) aims to produce a short string with the property that float(repr(x)) == x. This is the usual behaviour in Python 3.1 and later. Otherwise, float_repr_style has value 'legacy' and repr(x) behaves in the same way as it did in versions of Python prior to 3.1.

在 3.1 版被加入.

sys.getallocatedblocks()

Return the number of memory blocks currently allocated by the interpreter, regardless of their size. This function is mainly useful for tracking and debugging memory leaks. Because of the interpreter's internal caches, the result can vary from call to call; you may have to call _clear_internal_caches() and gc.collect() to get more predictable results.

If a Python build or implementation cannot reasonably compute this information, getallocatedblocks() is allowed to return 0 instead.

在 3.4 版被加入.

sys.getunicodeinternedsize()

Return the number of unicode objects that have been interned.

在 3.12 版被加入.

sys.getandroidapilevel()

Return the build-time API level of Android as an integer. This represents the minimum version of Android this build of Python can run on. For runtime version information, see platform.android_ver().

可用性: Android.

在 3.7 版被加入.

sys.getdefaultencoding()

Return 'utf-8'. This is the name of the default string encoding, used in methods like str.encode().

sys.getdlopenflags()

Return the current value of the flags that are used for dlopen() calls. Symbolic names for the flag values can be found in the os module (RTLD_xxx constants, e.g. os.RTLD_LAZY).

可用性: Unix.

sys.getfilesystemencoding()

Get the filesystem encoding: the encoding used with the filesystem error handler to convert between Unicode filenames and bytes filenames. The filesystem error handler is returned from getfilesystemencodeerrors().

For best compatibility, str should be used for filenames in all cases, although representing filenames as bytes is also supported. Functions accepting or returning filenames should support either str or bytes and internally convert to the system's preferred representation.

os.fsencode() and os.fsdecode() should be used to ensure that the correct encoding and errors mode are used.

The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read() function: see filesystem_encoding and filesystem_errors members of PyConfig.

在 3.2 版的變更: getfilesystemencoding() 的結果不再為 None。

在 3.6 版的變更: Windows is no longer guaranteed to return 'mbcs'. See PEP 529 [https://peps.python.org/pep-0529/] and _enablelegacywindowsfsencoding() for more information.

在 3.7 版的變更: Return 'utf-8' if the Python UTF-8 Mode is enabled.

sys.getfilesystemencodeerrors()

Get the filesystem error handler: the error handler used with the filesystem encoding to convert between Unicode filenames and bytes filenames. The filesystem encoding is returned from getfilesystemencoding().

os.fsencode() and os.fsdecode() should be used to ensure that the correct encoding and errors mode are used.

The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read() function: see filesystem_encoding and filesystem_errors members of PyConfig.

在 3.6 版被加入.

sys.get_int_max_str_digits()

Returns the current value for the integer string conversion length limitation. See also set_int_max_str_digits().

在 3.11 版被加入.

sys.getrefcount(object)

Return the reference count of the object. The count returned is generally one higher than you might expect, because it includes the (temporary) reference as an argument to getrefcount().

Note that the returned value may not actually reflect how many references to the object are actually held. For example, some objects are immortal and have a very high refcount that does not reflect the actual number of references. Consequently, do not rely on the returned value to be accurate, other than a value of 0 or 1.

CPython 實作細節： Immortal objects with a large reference count can be identified via _is_immortal().

在 3.12 版的變更: Immortal objects have very large refcounts that do not match the actual number of references to the object.

sys.getrecursionlimit()

Return the current value of the recursion limit, the maximum depth of the Python interpreter stack. This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python. It can be set by setrecursionlimit().

sys.getsizeof(object[, default])

Return the size of an object in bytes. The object can be any type of object. All built-in objects will return correct results, but this does not have to hold true for third-party extensions as it is implementation specific.

Only the memory consumption directly attributed to the object is accounted for, not the memory consumption of objects it refers to.

If given, default will be returned if the object does not provide means to retrieve the size. Otherwise a TypeError will be raised.

getsizeof() calls the object's __sizeof__ method and adds an additional garbage collector overhead if the object is managed by the garbage collector.

See recursive sizeof recipe [https://code.activestate.com/recipes/577504-compute-memory-footprint-of-an-object-and-its-cont/] for an example of using getsizeof() recursively to find the size of containers and all their contents.

sys.getswitchinterval()

Return the interpreter's "thread switch interval" in seconds; see setswitchinterval().

在 3.2 版被加入.

sys._getframe([depth])

Return a frame object from the call stack. If optional integer depth is given, return the frame object that many calls below the top of the stack. If that is deeper than the call stack, ValueError is raised. The default for depth is zero, returning the frame at the top of the call stack.

引發一個附帶引數 frame 的稽核事件 sys._getframe。

CPython 實作細節： This function should be used for internal and specialized purposes only. It is not guaranteed to exist in all implementations of Python.

sys._getframemodulename([depth])

Return the name of a module from the call stack. If optional integer depth is given, return the module that many calls below the top of the stack. If that is deeper than the call stack, or if the module is unidentifiable, None is returned. The default for depth is zero, returning the module at the top of the call stack.

引發一個附帶引數 depth 的稽核事件 sys._getframemodulename。

CPython 實作細節： This function should be used for internal and specialized purposes only. It is not guaranteed to exist in all implementations of Python.

在 3.12 版被加入.

sys.getobjects(limit[, type])

This function only exists if CPython was built using the specialized configure option --with-trace-refs. It is intended only for debugging garbage-collection issues.

Return a list of up to limit dynamically allocated Python objects. If type is given, only objects of that exact type (not subtypes) are included.

Objects from the list are not safe to use. Specifically, the result will include objects from all interpreters that share their object allocator state (that is, ones created with PyInterpreterConfig.use_main_obmalloc set to 1 or using Py_NewInterpreter(), and the main interpreter). Mixing objects from different interpreters may lead to crashes or other unexpected behavior.

CPython 實作細節： This function should be used for specialized purposes only. It is not guaranteed to exist in all implementations of Python.

在 3.14 版的變更: The result may include objects from other interpreters.

sys.getprofile()

Get the profiler function as set by setprofile().

sys.gettrace()

Get the trace function as set by settrace().

CPython 實作細節： The gettrace() function is intended only for implementing debuggers, profilers, coverage tools and the like. Its behavior is part of the implementation platform, rather than part of the language definition, and thus may not be available in all Python implementations.

sys.getwindowsversion()

Return a named tuple describing the Windows version currently running. The named elements are major, minor, build, platform, service_pack, service_pack_minor, service_pack_major, suite_mask, product_type and platform_version. service_pack contains a string, platform_version a 3-tuple and all other values are integers. The components can also be accessed by name, so sys.getwindowsversion()[0] is equivalent to sys.getwindowsversion().major. For compatibility with prior versions, only the first 5 elements are retrievable by indexing.

platform will be 2 (VER_PLATFORM_WIN32_NT).

product_type may be one of the following values:

Constant

含義

1 (VER_NT_WORKSTATION)

The system is a workstation.

2 (VER_NT_DOMAIN_CONTROLLER)

The system is a domain controller.

3 (VER_NT_SERVER)

The system is a server, but not a domain controller.

This function wraps the Win32 GetVersionEx() function; see the Microsoft documentation on OSVERSIONINFOEX() for more information about these fields.

platform_version returns the major version, minor version and build number of the current operating system, rather than the version that is being emulated for the process. It is intended for use in logging rather than for feature detection.

備註

platform_version derives the version from kernel32.dll which can be of a different version than the OS version. Please use platform module for achieving accurate OS version.

可用性: Windows.

在 3.2 版的變更: Changed to a named tuple and added service_pack_minor, service_pack_major, suite_mask, and product_type.

在 3.6 版的變更: 新增 platform_version

sys.get_asyncgen_hooks()

Returns an asyncgen_hooks object, which is similar to a namedtuple of the form (firstiter, finalizer), where firstiter and finalizer are expected to be either None or functions which take an asynchronous generator iterator as an argument, and are used to schedule finalization of an asynchronous generator by an event loop.

在 3.6 版被加入: 更多細節請見 PEP 525 [https://peps.python.org/pep-0525/]。

備註

This function has been added on a provisional basis (see PEP 411 [https://peps.python.org/pep-0411/] for details.)

sys.get_coroutine_origin_tracking_depth()

Get the current coroutine origin tracking depth, as set by set_coroutine_origin_tracking_depth().

在 3.7 版被加入.

備註

This function has been added on a provisional basis (see PEP 411 [https://peps.python.org/pep-0411/] for details.) Use it only for debugging purposes.

sys.hash_info

A named tuple giving parameters of the numeric hash implementation. For more details about hashing of numeric types, see 數值型別的雜湊.

hash_info.width

The width in bits used for hash values

hash_info.modulus

The prime modulus P used for numeric hash scheme

hash_info.inf

The hash value returned for a positive infinity

hash_info.nan

(This attribute is no longer used)

hash_info.imag

The multiplier used for the imaginary part of a complex number

hash_info.algorithm

The name of the algorithm for hashing of str, bytes, and memoryview

hash_info.hash_bits

The internal output size of the hash algorithm

hash_info.seed_bits

The size of the seed key of the hash algorithm

hash_info.cutoff

Cutoff for small string DJBX33A optimization in range [1, cutoff).

在 3.2 版被加入.

在 3.4 版的變更: 新增 algorithm、hash_bits、seed_bits 與 cutoff。

sys.hexversion

The version number encoded as a single integer. This is guaranteed to increase with each version, including proper support for non-production releases. For example, to test that the Python interpreter is at least version 1.5.2, use:

if sys.hexversion >= 0x010502F0:
    # use some advanced feature
    ...
else:
    # use an alternative implementation or warn the user
    ...

This is called hexversion since it only really looks meaningful when viewed as the result of passing it to the built-in hex() function. The named tuple sys.version_info may be used for a more human-friendly encoding of the same information.

More details of hexversion can be found at API 和 ABI 版本管理.

sys.implementation

An object containing information about the implementation of the currently running Python interpreter. The following attributes are required to exist in all Python implementations.

name is the implementation's identifier, e.g. 'cpython'. The actual string is defined by the Python implementation, but it is guaranteed to be lower case.

version is a named tuple, in the same format as sys.version_info. It represents the version of the Python implementation. This has a distinct meaning from the specific version of the Python language to which the currently running interpreter conforms, which sys.version_info represents. For example, for PyPy 1.8 sys.implementation.version might be sys.version_info(1, 8, 0, 'final', 0), whereas sys.version_info would be sys.version_info(2, 7, 2, 'final', 0). For CPython they are the same value, since it is the reference implementation.

hexversion is the implementation version in hexadecimal format, like sys.hexversion.

cache_tag is the tag used by the import machinery in the filenames of cached modules. By convention, it would be a composite of the implementation's name and version, like 'cpython-33'. However, a Python implementation may use some other value if appropriate. If cache_tag is set to None, it indicates that module caching should be disabled.

supports_isolated_interpreters is a boolean value, whether this implementation supports multiple isolated interpreters. It is True for CPython on most platforms. Platforms with this support implement the low-level _interpreters module.

也參考

PEP 684 [https://peps.python.org/pep-0684/]、PEP 734 [https://peps.python.org/pep-0734/] 和 concurrent.interpreters。

sys.implementation may contain additional attributes specific to the Python implementation. These non-standard attributes must start with an underscore, and are not described here. Regardless of its contents, sys.implementation will not change during a run of the interpreter, nor between implementation versions. (It may change between Python language versions, however.) See PEP 421 [https://peps.python.org/pep-0421/] for more information.

在 3.3 版被加入.

在 3.14 版的變更: Added supports_isolated_interpreters field.

備註

The addition of new required attributes must go through the normal PEP process. See PEP 421 [https://peps.python.org/pep-0421/] for more information.

sys.int_info

A named tuple that holds information about Python's internal representation of integers. The attributes are read only.

int_info.bits_per_digit

The number of bits held in each digit. Python integers are stored internally in base 2**int_info.bits_per_digit.

int_info.sizeof_digit

The size in bytes of the C type used to represent a digit.

int_info.default_max_str_digits

The default value for sys.get_int_max_str_digits() when it is not otherwise explicitly configured.

int_info.str_digits_check_threshold

The minimum non-zero value for sys.set_int_max_str_digits(), PYTHONINTMAXSTRDIGITS, or -X int_max_str_digits.

在 3.1 版被加入.

在 3.11 版的變更: 新增 default_max_str_digits 和 str_digits_check_threshold。

sys.__interactivehook__

When this attribute exists, its value is automatically called (with no arguments) when the interpreter is launched in interactive mode. This is done after the PYTHONSTARTUP file is read, so that you can set this hook there. The site module sets this.

Raises an auditing event cpython.run_interactivehook with the hook object as the argument when the hook is called on startup.

在 3.4 版被加入.

sys.intern(string)

Enter string in the table of "interned" strings and return the interned string -- which is string itself or a copy. Interning strings is useful to gain a little performance on dictionary lookup -- if the keys in a dictionary are interned, and the lookup key is interned, the key comparisons (after hashing) can be done by a pointer compare instead of a string compare. Normally, the names used in Python programs are automatically interned, and the dictionaries used to hold module, class or instance attributes have interned keys.

Interned strings are not immortal; you must keep a reference to the return value of intern() around to benefit from it.

sys._is_gil_enabled()

Return True if the GIL is enabled and False if it is disabled.

在 3.13 版被加入.

CPython 實作細節： It is not guaranteed to exist in all implementations of Python.

sys.is_finalizing()

Return True if the main Python interpreter is shutting down. Return False otherwise.

另請參閱 PythonFinalizationError 例外。

在 3.5 版被加入.

sys._jit

Utilities for observing just-in-time compilation.

CPython 實作細節： JIT compilation is an experimental implementation detail of CPython. sys._jit is not guaranteed to exist or behave the same way in all Python implementations, versions, or build configurations.

在 3.14 版被加入.

_jit.is_available()

Return True if the current Python executable supports JIT compilation, and False otherwise. This can be controlled by building CPython with the --experimental-jit option on Windows, and the --enable-experimental-jit option on all other platforms.

_jit.is_enabled()

Return True if JIT compilation is enabled for the current Python process (implies sys._jit.is_available()), and False otherwise. If JIT compilation is available, this can be controlled by setting the PYTHON_JIT environment variable to 0 (disabled) or 1 (enabled) at interpreter startup.

_jit.is_active()

Return True if the topmost Python frame is currently executing JIT code (implies sys._jit.is_enabled()), and False otherwise.

備註

This function is intended for testing and debugging the JIT itself. It should be avoided for any other purpose.

備註

Due to the nature of tracing JIT compilers, repeated calls to this function may give surprising results. For example, branching on its return value will likely lead to unexpected behavior (if doing so causes JIT code to be entered or exited):

>>> for warmup in range(BIG_NUMBER):
...     # This line is "hot", and is eventually JIT-compiled:
...     if sys._jit.is_active():
...         # This line is "cold", and is run in the interpreter:
...         assert sys._jit.is_active()
...
Traceback (most recent call last):
  File "<stdin>", line 5, in <module>
    assert sys._jit.is_active()
           ~~~~~~~~~~~~~~~~~~^^
AssertionError

sys.last_exc

This variable is not always defined; it is set to the exception instance when an exception is not handled and the interpreter prints an error message and a stack traceback. Its intended use is to allow an interactive user to import a debugger module and engage in post-mortem debugging without having to re-execute the command that caused the error. (Typical use is import pdb; pdb.pm() to enter the post-mortem debugger; see pdb module for more information.)

在 3.12 版被加入.

sys._is_immortal(op)

Return True if the given object is immortal, False otherwise.

備註

Objects that are immortal (and thus return True upon being passed to this function) are not guaranteed to be immortal in future versions, and vice versa for mortal objects.

在 3.14 版被加入.

CPython 實作細節： This function should be used for specialized purposes only. It is not guaranteed to exist in all implementations of Python.

sys._is_interned(string)

Return True if the given string is "interned", False otherwise.

在 3.13 版被加入.

CPython 實作細節： It is not guaranteed to exist in all implementations of Python.

sys.last_type

sys.last_value

sys.last_traceback

These three variables are deprecated; use sys.last_exc instead. They hold the legacy representation of sys.last_exc, as returned from exc_info() above.

sys.maxsize

An integer giving the maximum value a variable of type Py_ssize_t can take. It's usually 2**31 - 1 on a 32-bit platform and 2**63 - 1 on a 64-bit platform.

sys.maxunicode

An integer giving the value of the largest Unicode code point, i.e. 1114111 (0x10FFFF in hexadecimal).

在 3.3 版的變更: Before PEP 393 [https://peps.python.org/pep-0393/], sys.maxunicode used to be either 0xFFFF or 0x10FFFF, depending on the configuration option that specified whether Unicode characters were stored as UCS-2 or UCS-4.

sys.meta_path

A list of meta path finder objects that have their find_spec() methods called to see if one of the objects can find the module to be imported. By default, it holds entries that implement Python's default import semantics. The find_spec() method is called with at least the absolute name of the module being imported. If the module to be imported is contained in a package, then the parent package's __path__ attribute is passed in as a second argument. The method returns a module spec, or None if the module cannot be found.

也參考

importlib.abc.MetaPathFinder

The abstract base class defining the interface of finder objects on meta_path.

importlib.machinery.ModuleSpec

The concrete class which find_spec() should return instances of.

在 3.4 版的變更: Module specs were introduced in Python 3.4, by PEP 451 [https://peps.python.org/pep-0451/].

在 3.12 版的變更: Removed the fallback that looked for a find_module() method if a meta_path entry didn't have a find_spec() method.

sys.modules

This is a dictionary that maps module names to modules which have already been loaded. This can be manipulated to force reloading of modules and other tricks. However, replacing the dictionary will not necessarily work as expected and deleting essential items from the dictionary may cause Python to fail. If you want to iterate over this global dictionary always use sys.modules.copy() or tuple(sys.modules) to avoid exceptions as its size may change during iteration as a side effect of code or activity in other threads.

sys.orig_argv

The list of the original command line arguments passed to the Python executable.

The elements of sys.orig_argv are the arguments to the Python interpreter, while the elements of sys.argv are the arguments to the user's program. Arguments consumed by the interpreter itself will be present in sys.orig_argv and missing from sys.argv.

在 3.10 版被加入.

sys.path

A list of strings that specifies the search path for modules. Initialized from the environment variable PYTHONPATH, plus an installation-dependent default.

By default, as initialized upon program startup, a potentially unsafe path is prepended to sys.path (before the entries inserted as a result of PYTHONPATH):

python -m module command line: prepend the current working directory.

python script.py command line: prepend the script's directory. If it's a symbolic link, resolve symbolic links.

python -c code and python (REPL) command lines: prepend an empty string, which means the current working directory.

To not prepend this potentially unsafe path, use the -P command line option or the PYTHONSAFEPATH environment variable.

A program is free to modify this list for its own purposes. Only strings should be added to sys.path; all other data types are ignored during import.

也參考

Module site This describes how to use .pth files to extend sys.path.

sys.path_hooks

A list of callables that take a path argument to try to create a finder for the path. If a finder can be created, it is to be returned by the callable, else raise ImportError.

Originally specified in PEP 302 [https://peps.python.org/pep-0302/].

sys.path_importer_cache

A dictionary acting as a cache for finder objects. The keys are paths that have been passed to sys.path_hooks and the values are the finders that are found. If a path is a valid file system path but no finder is found on sys.path_hooks then None is stored.

Originally specified in PEP 302 [https://peps.python.org/pep-0302/].

sys.platform

A string containing a platform identifier. Known values are:

系統

platform 值

AIX

'aix'

Android

'android'

Emscripten

'emscripten'

FreeBSD

'freebsd'

iOS

'ios'

Linux

'linux'

macOS

'darwin'

Windows

'win32'

Windows/Cygwin

'cygwin'

WASI

'wasi'

On Unix systems not listed in the table, the value is the lowercased OS name as returned by uname -s, with the first part of the version as returned by uname -r appended, e.g. 'sunos5', at the time when Python was built. Unless you want to test for a specific system version, it is therefore recommended to use the following idiom:

if sys.platform.startswith('sunos'):
    # 這裡會是 SunOS 專屬的程式碼...

在 3.3 版的變更: On Linux, sys.platform doesn't contain the major version anymore. It is always 'linux', instead of 'linux2' or 'linux3'.

在 3.8 版的變更: On AIX, sys.platform doesn't contain the major version anymore. It is always 'aix', instead of 'aix5' or 'aix7'.

在 3.13 版的變更: On Android, sys.platform now returns 'android' rather than 'linux'.

在 3.14 版的變更: On FreeBSD, sys.platform doesn't contain the major version anymore. It is always 'freebsd', instead of 'freebsd13' or 'freebsd14'.

也參考

os.name has a coarser granularity. os.uname() gives system-dependent version information.

The platform module provides detailed checks for the system's identity.

sys.platlibdir

Name of the platform-specific library directory. It is used to build the path of standard library and the paths of installed extension modules.

It is equal to "lib" on most platforms. On Fedora and SuSE, it is equal to "lib64" on 64-bit platforms which gives the following sys.path paths (where X.Y is the Python major.minor version):

/usr/lib64/pythonX.Y/: Standard library (like os.py of the os module)

/usr/lib64/pythonX.Y/lib-dynload/: C extension modules of the standard library (like the errno module, the exact filename is platform specific)

/usr/lib/pythonX.Y/site-packages/ (always use lib, not sys.platlibdir): Third-party modules

/usr/lib64/pythonX.Y/site-packages/: C extension modules of third-party packages

在 3.9 版被加入.

sys.prefix

A string giving the site-specific directory prefix where the platform independent Python files are installed; on Unix, the default is /usr/local. This can be set at build time with the --prefix argument to the configure script. See Installation paths for derived paths.

備註

If a virtual environment is in effect, this prefix will point to the virtual environment. The value for the Python installation will still be available, via base_prefix. Refer to 虛擬環境 for more information.

在 3.14 版的變更: When running under a virtual environment, prefix and exec_prefix are now set to the virtual environment prefix by the path initialization, instead of site. This means that prefix and exec_prefix always point to the virtual environment, even when site is disabled (-S).

sys.ps1

sys.ps2

Strings specifying the primary and secondary prompt of the interpreter. These are only defined if the interpreter is in interactive mode. Their initial values in this case are '>>> ' and '... '. If a non-string object is assigned to either variable, its str() is re-evaluated each time the interpreter prepares to read a new interactive command; this can be used to implement a dynamic prompt.

sys.setdlopenflags(n)

Set the flags used by the interpreter for dlopen() calls, such as when the interpreter loads extension modules. Among other things, this will enable a lazy resolving of symbols when importing a module, if called as sys.setdlopenflags(0). To share symbols across extension modules, call as sys.setdlopenflags(os.RTLD_GLOBAL). Symbolic names for the flag values can be found in the os module (RTLD_xxx constants, e.g. os.RTLD_LAZY).

可用性: Unix.

sys.set_int_max_str_digits(maxdigits)

Set the integer string conversion length limitation used by this interpreter. See also get_int_max_str_digits().

在 3.11 版被加入.

sys.setprofile(profilefunc)

Set the system's profile function, which allows you to implement a Python source code profiler in Python. See chapter Python 的分析器 for more information on the Python profiler. The system's profile function is called similarly to the system's trace function (see settrace()), but it is called with different events, for example it isn't called for each executed line of code (only on call and return, but the return event is reported even when an exception has been set). The function is thread-specific, but there is no way for the profiler to know about context switches between threads, so it does not make sense to use this in the presence of multiple threads. Also, its return value is not used, so it can simply return None. Error in the profile function will cause itself unset.

備註

The same tracing mechanism is used for setprofile() as settrace(). To trace calls with setprofile() inside a tracing function (e.g. in a debugger breakpoint), see call_tracing().

Profile functions should have three arguments: frame, event, and arg. frame is the current stack frame. event is a string: 'call', 'return', 'c_call', 'c_return', or 'c_exception'. arg depends on the event type.

The events have the following meaning:

'call'

A function is called (or some other code block entered). The profile function is called; arg is None.

'return'

A function (or other code block) is about to return. The profile function is called; arg is the value that will be returned, or None if the event is caused by an exception being raised.

'c_call'

A C function is about to be called. This may be an extension function or a built-in. arg is the C function object.

'c_return'

A C function has returned. arg is the C function object.

'c_exception'

A C function has raised an exception. arg is the C function object.

引發一個不附帶引數的稽核事件 sys.setprofile。

sys.setrecursionlimit(limit)

Set the maximum depth of the Python interpreter stack to limit. This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python.

The highest possible limit is platform-dependent. A user may need to set the limit higher when they have a program that requires deep recursion and a platform that supports a higher limit. This should be done with care, because a too-high limit can lead to a crash.

If the new limit is too low at the current recursion depth, a RecursionError exception is raised.

在 3.5.1 版的變更: A RecursionError exception is now raised if the new limit is too low at the current recursion depth.

sys.setswitchinterval(interval)

Set the interpreter's thread switch interval (in seconds). This floating-point value determines the ideal duration of the "timeslices" allocated to concurrently running Python threads. Please note that the actual value can be higher, especially if long-running internal functions or methods are used. Also, which thread becomes scheduled at the end of the interval is the operating system's decision. The interpreter doesn't have its own scheduler.

在 3.2 版被加入.

sys.settrace(tracefunc)

Set the system's trace function, which allows you to implement a Python source code debugger in Python. The function is thread-specific; for a debugger to support multiple threads, it must register a trace function using settrace() for each thread being debugged or use threading.settrace().

Trace functions should have three arguments: frame, event, and arg. frame is the current stack frame. event is a string: 'call', 'line', 'return', 'exception' or 'opcode'. arg depends on the event type.

The trace function is invoked (with event set to 'call') whenever a new local scope is entered; it should return a reference to a local trace function to be used for the new scope, or None if the scope shouldn't be traced.

The local trace function should return a reference to itself, or to another function which would then be used as the local trace function for the scope.

If there is any error occurred in the trace function, it will be unset, just like settrace(None) is called.

備註

Tracing is disabled while calling the trace function (e.g. a function set by settrace()). For recursive tracing see call_tracing().

The events have the following meaning:

'call'

A function is called (or some other code block entered). The global trace function is called; arg is None; the return value specifies the local trace function.

'line'

The interpreter is about to execute a new line of code or re-execute the condition of a loop. The local trace function is called; arg is None; the return value specifies the new local trace function. See Objects/lnotab_notes.txt for a detailed explanation of how this works. Per-line events may be disabled for a frame by setting f_trace_lines to False on that frame.

'return'

A function (or other code block) is about to return. The local trace function is called; arg is the value that will be returned, or None if the event is caused by an exception being raised. The trace function's return value is ignored.

'exception'

An exception has occurred. The local trace function is called; arg is a tuple (exception, value, traceback); the return value specifies the new local trace function.

'opcode'

The interpreter is about to execute a new opcode (see dis for opcode details). The local trace function is called; arg is None; the return value specifies the new local trace function. Per-opcode events are not emitted by default: they must be explicitly requested by setting f_trace_opcodes to True on the frame.

Note that as an exception is propagated down the chain of callers, an 'exception' event is generated at each level.

For more fine-grained usage, it's possible to set a trace function by assigning frame.f_trace = tracefunc explicitly, rather than relying on it being set indirectly via the return value from an already installed trace function. This is also required for activating the trace function on the current frame, which settrace() doesn't do. Note that in order for this to work, a global tracing function must have been installed with settrace() in order to enable the runtime tracing machinery, but it doesn't need to be the same tracing function (e.g. it could be a low overhead tracing function that simply returns None to disable itself immediately on each frame).

For more information on code and frame objects, refer to 標準型別階層.

引發一個不附帶引數的稽核事件 sys.settrace。

CPython 實作細節： The settrace() function is intended only for implementing debuggers, profilers, coverage tools and the like. Its behavior is part of the implementation platform, rather than part of the language definition, and thus may not be available in all Python implementations.

在 3.7 版的變更: 'opcode' event type added; f_trace_lines and f_trace_opcodes attributes added to frames

sys.set_asyncgen_hooks([firstiter] [, finalizer])

Accepts two optional keyword arguments which are callables that accept an asynchronous generator iterator as an argument. The firstiter callable will be called when an asynchronous generator is iterated for the first time. The finalizer will be called when an asynchronous generator is about to be garbage collected.

引發一個不附帶引數的稽核事件 sys.set_asyncgen_hooks_firstiter。

引發一個不附帶引數的稽核事件 sys.set_asyncgen_hooks_finalizer。

Two auditing events are raised because the underlying API consists of two calls, each of which must raise its own event.

在 3.6 版被加入: See PEP 525 [https://peps.python.org/pep-0525/] for more details, and for a reference example of a finalizer method see the implementation of asyncio.Loop.shutdown_asyncgens in Lib/asyncio/base_events.py [https://github.com/python/cpython/tree/3.14/Lib/asyncio/base_events.py]

備註

This function has been added on a provisional basis (see PEP 411 [https://peps.python.org/pep-0411/] for details.)

sys.set_coroutine_origin_tracking_depth(depth)

Allows enabling or disabling coroutine origin tracking. When enabled, the cr_origin attribute on coroutine objects will contain a tuple of (filename, line number, function name) tuples describing the traceback where the coroutine object was created, with the most recent call first. When disabled, cr_origin will be None.

To enable, pass a depth value greater than zero; this sets the number of frames whose information will be captured. To disable, set depth to zero.

This setting is thread-specific.

在 3.7 版被加入.

備註

This function has been added on a provisional basis (see PEP 411 [https://peps.python.org/pep-0411/] for details.) Use it only for debugging purposes.

sys.activate_stack_trampoline(backend, /)

Activate the stack profiler trampoline backend. The only supported backend is "perf".

Stack trampolines cannot be activated if the JIT is active.

可用性: Linux.

在 3.12 版被加入.

也參考

Python 對 Linux perf 分析器的支援

https://perf.wiki.kernel.org

sys.deactivate_stack_trampoline()

Deactivate the current stack profiler trampoline backend.

If no stack profiler is activated, this function has no effect.

可用性: Linux.

在 3.12 版被加入.

sys.is_stack_trampoline_active()

Return True if a stack profiler trampoline is active.

可用性: Linux.

在 3.12 版被加入.

sys.remote_exec(pid, script)

Executes script, a file containing Python code in the remote process with the given pid.

This function returns immediately, and the code will be executed by the target process's main thread at the next available opportunity, similarly to how signals are handled. There is no interface to determine when the code has been executed. The caller is responsible for making sure that the file still exists whenever the remote process tries to read it and that it hasn't been overwritten.

The remote process must be running a CPython interpreter of the same major and minor version as the local process. If either the local or remote interpreter is pre-release (alpha, beta, or release candidate) then the local and remote interpreters must be the same exact version.

See 遠端偵錯附加協定 for more information about the remote debugging mechanism.

When the code is executed in the remote process, an auditing event sys.remote_exec is raised with the pid and the path to the script file. This event is raised in the process that called sys.remote_exec().

When the script is executed in the remote process, an auditing event cpython.remote_debugger_script is raised with the path in the remote process. This event is raised in the remote process, not the one that called sys.remote_exec().

可用性: Unix, Windows.

在 3.14 版被加入: 更多細節請見 PEP 768 [https://peps.python.org/pep-0768/]。

sys._enablelegacywindowsfsencoding()

Changes the filesystem encoding and error handler to 'mbcs' and 'replace' respectively, for consistency with versions of Python prior to 3.6.

This is equivalent to defining the PYTHONLEGACYWINDOWSFSENCODING environment variable before launching Python.

See also sys.getfilesystemencoding() and sys.getfilesystemencodeerrors().

可用性: Windows.

備註

Changing the filesystem encoding after Python startup is risky because the old fsencoding or paths encoded by the old fsencoding may be cached somewhere. Use PYTHONLEGACYWINDOWSFSENCODING instead.

在 3.6 版被加入: 更多細節請見 PEP 529 [https://peps.python.org/pep-0529/]。

自從版本 3.13 後不推薦使用，將會自版本 3.16 中移除。: Use PYTHONLEGACYWINDOWSFSENCODING instead.

sys.stdin

sys.stdout

sys.stderr

File objects used by the interpreter for standard input, output and errors:

stdin is used for all interactive input (including calls to input());

stdout is used for the output of print() and expression statements and for the prompts of input();

The interpreter's own prompts and its error messages go to stderr.

These streams are regular text files like those returned by the open() function. Their parameters are chosen as follows:

The encoding and error handling are is initialized from PyConfig.stdio_encoding and PyConfig.stdio_errors.

On Windows, UTF-8 is used for the console device. Non-character devices such as disk files and pipes use the system locale encoding (i.e. the ANSI codepage). Non-console character devices such as NUL (i.e. where isatty() returns True) use the value of the console input and output codepages at startup, respectively for stdin and stdout/stderr. This defaults to the system locale encoding if the process is not initially attached to a console.

The special behaviour of the console can be overridden by setting the environment variable PYTHONLEGACYWINDOWSSTDIO before starting Python. In that case, the console codepages are used as for any other character device.

Under all platforms, you can override the character encoding by setting the PYTHONIOENCODING environment variable before starting Python or by using the new -X utf8 command line option and PYTHONUTF8 environment variable. However, for the Windows console, this only applies when PYTHONLEGACYWINDOWSSTDIO is also set.

When interactive, the stdout stream is line-buffered. Otherwise, it is block-buffered like regular text files. The stderr stream is line-buffered in both cases. You can make both streams unbuffered by passing the -u command-line option or setting the PYTHONUNBUFFERED environment variable.

在 3.9 版的變更: Non-interactive stderr is now line-buffered instead of fully buffered.

備註

To write or read binary data from/to the standard streams, use the underlying binary buffer object. For example, to write bytes to stdout, use sys.stdout.buffer.write(b'abc').

However, if you are writing a library (and do not control in which context its code will be executed), be aware that the standard streams may be replaced with file-like objects like io.StringIO which do not support the buffer attribute.

sys.__stdin__

sys.__stdout__

sys.__stderr__

These objects contain the original values of stdin, stderr and stdout at the start of the program. They are used during finalization, and could be useful to print to the actual standard stream no matter if the sys.std* object has been redirected.

It can also be used to restore the actual files to known working file objects in case they have been overwritten with a broken object. However, the preferred way to do this is to explicitly save the previous stream before replacing it, and restore the saved object.

備註

Under some conditions stdin, stdout and stderr as well as the original values __stdin__, __stdout__ and __stderr__ can be None. It is usually the case for Windows GUI apps that aren't connected to a console and Python apps started with pythonw.

sys.stdlib_module_names

A frozenset of strings containing the names of standard library modules.

It is the same on all platforms. Modules which are not available on some platforms and modules disabled at Python build are also listed. All module kinds are listed: pure Python, built-in, frozen and extension modules. Test modules are excluded.

For packages, only the main package is listed: sub-packages and sub-modules are not listed. For example, the email package is listed, but the email.mime sub-package and the email.message sub-module are not listed.

另請參閱 sys.builtin_module_names 清單。

在 3.10 版被加入.

sys.thread_info

A named tuple holding information about the thread implementation.

thread_info.name

The name of the thread implementation:

"nt": Windows 執行緒

"pthread": POSIX 執行緒

"pthread-stubs": stub POSIX threads (on WebAssembly platforms without threading support)

"solaris": Solaris threads

thread_info.lock

The name of the lock implementation:

"semaphore": a lock uses a semaphore

"mutex+cond": a lock uses a mutex and a condition variable

為 None 表示此資訊未知

thread_info.version

The name and version of the thread library. It is a string, or None if this information is unknown.

在 3.3 版被加入.

sys.tracebacklimit

When this variable is set to an integer value, it determines the maximum number of levels of traceback information printed when an unhandled exception occurs. The default is 1000. When set to 0 or less, all traceback information is suppressed and only the exception type and value are printed.

sys.unraisablehook(unraisable, /)

處理一個不可被引發的例外。

Called when an exception has occurred but there is no way for Python to handle it. For example, when a destructor raises an exception or during garbage collection (gc.collect()).

unraisable 引數具有以下屬性：

exc_type: 例外型別。

exc_value: 例外值，可以為 None。

exc_traceback: 例外追蹤，可以為 None。

err_msg: 錯誤訊息，可以為 None。

object: 導致例外的物件，可以為 None。

The default hook formats err_msg and object as: f'{err_msg}: {object!r}'; use "Exception ignored in" error message if err_msg is None.

sys.unraisablehook() can be overridden to control how unraisable exceptions are handled.

也參考

處理未被捕捉到例外的 excepthook()。

警告

Storing exc_value using a custom hook can create a reference cycle. It should be cleared explicitly to break the reference cycle when the exception is no longer needed.

Storing object using a custom hook can resurrect it if it is set to an object which is being finalized. Avoid storing object after the custom hook completes to avoid resurrecting objects.

Raise an auditing event sys.unraisablehook with arguments hook, unraisable when an exception that cannot be handled occurs. The unraisable object is the same as what will be passed to the hook. If no hook has been set, hook may be None.

在 3.8 版被加入.

sys.version

A string containing the version number of the Python interpreter plus additional information on the build number and compiler used. This string is displayed when the interactive interpreter is started. Do not extract version information out of it, rather, use version_info and the functions provided by the platform module.

sys.api_version

The C API version, equivalent to the C macro PYTHON_API_VERSION. Defined for backwards compatibility.

Currently, this constant is not updated in new Python versions, and is not useful for versioning. This may change in the future.

sys.version_info

A tuple containing the five components of the version number: major, minor, micro, releaselevel, and serial. All values except releaselevel are integers; the release level is 'alpha', 'beta', 'candidate', or 'final'. The version_info value corresponding to the Python version 2.0 is (2, 0, 0, 'final', 0). The components can also be accessed by name, so sys.version_info[0] is equivalent to sys.version_info.major and so on.

在 3.1 版的變更: 新增了附名的元件屬性。

sys.warnoptions

This is an implementation detail of the warnings framework; do not modify this value. Refer to the warnings module for more information on the warnings framework.

sys.winver

The version number used to form registry keys on Windows platforms. This is stored as string resource 1000 in the Python DLL. The value is normally the major and minor versions of the running Python interpreter. It is provided in the sys module for informational purposes; modifying this value has no effect on the registry keys used by Python.

可用性: Windows.

sys.monitoring

Namespace containing functions and constants for register callbacks and controlling monitoring events. See sys.monitoring for details.

sys._xoptions

A dictionary of the various implementation-specific flags passed through the -X command-line option. Option names are either mapped to their values, if given explicitly, or to True. Example:

$ ./python -Xa=b -Xc
Python 3.2a3+ (py3k, Oct 16 2010, 20:14:50)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys._xoptions
{'a': 'b', 'c': True}

CPython 實作細節： This is a CPython-specific way of accessing options passed through -X. Other implementations may export them through other means, or not at all.

在 3.2 版被加入.

引用

[C99]

ISO/IEC 9899:1999. "Programming languages -- C." 公開草案可在以下網址取得 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf。

sys.monitoring --- 執行事件監控

在 3.12 版被加入.

備註

sys.monitoring 是 sys 模組內的一個命名空間，不是一個獨立的模組，所以不需要 import sys.monitoring，只需 import sys 然後使用 sys.monitoring。

此命名空間提供對啟動和控制事件監控所需的函式和常數的存取。

當程式執行時，會發生一些能被監控工具關注的事件。sys.monitoring 命名空間提供了在發生欲關注事件時接收回呼的方法。

監控 API 由三個元件組成：

工具識別器

事件

回呼 (callbacks)

工具識別器

工具識別器是一個整數和關聯的名稱。工具識別器用於防止工具相互干擾並允許多個工具同時運作。目前工具是完全獨立的，不能用來互相監控。將來此限制可能會取消。

在註冊或啟動事件之前，工具應選擇一個識別器。識別器是 0 到 5（含）範圍內的整數。

註冊和使用工具

sys.monitoring.use_tool_id(tool_id: int, name: str, /) → None

必須在使用 tool_id 之前呼叫。tool_id 必須在 0 到 5（含）範圍內。如果 tool_id 正在使用，則引發 ValueError。

sys.monitoring.clear_tool_id(tool_id: int, /) → None

取消註冊與 tool_id 關聯的所有事件和回呼函式。

sys.monitoring.free_tool_id(tool_id: int, /) → None

一旦工具不再需要 tool_id 就應該被呼叫。在釋放 tool_id 之前會呼叫 clear_tool_id()。

sys.monitoring.get_tool(tool_id: int, /) → str | None

如果 tool_id 正在使用，則回傳該工具的名稱，否則回傳 None。tool_id 必須在 0 到 5（含）範圍內。

對於事件，虛擬機器對所有 ID 的處理都是相同的，但預先定義了以下 ID，以使工具間的協作更容易：

sys.monitoring.DEBUGGER_ID = 0
sys.monitoring.COVERAGE_ID = 1
sys.monitoring.PROFILER_ID = 2
sys.monitoring.OPTIMIZER_ID = 5

事件

支援以下事件：

sys.monitoring.events.BRANCH_LEFT

一個條件分支往左。

It is up to the tool to determine how to present "left" and "right" branches. There is no guarantee which branch is "left" and which is "right", except that it will be consistent for the duration of the program.

sys.monitoring.events.BRANCH_RIGHT

一個條件分支往右。

sys.monitoring.events.CALL

Python 程式碼中的呼叫（事件發生在呼叫之前）。

sys.monitoring.events.C_RAISE

從任何可呼叫物件引發的例外，除 Python 函式外（事件發生在退出之後）。

sys.monitoring.events.C_RETURN

從任何可呼叫函式回傳，除 Python 函式外（事件發生在回傳之後）。

sys.monitoring.events.EXCEPTION_HANDLED

一個例外被處理。

sys.monitoring.events.INSTRUCTION

虛擬機器指令即將被執行。

sys.monitoring.events.JUMP

在控制流程圖中進行無條件跳轉。

sys.monitoring.events.LINE

即將執行的指令與前一條指令的列號不同。

sys.monitoring.events.PY_RESUME

Python 函式的繼續執行（對於產生器和協程函式），除了 throw() 呼叫。

sys.monitoring.events.PY_RETURN

從 Python 函式回傳（發生在即將回傳之前，被呼叫者的 frame 將位於堆疊上）。

sys.monitoring.events.PY_START

Python 函式的開始（在呼叫後立即發生，被呼叫者的 frame 將位於堆疊上）

sys.monitoring.events.PY_THROW

Python 函式透過 throw() 呼叫來繼續。

sys.monitoring.events.PY_UNWIND

Exit from a Python function during exception unwinding. This includes exceptions raised directly within the function and that are allowed to continue to propagate.

sys.monitoring.events.PY_YIELD

來自 Python 函式的 yield（在即將 yield 之前發生，被呼叫者的 frame 將位於堆疊上）。

sys.monitoring.events.RAISE

例外被引發，除了那些會導致 STOP_ITERATION 的事件外。

sys.monitoring.events.RERAISE

例外被重新引發 (re-raise)，例如在 finally 區塊的最後。

sys.monitoring.events.STOP_ITERATION

一個人為的 StopIteration 被引發；請參閱 STOP_ITERATION 事件。

將來可能會新增更多事件。

這些事件是 sys.monitoring.events 命名空間的屬性。每個事件以 2 次方的整數常數表示。要定義一組事件，只要將個別事件以 bitwise OR 相接即可。例如，若要指定 PY_RETURN 和 PY_START 兩個事件，請使用運算式 PY_RETURN | PY_START。

sys.monitoring.events.NO_EVENTS

0 的別名，以便使用者可以進行明確比較，例如：

if get_events(DEBUGGER_ID) == NO_EVENTS:
    ...

設定此事件會停用所有事件。

區域事件

區域事件與程式的正常執行相關，並發生在明確定義的位置。所有區域事件都可以被停用。區域事件有：

PY_START

PY_RESUME

PY_RETURN

PY_YIELD

CALL

LINE

INSTRUCTION

JUMP

BRANCH_LEFT

BRANCH_RIGHT

STOP_ITERATION

已棄用的事件

BRANCH

The BRANCH event is deprecated in 3.14. Using BRANCH_LEFT and BRANCH_RIGHT events will give much better performance as they can be disabled independently.

附屬事件 (ancillary events)

附屬事件可以像其他事件一樣被監控，但由另一個事件所控制：

C_RAISE

C_RETURN

C_RETURN 和 C_RAISE 事件由 CALL 事件控制。只有當對應的 CALL 事件受到監控時，才會看到 C_RETURN 和 C_RAISE 事件。

其他事件

其他事件不一定與程式中的特定位置相關聯，也不能透過 DISABLE 單獨停用。

其他可以監控的事件有：

PY_THROW

PY_UNWIND

RAISE

EXCEPTION_HANDLED

STOP_ITERATION 事件

PEP 380 [https://peps.python.org/pep-0380/#use-of-stopiteration-to-return-values] 指出從產生器或協程回傳值時要引發 StopIteration 例外。然而，這是一種非常低效的回傳值方式，因此有一些 Python 實作（特別是 CPython 3.12+）不會引發例外，除非它對其他程式碼是可見的。

為了允許工具去監控真正的例外而不減慢產生器和協程的速度，提供了 STOP_ITERATION 事件。與 RAISE 不同，STOP_ITERATION 可以區域停用。

Note that the STOP_ITERATION event and the RAISE event for a StopIteration exception are equivalent, and are treated as interchangeable when generating events. Implementations will favor STOP_ITERATION for performance reasons, but may generate a RAISE event with a StopIteration.

開啟和關閉事件

為了監控一個事件，必須打開它並註冊相應的回呼。可以透過將事件設定為全域與/或只為特定程式碼物件來開啟或關閉事件。即使事件在全域和區域都被打開，事件也只會觸發一次。

全域設定事件

可以透過修改正在監控的事件集合來全域地控制事件。

sys.monitoring.get_events(tool_id: int, /) → int

回傳代表所有有效事件的 int。

sys.monitoring.set_events(tool_id: int, event_set: int, /) → None

啟動 event_set 中設定的所有事件。如果 tool_id 並未正在被使用，則引發 ValueError。

預設沒有有效事件。

各別程式碼物件事件

事件還可以基於各別程式碼物件進行控制。下面定義的、接受 types.CodeType 的函式應該準備好接受來自 Python 中未定義函式的類似物件（請參閱 監控 C API）。

sys.monitoring.get_local_events(tool_id: int, code: CodeType, /) → int

回傳 code 的所有區域事件

sys.monitoring.set_local_events(tool_id: int, code: CodeType, event_set: int, /) → None

啟動 event_set 中針對 code 設定的所有區域事件。如果 tool_id 並未正在被使用，則引發 ValueError。

停用事件

sys.monitoring.DISABLE

可以從回呼函式回傳的特殊值，以停用目前程式碼位置的事件。

可透過回呼函式回傳 sys.monitoring.DISABLE 來停用特定程式碼位置的區域事件。這不會改變被設定的事件，或相同事件的任何其他程式碼位置。

停用特定位置的事件對於高效能監控非常重要。舉例來說，如果除少數斷點外，偵錯器可以停用所有監控，那麼在偵錯器下執行程式就不會有任何開銷 (overhead)。

如果回呼是為一個全域事件回傳 DISABLE，則直譯器會在非特定位置引發 ValueError（也就是不會提供回溯 (traceback)）。

sys.monitoring.restart_events() → None

為所有工具啟用由 sys.monitoring.DISABLE 停用的所有事件。

註冊回呼函式

sys.monitoring.register_callback(tool_id: int, event: int, func: Callable | None, /) → Callable | None

使用給定的 tool_id 來註冊對 event 的可呼叫物件 func

如果給定的 tool_id 和 event 已經註冊了另一個回呼，則會取消註冊並回傳。否則 register_callback() 會回傳 None。

以 func 引數引發一個稽核事件 (auditing event) sys.monitoring.register_callback。

可以透過呼叫 sys.monitoring.register_callback(tool_id, event, None) 來取消註冊函式。

回呼函式可以隨時被註冊和取消註冊。

Callbacks are called only once regardless if the event is turned on both globally and locally. As such, if an event could be turned on for both global and local events by your code then the callback needs to be written to handle either trigger.

回呼函式引數

sys.monitoring.MISSING

傳遞給回呼函式的特殊值，表示該呼叫沒有引數。

當有效事件發生時，已註冊的回呼函式會被呼叫。回傳非 DISABLE 物件的回呼函式將不會有任何效果。不同的事件會為回呼函式提供不同的引數，如下所示：

PY_START 和 PY_RESUME：

func(code: CodeType, instruction_offset: int) -> object

PY_RETURN 和 PY_YIELD：

func(code: CodeType, instruction_offset: int, retval: object) -> object

CALL、C_RAISE 和 C_RETURN（arg0 可以特別是 MISSING）：

func(code: CodeType, instruction_offset: int, callable: object, arg0: object) -> object

code represents the code object where the call is being made, while callable is the object that is about to be called (and thus triggered the event). If there are no arguments, arg0 is set to sys.monitoring.MISSING.

For instance methods, callable will be the function object as found on the class with arg0 set to the instance (i.e. the self argument to the method).

RAISE、RERAISE、EXCEPTION_HANDLED、PY_UNWIND、PY_THROW 和 STOP_ITERATION：

func(code: CodeType, instruction_offset: int, exception: BaseException) -> object

LINE：

func(code: CodeType, line_number: int) -> object

BRANCH_LEFT, BRANCH_RIGHT and JUMP:

func(code: CodeType, instruction_offset: int, destination_offset: int) -> object

請注意，destination_offset 是程式碼接下來要執行的地方。

INSTRUCTION：

func(code: CodeType, instruction_offset: int) -> object

sysconfig --- 提供 Python 設定資訊的存取

在 3.2 版被加入.

原始碼：Lib/sysconfig [https://github.com/python/cpython/tree/3.14/Lib/sysconfig]

The sysconfig module provides access to Python's configuration information like the list of installation paths and the configuration variables relevant for the current platform.

Configuration variables

A Python distribution contains a Makefile and a pyconfig.h header file that are necessary to build both the Python binary itself and third-party C extensions compiled using setuptools.

sysconfig puts all variables found in these files in a dictionary that can be accessed using get_config_vars() or get_config_var().

Notice that on Windows, it's a much smaller set.

sysconfig.get_config_vars(*args)

With no arguments, return a dictionary of all configuration variables relevant for the current platform.

With arguments, return a list of values that result from looking up each argument in the configuration variable dictionary.

For each argument, if the value is not found, return None.

sysconfig.get_config_var(name)

Return the value of a single variable name. Equivalent to get_config_vars().get(name).

If name is not found, return None.

用法範例：

>>> import sysconfig
>>> sysconfig.get_config_var('Py_ENABLE_SHARED')
0
>>> sysconfig.get_config_var('LIBDIR')
'/usr/local/lib'
>>> sysconfig.get_config_vars('AR', 'CXX')
['ar', 'g++']

Installation paths

Python uses an installation scheme that differs depending on the platform and on the installation options. These schemes are stored in sysconfig under unique identifiers based on the value returned by os.name. The schemes are used by package installers to determine where to copy files to.

Python currently supports nine schemes:

posix_prefix: scheme for POSIX platforms like Linux or macOS. This is the default scheme used when Python or a component is installed.

posix_home: scheme for POSIX platforms, when the home option is used. This scheme defines paths located under a specific home prefix.

posix_user: scheme for POSIX platforms, when the user option is used. This scheme defines paths located under the user's home directory (site.USER_BASE).

posix_venv: scheme for Python virtual environments on POSIX platforms; by default it is the same as posix_prefix.

nt: scheme for Windows. This is the default scheme used when Python or a component is installed.

nt_user: scheme for Windows, when the user option is used.

nt_venv: scheme for Python virtual environments on Windows; by default it is the same as nt.

venv: a scheme with values from either posix_venv or nt_venv depending on the platform Python runs on.

osx_framework_user: scheme for macOS, when the user option is used.

Each scheme is itself composed of a series of paths and each path has a unique identifier. Python currently uses eight paths:

stdlib: directory containing the standard Python library files that are not platform-specific.

platstdlib: directory containing the standard Python library files that are platform-specific.

platlib: directory for site-specific, platform-specific files.

purelib: directory for site-specific, non-platform-specific files ('pure' Python).

include: directory for non-platform-specific header files for the Python C-API.

platinclude: directory for platform-specific header files for the Python C-API.

scripts: directory for script files.

data: directory for data files.

User scheme

This scheme is designed to be the most convenient solution for users that don't have write permission to the global site-packages directory or don't want to install into it.

Files will be installed into subdirectories of site.USER_BASE (written as userbase hereafter). This scheme installs pure Python modules and extension modules in the same location (also known as site.USER_SITE).

posix_user

Path

Installation directory

stdlib

userbase/lib/pythonX.Y

platstdlib

userbase/lib/pythonX.Y

platlib

userbase/lib/pythonX.Y/site-packages

purelib

userbase/lib/pythonX.Y/site-packages

include

userbase/include/pythonX.Y

scripts

userbase/bin

data

userbase

nt_user

Path

Installation directory

stdlib

userbase\PythonXY

platstdlib

userbase\PythonXY

platlib

userbase\PythonXY\site-packages

purelib

userbase\PythonXY\site-packages

include

userbase\PythonXY\Include

scripts

userbase\PythonXY\Scripts

data

userbase

osx_framework_user

Path

Installation directory

stdlib

userbase/lib/python

platstdlib

userbase/lib/python

platlib

userbase/lib/python/site-packages

purelib

userbase/lib/python/site-packages

include

userbase/include/pythonX.Y

scripts

userbase/bin

data

userbase

Home scheme

The idea behind the "home scheme" is that you build and maintain a personal stash of Python modules. This scheme's name is derived from the idea of a "home" directory on Unix, since it's not unusual for a Unix user to make their home directory have a layout similar to /usr/ or /usr/local/. This scheme can be used by anyone, regardless of the operating system they are installing for.

posix_home

Path

Installation directory

stdlib

home/lib/python

platstdlib

home/lib/python

platlib

home/lib/python

purelib

home/lib/python

include

home/include/python

platinclude

home/include/python

scripts

home/bin

data

home

Prefix scheme

The "prefix scheme" is useful when you wish to use one Python installation to perform the build/install (i.e., to run the setup script), but install modules into the third-party module directory of a different Python installation (or something that looks like a different Python installation). If this sounds a trifle unusual, it is---that's why the user and home schemes come before. However, there are at least two known cases where the prefix scheme will be useful.

First, consider that many Linux distributions put Python in /usr, rather than the more traditional /usr/local. This is entirely appropriate, since in those cases Python is part of "the system" rather than a local add-on. However, if you are installing Python modules from source, you probably want them to go in /usr/local/lib/python2.X rather than /usr/lib/python2.X.

Another possibility is a network filesystem where the name used to write to a remote directory is different from the name used to read it: for example, the Python interpreter accessed as /usr/local/bin/python might search for modules in /usr/local/lib/python2.X, but those modules would have to be installed to, say, /mnt/@server/export/lib/python2.X.

posix_prefix

Path

Installation directory

stdlib

prefix/lib/pythonX.Y

platstdlib

prefix/lib/pythonX.Y

platlib

prefix/lib/pythonX.Y/site-packages

purelib

prefix/lib/pythonX.Y/site-packages

include

prefix/include/pythonX.Y

platinclude

prefix/include/pythonX.Y

scripts

prefix/bin

data

prefix

nt

Path

Installation directory

stdlib

prefix\Lib

platstdlib

prefix\Lib

platlib

prefix\Lib\site-packages

purelib

prefix\Lib\site-packages

include

prefix\Include

platinclude

prefix\Include

scripts

prefix\Scripts

data

prefix

安裝路徑函式

sysconfig provides some functions to determine these installation paths.

sysconfig.get_scheme_names()

Return a tuple containing all schemes currently supported in sysconfig.

sysconfig.get_default_scheme()

Return the default scheme name for the current platform.

在 3.10 版被加入: This function was previously named _get_default_scheme() and considered an implementation detail.

在 3.11 版的變更: When Python runs from a virtual environment, the venv scheme is returned.

sysconfig.get_preferred_scheme(key)

Return a preferred scheme name for an installation layout specified by key.

key must be either "prefix", "home", or "user".

The return value is a scheme name listed in get_scheme_names(). It can be passed to sysconfig functions that take a scheme argument, such as get_paths().

在 3.10 版被加入.

在 3.11 版的變更: When Python runs from a virtual environment and key="prefix", the venv scheme is returned.

sysconfig._get_preferred_schemes()

Return a dict containing preferred scheme names on the current platform. Python implementers and redistributors may add their preferred schemes to the _INSTALL_SCHEMES module-level global value, and modify this function to return those scheme names, to e.g. provide different schemes for system and language package managers to use, so packages installed by either do not mix with those by the other.

End users should not use this function, but get_default_scheme() and get_preferred_scheme() instead.

在 3.10 版被加入.

sysconfig.get_path_names()

Return a tuple containing all path names currently supported in sysconfig.

sysconfig.get_path(name[, scheme[, vars[, expand]]])

Return an installation path corresponding to the path name, from the install scheme named scheme.

name has to be a value from the list returned by get_path_names().

sysconfig stores installation paths corresponding to each path name, for each platform, with variables to be expanded. For instance the stdlib path for the nt scheme is: {base}/Lib.

get_path() will use the variables returned by get_config_vars() to expand the path. All variables have default values for each platform so one may call this function and get the default value.

If scheme is provided, it must be a value from the list returned by get_scheme_names(). Otherwise, the default scheme for the current platform is used.

If vars is provided, it must be a dictionary of variables that will update the dictionary returned by get_config_vars().

If expand is set to False, the path will not be expanded using the variables.

如果找不到 name，則引發 KeyError。

sysconfig.get_paths([scheme[, vars[, expand]]])

Return a dictionary containing all installation paths corresponding to an installation scheme. See get_path() for more information.

If scheme is not provided, will use the default scheme for the current platform.

If vars is provided, it must be a dictionary of variables that will update the dictionary used to expand the paths.

If expand is set to false, the paths will not be expanded.

If scheme is not an existing scheme, get_paths() will raise a KeyError.

其他函式

sysconfig.get_python_version()

回傳 MAJOR.MINOR Python 版本號碼字串。類似於 '%d.%d' % sys.version_info[:2]。

sysconfig.get_platform()

Return a string that identifies the current platform.

This is used mainly to distinguish platform-specific build directories and platform-specific built distributions. Typically includes the OS name and version and the architecture (as supplied by os.uname()), although the exact information included depends on the OS; e.g., on Linux, the kernel version isn't particularly important.

Examples of returned values:

Windows：

win-amd64 (64-bit Windows on AMD64, aka x86_64, Intel64, and EM64T)

win-arm64 (64-bit Windows on ARM64, aka AArch64)

win32 (all others - specifically, sys.platform is returned)

POSIX based OS:

linux-x86_64

macosx-15.5-arm64

macosx-26.0-universal2 (macOS on Apple Silicon or Intel)

android-24-arm64_v8a

For other non-POSIX platforms, currently just returns sys.platform.

sysconfig.is_python_build()

Return True if the running Python interpreter was built from source and is being run from its built location, and not from a location resulting from e.g. running make install or installing via a binary installer.

sysconfig.parse_config_h(fp[, vars])

剖析一個 config.h 風格的檔案。

fp is a file-like object pointing to the config.h-like file.

A dictionary containing name/value pairs is returned. If an optional dictionary is passed in as the second argument, it is used instead of a new dictionary, and updated with the values read in the file.

sysconfig.get_config_h_filename()

回傳 pyconfig.h 的路徑。

sysconfig.get_makefile_filename()

回傳 Makefile 的路徑。

命令列用法

You can use sysconfig as a script with Python's -m option:

$ python -m sysconfig
Platform: "macosx-10.4-i386"
Python version: "3.2"
Current installation scheme: "posix_prefix"

Paths:
        data = "/usr/local"
        include = "/Users/tarek/Dev/svn.python.org/py3k/Include"
        platinclude = "."
        platlib = "/usr/local/lib/python3.2/site-packages"
        platstdlib = "/usr/local/lib/python3.2"
        purelib = "/usr/local/lib/python3.2/site-packages"
        scripts = "/usr/local/bin"
        stdlib = "/usr/local/lib/python3.2"

Variables:
        AC_APPLE_UNIVERSAL_BUILD = "0"
        AIX_GENUINE_CPLUSPLUS = "0"
        AR = "ar"
        ARFLAGS = "rc"
        ...

This call will print in the standard output the information returned by get_platform(), get_python_version(), get_path() and get_config_vars().

builtins --- 內建物件

該模組提供對 Python 所有'內建'識別符號的直接存取；例如 builtins.open 是內建函式 open() 的全名。

大多數應用程式通常不會顯式地存取此模組，但在提供與內建值同名之物件的模組中可能很有用，不過其中還會需要內建該名稱。例如，在一個將內建 open() 包裝起來以實現另一版本 open() 函式的模組中，這個模組可以直接被使用：

import builtins

def open(path):
    f = builtins.open(path, 'r')
    return UpperCaser(f)

class UpperCaser:
    '''將輸出轉換成大寫的檔案包裝器'''

    def __init__(self, f):
        self._f = f

    def read(self, count=-1):
        return self._f.read(count).upper()

    # ...

有個實作細節是，大多數模組都將名稱 __builtins__ 作為其全域性變數的一部分以提使用。__builtins__ 的值通常是這個模組或者這個模組的 __dict__ 屬性值。由於這是一個實作細節，因此 Python 的其他實作可能不會使用它。

也參考

內建常數

內建的例外

內建函式

內建型別

__main__ --- 頂層程式碼環境

在 Python 中，特殊名稱 __main__ 用於兩個重要的建構：

程式頂層環境的名稱，可以使用 __name__ == '__main__' 運算式進行檢查；和

在 Python 套件中的 __main__.py 檔案。

這兩種機制都與 Python 模組有關；使用者如何與它們互動以及它們如何彼此互動。下面會詳細解釋它們。如果你不熟悉 Python 模組，請參閱教學章節 模組 (Module) 的介紹。

__name__ == '__main__'

當引入 Python 模組或套件時，__name__ 設定為模組的名稱。通常來說，這是 Python 檔案本身的名稱，且不含 .py 副檔名：

>>> import configparser
>>> configparser.__name__
'configparser'

如果檔案是套件的一部分，則 __name__ 也會包含父套件 (parent package) 的路徑：

>>> from concurrent.futures import process
>>> process.__name__
'concurrent.futures.process'

但是，如果模組在頂層程式碼環境中執行，則其 __name__ 將被設定為字串 '__main__'。

什麼是「頂層程式碼環境」？

__main__ 是執行頂層程式碼的環境名稱。「頂層程式碼」是使用者指定且第一個開始運作的 Python 模組。它是「頂層」的原因是因為它引入程式所需的所有其他模組。有時「頂層程式碼」被稱為應用程式的入口點。

頂層程式碼環境可以是：

互動式提示字元的作用域：

>>> __name__
'__main__'

將 Python 模組作為檔案引數傳遞給 Python 直譯器：

$ python helloworld.py
Hello, world!

使用 -m 引數傳遞給 Python 直譯器的 Python 模組或套件：

$ python -m tarfile
usage: tarfile.py [-h] [-v] (...)

Python 直譯器從標準輸入讀取 Python 程式碼：

$ echo "import this" | python
The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
...

使用 -c 引數傳遞給 Python 直譯器的 Python 程式碼：

$ python -c "import this"
The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
...

在這些情況下，頂層模組的 __name__ 都會設定為 '__main__'。

因此，模組可以透過檢查自己的 __name__ 來發現它是否在頂層環境中執行，這允許當模組未從 import 陳述式初始化時，使用常見的慣用語法 (idiom) 來有條件地執行程式碼：

if __name__ == '__main__':
    # Execute when the module is not initialized from an import statement.
    ...

也參考

若要更詳細地了解如何在所有情況下設定 __name__，請參閱教學章節 模組 (Module)。

慣用 (Idiomatic) 用法

某些模組包含僅供腳本使用的程式碼，例如剖析命令列引數或從標準輸入取得資料。如果從不同的模組匯入這樣的模組（例如對其進行單元測試 (unit test)），則腳本程式碼也會無意間執行。

這就是使用 if __name__ == '__main__' 程式碼區塊派上用場的地方。除非該模組在頂層環境中執行，否則此區塊中的程式碼不會執行。

在 if __name__ == '__main__' 下面的區塊中放置盡可能少的陳述式可以提高程式碼的清晰度和正確性。大多數情況下，名為 main 的函式封裝 (encapsulate) 了程式的主要行為：

# echo.py

import shlex
import sys

def echo(phrase: str) -> None:
   """A dummy wrapper around print."""
   # for demonstration purposes, you can imagine that there is some
   # valuable and reusable logic inside this function
   print(phrase)

def main() -> int:
    """Echo the input arguments to standard output"""
    phrase = shlex.join(sys.argv)
    echo(phrase)
    return 0

if __name__ == '__main__':
    sys.exit(main())  # next section explains the use of sys.exit

請注意，如果模組沒有將程式碼封裝在 main 函式中，而是直接將其放在 if __name__ == '__main__' 區塊中，則 phrase 變數對於整個模組來說將是全域的。這很容易出錯，因為模組中的其他函式可能會無意中使用此全域變數而不是區域變數。main 函式解決了這個問題。

使用 main 函式還有一個額外的好處，echo 函式本身是隔離的 (isolated) 並且可以在其他地方引入。當引入 echo.py 時，echo 和 main 函式將被定義，但它們都不會被呼叫，因為 __name__ != '__main__'。

打包時須考慮的事情

main 函式通常用於透過將它們指定為控制台腳本的入口點來建立命令列工具。完成後，pip [https://pip.pypa.io/] 將函式呼叫插入到模板腳本中，其中 main 的回傳值被傳遞到 sys.exit() 中。例如：

sys.exit(main())

由於對 main 的呼叫包含在 sys.exit() 中，因此期望你的函式將傳回一些可接受作為 sys.exit() 輸入的值；通常來說，會是一個整數或 None（如果你的函式沒有 return 陳述式，則相當於回傳此值）。

透過我們自己主動遵循這個慣例，我們的模組在直接執行時（即 python echo.py）的行為，將和我們稍後將其打包為 pip 可安裝套件中的控制台腳本入口點相同。

特別是，要謹慎處理從 main 函式回傳字串。sys.exit() 會將字串引數直譯為失敗訊息，因此你的程式將有一個表示失敗的結束代碼 1，並且該字串將被寫入 sys.stderr。前面的 echo.py 範例使用慣例的 sys.exit(main()) 進行示範。

也參考

Python 打包使用者指南 [https://packaging.python.org/]包含一系列如何使用現代工具發行和安裝 Python 套件的教學和參考資料。

Python 套件中的 __main__.py

如果你不熟悉 Python 套件，請參閱 套件 (Package) 的教學章節。最常見的是，__main__.py 檔案用於為套件提供命令列介面。假設下面有虛構的套件 "bandclass"：

bandclass
  ├── __init__.py
  ├── __main__.py
  └── student.py

當使用 -m 旗標 (flag) 直接從命令列呼叫套件本身時，將執行 __main__.py。例如：

$ python -m bandclass

該命令將導致 __main__.py 執行。如何利用此機制將取決於你正在編寫的套件的性質，但在這種虛構的情況下，允許教師搜尋學生可能是有意義的：

# bandclass/__main__.py

import sys
from .student import search_students

student_name = sys.argv[1] if len(sys.argv) >= 2 else ''
print(f'Found student: {search_students(student_name)}')

請注意，from .student import search_students 是相對引入的範例。在引用套件內的模組時，可以使用此引入樣式。有關更多詳細資訊，請參閱 模組 (Module) 教學章節中的 套件內引用。

慣用 (Idiomatic) 用法

__main__.py 的內容通常不會被 if __name__ == '__main__' 區塊包圍。相反的，這些檔案保持簡短並引入其他模組的函式來執行。那些其他模組就可以輕鬆地進行單元測試並且可以正確地重複使用。

如果在套件裡面的 __main__.py 檔案使用 if __name__ == '__main__' 區塊，它依然會如預期般地運作。因為當引入套件，其 __name__ 屬性將會包含套件的路徑：

>>> import asyncio.__main__
>>> asyncio.__main__.__name__
'asyncio.__main__'

但這對於 .zip 檔案根目錄中的 __main__.py 檔案不起作用。因此，為了保持一致性，最小的、沒有 __name__ 檢查的 __main__.py 會是首選。

也參考

請參閱 venv 作為標準函式庫中具有最小 __main__.py 的套件為範例。它不包含 if __name__ == '__main__' 區塊。你可以使用 python -m venv [directory] 來呼叫它。

請參閱 runpy 取得有關直譯器可執行檔的 -m 旗標的更多詳細資訊。

請參閱 zipapp 了解如何執行打包成 .zip 檔案的應用程式。在這種情況下，Python 會在封存檔案的根目錄中尋找 __main__.py 檔案。

import __main__

無論 Python 程式是從哪個模組啟動的，在同一程式中執行的其他模組都可以透過匯入 __main__ 模組來引入頂層環境的作用域 (namespace)。這不會引入 __main__.py 檔案，而是引入接收特殊名稱 '__main__' 的模組。

這是一個使用 __main__ 命名空間的範例模組：

# namely.py

import __main__

def did_user_define_their_name():
    return 'my_name' in dir(__main__)

def print_user_name():
    if not did_user_define_their_name():
        raise ValueError('Define the variable `my_name`!')

    print(__main__.my_name)

該模組的範例用法如下：

# start.py

import sys

from namely import print_user_name

# my_name = "Dinsdale"

def main():
    try:
        print_user_name()
    except ValueError as ve:
        return str(ve)

if __name__ == "__main__":
    sys.exit(main())

現在，如果我們啟動程式，結果將如下所示：

$ python start.py
Define the variable `my_name`!

程式的結束代碼將為 1，表示出現錯誤。取消註解 my_name = "Dinsdale" 而修復程式後，現在它以狀態碼 0 結束，表示成功：

$ python start.py
Dinsdale

請注意，引入 __main__ 並不會因為不經意地執行放在 start 模組中 if __name__ == "__main__" 區塊的頂層程式碼（本來是給腳本使用的）而造成任何問題。為什麼這樣做會如預期運作？

當 Python 直譯器啟動時，會在 sys.modules 中插入一個空的 __main__ 模組，並透過執行頂層程式碼來填充它。在我們的範例中，這是 start 模組，它將逐行執行並引入 namely。接著，namely 引入 __main__（其實是 start）。這就是一個引入循環！幸運的是，由於部分填充的 __main__ 模組存在於 sys.modules 中，Python 將其傳遞給 namely。請參閱引入系統參考文件中的關於 __main__ 的特別考量了解其工作原理的詳細資訊。

Python REPL 是「頂層環境」的另一個範例，因此 REPL 中定義的任何內容都成為 作域的一部分：

>>> import namely
>>> namely.did_user_define_their_name()
False
>>> namely.print_user_name()
Traceback (most recent call last):
...
ValueError: Define the variable `my_name`!
>>> my_name = 'Jabberwocky'
>>> namely.did_user_define_their_name()
True
>>> namely.print_user_name()
Jabberwocky

__main__ 作用域用於 pdb 和 rlcompleter 的實作。

warnings --- 警告控制

原始碼：Lib/warnings.py [https://github.com/python/cpython/tree/3.14/Lib/warnings.py]

警告訊息通常會在需要提醒使用者程式中的某些狀況時發出，而該狀況（通常）不至於需要引發例外並終止程式。舉例來說，當程式使用一個過時的模組時，就可能會需要發出警告。

Python 程式設計師可以透過呼叫此模組中定義的 warn() 函式來發出警告。（C 語言的程式設計師則使用 PyErr_WarnEx()；詳情請參閱 例外處理）。

警告訊息通常會被寫入 sys.stderr，但它們的處理方式可以被彈性地更改，從忽略所有警告到將它們轉為例外都可以。警告的處理方式會根據 警告類別、警告訊息的文本，以及發出警告的原始碼位置而有所不同。在同一個原始碼位置重複出現的特定警告通常會被抑制。

警告控制有兩個階段：首先，每當發出一個警告時，會先決定是否該發出訊息；接著，如果要發出訊息，它會使用一個可由使用者設定的掛鉤 (hook) 來格式化並印出。

是否要發出警告訊息是由 警告過濾器 所控制，它是一連串的匹配規則和動作。可以透過呼叫 filterwarnings() 來新增規則到過濾器中，並透過呼叫 resetwarnings() 將其重設為預設狀態。

警告訊息的印出是透過呼叫 showwarning() 來完成，而它可以被覆寫；此函式的預設實作會透過呼叫 formatwarning() 來格式化訊息，它也可以被自訂的實作使用。

也參考

logging.captureWarnings() 允許你使用標準的 logging 基礎設施來處理所有警告。

警告類別

有許多內建的例外代表警告類別。這種分類方式對於能夠過濾掉特定群組的警告很有用。

雖然這些在技術上是 內建例外，但它們被記錄在這裡，因為從概念上來說，它們屬於警告機制的一部分。

使用者程式碼可以透過繼承其中一個標準警告類別來定義額外的警告類別。一個警告類別必須永遠是 Warning 類別的子類別。

目前定義了以下警告類別：

類別

描述

Warning

這是所有警告類別的基底類別。它是 Exception 的子類別。

UserWarning

warn() 的預設類別。

DeprecationWarning

關於已棄用功能的警告的基底類別，當這些警告是針對其他 Python 開發者時（預設為忽略，除非由 __main__ 中的程式碼觸發）。

SyntaxWarning

Base category for warnings about dubious syntactic features (typically emitted when compiling Python source code, and hence may not be suppressed by runtime filters)

RuntimeWarning

關於可疑 runtime 功能的警告的基底類別。

FutureWarning

關於已棄用功能的警告的基底類別，當這些警告是針對以 Python 編寫的應用程式的終端使用者時。

PendingDeprecationWarning

關於未來將被棄用的功能的警告的基底類別（預設為忽略）。

ImportWarning

在引入模組過程中觸發的警告的基底類別（預設為忽略）。

UnicodeWarning

與 Unicode 相關的警告的基底類別。

BytesWarning

與 bytes 和 bytearray 相關的警告的基底類別。

ResourceWarning

與資源使用相關的警告的基底類別（預設為忽略）。

在 3.7 版的變更: 在過去，DeprecationWarning 和 FutureWarning 是根據一個功能是被完全移除還是改變其行為來區分的。它們現在是根據其目標受眾以及預設警告過濾器處理它們的方式來區分。

警告過濾器

警告過濾器控制警告是被忽略、顯示，還是轉為錯誤（引發一個例外）。

從概念上講，警告過濾器維護一個有序的過濾器規格串列；任何特定的警告都會依次與串列中的每個過濾器規格進行比對，直到找到匹配項；過濾器決定了匹配項的處理方式。每個條目都是一個 (action, message, category, module, lineno) 形式的元組，其中：

action 是以下字串之一：

值

處理方式

"default"

為發出警告的每個位置（模組 + 行號）印出第一次出現的匹配警告

"error"

將匹配的警告轉為例外

"ignore"

永不印出匹配的警告

"always"

總是印出匹配的警告

"all"

"always" 的別名

"module"

為發出警告的每個模組印出第一次出現的匹配警告（不論行號）

"once"

只印出第一次出現的匹配警告，不論位置

message 是一個包含正規表示式的字串，警告訊息的開頭必須與其匹配（不區分大小寫）。在 -W 和 PYTHONWARNINGS 中，message 是一個字面字串，警告訊息的開頭必須包含該字串（不區分大小寫），並忽略 message 開頭或結尾的任何空白字元。

category 是一個類別（Warning 的子類別），警告類別必須是它的子類別才能匹配。

module 是一個包含正規表示式的字串，完整限定模組名稱的開頭必須與其匹配（區分大小寫）。在 -W 和 PYTHONWARNINGS 中，module 是一個字面字串，完整限定模組名稱必須與其相等（區分大小寫），並忽略 module 開頭或結尾的任何空白字元。

lineno 是一個整數，發出警告的行號必須與其匹配，或者為 0 以匹配所有行號。

由於 Warning 類別衍生自內建的 Exception 類別，要將警告轉為錯誤，我們只需引發 category(message)。

如果一個警告被回報且不匹配任何已註冊的過濾器，則會套用 "default" 動作（因此得名）。

重複警告的抑制標準

抑制重複警告的過濾器會套用以下標準來判斷一個警告是否被視為重複：

"default"：只有當 (message, category, module, lineno) 都相同時，警告才被視為重複。

"module"：如果 (message, category, module) 相同，則警告被視為重複，忽略行號。

"once"：如果 (message, category) 相同，則警告被視為重複，忽略模組和行號。

描述警告過濾器

警告過濾器由傳遞給 Python 直譯器命令列的 -W 選項和 PYTHONWARNINGS 環境變數初始化。直譯器會將所有提供條目的引數未經直譯地儲存在 sys.warnoptions 中；warnings 模組在首次引入時會剖析這些引數（無效選項會被忽略，並在向 sys.stderr 印出一條訊息後）。

個別的警告過濾器被指定為一系列由冒號分隔的欄位：

action:message:category:module:line

這些欄位中每一個的含義都如 警告過濾器 中所述。當在單一行中列出多個過濾器時（例如 PYTHONWARNINGS），個別的過濾器會以逗號分隔，且後面列出的過濾器優先於前面列出的過濾器（因為它們是從左到右應用的，而最近應用的過濾器優先於較早的過濾器）。

常用的警告過濾器適用於所有警告、特定類別的警告，或由特定模組或套件引發的警告。一些範例如下：

default                      # 顯示所有警告（即使是預設忽略的警告）
ignore                       # 忽略所有警告
error                        # 將所有警告轉換為錯誤
error::ResourceWarning       # 將 ResourceWarning 訊息視為錯誤
default::DeprecationWarning  # 顯示 DeprecationWarning 訊息
ignore,default:::mymodule    # 只回報由 "mymodule" 觸發的警告
error:::mymodule             # 將 "mymodule" 中的警告轉換為錯誤

預設警告過濾器

預設情況下，Python 會安裝數個警告過濾器，這些過濾器可以被 -W 命令列選項、PYTHONWARNINGS 環境變數以及對 filterwarnings() 的呼叫所覆寫。

在常規的發行建置中，預設的警告過濾器有以下條目（按優先順序排列）：

default::DeprecationWarning:__main__
ignore::DeprecationWarning
ignore::PendingDeprecationWarning
ignore::ImportWarning
ignore::ResourceWarning

在 偵錯建置 中，預設警告過濾器串列是空的。

在 3.2 版的變更: 除了 PendingDeprecationWarning 之外，DeprecationWarning 現在也預設被忽略。

在 3.7 版的變更: 當直接由 __main__ 中的程式碼觸發時，DeprecationWarning 會再次預設顯示。

在 3.7 版的變更: BytesWarning 不再出現在預設過濾器串列中，而是在指定 -b 兩次時，透過 sys.warnoptions 進行設定。

覆寫預設過濾器

以 Python 編寫的應用程式的開發者可能希望預設對其使用者隱藏 所有 Python 層級的警告，並且只在執行測試或以其他方式處理應用程式時才顯示它們。用於將過濾器設定傳遞給直譯器的 sys.warnoptions 屬性可以用作一個標記，以指示是否應停用警告：

import sys

if not sys.warnoptions:
    import warnings
    warnings.simplefilter("ignore")

建議 Python 程式碼的測試執行器開發者，應確保在預設情況下，為受測程式碼顯示 所有 警告，可使用如下程式碼：

import sys

if not sys.warnoptions:
    import os, warnings
    warnings.simplefilter("default") # 在此行程中更改過濾器
    os.environ["PYTHONWARNINGS"] = "default" # 也會影響子行程

最後，建議在 __main__ 以外的命名空間中執行使用者程式碼的互動式 shell 開發者，應確保 DeprecationWarning 訊息預設為可見，可使用如下程式碼（其中 user_ns 是用於執行互動式輸入程式碼的模組）：

import warnings
warnings.filterwarnings("default", category=DeprecationWarning,
                                   module=user_ns.get("__name__"))

暫時抑制警告

如果你正在使用的程式碼，你知道它會引發一個警告（例如一個已棄用的函式），但你不想看到這個警告（即使警告已透過命令列明確設定），那麼可以使用 catch_warnings 情境管理器來抑制該警告：

import warnings

def fxn():
    warnings.warn("deprecated", DeprecationWarning)

with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    fxn()

在情境管理器中，所有警告都將被直接忽略。這允許你在使用已知的已棄用程式碼時不必看到警告，同時又不會抑制其他可能不知道自己正在使用已棄用程式碼的程式碼所發出的警告。

備註

See 情境管理器的並行安全性 for details on the concurrency-safety of the catch_warnings context manager when used in programs using multiple threads or async functions.

測試警告

要測試程式碼引發的警告，請使用 catch_warnings 情境管理器。透過它，你可以暫時改變警告過濾器以方便你的測試。例如，執行以下操作來捕獲所有引發的警告以進行檢查：

import warnings

def fxn():
    warnings.warn("deprecated", DeprecationWarning)

with warnings.catch_warnings(record=True) as w:
    # 讓所有警告總是會被觸發。
    warnings.simplefilter("always")
    # 觸發一個警告。
    fxn()
    # 驗證一些事情
    assert len(w) == 1
    assert issubclass(w[-1].category, DeprecationWarning)
    assert "deprecated" in str(w[-1].message)

也可以使用 error 而非 always 來讓所有警告都變成例外。需要注意的一點是，如果一個警告因為 once/default 規則已經被引發過，那麼無論設定什麼過濾器，這個警告都不會再出現，除非與該警告相關的警告註冊表已被清除。

一旦情境管理器退出，警告過濾器就會恢復到進入情境時的狀態。這可以防止測試在不同測試之間以意想不到的方式更改警告過濾器，從而導致不確定的測試結果。

備註

See 情境管理器的並行安全性 for details on the concurrency-safety of the catch_warnings context manager when used in programs using multiple threads or async functions.

在測試多個會引發同類警告的操作時，重要的是要以一種能確認每個操作都在引發新警告的方式來進行測試（例如，將警告設定為引發例外，並檢查操作是否引發例外；檢查警告串列的長度在每次操作後是否持續增加；或者在每次新操作前從警告串列中刪除先前的條目）。

為新版相依套件更新程式碼

主要針對 Python 開發者（而非以 Python 編寫的應用程式的終端使用者）的警告類別預設會被忽略。

值得注意的是，這個「預設忽略」串列包括 DeprecationWarning（除了 __main__ 以外的所有模組），這意味著開發者應該確保在測試他們的程式碼時，讓通常被忽略的警告可見，以便及時收到未來 API 破壞性變更的通知（無論是在標準函式庫還是第三方套件中）。

在理想情況下，程式碼會有一個合適的測試套件，而測試執行器會在執行測試時負責隱式地啟用所有警告（unittest 模組提供的測試執行器就是這樣做的）。

在較不理想的情況下，可以透過將 -Wd 傳遞給 Python 直譯器（這是 -W default 的簡寫）或在環境中設定 PYTHONWARNINGS=default 來檢查應用程式是否使用了已棄用的介面。這會為所有警告啟用預設處理，包括那些預設被忽略的警告。要更改對遇到的警告所採取的動作，你可以更改傳遞給 -W 的引數（例如 -W error）。有關更多可能性的詳細資訊，請參閱 -W 旗標。

可用的函式

warnings.warn(message, category=None, stacklevel=1, source=None, *, skip_file_prefixes=())

發出一個警告，或者可能忽略它或引發一個例外。category 引數（如果提供）必須是一個 警告類別；它預設為 UserWarning。或者，message 可以是一個 Warning 實例，在這種情況下 category 將被忽略，並使用 message.__class__。在這種情況下，訊息文本將是 str(message)。如果發出的特定警告被 警告過濾器 轉為錯誤，此函式會引發一個例外。stacklevel 引數可以被以 Python 編寫的包裝函式使用，如下所示：

def deprecated_api(message):
    warnings.warn(message, DeprecationWarning, stacklevel=2)

這會讓警告指向 deprecated_api 的呼叫者，而不是 deprecated_api 本身的原始碼（因為後者會違背警告訊息的目的）。

skip_file_prefixes 關鍵字引數可用於指示在計算堆疊層級時應忽略哪些堆疊框。當你希望警告總是在套件外部的呼叫點出現，而固定的 stacklevel 不適用於所有呼叫路徑或難以維護時，這會很有用。如果提供，它必須是一個字串的元組。當提供前綴時，stacklevel 會被隱式地覆寫為 max(2, stacklevel)。要讓警告歸因於目前套件外部的呼叫者，你可以這樣寫：

# example/lower.py
_warn_skips = (os.path.dirname(__file__),)

def one_way(r_luxury_yacht=None, t_wobbler_mangrove=None):
    if r_luxury_yacht:
        warnings.warn("Please migrate to t_wobbler_mangrove=.",
                      skip_file_prefixes=_warn_skips)

# example/higher.py
from . import lower

def another_way(**kw):
    lower.one_way(**kw)

這使得警告只會從存在於 example 套件之外的呼叫程式碼中，指向 example.lower.one_way() 和 example.higher.another_way() 的呼叫點。

source（如果提供）是發出 ResourceWarning 的已銷毀物件。

在 3.6 版的變更: 新增 source 參數。

在 3.12 版的變更: 新增 skip_file_prefixes。

warnings.warn_explicit(message, category, filename, lineno, module=None, registry=None, module_globals=None, source=None)

這是一個 warn() 功能的低階介面，明確傳入訊息、類別、檔名和行號，以及可選的其他引數。message 必須是字串，category 必須是 Warning 的子類別，或者 message 可以是 Warning 的實例，在這種情況下 category 將被忽略。

module, if supplied, should be the module name. If no module is passed, the filename with .py stripped is used.

registry, if supplied, should be the __warningregistry__ dictionary of the module. If no registry is passed, each warning is treated as the first occurrence, that is, filter actions "default", "module" and "once" are handled as "always".

module_globals（如果提供）應該是發出警告的程式碼所使用的全域命名空間。（此引數用於支援顯示在 zip 檔案或其他非檔案系統引入來源中找到的模組的原始碼）。

source（如果提供）是發出 ResourceWarning 的已銷毀物件。

在 3.6 版的變更: 新增 source 參數。

warnings.showwarning(message, category, filename, lineno, file=None, line=None)

將警告寫入一個檔案。預設實作會呼叫 formatwarning(message, category, filename, lineno, line) 並將結果字串寫入 file，預設為 sys.stderr。你可以透過賦值給 warnings.showwarning 來用任何可呼叫物件取代此函式。line 是要包含在警告訊息中的一行原始碼；如果未提供 line，showwarning() 將嘗試讀取由 filename 和 lineno 指定的行。

warnings.formatwarning(message, category, filename, lineno, line=None)

以標準方式格式化警告。這會回傳一個可能包含嵌入換行符並以換行符結尾的字串。line 是要包含在警告訊息中的一行原始碼；如果未提供 line，formatwarning() 將嘗試讀取由 filename 和 lineno 指定的行。

warnings.filterwarnings(action, message='', category=Warning, module='', lineno=0, append=False)

在 警告過濾器規格 串列中插入一個條目。預設情況下，條目會插入到最前面；如果 append 為 true，則會插入到最後面。這會檢查引數的型別，編譯 message 和 module 的正規表示式，並將它們作為一個元組插入到警告過濾器串列中。如果兩個條目都匹配一個特定的警告，那麼串列中較靠前的條目會覆寫較後面的條目。省略的引數預設為一個能匹配所有內容的值。

warnings.simplefilter(action, category=Warning, lineno=0, append=False)

在 警告過濾器規格 串列中插入一個簡單的條目。函式參數的含義與 filterwarnings() 相同，但不需要正規表示式，因為只要類別和行號匹配，插入的過濾器總是會匹配任何模組中的任何訊息。

warnings.resetwarnings()

重設警告過濾器。這會捨棄所有先前對 filterwarnings() 的呼叫效果，包括 -W 命令列選項和對 simplefilter() 的呼叫。

@warnings.deprecated(msg, *, category=DeprecationWarning, stacklevel=1)

用來指示一個類別、函式或重載 (overload) 已被棄用的裝飾器。

當此裝飾器應用於一個物件時，在使用該物件時，可能會在 runtime 發出棄用警告。靜態型別檢查器 也會在使用已棄用物件時產生診斷訊息。

用法：

from warnings import deprecated
from typing import overload

@deprecated("改用 B")
class A:
    pass

@deprecated("改用 g")
def f():
    pass

@overload
@deprecated("對 int 的支援已棄用")
def g(x: int) -> int: ...
@overload
def g(x: str) -> int: ...

由 category 指定的警告將在使用已棄用物件時於 runtime 發出。對於函式，這發生在呼叫時；對於類別，發生在實例化和建立子類別時。如果 category 是 None，則在 runtime 不會發出警告。stacklevel 決定了警告發出的位置。如果它是 1（預設值），警告會在已棄用物件的直接呼叫者處發出；如果更高，它會在堆疊的更上層發出。靜態型別檢查器的行為不受 category 和 stacklevel 引數的影響。

傳遞給裝飾器的棄用訊息會儲存在被裝飾物件的 __deprecated__ 屬性中。如果應用於重載，裝飾器必須在 @~typing.overload 裝飾器之後，這樣屬性才會存在於 typing.get_overloads() 回傳的重載上。

在 3.13 版被加入: 參閱 PEP 702 [https://peps.python.org/pep-0702/]。

可用的情境管理器

class warnings.catch_warnings(*, record=False, module=None, action=None, category=Warning, lineno=0, append=False)

一個情境管理器，它會複製並在退出時恢復警告過濾器和 showwarning() 函式。如果 record 引數為 False（預設值），情境管理器在進入時回傳 None。如果 record 為 True，則會回傳一個串列，該串列會由自訂的 showwarning() 函式（該函式也會抑制對 sys.stdout 的輸出）所看到的物件逐步填充。串列中的每個物件都具有與 showwarning() 的引數同名的屬性。

module 引數接受一個模組，用以取代預設的 warnings 模組，而該（被傳入）模組的過濾器將會受到保護。此引數主要用於測試 warnings 模組本身。

如果 action 引數不是 None，則其餘引數會傳遞給 simplefilter()，就像在進入情境時立即呼叫它一樣。

有關 category 和 lineno 參數的含義，請參閱 警告過濾器。

備註

See 情境管理器的並行安全性 for details on the concurrency-safety of the catch_warnings context manager when used in programs using multiple threads or async functions.

在 3.11 版的變更: 新增 action、category、lineno 和 append 參數。

情境管理器的並行安全性

The behavior of catch_warnings context manager depends on the sys.flags.context_aware_warnings flag. If the flag is true, the context manager behaves in a concurrent-safe fashion and otherwise not. Concurrent-safe means that it is both thread-safe and safe to use within asyncio coroutines and tasks. Being thread-safe means that behavior is predictable in a multi-threaded program. The flag defaults to true for free-threaded builds and false otherwise.

If the context_aware_warnings flag is false, then catch_warnings will modify the global attributes of the warnings module. This is not safe if used within a concurrent program (using multiple threads or using asyncio coroutines). For example, if two or more threads use the catch_warnings class at the same time, the behavior is undefined.

If the flag is true, catch_warnings will not modify global attributes and will instead use a ContextVar to store the newly established warning filtering state. A context variable provides thread-local storage and it makes the use of catch_warnings thread-safe.

The record parameter of the context handler also behaves differently depending on the value of the flag. When record is true and the flag is false, the context manager works by replacing and then later restoring the module's showwarning() function. That is not concurrent-safe.

When record is true and the flag is true, the showwarning() function is not replaced. Instead, the recording status is indicated by an internal property in the context variable. In this case, the showwarning() function will not be restored when exiting the context handler.

The context_aware_warnings flag can be set the -X context_aware_warnings command-line option or by the PYTHON_CONTEXT_AWARE_WARNINGS environment variable.

備註

It is likely that most programs that desire thread-safe behaviour of the warnings module will also want to set the thread_inherit_context flag to true. That flag causes threads created by threading.Thread to start with a copy of the context variables from the thread starting it. When true, the context established by catch_warnings in one thread will also apply to new threads started by it. If false, new threads will start with an empty warnings context variable, meaning that any filtering that was established by a catch_warnings context manager will no longer be active.

在 3.14 版的變更: 新增了 sys.flags.context_aware_warnings 旗標，以及在該旗標為 true 時用於 catch_warnings 的情境變數。先前 Python 版本的行為就像該旗標始終設置為 false 一樣。

dataclasses --- Data Classes

原始碼：Lib/dataclasses.py [https://github.com/python/cpython/tree/3.14/Lib/dataclasses.py]

This module provides a decorator and functions for automatically adding generated special methods such as __init__() and __repr__() to user-defined classes. It was originally described in PEP 557 [https://peps.python.org/pep-0557/].

The member variables to use in these generated methods are defined using PEP 526 [https://peps.python.org/pep-0526/] type annotations. For example, this code:

from dataclasses import dataclass

@dataclass
class InventoryItem:
    """Class for keeping track of an item in inventory."""
    name: str
    unit_price: float
    quantity_on_hand: int = 0

    def total_cost(self) -> float:
        return self.unit_price * self.quantity_on_hand

will add, among other things, a __init__() that looks like:

def __init__(self, name: str, unit_price: float, quantity_on_hand: int = 0):
    self.name = name
    self.unit_price = unit_price
    self.quantity_on_hand = quantity_on_hand

Note that this method is automatically added to the class: it is not directly specified in the InventoryItem definition shown above.

在 3.7 版被加入.

模組內容

@dataclasses.dataclass(*, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False, match_args=True, kw_only=False, slots=False, weakref_slot=False)

This function is a decorator that is used to add generated special methods to classes, as described below.

The @dataclass decorator examines the class to find fields. A field is defined as a class variable that has a type annotation. With two exceptions described below, nothing in @dataclass examines the type specified in the variable annotation.

The order of the fields in all of the generated methods is the order in which they appear in the class definition.

如下所述，@dataclass 裝飾器會向類別新增各種 "dunder" 方法。如果類別中已存在任何新增的方法，則行為會取決於參數，如下方文件所述。裝飾器會回傳呼叫它的同一個類別；不會建立新類別。

If @dataclass is used just as a simple decorator with no parameters, it acts as if it has the default values documented in this signature. That is, these three uses of @dataclass are equivalent:

@dataclass
class C:
    ...

@dataclass()
class C:
    ...

@dataclass(init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False,
           match_args=True, kw_only=False, slots=False, weakref_slot=False)
class C:
    ...

@dataclass 的參數是：

init：如果為真（預設值），將生成一個 __init__() 方法。

如果該類別已經定義了 __init__()，則此參數會被忽略。

repr: If true (the default), a __repr__() method will be generated. The generated repr string will have the class name and the name and repr of each field, in the order they are defined in the class. Fields that are marked as being excluded from the repr are not included. For example: InventoryItem(name='widget', unit_price=3.0, quantity_on_hand=10).

如果該類別已經定義了 __repr__()，則此參數會被忽略。

eq: If true (the default), an __eq__() method will be generated. This method compares the class as if it were a tuple of its fields, in order. Both instances in the comparison must be of the identical type.

如果該類別已經定義了 __eq__()，則此參數會被忽略。

order: If true (the default is False), __lt__(), __le__(), __gt__(), and __ge__() methods will be generated. These compare the class as if it were a tuple of its fields, in order. Both instances in the comparison must be of the identical type. If order is true and eq is false, a ValueError is raised.

如果該類別已經定義了 __lt__()、__le__()、__gt__() 或 __ge__() 中的任何一個，則引發 TypeError。

unsafe_hash: If true, force dataclasses to create a __hash__() method, even though it may not be safe to do so. Otherwise, generate a __hash__() method according to how eq and frozen are set. The default value is False.

__hash__() is used by built-in hash(), and when objects are added to hashed collections such as dictionaries and sets. Having a __hash__() implies that instances of the class are immutable. Mutability is a complicated property that depends on the programmer's intent, the existence and behavior of __eq__(), and the values of the eq and frozen flags in the @dataclass decorator.

By default, @dataclass will not implicitly add a __hash__() method unless it is safe to do so. Neither will it add or change an existing explicitly defined __hash__() method. Setting the class attribute __hash__ = None has a specific meaning to Python, as described in the __hash__() documentation.

If __hash__() is not explicitly defined, or if it is set to None, then @dataclass may add an implicit __hash__() method. Although not recommended, you can force @dataclass to create a __hash__() method with unsafe_hash=True. This might be the case if your class is logically immutable but can still be mutated. This is a specialized use case and should be considered carefully.

Here are the rules governing implicit creation of a __hash__() method. Note that you cannot both have an explicit __hash__() method in your dataclass and set unsafe_hash=True; this will result in a TypeError.

如果 eq 和 frozen 都為真，預設情況下 @dataclass 會為你生成一個 __hash__() 方法。如果 eq 為真且 frozen 為假，__hash__() 將被設定為 None，並將其標記為不可雜湊（因為它是可變的）。如果 eq 為假，__hash__() 將保持不變，這意味著將使用超類別的 __hash__() 方法（如果超類別是 object，這意味著它將回退到基於 id 的雜湊）。

frozen: If true (the default is False), assigning to fields will generate an exception. This emulates read-only frozen instances. See the discussion below.

如果類別中定義了 __setattr__() 或 __delattr__() 且 frozen 為真，則會引發 TypeError。

match_args: If true (the default is True), the __match_args__ tuple will be created from the list of non keyword-only parameters to the generated __init__() method (even if __init__() is not generated, see above). If false, or if __match_args__ is already defined in the class, then __match_args__ will not be generated.

在 3.10 版被加入.

kw_only: If true (the default value is False), then all fields will be marked as keyword-only. If a field is marked as keyword-only, then the only effect is that the __init__() parameter generated from a keyword-only field must be specified with a keyword when __init__() is called. See the parameter glossary entry for details. Also see the KW_ONLY section.

Keyword-only fields are not included in __match_args__.

在 3.10 版被加入.

slots: If true (the default is False), __slots__ attribute will be generated and new class will be returned instead of the original one. If __slots__ is already defined in the class, then TypeError is raised.

警告

Passing parameters to a base class __init_subclass__() when using slots=True will result in a TypeError. Either use __init_subclass__ with no parameters or use default values as a workaround. See gh-91126 [https://github.com/python/cpython/issues/91126] for full details.

在 3.10 版被加入.

在 3.11 版的變更: If a field name is already included in the __slots__ of a base class, it will not be included in the generated __slots__ to prevent overriding them. Therefore, do not use __slots__ to retrieve the field names of a dataclass. Use fields() instead. To be able to determine inherited slots, base class __slots__ may be any iterable, but not an iterator.

weakref_slot: If true (the default is False), add a slot named "__weakref__", which is required to make an instance weakref-able. It is an error to specify weakref_slot=True without also specifying slots=True.

在 3.11 版被加入.

fields may optionally specify a default value, using normal Python syntax:

@dataclass
class C:
    a: int       # 'a' has no default value
    b: int = 0   # assign a default value for 'b'

In this example, both a and b will be included in the added __init__() method, which will be defined as:

def __init__(self, a: int, b: int = 0):

TypeError will be raised if a field without a default value follows a field with a default value. This is true whether this occurs in a single class, or as a result of class inheritance.

dataclasses.field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, hash=None, compare=True, metadata=None, kw_only=MISSING, doc=None)

For common and simple use cases, no other functionality is required. There are, however, some dataclass features that require additional per-field information. To satisfy this need for additional information, you can replace the default field value with a call to the provided field() function. For example:

@dataclass
class C:
    mylist: list[int] = field(default_factory=list)

c = C()
c.mylist += [1, 2, 3]

As shown above, the MISSING value is a sentinel object used to detect if some parameters are provided by the user. This sentinel is used because None is a valid value for some parameters with a distinct meaning. No code should directly use the MISSING value.

field() 的參數是：

default：如果有提供，這將是該欄位的預設值。這是必需的，因為 field() 呼叫本身會替換預設值的正常位置。

default_factory: If provided, it must be a zero-argument callable that will be called when a default value is needed for this field. Among other purposes, this can be used to specify fields with mutable default values, as discussed below. It is an error to specify both default and default_factory.

init: If true (the default), this field is included as a parameter to the generated __init__() method.

repr: If true (the default), this field is included in the string returned by the generated __repr__() method.

hash: This can be a bool or None. If true, this field is included in the generated __hash__() method. If false, this field is excluded from the generated __hash__(). If None (the default), use the value of compare: this would normally be the expected behavior, since a field should be included in the hash if it's used for comparisons. Setting this value to anything other than None is discouraged.

One possible reason to set hash=False but compare=True would be if a field is expensive to compute a hash value for, that field is needed for equality testing, and there are other fields that contribute to the type's hash value. Even if a field is excluded from the hash, it will still be used for comparisons.

compare: If true (the default), this field is included in the generated equality and comparison methods (__eq__(), __gt__(), et al.).

metadata: This can be a mapping or None. None is treated as an empty dict. This value is wrapped in MappingProxyType() to make it read-only, and exposed on the Field object. It is not used at all by Data Classes, and is provided as a third-party extension mechanism. Multiple third-parties can each have their own key, to use as a namespace in the metadata.

kw_only: If true, this field will be marked as keyword-only. This is used when the generated __init__() method's parameters are computed.

Keyword-only fields are also not included in __match_args__.

在 3.10 版被加入.

doc: optional docstring for this field.

在 3.14 版被加入.

If the default value of a field is specified by a call to field(), then the class attribute for this field will be replaced by the specified default value. If default is not provided, then the class attribute will be deleted. The intent is that after the @dataclass decorator runs, the class attributes will all contain the default values for the fields, just as if the default value itself were specified. For example, after:

@dataclass
class C:
    x: int
    y: int = field(repr=False)
    z: int = field(repr=False, default=10)
    t: int = 20

The class attribute C.z will be 10, the class attribute C.t will be 20, and the class attributes C.x and C.y will not be set.

class dataclasses.Field

Field objects describe each defined field. These objects are created internally, and are returned by the fields() module-level method (see below). Users should never instantiate a Field object directly. Its documented attributes are:

name：欄位的名稱。

type：欄位的型別。

default, default_factory, init, repr, hash, compare, metadata, and kw_only have the identical meaning and values as they do in the field() function.

Other attributes may exist, but they are private and must not be inspected or relied on.

class dataclasses.InitVar

InitVar[T] type annotations describe variables that are init-only. Fields annotated with InitVar are considered pseudo-fields, and thus are neither returned by the fields() function nor used in any way except adding them as parameters to __init__() and an optional __post_init__().

dataclasses.fields(class_or_instance)

Returns a tuple of Field objects that define the fields for this dataclass. Accepts either a dataclass, or an instance of a dataclass. Raises TypeError if not passed a dataclass or instance of one. Does not return pseudo-fields which are ClassVar or InitVar.

dataclasses.asdict(obj, *, dict_factory=dict)

Converts the dataclass obj to a dict (by using the factory function dict_factory). Each dataclass is converted to a dict of its fields, as name: value pairs. dataclasses, dicts, lists, and tuples are recursed into. Other objects are copied with copy.deepcopy().

Example of using asdict() on nested dataclasses:

@dataclass
class Point:
     x: int
     y: int

@dataclass
class C:
     mylist: list[Point]

p = Point(10, 20)
assert asdict(p) == {'x': 10, 'y': 20}

c = C([Point(0, 0), Point(10, 4)])
assert asdict(c) == {'mylist': [{'x': 0, 'y': 0}, {'x': 10, 'y': 4}]}

To create a shallow copy, the following workaround may be used:

{field.name: getattr(obj, field.name) for field in fields(obj)}

asdict() raises TypeError if obj is not a dataclass instance.

dataclasses.astuple(obj, *, tuple_factory=tuple)

Converts the dataclass obj to a tuple (by using the factory function tuple_factory). Each dataclass is converted to a tuple of its field values. dataclasses, dicts, lists, and tuples are recursed into. Other objects are copied with copy.deepcopy().

從前面的例子繼續：

assert astuple(p) == (10, 20)
assert astuple(c) == ([(0, 0), (10, 4)],)

To create a shallow copy, the following workaround may be used:

tuple(getattr(obj, field.name) for field in dataclasses.fields(obj))

astuple() raises TypeError if obj is not a dataclass instance.

dataclasses.make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False, match_args=True, kw_only=False, slots=False, weakref_slot=False, module=None, decorator=dataclass)

Creates a new dataclass with name cls_name, fields as defined in fields, base classes as given in bases, and initialized with a namespace as given in namespace. fields is an iterable whose elements are each either name, (name, type), or (name, type, Field). If just name is supplied, typing.Any is used for type. The values of init, repr, eq, order, unsafe_hash, frozen, match_args, kw_only, slots, and weakref_slot have the same meaning as they do in @dataclass.

If module is defined, the __module__ attribute of the dataclass is set to that value. By default, it is set to the module name of the caller.

The decorator parameter is a callable that will be used to create the dataclass. It should take the class object as a first argument and the same keyword arguments as @dataclass. By default, the @dataclass function is used.

This function is not strictly required, because any Python mechanism for creating a new class with __annotations__ can then apply the @dataclass function to convert that class to a dataclass. This function is provided as a convenience. For example:

C = make_dataclass('C',
                   [('x', int),
                     'y',
                    ('z', int, field(default=5))],
                   namespace={'add_one': lambda self: self.x + 1})

相當於：

@dataclass
class C:
    x: int
    y: 'typing.Any'
    z: int = 5

    def add_one(self):
        return self.x + 1

在 3.14 版被加入: 新增了 decorator 參數。

dataclasses.replace(obj, /, **changes)

建立一個與 obj 型別相同的新物件，並用 changes 中的值替換欄位。如果 obj 不是資料類別則引發 TypeError。如果 changes 中的鍵不是給定 dataclass 的欄位則引發 TypeError。

The newly returned object is created by calling the __init__() method of the dataclass. This ensures that __post_init__(), if present, is also called.

Init-only variables without default values, if any exist, must be specified on the call to replace() so that they can be passed to __init__() and __post_init__().

It is an error for changes to contain any fields that are defined as having init=False. A ValueError will be raised in this case.

Be forewarned about how init=False fields work during a call to replace(). They are not copied from the source object, but rather are initialized in __post_init__(), if they're initialized at all. It is expected that init=False fields will be rarely and judiciously used. If they are used, it might be wise to have alternate class constructors, or perhaps a custom replace() (or similarly named) method which handles instance copying.

Dataclass instances are also supported by generic function copy.replace().

dataclasses.is_dataclass(obj)

如果它的參數是一個資料類別（包含一個資料類別的子類別）或一個實例則回傳 True，否則回傳 False。

If you need to know if a class is an instance of a dataclass (and not a dataclass itself), then add a further check for not isinstance(obj, type):

def is_dataclass_instance(obj):
    return is_dataclass(obj) and not isinstance(obj, type)

dataclasses.MISSING

A sentinel value signifying a missing default or default_factory.

dataclasses.KW_ONLY

A sentinel value used as a type annotation. Any fields after a pseudo-field with the type of KW_ONLY are marked as keyword-only fields. Note that a pseudo-field of type KW_ONLY is otherwise completely ignored. This includes the name of such a field. By convention, a name of _ is used for a KW_ONLY field. Keyword-only fields signify __init__() parameters that must be specified as keywords when the class is instantiated.

In this example, the fields y and z will be marked as keyword-only fields:

@dataclass
class Point:
    x: float
    _: KW_ONLY
    y: float
    z: float

p = Point(0, y=1.5, z=2.0)

In a single dataclass, it is an error to specify more than one field whose type is KW_ONLY.

在 3.10 版被加入.

exception dataclasses.FrozenInstanceError

Raised when an implicitly defined __setattr__() or __delattr__() is called on a dataclass which was defined with frozen=True. It is a subclass of AttributeError.

Post-init processing

dataclasses.__post_init__()

When defined on the class, it will be called by the generated __init__(), normally as self.__post_init__(). However, if any InitVar fields are defined, they will also be passed to __post_init__() in the order they were defined in the class. If no __init__() method is generated, then __post_init__() will not automatically be called.

Among other uses, this allows for initializing field values that depend on one or more other fields. For example:

@dataclass
class C:
    a: float
    b: float
    c: float = field(init=False)

    def __post_init__(self):
        self.c = self.a + self.b

The __init__() method generated by @dataclass does not call base class __init__() methods. If the base class has an __init__() method that has to be called, it is common to call this method in a __post_init__() method:

class Rectangle:
    def __init__(self, height, width):
        self.height = height
        self.width = width

@dataclass
class Square(Rectangle):
    side: float

    def __post_init__(self):
        super().__init__(self.side, self.side)

Note, however, that in general the dataclass-generated __init__() methods don't need to be called, since the derived dataclass will take care of initializing all fields of any base class that is a dataclass itself.

See the section below on init-only variables for ways to pass parameters to __post_init__(). Also see the warning about how replace() handles init=False fields.

類別變數

One of the few places where @dataclass actually inspects the type of a field is to determine if a field is a class variable as defined in PEP 526 [https://peps.python.org/pep-0526/]. It does this by checking if the type of the field is typing.ClassVar. If a field is a ClassVar, it is excluded from consideration as a field and is ignored by the dataclass mechanisms. Such ClassVar pseudo-fields are not returned by the module-level fields() function.

Init-only variables

Another place where @dataclass inspects a type annotation is to determine if a field is an init-only variable. It does this by seeing if the type of a field is of type InitVar. If a field is an InitVar, it is considered a pseudo-field called an init-only field. As it is not a true field, it is not returned by the module-level fields() function. Init-only fields are added as parameters to the generated __init__() method, and are passed to the optional __post_init__() method. They are not otherwise used by dataclasses.

For example, suppose a field will be initialized from a database, if a value is not provided when creating the class:

@dataclass
class C:
    i: int
    j: int | None = None
    database: InitVar[DatabaseType | None] = None

    def __post_init__(self, database):
        if self.j is None and database is not None:
            self.j = database.lookup('j')

c = C(10, database=my_database)

In this case, fields() will return Field objects for i and j, but not for database.

凍結實例

It is not possible to create truly immutable Python objects. However, by passing frozen=True to the @dataclass decorator you can emulate immutability. In that case, dataclasses will add __setattr__() and __delattr__() methods to the class. These methods will raise a FrozenInstanceError when invoked.

There is a tiny performance penalty when using frozen=True: __init__() cannot use simple assignment to initialize fields, and must use object.__setattr__().

繼承

When the dataclass is being created by the @dataclass decorator, it looks through all of the class's base classes in reverse MRO (that is, starting at object) and, for each dataclass that it finds, adds the fields from that base class to an ordered mapping of fields. After all of the base class fields are added, it adds its own fields to the ordered mapping. All of the generated methods will use this combined, calculated ordered mapping of fields. Because the fields are in insertion order, derived classes override base classes. An example:

@dataclass
class Base:
    x: Any = 15.0
    y: int = 0

@dataclass
class C(Base):
    z: int = 10
    x: int = 15

The final list of fields is, in order, x, y, z. The final type of x is int, as specified in class C.

The generated __init__() method for C will look like:

def __init__(self, x: int = 15, y: int = 0, z: int = 10):

Re-ordering of keyword-only parameters in __init__()

After the parameters needed for __init__() are computed, any keyword-only parameters are moved to come after all regular (non-keyword-only) parameters. This is a requirement of how keyword-only parameters are implemented in Python: they must come after non-keyword-only parameters.

In this example, Base.y, Base.w, and D.t are keyword-only fields, and Base.x and D.z are regular fields:

@dataclass
class Base:
    x: Any = 15.0
    _: KW_ONLY
    y: int = 0
    w: int = 1

@dataclass
class D(Base):
    z: int = 10
    t: int = field(kw_only=True, default=0)

The generated __init__() method for D will look like:

def __init__(self, x: Any = 15.0, z: int = 10, *, y: int = 0, w: int = 1, t: int = 0):

Note that the parameters have been re-ordered from how they appear in the list of fields: parameters derived from regular fields are followed by parameters derived from keyword-only fields.

The relative ordering of keyword-only parameters is maintained in the re-ordered __init__() parameter list.

預設工廠函式

If a field() specifies a default_factory, it is called with zero arguments when a default value for the field is needed. For example, to create a new instance of a list, use:

mylist: list = field(default_factory=list)

If a field is excluded from __init__() (using init=False) and the field also specifies default_factory, then the default factory function will always be called from the generated __init__() function. This happens because there is no other way to give the field an initial value.

可變預設值

Python stores default member variable values in class attributes. Consider this example, not using dataclasses:

class C:
    x = []
    def add(self, element):
        self.x.append(element)

o1 = C()
o2 = C()
o1.add(1)
o2.add(2)
assert o1.x == [1, 2]
assert o1.x is o2.x

Note that the two instances of class C share the same class variable x, as expected.

Using dataclasses, if this code was valid:

@dataclass
class D:
    x: list = []      # 這段程式碼會引發 ValueError
    def add(self, element):
        self.x.append(element)

它會生成類似的程式碼：

class D:
    x = []
    def __init__(self, x=x):
        self.x = x
    def add(self, element):
        self.x.append(element)

assert D().x is D().x

This has the same issue as the original example using class C. That is, two instances of class D that do not specify a value for x when creating a class instance will share the same copy of x. Because dataclasses just use normal Python class creation they also share this behavior. There is no general way for Data Classes to detect this condition. Instead, the @dataclass decorator will raise a ValueError if it detects an unhashable default parameter. The assumption is that if a value is unhashable, it is mutable. This is a partial solution, but it does protect against many common errors.

Using default factory functions is a way to create new instances of mutable types as default values for fields:

@dataclass
class D:
    x: list = field(default_factory=list)

assert D().x is not D().x

在 3.11 版的變更: Instead of looking for and disallowing objects of type list, dict, or set, unhashable objects are now not allowed as default values. Unhashability is used to approximate mutability.

Descriptor-typed fields

Fields that are assigned descriptor objects as their default value have the following special behaviors:

The value for the field passed to the dataclass's __init__() method is passed to the descriptor's __set__() method rather than overwriting the descriptor object.

Similarly, when getting or setting the field, the descriptor's __get__() or __set__() method is called rather than returning or overwriting the descriptor object.

To determine whether a field contains a default value, @dataclass will call the descriptor's __get__() method using its class access form: descriptor.__get__(obj=None, type=cls). If the descriptor returns a value in this case, it will be used as the field's default. On the other hand, if the descriptor raises AttributeError in this situation, no default value will be provided for the field.

class IntConversionDescriptor:
    def __init__(self, *, default):
        self._default = default

    def __set_name__(self, owner, name):
        self._name = "_" + name

    def __get__(self, obj, type):
        if obj is None:
            return self._default

        return getattr(obj, self._name, self._default)

    def __set__(self, obj, value):
        setattr(obj, self._name, int(value))

@dataclass
class InventoryItem:
    quantity_on_hand: IntConversionDescriptor = IntConversionDescriptor(default=100)

i = InventoryItem()
print(i.quantity_on_hand)   # 100
i.quantity_on_hand = 2.5    # 以 2.5 呼叫 __set__
print(i.quantity_on_hand)   # 2

Note that if a field is annotated with a descriptor type, but is not assigned a descriptor object as its default value, the field will act like a normal field.

contextlib --- with 陳述式工具程式

原始碼：Lib/contextlib.py [https://github.com/python/cpython/tree/3.14/Lib/contextlib.py]

This module provides utilities for common tasks involving the with statement. For more information see also 情境管理器型別 and With 陳述式的情境管理器.

Utilities

Functions and classes provided:

class contextlib.AbstractContextManager

An abstract base class for classes that implement object.__enter__() and object.__exit__(). A default implementation for object.__enter__() is provided which returns self while object.__exit__() is an abstract method which by default returns None. See also the definition of 情境管理器型別.

在 3.6 版被加入.

class contextlib.AbstractAsyncContextManager

An abstract base class for classes that implement object.__aenter__() and object.__aexit__(). A default implementation for object.__aenter__() is provided which returns self while object.__aexit__() is an abstract method which by default returns None. See also the definition of Asynchronous Context Managers.

在 3.7 版被加入.

@contextlib.contextmanager

This function is a decorator that can be used to define a factory function for with statement context managers, without needing to create a class or separate __enter__() and __exit__() methods.

While many objects natively support use in with statements, sometimes a resource needs to be managed that isn't a context manager in its own right, and doesn't implement a close() method for use with contextlib.closing.

An abstract example would be the following to ensure correct resource management:

from contextlib import contextmanager

@contextmanager
def managed_resource(*args, **kwds):
    # Code to acquire resource, e.g.:
    resource = acquire_resource(*args, **kwds)
    try:
        yield resource
    finally:
        # Code to release resource, e.g.:
        release_resource(resource)

The function can then be used like this:

>>> with managed_resource(timeout=3600) as resource:
...     # Resource is released at the end of this block,
...     # even if code in the block raises an exception

The function being decorated must return a generator-iterator when called. This iterator must yield exactly one value, which will be bound to the targets in the with statement's as clause, if any.

At the point where the generator yields, the block nested in the with statement is executed. The generator is then resumed after the block is exited. If an unhandled exception occurs in the block, it is reraised inside the generator at the point where the yield occurred. Thus, you can use a try...except...finally statement to trap the error (if any), or ensure that some cleanup takes place. If an exception is trapped merely in order to log it or to perform some action (rather than to suppress it entirely), the generator must reraise that exception. Otherwise the generator context manager will indicate to the with statement that the exception has been handled, and execution will resume with the statement immediately following the with statement.

contextmanager() uses ContextDecorator so the context managers it creates can be used as decorators as well as in with statements. When used as a decorator, a new generator instance is implicitly created on each function call (this allows the otherwise "one-shot" context managers created by contextmanager() to meet the requirement that context managers support multiple invocations in order to be used as decorators).

在 3.2 版的變更: Use of ContextDecorator.

@contextlib.asynccontextmanager

Similar to contextmanager(), but creates an asynchronous context manager.

This function is a decorator that can be used to define a factory function for async with statement asynchronous context managers, without needing to create a class or separate __aenter__() and __aexit__() methods. It must be applied to an asynchronous generator function.

一個簡單範例：

from contextlib import asynccontextmanager

@asynccontextmanager
async def get_connection():
    conn = await acquire_db_connection()
    try:
        yield conn
    finally:
        await release_db_connection(conn)

async def get_all_users():
    async with get_connection() as conn:
        return conn.query('SELECT ...')

在 3.7 版被加入.

Context managers defined with asynccontextmanager() can be used either as decorators or with async with statements:

import time
from contextlib import asynccontextmanager

@asynccontextmanager
async def timeit():
    now = time.monotonic()
    try:
        yield
    finally:
        print(f'it took {time.monotonic() - now}s to run')

@timeit()
async def main():
    # ... async code ...

When used as a decorator, a new generator instance is implicitly created on each function call. This allows the otherwise "one-shot" context managers created by asynccontextmanager() to meet the requirement that context managers support multiple invocations in order to be used as decorators.

在 3.10 版的變更: Async context managers created with asynccontextmanager() can be used as decorators.

contextlib.closing(thing)

Return a context manager that closes thing upon completion of the block. This is basically equivalent to:

from contextlib import contextmanager

@contextmanager
def closing(thing):
    try:
        yield thing
    finally:
        thing.close()

And lets you write code like this:

from contextlib import closing
from urllib.request import urlopen

with closing(urlopen('https://www.python.org')) as page:
    for line in page:
        print(line)

without needing to explicitly close page. Even if an error occurs, page.close() will be called when the with block is exited.

備註

Most types managing resources support the context manager protocol, which closes thing on leaving the with statement. As such, closing() is most useful for third party types that don't support context managers. This example is purely for illustration purposes, as urlopen() would normally be used in a context manager.

contextlib.aclosing(thing)

Return an async context manager that calls the aclose() method of thing upon completion of the block. This is basically equivalent to:

from contextlib import asynccontextmanager

@asynccontextmanager
async def aclosing(thing):
    try:
        yield thing
    finally:
        await thing.aclose()

Significantly, aclosing() supports deterministic cleanup of async generators when they happen to exit early by break or an exception. For example:

from contextlib import aclosing

async with aclosing(my_generator()) as values:
    async for value in values:
        if value == 42:
            break

This pattern ensures that the generator's async exit code is executed in the same context as its iterations (so that exceptions and context variables work as expected, and the exit code isn't run after the lifetime of some task it depends on).

在 3.10 版被加入.

contextlib.nullcontext(enter_result=None)

Return a context manager that returns enter_result from __enter__, but otherwise does nothing. It is intended to be used as a stand-in for an optional context manager, for example:

def myfunction(arg, ignore_exceptions=False):
    if ignore_exceptions:
        # Use suppress to ignore all exceptions.
        cm = contextlib.suppress(Exception)
    else:
        # Do not ignore any exceptions, cm has no effect.
        cm = contextlib.nullcontext()
    with cm:
        # Do something

一個使用 enter_result 的範例：

def process_file(file_or_path):
    if isinstance(file_or_path, str):
        # If string, open file
        cm = open(file_or_path)
    else:
        # Caller is responsible for closing file
        cm = nullcontext(file_or_path)

    with cm as file:
        # Perform processing on the file

It can also be used as a stand-in for asynchronous context managers:

async def send_http(session=None):
    if not session:
        # If no http session, create it with aiohttp
        cm = aiohttp.ClientSession()
    else:
        # Caller is responsible for closing the session
        cm = nullcontext(session)

    async with cm as session:
        # Send http requests with session

在 3.7 版被加入.

在 3.10 版的變更: asynchronous context manager support was added.

contextlib.suppress(*exceptions)

Return a context manager that suppresses any of the specified exceptions if they occur in the body of a with statement and then resumes execution with the first statement following the end of the with statement.

As with any other mechanism that completely suppresses exceptions, this context manager should be used only to cover very specific errors where silently continuing with program execution is known to be the right thing to do.

舉例來說：

from contextlib import suppress

with suppress(FileNotFoundError):
    os.remove('somefile.tmp')

with suppress(FileNotFoundError):
    os.remove('someotherfile.tmp')

This code is equivalent to:

try:
    os.remove('somefile.tmp')
except FileNotFoundError:
    pass

try:
    os.remove('someotherfile.tmp')
except FileNotFoundError:
    pass

This context manager is reentrant.

If the code within the with block raises a BaseExceptionGroup, suppressed exceptions are removed from the group. Any exceptions of the group which are not suppressed are re-raised in a new group which is created using the original group's derive() method.

在 3.4 版被加入.

在 3.12 版的變更: suppress now supports suppressing exceptions raised as part of a BaseExceptionGroup.

contextlib.redirect_stdout(new_target)

Context manager for temporarily redirecting sys.stdout to another file or file-like object.

This tool adds flexibility to existing functions or classes whose output is hardwired to stdout.

For example, the output of help() normally is sent to sys.stdout. You can capture that output in a string by redirecting the output to an io.StringIO object. The replacement stream is returned from the __enter__ method and so is available as the target of the with statement:

with redirect_stdout(io.StringIO()) as f:
    help(pow)
s = f.getvalue()

To send the output of help() to a file on disk, redirect the output to a regular file:

with open('help.txt', 'w') as f:
    with redirect_stdout(f):
        help(pow)

To send the output of help() to sys.stderr:

with redirect_stdout(sys.stderr):
    help(pow)

Note that the global side effect on sys.stdout means that this context manager is not suitable for use in library code and most threaded applications. It also has no effect on the output of subprocesses. However, it is still a useful approach for many utility scripts.

This context manager is reentrant.

在 3.4 版被加入.

contextlib.redirect_stderr(new_target)

Similar to redirect_stdout() but redirecting sys.stderr to another file or file-like object.

This context manager is reentrant.

在 3.5 版被加入.

contextlib.chdir(path)

Non parallel-safe context manager to change the current working directory. As this changes a global state, the working directory, it is not suitable for use in most threaded or async contexts. It is also not suitable for most non-linear code execution, like generators, where the program execution is temporarily relinquished -- unless explicitly desired, you should not yield when this context manager is active.

This is a simple wrapper around chdir(), it changes the current working directory upon entering and restores the old one on exit.

This context manager is reentrant.

在 3.11 版被加入.

class contextlib.ContextDecorator

A base class that enables a context manager to also be used as a decorator.

Context managers inheriting from ContextDecorator have to implement __enter__ and __exit__ as normal. __exit__ retains its optional exception handling even when used as a decorator.

ContextDecorator is used by contextmanager(), so you get this functionality automatically.

ContextDecorator 範例：

from contextlib import ContextDecorator

class mycontext(ContextDecorator):
    def __enter__(self):
        print('Starting')
        return self

    def __exit__(self, *exc):
        print('Finishing')
        return False

這個類別可以這樣使用：

>>> @mycontext()
... def function():
...     print('The bit in the middle')
...
>>> function()
Starting
The bit in the middle
Finishing

>>> with mycontext():
...     print('The bit in the middle')
...
Starting
The bit in the middle
Finishing

這個變更只是以下形式的語法糖：

def f():
    with cm():
        # Do stuff

ContextDecorator 讓你可以改寫成：

@cm()
def f():
    # Do stuff

It makes it clear that the cm applies to the whole function, rather than just a piece of it (and saving an indentation level is nice, too).

Existing context managers that already have a base class can be extended by using ContextDecorator as a mixin class:

from contextlib import ContextDecorator

class mycontext(ContextBaseClass, ContextDecorator):
    def __enter__(self):
        return self

    def __exit__(self, *exc):
        return False

備註

As the decorated function must be able to be called multiple times, the underlying context manager must support use in multiple with statements. If this is not the case, then the original construct with the explicit with statement inside the function should be used.

在 3.2 版被加入.

class contextlib.AsyncContextDecorator

和 ContextDecorator 類似，但僅用於非同步函式。

AsyncContextDecorator 範例：

from asyncio import run
from contextlib import AsyncContextDecorator

class mycontext(AsyncContextDecorator):
    async def __aenter__(self):
        print('Starting')
        return self

    async def __aexit__(self, *exc):
        print('Finishing')
        return False

這個類別可以這樣使用：

>>> @mycontext()
... async def function():
...     print('The bit in the middle')
...
>>> run(function())
Starting
The bit in the middle
Finishing

>>> async def function():
...    async with mycontext():
...         print('The bit in the middle')
...
>>> run(function())
Starting
The bit in the middle
Finishing

在 3.10 版被加入.

class contextlib.ExitStack

A context manager that is designed to make it easy to programmatically combine other context managers and cleanup functions, especially those that are optional or otherwise driven by input data.

For example, a set of files may easily be handled in a single with statement as follows:

with ExitStack() as stack:
    files = [stack.enter_context(open(fname)) for fname in filenames]
    # All opened files will automatically be closed at the end of
    # the with statement, even if attempts to open files later
    # in the list raise an exception

The __enter__() method returns the ExitStack instance, and performs no additional operations.

Each instance maintains a stack of registered callbacks that are called in reverse order when the instance is closed (either explicitly or implicitly at the end of a with statement). Note that callbacks are not invoked implicitly when the context stack instance is garbage collected.

This stack model is used so that context managers that acquire their resources in their __init__ method (such as file objects) can be handled correctly.

Since registered callbacks are invoked in the reverse order of registration, this ends up behaving as if multiple nested with statements had been used with the registered set of callbacks. This even extends to exception handling - if an inner callback suppresses or replaces an exception, then outer callbacks will be passed arguments based on that updated state.

This is a relatively low level API that takes care of the details of correctly unwinding the stack of exit callbacks. It provides a suitable foundation for higher level context managers that manipulate the exit stack in application specific ways.

在 3.3 版被加入.

enter_context(cm)

Enters a new context manager and adds its __exit__() method to the callback stack. The return value is the result of the context manager's own __enter__() method.

These context managers may suppress exceptions just as they normally would if used directly as part of a with statement.

在 3.11 版的變更: Raises TypeError instead of AttributeError if cm is not a context manager.

push(exit)

Adds a context manager's __exit__() method to the callback stack.

As __enter__ is not invoked, this method can be used to cover part of an __enter__() implementation with a context manager's own __exit__() method.

If passed an object that is not a context manager, this method assumes it is a callback with the same signature as a context manager's __exit__() method and adds it directly to the callback stack.

By returning true values, these callbacks can suppress exceptions the same way context manager __exit__() methods can.

The passed in object is returned from the function, allowing this method to be used as a function decorator.

callback(callback, /, *args, **kwds)

Accepts an arbitrary callback function and arguments and adds it to the callback stack.

Unlike the other methods, callbacks added this way cannot suppress exceptions (as they are never passed the exception details).

The passed in callback is returned from the function, allowing this method to be used as a function decorator.

pop_all()

Transfers the callback stack to a fresh ExitStack instance and returns it. No callbacks are invoked by this operation - instead, they will now be invoked when the new stack is closed (either explicitly or implicitly at the end of a with statement).

For example, a group of files can be opened as an "all or nothing" operation as follows:

with ExitStack() as stack:
    files = [stack.enter_context(open(fname)) for fname in filenames]
    # Hold onto the close method, but don't call it yet.
    close_files = stack.pop_all().close
    # If opening any file fails, all previously opened files will be
    # closed automatically. If all files are opened successfully,
    # they will remain open even after the with statement ends.
    # close_files() can then be invoked explicitly to close them all.

close()

Immediately unwinds the callback stack, invoking callbacks in the reverse order of registration. For any context managers and exit callbacks registered, the arguments passed in will indicate that no exception occurred.

class contextlib.AsyncExitStack

An asynchronous context manager, similar to ExitStack, that supports combining both synchronous and asynchronous context managers, as well as having coroutines for cleanup logic.

The close() method is not implemented; aclose() must be used instead.

async enter_async_context(cm)

Similar to ExitStack.enter_context() but expects an asynchronous context manager.

在 3.11 版的變更: Raises TypeError instead of AttributeError if cm is not an asynchronous context manager.

push_async_exit(exit)

Similar to ExitStack.push() but expects either an asynchronous context manager or a coroutine function.

push_async_callback(callback, /, *args, **kwds)

和 ExitStack.callback() 類似，但預期接受一個協程函式。

async aclose()

和 ExitStack.close() 類似，但能夠正確處理可等待物件。

延續 asynccontextmanager() 的範例：

async with AsyncExitStack() as stack:
    connections = [await stack.enter_async_context(get_connection())
        for i in range(5)]
    # All opened connections will automatically be released at the end of
    # the async with statement, even if attempts to open a connection
    # later in the list raise an exception.

在 3.7 版被加入.

Examples and Recipes

This section describes some examples and recipes for making effective use of the tools provided by contextlib.

Supporting a variable number of context managers

The primary use case for ExitStack is the one given in the class documentation: supporting a variable number of context managers and other cleanup operations in a single with statement. The variability may come from the number of context managers needed being driven by user input (such as opening a user specified collection of files), or from some of the context managers being optional:

with ExitStack() as stack:
    for resource in resources:
        stack.enter_context(resource)
    if need_special_resource():
        special = acquire_special_resource()
        stack.callback(release_special_resource, special)
    # Perform operations that use the acquired resources

As shown, ExitStack also makes it quite easy to use with statements to manage arbitrary resources that don't natively support the context management protocol.

Catching exceptions from __enter__ methods

It is occasionally desirable to catch exceptions from an __enter__ method implementation, without inadvertently catching exceptions from the with statement body or the context manager's __exit__ method. By using ExitStack the steps in the context management protocol can be separated slightly in order to allow this:

stack = ExitStack()
try:
    x = stack.enter_context(cm)
except Exception:
    # handle __enter__ exception
else:
    with stack:
        # Handle normal case

Actually needing to do this is likely to indicate that the underlying API should be providing a direct resource management interface for use with try/except/finally statements, but not all APIs are well designed in that regard. When a context manager is the only resource management API provided, then ExitStack can make it easier to handle various situations that can't be handled directly in a with statement.

Cleaning up in an __enter__ implementation

As noted in the documentation of ExitStack.push(), this method can be useful in cleaning up an already allocated resource if later steps in the __enter__() implementation fail.

Here's an example of doing this for a context manager that accepts resource acquisition and release functions, along with an optional validation function, and maps them to the context management protocol:

from contextlib import contextmanager, AbstractContextManager, ExitStack

class ResourceManager(AbstractContextManager):

    def __init__(self, acquire_resource, release_resource, check_resource_ok=None):
        self.acquire_resource = acquire_resource
        self.release_resource = release_resource
        if check_resource_ok is None:
            def check_resource_ok(resource):
                return True
        self.check_resource_ok = check_resource_ok

    @contextmanager
    def _cleanup_on_error(self):
        with ExitStack() as stack:
            stack.push(self)
            yield
            # The validation check passed and didn't raise an exception
            # Accordingly, we want to keep the resource, and pass it
            # back to our caller
            stack.pop_all()

    def __enter__(self):
        resource = self.acquire_resource()
        with self._cleanup_on_error():
            if not self.check_resource_ok(resource):
                msg = "Failed validation for {!r}"
                raise RuntimeError(msg.format(resource))
        return resource

    def __exit__(self, *exc_details):
        # We don't need to duplicate any of our resource release logic
        self.release_resource()

Replacing any use of try-finally and flag variables

A pattern you will sometimes see is a try-finally statement with a flag variable to indicate whether or not the body of the finally clause should be executed. In its simplest form (that can't already be handled just by using an except clause instead), it looks something like this:

cleanup_needed = True
try:
    result = perform_operation()
    if result:
        cleanup_needed = False
finally:
    if cleanup_needed:
        cleanup_resources()

As with any try statement based code, this can cause problems for development and review, because the setup code and the cleanup code can end up being separated by arbitrarily long sections of code.

ExitStack makes it possible to instead register a callback for execution at the end of a with statement, and then later decide to skip executing that callback:

from contextlib import ExitStack

with ExitStack() as stack:
    stack.callback(cleanup_resources)
    result = perform_operation()
    if result:
        stack.pop_all()

This allows the intended cleanup behaviour to be made explicit up front, rather than requiring a separate flag variable.

If a particular application uses this pattern a lot, it can be simplified even further by means of a small helper class:

from contextlib import ExitStack

class Callback(ExitStack):
    def __init__(self, callback, /, *args, **kwds):
        super().__init__()
        self.callback(callback, *args, **kwds)

    def cancel(self):
        self.pop_all()

with Callback(cleanup_resources) as cb:
    result = perform_operation()
    if result:
        cb.cancel()

If the resource cleanup isn't already neatly bundled into a standalone function, then it is still possible to use the decorator form of ExitStack.callback() to declare the resource cleanup in advance:

from contextlib import ExitStack

with ExitStack() as stack:
    @stack.callback
    def cleanup_resources():
        ...
    result = perform_operation()
    if result:
        stack.pop_all()

Due to the way the decorator protocol works, a callback function declared this way cannot take any parameters. Instead, any resources to be released must be accessed as closure variables.

Using a context manager as a function decorator

ContextDecorator makes it possible to use a context manager in both an ordinary with statement and also as a function decorator.

For example, it is sometimes useful to wrap functions or groups of statements with a logger that can track the time of entry and time of exit. Rather than writing both a function decorator and a context manager for the task, inheriting from ContextDecorator provides both capabilities in a single definition:

from contextlib import ContextDecorator
import logging

logging.basicConfig(level=logging.INFO)

class track_entry_and_exit(ContextDecorator):
    def __init__(self, name):
        self.name = name

    def __enter__(self):
        logging.info('Entering: %s', self.name)

    def __exit__(self, exc_type, exc, exc_tb):
        logging.info('Exiting: %s', self.name)

Instances of this class can be used as both a context manager:

with track_entry_and_exit('widget loader'):
    print('Some time consuming activity goes here')
    load_widget()

And also as a function decorator:

@track_entry_and_exit('widget loader')
def activity():
    print('Some time consuming activity goes here')
    load_widget()

Note that there is one additional limitation when using context managers as function decorators: there's no way to access the return value of __enter__(). If that value is needed, then it is still necessary to use an explicit with statement.

也參考

PEP 343 [https://peps.python.org/pep-0343/] - "with" 陳述式

The specification, background, and examples for the Python with statement.

Single use, reusable and reentrant context managers

Most context managers are written in a way that means they can only be used effectively in a with statement once. These single use context managers must be created afresh each time they're used - attempting to use them a second time will trigger an exception or otherwise not work correctly.

This common limitation means that it is generally advisable to create context managers directly in the header of the with statement where they are used (as shown in all of the usage examples above).

Files are an example of effectively single use context managers, since the first with statement will close the file, preventing any further IO operations using that file object.

Context managers created using contextmanager() are also single use context managers, and will complain about the underlying generator failing to yield if an attempt is made to use them a second time:

>>> from contextlib import contextmanager
>>> @contextmanager
... def singleuse():
...     print("Before")
...     yield
...     print("After")
...
>>> cm = singleuse()
>>> with cm:
...     pass
...
Before
After
>>> with cm:
...     pass
...
Traceback (most recent call last):
    ...
RuntimeError: generator didn't yield

Reentrant context managers

More sophisticated context managers may be "reentrant". These context managers can not only be used in multiple with statements, but may also be used inside a with statement that is already using the same context manager.

threading.RLock is an example of a reentrant context manager, as are suppress(), redirect_stdout(), and chdir(). Here's a very simple example of reentrant use:

>>> from contextlib import redirect_stdout
>>> from io import StringIO
>>> stream = StringIO()
>>> write_to_stream = redirect_stdout(stream)
>>> with write_to_stream:
...     print("This is written to the stream rather than stdout")
...     with write_to_stream:
...         print("This is also written to the stream")
...
>>> print("This is written directly to stdout")
This is written directly to stdout
>>> print(stream.getvalue())
This is written to the stream rather than stdout
This is also written to the stream

Real world examples of reentrancy are more likely to involve multiple functions calling each other and hence be far more complicated than this example.

Note also that being reentrant is not the same thing as being thread safe. redirect_stdout(), for example, is definitely not thread safe, as it makes a global modification to the system state by binding sys.stdout to a different stream.

Reusable context managers

Distinct from both single use and reentrant context managers are "reusable" context managers (or, to be completely explicit, "reusable, but not reentrant" context managers, since reentrant context managers are also reusable). These context managers support being used multiple times, but will fail (or otherwise not work correctly) if the specific context manager instance has already been used in a containing with statement.

threading.Lock is an example of a reusable, but not reentrant, context manager (for a reentrant lock, it is necessary to use threading.RLock instead).

Another example of a reusable, but not reentrant, context manager is ExitStack, as it invokes all currently registered callbacks when leaving any with statement, regardless of where those callbacks were added:

>>> from contextlib import ExitStack
>>> stack = ExitStack()
>>> with stack:
...     stack.callback(print, "Callback: from first context")
...     print("Leaving first context")
...
Leaving first context
Callback: from first context
>>> with stack:
...     stack.callback(print, "Callback: from second context")
...     print("Leaving second context")
...
Leaving second context
Callback: from second context
>>> with stack:
...     stack.callback(print, "Callback: from outer context")
...     with stack:
...         stack.callback(print, "Callback: from inner context")
...         print("Leaving inner context")
...     print("Leaving outer context")
...
Leaving inner context
Callback: from inner context
Callback: from outer context
Leaving outer context

As the output from the example shows, reusing a single stack object across multiple with statements works correctly, but attempting to nest them will cause the stack to be cleared at the end of the innermost with statement, which is unlikely to be desirable behaviour.

Using separate ExitStack instances instead of reusing a single instance avoids that problem:

>>> from contextlib import ExitStack
>>> with ExitStack() as outer_stack:
...     outer_stack.callback(print, "Callback: from outer context")
...     with ExitStack() as inner_stack:
...         inner_stack.callback(print, "Callback: from inner context")
...         print("Leaving inner context")
...     print("Leaving outer context")
...
Leaving inner context
Callback: from inner context
Leaving outer context
Callback: from outer context

abc --- 抽象基底類別

原始碼：Lib/abc.py [https://github.com/python/cpython/tree/3.14/Lib/abc.py]

如同在 PEP 3119 [https://peps.python.org/pep-3119/] 中所述，該模組提供了在 Python 中定義抽象基底類別 (ABC) 的基礎元件；若想瞭解為什麼需要在 Python 中增加這個模組，請見 PEP 文件。（也請見 PEP 3141 [https://peps.python.org/pep-3141/] 以及 numbers 模組以瞭解基於 ABC 的數字型別階層關係。）

collections 模組中有一些衍生自 ABC 的具體類別；當然這些類別還可以進一步衍生出其他類別。此外，collections.abc 子模組中有一些 ABC 可被用於測試一個類別或實例是否提供特定介面，例如它是否可雜湊 (hashable) 或它是否為對映。

該模組提供了一個用來定義 ABC 的元類別 (metaclass) ABCMeta 和另一個以繼承的方式定義 ABC 的工具類別 ABC：

class abc.ABC

一個使用 ABCMeta 作為元類別的工具類別。抽象基底類別可以透過自 ABC 衍生而建立，這就避免了在某些情況下會令人混淆的元類別用法，用法如以下範例：

from abc import ABC

class MyABC(ABC):
    pass

注意 ABC 的型別仍然是 ABCMeta，因此繼承 ABC 仍然需要關注使用元類別的注意事項，如多重繼承可能會導致元類別衝突。當然你也可以傳入元類別關鍵字並直接使用 ABCMeta 來定義一個抽象基底類別，例如：

from abc import ABCMeta

class MyABC(metaclass=ABCMeta):
    pass

在 3.4 版被加入.

class abc.ABCMeta

用於定義抽象基底類別（ABC）的元類別。

使用該元類別以建立一個 ABC。一個 ABC 可以像 mix-in 類別一樣直接被子類別繼承。你也可以將不相關的具體類別（甚至是內建類別）和 ABC 註冊為「虛擬子類別 (virtual subclass)」 —— 這些類別以及它們的子類別會被內建函式 issubclass() 識別為已註冊 ABC 的子類別，但是該 ABC 不會出現在其 MRO（Method Resolution Order，方法解析順序）中，由該 ABC 所定義的方法實作也不可呼叫（即使透過 super() 呼叫也不行）。[1]

使用 ABCMeta 作為元類別建立的類別含有以下的方法：

register(subclass)

將子類別註冊為該 ABC 的「抽象子類別」，例如：

from abc import ABC

class MyABC(ABC):
    pass

MyABC.register(tuple)

assert issubclass(tuple, MyABC)
assert isinstance((), MyABC)

在 3.3 版的變更: 回傳已註冊的子類別，使其能夠作為類別裝飾器。

在 3.4 版的變更: 你可以使用 get_cache_token() 函式來檢測對 register() 的呼叫。

你也可以覆寫 (override) 虛擬基底類別中的這個方法：

__subclasshook__(subclass)

（必須定義為類別方法。）

檢查 subclass 是否該被認為是該 ABC 的子類別，也就是說你可以直接自訂 issubclass() 的行為，而不用對於那些你希望定義為該 ABC 的子類別的類別都個別呼叫 register() 方法。（這個類別方法是在 ABC 的 __subclasscheck__() 方法中呼叫。）

此方法必須回傳 True、False 或是 NotImplemented。如果回傳 True，subclass 就會被認為是這個 ABC 的子類別。如果回傳 False，subclass 就會被判定並非該 ABC 的子類別，即便正常情況應如此。如果回傳 NotImplemented，子類別檢查會按照正常機制繼續執行。

為了對這些概念做一演示，請見以下定義 ABC 的範例：

class Foo:
    def __getitem__(self, index):
        ...
    def __len__(self):
        ...
    def get_iterator(self):
        return iter(self)

class MyIterable(ABC):

    @abstractmethod
    def __iter__(self):
        while False:
            yield None

    def get_iterator(self):
        return self.__iter__()

    @classmethod
    def __subclasshook__(cls, C):
        if cls is MyIterable:
            if any("__iter__" in B.__dict__ for B in C.__mro__):
                return True
        return NotImplemented

MyIterable.register(Foo)

ABC MyIterable 定義了作為抽象方法的一個標準疊代方法 __iter__()。這裡給定的實作仍可在子類別中被呼叫。get_iterator() 方法也是 MyIterable 抽象基底類別的一部分，但它不必被非抽象衍生類別覆寫。

這裡定義的 __subclasshook__() 類別方法說明任何在其 __dict__ (或在其透過 __mro__ 列表存取的基底類別) 中具有 __iter__() 方法的類別也都會被視為 MyIterable。

最後，即使 Foo 沒有定義 __iter__() 方法（它使用了以 __len__() 和 __getitem__() 所定義的舊式可疊代物件協定），最末一行使其成為 MyIterable 的一個虛擬子類別。請注意這不會使 get_iterator 成為 Foo 的一個可用方法，所以它是需要被另外提供的。

abc 模組也提供了這些裝飾器：

@abc.abstractmethod

用於表示抽象方法的裝飾器。

類別的元類別是 ABCMeta 或是從該類別衍生才能使用此裝飾器。一個具有衍生自 ABCMeta 之元類別的類別不可以被實例化，除非它全部的抽象方法和特性均已被覆寫。抽象方法可透過任何一般的 'super' 呼叫機制來呼叫。abstractmethod() 可被用於為特性和描述器宣告的抽象方法。

僅在使用 update_abstractmethods() 函式時，才能夠動態地為一個類別新增抽象方法，或者嘗試在方法或類別被建立後修改其抽象狀態。abstractmethod() 只會影響使用常規繼承所衍生出的子類別；透過 ABC 的 register() 方法註冊的「虛擬子類別」不會受到影響。

當 abstractmethod() 與其他方法描述器 (method descriptor) 配合應用時，它應被當最內層的裝飾器，如以下用法範例所示：

class C(ABC):
    @abstractmethod
    def my_abstract_method(self, arg1):
        ...
    @classmethod
    @abstractmethod
    def my_abstract_classmethod(cls, arg2):
        ...
    @staticmethod
    @abstractmethod
    def my_abstract_staticmethod(arg3):
        ...

    @property
    @abstractmethod
    def my_abstract_property(self):
        ...
    @my_abstract_property.setter
    @abstractmethod
    def my_abstract_property(self, val):
        ...

    @abstractmethod
    def _get_x(self):
        ...
    @abstractmethod
    def _set_x(self, val):
        ...
    x = property(_get_x, _set_x)

為了能正確地與 ABC 機制實作相互操作，描述器必須使用 __isabstractmethod__ 將自身標識為抽象的。一般來說，如果被用於組成描述器的任一方法是抽象的，則此屬性應當為 True。 例如，Python 的內建 property 所做的就等價於：

class Descriptor:
    ...
    @property
    def __isabstractmethod__(self):
        return any(getattr(f, '__isabstractmethod__', False) for
                   f in (self._fget, self._fset, self._fdel))

備註

不同於 Java 抽象方法，這些抽象方法可能具有一個實作。這個實作可在覆寫它的類別上透過 super() 機制來呼叫。這在使用協作多重繼承 (cooperative multiple-inheritance) 的框架中，可以被用作 super 呼叫的一個端點 (end-point)。

abc 模組還支援下列舊式裝飾器：

@abc.abstractclassmethod

在 3.2 版被加入.

在 3.3 版之後被棄用: 現在可以讓 classmethod 配合 abstractmethod() 使用，使得此裝飾器變得冗餘。

內建 classmethod() 的子類別，表示為一個抽象類別方法。在其他方面它都類似於 abstractmethod()。

這個特例已被棄用，因為現在當 classmethod() 裝飾器應用於抽象方法時已會被正確地標識為是抽象的：

class C(ABC):
    @classmethod
    @abstractmethod
    def my_abstract_classmethod(cls, arg):
        ...

@abc.abstractstaticmethod

在 3.2 版被加入.

在 3.3 版之後被棄用: 現在可以讓 staticmethod 配合 abstractmethod() 使用，使得此裝飾器變得冗餘。

內建 staticmethod() 的子類別，表示為一個抽象靜態方法。在其他方面它都類似於 abstractmethod()。

這個特例已被棄用，因為現在當 staticmethod() 裝飾器應用於抽象方法時已會被正確地標識為是抽象的：

class C(ABC):
    @staticmethod
    @abstractmethod
    def my_abstract_staticmethod(arg):
        ...

@abc.abstractproperty

在 3.3 版之後被棄用: 現在可以讓 property、property.getter()、property.setter() 和 property.deleter() 配合 abstractmethod() 使用，使得此裝飾器變得冗餘。

內建 property() 的子類別，表示為一個抽象特性。

這個特例已被棄用，因為現在當 property() 裝飾器應用於抽象方法時已會被正確地標識為是抽象的：

class C(ABC):
    @property
    @abstractmethod
    def my_abstract_property(self):
        ...

上面的例子定義了一個唯讀特性；你也可以透過適當地將一個或多個底層方法標記為抽象的來定義可讀寫的抽象特性：

class C(ABC):
    @property
    def x(self):
        ...

    @x.setter
    @abstractmethod
    def x(self, val):
        ...

如果只有某些元件是抽象的，則只需更新那些元件即可在子類別中建立具體的特性：

class D(C):
    @C.x.setter
    def x(self, val):
        ...

abc 模組也提供了這些函式：

abc.get_cache_token()

回傳目前 ABC 快取令牌 (cache token)。

此令牌是一個（支援相等性測試的）不透明物件 (opaque object)，用於為虛擬子類別標識抽象基底類別快取的目前版本。此令牌會在任何 ABC 上每次呼叫 ABCMeta.register() 時發生更改。

在 3.4 版被加入.

abc.update_abstractmethods(cls)

重新計算一個抽象類別之抽象狀態的函式。如果一個類別的抽象方法在建立後被實作或被修改，則應當呼叫此函式。通常此函式應在一個類別裝飾器內部被呼叫。

回傳 cls，使其能夠用作為類別的裝飾器。

如果 cls 不是 ABCMeta 的實例則不做任何操作。

備註

此函式會假定 cls 的超類別 (superclass) 已經被更新。它不會更新任何子類別。

在 3.10 版被加入.

註腳

[1]

C++ 程式設計師需要注意到 Python 中虛擬基底類別的概念和 C++ 中的並不相同。

atexit --- 退出處理函式

atexit 模組定義了註冊和註銷清理函式 (cleanup function) 的函式，這樣的註冊函式會在直譯器正常終止時自動執行。atexit 按照這些函式註冊之反序來運行這些函式；如果你有註冊 A、B 和 C，則在直譯器終止時它們將按 C、B、A 的順序運行。

注意：當程式被一個不是來自 Python 的訊號終止、偵測到有 Python 嚴重內部錯誤時或者 os._exit() 被呼叫時，透過此模組註冊的函式就不會被呼叫。

注意：在清理函式中註冊或註銷函式的作用並未定義。

在 3.7 版的變更: 當與 C-API 子直譯器 (subinterpreter) 一起使用時，已註冊函式對於它們所註冊的直譯器來說是區域的 (local)。

atexit.register(func, *args, **kwargs)

將 func 註冊為要在終止時執行的函式。任何要傳遞給 func 的可選引數都必須作為引數傳遞給 register()。可以多次註冊相同的函式和引數。

在程式正常終止時（例如呼叫 sys.exit() 或主要模組執行完成），所有已註冊函式都會依照後進先出的順序呼叫。這邊做的假設是較低階的模組通常會在較高階模組之前被引入，因此較低階模組必須在比較後面才被清理。

如果在執行退出處理函式期間引發例外，則會列印回溯 (traceback)（除非引發 SystemExit）並儲存例外資訊。在所有退出處理函式都有嘗試運作過後，將重新引發最後一個引發的例外。

該函式回傳 func，這使得可以將其作為裝飾器使用。

警告

啟動新執行緒或從已註冊函式呼叫 os.fork() 可能會導致 Python 主要 runtime 執行緒釋放執行緒狀態，而內部 threading 例程或新行程嘗試使用該狀態所形成的競態條件 (race condition)。這可能會導致崩潰 (crash) 而不是完整關閉中止。

在 3.12 版的變更: 嘗試在已註冊函式中啟動新執行緒或 os.fork() 新行程現在會導致 RuntimeError。

atexit.unregister(func)

從在直譯器中止時會執行之函式串列中刪除 func。如果 func 先前未被註冊，則 unregister() 不會執行任何操作。如果 func 已被註冊多次，則該函式在 atexit 呼叫堆疊 (call stack) 中的所有存在都會被刪除。會在註銷期間於內部使用相等性比較 (==)，因此函式參照不需要具有匹配的識別性。

也參考

readline 模組

atexit 用於讀取和寫入 readline 歷史檔案的一個不錯的範例。

atexit 範例

以下的簡單範例示範了模組如何在被引入時以檔案來初始化計數器，並在程式終止時自動儲存計數器的更新值，而不需要仰賴應用程式在終止時明確呼叫該模組。

try:
    with open('counterfile') as infile:
        _count = int(infile.read())
except FileNotFoundError:
    _count = 0

def incrcounter(n):
    global _count
    _count = _count + n

def savecounter():
    with open('counterfile', 'w') as outfile:
        outfile.write('%d' % _count)

import atexit

atexit.register(savecounter)

位置引數和關鍵字引數也可以被傳遞給 register()，以便在呼叫時也傳遞給已註冊函式：

def goodbye(name, adjective):
    print('Goodbye %s, it was %s to meet you.' % (name, adjective))

import atexit

atexit.register(goodbye, 'Donny', 'nice')
# 或是：
atexit.register(goodbye, adjective='nice', name='Donny')

作為裝飾器使用：

import atexit

@atexit.register
def goodbye():
    print('You are now leaving the Python sector.')

這只適用於可以不帶引數呼叫的函式。

traceback --- 列印或取得堆疊回溯 (stack traceback)

原始碼：Lib/traceback.py [https://github.com/python/cpython/tree/3.14/Lib/traceback.py]

This module provides a standard interface to extract, format and print stack traces of Python programs. It is more flexible than the interpreter's default traceback display, and therefore makes it possible to configure certain aspects of the output. Finally, it contains a utility for capturing enough information about an exception to print it later, without the need to save a reference to the actual exception. Since exceptions can be the roots of large objects graph, this utility can significantly improve memory management.

The module uses traceback objects --- these are objects of type types.TracebackType, which are assigned to the __traceback__ field of BaseException instances.

也參考

faulthandler 模組

Used to dump Python tracebacks explicitly, on a fault, after a timeout, or on a user signal.

pdb 模組

Interactive source code debugger for Python programs.

The module's API can be divided into two parts:

Module-level functions offering basic functionality, which are useful for interactive inspection of exceptions and tracebacks.

TracebackException class and its helper classes StackSummary and FrameSummary. These offer both more flexibility in the output generated and the ability to store the information necessary for later formatting without holding references to actual exception and traceback objects.

在 3.13 版被加入: Output is colorized by default and can be controlled using environment variables.

Module-Level Functions

traceback.print_tb(tb, limit=None, file=None)

Print up to limit stack trace entries from traceback object tb (starting from the caller's frame) if limit is positive. Otherwise, print the last abs(limit) entries. If limit is omitted or None, all entries are printed. If file is omitted or None, the output goes to sys.stderr; otherwise it should be an open file or file-like object to receive the output.

備註

The meaning of the limit parameter is different than the meaning of sys.tracebacklimit. A negative limit value corresponds to a positive value of sys.tracebacklimit, whereas the behaviour of a positive limit value cannot be achieved with sys.tracebacklimit.

在 3.5 版的變更: 新增負數 limit 的支援。

traceback.print_exception(exc, /, [value, tb, ]limit=None, file=None, chain=True)

Print exception information and stack trace entries from traceback object tb to file. This differs from print_tb() in the following ways:

if tb is not None, it prints a header Traceback (most recent call last):

it prints the exception type and value after the stack trace

if type(value) is SyntaxError and value has the appropriate format, it prints the line where the syntax error occurred with a caret indicating the approximate position of the error.

Since Python 3.10, instead of passing value and tb, an exception object can be passed as the first argument. If value and tb are provided, the first argument is ignored in order to provide backwards compatibility.

The optional limit argument has the same meaning as for print_tb(). If chain is true (the default), then chained exceptions (the __cause__ or __context__ attributes of the exception) will be printed as well, like the interpreter itself does when printing an unhandled exception.

在 3.5 版的變更: The etype argument is ignored and inferred from the type of value.

在 3.10 版的變更: The etype parameter has been renamed to exc and is now positional-only.

traceback.print_exc(limit=None, file=None, chain=True)

This is a shorthand for print_exception(sys.exception(), limit=limit, file=file, chain=chain).

traceback.print_last(limit=None, file=None, chain=True)

This is a shorthand for print_exception(sys.last_exc, limit=limit, file=file, chain=chain). In general it will work only after an exception has reached an interactive prompt (see sys.last_exc).

traceback.print_stack(f=None, limit=None, file=None)

Print up to limit stack trace entries (starting from the invocation point) if limit is positive. Otherwise, print the last abs(limit) entries. If limit is omitted or None, all entries are printed. The optional f argument can be used to specify an alternate stack frame to start. The optional file argument has the same meaning as for print_tb().

在 3.5 版的變更: 新增負數 limit 的支援。

traceback.extract_tb(tb, limit=None)

Return a StackSummary object representing a list of "pre-processed" stack trace entries extracted from the traceback object tb. It is useful for alternate formatting of stack traces. The optional limit argument has the same meaning as for print_tb(). A "pre-processed" stack trace entry is a FrameSummary object containing attributes filename, lineno, name, and line representing the information that is usually printed for a stack trace.

traceback.extract_stack(f=None, limit=None)

Extract the raw traceback from the current stack frame. The return value has the same format as for extract_tb(). The optional f and limit arguments have the same meaning as for print_stack().

traceback.print_list(extracted_list, file=None)

Print the list of tuples as returned by extract_tb() or extract_stack() as a formatted stack trace to the given file. If file is None, the output is written to sys.stderr.

traceback.format_list(extracted_list)

Given a list of tuples or FrameSummary objects as returned by extract_tb() or extract_stack(), return a list of strings ready for printing. Each string in the resulting list corresponds to the item with the same index in the argument list. Each string ends in a newline; the strings may contain internal newlines as well, for those items whose source text line is not None.

traceback.format_exception_only(exc, /, [value, ]*, show_group=False)

Format the exception part of a traceback using an exception value such as given by sys.last_value. The return value is a list of strings, each ending in a newline. The list contains the exception's message, which is normally a single string; however, for SyntaxError exceptions, it contains several lines that (when printed) display detailed information about where the syntax error occurred. Following the message, the list contains the exception's notes.

Since Python 3.10, instead of passing value, an exception object can be passed as the first argument. If value is provided, the first argument is ignored in order to provide backwards compatibility.

When show_group is True, and the exception is an instance of BaseExceptionGroup, the nested exceptions are included as well, recursively, with indentation relative to their nesting depth.

在 3.10 版的變更: The etype parameter has been renamed to exc and is now positional-only.

在 3.11 版的變更: The returned list now includes any notes attached to the exception.

在 3.13 版的變更: 新增 show_group 參數。

traceback.format_exception(exc, /, [value, tb, ]limit=None, chain=True)

Format a stack trace and the exception information. The arguments have the same meaning as the corresponding arguments to print_exception(). The return value is a list of strings, each ending in a newline and some containing internal newlines. When these lines are concatenated and printed, exactly the same text is printed as does print_exception().

在 3.5 版的變更: The etype argument is ignored and inferred from the type of value.

在 3.10 版的變更: This function's behavior and signature were modified to match print_exception().

traceback.format_exc(limit=None, chain=True)

This is like print_exc(limit) but returns a string instead of printing to a file.

traceback.format_tb(tb, limit=None)

format_list(extract_tb(tb, limit)) 的簡寫。

traceback.format_stack(f=None, limit=None)

format_list(extract_stack(f, limit)) 的簡寫。

traceback.clear_frames(tb)

Clears the local variables of all the stack frames in a traceback tb by calling the clear() method of each frame object.

在 3.4 版被加入.

traceback.walk_stack(f)

Walk a stack following f.f_back from the given frame, yielding the frame and line number for each frame. If f is None, the current stack is used. This helper is used with StackSummary.extract().

在 3.5 版被加入.

在 3.14 版的變更: This function previously returned a generator that would walk the stack when first iterated over. The generator returned now is the state of the stack when walk_stack is called.

traceback.walk_tb(tb)

Walk a traceback following tb_next yielding the frame and line number for each frame. This helper is used with StackSummary.extract().

在 3.5 版被加入.

TracebackException 物件

在 3.5 版被加入.

TracebackException objects are created from actual exceptions to capture data for later printing. They offer a more lightweight method of storing this information by avoiding holding references to traceback and frame objects. In addition, they expose more options to configure the output compared to the module-level functions described above.

class traceback.TracebackException(exc_type, exc_value, exc_traceback, *, limit=None, lookup_lines=True, capture_locals=False, compact=False, max_group_width=15, max_group_depth=10)

Capture an exception for later rendering. The meaning of limit, lookup_lines and capture_locals are as for the StackSummary class.

If compact is true, only data that is required by TracebackException's format() method is saved in the class attributes. In particular, the __context__ field is calculated only if __cause__ is None and __suppress_context__ is false.

Note that when locals are captured, they are also shown in the traceback.

max_group_width and max_group_depth control the formatting of exception groups (see BaseExceptionGroup). The depth refers to the nesting level of the group, and the width refers to the size of a single exception group's exceptions array. The formatted output is truncated when either limit is exceeded.

在 3.10 版的變更: 新增 compact 參數。

在 3.11 版的變更: 新增 max_group_width 和 max_group_depth 參數。

__cause__

A TracebackException of the original __cause__.

__context__

A TracebackException of the original __context__.

exceptions

If self represents an ExceptionGroup, this field holds a list of TracebackException instances representing the nested exceptions. Otherwise it is None.

在 3.11 版被加入.

__suppress_context__

The __suppress_context__ value from the original exception.

__notes__

The __notes__ value from the original exception, or None if the exception does not have any notes. If it is not None is it formatted in the traceback after the exception string.

在 3.11 版被加入.

stack

A StackSummary representing the traceback.

exc_type

The class of the original traceback.

在 3.13 版之後被棄用.

exc_type_str

String display of the class of the original exception.

在 3.13 版被加入.

filename

For syntax errors - the file name where the error occurred.

lineno

For syntax errors - the line number where the error occurred.

end_lineno

For syntax errors - the end line number where the error occurred. Can be None if not present.

在 3.10 版被加入.

text

For syntax errors - the text where the error occurred.

offset

For syntax errors - the offset into the text where the error occurred.

end_offset

For syntax errors - the end offset into the text where the error occurred. Can be None if not present.

在 3.10 版被加入.

msg

For syntax errors - the compiler error message.

classmethod from_exception(exc, *, limit=None, lookup_lines=True, capture_locals=False)

Capture an exception for later rendering. limit, lookup_lines and capture_locals are as for the StackSummary class.

Note that when locals are captured, they are also shown in the traceback.

print(*, file=None, chain=True)

Print to file (default sys.stderr) the exception information returned by format().

在 3.11 版被加入.

format(*, chain=True)

Format the exception.

If chain is not True, __cause__ and __context__ will not be formatted.

The return value is a generator of strings, each ending in a newline and some containing internal newlines. print_exception() is a wrapper around this method which just prints the lines to a file.

format_exception_only(*, show_group=False)

Format the exception part of the traceback.

The return value is a generator of strings, each ending in a newline.

When show_group is False, the generator emits the exception's message followed by its notes (if it has any). The exception message is normally a single string; however, for SyntaxError exceptions, it consists of several lines that (when printed) display detailed information about where the syntax error occurred.

When show_group is True, and the exception is an instance of BaseExceptionGroup, the nested exceptions are included as well, recursively, with indentation relative to their nesting depth.

在 3.11 版的變更: The exception's notes are now included in the output.

在 3.13 版的變更: 新增 show_group 參數。

StackSummary 物件

在 3.5 版被加入.

StackSummary objects represent a call stack ready for formatting.

class traceback.StackSummary

classmethod extract(frame_gen, *, limit=None, lookup_lines=True, capture_locals=False)

Construct a StackSummary object from a frame generator (such as is returned by walk_stack() or walk_tb()).

If limit is supplied, only this many frames are taken from frame_gen. If lookup_lines is False, the returned FrameSummary objects will not have read their lines in yet, making the cost of creating the StackSummary cheaper (which may be valuable if it may not actually get formatted). If capture_locals is True the local variables in each FrameSummary are captured as object representations.

在 3.12 版的變更: Exceptions raised from repr() on a local variable (when capture_locals is True) are no longer propagated to the caller.

classmethod from_list(a_list)

Construct a StackSummary object from a supplied list of FrameSummary objects or old-style list of tuples. Each tuple should be a 4-tuple with filename, lineno, name, line as the elements.

format()

Returns a list of strings ready for printing. Each string in the resulting list corresponds to a single frame from the stack. Each string ends in a newline; the strings may contain internal newlines as well, for those items with source text lines.

For long sequences of the same frame and line, the first few repetitions are shown, followed by a summary line stating the exact number of further repetitions.

在 3.6 版的變更: Long sequences of repeated frames are now abbreviated.

format_frame_summary(frame_summary)

Returns a string for printing one of the frames involved in the stack. This method is called for each FrameSummary object to be printed by StackSummary.format(). If it returns None, the frame is omitted from the output.

在 3.11 版被加入.

FrameSummary 物件

在 3.5 版被加入.

A FrameSummary object represents a single frame in a traceback.

class traceback.FrameSummary(filename, lineno, name, *, lookup_line=True, locals=None, line=None, end_lineno=None, colno=None, end_colno=None)

Represents a single frame in the traceback or stack that is being formatted or printed. It may optionally have a stringified version of the frame's locals included in it. If lookup_line is False, the source code is not looked up until the FrameSummary has the line attribute accessed (which also happens when casting it to a tuple). line may be directly provided, and will prevent line lookups happening at all. locals is an optional local variable mapping, and if supplied the variable representations are stored in the summary for later display.

FrameSummary instances have the following attributes:

filename

The filename of the source code for this frame. Equivalent to accessing f.f_code.co_filename on a frame object f.

lineno

The line number of the source code for this frame.

name

Equivalent to accessing f.f_code.co_name on a frame object f.

line

A string representing the source code for this frame, with leading and trailing whitespace stripped. If the source is not available, it is None.

end_lineno

The last line number of the source code for this frame. By default, it is set to lineno and indexation starts from 1.

在 3.13 版的變更: The default value changed from None to lineno.

colno

The column number of the source code for this frame. By default, it is None and indexation starts from 0.

end_colno

The last column number of the source code for this frame. By default, it is None and indexation starts from 0.

Examples of Using the Module-Level Functions

This simple example implements a basic read-eval-print loop, similar to (but less useful than) the standard Python interactive interpreter loop. For a more complete implementation of the interpreter loop, refer to the code module.

import sys, traceback

def run_user_code(envdir):
    source = input(">>> ")
    try:
        exec(source, envdir)
    except Exception:
        print("Exception in user code:")
        print("-"*60)
        traceback.print_exc(file=sys.stdout)
        print("-"*60)

envdir = {}
while True:
    run_user_code(envdir)

The following example demonstrates the different ways to print and format the exception and traceback:

import sys, traceback

def lumberjack():
    bright_side_of_life()

def bright_side_of_life():
    return tuple()[0]

try:
    lumberjack()
except IndexError as exc:
    print("*** print_tb:")
    traceback.print_tb(exc.__traceback__, limit=1, file=sys.stdout)
    print("*** print_exception:")
    traceback.print_exception(exc, limit=2, file=sys.stdout)
    print("*** print_exc:")
    traceback.print_exc(limit=2, file=sys.stdout)
    print("*** format_exc, first and last line:")
    formatted_lines = traceback.format_exc().splitlines()
    print(formatted_lines[0])
    print(formatted_lines[-1])
    print("*** format_exception:")
    print(repr(traceback.format_exception(exc)))
    print("*** extract_tb:")
    print(repr(traceback.extract_tb(exc.__traceback__)))
    print("*** format_tb:")
    print(repr(traceback.format_tb(exc.__traceback__)))
    print("*** tb_lineno:", exc.__traceback__.tb_lineno)

The output for the example would look similar to this:

*** print_tb:
  File "<doctest...>", line 10, in <module>
    lumberjack()
    ~~~~~~~~~~^^
*** print_exception:
Traceback (most recent call last):
  File "<doctest...>", line 10, in <module>
    lumberjack()
    ~~~~~~~~~~^^
  File "<doctest...>", line 4, in lumberjack
    bright_side_of_life()
    ~~~~~~~~~~~~~~~~~~~^^
IndexError: tuple index out of range
*** print_exc:
Traceback (most recent call last):
  File "<doctest...>", line 10, in <module>
    lumberjack()
    ~~~~~~~~~~^^
  File "<doctest...>", line 4, in lumberjack
    bright_side_of_life()
    ~~~~~~~~~~~~~~~~~~~^^
IndexError: tuple index out of range
*** format_exc, first and last line:
Traceback (most recent call last):
IndexError: tuple index out of range
*** format_exception:
['Traceback (most recent call last):\n',
 '  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n    ~~~~~~~~~~^^\n',
 '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_life()\n    ~~~~~~~~~~~~~~~~~~~^^\n',
 '  File "<doctest default[0]>", line 7, in bright_side_of_life\n    return tuple()[0]\n           ~~~~~~~^^^\n',
 'IndexError: tuple index out of range\n']
*** extract_tb:
[<FrameSummary file <doctest...>, line 10 in <module>>,
 <FrameSummary file <doctest...>, line 4 in lumberjack>,
 <FrameSummary file <doctest...>, line 7 in bright_side_of_life>]
*** format_tb:
['  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n    ~~~~~~~~~~^^\n',
 '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_life()\n    ~~~~~~~~~~~~~~~~~~~^^\n',
 '  File "<doctest default[0]>", line 7, in bright_side_of_life\n    return tuple()[0]\n           ~~~~~~~^^^\n']
*** tb_lineno: 10

The following example shows the different ways to print and format the stack:

>>> import traceback
>>> def another_function():
...     lumberstack()
...
>>> def lumberstack():
...     traceback.print_stack()
...     print(repr(traceback.extract_stack()))
...     print(repr(traceback.format_stack()))
...
>>> another_function()
  File "<doctest>", line 10, in <module>
    another_function()
  File "<doctest>", line 3, in another_function
    lumberstack()
  File "<doctest>", line 6, in lumberstack
    traceback.print_stack()
[('<doctest>', 10, '<module>', 'another_function()'),
 ('<doctest>', 3, 'another_function', 'lumberstack()'),
 ('<doctest>', 7, 'lumberstack', 'print(repr(traceback.extract_stack()))')]
['  File "<doctest>", line 10, in <module>\n    another_function()\n',
 '  File "<doctest>", line 3, in another_function\n    lumberstack()\n',
 '  File "<doctest>", line 8, in lumberstack\n    print(repr(traceback.format_stack()))\n']

This last example demonstrates the final few formatting functions:

>>> import traceback
>>> traceback.format_list([('spam.py', 3, '<module>', 'spam.eggs()'),
...                        ('eggs.py', 42, 'eggs', 'return "bacon"')])
['  File "spam.py", line 3, in <module>\n    spam.eggs()\n',
 '  File "eggs.py", line 42, in eggs\n    return "bacon"\n']
>>> an_error = IndexError('tuple index out of range')
>>> traceback.format_exception_only(an_error)
['IndexError: tuple index out of range\n']

TracebackException 的使用範例

With the helper class, we have more options:

>>> import sys
>>> from traceback import TracebackException
>>>
>>> def lumberjack():
...     bright_side_of_life()
...
>>> def bright_side_of_life():
...     t = "bright", "side", "of", "life"
...     return t[5]
...
>>> try:
...     lumberjack()
... except IndexError as e:
...     exc = e
...
>>> try:
...     try:
...         lumberjack()
...     except:
...         1/0
... except Exception as e:
...     chained_exc = e
...
>>> # limit works as with the module-level functions
>>> TracebackException.from_exception(exc, limit=-2).print()
Traceback (most recent call last):
  File "<python-input-1>", line 6, in lumberjack
    bright_side_of_life()
    ~~~~~~~~~~~~~~~~~~~^^
  File "<python-input-1>", line 10, in bright_side_of_life
    return t[5]
           ~^^^
IndexError: tuple index out of range

>>> # capture_locals adds local variables in frames
>>> TracebackException.from_exception(exc, limit=-2, capture_locals=True).print()
Traceback (most recent call last):
  File "<python-input-1>", line 6, in lumberjack
    bright_side_of_life()
    ~~~~~~~~~~~~~~~~~~~^^
  File "<python-input-1>", line 10, in bright_side_of_life
    return t[5]
           ~^^^
    t = ("bright", "side", "of", "life")
IndexError: tuple index out of range

>>> # The *chain* kwarg to print() controls whether chained
>>> # exceptions are displayed
>>> TracebackException.from_exception(chained_exc).print()
Traceback (most recent call last):
  File "<python-input-19>", line 4, in <module>
    lumberjack()
    ~~~~~~~~~~^^
  File "<python-input-8>", line 7, in lumberjack
    bright_side_of_life()
    ~~~~~~~~~~~~~~~~~~~^^
  File "<python-input-8>", line 11, in bright_side_of_life
    return t[5]
           ~^^^
IndexError: tuple index out of range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<python-input-19>", line 6, in <module>
    1/0
    ~^~
ZeroDivisionError: division by zero

>>> TracebackException.from_exception(chained_exc).print(chain=False)
Traceback (most recent call last):
  File "<python-input-19>", line 6, in <module>
    1/0
    ~^~
ZeroDivisionError: division by zero

__future__ --- Future 陳述式定義

原始碼：Lib/__future__.py [https://github.com/python/cpython/tree/3.14/Lib/__future__.py]

from __future__ import feature 形式的引入被稱為 future 陳述式。這些是 Python 編譯器的特殊情況，允許在該功能成為標準版本之前在包含 future 陳述式的模組中使用新的 Python 功能。

雖然這些 future 陳述式被 Python 編譯器賦予了額外的特殊意義，但它們仍然像任何其他 import 陳述式一樣執行，且 __future__ 由引入系統以和任何其他 Python 模組相同的方式處理。這個設計有三個目的：

為了避免混淆分析引入陳述式並預期要找到它們正在引入之模組的現有工具。

記錄何時出現不相容的變更，以及何時開始強制執行這些變更。這是一種可執行文件的形式，可以透過引入 __future__ 並檢查其內容以程式化的方式進行檢查。

確保 future 陳述式在 Python 2.1 之前的版本中運行至少會產生 runtime 例外（__future__ 的引入將會失敗，因為 2.1 之前沒有該名稱的模組）。

模組內容

不會從 __future__ 中刪除任何功能描述。自從在 Python 2.1 中引入以來，以下功能已透過這種機制引入到該語言中：

功能

可選的版本

強制性的版本

影響

__future__.nested_scopes

2.1.0b1

2.2

PEP 227 [https://peps.python.org/pep-0227/]: 靜態巢狀作用域 (Statically Nested Scopes)

__future__.generators

2.2.0a1

2.3

PEP 255 [https://peps.python.org/pep-0255/]: 簡單產生器 (Simple Generators)

__future__.division

2.2.0a2

3.0

PEP 238 [https://peps.python.org/pep-0238/]: 更改除法運算子 (Changing the Division Operator)

__future__.absolute_import

2.5.0a1

3.0

PEP 328 [https://peps.python.org/pep-0328/]: 引入：多列與絕對/相對 (Imports: Multi-Line and Absolute/Relative)

__future__.with_statement

2.5.0a1

2.6

PEP 343 [https://peps.python.org/pep-0343/]: "with" 陳述式 (The "with" Statement)

__future__.print_function

2.6.0a2

3.0

PEP 3105 [https://peps.python.org/pep-3105/]: 使 print 成為一個函式 (Make print a function)

__future__.unicode_literals

2.6.0a2

3.0

PEP 3112 [https://peps.python.org/pep-3112/]: Python 3000 中的位元組字面值 (Bytes literals in Python 3000)

__future__.generator_stop

3.5.0b1

3.7

PEP 479 [https://peps.python.org/pep-0479/]: 產生器內部的 StopIteration 處理 (StopIteration handling inside generators)

__future__.annotations

3.7.0b1

從未 [1]

PEP 563 [https://peps.python.org/pep-0563/]: 註釋的延後求值 (Postponed evaluation of annotations)、PEP 649 [https://peps.python.org/pep-0649/]: 使用描述器延遲求值註釋 (Deferred evaluation of annotations using descriptors)

class __future__._Feature

__future__.py 中的每個陳述式的形式如下：

FeatureName = _Feature(OptionalRelease, MandatoryRelease,
                       CompilerFlag)

通常，OptionalRelease 會小於 MandatoryRelease，且兩者都是與 sys.version_info 形式相同的 5 元組 (5-tuple)：

(PY_MAJOR_VERSION, # 2.1.0a3 裡面的 2；為一整數
 PY_MINOR_VERSION, # 1；為一整數
 PY_MICRO_VERSION, # 0；為一整數
 PY_RELEASE_LEVEL, # "alpha"、"beta"、"candidate" 或 "final"; ；為一字串
 PY_RELEASE_SERIAL # 3；為一整數
)

_Feature.getOptionalRelease()

OptionalRelease 記錄該功能首次發布時的 Python 版本。

_Feature.getMandatoryRelease()

如果 MandatoryRelease 尚未發布，MandatoryRelease 會預測該功能將成為該語言一部分的版本。

否則 MandatoryRelease 會記錄該功能是何時成為語言的一部分；在該版本或之後的版本中，模組不再需要 future 聲明來使用相關功能，但可以繼續使用此種引入方式。

MandatoryRelease 也可能是 None，這意味著計劃中的功能被丟棄或者仍未決定。

_Feature.compiler_flag

CompilerFlag 是（位元欄位 (bitfield)）旗標，應在第四個引數中傳遞給內建函式 compile() 以在動態編譯的程式碼中啟用該功能。此旗標儲存在 _Feature 實例上的 _Feature.compiler_flag 屬性中。

[1]

from __future__ import annotations 原本預定在 Python 3.10 中成為強制性功能，但該變更被延後並最終取消。此功能最終將被棄用並移除。請參閱 PEP 649 [https://peps.python.org/pep-0649/] 和 PEP 749 [https://peps.python.org/pep-0749/]。

也參考

Future statements

編譯器如何處理 future 引入。

PEP 236 [https://peps.python.org/pep-0236/] - 回到 __future__

__future__ 機制的原始提案。

gc --- 垃圾回收器介面 (Garbage Collector interface)

此 module（模組）提供可選的垃圾回收器介面，提供的功能包括：關閉回收器、調整回收頻率、設定除錯選項。它同時提供對回收器有找到但是無法釋放的不可達物件 (unreachable object) 的存取。由於 Python 使用了帶有參照計數的回收器，如果你確定你的程式不會產生參照迴圈 (reference cycle)，你可以關閉回收器。可以透過呼叫 gc.disable() 關閉自動垃圾回收。若要為一個存在記憶體流失的程式 (leaking program) 除錯，請呼叫 gc.set_debug(gc.DEBUG_LEAK)；需要注意的是，它包含 gc.DEBUG_SAVEALL，使得被回收的物件會被存放在 gc.garbage 中以待檢查。

gc module 提供下列函式：

gc.enable()

啟用自動垃圾回收。

gc.disable()

停用自動垃圾回收。

gc.isenabled()

如果啟用了自動回收則回傳 True。

gc.collect(generation=2)

啟動垃圾回收。可選的引數 generation 可以是一個指明需要回收哪一代垃圾的整數（從 0 到 2）。當 generation 數值無效時，會引發 ValueError 例外。可回收物件與不可回收物件的總和會被回傳。

呼叫 gc.collect(0) 將對年輕代執行 GC 回收。

呼叫 gc.collect(1) 將對年輕代執行 GC 回收並對年老代執行增量回收。

呼叫 gc.collect(2) 或 gc.collect() 執行完整回收

每當執行完整回收或最高代 (2) 回收時，為多個內建型別所維護的空閒列表會被清空。為了特定型別的實現，特別是 float，在某些空閒列表中並非所有項目都會被釋放。

當直譯器已經執行收集時呼叫 gc.collect() 的效果是未定義的。

在 3.14 版的變更: generation=1 會執行增量收集。

gc.set_debug(flags)

設定垃圾回收器的除錯旗標。除錯資訊會被寫入 sys.stderr。請見下方的除錯旗標列表，可以使用位元操作 (bit operation) 進行設定以控制除錯程式。

gc.get_debug()

回傳目前設置的除錯旗標。

gc.get_objects(generation=None)

回傳一個包含回收器正在追蹤的所有物件的 list，除去所回傳的 list。如果 generation 不為 None，只回傳以下物件。

0: 年輕代中的所有物件。

1: 沒有物件，因為不存在第一代（截至 Python 3.14）

2: 年老代中的所有物件。

在 3.8 版的變更: 新增 generation 參數。

在 3.14 版的變更: 第一代已被刪除

引發一個附帶引數 generation 的稽核事件 (auditing event) gc.get_objects。

gc.get_stats()

回傳一個包含三個字典物件的 list，每個字典分別包含對應代中自從直譯器開始執行後的垃圾回收統計資料。字典的鍵的數目在將來可能會改變，但目前每個字典包含以下項目：

collections 是該代被回收的次數；

collected 是該代中被回收的物件總數；

uncollectable 是在這一代中被發現無法回收的物件總數（因此被移到 garbage list 中）。

在 3.4 版被加入.

gc.set_threshold(threshold0[, threshold1[, threshold2]])

設定垃圾回收閾值（回收頻率）。 將 threshold0 設為零會停止回收。

GC 根據物件是否在回收中倖存下來而將其分為兩代。新的物件會被放置在年輕代中。如果一個物件在回收中倖存下來，它將被移動到年老代中。

為了決定何時運行，回收器會追蹤自上次回收以來物件分配和釋放的數量。當分配數量減去釋放數量超過 threshold0 時，回收就會開始。每次回收都會去回收年輕代中的所有物件和年老代的部分物件。

在自由執行緒建置 (free-threaded build) 中，在運行回收器之前還會檢查行程記憶體使用量的增加。如果自上次回收以來記憶體使用量未增加 10%，且物件分配的淨數量未超過 threshold0 的 40 倍，則不會運行回收。

年老代中被回收的物件比例與 threshold1 成反比。threshold1 越大，年老代中物件的回收就越慢。以預設值 10 來說，每次回收時會掃描年老代中的 1%。

threshold2 會被忽略。

有關更多資訊，請參閱垃圾回收器設計 [https://github.com/python/cpython/blob/3.14/InternalDocs/garbage_collector.md]。

在 3.14 版的變更: threshold2 會被忽略

gc.get_count()

將目前回收計數以 (count0, count1, count2) 形式的 tuple 回傳。

gc.get_threshold()

將目前回收閾值以 (threshold0, threshold1, threshold2) 形式的 tuple 回傳。

gc.get_referrers(*objs)

回傳包含直接參照 objs 中任一個物件的物件 list。這個函式只定位支援垃圾回收的容器；參照了其它物件但不支援垃圾回收的擴充套件型別無法被找到。

需要注意的是，已經解除參照的物件，但仍存在於參照迴圈中未被回收時，該物件仍然會被作為參照者出現在回傳的 list 中。若只要取得目前正在參照的物件，需要在呼叫 get_referrers() 之前呼叫 collect()。

警告

在使用 get_referrers() 回傳的物件時必須要小心，因為其中的一些物件可能仍在建構中而處於暫時無效的狀態。不要把 get_referrers() 用於除錯以外的其它目的。

引發一個附帶引數 objs 的稽核事件 gc.get_referrers。

gc.get_referents(*objs)

回傳包含被任意一個引數直接參照之物件的 list。回傳的被參照物件是有被引數的 C 語言級別 tp_traverse 方法（若存在）瀏覽到的物件，可能不是所有的實際直接可達物件。只有支援垃圾回收的物件支援 tp_traverse 方法，並且此方法只會瀏覽涉及參照迴圈的物件。因此，可以有以下例子：一個整數對於一個引數是直接可達的，這個整數物件有可能出現或不出現在結果的 list 當中。

引發一個附帶引數 objs 的稽核事件 gc.get_referents。

gc.is_tracked(obj)

當物件正在被垃圾回收器追蹤時回傳 True，否則回傳 False。一般來說，原子型別 (atomic type) 的實例不會被追蹤，而非原子型別（如容器、使用者自己定義的物件）會被追蹤。然而，有一些特定型別最佳化會被用來減少垃圾回收器在簡單實例（如只含有原子性的鍵和值的字典）上的足跡：

>>> gc.is_tracked(0)
False
>>> gc.is_tracked("a")
False
>>> gc.is_tracked([])
True
>>> gc.is_tracked({})
False
>>> gc.is_tracked({"a": 1})
True

在 3.1 版被加入.

gc.is_finalized(obj)

如果給定物件已被垃圾回收器終結則回傳 True，否則回傳 False。：

>>> x = None
>>> class Lazarus:
...     def __del__(self):
...         global x
...         x = self
...
>>> lazarus = Lazarus()
>>> gc.is_finalized(lazarus)
False
>>> del lazarus
>>> gc.is_finalized(x)
True

在 3.9 版被加入.

gc.freeze()

凍結 (freeze) 垃圾回收器所追蹤的所有物件；將它們移至永久代並忽略所有未來的收集動作。

如果一個行程將在沒有 exec() 的情況下進行 fork()，避免子行程中不必要的寫入時複製將最大化記憶體共享並減少整體記憶體使用。這需要避免在父行程的記憶體頁面中建立已釋放的「漏洞」，並確保子行程中的 GC 收集不會觸及源自父行程的長壽命物件的 gc_refs 計數器。要實現這兩個目標，請在父行程的早期呼叫 gc.disable()，在 fork() 之前呼叫 gc.freeze()，並儘早在子行程中呼叫 gc.enable()。

在 3.7 版被加入.

gc.unfreeze()

解凍 (unfreeze) 永久代中的物件，並將它們放回到最年老代中。

在 3.7 版被加入.

gc.get_freeze_count()

回傳永久代中的物件數量。

在 3.7 版被加入.

以下變數僅供唯讀存取（你可以修改其值但不應該重新繫結 (rebind) 它們）：

gc.garbage

一個回收器發現不可達而又無法被釋放的物件（不可回收物件）list。從 Python 3.4 開始，該 list 在大多數時候都應該是空的，除非使用了有非 NULL tp_del 槽位的 C 擴充套件型別的實例。

如果設定了 DEBUG_SAVEALL，則所有不可達物件將被加進該 list 而不會被釋放。

在 3.2 版的變更: 當 interpreter shutdown 即直譯器關閉時，若此 list 非空，會產生 ResourceWarning，在預設情況下此警告不會被提醒。如果設定了 DEBUG_UNCOLLECTABLE，所有無法被回收的物件會被印出。

在 3.4 版的變更: 根據 PEP 442 [https://peps.python.org/pep-0442/]，帶有 __del__() method 的物件最終不會在 gc.garbage 內。

gc.callbacks

會被垃圾回收器在回收開始前和完成後叫用的一系列回呼函式 (callback) 。這些回呼函式在被呼叫時附帶兩個引數：phase 和 info。

phase 可為以下兩者之一：

"start"：垃圾回收即將開始。

"stop"：垃圾回收已結束。

info 是一個字典，提供回呼函式更多資訊。已有定義的鍵有：

"generation"（代）：正在被回收的最年老的一代。

"collected"（已回收的）：當 phase 為 "stop" 時，被成功回收的物件的數目。

"uncollectable"（不可回收的）：當 phase 為 "stop" 時，不能被回收並被放入 garbage 的物件的數目。

應用程式可以把他們自己的回呼函式加入此 list。主要的使用場景有：

收集垃圾回收的統計資料，如：不同代的回收頻率、回收任務所花費的時間。

讓應用程式可以識別和清理他們自己在 garbage 中的不可回收型別物件。

在 3.3 版被加入.

以下常數是為了和 set_debug() 一起使用所提供：

gc.DEBUG_STATS

在回收完成後印出統計資訊。當調校回收頻率設定時，這些資訊會很有用。

gc.DEBUG_COLLECTABLE

當發現可回收物件時印出資訊。

gc.DEBUG_UNCOLLECTABLE

印出找到的不可回收物件的資訊（指不能被回收器回收的不可達物件）。這些物件會被新增到 garbage list 中。

在 3.2 版的變更: 當 interpreter shutdown（直譯器關閉）時，若 garbage list 不是空的，那這些內容也會被印出。

gc.DEBUG_SAVEALL

設定後，所有回收器找到的不可達物件會被加進 garbage 而不是直接被釋放。這在為一個記憶體流失的程式除錯時會很有用。

gc.DEBUG_LEAK

要印出記憶體流失程式之相關資訊時，回收器所需的除錯旗標。（等同於 DEBUG_COLLECTABLE | DEBUG_UNCOLLECTABLE | DEBUG_SAVEALL）。

inspect --- 檢視活動物件

原始碼：Lib/inspect.py [https://github.com/python/cpython/tree/3.14/Lib/inspect.py]

The inspect module provides several useful functions to help get information about live objects such as modules, classes, methods, functions, tracebacks, frame objects, and code objects. For example, it can help you examine the contents of a class, retrieve the source code of a method, extract and format the argument list for a function, or get all the information you need to display a detailed traceback.

There are four main kinds of services provided by this module: type checking, getting source code, inspecting classes and functions, and examining the interpreter stack.

Types and members

The getmembers() function retrieves the members of an object such as a class or module. The functions whose names begin with "is" are mainly provided as convenient choices for the second argument to getmembers(). They also help you determine when you can expect to find the following special attributes (see Import-related attributes on module objects for module attributes):

Type

屬性

描述

class

__doc__

documentation string

__name__

name with which this class was defined

__qualname__

qualified name

__module__

name of module in which this class was defined

__type_params__

A tuple containing the type parameters of a generic class

method

__doc__

documentation string

__name__

name with which this method was defined

__qualname__

qualified name

__func__

function object containing implementation of method

__self__

instance to which this method is bound, or None

__module__

name of module in which this method was defined

函式

__doc__

documentation string

__name__

name with which this function was defined

__qualname__

qualified name

__code__

code object containing compiled function bytecode

__defaults__

tuple of any default values for positional or keyword parameters

__kwdefaults__

mapping of any default values for keyword-only parameters

__globals__

global namespace in which this function was defined

__builtins__

builtins namespace

__annotations__

mapping of parameters names to annotations; "return" key is reserved for return annotations.

__type_params__

A tuple containing the type parameters of a generic function

__module__

name of module in which this function was defined

traceback

tb_frame

frame object at this level

tb_lasti

index of last attempted instruction in bytecode

tb_lineno

current line number in Python source code

tb_next

next inner traceback object (called by this level)

frame

f_back

next outer frame object (this frame's caller)

f_builtins

builtins namespace seen by this frame

f_code

code object being executed in this frame

f_globals

global namespace seen by this frame

f_lasti

index of last attempted instruction in bytecode

f_lineno

current line number in Python source code

f_locals

local namespace seen by this frame

f_generator

returns the generator or coroutine object that owns this frame, or None if the frame is of a regular function

f_trace

tracing function for this frame, or None

f_trace_lines

indicate whether a tracing event is triggered for each source source line

f_trace_opcodes

indicate whether per-opcode events are requested

clear()

used to clear all references to local variables

code（程式碼）

co_argcount

number of arguments (not including keyword only arguments, * or ** args)

co_code

string of raw compiled bytecode

co_cellvars

tuple of names of cell variables (referenced by containing scopes)

co_consts

tuple of constants used in the bytecode

co_filename

name of file in which this code object was created

co_firstlineno

number of first line in Python source code

co_flags

bitmap of CO_* flags, read more here

co_lnotab

encoded mapping of line numbers to bytecode indices

co_freevars

tuple of names of free variables (referenced via a function's closure)

co_posonlyargcount

number of positional only arguments

co_kwonlyargcount

number of keyword only arguments (not including ** arg)

co_name

name with which this code object was defined

co_qualname

fully qualified name with which this code object was defined

co_names

tuple of names other than arguments and function locals

co_nlocals

number of local variables

co_stacksize

virtual machine stack space required

co_varnames

tuple of names of arguments and local variables

co_lines()

returns an iterator that yields successive bytecode ranges

co_positions()

returns an iterator of source code positions for each bytecode instruction

replace()

returns a copy of the code object with new values

generator

__name__

name

__qualname__

qualified name

gi_frame

frame

gi_running

is the generator running?

gi_suspended

is the generator suspended?

gi_code

code（程式碼）

gi_yieldfrom

object being iterated by yield from, or None

async generator

__name__

name

__qualname__

qualified name

ag_await

object being awaited on, or None

ag_frame

frame

ag_running

is the generator running?

ag_suspended

is the generator suspended?

ag_code

code（程式碼）

coroutine

__name__

name

__qualname__

qualified name

cr_await

object being awaited on, or None

cr_frame

frame

cr_running

is the coroutine running?

cr_suspended

is the coroutine suspended?

cr_code

code（程式碼）

cr_origin

where coroutine was created, or None. See sys.set_coroutine_origin_tracking_depth()

builtin

__doc__

documentation string

__name__

original name of this function or method

__qualname__

qualified name

__self__

instance to which a method is bound, or None

在 3.5 版的變更: 新增產生器的 __qualname__ 和 gi_yieldfrom 屬性。

The __name__ attribute of generators is now set from the function name, instead of the code name, and it can now be modified.

在 3.7 版的變更: 新增協程的 cr_origin 屬性。

在 3.10 版的變更: 新增函式的 __builtins__ 屬性。

在 3.11 版的變更: 新增產生器的 gi_suspended 屬性。

在 3.11 版的變更: 新增協程的 cr_suspended 屬性。

在 3.12 版的變更: 新增非同步產生器的 ag_suspended 屬性。

在 3.14 版的變更: 新增 f_generator 屬性到 frame。

inspect.getmembers(object[, predicate])

Return all the members of an object in a list of (name, value) pairs sorted by name. If the optional predicate argument—which will be called with the value object of each member—is supplied, only members for which the predicate returns a true value are included.

備註

getmembers() will only return class attributes defined in the metaclass when the argument is a class and those attributes have been listed in the metaclass' custom __dir__().

inspect.getmembers_static(object[, predicate])

Return all the members of an object in a list of (name, value) pairs sorted by name without triggering dynamic lookup via the descriptor protocol, __getattr__ or __getattribute__. Optionally, only return members that satisfy a given predicate.

備註

getmembers_static() may not be able to retrieve all members that getmembers can fetch (like dynamically created attributes) and may find members that getmembers can't (like descriptors that raise AttributeError). It can also return descriptor objects instead of instance members in some cases.

在 3.11 版被加入.

inspect.getmodulename(path)

Return the name of the module named by the file path, without including the names of enclosing packages. The file extension is checked against all of the entries in importlib.machinery.all_suffixes(). If it matches, the final path component is returned with the extension removed. Otherwise, None is returned.

Note that this function only returns a meaningful name for actual Python modules - paths that potentially refer to Python packages will still return None.

在 3.3 版的變更: 此函式直接基於 importlib。

inspect.ismodule(object)

如果物件是模組，則回傳 True。

inspect.isclass(object)

Return True if the object is a class, whether built-in or created in Python code.

inspect.ismethod(object)

Return True if the object is a bound method written in Python.

inspect.ispackage(object)

如果物件是 package，則回傳 True。

在 3.14 版被加入.

inspect.isfunction(object)

Return True if the object is a Python function, which includes functions created by a lambda expression.

inspect.isgeneratorfunction(object)

如果物件是 Python 產生器函式，則回傳 True。

在 3.8 版的變更: Functions wrapped in functools.partial() now return True if the wrapped function is a Python generator function.

在 3.13 版的變更: Functions wrapped in functools.partialmethod() now return True if the wrapped function is a Python generator function.

inspect.isgenerator(object)

如果物件是產生器，則回傳 True。

inspect.iscoroutinefunction(object)

Return True if the object is a coroutine function (a function defined with an async def syntax), a functools.partial() wrapping a coroutine function, or a sync function marked with markcoroutinefunction().

在 3.5 版被加入.

在 3.8 版的變更: Functions wrapped in functools.partial() now return True if the wrapped function is a coroutine function.

在 3.12 版的變更: Sync functions marked with markcoroutinefunction() now return True.

在 3.13 版的變更: Functions wrapped in functools.partialmethod() now return True if the wrapped function is a coroutine function.

inspect.markcoroutinefunction(func)

Decorator to mark a callable as a coroutine function if it would not otherwise be detected by iscoroutinefunction().

This may be of use for sync functions that return a coroutine, if the function is passed to an API that requires iscoroutinefunction().

When possible, using an async def function is preferred. Also acceptable is calling the function and testing the return with iscoroutine().

在 3.12 版被加入.

inspect.iscoroutine(object)

Return True if the object is a coroutine created by an async def function.

在 3.5 版被加入.

inspect.isawaitable(object)

Return True if the object can be used in await expression.

Can also be used to distinguish generator-based coroutines from regular generators:

import types

def gen():
    yield
@types.coroutine
def gen_coro():
    yield

assert not isawaitable(gen())
assert isawaitable(gen_coro())

在 3.5 版被加入.

inspect.isasyncgenfunction(object)

Return True if the object is an asynchronous generator function, for example:

>>> async def agen():
...     yield 1
...
>>> inspect.isasyncgenfunction(agen)
True

在 3.6 版被加入.

在 3.8 版的變更: Functions wrapped in functools.partial() now return True if the wrapped function is an asynchronous generator function.

在 3.13 版的變更: Functions wrapped in functools.partialmethod() now return True if the wrapped function is a asynchronous generator function.

inspect.isasyncgen(object)

Return True if the object is an asynchronous generator iterator created by an asynchronous generator function.

在 3.6 版被加入.

inspect.istraceback(object)

Return True if the object is a traceback.

inspect.isframe(object)

Return True if the object is a frame.

inspect.iscode(object)

如果物件是程式碼，則回傳 True。

inspect.isbuiltin(object)

Return True if the object is a built-in function or a bound built-in method.

inspect.ismethodwrapper(object)

Return True if the type of object is a MethodWrapperType.

These are instances of MethodWrapperType, such as __str__(), __eq__() and __repr__().

在 3.11 版被加入.

inspect.isroutine(object)

如果物件是使用者定義或內建的函式或方法，則回傳 True。

inspect.isabstract(object)

如果物件是抽象基底類別，則回傳 True。

inspect.ismethoddescriptor(object)

Return True if the object is a method descriptor, but not if ismethod(), isclass(), isfunction() or isbuiltin() are true.

This, for example, is true of int.__add__. An object passing this test has a __get__() method, but not a __set__() method or a __delete__() method. Beyond that, the set of attributes varies. A __name__ attribute is usually sensible, and __doc__ often is.

Methods implemented via descriptors that also pass one of the other tests return False from the ismethoddescriptor() test, simply because the other tests promise more -- you can, e.g., count on having the __func__ attribute (etc) when an object passes ismethod().

在 3.13 版的變更: This function no longer incorrectly reports objects with __get__() and __delete__(), but not __set__(), as being method descriptors (such objects are data descriptors, not method descriptors).

inspect.isdatadescriptor(object)

如果物件是資料描述器，則回傳 True。

Data descriptors have a __set__ or a __delete__ method. Examples are properties (defined in Python), getsets, and members. The latter two are defined in C and there are more specific tests available for those types, which is robust across Python implementations. Typically, data descriptors will also have __name__ and __doc__ attributes (properties, getsets, and members have both of these attributes), but this is not guaranteed.

inspect.isgetsetdescriptor(object)

如果物件是 getset 描述器，則回傳 True。

CPython 實作細節： getsets are attributes defined in extension modules via PyGetSetDef structures. For Python implementations without such types, this method will always return False.

inspect.ismemberdescriptor(object)

如果物件是成員描述器，則回傳 True。

CPython 實作細節： Member descriptors are attributes defined in extension modules via PyMemberDef structures. For Python implementations without such types, this method will always return False.

取得原始碼

inspect.getdoc(object)

Get the documentation string for an object, cleaned up with cleandoc(). If the documentation string for an object is not provided and the object is a class, a method, a property or a descriptor, retrieve the documentation string from the inheritance hierarchy. Return None if the documentation string is invalid or missing.

在 3.5 版的變更: Documentation strings are now inherited if not overridden.

inspect.getcomments(object)

Return in a single string any lines of comments immediately preceding the object's source code (for a class, function, or method), or at the top of the Python source file (if the object is a module). If the object's source code is unavailable, return None. This could happen if the object has been defined in C or the interactive shell.

inspect.getfile(object)

Return the name of the (text or binary) file in which an object was defined. This will fail with a TypeError if the object is a built-in module, class, or function.

inspect.getmodule(object)

Try to guess which module an object was defined in. Return None if the module cannot be determined.

inspect.getsourcefile(object)

Return the name of the Python source file in which an object was defined or None if no way can be identified to get the source. This will fail with a TypeError if the object is a built-in module, class, or function.

inspect.getsourcelines(object)

Return a list of source lines and starting line number for an object. The argument may be a module, class, method, function, traceback, frame, or code object. The source code is returned as a list of the lines corresponding to the object and the line number indicates where in the original source file the first line of code was found. An OSError is raised if the source code cannot be retrieved. A TypeError is raised if the object is a built-in module, class, or function.

在 3.3 版的變更: OSError is raised instead of IOError, now an alias of the former.

inspect.getsource(object)

Return the text of the source code for an object. The argument may be a module, class, method, function, traceback, frame, or code object. The source code is returned as a single string. An OSError is raised if the source code cannot be retrieved. A TypeError is raised if the object is a built-in module, class, or function.

在 3.3 版的變更: OSError is raised instead of IOError, now an alias of the former.

inspect.cleandoc(doc)

Clean up indentation from docstrings that are indented to line up with blocks of code.

All leading whitespace is removed from the first line. Any leading whitespace that can be uniformly removed from the second line onwards is removed. Empty lines at the beginning and end are subsequently removed. Also, all tabs are expanded to spaces.

Introspecting callables with the Signature object

在 3.3 版被加入.

The Signature object represents the call signature of a callable object and its return annotation. To retrieve a Signature object, use the signature() function.

inspect.signature(callable, *, follow_wrapped=True, globals=None, locals=None, eval_str=False, annotation_format=Format.VALUE)

Return a Signature object for the given callable:

>>> from inspect import signature
>>> def foo(a, *, b:int, **kwargs):
...     pass

>>> sig = signature(foo)

>>> str(sig)
'(a, *, b: int, **kwargs)'

>>> str(sig.parameters['b'])
'b: int'

>>> sig.parameters['b'].annotation
<class 'int'>

Accepts a wide range of Python callables, from plain functions and classes to functools.partial() objects.

If some of the annotations are strings (e.g., because from __future__ import annotations was used), signature() will attempt to automatically un-stringize the annotations using annotationlib.get_annotations(). The globals, locals, and eval_str parameters are passed into annotationlib.get_annotations() when resolving the annotations; see the documentation for annotationlib.get_annotations() for instructions on how to use these parameters. A member of the annotationlib.Format enum can be passed to the annotation_format parameter to control the format of the returned annotations. For example, use annotation_format=annotationlib.Format.STRING to return annotations in string format.

Raises ValueError if no signature can be provided, and TypeError if that type of object is not supported. Also, if the annotations are stringized, and eval_str is not false, the eval() call(s) to un-stringize the annotations in annotationlib.get_annotations() could potentially raise any kind of exception.

A slash (/) in the signature of a function denotes that the parameters prior to it are positional-only. For more info, see the FAQ entry on positional-only parameters.

在 3.5 版的變更: The follow_wrapped parameter was added. Pass False to get a signature of callable specifically (callable.__wrapped__ will not be used to unwrap decorated callables.)

在 3.10 版的變更: The globals, locals, and eval_str parameters were added.

在 3.14 版的變更: 新增了 annotation_format 參數。

備註

Some callables may not be introspectable in certain implementations of Python. For example, in CPython, some built-in functions defined in C provide no metadata about their arguments.

CPython 實作細節： If the passed object has a __signature__ attribute, we may use it to create the signature. The exact semantics are an implementation detail and are subject to unannounced changes. Consult the source code for current semantics.

class inspect.Signature(parameters=None, *, return_annotation=Signature.empty)

A Signature object represents the call signature of a function and its return annotation. For each parameter accepted by the function it stores a Parameter object in its parameters collection.

The optional parameters argument is a sequence of Parameter objects, which is validated to check that there are no parameters with duplicate names, and that the parameters are in the right order, i.e. positional-only first, then positional-or-keyword, and that parameters with defaults follow parameters without defaults.

The optional return_annotation argument can be an arbitrary Python object. It represents the "return" annotation of the callable.

Signature objects are immutable. Use Signature.replace() or copy.replace() to make a modified copy.

在 3.5 版的變更: Signature objects are now picklable and hashable.

empty

A special class-level marker to specify absence of a return annotation.

parameters

An ordered mapping of parameters' names to the corresponding Parameter objects. Parameters appear in strict definition order, including keyword-only parameters.

在 3.7 版的變更: Python only explicitly guaranteed that it preserved the declaration order of keyword-only parameters as of version 3.7, although in practice this order had always been preserved in Python 3.

return_annotation

The "return" annotation for the callable. If the callable has no "return" annotation, this attribute is set to Signature.empty.

bind(*args, **kwargs)

Create a mapping from positional and keyword arguments to parameters. Returns BoundArguments if *args and **kwargs match the signature, or raises a TypeError.

bind_partial(*args, **kwargs)

Works the same way as Signature.bind(), but allows the omission of some required arguments (mimics functools.partial() behavior.) Returns BoundArguments, or raises a TypeError if the passed arguments do not match the signature.

replace(*[, parameters][, return_annotation])

Create a new Signature instance based on the instance replace() was invoked on. It is possible to pass different parameters and/or return_annotation to override the corresponding properties of the base signature. To remove return_annotation from the copied Signature, pass in Signature.empty.

>>> def test(a, b):
...     pass
...
>>> sig = signature(test)
>>> new_sig = sig.replace(return_annotation="new return anno")
>>> str(new_sig)
"(a, b) -> 'new return anno'"

Signature objects are also supported by the generic function copy.replace().

format(*, max_width=None, quote_annotation_strings=True)

Create a string representation of the Signature object.

If max_width is passed, the method will attempt to fit the signature into lines of at most max_width characters. If the signature is longer than max_width, all parameters will be on separate lines.

If quote_annotation_strings is False, annotations in the signature are displayed without opening and closing quotation marks if they are strings. This is useful if the signature was created with the STRING format or if from __future__ import annotations was used.

在 3.13 版被加入.

在 3.14 版的變更: 新增了 unquote_annotations 參數。

classmethod from_callable(obj, *, follow_wrapped=True, globals=None, locals=None, eval_str=False)

Return a Signature (or its subclass) object for a given callable obj.

此方法簡化了 Signature 的子類別化：

class MySignature(Signature):
    pass
sig = MySignature.from_callable(sum)
assert isinstance(sig, MySignature)

Its behavior is otherwise identical to that of signature().

在 3.5 版被加入.

在 3.10 版的變更: The globals, locals, and eval_str parameters were added.

class inspect.Parameter(name, kind, *, default=Parameter.empty, annotation=Parameter.empty)

Parameter objects are immutable. Instead of modifying a Parameter object, you can use Parameter.replace() or copy.replace() to create a modified copy.

在 3.5 版的變更: Parameter objects are now picklable and hashable.

empty

A special class-level marker to specify absence of default values and annotations.

name

The name of the parameter as a string. The name must be a valid Python identifier.

CPython 實作細節： CPython generates implicit parameter names of the form .0 on the code objects used to implement comprehensions and generator expressions.

在 3.6 版的變更: These parameter names are now exposed by this module as names like implicit0.

default

The default value for the parameter. If the parameter has no default value, this attribute is set to Parameter.empty.

annotation

The annotation for the parameter. If the parameter has no annotation, this attribute is set to Parameter.empty.

kind

Describes how argument values are bound to the parameter. The possible values are accessible via Parameter (like Parameter.KEYWORD_ONLY), and support comparison and ordering, in the following order:

名稱

意義

POSITIONAL_ONLY

Value must be supplied as a positional argument. Positional only parameters are those which appear before a / entry (if present) in a Python function definition.

POSITIONAL_OR_KEYWORD

Value may be supplied as either a keyword or positional argument (this is the standard binding behaviour for functions implemented in Python.)

VAR_POSITIONAL

A tuple of positional arguments that aren't bound to any other parameter. This corresponds to a *args parameter in a Python function definition.

KEYWORD_ONLY

Value must be supplied as a keyword argument. Keyword only parameters are those which appear after a * or *args entry in a Python function definition.

VAR_KEYWORD

A dict of keyword arguments that aren't bound to any other parameter. This corresponds to a **kwargs parameter in a Python function definition.

Example: print all keyword-only arguments without default values:

>>> def foo(a, b, *, c, d=10):
...     pass

>>> sig = signature(foo)
>>> for param in sig.parameters.values():
...     if (param.kind == param.KEYWORD_ONLY and
...                        param.default is param.empty):
...         print('Parameter:', param)
Parameter: c

kind.description

Describes an enum value of Parameter.kind.

在 3.8 版被加入.

範例：列印所有引數的描述：

>>> def foo(a, b, *, c, d=10):
...     pass

>>> sig = signature(foo)
>>> for param in sig.parameters.values():
...     print(param.kind.description)
positional or keyword
positional or keyword
keyword-only
keyword-only

replace(*[, name][, kind][, default][, annotation])

Create a new Parameter instance based on the instance replaced was invoked on. To override a Parameter attribute, pass the corresponding argument. To remove a default value or/and an annotation from a Parameter, pass Parameter.empty.

>>> from inspect import Parameter
>>> param = Parameter('foo', Parameter.KEYWORD_ONLY, default=42)
>>> str(param)
'foo=42'

>>> str(param.replace()) # Will create a shallow copy of 'param'
'foo=42'

>>> str(param.replace(default=Parameter.empty, annotation='spam'))
"foo: 'spam'"

Parameter objects are also supported by the generic function copy.replace().

在 3.4 版的變更: In Python 3.3 Parameter objects were allowed to have name set to None if their kind was set to POSITIONAL_ONLY. This is no longer permitted.

class inspect.BoundArguments

Result of a Signature.bind() or Signature.bind_partial() call. Holds the mapping of arguments to the function's parameters.

arguments

A mutable mapping of parameters' names to arguments' values. Contains only explicitly bound arguments. Changes in arguments will reflect in args and kwargs.

Should be used in conjunction with Signature.parameters for any argument processing purposes.

備註

Arguments for which Signature.bind() or Signature.bind_partial() relied on a default value are skipped. However, if needed, use BoundArguments.apply_defaults() to add them.

在 3.9 版的變更: arguments is now of type dict. Formerly, it was of type collections.OrderedDict.

args

A tuple of positional arguments values. Dynamically computed from the arguments attribute.

kwargs

A dict of keyword arguments values. Dynamically computed from the arguments attribute. Arguments that can be passed positionally are included in args instead.

signature

A reference to the parent Signature object.

apply_defaults()

為遺漏的引數設定預設值。

For variable-positional arguments (*args) the default is an empty tuple.

For variable-keyword arguments (**kwargs) the default is an empty dict.

>>> def foo(a, b='ham', *args): pass
>>> ba = inspect.signature(foo).bind('spam')
>>> ba.apply_defaults()
>>> ba.arguments
{'a': 'spam', 'b': 'ham', 'args': ()}

在 3.5 版被加入.

The args and kwargs properties can be used to invoke functions:

def test(a, *, b):
    ...

sig = signature(test)
ba = sig.bind(10, b=20)
test(*ba.args, **ba.kwargs)

也參考

PEP 362 [https://peps.python.org/pep-0362/] - 函式簽名物件。

詳細的規格、實作細節和範例。

類別與函式

inspect.getclasstree(classes, unique=False)

Arrange the given list of classes into a hierarchy of nested lists. Where a nested list appears, it contains classes derived from the class whose entry immediately precedes the list. Each entry is a 2-tuple containing a class and a tuple of its base classes. If the unique argument is true, exactly one entry appears in the returned structure for each class in the given list. Otherwise, classes using multiple inheritance and their descendants will appear multiple times.

inspect.getfullargspec(func)

Get the names and default values of a Python function's parameters. A named tuple is returned:

FullArgSpec(args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations)

args is a list of the positional parameter names. varargs is the name of the * parameter or None if arbitrary positional arguments are not accepted. varkw is the name of the ** parameter or None if arbitrary keyword arguments are not accepted. defaults is an n-tuple of default argument values corresponding to the last n positional parameters, or None if there are no such defaults defined. kwonlyargs is a list of keyword-only parameter names in declaration order. kwonlydefaults is a dictionary mapping parameter names from kwonlyargs to the default values used if no argument is supplied. annotations is a dictionary mapping parameter names to annotations. The special key "return" is used to report the function return value annotation (if any).

Note that signature() and Signature Object provide the recommended API for callable introspection, and support additional behaviours (like positional-only arguments) that are sometimes encountered in extension module APIs. This function is retained primarily for use in code that needs to maintain compatibility with the Python 2 inspect module API.

在 3.4 版的變更: This function is now based on signature(), but still ignores __wrapped__ attributes and includes the already bound first parameter in the signature output for bound methods.

在 3.6 版的變更: This method was previously documented as deprecated in favour of signature() in Python 3.5, but that decision has been reversed in order to restore a clearly supported standard interface for single-source Python 2/3 code migrating away from the legacy getargspec() API.

在 3.7 版的變更: Python only explicitly guaranteed that it preserved the declaration order of keyword-only parameters as of version 3.7, although in practice this order had always been preserved in Python 3.

inspect.getargvalues(frame)

Get information about arguments passed into a particular frame. A named tuple ArgInfo(args, varargs, keywords, locals) is returned. args is a list of the argument names. varargs and keywords are the names of the * and ** arguments or None. locals is the locals dictionary of the given frame.

備註

This function was inadvertently marked as deprecated in Python 3.5.

inspect.formatargvalues(args[, varargs, varkw, locals, formatarg, formatvarargs, formatvarkw, formatvalue])

Format a pretty argument spec from the four values returned by getargvalues(). The format* arguments are the corresponding optional formatting functions that are called to turn names and values into strings.

備註

This function was inadvertently marked as deprecated in Python 3.5.

inspect.getmro(cls)

Return a tuple of class cls's base classes, including cls, in method resolution order. No class appears more than once in this tuple. Note that the method resolution order depends on cls's type. Unless a very peculiar user-defined metatype is in use, cls will be the first element of the tuple.

inspect.getcallargs(func, /, *args, **kwds)

Bind the args and kwds to the argument names of the Python function or method func, as if it was called with them. For bound methods, bind also the first argument (typically named self) to the associated instance. A dict is returned, mapping the argument names (including the names of the * and ** arguments, if any) to their values from args and kwds. In case of invoking func incorrectly, i.e. whenever func(*args, **kwds) would raise an exception because of incompatible signature, an exception of the same type and the same or similar message is raised. For example:

>>> from inspect import getcallargs
>>> def f(a, b=1, *pos, **named):
...     pass
...
>>> getcallargs(f, 1, 2, 3) == {'a': 1, 'named': {}, 'b': 2, 'pos': (3,)}
True
>>> getcallargs(f, a=2, x=4) == {'a': 2, 'named': {'x': 4}, 'b': 1, 'pos': ()}
True
>>> getcallargs(f)
Traceback (most recent call last):
...
TypeError: f() missing 1 required positional argument: 'a'

在 3.2 版被加入.

在 3.5 版之後被棄用: 請改用 Signature.bind() 與 Signature.bind_partial()。

inspect.getclosurevars(func)

Get the mapping of external name references in a Python function or method func to their current values. A named tuple ClosureVars(nonlocals, globals, builtins, unbound) is returned. nonlocals maps referenced names to lexical closure variables, globals to the function's module globals and builtins to the builtins visible from the function body. unbound is the set of names referenced in the function that could not be resolved at all given the current module globals and builtins.

如果 func 不是 Python 函式或方法，則引發 TypeError。

在 3.3 版被加入.

inspect.unwrap(func, *, stop=None)

Get the object wrapped by func. It follows the chain of __wrapped__ attributes returning the last object in the chain.

stop is an optional callback accepting an object in the wrapper chain as its sole argument that allows the unwrapping to be terminated early if the callback returns a true value. If the callback never returns a true value, the last object in the chain is returned as usual. For example, signature() uses this to stop unwrapping if any object in the chain has a __signature__ attribute defined.

如果遇到循環，則引發 ValueError。

在 3.4 版被加入.

inspect.get_annotations(obj, *, globals=None, locals=None, eval_str=False, format=annotationlib.Format.VALUE)

Compute the annotations dict for an object.

This is an alias for annotationlib.get_annotations(); see the documentation of that function for more information.

警示

This function may execute arbitrary code contained in annotations. See Security implications of introspecting annotations for more information.

在 3.10 版被加入.

在 3.14 版的變更: This function is now an alias for annotationlib.get_annotations(). Calling it as inspect.get_annotations will continue to work.

直譯器堆疊

Some of the following functions return FrameInfo objects. For backwards compatibility these objects allow tuple-like operations on all attributes except positions. This behavior is considered deprecated and may be removed in the future.

class inspect.FrameInfo

frame

The frame object that the record corresponds to.

filename

The file name associated with the code being executed by the frame this record corresponds to.

lineno

The line number of the current line associated with the code being executed by the frame this record corresponds to.

function

The function name that is being executed by the frame this record corresponds to.

code_context

A list of lines of context from the source code that's being executed by the frame this record corresponds to.

index

The index of the current line being executed in the code_context list.

positions

A dis.Positions object containing the start line number, end line number, start column offset, and end column offset associated with the instruction being executed by the frame this record corresponds to.

在 3.5 版的變更: Return a named tuple instead of a tuple.

在 3.11 版的變更: FrameInfo is now a class instance (that is backwards compatible with the previous named tuple).

class inspect.Traceback

filename

The file name associated with the code being executed by the frame this traceback corresponds to.

lineno

The line number of the current line associated with the code being executed by the frame this traceback corresponds to.

function

The function name that is being executed by the frame this traceback corresponds to.

code_context

A list of lines of context from the source code that's being executed by the frame this traceback corresponds to.

index

The index of the current line being executed in the code_context list.

positions

A dis.Positions object containing the start line number, end line number, start column offset, and end column offset associated with the instruction being executed by the frame this traceback corresponds to.

在 3.11 版的變更: Traceback is now a class instance (that is backwards compatible with the previous named tuple).

備註

Keeping references to frame objects, as found in the first element of the frame records these functions return, can cause your program to create reference cycles. Once a reference cycle has been created, the lifespan of all objects which can be accessed from the objects which form the cycle can become much longer even if Python's optional cycle detector is enabled. If such cycles must be created, it is important to ensure they are explicitly broken to avoid the delayed destruction of objects and increased memory consumption which occurs.

Though the cycle detector will catch these, destruction of the frames (and local variables) can be made deterministic by removing the cycle in a finally clause. This is also important if the cycle detector was disabled when Python was compiled or using gc.disable(). For example:

def handle_stackframe_without_leak():
    frame = inspect.currentframe()
    try:
        # do something with the frame
    finally:
        del frame

If you want to keep the frame around (for example to print a traceback later), you can also break reference cycles by using the frame.clear() method.

The optional context argument supported by most of these functions specifies the number of lines of context to return, which are centered around the current line.

inspect.getframeinfo(frame, context=1)

Get information about a frame or traceback object. A Traceback object is returned.

在 3.11 版的變更: A Traceback object is returned instead of a named tuple.

inspect.getouterframes(frame, context=1)

Get a list of FrameInfo objects for a frame and all outer frames. These frames represent the calls that lead to the creation of frame. The first entry in the returned list represents frame; the last entry represents the outermost call on frame's stack.

在 3.5 版的變更: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

在 3.11 版的變更: 回傳一個 FrameInfo 物件串列。

inspect.getinnerframes(traceback, context=1)

Get a list of FrameInfo objects for a traceback's frame and all inner frames. These frames represent calls made as a consequence of frame. The first entry in the list represents traceback; the last entry represents where the exception was raised.

在 3.5 版的變更: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

在 3.11 版的變更: 回傳一個 FrameInfo 物件串列。

inspect.currentframe()

Return the frame object for the caller's stack frame.

CPython 實作細節： This function relies on Python stack frame support in the interpreter, which isn't guaranteed to exist in all implementations of Python. If running in an implementation without Python stack frame support this function returns None.

inspect.stack(context=1)

Return a list of FrameInfo objects for the caller's stack. The first entry in the returned list represents the caller; the last entry represents the outermost call on the stack.

在 3.5 版的變更: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

在 3.11 版的變更: 回傳一個 FrameInfo 物件串列。

inspect.trace(context=1)

Return a list of FrameInfo objects for the stack between the current frame and the frame in which an exception currently being handled was raised in. The first entry in the list represents the caller; the last entry represents where the exception was raised.

在 3.5 版的變更: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

在 3.11 版的變更: 回傳一個 FrameInfo 物件串列。

Fetching attributes statically

Both getattr() and hasattr() can trigger code execution when fetching or checking for the existence of attributes. Descriptors, like properties, will be invoked and __getattr__() and __getattribute__() may be called.

For cases where you want passive introspection, like documentation tools, this can be inconvenient. getattr_static() has the same signature as getattr() but avoids executing code when it fetches attributes.

inspect.getattr_static(obj, attr, default=None)

Retrieve attributes without triggering dynamic lookup via the descriptor protocol, __getattr__() or __getattribute__().

Note: this function may not be able to retrieve all attributes that getattr can fetch (like dynamically created attributes) and may find attributes that getattr can't (like descriptors that raise AttributeError). It can also return descriptors objects instead of instance members.

If the instance __dict__ is shadowed by another member (for example a property) then this function will be unable to find instance members.

在 3.2 版被加入.

getattr_static() does not resolve descriptors, for example slot descriptors or getset descriptors on objects implemented in C. The descriptor object is returned instead of the underlying attribute.

You can handle these with code like the following. Note that for arbitrary getset descriptors invoking these may trigger code execution:

# example code for resolving the builtin descriptor types
class _foo:
    __slots__ = ['foo']

slot_descriptor = type(_foo.foo)
getset_descriptor = type(type(open(__file__)).name)
wrapper_descriptor = type(str.__dict__['__add__'])
descriptor_types = (slot_descriptor, getset_descriptor, wrapper_descriptor)

result = getattr_static(some_object, 'foo')
if type(result) in descriptor_types:
    try:
        result = result.__get__()
    except AttributeError:
        # descriptors can raise AttributeError to
        # indicate there is no underlying value
        # in which case the descriptor itself will
        # have to do
        pass

Current State of Generators, Coroutines, and Asynchronous Generators

When implementing coroutine schedulers and for other advanced uses of generators, it is useful to determine whether a generator is currently executing, is waiting to start or resume or execution, or has already terminated. getgeneratorstate() allows the current state of a generator to be determined easily.

inspect.getgeneratorstate(generator)

Get current state of a generator-iterator.

Possible states are:

GEN_CREATED：等待開始執行。

GEN_RUNNING：目前正在被直譯器執行。

GEN_SUSPENDED: Currently suspended at a yield expression.

GEN_CLOSED：執行已完成。

在 3.2 版被加入.

inspect.getcoroutinestate(coroutine)

Get current state of a coroutine object. The function is intended to be used with coroutine objects created by async def functions, but will accept any coroutine-like object that has cr_running and cr_frame attributes.

Possible states are:

CORO_CREATED：等待開始執行。

CORO_RUNNING：目前正在被直譯器執行。

CORO_SUSPENDED: Currently suspended at an await expression.

CORO_CLOSED：執行已完成。

在 3.5 版被加入.

inspect.getasyncgenstate(agen)

Get current state of an asynchronous generator object. The function is intended to be used with asynchronous iterator objects created by async def functions which use the yield statement, but will accept any asynchronous generator-like object that has ag_running and ag_frame attributes.

Possible states are:

AGEN_CREATED: 等待開始執行。

AGEN_RUNNING: 目前正在被直譯器執行。

AGEN_SUSPENDED: 目前於 yield 運算式暫停。

AGEN_CLOSED: 執行已完成。

在 3.12 版被加入.

The current internal state of the generator can also be queried. This is mostly useful for testing purposes, to ensure that internal state is being updated as expected:

inspect.getgeneratorlocals(generator)

Get the mapping of live local variables in generator to their current values. A dictionary is returned that maps from variable names to values. This is the equivalent of calling locals() in the body of the generator, and all the same caveats apply.

If generator is a generator with no currently associated frame, then an empty dictionary is returned. TypeError is raised if generator is not a Python generator object.

CPython 實作細節： This function relies on the generator exposing a Python stack frame for introspection, which isn't guaranteed to be the case in all implementations of Python. In such cases, this function will always return an empty dictionary.

在 3.3 版被加入.

inspect.getcoroutinelocals(coroutine)

This function is analogous to getgeneratorlocals(), but works for coroutine objects created by async def functions.

在 3.5 版被加入.

inspect.getasyncgenlocals(agen)

This function is analogous to getgeneratorlocals(), but works for asynchronous generator objects created by async def functions which use the yield statement.

在 3.12 版被加入.

Code Objects Bit Flags

Python code objects have a co_flags attribute, which is a bitmap of the following flags:

inspect.CO_OPTIMIZED

The code object is optimized, using fast locals.

inspect.CO_NEWLOCALS

If set, a new dict will be created for the frame's f_locals when the code object is executed.

inspect.CO_VARARGS

The code object has a variable positional parameter (*args-like).

inspect.CO_VARKEYWORDS

The code object has a variable keyword parameter (**kwargs-like).

inspect.CO_NESTED

The flag is set when the code object is a nested function.

inspect.CO_GENERATOR

The flag is set when the code object is a generator function, i.e. a generator object is returned when the code object is executed.

inspect.CO_COROUTINE

The flag is set when the code object is a coroutine function. When the code object is executed it returns a coroutine object. See PEP 492 [https://peps.python.org/pep-0492/] for more details.

在 3.5 版被加入.

inspect.CO_ITERABLE_COROUTINE

The flag is used to transform generators into generator-based coroutines. Generator objects with this flag can be used in await expression, and can yield from coroutine objects. See PEP 492 [https://peps.python.org/pep-0492/] for more details.

在 3.5 版被加入.

inspect.CO_ASYNC_GENERATOR

The flag is set when the code object is an asynchronous generator function. When the code object is executed it returns an asynchronous generator object. See PEP 525 [https://peps.python.org/pep-0525/] for more details.

在 3.6 版被加入.

inspect.CO_HAS_DOCSTRING

The flag is set when there is a docstring for the code object in the source code. If set, it will be the first item in co_consts.

在 3.14 版被加入.

inspect.CO_METHOD

The flag is set when the code object is a function defined in class scope.

在 3.14 版被加入.

備註

The flags are specific to CPython, and may not be defined in other Python implementations. Furthermore, the flags are an implementation detail, and can be removed or deprecated in future Python releases. It's recommended to use public APIs from the inspect module for any introspection needs.

Buffer flags

class inspect.BufferFlags

This is an enum.IntFlag that represents the flags that can be passed to the __buffer__() method of objects implementing the buffer protocol.

The meaning of the flags is explained at Buffer request types.

SIMPLE

WRITABLE

FORMAT

ND

STRIDES

C_CONTIGUOUS

F_CONTIGUOUS

ANY_CONTIGUOUS

INDIRECT

CONTIG

CONTIG_RO

STRIDED

STRIDED_RO

RECORDS

RECORDS_RO

FULL

FULL_RO

READ

WRITE

在 3.12 版被加入.

命令列介面

The inspect module also provides a basic introspection capability from the command line.

By default, accepts the name of a module and prints the source of that module. A class or function within the module can be printed instead by appended a colon and the qualified name of the target object.

--details

Print information about the specified object rather than the source code

annotationlib --- 用於自我檢查註釋的功能

在 3.14 版被加入.

原始碼： Lib/annotationlib.py [https://github.com/python/cpython/tree/3.14/Lib/annotationlib.py]

The annotationlib module provides tools for introspecting annotations on modules, classes, and functions.

Annotations are lazily evaluated and often contain forward references to objects that are not yet defined when the annotation is created. This module provides a set of low-level tools that can be used to retrieve annotations in a reliable way, even in the presence of forward references and other edge cases.

This module supports retrieving annotations in three main formats (see Format), each of which works best for different use cases:

VALUE evaluates the annotations and returns their value. This is most straightforward to work with, but it may raise errors, for example if the annotations contain references to undefined names.

FORWARDREF returns ForwardRef objects for annotations that cannot be resolved, allowing you to inspect the annotations without evaluating them. This is useful when you need to work with annotations that may contain unresolved forward references.

STRING returns the annotations as a string, similar to how it would appear in the source file. This is useful for documentation generators that want to display annotations in a readable way.

The get_annotations() function is the main entry point for retrieving annotations. Given a function, class, or module, it returns an annotations dictionary in the requested format. This module also provides functionality for working directly with the annotate function that is used to evaluate annotations, such as get_annotate_from_class_namespace() and call_annotate_function(), as well as the call_evaluate_function() function for working with evaluate functions.

警示

Most functionality in this module can execute arbitrary code; see the security section for more information.

也參考

PEP 649 [https://peps.python.org/pep-0649/] proposed the current model for how annotations work in Python.

PEP 749 [https://peps.python.org/pep-0749/] expanded on various aspects of PEP 649 [https://peps.python.org/pep-0649/] and introduced the annotationlib module.

註釋 (annotation) 最佳實踐 provides best practices for working with annotations.

typing-extensions [https://pypi.org/project/typing-extensions/] provides a backport of get_annotations() that works on earlier versions of Python.

Annotation semantics

The way annotations are evaluated has changed over the history of Python 3, and currently still depends on a future import. There have been execution models for annotations:

Stock semantics (default in Python 3.0 through 3.13; see PEP 3107 [https://peps.python.org/pep-3107/] and PEP 526 [https://peps.python.org/pep-0526/]): Annotations are evaluated eagerly, as they are encountered in the source code.

Stringified annotations (used with from __future__ import annotations in Python 3.7 and newer; see PEP 563 [https://peps.python.org/pep-0563/]): Annotations are stored as strings only.

Deferred evaluation (default in Python 3.14 and newer; see PEP 649 [https://peps.python.org/pep-0649/] and PEP 749 [https://peps.python.org/pep-0749/]): Annotations are evaluated lazily, only when they are accessed.

As an example, consider the following program:

def func(a: Cls) -> None:
    print(a)

class Cls: pass

print(func.__annotations__)

這會有以下行為：

Under stock semantics (Python 3.13 and earlier), it will throw a NameError at the line where func is defined, because Cls is an undefined name at that point.

Under stringified annotations (if from __future__ import annotations is used), it will print {'a': 'Cls', 'return': 'None'}.

Under deferred evaluation (Python 3.14 and later), it will print {'a': <class 'Cls'>, 'return': None}.

Stock semantics were used when function annotations were first introduced in Python 3.0 (by PEP 3107 [https://peps.python.org/pep-3107/]) because this was the simplest, most obvious way to implement annotations. The same execution model was used when variable annotations were introduced in Python 3.6 (by PEP 526 [https://peps.python.org/pep-0526/]). However, stock semantics caused problems when using annotations as type hints, such as a need to refer to names that are not yet defined when the annotation is encountered. In addition, there were performance problems with executing annotations at module import time. Therefore, in Python 3.7, PEP 563 [https://peps.python.org/pep-0563/] introduced the ability to store annotations as strings using the from __future__ import annotations syntax. The plan at the time was to eventually make this behavior the default, but a problem appeared: stringified annotations are more difficult to process for those who introspect annotations at runtime. An alternative proposal, PEP 649 [https://peps.python.org/pep-0649/], introduced the third execution model, deferred evaluation, and was implemented in Python 3.14. Stringified annotations are still used if from __future__ import annotations is present, but this behavior will eventually be removed.

Classes

class annotationlib.Format

An IntEnum describing the formats in which annotations can be returned. Members of the enum, or their equivalent integer values, can be passed to get_annotations() and other functions in this module, as well as to __annotate__ functions.

VALUE = 1

Values are the result of evaluating the annotation expressions.

VALUE_WITH_FAKE_GLOBALS = 2

Special value used to signal that an annotate function is being evaluated in a special environment with fake globals. When passed this value, annotate functions should either return the same value as for the Format.VALUE format, or raise NotImplementedError to signal that they do not support execution in this environment. This format is only used internally and should not be passed to the functions in this module.

FORWARDREF = 3

Values are real annotation values (as per Format.VALUE format) for defined values, and ForwardRef proxies for undefined values. Real objects may contain references to ForwardRef proxy objects.

STRING = 4

Values are the text string of the annotation as it appears in the source code, up to modifications including, but not restricted to, whitespace normalizations and constant values optimizations.

The exact values of these strings may change in future versions of Python.

在 3.14 版被加入.

class annotationlib.ForwardRef

A proxy object for forward references in annotations.

Instances of this class are returned when the FORWARDREF format is used and annotations contain a name that cannot be resolved. This can happen when a forward reference is used in an annotation, such as when a class is referenced before it is defined.

__forward_arg__

A string containing the code that was evaluated to produce the ForwardRef. The string may not be exactly equivalent to the original source.

evaluate(*, owner=None, globals=None, locals=None, type_params=None, format=Format.VALUE)

Evaluate the forward reference, returning its value.

If the format argument is VALUE (the default), this method may throw an exception, such as NameError, if the forward reference refers to a name that cannot be resolved. The arguments to this method can be used to provide bindings for names that would otherwise be undefined. If the format argument is FORWARDREF, the method will never throw an exception, but may return a ForwardRef instance. For example, if the forward reference object contains the code list[undefined], where undefined is a name that is not defined, evaluating it with the FORWARDREF format will return list[ForwardRef('undefined')]. If the format argument is STRING, the method will return __forward_arg__.

The owner parameter provides the preferred mechanism for passing scope information to this method. The owner of a ForwardRef is the object that contains the annotation from which the ForwardRef derives, such as a module object, type object, or function object.

The globals, locals, and type_params parameters provide a more precise mechanism for influencing the names that are available when the ForwardRef is evaluated. globals and locals are passed to eval(), representing the global and local namespaces in which the name is evaluated. The type_params parameter is relevant for objects created using the native syntax for generic classes and functions. It is a tuple of type parameters that are in scope while the forward reference is being evaluated. For example, if evaluating a ForwardRef retrieved from an annotation found in the class namespace of a generic class C, type_params should be set to C.__type_params__.

ForwardRef instances returned by get_annotations() retain references to information about the scope they originated from, so calling this method with no further arguments may be sufficient to evaluate such objects. ForwardRef instances created by other means may not have any information about their scope, so passing arguments to this method may be necessary to evaluate them successfully.

If no owner, globals, locals, or type_params are provided and the ForwardRef does not contain information about its origin, empty globals and locals dictionaries are used.

在 3.14 版被加入.

Functions

annotationlib.annotations_to_string(annotations)

Convert an annotations dict containing runtime values to a dict containing only strings. If the values are not already strings, they are converted using type_repr(). This is meant as a helper for user-provided annotate functions that support the STRING format but do not have access to the code creating the annotations.

For example, this is used to implement the STRING for typing.TypedDict classes created through the functional syntax:

>>> from typing import TypedDict
>>> Movie = TypedDict("movie", {"name": str, "year": int})
>>> get_annotations(Movie, format=Format.STRING)
{'name': 'str', 'year': 'int'}

在 3.14 版被加入.

annotationlib.call_annotate_function(annotate, format, *, owner=None)

Call the annotate function annotate with the given format, a member of the Format enum, and return the annotations dictionary produced by the function.

This helper function is required because annotate functions generated by the compiler for functions, classes, and modules only support the VALUE format when called directly. To support other formats, this function calls the annotate function in a special environment that allows it to produce annotations in the other formats. This is a useful building block when implementing functionality that needs to partially evaluate annotations while a class is being constructed.

owner is the object that owns the annotation function, usually a function, class, or module. If provided, it is used in the FORWARDREF format to produce a ForwardRef object that carries more information.

也參考

PEP 649 [https://peps.python.org/pep-0649/#the-stringizer-and-the-fake-globals-environment] contains an explanation of the implementation technique used by this function.

在 3.14 版被加入.

annotationlib.call_evaluate_function(evaluate, format, *, owner=None)

Call the evaluate function evaluate with the given format, a member of the Format enum, and return the value produced by the function. This is similar to call_annotate_function(), but the latter always returns a dictionary mapping strings to annotations, while this function returns a single value.

This is intended for use with the evaluate functions generated for lazily evaluated elements related to type aliases and type parameters:

typing.TypeAliasType.evaluate_value(), the value of type aliases

typing.TypeVar.evaluate_bound(), the bound of type variables

typing.TypeVar.evaluate_constraints(), the constraints of type variables

typing.TypeVar.evaluate_default(), the default value of type variables

typing.ParamSpec.evaluate_default(), the default value of parameter specifications

typing.TypeVarTuple.evaluate_default(), the default value of type variable tuples

owner is the object that owns the evaluate function, such as the type alias or type variable object.

format can be used to control the format in which the value is returned:

>>> type Alias = undefined
>>> call_evaluate_function(Alias.evaluate_value, Format.VALUE)
Traceback (most recent call last):
...
NameError: name 'undefined' is not defined
>>> call_evaluate_function(Alias.evaluate_value, Format.FORWARDREF)
ForwardRef('undefined')
>>> call_evaluate_function(Alias.evaluate_value, Format.STRING)
'undefined'

在 3.14 版被加入.

annotationlib.get_annotate_from_class_namespace(namespace)

Retrieve the annotate function from a class namespace dictionary namespace. Return None if the namespace does not contain an annotate function. This is primarily useful before the class has been fully created (e.g., in a metaclass); after the class exists, the annotate function can be retrieved with cls.__annotate__. See below for an example using this function in a metaclass.

在 3.14 版被加入.

annotationlib.get_annotations(obj, *, globals=None, locals=None, eval_str=False, format=Format.VALUE)

Compute the annotations dict for an object.

obj may be a callable, class, module, or other object with __annotate__ or __annotations__ attributes. Passing any other object raises TypeError.

The format parameter controls the format in which annotations are returned, and must be a member of the Format enum or its integer equivalent. The different formats work as follows:

VALUE: object.__annotations__ is tried first; if that does not exist, the object.__annotate__ function is called if it exists.

FORWARDREF: If object.__annotations__ exists and can be evaluated successfully, it is used; otherwise, the object.__annotate__ function is called. If it does not exist either, object.__annotations__ is tried again and any error from accessing it is re-raised.

When calling object.__annotate__ it is first called with FORWARDREF. If this is not implemented, it will then check if VALUE_WITH_FAKE_GLOBALS is supported and use that in the fake globals environment. If neither of these formats are supported, it will fall back to using VALUE. If VALUE fails, the error from this call will be raised.

STRING: If object.__annotate__ exists, it is called first; otherwise, object.__annotations__ is used and stringified using annotations_to_string().

When calling object.__annotate__ it is first called with STRING. If this is not implemented, it will then check if VALUE_WITH_FAKE_GLOBALS is supported and use that in the fake globals environment. If neither of these formats are supported, it will fall back to using VALUE with the result converted using annotations_to_string(). If VALUE fails, the error from this call will be raised.

Returns a dict. get_annotations() returns a new dict every time it's called; calling it twice on the same object will return two different but equivalent dicts.

This function handles several details for you:

If eval_str is true, values of type str will be un-stringized using eval(). This is intended for use with stringized annotations (from __future__ import annotations). It is an error to set eval_str to true with formats other than Format.VALUE.

If obj doesn't have an annotations dict, returns an empty dict. (Functions and methods always have an annotations dict; classes, modules, and other types of callables may not.)

Ignores inherited annotations on classes, as well as annotations on metaclasses. If a class doesn't have its own annotations dict, returns an empty dict.

All accesses to object members and dict values are done using getattr() and dict.get() for safety.

eval_str controls whether or not values of type str are replaced with the result of calling eval() on those values:

If eval_str is true, eval() is called on values of type str. (Note that get_annotations() doesn't catch exceptions; if eval() raises an exception, it will unwind the stack past the get_annotations() call.)

If eval_str is false (the default), values of type str are unchanged.

globals and locals are passed in to eval(); see the documentation for eval() for more information. If globals or locals is None, this function may replace that value with a context-specific default, contingent on type(obj):

如果 obj 是模組，則 globals 預設為 obj.__dict__。

If obj is a class, globals defaults to sys.modules[obj.__module__].__dict__ and locals defaults to the obj class namespace.

If obj is a callable, globals defaults to obj.__globals__, although if obj is a wrapped function (using functools.update_wrapper()) or a functools.partial object, it is unwrapped until a non-wrapped function is found.

Calling get_annotations() is best practice for accessing the annotations dict of any object. See 註釋 (annotation) 最佳實踐 for more information on annotations best practices.

>>> def f(a: int, b: str) -> float:
...     pass
>>> get_annotations(f)
{'a': <class 'int'>, 'b': <class 'str'>, 'return': <class 'float'>}

在 3.14 版被加入.

annotationlib.type_repr(value)

Convert an arbitrary Python value to a format suitable for use by the STRING format. This calls repr() for most objects, but has special handling for some objects, such as type objects.

This is meant as a helper for user-provided annotate functions that support the STRING format but do not have access to the code creating the annotations. It can also be used to provide a user-friendly string representation for other objects that contain values that are commonly encountered in annotations.

在 3.14 版被加入.

Recipes

Using annotations in a metaclass

A metaclass may want to inspect or even modify the annotations in a class body during class creation. Doing so requires retrieving annotations from the class namespace dictionary. For classes created with from __future__ import annotations, the annotations will be in the __annotations__ key of the dictionary. For other classes with annotations, get_annotate_from_class_namespace() can be used to get the annotate function, and call_annotate_function() can be used to call it and retrieve the annotations. Using the FORWARDREF format will usually be best, because this allows the annotations to refer to names that cannot yet be resolved when the class is created.

To modify the annotations, it is best to create a wrapper annotate function that calls the original annotate function, makes any necessary adjustments, and returns the result.

Below is an example of a metaclass that filters out all typing.ClassVar annotations from the class and puts them in a separate attribute:

import annotationlib
import typing

class ClassVarSeparator(type):
   def __new__(mcls, name, bases, ns):
      if "__annotations__" in ns:  # from __future__ import annotations
         annotations = ns["__annotations__"]
         classvar_keys = {
            key for key, value in annotations.items()
            # Use string comparison for simplicity; a more robust solution
            # could use annotationlib.ForwardRef.evaluate
            if value.startswith("ClassVar")
         }
         classvars = {key: annotations[key] for key in classvar_keys}
         ns["__annotations__"] = {
            key: value for key, value in annotations.items()
            if key not in classvar_keys
         }
         wrapped_annotate = None
      elif annotate := annotationlib.get_annotate_from_class_namespace(ns):
         annotations = annotationlib.call_annotate_function(
            annotate, format=annotationlib.Format.FORWARDREF
         )
         classvar_keys = {
            key for key, value in annotations.items()
            if typing.get_origin(value) is typing.ClassVar
         }
         classvars = {key: annotations[key] for key in classvar_keys}

         def wrapped_annotate(format):
            annos = annotationlib.call_annotate_function(annotate, format, owner=typ)
            return {key: value for key, value in annos.items() if key not in classvar_keys}

      else:  # no annotations
         classvars = {}
         wrapped_annotate = None
      typ = super().__new__(mcls, name, bases, ns)

      if wrapped_annotate is not None:
         # Wrap the original __annotate__ with a wrapper that removes ClassVars
         typ.__annotate__ = wrapped_annotate
      typ.classvars = classvars  # Store the ClassVars in a separate attribute
      return typ

STRING 格式的限制

The STRING format is meant to approximate the source code of the annotation, but the implementation strategy used means that it is not always possible to recover the exact source code.

First, the stringifier of course cannot recover any information that is not present in the compiled code, including comments, whitespace, parenthesization, and operations that get simplified by the compiler.

Second, the stringifier can intercept almost all operations that involve names looked up in some scope, but it cannot intercept operations that operate fully on constants. As a corollary, this also means it is not safe to request the STRING format on untrusted code: Python is powerful enough that it is possible to achieve arbitrary code execution even with no access to any globals or builtins. For example:

>>> def f(x: (1).__class__.__base__.__subclasses__()[-1].__init__.__builtins__["print"]("Hello world")): pass
...
>>> annotationlib.get_annotations(f, format=annotationlib.Format.STRING)
Hello world
{'x': 'None'}

備註

This particular example works as of the time of writing, but it relies on implementation details and is not guaranteed to work in the future.

Among the different kinds of expressions that exist in Python, as represented by the ast module, some expressions are supported, meaning that the STRING format can generally recover the original source code; others are unsupported, meaning that they may result in incorrect output or an error.

The following are supported (sometimes with caveats):

ast.BinOp

ast.UnaryOp

ast.Invert (~)、ast.UAdd (+) 和 ast.USub (-) 有被支援

ast.Not (not) 並不被支援

ast.Dict（除了使用 ** 解包的情況）

ast.Set

ast.Compare

ast.Eq 和 ast.NotEq 有被支援

ast.Lt, ast.LtE, ast.Gt, and ast.GtE are supported, but the operand may be flipped

ast.Is, ast.IsNot, ast.In, and ast.NotIn are not supported

ast.Call (except when using ** unpacking)

ast.Constant (though not the exact representation of the constant; for example, escape sequences in strings are lost; hexadecimal numbers are converted to decimal)

ast.Attribute (assuming the value is not a constant)

ast.Subscript (assuming the value is not a constant)

ast.Starred (* unpacking)

ast.Name

ast.List

ast.Tuple

ast.Slice

The following are unsupported, but throw an informative error when encountered by the stringifier:

ast.FormattedValue (f-strings; error is not detected if conversion specifiers like !r are used)

ast.JoinedStr（f 字串）

以下是不支援的，並且會導致不正確的輸出：

ast.BoolOp（and 和 or）

ast.IfExp

ast.Lambda

ast.ListComp

ast.SetComp

ast.DictComp

ast.GeneratorExp

The following are disallowed in annotation scopes and therefore not relevant:

ast.NamedExpr (:=)

ast.Await

ast.Yield

ast.YieldFrom

FORWARDREF 格式的限制

The FORWARDREF format aims to produce real values as much as possible, with anything that cannot be resolved replaced with ForwardRef objects. It is affected by broadly the same Limitations as the STRING format: annotations that perform operations on literals or that use unsupported expression types may raise exceptions when evaluated using the FORWARDREF format.

Below are a few examples of the behavior with unsupported expressions:

>>> from annotationlib import get_annotations, Format
>>> def zerodiv(x: 1 / 0): ...
>>> get_annotations(zerodiv, format=Format.STRING)
Traceback (most recent call last):
  ...
ZeroDivisionError: division by zero
>>> get_annotations(zerodiv, format=Format.FORWARDREF)
Traceback (most recent call last):
  ...
ZeroDivisionError: division by zero
>>> def ifexp(x: 1 if y else 0): ...
>>> get_annotations(ifexp, format=Format.STRING)
{'x': '1'}

Security implications of introspecting annotations

Much of the functionality in this module involves executing code related to annotations, which can then do arbitrary things. For example, get_annotations() may call an arbitrary annotate function, and ForwardRef.evaluate() may call eval() on an arbitrary string. Code contained in an annotation might make arbitrary system calls, enter an infinite loop, or perform any other operation. This is also true for any access of the __annotations__ attribute, and for various functions in the typing module that work with annotations, such as typing.get_type_hints().

Any security issue arising from this also applies immediately after importing code that may contain untrusted annotations: importing code can always cause arbitrary operations to be performed. However, it is unsafe to accept strings or other input from an untrusted source and pass them to any of the APIs for introspecting annotations, for example by editing an __annotations__ dictionary or directly creating a ForwardRef object.

site --- Site-specific configuration hook

原始碼：Lib/site.py [https://github.com/python/cpython/tree/3.14/Lib/site.py]

This module is automatically imported during initialization. The automatic import can be suppressed using the interpreter's -S option.

Importing this module normally appends site-specific paths to the module search path and adds callables, including help() to the built-in namespace. However, Python startup option -S blocks this and this module can be safely imported with no automatic modifications to the module search path or additions to the builtins. To explicitly trigger the usual site-specific additions, call the main() function.

在 3.3 版的變更: Importing the module used to trigger paths manipulation even when using -S.

It starts by constructing up to four directories from a head and a tail part. For the head part, it uses sys.prefix and sys.exec_prefix; empty heads are skipped. For the tail part, it uses the empty string and then lib/site-packages (on Windows) or lib/pythonX.Y[t]/site-packages (on Unix and macOS). (The optional suffix "t" indicates the free threading build, and is appended if "t" is present in the sys.abiflags constant.) For each of the distinct head-tail combinations, it sees if it refers to an existing directory, and if so, adds it to sys.path and also inspects the newly added path for configuration files.

在 3.5 版的變更: Support for the "site-python" directory has been removed.

在 3.13 版的變更: On Unix, Free threading Python installations are identified by the "t" suffix in the version-specific directory name, such as lib/python3.13t/.

在 3.14 版的變更: site is no longer responsible for updating sys.prefix and sys.exec_prefix on 虛擬環境. This is now done during the path initialization. As a result, under 虛擬環境, sys.prefix and sys.exec_prefix no longer depend on the site initialization, and are therefore unaffected by -S.

When running under a virtual environment, the pyvenv.cfg file in sys.prefix is checked for site-specific configurations. If the include-system-site-packages key exists and is set to true (case-insensitive), the system-level prefixes will be searched for site-packages, otherwise they won't.

A path configuration file is a file whose name has the form name.pth and exists in one of the four directories mentioned above; its contents are additional items (one per line) to be added to sys.path. Non-existing items are never added to sys.path, and no check is made that the item refers to a directory rather than a file. No item is added to sys.path more than once. Blank lines and lines beginning with # are skipped. Lines starting with import (followed by space or tab) are executed.

備註

An executable line in a .pth file is run at every Python startup, regardless of whether a particular module is actually going to be used. Its impact should thus be kept to a minimum. The primary intended purpose of executable lines is to make the corresponding module(s) importable (load 3rd-party import hooks, adjust PATH etc). Any other initialization is supposed to be done upon a module's actual import, if and when it happens. Limiting a code chunk to a single line is a deliberate measure to discourage putting anything more complex here.

在 3.13 版的變更: The .pth files are now decoded by UTF-8 at first and then by the locale encoding if it fails.

For example, suppose sys.prefix and sys.exec_prefix are set to /usr/local. The Python X.Y library is then installed in /usr/local/lib/pythonX.Y. Suppose this has a subdirectory /usr/local/lib/pythonX.Y/site-packages with three subsubdirectories, foo, bar and spam, and two path configuration files, foo.pth and bar.pth. Assume foo.pth contains the following:

# foo package configuration

foo
bar
bletch

and bar.pth contains:

# bar package configuration

bar

Then the following version-specific directories are added to sys.path, in this order:

/usr/local/lib/pythonX.Y/site-packages/bar
/usr/local/lib/pythonX.Y/site-packages/foo

Note that bletch is omitted because it doesn't exist; the bar directory precedes the foo directory because bar.pth comes alphabetically before foo.pth; and spam is omitted because it is not mentioned in either path configuration file.

sitecustomize

After these path manipulations, an attempt is made to import a module named sitecustomize, which can perform arbitrary site-specific customizations. It is typically created by a system administrator in the site-packages directory. If this import fails with an ImportError or its subclass exception, and the exception's name attribute equals to 'sitecustomize', it is silently ignored. If Python is started without output streams available, as with pythonw.exe on Windows (which is used by default to start IDLE), attempted output from sitecustomize is ignored. Any other exception causes a silent and perhaps mysterious failure of the process.

usercustomize

After this, an attempt is made to import a module named usercustomize, which can perform arbitrary user-specific customizations, if ENABLE_USER_SITE is true. This file is intended to be created in the user site-packages directory (see below), which is part of sys.path unless disabled by -s. If this import fails with an ImportError or its subclass exception, and the exception's name attribute equals to 'usercustomize', it is silently ignored.

Note that for some non-Unix systems, sys.prefix and sys.exec_prefix are empty, and the path manipulations are skipped; however the import of sitecustomize and usercustomize is still attempted.

Readline configuration

On systems that support readline, this module will also import and configure the rlcompleter module, if Python is started in interactive mode and without the -S option. The default behavior is enable tab-completion and to use ~/.python_history as the history save file. To disable it, delete (or override) the sys.__interactivehook__ attribute in your sitecustomize or usercustomize module or your PYTHONSTARTUP file.

在 3.4 版的變更: Activation of rlcompleter and history was made automatic.

模組內容

site.PREFIXES

A list of prefixes for site-packages directories.

site.ENABLE_USER_SITE

Flag showing the status of the user site-packages directory. True means that it is enabled and was added to sys.path. False means that it was disabled by user request (with -s or PYTHONNOUSERSITE). None means it was disabled for security reasons (mismatch between user or group id and effective id) or by an administrator.

site.USER_SITE

Path to the user site-packages for the running Python. Can be None if getusersitepackages() hasn't been called yet. Default value is ~/.local/lib/pythonX.Y[t]/site-packages for UNIX and non-framework macOS builds, ~/Library/Python/X.Y/lib/python/site-packages for macOS framework builds, and %APPDATA%\Python\PythonXY\site-packages on Windows. The optional "t" indicates the free-threaded build. This directory is a site directory, which means that .pth files in it will be processed.

site.USER_BASE

Path to the base directory for the user site-packages. Can be None if getuserbase() hasn't been called yet. Default value is ~/.local for UNIX and macOS non-framework builds, ~/Library/Python/X.Y for macOS framework builds, and %APPDATA%\Python for Windows. This value is used to compute the installation directories for scripts, data files, Python modules, etc. for the user installation scheme. See also PYTHONUSERBASE.

site.main()

Adds all the standard site-specific directories to the module search path. This function is called automatically when this module is imported, unless the Python interpreter was started with the -S flag.

在 3.3 版的變更: This function used to be called unconditionally.

site.addsitedir(sitedir, known_paths=None)

Add a directory to sys.path and process its .pth files. Typically used in sitecustomize or usercustomize (see above).

site.getsitepackages()

Return a list containing all global site-packages directories.

在 3.2 版被加入.

site.getuserbase()

Return the path of the user base directory, USER_BASE. If it is not initialized yet, this function will also set it, respecting PYTHONUSERBASE.

在 3.2 版被加入.

site.getusersitepackages()

Return the path of the user-specific site-packages directory, USER_SITE. If it is not initialized yet, this function will also set it, respecting USER_BASE. To determine if the user-specific site-packages was added to sys.path ENABLE_USER_SITE should be used.

在 3.2 版被加入.

命令列介面

The site module also provides a way to get the user directories from the command line:

$ python -m site --user-site
/home/user/.local/lib/python3.11/site-packages

If it is called without arguments, it will print the contents of sys.path on the standard output, followed by the value of USER_BASE and whether the directory exists, then the same thing for USER_SITE, and finally the value of ENABLE_USER_SITE.

--user-base

Print the path to the user base directory.

--user-site

Print the path to the user site-packages directory.

If both options are given, user base and user site will be printed (always in this order), separated by os.pathsep.

If any option is given, the script will exit with one of these values: 0 if the user site-packages directory is enabled, 1 if it was disabled by the user, 2 if it is disabled for security reasons or by an administrator, and a value greater than 2 if there is an error.

也參考

PEP 370 [https://peps.python.org/pep-0370/] -- Per user site-packages directory

sys.path 模組搜尋路徑的初始化 -- sys.path 的初始化。

自訂 Python 直譯器

本章介紹的模組可用於編寫類似於 Python 交互式直譯器的介面。如果你需要一個在 Python 語言基礎上支援某些特殊功能的直譯器，可以參考 code 模組。（ codeop 模組屬於底層工具，用於支援編譯可能不完整的 Python 程式碼。）

本章節所描述的模組清單為：

code --- 直譯器基底類別

互動式直譯器物件

互動式控制台物件

codeop --- 編譯 Python 程式碼

code --- 直譯器基底類別

原始碼：Lib/code.py [https://github.com/python/cpython/tree/3.14/Lib/code.py]

code 模組提供在 Python 中實作讀取-求值-印出迴圈（read-eval-print loops）的設施。包含兩個類別和便利函式，可用於建立提供互動式直譯器提示的應用程式。

class code.InteractiveInterpreter(locals=None)

這個類別處理剖析和直譯器狀態（使用者的命名空間）；它不處理輸入緩衝、提示或輸入檔案命名（檔案名稱總是明確傳入）。可選的 locals 引數指定一個對映，作為執行程式碼的命名空間；它預設為新建立的字典，鍵 '__name__' 設為 '__console__' 而鍵 '__doc__' 會設為 None。

請注意，在 InteractiveInterpreter 實例下建立的函式和類別物件將屬於由 locals 指定的命名空間。只有當 locals 是現有模組的命名空間時，它們才會是可被 pickle 的。

class code.InteractiveConsole(locals=None, filename='<console>', local_exit=False)

近似地模擬出互動式 Python 直譯器的行為。這個類別建立在 InteractiveInterpreter 的基礎上，並加入使用熟悉的 sys.ps1 和 sys.ps2 的提示，以及輸入緩衝。如果 local_exit 為 true，控制台中的 exit() 和 quit() 將不會引發 SystemExit，而是回傳到呼叫程式碼。

在 3.13 版的變更: 新增 local_exit 參數。

code.interact(banner=None, readfunc=None, local=None, exitmsg=None, local_exit=False)

執行 read-eval-print 迴圈的便利函式。這會建立一個 InteractiveConsole 的新實例，並設定 readfunc 以用於 InteractiveConsole.raw_input() 方法（如有提供）。如果 local 有被提供，它會被傳給 InteractiveConsole 的建構函式以作為直譯器迴圈的預設命名空間。如果有提供 local_exit，它會被傳給 InteractiveConsole 構建函式。然後實例的 interact() 方法會執行，並傳入 banner 和 exitmsg 以作為要使用的橫幅和退出訊息（如有提供）。控制台物件在使用後就會被丟棄。

在 3.6 版的變更: 新增 exitmsg 參數。

在 3.13 版的變更: 新增 local_exit 參數。

code.compile_command(source, filename='<input>', symbol='single')

這個函式對於想要模擬 Python 的直譯器主迴圈（即讀取-求值-印出迴圈）的程式很有用。最棘手的部分是判斷使用者何時輸入了一個不完整的命令，而這個命令可以透過輸入更多文字來完成（相對於完整的命令或語法錯誤）。這個函式幾乎總是做出與真正的直譯器主迴圈相同的判斷。

source 是來源字串；filename 是讀取來源的可選檔案名稱，預設為 '<input>'；symbol 是可選的文法 (grammar) 起始符號，其應為 'single'（預設值）、'eval' 或 'exec'。

如果命令完整且有效，則回傳程式碼物件（與 compile(source,filename,symbol) 相同）；如果命令不完整，則回傳 None；如果命令完整但包含語法錯誤，則引發 SyntaxError，如果命令包含無效的字面值 (literal)，則引發 OverflowError 或 ValueError。

互動式直譯器物件

InteractiveInterpreter.runsource(source, filename='<input>', symbol='single')

在直譯器中編譯並執行某些原始碼。引數與 compile_command() 相同；filename 的預設值是 '<input>'，symbol 的預設值是 'single'。有幾種情況會發生：

輸入不正確；compile_command() 會引發例外（SyntaxError 或 OverflowError）。語法回溯 (syntax traceback) 會透過呼叫 showsyntaxerror() 方法來印出。runsource() 會回傳 False。

輸入不完整，需要更多輸入；compile_command() 回傳了 None。runsource() 會回傳 True。

輸入完整；compile_command() 回傳一個程式碼物件。程式碼會透過呼叫 runcode() 執行（它也會處理執行時的例外，除 SystemExit 以外）。runsource() 會回傳 False。

回傳值可用來決定是使用 sys.ps1 還是 sys.ps2 以提示下一列。

InteractiveInterpreter.runcode(code)

執行程式碼物件。當例外發生時，會呼叫 showtraceback() 來顯示回溯。除了 SystemExit 允許繼續傳播之外，所有的例外都會被捕獲。

關於 KeyboardInterrupt 的注意事項：此例外可能發生在此程式碼的其他地方，而且不一定會被捕獲到。呼叫者應該準備好處理它。

InteractiveInterpreter.showsyntaxerror(filename=None)

顯示剛剛發生的語法錯誤。這不會顯示堆疊追蹤 (stack trace)，因為語法錯誤沒有堆疊追蹤。如果給出 filename，它會被塞入例外，而不是 Python 剖析器提供的預設檔案名稱，因為它從字串讀取時總是使用 '<string>'。輸出會由 write() 方法寫入。

InteractiveInterpreter.showtraceback()

顯示剛剛發生的例外。我們移除第一個堆疊項目，因為它在直譯器物件的實作範圍內。輸出由 write() 方法寫入。

在 3.5 版的變更: 會顯示完整的連鎖回溯記錄，而不只是主要回溯。

InteractiveInterpreter.write(data)

寫入字串到標準錯誤串流 (sys.stderr)。衍生類別應覆寫此功能，以根據需求提供適當的輸出處理。

互動式控制台物件

InteractiveConsole 類別是 InteractiveInterpreter 的子類別，因此提供了所有直譯器物件的方法以及下列新增的功能。

InteractiveConsole.interact(banner=None, exitmsg=None)

近似地模擬互動式 Python 控制台。可選的 banner 引數指定在第一次互動之前要印出的横幅；預設會印出類似標準 Python 直譯器所列印的横幅，接著是控制台物件在括弧中的類別名稱 (以免與真正的直譯器混淆 -- 因為它是如此接近！)。

可選的 exitmsg 引數指定退出時列印的退出訊息。傳遞空字串以抑制退出訊息。如果沒有給 exitmsg 或 None，則會印出預設訊息。

在 3.4 版的變更: 若要抑制印出任何橫幅，請傳入空字串。

在 3.6 版的變更: 退出時印出退出訊息。

InteractiveConsole.push(line)

推送一行原始文字到直譯器。這一行不應該有尾部換行符號；它可能有內部換行符號。這行文字會被附加到緩衝區，並且直譯器的 runsource() 方法會被呼叫，並以緩衝區的串接內容做為原始碼。如果這表示命令已執行或無效，緩衝區會被重設；否則，命令會不完整，且緩衝區會保持該行被附加後的樣子。如果需要更多的輸入，回傳值是 True，如果該行已經以某種方式處理，回傳值是 False（這與 runsource() 相同）。

InteractiveConsole.resetbuffer()

從輸入緩衝區移除任何未處理的原始文字。

InteractiveConsole.raw_input(prompt='')

寫入一個提示並讀取一行。回傳的行不包括尾部的換行符號。當使用者輸入 EOF 鍵序時，會引發 EOFError。基底實作會從 sys.stdin 讀取；子類別可以用不同的實作替代。

codeop --- 編譯 Python 程式碼

原始碼：Lib/codeop.py [https://github.com/python/cpython/tree/3.14/Lib/codeop.py]

codeop 模組提供了可以模擬 Python read-eval-print 循環的工具程式 (utilities)，就像在 code 模組中所做的那樣。因此你可能不想直接使用該模組；如果你想在程式中包含這樣的循環，你可能需要使用 code 模組。

這個任務有兩個部分：

能夠判斷一列輸入是否完成了一項 Python 陳述式：簡而言之，判斷接下來是列印 '>>>' 還是 '...'。

記住使用者輸入了哪些未來陳述式，以便後續輸入可以在這些陳述式生效的情況下進行編譯。

codeop 模組提供了一種完成上述每項任務的方法，以及同時完成這兩項任務的方法。

只做前者：

codeop.compile_command(source, filename='<input>', symbol='single')

嘗試編譯 source，它應該是 Python 程式碼的字串，如果 source 是有效的 Python 程式碼，則回傳一個程式碼物件 (code object)。在這種情況下，程式碼物件的檔案名稱屬性將為 filename，預設為 '<input>'。如果 source 不是有效的 Python 程式碼，而是有效 Python 程式碼的前綴，則回傳 None。

如果 source 有問題，就會引發例外。如果存在無效的 Python 語法則會引發 SyntaxError；如果存在無效的文字 (literal)，則會引發 OverflowError 或 ValueError。

symbol 引數決定 source 是否編譯為陳述式（'single'，為預設值）、為陳述式序列 ('exec') 或為運算式 ('eval')。任何其他值都會導致引發 ValueError。

備註

剖析器 (parser) 有可能（但通常不會）在到達原始碼的結尾之前停止剖析並獲得成功的結果；在這種情況下，尾隨符號可能會被忽略而不是導致錯誤。例如，反斜線後面加上兩個換行符號後可以是任意的無意義符號。這個問題在未來會因為剖析器 API 的改善而被解決。

class codeop.Compile

此類別的實例具有 __call__() 方法，其簽名與內建函式 compile() 相同，區別在於如果實例編譯包含 __future__ 陳述式的程式文本，實例會「記住」並使用該陳述式開始編譯所有後續程式文本。

class codeop.CommandCompiler

此類別的實例具有 __call__() 方法，其簽名與內建函式 compile_command() 相同，區別在於如果實例編譯包含 __future__ 陳述式的程式文本，實例會「記住」並使用該陳述式開始編譯所有後續程式文本。

引入模組

本章節所描述的模組提供了引入其他 Python 模組的新方法，以及用於自訂引入過程的 hook。

本章節所描述的完整模組列表為：

zipimport --- 從 Zip 封存檔案匯入模組

zipimporter 物件

範例

pkgutil --- 套件擴充工具程式

modulefinder --- 搜尋腳本所使用的模組

ModuleFinder 的用法範例

runpy --- 定位並執行 Python 模組

importlib --- import 的實作

簡介

函式

importlib.abc -- Abstract base classes related to import

importlib.machinery -- Importers and path hooks

importlib.util -- Utility code for importers

範例

Importing programmatically

Checking if a module can be imported

Importing a source file directly

Implementing lazy imports

Setting up an importer

Approximating importlib.import_module()

importlib.resources -- 套件資源的讀取、開啟與存取

Functional API

importlib.resources.abc -- 資源的抽象基底類別

importlib.metadata -- 存取套件的元資料

Overview

Functional API

Entry points

Distribution metadata

Distribution versions

Distribution files

Distribution requirements

Mapping import to distribution packages

Distributions

Distribution Discovery

Implementing Custom Providers

範例

sys.path 模組搜尋路徑的初始化

虛擬環境

_pth 檔案

Embedded Python

zipimport --- 從 Zip 封存檔案匯入模組

原始碼：Lib/zipimport.py [https://github.com/python/cpython/tree/3.14/Lib/zipimport.py]

此模組新增了從 ZIP 格式封存檔案中引入 Python 模組（*.py、*.pyc）和套件的能力。通常不需要明確地使用 zipimport 模組；對於 sys.path 中指向 ZIP 封存檔案路徑的項目，內建的 import 機制會自動使用它。

通常 sys.path 是一個由目錄名稱字串組成的串列。此模組也允許 sys.path 的一個項目是命名 ZIP 封存檔案的字串。ZIP 封存檔案可以包含子目錄結構以支援套件引入，並且可以指定封存檔案內的路徑以僅從子目錄中引入。例如路徑 example.zip/lib/ 將只會從封存檔案內的 lib/ 子目錄中引入。

ZIP 封存檔案中可以存在任何檔案，但引入器只會對 .py 和 .pyc 檔案起作用。不允許從 ZIP 引入動態模組（.pyd、.so）。請注意，如果封存檔案只包含 .py 檔案，Python 將不會試圖透過新增對應的 .pyc 檔案來修改封存檔案，這意味著如果 ZIP 封存檔案不包含 .pyc 檔案，引入可能會相當慢。

在 3.13 版的變更: 支援 ZIP64。

在 3.8 版的變更: 在過去，不支援帶有封存檔案註解的 ZIP 封存檔案。

也參考

PKZIP Application Note [https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT]

由 ZIP 格式和所用演算法的創造者 Phil Katz 編寫的關於 ZIP 檔案格式的文件。

PEP 273 [https://peps.python.org/pep-0273/] - 從 Zip 封存檔案引入模組

由 James C. Ahlstrom 編寫，他也提供了一個實作。Python 2.3 遵循 PEP 273 [https://peps.python.org/pep-0273/] 中的規範，但使用由 Just van Rossum 編寫的實作，該實作使用了 PEP 302 [https://peps.python.org/pep-0302/] 中描述的引入掛鉤。

importlib - 引入機制的實作

提供所有引入器要實作的相關協定的套件。

此模組定義了一個例外：

exception zipimport.ZipImportError

由 zipimporter 物件引發的例外。它是 ImportError 的子類別，所以也可以被捕捉為 ImportError。

zipimporter 物件

zipimporter 是用於引入 ZIP 檔案的類別。

class zipimport.zipimporter(archivepath)

建立一個新的 zipimporter 實例。archivepath 必須是 ZIP 檔案的路徑，或是 ZIP 檔案內的特定路徑。例如，foo/bar.zip/lib 的 archivepath 將會在 ZIP 檔案 foo/bar.zip 內的 lib 目錄中尋找模組（如果該目錄存在的話）。

如果 archivepath 未指向一個有效的 ZIP 封存檔案，則會引發 ZipImportError。

在 3.12 版的變更: 在 3.10 版中已棄用的 find_loader() 和 find_module() 方法現已被移除。請改用 find_spec()。

create_module(spec)

importlib.abc.Loader.create_module() 的實作，回傳 None 以明確請求預設語意。

在 3.10 版被加入.

exec_module(module)

importlib.abc.Loader.exec_module() 的實作。

在 3.10 版被加入.

find_spec(fullname, target=None)

importlib.abc.PathEntryFinder.find_spec() 的一個實作。

在 3.10 版被加入.

get_code(fullname)

回傳指定模組的程式碼物件。如果模組無法被引入，則引發 ZipImportError。

get_data(pathname)

回傳與 pathname 相關的資料。如果找不到檔案，則引發 OSError。

在 3.3 版的變更: 過去會引發 IOError，現在它是 OSError 的別名。

get_filename(fullname)

回傳如果指定模組被引入時 __file__ 會被設定的值。如果模組無法被引入，則引發 ZipImportError。

在 3.1 版被加入.

get_source(fullname)

回傳指定模組的原始碼。如果找不到模組，則引發 ZipImportError；如果封存檔案包含該模組但沒有其原始碼，則回傳 None。

is_package(fullname)

如果由 fullname 指定的模組是一個套件，則回傳 True。如果找不到模組，則引發 ZipImportError。

load_module(fullname)

載入由 fullname 指定的模組。fullname 必須是完整限定（以點分隔）的模組名稱。成功時回傳引入的模組，失敗時引發 ZipImportError。

自從版本 3.10 後不推薦使用，將會自版本 3.15 中移除。: 請改用 exec_module()。

invalidate_caches()

清除關於在 ZIP 封存檔案中找到的檔案資訊的內部快取。

在 3.10 版被加入.

archive

引入器關聯的 ZIP 檔案的檔名，不包含可能的子路徑。

prefix

在 ZIP 檔案內搜尋模組的子路徑。對於指向 ZIP 檔案根目錄的 zipimporter 物件，這是一個空字串。

archive 和 prefix 屬性（attribute），當用斜線組合時，等於給予 zipimporter 建構函式的原始 archivepath 引數。

範例

這是一個從 ZIP 封存檔案引入模組的範例——請注意，zipimport 模組並未被明確使用。

$ unzip -l example_archive.zip
Archive:  example_archive.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
     8467  01-01-00 12:30   example.py
 --------                   -------
     8467                   1 file

>>> import sys
>>> # 將封存檔案新增到系統路徑的最前面
>>> sys.path.insert(0, 'example_archive.zip')
>>> import example
>>> example.__file__
'example_archive.zip/example.py'

pkgutil --- 套件擴充工具程式

原始碼：Lib/pkgutil.py [https://github.com/python/cpython/tree/3.14/Lib/pkgutil.py]

此模組提供了引入系統 (import system) 的工具程式，特別是套件相關支援。

class pkgutil.ModuleInfo(module_finder, name, ispkg)

一個包含模組資訊之簡短摘要的附名元組 (namedtuple)。

在 3.6 版被加入.

pkgutil.extend_path(path, name)

擴充組成一個套件之模組的搜尋路徑。預期用法是將以下程式碼放入套件的 __init__.py：

from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)

對於 sys.path 上具有與套件名稱相符的子目錄的每個目錄，將該子目錄新增至套件的 __path__ 中。如果想要將單一邏輯套件的不同部分給分配到多個目錄時，這會非常有用。

它還會尋找 *.pkg 檔案，其中開頭的 * 與 name 引數相符。此功能類似於 *.pth 檔案（更多資訊請參閱 site 模組），但他不特別處理以 import 為開頭的行。*.pkg 檔案從表面上看是受信任的：除了跳過空行和備註之外，在 *.pkg 檔案中找到的所有條目都將新增到路徑中，無論它們是否存在於檔案系統。（這是一個功能。）

如果輸入路徑不是串列（像是凍結套件 (frozen package) 的情況），它將原封不動地被回傳。輸入路徑不會被修改；而是回傳擴充後的副本。僅將項目附加到副本的尾端。

sys.path 被假設是一個序列，sys.path 中的項目裡，若不是代表現存目錄的字串則將被忽略。sys.path 上用作檔案名稱時導致錯誤的 Unicode 項目可能會導致此函式引發例外（與 os.path.isdir() 行為一致）。

pkgutil.get_importer(path_item)

取得給定之 path_item 的 finder。

如果回傳的尋檢器 (finder) 是由路徑勾點 (path hook) 所新建立的，則它會被快取在 sys.path_importer_cache 中。

如果需要重新掃描 sys.path_hooks，可以手動清除快取（或部分快取）。

在 3.3 版的變更: 更新為直接基於 importlib，而不是依賴套件內部 PEP 302 [https://peps.python.org/pep-0302/] 的引入模擬 (import emulation)。

pkgutil.iter_importers(fullname='')

yield 給定模組名稱的 finder 物件。

如果 fullname 包含 '.'，則尋檢器將針對包含 fullname 的套件，否則它們全部會是在頂層被註冊的尋檢器（即 sys.meta_path 和 sys.path_hooks 上的尋檢器）。

如果指定的模組位於套件中，則作為呼叫此函式的副作用 (side effect) ，該套件會被引入。

如果未指定模組名稱，則會產生所有頂層尋檢器。

在 3.3 版的變更: 更新為直接基於 importlib，而不是依賴套件內部 PEP 302 [https://peps.python.org/pep-0302/] 的引入模擬 (import emulation)。

pkgutil.iter_modules(path=None, prefix='')

yield path 上所有子模組的 ModuleInfo，或者如果 path 為 None，則產生 sys.path 上的所有頂層模組。

path 應該是 None 或用來尋找模組的路徑串列。

prefix 是在輸出的每個模組名稱前面的輸出字串。

備註

僅適用於有定義 iter_modules() 方法的 finder。此介面並非是標準的，因此該模組還提供了 importlib.machinery.FileFinder 和 zipimport.zipimporter 的實作。

在 3.3 版的變更: 更新為直接基於 importlib，而不是依賴套件內部 PEP 302 [https://peps.python.org/pep-0302/] 的引入模擬 (import emulation)。

pkgutil.walk_packages(path=None, prefix='', onerror=None)

為 path 上的所有模組遞迴 yield 出 ModuleInfo，或如果 path 為 None 則 yield 所有可存取的模組。

path 應該是 None 或用來尋找模組的路徑串列。

prefix 是在輸出的每個模組名稱前面的輸出字串。

請注意，此函式必須引入給定之 path 上的所有套件（不是所有模組！），以便存取 __path__ 屬性來尋找子模組。

onerror 是一個函式，如果在嘗試引入套件時發生任何例外，則使用一個引數（正在引入之套件的名稱）來呼叫函式。如果未提供 onerror 函式，則會捕獲並忽略 ImportError，同時傳播所有其他例外並終止搜尋。

範例：

# 列出 Python 可存取的所有模組
walk_packages()

# 列出 ctypes 的所有子模組
walk_packages(ctypes.__path__, ctypes.__name__ + '.')

備註

僅適用於有定義 iter_modules() 方法的 finder。此介面並非是標準的，因此該模組還提供了 importlib.machinery.FileFinder 和 zipimport.zipimporter 的實作。

在 3.3 版的變更: 更新為直接基於 importlib，而不是依賴套件內部 PEP 302 [https://peps.python.org/pep-0302/] 的引入模擬 (import emulation)。

pkgutil.get_data(package, resource)

從套件中取得資源。

這是 loader get_data API 的包裝器。package 引數應該是採用標準模組格式 (foo.bar) 的套件名稱。resource 引數應為相對檔案名稱的形式，並使用 / 作為路徑分隔符號。不允許使用父目錄名稱 ..，也不允許使用根目錄名稱（以 / 開頭）。

該函式回傳一個二進位字串，它是指定資源的內容。

對於位於檔案系統中且已被引入過的套件，這大致相當於：

d = os.path.dirname(sys.modules[package].__file__)
data = open(os.path.join(d, resource), 'rb').read()

如果無法定位或載入套件，或者它使用不支援 get_data 的 loader 則回傳 None。特別是命名空間套件的 loader 不支援 get_data。

pkgutil.resolve_name(name)

將名稱解析為物件。

標準函式庫中的許多地方都使用了此功能（請參閱 bpo-12915 [https://bugs.python.org/issue?@action=redirect&bpo=12915]），且相同功能也被用於擁有廣大使用者的第三方套件，如 setuptools、Django 和 Pyramid。

name 預期要是以下格式之一的字串，其中 W 是有效 Python 識別字的簡寫，而點 (dot) 代表這些偽正規表示式 (pseudo-regex) 中的字面句點 (literal period)：

W(.W)*

W(.W)*:(W(.W)*)?

第一種形式僅是為了要向後相容。它假設點名稱 (dotted name) 的某些部分是一個套件，其餘部分是該套件內某處的物件，其可能巢狀地存在於 (nested) 其他物件內。由於無法透過檢查 (inspection) 來推斷出套件停止的位置和物件層次結構的開始位置，因此必須使用此形式來重複嘗試引入。

在第二種形式中，呼叫者透過使用一個冒號來明確標明分隔點：冒號左側的點名稱是要引入的套件，右側的點名稱是該套件內的物件層次結構。這種形式只需要一次引入。如果它以冒號結尾，則回傳一個模組物件。

此函式會回傳一個物件（可能是一個模組），或引發以下其中一個例外：

ValueError -- 如果 name 不是可辨識的格式。

ImportError -- 如果在不應該失敗的情況下引入失敗。

AttributeError -- 如果在遍歷引入套件中的物件層次結構以取得所需物件時發生失敗。

在 3.9 版被加入.

modulefinder --- 搜尋腳本所使用的模組

原始碼：Lib/modulefinder.py [https://github.com/python/cpython/tree/3.14/Lib/modulefinder.py]

此模組提供了一個 ModuleFinder 類別，可用於確定腳本引入的模組集合。modulefinder.py 也可以作為腳本運行，其將 Python 腳本的檔案名稱作為它的引數，並在之後會列印出引入模組的報告。

modulefinder.AddPackagePath(pkg_name, path)

記錄在指定的 path 中可以找到名為 pkg_name 的套件。

modulefinder.ReplacePackage(oldname, newname)

允許指定名為 oldname 的模組實際上是名為 newname 的套件。

class modulefinder.ModuleFinder(path=None, debug=0, excludes=[], replace_paths=[])

此類別提供 run_script() 和 report() 方法來決定腳本引入的模組集合。path 可以是搜尋模組的目錄串列；如果未指定，則使用 sys.path。debug 設定偵錯等級；較高的值可使類別列印有關其即將執行之操作的偵錯訊息。excludes 是要從分析中排除的模組名稱串列。replace_paths 是將在模組路徑中替換的 (oldpath, newpath) 元組串列。

report()

將報告列印到標準輸出，其中列出了腳本引入的模組及其路徑，以及丟失或似乎丟失的模組。

run_script(pathname)

分析 pathname 檔案的內容，該檔案必須包含 Python 程式碼。

modules

將模組名稱對應到模組的字典。請參閱 ModuleFinder 的用法範例。

ModuleFinder 的用法範例

將被分析的腳本 (bacon.py)：

import re, itertools

try:
    import baconhameggs
except ImportError:
    pass

try:
    import guido.python.ham
except ImportError:
    pass

將輸出 bacon.py 報告的腳本：

from modulefinder import ModuleFinder

finder = ModuleFinder()
finder.run_script('bacon.py')

print('載入模組:')
for name, mod in finder.modules.items():
    print('%s: ' % name, end='')
    print(','.join(list(mod.globalnames.keys())[:3]))

print('-'*50)
print('模組沒有被引入:')
print('\n'.join(finder.badmodules.keys()))

範例輸出（可能因架構而異）：

載入模組:
_types:
copyreg:  _inverted_registry,_slotnames,__all__
re._compiler:  isstring,_sre,_optimize_unicode
_sre:
re._constants:  REPEAT_ONE,makedict,AT_END_LINE
sys:
re:  __module__,finditer,_expand
itertools:
__main__:  re,itertools,baconhameggs
re._parser:  _PATTERNENDERS,SRE_FLAG_UNICODE
array:
types:  __module__,IntType,TypeType
---------------------------------------------------
模組沒有被引入:
guido.python.ham
baconhameggs

runpy --- 定位並執行 Python 模組

原始碼：Lib/runpy.py [https://github.com/python/cpython/tree/3.14/Lib/runpy.py]

The runpy module is used to locate and run Python modules without importing them first. Its main use is to implement the -m command line switch that allows scripts to be located using the Python module namespace rather than the filesystem.

Note that this is not a sandbox module - all code is executed in the current process, and any side effects (such as cached imports of other modules) will remain in place after the functions have returned.

Furthermore, any functions and classes defined by the executed code are not guaranteed to work correctly after a runpy function has returned. If that limitation is not acceptable for a given use case, importlib is likely to be a more suitable choice than this module.

The runpy module provides two functions:

runpy.run_module(mod_name, init_globals=None, run_name=None, alter_sys=False)

Execute the code of the specified module and return the resulting module's globals dictionary. The module's code is first located using the standard import mechanism (refer to PEP 302 [https://peps.python.org/pep-0302/] for details) and then executed in a fresh module namespace.

The mod_name argument should be an absolute module name. If the module name refers to a package rather than a normal module, then that package is imported and the __main__ submodule within that package is then executed and the resulting module globals dictionary returned.

The optional dictionary argument init_globals may be used to pre-populate the module's globals dictionary before the code is executed. init_globals will not be modified. If any of the special global variables below are defined in init_globals, those definitions are overridden by run_module().

The special global variables __name__, __spec__, __file__, __cached__, __loader__ and __package__ are set in the globals dictionary before the module code is executed. (Note that this is a minimal set of variables - other variables may be set implicitly as an interpreter implementation detail.)

__name__ is set to run_name if this optional argument is not None, to mod_name + '.__main__' if the named module is a package and to the mod_name argument otherwise.

__spec__ will be set appropriately for the actually imported module (that is, __spec__.name will always be mod_name or mod_name + '.__main__', never run_name).

__file__, __cached__, __loader__ and __package__ are set as normal based on the module spec.

If the argument alter_sys is supplied and evaluates to True, then sys.argv[0] is updated with the value of __file__ and sys.modules[__name__] is updated with a temporary module object for the module being executed. Both sys.argv[0] and sys.modules[__name__] are restored to their original values before the function returns.

Note that this manipulation of sys is not thread-safe. Other threads may see the partially initialised module, as well as the altered list of arguments. It is recommended that the sys module be left alone when invoking this function from threaded code.

也參考

The -m option offering equivalent functionality from the command line.

在 3.1 版的變更: Added ability to execute packages by looking for a __main__ submodule.

在 3.2 版的變更: 新增 __cached__ 全域變數（請參閱 PEP 3147 [https://peps.python.org/pep-3147/]）。

在 3.4 版的變更: Updated to take advantage of the module spec feature added by PEP 451 [https://peps.python.org/pep-0451/]. This allows __cached__ to be set correctly for modules run this way, as well as ensuring the real module name is always accessible as __spec__.name.

在 3.12 版的變更: The setting of __cached__, __loader__, and __package__ are deprecated. See ModuleSpec for alternatives.

runpy.run_path(path_name, init_globals=None, run_name=None)

Execute the code at the named filesystem location and return the resulting module's globals dictionary. As with a script name supplied to the CPython command line, file_path may refer to a Python source file, a compiled bytecode file or a valid sys.path entry containing a __main__ module (e.g. a zipfile containing a top-level __main__.py file).

For a simple script, the specified code is simply executed in a fresh module namespace. For a valid sys.path entry (typically a zipfile or directory), the entry is first added to the beginning of sys.path. The function then looks for and executes a __main__ module using the updated path. Note that there is no special protection against invoking an existing __main__ entry located elsewhere on sys.path if there is no such module at the specified location.

The optional dictionary argument init_globals may be used to pre-populate the module's globals dictionary before the code is executed. init_globals will not be modified. If any of the special global variables below are defined in init_globals, those definitions are overridden by run_path().

The special global variables __name__, __spec__, __file__, __cached__, __loader__ and __package__ are set in the globals dictionary before the module code is executed. (Note that this is a minimal set of variables - other variables may be set implicitly as an interpreter implementation detail.)

__name__ is set to run_name if this optional argument is not None and to '<run_path>' otherwise.

If file_path directly references a script file (whether as source or as precompiled byte code), then __file__ will be set to file_path, and __spec__, __cached__, __loader__ and __package__ will all be set to None.

If file_path is a reference to a valid sys.path entry, then __spec__ will be set appropriately for the imported __main__ module (that is, __spec__.name will always be __main__). __file__, __cached__, __loader__ and __package__ will be set as normal based on the module spec.

A number of alterations are also made to the sys module. Firstly, sys.path may be altered as described above. sys.argv[0] is updated with the value of file_path and sys.modules[__name__] is updated with a temporary module object for the module being executed. All modifications to items in sys are reverted before the function returns.

Note that, unlike run_module(), the alterations made to sys are not optional in this function as these adjustments are essential to allowing the execution of sys.path entries. As the thread-safety limitations still apply, use of this function in threaded code should be either serialised with the import lock or delegated to a separate process.

也參考

介面選項 for equivalent functionality on the command line (python path/to/script).

在 3.2 版被加入.

在 3.4 版的變更: Updated to take advantage of the module spec feature added by PEP 451 [https://peps.python.org/pep-0451/]. This allows __cached__ to be set correctly in the case where __main__ is imported from a valid sys.path entry rather than being executed directly.

在 3.12 版的變更: The setting of __cached__, __loader__, and __package__ are deprecated.

也參考

PEP 338 [https://peps.python.org/pep-0338/] -- Executing modules as scripts

PEP written and implemented by Nick Coghlan.

PEP 366 [https://peps.python.org/pep-0366/] -- Main module explicit relative imports

PEP written and implemented by Nick Coghlan.

PEP 451 [https://peps.python.org/pep-0451/] -- A ModuleSpec Type for the Import System

PEP written and implemented by Eric Snow

命令列與環境 - CPython command line details

The importlib.import_module() function

importlib --- import 的實作

在 3.1 版被加入.

原始碼：Lib/importlib/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/__init__.py]

簡介

importlib 的目的可分為三個部分。

第一是提供 Python 原始碼中 import 陳述式的實作（因此，也延伸到 __import__() 函式）。這讓 import 實作可以移植到任何 Python 直譯器。同時，這也提供了一個比用其他程式語言實作更容易理解的版本。

Two, the components to implement import are exposed in this package, making it easier for users to create their own custom objects (known generically as an importer) to participate in the import process.

Three, the package contains modules exposing additional functionality for managing aspects of Python packages:

importlib.metadata presents access to metadata from third-party distributions.

importlib.resources provides routines for accessing non-code "resources" from Python packages.

也參考

import 陳述式

The language reference for the import statement.

Packages specification [https://www.python.org/doc/essays/packages/]

Original specification of packages. Some semantics have changed since the writing of this document (e.g. redirecting based on None in sys.modules).

__import__() 函式

The import statement is syntactic sugar for this function.

sys.path 模組搜尋路徑的初始化

The initialization of sys.path.

PEP 235 [https://peps.python.org/pep-0235/]

Import on Case-Insensitive Platforms

PEP 263 [https://peps.python.org/pep-0263/]

Defining Python Source Code Encodings

PEP 302 [https://peps.python.org/pep-0302/]

New Import Hooks

PEP 328 [https://peps.python.org/pep-0328/]

Imports: Multi-Line and Absolute/Relative

PEP 366 [https://peps.python.org/pep-0366/]

Main module explicit relative imports

PEP 420 [https://peps.python.org/pep-0420/]

Implicit namespace packages

PEP 451 [https://peps.python.org/pep-0451/]

A ModuleSpec Type for the Import System

PEP 488 [https://peps.python.org/pep-0488/]

Elimination of PYO files

PEP 489 [https://peps.python.org/pep-0489/]

多階段擴充模組初始化

PEP 552 [https://peps.python.org/pep-0552/]

Deterministic pycs

PEP 3120 [https://peps.python.org/pep-3120/]

Using UTF-8 as the Default Source Encoding

PEP 3147 [https://peps.python.org/pep-3147/]

PYC Repository Directories

函式

importlib.__import__(name, globals=None, locals=None, fromlist=(), level=0)

An implementation of the built-in __import__() function.

備註

Programmatic importing of modules should use import_module() instead of this function.

importlib.import_module(name, package=None)

Import a module. The name argument specifies what module to import in absolute or relative terms (e.g. either pkg.mod or ..mod). If the name is specified in relative terms, then the package argument must be set to the name of the package which is to act as the anchor for resolving the package name (e.g. import_module('..mod', 'pkg.subpkg') will import pkg.mod).

The import_module() function acts as a simplifying wrapper around importlib.__import__(). This means all semantics of the function are derived from importlib.__import__(). The most important difference between these two functions is that import_module() returns the specified package or module (e.g. pkg.mod), while __import__() returns the top-level package or module (e.g. pkg).

If you are dynamically importing a module that was created since the interpreter began execution (e.g., created a Python source file), you may need to call invalidate_caches() in order for the new module to be noticed by the import system.

在 3.3 版的變更: Parent packages are automatically imported.

importlib.invalidate_caches()

Invalidate the internal caches of finders stored at sys.meta_path. If a finder implements invalidate_caches() then it will be called to perform the invalidation. This function should be called if any modules are created/installed while your program is running to guarantee all finders will notice the new module's existence.

在 3.3 版被加入.

在 3.10 版的變更: Namespace packages created/installed in a different sys.path location after the same namespace was already imported are noticed.

importlib.reload(module)

Reload a previously imported module. The argument must be a module object, so it must have been successfully imported before. This is useful if you have edited the module source file using an external editor and want to try out the new version without leaving the Python interpreter. The return value is the module object (which can be different if re-importing causes a different object to be placed in sys.modules).

When reload() is executed:

Python module's code is recompiled and the module-level code re-executed, defining a new set of objects which are bound to names in the module's dictionary by reusing the loader which originally loaded the module. The init function of extension modules is not called a second time.

As with all other objects in Python the old objects are only reclaimed after their reference counts drop to zero.

The names in the module namespace are updated to point to any new or changed objects.

Other references to the old objects (such as names external to the module) are not rebound to refer to the new objects and must be updated in each namespace where they occur if that is desired.

There are a number of other caveats:

When a module is reloaded, its dictionary (containing the module's global variables) is retained. Redefinitions of names will override the old definitions, so this is generally not a problem. If the new version of a module does not define a name that was defined by the old version, the old definition remains. This feature can be used to the module's advantage if it maintains a global table or cache of objects --- with a try statement it can test for the table's presence and skip its initialization if desired:

try:
    cache
except NameError:
    cache = {}

It is generally not very useful to reload built-in or dynamically loaded modules. Reloading sys, __main__, builtins and other key modules is not recommended. In many cases extension modules are not designed to be initialized more than once, and may fail in arbitrary ways when reloaded.

If a module imports objects from another module using from ... import ..., calling reload() for the other module does not redefine the objects imported from it --- one way around this is to re-execute the from statement, another is to use import and qualified names (module.name) instead.

If a module instantiates instances of a class, reloading the module that defines the class does not affect the method definitions of the instances --- they continue to use the old class definition. The same is true for derived classes.

在 3.4 版被加入.

在 3.7 版的變更: ModuleNotFoundError is raised when the module being reloaded lacks a ModuleSpec.

警告

This function is not thread-safe. Calling it from multiple threads can result in unexpected behavior. It's recommended to use the threading.Lock or other synchronization primitives for thread-safe module reloading.

importlib.abc -- Abstract base classes related to import

原始碼：Lib/importlib/abc.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/abc.py]

The importlib.abc module contains all of the core abstract base classes used by import. Some subclasses of the core abstract base classes are also provided to help in implementing the core ABCs.

ABC hierarchy:

object
 +-- MetaPathFinder
 +-- PathEntryFinder
 +-- Loader
      +-- ResourceLoader --------+
      +-- InspectLoader          |
           +-- ExecutionLoader --+
                                 +-- FileLoader
                                 +-- SourceLoader

class importlib.abc.MetaPathFinder

An abstract base class representing a meta path finder.

在 3.3 版被加入.

在 3.10 版的變更: 不再是 Finder 的子類別。

find_spec(fullname, path, target=None)

An abstract method for finding a spec for the specified module. If this is a top-level import, path will be None. Otherwise, this is a search for a subpackage or module and path will be the value of __path__ from the parent package. If a spec cannot be found, None is returned. When passed in, target is a module object that the finder may use to make a more educated guess about what spec to return. importlib.util.spec_from_loader() may be useful for implementing concrete MetaPathFinders.

在 3.4 版被加入.

invalidate_caches()

An optional method which, when called, should invalidate any internal cache used by the finder. Used by importlib.invalidate_caches() when invalidating the caches of all finders on sys.meta_path.

在 3.4 版的變更: 呼叫時回傳 None 而非 NotImplemented。

class importlib.abc.PathEntryFinder

An abstract base class representing a path entry finder. Though it bears some similarities to MetaPathFinder, PathEntryFinder is meant for use only within the path-based import subsystem provided by importlib.machinery.PathFinder.

在 3.3 版被加入.

在 3.10 版的變更: 不再是 Finder 的子類別。

find_spec(fullname, target=None)

An abstract method for finding a spec for the specified module. The finder will search for the module only within the path entry to which it is assigned. If a spec cannot be found, None is returned. When passed in, target is a module object that the finder may use to make a more educated guess about what spec to return. importlib.util.spec_from_loader() may be useful for implementing concrete PathEntryFinders.

在 3.4 版被加入.

invalidate_caches()

An optional method which, when called, should invalidate any internal cache used by the finder. Used by importlib.machinery.PathFinder.invalidate_caches() when invalidating the caches of all cached finders.

class importlib.abc.Loader

An abstract base class for a loader. See PEP 302 [https://peps.python.org/pep-0302/] for the exact definition for a loader.

Loaders that wish to support resource reading should implement a get_resource_reader() method as specified by importlib.resources.abc.ResourceReader.

在 3.7 版的變更: Introduced the optional get_resource_reader() method.

create_module(spec)

A method that returns the module object to use when importing a module. This method may return None, indicating that default module creation semantics should take place.

在 3.4 版被加入.

在 3.6 版的變更: This method is no longer optional when exec_module() is defined.

exec_module(module)

An abstract method that executes the module in its own namespace when a module is imported or reloaded. The module should already be initialized when exec_module() is called. When this method exists, create_module() must be defined.

在 3.4 版被加入.

在 3.6 版的變更: create_module() 也必須被定義。

load_module(fullname)

A legacy method for loading a module. If the module cannot be loaded, ImportError is raised, otherwise the loaded module is returned.

If the requested module already exists in sys.modules, that module should be used and reloaded. Otherwise the loader should create a new module and insert it into sys.modules before any loading begins, to prevent recursion from the import. If the loader inserted a module and the load fails, it must be removed by the loader from sys.modules; modules already in sys.modules before the loader began execution should be left alone.

The loader should set several attributes on the module (note that some of these attributes can change when a module is reloaded):

module.__name__

module.__file__

module.__cached__ （已棄用）

module.__path__

module.__package__ （已棄用）

module.__loader__ （已棄用）

When exec_module() is available then backwards-compatible functionality is provided.

在 3.4 版的變更: Raise ImportError when called instead of NotImplementedError. Functionality provided when exec_module() is available.

自從版本 3.4 後不推薦使用，將會自版本 3.15 中移除。: The recommended API for loading a module is exec_module() (and create_module()). Loaders should implement it instead of load_module(). The import machinery takes care of all the other responsibilities of load_module() when exec_module() is implemented.

class importlib.abc.ResourceLoader

Superseded by TraversableResources

An abstract base class for a loader which implements the optional PEP 302 [https://peps.python.org/pep-0302/] protocol for loading arbitrary resources from the storage back-end.

在 3.7 版之後被棄用: This ABC is deprecated in favour of supporting resource loading through importlib.resources.abc.TraversableResources. This class exists for backwards compatibility only with other ABCs in this module.

abstractmethod get_data(path)

An abstract method to return the bytes for the data located at path. Loaders that have a file-like storage back-end that allows storing arbitrary data can implement this abstract method to give direct access to the data stored. OSError is to be raised if the path cannot be found. The path is expected to be constructed using a module's __file__ attribute or an item from a package's __path__.

在 3.4 版的變更: 引發 OSError 而非 NotImplementedError。

class importlib.abc.InspectLoader

An abstract base class for a loader which implements the optional PEP 302 [https://peps.python.org/pep-0302/] protocol for loaders that inspect modules.

get_code(fullname)

Return the code object for a module, or None if the module does not have a code object (as would be the case, for example, for a built-in module). Raise an ImportError if loader cannot find the requested module.

備註

While the method has a default implementation, it is suggested that it be overridden if possible for performance.

在 3.4 版的變更: No longer abstract and a concrete implementation is provided.

abstractmethod get_source(fullname)

An abstract method to return the source of a module. It is returned as a text string using universal newlines, translating all recognized line separators into '\n' characters. Returns None if no source is available (e.g. a built-in module). Raises ImportError if the loader cannot find the module specified.

在 3.4 版的變更: 引發 ImportError 而非 NotImplementedError。

is_package(fullname)

An optional method to return a true value if the module is a package, a false value otherwise. ImportError is raised if the loader cannot find the module.

在 3.4 版的變更: 引發 ImportError 而非 NotImplementedError。

static source_to_code(data, path='<string>')

Create a code object from Python source.

The data argument can be whatever the compile() function supports (i.e. string or bytes). The path argument should be the "path" to where the source code originated from, which can be an abstract concept (e.g. location in a zip file).

With the subsequent code object one can execute it in a module by running exec(code, module.__dict__).

在 3.4 版被加入.

在 3.5 版的變更: Made the method static.

exec_module(module)

Loader.exec_module() 的實作。

在 3.4 版被加入.

load_module(fullname)

Loader.load_module() 的實作。

自從版本 3.4 後不推薦使用，將會自版本 3.15 中移除。: 請改用 exec_module()。

class importlib.abc.ExecutionLoader

An abstract base class which inherits from InspectLoader that, when implemented, helps a module to be executed as a script. The ABC represents an optional PEP 302 [https://peps.python.org/pep-0302/] protocol.

abstractmethod get_filename(fullname)

An abstract method that is to return the value of __file__ for the specified module. If no path is available, ImportError is raised.

If source code is available, then the method should return the path to the source file, regardless of whether a bytecode was used to load the module.

在 3.4 版的變更: 引發 ImportError 而非 NotImplementedError。

class importlib.abc.FileLoader(fullname, path)

An abstract base class which inherits from ResourceLoader and ExecutionLoader, providing concrete implementations of ResourceLoader.get_data() and ExecutionLoader.get_filename().

The fullname argument is a fully resolved name of the module the loader is to handle. The path argument is the path to the file for the module.

在 3.3 版被加入.

name

The name of the module the loader can handle.

path

Path to the file of the module.

load_module(fullname)

Calls super's load_module().

自從版本 3.4 後不推薦使用，將會自版本 3.15 中移除。: 改用 Loader.exec_module()。

abstractmethod get_filename(fullname)

回傳 path。

abstractmethod get_data(path)

將 path 作為二進位檔案讀取並回傳其位元組。

class importlib.abc.SourceLoader

An abstract base class for implementing source (and optionally bytecode) file loading. The class inherits from both ResourceLoader and ExecutionLoader, requiring the implementation of:

ResourceLoader.get_data()

ExecutionLoader.get_filename()

Should only return the path to the source file; sourceless loading is not supported.

The abstract methods defined by this class are to add optional bytecode file support. Not implementing these optional methods (or causing them to raise NotImplementedError) causes the loader to only work with source code. Implementing the methods allows the loader to work with source and bytecode files; it does not allow for sourceless loading where only bytecode is provided. Bytecode files are an optimization to speed up loading by removing the parsing step of Python's compiler, and so no bytecode-specific API is exposed.

path_stats(path)

Optional abstract method which returns a dict containing metadata about the specified path. Supported dictionary keys are:

'mtime' (mandatory): an integer or floating-point number representing the modification time of the source code;

'size' (optional): the size in bytes of the source code.

Any other keys in the dictionary are ignored, to allow for future extensions. If the path cannot be handled, OSError is raised.

在 3.3 版被加入.

在 3.4 版的變更: 引發 OSError 而非 NotImplementedError。

path_mtime(path)

Optional abstract method which returns the modification time for the specified path.

在 3.3 版之後被棄用: This method is deprecated in favour of path_stats(). You don't have to implement it, but it is still available for compatibility purposes. Raise OSError if the path cannot be handled.

在 3.4 版的變更: 引發 OSError 而非 NotImplementedError。

set_data(path, data)

Optional abstract method which writes the specified bytes to a file path. Any intermediate directories which do not exist are to be created automatically.

When writing to the path fails because the path is read-only (errno.EACCES/PermissionError), do not propagate the exception.

在 3.4 版的變更: 呼叫時不再引發 NotImplementedError。

get_code(fullname)

InspectLoader.get_code() 的具體實作。

exec_module(module)

Loader.exec_module() 的具體實作。

在 3.4 版被加入.

load_module(fullname)

Loader.load_module() 的具體實作。

自從版本 3.4 後不推薦使用，將會自版本 3.15 中移除。: 改用 exec_module()。

get_source(fullname)

InspectLoader.get_source() 的具體實作。

is_package(fullname)

Concrete implementation of InspectLoader.is_package(). A module is determined to be a package if its file path (as provided by ExecutionLoader.get_filename()) is a file named __init__ when the file extension is removed and the module name itself does not end in __init__.

importlib.machinery -- Importers and path hooks

原始碼：Lib/importlib/machinery.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/machinery.py]

This module contains the various objects that help import find and load modules.

importlib.machinery.SOURCE_SUFFIXES

A list of strings representing the recognized file suffixes for source modules.

在 3.3 版被加入.

importlib.machinery.DEBUG_BYTECODE_SUFFIXES

A list of strings representing the file suffixes for non-optimized bytecode modules.

在 3.3 版被加入.

在 3.5 版之後被棄用: 改用 BYTECODE_SUFFIXES。

importlib.machinery.OPTIMIZED_BYTECODE_SUFFIXES

A list of strings representing the file suffixes for optimized bytecode modules.

在 3.3 版被加入.

在 3.5 版之後被棄用: 改用 BYTECODE_SUFFIXES。

importlib.machinery.BYTECODE_SUFFIXES

A list of strings representing the recognized file suffixes for bytecode modules (including the leading dot).

在 3.3 版被加入.

在 3.5 版的變更: The value is no longer dependent on __debug__.

importlib.machinery.EXTENSION_SUFFIXES

A list of strings representing the recognized file suffixes for extension modules.

在 3.3 版被加入.

importlib.machinery.all_suffixes()

Returns a combined list of strings representing all file suffixes for modules recognized by the standard import machinery. This is a helper for code which simply needs to know if a filesystem path potentially refers to a module without needing any details on the kind of module (for example, inspect.getmodulename()).

在 3.3 版被加入.

class importlib.machinery.BuiltinImporter

An importer for built-in modules. All known built-in modules are listed in sys.builtin_module_names. This class implements the importlib.abc.MetaPathFinder and importlib.abc.InspectLoader ABCs.

Only class methods are defined by this class to alleviate the need for instantiation.

在 3.5 版的變更: As part of PEP 489 [https://peps.python.org/pep-0489/], the builtin importer now implements Loader.create_module() and Loader.exec_module()

class importlib.machinery.FrozenImporter

An importer for frozen modules. This class implements the importlib.abc.MetaPathFinder and importlib.abc.InspectLoader ABCs.

Only class methods are defined by this class to alleviate the need for instantiation.

在 3.4 版的變更: Gained create_module() and exec_module() methods.

class importlib.machinery.WindowsRegistryFinder

Finder for modules declared in the Windows registry. This class implements the importlib.abc.MetaPathFinder ABC.

Only class methods are defined by this class to alleviate the need for instantiation.

在 3.3 版被加入.

在 3.6 版之後被棄用: Use site configuration instead. Future versions of Python may not enable this finder by default.

class importlib.machinery.PathFinder

A Finder for sys.path and package __path__ attributes. This class implements the importlib.abc.MetaPathFinder ABC.

Only class methods are defined by this class to alleviate the need for instantiation.

classmethod find_spec(fullname, path=None, target=None)

Class method that attempts to find a spec for the module specified by fullname on sys.path or, if defined, on path. For each path entry that is searched, sys.path_importer_cache is checked. If a non-false object is found then it is used as the path entry finder to look for the module being searched for. If no entry is found in sys.path_importer_cache, then sys.path_hooks is searched for a finder for the path entry and, if found, is stored in sys.path_importer_cache along with being queried about the module. If no finder is ever found then None is both stored in the cache and returned.

在 3.4 版被加入.

在 3.5 版的變更: If the current working directory -- represented by an empty string -- is no longer valid then None is returned but no value is cached in sys.path_importer_cache.

classmethod invalidate_caches()

Calls importlib.abc.PathEntryFinder.invalidate_caches() on all finders stored in sys.path_importer_cache that define the method. Otherwise entries in sys.path_importer_cache set to None are deleted.

在 3.7 版的變更: Entries of None in sys.path_importer_cache are deleted.

在 3.4 版的變更: Calls objects in sys.path_hooks with the current working directory for '' (i.e. the empty string).

class importlib.machinery.FileFinder(path, *loader_details)

A concrete implementation of importlib.abc.PathEntryFinder which caches results from the file system.

The path argument is the directory for which the finder is in charge of searching.

The loader_details argument is a variable number of 2-item tuples each containing a loader and a sequence of file suffixes the loader recognizes. The loaders are expected to be callables which accept two arguments of the module's name and the path to the file found.

The finder will cache the directory contents as necessary, making stat calls for each module search to verify the cache is not outdated. Because cache staleness relies upon the granularity of the operating system's state information of the file system, there is a potential race condition of searching for a module, creating a new file, and then searching for the module the new file represents. If the operations happen fast enough to fit within the granularity of stat calls, then the module search will fail. To prevent this from happening, when you create a module dynamically, make sure to call importlib.invalidate_caches().

在 3.3 版被加入.

path

The path the finder will search in.

find_spec(fullname, target=None)

Attempt to find the spec to handle fullname within path.

在 3.4 版被加入.

invalidate_caches()

Clear out the internal cache.

classmethod path_hook(*loader_details)

A class method which returns a closure for use on sys.path_hooks. An instance of FileFinder is returned by the closure using the path argument given to the closure directly and loader_details indirectly.

If the argument to the closure is not an existing directory, ImportError is raised.

class importlib.machinery.SourceFileLoader(fullname, path)

A concrete implementation of importlib.abc.SourceLoader by subclassing importlib.abc.FileLoader and providing some concrete implementations of other methods.

在 3.3 版被加入.

name

The name of the module that this loader will handle.

path

The path to the source file.

is_package(fullname)

Return True if path appears to be for a package.

path_stats(path)

Concrete implementation of importlib.abc.SourceLoader.path_stats().

set_data(path, data)

Concrete implementation of importlib.abc.SourceLoader.set_data().

load_module(name=None)

Concrete implementation of importlib.abc.Loader.load_module() where specifying the name of the module to load is optional.

自從版本 3.6 後不推薦使用，將會自版本 3.15 中移除。: Use importlib.abc.Loader.exec_module() instead.

class importlib.machinery.SourcelessFileLoader(fullname, path)

A concrete implementation of importlib.abc.FileLoader which can import bytecode files (i.e. no source code files exist).

Please note that direct use of bytecode files (and thus not source code files) inhibits your modules from being usable by all Python implementations or new versions of Python which change the bytecode format.

在 3.3 版被加入.

name

The name of the module the loader will handle.

path

The path to the bytecode file.

is_package(fullname)

Determines if the module is a package based on path.

get_code(fullname)

Returns the code object for name created from path.

get_source(fullname)

Returns None as bytecode files have no source when this loader is used.

load_module(name=None)

Concrete implementation of importlib.abc.Loader.load_module() where specifying the name of the module to load is optional.

自從版本 3.6 後不推薦使用，將會自版本 3.15 中移除。: Use importlib.abc.Loader.exec_module() instead.

class importlib.machinery.ExtensionFileLoader(fullname, path)

A concrete implementation of importlib.abc.ExecutionLoader for extension modules.

The fullname argument specifies the name of the module the loader is to support. The path argument is the path to the extension module's file.

Note that, by default, importing an extension module will fail in subinterpreters if it doesn't implement multi-phase init (see PEP 489 [https://peps.python.org/pep-0489/]), even if it would otherwise import successfully.

在 3.3 版被加入.

在 3.12 版的變更: Multi-phase init is now required for use in subinterpreters.

name

Name of the module the loader supports.

path

Path to the extension module.

create_module(spec)

Creates the module object from the given specification in accordance with PEP 489 [https://peps.python.org/pep-0489/].

在 3.5 版被加入.

exec_module(module)

Initializes the given module object in accordance with PEP 489 [https://peps.python.org/pep-0489/].

在 3.5 版被加入.

is_package(fullname)

Returns True if the file path points to a package's __init__ module based on EXTENSION_SUFFIXES.

get_code(fullname)

Returns None as extension modules lack a code object.

get_source(fullname)

Returns None as extension modules do not have source code.

get_filename(fullname)

回傳 path。

在 3.4 版被加入.

class importlib.machinery.NamespaceLoader(name, path, path_finder)

A concrete implementation of importlib.abc.InspectLoader for namespace packages. This is an alias for a private class and is only made public for introspecting the __loader__ attribute on namespace packages:

>>> from importlib.machinery import NamespaceLoader
>>> import my_namespace
>>> isinstance(my_namespace.__loader__, NamespaceLoader)
True
>>> import importlib.abc
>>> isinstance(my_namespace.__loader__, importlib.abc.Loader)
True

在 3.11 版被加入.

class importlib.machinery.ModuleSpec(name, loader, *, origin=None, loader_state=None, is_package=None)

A specification for a module's import-system-related state. This is typically exposed as the module's __spec__ attribute. Many of these attributes are also available directly on a module: for example, module.__spec__.origin == module.__file__. Note, however, that while the values are usually equivalent, they can differ since there is no synchronization between the two objects. For example, it is possible to update the module's __file__ at runtime and this will not be automatically reflected in the module's __spec__.origin, and vice versa.

在 3.4 版被加入.

name

The module's fully qualified name (see module.__name__). The finder should always set this attribute to a non-empty string.

loader

The loader used to load the module (see module.__loader__). The finder should always set this attribute.

origin

The location the loader should use to load the module (see module.__file__). For example, for modules loaded from a .py file this is the filename. The finder should always set this attribute to a meaningful value for the loader to use. In the uncommon case that there is not one (like for namespace packages), it should be set to None.

submodule_search_locations

A (possibly empty) sequence of strings enumerating the locations in which a package's submodules will be found (see module.__path__). Most of the time there will only be a single directory in this list.

The finder should set this attribute to a sequence, even an empty one, to indicate to the import system that the module is a package. It should be set to None for non-package modules. It is set automatically later to a special object for namespace packages.

loader_state

The finder may set this attribute to an object containing additional, module-specific data to use when loading the module. Otherwise it should be set to None.

cached

The filename of a compiled version of the module's code (see module.__cached__). The finder should always set this attribute but it may be None for modules that do not need compiled code stored.

parent

(Read-only) The fully qualified name of the package the module is in (or the empty string for a top-level module). See module.__package__. If the module is a package then this is the same as name.

has_location

True if the spec's origin refers to a loadable location, False otherwise. This value impacts how origin is interpreted and how the module's __file__ is populated.

class importlib.machinery.AppleFrameworkLoader(name, path)

A specialization of importlib.machinery.ExtensionFileLoader that is able to load extension modules in Framework format.

For compatibility with the iOS App Store, all binary modules in an iOS app must be dynamic libraries, contained in a framework with appropriate metadata, stored in the Frameworks folder of the packaged app. There can be only a single binary per framework, and there can be no executable binary material outside the Frameworks folder.

To accommodate this requirement, when running on iOS, extension module binaries are not packaged as .so files on sys.path, but as individual standalone frameworks. To discover those frameworks, this loader is registered against the .fwork file extension, with a .fwork file acting as a placeholder in the original location of the binary on sys.path. The .fwork file contains the path of the actual binary in the Frameworks folder, relative to the app bundle. To allow for resolving a framework-packaged binary back to the original location, the framework is expected to contain a .origin file that contains the location of the .fwork file, relative to the app bundle.

For example, consider the case of an import from foo.bar import _whiz, where _whiz is implemented with the binary module sources/foo/bar/_whiz.abi3.so, with sources being the location registered on sys.path, relative to the application bundle. This module must be distributed as Frameworks/foo.bar._whiz.framework/foo.bar._whiz (creating the framework name from the full import path of the module), with an Info.plist file in the .framework directory identifying the binary as a framework. The foo.bar._whiz module would be represented in the original location with a sources/foo/bar/_whiz.abi3.fwork marker file, containing the path Frameworks/foo.bar._whiz/foo.bar._whiz. The framework would also contain Frameworks/foo.bar._whiz.framework/foo.bar._whiz.origin, containing the path to the .fwork file.

When a module is loaded with this loader, the __file__ for the module will report as the location of the .fwork file. This allows code to use the __file__ of a module as an anchor for file system traversal. However, the spec origin will reference the location of the actual binary in the .framework folder.

The Xcode project building the app is responsible for converting any .so files from wherever they exist in the PYTHONPATH into frameworks in the Frameworks folder (including stripping extensions from the module file, the addition of framework metadata, and signing the resulting framework), and creating the .fwork and .origin files. This will usually be done with a build step in the Xcode project; see the iOS documentation for details on how to construct this build step.

在 3.13 版被加入.

可用性: iOS.

name

Name of the module the loader supports.

path

Path to the .fwork file for the extension module.

importlib.util -- Utility code for importers

原始碼：Lib/importlib/util.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/util.py]

This module contains the various objects that help in the construction of an importer.

importlib.util.MAGIC_NUMBER

The bytes which represent the bytecode version number. If you need help with loading/writing bytecode then consider importlib.abc.SourceLoader.

在 3.4 版被加入.

importlib.util.cache_from_source(path, debug_override=None, *, optimization=None)

Return the PEP 3147 [https://peps.python.org/pep-3147/]/PEP 488 [https://peps.python.org/pep-0488/] path to the byte-compiled file associated with the source path. For example, if path is /foo/bar/baz.py the return value would be /foo/bar/__pycache__/baz.cpython-32.pyc for Python 3.2. The cpython-32 string comes from the current magic tag (see get_tag(); if sys.implementation.cache_tag is not defined then NotImplementedError will be raised).

The optimization parameter is used to specify the optimization level of the bytecode file. An empty string represents no optimization, so /foo/bar/baz.py with an optimization of '' will result in a bytecode path of /foo/bar/__pycache__/baz.cpython-32.pyc. None causes the interpreter's optimization level to be used. Any other value's string representation is used, so /foo/bar/baz.py with an optimization of 2 will lead to the bytecode path of /foo/bar/__pycache__/baz.cpython-32.opt-2.pyc. The string representation of optimization can only be alphanumeric, else ValueError is raised.

The debug_override parameter is deprecated and can be used to override the system's value for __debug__. A True value is the equivalent of setting optimization to the empty string. A False value is the same as setting optimization to 1. If both debug_override an optimization are not None then TypeError is raised.

在 3.4 版被加入.

在 3.5 版的變更: The optimization parameter was added and the debug_override parameter was deprecated.

在 3.6 版的變更: 接受一個 path-like object。

importlib.util.source_from_cache(path)

Given the path to a PEP 3147 [https://peps.python.org/pep-3147/] file name, return the associated source code file path. For example, if path is /foo/bar/__pycache__/baz.cpython-32.pyc the returned path would be /foo/bar/baz.py. path need not exist, however if it does not conform to PEP 3147 [https://peps.python.org/pep-3147/] or PEP 488 [https://peps.python.org/pep-0488/] format, a ValueError is raised. If sys.implementation.cache_tag is not defined, NotImplementedError is raised.

在 3.4 版被加入.

在 3.6 版的變更: 接受一個 path-like object。

importlib.util.decode_source(source_bytes)

Decode the given bytes representing source code and return it as a string with universal newlines (as required by importlib.abc.InspectLoader.get_source()).

在 3.4 版被加入.

importlib.util.resolve_name(name, package)

Resolve a relative module name to an absolute one.

If name has no leading dots, then name is simply returned. This allows for usage such as importlib.util.resolve_name('sys', __spec__.parent) without doing a check to see if the package argument is needed.

ImportError is raised if name is a relative module name but package is a false value (e.g. None or the empty string). ImportError is also raised if a relative name would escape its containing package (e.g. requesting ..bacon from within the spam package).

在 3.3 版被加入.

在 3.9 版的變更: To improve consistency with import statements, raise ImportError instead of ValueError for invalid relative import attempts.

importlib.util.find_spec(name, package=None)

Find the spec for a module, optionally relative to the specified package name. If the module is in sys.modules, then sys.modules[name].__spec__ is returned (unless the spec would be None or is not set, in which case ValueError is raised). Otherwise a search using sys.meta_path is done. None is returned if no spec is found.

If name is for a submodule (contains a dot), the parent module is automatically imported.

name and package work the same as for import_module().

在 3.4 版被加入.

在 3.7 版的變更: Raises ModuleNotFoundError instead of AttributeError if package is in fact not a package (i.e. lacks a __path__ attribute).

importlib.util.module_from_spec(spec)

Create a new module based on spec and spec.loader.create_module.

If spec.loader.create_module does not return None, then any pre-existing attributes will not be reset. Also, no AttributeError will be raised if triggered while accessing spec or setting an attribute on the module.

This function is preferred over using types.ModuleType to create a new module as spec is used to set as many import-controlled attributes on the module as possible.

在 3.5 版被加入.

importlib.util.spec_from_loader(name, loader, *, origin=None, is_package=None)

A factory function for creating a ModuleSpec instance based on a loader. The parameters have the same meaning as they do for ModuleSpec. The function uses available loader APIs, such as InspectLoader.is_package(), to fill in any missing information on the spec.

在 3.4 版被加入.

importlib.util.spec_from_file_location(name, location, *, loader=None, submodule_search_locations=None)

A factory function for creating a ModuleSpec instance based on the path to a file. Missing information will be filled in on the spec by making use of loader APIs and by the implication that the module will be file-based.

在 3.4 版被加入.

在 3.6 版的變更: 接受一個 path-like object。

importlib.util.source_hash(source_bytes)

Return the hash of source_bytes as bytes. A hash-based .pyc file embeds the source_hash() of the corresponding source file's contents in its header.

在 3.7 版被加入.

importlib.util._incompatible_extension_module_restrictions(*, disable_check)

A context manager that can temporarily skip the compatibility check for extension modules. By default the check is enabled and will fail when a single-phase init module is imported in a subinterpreter. It will also fail for a multi-phase init module that doesn't explicitly support a per-interpreter GIL, when imported in an interpreter with its own GIL.

Note that this function is meant to accommodate an unusual case; one which is likely to eventually go away. There's is a pretty good chance this is not what you were looking for.

你可以透過實作多階段初始化的基本介面 (PEP 489 [https://peps.python.org/pep-0489/]) 並假稱有多個直譯器（或直譯器各別持有的 GIL）的支援，來達到與此函式相同的效果。

警告

Using this function to disable the check can lead to unexpected behavior and even crashes. It should only be used during extension module development.

在 3.12 版被加入.

class importlib.util.LazyLoader(loader)

A class which postpones the execution of the loader of a module until the module has an attribute accessed.

This class only works with loaders that define exec_module() as control over what module type is used for the module is required. For those same reasons, the loader's create_module() method must return None or a type for which its __class__ attribute can be mutated along with not using slots. Finally, modules which substitute the object placed into sys.modules will not work as there is no way to properly replace the module references throughout the interpreter safely; ValueError is raised if such a substitution is detected.

備註

For projects where startup time is critical, this class allows for potentially minimizing the cost of loading a module if it is never used. For projects where startup time is not essential then use of this class is heavily discouraged due to error messages created during loading being postponed and thus occurring out of context.

在 3.5 版被加入.

在 3.6 版的變更: Began calling create_module(), removing the compatibility warning for importlib.machinery.BuiltinImporter and importlib.machinery.ExtensionFileLoader.

classmethod factory(loader)

A class method which returns a callable that creates a lazy loader. This is meant to be used in situations where the loader is passed by class instead of by instance.

suffixes = importlib.machinery.SOURCE_SUFFIXES
loader = importlib.machinery.SourceFileLoader
lazy_loader = importlib.util.LazyLoader.factory(loader)
finder = importlib.machinery.FileFinder(path, (lazy_loader, suffixes))

範例

Importing programmatically

To programmatically import a module, use importlib.import_module().

import importlib

itertools = importlib.import_module('itertools')

Checking if a module can be imported

If you need to find out if a module can be imported without actually doing the import, then you should use importlib.util.find_spec().

Note that if name is a submodule (contains a dot), importlib.util.find_spec() will import the parent module.

import importlib.util
import sys

# For illustrative purposes.
name = 'itertools'

if name in sys.modules:
    print(f"{name!r} already in sys.modules")
elif (spec := importlib.util.find_spec(name)) is not None:
    # If you chose to perform the actual import ...
    module = importlib.util.module_from_spec(spec)
    sys.modules[name] = module
    spec.loader.exec_module(module)
    print(f"{name!r} has been imported")
else:
    print(f"can't find the {name!r} module")

Importing a source file directly

This recipe should be used with caution: it is an approximation of an import statement where the file path is specified directly, rather than sys.path being searched. Alternatives should first be considered first, such as modifying sys.path when a proper module is required, or using runpy.run_path() when the global namespace resulting from running a Python file is appropriate.

To import a Python source file directly from a path, use the following recipe:

import importlib.util
import sys

def import_from_path(module_name, file_path):
    spec = importlib.util.spec_from_file_location(module_name, file_path)
    module = importlib.util.module_from_spec(spec)
    sys.modules[module_name] = module
    spec.loader.exec_module(module)
    return module

# For illustrative purposes only (use of `json` is arbitrary).
import json
file_path = json.__file__
module_name = json.__name__

# Similar outcome as `import json`.
json = import_from_path(module_name, file_path)

Implementing lazy imports

The example below shows how to implement lazy imports:

>>> import importlib.util
>>> import sys
>>> def lazy_import(name):
...     spec = importlib.util.find_spec(name)
...     loader = importlib.util.LazyLoader(spec.loader)
...     spec.loader = loader
...     module = importlib.util.module_from_spec(spec)
...     sys.modules[name] = module
...     loader.exec_module(module)
...     return module
...
>>> lazy_typing = lazy_import("typing")
>>> # lazy_typing 是一個真實的模組物件，
>>> # 但它尚未載入到記憶體中。
>>> lazy_typing.TYPE_CHECKING
False

Setting up an importer

For deep customizations of import, you typically want to implement an importer. This means managing both the finder and loader side of things. For finders there are two flavours to choose from depending on your needs: a meta path finder or a path entry finder. The former is what you would put on sys.meta_path while the latter is what you create using a path entry hook on sys.path_hooks which works with sys.path entries to potentially create a finder. This example will show you how to register your own importers so that import will use them (for creating an importer for yourself, read the documentation for the appropriate classes defined within this package):

import importlib.machinery
import sys

# For illustrative purposes only.
SpamMetaPathFinder = importlib.machinery.PathFinder
SpamPathEntryFinder = importlib.machinery.FileFinder
loader_details = (importlib.machinery.SourceFileLoader,
                  importlib.machinery.SOURCE_SUFFIXES)

# Setting up a meta path finder.
# Make sure to put the finder in the proper location in the list in terms of
# priority.
sys.meta_path.append(SpamMetaPathFinder)

# Setting up a path entry finder.
# Make sure to put the path hook in the proper location in the list in terms
# of priority.
sys.path_hooks.append(SpamPathEntryFinder.path_hook(loader_details))

Approximating importlib.import_module()

Import itself is implemented in Python code, making it possible to expose most of the import machinery through importlib. The following helps illustrate the various APIs that importlib exposes by providing an approximate implementation of importlib.import_module():

import importlib.util
import sys

def import_module(name, package=None):
    """An approximate implementation of import."""
    absolute_name = importlib.util.resolve_name(name, package)
    try:
        return sys.modules[absolute_name]
    except KeyError:
        pass

    path = None
    if '.' in absolute_name:
        parent_name, _, child_name = absolute_name.rpartition('.')
        parent_module = import_module(parent_name)
        path = parent_module.__spec__.submodule_search_locations
    for finder in sys.meta_path:
        spec = finder.find_spec(absolute_name, path)
        if spec is not None:
            break
    else:
        msg = f'No module named {absolute_name!r}'
        raise ModuleNotFoundError(msg, name=absolute_name)
    module = importlib.util.module_from_spec(spec)
    sys.modules[absolute_name] = module
    spec.loader.exec_module(module)
    if path is not None:
        setattr(parent_module, child_name, module)
    return module

importlib.resources -- 套件資源的讀取、開啟與存取

原始碼：Lib/importlib/resources/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/resources/__init__.py]

在 3.7 版被加入.

This module leverages Python's import system to provide access to resources within packages.

"Resources" are file-like resources associated with a module or package in Python. The resources may be contained directly in a package, within a subdirectory contained in that package, or adjacent to modules outside a package. Resources may be text or binary. As a result, a package's Python module sources (.py), compilation artifacts (pycache), and installation artifacts (like reserved filenames in directories) are technically de-facto resources of that package. In practice, however, resources are primarily those non-Python artifacts exposed specifically by the package author.

Resources can be opened or read in either binary or text mode.

Resources are roughly akin to files inside directories, though it's important to keep in mind that this is just a metaphor. Resources and packages do not have to exist as physical files and directories on the file system: for example, a package and its resources can be imported from a zip file using zipimport.

備註

This module provides functionality similar to pkg_resources [https://setuptools.readthedocs.io/en/latest/pkg_resources.html] Basic Resource Access [https://setuptools.readthedocs.io/en/latest/pkg_resources.html#basic-resource-access] without the performance overhead of that package. This makes reading resources included in packages easier, with more stable and consistent semantics.

The standalone backport of this module provides more information on using importlib.resources [https://importlib-resources.readthedocs.io/en/latest/using.html] and migrating from pkg_resources to importlib.resources [https://importlib-resources.readthedocs.io/en/latest/migration.html].

Loaders that wish to support resource reading should implement a get_resource_reader(fullname) method as specified by importlib.resources.abc.ResourceReader.

class importlib.resources.Anchor

Represents an anchor for resources, either a module object or a module name as a string. Defined as Union[str, ModuleType].

importlib.resources.files(anchor: Anchor | None = None)

Returns a Traversable object representing the resource container (think directory) and its resources (think files). A Traversable may contain other containers (think subdirectories).

anchor is an optional Anchor. If the anchor is a package, resources are resolved from that package. If a module, resources are resolved adjacent to that module (in the same package or the package root). If the anchor is omitted, the caller's module is used.

在 3.9 版被加入.

在 3.12 版的變更: package parameter was renamed to anchor. anchor can now be a non-package module and if omitted will default to the caller's module. package is still accepted for compatibility but will raise a DeprecationWarning. Consider passing the anchor positionally or using importlib_resources >= 5.10 for a compatible interface on older Pythons.

importlib.resources.as_file(traversable)

Given a Traversable object representing a file or directory, typically from importlib.resources.files(), return a context manager for use in a with statement. The context manager provides a pathlib.Path object.

Exiting the context manager cleans up any temporary file or directory created when the resource was extracted from e.g. a zip file.

Use as_file when the Traversable methods (read_text, etc) are insufficient and an actual file or directory on the file system is required.

在 3.9 版被加入.

在 3.12 版的變更: Added support for traversable representing a directory.

Functional API

A set of simplified, backwards-compatible helpers is available. These allow common operations in a single function call.

For all the following functions:

anchor is an Anchor, as in files(). Unlike in files, it may not be omitted.

path_names are components of a resource's path name, relative to the anchor. For example, to get the text of resource named info.txt, use:

importlib.resources.read_text(my_module, "info.txt")

Like Traversable.joinpath, The individual components should use forward slashes (/) as path separators. For example, the following are equivalent:

importlib.resources.read_binary(my_module, "pics/painting.png")
importlib.resources.read_binary(my_module, "pics", "painting.png")

For backward compatibility reasons, functions that read text require an explicit encoding argument if multiple path_names are given. For example, to get the text of info/chapter1.txt, use:

importlib.resources.read_text(my_module, "info", "chapter1.txt",
                              encoding='utf-8')

importlib.resources.open_binary(anchor, *path_names)

Open the named resource for binary reading.

See the introduction for details on anchor and path_names.

This function returns a BinaryIO object, that is, a binary stream open for reading.

這個函式大致等同於：

files(anchor).joinpath(*path_names).open('rb')

在 3.13 版的變更: 多個 path_names 是被接受的。

importlib.resources.open_text(anchor, *path_names, encoding='utf-8', errors='strict')

Open the named resource for text reading. By default, the contents are read as strict UTF-8.

See the introduction for details on anchor and path_names. encoding and errors have the same meaning as in built-in open().

For backward compatibility reasons, the encoding argument must be given explicitly if there are multiple path_names. This limitation is scheduled to be removed in Python 3.15.

This function returns a TextIO object, that is, a text stream open for reading.

這個函式大致等同於：

files(anchor).joinpath(*path_names).open('r', encoding=encoding)

在 3.13 版的變更: Multiple path_names are accepted. encoding and errors must be given as keyword arguments.

importlib.resources.read_binary(anchor, *path_names)

以 bytes 形式讀取並回傳指定資源的內容。

See the introduction for details on anchor and path_names.

這個函式大致等同於：

files(anchor).joinpath(*path_names).read_bytes()

在 3.13 版的變更: 多個 path_names 是被接受的。

importlib.resources.read_text(anchor, *path_names, encoding='utf-8', errors='strict')

Read and return the contents of the named resource as str. By default, the contents are read as strict UTF-8.

See the introduction for details on anchor and path_names. encoding and errors have the same meaning as in built-in open().

For backward compatibility reasons, the encoding argument must be given explicitly if there are multiple path_names. This limitation is scheduled to be removed in Python 3.15.

這個函式大致等同於：

files(anchor).joinpath(*path_names).read_text(encoding=encoding)

在 3.13 版的變更: Multiple path_names are accepted. encoding and errors must be given as keyword arguments.

importlib.resources.path(anchor, *path_names)

Provides the path to the resource as an actual file system path. This function returns a context manager for use in a with statement. The context manager provides a pathlib.Path object.

Exiting the context manager cleans up any temporary files created, e.g. when the resource needs to be extracted from a zip file.

For example, the stat() method requires an actual file system path; it can be used like this:

with importlib.resources.path(anchor, "resource.txt") as fspath:
    result = fspath.stat()

See the introduction for details on anchor and path_names.

這個函式大致等同於：

as_file(files(anchor).joinpath(*path_names))

在 3.13 版的變更: Multiple path_names are accepted. encoding and errors must be given as keyword arguments.

importlib.resources.is_resource(anchor, *path_names)

Return True if the named resource exists, otherwise False. This function does not consider directories to be resources.

See the introduction for details on anchor and path_names.

這個函式大致等同於：

files(anchor).joinpath(*path_names).is_file()

在 3.13 版的變更: 多個 path_names 是被接受的。

importlib.resources.contents(anchor, *path_names)

Return an iterable over the named items within the package or path. The iterable returns names of resources (e.g. files) and non-resources (e.g. directories) as str. The iterable does not recurse into subdirectories.

See the introduction for details on anchor and path_names.

這個函式大致等同於：

for resource in files(anchor).joinpath(*path_names).iterdir():
    yield resource.name

在 3.11 版之後被棄用: Prefer iterdir() as above, which offers more control over the results and richer functionality.

importlib.resources.abc -- 資源的抽象基底類別

原始碼：Lib/importlib/resources/abc.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/resources/abc.py]

在 3.11 版被加入.

class importlib.resources.abc.ResourceReader

Superseded by TraversableResources

An abstract base class to provide the ability to read resources.

From the perspective of this ABC, a resource is a binary artifact that is shipped within a package. Typically this is something like a data file that lives next to the __init__.py file of the package. The purpose of this class is to help abstract out the accessing of such data files so that it does not matter if the package and its data file(s) are stored e.g. in a zip file versus on the file system.

For any of methods of this class, a resource argument is expected to be a path-like object which represents conceptually just a file name. This means that no subdirectory paths should be included in the resource argument. This is because the location of the package the reader is for, acts as the "directory". Hence the metaphor for directories and file names is packages and resources, respectively. This is also why instances of this class are expected to directly correlate to a specific package (instead of potentially representing multiple packages or a module).

Loaders that wish to support resource reading are expected to provide a method called get_resource_reader(fullname) which returns an object implementing this ABC's interface. If the module specified by fullname is not a package, this method should return None. An object compatible with this ABC should only be returned when the specified module is a package.

在 3.12 版之後被棄用: 請改用 importlib.resources.abc.TraversableResources。

abstractmethod open_resource(resource)

Returns an opened, file-like object for binary reading of the resource.

If the resource cannot be found, FileNotFoundError is raised.

abstractmethod resource_path(resource)

Returns the file system path to the resource.

If the resource does not concretely exist on the file system, raise FileNotFoundError.

abstractmethod is_resource(path)

Returns True if the named path is considered a resource. FileNotFoundError is raised if path does not exist.

在 3.10 版的變更: name 引數已重新命名為 path。

abstractmethod contents()

Returns an iterable of strings over the contents of the package. Do note that it is not required that all names returned by the iterator be actual resources, e.g. it is acceptable to return names for which is_resource() would be false.

Allowing non-resource names to be returned is to allow for situations where how a package and its resources are stored are known a priori and the non-resource names would be useful. For instance, returning subdirectory names is allowed so that when it is known that the package and resources are stored on the file system then those subdirectory names can be used directly.

The abstract method returns an iterable of no items.

class importlib.resources.abc.Traversable

An object with a subset of pathlib.Path methods suitable for traversing directories and opening files.

For a representation of the object on the file-system, use importlib.resources.as_file().

name

Abstract. The base name of this object without any parent references.

abstractmethod iterdir()

Yield Traversable objects in self.

abstractmethod is_dir()

Return True if self is a directory.

abstractmethod is_file()

Return True if self is a file.

abstractmethod joinpath(*pathsegments)

Traverse directories according to pathsegments and return the result as Traversable.

Each pathsegments argument may contain multiple names separated by forward slashes (/, posixpath.sep ). For example, the following are equivalent:

files.joinpath('subdir', 'subsuddir', 'file.txt')
files.joinpath('subdir/subsuddir/file.txt')

Note that some Traversable implementations might not be updated to the latest version of the protocol. For compatibility with such implementations, provide a single argument without path separators to each call to joinpath. For example:

files.joinpath('subdir').joinpath('subsubdir').joinpath('file.txt')

在 3.11 版的變更: joinpath accepts multiple pathsegments, and these segments may contain forward slashes as path separators. Previously, only a single child argument was accepted.

abstractmethod __truediv__(child)

Return Traversable child in self. Equivalent to joinpath(child).

abstractmethod open(mode='r', *args, **kwargs)

mode may be 'r' or 'rb' to open as text or binary. Return a handle suitable for reading (same as pathlib.Path.open).

When opening as text, accepts encoding parameters such as those accepted by io.TextIOWrapper.

read_bytes()

Read contents of self as bytes.

read_text(encoding=None)

Read contents of self as text.

class importlib.resources.abc.TraversableResources

An abstract base class for resource readers capable of serving the importlib.resources.files() interface. Subclasses ResourceReader and provides concrete implementations of the ResourceReader's abstract methods. Therefore, any loader supplying TraversableResources also supplies ResourceReader.

Loaders that wish to support resource reading are expected to implement this interface.

abstractmethod files()

Returns a importlib.resources.abc.Traversable object for the loaded package.

importlib.metadata -- 存取套件的元資料

在 3.8 版被加入.

在 3.10 版的變更: importlib.metadata is no longer provisional.

原始碼：Lib/importlib/metadata/__init__.py [https://github.com/python/cpython/tree/3.14/Lib/importlib/metadata/__init__.py]

importlib.metadata is a library that provides access to the metadata of an installed Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package], such as its entry points or its top-level names (Import Package [https://packaging.python.org/en/latest/glossary/#term-Import-Package]s, modules, if any). Built in part on Python's import system, this library intends to replace similar functionality in the entry point API [https://setuptools.readthedocs.io/en/latest/pkg_resources.html#entry-points] and metadata API [https://setuptools.readthedocs.io/en/latest/pkg_resources.html#metadata-api] of pkg_resources. Along with importlib.resources, this package can eliminate the need to use the older and less efficient pkg_resources package.

importlib.metadata operates on third-party distribution packages installed into Python's site-packages directory via tools such as pip [https://pypi.org/project/pip/]. Specifically, it works with distributions with discoverable dist-info or egg-info directories, and metadata defined by the Core metadata specifications [https://packaging.python.org/en/latest/specifications/core-metadata/#core-metadata].

重要

These are not necessarily equivalent to or correspond 1:1 with the top-level import package names that can be imported inside Python code. One distribution package can contain multiple import packages (and single modules), and one top-level import package may map to multiple distribution packages if it is a namespace package. You can use packages_distributions() to get a mapping between them.

By default, distribution metadata can live on the file system or in zip archives on sys.path. Through an extension mechanism, the metadata can live almost anywhere.

也參考

https://importlib-metadata.readthedocs.io/

The documentation for importlib_metadata, which supplies a backport of importlib.metadata. This includes an API reference [https://importlib-metadata.readthedocs.io/en/latest/api.html] for this module's classes and functions, as well as a migration guide [https://importlib-metadata.readthedocs.io/en/latest/migration.html] for existing users of pkg_resources.

Overview

Let's say you wanted to get the version string for a Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package] you've installed using pip. We start by creating a virtual environment and installing something into it:

$ python -m venv example
$ source example/bin/activate
(example) $ python -m pip install wheel

You can get the version string for wheel by running the following:

(example) $ python
>>> from importlib.metadata import version
>>> version('wheel')
'0.32.3'

You can also get a collection of entry points selectable by properties of the EntryPoint (typically 'group' or 'name'), such as console_scripts, distutils.commands and others. Each group contains a collection of EntryPoint objects.

You can get the metadata for a distribution:

>>> list(metadata('wheel'))
['Metadata-Version', 'Name', 'Version', 'Summary', 'Home-page', 'Author', 'Author-email', 'Maintainer', 'Maintainer-email', 'License', 'Project-URL', 'Project-URL', 'Project-URL', 'Keywords', 'Platform', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Requires-Python', 'Provides-Extra', 'Requires-Dist', 'Requires-Dist']

You can also get a distribution's version number, list its constituent files, and get a list of the distribution's Distribution requirements.

exception importlib.metadata.PackageNotFoundError

Subclass of ModuleNotFoundError raised by several functions in this module when queried for a distribution package which is not installed in the current Python environment.

Functional API

This package provides the following functionality via its public API.

Entry points

importlib.metadata.entry_points(**select_params)

Returns a EntryPoints instance describing entry points for the current environment. Any given keyword parameters are passed to the select() method for comparison to the attributes of the individual entry point definitions.

Note: it is not currently possible to query for entry points based on their EntryPoint.dist attribute (as different Distribution instances do not currently compare equal, even if they have the same attributes)

class importlib.metadata.EntryPoints

Details of a collection of installed entry points.

Also provides a .groups attribute that reports all identified entry point groups, and a .names attribute that reports all identified entry point names.

class importlib.metadata.EntryPoint

Details of an installed entry point.

Each EntryPoint instance has .name, .group, and .value attributes and a .load() method to resolve the value. There are also .module, .attr, and .extras attributes for getting the components of the .value attribute, and .dist for obtaining information regarding the distribution package that provides the entry point.

Query all entry points:

>>> eps = entry_points()

The entry_points() function returns a EntryPoints object, a collection of all EntryPoint objects with names and groups attributes for convenience:

>>> sorted(eps.groups)
['console_scripts', 'distutils.commands', 'distutils.setup_keywords', 'egg_info.writers', 'setuptools.installation']

EntryPoints has a select() method to select entry points matching specific properties. Select entry points in the console_scripts group:

>>> scripts = eps.select(group='console_scripts')

Equivalently, since entry_points() passes keyword arguments through to select:

>>> scripts = entry_points(group='console_scripts')

Pick out a specific script named "wheel" (found in the wheel project):

>>> 'wheel' in scripts.names
True
>>> wheel = scripts['wheel']

Equivalently, query for that entry point during selection:

>>> (wheel,) = entry_points(group='console_scripts', name='wheel')
>>> (wheel,) = entry_points().select(group='console_scripts', name='wheel')

Inspect the resolved entry point:

>>> wheel
EntryPoint(name='wheel', value='wheel.cli:main', group='console_scripts')
>>> wheel.module
'wheel.cli'
>>> wheel.attr
'main'
>>> wheel.extras
[]
>>> main = wheel.load()
>>> main
<function main at 0x103528488>

The group and name are arbitrary values defined by the package author and usually a client will wish to resolve all entry points for a particular group. Read the setuptools docs [https://setuptools.pypa.io/en/latest/userguide/entry_point.html] for more information on entry points, their definition, and usage.

在 3.12 版的變更: The "selectable" entry points were introduced in importlib_metadata 3.6 and Python 3.10. Prior to those changes, entry_points accepted no parameters and always returned a dictionary of entry points, keyed by group. With importlib_metadata 5.0 and Python 3.12, entry_points always returns an EntryPoints object. See backports.entry_points_selectable [https://pypi.org/project/backports.entry_points_selectable/] for compatibility options.

在 3.13 版的變更: EntryPoint objects no longer present a tuple-like interface (__getitem__()).

Distribution metadata

importlib.metadata.metadata(distribution_name)

Return the distribution metadata corresponding to the named distribution package as a PackageMetadata instance.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

class importlib.metadata.PackageMetadata

A concrete implementation of the PackageMetadata protocol [https://importlib-metadata.readthedocs.io/en/latest/api.html#importlib_metadata.PackageMetadata].

In addition to providing the defined protocol methods and attributes, subscripting the instance is equivalent to calling the get() method.

Every Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package] includes some metadata, which you can extract using the metadata() function:

>>> wheel_metadata = metadata('wheel')

The keys of the returned data structure name the metadata keywords, and the values are returned unparsed from the distribution metadata:

>>> wheel_metadata['Requires-Python']
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'

PackageMetadata also presents a json attribute that returns all the metadata in a JSON-compatible form per PEP 566 [https://peps.python.org/pep-0566/]:

>>> wheel_metadata.json['requires_python']
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'

The full set of available metadata is not described here. See the PyPA Core metadata specification [https://packaging.python.org/en/latest/specifications/core-metadata/#core-metadata] for additional details.

在 3.10 版的變更: The Description is now included in the metadata when presented through the payload. Line continuation characters have been removed.

新增 json 屬性。

Distribution versions

importlib.metadata.version(distribution_name)

Return the installed distribution package version [https://packaging.python.org/en/latest/specifications/core-metadata/#version] for the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

The version() function is the quickest way to get a Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package]'s version number, as a string:

>>> version('wheel')
'0.32.3'

Distribution files

importlib.metadata.files(distribution_name)

Return the full set of files contained within the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

Returns None if the distribution is found but the installation database records reporting the files associated with the distribution package are missing.

class importlib.metadata.PackagePath

A pathlib.PurePath derived object with additional dist, size, and hash properties corresponding to the distribution package's installation metadata for that file.

The files() function takes a Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package] name and returns all of the files installed by this distribution. Each file is reported as a PackagePath instance. For example:

>>> util = [p for p in files('wheel') if 'util.py' in str(p)][0]
>>> util
PackagePath('wheel/util.py')
>>> util.size
859
>>> util.dist
<importlib.metadata._hooks.PathDistribution object at 0x101e0cef0>
>>> util.hash
<FileHash mode: sha256 value: bYkw5oMccfazVCoYQwKkkemoVyMAFoR34mmKBx8R1NI>

Once you have the file, you can also read its contents:

>>> print(util.read_text())
import base64
import sys
...
def as_bytes(s):
    if isinstance(s, text_type):
        return s.encode('utf-8')
    return s

You can also use the locate() method to get the absolute path to the file:

>>> util.locate()
PosixPath('/home/gustav/example/lib/site-packages/wheel/util.py')

In the case where the metadata file listing files (RECORD or SOURCES.txt) is missing, files() will return None. The caller may wish to wrap calls to files() in always_iterable [https://more-itertools.readthedocs.io/en/stable/api.html#more_itertools.always_iterable] or otherwise guard against this condition if the target distribution is not known to have the metadata present.

Distribution requirements

importlib.metadata.requires(distribution_name)

Return the declared dependency specifiers for the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

To get the full set of requirements for a Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package], use the requires() function:

>>> requires('wheel')
["pytest (>=3.0.0) ; extra == 'test'", "pytest-cov ; extra == 'test'"]

Mapping import to distribution packages

importlib.metadata.packages_distributions()

Return a mapping from the top level module and import package names found via sys.meta_path to the names of the distribution packages (if any) that provide the corresponding files.

To allow for namespace packages (which may have members provided by multiple distribution packages), each top level import name maps to a list of distribution names rather than mapping directly to a single name.

A convenience method to resolve the Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package] name (or names, in the case of a namespace package) that provide each importable top-level Python module or Import Package [https://packaging.python.org/en/latest/glossary/#term-Import-Package]:

>>> packages_distributions()
{'importlib_metadata': ['importlib-metadata'], 'yaml': ['PyYAML'], 'jaraco': ['jaraco.classes', 'jaraco.functools'], ...}

Some editable installs, do not supply top-level names [https://github.com/pypa/packaging-problems/issues/609], and thus this function is not reliable with such installs.

在 3.10 版被加入.

Distributions

importlib.metadata.distribution(distribution_name)

Return a Distribution instance describing the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

class importlib.metadata.Distribution

Details of an installed distribution package.

Note: different Distribution instances do not currently compare equal, even if they relate to the same installed distribution and accordingly have the same attributes.

While the module level API described above is the most common and convenient usage, you can get all of that information from the Distribution class. Distribution is an abstract object that represents the metadata for a Python Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package]. You can get the concrete Distribution subclass instance for an installed distribution package by calling the distribution() function:

>>> from importlib.metadata import distribution
>>> dist = distribution('wheel')
>>> type(dist)
<class 'importlib.metadata.PathDistribution'>

Thus, an alternative way to get the version number is through the Distribution instance:

>>> dist.version
'0.32.3'

There are all kinds of additional metadata available on Distribution instances:

>>> dist.metadata['Requires-Python']
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'
>>> dist.metadata['License']
'MIT'

For editable packages, an origin property may present PEP 610 [https://peps.python.org/pep-0610/] metadata:

>>> dist.origin.url
'file:///path/to/wheel-0.32.3.editable-py3-none-any.whl'

The full set of available metadata is not described here. See the PyPA Core metadata specification [https://packaging.python.org/en/latest/specifications/core-metadata/#core-metadata] for additional details.

在 3.13 版被加入: 新增 .origin 屬性 (property)。

Distribution Discovery

By default, this package provides built-in support for discovery of metadata for file system and zip file Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package]s. This metadata finder search defaults to sys.path, but varies slightly in how it interprets those values from how other import machinery does. In particular:

importlib.metadata does not honor bytes objects on sys.path.

importlib.metadata will incidentally honor pathlib.Path objects on sys.path even though such values will be ignored for imports.

Implementing Custom Providers

importlib.metadata address two API surfaces, one for consumers and another for providers. Most users are consumers, consuming metadata provided by the packages. There are other use-cases, however, where users wish to expose metadata through some other mechanism, such as alongside a custom importer. Such a use case calls for a custom provider.

Because Distribution Package [https://packaging.python.org/en/latest/glossary/#term-Distribution-Package] metadata is not available through sys.path searches, or package loaders directly, the metadata for a distribution is found through import system finders. To find a distribution package's metadata, importlib.metadata queries the list of meta path finders on sys.meta_path.

The implementation has hooks integrated into the PathFinder, serving metadata for distribution packages found on the file system.

The abstract class importlib.abc.MetaPathFinder defines the interface expected of finders by Python's import system. importlib.metadata extends this protocol by looking for an optional find_distributions callable on the finders from sys.meta_path and presents this extended interface as the DistributionFinder abstract base class, which defines this abstract method:

@abc.abstractmethod
def find_distributions(context=DistributionFinder.Context()) -> Iterable[Distribution]:
    """Return an iterable of all Distribution instances capable of
    loading the metadata for packages for the indicated ``context``.
    """

The DistributionFinder.Context object provides .path and .name properties indicating the path to search and name to match and may supply other relevant context sought by the consumer.

In practice, to support finding distribution package metadata in locations other than the file system, subclass Distribution and implement the abstract methods. Then from a custom finder, return instances of this derived Distribution in the find_distributions() method.

範例

Imagine a custom finder that loads Python modules from a database:

class DatabaseImporter(importlib.abc.MetaPathFinder):
    def __init__(self, db):
        self.db = db

    def find_spec(self, fullname, target=None) -> ModuleSpec:
        return self.db.spec_from_name(fullname)

sys.meta_path.append(DatabaseImporter(connect_db(...)))

That importer now presumably provides importable modules from a database, but it provides no metadata or entry points. For this custom importer to provide metadata, it would also need to implement DistributionFinder:

from importlib.metadata import DistributionFinder

class DatabaseImporter(DistributionFinder):
    ...

    def find_distributions(self, context=DistributionFinder.Context()):
        query = dict(name=context.name) if context.name else {}
        for dist_record in self.db.query_distributions(query):
            yield DatabaseDistribution(dist_record)

In this way, query_distributions would return records for each distribution served by the database matching the query. For example, if requests-1.0 is in the database, find_distributions would yield a DatabaseDistribution for Context(name='requests') or Context(name=None).

For the sake of simplicity, this example ignores context.path. The path attribute defaults to sys.path and is the set of import paths to be considered in the search. A DatabaseImporter could potentially function without any concern for a search path. Assuming the importer does no partitioning, the "path" would be irrelevant. In order to illustrate the purpose of path, the example would need to illustrate a more complex DatabaseImporter whose behavior varied depending on sys.path/PYTHONPATH. In that case, the find_distributions should honor the context.path and only yield Distributions pertinent to that path.

DatabaseDistribution, then, would look something like:

class DatabaseDistribution(importlib.metadata.Distribution):
    def __init__(self, record):
        self.record = record

    def read_text(self, filename):
        """
        Read a file like "METADATA" for the current distribution.
        """
        if filename == "METADATA":
            return f"""Name: {self.record.name}
Version: {self.record.version}
"""
        if filename == "entry_points.txt":
            return "\n".join(
              f"""[{ep.group}]\n{ep.name}={ep.value}"""
              for ep in self.record.entry_points)

    def locate_file(self, path):
        raise RuntimeError("This distribution has no file system")

This basic implementation should provide metadata and entry points for packages served by the DatabaseImporter, assuming that the record supplies suitable .name, .version, and .entry_points attributes.

The DatabaseDistribution may also provide other metadata files, like RECORD (required for Distribution.files) or override the implementation of Distribution.files. See the source for more inspiration.

sys.path 模組搜尋路徑的初始化

A module search path is initialized when Python starts. This module search path may be accessed at sys.path.

The first entry in the module search path is the directory that contains the input script, if there is one. Otherwise, the first entry is the current directory, which is the case when executing the interactive shell, a -c command, or -m module.

The PYTHONPATH environment variable is often used to add directories to the search path. If this environment variable is found then the contents are added to the module search path.

備註

PYTHONPATH will affect all installed Python versions/environments. Be wary of setting this in your shell profile or global environment variables. The site module offers more nuanced techniques as mentioned below.

The next items added are the directories containing standard Python modules as well as any extension modules that these modules depend on. Extension modules are .pyd files on Windows and .so files on other platforms. The directory with the platform-independent Python modules is called prefix. The directory with the extension modules is called exec_prefix.

The PYTHONHOME environment variable may be used to set the prefix and exec_prefix locations. Otherwise these directories are found by using the Python executable as a starting point and then looking for various 'landmark' files and directories. Note that any symbolic links are followed so the real Python executable location is used as the search starting point. The Python executable location is called home.

Once home is determined, the prefix directory is found by first looking for pythonmajorversionminorversion.zip (python311.zip). On Windows the zip archive is searched for in home and on Unix the archive is expected to be in lib. Note that the expected zip archive location is added to the module search path even if the archive does not exist. If no archive was found, Python on Windows will continue the search for prefix by looking for Lib\os.py. Python on Unix will look for lib/pythonmajorversion.minorversion/os.py (lib/python3.11/os.py). On Windows prefix and exec_prefix are the same, however on other platforms lib/pythonmajorversion.minorversion/lib-dynload (lib/python3.11/lib-dynload) is searched for and used as an anchor for exec_prefix. On some platforms lib may be lib64 or another value, see sys.platlibdir and PYTHONPLATLIBDIR.

Once found, prefix and exec_prefix are available at sys.base_prefix and sys.base_exec_prefix respectively.

If PYTHONHOME is not set, and a pyvenv.cfg file is found alongside the main executable, or in its parent directory, sys.prefix and sys.exec_prefix get set to the directory containing pyvenv.cfg, otherwise they are set to the same value as sys.base_prefix and sys.base_exec_prefix, respectively. This is used by 虛擬環境.

Finally, the site module is processed and site-packages directories are added to the module search path. A common way to customize the search path is to create sitecustomize or usercustomize modules as described in the site module documentation.

備註

Certain command line options may further affect path calculations. See -E, -I, -s and -S for further details.

在 3.14 版的變更: sys.prefix and sys.exec_prefix are now set to the pyvenv.cfg directory during the path initialization. This was previously done by site, therefore affected by -S.

虛擬環境

Virtual environments place a pyvenv.cfg file in their prefix, which causes sys.prefix and sys.exec_prefix to point to them, instead of the base installation.

The prefix and exec_prefix values of the base installation are available at sys.base_prefix and sys.base_exec_prefix.

As well as being used as a marker to identify virtual environments, pyvenv.cfg may also be used to configure the site initialization. Please refer to site's virtual environments documentation.

備註

PYTHONHOME overrides the pyvenv.cfg detection.

備註

There are other ways how "virtual environments" could be implemented, this documentation refers implementations based on the pyvenv.cfg mechanism, such as venv. Most virtual environment implementations follow the model set by venv, but there may be exotic implementations that diverge from it.

_pth 檔案

To completely override sys.path create a ._pth file with the same name as the shared library or executable (python._pth or python311._pth). The shared library path is always known on Windows, however it may not be available on other platforms. In the ._pth file specify one line for each path to add to sys.path. The file based on the shared library name overrides the one based on the executable, which allows paths to be restricted for any program loading the runtime if desired.

When the file exists, all registry and environment variables are ignored, isolated mode is enabled, and site is not imported unless one line in the file specifies import site. Blank paths and lines starting with # are ignored. Each path may be absolute or relative to the location of the file. Import statements other than to site are not permitted, and arbitrary code cannot be specified.

Note that .pth files (without leading underscore) will be processed normally by the site module when import site has been specified.

Embedded Python

If Python is embedded within another application Py_InitializeFromConfig() and the PyConfig structure can be used to initialize Python. The path specific details are described at Python 路徑配置.

也參考

找尋模組 有關於 Windows 的詳細資訊。

在 Unix 平臺上使用 Python 有關於 Unix 的詳細資訊。

Python 語言服務

Python 提供了許多模組來協助處理 Python 語言。這些模組支援標記化、剖析、語法分析、位元組碼反組譯，以及其他各種設施。

這些模組包括：

ast --- 抽象語法樹 (Abstract Syntax Trees)

抽象文法 (Abstract Grammar)

節點 (Node) 類別

根節點

文本 (Literals)

變數

運算式

下標 (Subscripting)

綜合運算式 (comprehensions)

陳述式

引入 (imports)

流程控制

模式匹配 (pattern matching)

型別註釋

型別參數 (type parameters)

函式和類別定義

async 和 await

ast 輔助程式

編譯器旗標

命令列用法

symtable --- 存取編譯器的符號表

產生符號表

檢查符號表

命令列用法

token --- 與 Python 剖析樹一起使用的常數

keyword --- 檢驗 Python 關鍵字

tokenize --- Tokenizer for Python source

Tokenizing Input

命令列用法

範例

tabnanny --- 偵測不良縮排

pyclbr --- Python 模組瀏覽器支援

函式物件

類別物件

py_compile — 編譯 Python 來源檔案

命令列介面

compileall --- 位元組編譯 Python 函式庫

Command-line use

Public functions

dis --- Python bytecode 的反組譯器

命令列介面

Bytecode analysis

分析函式

Python 位元組碼指令

Opcode collections

pickletools --- pickle 開發者的工具

命令列用法

命令列選項

程式化介面

ast --- 抽象語法樹 (Abstract Syntax Trees)

原始碼：Lib/ast.py [https://github.com/python/cpython/tree/3.14/Lib/ast.py]

ast 模組可以幫助 Python 應用程式處理 Python 抽象語法文法 (abstract syntax grammar) 樹狀資料結構。抽象語法本身可能會隨著每個 Python 版本發布而改變；此模組有助於以程式化的方式來得知目前文法的面貌。

要生成抽象語法樹，可以透過將 ast.PyCF_ONLY_AST 作為旗標傳遞給內建函式 compile() 或使用此模組所提供的 parse() 輔助函式。結果將會是一個物件的樹，其類別都繼承自 ast.AST。可以使用內建的 compile() 函式將抽象語法樹編譯成 Python 程式碼物件。

抽象文法 (Abstract Grammar)

抽象文法目前定義如下：

-- ASDL's 4 builtin types are:
-- identifier, int, string, constant

module Python
{
    mod = Module(stmt* body, type_ignore* type_ignores)
        | Interactive(stmt* body)
        | Expression(expr body)
        | FunctionType(expr* argtypes, expr returns)

    stmt = FunctionDef(identifier name, arguments args,
                       stmt* body, expr* decorator_list, expr? returns,
                       string? type_comment, type_param* type_params)
          | AsyncFunctionDef(identifier name, arguments args,
                             stmt* body, expr* decorator_list, expr? returns,
                             string? type_comment, type_param* type_params)

          | ClassDef(identifier name,
             expr* bases,
             keyword* keywords,
             stmt* body,
             expr* decorator_list,
             type_param* type_params)
          | Return(expr? value)

          | Delete(expr* targets)
          | Assign(expr* targets, expr value, string? type_comment)
          | TypeAlias(expr name, type_param* type_params, expr value)
          | AugAssign(expr target, operator op, expr value)
          -- 'simple' indicates that we annotate simple name without parens
          | AnnAssign(expr target, expr annotation, expr? value, int simple)

          -- use 'orelse' because else is a keyword in target languages
          | For(expr target, expr iter, stmt* body, stmt* orelse, string? type_comment)
          | AsyncFor(expr target, expr iter, stmt* body, stmt* orelse, string? type_comment)
          | While(expr test, stmt* body, stmt* orelse)
          | If(expr test, stmt* body, stmt* orelse)
          | With(withitem* items, stmt* body, string? type_comment)
          | AsyncWith(withitem* items, stmt* body, string? type_comment)

          | Match(expr subject, match_case* cases)

          | Raise(expr? exc, expr? cause)
          | Try(stmt* body, excepthandler* handlers, stmt* orelse, stmt* finalbody)
          | TryStar(stmt* body, excepthandler* handlers, stmt* orelse, stmt* finalbody)
          | Assert(expr test, expr? msg)

          | Import(alias* names)
          | ImportFrom(identifier? module, alias* names, int? level)

          | Global(identifier* names)
          | Nonlocal(identifier* names)
          | Expr(expr value)
          | Pass | Break | Continue

          -- col_offset is the byte offset in the utf8 string the parser uses
          attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

          -- BoolOp() can use left & right?
    expr = BoolOp(boolop op, expr* values)
         | NamedExpr(expr target, expr value)
         | BinOp(expr left, operator op, expr right)
         | UnaryOp(unaryop op, expr operand)
         | Lambda(arguments args, expr body)
         | IfExp(expr test, expr body, expr orelse)
         | Dict(expr?* keys, expr* values)
         | Set(expr* elts)
         | ListComp(expr elt, comprehension* generators)
         | SetComp(expr elt, comprehension* generators)
         | DictComp(expr key, expr value, comprehension* generators)
         | GeneratorExp(expr elt, comprehension* generators)
         -- the grammar constrains where yield expressions can occur
         | Await(expr value)
         | Yield(expr? value)
         | YieldFrom(expr value)
         -- need sequences for compare to distinguish between
         -- x < 4 < 3 and (x < 4) < 3
         | Compare(expr left, cmpop* ops, expr* comparators)
         | Call(expr func, expr* args, keyword* keywords)
         | FormattedValue(expr value, int conversion, expr? format_spec)
         | Interpolation(expr value, constant str, int conversion, expr? format_spec)
         | JoinedStr(expr* values)
         | TemplateStr(expr* values)
         | Constant(constant value, string? kind)

         -- the following expression can appear in assignment context
         | Attribute(expr value, identifier attr, expr_context ctx)
         | Subscript(expr value, expr slice, expr_context ctx)
         | Starred(expr value, expr_context ctx)
         | Name(identifier id, expr_context ctx)
         | List(expr* elts, expr_context ctx)
         | Tuple(expr* elts, expr_context ctx)

         -- can appear only in Subscript
         | Slice(expr? lower, expr? upper, expr? step)

          -- col_offset is the byte offset in the utf8 string the parser uses
          attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    expr_context = Load | Store | Del

    boolop = And | Or

    operator = Add | Sub | Mult | MatMult | Div | Mod | Pow | LShift
                 | RShift | BitOr | BitXor | BitAnd | FloorDiv

    unaryop = Invert | Not | UAdd | USub

    cmpop = Eq | NotEq | Lt | LtE | Gt | GtE | Is | IsNot | In | NotIn

    comprehension = (expr target, expr iter, expr* ifs, int is_async)

    excepthandler = ExceptHandler(expr? type, identifier? name, stmt* body)
                    attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    arguments = (arg* posonlyargs, arg* args, arg? vararg, arg* kwonlyargs,
                 expr?* kw_defaults, arg? kwarg, expr* defaults)

    arg = (identifier arg, expr? annotation, string? type_comment)
           attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    -- keyword arguments supplied to call (NULL identifier for **kwargs)
    keyword = (identifier? arg, expr value)
               attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    -- import name with optional 'as' alias.
    alias = (identifier name, identifier? asname)
             attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    withitem = (expr context_expr, expr? optional_vars)

    match_case = (pattern pattern, expr? guard, stmt* body)

    pattern = MatchValue(expr value)
            | MatchSingleton(constant value)
            | MatchSequence(pattern* patterns)
            | MatchMapping(expr* keys, pattern* patterns, identifier? rest)
            | MatchClass(expr cls, pattern* patterns, identifier* kwd_attrs, pattern* kwd_patterns)

            | MatchStar(identifier? name)
            -- The optional "rest" MatchMapping parameter handles capturing extra mapping keys

            | MatchAs(pattern? pattern, identifier? name)
            | MatchOr(pattern* patterns)

             attributes (int lineno, int col_offset, int end_lineno, int end_col_offset)

    type_ignore = TypeIgnore(int lineno, string tag)

    type_param = TypeVar(identifier name, expr? bound, expr? default_value)
               | ParamSpec(identifier name, expr? default_value)
               | TypeVarTuple(identifier name, expr? default_value)
               attributes (int lineno, int col_offset, int end_lineno, int end_col_offset)
}

節點 (Node) 類別

class ast.AST

這是所有 AST 節點類別的基礎。實際的節點類別是衍生自 Parser/Python.asdl 檔案，該檔案在上方 重現。它們被定義於 _ast 的 C 模組中，並於 ast 中重新匯出。

抽象文法中為每個左側符號定義了一個類別（例如 ast.stmt 或 ast.expr）。此外，也為每個右側的建構函式 (constructor) 定義了一個類別；這些類別繼承自左側樹的類別。例如，ast.BinOp 繼承自 ast.expr。對於具有替代方案（即為「和 (sums)」）的生產規則，左側類別是抽象的：僅有特定建構函式節點的實例會被建立。

_fields

每個具體類別都有一個屬性 _fields，它會給出所有子節點的名稱。

具體類別的每個實例對於每個子節點都有一個屬性，其型別如文法中所定義。例如，ast.BinOp 實例具有型別為 ast.expr 的屬性 left。

如果這些屬性在文法中被標記為可選（使用問號），則該值可能為 None。如果屬性可以有零個或多個值（用星號標記），則這些值將表示為 Python 串列。使用 compile() 編譯 AST 時，所有可能的屬性都必須存在並且具有有效值。

_field_types

每個具體類別上的 _field_types 屬性是將欄位名稱（也在 _fields 中列出）對映到其型別的字典。

>>> ast.TypeVar._field_types
{'name': <class 'str'>, 'bound': ast.expr | None, 'default_value': ast.expr | None}

在 3.13 版被加入.

lineno

col_offset

end_lineno

end_col_offset

ast.expr 和 ast.stmt 子類別的實例具有 lineno、col_offset、end_lineno 和 end_col_offset 屬性。lineno 和 end_lineno 是原始文本跨度 (source text span) 的第一個和最後一個列號（1-indexed，因此第一列號是 1）以及 col_offset 和 end_col_offset 是生成節點的第一個和最後一個標記對應的 UTF-8 位元組偏移量。會記錄 UTF-8 偏移量是因為剖析器 (parser) 內部使用 UTF-8。

請注意，編譯器並不需要結束位置，因此其為可選的。結束偏移量在最後一個符號之後，例如可以使用 source_line[node.col_offset : node.end_col_offset] 來取得單列運算式節點 (expression node) 的原始片段。

ast.T 類別的建構函式按以下方式剖析其引數：

如果有位置引數，則必須與 T._fields 中的項目一樣多；它們將被賦値為這些名稱的屬性。

如果有關鍵字引數，它們會將相同名稱的屬性設定為給定值。

例如，要建立並填充 (populate) ast.UnaryOp 節點，你可以使用：

node = ast.UnaryOp(ast.USub(), ast.Constant(5, lineno=0, col_offset=0),
                   lineno=0, col_offset=0)

如果建構函式中省略了文法中可選的欄位，則它預設為 None。如果省略串列欄位，則預設為空串列。如果省略 ast.expr_context 型別的欄位，則預設為 Load()。如果省略任何其他欄位，則會引發 DeprecationWarning，且 AST 節點將沒有此欄位。在 Python 3.15 中，這種情況會引發錯誤。

在 3.8 版的變更: ast.Constant 類別現在用於所有常數。

在 3.9 版的變更: 以它們的值表示簡單索引，擴充切片 (slice) 則以元組 (tuple) 表示。

在 3.14 版的變更: AST 節點的 __repr__() 輸出包含節點欄位的值。

自從版本 3.8 後不推薦使用，已從版本 3.14 中移除。: 過去的 Python 版本提供了 AST 類別 ast.Num、ast.Str、ast.Bytes、ast.NameConstant 和 ast.Ellipsis，這些類別在 Python 3.8 中已被棄用。這些類別在 Python 3.14 中被移除，其功能已被 ast.Constant 取代。

在 3.9 版之後被棄用: 舊的類別 ast.Index 和 ast.ExtSlice 仍然可用，但它們將在未來的 Python 版本中刪除。同時，實例化它們會回傳不同類別的實例。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: 先前版本的 Python 允許建立缺少必填欄位的 AST 節點。同樣地，AST 節點建構函式允許將任意關鍵字引數設為 AST 節點的屬性，即使它們與 AST 節點的任何欄位都不匹配。此行為已被棄用，並將在 Python 3.15 中刪除。

備註

這裡顯示的特定節點類別的描述最初是從出色的 Green Tree Snakes [https://greentreesnakes.readthedocs.io/en/latest/] 專案和所有貢獻者那裡改編而來的。

根節點

class ast.Module(body, type_ignores)

一個 Python 模組，與檔案輸入 一樣。由 ast.parse() 在預設的 "exec" mode 下生成的節點型別。

body 是模組的陳述式 的一個 list。

type_ignores 是模組的忽略型別註解的 list；有關更多詳細資訊，請參閱 ast.parse()。

>>> print(ast.dump(ast.parse('x = 1'), indent=4))
Module(
    body=[
        Assign(
            targets=[
                Name(id='x', ctx=Store())],
            value=Constant(value=1))])

class ast.Expression(body)

單個 Python 運算式輸入。當 mode 是 "eval" 時節點型別由 ast.parse() 生成。

body 是單個節點，是運算式型別的其中之一。

>>> print(ast.dump(ast.parse('123', mode='eval'), indent=4))
Expression(
    body=Constant(value=123))

class ast.Interactive(body)

單個互動式輸入，和互動模式中所述的相似。當 mode 是 "single" 時節點型別由 ast.parse() 生成。

body 是陳述式節點 (statement nodes) 的 list。

>>> print(ast.dump(ast.parse('x = 1; y = 2', mode='single'), indent=4))
Interactive(
    body=[
        Assign(
            targets=[
                Name(id='x', ctx=Store())],
            value=Constant(value=1)),
        Assign(
            targets=[
                Name(id='y', ctx=Store())],
            value=Constant(value=2))])

class ast.FunctionType(argtypes, returns)

函式的舊式型別註解的表示法，因為 3.5 之前的 Python 版本不支援 PEP 484 [https://peps.python.org/pep-0484/] 註釋。當 mode 是 "func_type" 時節點型別由 ast.parse() 生成。

這種型別的註解看起來像這樣：

def sum_two_number(a, b):
    # type: (int, int) -> int
    return a + b

argtypes 是運算式節點的 list。

returns 是單個運算式節點。

>>> print(ast.dump(ast.parse('(int, str) -> List[int]', mode='func_type'), indent=4))
FunctionType(
    argtypes=[
        Name(id='int', ctx=Load()),
        Name(id='str', ctx=Load())],
    returns=Subscript(
        value=Name(id='List', ctx=Load()),
        slice=Name(id='int', ctx=Load()),
        ctx=Load()))

在 3.8 版被加入.

文本 (Literals)

class ast.Constant(value)

一個常數值。Constant 文本的 value 屬性包含它所代表的 Python 物件。表示的值可以是 str、bytes、int、float、complex 和 bool 的實例，以及常數 None 和 Ellipsis。

>>> print(ast.dump(ast.parse('123', mode='eval'), indent=4))
Expression(
    body=Constant(value=123))

class ast.FormattedValue(value, conversion, format_spec)

表示 f 字串 (f-string) 中的單個格式化欄位的節點。如果字串包含單個格式欄位並且沒有其他內容，則可以隔離 (isolate) 該節點，否則它將出現在 JoinedStr 中。

value 為任何運算式節點（例如文字、變數或函式呼叫）。

conversion 是一個整數：

-1: 無格式化

97 (ord('a'))：！a ASCII 格式化

114 (ord('r'))：!r repr() 格式化

115 (ord('s'))：!s string 格式化

format_spec 是一個 JoinedStr 節點，表示值的格式，若未指定格式則為 None。conversion 和 format_spec 可以同時設定。

class ast.JoinedStr(values)

一個 f 字串，包含一系列 FormattedValue 和 Constant 節點。

>>> print(ast.dump(ast.parse('f"sin({a}) is {sin(a):.3}"', mode='eval'), indent=4))
Expression(
    body=JoinedStr(
        values=[
            Constant(value='sin('),
            FormattedValue(
                value=Name(id='a', ctx=Load()),
                conversion=-1),
            Constant(value=') is '),
            FormattedValue(
                value=Call(
                    func=Name(id='sin', ctx=Load()),
                    args=[
                        Name(id='a', ctx=Load())]),
                conversion=-1,
                format_spec=JoinedStr(
                    values=[
                        Constant(value='.3')]))]))

class ast.TemplateStr(values, /)

在 3.14 版被加入.

表示模板字串字面值的節點，由一系列 Interpolation 和 Constant 節點組成。這些節點可以是任意順序，不需要交錯排列。

>>> expr = ast.parse('t"{name} finished {place:ordinal}"', mode='eval')
>>> print(ast.dump(expr, indent=4))
Expression(
    body=TemplateStr(
        values=[
            Interpolation(
                value=Name(id='name', ctx=Load()),
                str='name',
                conversion=-1),
            Constant(value=' finished '),
            Interpolation(
                value=Name(id='place', ctx=Load()),
                str='place',
                conversion=-1,
                format_spec=JoinedStr(
                    values=[
                        Constant(value='ordinal')]))]))

class ast.Interpolation(value, str, conversion, format_spec=None)

在 3.14 版被加入.

表示模板字串字面值中單一插值欄位的節點。

value 為任何運算式節點（例如文字、變數或函式呼叫）。這和 FormattedValue.value 的意思相同。

str 是一個包含插值運算式文字的常數。

如果 str 被設為 None，則在呼叫 ast.unparse() 時會使用 value 來產生程式碼。這不再保證產生的程式碼與原始程式碼相同，且適用於程式碼產生。

conversion 是一個整數：

-1：無規範

97 (ord('a'))：!a ASCII 轉換

114 (ord('r'))：!r repr() 轉換

115 (ord('s'))：!s string 轉換

這與 FormattedValue.conversion 的意思相同。

format_spec 是一個 JoinedStr 節點，表示值的格式，若未指定格式則為 None。conversion 和 format_spec 可以同時設定。這與 FormattedValue.format_spec 的意思相同。

class ast.List(elts, ctx)

class ast.Tuple(elts, ctx)

串列或元組。elts 保存表示元素的節點串列。如果容器是賦值目標（即 (x,y)=something ），則 ctx 是 Store，否則是 Load。

>>> print(ast.dump(ast.parse('[1, 2, 3]', mode='eval'), indent=4))
Expression(
    body=List(
        elts=[
            Constant(value=1),
            Constant(value=2),
            Constant(value=3)],
        ctx=Load()))
>>> print(ast.dump(ast.parse('(1, 2, 3)', mode='eval'), indent=4))
Expression(
    body=Tuple(
        elts=[
            Constant(value=1),
            Constant(value=2),
            Constant(value=3)],
        ctx=Load()))

class ast.Set(elts)

一個集合。elts 保存表示集合之元素的節點串列。

>>> print(ast.dump(ast.parse('{1, 2, 3}', mode='eval'), indent=4))
Expression(
    body=Set(
        elts=[
            Constant(value=1),
            Constant(value=2),
            Constant(value=3)]))

class ast.Dict(keys, values)

一個字典 (dictionary)。keys 和 values 分別按匹配順序保存表示鍵和值的節點串列（為呼叫 dictionary.keys() 和 dictionary.values() 時將回傳的內容）。

當使用字典文本進行字典解包 (unpack) 時，要擴充的運算式位於 values 串列中，在 keys 中的相應位置有一個 None。

>>> print(ast.dump(ast.parse('{"a":1, **d}', mode='eval'), indent=4))
Expression(
    body=Dict(
        keys=[
            Constant(value='a'),
            None],
        values=[
            Constant(value=1),
            Name(id='d', ctx=Load())]))

變數

class ast.Name(id, ctx)

一個變數名稱。id 將名稱以字串形式保存，且 ctx 是以下型別之一。

class ast.Load

class ast.Store

class ast.Del

變數參照可用於載入變數的值、為其分配新值或刪除它。變數參照被賦予情境 (context) 來區分這些情況。

>>> print(ast.dump(ast.parse('a'), indent=4))
Module(
    body=[
        Expr(
            value=Name(id='a', ctx=Load()))])

>>> print(ast.dump(ast.parse('a = 1'), indent=4))
Module(
    body=[
        Assign(
            targets=[
                Name(id='a', ctx=Store())],
            value=Constant(value=1))])

>>> print(ast.dump(ast.parse('del a'), indent=4))
Module(
    body=[
        Delete(
            targets=[
                Name(id='a', ctx=Del())])])

class ast.Starred(value, ctx)

一個 *var 變數參照。value 保存變數，通常是一個 Name 節點。在使用 *args 建置 Call 節點時必須使用此型別。

>>> print(ast.dump(ast.parse('a, *b = it'), indent=4))
Module(
    body=[
        Assign(
            targets=[
                Tuple(
                    elts=[
                        Name(id='a', ctx=Store()),
                        Starred(
                            value=Name(id='b', ctx=Store()),
                            ctx=Store())],
                    ctx=Store())],
            value=Name(id='it', ctx=Load()))])

運算式

class ast.Expr(value)

當運算式（例如函式呼叫）本身作為陳述式出現且未使用或儲存其回傳值時，它將被包裝在此容器中。value 保存此區段 (section) 中的一個其他節點：Constant、Name、Lambda、Yield 或 YieldFrom

>>> print(ast.dump(ast.parse('-a'), indent=4))
Module(
    body=[
        Expr(
            value=UnaryOp(
                op=USub(),
                operand=Name(id='a', ctx=Load())))])

class ast.UnaryOp(op, operand)

一元運算 (unary operation)。op 是運算子，operand 是任何運算式節點。

class ast.UAdd

class ast.USub

class ast.Not

class ast.Invert

一元運算子標記。 Not 是 not 關鍵字、Invert 是 ~ 運算子。

>>> print(ast.dump(ast.parse('not x', mode='eval'), indent=4))
Expression(
    body=UnaryOp(
        op=Not(),
        operand=Name(id='x', ctx=Load())))

class ast.BinOp(left, op, right)

二元運算 (binary operation)（如加法或除法）。 op 是運算子、left 和 right 是任意運算式節點。

>>> print(ast.dump(ast.parse('x + y', mode='eval'), indent=4))
Expression(
    body=BinOp(
        left=Name(id='x', ctx=Load()),
        op=Add(),
        right=Name(id='y', ctx=Load())))

class ast.Add

class ast.Sub

class ast.Mult

class ast.Div

class ast.FloorDiv

class ast.Mod

class ast.Pow

class ast.LShift

class ast.RShift

class ast.BitOr

class ast.BitXor

class ast.BitAnd

class ast.MatMult

二元運算子 token。

class ast.BoolOp(op, values)

布林運算 'or' 或 'and'。op 是 Or 或 And。values 是有所涉及的值。使用同一運算子的連續操作（例如 a or b or c）會被折疊為具有多個值的一個節點。

這不包括 not，它是一個 UnaryOp。

>>> print(ast.dump(ast.parse('x or y', mode='eval'), indent=4))
Expression(
    body=BoolOp(
        op=Or(),
        values=[
            Name(id='x', ctx=Load()),
            Name(id='y', ctx=Load())]))

class ast.And

class ast.Or

布林運算子 token。

class ast.Compare(left, ops, comparators)

兩個或多個值的比較。left 是比較中的第一個值、ops 是運算子串列、comparators 是要比較的第一個元素之後值的串列。

>>> print(ast.dump(ast.parse('1 <= a < 10', mode='eval'), indent=4))
Expression(
    body=Compare(
        left=Constant(value=1),
        ops=[
            LtE(),
            Lt()],
        comparators=[
            Name(id='a', ctx=Load()),
            Constant(value=10)]))

class ast.Eq

class ast.NotEq

class ast.Lt

class ast.LtE

class ast.Gt

class ast.GtE

class ast.Is

class ast.IsNot

class ast.In

class ast.NotIn

比較運算子 token。

class ast.Call(func, args, keywords)

一個函式呼叫。func 是該函式，通常是一個 Name 或 Attribute 物件。而在引數中：

args 保存按位置傳遞的引數串列。

keywords 保存一個 keyword 物件串列，表示透過關鍵字傳遞的引數。

args 和 keywords 引數是可選的，預設為空串列。

>>> print(ast.dump(ast.parse('func(a, b=c, *d, **e)', mode='eval'), indent=4))
Expression(
    body=Call(
        func=Name(id='func', ctx=Load()),
        args=[
            Name(id='a', ctx=Load()),
            Starred(
                value=Name(id='d', ctx=Load()),
                ctx=Load())],
        keywords=[
            keyword(
                arg='b',
                value=Name(id='c', ctx=Load())),
            keyword(
                value=Name(id='e', ctx=Load()))]))

class ast.keyword(arg, value)

函式呼叫或類別定義的關鍵字引數。arg 是參數名稱的原始字串，value 是要傳入的節點。

class ast.IfExp(test, body, orelse)

像是 a if b else c 之類的運算式。每個欄位都保存一個節點，因此在以下範例中，所有三個都是 Name 節點。

>>> print(ast.dump(ast.parse('a if b else c', mode='eval'), indent=4))
Expression(
    body=IfExp(
        test=Name(id='b', ctx=Load()),
        body=Name(id='a', ctx=Load()),
        orelse=Name(id='c', ctx=Load())))

class ast.Attribute(value, attr, ctx)

屬性的存取，例如 d.keys。value 是一個節點，通常是一個 Name。attr 是一個屬性名稱的字串，ctx 根據屬性的作用方式可能是 Load、Store 或 Del。

>>> print(ast.dump(ast.parse('snake.colour', mode='eval'), indent=4))
Expression(
    body=Attribute(
        value=Name(id='snake', ctx=Load()),
        attr='colour',
        ctx=Load()))

class ast.NamedExpr(target, value)

一個附名運算式 (named expression)。該 AST 節點由賦值運算式運算子（也稱為海象運算子）產生。相對於 Assign 節點之第一個引數可為多個節點，在這種情況下 target 和 value 都必須是單個節點。

>>> print(ast.dump(ast.parse('(x := 4)', mode='eval'), indent=4))
Expression(
    body=NamedExpr(
        target=Name(id='x', ctx=Store()),
        value=Constant(value=4)))

在 3.8 版被加入.

下標 (Subscripting)

class ast.Subscript(value, slice, ctx)

一個下標，例如 l[1]。value 是下標物件（通常是序列或對映）。slice 是索引、切片或鍵。它可以是一個 Tuple 並包含一個 Slice。根據下標執行的操作不同，ctx 可以是 Load、Store 或 Del。

>>> print(ast.dump(ast.parse('l[1:2, 3]', mode='eval'), indent=4))
Expression(
    body=Subscript(
        value=Name(id='l', ctx=Load()),
        slice=Tuple(
            elts=[
                Slice(
                    lower=Constant(value=1),
                    upper=Constant(value=2)),
                Constant(value=3)],
            ctx=Load()),
        ctx=Load()))

class ast.Slice(lower, upper, step)

常規切片（形式為 lower:upper 或 lower:upper:step）。只能直接或者或者作為 Tuple 的元素出現在 Subscript 的 slice 欄位內。

>>> print(ast.dump(ast.parse('l[1:2]', mode='eval'), indent=4))
Expression(
    body=Subscript(
        value=Name(id='l', ctx=Load()),
        slice=Slice(
            lower=Constant(value=1),
            upper=Constant(value=2)),
        ctx=Load()))

綜合運算式 (comprehensions)

class ast.ListComp(elt, generators)

class ast.SetComp(elt, generators)

class ast.GeneratorExp(elt, generators)

class ast.DictComp(key, value, generators)

串列和集合綜合運算、生成器運算式和字典綜合運算。elt（或 key 和 value）是單個節點，表示各個項目會被求值 (evaluate) 的部分。

generators 是一個 comprehension 節點的串列。

>>> print(ast.dump(
...     ast.parse('[x for x in numbers]', mode='eval'),
...     indent=4,
... ))
Expression(
    body=ListComp(
        elt=Name(id='x', ctx=Load()),
        generators=[
            comprehension(
                target=Name(id='x', ctx=Store()),
                iter=Name(id='numbers', ctx=Load()),
                is_async=0)]))
>>> print(ast.dump(
...     ast.parse('{x: x**2 for x in numbers}', mode='eval'),
...     indent=4,
... ))
Expression(
    body=DictComp(
        key=Name(id='x', ctx=Load()),
        value=BinOp(
            left=Name(id='x', ctx=Load()),
            op=Pow(),
            right=Constant(value=2)),
        generators=[
            comprehension(
                target=Name(id='x', ctx=Store()),
                iter=Name(id='numbers', ctx=Load()),
                is_async=0)]))
>>> print(ast.dump(
...     ast.parse('{x for x in numbers}', mode='eval'),
...     indent=4,
... ))
Expression(
    body=SetComp(
        elt=Name(id='x', ctx=Load()),
        generators=[
            comprehension(
                target=Name(id='x', ctx=Store()),
                iter=Name(id='numbers', ctx=Load()),
                is_async=0)]))

class ast.comprehension(target, iter, ifs, is_async)

綜合運算中的一個 for 子句。target 是用於每個元素的參照 - 通常是 Name 或 Tuple 節點。iter 是要疊代的物件。ifs 是測試運算式的串列：每個 for 子句可以有多個 ifs。

is_async 表示綜合運算式是非同步的（使用 async for 而不是 for ）。該值為整數（0 或 1）。

>>> print(ast.dump(ast.parse('[ord(c) for line in file for c in line]', mode='eval'),
...                indent=4)) # Multiple comprehensions in one.
Expression(
    body=ListComp(
        elt=Call(
            func=Name(id='ord', ctx=Load()),
            args=[
                Name(id='c', ctx=Load())]),
        generators=[
            comprehension(
                target=Name(id='line', ctx=Store()),
                iter=Name(id='file', ctx=Load()),
                is_async=0),
            comprehension(
                target=Name(id='c', ctx=Store()),
                iter=Name(id='line', ctx=Load()),
                is_async=0)]))

>>> print(ast.dump(ast.parse('(n**2 for n in it if n>5 if n<10)', mode='eval'),
...                indent=4)) # generator comprehension
Expression(
    body=GeneratorExp(
        elt=BinOp(
            left=Name(id='n', ctx=Load()),
            op=Pow(),
            right=Constant(value=2)),
        generators=[
            comprehension(
                target=Name(id='n', ctx=Store()),
                iter=Name(id='it', ctx=Load()),
                ifs=[
                    Compare(
                        left=Name(id='n', ctx=Load()),
                        ops=[
                            Gt()],
                        comparators=[
                            Constant(value=5)]),
                    Compare(
                        left=Name(id='n', ctx=Load()),
                        ops=[
                            Lt()],
                        comparators=[
                            Constant(value=10)])],
                is_async=0)]))

>>> print(ast.dump(ast.parse('[i async for i in soc]', mode='eval'),
...                indent=4)) # Async comprehension
Expression(
    body=ListComp(
        elt=Name(id='i', ctx=Load()),
        generators=[
            comprehension(
                target=Name(id='i', ctx=Store()),
                iter=Name(id='soc', ctx=Load()),
                is_async=1)]))

陳述式

class ast.Assign(targets, value, type_comment)

一個賦值。targets 是節點串列，value 是單個節點。

targets 中的多個節點表示為每個節點分配相同的值。解包是透過在 targets 中放置一個 Tuple 或 List 來表示的。

type_comment

type_comment 是一個可選字串，其中的註解為型別註釋。

>>> print(ast.dump(ast.parse('a = b = 1'), indent=4)) # Multiple assignment
Module(
    body=[
        Assign(
            targets=[
                Name(id='a', ctx=Store()),
                Name(id='b', ctx=Store())],
            value=Constant(value=1))])

>>> print(ast.dump(ast.parse('a,b = c'), indent=4)) # Unpacking
Module(
    body=[
        Assign(
            targets=[
                Tuple(
                    elts=[
                        Name(id='a', ctx=Store()),
                        Name(id='b', ctx=Store())],
                    ctx=Store())],
            value=Name(id='c', ctx=Load()))])

class ast.AnnAssign(target, annotation, value, simple)

帶有型別註釋的賦值。target 是單個節點，可以是 Name、Attribute 或 Subscript。annotation 是註釋，例如 Constant 或 Name 節點。value 是單個可選節點。

simple 總會是 0（表示一個「複雜」目標）或 1（表示一個「簡單」目標）。一個「簡單」目標僅包含一個 Name 節點，且不出現在括號之間；所有其他目標都被視為是複雜的。只有簡單目標會出現在模組和類別的 __annotations__ 字典中。

>>> print(ast.dump(ast.parse('c: int'), indent=4))
Module(
    body=[
        AnnAssign(
            target=Name(id='c', ctx=Store()),
            annotation=Name(id='int', ctx=Load()),
            simple=1)])

>>> print(ast.dump(ast.parse('(a): int = 1'), indent=4)) # Annotation with parenthesis
Module(
    body=[
        AnnAssign(
            target=Name(id='a', ctx=Store()),
            annotation=Name(id='int', ctx=Load()),
            value=Constant(value=1),
            simple=0)])

>>> print(ast.dump(ast.parse('a.b: int'), indent=4)) # Attribute annotation
Module(
    body=[
        AnnAssign(
            target=Attribute(
                value=Name(id='a', ctx=Load()),
                attr='b',
                ctx=Store()),
            annotation=Name(id='int', ctx=Load()),
            simple=0)])

>>> print(ast.dump(ast.parse('a[1]: int'), indent=4)) # Subscript annotation
Module(
    body=[
        AnnAssign(
            target=Subscript(
                value=Name(id='a', ctx=Load()),
                slice=Constant(value=1),
                ctx=Store()),
            annotation=Name(id='int', ctx=Load()),
            simple=0)])

class ast.AugAssign(target, op, value)

增加賦值 (augmented assignment)，例如 a += 1。在下面的範例中，target 是 x 的 Name 節點（帶有 Store 情境），op 是 Add，value 是一個值為 1 的 Constant。

與 Assign 的目標不同，target 屬性不能屬於 Tuple 或 List 類別。

>>> print(ast.dump(ast.parse('x += 2'), indent=4))
Module(
    body=[
        AugAssign(
            target=Name(id='x', ctx=Store()),
            op=Add(),
            value=Constant(value=2))])

class ast.Raise(exc, cause)

一個 raise 陳述式。exc 是要引發的例外物件，通常是 Call 或 Name，若是獨立的 raise 則為 None。cause 是 raise x from y 中的可選部分 y。

>>> print(ast.dump(ast.parse('raise x from y'), indent=4))
Module(
    body=[
        Raise(
            exc=Name(id='x', ctx=Load()),
            cause=Name(id='y', ctx=Load()))])

class ast.Assert(test, msg)

一個斷言 (assertion)。test 保存條件，例如 Compare 節點。msg 保存失敗訊息。

>>> print(ast.dump(ast.parse('assert x,y'), indent=4))
Module(
    body=[
        Assert(
            test=Name(id='x', ctx=Load()),
            msg=Name(id='y', ctx=Load()))])

class ast.Delete(targets)

代表一個 del 陳述式。targets 是節點串列，例如 Name、Attribute 或 Subscript 節點。

>>> print(ast.dump(ast.parse('del x,y,z'), indent=4))
Module(
    body=[
        Delete(
            targets=[
                Name(id='x', ctx=Del()),
                Name(id='y', ctx=Del()),
                Name(id='z', ctx=Del())])])

class ast.Pass

一個 pass 陳述式。

>>> print(ast.dump(ast.parse('pass'), indent=4))
Module(
    body=[
        Pass()])

class ast.TypeAlias(name, type_params, value)

透過 type 陳述式建立的型別別名 (type alias)。name 是別名的名稱、type_params 是型別參數 (type parameter) 的串列、value 是型別別名的值。

>>> print(ast.dump(ast.parse('type Alias = int'), indent=4))
Module(
    body=[
        TypeAlias(
            name=Name(id='Alias', ctx=Store()),
            value=Name(id='int', ctx=Load()))])

在 3.12 版被加入.

其他僅適用於函式或迴圈內部的陳述式將在其他部分中描述。

引入 (imports)

class ast.Import(names)

一個 import 陳述式。names 是 alias 節點的串列。

>>> print(ast.dump(ast.parse('import x,y,z'), indent=4))
Module(
    body=[
        Import(
            names=[
                alias(name='x'),
                alias(name='y'),
                alias(name='z')])])

class ast.ImportFrom(module, names, level)

代表 from x import y。module 是 'from' 名稱的原始字串，前面沒有任何的點 (dot)，或者對於諸如 from . import foo 之類的陳述式則為 None。level 是一個整數，保存相對引入的級別（0 表示絕對引入）。

>>> print(ast.dump(ast.parse('from y import x,y,z'), indent=4))
Module(
    body=[
        ImportFrom(
            module='y',
            names=[
                alias(name='x'),
                alias(name='y'),
                alias(name='z')],
            level=0)])

class ast.alias(name, asname)

這兩個參數都是名稱的原始字串。如果要使用常規名稱，asname 可以為 None。

>>> print(ast.dump(ast.parse('from ..foo.bar import a as b, c'), indent=4))
Module(
    body=[
        ImportFrom(
            module='foo.bar',
            names=[
                alias(name='a', asname='b'),
                alias(name='c')],
            level=2)])

流程控制

備註

諸如 else 之類的可選子句如果不存在，則將被儲存為空串列。

class ast.If(test, body, orelse)

一個 if 陳述式。test 保存單個節點，例如 Compare 節點。body 和 orelse 各自保存一個節點串列。

elif 子句在 AST 中沒有特殊表示，而是在前一個子句的 orelse 部分中作為額外的 If 節點出現。

>>> print(ast.dump(ast.parse("""
... if x:
...    ...
... elif y:
...    ...
... else:
...    ...
... """), indent=4))
Module(
    body=[
        If(
            test=Name(id='x', ctx=Load()),
            body=[
                Expr(
                    value=Constant(value=Ellipsis))],
            orelse=[
                If(
                    test=Name(id='y', ctx=Load()),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))],
                    orelse=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

class ast.For(target, iter, body, orelse, type_comment)

一個 for 迴圈。 target 保存迴圈賦予的變數，為單個 Name、Tuple、List、Attribute 或 Subscript 節點。iter 保存要迴圈跑過的項目，也為單個節點。body 和 orelse 包含要執行的節點串列。如果迴圈正常完成，則執行 orelse 中的內容，而不是透過 break 陳述式執行。

type_comment

type_comment 是一個可選字串，其中的註解為型別註釋。

>>> print(ast.dump(ast.parse("""
... for x in y:
...     ...
... else:
...     ...
... """), indent=4))
Module(
    body=[
        For(
            target=Name(id='x', ctx=Store()),
            iter=Name(id='y', ctx=Load()),
            body=[
                Expr(
                    value=Constant(value=Ellipsis))],
            orelse=[
                Expr(
                    value=Constant(value=Ellipsis))])])

class ast.While(test, body, orelse)

一個 while 迴圈。test 保存條件，例如 Compare 節點。

>>> print(ast.dump(ast.parse("""
... while x:
...    ...
... else:
...    ...
... """), indent=4))
Module(
    body=[
        While(
            test=Name(id='x', ctx=Load()),
            body=[
                Expr(
                    value=Constant(value=Ellipsis))],
            orelse=[
                Expr(
                    value=Constant(value=Ellipsis))])])

class ast.Break

class ast.Continue

break 和 continue 陳述式。

>>> print(ast.dump(ast.parse("""\
... for a in b:
...     if a > 5:
...         break
...     else:
...         continue
...
... """), indent=4))
Module(
    body=[
        For(
            target=Name(id='a', ctx=Store()),
            iter=Name(id='b', ctx=Load()),
            body=[
                If(
                    test=Compare(
                        left=Name(id='a', ctx=Load()),
                        ops=[
                            Gt()],
                        comparators=[
                            Constant(value=5)]),
                    body=[
                        Break()],
                    orelse=[
                        Continue()])])])

class ast.Try(body, handlers, orelse, finalbody)

try 區塊。除 handlers 是 ExceptHandler 節點的串列外，其他所有屬性都是要執行之節點的串列。

>>> print(ast.dump(ast.parse("""
... try:
...    ...
... except Exception:
...    ...
... except OtherException as e:
...    ...
... else:
...    ...
... finally:
...    ...
... """), indent=4))
Module(
    body=[
        Try(
            body=[
                Expr(
                    value=Constant(value=Ellipsis))],
            handlers=[
                ExceptHandler(
                    type=Name(id='Exception', ctx=Load()),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))]),
                ExceptHandler(
                    type=Name(id='OtherException', ctx=Load()),
                    name='e',
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])],
            orelse=[
                Expr(
                    value=Constant(value=Ellipsis))],
            finalbody=[
                Expr(
                    value=Constant(value=Ellipsis))])])

class ast.TryStar(body, handlers, orelse, finalbody)

try 區塊，後面跟著 except* 子句。這些屬性與 Try 相同，但是 handlers 中的 ExceptHandler 節點被直譯 (interpret) 為 except* 區塊而不是 except。

>>> print(ast.dump(ast.parse("""
... try:
...    ...
... except* Exception:
...    ...
... """), indent=4))
Module(
    body=[
        TryStar(
            body=[
                Expr(
                    value=Constant(value=Ellipsis))],
            handlers=[
                ExceptHandler(
                    type=Name(id='Exception', ctx=Load()),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.11 版被加入.

class ast.ExceptHandler(type, name, body)

單個 except 子句。type 是會被匹配的例外型別，通常是一個 Name 節點（或者 None 表示會捕捉到所有例外的 except: 子句）。name 是用於保存例外的名稱之原始字串，如果子句沒有 as foo ，則為 None。body 是節點串列。

>>> print(ast.dump(ast.parse("""\
... try:
...     a + 1
... except TypeError:
...     pass
... """), indent=4))
Module(
    body=[
        Try(
            body=[
                Expr(
                    value=BinOp(
                        left=Name(id='a', ctx=Load()),
                        op=Add(),
                        right=Constant(value=1)))],
            handlers=[
                ExceptHandler(
                    type=Name(id='TypeError', ctx=Load()),
                    body=[
                        Pass()])])])

class ast.With(items, body, type_comment)

一個 with 區塊。items 是表示情境管理器的 withitem 節點串列，body 是情境內的縮進區塊。

type_comment

type_comment 是一個可選字串，其中的註解為型別註釋。

class ast.withitem(context_expr, optional_vars)

with 區塊中的單個情境管理器。context_expr 是情境管理器，通常是一個 Call 節點。Optional_vars 是 as foo 部分的 Name、Tuple 或 List，或者如果不使用則為 None 。

>>> print(ast.dump(ast.parse("""\
... with a as b, c as d:
...    something(b, d)
... """), indent=4))
Module(
    body=[
        With(
            items=[
                withitem(
                    context_expr=Name(id='a', ctx=Load()),
                    optional_vars=Name(id='b', ctx=Store())),
                withitem(
                    context_expr=Name(id='c', ctx=Load()),
                    optional_vars=Name(id='d', ctx=Store()))],
            body=[
                Expr(
                    value=Call(
                        func=Name(id='something', ctx=Load()),
                        args=[
                            Name(id='b', ctx=Load()),
                            Name(id='d', ctx=Load())]))])])

模式匹配 (pattern matching)

class ast.Match(subject, cases)

一個 match 陳述式。subject 保存匹配的主題（與案例匹配的物件），cases 包含具有不同案例的 match_case 節點的可疊代物件。

在 3.10 版被加入.

class ast.match_case(pattern, guard, body)

match 陳述式中的單個案例模式。pattern 包含主題將與之匹配的匹配模式。請注意，為模式生成的 AST 節點與為運算式生成的節點不同，即使它們共享相同的語法。

guard 屬性包含一個運算式，如果模式與主題匹配，則將對該運算式求值。

body 包含一個節點串列，如果模式匹配並且為防護運算式 (guard expression) 的求值 (evaluate) 結果為真，則會執行該節點串列。

>>> print(ast.dump(ast.parse("""
... match x:
...     case [x] if x>0:
...         ...
...     case tuple():
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchSequence(
                        patterns=[
                            MatchAs(name='x')]),
                    guard=Compare(
                        left=Name(id='x', ctx=Load()),
                        ops=[
                            Gt()],
                        comparators=[
                            Constant(value=0)]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))]),
                match_case(
                    pattern=MatchClass(
                        cls=Name(id='tuple', ctx=Load())),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchValue(value)

以相等性進行比較的匹配文本或值的模式。value 是一個運算式節點。允許值節點受到匹配陳述式文件中所述的限制。如果匹配主題等於求出值，則此模式成功。

>>> print(ast.dump(ast.parse("""
... match x:
...     case "Relevant":
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchValue(
                        value=Constant(value='Relevant')),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchSingleton(value)

按識別性 (identity) 進行比較的匹配文本模式。value 是要與 None、True 或 False 進行比較的單例 (singleton)。如果匹配主題是給定的常數，則此模式成功。

>>> print(ast.dump(ast.parse("""
... match x:
...     case None:
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchSingleton(value=None),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchSequence(patterns)

匹配序列模式。如果主題是一個序列，patterns 包含與主題元素匹配的模式。如果子模式之一是 MatchStar 節點，則匹配可變長度序列，否則匹配固定長度序列。

>>> print(ast.dump(ast.parse("""
... match x:
...     case [1, 2]:
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchSequence(
                        patterns=[
                            MatchValue(
                                value=Constant(value=1)),
                            MatchValue(
                                value=Constant(value=2))]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchStar(name)

以可變長度匹配序列模式匹配序列的其餘部分。如果 name 不是 None，則如果整體序列模式成功，則包含其餘序列元素的串列將綁定到該名稱。

>>> print(ast.dump(ast.parse("""
... match x:
...     case [1, 2, *rest]:
...         ...
...     case [*_]:
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchSequence(
                        patterns=[
                            MatchValue(
                                value=Constant(value=1)),
                            MatchValue(
                                value=Constant(value=2)),
                            MatchStar(name='rest')]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))]),
                match_case(
                    pattern=MatchSequence(
                        patterns=[
                            MatchStar()]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchMapping(keys, patterns, rest)

匹配對映模式。keys 是運算式節點的序列。patterns 是相應的模式節點序列。rest 是一個可選名稱，可以指定它來捕獲剩餘的對映元素。允許的鍵運算式受到匹配陳述式文件中所述的限制。

如果主題是對映，所有求值出的鍵運算式都存在於對映中，並且與每個鍵對應的值與相應的子模式匹配，則此模式成功。如果 rest 不是 None，則如果整體對映模式成功，則包含其餘對映元素的字典將綁定到該名稱。

>>> print(ast.dump(ast.parse("""
... match x:
...     case {1: _, 2: _}:
...         ...
...     case {**rest}:
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchMapping(
                        keys=[
                            Constant(value=1),
                            Constant(value=2)],
                        patterns=[
                            MatchAs(),
                            MatchAs()]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))]),
                match_case(
                    pattern=MatchMapping(rest='rest'),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchClass(cls, patterns, kwd_attrs, kwd_patterns)

匹配類別模式。cls 是一個給定要匹配的名義類別 (nominal class) 的運算式。patterns 是要與類別定義的模式匹配屬性序列進行匹配的模式節點序列。kwd_attrs 是要匹配的附加屬性序列（在類別模式中指定為關鍵字引數），kwd_patterns 是相應的模式（在類別模式中指定為關鍵字的值）。

如果主題是指定類別的實例，所有位置模式都與相應的類別定義屬性匹配，並且任何指定的關鍵字屬性與其相應模式匹配，則此模式成功。

注意：類別可以定義一個回傳 self 的特性 (property)，以便將模式節點與正在匹配的實例進行匹配。一些內建型別也以這種方式匹配，如同匹配陳述式文件中所述。

>>> print(ast.dump(ast.parse("""
... match x:
...     case Point2D(0, 0):
...         ...
...     case Point3D(x=0, y=0, z=0):
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchClass(
                        cls=Name(id='Point2D', ctx=Load()),
                        patterns=[
                            MatchValue(
                                value=Constant(value=0)),
                            MatchValue(
                                value=Constant(value=0))]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))]),
                match_case(
                    pattern=MatchClass(
                        cls=Name(id='Point3D', ctx=Load()),
                        kwd_attrs=[
                            'x',
                            'y',
                            'z'],
                        kwd_patterns=[
                            MatchValue(
                                value=Constant(value=0)),
                            MatchValue(
                                value=Constant(value=0)),
                            MatchValue(
                                value=Constant(value=0))]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchAs(pattern, name)

匹配的 「as 模式 (as-pattern)」，為捕獲模式 (capture pattern) 或通配模式 (wildcard pattern)。pattern 包含主題將與之匹配的匹配模式。如果模式為 None，則該節點代表捕獲模式（即裸名 (bare name)）並且始終會成功。

name 屬性包含模式成功時將綁定的名稱。如果 name 為 None，則 pattern 也必須為 None，並且節點代表通配模式。

>>> print(ast.dump(ast.parse("""
... match x:
...     case [x] as y:
...         ...
...     case _:
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchAs(
                        pattern=MatchSequence(
                            patterns=[
                                MatchAs(name='x')]),
                        name='y'),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))]),
                match_case(
                    pattern=MatchAs(),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

class ast.MatchOr(patterns)

匹配的 「or 模式 (or-pattern)」。 or 模式依次將其每個子模式與主題進行匹配，直到成功為止，然後 or 模式就會被認為是成功的。如果沒有一個子模式成功，則 or 模式將失敗。 patterns 屬性包含將與主題進行匹配的匹配模式節點串列。

>>> print(ast.dump(ast.parse("""
... match x:
...     case [x] | (y):
...         ...
... """), indent=4))
Module(
    body=[
        Match(
            subject=Name(id='x', ctx=Load()),
            cases=[
                match_case(
                    pattern=MatchOr(
                        patterns=[
                            MatchSequence(
                                patterns=[
                                    MatchAs(name='x')]),
                            MatchAs(name='y')]),
                    body=[
                        Expr(
                            value=Constant(value=Ellipsis))])])])

在 3.10 版被加入.

型別註釋

class ast.TypeIgnore(lineno, tag)

位於 lineno 的 # type: ignore 註解。tag 是以 # type: ignore <tag> 形式指定的可選標籤。

>>> print(ast.dump(ast.parse('x = 1 # type: ignore', type_comments=True), indent=4))
Module(
    body=[
        Assign(
            targets=[
                Name(id='x', ctx=Store())],
            value=Constant(value=1))],
    type_ignores=[
        TypeIgnore(lineno=1, tag='')])
>>> print(ast.dump(ast.parse('x: bool = 1 # type: ignore[assignment]', type_comments=True), indent=4))
Module(
    body=[
        AnnAssign(
            target=Name(id='x', ctx=Store()),
            annotation=Name(id='bool', ctx=Load()),
            value=Constant(value=1),
            simple=1)],
    type_ignores=[
        TypeIgnore(lineno=1, tag='[assignment]')])

備註

當 type_comments 參數設為 False（預設值）時，不會產生 TypeIgnore 節點。更多細節請參閱 ast.parse()。

在 3.8 版被加入.

型別參數 (type parameters)

型別參數可以存在於類別、函式和型別別名上。

class ast.TypeVar(name, bound, default_value)

一個 typing.TypeVar。name 是型別變數的名稱。bound 是（如果有存在的）界限 (bound) 或約束 (constraint)。如果 bound 是一個 Tuple，它代表約束；否則它代表界限。default_value 為預設值；如果 TypeVar 沒有預設值，那此屬性會被設為 None。

>>> print(ast.dump(ast.parse("type Alias[T: int = bool] = list[T]"), indent=4))
Module(
    body=[
        TypeAlias(
            name=Name(id='Alias', ctx=Store()),
            type_params=[
                TypeVar(
                    name='T',
                    bound=Name(id='int', ctx=Load()),
                    default_value=Name(id='bool', ctx=Load()))],
            value=Subscript(
                value=Name(id='list', ctx=Load()),
                slice=Name(id='T', ctx=Load()),
                ctx=Load()))])

在 3.12 版被加入.

在 3.13 版的變更: 新增 default_value 參數。

class ast.ParamSpec(name, default_value)

一個 typing.ParamSpec。name 是參數規範的名稱。default_value 是預設值；如果 ParamSpec 沒有預設值，則該屬性將設定為 None。

>>> print(ast.dump(ast.parse("type Alias[**P = [int, str]] = Callable[P, int]"), indent=4))
Module(
    body=[
        TypeAlias(
            name=Name(id='Alias', ctx=Store()),
            type_params=[
                ParamSpec(
                    name='P',
                    default_value=List(
                        elts=[
                            Name(id='int', ctx=Load()),
                            Name(id='str', ctx=Load())],
                        ctx=Load()))],
            value=Subscript(
                value=Name(id='Callable', ctx=Load()),
                slice=Tuple(
                    elts=[
                        Name(id='P', ctx=Load()),
                        Name(id='int', ctx=Load())],
                    ctx=Load()),
                ctx=Load()))])

在 3.12 版被加入.

在 3.13 版的變更: 新增 default_value 參數。

class ast.TypeVarTuple(name, default_value)

一個 typing.TypeVarTuple。name 是型別變數元組的名稱。default_value 為預設值；如果 TypeVarTuple 沒有預設值，那此屬性會被設為 None。

>>> print(ast.dump(ast.parse("type Alias[*Ts = ()] = tuple[*Ts]"), indent=4))
Module(
    body=[
        TypeAlias(
            name=Name(id='Alias', ctx=Store()),
            type_params=[
                TypeVarTuple(
                    name='Ts',
                    default_value=Tuple(ctx=Load()))],
            value=Subscript(
                value=Name(id='tuple', ctx=Load()),
                slice=Tuple(
                    elts=[
                        Starred(
                            value=Name(id='Ts', ctx=Load()),
                            ctx=Load())],
                    ctx=Load()),
                ctx=Load()))])

在 3.12 版被加入.

在 3.13 版的變更: 新增 default_value 參數。

函式和類別定義

class ast.FunctionDef(name, args, body, decorator_list, returns, type_comment, type_params)

一個函式定義。

name 是函式名稱的原始字串。

args 是一個 arguments 節點。

body 是函式內節點的串列。

decorator_list 是要應用的裝飾器串列，在最外層者會被儲存在首位（即串列中首位將會是最後一個被應用的那個）。

returns 是回傳註釋。

type_params 是型別參數的串列。

type_comment

type_comment 是一個可選字串，其中的註解為型別註釋。

在 3.12 版的變更: 新增了 type_params。

class ast.Lambda(args, body)

lambda 是可以在運算式內使用的最小函式定義。與 FunctionDef 不同，body 保存單個節點。

>>> print(ast.dump(ast.parse('lambda x,y: ...'), indent=4))
Module(
    body=[
        Expr(
            value=Lambda(
                args=arguments(
                    args=[
                        arg(arg='x'),
                        arg(arg='y')]),
                body=Constant(value=Ellipsis)))])

class ast.arguments(posonlyargs, args, vararg, kwonlyargs, kw_defaults, kwarg, defaults)

函式的引數。

posonlyargs、args 和 kwonlyargs 是 arg 節點的串列。

vararg 和 kwarg 是單個 arg 節點，指的是 *args, **kwargs 參數。

kw_defaults 是僅限關鍵字引數的預設值串列。如果其中某個為 None，則相應參數就會是必要的。

defaults 是可以按位置傳遞的引數的預設值串列。如果預設值較少，則它們對應於最後 n 個引數。

class ast.arg(arg, annotation, type_comment)

串列中的單個引數。arg 是引數名稱的原始字串，annotation 是它的註釋，例如 Name 節點。

type_comment

type_comment 是一個可選字串，其註解為型別註釋

>>> print(ast.dump(ast.parse("""\
... @decorator1
... @decorator2
... def f(a: 'annotation', b=1, c=2, *d, e, f=3, **g) -> 'return annotation':
...     pass
... """), indent=4))
Module(
    body=[
        FunctionDef(
            name='f',
            args=arguments(
                args=[
                    arg(
                        arg='a',
                        annotation=Constant(value='annotation')),
                    arg(arg='b'),
                    arg(arg='c')],
                vararg=arg(arg='d'),
                kwonlyargs=[
                    arg(arg='e'),
                    arg(arg='f')],
                kw_defaults=[
                    None,
                    Constant(value=3)],
                kwarg=arg(arg='g'),
                defaults=[
                    Constant(value=1),
                    Constant(value=2)]),
            body=[
                Pass()],
            decorator_list=[
                Name(id='decorator1', ctx=Load()),
                Name(id='decorator2', ctx=Load())],
            returns=Constant(value='return annotation'))])

class ast.Return(value)

一個 return 陳述式。

>>> print(ast.dump(ast.parse('return 4'), indent=4))
Module(
    body=[
        Return(
            value=Constant(value=4))])

class ast.Yield(value)

class ast.YieldFrom(value)

一個 yield 或 yield from 運算式。因為這些是運算式，所以如果不使用發送回來的值，則必須將它們包裝在 Expr 節點中。

>>> print(ast.dump(ast.parse('yield x'), indent=4))
Module(
    body=[
        Expr(
            value=Yield(
                value=Name(id='x', ctx=Load())))])

>>> print(ast.dump(ast.parse('yield from x'), indent=4))
Module(
    body=[
        Expr(
            value=YieldFrom(
                value=Name(id='x', ctx=Load())))])

class ast.Global(names)

class ast.Nonlocal(names)

global 和 nonlocal 陳述式。names 是原始字串的串列。

>>> print(ast.dump(ast.parse('global x,y,z'), indent=4))
Module(
    body=[
        Global(
            names=[
                'x',
                'y',
                'z'])])

>>> print(ast.dump(ast.parse('nonlocal x,y,z'), indent=4))
Module(
    body=[
        Nonlocal(
            names=[
                'x',
                'y',
                'z'])])

class ast.ClassDef(name, bases, keywords, body, decorator_list, type_params)

一個類別定義。

name 是類別名稱的原始字串

bases 是被顯式指定的基底類別節點串列。

keywords 是一個 keyword 節點的串列，主要用於 'metaclass'（元類別）。如 PEP 3115 [https://peps.python.org/pep-3115/] 所述，其他關鍵字將被傳遞到 metaclass。

body 是表示類別定義中程式碼的節點串列。

decorator_list 是一個節點串列，如 FunctionDef 中所示。

type_params 是型別參數的串列。

>>> print(ast.dump(ast.parse("""\
... @decorator1
... @decorator2
... class Foo(base1, base2, metaclass=meta):
...     pass
... """), indent=4))
Module(
    body=[
        ClassDef(
            name='Foo',
            bases=[
                Name(id='base1', ctx=Load()),
                Name(id='base2', ctx=Load())],
            keywords=[
                keyword(
                    arg='metaclass',
                    value=Name(id='meta', ctx=Load()))],
            body=[
                Pass()],
            decorator_list=[
                Name(id='decorator1', ctx=Load()),
                Name(id='decorator2', ctx=Load())])])

在 3.12 版的變更: 新增了 type_params。

async 和 await

class ast.AsyncFunctionDef(name, args, body, decorator_list, returns, type_comment, type_params)

一個 async def 函式定義。與 FunctionDef 具有相同的欄位。

在 3.12 版的變更: 新增了 type_params。

class ast.Await(value)

一個 await 運算式。value 是它等待的東西。僅在 AsyncFunctionDef 主體 (body) 中有效。

>>> print(ast.dump(ast.parse("""\
... async def f():
...     await other_func()
... """), indent=4))
Module(
    body=[
        AsyncFunctionDef(
            name='f',
            args=arguments(),
            body=[
                Expr(
                    value=Await(
                        value=Call(
                            func=Name(id='other_func', ctx=Load()))))])])

class ast.AsyncFor(target, iter, body, orelse, type_comment)

class ast.AsyncWith(items, body, type_comment)

async for 迴圈和 async with 情境管理器。它們分別具有與 For 和 With 相同的欄位。僅在 AsyncFunctionDef 主體中有效。

備註

當字串被 ast.parse() 剖析時，回傳樹的運算子節點（ast.operator、ast.unaryop、ast.cmpop、ast.boolop 和 ast.expr_context 的子類別）將是單例。對其中之一的更改將反映在所有其他出現的相同值中（例如 ast.Add）。

ast 輔助程式

除了節點類別之外，ast 模組還定義了這些用於遍歷 (traverse) 抽象語法樹的實用函式和類別：

ast.parse(source, filename='<unknown>', mode='exec', *, type_comments=False, feature_version=None, optimize=-1)

將原始碼剖析為 AST 節點，相當於 compile(source, filename, mode, flags=FLAGS_VALUE, optimize=optimize)，其中 FLAGS_VALUE 在 optimize <= 0 時為 ast.PyCF_ONLY_AST，否則為 ast.PyCF_OPTIMIZED_AST。

如果給定 type_comments=True，剖析器將被修改為檢查並回傳 PEP 484 [https://peps.python.org/pep-0484/] 和 PEP 526 [https://peps.python.org/pep-0526/] 指定的型別註釋。這相當於將 ast.PyCF_TYPE_COMMENTS 新增到傳遞給 compile() 的旗標中。這將報告錯誤型別註釋的語法錯誤。如果沒有此旗標，型別註釋將被忽略，並且所選 AST 節點上的 type_comment 欄位將始終為 None。此外，# type: ignore 註釋的位置將作為 Module 的 type_ignores 屬性回傳（否則它始終是一個空串列）。

此外，如果 mode 是 'func_type'，則輸入語法將會依據 PEP 484 [https://peps.python.org/pep-0484/]「簽名型別註解 (signature type comments)」而被修改，例如 (str, int) -> List[str]。

將 feature_version 設定為元組 (major, minor) 將「盡可能」嘗試使用該 Python 版本的文法進行剖析。目前 major 必須等於 3。例如，設定 feature_version=(3, 9) 將嘗試禁止剖析 match 陳述式。目前 major 必須為 3、支援的最低版本為 (3, 7)（這在未來的 Python 版本中可能會增加）；最高的是 sys.version_info[0:2]。「盡可能」嘗試意味著不能保證剖析（或剖析的成功）與在與 feature_version 對應的 Python 版本上運行時相同。

如果來源包含 null 字元 (\0)，則會引發 ValueError。

警告

請注意，成功將原始碼剖析為 AST 物件並不能保證提供的原始碼是可以執行的有效 Python 程式碼，因為編譯步驟可能會引發進一步的 SyntaxError 例外。例如，原始的 return 42 為 return 陳述式生成一個有效的 AST 節點，但它不能單獨編譯（它需要位於函式節點內）。

特別是 ast.parse() 不會執行任何範圍檢查，而編譯步驟才會執行此操作。

警告

由於 Python AST 編譯器中的堆疊 (stack) 深度限制，太大或太複雜的字串可能會導致 Python 直譯器崩潰。

在 3.8 版的變更: 新增 type_comments、mode='func_type' 與 feature_version。

在 3.13 版的變更: feature_version 的最低支援版本現在是 (3, 7)。新增了 optimize 引數。

ast.unparse(ast_obj)

反剖析 ast.AST 物件並生成一個帶有程式碼的字串，如果使用 ast.parse() 剖析回來，該程式碼將生成等效的 ast.AST 物件。

警告

生成的程式碼字串不一定等於生成 ast.AST 物件的原始程式碼（沒有任何編譯器最佳化，例如常數元組/凍結集合）。

警告

嘗試剖析高度複雜的運算式會導致 RecursionError。

在 3.9 版被加入.

ast.literal_eval(node_or_string)

為僅包含 Python 文本或容器之顯示的運算式節點或字串來求值。提供的字串或節點只能包含以下 Python 文本結構：字串、位元組、數字、元組、串列、字典、集合、布林值、None 和 Ellipsis。

這可用於為包含 Python 值的字串求值，而無需自己剖析這些值。它無法計算任意複雜的運算式，例如涉及運算子或索引。

該函式過去被記錄為「安全」，但沒有定義其含義，這有點誤導讀者，它是特別設計為不去執行 Python 程式碼，與更通用的 eval() 不同。沒有命名空間、沒有名稱查找、也沒有呼叫的能力。但它也不能免受攻擊：相對較小的輸入可能會導致記憶體耗盡或 C 堆疊耗盡，從而導致行程崩潰。某些輸入也可能會出現 CPU 消耗過多而導致拒絕服務的情況。因此不建議在不受信任的資料上呼叫它。

警告

由於 Python AST 編譯器的堆疊深度限制，Python 直譯器可能會崩潰。

它可能會引發 ValueError、TypeError、SyntaxError、MemoryError 和 RecursionError，具體取決於格式錯誤的輸入。

在 3.2 版的變更: 現在允許位元組和集合文本 (set literal)。

在 3.9 版的變更: 現在支援使用 'set()' 建立空集合。

在 3.10 版的變更: 對於字串輸入，前導空格和定位字元 (tab) 現在已被去除。

ast.get_docstring(node, clean=True)

回傳給定 node 的文件字串 (docstring)（必須是 FunctionDef、AsyncFunctionDef、ClassDef 或 Module 節點）或如果它沒有文件字串則為 None。如果 clean 為 true，則使用 inspect.cleandoc() 清理文件字串的縮排。

在 3.5 版的變更: 目前已支援 AsyncFunctionDef。

ast.get_source_segment(source, node, *, padded=False)

取得生成 node 的 source 的原始碼片段。如果某些位置資訊（lineno、end_lineno、col_offset 或 end_col_offset）遺漏，則回傳 None。

如果 padded 為 True，則多列陳述式的第一列將用空格填充 (padded) 以匹配其原始位置。

在 3.8 版被加入.

ast.fix_missing_locations(node)

當你使用 compile() 編譯節點樹時，對於每個有支援 lineno 和 col_offset 屬性之節點，編譯器預期他們的這些屬性都要存在。填入生成的節點相當繁瑣，因此該輔助工具透過將這些屬性設定為父節點的值，在尚未設定的地方遞迴地新增這些屬性。它從 node 開始遞迴地作用。

ast.increment_lineno(node, n=1)

將樹中從 node 開始的每個節點的列號和結束列號增加 n。這對於「移動程式碼」到檔案中的不同位置很有用。

ast.copy_location(new_node, old_node)

如果可行，將原始位置（lineno、col_offset、end_lineno 和 end_col_offset ）從 old_node 複製到 new_node，並回傳 new_node 。

ast.iter_fields(node)

為 node 上存在的 node._fields 中的每個欄位生成一個 (fieldname, value) 元組。

ast.iter_child_nodes(node)

生成 node 的所有直接子節點，即作為節點的所有欄位以及作為節點串列欄位的所有項目。

ast.walk(node)

遞迴地生成樹中從 node 開始的所有後代節點（包括 node 本身），不按指定順序。如果你只想就地修改節點而不關心情境，這非常有用。

class ast.NodeVisitor

節點瀏覽者基底類別，它遍歷抽象語法樹並為找到的每個節點呼叫瀏覽者函式。該函式可能會回傳一個由 visit() 方法轉發的值。

這個類別應該被子類別化，子類別新增瀏覽者方法。

visit(node)

瀏覽一個節點。預設實作呼叫名為 self.visit_classname 的方法，其中 classname 是節點類別的名稱，或者在該方法不存在時呼叫 generic_visit()。

generic_visit(node)

該瀏覽者對該節點的所有子節點呼叫 visit()。

請注意，除非瀏覽者呼叫 generic_visit() 或瀏覽它們本身，否則不會瀏覽具有自訂瀏覽者方法的節點之子節點。

visit_Constant(node)

處理所有常數節點。

如果你想在遍歷期間將變更應用 (apply) 於節點，請不要使用 NodeVisitor。為此，有個允許修改的特殊遍歷瀏覽者工具 NodeTransformer。

自從版本 3.8 後不推薦使用，已從版本 3.14 中移除。: visit_Num()、visit_Str()、visit_Bytes()、visit_NameConstant() 和 visit_Ellipsis() 方法在 Python 3.14+ 中將不會被呼叫。請改為新增 visit_Constant() 方法來處理所有常數節點。

class ast.NodeTransformer

一個 NodeVisitor 子類別，它會遍歷抽象語法樹並允許修改節點。

NodeTransformer 將遍歷 AST 並使用瀏覽者方法的回傳值來替換或刪除舊節點。如果瀏覽者方法的回傳值為 None，則該節點將從其位置中刪除，否則將被替換為回傳值。回傳值可能是原始節點，在這種情況下不會發生替換。

下面是一個示範用的 transformer，它將查找所有出現名稱 (foo) 並改寫為 data['foo']：

class RewriteName(NodeTransformer):

    def visit_Name(self, node):
        return Subscript(
            value=Name(id='data', ctx=Load()),
            slice=Constant(value=node.id),
            ctx=node.ctx
        )

請記住，如果你正在操作的節點有子節點，你必須自己轉換子節點或先呼叫該節點的 generic_visit() 方法。

對於屬於陳述式總集 (collection) 一部分的節點（適用於所有陳述式節點），瀏覽者還可以回傳節點串列，而不僅僅是單個節點。

如果 NodeTransformer 引進了新節點（不屬於原始樹的一部分），但沒有給它們提供位置資訊（例如 lineno），則應使用新的子樹呼叫 fix_missing_locations() 以重新計算位置資訊：

tree = ast.parse('foo', mode='eval')
new_tree = fix_missing_locations(RewriteName().visit(tree))

你通常會像這樣使用 transformer：

node = YourTransformer().visit(node)

ast.dump(node, annotate_fields=True, include_attributes=False, *, indent=None, show_empty=False)

回傳 node 中樹的格式化傾印 (formatted dump)，這主要用於除錯。如果 annotate_fields 為 true（為預設值），則回傳的字串將顯示欄位的名稱和值。如果 annotate_fields 為 false，則透過省略明確的欄位名稱，結果字串將更加縮減簡潔。預設情況下，不會傾印列號和行偏移量等屬性。如果需要，可以設定 include_attributes 為 true。

如果 indent 是非負整數或字串，那麼樹將使用該縮排級別來做漂亮印出 (pretty-print)。縮排級別 0、負數或 "" 只會插入換列符號 (newlines)。None（預設值）代表選擇單列表示。使用正整數縮排可以在每個級別縮排相同數量的空格。如果 indent 是一個字串（例如 "\t"），則該字串用於縮排每個級別。

如果 show_empty 為 false（預設值），則輸出中將省略可選的空串列。可選的 None 值總是會被省略。

在 3.9 版的變更: 新增 indent 選項。

在 3.13 版的變更: 新增 show_empty 選項。

>>> print(ast.dump(ast.parse("""\
... async def f():
...     await other_func()
... """), indent=4, show_empty=True))
Module(
    body=[
        AsyncFunctionDef(
            name='f',
            args=arguments(
                posonlyargs=[],
                args=[],
                kwonlyargs=[],
                kw_defaults=[],
                defaults=[]),
            body=[
                Expr(
                    value=Await(
                        value=Call(
                            func=Name(id='other_func', ctx=Load()),
                            args=[],
                            keywords=[])))],
            decorator_list=[],
            type_params=[])],
    type_ignores=[])

編譯器旗標

可以將以下旗標傳遞給 compile() 以變更對程式的編譯效果：

ast.PyCF_ALLOW_TOP_LEVEL_AWAIT

啟用對最高階 await、async for、async with 和非同步綜合運算的支援。

在 3.8 版被加入.

ast.PyCF_ONLY_AST

生成並回傳抽象語法樹，而不是回傳已編譯的程式碼物件。

ast.PyCF_OPTIMIZED_AST

回傳的 AST 會根據 compile() 或 ast.parse() 中的 optimize 引數進行最佳化。

在 3.13 版被加入.

ast.PyCF_TYPE_COMMENTS

啟用對 PEP 484 [https://peps.python.org/pep-0484/] 和 PEP 526 [https://peps.python.org/pep-0526/] 樣式型別註釋的支援 (# type: <type>, # type: ignore <stuff>)。

在 3.8 版被加入.

ast.compare(a, b, /, *, compare_attributes=False)

遞迴比較兩個 AST。

compare_attributes 會影響比較時是否考慮 AST 屬性。如果 compare_attributes 為 False（預設值），則忽略屬性。否則所有屬性都必須相等。此選項用於檢查 AST 在結構上是否相等，但在空白或類似細節上有所不同。屬性包括列號和行偏移量。

在 3.14 版被加入.

命令列用法

在 3.9 版被加入.

ast 模組可以作為腳本從命令列執行，可以像這樣簡單地做到：

python -m ast [-m <mode>] [-a] [infile]

以下選項可被接受：

-h, --help

顯示幫助訊息並退出。

-m <mode>

--mode <mode>

指定必須編譯哪種類型的程式碼，像是 parse() 中的 mode 引數。

--no-type-comments

不要剖析型別註解。

-a, --include-attributes

包括列號和行偏移量等屬性。

-i <indent>

--indent <indent>

AST 中節點的縮進（空格數）。

--feature-version <version>

以 3.x 格式表示的 Python 版本（例如 3.10）。預設為直譯器的目前版本。

在 3.14 版被加入.

-O <level>

--optimize <level>

剖析器的最佳化層級。預設為不進行最佳化。

在 3.14 版被加入.

--show-empty

顯示空串列和值為 None 的欄位。預設為不顯示空物件。

在 3.14 版被加入.

如果指定了 infile，則其內容將被剖析為 AST 並傾印 (dump) 到 stdout。否則會從 stdin 讀取內容。

也參考

Green Tree Snakes [https://greentreesnakes.readthedocs.io/] 是一個外部文件資源，提供了有關使用 Python AST 的詳細資訊。

ASTTokens [https://asttokens.readthedocs.io/en/latest/user-guide.html] 使用生成它們的原始碼中的標記和文本的位置來註釋 Python AST。這對於進行原始碼轉換的工具很有幫助。

leoAst.py [https://leo-editor.github.io/leo-editor/appendices.html#leoast-py] 透過在 token 和 ast 節點之間插入雙向鏈結，統一了 python 程式的基於 token 和基於剖析樹的視圖。

LibCST [https://libcst.readthedocs.io/] 將程式碼剖析為具體語法樹 (Concrete Syntax Tree)，看起來像 ast 樹並保留所有格式詳細資訊。它對於建置自動重構 (codemod) 應用程式和 linter 非常有用。

Parso [https://parso.readthedocs.io] 是一個 Python 剖析器，支援不同 Python 版本的錯誤復原和往返剖析。Parso 還能夠列出 Python 檔案中的多個語法錯誤。

symtable --- 存取編譯器的符號表

原始碼：Lib/symtable.py [https://github.com/python/cpython/tree/3.14/Lib/symtable.py]

符號表 (symbol table) 是在生成位元組碼 (bytecode) 之前由編譯器從 AST 生成的。符號表負責計算程式碼中每個識別器 (identifier) 的作用域。symtable 提供了一個介面來檢查這些表。

產生符號表

symtable.symtable(code, filename, compile_type)

回傳 Python 原始 code 的頂層 SymbolTable。filename 是包含程式碼之檔案之名稱。compile_type 類似於 compile() 的 mode 引數。

檢查符號表

class symtable.SymbolTableType

表明 SymbolTable 物件型別的列舉。

MODULE = "module"

用於模組的符號表。

FUNCTION = "function"

用於函式的符號表。

CLASS = "class"

用於類別的符號表。

以下成員代表不同風格的註釋作用域。

ANNOTATION = "annotation"

如果 from __future__ import annotations 處於活動狀態，則用於註解。

TYPE_ALIAS = "type alias"

用於 type 結構的符號表。

TYPE_PARAMETERS = "type parameters"

用於泛型函式 (generic functions)或泛型類別 (generic classes)的符號表。

TYPE_VARIABLE = "type variable"

用於形式意義上 (formal sense) 的繫結、約束元組 (constraint tuple) 或單一型別變數的預設值的符號表，即 TypeVar、TypeVarTuple 或 ParamSpec 物件（後兩者不支援繫結或約束元組）。

在 3.13 版被加入.

class symtable.SymbolTable

一個區塊 (block) 的命名空間表 (namespace table) 。建構函式 (constructor) 並不公開。

get_type()

回傳符號表的類型。可能的值為 SymbolTableType 列舉的成員。

在 3.12 版的變更: 新增了 'annotation'、'TypeVar bound'、'type alias' 和 'type parameter' 作為可能的回傳值。

在 3.13 版的變更: 回傳值是 SymbolTableType 列舉的成員。

回傳字串的確切值在未來可能會發生變化，因此建議使用 SymbolTableType 成員而不是寫死 (hard-coded) 字串。

get_id()

回傳表的識別器。

get_name()

回傳表的名稱。如果表用於類別，則這是類別的名稱；如果表用於函式，則這是函式的名稱；如果表是全域的，則為 'top' （get_type() 會回傳 'module'）。對於型別參數作用域（用於泛型類別、函式和型別別名），它是底層類別、函式或型別別名的名稱。對於型別別名作用域，它是型別別名的名稱。對於 TypeVar 綁定作用域，它會是 TypeVar 的名稱。

get_lineno()

回傳此表所代表的區塊中第一行的編號。

is_optimized()

如果可以最佳化該表中的區域變數，則回傳 True。

is_nested()

如果區塊是巢狀類別或函式，則回傳 True。

has_children()

如果區塊內有巢狀命名空間，則回傳 True。這些可以透過 get_children() 獲得。

get_identifiers()

回傳包含表中符號之名稱的視圖物件 (view object)。請參閱視圖物件的文件。

lookup(name)

在表中查找 name 並回傳一個 Symbol 實例。

get_symbols()

回傳表中名稱的 Symbol 實例串列。

get_children()

回傳巢狀符號表的串列。

class symtable.Function

一個函式或方法的命名空間。該類別繼承自 SymbolTable。

get_parameters()

回傳一個包含此函式參數名稱的元組 (tuple)。

get_locals()

回傳一個包含此函式中區域變數 (locals) 名稱的元組。

get_globals()

回傳一個包含此函式中全域變數 (globals) 名稱的元組。

get_nonlocals()

回傳一個包含此函式中明確宣告的非區域變數 (nonlocals) 名稱的元組。

get_frees()

回傳一個包含此函式中的自由（閉包）變數 (free (closure) variables) 名稱的元組。

class symtable.Class

一個類別的命名空間。該類別繼承自 SymbolTable。

get_methods()

回傳一個包含類別中聲明的類似方法之函式名稱的元組。

在這裡，術語「方法 (method)」表示透過 def 或 async def 在類別主體中定義的任何函式。

get_methods() 不會取得更深作用域內定義的函式（例如在內部類別中）。

舉例來說：

>>> import symtable
>>> st = symtable.symtable('''
... def outer(): pass
...
... class A:
...    def f():
...        def w(): pass
...
...    def g(self): pass
...
...    @classmethod
...    async def h(cls): pass
...
...    global outer
...    def outer(self): pass
... ''', 'test', 'exec')
>>> class_A = st.get_children()[2]
>>> class_A.get_methods()
('f', 'g', 'h')

儘管 A().f() 會在 runtime 引發 TypeError，但 A.f 仍然被視為類似方法的函式。

自從版本 3.14 後不推薦使用，將會自版本 3.16 中移除。.

class symtable.Symbol

SymbolTable 中的條目對應於來源中的識別器。建構函式不是公開的。

get_name()

回傳符號的名稱。

is_referenced()

如果該符號在其區塊中使用，則回傳 True。

is_imported()

如果符號是從 import 陳述式建立的，則回傳 True。

is_parameter()

如果符號是一個參數，則回傳 True。

is_type_parameter()

如果符號是一個型別參數，則回傳 True。

在 3.14 版被加入.

is_global()

如果符號是全域的，則回傳 True。

is_nonlocal()

如果符號是非區域的，則回傳 True。

is_declared_global()

如果使用全域陳述式將符號聲明為全域的，則回傳 True。

is_local()

如果符號是其區塊的區域符號，則回傳 True。

is_annotated()

如果符號有被註釋，則回傳 True。

在 3.6 版被加入.

is_free()

如果該符號在其區塊中被參照 (referenced) 但未被賦值 (assigned)，則回傳 True。

is_free_class()

Return True if a class-scoped symbol is free from the perspective of a method.

參考以下範例：

def f():
    x = 1  # 函式範圍
    class C:
        x = 2  # 類別範圍
        def method(self):
            return x

In this example, the class-scoped symbol x is considered to be free from the perspective of C.method, thereby allowing the latter to return 1 at runtime and not 2.

在 3.14 版被加入.

is_assigned()

如果該符號被賦值到其區塊中，則回傳 True。

is_comp_iter()

Return True if the symbol is a comprehension iteration variable.

在 3.14 版被加入.

is_comp_cell()

Return True if the symbol is a cell in an inlined comprehension.

在 3.14 版被加入.

is_namespace()

如果名稱綁定引入 (introduce) 新的命名空間，則回傳 True。

如果名稱用作函式或類別陳述式的目標，則這將會是 true。

舉例來說：

>>> table = symtable.symtable("def some_func(): pass", "string", "exec")
>>> table.lookup("some_func").is_namespace()
True

請注意，單個名稱可以綁定到多個物件。如果結果為 True，則該名稱也可能被綁定到其他物件，例如 int 或 list，而不會引入新的命名空間。

get_namespaces()

回傳綁定到該名稱的命名空間的串列。

get_namespace()

回傳綁定到該名稱的命名空間。如果該名稱綁定了多個命名空間或沒有命名空間，則會引發 ValueError。

命令列用法

在 3.13 版被加入.

symtable 模組可以從命令列作為腳本執行。

python -m symtable [infile...]

為指定的 Python 原始檔產生符號表並轉儲 (dump) 到 stdout。如果未指定輸入檔案，則從 stdin 讀取內容。

token --- 與 Python 剖析樹一起使用的常數

原始碼：Lib/token.py [https://github.com/python/cpython/tree/3.14/Lib/token.py]

This module provides constants which represent the numeric values of leaf nodes of the parse tree (terminal tokens). Refer to the file Grammar/Tokens in the Python distribution for the definitions of the names in the context of the language grammar. The specific numeric values which the names map to may change between Python versions.

The module also provides a mapping from numeric codes to names and some functions. The functions mirror definitions in the Python C header files.

Note that a token's value may depend on tokenizer options. For example, a "+" token may be reported as either PLUS or OP, or a "match" token may be either NAME or SOFT_KEYWORD.

token.tok_name

Dictionary mapping the numeric values of the constants defined in this module back to name strings, allowing more human-readable representation of parse trees to be generated.

token.ISTERMINAL(x)

Return True for terminal token values.

token.ISNONTERMINAL(x)

Return True for non-terminal token values.

token.ISEOF(x)

Return True if x is the marker indicating the end of input.

The token constants are:

token.NAME

Token value that indicates an identifier. Note that keywords are also initially tokenized as NAME tokens.

token.NUMBER

Token value that indicates a numeric literal

token.STRING

Token value that indicates a string or byte literal, excluding formatted string literals. The token string is not interpreted: it includes the surrounding quotation marks and the prefix (if given); backslashes are included literally, without processing escape sequences.

token.OP

A generic token value that indicates an operator or delimiter.

CPython 實作細節： This value is only reported by the tokenize module. Internally, the tokenizer uses exact token types instead.

token.COMMENT

Token value used to indicate a comment. The parser ignores COMMENT tokens.

token.NEWLINE

Token value that indicates the end of a logical line.

token.NL

Token value used to indicate a non-terminating newline. NL tokens are generated when a logical line of code is continued over multiple physical lines. The parser ignores NL tokens.

token.INDENT

Token value used at the beginning of a logical line to indicate the start of an indented block.

token.DEDENT

Token value used at the beginning of a logical line to indicate the end of an indented block.

token.FSTRING_START

Token value used to indicate the beginning of an f-string literal.

CPython 實作細節： The token string includes the prefix and the opening quote(s), but none of the contents of the literal.

token.FSTRING_MIDDLE

Token value used for literal text inside an f-string literal, including format specifications.

CPython 實作細節： Replacement fields (that is, the non-literal parts of f-strings) use the same tokens as other expressions, and are delimited by LBRACE, RBRACE, EXCLAMATION and COLON tokens.

token.FSTRING_END

Token value used to indicate the end of a f-string.

CPython 實作細節： The token string contains the closing quote(s).

token.TSTRING_START

Token value used to indicate the beginning of a template string literal.

CPython 實作細節： The token string includes the prefix and the opening quote(s), but none of the contents of the literal.

在 3.14 版被加入.

token.TSTRING_MIDDLE

Token value used for literal text inside a template string literal including format specifications.

CPython 實作細節： Replacement fields (that is, the non-literal parts of t-strings) use the same tokens as other expressions, and are delimited by LBRACE, RBRACE, EXCLAMATION and COLON tokens.

在 3.14 版被加入.

token.TSTRING_END

Token value used to indicate the end of a template string literal.

CPython 實作細節： The token string contains the closing quote(s).

在 3.14 版被加入.

token.ENDMARKER

Token value that indicates the end of input. Used in top-level grammar rules.

token.ENCODING

Token value that indicates the encoding used to decode the source bytes into text. The first token returned by tokenize.tokenize() will always be an ENCODING token.

CPython 實作細節： This token type isn't used by the C tokenizer but is needed for the tokenize module.

The following token types are not produced by the tokenize module, and are defined for special uses in the tokenizer or parser:

token.TYPE_IGNORE

Token value indicating that a type: ignore comment was recognized. Such tokens are produced instead of regular COMMENT tokens only with the PyCF_TYPE_COMMENTS flag.

token.TYPE_COMMENT

Token value indicating that a type comment was recognized. Such tokens are produced instead of regular COMMENT tokens only with the PyCF_TYPE_COMMENTS flag.

token.SOFT_KEYWORD

Token value indicating a soft keyword.

The tokenizer never produces this value. To check for a soft keyword, pass a NAME token's string to keyword.issoftkeyword().

token.ERRORTOKEN

Token value used to indicate wrong input.

The tokenize module generally indicates errors by raising exceptions instead of emitting this token. It can also emit tokens such as OP or NAME with strings that are later rejected by the parser.

The remaining tokens represent specific operators and delimiters. (The tokenize module reports these as OP; see exact_type in the tokenize documentation for details.)

Token

Value

token.LPAR

"("

token.RPAR

")"

token.LSQB

"["

token.RSQB

"]"

token.COLON

":"

token.COMMA

","

token.SEMI

";"

token.PLUS

"+"

token.MINUS

"-"

token.STAR

"*"

token.SLASH

"/"

token.VBAR

"|"

token.AMPER

"&"

token.LESS

"<"

token.GREATER

">"

token.EQUAL

"="

token.DOT

"."

token.PERCENT

"%"

token.LBRACE

"{"

token.RBRACE

"}"

token.EQEQUAL

"=="

token.NOTEQUAL

"!="

token.LESSEQUAL

"<="

token.GREATEREQUAL

">="

token.TILDE

"~"

token.CIRCUMFLEX

"^"

token.LEFTSHIFT

"<<"

token.RIGHTSHIFT

">>"

token.DOUBLESTAR

"**"

token.PLUSEQUAL

"+="

token.MINEQUAL

"-="

token.STAREQUAL

"*="

token.SLASHEQUAL

"/="

token.PERCENTEQUAL

"%="

token.AMPEREQUAL

"&="

token.VBAREQUAL

"|="

token.CIRCUMFLEXEQUAL

"^="

token.LEFTSHIFTEQUAL

"<<="

token.RIGHTSHIFTEQUAL

">>="

token.DOUBLESTAREQUAL

"**="

token.DOUBLESLASH

"//"

token.DOUBLESLASHEQUAL

"//="

token.AT

"@"

token.ATEQUAL

"@="

token.RARROW

"->"

token.ELLIPSIS

"..."

token.COLONEQUAL

":="

token.EXCLAMATION

"!"

The following non-token constants are provided:

token.N_TOKENS

The number of token types defined in this module.

token.EXACT_TOKEN_TYPES

A dictionary mapping the string representation of a token to its numeric code.

在 3.8 版被加入.

在 3.5 版的變更: Added AWAIT and ASYNC tokens.

在 3.7 版的變更: Added COMMENT, NL and ENCODING tokens.

在 3.7 版的變更: Removed AWAIT and ASYNC tokens. "async" and "await" are now tokenized as NAME tokens.

在 3.8 版的變更: Added TYPE_COMMENT, TYPE_IGNORE, COLONEQUAL. Added AWAIT and ASYNC tokens back (they're needed to support parsing older Python versions for ast.parse() with feature_version set to 6 or lower).

在 3.12 版的變更: 新增 EXCLAMATION。

在 3.13 版的變更: Removed AWAIT and ASYNC tokens again.

keyword --- 檢驗 Python 關鍵字

原始碼：Lib/keyword.py [https://github.com/python/cpython/tree/3.14/Lib/keyword.py]

此模組允許 Python 程式確定某個字串是否為關鍵字 或軟關鍵字 (soft keyword)。

keyword.iskeyword(s)

如果 s 是一個 Python 關鍵字則回傳 True。

keyword.kwlist

包含直譯器定義的所有 關鍵字 的序列。如果所定義的任何關鍵字僅在特定 __future__ 陳述式生效時被啟用，它們也將被包含在內。

keyword.issoftkeyword(s)

如果 s 是一個 Python 軟關鍵字 則回傳 True。

在 3.9 版被加入.

keyword.softkwlist

包含直譯器定義的所有 軟關鍵字 的序列。如果所定義的任何軟關鍵字僅在特定 __future__ 陳述式生效時被啟用，它們也將被包含在內。

在 3.9 版被加入.

tokenize --- Tokenizer for Python source

原始碼：Lib/tokenize.py [https://github.com/python/cpython/tree/3.14/Lib/tokenize.py]

The tokenize module provides a lexical scanner for Python source code, implemented in Python. The scanner in this module returns comments as tokens as well, making it useful for implementing "pretty-printers", including colorizers for on-screen displays.

To simplify token stream handling, all operator and delimiter tokens and Ellipsis are returned using the generic OP token type. The exact type can be determined by checking the exact_type property on the named tuple returned from tokenize.tokenize().

警告

Note that the functions in this module are only designed to parse syntactically valid Python code (code that does not raise when parsed using ast.parse()). The behavior of the functions in this module is undefined when providing invalid Python code and it can change at any point.

Tokenizing Input

The primary entry point is a generator:

tokenize.tokenize(readline)

The tokenize() generator requires one argument, readline, which must be a callable object which provides the same interface as the io.IOBase.readline() method of file objects. Each call to the function should return one line of input as bytes.

The generator produces 5-tuples with these members: the token type; the token string; a 2-tuple (srow, scol) of ints specifying the row and column where the token begins in the source; a 2-tuple (erow, ecol) of ints specifying the row and column where the token ends in the source; and the line on which the token was found. The line passed (the last tuple item) is the physical line. The 5 tuple is returned as a named tuple with the field names: type string start end line.

The returned named tuple has an additional property named exact_type that contains the exact operator type for OP tokens. For all other token types exact_type equals the named tuple type field.

在 3.1 版的變更: 新增附名元組 (named tuple) 的支援。

在 3.3 版的變更: 新增 exact_type 的支援。

tokenize() determines the source encoding of the file by looking for a UTF-8 BOM or encoding cookie, according to PEP 263 [https://peps.python.org/pep-0263/].

tokenize.generate_tokens(readline)

Tokenize a source reading unicode strings instead of bytes.

Like tokenize(), the readline argument is a callable returning a single line of input. However, generate_tokens() expects readline to return a str object rather than bytes.

The result is an iterator yielding named tuples, exactly like tokenize(). It does not yield an ENCODING token.

All constants from the token module are also exported from tokenize.

Another function is provided to reverse the tokenization process. This is useful for creating tools that tokenize a script, modify the token stream, and write back the modified script.

tokenize.untokenize(iterable)

Converts tokens back into Python source code. The iterable must return sequences with at least two elements, the token type and the token string. Any additional sequence elements are ignored.

The result is guaranteed to tokenize back to match the input so that the conversion is lossless and round-trips are assured. The guarantee applies only to the token type and token string as the spacing between tokens (column positions) may change.

It returns bytes, encoded using the ENCODING token, which is the first token sequence output by tokenize(). If there is no encoding token in the input, it returns a str instead.

tokenize() needs to detect the encoding of source files it tokenizes. The function it uses to do this is available:

tokenize.detect_encoding(readline)

The detect_encoding() function is used to detect the encoding that should be used to decode a Python source file. It requires one argument, readline, in the same way as the tokenize() generator.

It will call readline a maximum of twice, and return the encoding used (as a string) and a list of any lines (not decoded from bytes) it has read in.

It detects the encoding from the presence of a UTF-8 BOM or an encoding cookie as specified in PEP 263 [https://peps.python.org/pep-0263/]. If both a BOM and a cookie are present, but disagree, a SyntaxError will be raised. Note that if the BOM is found, 'utf-8-sig' will be returned as an encoding.

If no encoding is specified, then the default of 'utf-8' will be returned.

Use open() to open Python source files: it uses detect_encoding() to detect the file encoding.

tokenize.open(filename)

Open a file in read only mode using the encoding detected by detect_encoding().

在 3.2 版被加入.

exception tokenize.TokenError

Raised when either a docstring or expression that may be split over several lines is not completed anywhere in the file, for example:

"""Beginning of
docstring

或是：

[1,
 2,
 3

命令列用法

在 3.3 版被加入.

The tokenize module can be executed as a script from the command line. It is as simple as:

python -m tokenize [-e] [filename.py]

可接受以下選項：

-h, --help

show this help message and exit

-e, --exact

display token names using the exact type

If filename.py is specified its contents are tokenized to stdout. Otherwise, tokenization is performed on stdin.

範例

Example of a script rewriter that transforms float literals into Decimal objects:

from tokenize import tokenize, untokenize, NUMBER, STRING, NAME, OP
from io import BytesIO

def decistmt(s):
    """Substitute Decimals for floats in a string of statements.

    >>> from decimal import Decimal
    >>> s = 'print(+21.3e-5*-.1234/81.7)'
    >>> decistmt(s)
    "print (+Decimal ('21.3e-5')*-Decimal ('.1234')/Decimal ('81.7'))"

    The format of the exponent is inherited from the platform C library.
    Known cases are "e-007" (Windows) and "e-07" (not Windows).  Since
    we're only showing 12 digits, and the 13th isn't close to 5, the
    rest of the output should be platform-independent.

    >>> exec(s)  #doctest: +ELLIPSIS
    -3.21716034272e-0...7

    Output from calculations with Decimal should be identical across all
    platforms.

    >>> exec(decistmt(s))
    -3.217160342717258261933904529E-7
    """
    result = []
    g = tokenize(BytesIO(s.encode('utf-8')).readline)  # tokenize the string
    for toknum, tokval, _, _, _ in g:
        if toknum == NUMBER and '.' in tokval:  # replace NUMBER tokens
            result.extend([
                (NAME, 'Decimal'),
                (OP, '('),
                (STRING, repr(tokval)),
                (OP, ')')
            ])
        else:
            result.append((toknum, tokval))
    return untokenize(result).decode('utf-8')

Example of tokenizing from the command line. The script:

def say_hello():
    print("Hello, World!")

say_hello()

will be tokenized to the following output where the first column is the range of the line/column coordinates where the token is found, the second column is the name of the token, and the final column is the value of the token (if any)

$ python -m tokenize hello.py
0,0-0,0:            ENCODING       'utf-8'
1,0-1,3:            NAME           'def'
1,4-1,13:           NAME           'say_hello'
1,13-1,14:          OP             '('
1,14-1,15:          OP             ')'
1,15-1,16:          OP             ':'
1,16-1,17:          NEWLINE        '\n'
2,0-2,4:            INDENT         '    '
2,4-2,9:            NAME           'print'
2,9-2,10:           OP             '('
2,10-2,25:          STRING         '"Hello, World!"'
2,25-2,26:          OP             ')'
2,26-2,27:          NEWLINE        '\n'
3,0-3,1:            NL             '\n'
4,0-4,0:            DEDENT         ''
4,0-4,9:            NAME           'say_hello'
4,9-4,10:           OP             '('
4,10-4,11:          OP             ')'
4,11-4,12:          NEWLINE        '\n'
5,0-5,0:            ENDMARKER      ''

The exact token type names can be displayed using the -e option:

$ python -m tokenize -e hello.py
0,0-0,0:            ENCODING       'utf-8'
1,0-1,3:            NAME           'def'
1,4-1,13:           NAME           'say_hello'
1,13-1,14:          LPAR           '('
1,14-1,15:          RPAR           ')'
1,15-1,16:          COLON          ':'
1,16-1,17:          NEWLINE        '\n'
2,0-2,4:            INDENT         '    '
2,4-2,9:            NAME           'print'
2,9-2,10:           LPAR           '('
2,10-2,25:          STRING         '"Hello, World!"'
2,25-2,26:          RPAR           ')'
2,26-2,27:          NEWLINE        '\n'
3,0-3,1:            NL             '\n'
4,0-4,0:            DEDENT         ''
4,0-4,9:            NAME           'say_hello'
4,9-4,10:           LPAR           '('
4,10-4,11:          RPAR           ')'
4,11-4,12:          NEWLINE        '\n'
5,0-5,0:            ENDMARKER      ''

Example of tokenizing a file programmatically, reading unicode strings instead of bytes with generate_tokens():

import tokenize

with tokenize.open('hello.py') as f:
    tokens = tokenize.generate_tokens(f.readline)
    for token in tokens:
        print(token)

Or reading bytes directly with tokenize():

import tokenize

with open('hello.py', 'rb') as f:
    tokens = tokenize.tokenize(f.readline)
    for token in tokens:
        print(token)

tabnanny --- 偵測不良縮排

原始碼：Lib/tabnanny.py [https://github.com/python/cpython/tree/3.14/Lib/tabnanny.py]

目前現況是此模組打算以腳本方式被呼叫使用，但也可以將其引入於 IDE 中並使用下方敘述的 check() 函式。

備註

此模組所提供的 API 很有可能會在未來的發佈版本中有所變更，且有可能不具有向後相容性。

tabnanny.check(file_or_dir)

如果 file_or_dir 是個目錄且並非符號鏈接 (symbolic link)，則會遞迴地在名為 file_or_dir 的目錄樹 (directory tree) 中不斷下行檢查所有 .py 檔案。如果 file_or_dir 是個一般 Python 原始檔案，則為其檢查空格相關問題。診斷訊息會以 print() 函式輸出至標準輸出 (standard output) 當中。

tabnanny.verbose

標示是否要印出詳細訊息 (verbose message) 的旗標，若是以腳本方式呼叫的話則可以用 -v 選項來增加。

tabnanny.filename_only

標示是否要只印出那些有空白相關問題檔案之檔名的旗標，若是以腳本方式呼叫的話則可以用 -q 選項來設為真值。

exception tabnanny.NannyNag

當偵測到不良縮排時，此例外會被 process_tokens() 引發，會在 check() 中捕獲與處理。

tabnanny.process_tokens(tokens)

此函式被 check() 用來處理由 tokenize 產生的標記 (token)。

也參考

tokenize 模組

Python 原始程式碼的詞彙掃描器 (lexical scanner)。

pyclbr --- Python 模組瀏覽器支援

原始碼：Lib/pyclbr.py [https://github.com/python/cpython/tree/3.14/Lib/pyclbr.py]

pyclbr 模組可以提供一個使用 Python 編寫的模組中定義的函式、類別和方法的有限資訊。這些資訊足以實作一個模組瀏覽器。這些資訊是從 Python 原始碼中抽取出來的，而不是透過引入模組，因此這個模組可以安全地與不信任的程式碼一起使用。此限制使得此模組無法與非 Python 實作的模組一起使用，包括所有標準與可選的擴充模組。

pyclbr.readmodule(module, path=None)

回傳模組層級的類別名稱與類別描述器對應的字典。如果可能的話，會包含引入基底類別的描述器。參數 module 是包含要讀取的模組名稱的字串；它可以是套件中的模組名稱。如果給定，path 是以 sys.path 為前綴的目錄路徑序列，用來定位模組原始碼。

此函式為原始介面，僅保留用於向後相容性。它回傳的會是 readmodule_ex 回傳結果的篩選後版本。

pyclbr.readmodule_ex(module, path=None)

回傳一個以字典為基礎的樹狀結構，包含在模組中以 def 或 class 陳述式定義的每個函式和類別的函式或類別描述器。回傳的字典會將模組層級的函式和類別名稱對映到它們的描述器。巢狀物件會輸入其父物件的子字典。與 readmodule 一樣，module 會指定要讀取的模組，而 path 則會預先加入 sys.path。如果要讀取的模組是一個套件，回傳的字典有一個 key '__path__'，其值是一個包含套件搜尋路徑的串列。

在 3.7 版被加入: 巢狀定義（nested definitions）的描述器。這些描述器可透過新的子屬性來存取。每個描述器都有一個新的父屬性。

這些函式所回傳的描述器是 Function 和 Class 類別的實例。使用者不需要建立這些類別的實例。

函式物件

class pyclbr.Function

Class Function 實例描述由 def 陳述式定義的函式。它們具有以下屬性：

file

定義函式的檔案名稱。

module

定義所述函式的模組名稱。

name

函式的名稱。

lineno

檔案中定義開始的行號。

parent

對於頂層函式（top-level functions）為 None。對於巢狀函式，則使用父函式。

在 3.7 版被加入.

children

一個 dictionary 將名稱對應到巢狀函式和類別的描述器。

在 3.7 版被加入.

is_async

對於使用 async 前綴定義的函式是 True，否則是 False。

在 3.10 版被加入.

類別物件

class pyclbr.Class

Class Class 實例描述由 class 陳述式定義的類別。它們具有與 Functions 相同的屬性，以及另外兩個屬性。

file

定義類別的檔案名稱。

module

定義所述類別的模組名稱。

name

類別的名稱。

lineno

檔案中定義開始的行號。

parent

對於頂層類別為 None。對於巢狀類別，則使用父類別。

在 3.7 版被加入.

children

將名稱對應到巢狀函式和類別的描述器的字典。

在 3.7 版被加入.

super

描述被描述類別的直接基底類別的 Class 物件串列。被命名為超類別（superclasses）但無法被 readmodule_ex() 發現的類別會以類別名稱的字串形式列出，而不是 Class 物件。

methods

一個 dictionary 方法名稱對應到行號。這可以從較新的 children 字典衍生出來，但為了向後相容性而保留。

py_compile — 編譯 Python 來源檔案

原始碼：Lib/py_compile.py [https://github.com/python/cpython/tree/3.14/Lib/py_compile.py]

The py_compile module provides a function to generate a byte-code file from a source file, and another function used when the module source file is invoked as a script.

Though not often needed, this function can be useful when installing modules for shared use, especially if some of the users may not have permission to write the byte-code cache files in the directory containing the source code.

exception py_compile.PyCompileError

Exception raised when an error occurs while attempting to compile the file.

py_compile.compile(file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP, quiet=0)

Compile a source file to byte-code and write out the byte-code cache file. The source code is loaded from the file named file. The byte-code is written to cfile, which defaults to the PEP 3147 [https://peps.python.org/pep-3147/]/PEP 488 [https://peps.python.org/pep-0488/] path, ending in .pyc. For example, if file is /foo/bar/baz.py cfile will default to /foo/bar/__pycache__/baz.cpython-32.pyc for Python 3.2. If dfile is specified, it is used instead of file as the name of the source file from which source lines are obtained for display in exception tracebacks. If doraise is true, a PyCompileError is raised when an error is encountered while compiling file. If doraise is false (the default), an error string is written to sys.stderr, but no exception is raised. This function returns the path to byte-compiled file, i.e. whatever cfile value was used.

The doraise and quiet arguments determine how errors are handled while compiling file. If quiet is 0 or 1, and doraise is false, the default behaviour is enabled: an error string is written to sys.stderr, and the function returns None instead of a path. If doraise is true, a PyCompileError is raised instead. However if quiet is 2, no message is written, and doraise has no effect.

If the path that cfile becomes (either explicitly specified or computed) is a symlink or non-regular file, FileExistsError will be raised. This is to act as a warning that import will turn those paths into regular files if it is allowed to write byte-compiled files to those paths. This is a side-effect of import using file renaming to place the final byte-compiled file into place to prevent concurrent file writing issues.

optimize controls the optimization level and is passed to the built-in compile() function. The default of -1 selects the optimization level of the current interpreter.

invalidation_mode should be a member of the PycInvalidationMode enum and controls how the generated bytecode cache is invalidated at runtime. The default is PycInvalidationMode.CHECKED_HASH if the SOURCE_DATE_EPOCH environment variable is set, otherwise the default is PycInvalidationMode.TIMESTAMP.

在 3.2 版的變更: Changed default value of cfile to be PEP 3147 [https://peps.python.org/pep-3147/]-compliant. Previous default was file + 'c' ('o' if optimization was enabled). Also added the optimize parameter.

在 3.4 版的變更: Changed code to use importlib for the byte-code cache file writing. This means file creation/writing semantics now match what importlib does, e.g. permissions, write-and-move semantics, etc. Also added the caveat that FileExistsError is raised if cfile is a symlink or non-regular file.

在 3.7 版的變更: The invalidation_mode parameter was added as specified in PEP 552 [https://peps.python.org/pep-0552/]. If the SOURCE_DATE_EPOCH environment variable is set, invalidation_mode will be forced to PycInvalidationMode.CHECKED_HASH.

在 3.7.2 版的變更: The SOURCE_DATE_EPOCH environment variable no longer overrides the value of the invalidation_mode argument, and determines its default value instead.

在 3.8 版的變更: 新增 quiet 參數。

class py_compile.PycInvalidationMode

An enumeration of possible methods the interpreter can use to determine whether a bytecode file is up to date with a source file. The .pyc file indicates the desired invalidation mode in its header. See Cached bytecode invalidation for more information on how Python invalidates .pyc files at runtime.

在 3.7 版被加入.

TIMESTAMP

The .pyc file includes the timestamp and size of the source file, which Python will compare against the metadata of the source file at runtime to determine if the .pyc file needs to be regenerated.

CHECKED_HASH

The .pyc file includes a hash of the source file content, which Python will compare against the source at runtime to determine if the .pyc file needs to be regenerated.

UNCHECKED_HASH

Like CHECKED_HASH, the .pyc file includes a hash of the source file content. However, Python will at runtime assume the .pyc file is up to date and not validate the .pyc against the source file at all.

This option is useful when the .pycs are kept up to date by some system external to Python like a build system.

命令列介面

This module can be invoked as a script to compile several source files. The files named in filenames are compiled and the resulting bytecode is cached in the normal manner. This program does not search a directory structure to locate source files; it only compiles files named explicitly. The exit status is nonzero if one of the files could not be compiled.

<file> ... <fileN>

-

Positional arguments are files to compile. If - is the only parameter, the list of files is taken from standard input.

-q, --quiet

Suppress errors output.

在 3.2 版的變更: 新增對 - 的支援。

在 3.10 版的變更: 新增對 -q 的支援。

也參考

compileall 模組

Utilities to compile all Python source files in a directory tree.

compileall --- 位元組編譯 Python 函式庫

原始碼：Lib/compileall.py [https://github.com/python/cpython/tree/3.14/Lib/compileall.py]

This module provides some utility functions to support installing Python libraries. These functions compile Python source files in a directory tree. This module can be used to create the cached byte-code files at library installation time, which makes them available for use even by users who don't have write permission to the library directories.

可用性: not WASI.

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

Command-line use

This module can work as a script (using python -m compileall) to compile Python sources.

directory ...

file ...

Positional arguments are files to compile or directories that contain source files, traversed recursively. If no argument is given, behave as if the command line was -l <directories from sys.path>.

-l

Do not recurse into subdirectories, only compile source code files directly contained in the named or implied directories.

-f

Force rebuild even if timestamps are up-to-date.

-q

Do not print the list of files compiled. If passed once, error messages will still be printed. If passed twice (-qq), all output is suppressed.

-d destdir

Directory prepended to the path to each file being compiled. This will appear in compilation time tracebacks, and is also compiled in to the byte-code file, where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte-code file is executed.

-s strip_prefix

Remove the given prefix from paths recorded in the .pyc files. Paths are made relative to the prefix.

This option can be used with -p but not with -d.

-p prepend_prefix

Prepend the given prefix to paths recorded in the .pyc files. Use -p / to make the paths absolute.

This option can be used with -s but not with -d.

-x regex

regex is used to search the full path to each file considered for compilation, and if the regex produces a match, the file is skipped.

-i list

Read the file list and add each line that it contains to the list of files and directories to compile. If list is -, read lines from stdin.

-b

Write the byte-code files to their legacy locations and names, which may overwrite byte-code files created by another version of Python. The default is to write files to their PEP 3147 [https://peps.python.org/pep-3147/] locations and names, which allows byte-code files from multiple versions of Python to coexist.

-r

Control the maximum recursion level for subdirectories. If this is given, then -l option will not be taken into account. python -m compileall <directory> -r 0 is equivalent to python -m compileall <directory> -l.

-j N

Use N workers to compile the files within the given directory. If 0 is used, then the result of os.process_cpu_count() will be used.

--invalidation-mode [timestamp|checked-hash|unchecked-hash]

Control how the generated byte-code files are invalidated at runtime. The timestamp value, means that .pyc files with the source timestamp and size embedded will be generated. The checked-hash and unchecked-hash values cause hash-based pycs to be generated. Hash-based pycs embed a hash of the source file contents rather than a timestamp. See Cached bytecode invalidation for more information on how Python validates bytecode cache files at runtime. The default is timestamp if the SOURCE_DATE_EPOCH environment variable is not set, and checked-hash if the SOURCE_DATE_EPOCH environment variable is set.

-o level

Compile with the given optimization level. May be used multiple times to compile for multiple levels at a time (for example, compileall -o 1 -o 2).

-e dir

Ignore symlinks pointing outside the given directory.

--hardlink-dupes

If two .pyc files with different optimization level have the same content, use hard links to consolidate duplicate files.

在 3.2 版的變更: 新增選項 -i、-b 與 -h。

在 3.5 版的變更: Added the -j, -r, and -qq options. -q option was changed to a multilevel value. -b will always produce a byte-code file ending in .pyc, never .pyo.

在 3.7 版的變更: 新增選項 --invalidation-mode。

在 3.9 版的變更: Added the -s, -p, -e and --hardlink-dupes options. Raised the default recursion limit from 10 to sys.getrecursionlimit(). Added the possibility to specify the -o option multiple times.

There is no command-line option to control the optimization level used by the compile() function, because the Python interpreter itself already provides the option: python -O -m compileall.

Similarly, the compile() function respects the sys.pycache_prefix setting. The generated bytecode cache will only be useful if compile() is run with the same sys.pycache_prefix (if any) that will be used at runtime.

Public functions

compileall.compile_dir(dir, maxlevels=sys.getrecursionlimit(), ddir=None, force=False, rx=None, quiet=0, legacy=False, optimize=-1, workers=1, invalidation_mode=None, *, stripdir=None, prependdir=None, limit_sl_dest=None, hardlink_dupes=False)

Recursively descend the directory tree named by dir, compiling all .py files along the way. Return a true value if all the files compiled successfully, and a false value otherwise.

The maxlevels parameter is used to limit the depth of the recursion; it defaults to sys.getrecursionlimit().

If ddir is given, it is prepended to the path to each file being compiled for use in compilation time tracebacks, and is also compiled in to the byte-code file, where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte-code file is executed.

If force is true, modules are re-compiled even if the timestamps are up to date.

If rx is given, its search method is called on the complete path to each file considered for compilation, and if it returns a true value, the file is skipped. This can be used to exclude files matching a regular expression, given as a re.Pattern object.

If quiet is False or 0 (the default), the filenames and other information are printed to standard out. Set to 1, only errors are printed. Set to 2, all output is suppressed.

If legacy is true, byte-code files are written to their legacy locations and names, which may overwrite byte-code files created by another version of Python. The default is to write files to their PEP 3147 [https://peps.python.org/pep-3147/] locations and names, which allows byte-code files from multiple versions of Python to coexist.

optimize specifies the optimization level for the compiler. It is passed to the built-in compile() function. Accepts also a sequence of optimization levels which lead to multiple compilations of one .py file in one call.

The argument workers specifies how many workers are used to compile files in parallel. The default is to not use multiple workers. If the platform can't use multiple workers and workers argument is given, then sequential compilation will be used as a fallback. If workers is 0, the number of cores in the system is used. If workers is lower than 0, a ValueError will be raised.

invalidation_mode should be a member of the py_compile.PycInvalidationMode enum and controls how the generated pycs are invalidated at runtime.

The stripdir, prependdir and limit_sl_dest arguments correspond to the -s, -p and -e options described above. They may be specified as str or os.PathLike.

If hardlink_dupes is true and two .pyc files with different optimization level have the same content, use hard links to consolidate duplicate files.

在 3.2 版的變更: 新增 legacy 與 optimize 參數。

在 3.5 版的變更: 新增 workers 參數。

在 3.5 版的變更: quiet parameter was changed to a multilevel value.

在 3.5 版的變更: The legacy parameter only writes out .pyc files, not .pyo files no matter what the value of optimize is.

在 3.6 版的變更: Accepts a path-like object.

在 3.7 版的變更: 新增 invalidation_mode 參數。

在 3.7.2 版的變更: 新增 invalidation_mode 參數的預設值被更新為 None。

在 3.8 版的變更: Setting workers to 0 now chooses the optimal number of cores.

在 3.9 版的變更: Added stripdir, prependdir, limit_sl_dest and hardlink_dupes arguments. Default value of maxlevels was changed from 10 to sys.getrecursionlimit()

compileall.compile_file(fullname, ddir=None, force=False, rx=None, quiet=0, legacy=False, optimize=-1, invalidation_mode=None, *, stripdir=None, prependdir=None, limit_sl_dest=None, hardlink_dupes=False)

Compile the file with path fullname. Return a true value if the file compiled successfully, and a false value otherwise.

If ddir is given, it is prepended to the path to the file being compiled for use in compilation time tracebacks, and is also compiled in to the byte-code file, where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte-code file is executed.

If rx is given, its search method is passed the full path name to the file being compiled, and if it returns a true value, the file is not compiled and True is returned. This can be used to exclude files matching a regular expression, given as a re.Pattern object.

If quiet is False or 0 (the default), the filenames and other information are printed to standard out. Set to 1, only errors are printed. Set to 2, all output is suppressed.

If legacy is true, byte-code files are written to their legacy locations and names, which may overwrite byte-code files created by another version of Python. The default is to write files to their PEP 3147 [https://peps.python.org/pep-3147/] locations and names, which allows byte-code files from multiple versions of Python to coexist.

optimize specifies the optimization level for the compiler. It is passed to the built-in compile() function. Accepts also a sequence of optimization levels which lead to multiple compilations of one .py file in one call.

invalidation_mode should be a member of the py_compile.PycInvalidationMode enum and controls how the generated pycs are invalidated at runtime.

The stripdir, prependdir and limit_sl_dest arguments correspond to the -s, -p and -e options described above. They may be specified as str or os.PathLike.

If hardlink_dupes is true and two .pyc files with different optimization level have the same content, use hard links to consolidate duplicate files.

在 3.2 版被加入.

在 3.5 版的變更: quiet parameter was changed to a multilevel value.

在 3.5 版的變更: The legacy parameter only writes out .pyc files, not .pyo files no matter what the value of optimize is.

在 3.7 版的變更: 新增 invalidation_mode 參數。

在 3.7.2 版的變更: 新增 invalidation_mode 參數的預設值被更新為 None。

在 3.9 版的變更: Added stripdir, prependdir, limit_sl_dest and hardlink_dupes arguments.

compileall.compile_path(skip_curdir=True, maxlevels=0, force=False, quiet=0, legacy=False, optimize=-1, invalidation_mode=None)

Byte-compile all the .py files found along sys.path. Return a true value if all the files compiled successfully, and a false value otherwise.

If skip_curdir is true (the default), the current directory is not included in the search. All other parameters are passed to the compile_dir() function. Note that unlike the other compile functions, maxlevels defaults to 0.

在 3.2 版的變更: 新增 legacy 與 optimize 參數。

在 3.5 版的變更: quiet parameter was changed to a multilevel value.

在 3.5 版的變更: The legacy parameter only writes out .pyc files, not .pyo files no matter what the value of optimize is.

在 3.7 版的變更: 新增 invalidation_mode 參數。

在 3.7.2 版的變更: 新增 invalidation_mode 參數的預設值被更新為 None。

To force a recompile of all the .py files in the Lib/ subdirectory and all its subdirectories:

import compileall

compileall.compile_dir('Lib/', force=True)

# 執行相同的編譯，但排除 .svn 目錄中的檔案。
import re
compileall.compile_dir('Lib/', rx=re.compile(r'[/\\][.]svn'), force=True)

# pathlib.Path 物件也可以使用。
import pathlib
compileall.compile_dir(pathlib.Path('Lib/'), force=True)

也參考

py_compile 模組

Byte-compile a single source file.

dis --- Python bytecode 的反組譯器

原始碼：Lib/dis.py [https://github.com/python/cpython/tree/3.14/Lib/dis.py]

dis 模組支援反組譯分析 CPython bytecode。CPython bytecode 作為輸入的模組被定義於 Include/opcode.h 並且被編譯器和直譯器所使用。

CPython 實作細節： Bytecode is an implementation detail of the CPython interpreter. No guarantees are made that bytecode will not be added, removed, or changed between versions of Python. Use of this module should not be considered to work across Python VMs or Python releases.

在 3.6 版的變更: Use 2 bytes for each instruction. Previously the number of bytes varied by instruction.

在 3.10 版的變更: The argument of jump, exception handling and loop instructions is now the instruction offset rather than the byte offset.

在 3.11 版的變更: Some instructions are accompanied by one or more inline cache entries, which take the form of CACHE instructions. These instructions are hidden by default, but can be shown by passing show_caches=True to any dis utility. Furthermore, the interpreter now adapts the bytecode to specialize it for different runtime conditions. The adaptive bytecode can be shown by passing adaptive=True.

在 3.12 版的變更: The argument of a jump is the offset of the target instruction relative to the instruction that appears immediately after the jump instruction's CACHE entries.

As a consequence, the presence of the CACHE instructions is transparent for forward jumps but needs to be taken into account when reasoning about backward jumps.

在 3.13 版的變更: The output shows logical labels rather than instruction offsets for jump targets and exception handlers. The -O command line option and the show_offsets argument were added.

在 3.14 版的變更: The -P command-line option and the show_positions argument were added.

The -S command-line option is added.

Example: Given the function myfunc():

def myfunc(alist):
    return len(alist)

可以使用以下指令來顯示 myfunc() 的反組譯：

>>> dis.dis(myfunc)
  2           RESUME                   0

  3           LOAD_GLOBAL              1 (len + NULL)
              LOAD_FAST_BORROW         0 (alist)
              CALL                     1
              RETURN_VALUE

(The "2" is a line number).

命令列介面

The dis module can be invoked as a script from the command line:

python -m dis [-h] [-C] [-O] [-P] [-S] [infile]

可接受以下選項：

-h, --help

Display usage and exit.

-C, --show-caches

Show inline caches.

在 3.13 版被加入.

-O, --show-offsets

Show offsets of instructions.

在 3.13 版被加入.

-P, --show-positions

Show positions of instructions in the source code.

在 3.14 版被加入.

-S, --specialized

Show specialized bytecode.

在 3.14 版被加入.

If infile is specified, its disassembled code will be written to stdout. Otherwise, disassembly is performed on compiled source code received from stdin.

Bytecode analysis

在 3.4 版被加入.

The bytecode analysis API allows pieces of Python code to be wrapped in a Bytecode object that provides easy access to details of the compiled code.

class dis.Bytecode(x, *, first_line=None, current_offset=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)

Analyse the bytecode corresponding to a function, generator, asynchronous generator, coroutine, method, string of source code, or a code object (as returned by compile()).

This is a convenience wrapper around many of the functions listed below, most notably get_instructions(), as iterating over a Bytecode instance yields the bytecode operations as Instruction instances.

If first_line is not None, it indicates the line number that should be reported for the first source line in the disassembled code. Otherwise, the source line information (if any) is taken directly from the disassembled code object.

If current_offset is not None, it refers to an instruction offset in the disassembled code. Setting this means dis() will display a "current instruction" marker against the specified opcode.

If show_caches is True, dis() will display inline cache entries used by the interpreter to specialize the bytecode.

If adaptive is True, dis() will display specialized bytecode that may be different from the original bytecode.

If show_offsets is True, dis() will include instruction offsets in the output.

If show_positions is True, dis() will include instruction source code positions in the output.

classmethod from_traceback(tb, *, show_caches=False)

Construct a Bytecode instance from the given traceback, setting current_offset to the instruction responsible for the exception.

codeobj

The compiled code object.

first_line

The first source line of the code object (if available)

dis()

Return a formatted view of the bytecode operations (the same as printed by dis.dis(), but returned as a multi-line string).

info()

Return a formatted multi-line string with detailed information about the code object, like code_info().

在 3.7 版的變更: This can now handle coroutine and asynchronous generator objects.

在 3.11 版的變更: 新增 show_caches 與 adaptive 參數。

在 3.13 版的變更: 新增 show_offsets 參數。

在 3.14 版的變更: 新增 show_positions 參數。

範例：

>>> bytecode = dis.Bytecode(myfunc)
>>> for instr in bytecode:
...     print(instr.opname)
...
RESUME
LOAD_GLOBAL
LOAD_FAST_BORROW
CALL
RETURN_VALUE

分析函式

The dis module also defines the following analysis functions that convert the input directly to the desired output. They can be useful if only a single operation is being performed, so the intermediate analysis object isn't useful:

dis.code_info(x)

Return a formatted multi-line string with detailed code object information for the supplied function, generator, asynchronous generator, coroutine, method, source code string or code object.

Note that the exact contents of code info strings are highly implementation dependent and they may change arbitrarily across Python VMs or Python releases.

在 3.2 版被加入.

在 3.7 版的變更: This can now handle coroutine and asynchronous generator objects.

dis.show_code(x, *, file=None)

Print detailed code object information for the supplied function, method, source code string or code object to file (or sys.stdout if file is not specified).

This is a convenient shorthand for print(code_info(x), file=file), intended for interactive exploration at the interpreter prompt.

在 3.2 版被加入.

在 3.4 版的變更: 新增 file 參數。

dis.dis(x=None, *, file=None, depth=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)

Disassemble the x object. x can denote either a module, a class, a method, a function, a generator, an asynchronous generator, a coroutine, a code object, a string of source code or a byte sequence of raw bytecode. For a module, it disassembles all functions. For a class, it disassembles all methods (including class and static methods). For a code object or sequence of raw bytecode, it prints one line per bytecode instruction. It also recursively disassembles nested code objects. These can include generator expressions, nested functions, the bodies of nested classes, and the code objects used for annotation scopes. Strings are first compiled to code objects with the compile() built-in function before being disassembled. If no object is provided, this function disassembles the last traceback.

The disassembly is written as text to the supplied file argument if provided and to sys.stdout otherwise.

The maximal depth of recursion is limited by depth unless it is None. depth=0 means no recursion.

If show_caches is True, this function will display inline cache entries used by the interpreter to specialize the bytecode.

If adaptive is True, this function will display specialized bytecode that may be different from the original bytecode.

在 3.4 版的變更: 新增 file 參數。

在 3.7 版的變更: Implemented recursive disassembling and added depth parameter.

在 3.7 版的變更: This can now handle coroutine and asynchronous generator objects.

在 3.11 版的變更: 新增 show_caches 與 adaptive 參數。

在 3.13 版的變更: 新增 show_offsets 參數。

在 3.14 版的變更: 新增 show_positions 參數。

dis.distb(tb=None, *, file=None, show_caches=False, adaptive=False, show_offset=False, show_positions=False)

Disassemble the top-of-stack function of a traceback, using the last traceback if none was passed. The instruction causing the exception is indicated.

The disassembly is written as text to the supplied file argument if provided and to sys.stdout otherwise.

在 3.4 版的變更: 新增 file 參數。

在 3.11 版的變更: 新增 show_caches 與 adaptive 參數。

在 3.13 版的變更: 新增 show_offsets 參數。

在 3.14 版的變更: 新增 show_positions 參數。

dis.disassemble(code, lasti=-1, *, file=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)

dis.disco(code, lasti=-1, *, file=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)

Disassemble a code object, indicating the last instruction if lasti was provided. The output is divided in the following columns:

the source code location of the instruction. Complete location information is shown if show_positions is true. Otherwise (the default) only the line number is displayed.

the current instruction, indicated as -->,

a labelled instruction, indicated with >>,

the address of the instruction,

the operation code name,

operation parameters, and

interpretation of the parameters in parentheses.

The parameter interpretation recognizes local and global variable names, constant values, branch targets, and compare operators.

The disassembly is written as text to the supplied file argument if provided and to sys.stdout otherwise.

在 3.4 版的變更: 新增 file 參數。

在 3.11 版的變更: 新增 show_caches 與 adaptive 參數。

在 3.13 版的變更: 新增 show_offsets 參數。

在 3.14 版的變更: 新增 show_positions 參數。

dis.get_instructions(x, *, first_line=None, show_caches=False, adaptive=False)

Return an iterator over the instructions in the supplied function, method, source code string or code object.

The iterator generates a series of Instruction named tuples giving the details of each operation in the supplied code.

If first_line is not None, it indicates the line number that should be reported for the first source line in the disassembled code. Otherwise, the source line information (if any) is taken directly from the disassembled code object.

The adaptive parameter works as it does in dis().

在 3.4 版被加入.

在 3.11 版的變更: 新增 show_caches 與 adaptive 參數。

在 3.13 版的變更: The show_caches parameter is deprecated and has no effect. The iterator generates the Instruction instances with the cache_info field populated (regardless of the value of show_caches) and it no longer generates separate items for the cache entries.

dis.findlinestarts(code)

This generator function uses the co_lines() method of the code object code to find the offsets which are starts of lines in the source code. They are generated as (offset, lineno) pairs.

在 3.6 版的變更: Line numbers can be decreasing. Before, they were always increasing.

在 3.10 版的變更: The PEP 626 [https://peps.python.org/pep-0626/] co_lines() method is used instead of the co_firstlineno and co_lnotab attributes of the code object.

在 3.13 版的變更: Line numbers can be None for bytecode that does not map to source lines.

dis.findlabels(code)

Detect all offsets in the raw compiled bytecode string code which are jump targets, and return a list of these offsets.

dis.stack_effect(opcode, oparg=None, *, jump=None)

Compute the stack effect of opcode with argument oparg.

If the code has a jump target and jump is True, stack_effect() will return the stack effect of jumping. If jump is False, it will return the stack effect of not jumping. And if jump is None (default), it will return the maximal stack effect of both cases.

在 3.4 版被加入.

在 3.8 版的變更: 新增 jump 參數。

在 3.13 版的變更: If oparg is omitted (or None), the stack effect is now returned for oparg=0. Previously this was an error for opcodes that use their arg. It is also no longer an error to pass an integer oparg when the opcode does not use it; the oparg in this case is ignored.

Python 位元組碼指令

The get_instructions() function and Bytecode class provide details of bytecode instructions as Instruction instances:

class dis.Instruction

位元組碼操作的詳細資訊

opcode

numeric code for operation, corresponding to the opcode values listed below and the bytecode values in the Opcode collections.

opname

操作的可讀名稱

baseopcode

numeric code for the base operation if operation is specialized; otherwise equal to opcode

baseopname

human readable name for the base operation if operation is specialized; otherwise equal to opname

arg

numeric argument to operation (if any), otherwise None

oparg

arg 的別名。

argval

resolved arg value (if any), otherwise None

argrepr

human readable description of operation argument (if any), otherwise an empty string.

offset

start index of operation within bytecode sequence

start_offset

start index of operation within bytecode sequence, including prefixed EXTENDED_ARG operations if present; otherwise equal to offset

cache_offset

start index of the cache entries following the operation

end_offset

end index of the cache entries following the operation

starts_line

True if this opcode starts a source line, otherwise False

line_number

source line number associated with this opcode (if any), otherwise None

is_jump_target

True if other code jumps to here, otherwise False

jump_target

bytecode index of the jump target if this is a jump operation, otherwise None

positions

dis.Positions object holding the start and end locations that are covered by this instruction.

cache_info

Information about the cache entries of this instruction, as triplets of the form (name, size, data), where the name and size describe the cache format and data is the contents of the cache. cache_info is None if the instruction does not have caches.

在 3.4 版被加入.

在 3.11 版的變更: Field positions is added.

在 3.13 版的變更: Changed field starts_line.

Added fields start_offset, cache_offset, end_offset, baseopname, baseopcode, jump_target, oparg, line_number and cache_info.

class dis.Positions

In case the information is not available, some fields might be None.

lineno

end_lineno

col_offset

end_col_offset

在 3.11 版被加入.

The Python compiler currently generates the following bytecode instructions.

一般指令

In the following, We will refer to the interpreter stack as STACK and describe operations on it as if it was a Python list. The top of the stack corresponds to STACK[-1] in this language.

NOP

Do nothing code. Used as a placeholder by the bytecode optimizer, and to generate line tracing events.

NOT_TAKEN

Do nothing code. Used by the interpreter to record BRANCH_LEFT and BRANCH_RIGHT events for sys.monitoring.

在 3.14 版被加入.

POP_ITER

Removes the iterator from the top of the stack.

在 3.14 版被加入.

POP_TOP

Removes the top-of-stack item:

STACK.pop()

END_FOR

Removes the top-of-stack item. Equivalent to POP_TOP. Used to clean up at the end of loops, hence the name.

在 3.12 版被加入.

END_SEND

Implements del STACK[-2]. Used to clean up when a generator exits.

在 3.12 版被加入.

COPY(i)

Push the i-th item to the top of the stack without removing it from its original location:

assert i > 0
STACK.append(STACK[-i])

在 3.11 版被加入.

SWAP(i)

Swap the top of the stack with the i-th element:

STACK[-i], STACK[-1] = STACK[-1], STACK[-i]

在 3.11 版被加入.

CACHE

Rather than being an actual instruction, this opcode is used to mark extra space for the interpreter to cache useful data directly in the bytecode itself. It is automatically hidden by all dis utilities, but can be viewed with show_caches=True.

Logically, this space is part of the preceding instruction. Many opcodes expect to be followed by an exact number of caches, and will instruct the interpreter to skip over them at runtime.

Populated caches can look like arbitrary instructions, so great care should be taken when reading or modifying raw, adaptive bytecode containing quickened data.

在 3.11 版被加入.

Unary operations

Unary operations take the top of the stack, apply the operation, and push the result back on the stack.

UNARY_NEGATIVE

實作 STACK[-1] = -STACK[-1]。

UNARY_NOT

實作 STACK[-1] = not STACK[-1]。

在 3.13 版的變更: This instruction now requires an exact bool operand.

UNARY_INVERT

實作 STACK[-1] = ~STACK[-1]。

GET_ITER

實作 STACK[-1] = iter(STACK[-1])。

GET_YIELD_FROM_ITER

If STACK[-1] is a generator iterator or coroutine object it is left as is. Otherwise, implements STACK[-1] = iter(STACK[-1]).

在 3.5 版被加入.

TO_BOOL

Implements STACK[-1] = bool(STACK[-1]).

在 3.13 版被加入.

Binary and in-place operations

Binary operations remove the top two items from the stack (STACK[-1] and STACK[-2]). They perform the operation, then put the result back on the stack.

In-place operations are like binary operations, but the operation is done in-place when STACK[-2] supports it, and the resulting STACK[-1] may be (but does not have to be) the original STACK[-2].

BINARY_OP(op)

Implements the binary and in-place operators (depending on the value of op):

rhs = STACK.pop()
lhs = STACK.pop()
STACK.append(lhs op rhs)

在 3.11 版被加入.

在 3.14 版的變更: With oparg :NB_SUBSCR, implements binary subscript (replaces opcode BINARY_SUBSCR)

STORE_SUBSCR

實作了：

key = STACK.pop()
container = STACK.pop()
value = STACK.pop()
container[key] = value

DELETE_SUBSCR

實作了：

key = STACK.pop()
container = STACK.pop()
del container[key]

BINARY_SLICE

實作了：

end = STACK.pop()
start = STACK.pop()
container = STACK.pop()
STACK.append(container[start:end])

在 3.12 版被加入.

STORE_SLICE

實作了：

end = STACK.pop()
start = STACK.pop()
container = STACK.pop()
value = STACK.pop()
container[start:end] = value

在 3.12 版被加入.

Coroutine opcodes

GET_AWAITABLE(where)

Implements STACK[-1] = get_awaitable(STACK[-1]), where get_awaitable(o) returns o if o is a coroutine object or a generator object with the CO_ITERABLE_COROUTINE flag, or resolves o.__await__.

If the where operand is nonzero, it indicates where the instruction occurs:

1: After a call to __aenter__

2: After a call to __aexit__

在 3.5 版被加入.

在 3.11 版的變更: 先前此指令沒有 oparg。

GET_AITER

Implements STACK[-1] = STACK[-1].__aiter__().

在 3.5 版被加入.

在 3.7 版的變更: Returning awaitable objects from __aiter__ is no longer supported.

GET_ANEXT

Implement STACK.append(get_awaitable(STACK[-1].__anext__())) to the stack. See GET_AWAITABLE for details about get_awaitable.

在 3.5 版被加入.

END_ASYNC_FOR

Terminates an async for loop. Handles an exception raised when awaiting a next item. The stack contains the async iterable in STACK[-2] and the raised exception in STACK[-1]. Both are popped. If the exception is not StopAsyncIteration, it is re-raised.

在 3.8 版被加入.

在 3.11 版的變更: Exception representation on the stack now consist of one, not three, items.

CLEANUP_THROW

Handles an exception raised during a throw() or close() call through the current frame. If STACK[-1] is an instance of StopIteration, pop three values from the stack and push its value member. Otherwise, re-raise STACK[-1].

在 3.12 版被加入.

Miscellaneous opcodes

SET_ADD(i)

實作了：

item = STACK.pop()
set.add(STACK[-i], item)

Used to implement set comprehensions.

LIST_APPEND(i)

實作了：

item = STACK.pop()
list.append(STACK[-i], item)

Used to implement list comprehensions.

MAP_ADD(i)

實作了：

value = STACK.pop()
key = STACK.pop()
dict.__setitem__(STACK[-i], key, value)

Used to implement dict comprehensions.

在 3.1 版被加入.

在 3.8 版的變更: Map value is STACK[-1] and map key is STACK[-2]. Before, those were reversed.

For all of the SET_ADD, LIST_APPEND and MAP_ADD instructions, while the added value or key/value pair is popped off, the container object remains on the stack so that it is available for further iterations of the loop.

RETURN_VALUE

Returns with STACK[-1] to the caller of the function.

YIELD_VALUE

Yields STACK.pop() from a generator.

在 3.11 版的變更: oparg set to be the stack depth.

在 3.12 版的變更: oparg set to be the exception block depth, for efficient closing of generators.

在 3.13 版的變更: oparg is 1 if this instruction is part of a yield-from or await, and 0 otherwise.

SETUP_ANNOTATIONS

Checks whether __annotations__ is defined in locals(), if not it is set up to an empty dict. This opcode is only emitted if a class or module body contains variable annotations statically.

在 3.6 版被加入.

POP_EXCEPT

Pops a value from the stack, which is used to restore the exception state.

在 3.11 版的變更: Exception representation on the stack now consist of one, not three, items.

RERAISE

Re-raises the exception currently on top of the stack. If oparg is non-zero, pops an additional value from the stack which is used to set f_lasti of the current frame.

在 3.9 版被加入.

在 3.11 版的變更: Exception representation on the stack now consist of one, not three, items.

PUSH_EXC_INFO

Pops a value from the stack. Pushes the current exception to the top of the stack. Pushes the value originally popped back to the stack. Used in exception handlers.

在 3.11 版被加入.

CHECK_EXC_MATCH

Performs exception matching for except. Tests whether the STACK[-2] is an exception matching STACK[-1]. Pops STACK[-1] and pushes the boolean result of the test.

在 3.11 版被加入.

CHECK_EG_MATCH

Performs exception matching for except*. Applies split(STACK[-1]) on the exception group representing STACK[-2].

In case of a match, pops two items from the stack and pushes the non-matching subgroup (None in case of full match) followed by the matching subgroup. When there is no match, pops one item (the match type) and pushes None.

在 3.11 版被加入.

WITH_EXCEPT_START

Calls the function in position 4 on the stack with arguments (type, val, tb) representing the exception at the top of the stack. Used to implement the call context_manager.__exit__(*exc_info()) when an exception has occurred in a with statement.

在 3.9 版被加入.

在 3.11 版的變更: The __exit__ function is in position 4 of the stack rather than 7. Exception representation on the stack now consist of one, not three, items.

LOAD_COMMON_CONSTANT

Pushes a common constant onto the stack. The interpreter contains a hardcoded list of constants supported by this instruction. Used by the assert statement to load AssertionError.

在 3.14 版被加入.

LOAD_BUILD_CLASS

Pushes builtins.__build_class__() onto the stack. It is later called to construct a class.

GET_LEN

Perform STACK.append(len(STACK[-1])). Used in match statements where comparison with structure of pattern is needed.

在 3.10 版被加入.

MATCH_MAPPING

If STACK[-1] is an instance of collections.abc.Mapping (or, more technically: if it has the Py_TPFLAGS_MAPPING flag set in its tp_flags), push True onto the stack. Otherwise, push False.

在 3.10 版被加入.

MATCH_SEQUENCE

If STACK[-1] is an instance of collections.abc.Sequence and is not an instance of str/bytes/bytearray (or, more technically: if it has the Py_TPFLAGS_SEQUENCE flag set in its tp_flags), push True onto the stack. Otherwise, push False.

在 3.10 版被加入.

MATCH_KEYS

STACK[-1] is a tuple of mapping keys, and STACK[-2] is the match subject. If STACK[-2] contains all of the keys in STACK[-1], push a tuple containing the corresponding values. Otherwise, push None.

在 3.10 版被加入.

在 3.11 版的變更: Previously, this instruction also pushed a boolean value indicating success (True) or failure (False).

STORE_NAME(namei)

Implements name = STACK.pop(). namei is the index of name in the attribute co_names of the code object. The compiler tries to use STORE_FAST or STORE_GLOBAL if possible.

DELETE_NAME(namei)

Implements del name, where namei is the index into co_names attribute of the code object.

UNPACK_SEQUENCE(count)

Unpacks STACK[-1] into count individual values, which are put onto the stack right-to-left. Require there to be exactly count values.:

assert(len(STACK[-1]) == count)
STACK.extend(STACK.pop()[:-count-1:-1])

UNPACK_EX(counts)

Implements assignment with a starred target: Unpacks an iterable in STACK[-1] into individual values, where the total number of values can be smaller than the number of items in the iterable: one of the new values will be a list of all leftover items.

The number of values before and after the list value is limited to 255.

The number of values before the list value is encoded in the argument of the opcode. The number of values after the list if any is encoded using an EXTENDED_ARG. As a consequence, the argument can be seen as a two bytes values where the low byte of counts is the number of values before the list value, the high byte of counts the number of values after it.

The extracted values are put onto the stack right-to-left, i.e. a, *b, c = d will be stored after execution as STACK.extend((a, b, c)).

STORE_ATTR(namei)

實作了：

obj = STACK.pop()
value = STACK.pop()
obj.name = value

where namei is the index of name in co_names of the code object.

DELETE_ATTR(namei)

實作了：

obj = STACK.pop()
del obj.name

where namei is the index of name into co_names of the code object.

STORE_GLOBAL(namei)

Works as STORE_NAME, but stores the name as a global.

DELETE_GLOBAL(namei)

Works as DELETE_NAME, but deletes a global name.

LOAD_CONST(consti)

Pushes co_consts[consti] onto the stack.

LOAD_SMALL_INT(i)

Pushes the integer i onto the stack. i must be in range(256)

在 3.14 版被加入.

LOAD_NAME(namei)

Pushes the value associated with co_names[namei] onto the stack. The name is looked up within the locals, then the globals, then the builtins.

LOAD_LOCALS

Pushes a reference to the locals dictionary onto the stack. This is used to prepare namespace dictionaries for LOAD_FROM_DICT_OR_DEREF and LOAD_FROM_DICT_OR_GLOBALS.

在 3.12 版被加入.

LOAD_FROM_DICT_OR_GLOBALS(i)

Pops a mapping off the stack and looks up the value for co_names[namei]. If the name is not found there, looks it up in the globals and then the builtins, similar to LOAD_GLOBAL. This is used for loading global variables in annotation scopes within class bodies.

在 3.12 版被加入.

BUILD_TEMPLATE

Constructs a new Template instance from a tuple of strings and a tuple of interpolations and pushes the resulting object onto the stack:

interpolations = STACK.pop()
strings = STACK.pop()
STACK.append(_build_template(strings, interpolations))

在 3.14 版被加入.

BUILD_INTERPOLATION(format)

Constructs a new Interpolation instance from a value and its source expression and pushes the resulting object onto the stack.

If no conversion or format specification is present, format is set to 2.

If the low bit of format is set, it indicates that the interpolation contains a format specification.

If format >> 2 is non-zero, it indicates that the interpolation contains a conversion. The value of format >> 2 is the conversion type (0 for no conversion, 1 for !s, 2 for !r, and 3 for !a):

conversion = format >> 2
if format & 1:
    format_spec = STACK.pop()
else:
    format_spec = None
expression = STACK.pop()
value = STACK.pop()
STACK.append(_build_interpolation(value, expression, conversion, format_spec))

在 3.14 版被加入.

BUILD_TUPLE(count)

Creates a tuple consuming count items from the stack, and pushes the resulting tuple onto the stack:

if count == 0:
    value = ()
else:
    value = tuple(STACK[-count:])
    STACK = STACK[:-count]

STACK.append(value)

BUILD_LIST(count)

Works as BUILD_TUPLE, but creates a list.

BUILD_SET(count)

Works as BUILD_TUPLE, but creates a set.

BUILD_MAP(count)

Pushes a new dictionary object onto the stack. Pops 2 * count items so that the dictionary holds count entries: {..., STACK[-4]: STACK[-3], STACK[-2]: STACK[-1]}.

在 3.5 版的變更: The dictionary is created from stack items instead of creating an empty dictionary pre-sized to hold count items.

BUILD_STRING(count)

Concatenates count strings from the stack and pushes the resulting string onto the stack.

在 3.6 版被加入.

LIST_EXTEND(i)

實作了：

seq = STACK.pop()
list.extend(STACK[-i], seq)

Used to build lists.

在 3.9 版被加入.

SET_UPDATE(i)

實作了：

seq = STACK.pop()
set.update(STACK[-i], seq)

Used to build sets.

在 3.9 版被加入.

DICT_UPDATE(i)

實作了：

map = STACK.pop()
dict.update(STACK[-i], map)

Used to build dicts.

在 3.9 版被加入.

DICT_MERGE(i)

Like DICT_UPDATE but raises an exception for duplicate keys.

在 3.9 版被加入.

LOAD_ATTR(namei)

If the low bit of namei is not set, this replaces STACK[-1] with getattr(STACK[-1], co_names[namei>>1]).

If the low bit of namei is set, this will attempt to load a method named co_names[namei>>1] from the STACK[-1] object. STACK[-1] is popped. This bytecode distinguishes two cases: if STACK[-1] has a method with the correct name, the bytecode pushes the unbound method and STACK[-1]. STACK[-1] will be used as the first argument (self) by CALL or CALL_KW when calling the unbound method. Otherwise, NULL and the object returned by the attribute lookup are pushed.

在 3.12 版的變更: If the low bit of namei is set, then a NULL or self is pushed to the stack before the attribute or unbound method respectively.

LOAD_SUPER_ATTR(namei)

This opcode implements super(), both in its zero-argument and two-argument forms (e.g. super().method(), super().attr and super(cls, self).method(), super(cls, self).attr).

It pops three values from the stack (from top of stack down):

self: the first argument to the current method

cls: the class within which the current method was defined

the global super

With respect to its argument, it works similarly to LOAD_ATTR, except that namei is shifted left by 2 bits instead of 1.

The low bit of namei signals to attempt a method load, as with LOAD_ATTR, which results in pushing NULL and the loaded method. When it is unset a single value is pushed to the stack.

The second-low bit of namei, if set, means that this was a two-argument call to super() (unset means zero-argument).

在 3.12 版被加入.

COMPARE_OP(opname)

Performs a Boolean operation. The operation name can be found in cmp_op[opname >> 5]. If the fifth-lowest bit of opname is set (opname & 16), the result should be coerced to bool.

在 3.13 版的變更: The fifth-lowest bit of the oparg now indicates a forced conversion to bool.

IS_OP(invert)

Performs is comparison, or is not if invert is 1.

在 3.9 版被加入.

CONTAINS_OP(invert)

Performs in comparison, or not in if invert is 1.

在 3.9 版被加入.

IMPORT_NAME(namei)

Imports the module co_names[namei]. STACK[-1] and STACK[-2] are popped and provide the fromlist and level arguments of __import__(). The module object is pushed onto the stack. The current namespace is not affected: for a proper import statement, a subsequent STORE_FAST instruction modifies the namespace.

IMPORT_FROM(namei)

Loads the attribute co_names[namei] from the module found in STACK[-1]. The resulting object is pushed onto the stack, to be subsequently stored by a STORE_FAST instruction.

JUMP_FORWARD(delta)

Increments bytecode counter by delta.

JUMP_BACKWARD(delta)

Decrements bytecode counter by delta. Checks for interrupts.

在 3.11 版被加入.

JUMP_BACKWARD_NO_INTERRUPT(delta)

Decrements bytecode counter by delta. Does not check for interrupts.

在 3.11 版被加入.

POP_JUMP_IF_TRUE(delta)

If STACK[-1] is true, increments the bytecode counter by delta. STACK[-1] is popped.

在 3.11 版的變更: The oparg is now a relative delta rather than an absolute target. This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).

在 3.12 版的變更: This is no longer a pseudo-instruction.

在 3.13 版的變更: This instruction now requires an exact bool operand.

POP_JUMP_IF_FALSE(delta)

If STACK[-1] is false, increments the bytecode counter by delta. STACK[-1] is popped.

在 3.11 版的變更: The oparg is now a relative delta rather than an absolute target. This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).

在 3.12 版的變更: This is no longer a pseudo-instruction.

在 3.13 版的變更: This instruction now requires an exact bool operand.

POP_JUMP_IF_NOT_NONE(delta)

If STACK[-1] is not None, increments the bytecode counter by delta. STACK[-1] is popped.

在 3.11 版被加入.

在 3.12 版的變更: This is no longer a pseudo-instruction.

POP_JUMP_IF_NONE(delta)

If STACK[-1] is None, increments the bytecode counter by delta. STACK[-1] is popped.

在 3.11 版被加入.

在 3.12 版的變更: This is no longer a pseudo-instruction.

FOR_ITER(delta)

STACK[-1] is an iterator. Call its __next__() method. If this yields a new value, push it on the stack (leaving the iterator below it). If the iterator indicates it is exhausted then the byte code counter is incremented by delta.

在 3.12 版的變更: Up until 3.11 the iterator was popped when it was exhausted.

LOAD_GLOBAL(namei)

Loads the global named co_names[namei>>1] onto the stack.

在 3.11 版的變更: If the low bit of namei is set, then a NULL is pushed to the stack before the global variable.

LOAD_FAST(var_num)

Pushes a reference to the local co_varnames[var_num] onto the stack.

在 3.12 版的變更: This opcode is now only used in situations where the local variable is guaranteed to be initialized. It cannot raise UnboundLocalError.

LOAD_FAST_BORROW(var_num)

Pushes a borrowed reference to the local co_varnames[var_num] onto the stack.

在 3.14 版被加入.

LOAD_FAST_LOAD_FAST(var_nums)

Pushes references to co_varnames[var_nums >> 4] and co_varnames[var_nums & 15] onto the stack.

在 3.13 版被加入.

LOAD_FAST_BORROW_LOAD_FAST_BORROW(var_nums)

Pushes borrowed references to co_varnames[var_nums >> 4] and co_varnames[var_nums & 15] onto the stack.

在 3.14 版被加入.

LOAD_FAST_CHECK(var_num)

Pushes a reference to the local co_varnames[var_num] onto the stack, raising an UnboundLocalError if the local variable has not been initialized.

在 3.12 版被加入.

LOAD_FAST_AND_CLEAR(var_num)

Pushes a reference to the local co_varnames[var_num] onto the stack (or pushes NULL onto the stack if the local variable has not been initialized) and sets co_varnames[var_num] to NULL.

在 3.12 版被加入.

STORE_FAST(var_num)

Stores STACK.pop() into the local co_varnames[var_num].

STORE_FAST_STORE_FAST(var_nums)

Stores STACK[-1] into co_varnames[var_nums >> 4] and STACK[-2] into co_varnames[var_nums & 15].

在 3.13 版被加入.

STORE_FAST_LOAD_FAST(var_nums)

Stores STACK.pop() into the local co_varnames[var_nums >> 4] and pushes a reference to the local co_varnames[var_nums & 15] onto the stack.

在 3.13 版被加入.

DELETE_FAST(var_num)

Deletes local co_varnames[var_num].

MAKE_CELL(i)

Creates a new cell in slot i. If that slot is nonempty then that value is stored into the new cell.

在 3.11 版被加入.

LOAD_DEREF(i)

Loads the cell contained in slot i of the "fast locals" storage. Pushes a reference to the object the cell contains on the stack.

在 3.11 版的變更: i is no longer offset by the length of co_varnames.

LOAD_FROM_DICT_OR_DEREF(i)

Pops a mapping off the stack and looks up the name associated with slot i of the "fast locals" storage in this mapping. If the name is not found there, loads it from the cell contained in slot i, similar to LOAD_DEREF. This is used for loading closure variables in class bodies (which previously used LOAD_CLASSDEREF) and in annotation scopes within class bodies.

在 3.12 版被加入.

STORE_DEREF(i)

Stores STACK.pop() into the cell contained in slot i of the "fast locals" storage.

在 3.11 版的變更: i is no longer offset by the length of co_varnames.

DELETE_DEREF(i)

Empties the cell contained in slot i of the "fast locals" storage. Used by the del statement.

在 3.2 版被加入.

在 3.11 版的變更: i is no longer offset by the length of co_varnames.

COPY_FREE_VARS(n)

Copies the n free (closure) variables from the closure into the frame. Removes the need for special code on the caller's side when calling closures.

在 3.11 版被加入.

RAISE_VARARGS(argc)

Raises an exception using one of the 3 forms of the raise statement, depending on the value of argc:

0: raise (re-raise previous exception)

1: raise STACK[-1] (raise exception instance or type at STACK[-1])

2: raise STACK[-2] from STACK[-1] (raise exception instance or type at STACK[-2] with __cause__ set to STACK[-1])

CALL(argc)

Calls a callable object with the number of arguments specified by argc. On the stack are (in ascending order):

The callable

self 或 NULL

剩餘的位置引數

argc is the total of the positional arguments, excluding self.

CALL pops all arguments and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.

在 3.11 版被加入.

在 3.13 版的變更: The callable now always appears at the same position on the stack.

在 3.13 版的變更: Calls with keyword arguments are now handled by CALL_KW.

CALL_KW(argc)

Calls a callable object with the number of arguments specified by argc, including one or more named arguments. On the stack are (in ascending order):

The callable

self 或 NULL

剩餘的位置引數

The named arguments

A tuple of keyword argument names

argc is the total of the positional and named arguments, excluding self. The length of the tuple of keyword argument names is the number of named arguments.

CALL_KW pops all arguments, the keyword names, and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.

在 3.13 版被加入.

CALL_FUNCTION_EX(flags)

Calls a callable object with variable set of positional and keyword arguments. If the lowest bit of flags is set, the top of the stack contains a mapping object containing additional keyword arguments. Before the callable is called, the mapping object and iterable object are each "unpacked" and their contents passed in as keyword and positional arguments respectively. CALL_FUNCTION_EX pops all arguments and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.

在 3.6 版被加入.

PUSH_NULL

Pushes a NULL to the stack. Used in the call sequence to match the NULL pushed by LOAD_METHOD for non-method calls.

在 3.11 版被加入.

MAKE_FUNCTION

Pushes a new function object on the stack built from the code object at STACK[-1].

在 3.10 版的變更: Flag value 0x04 is a tuple of strings instead of dictionary

在 3.11 版的變更: Qualified name at STACK[-1] was removed.

在 3.13 版的變更: Extra function attributes on the stack, signaled by oparg flags, were removed. They now use SET_FUNCTION_ATTRIBUTE.

SET_FUNCTION_ATTRIBUTE(flag)

Sets an attribute on a function object. Expects the function at STACK[-1] and the attribute value to set at STACK[-2]; consumes both and leaves the function at STACK[-1]. The flag determines which attribute to set:

0x01 a tuple of default values for positional-only and positional-or-keyword parameters in positional order

0x02 a dictionary of keyword-only parameters' default values

0x04 a tuple of strings containing parameters' annotations

0x08 a tuple containing cells for free variables, making a closure

0x10 the annotate function for the function object

在 3.13 版被加入.

在 3.14 版的變更: Added 0x10 to indicate the annotate function for the function object.

BUILD_SLICE(argc)

Pushes a slice object on the stack. argc must be 2 or 3. If it is 2, implements:

end = STACK.pop()
start = STACK.pop()
STACK.append(slice(start, end))

if it is 3, implements:

step = STACK.pop()
end = STACK.pop()
start = STACK.pop()
STACK.append(slice(start, end, step))

更多資訊請參閱內建函式 slice()。

EXTENDED_ARG(ext)

Prefixes any opcode which has an argument too big to fit into the default one byte. ext holds an additional byte which act as higher bits in the argument. For each opcode, at most three prefixal EXTENDED_ARG are allowed, forming an argument from two-byte to four-byte.

CONVERT_VALUE(oparg)

Convert value to a string, depending on oparg:

value = STACK.pop()
result = func(value)
STACK.append(result)

oparg == 1：對 value 呼叫 str()

oparg == 2：對 value 呼叫 repr()

oparg == 3：對 value 呼叫 ascii()

Used for implementing formatted string literals (f-strings).

在 3.13 版被加入.

FORMAT_SIMPLE

Formats the value on top of stack:

value = STACK.pop()
result = value.__format__("")
STACK.append(result)

Used for implementing formatted string literals (f-strings).

在 3.13 版被加入.

FORMAT_WITH_SPEC

Formats the given value with the given format spec:

spec = STACK.pop()
value = STACK.pop()
result = value.__format__(spec)
STACK.append(result)

Used for implementing formatted string literals (f-strings).

在 3.13 版被加入.

MATCH_CLASS(count)

STACK[-1] is a tuple of keyword attribute names, STACK[-2] is the class being matched against, and STACK[-3] is the match subject. count is the number of positional sub-patterns.

Pop STACK[-1], STACK[-2], and STACK[-3]. If STACK[-3] is an instance of STACK[-2] and has the positional and keyword attributes required by count and STACK[-1], push a tuple of extracted attributes. Otherwise, push None.

在 3.10 版被加入.

在 3.11 版的變更: Previously, this instruction also pushed a boolean value indicating success (True) or failure (False).

RESUME(context)

A no-op. Performs internal tracing, debugging and optimization checks.

The context operand consists of two parts. The lowest two bits indicate where the RESUME occurs:

0 The start of a function, which is neither a generator, coroutine nor an async generator

1 After a yield expression

2 After a yield from expression

3 After an await expression

The next bit is 1 if the RESUME is at except-depth 1, and 0 otherwise.

在 3.11 版被加入.

在 3.13 版的變更: The oparg value changed to include information about except-depth

RETURN_GENERATOR

Create a generator, coroutine, or async generator from the current frame. Used as first opcode of in code object for the above mentioned callables. Clear the current frame and return the newly created generator.

在 3.11 版被加入.

SEND(delta)

Equivalent to STACK[-1] = STACK[-2].send(STACK[-1]). Used in yield from and await statements.

If the call raises StopIteration, pop the top value from the stack, push the exception's value attribute, and increment the bytecode counter by delta.

在 3.11 版被加入.

HAVE_ARGUMENT

This is not really an opcode. It identifies the dividing line between opcodes in the range [0,255] which don't use their argument and those that do (< HAVE_ARGUMENT and >= HAVE_ARGUMENT, respectively).

If your application uses pseudo instructions or specialized instructions, use the hasarg collection instead.

在 3.6 版的變更: Now every instruction has an argument, but opcodes < HAVE_ARGUMENT ignore it. Before, only opcodes >= HAVE_ARGUMENT had an argument.

在 3.12 版的變更: Pseudo instructions were added to the dis module, and for them it is not true that comparison with HAVE_ARGUMENT indicates whether they use their arg.

在 3.13 版之後被棄用: 改用 hasarg。

CALL_INTRINSIC_1

Calls an intrinsic function with one argument. Passes STACK[-1] as the argument and sets STACK[-1] to the result. Used to implement functionality that is not performance critical.

The operand determines which intrinsic function is called:

運算元

描述

INTRINSIC_1_INVALID

Not valid

INTRINSIC_PRINT

Prints the argument to standard out. Used in the REPL.

INTRINSIC_IMPORT_STAR

Performs import * for the named module.

INTRINSIC_STOPITERATION_ERROR

Extracts the return value from a StopIteration exception.

INTRINSIC_ASYNC_GEN_WRAP

Wraps an async generator value

INTRINSIC_UNARY_POSITIVE

Performs the unary + operation

INTRINSIC_LIST_TO_TUPLE

Converts a list to a tuple

INTRINSIC_TYPEVAR

建立一個 typing.TypeVar

INTRINSIC_PARAMSPEC

建立一個 typing.ParamSpec

INTRINSIC_TYPEVARTUPLE

建立一個 typing.TypeVarTuple

INTRINSIC_SUBSCRIPT_GENERIC

Returns typing.Generic subscripted with the argument

INTRINSIC_TYPEALIAS

Creates a typing.TypeAliasType; used in the type statement. The argument is a tuple of the type alias's name, type parameters, and value.

在 3.12 版被加入.

CALL_INTRINSIC_2

Calls an intrinsic function with two arguments. Used to implement functionality that is not performance critical:

arg2 = STACK.pop()
arg1 = STACK.pop()
result = intrinsic2(arg1, arg2)
STACK.append(result)

The operand determines which intrinsic function is called:

運算元

描述

INTRINSIC_2_INVALID

Not valid

INTRINSIC_PREP_RERAISE_STAR

Calculates the ExceptionGroup to raise from a try-except*.

INTRINSIC_TYPEVAR_WITH_BOUND

Creates a typing.TypeVar with a bound.

INTRINSIC_TYPEVAR_WITH_CONSTRAINTS

Creates a typing.TypeVar with constraints.

INTRINSIC_SET_FUNCTION_TYPE_PARAMS

設定函式的 __type_params__ 屬性。

在 3.12 版被加入.

LOAD_SPECIAL

Performs special method lookup on STACK[-1]. If type(STACK[-1]).__xxx__ is a method, leave type(STACK[-1]).__xxx__; STACK[-1] on the stack. If type(STACK[-1]).__xxx__ is not a method, leave STACK[-1].__xxx__; NULL on the stack.

在 3.14 版被加入.

Pseudo-instructions

These opcodes do not appear in Python bytecode. They are used by the compiler but are replaced by real opcodes or removed before bytecode is generated.

SETUP_FINALLY(target)

Set up an exception handler for the following code block. If an exception occurs, the value stack level is restored to its current state and control is transferred to the exception handler at target.

SETUP_CLEANUP(target)

Like SETUP_FINALLY, but in case of an exception also pushes the last instruction (lasti) to the stack so that RERAISE can restore it. If an exception occurs, the value stack level and the last instruction on the frame are restored to their current state, and control is transferred to the exception handler at target.

SETUP_WITH(target)

Like SETUP_CLEANUP, but in case of an exception one more item is popped from the stack before control is transferred to the exception handler at target.

This variant is used in with and async with constructs, which push the return value of the context manager's __enter__() or __aenter__() to the stack.

POP_BLOCK

Marks the end of the code block associated with the last SETUP_FINALLY, SETUP_CLEANUP or SETUP_WITH.

LOAD_CONST_IMMORTAL(consti)

Works as LOAD_CONST, but is more efficient for immortal objects.

JUMP

JUMP_NO_INTERRUPT

Undirected relative jump instructions which are replaced by their directed (forward/backward) counterparts by the assembler.

JUMP_IF_TRUE

JUMP_IF_FALSE

Conditional jumps which do not impact the stack. Replaced by the sequence COPY 1, TO_BOOL, POP_JUMP_IF_TRUE/FALSE.

LOAD_CLOSURE(i)

Pushes a reference to the cell contained in slot i of the "fast locals" storage.

Note that LOAD_CLOSURE is replaced with LOAD_FAST in the assembler.

在 3.13 版的變更: This opcode is now a pseudo-instruction.

Opcode collections

These collections are provided for automatic introspection of bytecode instructions:

在 3.12 版的變更: The collections now contain pseudo instructions and instrumented instructions as well. These are opcodes with values >= MIN_PSEUDO_OPCODE and >= MIN_INSTRUMENTED_OPCODE.

dis.opname

Sequence of operation names, indexable using the bytecode.

dis.opmap

Dictionary mapping operation names to bytecodes.

dis.cmp_op

Sequence of all compare operation names.

dis.hasarg

Sequence of bytecodes that use their argument.

在 3.12 版被加入.

dis.hasconst

Sequence of bytecodes that access a constant.

dis.hasfree

Sequence of bytecodes that access a free (closure) variable. 'free' in this context refers to names in the current scope that are referenced by inner scopes or names in outer scopes that are referenced from this scope. It does not include references to global or builtin scopes.

dis.hasname

Sequence of bytecodes that access an attribute by name.

dis.hasjump

Sequence of bytecodes that have a jump target. All jumps are relative.

在 3.13 版被加入.

dis.haslocal

Sequence of bytecodes that access a local variable.

dis.hascompare

Sequence of bytecodes of Boolean operations.

dis.hasexc

Sequence of bytecodes that set an exception handler.

在 3.12 版被加入.

dis.hasjrel

Sequence of bytecodes that have a relative jump target.

在 3.13 版之後被棄用: All jumps are now relative. Use hasjump.

dis.hasjabs

Sequence of bytecodes that have an absolute jump target.

在 3.13 版之後被棄用: All jumps are now relative. This list is empty.

pickletools --- pickle 開發者的工具

原始碼：Lib/pickletools.py [https://github.com/python/cpython/tree/3.14/Lib/pickletools.py]

該模組包含與 pickle 模組的詳細資訊相關的各種常數、一些有關實作的冗長註釋以及一些用於分析已 pickle 資料的有用函式。該模組的內容對於有 pickle 相關工作的 Python 核心開發人員很有用；pickle 模組的一般使用者可能不會發現 pickletools 模組。

命令列用法

在 3.2 版被加入.

當從命令列呼叫時，python -m pickletools 將拆解 (disassemble) 一個或多個 pickle 檔案的內容。請注意，如果你想查看儲存在 pickle 中的 Python 物件而不是 pickle 格式的詳細資訊，你可能需要使用 -m pickle。但是，當你要檢查的 pickle 檔案來自不受信任的來源時，-m pickletools 是一個更安全的選項，因為它不執行 pickle 位元組碼。

例如，pickle 於檔案 x.pickle 中的元組 (1, 2)：

$ python -m pickle x.pickle
(1, 2)

$ python -m pickletools x.pickle
    0: \x80 PROTO      3
    2: K    BININT1    1
    4: K    BININT1    2
    6: \x86 TUPLE2
    7: q    BINPUT     0
    9: .    STOP
highest protocol among opcodes = 2

命令列選項

-a, --annotate

用簡短的操作碼 (opcode) 描述註釋每一行。

-o, --output=<file>

應將輸出結果寫入之檔案的名稱。

-l, --indentlevel=<num>

新 MARK 級別縮進的空格數。

-m, --memo

當拆解多個物件時，會在拆解間保留備忘錄。

-p, --preamble=<preamble>

當指定多個 pickle 檔案時，會在每次拆解之前印出給定的一段序言 (preamble)。

pickle_file

A pickle file to read, or - to indicate reading from standard input.

程式化介面

pickletools.dis(pickle, out=None, memo=None, indentlevel=4, annotate=0)

將 pickle 的符號拆解 (symbolic disassembly) 輸出到類檔案物件 out，預設為 sys.stdout。pickle 可以是字串或類檔案物件。memo 可以是一個 Python 字典，將用作 pickle 的備忘錄；它可用於對同一 pickler 建立的多個 pickle 執行拆解。串流中由 MARK 操作碼指示的連續級別由 indentlevel 空格縮進。如果為 annotate 指定非零值，則輸出中的每個操作碼都會用簡短的描述進行註釋。annotate 的值用作為註釋之起始行提示。

在 3.2 版的變更: 新增 annotate 參數。

pickletools.genops(pickle)

提供 pickle 中所有操作碼的一個 iterator，回傳形式為 (opcode, arg, pos) 三元組序列。opcode 是 OpcodeInfo 類別的實例；arg 是操作碼引數的解碼值（作為 Python 物件）；pos 是該操作碼所在的位置。pickle 可以是字串或類檔案物件。

pickletools.optimize(picklestring)

消除未使用的 PUT 操作碼後回傳一個新的等效 pickle 字串。最佳化後的 pickle 更短、傳輸時間更少、需要更小的儲存空間，且 unpickle 效率也更高。

MS Windows 特有服務

此章節描述僅在 MS Windows 系統上可用的模組 (module)。

msvcrt --- MS VC++ runtime 提供的有用例程

File Operations

Console I/O

Other Functions

winreg --- Windows 註冊表存取

函式

常數

HKEY_* Constants

Access Rights

64-bit Specific

Value Types

Registry Handle Objects

winsound --- Windows 的音效播放介面

msvcrt --- MS VC++ runtime 提供的有用例程

These functions provide access to some useful capabilities on Windows platforms. Some higher-level modules use these functions to build the Windows implementations of their services. For example, the getpass module uses this in the implementation of the getpass() function.

Further documentation on these functions can be found in the Platform API documentation.

The module implements both the normal and wide char variants of the console I/O api. The normal API deals only with ASCII characters and is of limited use for internationalized applications. The wide char API should be used where ever possible.

可用性: Windows.

在 3.3 版的變更: Operations in this module now raise OSError where IOError was raised.

File Operations

msvcrt.locking(fd, mode, nbytes)

Lock part of a file based on file descriptor fd from the C runtime. Raises OSError on failure. The locked region of the file extends from the current file position for nbytes bytes, and may continue beyond the end of the file. mode must be one of the LK_* constants listed below. Multiple regions in a file may be locked at the same time, but may not overlap. Adjacent regions are not merged; they must be unlocked individually.

引發一個附帶引數 fd、mode、nbytes 的稽核事件 msvcrt.locking。

msvcrt.LK_LOCK

msvcrt.LK_RLCK

Locks the specified bytes. If the bytes cannot be locked, the program immediately tries again after 1 second. If, after 10 attempts, the bytes cannot be locked, OSError is raised.

msvcrt.LK_NBLCK

msvcrt.LK_NBRLCK

Locks the specified bytes. If the bytes cannot be locked, OSError is raised.

msvcrt.LK_UNLCK

Unlocks the specified bytes, which must have been previously locked.

msvcrt.setmode(fd, flags)

Set the line-end translation mode for the file descriptor fd. To set it to text mode, flags should be os.O_TEXT; for binary, it should be os.O_BINARY.

msvcrt.open_osfhandle(handle, flags)

Create a C runtime file descriptor from the file handle handle. The flags parameter should be a bitwise OR of os.O_APPEND, os.O_RDONLY, os.O_TEXT and os.O_NOINHERIT. The returned file descriptor may be used as a parameter to os.fdopen() to create a file object.

The file descriptor is inheritable by default. Pass os.O_NOINHERIT flag to make it non inheritable.

引發一個附帶引數 handle、flags 的稽核事件 msvcrt.open_osfhandle。

msvcrt.get_osfhandle(fd)

Return the file handle for the file descriptor fd. Raises OSError if fd is not recognized.

引發一個附帶引數 fd 的稽核事件 msvcrt.get_osfhandle。

Console I/O

msvcrt.kbhit()

Returns a nonzero value if a keypress is waiting to be read. Otherwise, return 0.

msvcrt.getch()

Read a keypress and return the resulting character as a byte string. Nothing is echoed to the console. This call will block if a keypress is not already available, but will not wait for Enter to be pressed. If the pressed key was a special function key, this will return '\000' or '\xe0'; the next call will return the keycode. The Control-C keypress cannot be read with this function.

msvcrt.getwch()

Wide char variant of getch(), returning a Unicode value.

msvcrt.getche()

Similar to getch(), but the keypress will be echoed if it represents a printable character.

msvcrt.getwche()

Wide char variant of getche(), returning a Unicode value.

msvcrt.putch(char)

Print the byte string char to the console without buffering.

msvcrt.putwch(unicode_char)

Wide char variant of putch(), accepting a Unicode value.

msvcrt.ungetch(char)

Cause the byte string char to be "pushed back" into the console buffer; it will be the next character read by getch() or getche().

msvcrt.ungetwch(unicode_char)

Wide char variant of ungetch(), accepting a Unicode value.

Other Functions

msvcrt.heapmin()

Force the malloc() heap to clean itself up and return unused blocks to the operating system. On failure, this raises OSError.

msvcrt.set_error_mode(mode)

Changes the location where the C runtime writes an error message for an error that might end the program. mode must be one of the OUT_* constants listed below or REPORT_ERRMODE. Returns the old setting or -1 if an error occurs. Only available in debug build of Python.

msvcrt.OUT_TO_DEFAULT

Error sink is determined by the app's type. Only available in debug build of Python.

msvcrt.OUT_TO_STDERR

Error sink is a standard error. Only available in debug build of Python.

msvcrt.OUT_TO_MSGBOX

Error sink is a message box. Only available in debug build of Python.

msvcrt.REPORT_ERRMODE

Report the current error mode value. Only available in debug build of Python.

msvcrt.CrtSetReportMode(type, mode)

Specifies the destination or destinations for a specific report type generated by _CrtDbgReport() in the MS VC++ runtime. type must be one of the CRT_* constants listed below. mode must be one of the CRTDBG_* constants listed below. Only available in debug build of Python.

msvcrt.CrtSetReportFile(type, file)

After you use CrtSetReportMode() to specify CRTDBG_MODE_FILE, you can specify the file handle to receive the message text. type must be one of the CRT_* constants listed below. file should be the file handle your want specified. Only available in debug build of Python.

msvcrt.CRT_WARN

Warnings, messages, and information that doesn't need immediate attention.

msvcrt.CRT_ERROR

Errors, unrecoverable problems, and issues that require immediate attention.

msvcrt.CRT_ASSERT

Assertion failures.

msvcrt.CRTDBG_MODE_DEBUG

Writes the message to the debugger's output window.

msvcrt.CRTDBG_MODE_FILE

Writes the message to a user-supplied file handle. CrtSetReportFile() should be called to define the specific file or stream to use as the destination.

msvcrt.CRTDBG_MODE_WNDW

Creates a message box to display the message along with the Abort, Retry, and Ignore buttons.

msvcrt.CRTDBG_REPORT_MODE

Returns current mode for the specified type.

msvcrt.CRT_ASSEMBLY_VERSION

The CRT Assembly version, from the crtassem.h header file.

msvcrt.VC_ASSEMBLY_PUBLICKEYTOKEN

The VC Assembly public key token, from the crtassem.h header file.

msvcrt.LIBRARIES_ASSEMBLY_NAME_PREFIX

The Libraries Assembly name prefix, from the crtassem.h header file.

winreg --- Windows 註冊表存取

These functions expose the Windows registry API to Python. Instead of using an integer as the registry handle, a handle object is used to ensure that the handles are closed correctly, even if the programmer neglects to explicitly close them.

可用性: Windows.

在 3.3 版的變更: Several functions in this module used to raise a WindowsError, which is now an alias of OSError.

函式

This module offers the following functions:

winreg.CloseKey(hkey)

Closes a previously opened registry key. The hkey argument specifies a previously opened key.

備註

If hkey is not closed using this method (or via hkey.Close()), it is closed when the hkey object is destroyed by Python.

winreg.ConnectRegistry(computer_name, key)

Establishes a connection to a predefined registry handle on another computer, and returns a handle object.

computer_name is the name of the remote computer, of the form r"\\computername". If None, the local computer is used.

key is the predefined handle to connect to.

The return value is the handle of the opened key. If the function fails, an OSError exception is raised.

引發一個附帶引數 computer_name、key 的稽核事件 winreg.ConnectRegistry。

在 3.3 版的變更: See above.

winreg.CreateKey(key, sub_key)

Creates or opens the specified key, returning a handle object.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that names the key this method opens or creates.

If key is one of the predefined keys, sub_key may be None. In that case, the handle returned is the same key handle passed in to the function.

If the key already exists, this function opens the existing key.

The return value is the handle of the opened key. If the function fails, an OSError exception is raised.

引發一個附帶引數 key、sub_key、access 的稽核事件 winreg.CreateKey。

引發一個附帶引數 key 的稽核事件 winreg.OpenKey/result。

在 3.3 版的變更: See above.

winreg.CreateKeyEx(key, sub_key, reserved=0, access=KEY_WRITE)

Creates or opens the specified key, returning a handle object.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that names the key this method opens or creates.

reserved is a reserved integer, and must be zero. The default is zero.

access is an integer that specifies an access mask that describes the desired security access for the key. Default is KEY_WRITE. See Access Rights for other allowed values.

If key is one of the predefined keys, sub_key may be None. In that case, the handle returned is the same key handle passed in to the function.

If the key already exists, this function opens the existing key.

The return value is the handle of the opened key. If the function fails, an OSError exception is raised.

引發一個附帶引數 key、sub_key、access 的稽核事件 winreg.CreateKey。

引發一個附帶引數 key 的稽核事件 winreg.OpenKey/result。

在 3.2 版被加入.

在 3.3 版的變更: See above.

winreg.DeleteKey(key, sub_key)

Deletes the specified key.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that must be a subkey of the key identified by the key parameter. This value must not be None, and the key may not have subkeys.

This method can not delete keys with subkeys.

If the method succeeds, the entire key, including all of its values, is removed. If the method fails, an OSError exception is raised.

引發一個附帶引數 key、sub_key、access 的稽核事件 winreg.DeleteKey。

在 3.3 版的變更: See above.

winreg.DeleteKeyEx(key, sub_key, access=KEY_WOW64_64KEY, reserved=0)

Deletes the specified key.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that must be a subkey of the key identified by the key parameter. This value must not be None, and the key may not have subkeys.

reserved is a reserved integer, and must be zero. The default is zero.

access is an integer that specifies an access mask that describes the desired security access for the key. Default is KEY_WOW64_64KEY. On 32-bit Windows, the WOW64 constants are ignored. See Access Rights for other allowed values.

This method can not delete keys with subkeys.

If the method succeeds, the entire key, including all of its values, is removed. If the method fails, an OSError exception is raised.

On unsupported Windows versions, NotImplementedError is raised.

引發一個附帶引數 key、sub_key、access 的稽核事件 winreg.DeleteKey。

在 3.2 版被加入.

在 3.3 版的變更: See above.

winreg.DeleteValue(key, value)

Removes a named value from a registry key.

key is an already open key, or one of the predefined HKEY_* constants.

value 是用於識別要移除之值的字串。

引發一個附帶引數 key、value 的稽核事件 winreg.DeleteValue。

winreg.EnumKey(key, index)

Enumerates subkeys of an open registry key, returning a string.

key is an already open key, or one of the predefined HKEY_* constants.

index is an integer that identifies the index of the key to retrieve.

The function retrieves the name of one subkey each time it is called. It is typically called repeatedly until an OSError exception is raised, indicating, no more values are available.

引發一個附帶引數 key、index 的稽核事件 winreg.EnumKey。

在 3.3 版的變更: See above.

winreg.EnumValue(key, index)

Enumerates values of an open registry key, returning a tuple.

key is an already open key, or one of the predefined HKEY_* constants.

index is an integer that identifies the index of the value to retrieve.

The function retrieves the name of one subkey each time it is called. It is typically called repeatedly, until an OSError exception is raised, indicating no more values.

The result is a tuple of 3 items:

Index

含義

0

A string that identifies the value name

1

An object that holds the value data, and whose type depends on the underlying registry type

2

An integer that identifies the type of the value data (see table in docs for SetValueEx())

引發一個附帶引數 key、index 的稽核事件 winreg.EnumValue。

在 3.3 版的變更: See above.

winreg.ExpandEnvironmentStrings(str)

Expands environment variable placeholders %NAME% in strings like REG_EXPAND_SZ:

>>> ExpandEnvironmentStrings('%windir%')
'C:\\Windows'

引發一個附帶引數 str 的稽核事件 winreg.ExpandEnvironmentStrings。

winreg.FlushKey(key)

Writes all the attributes of a key to the registry.

key is an already open key, or one of the predefined HKEY_* constants.

It is not necessary to call FlushKey() to change a key. Registry changes are flushed to disk by the registry using its lazy flusher. Registry changes are also flushed to disk at system shutdown. Unlike CloseKey(), the FlushKey() method returns only when all the data has been written to the registry. An application should only call FlushKey() if it requires absolute certainty that registry changes are on disk.

備註

If you don't know whether a FlushKey() call is required, it probably isn't.

winreg.LoadKey(key, sub_key, file_name)

Creates a subkey under the specified key and stores registration information from a specified file into that subkey.

key is a handle returned by ConnectRegistry() or one of the constants HKEY_USERS or HKEY_LOCAL_MACHINE.

sub_key is a string that identifies the subkey to load.

file_name is the name of the file to load registry data from. This file must have been created with the SaveKey() function. Under the file allocation table (FAT) file system, the filename may not have an extension.

A call to LoadKey() fails if the calling process does not have the SE_RESTORE_PRIVILEGE privilege. Note that privileges are different from permissions -- see the RegLoadKey documentation [https://msdn.microsoft.com/en-us/library/ms724889%28v=VS.85%29.aspx] for more details.

If key is a handle returned by ConnectRegistry(), then the path specified in file_name is relative to the remote computer.

引發一個附帶引數 key、sub_key、file_name 的稽核事件 winreg.LoadKey。

winreg.OpenKey(key, sub_key, reserved=0, access=KEY_READ)

winreg.OpenKeyEx(key, sub_key, reserved=0, access=KEY_READ)

Opens the specified key, returning a handle object.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that identifies the sub_key to open.

reserved is a reserved integer, and must be zero. The default is zero.

access is an integer that specifies an access mask that describes the desired security access for the key. Default is KEY_READ. See Access Rights for other allowed values.

The result is a new handle to the specified key.

If the function fails, OSError is raised.

引發一個附帶引數 key、sub_key、access 的稽核事件 winreg.OpenKey。

引發一個附帶引數 key 的稽核事件 winreg.OpenKey/result。

在 3.2 版的變更: Allow the use of named arguments.

在 3.3 版的變更: See above.

winreg.QueryInfoKey(key)

Returns information about a key, as a tuple.

key is an already open key, or one of the predefined HKEY_* constants.

The result is a tuple of 3 items:

Index

含義

0

An integer giving the number of sub keys this key has.

1

An integer giving the number of values this key has.

2

An integer giving when the key was last modified (if available) as 100's of nanoseconds since Jan 1, 1601.

引發一個附帶引數 key 的稽核事件 winreg.QueryInfoKey。

winreg.QueryValue(key, sub_key)

Retrieves the unnamed value for a key, as a string.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that holds the name of the subkey with which the value is associated. If this parameter is None or empty, the function retrieves the value set by the SetValue() method for the key identified by key.

Values in the registry have name, type, and data components. This method retrieves the data for a key's first value that has a NULL name. But the underlying API call doesn't return the type, so always use QueryValueEx() if possible.

引發一個附帶引數 key、sub_key、value_name 的稽核事件 winreg.QueryKey。

winreg.QueryValueEx(key, value_name)

Retrieves the type and data for a specified value name associated with an open registry key.

key is an already open key, or one of the predefined HKEY_* constants.

value_name is a string indicating the value to query.

The result is a tuple of 2 items:

Index

含義

0

The value of the registry item.

1

An integer giving the registry type for this value (see table in docs for SetValueEx())

引發一個附帶引數 key、sub_key、value_name 的稽核事件 winreg.QueryKey。

winreg.SaveKey(key, file_name)

Saves the specified key, and all its subkeys to the specified file.

key is an already open key, or one of the predefined HKEY_* constants.

file_name is the name of the file to save registry data to. This file cannot already exist. If this filename includes an extension, it cannot be used on file allocation table (FAT) file systems by the LoadKey() method.

If key represents a key on a remote computer, the path described by file_name is relative to the remote computer. The caller of this method must possess the SeBackupPrivilege security privilege. Note that privileges are different than permissions -- see the Conflicts Between User Rights and Permissions documentation [https://msdn.microsoft.com/en-us/library/ms724878%28v=VS.85%29.aspx] for more details.

This function passes NULL for security_attributes to the API.

引發一個附帶引數 key、file_name 的稽核事件 winreg.SaveKey。

winreg.SetValue(key, sub_key, type, value)

Associates a value with a specified key.

key is an already open key, or one of the predefined HKEY_* constants.

sub_key is a string that names the subkey with which the value is associated.

type is an integer that specifies the type of the data. Currently this must be REG_SZ, meaning only strings are supported. Use the SetValueEx() function for support for other data types.

value is a string that specifies the new value.

If the key specified by the sub_key parameter does not exist, the SetValue function creates it.

Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the configuration registry. This helps the registry perform efficiently.

The key identified by the key parameter must have been opened with KEY_SET_VALUE access.

引發一個附帶引數 key、sub_key、type、value 的稽核事件 winreg.SetValue。

winreg.SetValueEx(key, value_name, reserved, type, value)

Stores data in the value field of an open registry key.

key is an already open key, or one of the predefined HKEY_* constants.

value_name is a string that names the subkey with which the value is associated.

reserved can be anything -- zero is always passed to the API.

type is an integer that specifies the type of the data. See Value Types for the available types.

value is a string that specifies the new value.

This method can also set additional value and type information for the specified key. The key identified by the key parameter must have been opened with KEY_SET_VALUE access.

To open the key, use the CreateKey() or OpenKey() methods.

Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the configuration registry. This helps the registry perform efficiently.

引發一個附帶引數 key、sub_key、type、value 的稽核事件 winreg.SetValue。

winreg.DisableReflectionKey(key)

Disables registry reflection for 32-bit processes running on a 64-bit operating system.

key is an already open key, or one of the predefined HKEY_* constants.

Will generally raise NotImplementedError if executed on a 32-bit operating system.

If the key is not on the reflection list, the function succeeds but has no effect. Disabling reflection for a key does not affect reflection of any subkeys.

引發一個附帶引數 key 的稽核事件 winreg.DsiableReflectionKey。

winreg.EnableReflectionKey(key)

Restores registry reflection for the specified disabled key.

key is an already open key, or one of the predefined HKEY_* constants.

Will generally raise NotImplementedError if executed on a 32-bit operating system.

Restoring reflection for a key does not affect reflection of any subkeys.

引發一個附帶引數 key 的稽核事件 winreg.EnableReflectionKey。

winreg.QueryReflectionKey(key)

Determines the reflection state for the specified key.

key is an already open key, or one of the predefined HKEY_* constants.

Returns True if reflection is disabled.

Will generally raise NotImplementedError if executed on a 32-bit operating system.

引發一個附帶引數 key 的稽核事件 winreg.QueryReflectionKey。

常數

The following constants are defined for use in many winreg functions.

HKEY_* Constants

winreg.HKEY_CLASSES_ROOT

Registry entries subordinate to this key define types (or classes) of documents and the properties associated with those types. Shell and COM applications use the information stored under this key.

winreg.HKEY_CURRENT_USER

Registry entries subordinate to this key define the preferences of the current user. These preferences include the settings of environment variables, data about program groups, colors, printers, network connections, and application preferences.

winreg.HKEY_LOCAL_MACHINE

Registry entries subordinate to this key define the physical state of the computer, including data about the bus type, system memory, and installed hardware and software.

winreg.HKEY_USERS

Registry entries subordinate to this key define the default user configuration for new users on the local computer and the user configuration for the current user.

winreg.HKEY_PERFORMANCE_DATA

Registry entries subordinate to this key allow you to access performance data. The data is not actually stored in the registry; the registry functions cause the system to collect the data from its source.

winreg.HKEY_CURRENT_CONFIG

Contains information about the current hardware profile of the local computer system.

winreg.HKEY_DYN_DATA

This key is not used in versions of Windows after 98.

Access Rights

For more information, see Registry Key Security and Access [https://msdn.microsoft.com/en-us/library/ms724878%28v=VS.85%29.aspx].

winreg.KEY_ALL_ACCESS

Combines the STANDARD_RIGHTS_REQUIRED, KEY_QUERY_VALUE, KEY_SET_VALUE, KEY_CREATE_SUB_KEY, KEY_ENUMERATE_SUB_KEYS, KEY_NOTIFY, and KEY_CREATE_LINK access rights.

winreg.KEY_WRITE

Combines the STANDARD_RIGHTS_WRITE, KEY_SET_VALUE, and KEY_CREATE_SUB_KEY access rights.

winreg.KEY_READ

Combines the STANDARD_RIGHTS_READ, KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY values.

winreg.KEY_EXECUTE

Equivalent to KEY_READ.

winreg.KEY_QUERY_VALUE

Required to query the values of a registry key.

winreg.KEY_SET_VALUE

Required to create, delete, or set a registry value.

winreg.KEY_CREATE_SUB_KEY

Required to create a subkey of a registry key.

winreg.KEY_ENUMERATE_SUB_KEYS

Required to enumerate the subkeys of a registry key.

winreg.KEY_NOTIFY

Required to request change notifications for a registry key or for subkeys of a registry key.

winreg.KEY_CREATE_LINK

Reserved for system use.

64-bit Specific

For more information, see Accessing an Alternate Registry View [https://msdn.microsoft.com/en-us/library/aa384129(v=VS.85).aspx].

winreg.KEY_WOW64_64KEY

Indicates that an application on 64-bit Windows should operate on the 64-bit registry view. On 32-bit Windows, this constant is ignored.

winreg.KEY_WOW64_32KEY

Indicates that an application on 64-bit Windows should operate on the 32-bit registry view. On 32-bit Windows, this constant is ignored.

Value Types

For more information, see Registry Value Types [https://msdn.microsoft.com/en-us/library/ms724884%28v=VS.85%29.aspx].

winreg.REG_BINARY

Binary data in any form.

winreg.REG_DWORD

32-bit number.

winreg.REG_DWORD_LITTLE_ENDIAN

A 32-bit number in little-endian format. Equivalent to REG_DWORD.

winreg.REG_DWORD_BIG_ENDIAN

A 32-bit number in big-endian format.

winreg.REG_EXPAND_SZ

Null-terminated string containing references to environment variables (%PATH%).

winreg.REG_LINK

A Unicode symbolic link.

winreg.REG_MULTI_SZ

A sequence of null-terminated strings, terminated by two null characters. (Python handles this termination automatically.)

winreg.REG_NONE

No defined value type.

winreg.REG_QWORD

A 64-bit number.

在 3.6 版被加入.

winreg.REG_QWORD_LITTLE_ENDIAN

A 64-bit number in little-endian format. Equivalent to REG_QWORD.

在 3.6 版被加入.

winreg.REG_RESOURCE_LIST

A device-driver resource list.

winreg.REG_FULL_RESOURCE_DESCRIPTOR

A hardware setting.

winreg.REG_RESOURCE_REQUIREMENTS_LIST

A hardware resource list.

winreg.REG_SZ

A null-terminated string.

Registry Handle Objects

This object wraps a Windows HKEY object, automatically closing it when the object is destroyed. To guarantee cleanup, you can call either the Close() method on the object, or the CloseKey() function.

All registry functions in this module return one of these objects.

All registry functions in this module which accept a handle object also accept an integer, however, use of the handle object is encouraged.

Handle objects provide semantics for __bool__() -- thus

if handle:
    print("Yes")

will print Yes if the handle is currently valid (has not been closed or detached).

Handle objects can be converted to an integer (e.g., using the built-in int() function), in which case the underlying Windows handle value is returned. You can also use the Detach() method to return the integer handle, and also disconnect the Windows handle from the handle object.

PyHKEY.Close()

Closes the underlying Windows handle.

If the handle is already closed, no error is raised.

PyHKEY.Detach()

Detaches the Windows handle from the handle object.

The result is an integer that holds the value of the handle before it is detached. If the handle is already detached or closed, this will return zero.

After calling this function, the handle is effectively invalidated, but the handle is not closed. You would call this function when you need the underlying Win32 handle to exist beyond the lifetime of the handle object.

引發一個附帶引數 key 的稽核事件 winreg.PyHKEY.Detach。

PyHKEY.__enter__()

PyHKEY.__exit__(*exc_info)

The HKEY object implements __enter__() and __exit__() and thus supports the context protocol for the with statement:

with OpenKey(HKEY_LOCAL_MACHINE, "foo") as key:
    ...  # work with key

will automatically close key when control leaves the with block.

winsound --- Windows 的音效播放介面

winsound 模組提供存取 Windows 平台所提供的基本音效播放機制。它包含數個函式與常數。

可用性: Windows.

winsound.Beep(frequency, duration)

讓電腦的喇叭發出嗶聲。frequency 參數指定音效的頻率（以赫茲為單位），範圍必須介於 37 到 32,767 之間。duration 參數指定音效持續的時間（以毫秒為單位）。若系統無法讓喇叭發出嗶聲，則會引發 RuntimeError。

winsound.PlaySound(sound, flags)

呼叫平台 API 中底層的 PlaySound() 函式。sound 參數可以是檔案名稱、系統音效別名、作為 bytes-like object 的音訊資料，或 None。其直譯方式取決於 flags 的值，該值可以是以下所述常數的位元 OR 組合。若 sound 為 None，則會停止任何正在播放的波形音效。若系統回報錯誤，則會引發 RuntimeError。

winsound.MessageBeep(type=MB_OK)

呼叫平台 API 中底層的 MessageBeep() 函式。此函式會播放登錄檔中指定的音效。type 引數指定要播放的音效類型，可接受的值包括 -1、MB_ICONASTERISK、MB_ICONEXCLAMATION、MB_ICONHAND、MB_ICONQUESTION 與 MB_OK，這些皆會在下文中說明。數值 -1 會產生「簡單嗶聲」，當無法播放其他音效時即作為最終退路。若系統回報錯誤，則會引發 RuntimeError。

winsound.SND_FILENAME

sound 參數為 WAV 檔案名稱。請勿與 SND_ALIAS 同時使用。

winsound.SND_ALIAS

sound 參數為登錄檔中的音效關聯名稱。若登錄檔中找不到此名稱，則會播放系統預設音效，除非同時指定了 SND_NODEFAULT。若沒有註冊預設音效，則會引發 RuntimeError。請勿與 SND_FILENAME 同時使用。

所有 Win32 系統至少支援以下項目；大多數系統支援更多：

PlaySound() name

對應的控制台音效名稱

'SystemAsterisk'

星號

'SystemExclamation'

驚嘆號

'SystemExit'

離開 Windows

'SystemHand'

關鍵性停止

'SystemQuestion'

問題

例如說：

import winsound
# 播放 Windows 的離開音效。
winsound.PlaySound("SystemExit", winsound.SND_ALIAS)

# 若有註冊預設音效，可能會播放該音效
# （因為 "*" 可能不是任何音效的註冊名稱）。
winsound.PlaySound("*", winsound.SND_ALIAS)

winsound.SND_LOOP

重複播放音效。必須同時使用 SND_ASYNC 旗標以避免阻塞。不能與 SND_MEMORY 一同使用。

winsound.SND_MEMORY

傳入 PlaySound() 的 sound 參數是 WAV 檔案的記憶體映像，型別為 bytes-like object。

備註

此模組不支援從記憶體映像非同步播放音效，因此若同時使用本旗標與 SND_ASYNC，將引發 RuntimeError。

winsound.SND_PURGE

停止播放指定音效的所有實例。

備註

此旗標在現代 Windows 平台上不支援。

winsound.SND_ASYNC

立即回傳，使音效可非同步播放。

winsound.SND_NODEFAULT

若找不到指定的音效，則不播放系統預設音效。

winsound.SND_NOSTOP

不中斷目前正在播放的音效。

winsound.SND_NOWAIT

若音效驅動程式正在忙碌，則立即回傳此。

備註

此旗標在現代 Windows 平台上不支援。

winsound.SND_APPLICATION

sound 參數為登錄檔中的應用程式特定別名。此旗標可與 SND_ALIAS 一同使用，以指定應用程式自訂的音效別名。

winsound.SND_SENTRY

當音效被播放時，會觸發 SoundSentry 事件。

在 3.14 版被加入.

winsound.SND_SYNC

音效會同步播放。這是預設行為。

在 3.14 版被加入.

winsound.SND_SYSTEM

將音效指派給系統通知音效的音訊工作階段 (audio session)。

在 3.14 版被加入.

winsound.MB_ICONASTERISK

播放 SystemDefault 音效。

winsound.MB_ICONEXCLAMATION

播放 SystemExclamation 音效。

winsound.MB_ICONHAND

播放 SystemHand 音效。

winsound.MB_ICONQUESTION

播放 SystemQuestion 音效。

winsound.MB_OK

播放 SystemDefault 音效。

winsound.MB_ICONERROR

播放 SystemHand 音效。

在 3.14 版被加入.

winsound.MB_ICONINFORMATION

播放 SystemDefault 音效。

在 3.14 版被加入.

winsound.MB_ICONSTOP

播放 SystemHand 音效。

在 3.14 版被加入.

winsound.MB_ICONWARNING

播放 SystemExclamation 音效。

在 3.14 版被加入.

Unix 特有服務

此章節所描述的模組 (module) 提供了針對 Unix 作業系統獨有特性的介面，或在某些情況下可用於其他 Unix 變形版本。以下為概述：

shlex --- 簡單的語法分析

shlex 物件

Parsing Rules

Improved Compatibility with Shells

posix --- 最常見的 POSIX 系統呼叫

對大檔案 (Large File) 的支援

值得注意的模組內容

pwd --- 密碼資料庫

grp --- 群組資料庫

termios --- POSIX 風格 tty 控制

範例

tty --- 終端機控制函式

pty --- 偽終端工具

範例

fcntl --- fcntl 和 ioctl 系統呼叫

resource --- 資源使用資訊

Resource Limits

Resource Usage

syslog --- Unix syslog 函式庫例程

範例

簡單範例

shlex --- 簡單的語法分析

原始碼：Lib/shlex.py [https://github.com/python/cpython/tree/3.14/Lib/shlex.py]

The shlex class makes it easy to write lexical analyzers for simple syntaxes resembling that of the Unix shell. This will often be useful for writing minilanguages, (for example, in run control files for Python applications) or for parsing quoted strings.

shlex 模組定義了以下函式：

shlex.split(s, comments=False, posix=True)

Split the string s using shell-like syntax. If comments is False (the default), the parsing of comments in the given string will be disabled (setting the commenters attribute of the shlex instance to the empty string). This function operates in POSIX mode by default, but uses non-POSIX mode if the posix argument is false.

在 3.12 版的變更: Passing None for s argument now raises an exception, rather than reading sys.stdin.

shlex.join(split_command)

Concatenate the tokens of the list split_command and return a string. This function is the inverse of split().

>>> from shlex import join
>>> print(join(['echo', '-n', 'Multiple words']))
echo -n 'Multiple words'

The returned value is shell-escaped to protect against injection vulnerabilities (see quote()).

在 3.8 版被加入.

shlex.quote(s)

Return a shell-escaped version of the string s. The returned value is a string that can safely be used as one token in a shell command line, for cases where you cannot use a list.

警告

The shlex module is only designed for Unix shells.

The quote() function is not guaranteed to be correct on non-POSIX compliant shells or shells from other operating systems such as Windows. Executing commands quoted by this module on such shells can open up the possibility of a command injection vulnerability.

Consider using functions that pass command arguments with lists such as subprocess.run() with shell=False.

This idiom would be unsafe:

>>> filename = 'somefile; rm -rf ~'
>>> command = 'ls -l {}'.format(filename)
>>> print(command)  # executed by a shell: boom!
ls -l somefile; rm -rf ~

quote() lets you plug the security hole:

>>> from shlex import quote
>>> command = 'ls -l {}'.format(quote(filename))
>>> print(command)
ls -l 'somefile; rm -rf ~'
>>> remote_command = 'ssh home {}'.format(quote(command))
>>> print(remote_command)
ssh home 'ls -l '"'"'somefile; rm -rf ~'"'"''

The quoting is compatible with UNIX shells and with split():

>>> from shlex import split
>>> remote_command = split(remote_command)
>>> remote_command
['ssh', 'home', "ls -l 'somefile; rm -rf ~'"]
>>> command = split(remote_command[-1])
>>> command
['ls', '-l', 'somefile; rm -rf ~']

在 3.3 版被加入.

shlex 模組定義了以下類別：

class shlex.shlex(instream=None, infile=None, posix=False, punctuation_chars=False)

A shlex instance or subclass instance is a lexical analyzer object. The initialization argument, if present, specifies where to read characters from. It must be a file-/stream-like object with read() and readline() methods, or a string. If no argument is given, input will be taken from sys.stdin. The second optional argument is a filename string, which sets the initial value of the infile attribute. If the instream argument is omitted or equal to sys.stdin, this second argument defaults to "stdin". The posix argument defines the operational mode: when posix is not true (default), the shlex instance will operate in compatibility mode. When operating in POSIX mode, shlex will try to be as close as possible to the POSIX shell parsing rules. The punctuation_chars argument provides a way to make the behaviour even closer to how real shells parse. This can take a number of values: the default value, False, preserves the behaviour seen under Python 3.5 and earlier. If set to True, then parsing of the characters ();<>|& is changed: any run of these characters (considered punctuation characters) is returned as a single token. If set to a non-empty string of characters, those characters will be used as the punctuation characters. Any characters in the wordchars attribute that appear in punctuation_chars will be removed from wordchars. See Improved Compatibility with Shells for more information. punctuation_chars can be set only upon shlex instance creation and can't be modified later.

在 3.6 版的變更: 新增 punctuation_chars 參數。

也參考

configparser 模組

Parser for configuration files similar to the Windows .ini files.

shlex 物件

shlex 實例有以下方法：

shlex.get_token()

Return a token. If tokens have been stacked using push_token(), pop a token off the stack. Otherwise, read one from the input stream. If reading encounters an immediate end-of-file, eof is returned (the empty string ('') in non-POSIX mode, and None in POSIX mode).

shlex.push_token(str)

Push the argument onto the token stack.

shlex.read_token()

Read a raw token. Ignore the pushback stack, and do not interpret source requests. (This is not ordinarily a useful entry point, and is documented here only for the sake of completeness.)

shlex.sourcehook(filename)

When shlex detects a source request (see source below) this method is given the following token as argument, and expected to return a tuple consisting of a filename and an open file-like object.

Normally, this method first strips any quotes off the argument. If the result is an absolute pathname, or there was no previous source request in effect, or the previous source was a stream (such as sys.stdin), the result is left alone. Otherwise, if the result is a relative pathname, the directory part of the name of the file immediately before it on the source inclusion stack is prepended (this behavior is like the way the C preprocessor handles #include "file.h").

The result of the manipulations is treated as a filename, and returned as the first component of the tuple, with open() called on it to yield the second component. (Note: this is the reverse of the order of arguments in instance initialization!)

This hook is exposed so that you can use it to implement directory search paths, addition of file extensions, and other namespace hacks. There is no corresponding 'close' hook, but a shlex instance will call the close() method of the sourced input stream when it returns EOF.

For more explicit control of source stacking, use the push_source() and pop_source() methods.

shlex.push_source(newstream, newfile=None)

Push an input source stream onto the input stack. If the filename argument is specified it will later be available for use in error messages. This is the same method used internally by the sourcehook() method.

shlex.pop_source()

Pop the last-pushed input source from the input stack. This is the same method used internally when the lexer reaches EOF on a stacked input stream.

shlex.error_leader(infile=None, lineno=None)

This method generates an error message leader in the format of a Unix C compiler error label; the format is '"%s", line %d: ', where the %s is replaced with the name of the current source file and the %d with the current input line number (the optional arguments can be used to override these).

This convenience is provided to encourage shlex users to generate error messages in the standard, parseable format understood by Emacs and other Unix tools.

Instances of shlex subclasses have some public instance variables which either control lexical analysis or can be used for debugging:

shlex.commenters

The string of characters that are recognized as comment beginners. All characters from the comment beginner to end of line are ignored. Includes just '#' by default.

shlex.wordchars

The string of characters that will accumulate into multi-character tokens. By default, includes all ASCII alphanumerics and underscore. In POSIX mode, the accented characters in the Latin-1 set are also included. If punctuation_chars is not empty, the characters ~-./*?=, which can appear in filename specifications and command line parameters, will also be included in this attribute, and any characters which appear in punctuation_chars will be removed from wordchars if they are present there. If whitespace_split is set to True, this will have no effect.

shlex.whitespace

Characters that will be considered whitespace and skipped. Whitespace bounds tokens. By default, includes space, tab, linefeed and carriage-return.

shlex.escape

Characters that will be considered as escape. This will be only used in POSIX mode, and includes just '\' by default.

shlex.quotes

Characters that will be considered string quotes. The token accumulates until the same quote is encountered again (thus, different quote types protect each other as in the shell.) By default, includes ASCII single and double quotes.

shlex.escapedquotes

Characters in quotes that will interpret escape characters defined in escape. This is only used in POSIX mode, and includes just '"' by default.

shlex.whitespace_split

If True, tokens will only be split in whitespaces. This is useful, for example, for parsing command lines with shlex, getting tokens in a similar way to shell arguments. When used in combination with punctuation_chars, tokens will be split on whitespace in addition to those characters.

在 3.8 版的變更: The punctuation_chars attribute was made compatible with the whitespace_split attribute.

shlex.infile

The name of the current input file, as initially set at class instantiation time or stacked by later source requests. It may be useful to examine this when constructing error messages.

shlex.instream

The input stream from which this shlex instance is reading characters.

shlex.source

This attribute is None by default. If you assign a string to it, that string will be recognized as a lexical-level inclusion request similar to the source keyword in various shells. That is, the immediately following token will be opened as a filename and input will be taken from that stream until EOF, at which point the close() method of that stream will be called and the input source will again become the original input stream. Source requests may be stacked any number of levels deep.

shlex.debug

If this attribute is numeric and 1 or more, a shlex instance will print verbose progress output on its behavior. If you need to use this, you can read the module source code to learn the details.

shlex.lineno

Source line number (count of newlines seen so far plus one).

shlex.token

The token buffer. It may be useful to examine this when catching exceptions.

shlex.eof

Token used to determine end of file. This will be set to the empty string (''), in non-POSIX mode, and to None in POSIX mode.

shlex.punctuation_chars

A read-only property. Characters that will be considered punctuation. Runs of punctuation characters will be returned as a single token. However, note that no semantic validity checking will be performed: for example, '>>>' could be returned as a token, even though it may not be recognised as such by shells.

在 3.6 版被加入.

Parsing Rules

When operating in non-POSIX mode, shlex will try to obey to the following rules.

Quote characters are not recognized within words (Do"Not"Separate is parsed as the single word Do"Not"Separate);

Escape characters are not recognized;

Enclosing characters in quotes preserve the literal value of all characters within the quotes;

Closing quotes separate words ("Do"Separate is parsed as "Do" and Separate);

If whitespace_split is False, any character not declared to be a word character, whitespace, or a quote will be returned as a single-character token. If it is True, shlex will only split words in whitespaces;

EOF is signaled with an empty string ('');

It's not possible to parse empty strings, even if quoted.

When operating in POSIX mode, shlex will try to obey to the following parsing rules.

Quotes are stripped out, and do not separate words ("Do"Not"Separate" is parsed as the single word DoNotSeparate);

Non-quoted escape characters (e.g. '\') preserve the literal value of the next character that follows;

Enclosing characters in quotes which are not part of escapedquotes (e.g. "'") preserve the literal value of all characters within the quotes;

Enclosing characters in quotes which are part of escapedquotes (e.g. '"') preserves the literal value of all characters within the quotes, with the exception of the characters mentioned in escape. The escape characters retain its special meaning only when followed by the quote in use, or the escape character itself. Otherwise the escape character will be considered a normal character.

EOF is signaled with a None value;

Quoted empty strings ('') are allowed.

Improved Compatibility with Shells

在 3.6 版被加入.

The shlex class provides compatibility with the parsing performed by common Unix shells like bash, dash, and sh. To take advantage of this compatibility, specify the punctuation_chars argument in the constructor. This defaults to False, which preserves pre-3.6 behaviour. However, if it is set to True, then parsing of the characters ();<>|& is changed: any run of these characters is returned as a single token. While this is short of a full parser for shells (which would be out of scope for the standard library, given the multiplicity of shells out there), it does allow you to perform processing of command lines more easily than you could otherwise. To illustrate, you can see the difference in the following snippet:

>>> import shlex
>>> text = "a && b; c && d || e; f >'abc'; (def \"ghi\")"
>>> s = shlex.shlex(text, posix=True)
>>> s.whitespace_split = True
>>> list(s)
['a', '&&', 'b;', 'c', '&&', 'd', '||', 'e;', 'f', '>abc;', '(def', 'ghi)']
>>> s = shlex.shlex(text, posix=True, punctuation_chars=True)
>>> s.whitespace_split = True
>>> list(s)
['a', '&&', 'b', ';', 'c', '&&', 'd', '||', 'e', ';', 'f', '>', 'abc', ';',
'(', 'def', 'ghi', ')']

Of course, tokens will be returned which are not valid for shells, and you'll need to implement your own error checks on the returned tokens.

Instead of passing True as the value for the punctuation_chars parameter, you can pass a string with specific characters, which will be used to determine which characters constitute punctuation. For example:

>>> import shlex
>>> s = shlex.shlex("a && b || c", punctuation_chars="|")
>>> list(s)
['a', '&', '&', 'b', '||', 'c']

備註

When punctuation_chars is specified, the wordchars attribute is augmented with the characters ~-./*?=. That is because these characters can appear in file names (including wildcards) and command-line arguments (e.g. --color=auto). Hence:

>>> import shlex
>>> s = shlex.shlex('~/a && b-c --color=auto || d *.py?',
...                 punctuation_chars=True)
>>> list(s)
['~/a', '&&', 'b-c', '--color=auto', '||', 'd', '*.py?']

However, to match the shell as closely as possible, it is recommended to always use posix and whitespace_split when using punctuation_chars, which will negate wordchars entirely.

For best effect, punctuation_chars should be set in conjunction with posix=True. (Note that posix=False is the default for shlex.)

posix --- 最常見的 POSIX 系統呼叫

該模組提供對由 C 標準和 POSIX 標準（一種偽裝的 Unix 介面）所標準化的作業系統功能的存取。

可用性: Unix.

不要直接引入此模組。請改為引入 os 模組，它提供了此介面的可移植 (portable) 版本。在 Unix 上，os 模組提供了 posix 介面的超集 (superset)。在非 Unix 作業系統上，posix 模組不可用，但始終可以通過 os 介面使用一個子集。一旦 os 有被引入，使用它代替 posix 不會有性能損失。此外，os 提供了一些額外的功能，例如當 os.environ 中的條目更改時自動呼叫 putenv()。

錯誤會以例外的形式被回報；常見的例外是因為型別錯誤而給出的，而系統呼叫回報的錯誤會引發 OSError。

對大檔案 (Large File) 的支援

一些作業系統（包括 AIX 和 Solaris）支援來自 C 程式模型且大於 2 GiB 的檔案，其中 int 和 long 是 32-bit（32 位元）的值。這通常透過將相關大小和偏移量 (offset) 種類定義為 64-bit 值來實作。此類檔案有時被稱為「大檔案 (large files)」。

當 off_t 的大小大於 long 且 long long 的大小至少與 off_t 相同時，對大檔案的支援會被啟用。可能需要使用某些編譯器旗標來配置和編譯 Python 以啟用此模式。例如，對於 Solaris 2.6 和 2.7，你需要執行如下操作：

CFLAGS="`getconf LFS_CFLAGS`" OPT="-g -O2 $CFLAGS" \
        ./configure

在支援大檔案的 Linux 系統上，這可能有效：

CFLAGS='-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64' OPT="-g -O2 $CFLAGS" \
        ./configure

值得注意的模組內容

除了 os 模組說明文件中描述的許多函式外，posix 還定義了以下資料項目：

posix.environ

表示直譯器啟動時的字串環境的字典。鍵和值在 Unix 上是位元組，在 Windows 上是 str。例如，environ[b'HOME']（Windows 上為 environ['HOME']）是你的主目錄的路徑名，等同於 C 語言中的 getenv("HOME")。

修改這個字典不會影響由 execv()、popen() 或 system() 傳遞的字串環境；如果你需要更改環境，請將 environ 傳遞給 execve() 或將變數賦值和匯出陳述句新增到 system() 或 popen() 的指令字串中。

在 3.2 版的變更: 在 Unix 上，鍵和值是位元組。

備註

os 模組提供了 environ 的替代實作，會在修改時更新環境。另請注意，更新 os.environ 將使該字典變成過時的。建議使用 os 模組版本，而不是直接存取 posix 模組。

pwd --- 密碼資料庫

此模組提供對 Unix 使用者帳戶和密碼資料庫的存取介面。它適用於所有 Unix 版本。

可用性: Unix, not WASI, not iOS.

密碼資料庫條目被報告為類似元組的物件 (tuple-like object)，其屬性會對應於 passwd 結構的成員（屬性欄位請見下面的 <pwd.h>）：

索引

屬性

意義

0

pw_name

登錄名

1

pw_passwd

可選的加密密碼

2

pw_uid

數值的使用者 ID

3

pw_gid

數值的群組 ID

4

pw_gecos

使用者名稱或註解欄位

5

pw_dir

使用者主目錄 (home directory)

6

pw_shell

使用者命令直譯器

uid 和 gid 項目為整數，其他項目都是字串。如果找不到請求的條目，則會引發 KeyError。

備註

在傳統的 Unix 中，pw_passwd 欄位通常包含一個使用 DES 衍生演算法加密的密碼。然而，大多數現代 Unix 是使用所謂的 shadow password 系統。在那些 Unix 上，pw_passwd 欄位僅包含一個星號 ('*') 或字母 'x'，其中加密密碼儲存在非全域可讀的 (not world readable) /etc/shadow 檔案中。pw_passwd 欄位是否包含任何有用的內容取決於系統。

它定義了以下項目：

pwd.getpwuid(uid)

回傳給定數值使用者 ID 的密碼資料庫條目。

pwd.getpwnam(name)

回傳給定使用者名稱的密碼資料庫條目。

pwd.getpwall()

以任意順序回傳所有可用密碼資料庫條目的 list。

也參考

grp 模組

群組資料庫的介面，與此模組類似。

grp --- 群組資料庫

該模組提供對 Unix 群組資料庫的存取， 所有 Unix 版本皆可使用。

可用性: Unix, not WASI, not Android, not iOS.

群組資料庫條目以類似 tuple 物件的方式報傳入， 其屬性對應於 group 結構的成員（屬性欄位如下， 請參閱 <grp.h>）：

索引

屬性

含義

0

gr_name

群組名稱

1

gr_passwd

（被加密後的）群組密碼；大部分情況下是空的

2

gr_gid

群組的數字 ID

3

gr_mem

所有群組成員的使用者名稱

gid 是整數，name 和 password 是字串， 而 member list 是字串串列。（請注意， 根據密碼資料庫， 大多數使用者並未被明確列為其所在群組的成員。 請檢查這兩個資料庫，以取得完整的成員資訊。 另外請注意，以 + 或 - 開頭的 gr_name 很可能是 YP/NIS 參照，可能無法透過 getgrnam() 或 getgrgid() 取得）。

它定義了以下項目：

grp.getgrgid(id)

回傳給定群組 ID 的群組資料庫條目。 KeyError 會在找不到所要求的條目時被引發。

在 3.10 版的變更: TypeError 會在非整數的引數如浮點數或字串被傳入時被引發。

grp.getgrnam(name)

回傳給定群組名稱的群組資料庫條目。 KeyError 會在找不到所要求的條目時引發。

grp.getgrall()

以任意順序傳回所有可用群組條目的串列。

也參考

pwd 模組

使用者資料庫的介面，與此類似。

termios --- POSIX 風格 tty 控制

This module provides an interface to the POSIX calls for tty I/O control. For a complete description of these calls, see termios(3) [https://manpages.debian.org/termios(3)] Unix manual page. It is only available for those Unix versions that support POSIX termios style tty I/O control configured during installation.

可用性: Unix.

All functions in this module take a file descriptor fd as their first argument. This can be an integer file descriptor, such as returned by sys.stdin.fileno(), or a file object, such as sys.stdin itself.

This module also defines all the constants needed to work with the functions provided here; these have the same name as their counterparts in C. Please refer to your system documentation for more information on using these terminal control interfaces.

此模組定義了以下函式：

termios.tcgetattr(fd)

Return a list containing the tty attributes for file descriptor fd, as follows: [iflag, oflag, cflag, lflag, ispeed, ospeed, cc] where cc is a list of the tty special characters (each a string of length 1, except the items with indices VMIN and VTIME, which are integers when these fields are defined). The interpretation of the flags and the speeds as well as the indexing in the cc array must be done using the symbolic constants defined in the termios module.

termios.tcsetattr(fd, when, attributes)

Set the tty attributes for file descriptor fd from the attributes, which is a list like the one returned by tcgetattr(). The when argument determines when the attributes are changed:

termios.TCSANOW

Change attributes immediately.

termios.TCSADRAIN

Change attributes after transmitting all queued output.

termios.TCSAFLUSH

Change attributes after transmitting all queued output and discarding all queued input.

termios.tcsendbreak(fd, duration)

Send a break on file descriptor fd. A zero duration sends a break for 0.25--0.5 seconds; a nonzero duration has a system dependent meaning.

termios.tcdrain(fd)

Wait until all output written to file descriptor fd has been transmitted.

termios.tcflush(fd, queue)

Discard queued data on file descriptor fd. The queue selector specifies which queue: TCIFLUSH for the input queue, TCOFLUSH for the output queue, or TCIOFLUSH for both queues.

termios.tcflow(fd, action)

Suspend or resume input or output on file descriptor fd. The action argument can be TCOOFF to suspend output, TCOON to restart output, TCIOFF to suspend input, or TCION to restart input.

termios.tcgetwinsize(fd)

Return a tuple (ws_row, ws_col) containing the tty window size for file descriptor fd. Requires termios.TIOCGWINSZ or termios.TIOCGSIZE.

在 3.11 版被加入.

termios.tcsetwinsize(fd, winsize)

Set the tty window size for file descriptor fd from winsize, which is a two-item tuple (ws_row, ws_col) like the one returned by tcgetwinsize(). Requires at least one of the pairs (termios.TIOCGWINSZ, termios.TIOCSWINSZ); (termios.TIOCGSIZE, termios.TIOCSSIZE) to be defined.

在 3.11 版被加入.

也參考

tty 模組

Convenience functions for common terminal control operations.

範例

Here's a function that prompts for a password with echoing turned off. Note the technique using a separate tcgetattr() call and a try ... finally statement to ensure that the old tty attributes are restored exactly no matter what happens:

def getpass(prompt="Password: "):
    import termios, sys
    fd = sys.stdin.fileno()
    old = termios.tcgetattr(fd)
    new = termios.tcgetattr(fd)
    new[3] = new[3] & ~termios.ECHO          # lflags
    try:
        termios.tcsetattr(fd, termios.TCSADRAIN, new)
        passwd = input(prompt)
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old)
    return passwd

tty --- 終端機控制函式

原始碼：Lib/tty.py [https://github.com/python/cpython/tree/3.14/Lib/tty.py]

tty 模組定義了將 tty 放入 cbreak 和 raw 模式的函式。

可用性: Unix.

因為它需要 termios 模組，所以只能在 Unix 上執行。

tty 模組定義了以下函式：

tty.cfmakeraw(mode)

將 tty 屬性串列 mode 轉換成原始模式下的 tty 屬性串列，這個串列就像 termios.tcgetattr() 所回傳的一樣。

在 3.12 版被加入.

tty.cfmakecbreak(mode)

將 tty 屬性串列 mode 轉換成 cbreak 模式下的 tty 屬性串列，這個串列就像 termios.tcgetattr() 所回傳的一樣。

這會清除 mode 中的 ECHO 和 ICANON 本地模式旗標，並將最小輸入設定為 1 位元組，且無延遲。

在 3.12 版被加入.

在 3.12.2 版的變更: 不再清除 ICRNL 標記。這符合 Linux 和 macOS 的 stty cbreak 行為，也符合 setcbreak() 歷來的做法。

tty.setraw(fd, when=termios.TCSAFLUSH)

將檔案描述器 fd 的模式更改為 raw。如果 when 被省略，則預設為 termios.TCSAFLUSH，並傳遞給 termios.tcsetattr()。termios.tcgetattr() 的回傳值會在設定 fd 模式為 raw 之前先儲存起來。此函式回傳這個值。

在 3.12 版的變更: 現在的回傳值為原本的 tty 屬性，而不是 None。

tty.setcbreak(fd, when=termios.TCSAFLUSH)

將檔案描述器 fd 的模式更改為 cbreak。如果 when 被省略，則預設為 termios.TCSAFLUSH，並傳遞給 termios.tcsetattr()。termios.tcgetattr() 的回傳值會在設定 fd 模式為 raw 之前先儲存起來。此函式回傳這個值。

這會清除 ECHO 和 ICANON 本地模式旗標，並將最小輸入設定為 1 位元組，且無延遲。

在 3.12 版的變更: 現在的回傳值為原本的 tty 屬性，而不是 None。

在 3.12.2 版的變更: 不再清除 ICRNL 旗標。這恢復了 Python 3.11 及更早版本的行為，也符合 Linux、macOS 及 BSD 在他們的 stty(1) man 頁面中描述的 cbreak 模式。

也參考

termios 模組

低階終端機控制介面。

pty --- 偽終端工具

原始碼：Lib/pty.py [https://github.com/python/cpython/tree/3.14/Lib/pty.py]

The pty module defines operations for handling the pseudo-terminal concept: starting another process and being able to write to and read from its controlling terminal programmatically.

可用性: Unix.

Pseudo-terminal handling is highly platform dependent. This code is mainly tested on Linux, FreeBSD, and macOS (it is supposed to work on other POSIX platforms but it's not been thoroughly tested).

pty 模組定義了以下函式：

pty.fork()

Fork. Connect the child's controlling terminal to a pseudo-terminal. Return value is (pid, fd). Note that the child gets pid 0, and the fd is invalid. The parent's return value is the pid of the child, and fd is a file descriptor connected to the child's controlling terminal (and also to the child's standard input and output).

警告

On macOS the use of this function is unsafe when mixed with using higher-level system APIs, and that includes using urllib.request.

pty.openpty()

Open a new pseudo-terminal pair, using os.openpty() if possible, or emulation code for generic Unix systems. Return a pair of file descriptors (master, slave), for the master and the slave end, respectively.

pty.spawn(argv[, master_read[, stdin_read]])

Spawn a process, and connect its controlling terminal with the current process's standard io. This is often used to baffle programs which insist on reading from the controlling terminal. It is expected that the process spawned behind the pty will eventually terminate, and when it does spawn will return.

A loop copies STDIN of the current process to the child and data received from the child to STDOUT of the current process. It is not signaled to the child if STDIN of the current process closes down.

The functions master_read and stdin_read are passed a file descriptor which they should read from, and they should always return a byte string. In order to force spawn to return before the child process exits an empty byte array should be returned to signal end of file.

The default implementation for both functions will read and return up to 1024 bytes each time the function is called. The master_read callback is passed the pseudoterminal’s master file descriptor to read output from the child process, and stdin_read is passed file descriptor 0, to read from the parent process's standard input.

Returning an empty byte string from either callback is interpreted as an end-of-file (EOF) condition, and that callback will not be called after that. If stdin_read signals EOF the controlling terminal can no longer communicate with the parent process OR the child process. Unless the child process will quit without any input, spawn will then loop forever. If master_read signals EOF the same behavior results (on linux at least).

Return the exit status value from os.waitpid() on the child process.

os.waitstatus_to_exitcode() can be used to convert the exit status into an exit code.

引發一個附帶引數 argv 的稽核事件 pty.spawn。

在 3.4 版的變更: spawn() now returns the status value from os.waitpid() on the child process.

範例

The following program acts like the Unix command script(1) [https://manpages.debian.org/script(1)], using a pseudo-terminal to record all input and output of a terminal session in a "typescript".

import argparse
import os
import pty
import sys
import time

parser = argparse.ArgumentParser()
parser.add_argument('-a', dest='append', action='store_true')
parser.add_argument('-p', dest='use_python', action='store_true')
parser.add_argument('filename', nargs='?', default='typescript')
options = parser.parse_args()

shell = sys.executable if options.use_python else os.environ.get('SHELL', 'sh')
filename = options.filename
mode = 'ab' if options.append else 'wb'

with open(filename, mode) as script:
    def read(fd):
        data = os.read(fd, 1024)
        script.write(data)
        return data

    print('Script started, file is', filename)
    script.write(('Script started on %s\n' % time.asctime()).encode())

    pty.spawn(shell, read)

    script.write(('Script done on %s\n' % time.asctime()).encode())
    print('Script done, file is', filename)

fcntl --- fcntl 和 ioctl 系統呼叫

This module performs file and I/O control on file descriptors. It is an interface to the fcntl() and ioctl() Unix routines. See the fcntl(2) [https://manpages.debian.org/fcntl(2)] and ioctl(2) [https://manpages.debian.org/ioctl(2)] Unix manual pages for full details.

可用性: Unix, not WASI.

All functions in this module take a file descriptor fd as their first argument. This can be an integer file descriptor, such as returned by sys.stdin.fileno(), or an io.IOBase object, such as sys.stdin itself, which provides a fileno() that returns a genuine file descriptor.

在 3.3 版的變更: Operations in this module used to raise an IOError where they now raise an OSError.

在 3.8 版的變更: The fcntl module now contains F_ADD_SEALS, F_GET_SEALS, and F_SEAL_* constants for sealing of os.memfd_create() file descriptors.

在 3.9 版的變更: On macOS, the fcntl module exposes the F_GETPATH constant, which obtains the path of a file from a file descriptor. On Linux(>=3.15), the fcntl module exposes the F_OFD_GETLK, F_OFD_SETLK and F_OFD_SETLKW constants, which are used when working with open file description locks.

在 3.10 版的變更: On Linux >= 2.6.11, the fcntl module exposes the F_GETPIPE_SZ and F_SETPIPE_SZ constants, which allow to check and modify a pipe's size respectively.

在 3.11 版的變更: On FreeBSD, the fcntl module exposes the F_DUP2FD and F_DUP2FD_CLOEXEC constants, which allow to duplicate a file descriptor, the latter setting FD_CLOEXEC flag in addition.

在 3.12 版的變更: On Linux >= 4.5, the fcntl module exposes the FICLONE and FICLONERANGE constants, which allow to share some data of one file with another file by reflinking on some filesystems (e.g., btrfs, OCFS2, and XFS). This behavior is commonly referred to as "copy-on-write".

在 3.13 版的變更: On Linux >= 2.6.32, the fcntl module exposes the F_GETOWN_EX, F_SETOWN_EX, F_OWNER_TID, F_OWNER_PID, F_OWNER_PGRP constants, which allow to direct I/O availability signals to a specific thread, process, or process group. On Linux >= 4.13, the fcntl module exposes the F_GET_RW_HINT, F_SET_RW_HINT, F_GET_FILE_RW_HINT, F_SET_FILE_RW_HINT, and RWH_WRITE_LIFE_* constants, which allow to inform the kernel about the relative expected lifetime of writes on a given inode or via a particular open file description. On Linux >= 5.1 and NetBSD, the fcntl module exposes the F_SEAL_FUTURE_WRITE constant for use with F_ADD_SEALS and F_GET_SEALS operations. On FreeBSD, the fcntl module exposes the F_READAHEAD, F_ISUNIONSTACK, and F_KINFO constants. On macOS and FreeBSD, the fcntl module exposes the F_RDAHEAD constant. On NetBSD and AIX, the fcntl module exposes the F_CLOSEM constant. On NetBSD, the fcntl module exposes the F_MAXFD constant. On macOS and NetBSD, the fcntl module exposes the F_GETNOSIGPIPE and F_SETNOSIGPIPE constant.

在 3.14 版的變更: On Linux >= 6.1, the fcntl module exposes the F_DUPFD_QUERY to query a file descriptor pointing to the same file.

這個模組定義了以下函式：

fcntl.fcntl(fd, cmd, arg=0, /)

Perform the operation cmd on file descriptor fd (file objects providing a fileno() method are accepted as well). The values used for cmd are operating system dependent, and are available as constants in the fcntl module, using the same names as used in the relevant C header files. The argument arg can either be an integer value, a bytes-like object, or a string. The type and size of arg must match the type and size of the argument of the operation as specified in the relevant C documentation.

When arg is an integer, the function returns the integer return value of the C fcntl() call.

When the argument is bytes-like object, it represents a binary structure, for example, created by struct.pack(). A string value is encoded to binary using the UTF-8 encoding. The binary data is copied to a buffer whose address is passed to the C fcntl() call. The return value after a successful call is the contents of the buffer, converted to a bytes object. The length of the returned object will be the same as the length of the arg argument. This is limited to 1024 bytes.

If the fcntl() call fails, an OSError is raised.

備註

If the type or the size of arg does not match the type or size of the argument of the operation (for example, if an integer is passed when a pointer is expected, or the information returned in the buffer by the operating system is larger than 1024 bytes), this is most likely to result in a segmentation violation or a more subtle data corruption.

引發一個附帶引數 fd、cmd、arg 的稽核事件 fcntl.fcntl。

在 3.14 版的變更: Add support of arbitrary bytes-like objects, not only bytes.

fcntl.ioctl(fd, request, arg=0, mutate_flag=True, /)

This function is identical to the fcntl() function, except that the argument handling is even more complicated.

The request parameter is limited to values that can fit in 32-bits or 64-bits, depending on the platform. Additional constants of interest for use as the request argument can be found in the termios module, under the same names as used in the relevant C header files.

The parameter arg can be an integer, a bytes-like object, or a string. The type and size of arg must match the type and size of the argument of the operation as specified in the relevant C documentation.

If arg does not support the read-write buffer interface or the mutate_flag is false, behavior is as for the fcntl() function.

If arg supports the read-write buffer interface (like bytearray) and mutate_flag is true (the default), then the buffer is (in effect) passed to the underlying ioctl() system call, the latter's return code is passed back to the calling Python, and the buffer's new contents reflect the action of the ioctl(). This is a slight simplification, because if the supplied buffer is less than 1024 bytes long it is first copied into a static buffer 1024 bytes long which is then passed to ioctl() and copied back into the supplied buffer.

If the ioctl() call fails, an OSError exception is raised.

備註

If the type or size of arg does not match the type or size of the operation's argument (for example, if an integer is passed when a pointer is expected, or the information returned in the buffer by the operating system is larger than 1024 bytes, or the size of the mutable bytes-like object is too small), this is most likely to result in a segmentation violation or a more subtle data corruption.

範例：

>>> import array, fcntl, struct, termios, os
>>> os.getpgrp()
13341
>>> struct.unpack('h', fcntl.ioctl(0, termios.TIOCGPGRP, "  "))[0]
13341
>>> buf = array.array('h', [0])
>>> fcntl.ioctl(0, termios.TIOCGPGRP, buf, 1)
0
>>> buf
array('h', [13341])

引發一個附帶引數 fd、request、arg 的稽核事件 fcntl.ioctl。

在 3.14 版的變更: The GIL is always released during a system call. System calls failing with EINTR are automatically retried.

fcntl.flock(fd, operation, /)

Perform the lock operation operation on file descriptor fd (file objects providing a fileno() method are accepted as well). See the Unix manual flock(2) [https://manpages.debian.org/flock(2)] for details. (On some systems, this function is emulated using fcntl().)

If the flock() call fails, an OSError exception is raised.

引發一個附帶引數 fd、operation 的稽核事件 fcntl.flock。

fcntl.lockf(fd, cmd, len=0, start=0, whence=0, /)

This is essentially a wrapper around the fcntl() locking calls. fd is the file descriptor (file objects providing a fileno() method are accepted as well) of the file to lock or unlock, and cmd is one of the following values:

fcntl.LOCK_UN

Release an existing lock.

fcntl.LOCK_SH

Acquire a shared lock.

fcntl.LOCK_EX

Acquire an exclusive lock.

fcntl.LOCK_NB

Bitwise OR with any of the other three LOCK_* constants to make the request non-blocking.

If LOCK_NB is used and the lock cannot be acquired, an OSError will be raised and the exception will have an errno attribute set to EACCES or EAGAIN (depending on the operating system; for portability, check for both values). On at least some systems, LOCK_EX can only be used if the file descriptor refers to a file opened for writing.

len is the number of bytes to lock, start is the byte offset at which the lock starts, relative to whence, and whence is as with io.IOBase.seek(), specifically:

0 -- relative to the start of the file (os.SEEK_SET)

1 -- relative to the current buffer position (os.SEEK_CUR)

2 -- relative to the end of the file (os.SEEK_END)

The default for start is 0, which means to start at the beginning of the file. The default for len is 0 which means to lock to the end of the file. The default for whence is also 0.

引發一個附帶引數 fd、cmd、len、start、whence 的稽核事件 fcntl.lockf。

Examples (all on a SVR4 compliant system):

import struct, fcntl, os

f = open(...)
rv = fcntl.fcntl(f, fcntl.F_SETFL, os.O_NDELAY)

lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0)
rv = fcntl.fcntl(f, fcntl.F_SETLKW, lockdata)

Note that in the first example the return value variable rv will hold an integer value; in the second example it will hold a bytes object. The structure lay-out for the lockdata variable is system dependent --- therefore using the flock() call may be better.

也參考

os 模組

If the locking flags O_SHLOCK and O_EXLOCK are present in the os module (on BSD only), the os.open() function provides an alternative to the lockf() and flock() functions.

resource --- 資源使用資訊

This module provides basic mechanisms for measuring and controlling system resources utilized by a program.

可用性: Unix, not WASI.

Symbolic constants are used to specify particular system resources and to request usage information about either the current process or its children.

An OSError is raised on syscall failure.

exception resource.error

A deprecated alias of OSError.

在 3.3 版的變更: Following PEP 3151 [https://peps.python.org/pep-3151/], this class was made an alias of OSError.

Resource Limits

Resources usage can be limited using the setrlimit() function described below. Each resource is controlled by a pair of limits: a soft limit and a hard limit. The soft limit is the current limit, and may be lowered or raised by a process over time. The soft limit can never exceed the hard limit. The hard limit can be lowered to any value greater than the soft limit, but not raised. (Only processes with the effective UID of the super-user can raise a hard limit.)

The specific resources that can be limited are system dependent. They are described in the getrlimit(2) [https://manpages.debian.org/getrlimit(2)] man page. The resources listed below are supported when the underlying operating system supports them; resources which cannot be checked or controlled by the operating system are not defined in this module for those platforms.

resource.RLIM_INFINITY

Constant used to represent the limit for an unlimited resource.

resource.getrlimit(resource)

Returns a tuple (soft, hard) with the current soft and hard limits of resource. Raises ValueError if an invalid resource is specified, or error if the underlying system call fails unexpectedly.

resource.setrlimit(resource, limits)

Sets new limits of consumption of resource. The limits argument must be a tuple (soft, hard) of two integers describing the new limits. A value of RLIM_INFINITY can be used to request a limit that is unlimited.

Raises ValueError if an invalid resource is specified, if the new soft limit exceeds the hard limit, or if a process tries to raise its hard limit. Specifying a limit of RLIM_INFINITY when the hard or system limit for that resource is not unlimited will result in a ValueError. A process with the effective UID of super-user can request any valid limit value, including unlimited, but ValueError will still be raised if the requested limit exceeds the system imposed limit.

setrlimit may also raise error if the underlying system call fails.

VxWorks only supports setting RLIMIT_NOFILE.

引發一個附帶引數 resource、limits 的稽核事件 resource.setrlimit。

resource.prlimit(pid, resource[, limits])

Combines setrlimit() and getrlimit() in one function and supports to get and set the resources limits of an arbitrary process. If pid is 0, then the call applies to the current process. resource and limits have the same meaning as in setrlimit(), except that limits is optional.

When limits is not given the function returns the resource limit of the process pid. When limits is given the resource limit of the process is set and the former resource limit is returned.

Raises ProcessLookupError when pid can't be found and PermissionError when the user doesn't have CAP_SYS_RESOURCE for the process.

引發一個附帶引數 pid、resource、limits 的稽核事件 resource.prlimit。

可用性: Linux >= 2.6.36 with glibc >= 2.13.

在 3.4 版被加入.

These symbols define resources whose consumption can be controlled using the setrlimit() and getrlimit() functions described below. The values of these symbols are exactly the constants used by C programs.

The Unix man page for getrlimit(2) [https://manpages.debian.org/getrlimit(2)] lists the available resources. Note that not all systems use the same symbol or same value to denote the same resource. This module does not attempt to mask platform differences --- symbols not defined for a platform will not be available from this module on that platform.

resource.RLIMIT_CORE

The maximum size (in bytes) of a core file that the current process can create. This may result in the creation of a partial core file if a larger core would be required to contain the entire process image.

resource.RLIMIT_CPU

The maximum amount of processor time (in seconds) that a process can use. If this limit is exceeded, a SIGXCPU signal is sent to the process. (See the signal module documentation for information about how to catch this signal and do something useful, e.g. flush open files to disk.)

resource.RLIMIT_FSIZE

The maximum size of a file which the process may create.

resource.RLIMIT_DATA

The maximum size (in bytes) of the process's heap.

resource.RLIMIT_STACK

The maximum size (in bytes) of the call stack for the current process. This only affects the stack of the main thread in a multi-threaded process.

resource.RLIMIT_RSS

The maximum resident set size that should be made available to the process.

resource.RLIMIT_NPROC

The maximum number of processes the current process may create.

resource.RLIMIT_NOFILE

The maximum number of open file descriptors for the current process.

resource.RLIMIT_OFILE

The BSD name for RLIMIT_NOFILE.

resource.RLIMIT_MEMLOCK

The maximum address space which may be locked in memory.

resource.RLIMIT_VMEM

The largest area of mapped memory which the process may occupy. Usually an alias of RLIMIT_AS.

可用性: Solaris, FreeBSD, NetBSD.

resource.RLIMIT_AS

The maximum area (in bytes) of address space which may be taken by the process.

resource.RLIMIT_MSGQUEUE

The number of bytes that can be allocated for POSIX message queues.

可用性: Linux >= 2.6.8.

在 3.4 版被加入.

resource.RLIMIT_NICE

The ceiling for the process's nice level (calculated as 20 - rlim_cur).

可用性: Linux >= 2.6.12.

在 3.4 版被加入.

resource.RLIMIT_RTPRIO

The ceiling of the real-time priority.

可用性: Linux >= 2.6.12.

在 3.4 版被加入.

resource.RLIMIT_RTTIME

The time limit (in microseconds) on CPU time that a process can spend under real-time scheduling without making a blocking syscall.

可用性: Linux >= 2.6.25.

在 3.4 版被加入.

resource.RLIMIT_SIGPENDING

The number of signals which the process may queue.

可用性: Linux >= 2.6.8.

在 3.4 版被加入.

resource.RLIMIT_SBSIZE

The maximum size (in bytes) of socket buffer usage for this user. This limits the amount of network memory, and hence the amount of mbufs, that this user may hold at any time.

可用性: FreeBSD, NetBSD.

在 3.4 版被加入.

resource.RLIMIT_SWAP

The maximum size (in bytes) of the swap space that may be reserved or used by all of this user id's processes. This limit is enforced only if bit 1 of the vm.overcommit sysctl is set. Please see tuning(7) [https://man.freebsd.org/cgi/man.cgi?query=tuning&sektion=7] for a complete description of this sysctl.

可用性: FreeBSD >= 8.

在 3.4 版被加入.

resource.RLIMIT_NPTS

The maximum number of pseudo-terminals created by this user id.

可用性: FreeBSD >= 8.

在 3.4 版被加入.

resource.RLIMIT_KQUEUES

The maximum number of kqueues this user id is allowed to create.

可用性: FreeBSD >= 11.

在 3.10 版被加入.

Resource Usage

These functions are used to retrieve resource usage information:

resource.getrusage(who)

This function returns an object that describes the resources consumed by either the current process or its children, as specified by the who parameter. The who parameter should be specified using one of the RUSAGE_* constants described below.

一個簡單範例：

from resource import *
import time

# a non CPU-bound task
time.sleep(3)
print(getrusage(RUSAGE_SELF))

# a CPU-bound task
for i in range(10 ** 8):
   _ = 1 + 1
print(getrusage(RUSAGE_SELF))

The fields of the return value each describe how a particular system resource has been used, e.g. amount of time spent running is user mode or number of times the process was swapped out of main memory. Some values are dependent on the clock tick internal, e.g. the amount of memory the process is using.

For backward compatibility, the return value is also accessible as a tuple of 16 elements.

The fields ru_utime and ru_stime of the return value are floating-point values representing the amount of time spent executing in user mode and the amount of time spent executing in system mode, respectively. The remaining values are integers. Consult the getrusage(2) [https://manpages.debian.org/getrusage(2)] man page for detailed information about these values. A brief summary is presented here:

Index

Field

Resource

0

ru_utime

time in user mode (float seconds)

1

ru_stime

time in system mode (float seconds)

2

ru_maxrss

maximum resident set size

3

ru_ixrss

shared memory size

4

ru_idrss

unshared memory size

5

ru_isrss

unshared stack size

6

ru_minflt

page faults not requiring I/O

7

ru_majflt

page faults requiring I/O

8

ru_nswap

number of swap outs

9

ru_inblock

block input operations

10

ru_oublock

block output operations

11

ru_msgsnd

messages sent

12

ru_msgrcv

messages received

13

ru_nsignals

signals received

14

ru_nvcsw

voluntary context switches

15

ru_nivcsw

involuntary context switches

This function will raise a ValueError if an invalid who parameter is specified. It may also raise error exception in unusual circumstances.

resource.getpagesize()

Returns the number of bytes in a system page. (This need not be the same as the hardware page size.)

The following RUSAGE_* symbols are passed to the getrusage() function to specify which processes information should be provided for.

resource.RUSAGE_SELF

Pass to getrusage() to request resources consumed by the calling process, which is the sum of resources used by all threads in the process.

resource.RUSAGE_CHILDREN

Pass to getrusage() to request resources consumed by child processes of the calling process which have been terminated and waited for.

resource.RUSAGE_BOTH

Pass to getrusage() to request resources consumed by both the current process and child processes. May not be available on all systems.

resource.RUSAGE_THREAD

Pass to getrusage() to request resources consumed by the current thread. May not be available on all systems.

在 3.2 版被加入.

syslog --- Unix syslog 函式庫例程

This module provides an interface to the Unix syslog library routines. Refer to the Unix manual pages for a detailed description of the syslog facility.

可用性: Unix, not WASI, not iOS.

This module wraps the system syslog family of routines. A pure Python library that can speak to a syslog server is available in the logging.handlers module as SysLogHandler.

該模組定義了以下函式：

syslog.syslog(message)

syslog.syslog(priority, message)

Send the string message to the system logger. A trailing newline is added if necessary. Each message is tagged with a priority composed of a facility and a level. The optional priority argument, which defaults to LOG_INFO, determines the message priority. If the facility is not encoded in priority using logical-or (LOG_INFO | LOG_USER), the value given in the openlog() call is used.

If openlog() has not been called prior to the call to syslog(), openlog() will be called with no arguments.

引發一個附帶引數 priority、message 的稽核事件 syslog.syslog。

在 3.2 版的變更: In previous versions, openlog() would not be called automatically if it wasn't called prior to the call to syslog(), deferring to the syslog implementation to call openlog().

在 3.12 版的變更: This function is restricted in subinterpreters. (Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users.) openlog() must be called in the main interpreter before syslog() may be used in a subinterpreter. Otherwise it will raise RuntimeError.

syslog.openlog([ident[, logoption[, facility]]])

Logging options of subsequent syslog() calls can be set by calling openlog(). syslog() will call openlog() with no arguments if the log is not currently open.

The optional ident keyword argument is a string which is prepended to every message, and defaults to sys.argv[0] with leading path components stripped. The optional logoption keyword argument (default is 0) is a bit field -- see below for possible values to combine. The optional facility keyword argument (default is LOG_USER) sets the default facility for messages which do not have a facility explicitly encoded.

引發一個附帶引數 ident、logoption、facility 的稽核事件 syslog.openlog。

在 3.2 版的變更: In previous versions, keyword arguments were not allowed, and ident was required.

在 3.12 版的變更: This function is restricted in subinterpreters. (Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users.) This may only be called in the main interpreter. It will raise RuntimeError if called in a subinterpreter.

syslog.closelog()

Reset the syslog module values and call the system library closelog().

This causes the module to behave as it does when initially imported. For example, openlog() will be called on the first syslog() call (if openlog() hasn't already been called), and ident and other openlog() parameters are reset to defaults.

引發一個不附帶引數的稽核事件 syslog.closelog。

在 3.12 版的變更: This function is restricted in subinterpreters. (Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users.) This may only be called in the main interpreter. It will raise RuntimeError if called in a subinterpreter.

syslog.setlogmask(maskpri)

Set the priority mask to maskpri and return the previous mask value. Calls to syslog() with a priority level not set in maskpri are ignored. The default is to log all priorities. The function LOG_MASK(pri) calculates the mask for the individual priority pri. The function LOG_UPTO(pri) calculates the mask for all priorities up to and including pri.

引發一個附帶引數 maskpri 的稽核事件 syslog.setlogmask。

這個模組定義了以下常數：

syslog.LOG_EMERG

syslog.LOG_ALERT

syslog.LOG_CRIT

syslog.LOG_ERR

syslog.LOG_WARNING

syslog.LOG_NOTICE

syslog.LOG_INFO

syslog.LOG_DEBUG

Priority levels (high to low).

syslog.LOG_AUTH

syslog.LOG_AUTHPRIV

syslog.LOG_CRON

syslog.LOG_DAEMON

syslog.LOG_FTP

syslog.LOG_INSTALL

syslog.LOG_KERN

syslog.LOG_LAUNCHD

syslog.LOG_LPR

syslog.LOG_MAIL

syslog.LOG_NETINFO

syslog.LOG_NEWS

syslog.LOG_RAS

syslog.LOG_REMOTEAUTH

syslog.LOG_SYSLOG

syslog.LOG_USER

syslog.LOG_UUCP

syslog.LOG_LOCAL0

syslog.LOG_LOCAL1

syslog.LOG_LOCAL2

syslog.LOG_LOCAL3

syslog.LOG_LOCAL4

syslog.LOG_LOCAL5

syslog.LOG_LOCAL6

syslog.LOG_LOCAL7

Facilities, depending on availability in <syslog.h> for LOG_AUTHPRIV, LOG_FTP, LOG_NETINFO, LOG_REMOTEAUTH, LOG_INSTALL and LOG_RAS.

在 3.13 版的變更: Added LOG_FTP, LOG_NETINFO, LOG_REMOTEAUTH, LOG_INSTALL, LOG_RAS, and LOG_LAUNCHD.

syslog.LOG_PID

syslog.LOG_CONS

syslog.LOG_NDELAY

syslog.LOG_ODELAY

syslog.LOG_NOWAIT

syslog.LOG_PERROR

Log options, depending on availability in <syslog.h> for LOG_ODELAY, LOG_NOWAIT and LOG_PERROR.

範例

簡單範例

一組簡單範例：

import syslog

syslog.syslog('Processing started')
if error:
    syslog.syslog(syslog.LOG_ERR, 'Processing started')

An example of setting some log options, these would include the process ID in logged messages, and write the messages to the destination facility used for mail logging:

syslog.openlog(logoption=syslog.LOG_PID, facility=syslog.LOG_MAIL)
syslog.syslog('E-mail processing initiated...')

模組命令列介面

以下模組具有命令列介面。

ast

asyncio

base64

calendar

code

compileall

cProfile: 請見 profile

dis

doctest

encodings.rot_13

ensurepip

filecmp

fileinput

ftplib

gzip

http.server

idlelib

inspect

json

mimetypes

pdb

pickle

pickletools

platform

poplib

profile

pstats

py_compile

pyclbr

pydoc

quopri

random

runpy

site

sqlite3

symtable

sysconfig

tabnanny

tarfile

this

timeit

tokenize

trace

turtledemo

unittest

uuid

venv

webbrowser

zipapp

zipfile

另請見 Python 命令列介面。

已被取代的模組

此章節所描述的模組在大多數使用情況下已被其他模組取代，僅為了向後相容性而被保留下來。

某些模組出現在本章節，可能是因為它們能解決的問題是問題空間的有限子集，而標準函式庫的其他地方提供了更通用的解決方案（例如，getopt 只處理「在 Python 中模擬 C 語言中 getopt() 這個 API 」這項非常具體的任務，而非像 optparse 和 argparse 那樣提供更廣泛的命令列選項剖析與引數剖析功能）。

或者， 某些模組出現在本章節，可能是因為它們已被明確棄用（deprecated），並將在未來版本中移除；又或者它們屬於 soft deprecated 狀態，官方強烈不建議在新專案中使用。隨著 PEP 594 [https://peps.python.org/pep-0594/] 移除了多個過時模組，目前標準函式庫中已不存在後者（軟性棄用）這類模組。

getopt --- 用於命令列選項的 C 風格剖析器

getopt --- 用於命令列選項的 C 風格剖析器

原始碼：Lib/getopt.py [https://github.com/python/cpython/tree/3.14/Lib/getopt.py]

備註

This module is considered feature complete. A more declarative and extensible alternative to this API is provided in the optparse module. Further functional enhancements for command line parameter processing are provided either as third party modules on PyPI, or else as features in the argparse module.

This module helps scripts to parse the command line arguments in sys.argv. It supports the same conventions as the Unix getopt() function (including the special meanings of arguments of the form '-' and '--'). Long options similar to those supported by GNU software may be used as well via an optional third argument.

Users who are unfamiliar with the Unix getopt() function should consider using the argparse module instead. Users who are familiar with the Unix getopt() function, but would like to get equivalent behavior while writing less code and getting better help and error messages should consider using the optparse module. See 選擇一個命令列參數剖析函式庫 for additional details.

這個模組提供兩個函式和一個例外：

getopt.getopt(args, shortopts, longopts=[])

Parses command line options and parameter list. args is the argument list to be parsed, without the leading reference to the running program. Typically, this means sys.argv[1:]. shortopts is the string of option letters that the script wants to recognize, with options that require an argument followed by a colon (':') and options that accept an optional argument followed by two colons ('::'); i.e., the same format that Unix getopt() uses.

備註

Unlike GNU getopt(), after a non-option argument, all further arguments are considered also non-options. This is similar to the way non-GNU Unix systems work.

longopts, if specified, must be a list of strings with the names of the long options which should be supported. The leading '--' characters should not be included in the option name. Long options which require an argument should be followed by an equal sign ('='). Long options which accept an optional argument should be followed by an equal sign and question mark ('=?'). To accept only long options, shortopts should be an empty string. Long options on the command line can be recognized so long as they provide a prefix of the option name that matches exactly one of the accepted options. For example, if longopts is ['foo', 'frob'], the option --fo will match as --foo, but --f will not match uniquely, so GetoptError will be raised.

The return value consists of two elements: the first is a list of (option, value) pairs; the second is the list of program arguments left after the option list was stripped (this is a trailing slice of args). Each option-and-value pair returned has the option as its first element, prefixed with a hyphen for short options (e.g., '-x') or two hyphens for long options (e.g., '--long-option'), and the option argument as its second element, or an empty string if the option has no argument. The options occur in the list in the same order in which they were found, thus allowing multiple occurrences. Long and short options may be mixed.

在 3.14 版的變更: Optional arguments are supported.

getopt.gnu_getopt(args, shortopts, longopts=[])

This function works like getopt(), except that GNU style scanning mode is used by default. This means that option and non-option arguments may be intermixed. The getopt() function stops processing options as soon as a non-option argument is encountered.

If the first character of the option string is '+', or if the environment variable POSIXLY_CORRECT is set, then option processing stops as soon as a non-option argument is encountered.

If the first character of the option string is '-', non-option arguments that are followed by options are added to the list of option-and-value pairs as a pair that has None as its first element and the list of non-option arguments as its second element. The second element of the gnu_getopt() result is a list of program arguments after the last option.

在 3.14 版的變更: Support for returning intermixed options and non-option arguments in order.

exception getopt.GetoptError

This is raised when an unrecognized option is found in the argument list or when an option requiring an argument is given none. The argument to the exception is a string indicating the cause of the error. For long options, an argument given to an option which does not require one will also cause this exception to be raised. The attributes msg and opt give the error message and related option; if there is no specific option to which the exception relates, opt is an empty string.

exception getopt.error

為了向後相容性而設的 GetoptError 別名。

一個僅使用 Unix 風格選項的範例：

>>> import getopt
>>> args = '-a -b -cfoo -d bar a1 a2'.split()
>>> args
['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'abc:d:')
>>> optlist
[('-a', ''), ('-b', ''), ('-c', 'foo'), ('-d', 'bar')]
>>> args
['a1', 'a2']

使用長選項名稱同樣容易：

>>> s = '--condition=foo --testing --output-file abc.def -x a1 a2'
>>> args = s.split()
>>> args
['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'x', [
...     'condition=', 'output-file=', 'testing'])
>>> optlist
[('--condition', 'foo'), ('--testing', ''), ('--output-file', 'abc.def'), ('-x', '')]
>>> args
['a1', 'a2']

Optional arguments should be specified explicitly:

>>> s = '-Con -C --color=off --color a1 a2'
>>> args = s.split()
>>> args
['-Con', '-C', '--color=off', '--color', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'C::', ['color=?'])
>>> optlist
[('-C', 'on'), ('-C', ''), ('--color', 'off'), ('--color', '')]
>>> args
['a1', 'a2']

The order of options and non-option arguments can be preserved:

>>> s = 'a1 -x a2 a3 a4 --long a5 a6'
>>> args = s.split()
>>> args
['a1', '-x', 'a2', 'a3', 'a4', '--long', 'a5', 'a6']
>>> optlist, args = getopt.gnu_getopt(args, '-x:', ['long='])
>>> optlist
[(None, ['a1']), ('-x', 'a2'), (None, ['a3', 'a4']), ('--long', 'a5')]
>>> args
['a6']

在腳本中，典型的用法如下：

import getopt, sys

def main():
    try:
        opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
    except getopt.GetoptError as err:
        # 印出幫助訊息並退出：
        print(err)  # 會印出像是 "option -a not recognized" 的訊息
        usage()
        sys.exit(2)
    output = None
    verbose = False
    for o, a in opts:
        if o == "-v":
            verbose = True
        elif o in ("-h", "--help"):
            usage()
            sys.exit()
        elif o in ("-o", "--output"):
            output = a
        else:
            assert False, "unhandled option"
    process(args, output=output, verbose=verbose)

if __name__ == "__main__":
    main()

Note that an equivalent command line interface could be produced with less code and more informative help and error messages by using the optparse module:

import optparse

if __name__ == '__main__':
    parser = optparse.OptionParser()
    parser.add_option('-o', '--output')
    parser.add_option('-v', dest='verbose', action='store_true')
    opts, args = parser.parse_args()
    process(args, output=opts.output, verbose=opts.verbose)

A roughly equivalent command line interface for this case can also be produced by using the argparse module:

import argparse

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('-o', '--output')
    parser.add_argument('-v', dest='verbose', action='store_true')
    parser.add_argument('rest', nargs='*')
    args = parser.parse_args()
    process(args.rest, output=args.output, verbose=args.verbose)

參見 選擇一個命令列參數剖析函式庫 以瞭解這段程式碼的 argparse 版本與 optparse（以及 getopt）版本在行為上的差異。

也參考

optparse 模組

宣告式命令列選項剖析。

argparse 模組

More opinionated command line option and argument parsing library.

已移除的模組

本章描述的模組已從 Python 標準函式庫中移除。這裡提供文件以協助尋找替代方案。

aifc --- 讀寫 AIFF 與 AIFC 檔案

asynchat --- 非同步 socket 指令/回應處理函式

asyncore --- 非同步 socket 處理函式

audioop --- 操作原始聲音檔案

cgi --- 通用閘道器介面支援

cgitb --- CGI 腳本的回溯管理器 (traceback manager)

chunk --- 讀取 IFF 分塊資料

crypt --- 用於檢查 Unix 密碼的函式

distutils --- 建置與安裝 Python 模組

imghdr --- 判定圖片種類

imp --- 存取引入系統內層

mailcap --- Mailcap 檔案處理

msilib --- 讀寫 Microsoft Installer 檔案

nis --- Sun NIS (Yellow Pages) 介面

nntplib --- NNTP 協定用戶端

ossaudiodev --- 對 OSS 相容聲音裝置的存取

pipes --- shell pipelines 介面

smtpd --- SMTP 伺服器

sndhdr --- 判定聲音檔案的種類

spwd --- shadow 密碼資料庫

sunau --- 讀寫 Sun AU 檔案

telnetlib --- Telnet 用戶端

uu --- uuencode 檔案的編碼與解碼

xdrlib --- XDR 資料的編碼與解碼

安全性注意事項

以下模組具有特定的安全性注意事項：

base64：base64 安全性注意事項在 RFC 4648 [https://datatracker.ietf.org/doc/html/rfc4648.html]

hashlib：所有建構函式都採用 "usedforsecurity" 僅限關鍵字引數，並禁用已知的不安全與被阻擋的演算法

http.server 不適合在正式環境使用，因其僅實作基本的安全檢查。請參閱安全注意事項。

logging：日誌配置使用 eval()

multiprocessing：Connection.recv() 使用 pickle

pickle：限制 pickle 中的全域變數

random 不該用於安全性相關用途，請改用 secrets

shelve：shelve 為基於 pickle，因此不適合用來處理不受信任的來源

ssl：SSL/TLS 安全性注意事項

subprocess：子行程安全性注意事項

tempfile：mktemp 由於存在競爭條件 (race condition) 漏洞而被棄用

xml：XML 安全性

zipfile：惡意準備的 .zip 檔案可能會導致硬碟空間耗盡

-I 命令列選項可用於在隔離模式下運行 Python。若其無法使用，可以改用 -P 選項或 PYTHONSAFEPATH 環境變數，避免 sys.path 新增潛在的不安全路徑，例如目前目錄、腳本的目錄或空字串。

擴充和嵌入 Python 直譯器

這份說明文件描述如何在 C 或 C++ 中編寫模組，並使用新模組來擴充 Python 直譯器功能。那些模組不僅可以定義新的函式，也可以定義新的物件型別及其方法 (method)。文件內容也會描述如何將 Python 直譯器嵌入另一個應用程式中，做為一種擴充語言 (extension language) 使用。最後，它會展示如何編譯及連結擴充模組，使那些模組可以動態地（在執行環境）被載入到直譯器中，前提是底層作業系統有支援這個功能。

這份說明文件假設你具備 Python 的基礎知識。關於此語言的非正式介紹，請參閱 Python 教學。Python 語言參考手冊給予此語言更為正式的定義。Python 標準函式庫 (Standard Library) 記錄了賦予此語言廣泛應用範圍的物件型別、函式與（內建的和以 Python 編寫的）模組。

關於完整的 Python/C API 詳細介紹，請參閱另外一份 Python/C API 參考手冊。

推薦的第三方工具

這份指南僅涵蓋了此 CPython 版本所提供的、用以建立擴充的基本工具。有一些第三方工具，提供了更為簡單及更為複雜的多種方法，來為 Python 建立 C 和 C++ 擴充。

不使用第三方工具建立擴充

本指南中的這一節將說明，在沒有第三方工具的協助下，如何建立 C 和 C ++ 擴充。它主要是寫給使用那些工具的創作者們，而不是讓你建立自己的 C 擴充的推薦方法。

也參考

PEP 489 [https://peps.python.org/pep-0489/] -- 多階段擴充模組初始化

1. 以 C 或 C++ 擴充 Python

1.1. 一個簡單範例

1.2. 插曲：錯誤與例外

1.3. 回到範例

1.4. 模組的方法表和初始化函式

1.5. Compilation and Linkage

1.6. Calling Python Functions from C

1.7. Extracting Parameters in Extension Functions

1.8. Keyword Parameters for Extension Functions

1.9. Building Arbitrary Values

1.10. 參照計數

1.11. Writing Extensions in C++

1.12. Providing a C API for an Extension Module

2. 擴充型別定義教學

2.1. The Basics

2.2. Adding data and methods to the Basic example

2.3. Providing finer control over data attributes

2.4. Supporting cyclic garbage collection

2.5. Subclassing other types

3. Defining Extension Types: Assorted Topics

3.1. Finalization and De-allocation

3.2. Object Presentation

3.3. Attribute Management

3.4. Object Comparison

3.5. Abstract Protocol Support

3.6. Weak Reference Support

3.7. More Suggestions

4. 建立 C 與 C++ 擴充套件

4.1. 用 setuptools 建置 C 與 C++ 擴充套件

5. 建置 Windows 上的 C 和 C++ 擴充

5.1. A Cookbook Approach

5.2. Differences Between Unix and Windows

5.3. Using DLLs in Practice

在更大的應用程式中嵌入 CPython 運行環境 (runtime)

有時候，相較於建立一個擴充，使其在 Python 直譯器中可作為主應用程式運行，還不如將 CPython 運行環境嵌入至一個更大的應用程式中更可取。本節將涵蓋一些要成功完成此任務所涉及的細節。

1. 在其它 App 內嵌入 Python

1.1. 非常高階的嵌入

1.2. 超越非常高階嵌入：概觀

1.3. 純嵌入

1.4. 擴充嵌入式 Python

1.5. 在 C++ 中嵌入 Python

1.6. 在類 Unix 系統下編譯和連結

1. 以 C 或 C++ 擴充 Python

如果你會撰寫 C 程式語言，那要向 Python 新增內建模組就不困難。這種擴充模組 (extension modules) 可以做兩件在 Python 中無法直接完成的事：它們可以實作新的內建物件型別，並且可以呼叫 C 的函式庫函式和系統呼叫。

為了支援擴充，Python API (Application Programmers Interface) 定義了一組函式、巨集和變數，提供對 Python run-time 系統大部分面向的存取。Python API 是透過引入標頭檔 "Python.h" 來被納入到一個 C 原始碼檔案中。

擴充模組的編譯取決於其預期用途以及你的系統設定；詳細資訊將在後面的章節中提供。

備註

C 擴充介面是 CPython 所特有的，擴充模組在其他 Python 實作上無法運作。在許多情況下，可以避免撰寫 C 擴充並保留對其他實作的可移植性。例如，如果你的用例是呼叫 C 函式庫函式或系統呼叫，你應該考慮使用 ctypes 模組或 cffi [https://cffi.readthedocs.io/] 函式庫，而不是編寫自訂的 C 程式碼。這些模組讓你可以撰寫 Python 程式碼來與 C 程式碼介接，而且比起撰寫和編譯 C 擴充模組，這些模組在 Python 實作之間更容易移植。

1.1. 一個簡單範例

讓我們來建立一個叫做 spam（Monty Python 粉絲最愛的食物...）的擴充模組。假設我們要建立一個 Python 介面給 C 函式庫的函式 system() [1] 使用，這個函式接受一個以 null 終止的 (null-terminated) 字元字串做為引數，並回傳一個整數。我們希望這個函式可以在 Python 中被呼叫，如下所示：

>>> import spam
>>> status = spam.system("ls -l")

首先建立一個檔案 spammodule.c。（從過去歷史來看，如果一個模組叫做 spam，包含其實作的 C 檔案就會叫做 spammodule.c；如果模組名稱很長，像是 spammify，模組名稱也可以只是 spammify.c）。

我們檔案的前兩列可以為：

#define PY_SSIZE_T_CLEAN
#include <Python.h>

這會將 Python API 拉進來（你可以加入註解來說明模組的目的，也可以加入版權聲明)。

備註

由於 Python 可能定義一些影響系統上某些標準標頭檔的預處理器定義，你必須在引入任何標準標頭檔之前引入 Python.h。

#define PY_SSIZE_T_CLEAN 被用來表示在某些 API 中應該使用 Py_ssize_t 而不是 int。自 Python 3.13 起，它就不再是必要的了，但我們在此保留它以便向後相容。關於這個巨集的描述請參閱 字串與緩衝區。

All user-visible symbols defined by Python.h have a prefix of Py or PY, except those defined in standard header files.

小訣竅

For backward compatibility, Python.h includes several standard header files. C extensions should include the standard headers that they use, and should not rely on these implicit includes. If using the limited C API version 3.13 or newer, the implicit includes are:

<assert.h>

<intrin.h>（在 Windows 上）

<inttypes.h>

<limits.h>

<math.h>

<stdarg.h>

<wchar.h>

<sys/types.h>（如果存在）

If Py_LIMITED_API is not defined, or is set to version 3.12 or older, the headers below are also included:

<ctype.h>

<unistd.h>（在 POSIX 上）

If Py_LIMITED_API is not defined, or is set to version 3.10 or older, the headers below are also included:

<errno.h>

<stdio.h>

<stdlib.h>

<string.h>

接下來我們要加入到模組檔案的是 C 函式，當 Python 運算式 spam.system(string) 要被求值 (evaluated) 時就會被呼叫（我們很快就會看到它最後是如何被呼叫的）：

static PyObject *
spam_system(PyObject *self, PyObject *args)
{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = system(command);
    return PyLong_FromLong(sts);
}

可以很直觀地從 Python 的引數串列（例如單一的運算式 "ls -l"）直接轉換成傳給 C 函式的引數。C 函式總是有兩個引數，習慣上會命名為 self 和 args。

對於模組層級的函式，self 引數會指向模組物件；而對於方法來說則是指向物件的實例。

args 引數會是一個指向包含引數的 Python 元組物件的指標。元組中的每一項都對應於呼叫的引數串列中的一個引數。引數是 Python 物件 --- 為了在我們的 C 函式中對它們做任何事情，我們必須先將它們轉換成 C 值。Python API 中的 PyArg_ParseTuple() 函式能夠檢查引數型別並將他們轉換為 C 值。它使用模板字串來決定所需的引數型別以及儲存轉換值的 C 變數型別。稍後會再詳細說明。

如果所有的引數都有正確的型別，且其元件已儲存在傳入位址的變數中，則 PyArg_ParseTuple() 會回傳 true（非零）。如果傳入的是無效引數串列則回傳 false（零）。在後者情況下，它也會產生適當的例外，因此呼叫函式可以立即回傳 NULL（就像我們在範例中所看到的）。

1.2. 插曲：錯誤與例外

在整個 Python 直譯器中的一個重要慣例為：當一個函式失敗時，它就應該設定一個例外條件，並回傳一個錯誤值（通常是 -1 或一個 NULL 指標）。例外資訊會儲存在直譯器執行緒狀態的三個成員中。如果沒有例外，它們就會是 NULL。否則，它們是由 sys.exc_info() 所回傳的 Python 元組中的 C 等效元組。它們是例外型別、例外實例和回溯物件。了解它們對於理解錯誤是如何傳遞是很重要的。

Python API 定義了許多能夠設定各種類型例外的函式。

最常見的是 PyErr_SetString()。它的引數是一個例外物件和一個 C 字串。例外物件通常是預先定義的物件，例如 PyExc_ZeroDivisionError。C 字串則指出錯誤的原因，並被轉換為 Python 字串物件且被儲存為例外的「關聯值 (associated value)」。

另一個有用的函式是 PyErr_SetFromErrno()，它只接受一個例外引數，並透過檢查全域變數 errno 來建立關聯值。最一般的函式是 PyErr_SetObject()，它接受兩個物件引數，即例外和它的關聯值。你不需要對傳給任何這些函式的物件呼叫 Py_INCREF()。

你可以使用 PyErr_Occurred() 來不具破壞性地測試例外是否已被設定。這會回傳目前的例外物件，如果沒有例外發生則回傳 NULL。你通常不需要呼叫 PyErr_Occurred() 來查看函式呼叫是否發生錯誤，因為你應可從回傳值就得知。

當函式 f 呼叫另一個函式 g 時檢測到後者失敗，f 本身應該回傳一個錯誤值（通常是 NULL 或 -1）。它不應該呼叫 PyErr_* 函式的其中一個，這會已被 g 呼叫過。f 的呼叫者然後也應該回傳一個錯誤指示給它的呼叫者，同樣不會呼叫 PyErr_*，依此類推 --- 最詳細的錯誤原因已經被首先檢測到它的函式回報了。一旦錯誤到達 Python 直譯器的主要迴圈，這會中止目前執行的 Python 程式碼，並嘗試尋找 Python 程式設計者指定的例外處理程式。

（在某些情況下，模組可以透過呼叫另一個 PyErr_* 函式來提供更詳細的錯誤訊息，在這種情況下這樣做是沒問題的。然而這一般來說並非必要，而且可能會導致錯誤原因資訊的遺失：大多數的操作都可能因為各種原因而失敗。）

要忽略由函式呼叫失敗所設定的例外，必須明確地呼叫 PyErr_Clear() 來清除例外條件。C 程式碼唯一要呼叫 PyErr_Clear() 的情況為當它不想將錯誤傳遞給直譯器而想要完全是自己來處理它時（可能是要再嘗試其他東西，或者假裝什麼都沒出錯）。

每個失敗的 malloc() 呼叫都必須被轉換成一個例外 --- malloc()（或 realloc()）的直接呼叫者必須呼叫 PyErr_NoMemory() 並回傳一個失敗指示器。所有建立物件的函式（例如 PyLong_FromLong()）都已經這麼做了，所以這個注意事項只和那些直接呼叫 malloc() 的函式有關。

還要注意的是，有 PyArg_ParseTuple() 及同系列函式的這些重要例外，回傳整數狀態的函式通常會回傳一個正值或 0 表示成功、回傳 -1 表示失敗，就像 Unix 系統呼叫一樣。

最後，在回傳錯誤指示器時要注意垃圾清理（透過對你已經建立的物件呼叫 Py_XDECREF() 或 Py_DECREF()）！

你完全可以自行選擇要產生的例外。有一些預先宣告的 C 物件會對應到所有內建的 Python 例外，例如 PyExc_ZeroDivisionError，你可以直接使用它們。當然，你應該明智地選擇例外，像是不要使用 PyExc_TypeError 來表示檔案無法打開（應該是 PyExc_OSError）。如果引數串列有問題，PyArg_ParseTuple() 函式通常會引發 PyExc_TypeError。如果你有一個引數的值必須在一個特定的範圍內或必須滿足其他條件，則可以使用 PyExc_ValueError。

你也可以定義一個你的模組特有的新例外。最簡單的方式是在檔案的開頭宣告一個靜態全域物件變數：

static PyObject *SpamError = NULL;

and initialize it by calling PyErr_NewException() in the module's Py_mod_exec function (spam_module_exec()):

SpamError = PyErr_NewException("spam.error", NULL, NULL);

Since SpamError is a global variable, it will be overwritten every time the module is reinitialized, when the Py_mod_exec function is called.

For now, let's avoid the issue: we will block repeated initialization by raising an ImportError:

static PyObject *SpamError = NULL;

static int
spam_module_exec(PyObject *m)
{
    if (SpamError != NULL) {
        PyErr_SetString(PyExc_ImportError,
                        "cannot initialize spam module more than once");
        return -1;
    }
    SpamError = PyErr_NewException("spam.error", NULL, NULL);
    if (PyModule_AddObjectRef(m, "SpamError", SpamError) < 0) {
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot spam_module_slots[] = {
    {Py_mod_exec, spam_module_exec},
    {0, NULL}
};

static struct PyModuleDef spam_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "spam",
    .m_size = 0,  // non-negative
    .m_slots = spam_module_slots,
};

PyMODINIT_FUNC
PyInit_spam(void)
{
    return PyModuleDef_Init(&spam_module);
}

請注意，例外物件的 Python 名稱是 spam.error。如同內建的例外所述，PyErr_NewException() 函式可能會建立一個基底類別為 Exception 的類別（除非傳入另一個類別來代替 NULL）。

請注意，SpamError 變數保留了對新建立的例外類別的參照；這是故意的！因為外部程式碼可能會從模組中移除這個例外，所以需要一個對這個類別的參照來確保它不會被丟棄而導致 SpamError 變成一個迷途指標 (dangling pointer)。如果它變成迷途指標，那產生例外的 C 程式碼可能會導致核心轉儲 (core dump) 或其他不預期的 side effect。

For now, the Py_DECREF() call to remove this reference is missing. Even when the Python interpreter shuts down, the global SpamError variable will not be garbage-collected. It will "leak". We did, however, ensure that this will happen at most once per process.

我們稍後會討論 PyMODINIT_FUNC 作為函式回傳型別的用法。

可以在你的擴充模組中呼叫 PyErr_SetString() 來引發 spam.error 例外，如下所示：

static PyObject *
spam_system(PyObject *self, PyObject *args)
{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = system(command);
    if (sts < 0) {
        PyErr_SetString(SpamError, "System command failed");
        return NULL;
    }
    return PyLong_FromLong(sts);
}

1.3. 回到範例

回到我們的範例函式，現在你應該可以理解這個陳述式了：

if (!PyArg_ParseTuple(args, "s", &command))
    return NULL;

如果在引數串列中檢測到錯誤則會回傳 NULL（回傳物件指標之函式的錯誤指示器），其依賴於 PyArg_ParseTuple() 設定的例外，否則引數的字串值會已被複製到區域變數 command 中。這是一個指標賦值，你不應該修改它所指向的字串（所以在標準 C 中，command 變數應該正確地被宣告為 const char *command）。

接下來的陳述式會呼叫 Unix 函式 system()，並將剛才從 PyArg_ParseTuple() 得到的字串傳給它：

sts = system(command);

我們的 spam.system() 函式必須以 Python 物件的形式來回傳 sts 的值。這是透過 PyLong_FromLong() 函式來達成。

return PyLong_FromLong(sts);

在這種情況下它會回傳一個整數物件。(是的，在 Python 中連整數也是堆積 (heap) 上的物件！)

如果你有一個不回傳任何有用引數的 C 函式（一個回傳 void 的函式），對應的 Python 函式必須回傳 None。你需要以下這個慣例來達成（由 Py_RETURN_NONE 巨集實作）：

Py_INCREF(Py_None);
return Py_None;

Py_None 是特殊 Python 物件 None 的 C 名稱。它是一個真正的 Python 物件而不是一個 NULL 指標，在大多數的情況下它的意思是「錯誤」，如我們所見過的那樣。

1.4. 模組的方法表和初始化函式

我承諾過要展示 spam_system() 是如何從 Python 程式中呼叫的。首先，我們需要在「方法表」中列出它的名稱和位址：

static PyMethodDef spam_methods[] = {
    ...
    {"system",  spam_system, METH_VARARGS,
     "Execute a shell command."},
    ...
    {NULL, NULL, 0, NULL}        /* Sentinel */
};

請注意第三個項目 (METH_VARARGS)。這是一個告訴直譯器 C 函式之呼叫方式的旗標。通常應該是 METH_VARARGS 或 METH_VARARGS | METH_KEYWORDS；0 表示是使用 PyArg_ParseTuple() 的一個過時變體。

當只使用 METH_VARARGS 時，函式應預期 Python 層級的參數是以元組形式傳入且能夠接受以 PyArg_ParseTuple() 進行剖析；有關此函式的更多資訊將在下面提供。

如果要將關鍵字引數傳給函式，可以在第三個欄位設定 METH_KEYWORDS 位元。在這種情況下，C 函式應該要能接受第三個 PyObject * 參數，這個參數將會是關鍵字的字典。可使用 PyArg_ParseTupleAndKeywords() 來剖析這種函式的引數。

方法表必須在模組定義結構中被參照：

static struct PyModuleDef spam_module = {
    ...
    .m_methods = spam_methods,
    ...
};

反過來說，這個結構必須在模組的初始化函式中被傳給直譯器。初始化函式必須被命名為 PyInit_name()，其中 name 是模組的名稱，且應該是模組檔案中唯一定義的非「靜態 (static)」項目：

PyMODINIT_FUNC
PyInit_spam(void)
{
    return PyModuleDef_Init(&spam_module);
}

請注意，PyMODINIT_FUNC 宣告函式的回傳型別為 PyObject *、宣告平台所需的任何特殊連結宣告、並針對 C++ 宣告函式為 extern "C"。

PyInit_spam() is called when each interpreter imports its module spam for the first time. (See below for comments about embedding Python.) A pointer to the module definition must be returned via PyModuleDef_Init(), so that the import machinery can create the module and store it in sys.modules.

嵌入 Python 時，除非在 PyImport_Inittab 表中有相關條目，否則不會自動呼叫 PyInit_spam() 函式。要將模組加入初始化表，請使用 PyImport_AppendInittab() 並在隨後選擇性地將該模組引入：

#define PY_SSIZE_T_CLEAN
#include <Python.h>

int
main(int argc, char *argv[])
{
    PyStatus status;
    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* 在 Py_Initialize 之前加入內建模組 */
    if (PyImport_AppendInittab("spam", PyInit_spam) == -1) {
        fprintf(stderr, "Error: could not extend in-built modules table\n");
        exit(1);
    }

    /* 將 argv[0] 傳給 Python 直譯器 */
    status = PyConfig_SetBytesString(&config, &config.program_name, argv[0]);
    if (PyStatus_Exception(status)) {
        goto exception;
    }

    /* 初始化 Python 直譯器。這會是必要的。
       如果此步驟失敗就會導致嚴重錯誤。*/
    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);

    /* 可選擇引入模組；或者
       可以延遲引入，直至嵌入式腳本
       將其引入。*/
    PyObject *pmodule = PyImport_ImportModule("spam");
    if (!pmodule) {
        PyErr_Print();
        fprintf(stderr, "Error: could not import module 'spam'\n");
    }

    // ... 在此使用 Python C API ...

    return 0;

  exception:
     PyConfig_Clear(&config);
     Py_ExitStatusException(status);
}

備註

If you declare a global variable or a local static one, the module may experience unintended side-effects on re-initialisation, for example when removing entries from sys.modules or importing compiled modules into multiple interpreters within a process (or following a fork() without an intervening exec()). If module state is not yet fully isolated, authors should consider marking the module as having no support for subinterpreters (via Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED).

Python 原始碼發行版本中包含了一個更實質的範例模組 Modules/xxlimited.c。這個檔案可以當作模板使用，也可以簡單地當作範例來閱讀。

1.5. Compilation and Linkage

There are two more things to do before you can use your new extension: compiling and linking it with the Python system. If you use dynamic loading, the details may depend on the style of dynamic loading your system uses; see the chapters about building extension modules (chapter 建立 C 與 C++ 擴充套件) and additional information that pertains only to building on Windows (chapter 建置 Windows 上的 C 和 C++ 擴充) for more information about this.

If you can't use dynamic loading, or if you want to make your module a permanent part of the Python interpreter, you will have to change the configuration setup and rebuild the interpreter. Luckily, this is very simple on Unix: just place your file (spammodule.c for example) in the Modules/ directory of an unpacked source distribution, add a line to the file Modules/Setup.local describing your file:

spam spammodule.o

and rebuild the interpreter by running make in the toplevel directory. You can also run make in the Modules/ subdirectory, but then you must first rebuild Makefile there by running 'make Makefile'. (This is necessary each time you change the Setup file.)

If your module requires additional libraries to link with, these can be listed on the line in the configuration file as well, for instance:

spam spammodule.o -lX11

1.6. Calling Python Functions from C

So far we have concentrated on making C functions callable from Python. The reverse is also useful: calling Python functions from C. This is especially the case for libraries that support so-called "callback" functions. If a C interface makes use of callbacks, the equivalent Python often needs to provide a callback mechanism to the Python programmer; the implementation will require calling the Python callback functions from a C callback. Other uses are also imaginable.

Fortunately, the Python interpreter is easily called recursively, and there is a standard interface to call a Python function. (I won't dwell on how to call the Python parser with a particular string as input --- if you're interested, have a look at the implementation of the -c command line option in Modules/main.c from the Python source code.)

Calling a Python function is easy. First, the Python program must somehow pass you the Python function object. You should provide a function (or some other interface) to do this. When this function is called, save a pointer to the Python function object (be careful to Py_INCREF() it!) in a global variable --- or wherever you see fit. For example, the following function might be part of a module definition:

static PyObject *my_callback = NULL;

static PyObject *
my_set_callback(PyObject *dummy, PyObject *args)
{
    PyObject *result = NULL;
    PyObject *temp;

    if (PyArg_ParseTuple(args, "O:set_callback", &temp)) {
        if (!PyCallable_Check(temp)) {
            PyErr_SetString(PyExc_TypeError, "parameter must be callable");
            return NULL;
        }
        Py_XINCREF(temp);         /* Add a reference to new callback */
        Py_XDECREF(my_callback);  /* Dispose of previous callback */
        my_callback = temp;       /* Remember new callback */
        /* Boilerplate to return "None" */
        Py_INCREF(Py_None);
        result = Py_None;
    }
    return result;
}

This function must be registered with the interpreter using the METH_VARARGS flag; this is described in section 模組的方法表和初始化函式. The PyArg_ParseTuple() function and its arguments are documented in section Extracting Parameters in Extension Functions.

The macros Py_XINCREF() and Py_XDECREF() increment/decrement the reference count of an object and are safe in the presence of NULL pointers (but note that temp will not be NULL in this context). More info on them in section 參照計數.

Later, when it is time to call the function, you call the C function PyObject_CallObject(). This function has two arguments, both pointers to arbitrary Python objects: the Python function, and the argument list. The argument list must always be a tuple object, whose length is the number of arguments. To call the Python function with no arguments, pass in NULL, or an empty tuple; to call it with one argument, pass a singleton tuple. Py_BuildValue() returns a tuple when its format string consists of zero or more format codes between parentheses. For example:

int arg;
PyObject *arglist;
PyObject *result;
...
arg = 123;
...
/* Time to call the callback */
arglist = Py_BuildValue("(i)", arg);
result = PyObject_CallObject(my_callback, arglist);
Py_DECREF(arglist);

PyObject_CallObject() returns a Python object pointer: this is the return value of the Python function. PyObject_CallObject() is "reference-count-neutral" with respect to its arguments. In the example a new tuple was created to serve as the argument list, which is Py_DECREF()-ed immediately after the PyObject_CallObject() call.

The return value of PyObject_CallObject() is "new": either it is a brand new object, or it is an existing object whose reference count has been incremented. So, unless you want to save it in a global variable, you should somehow Py_DECREF() the result, even (especially!) if you are not interested in its value.

Before you do this, however, it is important to check that the return value isn't NULL. If it is, the Python function terminated by raising an exception. If the C code that called PyObject_CallObject() is called from Python, it should now return an error indication to its Python caller, so the interpreter can print a stack trace, or the calling Python code can handle the exception. If this is not possible or desirable, the exception should be cleared by calling PyErr_Clear(). For example:

if (result == NULL)
    return NULL; /* Pass error back */
...use result...
Py_DECREF(result);

Depending on the desired interface to the Python callback function, you may also have to provide an argument list to PyObject_CallObject(). In some cases the argument list is also provided by the Python program, through the same interface that specified the callback function. It can then be saved and used in the same manner as the function object. In other cases, you may have to construct a new tuple to pass as the argument list. The simplest way to do this is to call Py_BuildValue(). For example, if you want to pass an integral event code, you might use the following code:

PyObject *arglist;
...
arglist = Py_BuildValue("(l)", eventcode);
result = PyObject_CallObject(my_callback, arglist);
Py_DECREF(arglist);
if (result == NULL)
    return NULL; /* Pass error back */
/* Here maybe use the result */
Py_DECREF(result);

Note the placement of Py_DECREF(arglist) immediately after the call, before the error check! Also note that strictly speaking this code is not complete: Py_BuildValue() may run out of memory, and this should be checked.

You may also call a function with keyword arguments by using PyObject_Call(), which supports arguments and keyword arguments. As in the above example, we use Py_BuildValue() to construct the dictionary.

PyObject *dict;
...
dict = Py_BuildValue("{s:i}", "name", val);
result = PyObject_Call(my_callback, NULL, dict);
Py_DECREF(dict);
if (result == NULL)
    return NULL; /* Pass error back */
/* Here maybe use the result */
Py_DECREF(result);

1.7. Extracting Parameters in Extension Functions

The PyArg_ParseTuple() function is declared as follows:

int PyArg_ParseTuple(PyObject *arg, const char *format, ...);

The arg argument must be a tuple object containing an argument list passed from Python to a C function. The format argument must be a format string, whose syntax is explained in 剖析引數與建置數值 in the Python/C API Reference Manual. The remaining arguments must be addresses of variables whose type is determined by the format string.

Note that while PyArg_ParseTuple() checks that the Python arguments have the required types, it cannot check the validity of the addresses of C variables passed to the call: if you make mistakes there, your code will probably crash or at least overwrite random bits in memory. So be careful!

Note that any Python object references which are provided to the caller are borrowed references; do not decrement their reference count!

一些呼叫範例：

#define PY_SSIZE_T_CLEAN
#include <Python.h>

int ok;
int i, j;
long k, l;
const char *s;
Py_ssize_t size;

ok = PyArg_ParseTuple(args, ""); /* 沒有引數 */
    /* Python 呼叫：f() */

ok = PyArg_ParseTuple(args, "s", &s); /* A string */
    /* Possible Python call: f('whoops!') */

ok = PyArg_ParseTuple(args, "lls", &k, &l, &s); /* Two longs and a string */
    /* Possible Python call: f(1, 2, 'three') */

ok = PyArg_ParseTuple(args, "(ii)s#", &i, &j, &s, &size);
    /* A pair of ints and a string, whose size is also returned */
    /* Possible Python call: f((1, 2), 'three') */

{
    const char *file;
    const char *mode = "r";
    int bufsize = 0;
    ok = PyArg_ParseTuple(args, "s|si", &file, &mode, &bufsize);
    /* A string, and optionally another string and an integer */
    /* Possible Python calls:
       f('spam')
       f('spam', 'w')
       f('spam', 'wb', 100000) */
}

{
    int left, top, right, bottom, h, v;
    ok = PyArg_ParseTuple(args, "((ii)(ii))(ii)",
             &left, &top, &right, &bottom, &h, &v);
    /* A rectangle and a point */
    /* Possible Python call:
       f(((0, 0), (400, 300)), (10, 10)) */
}

{
    Py_complex c;
    ok = PyArg_ParseTuple(args, "D:myfunction", &c);
    /* a complex, also providing a function name for errors */
    /* Possible Python call: myfunction(1+2j) */
}

1.8. Keyword Parameters for Extension Functions

The PyArg_ParseTupleAndKeywords() function is declared as follows:

int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict,
                                const char *format, char * const *kwlist, ...);

The arg and format parameters are identical to those of the PyArg_ParseTuple() function. The kwdict parameter is the dictionary of keywords received as the third parameter from the Python runtime. The kwlist parameter is a NULL-terminated list of strings which identify the parameters; the names are matched with the type information from format from left to right. On success, PyArg_ParseTupleAndKeywords() returns true, otherwise it returns false and raises an appropriate exception.

備註

Nested tuples cannot be parsed when using keyword arguments! Keyword parameters passed in which are not present in the kwlist will cause TypeError to be raised.

Here is an example module which uses keywords, based on an example by Geoff Philbrick (philbrick@hks.com):

#define PY_SSIZE_T_CLEAN
#include <Python.h>

static PyObject *
keywdarg_parrot(PyObject *self, PyObject *args, PyObject *keywds)
{
    int voltage;
    const char *state = "a stiff";
    const char *action = "voom";
    const char *type = "Norwegian Blue";

    static char *kwlist[] = {"voltage", "state", "action", "type", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, keywds, "i|sss", kwlist,
                                     &voltage, &state, &action, &type))
        return NULL;

    printf("-- This parrot wouldn't %s if you put %i Volts through it.\n",
           action, voltage);
    printf("-- Lovely plumage, the %s -- It's %s!\n", type, state);

    Py_RETURN_NONE;
}

static PyMethodDef keywdarg_methods[] = {
    /* The cast of the function is necessary since PyCFunction values
     * only take two PyObject* parameters, and keywdarg_parrot() takes
     * three.
     */
    {"parrot", (PyCFunction)(void(*)(void))keywdarg_parrot, METH_VARARGS | METH_KEYWORDS,
     "Print a lovely skit to standard output."},
    {NULL, NULL, 0, NULL}   /* sentinel */
};

static struct PyModuleDef keywdarg_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "keywdarg",
    .m_size = 0,
    .m_methods = keywdarg_methods,
};

PyMODINIT_FUNC
PyInit_keywdarg(void)
{
    return PyModuleDef_Init(&keywdarg_module);
}

1.9. Building Arbitrary Values

This function is the counterpart to PyArg_ParseTuple(). It is declared as follows:

PyObject *Py_BuildValue(const char *format, ...);

It recognizes a set of format units similar to the ones recognized by PyArg_ParseTuple(), but the arguments (which are input to the function, not output) must not be pointers, just values. It returns a new Python object, suitable for returning from a C function called from Python.

One difference with PyArg_ParseTuple(): while the latter requires its first argument to be a tuple (since Python argument lists are always represented as tuples internally), Py_BuildValue() does not always build a tuple. It builds a tuple only if its format string contains two or more format units. If the format string is empty, it returns None; if it contains exactly one format unit, it returns whatever object is described by that format unit. To force it to return a tuple of size 0 or one, parenthesize the format string.

Examples (to the left the call, to the right the resulting Python value):

Py_BuildValue("")                        None
Py_BuildValue("i", 123)                  123
Py_BuildValue("iii", 123, 456, 789)      (123, 456, 789)
Py_BuildValue("s", "hello")              'hello'
Py_BuildValue("y", "hello")              b'hello'
Py_BuildValue("ss", "hello", "world")    ('hello', 'world')
Py_BuildValue("s#", "hello", 4)          'hell'
Py_BuildValue("y#", "hello", 4)          b'hell'
Py_BuildValue("()")                      ()
Py_BuildValue("(i)", 123)                (123,)
Py_BuildValue("(ii)", 123, 456)          (123, 456)
Py_BuildValue("(i,i)", 123, 456)         (123, 456)
Py_BuildValue("[i,i]", 123, 456)         [123, 456]
Py_BuildValue("{s:i,s:i}",
              "abc", 123, "def", 456)    {'abc': 123, 'def': 456}
Py_BuildValue("((ii)(ii)) (ii)",
              1, 2, 3, 4, 5, 6)          (((1, 2), (3, 4)), (5, 6))

1.10. 參照計數

In languages like C or C++, the programmer is responsible for dynamic allocation and deallocation of memory on the heap. In C, this is done using the functions malloc() and free(). In C++, the operators new and delete are used with essentially the same meaning and we'll restrict the following discussion to the C case.

Every block of memory allocated with malloc() should eventually be returned to the pool of available memory by exactly one call to free(). It is important to call free() at the right time. If a block's address is forgotten but free() is not called for it, the memory it occupies cannot be reused until the program terminates. This is called a memory leak. On the other hand, if a program calls free() for a block and then continues to use the block, it creates a conflict with reuse of the block through another malloc() call. This is called using freed memory. It has the same bad consequences as referencing uninitialized data --- core dumps, wrong results, mysterious crashes.

Common causes of memory leaks are unusual paths through the code. For instance, a function may allocate a block of memory, do some calculation, and then free the block again. Now a change in the requirements for the function may add a test to the calculation that detects an error condition and can return prematurely from the function. It's easy to forget to free the allocated memory block when taking this premature exit, especially when it is added later to the code. Such leaks, once introduced, often go undetected for a long time: the error exit is taken only in a small fraction of all calls, and most modern machines have plenty of virtual memory, so the leak only becomes apparent in a long-running process that uses the leaking function frequently. Therefore, it's important to prevent leaks from happening by having a coding convention or strategy that minimizes this kind of errors.

Since Python makes heavy use of malloc() and free(), it needs a strategy to avoid memory leaks as well as the use of freed memory. The chosen method is called reference counting. The principle is simple: every object contains a counter, which is incremented when a reference to the object is stored somewhere, and which is decremented when a reference to it is deleted. When the counter reaches zero, the last reference to the object has been deleted and the object is freed.

An alternative strategy is called automatic garbage collection. (Sometimes, reference counting is also referred to as a garbage collection strategy, hence my use of "automatic" to distinguish the two.) The big advantage of automatic garbage collection is that the user doesn't need to call free() explicitly. (Another claimed advantage is an improvement in speed or memory usage --- this is no hard fact however.) The disadvantage is that for C, there is no truly portable automatic garbage collector, while reference counting can be implemented portably (as long as the functions malloc() and free() are available --- which the C Standard guarantees). Maybe some day a sufficiently portable automatic garbage collector will be available for C. Until then, we'll have to live with reference counts.

While Python uses the traditional reference counting implementation, it also offers a cycle detector that works to detect reference cycles. This allows applications to not worry about creating direct or indirect circular references; these are the weakness of garbage collection implemented using only reference counting. Reference cycles consist of objects which contain (possibly indirect) references to themselves, so that each object in the cycle has a reference count which is non-zero. Typical reference counting implementations are not able to reclaim the memory belonging to any objects in a reference cycle, or referenced from the objects in the cycle, even though there are no further references to the cycle itself.

The cycle detector is able to detect garbage cycles and can reclaim them. The gc module exposes a way to run the detector (the collect() function), as well as configuration interfaces and the ability to disable the detector at runtime.

1.10.1. Python 中的參照計數

There are two macros, Py_INCREF(x) and Py_DECREF(x), which handle the incrementing and decrementing of the reference count. Py_DECREF() also frees the object when the count reaches zero. For flexibility, it doesn't call free() directly --- rather, it makes a call through a function pointer in the object's type object. For this purpose (and others), every object also contains a pointer to its type object.

The big question now remains: when to use Py_INCREF(x) and Py_DECREF(x)? Let's first introduce some terms. Nobody "owns" an object; however, you can own a reference to an object. An object's reference count is now defined as the number of owned references to it. The owner of a reference is responsible for calling Py_DECREF() when the reference is no longer needed. Ownership of a reference can be transferred. There are three ways to dispose of an owned reference: pass it on, store it, or call Py_DECREF(). Forgetting to dispose of an owned reference creates a memory leak.

It is also possible to borrow [2] a reference to an object. The borrower of a reference should not call Py_DECREF(). The borrower must not hold on to the object longer than the owner from which it was borrowed. Using a borrowed reference after the owner has disposed of it risks using freed memory and should be avoided completely [3].

The advantage of borrowing over owning a reference is that you don't need to take care of disposing of the reference on all possible paths through the code --- in other words, with a borrowed reference you don't run the risk of leaking when a premature exit is taken. The disadvantage of borrowing over owning is that there are some subtle situations where in seemingly correct code a borrowed reference can be used after the owner from which it was borrowed has in fact disposed of it.

A borrowed reference can be changed into an owned reference by calling Py_INCREF(). This does not affect the status of the owner from which the reference was borrowed --- it creates a new owned reference, and gives full owner responsibilities (the new owner must dispose of the reference properly, as well as the previous owner).

1.10.2. Ownership Rules

Whenever an object reference is passed into or out of a function, it is part of the function's interface specification whether ownership is transferred with the reference or not.

Most functions that return a reference to an object pass on ownership with the reference. In particular, all functions whose function it is to create a new object, such as PyLong_FromLong() and Py_BuildValue(), pass ownership to the receiver. Even if the object is not actually new, you still receive ownership of a new reference to that object. For instance, PyLong_FromLong() maintains a cache of popular values and can return a reference to a cached item.

Many functions that extract objects from other objects also transfer ownership with the reference, for instance PyObject_GetAttrString(). The picture is less clear, here, however, since a few common routines are exceptions: PyTuple_GetItem(), PyList_GetItem(), PyDict_GetItem(), and PyDict_GetItemString() all return references that you borrow from the tuple, list or dictionary.

The function PyImport_AddModule() also returns a borrowed reference, even though it may actually create the object it returns: this is possible because an owned reference to the object is stored in sys.modules.

When you pass an object reference into another function, in general, the function borrows the reference from you --- if it needs to store it, it will use Py_INCREF() to become an independent owner. There are exactly two important exceptions to this rule: PyTuple_SetItem() and PyList_SetItem(). These functions take over ownership of the item passed to them --- even if they fail! (Note that PyDict_SetItem() and friends don't take over ownership --- they are "normal.")

When a C function is called from Python, it borrows references to its arguments from the caller. The caller owns a reference to the object, so the borrowed reference's lifetime is guaranteed until the function returns. Only when such a borrowed reference must be stored or passed on, it must be turned into an owned reference by calling Py_INCREF().

The object reference returned from a C function that is called from Python must be an owned reference --- ownership is transferred from the function to its caller.

1.10.3. Thin Ice

There are a few situations where seemingly harmless use of a borrowed reference can lead to problems. These all have to do with implicit invocations of the interpreter, which can cause the owner of a reference to dispose of it.

The first and most important case to know about is using Py_DECREF() on an unrelated object while borrowing a reference to a list item. For instance:

void
bug(PyObject *list)
{
    PyObject *item = PyList_GetItem(list, 0);

    PyList_SetItem(list, 1, PyLong_FromLong(0L));
    PyObject_Print(item, stdout, 0); /* BUG! */
}

This function first borrows a reference to list[0], then replaces list[1] with the value 0, and finally prints the borrowed reference. Looks harmless, right? But it's not!

Let's follow the control flow into PyList_SetItem(). The list owns references to all its items, so when item 1 is replaced, it has to dispose of the original item 1. Now let's suppose the original item 1 was an instance of a user-defined class, and let's further suppose that the class defined a __del__() method. If this class instance has a reference count of 1, disposing of it will call its __del__() method. Internally, PyList_SetItem() calls Py_DECREF() on the replaced item, which invokes replaced item's corresponding tp_dealloc function. During deallocation, tp_dealloc calls tp_finalize, which is mapped to the __del__() method for class instances (see PEP 442 [https://peps.python.org/pep-0442/]). This entire sequence happens synchronously within the PyList_SetItem() call.

Since it is written in Python, the __del__() method can execute arbitrary Python code. Could it perhaps do something to invalidate the reference to item in bug()? You bet! Assuming that the list passed into bug() is accessible to the __del__() method, it could execute a statement to the effect of del list[0], and assuming this was the last reference to that object, it would free the memory associated with it, thereby invalidating item.

The solution, once you know the source of the problem, is easy: temporarily increment the reference count. The correct version of the function reads:

void
no_bug(PyObject *list)
{
    PyObject *item = PyList_GetItem(list, 0);

    Py_INCREF(item);
    PyList_SetItem(list, 1, PyLong_FromLong(0L));
    PyObject_Print(item, stdout, 0);
    Py_DECREF(item);
}

This is a true story. An older version of Python contained variants of this bug and someone spent a considerable amount of time in a C debugger to figure out why his __del__() methods would fail...

The second case of problems with a borrowed reference is a variant involving threads. Normally, multiple threads in the Python interpreter can't get in each other's way, because there is a global lock protecting Python's entire object space. However, it is possible to temporarily release this lock using the macro Py_BEGIN_ALLOW_THREADS, and to re-acquire it using Py_END_ALLOW_THREADS. This is common around blocking I/O calls, to let other threads use the processor while waiting for the I/O to complete. Obviously, the following function has the same problem as the previous one:

void
bug(PyObject *list)
{
    PyObject *item = PyList_GetItem(list, 0);
    Py_BEGIN_ALLOW_THREADS
    ...some blocking I/O call...
    Py_END_ALLOW_THREADS
    PyObject_Print(item, stdout, 0); /* BUG! */
}

1.10.4. NULL 指標

In general, functions that take object references as arguments do not expect you to pass them NULL pointers, and will dump core (or cause later core dumps) if you do so. Functions that return object references generally return NULL only to indicate that an exception occurred. The reason for not testing for NULL arguments is that functions often pass the objects they receive on to other function --- if each function were to test for NULL, there would be a lot of redundant tests and the code would run more slowly.

It is better to test for NULL only at the "source:" when a pointer that may be NULL is received, for example, from malloc() or from a function that may raise an exception.

The macros Py_INCREF() and Py_DECREF() do not check for NULL pointers --- however, their variants Py_XINCREF() and Py_XDECREF() do.

The macros for checking for a particular object type (Pytype_Check()) don't check for NULL pointers --- again, there is much code that calls several of these in a row to test an object against various different expected types, and this would generate redundant tests. There are no variants with NULL checking.

The C function calling mechanism guarantees that the argument list passed to C functions (args in the examples) is never NULL --- in fact it guarantees that it is always a tuple [4].

It is a severe error to ever let a NULL pointer "escape" to the Python user.

1.11. Writing Extensions in C++

It is possible to write extension modules in C++. Some restrictions apply. If the main program (the Python interpreter) is compiled and linked by the C compiler, global or static objects with constructors cannot be used. This is not a problem if the main program is linked by the C++ compiler. Functions that will be called by the Python interpreter (in particular, module initialization functions) have to be declared using extern "C". It is unnecessary to enclose the Python header files in extern "C" {...} --- they use this form already if the symbol __cplusplus is defined (all recent C++ compilers define this symbol).

1.12. Providing a C API for an Extension Module

Many extension modules just provide new functions and types to be used from Python, but sometimes the code in an extension module can be useful for other extension modules. For example, an extension module could implement a type "collection" which works like lists without order. Just like the standard Python list type has a C API which permits extension modules to create and manipulate lists, this new collection type should have a set of C functions for direct manipulation from other extension modules.

At first sight this seems easy: just write the functions (without declaring them static, of course), provide an appropriate header file, and document the C API. And in fact this would work if all extension modules were always linked statically with the Python interpreter. When modules are used as shared libraries, however, the symbols defined in one module may not be visible to another module. The details of visibility depend on the operating system; some systems use one global namespace for the Python interpreter and all extension modules (Windows, for example), whereas others require an explicit list of imported symbols at module link time (AIX is one example), or offer a choice of different strategies (most Unices). And even if symbols are globally visible, the module whose functions one wishes to call might not have been loaded yet!

Portability therefore requires not to make any assumptions about symbol visibility. This means that all symbols in extension modules should be declared static, except for the module's initialization function, in order to avoid name clashes with other extension modules (as discussed in section 模組的方法表和初始化函式). And it means that symbols that should be accessible from other extension modules must be exported in a different way.

Python provides a special mechanism to pass C-level information (pointers) from one extension module to another one: Capsules. A Capsule is a Python data type which stores a pointer (void*). Capsules can only be created and accessed via their C API, but they can be passed around like any other Python object. In particular, they can be assigned to a name in an extension module's namespace. Other extension modules can then import this module, retrieve the value of this name, and then retrieve the pointer from the Capsule.

There are many ways in which Capsules can be used to export the C API of an extension module. Each function could get its own Capsule, or all C API pointers could be stored in an array whose address is published in a Capsule. And the various tasks of storing and retrieving the pointers can be distributed in different ways between the module providing the code and the client modules.

Whichever method you choose, it's important to name your Capsules properly. The function PyCapsule_New() takes a name parameter (const char*); you're permitted to pass in a NULL name, but we strongly encourage you to specify a name. Properly named Capsules provide a degree of runtime type-safety; there is no feasible way to tell one unnamed Capsule from another.

In particular, Capsules used to expose C APIs should be given a name following this convention:

modulename.attributename

The convenience function PyCapsule_Import() makes it easy to load a C API provided via a Capsule, but only if the Capsule's name matches this convention. This behavior gives C API users a high degree of certainty that the Capsule they load contains the correct C API.

The following example demonstrates an approach that puts most of the burden on the writer of the exporting module, which is appropriate for commonly used library modules. It stores all C API pointers (just one in the example!) in an array of void pointers which becomes the value of a Capsule. The header file corresponding to the module provides a macro that takes care of importing the module and retrieving its C API pointers; client modules only have to call this macro before accessing the C API.

The exporting module is a modification of the spam module from section 一個簡單範例. The function spam.system() does not call the C library function system() directly, but a function PySpam_System(), which would of course do something more complicated in reality (such as adding "spam" to every command). This function PySpam_System() is also exported to other extension modules.

The function PySpam_System() is a plain C function, declared static like everything else:

static int
PySpam_System(const char *command)
{
    return system(command);
}

The function spam_system() is modified in a trivial way:

static PyObject *
spam_system(PyObject *self, PyObject *args)
{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = PySpam_System(command);
    return PyLong_FromLong(sts);
}

In the beginning of the module, right after the line

#include <Python.h>

two more lines must be added:

#define SPAM_MODULE
#include "spammodule.h"

The #define is used to tell the header file that it is being included in the exporting module, not a client module. Finally, the module's mod_exec function must take care of initializing the C API pointer array:

static int
spam_module_exec(PyObject *m)
{
    static void *PySpam_API[PySpam_API_pointers];
    PyObject *c_api_object;

    /* Initialize the C API pointer array */
    PySpam_API[PySpam_System_NUM] = (void *)PySpam_System;

    /* Create a Capsule containing the API pointer array's address */
    c_api_object = PyCapsule_New((void *)PySpam_API, "spam._C_API", NULL);

    if (PyModule_Add(m, "_C_API", c_api_object) < 0) {
        return -1;
    }

    return 0;
}

Note that PySpam_API is declared static; otherwise the pointer array would disappear when PyInit_spam() terminates!

The bulk of the work is in the header file spammodule.h, which looks like this:

#ifndef Py_SPAMMODULE_H
#define Py_SPAMMODULE_H
#ifdef __cplusplus
extern "C" {
#endif

/* Header file for spammodule */

/* C API functions */
#define PySpam_System_NUM 0
#define PySpam_System_RETURN int
#define PySpam_System_PROTO (const char *command)

/* Total number of C API pointers */
#define PySpam_API_pointers 1

#ifdef SPAM_MODULE
/* This section is used when compiling spammodule.c */

static PySpam_System_RETURN PySpam_System PySpam_System_PROTO;

#else
/* This section is used in modules that use spammodule's API */

static void **PySpam_API;

#define PySpam_System \
 (*(PySpam_System_RETURN (*)PySpam_System_PROTO) PySpam_API[PySpam_System_NUM])

/* Return -1 on error, 0 on success.
 * PyCapsule_Import will set an exception if there's an error.
 */
static int
import_spam(void)
{
    PySpam_API = (void **)PyCapsule_Import("spam._C_API", 0);
    return (PySpam_API != NULL) ? 0 : -1;
}

#endif

#ifdef __cplusplus
}
#endif

#endif /* !defined(Py_SPAMMODULE_H) */

All that a client module must do in order to have access to the function PySpam_System() is to call the function (or rather macro) import_spam() in its mod_exec function:

static int
client_module_exec(PyObject *m)
{
    if (import_spam() < 0) {
        return -1;
    }
    /* additional initialization can happen here */
    return 0;
}

The main disadvantage of this approach is that the file spammodule.h is rather complicated. However, the basic structure is the same for each function that is exported, so it has to be learned only once.

Finally it should be mentioned that Capsules offer additional functionality, which is especially useful for memory allocation and deallocation of the pointer stored in a Capsule. The details are described in the Python/C API Reference Manual in the section Capsules and in the implementation of Capsules (files Include/pycapsule.h and Objects/pycapsule.c in the Python source code distribution).

註腳

[1]

An interface for this function already exists in the standard module os --- it was chosen as a simple and straightforward example.

[2]

The metaphor of "borrowing" a reference is not completely correct: the owner still has a copy of the reference.

[3]

Checking that the reference count is at least 1 does not work --- the reference count itself could be in freed memory and may thus be reused for another object!

[4]

These guarantees don't hold when you use the "old" style calling convention --- this is still found in much existing code.

2. 擴充型別定義教學

Python allows the writer of a C extension module to define new types that can be manipulated from Python code, much like the built-in str and list types. The code for all extension types follows a pattern, but there are some details that you need to understand before you can get started. This document is a gentle introduction to the topic.

2.1. The Basics

The CPython runtime sees all Python objects as variables of type PyObject*, which serves as a "base type" for all Python objects. The PyObject structure itself only contains the object's reference count and a pointer to the object's "type object". This is where the action is; the type object determines which (C) functions get called by the interpreter when, for instance, an attribute gets looked up on an object, a method called, or it is multiplied by another object. These C functions are called "type methods".

So, if you want to define a new extension type, you need to create a new type object.

This sort of thing can only be explained by example, so here's a minimal, but complete, module that defines a new type named Custom inside a C extension module custom:

備註

What we're showing here is the traditional way of defining static extension types. It should be adequate for most uses. The C API also allows defining heap-allocated extension types using the PyType_FromSpec() function, which isn't covered in this tutorial.

#define PY_SSIZE_T_CLEAN
#include <Python.h>

typedef struct {
    PyObject_HEAD
    /* Type-specific fields go here. */
} CustomObject;

static PyTypeObject CustomType = {
    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom.Custom",
    .tp_doc = PyDoc_STR("Custom objects"),
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT,
    .tp_new = PyType_GenericNew,
};

static int
custom_module_exec(PyObject *m)
{
    if (PyType_Ready(&CustomType) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(m, "Custom", (PyObject *) &CustomType) < 0) {
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot custom_module_slots[] = {
    {Py_mod_exec, custom_module_exec},
    // Just use this while using static types
    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},
    {0, NULL}
};

static PyModuleDef custom_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "custom",
    .m_doc = "Example module that creates an extension type.",
    .m_size = 0,
    .m_slots = custom_module_slots,
};

PyMODINIT_FUNC
PyInit_custom(void)
{
    return PyModuleDef_Init(&custom_module);
}

Now that's quite a bit to take in at once, but hopefully bits will seem familiar from the previous chapter. This file defines three things:

What a Custom object contains: this is the CustomObject struct, which is allocated once for each Custom instance.

How the Custom type behaves: this is the CustomType struct, which defines a set of flags and function pointers that the interpreter inspects when specific operations are requested.

How to define and execute the custom module: this is the PyInit_custom function and the associated custom_module struct for defining the module, and the custom_module_exec function to set up a fresh module object.

The first bit is:

typedef struct {
    PyObject_HEAD
} CustomObject;

This is what a Custom object will contain. PyObject_HEAD is mandatory at the start of each object struct and defines a field called ob_base of type PyObject, containing a pointer to a type object and a reference count (these can be accessed using the macros Py_TYPE and Py_REFCNT respectively). The reason for the macro is to abstract away the layout and to enable additional fields in debug builds.

備註

There is no semicolon above after the PyObject_HEAD macro. Be wary of adding one by accident: some compilers will complain.

Of course, objects generally store additional data besides the standard PyObject_HEAD boilerplate; for example, here is the definition for standard Python floats:

typedef struct {
    PyObject_HEAD
    double ob_fval;
} PyFloatObject;

The second bit is the definition of the type object.

static PyTypeObject CustomType = {
    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom.Custom",
    .tp_doc = PyDoc_STR("Custom objects"),
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT,
    .tp_new = PyType_GenericNew,
};

備註

We recommend using C99-style designated initializers as above, to avoid listing all the PyTypeObject fields that you don't care about and also to avoid caring about the fields' declaration order.

The actual definition of PyTypeObject in object.h has many more fields than the definition above. The remaining fields will be filled with zeros by the C compiler, and it's common practice to not specify them explicitly unless you need them.

We're going to pick it apart, one field at a time:

.ob_base = PyVarObject_HEAD_INIT(NULL, 0)

This line is mandatory boilerplate to initialize the ob_base field mentioned above.

.tp_name = "custom.Custom",

The name of our type. This will appear in the default textual representation of our objects and in some error messages, for example:

>>> "" + custom.Custom()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate str (not "custom.Custom") to str

Note that the name is a dotted name that includes both the module name and the name of the type within the module. The module in this case is custom and the type is Custom, so we set the type name to custom.Custom. Using the real dotted import path is important to make your type compatible with the pydoc and pickle modules.

.tp_basicsize = sizeof(CustomObject),
.tp_itemsize = 0,

This is so that Python knows how much memory to allocate when creating new Custom instances. tp_itemsize is only used for variable-sized objects and should otherwise be zero.

備註

If you want your type to be subclassable from Python, and your type has the same tp_basicsize as its base type, you may have problems with multiple inheritance. A Python subclass of your type will have to list your type first in its __bases__, or else it will not be able to call your type's __new__() method without getting an error. You can avoid this problem by ensuring that your type has a larger value for tp_basicsize than its base type does. Most of the time, this will be true anyway, because either your base type will be object, or else you will be adding data members to your base type, and therefore increasing its size.

We set the class flags to Py_TPFLAGS_DEFAULT.

.tp_flags = Py_TPFLAGS_DEFAULT,

All types should include this constant in their flags. It enables all of the members defined until at least Python 3.3. If you need further members, you will need to OR the corresponding flags.

We provide a doc string for the type in tp_doc.

.tp_doc = PyDoc_STR("Custom objects"),

To enable object creation, we have to provide a tp_new handler. This is the equivalent of the Python method __new__(), but has to be specified explicitly. In this case, we can just use the default implementation provided by the API function PyType_GenericNew().

.tp_new = PyType_GenericNew,

Everything else in the file should be familiar, except for some code in custom_module_exec():

if (PyType_Ready(&CustomType) < 0) {
    return -1;
}

This initializes the Custom type, filling in a number of members to the appropriate default values, including ob_type that we initially set to NULL.

if (PyModule_AddObjectRef(m, "Custom", (PyObject *) &CustomType) < 0) {
    return -1;
}

This adds the type to the module dictionary. This allows us to create Custom instances by calling the Custom class:

>>> import custom
>>> mycustom = custom.Custom()

That's it! All that remains is to build it; put the above code in a file called custom.c,

[build-system]
requires = ["setuptools"]
build-backend = "setuptools.build_meta"

[project]
name = "custom"
version = "1"

in a file called pyproject.toml, and

from setuptools import Extension, setup
setup(ext_modules=[Extension("custom", ["custom.c"])])

in a file called setup.py; then typing

$ python -m pip install .

in a shell should produce a file custom.so in a subdirectory and install it; now fire up Python --- you should be able to import custom and play around with Custom objects.

That wasn't so hard, was it?

Of course, the current Custom type is pretty uninteresting. It has no data and doesn't do anything. It can't even be subclassed.

2.2. Adding data and methods to the Basic example

Let's extend the basic example to add some data and methods. Let's also make the type usable as a base class. We'll create a new module, custom2 that adds these capabilities:

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <stddef.h> /* for offsetof() */

typedef struct {
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
} CustomObject;

static void
Custom_dealloc(PyObject *op)
{
    CustomObject *self = (CustomObject *) op;
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free(self);
}

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) {
        self->first = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
        if (self->first == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->last = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
        if (self->last == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->number = 0;
    }
    return (PyObject *) self;
}

static int
Custom_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    CustomObject *self = (CustomObject *) op;
    static char *kwlist[] = {"first", "last", "number", NULL};
    PyObject *first = NULL, *last = NULL;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) {
        Py_XSETREF(self->first, Py_NewRef(first));
    }
    if (last) {
        Py_XSETREF(self->last, Py_NewRef(last));
    }
    return 0;
}

static PyMemberDef Custom_members[] = {
    {"first", Py_T_OBJECT_EX, offsetof(CustomObject, first), 0,
     "first name"},
    {"last", Py_T_OBJECT_EX, offsetof(CustomObject, last), 0,
     "last name"},
    {"number", Py_T_INT, offsetof(CustomObject, number), 0,
     "custom number"},
    {NULL}  /* Sentinel */
};

static PyObject *
Custom_name(PyObject *op, PyObject *Py_UNUSED(dummy))
{
    CustomObject *self = (CustomObject *) op;
    if (self->first == NULL) {
        PyErr_SetString(PyExc_AttributeError, "first");
        return NULL;
    }
    if (self->last == NULL) {
        PyErr_SetString(PyExc_AttributeError, "last");
        return NULL;
    }
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
}

static PyMethodDef Custom_methods[] = {
    {"name", Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    },
    {NULL}  /* Sentinel */
};

static PyTypeObject CustomType = {
    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom2.Custom",
    .tp_doc = PyDoc_STR("Custom objects"),
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_new = Custom_new,
    .tp_init = Custom_init,
    .tp_dealloc = Custom_dealloc,
    .tp_members = Custom_members,
    .tp_methods = Custom_methods,
};

static int
custom_module_exec(PyObject *m)
{
    if (PyType_Ready(&CustomType) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(m, "Custom", (PyObject *) &CustomType) < 0) {
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot custom_module_slots[] = {
    {Py_mod_exec, custom_module_exec},
    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},
    {0, NULL}
};

static PyModuleDef custom_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "custom2",
    .m_doc = "Example module that creates an extension type.",
    .m_size = 0,
    .m_slots = custom_module_slots,
};

PyMODINIT_FUNC
PyInit_custom2(void)
{
    return PyModuleDef_Init(&custom_module);
}

This version of the module has a number of changes.

The Custom type now has three data attributes in its C struct, first, last, and number. The first and last variables are Python strings containing first and last names. The number attribute is a C integer.

The object structure is updated accordingly:

typedef struct {
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
} CustomObject;

Because we now have data to manage, we have to be more careful about object allocation and deallocation. At a minimum, we need a deallocation method:

static void
Custom_dealloc(PyObject *op)
{
    CustomObject *self = (CustomObject *) op;
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free(self);
}

which is assigned to the tp_dealloc member:

.tp_dealloc = Custom_dealloc,

This method first clears the reference counts of the two Python attributes. Py_XDECREF() correctly handles the case where its argument is NULL (which might happen here if tp_new failed midway). It then calls the tp_free member of the object's type (computed by Py_TYPE(self)) to free the object's memory. Note that the object's type might not be CustomType, because the object may be an instance of a subclass.

備註

The explicit cast to CustomObject * above is needed because we defined Custom_dealloc to take a PyObject * argument, as the tp_dealloc function pointer expects to receive a PyObject * argument. By assigning to the tp_dealloc slot of a type, we declare that it can only be called with instances of our CustomObject class, so the cast to (CustomObject *) is safe. This is object-oriented polymorphism, in C!

In existing code, or in previous versions of this tutorial, you might see similar functions take a pointer to the subtype object structure (CustomObject*) directly, like this:

Custom_dealloc(CustomObject *self)
{
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free((PyObject *) self);
}
...
.tp_dealloc = (destructor) Custom_dealloc,

This does the same thing on all architectures that CPython supports, but according to the C standard, it invokes undefined behavior.

We want to make sure that the first and last names are initialized to empty strings, so we provide a tp_new implementation:

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) {
        self->first = PyUnicode_FromString("");
        if (self->first == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->last = PyUnicode_FromString("");
        if (self->last == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->number = 0;
    }
    return (PyObject *) self;
}

and install it in the tp_new member:

.tp_new = Custom_new,

The tp_new handler is responsible for creating (as opposed to initializing) objects of the type. It is exposed in Python as the __new__() method. It is not required to define a tp_new member, and indeed many extension types will simply reuse PyType_GenericNew() as done in the first version of the Custom type above. In this case, we use the tp_new handler to initialize the first and last attributes to non-NULL default values.

tp_new is passed the type being instantiated (not necessarily CustomType, if a subclass is instantiated) and any arguments passed when the type was called, and is expected to return the instance created. tp_new handlers always accept positional and keyword arguments, but they often ignore the arguments, leaving the argument handling to initializer (a.k.a. tp_init in C or __init__ in Python) methods.

備註

tp_new shouldn't call tp_init explicitly, as the interpreter will do it itself.

The tp_new implementation calls the tp_alloc slot to allocate memory:

self = (CustomObject *) type->tp_alloc(type, 0);

Since memory allocation may fail, we must check the tp_alloc result against NULL before proceeding.

備註

We didn't fill the tp_alloc slot ourselves. Rather PyType_Ready() fills it for us by inheriting it from our base class, which is object by default. Most types use the default allocation strategy.

備註

If you are creating a co-operative tp_new (one that calls a base type's tp_new or __new__()), you must not try to determine what method to call using method resolution order at runtime. Always statically determine what type you are going to call, and call its tp_new directly, or via type->tp_base->tp_new. If you do not do this, Python subclasses of your type that also inherit from other Python-defined classes may not work correctly. (Specifically, you may not be able to create instances of such subclasses without getting a TypeError.)

We also define an initialization function which accepts arguments to provide initial values for our instance:

static int
Custom_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    CustomObject *self = (CustomObject *) op;
    static char *kwlist[] = {"first", "last", "number", NULL};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) {
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_XDECREF(tmp);
    }
    if (last) {
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_XDECREF(tmp);
    }
    return 0;
}

by filling the tp_init slot.

.tp_init = Custom_init,

The tp_init slot is exposed in Python as the __init__() method. It is used to initialize an object after it's created. Initializers always accept positional and keyword arguments, and they should return either 0 on success or -1 on error.

Unlike the tp_new handler, there is no guarantee that tp_init is called at all (for example, the pickle module by default doesn't call __init__() on unpickled instances). It can also be called multiple times. Anyone can call the __init__() method on our objects. For this reason, we have to be extra careful when assigning the new attribute values. We might be tempted, for example to assign the first member like this:

if (first) {
    Py_XDECREF(self->first);
    Py_INCREF(first);
    self->first = first;
}

But this would be risky. Our type doesn't restrict the type of the first member, so it could be any kind of object. It could have a destructor that causes code to be executed that tries to access the first member; or that destructor could detach the thread state and let arbitrary code run in other threads that accesses and modifies our object.

To be paranoid and protect ourselves against this possibility, we almost always reassign members before decrementing their reference counts. When don't we have to do this?

when we absolutely know that the reference count is greater than 1;

when we know that deallocation of the object [1] will neither detach the thread state nor cause any calls back into our type's code;

when decrementing a reference count in a tp_dealloc handler on a type which doesn't support cyclic garbage collection [2].

We want to expose our instance variables as attributes. There are a number of ways to do that. The simplest way is to define member definitions:

static PyMemberDef Custom_members[] = {
    {"first", Py_T_OBJECT_EX, offsetof(CustomObject, first), 0,
     "first name"},
    {"last", Py_T_OBJECT_EX, offsetof(CustomObject, last), 0,
     "last name"},
    {"number", Py_T_INT, offsetof(CustomObject, number), 0,
     "custom number"},
    {NULL}  /* Sentinel */
};

and put the definitions in the tp_members slot:

.tp_members = Custom_members,

Each member definition has a member name, type, offset, access flags and documentation string. See the Generic Attribute Management section below for details.

A disadvantage of this approach is that it doesn't provide a way to restrict the types of objects that can be assigned to the Python attributes. We expect the first and last names to be strings, but any Python objects can be assigned. Further, the attributes can be deleted, setting the C pointers to NULL. Even though we can make sure the members are initialized to non-NULL values, the members can be set to NULL if the attributes are deleted.

We define a single method, Custom.name(), that outputs the objects name as the concatenation of the first and last names.

static PyObject *
Custom_name(PyObject *op, PyObject *Py_UNUSED(dummy))
{
    CustomObject *self = (CustomObject *) op;
    if (self->first == NULL) {
        PyErr_SetString(PyExc_AttributeError, "first");
        return NULL;
    }
    if (self->last == NULL) {
        PyErr_SetString(PyExc_AttributeError, "last");
        return NULL;
    }
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
}

The method is implemented as a C function that takes a Custom (or Custom subclass) instance as the first argument. Methods always take an instance as the first argument. Methods often take positional and keyword arguments as well, but in this case we don't take any and don't need to accept a positional argument tuple or keyword argument dictionary. This method is equivalent to the Python method:

def name(self):
    return "%s %s" % (self.first, self.last)

Note that we have to check for the possibility that our first and last members are NULL. This is because they can be deleted, in which case they are set to NULL. It would be better to prevent deletion of these attributes and to restrict the attribute values to be strings. We'll see how to do that in the next section.

Now that we've defined the method, we need to create an array of method definitions:

static PyMethodDef Custom_methods[] = {
    {"name", Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    },
    {NULL}  /* Sentinel */
};

(note that we used the METH_NOARGS flag to indicate that the method is expecting no arguments other than self)

and assign it to the tp_methods slot:

.tp_methods = Custom_methods,

Finally, we'll make our type usable as a base class for subclassing. We've written our methods carefully so far so that they don't make any assumptions about the type of the object being created or used, so all we need to do is to add the Py_TPFLAGS_BASETYPE to our class flag definition:

.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,

We rename PyInit_custom() to PyInit_custom2(), update the module name in the PyModuleDef struct, and update the full class name in the PyTypeObject struct.

Finally, we update our setup.py file to include the new module,

from setuptools import Extension, setup
setup(ext_modules=[
    Extension("custom", ["custom.c"]),
    Extension("custom2", ["custom2.c"]),
])

and then we re-install so that we can import custom2:

$ python -m pip install .

2.3. Providing finer control over data attributes

In this section, we'll provide finer control over how the first and last attributes are set in the Custom example. In the previous version of our module, the instance variables first and last could be set to non-string values or even deleted. We want to make sure that these attributes always contain strings.

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <stddef.h> /* for offsetof() */

typedef struct {
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
} CustomObject;

static void
Custom_dealloc(PyObject *op)
{
    CustomObject *self = (CustomObject *) op;
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free(self);
}

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) {
        self->first = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
        if (self->first == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->last = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
        if (self->last == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->number = 0;
    }
    return (PyObject *) self;
}

static int
Custom_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    CustomObject *self = (CustomObject *) op;
    static char *kwlist[] = {"first", "last", "number", NULL};
    PyObject *first = NULL, *last = NULL;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|UUi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) {
        Py_SETREF(self->first, Py_NewRef(first));
    }
    if (last) {
        Py_SETREF(self->last, Py_NewRef(last));
    }
    return 0;
}

static PyMemberDef Custom_members[] = {
    {"number", Py_T_INT, offsetof(CustomObject, number), 0,
     "custom number"},
    {NULL}  /* Sentinel */
};

static PyObject *
Custom_getfirst(PyObject *op, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    return Py_NewRef(self->first);
}

static int
Custom_setfirst(PyObject *op, PyObject *value, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    if (value == NULL) {
        PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
        return -1;
    }
    if (!PyUnicode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "The first attribute value must be a string");
        return -1;
    }
    Py_SETREF(self->first, Py_NewRef(value));
    return 0;
}

static PyObject *
Custom_getlast(PyObject *op, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    return Py_NewRef(self->last);
}

static int
Custom_setlast(PyObject *op, PyObject *value, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    if (value == NULL) {
        PyErr_SetString(PyExc_TypeError, "Cannot delete the last attribute");
        return -1;
    }
    if (!PyUnicode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "The last attribute value must be a string");
        return -1;
    }
    Py_SETREF(self->last, Py_NewRef(value));
    return 0;
}

static PyGetSetDef Custom_getsetters[] = {
    {"first", Custom_getfirst, Custom_setfirst,
     "first name", NULL},
    {"last", Custom_getlast, Custom_setlast,
     "last name", NULL},
    {NULL}  /* Sentinel */
};

static PyObject *
Custom_name(PyObject *op, PyObject *Py_UNUSED(dummy))
{
    CustomObject *self = (CustomObject *) op;
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
}

static PyMethodDef Custom_methods[] = {
    {"name", Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    },
    {NULL}  /* Sentinel */
};

static PyTypeObject CustomType = {
    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom3.Custom",
    .tp_doc = PyDoc_STR("Custom objects"),
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_new = Custom_new,
    .tp_init = Custom_init,
    .tp_dealloc = Custom_dealloc,
    .tp_members = Custom_members,
    .tp_methods = Custom_methods,
    .tp_getset = Custom_getsetters,
};

static int
custom_module_exec(PyObject *m)
{
    if (PyType_Ready(&CustomType) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(m, "Custom", (PyObject *) &CustomType) < 0) {
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot custom_module_slots[] = {
    {Py_mod_exec, custom_module_exec},
    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},
    {0, NULL}
};

static PyModuleDef custom_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "custom3",
    .m_doc = "Example module that creates an extension type.",
    .m_size = 0,
    .m_slots = custom_module_slots,
};

PyMODINIT_FUNC
PyInit_custom3(void)
{
    return PyModuleDef_Init(&custom_module);
}

To provide greater control, over the first and last attributes, we'll use custom getter and setter functions. Here are the functions for getting and setting the first attribute:

static PyObject *
Custom_getfirst(PyObject *op, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    Py_INCREF(self->first);
    return self->first;
}

static int
Custom_setfirst(PyObject *op, PyObject *value, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    PyObject *tmp;
    if (value == NULL) {
        PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
        return -1;
    }
    if (!PyUnicode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "The first attribute value must be a string");
        return -1;
    }
    tmp = self->first;
    Py_INCREF(value);
    self->first = value;
    Py_DECREF(tmp);
    return 0;
}

The getter function is passed a Custom object and a "closure", which is a void pointer. In this case, the closure is ignored. (The closure supports an advanced usage in which definition data is passed to the getter and setter. This could, for example, be used to allow a single set of getter and setter functions that decide the attribute to get or set based on data in the closure.)

The setter function is passed the Custom object, the new value, and the closure. The new value may be NULL, in which case the attribute is being deleted. In our setter, we raise an error if the attribute is deleted or if its new value is not a string.

We create an array of PyGetSetDef structures:

static PyGetSetDef Custom_getsetters[] = {
    {"first", Custom_getfirst, Custom_setfirst,
     "first name", NULL},
    {"last", Custom_getlast, Custom_setlast,
     "last name", NULL},
    {NULL}  /* Sentinel */
};

and register it in the tp_getset slot:

.tp_getset = Custom_getsetters,

The last item in a PyGetSetDef structure is the "closure" mentioned above. In this case, we aren't using a closure, so we just pass NULL.

We also remove the member definitions for these attributes:

static PyMemberDef Custom_members[] = {
    {"number", Py_T_INT, offsetof(CustomObject, number), 0,
     "custom number"},
    {NULL}  /* Sentinel */
};

We also need to update the tp_init handler to only allow strings [3] to be passed:

static int
Custom_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    CustomObject *self = (CustomObject *) op;
    static char *kwlist[] = {"first", "last", "number", NULL};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|UUi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) {
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_DECREF(tmp);
    }
    if (last) {
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_DECREF(tmp);
    }
    return 0;
}

With these changes, we can assure that the first and last members are never NULL so we can remove checks for NULL values in almost all cases. This means that most of the Py_XDECREF() calls can be converted to Py_DECREF() calls. The only place we can't change these calls is in the tp_dealloc implementation, where there is the possibility that the initialization of these members failed in tp_new.

We also rename the module initialization function and module name in the initialization function, as we did before, and we add an extra definition to the setup.py file.

2.4. Supporting cyclic garbage collection

Python has a cyclic garbage collector (GC) that can identify unneeded objects even when their reference counts are not zero. This can happen when objects are involved in cycles. For example, consider:

>>> l = []
>>> l.append(l)
>>> del l

In this example, we create a list that contains itself. When we delete it, it still has a reference from itself. Its reference count doesn't drop to zero. Fortunately, Python's cyclic garbage collector will eventually figure out that the list is garbage and free it.

In the second version of the Custom example, we allowed any kind of object to be stored in the first or last attributes [4]. Besides, in the second and third versions, we allowed subclassing Custom, and subclasses may add arbitrary attributes. For any of those two reasons, Custom objects can participate in cycles:

>>> import custom3
>>> class Derived(custom3.Custom): pass
...
>>> n = Derived()
>>> n.some_attribute = n

To allow a Custom instance participating in a reference cycle to be properly detected and collected by the cyclic GC, our Custom type needs to fill two additional slots and to enable a flag that enables these slots:

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <stddef.h> /* for offsetof() */

typedef struct {
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
} CustomObject;

static int
Custom_traverse(PyObject *op, visitproc visit, void *arg)
{
    CustomObject *self = (CustomObject *) op;
    Py_VISIT(self->first);
    Py_VISIT(self->last);
    return 0;
}

static int
Custom_clear(PyObject *op)
{
    CustomObject *self = (CustomObject *) op;
    Py_CLEAR(self->first);
    Py_CLEAR(self->last);
    return 0;
}

static void
Custom_dealloc(PyObject *op)
{
    PyObject_GC_UnTrack(op);
    (void)Custom_clear(op);
    Py_TYPE(op)->tp_free(op);
}

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) {
        self->first = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
        if (self->first == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->last = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
        if (self->last == NULL) {
            Py_DECREF(self);
            return NULL;
        }
        self->number = 0;
    }
    return (PyObject *) self;
}

static int
Custom_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    CustomObject *self = (CustomObject *) op;
    static char *kwlist[] = {"first", "last", "number", NULL};
    PyObject *first = NULL, *last = NULL;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|UUi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) {
        Py_SETREF(self->first, Py_NewRef(first));
    }
    if (last) {
        Py_SETREF(self->last, Py_NewRef(last));
    }
    return 0;
}

static PyMemberDef Custom_members[] = {
    {"number", Py_T_INT, offsetof(CustomObject, number), 0,
     "custom number"},
    {NULL}  /* Sentinel */
};

static PyObject *
Custom_getfirst(PyObject *op, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    return Py_NewRef(self->first);
}

static int
Custom_setfirst(PyObject *op, PyObject *value, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    if (value == NULL) {
        PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
        return -1;
    }
    if (!PyUnicode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "The first attribute value must be a string");
        return -1;
    }
    Py_XSETREF(self->first, Py_NewRef(value));
    return 0;
}

static PyObject *
Custom_getlast(PyObject *op, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    return Py_NewRef(self->last);
}

static int
Custom_setlast(PyObject *op, PyObject *value, void *closure)
{
    CustomObject *self = (CustomObject *) op;
    if (value == NULL) {
        PyErr_SetString(PyExc_TypeError, "Cannot delete the last attribute");
        return -1;
    }
    if (!PyUnicode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "The last attribute value must be a string");
        return -1;
    }
    Py_XSETREF(self->last, Py_NewRef(value));
    return 0;
}

static PyGetSetDef Custom_getsetters[] = {
    {"first", Custom_getfirst, Custom_setfirst,
     "first name", NULL},
    {"last", Custom_getlast, Custom_setlast,
     "last name", NULL},
    {NULL}  /* Sentinel */
};

static PyObject *
Custom_name(PyObject *op, PyObject *Py_UNUSED(dummy))
{
    CustomObject *self = (CustomObject *) op;
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
}

static PyMethodDef Custom_methods[] = {
    {"name", Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    },
    {NULL}  /* Sentinel */
};

static PyTypeObject CustomType = {
    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom4.Custom",
    .tp_doc = PyDoc_STR("Custom objects"),
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
    .tp_new = Custom_new,
    .tp_init = Custom_init,
    .tp_dealloc = Custom_dealloc,
    .tp_traverse = Custom_traverse,
    .tp_clear = Custom_clear,
    .tp_members = Custom_members,
    .tp_methods = Custom_methods,
    .tp_getset = Custom_getsetters,
};

static int
custom_module_exec(PyObject *m)
{
    if (PyType_Ready(&CustomType) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(m, "Custom", (PyObject *) &CustomType) < 0) {
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot custom_module_slots[] = {
    {Py_mod_exec, custom_module_exec},
    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},
    {0, NULL}
};

static PyModuleDef custom_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "custom4",
    .m_doc = "Example module that creates an extension type.",
    .m_size = 0,
    .m_slots = custom_module_slots,
};

PyMODINIT_FUNC
PyInit_custom4(void)
{
    return PyModuleDef_Init(&custom_module);
}

First, the traversal method lets the cyclic GC know about subobjects that could participate in cycles:

static int
Custom_traverse(PyObject *op, visitproc visit, void *arg)
{
    CustomObject *self = (CustomObject *) op;
    int vret;
    if (self->first) {
        vret = visit(self->first, arg);
        if (vret != 0)
            return vret;
    }
    if (self->last) {
        vret = visit(self->last, arg);
        if (vret != 0)
            return vret;
    }
    return 0;
}

For each subobject that can participate in cycles, we need to call the visit() function, which is passed to the traversal method. The visit() function takes as arguments the subobject and the extra argument arg passed to the traversal method. It returns an integer value that must be returned if it is non-zero.

Python provides a Py_VISIT() macro that automates calling visit functions. With Py_VISIT(), we can minimize the amount of boilerplate in Custom_traverse:

static int
Custom_traverse(PyObject *op, visitproc visit, void *arg)
{
    CustomObject *self = (CustomObject *) op;
    Py_VISIT(self->first);
    Py_VISIT(self->last);
    return 0;
}

備註

The tp_traverse implementation must name its arguments exactly visit and arg in order to use Py_VISIT().

Second, we need to provide a method for clearing any subobjects that can participate in cycles:

static int
Custom_clear(PyObject *op)
{
    CustomObject *self = (CustomObject *) op;
    Py_CLEAR(self->first);
    Py_CLEAR(self->last);
    return 0;
}

Notice the use of the Py_CLEAR() macro. It is the recommended and safe way to clear data attributes of arbitrary types while decrementing their reference counts. If you were to call Py_XDECREF() instead on the attribute before setting it to NULL, there is a possibility that the attribute's destructor would call back into code that reads the attribute again (especially if there is a reference cycle).

備註

You could emulate Py_CLEAR() by writing:

PyObject *tmp;
tmp = self->first;
self->first = NULL;
Py_XDECREF(tmp);

Nevertheless, it is much easier and less error-prone to always use Py_CLEAR() when deleting an attribute. Don't try to micro-optimize at the expense of robustness!

The deallocator Custom_dealloc may call arbitrary code when clearing attributes. It means the circular GC can be triggered inside the function. Since the GC assumes reference count is not zero, we need to untrack the object from the GC by calling PyObject_GC_UnTrack() before clearing members. Here is our reimplemented deallocator using PyObject_GC_UnTrack() and Custom_clear:

static void
Custom_dealloc(PyObject *op)
{
    PyObject_GC_UnTrack(op);
    (void)Custom_clear(op);
    Py_TYPE(op)->tp_free(op);
}

Finally, we add the Py_TPFLAGS_HAVE_GC flag to the class flags:

.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,

That's pretty much it. If we had written custom tp_alloc or tp_free handlers, we'd need to modify them for cyclic garbage collection. Most extensions will use the versions automatically provided.

2.5. Subclassing other types

It is possible to create new extension types that are derived from existing types. It is easiest to inherit from the built in types, since an extension can easily use the PyTypeObject it needs. It can be difficult to share these PyTypeObject structures between extension modules.

In this example we will create a SubList type that inherits from the built-in list type. The new type will be completely compatible with regular lists, but will have an additional increment() method that increases an internal counter:

>>> import sublist
>>> s = sublist.SubList(range(3))
>>> s.extend(s)
>>> print(len(s))
6
>>> print(s.increment())
1
>>> print(s.increment())
2

#define PY_SSIZE_T_CLEAN
#include <Python.h>

typedef struct {
    PyListObject list;
    int state;
} SubListObject;

static PyObject *
SubList_increment(PyObject *op, PyObject *Py_UNUSED(dummy))
{
    SubListObject *self = (SubListObject *) op;
    self->state++;
    return PyLong_FromLong(self->state);
}

static PyMethodDef SubList_methods[] = {
    {"increment", SubList_increment, METH_NOARGS,
     PyDoc_STR("increment state counter")},
    {NULL},
};

static int
SubList_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    SubListObject *self = (SubListObject *) op;
    if (PyList_Type.tp_init(op, args, kwds) < 0)
        return -1;
    self->state = 0;
    return 0;
}

static PyTypeObject SubListType = {
    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "sublist.SubList",
    .tp_doc = PyDoc_STR("SubList objects"),
    .tp_basicsize = sizeof(SubListObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_init = SubList_init,
    .tp_methods = SubList_methods,
};

static int
sublist_module_exec(PyObject *m)
{
    SubListType.tp_base = &PyList_Type;
    if (PyType_Ready(&SubListType) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(m, "SubList", (PyObject *) &SubListType) < 0) {
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot sublist_module_slots[] = {
    {Py_mod_exec, sublist_module_exec},
    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},
    {0, NULL}
};

static PyModuleDef sublist_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "sublist",
    .m_doc = "Example module that creates an extension type.",
    .m_size = 0,
    .m_slots = sublist_module_slots,
};

PyMODINIT_FUNC
PyInit_sublist(void)
{
    return PyModuleDef_Init(&sublist_module);
}

As you can see, the source code closely resembles the Custom examples in previous sections. We will break down the main differences between them.

typedef struct {
    PyListObject list;
    int state;
} SubListObject;

The primary difference for derived type objects is that the base type's object structure must be the first value. The base type will already include the PyObject_HEAD() at the beginning of its structure.

When a Python object is a SubList instance, its PyObject * pointer can be safely cast to both PyListObject * and SubListObject *:

static int
SubList_init(PyObject *op, PyObject *args, PyObject *kwds)
{
    SubListObject *self = (SubListObject *) op;
    if (PyList_Type.tp_init(op, args, kwds) < 0)
        return -1;
    self->state = 0;
    return 0;
}

We see above how to call through to the __init__() method of the base type.

This pattern is important when writing a type with custom tp_new and tp_dealloc members. The tp_new handler should not actually create the memory for the object with its tp_alloc, but let the base class handle it by calling its own tp_new.

The PyTypeObject struct supports a tp_base specifying the type's concrete base class. Due to cross-platform compiler issues, you can't fill that field directly with a reference to PyList_Type; it should be done in the Py_mod_exec function:

static int
sublist_module_exec(PyObject *m)
{
    SubListType.tp_base = &PyList_Type;
    if (PyType_Ready(&SubListType) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(m, "SubList", (PyObject *) &SubListType) < 0) {
        return -1;
    }

    return 0;
}

Before calling PyType_Ready(), the type structure must have the tp_base slot filled in. When we are deriving an existing type, it is not necessary to fill out the tp_alloc slot with PyType_GenericNew() -- the allocation function from the base type will be inherited.

After that, calling PyType_Ready() and adding the type object to the module is the same as with the basic Custom examples.

註腳

[1]

This is true when we know that the object is a basic type, like a string or a float.

[2]

We relied on this in the tp_dealloc handler in this example, because our type doesn't support garbage collection.

[3]

We now know that the first and last members are strings, so perhaps we could be less careful about decrementing their reference counts, however, we accept instances of string subclasses. Even though deallocating normal strings won't call back into our objects, we can't guarantee that deallocating an instance of a string subclass won't call back into our objects.

[4]

Also, even with our attributes restricted to strings instances, the user could pass arbitrary str subclasses and therefore still create reference cycles.

3. Defining Extension Types: Assorted Topics

This section aims to give a quick fly-by on the various type methods you can implement and what they do.

Here is the definition of PyTypeObject, with some fields only used in debug builds omitted:

typedef struct _typeobject {
    PyObject_VAR_HEAD
    const char *tp_name; /* For printing, in format "<module>.<name>" */
    Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */

    /* Methods to implement standard operations */

    destructor tp_dealloc;
    Py_ssize_t tp_vectorcall_offset;
    getattrfunc tp_getattr;
    setattrfunc tp_setattr;
    PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
                                    or tp_reserved (Python 3) */
    reprfunc tp_repr;

    /* Method suites for standard classes */

    PyNumberMethods *tp_as_number;
    PySequenceMethods *tp_as_sequence;
    PyMappingMethods *tp_as_mapping;

    /* More standard operations (here for binary compatibility) */

    hashfunc tp_hash;
    ternaryfunc tp_call;
    reprfunc tp_str;
    getattrofunc tp_getattro;
    setattrofunc tp_setattro;

    /* Functions to access object as input/output buffer */
    PyBufferProcs *tp_as_buffer;

    /* Flags to define presence of optional/expanded features */
    unsigned long tp_flags;

    const char *tp_doc; /* Documentation string */

    /* Assigned meaning in release 2.0 */
    /* call function for all accessible objects */
    traverseproc tp_traverse;

    /* delete references to contained objects */
    inquiry tp_clear;

    /* Assigned meaning in release 2.1 */
    /* rich comparisons */
    richcmpfunc tp_richcompare;

    /* weak reference enabler */
    Py_ssize_t tp_weaklistoffset;

    /* Iterators */
    getiterfunc tp_iter;
    iternextfunc tp_iternext;

    /* Attribute descriptor and subclassing stuff */
    PyMethodDef *tp_methods;
    PyMemberDef *tp_members;
    PyGetSetDef *tp_getset;
    // Strong reference on a heap type, borrowed reference on a static type
    PyTypeObject *tp_base;
    PyObject *tp_dict;
    descrgetfunc tp_descr_get;
    descrsetfunc tp_descr_set;
    Py_ssize_t tp_dictoffset;
    initproc tp_init;
    allocfunc tp_alloc;
    newfunc tp_new;
    freefunc tp_free; /* Low-level free-memory routine */
    inquiry tp_is_gc; /* For PyObject_IS_GC */
    PyObject *tp_bases;
    PyObject *tp_mro; /* method resolution order */
    PyObject *tp_cache; /* no longer used */
    void *tp_subclasses;  /* for static builtin types this is an index */
    PyObject *tp_weaklist; /* not used for static builtin types */
    destructor tp_del;

    /* Type attribute cache version tag. Added in version 2.6.
     * If zero, the cache is invalid and must be initialized.
     */
    unsigned int tp_version_tag;

    destructor tp_finalize;
    vectorcallfunc tp_vectorcall;

    /* bitset of which type-watchers care about this type */
    unsigned char tp_watched;

    /* Number of tp_version_tag values used.
     * Set to _Py_ATTR_CACHE_UNUSED if the attribute cache is
     * disabled for this type (e.g. due to custom MRO entries).
     * Otherwise, limited to MAX_VERSIONS_PER_CLASS (defined elsewhere).
     */
    uint16_t tp_versions_used;
} PyTypeObject;

Now that's a lot of methods. Don't worry too much though -- if you have a type you want to define, the chances are very good that you will only implement a handful of these.

As you probably expect by now, we're going to go over this and give more information about the various handlers. We won't go in the order they are defined in the structure, because there is a lot of historical baggage that impacts the ordering of the fields. It's often easiest to find an example that includes the fields you need and then change the values to suit your new type.

const char *tp_name; /* For printing */

The name of the type -- as mentioned in the previous chapter, this will appear in various places, almost entirely for diagnostic purposes. Try to choose something that will be helpful in such a situation!

Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */

These fields tell the runtime how much memory to allocate when new objects of this type are created. Python has some built-in support for variable length structures (think: strings, tuples) which is where the tp_itemsize field comes in. This will be dealt with later.

const char *tp_doc;

Here you can put a string (or its address) that you want returned when the Python script references obj.__doc__ to retrieve the doc string.

Now we come to the basic type methods -- the ones most extension types will implement.

3.1. Finalization and De-allocation

destructor tp_dealloc;

This function is called when the reference count of the instance of your type is reduced to zero and the Python interpreter wants to reclaim it. If your type has memory to free or other clean-up to perform, you can put it here. The object itself needs to be freed here as well. Here is an example of this function:

static void
newdatatype_dealloc(PyObject *op)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    free(self->obj_UnderlyingDatatypePtr);
    Py_TYPE(self)->tp_free(self);
}

If your type supports garbage collection, the destructor should call PyObject_GC_UnTrack() before clearing any member fields:

static void
newdatatype_dealloc(PyObject *op)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    PyObject_GC_UnTrack(op);
    Py_CLEAR(self->other_obj);
    ...
    Py_TYPE(self)->tp_free(self);
}

One important requirement of the deallocator function is that it leaves any pending exceptions alone. This is important since deallocators are frequently called as the interpreter unwinds the Python stack; when the stack is unwound due to an exception (rather than normal returns), nothing is done to protect the deallocators from seeing that an exception has already been set. Any actions which a deallocator performs which may cause additional Python code to be executed may detect that an exception has been set. This can lead to misleading errors from the interpreter. The proper way to protect against this is to save a pending exception before performing the unsafe action, and restoring it when done. This can be done using the PyErr_Fetch() and PyErr_Restore() functions:

static void
my_dealloc(PyObject *obj)
{
    MyObject *self = (MyObject *) obj;
    PyObject *cbresult;

    if (self->my_callback != NULL) {
        PyObject *err_type, *err_value, *err_traceback;

        /* This saves the current exception state */
        PyErr_Fetch(&err_type, &err_value, &err_traceback);

        cbresult = PyObject_CallNoArgs(self->my_callback);
        if (cbresult == NULL) {
           PyErr_WriteUnraisable(self->my_callback);
        }
        else {
            Py_DECREF(cbresult);
        }

        /* This restores the saved exception state */
        PyErr_Restore(err_type, err_value, err_traceback);

        Py_DECREF(self->my_callback);
    }
    Py_TYPE(self)->tp_free(self);
}

備註

There are limitations to what you can safely do in a deallocator function. First, if your type supports garbage collection (using tp_traverse and/or tp_clear), some of the object's members can have been cleared or finalized by the time tp_dealloc is called. Second, in tp_dealloc, your object is in an unstable state: its reference count is equal to zero. Any call to a non-trivial object or API (as in the example above) might end up calling tp_dealloc again, causing a double free and a crash.

Starting with Python 3.4, it is recommended not to put any complex finalization code in tp_dealloc, and instead use the new tp_finalize type method.

也參考

PEP 442 [https://peps.python.org/pep-0442/] explains the new finalization scheme.

3.2. Object Presentation

In Python, there are two ways to generate a textual representation of an object: the repr() function, and the str() function. (The print() function just calls str().) These handlers are both optional.

reprfunc tp_repr;
reprfunc tp_str;

The tp_repr handler should return a string object containing a representation of the instance for which it is called. Here is a simple example:

static PyObject *
newdatatype_repr(PyObject *op)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    return PyUnicode_FromFormat("Repr-ified_newdatatype{{size:%d}}",
                                self->obj_UnderlyingDatatypePtr->size);
}

If no tp_repr handler is specified, the interpreter will supply a representation that uses the type's tp_name and a uniquely identifying value for the object.

The tp_str handler is to str() what the tp_repr handler described above is to repr(); that is, it is called when Python code calls str() on an instance of your object. Its implementation is very similar to the tp_repr function, but the resulting string is intended for human consumption. If tp_str is not specified, the tp_repr handler is used instead.

以下是個簡單的範例：

static PyObject *
newdatatype_str(PyObject *op)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    return PyUnicode_FromFormat("Stringified_newdatatype{{size:%d}}",
                                self->obj_UnderlyingDatatypePtr->size);
}

3.3. Attribute Management

For every object which can support attributes, the corresponding type must provide the functions that control how the attributes are resolved. There needs to be a function which can retrieve attributes (if any are defined), and another to set attributes (if setting attributes is allowed). Removing an attribute is a special case, for which the new value passed to the handler is NULL.

Python supports two pairs of attribute handlers; a type that supports attributes only needs to implement the functions for one pair. The difference is that one pair takes the name of the attribute as a char*, while the other accepts a PyObject*. Each type can use whichever pair makes more sense for the implementation's convenience.

getattrfunc  tp_getattr;        /* char * version */
setattrfunc  tp_setattr;
/* ... */
getattrofunc tp_getattro;       /* PyObject * version */
setattrofunc tp_setattro;

If accessing attributes of an object is always a simple operation (this will be explained shortly), there are generic implementations which can be used to provide the PyObject* version of the attribute management functions. The actual need for type-specific attribute handlers almost completely disappeared starting with Python 2.2, though there are many examples which have not been updated to use some of the new generic mechanism that is available.

3.3.1. Generic Attribute Management

Most extension types only use simple attributes. So, what makes the attributes simple? There are only a couple of conditions that must be met:

The name of the attributes must be known when PyType_Ready() is called.

No special processing is needed to record that an attribute was looked up or set, nor do actions need to be taken based on the value.

Note that this list does not place any restrictions on the values of the attributes, when the values are computed, or how relevant data is stored.

When PyType_Ready() is called, it uses three tables referenced by the type object to create descriptors which are placed in the dictionary of the type object. Each descriptor controls access to one attribute of the instance object. Each of the tables is optional; if all three are NULL, instances of the type will only have attributes that are inherited from their base type, and should leave the tp_getattro and tp_setattro fields NULL as well, allowing the base type to handle attributes.

The tables are declared as three fields of the type object:

struct PyMethodDef *tp_methods;
struct PyMemberDef *tp_members;
struct PyGetSetDef *tp_getset;

If tp_methods is not NULL, it must refer to an array of PyMethodDef structures. Each entry in the table is an instance of this structure:

typedef struct PyMethodDef {
    const char  *ml_name;       /* method name */
    PyCFunction  ml_meth;       /* implementation function */
    int          ml_flags;      /* flags */
    const char  *ml_doc;        /* docstring */
} PyMethodDef;

One entry should be defined for each method provided by the type; no entries are needed for methods inherited from a base type. One additional entry is needed at the end; it is a sentinel that marks the end of the array. The ml_name field of the sentinel must be NULL.

The second table is used to define attributes which map directly to data stored in the instance. A variety of primitive C types are supported, and access may be read-only or read-write. The structures in the table are defined as:

typedef struct PyMemberDef {
    const char *name;
    int         type;
    int         offset;
    int         flags;
    const char *doc;
} PyMemberDef;

For each entry in the table, a descriptor will be constructed and added to the type which will be able to extract a value from the instance structure. The type field should contain a type code like Py_T_INT or Py_T_DOUBLE; the value will be used to determine how to convert Python values to and from C values. The flags field is used to store flags which control how the attribute can be accessed: you can set it to Py_READONLY to prevent Python code from setting it.

An interesting advantage of using the tp_members table to build descriptors that are used at runtime is that any attribute defined this way can have an associated doc string simply by providing the text in the table. An application can use the introspection API to retrieve the descriptor from the class object, and get the doc string using its __doc__ attribute.

As with the tp_methods table, a sentinel entry with a ml_name value of NULL is required.

3.3.2. Type-specific Attribute Management

For simplicity, only the char* version will be demonstrated here; the type of the name parameter is the only difference between the char* and PyObject* flavors of the interface. This example effectively does the same thing as the generic example above, but does not use the generic support added in Python 2.2. It explains how the handler functions are called, so that if you do need to extend their functionality, you'll understand what needs to be done.

The tp_getattr handler is called when the object requires an attribute look-up. It is called in the same situations where the __getattr__() method of a class would be called.

舉例來說：

static PyObject *
newdatatype_getattr(PyObject *op, char *name)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    if (strcmp(name, "data") == 0) {
        return PyLong_FromLong(self->data);
    }

    PyErr_Format(PyExc_AttributeError,
                 "'%.100s' object has no attribute '%.400s'",
                 Py_TYPE(self)->tp_name, name);
    return NULL;
}

The tp_setattr handler is called when the __setattr__() or __delattr__() method of a class instance would be called. When an attribute should be deleted, the third parameter will be NULL. Here is an example that simply raises an exception; if this were really all you wanted, the tp_setattr handler should be set to NULL.

static int
newdatatype_setattr(PyObject *op, char *name, PyObject *v)
{
    PyErr_Format(PyExc_RuntimeError, "Read-only attribute: %s", name);
    return -1;
}

3.4. Object Comparison

richcmpfunc tp_richcompare;

The tp_richcompare handler is called when comparisons are needed. It is analogous to the rich comparison methods, like __lt__(), and also called by PyObject_RichCompare() and PyObject_RichCompareBool().

This function is called with two Python objects and the operator as arguments, where the operator is one of Py_EQ, Py_NE, Py_LE, Py_GE, Py_LT or Py_GT. It should compare the two objects with respect to the specified operator and return Py_True or Py_False if the comparison is successful, Py_NotImplemented to indicate that comparison is not implemented and the other object's comparison method should be tried, or NULL if an exception was set.

Here is a sample implementation, for a datatype that is considered equal if the size of an internal pointer is equal:

static PyObject *
newdatatype_richcmp(PyObject *lhs, PyObject *rhs, int op)
{
    newdatatypeobject *obj1 = (newdatatypeobject *) lhs;
    newdatatypeobject *obj2 = (newdatatypeobject *) rhs;
    PyObject *result;
    int c, size1, size2;

    /* code to make sure that both arguments are of type
       newdatatype omitted */

    size1 = obj1->obj_UnderlyingDatatypePtr->size;
    size2 = obj2->obj_UnderlyingDatatypePtr->size;

    switch (op) {
    case Py_LT: c = size1 <  size2; break;
    case Py_LE: c = size1 <= size2; break;
    case Py_EQ: c = size1 == size2; break;
    case Py_NE: c = size1 != size2; break;
    case Py_GT: c = size1 >  size2; break;
    case Py_GE: c = size1 >= size2; break;
    }
    result = c ? Py_True : Py_False;
    return Py_NewRef(result);
 }

3.5. Abstract Protocol Support

Python supports a variety of abstract 'protocols;' the specific interfaces provided to use these interfaces are documented in 抽象物件層 (Abstract Objects Layer).

A number of these abstract interfaces were defined early in the development of the Python implementation. In particular, the number, mapping, and sequence protocols have been part of Python since the beginning. Other protocols have been added over time. For protocols which depend on several handler routines from the type implementation, the older protocols have been defined as optional blocks of handlers referenced by the type object. For newer protocols there are additional slots in the main type object, with a flag bit being set to indicate that the slots are present and should be checked by the interpreter. (The flag bit does not indicate that the slot values are non-NULL. The flag may be set to indicate the presence of a slot, but a slot may still be unfilled.)

PyNumberMethods   *tp_as_number;
PySequenceMethods *tp_as_sequence;
PyMappingMethods  *tp_as_mapping;

If you wish your object to be able to act like a number, a sequence, or a mapping object, then you place the address of a structure that implements the C type PyNumberMethods, PySequenceMethods, or PyMappingMethods, respectively. It is up to you to fill in this structure with appropriate values. You can find examples of the use of each of these in the Objects directory of the Python source distribution.

hashfunc tp_hash;

This function, if you choose to provide it, should return a hash number for an instance of your data type. Here is a simple example:

static Py_hash_t
newdatatype_hash(PyObject *op)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    Py_hash_t result;
    result = self->some_size + 32767 * self->some_number;
    if (result == -1) {
        result = -2;
    }
    return result;
}

Py_hash_t is a signed integer type with a platform-varying width. Returning -1 from tp_hash indicates an error, which is why you should be careful to avoid returning it when hash computation is successful, as seen above.

ternaryfunc tp_call;

This function is called when an instance of your data type is "called", for example, if obj1 is an instance of your data type and the Python script contains obj1('hello'), the tp_call handler is invoked.

This function takes three arguments:

self is the instance of the data type which is the subject of the call. If the call is obj1('hello'), then self is obj1.

args is a tuple containing the arguments to the call. You can use PyArg_ParseTuple() to extract the arguments.

kwds is a dictionary of keyword arguments that were passed. If this is non-NULL and you support keyword arguments, use PyArg_ParseTupleAndKeywords() to extract the arguments. If you do not want to support keyword arguments and this is non-NULL, raise a TypeError with a message saying that keyword arguments are not supported.

Here is a toy tp_call implementation:

static PyObject *
newdatatype_call(PyObject *op, PyObject *args, PyObject *kwds)
{
    newdatatypeobject *self = (newdatatypeobject *) op;
    PyObject *result;
    const char *arg1;
    const char *arg2;
    const char *arg3;

    if (!PyArg_ParseTuple(args, "sss:call", &arg1, &arg2, &arg3)) {
        return NULL;
    }
    result = PyUnicode_FromFormat(
        "Returning -- value: [%d] arg1: [%s] arg2: [%s] arg3: [%s]\n",
        self->obj_UnderlyingDatatypePtr->size,
        arg1, arg2, arg3);
    return result;
}

/* 疊代器 */
getiterfunc tp_iter;
iternextfunc tp_iternext;

These functions provide support for the iterator protocol. Both handlers take exactly one parameter, the instance for which they are being called, and return a new reference. In the case of an error, they should set an exception and return NULL. tp_iter corresponds to the Python __iter__() method, while tp_iternext corresponds to the Python __next__() method.

Any iterable object must implement the tp_iter handler, which must return an iterator object. Here the same guidelines apply as for Python classes:

For collections (such as lists and tuples) which can support multiple independent iterators, a new iterator should be created and returned by each call to tp_iter.

Objects which can only be iterated over once (usually due to side effects of iteration, such as file objects) can implement tp_iter by returning a new reference to themselves -- and should also therefore implement the tp_iternext handler.

Any iterator object should implement both tp_iter and tp_iternext. An iterator's tp_iter handler should return a new reference to the iterator. Its tp_iternext handler should return a new reference to the next object in the iteration, if there is one. If the iteration has reached the end, tp_iternext may return NULL without setting an exception, or it may set StopIteration in addition to returning NULL; avoiding the exception can yield slightly better performance. If an actual error occurs, tp_iternext should always set an exception and return NULL.

3.6. Weak Reference Support

One of the goals of Python's weak reference implementation is to allow any type to participate in the weak reference mechanism without incurring the overhead on performance-critical objects (such as numbers).

也參考

Documentation for the weakref module.

For an object to be weakly referenceable, the extension type must set the Py_TPFLAGS_MANAGED_WEAKREF bit of the tp_flags field. The legacy tp_weaklistoffset field should be left as zero.

Concretely, here is how the statically declared type object would look:

static PyTypeObject TrivialType = {
    PyVarObject_HEAD_INIT(NULL, 0)
    /* ... other members omitted for brevity ... */
    .tp_flags = Py_TPFLAGS_MANAGED_WEAKREF | ...,
};

The only further addition is that tp_dealloc needs to clear any weak references (by calling PyObject_ClearWeakRefs()):

static void
Trivial_dealloc(PyObject *op)
{
    /* Clear weakrefs first before calling any destructors */
    PyObject_ClearWeakRefs(op);
    /* ... remainder of destruction code omitted for brevity ... */
    Py_TYPE(op)->tp_free(op);
}

3.7. More Suggestions

In order to learn how to implement any specific method for your new data type, get the CPython source code. Go to the Objects directory, then search the C source files for tp_ plus the function you want (for example, tp_richcompare). You will find examples of the function you want to implement.

When you need to verify that an object is a concrete instance of the type you are implementing, use the PyObject_TypeCheck() function. A sample of its use might be something like the following:

if (!PyObject_TypeCheck(some_object, &MyType)) {
    PyErr_SetString(PyExc_TypeError, "arg #1 not a mything");
    return NULL;
}

也參考

Download CPython source releases.

https://www.python.org/downloads/source/

The CPython project on GitHub, where the CPython source code is developed.

https://github.com/python/cpython

4. 建立 C 與 C++ 擴充套件

一個 CPython 的 C 擴充套件是一個共用函式庫（例如在 Linux 上的 .so 檔案，在 Windows 上的 .pyd），會匯出一個初始化函式。

詳見 Defining extension modules。

4.1. 用 setuptools 建置 C 與 C++ 擴充套件

Building, packaging and distributing extension modules is best done with third-party tools, and is out of scope of this document. One suitable tool is Setuptools, whose documentation can be found at https://setuptools.pypa.io/en/latest/setuptools.html.

直到 Python 3.12 版本前，distutils 模組都被包含在標準函式庫中，現在是作為 Setuptools 的一部分來維護。

5. 建置 Windows 上的 C 和 C++ 擴充

This chapter briefly explains how to create a Windows extension module for Python using Microsoft Visual C++, and follows with more detailed background information on how it works. The explanatory material is useful for both the Windows programmer learning to build Python extensions and the Unix programmer interested in producing software which can be successfully built on both Unix and Windows.

Module authors are encouraged to use the distutils approach for building extension modules, instead of the one described in this section. You will still need the C compiler that was used to build Python; typically Microsoft Visual C++.

備註

This chapter mentions a number of filenames that include an encoded Python version number. These filenames are represented with the version number shown as XY; in practice, 'X' will be the major version number and 'Y' will be the minor version number of the Python release you're working with. For example, if you are using Python 2.2.1, XY will actually be 22.

5.1. A Cookbook Approach

There are two approaches to building extension modules on Windows, just as there are on Unix: use the setuptools package to control the build process, or do things manually. The setuptools approach works well for most extensions; documentation on using setuptools to build and package extension modules is available in 用 setuptools 建置 C 與 C++ 擴充套件. If you find you really need to do things manually, it may be instructive to study the project file for the winsound [https://github.com/python/cpython/tree/3.14/PCbuild/winsound.vcxproj] standard library module.

5.2. Differences Between Unix and Windows

Unix and Windows use completely different paradigms for run-time loading of code. Before you try to build a module that can be dynamically loaded, be aware of how your system works.

In Unix, a shared object (.so) file contains code to be used by the program, and also the names of functions and data that it expects to find in the program. When the file is joined to the program, all references to those functions and data in the file's code are changed to point to the actual locations in the program where the functions and data are placed in memory. This is basically a link operation.

In Windows, a dynamic-link library (.dll) file has no dangling references. Instead, an access to functions or data goes through a lookup table. So the DLL code does not have to be fixed up at runtime to refer to the program's memory; instead, the code already uses the DLL's lookup table, and the lookup table is modified at runtime to point to the functions and data.

In Unix, there is only one type of library file (.a) which contains code from several object files (.o). During the link step to create a shared object file (.so), the linker may find that it doesn't know where an identifier is defined. The linker will look for it in the object files in the libraries; if it finds it, it will include all the code from that object file.

In Windows, there are two types of library, a static library and an import library (both called .lib). A static library is like a Unix .a file; it contains code to be included as necessary. An import library is basically used only to reassure the linker that a certain identifier is legal, and will be present in the program when the DLL is loaded. So the linker uses the information from the import library to build the lookup table for using identifiers that are not included in the DLL. When an application or a DLL is linked, an import library may be generated, which will need to be used for all future DLLs that depend on the symbols in the application or DLL.

Suppose you are building two dynamic-load modules, B and C, which should share another block of code A. On Unix, you would not pass A.a to the linker for B.so and C.so; that would cause it to be included twice, so that B and C would each have their own copy. In Windows, building A.dll will also build A.lib. You do pass A.lib to the linker for B and C. A.lib does not contain code; it just contains information which will be used at runtime to access A's code.

In Windows, using an import library is sort of like using import spam; it gives you access to spam's names, but does not create a separate copy. On Unix, linking with a library is more like from spam import *; it does create a separate copy.

Py_NO_LINK_LIB

Turn off the implicit, #pragma-based linkage with the Python library, performed inside CPython header files.

在 3.14 版被加入.

5.3. Using DLLs in Practice

Windows Python is built in Microsoft Visual C++; using other compilers may or may not work. The rest of this section is MSVC++ specific.

When creating DLLs in Windows, you can use the CPython library in two ways:

By default, inclusion of PC/pyconfig.h directly or via Python.h triggers an implicit, configure-aware link with the library. The header file chooses pythonXY_d.lib for Debug, pythonXY.lib for Release, and pythonX.lib for Release with the Limited API enabled.

To build two DLLs, spam and ni (which uses C functions found in spam), you could use these commands:

cl /LD /I/python/include spam.c
cl /LD /I/python/include ni.c spam.lib

The first command created three files: spam.obj, spam.dll and spam.lib. Spam.dll does not contain any Python functions (such as PyArg_ParseTuple()), but it does know how to find the Python code thanks to the implicitly linked pythonXY.lib.

The second command created ni.dll (and .obj and .lib), which knows how to find the necessary functions from spam, and also from the Python executable.

Manually by defining Py_NO_LINK_LIB macro before including Python.h. You must pass pythonXY.lib to the linker.

To build two DLLs, spam and ni (which uses C functions found in spam), you could use these commands:

cl /LD /DPy_NO_LINK_LIB /I/python/include spam.c ../libs/pythonXY.lib
cl /LD /DPy_NO_LINK_LIB /I/python/include ni.c spam.lib ../libs/pythonXY.lib

The first command created three files: spam.obj, spam.dll and spam.lib. Spam.dll does not contain any Python functions (such as PyArg_ParseTuple()), but it does know how to find the Python code thanks to pythonXY.lib.

The second command created ni.dll (and .obj and .lib), which knows how to find the necessary functions from spam, and also from the Python executable.

Not every identifier is exported to the lookup table. If you want any other modules (including Python) to be able to see your identifiers, you have to say _declspec(dllexport), as in void _declspec(dllexport) initspam(void) or PyObject _declspec(dllexport) *NiGetSpamData(void).

Developer Studio will throw in a lot of import libraries that you do not really need, adding about 100K to your executable. To get rid of them, use the Project Settings dialog, Link tab, to specify ignore default libraries. Add the correct msvcrtxx.lib to the list of libraries.

1. 在其它 App 內嵌入 Python

前面的章節討論了如何擴充 Python，也就是如何透過附加一個 C 函式庫來擴充 Python 的功能。但也可以反過來做：將 Python 嵌入你的 C/C++ 應用程式中。嵌入讓你的應用程式能夠以 Python 而非 C 或 C++ 來實作應用程式的某些功能。這可以用於許多目的；其中一個例子是允許使用者透過撰寫一些 Python 腳本來根據他們的需求客製化應用程式。如果某些功能用 Python 寫起來比較容易，你也可以自己使用這種方法。

嵌入 Python 與擴充 Python 類似，但不完全相同。差別在於當你擴充 Python 時，應用程式的主程式仍然是 Python 直譯器，而當你嵌入 Python，主程式可能與 Python 無關 — 相反地，應用程式的某些部分偶爾會呼叫 Python 直譯器來執行一些 Python 程式碼。

所以如果你要嵌入 Python，你要提供自己的主程式。這個主程式必須做的事情之一是初始化 Python 直譯器，或至少必須要呼叫函式 Py_Initialize()。還有一些可選的呼叫來傳遞命令列引數給 Python。然後你就可以在應用程式的任何部分呼叫直譯器。

有幾種不同的方式來呼叫直譯器：你可以傳遞一個包含 Python 陳述式的字串給 PyRun_SimpleString()，或者你可以傳遞一個 stdio 檔案指標和檔案名稱（僅用於錯誤訊息中的識別）給 PyRun_SimpleFile()。你也可以呼叫前面章節中描述的較低層級操作來建構和使用 Python 物件。

也參考

Python/C API 參考手冊

Python 的 C 介面詳細資訊在此手冊中提供。大量必要的資訊可以在這裡找到。

1.1. 非常高階的嵌入

嵌入 Python 最簡單的形式是使用非常高階的介面。此介面用於執行 Python 腳本而無需直接與應用程式互動。例如這可以用來對檔案執行一些操作。

#define PY_SSIZE_T_CLEAN
#include <Python.h>

int
main(int argc, char *argv[])
{
    PyStatus status;
    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* 建議但非必要 */
    status = PyConfig_SetBytesString(&config, &config.program_name, argv[0]);
    if (PyStatus_Exception(status)) {
        goto exception;
    }

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);

    PyRun_SimpleString("from time import time,ctime\n"
                       "print('Today is', ctime(time()))\n");
    if (Py_FinalizeEx() < 0) {
        exit(120);
    }
    return 0;

  exception:
     PyConfig_Clear(&config);
     Py_ExitStatusException(status);
}

備註

#define PY_SSIZE_T_CLEAN 被用來指示某些 API 應該使用 Py_ssize_t 而不是 int。從 Python 3.13 開始不再需要它，但我們保留它以維持向後相容性。關於此巨集的描述請參閱 字串與緩衝區。

PyConfig.program_name 的設定應該在 Py_InitializeFromConfig() 前呼叫，以告知直譯器 Python run-time 函式庫的路徑。接下來，Python 直譯器會用 Py_Initialize() 初始化，然後執行一個硬編碼的 Python 腳本來印出日期和時間。之後，Py_FinalizeEx() 呼叫會關閉直譯器，接著程式結束。在真實的程式中，你可能想要從另一個來源取得 Python 腳本，或許是文字編輯器例程、檔案或資料庫。從檔案取得 Python 程式碼可以更好地使用 PyRun_SimpleFile() 函式來完成，這樣可以省去分配記憶體空間和載入檔案內容的麻煩。

1.2. 超越非常高階嵌入：概觀

高階介面讓你能夠從應用程式中執行任意的 Python 程式碼片段，但交換資料值的過程可以說相當繁瑣。如果你想進行這類操作，應該使用較低階的呼叫。雖然需要撰寫更多的 C 程式碼，但幾乎可以實現任何功能。

需要注意的是，雖然目的不同，但擴充 Python 與嵌入 Python 其實是非常相似的操作，前面章節討論的大多數主題在這裡同樣適用。為了說明這一點，請思考從 Python 到 C 的擴充程式碼實際上做了什麼：

將資料值從 Python 轉換為 C，

使用轉換後的值呼叫 C 例程，並

將呼叫中的資料值從 C 轉換為 Python。

當嵌入 Python 時，介面程式碼會：

將資料值從 C 轉換為 Python，

使用轉換後的值呼叫 Python 介面例程，並

將呼叫中的資料值從 Python 轉換為 C。

如你所見，資料轉換的步驟只是互換了順序，以配合跨語言傳遞方向的不同。唯一的差別在於兩個資料轉換之間所呼叫的例程：在擴充時你呼叫的是 C 例程；在嵌入時則呼叫 Python 例程。

本章不會討論如何將資料從 Python 轉換為 C 或從 C 轉換回 Python，且假設讀者已經知道參照的正確使用方式與錯誤處理。由於這些部分與擴充直譯器時相同，相關資訊可參考前面的章節。

1.3. 純嵌入

第一個程式的目標是執行 Python 腳本中的函式。就像在非常高階介面的章節中一樣，Python 直譯器不會直接與應用程式互動（但這在下一節會改變）。

執行 Python 腳本中定義函式的程式碼是：

#define PY_SSIZE_T_CLEAN
#include <Python.h>

int
main(int argc, char *argv[])
{
    PyObject *pName, *pModule, *pFunc;
    PyObject *pArgs, *pValue;
    int i;

    if (argc < 3) {
        fprintf(stderr,"Usage: call pythonfile funcname [args]\n");
        return 1;
    }

    Py_Initialize();
    pName = PyUnicode_DecodeFSDefault(argv[1]);
    /* Error checking of pName left out */

    pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    if (pModule != NULL) {
        pFunc = PyObject_GetAttrString(pModule, argv[2]);
        /* pFunc is a new reference */

        if (pFunc && PyCallable_Check(pFunc)) {
            pArgs = PyTuple_New(argc - 3);
            for (i = 0; i < argc - 3; ++i) {
                pValue = PyLong_FromLong(atoi(argv[i + 3]));
                if (!pValue) {
                    Py_DECREF(pArgs);
                    Py_DECREF(pModule);
                    fprintf(stderr, "Cannot convert argument\n");
                    return 1;
                }
                /* pValue reference stolen here: */
                PyTuple_SetItem(pArgs, i, pValue);
            }
            pValue = PyObject_CallObject(pFunc, pArgs);
            Py_DECREF(pArgs);
            if (pValue != NULL) {
                printf("Result of call: %ld\n", PyLong_AsLong(pValue));
                Py_DECREF(pValue);
            }
            else {
                Py_DECREF(pFunc);
                Py_DECREF(pModule);
                PyErr_Print();
                fprintf(stderr,"Call failed\n");
                return 1;
            }
        }
        else {
            if (PyErr_Occurred())
                PyErr_Print();
            fprintf(stderr, "Cannot find function \"%s\"\n", argv[2]);
        }
        Py_XDECREF(pFunc);
        Py_DECREF(pModule);
    }
    else {
        PyErr_Print();
        fprintf(stderr, "Failed to load \"%s\"\n", argv[1]);
        return 1;
    }
    if (Py_FinalizeEx() < 0) {
        return 120;
    }
    return 0;
}

此程式碼使用 argv[1] 載入 Python 腳本，並呼叫 argv[2] 中所指定的函式。其整數引數則來自 argv 陣列中的其他值。如果你編譯並連結此程式（我們稱完成的可執行檔為 call），並用它來執行 Python 腳本，例如：

def multiply(a,b):
    print("Will compute", a, "times", b)
    c = 0
    for i in range(0, a):
        c = c + b
    return c

那麼結果應該是：

$ call multiply multiply 3 2
Will compute 3 times 2
Result of call: 6

雖然以其功能而言這個程式相當龐大，但大部分的程式碼是用於 Python 與 C 之間的資料轉換以及錯誤回報。至於與嵌入 Python 有關的重點部分，則從以下開始：

Py_Initialize();
pName = PyUnicode_DecodeFSDefault(argv[1]);
/* Error checking of pName left out */
pModule = PyImport_Import(pName);

在初始化直譯器後，腳本使用 PyImport_Import() 載入。此例程需要一個 Python 字串作為其引數，該字串使用 PyUnicode_DecodeFSDefault() 資料轉換例程建構。

pFunc = PyObject_GetAttrString(pModule, argv[2]);
/* pFunc is a new reference */

if (pFunc && PyCallable_Check(pFunc)) {
    ...
}
Py_XDECREF(pFunc);

腳本載入後，會使用 PyObject_GetAttrString() 來取得所需的名稱。如果該名稱存在，且回傳的物件是可呼叫的，便可安全地假設它是一個函式。接著，程式會以一般方式建立引數的元組。之後便以下列方式呼叫該 Python 函式：

pValue = PyObject_CallObject(pFunc, pArgs);

函式回傳時，pValue 要不是 NULL 就是包含函式回傳值的參照。請務必在檢查值之後釋放參照。

1.4. 擴充嵌入式 Python

到目前為止，嵌入式 Python 直譯器尚無法存取應用程式本身的功能。Python API 允許透過擴充嵌入式直譯器來達成這點。也就是說，嵌入式直譯器可以由應用程式所提供的例程加以擴充。雖然聽起來複雜但其實並不難。只要暫時忘記是應用程式啟動了 Python 直譯器，改以將應用程式視為一組子程序，並撰寫一些膠合程式碼讓 Python 能夠存取這些例程，就像你撰寫一般 Python 擴充一樣。例如：

static int numargs=0;

/* Return the number of arguments of the application command line */
static PyObject*
emb_numargs(PyObject *self, PyObject *args)
{
    if(!PyArg_ParseTuple(args, ":numargs"))
        return NULL;
    return PyLong_FromLong(numargs);
}

static PyMethodDef emb_module_methods[] = {
    {"numargs", emb_numargs, METH_VARARGS,
     "Return the number of arguments received by the process."},
    {NULL, NULL, 0, NULL}
};

static struct PyModuleDef emb_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "emb",
    .m_size = 0,
    .m_methods = emb_module_methods,
};

static PyObject*
PyInit_emb(void)
{
    return PyModuleDef_Init(&emb_module);
}

在 main() 函式的正上方插入上述程式碼。同時，在呼叫 Py_Initialize() 之前插入以下兩個陳述式：

numargs = argc;
PyImport_AppendInittab("emb", &PyInit_emb);

這兩行初始化 numargs 變數，並讓 emb.numargs() 函式可供嵌入式 Python 直譯器使用。有了這些擴充後，Python 腳本便可以執行像是以下的操作

import emb
print("Number of arguments", emb.numargs())

在真實的應用程式中，這些方法會向 Python 公開應用程式的 API。

1.5. 在 C++ 中嵌入 Python

也可以將 Python 嵌入 C++ 程式中；具體如何做取決於所使用的 C++ 系統的細節；一般來說，你需要用 C++ 撰寫主程式，並使用 C++ 編譯器來編譯和連結你的程式。不需要使用 C++ 重新編譯 Python 本身。

1.6. 在類 Unix 系統下編譯和連結

要找到傳遞給編譯器（和連結器）的正確旗標以便將 Python 直譯器嵌入你的應用程式中，並不一定是簡單的事，特別是因為 Python 需要載入作為 C 動態擴充（.so 檔案）實作的函式庫模組，而這些模組又必須與 Python 進行連結。

要找出所需的編譯器和連結器旗標，你可以執行作為安裝過程的一部分產生的 pythonX.Y-config 腳本（也可能有 python3-config 腳本可用）。此腳本提供多種選項，其中以下幾個最為實用：

pythonX.Y-config --cflags 會給你編譯時建議的旗標：

$ /opt/bin/python3.11-config --cflags
-I/opt/include/python3.11 -I/opt/include/python3.11 -Wsign-compare  -DNDEBUG -g -fwrapv -O3 -Wall

pythonX.Y-config --ldflags --embed 會給你連結時建議的旗標：

$ /opt/bin/python3.11-config --ldflags --embed
-L/opt/lib/python3.11/config-3.11-x86_64-linux-gnu -L/opt/lib -lpython3.11 -lpthread -ldl  -lutil -lm

備註

為了避免多個 Python 安裝之間產生混淆（特別是系統自帶的 Python 與自行編譯的 Python 之間），建議使用 pythonX.Y-config 的絕對路徑，如上面的例子所示。

如果此程序對你不起作用（並不保證在所有類 Unix 平台上都能運作；不過我們歡迎錯誤回報），你將需要參閱系統的動態連結相關文件，並／或檢查 Python 的 Makefile（可使用 sysconfig.get_makefile_filename() 來找到其位置）和編譯選項。在這種情況下，sysconfig 模組是一個實用的工具，可用於以程式化方式擷取並組合所需的組態值。例如：

>>> import sysconfig
>>> sysconfig.get_config_var('LIBS')
'-lpthread -ldl  -lutil'
>>> sysconfig.get_config_var('LINKFORSHARED')
'-Xlinker -export-dynamic'

Python/C API 參考手冊

對於想要編寫擴充模組或是嵌入 Python 的 C 和 C++ 程式設計師們，這份手冊記錄了可使用的 API（應用程式介面）。在擴充和嵌入 Python 直譯器中也有相關的內容，它描述了編寫擴充的一般原則，但並沒有詳細說明 API 函式。

簡介

語言版本相容性

編寫標準

引入檔案 (include files)

有用的巨集

物件、型別和參照計數

例外

嵌入式Python

除錯建置

建議的第三方工具

C API 穩定性

不穩定的 C API

穩定的應用程式二進位介面

平台注意事項

受限 API 的內容

The Very High Level Layer

可用的起始符號

Stack Effects

參照計數

例外處理

Printing and clearing

引發例外

發出警告

Querying the error indicator

訊號處理

例外類別

例外物件

Unicode 例外物件

遞迴控制

例外和警告型別

Tracebacks

Defining extension modules

Multiple module instances

Initialization function

Multi-phase initialization

Legacy single-phase initialization

工具

作業系統工具

系統函式

行程控制

引入模組

資料 marshal 操作的支援

剖析引數與建置數值

字串轉換與格式化

Character classification and conversion

PyHash API

Reflection

編解碼器註冊表和支援函式

PyTime C API

對 Perf Map 的支援

抽象物件層 (Abstract Objects Layer)

物件協定

呼叫協定 (Call Protocol)

數字協定

序列協定

對映協定

疊代器協定

緩衝協定 (Buffer Protocol)

具體物件層

基礎物件

數值物件

序列物件

容器物件

函式物件

其他物件

擴充模組的 C API

初始化、終結化與執行緒

Python 初始化之前

Global configuration variables

Initializing and finalizing the interpreter

Process-wide parameters

Thread State and the Global Interpreter Lock

Sub-interpreter support

Asynchronous Notifications

Profiling and Tracing

Reference tracing

Advanced Debugger Support

Thread Local Storage Support

Synchronization Primitives

Operating System Thread APIs

Python 初始化設定

PyInitConfig C API

Configuration Options

Runtime Python configuration API

PyConfig C API

Py_GetArgcArgv()

Delaying main module execution

記憶體管理

總覽

Allocator Domains

Raw Memory Interface

記憶體介面

Object allocators

Default Memory Allocators

Customize Memory Allocators

Debug hooks on the Python memory allocators

The pymalloc allocator

The mimalloc allocator

tracemalloc C API

範例

物件實作支援

在 heap 上分配物件

物件生命週期

通用物件結構

型別物件結構

循環垃圾回收的支援

API 和 ABI 版本管理

Build-time version constants

Run-time version

Bit-packing macros

監控 C API

Generating Execution Events

Managing the Monitoring State

簡介

對於 Python 的應用程式開發介面使得 C 和 C++ 開發者能夠在各種層級存取 Python 直譯器。該 API 同樣可用於 C++，但為簡潔起見，通常將其稱為 Python/C API。使用 Python/C API 有兩個不同的原因，第一個是為特定目的來編寫擴充模組；這些是擴充 Python 直譯器的 C 模組，這可能是最常見的用法。第二個原因是在更大的應用程式中將 Python 作為零件使用；這種技術通常在應用程式中稱為 embedding（嵌入式）Python。

編寫擴充模組是一個相對容易理解的過程，其中「食譜 (cookbook)」方法很有效。有幾種工具可以在一定程度上自動化該過程，儘管人們從早期就將 Python 嵌入到其他應用程式中，但嵌入 Python 的過程並不像編寫擴充那樣簡單。

不論你是嵌入還是擴充 Python，許多 API 函式都是很有用的；此外，大多數嵌入 Python 的應用程式也需要提供自訂擴充模組，因此在嘗試將 Python 嵌入實際應用程式之前熟悉編寫擴充可能是個好主意。

語言版本相容性

Python 的 C API 與 C11 和 C++11 版本的 C 和 C++ 相容。

This is a lower limit: the C API does not require features from later C/C++ versions. You do not need to enable your compiler's "c11 mode".

編寫標準

如果你正在編寫要引入於 CPython 中的 C 程式碼，你必須遵循 PEP 7 [https://peps.python.org/pep-0007/] 中定義的指南和標準。無論你貢獻的 Python 版本如何，這些指南都適用。對於你自己的第三方擴充模組，則不必遵循這些約定，除非你希望最終將它們貢獻給 Python。

引入檔案 (include files)

使用 Python/C API 所需的所有函式、型別和巨集的定義都透過以下這幾行來在你的程式碼中引入：

#define PY_SSIZE_T_CLEAN
#include <Python.h>

這意味著會引入以下標準標頭：<stdio.h>、<string.h>、<errno.h>、<limits.h>、<assert.h> 和 <stdlib.h>（如果可用）。

備註

由於 Python 可能會定義一些會影響某些系統上標準標頭檔的預處理器 (pre-processor)，因此你必須在引入任何標準標頭檔之前引入 Python.h。

建議在引入 Python.h 之前都要定義 PY_SSIZE_T_CLEAN。有關此巨集的說明，請參閱剖析引數與建置數值。

所有定義於 Python.h 中且使用者可見的名稱（另外透過標準標頭檔引入的除外）都具有 Py 或 _Py 前綴。以 _Py 開頭的名稱供 Python 實作內部使用，擴充編寫者不應使用。結構成員名稱沒有保留前綴。

備註

使用者程式碼不應定義任何以 Py 或 _Py 開頭的名稱。這會讓讀者感到困惑，並危及使用者程式碼在未來 Python 版本上的可移植性，這些版本可能會定義以這些前綴之一開頭的其他名稱。

標頭檔通常隨 Python 一起安裝。在 Unix 上它們位於目錄 prefix/include/pythonversion/ 和 exec_prefix/include/pythonversion/，其中 prefix 和 exec_prefix 由 Python 的 configure 腳本的相應參數定義，version 是 '%d.%d' % sys.version_info[:2]。在 Windows 上，標頭安裝在 prefix/include 中，其中 prefix 是指定給安裝程式 (installer) 用的安裝目錄。

要引入標頭，請將兩個（如果不同）目錄放在編譯器的引入搜尋路徑 (search path) 中。不要將父目錄放在搜尋路徑上，然後使用 #include <pythonX.Y/Python.h>；這會在多平台建置上壞掉，因為 prefix 下獨立於平台的標頭包括來自 exec_prefix 的平台特定標頭。

C++ 使用者應注意，儘管 API 完全使用 C 來定義，但標頭檔適當地將入口點聲明為 extern "C"。因此，無需執行任何特殊操作即可使用 C++ 中的 API。

有用的巨集

Python 標頭檔中定義了幾個有用的巨集，大多被定義在它們有用的地方附近（例如 Py_RETURN_NONE、PyMODINIT_FUNC），其他是更通用的工具程式。以下並不一定是完整的列表。

Py_ABS(x)

回傳 x 的絕對值。

If the result cannot be represented (for example, if x has INT_MIN value for int type), the behavior is undefined.

在 3.3 版被加入.

Py_ALWAYS_INLINE

要求編譯器總是嵌入靜態行內函式 (static inline function)，編譯器可以忽略它並決定不嵌入該函式。

在禁用函式嵌入的除錯模式下建置 Python 時，它可用於嵌入有性能要求的靜態行內函式。例如，MSC 在除錯模式下建置時禁用函式嵌入。

盲目地使用 Py_ALWAYS_INLINE 標記靜態行內函式可能會導致更差的性能（例如程式碼大小增加）。在成本/收益分析方面，編譯器通常比開發人員更聰明。

如果 Python 是在除錯模式下建置（如果 Py_DEBUG 巨集有被定義），Py_ALWAYS_INLINE 巨集就什麼都不會做。

它必須在函式回傳型別之前被指定。用法：

static inline Py_ALWAYS_INLINE int random(void) { return 4; }

在 3.11 版被加入.

Py_CHARMASK(c)

引數必須是 [-128, 127] 或 [0, 255] 範圍內的字元或整數。這個巨集會將 c 轉換為 unsigned char 並回傳。

Py_DEPRECATED(version)

將其用於已棄用的聲明。巨集必須放在符號名稱之前。

範例：

Py_DEPRECATED(3.8) PyAPI_FUNC(int) Py_OldFunction(void);

在 3.8 版的變更: 新增了 MSVC 支援。

Py_GETENV(s)

類似於 getenv(s)，但如果在命令列上傳遞了 -E 則回傳 NULL （請見 PyConfig.use_environment）。

Py_LOCAL(type)

Declare a function returning the specified type using a fast-calling qualifier for functions that are local to the current file. Semantically, this is equivalent to static type.

Py_LOCAL_INLINE(type)

Equivalent to Py_LOCAL but additionally requests the function be inlined.

Py_LOCAL_SYMBOL

Macro used to declare a symbol as local to the shared library (hidden). On supported platforms, it ensures the symbol is not exported.

On compatible versions of GCC/Clang, it expands to __attribute__((visibility("hidden"))).

Py_MAX(x, y)

回傳 x 和 y 之間的最大值。

在 3.3 版被加入.

Py_MEMBER_SIZE(type, member)

以位元組為單位回傳結構 (type) member 的大小。

在 3.6 版被加入.

Py_MEMCPY(dest, src, n)

這是 memcpy() 的已軟性棄用別名。請直接使用 memcpy()。

在 3.14 版之後被棄用: 這個巨集已被軟性棄用。

Py_MIN(x, y)

回傳 x 和 y 之間的最小值。

在 3.3 版被加入.

Py_NO_INLINE

禁用函式的嵌入。例如，它減少了 C 堆疊的消耗：對大量嵌入程式碼的 LTO+PGO 建置很有用（請參閱 bpo-33720 [https://bugs.python.org/issue?@action=redirect&bpo=33720]）。

用法：

Py_NO_INLINE static int random(void) { return 4; }

在 3.11 版被加入.

Py_STRINGIFY(x)

將 x 轉換為 C 字串。例如 Py_STRINGIFY(123) 會回傳 "123"。

在 3.4 版被加入.

Py_UNREACHABLE()

當你的設計中有無法達到的程式碼路徑時，請使用此選項。例如在 case 語句已涵蓋了所有可能值的 switch 陳述式中的 default: 子句。在你可能想要呼叫 assert(0) 或 abort() 的地方使用它。

在發布模式 (release mode) 下，巨集幫助編譯器最佳化程式碼，並避免有關無法存取程式碼的警告。例如該巨集是在發布模式下於 GCC 使用 __builtin_unreachable() 來實作。

Py_UNREACHABLE() 的一個用途是，在對一個永不回傳但並未聲明為 _Py_NO_RETURN 的函式之呼叫後使用。

如果程式碼路徑是極不可能但在特殊情況下可以到達，則不得使用此巨集。例如在低記憶體條件下或系統呼叫回傳了超出預期範圍的值。在這種情況下，最好將錯誤回報給呼叫者。如果無法回報錯誤則可以使用 Py_FatalError()。

在 3.7 版被加入.

Py_UNUSED(arg)

將此用於函式定義中未使用的參數以消除編譯器警告。例如：int func(int a, int Py_UNUSED(b)) { return a; }。

在 3.4 版被加入.

Py_BUILD_ASSERT(cond)

Asserts a compile-time condition cond, as a statement. The build will fail if the condition is false or cannot be evaluated at compile time.

範例：

Py_BUILD_ASSERT(sizeof(PyTime_t) == sizeof(int64_t));

在 3.3 版被加入.

Py_BUILD_ASSERT_EXPR(cond)

Asserts a compile-time condition cond, as an expression that evaluates to 0. The build will fail if the condition is false or cannot be evaluated at compile time.

範例：

#define foo_to_char(foo) \
    ((char *)(foo) + Py_BUILD_ASSERT_EXPR(offsetof(struct foo, string) == 0))

在 3.3 版被加入.

PyDoc_STRVAR(name, str)

建立一個名為 name 的變數，可以在文件字串中使用。如果 Python 是在沒有文件字串的情況下建置，則該值將為空。

如 PEP 7 [https://peps.python.org/pep-0007/] 中所指明，使用 PyDoc_STRVAR 作為文件字串可以支援在沒有文件字串的情況下建置 Python。

範例：

PyDoc_STRVAR(pop_doc, "Remove and return the rightmost element.");

static PyMethodDef deque_methods[] = {
    // ...
    {"pop", (PyCFunction)deque_pop, METH_NOARGS, pop_doc},
    // ...
}

PyDoc_STR(str)

為給定的輸入字串建立一個文件字串，如果文件字串被禁用則建立空字串。

如 PEP 7 [https://peps.python.org/pep-0007/] 中所指明，使用 PyDoc_STR 指定文件字串以支援在沒有文件字串下建置 Python。

範例：

static PyMethodDef pysqlite_row_methods[] = {
    {"keys", (PyCFunction)pysqlite_row_keys, METH_NOARGS,
        PyDoc_STR("Returns the keys of the row.")},
    {NULL, NULL}
};

PyDoc_VAR(name)

Declares a static character array variable with the given name name.

範例：

PyDoc_VAR(python_doc) = PyDoc_STR("A genus of constricting snakes in the Pythonidae family native "
                                  "to the tropics and subtropics of the Eastern Hemisphere.");

Py_ARRAY_LENGTH(array)

Compute the length of a statically allocated C array at compile time.

The array argument must be a C array with a size known at compile time. Passing an array with an unknown size, such as a heap-allocated array, will result in a compilation error on some compilers, or otherwise produce incorrect results.

這大致上相當於：

sizeof(array) / sizeof((array)[0])

Py_EXPORTED_SYMBOL

Macro used to declare a symbol (function or data) as exported. On Windows, this expands to __declspec(dllexport). On compatible versions of GCC/Clang, it expands to __attribute__((visibility("default"))). This macro is for defining the C API itself; extension modules should not use it.

Py_IMPORTED_SYMBOL

Macro used to declare a symbol as imported. On Windows, this expands to __declspec(dllimport). This macro is for defining the C API itself; extension modules should not use it.

PyAPI_FUNC(type)

Macro used by CPython to declare a function as part of the C API. Its expansion depends on the platform and build configuration. This macro is intended for defining CPython's C API itself; extension modules should not use it for their own symbols.

PyAPI_DATA(type)

Macro used by CPython to declare a public global variable as part of the C API. Its expansion depends on the platform and build configuration. This macro is intended for defining CPython's C API itself; extension modules should not use it for their own symbols.

物件、型別和參照計數

大多數 Python/C API 函式都有一個或多個引數以及一個型別為 PyObject* 的回傳值，此型別是一個指標，指向一個表示任意 Python 物件的晦暗 (opaque) 資料型別。由於在大多數情況下，Python 語言以相同的方式處理所有 Python 物件型別（例如賦值、作用域規則和引數傳遞），因此它們應該由單個 C 型別來表示。幾乎所有的 Python 物件都存在於堆積 (heap) 中：你永遠不會聲明 PyObject 型別的自動變數或靜態變數，只能聲明 PyObject* 型別的指標變數。唯一的例外是型別物件；由於它們絕不能被釋放，因此它們通常是靜態 PyTypeObject 物件。

所有 Python 物件（甚至是 Python 整數）都有一個型別 (type) 和一個參照計數 (reference count)。一個物件的型別決定了它是什麼種類的物件（例如一個整數、一個 list 或一個使用者定義的函式；還有更多型別，請見標準型別階層）。對於每個眾所周知的型別，都有一個巨集來檢查物件是否屬於該型別；例如，若（且唯若）*a* 指向的物件是 Python list 時，PyList_Check(a) 為真。

參照計數

參照計數很重要，因為現今的電腦記憶體大小是有限的（而且通常是非常有限的）；它計算有多少個不同的地方用有了一個物件的強參照。這樣的地方可以是另一個物件，或者全域（或靜態）C 變數，或者某個 C 函式中的本地變數。當一個物件的最後一個強參照被釋放時（即其的參照計數變為零），該物件將被解除配置 (deallocated)。如果它包含對其他物件的參照，則它們的參照會被釋放。如果這樣的釋放使得再也沒有任何對於它們的參照，則可以依次為那些其他物件解除配置，依此類推。（此處相互參照物件的存在是個明顯的問題；目前，解決方案是「就不要那樣做」。）

參照計數總是被明確地操作。正常的方法是使用巨集 Py_INCREF() 來取得對於物件的參照（即參照計數加一），並使用巨集 Py_DECREF() 來釋放參照（即將參照計數減一）。Py_DECREF() 巨集比 incref 巨集複雜得多，因為它必須檢查參照計數是否變為零，然後呼叫物件的釋放器 (deallocator)。釋放器是包含在物件型別結構中的函式指標。特定型別的釋放器，在如果是一個複合物件型別（例如 list）時負責釋放物件中包含的其他物件的參照，並執行任何需要的額外完結步驟。參照計數不可能溢出；至少與虛擬記憶體中用來保存參照計數的不同記憶體位置數量一樣多的位元會被使用（假設 sizeof(Py_ssize_t) >= sizeof(void*)）。因此參照計數增加是一個簡單的操作。

沒有必要為每個包含物件指標的本地變數物件都持有一個強參照（即增加參照計數）。理論上，當變數指向它時，物件的參照計數會增加 1，而當變數離開作用域時就會減少 1。然而這兩者會相互抵消，所以最後參照計數沒有改變。使用參照計數的唯一真正原因是防止物件還有變數指向它時被解除配置。如果我們知道至少有一個物件的其他參照生存了至少與我們的變數一樣久，就不需要臨時增加建立新的強參照（即增加參照計數）。出現這種情況的一個重要情況是在從 Python 呼叫的擴充模組中作為引數傳遞給 C 函式的物件；呼叫機制保證在呼叫期間保持對每個參數的參照。

然而，一個常見的陷阱是從一個 list 中提取一個物件並保留它一段時間而不取得其參照。某些其他操作可能會從列表中刪除該物件，減少其參照計數並可能取消分配它。真正的危險是看似無害的操作可能會叫用可以執行此操作的任意 Python 程式碼；有一個程式碼路徑允許控制權從 Py_DECREF() 回歸使用者，因此幾乎任何操作都有潛在危險。

一種安全的方法是都使用通用 (generics) 操作（名稱以 PyObject_、PyNumber_、PySequence_ 或 PyMapping_ 開頭的函式）。這些操作總是建立新的對於它們回傳物件的強參照（即增加其參照計數）。這讓呼叫者有責任在處理完結果後呼叫 Py_DECREF()；這就成為第二本質。

參照計數詳細資訊

Python/C API 中函式的參照計數行為最好用參照的所有權來解釋。所有權附屬於參照而非物件（物件並非被擁有，它們總是共享的）。「擁有參照」意味著當不再需要該參照時，負責在其上呼叫 Py_DECREF。所有權也可以轉移，這意味著接收參照所有權的程式碼最終會負責在不需要參照時透過呼叫 Py_DECREF() 或 Py_XDECREF() 釋放參照 --- 或者將這個責任再傳遞出去（通常是給它的呼叫者）。當一個函式將參照的所有權傳遞給它的呼叫者時，呼叫者被稱為接收到一個新參照。當沒有所有權轉移時，呼叫者被稱為借用參照。如果是借用參照就不需要做任何事情。

相反地，當呼叫的函式傳入物件的參照時，有兩種可能性：函式有竊取 (steal) 物件的參照，或者沒有。 竊取參照意味著當你將參照傳遞給函式時，該函式假定它現在擁有該參照，並且你不再對它負責。

很少有函式會竊取參照；兩個值得注意的例外是 PyList_SetItem() 和 PyTuple_SetItem()，它們竊取了對項目的參照（但不是對項目所在的 tuple 或 list 的參照！）。因為有著使用新建立的物件來增加 (populate) tuple 或 list 的習慣，這些函式旨在竊取參照；例如，建立 tuple (1, 2, "three") 的程式碼可以如下所示（先暫時忘記錯誤處理；更好的編寫方式如下所示）：

PyObject *t;

t = PyTuple_New(3);
PyTuple_SetItem(t, 0, PyLong_FromLong(1L));
PyTuple_SetItem(t, 1, PyLong_FromLong(2L));
PyTuple_SetItem(t, 2, PyUnicode_FromString("three"));

這裡 PyLong_FromLong() 會回傳一個新的參照，它立即被 PyTuple_SetItem() 竊取。如果你想繼續使用一個物件，儘管對它的參照將被竊取，請在呼叫參照竊取函式之前使用 Py_INCREF() 來取得另一個參照。

附帶地說，PyTuple_SetItem() 是設定 tuple 項目的唯一方法； PySequence_SetItem() 和 PyObject_SetItem() 拒絕這樣做，因為 tuple 是一種不可變 (immutable) 的資料型別。你應該只對你自己建立的 tuple 使用 PyTuple_SetItem()。

可以使用 PyList_New() 和 PyList_SetItem() 編寫用於填充列表的等效程式碼。

但是在實際操作中你很少會使用這些方法來建立和增加 tuple 和 list。有一個通用函式 Py_BuildValue() 可以從 C 值建立最常見的物件，由 format string 引導。例如上面的兩個程式碼可以用以下程式碼替換（它還負責了錯誤檢查）：

PyObject *tuple, *list;

tuple = Py_BuildValue("(iis)", 1, 2, "three");
list = Py_BuildValue("[iis]", 1, 2, "three");

更常見的是以那些借用參照的項目來使用 PyObject_SetItem() 及其系列函式，比如傳遞給你正在編寫的函式的引數。在那種情況下，他們關於參照的行為會比較穩健，因為你不取得新的一個參照就可以放棄參照（「讓它被竊取」）。例如，此函式將 list（實際上是任何可變序列）的所有項目設定於給定項目：

int
set_all(PyObject *target, PyObject *item)
{
    Py_ssize_t i, n;

    n = PyObject_Length(target);
    if (n < 0)
        return -1;
    for (i = 0; i < n; i++) {
        PyObject *index = PyLong_FromSsize_t(i);
        if (!index)
            return -1;
        if (PyObject_SetItem(target, index, item) < 0) {
            Py_DECREF(index);
            return -1;
        }
        Py_DECREF(index);
    }
    return 0;
}

函式回傳值的情況略有不同。雖然傳遞對大多數函式的參照不會改變你對該參照的所有權責任，但許多回傳物件參照的函式會給你該參照的所有權。原因很簡單：在很多情況下，回傳的物件是即時建立的，你獲得的參照是對該物件的唯一參照。因此回傳物件參照的通用函式，如 PyObject_GetItem() 和 PySequence_GetItem()，總是回傳一個新的參照（呼叫者成為參照的所有者）。

重要的是要意識到你是否擁有一個函式回傳的參照只取決於你呼叫哪個函式 --- 羽毛 (plumage)（作為引數傳遞給函式的物件之型別）不會進入它！因此，如果你使用 PyList_GetItem() 從 list 中提取一個項目，你不會擁有其參照 --- 但如果你使用 PySequence_GetItem() 從同一 list 中取得相同的項目（且恰好使用完全相同的引數），你確實會擁有對回傳物件的參照。

以下是一個範例，說明如何編寫函式來計算一個整數 list 中項目的總和；一次使用 PyList_GetItem()，一次使用 PySequence_GetItem()：

long
sum_list(PyObject *list)
{
    Py_ssize_t i, n;
    long total = 0, value;
    PyObject *item;

    n = PyList_Size(list);
    if (n < 0)
        return -1; /* 不是 list */
    for (i = 0; i < n; i++) {
        item = PyList_GetItem(list, i); /* 不會失敗 */
        if (!PyLong_Check(item)) continue; /* 跳過非整數 */
        value = PyLong_AsLong(item);
        if (value == -1 && PyErr_Occurred())
            /* 整數太大，無法放入 C long，退出 */
            return -1;
        total += value;
    }
    return total;
}

long
sum_sequence(PyObject *sequence)
{
    Py_ssize_t i, n;
    long total = 0, value;
    PyObject *item;
    n = PySequence_Length(sequence);
    if (n < 0)
        return -1; /* 沒有長度 */
    for (i = 0; i < n; i++) {
        item = PySequence_GetItem(sequence, i);
        if (item == NULL)
            return -1; /* 不是序列或其他錯誤 */
        if (PyLong_Check(item)) {
            value = PyLong_AsLong(item);
            Py_DECREF(item);
            if (value == -1 && PyErr_Occurred())
                /* 整數太大，無法放入 C long，退出 */
                return -1;
            total += value;
        }
        else {
            Py_DECREF(item); /* 丟棄參照所有權 */
        }
    }
    return total;
}

型別

有少數幾個其他的資料型別在 Python/C API 中發揮重要作用；大多數是簡單的 C 型別，例如 int、long、double 和 char*。一些結構型別被用於描述用於列出模組所匯出的函式或新物件型別的資料屬性的靜態表，其他則用於描述複數的值。這些將與使用它們的函式一起討論。

type Py_ssize_t

為 穩定 ABI 的一部分.

一個帶符號的整數型別，使得 sizeof(Py_ssize_t) == sizeof(size_t)。 C99 沒有直接定義這樣的東西（size_t 是無符號整數型別）。有關詳細資訊，請參閱 PEP 353 [https://peps.python.org/pep-0353/]。 PY_SSIZE_T_MAX 是 Py_ssize_t 型別的最大正值。

例外

如果需要特定的錯誤處理，Python 開發者就只需要處理例外；未處理的例外會自動傳遞給呼叫者，然後傳遞給呼叫者的呼叫者，依此類推，直到它們到達頂層直譯器，在那裡它們透過堆疊回溯 (stack trace) 回報給使用者。

然而，對於 C 開發者來說，錯誤檢查總是必須是顯式的。除非在函式的文件中另有明確聲明，否則 Python/C API 中的所有函式都可以引發例外。通常當一個函式遇到錯誤時，它會設定一個例外，丟棄它擁有的任何物件參照，並回傳一個錯誤指示器。如果沒有另外文件記錄，這個指示器要麼是 NULL 不然就是 -1，取決於函式的回傳型別。有些函式會回傳布林值 true/false 結果，false 表示錯誤。很少有函式不回傳明確的錯誤指示器或者有不明確的回傳值，而需要使用 PyErr_Occurred() 明確測試錯誤。這些例外都會被明確地記錄於文件。

例外的狀態會在個別執行緒的儲存空間 (per-thread storage) 中維護（這相當於在非執行緒應用程式中使用全域儲存空間）。執行緒可以處於兩種狀態之一：發生例外或未發生例外。函式 PyErr_Occurred() 可用於檢查這一點：當例外發生時，它回傳對例外型別物件的借用參照，否則回傳 NULL。設定例外狀態的函式有很多：PyErr_SetString() 是最常見的（儘管不是最通用的）設定例外狀態的函式，而 PyErr_Clear() 是用來清除例外狀態。

完整的例外狀態由三個（都可以為 NULL 的）物件組成：例外型別、對應的例外值和回溯。這些與 sys.exc_info() 的 Python 結果具有相同的含義；但是它們並不相同：Python 物件表示由 Python try ... except 陳述式處理的最後一個例外，而 C 層級的例外狀態僅在例外在 C 函式間傳遞時存在，直到它到達 Python 位元組碼直譯器的主迴圈，該迴圈負責將它傳遞給 sys.exc_info() 和其系列函式。

請注意，從 Python 1.5 開始，從 Python 程式碼存取例外狀態的首選且支援執行緒安全的方法是呼叫 sys.exc_info() 函式，它回傳 Python 程式碼的個別執行緒例外狀態。此外，兩種存取例外狀態方法的語義都發生了變化，因此捕獲例外的函式將保存和恢復其執行緒的例外狀態，從而保留其呼叫者的例外狀態。這可以防止例外處理程式碼中的常見錯誤，這些錯誤是由看似無辜的函式覆蓋了正在處理的例外而引起的；它還替回溯中被堆疊框 (stack frame) 參照的物件減少了通常不需要的生命週期延長。

作為一般原則，呼叫另一個函式來執行某些任務的函式應該檢查被呼叫函式是否引發了例外，如果是，則將例外狀態傳遞給它的呼叫者。它應該丟棄它擁有的任何物件參照，並回傳一個錯誤指示符，但它不應該設定另一個例外 --- 這將覆蓋剛剛引發的例外，並丟失關於錯誤確切原因的重要資訊。

上面的 sum_sequence() 範例展示了一個檢測例外並將其繼續傳遞的例子。碰巧這個例子在檢測到錯誤時不需要清理任何擁有的參照。以下範例函式展示了一些錯誤清理。首先，為了提醒你為什麼喜歡 Python，我們展示了等效的 Python 程式碼：

def incr_item(dict, key):
    try:
        item = dict[key]
    except KeyError:
        item = 0
    dict[key] = item + 1

這是相應的 C 程式碼：

int
incr_item(PyObject *dict, PyObject *key)
{
    /* Objects all initialized to NULL for Py_XDECREF */
    PyObject *item = NULL, *const_one = NULL, *incremented_item = NULL;
    int rv = -1; /* Return value initialized to -1 (failure) */

    item = PyObject_GetItem(dict, key);
    if (item == NULL) {
        /* Handle KeyError only: */
        if (!PyErr_ExceptionMatches(PyExc_KeyError))
            goto error;

        /* Clear the error and use zero: */
        PyErr_Clear();
        item = PyLong_FromLong(0L);
        if (item == NULL)
            goto error;
    }
    const_one = PyLong_FromLong(1L);
    if (const_one == NULL)
        goto error;

    incremented_item = PyNumber_Add(item, const_one);
    if (incremented_item == NULL)
        goto error;

    if (PyObject_SetItem(dict, key, incremented_item) < 0)
        goto error;
    rv = 0; /* Success */
    /* Continue with cleanup code */

 error:
    /* Cleanup code, shared by success and failure path */

    /* Use Py_XDECREF() to ignore NULL references */
    Py_XDECREF(item);
    Py_XDECREF(const_one);
    Py_XDECREF(incremented_item);

    return rv; /* -1 for error, 0 for success */
}

這個例子代表了在 C 語言中對使用 goto 陳述句的認同！它闡述了以 PyErr_ExceptionMatches() 和 PyErr_Clear() 來處理特定的例外，以及以 Py_XDECREF() 來配置其所擁有且可能為 NULL 的參照（注意名稱中的 'X'；Py_DECREF() 在遇到 NULL 參照時會崩潰）。重要的是，用於保存擁有的參照的變數被初始化為 NULL 以使其能夠順利作用；同樣地，回傳值被初始化為 -1（失敗），並且僅在最後一次呼叫成功後才設定為成功。

嵌入式Python

只有 Python 直譯器的嵌入者（而不是擴充編寫者）需要擔心的一項重要任務是 Python 直譯器的初始化與完成階段。直譯器的大部分功能只能在直譯器初始化後使用。

基本的初始化函式是 Py_Initialize()。這會初始化帶有載入模組的表，並建立基礎模組 builtins、__main__ 和 sys。它還會初始化模組搜索路徑 (sys.path)。

Py_Initialize() 不設定「腳本引數列表 (script argument list)」 (sys.argv)。如果稍後將要執行的 Python 程式碼需要此變數，則必須設定 PyConfig.argv 和 PyConfig.parse_argv，請見 Python 初始化配置。

在大多數系統上（特別是在 Unix 和 Windows 上，儘管細節略有不同），Py_Initialize() 會假設Python 函式庫相對於 Python 直譯器可執行檔案的位置固定，並根據其對標準 Python 直譯器可執行檔案位置的最佳猜測來計算模組搜尋路徑。或者更詳細地說，它會在 shell 命令搜尋路徑（環境變數 PATH）中找到名為 python 的可執行檔案，並在其父目錄中查找一個名為 lib/pythonX.Y 的目錄的相對位置。

例如，如果在 /usr/local/bin/python 中找到 Python 可執行檔案，它將假定函式庫位於 /usr/local/lib/pythonX.Y 中。（事實上這個特定的路徑也是「後備 (fallback)」位置，當在 PATH 中找不到名為 python 的可執行檔案時使用。）使用者可以透過設定環境變數來覆蓋此行為 PYTHONHOME，或者透過設定 PYTHONPATH 在標準路徑前面插入額外的目錄。

嵌入的應用程式可以透過在呼叫 Py_InitializeFromConfig() 之前設定 PyConfig.program_name 來引導搜尋。請注意 PYTHONHOME 仍然覆蓋它並且 PYTHONPATH 仍然插入在標準路徑的前面。需要完全控制權的應用程式必須實作自己的 Py_GetPath()、Py_GetPrefix()、Py_GetExecPrefix() 和 Py_GetProgramFullPath()（全部定義在 Modules/getpath.c)。

有時會希望能夠「取消初始化 (uninitialize)」Python。例如，應用程式可能想要重新開始（再次呼叫 Py_Initialize()）或者應用程式簡單地完成了對 Python 的使用並想要釋放 Python 分配的記憶體。這可以透過呼叫 Py_FinalizeEx() 來完成。如果 Python 目前處於初始化狀態，函式 Py_IsInitialized() 會回傳 true。有關這些功能的更多資訊將在後面的章節中給出。請注意 Py_FinalizeEx() 不會釋放由 Python 直譯器分配的所有記憶體，例如目前無法釋放被擴充模組所分配的記憶體。

除錯建置

Python 可以在建置時使用多個巨集來啟用對直譯器和擴充模組的額外檢查，這些檢查往往會在執行環境 (runtime) 增加大量開銷 (overhead)，因此預設情況下不啟用它們。

Python 原始碼發佈版本中的 Misc/SpecialBuilds.txt 檔案有一份包含多種除錯構置的完整列表，為支援追蹤參照計數、為記憶體分配器除錯或對主直譯器迴圈進行低階分析的建置。本節的其餘部分將僅描述最常用的建置。

Py_DEBUG

使用定義的 Py_DEBUG 巨集編譯直譯器會生成 Python 的除錯建置。 Py_DEBUG 在 Unix 建置中要透過在 ./configure 命令中加入 --with-pydebug 來啟用。非 Python 限定的 _DEBUG 巨集的存在也暗示了這一點。當 Py_DEBUG 在 Unix 建置中啟用時，編譯器最佳化會被禁用。

除了下面描述的參照計數除錯之外，還會執行額外的檢查，請參閱 Python 除錯建置。

定義 Py_TRACE_REFS 來啟用參照追蹤（參見設定 --with-trace-refs 選項）。當有定義時，透過向每個 PyObject 新增兩個額外欄位來維護有效物件的循環雙向鍊表 (circular doubly linked list)。全體分配也有被追蹤。退出時將印出所有現行參照。（在交互模式下，這發生在直譯器運行的每個陳述句之後。）

有關更多詳細資訊，請參閱 Python 原始碼發布版中的 Misc/SpecialBuilds.txt。

建議的第三方工具

以下第三方工具提供了更簡單且更細緻的方法來為 Python 建立 C、C++ 和 Rust 擴充模組：

Cython [https://cython.org/]

cffi [https://cffi.readthedocs.io]

HPy [https://hpyproject.org/]

nanobind [https://github.com/wjakob/nanobind] (C++)

Numba [https://numba.pydata.org/]

pybind11 [https://pybind11.readthedocs.io/] (C++)

PyO3 [https://pyo3.rs/] (Rust)

SWIG [https://www.swig.org]

Using tools such as these can help avoid writing code that is tightly bound to a particular version of CPython, avoid reference counting errors, and focus more on your own code than on using the CPython API. In general, new versions of Python can be supported by updating the tool, and your code will often use newer and more efficient APIs automatically. Some tools also support compiling for other implementations of Python from a single set of sources.

These projects are not supported by the same people who maintain Python, and issues need to be raised with the projects directly. Remember to check that the project is still maintained and supported, as the list above may become outdated.

也參考

Python Packaging User Guide: Binary Extensions [https://packaging.python.org/guides/packaging-binary-extensions/]

The Python Packaging User Guide not only covers several available tools that simplify the creation of binary extensions, but also discusses the various reasons why creating an extension module may be desirable in the first place.

C API 穩定性

除非有另外記錄於文件，Python 的 C API 被包含在向後相容性策略 PEP 387 [https://peps.python.org/pep-0387/] 中。大多數改動都是相容於原始碼的（通常只會增加新的 API）。更改現有 API 或刪除 API 僅在棄用期後或修復嚴重問題時進行。

CPython 的應用程式二進位介面 (Application Binary Interface, ABI) 在次要版本中是向前和向後相容的（如果它們以相同的方式編譯；請參閱下面的平台注意事項）。因此，為 Python 3.10.0 編譯的程式碼將能夠在 3.10.8 上運行，反之亦然，但 3.9.x 和 3.11.x 就需要分別編譯。

C API 有兩層級，有不同的穩定性期望：

不穩定 API，可能會在次要版本中發生變化，而沒有棄用階段。會在名稱中以 PyUnstable 前綴來標記。

受限 API，在多個次要版本之間相容。當有定義 Py_LIMITED_API 時，只有這個子集會從 Python.h 公開。

下面將更詳細地討論這些內容。

帶有底線前綴的名稱是私有 API (private API)，像是 _Py_InternalState，即使在補丁版本 (patch release) 中也可能被更改，不會另行通知。如果你需要使用這個 API，可以聯繫 CPython 開發者 [https://discuss.python.org/c/core-dev/c-api/30] 並針對你的使用方法來討論是否新增公開的 API。

不穩定的 C API

任何以 PyUnstable 前綴命名的 API 都會公開 CPython 實作細節，並可能在每個次要版本中進行更改（例如從 3.9 到 3.10），而不會出現任何棄用警告。但是它不會在錯誤修復發布版本中發生變化（例如從 3.10.0 到 3.10.1）。

它通常用於專門的低階工具，例如偵錯器。

使用此 API 的專案應該要遵循 CPython 開發細節，並花費額外的力氣來針對這些變動來做調整。

穩定的應用程式二進位介面

為簡單起見，本文件討論擴充 (extension)，但受限 API 和穩定 ABI 在所有 API 使用方式中都以相同的方式運作 -- 例如在嵌入式 Python (embedding Python) 中。

受限 C API

Python 3.2 引入了受限 API (Limited API)，它是 Python C API 的一個子集。僅使用受限 API 的擴充可以只編譯一次就被載入於多個版本的 Python。受限 API 的內容列在下方。

Py_LIMITED_API

在包含 Python.h 之前定義此巨集以選擇只使用受限 API，並挑選受限 API 版本。

將 Py_LIMITED_API 定義為對應於你的擴充有支援的最低 Python 版本的 PY_VERSION_HEX 值。該擴充與從指定版本開始的所有 Python 3 版本之 ABI 相容，並且可以使用過去版本有引入的受限 API。

與其直接使用 PY_VERSION_HEX 巨集，不如寫死 (hardcode) 最小次要版本（例如代表 Python 3.10 的 0x030A0000），以便在使用未來的 Python 版本進行編譯時仍保持穩定性。

你還可以將 Py_LIMITED_API 定義為 3，這與 0x03020000（Python 3.2，引入了受限 API 的版本）相同。

穩定 ABI

為了實現它，Python 提供了一個穩定 ABI (Stable ABI)：一組將在各個 Python 3.x 版本之間保持 ABI 相容的符號。

備註

穩定 ABI 可以防止 ABI 問題，例如由於結構布局或函式簽名變化導致缺少符號或數據損壞的鏈接器 (linker) 錯誤。然而，Python 的其他變化可能會改變 行為 的擴充。有關詳細資訊，請參閱 Python 的向後相容性政策 (PEP 387 [https://peps.python.org/pep-0387/])。

穩定 ABI 被包含在受限 API 中開放的符號，但也包含其他符號 - 例如，支援舊版受限 API 所必需的函式。

在 Windows 上，使用穩定 ABI 的擴充應該連接到 python3.dll 而不是特定版本的函式庫，例如 python39.dll。

在某些平台上，Python 將查找並加載以 abi3 標籤命名的共享函式庫檔案（例如 mymodule.abi3.so）。它不檢查此類擴充是否符合穩定的 ABI。確保的責任在使用者（或者打包工具）身上，例如使用 3.10+ 受限 API 建置的擴充不會為較低版本的 Python 所安裝。

穩定 ABI 中的所有函式都作為函式存在於 Python 的共享函式庫中，而不僅是作為巨集。這使得它們可被用於不使用 C 預處理器 (preprocessor) 的語言。

受限 API 範圍和性能

受限 API 的目標是允許使用完整的 C API 進行所有可能的操作，但可能會降低性能。

例如，雖然 PyList_GetItem() 可用，但它的「不安全」巨集變體 PyList_GET_ITEM() 為不可用。巨集運行可以更快，因為它可以依賴 list 物件的特定版本實作細節。

如果沒有定義 Py_LIMITED_API，一些 C API 函式將被嵌入或被替換為巨集。定義 Py_LIMITED_API 會禁用嵌入，從而隨著 Python 資料結構的改進而提高穩定性，但可能會降低性能。

透過省略 Py_LIMITED_API 定義，可以使用特定版本的 ABI 編譯受限 API 擴充。這可以提高該 Python 版本的性能，但會限制相容性。使用 Py_LIMITED_API 編譯將產生一個擴充，可以在特定版本的擴充不可用的地方發布 — 例如，用於即將發布的 Python 版本的預發布版本 (prerelease)。

受限 API 注意事項

請注意，使用 Py_LIMITED_API 進行編譯不完全保證程式碼符合受限 API 或穩定 ABI。Py_LIMITED_API 僅涵蓋定義，但 API 還包括其他議題，例如預期的語義 (semantic)。

Py_LIMITED_API 無法防範的一個問題是使用在較低 Python 版本中無效的引數來呼叫函式。例如一個開始接受 NULL 作為引數的函式。在 Python 3.9 中，NULL 現在代表選擇預設行為，但在 Python 3.8 中，引數將被直接使用，導致 NULL 取消參照 (dereference) 且崩潰 (crash)。類似的引數適用於結構 (struct) 的欄位。

另一個問題是，當有定義 Py_LIMITED_API 時，一些結構欄位目前不會被隱藏，即使它們是受限 API 的一部分。

出於這些原因，我們建議要以它支援的所有次要 Python 版本來測試擴充，並且最好使用最低版本進行建置。

我們也建議要查看所有使用過的 API 的文件，檢查它是否明確屬於受限 API。即使有定義 Py_LIMITED_API，一些私有聲明也會因為技術原因（或者甚至是無意地，例如臭蟲）而被公開出來。

另請注意，受限 API 不一定是穩定的：在 Python 3.8 中使用 Py_LIMITED_API 進行編譯意味著擴充將能以 Python 3.12 運行，但不一定能以 Python 3.12 編譯。特別是如果穩定 ABI 保持穩定，部分受限 API 可能會被棄用和刪除。

平台注意事項

ABI 穩定性不僅取決於 Python，還取決於使用的編譯器、低階函式庫和編譯器選項。出於穩定 ABI 的目的，這些細節定義了一個「平台」。它們通常取決於作業系統種類和處理器架構

每個特定的 Python 發布者都有責任確保特定平台上的所有 Python 版本都以不破壞穩定 ABI 的方式建置。python.org 和許多第三方發布者發布的 Windows 和 macOS 版本就是這種情況。

受限 API 的內容

目前，受限 API 包括以下項目：

METH_CLASS

METH_COEXIST

METH_FASTCALL

METH_METHOD

METH_NOARGS

METH_O

METH_STATIC

METH_VARARGS

PY_VECTORCALL_ARGUMENTS_OFFSET

PyAIter_Check()

PyArg_Parse()

PyArg_ParseTuple()

PyArg_ParseTupleAndKeywords()

PyArg_UnpackTuple()

PyArg_VaParse()

PyArg_VaParseTupleAndKeywords()

PyArg_ValidateKeywordArguments()

PyBUF_ANY_CONTIGUOUS

PyBUF_CONTIG

PyBUF_CONTIG_RO

PyBUF_C_CONTIGUOUS

PyBUF_FORMAT

PyBUF_FULL

PyBUF_FULL_RO

PyBUF_F_CONTIGUOUS

PyBUF_INDIRECT

PyBUF_MAX_NDIM

PyBUF_ND

PyBUF_READ

PyBUF_RECORDS

PyBUF_RECORDS_RO

PyBUF_SIMPLE

PyBUF_STRIDED

PyBUF_STRIDED_RO

PyBUF_STRIDES

PyBUF_WRITABLE

PyBUF_WRITE

PyBaseObject_Type

PyBool_FromLong()

PyBool_Type

PyBuffer_FillContiguousStrides()

PyBuffer_FillInfo()

PyBuffer_FromContiguous()

PyBuffer_GetPointer()

PyBuffer_IsContiguous()

PyBuffer_Release()

PyBuffer_SizeFromFormat()

PyBuffer_ToContiguous()

PyByteArrayIter_Type

PyByteArray_AsString()

PyByteArray_Concat()

PyByteArray_FromObject()

PyByteArray_FromStringAndSize()

PyByteArray_Resize()

PyByteArray_Size()

PyByteArray_Type

PyBytesIter_Type

PyBytes_AsString()

PyBytes_AsStringAndSize()

PyBytes_Concat()

PyBytes_ConcatAndDel()

PyBytes_DecodeEscape()

PyBytes_FromFormat()

PyBytes_FromFormatV()

PyBytes_FromObject()

PyBytes_FromString()

PyBytes_FromStringAndSize()

PyBytes_Repr()

PyBytes_Size()

PyBytes_Type

PyCFunction

PyCFunctionFast

PyCFunctionFastWithKeywords

PyCFunctionWithKeywords

PyCFunction_GetFlags()

PyCFunction_GetFunction()

PyCFunction_GetSelf()

PyCFunction_New()

PyCFunction_NewEx()

PyCFunction_Type

PyCMethod_New()

PyCallIter_New()

PyCallIter_Type

PyCallable_Check()

PyCapsule_Destructor

PyCapsule_GetContext()

PyCapsule_GetDestructor()

PyCapsule_GetName()

PyCapsule_GetPointer()

PyCapsule_Import()

PyCapsule_IsValid()

PyCapsule_New()

PyCapsule_SetContext()

PyCapsule_SetDestructor()

PyCapsule_SetName()

PyCapsule_SetPointer()

PyCapsule_Type

PyClassMethodDescr_Type

PyCodec_BackslashReplaceErrors()

PyCodec_Decode()

PyCodec_Decoder()

PyCodec_Encode()

PyCodec_Encoder()

PyCodec_IgnoreErrors()

PyCodec_IncrementalDecoder()

PyCodec_IncrementalEncoder()

PyCodec_KnownEncoding()

PyCodec_LookupError()

PyCodec_NameReplaceErrors()

PyCodec_Register()

PyCodec_RegisterError()

PyCodec_ReplaceErrors()

PyCodec_StreamReader()

PyCodec_StreamWriter()

PyCodec_StrictErrors()

PyCodec_Unregister()

PyCodec_XMLCharRefReplaceErrors()

PyComplex_FromDoubles()

PyComplex_ImagAsDouble()

PyComplex_RealAsDouble()

PyComplex_Type

PyDescr_NewClassMethod()

PyDescr_NewGetSet()

PyDescr_NewMember()

PyDescr_NewMethod()

PyDictItems_Type

PyDictIterItem_Type

PyDictIterKey_Type

PyDictIterValue_Type

PyDictKeys_Type

PyDictProxy_New()

PyDictProxy_Type

PyDictRevIterItem_Type

PyDictRevIterKey_Type

PyDictRevIterValue_Type

PyDictValues_Type

PyDict_Clear()

PyDict_Contains()

PyDict_Copy()

PyDict_DelItem()

PyDict_DelItemString()

PyDict_GetItem()

PyDict_GetItemRef()

PyDict_GetItemString()

PyDict_GetItemStringRef()

PyDict_GetItemWithError()

PyDict_Items()

PyDict_Keys()

PyDict_Merge()

PyDict_MergeFromSeq2()

PyDict_New()

PyDict_Next()

PyDict_SetItem()

PyDict_SetItemString()

PyDict_Size()

PyDict_Type

PyDict_Update()

PyDict_Values()

PyEllipsis_Type

PyEnum_Type

PyErr_BadArgument()

PyErr_BadInternalCall()

PyErr_CheckSignals()

PyErr_Clear()

PyErr_Display()

PyErr_DisplayException()

PyErr_ExceptionMatches()

PyErr_Fetch()

PyErr_Format()

PyErr_FormatV()

PyErr_GetExcInfo()

PyErr_GetHandledException()

PyErr_GetRaisedException()

PyErr_GivenExceptionMatches()

PyErr_NewException()

PyErr_NewExceptionWithDoc()

PyErr_NoMemory()

PyErr_NormalizeException()

PyErr_Occurred()

PyErr_Print()

PyErr_PrintEx()

PyErr_ProgramText()

PyErr_ResourceWarning()

PyErr_Restore()

PyErr_SetExcFromWindowsErr()

PyErr_SetExcFromWindowsErrWithFilename()

PyErr_SetExcFromWindowsErrWithFilenameObject()

PyErr_SetExcFromWindowsErrWithFilenameObjects()

PyErr_SetExcInfo()

PyErr_SetFromErrno()

PyErr_SetFromErrnoWithFilename()

PyErr_SetFromErrnoWithFilenameObject()

PyErr_SetFromErrnoWithFilenameObjects()

PyErr_SetFromWindowsErr()

PyErr_SetFromWindowsErrWithFilename()

PyErr_SetHandledException()

PyErr_SetImportError()

PyErr_SetImportErrorSubclass()

PyErr_SetInterrupt()

PyErr_SetInterruptEx()

PyErr_SetNone()

PyErr_SetObject()

PyErr_SetRaisedException()

PyErr_SetString()

PyErr_SyntaxLocation()

PyErr_SyntaxLocationEx()

PyErr_WarnEx()

PyErr_WarnExplicit()

PyErr_WarnFormat()

PyErr_WriteUnraisable()

PyEval_AcquireThread()

PyEval_EvalCode()

PyEval_EvalCodeEx()

PyEval_EvalFrame()

PyEval_EvalFrameEx()

PyEval_GetBuiltins()

PyEval_GetFrame()

PyEval_GetFrameBuiltins()

PyEval_GetFrameGlobals()

PyEval_GetFrameLocals()

PyEval_GetFuncDesc()

PyEval_GetFuncName()

PyEval_GetGlobals()

PyEval_GetLocals()

PyEval_InitThreads()

PyEval_ReleaseThread()

PyEval_RestoreThread()

PyEval_SaveThread()

PyExc_ArithmeticError

PyExc_AssertionError

PyExc_AttributeError

PyExc_BaseException

PyExc_BaseExceptionGroup

PyExc_BlockingIOError

PyExc_BrokenPipeError

PyExc_BufferError

PyExc_BytesWarning

PyExc_ChildProcessError

PyExc_ConnectionAbortedError

PyExc_ConnectionError

PyExc_ConnectionRefusedError

PyExc_ConnectionResetError

PyExc_DeprecationWarning

PyExc_EOFError

PyExc_EncodingWarning

PyExc_EnvironmentError

PyExc_Exception

PyExc_FileExistsError

PyExc_FileNotFoundError

PyExc_FloatingPointError

PyExc_FutureWarning

PyExc_GeneratorExit

PyExc_IOError

PyExc_ImportError

PyExc_ImportWarning

PyExc_IndentationError

PyExc_IndexError

PyExc_InterruptedError

PyExc_IsADirectoryError

PyExc_KeyError

PyExc_KeyboardInterrupt

PyExc_LookupError

PyExc_MemoryError

PyExc_ModuleNotFoundError

PyExc_NameError

PyExc_NotADirectoryError

PyExc_NotImplementedError

PyExc_OSError

PyExc_OverflowError

PyExc_PendingDeprecationWarning

PyExc_PermissionError

PyExc_ProcessLookupError

PyExc_RecursionError

PyExc_ReferenceError

PyExc_ResourceWarning

PyExc_RuntimeError

PyExc_RuntimeWarning

PyExc_StopAsyncIteration

PyExc_StopIteration

PyExc_SyntaxError

PyExc_SyntaxWarning

PyExc_SystemError

PyExc_SystemExit

PyExc_TabError

PyExc_TimeoutError

PyExc_TypeError

PyExc_UnboundLocalError

PyExc_UnicodeDecodeError

PyExc_UnicodeEncodeError

PyExc_UnicodeError

PyExc_UnicodeTranslateError

PyExc_UnicodeWarning

PyExc_UserWarning

PyExc_ValueError

PyExc_Warning

PyExc_WindowsError

PyExc_ZeroDivisionError

PyExceptionClass_Name()

PyException_GetArgs()

PyException_GetCause()

PyException_GetContext()

PyException_GetTraceback()

PyException_SetArgs()

PyException_SetCause()

PyException_SetContext()

PyException_SetTraceback()

PyFile_FromFd()

PyFile_GetLine()

PyFile_WriteObject()

PyFile_WriteString()

PyFilter_Type

PyFloat_AsDouble()

PyFloat_FromDouble()

PyFloat_FromString()

PyFloat_GetInfo()

PyFloat_GetMax()

PyFloat_GetMin()

PyFloat_Type

PyFrameObject

PyFrame_GetCode()

PyFrame_GetLineNumber()

PyFrozenSet_New()

PyFrozenSet_Type

PyGC_Collect()

PyGC_Disable()

PyGC_Enable()

PyGC_IsEnabled()

PyGILState_Ensure()

PyGILState_GetThisThreadState()

PyGILState_Release()

PyGILState_STATE

PyGetSetDef

PyGetSetDescr_Type

PyImport_AddModule()

PyImport_AddModuleObject()

PyImport_AddModuleRef()

PyImport_AppendInittab()

PyImport_ExecCodeModule()

PyImport_ExecCodeModuleEx()

PyImport_ExecCodeModuleObject()

PyImport_ExecCodeModuleWithPathnames()

PyImport_GetImporter()

PyImport_GetMagicNumber()

PyImport_GetMagicTag()

PyImport_GetModule()

PyImport_GetModuleDict()

PyImport_Import()

PyImport_ImportFrozenModule()

PyImport_ImportFrozenModuleObject()

PyImport_ImportModule()

PyImport_ImportModuleLevel()

PyImport_ImportModuleLevelObject()

PyImport_ImportModuleNoBlock()

PyImport_ReloadModule()

PyIndex_Check()

PyInterpreterState

PyInterpreterState_Clear()

PyInterpreterState_Delete()

PyInterpreterState_Get()

PyInterpreterState_GetDict()

PyInterpreterState_GetID()

PyInterpreterState_New()

PyIter_Check()

PyIter_Next()

PyIter_NextItem()

PyIter_Send()

PyListIter_Type

PyListRevIter_Type

PyList_Append()

PyList_AsTuple()

PyList_GetItem()

PyList_GetItemRef()

PyList_GetSlice()

PyList_Insert()

PyList_New()

PyList_Reverse()

PyList_SetItem()

PyList_SetSlice()

PyList_Size()

PyList_Sort()

PyList_Type

PyLongObject

PyLongRangeIter_Type

PyLong_AsDouble()

PyLong_AsInt()

PyLong_AsInt32()

PyLong_AsInt64()

PyLong_AsLong()

PyLong_AsLongAndOverflow()

PyLong_AsLongLong()

PyLong_AsLongLongAndOverflow()

PyLong_AsNativeBytes()

PyLong_AsSize_t()

PyLong_AsSsize_t()

PyLong_AsUInt32()

PyLong_AsUInt64()

PyLong_AsUnsignedLong()

PyLong_AsUnsignedLongLong()

PyLong_AsUnsignedLongLongMask()

PyLong_AsUnsignedLongMask()

PyLong_AsVoidPtr()

PyLong_FromDouble()

PyLong_FromInt32()

PyLong_FromInt64()

PyLong_FromLong()

PyLong_FromLongLong()

PyLong_FromNativeBytes()

PyLong_FromSize_t()

PyLong_FromSsize_t()

PyLong_FromString()

PyLong_FromUInt32()

PyLong_FromUInt64()

PyLong_FromUnsignedLong()

PyLong_FromUnsignedLongLong()

PyLong_FromUnsignedNativeBytes()

PyLong_FromVoidPtr()

PyLong_GetInfo()

PyLong_Type

PyMap_Type

PyMapping_Check()

PyMapping_GetItemString()

PyMapping_GetOptionalItem()

PyMapping_GetOptionalItemString()

PyMapping_HasKey()

PyMapping_HasKeyString()

PyMapping_HasKeyStringWithError()

PyMapping_HasKeyWithError()

PyMapping_Items()

PyMapping_Keys()

PyMapping_Length()

PyMapping_SetItemString()

PyMapping_Size()

PyMapping_Values()

PyMem_Calloc()

PyMem_Free()

PyMem_Malloc()

PyMem_RawCalloc()

PyMem_RawFree()

PyMem_RawMalloc()

PyMem_RawRealloc()

PyMem_Realloc()

PyMemberDef

PyMemberDescr_Type

PyMember_GetOne()

PyMember_SetOne()

PyMemoryView_FromBuffer()

PyMemoryView_FromMemory()

PyMemoryView_FromObject()

PyMemoryView_GetContiguous()

PyMemoryView_Type

PyMethodDef

PyMethodDescr_Type

PyModuleDef

PyModuleDef_Base

PyModuleDef_Init()

PyModuleDef_Slot

PyModuleDef_Type

PyModule_Add()

PyModule_AddFunctions()

PyModule_AddIntConstant()

PyModule_AddObject()

PyModule_AddObjectRef()

PyModule_AddStringConstant()

PyModule_AddType()

PyModule_Create2()

PyModule_ExecDef()

PyModule_FromDefAndSpec2()

PyModule_GetDef()

PyModule_GetDict()

PyModule_GetFilename()

PyModule_GetFilenameObject()

PyModule_GetName()

PyModule_GetNameObject()

PyModule_GetState()

PyModule_New()

PyModule_NewObject()

PyModule_SetDocString()

PyModule_Type

PyNumber_Absolute()

PyNumber_Add()

PyNumber_And()

PyNumber_AsSsize_t()

PyNumber_Check()

PyNumber_Divmod()

PyNumber_Float()

PyNumber_FloorDivide()

PyNumber_InPlaceAdd()

PyNumber_InPlaceAnd()

PyNumber_InPlaceFloorDivide()

PyNumber_InPlaceLshift()

PyNumber_InPlaceMatrixMultiply()

PyNumber_InPlaceMultiply()

PyNumber_InPlaceOr()

PyNumber_InPlacePower()

PyNumber_InPlaceRemainder()

PyNumber_InPlaceRshift()

PyNumber_InPlaceSubtract()

PyNumber_InPlaceTrueDivide()

PyNumber_InPlaceXor()

PyNumber_Index()

PyNumber_Invert()

PyNumber_Long()

PyNumber_Lshift()

PyNumber_MatrixMultiply()

PyNumber_Multiply()

PyNumber_Negative()

PyNumber_Or()

PyNumber_Positive()

PyNumber_Power()

PyNumber_Remainder()

PyNumber_Rshift()

PyNumber_Subtract()

PyNumber_ToBase()

PyNumber_TrueDivide()

PyNumber_Xor()

PyOS_AfterFork()

PyOS_AfterFork_Child()

PyOS_AfterFork_Parent()

PyOS_BeforeFork()

PyOS_CheckStack()

PyOS_FSPath()

PyOS_InputHook

PyOS_InterruptOccurred()

PyOS_double_to_string()

PyOS_getsig()

PyOS_mystricmp()

PyOS_mystrnicmp()

PyOS_setsig()

PyOS_sighandler_t

PyOS_snprintf()

PyOS_string_to_double()

PyOS_strtol()

PyOS_strtoul()

PyOS_vsnprintf()

PyObject

PyObject.ob_refcnt

PyObject.ob_type

PyObject_ASCII()

PyObject_AsFileDescriptor()

PyObject_Bytes()

PyObject_Call()

PyObject_CallFunction()

PyObject_CallFunctionObjArgs()

PyObject_CallMethod()

PyObject_CallMethodObjArgs()

PyObject_CallNoArgs()

PyObject_CallObject()

PyObject_Calloc()

PyObject_CheckBuffer()

PyObject_ClearWeakRefs()

PyObject_CopyData()

PyObject_DelAttr()

PyObject_DelAttrString()

PyObject_DelItem()

PyObject_DelItemString()

PyObject_Dir()

PyObject_Format()

PyObject_Free()

PyObject_GC_Del()

PyObject_GC_IsFinalized()

PyObject_GC_IsTracked()

PyObject_GC_Track()

PyObject_GC_UnTrack()

PyObject_GenericGetAttr()

PyObject_GenericGetDict()

PyObject_GenericSetAttr()

PyObject_GenericSetDict()

PyObject_GetAIter()

PyObject_GetAttr()

PyObject_GetAttrString()

PyObject_GetBuffer()

PyObject_GetItem()

PyObject_GetIter()

PyObject_GetOptionalAttr()

PyObject_GetOptionalAttrString()

PyObject_GetTypeData()

PyObject_HasAttr()

PyObject_HasAttrString()

PyObject_HasAttrStringWithError()

PyObject_HasAttrWithError()

PyObject_Hash()

PyObject_HashNotImplemented()

PyObject_Init()

PyObject_InitVar()

PyObject_IsInstance()

PyObject_IsSubclass()

PyObject_IsTrue()

PyObject_Length()

PyObject_Malloc()

PyObject_Not()

PyObject_Realloc()

PyObject_Repr()

PyObject_RichCompare()

PyObject_RichCompareBool()

PyObject_SelfIter()

PyObject_SetAttr()

PyObject_SetAttrString()

PyObject_SetItem()

PyObject_Size()

PyObject_Str()

PyObject_Type()

PyObject_Vectorcall()

PyObject_VectorcallMethod()

PyProperty_Type

PyRangeIter_Type

PyRange_Type

PyReversed_Type

PySeqIter_New()

PySeqIter_Type

PySequence_Check()

PySequence_Concat()

PySequence_Contains()

PySequence_Count()

PySequence_DelItem()

PySequence_DelSlice()

PySequence_Fast()

PySequence_GetItem()

PySequence_GetSlice()

PySequence_In()

PySequence_InPlaceConcat()

PySequence_InPlaceRepeat()

PySequence_Index()

PySequence_Length()

PySequence_List()

PySequence_Repeat()

PySequence_SetItem()

PySequence_SetSlice()

PySequence_Size()

PySequence_Tuple()

PySetIter_Type

PySet_Add()

PySet_Clear()

PySet_Contains()

PySet_Discard()

PySet_New()

PySet_Pop()

PySet_Size()

PySet_Type

PySlice_AdjustIndices()

PySlice_GetIndices()

PySlice_GetIndicesEx()

PySlice_New()

PySlice_Type

PySlice_Unpack()

PyState_AddModule()

PyState_FindModule()

PyState_RemoveModule()

PyStructSequence_Desc

PyStructSequence_Field

PyStructSequence_GetItem()

PyStructSequence_New()

PyStructSequence_NewType()

PyStructSequence_SetItem()

PyStructSequence_UnnamedField

PySuper_Type

PySys_Audit()

PySys_AuditTuple()

PySys_FormatStderr()

PySys_FormatStdout()

PySys_GetObject()

PySys_GetXOptions()

PySys_ResetWarnOptions()

PySys_SetArgv()

PySys_SetArgvEx()

PySys_SetObject()

PySys_WriteStderr()

PySys_WriteStdout()

PyThreadState

PyThreadState_Clear()

PyThreadState_Delete()

PyThreadState_Get()

PyThreadState_GetDict()

PyThreadState_GetFrame()

PyThreadState_GetID()

PyThreadState_GetInterpreter()

PyThreadState_New()

PyThreadState_SetAsyncExc()

PyThreadState_Swap()

PyThread_GetInfo()

PyThread_ReInitTLS()

PyThread_acquire_lock()

PyThread_acquire_lock_timed()

PyThread_allocate_lock()

PyThread_create_key()

PyThread_delete_key()

PyThread_delete_key_value()

PyThread_exit_thread()

PyThread_free_lock()

PyThread_get_key_value()

PyThread_get_stacksize()

PyThread_get_thread_ident()

PyThread_get_thread_native_id()

PyThread_init_thread()

PyThread_release_lock()

PyThread_set_key_value()

PyThread_set_stacksize()

PyThread_start_new_thread()

PyThread_tss_alloc()

PyThread_tss_create()

PyThread_tss_delete()

PyThread_tss_free()

PyThread_tss_get()

PyThread_tss_is_created()

PyThread_tss_set()

PyTraceBack_Here()

PyTraceBack_Print()

PyTraceBack_Type

PyTupleIter_Type

PyTuple_GetItem()

PyTuple_GetSlice()

PyTuple_New()

PyTuple_Pack()

PyTuple_SetItem()

PyTuple_Size()

PyTuple_Type

PyTypeObject

PyType_ClearCache()

PyType_Freeze()

PyType_FromMetaclass()

PyType_FromModuleAndSpec()

PyType_FromSpec()

PyType_FromSpecWithBases()

PyType_GenericAlloc()

PyType_GenericNew()

PyType_GetBaseByToken()

PyType_GetFlags()

PyType_GetFullyQualifiedName()

PyType_GetModule()

PyType_GetModuleByDef()

PyType_GetModuleName()

PyType_GetModuleState()

PyType_GetName()

PyType_GetQualName()

PyType_GetSlot()

PyType_GetTypeDataSize()

PyType_IsSubtype()

PyType_Modified()

PyType_Ready()

PyType_Slot

PyType_Spec

PyType_Type

PyUnicodeDecodeError_Create()

PyUnicodeDecodeError_GetEncoding()

PyUnicodeDecodeError_GetEnd()

PyUnicodeDecodeError_GetObject()

PyUnicodeDecodeError_GetReason()

PyUnicodeDecodeError_GetStart()

PyUnicodeDecodeError_SetEnd()

PyUnicodeDecodeError_SetReason()

PyUnicodeDecodeError_SetStart()

PyUnicodeEncodeError_GetEncoding()

PyUnicodeEncodeError_GetEnd()

PyUnicodeEncodeError_GetObject()

PyUnicodeEncodeError_GetReason()

PyUnicodeEncodeError_GetStart()

PyUnicodeEncodeError_SetEnd()

PyUnicodeEncodeError_SetReason()

PyUnicodeEncodeError_SetStart()

PyUnicodeIter_Type

PyUnicodeTranslateError_GetEnd()

PyUnicodeTranslateError_GetObject()

PyUnicodeTranslateError_GetReason()

PyUnicodeTranslateError_GetStart()

PyUnicodeTranslateError_SetEnd()

PyUnicodeTranslateError_SetReason()

PyUnicodeTranslateError_SetStart()

PyUnicode_Append()

PyUnicode_AppendAndDel()

PyUnicode_AsASCIIString()

PyUnicode_AsCharmapString()

PyUnicode_AsDecodedObject()

PyUnicode_AsDecodedUnicode()

PyUnicode_AsEncodedObject()

PyUnicode_AsEncodedString()

PyUnicode_AsEncodedUnicode()

PyUnicode_AsLatin1String()

PyUnicode_AsMBCSString()

PyUnicode_AsRawUnicodeEscapeString()

PyUnicode_AsUCS4()

PyUnicode_AsUCS4Copy()

PyUnicode_AsUTF16String()

PyUnicode_AsUTF32String()

PyUnicode_AsUTF8AndSize()

PyUnicode_AsUTF8String()

PyUnicode_AsUnicodeEscapeString()

PyUnicode_AsWideChar()

PyUnicode_AsWideCharString()

PyUnicode_BuildEncodingMap()

PyUnicode_Compare()

PyUnicode_CompareWithASCIIString()

PyUnicode_Concat()

PyUnicode_Contains()

PyUnicode_Count()

PyUnicode_Decode()

PyUnicode_DecodeASCII()

PyUnicode_DecodeCharmap()

PyUnicode_DecodeCodePageStateful()

PyUnicode_DecodeFSDefault()

PyUnicode_DecodeFSDefaultAndSize()

PyUnicode_DecodeLatin1()

PyUnicode_DecodeLocale()

PyUnicode_DecodeLocaleAndSize()

PyUnicode_DecodeMBCS()

PyUnicode_DecodeMBCSStateful()

PyUnicode_DecodeRawUnicodeEscape()

PyUnicode_DecodeUTF16()

PyUnicode_DecodeUTF16Stateful()

PyUnicode_DecodeUTF32()

PyUnicode_DecodeUTF32Stateful()

PyUnicode_DecodeUTF7()

PyUnicode_DecodeUTF7Stateful()

PyUnicode_DecodeUTF8()

PyUnicode_DecodeUTF8Stateful()

PyUnicode_DecodeUnicodeEscape()

PyUnicode_EncodeCodePage()

PyUnicode_EncodeFSDefault()

PyUnicode_EncodeLocale()

PyUnicode_Equal()

PyUnicode_EqualToUTF8()

PyUnicode_EqualToUTF8AndSize()

PyUnicode_FSConverter()

PyUnicode_FSDecoder()

PyUnicode_Find()

PyUnicode_FindChar()

PyUnicode_Format()

PyUnicode_FromEncodedObject()

PyUnicode_FromFormat()

PyUnicode_FromFormatV()

PyUnicode_FromObject()

PyUnicode_FromOrdinal()

PyUnicode_FromString()

PyUnicode_FromStringAndSize()

PyUnicode_FromWideChar()

PyUnicode_GetDefaultEncoding()

PyUnicode_GetLength()

PyUnicode_InternFromString()

PyUnicode_InternInPlace()

PyUnicode_IsIdentifier()

PyUnicode_Join()

PyUnicode_Partition()

PyUnicode_RPartition()

PyUnicode_RSplit()

PyUnicode_ReadChar()

PyUnicode_Replace()

PyUnicode_Resize()

PyUnicode_RichCompare()

PyUnicode_Split()

PyUnicode_Splitlines()

PyUnicode_Substring()

PyUnicode_Tailmatch()

PyUnicode_Translate()

PyUnicode_Type

PyUnicode_WriteChar()

PyVarObject

PyVarObject.ob_base

PyVarObject.ob_size

PyVectorcall_Call()

PyVectorcall_NARGS()

PyWeakReference

PyWeakref_GetObject()

PyWeakref_GetRef()

PyWeakref_NewProxy()

PyWeakref_NewRef()

PyWrapperDescr_Type

PyWrapper_New()

PyZip_Type

Py_ASNATIVEBYTES_ALLOW_INDEX

Py_ASNATIVEBYTES_BIG_ENDIAN

Py_ASNATIVEBYTES_DEFAULTS

Py_ASNATIVEBYTES_LITTLE_ENDIAN

Py_ASNATIVEBYTES_NATIVE_ENDIAN

Py_ASNATIVEBYTES_REJECT_NEGATIVE

Py_ASNATIVEBYTES_UNSIGNED_BUFFER

Py_AUDIT_READ

Py_AddPendingCall()

Py_AtExit()

Py_BEGIN_ALLOW_THREADS

Py_BLOCK_THREADS

Py_BuildValue()

Py_BytesMain()

Py_CompileString()

Py_DecRef()

Py_DecodeLocale()

Py_END_ALLOW_THREADS

Py_EncodeLocale()

Py_EndInterpreter()

Py_EnterRecursiveCall()

Py_Exit()

Py_FatalError()

Py_FileSystemDefaultEncodeErrors

Py_FileSystemDefaultEncoding

Py_Finalize()

Py_FinalizeEx()

Py_GenericAlias()

Py_GenericAliasType

Py_GetBuildInfo()

Py_GetCompiler()

Py_GetConstant()

Py_GetConstantBorrowed()

Py_GetCopyright()

Py_GetExecPrefix()

Py_GetPath()

Py_GetPlatform()

Py_GetPrefix()

Py_GetProgramFullPath()

Py_GetProgramName()

Py_GetPythonHome()

Py_GetRecursionLimit()

Py_GetVersion()

Py_HasFileSystemDefaultEncoding

Py_IncRef()

Py_Initialize()

Py_InitializeEx()

Py_Is()

Py_IsFalse()

Py_IsFinalizing()

Py_IsInitialized()

Py_IsNone()

Py_IsTrue()

Py_LeaveRecursiveCall()

Py_Main()

Py_MakePendingCalls()

Py_NewInterpreter()

Py_NewRef()

Py_PACK_FULL_VERSION()

Py_PACK_VERSION()

Py_READONLY

Py_REFCNT()

Py_RELATIVE_OFFSET

Py_ReprEnter()

Py_ReprLeave()

Py_SetProgramName()

Py_SetPythonHome()

Py_SetRecursionLimit()

Py_TPFLAGS_BASETYPE

Py_TPFLAGS_DEFAULT

Py_TPFLAGS_HAVE_GC

Py_TPFLAGS_HAVE_VECTORCALL

Py_TPFLAGS_ITEMS_AT_END

Py_TPFLAGS_METHOD_DESCRIPTOR

Py_TP_USE_SPEC

Py_TYPE()

Py_T_BOOL

Py_T_BYTE

Py_T_CHAR

Py_T_DOUBLE

Py_T_FLOAT

Py_T_INT

Py_T_LONG

Py_T_LONGLONG

Py_T_OBJECT_EX

Py_T_PYSSIZET

Py_T_SHORT

Py_T_STRING

Py_T_STRING_INPLACE

Py_T_UBYTE

Py_T_UINT

Py_T_ULONG

Py_T_ULONGLONG

Py_T_USHORT

Py_UCS4

Py_UNBLOCK_THREADS

Py_UTF8Mode

Py_VaBuildValue()

Py_Version

Py_XNewRef()

Py_am_aiter

Py_am_anext

Py_am_await

Py_am_send

Py_bf_getbuffer

Py_bf_releasebuffer

Py_buffer

Py_intptr_t

Py_mod_create

Py_mod_exec

Py_mod_gil

Py_mod_multiple_interpreters

Py_mp_ass_subscript

Py_mp_length

Py_mp_subscript

Py_nb_absolute

Py_nb_add

Py_nb_and

Py_nb_bool

Py_nb_divmod

Py_nb_float

Py_nb_floor_divide

Py_nb_index

Py_nb_inplace_add

Py_nb_inplace_and

Py_nb_inplace_floor_divide

Py_nb_inplace_lshift

Py_nb_inplace_matrix_multiply

Py_nb_inplace_multiply

Py_nb_inplace_or

Py_nb_inplace_power

Py_nb_inplace_remainder

Py_nb_inplace_rshift

Py_nb_inplace_subtract

Py_nb_inplace_true_divide

Py_nb_inplace_xor

Py_nb_int

Py_nb_invert

Py_nb_lshift

Py_nb_matrix_multiply

Py_nb_multiply

Py_nb_negative

Py_nb_or

Py_nb_positive

Py_nb_power

Py_nb_remainder

Py_nb_rshift

Py_nb_subtract

Py_nb_true_divide

Py_nb_xor

Py_sq_ass_item

Py_sq_concat

Py_sq_contains

Py_sq_inplace_concat

Py_sq_inplace_repeat

Py_sq_item

Py_sq_length

Py_sq_repeat

Py_ssize_t

Py_tp_alloc

Py_tp_base

Py_tp_bases

Py_tp_call

Py_tp_clear

Py_tp_dealloc

Py_tp_del

Py_tp_descr_get

Py_tp_descr_set

Py_tp_doc

Py_tp_finalize

Py_tp_free

Py_tp_getattr

Py_tp_getattro

Py_tp_getset

Py_tp_hash

Py_tp_init

Py_tp_is_gc

Py_tp_iter

Py_tp_iternext

Py_tp_members

Py_tp_methods

Py_tp_new

Py_tp_repr

Py_tp_richcompare

Py_tp_setattr

Py_tp_setattro

Py_tp_str

Py_tp_token

Py_tp_traverse

Py_tp_vectorcall

Py_uintptr_t

allocfunc

binaryfunc

descrgetfunc

descrsetfunc

destructor

getattrfunc

getattrofunc

getbufferproc

getiterfunc

getter

hashfunc

initproc

inquiry

iternextfunc

lenfunc

newfunc

objobjargproc

objobjproc

releasebufferproc

reprfunc

richcmpfunc

setattrfunc

setattrofunc

setter

ssizeargfunc

ssizeobjargproc

ssizessizeargfunc

ssizessizeobjargproc

symtable

ternaryfunc

traverseproc

unaryfunc

vectorcallfunc

visitproc

The Very High Level Layer

The functions in this chapter will let you execute Python source code given in a file or a buffer, but they will not let you interact in a more detailed way with the interpreter.

Several of these functions accept a start symbol from the grammar as a parameter. The available start symbols are Py_eval_input, Py_file_input, Py_single_input, and Py_func_type_input. These are described following the functions which accept them as parameters.

Note also that several of these functions take FILE* parameters. One particular issue which needs to be handled carefully is that the FILE structure for different C libraries can be different and incompatible. Under Windows (at least), it is possible for dynamically linked extensions to actually use different libraries, so care should be taken that FILE* parameters are only passed to these functions if it is certain that they were created by the same library that the Python runtime is using.

int PyRun_AnyFile(FILE *fp, const char *filename)

This is a simplified interface to PyRun_AnyFileExFlags() below, leaving closeit set to 0 and flags set to NULL.

int PyRun_AnyFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

This is a simplified interface to PyRun_AnyFileExFlags() below, leaving the closeit argument set to 0.

int PyRun_AnyFileEx(FILE *fp, const char *filename, int closeit)

This is a simplified interface to PyRun_AnyFileExFlags() below, leaving the flags argument set to NULL.

int PyRun_AnyFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)

If fp refers to a file associated with an interactive device (console or terminal input or Unix pseudo-terminal), return the value of PyRun_InteractiveLoop(), otherwise return the result of PyRun_SimpleFile(). filename is decoded from the filesystem encoding (sys.getfilesystemencoding()). If filename is NULL, this function uses "???" as the filename. If closeit is true, the file is closed before PyRun_SimpleFileExFlags() returns.

int PyRun_SimpleString(const char *command)

This is a simplified interface to PyRun_SimpleStringFlags() below, leaving the PyCompilerFlags* argument set to NULL.

int PyRun_SimpleStringFlags(const char *command, PyCompilerFlags *flags)

Executes the Python source code from command in the __main__ module according to the flags argument. If __main__ does not already exist, it is created. Returns 0 on success or -1 if an exception was raised. If there was an error, there is no way to get the exception information. For the meaning of flags, see below.

Note that if an otherwise unhandled SystemExit is raised, this function will not return -1, but exit the process, as long as PyConfig.inspect is zero.

int PyRun_SimpleFile(FILE *fp, const char *filename)

This is a simplified interface to PyRun_SimpleFileExFlags() below, leaving closeit set to 0 and flags set to NULL.

int PyRun_SimpleFileEx(FILE *fp, const char *filename, int closeit)

This is a simplified interface to PyRun_SimpleFileExFlags() below, leaving flags set to NULL.

int PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)

Similar to PyRun_SimpleStringFlags(), but the Python source code is read from fp instead of an in-memory string. filename should be the name of the file, it is decoded from filesystem encoding and error handler. If closeit is true, the file is closed before PyRun_SimpleFileExFlags() returns.

備註

On Windows, fp should be opened as binary mode (e.g. fopen(filename, "rb")). Otherwise, Python may not handle script file with LF line ending correctly.

int PyRun_InteractiveOneObject(FILE *fp, PyObject *filename, PyCompilerFlags *flags)

Read and execute a single statement from a file associated with an interactive device according to the flags argument. The user will be prompted using sys.ps1 and sys.ps2. filename must be a Python str object.

Returns 0 when the input was executed successfully, -1 if there was an exception, or an error code from the errcode.h include file distributed as part of Python if there was a parse error. (Note that errcode.h is not included by Python.h, so must be included specifically if needed.)

int PyRun_InteractiveOne(FILE *fp, const char *filename)

This is a simplified interface to PyRun_InteractiveOneFlags() below, leaving flags set to NULL.

int PyRun_InteractiveOneFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

Similar to PyRun_InteractiveOneObject(), but filename is a const char*, which is decoded from the filesystem encoding and error handler.

int PyRun_InteractiveLoop(FILE *fp, const char *filename)

This is a simplified interface to PyRun_InteractiveLoopFlags() below, leaving flags set to NULL.

int PyRun_InteractiveLoopFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

Read and execute statements from a file associated with an interactive device until EOF is reached. The user will be prompted using sys.ps1 and sys.ps2. filename is decoded from the filesystem encoding and error handler. Returns 0 at EOF or a negative number upon failure.

int (*PyOS_InputHook)(void)

為 穩定 ABI 的一部分.

Can be set to point to a function with the prototype int func(void). The function will be called when Python's interpreter prompt is about to become idle and wait for user input from the terminal. The return value is ignored. Overriding this hook can be used to integrate the interpreter's prompt with other event loops, as done in Modules/_tkinter.c in the Python source code.

在 3.12 版的變更: This function is only called from the main interpreter.

char *(*PyOS_ReadlineFunctionPointer)(FILE*, FILE*, const char*)

Can be set to point to a function with the prototype char *func(FILE *stdin, FILE *stdout, char *prompt), overriding the default function used to read a single line of input at the interpreter's prompt. The function is expected to output the string prompt if it's not NULL, and then read a line of input from the provided standard input file, returning the resulting string. For example, The readline module sets this hook to provide line-editing and tab-completion features.

The result must be a string allocated by PyMem_RawMalloc() or PyMem_RawRealloc(), or NULL if an error occurred.

在 3.4 版的變更: The result must be allocated by PyMem_RawMalloc() or PyMem_RawRealloc(), instead of being allocated by PyMem_Malloc() or PyMem_Realloc().

在 3.12 版的變更: This function is only called from the main interpreter.

PyObject *PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)

回傳值：新的參照。

This is a simplified interface to PyRun_StringFlags() below, leaving flags set to NULL.

PyObject *PyRun_StringFlags(const char *str, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)

回傳值：新的參照。

Execute Python source code from str in the context specified by the objects globals and locals with the compiler flags specified by flags. globals must be a dictionary; locals can be any object that implements the mapping protocol. The parameter start specifies the start symbol and must one of the available start symbols.

Returns the result of executing the code as a Python object, or NULL if an exception was raised.

PyObject *PyRun_File(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals)

回傳值：新的參照。

This is a simplified interface to PyRun_FileExFlags() below, leaving closeit set to 0 and flags set to NULL.

PyObject *PyRun_FileEx(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit)

回傳值：新的參照。

This is a simplified interface to PyRun_FileExFlags() below, leaving flags set to NULL.

PyObject *PyRun_FileFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)

回傳值：新的參照。

This is a simplified interface to PyRun_FileExFlags() below, leaving closeit set to 0.

PyObject *PyRun_FileExFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit, PyCompilerFlags *flags)

回傳值：新的參照。

Similar to PyRun_StringFlags(), but the Python source code is read from fp instead of an in-memory string. filename should be the name of the file, it is decoded from the filesystem encoding and error handler. If closeit is true, the file is closed before PyRun_FileExFlags() returns.

PyObject *Py_CompileString(const char *str, const char *filename, int start)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is a simplified interface to Py_CompileStringFlags() below, leaving flags set to NULL.

PyObject *Py_CompileStringFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags)

回傳值：新的參照。

This is a simplified interface to Py_CompileStringExFlags() below, with optimize set to -1.

PyObject *Py_CompileStringObject(const char *str, PyObject *filename, int start, PyCompilerFlags *flags, int optimize)

回傳值：新的參照。

Parse and compile the Python source code in str, returning the resulting code object. The start symbol is given by start; this can be used to constrain the code which can be compiled and should be available start symbols. The filename specified by filename is used to construct the code object and may appear in tracebacks or SyntaxError exception messages. This returns NULL if the code cannot be parsed or compiled.

The integer optimize specifies the optimization level of the compiler; a value of -1 selects the optimization level of the interpreter as given by -O options. Explicit levels are 0 (no optimization; __debug__ is true), 1 (asserts are removed, __debug__ is false) or 2 (docstrings are removed too).

在 3.4 版被加入.

PyObject *Py_CompileStringExFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags, int optimize)

回傳值：新的參照。

Like Py_CompileStringObject(), but filename is a byte string decoded from the filesystem encoding and error handler.

在 3.2 版被加入.

PyObject *PyEval_EvalCode(PyObject *co, PyObject *globals, PyObject *locals)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is a simplified interface to PyEval_EvalCodeEx(), with just the code object, and global and local variables. The other arguments are set to NULL.

PyObject *PyEval_EvalCodeEx(PyObject *co, PyObject *globals, PyObject *locals, PyObject *const *args, int argcount, PyObject *const *kws, int kwcount, PyObject *const *defs, int defcount, PyObject *kwdefs, PyObject *closure)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Evaluate a precompiled code object, given a particular environment for its evaluation. This environment consists of a dictionary of global variables, a mapping object of local variables, arrays of arguments, keywords and defaults, a dictionary of default values for keyword-only arguments and a closure tuple of cells.

PyObject *PyEval_EvalFrame(PyFrameObject *f)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Evaluate an execution frame. This is a simplified interface to PyEval_EvalFrameEx(), for backward compatibility.

PyObject *PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is the main, unvarnished function of Python interpretation. The code object associated with the execution frame f is executed, interpreting bytecode and executing calls as needed. The additional throwflag parameter can mostly be ignored - if true, then it causes an exception to immediately be thrown; this is used for the throw() methods of generator objects.

在 3.4 版的變更: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

int PyEval_MergeCompilerFlags(PyCompilerFlags *cf)

This function changes the flags of the current evaluation frame, and returns true on success, false on failure.

struct PyCompilerFlags

This is the structure used to hold compiler flags. In cases where code is only being compiled, it is passed as int flags, and in cases where code is being executed, it is passed as PyCompilerFlags *flags. In this case, from __future__ import can modify flags.

Whenever PyCompilerFlags *flags is NULL, cf_flags is treated as equal to 0, and any modification due to from __future__ import is discarded.

int cf_flags

編譯器旗標。

int cf_feature_version

cf_feature_version is the minor Python version. It should be initialized to PY_MINOR_VERSION.

The field is ignored by default, it is used if and only if PyCF_ONLY_AST flag is set in cf_flags.

在 3.8 版的變更: 新增 cf_feature_version 欄位。

可用的編譯器旗標可透過巨集存取：

PyCF_ALLOW_TOP_LEVEL_AWAIT

PyCF_ONLY_AST

PyCF_OPTIMIZED_AST

PyCF_TYPE_COMMENTS

See compiler flags in documentation of the ast Python module, which exports these constants under the same names.

The "PyCF" flags above can be combined with "CO_FUTURE" flags such as CO_FUTURE_ANNOTATIONS to enable features normally selectable using future statements. See 程式碼物件旗標 for a complete list.

可用的起始符號

int Py_eval_input

The start symbol from the Python grammar for isolated expressions; for use with Py_CompileString().

int Py_file_input

The start symbol from the Python grammar for sequences of statements as read from a file or other source; for use with Py_CompileString(). This is the symbol to use when compiling arbitrarily long Python source code.

int Py_single_input

The start symbol from the Python grammar for a single statement; for use with Py_CompileString(). This is the symbol used for the interactive interpreter loop.

int Py_func_type_input

The start symbol from the Python grammar for a function type; for use with Py_CompileString(). This is used to parse "signature type comments" from PEP 484 [https://peps.python.org/pep-0484/].

這需要設定 PyCF_ONLY_AST 旗標。

也參考

ast.FunctionType

PEP 484 [https://peps.python.org/pep-0484/]

在 3.8 版被加入.

Stack Effects

也參考

dis.stack_effect()

PY_INVALID_STACK_EFFECT

Sentinel value representing an invalid stack effect.

這目前等同於 INT_MAX。

在 3.8 版被加入.

int PyCompile_OpcodeStackEffect(int opcode, int oparg)

Compute the stack effect of opcode with argument oparg.

On success, this function returns the stack effect; on failure, this returns PY_INVALID_STACK_EFFECT.

在 3.4 版被加入.

int PyCompile_OpcodeStackEffectWithJump(int opcode, int oparg, int jump)

Similar to PyCompile_OpcodeStackEffect(), but don't include the stack effect of jumping if jump is zero.

If jump is 0, this will not include the stack effect of jumping, but if jump is 1 or -1, this will include it.

On success, this function returns the stack effect; on failure, this returns PY_INVALID_STACK_EFFECT.

在 3.8 版被加入.

參照計數

本節中的函式與巨集用於管理 Python 物件的參照計數。

Py_ssize_t Py_REFCNT(PyObject *o)

為 穩定 ABI 的一部分 自 3.14 版本開始.

取得物件 o 的參照計數。

請注意，回傳的值可能實際上並不反映實際保存了多少對該物件的參照。例如，某些物件是「不滅的 (immortal)」，並且具有非常高的參照計數，不能反映實際的參照數量。因此，除了 0 或 1 以外，不要依賴回傳值的準確性。

使用 Py_SET_REFCNT() 函式設定物件參照計數。

備註

On free threaded builds of Python, returning 1 isn't sufficient to determine if it's safe to treat o as having no access by other threads. Use PyUnstable_Object_IsUniquelyReferenced() for that instead.

See also the function PyUnstable_Object_IsUniqueReferencedTemporary().

在 3.10 版的變更: Py_REFCNT() 更改為行內靜態函式 (inline static function)。

在 3.11 版的變更: 參數型別不再是 const PyObject*。

void Py_SET_REFCNT(PyObject *o, Py_ssize_t refcnt)

設定物件 o 的參照計數。

在啟用自由執行緒的 Python 建置中，如果 refcnt 大於 UINT32_MAX，則該物件會被設為不滅的 (immortal)。

請注意，此函式對不滅的物件沒有影響。

在 3.9 版被加入.

在 3.12 版的變更: 不滅的物件不會被修改。

void Py_INCREF(PyObject *o)

代表取得對於物件 o 的新強參照，即它正在使用且不應被銷毀。

請注意，此函式對不滅的物件沒有影響。

此函式通常用於將借用參照原地 (in-place) 轉換為強參照。Py_NewRef() 函式可用於建立新的強參照。

使用完該物件後，透過呼叫 Py_DECREF() 來釋放它。

該物件不能為 NULL；如果你不確定它不是 NULL，請使用 Py_XINCREF()。

不要期望此函式會以任何方式實際修改 o，至少對於某些物件 [https://peps.python.org/pep-0683/]來說，此函式沒有任何效果。

在 3.12 版的變更: 不滅的物件不會被修改。

void Py_XINCREF(PyObject *o)

與 Py_INCREF() 類似，但物件 o 可以為 NULL，在這種情況下這就不會有任何效果。

另請見 Py_XNewRef()。

PyObject *Py_NewRef(PyObject *o)

為 穩定 ABI 的一部分 自 3.10 版本開始.

建立對物件的新強參照：於 o 呼叫 Py_INCREF() 並回傳物件 o。

當不再需要強參照時，應對其呼叫 Py_DECREF() 以釋放該參照。

物件 o 不能為 NULL；如果 o 可以為 NULL，則使用 Py_XNewRef()。

舉例來說：

Py_INCREF(obj);
self->attr = obj;

可以寫成：

self->attr = Py_NewRef(obj);

另請參閱 Py_INCREF()。

在 3.10 版被加入.

PyObject *Py_XNewRef(PyObject *o)

為 穩定 ABI 的一部分 自 3.10 版本開始.

與 Py_NewRef() 類似，但物件 o 可以為 NULL。

如果物件 o 為 NULL，則該函式僅回傳 NULL。

在 3.10 版被加入.

void Py_DECREF(PyObject *o)

釋放一個對物件 o 的強參照，代表該參照不會再被使用。

請注意，此函式對不滅的物件沒有影響。

如果最後一個強參照被釋放（即物件的參照計數達到零），則觸發物件之型別的釋放函式 (deallocation function)（不得為 NULL）。

此函式通常用於在退出作用域之前刪除強參照。

該物件不能為 NULL；如果你不確定它不是 NULL，請改用 Py_XDECREF()。

不要期望此函式會以任何方式實際修改 o，至少對於某些物件 [https://peps.python.org/pep-0683/]來說，此函式沒有任何效果。

警告

釋放函式可以導致任意 Python 程式碼被叫用（例如，當釋放具有 __del__() 方法的類別實例時）。雖然此類程式碼中的例外不會被傳遞出來，但​​執行的程式碼可以自由存取所有 Python 全域變數。這意味著在叫用 Py_DECREF() 之前，可從全域變數存取的任何物件都應處於一致狀態。例如，從 list 中刪除物件的程式碼應將已刪除物件的參照複製到臨時變數中，更新 list 資料結構，然後為臨時變數呼叫 Py_DECREF()。

在 3.12 版的變更: 不滅的物件不會被修改。

void Py_XDECREF(PyObject *o)

和 Py_DECREF() 類似，但該物件可以是 NULL，在這種情況下巨集不起作用。在這裡也會出現與 Py_DECREF() 相同的警告。

void Py_CLEAR(PyObject *o)

釋放對於物件 o 的強參照。該物件可能是 NULL，在這種情況下巨集不起作用；否則，效果與 Py_DECREF() 相同，除非引數也設定為 NULL。Py_DECREF() 的警告不適用於傳遞的物件，因為巨集在釋放其參照之前小心地使用臨時變數並將引數設定為 NULL。

每當要釋放垃圾回收 (garbage collection) 期間可能被遍歷到之對於物件的參照時，使用此巨集是個好主意。

在 3.12 版的變更: 巨集引數現在僅會被求值 (evaluate) 一次。如果引數有其他副作用，則不再重複作用。

void Py_IncRef(PyObject *o)

為 穩定 ABI 的一部分.

代表取得對於物件 o 的強參照。Py_XINCREF() 的函式版本。它可用於 Python 的 runtime 動態嵌入。

void Py_DecRef(PyObject *o)

為 穩定 ABI 的一部分.

釋放對物件 o 的強參照。Py_XDECREF() 的函式版本。它可用於 Python 的 runtime 動態嵌入。

Py_SETREF(dst, src)

巨集安全地釋放對於物件 dst 的強參照並將 dst 設定為 src。

與 Py_CLEAR() 的情況一樣，「明顯的」程式碼可能是致命的：

Py_DECREF(dst);
dst = src;

安全的方法是：

Py_SETREF(dst, src);

這會在釋放對 dst 舊值的參照之前將 dst 設定為 src，使得因 dst 被拆除而觸發的任何副作用 (side-effect) 之程式碼不會相信 dst 是指向一個有效物件。

在 3.6 版被加入.

在 3.12 版的變更: 巨集引數現在僅會被求值一次。如果引數有其他副作用，則不再重複作用。

Py_XSETREF(dst, src)

Py_SETREF 巨集的變體，請改用 Py_XDECREF() 而非 Py_DECREF()。

在 3.6 版被加入.

在 3.12 版的變更: 巨集引數現在僅會被求值一次。如果引數有其他副作用，則不再重複作用。

例外處理

The functions described in this chapter will let you handle and raise Python exceptions. It is important to understand some of the basics of Python exception handling. It works somewhat like the POSIX errno variable: there is a global indicator (per thread) of the last error that occurred. Most C API functions don't clear this on success, but will set it to indicate the cause of the error on failure. Most C API functions also return an error indicator, usually NULL if they are supposed to return a pointer, or -1 if they return an integer (exception: the PyArg_* functions return 1 for success and 0 for failure).

Concretely, the error indicator consists of three object pointers: the exception's type, the exception's value, and the traceback object. Any of those pointers can be NULL if non-set (although some combinations are forbidden, for example you can't have a non-NULL traceback if the exception type is NULL).

When a function must fail because some function it called failed, it generally doesn't set the error indicator; the function it called already set it. It is responsible for either handling the error and clearing the exception or returning after cleaning up any resources it holds (such as object references or memory allocations); it should not continue normally if it is not prepared to handle the error. If returning due to an error, it is important to indicate to the caller that an error has been set. If the error is not handled or carefully propagated, additional calls into the Python/C API may not behave as intended and may fail in mysterious ways.

備註

The error indicator is not the result of sys.exc_info(). The former corresponds to an exception that is not yet caught (and is therefore still propagating), while the latter returns an exception after it is caught (and has therefore stopped propagating).

Printing and clearing

void PyErr_Clear()

為 穩定 ABI 的一部分.

Clear the error indicator. If the error indicator is not set, there is no effect.

void PyErr_PrintEx(int set_sys_last_vars)

為 穩定 ABI 的一部分.

Print a standard traceback to sys.stderr and clear the error indicator. Unless the error is a SystemExit, in that case no traceback is printed and the Python process will exit with the error code specified by the SystemExit instance.

Call this function only when the error indicator is set. Otherwise it will cause a fatal error!

If set_sys_last_vars is nonzero, the variable sys.last_exc is set to the printed exception. For backwards compatibility, the deprecated variables sys.last_type, sys.last_value and sys.last_traceback are also set to the type, value and traceback of this exception, respectively.

在 3.12 版的變更: 新增 sys.last_exc 設定。

void PyErr_Print()

為 穩定 ABI 的一部分.

PyErr_PrintEx(1) 的別名。

void PyErr_WriteUnraisable(PyObject *obj)

為 穩定 ABI 的一部分.

Call sys.unraisablehook() using the current exception and obj argument.

This utility function prints a warning message to sys.stderr when an exception has been set but it is impossible for the interpreter to actually raise the exception. It is used, for example, when an exception occurs in an __del__() method.

The function is called with a single argument obj that identifies the context in which the unraisable exception occurred. If possible, the repr of obj will be printed in the warning message. If obj is NULL, only the traceback is printed.

An exception must be set when calling this function.

在 3.4 版的變更: Print a traceback. Print only traceback if obj is NULL.

在 3.8 版的變更: 使用 sys.unraisablehook()。

void PyErr_FormatUnraisable(const char *format, ...)

Similar to PyErr_WriteUnraisable(), but the format and subsequent parameters help format the warning message; they have the same meaning and values as in PyUnicode_FromFormat(). PyErr_WriteUnraisable(obj) is roughly equivalent to PyErr_FormatUnraisable("Exception ignored in: %R", obj). If format is NULL, only the traceback is printed.

在 3.13 版被加入.

void PyErr_DisplayException(PyObject *exc)

為 穩定 ABI 的一部分 自 3.12 版本開始.

Print the standard traceback display of exc to sys.stderr, including chained exceptions and notes.

在 3.12 版被加入.

引發例外

These functions help you set the current thread's error indicator. For convenience, some of these functions will always return a NULL pointer for use in a return statement.

void PyErr_SetString(PyObject *type, const char *message)

為 穩定 ABI 的一部分.

This is the most common way to set the error indicator. The first argument specifies the exception type; it is normally one of the standard exceptions, e.g. PyExc_RuntimeError. You need not create a new strong reference to it (e.g. with Py_INCREF()). The second argument is an error message; it is decoded from 'utf-8'.

void PyErr_SetObject(PyObject *type, PyObject *value)

為 穩定 ABI 的一部分.

This function is similar to PyErr_SetString() but lets you specify an arbitrary Python object for the "value" of the exception.

PyObject *PyErr_Format(PyObject *exception, const char *format, ...)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分.

This function sets the error indicator and returns NULL. exception should be a Python exception class. The format and subsequent parameters help format the error message; they have the same meaning and values as in PyUnicode_FromFormat(). format is an ASCII-encoded string.

PyObject *PyErr_FormatV(PyObject *exception, const char *format, va_list vargs)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 自 3.5 版本開始.

Same as PyErr_Format(), but taking a va_list argument rather than a variable number of arguments.

在 3.5 版被加入.

void PyErr_SetNone(PyObject *type)

為 穩定 ABI 的一部分.

This is a shorthand for PyErr_SetObject(type, Py_None).

int PyErr_BadArgument()

為 穩定 ABI 的一部分.

This is a shorthand for PyErr_SetString(PyExc_TypeError, message), where message indicates that a built-in operation was invoked with an illegal argument. It is mostly for internal use.

PyObject *PyErr_NoMemory()

回傳值：總是為 NULL。 為 穩定 ABI 的一部分.

This is a shorthand for PyErr_SetNone(PyExc_MemoryError); it returns NULL so an object allocation function can write return PyErr_NoMemory(); when it runs out of memory.

PyObject *PyErr_SetFromErrno(PyObject *type)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分.

This is a convenience function to raise an exception when a C library function has returned an error and set the C variable errno. It constructs a tuple object whose first item is the integer errno value and whose second item is the corresponding error message (gotten from strerror()), and then calls PyErr_SetObject(type, object). On Unix, when the errno value is EINTR, indicating an interrupted system call, this calls PyErr_CheckSignals(), and if that set the error indicator, leaves it set to that. The function always returns NULL, so a wrapper function around a system call can write return PyErr_SetFromErrno(type); when the system call returns an error.

PyObject *PyErr_SetFromErrnoWithFilenameObject(PyObject *type, PyObject *filenameObject)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分.

Similar to PyErr_SetFromErrno(), with the additional behavior that if filenameObject is not NULL, it is passed to the constructor of type as a third parameter. In the case of OSError exception, this is used to define the filename attribute of the exception instance.

PyObject *PyErr_SetFromErrnoWithFilenameObjects(PyObject *type, PyObject *filenameObject, PyObject *filenameObject2)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Similar to PyErr_SetFromErrnoWithFilenameObject(), but takes a second filename object, for raising errors when a function that takes two filenames fails.

在 3.4 版被加入.

PyObject *PyErr_SetFromErrnoWithFilename(PyObject *type, const char *filename)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分.

Similar to PyErr_SetFromErrnoWithFilenameObject(), but the filename is given as a C string. filename is decoded from the filesystem encoding and error handler.

PyObject *PyErr_SetFromWindowsErr(int ierr)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

This is a convenience function to raise OSError. If called with ierr of 0, the error code returned by a call to GetLastError() is used instead. It calls the Win32 function FormatMessage() to retrieve the Windows description of error code given by ierr or GetLastError(), then it constructs a OSError object with the winerror attribute set to the error code, the strerror attribute set to the corresponding error message (gotten from FormatMessage()), and then calls PyErr_SetObject(PyExc_OSError, object). This function always returns NULL.

可用性: Windows.

PyObject *PyErr_SetExcFromWindowsErr(PyObject *type, int ierr)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Similar to PyErr_SetFromWindowsErr(), with an additional parameter specifying the exception type to be raised.

可用性: Windows.

PyObject *PyErr_SetFromWindowsErrWithFilename(int ierr, const char *filename)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Similar to PyErr_SetFromWindowsErr(), with the additional behavior that if filename is not NULL, it is decoded from the filesystem encoding (os.fsdecode()) and passed to the constructor of OSError as a third parameter to be used to define the filename attribute of the exception instance.

可用性: Windows.

PyObject *PyErr_SetExcFromWindowsErrWithFilenameObject(PyObject *type, int ierr, PyObject *filename)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Similar to PyErr_SetExcFromWindowsErr(), with the additional behavior that if filename is not NULL, it is passed to the constructor of OSError as a third parameter to be used to define the filename attribute of the exception instance.

可用性: Windows.

PyObject *PyErr_SetExcFromWindowsErrWithFilenameObjects(PyObject *type, int ierr, PyObject *filename, PyObject *filename2)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Similar to PyErr_SetExcFromWindowsErrWithFilenameObject(), but accepts a second filename object.

可用性: Windows.

在 3.4 版被加入.

PyObject *PyErr_SetExcFromWindowsErrWithFilename(PyObject *type, int ierr, const char *filename)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Similar to PyErr_SetFromWindowsErrWithFilename(), with an additional parameter specifying the exception type to be raised.

可用性: Windows.

PyObject *PyErr_SetImportError(PyObject *msg, PyObject *name, PyObject *path)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 自 3.7 版本開始.

This is a convenience function to raise ImportError. msg will be set as the exception's message string. name and path, both of which can be NULL, will be set as the ImportError's respective name and path attributes.

在 3.3 版被加入.

PyObject *PyErr_SetImportErrorSubclass(PyObject *exception, PyObject *msg, PyObject *name, PyObject *path)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分 自 3.6 版本開始.

Much like PyErr_SetImportError() but this function allows for specifying a subclass of ImportError to raise.

在 3.6 版被加入.

void PyErr_SyntaxLocationObject(PyObject *filename, int lineno, int col_offset)

Set file, line, and offset information for the current exception. If the current exception is not a SyntaxError, then it sets additional attributes, which make the exception printing subsystem think the exception is a SyntaxError.

在 3.4 版被加入.

void PyErr_RangedSyntaxLocationObject(PyObject *filename, int lineno, int col_offset, int end_lineno, int end_col_offset)

Similar to PyErr_SyntaxLocationObject(), but also sets the end_lineno and end_col_offset information for the current exception.

在 3.10 版被加入.

void PyErr_SyntaxLocationEx(const char *filename, int lineno, int col_offset)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Like PyErr_SyntaxLocationObject(), but filename is a byte string decoded from the filesystem encoding and error handler.

在 3.2 版被加入.

void PyErr_SyntaxLocation(const char *filename, int lineno)

為 穩定 ABI 的一部分.

Like PyErr_SyntaxLocationEx(), but the col_offset parameter is omitted.

void PyErr_BadInternalCall()

為 穩定 ABI 的一部分.

This is a shorthand for PyErr_SetString(PyExc_SystemError, message), where message indicates that an internal operation (e.g. a Python/C API function) was invoked with an illegal argument. It is mostly for internal use.

PyObject *PyErr_ProgramTextObject(PyObject *filename, int lineno)

Get the source line in filename at line lineno. filename should be a Python str object.

On success, this function returns a Python string object with the found line. On failure, this function returns NULL without an exception set.

PyObject *PyErr_ProgramText(const char *filename, int lineno)

為 穩定 ABI 的一部分.

Similar to PyErr_ProgramTextObject(), but filename is a const char*, which is decoded with the filesystem encoding and error handler, instead of a Python object reference.

發出警告

Use these functions to issue warnings from C code. They mirror similar functions exported by the Python warnings module. They normally print a warning message to sys.stderr; however, it is also possible that the user has specified that warnings are to be turned into errors, and in that case they will raise an exception. It is also possible that the functions raise an exception because of a problem with the warning machinery. The return value is 0 if no exception is raised, or -1 if an exception is raised. (It is not possible to determine whether a warning message is actually printed, nor what the reason is for the exception; this is intentional.) If an exception is raised, the caller should do its normal exception handling (for example, Py_DECREF() owned references and return an error value).

int PyErr_WarnEx(PyObject *category, const char *message, Py_ssize_t stack_level)

為 穩定 ABI 的一部分.

Issue a warning message. The category argument is a warning category (see below) or NULL; the message argument is a UTF-8 encoded string. stack_level is a positive number giving a number of stack frames; the warning will be issued from the currently executing line of code in that stack frame. A stack_level of 1 is the function calling PyErr_WarnEx(), 2 is the function above that, and so forth.

Warning categories must be subclasses of PyExc_Warning; PyExc_Warning is a subclass of PyExc_Exception; the default warning category is PyExc_RuntimeWarning. The standard Python warning categories are available as global variables whose names are enumerated at 警告型別.

For information about warning control, see the documentation for the warnings module and the -W option in the command line documentation. There is no C API for warning control.

int PyErr_WarnExplicitObject(PyObject *category, PyObject *message, PyObject *filename, int lineno, PyObject *module, PyObject *registry)

Issue a warning message with explicit control over all warning attributes. This is a straightforward wrapper around the Python function warnings.warn_explicit(); see there for more information. The module and registry arguments may be set to NULL to get the default effect described there.

在 3.4 版被加入.

int PyErr_WarnExplicit(PyObject *category, const char *message, const char *filename, int lineno, const char *module, PyObject *registry)

為 穩定 ABI 的一部分.

Similar to PyErr_WarnExplicitObject() except that message and module are UTF-8 encoded strings, and filename is decoded from the filesystem encoding and error handler.

int PyErr_WarnFormat(PyObject *category, Py_ssize_t stack_level, const char *format, ...)

為 穩定 ABI 的一部分.

Function similar to PyErr_WarnEx(), but use PyUnicode_FromFormat() to format the warning message. format is an ASCII-encoded string.

在 3.2 版被加入.

int PyErr_WarnExplicitFormat(PyObject *category, const char *filename, int lineno, const char *module, PyObject *registry, const char *format, ...)

Similar to PyErr_WarnExplicit(), but uses PyUnicode_FromFormat() to format the warning message. format is an ASCII-encoded string.

在 3.2 版被加入.

int PyErr_ResourceWarning(PyObject *source, Py_ssize_t stack_level, const char *format, ...)

為 穩定 ABI 的一部分 自 3.6 版本開始.

Function similar to PyErr_WarnFormat(), but category is ResourceWarning and it passes source to warnings.WarningMessage.

在 3.6 版被加入.

Querying the error indicator

PyObject *PyErr_Occurred()

回傳值：借用參照。 為 穩定 ABI 的一部分.

Test whether the error indicator is set. If set, return the exception type (the first argument to the last call to one of the PyErr_Set* functions or to PyErr_Restore()). If not set, return NULL. You do not own a reference to the return value, so you do not need to Py_DECREF() it.

The caller must have an attached thread state.

備註

Do not compare the return value to a specific exception; use PyErr_ExceptionMatches() instead, shown below. (The comparison could easily fail since the exception may be an instance instead of a class, in the case of a class exception, or it may be a subclass of the expected exception.)

int PyErr_ExceptionMatches(PyObject *exc)

為 穩定 ABI 的一部分.

Equivalent to PyErr_GivenExceptionMatches(PyErr_Occurred(), exc). This should only be called when an exception is actually set; a memory access violation will occur if no exception has been raised.

int PyErr_GivenExceptionMatches(PyObject *given, PyObject *exc)

為 穩定 ABI 的一部分.

Return true if the given exception matches the exception type in exc. If exc is a class object, this also returns true when given is an instance of a subclass. If exc is a tuple, all exception types in the tuple (and recursively in subtuples) are searched for a match.

PyObject *PyErr_GetRaisedException(void)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.12 版本開始.

Return the exception currently being raised, clearing the error indicator at the same time. Return NULL if the error indicator is not set.

This function is used by code that needs to catch exceptions, or code that needs to save and restore the error indicator temporarily.

舉例來說：

{
   PyObject *exc = PyErr_GetRaisedException();

   /* ... 可能會產生其他錯誤的程式碼 ... */

   PyErr_SetRaisedException(exc);
}

也參考

PyErr_GetHandledException(), to save the exception currently being handled.

在 3.12 版被加入.

void PyErr_SetRaisedException(PyObject *exc)

為 穩定 ABI 的一部分 自 3.12 版本開始.

Set exc as the exception currently being raised, clearing the existing exception if one is set.

警告

This call steals a reference to exc, which must be a valid exception.

在 3.12 版被加入.

void PyErr_Fetch(PyObject **ptype, PyObject **pvalue, PyObject **ptraceback)

為 穩定 ABI 的一部分.

在 3.12 版之後被棄用: 請改用 PyErr_GetRaisedException()。

Retrieve the error indicator into three variables whose addresses are passed. If the error indicator is not set, set all three variables to NULL. If it is set, it will be cleared and you own a reference to each object retrieved. The value and traceback object may be NULL even when the type object is not.

備註

This function is normally only used by legacy code that needs to catch exceptions or save and restore the error indicator temporarily.

舉例來說：

{
   PyObject *type, *value, *traceback;
   PyErr_Fetch(&type, &value, &traceback);

   /* ... 可能會產生其他錯誤的程式碼 ... */

   PyErr_Restore(type, value, traceback);
}

void PyErr_Restore(PyObject *type, PyObject *value, PyObject *traceback)

為 穩定 ABI 的一部分.

在 3.12 版之後被棄用: 請改用 PyErr_SetRaisedException()。

Set the error indicator from the three objects, type, value, and traceback, clearing the existing exception if one is set. If the objects are NULL, the error indicator is cleared. Do not pass a NULL type and non-NULL value or traceback. The exception type should be a class. Do not pass an invalid exception type or value. (Violating these rules will cause subtle problems later.) This call takes away a reference to each object: you must own a reference to each object before the call and after the call you no longer own these references. (If you don't understand this, don't use this function. I warned you.)

備註

This function is normally only used by legacy code that needs to save and restore the error indicator temporarily. Use PyErr_Fetch() to save the current error indicator.

void PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)

為 穩定 ABI 的一部分.

在 3.12 版之後被棄用: Use PyErr_GetRaisedException() instead, to avoid any possible de-normalization.

Under certain circumstances, the values returned by PyErr_Fetch() below can be "unnormalized", meaning that *exc is a class object but *val is not an instance of the same class. This function can be used to instantiate the class in that case. If the values are already normalized, nothing happens. The delayed normalization is implemented to improve performance.

備註

This function does not implicitly set the __traceback__ attribute on the exception value. If setting the traceback appropriately is desired, the following additional snippet is needed:

if (tb != NULL) {
  PyException_SetTraceback(val, tb);
}

PyObject *PyErr_GetHandledException(void)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Retrieve the active exception instance, as would be returned by sys.exception(). This refers to an exception that was already caught, not to an exception that was freshly raised. Returns a new reference to the exception or NULL. Does not modify the interpreter's exception state.

備註

This function is not normally used by code that wants to handle exceptions. Rather, it can be used when code needs to save and restore the exception state temporarily. Use PyErr_SetHandledException() to restore or clear the exception state.

在 3.11 版被加入.

void PyErr_SetHandledException(PyObject *exc)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Set the active exception, as known from sys.exception(). This refers to an exception that was already caught, not to an exception that was freshly raised. To clear the exception state, pass NULL.

備註

This function is not normally used by code that wants to handle exceptions. Rather, it can be used when code needs to save and restore the exception state temporarily. Use PyErr_GetHandledException() to get the exception state.

在 3.11 版被加入.

void PyErr_GetExcInfo(PyObject **ptype, PyObject **pvalue, PyObject **ptraceback)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Retrieve the old-style representation of the exception info, as known from sys.exc_info(). This refers to an exception that was already caught, not to an exception that was freshly raised. Returns new references for the three objects, any of which may be NULL. Does not modify the exception info state. This function is kept for backwards compatibility. Prefer using PyErr_GetHandledException().

備註

This function is not normally used by code that wants to handle exceptions. Rather, it can be used when code needs to save and restore the exception state temporarily. Use PyErr_SetExcInfo() to restore or clear the exception state.

在 3.3 版被加入.

void PyErr_SetExcInfo(PyObject *type, PyObject *value, PyObject *traceback)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Set the exception info, as known from sys.exc_info(). This refers to an exception that was already caught, not to an exception that was freshly raised. This function steals the references of the arguments. To clear the exception state, pass NULL for all three arguments. This function is kept for backwards compatibility. Prefer using PyErr_SetHandledException().

備註

This function is not normally used by code that wants to handle exceptions. Rather, it can be used when code needs to save and restore the exception state temporarily. Use PyErr_GetExcInfo() to read the exception state.

在 3.3 版被加入.

在 3.11 版的變更: The type and traceback arguments are no longer used and can be NULL. The interpreter now derives them from the exception instance (the value argument). The function still steals references of all three arguments.

訊號處理

int PyErr_CheckSignals()

為 穩定 ABI 的一部分.

This function interacts with Python's signal handling.

If the function is called from the main thread and under the main Python interpreter, it checks whether a signal has been sent to the processes and if so, invokes the corresponding signal handler. If the signal module is supported, this can invoke a signal handler written in Python.

The function attempts to handle all pending signals, and then returns 0. However, if a Python signal handler raises an exception, the error indicator is set and the function returns -1 immediately (such that other pending signals may not have been handled yet: they will be on the next PyErr_CheckSignals() invocation).

If the function is called from a non-main thread, or under a non-main Python interpreter, it does nothing and returns 0.

This function can be called by long-running C code that wants to be interruptible by user requests (such as by pressing Ctrl-C).

備註

The default Python signal handler for SIGINT raises the KeyboardInterrupt exception.

void PyErr_SetInterrupt()

為 穩定 ABI 的一部分.

Simulate the effect of a SIGINT signal arriving. This is equivalent to PyErr_SetInterruptEx(SIGINT).

備註

This function is async-signal-safe. It can be called without an attached thread state and from a C signal handler.

int PyErr_SetInterruptEx(int signum)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Simulate the effect of a signal arriving. The next time PyErr_CheckSignals() is called, the Python signal handler for the given signal number will be called.

This function can be called by C code that sets up its own signal handling and wants Python signal handlers to be invoked as expected when an interruption is requested (for example when the user presses Ctrl-C to interrupt an operation).

If the given signal isn't handled by Python (it was set to signal.SIG_DFL or signal.SIG_IGN), it will be ignored.

If signum is outside of the allowed range of signal numbers, -1 is returned. Otherwise, 0 is returned. The error indicator is never changed by this function.

備註

This function is async-signal-safe. It can be called without an attached thread state and from a C signal handler.

在 3.10 版被加入.

int PySignal_SetWakeupFd(int fd)

This utility function specifies a file descriptor to which the signal number is written as a single byte whenever a signal is received. fd must be non-blocking. It returns the previous such file descriptor.

The value -1 disables the feature; this is the initial state. This is equivalent to signal.set_wakeup_fd() in Python, but without any error checking. fd should be a valid file descriptor. The function should only be called from the main thread.

在 3.5 版的變更: On Windows, the function now also supports socket handles.

例外類別

PyObject *PyErr_NewException(const char *name, PyObject *base, PyObject *dict)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This utility function creates and returns a new exception class. The name argument must be the name of the new exception, a C string of the form module.classname. The base and dict arguments are normally NULL. This creates a class object derived from Exception (accessible in C as PyExc_Exception).

The __module__ attribute of the new class is set to the first part (up to the last dot) of the name argument, and the class name is set to the last part (after the last dot). The base argument can be used to specify alternate base classes; it can either be only one class or a tuple of classes. The dict argument can be used to specify a dictionary of class variables and methods.

PyObject *PyErr_NewExceptionWithDoc(const char *name, const char *doc, PyObject *base, PyObject *dict)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Same as PyErr_NewException(), except that the new exception class can easily be given a docstring: If doc is non-NULL, it will be used as the docstring for the exception class.

在 3.2 版被加入.

int PyExceptionClass_Check(PyObject *ob)

Return non-zero if ob is an exception class, zero otherwise. This function always succeeds.

const char *PyExceptionClass_Name(PyObject *ob)

為 穩定 ABI 的一部分 自 3.8 版本開始.

回傳例外類別 ob 的 tp_name。

例外物件

int PyExceptionInstance_Check(PyObject *op)

Return true if op is an instance of BaseException, false otherwise. This function always succeeds.

PyExceptionInstance_Class(op)

Equivalent to Py_TYPE(op).

PyObject *PyException_GetTraceback(PyObject *ex)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the traceback associated with the exception as a new reference, as accessible from Python through the __traceback__ attribute. If there is no traceback associated, this returns NULL.

int PyException_SetTraceback(PyObject *ex, PyObject *tb)

為 穩定 ABI 的一部分.

Set the traceback associated with the exception to tb. Use Py_None to clear it.

PyObject *PyException_GetContext(PyObject *ex)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the context (another exception instance during whose handling ex was raised) associated with the exception as a new reference, as accessible from Python through the __context__ attribute. If there is no context associated, this returns NULL.

void PyException_SetContext(PyObject *ex, PyObject *ctx)

為 穩定 ABI 的一部分.

Set the context associated with the exception to ctx. Use NULL to clear it. There is no type check to make sure that ctx is an exception instance. This steals a reference to ctx.

PyObject *PyException_GetCause(PyObject *ex)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the cause (either an exception instance, or None, set by raise ... from ...) associated with the exception as a new reference, as accessible from Python through the __cause__ attribute.

void PyException_SetCause(PyObject *ex, PyObject *cause)

為 穩定 ABI 的一部分.

Set the cause associated with the exception to cause. Use NULL to clear it. There is no type check to make sure that cause is either an exception instance or None. This steals a reference to cause.

The __suppress_context__ attribute is implicitly set to True by this function.

PyObject *PyException_GetArgs(PyObject *ex)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.12 版本開始.

回傳例外 ex 的 args。

void PyException_SetArgs(PyObject *ex, PyObject *args)

為 穩定 ABI 的一部分 自 3.12 版本開始.

設定例外 ex 的 args 為 args。

PyObject *PyUnstable_Exc_PrepReraiseStar(PyObject *orig, PyObject *excs)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Implement part of the interpreter's implementation of except*. orig is the original exception that was caught, and excs is the list of the exceptions that need to be raised. This list contains the unhandled part of orig, if any, as well as the exceptions that were raised from the except* clauses (so they have a different traceback from orig) and those that were reraised (and have the same traceback as orig). Return the ExceptionGroup that needs to be reraised in the end, or None if there is nothing to reraise.

在 3.12 版被加入.

Unicode 例外物件

The following functions are used to create and modify Unicode exceptions from C.

PyObject *PyUnicodeDecodeError_Create(const char *encoding, const char *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a UnicodeDecodeError object with the attributes encoding, object, length, start, end and reason. encoding and reason are UTF-8 encoded strings.

PyObject *PyUnicodeDecodeError_GetEncoding(PyObject *exc)

PyObject *PyUnicodeEncodeError_GetEncoding(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the encoding attribute of the given exception object.

PyObject *PyUnicodeDecodeError_GetObject(PyObject *exc)

PyObject *PyUnicodeEncodeError_GetObject(PyObject *exc)

PyObject *PyUnicodeTranslateError_GetObject(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the object attribute of the given exception object.

int PyUnicodeDecodeError_GetStart(PyObject *exc, Py_ssize_t *start)

int PyUnicodeEncodeError_GetStart(PyObject *exc, Py_ssize_t *start)

int PyUnicodeTranslateError_GetStart(PyObject *exc, Py_ssize_t *start)

為 穩定 ABI 的一部分.

Get the start attribute of the given exception object and place it into *start. start must not be NULL. Return 0 on success, -1 on failure.

If the UnicodeError.object is an empty sequence, the resulting start is 0. Otherwise, it is clipped to [0, len(object) - 1].

也參考

UnicodeError.start

int PyUnicodeDecodeError_SetStart(PyObject *exc, Py_ssize_t start)

int PyUnicodeEncodeError_SetStart(PyObject *exc, Py_ssize_t start)

int PyUnicodeTranslateError_SetStart(PyObject *exc, Py_ssize_t start)

為 穩定 ABI 的一部分.

Set the start attribute of the given exception object to start. Return 0 on success, -1 on failure.

備註

While passing a negative start does not raise an exception, the corresponding getters will not consider it as a relative offset.

int PyUnicodeDecodeError_GetEnd(PyObject *exc, Py_ssize_t *end)

int PyUnicodeEncodeError_GetEnd(PyObject *exc, Py_ssize_t *end)

int PyUnicodeTranslateError_GetEnd(PyObject *exc, Py_ssize_t *end)

為 穩定 ABI 的一部分.

Get the end attribute of the given exception object and place it into *end. end must not be NULL. Return 0 on success, -1 on failure.

If the UnicodeError.object is an empty sequence, the resulting end is 0. Otherwise, it is clipped to [1, len(object)].

int PyUnicodeDecodeError_SetEnd(PyObject *exc, Py_ssize_t end)

int PyUnicodeEncodeError_SetEnd(PyObject *exc, Py_ssize_t end)

int PyUnicodeTranslateError_SetEnd(PyObject *exc, Py_ssize_t end)

為 穩定 ABI 的一部分.

Set the end attribute of the given exception object to end. Return 0 on success, -1 on failure.

也參考

UnicodeError.end

PyObject *PyUnicodeDecodeError_GetReason(PyObject *exc)

PyObject *PyUnicodeEncodeError_GetReason(PyObject *exc)

PyObject *PyUnicodeTranslateError_GetReason(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳給定例外物件的 reason 屬性。

int PyUnicodeDecodeError_SetReason(PyObject *exc, const char *reason)

int PyUnicodeEncodeError_SetReason(PyObject *exc, const char *reason)

int PyUnicodeTranslateError_SetReason(PyObject *exc, const char *reason)

為 穩定 ABI 的一部分.

Set the reason attribute of the given exception object to reason. Return 0 on success, -1 on failure.

遞迴控制

These two functions provide a way to perform safe recursive calls at the C level, both in the core and in extension modules. They are needed if the recursive code does not necessarily invoke Python code (which tracks its recursion depth automatically). They are also not needed for tp_call implementations because the call protocol takes care of recursion handling.

int Py_EnterRecursiveCall(const char *where)

為 穩定 ABI 的一部分 自 3.9 版本開始.

Marks a point where a recursive C-level call is about to be performed.

The function then checks if the stack limit is reached. If this is the case, a RecursionError is set and a nonzero value is returned. Otherwise, zero is returned.

where should be a UTF-8 encoded string such as " in instance check" to be concatenated to the RecursionError message caused by the recursion depth limit.

也參考

The PyUnstable_ThreadState_SetStackProtection() function.

在 3.9 版的變更: This function is now also available in the limited API.

void Py_LeaveRecursiveCall(void)

為 穩定 ABI 的一部分 自 3.9 版本開始.

Ends a Py_EnterRecursiveCall(). Must be called once for each successful invocation of Py_EnterRecursiveCall().

在 3.9 版的變更: This function is now also available in the limited API.

Properly implementing tp_repr for container types requires special recursion handling. In addition to protecting the stack, tp_repr also needs to track objects to prevent cycles. The following two functions facilitate this functionality. Effectively, these are the C equivalent to reprlib.recursive_repr().

int Py_ReprEnter(PyObject *object)

為 穩定 ABI 的一部分.

Called at the beginning of the tp_repr implementation to detect cycles.

If the object has already been processed, the function returns a positive integer. In that case the tp_repr implementation should return a string object indicating a cycle. As examples, dict objects return {...} and list objects return [...].

The function will return a negative integer if the recursion limit is reached. In that case the tp_repr implementation should typically return NULL.

Otherwise, the function returns zero and the tp_repr implementation can continue normally.

void Py_ReprLeave(PyObject *object)

為 穩定 ABI 的一部分.

Ends a Py_ReprEnter(). Must be called once for each invocation of Py_ReprEnter() that returns zero.

int Py_GetRecursionLimit(void)

為 穩定 ABI 的一部分.

Get the recursion limit for the current interpreter. It can be set with Py_SetRecursionLimit(). The recursion limit prevents the Python interpreter stack from growing infinitely.

This function cannot fail, and the caller must hold an attached thread state.

也參考

sys.getrecursionlimit()

void Py_SetRecursionLimit(int new_limit)

為 穩定 ABI 的一部分.

Set the recursion limit for the current interpreter.

This function cannot fail, and the caller must hold an attached thread state.

也參考

sys.setrecursionlimit()

例外和警告型別

All standard Python exceptions and warning categories are available as global variables whose names are PyExc_ followed by the Python exception name. These have the type PyObject*; they are all class objects.

For completeness, here are all the variables:

例外型別

C 名稱

Python 名稱

PyObject *PyExc_BaseException

為 穩定 ABI 的一部分.

BaseException

PyObject *PyExc_BaseExceptionGroup

為 穩定 ABI 的一部分 自 3.11 版本開始.

BaseExceptionGroup

PyObject *PyExc_Exception

為 穩定 ABI 的一部分.

Exception

PyObject *PyExc_ArithmeticError

為 穩定 ABI 的一部分.

ArithmeticError

PyObject *PyExc_AssertionError

為 穩定 ABI 的一部分.

AssertionError

PyObject *PyExc_AttributeError

為 穩定 ABI 的一部分.

AttributeError

PyObject *PyExc_BlockingIOError

為 穩定 ABI 的一部分 自 3.7 版本開始.

BlockingIOError

PyObject *PyExc_BrokenPipeError

為 穩定 ABI 的一部分 自 3.7 版本開始.

BrokenPipeError

PyObject *PyExc_BufferError

為 穩定 ABI 的一部分.

BufferError

PyObject *PyExc_ChildProcessError

為 穩定 ABI 的一部分 自 3.7 版本開始.

ChildProcessError

PyObject *PyExc_ConnectionAbortedError

為 穩定 ABI 的一部分 自 3.7 版本開始.

ConnectionAbortedError

PyObject *PyExc_ConnectionError

為 穩定 ABI 的一部分 自 3.7 版本開始.

ConnectionError

PyObject *PyExc_ConnectionRefusedError

為 穩定 ABI 的一部分 自 3.7 版本開始.

ConnectionRefusedError

PyObject *PyExc_ConnectionResetError

為 穩定 ABI 的一部分 自 3.7 版本開始.

ConnectionResetError

PyObject *PyExc_EOFError

為 穩定 ABI 的一部分.

EOFError

PyObject *PyExc_FileExistsError

為 穩定 ABI 的一部分 自 3.7 版本開始.

FileExistsError

PyObject *PyExc_FileNotFoundError

為 穩定 ABI 的一部分 自 3.7 版本開始.

FileNotFoundError

PyObject *PyExc_FloatingPointError

為 穩定 ABI 的一部分.

FloatingPointError

PyObject *PyExc_GeneratorExit

為 穩定 ABI 的一部分.

GeneratorExit

PyObject *PyExc_ImportError

為 穩定 ABI 的一部分.

ImportError

PyObject *PyExc_IndentationError

為 穩定 ABI 的一部分.

IndentationError

PyObject *PyExc_IndexError

為 穩定 ABI 的一部分.

IndexError

PyObject *PyExc_InterruptedError

為 穩定 ABI 的一部分 自 3.7 版本開始.

InterruptedError

PyObject *PyExc_IsADirectoryError

為 穩定 ABI 的一部分 自 3.7 版本開始.

IsADirectoryError

PyObject *PyExc_KeyError

為 穩定 ABI 的一部分.

KeyError

PyObject *PyExc_KeyboardInterrupt

為 穩定 ABI 的一部分.

KeyboardInterrupt

PyObject *PyExc_LookupError

為 穩定 ABI 的一部分.

LookupError

PyObject *PyExc_MemoryError

為 穩定 ABI 的一部分.

MemoryError

PyObject *PyExc_ModuleNotFoundError

為 穩定 ABI 的一部分 自 3.6 版本開始.

ModuleNotFoundError

PyObject *PyExc_NameError

為 穩定 ABI 的一部分.

NameError

PyObject *PyExc_NotADirectoryError

為 穩定 ABI 的一部分 自 3.7 版本開始.

NotADirectoryError

PyObject *PyExc_NotImplementedError

為 穩定 ABI 的一部分.

NotImplementedError

PyObject *PyExc_OSError

為 穩定 ABI 的一部分.

OSError

PyObject *PyExc_OverflowError

為 穩定 ABI 的一部分.

OverflowError

PyObject *PyExc_PermissionError

為 穩定 ABI 的一部分 自 3.7 版本開始.

PermissionError

PyObject *PyExc_ProcessLookupError

為 穩定 ABI 的一部分 自 3.7 版本開始.

ProcessLookupError

PyObject *PyExc_PythonFinalizationError

PythonFinalizationError

PyObject *PyExc_RecursionError

為 穩定 ABI 的一部分 自 3.7 版本開始.

RecursionError

PyObject *PyExc_ReferenceError

為 穩定 ABI 的一部分.

ReferenceError

PyObject *PyExc_RuntimeError

為 穩定 ABI 的一部分.

RuntimeError

PyObject *PyExc_StopAsyncIteration

為 穩定 ABI 的一部分 自 3.7 版本開始.

StopAsyncIteration

PyObject *PyExc_StopIteration

為 穩定 ABI 的一部分.

StopIteration

PyObject *PyExc_SyntaxError

為 穩定 ABI 的一部分.

SyntaxError

PyObject *PyExc_SystemError

為 穩定 ABI 的一部分.

SystemError

PyObject *PyExc_SystemExit

為 穩定 ABI 的一部分.

SystemExit

PyObject *PyExc_TabError

為 穩定 ABI 的一部分.

TabError

PyObject *PyExc_TimeoutError

為 穩定 ABI 的一部分 自 3.7 版本開始.

TimeoutError

PyObject *PyExc_TypeError

為 穩定 ABI 的一部分.

TypeError

PyObject *PyExc_UnboundLocalError

為 穩定 ABI 的一部分.

UnboundLocalError

PyObject *PyExc_UnicodeDecodeError

為 穩定 ABI 的一部分.

UnicodeDecodeError

PyObject *PyExc_UnicodeEncodeError

為 穩定 ABI 的一部分.

UnicodeEncodeError

PyObject *PyExc_UnicodeError

為 穩定 ABI 的一部分.

UnicodeError

PyObject *PyExc_UnicodeTranslateError

為 穩定 ABI 的一部分.

UnicodeTranslateError

PyObject *PyExc_ValueError

為 穩定 ABI 的一部分.

ValueError

PyObject *PyExc_ZeroDivisionError

為 穩定 ABI 的一部分.

ZeroDivisionError

在 3.3 版被加入: PyExc_BlockingIOError, PyExc_BrokenPipeError, PyExc_ChildProcessError, PyExc_ConnectionError, PyExc_ConnectionAbortedError, PyExc_ConnectionRefusedError, PyExc_ConnectionResetError, PyExc_FileExistsError, PyExc_FileNotFoundError, PyExc_InterruptedError, PyExc_IsADirectoryError, PyExc_NotADirectoryError, PyExc_PermissionError, PyExc_ProcessLookupError 和 PyExc_TimeoutError 是在 PEP 3151 [https://peps.python.org/pep-3151/] 被引入。

在 3.5 版被加入: PyExc_StopAsyncIteration 和 PyExc_RecursionError。

在 3.6 版被加入: PyExc_ModuleNotFoundError。

在 3.11 版被加入: PyExc_BaseExceptionGroup

OSError 別名

The following are a compatibility aliases to PyExc_OSError.

在 3.3 版的變更: These aliases used to be separate exception types.

C 名稱

Python 名稱

註解

PyObject *PyExc_EnvironmentError

為 穩定 ABI 的一部分.

OSError

PyObject *PyExc_IOError

為 穩定 ABI 的一部分.

OSError

PyObject *PyExc_WindowsError

為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

OSError

[win]

註解：

[win]

PyExc_WindowsError is only defined on Windows; protect code that uses this by testing that the preprocessor macro MS_WINDOWS is defined.

警告型別

C 名稱

Python 名稱

PyObject *PyExc_Warning

為 穩定 ABI 的一部分.

Warning

PyObject *PyExc_BytesWarning

為 穩定 ABI 的一部分.

BytesWarning

PyObject *PyExc_DeprecationWarning

為 穩定 ABI 的一部分.

DeprecationWarning

PyObject *PyExc_EncodingWarning

為 穩定 ABI 的一部分 自 3.10 版本開始.

EncodingWarning

PyObject *PyExc_FutureWarning

為 穩定 ABI 的一部分.

FutureWarning

PyObject *PyExc_ImportWarning

為 穩定 ABI 的一部分.

ImportWarning

PyObject *PyExc_PendingDeprecationWarning

為 穩定 ABI 的一部分.

PendingDeprecationWarning

PyObject *PyExc_ResourceWarning

為 穩定 ABI 的一部分 自 3.7 版本開始.

ResourceWarning

PyObject *PyExc_RuntimeWarning

為 穩定 ABI 的一部分.

RuntimeWarning

PyObject *PyExc_SyntaxWarning

為 穩定 ABI 的一部分.

SyntaxWarning

PyObject *PyExc_UnicodeWarning

為 穩定 ABI 的一部分.

UnicodeWarning

PyObject *PyExc_UserWarning

為 穩定 ABI 的一部分.

UserWarning

在 3.2 版被加入: PyExc_ResourceWarning。

在 3.10 版被加入: PyExc_EncodingWarning。

Tracebacks

PyTypeObject PyTraceBack_Type

為 穩定 ABI 的一部分.

Type object for traceback objects. This is available as types.TracebackType in the Python layer.

int PyTraceBack_Check(PyObject *op)

Return true if op is a traceback object, false otherwise. This function does not account for subtypes.

int PyTraceBack_Here(PyFrameObject *f)

為 穩定 ABI 的一部分.

Replace the __traceback__ attribute on the current exception with a new traceback prepending f to the existing chain.

Calling this function without an exception set is undefined behavior.

This function returns 0 on success, and returns -1 with an exception set on failure.

int PyTraceBack_Print(PyObject *tb, PyObject *f)

為 穩定 ABI 的一部分.

Write the traceback tb into the file f.

This function returns 0 on success, and returns -1 with an exception set on failure.

Defining extension modules

A C extension for CPython is a shared library (for example, a .so file on Linux, .pyd DLL on Windows), which is loadable into the Python process (for example, it is compiled with compatible compiler settings), and which exports an initialization function.

To be importable by default (that is, by importlib.machinery.ExtensionFileLoader), the shared library must be available on sys.path, and must be named after the module name plus an extension listed in importlib.machinery.EXTENSION_SUFFIXES.

備註

Building, packaging and distributing extension modules is best done with third-party tools, and is out of scope of this document. One suitable tool is Setuptools, whose documentation can be found at https://setuptools.pypa.io/en/latest/setuptools.html.

Normally, the initialization function returns a module definition initialized using PyModuleDef_Init(). This allows splitting the creation process into several phases:

Before any substantial code is executed, Python can determine which capabilities the module supports, and it can adjust the environment or refuse loading an incompatible extension.

By default, Python itself creates the module object -- that is, it does the equivalent of object.__new__() for classes. It also sets initial attributes like __package__ and __loader__.

Afterwards, the module object is initialized using extension-specific code -- the equivalent of __init__() on classes.

This is called multi-phase initialization to distinguish it from the legacy (but still supported) single-phase initialization scheme, where the initialization function returns a fully constructed module. See the single-phase-initialization section below for details.

在 3.5 版的變更: Added support for multi-phase initialization (PEP 489 [https://peps.python.org/pep-0489/]).

Multiple module instances

By default, extension modules are not singletons. For example, if the sys.modules entry is removed and the module is re-imported, a new module object is created, and typically populated with fresh method and type objects. The old module is subject to normal garbage collection. This mirrors the behavior of pure-Python modules.

Additional module instances may be created in sub-interpreters or after Python runtime reinitialization (Py_Finalize() and Py_Initialize()). In these cases, sharing Python objects between module instances would likely cause crashes or undefined behavior.

To avoid such issues, each instance of an extension module should be isolated: changes to one instance should not implicitly affect the others, and all state owned by the module, including references to Python objects, should be specific to a particular module instance. See 隔離擴充模組 for more details and a practical guide.

A simpler way to avoid these issues is raising an error on repeated initialization.

All modules are expected to support sub-interpreters, or otherwise explicitly signal a lack of support. This is usually achieved by isolation or blocking repeated initialization, as above. A module may also be limited to the main interpreter using the Py_mod_multiple_interpreters slot.

Initialization function

The initialization function defined by an extension module has the following signature:

PyObject *PyInit_modulename(void)

Its name should be PyInit_<name>, with <name> replaced by the name of the module.

For modules with ASCII-only names, the function must instead be named PyInit_<name>, with <name> replaced by the name of the module. When using Multi-phase initialization, non-ASCII module names are allowed. In this case, the initialization function name is PyInitU_<name>, with <name> encoded using Python's punycode encoding with hyphens replaced by underscores. In Python:

def initfunc_name(name):
    try:
        suffix = b'_' + name.encode('ascii')
    except UnicodeEncodeError:
        suffix = b'U_' + name.encode('punycode').replace(b'-', b'_')
    return b'PyInit' + suffix

It is recommended to define the initialization function using a helper macro:

PyMODINIT_FUNC

Declare an extension module initialization function. This macro:

specifies the PyObject* return type,

adds any special linkage declarations required by the platform, and

for C++, declares the function as extern "C".

For example, a module called spam would be defined like this:

static struct PyModuleDef spam_module = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "spam",
    ...
};

PyMODINIT_FUNC
PyInit_spam(void)
{
    return PyModuleDef_Init(&spam_module);
}

It is possible to export multiple modules from a single shared library by defining multiple initialization functions. However, importing them requires using symbolic links or a custom importer, because by default only the function corresponding to the filename is found. See the Multiple modules in one library [https://peps.python.org/pep-0489/#multiple-modules-in-one-library] section in PEP 489 [https://peps.python.org/pep-0489/] for details.

The initialization function is typically the only non-static item defined in the module's C source.

Multi-phase initialization

Normally, the initialization function (PyInit_modulename) returns a PyModuleDef instance with non-NULL m_slots. Before it is returned, the PyModuleDef instance must be initialized using the following function:

PyObject *PyModuleDef_Init(PyModuleDef *def)

為 穩定 ABI 的一部分 自 3.5 版本開始.

Ensure a module definition is a properly initialized Python object that correctly reports its type and a reference count.

Return def cast to PyObject*, or NULL if an error occurred.

Calling this function is required for Multi-phase initialization. It should not be used in other contexts.

Note that Python assumes that PyModuleDef structures are statically allocated. This function may return either a new reference or a borrowed one; this reference must not be released.

在 3.5 版被加入.

Legacy single-phase initialization

注意

Single-phase initialization is a legacy mechanism to initialize extension modules, with known drawbacks and design flaws. Extension module authors are encouraged to use multi-phase initialization instead.

In single-phase initialization, the initialization function (PyInit_modulename) should create, populate and return a module object. This is typically done using PyModule_Create() and functions like PyModule_AddObjectRef().

Single-phase initialization differs from the default in the following ways:

Single-phase modules are, or rather contain, “singletons”.

When the module is first initialized, Python saves the contents of the module's __dict__ (that is, typically, the module's functions and types).

For subsequent imports, Python does not call the initialization function again. Instead, it creates a new module object with a new __dict__, and copies the saved contents to it. For example, given a single-phase module _testsinglephase [1] that defines a function sum and an exception class error:

>>> import sys
>>> import _testsinglephase as one
>>> del sys.modules['_testsinglephase']
>>> import _testsinglephase as two
>>> one is two
False
>>> one.__dict__ is two.__dict__
False
>>> one.sum is two.sum
True
>>> one.error is two.error
True

The exact behavior should be considered a CPython implementation detail.

To work around the fact that PyInit_modulename does not take a spec argument, some state of the import machinery is saved and applied to the first suitable module created during the PyInit_modulename call. Specifically, when a sub-module is imported, this mechanism prepends the parent package name to the name of the module.

A single-phase PyInit_modulename function should create “its” module object as soon as possible, before any other module objects can be created.

Non-ASCII module names (PyInitU_modulename) are not supported.

Single-phase modules support module lookup functions like PyState_FindModule().

[1]

_testsinglephase is an internal module used in CPython's self-test suite; your installation may or may not include it.

工具

本章中的函式可用來執行各種工具任務，包括幫助 C 程式碼提升跨平臺可攜性 (portable)、在 C 中使用 Python module（模組）、以及剖析函式引數並基於 C 中的值來構建 Python 中的值等。

作業系統工具

系統函式

行程控制

引入模組

資料 marshal 操作的支援

剖析引數與建置數值

剖析引數

字串與緩衝區

數字

其他物件

API 函式

建置數值

字串轉換與格式化

Character classification and conversion

PyHash API

Reflection

編解碼器註冊表和支援函式

編解碼器查找 API

用於 Unicode 編碼錯誤處理程式的註冊 API

Codec utility variables

PyTime C API

型別

時鐘函式

原始時鐘函式

轉換函式

對 Perf Map 的支援

作業系統工具

PyObject *PyOS_FSPath(PyObject *path)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.6 版本開始.

Return the file system representation for path. If the object is a str or bytes object, then a new strong reference is returned. If the object implements the os.PathLike interface, then __fspath__() is returned as long as it is a str or bytes object. Otherwise TypeError is raised and NULL is returned.

在 3.6 版被加入.

int Py_FdIsInteractive(FILE *fp, const char *filename)

Return true (nonzero) if the standard I/O file fp with name filename is deemed interactive. This is the case for files for which isatty(fileno(fp)) is true. If the PyConfig.interactive is non-zero, this function also returns true if the filename pointer is NULL or if the name is equal to one of the strings '<stdin>' or '???'.

This function must not be called before Python is initialized.

void PyOS_BeforeFork()

為 穩定 ABI 的一部分 on platforms with fork() 自 3.7 版本開始.

Function to prepare some internal state before a process fork. This should be called before calling fork() or any similar function that clones the current process. Only available on systems where fork() is defined.

警告

The C fork() call should only be made from the "main" thread (of the "main" interpreter). The same is true for PyOS_BeforeFork().

在 3.7 版被加入.

void PyOS_AfterFork_Parent()

為 穩定 ABI 的一部分 on platforms with fork() 自 3.7 版本開始.

Function to update some internal state after a process fork. This should be called from the parent process after calling fork() or any similar function that clones the current process, regardless of whether process cloning was successful. Only available on systems where fork() is defined.

警告

The C fork() call should only be made from the "main" thread (of the "main" interpreter). The same is true for PyOS_AfterFork_Parent().

在 3.7 版被加入.

void PyOS_AfterFork_Child()

為 穩定 ABI 的一部分 on platforms with fork() 自 3.7 版本開始.

Function to update internal interpreter state after a process fork. This must be called from the child process after calling fork(), or any similar function that clones the current process, if there is any chance the process will call back into the Python interpreter. Only available on systems where fork() is defined.

警告

The C fork() call should only be made from the "main" thread (of the "main" interpreter). The same is true for PyOS_AfterFork_Child().

在 3.7 版被加入.

也參考

os.register_at_fork() allows registering custom Python functions to be called by PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

void PyOS_AfterFork()

為 穩定 ABI 的一部分 on platforms with fork().

Function to update some internal state after a process fork; this should be called in the new process if the Python interpreter will continue to be used. If a new executable is loaded into the new process, this function does not need to be called.

在 3.7 版之後被棄用: This function is superseded by PyOS_AfterFork_Child().

int PyOS_CheckStack()

為 穩定 ABI 的一部分 on platforms with USE_STACKCHECK 自 3.7 版本開始.

Return true when the interpreter runs out of stack space. This is a reliable check, but is only available when USE_STACKCHECK is defined (currently on certain versions of Windows using the Microsoft Visual C++ compiler). USE_STACKCHECK will be defined automatically; you should never change the definition in your own code.

typedef void (*PyOS_sighandler_t)(int)

為 穩定 ABI 的一部分.

PyOS_sighandler_t PyOS_getsig(int i)

為 穩定 ABI 的一部分.

Return the current signal handler for signal i. This is a thin wrapper around either sigaction() or signal(). Do not call those functions directly!

PyOS_sighandler_t PyOS_setsig(int i, PyOS_sighandler_t h)

為 穩定 ABI 的一部分.

Set the signal handler for signal i to be h; return the old signal handler. This is a thin wrapper around either sigaction() or signal(). Do not call those functions directly!

int PyOS_InterruptOccurred(void)

為 穩定 ABI 的一部分.

Check if a SIGINT signal has been received.

Returns 1 if a SIGINT has occurred and clears the signal flag, or 0 otherwise.

In most cases, you should prefer PyErr_CheckSignals() over this function. PyErr_CheckSignals() invokes the appropriate signal handlers for all pending signals, allowing Python code to handle the signal properly. This function only detects SIGINT and does not invoke any Python signal handlers.

This function is async-signal-safe and this function cannot fail. The caller must hold an attached thread state.

wchar_t *Py_DecodeLocale(const char *arg, size_t *size)

為 穩定 ABI 的一部分 自 3.7 版本開始.

警告

This function should not be called directly: use the PyConfig API with the PyConfig_SetBytesString() function which ensures that Python is preinitialized.

This function must not be called before Python is preinitialized and so that the LC_CTYPE locale is properly configured: see the Py_PreInitialize() function.

Decode a byte string from the filesystem encoding and error handler. If the error handler is surrogateescape error handler, undecodable bytes are decoded as characters in range U+DC80..U+DCFF; and if a byte sequence can be decoded as a surrogate character, the bytes are escaped using the surrogateescape error handler instead of decoding them.

Return a pointer to a newly allocated wide character string, use PyMem_RawFree() to free the memory. If size is not NULL, write the number of wide characters excluding the null character into *size

Return NULL on decoding error or memory allocation error. If size is not NULL, *size is set to (size_t)-1 on memory error or set to (size_t)-2 on decoding error.

The filesystem encoding and error handler are selected by PyConfig_Read(): see filesystem_encoding and filesystem_errors members of PyConfig.

Decoding errors should never happen, unless there is a bug in the C library.

Use the Py_EncodeLocale() function to encode the character string back to a byte string.

也參考

The PyUnicode_DecodeFSDefaultAndSize() and PyUnicode_DecodeLocaleAndSize() functions.

在 3.5 版被加入.

在 3.7 版的變更: The function now uses the UTF-8 encoding in the Python UTF-8 Mode.

在 3.8 版的變更: The function now uses the UTF-8 encoding on Windows if PyPreConfig.legacy_windows_fs_encoding is zero;

char *Py_EncodeLocale(const wchar_t *text, size_t *error_pos)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Encode a wide character string to the filesystem encoding and error handler. If the error handler is surrogateescape error handler, surrogate characters in the range U+DC80..U+DCFF are converted to bytes 0x80..0xFF.

Return a pointer to a newly allocated byte string, use PyMem_Free() to free the memory. Return NULL on encoding error or memory allocation error.

If error_pos is not NULL, *error_pos is set to (size_t)-1 on success, or set to the index of the invalid character on encoding error.

The filesystem encoding and error handler are selected by PyConfig_Read(): see filesystem_encoding and filesystem_errors members of PyConfig.

Use the Py_DecodeLocale() function to decode the bytes string back to a wide character string.

警告

This function must not be called before Python is preinitialized and so that the LC_CTYPE locale is properly configured: see the Py_PreInitialize() function.

也參考

The PyUnicode_EncodeFSDefault() and PyUnicode_EncodeLocale() functions.

在 3.5 版被加入.

在 3.7 版的變更: The function now uses the UTF-8 encoding in the Python UTF-8 Mode.

在 3.8 版的變更: The function now uses the UTF-8 encoding on Windows if PyPreConfig.legacy_windows_fs_encoding is zero.

FILE *Py_fopen(PyObject *path, const char *mode)

Similar to fopen(), but path is a Python object and an exception is set on error.

path must be a str object, a bytes object, or a path-like object.

On success, return the new file pointer. On error, set an exception and return NULL.

The file must be closed by Py_fclose() rather than calling directly fclose().

The file descriptor is created non-inheritable (PEP 446 [https://peps.python.org/pep-0446/]).

The caller must have an attached thread state.

在 3.14 版被加入.

int Py_fclose(FILE *file)

Close a file that was opened by Py_fopen().

On success, return 0. On error, return EOF and errno is set to indicate the error. In either case, any further access (including another call to Py_fclose()) to the stream results in undefined behavior.

在 3.14 版被加入.

系統函式

These are utility functions that make functionality from the sys module accessible to C code. They all work with the current interpreter thread's sys module's dict, which is contained in the internal thread state structure.

PyObject *PySys_GetObject(const char *name)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Return the object name from the sys module or NULL if it does not exist, without setting an exception.

int PySys_SetObject(const char *name, PyObject *v)

為 穩定 ABI 的一部分.

Set name in the sys module to v unless v is NULL, in which case name is deleted from the sys module. Returns 0 on success, -1 on error.

void PySys_ResetWarnOptions()

為 穩定 ABI 的一部分.

Reset sys.warnoptions to an empty list. This function may be called prior to Py_Initialize().

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Clear sys.warnoptions and warnings.filters instead.

void PySys_WriteStdout(const char *format, ...)

為 穩定 ABI 的一部分.

Write the output string described by format to sys.stdout. No exceptions are raised, even if truncation occurs (see below).

format should limit the total size of the formatted output string to 1000 bytes or less -- after 1000 bytes, the output string is truncated. In particular, this means that no unrestricted "%s" formats should occur; these should be limited using "%.<N>s" where <N> is a decimal number calculated so that <N> plus the maximum size of other formatted text does not exceed 1000 bytes. Also watch out for "%f", which can print hundreds of digits for very large numbers.

If a problem occurs, or sys.stdout is unset, the formatted message is written to the real (C level) stdout.

void PySys_WriteStderr(const char *format, ...)

為 穩定 ABI 的一部分.

As PySys_WriteStdout(), but write to sys.stderr or stderr instead.

void PySys_FormatStdout(const char *format, ...)

為 穩定 ABI 的一部分.

Function similar to PySys_WriteStdout() but format the message using PyUnicode_FromFormatV() and don't truncate the message to an arbitrary length.

在 3.2 版被加入.

void PySys_FormatStderr(const char *format, ...)

為 穩定 ABI 的一部分.

As PySys_FormatStdout(), but write to sys.stderr or stderr instead.

在 3.2 版被加入.

PyObject *PySys_GetXOptions()

回傳值：借用參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Return the current dictionary of -X options, similarly to sys._xoptions. On error, NULL is returned and an exception is set.

在 3.2 版被加入.

int PySys_Audit(const char *event, const char *format, ...)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Raise an auditing event with any active hooks. Return zero for success and non-zero with an exception set on failure.

The event string argument must not be NULL.

If any hooks have been added, format and other arguments will be used to construct a tuple to pass. Apart from N, the same format characters as used in Py_BuildValue() are available. If the built value is not a tuple, it will be added into a single-element tuple.

The N format option must not be used. It consumes a reference, but since there is no way to know whether arguments to this function will be consumed, using it may cause reference leaks.

Note that # format characters should always be treated as Py_ssize_t, regardless of whether PY_SSIZE_T_CLEAN was defined.

sys.audit() performs the same function from Python code.

請參閱 PySys_AuditTuple()。

在 3.8 版被加入.

在 3.8.2 版的變更: Require Py_ssize_t for # format characters. Previously, an unavoidable deprecation warning was raised.

int PySys_AuditTuple(const char *event, PyObject *args)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Similar to PySys_Audit(), but pass arguments as a Python object. args must be a tuple. To pass no arguments, args can be NULL.

在 3.13 版被加入.

int PySys_AddAuditHook(Py_AuditHookFunction hook, void *userData)

Append the callable hook to the list of active auditing hooks. Return zero on success and non-zero on failure. If the runtime has been initialized, also set an error on failure. Hooks added through this API are called for all interpreters created by the runtime.

The userData pointer is passed into the hook function. Since hook functions may be called from different runtimes, this pointer should not refer directly to Python state.

This function is safe to call before Py_Initialize(). When called after runtime initialization, existing audit hooks are notified and may silently abort the operation by raising an error subclassed from Exception (other errors will not be silenced).

The hook function is always called with an attached thread state by the Python interpreter that raised the event.

See PEP 578 [https://peps.python.org/pep-0578/] for a detailed description of auditing. Functions in the runtime and standard library that raise events are listed in the audit events table. Details are in each function's documentation.

If the interpreter is initialized, this function raises an auditing event sys.addaudithook with no arguments. If any existing hooks raise an exception derived from Exception, the new hook will not be added and the exception is cleared. As a result, callers cannot assume that their hook has been added unless they control all existing hooks.

typedef int (*Py_AuditHookFunction)(const char *event, PyObject *args, void *userData)

The type of the hook function. event is the C string event argument passed to PySys_Audit() or PySys_AuditTuple(). args is guaranteed to be a PyTupleObject. userData is the argument passed to PySys_AddAuditHook().

在 3.8 版被加入.

行程控制

void Py_FatalError(const char *message)

為 穩定 ABI 的一部分.

Print a fatal error message and kill the process. No cleanup is performed. This function should only be invoked when a condition is detected that would make it dangerous to continue using the Python interpreter; e.g., when the object administration appears to be corrupted. On Unix, the standard C library function abort() is called which will attempt to produce a core file.

The Py_FatalError() function is replaced with a macro which logs automatically the name of the current function, unless the Py_LIMITED_API macro is defined.

在 3.9 版的變更: Log the function name automatically.

void Py_Exit(int status)

為 穩定 ABI 的一部分.

Exit the current process. This calls Py_FinalizeEx() and then calls the standard C library function exit(status). If Py_FinalizeEx() indicates an error, the exit status is set to 120.

在 3.6 版的變更: Errors from finalization no longer ignored.

int Py_AtExit(void (*func)())

為 穩定 ABI 的一部分.

Register a cleanup function to be called by Py_FinalizeEx(). The cleanup function will be called with no arguments and should return no value. At most 32 cleanup functions can be registered. When the registration is successful, Py_AtExit() returns 0; on failure, it returns -1. The cleanup function registered last is called first. Each cleanup function will be called at most once. Since Python's internal finalization will have completed before the cleanup function, no Python APIs should be called by func.

也參考

PyUnstable_AtExit() for passing a void *data argument.

引入模組

PyObject *PyImport_ImportModule(const char *name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

這是 PyImport_Import() 的包裝器 (wrapper)，它使用 const char* 作為引數，而不是 PyObject*。

PyObject *PyImport_ImportModuleNoBlock(const char *name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

這個函式是 PyImport_ImportModule() 的已棄用別名。

在 3.3 版的變更: 當引入鎖被其他執行緒持有時，這個函式過去會立即失敗。但在 Python 3.3 中，鎖機制轉換成針對每個模組的鎖 (per-module lock) 來達到大多數目的，所以這個函式的特殊行為就不再需要了。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: 請改用 PyImport_ImportModule()。

PyObject *PyImport_ImportModuleEx(const char *name, PyObject *globals, PyObject *locals, PyObject *fromlist)

回傳值：新的參照。

引入一個模組。這最好透過參考 Python 內建函式 __import__() 來說明。

回傳值是對引入的模組或頂層套件的新參照，或者是 NULL，失敗時會設定例外。就像 __import__() 一樣，當要求一個套件的子模組時，回傳值通常是頂層套件，除非給定一個非空的 fromlist。

失敗的引入會移除不完整的模組物件，就像 PyImport_ImportModule() 一樣。

PyObject *PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

引入一個模組。這最好透過參考內建的 Python 函式 __import__() 來說明，因為標準的 __import__() 函式會直接呼叫這個函式。

回傳值是對引入的模組或頂層套件的新參照，或者是 NULL，失敗時會設定例外。就像 __import__() 一樣，當要求一個套件的子模組時，回傳值通常是頂層套件，除非給定一個非空的 fromlist。

在 3.3 版被加入.

PyObject *PyImport_ImportModuleLevel(const char *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)

回傳值：新的參照。 為 穩定 ABI 的一部分.

類似於 PyImport_ImportModuleLevelObject()，但名稱是 UTF-8 編碼字串，而不是 Unicode 物件。

在 3.3 版的變更: 不再接受負的 level 值。

PyObject *PyImport_Import(PyObject *name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

這是一個較高階的介面，用來呼叫目前的「引入掛勾函式 (import hook function)」（明確的 level 為 0，表示絕對引入 (absolute import)）。它從目前全域變數的 __builtins__ 中呼叫 __import__() 函式。這表示引入是使用目前環境所安裝的引入掛勾來完成的。

此函式總是使用絕對引入。

PyObject *PyImport_ReloadModule(PyObject *m)

回傳值：新的參照。 為 穩定 ABI 的一部分.

重新載入一個模組。回傳重新載入模組的新參照，或在失敗時回傳 NULL 並設定例外（在這種情況下模組仍然存在）。

PyObject *PyImport_AddModuleRef(const char *name)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.13 版本開始.

回傳與模組名稱對應的模組物件。

name 引數的形式可以是 package.module。首先檢查模組字典中是否有，如果沒有，則建立新的模組並插入模組字典中。

成功時回傳模組的強參照。失敗時回傳 NULL 並設定例外。

模組名稱 name 是以 UTF-8 解碼。

這個函式不會載入或引入模組；如果模組尚未載入，你將會得到一個空的模組物件。使用 PyImport_ImportModule() 或其變體來引入一個模組。如果尚未存在，則不會建立由 name 的點名稱 (dotted name) 所隱含的套件結構。

在 3.13 版被加入.

PyObject *PyImport_AddModuleObject(PyObject *name)

回傳值：借用參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

類似於 PyImport_AddModuleRef()，但是會回傳一個借用參照且 name 為 Python 的 str 物件。

在 3.3 版被加入.

PyObject *PyImport_AddModule(const char *name)

回傳值：借用參照。 為 穩定 ABI 的一部分.

類似於 PyImport_AddModuleRef()，但是會回傳一個借用參照。

PyObject *PyImport_ExecCodeModule(const char *name, PyObject *co)

回傳值：新的參照。 為 穩定 ABI 的一部分.

給定一個模組名稱（可能為 package.module 的形式），以及一個從 Python 位元組碼檔讀取或從內建函式 compile() 取得的程式碼物件，載入模組。回傳模組物件的新參照，如果發生錯誤，則回傳 NULL 並設定例外。在出錯的情況下，name 會從 sys.modules 中移除，即使 name 在進入 PyImport_ExecCodeModule() 時已經在 sys.modules 中。在 sys.modules 中留下未完全初始化的模組是很危險的，因為這種模組的引入無法知道模組物件處於未知狀態（且相對於模組作者的意圖，很可能已經損壞）。

如果尚未設定，模組的 __spec__ 和 __loader__ 將會被設定為適當的值。規格的載入器將被設定為模組的 __loader__（如果有設定），否則將被設定為 SourceFileLoader 的實例。

模組的 __file__ 屬性將會設定為程式碼物件的 co_filename。如果適用，__cached__ 也會被設定。

如果模組已經被引入，這個函式會重新載入模組。請參閱 PyImport_ReloadModule() 以取得重新載入模組的預期方法。

如果 name 指向形式為 package.module 的點名稱，則任何尚未建立的套件結構仍不會被建立。

另請參閱 PyImport_ExecCodeModuleEx() 及 PyImport_ExecCodeModuleWithPathnames()。

在 3.12 版的變更: __cached__ 和 __loader__ 的設定已被棄用。請參閱 ModuleSpec 以取得替代方案。

PyObject *PyImport_ExecCodeModuleEx(const char *name, PyObject *co, const char *pathname)

回傳值：新的參照。 為 穩定 ABI 的一部分.

類似於 PyImport_ExecCodeModule()，但是如果 pathname 不是 NULL，模組物件的 __file__ 屬性會被設定為 pathname。

另請參閱 PyImport_ExecCodeModuleWithPathnames()。

PyObject *PyImport_ExecCodeModuleObject(PyObject *name, PyObject *co, PyObject *pathname, PyObject *cpathname)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

類似於 PyImport_ExecCodeModuleEx()，但是如果 cpathname 不是 NULL，模組物件的 __cached__ 屬性會被設定為 cpathname。在這三個函式中，這是首選的函式。

在 3.3 版被加入.

在 3.12 版的變更: 設定 __cached__ 已被棄用。請參閱 ModuleSpec 以取得替代方案。

PyObject *PyImport_ExecCodeModuleWithPathnames(const char *name, PyObject *co, const char *pathname, const char *cpathname)

回傳值：新的參照。 為 穩定 ABI 的一部分.

類似於 PyImport_ExecCodeModuleObject()，但是 name、pathname 和 cpathname 是 UTF-8 編碼的字串。如果 pathname 被設定為 NULL，也會嘗試從 cpathname 中找出 pathname 的值應該是什麼。

在 3.2 版被加入.

在 3.3 版的變更: 如果只提供了位元組碼路徑，則在計算原始碼路徑時使用 imp.source_from_cache()。

在 3.12 版的變更: 不再使用已被移除的 imp 模組。

long PyImport_GetMagicNumber()

為 穩定 ABI 的一部分.

回傳 Python 位元組碼檔案（也稱為 .pyc 檔案）的魔術數字（magic number）。魔術數字應該出現在位元組碼檔案的前四個位元組，以小端序（little-endian）位元組順序排列。錯誤時會回傳 -1。

在 3.3 版的變更: 當失敗時回傳 -1。

const char *PyImport_GetMagicTag()

為 穩定 ABI 的一部分.

回傳 PEP 3147 [https://peps.python.org/pep-3147/] 格式 Python 位元組碼檔名的魔術標籤字串。請記住，sys.implementation.cache_tag 的值是權威的，應該使用它來取代這個函式。

在 3.2 版被加入.

PyObject *PyImport_GetModuleDict()

回傳值：借用參照。 為 穩定 ABI 的一部分.

回傳用於模組管理的字典（也稱為 sys.modules）。請注意，這是一個針對每個直譯器的變數 (per-interpreter variable)。

PyObject *PyImport_GetModule(PyObject *name)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.8 版本開始.

回傳已以給定名稱引入的模組。如果模組尚未引入，則會回傳 NULL 但不會設定錯誤。如果查找失敗，則回傳 NULL 並設定錯誤。

在 3.7 版被加入.

PyObject *PyImport_GetImporter(PyObject *path)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳 sys.path/pkg.__path__ 項 path 的查找器物件 (finder object)，可能的方式是從 sys.path_importer_cache 字典取得。如果它還沒有被快取，就遍歷 sys.path_hooks 直到找到可以處理路徑項的掛勾。如果沒有掛勾可以處理，則回傳 None；這會告訴我們的呼叫者 path based finder 找不到這個路徑項的查找器。將結果快取到 sys.path_importer_cache。回傳查找器物件的新參照。

int PyImport_ImportFrozenModuleObject(PyObject *name)

為 穩定 ABI 的一部分 自 3.7 版本開始.

載入一個名為 name 的凍結模組。成功則回傳 1，找不到模組則回傳 0，初始化失敗則回傳 -1 並設定例外。要在成功載入時存取引入的模組，請使用 PyImport_ImportModule()。（請注意這個名稱並不恰當 --- 如果模組已經被引入，這個函式會重新載入模組）。

在 3.3 版被加入.

在 3.4 版的變更: 不會再於模組設定 __file__ 屬性。

int PyImport_ImportFrozenModule(const char *name)

為 穩定 ABI 的一部分.

類似於 PyImport_ImportFrozenModuleObject()，但名稱是 UTF-8 編碼字串，而不是 Unicode 物件。

struct _frozen

這是由 freeze 工具程式產生的凍結模組描述器的結構型別定義（請參閱 Python 原始碼發行版中的 Tools/freeze/）。它的定義在 Include/import.h 中，為：

struct _frozen {
    const char *name;
    const unsigned char *code;
    int size;
    bool is_package;
};

在 3.11 版的變更: 新的 is_package 欄位指出模組是否為套件。這取代了將 size 欄位設定為負值的方式。

const struct _frozen *PyImport_FrozenModules

這個指標會被初始化為指向一個 _frozen 記錄的陣列，以一個其成員都是 NULL 或 0 的記錄為結尾。當一個凍結的模組被引入時，它會在這個表格中被搜尋。第三方程式碼可以利用這一點來提供一個動態建立的凍結模組集合。

int PyImport_AppendInittab(const char *name, PyObject *(*initfunc)(void))

為 穩定 ABI 的一部分.

新增單一模組到現有的內建模組表格。這是 PyImport_ExtendInittab() 的便利包裝器，如果表格無法擴充會回傳 -1。新的模組可以用 name 的名稱引入，並使用函式 initfunc 作為第一次嘗試引入時呼叫的初始化函式。這應該在 Py_Initialize() 之前呼叫。

struct _inittab

描述內建模組列表中單一項目的結構。嵌入 Python 的程式可以使用這些結構的陣列與 PyImport_ExtendInittab() 結合來提供額外的內建模組。這個結構包含兩個成員：

const char *name

模組名稱，為 ASCII 編碼的字串。

PyObject *(*initfunc)(void)

內建於直譯器中的模組的初始化函式。

int PyImport_ExtendInittab(struct _inittab *newtab)

新增一個模組集合到內建模組表格。newtab 陣列必須以包含 NULL 的 name 欄位的哨兵項目（sentinel entry）結尾；如果沒有提供哨兵值，可能會導致記憶體錯誤。成功時會回傳 0，如果沒有足夠的記憶體可以分配來擴充內部表格則回傳 -1。在失敗的情況下，沒有模組會被加入內部表格。這個函式必須在 Py_Initialize() 之前呼叫。

如果 Python 被多次初始化，PyImport_AppendInittab() 或 PyImport_ExtendInittab() 必須在每次 Python 初始化之前被呼叫。

struct _inittab *PyImport_Inittab

Python 初始化所使用的內建模組表格。請勿直接使用它，請改用 PyImport_AppendInittab() 與 PyImport_ExtendInittab()。

PyObject *PyImport_ImportModuleAttr(PyObject *mod_name, PyObject *attr_name)

回傳值：新的參照。

引入模組 mod_name 並取得其屬性 attr_name。

名稱必須是 Python str 物件。

結合 PyImport_Import() 和 PyObject_GetAttr() 的輔助函式。例如，如果找不到模組，它會引發 ImportError，如果屬性不存在，則會引發 AttributeError。

在 3.14 版被加入.

PyObject *PyImport_ImportModuleAttrString(const char *mod_name, const char *attr_name)

回傳值：新的參照。

類似於 PyImport_ImportModuleAttr()，但名稱是 UTF-8 編碼字串，而不是 Python str 物件。

在 3.14 版被加入.

資料 marshal 操作的支援

這些例程允許 C 程式碼使用與 marshal 模組相同的資料格式來處理序列化物件。有函式可以將資料寫入序列化格式，還有其他函式可以用來讀取回資料。用來儲存 marshal 過的資料的檔案必須以二進位模式開啟。

數值會以最低有效位元組 (the least significant byte) 優先的方式儲存。

The module supports several versions of the data format; see the Python module documentation for details.

Py_MARSHAL_VERSION

The current format version. See marshal.version.

void PyMarshal_WriteLongToFile(long value, FILE *file, int version)

將一個 long 整數 value marshal 為 file。這只會寫入 value 的最低有效 32 位元；無論原生 long 型別的大小如何。version 表示檔案的格式。

這個函式可能會失敗，這時會設定錯誤指示器。使用 PyErr_Occurred() 來檢查是否發生錯誤。

void PyMarshal_WriteObjectToFile(PyObject *value, FILE *file, int version)

將一個 Python 物件 value marshal 為 file。version 表示檔案的格式。

這個函式可能會失敗，這時會設定錯誤指示器。使用 PyErr_Occurred() 來檢查是否發生錯誤。

PyObject *PyMarshal_WriteObjectToString(PyObject *value, int version)

回傳值：新的參照。

回傳一個位元組物件，包含 value 的 marshal 表示。version 為檔案的格式。

以下函式允許將 marshal 過後的值讀取回來。

long PyMarshal_ReadLongFromFile(FILE *file)

從一個為讀取而開啟的 FILE* 中的資料串流回傳一個 C long。無論 long 的原生大小如何，這個函式只能讀取 32 位元的值。

在錯誤發生時，會設定合適的例外（EOFError）並回傳 -1。

int PyMarshal_ReadShortFromFile(FILE *file)

從一個為讀取而開啟的 FILE* 中的資料串流回傳一個 C short。無論 short 的原生大小如何，這個函式只能讀取 16 位元的值。

在錯誤發生時，會設定合適的例外（EOFError）並回傳 -1。

PyObject *PyMarshal_ReadObjectFromFile(FILE *file)

回傳值：新的參照。

從一個為讀取而開啟的 FILE* 中的資料串流回傳一個 Python 物件。

在錯誤發生時，會設定合適的例外（EOFError、ValueError 或 TypeError）並回傳 NULL。

PyObject *PyMarshal_ReadLastObjectFromFile(FILE *file)

回傳值：新的參照。

從一個為讀取而開啟的 FILE* 中的資料串流回傳一個 Python 物件。與 PyMarshal_ReadObjectFromFile() 不同，這個函式假設不會從檔案中讀取其他物件，允許它積極地將檔案資料載入記憶體，以便反序列化可以從記憶體中的資料操作，而不是從檔案中逐位元組讀取。只有在確定不會從檔案中讀取其他內容時，才使用這個變體。

在錯誤發生時，會設定合適的例外（EOFError、ValueError 或 TypeError）並回傳 NULL。

PyObject *PyMarshal_ReadObjectFromString(const char *data, Py_ssize_t len)

回傳值：新的參照。

從一個包含 len 位元組、被 data 指向的位元組緩衝區中的資料串流回傳一個 Python 物件。

在錯誤發生時，會設定合適的例外（EOFError、ValueError 或 TypeError）並回傳 NULL。

剖析引數與建置數值

These functions are useful when creating your own extension functions and methods. Additional information and examples are available in 擴充和嵌入 Python 直譯器.

The first three of these functions described, PyArg_ParseTuple(), PyArg_ParseTupleAndKeywords(), and PyArg_Parse(), all use format strings which are used to tell the function about the expected arguments. The format strings use the same syntax for each of these functions.

剖析引數

A format string consists of zero or more "format units." A format unit describes one Python object; it is usually a single character or a parenthesized sequence of format units. With a few exceptions, a format unit that is not a parenthesized sequence normally corresponds to a single address argument to these functions. In the following description, the quoted form is the format unit; the entry in (round) parentheses is the Python object type that matches the format unit; and the entry in [square] brackets is the type of the C variable(s) whose address should be passed.

字串與緩衝區

備註

On Python 3.12 and older, the macro PY_SSIZE_T_CLEAN must be defined before including Python.h to use all # variants of formats (s#, y#, etc.) explained below. This is not necessary on Python 3.13 and later.

These formats allow accessing an object as a contiguous chunk of memory. You don't have to provide raw storage for the returned unicode or bytes area.

Unless otherwise stated, buffers are not NUL-terminated.

There are three ways strings and buffers can be converted to C:

Formats such as y* and s* fill a Py_buffer structure. This locks the underlying buffer so that the caller can subsequently use the buffer even inside a Py_BEGIN_ALLOW_THREADS block without the risk of mutable data being resized or destroyed. As a result, you have to call PyBuffer_Release() after you have finished processing the data (or in any early abort case).

The es, es#, et and et# formats allocate the result buffer. You have to call PyMem_Free() after you have finished processing the data (or in any early abort case).

Other formats take a str or a read-only bytes-like object, such as bytes, and provide a const char * pointer to its buffer. In this case the buffer is "borrowed": it is managed by the corresponding Python object, and shares the lifetime of this object. You won't have to release any memory yourself.

To ensure that the underlying buffer may be safely borrowed, the object's PyBufferProcs.bf_releasebuffer field must be NULL. This disallows common mutable objects such as bytearray, but also some read-only objects such as memoryview of bytes.

Besides this bf_releasebuffer requirement, there is no check to verify whether the input object is immutable (e.g. whether it would honor a request for a writable buffer, or whether another thread can mutate the data).

s (str) [const char *]

Convert a Unicode object to a C pointer to a character string. A pointer to an existing string is stored in the character pointer variable whose address you pass. The C string is NUL-terminated. The Python string must not contain embedded null code points; if it does, a ValueError exception is raised. Unicode objects are converted to C strings using 'utf-8' encoding. If this conversion fails, a UnicodeError is raised.

備註

This format does not accept bytes-like objects. If you want to accept filesystem paths and convert them to C character strings, it is preferable to use the O& format with PyUnicode_FSConverter() as converter.

在 3.5 版的變更: Previously, TypeError was raised when embedded null code points were encountered in the Python string.

s* (str 或 bytes-like object) [Py_buffer]

This format accepts Unicode objects as well as bytes-like objects. It fills a Py_buffer structure provided by the caller. In this case the resulting C string may contain embedded NUL bytes. Unicode objects are converted to C strings using 'utf-8' encoding.

s# (str、唯讀的 bytes-like object) [const char *, Py_ssize_t]

Like s*, except that it provides a borrowed buffer. The result is stored into two C variables, the first one a pointer to a C string, the second one its length. The string may contain embedded null bytes. Unicode objects are converted to C strings using 'utf-8' encoding.

z (str 或 None) [const char *]

Like s, but the Python object may also be None, in which case the C pointer is set to NULL.

z* (str、bytes-like object 或 None) [Py_buffer]

Like s*, but the Python object may also be None, in which case the buf member of the Py_buffer structure is set to NULL.

z# (str、唯讀的 bytes-like object 或 None) [const char *, Py_ssize_t]

Like s#, but the Python object may also be None, in which case the C pointer is set to NULL.

y (唯讀的 bytes-like object) [const char *]

This format converts a bytes-like object to a C pointer to a borrowed character string; it does not accept Unicode objects. The bytes buffer must not contain embedded null bytes; if it does, a ValueError exception is raised.

在 3.5 版的變更: Previously, TypeError was raised when embedded null bytes were encountered in the bytes buffer.

y* (bytes-like object) [Py_buffer]

This variant on s* doesn't accept Unicode objects, only bytes-like objects. This is the recommended way to accept binary data.

y# (唯讀的 bytes-like object) [const char *, Py_ssize_t]

This variant on s# doesn't accept Unicode objects, only bytes-like objects.

S (bytes) [PyBytesObject *]

Requires that the Python object is a bytes object, without attempting any conversion. Raises TypeError if the object is not a bytes object. The C variable may also be declared as PyObject*.

Y (bytearray) [PyByteArrayObject *]

Requires that the Python object is a bytearray object, without attempting any conversion. Raises TypeError if the object is not a bytearray object. The C variable may also be declared as PyObject*.

U (str) [PyObject *]

Requires that the Python object is a Unicode object, without attempting any conversion. Raises TypeError if the object is not a Unicode object. The C variable may also be declared as PyObject*.

w* (可讀寫 bytes-like object) [Py_buffer]

This format accepts any object which implements the read-write buffer interface. It fills a Py_buffer structure provided by the caller. The buffer may contain embedded null bytes. The caller has to call PyBuffer_Release() when it is done with the buffer.

es (str) [const char *encoding, char **buffer]

This variant on s is used for encoding Unicode into a character buffer. It only works for encoded data without embedded NUL bytes.

This format requires two arguments. The first is only used as input, and must be a const char* which points to the name of an encoding as a NUL-terminated string, or NULL, in which case 'utf-8' encoding is used. An exception is raised if the named encoding is not known to Python. The second argument must be a char**; the value of the pointer it references will be set to a buffer with the contents of the argument text. The text will be encoded in the encoding specified by the first argument.

PyArg_ParseTuple() will allocate a buffer of the needed size, copy the encoded data into this buffer and adjust *buffer to reference the newly allocated storage. The caller is responsible for calling PyMem_Free() to free the allocated buffer after use.

et (str、bytes 或 bytearray) [const char *encoding, char **buffer]

Same as es except that byte string objects are passed through without recoding them. Instead, the implementation assumes that the byte string object uses the encoding passed in as parameter.

es# (str) [const char *encoding, char **buffer, Py_ssize_t *buffer_length]

This variant on s# is used for encoding Unicode into a character buffer. Unlike the es format, this variant allows input data which contains NUL characters.

It requires three arguments. The first is only used as input, and must be a const char* which points to the name of an encoding as a NUL-terminated string, or NULL, in which case 'utf-8' encoding is used. An exception is raised if the named encoding is not known to Python. The second argument must be a char**; the value of the pointer it references will be set to a buffer with the contents of the argument text. The text will be encoded in the encoding specified by the first argument. The third argument must be a pointer to an integer; the referenced integer will be set to the number of bytes in the output buffer.

有兩個操作模式：

If *buffer points a NULL pointer, the function will allocate a buffer of the needed size, copy the encoded data into this buffer and set *buffer to reference the newly allocated storage. The caller is responsible for calling PyMem_Free() to free the allocated buffer after usage.

If *buffer points to a non-NULL pointer (an already allocated buffer), PyArg_ParseTuple() will use this location as the buffer and interpret the initial value of *buffer_length as the buffer size. It will then copy the encoded data into the buffer and NUL-terminate it. If the buffer is not large enough, a ValueError will be set.

In both cases, *buffer_length is set to the length of the encoded data without the trailing NUL byte.

et# (str, bytes or bytearray) [const char *encoding, char **buffer, Py_ssize_t *buffer_length]

Same as es# except that byte string objects are passed through without recoding them. Instead, the implementation assumes that the byte string object uses the encoding passed in as parameter.

在 3.12 版的變更: u, u#, Z, and Z# are removed because they used a legacy Py_UNICODE* representation.

數字

These formats allow representing Python numbers or single characters as C numbers. Formats that require int, float or complex can also use the corresponding special methods __index__(), __float__() or __complex__() to convert the Python object to the required type.

For signed integer formats, OverflowError is raised if the value is out of range for the C type. For unsigned integer formats, no range checking is done --- the most significant bits are silently truncated when the receiving field is too small to receive the value.

b (int) [unsigned char]

將一個 Python 非負整數轉換成無符號 tiny integer（小整數），儲存在 C 的 unsigned

B (int) [unsigned char]

將一個 Python 整數轉換成 tiny integer，轉換過程無溢位檢查，儲存在 C 的 unsigned char。

h (int) [short int]

將一個 Python 整數轉換成 C 的 short int。

H (int) [unsigned short int]

將一個 Python 整數轉換成 C 的 unsigned short int，轉換過程無溢位檢查。

i (int) [int]

將一個 Python 整數轉換成 C 的 int。

I (int) [unsigned int]

將一個 Python 整數轉換成 C 的 unsigned int，轉換過程無溢位檢查。

l (int) [long int]

將一個 Python 整數轉換成 C 的 long int。

k (int) [unsigned long]

將一個 Python 整數轉換成 C 的 unsigned long，轉換過程無溢位檢查。

在 3.14 版的變更: 如有提供則使用 __index__()。

L (int) [long long]

將一個 Python 整數轉換成 C 的 long long。

K (int) [unsigned long long]

將一個 Python 整數轉換成 C 的 unsigned long long，轉換過程無溢位檢查。

在 3.14 版的變更: 如有提供則使用 __index__()。

n (int) [Py_ssize_t]

將一個 Python 整數轉換成 C 的 Py_ssize_t。

c (bytes 或長度為 1 的 bytearray) [char]

Convert a Python byte, represented as a bytes or bytearray object of length 1, to a C char.

在 3.3 版的變更: 允許 bytearray 物件。

C (長度為 1 的 str) [int]

Convert a Python character, represented as a str object of length 1, to a C int.

f (float) [float]

將一個 Python 浮點數轉換成 C 的 :c:type:float。

d (float) [double]

將一個 Python 浮點數轉換成 C 的 :c:type:double。

D (complex) [Py_complex]

將一個 Python 複數轉換成 C 的 Py_complex 結構。

其他物件

O (object) [PyObject *]

Store a Python object (without any conversion) in a C object pointer. The C program thus receives the actual object that was passed. A new strong reference to the object is not created (i.e. its reference count is not increased). The pointer stored is not NULL.

O! (object) [typeobject, PyObject *]

Store a Python object in a C object pointer. This is similar to O, but takes two C arguments: the first is the address of a Python type object, the second is the address of the C variable (of type PyObject*) into which the object pointer is stored. If the Python object does not have the required type, TypeError is raised.

O& (object) [converter, address]

Convert a Python object to a C variable through a converter function. This takes two arguments: the first is a function, the second is the address of a C variable (of arbitrary type), converted to void*. The converter function in turn is called as follows:

status = converter(object, address);

where object is the Python object to be converted and address is the void* argument that was passed to the PyArg_Parse* function. The returned status should be 1 for a successful conversion and 0 if the conversion has failed. When the conversion fails, the converter function should raise an exception and leave the content of address unmodified.

If the converter returns Py_CLEANUP_SUPPORTED, it may get called a second time if the argument parsing eventually fails, giving the converter a chance to release any memory that it had already allocated. In this second call, the object parameter will be NULL; address will have the same value as in the original call.

Examples of converters: PyUnicode_FSConverter() and PyUnicode_FSDecoder().

在 3.1 版的變更: 新增 Py_CLEANUP_SUPPORTED。

p (bool) [int]

Tests the value passed in for truth (a boolean predicate) and converts the result to its equivalent C true/false integer value. Sets the int to 1 if the expression was true and 0 if it was false. This accepts any valid Python value. See 真值檢測 for more information about how Python tests values for truth.

在 3.3 版被加入.

(items) (sequence) [matching-items]

The object must be a Python sequence (except str, bytes or bytearray) whose length is the number of format units in items. The C arguments must correspond to the individual format units in items. Format units for sequences may be nested.

If items contains format units which store a borrowed buffer (s, s#, z, z#, y, or y#) or a borrowed reference (S, Y, U, O, or O!), the object must be a Python tuple. The converter for the O& format unit in items must not store a borrowed buffer or a borrowed reference.

在 3.14 版的變更: str and bytearray objects no longer accepted as a sequence.

在 3.14 版之後被棄用: Non-tuple sequences are deprecated if items contains format units which store a borrowed buffer or a borrowed reference.

A few other characters have a meaning in a format string. These may not occur inside nested parentheses. They are:

|

Indicates that the remaining arguments in the Python argument list are optional. The C variables corresponding to optional arguments should be initialized to their default value --- when an optional argument is not specified, PyArg_ParseTuple() does not touch the contents of the corresponding C variable(s).

$

PyArg_ParseTupleAndKeywords() only: Indicates that the remaining arguments in the Python argument list are keyword-only. Currently, all keyword-only arguments must also be optional arguments, so | must always be specified before $ in the format string.

在 3.3 版被加入.

:

The list of format units ends here; the string after the colon is used as the function name in error messages (the "associated value" of the exception that PyArg_ParseTuple() raises).

;

The list of format units ends here; the string after the semicolon is used as the error message instead of the default error message. : and ; mutually exclude each other.

Note that any Python object references which are provided to the caller are borrowed references; do not release them (i.e. do not decrement their reference count)!

Additional arguments passed to these functions must be addresses of variables whose type is determined by the format string; these are used to store values from the input tuple. There are a few cases, as described in the list of format units above, where these parameters are used as input values; they should match what is specified for the corresponding format unit in that case.

For the conversion to succeed, the arg object must match the format and the format must be exhausted. On success, the PyArg_Parse* functions return true, otherwise they return false and raise an appropriate exception. When the PyArg_Parse* functions fail due to conversion failure in one of the format units, the variables at the addresses corresponding to that and the following format units are left untouched.

API 函式

int PyArg_ParseTuple(PyObject *args, const char *format, ...)

為 穩定 ABI 的一部分.

Parse the parameters of a function that takes only positional parameters into local variables. Returns true on success; on failure, it returns false and raises the appropriate exception.

int PyArg_VaParse(PyObject *args, const char *format, va_list vargs)

為 穩定 ABI 的一部分.

Identical to PyArg_ParseTuple(), except that it accepts a va_list rather than a variable number of arguments.

int PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *const *keywords, ...)

為 穩定 ABI 的一部分.

Parse the parameters of a function that takes both positional and keyword parameters into local variables. The keywords argument is a NULL-terminated array of keyword parameter names specified as null-terminated ASCII or UTF-8 encoded C strings. Empty names denote positional-only parameters. Returns true on success; on failure, it returns false and raises the appropriate exception.

備註

The keywords parameter declaration is char *const* in C and const char *const* in C++. This can be overridden with the PY_CXX_CONST macro.

在 3.6 版的變更: 新增對僅限位置參數的支援。

在 3.13 版的變更: The keywords parameter has now type char *const* in C and const char *const* in C++, instead of char**. Added support for non-ASCII keyword parameter names.

int PyArg_VaParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *const *keywords, va_list vargs)

為 穩定 ABI 的一部分.

Identical to PyArg_ParseTupleAndKeywords(), except that it accepts a va_list rather than a variable number of arguments.

int PyArg_ValidateKeywordArguments(PyObject*)

為 穩定 ABI 的一部分.

Ensure that the keys in the keywords argument dictionary are strings. This is only needed if PyArg_ParseTupleAndKeywords() is not used, since the latter already does this check.

在 3.2 版被加入.

int PyArg_Parse(PyObject *args, const char *format, ...)

為 穩定 ABI 的一部分.

Parse the parameter of a function that takes a single positional parameter into a local variable. Returns true on success; on failure, it returns false and raises the appropriate exception.

舉例來說：

// Function using METH_O calling convention
static PyObject*
my_function(PyObject *module, PyObject *arg)
{
    int value;
    if (!PyArg_Parse(arg, "i:my_function", &value)) {
        return NULL;
    }
    // ... use value ...
}

int PyArg_UnpackTuple(PyObject *args, const char *name, Py_ssize_t min, Py_ssize_t max, ...)

為 穩定 ABI 的一部分.

A simpler form of parameter retrieval which does not use a format string to specify the types of the arguments. Functions which use this method to retrieve their parameters should be declared as METH_VARARGS in function or method tables. The tuple containing the actual parameters should be passed as args; it must actually be a tuple. The length of the tuple must be at least min and no more than max; min and max may be equal. Additional arguments must be passed to the function, each of which should be a pointer to a PyObject* variable; these will be filled in with the values from args; they will contain borrowed references. The variables which correspond to optional parameters not given by args will not be filled in; these should be initialized by the caller. This function returns true on success and false if args is not a tuple or contains the wrong number of elements; an exception will be set if there was a failure.

This is an example of the use of this function, taken from the sources for the _weakref helper module for weak references:

static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
    PyObject *object;
    PyObject *callback = NULL;
    PyObject *result = NULL;

    if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
        result = PyWeakref_NewRef(object, callback);
    }
    return result;
}

The call to PyArg_UnpackTuple() in this example is entirely equivalent to this call to PyArg_ParseTuple():

PyArg_ParseTuple(args, "O|O:ref", &object, &callback)

PY_CXX_CONST

The value to be inserted, if any, before char *const* in the keywords parameter declaration of PyArg_ParseTupleAndKeywords() and PyArg_VaParseTupleAndKeywords(). Default empty for C and const for C++ (const char *const*). To override, define it to the desired value before including Python.h.

在 3.13 版被加入.

建置數值

PyObject *Py_BuildValue(const char *format, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a new value based on a format string similar to those accepted by the PyArg_Parse* family of functions and a sequence of values. Returns the value or NULL in the case of an error; an exception will be raised if NULL is returned.

Py_BuildValue() does not always build a tuple. It builds a tuple only if its format string contains two or more format units. If the format string is empty, it returns None; if it contains exactly one format unit, it returns whatever object is described by that format unit. To force it to return a tuple of size 0 or one, parenthesize the format string.

When memory buffers are passed as parameters to supply data to build objects, as for the s and s# formats, the required data is copied. Buffers provided by the caller are never referenced by the objects created by Py_BuildValue(). In other words, if your code invokes malloc() and passes the allocated memory to Py_BuildValue(), your code is responsible for calling free() for that memory once Py_BuildValue() returns.

In the following description, the quoted form is the format unit; the entry in (round) parentheses is the Python object type that the format unit will return; and the entry in [square] brackets is the type of the C value(s) to be passed.

The characters space, tab, colon and comma are ignored in format strings (but not within format units such as s#). This can be used to make long format strings a tad more readable.

s (str 或 None) [const char *]

Convert a null-terminated C string to a Python str object using 'utf-8' encoding. If the C string pointer is NULL, None is used.

s# (str 或 None) [const char *, Py_ssize_t]

Convert a C string and its length to a Python str object using 'utf-8' encoding. If the C string pointer is NULL, the length is ignored and None is returned.

y (bytes) [const char *]

This converts a C string to a Python bytes object. If the C string pointer is NULL, None is returned.

y# (bytes) [const char *, Py_ssize_t]

This converts a C string and its lengths to a Python object. If the C string pointer is NULL, None is returned.

z (str 或 None) [const char *]

和 s 相同。

z# (str 或 None) [const char *, Py_ssize_t]

和 s# 相同。

u (str) [const wchar_t *]

Convert a null-terminated wchar_t buffer of Unicode (UTF-16 or UCS-4) data to a Python Unicode object. If the Unicode buffer pointer is NULL, None is returned.

u# (str) [const wchar_t *, Py_ssize_t]

Convert a Unicode (UTF-16 or UCS-4) data buffer and its length to a Python Unicode object. If the Unicode buffer pointer is NULL, the length is ignored and None is returned.

U (str 或 None) [const char *]

和 s 相同。

U# (str 或 None) [const char *, Py_ssize_t]

和 s# 相同。

i (int) [int]

將一個 C 的 int 轉換成 Python 整數物件。

b (int) [char]

將一個 C 的 char 轉換成 Python 整數物件。

h (int) [short int]

將一個 C 的 short int 轉換成 Python 整數物件。

l (int) [long int]

將一個 C 的 long int 轉換成 Python 整數物件。

B (int) [unsigned char]

將一個 C 的 unsigned char 轉換成 Python 整數物件。

H (int) [unsigned short int]

將一個 C 的 unsigned short int 轉換成 Python 整數物件。

I (int) [unsigned int]

將一個 C 的 unsigned int 轉換成 Python 整數物件。

k (int) [unsigned long]

將一個 C 的 unsigned long 轉換成 Python 整數物件。

L (int) [long long]

將一個 C 的 long long 轉換成 Python 整數物件。

K (int) [unsigned long long]

將一個 C 的 unsigned long long 轉換成 Python 整數物件。

n (int) [Py_ssize_t]

將一個 C 的 Py_ssize_t 轉換成 Python 整數。

p (bool) [int]

將一個 C 的 int 轉換成 Python bool 物件。

Be aware that this format requires an int argument. Unlike most other contexts in C, variadic arguments are not coerced to a suitable type automatically. You can convert another type (for example, a pointer or a float) to a suitable int value using (x) ? 1 : 0 or !!x.

在 3.14 版被加入.

c (長度為 1 的 bytes) [char]

將一個 C 中代表一個位元組的 int 轉換成 Python 中長度為一的 bytes。

C (長度為 1 的 str) [int]

將一個 C 中代表一個字元的 int 轉換成 Python 中長度為一的 str。

d (float) [double]

將一個 C 的 double 轉換成 Python 浮點數。

f (float) [float]

將一個 C 的 float 轉換成 Python 浮點數。

D (complex) [Py_complex *]

將一個 C 的 Py_complex 結構轉換成 Python 複數。

O (object) [PyObject *]

Pass a Python object untouched but create a new strong reference to it (i.e. its reference count is incremented by one). If the object passed in is a NULL pointer, it is assumed that this was caused because the call producing the argument found an error and set an exception. Therefore, Py_BuildValue() will return NULL but won't raise an exception. If no exception has been raised yet, SystemError is set.

S (object) [PyObject *]

和 O 相同。

N (object) [PyObject *]

Same as O, except it doesn't create a new strong reference. Useful when the object is created by a call to an object constructor in the argument list.

O& (object) [converter, anything]

Convert anything to a Python object through a converter function. The function is called with anything (which should be compatible with void*) as its argument and should return a "new" Python object, or NULL if an error occurred.

(items) (tuple) [matching-items]

Convert a sequence of C values to a Python tuple with the same number of items.

[items] (list) [matching-items]

Convert a sequence of C values to a Python list with the same number of items.

{items} (dict) [matching-items]

Convert a sequence of C values to a Python dictionary. Each pair of consecutive C values adds one item to the dictionary, serving as key and value, respectively.

If there is an error in the format string, the SystemError exception is set and NULL returned.

PyObject *Py_VaBuildValue(const char *format, va_list vargs)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Identical to Py_BuildValue(), except that it accepts a va_list rather than a variable number of arguments.

字串轉換與格式化

用於數字轉換和格式化字串輸出的函式。

int PyOS_snprintf(char *str, size_t size, const char *format, ...)

為 穩定 ABI 的一部分.

根據格式字串 format 和額外引數，輸出不超過 size 位元組給 str。請參閱 Unix 使用手冊 snprintf(3) [https://manpages.debian.org/snprintf(3)]。

int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)

為 穩定 ABI 的一部分.

根據格式字串 format 和變數引數串列 va，輸出不超過 size 位元組給 str。Unix 使用手冊 vsnprintf(3) [https://manpages.debian.org/vsnprintf(3)]。

PyOS_snprintf() 和 PyOS_vsnprintf() 包裝標準 C 函式庫函式 snprintf() 和 vsnprintf()。它們的目的是確保邊角案例 (corner case) 下的行為一致，而標準 C 函式則不然。

包裝器確保回傳時 str[size-1] 始終為 '\0'。他們永遠不會在 str 中寫入超過 size 位元組（包括尾隨的 '\0'）。這兩個函式都要求 str != NULL、size > 0、format != NULL 和 size < INT_MAX。請注意，這表示沒有與 C99 n = snprintf(NULL, 0, ...) 等效的函式來決定必要的緩衝區大小。

這些函式的回傳值 (rv) 應如下被直譯：

當 0 <= rv < size 時，輸出轉換成功，rv 字元被寫入 str（不包括 str[rv] 處的尾隨 '\0' 位元組）。

當 rv >= size 時，輸出轉換被截斷，並且需要具有 rv + 1 位元組的緩衝區才能成功。在這種情況下，str[size-1] 是 '\0'。

當 rv < 0 時，代表輸出的轉換失敗，且在這種情況下 str[size-1] 也是 '\0'，但 str 的其餘部分未定義。錯誤的確切原因取決於底層平台。

以下函式提供與區域設定無關 (locale-independent) 的字串到數字的轉換。

unsigned long PyOS_strtoul(const char *str, char **ptr, int base)

為 穩定 ABI 的一部分.

將字串 str 的初始部分根據給定的 base 轉換為 unsigned long 值，底 (base) 必須介於 2 到 36（包含）之間，或為特殊值 0。

忽略前導空白和字元大小寫。如果 base 為零，則會尋找前導的 0b、0o 或 0x 來判斷使用哪個進位。如果這些前綴不存在，則預設為 10。底必須為 0 或介於 2 到 36（包含）之間。如果 ptr 為非 NULL，它將包含指向掃描結束處的指標。

如果轉換後的值超出對應回傳型別的範圍，則會發生範圍錯誤（errno 會被設定為 ERANGE）並回傳 ULONG_MAX。如果無法執行任何轉換，則回傳 0。

也請見 Unix 使用手冊 strtoul(3) [https://manpages.debian.org/strtoul(3)]。

在 3.2 版被加入.

long PyOS_strtol(const char *str, char **ptr, int base)

為 穩定 ABI 的一部分.

將字串 str 的初始部分根據給定的 base 轉換為 long 值，底 必須介於 2 到 36 （包含）之間，或為特殊值 0。

與 PyOS_strtoul() 相同，但回傳 long 值，並在溢位時回傳 LONG_MAX。

也請見 Unix 使用手冊 strtol(3) [https://manpages.debian.org/strtol(3)]。

在 3.2 版被加入.

double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception)

為 穩定 ABI 的一部分.

將字串 s 轉換為 double，失敗時引發 Python 例外。接受的字串集合對應於 Python 的 float() 建構函式接受的字串集合，但 s 不得有前導或尾隨的空格。轉換與目前區域設定無關。

如果 endptr 為 NULL，則轉換整個字串。如果字串不是浮點數的有效表示，則引發 ValueError 並回傳 -1.0。

如果 endptr 不是 NULL，則盡可能轉換字串，並將 *endptr 設定為指向第一個未轉換的字元。如果字串的初始片段都不是浮點數的有效表示，則設定 *endptr 指向字串的開頭，引發 ValueError 並回傳 -1.0。

如果 s 表示的值太大而無法儲存在浮點數中（例如 "1e500" 在許多平台上都是這樣的字串），如果 overflow_exception 為 NULL 則回傳 Py_INFINITY（會帶有適當的符號）並且不設定任何例外。否則， overflow_exception 必須指向一個 Python 例外物件；引發該例外並回傳 -1.0。在這兩種情況下，將 *endptr 設定為指向轉換後的值之後的第一個字元。

如果轉換期間發生任何其他錯誤（例如記憶體不足的錯誤），請設定適當的 Python 例外並回傳 -1.0。

在 3.1 版被加入.

char *PyOS_double_to_string(double val, char format_code, int precision, int flags, int *ptype)

為 穩定 ABI 的一部分.

使用提供的 format_code、precision 和 flags 將 double val 轉換為字串。

format_code 必須是 'e'、'E'、'f'、'F'、'g'、'G' 或 'r' 其中之一。對於 'r'，提供的 precision 必須為 0 並會被忽略。'r' 格式碼指定標準 repr() 格式。

flags 可以是零個或多個以下的值被聯集在一起：

Py_DTSF_SIGN

總是在回傳的字串前面加上正負號字元 (sign character)，即使 val 非負數。

Py_DTSF_ADD_DOT_0

確保回傳的字串看起來不會像整數。

Py_DTSF_ALT

套用「備用的 (alternate)」格式化規則。有關詳細資訊，請參閱 PyOS_snprintf() '#' 的文件。

Py_DTSF_NO_NEG_0

負零會被轉換為正零。

在 3.11 版被加入.

如果 ptype 是非 NULL，那麼它指向的值將根據 val 的類型被設定為以下常數之一。

*ptype

val 的類型

Py_DTST_FINITE

有限數

Py_DTST_INFINITE

無限數

Py_DTST_NAN

非數字

回傳值是指向 buffer 的指標，其中包含轉換後的字串，如果轉換失敗則回傳 NULL。呼叫者負責透過呼叫 PyMem_Free() 來釋放回傳的字串。

在 3.1 版被加入.

int PyOS_mystricmp(const char *str1, const char *str2)

int PyOS_mystrnicmp(const char *str1, const char *str2, Py_ssize_t size)

為 穩定 ABI 的一部分.

不區分大小寫的字串比較。函式的作用方式幾乎與 strcmp() 和 strncmp() 相同，只是它們忽略大小寫。

Return 0 if the strings are equal, a negative value if str1 sorts lexicographically before str2, or a positive value if it sorts after.

In the str1 or str2 arguments, a NUL byte marks the end of the string. For PyOS_mystrnicmp(), the size argument gives the maximum size of the string, as if NUL was present at the index given by size.

These functions do not use the locale.

int PyOS_stricmp(const char *str1, const char *str2)

int PyOS_strnicmp(const char *str1, const char *str2, Py_ssize_t size)

不區分大小寫的字串比較。

On Windows, these are aliases of stricmp() and strnicmp(), respectively.

On other platforms, they are aliases of PyOS_mystricmp() and PyOS_mystrnicmp(), respectively.

Character classification and conversion

The following macros provide locale-independent (unlike the C standard library ctype.h) character classification and conversion. The argument must be a signed or unsigned char.

Py_ISALNUM(c)

Return true if the character c is an alphanumeric character.

Py_ISALPHA(c)

Return true if the character c is an alphabetic character (a-z and A-Z).

Py_ISDIGIT(c)

Return true if the character c is a decimal digit (0-9).

Py_ISLOWER(c)

Return true if the character c is a lowercase ASCII letter (a-z).

Py_ISUPPER(c)

Return true if the character c is an uppercase ASCII letter (A-Z).

Py_ISSPACE(c)

Return true if the character c is a whitespace character (space, tab, carriage return, newline, vertical tab, or form feed).

Py_ISXDIGIT(c)

Return true if the character c is a hexadecimal digit (0-9, a-f, and A-F).

Py_TOLOWER(c)

Return the lowercase equivalent of the character c.

Py_TOUPPER(c)

Return the uppercase equivalent of the character c.

PyHash API

另請參閱 PyTypeObject.tp_hash 成員和 數值型別的雜湊。

type Py_hash_t

雜湊值型別：有符號整數。

在 3.2 版被加入.

type Py_uhash_t

雜湊值型別：無符號整數。

在 3.2 版被加入.

Py_HASH_ALGORITHM

A numerical value indicating the algorithm for hashing of str, bytes, and memoryview.

演算式名稱由 sys.hash_info.algorithm 公開。

在 3.4 版被加入.

Py_HASH_FNV

Py_HASH_SIPHASH24

Py_HASH_SIPHASH13

Numerical values to compare to Py_HASH_ALGORITHM to determine which algorithm is used for hashing. The hash algorithm can be configured via the configure --with-hash-algorithm option.

在 3.4 版被加入: 新增 Py_HASH_FNV 和 Py_HASH_SIPHASH24。

在 3.11 版被加入: 新增 Py_HASH_SIPHASH13。

Py_HASH_CUTOFF

Buffers of length in range [1, Py_HASH_CUTOFF) are hashed using DJBX33A instead of the algorithm described by Py_HASH_ALGORITHM.

將 Py_HASH_CUTOFF 設為 0 可停用此最佳化。

Py_HASH_CUTOFF 必須為非負且小於或等於 7。

32-bit platforms should use a cutoff smaller than 64-bit platforms because it is easier to create colliding strings. A cutoff of 7 on 64-bit platforms and 5 on 32-bit platforms should provide a decent safety margin.

這對應到 sys.hash_info.cutoff 常數。

在 3.4 版被加入.

PyHASH_MODULUS

用於數值雜湊方案的梅森質數 (Mersenne prime) [https://en.wikipedia.org/wiki/Mersenne_prime] P = 2**n -1。

這對應到 sys.hash_info.modulus 常數。

在 3.13 版被加入.

PyHASH_BITS

PyHASH_MODULUS 中 P 的指數 n。

在 3.13 版被加入.

PyHASH_MULTIPLIER

用於字串和其他各種雜湊的質數乘數 (prime multiplier)。

在 3.13 版被加入.

PyHASH_INF

正無窮大回傳的雜湊值。

這對應到 sys.hash_info.inf 常數。

在 3.13 版被加入.

PyHASH_IMAG

用於複數虛數部分的乘數。

這對應到 sys.hash_info.imag 常數。

在 3.13 版被加入.

type PyHash_FuncDef

PyHash_GetFuncDef() 所使用的雜湊函式定義。

Py_hash_t (*const hash)(const void*, Py_ssize_t)

雜湊函式。

const char *name

雜湊函式名稱（UTF-8 編碼字串）。

這對應到 sys.hash_info.algorithm 常數。

const int hash_bits

雜湊值的內部大小（以位元為單位）。

這對應到 sys.hash_info.hash_bits 常數。

const int seed_bits

Seed 輸入的大小（以位元為單位）。

這對應到 sys.hash_info.seed_bits 常數。

在 3.4 版被加入.

PyHash_FuncDef *PyHash_GetFuncDef(void)

取得雜湊函式定義。

也參考

PEP 456 [https://peps.python.org/pep-0456/]「安全且可交替使用的雜湊演算法 (Secure and interchangeable hash algorithm)」。

在 3.4 版被加入.

Py_hash_t Py_HashPointer(const void *ptr)

雜湊指標值：將指標值作為整數處理（在內部轉型為 uintptr_t）。指標不會被取值 (dereference)。

此函式不會失敗：它不會回傳 -1。

在 3.13 版被加入.

Py_hash_t Py_HashBuffer(const void *ptr, Py_ssize_t len)

Compute and return the hash value of a buffer of len bytes starting at address ptr. The hash is guaranteed to match that of bytes, memoryview, and other built-in objects that implement the buffer protocol.

Use this function to implement hashing for immutable objects whose tp_richcompare function compares to another object's buffer.

len 必須大於或等於 0。

此函式總是會成功執行。

在 3.14 版被加入.

Py_hash_t PyObject_GenericHash(PyObject *obj)

泛用雜湊函式，旨在放入型別物件的 tp_hash 插槽中。其結果僅取決於物件的識別性。

在 CPython 中，它等價於 Py_HashPointer()。

在 3.13 版被加入.

Reflection

PyObject *PyEval_GetBuiltins(void)

回傳值：借用參照。 為 穩定 ABI 的一部分.

在 3.13 版之後被棄用: Use PyEval_GetFrameBuiltins() instead.

Return a dictionary of the builtins in the current execution frame, or the interpreter of the thread state if no frame is currently executing.

PyObject *PyEval_GetLocals(void)

回傳值：借用參照。 為 穩定 ABI 的一部分.

在 3.13 版之後被棄用: Use either PyEval_GetFrameLocals() to obtain the same behaviour as calling locals() in Python code, or else call PyFrame_GetLocals() on the result of PyEval_GetFrame() to access the f_locals attribute of the currently executing frame.

Return a mapping providing access to the local variables in the current execution frame, or NULL if no frame is currently executing.

Refer to locals() for details of the mapping returned at different scopes.

As this function returns a borrowed reference, the dictionary returned for optimized scopes is cached on the frame object and will remain alive as long as the frame object does. Unlike PyEval_GetFrameLocals() and locals(), subsequent calls to this function in the same frame will update the contents of the cached dictionary to reflect changes in the state of the local variables rather than returning a new snapshot.

在 3.13 版的變更: As part of PEP 667 [https://peps.python.org/pep-0667/], PyFrame_GetLocals(), locals(), and FrameType.f_locals no longer make use of the shared cache dictionary. Refer to the What's New entry for additional details.

PyObject *PyEval_GetGlobals(void)

回傳值：借用參照。 為 穩定 ABI 的一部分.

在 3.13 版之後被棄用: Use PyEval_GetFrameGlobals() instead.

Return a dictionary of the global variables in the current execution frame, or NULL if no frame is currently executing.

PyFrameObject *PyEval_GetFrame(void)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Return the attached thread state's frame, which is NULL if no frame is currently executing.

另請見 PyThreadState_GetFrame()。

PyObject *PyEval_GetFrameBuiltins(void)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.13 版本開始.

Return a dictionary of the builtins in the current execution frame, or the interpreter of the thread state if no frame is currently executing.

在 3.13 版被加入.

PyObject *PyEval_GetFrameLocals(void)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.13 版本開始.

Return a dictionary of the local variables in the current execution frame, or NULL if no frame is currently executing. Equivalent to calling locals() in Python code.

To access f_locals on the current frame without making an independent snapshot in optimized scopes, call PyFrame_GetLocals() on the result of PyEval_GetFrame().

在 3.13 版被加入.

PyObject *PyEval_GetFrameGlobals(void)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.13 版本開始.

Return a dictionary of the global variables in the current execution frame, or NULL if no frame is currently executing. Equivalent to calling globals() in Python code.

在 3.13 版被加入.

const char *PyEval_GetFuncName(PyObject *func)

為 穩定 ABI 的一部分.

Return the name of func if it is a function, class or instance object, else the name of funcs type.

const char *PyEval_GetFuncDesc(PyObject *func)

為 穩定 ABI 的一部分.

Return a description string, depending on the type of func. Return values include "()" for functions and methods, " constructor", " instance", and " object". Concatenated with the result of PyEval_GetFuncName(), the result will be a description of func.

編解碼器註冊表和支援函式

int PyCodec_Register(PyObject *search_function)

為 穩定 ABI 的一部分.

註冊一個新的編解碼器搜尋函式。

作為副作用 (side effect)，這會嘗試載入 encodings（如果尚未完成），以確保它始終位於搜尋函式列表中的第一個。

int PyCodec_Unregister(PyObject *search_function)

為 穩定 ABI 的一部分 自 3.10 版本開始.

取消註冊編解碼器搜尋函式並清除註冊表 (registry) 的快取。如果搜尋函式並未被註冊，則不執行任何操作。成功回傳 0，發生錯誤時會引發例外並回傳 -1。

在 3.10 版被加入.

int PyCodec_KnownEncoding(const char *encoding)

為 穩定 ABI 的一部分.

回傳 1 或 0，具體取決於是否有給定 encoding 的已註冊編解碼器。這個函式總會成功。

PyObject *PyCodec_Encode(PyObject *object, const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

基於泛用編解碼器的編碼 API。

object 被傳遞給以給定 encoding 所查找到的編碼器函式，並使用以 errors 定義的錯誤處理方法。errors 可以設為 NULL 來使用編解碼器定義的預設方法。如果找不到編碼器，則引發 LookupError。

PyObject *PyCodec_Decode(PyObject *object, const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

基於泛用編解碼器的解碼 API。

object 被傳遞給以給定 encoding 所查找到的解碼器函式，並使用以 errors 定義的錯誤處理方法。errors 可以設為 NULL 來使用編解碼器定義的預設方法。如果找不到解碼器，則引發 LookupError。

編解碼器查找 API

在以下函式中，查找的 encoding 字串的所有字元將轉換為小寫，這使得透過此機制查找的編碼可以不區分大小寫而更有效率。如果未找到編解碼器，則會設定 KeyError 並回傳 NULL。

PyObject *PyCodec_Encoder(const char *encoding)

回傳值：新的參照。 為 穩定 ABI 的一部分.

取得給定 encoding 的編碼器函式。

PyObject *PyCodec_Decoder(const char *encoding)

回傳值：新的參照。 為 穩定 ABI 的一部分.

取得給定 encoding 的解碼器函式。

PyObject *PyCodec_IncrementalEncoder(const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

取得給定 encoding 的 IncrementalEncoder 物件。

PyObject *PyCodec_IncrementalDecoder(const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

取得給定 encoding 的 IncrementalDecoder 物件。

PyObject *PyCodec_StreamReader(const char *encoding, PyObject *stream, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

取得給定 encoding 的 StreamReader 工廠函式。

PyObject *PyCodec_StreamWriter(const char *encoding, PyObject *stream, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

取得給定 encoding 的 StreamWriter 工廠函式。

用於 Unicode 編碼錯誤處理程式的註冊 API

int PyCodec_RegisterError(const char *name, PyObject *error)

為 穩定 ABI 的一部分.

在給定的 name 下註冊錯誤處理回呼 (callback) 函式 error。當編解碼器遇到無法編碼的字元/無法解碼的位元組並且 name 被指定為呼叫編碼/解碼函式時的錯誤參數時，將呼叫此回呼函式。

回呼取得單個引數，即 UnicodeEncodeError、UnicodeDecodeError 或 UnicodeTranslateError 的實例，其中包含關於有問題的字元或位元組序列及其在原始字串中偏移量的資訊（有關取得此資訊的函式，請參閱 Unicode 例外物件）。回呼必須引發給定的例外，或者回傳一個包含有問題序列的替換的二元組 (two-item tuple)，以及一個代表原始字串中應該被恢復的編碼/解碼偏移量的整數。

成功時回傳 0，錯誤時回傳 -1。

PyObject *PyCodec_LookupError(const char *name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

查找 name 下已註冊的錯誤處理回呼函式。作為一種特殊情況，可以傳遞 NULL，在這種情況下，將回傳 "strict" 的錯誤處理回呼。

PyObject *PyCodec_StrictErrors(PyObject *exc)

回傳值：總是為 NULL。 為 穩定 ABI 的一部分.

引發 exc 作為例外。

PyObject *PyCodec_IgnoreErrors(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

忽略 unicode 錯誤，跳過錯誤的輸入。

PyObject *PyCodec_ReplaceErrors(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

將 unicode 編碼錯誤替換為 ? 或 U+FFFD。

PyObject *PyCodec_XMLCharRefReplaceErrors(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

將 unicode 編碼錯誤替換為 XML 字元參照。

PyObject *PyCodec_BackslashReplaceErrors(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

將 unicode 編碼錯誤替換為反斜線跳脫（\x、\u 和 \U）。

PyObject *PyCodec_NameReplaceErrors(PyObject *exc)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

將 unicode 編碼錯誤替換為 \N{...} 跳脫。

在 3.5 版被加入.

Codec utility variables

const char *Py_hexdigits

A string constant containing the lowercase hexadecimal digits: "0123456789abcdef".

在 3.3 版被加入.

PyTime C API

在 3.13 版被加入.

時鐘 C API 提供對系統時鐘的存取。它類似於 Python 的 time 模組。

對於與 datetime 模組相關的 C API，請參閱 DateTime 物件。

型別

type PyTime_t

以奈秒為單位的時間戳記或持續時長，以有符號的 64 位元整數表示。

時間戳記的參照點取決於所使用的時鐘。例如 PyTime_Time() 回傳相對於 UNIX 紀元 (UNIX epoch) 的時間戳記。

支援的範圍約為 [-292.3 年；+292.3 年]。以 Unix 紀元 (1970 年 1 月 1 日) 為參照，支援的日期範圍約為 [1677-09-21; 2262-04-11]。確切的限制是以常數的形式公開出來：

PyTime_t PyTime_MIN

PyTime_t 的最小值。

PyTime_t PyTime_MAX

PyTime_t 的最大值。

時鐘函式

以下的函式接受一個指向 PyTime_t 的指標，並將其設定為特定時鐘的值。每個時鐘的詳細資訊紀錄在相對應的 Python 函式說明文件中。

函式成功時會回傳 0 或在失敗時回傳 -1（並設定一個例外）。

在整數溢位時，它們會設定 PyExc_OverflowError 例外，並將 *result 設定為夾在 [PyTime_MIN; PyTime_MAX] 範圍內的值。（在目前的系統上，整數溢位很可能是由於錯誤設定的系統時間所造成。）

如同任何其他 C API（除非另有指定），必須在具有 attached thread state 的情況下呼叫函式。

int PyTime_Monotonic(PyTime_t *result)

讀取單調時鐘。請參閱 time.monotonic() 取得此時鐘的重要詳細資訊。

int PyTime_PerfCounter(PyTime_t *result)

讀取效能計數器。請參閱 time.perf_counter() 以取得此時鐘的重要詳細資訊。

int PyTime_Time(PyTime_t *result)

讀取「牆上時鐘 (wall clock)」的時間。請參閱 time.time() 以取得詳細資訊。

原始時鐘函式

類似於時鐘函式，但不會在出錯時設定例外，也不需要呼叫者擁有 attached thread state。

成功時函式會回傳 0。

失敗時，它們會將 *result 設為 0 並回傳 -1, 而不設定例外。要取得錯誤原因，請附加一個 thread state，並呼叫常規（非 Raw）函式。請注意，常規函式可能會在 Raw 的函式失敗後成功。

int PyTime_MonotonicRaw(PyTime_t *result)

類似於 PyTime_Monotonic()，但不會在錯誤時設定例外，也不需要擁有 attached thread state。

int PyTime_PerfCounterRaw(PyTime_t *result)

類似於 PyTime_PerfCounter()，但不會在錯誤時設定例外，也不需要擁有 attached thread state。

int PyTime_TimeRaw(PyTime_t *result)

類似於 PyTime_Time()，但不會在錯誤時設定例外，也不需要擁有 attached thread state。

轉換函式

double PyTime_AsSecondsDouble(PyTime_t t)

將時間戳記轉換為 C double 的秒數。

此函式不會失敗，但請注意 double 對於大數值的精確度有限。

對 Perf Map 的支援

在支援的平台上（截至撰寫本文時，僅限 Linux），runtime 可以利用 perf map 檔案使得外部分析工具（例如 perf [https://perf.wiki.kernel.org/index.php/Main_Page]）可以見到 Python 函式。正在運行的行程可能會在 /tmp 目錄中建立一個檔案，其中包含可以將一段可執行程式碼對映到名稱的各個條目。此介面在 Linux Perf 工具的文件 [https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jit-interface.txt]中有被描述。

在 Python 中，這些輔助 API 可以被依賴於運行期間 (on the fly) 產生機器碼的函式庫和功能所使用。

請注意，這些 API 不需要持有 attached thread state。

int PyUnstable_PerfMapState_Init(void)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

打開 /tmp/perf-$pid.map 檔案，除非它已經打開，並建立一個鎖以確保執行緒安全地 (thread-safe) 寫入該檔案（前提是寫入是透過 PyUnstable_WritePerfMapEntry() 完成的）。通常不需要明確地呼叫它；只需使用 PyUnstable_WritePerfMapEntry() 它就會在首次呼叫時初始化狀態。

建立/打開 perf map 檔案成功時回傳 0，失敗時回傳 -1，建立鎖時失敗則回傳 -2。檢查 errno 以取得更多造成失敗的資訊。

int PyUnstable_WritePerfMapEntry(const void *code_addr, unsigned int code_size, const char *entry_name)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

將單一條目寫入 /tmp/perf-$pid.map 檔案。此函式是執行緒安全的。以下是一個條目的範例：

# 位址        大小  名稱
7f3529fcf759 b     py::bar:/run/t.py

如果尚未開啟 perf map 檔案，將在寫入條目之前呼叫 PyUnstable_PerfMapState_Init()。成功時回傳 0，失敗時回傳與 PyUnstable_PerfMapState_Init() 失敗時相同的錯誤碼。

void PyUnstable_PerfMapState_Fini(void)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

關閉由 PyUnstable_PerfMapState_Init() 開啟的 perf map 檔案，這是在直譯器關閉期間由 runtime 本身呼叫的。一般來說，除了處理 forking 等特定場景外，不應該明確地呼叫它。

抽象物件層 (Abstract Objects Layer)

本章中的函式與 Python 物件相互作用，無論其型別、或具有廣泛類別的物件型別（例如所有數值型別或所有序列型別）。當使用於不適用的物件型別時，他們會引發一個 Python 異常 (exception)。

這些函式是不可能用於未正確初始化的物件（例如一個由 PyList_New() 建立的 list 物件），而其中的項目沒有被設為一些非 NULL 的值。

物件協定

呼叫協定 (Call Protocol)

tp_call 協定

Vectorcall 協定

遞迴控制

Vectorcall 支援 API

物件呼叫 API

呼叫支援 API

數字協定

序列協定

對映協定

疊代器協定

緩衝協定 (Buffer Protocol)

緩衝區結構

Buffer request types

request-independent fields

readonly, format

shape, strides, suboffsets

contiguity requests

compound requests

Complex arrays

NumPy 風格：形狀與步幅

PIL-style: shape, strides and suboffsets

與緩衝相關的函式

物件協定

PyObject *Py_GetConstant(unsigned int constant_id)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Get a strong reference to a constant.

如果 constant_id 無效，則設定一個例外並回傳 NULL。

constant_id 必須是這些常數識別字之一：

常數識別字

數值

回傳物件

Py_CONSTANT_NONE

0

None

Py_CONSTANT_FALSE

1

False

Py_CONSTANT_TRUE

2

True

Py_CONSTANT_ELLIPSIS

3

Ellipsis

Py_CONSTANT_NOT_IMPLEMENTED

4

NotImplemented

Py_CONSTANT_ZERO

5

0

Py_CONSTANT_ONE

6

1

Py_CONSTANT_EMPTY_STR

7

''

Py_CONSTANT_EMPTY_BYTES

8

b''

Py_CONSTANT_EMPTY_TUPLE

9

()

Numeric values are only given for projects which cannot use the constant identifiers.

在 3.13 版被加入.

在 CPython 中，所有這些常數都是不滅的。

PyObject *Py_GetConstantBorrowed(unsigned int constant_id)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Similar to Py_GetConstant(), but return a borrowed reference.

This function is primarily intended for backwards compatibility: using Py_GetConstant() is recommended for new code.

The reference is borrowed from the interpreter, and is valid until the interpreter finalization.

在 3.13 版被加入.

PyObject *Py_NotImplemented

The NotImplemented singleton, used to signal that an operation is not implemented for the given type combination.

Py_RETURN_NOTIMPLEMENTED

Properly handle returning Py_NotImplemented from within a C function (that is, create a new strong reference to NotImplemented and return it).

Py_PRINT_RAW

Flag to be used with multiple functions that print the object (like PyObject_Print() and PyFile_WriteObject()). If passed, these functions use the str() of the object instead of the repr().

int PyObject_Print(PyObject *o, FILE *fp, int flags)

Print an object o, on file fp. Returns -1 on error. The flags argument is used to enable certain printing options. The only option currently supported is Py_PRINT_RAW; if given, the str() of the object is written instead of the repr().

int PyObject_HasAttrWithError(PyObject *o, PyObject *attr_name)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Returns 1 if o has the attribute attr_name, and 0 otherwise. This is equivalent to the Python expression hasattr(o, attr_name). On failure, return -1.

在 3.13 版被加入.

int PyObject_HasAttrStringWithError(PyObject *o, const char *attr_name)

為 穩定 ABI 的一部分 自 3.13 版本開始.

This is the same as PyObject_HasAttrWithError(), but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

在 3.13 版被加入.

int PyObject_HasAttr(PyObject *o, PyObject *attr_name)

為 穩定 ABI 的一部分.

Returns 1 if o has the attribute attr_name, and 0 otherwise. This function always succeeds.

備註

Exceptions that occur when this calls __getattr__() and __getattribute__() methods aren't propagated, but instead given to sys.unraisablehook(). For proper error handling, use PyObject_HasAttrWithError(), PyObject_GetOptionalAttr() or PyObject_GetAttr() instead.

int PyObject_HasAttrString(PyObject *o, const char *attr_name)

為 穩定 ABI 的一部分.

This is the same as PyObject_HasAttr(), but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

備註

Exceptions that occur when this calls __getattr__() and __getattribute__() methods or while creating the temporary str object are silently ignored. For proper error handling, use PyObject_HasAttrStringWithError(), PyObject_GetOptionalAttrString() or PyObject_GetAttrString() instead.

PyObject *PyObject_GetAttr(PyObject *o, PyObject *attr_name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Retrieve an attribute named attr_name from object o. Returns the attribute value on success, or NULL on failure. This is the equivalent of the Python expression o.attr_name.

If the missing attribute should not be treated as a failure, you can use PyObject_GetOptionalAttr() instead.

PyObject *PyObject_GetAttrString(PyObject *o, const char *attr_name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is the same as PyObject_GetAttr(), but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

If the missing attribute should not be treated as a failure, you can use PyObject_GetOptionalAttrString() instead.

int PyObject_GetOptionalAttr(PyObject *obj, PyObject *attr_name, PyObject **result);

為 穩定 ABI 的一部分 自 3.13 版本開始.

Variant of PyObject_GetAttr() which doesn't raise AttributeError if the attribute is not found.

If the attribute is found, return 1 and set *result to a new strong reference to the attribute. If the attribute is not found, return 0 and set *result to NULL; the AttributeError is silenced. If an error other than AttributeError is raised, return -1 and set *result to NULL.

在 3.13 版被加入.

int PyObject_GetOptionalAttrString(PyObject *obj, const char *attr_name, PyObject **result);

為 穩定 ABI 的一部分 自 3.13 版本開始.

This is the same as PyObject_GetOptionalAttr(), but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

在 3.13 版被加入.

PyObject *PyObject_GenericGetAttr(PyObject *o, PyObject *name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Generic attribute getter function that is meant to be put into a type object's tp_getattro slot. It looks for a descriptor in the dictionary of classes in the object's MRO as well as an attribute in the object's __dict__ (if present). As outlined in 實作描述器, data descriptors take preference over instance attributes, while non-data descriptors don't. Otherwise, an AttributeError is raised.

int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)

為 穩定 ABI 的一部分.

Set the value of the attribute named attr_name, for object o, to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o.attr_name = v.

If v is NULL, the attribute is deleted. This behaviour is deprecated in favour of using PyObject_DelAttr(), but there are currently no plans to remove it.

int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)

為 穩定 ABI 的一部分.

This is the same as PyObject_SetAttr(), but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

If v is NULL, the attribute is deleted, but this feature is deprecated in favour of using PyObject_DelAttrString().

The number of different attribute names passed to this function should be kept small, usually by using a statically allocated string as attr_name. For attribute names that aren't known at compile time, prefer calling PyUnicode_FromString() and PyObject_SetAttr() directly. For more details, see PyUnicode_InternFromString(), which may be used internally to create a key object.

int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)

為 穩定 ABI 的一部分.

Generic attribute setter and deleter function that is meant to be put into a type object's tp_setattro slot. It looks for a data descriptor in the dictionary of classes in the object's MRO, and if found it takes preference over setting or deleting the attribute in the instance dictionary. Otherwise, the attribute is set or deleted in the object's __dict__ (if present). On success, 0 is returned, otherwise an AttributeError is raised and -1 is returned.

int PyObject_DelAttr(PyObject *o, PyObject *attr_name)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Delete attribute named attr_name, for object o. Returns -1 on failure. This is the equivalent of the Python statement del o.attr_name.

int PyObject_DelAttrString(PyObject *o, const char *attr_name)

為 穩定 ABI 的一部分 自 3.13 版本開始.

This is the same as PyObject_DelAttr(), but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

The number of different attribute names passed to this function should be kept small, usually by using a statically allocated string as attr_name. For attribute names that aren't known at compile time, prefer calling PyUnicode_FromString() and PyObject_DelAttr() directly. For more details, see PyUnicode_InternFromString(), which may be used internally to create a key object for lookup.

PyObject *PyObject_GenericGetDict(PyObject *o, void *context)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.10 版本開始.

A generic implementation for the getter of a __dict__ descriptor. It creates the dictionary if necessary.

This function may also be called to get the __dict__ of the object o. Pass NULL for context when calling it. Since this function may need to allocate memory for the dictionary, it may be more efficient to call PyObject_GetAttr() when accessing an attribute on the object.

在失敗時，會回傳 NULL 並設定例外。

在 3.3 版被加入.

int PyObject_GenericSetDict(PyObject *o, PyObject *value, void *context)

為 穩定 ABI 的一部分 自 3.7 版本開始.

A generic implementation for the setter of a __dict__ descriptor. This implementation does not allow the dictionary to be deleted.

在 3.3 版被加入.

PyObject **_PyObject_GetDictPtr(PyObject *obj)

Return a pointer to __dict__ of the object obj. If there is no __dict__, return NULL without setting an exception.

This function may need to allocate memory for the dictionary, so it may be more efficient to call PyObject_GetAttr() when accessing an attribute on the object.

PyObject *PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Compare the values of o1 and o2 using the operation specified by opid, which must be one of Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, or Py_GE, corresponding to <, <=, ==, !=, >, or >= respectively. This is the equivalent of the Python expression o1 op o2, where op is the operator corresponding to opid. Returns the value of the comparison on success, or NULL on failure.

int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)

為 穩定 ABI 的一部分.

Compare the values of o1 and o2 using the operation specified by opid, like PyObject_RichCompare(), but returns -1 on error, 0 if the result is false, 1 otherwise.

備註

If o1 and o2 are the same object, PyObject_RichCompareBool() will always return 1 for Py_EQ and 0 for Py_NE.

PyObject *PyObject_Format(PyObject *obj, PyObject *format_spec)

為 穩定 ABI 的一部分.

Format obj using format_spec. This is equivalent to the Python expression format(obj, format_spec).

format_spec may be NULL. In this case the call is equivalent to format(obj). Returns the formatted string on success, NULL on failure.

PyObject *PyObject_Repr(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Compute a string representation of object o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression repr(o). Called by the repr() built-in function.

在 3.4 版的變更: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_ASCII(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

As PyObject_Repr(), compute a string representation of object o, but escape the non-ASCII characters in the string returned by PyObject_Repr() with \x, \u or \U escapes. This generates a string similar to that returned by PyObject_Repr() in Python 2. Called by the ascii() built-in function.

PyObject *PyObject_Str(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Compute a string representation of object o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression str(o). Called by the str() built-in function and, therefore, by the print() function.

在 3.4 版的變更: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_Bytes(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Compute a bytes representation of object o. NULL is returned on failure and a bytes object on success. This is equivalent to the Python expression bytes(o), when o is not an integer. Unlike bytes(o), a TypeError is raised when o is an integer instead of a zero-initialized bytes object.

int PyObject_IsSubclass(PyObject *derived, PyObject *cls)

為 穩定 ABI 的一部分.

Return 1 if the class derived is identical to or derived from the class cls, otherwise return 0. In case of an error, return -1.

If cls is a tuple, the check will be done against every entry in cls. The result will be 1 when at least one of the checks returns 1, otherwise it will be 0.

If cls has a __subclasscheck__() method, it will be called to determine the subclass status as described in PEP 3119 [https://peps.python.org/pep-3119/]. Otherwise, derived is a subclass of cls if it is a direct or indirect subclass, i.e. contained in cls.__mro__.

Normally only class objects, i.e. instances of type or a derived class, are considered classes. However, objects can override this by having a __bases__ attribute (which must be a tuple of base classes).

int PyObject_IsInstance(PyObject *inst, PyObject *cls)

為 穩定 ABI 的一部分.

Return 1 if inst is an instance of the class cls or a subclass of cls, or 0 if not. On error, returns -1 and sets an exception.

If cls is a tuple, the check will be done against every entry in cls. The result will be 1 when at least one of the checks returns 1, otherwise it will be 0.

If cls has a __instancecheck__() method, it will be called to determine the subclass status as described in PEP 3119 [https://peps.python.org/pep-3119/]. Otherwise, inst is an instance of cls if its class is a subclass of cls.

An instance inst can override what is considered its class by having a __class__ attribute.

An object cls can override if it is considered a class, and what its base classes are, by having a __bases__ attribute (which must be a tuple of base classes).

Py_hash_t PyObject_Hash(PyObject *o)

為 穩定 ABI 的一部分.

Compute and return the hash value of an object o. On failure, return -1. This is the equivalent of the Python expression hash(o).

在 3.2 版的變更: The return type is now Py_hash_t. This is a signed integer the same size as Py_ssize_t.

Py_hash_t PyObject_HashNotImplemented(PyObject *o)

為 穩定 ABI 的一部分.

Set a TypeError indicating that type(o) is not hashable and return -1. This function receives special treatment when stored in a tp_hash slot, allowing a type to explicitly indicate to the interpreter that it is not hashable.

int PyObject_IsTrue(PyObject *o)

為 穩定 ABI 的一部分.

Returns 1 if the object o is considered to be true, and 0 otherwise. This is equivalent to the Python expression not not o. On failure, return -1.

int PyObject_Not(PyObject *o)

為 穩定 ABI 的一部分.

Returns 0 if the object o is considered to be true, and 1 otherwise. This is equivalent to the Python expression not o. On failure, return -1.

PyObject *PyObject_Type(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

When o is non-NULL, returns a type object corresponding to the object type of object o. On failure, raises SystemError and returns NULL. This is equivalent to the Python expression type(o). This function creates a new strong reference to the return value. There's really no reason to use this function instead of the Py_TYPE() function, which returns a pointer of type PyTypeObject*, except when a new strong reference is needed.

int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)

Return non-zero if the object o is of type type or a subtype of type, and 0 otherwise. Both parameters must be non-NULL.

Py_ssize_t PyObject_Size(PyObject *o)

Py_ssize_t PyObject_Length(PyObject *o)

為 穩定 ABI 的一部分.

Return the length of object o. If the object o provides either the sequence and mapping protocols, the sequence length is returned. On error, -1 is returned. This is the equivalent to the Python expression len(o).

Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)

Return an estimated length for the object o. First try to return its actual length, then an estimate using __length_hint__(), and finally return the default value. On error return -1. This is the equivalent to the Python expression operator.length_hint(o, defaultvalue).

在 3.4 版被加入.

PyObject *PyObject_GetItem(PyObject *o, PyObject *key)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return element of o corresponding to the object key or NULL on failure. This is the equivalent of the Python expression o[key].

int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)

為 穩定 ABI 的一部分.

Map the object key to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o[key] = v. This function does not steal a reference to v.

int PyObject_DelItem(PyObject *o, PyObject *key)

為 穩定 ABI 的一部分.

Remove the mapping for the object key from the object o. Return -1 on failure. This is equivalent to the Python statement del o[key].

int PyObject_DelItemString(PyObject *o, const char *key)

為 穩定 ABI 的一部分.

This is the same as PyObject_DelItem(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

PyObject *PyObject_Dir(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is equivalent to the Python expression dir(o), returning a (possibly empty) list of strings appropriate for the object argument, or NULL if there was an error. If the argument is NULL, this is like the Python dir(), returning the names of the current locals; in this case, if no execution frame is active then NULL is returned but PyErr_Occurred() will return false.

PyObject *PyObject_GetIter(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is equivalent to the Python expression iter(o). It returns a new iterator for the object argument, or the object itself if the object is already an iterator. Raises TypeError and returns NULL if the object cannot be iterated.

PyObject *PyObject_SelfIter(PyObject *obj)

回傳值：新的參照。 為 穩定 ABI 的一部分.

This is equivalent to the Python __iter__(self): return self method. It is intended for iterator types, to be used in the PyTypeObject.tp_iter slot.

PyObject *PyObject_GetAIter(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.10 版本開始.

This is the equivalent to the Python expression aiter(o). Takes an AsyncIterable object and returns an AsyncIterator for it. This is typically a new iterator but if the argument is an AsyncIterator, this returns itself. Raises TypeError and returns NULL if the object cannot be iterated.

在 3.10 版被加入.

void *PyObject_GetTypeData(PyObject *o, PyTypeObject *cls)

為 穩定 ABI 的一部分 自 3.12 版本開始.

Get a pointer to subclass-specific data reserved for cls.

The object o must be an instance of cls, and cls must have been created using negative PyType_Spec.basicsize. Python does not check this.

錯誤時設定一個例外並回傳 NULL。

在 3.12 版被加入.

Py_ssize_t PyType_GetTypeDataSize(PyTypeObject *cls)

為 穩定 ABI 的一部分 自 3.12 版本開始.

Return the size of the instance memory space reserved for cls, i.e. the size of the memory PyObject_GetTypeData() returns.

This may be larger than requested using -PyType_Spec.basicsize; it is safe to use this larger size (e.g. with memset()).

The type cls must have been created using negative PyType_Spec.basicsize. Python does not check this.

錯誤時設定一個例外並回傳一個負值。

在 3.12 版被加入.

void *PyObject_GetItemData(PyObject *o)

Get a pointer to per-item data for a class with Py_TPFLAGS_ITEMS_AT_END.

錯誤時設定一個例外並回傳 NULL。如果 o 沒有設定 Py_TPFLAGS_ITEMS_AT_END，則會引發 TypeError。

在 3.12 版被加入.

int PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg)

Visit the managed dictionary of obj.

This function must only be called in a traverse function of the type which has the Py_TPFLAGS_MANAGED_DICT flag set.

在 3.13 版被加入.

void PyObject_ClearManagedDict(PyObject *obj)

Clear the managed dictionary of obj.

This function must only be called in a clear function of the type which has the Py_TPFLAGS_MANAGED_DICT flag set.

在 3.13 版被加入.

int PyUnstable_Object_EnableDeferredRefcount(PyObject *obj)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Enable deferred reference counting [https://peps.python.org/pep-0703/#deferred-reference-counting] on obj, if supported by the runtime. In the free-threaded build, this allows the interpreter to avoid reference count adjustments to obj, which may improve multi-threaded performance. The tradeoff is that obj will only be deallocated by the tracing garbage collector, and not when the interpreter no longer has any references to it.

This function returns 1 if deferred reference counting is enabled on obj, and 0 if deferred reference counting is not supported or if the hint was ignored by the interpreter, such as when deferred reference counting is already enabled on obj. This function is thread-safe, and cannot fail.

This function does nothing on builds with the GIL enabled, which do not support deferred reference counting. This also does nothing if obj is not an object tracked by the garbage collector (see gc.is_tracked() and PyObject_GC_IsTracked()).

This function is intended to be used soon after obj is created, by the code that creates it, such as in the object's tp_new slot.

在 3.14 版被加入.

int PyUnstable_Object_IsUniqueReferencedTemporary(PyObject *obj)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Check if obj is a unique temporary object. Returns 1 if obj is known to be a unique temporary object, and 0 otherwise. This function cannot fail, but the check is conservative, and may return 0 in some cases even if obj is a unique temporary object.

If an object is a unique temporary, it is guaranteed that the current code has the only reference to the object. For arguments to C functions, this should be used instead of checking if the reference count is 1. Starting with Python 3.14, the interpreter internally avoids some reference count modifications when loading objects onto the operands stack by borrowing references when possible, which means that a reference count of 1 by itself does not guarantee that a function argument uniquely referenced.

In the example below, my_func is called with a unique temporary object as its argument:

my_func([1, 2, 3])

In the example below, my_func is not called with a unique temporary object as its argument, even if its refcount is 1:

my_list = [1, 2, 3]
my_func(my_list)

另請參閱 Py_REFCNT() 函式。

在 3.14 版被加入.

int PyUnstable_IsImmortal(PyObject *obj)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

This function returns non-zero if obj is immortal, and zero otherwise. This function cannot fail.

備註

Objects that are immortal in one CPython version are not guaranteed to be immortal in another.

在 3.14 版被加入.

int PyUnstable_TryIncRef(PyObject *obj)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Increments the reference count of obj if it is not zero. Returns 1 if the object's reference count was successfully incremented. Otherwise, this function returns 0.

PyUnstable_EnableTryIncRef() must have been called earlier on obj or this function may spuriously return 0 in the free threading build.

This function is logically equivalent to the following C code, except that it behaves atomically in the free threading build:

if (Py_REFCNT(op) > 0) {
   Py_INCREF(op);
   return 1;
}
return 0;

This is intended as a building block for managing weak references without the overhead of a Python weak reference object.

Typically, correct use of this function requires support from obj's deallocator (tp_dealloc). For example, the following sketch could be adapted to implement a "weakmap" that works like a WeakValueDictionary for a specific type:

PyMutex mutex;

PyObject *
add_entry(weakmap_key_type *key, PyObject *value)
{
    PyUnstable_EnableTryIncRef(value);
    weakmap_type weakmap = ...;
    PyMutex_Lock(&mutex);
    weakmap_add_entry(weakmap, key, value);
    PyMutex_Unlock(&mutex);
    Py_RETURN_NONE;
}

PyObject *
get_value(weakmap_key_type *key)
{
    weakmap_type weakmap = ...;
    PyMutex_Lock(&mutex);
    PyObject *result = weakmap_find(weakmap, key);
    if (PyUnstable_TryIncRef(result)) {
        // `result` is safe to use
        PyMutex_Unlock(&mutex);
        return result;
    }
    // if we get here, `result` is starting to be garbage-collected,
    // but has not been removed from the weakmap yet
    PyMutex_Unlock(&mutex);
    return NULL;
}

// tp_dealloc function for weakmap values
void
value_dealloc(PyObject *value)
{
    weakmap_type weakmap = ...;
    PyMutex_Lock(&mutex);
    weakmap_remove_value(weakmap, value);

    ...
    PyMutex_Unlock(&mutex);
}

在 3.14 版被加入.

void PyUnstable_EnableTryIncRef(PyObject *obj)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Enables subsequent uses of PyUnstable_TryIncRef() on obj. The caller must hold a strong reference to obj when calling this.

在 3.14 版被加入.

int PyUnstable_Object_IsUniquelyReferenced(PyObject *op)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Determine if op only has one reference.

On GIL-enabled builds, this function is equivalent to Py_REFCNT(op) == 1.

On a free threaded build, this checks if op's reference count is equal to one and additionally checks if op is only used by this thread. Py_REFCNT(op) == 1 is not thread-safe on free threaded builds; prefer this function.

The caller must hold an attached thread state, despite the fact that this function doesn't call into the Python interpreter. This function cannot fail.

在 3.14 版被加入.

呼叫協定 (Call Protocol)

CPython 支援兩種不同的呼叫協定：tp_call 和 vectorcall（向量呼叫）。

tp_call 協定

設定 tp_call 的類別之實例都是可呼叫的。該插槽 (slot) 的簽章為：

PyObject *tp_call(PyObject *callable, PyObject *args, PyObject *kwargs);

要達成一個呼叫會使用一個 tuple（元組）表示位置引數、一個 dict 表示關鍵字引數，類似於 Python 程式碼中的 callable(*args, **kwargs)。args 必須不為 NULL（如果沒有引數，會使用一個空 tuple），但如果沒有關鍵字引數，kwargs 可以是 NULL。

這個慣例不僅會被 tp_call 使用，tp_new 和 tp_init 也這樣傳遞引數。

使用 PyObject_Call() 或其他呼叫 API 來呼叫一個物件。

Vectorcall 協定

在 3.9 版被加入.

Vectorcall 協定是在 PEP 590 [https://peps.python.org/pep-0590/] 被引入的，它是使函式呼叫更加有效率的附加協定。

經驗法則上，如果可呼叫物件有支援，CPython 於內部呼叫中會更傾向使用 vectorcall。然而，這並不是一個硬性規定。此外，有些第三方擴充套件會直接使用 tp_call（而不是使用 PyObject_Call()）。因此，一個支援 vectorcall 的類別也必須實作 tp_call。此外，無論使用哪種協定，可呼叫物件的行為都必須是相同的。要達成這個目的的推薦做法是將 tp_call 設定為 PyVectorcall_Call()。這值得一再提醒：

警告

一個支援 vectorcall 的類別必須也實作具有相同語義的 tp_call。

在 3.12 版的變更: 當一個類別的 __call__() 方法被重新賦值時，Py_TPFLAGS_HAVE_VECTORCALL 旗標現在會被移除。（這會在內部設定 tp_call，因此可能會使它與 vectorcall 函式有不同的行為。）在較早的 Python 版本中，vectorcall 應該只與 immutable 或靜態型別一起使用。

如果一個類別的 vectorcall 比 tp_call 慢，就不應該實作 vectorcall。例如，如果被呼叫者需要將引數轉換為 args tuple（引數元組）和 kwargs dict（關鍵字引數字典），那麼實作 vectorcall 就沒有意義。

類別可以透過啟用 Py_TPFLAGS_HAVE_VECTORCALL 旗標並將 tp_vectorcall_offset 設定為物件結構中有出現 vectorcallfunc 的 offset 來實作 vectorcall 協定。這是一個指向具有以下簽章之函式的指標：

typedef PyObject *(*vectorcallfunc)(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwnames)

為 穩定 ABI 的一部分 自 3.12 版本開始.

callable 是指被呼叫的物件。

args 是一個 C 語言陣列 (array)，包含位置引數與後面

關鍵字引數的值。如果沒有引數，這個值可以是 NULL。

nargsf 是位置引數的數量加上可能會有的

PY_VECTORCALL_ARGUMENTS_OFFSET 旗標。如果要從 nargsf 獲得實際的位置引數數量，請使用 PyVectorcall_NARGS()。

kwnames 是一個包含所有關鍵字引數名稱的 tuple；

換句話說，就是 kwargs 字典的鍵。這些名字必須是字串（str 或其子類別的實例)，並且它們必須是不重複的。如果沒有關鍵字引數，那麼 kwnames 可以用 NULL 代替。

PY_VECTORCALL_ARGUMENTS_OFFSET

為 穩定 ABI 的一部分 自 3.12 版本開始.

如果在 vectorcall 的 nargsf 引數中設定了此旗標，則允許被呼叫者臨時更改 args[-1] 的值。換句話說，args 指向向量中的引數 1（不是 0）。被呼叫方必須在回傳之前還原 args[-1] 的值。

對於 PyObject_VectorcallMethod()，這個旗標的改變意味著可能是 args[0] 被改變。

當可以以幾乎無代價的方式（無需佔據額外的記憶體）來達成，那麼會推薦呼叫者使用 PY_VECTORCALL_ARGUMENTS_OFFSET。這樣做會讓如 bound method（繫結方法）之類的可呼叫函式非常有效地繼續向前呼叫（這類函式包含一個在首位的 self 引數）。

在 3.8 版被加入.

要呼叫一個實作了 vectorcall 的物件，請就像其他可呼叫物件一樣使用呼叫 API 中的函式。PyObject_Vectorcall() 通常是最有效率的。

遞迴控制

在使用 tp_call 時，被呼叫者不必擔心遞迴：CPython 對於使用 tp_call 的呼叫會使用 Py_EnterRecursiveCall() 和 Py_LeaveRecursiveCall()。

為保證效率，這不適用於使用 vectorcall 的呼叫：被呼叫方在需要時應當使用 Py_EnterRecursiveCall 和 Py_LeaveRecursiveCall。

Vectorcall 支援 API

Py_ssize_t PyVectorcall_NARGS(size_t nargsf)

為 穩定 ABI 的一部分 自 3.12 版本開始.

給定一個 vectorcall nargsf 引數，回傳引數的實際數量。目前等同於：

(Py_ssize_t)(nargsf & ~PY_VECTORCALL_ARGUMENTS_OFFSET)

然而，應使用 PyVectorcall_NARGS 函式以便將來需要擴充。

在 3.8 版被加入.

vectorcallfunc PyVectorcall_Function(PyObject *op)

如果 op 不支援 vectorcall 協定（因為型別不支援或特定實例不支援），就回傳 NULL。否則，回傳儲存在 op 中的 vectorcall 函式指標。這個函式不會引發例外。

這大多在檢查 op 是否支援 vectorcall 時能派上用場，可以透過檢查 PyVectorcall_Function(op) != NULL 來達成。

在 3.9 版被加入.

PyObject *PyVectorcall_Call(PyObject *callable, PyObject *tuple, PyObject *dict)

為 穩定 ABI 的一部分 自 3.12 版本開始.

呼叫 callable 的 vectorcallfunc，其位置引數和關鍵字引數分別以 tuple 和 dict 格式給定。

這是一個專門函式，其目的是被放入 tp_call 插槽或是用於 tp_call 的實作。它不會檢查 Py_TPFLAGS_HAVE_VECTORCALL 旗標並且它不會退回 (fall back) 使用 tp_call。

在 3.8 版被加入.

物件呼叫 API

有多個函式可被用來呼叫 Python 物件。各個函式會將其引數轉換為被呼叫物件所支援的慣用形式 – 可以是 tp_call 或 vectorcall。為了儘可能減少轉換的進行，請選擇一個適合你所擁有資料格式的函式。

下表總結了可用的函式；請參閱各個說明文件以瞭解詳情。

函式

callable

args

kwargs

PyObject_Call()

PyObject *

tuple

dict/NULL

PyObject_CallNoArgs()

PyObject *

---

---

PyObject_CallOneArg()

PyObject *

一個物件

---

PyObject_CallObject()

PyObject *

tuple/NULL

---

PyObject_CallFunction()

PyObject *

format

---

PyObject_CallMethod()

物件 + char*

format

---

PyObject_CallFunctionObjArgs()

PyObject *

可變引數

---

PyObject_CallMethodObjArgs()

物件 + 名稱

可變引數

---

PyObject_CallMethodNoArgs()

物件 + 名稱

---

---

PyObject_CallMethodOneArg()

物件 + 名稱

一個物件

---

PyObject_Vectorcall()

PyObject *

vectorcall

vectorcall

PyObject_VectorcallDict()

PyObject *

vectorcall

dict/NULL

PyObject_VectorcallMethod()

引數 + 名稱

vectorcall

vectorcall

PyObject *PyObject_Call(PyObject *callable, PyObject *args, PyObject *kwargs)

回傳值：新的參照。 為 穩定 ABI 的一部分.

呼叫一個可呼叫的 Python 物件 callable，附帶由 tuple args 所給定的引數及由字典 kwargs 所給定的關鍵字引數。

args 必須不為 NULL；如果不需要引數，請使用一個空 tuple。如果不需要關鍵字引數，則 kwargs 可以為 NULL。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

這等價於 Python 運算式 callable(*args, **kwargs)。

PyObject *PyObject_CallNoArgs(PyObject *callable)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.10 版本開始.

呼叫一個可呼叫的 Python 物件 callable 並不附帶任何引數。這是不帶引數呼叫 Python 可呼叫物件的最有效方式。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

在 3.9 版被加入.

PyObject *PyObject_CallOneArg(PyObject *callable, PyObject *arg)

回傳值：新的參照。

呼叫一個可呼叫的 Python 物件 callable 並附帶正好一個位置引數 arg 而沒有關鍵字引數。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

在 3.9 版被加入.

PyObject *PyObject_CallObject(PyObject *callable, PyObject *args)

回傳值：新的參照。 為 穩定 ABI 的一部分.

呼叫一個可呼叫的 Python 物件 callable，附帶由 tuple args 所給定的引數。如果不需要傳入引數，則 args 可以為 NULL。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

這等價於 Python 運算式 callable(*args)。

PyObject *PyObject_CallFunction(PyObject *callable, const char *format, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

呼叫一個可呼叫的 Python 物件 callable，附帶數量可變的 C 引數。這些 C 引數使用 Py_BuildValue() 風格的格式字串來描述。格式可以為 NULL，表示沒有提供任何引數。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

這等價於 Python 運算式 callable(*args)。

注意，如果你只傳入 PyObject* 引數，則 PyObject_CallFunctionObjArgs() 是另一個更快速的選擇。

在 3.4 版的變更: 這個 format 的型別已從 char * 更改。

PyObject *PyObject_CallMethod(PyObject *obj, const char *name, const char *format, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

呼叫 obj 物件中名為 name 的 method 並附帶數量可變的 C 引數。這些 C 引數由 Py_BuildValue() 格式字串來描述，並應當生成一個 tuple。

格式可以為 NULL，表示沒有提供任何引數。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

這等價於 Python 運算式 obj.name(arg1, arg2, ...)。

注意，如果你只傳入 PyObject* 引數，則 PyObject_CallMethodObjArgs() 是另一個更快速的選擇。

在 3.4 版的變更: name 和 format 的型別已從 char * 更改。

PyObject *PyObject_CallFunctionObjArgs(PyObject *callable, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

呼叫一個可呼叫的 Python 物件 callable，附帶數量可變的 PyObject* 引數。這些引數是以位置在 NULL 後面、數量可變的參數來提供。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

這等價於 Python 運算式 callable(arg1, arg2, ...)。

PyObject *PyObject_CallMethodObjArgs(PyObject *obj, PyObject *name, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

呼叫 Python 物件 obj 中的一個 method，其中 method 名稱由 name 中的 Python 字串物件給定。被呼叫時會附帶數量可變的 PyObject* 引數。這些引數是以位置在 NULL 後面、且數量可變的參數來提供。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

PyObject *PyObject_CallMethodNoArgs(PyObject *obj, PyObject *name)

不附帶任何引數地呼叫 Python 物件 obj 中的一個 method，其中 method 名稱由 name 中的 Python 字串物件給定。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

在 3.9 版被加入.

PyObject *PyObject_CallMethodOneArg(PyObject *obj, PyObject *name, PyObject *arg)

附帶一個位置引數 arg 地呼叫 Python 物件 obj 中的一個 method，其中 method 名稱由 name 中的 Python 字串物件給定。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

在 3.9 版被加入.

PyObject *PyObject_Vectorcall(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwnames)

為 穩定 ABI 的一部分 自 3.12 版本開始.

呼叫一個可呼叫的 Python 物件 callable。附帶引數與 vectorcallfunc 的相同。如果 callable 支援 vectorcall，則它會直接呼叫存放在 callable 中的 vectorcall 函式。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

在 3.8 版被加入: 名為 _PyObject_Vectorcall

在 3.9 版的變更: 重新命名為目前的名稱，且不帶前導底線。舊的暫定名稱已被軟性棄用。

PyObject *PyObject_VectorcallDict(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwdict)

附帶與在 vectorcall 協定中傳入的相同位置引數來呼叫 callable，但會加上以字典 kwdict 格式傳入的關鍵字引數。args 陣列將只包含位置引數。

無論內部使用了哪一種協定，都會需要進行引數的轉換。因此，此函式應該只有在呼叫方已經擁有一個要作為關鍵字引數的字典、但沒有作為位置引數的 tuple 時才被使用。

在 3.9 版被加入.

PyObject *PyObject_VectorcallMethod(PyObject *name, PyObject *const *args, size_t nargsf, PyObject *kwnames)

為 穩定 ABI 的一部分 自 3.12 版本開始.

使用 vectorcall 呼叫慣例來呼叫一個 method。method 的名稱以 Python 字串 name 的格式給定。被呼叫 method 的物件為 args[0]，而 args 陣列從 args[1] 開始的部分則代表呼叫的引數。必須傳入至少一個位置引數。nargsf 為包括 args[0] 在內的位置引數的數量，如果 args[0] 的值可能被臨時改變則要再加上 PY_VECTORCALL_ARGUMENTS_OFFSET。關鍵字引數可以像在 PyObject_Vectorcall() 中一樣被傳入。

如果物件具有 Py_TPFLAGS_METHOD_DESCRIPTOR 特性，這將以完整的 args 向量作為引數來呼叫 unbound method（未繫結方法）物件。

成功時回傳結果，或在失敗時引發一個例外並回傳 NULL。

在 3.9 版被加入.

呼叫支援 API

int PyCallable_Check(PyObject *o)

為 穩定 ABI 的一部分.

判定物件 o 是否為可呼叫的。如果物件是可呼叫物件則回傳 1，其他情況回傳 0。這個函式不會呼叫失敗。

數字協定

int PyNumber_Check(PyObject *o)

為 穩定 ABI 的一部分.

Returns 1 if the object o provides numeric protocols, and false otherwise. This function always succeeds.

在 3.8 版的變更: Returns 1 if o is an index integer.

PyObject *PyNumber_Add(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of adding o1 and o2, or NULL on failure. This is the equivalent of the Python expression o1 + o2.

PyObject *PyNumber_Subtract(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of subtracting o2 from o1, or NULL on failure. This is the equivalent of the Python expression o1 - o2.

PyObject *PyNumber_Multiply(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of multiplying o1 and o2, or NULL on failure. This is the equivalent of the Python expression o1 * o2.

PyObject *PyNumber_MatrixMultiply(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Returns the result of matrix multiplication on o1 and o2, or NULL on failure. This is the equivalent of the Python expression o1 @ o2.

在 3.5 版被加入.

PyObject *PyNumber_FloorDivide(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the floor of o1 divided by o2, or NULL on failure. This is the equivalent of the Python expression o1 // o2.

PyObject *PyNumber_TrueDivide(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a reasonable approximation for the mathematical value of o1 divided by o2, or NULL on failure. The return value is "approximate" because binary floating-point numbers are approximate; it is not possible to represent all real numbers in base two. This function can return a floating-point value when passed two integers. This is the equivalent of the Python expression o1 / o2.

PyObject *PyNumber_Remainder(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the remainder of dividing o1 by o2, or NULL on failure. This is the equivalent of the Python expression o1 % o2.

PyObject *PyNumber_Divmod(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

See the built-in function divmod(). Returns NULL on failure. This is the equivalent of the Python expression divmod(o1, o2).

PyObject *PyNumber_Power(PyObject *o1, PyObject *o2, PyObject *o3)

回傳值：新的參照。 為 穩定 ABI 的一部分.

See the built-in function pow(). Returns NULL on failure. This is the equivalent of the Python expression pow(o1, o2, o3), where o3 is optional. If o3 is to be ignored, pass Py_None in its place (passing NULL for o3 would cause an illegal memory access).

PyObject *PyNumber_Negative(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the negation of o on success, or NULL on failure. This is the equivalent of the Python expression -o.

PyObject *PyNumber_Positive(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns o on success, or NULL on failure. This is the equivalent of the Python expression +o.

PyObject *PyNumber_Absolute(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the absolute value of o, or NULL on failure. This is the equivalent of the Python expression abs(o).

PyObject *PyNumber_Invert(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the bitwise negation of o on success, or NULL on failure. This is the equivalent of the Python expression ~o.

PyObject *PyNumber_Lshift(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of left shifting o1 by o2 on success, or NULL on failure. This is the equivalent of the Python expression o1 << o2.

PyObject *PyNumber_Rshift(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of right shifting o1 by o2 on success, or NULL on failure. This is the equivalent of the Python expression o1 >> o2.

PyObject *PyNumber_And(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the "bitwise and" of o1 and o2 on success and NULL on failure. This is the equivalent of the Python expression o1 & o2.

PyObject *PyNumber_Xor(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the "bitwise exclusive or" of o1 by o2 on success, or NULL on failure. This is the equivalent of the Python expression o1 ^ o2.

PyObject *PyNumber_Or(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the "bitwise or" of o1 and o2 on success, or NULL on failure. This is the equivalent of the Python expression o1 | o2.

PyObject *PyNumber_InPlaceAdd(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of adding o1 and o2, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 += o2.

PyObject *PyNumber_InPlaceSubtract(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of subtracting o2 from o1, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 -= o2.

PyObject *PyNumber_InPlaceMultiply(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of multiplying o1 and o2, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 *= o2.

PyObject *PyNumber_InPlaceMatrixMultiply(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Returns the result of matrix multiplication on o1 and o2, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 @= o2.

在 3.5 版被加入.

PyObject *PyNumber_InPlaceFloorDivide(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the mathematical floor of dividing o1 by o2, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 //= o2.

PyObject *PyNumber_InPlaceTrueDivide(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a reasonable approximation for the mathematical value of o1 divided by o2, or NULL on failure. The return value is "approximate" because binary floating-point numbers are approximate; it is not possible to represent all real numbers in base two. This function can return a floating-point value when passed two integers. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 /= o2.

PyObject *PyNumber_InPlaceRemainder(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the remainder of dividing o1 by o2, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 %= o2.

PyObject *PyNumber_InPlacePower(PyObject *o1, PyObject *o2, PyObject *o3)

回傳值：新的參照。 為 穩定 ABI 的一部分.

See the built-in function pow(). Returns NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 **= o2 when o3 is Py_None, or an in-place variant of pow(o1, o2, o3) otherwise. If o3 is to be ignored, pass Py_None in its place (passing NULL for o3 would cause an illegal memory access).

PyObject *PyNumber_InPlaceLshift(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of left shifting o1 by o2 on success, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 <<= o2.

PyObject *PyNumber_InPlaceRshift(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the result of right shifting o1 by o2 on success, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 >>= o2.

PyObject *PyNumber_InPlaceAnd(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the "bitwise and" of o1 and o2 on success and NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 &= o2.

PyObject *PyNumber_InPlaceXor(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the "bitwise exclusive or" of o1 by o2 on success, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 ^= o2.

PyObject *PyNumber_InPlaceOr(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the "bitwise or" of o1 and o2 on success, or NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python statement o1 |= o2.

PyObject *PyNumber_Long(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the o converted to an integer object on success, or NULL on failure. This is the equivalent of the Python expression int(o).

PyObject *PyNumber_Float(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the o converted to a float object on success, or NULL on failure. This is the equivalent of the Python expression float(o).

PyObject *PyNumber_Index(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the o converted to a Python int on success or NULL with a TypeError exception raised on failure.

在 3.10 版的變更: The result always has exact type int. Previously, the result could have been an instance of a subclass of int.

PyObject *PyNumber_ToBase(PyObject *n, int base)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Returns the integer n converted to base base as a string. The base argument must be one of 2, 8, 10, or 16. For base 2, 8, or 16, the returned string is prefixed with a base marker of '0b', '0o', or '0x', respectively. If n is not a Python int, it is converted with PyNumber_Index() first.

Py_ssize_t PyNumber_AsSsize_t(PyObject *o, PyObject *exc)

為 穩定 ABI 的一部分.

Returns o converted to a Py_ssize_t value if o can be interpreted as an integer. If the call fails, an exception is raised and -1 is returned.

If o can be converted to a Python int but the attempt to convert to a Py_ssize_t value would raise an OverflowError, then the exc argument is the type of exception that will be raised (usually IndexError or OverflowError). If exc is NULL, then the exception is cleared and the value is clipped to PY_SSIZE_T_MIN for a negative integer or PY_SSIZE_T_MAX for a positive integer.

int PyIndex_Check(PyObject *o)

為 穩定 ABI 的一部分 自 3.8 版本開始.

Returns 1 if o is an index integer (has the nb_index slot of the tp_as_number structure filled in), and 0 otherwise. This function always succeeds.

序列協定

int PySequence_Check(PyObject *o)

為 穩定 ABI 的一部分.

Return 1 if the object provides the sequence protocol, and 0 otherwise. Note that it returns 1 for Python classes with a __getitem__() method, unless they are dict subclasses, since in general it is impossible to determine what type of keys the class supports. This function always succeeds.

Py_ssize_t PySequence_Size(PyObject *o)

Py_ssize_t PySequence_Length(PyObject *o)

為 穩定 ABI 的一部分.

Returns the number of objects in sequence o on success, and -1 on failure. This is equivalent to the Python expression len(o).

PyObject *PySequence_Concat(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the concatenation of o1 and o2 on success, and NULL on failure. This is the equivalent of the Python expression o1 + o2.

PyObject *PySequence_Repeat(PyObject *o, Py_ssize_t count)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the result of repeating sequence object o count times, or NULL on failure. This is the equivalent of the Python expression o * count.

PyObject *PySequence_InPlaceConcat(PyObject *o1, PyObject *o2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the concatenation of o1 and o2 on success, and NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python expression o1 += o2.

PyObject *PySequence_InPlaceRepeat(PyObject *o, Py_ssize_t count)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the result of repeating sequence object o count times, or NULL on failure. The operation is done in-place when o supports it. This is the equivalent of the Python expression o *= count.

PyObject *PySequence_GetItem(PyObject *o, Py_ssize_t i)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the ith element of o, or NULL on failure. This is the equivalent of the Python expression o[i].

PyObject *PySequence_GetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the slice of sequence object o between i1 and i2, or NULL on failure. This is the equivalent of the Python expression o[i1:i2].

int PySequence_SetItem(PyObject *o, Py_ssize_t i, PyObject *v)

為 穩定 ABI 的一部分.

Assign object v to the ith element of o. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o[i] = v. This function does not steal a reference to v.

If v is NULL, the element is deleted, but this feature is deprecated in favour of using PySequence_DelItem().

int PySequence_DelItem(PyObject *o, Py_ssize_t i)

為 穩定 ABI 的一部分.

Delete the ith element of object o. Returns -1 on failure. This is the equivalent of the Python statement del o[i].

int PySequence_SetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2, PyObject *v)

為 穩定 ABI 的一部分.

Assign the sequence object v to the slice in sequence object o from i1 to i2. This is the equivalent of the Python statement o[i1:i2] = v.

int PySequence_DelSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)

為 穩定 ABI 的一部分.

Delete the slice in sequence object o from i1 to i2. Returns -1 on failure. This is the equivalent of the Python statement del o[i1:i2].

Py_ssize_t PySequence_Count(PyObject *o, PyObject *value)

為 穩定 ABI 的一部分.

Return the number of occurrences of value in o, that is, return the number of keys for which o[key] == value. On failure, return -1. This is equivalent to the Python expression o.count(value).

int PySequence_Contains(PyObject *o, PyObject *value)

為 穩定 ABI 的一部分.

Determine if o contains value. If an item in o is equal to value, return 1, otherwise return 0. On error, return -1. This is equivalent to the Python expression value in o.

int PySequence_In(PyObject *o, PyObject *value)

為 穩定 ABI 的一部分.

PySequence_Contains() 的別名。

在 3.14 版之後被棄用: The function is soft deprecated and should no longer be used to write new code.

Py_ssize_t PySequence_Index(PyObject *o, PyObject *value)

為 穩定 ABI 的一部分.

Return the first index i for which o[i] == value. On error, return -1. This is equivalent to the Python expression o.index(value).

PyObject *PySequence_List(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a list object with the same contents as the sequence or iterable o, or NULL on failure. The returned list is guaranteed to be new. This is equivalent to the Python expression list(o).

PyObject *PySequence_Tuple(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a tuple object with the same contents as the sequence or iterable o, or NULL on failure. If o is a tuple, a new reference will be returned, otherwise a tuple will be constructed with the appropriate contents. This is equivalent to the Python expression tuple(o).

PyObject *PySequence_Fast(PyObject *o, const char *m)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the sequence or iterable o as an object usable by the other PySequence_Fast* family of functions. If the object is not a sequence or iterable, raises TypeError with m as the message text. Returns NULL on failure.

The PySequence_Fast* functions are thus named because they assume o is a PyTupleObject or a PyListObject and access the data fields of o directly.

As a CPython implementation detail, if o is already a sequence or list, it will be returned.

Py_ssize_t PySequence_Fast_GET_SIZE(PyObject *o)

Returns the length of o, assuming that o was returned by PySequence_Fast() and that o is not NULL. The size can also be retrieved by calling PySequence_Size() on o, but PySequence_Fast_GET_SIZE() is faster because it can assume o is a list or tuple.

PyObject *PySequence_Fast_GET_ITEM(PyObject *o, Py_ssize_t i)

回傳值：借用參照。

Return the ith element of o, assuming that o was returned by PySequence_Fast(), o is not NULL, and that i is within bounds.

PyObject **PySequence_Fast_ITEMS(PyObject *o)

Return the underlying array of PyObject pointers. Assumes that o was returned by PySequence_Fast() and o is not NULL.

Note, if a list gets resized, the reallocation may relocate the items array. So, only use the underlying array pointer in contexts where the sequence cannot change.

PyObject *PySequence_ITEM(PyObject *o, Py_ssize_t i)

回傳值：新的參照。

Return the ith element of o or NULL on failure. Faster form of PySequence_GetItem() but without checking that PySequence_Check() on o is true and without adjustment for negative indices.

對映協定

另請參閱 PyObject_GetItem()、PyObject_SetItem() 和 PyObject_DelItem()。

int PyMapping_Check(PyObject *o)

為 穩定 ABI 的一部分.

如果物件有提供對映協定或支援切片 (slicing) 則回傳 1，否則回傳 0。請注意，對於具有 __getitem__() 方法的 Python 類別，它會回傳 1，因為通常無法確定該類別支援什麼類型的鍵。這個函式總會是成功的。

Py_ssize_t PyMapping_Size(PyObject *o)

Py_ssize_t PyMapping_Length(PyObject *o)

為 穩定 ABI 的一部分.

成功時回傳物件 o 中的鍵數，失敗時回傳 -1。這相當於 Python 運算式 len(o)。

PyObject *PyMapping_GetItemString(PyObject *o, const char *key)

回傳值：新的參照。 為 穩定 ABI 的一部分.

這與 PyObject_GetItem() 相同，但 key 被指定為 const char* UTF-8 編碼位元組字串，而不是 PyObject*。

int PyMapping_GetOptionalItem(PyObject *obj, PyObject *key, PyObject **result)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Variant of PyObject_GetItem() which doesn't raise KeyError if the key is not found.

If the key is found, return 1 and set *result to a new strong reference to the corresponding value. If the key is not found, return 0 and set *result to NULL; the KeyError is silenced. If an error other than KeyError is raised, return -1 and set *result to NULL.

在 3.13 版被加入.

int PyMapping_GetOptionalItemString(PyObject *obj, const char *key, PyObject **result)

為 穩定 ABI 的一部分 自 3.13 版本開始.

這與 PyMapping_GetOptionalItem() 相同，但 key 被指定為 const char* UTF-8 編碼位元組字串，而不是 PyObject*。

在 3.13 版被加入.

int PyMapping_SetItemString(PyObject *o, const char *key, PyObject *v)

為 穩定 ABI 的一部分.

這與 PyObject_SetItem() 相同，但 key 被指定為 const char* UTF-8 編碼位元組字串，而不是 PyObject*。

int PyMapping_DelItem(PyObject *o, PyObject *key)

這是 PyObject_DelItem() 的別名。

int PyMapping_DelItemString(PyObject *o, const char *key)

這與 PyObject_DelItem() 相同，但 key 被指定為 const char* UTF-8 編碼位元組字串，而不是 PyObject*。

int PyMapping_HasKeyWithError(PyObject *o, PyObject *key)

為 穩定 ABI 的一部分 自 3.13 版本開始.

如果對映物件具有鍵 key 則回傳 1，否則回傳 0。這相當於 Python 運算式 key in o。失敗時回傳 -1。

在 3.13 版被加入.

int PyMapping_HasKeyStringWithError(PyObject *o, const char *key)

為 穩定 ABI 的一部分 自 3.13 版本開始.

這與 PyMapping_HasKeyWithError() 相同，但 key 被指定為 const char* UTF-8 編碼位元組字串，而不是 PyObject*。

在 3.13 版被加入.

int PyMapping_HasKey(PyObject *o, PyObject *key)

為 穩定 ABI 的一部分.

如果對映物件具有鍵 key 則回傳 1，否則回傳 0。這相當於 Python 運算式 key in o。這個函式總會是成功的。

備註

當它呼叫 __getitem__() 方法時發生的例外將被默默忽略。為了適當地處理錯誤，請改用 PyMapping_HasKeyWithError()、PyMapping_GetOptionalItem() 或 PyObject_GetItem()。

int PyMapping_HasKeyString(PyObject *o, const char *key)

為 穩定 ABI 的一部分.

這與 PyMapping_HasKey() 相同，但 key 被指定為 const char* UTF-8 編碼位元組字串，而不是 PyObject*。

備註

當它呼叫 __getitem__() 方法或建立臨時 str 物件時發生的例外將被默默忽略。為了適當地處理錯誤，請改用 PyMapping_HasKeyStringWithError()、PyMapping_GetOptionalItemString() 或 PyMapping_GetItemString()。

PyObject *PyMapping_Keys(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

成功時回傳一個物件 o 內之鍵的串列，失敗時回傳 NULL。

在 3.7 版的變更: 在以前，該函式會回傳串列或元組。

PyObject *PyMapping_Values(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

成功時回傳物件 o 中值的串列。失敗時回傳 NULL。

在 3.7 版的變更: 在以前，該函式會回傳串列或元組。

PyObject *PyMapping_Items(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

成功時回傳物件 o 內之項目的串列，其中每個項目都是包含鍵值對的元組。失敗時回傳 NULL。

在 3.7 版的變更: 在以前，該函式會回傳串列或元組。

疊代器協定

有兩個專門用於疊代器的函式。

int PyIter_Check(PyObject *o)

為 穩定 ABI 的一部分 自 3.8 版本開始.

如果物件 o 可以安全地傳遞給 PyIter_NextItem() 則回傳非零 (non-zero)，否則回傳 0。這個函式一定會執行成功。

int PyAIter_Check(PyObject *o)

為 穩定 ABI 的一部分 自 3.10 版本開始.

如果物件 o 有提供 AsyncIterator 協定，則回傳非零，否則回傳 0。這個函式一定會執行成功。

在 3.10 版被加入.

int PyIter_NextItem(PyObject *iter, PyObject **item)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Return 1 and set item to a strong reference of the next value of the iterator iter on success. Return 0 and set item to NULL if there are no remaining values. Return -1, set item to NULL and set an exception on error.

在 3.14 版被加入.

PyObject *PyIter_Next(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

這是 PyIter_NextItem() 的舊版本，為了向後相容而保留。請優先使用 PyIter_NextItem()。

回傳疊代器 o 的下一個值。根據 PyIter_Check()，該物件必須是一個疊代器（由呼叫者檢查）。如果沒有剩餘值，則回傳 NULL 且不設定例外。如果檢索項目時發生錯誤，則回傳 NULL 並傳遞例外。

type PySendResult

用於表示 PyIter_Send() 不同結果的列舉 (enum) 值。

在 3.10 版被加入.

PySendResult PyIter_Send(PyObject *iter, PyObject *arg, PyObject **presult)

為 穩定 ABI 的一部分 自 3.10 版本開始.

將 arg 值發送到疊代器 iter 中。回傳：

如果疊代器有回傳則為 PYGEN_RETURN。回傳值透過 presult 回傳。

如果疊代器有產生 (yield) 則為 PYGEN_NEXT。產生值透過 presult 回傳。

如果疊代器引發例外則為 PYGEN_ERROR。 presult 被設定為 NULL。

在 3.10 版被加入.

緩衝協定 (Buffer Protocol)

Certain objects available in Python wrap access to an underlying memory array or buffer. Such objects include the built-in bytes and bytearray, and some extension types like array.array. Third-party libraries may define their own types for special purposes, such as image processing or numeric analysis.

While each of these types have their own semantics, they share the common characteristic of being backed by a possibly large memory buffer. It is then desirable, in some situations, to access that buffer directly and without intermediate copying.

Python provides such a facility at the C and Python level in the form of the buffer protocol. This protocol has two sides:

on the producer side, a type can export a "buffer interface" which allows objects of that type to expose information about their underlying buffer. This interface is described in the section 緩衝區物件結構; for Python see Emulating buffer types.

on the consumer side, several means are available to obtain a pointer to the raw underlying data of an object (for example a method parameter). For Python see memoryview.

Simple objects such as bytes and bytearray expose their underlying buffer in byte-oriented form. Other forms are possible; for example, the elements exposed by an array.array can be multi-byte values.

An example consumer of the buffer interface is the write() method of file objects: any object that can export a series of bytes through the buffer interface can be written to a file. While write() only needs read-only access to the internal contents of the object passed to it, other methods such as readinto() need write access to the contents of their argument. The buffer interface allows objects to selectively allow or reject exporting of read-write and read-only buffers.

There are two ways for a consumer of the buffer interface to acquire a buffer over a target object:

以適當的參數呼叫 PyObject_GetBuffer()；

call PyArg_ParseTuple() (or one of its siblings) with one of the y*, w* or s* format codes.

In both cases, PyBuffer_Release() must be called when the buffer isn't needed anymore. Failure to do so could lead to various issues such as resource leaks.

在 3.12 版被加入: The buffer protocol is now accessible in Python, see Emulating buffer types and memoryview.

緩衝區結構

Buffer structures (or simply "buffers") are useful as a way to expose the binary data from another object to the Python programmer. They can also be used as a zero-copy slicing mechanism. Using their ability to reference a block of memory, it is possible to expose any data to the Python programmer quite easily. The memory could be a large, constant array in a C extension, it could be a raw block of memory for manipulation before passing to an operating system library, or it could be used to pass around structured data in its native, in-memory format.

Contrary to most data types exposed by the Python interpreter, buffers are not PyObject pointers but rather simple C structures. This allows them to be created and copied very simply. When a generic wrapper around a buffer is needed, a memoryview object can be created.

For short instructions how to write an exporting object, see Buffer Object Structures. For obtaining a buffer, see PyObject_GetBuffer().

type Py_buffer

為 穩定 ABI 的一部分 （包含所有成員） 自 3.11 版本開始.

void *buf

A pointer to the start of the logical structure described by the buffer fields. This can be any location within the underlying physical memory block of the exporter. For example, with negative strides the value may point to the end of the memory block.

For contiguous arrays, the value points to the beginning of the memory block.

PyObject *obj

A new reference to the exporting object. The reference is owned by the consumer and automatically released (i.e. reference count decremented) and set to NULL by PyBuffer_Release(). The field is the equivalent of the return value of any standard C-API function.

As a special case, for temporary buffers that are wrapped by PyMemoryView_FromBuffer() or PyBuffer_FillInfo() this field is NULL. In general, exporting objects MUST NOT use this scheme.

Py_ssize_t len

product(shape) * itemsize. For contiguous arrays, this is the length of the underlying memory block. For non-contiguous arrays, it is the length that the logical structure would have if it were copied to a contiguous representation.

Accessing ((char *)buf)[0] up to ((char *)buf)[len-1] is only valid if the buffer has been obtained by a request that guarantees contiguity. In most cases such a request will be PyBUF_SIMPLE or PyBUF_WRITABLE.

int readonly

An indicator of whether the buffer is read-only. This field is controlled by the PyBUF_WRITABLE flag.

Py_ssize_t itemsize

Item size in bytes of a single element. Same as the value of struct.calcsize() called on non-NULL format values.

Important exception: If a consumer requests a buffer without the PyBUF_FORMAT flag, format will be set to NULL, but itemsize still has the value for the original format.

If shape is present, the equality product(shape) * itemsize == len still holds and the consumer can use itemsize to navigate the buffer.

If shape is NULL as a result of a PyBUF_SIMPLE or a PyBUF_WRITABLE request, the consumer must disregard itemsize and assume itemsize == 1.

char *format

A NULL terminated string in struct module style syntax describing the contents of a single item. If this is NULL, "B" (unsigned bytes) is assumed.

此欄位受 PyBUF_FORMAT 旗標控制。

int ndim

The number of dimensions the memory represents as an n-dimensional array. If it is 0, buf points to a single item representing a scalar. In this case, shape, strides and suboffsets MUST be NULL. The maximum number of dimensions is given by PyBUF_MAX_NDIM.

Py_ssize_t *shape

An array of Py_ssize_t of length ndim indicating the shape of the memory as an n-dimensional array. Note that shape[0] * ... * shape[ndim-1] * itemsize MUST be equal to len.

Shape values are restricted to shape[n] >= 0. The case shape[n] == 0 requires special attention. See complex arrays for further information.

The shape array is read-only for the consumer.

Py_ssize_t *strides

An array of Py_ssize_t of length ndim giving the number of bytes to skip to get to a new element in each dimension.

Stride values can be any integer. For regular arrays, strides are usually positive, but a consumer MUST be able to handle the case strides[n] <= 0. See complex arrays for further information.

The strides array is read-only for the consumer.

Py_ssize_t *suboffsets

An array of Py_ssize_t of length ndim. If suboffsets[n] >= 0, the values stored along the nth dimension are pointers and the suboffset value dictates how many bytes to add to each pointer after de-referencing. A suboffset value that is negative indicates that no de-referencing should occur (striding in a contiguous memory block).

If all suboffsets are negative (i.e. no de-referencing is needed), then this field must be NULL (the default value).

This type of array representation is used by the Python Imaging Library (PIL). See complex arrays for further information how to access elements of such an array.

The suboffsets array is read-only for the consumer.

void *internal

This is for use internally by the exporting object. For example, this might be re-cast as an integer by the exporter and used to store flags about whether or not the shape, strides, and suboffsets arrays must be freed when the buffer is released. The consumer MUST NOT alter this value.

常數：

PyBUF_MAX_NDIM

為 穩定 ABI 的一部分 自 3.11 版本開始.

The maximum number of dimensions the memory represents. Exporters MUST respect this limit, consumers of multi-dimensional buffers SHOULD be able to handle up to PyBUF_MAX_NDIM dimensions. Currently set to 64.

Buffer request types

Buffers are usually obtained by sending a buffer request to an exporting object via PyObject_GetBuffer(). Since the complexity of the logical structure of the memory can vary drastically, the consumer uses the flags argument to specify the exact buffer type it can handle.

All Py_buffer fields are unambiguously defined by the request type.

request-independent fields

The following fields are not influenced by flags and must always be filled in with the correct values: obj, buf, len, itemsize, ndim.

readonly, format

PyBUF_WRITABLE

為 穩定 ABI 的一部分 自 3.11 版本開始.

Controls the readonly field. If set, the exporter MUST provide a writable buffer or else report failure. Otherwise, the exporter MAY provide either a read-only or writable buffer, but the choice MUST be consistent for all consumers. For example, PyBUF_SIMPLE | PyBUF_WRITABLE can be used to request a simple writable buffer.

PyBUF_WRITEABLE

這是 PyBUF_WRITABLE 的軟性棄用別名。

PyBUF_FORMAT

為 穩定 ABI 的一部分 自 3.11 版本開始.

Controls the format field. If set, this field MUST be filled in correctly. Otherwise, this field MUST be NULL.

PyBUF_WRITABLE can be |'d to any of the flags in the next section. Since PyBUF_SIMPLE is defined as 0, PyBUF_WRITABLE can be used as a stand-alone flag to request a simple writable buffer.

PyBUF_FORMAT must be |'d to any of the flags except PyBUF_SIMPLE, because the latter already implies format B (unsigned bytes). PyBUF_FORMAT cannot be used on its own.

shape, strides, suboffsets

The flags that control the logical structure of the memory are listed in decreasing order of complexity. Note that each flag contains all bits of the flags below it.

Request

shape

strides

suboffsets

PyBUF_INDIRECT

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

if needed

PyBUF_STRIDES

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

PyBUF_ND

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

NULL

NULL

PyBUF_SIMPLE

為 穩定 ABI 的一部分 自 3.11 版本開始.

NULL

NULL

NULL

contiguity requests

C or Fortran contiguity can be explicitly requested, with and without stride information. Without stride information, the buffer must be C-contiguous.

Request

shape

strides

suboffsets

contig

PyBUF_C_CONTIGUOUS

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

C

PyBUF_F_CONTIGUOUS

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

F

PyBUF_ANY_CONTIGUOUS

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

C 或 F

PyBUF_ND

yes

NULL

NULL

C

compound requests

All possible requests are fully defined by some combination of the flags in the previous section. For convenience, the buffer protocol provides frequently used combinations as single flags.

In the following table U stands for undefined contiguity. The consumer would have to call PyBuffer_IsContiguous() to determine contiguity.

Request

shape

strides

suboffsets

contig

readonly

format

PyBUF_FULL

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

if needed

U

0

yes

PyBUF_FULL_RO

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

if needed

U

1 或 0

yes

PyBUF_RECORDS

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

U

0

yes

PyBUF_RECORDS_RO

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

U

1 或 0

yes

PyBUF_STRIDED

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

U

0

NULL

PyBUF_STRIDED_RO

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

yes

NULL

U

1 或 0

NULL

PyBUF_CONTIG

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

NULL

NULL

C

0

NULL

PyBUF_CONTIG_RO

為 穩定 ABI 的一部分 自 3.11 版本開始.

yes

NULL

NULL

C

1 或 0

NULL

Complex arrays

NumPy 風格：形狀與步幅

The logical structure of NumPy-style arrays is defined by itemsize, ndim, shape and strides.

If ndim == 0, the memory location pointed to by buf is interpreted as a scalar of size itemsize. In that case, both shape and strides are NULL.

If strides is NULL, the array is interpreted as a standard n-dimensional C-array. Otherwise, the consumer must access an n-dimensional array as follows:

ptr = (char *)buf + indices[0] * strides[0] + ... + indices[n-1] * strides[n-1];
item = *((typeof(item) *)ptr);

As noted above, buf can point to any location within the actual memory block. An exporter can check the validity of a buffer with this function:

def verify_structure(memlen, itemsize, ndim, shape, strides, offset):
    """Verify that the parameters represent a valid array within
       the bounds of the allocated memory:
           char *mem: start of the physical memory block
           memlen: length of the physical memory block
           offset: (char *)buf - mem
    """
    if offset % itemsize:
        return False
    if offset < 0 or offset+itemsize > memlen:
        return False
    if any(v % itemsize for v in strides):
        return False

    if ndim <= 0:
        return ndim == 0 and not shape and not strides
    if 0 in shape:
        return True

    imin = sum(strides[j]*(shape[j]-1) for j in range(ndim)
               if strides[j] <= 0)
    imax = sum(strides[j]*(shape[j]-1) for j in range(ndim)
               if strides[j] > 0)

    return 0 <= offset+imin and offset+imax+itemsize <= memlen

PIL-style: shape, strides and suboffsets

In addition to the regular items, PIL-style arrays can contain pointers that must be followed in order to get to the next element in a dimension. For example, the regular three-dimensional C-array char v[2][2][3] can also be viewed as an array of 2 pointers to 2 two-dimensional arrays: char (*v[2])[2][3]. In suboffsets representation, those two pointers can be embedded at the start of buf, pointing to two char x[2][3] arrays that can be located anywhere in memory.

Here is a function that returns a pointer to the element in an N-D array pointed to by an N-dimensional index when there are both non-NULL strides and suboffsets:

void *get_item_pointer(int ndim, void *buf, Py_ssize_t *strides,
                       Py_ssize_t *suboffsets, Py_ssize_t *indices) {
    char *pointer = (char*)buf;
    int i;
    for (i = 0; i < ndim; i++) {
        pointer += strides[i] * indices[i];
        if (suboffsets[i] >=0 ) {
            pointer = *((char**)pointer) + suboffsets[i];
        }
    }
    return (void*)pointer;
}

與緩衝相關的函式

int PyObject_CheckBuffer(PyObject *obj)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Return 1 if obj supports the buffer interface otherwise 0. When 1 is returned, it doesn't guarantee that PyObject_GetBuffer() will succeed. This function always succeeds.

int PyObject_GetBuffer(PyObject *exporter, Py_buffer *view, int flags)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Send a request to exporter to fill in view as specified by flags. If the exporter cannot provide a buffer of the exact type, it MUST raise BufferError, set view->obj to NULL and return -1.

On success, fill in view, set view->obj to a new reference to exporter and return 0. In the case of chained buffer providers that redirect requests to a single object, view->obj MAY refer to this object instead of exporter (See Buffer Object Structures).

Successful calls to PyObject_GetBuffer() must be paired with calls to PyBuffer_Release(), similar to malloc() and free(). Thus, after the consumer is done with the buffer, PyBuffer_Release() must be called exactly once.

void PyBuffer_Release(Py_buffer *view)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Release the buffer view and release the strong reference (i.e. decrement the reference count) to the view's supporting object, view->obj. This function MUST be called when the buffer is no longer being used, otherwise reference leaks may occur.

It is an error to call this function on a buffer that was not obtained via PyObject_GetBuffer().

Py_ssize_t PyBuffer_SizeFromFormat(const char *format)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Return the implied itemsize from format. On error, raise an exception and return -1.

在 3.9 版被加入.

int PyBuffer_IsContiguous(const Py_buffer *view, char order)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Return 1 if the memory defined by the view is C-style (order is 'C') or Fortran-style (order is 'F') contiguous or either one (order is 'A'). Return 0 otherwise. This function always succeeds.

void *PyBuffer_GetPointer(const Py_buffer *view, const Py_ssize_t *indices)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Get the memory area pointed to by the indices inside the given view. indices must point to an array of view->ndim indices.

int PyBuffer_FromContiguous(const Py_buffer *view, const void *buf, Py_ssize_t len, char fort)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Copy contiguous len bytes from buf to view. fort can be 'C' or 'F' (for C-style or Fortran-style ordering). 0 is returned on success, -1 on error.

int PyBuffer_ToContiguous(void *buf, const Py_buffer *src, Py_ssize_t len, char order)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Copy len bytes from src to its contiguous representation in buf. order can be 'C' or 'F' or 'A' (for C-style or Fortran-style ordering or either one). 0 is returned on success, -1 on error.

此函式在 len != src->len 時失敗。

int PyObject_CopyData(PyObject *dest, PyObject *src)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Copy data from src to dest buffer. Can convert between C-style and or Fortran-style buffers.

成功時回傳 0，錯誤時回傳 -1。

void PyBuffer_FillContiguousStrides(int ndims, Py_ssize_t *shape, Py_ssize_t *strides, int itemsize, char order)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Fill the strides array with byte-strides of a contiguous (C-style if order is 'C' or Fortran-style if order is 'F') array of the given shape with the given number of bytes per element.

int PyBuffer_FillInfo(Py_buffer *view, PyObject *exporter, void *buf, Py_ssize_t len, int readonly, int flags)

為 穩定 ABI 的一部分 自 3.11 版本開始.

Handle buffer requests for an exporter that wants to expose buf of size len with writability set according to readonly. buf is interpreted as a sequence of unsigned bytes.

The flags argument indicates the request type. This function always fills in view as specified by flags, unless buf has been designated as read-only and PyBUF_WRITABLE is set in flags.

On success, set view->obj to a new reference to exporter and return 0. Otherwise, raise BufferError, set view->obj to NULL and return -1;

If this function is used as part of a getbufferproc, exporter MUST be set to the exporting object and flags must be passed unmodified. Otherwise, exporter MUST be NULL.

具體物件層

此章節列出的函式僅能接受某些特定的 Python 物件型別，將錯誤型別的物件傳遞給它們並不是什麼好事，如果你從 Python 程式當中接收到一個不確定是否為正確型別的物件，那麼請一定要先做型別檢查。例如使用 PyDict_Check() 來確認一個物件是否為字典。本章結構類似於 Python 物件型別的"族譜圖 (family tree)"。

警告

雖然本章所述之函式仔細地檢查了傳入物件的型別，但大多並無檢查是否為 NULL。允許 NULL 的傳入可能造成記憶體的不合法存取和直譯器的立即中止。

基礎物件

此段落描述 Python 型別物件與單例 (singleton) 物件 None。

型別物件

Creating Heap-Allocated Types

None 物件

數值物件

整數物件

匯出 API

PyLongWriter API

已棄用的 API

Boolean（布林）物件

浮點數（Floating-Point）物件

打包和解包函式

打包函式

解包函式

複數物件

作為 C 結構的複數

作為 Python 物件的複數

序列物件

序列物件的一般操作在前一章節討論過了；此段落將討論 Python 語言特有的特定型別序列物件。

位元組物件 (Bytes Objects)

位元組陣列物件 (Byte Array Objects)

型別檢查巨集

直接 API 函式

巨集

Unicode 物件與編解碼器

Unicode 物件

Unicode 型別

Unicode Character Properties

Creating and accessing Unicode strings

Locale Encoding

檔案系統編碼

wchar_t 支援

內建編解碼器

泛用編解碼器

UTF-8 編解碼器

UTF-32 編解碼器

UTF-16 編解碼器

UTF-7 編解碼器

Unicode-Escape Codecs

Raw-Unicode-Escape Codecs

Latin-1 編解碼器

ASCII 編解碼器

Character Map Codecs

Windows 的 MBCS 編解碼器

Methods and Slot Functions

PyUnicodeWriter

已棄用的 API

Tuple（元組）物件

結構序列物件

List（串列）物件

容器物件

字典物件

字典視圖物件

有序字典

集合物件

已棄用的 API

函式物件

函式物件 (Function Objects)

實例方法物件 (Instance Method Objects)

方法物件 (Method Objects)

Cell 物件

程式碼物件

程式碼物件旗標

額外資訊

其他物件

檔案物件 (File Objects)

已棄用的 API

模組物件

模組定義

模組槽 (Module slots)

Creating extension modules dynamically

支援的函式

Module lookup (single-phase initialization)

疊代器（Iterator）物件

Range 物件

內建疊代器型別

其他疊代器物件

Descriptor（描述器）物件

內建描述器

切片物件

Ellipsis 物件

MemoryView 物件

Pickle buffer objects

弱參照物件

Capsules

Frame 物件

Frame Locals Proxies

Legacy Local Variable APIs

Internal Frames

產生器 (Generator) 物件

非同步產生器 (Asynchronous Generator) 物件

已棄用的 API

Coroutine（協程）物件

情境變數物件（Context Variables Objects）

型別提示物件

擴充模組的 C API

Curses C API

內部資料

DateTime 物件

內部資料

型別物件

type PyTypeObject

為 受限 API 的一部分 （做為一個不透明結構 (opaque struct)）.

The C structure of the objects used to describe built-in types.

PyTypeObject PyType_Type

為 穩定 ABI 的一部分.

This is the type object for type objects; it is the same object as type in the Python layer.

int PyType_Check(PyObject *o)

Return non-zero if the object o is a type object, including instances of types derived from the standard type object. Return 0 in all other cases. This function always succeeds.

int PyType_CheckExact(PyObject *o)

Return non-zero if the object o is a type object, but not a subtype of the standard type object. Return 0 in all other cases. This function always succeeds.

unsigned int PyType_ClearCache()

為 穩定 ABI 的一部分.

Clear the internal lookup cache. Return the current version tag.

unsigned long PyType_GetFlags(PyTypeObject *type)

為 穩定 ABI 的一部分.

Return the tp_flags member of type. This function is primarily meant for use with Py_LIMITED_API; the individual flag bits are guaranteed to be stable across Python releases, but access to tp_flags itself is not part of the limited API.

在 3.2 版被加入.

在 3.4 版的變更: The return type is now unsigned long rather than long.

PyObject *PyType_GetDict(PyTypeObject *type)

Return the type object's internal namespace, which is otherwise only exposed via a read-only proxy (cls.__dict__). This is a replacement for accessing tp_dict directly. The returned dictionary must be treated as read-only.

This function is meant for specific embedding and language-binding cases, where direct access to the dict is necessary and indirect access (e.g. via the proxy or PyObject_GetAttr()) isn't adequate.

Extension modules should continue to use tp_dict, directly or indirectly, when setting up their own types.

在 3.12 版被加入.

void PyType_Modified(PyTypeObject *type)

為 穩定 ABI 的一部分.

Invalidate the internal lookup cache for the type and all of its subtypes. This function must be called after any manual modification of the attributes or base classes of the type.

int PyType_AddWatcher(PyType_WatchCallback callback)

Register callback as a type watcher. Return a non-negative integer ID which must be passed to future calls to PyType_Watch(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

In free-threaded builds, PyType_AddWatcher() is not thread-safe, so it must be called at start up (before spawning the first thread).

在 3.12 版被加入.

int PyType_ClearWatcher(int watcher_id)

Clear watcher identified by watcher_id (previously returned from PyType_AddWatcher()). Return 0 on success, -1 on error (e.g. if watcher_id was never registered.)

An extension should never call PyType_ClearWatcher with a watcher_id that was not returned to it by a previous call to PyType_AddWatcher().

在 3.12 版被加入.

int PyType_Watch(int watcher_id, PyObject *type)

Mark type as watched. The callback granted watcher_id by PyType_AddWatcher() will be called whenever PyType_Modified() reports a change to type. (The callback may be called only once for a series of consecutive modifications to type, if _PyType_Lookup() is not called on type between the modifications; this is an implementation detail and subject to change.)

An extension should never call PyType_Watch with a watcher_id that was not returned to it by a previous call to PyType_AddWatcher().

在 3.12 版被加入.

int PyType_Unwatch(int watcher_id, PyObject *type)

Mark type as not watched. This undoes a previous call to PyType_Watch(). type must not be NULL.

An extension should never call this function with a watcher_id that was not returned to it by a previous call to PyType_AddWatcher().

成功時此函式會回傳 0。失敗時此函式回傳 -1 並設定例外。

在 3.12 版被加入.

typedef int (*PyType_WatchCallback)(PyObject *type)

Type of a type-watcher callback function.

The callback must not modify type or cause PyType_Modified() to be called on type or any type in its MRO; violating this rule could cause infinite recursion.

在 3.12 版被加入.

int PyType_HasFeature(PyTypeObject *o, int feature)

Return non-zero if the type object o sets the feature feature. Type features are denoted by single bit flags.

int PyType_FastSubclass(PyTypeObject *type, int flag)

Return non-zero if the type object type sets the subclass flag flag. Subclass flags are denoted by Py_TPFLAGS_*_SUBCLASS. This function is used by many _Check functions for common types.

也參考

PyObject_TypeCheck(), which is used as a slower alternative in _Check functions for types that don't come with subclass flags.

int PyType_IS_GC(PyTypeObject *o)

Return true if the type object includes support for the cycle detector; this tests the type flag Py_TPFLAGS_HAVE_GC.

int PyType_IsSubtype(PyTypeObject *a, PyTypeObject *b)

為 穩定 ABI 的一部分.

如果 a 是 b 的子類別則回傳 true。

This function only checks for actual subtypes, which means that __subclasscheck__() is not called on b. Call PyObject_IsSubclass() to do the same check that issubclass() would do.

PyObject *PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Generic handler for the tp_alloc slot of a type object. Uses Python's default memory allocation mechanism to allocate memory for a new instance, zeros the memory, then initializes the memory as if by calling PyObject_Init() or PyObject_InitVar().

Do not call this directly to allocate memory for an object; call the type's tp_alloc slot instead.

For types that support garbage collection (i.e., the Py_TPFLAGS_HAVE_GC flag is set), this function behaves like PyObject_GC_New or PyObject_GC_NewVar (except the memory is guaranteed to be zeroed before initialization), and should be paired with PyObject_GC_Del() in tp_free. Otherwise, it behaves like PyObject_New or PyObject_NewVar (except the memory is guaranteed to be zeroed before initialization) and should be paired with PyObject_Free() in tp_free.

PyObject *PyType_GenericNew(PyTypeObject *type, PyObject *args, PyObject *kwds)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Generic handler for the tp_new slot of a type object. Creates a new instance using the type's tp_alloc slot and returns the resulting object.

int PyType_Ready(PyTypeObject *type)

為 穩定 ABI 的一部分.

Finalize a type object. This should be called on all type objects to finish their initialization. This function is responsible for adding inherited slots from a type's base class. Return 0 on success, or return -1 and sets an exception on error.

備註

If some of the base classes implements the GC protocol and the provided type does not include the Py_TPFLAGS_HAVE_GC in its flags, then the GC protocol will be automatically implemented from its parents. On the contrary, if the type being created does include Py_TPFLAGS_HAVE_GC in its flags then it must implement the GC protocol itself by at least implementing the tp_traverse handle.

PyObject *PyType_GetName(PyTypeObject *type)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.11 版本開始.

Return the type's name. Equivalent to getting the type's __name__ attribute.

在 3.11 版被加入.

PyObject *PyType_GetQualName(PyTypeObject *type)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.11 版本開始.

Return the type's qualified name. Equivalent to getting the type's __qualname__ attribute.

在 3.11 版被加入.

PyObject *PyType_GetFullyQualifiedName(PyTypeObject *type)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Return the type's fully qualified name. Equivalent to f"{type.__module__}.{type.__qualname__}", or type.__qualname__ if type.__module__ is not a string or is equal to "builtins".

在 3.13 版被加入.

PyObject *PyType_GetModuleName(PyTypeObject *type)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Return the type's module name. Equivalent to getting the type.__module__ attribute.

在 3.13 版被加入.

void *PyType_GetSlot(PyTypeObject *type, int slot)

為 穩定 ABI 的一部分 自 3.4 版本開始.

Return the function pointer stored in the given slot. If the result is NULL, this indicates that either the slot is NULL, or that the function was called with invalid parameters. Callers will typically cast the result pointer into the appropriate function type.

See PyType_Slot.slot for possible values of the slot argument.

在 3.4 版被加入.

在 3.10 版的變更: PyType_GetSlot() can now accept all types. Previously, it was limited to heap types.

PyObject *PyType_GetModule(PyTypeObject *type)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Return the module object associated with the given type when the type was created using PyType_FromModuleAndSpec().

If no module is associated with the given type, sets TypeError and returns NULL.

This function is usually used to get the module in which a method is defined. Note that in such a method, PyType_GetModule(Py_TYPE(self)) may not return the intended result. Py_TYPE(self) may be a subclass of the intended class, and subclasses are not necessarily defined in the same module as their superclass. See PyCMethod to get the class that defines the method. See PyType_GetModuleByDef() for cases when PyCMethod cannot be used.

在 3.9 版被加入.

void *PyType_GetModuleState(PyTypeObject *type)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Return the state of the module object associated with the given type. This is a shortcut for calling PyModule_GetState() on the result of PyType_GetModule().

If no module is associated with the given type, sets TypeError and returns NULL.

If the type has an associated module but its state is NULL, returns NULL without setting an exception.

在 3.9 版被加入.

PyObject *PyType_GetModuleByDef(PyTypeObject *type, struct PyModuleDef *def)

回傳值：借用參照。 為 穩定 ABI 的一部分 自 3.13 版本開始.

Find the first superclass whose module was created from the given PyModuleDef def, and return that module.

If no module is found, raises a TypeError and returns NULL.

This function is intended to be used together with PyModule_GetState() to get module state from slot methods (such as tp_init or nb_add) and other places where a method's defining class cannot be passed using the PyCMethod calling convention.

The returned reference is borrowed from type, and will be valid as long as you hold a reference to type. Do not release it with Py_DECREF() or similar.

在 3.11 版被加入.

int PyType_GetBaseByToken(PyTypeObject *type, void *token, PyTypeObject **result)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Find the first superclass in type's method resolution order whose Py_tp_token token is equal to the given one.

If found, set *result to a new strong reference to it and return 1.

如果沒找到，則將 *result 設為 NULL 並回傳 0。

在發生錯誤時，將 *result 設為 NULL 並回傳 -1，同時設定例外。

如果 result 引數為 NULL，則不會設定 *result。如果你只需要回傳值，請使用此選項。

token 引數不可為 NULL。

在 3.14 版被加入.

int PyUnstable_Type_AssignVersionTag(PyTypeObject *type)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Attempt to assign a version tag to the given type.

Returns 1 if the type already had a valid version tag or a new one was assigned, or 0 if a new tag could not be assigned.

在 3.12 版被加入.

int PyType_SUPPORTS_WEAKREFS(PyTypeObject *type)

Return true if instances of type support creating weak references, false otherwise. This function always succeeds. type must not be NULL.

也參考

弱參照物件

weakref

Creating Heap-Allocated Types

The following functions and structs are used to create heap types.

PyObject *PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module, PyType_Spec *spec, PyObject *bases)

為 穩定 ABI 的一部分 自 3.12 版本開始.

Create and return a heap type from the spec (see Py_TPFLAGS_HEAPTYPE).

The metaclass metaclass is used to construct the resulting type object. When metaclass is NULL, the metaclass is derived from bases (or Py_tp_base[s] slots if bases is NULL, see below).

Metaclasses that override tp_new are not supported, except if tp_new is NULL.

The bases argument can be used to specify base classes; it can either be only one class or a tuple of classes. If bases is NULL, the Py_tp_bases slot is used instead. If that also is NULL, the Py_tp_base slot is used instead. If that also is NULL, the new type derives from object.

The module argument can be used to record the module in which the new class is defined. It must be a module object or NULL. If not NULL, the module is associated with the new type and can later be retrieved with PyType_GetModule(). The associated module is not inherited by subclasses; it must be specified for each class individually.

This function calls PyType_Ready() on the new type.

Note that this function does not fully match the behavior of calling type() or using the class statement. With user-provided base types or metaclasses, prefer calling type (or the metaclass) over PyType_From* functions. Specifically:

__new__() 不會在新類別上被呼叫（且它必須被設為 type.__new__）。

__init__() 不會在新類別上被呼叫。

__init_subclass__() 不會在任何基底上被呼叫。

__set_name__() 不會在新的描述器上被呼叫。

在 3.12 版被加入.

PyObject *PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.10 版本開始.

等價於 PyType_FromMetaclass(NULL, module, spec, bases)。

在 3.9 版被加入.

在 3.10 版的變更: The function now accepts a single class as the bases argument and NULL as the tp_doc slot.

在 3.12 版的變更: The function now finds and uses a metaclass corresponding to the provided base classes. Previously, only type instances were returned.

The tp_new of the metaclass is ignored. which may result in incomplete initialization. Creating classes whose metaclass overrides tp_new is deprecated.

在 3.14 版的變更: Creating classes whose metaclass overrides tp_new is no longer allowed.

PyObject *PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.3 版本開始.

等價於 PyType_FromMetaclass(NULL, NULL, spec, bases)。

在 3.3 版被加入.

在 3.12 版的變更: The function now finds and uses a metaclass corresponding to the provided base classes. Previously, only type instances were returned.

The tp_new of the metaclass is ignored. which may result in incomplete initialization. Creating classes whose metaclass overrides tp_new is deprecated.

在 3.14 版的變更: Creating classes whose metaclass overrides tp_new is no longer allowed.

PyObject *PyType_FromSpec(PyType_Spec *spec)

回傳值：新的參照。 為 穩定 ABI 的一部分.

等價於 PyType_FromMetaclass(NULL, NULL, spec, NULL)。

在 3.12 版的變更: The function now finds and uses a metaclass corresponding to the base classes provided in Py_tp_base[s] slots. Previously, only type instances were returned.

The tp_new of the metaclass is ignored. which may result in incomplete initialization. Creating classes whose metaclass overrides tp_new is deprecated.

在 3.14 版的變更: Creating classes whose metaclass overrides tp_new is no longer allowed.

int PyType_Freeze(PyTypeObject *type)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Make a type immutable: set the Py_TPFLAGS_IMMUTABLETYPE flag.

所有 type 的基底類別都必須是不可變的。

On success, return 0. On error, set an exception and return -1.

The type must not be used before it's made immutable. For example, type instances must not be created before the type is made immutable.

在 3.14 版被加入.

type PyType_Spec

為 穩定 ABI 的一部分 （包含所有成員）.

Structure defining a type's behavior.

const char *name

Name of the type, used to set PyTypeObject.tp_name.

int basicsize

If positive, specifies the size of the instance in bytes. It is used to set PyTypeObject.tp_basicsize.

If zero, specifies that tp_basicsize should be inherited.

If negative, the absolute value specifies how much space instances of the class need in addition to the superclass. Use PyObject_GetTypeData() to get a pointer to subclass-specific memory reserved this way. For negative basicsize, Python will insert padding when needed to meet tp_basicsize's alignment requirements.

在 3.12 版的變更: 在過去此欄位不可為負值。

int itemsize

Size of one element of a variable-size type, in bytes. Used to set PyTypeObject.tp_itemsize. See tp_itemsize documentation for caveats.

If zero, tp_itemsize is inherited. Extending arbitrary variable-sized classes is dangerous, since some types use a fixed offset for variable-sized memory, which can then overlap fixed-sized memory used by a subclass. To help prevent mistakes, inheriting itemsize is only possible in the following situations:

The base is not variable-sized (its tp_itemsize).

The requested PyType_Spec.basicsize is positive, suggesting that the memory layout of the base class is known.

The requested PyType_Spec.basicsize is zero, suggesting that the subclass does not access the instance's memory directly.

With the Py_TPFLAGS_ITEMS_AT_END flag.

unsigned int flags

Type flags, used to set PyTypeObject.tp_flags.

如果未設定 Py_TPFLAGS_HEAPTYPE 旗標，則 PyType_FromSpecWithBases() 會自動設定它。

PyType_Slot *slots

Array of PyType_Slot structures. Terminated by the special slot value {0, NULL}.

Each slot ID should be specified at most once.

type PyType_Slot

為 穩定 ABI 的一部分 （包含所有成員）.

Structure defining optional functionality of a type, containing a slot ID and a value pointer.

int slot

A slot ID.

Slot IDs are named like the field names of the structures PyTypeObject, PyNumberMethods, PySequenceMethods, PyMappingMethods and PyAsyncMethods with an added Py_ prefix. For example, use:

Py_tp_dealloc 以設定 PyTypeObject.tp_dealloc

Py_nb_add 以設定 PyNumberMethods.nb_add

Py_sq_length 以設定 PySequenceMethods.sq_length

An additional slot is supported that does not correspond to a PyTypeObject struct field:

Py_tp_token

The following “offset” fields cannot be set using PyType_Slot:

tp_weaklistoffset（如果可能，請改用 Py_TPFLAGS_MANAGED_WEAKREF）

tp_dictoffset（如果可能，請改用 Py_TPFLAGS_MANAGED_DICT）

tp_vectorcall_offset（請用 PyMemberDef 中的 "__vectorcalloffset__"）

If it is not possible to switch to a MANAGED flag (for example, for vectorcall or to support Python older than 3.12), specify the offset in Py_tp_members. See PyMemberDef documentation for details.

The following internal fields cannot be set at all when creating a heap type:

tp_dict, tp_mro, tp_cache, tp_subclasses, and tp_weaklist.

Setting Py_tp_bases or Py_tp_base may be problematic on some platforms. To avoid issues, use the bases argument of PyType_FromSpecWithBases() instead.

在 3.9 版的變更: Slots in PyBufferProcs may be set in the unlimited API.

在 3.11 版的變更: bf_getbuffer and bf_releasebuffer are now available under the limited API.

在 3.14 版的變更: The field tp_vectorcall can now be set using Py_tp_vectorcall. See the field's documentation for details.

void *pfunc

The desired value of the slot. In most cases, this is a pointer to a function.

pfunc values may not be NULL, except for the following slots:

Py_tp_doc

Py_tp_token (for clarity, prefer Py_TP_USE_SPEC rather than NULL)

Py_tp_token

為 穩定 ABI 的一部分 自 3.14 版本開始.

A slot that records a static memory layout ID for a class.

If the PyType_Spec of the class is statically allocated, the token can be set to the spec using the special value Py_TP_USE_SPEC:

static PyType_Slot foo_slots[] = {
   {Py_tp_token, Py_TP_USE_SPEC},

It can also be set to an arbitrary pointer, but you must ensure that:

The pointer outlives the class, so it's not reused for something else while the class exists.

It "belongs" to the extension module where the class lives, so it will not clash with other extensions.

Use PyType_GetBaseByToken() to check if a class's superclass has a given token -- that is, check whether the memory layout is compatible.

To get the token for a given class (without considering superclasses), use PyType_GetSlot() with Py_tp_token.

在 3.14 版被加入.

Py_TP_USE_SPEC

為 穩定 ABI 的一部分 自 3.14 版本開始.

Used as a value with Py_tp_token to set the token to the class's PyType_Spec. Expands to NULL.

在 3.14 版被加入.

None 物件

Note that the PyTypeObject for None is not directly exposed in the Python/C API. Since None is a singleton, testing for object identity (using == in C) is sufficient. There is no PyNone_Check() function for the same reason.

PyObject *Py_None

The Python None object, denoting lack of value. This object has no methods and is immortal.

在 3.12 版的變更: Py_None 為不滅的 (immortal)。

Py_RETURN_NONE

Return Py_None from a function.

整數物件

All integers are implemented as "long" integer objects of arbitrary size.

On error, most PyLong_As* APIs return (return type)-1 which cannot be distinguished from a number. Use PyErr_Occurred() to disambiguate.

type PyLongObject

為 受限 API 的一部分 （做為一個不透明結構 (opaque struct)）.

This subtype of PyObject represents a Python integer object.

PyTypeObject PyLong_Type

為 穩定 ABI 的一部分.

This instance of PyTypeObject represents the Python integer type. This is the same object as int in the Python layer.

int PyLong_Check(PyObject *p)

Return true if its argument is a PyLongObject or a subtype of PyLongObject. This function always succeeds.

int PyLong_CheckExact(PyObject *p)

Return true if its argument is a PyLongObject, but not a subtype of PyLongObject. This function always succeeds.

PyObject *PyLong_FromLong(long v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from v, or NULL on failure.

CPython 實作細節： CPython keeps an array of integer objects for all integers between -5 and 256. When you create an int in that range you actually just get back a reference to the existing object.

PyObject *PyLong_FromUnsignedLong(unsigned long v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from a C unsigned long, or NULL on failure.

PyObject *PyLong_FromSsize_t(Py_ssize_t v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from a C Py_ssize_t, or NULL on failure.

PyObject *PyLong_FromSize_t(size_t v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from a C size_t, or NULL on failure.

PyObject *PyLong_FromLongLong(long long v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from a C long long, or NULL on failure.

PyObject *PyLong_FromInt32(int32_t value)

PyObject *PyLong_FromInt64(int64_t value)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Return a new PyLongObject object from a signed C int32_t or int64_t, or NULL with an exception set on failure.

在 3.14 版被加入.

PyObject *PyLong_FromUnsignedLongLong(unsigned long long v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from a C unsigned long long, or NULL on failure.

PyObject *PyLong_FromUInt32(uint32_t value)

PyObject *PyLong_FromUInt64(uint64_t value)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Return a new PyLongObject object from an unsigned C uint32_t or uint64_t, or NULL with an exception set on failure.

在 3.14 版被加入.

PyObject *PyLong_FromDouble(double v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject object from the integer part of v, or NULL on failure.

PyObject *PyLong_FromString(const char *str, char **pend, int base)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new PyLongObject based on the string value in str, which is interpreted according to the radix in base, or NULL on failure. If pend is non-NULL, *pend will point to the end of str on success or to the first character that could not be processed on error. If base is 0, str is interpreted using the Integer literals definition; in this case, leading zeros in a non-zero decimal number raises a ValueError. If base is not 0, it must be between 2 and 36, inclusive. Leading and trailing whitespace and single underscores after a base specifier and between digits are ignored. If there are no digits or str is not NULL-terminated following the digits and trailing whitespace, ValueError will be raised.

也參考

PyLong_AsNativeBytes() and PyLong_FromNativeBytes() functions can be used to convert a PyLongObject to/from an array of bytes in base 256.

PyObject *PyLong_FromUnicodeObject(PyObject *u, int base)

回傳值：新的參照。

Convert a sequence of Unicode digits in the string u to a Python integer value.

在 3.3 版被加入.

PyObject *PyLong_FromVoidPtr(void *p)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Python integer from the pointer p. The pointer value can be retrieved from the resulting value using PyLong_AsVoidPtr().

PyObject *PyLong_FromNativeBytes(const void *buffer, size_t n_bytes, int flags)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Create a Python integer from the value contained in the first n_bytes of buffer, interpreted as a two's-complement signed number.

flags are as for PyLong_AsNativeBytes(). Passing -1 will select the native endian that CPython was compiled with and assume that the most-significant bit is a sign bit. Passing Py_ASNATIVEBYTES_UNSIGNED_BUFFER will produce the same result as calling PyLong_FromUnsignedNativeBytes(). Other flags are ignored.

在 3.13 版被加入.

PyObject *PyLong_FromUnsignedNativeBytes(const void *buffer, size_t n_bytes, int flags)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Create a Python integer from the value contained in the first n_bytes of buffer, interpreted as an unsigned number.

flags are as for PyLong_AsNativeBytes(). Passing -1 will select the native endian that CPython was compiled with and assume that the most-significant bit is not a sign bit. Flags other than endian are ignored.

在 3.13 版被加入.

PyLong_FromPid(pid)

Macro for creating a Python integer from a process identifier.

This can be defined as an alias to PyLong_FromLong() or PyLong_FromLongLong(), depending on the size of the system's PID type.

在 3.2 版被加入.

long PyLong_AsLong(PyObject *obj)

為 穩定 ABI 的一部分.

Return a C long representation of obj. If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

Raise OverflowError if the value of obj is out of range for a long.

Returns -1 on error. Use PyErr_Occurred() to disambiguate.

在 3.8 版的變更: Use __index__() if available.

在 3.10 版的變更: This function will no longer use __int__().

long PyLong_AS_LONG(PyObject *obj)

A soft deprecated alias. Exactly equivalent to the preferred PyLong_AsLong. In particular, it can fail with OverflowError or another exception.

在 3.14 版之後被棄用: The function is soft deprecated.

int PyLong_AsInt(PyObject *obj)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Similar to PyLong_AsLong(), but store the result in a C int instead of a C long.

在 3.13 版被加入.

long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)

為 穩定 ABI 的一部分.

Return a C long representation of obj. If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

If the value of obj is greater than LONG_MAX or less than LONG_MIN, set *overflow to 1 or -1, respectively, and return -1; otherwise, set *overflow to 0. If any other exception occurs set *overflow to 0 and return -1 as usual.

Returns -1 on error. Use PyErr_Occurred() to disambiguate.

在 3.8 版的變更: Use __index__() if available.

在 3.10 版的變更: This function will no longer use __int__().

long long PyLong_AsLongLong(PyObject *obj)

為 穩定 ABI 的一部分.

Return a C long long representation of obj. If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

Raise OverflowError if the value of obj is out of range for a long long.

Returns -1 on error. Use PyErr_Occurred() to disambiguate.

在 3.8 版的變更: Use __index__() if available.

在 3.10 版的變更: This function will no longer use __int__().

long long PyLong_AsLongLongAndOverflow(PyObject *obj, int *overflow)

為 穩定 ABI 的一部分.

Return a C long long representation of obj. If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

If the value of obj is greater than LLONG_MAX or less than LLONG_MIN, set *overflow to 1 or -1, respectively, and return -1; otherwise, set *overflow to 0. If any other exception occurs set *overflow to 0 and return -1 as usual.

Returns -1 on error. Use PyErr_Occurred() to disambiguate.

在 3.2 版被加入.

在 3.8 版的變更: Use __index__() if available.

在 3.10 版的變更: This function will no longer use __int__().

Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)

為 穩定 ABI 的一部分.

Return a C Py_ssize_t representation of pylong. pylong must be an instance of PyLongObject.

Raise OverflowError if the value of pylong is out of range for a Py_ssize_t.

Returns -1 on error. Use PyErr_Occurred() to disambiguate.

unsigned long PyLong_AsUnsignedLong(PyObject *pylong)

為 穩定 ABI 的一部分.

Return a C unsigned long representation of pylong. pylong must be an instance of PyLongObject.

Raise OverflowError if the value of pylong is out of range for a unsigned long.

Returns (unsigned long)-1 on error. Use PyErr_Occurred() to disambiguate.

size_t PyLong_AsSize_t(PyObject *pylong)

為 穩定 ABI 的一部分.

Return a C size_t representation of pylong. pylong must be an instance of PyLongObject.

Raise OverflowError if the value of pylong is out of range for a size_t.

Returns (size_t)-1 on error. Use PyErr_Occurred() to disambiguate.

unsigned long long PyLong_AsUnsignedLongLong(PyObject *pylong)

為 穩定 ABI 的一部分.

Return a C unsigned long long representation of pylong. pylong must be an instance of PyLongObject.

Raise OverflowError if the value of pylong is out of range for an unsigned long long.

Returns (unsigned long long)-1 on error. Use PyErr_Occurred() to disambiguate.

在 3.1 版的變更: A negative pylong now raises OverflowError, not TypeError.

unsigned long PyLong_AsUnsignedLongMask(PyObject *obj)

為 穩定 ABI 的一部分.

Return a C unsigned long representation of obj. If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

If the value of obj is out of range for an unsigned long, return the reduction of that value modulo ULONG_MAX + 1.

Returns (unsigned long)-1 on error. Use PyErr_Occurred() to disambiguate.

在 3.8 版的變更: Use __index__() if available.

在 3.10 版的變更: This function will no longer use __int__().

unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)

為 穩定 ABI 的一部分.

Return a C unsigned long long representation of obj. If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

If the value of obj is out of range for an unsigned long long, return the reduction of that value modulo ULLONG_MAX + 1.

Returns (unsigned long long)-1 on error. Use PyErr_Occurred() to disambiguate.

在 3.8 版的變更: Use __index__() if available.

在 3.10 版的變更: This function will no longer use __int__().

int PyLong_AsInt32(PyObject *obj, int32_t *value)

int PyLong_AsInt64(PyObject *obj, int64_t *value)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Set *value to a signed C int32_t or int64_t representation of obj.

If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

If the obj value is out of range, raise an OverflowError.

Set *value and return 0 on success. Set an exception and return -1 on error.

value must not be NULL.

在 3.14 版被加入.

int PyLong_AsUInt32(PyObject *obj, uint32_t *value)

int PyLong_AsUInt64(PyObject *obj, uint64_t *value)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Set *value to an unsigned C uint32_t or uint64_t representation of obj.

If obj is not an instance of PyLongObject, first call its __index__() method (if present) to convert it to a PyLongObject.

If obj is negative, raise a ValueError.

If the obj value is out of range, raise an OverflowError.

Set *value and return 0 on success. Set an exception and return -1 on error.

value must not be NULL.

在 3.14 版被加入.

double PyLong_AsDouble(PyObject *pylong)

為 穩定 ABI 的一部分.

Return a C double representation of pylong. pylong must be an instance of PyLongObject.

Raise OverflowError if the value of pylong is out of range for a double.

Returns -1.0 on error. Use PyErr_Occurred() to disambiguate.

void *PyLong_AsVoidPtr(PyObject *pylong)

為 穩定 ABI 的一部分.

Convert a Python integer pylong to a C void pointer. If pylong cannot be converted, an OverflowError will be raised. This is only assured to produce a usable void pointer for values created with PyLong_FromVoidPtr().

Returns NULL on error. Use PyErr_Occurred() to disambiguate.

Py_ssize_t PyLong_AsNativeBytes(PyObject *pylong, void *buffer, Py_ssize_t n_bytes, int flags)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Copy the Python integer value pylong to a native buffer of size n_bytes. The flags can be set to -1 to behave similarly to a C cast, or to values documented below to control the behavior.

Returns -1 with an exception raised on error. This may happen if pylong cannot be interpreted as an integer, or if pylong was negative and the Py_ASNATIVEBYTES_REJECT_NEGATIVE flag was set.

Otherwise, returns the number of bytes required to store the value. If this is equal to or less than n_bytes, the entire value was copied. All n_bytes of the buffer are written: remaining bytes filled by copies of the sign bit.

If the returned value is greater than n_bytes, the value was truncated: as many of the lowest bits of the value as could fit are written, and the higher bits are ignored. This matches the typical behavior of a C-style downcast.

備註

Overflow is not considered an error. If the returned value is larger than n_bytes, most significant bits were discarded.

0 將永不被回傳。

Values are always copied as two's-complement.

使用範例：

int32_t value;
Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, &value, sizeof(value), -1);
if (bytes < 0) {
    // Failed. A Python exception was set with the reason.
    return NULL;
}
else if (bytes <= (Py_ssize_t)sizeof(value)) {
    // Success!
}
else {
    // Overflow occurred, but 'value' contains the truncated
    // lowest bits of pylong.
}

Passing zero to n_bytes will return the size of a buffer that would be large enough to hold the value. This may be larger than technically necessary, but not unreasonably so. If n_bytes=0, buffer may be NULL.

備註

Passing n_bytes=0 to this function is not an accurate way to determine the bit length of the value.

To get at the entire Python value of an unknown size, the function can be called twice: first to determine the buffer size, then to fill it:

// Ask how much space we need.
Py_ssize_t expected = PyLong_AsNativeBytes(pylong, NULL, 0, -1);
if (expected < 0) {
    // Failed. A Python exception was set with the reason.
    return NULL;
}
assert(expected != 0);  // Impossible per the API definition.
uint8_t *bignum = malloc(expected);
if (!bignum) {
    PyErr_SetString(PyExc_MemoryError, "bignum malloc failed.");
    return NULL;
}
// Safely get the entire value.
Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, bignum, expected, -1);
if (bytes < 0) {  // Exception has been set.
    free(bignum);
    return NULL;
}
else if (bytes > expected) {  // This should not be possible.
    PyErr_SetString(PyExc_RuntimeError,
        "Unexpected bignum truncation after a size check.");
    free(bignum);
    return NULL;
}
// The expected success given the above pre-check.
// ... use bignum ...
free(bignum);

flags is either -1 (Py_ASNATIVEBYTES_DEFAULTS) to select defaults that behave most like a C cast, or a combination of the other flags in the table below. Note that -1 cannot be combined with other flags.

Currently, -1 corresponds to Py_ASNATIVEBYTES_NATIVE_ENDIAN | Py_ASNATIVEBYTES_UNSIGNED_BUFFER.

旗標

數值

Py_ASNATIVEBYTES_DEFAULTS

為 穩定 ABI 的一部分 自 3.14 版本開始.

-1

Py_ASNATIVEBYTES_BIG_ENDIAN

為 穩定 ABI 的一部分 自 3.14 版本開始.

0

Py_ASNATIVEBYTES_LITTLE_ENDIAN

為 穩定 ABI 的一部分 自 3.14 版本開始.

1

Py_ASNATIVEBYTES_NATIVE_ENDIAN

為 穩定 ABI 的一部分 自 3.14 版本開始.

3

Py_ASNATIVEBYTES_UNSIGNED_BUFFER

為 穩定 ABI 的一部分 自 3.14 版本開始.

4

Py_ASNATIVEBYTES_REJECT_NEGATIVE

為 穩定 ABI 的一部分 自 3.14 版本開始.

8

Py_ASNATIVEBYTES_ALLOW_INDEX

為 穩定 ABI 的一部分 自 3.14 版本開始.

16

Specifying Py_ASNATIVEBYTES_NATIVE_ENDIAN will override any other endian flags. Passing 2 is reserved.

By default, sufficient buffer will be requested to include a sign bit. For example, when converting 128 with n_bytes=1, the function will return 2 (or more) in order to store a zero sign bit.

If Py_ASNATIVEBYTES_UNSIGNED_BUFFER is specified, a zero sign bit will be omitted from size calculations. This allows, for example, 128 to fit in a single-byte buffer. If the destination buffer is later treated as signed, a positive input value may become negative. Note that the flag does not affect handling of negative values: for those, space for a sign bit is always requested.

Specifying Py_ASNATIVEBYTES_REJECT_NEGATIVE causes an exception to be set if pylong is negative. Without this flag, negative values will be copied provided there is enough space for at least one sign bit, regardless of whether Py_ASNATIVEBYTES_UNSIGNED_BUFFER was specified.

If Py_ASNATIVEBYTES_ALLOW_INDEX is specified and a non-integer value is passed, its __index__() method will be called first. This may result in Python code executing and other threads being allowed to run, which could cause changes to other objects or values in use. When flags is -1, this option is not set, and non-integer values will raise TypeError.

備註

With the default flags (-1, or UNSIGNED_BUFFER without REJECT_NEGATIVE), multiple Python integers can map to a single value without overflow. For example, both 255 and -1 fit a single-byte buffer and set all its bits. This matches typical C cast behavior.

在 3.13 版被加入.

PyLong_AsPid(pid)

Macro for converting a Python integer into a process identifier.

This can be defined as an alias to PyLong_AsLong(), PyLong_FromLongLong(), or PyLong_AsInt(), depending on the size of the system's PID type.

在 3.2 版被加入.

int PyLong_GetSign(PyObject *obj, int *sign)

Get the sign of the integer object obj.

On success, set *sign to the integer sign (0, -1 or +1 for zero, negative or positive integer, respectively) and return 0.

On failure, return -1 with an exception set. This function always succeeds if obj is a PyLongObject or its subtype.

在 3.14 版被加入.

int PyLong_IsPositive(PyObject *obj)

檢查整數物件 obj 是否為正（obj > 0）。

如果 obj 是 PyLongObject 或其子類別的實例，當它為正數時回傳 1，否則回傳 0。其餘情況則設定例外並回傳 -1。

在 3.14 版被加入.

int PyLong_IsNegative(PyObject *obj)

檢查整數物件 obj 是否為負（obj < 0）。

如果 obj 是 PyLongObject 或其子類別的實例，當它為負數時回傳 1，否則回傳 0。其餘情況則設定例外並回傳 -1。

在 3.14 版被加入.

int PyLong_IsZero(PyObject *obj)

檢查整數物件 obj 是否為零。

如果 obj 是 PyLongObject 或其子類別的實例，當它為零時回傳 1，否則回傳 0。其餘情況則設定例外並回傳 -1。

在 3.14 版被加入.

PyObject *PyLong_GetInfo(void)

為 穩定 ABI 的一部分.

On success, return a read only named tuple, that holds information about Python's internal representation of integers. See sys.int_info for description of individual fields.

在失敗時，會回傳 NULL 並設定例外。

在 3.1 版被加入.

int PyUnstable_Long_IsCompact(const PyLongObject *op)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Return 1 if op is compact, 0 otherwise.

This function makes it possible for performance-critical code to implement a “fast path” for small integers. For compact values use PyUnstable_Long_CompactValue(); for others fall back to a PyLong_As* function or PyLong_AsNativeBytes().

The speedup is expected to be negligible for most users.

Exactly what values are considered compact is an implementation detail and is subject to change.

在 3.12 版被加入.

Py_ssize_t PyUnstable_Long_CompactValue(const PyLongObject *op)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

If op is compact, as determined by PyUnstable_Long_IsCompact(), return its value.

Otherwise, the return value is undefined.

在 3.12 版被加入.

匯出 API

在 3.14 版被加入.

struct PyLongLayout

Layout of an array of "digits" ("limbs" in the GMP terminology), used to represent absolute value for arbitrary precision integers.

Use PyLong_GetNativeLayout() to get the native layout of Python int objects, used internally for integers with "big enough" absolute value.

See also sys.int_info which exposes similar information in Python.

uint8_t bits_per_digit

Bits per digit. For example, a 15 bit digit means that bits 0-14 contain meaningful information.

uint8_t digit_size

Digit size in bytes. For example, a 15 bit digit will require at least 2 bytes.

int8_t digits_order

Digits order:

1 for most significant digit first

-1 for least significant digit first

int8_t digit_endianness

Digit endianness:

1 for most significant byte first (big endian)

-1 for least significant byte first (little endian)

const PyLongLayout *PyLong_GetNativeLayout(void)

Get the native layout of Python int objects.

請見 PyLongLayout 結構。

The function must not be called before Python initialization nor after Python finalization. The returned layout is valid until Python is finalized. The layout is the same for all Python sub-interpreters in a process, and so it can be cached.

struct PyLongExport

Export of a Python int object.

There are two cases:

If digits is NULL, only use the value member.

If digits is not NULL, use negative, ndigits and digits members.

int64_t value

The native integer value of the exported int object. Only valid if digits is NULL.

uint8_t negative

1 if the number is negative, 0 otherwise. Only valid if digits is not NULL.

Py_ssize_t ndigits

Number of digits in digits array. Only valid if digits is not NULL.

const void *digits

Read-only array of unsigned digits. Can be NULL.

int PyLong_Export(PyObject *obj, PyLongExport *export_long)

Export a Python int object.

export_long must point to a PyLongExport structure allocated by the caller. It must not be NULL.

On success, fill in *export_long and return 0. On error, set an exception and return -1.

PyLong_FreeExport() must be called when the export is no longer needed.

CPython 實作細節： This function always succeeds if obj is a Python int object or a subclass.

void PyLong_FreeExport(PyLongExport *export_long)

Release the export export_long created by PyLong_Export().

CPython 實作細節： Calling PyLong_FreeExport() is optional if export_long->digits is NULL.

PyLongWriter API

The PyLongWriter API can be used to import an integer.

在 3.14 版被加入.

struct PyLongWriter

A Python int writer instance.

The instance must be destroyed by PyLongWriter_Finish() or PyLongWriter_Discard().

PyLongWriter *PyLongWriter_Create(int negative, Py_ssize_t ndigits, void **digits)

建立一個 PyLongWriter。

On success, allocate *digits and return a writer. On error, set an exception and return NULL.

negative is 1 if the number is negative, or 0 otherwise.

ndigits is the number of digits in the digits array. It must be greater than 0.

digits 不得為 NULL。

After a successful call to this function, the caller should fill in the array of digits digits and then call PyLongWriter_Finish() to get a Python int. The layout of digits is described by PyLong_GetNativeLayout().

Digits must be in the range [0; (1 << bits_per_digit) - 1] (where the bits_per_digit is the number of bits per digit). Any unused most significant digits must be set to 0.

Alternately, call PyLongWriter_Discard() to destroy the writer instance without creating an int object.

PyObject *PyLongWriter_Finish(PyLongWriter *writer)

回傳值：新的參照。

Finish a PyLongWriter created by PyLongWriter_Create().

On success, return a Python int object. On error, set an exception and return NULL.

The function takes care of normalizing the digits and converts the object to a compact integer if needed.

The writer instance and the digits array are invalid after the call.

void PyLongWriter_Discard(PyLongWriter *writer)

丟棄由 PyLongWriter_Create() 建立的 PyLongWriter。

如果 writer 為 NULL，則不執行任何操作。

The writer instance and the digits array are invalid after the call.

已棄用的 API

這些巨集已被軟性棄用。它們描述了 PyLongObject 實例的內部表示參數。

請改用 PyLong_GetNativeLayout()，並與 PyLong_Export() 使用來讀取整數資料，或者 PyLongWriter 來寫入它們。它們目前使用相同的佈局，不過即使 CPython 的內部整數表示發生變化，也能繼續正確運作。

PyLong_SHIFT

這等同於 PyLong_GetNativeLayout() 輸出中的 bits_per_digit。

PyLong_BASE

這目前等同於 1 << PyLong_SHIFT。

PyLong_MASK

這目前等同於 (1 << PyLong_SHIFT) - 1

Boolean（布林）物件

Python 中的 boolean 是以整數子類別化來實現的。只有 Py_False 和 Py_True 兩個 boolean。因此一般的建立和刪除函式並不適用於 boolean。但下列巨集 (macro) 是可用的。

PyTypeObject PyBool_Type

為 穩定 ABI 的一部分.

此 PyTypeObject 實例代表 Python 的布林型別；它與 Python 層級中的 bool 是同一個物件。

int PyBool_Check(PyObject *o)

如果 o 的型別為 PyBool_Type 則回傳真值。此函式總是會成功執行。

PyObject *Py_False

Python 的 False 物件。此物件沒有任何方法且為不滅的 (immortal)。

在 3.12 版的變更: Py_False 為不滅的。

PyObject *Py_True

Python 的 True 物件。此物件沒有任何方法且為不滅的。

在 3.12 版的變更: Py_True 為不滅的。

Py_RETURN_FALSE

從函式回傳 Py_False。

Py_RETURN_TRUE

從函式回傳 Py_True。

PyObject *PyBool_FromLong(long v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

根據 v 的實際值來回傳 Py_True 或者 Py_False。

浮點數（Floating-Point）物件

type PyFloatObject

這個 PyObject 的子型別代表一個 Python 浮點數物件。

PyTypeObject PyFloat_Type

為 穩定 ABI 的一部分.

這個 PyTypeObject 的實例代表 Python 浮點數型別。這與 Python 層中的 float 物件相同。

int PyFloat_Check(PyObject *p)

如果其引數是 PyFloatObject 或 PyFloatObject 的子型別，則回傳 true。這個函式不會失敗。

int PyFloat_CheckExact(PyObject *p)

如果其引數是 PyFloatObject，但不是 PyFloatObject 的子型別，則回傳 true。這個函式不會失敗。

PyObject *PyFloat_FromString(PyObject *str)

回傳值：新的參照。 為 穩定 ABI 的一部分.

建立一個基於字串值 str 的 PyFloatObject 物件，失敗時回傳 NULL。

PyObject *PyFloat_FromDouble(double v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

建立一個來自 v 的 PyFloatObject 物件，失敗時回傳 NULL。

double PyFloat_AsDouble(PyObject *pyfloat)

為 穩定 ABI 的一部分.

回傳 pyfloat 內容的 C double 表示形式。如果 pyfloat 不是 Python 浮點數物件，但具有 __float__() 方法，則會先呼叫此方法將 pyfloat 轉換為浮點數。如果未定義 __float__()，則會用後備方法 __index__()。此方法在失敗時回傳 -1.0，因此應該呼叫 PyErr_Occurred() 來檢查錯誤。

在 3.8 版的變更: 請使用 __index__()（如果可用）。

double PyFloat_AS_DOUBLE(PyObject *pyfloat)

回傳 pyfloat 內容的 C double 表示形式，但不進行錯誤檢查。

PyObject *PyFloat_GetInfo(void)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個 structseq 實例，其中包含有關浮點數的精度、最小值和最大值的資訊。它是對標頭檔 float.h 的簡單封裝。

double PyFloat_GetMax()

為 穩定 ABI 的一部分.

將可表示的最大有限浮點數 DBL_MAX 作為 C double 回傳。

double PyFloat_GetMin()

為 穩定 ABI 的一部分.

將最小的正規化浮點數 DBL_MIN 作為 C double 回傳。

Py_INFINITY

這個巨集會展開為一型別為 double 的常數運算式，表示正無窮大。

在大多數平台上，這相當於 C11 標準 <math.h> 標頭檔中的 INFINITY 巨集。

Py_NAN

這個巨集會展開為一型別為 double 的常數運算式，表示安靜型 NaN (qNaN) 值。

在大多數平台上，這相當於 C11 標準 <math.h> 標頭檔中的 NAN 巨集。

Py_HUGE_VAL

與 INFINITY 等價。

在 3.14 版之後被棄用: 這個巨集已被軟性棄用。

Py_MATH_E

math.e 常數的定義（對 double 型別而言是準確的）。

Py_MATH_El

高精度（long double）定義的 e 常數。

Py_MATH_PI

math.pi 常數的定義（對 double 型別而言是準確的）。

Py_MATH_PIl

高精度（long double）定義的 pi 常數。

Py_MATH_TAU

math.tau 常數的定義（對 double 型別而言是準確的）。

在 3.6 版被加入.

Py_RETURN_NAN

從函式回傳 math.nan。

在大多數平台上，這相當於 return PyFloat_FromDouble(NAN)。

Py_RETURN_INF(sign)

根據 sign 的正負號，從函式回傳 math.inf 或 -math.inf。

在大多數平台上，這相當於以下內容：

return PyFloat_FromDouble(copysign(INFINITY, sign));

Py_IS_FINITE(X)

如果給定的浮點數 X 是有限的（即為正規數 (normal)、次正規數 (subnormal) 或零，但不是無窮大或 NaN），則回傳 1。否則回傳 0。

在 3.14 版之後被棄用: 此巨集已被軟性棄用。請改用 isfinite。

Py_IS_INFINITY(X)

如果給定的浮點數 X 是正無窮大或負無窮大，則回傳 1。否則回傳 0。

在 3.14 版之後被棄用: 此巨集已被軟性棄用。請改用 isinf。

Py_IS_NAN(X)

如果給定的浮點數 X 是非數值 (NaN)，則回傳 1。否則回傳 0。

在 3.14 版之後被棄用: 此巨集已被軟性棄用。請改用 isnan。

打包和解包函式

打包和解包函式提供了一種有效的跨平台方式，來將浮點數值儲存為位元組字串。打包例程從 C double 產生位元組字串，而解包例程則從這樣的位元組字串產生 C double。後綴（2、4 或 8）標示了位元組字串中的位元組數。

在看似使用 IEEE 754 格式的平台上，這些函式是透過複製位元來運作的。在其他平台上，2 位元組格式與 IEEE 754 binary16 半精度格式相同，4 位元組格式（32 位元）與 IEEE 754 binary32 單精度格式相同，8 位元組格式與 IEEE 754 binary64 雙精度格式相同。儘管如此，INF 和 NaN（如果這些東西在平台上存在）的打包並未正確處理，並且嘗試解包包含 IEEE INF 或 NaN 的位元組字串將引發例外。

請注意，在 IEEE 平台上可能無法保留 NaN 型別（「訊號型 NaN (signaling NaN)」會變成「安靜型 NaN (quiet NaN)」），例如在 32 位元模式的 x86 系統上。

在非 IEEE 平台上，如果精度更高或動態範圍比 IEEE 754 支援的更大，則無法打包所有值；在非 IEEE 平台上，如果精度較低或動態範圍較小，則無法解包所有值。在這種案例下發生的情況在某種程度上是偶然的（唉）。

在 3.11 版被加入.

打包函式

打包例程會從 p 開始寫入 2、4 或 8 位元組。le 是一個 int 引數，如果你想要位元組字串為小端序格式（指數在最後，位於 p+1、p+3、p+6 或 p+7），則用非零值；如果你想要大端序格式（指數在最前，位於 p），則用零。可以使用 PY_BIG_ENDIAN 常數來使用原生端序：在大端序處理器上它等於 1，在小端序處理器上它等於 0。

回傳值：如果一切正常則為 0，如果發生錯誤則為 -1（並且會設定一個例外，最有可能是 OverflowError）。

在非 IEEE 平台上有兩個問題：

如果 x 是 NaN 或無窮大，則這樣做是未定義的。

-0.0 和 +0.0 會產生同樣的位元組字串。

int PyFloat_Pack2(double x, char *p, int le)

將 C double 打包為 IEEE 754 binary16 半精度格式。

int PyFloat_Pack4(double x, char *p, int le)

將 C double 打包為 IEEE 754 binary32 單精度格式。

int PyFloat_Pack8(double x, char *p, int le)

將 C double 打包為 IEEE 754 binary64 雙精度格式。

解包函式

解包例程會從 p 開始讀取 2、4 或 8 位元組。le 是一個 int 引數，如果位元組字串為小端序格式（指數在最後，位於 p+1、p+3、p+6 或 p+7），則用非零值；如果為大端序格式（指數在最前，位於 p），則用零。可以使用 PY_BIG_ENDIAN 常數來使用原生端序：在大端序處理器上它等於 1，在小端序處理器上它等於 0。

回傳值：解包後的 double。發生錯誤時，這是 -1.0 且 PyErr_Occurred() 為 true（並且會設置一個例外，最有可能是 OverflowError）。

請注意，在非 IEEE 平台上，這將拒絕解包會表示為 NaN 或無窮大的位元組字串。

double PyFloat_Unpack2(const char *p, int le)

將 IEEE 754 binary16 半精度格式解包為 C double。

double PyFloat_Unpack4(const char *p, int le)

將 IEEE 754 binary32 單精度格式解包為 C double。

double PyFloat_Unpack8(const char *p, int le)

將 IEEE 754 binary64 雙精度格式解包為 C double。

複數物件

從 C API 來看，Python 的複數物件被實作為兩種不同的型別：一種是公開給 Python 程式的 Python 物件，另一種是表示實際複數值的 C 結構。API 提供了與兩者一起作用的函式。

作為 C 結構的複數

請注意，接受這些結構作為參數並將它們作為結果回傳的函式是按值 (by value) 執行的，而不是透過指標取消參照 (dereference) 它們。這在整個 API 中都是一致的。

type Py_complex

相對於 Python 複數物件之數值部分的 C 結構。大多數處理複數物件的函式根據需求會使用這種型別的結構作為輸入或輸出值。

double real

double imag

該結構被定義為：

typedef struct {
    double real;
    double imag;
} Py_complex;

Py_complex _Py_c_sum(Py_complex left, Py_complex right)

以 C 的 Py_complex 表示形式來回傳兩個複數之和。

Py_complex _Py_c_diff(Py_complex left, Py_complex right)

以 C 的 Py_complex 表示形式來回傳兩個複數間的差。

Py_complex _Py_c_neg(Py_complex num)

以 C 的 Py_complex 表示形式來回傳複數 num 的相反數 (negation)。

Py_complex _Py_c_prod(Py_complex left, Py_complex right)

以 C 的 Py_complex 表示形式來回傳兩個複數的乘積。

Py_complex _Py_c_quot(Py_complex dividend, Py_complex divisor)

以 C 的 Py_complex 表示形式來回傳兩個複數的商。

如果 divisor 為 null，則此方法會回傳零並將 errno 設定為 EDOM。

Py_complex _Py_c_pow(Py_complex num, Py_complex exp)

以 C 的 Py_complex 表示形式來回傳 num 的 exp 次方的結果。

如果 num 為 null 且 exp 不是正實數，則此方法會回傳零並將 errno 設定為 EDOM。

Set errno to ERANGE on overflows.

作為 Python 物件的複數

type PyComplexObject

這個 PyObject 的子型別代表一個 Python 複數物件。

PyTypeObject PyComplex_Type

為 穩定 ABI 的一部分.

這個 PyTypeObject 的實例代表 Python 複數型別。它與 Python 層中的 complex 是同一個物件。

int PyComplex_Check(PyObject *p)

如果其引數是一個 PyComplexObject 或者是 PyComplexObject 的子型別，則會回傳 true。這個函式不會失敗。

int PyComplex_CheckExact(PyObject *p)

如果其引數是一個 PyComplexObject，但不是 PyComplexObject 的子型別，則會回傳 true。這個函式不會失敗。

PyObject *PyComplex_FromCComplex(Py_complex v)

回傳值：新的參照。

從 C 的 Py_complex 值建立一個新的 Python 複數物件。在錯誤時回傳 NULL 並設定例外。

PyObject *PyComplex_FromDoubles(double real, double imag)

回傳值：新的參照。 為 穩定 ABI 的一部分.

從 real 和 imag 回傳一個新的 PyComplexObject 物件。在錯誤時回傳 NULL 並設定例外。

double PyComplex_RealAsDouble(PyObject *op)

為 穩定 ABI 的一部分.

以 C 的 double 形式回傳 op 的實部。

如果 op 不是 Python 複數物件，但有一個 __complex__() 方法，則首先會呼叫該方法將 op 轉換為 Python 複數物件。如果 __complex__() 並未定義，那麼它會回退到呼叫 PyFloat_AsDouble() 並回傳其結果。

失敗時，此方法回傳 -1.0 並設定例外，因此應該呼叫 PyErr_Occurred() 來檢查錯誤。

在 3.13 版的變更: 如果可用則使用 __complex__()。

double PyComplex_ImagAsDouble(PyObject *op)

為 穩定 ABI 的一部分.

將 op 的虛部作為 C 的 double 回傳。

如果 op 不是 Python 複數物件，但有一個 __complex__() 方法，則首先會呼叫該方法將 op 轉換為 Python 複數物件。如果 __complex__() 並未定義，那麼它會回退到呼叫 PyFloat_AsDouble() 並於成功時回傳 0.0。

失敗時，此方法回傳 -1.0 並設定例外，因此應該呼叫 PyErr_Occurred() 來檢查錯誤。

在 3.13 版的變更: 如果可用則使用 __complex__()。

Py_complex PyComplex_AsCComplex(PyObject *op)

回傳複數 op 的 Py_complex 值。

如果 op 不是 Python 複數物件，但有一個 __complex__() 方法，則首先會呼叫該方法將 op 轉換為 Python 複數物件。如果 __complex__() 並未定義，那麼它會回退到 __float__()。如果 __float__() 未定義，則它將繼續回退為 __index__()。

失敗時，此方法回傳 Py_complex 並將 real 設為 -1.0，並設定例外，因此應該呼叫 PyErr_Occurred() 來檢查錯誤。

在 3.8 版的變更: 如果可用則使用 __index__()。

位元組物件 (Bytes Objects)

These functions raise TypeError when expecting a bytes parameter and called with a non-bytes parameter.

type PyBytesObject

This subtype of PyObject represents a Python bytes object.

PyTypeObject PyBytes_Type

為 穩定 ABI 的一部分.

This instance of PyTypeObject represents the Python bytes type; it is the same object as bytes in the Python layer.

int PyBytes_Check(PyObject *o)

Return true if the object o is a bytes object or an instance of a subtype of the bytes type. This function always succeeds.

int PyBytes_CheckExact(PyObject *o)

Return true if the object o is a bytes object, but not an instance of a subtype of the bytes type. This function always succeeds.

PyObject *PyBytes_FromString(const char *v)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new bytes object with a copy of the string v as value on success, and NULL on failure. The parameter v must not be NULL; it will not be checked.

PyObject *PyBytes_FromStringAndSize(const char *v, Py_ssize_t len)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new bytes object with a copy of the string v as value and length len on success, and NULL on failure. If v is NULL, the contents of the bytes object are uninitialized.

PyObject *PyBytes_FromFormat(const char *format, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Take a C printf()-style format string and a variable number of arguments, calculate the size of the resulting Python bytes object and return a bytes object with the values formatted into it. The variable arguments must be C types and must correspond exactly to the format characters in the format string. The following format characters are allowed:

Format Characters

Type

Comment

%%

n/a

The literal % character.

%c

int

A single byte, represented as a C int.

%d

int

等價於 printf("%d"). [1]

%u

unsigned int

等價於 printf("%u"). [1]

%ld

long

等價於 printf("%ld"). [1]

%lu

unsigned long

等價於 printf("%lu"). [1]

%zd

Py_ssize_t

等價於 printf("%zd"). [1]

%zu

size_t

等價於 printf("%zu"). [1]

%i

int

等價於 printf("%i"). [1]

%x

int

等價於 printf("%x"). [1]

%s

const char*

A null-terminated C character array.

%p

const void*

The hex representation of a C pointer. Mostly equivalent to printf("%p") except that it is guaranteed to start with the literal 0x regardless of what the platform's printf yields.

An unrecognized format character causes all the rest of the format string to be copied as-is to the result object, and any extra arguments discarded.

[1] (1,2,3,4,5,6,7,8)

For integer specifiers (d, u, ld, lu, zd, zu, i, x): the 0-conversion flag has effect even when a precision is given.

PyObject *PyBytes_FromFormatV(const char *format, va_list vargs)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Identical to PyBytes_FromFormat() except that it takes exactly two arguments.

PyObject *PyBytes_FromObject(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the bytes representation of object o that implements the buffer protocol.

Py_ssize_t PyBytes_Size(PyObject *o)

為 穩定 ABI 的一部分.

Return the length of the bytes in bytes object o.

Py_ssize_t PyBytes_GET_SIZE(PyObject *o)

和 PyBytes_Size() 類似，但不進行錯誤檢查。

char *PyBytes_AsString(PyObject *o)

為 穩定 ABI 的一部分.

Return a pointer to the contents of o. The pointer refers to the internal buffer of o, which consists of len(o) + 1 bytes. The last byte in the buffer is always null, regardless of whether there are any other null bytes. The data must not be modified in any way, unless the object was just created using PyBytes_FromStringAndSize(NULL, size). It must not be deallocated. If o is not a bytes object at all, PyBytes_AsString() returns NULL and raises TypeError.

char *PyBytes_AS_STRING(PyObject *string)

和 PyBytes_AsString() 類似，但不進行錯誤檢查。

int PyBytes_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)

為 穩定 ABI 的一部分.

Return the null-terminated contents of the object obj through the output variables buffer and length. Returns 0 on success.

If length is NULL, the bytes object may not contain embedded null bytes; if it does, the function returns -1 and a ValueError is raised.

The buffer refers to an internal buffer of obj, which includes an additional null byte at the end (not counted in length). The data must not be modified in any way, unless the object was just created using PyBytes_FromStringAndSize(NULL, size). It must not be deallocated. If obj is not a bytes object at all, PyBytes_AsStringAndSize() returns -1 and raises TypeError.

在 3.5 版的變更: Previously, TypeError was raised when embedded null bytes were encountered in the bytes object.

void PyBytes_Concat(PyObject **bytes, PyObject *newpart)

為 穩定 ABI 的一部分.

Create a new bytes object in *bytes containing the contents of newpart appended to bytes; the caller will own the new reference. The reference to the old value of bytes will be stolen. If the new object cannot be created, the old reference to bytes will still be discarded and the value of *bytes will be set to NULL; the appropriate exception will be set.

void PyBytes_ConcatAndDel(PyObject **bytes, PyObject *newpart)

為 穩定 ABI 的一部分.

Create a new bytes object in *bytes containing the contents of newpart appended to bytes. This version releases the strong reference to newpart (i.e. decrements its reference count).

PyObject *PyBytes_Join(PyObject *sep, PyObject *iterable)

類似 Python 中的 sep.join(iterable)。

sep must be Python bytes object. (Note that PyUnicode_Join() accepts NULL separator and treats it as a space, whereas PyBytes_Join() doesn't accept NULL separator.)

iterable must be an iterable object yielding objects that implement the buffer protocol.

On success, return a new bytes object. On error, set an exception and return NULL.

在 3.14 版被加入.

int _PyBytes_Resize(PyObject **bytes, Py_ssize_t newsize)

Resize a bytes object. newsize will be the new length of the bytes object. You can think of it as creating a new bytes object and destroying the old one, only more efficiently. Pass the address of an existing bytes object as an lvalue (it may be written into), and the new size desired. On success, *bytes holds the resized bytes object and 0 is returned; the address in *bytes may differ from its input value. If the reallocation fails, the original bytes object at *bytes is deallocated, *bytes is set to NULL, MemoryError is set, and -1 is returned.

PyObject *PyBytes_Repr(PyObject *bytes, int smartquotes)

為 穩定 ABI 的一部分.

Get the string representation of bytes. This function is currently used to implement bytes.__repr__() in Python.

This function does not do type checking; it is undefined behavior to pass bytes as a non-bytes object or NULL.

If smartquotes is true, the representation will use a double-quoted string instead of single-quoted string when single-quotes are present in bytes. For example, the byte string 'Python' would be represented as b"'Python'" when smartquotes is true, or b'\'Python\'' when it is false.

On success, this function returns a strong reference to a str object containing the representation. On failure, this returns NULL with an exception set.

PyObject *PyBytes_DecodeEscape(const char *s, Py_ssize_t len, const char *errors, Py_ssize_t unicode, const char *recode_encoding)

為 穩定 ABI 的一部分.

Unescape a backslash-escaped string s. s must not be NULL. len must be the size of s.

errors must be one of "strict", "replace", or "ignore". If errors is NULL, then "strict" is used by default.

On success, this function returns a strong reference to a Python bytes object containing the unescaped string. On failure, this function returns NULL with an exception set.

在 3.9 版的變更: unicode and recode_encoding are now unused.

位元組陣列物件 (Byte Array Objects)

type PyByteArrayObject

這個 PyObject 的子型別代表了 Python 的位元組陣列物件。

PyTypeObject PyByteArray_Type

為 穩定 ABI 的一部分.

這個 PyTypeObject 的實例代表了 Python 的位元組陣列型別；在 Python 層中的 bytearray 為同一個物件。

型別檢查巨集

int PyByteArray_Check(PyObject *o)

如果物件 o 是一個位元組陣列物件，或者是位元組陣列型別的子型別的實例，則回傳真值。此函式總是會成功執行。

int PyByteArray_CheckExact(PyObject *o)

如果物件 o 是一個位元組陣列物件，但不是位元組陣列型別的子型別的實例，則回傳真值。此函式總是會成功執行。

直接 API 函式

PyObject *PyByteArray_FromObject(PyObject *o)

回傳值：新的參照。 為 穩定 ABI 的一部分.

由任意物件 o 回傳一個新的位元組陣列物件，並實作了緩衝協定 (buffer protocol)。

在失敗時，會回傳 NULL 並設定例外。

PyObject *PyByteArray_FromStringAndSize(const char *string, Py_ssize_t len)

回傳值：新的參照。 為 穩定 ABI 的一部分.

從 string 及其長度 len 建立一個新的位元組陣列物件。

在失敗時，會回傳 NULL 並設定例外。

PyObject *PyByteArray_Concat(PyObject *a, PyObject *b)

回傳值：新的參照。 為 穩定 ABI 的一部分.

連接位元組陣列 a 和 b，並回傳一個包含結果的新位元組陣列。

在失敗時，會回傳 NULL 並設定例外。

Py_ssize_t PyByteArray_Size(PyObject *bytearray)

為 穩定 ABI 的一部分.

在檢查為 NULL 指標後，回傳 bytearray 的大小。

char *PyByteArray_AsString(PyObject *bytearray)

為 穩定 ABI 的一部分.

在檢查是否為 NULL 指標後，將 bytearray 的內容回傳為字元陣列。回傳的陣列總是會多附加一個空位元組。

int PyByteArray_Resize(PyObject *bytearray, Py_ssize_t len)

為 穩定 ABI 的一部分.

將 bytearray 的內部緩衝區大小調整為 len。失敗時會回傳 -1 並設定例外。

在 3.14 版的變更: 負的 len 現在會設定例外並回傳 -1。

巨集

這些巨集犧牲了安全性以換取速度，並且它們不會檢查指標。

char *PyByteArray_AS_STRING(PyObject *bytearray)

與 PyByteArray_AsString() 類似，但沒有錯誤檢查。

Py_ssize_t PyByteArray_GET_SIZE(PyObject *bytearray)

與 PyByteArray_Size() 類似，但沒有錯誤檢查。

Unicode 物件與編解碼器

Unicode 物件

Since the implementation of PEP 393 [https://peps.python.org/pep-0393/] in Python 3.3, Unicode objects internally use a variety of representations, in order to allow handling the complete range of Unicode characters while staying memory efficient. There are special cases for strings where all code points are below 128, 256, or 65536; otherwise, code points must be below 1114112 (which is the full Unicode range).

UTF-8 表示法會在需要時建立並快取在 Unicode 物件中。

備註

自 Python 3.12 起，已移除 Py_UNICODE 表示法，並標示為已棄用的 API。更多資訊請參閱 PEP 623 [https://peps.python.org/pep-0623/]。

Unicode 型別

這些是 Python 中用於 Unicode 實作的基本 Unicode 物件型別：

PyTypeObject PyUnicode_Type

為 穩定 ABI 的一部分.

This instance of PyTypeObject represents the Python Unicode type. It is exposed to Python code as str.

PyTypeObject PyUnicodeIter_Type

為 穩定 ABI 的一部分.

This instance of PyTypeObject represents the Python Unicode iterator type. It is used to iterate over Unicode string objects.

type Py_UCS4

type Py_UCS2

type Py_UCS1

為 穩定 ABI 的一部分.

These types are typedefs for unsigned integer types wide enough to contain characters of 32 bits, 16 bits and 8 bits, respectively. When dealing with single Unicode characters, use Py_UCS4.

在 3.3 版被加入.

type PyASCIIObject

type PyCompactUnicodeObject

type PyUnicodeObject

These subtypes of PyObject represent a Python Unicode object. In almost all cases, they shouldn't be used directly, since all API functions that deal with Unicode objects take and return PyObject pointers.

在 3.3 版被加入.

The structure of a particular object can be determined using the following macros. The macros cannot fail; their behavior is undefined if their argument is not a Python Unicode object.

PyUnicode_IS_COMPACT(o)

True if o uses the PyCompactUnicodeObject structure.

在 3.3 版被加入.

PyUnicode_IS_COMPACT_ASCII(o)

True if o uses the PyASCIIObject structure.

在 3.3 版被加入.

The following APIs are C macros and static inlined functions for fast checks and access to internal read-only data of Unicode objects:

int PyUnicode_Check(PyObject *obj)

Return true if the object obj is a Unicode object or an instance of a Unicode subtype. This function always succeeds.

int PyUnicode_CheckExact(PyObject *obj)

Return true if the object obj is a Unicode object, but not an instance of a subtype. This function always succeeds.

Py_ssize_t PyUnicode_GET_LENGTH(PyObject *unicode)

Return the length of the Unicode string, in code points. unicode has to be a Unicode object in the "canonical" representation (not checked).

在 3.3 版被加入.

Py_UCS1 *PyUnicode_1BYTE_DATA(PyObject *unicode)

Py_UCS2 *PyUnicode_2BYTE_DATA(PyObject *unicode)

Py_UCS4 *PyUnicode_4BYTE_DATA(PyObject *unicode)

Return a pointer to the canonical representation cast to UCS1, UCS2 or UCS4 integer types for direct character access. No checks are performed if the canonical representation has the correct character size; use PyUnicode_KIND() to select the right function.

在 3.3 版被加入.

PyUnicode_1BYTE_KIND

PyUnicode_2BYTE_KIND

PyUnicode_4BYTE_KIND

Return values of the PyUnicode_KIND() macro.

在 3.3 版被加入.

在 3.12 版的變更: PyUnicode_WCHAR_KIND 已被移除。

int PyUnicode_KIND(PyObject *unicode)

Return one of the PyUnicode kind constants (see above) that indicate how many bytes per character this Unicode object uses to store its data. unicode has to be a Unicode object in the "canonical" representation (not checked).

在 3.3 版被加入.

void *PyUnicode_DATA(PyObject *unicode)

Return a void pointer to the raw Unicode buffer. unicode has to be a Unicode object in the "canonical" representation (not checked).

在 3.3 版被加入.

void PyUnicode_WRITE(int kind, void *data, Py_ssize_t index, Py_UCS4 value)

Write the code point value to the given zero-based index in a string.

The kind value and data pointer must have been obtained from a string using PyUnicode_KIND() and PyUnicode_DATA() respectively. You must hold a reference to that string while calling PyUnicode_WRITE(). All requirements of PyUnicode_WriteChar() also apply.

The function performs no checks for any of its requirements, and is intended for usage in loops.

在 3.3 版被加入.

Py_UCS4 PyUnicode_READ(int kind, void *data, Py_ssize_t index)

Read a code point from a canonical representation data (as obtained with PyUnicode_DATA()). No checks or ready calls are performed.

在 3.3 版被加入.

Py_UCS4 PyUnicode_READ_CHAR(PyObject *unicode, Py_ssize_t index)

Read a character from a Unicode object unicode, which must be in the "canonical" representation. This is less efficient than PyUnicode_READ() if you do multiple consecutive reads.

在 3.3 版被加入.

Py_UCS4 PyUnicode_MAX_CHAR_VALUE(PyObject *unicode)

Return the maximum code point that is suitable for creating another string based on unicode, which must be in the "canonical" representation. This is always an approximation but more efficient than iterating over the string.

在 3.3 版被加入.

int PyUnicode_IsIdentifier(PyObject *unicode)

為 穩定 ABI 的一部分.

Return 1 if the string is a valid identifier according to the language definition, section Names (identifiers and keywords). Return 0 otherwise.

在 3.9 版的變更: The function does not call Py_FatalError() anymore if the string is not ready.

unsigned int PyUnicode_IS_ASCII(PyObject *unicode)

Return true if the string only contains ASCII characters. Equivalent to str.isascii().

在 3.2 版被加入.

Unicode Character Properties

Unicode provides many different character properties. The most often needed ones are available through these macros which are mapped to C functions depending on the Python configuration.

int Py_UNICODE_ISSPACE(Py_UCS4 ch)

根據 ch 是否為空白字元來回傳 1 或 0。

int Py_UNICODE_ISLOWER(Py_UCS4 ch)

根據 ch 是否為小寫字元來回傳 1 或 0。

int Py_UNICODE_ISUPPER(Py_UCS4 ch)

根據 ch 是否為大寫字元來回傳 1 或 0。

int Py_UNICODE_ISTITLE(Py_UCS4 ch)

根據 ch 是否為首字大寫字元來回傳 1 或 0。

int Py_UNICODE_ISLINEBREAK(Py_UCS4 ch)

根據 ch 是否為換行字元來回傳 1 或 0。

int Py_UNICODE_ISDECIMAL(Py_UCS4 ch)

根據 ch 是否為十進位字元來回傳 1 或 0。

int Py_UNICODE_ISDIGIT(Py_UCS4 ch)

根據 ch 是否為數字 (digit) 字元來回傳 1 或 0。

int Py_UNICODE_ISNUMERIC(Py_UCS4 ch)

根據 ch 是否為數值 (numeric) 字元來回傳 1 或 0。

int Py_UNICODE_ISALPHA(Py_UCS4 ch)

根據 ch 是否為字母字元來回傳 1 或 0。

int Py_UNICODE_ISALNUM(Py_UCS4 ch)

根據 ch 是否為字母數字 (alphanumeric) 字元來回傳 1 或 0。

int Py_UNICODE_ISPRINTABLE(Py_UCS4 ch)

根據 ch 是否為可列印字元（如 str.isprintable() 所定義）來回傳 1 或 0。

這些 API 可用於快速直接字元轉換：

Py_UCS4 Py_UNICODE_TOLOWER(Py_UCS4 ch)

回傳轉換為小寫的 ch 字元。

Py_UCS4 Py_UNICODE_TOUPPER(Py_UCS4 ch)

回傳轉換為大寫的 ch 字元。

Py_UCS4 Py_UNICODE_TOTITLE(Py_UCS4 ch)

回傳轉換為首字大寫的 ch 字元。

int Py_UNICODE_TODECIMAL(Py_UCS4 ch)

回傳轉換為十進位正整數的 ch 字元，若無法轉換則回傳 -1。此函式不會引發例外。

int Py_UNICODE_TODIGIT(Py_UCS4 ch)

回傳轉換為單一數字整數的 ch 字元，若無法轉換則回傳 -1。此函式不會引發例外。

double Py_UNICODE_TONUMERIC(Py_UCS4 ch)

回傳轉換為雙精度浮點數 (double) 的 ch 字元，若無法轉換則回傳 -1.0。此函式不會引發例外。

這些 API 可用於處理代理字元：

int Py_UNICODE_IS_SURROGATE(Py_UCS4 ch)

檢查 ch 是否為代理字元 (surrogate, 0xD800 <= ch <= 0xDFFF)。

int Py_UNICODE_IS_HIGH_SURROGATE(Py_UCS4 ch)

檢查 ch 是否為高代理字元 (high surrogate, 0xD800 <= ch <= 0xDBFF)。

int Py_UNICODE_IS_LOW_SURROGATE(Py_UCS4 ch)

檢查 ch 是否為低代理字元 (low surrogate, 0xDC00 <= ch <= 0xDFFF)。

Py_UCS4 Py_UNICODE_HIGH_SURROGATE(Py_UCS4 ch)

Return the high UTF-16 surrogate (0xD800 to 0xDBFF) for a Unicode code point in the range [0x10000; 0x10FFFF].

Py_UCS4 Py_UNICODE_LOW_SURROGATE(Py_UCS4 ch)

Return the low UTF-16 surrogate (0xDC00 to 0xDFFF) for a Unicode code point in the range [0x10000; 0x10FFFF].

Py_UCS4 Py_UNICODE_JOIN_SURROGATES(Py_UCS4 high, Py_UCS4 low)

Join two surrogate code points and return a single Py_UCS4 value. high and low are respectively the leading and trailing surrogates in a surrogate pair. high must be in the range [0xD800; 0xDBFF] and low must be in the range [0xDC00; 0xDFFF].

Creating and accessing Unicode strings

To create Unicode objects and access their basic sequence properties, use these APIs:

PyObject *PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)

回傳值：新的參照。

Create a new Unicode object. maxchar should be the true maximum code point to be placed in the string. As an approximation, it can be rounded up to the nearest value in the sequence 127, 255, 65535, 1114111.

On error, set an exception and return NULL.

After creation, the string can be filled by PyUnicode_WriteChar(), PyUnicode_CopyCharacters(), PyUnicode_Fill(), PyUnicode_WRITE() or similar. Since strings are supposed to be immutable, take care to not “use” the result while it is being modified. In particular, before it's filled with its final contents, a string:

must not be hashed,

must not be converted to UTF-8, or another non-"canonical" representation,

must not have its reference count changed,

must not be shared with code that might do one of the above.

This list is not exhaustive. Avoiding these uses is your responsibility; Python does not always check these requirements.

To avoid accidentally exposing a partially-written string object, prefer using the PyUnicodeWriter API, or one of the PyUnicode_From* functions below.

在 3.3 版被加入.

PyObject *PyUnicode_FromKindAndData(int kind, const void *buffer, Py_ssize_t size)

回傳值：新的參照。

Create a new Unicode object with the given kind (possible values are PyUnicode_1BYTE_KIND etc., as returned by PyUnicode_KIND()). The buffer must point to an array of size units of 1, 2 or 4 bytes per character, as given by the kind.

If necessary, the input buffer is copied and transformed into the canonical representation. For example, if the buffer is a UCS4 string (PyUnicode_4BYTE_KIND) and it consists only of codepoints in the UCS1 range, it will be transformed into UCS1 (PyUnicode_1BYTE_KIND).

在 3.3 版被加入.

PyObject *PyUnicode_FromStringAndSize(const char *str, Py_ssize_t size)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object from the char buffer str. The bytes will be interpreted as being UTF-8 encoded. The buffer is copied into the new object. The return value might be a shared object, i.e. modification of the data is not allowed.

此函式在以下情況下會引發 SystemError：

size < 0，

str 為 NULL 且 size > 0

在 3.12 版的變更: str == NULL 且 size > 0 不再被允許。

PyObject *PyUnicode_FromString(const char *str)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object from a UTF-8 encoded null-terminated char buffer str.

PyObject *PyUnicode_FromFormat(const char *format, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Take a C printf()-style format string and a variable number of arguments, calculate the size of the resulting Python Unicode string and return a string with the values formatted into it. The variable arguments must be C types and must correspond exactly to the format characters in the format ASCII-encoded string.

A conversion specifier contains two or more characters and has the following components, which must occur in this order:

The '%' character, which marks the start of the specifier.

Conversion flags (optional), which affect the result of some conversion types.

Minimum field width (optional). If specified as an '*' (asterisk), the actual width is given in the next argument, which must be of type int, and the object to convert comes after the minimum field width and optional precision.

Precision (optional), given as a '.' (dot) followed by the precision. If specified as '*' (an asterisk), the actual precision is given in the next argument, which must be of type int, and the value to convert comes after the precision.

Length modifier (optional).

Conversion type.

The conversion flag characters are:

旗標

含義

0

The conversion will be zero padded for numeric values.

-

The converted value is left adjusted (overrides the 0 flag if both are given).

The length modifiers for following integer conversions (d, i, o, u, x, or X) specify the type of the argument (int by default):

Modifier

Types

l

long 或 unsigned long

ll

long long 或 unsigned long long

j

intmax_t 或 uintmax_t

z

size_t 或 ssize_t

t

ptrdiff_t

The length modifier l for following conversions s or V specify that the type of the argument is const wchar_t*.

The conversion specifiers are:

Conversion Specifier

Type

Comment

%

n/a

字面 % 字元。

d, i

Specified by the length modifier

一個有符號 C 整數的十進位表示法。

u

Specified by the length modifier

一個無符號 C 整數的十進位表示法。

o

Specified by the length modifier

一個無符號 C 整數的八進位表示法。

x

Specified by the length modifier

一個無符號 C 整數的十六進位表示法（小寫）。

X

Specified by the length modifier

一個無符號 C 整數的十六進位表示法（大寫）。

c

int

一個單一字元。

s

const char* 或 const wchar_t*

一個以 null 結尾的 C 字元陣列。

p

const void*

The hex representation of a C pointer. Mostly equivalent to printf("%p") except that it is guaranteed to start with the literal 0x regardless of what the platform's printf yields.

A

PyObject*

呼叫 ascii() 的結果。

U

PyObject*

一個 Unicode 物件。

V

PyObject*、const char* 或 const wchar_t*

A Unicode object (which may be NULL) and a null-terminated C character array as a second parameter (which will be used, if the first parameter is NULL).

S

PyObject*

呼叫 PyObject_Str() 的結果。

R

PyObject*

呼叫 PyObject_Repr() 的結果。

T

PyObject*

Get the fully qualified name of an object type; call PyType_GetFullyQualifiedName().

#T

PyObject*

Similar to T format, but use a colon (:) as separator between the module name and the qualified name.

N

PyTypeObject*

Get the fully qualified name of a type; call PyType_GetFullyQualifiedName().

#N

PyTypeObject*

Similar to N format, but use a colon (:) as separator between the module name and the qualified name.

備註

The width formatter unit is number of characters rather than bytes. The precision formatter unit is number of bytes or wchar_t items (if the length modifier l is used) for "%s" and "%V" (if the PyObject* argument is NULL), and a number of characters for "%A", "%U", "%S", "%R" and "%V" (if the PyObject* argument is not NULL).

備註

Unlike to C printf() the 0 flag has effect even when a precision is given for integer conversions (d, i, u, o, x, or X).

在 3.2 版的變更: 新增對 "%lld" 和 "%llu" 的支援。

在 3.3 版的變更: 新增對 "%li"、"%lli" 和 "%zi" 的支援。

在 3.4 版的變更: 新增對 "%s"、"%A"、"%U"、"%V"、"%S"、"%R" 的寬度和精確度格式化支援。

在 3.12 版的變更: Support for conversion specifiers o and X. Support for length modifiers j and t. Length modifiers are now applied to all integer conversions. Length modifier l is now applied to conversion specifiers s and V. Support for variable width and precision *. Support for flag -.

An unrecognized format character now sets a SystemError. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded.

在 3.13 版的變更: 新增對 %T、%#T、%N 和 %#N 格式的支援。

PyObject *PyUnicode_FromFormatV(const char *format, va_list vargs)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Identical to PyUnicode_FromFormat() except that it takes exactly two arguments.

PyObject *PyUnicode_FromObject(PyObject *obj)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Copy an instance of a Unicode subtype to a new true Unicode object if necessary. If obj is already a true Unicode object (not a subtype), return a new strong reference to the object.

Objects other than Unicode or its subtypes will cause a TypeError.

PyObject *PyUnicode_FromOrdinal(int ordinal)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode Object from the given Unicode code point ordinal.

The ordinal must be in range(0x110000). A ValueError is raised in the case it is not.

PyObject *PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Decode an encoded object obj to a Unicode object.

bytes, bytearray and other bytes-like objects are decoded according to the given encoding and using the error handling defined by errors. Both can be NULL to have the interface use the default values (see 內建編解碼器 for details).

All other objects, including Unicode objects, cause a TypeError to be set.

The API returns NULL if there was an error. The caller is responsible for decref'ing the returned objects.

void PyUnicode_Append(PyObject **p_left, PyObject *right)

為 穩定 ABI 的一部分.

Append the string right to the end of p_left. p_left must point to a strong reference to a Unicode object; PyUnicode_Append() releases ("steals") this reference.

於錯誤發生時，將 *p_left 設為 NULL 並設定例外。

On success, set *p_left to a new strong reference to the result.

void PyUnicode_AppendAndDel(PyObject **p_left, PyObject *right)

為 穩定 ABI 的一部分.

The function is similar to PyUnicode_Append(), with the only difference being that it decrements the reference count of right by one.

PyObject *PyUnicode_BuildEncodingMap(PyObject *string)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a mapping suitable for decoding a custom single-byte encoding. Given a Unicode string string of up to 256 characters representing an encoding table, returns either a compact internal mapping object or a dictionary mapping character ordinals to byte values. Raises a TypeError and return NULL on invalid input.

在 3.2 版被加入.

const char *PyUnicode_GetDefaultEncoding(void)

為 穩定 ABI 的一部分.

Return the name of the default string encoding, "utf-8". See sys.getdefaultencoding().

The returned string does not need to be freed, and is valid until interpreter shutdown.

Py_ssize_t PyUnicode_GetLength(PyObject *unicode)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return the length of the Unicode object, in code points.

發生錯誤時，設定例外並回傳 -1。

在 3.3 版被加入.

Py_ssize_t PyUnicode_CopyCharacters(PyObject *to, Py_ssize_t to_start, PyObject *from, Py_ssize_t from_start, Py_ssize_t how_many)

Copy characters from one Unicode object into another. This function performs character conversion when necessary and falls back to memcpy() if possible. Returns -1 and sets an exception on error, otherwise returns the number of copied characters.

The string must not have been “used” yet. See PyUnicode_New() for details.

在 3.3 版被加入.

int PyUnicode_Resize(PyObject **unicode, Py_ssize_t length);

為 穩定 ABI 的一部分.

Resize a Unicode object *unicode to the new length in code points.

Try to resize the string in place (which is usually faster than allocating a new string and copying characters), or create a new string.

*unicode is modified to point to the new (resized) object and 0 is returned on success. Otherwise, -1 is returned and an exception is set, and *unicode is left untouched.

The function doesn't check string content, the result may not be a string in canonical representation.

Py_ssize_t PyUnicode_Fill(PyObject *unicode, Py_ssize_t start, Py_ssize_t length, Py_UCS4 fill_char)

Fill a string with a character: write fill_char into unicode[start:start+length].

Fail if fill_char is bigger than the string maximum character, or if the string has more than 1 reference.

The string must not have been “used” yet. See PyUnicode_New() for details.

Return the number of written character, or return -1 and raise an exception on error.

在 3.3 版被加入.

int PyUnicode_WriteChar(PyObject *unicode, Py_ssize_t index, Py_UCS4 character)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Write a character to the string unicode at the zero-based index. Return 0 on success, -1 on error with an exception set.

This function checks that unicode is a Unicode object, that the index is not out of bounds, and that the object's reference count is one. See PyUnicode_WRITE() for a version that skips these checks, making them your responsibility.

The string must not have been “used” yet. See PyUnicode_New() for details.

在 3.3 版被加入.

Py_UCS4 PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Read a character from a string. This function checks that unicode is a Unicode object and the index is not out of bounds, in contrast to PyUnicode_READ_CHAR(), which performs no error checking.

成功時回傳字元，發生錯誤時設定例外並回傳 -1。

在 3.3 版被加入.

PyObject *PyUnicode_Substring(PyObject *unicode, Py_ssize_t start, Py_ssize_t end)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Return a substring of unicode, from character index start (included) to character index end (excluded). Negative indices are not supported. On error, set an exception and return NULL.

在 3.3 版被加入.

Py_UCS4 *PyUnicode_AsUCS4(PyObject *unicode, Py_UCS4 *buffer, Py_ssize_t buflen, int copy_null)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Copy the string unicode into a UCS4 buffer, including a null character, if copy_null is set. Returns NULL and sets an exception on error (in particular, a SystemError if buflen is smaller than the length of unicode). buffer is returned on success.

在 3.3 版被加入.

Py_UCS4 *PyUnicode_AsUCS4Copy(PyObject *unicode)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Copy the string unicode into a new UCS4 buffer that is allocated using PyMem_Malloc(). If this fails, NULL is returned with a MemoryError set. The returned buffer always has an extra null code point appended.

在 3.3 版被加入.

Locale Encoding

The current locale encoding can be used to decode text from the operating system.

PyObject *PyUnicode_DecodeLocaleAndSize(const char *str, Py_ssize_t length, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Decode a string from UTF-8 on Android and VxWorks, or from the current locale encoding on other platforms. The supported error handlers are "strict" and "surrogateescape" (PEP 383 [https://peps.python.org/pep-0383/]). The decoder uses "strict" error handler if errors is NULL. str must end with a null character but cannot contain embedded null characters.

Use PyUnicode_DecodeFSDefaultAndSize() to decode a string from the filesystem encoding and error handler.

此函式會忽略 Python UTF-8 模式。

也參考

Py_DecodeLocale() 函式。

在 3.3 版被加入.

在 3.7 版的變更: The function now also uses the current locale encoding for the surrogateescape error handler, except on Android. Previously, Py_DecodeLocale() was used for the surrogateescape, and the current locale encoding was used for strict.

PyObject *PyUnicode_DecodeLocale(const char *str, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

類似於 PyUnicode_DecodeLocaleAndSize()，但使用 strlen() 計算字串長度。

在 3.3 版被加入.

PyObject *PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Encode a Unicode object to UTF-8 on Android and VxWorks, or to the current locale encoding on other platforms. The supported error handlers are "strict" and "surrogateescape" (PEP 383 [https://peps.python.org/pep-0383/]). The encoder uses "strict" error handler if errors is NULL. Return a bytes object. unicode cannot contain embedded null characters.

Use PyUnicode_EncodeFSDefault() to encode a string to the filesystem encoding and error handler.

此函式會忽略 Python UTF-8 模式。

也參考

Py_EncodeLocale() 函式。

在 3.3 版被加入.

在 3.7 版的變更: The function now also uses the current locale encoding for the surrogateescape error handler, except on Android. Previously, Py_EncodeLocale() was used for the surrogateescape, and the current locale encoding was used for strict.

檔案系統編碼

Functions encoding to and decoding from the filesystem encoding and error handler (PEP 383 [https://peps.python.org/pep-0383/] and PEP 529 [https://peps.python.org/pep-0529/]).

To encode file names to bytes during argument parsing, the "O&" converter should be used, passing PyUnicode_FSConverter() as the conversion function:

int PyUnicode_FSConverter(PyObject *obj, void *result)

為 穩定 ABI 的一部分.

PyArg_Parse* converter: encode str objects -- obtained directly or through the os.PathLike interface -- to bytes using PyUnicode_EncodeFSDefault(); bytes objects are output as-is. result must be an address of a C variable of type PyObject* (or PyBytesObject*). On success, set the variable to a new strong reference to a bytes object which must be released when it is no longer used and return a non-zero value (Py_CLEANUP_SUPPORTED). Embedded null bytes are not allowed in the result. On failure, return 0 with an exception set.

If obj is NULL, the function releases a strong reference stored in the variable referred by result and returns 1.

在 3.1 版被加入.

在 3.6 版的變更: 接受一個 path-like object。

To decode file names to str during argument parsing, the "O&" converter should be used, passing PyUnicode_FSDecoder() as the conversion function:

int PyUnicode_FSDecoder(PyObject *obj, void *result)

為 穩定 ABI 的一部分.

PyArg_Parse* converter: decode bytes objects -- obtained either directly or indirectly through the os.PathLike interface -- to str using PyUnicode_DecodeFSDefaultAndSize(); str objects are output as-is. result must be an address of a C variable of type PyObject* (or PyUnicodeObject*). On success, set the variable to a new strong reference to a Unicode object which must be released when it is no longer used and return a non-zero value (Py_CLEANUP_SUPPORTED). Embedded null characters are not allowed in the result. On failure, return 0 with an exception set.

If obj is NULL, release the strong reference to the object referred to by result and return 1.

在 3.2 版被加入.

在 3.6 版的變更: 接受一個 path-like object。

PyObject *PyUnicode_DecodeFSDefaultAndSize(const char *str, Py_ssize_t size)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Decode a string from the filesystem encoding and error handler.

If you need to decode a string from the current locale encoding, use PyUnicode_DecodeLocaleAndSize().

也參考

Py_DecodeLocale() 函式。

在 3.6 版的變更: The filesystem error handler is now used.

PyObject *PyUnicode_DecodeFSDefault(const char *str)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Decode a null-terminated string from the filesystem encoding and error handler.

如果字串長度已知，請使用 PyUnicode_DecodeFSDefaultAndSize()。

在 3.6 版的變更: The filesystem error handler is now used.

PyObject *PyUnicode_EncodeFSDefault(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object to the filesystem encoding and error handler, and return bytes. Note that the resulting bytes object can contain null bytes.

If you need to encode a string to the current locale encoding, use PyUnicode_EncodeLocale().

也參考

Py_EncodeLocale() 函式。

在 3.2 版被加入.

在 3.6 版的變更: The filesystem error handler is now used.

wchar_t 支援

對支援 wchar_t 的平台提供支援：

PyObject *PyUnicode_FromWideChar(const wchar_t *wstr, Py_ssize_t size)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object from the wchar_t buffer wstr of the given size. Passing -1 as the size indicates that the function must itself compute the length, using wcslen(). Return NULL on failure.

Py_ssize_t PyUnicode_AsWideChar(PyObject *unicode, wchar_t *wstr, Py_ssize_t size)

為 穩定 ABI 的一部分.

Copy the Unicode object contents into the wchar_t buffer wstr. At most size wchar_t characters are copied (excluding a possibly trailing null termination character). Return the number of wchar_t characters copied or -1 in case of an error.

When wstr is NULL, instead return the size that would be required to store all of unicode including a terminating null.

Note that the resulting wchar_t* string may or may not be null-terminated. It is the responsibility of the caller to make sure that the wchar_t* string is null-terminated in case this is required by the application. Also, note that the wchar_t* string might contain null characters, which would cause the string to be truncated when used with most C functions.

wchar_t *PyUnicode_AsWideCharString(PyObject *unicode, Py_ssize_t *size)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Convert the Unicode object to a wide character string. The output string always ends with a null character. If size is not NULL, write the number of wide characters (excluding the trailing null termination character) into *size. Note that the resulting wchar_t string might contain null characters, which would cause the string to be truncated when used with most C functions. If size is NULL and the wchar_t* string contains null characters a ValueError is raised.

Returns a buffer allocated by PyMem_New (use PyMem_Free() to free it) on success. On error, returns NULL and *size is undefined. Raises a MemoryError if memory allocation is failed.

在 3.2 版被加入.

在 3.7 版的變更: Raises a ValueError if size is NULL and the wchar_t* string contains null characters.

內建編解碼器

Python provides a set of built-in codecs which are written in C for speed. All of these codecs are directly usable via the following functions.

Many of the following APIs take two arguments encoding and errors, and they have the same semantics as the ones of the built-in str() string object constructor.

Setting encoding to NULL causes the default encoding to be used which is UTF-8. The file system calls should use PyUnicode_FSConverter() for encoding file names. This uses the filesystem encoding and error handler internally.

Error handling is set by errors which may also be set to NULL meaning to use the default handling defined for the codec. Default error handling for all built-in codecs is "strict" (ValueError is raised).

The codecs all use a similar interface. Only deviations from the following generic ones are documented for simplicity.

泛用編解碼器

The following macro is provided:

Py_UNICODE_REPLACEMENT_CHARACTER

The Unicode code point U+FFFD (replacement character).

This Unicode character is used as the replacement character during decoding if the errors argument is set to "replace".

這些是泛用編解碼器的 API：

PyObject *PyUnicode_Decode(const char *str, Py_ssize_t size, const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the encoded string str. encoding and errors have the same meaning as the parameters of the same name in the str() built-in function. The codec to be used is looked up using the Python codec registry. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_AsEncodedString(PyObject *unicode, const char *encoding, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object and return the result as Python bytes object. encoding and errors have the same meaning as the parameters of the same name in the Unicode encode() method. The codec to be used is looked up using the Python codec registry. Return NULL if an exception was raised by the codec.

UTF-8 編解碼器

這些是 UTF-8 編解碼器的 API：

PyObject *PyUnicode_DecodeUTF8(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the UTF-8 encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_DecodeUTF8Stateful(const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)

回傳值：新的參照。 為 穩定 ABI 的一部分.

If consumed is NULL, behave like PyUnicode_DecodeUTF8(). If consumed is not NULL, trailing incomplete UTF-8 byte sequences will not be treated as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.

PyObject *PyUnicode_AsUTF8String(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object using UTF-8 and return the result as Python bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

The function fails if the string contains surrogate code points (U+D800 - U+DFFF).

const char *PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *size)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Return a pointer to the UTF-8 encoding of the Unicode object, and store the size of the encoded representation (in bytes) in size. The size argument can be NULL; in this case no size will be stored. The returned buffer always has an extra null byte appended (not included in size), regardless of whether there are any other null code points.

發生錯誤時，設定例外並將 size 設為 -1（如果不是 NULL），並回傳 NULL。

The function fails if the string contains surrogate code points (U+D800 - U+DFFF).

This caches the UTF-8 representation of the string in the Unicode object, and subsequent calls will return a pointer to the same buffer. The caller is not responsible for deallocating the buffer. The buffer is deallocated and pointers to it become invalid when the Unicode object is garbage collected.

在 3.3 版被加入.

在 3.7 版的變更: 回傳型別現在是 const char * 而不是 char *。

在 3.10 版的變更: This function is a part of the limited API.

const char *PyUnicode_AsUTF8(PyObject *unicode)

與 PyUnicode_AsUTF8AndSize() 類似，但不儲存大小。

警告

This function does not have any special behavior for null characters [https://en.wikipedia.org/wiki/Null_character] embedded within unicode. As a result, strings containing null characters will remain in the returned string, which some C functions might interpret as the end of the string, leading to truncation. If truncation is an issue, it is recommended to use PyUnicode_AsUTF8AndSize() instead.

在 3.3 版被加入.

在 3.7 版的變更: 回傳型別現在是 const char * 而不是 char *。

UTF-32 編解碼器

這些是 UTF-32 編解碼器的 API：

PyObject *PyUnicode_DecodeUTF32(const char *str, Py_ssize_t size, const char *errors, int *byteorder)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Decode size bytes from a UTF-32 encoded buffer string and return the corresponding Unicode object. errors (if non-NULL) defines the error handling. It defaults to "strict".

If byteorder is non-NULL, the decoder starts decoding using the given byte order:

*byteorder == -1: little endian
*byteorder == 0:  native order
*byteorder == 1:  big endian

If *byteorder is zero, and the first four bytes of the input data are a byte order mark (BOM), the decoder switches to this byte order and the BOM is not copied into the resulting Unicode string. If *byteorder is -1 or 1, any byte order mark is copied to the output.

After completion, *byteorder is set to the current byte order at the end of input data.

If byteorder is NULL, the codec starts in native order mode.

如果編解碼器引發例外則回傳 NULL。

PyObject *PyUnicode_DecodeUTF32Stateful(const char *str, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)

回傳值：新的參照。 為 穩定 ABI 的一部分.

If consumed is NULL, behave like PyUnicode_DecodeUTF32(). If consumed is not NULL, PyUnicode_DecodeUTF32Stateful() will not treat trailing incomplete UTF-32 byte sequences (such as a number of bytes not divisible by four) as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.

PyObject *PyUnicode_AsUTF32String(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a Python byte string using the UTF-32 encoding in native byte order. The string always starts with a BOM mark. Error handling is "strict". Return NULL if an exception was raised by the codec.

UTF-16 編解碼器

這些是 UTF-16 編解碼器的 API：

PyObject *PyUnicode_DecodeUTF16(const char *str, Py_ssize_t size, const char *errors, int *byteorder)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Decode size bytes from a UTF-16 encoded buffer string and return the corresponding Unicode object. errors (if non-NULL) defines the error handling. It defaults to "strict".

If byteorder is non-NULL, the decoder starts decoding using the given byte order:

*byteorder == -1: little endian
*byteorder == 0:  native order
*byteorder == 1:  big endian

If *byteorder is zero, and the first two bytes of the input data are a byte order mark (BOM), the decoder switches to this byte order and the BOM is not copied into the resulting Unicode string. If *byteorder is -1 or 1, any byte order mark is copied to the output (where it will result in either a \ufeff or a \ufffe character).

After completion, *byteorder is set to the current byte order at the end of input data.

If byteorder is NULL, the codec starts in native order mode.

如果編解碼器引發例外則回傳 NULL。

PyObject *PyUnicode_DecodeUTF16Stateful(const char *str, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)

回傳值：新的參照。 為 穩定 ABI 的一部分.

If consumed is NULL, behave like PyUnicode_DecodeUTF16(). If consumed is not NULL, PyUnicode_DecodeUTF16Stateful() will not treat trailing incomplete UTF-16 byte sequences (such as an odd number of bytes or a split surrogate pair) as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.

PyObject *PyUnicode_AsUTF16String(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a Python byte string using the UTF-16 encoding in native byte order. The string always starts with a BOM mark. Error handling is "strict". Return NULL if an exception was raised by the codec.

UTF-7 編解碼器

這些是 UTF-7 編解碼器的 API：

PyObject *PyUnicode_DecodeUTF7(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the UTF-7 encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_DecodeUTF7Stateful(const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)

回傳值：新的參照。 為 穩定 ABI 的一部分.

If consumed is NULL, behave like PyUnicode_DecodeUTF7(). If consumed is not NULL, trailing incomplete UTF-7 base-64 sections will not be treated as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.

Unicode-Escape Codecs

These are the "Unicode Escape" codec APIs:

PyObject *PyUnicode_DecodeUnicodeEscape(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the Unicode-Escape encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_AsUnicodeEscapeString(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object using Unicode-Escape and return the result as a bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

Raw-Unicode-Escape Codecs

These are the "Raw Unicode Escape" codec APIs:

PyObject *PyUnicode_DecodeRawUnicodeEscape(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the Raw-Unicode-Escape encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object using Raw-Unicode-Escape and return the result as a bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

Latin-1 編解碼器

These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256 Unicode ordinals and only these are accepted by the codecs during encoding.

PyObject *PyUnicode_DecodeLatin1(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the Latin-1 encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_AsLatin1String(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object using Latin-1 and return the result as Python bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

ASCII 編解碼器

These are the ASCII codec APIs. Only 7-bit ASCII data is accepted. All other codes generate errors.

PyObject *PyUnicode_DecodeASCII(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the ASCII encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_AsASCIIString(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object using ASCII and return the result as Python bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

Character Map Codecs

This codec is special in that it can be used to implement many different codecs (and this is in fact what was done to obtain most of the standard codecs included in the encodings package). The codec uses mappings to encode and decode characters. The mapping objects provided must support the __getitem__() mapping interface; dictionaries and sequences work well.

這些是對映編解碼器的 API：

PyObject *PyUnicode_DecodeCharmap(const char *str, Py_ssize_t length, PyObject *mapping, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a Unicode object by decoding size bytes of the encoded string str using the given mapping object. Return NULL if an exception was raised by the codec.

If mapping is NULL, Latin-1 decoding will be applied. Else mapping must map bytes ordinals (integers in the range from 0 to 255) to Unicode strings, integers (which are then interpreted as Unicode ordinals) or None. Unmapped data bytes -- ones which cause a LookupError, as well as ones which get mapped to None, 0xFFFE or '\ufffe', are treated as undefined mappings and cause an error.

PyObject *PyUnicode_AsCharmapString(PyObject *unicode, PyObject *mapping)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Encode a Unicode object using the given mapping object and return the result as a bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

The mapping object must map Unicode ordinal integers to bytes objects, integers in the range from 0 to 255 or None. Unmapped character ordinals (ones which cause a LookupError) as well as mapped to None are treated as "undefined mapping" and cause an error.

The following codec API is special in that maps Unicode to Unicode.

PyObject *PyUnicode_Translate(PyObject *unicode, PyObject *table, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Translate a string by applying a character mapping table to it and return the resulting Unicode object. Return NULL if an exception was raised by the codec.

The mapping table must map Unicode ordinal integers to Unicode ordinal integers or None (causing deletion of the character).

Mapping tables need only provide the __getitem__() interface; dictionaries and sequences work well. Unmapped character ordinals (ones which cause a LookupError) are left untouched and are copied as-is.

errors has the usual meaning for codecs. It may be NULL which indicates to use the default error handling.

Windows 的 MBCS 編解碼器

These are the MBCS codec APIs. They are currently only available on Windows and use the Win32 MBCS converters to implement the conversions. Note that MBCS (or DBCS) is a class of encodings, not just one. The target encoding is defined by the user settings on the machine running the codec.

PyObject *PyUnicode_DecodeMBCS(const char *str, Py_ssize_t size, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Create a Unicode object by decoding size bytes of the MBCS encoded string str. Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_DecodeMBCSStateful(const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)

回傳值：新的參照。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

If consumed is NULL, behave like PyUnicode_DecodeMBCS(). If consumed is not NULL, PyUnicode_DecodeMBCSStateful() will not decode trailing lead byte and the number of bytes that have been decoded will be stored in consumed.

PyObject *PyUnicode_DecodeCodePageStateful(int code_page, const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)

回傳值：新的參照。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Similar to PyUnicode_DecodeMBCSStateful(), except uses the code page specified by code_page.

PyObject *PyUnicode_AsMBCSString(PyObject *unicode)

回傳值：新的參照。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Encode a Unicode object using MBCS and return the result as Python bytes object. Error handling is "strict". Return NULL if an exception was raised by the codec.

PyObject *PyUnicode_EncodeCodePage(int code_page, PyObject *unicode, const char *errors)

回傳值：新的參照。 為 穩定 ABI 的一部分 on Windows 自 3.7 版本開始.

Encode the Unicode object using the specified code page and return a Python bytes object. Return NULL if an exception was raised by the codec. Use CP_ACP code page to get the MBCS encoder.

在 3.3 版被加入.

Methods and Slot Functions

The following APIs are capable of handling Unicode objects and strings on input (we refer to them as strings in the descriptions) and return Unicode objects or integers as appropriate.

如果發生例外，則回傳 NULL 或 -1。

PyObject *PyUnicode_Concat(PyObject *left, PyObject *right)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Concat two strings giving a new Unicode string.

PyObject *PyUnicode_Split(PyObject *unicode, PyObject *sep, Py_ssize_t maxsplit)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Split a string giving a list of Unicode strings. If sep is NULL, splitting will be done at all whitespace substrings. Otherwise, splits occur at the given separator. At most maxsplit splits will be done. If negative, no limit is set. Separators are not included in the resulting list.

於錯誤發生時回傳 NULL 並設定例外。

等價於 str.split()。

PyObject *PyUnicode_RSplit(PyObject *unicode, PyObject *sep, Py_ssize_t maxsplit)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Similar to PyUnicode_Split(), but splitting will be done beginning at the end of the string.

於錯誤發生時回傳 NULL 並設定例外。

等價於 str.rsplit()。

PyObject *PyUnicode_Splitlines(PyObject *unicode, int keepends)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Split a Unicode string at line breaks, returning a list of Unicode strings. CRLF is considered to be one line break. If keepends is 0, the Line break characters are not included in the resulting strings.

PyObject *PyUnicode_Partition(PyObject *unicode, PyObject *sep)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Split a Unicode string at the first occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing the string itself, followed by two empty strings.

sep 不得為空。

於錯誤發生時回傳 NULL 並設定例外。

等價於 str.partition()。

PyObject *PyUnicode_RPartition(PyObject *unicode, PyObject *sep)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Similar to PyUnicode_Partition(), but split a Unicode string at the last occurrence of sep. If the separator is not found, return a 3-tuple containing two empty strings, followed by the string itself.

sep 不得為空。

於錯誤發生時回傳 NULL 並設定例外。

等價於 str.rpartition()。

PyObject *PyUnicode_Join(PyObject *separator, PyObject *seq)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Join a sequence of strings using the given separator and return the resulting Unicode string.

Py_ssize_t PyUnicode_Tailmatch(PyObject *unicode, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)

為 穩定 ABI 的一部分.

Return 1 if substr matches unicode[start:end] at the given tail end (direction == -1 means to do a prefix match, direction == 1 a suffix match), 0 otherwise. Return -1 if an error occurred.

Py_ssize_t PyUnicode_Find(PyObject *unicode, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)

為 穩定 ABI 的一部分.

Return the first position of substr in unicode[start:end] using the given direction (direction == 1 means to do a forward search, direction == -1 a backward search). The return value is the index of the first match; a value of -1 indicates that no match was found, and -2 indicates that an error occurred and an exception has been set.

Py_ssize_t PyUnicode_FindChar(PyObject *unicode, Py_UCS4 ch, Py_ssize_t start, Py_ssize_t end, int direction)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return the first position of the character ch in unicode[start:end] using the given direction (direction == 1 means to do a forward search, direction == -1 a backward search). The return value is the index of the first match; a value of -1 indicates that no match was found, and -2 indicates that an error occurred and an exception has been set.

在 3.3 版被加入.

在 3.7 版的變更: start and end are now adjusted to behave like unicode[start:end].

Py_ssize_t PyUnicode_Count(PyObject *unicode, PyObject *substr, Py_ssize_t start, Py_ssize_t end)

為 穩定 ABI 的一部分.

Return the number of non-overlapping occurrences of substr in unicode[start:end]. Return -1 if an error occurred.

PyObject *PyUnicode_Replace(PyObject *unicode, PyObject *substr, PyObject *replstr, Py_ssize_t maxcount)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Replace at most maxcount occurrences of substr in unicode with replstr and return the resulting Unicode object. maxcount == -1 means replace all occurrences.

int PyUnicode_Compare(PyObject *left, PyObject *right)

為 穩定 ABI 的一部分.

Compare two strings and return -1, 0, 1 for less than, equal, and greater than, respectively.

This function returns -1 upon failure, so one should call PyErr_Occurred() to check for errors.

也參考

PyUnicode_Equal() 函式。

int PyUnicode_Equal(PyObject *a, PyObject *b)

為 穩定 ABI 的一部分 自 3.14 版本開始.

測試兩個字串是否相等：

如果 a 等於 b，則回傳 1。

如果 a 不等於 b，則回傳 0。

Set a TypeError exception and return -1 if a or b is not a str object.

The function always succeeds if a and b are str objects.

The function works for str subclasses, but does not honor custom __eq__() method.

也參考

PyUnicode_Compare() 函式。

在 3.14 版被加入.

int PyUnicode_EqualToUTF8AndSize(PyObject *unicode, const char *string, Py_ssize_t size)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Compare a Unicode object with a char buffer which is interpreted as being UTF-8 or ASCII encoded and return true (1) if they are equal, or false (0) otherwise. If the Unicode object contains surrogate code points (U+D800 - U+DFFF) or the C string is not valid UTF-8, false (0) is returned.

此函式不會引發例外。

在 3.13 版被加入.

int PyUnicode_EqualToUTF8(PyObject *unicode, const char *string)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Similar to PyUnicode_EqualToUTF8AndSize(), but compute string length using strlen(). If the Unicode object contains null characters, false (0) is returned.

在 3.13 版被加入.

int PyUnicode_CompareWithASCIIString(PyObject *unicode, const char *string)

為 穩定 ABI 的一部分.

Compare a Unicode object, unicode, with string and return -1, 0, 1 for less than, equal, and greater than, respectively. It is best to pass only ASCII-encoded strings, but the function interprets the input string as ISO-8859-1 if it contains non-ASCII characters.

此函式不會引發例外。

PyObject *PyUnicode_RichCompare(PyObject *left, PyObject *right, int op)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Rich compare two Unicode strings and return one of the following:

NULL in case an exception was raised

Py_True or Py_False for successful comparisons

Py_NotImplemented in case the type combination is unknown

Possible values for op are Py_GT, Py_GE, Py_EQ, Py_NE, Py_LT, and Py_LE.

PyObject *PyUnicode_Format(PyObject *format, PyObject *args)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new string object from format and args; this is analogous to format % args.

int PyUnicode_Contains(PyObject *unicode, PyObject *substr)

為 穩定 ABI 的一部分.

Check whether substr is contained in unicode and return true or false accordingly.

substr has to coerce to a one element Unicode string. -1 is returned if there was an error.

void PyUnicode_InternInPlace(PyObject **p_unicode)

為 穩定 ABI 的一部分.

Intern the argument *p_unicode in place. The argument must be the address of a pointer variable pointing to a Python Unicode string object. If there is an existing interned string that is the same as *p_unicode, it sets *p_unicode to it (releasing the reference to the old string object and creating a new strong reference to the interned string object), otherwise it leaves *p_unicode alone and interns it.

(Clarification: even though there is a lot of talk about references, think of this function as reference-neutral. You must own the object you pass in; after the call you no longer own the passed-in reference, but you newly own the result.)

This function never raises an exception. On error, it leaves its argument unchanged without interning it.

Instances of subclasses of str may not be interned, that is, PyUnicode_CheckExact(*p_unicode) must be true. If it is not, then -- as with any other error -- the argument is left unchanged.

Note that interned strings are not “immortal”. You must keep a reference to the result to benefit from interning.

PyObject *PyUnicode_InternFromString(const char *str)

回傳值：新的參照。 為 穩定 ABI 的一部分.

A combination of PyUnicode_FromString() and PyUnicode_InternInPlace(), meant for statically allocated strings.

Return a new ("owned") reference to either a new Unicode string object that has been interned, or an earlier interned string object with the same value.

Python may keep a reference to the result, or make it immortal, preventing it from being garbage-collected promptly. For interning an unbounded number of different strings, such as ones coming from user input, prefer calling PyUnicode_FromString() and PyUnicode_InternInPlace() directly.

unsigned int PyUnicode_CHECK_INTERNED(PyObject *str)

Return a non-zero value if str is interned, zero if not. The str argument must be a string; this is not checked. This function always succeeds.

CPython 實作細節： A non-zero return value may carry additional information about how the string is interned. The meaning of such non-zero values, as well as each specific string's intern-related details, may change between CPython versions.

PyUnicodeWriter

The PyUnicodeWriter API can be used to create a Python str object.

在 3.14 版被加入.

type PyUnicodeWriter

一個 Unicode 寫入器實例。

The instance must be destroyed by PyUnicodeWriter_Finish() on success, or PyUnicodeWriter_Discard() on error.

PyUnicodeWriter *PyUnicodeWriter_Create(Py_ssize_t length)

Create a Unicode writer instance.

length must be greater than or equal to 0.

If length is greater than 0, preallocate an internal buffer of length characters.

發生錯誤時，設定例外並回傳 NULL。

PyObject *PyUnicodeWriter_Finish(PyUnicodeWriter *writer)

Return the final Python str object and destroy the writer instance.

發生錯誤時，設定例外並回傳 NULL。

The writer instance is invalid after this call.

void PyUnicodeWriter_Discard(PyUnicodeWriter *writer)

Discard the internal Unicode buffer and destroy the writer instance.

If writer is NULL, no operation is performed.

The writer instance is invalid after this call.

int PyUnicodeWriter_WriteChar(PyUnicodeWriter *writer, Py_UCS4 ch)

Write the single Unicode character ch into writer.

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_WriteUTF8(PyUnicodeWriter *writer, const char *str, Py_ssize_t size)

Decode the string str from UTF-8 in strict mode and write the output into writer.

size is the string length in bytes. If size is equal to -1, call strlen(str) to get the string length.

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

另請參閱 PyUnicodeWriter_DecodeUTF8Stateful()。

int PyUnicodeWriter_WriteASCII(PyUnicodeWriter *writer, const char *str, Py_ssize_t size)

Write the ASCII string str into writer.

size is the string length in bytes. If size is equal to -1, call strlen(str) to get the string length.

str must only contain ASCII characters. The behavior is undefined if str contains non-ASCII characters.

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

在 3.14 版被加入.

int PyUnicodeWriter_WriteWideChar(PyUnicodeWriter *writer, const wchar_t *str, Py_ssize_t size)

Write the wide string str into writer.

size is a number of wide characters. If size is equal to -1, call wcslen(str) to get the string length.

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_WriteUCS4(PyUnicodeWriter *writer, Py_UCS4 *str, Py_ssize_t size)

Writer the UCS4 string str into writer.

size 是 UCS4 字元的數量。

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_WriteStr(PyUnicodeWriter *writer, PyObject *obj)

於 obj 上呼叫 PyObject_Str() 並將輸出寫入 writer。

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_WriteRepr(PyUnicodeWriter *writer, PyObject *obj)

於 obj 上呼叫 PyObject_Repr() 並將輸出寫入 writer。

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_WriteSubstring(PyUnicodeWriter *writer, PyObject *str, Py_ssize_t start, Py_ssize_t end)

Write the substring str[start:end] into writer.

str must be Python str object. start must be greater than or equal to 0, and less than or equal to end. end must be less than or equal to str length.

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_Format(PyUnicodeWriter *writer, const char *format, ...)

類似於 PyUnicode_FromFormat()，但是直接將輸出寫入 writer。

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

int PyUnicodeWriter_DecodeUTF8Stateful(PyUnicodeWriter *writer, const char *string, Py_ssize_t length, const char *errors, Py_ssize_t *consumed)

Decode the string str from UTF-8 with errors error handler and write the output into writer.

size is the string length in bytes. If size is equal to -1, call strlen(str) to get the string length.

errors is an error handler name, such as "replace". If errors is NULL, use the strict error handler.

If consumed is not NULL, set *consumed to the number of decoded bytes on success. If consumed is NULL, treat trailing incomplete UTF-8 byte sequences as an error.

成功時回傳 0，發生錯誤時設定例外、保持寫入器不變，並回傳 -1。

另請參閱 PyUnicodeWriter_WriteUTF8()。

已棄用的 API

以下 API 已棄用。

type Py_UNICODE

This is a typedef of wchar_t, which is a 16-bit type or 32-bit type depending on the platform. Please use wchar_t directly instead.

在 3.3 版的變更: In previous versions, this was a 16-bit type or a 32-bit type depending on whether you selected a "narrow" or "wide" Unicode version of Python at build time.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。.

int PyUnicode_READY(PyObject *unicode)

Do nothing and return 0. This API is kept only for backward compatibility, but there are no plans to remove it.

在 3.3 版被加入.

在 3.10 版之後被棄用: This API does nothing since Python 3.12. Previously, this needed to be called for each string created using the old API (PyUnicode_FromUnicode() or similar).

unsigned int PyUnicode_IS_READY(PyObject *unicode)

Do nothing and return 1. This API is kept only for backward compatibility, but there are no plans to remove it.

在 3.3 版被加入.

在 3.14 版之後被棄用: This API does nothing since Python 3.12. Previously, this could be called to check if PyUnicode_READY() is necessary.

Tuple（元組）物件

type PyTupleObject

此 PyObject 子型別代表 Python 元組物件

PyTypeObject PyTuple_Type

為 穩定 ABI 的一部分.

此 PyTypeObject 實例代表 Python 元組型別，與 Python 層中的 tuple 是同一物件

int PyTuple_Check(PyObject *p)

如果 p 為一元組物件或是元組型別的子型別實例時回傳 true。此函式總會執行成功

int PyTuple_CheckExact(PyObject *p)

如果 p 為一元組物件但不是元組型別的子型別實例時回傳 true。此函式總會執行成功

PyObject *PyTuple_New(Py_ssize_t len)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個長度為 len 的新元組物件，失敗會時回傳 NULL 並設定例外。

PyObject *PyTuple_Pack(Py_ssize_t n, ...)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個長度為 n 的新元組物件，失敗時會回傳 NULL 並設定例外。元組值被初始化為指向 Python 物件的接續 n 個 C 引數。PyTuple_Pack(2, a, b) 等價於 Py_BuildValue("(OO)", a, b)。

Py_ssize_t PyTuple_Size(PyObject *p)

為 穩定 ABI 的一部分.

拿取一個元組物件的指標，然後回傳此元組的大小。錯誤發生時，回傳 -1 並設定例外。

Py_ssize_t PyTuple_GET_SIZE(PyObject *p)

就像 PyTuple_Size() 但沒有錯誤檢查。

PyObject *PyTuple_GetItem(PyObject *p, Py_ssize_t pos)

回傳值：借用參照。 為 穩定 ABI 的一部分.

回傳 p 指向的元組中位置 pos 處的物件。如果 pos 為負數或超出範圍，回傳 NULL 並設定 IndexError 例外。

回傳的參照借自元組 p（也就是說：它僅在你持有 p 的參照時有效）。若要取得一個 strong reference，請使用 Py_NewRef(PyTuple_GetItem(...)) 或 PySequence_GetItem()。

PyObject *PyTuple_GET_ITEM(PyObject *p, Py_ssize_t pos)

回傳值：借用參照。

與 PyTuple_GetItem() 相似，但不檢查其引數。

PyObject *PyTuple_GetSlice(PyObject *p, Py_ssize_t low, Py_ssize_t high)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳由 p 指向的元組中介於 low 和 high 之間的切片或在錯誤時回傳 NULL 並設定例外。

這與 Python p[low:high] 運算式等價。但不支援從元組末端開始索引。

int PyTuple_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)

為 穩定 ABI 的一部分.

於 p 指向的元組 pos 位置處插入對物件 o 的參照。成功時回傳 0，如果 pos 超出邊界則回傳 -1，並設定 IndexError 例外。

備註

此函式 "竊取" 對 o 的參照，並丟棄對元組中受影響位置的項目的參照。

void PyTuple_SET_ITEM(PyObject *p, Py_ssize_t pos, PyObject *o)

與 PyTuple_SetItem() 相似，但不進行錯誤檢查，且應 只 用於填充全新的元組。

若 Python 以 debug mode 或 with assertions 建置，則會進行作為斷言（asserting）的邊界檢查。

備註

此函式 "竊取" 對 o 的參照，且與 PyTuple_SetItem() 不同的是，此函式並 不 丟棄任何被替代項目的參照；元組中 pos 位置的所有參照皆會被洩漏。

警告

此巨集應 僅 用於新建立的元組。在正被使用中的元組（或換句話說，參照計數大於 1 的元組）上使用此巨集可能會導致未定義行為。

int _PyTuple_Resize(PyObject **p, Py_ssize_t newsize)

可用於調整元組的大小。newsize 將是元組的新長度。由於元組 應該 是不可變的，因此僅當物件只有一個參照時才應使用此方法。如果程式碼的其他部分已經知道該元組，則 不要 使用此方法。最終元組總會變大或縮小。可以將其理解為銷毀舊元組並建立一個新元組，只是有著更高的效率。成功時回傳 0。用戶端程式碼絕不應假設 *p 的結果值與呼叫此函式之前的值相同。如果 *p 參照的物件被替換，則原始的 *p 將被銷毀。失敗時，回傳 -1，並將 *p 設定為 NULL，並引發 MemoryError 或 SystemError 例外。

結構序列物件

結構序列物件是 namedtuple() 物件在 C 語言中的等價，換言之，一個序列的元素也可以透過屬性存取。要建立結構序列，首先需要建立特定的結構序列型別。

PyTypeObject *PyStructSequence_NewType(PyStructSequence_Desc *desc)

回傳值：新的參照。 為 穩定 ABI 的一部分.

從 desc 中的資料建立一個新的結構序列型別，如下所述。可以使用 PyStructSequence_New() 以建立產生結構序列型別的實例。

失敗時回傳 NULL 並設定例外。

void PyStructSequence_InitType(PyTypeObject *type, PyStructSequence_Desc *desc)

從 desc 原地（in place）初始化結構序列型別 type。

int PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)

與 PyStructSequence_InitType() 相似，但運行成功時回傳 0，運行失敗時回傳 -1 並設定例外。

在 3.4 版被加入.

type PyStructSequence_Desc

為 穩定 ABI 的一部分 （包含所有成員）.

包含要建立的結構序列化型別的中介資訊（meta information）。

const char *name

型別的完整限定名稱（Fully qualified name）；以 UTF-8 編碼並以空字元結尾。名稱必須包含完整的模組名稱。

const char *doc

指向型別說明文件（docstring）的指標或使用 NULL 表示忽略。

PyStructSequence_Field *fields

指向一個以 NULL 結尾的陣列指標，其包含新型別的欄位名稱。

int n_in_sequence

Python 端可以看到欄位的數目（如果作為元組使用）。

type PyStructSequence_Field

為 穩定 ABI 的一部分 （包含所有成員）.

描述結構序列的一個欄位。由於結構序列以元組作為原型，所有欄位的型別均為 PyObject*。PyStructSequence_Desc 在 fields 陣列中的索引決定了描述的是結構序列的哪個欄位。

const char *name

欄位名稱，或 NULL 表示命名欄位串列結束，設定為 PyStructSequence_UnnamedField 表示該欄位不命名。

const char *doc

欄位說明字串或為 NULL 表示忽略。

const char *const PyStructSequence_UnnamedField

為 穩定 ABI 的一部分 自 3.11 版本開始.

給定欄位名稱一個特別值，表示該欄位不命名。

在 3.9 版的變更: 型別原本是 char *，現已被修改。

PyObject *PyStructSequence_New(PyTypeObject *type)

回傳值：新的參照。 為 穩定 ABI 的一部分.

建立 type 的實例，必須以 PyStructSequence_NewType() 建立。

失敗時回傳 NULL 並設定例外。

PyObject *PyStructSequence_GetItem(PyObject *p, Py_ssize_t pos)

回傳值：借用參照。 為 穩定 ABI 的一部分.

回傳結構序列中由 p 指向 pos 處的物件。

若 Python 以 debug mode 或 with assertions 建置，則會進行作為斷言（asserting）的邊界檢查。

PyObject *PyStructSequence_GET_ITEM(PyObject *p, Py_ssize_t pos)

回傳值：借用參照。

PyStructSequence_GetItem() 的別名。

在 3.13 版的變更: 現在是被實作為 PyStructSequence_GetItem() 的一個別名。

void PyStructSequence_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)

為 穩定 ABI 的一部分.

將結構序列 p 中索引 pos 處的欄位值設為 o。與 PyTuple_SET_ITEM() 類似，此函式僅套用於填充全新實例。

若 Python 以 debug mode 或 with assertions 建置，則會進行作為斷言（asserting）的邊界檢查。

備註

此函式 "竊取" o 的參照。

void PyStructSequence_SET_ITEM(PyObject *p, Py_ssize_t *pos, PyObject *o)

PyStructSequence_SetItem() 的別名。

在 3.13 版的變更: 現在是被實作為 PyStructSequence_SetItem() 的一個別名。

List（串列）物件

type PyListObject

PyObject 的這個子型別表示 Python 的 list（串列）物件。

PyTypeObject PyList_Type

為 穩定 ABI 的一部分.

此 PyTypeObject 實例表示 Python 的 list 型別。這與 Python 層中的 list 是同一個物件。

int PyList_Check(PyObject *p)

如果 p 是一個 list 物件或者是 list 型別之子型別的實例，就回傳 true。這個函式永遠會成功執行。

int PyList_CheckExact(PyObject *p)

如果 p 是一個 list 物件但不是 list 型別的子型別的實例，就回傳 true。這個函式永遠會成功執行。

PyObject *PyList_New(Py_ssize_t len)

回傳值：新的參照。 為 穩定 ABI 的一部分.

成功時回傳長度為 len 的新串列，失敗時回傳 NULL。

備註

如果 len 大於零，則回傳的串列物件之項目將被設定為 NULL。因此，在使用 PyList_SetItem() 或 PyList_SET_ITEM() 來將所有項目設定為一個真實物件前，你無法使用像是 PySequence_SetItem() 的抽象 API 函式，也不能將物件暴露 (expose) 給 Python 程式碼。以下 API 在串列完全初始化之前是安全的：PyList_SetItem() 和 PyList_SET_ITEM()。

Py_ssize_t PyList_Size(PyObject *list)

為 穩定 ABI 的一部分.

回傳 list 串列物件的長度；這相當於串列物件的 len(list)。

Py_ssize_t PyList_GET_SIZE(PyObject *list)

與 PyList_Size() 類似，但沒有錯誤檢查。

PyObject *PyList_GetItemRef(PyObject *list, Py_ssize_t index)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.13 版本開始.

回傳 list 指向的串列中位於 index 位置的物件。該位置不可為負數；並不支援從串列尾末開始索引。如果 index 超出邊界範圍 (<0 or >=len(list)) 則回傳 NULL 並設定 IndexError 例外。

在 3.13 版被加入.

PyObject *PyList_GetItem(PyObject *list, Py_ssize_t index)

回傳值：借用參照。 為 穩定 ABI 的一部分.

與 PyList_GetItemRef() 類似，但回傳一個 borrowed reference 而非一個 strong reference。

PyObject *PyList_GET_ITEM(PyObject *list, Py_ssize_t i)

回傳值：借用參照。

與 PyList_GetItem() 類似，但沒有錯誤檢查。

int PyList_SetItem(PyObject *list, Py_ssize_t index, PyObject *item)

為 穩定 ABI 的一部分.

將串列中索引 index 處的項目設定為 item。成功時回傳 0。如果 index 超出邊界範圍則回傳 -1 並設定一個 IndexError 例外。

備註

此函式「竊取」對 item 的參照，並丟棄對串列中受影響位置上已存在項目的參照。

void PyList_SET_ITEM(PyObject *list, Py_ssize_t i, PyObject *o)

PyList_SetItem() 的巨集形式，沒有錯誤檢查。這通常僅用於填充沒有已存在內容的新串列。

如果 Python 是以偵錯模式或 with assertions 建置，則會進行作為斷言（asserting）的邊界檢查。

備註

該巨集「竊取」對 item 的參照，並且與 PyList_SetItem() 不同的是，它不會丟棄對任意被替換項目的參照；list 中位置 i 的任何參照都將被洩漏 (leak)。

int PyList_Insert(PyObject *list, Py_ssize_t index, PyObject *item)

為 穩定 ABI 的一部分.

將項目 item 插入串列 list 中索引 index 的位置之前。如果成功則回傳 0；如果失敗則回傳 -1 並設定例外。類似於 list.insert(index, item)。

int PyList_Append(PyObject *list, PyObject *item)

為 穩定 ABI 的一部分.

將物件 item 附加到串列 list 的最後面。如果成功則回傳 0；如果不成功，則回傳 -1 並設定例外。類似於 list.append(item)。

PyObject *PyList_GetSlice(PyObject *list, Py_ssize_t low, Py_ssize_t high)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳 list 中的物件串列，其中包含 low 和 high 之間的物件。如果沒有成功則回傳 NULL 並設定例外。類似於 list[low:high]。不支援從串列尾末開始索引。

int PyList_SetSlice(PyObject *list, Py_ssize_t low, Py_ssize_t high, PyObject *itemlist)

為 穩定 ABI 的一部分.

將 low 和 high 之間的 list 切片設定為 itemlist 的內容。類似於 list[low:high] = itemlist。itemlist 可能為 NULL，表示分配一個空串列（切片刪除）。成功時回傳 0，失敗時則回傳 -1。不支援從串列尾末開始索引。

int PyList_Extend(PyObject *list, PyObject *iterable)

以 iterable 中的內容擴展 list。這與 PyList_SetSlice(list, PY_SSIZE_T_MAX, PY_SSIZE_T_MAX, iterable) 相同，類似於 list.extend(iterable) 或 list += iterable。

引發一個例外並回傳 -1 如果 list 不是一個 list 物件。如果成功回傳 0。

在 3.13 版被加入.

int PyList_Clear(PyObject *list)

移除 list 中的所有項目。這與 PyList_SetSlice(list, 0, PY_SSIZE_T_MAX, NULL) 相同，類似於 list.clear() 或 del list[:]。

引發一個例外並回傳 -1 如果 list 不是一個 list 物件。如果成功回傳 0。

在 3.13 版被加入.

int PyList_Sort(PyObject *list)

為 穩定 ABI 的一部分.

對 list 的項目進行原地 (in place) 排序。成功時回傳 0，失敗時回傳 -1。這相當於 list.sort()。

int PyList_Reverse(PyObject *list)

為 穩定 ABI 的一部分.

原地反轉 list 的項目。成功時回傳 0，失敗時回傳 -1。這相當於 list.reverse()。

PyObject *PyList_AsTuple(PyObject *list)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個新的 tuple（元組）物件，其中包含 list 的內容；相當於 tuple(list)。

字典物件

type PyDictObject

PyObject 子型別代表一個 Python 字典物件。

PyTypeObject PyDict_Type

為 穩定 ABI 的一部分.

PyTypeObject 實例代表一個 Python 字典型別。此與 Python 層中的 dict 為同一個物件。

int PyDict_Check(PyObject *p)

若 p 是一個字典物件或字典的子型別實例則會回傳 true。此函式每次都會執行成功。

int PyDict_CheckExact(PyObject *p)

若 p 是一個字典物件但並不是一個字典子型別的實例，則回傳 true。此函式每次都會執行成功。

PyObject *PyDict_New()

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個新的空字典，或在失敗時回傳 NULL。

PyObject *PyDictProxy_New(PyObject *mapping)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a types.MappingProxyType object for a mapping which enforces read-only behavior. This is normally used to create a view to prevent modification of the dictionary for non-dynamic class types.

PyTypeObject PyDictProxy_Type

為 穩定 ABI 的一部分.

The type object for mapping proxy objects created by PyDictProxy_New() and for the read-only __dict__ attribute of many built-in types. A PyDictProxy_Type instance provides a dynamic, read-only view of an underlying dictionary: changes to the underlying dictionary are reflected in the proxy, but the proxy itself does not support mutation operations. This corresponds to types.MappingProxyType in Python.

void PyDict_Clear(PyObject *p)

為 穩定 ABI 的一部分.

清空現有字典中的所有鍵值對。

int PyDict_Contains(PyObject *p, PyObject *key)

為 穩定 ABI 的一部分.

Determine if dictionary p contains key. If an item in p matches key, return 1, otherwise return 0. On error, return -1. This is equivalent to the Python expression key in p.

int PyDict_ContainsString(PyObject *p, const char *key)

This is the same as PyDict_Contains(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

在 3.13 版被加入.

PyObject *PyDict_Copy(PyObject *p)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個新的字典，包含與 p 相同的鍵值對。

int PyDict_SetItem(PyObject *p, PyObject *key, PyObject *val)

為 穩定 ABI 的一部分.

Insert val into the dictionary p with a key of key. key must be hashable; if it isn't, TypeError will be raised. Return 0 on success or -1 on failure. This function does not steal a reference to val.

int PyDict_SetItemString(PyObject *p, const char *key, PyObject *val)

為 穩定 ABI 的一部分.

This is the same as PyDict_SetItem(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

int PyDict_DelItem(PyObject *p, PyObject *key)

為 穩定 ABI 的一部分.

Remove the entry in dictionary p with key key. key must be hashable; if it isn't, TypeError is raised. If key is not in the dictionary, KeyError is raised. Return 0 on success or -1 on failure.

int PyDict_DelItemString(PyObject *p, const char *key)

為 穩定 ABI 的一部分.

This is the same as PyDict_DelItem(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

int PyDict_GetItemRef(PyObject *p, PyObject *key, PyObject **result)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Return a new strong reference to the object from dictionary p which has a key key:

If the key is present, set *result to a new strong reference to the value and return 1.

如果鍵不存在，將 *result 設為 NULL 並回傳 0。

錯誤發生時，引發一個例外並回傳 -1。

在 3.13 版被加入.

另見 PyObject_GetItem() 函式。

PyObject *PyDict_GetItem(PyObject *p, PyObject *key)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Return a borrowed reference to the object from dictionary p which has a key key. Return NULL if the key key is missing without setting an exception.

備註

Exceptions that occur while this calls __hash__() and __eq__() methods are silently ignored. Prefer the PyDict_GetItemWithError() function instead.

在 3.10 版的變更: Calling this API without an attached thread state had been allowed for historical reason. It is no longer allowed.

PyObject *PyDict_GetItemWithError(PyObject *p, PyObject *key)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Variant of PyDict_GetItem() that does not suppress exceptions. Return NULL with an exception set if an exception occurred. Return NULL without an exception set if the key wasn't present.

PyObject *PyDict_GetItemString(PyObject *p, const char *key)

回傳值：借用參照。 為 穩定 ABI 的一部分.

This is the same as PyDict_GetItem(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

備註

Exceptions that occur while this calls __hash__() and __eq__() methods or while creating the temporary str object are silently ignored. Prefer using the PyDict_GetItemWithError() function with your own PyUnicode_FromString() key instead.

int PyDict_GetItemStringRef(PyObject *p, const char *key, PyObject **result)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Similar to PyDict_GetItemRef(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

在 3.13 版被加入.

PyObject *PyDict_SetDefault(PyObject *p, PyObject *key, PyObject *defaultobj)

回傳值：借用參照。

This is the same as the Python-level dict.setdefault(). If present, it returns the value corresponding to key from the dictionary p. If the key is not in the dict, it is inserted with value defaultobj and defaultobj is returned. This function evaluates the hash function of key only once, instead of evaluating it independently for the lookup and the insertion.

在 3.4 版被加入.

int PyDict_SetDefaultRef(PyObject *p, PyObject *key, PyObject *default_value, PyObject **result)

Inserts default_value into the dictionary p with a key of key if the key is not already present in the dictionary. If result is not NULL, then *result is set to a strong reference to either default_value, if the key was not present, or the existing value, if key was already present in the dictionary. Returns 1 if the key was present and default_value was not inserted, or 0 if the key was not present and default_value was inserted. On failure, returns -1, sets an exception, and sets *result to NULL.

For clarity: if you have a strong reference to default_value before calling this function, then after it returns, you hold a strong reference to both default_value and *result (if it's not NULL). These may refer to the same object: in that case you hold two separate references to it.

在 3.13 版被加入.

int PyDict_Pop(PyObject *p, PyObject *key, PyObject **result)

Remove key from dictionary p and optionally return the removed value. Do not raise KeyError if the key is missing.

If the key is present, set *result to a new reference to the removed value if result is not NULL, and return 1.

If the key is missing, set *result to NULL if result is not NULL, and return 0.

錯誤發生時，引發一個例外並回傳 -1。

Similar to dict.pop(), but without the default value and not raising KeyError if the key is missing.

在 3.13 版被加入.

int PyDict_PopString(PyObject *p, const char *key, PyObject **result)

Similar to PyDict_Pop(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

在 3.13 版被加入.

PyObject *PyDict_Items(PyObject *p)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個包含字典中所有項目的 PyListObject。

PyObject *PyDict_Keys(PyObject *p)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個包含字典中所有鍵的 PyListObject。

PyObject *PyDict_Values(PyObject *p)

回傳值：新的參照。 為 穩定 ABI 的一部分.

回傳一個包含字典 p 中所有值的 PyListObject。

Py_ssize_t PyDict_Size(PyObject *p)

為 穩定 ABI 的一部分.

回傳字典中項目的數量。此與於字典呼叫 len(p) 等效。

Py_ssize_t PyDict_GET_SIZE(PyObject *p)

和 PyDict_Size() 類似，但沒有錯誤檢查。

int PyDict_Next(PyObject *p, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue)

為 穩定 ABI 的一部分.

Iterate over all key-value pairs in the dictionary p. The Py_ssize_t referred to by ppos must be initialized to 0 prior to the first call to this function to start the iteration; the function returns true for each pair in the dictionary, and false once all pairs have been reported. The parameters pkey and pvalue should either point to PyObject* variables that will be filled in with each key and value, respectively, or may be NULL. Any references returned through them are borrowed. ppos should not be altered during iteration. Its value represents offsets within the internal dictionary structure, and since the structure is sparse, the offsets are not consecutive.

舉例來說：

PyObject *key, *value;
Py_ssize_t pos = 0;

while (PyDict_Next(self->dict, &pos, &key, &value)) {
    /* 用值做一些有趣的事情... */
    ...
}

The dictionary p should not be mutated during iteration. It is safe to modify the values of the keys as you iterate over the dictionary, but only so long as the set of keys does not change. For example:

PyObject *key, *value;
Py_ssize_t pos = 0;

while (PyDict_Next(self->dict, &pos, &key, &value)) {
    long i = PyLong_AsLong(value);
    if (i == -1 && PyErr_Occurred()) {
        return -1;
    }
    PyObject *o = PyLong_FromLong(i + 1);
    if (o == NULL)
        return -1;
    if (PyDict_SetItem(self->dict, key, o) < 0) {
        Py_DECREF(o);
        return -1;
    }
    Py_DECREF(o);
}

The function is not thread-safe in the free-threaded build without external synchronization. You can use Py_BEGIN_CRITICAL_SECTION to lock the dictionary while iterating over it:

Py_BEGIN_CRITICAL_SECTION(self->dict);
while (PyDict_Next(self->dict, &pos, &key, &value)) {
    ...
}
Py_END_CRITICAL_SECTION();

備註

On the free-threaded build, this function can be used safely inside a critical section. However, the references returned for pkey and pvalue are borrowed and are only valid while the critical section is held. If you need to use these objects outside the critical section or when the critical section can be suspended, create a strong reference (for example, using Py_NewRef()).

int PyDict_Merge(PyObject *a, PyObject *b, int override)

為 穩定 ABI 的一部分.

Iterate over mapping object b adding key-value pairs to dictionary a. b may be a dictionary, or any object supporting PyMapping_Keys() and PyObject_GetItem(). If override is true, existing pairs in a will be replaced if a matching key is found in b, otherwise pairs will only be added if there is not a matching key in a. Return 0 on success or -1 if an exception was raised.

int PyDict_Update(PyObject *a, PyObject *b)

為 穩定 ABI 的一部分.

This is the same as PyDict_Merge(a, b, 1) in C, and is similar to a.update(b) in Python except that PyDict_Update() doesn't fall back to the iterating over a sequence of key value pairs if the second argument has no "keys" attribute. Return 0 on success or -1 if an exception was raised.

int PyDict_MergeFromSeq2(PyObject *a, PyObject *seq2, int override)

為 穩定 ABI 的一部分.

Update or merge into dictionary a, from the key-value pairs in seq2. seq2 must be an iterable object producing iterable objects of length 2, viewed as key-value pairs. In case of duplicate keys, the last wins if override is true, else the first wins. Return 0 on success or -1 if an exception was raised. Equivalent Python (except for the return value):

def PyDict_MergeFromSeq2(a, seq2, override):
    for key, value in seq2:
        if override or key not in a:
            a[key] = value

int PyDict_AddWatcher(PyDict_WatchCallback callback)

Register callback as a dictionary watcher. Return a non-negative integer id which must be passed to future calls to PyDict_Watch(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

在 3.12 版被加入.

int PyDict_ClearWatcher(int watcher_id)

Clear watcher identified by watcher_id previously returned from PyDict_AddWatcher(). Return 0 on success, -1 on error (e.g. if the given watcher_id was never registered.)

在 3.12 版被加入.

int PyDict_Watch(int watcher_id, PyObject *dict)

Mark dictionary dict as watched. The callback granted watcher_id by PyDict_AddWatcher() will be called when dict is modified or deallocated. Return 0 on success or -1 on error.

在 3.12 版被加入.

int PyDict_Unwatch(int watcher_id, PyObject *dict)

Mark dictionary dict as no longer watched. The callback granted watcher_id by PyDict_AddWatcher() will no longer be called when dict is modified or deallocated. The dict must previously have been watched by this watcher. Return 0 on success or -1 on error.

在 3.12 版被加入.

type PyDict_WatchEvent

Enumeration of possible dictionary watcher events: PyDict_EVENT_ADDED, PyDict_EVENT_MODIFIED, PyDict_EVENT_DELETED, PyDict_EVENT_CLONED, PyDict_EVENT_CLEARED, or PyDict_EVENT_DEALLOCATED.

在 3.12 版被加入.

typedef int (*PyDict_WatchCallback)(PyDict_WatchEvent event, PyObject *dict, PyObject *key, PyObject *new_value)

Type of a dict watcher callback function.

If event is PyDict_EVENT_CLEARED or PyDict_EVENT_DEALLOCATED, both key and new_value will be NULL. If event is PyDict_EVENT_ADDED or PyDict_EVENT_MODIFIED, new_value will be the new value for key. If event is PyDict_EVENT_DELETED, key is being deleted from the dictionary and new_value will be NULL.

PyDict_EVENT_CLONED occurs when dict was previously empty and another dict is merged into it. To maintain efficiency of this operation, per-key PyDict_EVENT_ADDED events are not issued in this case; instead a single PyDict_EVENT_CLONED is issued, and key will be the source dictionary.

The callback may inspect but must not modify dict; doing so could have unpredictable effects, including infinite recursion. Do not trigger Python code execution in the callback, as it could modify the dict as a side effect.

If event is PyDict_EVENT_DEALLOCATED, taking a new reference in the callback to the about-to-be-destroyed dictionary will resurrect it and prevent it from being freed at this time. When the resurrected object is destroyed later, any watcher callbacks active at that time will be called again.

Callbacks occur before the notified modification to dict takes place, so the prior state of dict can be inspected.

If the callback sets an exception, it must return -1; this exception will be printed as an unraisable exception using PyErr_WriteUnraisable(). Otherwise it should return 0.

There may already be a pending exception set on entry to the callback. In this case, the callback should return 0 with the same exception still set. This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first, and restores it before returning.

在 3.12 版被加入.

字典視圖物件

int PyDictViewSet_Check(PyObject *op)

若 op 是一個字典中集合的視圖則會回傳 true。這目前等同於 PyDictKeys_Check(op) || PyDictItems_Check(op)。此函式每次都會執行成功。

PyTypeObject PyDictKeys_Type

為 穩定 ABI 的一部分.

Type object for a view of dictionary keys. In Python, this is the type of the object returned by dict.keys().

int PyDictKeys_Check(PyObject *op)

若 op 是一個字典鍵視圖的實例則會回傳 true。此函式每次都會執行成功。

PyTypeObject PyDictValues_Type

為 穩定 ABI 的一部分.

Type object for a view of dictionary values. In Python, this is the type of the object returned by dict.values().

int PyDictValues_Check(PyObject *op)

若 op 是一個字典值視圖的實例則會回傳 true。此函式每次都會執行成功。

PyTypeObject PyDictItems_Type

為 穩定 ABI 的一部分.

Type object for a view of dictionary items. In Python, this is the type of the object returned by dict.items().

int PyDictItems_Check(PyObject *op)

若 op 是一個字典項目視圖的實例則會回傳 true。此函式每次都會執行成功。

有序字典

Python's C API provides interface for collections.OrderedDict from C. Since Python 3.7, dictionaries are ordered by default, so there is usually little need for these functions; prefer PyDict* where possible.

PyTypeObject PyODict_Type

有序字典的型別物件。此與 Python 層中的 collections.OrderedDict 為同一個物件。

int PyODict_Check(PyObject *od)

若 od 是一個有序字典物件或 OrderedDict 的子型別實例則會回傳 true。此函式每次都會執行成功。

int PyODict_CheckExact(PyObject *od)

若 od 是一個有序字典物件但並不是一個 OrderedDict 子型別的實例，則回傳 true。此函式每次都會執行成功。

PyTypeObject PyODictKeys_Type

Analogous to PyDictKeys_Type for ordered dictionaries.

PyTypeObject PyODictValues_Type

Analogous to PyDictValues_Type for ordered dictionaries.

PyTypeObject PyODictItems_Type

Analogous to PyDictItems_Type for ordered dictionaries.

PyObject *PyODict_New(void)

回傳一個新的空有序字典，或在失敗時回傳 NULL。

這和 PyDict_New() 類似。

int PyODict_SetItem(PyObject *od, PyObject *key, PyObject *value)

Insert value into the ordered dictionary od with a key of key. Return 0 on success or -1 with an exception set on failure.

這和 PyDict_SetItem() 類似。

int PyODict_DelItem(PyObject *od, PyObject *key)

Remove the entry in the ordered dictionary od with key key. Return 0 on success or -1 with an exception set on failure.

這和 PyDict_DelItem() 類似。

These are soft deprecated aliases to PyDict APIs:

PyODict

PyDict

PyODict_GetItem(od, key)

PyDict_GetItem()

PyODict_GetItemWithError(od, key)

PyDict_GetItemWithError()

PyODict_GetItemString(od, key)

PyDict_GetItemString()

PyODict_Contains(od, key)

PyDict_Contains()

PyODict_Size(od)

PyDict_Size()

PyODict_SIZE(od)

PyDict_GET_SIZE()

集合物件

This section details the public API for set and frozenset objects. Any functionality not listed below is best accessed using either the abstract object protocol (including PyObject_CallMethod(), PyObject_RichCompareBool(), PyObject_Hash(), PyObject_Repr(), PyObject_IsTrue(), PyObject_Print(), and PyObject_GetIter()) or the abstract number protocol (including PyNumber_And(), PyNumber_Subtract(), PyNumber_Or(), PyNumber_Xor(), PyNumber_InPlaceAnd(), PyNumber_InPlaceSubtract(), PyNumber_InPlaceOr(), and PyNumber_InPlaceXor()).

type PySetObject

This subtype of PyObject is used to hold the internal data for both set and frozenset objects. It is like a PyDictObject in that it is a fixed size for small sets (much like tuple storage) and will point to a separate, variable sized block of memory for medium and large sized sets (much like list storage). None of the fields of this structure should be considered public and all are subject to change. All access should be done through the documented API rather than by manipulating the values in the structure.

PyTypeObject PySet_Type

為 穩定 ABI 的一部分.

This is an instance of PyTypeObject representing the Python set type.

PyTypeObject PyFrozenSet_Type

為 穩定 ABI 的一部分.

This is an instance of PyTypeObject representing the Python frozenset type.

The following type check macros work on pointers to any Python object. Likewise, the constructor functions work with any iterable Python object.

int PySet_Check(PyObject *p)

如果 p 是 set 物件或是子類別的實例，則回傳 true。此函式總會成功執行。

int PyFrozenSet_Check(PyObject *p)

如果 p 是 frozenset 物件或是子類別的實例，則回傳 true。此函式總會成功執行。

int PyAnySet_Check(PyObject *p)

如果 p 是 set 物件、frozenset 物件，或是子類別的實例，則回傳 true。此函式總會成功執行。

int PySet_CheckExact(PyObject *p)

如果 p 是 set 物件但不是子類別的實例，則回傳 true。此函式總會成功執行。

在 3.10 版被加入.

int PyAnySet_CheckExact(PyObject *p)

如果 p 是 set 物件或 frozenset 物件但不是子類別的實例，則回傳 true。此函式總會成功執行。

int PyFrozenSet_CheckExact(PyObject *p)

如果 p 是 frozenset 物件但不是子類別的實例，則回傳 true。此函式總會成功執行。

PyObject *PySet_New(PyObject *iterable)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new set containing objects returned by the iterable. The iterable may be NULL to create a new empty set. Return the new set on success or NULL on failure. Raise TypeError if iterable is not actually iterable. The constructor is also useful for copying a set (c=set(s)).

PyObject *PyFrozenSet_New(PyObject *iterable)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new frozenset containing objects returned by the iterable. The iterable may be NULL to create a new empty frozenset. Return the new set on success or NULL on failure. Raise TypeError if iterable is not actually iterable.

The following functions and macros are available for instances of set or frozenset or instances of their subtypes.

Py_ssize_t PySet_Size(PyObject *anyset)

為 穩定 ABI 的一部分.

Return the length of a set or frozenset object. Equivalent to len(anyset). Raises a SystemError if anyset is not a set, frozenset, or an instance of a subtype.

Py_ssize_t PySet_GET_SIZE(PyObject *anyset)

Macro form of PySet_Size() without error checking.

int PySet_Contains(PyObject *anyset, PyObject *key)

為 穩定 ABI 的一部分.

Return 1 if found, 0 if not found, and -1 if an error is encountered. Unlike the Python __contains__() method, this function does not automatically convert unhashable sets into temporary frozensets. Raise a TypeError if the key is unhashable. Raise SystemError if anyset is not a set, frozenset, or an instance of a subtype.

int PySet_Add(PyObject *set, PyObject *key)

為 穩定 ABI 的一部分.

Add key to a set instance. Also works with frozenset instances (like PyTuple_SetItem() it can be used to fill in the values of brand new frozensets before they are exposed to other code). Return 0 on success or -1 on failure. Raise a TypeError if the key is unhashable. Raise a MemoryError if there is no room to grow. Raise a SystemError if set is not an instance of set or its subtype.

The following functions are available for instances of set or its subtypes but not for instances of frozenset or its subtypes.

int PySet_Discard(PyObject *set, PyObject *key)

為 穩定 ABI 的一部分.

Return 1 if found and removed, 0 if not found (no action taken), and -1 if an error is encountered. Does not raise KeyError for missing keys. Raise a TypeError if the key is unhashable. Unlike the Python discard() method, this function does not automatically convert unhashable sets into temporary frozensets. Raise SystemError if set is not an instance of set or its subtype.

PyObject *PySet_Pop(PyObject *set)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new reference to an arbitrary object in the set, and removes the object from the set. Return NULL on failure. Raise KeyError if the set is empty. Raise a SystemError if set is not an instance of set or its subtype.

int PySet_Clear(PyObject *set)

為 穩定 ABI 的一部分.

Empty an existing set of all elements. Return 0 on success. Return -1 and raise SystemError if set is not an instance of set or its subtype.

已棄用的 API

PySet_MINSIZE

一個被軟性棄用的常數，代表 PySetObject 實例內部預分配表格的大小。

這僅為完整性而記錄於文件，且因為無法保證特定版本的 CPython 會使用具有固定大小的預分配表格。在不處理不穩定集合內部結構的程式碼中，PySet_MINSIZE 可以替換為像 8 這樣的小常數。

如果要查詢集合的大小，請使用 PySet_Size()。

函式物件 (Function Objects)

這有一些特用於 Python 函式的函式。

type PyFunctionObject

用於函式的 C 結構。

PyTypeObject PyFunction_Type

這是個 PyTypeObject 的實例，且代表了 Python 函式型別，Python 程式設計者可透過 types.FunctionType 使用它。

int PyFunction_Check(PyObject *o)

如果 o 是個函式物件（擁有 PyFunction_Type 的型別）則回傳 true。參數必須不為 NULL。此函式必能成功執行。

PyObject *PyFunction_New(PyObject *code, PyObject *globals)

回傳值：新的參照。

回傳一個與程式碼物件 code 相關聯的函式物件。globals 必須是一個帶有函式能夠存取的全域變數的字典。

函式的文件字串 (docstring) 和名稱是從程式碼物件所取得，__module__ 是自 globals 所取得。引數預設值、標註 (annotation) 和閉包 (closure) 被設為 NULL，__qualname__ 被設為和程式碼物件 co_qualname 欄位相同的值。

PyObject *PyFunction_NewWithQualName(PyObject *code, PyObject *globals, PyObject *qualname)

回傳值：新的參照。

和 PyFunction_New() 相似，但也允許函式物件 __qualname__ 屬性的設定，qualname 應為一個 unicode 物件或是 NULL；如為 NULL，__qualname__ 屬性會被設為與程式碼物件 co_qualname 欄位相同的值。

在 3.3 版被加入.

PyObject *PyFunction_GetCode(PyObject *op)

回傳值：借用參照。

回傳與程式碼物件相關的函式物件 op。

PyObject *PyFunction_GetGlobals(PyObject *op)

回傳值：借用參照。

回傳與全域函式字典相關的函式物件 op。

PyObject *PyFunction_GetModule(PyObject *op)

回傳值：借用參照。

回傳一個函式物件 op 之 __module__ 屬性的 borrowed reference，它可以是 NULL。

這通常是個包含模組名稱的字串，但可以被 Python 程式設為任何其他物件。

PyObject *PyFunction_GetDefaults(PyObject *op)

回傳值：借用參照。

回傳函式物件 op 的引數預設值，這可以是一個含有多個引數的 tuple（元組）或 NULL。

int PyFunction_SetDefaults(PyObject *op, PyObject *defaults)

設定函式物件 op 的引數預設值。defaults 必須是 Py_None 或一個 tuple。

引發 SystemError 且在失敗時回傳 -1。

void PyFunction_SetVectorcall(PyFunctionObject *func, vectorcallfunc vectorcall)

為一個給定的函式物件 func 設定 vectorcall 欄位。

警告：使用此 API 的擴充套件必須保留未更改（預設）vectorcall 函式的行為！

在 3.12 版被加入.

PyObject *PyFunction_GetKwDefaults(PyObject *op)

回傳值：借用參照。

回傳函式物件 op 的僅限關鍵字引數預設值，這可以是一個含有多個引數的字典或 NULL。

int PyFunction_SetKwDefaults(PyObject *op, PyObject *defaults)

設定函式物件 op 的僅限關鍵字引數預設值。defaults 必須是僅限關鍵字引數的字典或 Py_None。

此函式在成功時回傳 0，在失敗時回傳 -1 且設定一個例外。

PyObject *PyFunction_GetClosure(PyObject *op)

回傳值：借用參照。

回傳與函式物件 op 相關聯的閉包，這可以是個 NULL 或是一個包含 cell 物件的 tuple。

int PyFunction_SetClosure(PyObject *op, PyObject *closure)

設定與函式物件 op 相關聯的閉包，closure 必須是 Py_None 或是一個包含 cell 物件的 tuple。

引發 SystemError 且在失敗時回傳 -1。

PyObject *PyFunction_GetAnnotations(PyObject *op)

回傳值：借用參照。

回傳函式物件 op 的標註，這可以是一個可變動的 (mutable) 字典或 NULL。

int PyFunction_SetAnnotations(PyObject *op, PyObject *annotations)

設定函式物件 op 的標註，annotations 必須是一個字典或 Py_None。

引發 SystemError 且在失敗時回傳 -1。

PyObject *PyFunction_GET_CODE(PyObject *op)

PyObject *PyFunction_GET_GLOBALS(PyObject *op)

PyObject *PyFunction_GET_MODULE(PyObject *op)

PyObject *PyFunction_GET_DEFAULTS(PyObject *op)

PyObject *PyFunction_GET_KW_DEFAULTS(PyObject *op)

PyObject *PyFunction_GET_CLOSURE(PyObject *op)

PyObject *PyFunction_GET_ANNOTATIONS(PyObject *op)

回傳值：借用參照。

These functions are similar to their PyFunction_Get* counterparts, but do not do type checking. Passing anything other than an instance of PyFunction_Type is undefined behavior.

int PyFunction_AddWatcher(PyFunction_WatchCallback callback)

Register callback as a function watcher for the current interpreter. Return an ID which may be passed to PyFunction_ClearWatcher(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

在 3.12 版被加入.

int PyFunction_ClearWatcher(int watcher_id)

Clear watcher identified by watcher_id previously returned from PyFunction_AddWatcher() for the current interpreter. Return 0 on success, or -1 and set an exception on error (e.g. if the given watcher_id was never registered.)

在 3.12 版被加入.

type PyFunction_WatchEvent

Enumeration of possible function watcher events:

PyFunction_EVENT_CREATE

PyFunction_EVENT_DESTROY

PyFunction_EVENT_MODIFY_CODE

PyFunction_EVENT_MODIFY_DEFAULTS

PyFunction_EVENT_MODIFY_KWDEFAULTS

在 3.12 版被加入.

typedef int (*PyFunction_WatchCallback)(PyFunction_WatchEvent event, PyFunctionObject *func, PyObject *new_value)

Type of a function watcher callback function.

If event is PyFunction_EVENT_CREATE or PyFunction_EVENT_DESTROY then new_value will be NULL. Otherwise, new_value will hold a borrowed reference to the new value that is about to be stored in func for the attribute that is being modified.

The callback may inspect but must not modify func; doing so could have unpredictable effects, including infinite recursion.

If event is PyFunction_EVENT_CREATE, then the callback is invoked after func has been fully initialized. Otherwise, the callback is invoked before the modification to func takes place, so the prior state of func can be inspected. The runtime is permitted to optimize away the creation of function objects when possible. In such cases no event will be emitted. Although this creates the possibility of an observable difference of runtime behavior depending on optimization decisions, it does not change the semantics of the Python code being executed.

If event is PyFunction_EVENT_DESTROY, Taking a reference in the callback to the about-to-be-destroyed function will resurrect it, preventing it from being freed at this time. When the resurrected object is destroyed later, any watcher callbacks active at that time will be called again.

If the callback sets an exception, it must return -1; this exception will be printed as an unraisable exception using PyErr_WriteUnraisable(). Otherwise it should return 0.

There may already be a pending exception set on entry to the callback. In this case, the callback should return 0 with the same exception still set. This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first, and restores it before returning.

在 3.12 版被加入.

實例方法物件 (Instance Method Objects)

實例方法是 PyCFunction 的包裝器 (wrapper)，也是將 PyCFunction 繫結 (bind) 到類別物件的一種新方式。它替代了原先對 PyMethod_New(func, NULL, class) 的呼叫。

PyTypeObject PyInstanceMethod_Type

PyTypeObject 的實例代表 Python 實例方法型別。它不會公開 (expose) 給 Python 程式。

int PyInstanceMethod_Check(PyObject *o)

如果 o 是一個實例方法物件（型別為 PyInstanceMethod_Type）則回傳 true。參數必須不為 NULL。此函式總是會成功執行。

PyObject *PyInstanceMethod_New(PyObject *func)

回傳值：新的參照。

回傳一個新的實例方法物件，func 為任意可呼叫物件，在實例方法被呼叫時 func 函式也會被呼叫。

PyObject *PyInstanceMethod_Function(PyObject *im)

回傳值：借用參照。

回傳關聯到實例方法 im 的函式物件。

PyObject *PyInstanceMethod_GET_FUNCTION(PyObject *im)

回傳值：借用參照。

巨集 (macro) 版本的 PyInstanceMethod_Function()，忽略了錯誤檢查。

方法物件 (Method Objects)

方法為繫結函式 (bound function) 物件。方法總是會被繫結到一個使用者定義類別的實例。未繫結方法（繫結到一個類別的方法）已不可用。

PyTypeObject PyMethod_Type

這個 PyTypeObject 實例代表 Python 方法型別。它作為 types.MethodType 公開給 Python 程式。

int PyMethod_Check(PyObject *o)

如果 o 是一個方法物件（型別為 PyMethod_Type）則回傳 true。參數必須不為 NULL。此函式總是會成功執行。

PyObject *PyMethod_New(PyObject *func, PyObject *self)

回傳值：新的參照。

回傳一個新的方法物件，func 應為任意可呼叫物件，self 為該方法應繫結的實例。在方法被呼叫時，func 函式也會被呼叫。self 必須不為 NULL。

PyObject *PyMethod_Function(PyObject *meth)

回傳值：借用參照。

回傳關聯到方法 meth 的函式物件。

PyObject *PyMethod_GET_FUNCTION(PyObject *meth)

回傳值：借用參照。

巨集版本的 PyMethod_Function()，忽略了錯誤檢查。

PyObject *PyMethod_Self(PyObject *meth)

回傳值：借用參照。

回傳關聯到方法 meth 的實例。

PyObject *PyMethod_GET_SELF(PyObject *meth)

回傳值：借用參照。

巨集版本的 PyMethod_Self()，忽略了錯誤檢查。

Cell 物件

"Cell" 物件用於實現被多個作用域所參照 (reference) 的變數。對於每個這樣的變數，都會有個 cell 物件為了儲存該值而被建立；參照該值的每個 stack frame 中的區域性變數包含外部作用域的 cell 參照，它同樣使用了該變數。存取該值時，將使用 cell 中包含的值而不是 cell 物件本身。這種對 cell 物件的去除參照 (de-reference) 需要生成的位元組碼 (byte-code) 有支援；存取時不會自動去除參照。cell 物件在其他地方可能不太有用。

type PyCellObject

Cell 物件所用之 C 結構。

PyTypeObject PyCell_Type

對應 cell 物件的物件型別。

int PyCell_Check(PyObject *ob)

如果 ob 是一個 cell 物件則回傳真值；ob 必須不為 NULL。此函式總是會成功執行。

PyObject *PyCell_New(PyObject *ob)

回傳值：新的參照。

建立並回傳一個包含 ob 的新 cell 物件。參數可以為 NULL。

PyObject *PyCell_Get(PyObject *cell)

回傳值：新的參照。

回傳 cell 物件 cell 的內容，其可能為 NULL。如果 cell 不是一個 cell 物件，則將回傳 NULL 並設定例外。

PyObject *PyCell_GET(PyObject *cell)

回傳值：借用參照。

回傳 cell 物件 cell 的內容，但是不檢查 cell 是否非 NULL 並且為一個 cell 物件。

int PyCell_Set(PyObject *cell, PyObject *value)

將 cell 物件 cell 的內容設為 value。這將釋放任何對 cell 物件目前內容的參照。value 可以為 NULL。cell 必須不為 NULL。

在成功時回傳 0。如果 cell 不是一個 cell 物件，則將設定例外並回傳 -1。

void PyCell_SET(PyObject *cell, PyObject *value)

將 cell 物件 cell 的值設為 value。不會調整參照計數，並且不會進行任何安全檢查；cell 必須為非 NULL 並且為一個 cell 物件。

程式碼物件

程式碼物件是 CPython 實作的低階細節。每個程式碼物件都代表一段尚未綁定到函式的可執行程式碼。

type PyCodeObject

用於描述程式碼物件的 C 結構。此型別的欄位隨時可能變更。

PyTypeObject PyCode_Type

這是 PyTypeObject 的一個實例，代表 Python 的程式碼物件。

int PyCode_Check(PyObject *co)

如果 co 是程式碼物件，則回傳 true。此函式總會成功執行。

Py_ssize_t PyCode_GetNumFree(PyCodeObject *co)

回傳程式碼物件中 自由（閉包）變數的數量。

int PyUnstable_Code_GetFirstFree(PyCodeObject *co)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

回傳程式碼物件中第一個自由（閉包）變數的位置。

在 3.13 版的變更: Renamed from PyCode_GetFirstFree as part of 不穩定的 C API. The old name is deprecated, but will remain available until the signature changes again.

PyCodeObject *PyUnstable_Code_New(int argcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, PyObject *qualname, int firstlineno, PyObject *linetable, PyObject *exceptiontable)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Return a new code object. If you need a dummy code object to create a frame, use PyCode_NewEmpty() instead.

Since the definition of the bytecode changes often, calling PyUnstable_Code_New() directly can bind you to a precise Python version.

The many arguments of this function are inter-dependent in complex ways, meaning that subtle changes to values are likely to result in incorrect execution or VM crashes. Use this function only with extreme care.

在 3.11 版的變更: 新增 qualname 和 exceptiontable 參數。

在 3.12 版的變更: Renamed from PyCode_New as part of 不穩定的 C API. The old name is deprecated, but will remain available until the signature changes again.

PyCodeObject *PyUnstable_Code_NewWithPosOnlyArgs(int argcount, int posonlyargcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, PyObject *qualname, int firstlineno, PyObject *linetable, PyObject *exceptiontable)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Similar to PyUnstable_Code_New(), but with an extra "posonlyargcount" for positional-only arguments. The same caveats that apply to PyUnstable_Code_New also apply to this function.

在 3.8 版被加入: 名為 PyCode_NewWithPosOnlyArgs

在 3.11 版的變更: 新增 qualname 和 exceptiontable 參數。

在 3.12 版的變更: 重新命名為 PyUnstable_Code_NewWithPosOnlyArgs。舊的名稱已被棄用，但在簽名再次變更前仍可使用。

PyCodeObject *PyCode_NewEmpty(const char *filename, const char *funcname, int firstlineno)

回傳值：新的參照。

Return a new empty code object with the specified filename, function name, and first line number. The resulting code object will raise an Exception if executed.

int PyCode_Addr2Line(PyCodeObject *co, int byte_offset)

Return the line number of the instruction that occurs on or before byte_offset and ends after it. If you just need the line number of a frame, use PyFrame_GetLineNumber() instead.

For efficiently iterating over the line numbers in a code object, use the API described in PEP 626 [https://peps.python.org/pep-0626/#out-of-process-debuggers-and-profilers].

int PyCode_Addr2Location(PyObject *co, int byte_offset, int *start_line, int *start_column, int *end_line, int *end_column)

Sets the passed int pointers to the source code line and column numbers for the instruction at byte_offset. Sets the value to 0 when information is not available for any particular element.

如果函式成功則回傳 1，否則回傳 0。

在 3.11 版被加入.

PyObject *PyCode_GetCode(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_code'). Returns a strong reference to a PyBytesObject representing the bytecode in a code object. On error, NULL is returned and an exception is raised.

This PyBytesObject may be created on-demand by the interpreter and does not necessarily represent the bytecode actually executed by CPython. The primary use case for this function is debuggers and profilers.

在 3.11 版被加入.

PyObject *PyCode_GetVarnames(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_varnames'). Returns a new reference to a PyTupleObject containing the names of the local variables. On error, NULL is returned and an exception is raised.

在 3.11 版被加入.

PyObject *PyCode_GetCellvars(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_cellvars'). Returns a new reference to a PyTupleObject containing the names of the local variables that are referenced by nested functions. On error, NULL is returned and an exception is raised.

在 3.11 版被加入.

PyObject *PyCode_GetFreevars(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_freevars'). Returns a new reference to a PyTupleObject containing the names of the free (closure) variables. On error, NULL is returned and an exception is raised.

在 3.11 版被加入.

int PyCode_AddWatcher(PyCode_WatchCallback callback)

Register callback as a code object watcher for the current interpreter. Return an ID which may be passed to PyCode_ClearWatcher(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

在 3.12 版被加入.

int PyCode_ClearWatcher(int watcher_id)

Clear watcher identified by watcher_id previously returned from PyCode_AddWatcher() for the current interpreter. Return 0 on success, or -1 and set an exception on error (e.g. if the given watcher_id was never registered.)

在 3.12 版被加入.

type PyCodeEvent

Enumeration of possible code object watcher events: - PY_CODE_EVENT_CREATE - PY_CODE_EVENT_DESTROY

在 3.12 版被加入.

typedef int (*PyCode_WatchCallback)(PyCodeEvent event, PyCodeObject *co)

Type of a code object watcher callback function.

If event is PY_CODE_EVENT_CREATE, then the callback is invoked after co has been fully initialized. Otherwise, the callback is invoked before the destruction of co takes place, so the prior state of co can be inspected.

If event is PY_CODE_EVENT_DESTROY, taking a reference in the callback to the about-to-be-destroyed code object will resurrect it and prevent it from being freed at this time. When the resurrected object is destroyed later, any watcher callbacks active at that time will be called again.

Users of this API should not rely on internal runtime implementation details. Such details may include, but are not limited to, the exact order and timing of creation and destruction of code objects. While changes in these details may result in differences observable by watchers (including whether a callback is invoked or not), it does not change the semantics of the Python code being executed.

If the callback sets an exception, it must return -1; this exception will be printed as an unraisable exception using PyErr_WriteUnraisable(). Otherwise it should return 0.

There may already be a pending exception set on entry to the callback. In this case, the callback should return 0 with the same exception still set. This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first, and restores it before returning.

在 3.12 版被加入.

PyObject *PyCode_Optimize(PyObject *code, PyObject *consts, PyObject *names, PyObject *lnotab_obj)

This is a soft deprecated function that does nothing.

Prior to Python 3.10, this function would perform basic optimizations to a code object.

在 3.10 版的變更: This function now does nothing.

程式碼物件旗標

Code objects contain a bit-field of flags, which can be retrieved as the co_flags Python attribute (for example using PyObject_GetAttrString()), and set using a flags argument to PyUnstable_Code_New() and similar functions.

Flags whose names start with CO_FUTURE_ correspond to features normally selectable by future statements. These flags can be used in PyCompilerFlags.cf_flags. Note that many CO_FUTURE_ flags are mandatory in current versions of Python, and setting them has no effect.

The following flags are available. For their meaning, see the linked documentation of their Python equivalents.

旗標

意義

CO_OPTIMIZED

inspect.CO_OPTIMIZED

CO_NEWLOCALS

inspect.CO_NEWLOCALS

CO_VARARGS

inspect.CO_VARARGS

CO_VARKEYWORDS

inspect.CO_VARKEYWORDS

CO_NESTED

inspect.CO_NESTED

CO_GENERATOR

inspect.CO_GENERATOR

CO_COROUTINE

inspect.CO_COROUTINE

CO_ITERABLE_COROUTINE

inspect.CO_ITERABLE_COROUTINE

CO_ASYNC_GENERATOR

inspect.CO_ASYNC_GENERATOR

CO_HAS_DOCSTRING

inspect.CO_HAS_DOCSTRING

CO_METHOD

inspect.CO_METHOD

CO_FUTURE_DIVISION

無效果（__future__.division）

CO_FUTURE_ABSOLUTE_IMPORT

無效果（__future__.absolute_import）

CO_FUTURE_WITH_STATEMENT

無效果（__future__.with_statement）

CO_FUTURE_PRINT_FUNCTION

無效果（__future__.print_function）

CO_FUTURE_UNICODE_LITERALS

無效果（__future__.unicode_literals）

CO_FUTURE_GENERATOR_STOP

無效果（__future__.generator_stop）

CO_FUTURE_ANNOTATIONS

__future__.annotations

額外資訊

To support low-level extensions to frame evaluation, such as external just-in-time compilers, it is possible to attach arbitrary extra data to code objects.

These functions are part of the unstable C API tier: this functionality is a CPython implementation detail, and the API may change without deprecation warnings.

Py_ssize_t PyUnstable_Eval_RequestCodeExtraIndex(freefunc free)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Return a new opaque index value used to adding data to code objects.

You generally call this function once (per interpreter) and use the result with PyCode_GetExtra and PyCode_SetExtra to manipulate data on individual code objects.

If free is not NULL: when a code object is deallocated, free will be called on non-NULL data stored under the new index. Use Py_DecRef() when storing PyObject.

在 3.6 版被加入: 名為 _PyEval_RequestCodeExtraIndex

在 3.12 版的變更: 重新命名為 PyUnstable_Eval_RequestCodeExtraIndex。舊的私有名稱已被棄用，但在 API 變更前仍可使用。

int PyUnstable_Code_GetExtra(PyObject *code, Py_ssize_t index, void **extra)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Set extra to the extra data stored under the given index. Return 0 on success. Set an exception and return -1 on failure.

If no data was set under the index, set extra to NULL and return 0 without setting an exception.

在 3.6 版被加入: 名為 _PyCode_GetExtra

在 3.12 版的變更: 重新命名為 PyUnstable_Code_GetExtra。舊的私有名稱已被棄用，但在 API 變更前仍可使用。

int PyUnstable_Code_SetExtra(PyObject *code, Py_ssize_t index, void *extra)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Set the extra data stored under the given index to extra. Return 0 on success. Set an exception and return -1 on failure.

在 3.6 版被加入: 名為 _PyCode_SetExtra

在 3.12 版的變更: 重新命名為 PyUnstable_Code_SetExtra。舊的私有名稱已被棄用，但在 API 變更前仍可使用。

檔案物件 (File Objects)

這些 API 是用於內建檔案物件的 Python 2 C API 的最小模擬 (minimal emulation)，它過去依賴於 C 標準函式庫對於緩衝 I/O (FILE*) 的支援。在 Python 3 中，檔案和串流使用新的 io 模組，它在作業系統的低階無緩衝 I/O 上定義了多個層級。下面描述的函式是這些新 API 的便捷 C 包裝器，主要用於直譯器中的內部錯誤報告；建議第三方程式碼改為存取 io API。

PyObject *PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const char *encoding, const char *errors, const char *newline, int closefd)

回傳值：新的參照。 為 穩定 ABI 的一部分.

從已打開檔案 fd 的檔案描述器建立一個 Python 檔案物件。引數 name、encoding、errors 和 newline 可以為 NULL 以使用預設值； buffering 可以是 -1 以使用預設值。 name 被忽略並保留以實作向後相容性。失敗時回傳 NULL。有關引數的更全面描述，請參閱 io.open() 函式文件。

警告

由於 Python 串流有自己的緩衝層，將它們與作業系統層級檔案描述器混合使用會產生各種問題（例如資料的排序不符合預期）。

在 3.2 版的變更: 忽略 name 屬性。

int PyObject_AsFileDescriptor(PyObject *p)

為 穩定 ABI 的一部分.

回傳與 p 關聯的檔案描述器作為 int。如果物件是整數，則回傳其值。如果不是整數，則呼叫物件的 fileno() 方法（如果存在）；該方法必須回傳一個整數，它作為檔案描述器值回傳。設定例外並在失敗時回傳 -1。

PyObject *PyFile_GetLine(PyObject *p, int n)

回傳值：新的參照。 為 穩定 ABI 的一部分.

相當於 p.readline([n])，這個函式從物件 p 中讀取一行。 p 可以是檔案物件或任何具有 readline() 方法的物件。如果 n 為 0，則不管該行的長度都只會讀取一行。如果 n 大於 0，則不會從檔案中讀取超過 n 個位元組；可以回傳該行的一部分。在這兩種情況下，如果立即到達檔案末尾，則回傳一個空字串。但是，如果 n 小於 0，無論長度如何，都會讀取一行，但如果立即到達檔案末尾，則會引發 EOFError。

int PyFile_SetOpenCodeHook(Py_OpenCodeHookFunction handler)

覆蓋 io.open_code() 的正常行為以透過提供的處理程式 (handler) 傳遞其參數。

handler 是以下類型的函式：

typedef PyObject *(*Py_OpenCodeHookFunction)(PyObject*, void*)

相當於 PyObject *(*)(PyObject *path, void *userData)，其中 path 保證為 PyUnicodeObject。

userData 指標被傳遞到掛鉤函式 (hook function) 中。由於可能會從不同的執行環境 (runtime) 呼叫掛鉤函式，因此該指標不應直接指向 Python 狀態。

由於此掛鉤函式是在導入期間有意使用的，因此請避免在其執行期間導入新模組，除非它們已知有被凍結或在 sys.modules 中可用。

一旦設定了一個掛鉤函式，它就不能被刪除或替換，且後續對 PyFile_SetOpenCodeHook() 的呼叫將會失敗。失敗時，函式回傳 -1 且若直譯器已初始化便會設定例外。

在 Py_Initialize() 之前呼叫此函式是安全的。

不帶引數地引發一個稽核事件 (auditing event) setopencodehook。

在 3.8 版被加入.

PyObject *PyFile_OpenCodeObject(PyObject *path)

以模式 'rb' 開啟 path。path 必須是 Python str 物件。此函式的行為可能會被 PyFile_SetOpenCodeHook() 覆蓋，以允許對文字進行某些預處理。

這類似於 Python 中的 io.open_code()。

成功時，此函式回傳對 Python 檔案物件的 strong reference。失敗時，回傳 NULL 並設定例外。

在 3.8 版被加入.

PyObject *PyFile_OpenCode(const char *path)

類似於 PyFile_OpenCodeObject()，但 path 是 UTF-8 編碼的 const char*。

在 3.8 版被加入.

int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)

為 穩定 ABI 的一部分.

將物件 obj 寫入檔案物件 p。 flags 唯一支援的旗標是 Py_PRINT_RAW；如果有給定，則寫入物件的 str() 而不是 repr()。在成功回傳 0 或在失敗回傳 -1；將設定適當的例外。

int PyFile_WriteString(const char *s, PyObject *p)

為 穩定 ABI 的一部分.

寫入字串 s 到 檔案物件 p。當成功時回傳 0，而當失敗時回傳 -1，並會設定合適的例外狀況。

已棄用的 API

這些是被錯誤地包含在 Python C API 中的軟性棄用 API。它們僅為了完整性而記錄於文件中；請改用其他 PyFile* API。

PyObject *PyFile_NewStdPrinter(int fd)

請改用帶有預設值 (fd, NULL, "w", -1, NULL, NULL, NULL, 0) 的 PyFile_FromFd()。

PyTypeObject PyStdPrinter_Type

在 Python 啟動期間，當 io 尚不可用時會在內部使用的類檔案物件的型別。請改用 Python open() 或 PyFile_FromFd() 來建立檔案物件。

模組物件

PyTypeObject PyModule_Type

為 穩定 ABI 的一部分.

This instance of PyTypeObject represents the Python module type. This is exposed to Python programs as types.ModuleType.

int PyModule_Check(PyObject *p)

Return true if p is a module object, or a subtype of a module object. This function always succeeds.

int PyModule_CheckExact(PyObject *p)

Return true if p is a module object, but not a subtype of PyModule_Type. This function always succeeds.

PyObject *PyModule_NewObject(PyObject *name)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Return a new module object with module.__name__ set to name. The module's __name__, __doc__, __package__ and __loader__ attributes are filled in (all but __name__ are set to None). The caller is responsible for setting a __file__ attribute.

在失敗時回傳 NULL 並設定例外。

在 3.3 版被加入.

在 3.4 版的變更: __package__ 和 __loader__ 現在被設為 None。

PyObject *PyModule_New(const char *name)

回傳值：新的參照。 為 穩定 ABI 的一部分.

類似於 PyModule_NewObject()，但名稱是以 UTF-8 編碼的字串，而非 Unicode 物件。

PyObject *PyModule_GetDict(PyObject *module)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Return the dictionary object that implements module's namespace; this object is the same as the __dict__ attribute of the module object. If module is not a module object (or a subtype of a module object), SystemError is raised and NULL is returned.

It is recommended extensions use other PyModule_* and PyObject_* functions rather than directly manipulate a module's __dict__.

The returned reference is borrowed from the module; it is valid until the module is destroyed.

PyObject *PyModule_GetNameObject(PyObject *module)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Return module's __name__ value. If the module does not provide one, or if it is not a string, SystemError is raised and NULL is returned.

在 3.3 版被加入.

const char *PyModule_GetName(PyObject *module)

為 穩定 ABI 的一部分.

類似於 PyModule_GetNameObject()，但回傳以 'utf-8' 編碼的名稱。

The returned buffer is only valid until the module is renamed or destroyed. Note that Python code may rename a module by setting its __name__ attribute.

void *PyModule_GetState(PyObject *module)

為 穩定 ABI 的一部分.

Return the "state" of the module, that is, a pointer to the block of memory allocated at module creation time, or NULL. See PyModuleDef.m_size.

PyModuleDef *PyModule_GetDef(PyObject *module)

為 穩定 ABI 的一部分.

Return a pointer to the PyModuleDef struct from which the module was created, or NULL if the module wasn't created from a definition.

On error, return NULL with an exception set. Use PyErr_Occurred() to tell this case apart from a missing PyModuleDef.

PyObject *PyModule_GetFilenameObject(PyObject *module)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return the name of the file from which module was loaded using module's __file__ attribute. If this is not defined, or if it is not a string, raise SystemError and return NULL; otherwise return a reference to a Unicode object.

在 3.2 版被加入.

const char *PyModule_GetFilename(PyObject *module)

為 穩定 ABI 的一部分.

類似於 PyModule_GetFilenameObject()，但回傳以 'utf-8' 編碼的檔案名稱。

The returned buffer is only valid until the module's __file__ attribute is reassigned or the module is destroyed.

在 3.2 版之後被棄用: PyModule_GetFilename() raises UnicodeEncodeError on unencodable filenames, use PyModule_GetFilenameObject() instead.

模組定義

The functions in the previous section work on any module object, including modules imported from Python code.

Modules defined using the C API typically use a module definition, PyModuleDef -- a statically allocated, constant “description" of how a module should be created.

The definition is usually used to define an extension's “main” module object (see Defining extension modules for details). It is also used to create extension modules dynamically.

Unlike PyModule_New(), the definition allows management of module state -- a piece of memory that is allocated and cleared together with the module object. Unlike the module's Python attributes, Python code cannot replace or delete data stored in module state.

type PyModuleDef

為 穩定 ABI 的一部分 （包含所有成員）.

The module definition struct, which holds all information needed to create a module object. This structure must be statically allocated (or be otherwise guaranteed to be valid while any modules created from it exist). Usually, there is only one variable of this type for each extension module.

PyModuleDef_Base m_base

Always initialize this member to PyModuleDef_HEAD_INIT.

const char *m_name

Name for the new module.

const char *m_doc

Docstring for the module; usually a docstring variable created with PyDoc_STRVAR is used.

Py_ssize_t m_size

Module state may be kept in a per-module memory area that can be retrieved with PyModule_GetState(), rather than in static globals. This makes modules safe for use in multiple sub-interpreters.

This memory area is allocated based on m_size on module creation, and freed when the module object is deallocated, after the m_free function has been called, if present.

Setting it to a non-negative value means that the module can be re-initialized and specifies the additional amount of memory it requires for its state.

Setting m_size to -1 means that the module does not support sub-interpreters, because it has global state. Negative m_size is only allowed when using legacy single-phase initialization or when creating modules dynamically.

更多詳情請見 PEP 3121 [https://peps.python.org/pep-3121/]。

PyMethodDef *m_methods

A pointer to a table of module-level functions, described by PyMethodDef values. Can be NULL if no functions are present.

PyModuleDef_Slot *m_slots

An array of slot definitions for multi-phase initialization, terminated by a {0, NULL} entry. When using legacy single-phase initialization, m_slots must be NULL.

在 3.5 版的變更: 在 3.5 版本之前，這個成員總是被設為 NULL，並被定義為：

inquiry m_reload

traverseproc m_traverse

A traversal function to call during GC traversal of the module object, or NULL if not needed.

This function is not called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, this function is not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

在 3.9 版的變更: No longer called before the module state is allocated.

inquiry m_clear

A clear function to call during GC clearing of the module object, or NULL if not needed.

This function is not called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, this function is not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

Like PyTypeObject.tp_clear, this function is not always called before a module is deallocated. For example, when reference counting is enough to determine that an object is no longer used, the cyclic garbage collector is not involved and m_free is called directly.

在 3.9 版的變更: No longer called before the module state is allocated.

freefunc m_free

A function to call during deallocation of the module object, or NULL if not needed.

This function is not called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, this function is not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

在 3.9 版的變更: No longer called before the module state is allocated.

模組槽 (Module slots)

type PyModuleDef_Slot

為 穩定 ABI 的一部分 （包含所有成員） 自 3.5 版本開始.

int slot

A slot ID, chosen from the available values explained below.

void *value

Value of the slot, whose meaning depends on the slot ID.

在 3.5 版被加入.

The available slot types are:

Py_mod_create

為 穩定 ABI 的一部分 自 3.5 版本開始.

Specifies a function that is called to create the module object itself. The value pointer of this slot must point to a function of the signature:

PyObject *create_module(PyObject *spec, PyModuleDef *def)

The function receives a ModuleSpec instance, as defined in PEP 451 [https://peps.python.org/pep-0451/], and the module definition. It should return a new module object, or set an error and return NULL.

This function should be kept minimal. In particular, it should not call arbitrary Python code, as trying to import the same module again may result in an infinite loop.

Multiple Py_mod_create slots may not be specified in one module definition.

If Py_mod_create is not specified, the import machinery will create a normal module object using PyModule_New(). The name is taken from spec, not the definition, to allow extension modules to dynamically adjust to their place in the module hierarchy and be imported under different names through symlinks, all while sharing a single module definition.

There is no requirement for the returned object to be an instance of PyModule_Type. Any type can be used, as long as it supports setting and getting import-related attributes. However, only PyModule_Type instances may be returned if the PyModuleDef has non-NULL m_traverse, m_clear, m_free; non-zero m_size; or slots other than Py_mod_create.

在 3.5 版被加入.

Py_mod_exec

為 穩定 ABI 的一部分 自 3.5 版本開始.

Specifies a function that is called to execute the module. This is equivalent to executing the code of a Python module: typically, this function adds classes and constants to the module. The signature of the function is:

int exec_module(PyObject *module)

If multiple Py_mod_exec slots are specified, they are processed in the order they appear in the m_slots array.

在 3.5 版被加入.

Py_mod_multiple_interpreters

為 穩定 ABI 的一部分 自 3.12 版本開始.

Specifies one of the following values:

Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED

The module does not support being imported in subinterpreters.

Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED

The module supports being imported in subinterpreters, but only when they share the main interpreter's GIL. (See 隔離擴充模組.)

Py_MOD_PER_INTERPRETER_GIL_SUPPORTED

The module supports being imported in subinterpreters, even when they have their own GIL. (See 隔離擴充模組.)

This slot determines whether or not importing this module in a subinterpreter will fail.

Multiple Py_mod_multiple_interpreters slots may not be specified in one module definition.

If Py_mod_multiple_interpreters is not specified, the import machinery defaults to Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED.

在 3.12 版被加入.

Py_mod_gil

為 穩定 ABI 的一部分 自 3.13 版本開始.

Specifies one of the following values:

Py_MOD_GIL_USED

The module depends on the presence of the global interpreter lock (GIL), and may access global state without synchronization.

Py_MOD_GIL_NOT_USED

The module is safe to run without an active GIL.

This slot is ignored by Python builds not configured with --disable-gil. Otherwise, it determines whether or not importing this module will cause the GIL to be automatically enabled. See Free-threaded CPython for more detail.

Multiple Py_mod_gil slots may not be specified in one module definition.

If Py_mod_gil is not specified, the import machinery defaults to Py_MOD_GIL_USED.

在 3.13 版被加入.

Creating extension modules dynamically

The following functions may be used to create a module outside of an extension's initialization function. They are also used in single-phase initialization.

PyObject *PyModule_Create(PyModuleDef *def)

回傳值：新的參照。

Create a new module object, given the definition in def. This is a macro that calls PyModule_Create2() with module_api_version set to PYTHON_API_VERSION, or to PYTHON_ABI_VERSION if using the limited API.

PyObject *PyModule_Create2(PyModuleDef *def, int module_api_version)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a new module object, given the definition in def, assuming the API version module_api_version. If that version does not match the version of the running interpreter, a RuntimeWarning is emitted.

在失敗時回傳 NULL 並設定例外。

This function does not support slots. The m_slots member of def must be NULL.

備註

Most uses of this function should be using PyModule_Create() instead; only use this if you are sure you need it.

PyObject *PyModule_FromDefAndSpec(PyModuleDef *def, PyObject *spec)

回傳值：新的參照。

This macro calls PyModule_FromDefAndSpec2() with module_api_version set to PYTHON_API_VERSION, or to PYTHON_ABI_VERSION if using the limited API.

在 3.5 版被加入.

PyObject *PyModule_FromDefAndSpec2(PyModuleDef *def, PyObject *spec, int module_api_version)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Create a new module object, given the definition in def and the ModuleSpec spec, assuming the API version module_api_version. If that version does not match the version of the running interpreter, a RuntimeWarning is emitted.

在失敗時回傳 NULL 並設定例外。

Note that this does not process execution slots (Py_mod_exec). Both PyModule_FromDefAndSpec and PyModule_ExecDef must be called to fully initialize a module.

備註

Most uses of this function should be using PyModule_FromDefAndSpec() instead; only use this if you are sure you need it.

在 3.5 版被加入.

int PyModule_ExecDef(PyObject *module, PyModuleDef *def)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Process any execution slots (Py_mod_exec) given in def.

在 3.5 版被加入.

PYTHON_API_VERSION

The C API version. Defined for backwards compatibility.

Currently, this constant is not updated in new Python versions, and is not useful for versioning. This may change in the future.

PYTHON_ABI_VERSION

Defined as 3 for backwards compatibility.

Currently, this constant is not updated in new Python versions, and is not useful for versioning. This may change in the future.

支援的函式

The following functions are provided to help initialize a module state. They are intended for a module's execution slots (Py_mod_exec), the initialization function for legacy single-phase initialization, or code that creates modules dynamically.

int PyModule_AddObjectRef(PyObject *module, const char *name, PyObject *value)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Add an object to module as name. This is a convenience function which can be used from the module's initialization function.

On success, return 0. On error, raise an exception and return -1.

用法範例：

static int
add_spam(PyObject *module, int value)
{
    PyObject *obj = PyLong_FromLong(value);
    if (obj == NULL) {
        return -1;
    }
    int res = PyModule_AddObjectRef(module, "spam", obj);
    Py_DECREF(obj);
    return res;
 }

To be convenient, the function accepts NULL value with an exception set. In this case, return -1 and just leave the raised exception unchanged.

The example can also be written without checking explicitly if obj is NULL:

static int
add_spam(PyObject *module, int value)
{
    PyObject *obj = PyLong_FromLong(value);
    int res = PyModule_AddObjectRef(module, "spam", obj);
    Py_XDECREF(obj);
    return res;
 }

Note that Py_XDECREF() should be used instead of Py_DECREF() in this case, since obj can be NULL.

The number of different name strings passed to this function should be kept small, usually by only using statically allocated strings as name. For names that aren't known at compile time, prefer calling PyUnicode_FromString() and PyObject_SetAttr() directly. For more details, see PyUnicode_InternFromString(), which may be used internally to create a key object.

在 3.10 版被加入.

int PyModule_Add(PyObject *module, const char *name, PyObject *value)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Similar to PyModule_AddObjectRef(), but "steals" a reference to value. It can be called with a result of function that returns a new reference without bothering to check its result or even saving it to a variable.

用法範例：

if (PyModule_Add(module, "spam", PyBytes_FromString(value)) < 0) {
    goto error;
}

在 3.13 版被加入.

int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)

為 穩定 ABI 的一部分.

類似於 PyModule_AddObjectRef()，但在成功時（如果回傳 0）會偷走對 value 的參照。

The new PyModule_Add() or PyModule_AddObjectRef() functions are recommended, since it is easy to introduce reference leaks by misusing the PyModule_AddObject() function.

備註

Unlike other functions that steal references, PyModule_AddObject() only releases the reference to value on success.

This means that its return value must be checked, and calling code must Py_XDECREF() value manually on error.

用法範例：

PyObject *obj = PyBytes_FromString(value);
if (PyModule_AddObject(module, "spam", obj) < 0) {
    // If 'obj' is not NULL and PyModule_AddObject() failed,
    // 'obj' strong reference must be deleted with Py_XDECREF().
    // If 'obj' is NULL, Py_XDECREF() does nothing.
    Py_XDECREF(obj);
    goto error;
}
// PyModule_AddObject() stole a reference to obj:
// Py_XDECREF(obj) is not needed here.

在 3.13 版之後被棄用: PyModule_AddObject() 已被軟性棄用。

int PyModule_AddIntConstant(PyObject *module, const char *name, long value)

為 穩定 ABI 的一部分.

Add an integer constant to module as name. This convenience function can be used from the module's initialization function. Return -1 with an exception set on error, 0 on success.

This is a convenience function that calls PyLong_FromLong() and PyModule_AddObjectRef(); see their documentation for details.

int PyModule_AddStringConstant(PyObject *module, const char *name, const char *value)

為 穩定 ABI 的一部分.

Add a string constant to module as name. This convenience function can be used from the module's initialization function. The string value must be NULL-terminated. Return -1 with an exception set on error, 0 on success.

This is a convenience function that calls PyUnicode_InternFromString() and PyModule_AddObjectRef(); see their documentation for details.

PyModule_AddIntMacro(module, macro)

Add an int constant to module. The name and the value are taken from macro. For example PyModule_AddIntMacro(module, AF_INET) adds the int constant AF_INET with the value of AF_INET to module. Return -1 with an exception set on error, 0 on success.

PyModule_AddStringMacro(module, macro)

將字串常數加入到 module 中。

int PyModule_AddType(PyObject *module, PyTypeObject *type)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Add a type object to module. The type object is finalized by calling internally PyType_Ready(). The name of the type object is taken from the last component of tp_name after dot. Return -1 with an exception set on error, 0 on success.

在 3.9 版被加入.

int PyModule_AddFunctions(PyObject *module, PyMethodDef *functions)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Add the functions from the NULL terminated functions array to module. Refer to the PyMethodDef documentation for details on individual entries (due to the lack of a shared module namespace, module level "functions" implemented in C typically receive the module as their first parameter, making them similar to instance methods on Python classes).

This function is called automatically when creating a module from PyModuleDef (such as when using Multi-phase initialization, PyModule_Create, or PyModule_FromDefAndSpec). Some module authors may prefer defining functions in multiple PyMethodDef arrays; in that case they should call this function directly.

The functions array must be statically allocated (or otherwise guaranteed to outlive the module object).

在 3.5 版被加入.

int PyModule_SetDocString(PyObject *module, const char *docstring)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Set the docstring for module to docstring. This function is called automatically when creating a module from PyModuleDef (such as when using Multi-phase initialization, PyModule_Create, or PyModule_FromDefAndSpec).

Return 0 on success. Return -1 with an exception set on error.

在 3.5 版被加入.

int PyUnstable_Module_SetGIL(PyObject *module, void *gil)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Indicate that module does or does not support running without the global interpreter lock (GIL), using one of the values from Py_mod_gil. It must be called during module's initialization function when using Legacy single-phase initialization. If this function is not called during module initialization, the import machinery assumes the module does not support running without the GIL. This function is only available in Python builds configured with --disable-gil. Return -1 with an exception set on error, 0 on success.

在 3.13 版被加入.

Module lookup (single-phase initialization)

The legacy single-phase initialization initialization scheme creates singleton modules that can be looked up in the context of the current interpreter. This allows the module object to be retrieved later with only a reference to the module definition.

These functions will not work on modules created using multi-phase initialization, since multiple such modules can be created from a single definition.

PyObject *PyState_FindModule(PyModuleDef *def)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Returns the module object that was created from def for the current interpreter. This method requires that the module object has been attached to the interpreter state with PyState_AddModule() beforehand. In case the corresponding module object is not found or has not been attached to the interpreter state yet, it returns NULL.

int PyState_AddModule(PyObject *module, PyModuleDef *def)

為 穩定 ABI 的一部分 自 3.3 版本開始.

Attaches the module object passed to the function to the interpreter state. This allows the module object to be accessible via PyState_FindModule().

Only effective on modules created using single-phase initialization.

Python calls PyState_AddModule automatically after importing a module that uses single-phase initialization, so it is unnecessary (but harmless) to call it from module initialization code. An explicit call is needed only if the module's own init code subsequently calls PyState_FindModule. The function is mainly intended for implementing alternative import mechanisms (either by calling it directly, or by referring to its implementation for details of the required state updates).

If a module was attached previously using the same def, it is replaced by the new module.

The caller must have an attached thread state.

成功時回傳 0，在失敗時回傳 -1 並設定例外。

在 3.3 版被加入.

int PyState_RemoveModule(PyModuleDef *def)

為 穩定 ABI 的一部分 自 3.3 版本開始.

Removes the module object created from def from the interpreter state. Return -1 with an exception set on error, 0 on success.

The caller must have an attached thread state.

在 3.3 版被加入.

疊代器（Iterator）物件

Python 提供了兩種通用的疊代器 (iterator) 物件，第一種是序列疊代器 (sequence iterator)，適用於支援 __getitem__() 方法的任意序列，第二種是與可呼叫 (callable) 物件和哨兵值 (sentinel value) 一起使用，會呼叫序列中的每個可呼叫物件，當回傳哨兵值時就結束疊代。

PyTypeObject PySeqIter_Type

為 穩定 ABI 的一部分.

此型別物件用於由 PySeqIter_New() 所回傳的疊代器物件以及用於內建序列型別的內建函式 iter() 的單引數形式。

int PySeqIter_Check(PyObject *op)

Return true if the type of op is PySeqIter_Type. This function always succeeds.

PyObject *PySeqIter_New(PyObject *seq)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return an iterator that works with a general sequence object, seq. The iteration ends when the sequence raises IndexError for the subscripting operation.

PyTypeObject PyCallIter_Type

為 穩定 ABI 的一部分.

Type object for iterator objects returned by PyCallIter_New() and the two-argument form of the iter() built-in function.

int PyCallIter_Check(PyObject *op)

Return true if the type of op is PyCallIter_Type. This function always succeeds.

PyObject *PyCallIter_New(PyObject *callable, PyObject *sentinel)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a new iterator. The first parameter, callable, can be any Python callable object that can be called with no parameters; each call to it should return the next item in the iteration. When callable returns a value equal to sentinel, the iteration will be terminated.

Range 物件

PyTypeObject PyRange_Type

為 穩定 ABI 的一部分.

range 物件的型別物件。

int PyRange_Check(PyObject *o)

Return true if the object o is an instance of a range object. This function always succeeds.

內建疊代器型別

These are built-in iteration types that are included in Python's C API, but provide no additional functions. They are here for completeness.

C 型別

Python 型別

PyTypeObject PyEnum_Type

為 穩定 ABI 的一部分.

enumerate

PyTypeObject PyFilter_Type

為 穩定 ABI 的一部分.

filter

PyTypeObject PyMap_Type

為 穩定 ABI 的一部分.

map

PyTypeObject PyReversed_Type

為 穩定 ABI 的一部分.

reversed

PyTypeObject PyZip_Type

為 穩定 ABI 的一部分.

zip

其他疊代器物件

PyTypeObject PyByteArrayIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyBytesIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyListIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyListRevIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PySetIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyTupleIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyRangeIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyLongRangeIter_Type

為 穩定 ABI 的一部分.

PyTypeObject PyDictIterKey_Type

為 穩定 ABI 的一部分.

PyTypeObject PyDictRevIterKey_Type

為 穩定 ABI 的一部分 自 3.8 版本開始.

PyTypeObject PyDictIterValue_Type

為 穩定 ABI 的一部分.

PyTypeObject PyDictRevIterValue_Type

為 穩定 ABI 的一部分 自 3.8 版本開始.

PyTypeObject PyDictIterItem_Type

為 穩定 ABI 的一部分.

PyTypeObject PyDictRevIterItem_Type

為 穩定 ABI 的一部分 自 3.8 版本開始.

PyTypeObject PyODictIter_Type

各種內建物件的疊代器型別物件。

Do not create instances of these directly; prefer calling PyObject_GetIter() instead.

Note that there is no guarantee that a given built-in type uses a given iterator type. For example, iterating over range will use one of two iterator types depending on the size of the range. Other types may start using a similar scheme in the future, without warning.

Descriptor（描述器）物件

"Descriptor" 是描述物件某些屬性的物件，它們存在於型別物件的 dictionary（字典）中。

PyTypeObject PyProperty_Type

為 穩定 ABI 的一部分.

內建 descriptor 型別的型別物件。

PyObject *PyDescr_NewGetSet(PyTypeObject *type, struct PyGetSetDef *getset)

回傳值：新的參照。 為 穩定 ABI 的一部分.

PyObject *PyDescr_NewMember(PyTypeObject *type, struct PyMemberDef *meth)

回傳值：新的參照。 為 穩定 ABI 的一部分.

PyTypeObject PyMemberDescr_Type

為 穩定 ABI 的一部分.

The type object for member descriptor objects created from PyMemberDef structures. These descriptors expose fields of a C struct as attributes on a type, and correspond to types.MemberDescriptorType objects in Python.

PyTypeObject PyGetSetDescr_Type

為 穩定 ABI 的一部分.

The type object for get/set descriptor objects created from PyGetSetDef structures. These descriptors implement attributes whose value is computed by C getter and setter functions, and are used for many built-in type attributes.

PyObject *PyDescr_NewMethod(PyTypeObject *type, struct PyMethodDef *meth)

回傳值：新的參照。 為 穩定 ABI 的一部分.

PyTypeObject PyMethodDescr_Type

為 穩定 ABI 的一部分.

The type object for method descriptor objects created from PyMethodDef structures. These descriptors expose C functions as methods on a type, and correspond to types.MemberDescriptorType objects in Python.

PyObject *PyDescr_NewWrapper(PyTypeObject *type, struct wrapperbase *wrapper, void *wrapped)

回傳值：新的參照。

PyTypeObject PyWrapperDescr_Type

為 穩定 ABI 的一部分.

The type object for wrapper descriptor objects created by PyDescr_NewWrapper() and PyWrapper_New(). Wrapper descriptors are used internally to expose special methods implemented via wrapper structures, and appear in Python as types.WrapperDescriptorType objects.

PyObject *PyDescr_NewClassMethod(PyTypeObject *type, PyMethodDef *method)

回傳值：新的參照。 為 穩定 ABI 的一部分.

int PyDescr_IsData(PyObject *descr)

如果 descriptor 物件 descr 描述的是一個資料屬性則回傳非零值，或者如果它描述的是一個方法則回傳 0。descr 必須為一個 descriptor 物件；沒有錯誤檢查。

PyObject *PyWrapper_New(PyObject*, PyObject*)

回傳值：新的參照。 為 穩定 ABI 的一部分.

內建描述器

PyTypeObject PySuper_Type

為 穩定 ABI 的一部分.

The type object for super objects. This is the same object as super in the Python layer.

PyTypeObject PyClassMethod_Type

The type of class method objects. This is the same object as classmethod in the Python layer.

PyTypeObject PyClassMethodDescr_Type

為 穩定 ABI 的一部分.

The type object for C-level class method descriptor objects. This is the type of the descriptors created for classmethod() defined in C extension types, and is the same object as classmethod in Python.

PyObject *PyClassMethod_New(PyObject *callable)

Create a new classmethod object wrapping callable. callable must be a callable object and must not be NULL.

On success, this function returns a strong reference to a new class method descriptor. On failure, this function returns NULL with an exception set.

PyTypeObject PyStaticMethod_Type

The type of static method objects. This is the same object as staticmethod in the Python layer.

PyObject *PyStaticMethod_New(PyObject *callable)

Create a new staticmethod object wrapping callable. callable must be a callable object and must not be NULL.

On success, this function returns a strong reference to a new static method descriptor. On failure, this function returns NULL with an exception set.

切片物件

PyTypeObject PySlice_Type

為 穩定 ABI 的一部分.

slice 物件的型別物件。這與 Python 層中的 slice 相同。

int PySlice_Check(PyObject *ob)

如果 ob 是 slice 物件，則回傳 true；ob 不能是 NULL 。此函式永遠成功。

PyObject *PySlice_New(PyObject *start, PyObject *stop, PyObject *step)

回傳值：新的參照。 為 穩定 ABI 的一部分.

以指定的值回傳一個新的切片物件。start、stop 及 step 參數會被用為同名的 slice 物件屬性值。任何值都可能是 NULL，在這種情況下，None 將用於相對應的屬性。

如果無法分配新物件，則回傳 NULL 並設定例外。

int PySlice_GetIndices(PyObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)

為 穩定 ABI 的一部分.

從 slice 物件 slice 讀取開始、停止和步進索引，假設序列長度為 length。將大於 length 的索引視為錯誤。

成功時回傳 0，錯誤時回傳 -1，並無例外設定（除非其中一個索引不是 None 並且未能轉換成整數，在這種情況下會回傳 -1 ，並有設定例外）。

你可能不想使用此功能。

在 3.2 版的變更: 之前 slice 的參數型別是 PySliceObject* 。

int PySlice_GetIndicesEx(PyObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)

為 穩定 ABI 的一部分.

可用來取代 PySlice_GetIndices()。從假設序列長度為 length 的 slice 物件 slice 擷取開始、停止和步長索引，並將 slice 的長度存入 slicelength。超出範圍的索引會被剪切，剪切方式與一般切片的處理方式一致。

成功時回傳 0 ，在失敗時回傳 -1 並設定例外。

備註

這個函式對於可調整大小的序列並不安全。它的呼叫應該被 PySlice_Unpack() 和 PySlice_AdjustIndices() 的組合取代，其中：

if (PySlice_GetIndicesEx(slice, length, &start, &stop, &step, &slicelength) < 0) {
    // return error
}

被更換為：

if (PySlice_Unpack(slice, &start, &stop, &step) < 0) {
    // return error
}
slicelength = PySlice_AdjustIndices(length, &start, &stop, step);

在 3.2 版的變更: 之前 slice 的參數型別是 PySliceObject* 。

在 3.6.1 版的變更: 如果 Py_LIMITED_API 沒有設定或設定為 0x03050400 和 0x03060000 (不包括) 或 0x03060100 或更高的值 PySlice_GetIndicesEx() 是使用 PySlice_Unpack() 和 PySlice_AdjustIndices() 來實作一個巨集。引數 start、stop 和 step 會被計算多次。

在 3.6.1 版之後被棄用: 如果 Py_LIMITED_API 設定為小於 0x03050400 或介於 0x03060000 和 0x03060100 之間 (不包括邊界值) PySlice_GetIndicesEx() 是一個已廢棄的函式。

int PySlice_Unpack(PyObject *slice, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)

為 穩定 ABI 的一部分 自 3.7 版本開始.

以 C 整數的形式從 slice 物件中抽取 start、stop 及 step 資料成員。將大於 PY_SSIZE_T_MAX 的值靜默減少為 PY_SSIZE_T_MAX，將小於 PY_SSIZE_T_MIN 的 start 和 stop 值靜默提升為 PY_SSIZE_T_MIN，將小於 -PY_SSIZE_T_MAX 的 step 值靜默提升為 -PY_SSIZE_T_MAX。

成功時回傳 0，在失敗時回傳 -1 並設定例外。

在 3.6.1 版被加入.

Py_ssize_t PySlice_AdjustIndices(Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t step)

為 穩定 ABI 的一部分 自 3.7 版本開始.

假設序列長度為指定長度，調整開始/結束切片索引。超出範圍的索引會以與處理正常切片一致的方式切除。

回傳切片的長度。永遠成功。不呼叫 Python 程式碼。

在 3.6.1 版被加入.

Ellipsis 物件

PyTypeObject PyEllipsis_Type

為 穩定 ABI 的一部分.

Python Ellipsis 物件的型別。與 Python 層中的 types.EllipsisType 相同。

PyObject *Py_Ellipsis

Python Ellipsis 物件。這個物件沒有方法。就像 Py_None 一樣，它是一個 immortal 單一物件。

在 3.12 版的變更: Py_Ellipsis 為不滅的 (immortal)。

MemoryView 物件

A memoryview object exposes the C level buffer interface as a Python object which can then be passed around like any other object.

PyTypeObject PyMemoryView_Type

為 穩定 ABI 的一部分.

This instance of PyTypeObject represents the Python memoryview type. This is the same object as memoryview in the Python layer.

PyObject *PyMemoryView_FromObject(PyObject *obj)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a memoryview object from an object that provides the buffer interface. If obj supports writable buffer exports, the memoryview object will be read/write, otherwise it may be either read-only or read/write at the discretion of the exporter.

PyBUF_READ

為 穩定 ABI 的一部分 自 3.11 版本開始.

Flag to request a readonly buffer.

PyBUF_WRITE

為 穩定 ABI 的一部分 自 3.11 版本開始.

Flag to request a writable buffer.

PyObject *PyMemoryView_FromMemory(char *mem, Py_ssize_t size, int flags)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.7 版本開始.

Create a memoryview object using mem as the underlying buffer. flags can be one of PyBUF_READ or PyBUF_WRITE.

在 3.3 版被加入.

PyObject *PyMemoryView_FromBuffer(const Py_buffer *view)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.11 版本開始.

Create a memoryview object wrapping the given buffer structure view. For simple byte buffers, PyMemoryView_FromMemory() is the preferred function.

PyObject *PyMemoryView_GetContiguous(PyObject *obj, int buffertype, char order)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a memoryview object to a contiguous chunk of memory (in either 'C' or 'F'ortran order) from an object that defines the buffer interface. If memory is contiguous, the memoryview object points to the original memory. Otherwise, a copy is made and the memoryview points to a new bytes object.

buffertype can be one of PyBUF_READ or PyBUF_WRITE.

int PyMemoryView_Check(PyObject *obj)

Return true if the object obj is a memoryview object. It is not currently allowed to create subclasses of memoryview. This function always succeeds.

Py_buffer *PyMemoryView_GET_BUFFER(PyObject *mview)

Return a pointer to the memoryview's private copy of the exporter's buffer. mview must be a memoryview instance; this macro doesn't check its type, you must do it yourself or you will risk crashes.

PyObject *PyMemoryView_GET_BASE(PyObject *mview)

Return either a pointer to the exporting object that the memoryview is based on or NULL if the memoryview has been created by one of the functions PyMemoryView_FromMemory() or PyMemoryView_FromBuffer(). mview must be a memoryview instance.

Pickle buffer objects

在 3.8 版被加入.

A pickle.PickleBuffer object wraps a buffer-providing object for out-of-band data transfer with the pickle module.

PyTypeObject PyPickleBuffer_Type

This instance of PyTypeObject represents the Python pickle buffer type. This is the same object as pickle.PickleBuffer in the Python layer.

int PyPickleBuffer_Check(PyObject *op)

Return true if op is a pickle buffer instance. This function always succeeds.

PyObject *PyPickleBuffer_FromObject(PyObject *obj)

Create a pickle buffer from the object obj.

This function will fail if obj doesn't support the buffer protocol.

On success, return a new pickle buffer instance. On failure, set an exception and return NULL.

Analogous to calling pickle.PickleBuffer with obj in Python.

const Py_buffer *PyPickleBuffer_GetBuffer(PyObject *picklebuf)

Get a pointer to the underlying Py_buffer that the pickle buffer wraps.

The returned pointer is valid as long as picklebuf is alive and has not been released. The caller must not modify or free the returned Py_buffer. If the pickle buffer has been released, raise ValueError.

On success, return a pointer to the buffer view. On failure, set an exception and return NULL.

int PyPickleBuffer_Release(PyObject *picklebuf)

Release the underlying buffer held by the pickle buffer.

Return 0 on success. On failure, set an exception and return -1.

Analogous to calling pickle.PickleBuffer.release() in Python.

弱參照物件

Python supports weak references as first-class objects. There are two specific object types which directly implement weak references. The first is a simple reference object, and the second acts as a proxy for the original object as much as it can.

int PyWeakref_Check(PyObject *ob)

Return non-zero if ob is either a reference or proxy object. This function always succeeds.

int PyWeakref_CheckRef(PyObject *ob)

Return non-zero if ob is a reference object or a subclass of the reference type. This function always succeeds.

int PyWeakref_CheckRefExact(PyObject *ob)

Return non-zero if ob is a reference object, but not a subclass of the reference type. This function always succeeds.

int PyWeakref_CheckProxy(PyObject *ob)

Return non-zero if ob is a proxy object. This function always succeeds.

PyObject *PyWeakref_NewRef(PyObject *ob, PyObject *callback)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a weak reference object for the object ob. This will always return a new reference, but is not guaranteed to create a new object; an existing reference object may be returned. The second parameter, callback, can be a callable object that receives notification when ob is garbage collected; it should accept a single parameter, which will be the weak reference object itself. callback may also be None or NULL. If ob is not a weakly referenceable object, or if callback is not callable, None, or NULL, this will return NULL and raise TypeError.

也參考

PyType_SUPPORTS_WEAKREFS() for checking if ob is weakly referenceable.

PyObject *PyWeakref_NewProxy(PyObject *ob, PyObject *callback)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Return a weak reference proxy object for the object ob. This will always return a new reference, but is not guaranteed to create a new object; an existing proxy object may be returned. The second parameter, callback, can be a callable object that receives notification when ob is garbage collected; it should accept a single parameter, which will be the weak reference object itself. callback may also be None or NULL. If ob is not a weakly referenceable object, or if callback is not callable, None, or NULL, this will return NULL and raise TypeError.

也參考

PyType_SUPPORTS_WEAKREFS() for checking if ob is weakly referenceable.

int PyWeakref_GetRef(PyObject *ref, PyObject **pobj)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Get a strong reference to the referenced object from a weak reference, ref, into *pobj.

On success, set *pobj to a new strong reference to the referenced object and return 1.

If the reference is dead, set *pobj to NULL and return 0.

On error, raise an exception and return -1.

在 3.13 版被加入.

PyObject *PyWeakref_GetObject(PyObject *ref)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Return a borrowed reference to the referenced object from a weak reference, ref. If the referent is no longer live, returns Py_None.

備註

This function returns a borrowed reference to the referenced object. This means that you should always call Py_INCREF() on the object except when it cannot be destroyed before the last usage of the borrowed reference.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyWeakref_GetRef() instead.

PyObject *PyWeakref_GET_OBJECT(PyObject *ref)

回傳值：借用參照。

Similar to PyWeakref_GetObject(), but does no error checking.

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyWeakref_GetRef() instead.

int PyWeakref_IsDead(PyObject *ref)

Test if the weak reference ref is dead. Returns 1 if the reference is dead, 0 if it is alive, and -1 with an error set if ref is not a weak reference object.

在 3.14 版被加入.

void PyObject_ClearWeakRefs(PyObject *object)

為 穩定 ABI 的一部分.

This function is called by the tp_dealloc handler to clear weak references.

This iterates through the weak references for object and calls callbacks for those references which have one. It returns when all callbacks have been attempted.

void PyUnstable_Object_ClearWeakRefsNoCallbacks(PyObject *object)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Clears the weakrefs for object without calling the callbacks.

This function is called by the tp_dealloc handler for types with finalizers (i.e., __del__()). The handler for those objects first calls PyObject_ClearWeakRefs() to clear weakrefs and call their callbacks, then the finalizer, and finally this function to clear any weakrefs that may have been created by the finalizer.

In most circumstances, it's more appropriate to use PyObject_ClearWeakRefs() to clear weakrefs instead of this function.

在 3.13 版被加入.

Capsules

Refer to Providing a C API for an Extension Module for more information on using these objects.

在 3.1 版被加入.

type PyCapsule

This subtype of PyObject represents an opaque value, useful for C extension modules which need to pass an opaque value (as a void* pointer) through Python code to other C code. It is often used to make a C function pointer defined in one module available to other modules, so the regular import mechanism can be used to access C APIs defined in dynamically loaded modules.

PyTypeObject PyCapsule_Type

為 穩定 ABI 的一部分.

The type object corresponding to capsule objects. This is the same object as types.CapsuleType in the Python layer.

type PyCapsule_Destructor

為 穩定 ABI 的一部分.

The type of a destructor callback for a capsule. Defined as:

typedef void (*PyCapsule_Destructor)(PyObject *);

See PyCapsule_New() for the semantics of PyCapsule_Destructor callbacks.

int PyCapsule_CheckExact(PyObject *p)

Return true if its argument is a PyCapsule. This function always succeeds.

PyObject *PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor)

回傳值：新的參照。 為 穩定 ABI 的一部分.

Create a PyCapsule encapsulating the pointer. The pointer argument may not be NULL.

On failure, set an exception and return NULL.

The name string may either be NULL or a pointer to a valid C string. If non-NULL, this string must outlive the capsule. (Though it is permitted to free it inside the destructor.)

If the destructor argument is not NULL, it will be called with the capsule as its argument when it is destroyed.

If this capsule will be stored as an attribute of a module, the name should be specified as modulename.attributename. This will enable other modules to import the capsule using PyCapsule_Import().

void *PyCapsule_GetPointer(PyObject *capsule, const char *name)

為 穩定 ABI 的一部分.

Retrieve the pointer stored in the capsule. On failure, set an exception and return NULL.

The name parameter must compare exactly to the name stored in the capsule. If the name stored in the capsule is NULL, the name passed in must also be NULL. Python uses the C function strcmp() to compare capsule names.

PyCapsule_Destructor PyCapsule_GetDestructor(PyObject *capsule)

為 穩定 ABI 的一部分.

Return the current destructor stored in the capsule. On failure, set an exception and return NULL.

It is legal for a capsule to have a NULL destructor. This makes a NULL return code somewhat ambiguous; use PyCapsule_IsValid() or PyErr_Occurred() to disambiguate.

void *PyCapsule_GetContext(PyObject *capsule)

為 穩定 ABI 的一部分.

Return the current context stored in the capsule. On failure, set an exception and return NULL.

It is legal for a capsule to have a NULL context. This makes a NULL return code somewhat ambiguous; use PyCapsule_IsValid() or PyErr_Occurred() to disambiguate.

const char *PyCapsule_GetName(PyObject *capsule)

為 穩定 ABI 的一部分.

Return the current name stored in the capsule. On failure, set an exception and return NULL.

It is legal for a capsule to have a NULL name. This makes a NULL return code somewhat ambiguous; use PyCapsule_IsValid() or PyErr_Occurred() to disambiguate.

void *PyCapsule_Import(const char *name, int no_block)

為 穩定 ABI 的一部分.

Import a pointer to a C object from a capsule attribute in a module. The name parameter should specify the full name to the attribute, as in module.attribute. The name stored in the capsule must match this string exactly.

This function splits name on the . character, and imports the first element. It then processes further elements using attribute lookups.

Return the capsule's internal pointer on success. On failure, set an exception and return NULL.

備註

If name points to an attribute of some submodule or subpackage, this submodule or subpackage must be previously imported using other means (for example, by using PyImport_ImportModule()) for the attribute lookups to succeed.

在 3.3 版的變更: no_block has no effect anymore.

int PyCapsule_IsValid(PyObject *capsule, const char *name)

為 穩定 ABI 的一部分.

Determines whether or not capsule is a valid capsule. A valid capsule is non-NULL, passes PyCapsule_CheckExact(), has a non-NULL pointer stored in it, and its internal name matches the name parameter. (See PyCapsule_GetPointer() for information on how capsule names are compared.)

In other words, if PyCapsule_IsValid() returns a true value, calls to any of the accessors (any function starting with PyCapsule_Get) are guaranteed to succeed.

Return a nonzero value if the object is valid and matches the name passed in. Return 0 otherwise. This function will not fail.

int PyCapsule_SetContext(PyObject *capsule, void *context)

為 穩定 ABI 的一部分.

Set the context pointer inside capsule to context.

Return 0 on success. Return nonzero and set an exception on failure.

int PyCapsule_SetDestructor(PyObject *capsule, PyCapsule_Destructor destructor)

為 穩定 ABI 的一部分.

Set the destructor inside capsule to destructor.

Return 0 on success. Return nonzero and set an exception on failure.

int PyCapsule_SetName(PyObject *capsule, const char *name)

為 穩定 ABI 的一部分.

Set the name inside capsule to name. If non-NULL, the name must outlive the capsule. If the previous name stored in the capsule was not NULL, no attempt is made to free it.

Return 0 on success. Return nonzero and set an exception on failure.

int PyCapsule_SetPointer(PyObject *capsule, void *pointer)

為 穩定 ABI 的一部分.

Set the void pointer inside capsule to pointer. The pointer may not be NULL.

Return 0 on success. Return nonzero and set an exception on failure.

Frame 物件

type PyFrameObject

為 受限 API 的一部分 （做為一個不透明結構 (opaque struct)）.

用來描述 frame 物件的 C 結構。

在這個結構中沒有公開的成員。

在 3.11 版的變更: The members of this structure were removed from the public C API. Refer to the What's New entry for details.

The PyEval_GetFrame() and PyThreadState_GetFrame() functions can be used to get a frame object.

另請參閱 Reflection。

PyTypeObject PyFrame_Type

The type of frame objects. It is the same object as types.FrameType in the Python layer.

在 3.11 版的變更: Previously, this type was only available after including <frameobject.h>.

PyFrameObject *PyFrame_New(PyThreadState *tstate, PyCodeObject *code, PyObject *globals, PyObject *locals)

Create a new frame object. This function returns a strong reference to the new frame object on success, and returns NULL with an exception set on failure.

int PyFrame_Check(PyObject *obj)

Return non-zero if obj is a frame object.

在 3.11 版的變更: Previously, this function was only available after including <frameobject.h>.

PyFrameObject *PyFrame_GetBack(PyFrameObject *frame)

回傳值：新的參照。

Get the frame next outer frame.

Return a strong reference, or NULL if frame has no outer frame.

在 3.9 版被加入.

PyObject *PyFrame_GetBuiltins(PyFrameObject *frame)

回傳值：新的參照。

取得 frame 的 f_builtins 屬性。

回傳 strong reference。結果不能為 NULL。

在 3.11 版被加入.

PyCodeObject *PyFrame_GetCode(PyFrameObject *frame)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.10 版本開始.

Get the frame code.

回傳 strong reference。

The result (frame code) cannot be NULL.

在 3.9 版被加入.

PyObject *PyFrame_GetGenerator(PyFrameObject *frame)

回傳值：新的參照。

Get the generator, coroutine, or async generator that owns this frame, or NULL if this frame is not owned by a generator. Does not raise an exception, even if the return value is NULL.

回傳 strong reference 或 NULL。

在 3.11 版被加入.

PyObject *PyFrame_GetGlobals(PyFrameObject *frame)

回傳值：新的參照。

取得 frame 的 f_globals 屬性。

回傳 strong reference。結果不能為 NULL。

在 3.11 版被加入.

int PyFrame_GetLasti(PyFrameObject *frame)

取得 frame 的 f_lasti 屬性。

如果 frame.f_lasti 是 None 則回傳 -1。

在 3.11 版被加入.

PyObject *PyFrame_GetVar(PyFrameObject *frame, PyObject *name)

回傳值：新的參照。

取得 frame 的變數 name。

在成功時回傳變數值的 strong reference。

如果變數不存在，則引發 NameError 並回傳 NULL。

在錯誤時引發例外並回傳 NULL。

name 的型別必須是 str。

在 3.12 版被加入.

PyObject *PyFrame_GetVarString(PyFrameObject *frame, const char *name)

回傳值：新的參照。

Similar to PyFrame_GetVar(), but the variable name is a C string encoded in UTF-8.

在 3.12 版被加入.

PyObject *PyFrame_GetLocals(PyFrameObject *frame)

回傳值：新的參照。

Get the frame's f_locals attribute. If the frame refers to an optimized scope, this returns a write-through proxy object that allows modifying the locals. In all other cases (classes, modules, exec(), eval()) it returns the mapping representing the frame locals directly (as described for locals()).

回傳 strong reference。

在 3.11 版被加入.

在 3.13 版的變更: As part of PEP 667 [https://peps.python.org/pep-0667/], return an instance of PyFrameLocalsProxy_Type.

int PyFrame_GetLineNumber(PyFrameObject *frame)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Return the line number that frame is currently executing.

Frame Locals Proxies

在 3.13 版被加入.

The f_locals attribute on a frame object is an instance of a "frame-locals proxy". The proxy object exposes a write-through view of the underlying locals dictionary for the frame. This ensures that the variables exposed by f_locals are always up to date with the live local variables in the frame itself.

更多資訊請參閱 PEP 667 [https://peps.python.org/pep-0667/]。

PyTypeObject PyFrameLocalsProxy_Type

The type of frame locals() proxy objects.

int PyFrameLocalsProxy_Check(PyObject *obj)

Return non-zero if obj is a frame locals() proxy.

Legacy Local Variable APIs

These APIs are soft deprecated. As of Python 3.13, they do nothing. They exist solely for backwards compatibility.

void PyFrame_LocalsToFast(PyFrameObject *f, int clear)

This function is soft deprecated and does nothing.

Prior to Python 3.13, this function would copy the f_locals attribute of f to the internal "fast" array of local variables, allowing changes in frame objects to be visible to the interpreter. If clear was true, this function would process variables that were unset in the locals dictionary.

在 3.13 版的變更: This function now does nothing.

void PyFrame_FastToLocals(PyFrameObject *f)

This function is soft deprecated and does nothing.

Prior to Python 3.13, this function would copy the internal "fast" array of local variables (which is used by the interpreter) to the f_locals attribute of f, allowing changes in local variables to be visible to frame objects.

在 3.13 版的變更: This function now does nothing.

int PyFrame_FastToLocalsWithError(PyFrameObject *f)

This function is soft deprecated and does nothing.

Prior to Python 3.13, this function was similar to PyFrame_FastToLocals(), but would return 0 on success, and -1 with an exception set on failure.

在 3.13 版的變更: This function now does nothing.

也參考

PEP 667 [https://peps.python.org/pep-0667/]

Internal Frames

Unless using PEP 523 [https://peps.python.org/pep-0523/], you will not need this.

struct _PyInterpreterFrame

The interpreter's internal frame representation.

在 3.11 版被加入.

PyObject *PyUnstable_InterpreterFrame_GetCode(struct _PyInterpreterFrame *frame);

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Return a strong reference to the code object for the frame.

在 3.12 版被加入.

int PyUnstable_InterpreterFrame_GetLasti(struct _PyInterpreterFrame *frame);

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Return the byte offset into the last executed instruction.

在 3.12 版被加入.

int PyUnstable_InterpreterFrame_GetLine(struct _PyInterpreterFrame *frame);

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Return the currently executing line number, or -1 if there is no line number.

在 3.12 版被加入.

產生器 (Generator) 物件

產生器物件是 Python 用來實現產生器疊代器 (generator iterator) 的物件。它們通常透過疊代會產生值的函式來建立，而不是顯式呼叫 PyGen_New() 或 PyGen_NewWithQualName()。

type PyGenObject

用於產生器物件的 C 結構。

PyTypeObject PyGen_Type

與產生器物件對應的型別物件。

int PyGen_Check(PyObject *ob)

如果 ob 是一個產生器 (generator) 物件則回傳真值；ob 必須不為 NULL。此函式總是會成功執行。

int PyGen_CheckExact(PyObject *ob)

如果 ob 的型別是 PyGen_Type 則回傳真值；ob 必須不為 NULL。此函式總是會成功執行。

PyObject *PyGen_New(PyFrameObject *frame)

回傳值：新的參照。

基於 frame 物件建立並回傳一個新的產生器物件。此函式會取走一個對 frame 的參照 (reference)。引數必須不為 NULL。

PyObject *PyGen_NewWithQualName(PyFrameObject *frame, PyObject *name, PyObject *qualname)

回傳值：新的參照。

基於 frame 物件建立並回傳一個新的產生器物件，其中 __name__ 和 __qualname__ 設為 name 和 qualname。此函式會取走一個對 frame 的參照。frame 引數必須不為 NULL。

PyCodeObject *PyGen_GetCode(PyGenObject *gen)

回傳一個對 gen 所包裝的程式碼物件的新強參照。此函式總是會成功執行。

非同步產生器 (Asynchronous Generator) 物件

也參考

PEP 525 [https://peps.python.org/pep-0525/]

PyTypeObject PyAsyncGen_Type

與非同步產生器物件對應的型別物件。在 Python 層中可以 types.AsyncGeneratorType 使用。

在 3.6 版被加入.

PyObject *PyAsyncGen_New(PyFrameObject *frame, PyObject *name, PyObject *qualname)

建立一個包裝 frame 的非同步產生器，並將 __name__ 和 __qualname__ 設為 name 和 qualname。frame 會被此函式取走，且不得為 NULL。

成功時此函式回傳對新的非同步產生器的強參照。失敗時此函式回傳 NULL 並設定一個例外。

在 3.6 版被加入.

int PyAsyncGen_CheckExact(PyObject *op)

如果 op 是一個非同步產生器物件則回傳 true，否則回傳 false。此函式總是會成功執行。

在 3.6 版被加入.

已棄用的 API

PyAsyncGenASend_CheckExact(op)

這是一個被軟性棄用的 API，它被錯誤地包含在 Python 的 C API 中。

它僅僅是為了完整性而存在；請勿使用此 API。

Coroutine（協程）物件

在 3.5 版被加入.

Coroutine 物件是那些以 async 關鍵字來宣告的函式所回傳的物件。

type PyCoroObject

用於 coroutine 物件的 C 結構。

PyTypeObject PyCoro_Type

與 coroutine 物件對應的型別物件。

int PyCoro_CheckExact(PyObject *ob)

如果 ob 的型別是 PyCoro_Type 則回傳真值；ob 必須不為 NULL。此函式總是會執行成功。

PyObject *PyCoro_New(PyFrameObject *frame, PyObject *name, PyObject *qualname)

回傳值：新的參照。

基於 frame 物件來建立並回傳一個新的 coroutine 物件，其中 __name__ 和 __qualname__ 被設為 name 和 qualname。此函式會取得一個對 frame 的參照 (reference)。frame 引數必須不為 NULL。

情境變數物件（Context Variables Objects）

在 3.7 版被加入.

在 3.7.1 版的變更:

備註

在 Python 3.7.1 中所有情境變數 C API 的簽名都被改為使用 PyObject 指標，而不是 PyContext、PyContextVar 或 PyContextToken，例如：

// 在 3.7.0：
PyContext *PyContext_New(void);

// 在 3.7.1+：
PyObject *PyContext_New(void);

更多細節請見 bpo-34762 [https://bugs.python.org/issue?@action=redirect&bpo=34762]。

本節詳述 contextvars 模組的公開 C API。

type PyContext

用來代表 contextvars.Context 物件的 C 結構。

type PyContextVar

用來代表 contextvars.ContextVar 物件的 C 結構。

type PyContextToken

用來代表 contextvars.Token 物件的 C 結構。

PyTypeObject PyContext_Type

代表 context 型別的型別物件。

PyTypeObject PyContextVar_Type

代表 情境變數 型別的型別物件。

PyTypeObject PyContextToken_Type

代表 情境變數 token 型別的型別物件。

型別檢查巨集：

int PyContext_CheckExact(PyObject *o)

如果 o 的型別為 PyContext_Type 則回傳 true。o 不得為 NULL。此函式一定會成功回傳。

int PyContextVar_CheckExact(PyObject *o)

如果 o 的類型為 PyContextVar_Type 則回傳 true。o 不得為 NULL。此函式一定會成功回傳。

int PyContextToken_CheckExact(PyObject *o)

如果 o 的類型為 PyContextToken_Type 則回傳 true。 o 不得為 NULL。此函式一定會成功回傳。

情境物件管理函式：

PyObject *PyContext_New(void)

回傳值：新的參照。

建立一個新的空的情境物件。 如果發生錯誤，則回傳 NULL。

PyObject *PyContext_Copy(PyObject *ctx)

回傳值：新的參照。

建立傳入的 ctx 情境物件的淺層複製 (shallow copy)。如果發生錯誤，則回傳 NULL。

PyObject *PyContext_CopyCurrent(void)

回傳值：新的參照。

建立目前執行緒上的情境的淺層複製。如果發生錯誤，則回傳 NULL。

int PyContext_Enter(PyObject *ctx)

設定 ctx 為目前執行緒上的目前情境。成功時回傳 0，錯誤時回傳 -1。

int PyContext_Exit(PyObject *ctx)

關閉 ctx 情境，並將目前執行緒的目前情境設回之前的情境。 成功時回傳 0，錯誤時回傳 -1。

int PyContext_AddWatcher(PyContext_WatchCallback callback)

Register callback as a context object watcher for the current interpreter. Return an ID which may be passed to PyContext_ClearWatcher(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

在 3.14 版被加入.

int PyContext_ClearWatcher(int watcher_id)

Clear watcher identified by watcher_id previously returned from PyContext_AddWatcher() for the current interpreter. Return 0 on success, or -1 and set an exception on error (e.g. if the given watcher_id was never registered.)

在 3.14 版被加入.

type PyContextEvent

Enumeration of possible context object watcher events:

Py_CONTEXT_SWITCHED: The current context has switched to a different context. The object passed to the watch callback is the now-current contextvars.Context object, or None if no context is current.

在 3.14 版被加入.

typedef int (*PyContext_WatchCallback)(PyContextEvent event, PyObject *obj)

Context object watcher callback function. The object passed to the callback is event-specific; see PyContextEvent for details.

If the callback returns with an exception set, it must return -1; this exception will be printed as an unraisable exception using PyErr_FormatUnraisable(). Otherwise it should return 0.

There may already be a pending exception set on entry to the callback. In this case, the callback should return 0 with the same exception still set. This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first, and restores it before returning.

在 3.14 版被加入.

情境變數函式：

PyObject *PyContextVar_New(const char *name, PyObject *def)

回傳值：新的參照。

建立一個新的 ContextVar 物件。name 參數用於自我檢查（introspection）和除錯目的。def 參數指定情境變數的預設值，亦可用 NULL 表示沒有預設值。 如果發生錯誤，此函式會回傳 NULL。

int PyContextVar_Get(PyObject *var, PyObject *default_value, PyObject **value)

取得情境變數的值。如果在查找過程中發生錯誤則回傳 -1，如果沒有發生錯誤則無論是否找到值都會回傳 0。

如果找到情境變數，value 將會是指向它的指標。如果 沒有 找到情境變數，value 將會指到：

default_value 預設值，但前提是預設值不是 NULL；

var 的預設值，但前提是預設值不是 NULL；

NULL

除了 NULL 之外，此函式會回傳一個新的參照（reference）。

PyObject *PyContextVar_Set(PyObject *var, PyObject *value)

回傳值：新的參照。

在目前的情境中將 var 的值設為 value。會回傳一個用來代表此變更的新 token 物件，如果發生錯誤則回傳 NULL。

int PyContextVar_Reset(PyObject *var, PyObject *token)

將 var 情境變數的狀態設回之前的狀態，亦即上一次回傳 token 的 PyContextVar_Set() 被呼叫前的狀態。此函式在成功時回傳 0，錯誤時回傳 -1。

型別提示物件

提供了數個用於型別提示的內建型別。目前有兩種 -- GenericAlias 和 Union。只有 GenericAlias 有公開 (expose) 給 C。

PyObject *Py_GenericAlias(PyObject *origin, PyObject *args)

為 穩定 ABI 的一部分 自 3.9 版本開始.

建立一個 GenericAlias 物件，等同於呼叫 Python 的 types.GenericAlias class。 origin 和 args 引數分別設定了 GenericAlias 的 __origin__ 與 __args__ 屬性。origin 應該要是個 PyTypeObject* 且 args 可以是個 PyTupleObject* 或任意 PyObject*。如果傳入的 args 不是個 tuple（元組），則會自動建立一個長度為 1 的 tuple 且 __args__ 會被設為 (args,)。只會進行最少的引數檢查，所以即便 origin 不是個型別，函式也會不會失敗。 GenericAlias 的 __parameters__ 屬性會自 __args__ 惰性地建立 (constructed lazily)。當失敗時，會引發一個例外並回傳 NULL。

以下是個讓一個擴充型別泛用化 (generic) 的例子：

...
static PyMethodDef my_obj_methods[] = {
    // 其他方法。
    ...
    {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, "See PEP 585"}
    ...
}

也參考

資料模型方法 __class_getitem__()。

在 3.9 版被加入.

PyTypeObject Py_GenericAliasType

為 穩定 ABI 的一部分 自 3.9 版本開始.

Py_GenericAlias() 所回傳該物件的 C 型別。等價於 Python 中的 types.GenericAlias。

在 3.9 版被加入.

Curses C API

curses 為擴充模組公開了一個小型的 C 介面。使用者必須包含標頭檔 py_curses.h（此檔案不會由 Python.h 預設包含），並且必須觸發 import_curses() 以填充 (populate) PyCurses_API，通常是作為模組初始化函式的一部分。

警告

Neither the C API nor the pure Python curses module are compatible with subinterpreters.

import_curses()

引入 curses C API。呼叫此巨集不需要寫分號。

On success, populate the PyCurses_API pointer.

On failure, set PyCurses_API to NULL and set an exception. The caller must check if an error occurred via PyErr_Occurred():

import_curses();  // 建議要寫分號但非必要
if (PyErr_Occurred()) { /* 清理 */ }

void **PyCurses_API

Dynamically allocated object containing the curses C API. This variable is only available once import_curses succeeds.

PyCurses_API[0] corresponds to PyCursesWindow_Type.

PyCurses_API[1]、PyCurses_API[2] 和 PyCurses_API[3] 是指向 型別為 int (*)(void) 的謂詞函式 (predicate functions) 的指標。

When called, these predicates return whether curses.setupterm(), curses.initscr(), and curses.start_color() have been called respectively.

See also the convenience macros PyCursesSetupTermCalled, PyCursesInitialised, and PyCursesInitialisedColor.

備註

The number of entries in this structure is subject to changes. Consider using PyCurses_API_pointers to check if new fields are available or not.

PyCurses_API_pointers

The number of accessible fields (4) in PyCurses_API. This number is incremented whenever new fields are added.

PyTypeObject PyCursesWindow_Type

The heap type corresponding to curses.window.

int PyCursesWindow_Check(PyObject *op)

如果 op 是 curses.window 實例則回傳 true，否則回傳 false。

The following macros are convenience macros expanding into C statements. In particular, they can only be used as macro; or macro, but not macro() or macro();.

PyCursesSetupTermCalled

如果已呼叫 curses.setupterm()，則為巨集檢查。

巨集展開大致相當於：

{
    typedef int (*predicate_t)(void);
    predicate_t was_setupterm_called = (predicate_t)PyCurses_API[1];
    if (!was_setupterm_called()) {
        return NULL;
    }
}

PyCursesInitialised

如果已呼叫 curses.initscr()，則為巨集檢查。

巨集展開大致相當於：

{
    typedef int (*predicate_t)(void);
    predicate_t was_initscr_called = (predicate_t)PyCurses_API[2];
    if (!was_initscr_called()) {
        return NULL;
    }
}

PyCursesInitialisedColor

如果已呼叫 curses.start_color()，則為巨集檢查。

巨集展開大致相當於：

{
    typedef int (*predicate_t)(void);
    predicate_t was_start_color_called = (predicate_t)PyCurses_API[3];
    if (!was_start_color_called()) {
        return NULL;
    }
}

內部資料

以下物件由 C API 所公開，但應視為僅供內部使用。

PyCurses_CAPSULE_NAME

Name of the curses capsule to pass to PyCapsule_Import().

僅供內部使用。請改用 import_curses。

DateTime 物件

datetime 模組提供各種日期和時間物件。在使用任何這些函式之前，必須將標頭檔 datetime.h 引入於原始碼中（請注意，Python.h 並無引入該標頭檔），且巨集 PyDateTime_IMPORT 必須被叫用，而這通常作為模組初始化函式的一部分。該巨集將指向 C 結構的指標放入靜態變數 PyDateTimeAPI 中，該變數會被以下巨集使用。

PyDateTime_IMPORT()

引入 datetime C API。

成功時填充 (populate) PyDateTimeAPI 指標。失敗時將 PyDateTimeAPI 設為 NULL 並設定一個例外。呼叫者必須透過 PyErr_Occurred() 檢查是否發生錯誤：

PyDateTime_IMPORT;
if (PyErr_Occurred()) { /* cleanup */ }

警告

這和子直譯器 (subinterpreters) 不相容。

type PyDateTime_CAPI

包含 datetime C API 欄位的結構。

此結構的欄位為私有且可能會變動。

不要直接使用這個；請改用 PyDateTime_* API。

PyDateTime_CAPI *PyDateTimeAPI

動態配置的物件，包含 datetime C API。

此變數僅在 PyDateTime_IMPORT 成功後可用。

type PyDateTime_Date

此 PyObject 子型別代表 Python date 物件

type PyDateTime_DateTime

此 PyObject 子型別代表 Python datetime 物件

type PyDateTime_Time

此 PyObject 子型別代表 Python time 物件

type PyDateTime_Delta

此 PyObject 子型別代表兩個 datetime 物件的差值

PyTypeObject PyDateTime_DateType

此 PyTypeObject 實例代表 Python date 型別，與 Python layer 中的 datetime.date 是同一物件

PyTypeObject PyDateTime_DateTimeType

此 PyTypeObject 實例代表 Python datetime 型別，與 Python layer 中的 datetime.datetime 是同一物件

PyTypeObject PyDateTime_TimeType

此 PyTypeObject 實例代表 Python time 型別，與 Python layer 中的 datetime.time 是同一物件

PyTypeObject PyDateTime_DeltaType

此 PyTypeObject 實例代表 Python 兩個 datetime 物件的型別，與 Python layer 中的 datetime.timedelta 是同一物件

PyTypeObject PyDateTime_TZInfoType

此 PyTypeObject 實例代表 Python 時區資訊型別，與 Python layer 中的 datetime.tzinfo 是同一物件

用於存取 UTC 單例 (singleton) 的巨集：

PyObject *PyDateTime_TimeZone_UTC

回傳表示 UTC 的時區單例，是與 datetime.timezone.utc 相同的物件。

在 3.7 版被加入.

型別檢查巨集：

int PyDate_Check(PyObject *ob)

如果 ob 的型別為 PyDateTime_DateType 或 PyDateTime_DateType 的子型別，則回傳 true。 ob 不得為 NULL。這個函式一定會執行成功。

int PyDate_CheckExact(PyObject *ob)

如果 ob 的型別為 PyDateTime_DateType，則回傳 true。 ob 不得為 NULL。這個函式一定會執行成功。

int PyDateTime_Check(PyObject *ob)

如果 ob 的型別為 PyDateTime_DateTimeType 或 PyDateTime_DateTimeType 的子型別，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyDateTime_CheckExact(PyObject *ob)

如果 ob 的型別為 PyDateTime_DateTimeType，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyTime_Check(PyObject *ob)

如果 ob 的型別為 PyDateTime_TimeType 或 PyDateTime_TimeType 的子型別，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyTime_CheckExact(PyObject *ob)

如果 ob 的型別為 PyDateTime_TimeType，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyDelta_Check(PyObject *ob)

如果 ob 的型別為 PyDateTime_DeltaType 或 PyDateTime_DeltaType 的子型別，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyDelta_CheckExact(PyObject *ob)

如果 ob 的型別為 PyDateTime_DeltaType，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyTZInfo_Check(PyObject *ob)

如果 ob 的型別為 PyDateTime_TZInfoType 或 PyDateTime_TZInfoType 的子型別，則回傳 true。ob 不得為 NULL。這個函式一定會執行成功。

int PyTZInfo_CheckExact(PyObject *ob)

如果 ob 的型別為 PyDateTime_TZInfoType，則回傳 true。 ob 不得為 NULL。這個函式一定會執行成功。

建立物件的巨集：

PyObject *PyDate_FromDate(int year, int month, int day)

回傳值：新的參照。

回傳一個有特定年、月、日的物件 datetime.date。

PyObject *PyDateTime_FromDateAndTime(int year, int month, int day, int hour, int minute, int second, int usecond)

回傳值：新的參照。

回傳一個有特定年、月、日、時、分、秒、微秒的物件 datetime.datetime。

PyObject *PyDateTime_FromDateAndTimeAndFold(int year, int month, int day, int hour, int minute, int second, int usecond, int fold)

回傳值：新的參照。

回傳一個有特定年、月、日、時、分、秒、微秒與 fold（時間折疊）的物件 datetime.datetime。

在 3.6 版被加入.

PyObject *PyTime_FromTime(int hour, int minute, int second, int usecond)

回傳值：新的參照。

回傳一個有特定時、分、秒、微秒的物件 datetime.time。

PyObject *PyTime_FromTimeAndFold(int hour, int minute, int second, int usecond, int fold)

回傳值：新的參照。

回傳一個有特定時、分、秒、微秒與 fold（時間折疊）的物件 datetime.time。

在 3.6 版被加入.

PyObject *PyDelta_FromDSU(int days, int seconds, int useconds)

回傳值：新的參照。

回傳一個 datetime.timedelta 物件，表示給定的天數、秒數和微秒數。執行標準化 (normalization) 以便生成的微秒數和秒數位於 datetime.timedelta 物件記錄的範圍內。

PyObject *PyTimeZone_FromOffset(PyObject *offset)

回傳值：新的參照。

回傳一個 datetime.timezone 物件，其未命名的固定偏移量由 offset 引數表示。

在 3.7 版被加入.

PyObject *PyTimeZone_FromOffsetAndName(PyObject *offset, PyObject *name)

回傳值：新的參照。

回傳一個 datetime.timezone 物件，其固定偏移量由 offset 引數表示，並帶有 tzname name。

在 3.7 版被加入.

從 date 物件中提取欄位的巨集。引數必須是個 PyDateTime_Date 的實例，包括子類別（例如 PyDateTime_DateTime）。引數不得為 NULL，並且不會檢查型別：

int PyDateTime_GET_YEAR(PyDateTime_Date *o)

回傳年份，為正整數。

int PyDateTime_GET_MONTH(PyDateTime_Date *o)

回傳月份，為正整數，從 1 到 12。

int PyDateTime_GET_DAY(PyDateTime_Date *o)

回傳日期，為正整數，從 1 到 31。

從 datetime 物件中提取欄位的巨集。引數必須是個 PyDateTime_DateTime 的實例，包括子類別。引數不得為 NULL，並且不會檢查型別：

int PyDateTime_DATE_GET_HOUR(PyDateTime_DateTime *o)

回傳小時，為正整數，從 0 到 23。

int PyDateTime_DATE_GET_MINUTE(PyDateTime_DateTime *o)

回傳分鐘，為正整數，從 0 到 59。

int PyDateTime_DATE_GET_SECOND(PyDateTime_DateTime *o)

回傳秒，為正整數，從0 到59。

int PyDateTime_DATE_GET_MICROSECOND(PyDateTime_DateTime *o)

回傳微秒，為正整數，從 0 到 999999。

int PyDateTime_DATE_GET_FOLD(PyDateTime_DateTime *o)

回傳 fold，為 0 或 1 的正整數。

在 3.6 版被加入.

PyObject *PyDateTime_DATE_GET_TZINFO(PyDateTime_DateTime *o)

回傳 tzinfo（可能是 None）。

在 3.10 版被加入.

從 time 物件中提取欄位的巨集。引數必須是個 PyDateTime_Time 的實例，包括子類別。引數不得為 NULL，並且不會檢查型別：

int PyDateTime_TIME_GET_HOUR(PyDateTime_Time *o)

回傳小時，為正整數，從 0 到 23。

int PyDateTime_TIME_GET_MINUTE(PyDateTime_Time *o)

回傳分鐘，為正整數，從 0 到 59。

int PyDateTime_TIME_GET_SECOND(PyDateTime_Time *o)

回傳秒，為正整數，從0 到59。

int PyDateTime_TIME_GET_MICROSECOND(PyDateTime_Time *o)

回傳微秒，為正整數，從 0 到 999999。

int PyDateTime_TIME_GET_FOLD(PyDateTime_Time *o)

回傳 fold，為 0 或 1 的正整數。

在 3.6 版被加入.

PyObject *PyDateTime_TIME_GET_TZINFO(PyDateTime_Time *o)

回傳 tzinfo（可能是 None）。

在 3.10 版被加入.

從 time delta 物件中提取欄位的巨集。引數必須是個 PyDateTime_Delta 的實例，包括子類別。引數不能為 NULL，並且不會檢查型別：

int PyDateTime_DELTA_GET_DAYS(PyDateTime_Delta *o)

以 -999999999 到 999999999 之間的整數形式回傳天數。

在 3.3 版被加入.

int PyDateTime_DELTA_GET_SECONDS(PyDateTime_Delta *o)

以 0 到 86399 之間的整數形式回傳秒數。

在 3.3 版被加入.

int PyDateTime_DELTA_GET_MICROSECONDS(PyDateTime_Delta *o)

以 0 到 999999 之間的整數形式回傳微秒數。

在 3.3 版被加入.

為了方便模組實作 DB API 的巨集：

PyObject *PyDateTime_FromTimestamp(PyObject *args)

回傳值：新的參照。

給定一個適合傳遞給 datetime.datetime.fromtimestamp() 的引數元組，建立並回傳一個新的 datetime.datetime 物件。

PyObject *PyDate_FromTimestamp(PyObject *args)

回傳值：新的參照。

給定一個適合傳遞給 datetime.date.fromtimestamp() 的引數元組，建立並回傳一個新的 datetime.date 物件。

內部資料

以下符號由 C API 公開，但應視為僅供內部使用。

PyDateTime_CAPSULE_NAME

傳遞給 PyCapsule_Import() 的 datetime capsule 名稱。

僅供內部使用。請改用 PyDateTime_IMPORT。

初始化、終結化與執行緒

關於如何在初始化之前設定直譯器的細節，請參見 Python 初始化設定。

Python 初始化之前

In an application embedding Python, the Py_Initialize() function must be called before using any other Python/C API functions; with the exception of a few functions and the global configuration variables.

The following functions can be safely called before Python is initialized:

Functions that initialize the interpreter:

Py_Initialize()

Py_InitializeEx()

Py_InitializeFromConfig()

Py_BytesMain()

Py_Main()

the runtime pre-initialization functions covered in Python 初始化設定

Configuration functions:

PyImport_AppendInittab()

PyImport_ExtendInittab()

PyInitFrozenExtensions()

PyMem_SetAllocator()

PyMem_SetupDebugHooks()

PyObject_SetArenaAllocator()

Py_SetProgramName()

Py_SetPythonHome()

PySys_ResetWarnOptions()

the configuration functions covered in Python 初始化設定

Informative functions:

Py_IsInitialized()

PyMem_GetAllocator()

PyObject_GetArenaAllocator()

Py_GetBuildInfo()

Py_GetCompiler()

Py_GetCopyright()

Py_GetPlatform()

Py_GetVersion()

Py_IsInitialized()

Utilities:

Py_DecodeLocale()

the status reporting and utility functions covered in Python 初始化設定

Memory allocators:

PyMem_RawMalloc()

PyMem_RawRealloc()

PyMem_RawCalloc()

PyMem_RawFree()

Synchronization:

PyMutex_Lock()

PyMutex_Unlock()

備註

Despite their apparent similarity to some of the functions listed above, the following functions should not be called before the interpreter has been initialized: Py_EncodeLocale(), Py_GetPath(), Py_GetPrefix(), Py_GetExecPrefix(), Py_GetProgramFullPath(), Py_GetPythonHome(), Py_GetProgramName(), PyEval_InitThreads(), and Py_RunMain().

Global configuration variables

Python has variables for the global configuration to control different features and options. By default, these flags are controlled by command line options.

When a flag is set by an option, the value of the flag is the number of times that the option was set. For example, -b sets Py_BytesWarningFlag to 1 and -bb sets Py_BytesWarningFlag to 2.

int Py_BytesWarningFlag

This API is kept for backward compatibility: setting PyConfig.bytes_warning should be used instead, see Python Initialization Configuration.

Issue a warning when comparing bytes or bytearray with str or bytes with int. Issue an error if greater or equal to 2.

由 -b 選項設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_DebugFlag

This API is kept for backward compatibility: setting PyConfig.parser_debug should be used instead, see Python Initialization Configuration.

Turn on parser debugging output (for expert only, depending on compilation options).

由 -d 選項與 PYTHONDEBUG 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_DontWriteBytecodeFlag

This API is kept for backward compatibility: setting PyConfig.write_bytecode should be used instead, see Python Initialization Configuration.

If set to non-zero, Python won't try to write .pyc files on the import of source modules.

由 -B 選項與 PYTHONDONTWRITEBYTECODE 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_FrozenFlag

This API is kept for backward compatibility: setting PyConfig.pathconfig_warnings should be used instead, see Python Initialization Configuration.

Suppress error messages when calculating the module search path in Py_GetPath().

Private flag used by _freeze_module and frozenmain programs.

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_HashRandomizationFlag

This API is kept for backward compatibility: setting PyConfig.hash_seed and PyConfig.use_hash_seed should be used instead, see Python Initialization Configuration.

如果環境變數 PYTHONHASHSEED 被設定為一個非空字串則設為 1。

If the flag is non-zero, read the PYTHONHASHSEED environment variable to initialize the secret hash seed.

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_IgnoreEnvironmentFlag

This API is kept for backward compatibility: setting PyConfig.use_environment should be used instead, see Python Initialization Configuration.

忽略所有可能被設定的 PYTHON* 環境變數，例如 PYTHONPATH 與 PYTHONHOME。

由 -E 與 -I 選項設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_InspectFlag

This API is kept for backward compatibility: setting PyConfig.inspect should be used instead, see Python Initialization Configuration.

When a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command, even when sys.stdin does not appear to be a terminal.

由 -i 選項與 PYTHONINSPECT 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_InteractiveFlag

This API is kept for backward compatibility: setting PyConfig.interactive should be used instead, see Python Initialization Configuration.

由 -i 選項設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_IsolatedFlag

This API is kept for backward compatibility: setting PyConfig.isolated should be used instead, see Python Initialization Configuration.

Run Python in isolated mode. In isolated mode sys.path contains neither the script's directory nor the user's site-packages directory.

由 -I 選項設定。

在 3.4 版被加入.

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_LegacyWindowsFSEncodingFlag

This API is kept for backward compatibility: setting PyPreConfig.legacy_windows_fs_encoding should be used instead, see Python Initialization Configuration.

If the flag is non-zero, use the mbcs encoding with replace error handler, instead of the UTF-8 encoding with surrogatepass error handler, for the filesystem encoding and error handler.

如果環境變數 PYTHONLEGACYWINDOWSFSENCODING 被設定為一個非空字串則設為 1。

更多詳情請見 PEP 529 [https://peps.python.org/pep-0529/]。

可用性: Windows.

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_LegacyWindowsStdioFlag

This API is kept for backward compatibility: setting PyConfig.legacy_windows_stdio should be used instead, see Python Initialization Configuration.

If the flag is non-zero, use io.FileIO instead of io._WindowsConsoleIO for sys standard streams.

Set to 1 if the PYTHONLEGACYWINDOWSSTDIO environment variable is set to a non-empty string.

更多詳情請見 PEP 528 [https://peps.python.org/pep-0528/]。

可用性: Windows.

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_NoSiteFlag

This API is kept for backward compatibility: setting PyConfig.site_import should be used instead, see Python Initialization Configuration.

Disable the import of the module site and the site-dependent manipulations of sys.path that it entails. Also disable these manipulations if site is explicitly imported later (call site.main() if you want them to be triggered).

由 -S 選項設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_NoUserSiteDirectory

This API is kept for backward compatibility: setting PyConfig.user_site_directory should be used instead, see Python Initialization Configuration.

Don't add the user site-packages directory to sys.path.

由 -s 選項、-I 選項與 PYTHONNOUSERSITE 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_OptimizeFlag

This API is kept for backward compatibility: setting PyConfig.optimization_level should be used instead, see Python Initialization Configuration.

由 -O 選項與 PYTHONOPTIMIZE 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_QuietFlag

This API is kept for backward compatibility: setting PyConfig.quiet should be used instead, see Python Initialization Configuration.

Don't display the copyright and version messages even in interactive mode.

由 -q 選項設定。

在 3.2 版被加入.

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_UnbufferedStdioFlag

This API is kept for backward compatibility: setting PyConfig.buffered_stdio should be used instead, see Python Initialization Configuration.

Force the stdout and stderr streams to be unbuffered.

由 -u 選項與 PYTHONUNBUFFERED 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

int Py_VerboseFlag

This API is kept for backward compatibility: setting PyConfig.verbose should be used instead, see Python Initialization Configuration.

Print a message each time a module is initialized, showing the place (filename or built-in module) from which it is loaded. If greater or equal to 2, print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit.

由 -v 選項與 PYTHONVERBOSE 環境變數設定。

自從版本 3.12 後不推薦使用，將會自版本 3.15 中移除。.

Initializing and finalizing the interpreter

void Py_Initialize()

為 穩定 ABI 的一部分.

Initialize the Python interpreter. In an application embedding Python, this should be called before using any other Python/C API functions; see Before Python Initialization for the few exceptions.

This initializes the table of loaded modules (sys.modules), and creates the fundamental modules builtins, __main__ and sys. It also initializes the module search path (sys.path). It does not set sys.argv; use the Python Initialization Configuration API for that. This is a no-op when called for a second time (without calling Py_FinalizeEx() first). There is no return value; it is a fatal error if the initialization fails.

Use Py_InitializeFromConfig() to customize the Python Initialization Configuration.

備註

On Windows, changes the console mode from O_TEXT to O_BINARY, which will also affect non-Python uses of the console using the C Runtime.

void Py_InitializeEx(int initsigs)

為 穩定 ABI 的一部分.

This function works like Py_Initialize() if initsigs is 1. If initsigs is 0, it skips initialization registration of signal handlers, which may be useful when CPython is embedded as part of a larger application.

Use Py_InitializeFromConfig() to customize the Python Initialization Configuration.

PyStatus Py_InitializeFromConfig(const PyConfig *config)

Initialize Python from config configuration, as described in Initialization with PyConfig.

See the Python 初始化設定 section for details on pre-initializing the interpreter, populating the runtime configuration structure, and querying the returned status structure.

int Py_IsInitialized()

為 穩定 ABI 的一部分.

Return true (nonzero) when the Python interpreter has been initialized, false (zero) if not. After Py_FinalizeEx() is called, this returns false until Py_Initialize() is called again.

int Py_IsFinalizing()

為 穩定 ABI 的一部分 自 3.13 版本開始.

Return true (non-zero) if the main Python interpreter is shutting down. Return false (zero) otherwise.

在 3.13 版被加入.

int Py_FinalizeEx()

為 穩定 ABI 的一部分 自 3.6 版本開始.

Undo all initializations made by Py_Initialize() and subsequent use of Python/C API functions, and destroy all sub-interpreters (see Py_NewInterpreter() below) that were created and not yet destroyed since the last call to Py_Initialize(). This is a no-op when called for a second time (without calling Py_Initialize() again first).

Since this is the reverse of Py_Initialize(), it should be called in the same thread with the same interpreter active. That means the main thread and the main interpreter. This should never be called while Py_RunMain() is running.

Normally the return value is 0. If there were errors during finalization (flushing buffered data), -1 is returned.

Note that Python will do a best effort at freeing all memory allocated by the Python interpreter. Therefore, any C-Extension should make sure to correctly clean up all of the preveiously allocated PyObjects before using them in subsequent calls to Py_Initialize(). Otherwise it could introduce vulnerabilities and incorrect behavior.

This function is provided for a number of reasons. An embedding application might want to restart Python without having to restart the application itself. An application that has loaded the Python interpreter from a dynamically loadable library (or DLL) might want to free all memory allocated by Python before unloading the DLL. During a hunt for memory leaks in an application a developer might want to free all memory allocated by Python before exiting from the application.

Bugs and caveats: The destruction of modules and objects in modules is done in random order; this may cause destructors (__del__() methods) to fail when they depend on other objects (even functions) or modules. Dynamically loaded extension modules loaded by Python are not unloaded. Small amounts of memory allocated by the Python interpreter may not be freed (if you find a leak, please report it). Memory tied up in circular references between objects is not freed. Interned strings will all be deallocated regardless of their reference count. Some memory allocated by extension modules may not be freed. Some extensions may not work properly if their initialization routine is called more than once; this can happen if an application calls Py_Initialize() and Py_FinalizeEx() more than once. Py_FinalizeEx() must not be called recursively from within itself. Therefore, it must not be called by any code that may be run as part of the interpreter shutdown process, such as atexit handlers, object finalizers, or any code that may be run while flushing the stdout and stderr files.

引發一個不附帶引數的稽核事件 cpython._PySys_ClearAuditHooks。

在 3.6 版被加入.

void Py_Finalize()

為 穩定 ABI 的一部分.

This is a backwards-compatible version of Py_FinalizeEx() that disregards the return value.

int Py_BytesMain(int argc, char **argv)

為 穩定 ABI 的一部分 自 3.8 版本開始.

Similar to Py_Main() but argv is an array of bytes strings, allowing the calling application to delegate the text decoding step to the CPython runtime.

在 3.8 版被加入.

int Py_Main(int argc, wchar_t **argv)

為 穩定 ABI 的一部分.

The main program for the standard interpreter, encapsulating a full initialization/finalization cycle, as well as additional behaviour to implement reading configurations settings from the environment and command line, and then executing __main__ in accordance with 命令列.

This is made available for programs which wish to support the full CPython command line interface, rather than just embedding a Python runtime in a larger application.

The argc and argv parameters are similar to those which are passed to a C program's main() function, except that the argv entries are first converted to wchar_t using Py_DecodeLocale(). It is also important to note that the argument list entries may be modified to point to strings other than those passed in (however, the contents of the strings pointed to by the argument list are not modified).

The return value is 2 if the argument list does not represent a valid Python command line, and otherwise the same as Py_RunMain().

In terms of the CPython runtime configuration APIs documented in the runtime configuration section (and without accounting for error handling), Py_Main is approximately equivalent to:

PyConfig config;
PyConfig_InitPythonConfig(&config);
PyConfig_SetArgv(&config, argc, argv);
Py_InitializeFromConfig(&config);
PyConfig_Clear(&config);

Py_RunMain();

In normal usage, an embedding application will call this function instead of calling Py_Initialize(), Py_InitializeEx() or Py_InitializeFromConfig() directly, and all settings will be applied as described elsewhere in this documentation. If this function is instead called after a preceding runtime initialization API call, then exactly which environmental and command line configuration settings will be updated is version dependent (as it depends on which settings correctly support being modified after they have already been set once when the runtime was first initialized).

int Py_RunMain(void)

Executes the main module in a fully configured CPython runtime.

Executes the command (PyConfig.run_command), the script (PyConfig.run_filename) or the module (PyConfig.run_module) specified on the command line or in the configuration. If none of these values are set, runs the interactive Python prompt (REPL) using the __main__ module's global namespace.

If PyConfig.inspect is not set (the default), the return value will be 0 if the interpreter exits normally (that is, without raising an exception), the exit status of an unhandled SystemExit, or 1 for any other unhandled exception.

If PyConfig.inspect is set (such as when the -i option is used), rather than returning when the interpreter exits, execution will instead resume in an interactive Python prompt (REPL) using the __main__ module's global namespace. If the interpreter exited with an exception, it is immediately raised in the REPL session. The function return value is then determined by the way the REPL session terminates: 0, 1, or the status of a SystemExit, as specified above.

This function always finalizes the Python interpreter before it returns.

See Python Configuration for an example of a customized Python that always runs in isolated mode using Py_RunMain().

int PyUnstable_AtExit(PyInterpreterState *interp, void (*func)(void*), void *data)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Register an atexit callback for the target interpreter interp. This is similar to Py_AtExit(), but takes an explicit interpreter and data pointer for the callback.

There must be an attached thread state for interp.

在 3.13 版被加入.

Process-wide parameters

void Py_SetProgramName(const wchar_t *name)

為 穩定 ABI 的一部分.

This API is kept for backward compatibility: setting PyConfig.program_name should be used instead, see Python Initialization Configuration.

This function should be called before Py_Initialize() is called for the first time, if it is called at all. It tells the interpreter the value of the argv[0] argument to the main() function of the program (converted to wide characters). This is used by Py_GetPath() and some other functions below to find the Python run-time libraries relative to the interpreter executable. The default value is 'python'. The argument should point to a zero-terminated wide character string in static storage whose contents will not change for the duration of the program's execution. No code in the Python interpreter will change the contents of this storage.

Use Py_DecodeLocale() to decode a bytes string to get a wchar_t* string.

自從版本 3.11 後不推薦使用，將會自版本 3.15 中移除。.

wchar_t *Py_GetProgramName()

為 穩定 ABI 的一部分.

Return the program name set with PyConfig.program_name, or the default. The returned string points into static storage; the caller should not modify its value.

此函式不應該在 Py_Initialize() 之前呼叫，否則會回傳 NULL。

在 3.10 版的變更: 如果在 Py_Initialize() 之前呼叫，現在會回傳 NULL。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyConfig_Get("executable") (sys.executable) instead.

wchar_t *Py_GetPrefix()

為 穩定 ABI 的一部分.

Return the prefix for installed platform-independent files. This is derived through a number of complicated rules from the program name set with PyConfig.program_name and some environment variables; for example, if the program name is '/usr/local/bin/python', the prefix is '/usr/local'. The returned string points into static storage; the caller should not modify its value. This corresponds to the prefix variable in the top-level Makefile and the --prefix argument to the configure script at build time. The value is available to Python code as sys.base_prefix. It is only useful on Unix. See also the next function.

此函式不應該在 Py_Initialize() 之前呼叫，否則會回傳 NULL。

在 3.10 版的變更: 如果在 Py_Initialize() 之前呼叫，現在會回傳 NULL。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyConfig_Get("base_prefix") (sys.base_prefix) instead. Use PyConfig_Get("prefix") (sys.prefix) if virtual environments need to be handled.

wchar_t *Py_GetExecPrefix()

為 穩定 ABI 的一部分.

Return the exec-prefix for installed platform-dependent files. This is derived through a number of complicated rules from the program name set with PyConfig.program_name and some environment variables; for example, if the program name is '/usr/local/bin/python', the exec-prefix is '/usr/local'. The returned string points into static storage; the caller should not modify its value. This corresponds to the exec_prefix variable in the top-level Makefile and the --exec-prefix argument to the configure script at build time. The value is available to Python code as sys.base_exec_prefix. It is only useful on Unix.

Background: The exec-prefix differs from the prefix when platform dependent files (such as executables and shared libraries) are installed in a different directory tree. In a typical installation, platform dependent files may be installed in the /usr/local/plat subtree while platform independent may be installed in /usr/local.

Generally speaking, a platform is a combination of hardware and software families, e.g. Sparc machines running the Solaris 2.x operating system are considered the same platform, but Intel machines running Solaris 2.x are another platform, and Intel machines running Linux are yet another platform. Different major revisions of the same operating system generally also form different platforms. Non-Unix operating systems are a different story; the installation strategies on those systems are so different that the prefix and exec-prefix are meaningless, and set to the empty string. Note that compiled Python bytecode files are platform independent (but not independent from the Python version by which they were compiled!).

System administrators will know how to configure the mount or automount programs to share /usr/local between platforms while having /usr/local/plat be a different filesystem for each platform.

此函式不應該在 Py_Initialize() 之前呼叫，否則會回傳 NULL。

在 3.10 版的變更: 如果在 Py_Initialize() 之前呼叫，現在會回傳 NULL。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyConfig_Get("base_exec_prefix") (sys.base_exec_prefix) instead. Use PyConfig_Get("exec_prefix") (sys.exec_prefix) if virtual environments need to be handled.

wchar_t *Py_GetProgramFullPath()

為 穩定 ABI 的一部分.

Return the full program name of the Python executable; this is computed as a side-effect of deriving the default module search path from the program name (set by PyConfig.program_name). The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.executable.

此函式不應該在 Py_Initialize() 之前呼叫，否則會回傳 NULL。

在 3.10 版的變更: 如果在 Py_Initialize() 之前呼叫，現在會回傳 NULL。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyConfig_Get("executable") (sys.executable) instead.

wchar_t *Py_GetPath()

為 穩定 ABI 的一部分.

Return the default module search path; this is computed from the program name (set by PyConfig.program_name) and some environment variables. The returned string consists of a series of directory names separated by a platform dependent delimiter character. The delimiter character is ':' on Unix and macOS, ';' on Windows. The returned string points into static storage; the caller should not modify its value. The list sys.path is initialized with this value on interpreter startup; it can be (and usually is) modified later to change the search path for loading modules.

此函式不應該在 Py_Initialize() 之前呼叫，否則會回傳 NULL。

在 3.10 版的變更: 如果在 Py_Initialize() 之前呼叫，現在會回傳 NULL。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: Use PyConfig_Get("module_search_paths") (sys.path) instead.

const char *Py_GetVersion()

為 穩定 ABI 的一部分.

Return the version of this Python interpreter. This is a string that looks something like

"3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) \n[GCC 4.2.3]"

The first word (up to the first space character) is the current Python version; the first characters are the major and minor version separated by a period. The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.version.

另請參閱 Py_Version 常數。

const char *Py_GetPlatform()

為 穩定 ABI 的一部分.

Return the platform identifier for the current platform. On Unix, this is formed from the "official" name of the operating system, converted to lower case, followed by the major revision number; e.g., for Solaris 2.x, which is also known as SunOS 5.x, the value is 'sunos5'. On macOS, it is 'darwin'. On Windows, it is 'win'. The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.platform.

const char *Py_GetCopyright()

為 穩定 ABI 的一部分.

Return the official copyright string for the current Python version, for example

'Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam'

The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.copyright.

const char *Py_GetCompiler()

為 穩定 ABI 的一部分.

Return an indication of the compiler used to build the current Python version, in square brackets, for example:

"[GCC 2.7.2.2]"

The returned string points into static storage; the caller should not modify its value. The value is available to Python code as part of the variable sys.version.

const char *Py_GetBuildInfo()

為 穩定 ABI 的一部分.

Return information about the sequence number and build date and time of the current Python interpreter instance, for example

"#67, Aug  1 1997, 22:34:28"

The returned string points into static storage; the caller should not modify its value. The value is available to Python code as part of the variable sys.version.

void PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath)

為 穩定 ABI 的一部分.

This API is kept for backward compatibility: setting PyConfig.argv, PyConfig.parse_argv and PyConfig.safe_path should be used instead, see Python Initialization Configuration.

Set sys.argv based on argc and argv. These parameters are similar to those passed to the program's main() function with the difference that the first entry should refer to the script file to be executed rather than the executable hosting the Python interpreter. If there isn't a script that will be run, the first entry in argv can be an empty string. If this function fails to initialize sys.argv, a fatal condition is signalled using Py_FatalError().

If updatepath is zero, this is all the function does. If updatepath is non-zero, the function also modifies sys.path according to the following algorithm:

If the name of an existing script is passed in argv[0], the absolute path of the directory where the script is located is prepended to sys.path.

Otherwise (that is, if argc is 0 or argv[0] doesn't point to an existing file name), an empty string is prepended to sys.path, which is the same as prepending the current working directory (".").

Use Py_DecodeLocale() to decode a bytes string to get a wchar_t* string.

See also PyConfig.orig_argv and PyConfig.argv members of the Python Initialization Configuration.

備註

It is recommended that applications embedding the Python interpreter for purposes other than executing a single script pass 0 as updatepath, and update sys.path themselves if desired. See CVE 2008-5983 [https://www.cve.org/CVERecord?id=CVE-2008-5983].

On versions before 3.1.3, you can achieve the same effect by manually popping the first sys.path element after having called PySys_SetArgv(), for example using:

PyRun_SimpleString("import sys; sys.path.pop(0)\n");

在 3.1.3 版被加入.

自從版本 3.11 後不推薦使用，將會自版本 3.15 中移除。.

void PySys_SetArgv(int argc, wchar_t **argv)

為 穩定 ABI 的一部分.

This API is kept for backward compatibility: setting PyConfig.argv and PyConfig.parse_argv should be used instead, see Python Initialization Configuration.

This function works like PySys_SetArgvEx() with updatepath set to 1 unless the python interpreter was started with the -I.

Use Py_DecodeLocale() to decode a bytes string to get a wchar_t* string.

See also PyConfig.orig_argv and PyConfig.argv members of the Python Initialization Configuration.

在 3.4 版的變更: The updatepath value depends on -I.

自從版本 3.11 後不推薦使用，將會自版本 3.15 中移除。.

void Py_SetPythonHome(const wchar_t *home)

為 穩定 ABI 的一部分.

This API is kept for backward compatibility: setting PyConfig.home should be used instead, see Python Initialization Configuration.

Set the default "home" directory, that is, the location of the standard Python libraries. See PYTHONHOME for the meaning of the argument string.

The argument should point to a zero-terminated character string in static storage whose contents will not change for the duration of the program's execution. No code in the Python interpreter will change the contents of this storage.

Use Py_DecodeLocale() to decode a bytes string to get a wchar_t* string.

自從版本 3.11 後不推薦使用，將會自版本 3.15 中移除。.

wchar_t *Py_GetPythonHome()

為 穩定 ABI 的一部分.

Return the default "home", that is, the value set by PyConfig.home, or the value of the PYTHONHOME environment variable if it is set.

此函式不應該在 Py_Initialize() 之前呼叫，否則會回傳 NULL。

在 3.10 版的變更: 如果在 Py_Initialize() 之前呼叫，現在會回傳 NULL。

自從版本 3.13 後不推薦使用，將會自版本 3.15 中移除。: 改為使用 PyConfig_Get("home") 或 PYTHONHOME 環境變數。

Thread State and the Global Interpreter Lock

Unless on a free-threaded build of CPython, the Python interpreter is not fully thread-safe. In order to support multi-threaded Python programs, there's a global lock, called the global interpreter lock or GIL, that must be held by the current thread before it can safely access Python objects. Without the lock, even the simplest operations could cause problems in a multi-threaded program: for example, when two threads simultaneously increment the reference count of the same object, the reference count could end up being incremented only once instead of twice.

Therefore, the rule exists that only the thread that has acquired the GIL may operate on Python objects or call Python/C API functions. In order to emulate concurrency of execution, the interpreter regularly tries to switch threads (see sys.setswitchinterval()). The lock is also released around potentially blocking I/O operations like reading or writing a file, so that other Python threads can run in the meantime.

The Python interpreter keeps some thread-specific bookkeeping information inside a data structure called PyThreadState, known as a thread state. Each OS thread has a thread-local pointer to a PyThreadState; a thread state referenced by this pointer is considered to be attached.

A thread can only have one attached thread state at a time. An attached thread state is typically analogous with holding the GIL, except on free-threaded builds. On builds with the GIL enabled, attaching a thread state will block until the GIL can be acquired. However, even on builds with the GIL disabled, it is still required to have an attached thread state to call most of the C API.

In general, there will always be an attached thread state when using Python's C API. Only in some specific cases (such as in a Py_BEGIN_ALLOW_THREADS block) will the thread not have an attached thread state. If uncertain, check if PyThreadState_GetUnchecked() returns NULL.

Detaching the thread state from extension code

Most extension code manipulating the thread state has the following simple structure:

Save the thread state in a local variable.
... Do some blocking I/O operation ...
Restore the thread state from the local variable.

This is so common that a pair of macros exists to simplify it:

Py_BEGIN_ALLOW_THREADS
... Do some blocking I/O operation ...
Py_END_ALLOW_THREADS

The Py_BEGIN_ALLOW_THREADS macro opens a new block and declares a hidden local variable; the Py_END_ALLOW_THREADS macro closes the block.

The block above expands to the following code:

PyThreadState *_save;

_save = PyEval_SaveThread();
... Do some blocking I/O operation ...
PyEval_RestoreThread(_save);

Here is how these functions work:

The attached thread state holds the GIL for the entire interpreter. When detaching the attached thread state, the GIL is released, allowing other threads to attach a thread state to their own thread, thus getting the GIL and can start executing. The pointer to the prior attached thread state is stored as a local variable. Upon reaching Py_END_ALLOW_THREADS, the thread state that was previously attached is passed to PyEval_RestoreThread(). This function will block until another releases its thread state, thus allowing the old thread state to get re-attached and the C API can be called again.

For free-threaded builds, the GIL is normally out of the question, but detaching the thread state is still required for blocking I/O and long operations. The difference is that threads don't have to wait for the GIL to be released to attach their thread state, allowing true multi-core parallelism.

備註

Calling system I/O functions is the most common use case for detaching the thread state, but it can also be useful before calling long-running computations which don't need access to Python objects, such as compression or cryptographic functions operating over memory buffers. For example, the standard zlib and hashlib modules detach the thread state when compressing or hashing data.

Non-Python created threads

When threads are created using the dedicated Python APIs (such as the threading module), a thread state is automatically associated to them and the code showed above is therefore correct. However, when threads are created from C (for example by a third-party library with its own thread management), they don't hold the GIL, because they don't have an attached thread state.

If you need to call Python code from these threads (often this will be part of a callback API provided by the aforementioned third-party library), you must first register these threads with the interpreter by creating an attached thread state before you can start using the Python/C API. When you are done, you should detach the thread state, and finally free it.

The PyGILState_Ensure() and PyGILState_Release() functions do all of the above automatically. The typical idiom for calling into Python from a C thread is:

PyGILState_STATE gstate;
gstate = PyGILState_Ensure();

/* Perform Python actions here. */
result = CallSomeFunction();
/* evaluate result or handle exception */

/* Release the thread. No Python API allowed beyond this point. */
PyGILState_Release(gstate);

Note that the PyGILState_* functions assume there is only one global interpreter (created automatically by Py_Initialize()). Python supports the creation of additional interpreters (using Py_NewInterpreter()), but mixing multiple interpreters and the PyGILState_* API is unsupported. This is because PyGILState_Ensure() and similar functions default to attaching a thread state for the main interpreter, meaning that the thread can't safely interact with the calling subinterpreter.

Supporting subinterpreters in non-Python threads

If you would like to support subinterpreters with non-Python created threads, you must use the PyThreadState_* API instead of the traditional PyGILState_* API.

In particular, you must store the interpreter state from the calling function and pass it to PyThreadState_New(), which will ensure that the thread state is targeting the correct interpreter:

/* The return value of PyInterpreterState_Get() from the
   function that created this thread. */
PyInterpreterState *interp = ThreadData->interp;
PyThreadState *tstate = PyThreadState_New(interp);
PyThreadState_Swap(tstate);

/* GIL of the subinterpreter is now held.
   Perform Python actions here. */
result = CallSomeFunction();
/* evaluate result or handle exception */

/* Destroy the thread state. No Python API allowed beyond this point. */
PyThreadState_Clear(tstate);
PyThreadState_DeleteCurrent();

Cautions about fork()

Another important thing to note about threads is their behaviour in the face of the C fork() call. On most systems with fork(), after a process forks only the thread that issued the fork will exist. This has a concrete impact both on how locks must be handled and on all stored state in CPython's runtime.

The fact that only the "current" thread remains means any locks held by other threads will never be released. Python solves this for os.fork() by acquiring the locks it uses internally before the fork, and releasing them afterwards. In addition, it resets any Lock 物件 in the child. When extending or embedding Python, there is no way to inform Python of additional (non-Python) locks that need to be acquired before or reset after a fork. OS facilities such as pthread_atfork() would need to be used to accomplish the same thing. Additionally, when extending or embedding Python, calling fork() directly rather than through os.fork() (and returning to or calling into Python) may result in a deadlock by one of Python's internal locks being held by a thread that is defunct after the fork. PyOS_AfterFork_Child() tries to reset the necessary locks, but is not always able to.

The fact that all other threads go away also means that CPython's runtime state there must be cleaned up properly, which os.fork() does. This means finalizing all other PyThreadState objects belonging to the current interpreter and all other PyInterpreterState objects. Due to this and the special nature of the "main" interpreter, fork() should only be called in that interpreter's "main" thread, where the CPython global runtime was originally initialized. The only exception is if exec() will be called immediately after.

Cautions regarding runtime finalization

In the late stage of interpreter shutdown, after attempting to wait for non-daemon threads to exit (though this can be interrupted by KeyboardInterrupt) and running the atexit functions, the runtime is marked as finalizing: Py_IsFinalizing() and sys.is_finalizing() return true. At this point, only the finalization thread that initiated finalization (typically the main thread) is allowed to acquire the GIL.

If any thread, other than the finalization thread, attempts to attach a thread state during finalization, either explicitly or implicitly, the thread enters a permanently blocked state where it remains until the program exits. In most cases this is harmless, but this can result in deadlock if a later stage of finalization attempts to acquire a lock owned by the blocked thread, or otherwise waits on the blocked thread.

Gross? Yes. This prevents random crashes and/or unexpectedly skipped C++ finalizations further up the call stack when such threads were forcibly exited here in CPython 3.13 and earlier. The CPython runtime thread state C APIs have never had any error reporting or handling expectations at thread state attachment time that would've allowed for graceful exit from this situation. Changing that would require new stable C APIs and rewriting the majority of C code in the CPython ecosystem to use those with error handling.

高階 API

These are the most commonly used types and functions when writing C extension code, or when embedding the Python interpreter:

type PyInterpreterState

為 受限 API 的一部分 （做為一個不透明結構 (opaque struct)）.

This data structure represents the state shared by a number of cooperating threads. Threads belonging to the same interpreter share their module administration and a few other internal items. There are no public members in this structure.

Threads belonging to different interpreters initially share nothing, except process state like available memory, open file descriptors and such. The global interpreter lock is also shared by all threads, regardless of to which interpreter they belong.

在 3.12 版的變更: PEP 684 [https://peps.python.org/pep-0684/] introduced the possibility of a per-interpreter GIL. See Py_NewInterpreterFromConfig().

type PyThreadState

為 受限 API 的一部分 （做為一個不透明結構 (opaque struct)）.

This data structure represents the state of a single thread. The only public data member is:

PyInterpreterState *interp

This thread's interpreter state.

void PyEval_InitThreads()

為 穩定 ABI 的一部分.

Deprecated function which does nothing.

In Python 3.6 and older, this function created the GIL if it didn't exist.

在 3.9 版的變更: 此函式現在不會做任何事情。

在 3.7 版的變更: This function is now called by Py_Initialize(), so you don't have to call it yourself anymore.

在 3.2 版的變更: This function cannot be called before Py_Initialize() anymore.

在 3.9 版之後被棄用.

PyThreadState *PyEval_SaveThread()

為 穩定 ABI 的一部分.

Detach the attached thread state and return it. The thread will have no thread state upon returning.

void PyEval_RestoreThread(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Set the attached thread state to tstate. The passed thread state should not be attached, otherwise deadlock ensues. tstate will be attached upon returning.

備註

Calling this function from a thread when the runtime is finalizing will hang the thread until the program exits, even if the thread was not created by Python. Refer to Cautions regarding runtime finalization for more details.

在 3.14 版的變更: Hangs the current thread, rather than terminating it, if called while the interpreter is finalizing.

PyThreadState *PyThreadState_Get()

為 穩定 ABI 的一部分.

Return the attached thread state. If the thread has no attached thread state, (such as when inside of Py_BEGIN_ALLOW_THREADS block), then this issues a fatal error (so that the caller needn't check for NULL).

也請見 PyThreadState_GetUnchecked()。

PyThreadState *PyThreadState_GetUnchecked()

Similar to PyThreadState_Get(), but don't kill the process with a fatal error if it is NULL. The caller is responsible to check if the result is NULL.

在 3.13 版被加入: In Python 3.5 to 3.12, the function was private and known as _PyThreadState_UncheckedGet().

PyThreadState *PyThreadState_Swap(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Set the attached thread state to tstate, and return the thread state that was attached prior to calling.

This function is safe to call without an attached thread state; it will simply return NULL indicating that there was no prior thread state.

也參考

PyEval_ReleaseThread()

備註

Similar to PyGILState_Ensure(), this function will hang the thread if the runtime is finalizing.

The following functions use thread-local storage, and are not compatible with sub-interpreters:

type PyGILState_STATE

為 穩定 ABI 的一部分.

The type of the value returned by PyGILState_Ensure() and passed to PyGILState_Release().

enumerator PyGILState_LOCKED

The GIL was already held when PyGILState_Ensure() was called.

enumerator PyGILState_UNLOCKED

The GIL was not held when PyGILState_Ensure() was called.

PyGILState_STATE PyGILState_Ensure()

為 穩定 ABI 的一部分.

Ensure that the current thread is ready to call the Python C API regardless of the current state of Python, or of the attached thread state. This may be called as many times as desired by a thread as long as each call is matched with a call to PyGILState_Release(). In general, other thread-related APIs may be used between PyGILState_Ensure() and PyGILState_Release() calls as long as the thread state is restored to its previous state before the Release(). For example, normal usage of the Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS macros is acceptable.

The return value is an opaque "handle" to the attached thread state when PyGILState_Ensure() was called, and must be passed to PyGILState_Release() to ensure Python is left in the same state. Even though recursive calls are allowed, these handles cannot be shared - each unique call to PyGILState_Ensure() must save the handle for its call to PyGILState_Release().

When the function returns, there will be an attached thread state and the thread will be able to call arbitrary Python code. Failure is a fatal error.

警告

Calling this function when the runtime is finalizing is unsafe. Doing so will either hang the thread until the program ends, or fully crash the interpreter in rare cases. Refer to Cautions regarding runtime finalization for more details.

在 3.14 版的變更: Hangs the current thread, rather than terminating it, if called while the interpreter is finalizing.

void PyGILState_Release(PyGILState_STATE)

為 穩定 ABI 的一部分.

Release any resources previously acquired. After this call, Python's state will be the same as it was prior to the corresponding PyGILState_Ensure() call (but generally this state will be unknown to the caller, hence the use of the GILState API).

Every call to PyGILState_Ensure() must be matched by a call to PyGILState_Release() on the same thread.

PyThreadState *PyGILState_GetThisThreadState()

為 穩定 ABI 的一部分.

Get the attached thread state for this thread. May return NULL if no GILState API has been used on the current thread. Note that the main thread always has such a thread-state, even if no auto-thread-state call has been made on the main thread. This is mainly a helper/diagnostic function.

備註

This function may return non-NULL even when the thread state is detached. Prefer PyThreadState_Get() or PyThreadState_GetUnchecked() for most cases.

也參考

PyThreadState_Get()

int PyGILState_Check()

Return 1 if the current thread is holding the GIL and 0 otherwise. This function can be called from any thread at any time. Only if it has had its thread state initialized via PyGILState_Ensure() will it return 1. This is mainly a helper/diagnostic function. It can be useful for example in callback contexts or memory allocation functions when knowing that the GIL is locked can allow the caller to perform sensitive actions or otherwise behave differently.

備註

If the current Python process has ever created a subinterpreter, this function will always return 1. Prefer PyThreadState_GetUnchecked() for most cases.

在 3.4 版被加入.

The following macros are normally used without a trailing semicolon; look for example usage in the Python source distribution.

Py_BEGIN_ALLOW_THREADS

為 穩定 ABI 的一部分.

This macro expands to { PyThreadState *_save; _save = PyEval_SaveThread();. Note that it contains an opening brace; it must be matched with a following Py_END_ALLOW_THREADS macro. See above for further discussion of this macro.

Py_END_ALLOW_THREADS

為 穩定 ABI 的一部分.

This macro expands to PyEval_RestoreThread(_save); }. Note that it contains a closing brace; it must be matched with an earlier Py_BEGIN_ALLOW_THREADS macro. See above for further discussion of this macro.

Py_BLOCK_THREADS

為 穩定 ABI 的一部分.

This macro expands to PyEval_RestoreThread(_save);: it is equivalent to Py_END_ALLOW_THREADS without the closing brace.

Py_UNBLOCK_THREADS

為 穩定 ABI 的一部分.

This macro expands to _save = PyEval_SaveThread();: it is equivalent to Py_BEGIN_ALLOW_THREADS without the opening brace and variable declaration.

低階 API

All of the following functions must be called after Py_Initialize().

在 3.7 版的變更: Py_Initialize() now initializes the GIL and sets an attached thread state.

PyInterpreterState *PyInterpreterState_New()

為 穩定 ABI 的一部分.

Create a new interpreter state object. An attached thread state is not needed, but may optionally exist if it is necessary to serialize calls to this function.

引發一個不附帶引數的稽核事件 cpython.PyInterpreterState_New。

void PyInterpreterState_Clear(PyInterpreterState *interp)

為 穩定 ABI 的一部分.

Reset all information in an interpreter state object. There must be an attached thread state for the interpreter.

引發一個不附帶引數的稽核事件 cpython.PyInterpreterState_Clear。

void PyInterpreterState_Delete(PyInterpreterState *interp)

為 穩定 ABI 的一部分.

Destroy an interpreter state object. There should not be an attached thread state for the target interpreter. The interpreter state must have been reset with a previous call to PyInterpreterState_Clear().

PyThreadState *PyThreadState_New(PyInterpreterState *interp)

為 穩定 ABI 的一部分.

Create a new thread state object belonging to the given interpreter object. An attached thread state is not needed.

void PyThreadState_Clear(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Reset all information in a thread state object. tstate must be attached

在 3.9 版的變更: This function now calls the PyThreadState.on_delete callback. Previously, that happened in PyThreadState_Delete().

在 3.13 版的變更: PyThreadState.on_delete 回呼已被移除。

void PyThreadState_Delete(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Destroy a thread state object. tstate should not be attached to any thread. tstate must have been reset with a previous call to PyThreadState_Clear().

void PyThreadState_DeleteCurrent(void)

Detach the attached thread state (which must have been reset with a previous call to PyThreadState_Clear()) and then destroy it.

No thread state will be attached upon returning.

PyFrameObject *PyThreadState_GetFrame(PyThreadState *tstate)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Get the current frame of the Python thread state tstate.

Return a strong reference. Return NULL if no frame is currently executing.

也請見 PyEval_GetFrame()。

tstate must not be NULL, and must be attached.

在 3.9 版被加入.

uint64_t PyThreadState_GetID(PyThreadState *tstate)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Get the unique thread state identifier of the Python thread state tstate.

tstate must not be NULL, and must be attached.

在 3.9 版被加入.

PyInterpreterState *PyThreadState_GetInterpreter(PyThreadState *tstate)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Get the interpreter of the Python thread state tstate.

tstate must not be NULL, and must be attached.

在 3.9 版被加入.

void PyThreadState_EnterTracing(PyThreadState *tstate)

Suspend tracing and profiling in the Python thread state tstate.

Resume them using the PyThreadState_LeaveTracing() function.

在 3.11 版被加入.

void PyThreadState_LeaveTracing(PyThreadState *tstate)

Resume tracing and profiling in the Python thread state tstate suspended by the PyThreadState_EnterTracing() function.

See also PyEval_SetTrace() and PyEval_SetProfile() functions.

在 3.11 版被加入.

int PyUnstable_ThreadState_SetStackProtection(PyThreadState *tstate, void *stack_start_addr, size_t stack_size)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Set the stack protection start address and stack protection size of a Python thread state.

On success, return 0. On failure, set an exception and return -1.

CPython implements recursion control for C code by raising RecursionError when it notices that the machine execution stack is close to overflow. See for example the Py_EnterRecursiveCall() function. For this, it needs to know the location of the current thread's stack, which it normally gets from the operating system. When the stack is changed, for example using context switching techniques like the Boost library's boost::context, you must call PyUnstable_ThreadState_SetStackProtection() to inform CPython of the change.

Call PyUnstable_ThreadState_SetStackProtection() either before or after changing the stack. Do not call any other Python C API between the call and the stack change.

See PyUnstable_ThreadState_ResetStackProtection() for undoing this operation.

在 3.14.1 版被加入:

警告

This function was added in a bugfix release, and extensions that use it will be incompatible with Python 3.14.0. Most packaging tools for Python are not able to handle this incompatibility automatically, and will need explicit configuration. When using PyPA standards (wheels and source distributions), specify Requires-Python: != 3.14.0.* in core metadata [https://packaging.python.org/en/latest/specifications/core-metadata/#requires-python].

void PyUnstable_ThreadState_ResetStackProtection(PyThreadState *tstate)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Reset the stack protection start address and stack protection size of a Python thread state to the operating system defaults.

See PyUnstable_ThreadState_SetStackProtection() for an explanation.

在 3.14.1 版被加入:

警告

This function was added in a bugfix release, and extensions that use it will be incompatible with Python 3.14.0. Most packaging tools for Python are not able to handle this incompatibility automatically, and will need explicit configuration. When using PyPA standards (wheels and source distributions), specify Requires-Python: != 3.14.0.* in core metadata [https://packaging.python.org/en/latest/specifications/core-metadata/#requires-python].

PyInterpreterState *PyInterpreterState_Get(void)

為 穩定 ABI 的一部分 自 3.9 版本開始.

Get the current interpreter.

Issue a fatal error if there no attached thread state. It cannot return NULL.

在 3.9 版被加入.

int64_t PyInterpreterState_GetID(PyInterpreterState *interp)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return the interpreter's unique ID. If there was any error in doing so then -1 is returned and an error is set.

呼叫者必須擁有一個 attached thread state。

在 3.7 版被加入.

PyObject *PyInterpreterState_GetDict(PyInterpreterState *interp)

回傳值：借用參照。 為 穩定 ABI 的一部分 自 3.8 版本開始.

Return a dictionary in which interpreter-specific data may be stored. If this function returns NULL then no exception has been raised and the caller should assume no interpreter-specific dict is available.

This is not a replacement for PyModule_GetState(), which extensions should use to store interpreter-specific state information.

The returned dictionary is borrowed from the interpreter and is valid until interpreter shutdown.

在 3.8 版被加入.

typedef PyObject *(*_PyFrameEvalFunction)(PyThreadState *tstate, _PyInterpreterFrame *frame, int throwflag)

Type of a frame evaluation function.

The throwflag parameter is used by the throw() method of generators: if non-zero, handle the current exception.

在 3.9 版的變更: The function now takes a tstate parameter.

在 3.11 版的變更: The frame parameter changed from PyFrameObject* to _PyInterpreterFrame*.

_PyFrameEvalFunction _PyInterpreterState_GetEvalFrameFunc(PyInterpreterState *interp)

Get the frame evaluation function.

See the PEP 523 [https://peps.python.org/pep-0523/] "Adding a frame evaluation API to CPython".

在 3.9 版被加入.

void _PyInterpreterState_SetEvalFrameFunc(PyInterpreterState *interp, _PyFrameEvalFunction eval_frame)

Set the frame evaluation function.

See the PEP 523 [https://peps.python.org/pep-0523/] "Adding a frame evaluation API to CPython".

在 3.9 版被加入.

PyObject *PyThreadState_GetDict()

回傳值：借用參照。 為 穩定 ABI 的一部分.

Return a dictionary in which extensions can store thread-specific state information. Each extension should use a unique key to use to store state in the dictionary. It is okay to call this function when no thread state is attached. If this function returns NULL, no exception has been raised and the caller should assume no thread state is attached.

int PyThreadState_SetAsyncExc(unsigned long id, PyObject *exc)

為 穩定 ABI 的一部分.

Asynchronously raise an exception in a thread. The id argument is the thread id of the target thread; exc is the exception object to be raised. This function does not steal any references to exc. To prevent naive misuse, you must write your own C extension to call this. Must be called with an attached thread state. Returns the number of thread states modified; this is normally one, but will be zero if the thread id isn't found. If exc is NULL, the pending exception (if any) for the thread is cleared. This raises no exceptions.

在 3.7 版的變更: The type of the id parameter changed from long to unsigned long.

void PyEval_AcquireThread(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Attach tstate to the current thread, which must not be NULL or already attached.

The calling thread must not already have an attached thread state.

備註

Calling this function from a thread when the runtime is finalizing will hang the thread until the program exits, even if the thread was not created by Python. Refer to Cautions regarding runtime finalization for more details.

在 3.8 版的變更: Updated to be consistent with PyEval_RestoreThread(), Py_END_ALLOW_THREADS(), and PyGILState_Ensure(), and terminate the current thread if called while the interpreter is finalizing.

在 3.14 版的變更: Hangs the current thread, rather than terminating it, if called while the interpreter is finalizing.

PyEval_RestoreThread() is a higher-level function which is always available (even when threads have not been initialized).

void PyEval_ReleaseThread(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Detach the attached thread state. The tstate argument, which must not be NULL, is only used to check that it represents the attached thread state --- if it isn't, a fatal error is reported.

PyEval_SaveThread() is a higher-level function which is always available (even when threads have not been initialized).

Sub-interpreter support

While in most uses, you will only embed a single Python interpreter, there are cases where you need to create several independent interpreters in the same process and perhaps even in the same thread. Sub-interpreters allow you to do that.

The "main" interpreter is the first one created when the runtime initializes. It is usually the only Python interpreter in a process. Unlike sub-interpreters, the main interpreter has unique process-global responsibilities like signal handling. It is also responsible for execution during runtime initialization and is usually the active interpreter during runtime finalization. The PyInterpreterState_Main() function returns a pointer to its state.

You can switch between sub-interpreters using the PyThreadState_Swap() function. You can create and destroy them using the following functions:

type PyInterpreterConfig

Structure containing most parameters to configure a sub-interpreter. Its values are used only in Py_NewInterpreterFromConfig() and never modified by the runtime.

在 3.12 版被加入.

Structure fields:

int use_main_obmalloc

If this is 0 then the sub-interpreter will use its own "object" allocator state. Otherwise it will use (share) the main interpreter's.

If this is 0 then check_multi_interp_extensions must be 1 (non-zero). If this is 1 then gil must not be PyInterpreterConfig_OWN_GIL.

int allow_fork

If this is 0 then the runtime will not support forking the process in any thread where the sub-interpreter is currently active. Otherwise fork is unrestricted.

Note that the subprocess module still works when fork is disallowed.

int allow_exec

If this is 0 then the runtime will not support replacing the current process via exec (e.g. os.execv()) in any thread where the sub-interpreter is currently active. Otherwise exec is unrestricted.

Note that the subprocess module still works when exec is disallowed.

int allow_threads

If this is 0 then the sub-interpreter's threading module won't create threads. Otherwise threads are allowed.

int allow_daemon_threads

If this is 0 then the sub-interpreter's threading module won't create daemon threads. Otherwise daemon threads are allowed (as long as allow_threads is non-zero).

int check_multi_interp_extensions

If this is 0 then all extension modules may be imported, including legacy (single-phase init) modules, in any thread where the sub-interpreter is currently active. Otherwise only multi-phase init extension modules (see PEP 489 [https://peps.python.org/pep-0489/]) may be imported. (Also see Py_mod_multiple_interpreters.)

This must be 1 (non-zero) if use_main_obmalloc is 0.

int gil

This determines the operation of the GIL for the sub-interpreter. It may be one of the following:

PyInterpreterConfig_DEFAULT_GIL

Use the default selection (PyInterpreterConfig_SHARED_GIL).

PyInterpreterConfig_SHARED_GIL

Use (share) the main interpreter's GIL.

PyInterpreterConfig_OWN_GIL

Use the sub-interpreter's own GIL.

If this is PyInterpreterConfig_OWN_GIL then PyInterpreterConfig.use_main_obmalloc must be 0.

PyStatus Py_NewInterpreterFromConfig(PyThreadState **tstate_p, const PyInterpreterConfig *config)

Create a new sub-interpreter. This is an (almost) totally separate environment for the execution of Python code. In particular, the new interpreter has separate, independent versions of all imported modules, including the fundamental modules builtins, __main__ and sys. The table of loaded modules (sys.modules) and the module search path (sys.path) are also separate. The new environment has no sys.argv variable. It has new standard I/O stream file objects sys.stdin, sys.stdout and sys.stderr (however these refer to the same underlying file descriptors).

The given config controls the options with which the interpreter is initialized.

Upon success, tstate_p will be set to the first thread state created in the new sub-interpreter. This thread state is attached. Note that no actual thread is created; see the discussion of thread states below. If creation of the new interpreter is unsuccessful, tstate_p is set to NULL; no exception is set since the exception state is stored in the attached thread state, which might not exist.

Like all other Python/C API functions, an attached thread state must be present before calling this function, but it might be detached upon returning. On success, the returned thread state will be attached. If the sub-interpreter is created with its own GIL then the attached thread state of the calling interpreter will be detached. When the function returns, the new interpreter's thread state will be attached to the current thread and the previous interpreter's attached thread state will remain detached.

在 3.12 版被加入.

Sub-interpreters are most effective when isolated from each other, with certain functionality restricted:

PyInterpreterConfig config = {
    .use_main_obmalloc = 0,
    .allow_fork = 0,
    .allow_exec = 0,
    .allow_threads = 1,
    .allow_daemon_threads = 0,
    .check_multi_interp_extensions = 1,
    .gil = PyInterpreterConfig_OWN_GIL,
};
PyThreadState *tstate = NULL;
PyStatus status = Py_NewInterpreterFromConfig(&tstate, &config);
if (PyStatus_Exception(status)) {
    Py_ExitStatusException(status);
}

Note that the config is used only briefly and does not get modified. During initialization the config's values are converted into various PyInterpreterState values. A read-only copy of the config may be stored internally on the PyInterpreterState.

Extension modules are shared between (sub-)interpreters as follows:

For modules using multi-phase initialization, e.g. PyModule_FromDefAndSpec(), a separate module object is created and initialized for each interpreter. Only C-level static and global variables are shared between these module objects.

For modules using single-phase initialization, e.g. PyModule_Create(), the first time a particular extension is imported, it is initialized normally, and a (shallow) copy of its module's dictionary is squirreled away. When the same extension is imported by another (sub-)interpreter, a new module is initialized and filled with the contents of this copy; the extension's init function is not called. Objects in the module's dictionary thus end up shared across (sub-)interpreters, which might cause unwanted behavior (see Bugs and caveats below).

Note that this is different from what happens when an extension is imported after the interpreter has been completely re-initialized by calling Py_FinalizeEx() and Py_Initialize(); in that case, the extension's initmodule function is called again. As with multi-phase initialization, this means that only C-level static and global variables are shared between these modules.

PyThreadState *Py_NewInterpreter(void)

為 穩定 ABI 的一部分.

Create a new sub-interpreter. This is essentially just a wrapper around Py_NewInterpreterFromConfig() with a config that preserves the existing behavior. The result is an unisolated sub-interpreter that shares the main interpreter's GIL, allows fork/exec, allows daemon threads, and allows single-phase init modules.

void Py_EndInterpreter(PyThreadState *tstate)

為 穩定 ABI 的一部分.

Destroy the (sub-)interpreter represented by the given thread state. The given thread state must be attached. When the call returns, there will be no attached thread state. All thread states associated with this interpreter are destroyed.

Py_FinalizeEx() will destroy all sub-interpreters that haven't been explicitly destroyed at that point.

直譯器各別持有的 GIL

Using Py_NewInterpreterFromConfig() you can create a sub-interpreter that is completely isolated from other interpreters, including having its own GIL. The most important benefit of this isolation is that such an interpreter can execute Python code without being blocked by other interpreters or blocking any others. Thus a single Python process can truly take advantage of multiple CPU cores when running Python code. The isolation also encourages a different approach to concurrency than that of just using threads. (See PEP 554 [https://peps.python.org/pep-0554/] and PEP 684 [https://peps.python.org/pep-0684/].)

Using an isolated interpreter requires vigilance in preserving that isolation. That especially means not sharing any objects or mutable state without guarantees about thread-safety. Even objects that are otherwise immutable (e.g. None, (1, 5)) can't normally be shared because of the refcount. One simple but less-efficient approach around this is to use a global lock around all use of some state (or object). Alternately, effectively immutable objects (like integers or strings) can be made safe in spite of their refcounts by making them immortal. In fact, this has been done for the builtin singletons, small integers, and a number of other builtin objects.

If you preserve isolation then you will have access to proper multi-core computing without the complications that come with free-threading. Failure to preserve isolation will expose you to the full consequences of free-threading, including races and hard-to-debug crashes.

Aside from that, one of the main challenges of using multiple isolated interpreters is how to communicate between them safely (not break isolation) and efficiently. The runtime and stdlib do not provide any standard approach to this yet. A future stdlib module would help mitigate the effort of preserving isolation and expose effective tools for communicating (and sharing) data between interpreters.

在 3.12 版被加入.

Bugs and caveats

Because sub-interpreters (and the main interpreter) are part of the same process, the insulation between them isn't perfect --- for example, using low-level file operations like os.close() they can (accidentally or maliciously) affect each other's open files. Because of the way extensions are shared between (sub-)interpreters, some extensions may not work properly; this is especially likely when using single-phase initialization or (static) global variables. It is possible to insert objects created in one sub-interpreter into a namespace of another (sub-)interpreter; this should be avoided if possible.

Special care should be taken to avoid sharing user-defined functions, methods, instances or classes between sub-interpreters, since import operations executed by such objects may affect the wrong (sub-)interpreter's dictionary of loaded modules. It is equally important to avoid sharing objects from which the above are reachable.

Also note that combining this functionality with PyGILState_* APIs is delicate, because these APIs assume a bijection between Python thread states and OS-level threads, an assumption broken by the presence of sub-interpreters. It is highly recommended that you don't switch sub-interpreters between a pair of matching PyGILState_Ensure() and PyGILState_Release() calls. Furthermore, extensions (such as ctypes) using these APIs to allow calling of Python code from non-Python created threads will probably be broken when using sub-interpreters.

Asynchronous Notifications

A mechanism is provided to make asynchronous notifications to the main interpreter thread. These notifications take the form of a function pointer and a void pointer argument.

int Py_AddPendingCall(int (*func)(void*), void *arg)

為 穩定 ABI 的一部分.

Schedule a function to be called from the main interpreter thread. On success, 0 is returned and func is queued for being called in the main thread. On failure, -1 is returned without setting any exception.

When successfully queued, func will be eventually called from the main interpreter thread with the argument arg. It will be called asynchronously with respect to normally running Python code, but with both these conditions met:

on a bytecode boundary;

with the main thread holding an attached thread state (func can therefore use the full C API).

func must return 0 on success, or -1 on failure with an exception set. func won't be interrupted to perform another asynchronous notification recursively, but it can still be interrupted to switch threads if the thread state is detached.

This function doesn't need an attached thread state. However, to call this function in a subinterpreter, the caller must have an attached thread state. Otherwise, the function func can be scheduled to be called from the wrong interpreter.

警告

This is a low-level function, only useful for very special cases. There is no guarantee that func will be called as quick as possible. If the main thread is busy executing a system call, func won't be called before the system call returns. This function is generally not suitable for calling Python code from arbitrary C threads. Instead, use the PyGILState API.

在 3.1 版被加入.

在 3.9 版的變更: If this function is called in a subinterpreter, the function func is now scheduled to be called from the subinterpreter, rather than being called from the main interpreter. Each subinterpreter now has its own list of scheduled calls.

在 3.12 版的變更: This function now always schedules func to be run in the main interpreter.

int Py_MakePendingCalls(void)

為 穩定 ABI 的一部分.

Execute all pending calls. This is usually executed automatically by the interpreter.

This function returns 0 on success, and returns -1 with an exception set on failure.

If this is not called in the main thread of the main interpreter, this function does nothing and returns 0. The caller must hold an attached thread state.

在 3.1 版被加入.

在 3.12 版的變更: This function only runs pending calls in the main interpreter.

Profiling and Tracing

The Python interpreter provides some low-level support for attaching profiling and execution tracing facilities. These are used for profiling, debugging, and coverage analysis tools.

This C interface allows the profiling or tracing code to avoid the overhead of calling through Python-level callable objects, making a direct C function call instead. The essential attributes of the facility have not changed; the interface allows trace functions to be installed per-thread, and the basic events reported to the trace function are the same as had been reported to the Python-level trace functions in previous versions.

typedef int (*Py_tracefunc)(PyObject *obj, PyFrameObject *frame, int what, PyObject *arg)

The type of the trace function registered using PyEval_SetProfile() and PyEval_SetTrace(). The first parameter is the object passed to the registration function as obj, frame is the frame object to which the event pertains, what is one of the constants PyTrace_CALL, PyTrace_EXCEPTION, PyTrace_LINE, PyTrace_RETURN, PyTrace_C_CALL, PyTrace_C_EXCEPTION, PyTrace_C_RETURN, or PyTrace_OPCODE, and arg depends on the value of what:

what 的值

arg 的含義

PyTrace_CALL

Always Py_None.

PyTrace_EXCEPTION

Exception information as returned by sys.exc_info().

PyTrace_LINE

Always Py_None.

PyTrace_RETURN

Value being returned to the caller, or NULL if caused by an exception.

PyTrace_C_CALL

被呼叫的函式物件。

PyTrace_C_EXCEPTION

被呼叫的函式物件。

PyTrace_C_RETURN

被呼叫的函式物件。

PyTrace_OPCODE

Always Py_None.

int PyTrace_CALL

The value of the what parameter to a Py_tracefunc function when a new call to a function or method is being reported, or a new entry into a generator. Note that the creation of the iterator for a generator function is not reported as there is no control transfer to the Python bytecode in the corresponding frame.

int PyTrace_EXCEPTION

The value of the what parameter to a Py_tracefunc function when an exception has been raised. The callback function is called with this value for what when after any bytecode is processed after which the exception becomes set within the frame being executed. The effect of this is that as exception propagation causes the Python stack to unwind, the callback is called upon return to each frame as the exception propagates. Only trace functions receives these events; they are not needed by the profiler.

int PyTrace_LINE

The value passed as the what parameter to a Py_tracefunc function (but not a profiling function) when a line-number event is being reported. It may be disabled for a frame by setting f_trace_lines to 0 on that frame.

int PyTrace_RETURN

The value for the what parameter to Py_tracefunc functions when a call is about to return.

int PyTrace_C_CALL

The value for the what parameter to Py_tracefunc functions when a C function is about to be called.

int PyTrace_C_EXCEPTION

The value for the what parameter to Py_tracefunc functions when a C function has raised an exception.

int PyTrace_C_RETURN

The value for the what parameter to Py_tracefunc functions when a C function has returned.

int PyTrace_OPCODE

The value for the what parameter to Py_tracefunc functions (but not profiling functions) when a new opcode is about to be executed. This event is not emitted by default: it must be explicitly requested by setting f_trace_opcodes to 1 on the frame.

void PyEval_SetProfile(Py_tracefunc func, PyObject *obj)

Set the profiler function to func. The obj parameter is passed to the function as its first parameter, and may be any Python object, or NULL. If the profile function needs to maintain state, using a different value for obj for each thread provides a convenient and thread-safe place to store it. The profile function is called for all monitored events except PyTrace_LINE PyTrace_OPCODE and PyTrace_EXCEPTION.

另請參閱 sys.setprofile() 函式。

呼叫者必須擁有一個 attached thread state。

void PyEval_SetProfileAllThreads(Py_tracefunc func, PyObject *obj)

Like PyEval_SetProfile() but sets the profile function in all running threads belonging to the current interpreter instead of the setting it only on the current thread.

呼叫者必須擁有一個 attached thread state。

As PyEval_SetProfile(), this function ignores any exceptions raised while setting the profile functions in all threads.

在 3.12 版被加入.

void PyEval_SetTrace(Py_tracefunc func, PyObject *obj)

Set the tracing function to func. This is similar to PyEval_SetProfile(), except the tracing function does receive line-number events and per-opcode events, but does not receive any event related to C function objects being called. Any trace function registered using PyEval_SetTrace() will not receive PyTrace_C_CALL, PyTrace_C_EXCEPTION or PyTrace_C_RETURN as a value for the what parameter.

也請見 sys.settrace() 函式。

呼叫者必須擁有一個 attached thread state。

void PyEval_SetTraceAllThreads(Py_tracefunc func, PyObject *obj)

Like PyEval_SetTrace() but sets the tracing function in all running threads belonging to the current interpreter instead of the setting it only on the current thread.

呼叫者必須擁有一個 attached thread state。

As PyEval_SetTrace(), this function ignores any exceptions raised while setting the trace functions in all threads.

在 3.12 版被加入.

Reference tracing

在 3.13 版被加入.

typedef int (*PyRefTracer)(PyObject*, int event, void *data)

The type of the trace function registered using PyRefTracer_SetTracer(). The first parameter is a Python object that has been just created (when event is set to PyRefTracer_CREATE) or about to be destroyed (when event is set to PyRefTracer_DESTROY). The data argument is the opaque pointer that was provided when PyRefTracer_SetTracer() was called.

在 3.13 版被加入.

int PyRefTracer_CREATE

The value for the event parameter to PyRefTracer functions when a Python object has been created.

int PyRefTracer_DESTROY

The value for the event parameter to PyRefTracer functions when a Python object has been destroyed.

int PyRefTracer_SetTracer(PyRefTracer tracer, void *data)

Register a reference tracer function. The function will be called when a new Python has been created or when an object is going to be destroyed. If data is provided it must be an opaque pointer that will be provided when the tracer function is called. Return 0 on success. Set an exception and return -1 on error.

Not that tracer functions must not create Python objects inside or otherwise the call will be re-entrant. The tracer also must not clear any existing exception or set an exception. A thread state will be active every time the tracer function is called.

There must be an attached thread state when calling this function.

在 3.13 版被加入.

PyRefTracer PyRefTracer_GetTracer(void **data)

Get the registered reference tracer function and the value of the opaque data pointer that was registered when PyRefTracer_SetTracer() was called. If no tracer was registered this function will return NULL and will set the data pointer to NULL.

There must be an attached thread state when calling this function.

在 3.13 版被加入.

Advanced Debugger Support

These functions are only intended to be used by advanced debugging tools.

PyInterpreterState *PyInterpreterState_Head()

Return the interpreter state object at the head of the list of all such objects.

PyInterpreterState *PyInterpreterState_Main()

Return the main interpreter state object.

PyInterpreterState *PyInterpreterState_Next(PyInterpreterState *interp)

Return the next interpreter state object after interp from the list of all such objects.

PyThreadState *PyInterpreterState_ThreadHead(PyInterpreterState *interp)

Return the pointer to the first PyThreadState object in the list of threads associated with the interpreter interp.

PyThreadState *PyThreadState_Next(PyThreadState *tstate)

Return the next thread state object after tstate from the list of all such objects belonging to the same PyInterpreterState object.

Thread Local Storage Support

The Python interpreter provides low-level support for thread-local storage (TLS) which wraps the underlying native TLS implementation to support the Python-level thread local storage API (threading.local). The CPython C level APIs are similar to those offered by pthreads and Windows: use a thread key and functions to associate a void* value per thread.

A thread state does not need to be attached when calling these functions; they suppl their own locking.

Note that Python.h does not include the declaration of the TLS APIs, you need to include pythread.h to use thread-local storage.

備註

None of these API functions handle memory management on behalf of the void* values. You need to allocate and deallocate them yourself. If the void* values happen to be PyObject*, these functions don't do refcount operations on them either.

Thread Specific Storage (TSS) API

TSS API is introduced to supersede the use of the existing TLS API within the CPython interpreter. This API uses a new type Py_tss_t instead of int to represent thread keys.

在 3.7 版被加入.

也參考

"A New C-API for Thread-Local Storage in CPython" (PEP 539 [https://peps.python.org/pep-0539/])

type Py_tss_t

This data structure represents the state of a thread key, the definition of which may depend on the underlying TLS implementation, and it has an internal field representing the key's initialization state. There are no public members in this structure.

When Py_LIMITED_API is not defined, static allocation of this type by Py_tss_NEEDS_INIT is allowed.

Py_tss_NEEDS_INIT

This macro expands to the initializer for Py_tss_t variables. Note that this macro won't be defined with Py_LIMITED_API.

Dynamic Allocation

Dynamic allocation of the Py_tss_t, required in extension modules built with Py_LIMITED_API, where static allocation of this type is not possible due to its implementation being opaque at build time.

Py_tss_t *PyThread_tss_alloc()

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return a value which is the same state as a value initialized with Py_tss_NEEDS_INIT, or NULL in the case of dynamic allocation failure.

void PyThread_tss_free(Py_tss_t *key)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Free the given key allocated by PyThread_tss_alloc(), after first calling PyThread_tss_delete() to ensure any associated thread locals have been unassigned. This is a no-op if the key argument is NULL.

備註

A freed key becomes a dangling pointer. You should reset the key to NULL.

方法

The parameter key of these functions must not be NULL. Moreover, the behaviors of PyThread_tss_set() and PyThread_tss_get() are undefined if the given Py_tss_t has not been initialized by PyThread_tss_create().

int PyThread_tss_is_created(Py_tss_t *key)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return a non-zero value if the given Py_tss_t has been initialized by PyThread_tss_create().

int PyThread_tss_create(Py_tss_t *key)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return a zero value on successful initialization of a TSS key. The behavior is undefined if the value pointed to by the key argument is not initialized by Py_tss_NEEDS_INIT. This function can be called repeatedly on the same key -- calling it on an already initialized key is a no-op and immediately returns success.

void PyThread_tss_delete(Py_tss_t *key)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Destroy a TSS key to forget the values associated with the key across all threads, and change the key's initialization state to uninitialized. A destroyed key is able to be initialized again by PyThread_tss_create(). This function can be called repeatedly on the same key -- calling it on an already destroyed key is a no-op.

int PyThread_tss_set(Py_tss_t *key, void *value)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return a zero value to indicate successfully associating a void* value with a TSS key in the current thread. Each thread has a distinct mapping of the key to a void* value.

void *PyThread_tss_get(Py_tss_t *key)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Return the void* value associated with a TSS key in the current thread. This returns NULL if no value is associated with the key in the current thread.

執行緒局部儲存 (Thread Local Storage, TLS) API：

在 3.7 版之後被棄用: This API is superseded by Thread Specific Storage (TSS) API.

備註

This version of the API does not support platforms where the native TLS key is defined in a way that cannot be safely cast to int. On such platforms, PyThread_create_key() will return immediately with a failure status, and the other TLS functions will all be no-ops on such platforms.

Due to the compatibility problem noted above, this version of the API should not be used in new code.

int PyThread_create_key()

為 穩定 ABI 的一部分.

void PyThread_delete_key(int key)

為 穩定 ABI 的一部分.

int PyThread_set_key_value(int key, void *value)

為 穩定 ABI 的一部分.

void *PyThread_get_key_value(int key)

為 穩定 ABI 的一部分.

void PyThread_delete_key_value(int key)

為 穩定 ABI 的一部分.

void PyThread_ReInitTLS()

為 穩定 ABI 的一部分.

Synchronization Primitives

The C-API provides a basic mutual exclusion lock.

type PyMutex

A mutual exclusion lock. The PyMutex should be initialized to zero to represent the unlocked state. For example:

PyMutex mutex = {0};

Instances of PyMutex should not be copied or moved. Both the contents and address of a PyMutex are meaningful, and it must remain at a fixed, writable location in memory.

備註

A PyMutex currently occupies one byte, but the size should be considered unstable. The size may change in future Python releases without a deprecation period.

在 3.13 版被加入.

void PyMutex_Lock(PyMutex *m)

Lock mutex m. If another thread has already locked it, the calling thread will block until the mutex is unlocked. While blocked, the thread will temporarily detach the thread state if one exists.

在 3.13 版被加入.

void PyMutex_Unlock(PyMutex *m)

Unlock mutex m. The mutex must be locked --- otherwise, the function will issue a fatal error.

在 3.13 版被加入.

int PyMutex_IsLocked(PyMutex *m)

Returns non-zero if the mutex m is currently locked, zero otherwise.

備註

This function is intended for use in assertions and debugging only and should not be used to make concurrency control decisions, as the lock state may change immediately after the check.

在 3.14 版被加入.

Python Critical Section API

The critical section API provides a deadlock avoidance layer on top of per-object locks for free-threaded CPython. They are intended to replace reliance on the global interpreter lock, and are no-ops in versions of Python with the global interpreter lock.

Critical sections are intended to be used for custom types implemented in C-API extensions. They should generally not be used with built-in types like list and dict because their public C-APIs already use critical sections internally, with the notable exception of PyDict_Next(), which requires critical section to be acquired externally.

Critical sections avoid deadlocks by implicitly suspending active critical sections, hence, they do not provide exclusive access such as provided by traditional locks like PyMutex. When a critical section is started, the per-object lock for the object is acquired. If the code executed inside the critical section calls C-API functions then it can suspend the critical section thereby releasing the per-object lock, so other threads can acquire the per-object lock for the same object.

Variants that accept PyMutex pointers rather than Python objects are also available. Use these variants to start a critical section in a situation where there is no PyObject -- for example, when working with a C type that does not extend or wrap PyObject but still needs to call into the C API in a manner that might lead to deadlocks.

The functions and structs used by the macros are exposed for cases where C macros are not available. They should only be used as in the given macro expansions. Note that the sizes and contents of the structures may change in future Python versions.

備註

Operations that need to lock two objects at once must use Py_BEGIN_CRITICAL_SECTION2. You cannot use nested critical sections to lock more than one object at once, because the inner critical section may suspend the outer critical sections. This API does not provide a way to lock more than two objects at once.

範例用法：

static PyObject *
set_field(MyObject *self, PyObject *value)
{
   Py_BEGIN_CRITICAL_SECTION(self);
   Py_SETREF(self->field, Py_XNewRef(value));
   Py_END_CRITICAL_SECTION();
   Py_RETURN_NONE;
}

In the above example, Py_SETREF calls Py_DECREF, which can call arbitrary code through an object's deallocation function. The critical section API avoids potential deadlocks due to reentrancy and lock ordering by allowing the runtime to temporarily suspend the critical section if the code triggered by the finalizer blocks and calls PyEval_SaveThread().

Py_BEGIN_CRITICAL_SECTION(op)

Acquires the per-object lock for the object op and begins a critical section.

In the free-threaded build, this macro expands to:

{
    PyCriticalSection _py_cs;
    PyCriticalSection_Begin(&_py_cs, (PyObject*)(op))

In the default build, this macro expands to {.

在 3.13 版被加入.

Py_BEGIN_CRITICAL_SECTION_MUTEX(m)

Locks the mutex m and begins a critical section.

In the free-threaded build, this macro expands to:

{
     PyCriticalSection _py_cs;
     PyCriticalSection_BeginMutex(&_py_cs, m)

Note that unlike Py_BEGIN_CRITICAL_SECTION, there is no cast for the argument of the macro - it must be a PyMutex pointer.

On the default build, this macro expands to {.

在 3.14 版被加入.

Py_END_CRITICAL_SECTION()

Ends the critical section and releases the per-object lock.

In the free-threaded build, this macro expands to:

    PyCriticalSection_End(&_py_cs);
}

In the default build, this macro expands to }.

在 3.13 版被加入.

Py_BEGIN_CRITICAL_SECTION2(a, b)

Acquires the per-objects locks for the objects a and b and begins a critical section. The locks are acquired in a consistent order (lowest address first) to avoid lock ordering deadlocks.

In the free-threaded build, this macro expands to:

{
    PyCriticalSection2 _py_cs2;
    PyCriticalSection2_Begin(&_py_cs2, (PyObject*)(a), (PyObject*)(b))

In the default build, this macro expands to {.

在 3.13 版被加入.

Py_BEGIN_CRITICAL_SECTION2_MUTEX(m1, m2)

Locks the mutexes m1 and m2 and begins a critical section.

In the free-threaded build, this macro expands to:

{
     PyCriticalSection2 _py_cs2;
     PyCriticalSection2_BeginMutex(&_py_cs2, m1, m2)

Note that unlike Py_BEGIN_CRITICAL_SECTION2, there is no cast for the arguments of the macro - they must be PyMutex pointers.

On the default build, this macro expands to {.

在 3.14 版被加入.

Py_END_CRITICAL_SECTION2()

Ends the critical section and releases the per-object locks.

In the free-threaded build, this macro expands to:

    PyCriticalSection2_End(&_py_cs2);
}

In the default build, this macro expands to }.

在 3.13 版被加入.

Legacy Locking APIs

These APIs are obsolete since Python 3.13 with the introduction of PyMutex.

在 3.15 版的變更: These APIs are now a simple wrapper around PyMutex.

type PyThread_type_lock

A pointer to a mutual exclusion lock.

type PyLockStatus

The result of acquiring a lock with a timeout.

enumerator PY_LOCK_FAILURE

Failed to acquire the lock.

enumerator PY_LOCK_ACQUIRED

The lock was successfully acquired.

enumerator PY_LOCK_INTR

The lock was interrupted by a signal.

PyThread_type_lock PyThread_allocate_lock(void)

為 穩定 ABI 的一部分.

Allocate a new lock.

On success, this function returns a lock; on failure, this function returns 0 without an exception set.

呼叫者不需擁有一個 attached thread state。

在 3.15 版的變更: This function now always uses PyMutex. In prior versions, this would use a lock provided by the operating system.

void PyThread_free_lock(PyThread_type_lock lock)

為 穩定 ABI 的一部分.

Destroy lock. The lock should not be held by any thread when calling this.

呼叫者不需擁有一個 attached thread state。

PyLockStatus PyThread_acquire_lock_timed(PyThread_type_lock lock, long long microseconds, int intr_flag)

為 穩定 ABI 的一部分.

Acquire lock with a timeout.

This will wait for microseconds microseconds to acquire the lock. If the timeout expires, this function returns PY_LOCK_FAILURE. If microseconds is -1, this will wait indefinitely until the lock has been released.

If intr_flag is 1, acquiring the lock may be interrupted by a signal, in which case this function returns PY_LOCK_INTR. Upon interruption, it's generally expected that the caller makes a call to Py_MakePendingCalls() to propagate an exception to Python code.

If the lock is successfully acquired, this function returns PY_LOCK_ACQUIRED.

呼叫者不需擁有一個 attached thread state。

int PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)

為 穩定 ABI 的一部分.

Acquire lock.

If waitflag is 1 and another thread currently holds the lock, this function will wait until the lock can be acquired and will always return 1.

If waitflag is 0 and another thread holds the lock, this function will not wait and instead return 0. If the lock is not held by any other thread, then this function will acquire it and return 1.

Unlike PyThread_acquire_lock_timed(), acquiring the lock cannot be interrupted by a signal.

呼叫者不需擁有一個 attached thread state。

int PyThread_release_lock(PyThread_type_lock lock)

為 穩定 ABI 的一部分.

Release lock. If lock is not held, then this function issues a fatal error.

呼叫者不需擁有一個 attached thread state。

Operating System Thread APIs

PYTHREAD_INVALID_THREAD_ID

Sentinel value for an invalid thread ID.

This is currently equivalent to (unsigned long)-1.

unsigned long PyThread_start_new_thread(void (*func)(void*), void *arg)

為 穩定 ABI 的一部分.

Start function func in a new thread with argument arg. The resulting thread is not intended to be joined.

func must not be NULL, but arg may be NULL.

On success, this function returns the identifier of the new thread; on failure, this returns PYTHREAD_INVALID_THREAD_ID.

呼叫者不需擁有一個 attached thread state。

unsigned long PyThread_get_thread_ident(void)

為 穩定 ABI 的一部分.

Return the identifier of the current thread, which will never be zero.

This function cannot fail, and the caller does not need to hold an attached thread state.

也參考

threading.get_ident()

PyObject *PyThread_GetInfo(void)

為 穩定 ABI 的一部分 自 3.3 版本開始.

Get general information about the current thread in the form of a struct sequence object. This information is accessible as sys.thread_info in Python.

On success, this returns a new strong reference to the thread information; on failure, this returns NULL with an exception set.

呼叫者必須擁有一個 attached thread state。

PY_HAVE_THREAD_NATIVE_ID

This macro is defined when the system supports native thread IDs.

unsigned long PyThread_get_thread_native_id(void)

為 穩定 ABI 的一部分 on platforms with native thread IDs.

Get the native identifier of the current thread as it was assigned by the operating system's kernel, which will never be less than zero.

This function is only available when PY_HAVE_THREAD_NATIVE_ID is defined.

This function cannot fail, and the caller does not need to hold an attached thread state.

也參考

threading.get_native_id()

void PyThread_exit_thread(void)

為 穩定 ABI 的一部分.

Terminate the current thread. This function is generally considered unsafe and should be avoided. It is kept solely for backwards compatibility.

This function is only safe to call if all functions in the full call stack are written to safely allow it.

警告

If the current system uses POSIX threads (also known as "pthreads"), this calls pthread_exit(3) [https://manpages.debian.org/pthread_exit(3)], which attempts to unwind the stack and call C++ destructors on some libc implementations. However, if a noexcept function is reached, it may terminate the process. Other systems, such as macOS, do unwinding.

On Windows, this function calls _endthreadex(), which kills the thread without calling C++ destructors.

In any case, there is a risk of corruption on the thread's stack.

在 3.14 版之後被棄用.

void PyThread_init_thread(void)

為 穩定 ABI 的一部分.

Initialize PyThread* APIs. Python executes this function automatically, so there's little need to call it from an extension module.

int PyThread_set_stacksize(size_t size)

為 穩定 ABI 的一部分.

Set the stack size of the current thread to size bytes.

This function returns 0 on success, -1 if size is invalid, or -2 if the system does not support changing the stack size. This function does not set exceptions.

呼叫者不需擁有一個 attached thread state。

size_t PyThread_get_stacksize(void)

為 穩定 ABI 的一部分.

Return the stack size of the current thread in bytes, or 0 if the system's default stack size is in use.

呼叫者不需擁有一個 attached thread state。

Python 初始化設定

PyInitConfig C API

在 3.14 版被加入.

Python 可以使用 Py_InitializeFromInitConfig() 來初始化。

The Py_RunMain() function can be used to write a customized Python program.

See also Initialization, Finalization, and Threads.

也參考

PEP 741 [https://peps.python.org/pep-0741/] "Python Configuration C API".

範例

Example of customized Python always running with the Python Development Mode enabled; return -1 on error:

int init_python(void)
{
    PyInitConfig *config = PyInitConfig_Create();
    if (config == NULL) {
        printf("PYTHON INIT ERROR: memory allocation failed\n");
        return -1;
    }

    // Enable the Python Development Mode
    if (PyInitConfig_SetInt(config, "dev_mode", 1) < 0) {
        goto error;
    }

    // Initialize Python with the configuration
    if (Py_InitializeFromInitConfig(config) < 0) {
        goto error;
    }
    PyInitConfig_Free(config);
    return 0;

error:
    {
        // Display the error message.
        //
        // This uncommon braces style is used, because you cannot make
        // goto targets point to variable declarations.
        const char *err_msg;
        (void)PyInitConfig_GetError(config, &err_msg);
        printf("PYTHON INIT ERROR: %s\n", err_msg);
        PyInitConfig_Free(config);
        return -1;
    }
}

建立設定

struct PyInitConfig

Opaque structure to configure the Python initialization.

PyInitConfig *PyInitConfig_Create(void)

Create a new initialization configuration using Isolated Configuration default values.

必須由 PyInitConfig_Free() 來釋放。

在記憶體配置失敗時回傳 NULL。

void PyInitConfig_Free(PyInitConfig *config)

釋放初始化配置 config 的記憶體。

如果 config 是 NULL，則不執行任何操作。

錯誤處理

int PyInitConfig_GetError(PyInitConfig *config, const char **err_msg)

取得 config 錯誤訊息。

如果設定了錯誤，則設置 *err_msg 並回傳 1。

如果沒有設定錯誤，則設定 *err_msg 為 NULL 並回傳 0。

錯誤訊息是 UTF-8 編碼的字串。

If config has an exit code, format the exit code as an error message.

The error message remains valid until another PyInitConfig function is called with config. The caller doesn't have to free the error message.

int PyInitConfig_GetExitCode(PyInitConfig *config, int *exitcode)

Get the config exit code.

Set *exitcode and return 1 if config has an exit code set.

Return 0 if config has no exit code set.

Only the Py_InitializeFromInitConfig() function can set an exit code if the parse_argv option is non-zero.

An exit code can be set when parsing the command line failed (exit code 2) or when a command line option asks to display the command line help (exit code 0).

Get Options

The configuration option name parameter must be a non-NULL null-terminated UTF-8 encoded string. See Configuration Options.

int PyInitConfig_HasOption(PyInitConfig *config, const char *name)

測試配置是否有名為 name 的選項。

如果選項存在則回傳 1，否則回傳 0。

int PyInitConfig_GetInt(PyInitConfig *config, const char *name, int64_t *value)

Get an integer configuration option.

Set *value, and return 0 on success.

Set an error in config and return -1 on error.

int PyInitConfig_GetStr(PyInitConfig *config, const char *name, char **value)

Get a string configuration option as a null-terminated UTF-8 encoded string.

Set *value, and return 0 on success.

Set an error in config and return -1 on error.

*value can be set to NULL if the option is an optional string and the option is unset.

On success, the string must be released with free(value) if it's not NULL.

int PyInitConfig_GetStrList(PyInitConfig *config, const char *name, size_t *length, char ***items)

Get a string list configuration option as an array of null-terminated UTF-8 encoded strings.

Set *length and *value, and return 0 on success.

Set an error in config and return -1 on error.

On success, the string list must be released with PyInitConfig_FreeStrList(length, items).

void PyInitConfig_FreeStrList(size_t length, char **items)

Free memory of a string list created by PyInitConfig_GetStrList().

Set Options

The configuration option name parameter must be a non-NULL null-terminated UTF-8 encoded string. See Configuration Options.

Some configuration options have side effects on other options. This logic is only implemented when Py_InitializeFromInitConfig() is called, not by the "Set" functions below. For example, setting dev_mode to 1 does not set faulthandler to 1.

int PyInitConfig_SetInt(PyInitConfig *config, const char *name, int64_t value)

Set an integer configuration option.

成功時回傳 0。

Set an error in config and return -1 on error.

int PyInitConfig_SetStr(PyInitConfig *config, const char *name, const char *value)

Set a string configuration option from a null-terminated UTF-8 encoded string. The string is copied.

成功時回傳 0。

Set an error in config and return -1 on error.

int PyInitConfig_SetStrList(PyInitConfig *config, const char *name, size_t length, char *const *items)

Set a string list configuration option from an array of null-terminated UTF-8 encoded strings. The string list is copied.

成功時回傳 0。

Set an error in config and return -1 on error.

模組

int PyInitConfig_AddModule(PyInitConfig *config, const char *name, PyObject *(*initfunc)(void))

Add a built-in extension module to the table of built-in modules.

The new module can be imported by the name name, and uses the function initfunc as the initialization function called on the first attempted import.

成功時回傳 0。

Set an error in config and return -1 on error.

If Python is initialized multiple times, PyInitConfig_AddModule() must be called at each Python initialization.

和 PyImport_AppendInittab() 函式類似。

初始化 Python

int Py_InitializeFromInitConfig(PyInitConfig *config)

Initialize Python from the initialization configuration.

成功時回傳 0。

Set an error in config and return -1 on error.

Set an exit code in config and return -1 if Python wants to exit.

See PyInitConfig_GetExitcode() for the exit code case.

Configuration Options

選項

PyConfig/PyPreConfig 成員

Type

Visibility

"allocator"

allocator

int

唯讀

"argv"

argv

list[str]

公開

"base_exec_prefix"

base_exec_prefix

str

公開

"base_executable"

base_executable

str

公開

"base_prefix"

base_prefix

str

公開

"buffered_stdio"

buffered_stdio

bool

唯讀

"bytes_warning"

bytes_warning

int

公開

"check_hash_pycs_mode"

check_hash_pycs_mode

str

唯讀

"code_debug_ranges"

code_debug_ranges

bool

唯讀

"coerce_c_locale"

coerce_c_locale

bool

唯讀

"coerce_c_locale_warn"

coerce_c_locale_warn

bool

唯讀

"configure_c_stdio"

configure_c_stdio

bool

唯讀

"configure_locale"

configure_locale

bool

唯讀

"cpu_count"

cpu_count

int

公開

"dev_mode"

dev_mode

bool

唯讀

"dump_refs"

dump_refs

bool

唯讀

"dump_refs_file"

dump_refs_file

str

唯讀

"exec_prefix"

exec_prefix

str

公開

"executable"

executable

str

公開

"faulthandler"

faulthandler

bool

唯讀

"filesystem_encoding"

filesystem_encoding

str

唯讀

"filesystem_errors"

filesystem_errors

str

唯讀

"hash_seed"

hash_seed

int

唯讀

"home"

home

str

唯讀

"import_time"

import_time

int

唯讀

"inspect"

inspect

bool

公開

"install_signal_handlers"

install_signal_handlers

bool

唯讀

"int_max_str_digits"

int_max_str_digits

int

公開

"interactive"

interactive

bool

公開

"isolated"

isolated

bool

唯讀

"legacy_windows_fs_encoding"

legacy_windows_fs_encoding

bool

唯讀

"legacy_windows_stdio"

legacy_windows_stdio

bool

唯讀

"malloc_stats"

malloc_stats

bool

唯讀

"module_search_paths"

module_search_paths

list[str]

公開

"optimization_level"

optimization_level

int

公開

"orig_argv"

orig_argv

list[str]

唯讀

"parse_argv"

parse_argv

bool

唯讀

"parser_debug"

parser_debug

bool

公開

"pathconfig_warnings"

pathconfig_warnings

bool

唯讀

"perf_profiling"

perf_profiling

bool

唯讀

"platlibdir"

platlibdir

str

公開

"prefix"

prefix

str

公開

"surrogateescape"

program_name

str

唯讀

"pycache_prefix"

pycache_prefix

str

公開

"quiet"

quiet

bool

公開

"run_command"

run_command

str

唯讀

"run_filename"

run_filename

str

唯讀

"run_module"

run_module

str

唯讀

"run_presite"

run_presite

str

唯讀

"safe_path"

safe_path

bool

唯讀

"show_ref_count"

show_ref_count

bool

唯讀

"site_import"

site_import

bool

唯讀

"skip_source_first_line"

skip_source_first_line

bool

唯讀

"stdio_encoding"

stdio_encoding

str

唯讀

"stdio_errors"

stdio_errors

str

唯讀

"stdlib_dir"

stdlib_dir

str

公開

"tracemalloc"

tracemalloc

int

唯讀

"use_environment"

use_environment

bool

公開

"use_frozen_modules"

use_frozen_modules

bool

唯讀

"use_hash_seed"

use_hash_seed

bool

唯讀

"use_system_logger"

use_system_logger

bool

唯讀

"user_site_directory"

user_site_directory

bool

唯讀

"utf8_mode"

utf8_mode

bool

唯讀

"verbose"

verbose

int

公開

"warn_default_encoding"

warn_default_encoding

bool

唯讀

"warnoptions"

warnoptions

list[str]

公開

"write_bytecode"

write_bytecode

bool

公開

"xoptions"

xoptions

dict[str, str]

公開

"_pystats"

_pystats

bool

唯讀

Visibility:

Public: Can by get by PyConfig_Get() and set by PyConfig_Set().

Read-only: Can by get by PyConfig_Get(), but cannot be set by PyConfig_Set().

Runtime Python configuration API

At runtime, it's possible to get and set configuration options using PyConfig_Get() and PyConfig_Set() functions.

The configuration option name parameter must be a non-NULL null-terminated UTF-8 encoded string. See Configuration Options.

Some options are read from the sys attributes. For example, the option "argv" is read from sys.argv.

PyObject *PyConfig_Get(const char *name)

Get the current runtime value of a configuration option as a Python object.

Return a new reference on success.

Set an exception and return NULL on error.

The object type depends on the configuration option. It can be:

bool

int

str

list[str]

dict[str, str]

The caller must have an attached thread state. The function cannot be called before Python initialization nor after Python finalization.

在 3.14 版被加入.

int PyConfig_GetInt(const char *name, int *value)

Similar to PyConfig_Get(), but get the value as a C int.

成功時回傳 0。

Set an exception and return -1 on error.

在 3.14 版被加入.

PyObject *PyConfig_Names(void)

Get all configuration option names as a frozenset.

Return a new reference on success.

Set an exception and return NULL on error.

The caller must have an attached thread state. The function cannot be called before Python initialization nor after Python finalization.

在 3.14 版被加入.

int PyConfig_Set(const char *name, PyObject *value)

Set the current runtime value of a configuration option.

如果沒有選項 name，則引發 ValueError。

如果 value 是無效值，則引發 ValueError。

如果選項是唯讀的（無法設定），則引發 ValueError。

Raise a TypeError if value has not the proper type.

The caller must have an attached thread state. The function cannot be called before Python initialization nor after Python finalization.

Raises an auditing event cpython.PyConfig_Set with arguments name, value.

在 3.14 版被加入.

PyConfig C API

在 3.8 版被加入.

Python can be initialized with Py_InitializeFromConfig() and the PyConfig structure. It can be preinitialized with Py_PreInitialize() and the PyPreConfig structure.

There are two kinds of configuration:

The Python Configuration can be used to build a customized Python which behaves as the regular Python. For example, environment variables and command line arguments are used to configure Python.

The Isolated Configuration can be used to embed Python into an application. It isolates Python from the system. For example, environment variables are ignored, the LC_CTYPE locale is left unchanged and no signal handler is registered.

The Py_RunMain() function can be used to write a customized Python program.

See also Initialization, Finalization, and Threads.

也參考

PEP 587 [https://peps.python.org/pep-0587/] "Python Initialization Configuration".

範例

Example of customized Python always running in isolated mode:

int main(int argc, char **argv)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    config.isolated = 1;

    /* Decode command line arguments.
       Implicitly preinitialize Python (in isolated mode). */
    status = PyConfig_SetBytesArgv(&config, argc, argv);
    if (PyStatus_Exception(status)) {
        goto exception;
    }

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);

    return Py_RunMain();

exception:
    PyConfig_Clear(&config);
    if (PyStatus_IsExit(status)) {
        return status.exitcode;
    }
    /* Display the error message and exit the process with
       non-zero exit code */
    Py_ExitStatusException(status);
}

PyWideStringList

type PyWideStringList

wchar_t* 字串串列。

If length is non-zero, items must be non-NULL and all strings must be non-NULL.

方法：

PyStatus PyWideStringList_Append(PyWideStringList *list, const wchar_t *item)

Append item to list.

Python must be preinitialized to call this function.

PyStatus PyWideStringList_Insert(PyWideStringList *list, Py_ssize_t index, const wchar_t *item)

Insert item into list at index.

If index is greater than or equal to list length, append item to list.

index must be greater than or equal to 0.

Python must be preinitialized to call this function.

Structure fields:

Py_ssize_t length

串列長度。

wchar_t **items

List items.

PyStatus

type PyStatus

Structure to store an initialization function status: success, error or exit.

For an error, it can store the C function name which created the error.

Structure fields:

int exitcode

Exit code. Argument passed to exit().

const char *err_msg

錯誤訊息。

const char *func

Name of the function which created an error, can be NULL.

建立狀態的函式：

PyStatus PyStatus_Ok(void)

成功。

PyStatus PyStatus_Error(const char *err_msg)

附帶訊息的初始化錯誤。

err_msg 不可為 NULL。

PyStatus PyStatus_NoMemory(void)

Memory allocation failure (out of memory).

PyStatus PyStatus_Exit(int exitcode)

以指定的退出代號退出 Python。

處理狀態的函式：

int PyStatus_Exception(PyStatus status)

Is the status an error or an exit? If true, the exception must be handled; by calling Py_ExitStatusException() for example.

int PyStatus_IsError(PyStatus status)

Is the result an error?

int PyStatus_IsExit(PyStatus status)

Is the result an exit?

void Py_ExitStatusException(PyStatus status)

Call exit(exitcode) if status is an exit. Print the error message and exit with a non-zero exit code if status is an error. Must only be called if PyStatus_Exception(status) is non-zero.

備註

Internally, Python uses macros which set PyStatus.func, whereas functions to create a status set func to NULL.

範例：

PyStatus alloc(void **ptr, size_t size)
{
    *ptr = PyMem_RawMalloc(size);
    if (*ptr == NULL) {
        return PyStatus_NoMemory();
    }
    return PyStatus_Ok();
}

int main(int argc, char **argv)
{
    void *ptr;
    PyStatus status = alloc(&ptr, 16);
    if (PyStatus_Exception(status)) {
        Py_ExitStatusException(status);
    }
    PyMem_Free(ptr);
    return 0;
}

PyPreConfig

type PyPreConfig

Structure used to preinitialize Python.

Function to initialize a preconfiguration:

void PyPreConfig_InitPythonConfig(PyPreConfig *preconfig)

Initialize the preconfiguration with Python Configuration.

void PyPreConfig_InitIsolatedConfig(PyPreConfig *preconfig)

Initialize the preconfiguration with Isolated Configuration.

Structure fields:

int allocator

Name of the Python memory allocators:

PYMEM_ALLOCATOR_NOT_SET (0): don't change memory allocators (use defaults).

PYMEM_ALLOCATOR_DEFAULT (1): default memory allocators.

PYMEM_ALLOCATOR_DEBUG (2): default memory allocators with debug hooks.

PYMEM_ALLOCATOR_MALLOC (3): use malloc() of the C library.

PYMEM_ALLOCATOR_MALLOC_DEBUG (4): force usage of malloc() with debug hooks.

PYMEM_ALLOCATOR_PYMALLOC (5): Python pymalloc memory allocator.

PYMEM_ALLOCATOR_PYMALLOC_DEBUG (6): Python pymalloc memory allocator with debug hooks.

PYMEM_ALLOCATOR_MIMALLOC (6): use mimalloc, a fast malloc replacement.

PYMEM_ALLOCATOR_MIMALLOC_DEBUG (7): use mimalloc, a fast malloc replacement with debug hooks.

PYMEM_ALLOCATOR_PYMALLOC and PYMEM_ALLOCATOR_PYMALLOC_DEBUG are not supported if Python is configured using --without-pymalloc.

PYMEM_ALLOCATOR_MIMALLOC and PYMEM_ALLOCATOR_MIMALLOC_DEBUG are not supported if Python is configured using --without-mimalloc or if the underlying atomic support isn't available.

請見記憶體管理。

預設：PYMEM_ALLOCATOR_NOT_SET。

int configure_locale

Set the LC_CTYPE locale to the user preferred locale.

If equals to 0, set coerce_c_locale and coerce_c_locale_warn members to 0.

請見 locale encoding。

Default: 1 in Python config, 0 in isolated config.

int coerce_c_locale

If equals to 2, coerce the C locale.

If equals to 1, read the LC_CTYPE locale to decide if it should be coerced.

請見 locale encoding。

Default: -1 in Python config, 0 in isolated config.

int coerce_c_locale_warn

If non-zero, emit a warning if the C locale is coerced.

Default: -1 in Python config, 0 in isolated config.

int dev_mode

Python Development Mode: see PyConfig.dev_mode.

Default: -1 in Python mode, 0 in isolated mode.

int isolated

Isolated mode: see PyConfig.isolated.

Default: 0 in Python mode, 1 in isolated mode.

int legacy_windows_fs_encoding

如果不為 0：

將 PyPreConfig.utf8_mode 設為 0、

將 PyConfig.filesystem_encoding 設為 "mbcs"、

將 PyConfig.filesystem_errors 設為 "replace"。

Initialized from the PYTHONLEGACYWINDOWSFSENCODING environment variable value.

Only available on Windows. #ifdef MS_WINDOWS macro can be used for Windows specific code.

預設：0。

int parse_argv

If non-zero, Py_PreInitializeFromArgs() and Py_PreInitializeFromBytesArgs() parse their argv argument the same way the regular Python parses command line arguments: see Command Line Arguments.

Default: 1 in Python config, 0 in isolated config.

int use_environment

Use environment variables? See PyConfig.use_environment.

Default: 1 in Python config and 0 in isolated config.

int utf8_mode

If non-zero, enable the Python UTF-8 Mode.

Set to 0 or 1 by the -X utf8 command line option and the PYTHONUTF8 environment variable.

Also set to 1 if the LC_CTYPE locale is C or POSIX.

Default: -1 in Python config and 0 in isolated config.

Preinitialize Python with PyPreConfig

The preinitialization of Python:

Set the Python memory allocators (PyPreConfig.allocator)

Configure the LC_CTYPE locale (locale encoding)

Set the Python UTF-8 Mode (PyPreConfig.utf8_mode)

The current preconfiguration (PyPreConfig type) is stored in _PyRuntime.preconfig.

Functions to preinitialize Python:

PyStatus Py_PreInitialize(const PyPreConfig *preconfig)

Preinitialize Python from preconfig preconfiguration.

preconfig 不可為 NULL。

PyStatus Py_PreInitializeFromBytesArgs(const PyPreConfig *preconfig, int argc, char *const *argv)

Preinitialize Python from preconfig preconfiguration.

Parse argv command line arguments (bytes strings) if parse_argv of preconfig is non-zero.

preconfig 不可為 NULL。

PyStatus Py_PreInitializeFromArgs(const PyPreConfig *preconfig, int argc, wchar_t *const *argv)

Preinitialize Python from preconfig preconfiguration.

Parse argv command line arguments (wide strings) if parse_argv of preconfig is non-zero.

preconfig 不可為 NULL。

The caller is responsible to handle exceptions (error or exit) using PyStatus_Exception() and Py_ExitStatusException().

For Python Configuration (PyPreConfig_InitPythonConfig()), if Python is initialized with command line arguments, the command line arguments must also be passed to preinitialize Python, since they have an effect on the pre-configuration like encodings. For example, the -X utf8 command line option enables the Python UTF-8 Mode.

PyMem_SetAllocator() can be called after Py_PreInitialize() and before Py_InitializeFromConfig() to install a custom memory allocator. It can be called before Py_PreInitialize() if PyPreConfig.allocator is set to PYMEM_ALLOCATOR_NOT_SET.

Python memory allocation functions like PyMem_RawMalloc() must not be used before the Python preinitialization, whereas calling directly malloc() and free() is always safe. Py_DecodeLocale() must not be called before the Python preinitialization.

Example using the preinitialization to enable the Python UTF-8 Mode:

PyStatus status;
PyPreConfig preconfig;
PyPreConfig_InitPythonConfig(&preconfig);

preconfig.utf8_mode = 1;

status = Py_PreInitialize(&preconfig);
if (PyStatus_Exception(status)) {
    Py_ExitStatusException(status);
}

/* at this point, Python speaks UTF-8 */

Py_Initialize();
/* ... use Python API here ... */
Py_Finalize();

PyConfig

type PyConfig

Structure containing most parameters to configure Python.

When done, the PyConfig_Clear() function must be used to release the configuration memory.

Structure methods:

void PyConfig_InitPythonConfig(PyConfig *config)

Initialize configuration with the Python Configuration.

void PyConfig_InitIsolatedConfig(PyConfig *config)

Initialize configuration with the Isolated Configuration.

PyStatus PyConfig_SetString(PyConfig *config, wchar_t *const *config_str, const wchar_t *str)

Copy the wide character string str into *config_str.

Preinitialize Python if needed.

PyStatus PyConfig_SetBytesString(PyConfig *config, wchar_t *const *config_str, const char *str)

Decode str using Py_DecodeLocale() and set the result into *config_str.

Preinitialize Python if needed.

PyStatus PyConfig_SetArgv(PyConfig *config, int argc, wchar_t *const *argv)

Set command line arguments (argv member of config) from the argv list of wide character strings.

Preinitialize Python if needed.

PyStatus PyConfig_SetBytesArgv(PyConfig *config, int argc, char *const *argv)

Set command line arguments (argv member of config) from the argv list of bytes strings. Decode bytes using Py_DecodeLocale().

Preinitialize Python if needed.

PyStatus PyConfig_SetWideStringList(PyConfig *config, PyWideStringList *list, Py_ssize_t length, wchar_t **items)

Set the list of wide strings list to length and items.

Preinitialize Python if needed.

PyStatus PyConfig_Read(PyConfig *config)

讀取所有 Python 配置。

已經初始化的欄位將保持不變。

Fields for path configuration are no longer calculated or modified when calling this function, as of Python 3.11.

The PyConfig_Read() function only parses PyConfig.argv arguments once: PyConfig.parse_argv is set to 2 after arguments are parsed. Since Python arguments are stripped from PyConfig.argv, parsing arguments twice would parse the application options as Python options.

Preinitialize Python if needed.

在 3.10 版的變更: The PyConfig.argv arguments are now only parsed once, PyConfig.parse_argv is set to 2 after arguments are parsed, and arguments are only parsed if PyConfig.parse_argv equals 1.

在 3.11 版的變更: PyConfig_Read() no longer calculates all paths, and so fields listed under Python Path Configuration may no longer be updated until Py_InitializeFromConfig() is called.

void PyConfig_Clear(PyConfig *config)

Release configuration memory.

Most PyConfig methods preinitialize Python if needed. In that case, the Python preinitialization configuration (PyPreConfig) in based on the PyConfig. If configuration fields which are in common with PyPreConfig are tuned, they must be set before calling a PyConfig method:

PyConfig.dev_mode

PyConfig.isolated

PyConfig.parse_argv

PyConfig.use_environment

Moreover, if PyConfig_SetArgv() or PyConfig_SetBytesArgv() is used, this method must be called before other methods, since the preinitialization configuration depends on command line arguments (if parse_argv is non-zero).

The caller of these methods is responsible to handle exceptions (error or exit) using PyStatus_Exception() and Py_ExitStatusException().

Structure fields:

PyWideStringList argv

Set sys.argv command line arguments based on argv. These parameters are similar to those passed to the program's main() function with the difference that the first entry should refer to the script file to be executed rather than the executable hosting the Python interpreter. If there isn't a script that will be run, the first entry in argv can be an empty string.

Set parse_argv to 1 to parse argv the same way the regular Python parses Python command line arguments and then to strip Python arguments from argv.

If argv is empty, an empty string is added to ensure that sys.argv always exists and is never empty.

預設值：NULL。

另請參閱 orig_argv 成員。

int safe_path

If equals to zero, Py_RunMain() prepends a potentially unsafe path to sys.path at startup:

If argv[0] is equal to L"-m" (python -m module), prepend the current working directory.

If running a script (python script.py), prepend the script's directory. If it's a symbolic link, resolve symbolic links.

Otherwise (python -c code and python), prepend an empty string, which means the current working directory.

Set to 1 by the -P command line option and the PYTHONSAFEPATH environment variable.

Default: 0 in Python config, 1 in isolated config.

在 3.11 版被加入.

wchar_t *base_exec_prefix

sys.base_exec_prefix。

預設值：NULL。

Part of the Python Path Configuration output.

也請見 PyConfig.exec_prefix

wchar_t *base_executable

Python base executable: sys._base_executable.

由 __PYVENV_LAUNCHER__ 環境變數設定。

如果為 NULL，則從 PyConfig.executable 設定。

預設值：NULL。

Part of the Python Path Configuration output.

也請見 PyConfig.executable

wchar_t *base_prefix

sys.base_prefix。

預設值：NULL。

Part of the Python Path Configuration output.

也請見 PyConfig.prefix

int buffered_stdio

If equals to 0 and configure_c_stdio is non-zero, disable buffering on the C streams stdout and stderr.

Set to 0 by the -u command line option and the PYTHONUNBUFFERED environment variable.

stdin is always opened in buffered mode.

預設值：1。

int bytes_warning

If equals to 1, issue a warning when comparing bytes or bytearray with str, or comparing bytes with int.

If equal or greater to 2, raise a BytesWarning exception in these cases.

Incremented by the -b command line option.

預設：0。

int warn_default_encoding

If non-zero, emit a EncodingWarning warning when io.TextIOWrapper uses its default encoding. See 選擇性加入的編碼警告 for details.

預設：0。

在 3.10 版被加入.

int code_debug_ranges

If equals to 0, disables the inclusion of the end line and column mappings in code objects. Also disables traceback printing carets to specific error locations.

Set to 0 by the PYTHONNODEBUGRANGES environment variable and by the -X no_debug_ranges command line option.

預設值：1。

在 3.11 版被加入.

wchar_t *check_hash_pycs_mode

Control the validation behavior of hash-based .pyc files: value of the --check-hash-based-pycs command line option.

有效值：

L"always": Hash the source file for invalidation regardless of value of the 'check_source' flag.

L"never": Assume that hash-based pycs always are valid.

L"default": The 'check_source' flag in hash-based pycs determines invalidation.

預設：L"default"。

See also PEP 552 [https://peps.python.org/pep-0552/] "Deterministic pycs".

int configure_c_stdio

If non-zero, configure C standard streams:

On Windows, set the binary mode (O_BINARY) on stdin, stdout and stderr.

If buffered_stdio equals zero, disable buffering of stdin, stdout and stderr streams.

If interactive is non-zero, enable stream buffering on stdin and stdout (only stdout on Windows).

Default: 1 in Python config, 0 in isolated config.

int dev_mode

If non-zero, enable the Python Development Mode.

Set to 1 by the -X dev option and the PYTHONDEVMODE environment variable.

Default: -1 in Python mode, 0 in isolated mode.

int dump_refs

Dump Python references?

If non-zero, dump all objects which are still alive at exit.

Set to 1 by the PYTHONDUMPREFS environment variable.

Needs a special build of Python with the Py_TRACE_REFS macro defined: see the configure --with-trace-refs option.

預設：0。

wchar_t *dump_refs_file

Filename where to dump Python references.

由 PYTHONDUMPREFSFILE 環境變數設定。

預設值：NULL。

在 3.11 版被加入.

wchar_t *exec_prefix

The site-specific directory prefix where the platform-dependent Python files are installed: sys.exec_prefix.

預設值：NULL。

Part of the Python Path Configuration output.

也請見 PyConfig.base_exec_prefix

wchar_t *executable

The absolute path of the executable binary for the Python interpreter: sys.executable.

預設值：NULL。

Part of the Python Path Configuration output.

也請見 PyConfig.base_executable

int faulthandler

啟用 faulthandler？

如果非零，則在啟動時呼叫 faulthandler.enable()。

Set to 1 by -X faulthandler and the PYTHONFAULTHANDLER environment variable.

Default: -1 in Python mode, 0 in isolated mode.

wchar_t *filesystem_encoding

Filesystem encoding: sys.getfilesystemencoding().

On macOS, Android and VxWorks: use "utf-8" by default.

On Windows: use "utf-8" by default, or "mbcs" if legacy_windows_fs_encoding of PyPreConfig is non-zero.

其他平台的預設編碼：

如果 PyPreConfig.utf8_mode 非零，則為 "utf-8"。

"ascii" if Python detects that nl_langinfo(CODESET) announces the ASCII encoding, whereas the mbstowcs() function decodes from a different encoding (usually Latin1).

"utf-8" if nl_langinfo(CODESET) returns an empty string.

Otherwise, use the locale encoding: nl_langinfo(CODESET) result.

At Python startup, the encoding name is normalized to the Python codec name. For example, "ANSI_X3.4-1968" is replaced with "ascii".

另請參閱 filesystem_errors 成員。

wchar_t *filesystem_errors

Filesystem error handler: sys.getfilesystemencodeerrors().

On Windows: use "surrogatepass" by default, or "replace" if legacy_windows_fs_encoding of PyPreConfig is non-zero.

其他平台：預設使用 "surrogateescape"。

支援的錯誤處理器：

"strict"

"surrogateescape"

"surrogatepass"（僅支援 UTF-8 編碼）

另請參閱 filesystem_encoding 成員。

int use_frozen_modules

如果非零，則使用凍結模組。

由 PYTHON_FROZEN_MODULES 環境變數設定。

Default: 1 in a release build, or 0 in a debug build.

unsigned long hash_seed

int use_hash_seed

Randomized hash function seed.

If use_hash_seed is zero, a seed is chosen randomly at Python startup, and hash_seed is ignored.

由 PYTHONHASHSEED 環境變數設定。

Default use_hash_seed value: -1 in Python mode, 0 in isolated mode.

wchar_t *home

Set the default Python "home" directory, that is, the location of the standard Python libraries (see PYTHONHOME).

由 PYTHONHOME 環境變數設定。

預設值：NULL。

Part of the Python Path Configuration input.

int import_time

If 1, profile import time. If 2, include additional output that indicates when an imported module has already been loaded.

由 -X importtime 選項與 PYTHONPROFILEIMPORTTIME 環境變數設定。

預設：0。

在 3.14 版的變更: 新增對 import_time = 2 的支援

int inspect

在執行腳本或命令後進入互動模式。

If greater than 0, enable inspect: when a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command, even when sys.stdin does not appear to be a terminal.

Incremented by the -i command line option. Set to 1 if the PYTHONINSPECT environment variable is non-empty.

預設：0。

int install_signal_handlers

Install Python signal handlers?

Default: 1 in Python mode, 0 in isolated mode.

int interactive

If greater than 0, enable the interactive mode (REPL).

Incremented by the -i command line option.

預設：0。

int int_max_str_digits

Configures the integer string conversion length limitation. An initial value of -1 means the value will be taken from the command line or environment or otherwise default to 4300 (sys.int_info.default_max_str_digits). A value of 0 disables the limitation. Values greater than zero but less than 640 (sys.int_info.str_digits_check_threshold) are unsupported and will produce an error.

Configured by the -X int_max_str_digits command line flag or the PYTHONINTMAXSTRDIGITS environment variable.

Default: -1 in Python mode. 4300 (sys.int_info.default_max_str_digits) in isolated mode.

在 3.12 版被加入.

int cpu_count

If the value of cpu_count is not -1 then it will override the return values of os.cpu_count(), os.process_cpu_count(), and multiprocessing.cpu_count().

Configured by the -X cpu_count=n|default command line flag or the PYTHON_CPU_COUNT environment variable.

預設值：1。

在 3.13 版被加入.

int isolated

If greater than 0, enable isolated mode:

Set safe_path to 1: don't prepend a potentially unsafe path to sys.path at Python startup, such as the current directory, the script's directory or an empty string.

將 use_environment 設定為 0：忽略 PYTHON 環境變數。

Set user_site_directory to 0: don't add the user site directory to sys.path.

Python REPL doesn't import readline nor enable default readline configuration on interactive prompts.

Set to 1 by the -I command line option.

Default: 0 in Python mode, 1 in isolated mode.

See also the Isolated Configuration and PyPreConfig.isolated.

int legacy_windows_stdio

If non-zero, use io.FileIO instead of io._WindowsConsoleIO for sys.stdin, sys.stdout and sys.stderr.

Set to 1 if the PYTHONLEGACYWINDOWSSTDIO environment variable is set to a non-empty string.

Only available on Windows. #ifdef MS_WINDOWS macro can be used for Windows specific code.

預設：0。

See also the PEP 528 [https://peps.python.org/pep-0528/] (Change Windows console encoding to UTF-8).

int malloc_stats

If non-zero, dump statistics on Python pymalloc memory allocator at exit.

Set to 1 by the PYTHONMALLOCSTATS environment variable.

The option is ignored if Python is configured using the --without-pymalloc option.

預設：0。

wchar_t *platlibdir

Platform library directory name: sys.platlibdir.

Set by the PYTHONPLATLIBDIR environment variable.

Default: value of the PLATLIBDIR macro which is set by the configure --with-platlibdir option (default: "lib", or "DLLs" on Windows).

Part of the Python Path Configuration input.

在 3.9 版被加入.

在 3.11 版的變更: This macro is now used on Windows to locate the standard library extension modules, typically under DLLs. However, for compatibility, note that this value is ignored for any non-standard layouts, including in-tree builds and virtual environments.

wchar_t *pythonpath_env

Module search paths (sys.path) as a string separated by DELIM (os.pathsep).

Set by the PYTHONPATH environment variable.

預設值：NULL。

Part of the Python Path Configuration input.

PyWideStringList module_search_paths

int module_search_paths_set

Module search paths: sys.path.

If module_search_paths_set is equal to 0, Py_InitializeFromConfig() will replace module_search_paths and sets module_search_paths_set to 1.

Default: empty list (module_search_paths) and 0 (module_search_paths_set).

Part of the Python Path Configuration output.

int optimization_level

Compilation optimization level:

0: Peephole optimizer, set __debug__ to True.

1: Level 0, remove assertions, set __debug__ to False.

2: Level 1, strip docstrings.

Incremented by the -O command line option. Set to the PYTHONOPTIMIZE environment variable value.

預設：0。

PyWideStringList orig_argv

The list of the original command line arguments passed to the Python executable: sys.orig_argv.

If orig_argv list is empty and argv is not a list only containing an empty string, PyConfig_Read() copies argv into orig_argv before modifying argv (if parse_argv is non-zero).

See also the argv member and the Py_GetArgcArgv() function.

Default: empty list.

在 3.10 版被加入.

int parse_argv

Parse command line arguments?

If equals to 1, parse argv the same way the regular Python parses command line arguments, and strip Python arguments from argv.

The PyConfig_Read() function only parses PyConfig.argv arguments once: PyConfig.parse_argv is set to 2 after arguments are parsed. Since Python arguments are stripped from PyConfig.argv, parsing arguments twice would parse the application options as Python options.

Default: 1 in Python mode, 0 in isolated mode.

在 3.10 版的變更: The PyConfig.argv arguments are now only parsed if PyConfig.parse_argv equals to 1.

int parser_debug

Parser debug mode. If greater than 0, turn on parser debugging output (for expert only, depending on compilation options).

Incremented by the -d command line option. Set to the PYTHONDEBUG environment variable value.

Needs a debug build of Python (the Py_DEBUG macro must be defined).

預設：0。

int pathconfig_warnings

If non-zero, calculation of path configuration is allowed to log warnings into stderr. If equals to 0, suppress these warnings.

Default: 1 in Python mode, 0 in isolated mode.

Part of the Python Path Configuration input.

在 3.11 版的變更: 現在也適用於 Windows。

wchar_t *prefix

The site-specific directory prefix where the platform independent Python files are installed: sys.prefix.

預設值：NULL。

Part of the Python Path Configuration output.

也請見 PyConfig.base_prefix

wchar_t *program_name

Program name used to initialize executable and in early error messages during Python initialization.

On macOS, use PYTHONEXECUTABLE environment variable if set.

If the WITH_NEXT_FRAMEWORK macro is defined, use __PYVENV_LAUNCHER__ environment variable if set.

Use argv[0] of argv if available and non-empty.

Otherwise, use L"python" on Windows, or L"python3" on other platforms.

預設值：NULL。

Part of the Python Path Configuration input.

wchar_t *pycache_prefix

Directory where cached .pyc files are written: sys.pycache_prefix.

Set by the -X pycache_prefix=PATH command line option and the PYTHONPYCACHEPREFIX environment variable. The command-line option takes precedence.

If NULL, sys.pycache_prefix is set to None.

預設值：NULL。

int quiet

Quiet mode. If greater than 0, don't display the copyright and version at Python startup in interactive mode.

Incremented by the -q command line option.

預設：0。

wchar_t *run_command

Value of the -c command line option.

被 Py_RunMain() 使用。

預設值：NULL。

wchar_t *run_filename

Filename passed on the command line: trailing command line argument without -c or -m. It is used by the Py_RunMain() function.

For example, it is set to script.py by the python3 script.py arg command line.

也請見 PyConfig.skip_source_first_line 選項。

預設值：NULL。

wchar_t *run_module

Value of the -m command line option.

被 Py_RunMain() 使用。

預設值：NULL。

wchar_t *run_presite

package.module path to module that should be imported before site.py is run.

Set by the -X presite=package.module command-line option and the PYTHON_PRESITE environment variable. The command-line option takes precedence.

Needs a debug build of Python (the Py_DEBUG macro must be defined).

預設值：NULL。

int show_ref_count

Show total reference count at exit (excluding immortal objects)?

Set to 1 by -X showrefcount command line option.

Needs a debug build of Python (the Py_REF_DEBUG macro must be defined).

預設：0。

int site_import

Import the site module at startup?

If equal to zero, disable the import of the module site and the site-dependent manipulations of sys.path that it entails.

Also disable these manipulations if the site module is explicitly imported later (call site.main() if you want them to be triggered).

Set to 0 by the -S command line option.

sys.flags.no_site is set to the inverted value of site_import.

預設值：1。

int skip_source_first_line

If non-zero, skip the first line of the PyConfig.run_filename source.

It allows the usage of non-Unix forms of #!cmd. This is intended for a DOS specific hack only.

Set to 1 by the -x command line option.

預設：0。

wchar_t *stdio_encoding

wchar_t *stdio_errors

Encoding and encoding errors of sys.stdin, sys.stdout and sys.stderr (but sys.stderr always uses "backslashreplace" error handler).

Use the PYTHONIOENCODING environment variable if it is non-empty.

預設編碼：

如果 PyPreConfig.utf8_mode 非零，則為 "UTF-8"。

否則使用 locale encoding。

Default error handler:

在 Windows 上：使用 "surrogateescape"。

"surrogateescape" if PyPreConfig.utf8_mode is non-zero, or if the LC_CTYPE locale is "C" or "POSIX".

"strict" otherwise.

也請見 PyConfig.legacy_windows_stdio。

int tracemalloc

Enable tracemalloc?

If non-zero, call tracemalloc.start() at startup.

Set by -X tracemalloc=N command line option and by the PYTHONTRACEMALLOC environment variable.

Default: -1 in Python mode, 0 in isolated mode.

int perf_profiling

要啟用 Linux perf 分析器支援嗎？

如果等於 1，則啟用對 Linux perf 分析器的支援。

如果等於 2，則啟用有 DWARF JIT 支援的 Linux perf 分析器的支援。

Set to 1 by -X perf command-line option and the PYTHONPERFSUPPORT environment variable.

Set to 2 by the -X perf_jit command-line option and the PYTHON_PERF_JIT_SUPPORT environment variable.

預設值：1。

也參考

更多資訊請參見 Python 對 Linux perf 分析器的支援。

在 3.12 版被加入.

wchar_t *stdlib_dir

Directory of the Python standard library.

預設值：NULL。

在 3.11 版被加入.

int use_environment

Use environment variables?

If equals to zero, ignore the environment variables.

Set to 0 by the -E environment variable.

Default: 1 in Python config and 0 in isolated config.

int use_system_logger

If non-zero, stdout and stderr will be redirected to the system log.

Only available on macOS 10.12 and later, and on iOS.

Default: 0 (don't use the system log) on macOS; 1 on iOS (use the system log).

在 3.14 版被加入.

int user_site_directory

If non-zero, add the user site directory to sys.path.

Set to 0 by the -s and -I command line options.

Set to 0 by the PYTHONNOUSERSITE environment variable.

Default: 1 in Python mode, 0 in isolated mode.

int verbose

Verbose mode. If greater than 0, print a message each time a module is imported, showing the place (filename or built-in module) from which it is loaded.

If greater than or equal to 2, print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit.

Incremented by the -v command line option.

Set by the PYTHONVERBOSE environment variable value.

預設：0。

PyWideStringList warnoptions

Options of the warnings module to build warnings filters, lowest to highest priority: sys.warnoptions.

The warnings module adds sys.warnoptions in the reverse order: the last PyConfig.warnoptions item becomes the first item of warnings.filters which is checked first (highest priority).

The -W command line options adds its value to warnoptions, it can be used multiple times.

The PYTHONWARNINGS environment variable can also be used to add warning options. Multiple options can be specified, separated by commas (,).

Default: empty list.

int write_bytecode

If equal to 0, Python won't try to write .pyc files on the import of source modules.

Set to 0 by the -B command line option and the PYTHONDONTWRITEBYTECODE environment variable.

sys.dont_write_bytecode is initialized to the inverted value of write_bytecode.

預設值：1。

PyWideStringList xoptions

Values of the -X command line options: sys._xoptions.

Default: empty list.

int _pystats

If non-zero, write performance statistics at Python exit.

Need a special build with the Py_STATS macro: see --enable-pystats.

預設：0。

If parse_argv is non-zero, argv arguments are parsed the same way the regular Python parses command line arguments, and Python arguments are stripped from argv.

The xoptions options are parsed to set other options: see the -X command line option.

在 3.9 版的變更: The show_alloc_count field has been removed.

Initialization with PyConfig

Initializing the interpreter from a populated configuration struct is handled by calling Py_InitializeFromConfig().

The caller is responsible to handle exceptions (error or exit) using PyStatus_Exception() and Py_ExitStatusException().

If PyImport_FrozenModules(), PyImport_AppendInittab() or PyImport_ExtendInittab() are used, they must be set or called after Python preinitialization and before the Python initialization. If Python is initialized multiple times, PyImport_AppendInittab() or PyImport_ExtendInittab() must be called before each Python initialization.

The current configuration (PyConfig type) is stored in PyInterpreterState.config.

Example setting the program name:

void init_python(void)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* Set the program name. Implicitly preinitialize Python. */
    status = PyConfig_SetString(&config, &config.program_name,
                                L"/path/to/my_program");
    if (PyStatus_Exception(status)) {
        goto exception;
    }

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);
    return;

exception:
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
}

More complete example modifying the default configuration, read the configuration, and then override some parameters. Note that since 3.11, many parameters are not calculated until initialization, and so values cannot be read from the configuration structure. Any values set before initialize is called will be left unchanged by initialization:

PyStatus init_python(const char *program_name)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* Set the program name before reading the configuration
       (decode byte string from the locale encoding).

       Implicitly preinitialize Python. */
    status = PyConfig_SetBytesString(&config, &config.program_name,
                                     program_name);
    if (PyStatus_Exception(status)) {
        goto done;
    }

    /* Read all configuration at once */
    status = PyConfig_Read(&config);
    if (PyStatus_Exception(status)) {
        goto done;
    }

    /* Specify sys.path explicitly */
    /* If you want to modify the default set of paths, finish
       initialization first and then use PySys_GetObject("path") */
    config.module_search_paths_set = 1;
    status = PyWideStringList_Append(&config.module_search_paths,
                                     L"/path/to/stdlib");
    if (PyStatus_Exception(status)) {
        goto done;
    }
    status = PyWideStringList_Append(&config.module_search_paths,
                                     L"/path/to/more/modules");
    if (PyStatus_Exception(status)) {
        goto done;
    }

    /* Override executable computed by PyConfig_Read() */
    status = PyConfig_SetString(&config, &config.executable,
                                L"/path/to/my_executable");
    if (PyStatus_Exception(status)) {
        goto done;
    }

    status = Py_InitializeFromConfig(&config);

done:
    PyConfig_Clear(&config);
    return status;
}

Isolated Configuration

PyPreConfig_InitIsolatedConfig() and PyConfig_InitIsolatedConfig() functions create a configuration to isolate Python from the system. For example, to embed Python into an application.

This configuration ignores global configuration variables, environment variables, command line arguments (PyConfig.argv is not parsed) and user site directory. The C standard streams (ex: stdout) and the LC_CTYPE locale are left unchanged. Signal handlers are not installed.

Configuration files are still used with this configuration to determine paths that are unspecified. Ensure PyConfig.home is specified to avoid computing the default path configuration.

Python Configuration

PyPreConfig_InitPythonConfig() and PyConfig_InitPythonConfig() functions create a configuration to build a customized Python which behaves as the regular Python.

Environments variables and command line arguments are used to configure Python, whereas global configuration variables are ignored.

This function enables C locale coercion (PEP 538 [https://peps.python.org/pep-0538/]) and Python UTF-8 Mode (PEP 540 [https://peps.python.org/pep-0540/]) depending on the LC_CTYPE locale, PYTHONUTF8 and PYTHONCOERCECLOCALE environment variables.

Python 路徑配置

PyConfig contains multiple fields for the path configuration:

Path configuration inputs:

PyConfig.home

PyConfig.platlibdir

PyConfig.pathconfig_warnings

PyConfig.program_name

PyConfig.pythonpath_env

current working directory: to get absolute paths

PATH environment variable to get the program full path (from PyConfig.program_name)

__PYVENV_LAUNCHER__ 環境變數

(Windows only) Application paths in the registry under "SoftwarePythonPythonCoreX.YPythonPath" of HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE (where X.Y is the Python version).

Path configuration output fields:

PyConfig.base_exec_prefix

PyConfig.base_executable

PyConfig.base_prefix

PyConfig.exec_prefix

PyConfig.executable

PyConfig.module_search_paths_set, PyConfig.module_search_paths

PyConfig.prefix

If at least one "output field" is not set, Python calculates the path configuration to fill unset fields. If module_search_paths_set is equal to 0, module_search_paths is overridden and module_search_paths_set is set to 1.

It is possible to completely ignore the function calculating the default path configuration by setting explicitly all path configuration output fields listed above. A string is considered as set even if it is non-empty. module_search_paths is considered as set if module_search_paths_set is set to 1. In this case, module_search_paths will be used without modification.

Set pathconfig_warnings to 0 to suppress warnings when calculating the path configuration (Unix only, Windows does not log any warning).

If base_prefix or base_exec_prefix fields are not set, they inherit their value from prefix and exec_prefix respectively.

Py_RunMain() 和 Py_Main() 會修改 sys.path：

If run_filename is set and is a directory which contains a __main__.py script, prepend run_filename to sys.path.

如果 isolated 為零：

If run_module is set, prepend the current directory to sys.path. Do nothing if the current directory cannot be read.

If run_filename is set, prepend the directory of the filename to sys.path.

Otherwise, prepend an empty string to sys.path.

If site_import is non-zero, sys.path can be modified by the site module. If user_site_directory is non-zero and the user's site-package directory exists, the site module appends the user's site-package directory to sys.path.

The following configuration files are used by the path configuration:

pyvenv.cfg

._pth file (ex: python._pth)

pybuilddir.txt（僅限 Unix）

If a ._pth file is present:

將 isolated 設定為 1。

將 use_environment 設定為 0。

將 site_import 設定為 0。

將 safe_path 設定為 1。

If home is not set and a pyvenv.cfg file is present in the same directory as executable, or its parent, prefix and exec_prefix are set that location. When this happens, base_prefix and base_exec_prefix still keep their value, pointing to the base installation. See 虛擬環境 for more information.

The __PYVENV_LAUNCHER__ environment variable is used to set PyConfig.base_executable.

在 3.14 版的變更: prefix, and exec_prefix, are now set to the pyvenv.cfg directory. This was previously done by site, therefore affected by -S.

Py_GetArgcArgv()

void Py_GetArgcArgv(int *argc, wchar_t ***argv)

Get the original command line arguments, before Python modified them.

也請參與 PyConfig.orig_argv 成員。

Delaying main module execution

In some embedding use cases, it may be desirable to separate interpreter initialization from the execution of the main module.

This separation can be achieved by setting PyConfig.run_command to the empty string during initialization (to prevent the interpreter from dropping into the interactive prompt), and then subsequently executing the desired main module code using __main__.__dict__ as the global namespace.

記憶體管理

總覽

Memory management in Python involves a private heap containing all Python objects and data structures. The management of this private heap is ensured internally by the Python memory manager. The Python memory manager has different components which deal with various dynamic storage management aspects, like sharing, segmentation, preallocation or caching.

At the lowest level, a raw memory allocator ensures that there is enough room in the private heap for storing all Python-related data by interacting with the memory manager of the operating system. On top of the raw memory allocator, several object-specific allocators operate on the same heap and implement distinct memory management policies adapted to the peculiarities of every object type. For example, integer objects are managed differently within the heap than strings, tuples or dictionaries because integers imply different storage requirements and speed/space tradeoffs. The Python memory manager thus delegates some of the work to the object-specific allocators, but ensures that the latter operate within the bounds of the private heap.

It is important to understand that the management of the Python heap is performed by the interpreter itself and that the user has no control over it, even if they regularly manipulate object pointers to memory blocks inside that heap. The allocation of heap space for Python objects and other internal buffers is performed on demand by the Python memory manager through the Python/C API functions listed in this document.

To avoid memory corruption, extension writers should never try to operate on Python objects with the functions exported by the C library: malloc(), calloc(), realloc() and free(). This will result in mixed calls between the C allocator and the Python memory manager with fatal consequences, because they implement different algorithms and operate on different heaps. However, one may safely allocate and release memory blocks with the C library allocator for individual purposes, as shown in the following example:

PyObject *res;
char *buf = (char *) malloc(BUFSIZ); /* for I/O */

if (buf == NULL)
    return PyErr_NoMemory();
...Do some I/O operation involving buf...
res = PyBytes_FromString(buf);
free(buf); /* malloc'ed */
return res;

In this example, the memory request for the I/O buffer is handled by the C library allocator. The Python memory manager is involved only in the allocation of the bytes object returned as a result.

In most situations, however, it is recommended to allocate memory from the Python heap specifically because the latter is under control of the Python memory manager. For example, this is required when the interpreter is extended with new object types written in C. Another reason for using the Python heap is the desire to inform the Python memory manager about the memory needs of the extension module. Even when the requested memory is used exclusively for internal, highly specific purposes, delegating all memory requests to the Python memory manager causes the interpreter to have a more accurate image of its memory footprint as a whole. Consequently, under certain circumstances, the Python memory manager may or may not trigger appropriate actions, like garbage collection, memory compaction or other preventive procedures. Note that by using the C library allocator as shown in the previous example, the allocated memory for the I/O buffer escapes completely the Python memory manager.

也參考

The PYTHONMALLOC environment variable can be used to configure the memory allocators used by Python.

The PYTHONMALLOCSTATS environment variable can be used to print statistics of the pymalloc memory allocator every time a new pymalloc object arena is created, and on shutdown.

Allocator Domains

All allocating functions belong to one of three different "domains" (see also PyMemAllocatorDomain). These domains represent different allocation strategies and are optimized for different purposes. The specific details on how every domain allocates memory or what internal functions each domain calls is considered an implementation detail, but for debugging purposes a simplified table can be found at Default Memory Allocators. The APIs used to allocate and free a block of memory must be from the same domain. For example, PyMem_Free() must be used to free memory allocated using PyMem_Malloc().

The three allocation domains are:

Raw domain: intended for allocating memory for general-purpose memory buffers where the allocation must go to the system allocator or where the allocator can operate without an attached thread state. The memory is requested directly from the system. See Raw Memory Interface.

"Mem" domain: intended for allocating memory for Python buffers and general-purpose memory buffers where the allocation must be performed with an attached thread state. The memory is taken from the Python private heap. See Memory Interface.

Object domain: intended for allocating memory for Python objects. The memory is taken from the Python private heap. See Object allocators.

備註

The free-threaded build requires that only Python objects are allocated using the "object" domain and that all Python objects are allocated using that domain. This differs from the prior Python versions, where this was only a best practice and not a hard requirement.

For example, buffers (non-Python objects) should be allocated using PyMem_Malloc(), PyMem_RawMalloc(), or malloc(), but not PyObject_Malloc().

See Memory Allocation APIs.

Raw Memory Interface

The following function sets are wrappers to the system allocator. These functions are thread-safe, so a thread state does not need to be attached.

The default raw memory allocator uses the following functions: malloc(), calloc(), realloc() and free(); call malloc(1) (or calloc(1, 1)) when requesting zero bytes.

在 3.4 版被加入.

void *PyMem_RawMalloc(size_t n)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Allocates n bytes and returns a pointer of type void* to the allocated memory, or NULL if the request fails.

Requesting zero bytes returns a distinct non-NULL pointer if possible, as if PyMem_RawMalloc(1) had been called instead. The memory will not have been initialized in any way.

void *PyMem_RawCalloc(size_t nelem, size_t elsize)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Allocates nelem elements each whose size in bytes is elsize and returns a pointer of type void* to the allocated memory, or NULL if the request fails. The memory is initialized to zeros.

Requesting zero elements or elements of size zero bytes returns a distinct non-NULL pointer if possible, as if PyMem_RawCalloc(1, 1) had been called instead.

在 3.5 版被加入.

void *PyMem_RawRealloc(void *p, size_t n)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Resizes the memory block pointed to by p to n bytes. The contents will be unchanged to the minimum of the old and the new sizes.

If p is NULL, the call is equivalent to PyMem_RawMalloc(n); else if n is equal to zero, the memory block is resized but is not freed, and the returned pointer is non-NULL.

Unless p is NULL, it must have been returned by a previous call to PyMem_RawMalloc(), PyMem_RawRealloc() or PyMem_RawCalloc().

If the request fails, PyMem_RawRealloc() returns NULL and p remains a valid pointer to the previous memory area.

void PyMem_RawFree(void *p)

為 穩定 ABI 的一部分 自 3.13 版本開始.

Frees the memory block pointed to by p, which must have been returned by a previous call to PyMem_RawMalloc(), PyMem_RawRealloc() or PyMem_RawCalloc(). Otherwise, or if PyMem_RawFree(p) has been called before, undefined behavior occurs.

If p is NULL, no operation is performed.

記憶體介面

The following function sets, modeled after the ANSI C standard, but specifying behavior when requesting zero bytes, are available for allocating and releasing memory from the Python heap.

The default memory allocator uses the pymalloc memory allocator.

警告

There must be an attached thread state when using these functions.

在 3.6 版的變更: The default allocator is now pymalloc instead of system malloc().

void *PyMem_Malloc(size_t n)

為 穩定 ABI 的一部分.

Allocates n bytes and returns a pointer of type void* to the allocated memory, or NULL if the request fails.

Requesting zero bytes returns a distinct non-NULL pointer if possible, as if PyMem_Malloc(1) had been called instead. The memory will not have been initialized in any way.

void *PyMem_Calloc(size_t nelem, size_t elsize)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Allocates nelem elements each whose size in bytes is elsize and returns a pointer of type void* to the allocated memory, or NULL if the request fails. The memory is initialized to zeros.

Requesting zero elements or elements of size zero bytes returns a distinct non-NULL pointer if possible, as if PyMem_Calloc(1, 1) had been called instead.

在 3.5 版被加入.

void *PyMem_Realloc(void *p, size_t n)

為 穩定 ABI 的一部分.

Resizes the memory block pointed to by p to n bytes. The contents will be unchanged to the minimum of the old and the new sizes.

If p is NULL, the call is equivalent to PyMem_Malloc(n); else if n is equal to zero, the memory block is resized but is not freed, and the returned pointer is non-NULL.

Unless p is NULL, it must have been returned by a previous call to PyMem_Malloc(), PyMem_Realloc() or PyMem_Calloc().

If the request fails, PyMem_Realloc() returns NULL and p remains a valid pointer to the previous memory area.

void PyMem_Free(void *p)

為 穩定 ABI 的一部分.

Frees the memory block pointed to by p, which must have been returned by a previous call to PyMem_Malloc(), PyMem_Realloc() or PyMem_Calloc(). Otherwise, or if PyMem_Free(p) has been called before, undefined behavior occurs.

If p is NULL, no operation is performed.

The following type-oriented macros are provided for convenience. Note that TYPE refers to any C type.

PyMem_New(TYPE, n)

Same as PyMem_Malloc(), but allocates (n * sizeof(TYPE)) bytes of memory. Returns a pointer cast to TYPE*. The memory will not have been initialized in any way.

PyMem_Resize(p, TYPE, n)

Same as PyMem_Realloc(), but the memory block is resized to (n * sizeof(TYPE)) bytes. Returns a pointer cast to TYPE*. On return, p will be a pointer to the new memory area, or NULL in the event of failure.

This is a C preprocessor macro; p is always reassigned. Save the original value of p to avoid losing memory when handling errors.

void PyMem_Del(void *p)

和 PyMem_Free() 相同。

已棄用的別名

These are soft deprecated aliases to existing functions and macros. They exist solely for backwards compatibility.

已棄用的別名

對應的函式或巨集

PyMem_MALLOC(size)

PyMem_Malloc()

PyMem_NEW(type, size)

PyMem_New

PyMem_REALLOC(ptr, size)

PyMem_Realloc()

PyMem_RESIZE(ptr, type, size)

PyMem_Resize

PyMem_FREE(ptr)

PyMem_Free()

PyMem_DEL(ptr)

PyMem_Free()

在 3.4 版的變更: The macros are now aliases of the corresponding functions and macros. Previously, their behavior was the same, but their use did not necessarily preserve binary compatibility across Python versions.

在 2.0 版之後被棄用.

Object allocators

The following function sets, modeled after the ANSI C standard, but specifying behavior when requesting zero bytes, are available for allocating and releasing memory from the Python heap.

備註

There is no guarantee that the memory returned by these allocators can be successfully cast to a Python object when intercepting the allocating functions in this domain by the methods described in the Customize Memory Allocators section.

The default object allocator uses the pymalloc memory allocator.

警告

There must be an attached thread state when using these functions.

void *PyObject_Malloc(size_t n)

為 穩定 ABI 的一部分.

Allocates n bytes and returns a pointer of type void* to the allocated memory, or NULL if the request fails.

Requesting zero bytes returns a distinct non-NULL pointer if possible, as if PyObject_Malloc(1) had been called instead. The memory will not have been initialized in any way.

void *PyObject_Calloc(size_t nelem, size_t elsize)

為 穩定 ABI 的一部分 自 3.7 版本開始.

Allocates nelem elements each whose size in bytes is elsize and returns a pointer of type void* to the allocated memory, or NULL if the request fails. The memory is initialized to zeros.

Requesting zero elements or elements of size zero bytes returns a distinct non-NULL pointer if possible, as if PyObject_Calloc(1, 1) had been called instead.

在 3.5 版被加入.

void *PyObject_Realloc(void *p, size_t n)

為 穩定 ABI 的一部分.

Resizes the memory block pointed to by p to n bytes. The contents will be unchanged to the minimum of the old and the new sizes.

If p is NULL, the call is equivalent to PyObject_Malloc(n); else if n is equal to zero, the memory block is resized but is not freed, and the returned pointer is non-NULL.

Unless p is NULL, it must have been returned by a previous call to PyObject_Malloc(), PyObject_Realloc() or PyObject_Calloc().

If the request fails, PyObject_Realloc() returns NULL and p remains a valid pointer to the previous memory area.

void PyObject_Free(void *p)

為 穩定 ABI 的一部分.

Frees the memory block pointed to by p, which must have been returned by a previous call to PyObject_Malloc(), PyObject_Realloc() or PyObject_Calloc(). Otherwise, or if PyObject_Free(p) has been called before, undefined behavior occurs.

If p is NULL, no operation is performed.

Do not call this directly to free an object's memory; call the type's tp_free slot instead.

Do not use this for memory allocated by PyObject_GC_New or PyObject_GC_NewVar; use PyObject_GC_Del() instead.

也參考

PyObject_GC_Del() is the equivalent of this function for memory allocated by types that support garbage collection.

PyObject_Malloc()

PyObject_Realloc()

PyObject_Calloc()

PyObject_New

PyObject_NewVar

PyType_GenericAlloc()

tp_free

Default Memory Allocators

Default memory allocators:

配置

名稱

PyMem_RawMalloc

PyMem_Malloc

PyObject_Malloc

Release build

"pymalloc"

malloc

pymalloc

pymalloc

Debug build

"pymalloc_debug"

malloc + debug

pymalloc + debug

pymalloc + debug

Release build, without pymalloc

"malloc"

malloc

malloc

malloc

Debug build, without pymalloc

"malloc_debug"

malloc + debug

malloc + debug

malloc + debug

Legend:

Name: value for PYTHONMALLOC environment variable.

malloc: system allocators from the standard C library, C functions: malloc(), calloc(), realloc() and free().

pymalloc: pymalloc memory allocator.

mimalloc: mimalloc memory allocator. The pymalloc allocator will be used if mimalloc support isn't available.

"+ debug": with debug hooks on the Python memory allocators.

"Debug build": Python build in debug mode.

Customize Memory Allocators

在 3.4 版被加入.

type PyMemAllocatorEx

Structure used to describe a memory block allocator. The structure has the following fields:

欄位

意義

void *ctx

user context passed as first argument

void* malloc(void *ctx, size_t size)

allocate a memory block

void* calloc(void *ctx, size_t nelem, size_t elsize)

allocate a memory block initialized with zeros

void* realloc(void *ctx, void *ptr, size_t new_size)

allocate or resize a memory block

void free(void *ctx, void *ptr)

free a memory block

在 3.5 版的變更: The PyMemAllocator structure was renamed to PyMemAllocatorEx and a new calloc field was added.

type PyMemAllocatorDomain

Enum used to identify an allocator domain. Domains:

PYMEM_DOMAIN_RAW

函式：

PyMem_RawMalloc()

PyMem_RawRealloc()

PyMem_RawCalloc()

PyMem_RawFree()

PYMEM_DOMAIN_MEM

函式：

PyMem_Malloc(),

PyMem_Realloc()

PyMem_Calloc()

PyMem_Free()

PYMEM_DOMAIN_OBJ

函式：

PyObject_Malloc()

PyObject_Realloc()

PyObject_Calloc()

PyObject_Free()

void PyMem_GetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)

Get the memory block allocator of the specified domain.

void PyMem_SetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)

Set the memory block allocator of the specified domain.

The new allocator must return a distinct non-NULL pointer when requesting zero bytes.

For the PYMEM_DOMAIN_RAW domain, the allocator must be thread-safe: a thread state is not attached when the allocator is called.

For the remaining domains, the allocator must also be thread-safe: the allocator may be called in different interpreters that do not share a GIL.

If the new allocator is not a hook (does not call the previous allocator), the PyMem_SetupDebugHooks() function must be called to reinstall the debug hooks on top on the new allocator.

See also PyPreConfig.allocator and Preinitialize Python with PyPreConfig.

警告

PyMem_SetAllocator() does have the following contract:

It can be called after Py_PreInitialize() and before Py_InitializeFromConfig() to install a custom memory allocator. There are no restrictions over the installed allocator other than the ones imposed by the domain (for instance, the Raw Domain allows the allocator to be called without an attached thread state). See the section on allocator domains for more information.

If called after Python has finish initializing (after Py_InitializeFromConfig() has been called) the allocator must wrap the existing allocator. Substituting the current allocator for some other arbitrary one is not supported.

在 3.12 版的變更: All allocators must be thread-safe.

void PyMem_SetupDebugHooks(void)

Setup debug hooks in the Python memory allocators to detect memory errors.

Debug hooks on the Python memory allocators

When Python is built in debug mode, the PyMem_SetupDebugHooks() function is called at the Python preinitialization to setup debug hooks on Python memory allocators to detect memory errors.

The PYTHONMALLOC environment variable can be used to install debug hooks on a Python compiled in release mode (ex: PYTHONMALLOC=debug).

The PyMem_SetupDebugHooks() function can be used to set debug hooks after calling PyMem_SetAllocator().

These debug hooks fill dynamically allocated memory blocks with special, recognizable bit patterns. Newly allocated memory is filled with the byte 0xCD (PYMEM_CLEANBYTE), freed memory is filled with the byte 0xDD (PYMEM_DEADBYTE). Memory blocks are surrounded by "forbidden bytes" filled with the byte 0xFD (PYMEM_FORBIDDENBYTE). Strings of these bytes are unlikely to be valid addresses, floats, or ASCII strings.

Runtime 檢查：

Detect API violations. For example, detect if PyObject_Free() is called on a memory block allocated by PyMem_Malloc().

Detect write before the start of the buffer (buffer underflow).

Detect write after the end of the buffer (buffer overflow).

Check that there is an attached thread state when allocator functions of PYMEM_DOMAIN_OBJ (ex: PyObject_Malloc()) and PYMEM_DOMAIN_MEM (ex: PyMem_Malloc()) domains are called.

On error, the debug hooks use the tracemalloc module to get the traceback where a memory block was allocated. The traceback is only displayed if tracemalloc is tracing Python memory allocations and the memory block was traced.

Let S = sizeof(size_t). 2*S bytes are added at each end of each block of N bytes requested. The memory layout is like so, where p represents the address returned by a malloc-like or realloc-like function (p[i:j] means the slice of bytes from *(p+i) inclusive up to *(p+j) exclusive; note that the treatment of negative indices differs from a Python slice):

p[-2*S:-S]

Number of bytes originally asked for. This is a size_t, big-endian (easier to read in a memory dump).

p[-S]

API identifier (ASCII character):

'r' 代表 PYMEM_DOMAIN_RAW。

'm' 代表 PYMEM_DOMAIN_MEM。

'o' 代表 PYMEM_DOMAIN_OBJ。

p[-S+1:0]

Copies of PYMEM_FORBIDDENBYTE. Used to catch under- writes and reads.

p[0:N]

The requested memory, filled with copies of PYMEM_CLEANBYTE, used to catch reference to uninitialized memory. When a realloc-like function is called requesting a larger memory block, the new excess bytes are also filled with PYMEM_CLEANBYTE. When a free-like function is called, these are overwritten with PYMEM_DEADBYTE, to catch reference to freed memory. When a realloc- like function is called requesting a smaller memory block, the excess old bytes are also filled with PYMEM_DEADBYTE.

p[N:N+S]

Copies of PYMEM_FORBIDDENBYTE. Used to catch over- writes and reads.

p[N+S:N+2*S]

Only used if the PYMEM_DEBUG_SERIALNO macro is defined (not defined by default).

A serial number, incremented by 1 on each call to a malloc-like or realloc-like function. Big-endian size_t. If "bad memory" is detected later, the serial number gives an excellent way to set a breakpoint on the next run, to capture the instant at which this block was passed out. The static function bumpserialno() in obmalloc.c is the only place the serial number is incremented, and exists so you can set such a breakpoint easily.

A realloc-like or free-like function first checks that the PYMEM_FORBIDDENBYTE bytes at each end are intact. If they've been altered, diagnostic output is written to stderr, and the program is aborted via Py_FatalError(). The other main failure mode is provoking a memory error when a program reads up one of the special bit patterns and tries to use it as an address. If you get in a debugger then and look at the object, you're likely to see that it's entirely filled with PYMEM_DEADBYTE (meaning freed memory is getting used) or PYMEM_CLEANBYTE (meaning uninitialized memory is getting used).

在 3.6 版的變更: The PyMem_SetupDebugHooks() function now also works on Python compiled in release mode. On error, the debug hooks now use tracemalloc to get the traceback where a memory block was allocated. The debug hooks now also check if there is an attached thread state when functions of PYMEM_DOMAIN_OBJ and PYMEM_DOMAIN_MEM domains are called.

在 3.8 版的變更: Byte patterns 0xCB (PYMEM_CLEANBYTE), 0xDB (PYMEM_DEADBYTE) and 0xFB (PYMEM_FORBIDDENBYTE) have been replaced with 0xCD, 0xDD and 0xFD to use the same values than Windows CRT debug malloc() and free().

The pymalloc allocator

Python has a pymalloc allocator optimized for small objects (smaller or equal to 512 bytes) with a short lifetime. It uses memory mappings called "arenas" with a fixed size of either 256 KiB on 32-bit platforms or 1 MiB on 64-bit platforms. It falls back to PyMem_RawMalloc() and PyMem_RawRealloc() for allocations larger than 512 bytes.

pymalloc is the default allocator of the PYMEM_DOMAIN_MEM (ex: PyMem_Malloc()) and PYMEM_DOMAIN_OBJ (ex: PyObject_Malloc()) domains.

The arena allocator uses the following functions:

Windows 上的 VirtualAlloc() 和 VirtualFree()，

如果可用，則使用 mmap() 和 munmap()，

否則使用 malloc() 和 free()。

This allocator is disabled if Python is configured with the --without-pymalloc option. It can also be disabled at runtime using the PYTHONMALLOC environment variable (ex: PYTHONMALLOC=malloc).

Typically, it makes sense to disable the pymalloc allocator when building Python with AddressSanitizer (--with-address-sanitizer) which helps uncover low level bugs within the C code.

Customize pymalloc Arena Allocator

在 3.4 版被加入.

type PyObjectArenaAllocator

Structure used to describe an arena allocator. The structure has three fields:

欄位

意義

void *ctx

user context passed as first argument

void* alloc(void *ctx, size_t size)

allocate an arena of size bytes

void free(void *ctx, void *ptr, size_t size)

free an arena

void PyObject_GetArenaAllocator(PyObjectArenaAllocator *allocator)

Get the arena allocator.

void PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator)

Set the arena allocator.

The mimalloc allocator

在 3.13 版被加入.

Python supports the mimalloc allocator when the underlying platform support is available. mimalloc "is a general purpose allocator with excellent performance characteristics. Initially developed by Daan Leijen for the runtime systems of the Koka and Lean languages."

tracemalloc C API

在 3.7 版被加入.

int PyTraceMalloc_Track(unsigned int domain, uintptr_t ptr, size_t size)

Track an allocated memory block in the tracemalloc module.

Return 0 on success, return -1 on error (failed to allocate memory to store the trace). Return -2 if tracemalloc is disabled.

If memory block is already tracked, update the existing trace.

int PyTraceMalloc_Untrack(unsigned int domain, uintptr_t ptr)

Untrack an allocated memory block in the tracemalloc module. Do nothing if the block was not tracked.

如果 tracemalloc 被停用，則回傳 -2，否則回傳 0。

範例

Here is the example from section 總覽, rewritten so that the I/O buffer is allocated from the Python heap by using the first function set:

PyObject *res;
char *buf = (char *) PyMem_Malloc(BUFSIZ); /* for I/O */

if (buf == NULL)
    return PyErr_NoMemory();
/* ...Do some I/O operation involving buf... */
res = PyBytes_FromString(buf);
PyMem_Free(buf); /* allocated with PyMem_Malloc */
return res;

The same code using the type-oriented function set:

PyObject *res;
char *buf = PyMem_New(char, BUFSIZ); /* for I/O */

if (buf == NULL)
    return PyErr_NoMemory();
/* ...Do some I/O operation involving buf... */
res = PyBytes_FromString(buf);
PyMem_Free(buf); /* allocated with PyMem_New */
return res;

Note that in the two examples above, the buffer is always manipulated via functions belonging to the same set. Indeed, it is required to use the same memory API family for a given memory block, so that the risk of mixing different allocators is reduced to a minimum. The following code sequence contains two errors, one of which is labeled as fatal because it mixes two different allocators operating on different heaps.

char *buf1 = PyMem_New(char, BUFSIZ);
char *buf2 = (char *) malloc(BUFSIZ);
char *buf3 = (char *) PyMem_Malloc(BUFSIZ);
...
PyMem_Del(buf3);  /* Wrong -- should be PyMem_Free() */
free(buf2);       /* Right -- allocated via malloc() */
free(buf1);       /* Fatal -- should be PyMem_Free()  */

In addition to the functions aimed at handling raw memory blocks from the Python heap, objects in Python are allocated and released with PyObject_New, PyObject_NewVar and PyObject_Free().

These will be explained in the next chapter on defining and implementing new object types in C.

物件實作支援

本章節說明在定義新的物件型別時所使用的函式、型別和巨集。

在 heap 上分配物件

被棄用的別名

物件生命週期

生命事件

Cyclic Isolate Destruction

函式

通用物件結構

Base object types and macros

實作函式與方法

Accessing attributes of extension types

Member flags

Member types

Defining Getters and Setters

型別物件結構

Quick Reference

"tp slots"

sub-slots

slot typedefs

PyTypeObject Definition

PyObject Slots

PyVarObject Slots

PyTypeObject Slots

靜態型別

堆積型別

Number Object Structures

對映物件結構

序列物件結構

緩衝區物件結構

非同步物件結構

Slot Type typedefs

範例

循環垃圾回收的支援

Controlling the Garbage Collector State

Querying Garbage Collector State

在 heap 上分配物件

PyObject *_PyObject_New(PyTypeObject *type)

回傳值：新的參照。

PyVarObject *_PyObject_NewVar(PyTypeObject *type, Py_ssize_t size)

回傳值：新的參照。

PyObject *PyObject_Init(PyObject *op, PyTypeObject *type)

回傳值：借用參照。 為 穩定 ABI 的一部分.

Initialize a newly allocated object op with its type and initial reference. Returns the initialized object. Other fields of the object are not initialized. Despite its name, this function is unrelated to the object's __init__() method (tp_init slot). Specifically, this function does not call the object's __init__() method.

In general, consider this function to be a low-level routine. Use tp_alloc where possible. For implementing tp_alloc for your type, prefer PyType_GenericAlloc() or PyObject_New().

備註

This function only initializes the object's memory corresponding to the initial PyObject structure. It does not zero the rest.

PyVarObject *PyObject_InitVar(PyVarObject *op, PyTypeObject *type, Py_ssize_t size)

回傳值：借用參照。 為 穩定 ABI 的一部分.

它會做到 PyObject_Init() 的所有功能，並且會初始化一個大小可變物件的長度資訊。

備註

This function only initializes some of the object's memory. It does not zero the rest.

PyObject_New(TYPE, typeobj)

使用 C 結構型別 TYPE 和 Python 型別物件 typeobj (PyTypeObject*) 分配一個新的 Python 物件。它會呼叫 PyObject_Malloc() 來分配記憶體，並且會像 PyObject_Init() 一樣初始化它。呼叫者會擁有該物件的唯一參照（也就是它的參照計數會是 1）。

Avoid calling this directly to allocate memory for an object; call the type's tp_alloc slot instead.

When populating a type's tp_alloc slot, PyType_GenericAlloc() is preferred over a custom function that simply calls this macro.

這個巨集不會呼叫 tp_alloc、tp_new (__new__())、或 tp_init (__init__())。

這不能用於有在 tp_flags 中設定 Py_TPFLAGS_HAVE_GC 的物件；請改用 PyObject_GC_New。

Memory allocated by this macro must be freed with PyObject_Free() (usually called via the object's tp_free slot).

備註

The returned memory is not guaranteed to have been completely zeroed before it was initialized.

備註

This macro does not construct a fully initialized object of the given type; it merely allocates memory and prepares it for further initialization by tp_init. To construct a fully initialized object, call typeobj instead. For example:

PyObject *foo = PyObject_CallNoArgs((PyObject *)&PyFoo_Type);

也參考

PyObject_Free()

PyObject_GC_New

PyType_GenericAlloc()

tp_alloc

PyObject_NewVar(TYPE, typeobj, size)

和 PyObject_New 類似，但有以下差異：

It allocates enough memory for the TYPE structure plus size (Py_ssize_t) fields of the size given by the tp_itemsize field of typeobj.

記憶體會像 PyObject_InitVar() 一樣被初始化。

This is useful for implementing objects like tuples, which are able to determine their size at construction time. Embedding the array of fields into the same allocation decreases the number of allocations, improving the memory management efficiency.

Avoid calling this directly to allocate memory for an object; call the type's tp_alloc slot instead.

When populating a type's tp_alloc slot, PyType_GenericAlloc() is preferred over a custom function that simply calls this macro.

這不能用於有在 tp_flags 中設定 Py_TPFLAGS_HAVE_GC 的物件；請改用 PyObject_GC_NewVar。

Memory allocated by this function must be freed with PyObject_Free() (usually called via the object's tp_free slot).

備註

The returned memory is not guaranteed to have been completely zeroed before it was initialized.

備註

This macro does not construct a fully initialized object of the given type; it merely allocates memory and prepares it for further initialization by tp_init. To construct a fully initialized object, call typeobj instead. For example:

PyObject *list_instance = PyObject_CallNoArgs((PyObject *)&PyList_Type);

也參考

PyObject_Free()

PyObject_GC_NewVar

PyType_GenericAlloc()

tp_alloc

PyObject _Py_NoneStruct

這個物件像是 Python 中的 None。它只應該透過 Py_None 巨集來存取，該巨集的拿到指向該物件的指標。

也參考

模組物件

分配記憶體和建立擴充模組。

被棄用的別名

These are soft deprecated aliases to existing functions and macros. They exist solely for backwards compatibility.

已棄用的別名

函式

PyObject_NEW(type, typeobj)

PyObject_New

PyObject_NEW_VAR(type, typeobj, n)

PyObject_NewVar

PyObject_INIT(op, typeobj)

PyObject_Init()

PyObject_INIT_VAR(op, typeobj, n)

PyObject_InitVar()

PyObject_MALLOC(n)

PyObject_Malloc()

PyObject_REALLOC(p, n)

PyObject_Realloc()

PyObject_FREE(p)

PyObject_Free()

PyObject_DEL(p)

PyObject_Free()

PyObject_Del(p)

PyObject_Free()

物件生命週期

此章節說明型別的插槽如何與物件的生命週期相關聯。它並非旨在成為插槽的完整權威參考；請參閱 型別物件結構 中的插槽部分文件來了解有關於插槽的詳細資訊。

生命事件

The figure below illustrates the order of events that can occur throughout an object's life. An arrow from A to B indicates that event B can occur after event A has occurred, with the arrow's label indicating the condition that must be true for B to occur after A.

說明：

當一個新物件透過其型別來建構時：

tp_new 會被呼叫來建立一個新物件。

tp_alloc is directly called by tp_new to allocate the memory for the new object.

tp_init initializes the newly created object. tp_init can be called again to re-initialize an object, if desired. The tp_init call can also be skipped entirely, for example by Python code calling __new__().

在 tp_init 完成後，該物件即可使用。

在最後一個對物件的參照被移除一段時間後：

If an object is not marked as finalized, it might be finalized by marking it as finalized and calling its tp_finalize function. Python does not finalize an object when the last reference to it is deleted; use PyObject_CallFinalizerFromDealloc() to ensure that tp_finalize is always called.

If the object is marked as finalized, tp_clear might be called by the garbage collector to clear references held by the object. It is not called when the object's reference count reaches zero.

tp_dealloc is called to destroy the object. To avoid code duplication, tp_dealloc typically calls into tp_clear to free up the object's references.

When tp_dealloc finishes object destruction, it directly calls tp_free (usually set to PyObject_Free() or PyObject_GC_Del() automatically as appropriate for the type) to deallocate the memory.

The tp_finalize function is permitted to add a reference to the object if desired. If it does, the object is resurrected, preventing its pending destruction. (Only tp_finalize is allowed to resurrect an object; tp_clear and tp_dealloc cannot without calling into tp_finalize.) Resurrecting an object may or may not cause the object's finalized mark to be removed. Currently, Python does not remove the finalized mark from a resurrected object if it supports garbage collection (i.e., the Py_TPFLAGS_HAVE_GC flag is set) but does remove the mark if the object does not support garbage collection; either or both of these behaviors may change in the future.

tp_dealloc can optionally call tp_finalize via PyObject_CallFinalizerFromDealloc() if it wishes to reuse that code to help with object destruction. This is recommended because it guarantees that tp_finalize is always called before destruction. See the tp_dealloc documentation for example code.

If the object is a member of a cyclic isolate and either tp_clear fails to break the reference cycle or the cyclic isolate is not detected (perhaps gc.disable() was called, or the Py_TPFLAGS_HAVE_GC flag was erroneously omitted in one of the involved types), the objects remain indefinitely uncollectable (they "leak"). See gc.garbage.

If the object is marked as supporting garbage collection (the Py_TPFLAGS_HAVE_GC flag is set in tp_flags), the following events are also possible:

The garbage collector occasionally calls tp_traverse to identify cyclic isolates.

When the garbage collector discovers a cyclic isolate, it finalizes one of the objects in the group by marking it as finalized and calling its tp_finalize function, if it has one. This repeats until the cyclic isolate doesn't exist or all of the objects have been finalized.

tp_finalize is permitted to resurrect the object by adding a reference from outside the cyclic isolate. The new reference causes the group of objects to no longer form a cyclic isolate (the reference cycle may still exist, but if it does the objects are no longer isolated).

When the garbage collector discovers a cyclic isolate and all of the objects in the group have already been marked as finalized, the garbage collector clears one or more of the uncleared objects in the group (possibly concurrently) by calling each's tp_clear function. This repeats as long as the cyclic isolate still exists and not all of the objects have been cleared.

Cyclic Isolate Destruction

Listed below are the stages of life of a hypothetical cyclic isolate that continues to exist after each member object is finalized or cleared. It is a memory leak if a cyclic isolate progresses through all of these stages; it should vanish once all objects are cleared, if not sooner. A cyclic isolate can vanish either because the reference cycle is broken or because the objects are no longer isolated due to finalizer resurrection (see tp_finalize).

Reachable (not yet a cyclic isolate): All objects are in their normal, reachable state. A reference cycle could exist, but an external reference means the objects are not yet isolated.

Unreachable but consistent: The final reference from outside the cyclic group of objects has been removed, causing the objects to become isolated (thus a cyclic isolate is born). None of the group's objects have been finalized or cleared yet. The cyclic isolate remains at this stage until some future run of the garbage collector (not necessarily the next run because the next run might not scan every object).

Mix of finalized and not finalized: Objects in a cyclic isolate are finalized one at a time, which means that there is a period of time when the cyclic isolate is composed of a mix of finalized and non-finalized objects. Finalization order is unspecified, so it can appear random. A finalized object must behave in a sane manner when non-finalized objects interact with it, and a non-finalized object must be able to tolerate the finalization of an arbitrary subset of its referents.

All finalized: All objects in a cyclic isolate are finalized before any of them are cleared.

Mix of finalized and cleared: The objects can be cleared serially or concurrently (but with the GIL held); either way, some will finish before others. A finalized object must be able to tolerate the clearing of a subset of its referents. PEP 442 [https://peps.python.org/pep-0442/] calls this stage "cyclic trash".

Leaked: If a cyclic isolate still exists after all objects in the group have been finalized and cleared, then the objects remain indefinitely uncollectable (see gc.garbage). It is a bug if a cyclic isolate reaches this stage---it means the tp_clear methods of the participating objects have failed to break the reference cycle as required.

If tp_clear did not exist, then Python would have no way to safely break a reference cycle. Simply destroying an object in a cyclic isolate would result in a dangling pointer, triggering undefined behavior when an object referencing the destroyed object is itself destroyed. The clearing step makes object destruction a two-phase process: first tp_clear is called to partially destroy the objects enough to detangle them from each other, then tp_dealloc is called to complete the destruction.

Unlike clearing, finalization is not a phase of destruction. A finalized object must still behave properly by continuing to fulfill its design contracts. An object's finalizer is allowed to execute arbitrary Python code, and is even allowed to prevent the impending destruction by adding a reference. The finalizer is only related to destruction by call order---if it runs, it runs before destruction, which starts with tp_clear (if called) and concludes with tp_dealloc.

The finalization step is not necessary to safely reclaim the objects in a cyclic isolate, but its existence makes it easier to design types that behave in a sane manner when objects are cleared. Clearing an object might necessarily leave it in a broken, partially destroyed state---it might be unsafe to call any of the cleared object's methods or access any of its attributes. With finalization, only finalized objects can possibly interact with cleared objects; non-finalized objects are guaranteed to interact with only non-cleared (but potentially finalized) objects.

To summarize the possible interactions:

A non-finalized object might have references to or from non-finalized and finalized objects, but not to or from cleared objects.

A finalized object might have references to or from non-finalized, finalized, and cleared objects.

A cleared object might have references to or from finalized and cleared objects, but not to or from non-finalized objects.

Without any reference cycles, an object can be simply destroyed once its last reference is deleted; the finalization and clearing steps are not necessary to safely reclaim unused objects. However, it can be useful to automatically call tp_finalize and tp_clear before destruction anyway because type design is simplified when all objects always experience the same series of events regardless of whether they participated in a cyclic isolate. Python currently only calls tp_finalize and tp_clear as needed to destroy a cyclic isolate; this may change in a future version.

函式

要分配和釋放記憶體，請參見 在 heap 上分配物件。

void PyObject_CallFinalizer(PyObject *op)

Finalizes the object as described in tp_finalize. Call this function (or PyObject_CallFinalizerFromDealloc()) instead of calling tp_finalize directly because this function may deduplicate multiple calls to tp_finalize. Currently, calls are only deduplicated if the type supports garbage collection (i.e., the Py_TPFLAGS_HAVE_GC flag is set); this may change in the future.

在 3.4 版被加入.

int PyObject_CallFinalizerFromDealloc(PyObject *op)

Same as PyObject_CallFinalizer() but meant to be called at the beginning of the object's destructor (tp_dealloc). There must not be any references to the object. If the object's finalizer resurrects the object, this function returns -1; no further destruction should happen. Otherwise, this function returns 0 and destruction can continue normally.

在 3.4 版被加入.

也參考

tp_dealloc for example code.

通用物件結構

There are a large number of structures which are used in the definition of object types for Python. This section describes these structures and how they are used.

Base object types and macros

All Python objects ultimately share a small number of fields at the beginning of the object's representation in memory. These are represented by the PyObject and PyVarObject types, which are defined, in turn, by the expansions of some macros also used, whether directly or indirectly, in the definition of all other Python objects. Additional macros can be found under reference counting.

type PyObject

為 受限 API 的一部分. （只有部分成員是穩定 ABI 的一部分。）

All object types are extensions of this type. This is a type which contains the information Python needs to treat a pointer to an object as an object. In a normal "release" build, it contains only the object's reference count and a pointer to the corresponding type object. Nothing is actually declared to be a PyObject, but every pointer to a Python object can be cast to a PyObject*.

The members must not be accessed directly; instead use macros such as Py_REFCNT and Py_TYPE.

Py_ssize_t ob_refcnt

為 穩定 ABI 的一部分.

The object's reference count, as returned by Py_REFCNT. Do not use this field directly; instead use functions and macros such as Py_REFCNT, Py_INCREF() and Py_DecRef().

The field type may be different from Py_ssize_t, depending on build configuration and platform.

PyTypeObject *ob_type

為 穩定 ABI 的一部分.

The object's type. Do not use this field directly; use Py_TYPE and Py_SET_TYPE() instead.

type PyVarObject

為 受限 API 的一部分. （只有部分成員是穩定 ABI 的一部分。）

An extension of PyObject that adds the ob_size field. This is intended for objects that have some notion of length.

As with PyObject, the members must not be accessed directly; instead use macros such as Py_SIZE, Py_REFCNT and Py_TYPE.

Py_ssize_t ob_size

為 穩定 ABI 的一部分.

A size field, whose contents should be considered an object's internal implementation detail.

Do not use this field directly; use Py_SIZE instead.

Object creation functions such as PyObject_NewVar() will generally set this field to the requested size (number of items). After creation, arbitrary values can be stored in ob_size using Py_SET_SIZE.

To get an object's publicly exposed length, as returned by the Python function len(), use PyObject_Length() instead.

PyObject_HEAD

This is a macro used when declaring new types which represent objects without a varying length. The PyObject_HEAD macro expands to:

PyObject ob_base;

請見上面 PyObject 的文件。

PyObject_VAR_HEAD

This is a macro used when declaring new types which represent objects with a length that varies from instance to instance. The PyObject_VAR_HEAD macro expands to:

PyVarObject ob_base;

請見上面 PyVarObject 的文件。

PyTypeObject PyBaseObject_Type

為 穩定 ABI 的一部分.

The base class of all other objects, the same as object in Python.

int Py_Is(PyObject *x, PyObject *y)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Test if the x object is the y object, the same as x is y in Python.

在 3.10 版被加入.

int Py_IsNone(PyObject *x)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Test if an object is the None singleton, the same as x is None in Python.

在 3.10 版被加入.

int Py_IsTrue(PyObject *x)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Test if an object is the True singleton, the same as x is True in Python.

在 3.10 版被加入.

int Py_IsFalse(PyObject *x)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Test if an object is the False singleton, the same as x is False in Python.

在 3.10 版被加入.

PyTypeObject *Py_TYPE(PyObject *o)

回傳值：借用參照。 為 穩定 ABI 的一部分 自 3.14 版本開始.

Get the type of the Python object o.

The returned reference is borrowed from o. Do not release it with Py_DECREF() or similar.

在 3.11 版的變更: Py_TYPE() is changed to an inline static function. The parameter type is no longer const PyObject*.

int Py_IS_TYPE(PyObject *o, PyTypeObject *type)

Return non-zero if the object o type is type. Return zero otherwise. Equivalent to: Py_TYPE(o) == type.

在 3.9 版被加入.

void Py_SET_TYPE(PyObject *o, PyTypeObject *type)

Set the type of object o to type, without any checking or reference counting.

This is a very low-level operation. Consider instead setting the Python attribute __class__ using PyObject_SetAttrString() or similar.

Note that assigning an incompatible type can lead to undefined behavior.

If type is a heap type, the caller must create a new reference to it. Similarly, if the old type of o is a heap type, the caller must release a reference to that type.

在 3.9 版被加入.

Py_ssize_t Py_SIZE(PyVarObject *o)

Get the ob_size field of o.

在 3.11 版的變更: Py_SIZE() is changed to an inline static function. The parameter type is no longer const PyVarObject*.

void Py_SET_SIZE(PyVarObject *o, Py_ssize_t size)

Set the ob_size field of o to size.

在 3.9 版被加入.

PyObject_HEAD_INIT(type)

This is a macro which expands to initialization values for a new PyObject type. This macro expands to:

_PyObject_EXTRA_INIT
1, type,

PyVarObject_HEAD_INIT(type, size)

This is a macro which expands to initialization values for a new PyVarObject type, including the ob_size field. This macro expands to:

_PyObject_EXTRA_INIT
1, type, size,

實作函式與方法

type PyCFunction

為 穩定 ABI 的一部分.

Type of the functions used to implement most Python callables in C. Functions of this type take two PyObject* parameters and return one such value. If the return value is NULL, an exception shall have been set. If not NULL, the return value is interpreted as the return value of the function as exposed in Python. The function must return a new reference.

The function signature is:

PyObject *PyCFunction(PyObject *self,
                      PyObject *args);

type PyCFunctionWithKeywords

為 穩定 ABI 的一部分.

Type of the functions used to implement Python callables in C with signature METH_VARARGS | METH_KEYWORDS. The function signature is:

PyObject *PyCFunctionWithKeywords(PyObject *self,
                                  PyObject *args,
                                  PyObject *kwargs);

type PyCFunctionFast

為 穩定 ABI 的一部分 自 3.13 版本開始.

Type of the functions used to implement Python callables in C with signature METH_FASTCALL. The function signature is:

PyObject *PyCFunctionFast(PyObject *self,
                          PyObject *const *args,
                          Py_ssize_t nargs);

type PyCFunctionFastWithKeywords

為 穩定 ABI 的一部分 自 3.13 版本開始.

Type of the functions used to implement Python callables in C with signature METH_FASTCALL | METH_KEYWORDS. The function signature is:

PyObject *PyCFunctionFastWithKeywords(PyObject *self,
                                      PyObject *const *args,
                                      Py_ssize_t nargs,
                                      PyObject *kwnames);

type PyCMethod

Type of the functions used to implement Python callables in C with signature METH_METHOD | METH_FASTCALL | METH_KEYWORDS. The function signature is:

PyObject *PyCMethod(PyObject *self,
                    PyTypeObject *defining_class,
                    PyObject *const *args,
                    Py_ssize_t nargs,
                    PyObject *kwnames)

在 3.9 版被加入.

type PyMethodDef

為 穩定 ABI 的一部分 （包含所有成員）.

Structure used to describe a method of an extension type. This structure has four fields:

const char *ml_name

Name of the method.

PyCFunction ml_meth

Pointer to the C implementation.

int ml_flags

Flags bits indicating how the call should be constructed.

const char *ml_doc

Points to the contents of the docstring.

The ml_meth is a C function pointer. The functions may be of different types, but they always return PyObject*. If the function is not of the PyCFunction, the compiler will require a cast in the method table. Even though PyCFunction defines the first parameter as PyObject*, it is common that the method implementation uses the specific C type of the self object.

The ml_flags field is a bitfield which can include the following flags. The individual flags indicate either a calling convention or a binding convention.

There are these calling conventions:

METH_VARARGS

為 穩定 ABI 的一部分.

This is the typical calling convention, where the methods have the type PyCFunction. The function expects two PyObject* values. The first one is the self object for methods; for module functions, it is the module object. The second parameter (often called args) is a tuple object representing all arguments. This parameter is typically processed using PyArg_ParseTuple() or PyArg_UnpackTuple().

METH_KEYWORDS

Can only be used in certain combinations with other flags: METH_VARARGS | METH_KEYWORDS, METH_FASTCALL | METH_KEYWORDS and METH_METHOD | METH_FASTCALL | METH_KEYWORDS.

METH_VARARGS | METH_KEYWORDS

Methods with these flags must be of type PyCFunctionWithKeywords. The function expects three parameters: self, args, kwargs where kwargs is a dictionary of all the keyword arguments or possibly NULL if there are no keyword arguments. The parameters are typically processed using PyArg_ParseTupleAndKeywords().

METH_FASTCALL

為 穩定 ABI 的一部分 自 3.7 版本開始.

Fast calling convention supporting only positional arguments. The methods have the type PyCFunctionFast. The first parameter is self, the second parameter is a C array of PyObject* values indicating the arguments and the third parameter is the number of arguments (the length of the array).

在 3.7 版被加入.

在 3.10 版的變更: METH_FASTCALL is now part of the stable ABI.

METH_FASTCALL | METH_KEYWORDS

Extension of METH_FASTCALL supporting also keyword arguments, with methods of type PyCFunctionFastWithKeywords. Keyword arguments are passed the same way as in the vectorcall protocol: there is an additional fourth PyObject* parameter which is a tuple representing the names of the keyword arguments (which are guaranteed to be strings) or possibly NULL if there are no keywords. The values of the keyword arguments are stored in the args array, after the positional arguments.

在 3.7 版被加入.

METH_METHOD

為 穩定 ABI 的一部分 自 3.7 版本開始.

Can only be used in the combination with other flags: METH_METHOD | METH_FASTCALL | METH_KEYWORDS.

METH_METHOD | METH_FASTCALL | METH_KEYWORDS

Extension of METH_FASTCALL | METH_KEYWORDS supporting the defining class, that is, the class that contains the method in question. The defining class might be a superclass of Py_TYPE(self).

The method needs to be of type PyCMethod, the same as for METH_FASTCALL | METH_KEYWORDS with defining_class argument added after self.

在 3.9 版被加入.

METH_NOARGS

為 穩定 ABI 的一部分.

Methods without parameters don't need to check whether arguments are given if they are listed with the METH_NOARGS flag. They need to be of type PyCFunction. The first parameter is typically named self and will hold a reference to the module or object instance. In all cases the second parameter will be NULL.

The function must have 2 parameters. Since the second parameter is unused, Py_UNUSED can be used to prevent a compiler warning.

METH_O

為 穩定 ABI 的一部分.

Methods with a single object argument can be listed with the METH_O flag, instead of invoking PyArg_ParseTuple() with a "O" argument. They have the type PyCFunction, with the self parameter, and a PyObject* parameter representing the single argument.

These two constants are not used to indicate the calling convention but the binding when use with methods of classes. These may not be used for functions defined for modules. At most one of these flags may be set for any given method.

METH_CLASS

為 穩定 ABI 的一部分.

The method will be passed the type object as the first parameter rather than an instance of the type. This is used to create class methods, similar to what is created when using the classmethod() built-in function.

METH_STATIC

為 穩定 ABI 的一部分.

The method will be passed NULL as the first parameter rather than an instance of the type. This is used to create static methods, similar to what is created when using the staticmethod() built-in function.

One other constant controls whether a method is loaded in place of another definition with the same method name.

METH_COEXIST

為 穩定 ABI 的一部分.

The method will be loaded in place of existing definitions. Without METH_COEXIST, the default is to skip repeated definitions. Since slot wrappers are loaded before the method table, the existence of a sq_contains slot, for example, would generate a wrapped method named __contains__() and preclude the loading of a corresponding PyCFunction with the same name. With the flag defined, the PyCFunction will be loaded in place of the wrapper object and will co-exist with the slot. This is helpful because calls to PyCFunctions are optimized more than wrapper object calls.

PyTypeObject PyCMethod_Type

The type object corresponding to Python C method objects. This is available as types.BuiltinMethodType in the Python layer.

int PyCMethod_Check(PyObject *op)

Return true if op is an instance of the PyCMethod_Type type or a subtype of it. This function always succeeds.

int PyCMethod_CheckExact(PyObject *op)

This is the same as PyCMethod_Check(), but does not account for subtypes.

PyObject *PyCMethod_New(PyMethodDef *ml, PyObject *self, PyObject *module, PyTypeObject *cls)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.9 版本開始.

Turn ml into a Python callable object. The caller must ensure that ml outlives the callable. Typically, ml is defined as a static variable.

The self parameter will be passed as the self argument to the C function in ml->ml_meth when invoked. self can be NULL.

The callable object's __module__ attribute can be set from the given module argument. module should be a Python string, which will be used as name of the module the function is defined in. If unavailable, it can be set to None or NULL.

也參考

function.__module__

The cls parameter will be passed as the defining_class argument to the C function. Must be set if METH_METHOD is set on ml->ml_flags.

在 3.9 版被加入.

PyTypeObject PyCFunction_Type

為 穩定 ABI 的一部分.

The type object corresponding to Python C function objects. This is available as types.BuiltinFunctionType in the Python layer.

int PyCFunction_Check(PyObject *op)

Return true if op is an instance of the PyCFunction_Type type or a subtype of it. This function always succeeds.

int PyCFunction_CheckExact(PyObject *op)

This is the same as PyCFunction_Check(), but does not account for subtypes.

PyObject *PyCFunction_NewEx(PyMethodDef *ml, PyObject *self, PyObject *module)

回傳值：新的參照。 為 穩定 ABI 的一部分.

等價於 PyCMethod_New(ml, self, module, NULL)。

PyObject *PyCFunction_New(PyMethodDef *ml, PyObject *self)

回傳值：新的參照。 為 穩定 ABI 的一部分 自 3.4 版本開始.

等價於 PyCMethod_New(ml, self, NULL, NULL)。

int PyCFunction_GetFlags(PyObject *func)

為 穩定 ABI 的一部分.

Get the function's flags on func as they were passed to ml_flags.

If func is not a C function object, this fails with an exception. func must not be NULL.

This function returns the function's flags on success, and -1 with an exception set on failure.

int PyCFunction_GET_FLAGS(PyObject *func)

This is the same as PyCFunction_GetFlags(), but without error or type checking.

PyCFunction PyCFunction_GetFunction(PyObject *func)

為 穩定 ABI 的一部分.

Get the function pointer on func as it was passed to ml_meth.

If func is not a C function object, this fails with an exception. func must not be NULL.

This function returns the function pointer on success, and NULL with an exception set on failure.

int PyCFunction_GET_FUNCTION(PyObject *func)

This is the same as PyCFunction_GetFunction(), but without error or type checking.

PyObject *PyCFunction_GetSelf(PyObject *func)

為 穩定 ABI 的一部分.

Get the "self" object on func. This is the object that would be passed to the first argument of a PyCFunction. For C function objects created through a PyMethodDef on a PyModuleDef, this is the resulting module object.

If func is not a C function object, this fails with an exception. func must not be NULL.

This function returns a borrowed reference to the "self" object on success, and NULL with an exception set on failure.

PyObject *PyCFunction_GET_SELF(PyObject *func)

This is the same as PyCFunction_GetSelf(), but without error or type checking.

Accessing attributes of extension types

type PyMemberDef

為 穩定 ABI 的一部分 （包含所有成員）.

Structure which describes an attribute of a type which corresponds to a C struct member. When defining a class, put a NULL-terminated array of these structures in the tp_members slot.

Its fields are, in order:

const char *name

Name of the member. A NULL value marks the end of a PyMemberDef[] array.

The string should be static, no copy is made of it.

int type

The type of the member in the C struct. See Member types for the possible values.

Py_ssize_t offset

The offset in bytes that the member is located on the type’s object struct.

int flags

Zero or more of the Member flags, combined using bitwise OR.

const char *doc

The docstring, or NULL. The string should be static, no copy is made of it. Typically, it is defined using PyDoc_STR.

By default (when flags is 0), members allow both read and write access. Use the Py_READONLY flag for read-only access. Certain types, like Py_T_STRING, imply Py_READONLY. Only Py_T_OBJECT_EX (and legacy T_OBJECT) members can be deleted.

For heap-allocated types (created using PyType_FromSpec() or similar), PyMemberDef may contain a definition for the special member "__vectorcalloffset__", corresponding to tp_vectorcall_offset in type objects. This member must be defined with Py_T_PYSSIZET, and either Py_READONLY or Py_READONLY | Py_RELATIVE_OFFSET. For example:

static PyMemberDef spam_type_members[] = {
    {"__vectorcalloffset__", Py_T_PYSSIZET,
     offsetof(Spam_object, vectorcall), Py_READONLY},
    {NULL}  /* Sentinel */
};

(You may need to #include <stddef.h> for offsetof().)

The legacy offsets tp_dictoffset and tp_weaklistoffset can be defined similarly using "__dictoffset__" and "__weaklistoffset__" members, but extensions are strongly encouraged to use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead.

在 3.12 版的變更: PyMemberDef is always available. Previously, it required including "structmember.h".

在 3.14 版的變更: Py_RELATIVE_OFFSET is now allowed for "__vectorcalloffset__", "__dictoffset__" and "__weaklistoffset__".

PyObject *PyMember_GetOne(const char *obj_addr, struct PyMemberDef *m)

為 穩定 ABI 的一部分.

Get an attribute belonging to the object at address obj_addr. The attribute is described by PyMemberDef m. Returns NULL on error.

在 3.12 版的變更: PyMember_GetOne is always available. Previously, it required including "structmember.h".

int PyMember_SetOne(char *obj_addr, struct PyMemberDef *m, PyObject *o)

為 穩定 ABI 的一部分.

Set an attribute belonging to the object at address obj_addr to object o. The attribute to set is described by PyMemberDef m. Returns 0 if successful and a negative value on failure.

在 3.12 版的變更: PyMember_SetOne is always available. Previously, it required including "structmember.h".

Member flags

The following flags can be used with PyMemberDef.flags:

Py_READONLY

為 穩定 ABI 的一部分 自 3.12 版本開始.

不可寫入。

Py_AUDIT_READ

為 穩定 ABI 的一部分 自 3.12 版本開始.

Emit an object.__getattr__ audit event before reading.

Py_RELATIVE_OFFSET

為 穩定 ABI 的一部分 自 3.12 版本開始.

Indicates that the offset of this PyMemberDef entry indicates an offset from the subclass-specific data, rather than from PyObject.

Can only be used as part of the Py_tp_members slot when creating a class using negative basicsize. It is mandatory in that case. When setting tp_members from the slot during class creation, Python clears the flag and sets PyMemberDef.offset to the offset from the PyObject struct.

在 3.10 版的變更: The RESTRICTED, READ_RESTRICTED and WRITE_RESTRICTED macros available with #include "structmember.h" are deprecated. READ_RESTRICTED and RESTRICTED are equivalent to Py_AUDIT_READ; WRITE_RESTRICTED does nothing.

在 3.12 版的變更: The READONLY macro was renamed to Py_READONLY. The PY_AUDIT_READ macro was renamed with the Py_ prefix. The new names are now always available. Previously, these required #include "structmember.h". The header is still available and it provides the old names.

Member types

PyMemberDef.type can be one of the following macros corresponding to various C types. When the member is accessed in Python, it will be converted to the equivalent Python type. When it is set from Python, it will be converted back to the C type. If that is not possible, an exception such as TypeError or ValueError is raised.

Unless marked (D), attributes defined this way cannot be deleted using e.g. del or delattr().

巨集名稱

C type

Python type

Py_T_BYTE

為 穩定 ABI 的一部分 自 3.12 版本開始.

char

int

Py_T_SHORT

為 穩定 ABI 的一部分 自 3.12 版本開始.

short

int

Py_T_INT

為 穩定 ABI 的一部分 自 3.12 版本開始.

int

int

Py_T_LONG

為 穩定 ABI 的一部分 自 3.12 版本開始.

long

int

Py_T_LONGLONG

為 穩定 ABI 的一部分 自 3.12 版本開始.

long long

int

Py_T_UBYTE

為 穩定 ABI 的一部分 自 3.12 版本開始.

unsigned char

int

Py_T_UINT

為 穩定 ABI 的一部分 自 3.12 版本開始.

unsigned int

int

Py_T_USHORT

為 穩定 ABI 的一部分 自 3.12 版本開始.

unsigned short

int

Py_T_ULONG

為 穩定 ABI 的一部分 自 3.12 版本開始.

unsigned long

int

Py_T_ULONGLONG

為 穩定 ABI 的一部分 自 3.12 版本開始.

unsigned long long

int

Py_T_PYSSIZET

為 穩定 ABI 的一部分 自 3.12 版本開始.

Py_ssize_t

int

Py_T_FLOAT

為 穩定 ABI 的一部分 自 3.12 版本開始.

float

float

Py_T_DOUBLE

為 穩定 ABI 的一部分 自 3.12 版本開始.

double

float

Py_T_BOOL

為 穩定 ABI 的一部分 自 3.12 版本開始.

char （寫成 0 或 1）

bool

Py_T_STRING

為 穩定 ABI 的一部分 自 3.12 版本開始.

const char* (*)

str (RO)

Py_T_STRING_INPLACE

為 穩定 ABI 的一部分 自 3.12 版本開始.

const char[] (*)

str (RO)

Py_T_CHAR

為 穩定 ABI 的一部分 自 3.12 版本開始.

char (0-127)

str (**)

Py_T_OBJECT_EX

為 穩定 ABI 的一部分 自 3.12 版本開始.

PyObject*

object (D)

(*): Zero-terminated, UTF8-encoded C string. With Py_T_STRING the C representation is a pointer; with Py_T_STRING_INPLACE the string is stored directly in the structure.

(**): String of length 1. Only ASCII is accepted.

(RO): Implies Py_READONLY.

(D): Can be deleted, in which case the pointer is set to NULL. Reading a NULL pointer raises AttributeError.

在 3.12 版被加入: In previous versions, the macros were only available with #include "structmember.h" and were named without the Py_ prefix (e.g. as T_INT). The header is still available and contains the old names, along with the following deprecated types:

T_OBJECT

Like Py_T_OBJECT_EX, but NULL is converted to None. This results in surprising behavior in Python: deleting the attribute effectively sets it to None.

T_NONE

Always None. Must be used with Py_READONLY.

Defining Getters and Setters

type PyGetSetDef

為 穩定 ABI 的一部分 （包含所有成員）.

Structure to define property-like access for a type. See also description of the PyTypeObject.tp_getset slot.

const char *name

屬性名稱

getter get

C function to get the attribute.

setter set

Optional C function to set or delete the attribute. If NULL, the attribute is read-only.

const char *doc

可選的文件字串

void *closure

Optional user data pointer, providing additional data for getter and setter.

typedef PyObject *(*getter)(PyObject*, void*)

為 穩定 ABI 的一部分.

The get function takes one PyObject* parameter (the instance) and a user data pointer (the associated closure):

It should return a new reference on success or NULL with a set exception on failure.

typedef int (*setter)(PyObject*, PyObject*, void*)

為 穩定 ABI 的一部分.

set functions take two PyObject* parameters (the instance and the value to be set) and a user data pointer (the associated closure):

In case the attribute should be deleted the second parameter is NULL. Should return 0 on success or -1 with a set exception on failure.

型別物件結構

Perhaps one of the most important structures of the Python object system is the structure that defines a new type: the PyTypeObject structure. Type objects can be handled using any of the PyObject_* or PyType_* functions, but do not offer much that's interesting to most Python applications. These objects are fundamental to how objects behave, so they are very important to the interpreter itself and to any extension module that implements new types.

Type objects are fairly large compared to most of the standard types. The reason for the size is that each type object stores a large number of values, mostly C function pointers, each of which implements a small part of the type's functionality. The fields of the type object are examined in detail in this section. The fields will be described in the order in which they occur in the structure.

In addition to the following quick reference, the 範例 section provides at-a-glance insight into the meaning and use of PyTypeObject.

Quick Reference

"tp slots"

PyTypeObject Slot [1]

Type

special methods/attrs

Info [2]

O

T

D

I

<R> tp_name

const char *

__name__

X

X

tp_basicsize

Py_ssize_t

X

X

X

tp_itemsize

Py_ssize_t

X

X

tp_dealloc

destructor

X

X

X

tp_vectorcall_offset

Py_ssize_t

X

X

(tp_getattr)

getattrfunc

__getattribute__, __getattr__

G

(tp_setattr)

setattrfunc

__setattr__, __delattr__

G

tp_as_async

PyAsyncMethods *

sub-slots

%

tp_repr

reprfunc

__repr__

X

X

X

tp_as_number

PyNumberMethods *

sub-slots

%

tp_as_sequence

PySequenceMethods *

sub-slots

%

tp_as_mapping

PyMappingMethods *

sub-slots

%

tp_hash

hashfunc

__hash__

X

G

tp_call

ternaryfunc

__call__

X

X

tp_str

reprfunc

__str__

X

X

tp_getattro

getattrofunc

__getattribute__, __getattr__

X

X

G

tp_setattro

setattrofunc

__setattr__, __delattr__

X

X

G

tp_as_buffer

PyBufferProcs *

sub-slots

%

tp_flags

unsigned long

X

X

?

tp_doc

const char *

__doc__

X

X

tp_traverse

traverseproc

X

G

tp_clear

inquiry

X

G

tp_richcompare

richcmpfunc

__lt__, __le__, __eq__, __ne__, __gt__, __ge__

X

G

(tp_weaklistoffset)

Py_ssize_t

X

?

tp_iter

getiterfunc

__iter__

X

tp_iternext

iternextfunc

__next__

X

tp_methods

PyMethodDef []

X

X

tp_members

PyMemberDef []

X

tp_getset

PyGetSetDef []

X

X

tp_base

PyTypeObject *

__base__

X

tp_dict

PyObject *

__dict__

?

tp_descr_get

descrgetfunc

__get__

X

tp_descr_set

descrsetfunc

__set__, __delete__

X

(tp_dictoffset)

Py_ssize_t

X

?

tp_init

initproc

__init__

X

X

X

tp_alloc

allocfunc

X

?

?

tp_new

newfunc

__new__

X

X

?

?

tp_free

freefunc

X

X

?

?

tp_is_gc

inquiry

X

X

<tp_bases>

PyObject *

__bases__

~

<tp_mro>

PyObject *

__mro__

~

[tp_cache]

PyObject *

[tp_subclasses]

void *

__subclasses__

[tp_weaklist]

PyObject *

(tp_del)

destructor

[tp_version_tag]

unsigned int

tp_finalize

destructor

__del__

X

tp_vectorcall

vectorcallfunc

[tp_watched]

unsigned char

[1]

(): A slot name in parentheses indicates it is (effectively) deprecated.

<>: Names in angle brackets should be initially set to NULL and treated as read-only.

[]: Names in square brackets are for internal use only.

<R> (as a prefix) means the field is required (must be non-NULL).

[2]

Columns:

"O": set on PyBaseObject_Type

"T": set on PyType_Type

"D": default (if slot is set to NULL)

X - PyType_Ready sets this value if it is NULL
~ - PyType_Ready always sets this value (it should be NULL)
? - PyType_Ready may set this value depending on other slots

Also see the inheritance column ("I").

"I": inheritance

X - type slot is inherited via *PyType_Ready* if defined with a *NULL* value
% - the slots of the sub-struct are inherited individually
G - inherited, but only in combination with other slots; see the slot's description
? - it's complicated; see the slot's description

Note that some slots are effectively inherited through the normal attribute lookup chain.

sub-slots

Slot

Type

special methods

am_await

unaryfunc

__await__

am_aiter

unaryfunc

__aiter__

am_anext

unaryfunc

__anext__

am_send

sendfunc

nb_add

binaryfunc

__add__ __radd__

nb_inplace_add

binaryfunc

__iadd__

nb_subtract

binaryfunc

__sub__ __rsub__

nb_inplace_subtract

binaryfunc

__isub__

nb_multiply

binaryfunc

__mul__ __rmul__

nb_inplace_multiply

binaryfunc

__imul__

nb_remainder

binaryfunc

__mod__ __rmod__

nb_inplace_remainder

binaryfunc

__imod__

nb_divmod

binaryfunc

__divmod__ __rdivmod__

nb_power

ternaryfunc

__pow__ __rpow__

nb_inplace_power

ternaryfunc

__ipow__

nb_negative

unaryfunc

__neg__

nb_positive

unaryfunc

__pos__

nb_absolute

unaryfunc

__abs__

nb_bool

inquiry

__bool__

nb_invert

unaryfunc

__invert__

nb_lshift

binaryfunc

__lshift__ __rlshift__

nb_inplace_lshift

binaryfunc

__ilshift__

nb_rshift

binaryfunc

__rshift__ __rrshift__

nb_inplace_rshift

binaryfunc

__irshift__

nb_and

binaryfunc

__and__ __rand__

nb_inplace_and

binaryfunc

__iand__

nb_xor

binaryfunc

__xor__ __rxor__

nb_inplace_xor

binaryfunc

__ixor__

nb_or

binaryfunc

__or__ __ror__

nb_inplace_or

binaryfunc

__ior__

nb_int

unaryfunc

__int__

nb_reserved

void *

nb_float

unaryfunc

__float__

nb_floor_divide

binaryfunc

__floordiv__

nb_inplace_floor_divide

binaryfunc

__ifloordiv__

nb_true_divide

binaryfunc

__truediv__

nb_inplace_true_divide

binaryfunc

__itruediv__

nb_index

unaryfunc

__index__

nb_matrix_multiply

binaryfunc

__matmul__ __rmatmul__

nb_inplace_matrix_multiply

binaryfunc

__imatmul__

mp_length

lenfunc

__len__

mp_subscript

binaryfunc

__getitem__

mp_ass_subscript

objobjargproc

__setitem__, __delitem__

sq_length

lenfunc

__len__

sq_concat

binaryfunc

__add__

sq_repeat

ssizeargfunc

__mul__

sq_item

ssizeargfunc

__getitem__

sq_ass_item

ssizeobjargproc

__setitem__ __delitem__

sq_contains

objobjproc

__contains__

sq_inplace_concat

binaryfunc

__iadd__

sq_inplace_repeat

ssizeargfunc

__imul__

bf_getbuffer

getbufferproc()

__buffer__

bf_releasebuffer

releasebufferproc()

__release_buffer__

slot typedefs

typedef

Parameter Types

Return Type

allocfunc

PyTypeObject *

Py_ssize_t

PyObject *

destructor

PyObject *

void

freefunc

void *

void

traverseproc

PyObject *

visitproc

void *

int

newfunc

PyTypeObject *

PyObject *

PyObject *

PyObject *

initproc

PyObject *

PyObject *

PyObject *

int

reprfunc

PyObject *

PyObject *

getattrfunc

PyObject *

const char *

PyObject *

setattrfunc

PyObject *

const char *

PyObject *

int

getattrofunc

PyObject *

PyObject *

PyObject *

setattrofunc

PyObject *

PyObject *

PyObject *

int

descrgetfunc

PyObject *

PyObject *

PyObject *

PyObject *

descrsetfunc

PyObject *

PyObject *

PyObject *

int

hashfunc

PyObject *

Py_hash_t

richcmpfunc

PyObject *

PyObject *

int

PyObject *

getiterfunc

PyObject *

PyObject *

iternextfunc

PyObject *

PyObject *

lenfunc

PyObject *

Py_ssize_t

getbufferproc

PyObject *

Py_buffer *

int

int

releasebufferproc

PyObject *

Py_buffer *

void

inquiry

PyObject *

int

unaryfunc

PyObject *

PyObject *

binaryfunc

PyObject *

PyObject *

PyObject *

ternaryfunc

PyObject *

PyObject *

PyObject *

PyObject *

ssizeargfunc

PyObject *

Py_ssize_t

PyObject *

ssizeobjargproc

PyObject *

Py_ssize_t

PyObject *

int

objobjproc

PyObject *

PyObject *

int

objobjargproc

PyObject *

PyObject *

PyObject *

int

更多細節請見下方的 Slot Type typedefs。

PyTypeObject Definition

The structure definition for PyTypeObject can be found in Include/cpython/object.h. For convenience of reference, this repeats the definition found there:

typedef struct _typeobject {
    PyObject_VAR_HEAD
    const char *tp_name; /* For printing, in format "<module>.<name>" */
    Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */

    /* Methods to implement standard operations */

    destructor tp_dealloc;
    Py_ssize_t tp_vectorcall_offset;
    getattrfunc tp_getattr;
    setattrfunc tp_setattr;
    PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
                                    or tp_reserved (Python 3) */
    reprfunc tp_repr;

    /* Method suites for standard classes */

    PyNumberMethods *tp_as_number;
    PySequenceMethods *tp_as_sequence;
    PyMappingMethods *tp_as_mapping;

    /* More standard operations (here for binary compatibility) */

    hashfunc tp_hash;
    ternaryfunc tp_call;
    reprfunc tp_str;
    getattrofunc tp_getattro;
    setattrofunc tp_setattro;

    /* Functions to access object as input/output buffer */
    PyBufferProcs *tp_as_buffer;

    /* Flags to define presence of optional/expanded features */
    unsigned long tp_flags;

    const char *tp_doc; /* Documentation string */

    /* Assigned meaning in release 2.0 */
    /* call function for all accessible objects */
    traverseproc tp_traverse;

    /* delete references to contained objects */
    inquiry tp_clear;

    /* Assigned meaning in release 2.1 */
    /* rich comparisons */
    richcmpfunc tp_richcompare;

    /* weak reference enabler */
    Py_ssize_t tp_weaklistoffset;

    /* Iterators */
    getiterfunc tp_iter;
    iternextfunc tp_iternext;

    /* Attribute descriptor and subclassing stuff */
    PyMethodDef *tp_methods;
    PyMemberDef *tp_members;
    PyGetSetDef *tp_getset;
    // Strong reference on a heap type, borrowed reference on a static type
    PyTypeObject *tp_base;
    PyObject *tp_dict;
    descrgetfunc tp_descr_get;
    descrsetfunc tp_descr_set;
    Py_ssize_t tp_dictoffset;
    initproc tp_init;
    allocfunc tp_alloc;
    newfunc tp_new;
    freefunc tp_free; /* Low-level free-memory routine */
    inquiry tp_is_gc; /* For PyObject_IS_GC */
    PyObject *tp_bases;
    PyObject *tp_mro; /* method resolution order */
    PyObject *tp_cache; /* no longer used */
    void *tp_subclasses;  /* for static builtin types this is an index */
    PyObject *tp_weaklist; /* not used for static builtin types */
    destructor tp_del;

    /* Type attribute cache version tag. Added in version 2.6.
     * If zero, the cache is invalid and must be initialized.
     */
    unsigned int tp_version_tag;

    destructor tp_finalize;
    vectorcallfunc tp_vectorcall;

    /* bitset of which type-watchers care about this type */
    unsigned char tp_watched;

    /* Number of tp_version_tag values used.
     * Set to _Py_ATTR_CACHE_UNUSED if the attribute cache is
     * disabled for this type (e.g. due to custom MRO entries).
     * Otherwise, limited to MAX_VERSIONS_PER_CLASS (defined elsewhere).
     */
    uint16_t tp_versions_used;
} PyTypeObject;

PyObject Slots

The type object structure extends the PyVarObject structure. The ob_size field is used for dynamic types (created by type_new(), usually called from a class statement). Note that PyType_Type (the metatype) initializes tp_itemsize, which means that its instances (i.e. type objects) must have the ob_size field.

PyObject.ob_refcnt

The type object's reference count is initialized to 1 by the PyObject_HEAD_INIT macro. Note that for statically allocated type objects, the type's instances (objects whose ob_type points back to the type) do not count as references. But for dynamically allocated type objects, the instances do count as references.

Inheritance:

This field is not inherited by subtypes.

PyObject.ob_type

This is the type's type, in other words its metatype. It is initialized by the argument to the PyObject_HEAD_INIT macro, and its value should normally be &PyType_Type. However, for dynamically loadable extension modules that must be usable on Windows (at least), the compiler complains that this is not a valid initializer. Therefore, the convention is to pass NULL to the PyObject_HEAD_INIT macro and to initialize this field explicitly at the start of the module's initialization function, before doing anything else. This is typically done like this:

Foo_Type.ob_type = &PyType_Type;

This should be done before any instances of the type are created. PyType_Ready() checks if ob_type is NULL, and if so, initializes it to the ob_type field of the base class. PyType_Ready() will not change this field if it is non-zero.

Inheritance:

This field is inherited by subtypes.

PyVarObject Slots

PyVarObject.ob_size

For statically allocated type objects, this should be initialized to zero. For dynamically allocated type objects, this field has a special internal meaning.

This field should be accessed using the Py_SIZE() macro.

Inheritance:

This field is not inherited by subtypes.

PyTypeObject Slots

Each slot has a section describing inheritance. If PyType_Ready() may set a value when the field is set to NULL then there will also be a "Default" section. (Note that many fields set on PyBaseObject_Type and PyType_Type effectively act as defaults.)

const char *PyTypeObject.tp_name

Pointer to a NUL-terminated string containing the name of the type. For types that are accessible as module globals, the string should be the full module name, followed by a dot, followed by the type name; for built-in types, it should be just the type name. If the module is a submodule of a package, the full package name is part of the full module name. For example, a type named T defined in module M in subpackage Q in package P should have the tp_name initializer "P.Q.M.T".

For dynamically allocated type objects, this should just be the type name, and the module name explicitly stored in the type dict as the value for key '__module__'.

For statically allocated type objects, the tp_name field should contain a dot. Everything before the last dot is made accessible as the __module__ attribute, and everything after the last dot is made accessible as the __name__ attribute.

If no dot is present, the entire tp_name field is made accessible as the __name__ attribute, and the __module__ attribute is undefined (unless explicitly set in the dictionary, as explained above). This means your type will be impossible to pickle. Additionally, it will not be listed in module documentations created with pydoc.

This field must not be NULL. It is the only required field in PyTypeObject() (other than potentially tp_itemsize).

Inheritance:

This field is not inherited by subtypes.

Py_ssize_t PyTypeObject.tp_basicsize

Py_ssize_t PyTypeObject.tp_itemsize

These fields allow calculating the size in bytes of instances of the type.

There are two kinds of types: types with fixed-length instances have a zero tp_itemsize field, types with variable-length instances have a non-zero tp_itemsize field. For a type with fixed-length instances, all instances have the same size, given in tp_basicsize. (Exceptions to this rule can be made using PyUnstable_Object_GC_NewWithExtraData().)

For a type with variable-length instances, the instances must have an ob_size field, and the instance size is tp_basicsize plus N times tp_itemsize, where N is the "length" of the object.

Functions like PyObject_NewVar() will take the value of N as an argument, and store in the instance's ob_size field. Note that the ob_size field may later be used for other purposes. For example, int instances use the bits of ob_size in an implementation-defined way; the underlying storage and its size should be accessed using PyLong_Export().

備註

The ob_size field should be accessed using the Py_SIZE() and Py_SET_SIZE() macros.

Also, the presence of an ob_size field in the instance layout doesn't mean that the instance structure is variable-length. For example, the list type has fixed-length instances, yet those instances have a ob_size field. (As with int, avoid reading lists' ob_size directly. Call PyList_Size() instead.)

The tp_basicsize includes size needed for data of the type's tp_base, plus any extra data needed by each instance.

The correct way to set tp_basicsize is to use the sizeof operator on the struct used to declare the instance layout. This struct must include the struct used to declare the base type. In other words, tp_basicsize must be greater than or equal to the base's tp_basicsize.

Since every type is a subtype of object, this struct must include PyObject or PyVarObject (depending on whether ob_size should be included). These are usually defined by the macro PyObject_HEAD or PyObject_VAR_HEAD, respectively.

The basic size does not include the GC header size, as that header is not part of PyObject_HEAD.

For cases where struct used to declare the base type is unknown, see PyType_Spec.basicsize and PyType_FromMetaclass().

Notes about alignment:

tp_basicsize must be a multiple of _Alignof(PyObject). When using sizeof on a struct that includes PyObject_HEAD, as recommended, the compiler ensures this. When not using a C struct, or when using compiler extensions like __attribute__((packed)), it is up to you.

If the variable items require a particular alignment, tp_basicsize and tp_itemsize must each be a multiple of that alignment. For example, if a type's variable part stores a double, it is your responsibility that both fields are a multiple of _Alignof(double).

Inheritance:

These fields are inherited separately by subtypes. (That is, if the field is set to zero, PyType_Ready() will copy the value from the base type, indicating that the instances do not need additional storage.)

If the base type has a non-zero tp_itemsize, it is generally not safe to set tp_itemsize to a different non-zero value in a subtype (though this depends on the implementation of the base type).

destructor PyTypeObject.tp_dealloc

The corresponding slot ID Py_tp_dealloc is part of the 穩定 ABI 的一部分.

A pointer to the instance destructor function. The function signature is:

void tp_dealloc(PyObject *self);

The destructor function should remove all references which the instance owns (e.g., call Py_CLEAR()), free all memory buffers owned by the instance, and call the type's tp_free function to free the object itself.

If you may call functions that may set the error indicator, you must use PyErr_GetRaisedException() and PyErr_SetRaisedException() to ensure you don't clobber a preexisting error indicator (the deallocation could have occurred while processing a different error):

static void
foo_dealloc(foo_object *self)
{
    PyObject *et, *ev, *etb;
    PyObject *exc = PyErr_GetRaisedException();
    ...
    PyErr_SetRaisedException(exc);
}

The dealloc handler itself must not raise an exception; if it hits an error case it should call PyErr_FormatUnraisable() to log (and clear) an unraisable exception.

No guarantees are made about when an object is destroyed, except:

Python will destroy an object immediately or some time after the final reference to the object is deleted, unless its finalizer (tp_finalize) subsequently resurrects the object.

An object will not be destroyed while it is being automatically finalized (tp_finalize) or automatically cleared (tp_clear).

CPython currently destroys an object immediately from Py_DECREF() when the new reference count is zero, but this may change in a future version.

It is recommended to call PyObject_CallFinalizerFromDealloc() at the beginning of tp_dealloc to guarantee that the object is always finalized before destruction.

If the type supports garbage collection (the Py_TPFLAGS_HAVE_GC flag is set), the destructor should call PyObject_GC_UnTrack() before clearing any member fields.

It is permissible to call tp_clear from tp_dealloc to reduce code duplication and to guarantee that the object is always cleared before destruction. Beware that tp_clear might have already been called.

If the type is heap allocated (Py_TPFLAGS_HEAPTYPE), the deallocator should release the owned reference to its type object (via Py_DECREF()) after calling the type deallocator. See the example code below.:

static void
foo_dealloc(PyObject *op)
{
   foo_object *self = (foo_object *) op;
   PyObject_GC_UnTrack(self);
   Py_CLEAR(self->ref);
   Py_TYPE(self)->tp_free(self);
}

tp_dealloc must leave the exception status unchanged. If it needs to call something that might raise an exception, the exception state must be backed up first and restored later (after logging any exceptions with PyErr_WriteUnraisable()).

範例：

static void
foo_dealloc(PyObject *self)
{
    PyObject *exc = PyErr_GetRaisedException();

    if (PyObject_CallFinalizerFromDealloc(self) < 0) {
        // self was resurrected.
        goto done;
    }

    PyTypeObject *tp = Py_TYPE(self);

    if (tp->tp_flags & Py_TPFLAGS_HAVE_GC) {
        PyObject_GC_UnTrack(self);
    }

    // Optional, but convenient to avoid code duplication.
    if (tp->tp_clear && tp->tp_clear(self) < 0) {
        PyErr_WriteUnraisable(self);
    }

    // Any additional destruction goes here.

    tp->tp_free(self);
    self = NULL;  // In case PyErr_WriteUnraisable() is called below.

    if (tp->tp_flags & Py_TPFLAGS_HEAPTYPE) {
        Py_CLEAR(tp);
    }

done:
    // Optional, if something was called that might have raised an
    // exception.
    if (PyErr_Occurred()) {
        PyErr_WriteUnraisable(self);
    }
    PyErr_SetRaisedException(exc);
}

tp_dealloc may be called from any Python thread, not just the thread which created the object (if the object becomes part of a refcount cycle, that cycle might be collected by a garbage collection on any thread). This is not a problem for Python API calls, since the thread on which tp_dealloc is called with an attached thread state. However, if the object being destroyed in turn destroys objects from some other C library, care should be taken to ensure that destroying those objects on the thread which called tp_dealloc will not violate any assumptions of the library.

Inheritance:

This field is inherited by subtypes.

也參考

物件生命週期 for details about how this slot relates to other slots.

Py_ssize_t PyTypeObject.tp_vectorcall_offset

An optional offset to a per-instance function that implements calling the object using the vectorcall protocol, a more efficient alternative of the simpler tp_call.

This field is only used if the flag Py_TPFLAGS_HAVE_VECTORCALL is set. If so, this must be a positive integer containing the offset in the instance of a vectorcallfunc pointer.

The vectorcallfunc pointer may be NULL, in which case the instance behaves as if Py_TPFLAGS_HAVE_VECTORCALL was not set: calling the instance falls back to tp_call.

Any class that sets Py_TPFLAGS_HAVE_VECTORCALL must also set tp_call and make sure its behaviour is consistent with the vectorcallfunc function. This can be done by setting tp_call to PyVectorcall_Call().

在 3.8 版的變更: Before version 3.8, this slot was named tp_print. In Python 2.x, it was used for printing to a file. In Python 3.0 to 3.7, it was unused.

在 3.12 版的變更: Before version 3.12, it was not recommended for mutable heap types to implement the vectorcall protocol. When a user sets __call__ in Python code, only tp_call is updated, likely making it inconsistent with the vectorcall function. Since 3.12, setting __call__ will disable vectorcall optimization by clearing the Py_TPFLAGS_HAVE_VECTORCALL flag.

Inheritance:

This field is always inherited. However, the Py_TPFLAGS_HAVE_VECTORCALL flag is not always inherited. If it's not set, then the subclass won't use vectorcall, except when PyVectorcall_Call() is explicitly called.

getattrfunc PyTypeObject.tp_getattr

The corresponding slot ID Py_tp_getattr is part of the 穩定 ABI 的一部分.

An optional pointer to the get-attribute-string function.

此欄位已被棄用。當它被定義時，它應該指向一個與 tp_getattro 行為相同但使用 C 字串而非 Python 字串物件來提供屬性名稱的函式。

Inheritance:

群組：tp_getattr、tp_getattro

This field is inherited by subtypes together with tp_getattro: a subtype inherits both tp_getattr and tp_getattro from its base type when the subtype's tp_getattr and tp_getattro are both NULL.

setattrfunc PyTypeObject.tp_setattr

The corresponding slot ID Py_tp_setattr is part of the 穩定 ABI 的一部分.

An optional pointer to the function for setting and deleting attributes.

此欄位已被棄用。當它被定義時，它應該指向一個與 tp_setattro 行為相同但使用 C 字串而非 Python 字串物件來提供屬性名稱的函式。

Inheritance:

群組：tp_setattr、tp_setattro

This field is inherited by subtypes together with tp_setattro: a subtype inherits both tp_setattr and tp_setattro from its base type when the subtype's tp_setattr and tp_setattro are both NULL.

PyAsyncMethods *PyTypeObject.tp_as_async

Pointer to an additional structure that contains fields relevant only to objects which implement awaitable and asynchronous iterator protocols at the C-level. See 非同步物件結構 for details.

在 3.5 版被加入: 以前稱為 tp_compare 和 tp_reserved。

Inheritance:

The tp_as_async field is not inherited, but the contained fields are inherited individually.

reprfunc PyTypeObject.tp_repr

The corresponding slot ID Py_tp_repr is part of the 穩定 ABI 的一部分.

An optional pointer to a function that implements the built-in function repr().

函式簽名與 PyObject_Repr() 相同：

PyObject *tp_repr(PyObject *self);

The function must return a string or a Unicode object. Ideally, this function should return a string that, when passed to eval(), given a suitable environment, returns an object with the same value. If this is not feasible, it should return a string starting with '<' and ending with '>' from which both the type and the value of the object can be deduced.

Inheritance:

This field is inherited by subtypes.

預設：

When this field is not set, a string of the form <%s object at %p> is returned, where %s is replaced by the type name, and %p by the object's memory address.

PyNumberMethods *PyTypeObject.tp_as_number

Pointer to an additional structure that contains fields relevant only to objects which implement the number protocol. These fields are documented in Number Object Structures.

Inheritance:

The tp_as_number field is not inherited, but the contained fields are inherited individually.

PySequenceMethods *PyTypeObject.tp_as_sequence

Pointer to an additional structure that contains fields relevant only to objects which implement the sequence protocol. These fields are documented in 序列物件結構.

Inheritance:

The tp_as_sequence field is not inherited, but the contained fields are inherited individually.

PyMappingMethods *PyTypeObject.tp_as_mapping

Pointer to an additional structure that contains fields relevant only to objects which implement the mapping protocol. These fields are documented in 對映物件結構.

Inheritance:

The tp_as_mapping field is not inherited, but the contained fields are inherited individually.

hashfunc PyTypeObject.tp_hash

The corresponding slot ID Py_tp_hash is part of the 穩定 ABI 的一部分.

An optional pointer to a function that implements the built-in function hash().

函式簽名與 PyObject_Hash() 相同：

Py_hash_t tp_hash(PyObject *);

The value -1 should not be returned as a normal return value; when an error occurs during the computation of the hash value, the function should set an exception and return -1.

When this field is not set (and tp_richcompare is not set), an attempt to take the hash of the object raises TypeError. This is the same as setting it to PyObject_HashNotImplemented().

This field can be set explicitly to PyObject_HashNotImplemented() to block inheritance of the hash method from a parent type. This is interpreted as the equivalent of __hash__ = None at the Python level, causing isinstance(o, collections.Hashable) to correctly return False. Note that the converse is also true - setting __hash__ = None on a class at the Python level will result in the tp_hash slot being set to PyObject_HashNotImplemented().

Inheritance:

群組：tp_hash、tp_richcompare

This field is inherited by subtypes together with tp_richcompare: a subtype inherits both of tp_richcompare and tp_hash, when the subtype's tp_richcompare and tp_hash are both NULL.

預設：

PyBaseObject_Type 會使用 PyObject_GenericHash()。

ternaryfunc PyTypeObject.tp_call

The corresponding slot ID Py_tp_call is part of the 穩定 ABI 的一部分.

An optional pointer to a function that implements calling the object. This should be NULL if the object is not callable. The signature is the same as for PyObject_Call():

PyObject *tp_call(PyObject *self, PyObject *args, PyObject *kwargs);

Inheritance:

This field is inherited by subtypes.

reprfunc PyTypeObject.tp_str

The corresponding slot ID Py_tp_str is part of the 穩定 ABI 的一部分.

An optional pointer to a function that implements the built-in operation str(). (Note that str is a type now, and str() calls the constructor for that type. This constructor calls PyObject_Str() to do the actual work, and PyObject_Str() will call this handler.)

函式簽名與 PyObject_Str() 相同：

PyObject *tp_str(PyObject *self);

The function must return a string or a Unicode object. It should be a "friendly" string representation of the object, as this is the representation that will be used, among other things, by the print() function.

Inheritance:

This field is inherited by subtypes.

預設：

When this field is not set, PyObject_Repr() is called to return a string representation.

getattrofunc PyTypeObject.tp_getattro

The corresponding slot ID Py_tp_getattro is part of the 穩定 ABI 的一部分.

An optional pointer to the get-attribute function.

函式簽名與 PyObject_GetAttr() 相同：

PyObject *tp_getattro(PyObject *self, PyObject *attr);

It is usually convenient to set this field to PyObject_GenericGetAttr(), which implements the normal way of looking for object attributes.

Inheritance:

群組：tp_getattr、tp_getattro

This field is inherited by subtypes together with tp_getattr: a subtype inherits both tp_getattr and tp_getattro from its base type when the subtype's tp_getattr and tp_getattro are both NULL.

預設：

PyBaseObject_Type 會使用 PyObject_GenericGetAttr()。

setattrofunc PyTypeObject.tp_setattro

The corresponding slot ID Py_tp_setattro is part of the 穩定 ABI 的一部分.

An optional pointer to the function for setting and deleting attributes.

函式簽名與 PyObject_SetAttr() 相同：

int tp_setattro(PyObject *self, PyObject *attr, PyObject *value);

In addition, setting value to NULL to delete an attribute must be supported. It is usually convenient to set this field to PyObject_GenericSetAttr(), which implements the normal way of setting object attributes.

Inheritance:

群組：tp_setattr、tp_setattro

This field is inherited by subtypes together with tp_setattr: a subtype inherits both tp_setattr and tp_setattro from its base type when the subtype's tp_setattr and tp_setattro are both NULL.

預設：

PyBaseObject_Type uses PyObject_GenericSetAttr().

PyBufferProcs *PyTypeObject.tp_as_buffer

Pointer to an additional structure that contains fields relevant only to objects which implement the buffer interface. These fields are documented in 緩衝區物件結構.

Inheritance:

The tp_as_buffer field is not inherited, but the contained fields are inherited individually.

unsigned long PyTypeObject.tp_flags

This field is a bit mask of various flags. Some flags indicate variant semantics for certain situations; others are used to indicate that certain fields in the type object (or in the extension structures referenced via tp_as_number, tp_as_sequence, tp_as_mapping, and tp_as_buffer) that were historically not always present are valid; if such a flag bit is clear, the type fields it guards must not be accessed and must be considered to have a zero or NULL value instead.

Inheritance:

Inheritance of this field is complicated. Most flag bits are inherited individually, i.e. if the base type has a flag bit set, the subtype inherits this flag bit. The flag bits that pertain to extension structures are strictly inherited if the extension structure is inherited, i.e. the base type's value of the flag bit is copied into the subtype together with a pointer to the extension structure. The Py_TPFLAGS_HAVE_GC flag bit is inherited together with the tp_traverse and tp_clear fields, i.e. if the Py_TPFLAGS_HAVE_GC flag bit is clear in the subtype and the tp_traverse and tp_clear fields in the subtype exist and have NULL values.

預設：

PyBaseObject_Type 使用 Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE。

Bit Masks:

The following bit masks are currently defined; these can be ORed together using the | operator to form the value of the tp_flags field. The macro PyType_HasFeature() takes a type and a flags value, tp and f, and checks whether tp->tp_flags & f is non-zero.

Py_TPFLAGS_HEAPTYPE

This bit is set when the type object itself is allocated on the heap, for example, types created dynamically using PyType_FromSpec(). In this case, the ob_type field of its instances is considered a reference to the type, and the type object is INCREF'ed when a new instance is created, and DECREF'ed when an instance is destroyed (this does not apply to instances of subtypes; only the type referenced by the instance's ob_type gets INCREF'ed or DECREF'ed). Heap types should also support garbage collection as they can form a reference cycle with their own module object.

Inheritance:

???

Py_TPFLAGS_BASETYPE

為 穩定 ABI 的一部分.

This bit is set when the type can be used as the base type of another type. If this bit is clear, the type cannot be subtyped (similar to a "final" class in Java).

Inheritance:

???

Py_TPFLAGS_READY

This bit is set when the type object has been fully initialized by PyType_Ready().

Inheritance:

???

Py_TPFLAGS_READYING

This bit is set while PyType_Ready() is in the process of initializing the type object.

Inheritance:

???

Py_TPFLAGS_HAVE_GC

為 穩定 ABI 的一部分.

This bit is set when the object supports garbage collection. If this bit is set, memory for new instances (see tp_alloc) must be allocated using PyObject_GC_New or PyType_GenericAlloc() and deallocated (see tp_free) using PyObject_GC_Del(). More information in section 循環垃圾回收的支援.

Inheritance:

Group: Py_TPFLAGS_HAVE_GC, tp_traverse, tp_clear

The Py_TPFLAGS_HAVE_GC flag bit is inherited together with the tp_traverse and tp_clear fields, i.e. if the Py_TPFLAGS_HAVE_GC flag bit is clear in the subtype and the tp_traverse and tp_clear fields in the subtype exist and have NULL values.

Py_TPFLAGS_DEFAULT

為 穩定 ABI 的一部分.

This is a bitmask of all the bits that pertain to the existence of certain fields in the type object and its extension structures. Currently, it includes the following bits: Py_TPFLAGS_HAVE_STACKLESS_EXTENSION.

Inheritance:

???

Py_TPFLAGS_METHOD_DESCRIPTOR

為 穩定 ABI 的一部分 自 3.8 版本開始.

This bit indicates that objects behave like unbound methods.

如果此旗標為 type(meth) 所設定，則：

meth.__get__(obj, cls)(*args, **kwds)（其中 obj 並非 None）必須等價於 meth(obj, *args, **kwds)。

meth.__get__(None, cls)(*args, **kwds) 必須等價於 meth(*args, **kwds)。

This flag enables an optimization for typical method calls like obj.meth(): it avoids creating a temporary "bound method" object for obj.meth.

在 3.8 版被加入.

Inheritance:

This flag is never inherited by types without the Py_TPFLAGS_IMMUTABLETYPE flag set. For extension types, it is inherited whenever tp_descr_get is inherited.

Py_TPFLAGS_MANAGED_DICT

This bit indicates that instances of the class have a __dict__ attribute, and that the space for the dictionary is managed by the VM.

如果有設定此旗標，則也應該設定 Py_TPFLAGS_HAVE_GC。

The type traverse function must call PyObject_VisitManagedDict() and its clear function must call PyObject_ClearManagedDict().

在 3.12 版被加入.

Inheritance:

This flag is inherited unless the tp_dictoffset field is set in a superclass.

Py_TPFLAGS_MANAGED_WEAKREF

This bit indicates that instances of the class should be weakly referenceable.

在 3.12 版被加入.

Inheritance:

This flag is inherited unless the tp_weaklistoffset field is set in a superclass.

Py_TPFLAGS_ITEMS_AT_END

為 穩定 ABI 的一部分 自 3.12 版本開始.

Only usable with variable-size types, i.e. ones with non-zero tp_itemsize.

Indicates that the variable-sized portion of an instance of this type is at the end of the instance's memory area, at an offset of Py_TYPE(obj)->tp_basicsize (which may be different in each subclass).

When setting this flag, be sure that all superclasses either use this memory layout, or are not variable-sized. Python does not check this.

在 3.12 版被加入.

Inheritance:

This flag is inherited.

Py_TPFLAGS_LONG_SUBCLASS

Py_TPFLAGS_LIST_SUBCLASS

Py_TPFLAGS_TUPLE_SUBCLASS

Py_TPFLAGS_BYTES_SUBCLASS

Py_TPFLAGS_UNICODE_SUBCLASS

Py_TPFLAGS_DICT_SUBCLASS

Py_TPFLAGS_BASE_EXC_SUBCLASS

Py_TPFLAGS_TYPE_SUBCLASS

Functions such as PyLong_Check() will call PyType_FastSubclass() with one of these flags to quickly determine if a type is a subclass of a built-in type; such specific checks are faster than a generic check, like PyObject_IsInstance(). Custom types that inherit from built-ins should have their tp_flags set appropriately, or the code that interacts with such types will behave differently depending on what kind of check is used.

Py_TPFLAGS_HAVE_FINALIZE

This bit is set when the tp_finalize slot is present in the type structure.

在 3.4 版被加入.

在 3.8 版之後被棄用: This flag isn't necessary anymore, as the interpreter assumes the tp_finalize slot is always present in the type structure.

Py_TPFLAGS_HAVE_VECTORCALL

為 穩定 ABI 的一部分 自 3.12 版本開始.

This bit is set when the class implements the vectorcall protocol. See tp_vectorcall_offset for details.

Inheritance:

This bit is inherited if tp_call is also inherited.

在 3.8 版被加入: 名為 _Py_TPFLAGS_HAVE_VECTORCALL

在 3.9 版的變更.

重新命名為目前的名稱，沒有前導底線。舊的臨時名稱已被 軟性棄用。

在 3.12 版的變更: This flag is now removed from a class when the class's __call__() method is reassigned.

This flag can now be inherited by mutable classes.

Py_TPFLAGS_IMMUTABLETYPE

This bit is set for type objects that are immutable: type attributes cannot be set nor deleted.

PyType_Ready() automatically applies this flag to static types.

Inheritance:

This flag is not inherited.

在 3.10 版被加入.

Py_TPFLAGS_DISALLOW_INSTANTIATION

Disallow creating instances of the type: set tp_new to NULL and don't create the __new__ key in the type dictionary.

The flag must be set before creating the type, not after. For example, it must be set before PyType_Ready() is called on the type.

The flag is set automatically on static types if tp_base is NULL or &PyBaseObject_Type and tp_new is NULL.

Inheritance:

This flag is not inherited. However, subclasses will not be instantiable unless they provide a non-NULL tp_new (which is only possible via the C API).

備註

To disallow instantiating a class directly but allow instantiating its subclasses (e.g. for an abstract base class), do not use this flag. Instead, make tp_new only succeed for subclasses.

在 3.10 版被加入.

Py_TPFLAGS_MAPPING

This bit indicates that instances of the class may match mapping patterns when used as the subject of a match block. It is automatically set when registering or subclassing collections.abc.Mapping, and unset when registering collections.abc.Sequence.

備註

Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE are mutually exclusive; it is an error to enable both flags simultaneously.

Inheritance:

This flag is inherited by types that do not already set Py_TPFLAGS_SEQUENCE.

也參考

PEP 634 [https://peps.python.org/pep-0634/] -- Structural Pattern Matching: Specification

在 3.10 版被加入.

Py_TPFLAGS_SEQUENCE

This bit indicates that instances of the class may match sequence patterns when used as the subject of a match block. It is automatically set when registering or subclassing collections.abc.Sequence, and unset when registering collections.abc.Mapping.

備註

Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE are mutually exclusive; it is an error to enable both flags simultaneously.

Inheritance:

This flag is inherited by types that do not already set Py_TPFLAGS_MAPPING.

也參考

PEP 634 [https://peps.python.org/pep-0634/] -- Structural Pattern Matching: Specification

在 3.10 版被加入.

Py_TPFLAGS_VALID_VERSION_TAG

Internal. Do not set or unset this flag. To indicate that a class has changed call PyType_Modified()

警告

This flag is present in header files, but is not be used. It will be removed in a future version of CPython

const char *PyTypeObject.tp_doc

The corresponding slot ID Py_tp_doc is part of the 穩定 ABI 的一部分.

An optional pointer to a NUL-terminated C string giving the docstring for this type object. This is exposed as the __doc__ attribute on the type and instances of the type.

Inheritance:

此欄位不會被子型別繼承。

traverseproc PyTypeObject.tp_traverse

The corresponding slot ID Py_tp_traverse is part of the 穩定 ABI 的一部分.

An optional pointer to a traversal function for the garbage collector. This is only used if the Py_TPFLAGS_HAVE_GC flag bit is set. The signature is:

int tp_traverse(PyObject *self, visitproc visit, void *arg);

More information about Python's garbage collection scheme can be found in section 循環垃圾回收的支援.

The tp_traverse pointer is used by the garbage collector to detect reference cycles. A typical implementation of a tp_traverse function simply calls Py_VISIT() on each of the instance's members that are Python objects that the instance owns. For example, this is function local_traverse() from the _thread extension module:

static int
local_traverse(PyObject *op, visitproc visit, void *arg)
{
    localobject *self = (localobject *) op;
    Py_VISIT(self->args);
    Py_VISIT(self->kw);
    Py_VISIT(self->dict);
    return 0;
}

Note that Py_VISIT() is called only on those members that can participate in reference cycles. Although there is also a self->key member, it can only be NULL or a Python string and therefore cannot be part of a reference cycle.

On the other hand, even if you know a member can never be part of a cycle, as a debugging aid you may want to visit it anyway just so the gc module's get_referents() function will include it.

Heap types (Py_TPFLAGS_HEAPTYPE) must visit their type with:

Py_VISIT(Py_TYPE(self));

It is only needed since Python 3.9. To support Python 3.8 and older, this line must be conditional:

#if PY_VERSION_HEX >= 0x03090000
    Py_VISIT(Py_TYPE(self));
#endif

If the Py_TPFLAGS_MANAGED_DICT bit is set in the tp_flags field, the traverse function must call PyObject_VisitManagedDict() like this:

PyObject_VisitManagedDict((PyObject*)self, visit, arg);

警告

When implementing tp_traverse, only the members that the instance owns (by having strong references to them) must be visited. For instance, if an object supports weak references via the tp_weaklist slot, the pointer supporting the linked list (what tp_weaklist points to) must not be visited as the instance does not directly own the weak references to itself (the weakreference list is there to support the weak reference machinery, but the instance has no strong reference to the elements inside it, as they are allowed to be removed even if the instance is still alive).

警告

The traversal function must not have any side effects. It must not modify the reference counts of any Python objects nor create or destroy any Python objects.

Note that Py_VISIT() requires the visit and arg parameters to local_traverse() to have these specific names; don't name them just anything.

Instances of heap-allocated types hold a reference to their type. Their traversal function must therefore either visit Py_TYPE(self), or delegate this responsibility by calling tp_traverse of another heap-allocated type (such as a heap-allocated superclass). If they do not, the type object may not be garbage-collected.

備註

tp_traverse 函式可以從任何執行緒呼叫。

在 3.9 版的變更: Heap-allocated types are expected to visit Py_TYPE(self) in tp_traverse. In earlier versions of Python, due to bug 40217 [https://bugs.python.org/issue40217], doing this may lead to crashes in subclasses.

Inheritance:

Group: Py_TPFLAGS_HAVE_GC, tp_traverse, tp_clear

This field is inherited by subtypes together with tp_clear and the Py_TPFLAGS_HAVE_GC flag bit: the flag bit, tp_traverse, and tp_clear are all inherited from the base type if they are all zero in the subtype.

inquiry PyTypeObject.tp_clear

The corresponding slot ID Py_tp_clear is part of the 穩定 ABI 的一部分.

An optional pointer to a clear function. The signature is:

int tp_clear(PyObject *);

The purpose of this function is to break reference cycles that are causing a cyclic isolate so that the objects can be safely destroyed. A cleared object is a partially destroyed object; the object is not obligated to satisfy design invariants held during normal use.

tp_clear does not need to delete references to objects that can't participate in reference cycles, such as Python strings or Python integers. However, it may be convenient to clear all references, and write the type's tp_dealloc function to invoke tp_clear to avoid code duplication. (Beware that tp_clear might have already been called. Prefer calling idempotent functions like Py_CLEAR().)

Any non-trivial cleanup should be performed in tp_finalize instead of tp_clear.

備註

If tp_clear fails to break a reference cycle then the objects in the cyclic isolate may remain indefinitely uncollectable ("leak"). See gc.garbage.

備註

Referents (direct and indirect) might have already been cleared; they are not guaranteed to be in a consistent state.

備註

tp_clear 函式可以從任何執行緒呼叫。

備註

An object is not guaranteed to be automatically cleared before its destructor (tp_dealloc) is called.

This function differs from the destructor (tp_dealloc) in the following ways:

The purpose of clearing an object is to remove references to other objects that might participate in a reference cycle. The purpose of the destructor, on the other hand, is a superset: it must release all resources it owns, including references to objects that cannot participate in a reference cycle (e.g., integers) as well as the object's own memory (by calling tp_free).

When tp_clear is called, other objects might still hold references to the object being cleared. Because of this, tp_clear must not deallocate the object's own memory (tp_free). The destructor, on the other hand, is only called when no (strong) references exist, and as such, must safely destroy the object itself by deallocating it.

tp_clear might never be automatically called. An object's destructor, on the other hand, will be automatically called some time after the object becomes unreachable (i.e., either there are no references to the object or the object is a member of a cyclic isolate).

No guarantees are made about when, if, or how often Python automatically clears an object, except:

Python will not automatically clear an object if it is reachable, i.e., there is a reference to it and it is not a member of a cyclic isolate.

Python will not automatically clear an object if it has not been automatically finalized (see tp_finalize). (If the finalizer resurrected the object, the object may or may not be automatically finalized again before it is cleared.)

If an object is a member of a cyclic isolate, Python will not automatically clear it if any member of the cyclic isolate has not yet been automatically finalized (tp_finalize).

Python will not destroy an object until after any automatic calls to its tp_clear function have returned. This ensures that the act of breaking a reference cycle does not invalidate the self pointer while tp_clear is still executing.

Python will not automatically call tp_clear multiple times concurrently.

CPython currently only automatically clears objects as needed to break reference cycles in a cyclic isolate, but future versions might clear objects regularly before their destruction.

Taken together, all tp_clear functions in the system must combine to break all reference cycles. This is subtle, and if in any doubt supply a tp_clear function. For example, the tuple type does not implement a tp_clear function, because it's possible to prove that no reference cycle can be composed entirely of tuples. Therefore the tp_clear functions of other types are responsible for breaking any cycle containing a tuple. This isn't immediately obvious, and there's rarely a good reason to avoid implementing tp_clear.

Implementations of tp_clear should drop the instance's references to those of its members that may be Python objects, and set its pointers to those members to NULL, as in the following example:

static int
local_clear(PyObject *op)
{
    localobject *self = (localobject *) op;
    Py_CLEAR(self->key);
    Py_CLEAR(self->args);
    Py_CLEAR(self->kw);
    Py_CLEAR(self->dict);
    return 0;
}

The Py_CLEAR() macro should be used, because clearing references is delicate: the reference to the contained object must not be released (via Py_DECREF()) until after the pointer to the contained object is set to NULL. This is because releasing the reference may cause the contained object to become trash, triggering a chain of reclamation activity that may include invoking arbitrary Python code (due to finalizers, or weakref callbacks, associated with the contained object). If it's possible for such code to reference self again, it's important that the pointer to the contained object be NULL at that time, so that self knows the contained object can no longer be used. The Py_CLEAR() macro performs the operations in a safe order.

If the Py_TPFLAGS_MANAGED_DICT bit is set in the tp_flags field, the clear function must call PyObject_ClearManagedDict() like this:

PyObject_ClearManagedDict((PyObject*)self);

More information about Python's garbage collection scheme can be found in section 循環垃圾回收的支援.

Inheritance:

Group: Py_TPFLAGS_HAVE_GC, tp_traverse, tp_clear

This field is inherited by subtypes together with tp_traverse and the Py_TPFLAGS_HAVE_GC flag bit: the flag bit, tp_traverse, and tp_clear are all inherited from the base type if they are all zero in the subtype.

也參考

物件生命週期 for details about how this slot relates to other slots.

richcmpfunc PyTypeObject.tp_richcompare

The corresponding slot ID Py_tp_richcompare is part of the 穩定 ABI 的一部分.

An optional pointer to the rich comparison function, whose signature is:

PyObject *tp_richcompare(PyObject *self, PyObject *other, int op);

The first parameter is guaranteed to be an instance of the type that is defined by PyTypeObject.

The function should return the result of the comparison (usually Py_True or Py_False). If the comparison is undefined, it must return Py_NotImplemented, if another error occurred it must return NULL and set an exception condition.

The following constants are defined to be used as the third argument for tp_richcompare and for PyObject_RichCompare():

常數

Comparison

Py_LT

<

Py_LE

<=

Py_EQ

==

Py_NE

!=

Py_GT

>

Py_GE

>=

The following macro is defined to ease writing rich comparison functions:

Py_RETURN_RICHCOMPARE(VAL_A, VAL_B, op)

Return Py_True or Py_False from the function, depending on the result of a comparison. VAL_A and VAL_B must be orderable by C comparison operators (for example, they may be C ints or floats). The third argument specifies the requested operation, as for PyObject_RichCompare().

The returned value is a new strong reference.

On error, sets an exception and returns NULL from the function.

在 3.7 版被加入.

Inheritance:

群組：tp_hash、tp_richcompare

This field is inherited by subtypes together with tp_hash: a subtype inherits tp_richcompare and tp_hash when the subtype's tp_richcompare and tp_hash are both NULL.

預設：

PyBaseObject_Type provides a tp_richcompare implementation, which may be inherited. However, if only tp_hash is defined, not even the inherited function is used and instances of the type will not be able to participate in any comparisons.

Py_ssize_t PyTypeObject.tp_weaklistoffset

While this field is still supported, Py_TPFLAGS_MANAGED_WEAKREF should be used instead, if at all possible.

If the instances of this type are weakly referenceable, this field is greater than zero and contains the offset in the instance structure of the weak reference list head (ignoring the GC header, if present); this offset is used by PyObject_ClearWeakRefs() and the PyWeakref_* functions. The instance structure needs to include a field of type PyObject* which is initialized to NULL.

Do not confuse this field with tp_weaklist; that is the list head for weak references to the type object itself.

It is an error to set both the Py_TPFLAGS_MANAGED_WEAKREF bit and tp_weaklistoffset.

Inheritance:

This field is inherited by subtypes, but see the rules listed below. A subtype may override this offset; this means that the subtype uses a different weak reference list head than the base type. Since the list head is always found via tp_weaklistoffset, this should not be a problem.

預設：

If the Py_TPFLAGS_MANAGED_WEAKREF bit is set in the tp_flags field, then tp_weaklistoffset will be set to a negative value, to indicate that it is unsafe to use this field.

getiterfunc PyTypeObject.tp_iter

The corresponding slot ID Py_tp_iter is part of the 穩定 ABI 的一部分.

An optional pointer to a function that returns an iterator for the object. Its presence normally signals that the instances of this type are iterable (although sequences may be iterable without this function).

This function has the same signature as PyObject_GetIter():

PyObject *tp_iter(PyObject *self);

Inheritance:

This field is inherited by subtypes.

iternextfunc PyTypeObject.tp_iternext

The corresponding slot ID Py_tp_iternext is part of the 穩定 ABI 的一部分.

An optional pointer to a function that returns the next item in an iterator. The signature is:

PyObject *tp_iternext(PyObject *self);

When the iterator is exhausted, it must return NULL; a StopIteration exception may or may not be set. When another error occurs, it must return NULL too. Its presence signals that the instances of this type are iterators.

Iterator types should also define the tp_iter function, and that function should return the iterator instance itself (not a new iterator instance).

This function has the same signature as PyIter_Next().

Inheritance:

This field is inherited by subtypes.

struct PyMethodDef *PyTypeObject.tp_methods

The corresponding slot ID Py_tp_methods is part of the 穩定 ABI 的一部分.

An optional pointer to a static NULL-terminated array of PyMethodDef structures, declaring regular methods of this type.

For each entry in the array, an entry is added to the type's dictionary (see tp_dict below) containing a method descriptor.

Inheritance:

This field is not inherited by subtypes (methods are inherited through a different mechanism).

struct PyMemberDef *PyTypeObject.tp_members

The corresponding slot ID Py_tp_members is part of the 穩定 ABI 的一部分.

An optional pointer to a static NULL-terminated array of PyMemberDef structures, declaring regular data members (fields or slots) of instances of this type.

For each entry in the array, an entry is added to the type's dictionary (see tp_dict below) containing a member descriptor.

Inheritance:

This field is not inherited by subtypes (members are inherited through a different mechanism).

struct PyGetSetDef *PyTypeObject.tp_getset

The corresponding slot ID Py_tp_getset is part of the 穩定 ABI 的一部分.

An optional pointer to a static NULL-terminated array of PyGetSetDef structures, declaring computed attributes of instances of this type.

For each entry in the array, an entry is added to the type's dictionary (see tp_dict below) containing a getset descriptor.

Inheritance:

This field is not inherited by subtypes (computed attributes are inherited through a different mechanism).

PyTypeObject *PyTypeObject.tp_base

The corresponding slot ID Py_tp_base is part of the 穩定 ABI 的一部分.

An optional pointer to a base type from which type properties are inherited. At this level, only single inheritance is supported; multiple inheritance require dynamically creating a type object by calling the metatype.

備註

Slot initialization is subject to the rules of initializing globals. C99 requires the initializers to be "address constants". Function designators like PyType_GenericNew(), with implicit conversion to a pointer, are valid C99 address constants.

However, the unary '&' operator applied to a non-static variable like PyBaseObject_Type is not required to produce an address constant. Compilers may support this (gcc does), MSVC does not. Both compilers are strictly standard conforming in this particular behavior.

Consequently, tp_base should be set in the extension module's init function.

Inheritance:

This field is not inherited by subtypes (obviously).

預設：

This field defaults to &PyBaseObject_Type (which to Python programmers is known as the type object).

PyObject *PyTypeObject.tp_dict

The type's dictionary is stored here by PyType_Ready().

This field should normally be initialized to NULL before PyType_Ready is called; it may also be initialized to a dictionary containing initial attributes for the type. Once PyType_Ready() has initialized the type, extra attributes for the type may be added to this dictionary only if they don't correspond to overloaded operations (like __add__()). Once initialization for the type has finished, this field should be treated as read-only.

Some types may not store their dictionary in this slot. Use PyType_GetDict() to retrieve the dictionary for an arbitrary type.

在 3.12 版的變更: Internals detail: For static builtin types, this is always NULL. Instead, the dict for such types is stored on PyInterpreterState. Use PyType_GetDict() to get the dict for an arbitrary type.

Inheritance:

This field is not inherited by subtypes (though the attributes defined in here are inherited through a different mechanism).

預設：

If this field is NULL, PyType_Ready() will assign a new dictionary to it.

警告

It is not safe to use PyDict_SetItem() on or otherwise modify tp_dict with the dictionary C-API.

descrgetfunc PyTypeObject.tp_descr_get

The corresponding slot ID Py_tp_descr_get is part of the 穩定 ABI 的一部分.

An optional pointer to a "descriptor get" function.

The function signature is:

PyObject * tp_descr_get(PyObject *self, PyObject *obj, PyObject *type);

Inheritance:

This field is inherited by subtypes.

descrsetfunc PyTypeObject.tp_descr_set

The corresponding slot ID Py_tp_descr_set is part of the 穩定 ABI 的一部分.

An optional pointer to a function for setting and deleting a descriptor's value.

The function signature is:

int tp_descr_set(PyObject *self, PyObject *obj, PyObject *value);

The value argument is set to NULL to delete the value.

Inheritance:

This field is inherited by subtypes.

Py_ssize_t PyTypeObject.tp_dictoffset

While this field is still supported, Py_TPFLAGS_MANAGED_DICT should be used instead, if at all possible.

If the instances of this type have a dictionary containing instance variables, this field is non-zero and contains the offset in the instances of the type of the instance variable dictionary; this offset is used by PyObject_GenericGetAttr().

Do not confuse this field with tp_dict; that is the dictionary for attributes of the type object itself.

The value specifies the offset of the dictionary from the start of the instance structure.

The tp_dictoffset should be regarded as write-only. To get the pointer to the dictionary call PyObject_GenericGetDict(). Calling PyObject_GenericGetDict() may need to allocate memory for the dictionary, so it is may be more efficient to call PyObject_GetAttr() when accessing an attribute on the object.

It is an error to set both the Py_TPFLAGS_MANAGED_DICT bit and tp_dictoffset.

Inheritance:

This field is inherited by subtypes. A subtype should not override this offset; doing so could be unsafe, if C code tries to access the dictionary at the previous offset. To properly support inheritance, use Py_TPFLAGS_MANAGED_DICT.

預設：

This slot has no default. For static types, if the field is NULL then no __dict__ gets created for instances.

If the Py_TPFLAGS_MANAGED_DICT bit is set in the tp_flags field, then tp_dictoffset will be set to -1, to indicate that it is unsafe to use this field.

initproc PyTypeObject.tp_init

The corresponding slot ID Py_tp_init is part of the 穩定 ABI 的一部分.

An optional pointer to an instance initialization function.

This function corresponds to the __init__() method of classes. Like __init__(), it is possible to create an instance without calling __init__(), and it is possible to reinitialize an instance by calling its __init__() method again.

The function signature is:

int tp_init(PyObject *self, PyObject *args, PyObject *kwds);

The self argument is the instance to be initialized; the args and kwds arguments represent positional and keyword arguments of the call to __init__().

The tp_init function, if not NULL, is called when an instance is created normally by calling its type, after the type's tp_new function has returned an instance of the type. If the tp_new function returns an instance of some other type that is not a subtype of the original type, no tp_init function is called; if tp_new returns an instance of a subtype of the original type, the subtype's tp_init is called.

Returns 0 on success, -1 and sets an exception on error.

Inheritance:

This field is inherited by subtypes.

預設：

For static types this field does not have a default.

allocfunc PyTypeObject.tp_alloc

The corresponding slot ID Py_tp_alloc is part of the 穩定 ABI 的一部分.

An optional pointer to an instance allocation function.

The function signature is:

PyObject *tp_alloc(PyTypeObject *self, Py_ssize_t nitems);

Inheritance:

Static subtypes inherit this slot, which will be PyType_GenericAlloc() if inherited from object.

Heap subtypes do not inherit this slot.

預設：

For heap subtypes, this field is always set to PyType_GenericAlloc().

For static subtypes, this slot is inherited (see above).

newfunc PyTypeObject.tp_new

The corresponding slot ID Py_tp_new is part of the 穩定 ABI 的一部分.

An optional pointer to an instance creation function.

The function signature is:

PyObject *tp_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds);

The subtype argument is the type of the object being created; the args and kwds arguments represent positional and keyword arguments of the call to the type. Note that subtype doesn't have to equal the type whose tp_new function is called; it may be a subtype of that type (but not an unrelated type).

The tp_new function should call subtype->tp_alloc(subtype, nitems) to allocate space for the object, and then do only as much further initialization as is absolutely necessary. Initialization that can safely be ignored or repeated should be placed in the tp_init handler. A good rule of thumb is that for immutable types, all initialization should take place in tp_new, while for mutable types, most initialization should be deferred to tp_init.

Set the Py_TPFLAGS_DISALLOW_INSTANTIATION flag to disallow creating instances of the type in Python.

Inheritance:

This field is inherited by subtypes, except it is not inherited by static types whose tp_base is NULL or &PyBaseObject_Type.

預設：

For static types this field has no default. This means if the slot is defined as NULL, the type cannot be called to create new instances; presumably there is some other way to create instances, like a factory function.

freefunc PyTypeObject.tp_free

The corresponding slot ID Py_tp_free is part of the 穩定 ABI 的一部分.

An optional pointer to an instance deallocation function. Its signature is:

void tp_free(void *self);

This function must free the memory allocated by tp_alloc.

Inheritance:

Static subtypes inherit this slot, which will be PyObject_Free() if inherited from object. Exception: If the type supports garbage collection (i.e., the Py_TPFLAGS_HAVE_GC flag is set in tp_flags) and it would inherit PyObject_Free(), then this slot is not inherited but instead defaults to PyObject_GC_Del().

Heap subtypes do not inherit this slot.

預設：

For heap subtypes, this slot defaults to a deallocator suitable to match PyType_GenericAlloc() and the value of the Py_TPFLAGS_HAVE_GC flag.

For static subtypes, this slot is inherited (see above).

inquiry PyTypeObject.tp_is_gc

The corresponding slot ID Py_tp_is_gc is part of the 穩定 ABI 的一部分.

An optional pointer to a function called by the garbage collector.

The garbage collector needs to know whether a particular object is collectible or not. Normally, it is sufficient to look at the object's type's tp_flags field, and check the Py_TPFLAGS_HAVE_GC flag bit. But some types have a mixture of statically and dynamically allocated instances, and the statically allocated instances are not collectible. Such types should define this function; it should return 1 for a collectible instance, and 0 for a non-collectible instance. The signature is:

int tp_is_gc(PyObject *self);

(The only example of this are types themselves. The metatype, PyType_Type, defines this function to distinguish between statically and dynamically allocated types.)

Inheritance:

This field is inherited by subtypes.

預設：

This slot has no default. If this field is NULL, Py_TPFLAGS_HAVE_GC is used as the functional equivalent.

PyObject *PyTypeObject.tp_bases

The corresponding slot ID Py_tp_bases is part of the 穩定 ABI 的一部分.

Tuple of base types.

This field should be set to NULL and treated as read-only. Python will fill it in when the type is initialized.

For dynamically created classes, the Py_tp_bases slot can be used instead of the bases argument of PyType_FromSpecWithBases(). The argument form is preferred.

警告

Multiple inheritance does not work well for statically defined types. If you set tp_bases to a tuple, Python will not raise an error, but some slots will only be inherited from the first base.

Inheritance:

This field is not inherited.

PyObject *PyTypeObject.tp_mro

Tuple containing the expanded set of base types, starting with the type itself and ending with object, in Method Resolution Order.

This field should be set to NULL and treated as read-only. Python will fill it in when the type is initialized.

Inheritance:

This field is not inherited; it is calculated fresh by PyType_Ready().

PyObject *PyTypeObject.tp_cache

Unused. Internal use only.

Inheritance:

This field is not inherited.

void *PyTypeObject.tp_subclasses

A collection of subclasses. Internal use only. May be an invalid pointer.

To get a list of subclasses, call the Python method __subclasses__().

在 3.12 版的變更: For some types, this field does not hold a valid PyObject*. The type was changed to void* to indicate this.

Inheritance:

This field is not inherited.

PyObject *PyTypeObject.tp_weaklist

Weak reference list head, for weak references to this type object. Not inherited. Internal use only.

在 3.12 版的變更: Internals detail: For the static builtin types this is always NULL, even if weakrefs are added. Instead, the weakrefs for each are stored on PyInterpreterState. Use the public C-API or the internal _PyObject_GET_WEAKREFS_LISTPTR() macro to avoid the distinction.

Inheritance:

This field is not inherited.

destructor PyTypeObject.tp_del

The corresponding slot ID Py_tp_del is part of the 穩定 ABI 的一部分.

此欄位已被棄用。請改用 tp_finalize。

unsigned int PyTypeObject.tp_version_tag

Used to index into the method cache. Internal use only.

Inheritance:

This field is not inherited.

destructor PyTypeObject.tp_finalize

The corresponding slot ID Py_tp_finalize is part of the 穩定 ABI 的一部分 自 3.5 版本開始.

An optional pointer to an instance finalization function. This is the C implementation of the __del__() special method. Its signature is:

void tp_finalize(PyObject *self);

The primary purpose of finalization is to perform any non-trivial cleanup that must be performed before the object is destroyed, while the object and any other objects it directly or indirectly references are still in a consistent state. The finalizer is allowed to execute arbitrary Python code.

Before Python automatically finalizes an object, some of the object's direct or indirect referents might have themselves been automatically finalized. However, none of the referents will have been automatically cleared (tp_clear) yet.

Other non-finalized objects might still be using a finalized object, so the finalizer must leave the object in a sane state (e.g., invariants are still met).

備註

After Python automatically finalizes an object, Python might start automatically clearing (tp_clear) the object and its referents (direct and indirect). Cleared objects are not guaranteed to be in a consistent state; a finalized object must be able to tolerate cleared referents.

備註

An object is not guaranteed to be automatically finalized before its destructor (tp_dealloc) is called. It is recommended to call PyObject_CallFinalizerFromDealloc() at the beginning of tp_dealloc to guarantee that the object is always finalized before destruction.

備註

The tp_finalize function can be called from any thread, although the GIL will be held.

備註

The tp_finalize function can be called during shutdown, after some global variables have been deleted. See the documentation of the __del__() method for details.

When Python finalizes an object, it behaves like the following algorithm:

Python might mark the object as finalized. Currently, Python always marks objects whose type supports garbage collection (i.e., the Py_TPFLAGS_HAVE_GC flag is set in tp_flags) and never marks other types of objects; this might change in a future version.

If the object is not marked as finalized and its tp_finalize finalizer function is non-NULL, the finalizer function is called.

If the finalizer function was called and the finalizer made the object reachable (i.e., there is a reference to the object and it is not a member of a cyclic isolate), then the finalizer is said to have resurrected the object. It is unspecified whether the finalizer can also resurrect the object by adding a new reference to the object that does not make it reachable, i.e., the object is (still) a member of a cyclic isolate.

If the finalizer resurrected the object, the object's pending destruction is canceled and the object's finalized mark might be removed if present. Currently, Python never removes the finalized mark; this might change in a future version.

Automatic finalization refers to any finalization performed by Python except via calls to PyObject_CallFinalizer() or PyObject_CallFinalizerFromDealloc(). No guarantees are made about when, if, or how often an object is automatically finalized, except:

Python will not automatically finalize an object if it is reachable, i.e., there is a reference to it and it is not a member of a cyclic isolate.

Python will not automatically finalize an object if finalizing it would not mark the object as finalized. Currently, this applies to objects whose type does not support garbage collection, i.e., the Py_TPFLAGS_HAVE_GC flag is not set. Such objects can still be manually finalized by calling PyObject_CallFinalizer() or PyObject_CallFinalizerFromDealloc().

Python will not automatically finalize any two members of a cyclic isolate concurrently.

Python will not automatically finalize an object after it has automatically cleared (tp_clear) the object.

If an object is a member of a cyclic isolate, Python will not automatically finalize it after automatically clearing (see tp_clear) any other member.

Python will automatically finalize every member of a cyclic isolate before it automatically clears (see tp_clear) any of them.

If Python is going to automatically clear an object (tp_clear), it will automatically finalize the object first.

Python currently only automatically finalizes objects that are members of a cyclic isolate, but future versions might finalize objects regularly before their destruction.

To manually finalize an object, do not call this function directly; call PyObject_CallFinalizer() or PyObject_CallFinalizerFromDealloc() instead.

tp_finalize should leave the current exception status unchanged. The recommended way to write a non-trivial finalizer is to back up the exception at the beginning by calling PyErr_GetRaisedException() and restore the exception at the end by calling PyErr_SetRaisedException(). If an exception is encountered in the middle of the finalizer, log and clear it with PyErr_WriteUnraisable() or PyErr_FormatUnraisable(). For example:

static void
foo_finalize(PyObject *self)
{
    // Save the current exception, if any.
    PyObject *exc = PyErr_GetRaisedException();

    // ...

    if (do_something_that_might_raise() != success_indicator) {
        PyErr_WriteUnraisable(self);
        goto done;
    }

done:
    // Restore the saved exception.  This silently discards any exception
    // raised above, so be sure to call PyErr_WriteUnraisable first if
    // necessary.
    PyErr_SetRaisedException(exc);
}

Inheritance:

This field is inherited by subtypes.

在 3.4 版被加入.

在 3.8 版的變更: Before version 3.8 it was necessary to set the Py_TPFLAGS_HAVE_FINALIZE flags bit in order for this field to be used. This is no longer required.

也參考

PEP 442 [https://peps.python.org/pep-0442/]: "Safe object finalization"

物件生命週期 for details about how this slot relates to other slots.

PyObject_CallFinalizer()

PyObject_CallFinalizerFromDealloc()

vectorcallfunc PyTypeObject.tp_vectorcall

The corresponding slot ID Py_tp_vectorcall is part of the 穩定 ABI 的一部分 自 3.14 版本開始.

A vectorcall function to use for calls of this type object (rather than instances). In other words, tp_vectorcall can be used to optimize type.__call__, which typically returns a new instance of type.

As with any vectorcall function, if tp_vectorcall is NULL, the tp_call protocol (Py_TYPE(type)->tp_call) is used instead.

備註

The vectorcall protocol requires that the vectorcall function has the same behavior as the corresponding tp_call. This means that type->tp_vectorcall must match the behavior of Py_TYPE(type)->tp_call.

Specifically, if type uses the default metaclass, type->tp_vectorcall must behave the same as PyType_Type->tp_call, which:

呼叫 type->tp_new，

if the result is a subclass of type, calls type->tp_init on the result of tp_new, and

回傳 tp_new 的結果。

Typically, tp_vectorcall is overridden to optimize this process for specific tp_new and tp_init. When doing this for user-subclassable types, note that both can be overridden (using __new__() and __init__(), respectively).

Inheritance:

This field is never inherited.

在 3.9 版被加入: (the field exists since 3.8 but it's only used since 3.9)

unsigned char PyTypeObject.tp_watched

Internal. Do not use.

在 3.12 版被加入.

靜態型別

Traditionally, types defined in C code are static, that is, a static PyTypeObject structure is defined directly in code and initialized using PyType_Ready().

This results in types that are limited relative to types defined in Python:

Static types are limited to one base, i.e. they cannot use multiple inheritance.

Static type objects (but not necessarily their instances) are immutable. It is not possible to add or modify the type object's attributes from Python.

Static type objects are shared across sub-interpreters, so they should not include any subinterpreter-specific state.

Also, since PyTypeObject is only part of the Limited API as an opaque struct, any extension modules using static types must be compiled for a specific Python minor version.

堆積型別

An alternative to static types is heap-allocated types, or heap types for short, which correspond closely to classes created by Python's class statement. Heap types have the Py_TPFLAGS_HEAPTYPE flag set.

This is done by filling a PyType_Spec structure and calling PyType_FromSpec(), PyType_FromSpecWithBases(), PyType_FromModuleAndSpec(), or PyType_FromMetaclass().

Number Object Structures

type PyNumberMethods

This structure holds pointers to the functions which an object uses to implement the number protocol. Each function is used by the function of similar name documented in the 數字協定 section.

Here is the structure definition:

typedef struct {
     binaryfunc nb_add;
     binaryfunc nb_subtract;
     binaryfunc nb_multiply;
     binaryfunc nb_remainder;
     binaryfunc nb_divmod;
     ternaryfunc nb_power;
     unaryfunc nb_negative;
     unaryfunc nb_positive;
     unaryfunc nb_absolute;
     inquiry nb_bool;
     unaryfunc nb_invert;
     binaryfunc nb_lshift;
     binaryfunc nb_rshift;
     binaryfunc nb_and;
     binaryfunc nb_xor;
     binaryfunc nb_or;
     unaryfunc nb_int;
     void *nb_reserved;
     unaryfunc nb_float;

     binaryfunc nb_inplace_add;
     binaryfunc nb_inplace_subtract;
     binaryfunc nb_inplace_multiply;
     binaryfunc nb_inplace_remainder;
     ternaryfunc nb_inplace_power;
     binaryfunc nb_inplace_lshift;
     binaryfunc nb_inplace_rshift;
     binaryfunc nb_inplace_and;
     binaryfunc nb_inplace_xor;
     binaryfunc nb_inplace_or;

     binaryfunc nb_floor_divide;
     binaryfunc nb_true_divide;
     binaryfunc nb_inplace_floor_divide;
     binaryfunc nb_inplace_true_divide;

     unaryfunc nb_index;

     binaryfunc nb_matrix_multiply;
     binaryfunc nb_inplace_matrix_multiply;
} PyNumberMethods;

備註

Binary and ternary functions must check the type of all their operands, and implement the necessary conversions (at least one of the operands is an instance of the defined type). If the operation is not defined for the given operands, binary and ternary functions must return Py_NotImplemented, if another error occurred they must return NULL and set an exception.

備註

The nb_reserved field should always be NULL. It was previously called nb_long, and was renamed in Python 3.0.1.

binaryfunc PyNumberMethods.nb_add

The corresponding slot ID Py_nb_add is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_subtract

The corresponding slot ID Py_nb_subtract is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_multiply

The corresponding slot ID Py_nb_multiply is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_remainder

The corresponding slot ID Py_nb_remainder is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_divmod

The corresponding slot ID Py_nb_divmod is part of the 穩定 ABI 的一部分.

ternaryfunc PyNumberMethods.nb_power

The corresponding slot ID Py_nb_power is part of the 穩定 ABI 的一部分.

unaryfunc PyNumberMethods.nb_negative

The corresponding slot ID Py_nb_negative is part of the 穩定 ABI 的一部分.

unaryfunc PyNumberMethods.nb_positive

The corresponding slot ID Py_nb_positive is part of the 穩定 ABI 的一部分.

unaryfunc PyNumberMethods.nb_absolute

The corresponding slot ID Py_nb_absolute is part of the 穩定 ABI 的一部分.

inquiry PyNumberMethods.nb_bool

The corresponding slot ID Py_nb_bool is part of the 穩定 ABI 的一部分.

unaryfunc PyNumberMethods.nb_invert

The corresponding slot ID Py_nb_invert is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_lshift

The corresponding slot ID Py_nb_lshift is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_rshift

The corresponding slot ID Py_nb_rshift is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_and

The corresponding slot ID Py_nb_and is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_xor

The corresponding slot ID Py_nb_xor is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_or

The corresponding slot ID Py_nb_or is part of the 穩定 ABI 的一部分.

unaryfunc PyNumberMethods.nb_int

The corresponding slot ID Py_nb_int is part of the 穩定 ABI 的一部分.

void *PyNumberMethods.nb_reserved

unaryfunc PyNumberMethods.nb_float

The corresponding slot ID Py_nb_float is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_add

The corresponding slot ID Py_nb_inplace_add is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_subtract

The corresponding slot ID Py_nb_inplace_subtract is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_multiply

The corresponding slot ID Py_nb_inplace_multiply is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_remainder

The corresponding slot ID Py_nb_inplace_remainder is part of the 穩定 ABI 的一部分.

ternaryfunc PyNumberMethods.nb_inplace_power

The corresponding slot ID Py_nb_inplace_power is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_lshift

The corresponding slot ID Py_nb_inplace_lshift is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_rshift

The corresponding slot ID Py_nb_inplace_rshift is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_and

The corresponding slot ID Py_nb_inplace_and is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_xor

The corresponding slot ID Py_nb_inplace_xor is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_or

The corresponding slot ID Py_nb_inplace_or is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_floor_divide

The corresponding slot ID Py_nb_floor_divide is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_true_divide

The corresponding slot ID Py_nb_true_divide is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_floor_divide

The corresponding slot ID Py_nb_inplace_floor_divide is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_inplace_true_divide

The corresponding slot ID Py_nb_inplace_true_divide is part of the 穩定 ABI 的一部分.

unaryfunc PyNumberMethods.nb_index

The corresponding slot ID Py_nb_index is part of the 穩定 ABI 的一部分.

binaryfunc PyNumberMethods.nb_matrix_multiply

The corresponding slot ID Py_nb_matrix_multiply is part of the 穩定 ABI 的一部分 自 3.5 版本開始.

binaryfunc PyNumberMethods.nb_inplace_matrix_multiply

The corresponding slot ID Py_nb_inplace_matrix_multiply is part of the 穩定 ABI 的一部分 自 3.5 版本開始.

對映物件結構

type PyMappingMethods

This structure holds pointers to the functions which an object uses to implement the mapping protocol. It has three members:

lenfunc PyMappingMethods.mp_length

The corresponding slot ID Py_mp_length is part of the 穩定 ABI 的一部分.

This function is used by PyMapping_Size() and PyObject_Size(), and has the same signature. This slot may be set to NULL if the object has no defined length.

binaryfunc PyMappingMethods.mp_subscript

The corresponding slot ID Py_mp_subscript is part of the 穩定 ABI 的一部分.

This function is used by PyObject_GetItem() and PySequence_GetSlice(), and has the same signature as PyObject_GetItem(). This slot must be filled for the PyMapping_Check() function to return 1, it can be NULL otherwise.

objobjargproc PyMappingMethods.mp_ass_subscript

The corresponding slot ID Py_mp_ass_subscript is part of the 穩定 ABI 的一部分.

This function is used by PyObject_SetItem(), PyObject_DelItem(), PySequence_SetSlice() and PySequence_DelSlice(). It has the same signature as PyObject_SetItem(), but v can also be set to NULL to delete an item. If this slot is NULL, the object does not support item assignment and deletion.

序列物件結構

type PySequenceMethods

This structure holds pointers to the functions which an object uses to implement the sequence protocol.

lenfunc PySequenceMethods.sq_length

The corresponding slot ID Py_sq_length is part of the 穩定 ABI 的一部分.

This function is used by PySequence_Size() and PyObject_Size(), and has the same signature. It is also used for handling negative indices via the sq_item and the sq_ass_item slots.

binaryfunc PySequenceMethods.sq_concat

The corresponding slot ID Py_sq_concat is part of the 穩定 ABI 的一部分.

This function is used by PySequence_Concat() and has the same signature. It is also used by the + operator, after trying the numeric addition via the nb_add slot.

ssizeargfunc PySequenceMethods.sq_repeat

The corresponding slot ID Py_sq_repeat is part of the 穩定 ABI 的一部分.

This function is used by PySequence_Repeat() and has the same signature. It is also used by the * operator, after trying numeric multiplication via the nb_multiply slot.

ssizeargfunc PySequenceMethods.sq_item

The corresponding slot ID Py_sq_item is part of the 穩定 ABI 的一部分.

This function is used by PySequence_GetItem() and has the same signature. It is also used by PyObject_GetItem(), after trying the subscription via the mp_subscript slot. This slot must be filled for the PySequence_Check() function to return 1, it can be NULL otherwise.

Negative indexes are handled as follows: if the sq_length slot is filled, it is called and the sequence length is used to compute a positive index which is passed to sq_item. If sq_length is NULL, the index is passed as is to the function.

ssizeobjargproc PySequenceMethods.sq_ass_item

The corresponding slot ID Py_sq_ass_item is part of the 穩定 ABI 的一部分.

This function is used by PySequence_SetItem() and has the same signature. It is also used by PyObject_SetItem() and PyObject_DelItem(), after trying the item assignment and deletion via the mp_ass_subscript slot. This slot may be left to NULL if the object does not support item assignment and deletion.

objobjproc PySequenceMethods.sq_contains

The corresponding slot ID Py_sq_contains is part of the 穩定 ABI 的一部分.

This function may be used by PySequence_Contains() and has the same signature. This slot may be left to NULL, in this case PySequence_Contains() simply traverses the sequence until it finds a match.

binaryfunc PySequenceMethods.sq_inplace_concat

The corresponding slot ID Py_sq_inplace_concat is part of the 穩定 ABI 的一部分.

This function is used by PySequence_InPlaceConcat() and has the same signature. It should modify its first operand, and return it. This slot may be left to NULL, in this case PySequence_InPlaceConcat() will fall back to PySequence_Concat(). It is also used by the augmented assignment +=, after trying numeric in-place addition via the nb_inplace_add slot.

ssizeargfunc PySequenceMethods.sq_inplace_repeat

The corresponding slot ID Py_sq_inplace_repeat is part of the 穩定 ABI 的一部分.

This function is used by PySequence_InPlaceRepeat() and has the same signature. It should modify its first operand, and return it. This slot may be left to NULL, in this case PySequence_InPlaceRepeat() will fall back to PySequence_Repeat(). It is also used by the augmented assignment *=, after trying numeric in-place multiplication via the nb_inplace_multiply slot.

緩衝區物件結構

type PyBufferProcs

This structure holds pointers to the functions required by the Buffer protocol. The protocol defines how an exporter object can expose its internal data to consumer objects.

getbufferproc PyBufferProcs.bf_getbuffer

The corresponding slot ID Py_bf_getbuffer is part of the 穩定 ABI 的一部分 自 3.11 版本開始.

函式的簽名為：

int (PyObject *exporter, Py_buffer *view, int flags);

Handle a request to exporter to fill in view as specified by flags. Except for point (3), an implementation of this function MUST take these steps:

Check if the request can be met. If not, raise BufferError, set view->obj to NULL and return -1.

Fill in the requested fields.

Increment an internal counter for the number of exports.

Set view->obj to exporter and increment view->obj.

回傳 0。

If exporter is part of a chain or tree of buffer providers, two main schemes can be used:

Re-export: Each member of the tree acts as the exporting object and sets view->obj to a new reference to itself.

Redirect: The buffer request is redirected to the root object of the tree. Here, view->obj will be a new reference to the root object.

The individual fields of view are described in section Buffer structure, the rules how an exporter must react to specific requests are in section Buffer request types.

All memory pointed to in the Py_buffer structure belongs to the exporter and must remain valid until there are no consumers left. format, shape, strides, suboffsets and internal are read-only for the consumer.

PyBuffer_FillInfo() provides an easy way of exposing a simple bytes buffer while dealing correctly with all request types.

PyObject_GetBuffer() is the interface for the consumer that wraps this function.

releasebufferproc PyBufferProcs.bf_releasebuffer

The corresponding slot ID Py_bf_releasebuffer is part of the 穩定 ABI 的一部分 自 3.11 版本開始.

函式的簽名為：

void (PyObject *exporter, Py_buffer *view);

Handle a request to release the resources of the buffer. If no resources need to be released, PyBufferProcs.bf_releasebuffer may be NULL. Otherwise, a standard implementation of this function will take these optional steps:

Decrement an internal counter for the number of exports.

If the counter is 0, free all memory associated with view.

The exporter MUST use the internal field to keep track of buffer-specific resources. This field is guaranteed to remain constant, while a consumer MAY pass a copy of the original buffer as the view argument.

This function MUST NOT decrement view->obj, since that is done automatically in PyBuffer_Release() (this scheme is useful for breaking reference cycles).

PyBuffer_Release() is the interface for the consumer that wraps this function.

非同步物件結構

在 3.5 版被加入.

type PyAsyncMethods

This structure holds pointers to the functions required to implement awaitable and asynchronous iterator objects.

Here is the structure definition:

typedef struct {
    unaryfunc am_await;
    unaryfunc am_aiter;
    unaryfunc am_anext;
    sendfunc am_send;
} PyAsyncMethods;

unaryfunc PyAsyncMethods.am_await

The corresponding slot ID Py_am_await is part of the 穩定 ABI 的一部分 自 3.5 版本開始.

函式的簽名為：

PyObject *am_await(PyObject *self);

The returned object must be an iterator, i.e. PyIter_Check() must return 1 for it.

This slot may be set to NULL if an object is not an awaitable.

unaryfunc PyAsyncMethods.am_aiter

The corresponding slot ID Py_am_aiter is part of the 穩定 ABI 的一部分 自 3.5 版本開始.

函式的簽名為：

PyObject *am_aiter(PyObject *self);

Must return an asynchronous iterator object. See __anext__() for details.

This slot may be set to NULL if an object does not implement asynchronous iteration protocol.

unaryfunc PyAsyncMethods.am_anext

The corresponding slot ID Py_am_anext is part of the 穩定 ABI 的一部分 自 3.5 版本開始.

函式的簽名為：

PyObject *am_anext(PyObject *self);

Must return an awaitable object. See __anext__() for details. This slot may be set to NULL.

sendfunc PyAsyncMethods.am_send

The corresponding slot ID Py_am_send is part of the 穩定 ABI 的一部分 自 3.10 版本開始.

函式的簽名為：

PySendResult am_send(PyObject *self, PyObject *arg, PyObject **result);

See PyIter_Send() for details. This slot may be set to NULL.

在 3.10 版被加入.

Slot Type typedefs

typedef PyObject *(*allocfunc)(PyTypeObject *cls, Py_ssize_t nitems)

為 穩定 ABI 的一部分.

The purpose of this function is to separate memory allocation from memory initialization. It should return a pointer to a block of memory of adequate length for the instance, suitably aligned, and initialized to zeros, but with ob_refcnt set to 1 and ob_type set to the type argument. If the type's tp_itemsize is non-zero, the object's ob_size field should be initialized to nitems and the length of the allocated memory block should be tp_basicsize + nitems*tp_itemsize, rounded up to a multiple of sizeof(void*); otherwise, nitems is not used and the length of the block should be tp_basicsize.

This function should not do any other instance initialization, not even to allocate additional memory; that should be done by tp_new.

typedef void (*destructor)(PyObject*)

為 穩定 ABI 的一部分.

typedef void (*freefunc)(void*)

請見 tp_free。

typedef PyObject *(*newfunc)(PyTypeObject*, PyObject*, PyObject*)

為 穩定 ABI 的一部分.

請見 tp_new。

typedef int (*initproc)(PyObject*, PyObject*, PyObject*)

為 穩定 ABI 的一部分.

請見 tp_init。

typedef PyObject *(*reprfunc)(PyObject*)

為 穩定 ABI 的一部分.

請見 tp_repr。

typedef PyObject *(*getattrfunc)(PyObject *self, char *attr)

為 穩定 ABI 的一部分.

Return the value of the named attribute for the object.

typedef int (*setattrfunc)(PyObject *self, char *attr, PyObject *value)

為 穩定 ABI 的一部分.

Set the value of the named attribute for the object. The value argument is set to NULL to delete the attribute.

typedef PyObject *(*getattrofunc)(PyObject *self, PyObject *attr)

為 穩定 ABI 的一部分.

Return the value of the named attribute for the object.

請見 tp_getattro。

typedef int (*setattrofunc)(PyObject *self, PyObject *attr, PyObject *value)

為 穩定 ABI 的一部分.

Set the value of the named attribute for the object. The value argument is set to NULL to delete the attribute.

請見 tp_setattro。

typedef PyObject *(*descrgetfunc)(PyObject*, PyObject*, PyObject*)

為 穩定 ABI 的一部分.

請見 tp_descr_get。

typedef int (*descrsetfunc)(PyObject*, PyObject*, PyObject*)

為 穩定 ABI 的一部分.

請見 tp_descr_set。

typedef Py_hash_t (*hashfunc)(PyObject*)

為 穩定 ABI 的一部分.

請見 tp_hash。

typedef PyObject *(*richcmpfunc)(PyObject*, PyObject*, int)

為 穩定 ABI 的一部分.

請見 tp_richcompare。

typedef PyObject *(*getiterfunc)(PyObject*)

為 穩定 ABI 的一部分.

請見 tp_iter。

typedef PyObject *(*iternextfunc)(PyObject*)

為 穩定 ABI 的一部分.

請見 tp_iternext。

typedef Py_ssize_t (*lenfunc)(PyObject*)

為 穩定 ABI 的一部分.

typedef int (*getbufferproc)(PyObject*, Py_buffer*, int)

為 穩定 ABI 的一部分 自 3.12 版本開始.

typedef void (*releasebufferproc)(PyObject*, Py_buffer*)

為 穩定 ABI 的一部分 自 3.12 版本開始.

typedef PyObject *(*unaryfunc)(PyObject*)

為 穩定 ABI 的一部分.

typedef PyObject *(*binaryfunc)(PyObject*, PyObject*)

為 穩定 ABI 的一部分.

typedef PySendResult (*sendfunc)(PyObject*, PyObject*, PyObject**)

請見 am_send。

typedef PyObject *(*ternaryfunc)(PyObject*, PyObject*, PyObject*)

為 穩定 ABI 的一部分.

typedef PyObject *(*ssizeargfunc)(PyObject*, Py_ssize_t)

為 穩定 ABI 的一部分.

typedef int (*ssizeobjargproc)(PyObject*, Py_ssize_t, PyObject*)

為 穩定 ABI 的一部分.

typedef int (*objobjproc)(PyObject*, PyObject*)

為 穩定 ABI 的一部分.

typedef int (*objobjargproc)(PyObject*, PyObject*, PyObject*)

為 穩定 ABI 的一部分.

範例

The following are simple examples of Python type definitions. They include common usage you may encounter. Some demonstrate tricky corner cases. For more examples, practical info, and a tutorial, see 擴充型別定義教學 and Defining Extension Types: Assorted Topics.

A basic static type:

typedef struct {
    PyObject_HEAD
    const char *data;
} MyObject;

static PyTypeObject MyObject_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
    .tp_basicsize = sizeof(MyObject),
    .tp_doc = PyDoc_STR("My objects"),
    .tp_new = myobj_new,
    .tp_dealloc = (destructor)myobj_dealloc,
    .tp_repr = (reprfunc)myobj_repr,
};

You may also find older code (especially in the CPython code base) with a more verbose initializer:

static PyTypeObject MyObject_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "mymod.MyObject",               /* tp_name */
    sizeof(MyObject),               /* tp_basicsize */
    0,                              /* tp_itemsize */
    (destructor)myobj_dealloc,      /* tp_dealloc */
    0,                              /* tp_vectorcall_offset */
    0,                              /* tp_getattr */
    0,                              /* tp_setattr */
    0,                              /* tp_as_async */
    (reprfunc)myobj_repr,           /* tp_repr */
    0,                              /* tp_as_number */
    0,                              /* tp_as_sequence */
    0,                              /* tp_as_mapping */
    0,                              /* tp_hash */
    0,                              /* tp_call */
    0,                              /* tp_str */
    0,                              /* tp_getattro */
    0,                              /* tp_setattro */
    0,                              /* tp_as_buffer */
    0,                              /* tp_flags */
    PyDoc_STR("My objects"),        /* tp_doc */
    0,                              /* tp_traverse */
    0,                              /* tp_clear */
    0,                              /* tp_richcompare */
    0,                              /* tp_weaklistoffset */
    0,                              /* tp_iter */
    0,                              /* tp_iternext */
    0,                              /* tp_methods */
    0,                              /* tp_members */
    0,                              /* tp_getset */
    0,                              /* tp_base */
    0,                              /* tp_dict */
    0,                              /* tp_descr_get */
    0,                              /* tp_descr_set */
    0,                              /* tp_dictoffset */
    0,                              /* tp_init */
    0,                              /* tp_alloc */
    myobj_new,                      /* tp_new */
};

A type that supports weakrefs, instance dicts, and hashing:

typedef struct {
    PyObject_HEAD
    const char *data;
} MyObject;

static PyTypeObject MyObject_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
    .tp_basicsize = sizeof(MyObject),
    .tp_doc = PyDoc_STR("My objects"),
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
         Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_MANAGED_DICT |
         Py_TPFLAGS_MANAGED_WEAKREF,
    .tp_new = myobj_new,
    .tp_traverse = (traverseproc)myobj_traverse,
    .tp_clear = (inquiry)myobj_clear,
    .tp_alloc = PyType_GenericNew,
    .tp_dealloc = (destructor)myobj_dealloc,
    .tp_repr = (reprfunc)myobj_repr,
    .tp_hash = (hashfunc)myobj_hash,
    .tp_richcompare = PyBaseObject_Type.tp_richcompare,
};

A str subclass that cannot be subclassed and cannot be called to create instances (e.g. uses a separate factory func) using Py_TPFLAGS_DISALLOW_INSTANTIATION flag:

typedef struct {
    PyUnicodeObject raw;
    char *extra;
} MyStr;

static PyTypeObject MyStr_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyStr",
    .tp_basicsize = sizeof(MyStr),
    .tp_base = NULL,  // set to &PyUnicode_Type in module init
    .tp_doc = PyDoc_STR("my custom str"),
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
    .tp_repr = (reprfunc)myobj_repr,
};

The simplest static type with fixed-length instances:

typedef struct {
    PyObject_HEAD
} MyObject;

static PyTypeObject MyObject_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
};

The simplest static type with variable-length instances:

typedef struct {
    PyObject_VAR_HEAD
    const char *data[1];
} MyObject;

static PyTypeObject MyObject_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
    .tp_basicsize = sizeof(MyObject) - sizeof(char *),
    .tp_itemsize = sizeof(char *),
};

循環垃圾回收的支援

Python's support for detecting and collecting garbage which involves circular references requires support from object types which are "containers" for other objects which may also be containers. Types which do not store references to other objects, or which only store references to atomic types (such as numbers or strings), do not need to provide any explicit support for garbage collection.

To create a container type, the tp_flags field of the type object must include the Py_TPFLAGS_HAVE_GC and provide an implementation of the tp_traverse handler. If instances of the type are mutable, a tp_clear implementation must also be provided.

Py_TPFLAGS_HAVE_GC

Objects with a type with this flag set must conform with the rules documented here. For convenience these objects will be referred to as container objects.

Constructors for container types must conform to two rules:

The memory for the object must be allocated using PyObject_GC_New or PyObject_GC_NewVar.

Once all the fields which may contain references to other containers are initialized, it must call PyObject_GC_Track().

Similarly, the deallocator for the object must conform to a similar pair of rules:

Before fields which refer to other containers are invalidated, PyObject_GC_UnTrack() must be called.

The object's memory must be deallocated using PyObject_GC_Del().

警告

If a type adds the Py_TPFLAGS_HAVE_GC, then it must implement at least a tp_traverse handler or explicitly use one from its subclass or subclasses.

When calling PyType_Ready() or some of the APIs that indirectly call it like PyType_FromSpecWithBases() or PyType_FromSpec() the interpreter will automatically populate the tp_flags, tp_traverse and tp_clear fields if the type inherits from a class that implements the garbage collector protocol and the child class does not include the Py_TPFLAGS_HAVE_GC flag.

PyObject_GC_New(TYPE, typeobj)

Analogous to PyObject_New but for container objects with the Py_TPFLAGS_HAVE_GC flag set.

Do not call this directly to allocate memory for an object; call the type's tp_alloc slot instead.

When populating a type's tp_alloc slot, PyType_GenericAlloc() is preferred over a custom function that simply calls this macro.

Memory allocated by this macro must be freed with PyObject_GC_Del() (usually called via the object's tp_free slot).

也參考

PyObject_GC_Del()

PyObject_New

PyType_GenericAlloc()

tp_alloc

PyObject_GC_NewVar(TYPE, typeobj, size)

Analogous to PyObject_NewVar but for container objects with the Py_TPFLAGS_HAVE_GC flag set.

Do not call this directly to allocate memory for an object; call the type's tp_alloc slot instead.

When populating a type's tp_alloc slot, PyType_GenericAlloc() is preferred over a custom function that simply calls this macro.

Memory allocated by this macro must be freed with PyObject_GC_Del() (usually called via the object's tp_free slot).

也參考

PyObject_GC_Del()

PyObject_NewVar

PyType_GenericAlloc()

tp_alloc

PyObject *PyUnstable_Object_GC_NewWithExtraData(PyTypeObject *type, size_t extra_size)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Analogous to PyObject_GC_New but allocates extra_size bytes at the end of the object (at offset tp_basicsize). The allocated memory is initialized to zeros, except for the Python object header.

The extra data will be deallocated with the object, but otherwise it is not managed by Python.

Memory allocated by this function must be freed with PyObject_GC_Del() (usually called via the object's tp_free slot).

警告

The function is marked as unstable because the final mechanism for reserving extra data after an instance is not yet decided. For allocating a variable number of fields, prefer using PyVarObject and tp_itemsize instead.

在 3.12 版被加入.

PyObject_GC_Resize(TYPE, op, newsize)

Resize an object allocated by PyObject_NewVar. Returns the resized object of type TYPE* (refers to any C type) or NULL on failure.

op must be of type PyVarObject* and must not be tracked by the collector yet. newsize must be of type Py_ssize_t.

void PyObject_GC_Track(PyObject *op)

為 穩定 ABI 的一部分.

Adds the object op to the set of container objects tracked by the collector. The collector can run at unexpected times so objects must be valid while being tracked. This should be called once all the fields followed by the tp_traverse handler become valid, usually near the end of the constructor.

int PyObject_IS_GC(PyObject *obj)

Returns non-zero if the object implements the garbage collector protocol, otherwise returns 0.

The object cannot be tracked by the garbage collector if this function returns 0.

int PyObject_GC_IsTracked(PyObject *op)

為 穩定 ABI 的一部分 自 3.9 版本開始.

Returns 1 if the object type of op implements the GC protocol and op is being currently tracked by the garbage collector and 0 otherwise.

This is analogous to the Python function gc.is_tracked().

在 3.9 版被加入.

int PyObject_GC_IsFinalized(PyObject *op)

為 穩定 ABI 的一部分 自 3.9 版本開始.

Returns 1 if the object type of op implements the GC protocol and op has been already finalized by the garbage collector and 0 otherwise.

This is analogous to the Python function gc.is_finalized().

在 3.9 版被加入.

void PyObject_GC_Del(void *op)

為 穩定 ABI 的一部分.

Releases memory allocated to an object using PyObject_GC_New or PyObject_GC_NewVar.

Do not call this directly to free an object's memory; call the type's tp_free slot instead.

Do not use this for memory allocated by PyObject_New, PyObject_NewVar, or related allocation functions; use PyObject_Free() instead.

也參考

PyObject_Free() is the non-GC equivalent of this function.

PyObject_GC_New

PyObject_GC_NewVar

PyType_GenericAlloc()

tp_free

void PyObject_GC_UnTrack(void *op)

為 穩定 ABI 的一部分.

Remove the object op from the set of container objects tracked by the collector. Note that PyObject_GC_Track() can be called again on this object to add it back to the set of tracked objects. The deallocator (tp_dealloc handler) should call this for the object before any of the fields used by the tp_traverse handler become invalid.

在 3.8 版的變更: The _PyObject_GC_TRACK() and _PyObject_GC_UNTRACK() macros have been removed from the public C API.

The tp_traverse handler accepts a function parameter of this type:

typedef int (*visitproc)(PyObject *object, void *arg)

為 穩定 ABI 的一部分.

Type of the visitor function passed to the tp_traverse handler. The function should be called with an object to traverse as object and the third parameter to the tp_traverse handler as arg. The Python core uses several visitor functions to implement cyclic garbage detection; it's not expected that users will need to write their own visitor functions.

The tp_traverse handler must have the following type:

typedef int (*traverseproc)(PyObject *self, visitproc visit, void *arg)

為 穩定 ABI 的一部分.

Traversal function for a container object. Implementations must call the visit function for each object directly contained by self, with the parameters to visit being the contained object and the arg value passed to the handler. The visit function must not be called with a NULL object argument. If visit returns a non-zero value that value should be returned immediately.

The traversal function must not have any side effects. Implementations may not modify the reference counts of any Python objects nor create or destroy any Python objects.

To simplify writing tp_traverse handlers, a Py_VISIT() macro is provided. In order to use this macro, the tp_traverse implementation must name its arguments exactly visit and arg:

Py_VISIT(o)

If the PyObject* o is not NULL, call the visit callback, with arguments o and arg. If visit returns a non-zero value, then return it. Using this macro, tp_traverse handlers look like:

static int
my_traverse(Noddy *self, visitproc visit, void *arg)
{
    Py_VISIT(self->foo);
    Py_VISIT(self->bar);
    return 0;
}

The tp_clear handler must be of the inquiry type, or NULL if the object is immutable.

typedef int (*inquiry)(PyObject *self)

為 穩定 ABI 的一部分.

Drop references that may have created reference cycles. Immutable objects do not have to define this method since they can never directly create reference cycles. Note that the object must still be valid after calling this method (don't just call Py_DECREF() on a reference). The collector will call this method if it detects that this object is involved in a reference cycle.

Controlling the Garbage Collector State

The C-API provides the following functions for controlling garbage collection runs.

Py_ssize_t PyGC_Collect(void)

為 穩定 ABI 的一部分.

Perform a full garbage collection, if the garbage collector is enabled. (Note that gc.collect() runs it unconditionally.)

Returns the number of collected + unreachable objects which cannot be collected. If the garbage collector is disabled or already collecting, returns 0 immediately. Errors during garbage collection are passed to sys.unraisablehook. This function does not raise exceptions.

int PyGC_Enable(void)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Enable the garbage collector: similar to gc.enable(). Returns the previous state, 0 for disabled and 1 for enabled.

在 3.10 版被加入.

int PyGC_Disable(void)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Disable the garbage collector: similar to gc.disable(). Returns the previous state, 0 for disabled and 1 for enabled.

在 3.10 版被加入.

int PyGC_IsEnabled(void)

為 穩定 ABI 的一部分 自 3.10 版本開始.

Query the state of the garbage collector: similar to gc.isenabled(). Returns the current state, 0 for disabled and 1 for enabled.

在 3.10 版被加入.

Querying Garbage Collector State

The C-API provides the following interface for querying information about the garbage collector.

void PyUnstable_GC_VisitObjects(gcvisitobjects_t callback, void *arg)

這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。

Run supplied callback on all live GC-capable objects. arg is passed through to all invocations of callback.

警告

If new objects are (de)allocated by the callback it is undefined if they will be visited.

Garbage collection is disabled during operation. Explicitly running a collection in the callback may lead to undefined behaviour e.g. visiting the same objects multiple times or not at all.

在 3.12 版被加入.

typedef int (*gcvisitobjects_t)(PyObject *object, void *arg)

Type of the visitor function to be passed to PyUnstable_GC_VisitObjects(). arg is the same as the arg passed to PyUnstable_GC_VisitObjects. Return 1 to continue iteration, return 0 to stop iteration. Other return values are reserved for now so behavior on returning anything else is undefined.

在 3.12 版被加入.

API 和 ABI 版本管理

Build-time version constants

CPython 透過以下巨集 (macro) 公開其版本號。請注意，對應到的是建置 (built) 所用到的版本。關於run time 所使用的版本，請見 Py_Version。

關於跨版本 API 和 ABI 穩定性的討論，請見 C API 穩定性。

PY_MAJOR_VERSION

在 3.4.1a2 中的 3。

PY_MINOR_VERSION

在 3.4.1a2 中的 4。

PY_MICRO_VERSION

在 3.4.1a2 中的 1。

PY_RELEASE_LEVEL

在 3.4.1a2 中的 a。0xA 代表 alpha 版本、0xB 代表 beta 版本、0xC 為發布候選版本、0xF 則為最終版。

PY_RELEASE_SERIAL

在 3.4.1a2 中的 2。零則為最終發布版本。

PY_VERSION_HEX

被編碼為單一整數的 Python 版本號。詳見 Py_PACK_FULL_VERSION() 以了解編碼詳細資訊。

使用它進行數值比較，例如 #if PY_VERSION_HEX >= ...。

These macros are defined in Include/patchlevel.h [https://github.com/python/cpython/tree/3.14/Include/patchlevel.h].

Run-time version

const unsigned long Py_Version

為 穩定 ABI 的一部分 自 3.11 版本開始.

編碼為單個常數整數的 Python runtime 版本號。詳見 Py_PACK_FULL_VERSION() 以了解編碼詳細資訊。這包含在 runtime 使用的 Python 版本。

使用它進行數值比較，例如 if (Py_Version >= ...)。

在 3.11 版被加入.

Bit-packing macros

uint32_t Py_PACK_FULL_VERSION(int major, int minor, int micro, int release_level, int release_serial)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Return the given version, encoded as a single 32-bit integer with the following structure:

引數

No. of bits

Bit mask

Bit shift

Example values

3.4.1a2

3.10.0

major

8

0xFF000000

24

0x03

0x03

minor

8

0x00FF0000

16

0x04

0x0A

micro

8

0x0000FF00

8

0x01

0x00

release_level

4

0x000000F0

4

0xA

0xF

release_serial

4

0x0000000F

0

0x2

0x0

例如：

版本

Py_PACK_FULL_VERSION 引數

Encoded version

3.4.1a2

(3, 4, 1, 0xA, 2)

0x030401a2

3.10.0

(3, 10, 0, 0xF, 0)

0x030a00f0

Out-of range bits in the arguments are ignored. That is, the macro can be defined as:

#ifndef Py_PACK_FULL_VERSION
#define Py_PACK_FULL_VERSION(X, Y, Z, LEVEL, SERIAL) ( \
   (((X) & 0xff) << 24) |                              \
   (((Y) & 0xff) << 16) |                              \
   (((Z) & 0xff) << 8) |                               \
   (((LEVEL) & 0xf) << 4) |                            \
   (((SERIAL) & 0xf) << 0))
#endif

Py_PACK_FULL_VERSION is primarily a macro, intended for use in #if directives, but it is also available as an exported function.

在 3.14 版被加入.

uint32_t Py_PACK_VERSION(int major, int minor)

為 穩定 ABI 的一部分 自 3.14 版本開始.

Equivalent to Py_PACK_FULL_VERSION(major, minor, 0, 0, 0). The result does not correspond to any Python release, but is useful in numeric comparisons.

在 3.14 版被加入.

監控 C API

於 3.13 版本中新增。

An extension may need to interact with the event monitoring system. Subscribing to events and registering callbacks can be done via the Python API exposed in sys.monitoring.

Generating Execution Events

The functions below make it possible for an extension to fire monitoring events as it emulates the execution of Python code. Each of these functions accepts a PyMonitoringState struct which contains concise information about the activation state of events, as well as the event arguments, which include a PyObject* representing the code object, the instruction offset and sometimes additional, event-specific arguments (see sys.monitoring for details about the signatures of the different event callbacks). The codelike argument should be an instance of types.CodeType or of a type that emulates it.

The VM disables tracing when firing an event, so there is no need for user code to do that.

Monitoring functions should not be called with an exception set, except those listed below as working with the current exception.

type PyMonitoringState

Representation of the state of an event type. It is allocated by the user while its contents are maintained by the monitoring API functions described below.

All of the functions below return 0 on success and -1 (with an exception set) on error.

關於事件的敘述請見 sys.monitoring。

int PyMonitoring_FirePyStartEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

發出一個 PY_START 事件。

int PyMonitoring_FirePyResumeEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

發出一個 PY_RESUME 事件。

int PyMonitoring_FirePyReturnEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *retval)

發出一個 PY_RETURN 事件。

int PyMonitoring_FirePyYieldEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *retval)

發出一個 PY_YIELD 事件。

int PyMonitoring_FireCallEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *callable, PyObject *arg0)

發出一個 CALL 事件。

int PyMonitoring_FireLineEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, int lineno)

發出一個 LINE 事件。

int PyMonitoring_FireJumpEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *target_offset)

發出一個 JUMP 事件。

int PyMonitoring_FireBranchLeftEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *target_offset)

發出一個 BRANCH_LEFT 事件。

int PyMonitoring_FireBranchRightEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *target_offset)

發出一個 BRANCH_RIGHT 事件。

int PyMonitoring_FireCReturnEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *retval)

發出一個 C_RETURN 事件。

int PyMonitoring_FirePyThrowEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

Fire a PY_THROW event with the current exception (as returned by PyErr_GetRaisedException()).

int PyMonitoring_FireRaiseEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

Fire a RAISE event with the current exception (as returned by PyErr_GetRaisedException()).

int PyMonitoring_FireCRaiseEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

Fire a C_RAISE event with the current exception (as returned by PyErr_GetRaisedException()).

int PyMonitoring_FireReraiseEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

Fire a RERAISE event with the current exception (as returned by PyErr_GetRaisedException()).

int PyMonitoring_FireExceptionHandledEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

Fire an EXCEPTION_HANDLED event with the current exception (as returned by PyErr_GetRaisedException()).

int PyMonitoring_FirePyUnwindEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)

Fire a PY_UNWIND event with the current exception (as returned by PyErr_GetRaisedException()).

int PyMonitoring_FireStopIterationEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *value)

Fire a STOP_ITERATION event. If value is an instance of StopIteration, it is used. Otherwise, a new StopIteration instance is created with value as its argument.

Managing the Monitoring State

Monitoring states can be managed with the help of monitoring scopes. A scope would typically correspond to a Python function.

int PyMonitoring_EnterScope(PyMonitoringState *state_array, uint64_t *version, const uint8_t *event_types, Py_ssize_t length)

Enter a monitored scope. event_types is an array of the event IDs for events that may be fired from the scope. For example, the ID of a PY_START event is the value PY_MONITORING_EVENT_PY_START, which is numerically equal to the base-2 logarithm of sys.monitoring.events.PY_START. state_array is an array with a monitoring state entry for each event in event_types, it is allocated by the user but populated by PyMonitoring_EnterScope() with information about the activation state of the event. The size of event_types (and hence also of state_array) is given in length.

The version argument is a pointer to a value which should be allocated by the user together with state_array and initialized to 0, and then set only by PyMonitoring_EnterScope() itself. It allows this function to determine whether event states have changed since the previous call, and to return quickly if they have not.

The scopes referred to here are lexical scopes: a function, class or method. PyMonitoring_EnterScope() should be called whenever the lexical scope is entered. Scopes can be reentered, reusing the same state_array and version, in situations like when emulating a recursive Python function. When a code-like's execution is paused, such as when emulating a generator, the scope needs to be exited and re-entered.

event_types 的巨集有：

巨集

事件

PY_MONITORING_EVENT_BRANCH_LEFT

BRANCH_LEFT

PY_MONITORING_EVENT_BRANCH_RIGHT

BRANCH_RIGHT

PY_MONITORING_EVENT_CALL

CALL

PY_MONITORING_EVENT_C_RAISE

C_RAISE

PY_MONITORING_EVENT_C_RETURN

C_RETURN

PY_MONITORING_EVENT_EXCEPTION_HANDLED

EXCEPTION_HANDLED

PY_MONITORING_EVENT_INSTRUCTION

INSTRUCTION

PY_MONITORING_EVENT_JUMP

JUMP

PY_MONITORING_EVENT_LINE

LINE

PY_MONITORING_EVENT_PY_RESUME

PY_RESUME

PY_MONITORING_EVENT_PY_RETURN

PY_RETURN

PY_MONITORING_EVENT_PY_START

PY_START

PY_MONITORING_EVENT_PY_THROW

PY_THROW

PY_MONITORING_EVENT_PY_UNWIND

PY_UNWIND

PY_MONITORING_EVENT_PY_YIELD

PY_YIELD

PY_MONITORING_EVENT_RAISE

RAISE

PY_MONITORING_EVENT_RERAISE

RERAISE

PY_MONITORING_EVENT_STOP_ITERATION

STOP_ITERATION

int PyMonitoring_ExitScope(void)

Exit the last scope that was entered with PyMonitoring_EnterScope().

int PY_MONITORING_IS_INSTRUMENTED_EVENT(uint8_t ev)

Return true if the event corresponding to the event ID ev is a local event.

在 3.13 版被加入.

在 3.14 版之後被棄用: This function is soft deprecated.

安裝 Python 模組

電子郵件:

distutils-sig@python.org

作為一個普及的開源開發專案，Python 有一個活躍的支持社群，由其貢獻者及使用者組成，而他們也讓他們的軟體可被其他 Python 開發者在開源授權條款下使用。

這樣可以讓 Python 使用者們有效地共享和合作，並受益於其他人對常見（有時甚至是罕見）的問題已經建立的解決方案，更可以在公用社群中潛在地貢獻他們自己的解決方案。

這份指南涵蓋了上述過程中的安裝部分。如果是要建立及分享你自己的 Python 專案，請參考 Python packaging user guide [https://packaging.python.org/en/latest/tutorials/packaging-projects/]。

備註

對於企業和其他機構的使用者，要注意到，許多組織對於使用和貢獻開源軟體都有自己的政策。在開始使用配備 Python 的發布及安裝工具時，請將那些政策納入考量。

關鍵術語

pip 是首選的安裝程式。從 Python 3.4 開始，它被預設包含在 Python 二進制安裝程式中。

virtual environment（虛擬環境）是一種半隔離的 Python 環境，可以為某個特定應用程式安裝其所需的套件，而不用在整個系統上安裝它們。

venv 是建立虛擬環境的標準工具，它從 Python 3.3 開始成為 Python 的一部分。從 Python 3.4 開始，它會預設地安裝 pip 到所有被建立的虛擬環境。

virtualenv 是 venv 的一個第三方替代方案（及其前身）。它使虛擬環境可以在 Python 3.4 之前的版本被使用，那些版本要不是根本沒提供 venv，就是無法自動安裝 pip 到所建立的環境中。

Python 套件索引 (Python Package Index) [https://pypi.org] 是開源授權套件的一個公共儲存庫，其中的套件皆可被其他 Python 使用者所使用。

Python 封裝管理站 (Python Packaging Authority) [https://www.pypa.io/] 是一個由開發者和說明文件作者組成的團隊，負責維護及改進標準封裝工具，以及相關的元資料 (metadata) 和檔案格式標準。他們在 GitHub [https://github.com/pypa] 平台上維護各種工具、說明文件及問題追蹤系統。

distutils 是最早的建置和發布系統，於 1998 年首次被加入 Python 標準函式庫。雖然直接使用 distutils 的方式已經被逐步淘汰，它仍然是現今封裝和發布的基礎結構根基，而且它不僅仍然是標準函式庫的一部分，它的名稱也以其他的方式存活著（例如：用於協調 Python 封裝標準開發的郵寄清單就是以它命名）。

在 3.5 版的變更: 對於建立虛擬環境，現在推薦使用 venv。

也參考

Python 封裝使用者指南：建立和使用虛擬環境 [https://packaging.python.org/installing/#creating-virtual-environments]

基本用法

標準封裝工具皆是以能從命令列使用的方式被設計的。

以下指令將從 Python 套件索引安裝一個模組的最新版本及其依賴套件 (dependencies)：

python -m pip install SomePackage

備註

對於 POSIX 使用者（包括 macOS 和 Linux 使用者），本指南中的範例皆假設有使用 virtual environment。

對於 Windows 使用者，本指南中的範例皆假設在安裝 Python 時，「可調整系統 PATH 環境變數」的選項已被選取。

在命令列中直接指定一個明確的或最小的版本也是可行的。當使用像是 >、< 的比較運算子，或某些可被 shell 所解釋的其他特殊字元時，套件名稱與版本編號應該要放在雙引號內：

python -m pip install SomePackage==1.0.4    # 明確版本
python -m pip install "SomePackage>=1.0.4"  # 最小版本

通常，如果一個合適的模組已被安裝，嘗試再次安裝它將不會有任何效果。要升級現有的模組就必須明確地請求：

python -m pip install --upgrade SomePackage

關於 pip 及其能力的更多資訊和資源，可以在 Python 封裝使用者指南 [https://packaging.python.org]中找到。

虛擬環境的建立是使用 venv 模組來完成。要在一個已啟用的虛擬環境中安裝套件，可使用前面展示的指令。

也參考

Python 封裝使用者指南：安裝 Python 發布套件 [https://packaging.python.org/installing/]

我該如何...？

接下來是關於一些常見任務的快速解答或連結。

...在 Python 3.4 之前的 Python 版本中安裝 pip？

Python 是從 Python 3.4 才開始綁定 pip 的。對於更早的版本，pip 需要被「自助安裝 (bootstrapped)」，請參考 Python 封裝使用者指南中的說明。

也參考

Python 封裝使用者指南：安裝套件的需求 [https://packaging.python.org/installing/#requirements-for-installing-packages]

...只為目前的使用者安裝套件？

把 --user 選項傳給 python -m pip install，這樣將會只為目前使用者而非系統的所有使用者安裝套件。

...安裝科學的 Python 套件？

許多科學類 Python 套件都有複雜的二進制依賴套件，且目前不太容易直接使用 pip 安裝。目前為止，使用其他方法 [https://packaging.python.org/science/]而非嘗試用 pip 來安裝它們，對使用者來說通常會更簡單。

也參考

Python 封裝使用者指南：安裝科學套件 [https://packaging.python.org/science/]

...平行安裝多個 Python 版本並使用它們？

在 Linux、macOS 以及其他 POSIX 系統中，使用帶有版本編號的 Python 指令並結合 -m 開關參數 (switch)，來運行 pip 的適當副本：

python2   -m pip install SomePackage  # 預設 Python 2
python2.7 -m pip install SomePackage  # 指定 Python 2.7
python3   -m pip install SomePackage  # 預設 Python 3
python3.4 -m pip install SomePackage  # 指定 Python 3.4

使用帶有合適版本編號的 pip 指令，也是可行的。

在 Windows 中，使用 Python 啟動指令 py 並結合 -m 開關參數 (switch)：

py -2   -m pip install SomePackage  # 預設 Python 2
py -2.7 -m pip install SomePackage  # 指定 Python 2.7
py -3   -m pip install SomePackage  # 預設 Python 3
py -3.4 -m pip install SomePackage  # 指定 Python 3.4

常見的安裝問題

在 Linux 上安裝套件至系統 Python

在 Linux 系統，Python 的某個安裝版本通常會被內含在 Linux 的發行版中。要安裝套件到這個 Python 版本上需要系統的 root 權限，並且可能會干擾到系統套件管理器的運作。如果其他系統組件非預期地以 pip 被升級，也會干擾這些組件的運作。

在這樣的系統上，以 pip 安裝套件時，通常較好的方式是使用虛擬環境，或以個別使用者安裝。

未安裝 pip

pip 沒有預設被安裝也是有可能的。一個潛在的解法是：

python -m ensurepip --default-pip

這裡還有其他關於安裝 pip [https://packaging.python.org/en/latest/tutorials/installing-packages/#ensure-pip-setuptools-and-wheel-are-up-to-date]的資源。

安裝二進制擴充 (binary extension)

Python 基本上相當倚賴以原始碼為基礎的發布方式，也會期望使用者在安裝過程的某個階段，從原始碼來編譯擴充模組。

隨著引入對二進制 wheel 格式的支援，以及透過 Python 套件索引能夠至少在 Windows 和 macOS 發布 wheel 檔案，這個問題預期將會逐漸消失，因為使用者將能夠更頻繁地安裝預建置 (pre-built) 的擴充，而不再需要自己建置它們。

有一些解決方案，可用來安裝那些還無法以預建置的 wheel 檔案被使用的科學軟體 [https://packaging.python.org/science/]，這些方案也有助於取得其他的二進制擴充，且無需在本機對它們進行建置。

也參考

Python 封裝使用者指南：二進制擴充 [https://packaging.python.org/extensions/]

Python 如何達成任務

「Python 如何達成任務 (HOWTOs)」是一系列的說明文件，其內容會深度地涵蓋某些特定的主題。以 Linux 說明文件專案的 HOWTO 系列為模範，本系列的目標是提供比 Python 函式庫參考手冊更實用的說明文件。

一般：

asyncio 的概念性總覽

註釋 (annotation) 最佳實踐

Argparse 教學

描述器 (Descriptor) 指南

Enum HOWTO

函式程式設計 HOWTO

ipaddress 模組介紹

如何使用 Logging 模組

Logging Cookbook

如何使用正規表示式

排序技法

Unicode HOWTO

如何使用 urllib 套件取得網路資源

進階開發：

Curses Programming with Python

Python 自由執行緒的支援

支援自由執行緒的 C API 擴充

隔離擴充模組

Python 2.3 方法解析順序

Socket 程式設計指南

計時器檔案描述器 (timerfd) 指南

遷移延伸模組到 Python 3

偵錯與效能分析：

使用 GDB 來為 C API 擴充功能和 CPython 內部偵錯

使用 DTrace 和 SystemTap 檢測 CPython

Python 對 Linux perf 分析器的支援

遠端偵錯附加協定

asyncio 的概念性總覽

This HOWTO article seeks to help you build a sturdy mental model of how asyncio fundamentally works, helping you understand the how and why behind the recommended patterns.

You might be curious about some key asyncio concepts. By the end of this article, you'll be able to comfortably answer these questions:

What's happening behind the scenes when an object is awaited?

How does asyncio differentiate between a task which doesn't need CPU time (such as a network request or file read) as opposed to a task that does (such as computing n-factorial)?

How to write an asynchronous variant of an operation, such as an async sleep or database request.

也參考

The guide [https://github.com/anordin95/a-conceptual-overview-of-asyncio/tree/main] that inspired this HOWTO article, by Alexander Nordin.

This in-depth YouTube tutorial series [https://www.youtube.com/watch?v=Xbl7XjFYsN4&list=PLhNSoGM2ik6SIkVGXWBwerucXjgP1rHmB] on asyncio created by Python core team member, Łukasz Langa.

500 Lines or Less: A Web Crawler With asyncio Coroutines [https://aosabook.org/en/500L/a-web-crawler-with-asyncio-coroutines.html] by A. Jesse Jiryu Davis and Guido van Rossum.

A conceptual overview part 1: the high-level

In part 1, we'll cover the main, high-level building blocks of asyncio: the event loop, coroutine functions, coroutine objects, tasks, and await.

事件迴圈

Everything in asyncio happens relative to the event loop. It's the star of the show. It's like an orchestra conductor. It's behind the scenes managing resources. Some power is explicitly granted to it, but a lot of its ability to get things done comes from the respect and cooperation of its worker bees.

In more technical terms, the event loop contains a collection of jobs to be run. Some jobs are added directly by you, and some indirectly by asyncio. The event loop takes a job from its backlog of work and invokes it (or "gives it control"), similar to calling a function, and then that job runs. Once it pauses or completes, it returns control to the event loop. The event loop will then select another job from its pool and invoke it. You can roughly think of the collection of jobs as a queue: jobs are added and then processed one at a time, generally (but not always) in order. This process repeats indefinitely, with the event loop cycling endlessly onwards. If there are no more jobs pending execution, the event loop is smart enough to rest and avoid needlessly wasting CPU cycles, and will come back when there's more work to be done.

Effective execution relies on jobs sharing well and cooperating; a greedy job could hog control and leave the other jobs to starve, rendering the overall event loop approach rather useless.

import asyncio

# This creates an event loop and indefinitely cycles through
# its collection of jobs.
event_loop = asyncio.new_event_loop()
event_loop.run_forever()

非同步函式與協程

這是一個基本的、無聊的 Python 函式：

def hello_printer():
    print(
        "Hi, I am a lowly, simple printer, though I have all I "
        "need in life -- \nfresh paper and my dearly beloved octopus "
        "partner in crime."
    )

Calling a regular function invokes its logic or body:

>>> hello_printer()
Hi, I am a lowly, simple printer, though I have all I need in life --
fresh paper and my dearly beloved octopus partner in crime.

The async def, as opposed to just a plain def, makes this an asynchronous function (or "coroutine function"). Calling it creates and returns a coroutine object.

async def loudmouth_penguin(magic_number: int):
    print(
     "I am a super special talking penguin. Far cooler than that printer. "
     f"By the way, my lucky number is: {magic_number}."
    )

Calling the async function, loudmouth_penguin, does not execute the print statement; instead, it creates a coroutine object:

>>> loudmouth_penguin(magic_number=3)
<coroutine object loudmouth_penguin at 0x104ed2740>

The terms "coroutine function" and "coroutine object" are often conflated as coroutine. That can be confusing! In this article, coroutine specifically refers to a coroutine object, or more precisely, an instance of types.CoroutineType (native coroutine). Note that coroutines can also exist as instances of collections.abc.Coroutine -- a distinction that matters for type checking.

A coroutine represents the function's body or logic. A coroutine has to be explicitly started; again, merely creating the coroutine does not start it. Notably, the coroutine can be paused and resumed at various points within the function's body. That pausing and resuming ability is what allows for asynchronous behavior!

Coroutines and coroutine functions were built by leveraging the functionality of generators and generator functions. Recall, a generator function is a function that yields, like this one:

def get_random_number():
    # 這是個很爛的隨機數產生器！
    print("Hi")
    yield 1
    print("Hello")
    yield 7
    print("Howdy")
    yield 4
    ...

Similar to a coroutine function, calling a generator function does not run it. Instead, it creates a generator object:

>>> get_random_number()
<generator object get_random_number at 0x1048671c0>

You can proceed to the next yield of a generator by using the built-in function next(). In other words, the generator runs, then pauses. For example:

>>> generator = get_random_number()
>>> next(generator)
Hi
1
>>> next(generator)
Hello
7

Tasks

Roughly speaking, tasks are coroutines (not coroutine functions) tied to an event loop. A task also maintains a list of callback functions whose importance will become clear in a moment when we discuss await. The recommended way to create tasks is via asyncio.create_task().

Creating a task automatically schedules it for execution (by adding a callback to run it in the event loop's to-do list, that is, collection of jobs).

asyncio automatically associates tasks with the event loop for you. This automatic association was purposely designed into asyncio for the sake of simplicity. Without it, you'd have to keep track of the event loop object and pass it to any coroutine function that wants to create tasks, adding redundant clutter to your code.

coroutine = loudmouth_penguin(magic_number=5)
# This creates a Task object and schedules its execution via the event loop.
task = asyncio.create_task(coroutine)

Earlier, we manually created the event loop and set it to run forever. In practice, it's recommended to use (and common to see) asyncio.run(), which takes care of managing the event loop and ensuring the provided coroutine finishes before advancing. For example, many async programs follow this setup:

import asyncio

async def main():
    # Perform all sorts of wacky, wild asynchronous things...
    ...

if __name__ == "__main__":
    asyncio.run(main())
    # The program will not reach the following print statement until the
    # coroutine main() finishes.
    print("coroutine main() is done!")

It's important to be aware that the task itself is not added to the event loop, only a callback to the task is. This matters if the task object you created is garbage collected before it's called by the event loop. For example, consider this program:

 1async def hello():
 2    print("hello!")
 3
 4async def main():
 5    asyncio.create_task(hello())
 6    # Other asynchronous instructions which run for a while
 7    # and cede control to the event loop...
 8    ...
 9
10asyncio.run(main())

Because there's no reference to the task object created on line 5, it might be garbage collected before the event loop invokes it. Later instructions in the coroutine main() hand control back to the event loop so it can invoke other jobs. When the event loop eventually tries to run the task, it might fail and discover the task object does not exist! This can also happen even if a coroutine keeps a reference to a task but completes before that task finishes. When the coroutine exits, local variables go out of scope and may be subject to garbage collection. In practice, asyncio and Python's garbage collector work pretty hard to ensure this sort of thing doesn't happen. But that's no reason to be reckless!

await

await is a Python keyword that's commonly used in one of two different ways:

await task
await coroutine

In a crucial way, the behavior of await depends on the type of object being awaited.

Awaiting a task will cede control from the current task or coroutine to the event loop. In the process of relinquishing control, a few important things happen. We'll use the following code example to illustrate:

async def plant_a_tree():
    dig_the_hole_task = asyncio.create_task(dig_the_hole())
    await dig_the_hole_task

    # Other instructions associated with planting a tree.
    ...

In this example, imagine the event loop has passed control to the start of the coroutine plant_a_tree(). As seen above, the coroutine creates a task and then awaits it. The await dig_the_hole_task instruction adds a callback (which will resume plant_a_tree()) to the dig_the_hole_task object's list of callbacks. And then, the instruction cedes control to the event loop. Some time later, the event loop will pass control to dig_the_hole_task and the task will finish whatever it needs to do. Once the task finishes, it will add its various callbacks to the event loop, in this case, a call to resume plant_a_tree().

Generally speaking, when the awaited task finishes (dig_the_hole_task), the original task or coroutine (plant_a_tree()) is added back to the event loop's to-do list to be resumed.

This is a basic, yet reliable mental model. In practice, the control handoffs are slightly more complex, but not by much. In part 2, we'll walk through the details that make this possible.

Unlike tasks, awaiting a coroutine does not hand control back to the event loop! Wrapping a coroutine in a task first, then awaiting that would cede control. The behavior of await coroutine is effectively the same as invoking a regular, synchronous Python function. Consider this program:

import asyncio

async def coro_a():
   print("I am coro_a(). Hi!")

async def coro_b():
   print("I am coro_b(). I sure hope no one hogs the event loop...")

async def main():
   task_b = asyncio.create_task(coro_b())
   num_repeats = 3
   for _ in range(num_repeats):
      await coro_a()
   await task_b

asyncio.run(main())

The first statement in the coroutine main() creates task_b and schedules it for execution via the event loop. Then, coro_a() is repeatedly awaited. Control never cedes to the event loop, which is why we see the output of all three coro_a() invocations before coro_b()'s output:

I am coro_a(). Hi!
I am coro_a(). Hi!
I am coro_a(). Hi!
I am coro_b(). I sure hope no one hogs the event loop...

If we change await coro_a() to await asyncio.create_task(coro_a()), the behavior changes. The coroutine main() cedes control to the event loop with that statement. The event loop then proceeds through its backlog of work, calling task_b and then the task which wraps coro_a() before resuming the coroutine main().

I am coro_b(). I sure hope no one hogs the event loop...
I am coro_a(). Hi!
I am coro_a(). Hi!
I am coro_a(). Hi!

This behavior of await coroutine can trip a lot of people up! That example highlights how using only await coroutine could unintentionally hog control from other tasks and effectively stall the event loop. asyncio.run() can help you detect such occurrences via the debug=True flag, which enables debug mode. Among other things, it will log any coroutines that monopolize execution for 100ms or longer.

The design intentionally trades off some conceptual clarity around usage of await for improved performance. Each time a task is awaited, control needs to be passed all the way up the call stack to the event loop. That might sound minor, but in a large program with many await statements and a deep call stack, that overhead can add up to a meaningful performance drag.

A conceptual overview part 2: the nuts and bolts

Part 2 goes into detail on the mechanisms asyncio uses to manage control flow. This is where the magic happens. You'll come away from this section knowing what await does behind the scenes and how to make your own asynchronous operators.

The inner workings of coroutines

asyncio leverages four components to pass around control.

coroutine.send(arg) is the method used to start or resume a coroutine. If the coroutine was paused and is now being resumed, the argument arg will be sent in as the return value of the yield statement which originally paused it. If the coroutine is being used for the first time (as opposed to being resumed), arg must be None.

 1class Rock:
 2    def __await__(self):
 3        value_sent_in = yield 7
 4        print(f"Rock.__await__ resuming with value: {value_sent_in}.")
 5        return value_sent_in
 6
 7async def main():
 8    print("Beginning coroutine main().")
 9    rock = Rock()
10    print("Awaiting rock...")
11    value_from_rock = await rock
12    print(f"Coroutine received value: {value_from_rock} from rock.")
13    return 23
14
15coroutine = main()
16intermediate_result = coroutine.send(None)
17print(f"Coroutine paused and returned intermediate value: {intermediate_result}.")
18
19print(f"Resuming coroutine and sending in value: 42.")
20try:
21    coroutine.send(42)
22except StopIteration as e:
23    returned_value = e.value
24print(f"Coroutine main() finished and provided value: {returned_value}.")

yield, as usual, pauses execution and returns control to the caller. In the example above, the yield, on line 3, is called by ... = await rock on line 11. More broadly speaking, await calls the __await__() method of the given object. await also does one more very special thing: it propagates (or "passes along") any yields it receives up the call chain. In this case, that's back to ... = coroutine.send(None) on line 16.

The coroutine is resumed via the coroutine.send(42) call on line 21. The coroutine picks back up from where it yielded (or paused) on line 3 and executes the remaining statements in its body. When a coroutine finishes, it raises a StopIteration exception with the return value attached in the value attribute.

That snippet produces this output:

Beginning coroutine main().
Awaiting rock...
Coroutine paused and returned intermediate value: 7.
Resuming coroutine and sending in value: 42.
Rock.__await__ resuming with value: 42.
Coroutine received value: 42 from rock.
Coroutine main() finished and provided value: 23.

It's worth pausing for a moment here and making sure you followed the various ways that control flow and values were passed. A lot of important ideas were covered and it's worth ensuring your understanding is firm.

The only way to yield (or effectively cede control) from a coroutine is to await an object that yields in its __await__ method. That might sound odd to you. You might be thinking:

1. What about a yield directly within the coroutine function? The coroutine function becomes an async generator function, a different beast entirely.

2. What about a yield from within the coroutine function to a (plain) generator? That causes the error: SyntaxError: yield from not allowed in a coroutine. This was intentionally designed for the sake of simplicity -- mandating only one way of using coroutines. Initially yield was barred as well, but was re-accepted to allow for async generators. Despite that, yield from and await effectively do the same thing.

Futures

A future is an object meant to represent a computation's status and result. The term is a nod to the idea of something still to come or not yet happened, and the object is a way to keep an eye on that something.

A future has a few important attributes. One is its state, which can be either "pending", "cancelled", or "done". Another is its result, which is set when the state transitions to done. Unlike a coroutine, a future does not represent the actual computation to be done; instead, it represents the status and result of that computation, kind of like a status light (red, yellow, or green) or indicator.

asyncio.Task subclasses asyncio.Future in order to gain these various capabilities. The prior section said tasks store a list of callbacks, which wasn't entirely accurate. It's actually the Future class that implements this logic, which Task inherits.

Futures may also be used directly (not via tasks). Tasks mark themselves as done when their coroutine is complete. Futures are much more versatile and will be marked as done when you say so. In this way, they're the flexible interface for you to make your own conditions for waiting and resuming.

A homemade asyncio.sleep

We'll go through an example of how you could leverage a future to create your own variant of asynchronous sleep (async_sleep) which mimics asyncio.sleep().

This snippet registers a few tasks with the event loop and then awaits the task created by asyncio.create_task, which wraps the async_sleep(3) coroutine. We want that task to finish only after three seconds have elapsed, but without preventing other tasks from running.

async def other_work():
    print("I like work. Work work.")

async def main():
    # Add a few other tasks to the event loop, so there's something
    # to do while asynchronously sleeping.
    work_tasks = [
        asyncio.create_task(other_work()),
        asyncio.create_task(other_work()),
        asyncio.create_task(other_work())
    ]
    print(
        "Beginning asynchronous sleep at time: "
        f"{datetime.datetime.now().strftime("%H:%M:%S")}."
    )
    await asyncio.create_task(async_sleep(3))
    print(
        "Done asynchronous sleep at time: "
        f"{datetime.datetime.now().strftime("%H:%M:%S")}."
    )
    # asyncio.gather effectively awaits each task in the collection.
    await asyncio.gather(*work_tasks)

Below, we use a future to enable custom control over when that task will be marked as done. If future.set_result() (the method responsible for marking that future as done) is never called, then this task will never finish. We've also enlisted the help of another task, which we'll see in a moment, that will monitor how much time has elapsed and, accordingly, call future.set_result().

async def async_sleep(seconds: float):
    future = asyncio.Future()
    time_to_wake = time.time() + seconds
    # Add the watcher-task to the event loop.
    watcher_task = asyncio.create_task(_sleep_watcher(future, time_to_wake))
    # Block until the future is marked as done.
    await future

Below, we use a rather bare YieldToEventLoop() object to yield from its __await__ method, ceding control to the event loop. This is effectively the same as calling asyncio.sleep(0), but this approach offers more clarity, not to mention it's somewhat cheating to use asyncio.sleep when showcasing how to implement it!

As usual, the event loop cycles through its tasks, giving them control and receiving control back when they pause or finish. The watcher_task, which runs the coroutine _sleep_watcher(...), will be invoked once per full cycle of the event loop. On each resumption, it'll check the time and if not enough has elapsed, then it'll pause once again and hand control back to the event loop. Once enough time has elapsed, _sleep_watcher(...) marks the future as done and completes by exiting its infinite while loop. Given this helper task is only invoked once per cycle of the event loop, you'd be correct to note that this asynchronous sleep will sleep at least three seconds, rather than exactly three seconds. Note this is also true of asyncio.sleep.

class YieldToEventLoop:
    def __await__(self):
        yield

async def _sleep_watcher(future, time_to_wake):
    while True:
        if time.time() >= time_to_wake:
            # This marks the future as done.
            future.set_result(None)
            break
        else:
            await YieldToEventLoop()

Here is the full program's output:

$ python custom-async-sleep.py
Beginning asynchronous sleep at time: 14:52:22.
I like work. Work work.
I like work. Work work.
I like work. Work work.
Done asynchronous sleep at time: 14:52:25.

You might feel this implementation of asynchronous sleep was unnecessarily convoluted. And, well, it was. The example was meant to showcase the versatility of futures with a simple example that could be mimicked for more complex needs. For reference, you could implement it without futures, like so:

async def simpler_async_sleep(seconds):
    time_to_wake = time.time() + seconds
    while True:
        if time.time() >= time_to_wake:
            return
        else:
            await YieldToEventLoop()

But that's all for now. Hopefully you're ready to more confidently dive into some async programming or check out advanced topics in the rest of the documentation.

遷移延伸模組到 Python 3

We recommend the following resources for porting extension modules to Python 3:

The Migrating C extensions [http://python3porting.com/cextensions.html] chapter from Supporting Python 3: An in-depth guide, a book on moving from Python 2 to Python 3 in general, guides the reader through porting an extension module.

The Porting guide [https://py3c.readthedocs.io/en/latest/guide.html] from the py3c project provides opinionated suggestions with supporting code.

Recommended third party tools offer abstractions over the Python's C API. Extensions generally need to be re-written to use one of them, but the library then handles differences between various Python versions and implementations.

Curses Programming with Python

作者:

A.M. Kuchling, Eric S. Raymond

發佈版本:

2.04

摘要

This document describes how to use the curses extension module to control text-mode displays.

What is curses?

The curses library supplies a terminal-independent screen-painting and keyboard-handling facility for text-based terminals; such terminals include VT100s, the Linux console, and the simulated terminal provided by various programs. Display terminals support various control codes to perform common operations such as moving the cursor, scrolling the screen, and erasing areas. Different terminals use widely differing codes, and often have their own minor quirks.

In a world of graphical displays, one might ask "why bother"? It's true that character-cell display terminals are an obsolete technology, but there are niches in which being able to do fancy things with them are still valuable. One niche is on small-footprint or embedded Unixes that don't run an X server. Another is tools such as OS installers and kernel configurators that may have to run before any graphical support is available.

The curses library provides fairly basic functionality, providing the programmer with an abstraction of a display containing multiple non-overlapping windows of text. The contents of a window can be changed in various ways---adding text, erasing it, changing its appearance---and the curses library will figure out what control codes need to be sent to the terminal to produce the right output. curses doesn't provide many user-interface concepts such as buttons, checkboxes, or dialogs; if you need such features, consider a user interface library such as Urwid [https://pypi.org/project/Urwid/].

The curses library was originally written for BSD Unix; the later System V versions of Unix from AT&T added many enhancements and new functions. BSD curses is no longer maintained, having been replaced by ncurses, which is an open-source implementation of the AT&T interface. If you're using an open-source Unix such as Linux or FreeBSD, your system almost certainly uses ncurses. Since most current commercial Unix versions are based on System V code, all the functions described here will probably be available. The older versions of curses carried by some proprietary Unixes may not support everything, though.

The Windows version of Python doesn't include the curses module. A ported version called UniCurses [https://pypi.org/project/UniCurses/] is available.

Python curses 模組

The Python module is a fairly simple wrapper over the C functions provided by curses; if you're already familiar with curses programming in C, it's really easy to transfer that knowledge to Python. The biggest difference is that the Python interface makes things simpler by merging different C functions such as addstr(), mvaddstr(), and mvwaddstr() into a single addstr() method. You'll see this covered in more detail later.

This HOWTO is an introduction to writing text-mode programs with curses and Python. It doesn't attempt to be a complete guide to the curses API; for that, see the Python library guide's section on ncurses, and the C manual pages for ncurses. It will, however, give you the basic ideas.

Starting and ending a curses application

Before doing anything, curses must be initialized. This is done by calling the initscr() function, which will determine the terminal type, send any required setup codes to the terminal, and create various internal data structures. If successful, initscr() returns a window object representing the entire screen; this is usually called stdscr after the name of the corresponding C variable.

import curses
stdscr = curses.initscr()

Usually curses applications turn off automatic echoing of keys to the screen, in order to be able to read keys and only display them under certain circumstances. This requires calling the noecho() function.

curses.noecho()

Applications will also commonly need to react to keys instantly, without requiring the Enter key to be pressed; this is called cbreak mode, as opposed to the usual buffered input mode.

curses.cbreak()

Terminals usually return special keys, such as the cursor keys or navigation keys such as Page Up and Home, as a multibyte escape sequence. While you could write your application to expect such sequences and process them accordingly, curses can do it for you, returning a special value such as curses.KEY_LEFT. To get curses to do the job, you'll have to enable keypad mode.

stdscr.keypad(True)

Terminating a curses application is much easier than starting one. You'll need to call:

curses.nocbreak()
stdscr.keypad(False)
curses.echo()

to reverse the curses-friendly terminal settings. Then call the endwin() function to restore the terminal to its original operating mode.

curses.endwin()

A common problem when debugging a curses application is to get your terminal messed up when the application dies without restoring the terminal to its previous state. In Python this commonly happens when your code is buggy and raises an uncaught exception. Keys are no longer echoed to the screen when you type them, for example, which makes using the shell difficult.

In Python you can avoid these complications and make debugging much easier by importing the curses.wrapper() function and using it like this:

from curses import wrapper

def main(stdscr):
    # Clear screen
    stdscr.clear()

    # This raises ZeroDivisionError when i == 10.
    for i in range(0, 11):
        v = i-10
        stdscr.addstr(i, 0, '10 divided by {} is {}'.format(v, 10/v))

        stdscr.refresh()
        stdscr.getkey()

wrapper(main)

The wrapper() function takes a callable object and does the initializations described above, also initializing colors if color support is present. wrapper() then runs your provided callable. Once the callable returns, wrapper() will restore the original state of the terminal. The callable is called inside a try...except that catches exceptions, restores the state of the terminal, and then re-raises the exception. Therefore your terminal won't be left in a funny state on exception and you'll be able to read the exception's message and traceback.

Windows and Pads

Windows are the basic abstraction in curses. A window object represents a rectangular area of the screen, and supports methods to display text, erase it, allow the user to input strings, and so forth.

The stdscr object returned by the initscr() function is a window object that covers the entire screen. Many programs may need only this single window, but you might wish to divide the screen into smaller windows, in order to redraw or clear them separately. The newwin() function creates a new window of a given size, returning the new window object.

begin_x = 20; begin_y = 7
height = 5; width = 40
win = curses.newwin(height, width, begin_y, begin_x)

Note that the coordinate system used in curses is unusual. Coordinates are always passed in the order y,x, and the top-left corner of a window is coordinate (0,0). This breaks the normal convention for handling coordinates where the x coordinate comes first. This is an unfortunate difference from most other computer applications, but it's been part of curses since it was first written, and it's too late to change things now.

Your application can determine the size of the screen by using the curses.LINES and curses.COLS variables to obtain the y and x sizes. Legal coordinates will then extend from (0,0) to (curses.LINES - 1, curses.COLS - 1).

When you call a method to display or erase text, the effect doesn't immediately show up on the display. Instead you must call the refresh() method of window objects to update the screen.

This is because curses was originally written with slow 300-baud terminal connections in mind; with these terminals, minimizing the time required to redraw the screen was very important. Instead curses accumulates changes to the screen and displays them in the most efficient manner when you call refresh(). For example, if your program displays some text in a window and then clears the window, there's no need to send the original text because they're never visible.

In practice, explicitly telling curses to redraw a window doesn't really complicate programming with curses much. Most programs go into a flurry of activity, and then pause waiting for a keypress or some other action on the part of the user. All you have to do is to be sure that the screen has been redrawn before pausing to wait for user input, by first calling stdscr.refresh() or the refresh() method of some other relevant window.

A pad is a special case of a window; it can be larger than the actual display screen, and only a portion of the pad displayed at a time. Creating a pad requires the pad's height and width, while refreshing a pad requires giving the coordinates of the on-screen area where a subsection of the pad will be displayed.

pad = curses.newpad(100, 100)
# These loops fill the pad with letters; addch() is
# explained in the next section
for y in range(0, 99):
    for x in range(0, 99):
        pad.addch(y,x, ord('a') + (x*x+y*y) % 26)

# Displays a section of the pad in the middle of the screen.
# (0,0) : coordinate of upper-left corner of pad area to display.
# (5,5) : coordinate of upper-left corner of window area to be filled
#         with pad content.
# (20, 75) : coordinate of lower-right corner of window area to be
#          : filled with pad content.
pad.refresh( 0,0, 5,5, 20,75)

The refresh() call displays a section of the pad in the rectangle extending from coordinate (5,5) to coordinate (20,75) on the screen; the upper left corner of the displayed section is coordinate (0,0) on the pad. Beyond that difference, pads are exactly like ordinary windows and support the same methods.

If you have multiple windows and pads on screen there is a more efficient way to update the screen and prevent annoying screen flicker as each part of the screen gets updated. refresh() actually does two things:

Calls the noutrefresh() method of each window to update an underlying data structure representing the desired state of the screen.

Calls the function doupdate() function to change the physical screen to match the desired state recorded in the data structure.

Instead you can call noutrefresh() on a number of windows to update the data structure, and then call doupdate() to update the screen.

Displaying Text

From a C programmer's point of view, curses may sometimes look like a twisty maze of functions, all subtly different. For example, addstr() displays a string at the current cursor location in the stdscr window, while mvaddstr() moves to a given y,x coordinate first before displaying the string. waddstr() is just like addstr(), but allows specifying a window to use instead of using stdscr by default. mvwaddstr() allows specifying both a window and a coordinate.

Fortunately the Python interface hides all these details. stdscr is a window object like any other, and methods such as addstr() accept multiple argument forms. Usually there are four different forms.

Form

描述

str 或 ch

Display the string str or character ch at the current position

str or ch, attr

Display the string str or character ch, using attribute attr at the current position

y、x、str 或 ch

Move to position y,x within the window, and display str or ch

y、x、str 或 ch、attr

Move to position y,x within the window, and display str or ch, using attribute attr

Attributes allow displaying text in highlighted forms such as boldface, underline, reverse code, or in color. They'll be explained in more detail in the next subsection.

The addstr() method takes a Python string or bytestring as the value to be displayed. The contents of bytestrings are sent to the terminal as-is. Strings are encoded to bytes using the value of the window's encoding attribute; this defaults to the default system encoding as returned by locale.getencoding().

The addch() methods take a character, which can be either a string of length 1, a bytestring of length 1, or an integer.

Constants are provided for extension characters; these constants are integers greater than 255. For example, ACS_PLMINUS is a +/- symbol, and ACS_ULCORNER is the upper left corner of a box (handy for drawing borders). You can also use the appropriate Unicode character.

Windows remember where the cursor was left after the last operation, so if you leave out the y,x coordinates, the string or character will be displayed wherever the last operation left off. You can also move the cursor with the move(y,x) method. Because some terminals always display a flashing cursor, you may want to ensure that the cursor is positioned in some location where it won't be distracting; it can be confusing to have the cursor blinking at some apparently random location.

If your application doesn't need a blinking cursor at all, you can call curs_set(False) to make it invisible. For compatibility with older curses versions, there's a leaveok(bool) function that's a synonym for curs_set(). When bool is true, the curses library will attempt to suppress the flashing cursor, and you won't need to worry about leaving it in odd locations.

Attributes and Color

Characters can be displayed in different ways. Status lines in a text-based application are commonly shown in reverse video, or a text viewer may need to highlight certain words. curses supports this by allowing you to specify an attribute for each cell on the screen.

An attribute is an integer, each bit representing a different attribute. You can try to display text with multiple attribute bits set, but curses doesn't guarantee that all the possible combinations are available, or that they're all visually distinct. That depends on the ability of the terminal being used, so it's safest to stick to the most commonly available attributes, listed here.

屬性

描述

A_BLINK

Blinking text

A_BOLD

Extra bright or bold text

A_DIM

Half bright text

A_REVERSE

Reverse-video text

A_STANDOUT

The best highlighting mode available

A_UNDERLINE

Underlined text

So, to display a reverse-video status line on the top line of the screen, you could code:

stdscr.addstr(0, 0, "Current mode: Typing mode",
              curses.A_REVERSE)
stdscr.refresh()

The curses library also supports color on those terminals that provide it. The most common such terminal is probably the Linux console, followed by color xterms.

To use color, you must call the start_color() function soon after calling initscr(), to initialize the default color set (the curses.wrapper() function does this automatically). Once that's done, the has_colors() function returns TRUE if the terminal in use can actually display color. (Note: curses uses the American spelling 'color', instead of the Canadian/British spelling 'colour'. If you're used to the British spelling, you'll have to resign yourself to misspelling it for the sake of these functions.)

The curses library maintains a finite number of color pairs, containing a foreground (or text) color and a background color. You can get the attribute value corresponding to a color pair with the color_pair() function; this can be bitwise-OR'ed with other attributes such as A_REVERSE, but again, such combinations are not guaranteed to work on all terminals.

An example, which displays a line of text using color pair 1:

stdscr.addstr("Pretty text", curses.color_pair(1))
stdscr.refresh()

As I said before, a color pair consists of a foreground and background color. The init_pair(n, f, b) function changes the definition of color pair n, to foreground color f and background color b. Color pair 0 is hard-wired to white on black, and cannot be changed.

Colors are numbered, and start_color() initializes 8 basic colors when it activates color mode. They are: 0:black, 1:red, 2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white. The curses module defines named constants for each of these colors: curses.COLOR_BLACK, curses.COLOR_RED, and so forth.

Let's put all this together. To change color 1 to red text on a white background, you would call:

curses.init_pair(1, curses.COLOR_RED, curses.COLOR_WHITE)

When you change a color pair, any text already displayed using that color pair will change to the new colors. You can also display new text in this color with:

stdscr.addstr(0,0, "RED ALERT!", curses.color_pair(1))

Very fancy terminals can change the definitions of the actual colors to a given RGB value. This lets you change color 1, which is usually red, to purple or blue or any other color you like. Unfortunately, the Linux console doesn't support this, so I'm unable to try it out, and can't provide any examples. You can check if your terminal can do this by calling can_change_color(), which returns True if the capability is there. If you're lucky enough to have such a talented terminal, consult your system's man pages for more information.

使用者輸入

The C curses library offers only very simple input mechanisms. Python's curses module adds a basic text-input widget. (Other libraries such as Urwid [https://pypi.org/project/Urwid/] have more extensive collections of widgets.)

There are two methods for getting input from a window:

getch() refreshes the screen and then waits for the user to hit a key, displaying the key if echo() has been called earlier. You can optionally specify a coordinate to which the cursor should be moved before pausing.

getkey() does the same thing but converts the integer to a string. Individual characters are returned as 1-character strings, and special keys such as function keys return longer strings containing a key name such as KEY_UP or ^G.

It's possible to not wait for the user using the nodelay() window method. After nodelay(True), getch() and getkey() for the window become non-blocking. To signal that no input is ready, getch() returns curses.ERR (a value of -1) and getkey() raises an exception. There's also a halfdelay() function, which can be used to (in effect) set a timer on each getch(); if no input becomes available within a specified delay (measured in tenths of a second), curses raises an exception.

The getch() method returns an integer; if it's between 0 and 255, it represents the ASCII code of the key pressed. Values greater than 255 are special keys such as Page Up, Home, or the cursor keys. You can compare the value returned to constants such as curses.KEY_PPAGE, curses.KEY_HOME, or curses.KEY_LEFT. The main loop of your program may look something like this:

while True:
    c = stdscr.getch()
    if c == ord('p'):
        PrintDocument()
    elif c == ord('q'):
        break  # Exit the while loop
    elif c == curses.KEY_HOME:
        x = y = 0

The curses.ascii module supplies ASCII class membership functions that take either integer or 1-character string arguments; these may be useful in writing more readable tests for such loops. It also supplies conversion functions that take either integer or 1-character-string arguments and return the same type. For example, curses.ascii.ctrl() returns the control character corresponding to its argument.

There's also a method to retrieve an entire string, getstr(). It isn't used very often, because its functionality is quite limited; the only editing keys available are the backspace key and the Enter key, which terminates the string. It can optionally be limited to a fixed number of characters.

curses.echo()            # Enable echoing of characters

# Get a 15-character string, with the cursor on the top line
s = stdscr.getstr(0,0, 15)

The curses.textpad module supplies a text box that supports an Emacs-like set of keybindings. Various methods of the Textbox class support editing with input validation and gathering the edit results either with or without trailing spaces. Here's an example:

import curses
from curses.textpad import Textbox, rectangle

def main(stdscr):
    stdscr.addstr(0, 0, "Enter IM message: (hit Ctrl-G to send)")

    editwin = curses.newwin(5,30, 2,1)
    rectangle(stdscr, 1,0, 1+5+1, 1+30+1)
    stdscr.refresh()

    box = Textbox(editwin)

    # Let the user edit until Ctrl-G is struck.
    box.edit()

    # Get resulting contents
    message = box.gather()

See the library documentation on curses.textpad for more details.

For More Information

This HOWTO doesn't cover some advanced topics, such as reading the contents of the screen or capturing mouse events from an xterm instance, but the Python library page for the curses module is now reasonably complete. You should browse it next.

If you're in doubt about the detailed behavior of the curses functions, consult the manual pages for your curses implementation, whether it's ncurses or a proprietary Unix vendor's. The manual pages will document any quirks, and provide complete lists of all the functions, attributes, and ACS_* characters available to you.

Because the curses API is so large, some functions aren't supported in the Python interface. Often this isn't because they're difficult to implement, but because no one has needed them yet. Also, Python doesn't yet support the menu library associated with ncurses. Patches adding support for these would be welcome; see the Python Developer's Guide [https://devguide.python.org/] to learn more about submitting patches to Python.

Writing Programs with NCURSES [https://invisible-island.net/ncurses/ncurses-intro.html]: a lengthy tutorial for C programmers.

ncurses 使用者手冊 [https://linux.die.net/man/3/ncurses]

ncurses 問答集 [https://invisible-island.net/ncurses/ncurses.faq.html]

"Use curses... don't swear" [https://www.youtube.com/watch?v=eN1eZtjLEnU]: video of a PyCon 2013 talk on controlling terminals using curses or Urwid.

"Console Applications with Urwid" [https://pyvideo.org/video/1568/console-applications-with-urwid]: video of a PyCon CA 2012 talk demonstrating some applications written using Urwid.

描述器 (Descriptor) 指南

作者:

Raymond Hettinger

聯絡方式:

<python at rcn dot com>

目錄

描述器 (Descriptor) 指南

Primer

Simple example: A descriptor that returns a constant

Dynamic lookups

Managed attributes

Customized names

Closing thoughts

Complete Practical Example

Validator class

Custom validators

Practical application

Technical Tutorial

摘要

Definition and introduction

描述器協定

Overview of descriptor invocation

Invocation from an instance

Invocation from a class

Invocation from super

Summary of invocation logic

Automatic name notification

ORM 範例

Pure Python Equivalents

Properties

Functions and methods

Kinds of methods

Static methods

Class methods

Member objects and __slots__

描述器讓物件自訂屬性能夠被查找、儲存和刪除。

此指南有四個主要章節：

The "primer" gives a basic overview, moving gently from simple examples, adding one feature at a time. Start here if you're new to descriptors.

The second section shows a complete, practical descriptor example. If you already know the basics, start there.

The third section provides a more technical tutorial that goes into the detailed mechanics of how descriptors work. Most people don't need this level of detail.

The last section has pure Python equivalents for built-in descriptors that are written in C. Read this if you're curious about how functions turn into bound methods or about the implementation of common tools like classmethod(), staticmethod(), property(), and __slots__.

Primer

In this primer, we start with the most basic possible example and then we'll add new capabilities one by one.

Simple example: A descriptor that returns a constant

The Ten class is a descriptor whose __get__() method always returns the constant 10:

class Ten:
    def __get__(self, obj, objtype=None):
        return 10

To use the descriptor, it must be stored as a class variable in another class:

class A:
    x = 5                       # Regular class attribute
    y = Ten()                   # Descriptor instance

An interactive session shows the difference between normal attribute lookup and descriptor lookup:

>>> a = A()                     # Make an instance of class A
>>> a.x                         # Normal attribute lookup
5
>>> a.y                         # Descriptor lookup
10

In the a.x attribute lookup, the dot operator finds 'x': 5 in the class dictionary. In the a.y lookup, the dot operator finds a descriptor instance, recognized by its __get__ method. Calling that method returns 10.

Note that the value 10 is not stored in either the class dictionary or the instance dictionary. Instead, the value 10 is computed on demand.

This example shows how a simple descriptor works, but it isn't very useful. For retrieving constants, normal attribute lookup would be better.

In the next section, we'll create something more useful, a dynamic lookup.

Dynamic lookups

Interesting descriptors typically run computations instead of returning constants:

import os

class DirectorySize:

    def __get__(self, obj, objtype=None):
        return len(os.listdir(obj.dirname))

class Directory:

    size = DirectorySize()              # Descriptor instance

    def __init__(self, dirname):
        self.dirname = dirname          # Regular instance attribute

An interactive session shows that the lookup is dynamic — it computes different, updated answers each time:

>>> s = Directory('songs')
>>> g = Directory('games')
>>> s.size                              # The songs directory has twenty files
20
>>> g.size                              # The games directory has three files
3
>>> os.remove('games/chess')            # Delete a game
>>> g.size                              # File count is automatically updated
2

Besides showing how descriptors can run computations, this example also reveals the purpose of the parameters to __get__(). The self parameter is size, an instance of DirectorySize. The obj parameter is either g or s, an instance of Directory. It is the obj parameter that lets the __get__() method learn the target directory. The objtype parameter is the class Directory.

Managed attributes

A popular use for descriptors is managing access to instance data. The descriptor is assigned to a public attribute in the class dictionary while the actual data is stored as a private attribute in the instance dictionary. The descriptor's __get__() and __set__() methods are triggered when the public attribute is accessed.

In the following example, age is the public attribute and _age is the private attribute. When the public attribute is accessed, the descriptor logs the lookup or update:

import logging

logging.basicConfig(level=logging.INFO)

class LoggedAgeAccess:

    def __get__(self, obj, objtype=None):
        value = obj._age
        logging.info('Accessing %r giving %r', 'age', value)
        return value

    def __set__(self, obj, value):
        logging.info('Updating %r to %r', 'age', value)
        obj._age = value

class Person:

    age = LoggedAgeAccess()             # Descriptor instance

    def __init__(self, name, age):
        self.name = name                # Regular instance attribute
        self.age = age                  # Calls __set__()

    def birthday(self):
        self.age += 1                   # Calls both __get__() and __set__()

An interactive session shows that all access to the managed attribute age is logged, but that the regular attribute name is not logged:

>>> mary = Person('Mary M', 30)         # The initial age update is logged
INFO:root:Updating 'age' to 30
>>> dave = Person('David D', 40)
INFO:root:Updating 'age' to 40

>>> vars(mary)                          # The actual data is in a private attribute
{'name': 'Mary M', '_age': 30}
>>> vars(dave)
{'name': 'David D', '_age': 40}

>>> mary.age                            # Access the data and log the lookup
INFO:root:Accessing 'age' giving 30
30
>>> mary.birthday()                     # Updates are logged as well
INFO:root:Accessing 'age' giving 30
INFO:root:Updating 'age' to 31

>>> dave.name                           # Regular attribute lookup isn't logged
'David D'
>>> dave.age                            # Only the managed attribute is logged
INFO:root:Accessing 'age' giving 40
40

One major issue with this example is that the private name _age is hardwired in the LoggedAgeAccess class. That means that each instance can only have one logged attribute and that its name is unchangeable. In the next example, we'll fix that problem.

Customized names

When a class uses descriptors, it can inform each descriptor about which variable name was used.

In this example, the Person class has two descriptor instances, name and age. When the Person class is defined, it makes a callback to __set_name__() in LoggedAccess so that the field names can be recorded, giving each descriptor its own public_name and private_name:

import logging

logging.basicConfig(level=logging.INFO)

class LoggedAccess:

    def __set_name__(self, owner, name):
        self.public_name = name
        self.private_name = '_' + name

    def __get__(self, obj, objtype=None):
        value = getattr(obj, self.private_name)
        logging.info('Accessing %r giving %r', self.public_name, value)
        return value

    def __set__(self, obj, value):
        logging.info('Updating %r to %r', self.public_name, value)
        setattr(obj, self.private_name, value)

class Person:

    name = LoggedAccess()                # First descriptor instance
    age = LoggedAccess()                 # Second descriptor instance

    def __init__(self, name, age):
        self.name = name                 # Calls the first descriptor
        self.age = age                   # Calls the second descriptor

    def birthday(self):
        self.age += 1

An interactive session shows that the Person class has called __set_name__() so that the field names would be recorded. Here we call vars() to look up the descriptor without triggering it:

>>> vars(vars(Person)['name'])
{'public_name': 'name', 'private_name': '_name'}
>>> vars(vars(Person)['age'])
{'public_name': 'age', 'private_name': '_age'}

The new class now logs access to both name and age:

>>> pete = Person('Peter P', 10)
INFO:root:Updating 'name' to 'Peter P'
INFO:root:Updating 'age' to 10
>>> kate = Person('Catherine C', 20)
INFO:root:Updating 'name' to 'Catherine C'
INFO:root:Updating 'age' to 20

The two Person instances contain only the private names:

>>> vars(pete)
{'_name': 'Peter P', '_age': 10}
>>> vars(kate)
{'_name': 'Catherine C', '_age': 20}

Closing thoughts

A descriptor is what we call any object that defines __get__(), __set__(), or __delete__().

Optionally, descriptors can have a __set_name__() method. This is only used in cases where a descriptor needs to know either the class where it was created or the name of class variable it was assigned to. (This method, if present, is called even if the class is not a descriptor.)

Descriptors get invoked by the dot operator during attribute lookup. If a descriptor is accessed indirectly with vars(some_class)[descriptor_name], the descriptor instance is returned without invoking it.

Descriptors only work when used as class variables. When put in instances, they have no effect.

The main motivation for descriptors is to provide a hook allowing objects stored in class variables to control what happens during attribute lookup.

Traditionally, the calling class controls what happens during lookup. Descriptors invert that relationship and allow the data being looked-up to have a say in the matter.

Descriptors are used throughout the language. It is how functions turn into bound methods. Common tools like classmethod(), staticmethod(), property(), and functools.cached_property() are all implemented as descriptors.

Complete Practical Example

In this example, we create a practical and powerful tool for locating notoriously hard to find data corruption bugs.

Validator class

A validator is a descriptor for managed attribute access. Prior to storing any data, it verifies that the new value meets various type and range restrictions. If those restrictions aren't met, it raises an exception to prevent data corruption at its source.

This Validator class is both an abstract base class and a managed attribute descriptor:

from abc import ABC, abstractmethod

class Validator(ABC):

    def __set_name__(self, owner, name):
        self.private_name = '_' + name

    def __get__(self, obj, objtype=None):
        return getattr(obj, self.private_name)

    def __set__(self, obj, value):
        self.validate(value)
        setattr(obj, self.private_name, value)

    @abstractmethod
    def validate(self, value):
        pass

Custom validators need to inherit from Validator and must supply a validate() method to test various restrictions as needed.

Custom validators

Here are three practical data validation utilities:

OneOf verifies that a value is one of a restricted set of options.

Number verifies that a value is either an int or float. Optionally, it verifies that a value is between a given minimum or maximum.

String verifies that a value is a str. Optionally, it validates a given minimum or maximum length. It can validate a user-defined predicate [https://en.wikipedia.org/wiki/Predicate_(mathematical_logic)] as well.

class OneOf(Validator):

    def __init__(self, *options):
        self.options = set(options)

    def validate(self, value):
        if value not in self.options:
            raise ValueError(
                f'Expected {value!r} to be one of {self.options!r}'
            )

class Number(Validator):

    def __init__(self, minvalue=None, maxvalue=None):
        self.minvalue = minvalue
        self.maxvalue = maxvalue

    def validate(self, value):
        if not isinstance(value, (int, float)):
            raise TypeError(f'Expected {value!r} to be an int or float')
        if self.minvalue is not None and value < self.minvalue:
            raise ValueError(
                f'Expected {value!r} to be at least {self.minvalue!r}'
            )
        if self.maxvalue is not None and value > self.maxvalue:
            raise ValueError(
                f'Expected {value!r} to be no more than {self.maxvalue!r}'
            )

class String(Validator):

    def __init__(self, minsize=None, maxsize=None, predicate=None):
        self.minsize = minsize
        self.maxsize = maxsize
        self.predicate = predicate

    def validate(self, value):
        if not isinstance(value, str):
            raise TypeError(f'Expected {value!r} to be a str')
        if self.minsize is not None and len(value) < self.minsize:
            raise ValueError(
                f'Expected {value!r} to be no smaller than {self.minsize!r}'
            )
        if self.maxsize is not None and len(value) > self.maxsize:
            raise ValueError(
                f'Expected {value!r} to be no bigger than {self.maxsize!r}'
            )
        if self.predicate is not None and not self.predicate(value):
            raise ValueError(
                f'Expected {self.predicate} to be true for {value!r}'
            )

Practical application

Here's how the data validators can be used in a real class:

class Component:

    name = String(minsize=3, maxsize=10, predicate=str.isupper)
    kind = OneOf('wood', 'metal', 'plastic')
    quantity = Number(minvalue=0)

    def __init__(self, name, kind, quantity):
        self.name = name
        self.kind = kind
        self.quantity = quantity

The descriptors prevent invalid instances from being created:

>>> Component('Widget', 'metal', 5)      # Blocked: 'Widget' is not all uppercase
Traceback (most recent call last):
    ...
ValueError: Expected <method 'isupper' of 'str' objects> to be true for 'Widget'

>>> Component('WIDGET', 'metle', 5)      # Blocked: 'metle' is misspelled
Traceback (most recent call last):
    ...
ValueError: Expected 'metle' to be one of {'metal', 'plastic', 'wood'}

>>> Component('WIDGET', 'metal', -5)     # Blocked: -5 is negative
Traceback (most recent call last):
    ...
ValueError: Expected -5 to be at least 0

>>> Component('WIDGET', 'metal', 'V')    # Blocked: 'V' isn't a number
Traceback (most recent call last):
    ...
TypeError: Expected 'V' to be an int or float

>>> c = Component('WIDGET', 'metal', 5)  # Allowed:  The inputs are valid

Technical Tutorial

What follows is a more technical tutorial for the mechanics and details of how descriptors work.

摘要

Defines descriptors, summarizes the protocol, and shows how descriptors are called. Provides an example showing how object relational mappings work.

Learning about descriptors not only provides access to a larger toolset, it creates a deeper understanding of how Python works.

Definition and introduction

In general, a descriptor is an attribute value that has one of the methods in the descriptor protocol. Those methods are __get__(), __set__(), and __delete__(). If any of those methods are defined for an attribute, it is said to be a descriptor.

The default behavior for attribute access is to get, set, or delete the attribute from an object's dictionary. For instance, a.x has a lookup chain starting with a.__dict__['x'], then type(a).__dict__['x'], and continuing through the method resolution order of type(a). If the looked-up value is an object defining one of the descriptor methods, then Python may override the default behavior and invoke the descriptor method instead. Where this occurs in the precedence chain depends on which descriptor methods were defined.

Descriptors are a powerful, general purpose protocol. They are the mechanism behind properties, methods, static methods, class methods, and super(). They are used throughout Python itself. Descriptors simplify the underlying C code and offer a flexible set of new tools for everyday Python programs.

描述器協定

descr.__get__(self, obj, type=None)

descr.__set__(self, obj, value)

descr.__delete__(self, obj)

That is all there is to it. Define any of these methods and an object is considered a descriptor and can override default behavior upon being looked up as an attribute.

If an object defines __set__() or __delete__(), it is considered a data descriptor. Descriptors that only define __get__() are called non-data descriptors (they are often used for methods but other uses are possible).

Data and non-data descriptors differ in how overrides are calculated with respect to entries in an instance's dictionary. If an instance's dictionary has an entry with the same name as a data descriptor, the data descriptor takes precedence. If an instance's dictionary has an entry with the same name as a non-data descriptor, the dictionary entry takes precedence.

To make a read-only data descriptor, define both __get__() and __set__() with the __set__() raising an AttributeError when called. Defining the __set__() method with an exception raising placeholder is enough to make it a data descriptor.

Overview of descriptor invocation

A descriptor can be called directly with desc.__get__(obj) or desc.__get__(None, cls).

But it is more common for a descriptor to be invoked automatically from attribute access.

The expression obj.x looks up the attribute x in the chain of namespaces for obj. If the search finds a descriptor outside of the instance __dict__, its __get__() method is invoked according to the precedence rules listed below.

The details of invocation depend on whether obj is an object, class, or instance of super.

Invocation from an instance

Instance lookup scans through a chain of namespaces giving data descriptors the highest priority, followed by instance variables, then non-data descriptors, then class variables, and lastly __getattr__() if it is provided.

If a descriptor is found for a.x, then it is invoked with: desc.__get__(a, type(a)).

The logic for a dotted lookup is in object.__getattribute__(). Here is a pure Python equivalent:

def find_name_in_mro(cls, name, default):
    "Emulate _PyType_Lookup() in Objects/typeobject.c"
    for base in cls.__mro__:
        if name in vars(base):
            return vars(base)[name]
    return default

def object_getattribute(obj, name):
    "Emulate PyObject_GenericGetAttr() in Objects/object.c"
    null = object()
    objtype = type(obj)
    cls_var = find_name_in_mro(objtype, name, null)
    descr_get = getattr(type(cls_var), '__get__', null)
    if descr_get is not null:
        if (hasattr(type(cls_var), '__set__')
            or hasattr(type(cls_var), '__delete__')):
            return descr_get(cls_var, obj, objtype)     # data descriptor
    if hasattr(obj, '__dict__') and name in vars(obj):
        return vars(obj)[name]                          # instance variable
    if descr_get is not null:
        return descr_get(cls_var, obj, objtype)         # non-data descriptor
    if cls_var is not null:
        return cls_var                                  # class variable
    raise AttributeError(name)

Note, there is no __getattr__() hook in the __getattribute__() code. That is why calling __getattribute__() directly or with super().__getattribute__ will bypass __getattr__() entirely.

Instead, it is the dot operator and the getattr() function that are responsible for invoking __getattr__() whenever __getattribute__() raises an AttributeError. Their logic is encapsulated in a helper function:

def getattr_hook(obj, name):
    "Emulate slot_tp_getattr_hook() in Objects/typeobject.c"
    try:
        return obj.__getattribute__(name)
    except AttributeError:
        if not hasattr(type(obj), '__getattr__'):
            raise
    return type(obj).__getattr__(obj, name)             # __getattr__

Invocation from a class

The logic for a dotted lookup such as A.x is in type.__getattribute__(). The steps are similar to those for object.__getattribute__() but the instance dictionary lookup is replaced by a search through the class's method resolution order.

If a descriptor is found, it is invoked with desc.__get__(None, A).

The full C implementation can be found in type_getattro() and _PyType_Lookup() in Objects/typeobject.c [https://github.com/python/cpython/tree/3.14/Objects/typeobject.c].

Invocation from super

The logic for super's dotted lookup is in the __getattribute__() method for object returned by super().

A dotted lookup such as super(A, obj).m searches obj.__class__.__mro__ for the base class B immediately following A and then returns B.__dict__['m'].__get__(obj, A). If not a descriptor, m is returned unchanged.

The full C implementation can be found in super_getattro() in Objects/typeobject.c [https://github.com/python/cpython/tree/3.14/Objects/typeobject.c]. A pure Python equivalent can be found in Guido's Tutorial [https://www.python.org/download/releases/2.2.3/descrintro/#cooperation].

Summary of invocation logic

The mechanism for descriptors is embedded in the __getattribute__() methods for object, type, and super().

要記住的重點是：

Descriptors are invoked by the __getattribute__() method.

Classes inherit this machinery from object, type, or super().

Overriding __getattribute__() prevents automatic descriptor calls because all the descriptor logic is in that method.

object.__getattribute__() and type.__getattribute__() make different calls to __get__(). The first includes the instance and may include the class. The second puts in None for the instance and always includes the class.

Data descriptors always override instance dictionaries.

Non-data descriptors may be overridden by instance dictionaries.

Automatic name notification

Sometimes it is desirable for a descriptor to know what class variable name it was assigned to. When a new class is created, the type metaclass scans the dictionary of the new class. If any of the entries are descriptors and if they define __set_name__(), that method is called with two arguments. The owner is the class where the descriptor is used, and the name is the class variable the descriptor was assigned to.

The implementation details are in type_new() and set_names() in Objects/typeobject.c [https://github.com/python/cpython/tree/3.14/Objects/typeobject.c].

Since the update logic is in type.__new__(), notifications only take place at the time of class creation. If descriptors are added to the class afterwards, __set_name__() will need to be called manually.

ORM 範例

The following code is a simplified skeleton showing how data descriptors could be used to implement an object relational mapping [https://en.wikipedia.org/wiki/Object%E2%80%93relational_mapping].

The essential idea is that the data is stored in an external database. The Python instances only hold keys to the database's tables. Descriptors take care of lookups or updates:

class Field:

    def __set_name__(self, owner, name):
        self.fetch = f'SELECT {name} FROM {owner.table} WHERE {owner.key}=?;'
        self.store = f'UPDATE {owner.table} SET {name}=? WHERE {owner.key}=?;'

    def __get__(self, obj, objtype=None):
        return conn.execute(self.fetch, [obj.key]).fetchone()[0]

    def __set__(self, obj, value):
        conn.execute(self.store, [value, obj.key])
        conn.commit()

We can use the Field class to define models [https://en.wikipedia.org/wiki/Database_model] that describe the schema for each table in a database:

class Movie:
    table = 'Movies'                    # Table name
    key = 'title'                       # Primary key
    director = Field()
    year = Field()

    def __init__(self, key):
        self.key = key

class Song:
    table = 'Music'
    key = 'title'
    artist = Field()
    year = Field()
    genre = Field()

    def __init__(self, key):
        self.key = key

To use the models, first connect to the database:

>>> import sqlite3
>>> conn = sqlite3.connect('entertainment.db')

An interactive session shows how data is retrieved from the database and how it can be updated:

>>> Movie('Star Wars').director
'George Lucas'
>>> jaws = Movie('Jaws')
>>> f'Released in {jaws.year} by {jaws.director}'
'Released in 1975 by Steven Spielberg'

>>> Song('Country Roads').artist
'John Denver'

>>> Movie('Star Wars').director = 'J.J. Abrams'
>>> Movie('Star Wars').director
'J.J. Abrams'

Pure Python Equivalents

The descriptor protocol is simple and offers exciting possibilities. Several use cases are so common that they have been prepackaged into built-in tools. Properties, bound methods, static methods, class methods, and __slots__ are all based on the descriptor protocol.

Properties

Calling property() is a succinct way of building a data descriptor that triggers a function call upon access to an attribute. Its signature is:

property(fget=None, fset=None, fdel=None, doc=None) -> property

The documentation shows a typical use to define a managed attribute x:

class C:
    def getx(self): return self.__x
    def setx(self, value): self.__x = value
    def delx(self): del self.__x
    x = property(getx, setx, delx, "I'm the 'x' property.")

To see how property() is implemented in terms of the descriptor protocol, here is a pure Python equivalent that implements most of the core functionality:

class Property:
    "Emulate PyProperty_Type() in Objects/descrobject.c"

    def __init__(self, fget=None, fset=None, fdel=None, doc=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel
        if doc is None and fget is not None:
            doc = fget.__doc__
        self.__doc__ = doc

    def __set_name__(self, owner, name):
        self.__name__ = name

    def __get__(self, obj, objtype=None):
        if obj is None:
            return self
        if self.fget is None:
            raise AttributeError
        return self.fget(obj)

    def __set__(self, obj, value):
        if self.fset is None:
            raise AttributeError
        self.fset(obj, value)

    def __delete__(self, obj):
        if self.fdel is None:
            raise AttributeError
        self.fdel(obj)

    def getter(self, fget):
        return type(self)(fget, self.fset, self.fdel, self.__doc__)

    def setter(self, fset):
        return type(self)(self.fget, fset, self.fdel, self.__doc__)

    def deleter(self, fdel):
        return type(self)(self.fget, self.fset, fdel, self.__doc__)

The property() builtin helps whenever a user interface has granted attribute access and then subsequent changes require the intervention of a method.

For instance, a spreadsheet class may grant access to a cell value through Cell('b10').value. Subsequent improvements to the program require the cell to be recalculated on every access; however, the programmer does not want to affect existing client code accessing the attribute directly. The solution is to wrap access to the value attribute in a property data descriptor:

class Cell:
    ...

    @property
    def value(self):
        "Recalculate the cell before returning value"
        self.recalc()
        return self._value

Either the built-in property() or our Property() equivalent would work in this example.

Functions and methods

Python's object oriented features are built upon a function based environment. Using non-data descriptors, the two are merged seamlessly.

Functions stored in class dictionaries get turned into methods when invoked. Methods only differ from regular functions in that the object instance is prepended to the other arguments. By convention, the instance is called self but could be called this or any other variable name.

Methods can be created manually with types.MethodType which is roughly equivalent to:

class MethodType:
    "Emulate PyMethod_Type in Objects/classobject.c"

    def __init__(self, func, obj):
        self.__func__ = func
        self.__self__ = obj

    def __call__(self, *args, **kwargs):
        func = self.__func__
        obj = self.__self__
        return func(obj, *args, **kwargs)

    def __getattribute__(self, name):
        "Emulate method_getset() in Objects/classobject.c"
        if name == '__doc__':
            return self.__func__.__doc__
        return object.__getattribute__(self, name)

    def __getattr__(self, name):
        "Emulate method_getattro() in Objects/classobject.c"
        return getattr(self.__func__, name)

    def __get__(self, obj, objtype=None):
        "Emulate method_descr_get() in Objects/classobject.c"
        return self

To support automatic creation of methods, functions include the __get__() method for binding methods during attribute access. This means that functions are non-data descriptors that return bound methods during dotted lookup from an instance. Here's how it works:

class Function:
    ...

    def __get__(self, obj, objtype=None):
        "Simulate func_descr_get() in Objects/funcobject.c"
        if obj is None:
            return self
        return MethodType(self, obj)

Running the following class in the interpreter shows how the function descriptor works in practice:

class D:
    def f(self):
         return self

class D2:
    pass

The function has a qualified name attribute to support introspection:

>>> D.f.__qualname__
'D.f'

Accessing the function through the class dictionary does not invoke __get__(). Instead, it just returns the underlying function object:

>>> D.__dict__['f']
<function D.f at 0x00C45070>

Dotted access from a class calls __get__() which just returns the underlying function unchanged:

>>> D.f
<function D.f at 0x00C45070>

The interesting behavior occurs during dotted access from an instance. The dotted lookup calls __get__() which returns a bound method object:

>>> d = D()
>>> d.f
<bound method D.f of <__main__.D object at 0x00B18C90>>

Internally, the bound method stores the underlying function and the bound instance:

>>> d.f.__func__
<function D.f at 0x00C45070>

>>> d.f.__self__
<__main__.D object at 0x00B18C90>

If you have ever wondered where self comes from in regular methods or where cls comes from in class methods, this is it!

Kinds of methods

Non-data descriptors provide a simple mechanism for variations on the usual patterns of binding functions into methods.

To recap, functions have a __get__() method so that they can be converted to a method when accessed as attributes. The non-data descriptor transforms an obj.f(*args) call into f(obj, *args). Calling cls.f(*args) becomes f(*args).

This chart summarizes the binding and its two most useful variants:

Transformation

Called from an object

Called from a class

函式

f(obj, *args)

f(*args)

staticmethod

f(*args)

f(*args)

classmethod

f(type(obj), *args)

f(cls, *args)

Static methods

Static methods return the underlying function without changes. Calling either c.f or C.f is the equivalent of a direct lookup into object.__getattribute__(c, "f") or object.__getattribute__(C, "f"). As a result, the function becomes identically accessible from either an object or a class.

Good candidates for static methods are methods that do not reference the self variable.

For instance, a statistics package may include a container class for experimental data. The class provides normal methods for computing the average, mean, median, and other descriptive statistics that depend on the data. However, there may be useful functions which are conceptually related but do not depend on the data. For instance, erf(x) is handy conversion routine that comes up in statistical work but does not directly depend on a particular dataset. It can be called either from an object or the class: s.erf(1.5) --> 0.9332 or Sample.erf(1.5) --> 0.9332.

Since static methods return the underlying function with no changes, the example calls are unexciting:

class E:
    @staticmethod
    def f(x):
        return x * 10

>>> E.f(3)
30
>>> E().f(3)
30

Using the non-data descriptor protocol, a pure Python version of staticmethod() would look like this:

import functools

class StaticMethod:
    "Emulate PyStaticMethod_Type() in Objects/funcobject.c"

    def __init__(self, f):
        self.f = f
        functools.update_wrapper(self, f)

    def __get__(self, obj, objtype=None):
        return self.f

    def __call__(self, *args, **kwds):
        return self.f(*args, **kwds)

    @property
    def __annotations__(self):
        return self.f.__annotations__

The functools.update_wrapper() call adds a __wrapped__ attribute that refers to the underlying function. Also it carries forward the attributes necessary to make the wrapper look like the wrapped function, including __name__, __qualname__, and __doc__.

Class methods

Unlike static methods, class methods prepend the class reference to the argument list before calling the function. This format is the same for whether the caller is an object or a class:

class F:
    @classmethod
    def f(cls, x):
        return cls.__name__, x

>>> F.f(3)
('F', 3)
>>> F().f(3)
('F', 3)

This behavior is useful whenever the method only needs to have a class reference and does not rely on data stored in a specific instance. One use for class methods is to create alternate class constructors. For example, the classmethod dict.fromkeys() creates a new dictionary from a list of keys. The pure Python equivalent is:

class Dict(dict):
    @classmethod
    def fromkeys(cls, iterable, value=None):
        "Emulate dict_fromkeys() in Objects/dictobject.c"
        d = cls()
        for key in iterable:
            d[key] = value
        return d

Now a new dictionary of unique keys can be constructed like this:

>>> d = Dict.fromkeys('abracadabra')
>>> type(d) is Dict
True
>>> d
{'a': None, 'b': None, 'r': None, 'c': None, 'd': None}

Using the non-data descriptor protocol, a pure Python version of classmethod() would look like this:

import functools

class ClassMethod:
    "Emulate PyClassMethod_Type() in Objects/funcobject.c"

    def __init__(self, f):
        self.f = f
        functools.update_wrapper(self, f)

    def __get__(self, obj, cls=None):
        if cls is None:
            cls = type(obj)
        return MethodType(self.f, cls)

The functools.update_wrapper() call in ClassMethod adds a __wrapped__ attribute that refers to the underlying function. Also it carries forward the attributes necessary to make the wrapper look like the wrapped function: __name__, __qualname__, __doc__, and __annotations__.

Member objects and __slots__

When a class defines __slots__, it replaces instance dictionaries with a fixed-length array of slot values. From a user point of view that has several effects:

1. Provides immediate detection of bugs due to misspelled attribute assignments. Only attribute names specified in __slots__ are allowed:

class Vehicle:
    __slots__ = ('id_number', 'make', 'model')

>>> auto = Vehicle()
>>> auto.id_nubmer = 'VYE483814LQEX'
Traceback (most recent call last):
    ...
AttributeError: 'Vehicle' object has no attribute 'id_nubmer'

2. Helps create immutable objects where descriptors manage access to private attributes stored in __slots__:

class Immutable:

    __slots__ = ('_dept', '_name')          # Replace the instance dictionary

    def __init__(self, dept, name):
        self._dept = dept                   # Store to private attribute
        self._name = name                   # Store to private attribute

    @property                               # Read-only descriptor
    def dept(self):
        return self._dept

    @property
    def name(self):                         # Read-only descriptor
        return self._name

>>> mark = Immutable('Botany', 'Mark Watney')
>>> mark.dept
'Botany'
>>> mark.dept = 'Space Pirate'
Traceback (most recent call last):
    ...
AttributeError: property 'dept' of 'Immutable' object has no setter
>>> mark.location = 'Mars'
Traceback (most recent call last):
    ...
AttributeError: 'Immutable' object has no attribute 'location'

3. Saves memory. On a 64-bit Linux build, an instance with two attributes takes 48 bytes with __slots__ and 152 bytes without. This flyweight design pattern [https://en.wikipedia.org/wiki/Flyweight_pattern] likely only matters when a large number of instances are going to be created.

4. Improves speed. Reading instance variables is 35% faster with __slots__ (as measured with Python 3.10 on an Apple M1 processor).

5. Blocks tools like functools.cached_property() which require an instance dictionary to function correctly:

from functools import cached_property

class CP:
    __slots__ = ()                          # Eliminates the instance dict

    @cached_property                        # Requires an instance dict
    def pi(self):
        return 4 * sum((-1.0)**n / (2.0*n + 1.0)
                       for n in reversed(range(100_000)))

>>> CP().pi
Traceback (most recent call last):
  ...
TypeError: No '__dict__' attribute on 'CP' instance to cache 'pi' property.

It is not possible to create an exact drop-in pure Python version of __slots__ because it requires direct access to C structures and control over object memory allocation. However, we can build a mostly faithful simulation where the actual C structure for slots is emulated by a private _slotvalues list. Reads and writes to that private structure are managed by member descriptors:

null = object()

class Member:

    def __init__(self, name, clsname, offset):
        'Emulate PyMemberDef in Include/structmember.h'
        # Also see descr_new() in Objects/descrobject.c
        self.name = name
        self.clsname = clsname
        self.offset = offset

    def __get__(self, obj, objtype=None):
        'Emulate member_get() in Objects/descrobject.c'
        # Also see PyMember_GetOne() in Python/structmember.c
        if obj is None:
            return self
        value = obj._slotvalues[self.offset]
        if value is null:
            raise AttributeError(self.name)
        return value

    def __set__(self, obj, value):
        'Emulate member_set() in Objects/descrobject.c'
        obj._slotvalues[self.offset] = value

    def __delete__(self, obj):
        'Emulate member_delete() in Objects/descrobject.c'
        value = obj._slotvalues[self.offset]
        if value is null:
            raise AttributeError(self.name)
        obj._slotvalues[self.offset] = null

    def __repr__(self):
        'Emulate member_repr() in Objects/descrobject.c'
        return f'<Member {self.name!r} of {self.clsname!r}>'

The type.__new__() method takes care of adding member objects to class variables:

class Type(type):
    'Simulate how the type metaclass adds member objects for slots'

    def __new__(mcls, clsname, bases, mapping, **kwargs):
        'Emulate type_new() in Objects/typeobject.c'
        # type_new() calls PyTypeReady() which calls add_methods()
        slot_names = mapping.get('slot_names', [])
        for offset, name in enumerate(slot_names):
            mapping[name] = Member(name, clsname, offset)
        return type.__new__(mcls, clsname, bases, mapping, **kwargs)

The object.__new__() method takes care of creating instances that have slots instead of an instance dictionary. Here is a rough simulation in pure Python:

class Object:
    'Simulate how object.__new__() allocates memory for __slots__'

    def __new__(cls, *args, **kwargs):
        'Emulate object_new() in Objects/typeobject.c'
        inst = super().__new__(cls)
        if hasattr(cls, 'slot_names'):
            empty_slots = [null] * len(cls.slot_names)
            object.__setattr__(inst, '_slotvalues', empty_slots)
        return inst

    def __setattr__(self, name, value):
        'Emulate _PyObject_GenericSetAttrWithDict() Objects/object.c'
        cls = type(self)
        if hasattr(cls, 'slot_names') and name not in cls.slot_names:
            raise AttributeError(
                f'{cls.__name__!r} object has no attribute {name!r}'
            )
        super().__setattr__(name, value)

    def __delattr__(self, name):
        'Emulate _PyObject_GenericSetAttrWithDict() Objects/object.c'
        cls = type(self)
        if hasattr(cls, 'slot_names') and name not in cls.slot_names:
            raise AttributeError(
                f'{cls.__name__!r} object has no attribute {name!r}'
            )
        super().__delattr__(name)

To use the simulation in a real class, just inherit from Object and set the metaclass to Type:

class H(Object, metaclass=Type):
    'Instance variables stored in slots'

    slot_names = ['x', 'y']

    def __init__(self, x, y):
        self.x = x
        self.y = y

At this point, the metaclass has loaded member objects for x and y:

>>> from pprint import pp
>>> pp(dict(vars(H)))
{'__module__': '__main__',
 '__doc__': 'Instance variables stored in slots',
 'slot_names': ['x', 'y'],
 '__init__': <function H.__init__ at 0x7fb5d302f9d0>,
 'x': <Member 'x' of 'H'>,
 'y': <Member 'y' of 'H'>}

When instances are created, they have a slot_values list where the attributes are stored:

>>> h = H(10, 20)
>>> vars(h)
{'_slotvalues': [10, 20]}
>>> h.x = 55
>>> vars(h)
{'_slotvalues': [55, 20]}

Misspelled or unassigned attributes will raise an exception:

>>> h.xz
Traceback (most recent call last):
    ...
AttributeError: 'H' object has no attribute 'xz'

使用 GDB 來為 C API 擴充功能和 CPython 內部偵錯

本文件解釋如何將 Python GDB 擴充功能 python-gdb.py 與 GDB 偵錯器一起使用來為 CPython 擴充功能和 CPython 直譯器本身偵錯。

在為崩潰或死鎖等低階問題幀錯時，低階偵錯器（例如 GDB）對於診斷和修正問題非常有用。預設情況下，GDB（或其任何前端）不支援特定於 CPython 直譯器的高階資訊。

python-gdb.py 擴充功能將 CPython 直譯器資訊新增至 GDB。此擴充有助於內省 (introspect) 目前執行的 Python 函式的堆疊。給定一個由 PyObject* 指標表示的 Python 物件，擴充功能會顯示該物件的型別和值。

正在開發 CPython 擴充功能或修補用 C 編寫之 CPython 部分的開發人員可以使用本文件來學習如何將 python-gdb.py 擴充功能與 GDB 一起使用。

備註

本文件假設你熟悉 GDB 和 CPython C API 的基礎知識。它整合了 devguide [https://devguide.python.org] 和 Python wiki [https://wiki.python.org/moin/DebuggingWithGdb] 的指引。

先決條件

你需要有：

GDB 7 或更之後的版本。（對於早期版本的 GDB，請參閱 Python 3.11 或更早版本的原始程式碼中的 Misc/gdbinit。）

對 Python 和你在偵錯的任何擴充功能來說的與 GDB 相容的偵錯資訊。

python-gdb.py 擴充。

該擴充功能是用 Python 建置的，但可能會單獨發布或根本不發布。以下我們將一些常見系統的提示作為範例。請注意，即使說明與你的系統匹配，它們也可能已過時。

使用從原始碼建置的 Python 進行設定

當你從原始程式碼建立 CPython 時，偵錯資訊應該可用，並且建置應該將 python-gdb.py 檔案新增至儲存庫的根目錄中。

若要啟用支援，你必須將包含 python-gdb.py 的目錄新增至 GDB 的 "auto-load-safe-path"。如果你還沒有這樣做，最新版本的 GDB 將列印警告，其中包含有關如何執行此操作的說明。

備註

如果你沒有看到適合你的 GDB 版本的說明，請將其放入你的設定檔中（~/.gdbinit 或 ~/.config/gdb/gdbinit）：

add-auto-load-safe-path /path/to/cpython

你也可以新增多個路徑，要以 : 分隔。

從 Linux 發行版設定 Python

大多數 Linux 系統在名為 python-debuginfo、python-dbg 或類似的套件中提供系統 Python 的偵錯資訊。例如：

Fedora：

sudo dnf install gdb
sudo dnf debuginfo-install python3

Ubuntu：

sudo apt install gdb python3-dbg

在最近的幾個 Linux 系統上，GDB 可以使用 debuginfod 自動下載偵錯符號。但是這不會安裝 python-gdb.py 擴充功能；你通常需要另外安裝偵錯資訊套件。

使用偵錯建置與使用開發模式

為了更輕鬆地進行偵錯，你可能需要：

使用 Python 的偵錯建置。（從原始碼建置時，請使用 configure --with-pydebug。在 Linux 發行版上，安裝並執行諸如 python-debug 或 python-dbg 之類的套件（如果可用））。

使用 runtime 開發模式 (-X dev)。

兩者都啟用額外的斷言 (assertion) 並停用一些最佳化。有時這會隱藏你試圖想尋找的錯誤，但在大多數情況下，它們會使過程變得更容易。

使用 python-gdb 擴充功能

載入擴充功能後，它提供兩個主要功能：Python 值的漂亮列印器和附加命令。

漂亮列印器

這是啟用此擴充功能時 GDB 回溯 (backtrace) 的樣子（有被截斷）：

#0  0x000000000041a6b1 in PyObject_Malloc (nbytes=Cannot access memory at address 0x7fffff7fefe8
) at Objects/obmalloc.c:748
#1  0x000000000041b7c0 in _PyObject_DebugMallocApi (id=111 'o', nbytes=24) at Objects/obmalloc.c:1445
#2  0x000000000041b717 in _PyObject_DebugMalloc (nbytes=24) at Objects/obmalloc.c:1412
#3  0x000000000044060a in _PyUnicode_New (length=11) at Objects/unicodeobject.c:346
#4  0x00000000004466aa in PyUnicodeUCS2_DecodeUTF8Stateful (s=0x5c2b8d "__lltrace__", size=11, errors=0x0, consumed=
    0x0) at Objects/unicodeobject.c:2531
#5  0x0000000000446647 in PyUnicodeUCS2_DecodeUTF8 (s=0x5c2b8d "__lltrace__", size=11, errors=0x0)
    at Objects/unicodeobject.c:2495
#6  0x0000000000440d1b in PyUnicodeUCS2_FromStringAndSize (u=0x5c2b8d "__lltrace__", size=11)
    at Objects/unicodeobject.c:551
#7  0x0000000000440d94 in PyUnicodeUCS2_FromString (u=0x5c2b8d "__lltrace__") at Objects/unicodeobject.c:569
#8  0x0000000000584abd in PyDict_GetItemString (v=
    {'Yuck': <type at remote 0xad4730>, '__builtins__': <module at remote 0x7ffff7fd5ee8>, '__file__': 'Lib/test/crashers/nasty_eq_vs_dict.py', '__package__': None, 'y': <Yuck(i=0) at remote 0xaacd80>, 'dict': {0: 0, 1: 1, 2: 2, 3: 3}, '__cached__': None, '__name__': '__main__', 'z': <Yuck(i=0) at remote 0xaace60>, '__doc__': None}, key=
    0x5c2b8d "__lltrace__") at Objects/dictobject.c:2171

請注意 PyDict_GetItemString 的字典引數如何顯示為其 repr()，而不是不透明的 PyObject * 指標。

該擴充功能透過為 PyObject * 型別的值提供自訂列印例程來運作。如果需要存取物件較低階的詳細資訊，請將值轉換為適當型別的指標。例如：

(gdb) p globals
$1 = {'__builtins__': <module at remote 0x7ffff7fb1868>, '__name__':
'__main__', 'ctypes': <module at remote 0x7ffff7f14360>, '__doc__': None,
'__package__': None}

(gdb) p *(PyDictObject*)globals
$2 = {ob_refcnt = 3, ob_type = 0x3dbdf85820, ma_fill = 5, ma_used = 5,
ma_mask = 7, ma_table = 0x63d0f8, ma_lookup = 0x3dbdc7ea70
<lookdict_string>, ma_smalltable = {{me_hash = 7065186196740147912,
me_key = '__builtins__', me_value = <module at remote 0x7ffff7fb1868>},
{me_hash = -368181376027291943, me_key = '__name__',
me_value ='__main__'}, {me_hash = 0, me_key = 0x0, me_value = 0x0},
{me_hash = 0, me_key = 0x0, me_value = 0x0},
{me_hash = -9177857982131165996, me_key = 'ctypes',
me_value = <module at remote 0x7ffff7f14360>},
{me_hash = -8518757509529533123, me_key = '__doc__', me_value = None},
{me_hash = 0, me_key = 0x0, me_value = 0x0}, {
  me_hash = 6614918939584953775, me_key = '__package__', me_value = None}}}

請注意，漂亮列印器其實並不呼叫 repr()。對於基本型別，他們嘗試緊密匹配其結果。

一個可能令人困惑的地方是，某些型別的自訂列印器看起來很像 GDB 標準類型的內建列印器。例如，Python int (PyLongObject*) 的漂亮列印器給出的表示法無法與常規機器層級整數之其一區分：

(gdb) p some_machine_integer
$3 = 42

(gdb) p some_python_integer
$4 = 42

可以透過轉換 (cast) 為 PyLongObject* 來揭示內部結構：

(gdb) p *(PyLongObject*)some_python_integer
$5 = {ob_base = {ob_base = {ob_refcnt = 8, ob_type = 0x3dad39f5e0}, ob_size = 1},
ob_digit = {42}}

使用 str 型別時也可能會出現類似的困惑，其中的輸出看起來很像對於 char * 的 gdb 內建列印器 ：

(gdb) p ptr_to_python_str
$6 = '__builtins__'

str 實例的漂亮列印器預設使用單引號（Python 的 repr 對於字串也是如此），而 char * 值的標準列印器使用雙引號並包含十六進位位址：

(gdb) p ptr_to_char_star
$7 = 0x6d72c0 "hello world"

同樣，可以透過轉換為 PyUnicodeObject* 來揭示實作細節：

(gdb) p *(PyUnicodeObject*)$6
$8 = {ob_base = {ob_refcnt = 33, ob_type = 0x3dad3a95a0}, length = 12,
str = 0x7ffff2128500, hash = 7065186196740147912, state = 1, defenc = 0x0}

py-list

該擴充功能新增了一個 py-list 命令，該命令列出了所選執行緒中目前 frame 的 Python 原始程式碼（如果有）。目前的列會標有 ">"：

(gdb) py-list
 901        if options.profile:
 902            options.profile = False
 903            profile_me()
 904            return
 905
>906        u = UI()
 907        if not u.quit:
 908            try:
 909                gtk.main()
 910            except KeyboardInterrupt:
 911                # properly quit on a keyboard interrupt...

使用 py-list START 列出 Python 原始碼中不同的列號，使用 py-list START,END 列出 Python 原始碼中特定範圍的列。

py-up 和 py-down

py-up 和 py-down 命令類似於 GDB 的常規 up 和 down 命令，但嘗試在 CPython frame 層級移動，而不是 C frame。

GDB 並不總是能夠讀取相關的 frame 資訊，這取決於編譯 CPython 的最佳化等級。在內部，這些指令會尋找正在執行預設 frame 計算 (evaluation) 函式（即 CPython 中迴圈的核心位元組碼直譯器）的 C frame，並尋找相關 PyFrameObject * 的值。

它們在執行緒內發出（於 C 層級的）frame 編號。

例如：

(gdb) py-up
#37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/
gnome_sudoku/main.py, line 906, in start_game ()
    u = UI()
(gdb) py-up
#40 Frame 0x948e82c, for file /usr/lib/python2.6/site-packages/
gnome_sudoku/gnome_sudoku.py, line 22, in start_game(main=<module at remote 0xb771b7f4>)
    main.start_game()
(gdb) py-up
Unable to find an older python frame

所以現在我們處於 Python 堆疊的頂端。

frame 編號與 GDB 標準 backtrace 指令顯示的 frame 編號相對應。此指令會跳過不執行 Python 程式碼的 C frame。

回到下面：

(gdb) py-down
#37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/gnome_sudoku/main.py, line 906, in start_game ()
    u = UI()
(gdb) py-down
#34 (unable to read python frame information)
(gdb) py-down
#23 (unable to read python frame information)
(gdb) py-down
#19 (unable to read python frame information)
(gdb) py-down
#14 Frame 0x99262ac, for file /usr/lib/python2.6/site-packages/gnome_sudoku/game_selector.py, line 201, in run_swallowed_dialog (self=<NewOrSavedGameSelector(new_game_model=<gtk.ListStore at remote 0x98fab44>, puzzle=None, saved_games=[{'gsd.auto_fills': 0, 'tracking': {}, 'trackers': {}, 'notes': [], 'saved_at': 1270084485, 'game': '7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5\n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5', 'gsd.impossible_hints': 0, 'timer.__absolute_start_time__': <float at remote 0x984b474>, 'gsd.hints': 0, 'timer.active_time': <float at remote 0x984b494>, 'timer.total_time': <float at remote 0x984b464>}], dialog=<gtk.Dialog at remote 0x98faaa4>, saved_game_model=<gtk.ListStore at remote 0x98fad24>, sudoku_maker=<SudokuMaker(terminated=False, played=[], batch_siz...(truncated)
            swallower.run_dialog(self.dialog)
(gdb) py-down
#11 Frame 0x9aead74, for file /usr/lib/python2.6/site-packages/gnome_sudoku/dialog_swallower.py, line 48, in run_dialog (self=<SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>, main_page=0) at remote 0x98fa6e4>, d=<gtk.Dialog at remote 0x98faaa4>)
            gtk.main()
(gdb) py-down
#8 (unable to read python frame information)
(gdb) py-down
Unable to find a newer python frame

我們現在處於 Python 堆疊的底部。

請注意，在 Python 3.12 及更高版本中，同一個 C 堆疊 frame 可用於多個 Python 堆疊 frame。這意味著 py-up 和 py-down 可以一次移動多個 Python frame。例如：

(gdb) py-up
#6 Frame 0x7ffff7fb62b0, for file /tmp/rec.py, line 5, in recursive_function (n=0)
   time.sleep(5)
#6 Frame 0x7ffff7fb6240, for file /tmp/rec.py, line 7, in recursive_function (n=1)
   recursive_function(n-1)
#6 Frame 0x7ffff7fb61d0, for file /tmp/rec.py, line 7, in recursive_function (n=2)
   recursive_function(n-1)
#6 Frame 0x7ffff7fb6160, for file /tmp/rec.py, line 7, in recursive_function (n=3)
   recursive_function(n-1)
#6 Frame 0x7ffff7fb60f0, for file /tmp/rec.py, line 7, in recursive_function (n=4)
   recursive_function(n-1)
#6 Frame 0x7ffff7fb6080, for file /tmp/rec.py, line 7, in recursive_function (n=5)
   recursive_function(n-1)
#6 Frame 0x7ffff7fb6020, for file /tmp/rec.py, line 9, in <module> ()
   recursive_function(5)
(gdb) py-up
Unable to find an older python frame

py-bt

py-bt 指令嘗試顯示目前執行緒的 Python 層級回溯。

例如：

(gdb) py-bt
#8 (unable to read python frame information)
#11 Frame 0x9aead74, for file /usr/lib/python2.6/site-packages/gnome_sudoku/dialog_swallower.py, line 48, in run_dialog (self=<SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>, main_page=0) at remote 0x98fa6e4>, d=<gtk.Dialog at remote 0x98faaa4>)
            gtk.main()
#14 Frame 0x99262ac, for file /usr/lib/python2.6/site-packages/gnome_sudoku/game_selector.py, line 201, in run_swallowed_dialog (self=<NewOrSavedGameSelector(new_game_model=<gtk.ListStore at remote 0x98fab44>, puzzle=None, saved_games=[{'gsd.auto_fills': 0, 'tracking': {}, 'trackers': {}, 'notes': [], 'saved_at': 1270084485, 'game': '7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5\n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5', 'gsd.impossible_hints': 0, 'timer.__absolute_start_time__': <float at remote 0x984b474>, 'gsd.hints': 0, 'timer.active_time': <float at remote 0x984b494>, 'timer.total_time': <float at remote 0x984b464>}], dialog=<gtk.Dialog at remote 0x98faaa4>, saved_game_model=<gtk.ListStore at remote 0x98fad24>, sudoku_maker=<SudokuMaker(terminated=False, played=[], batch_siz...(truncated)
            swallower.run_dialog(self.dialog)
#19 (unable to read python frame information)
#23 (unable to read python frame information)
#34 (unable to read python frame information)
#37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/gnome_sudoku/main.py, line 906, in start_game ()
    u = UI()
#40 Frame 0x948e82c, for file /usr/lib/python2.6/site-packages/gnome_sudoku/gnome_sudoku.py, line 22, in start_game (main=<module at remote 0xb771b7f4>)
    main.start_game()

The frame numbers correspond to those displayed by GDB's standard backtrace command.

py-print

py-print 命令查找 Python 名稱並嘗試列印它。它在目前執行緒中尋找局部變數，然後是全域變數，最後是內建變數：

(gdb) py-print self
local 'self' = <SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>,
main_page=0) at remote 0x98fa6e4>
(gdb) py-print __name__
global '__name__' = 'gnome_sudoku.dialog_swallower'
(gdb) py-print len
builtin 'len' = <built-in function len>
(gdb) py-print scarlet_pimpernel
'scarlet_pimpernel' not found

如果目前 C frame 對應多個 Python frame，則 py-print 僅考慮第一個。

py-locals

py-locals 命令尋找所選執行緒中目前 Python frame 內的所有 Python 局部變數，並列印它們的表示：

(gdb) py-locals
self = <SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>,
main_page=0) at remote 0x98fa6e4>
d = <gtk.Dialog at remote 0x98faaa4>

如果目前 C frame 對應於多個 Python frame，則會顯示所有這些 frame 的局部變數：

(gdb) py-locals
Locals for recursive_function
n = 0
Locals for recursive_function
n = 1
Locals for recursive_function
n = 2
Locals for recursive_function
n = 3
Locals for recursive_function
n = 4
Locals for recursive_function
n = 5
Locals for <module>

與 GDB 指令一起使用

擴充命令補充了 GDB 的內建命令。例如，你可以將 py-bt 顯示的 frame 編號與 frame 命令一同使用來跳到所選執行緒中的特定 frame，如下所示：

(gdb) py-bt
(output snipped)
#68 Frame 0xaa4560, for file Lib/test/regrtest.py, line 1548, in <module> ()
        main()
(gdb) frame 68
#68 0x00000000004cd1e6 in PyEval_EvalFrameEx (f=Frame 0xaa4560, for file Lib/test/regrtest.py, line 1548, in <module> (), throwflag=0) at Python/ceval.c:2665
2665                            x = call_function(&sp, oparg);
(gdb) py-list
1543        # 在暫時改變 CWD 到一個臨時且可寫入的目錄的
1544        # 情境管理器中運行測試。
1545        # 如果無法建立或更改 CWD，則使用原始的 CWD。
1546        # 原始 CWD 可從 test_support.SAVEDCWD 獲得。
1547        with test_support.temp_cwd(TESTCWD, quiet=True):
>1548            main()

info threads 命令將為你提供行程內的執行緒串列，你可以使用 thread 命令選擇不同的執行緒：

(gdb) info threads
  105 Thread 0x7fffefa18710 (LWP 10260)  sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
  104 Thread 0x7fffdf5fe710 (LWP 10259)  sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
* 1 Thread 0x7ffff7fe2700 (LWP 10145)  0x00000038e46d73e3 in select () at ../sysdeps/unix/syscall-template.S:82

你可以使用 thread apply all COMMAND（或簡短地用 t a a COMMAND）在所有執行緒上執行命令。使用 py-bt 你可以看到每個執行緒在 Python 層級正在做什麼：

(gdb) t a a py-bt

Thread 105 (Thread 0x7fffefa18710 (LWP 10260)):
#5 Frame 0x7fffd00019d0, for file /home/david/coding/python-svn/Lib/threading.py, line 155, in _acquire_restore (self=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, count_owner=(1, 140737213728528), count=1, owner=140737213728528)
        self.__block.acquire()
#8 Frame 0x7fffac001640, for file /home/david/coding/python-svn/Lib/threading.py, line 269, in wait (self=<_Condition(_Condition__lock=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, acquire=<instancemethod at remote 0xd80260>, _is_owned=<instancemethod at remote 0xd80160>, _release_save=<instancemethod at remote 0xd803e0>, release=<instancemethod at remote 0xd802e0>, _acquire_restore=<instancemethod at remote 0xd7ee60>, _Verbose__verbose=False, _Condition__waiters=[]) at remote 0xd7fd10>, timeout=None, waiter=<thread.lock at remote 0x858a90>, saved_state=(1, 140737213728528))
            self._acquire_restore(saved_state)
#12 Frame 0x7fffb8001a10, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 348, in f ()
            cond.wait()
#16 Frame 0x7fffb8001c40, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 37, in task (tid=140737213728528)
                f()

Thread 104 (Thread 0x7fffdf5fe710 (LWP 10259)):
#5 Frame 0x7fffe4001580, for file /home/david/coding/python-svn/Lib/threading.py, line 155, in _acquire_restore (self=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, count_owner=(1, 140736940992272), count=1, owner=140736940992272)
        self.__block.acquire()
#8 Frame 0x7fffc8002090, for file /home/david/coding/python-svn/Lib/threading.py, line 269, in wait (self=<_Condition(_Condition__lock=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, acquire=<instancemethod at remote 0xd80260>, _is_owned=<instancemethod at remote 0xd80160>, _release_save=<instancemethod at remote 0xd803e0>, release=<instancemethod at remote 0xd802e0>, _acquire_restore=<instancemethod at remote 0xd7ee60>, _Verbose__verbose=False, _Condition__waiters=[]) at remote 0xd7fd10>, timeout=None, waiter=<thread.lock at remote 0x858860>, saved_state=(1, 140736940992272))
            self._acquire_restore(saved_state)
#12 Frame 0x7fffac001c90, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 348, in f ()
            cond.wait()
#16 Frame 0x7fffac0011c0, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 37, in task (tid=140736940992272)
                f()

Thread 1 (Thread 0x7ffff7fe2700 (LWP 10145)):
#5 Frame 0xcb5380, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 16, in _wait ()
    time.sleep(0.01)
#8 Frame 0x7fffd00024a0, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 378, in _check_notify (self=<ConditionTests(_testMethodName='test_notify', _resultForDoCleanups=<TestResult(_original_stdout=<cStringIO.StringO at remote 0xc191e0>, skipped=[], _mirrorOutput=False, testsRun=39, buffer=False, _original_stderr=<file at remote 0x7ffff7fc6340>, _stdout_buffer=<cStringIO.StringO at remote 0xc9c7f8>, _stderr_buffer=<cStringIO.StringO at remote 0xc9c790>, _moduleSetUpFailed=False, expectedFailures=[], errors=[], _previousTestClass=<type at remote 0x928310>, unexpectedSuccesses=[], failures=[], shouldStop=False, failfast=False) at remote 0xc185a0>, _threads=(0,), _cleanups=[], _type_equality_funcs={<type at remote 0x7eba00>: <instancemethod at remote 0xd750e0>, <type at remote 0x7e7820>: <instancemethod at remote 0xd75160>, <type at remote 0x7e30e0>: <instancemethod at remote 0xd75060>, <type at remote 0x7e7d20>: <instancemethod at remote 0xd751e0>, <type at remote 0x7f19e0...(truncated)
        _wait()

Enum HOWTO

An Enum is a set of symbolic names bound to unique values. They are similar to global variables, but they offer a more useful repr(), grouping, type-safety, and a few other features.

They are most useful when you have a variable that can take one of a limited selection of values. For example, the days of the week:

>>> from enum import Enum
>>> class Weekday(Enum):
...     MONDAY = 1
...     TUESDAY = 2
...     WEDNESDAY = 3
...     THURSDAY = 4
...     FRIDAY = 5
...     SATURDAY = 6
...     SUNDAY = 7

Or perhaps the RGB primary colors:

>>> from enum import Enum
>>> class Color(Enum):
...     RED = 1
...     GREEN = 2
...     BLUE = 3

As you can see, creating an Enum is as simple as writing a class that inherits from Enum itself.

備註

Case of Enum Members

Because Enums are used to represent constants, and to help avoid issues with name clashes between mixin-class methods/attributes and enum names, we strongly recommend using UPPER_CASE names for members, and will be using that style in our examples.

Depending on the nature of the enum a member's value may or may not be important, but either way that value can be used to get the corresponding member:

>>> Weekday(3)
<Weekday.WEDNESDAY: 3>

As you can see, the repr() of a member shows the enum name, the member name, and the value. The str() of a member shows only the enum name and member name:

>>> print(Weekday.THURSDAY)
Weekday.THURSDAY

The type of an enumeration member is the enum it belongs to:

>>> type(Weekday.MONDAY)
<enum 'Weekday'>
>>> isinstance(Weekday.FRIDAY, Weekday)
True>>> type(Weekday.MONDAY)
<enum 'Weekday'>
>>> isinstance(Weekday.FRIDAY, Weekday)
True

Enum members have an attribute that contains just their name:

>>> print(Weekday.TUESDAY.name)
TUESDAY

Likewise, they have an attribute for their value:

>>> Weekday.WEDNESDAY.value
3

Unlike many languages that treat enumerations solely as name/value pairs, Python Enums can have behavior added. For example, datetime.date has two methods for returning the weekday: weekday() and isoweekday(). The difference is that one of them counts from 0-6 and the other from 1-7. Rather than keep track of that ourselves we can add a method to the Weekday enum to extract the day from the date instance and return the matching enum member:

@classmethod
def from_date(cls, date):
    return cls(date.isoweekday())

The complete Weekday enum now looks like this:

>>> class Weekday(Enum):
...     MONDAY = 1
...     TUESDAY = 2
...     WEDNESDAY = 3
...     THURSDAY = 4
...     FRIDAY = 5
...     SATURDAY = 6
...     SUNDAY = 7
...     #
...     @classmethod
...     def from_date(cls, date):
...         return cls(date.isoweekday())

Now we can find out what today is! Observe:

>>> from datetime import date
>>> Weekday.from_date(date.today())
<Weekday.TUESDAY: 2>

Of course, if you're reading this on some other day, you'll see that day instead.

This Weekday enum is great if our variable only needs one day, but what if we need several? Maybe we're writing a function to plot chores during a week, and don't want to use a list -- we could use a different type of Enum:

>>> from enum import Flag
>>> class Weekday(Flag):
...     MONDAY = 1
...     TUESDAY = 2
...     WEDNESDAY = 4
...     THURSDAY = 8
...     FRIDAY = 16
...     SATURDAY = 32
...     SUNDAY = 64

We've changed two things: we're inherited from Flag, and the values are all powers of 2.

Just like the original Weekday enum above, we can have a single selection:

>>> first_week_day = Weekday.MONDAY
>>> first_week_day
<Weekday.MONDAY: 1>

But Flag also allows us to combine several members into a single variable:

>>> weekend = Weekday.SATURDAY | Weekday.SUNDAY
>>> weekend
<Weekday.SATURDAY|SUNDAY: 96>

You can even iterate over a Flag variable:

>>> for day in weekend:
...     print(day)
Weekday.SATURDAY
Weekday.SUNDAY

Okay, let's get some chores set up:

>>> chores_for_ethan = {
...     'feed the cat': Weekday.MONDAY | Weekday.WEDNESDAY | Weekday.FRIDAY,
...     'do the dishes': Weekday.TUESDAY | Weekday.THURSDAY,
...     'answer SO questions': Weekday.SATURDAY,
...     }

And a function to display the chores for a given day:

>>> def show_chores(chores, day):
...     for chore, days in chores.items():
...         if day in days:
...             print(chore)
...
>>> show_chores(chores_for_ethan, Weekday.SATURDAY)
answer SO questions

In cases where the actual values of the members do not matter, you can save yourself some work and use auto() for the values:

>>> from enum import auto
>>> class Weekday(Flag):
...     MONDAY = auto()
...     TUESDAY = auto()
...     WEDNESDAY = auto()
...     THURSDAY = auto()
...     FRIDAY = auto()
...     SATURDAY = auto()
...     SUNDAY = auto()
...     WEEKEND = SATURDAY | SUNDAY

Programmatic access to enumeration members and their attributes

Sometimes it's useful to access members in enumerations programmatically (i.e. situations where Color.RED won't do because the exact color is not known at program-writing time). Enum allows such access:

>>> Color(1)
<Color.RED: 1>
>>> Color(3)
<Color.BLUE: 3>

If you want to access enum members by name, use item access:

>>> Color['RED']
<Color.RED: 1>
>>> Color['GREEN']
<Color.GREEN: 2>

If you have an enum member and need its name or value:

>>> member = Color.RED
>>> member.name
'RED'
>>> member.value
1

Duplicating enum members and values

Having two enum members with the same name is invalid:

>>> class Shape(Enum):
...     SQUARE = 2
...     SQUARE = 3
...
Traceback (most recent call last):
...
TypeError: 'SQUARE' already defined as 2

However, an enum member can have other names associated with it. Given two entries A and B with the same value (and A defined first), B is an alias for the member A. By-value lookup of the value of A will return the member A. By-name lookup of A will return the member A. By-name lookup of B will also return the member A:

>>> class Shape(Enum):
...     SQUARE = 2
...     DIAMOND = 1
...     CIRCLE = 3
...     ALIAS_FOR_SQUARE = 2
...
>>> Shape.SQUARE
<Shape.SQUARE: 2>
>>> Shape.ALIAS_FOR_SQUARE
<Shape.SQUARE: 2>
>>> Shape(2)
<Shape.SQUARE: 2>

備註

Attempting to create a member with the same name as an already defined attribute (another member, a method, etc.) or attempting to create an attribute with the same name as a member is not allowed.

Ensuring unique enumeration values

By default, enumerations allow multiple names as aliases for the same value. When this behavior isn't desired, you can use the unique() decorator:

>>> from enum import Enum, unique
>>> @unique
... class Mistake(Enum):
...     ONE = 1
...     TWO = 2
...     THREE = 3
...     FOUR = 3
...
Traceback (most recent call last):
...
ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE

Using automatic values

If the exact value is unimportant you can use auto:

>>> from enum import Enum, auto
>>> class Color(Enum):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> [member.value for member in Color]
[1, 2, 3]

The values are chosen by _generate_next_value_(), which can be overridden:

>>> class AutoName(Enum):
...     @staticmethod
...     def _generate_next_value_(name, start, count, last_values):
...         return name
...
>>> class Ordinal(AutoName):
...     NORTH = auto()
...     SOUTH = auto()
...     EAST = auto()
...     WEST = auto()
...
>>> [member.value for member in Ordinal]
['NORTH', 'SOUTH', 'EAST', 'WEST']

備註

The _generate_next_value_() method must be defined before any members.

Iteration

Iterating over the members of an enum does not provide the aliases:

>>> list(Shape)
[<Shape.SQUARE: 2>, <Shape.DIAMOND: 1>, <Shape.CIRCLE: 3>]
>>> list(Weekday)
[<Weekday.MONDAY: 1>, <Weekday.TUESDAY: 2>, <Weekday.WEDNESDAY: 4>, <Weekday.THURSDAY: 8>, <Weekday.FRIDAY: 16>, <Weekday.SATURDAY: 32>, <Weekday.SUNDAY: 64>]

Note that the aliases Shape.ALIAS_FOR_SQUARE and Weekday.WEEKEND aren't shown.

The special attribute __members__ is a read-only ordered mapping of names to members. It includes all names defined in the enumeration, including the aliases:

>>> for name, member in Shape.__members__.items():
...     name, member
...
('SQUARE', <Shape.SQUARE: 2>)
('DIAMOND', <Shape.DIAMOND: 1>)
('CIRCLE', <Shape.CIRCLE: 3>)
('ALIAS_FOR_SQUARE', <Shape.SQUARE: 2>)

The __members__ attribute can be used for detailed programmatic access to the enumeration members. For example, finding all the aliases:

>>> [name for name, member in Shape.__members__.items() if member.name != name]
['ALIAS_FOR_SQUARE']

備註

Aliases for flags include values with multiple flags set, such as 3, and no flags set, i.e. 0.

比較

Enumeration members are compared by identity:

>>> Color.RED is Color.RED
True
>>> Color.RED is Color.BLUE
False
>>> Color.RED is not Color.BLUE
True

Ordered comparisons between enumeration values are not supported. Enum members are not integers (but see IntEnum below):

>>> Color.RED < Color.BLUE
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '<' not supported between instances of 'Color' and 'Color'

Equality comparisons are defined though:

>>> Color.BLUE == Color.RED
False
>>> Color.BLUE != Color.RED
True
>>> Color.BLUE == Color.BLUE
True

Comparisons against non-enumeration values will always compare not equal (again, IntEnum was explicitly designed to behave differently, see below):

>>> Color.BLUE == 2
False

警告

It is possible to reload modules -- if a reloaded module contains enums, they will be recreated, and the new members may not compare identical/equal to the original members.

Allowed members and attributes of enumerations

Most of the examples above use integers for enumeration values. Using integers is short and handy (and provided by default by the Functional API), but not strictly enforced. In the vast majority of use-cases, one doesn't care what the actual value of an enumeration is. But if the value is important, enumerations can have arbitrary values.

Enumerations are Python classes, and can have methods and special methods as usual. If we have this enumeration:

>>> class Mood(Enum):
...     FUNKY = 1
...     HAPPY = 3
...
...     def describe(self):
...         # self is the member here
...         return self.name, self.value
...
...     def __str__(self):
...         return 'my custom str! {0}'.format(self.value)
...
...     @classmethod
...     def favorite_mood(cls):
...         # cls here is the enumeration
...         return cls.HAPPY
...

然後：

>>> Mood.favorite_mood()
<Mood.HAPPY: 3>
>>> Mood.HAPPY.describe()
('HAPPY', 3)
>>> str(Mood.FUNKY)
'my custom str! 1'

The rules for what is allowed are as follows: names that start and end with a single underscore are reserved by enum and cannot be used; all other attributes defined within an enumeration will become members of this enumeration, with the exception of special methods (__str__(), __add__(), etc.), descriptors (methods are also descriptors), and variable names listed in _ignore_.

Note: if your enumeration defines __new__() and/or __init__(), any value(s) given to the enum member will be passed into those methods. See Planet for an example.

備註

The __new__() method, if defined, is used during creation of the Enum members; it is then replaced by Enum's __new__() which is used after class creation for lookup of existing members. See When to use __new__() vs. __init__() for more details.

Restricted Enum subclassing

A new Enum class must have one base enum class, up to one concrete data type, and as many object-based mixin classes as needed. The order of these base classes is:

class EnumName([mix-in, ...,] [data-type,] base-enum):
    pass

Also, subclassing an enumeration is allowed only if the enumeration does not define any members. So this is forbidden:

>>> class MoreColor(Color):
...     PINK = 17
...
Traceback (most recent call last):
...
TypeError: <enum 'MoreColor'> cannot extend <enum 'Color'>

但這是允許的：

>>> class Foo(Enum):
...     def some_behavior(self):
...         pass
...
>>> class Bar(Foo):
...     HAPPY = 1
...     SAD = 2
...

Allowing subclassing of enums that define members would lead to a violation of some important invariants of types and instances. On the other hand, it makes sense to allow sharing some common behavior between a group of enumerations. (See OrderedEnum for an example.)

Dataclass support

When inheriting from a dataclass, the __repr__() omits the inherited class' name. For example:

>>> from dataclasses import dataclass, field
>>> @dataclass
... class CreatureDataMixin:
...     size: str
...     legs: int
...     tail: bool = field(repr=False, default=True)
...
>>> class Creature(CreatureDataMixin, Enum):
...     BEETLE = 'small', 6
...     DOG = 'medium', 4
...
>>> Creature.DOG
<Creature.DOG: size='medium', legs=4>

Use the dataclass() argument repr=False to use the standard repr().

在 3.12 版的變更: Only the dataclass fields are shown in the value area, not the dataclass' name.

備註

Adding dataclass() decorator to Enum and its subclasses is not supported. It will not raise any errors, but it will produce very strange results at runtime, such as members being equal to each other:

>>> @dataclass               # 不要這樣做，這並不合理
... class Color(Enum):
...    RED = 1
...    BLUE = 2
...
>>> Color.RED is Color.BLUE
False
>>> Color.RED == Color.BLUE  # 問題在此：它們不應該相等
True

Pickling

Enumerations can be pickled and unpickled:

>>> from test.test_enum import Fruit
>>> from pickle import dumps, loads
>>> Fruit.TOMATO is loads(dumps(Fruit.TOMATO))
True

The usual restrictions for pickling apply: picklable enums must be defined in the top level of a module, since unpickling requires them to be importable from that module.

備註

With pickle protocol version 4 it is possible to easily pickle enums nested in other classes.

It is possible to modify how enum members are pickled/unpickled by defining __reduce_ex__() in the enumeration class. The default method is by-value, but enums with complicated values may want to use by-name:

>>> import enum
>>> class MyEnum(enum.Enum):
...     __reduce_ex__ = enum.pickle_by_enum_name

備註

Using by-name for flags is not recommended, as unnamed aliases will not unpickle.

Functional API

The Enum class is callable, providing the following functional API:

>>> Animal = Enum('Animal', 'ANT BEE CAT DOG')
>>> Animal
<enum 'Animal'>
>>> Animal.ANT
<Animal.ANT: 1>
>>> list(Animal)
[<Animal.ANT: 1>, <Animal.BEE: 2>, <Animal.CAT: 3>, <Animal.DOG: 4>]

The semantics of this API resemble namedtuple. The first argument of the call to Enum is the name of the enumeration.

The second argument is the source of enumeration member names. It can be a whitespace-separated string of names, a sequence of names, a sequence of 2-tuples with key/value pairs, or a mapping (e.g. dictionary) of names to values. The last two options enable assigning arbitrary values to enumerations; the others auto-assign increasing integers starting with 1 (use the start parameter to specify a different starting value). A new class derived from Enum is returned. In other words, the above assignment to Animal is equivalent to:

>>> class Animal(Enum):
...     ANT = 1
...     BEE = 2
...     CAT = 3
...     DOG = 4
...

The reason for defaulting to 1 as the starting number and not 0 is that 0 is False in a boolean sense, but by default enum members all evaluate to True.

Pickling enums created with the functional API can be tricky as frame stack implementation details are used to try and figure out which module the enumeration is being created in (e.g. it will fail if you use a utility function in a separate module, and also may not work on IronPython or Jython). The solution is to specify the module name explicitly as follows:

>>> Animal = Enum('Animal', 'ANT BEE CAT DOG', module=__name__)

警告

If module is not supplied, and Enum cannot determine what it is, the new Enum members will not be unpicklable; to keep errors closer to the source, pickling will be disabled.

The new pickle protocol 4 also, in some circumstances, relies on __qualname__ being set to the location where pickle will be able to find the class. For example, if the class was made available in class SomeData in the global scope:

>>> Animal = Enum('Animal', 'ANT BEE CAT DOG', qualname='SomeData.Animal')

The complete signature is:

Enum(
    value='NewEnumName',
    names=<...>,
    *,
    module='...',
    qualname='...',
    type=<mixed-in class>,
    start=1,
    )

value: What the new enum class will record as its name.

names: The enum members. This can be a whitespace- or comma-separated string (values will start at 1 unless otherwise specified):

'RED GREEN BLUE' | 'RED,GREEN,BLUE' | 'RED, GREEN, BLUE'

or an iterator of names:

['RED', 'GREEN', 'BLUE']

or an iterator of (name, value) pairs:

[('CYAN', 4), ('MAGENTA', 5), ('YELLOW', 6)]

or a mapping:

{'CHARTREUSE': 7, 'SEA_GREEN': 11, 'ROSEMARY': 42}

module: name of module where new enum class can be found.

qualname: where in module new enum class can be found.

type: type to mix in to new enum class.

start: number to start counting at if only names are passed in.

在 3.5 版的變更: 新增 start 參數。

Derived Enumerations

IntEnum

The first variation of Enum that is provided is also a subclass of int. Members of an IntEnum can be compared to integers; by extension, integer enumerations of different types can also be compared to each other:

>>> from enum import IntEnum
>>> class Shape(IntEnum):
...     CIRCLE = 1
...     SQUARE = 2
...
>>> class Request(IntEnum):
...     POST = 1
...     GET = 2
...
>>> Shape == 1
False
>>> Shape.CIRCLE == 1
True
>>> Shape.CIRCLE == Request.POST
True

However, they still can't be compared to standard Enum enumerations:

>>> class Shape(IntEnum):
...     CIRCLE = 1
...     SQUARE = 2
...
>>> class Color(Enum):
...     RED = 1
...     GREEN = 2
...
>>> Shape.CIRCLE == Color.RED
False

IntEnum values behave like integers in other ways you'd expect:

>>> int(Shape.CIRCLE)
1
>>> ['a', 'b', 'c'][Shape.CIRCLE]
'b'
>>> [i for i in range(Shape.SQUARE)]
[0, 1]

StrEnum

The second variation of Enum that is provided is also a subclass of str. Members of a StrEnum can be compared to strings; by extension, string enumerations of different types can also be compared to each other.

在 3.11 版被加入.

IntFlag

The next variation of Enum provided, IntFlag, is also based on int. The difference being IntFlag members can be combined using the bitwise operators (&, |, ^, ~) and the result is still an IntFlag member, if possible. Like IntEnum, IntFlag members are also integers and can be used wherever an int is used.

備註

Any operation on an IntFlag member besides the bit-wise operations will lose the IntFlag membership.

Bit-wise operations that result in invalid IntFlag values will lose the IntFlag membership. See FlagBoundary for details.

在 3.6 版被加入.

在 3.11 版的變更.

Sample IntFlag class:

>>> from enum import IntFlag
>>> class Perm(IntFlag):
...     R = 4
...     W = 2
...     X = 1
...
>>> Perm.R | Perm.W
<Perm.R|W: 6>
>>> Perm.R + Perm.W
6
>>> RW = Perm.R | Perm.W
>>> Perm.R in RW
True

It is also possible to name the combinations:

>>> class Perm(IntFlag):
...     R = 4
...     W = 2
...     X = 1
...     RWX = 7
...
>>> Perm.RWX
<Perm.RWX: 7>
>>> ~Perm.RWX
<Perm: 0>
>>> Perm(7)
<Perm.RWX: 7>

備註

Named combinations are considered aliases. Aliases do not show up during iteration, but can be returned from by-value lookups.

在 3.11 版的變更.

Another important difference between IntFlag and Enum is that if no flags are set (the value is 0), its boolean evaluation is False:

>>> Perm.R & Perm.X
<Perm: 0>
>>> bool(Perm.R & Perm.X)
False

Because IntFlag members are also subclasses of int they can be combined with them (but may lose IntFlag membership:

>>> Perm.X | 4
<Perm.R|X: 5>

>>> Perm.X + 8
9

備註

The negation operator, ~, always returns an IntFlag member with a positive value:

>>> (~Perm.X).value == (Perm.R|Perm.W).value == 6
True

IntFlag 成員也可以被疊代：

>>> list(RW)
[<Perm.R: 4>, <Perm.W: 2>]

在 3.11 版被加入.

Flag

The last variation is Flag. Like IntFlag, Flag members can be combined using the bitwise operators (&, |, ^, ~). Unlike IntFlag, they cannot be combined with, nor compared against, any other Flag enumeration, nor int. While it is possible to specify the values directly it is recommended to use auto as the value and let Flag select an appropriate value.

在 3.6 版被加入.

Like IntFlag, if a combination of Flag members results in no flags being set, the boolean evaluation is False:

>>> from enum import Flag, auto
>>> class Color(Flag):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> Color.RED & Color.GREEN
<Color: 0>
>>> bool(Color.RED & Color.GREEN)
False

Individual flags should have values that are powers of two (1, 2, 4, 8, ...), while combinations of flags will not:

>>> class Color(Flag):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...     WHITE = RED | BLUE | GREEN
...
>>> Color.WHITE
<Color.WHITE: 7>

Giving a name to the "no flags set" condition does not change its boolean value:

>>> class Color(Flag):
...     BLACK = 0
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> Color.BLACK
<Color.BLACK: 0>
>>> bool(Color.BLACK)
False

Flag 成員也可以被疊代：

>>> purple = Color.RED | Color.BLUE
>>> list(purple)
[<Color.RED: 1>, <Color.BLUE: 2>]

在 3.11 版被加入.

備註

For the majority of new code, Enum and Flag are strongly recommended, since IntEnum and IntFlag break some semantic promises of an enumeration (by being comparable to integers, and thus by transitivity to other unrelated enumerations). IntEnum and IntFlag should be used only in cases where Enum and Flag will not do; for example, when integer constants are replaced with enumerations, or for interoperability with other systems.

其他

While IntEnum is part of the enum module, it would be very simple to implement independently:

class IntEnum(int, ReprEnum):   # 或用 Enum 取代 ReprEnum
    pass

This demonstrates how similar derived enumerations can be defined; for example a FloatEnum that mixes in float instead of int.

一些規則：

When subclassing Enum, mix-in types must appear before the Enum class itself in the sequence of bases, as in the IntEnum example above.

Mix-in types must be subclassable. For example, bool and range are not subclassable and will throw an error during Enum creation if used as the mix-in type.

While Enum can have members of any type, once you mix in an additional type, all the members must have values of that type, e.g. int above. This restriction does not apply to mix-ins which only add methods and don't specify another type.

When another data type is mixed in, the value attribute is not the same as the enum member itself, although it is equivalent and will compare equal.

A data type is a mixin that defines __new__(), or a dataclass

%-style formatting: %s and %r call the Enum class's __str__() and __repr__() respectively; other codes (such as %i or %h for IntEnum) treat the enum member as its mixed-in type.

Formatted string literals, str.format(), and format() will use the enum's __str__() method.

備註

Because IntEnum, IntFlag, and StrEnum are designed to be drop-in replacements for existing constants, their __str__() method has been reset to their data types' __str__() method.

When to use __new__() vs. __init__()

__new__() must be used whenever you want to customize the actual value of the Enum member. Any other modifications may go in either __new__() or __init__(), with __init__() being preferred.

For example, if you want to pass several items to the constructor, but only want one of them to be the value:

>>> class Coordinate(bytes, Enum):
...     """
...     Coordinate with binary codes that can be indexed by the int code.
...     """
...     def __new__(cls, value, label, unit):
...         obj = bytes.__new__(cls, [value])
...         obj._value_ = value
...         obj.label = label
...         obj.unit = unit
...         return obj
...     PX = (0, 'P.X', 'km')
...     PY = (1, 'P.Y', 'km')
...     VX = (2, 'V.X', 'km/s')
...     VY = (3, 'V.Y', 'km/s')
...

>>> print(Coordinate['PY'])
Coordinate.PY

>>> print(Coordinate(3))
Coordinate.VY

警告

Do not call super().__new__(), as the lookup-only __new__ is the one that is found; instead, use the data type directly.

Finer Points

有支援的 __dunder__ 名稱

__members__ is a read-only ordered mapping of member_name:member items. It is only available on the class.

__new__(), if specified, must create and return the enum members; it is also a very good idea to set the member's _value_ appropriately. Once all the members are created it is no longer used.

有支援的 _sunder_ 名稱

_name_ -- 成員的名稱

_value_ -- value of the member; can be set in __new__

_missing_() -- a lookup function used when a value is not found; may be overridden

_ignore_ -- a list of names, either as a list or a str, that will not be transformed into members, and will be removed from the final class

_generate_next_value_() -- used to get an appropriate value for an enum member; may be overridden

_add_alias_() -- adds a new name as an alias to an existing member.

_add_value_alias_() -- adds a new value as an alias to an existing member. See MultiValueEnum for an example.

備註

For standard Enum classes the next value chosen is the highest value seen incremented by one.

For Flag classes the next value chosen will be the next highest power-of-two.

在 3.13 版的變更: Prior versions would use the last seen value instead of the highest value.

在 3.6 版被加入: _missing_、_order_、_generate_next_value_

在 3.7 版被加入: _ignore_

在 3.13 版被加入: _add_alias_、_add_value_alias_

To help keep Python 2 / Python 3 code in sync an _order_ attribute can be provided. It will be checked against the actual order of the enumeration and raise an error if the two do not match:

>>> class Color(Enum):
...     _order_ = 'RED GREEN BLUE'
...     RED = 1
...     BLUE = 3
...     GREEN = 2
...
Traceback (most recent call last):
...
TypeError: member order does not match _order_:
  ['RED', 'BLUE', 'GREEN']
  ['RED', 'GREEN', 'BLUE']

備註

In Python 2 code the _order_ attribute is necessary as definition order is lost before it can be recorded.

_Private__names

Private names are not converted to enum members, but remain normal attributes.

在 3.11 版的變更.

Enum member type

Enum members are instances of their enum class, and are normally accessed as EnumClass.member. In certain situations, such as writing custom enum behavior, being able to access one member directly from another is useful, and is supported; however, in order to avoid name clashes between member names and attributes/methods from mixed-in classes, upper-case names are strongly recommended.

在 3.5 版的變更.

Creating members that are mixed with other data types

When subclassing other data types, such as int or str, with an Enum, all values after the = are passed to that data type's constructor. For example:

>>> class MyEnum(IntEnum):      # help(int) -> int(x, base=10) -> integer
...     example = '11', 16      # 所以 x='11' 且 base=16
...
>>> MyEnum.example.value        # 且 hex(11) 為...
17

Boolean value of Enum classes and members

Enum classes that are mixed with non-Enum types (such as int, str, etc.) are evaluated according to the mixed-in type's rules; otherwise, all members evaluate as True. To make your own enum's boolean evaluation depend on the member's value add the following to your class:

def __bool__(self):
    return bool(self.value)

Plain Enum classes always evaluate as True.

Enum classes with methods

If you give your enum subclass extra methods, like the Planet class below, those methods will show up in a dir() of the member, but not of the class:

>>> dir(Planet)
['EARTH', 'JUPITER', 'MARS', 'MERCURY', 'NEPTUNE', 'SATURN', 'URANUS', 'VENUS', '__class__', '__doc__', '__members__', '__module__']
>>> dir(Planet.EARTH)
['__class__', '__doc__', '__module__', 'mass', 'name', 'radius', 'surface_gravity', 'value']

Flag 的成員組合

Iterating over a combination of Flag members will only return the members that are comprised of a single bit:

>>> class Color(Flag):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...     MAGENTA = RED | BLUE
...     YELLOW = RED | GREEN
...     CYAN = GREEN | BLUE
...
>>> Color(3)  # named combination
<Color.YELLOW: 3>
>>> Color(7)      # not named combination
<Color.RED|GREEN|BLUE: 7>

Flag and IntFlag minutia

Using the following snippet for our examples:

>>> class Color(IntFlag):
...     BLACK = 0
...     RED = 1
...     GREEN = 2
...     BLUE = 4
...     PURPLE = RED | BLUE
...     WHITE = RED | GREEN | BLUE
...

the following are true:

single-bit flags are canonical

multi-bit and zero-bit flags are aliases

only canonical flags are returned during iteration:

>>> list(Color.WHITE)
[<Color.RED: 1>, <Color.GREEN: 2>, <Color.BLUE: 4>]

negating a flag or flag set returns a new flag/flag set with the corresponding positive integer value:

>>> Color.BLUE
<Color.BLUE: 4>

>>> ~Color.BLUE
<Color.RED|GREEN: 3>

names of pseudo-flags are constructed from their members' names:

>>> (Color.RED | Color.GREEN).name
'RED|GREEN'

>>> class Perm(IntFlag):
...     R = 4
...     W = 2
...     X = 1
...
>>> (Perm.R & Perm.W).name is None  # 效果為 Perm(0)
True

multi-bit flags, aka aliases, can be returned from operations:

>>> Color.RED | Color.BLUE
<Color.PURPLE: 5>

>>> Color(7)  # 或 Color(-1)
<Color.WHITE: 7>

>>> Color(0)
<Color.BLACK: 0>

membership / containment checking: zero-valued flags are always considered to be contained:

>>> Color.BLACK in Color.WHITE
True

otherwise, only if all bits of one flag are in the other flag will True be returned:

>>> Color.PURPLE in Color.WHITE
True

>>> Color.GREEN in Color.PURPLE
False

There is a new boundary mechanism that controls how out-of-range / invalid bits are handled: STRICT, CONFORM, EJECT, and KEEP:

STRICT --> 當遇到無效值時引發例外

CONFORM --> 捨棄任何無效位元

EJECT --> 失去 Flag 狀態並成為具有給定值的普通 int

KEEP --> 保留額外位元

保留 Flag 狀態和額外位元

extra bits do not show up in iteration

extra bits do show up in repr() and str()

The default for Flag is STRICT, the default for IntFlag is EJECT, and the default for _convert_ is KEEP (see ssl.Options for an example of when KEEP is needed).

Enums 和 Flags 有何不同？

Enums have a custom metaclass that affects many aspects of both derived Enum classes and their instances (members).

Enum 類別

The EnumType metaclass is responsible for providing the __contains__(), __dir__(), __iter__() and other methods that allow one to do things with an Enum class that fail on a typical class, such as list(Color) or some_enum_var in Color. EnumType is responsible for ensuring that various other methods on the final Enum class are correct (such as __new__(), __getnewargs__(), __str__() and __repr__()).

Flag 類別

Flags have an expanded view of aliasing: to be canonical, the value of a flag needs to be a power-of-two value, and not a duplicate name. So, in addition to the Enum definition of alias, a flag with no value (a.k.a. 0) or with more than one power-of-two value (e.g. 3) is considered an alias.

Enum Members (aka instances)

The most interesting thing about enum members is that they are singletons. EnumType creates them all while it is creating the enum class itself, and then puts a custom __new__() in place to ensure that no new ones are ever instantiated by returning only the existing member instances.

Flag 成員

Flag members can be iterated over just like the Flag class, and only the canonical members will be returned. For example:

>>> list(Color)
[<Color.RED: 1>, <Color.GREEN: 2>, <Color.BLUE: 4>]

(Note that BLACK, PURPLE, and WHITE do not show up.)

Inverting a flag member returns the corresponding positive value, rather than a negative value --- for example:

>>> ~Color.RED
<Color.GREEN|BLUE: 6>

Flag members have a length corresponding to the number of power-of-two values they contain. For example:

>>> len(Color.PURPLE)
2

Enum Cookbook

While Enum, IntEnum, StrEnum, Flag, and IntFlag are expected to cover the majority of use-cases, they cannot cover them all. Here are recipes for some different types of enumerations that can be used directly, or as examples for creating one's own.

省略值

In many use-cases, one doesn't care what the actual value of an enumeration is. There are several ways to define this type of simple enumeration:

use instances of auto for the value

use instances of object as the value

use a descriptive string as the value

use a tuple as the value and a custom __new__() to replace the tuple with an int value

Using any of these methods signifies to the user that these values are not important, and also enables one to add, remove, or reorder members without having to renumber the remaining members.

使用 auto

使用 auto 會像這樣：

>>> class Color(Enum):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> Color.GREEN
<Color.GREEN: 3>

使用 object

使用 object 會像這樣：

>>> class Color(Enum):
...     RED = object()
...     GREEN = object()
...     BLUE = object()
...
>>> Color.GREEN
<Color.GREEN: <object object at 0x...>>

This is also a good example of why you might want to write your own __repr__():

>>> class Color(Enum):
...     RED = object()
...     GREEN = object()
...     BLUE = object()
...     def __repr__(self):
...         return "<%s.%s>" % (self.__class__.__name__, self._name_)
...
>>> Color.GREEN
<Color.GREEN>

Using a descriptive string

Using a string as the value would look like:

>>> class Color(Enum):
...     RED = 'stop'
...     GREEN = 'go'
...     BLUE = 'too fast!'
...
>>> Color.GREEN
<Color.GREEN: 'go'>

使用自訂的 __new__()

Using an auto-numbering __new__() would look like:

>>> class AutoNumber(Enum):
...     def __new__(cls):
...         value = len(cls.__members__) + 1
...         obj = object.__new__(cls)
...         obj._value_ = value
...         return obj
...
>>> class Color(AutoNumber):
...     RED = ()
...     GREEN = ()
...     BLUE = ()
...
>>> Color.GREEN
<Color.GREEN: 2>

To make a more general purpose AutoNumber, add *args to the signature:

>>> class AutoNumber(Enum):
...     def __new__(cls, *args):      # 這是和上面相比唯一的變更
...         value = len(cls.__members__) + 1
...         obj = object.__new__(cls)
...         obj._value_ = value
...         return obj
...

Then when you inherit from AutoNumber you can write your own __init__ to handle any extra arguments:

>>> class Swatch(AutoNumber):
...     def __init__(self, pantone='unknown'):
...         self.pantone = pantone
...     AUBURN = '3497'
...     SEA_GREEN = '1246'
...     BLEACHED_CORAL = () # New color, no Pantone code yet!
...
>>> Swatch.SEA_GREEN
<Swatch.SEA_GREEN: 2>
>>> Swatch.SEA_GREEN.pantone
'1246'
>>> Swatch.BLEACHED_CORAL.pantone
'unknown'

備註

The __new__() method, if defined, is used during creation of the Enum members; it is then replaced by Enum's __new__() which is used after class creation for lookup of existing members.

警告

Do not call super().__new__(), as the lookup-only __new__ is the one that is found; instead, use the data type directly -- e.g.:

obj = int.__new__(cls, value)

OrderedEnum

An ordered enumeration that is not based on IntEnum and so maintains the normal Enum invariants (such as not being comparable to other enumerations):

>>> class OrderedEnum(Enum):
...     def __ge__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value >= other.value
...         return NotImplemented
...     def __gt__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value > other.value
...         return NotImplemented
...     def __le__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value <= other.value
...         return NotImplemented
...     def __lt__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value < other.value
...         return NotImplemented
...
>>> class Grade(OrderedEnum):
...     A = 5
...     B = 4
...     C = 3
...     D = 2
...     F = 1
...
>>> Grade.C < Grade.A
True

DuplicateFreeEnum

Raises an error if a duplicate member value is found instead of creating an alias:

>>> class DuplicateFreeEnum(Enum):
...     def __init__(self, *args):
...         cls = self.__class__
...         if any(self.value == e.value for e in cls):
...             a = self.name
...             e = cls(self.value).name
...             raise ValueError(
...                 "aliases not allowed in DuplicateFreeEnum:  %r --> %r"
...                 % (a, e))
...
>>> class Color(DuplicateFreeEnum):
...     RED = 1
...     GREEN = 2
...     BLUE = 3
...     GRENE = 2
...
Traceback (most recent call last):
  ...
ValueError: aliases not allowed in DuplicateFreeEnum:  'GRENE' --> 'GREEN'

備註

This is a useful example for subclassing Enum to add or change other behaviors as well as disallowing aliases. If the only desired change is disallowing aliases, the unique() decorator can be used instead.

MultiValueEnum

Supports having more than one value per member:

>>> class MultiValueEnum(Enum):
...     def __new__(cls, value, *values):
...         self = object.__new__(cls)
...         self._value_ = value
...         for v in values:
...             self._add_value_alias_(v)
...         return self
...
>>> class DType(MultiValueEnum):
...     float32 = 'f', 8
...     double64 = 'd', 9
...
>>> DType('f')
<DType.float32: 'f'>
>>> DType(9)
<DType.double64: 'd'>

Planet

If __new__() or __init__() is defined, the value of the enum member will be passed to those methods:

>>> class Planet(Enum):
...     MERCURY = (3.303e+23, 2.4397e6)
...     VENUS   = (4.869e+24, 6.0518e6)
...     EARTH   = (5.976e+24, 6.37814e6)
...     MARS    = (6.421e+23, 3.3972e6)
...     JUPITER = (1.9e+27,   7.1492e7)
...     SATURN  = (5.688e+26, 6.0268e7)
...     URANUS  = (8.686e+25, 2.5559e7)
...     NEPTUNE = (1.024e+26, 2.4746e7)
...     def __init__(self, mass, radius):
...         self.mass = mass       # 以公斤表示
...         self.radius = radius   # 以公尺表示
...     @property
...     def surface_gravity(self):
...         # 萬有引力常數  (m3 kg-1 s-2)
...         G = 6.67300E-11
...         return G * self.mass / (self.radius * self.radius)
...
>>> Planet.EARTH.value
(5.976e+24, 6378140.0)
>>> Planet.EARTH.surface_gravity
9.802652743337129

TimePeriod

An example to show the _ignore_ attribute in use:

>>> from datetime import timedelta
>>> class Period(timedelta, Enum):
...     "不同長度的時間"
...     _ignore_ = 'Period i'
...     Period = vars()
...     for i in range(367):
...         Period['day_%d' % i] = i
...
>>> list(Period)[:2]
[<Period.day_0: datetime.timedelta(0)>, <Period.day_1: datetime.timedelta(days=1)>]
>>> list(Period)[-2:]
[<Period.day_365: datetime.timedelta(days=365)>, <Period.day_366: datetime.timedelta(days=366)>]

子類別化 EnumType

While most enum needs can be met by customizing Enum subclasses, either with class decorators or custom functions, EnumType can be subclassed to provide a different Enum experience.

函式程式設計 HOWTO

作者:

A. M. Kuchling

發佈版本:

0.32

In this document, we'll take a tour of Python's features suitable for implementing programs in a functional style. After an introduction to the concepts of functional programming, we'll look at language features such as iterators and generators and relevant library modules such as itertools and functools.

簡介

This section explains the basic concept of functional programming; if you're just interested in learning about Python language features, skip to the next section on 疊代器.

Programming languages support decomposing problems in several different ways:

Most programming languages are procedural: programs are lists of instructions that tell the computer what to do with the program's input. C, Pascal, and even Unix shells are procedural languages.

In declarative languages, you write a specification that describes the problem to be solved, and the language implementation figures out how to perform the computation efficiently. SQL is the declarative language you're most likely to be familiar with; a SQL query describes the data set you want to retrieve, and the SQL engine decides whether to scan tables or use indexes, which subclauses should be performed first, etc.

Object-oriented programs manipulate collections of objects. Objects have internal state and support methods that query or modify this internal state in some way. Smalltalk and Java are object-oriented languages. C++ and Python are languages that support object-oriented programming, but don't force the use of object-oriented features.

Functional programming decomposes a problem into a set of functions. Ideally, functions only take inputs and produce outputs, and don't have any internal state that affects the output produced for a given input. Well-known functional languages include the ML family (Standard ML, OCaml, and other variants) and Haskell.

The designers of some computer languages choose to emphasize one particular approach to programming. This often makes it difficult to write programs that use a different approach. Other languages are multi-paradigm languages that support several different approaches. Lisp, C++, and Python are multi-paradigm; you can write programs or libraries that are largely procedural, object-oriented, or functional in all of these languages. In a large program, different sections might be written using different approaches; the GUI might be object-oriented while the processing logic is procedural or functional, for example.

In a functional program, input flows through a set of functions. Each function operates on its input and produces some output. Functional style discourages functions with side effects that modify internal state or make other changes that aren't visible in the function's return value. Functions that have no side effects at all are called purely functional. Avoiding side effects means not using data structures that get updated as a program runs; every function's output must only depend on its input.

Some languages are very strict about purity and don't even have assignment statements such as a=3 or c = a + b, but it's difficult to avoid all side effects, such as printing to the screen or writing to a disk file. Another example is a call to the print() or time.sleep() function, neither of which returns a useful value. Both are called only for their side effects of sending some text to the screen or pausing execution for a second.

Python programs written in functional style usually won't go to the extreme of avoiding all I/O or all assignments; instead, they'll provide a functional-appearing interface but will use non-functional features internally. For example, the implementation of a function will still use assignments to local variables, but won't modify global variables or have other side effects.

Functional programming can be considered the opposite of object-oriented programming. Objects are little capsules containing some internal state along with a collection of method calls that let you modify this state, and programs consist of making the right set of state changes. Functional programming wants to avoid state changes as much as possible and works with data flowing between functions. In Python you might combine the two approaches by writing functions that take and return instances representing objects in your application (e-mail messages, transactions, etc.).

Functional design may seem like an odd constraint to work under. Why should you avoid objects and side effects? There are theoretical and practical advantages to the functional style:

形式可證明性 (Formal provability)。

模組化 (Modularity)。

可組合性 (Composability)。

容易除錯與測試。

形式可證明性

A theoretical benefit is that it's easier to construct a mathematical proof that a functional program is correct.

For a long time researchers have been interested in finding ways to mathematically prove programs correct. This is different from testing a program on numerous inputs and concluding that its output is usually correct, or reading a program's source code and concluding that the code looks right; the goal is instead a rigorous proof that a program produces the right result for all possible inputs.

The technique used to prove programs correct is to write down invariants, properties of the input data and of the program's variables that are always true. For each line of code, you then show that if invariants X and Y are true before the line is executed, the slightly different invariants X' and Y' are true after the line is executed. This continues until you reach the end of the program, at which point the invariants should match the desired conditions on the program's output.

Functional programming's avoidance of assignments arose because assignments are difficult to handle with this technique; assignments can break invariants that were true before the assignment without producing any new invariants that can be propagated onward.

Unfortunately, proving programs correct is largely impractical and not relevant to Python software. Even trivial programs require proofs that are several pages long; the proof of correctness for a moderately complicated program would be enormous, and few or none of the programs you use daily (the Python interpreter, your XML parser, your web browser) could be proven correct. Even if you wrote down or generated a proof, there would then be the question of verifying the proof; maybe there's an error in it, and you wrongly believe you've proved the program correct.

模組化

A more practical benefit of functional programming is that it forces you to break apart your problem into small pieces. Programs are more modular as a result. It's easier to specify and write a small function that does one thing than a large function that performs a complicated transformation. Small functions are also easier to read and to check for errors.

容易除錯與測試

Testing and debugging a functional-style program is easier.

Debugging is simplified because functions are generally small and clearly specified. When a program doesn't work, each function is an interface point where you can check that the data are correct. You can look at the intermediate inputs and outputs to quickly isolate the function that's responsible for a bug.

Testing is easier because each function is a potential subject for a unit test. Functions don't depend on system state that needs to be replicated before running a test; instead you only have to synthesize the right input and then check that the output matches expectations.

可組合性

As you work on a functional-style program, you'll write a number of functions with varying inputs and outputs. Some of these functions will be unavoidably specialized to a particular application, but others will be useful in a wide variety of programs. For example, a function that takes a directory path and returns all the XML files in the directory, or a function that takes a filename and returns its contents, can be applied to many different situations.

Over time you'll form a personal library of utilities. Often you'll assemble new programs by arranging existing functions in a new configuration and writing a few functions specialized for the current task.

疊代器

I'll start by looking at a Python language feature that's an important foundation for writing functional-style programs: iterators.

An iterator is an object representing a stream of data; this object returns the data one element at a time. A Python iterator must support a method called __next__() that takes no arguments and always returns the next element of the stream. If there are no more elements in the stream, __next__() must raise the StopIteration exception. Iterators don't have to be finite, though; it's perfectly reasonable to write an iterator that produces an infinite stream of data.

The built-in iter() function takes an arbitrary object and tries to return an iterator that will return the object's contents or elements, raising TypeError if the object doesn't support iteration. Several of Python's built-in data types support iteration, the most common being lists and dictionaries. An object is called iterable if you can get an iterator for it.

You can experiment with the iteration interface manually:

>>> L = [1, 2, 3]
>>> it = iter(L)
>>> it
<...iterator object at ...>
>>> it.__next__()  # same as next(it)
1
>>> next(it)
2
>>> next(it)
3
>>> next(it)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>>

Python expects iterable objects in several different contexts, the most important being the for statement. In the statement for X in Y, Y must be an iterator or some object for which iter() can create an iterator. These two statements are equivalent:

for i in iter(obj):
    print(i)

for i in obj:
    print(i)

Iterators can be materialized as lists or tuples by using the list() or tuple() constructor functions:

>>> L = [1, 2, 3]
>>> iterator = iter(L)
>>> t = tuple(iterator)
>>> t
(1, 2, 3)

Sequence unpacking also supports iterators: if you know an iterator will return N elements, you can unpack them into an N-tuple:

>>> L = [1, 2, 3]
>>> iterator = iter(L)
>>> a, b, c = iterator
>>> a, b, c
(1, 2, 3)

Built-in functions such as max() and min() can take a single iterator argument and will return the largest or smallest element. The "in" and "not in" operators also support iterators: X in iterator is true if X is found in the stream returned by the iterator. You'll run into obvious problems if the iterator is infinite; max(), min() will never return, and if the element X never appears in the stream, the "in" and "not in" operators won't return either.

Note that you can only go forward in an iterator; there's no way to get the previous element, reset the iterator, or make a copy of it. Iterator objects can optionally provide these additional capabilities, but the iterator protocol only specifies the __next__() method. Functions may therefore consume all of the iterator's output, and if you need to do something different with the same stream, you'll have to create a new iterator.

Data Types That Support Iterators

We've already seen how lists and tuples support iterators. In fact, any Python sequence type, such as strings, will automatically support creation of an iterator.

Calling iter() on a dictionary returns an iterator that will loop over the dictionary's keys:

>>> m = {'Jan': 1, 'Feb': 2, 'Mar': 3, 'Apr': 4, 'May': 5, 'Jun': 6,
...      'Jul': 7, 'Aug': 8, 'Sep': 9, 'Oct': 10, 'Nov': 11, 'Dec': 12}
>>> for key in m:
...     print(key, m[key])
Jan 1
Feb 2
Mar 3
Apr 4
May 5
Jun 6
Jul 7
Aug 8
Sep 9
Oct 10
Nov 11
Dec 12

Note that starting with Python 3.7, dictionary iteration order is guaranteed to be the same as the insertion order. In earlier versions, the behaviour was unspecified and could vary between implementations.

Applying iter() to a dictionary always loops over the keys, but dictionaries have methods that return other iterators. If you want to iterate over values or key/value pairs, you can explicitly call the values() or items() methods to get an appropriate iterator.

The dict() constructor can accept an iterator that returns a finite stream of (key, value) tuples:

>>> L = [('Italy', 'Rome'), ('France', 'Paris'), ('US', 'Washington DC')]
>>> dict(iter(L))
{'Italy': 'Rome', 'France': 'Paris', 'US': 'Washington DC'}

Files also support iteration by calling the readline() method until there are no more lines in the file. This means you can read each line of a file like this:

for line in file:
    # do something for each line
    ...

Sets can take their contents from an iterable and let you iterate over the set's elements:

>>> S = {2, 3, 5, 7, 11, 13}
>>> for i in S:
...     print(i)
2
3
5
7
11
13

產生器運算式與串列綜合運算式

Two common operations on an iterator's output are 1) performing some operation for every element, 2) selecting a subset of elements that meet some condition. For example, given a list of strings, you might want to strip off trailing whitespace from each line or extract all the strings containing a given substring.

List comprehensions and generator expressions (short form: "listcomps" and "genexps") are a concise notation for such operations, borrowed from the functional programming language Haskell (https://www.haskell.org/). You can strip all the whitespace from a stream of strings with the following code:

>>> line_list = ['  line 1\n', 'line 2  \n', ' \n', '']

>>> # 產生器運算式 -- 回傳疊代器
>>> stripped_iter = (line.strip() for line in line_list)

>>> # 串列綜合運算式 -- 回傳串列
>>> stripped_list = [line.strip() for line in line_list]

You can select only certain elements by adding an "if" condition:

>>> stripped_list = [line.strip() for line in line_list
...                  if line != ""]

With a list comprehension, you get back a Python list; stripped_list is a list containing the resulting lines, not an iterator. Generator expressions return an iterator that computes the values as necessary, not needing to materialize all the values at once. This means that list comprehensions aren't useful if you're working with iterators that return an infinite stream or a very large amount of data. Generator expressions are preferable in these situations.

Generator expressions are surrounded by parentheses ("()") and list comprehensions are surrounded by square brackets ("[]"). Generator expressions have the form:

( expression for expr in sequence1
             if condition1
             for expr2 in sequence2
             if condition2
             for expr3 in sequence3
             ...
             if condition3
             for exprN in sequenceN
             if conditionN )

Again, for a list comprehension only the outside brackets are different (square brackets instead of parentheses).

The elements of the generated output will be the successive values of expression. The if clauses are all optional; if present, expression is only evaluated and added to the result when condition is true.

Generator expressions always have to be written inside parentheses, but the parentheses signalling a function call also count. If you want to create an iterator that will be immediately passed to a function you can write:

obj_total = sum(obj.count for obj in list_all_objects())

The for...in clauses contain the sequences to be iterated over. The sequences do not have to be the same length, because they are iterated over from left to right, not in parallel. For each element in sequence1, sequence2 is looped over from the beginning. sequence3 is then looped over for each resulting pair of elements from sequence1 and sequence2.

To put it another way, a list comprehension or generator expression is equivalent to the following Python code:

for expr1 in sequence1:
    if not (condition1):
        continue   # Skip this element
    for expr2 in sequence2:
        if not (condition2):
            continue   # Skip this element
        ...
        for exprN in sequenceN:
            if not (conditionN):
                continue   # Skip this element

            # Output the value of
            # the expression.

This means that when there are multiple for...in clauses but no if clauses, the length of the resulting output will be equal to the product of the lengths of all the sequences. If you have two lists of length 3, the output list is 9 elements long:

>>> seq1 = 'abc'
>>> seq2 = (1, 2, 3)
>>> [(x, y) for x in seq1 for y in seq2]
[('a', 1), ('a', 2), ('a', 3),
 ('b', 1), ('b', 2), ('b', 3),
 ('c', 1), ('c', 2), ('c', 3)]

To avoid introducing an ambiguity into Python's grammar, if expression is creating a tuple, it must be surrounded with parentheses. The first list comprehension below is a syntax error, while the second one is correct:

# 語法錯誤
[x, y for x in seq1 for y in seq2]
# 正確
[(x, y) for x in seq1 for y in seq2]

產生器

Generators are a special class of functions that simplify the task of writing iterators. Regular functions compute a value and return it, but generators return an iterator that returns a stream of values.

You're doubtless familiar with how regular function calls work in Python or C. When you call a function, it gets a private namespace where its local variables are created. When the function reaches a return statement, the local variables are destroyed and the value is returned to the caller. A later call to the same function creates a new private namespace and a fresh set of local variables. But, what if the local variables weren't thrown away on exiting a function? What if you could later resume the function where it left off? This is what generators provide; they can be thought of as resumable functions.

以下是最簡單的產生器函式範例：

>>> def generate_ints(N):
...    for i in range(N):
...        yield i

Any function containing a yield keyword is a generator function; this is detected by Python's bytecode compiler which compiles the function specially as a result.

When you call a generator function, it doesn't return a single value; instead it returns a generator object that supports the iterator protocol. On executing the yield expression, the generator outputs the value of i, similar to a return statement. The big difference between yield and a return statement is that on reaching a yield the generator's state of execution is suspended and local variables are preserved. On the next call to the generator's __next__() method, the function will resume executing.

以下是 generate_ints() 產生器的使用範例：

>>> gen = generate_ints(3)
>>> gen
<generator object generate_ints at ...>
>>> next(gen)
0
>>> next(gen)
1
>>> next(gen)
2
>>> next(gen)
Traceback (most recent call last):
  File "stdin", line 1, in <module>
  File "stdin", line 2, in generate_ints
StopIteration

You could equally write for i in generate_ints(5), or a, b, c = generate_ints(3).

Inside a generator function, return value causes StopIteration(value) to be raised from the __next__() method. Once this happens, or the bottom of the function is reached, the procession of values ends and the generator cannot yield any further values.

You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables. For example, returning a list of integers could be done by setting self.count to 0, and having the __next__() method increment self.count and return it. However, for a moderately complicated generator, writing a corresponding class can be much messier.

The test suite included with Python's library, Lib/test/test_generators.py [https://github.com/python/cpython/tree/3.14/Lib/test/test_generators.py], contains a number of more interesting examples. Here's one generator that implements an in-order traversal of a tree using generators recursively.

# A recursive generator that generates Tree leaves in in-order.
def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x

        yield t.label

        for x in inorder(t.right):
            yield x

Two other examples in test_generators.py produce solutions for the N-Queens problem (placing N queens on an NxN chess board so that no queen threatens another) and the Knight's Tour (finding a route that takes a knight to every square of an NxN chessboard without visiting any square twice).

Passing values into a generator

In Python 2.4 and earlier, generators only produced output. Once a generator's code was invoked to create an iterator, there was no way to pass any new information into the function when its execution is resumed. You could hack together this ability by making the generator look at a global variable or by passing in some mutable object that callers then modify, but these approaches are messy.

In Python 2.5 there's a simple way to pass values into a generator. yield became an expression, returning a value that can be assigned to a variable or otherwise operated on:

val = (yield i)

I recommend that you always put parentheses around a yield expression when you're doing something with the returned value, as in the above example. The parentheses aren't always necessary, but it's easier to always add them instead of having to remember when they're needed.

(PEP 342 [https://peps.python.org/pep-0342/] explains the exact rules, which are that a yield-expression must always be parenthesized except when it occurs at the top-level expression on the right-hand side of an assignment. This means you can write val = yield i but have to use parentheses when there's an operation, as in val = (yield i) + 12.)

Values are sent into a generator by calling its send(value) method. This method resumes the generator's code and the yield expression returns the specified value. If the regular __next__() method is called, the yield returns None.

Here's a simple counter that increments by 1 and allows changing the value of the internal counter.

def counter(maximum):
    i = 0
    while i < maximum:
        val = (yield i)
        # 如有提供值則改變計數器
        if val is not None:
            i = val
        else:
            i += 1

And here's an example of changing the counter:

>>> it = counter(10)
>>> next(it)
0
>>> next(it)
1
>>> it.send(8)
8
>>> next(it)
9
>>> next(it)
Traceback (most recent call last):
  File "t.py", line 15, in <module>
    it.next()
StopIteration

Because yield will often be returning None, you should always check for this case. Don't just use its value in expressions unless you're sure that the send() method will be the only method used to resume your generator function.

In addition to send(), there are two other methods on generators:

throw(value) is used to raise an exception inside the generator; the exception is raised by the yield expression where the generator's execution is paused.

close() sends a GeneratorExit exception to the generator to terminate the iteration. On receiving this exception, the generator's code must either raise GeneratorExit or StopIteration; catching the exception and doing anything else is illegal and will trigger a RuntimeError. close() will also be called by Python's garbage collector when the generator is garbage-collected.

If you need to run cleanup code when a GeneratorExit occurs, I suggest using a try: ... finally: suite instead of catching GeneratorExit.

The cumulative effect of these changes is to turn generators from one-way producers of information into both producers and consumers.

Generators also become coroutines, a more generalized form of subroutines. Subroutines are entered at one point and exited at another point (the top of the function, and a return statement), but coroutines can be entered, exited, and resumed at many different points (the yield statements).

內建函式

Let's look in more detail at built-in functions often used with iterators.

Two of Python's built-in functions, map() and filter() duplicate the features of generator expressions:

map(f, iterA, iterB, ...) 回傳一個元素為序列的疊代器

f(iterA[0], iterB[0]), f(iterA[1], iterB[1]), f(iterA[2], iterB[2]), ...。

>>> def upper(s):
...     return s.upper()

>>> list(map(upper, ['sentence', 'fragment']))
['SENTENCE', 'FRAGMENT']
>>> [upper(s) for s in ['sentence', 'fragment']]
['SENTENCE', 'FRAGMENT']

You can of course achieve the same effect with a list comprehension.

filter(predicate, iter) returns an iterator over all the sequence elements that meet a certain condition, and is similarly duplicated by list comprehensions. A predicate is a function that returns the truth value of some condition; for use with filter(), the predicate must take a single value.

>>> def is_even(x):
...     return (x % 2) == 0

>>> list(filter(is_even, range(10)))
[0, 2, 4, 6, 8]

This can also be written as a list comprehension:

>>> list(x for x in range(10) if is_even(x))
[0, 2, 4, 6, 8]

enumerate(iter, start=0) counts off the elements in the iterable returning 2-tuples containing the count (from start) and each element.

>>> for item in enumerate(['subject', 'verb', 'object']):
...     print(item)
(0, 'subject')
(1, 'verb')
(2, 'object')

enumerate() is often used when looping through a list and recording the indexes at which certain conditions are met:

f = open('data.txt', 'r')
for i, line in enumerate(f):
    if line.strip() == '':
        print('Blank line at line #%i' % i)

sorted(iterable, key=None, reverse=False) collects all the elements of the iterable into a list, sorts the list, and returns the sorted result. The key and reverse arguments are passed through to the constructed list's sort() method.

>>> import random
>>> # Generate 8 random numbers between [0, 10000)
>>> rand_list = random.sample(range(10000), 8)
>>> rand_list
[769, 7953, 9828, 6431, 8442, 9878, 6213, 2207]
>>> sorted(rand_list)
[769, 2207, 6213, 6431, 7953, 8442, 9828, 9878]
>>> sorted(rand_list, reverse=True)
[9878, 9828, 8442, 7953, 6431, 6213, 2207, 769]

(For a more detailed discussion of sorting, see the 排序技法.)

The any(iter) and all(iter) built-ins look at the truth values of an iterable's contents. any() returns True if any element in the iterable is a true value, and all() returns True if all of the elements are true values:

>>> any([0, 1, 0])
True
>>> any([0, 0, 0])
False
>>> any([1, 1, 1])
True
>>> all([0, 1, 0])
False
>>> all([0, 0, 0])
False
>>> all([1, 1, 1])
True

zip(iterA, iterB, ...) takes one element from each iterable and returns them in a tuple:

zip(['a', 'b', 'c'], (1, 2, 3)) =>
  ('a', 1), ('b', 2), ('c', 3)

It doesn't construct an in-memory list and exhaust all the input iterators before returning; instead tuples are constructed and returned only if they're requested. (The technical term for this behaviour is lazy evaluation [https://en.wikipedia.org/wiki/Lazy_evaluation].)

This iterator is intended to be used with iterables that are all of the same length. If the iterables are of different lengths, the resulting stream will be the same length as the shortest iterable.

zip(['a', 'b'], (1, 2, 3)) =>
  ('a', 1), ('b', 2)

You should avoid doing this, though, because an element may be taken from the longer iterators and discarded. This means you can't go on to use the iterators further because you risk skipping a discarded element.

itertools 模組

The itertools module contains a number of commonly used iterators as well as functions for combining several iterators. This section will introduce the module's contents by showing small examples.

The module's functions fall into a few broad classes:

Functions that create a new iterator based on an existing iterator.

Functions for treating an iterator's elements as function arguments.

Functions for selecting portions of an iterator's output.

A function for grouping an iterator's output.

建立新的疊代器

itertools.count(start, step) returns an infinite stream of evenly spaced values. You can optionally supply the starting number, which defaults to 0, and the interval between numbers, which defaults to 1:

itertools.count() =>
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...
itertools.count(10) =>
  10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...
itertools.count(10, 5) =>
  10, 15, 20, 25, 30, 35, 40, 45, 50, 55, ...

itertools.cycle(iter) saves a copy of the contents of a provided iterable and returns a new iterator that returns its elements from first to last. The new iterator will repeat these elements infinitely.

itertools.cycle([1, 2, 3, 4, 5]) =>
  1, 2, 3, 4, 5, 1, 2, 3, 4, 5, ...

itertools.repeat(elem, [n]) returns the provided element n times, or returns the element endlessly if n is not provided.

itertools.repeat('abc') =>
  abc, abc, abc, abc, abc, abc, abc, abc, abc, abc, ...
itertools.repeat('abc', 5) =>
  abc, abc, abc, abc, abc

itertools.chain(iterA, iterB, ...) takes an arbitrary number of iterables as input, and returns all the elements of the first iterator, then all the elements of the second, and so on, until all of the iterables have been exhausted.

itertools.chain(['a', 'b', 'c'], (1, 2, 3)) =>
  a, b, c, 1, 2, 3

itertools.islice(iter, [start], stop, [step]) returns a stream that's a slice of the iterator. With a single stop argument, it will return the first stop elements. If you supply a starting index, you'll get stop-start elements, and if you supply a value for step, elements will be skipped accordingly. Unlike Python's string and list slicing, you can't use negative values for start, stop, or step.

itertools.islice(range(10), 8) =>
  0, 1, 2, 3, 4, 5, 6, 7
itertools.islice(range(10), 2, 8) =>
  2, 3, 4, 5, 6, 7
itertools.islice(range(10), 2, 8, 2) =>
  2, 4, 6

itertools.tee(iter, [n]) replicates an iterator; it returns n independent iterators that will all return the contents of the source iterator. If you don't supply a value for n, the default is 2. Replicating iterators requires saving some of the contents of the source iterator, so this can consume significant memory if the iterator is large and one of the new iterators is consumed more than the others.

itertools.tee( itertools.count() ) =>
   iterA, iterB

where iterA ->
   0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...

and   iterB ->
   0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...

Calling functions on elements

The operator module contains a set of functions corresponding to Python's operators. Some examples are operator.add(a, b) (adds two values), operator.ne(a, b) (same as a != b), and operator.attrgetter('id') (returns a callable that fetches the .id attribute).

itertools.starmap(func, iter) assumes that the iterable will return a stream of tuples, and calls func using these tuples as the arguments:

itertools.starmap(os.path.join,
                  [('/bin', 'python'), ('/usr', 'bin', 'java'),
                   ('/usr', 'bin', 'perl'), ('/usr', 'bin', 'ruby')])
=>
  /bin/python, /usr/bin/java, /usr/bin/perl, /usr/bin/ruby

Selecting elements

Another group of functions chooses a subset of an iterator's elements based on a predicate.

itertools.filterfalse(predicate, iter) is the opposite of filter(), returning all elements for which the predicate returns false:

itertools.filterfalse(is_even, itertools.count()) =>
  1, 3, 5, 7, 9, 11, 13, 15, ...

itertools.takewhile(predicate, iter) returns elements for as long as the predicate returns true. Once the predicate returns false, the iterator will signal the end of its results.

def less_than_10(x):
    return x < 10

itertools.takewhile(less_than_10, itertools.count()) =>
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9

itertools.takewhile(is_even, itertools.count()) =>
  0

itertools.dropwhile(predicate, iter) discards elements while the predicate returns true, and then returns the rest of the iterable's results.

itertools.dropwhile(less_than_10, itertools.count()) =>
  10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...

itertools.dropwhile(is_even, itertools.count()) =>
  1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...

itertools.compress(data, selectors) takes two iterators and returns only those elements of data for which the corresponding element of selectors is true, stopping whenever either one is exhausted:

itertools.compress([1, 2, 3, 4, 5], [True, True, False, False, True]) =>
   1, 2, 5

Combinatoric functions

The itertools.combinations(iterable, r) returns an iterator giving all possible r-tuple combinations of the elements contained in iterable.

itertools.combinations([1, 2, 3, 4, 5], 2) =>
  (1, 2), (1, 3), (1, 4), (1, 5),
  (2, 3), (2, 4), (2, 5),
  (3, 4), (3, 5),
  (4, 5)

itertools.combinations([1, 2, 3, 4, 5], 3) =>
  (1, 2, 3), (1, 2, 4), (1, 2, 5), (1, 3, 4), (1, 3, 5), (1, 4, 5),
  (2, 3, 4), (2, 3, 5), (2, 4, 5),
  (3, 4, 5)

The elements within each tuple remain in the same order as iterable returned them. For example, the number 1 is always before 2, 3, 4, or 5 in the examples above. A similar function, itertools.permutations(iterable, r=None), removes this constraint on the order, returning all possible arrangements of length r:

itertools.permutations([1, 2, 3, 4, 5], 2) =>
  (1, 2), (1, 3), (1, 4), (1, 5),
  (2, 1), (2, 3), (2, 4), (2, 5),
  (3, 1), (3, 2), (3, 4), (3, 5),
  (4, 1), (4, 2), (4, 3), (4, 5),
  (5, 1), (5, 2), (5, 3), (5, 4)

itertools.permutations([1, 2, 3, 4, 5]) =>
  (1, 2, 3, 4, 5), (1, 2, 3, 5, 4), (1, 2, 4, 3, 5),
  ...
  (5, 4, 3, 2, 1)

If you don't supply a value for r the length of the iterable is used, meaning that all the elements are permuted.

Note that these functions produce all of the possible combinations by position and don't require that the contents of iterable are unique:

itertools.permutations('aba', 3) =>
  ('a', 'b', 'a'), ('a', 'a', 'b'), ('b', 'a', 'a'),
  ('b', 'a', 'a'), ('a', 'a', 'b'), ('a', 'b', 'a')

The identical tuple ('a', 'a', 'b') occurs twice, but the two 'a' strings came from different positions.

The itertools.combinations_with_replacement(iterable, r) function relaxes a different constraint: elements can be repeated within a single tuple. Conceptually an element is selected for the first position of each tuple and then is replaced before the second element is selected.

itertools.combinations_with_replacement([1, 2, 3, 4, 5], 2) =>
  (1, 1), (1, 2), (1, 3), (1, 4), (1, 5),
  (2, 2), (2, 3), (2, 4), (2, 5),
  (3, 3), (3, 4), (3, 5),
  (4, 4), (4, 5),
  (5, 5)

Grouping elements

The last function I'll discuss, itertools.groupby(iter, key_func=None), is the most complicated. key_func(elem) is a function that can compute a key value for each element returned by the iterable. If you don't supply a key function, the key is simply each element itself.

groupby() collects all the consecutive elements from the underlying iterable that have the same key value, and returns a stream of 2-tuples containing a key value and an iterator for the elements with that key.

city_list = [('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL'),
             ('Anchorage', 'AK'), ('Nome', 'AK'),
             ('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ'),
             ...
            ]

def get_state(city_state):
    return city_state[1]

itertools.groupby(city_list, get_state) =>
  ('AL', iterator-1),
  ('AK', iterator-2),
  ('AZ', iterator-3), ...

where
iterator-1 =>
  ('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL')
iterator-2 =>
  ('Anchorage', 'AK'), ('Nome', 'AK')
iterator-3 =>
  ('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ')

groupby() assumes that the underlying iterable's contents will already be sorted based on the key. Note that the returned iterators also use the underlying iterable, so you have to consume the results of iterator-1 before requesting iterator-2 and its corresponding key.

functools 模組

The functools module contains some higher-order functions. A higher-order function takes one or more functions as input and returns a new function. The most useful tool in this module is the functools.partial() function.

For programs written in a functional style, you'll sometimes want to construct variants of existing functions that have some of the parameters filled in. Consider a Python function f(a, b, c); you may wish to create a new function g(b, c) that's equivalent to f(1, b, c); you're filling in a value for one of f()'s parameters. This is called "partial function application".

The constructor for partial() takes the arguments (function, arg1, arg2, ..., kwarg1=value1, kwarg2=value2). The resulting object is callable, so you can just call it to invoke function with the filled-in arguments.

以下是個很小但實際的範例：

import functools

def log(message, subsystem):
    """Write the contents of 'message' to the specified subsystem."""
    print('%s: %s' % (subsystem, message))
    ...

server_log = functools.partial(log, subsystem='server')
server_log('Unable to open socket')

functools.reduce(func, iter, [initial_value]) cumulatively performs an operation on all the iterable's elements and, therefore, can't be applied to infinite iterables. func must be a function that takes two elements and returns a single value. functools.reduce() takes the first two elements A and B returned by the iterator and calculates func(A, B). It then requests the third element, C, calculates func(func(A, B), C), combines this result with the fourth element returned, and continues until the iterable is exhausted. If the iterable returns no values at all, a TypeError exception is raised. If the initial value is supplied, it's used as a starting point and func(initial_value, A) is the first calculation.

>>> import operator, functools
>>> functools.reduce(operator.concat, ['A', 'BB', 'C'])
'ABBC'
>>> functools.reduce(operator.concat, [])
Traceback (most recent call last):
  ...
TypeError: reduce() of empty sequence with no initial value
>>> functools.reduce(operator.mul, [1, 2, 3], 1)
6
>>> functools.reduce(operator.mul, [], 1)
1

If you use operator.add() with functools.reduce(), you'll add up all the elements of the iterable. This case is so common that there's a special built-in called sum() to compute it:

>>> import functools, operator
>>> functools.reduce(operator.add, [1, 2, 3, 4], 0)
10
>>> sum([1, 2, 3, 4])
10
>>> sum([])
0

For many uses of functools.reduce(), though, it can be clearer to just write the obvious for loop:

import functools
# Instead of:
product = functools.reduce(operator.mul, [1, 2, 3], 1)

# You can write:
product = 1
for i in [1, 2, 3]:
    product *= i

A related function is itertools.accumulate(iterable, func=operator.add). It performs the same calculation, but instead of returning only the final result, accumulate() returns an iterator that also yields each partial result:

itertools.accumulate([1, 2, 3, 4, 5]) =>
  1, 3, 6, 10, 15

itertools.accumulate([1, 2, 3, 4, 5], operator.mul) =>
  1, 2, 6, 24, 120

operator 模組

The operator module was mentioned earlier. It contains a set of functions corresponding to Python's operators. These functions are often useful in functional-style code because they save you from writing trivial functions that perform a single operation.

Some of the functions in this module are:

數學運算：add()、sub()、mul()、floordiv()、abs()...

Logical operations: not_(), truth().

Bitwise operations: and_(), or_(), invert().

Comparisons: eq(), ne(), lt(), le(), gt(), and ge().

Object identity: is_(), is_not().

Consult the operator module's documentation for a complete list.

Small functions and the lambda expression

When writing functional-style programs, you'll often need little functions that act as predicates or that combine elements in some way.

If there's a Python built-in or a module function that's suitable, you don't need to define a new function at all:

stripped_lines = [line.strip() for line in lines]
existing_files = filter(os.path.exists, file_list)

If the function you need doesn't exist, you need to write it. One way to write small functions is to use the lambda expression. lambda takes a number of parameters and an expression combining these parameters, and creates an anonymous function that returns the value of the expression:

adder = lambda x, y: x+y

print_assign = lambda name, value: name + '=' + str(value)

An alternative is to just use the def statement and define a function in the usual way:

def adder(x, y):
    return x + y

def print_assign(name, value):
    return name + '=' + str(value)

Which alternative is preferable? That's a style question; my usual course is to avoid using lambda.

One reason for my preference is that lambda is quite limited in the functions it can define. The result has to be computable as a single expression, which means you can't have multiway if... elif... else comparisons or try... except statements. If you try to do too much in a lambda statement, you'll end up with an overly complicated expression that's hard to read. Quick, what's the following code doing?

import functools
total = functools.reduce(lambda a, b: (0, a[1] + b[1]), items)[1]

You can figure it out, but it takes time to disentangle the expression to figure out what's going on. Using a short nested def statements makes things a little bit better:

import functools
def combine(a, b):
    return 0, a[1] + b[1]

total = functools.reduce(combine, items)[1]

But it would be best of all if I had simply used a for loop:

total = 0
for a, b in items:
    total += b

Or the sum() built-in and a generator expression:

total = sum(b for a, b in items)

Many uses of functools.reduce() are clearer when written as for loops.

Fredrik Lundh once suggested the following set of rules for refactoring uses of lambda:

Write a lambda function.

Write a comment explaining what the heck that lambda does.

Study the comment for a while, and think of a name that captures the essence of the comment.

Convert the lambda to a def statement, using that name.

Remove the comment.

I really like these rules, but you're free to disagree about whether this lambda-free style is better.

Revision History and Acknowledgements

The author would like to thank the following people for offering suggestions, corrections and assistance with various drafts of this article: Ian Bicking, Nick Coghlan, Nick Efford, Raymond Hettinger, Jim Jewett, Mike Krell, Leandro Lameiro, Jussi Salmela, Collin Winter, Blake Winton.

Version 0.1: posted June 30 2006.

Version 0.11: posted July 1 2006. Typo fixes.

Version 0.2: posted July 10 2006. Merged genexp and listcomp sections into one. Typo fixes.

Version 0.21: Added more references suggested on the tutor mailing list.

Version 0.30: Adds a section on the functional module written by Collin Winter; adds short section on the operator module; a few other edits.

References

General

Structure and Interpretation of Computer Programs, by Harold Abelson and Gerald Jay Sussman with Julie Sussman. The book can be found at https://mitpress.mit.edu/sicp. In this classic textbook of computer science, chapters 2 and 3 discuss the use of sequences and streams to organize the data flow inside a program. The book uses Scheme for its examples, but many of the design approaches described in these chapters are applicable to functional-style Python code.

https://defmacro.org/2006/06/19/fp.html: A general introduction to functional programming that uses Java examples and has a lengthy historical introduction.

https://en.wikipedia.org/wiki/Functional_programming: General Wikipedia entry describing functional programming.

https://en.wikipedia.org/wiki/Coroutine: 協程 (coroutines) 的條目。

https://en.wikipedia.org/wiki/Partial_application: 偏函式 (partial application) 概念的條目。

https://en.wikipedia.org/wiki/Currying: currying 概念的條目。

Python 特有的

https://gnosis.cx/TPiP/: The first chapter of David Mertz's book Text Processing in Python discusses functional programming for text processing, in the section titled "Utilizing Higher-Order Functions in Text Processing".

Mertz also wrote a 3-part series of articles on functional programming for IBM's DeveloperWorks site; see part 1 [https://developer.ibm.com/articles/l-prog/], part 2 [https://developer.ibm.com/tutorials/l-prog2/], and part 3 [https://developer.ibm.com/tutorials/l-prog3/],

Python 說明文件

itertools 模組的說明文件。

functools 模組的說明文件。

operator 模組的說明文件。

PEP 289 [https://peps.python.org/pep-0289/]：「產生器運算式 (Generator Expressions)」

PEP 342 [https://peps.python.org/pep-0342/]: "Coroutines via Enhanced Generators" describes the new generator features in Python 2.5.

如何使用 Logging 模組

作者:

Vinay Sajip <vinay_sajip at red-dove dot com>

This page contains tutorial information. For links to reference information and a logging cookbook, please see 其他資源.

基礎 Logging 指南

軟體執行時，追蹤有什麼事件發生的動作稱為 Logging。軟體開發者會使用 Logging 這樣的機制是因為想知道在運行過程中是否有特定的事件發生。事件會被一段訊息所描述。這段訊息可能包含一些因為此事件發生而改變的資料。開發者也可以指派事件的重要程度，重要程度有時候也會被稱作 程度 或是 嚴重性 。

什麼時候使用 logging

You can access logging functionality by creating a logger via logger = getLogger(__name__), and then calling the logger's debug(), info(), warning(), error() and critical() methods. To determine when to use logging, and to see which logger methods to use when, see the table below. It states, for each of a set of common tasks, the best tool to use for that task.

Task you want to perform

The best tool for the task

Display console output for ordinary usage of a command line script or program

print()

Report events that occur during normal operation of a program (e.g. for status monitoring or fault investigation)

A logger's info() (or debug() method for very detailed output for diagnostic purposes)

Issue a warning regarding a particular runtime event

warnings.warn() in library code if the issue is avoidable and the client application should be modified to eliminate the warning

A logger's warning() method if there is nothing the client application can do about the situation, but the event should still be noted

Report an error regarding a particular runtime event

引發一個例外

Report suppression of an error without raising an exception (e.g. error handler in a long-running server process)

A logger's error(), exception() or critical() method as appropriate for the specific error and application domain

The logger methods are named after the level or severity of the events they are used to track. The standard levels and their applicability are described below (in increasing order of severity):

Level

When it's used

DEBUG

Detailed information, typically of interest only when diagnosing problems.

INFO

Confirmation that things are working as expected.

WARNING

An indication that something unexpected happened, or indicative of some problem in the near future (e.g. 'disk space low'). The software is still working as expected.

ERROR

Due to a more serious problem, the software has not been able to perform some function.

CRITICAL

A serious error, indicating that the program itself may be unable to continue running.

The default level is WARNING, which means that only events of this severity and higher will be tracked, unless the logging package is configured to do otherwise.

Events that are tracked can be handled in different ways. The simplest way of handling tracked events is to print them to the console. Another common way is to write them to a disk file.

一個簡單範例

一個非常簡單的例子是：

import logging
logging.warning('Watch out!')  # 將會印出訊息至控制台
logging.info('I told you so')  # 不會印出任何東西

If you type these lines into a script and run it, you'll see:

WARNING:root:Watch out!

printed out on the console. The INFO message doesn't appear because the default level is WARNING. The printed message includes the indication of the level and the description of the event provided in the logging call, i.e. 'Watch out!'. The actual output can be formatted quite flexibly if you need that; formatting options will also be explained later.

Notice that in this example, we use functions directly on the logging module, like logging.debug, rather than creating a logger and calling functions on it. These functions operate on the root logger, but can be useful as they will call basicConfig() for you if it has not been called yet, like in this example. In larger programs you'll usually want to control the logging configuration explicitly however - so for that reason as well as others, it's better to create loggers and call their methods.

Logging to a file

A very common situation is that of recording logging events in a file, so let's look at that next. Be sure to try the following in a newly started Python interpreter, and don't just continue from the session described above:

import logging
logger = logging.getLogger(__name__)
logging.basicConfig(filename='example.log', encoding='utf-8', level=logging.DEBUG)
logger.debug('This message should go to the log file')
logger.info('So should this')
logger.warning('And this, too')
logger.error('And non-ASCII stuff, too, like Øresund and Malmö')

在 3.9 版的變更: The encoding argument was added. In earlier Python versions, or if not specified, the encoding used is the default value used by open(). While not shown in the above example, an errors argument can also now be passed, which determines how encoding errors are handled. For available values and the default, see the documentation for open().

And now if we open the file and look at what we have, we should find the log messages:

DEBUG:__main__:This message should go to the log file
INFO:__main__:So should this
WARNING:__main__:And this, too
ERROR:__main__:And non-ASCII stuff, too, like Øresund and Malmö

This example also shows how you can set the logging level which acts as the threshold for tracking. In this case, because we set the threshold to DEBUG, all of the messages were printed.

If you want to set the logging level from a command-line option such as:

--log=INFO

and you have the value of the parameter passed for --log in some variable loglevel, you can use:

getattr(logging, loglevel.upper())

to get the value which you'll pass to basicConfig() via the level argument. You may want to error check any user input value, perhaps as in the following example:

# assuming loglevel is bound to the string value obtained from the
# command line argument. Convert to upper case to allow the user to
# specify --log=DEBUG or --log=debug
numeric_level = getattr(logging, loglevel.upper(), None)
if not isinstance(numeric_level, int):
    raise ValueError('Invalid log level: %s' % loglevel)
logging.basicConfig(level=numeric_level, ...)

The call to basicConfig() should come before any calls to a logger's methods such as debug(), info(), etc. Otherwise, that logging event may not be handled in the desired manner.

If you run the above script several times, the messages from successive runs are appended to the file example.log. If you want each run to start afresh, not remembering the messages from earlier runs, you can specify the filemode argument, by changing the call in the above example to:

logging.basicConfig(filename='example.log', filemode='w', level=logging.DEBUG)

The output will be the same as before, but the log file is no longer appended to, so the messages from earlier runs are lost.

Logging variable data

To log variable data, use a format string for the event description message and append the variable data as arguments. For example:

import logging
logging.warning('%s before you %s', 'Look', 'leap!')

will display:

WARNING:root:Look before you leap!

As you can see, merging of variable data into the event description message uses the old, %-style of string formatting. This is for backwards compatibility: the logging package pre-dates newer formatting options such as str.format() and string.Template. These newer formatting options are supported, but exploring them is outside the scope of this tutorial: see Using particular formatting styles throughout your application for more information.

Changing the format of displayed messages

To change the format which is used to display messages, you need to specify the format you want to use:

import logging
logging.basicConfig(format='%(levelname)s:%(message)s', level=logging.DEBUG)
logging.debug('This message should appear on the console')
logging.info('So should this')
logging.warning('And this, too')

which would print:

DEBUG:This message should appear on the console
INFO:So should this
WARNING:And this, too

Notice that the 'root' which appeared in earlier examples has disappeared. For a full set of things that can appear in format strings, you can refer to the documentation for LogRecord 屬性, but for simple usage, you just need the levelname (severity), message (event description, including variable data) and perhaps to display when the event occurred. This is described in the next section.

Displaying the date/time in messages

To display the date and time of an event, you would place '%(asctime)s' in your format string:

import logging
logging.basicConfig(format='%(asctime)s %(message)s')
logging.warning('is when this event was logged.')

which should print something like this:

2010-12-12 11:41:42,612 is when this event was logged.

The default format for date/time display (shown above) is like ISO8601 or RFC 3339 [https://datatracker.ietf.org/doc/html/rfc3339.html]. If you need more control over the formatting of the date/time, provide a datefmt argument to basicConfig, as in this example:

import logging
logging.basicConfig(format='%(asctime)s %(message)s', datefmt='%m/%d/%Y %I:%M:%S %p')
logging.warning('is when this event was logged.')

which would display something like this:

12/12/2010 11:46:36 AM is when this event was logged.

The format of the datefmt argument is the same as supported by time.strftime().

Next Steps

That concludes the basic tutorial. It should be enough to get you up and running with logging. There's a lot more that the logging package offers, but to get the best out of it, you'll need to invest a little more of your time in reading the following sections. If you're ready for that, grab some of your favourite beverage and carry on.

If your logging needs are simple, then use the above examples to incorporate logging into your own scripts, and if you run into problems or don't understand something, please post a question in the Help category of the Python discussion forum [https://discuss.python.org/c/help/7] and you should receive help before too long.

Still here? You can carry on reading the next few sections, which provide a slightly more advanced/in-depth tutorial than the basic one above. After that, you can take a look at the Logging Cookbook.

Advanced Logging Tutorial

The logging library takes a modular approach and offers several categories of components: loggers, handlers, filters, and formatters.

Loggers expose the interface that application code directly uses.

Handlers send the log records (created by loggers) to the appropriate destination.

Filters provide a finer grained facility for determining which log records to output.

Formatters specify the layout of log records in the final output.

Log event information is passed between loggers, handlers, filters and formatters in a LogRecord instance.

Logging is performed by calling methods on instances of the Logger class (hereafter called loggers). Each instance has a name, and they are conceptually arranged in a namespace hierarchy using dots (periods) as separators. For example, a logger named 'scan' is the parent of loggers 'scan.text', 'scan.html' and 'scan.pdf'. Logger names can be anything you want, and indicate the area of an application in which a logged message originates.

A good convention to use when naming loggers is to use a module-level logger, in each module which uses logging, named as follows:

logger = logging.getLogger(__name__)

This means that logger names track the package/module hierarchy, and it's intuitively obvious where events are logged just from the logger name.

The root of the hierarchy of loggers is called the root logger. That's the logger used by the functions debug(), info(), warning(), error() and critical(), which just call the same-named method of the root logger. The functions and the methods have the same signatures. The root logger's name is printed as 'root' in the logged output.

It is, of course, possible to log messages to different destinations. Support is included in the package for writing log messages to files, HTTP GET/POST locations, email via SMTP, generic sockets, queues, or OS-specific logging mechanisms such as syslog or the Windows NT event log. Destinations are served by handler classes. You can create your own log destination class if you have special requirements not met by any of the built-in handler classes.

By default, no destination is set for any logging messages. You can specify a destination (such as console or file) by using basicConfig() as in the tutorial examples. If you call the functions debug(), info(), warning(), error() and critical(), they will check to see if no destination is set; and if one is not set, they will set a destination of the console (sys.stderr) and a default format for the displayed message before delegating to the root logger to do the actual message output.

The default format set by basicConfig() for messages is:

severity:logger name:message

You can change this by passing a format string to basicConfig() with the format keyword argument. For all options regarding how a format string is constructed, see Formatter Objects.

Logging Flow

The flow of log event information in loggers and handlers is illustrated in the following diagram.

Loggers

Logger objects have a threefold job. First, they expose several methods to application code so that applications can log messages at runtime. Second, logger objects determine which log messages to act upon based upon severity (the default filtering facility) or filter objects. Third, logger objects pass along relevant log messages to all interested log handlers.

The most widely used methods on logger objects fall into two categories: configuration and message sending.

These are the most common configuration methods:

Logger.setLevel() specifies the lowest-severity log message a logger will handle, where debug is the lowest built-in severity level and critical is the highest built-in severity. For example, if the severity level is INFO, the logger will handle only INFO, WARNING, ERROR, and CRITICAL messages and will ignore DEBUG messages.

Logger.addHandler() and Logger.removeHandler() add and remove handler objects from the logger object. Handlers are covered in more detail in Handlers.

Logger.addFilter() and Logger.removeFilter() add and remove filter objects from the logger object. Filters are covered in more detail in Filter Objects.

You don't need to always call these methods on every logger you create. See the last two paragraphs in this section.

With the logger object configured, the following methods create log messages:

Logger.debug(), Logger.info(), Logger.warning(), Logger.error(), and Logger.critical() all create log records with a message and a level that corresponds to their respective method names. The message is actually a format string, which may contain the standard string substitution syntax of %s, %d, %f, and so on. The rest of their arguments is a list of objects that correspond with the substitution fields in the message. With regard to **kwargs, the logging methods care only about a keyword of exc_info and use it to determine whether to log exception information.

Logger.exception() creates a log message similar to Logger.error(). The difference is that Logger.exception() dumps a stack trace along with it. Call this method only from an exception handler.

Logger.log() takes a log level as an explicit argument. This is a little more verbose for logging messages than using the log level convenience methods listed above, but this is how to log at custom log levels.

getLogger() returns a reference to a logger instance with the specified name if it is provided, or root if not. The names are period-separated hierarchical structures. Multiple calls to getLogger() with the same name will return a reference to the same logger object. Loggers that are further down in the hierarchical list are children of loggers higher up in the list. For example, given a logger with a name of foo, loggers with names of foo.bar, foo.bar.baz, and foo.bam are all descendants of foo.

Loggers have a concept of effective level. If a level is not explicitly set on a logger, the level of its parent is used instead as its effective level. If the parent has no explicit level set, its parent is examined, and so on - all ancestors are searched until an explicitly set level is found. The root logger always has an explicit level set (WARNING by default). When deciding whether to process an event, the effective level of the logger is used to determine whether the event is passed to the logger's handlers.

Child loggers propagate messages up to the handlers associated with their ancestor loggers. Because of this, it is unnecessary to define and configure handlers for all the loggers an application uses. It is sufficient to configure handlers for a top-level logger and create child loggers as needed. (You can, however, turn off propagation by setting the propagate attribute of a logger to False.)

Handlers

Handler objects are responsible for dispatching the appropriate log messages (based on the log messages' severity) to the handler's specified destination. Logger objects can add zero or more handler objects to themselves with an addHandler() method. As an example scenario, an application may want to send all log messages to a log file, all log messages of error or higher to stdout, and all messages of critical to an email address. This scenario requires three individual handlers where each handler is responsible for sending messages of a specific severity to a specific location.

The standard library includes quite a few handler types (see Useful Handlers); the tutorials use mainly StreamHandler and FileHandler in its examples.

There are very few methods in a handler for application developers to concern themselves with. The only handler methods that seem relevant for application developers who are using the built-in handler objects (that is, not creating custom handlers) are the following configuration methods:

The setLevel() method, just as in logger objects, specifies the lowest severity that will be dispatched to the appropriate destination. Why are there two setLevel() methods? The level set in the logger determines which severity of messages it will pass to its handlers. The level set in each handler determines which messages that handler will send on.

setFormatter() selects a Formatter object for this handler to use.

addFilter() and removeFilter() respectively configure and deconfigure filter objects on handlers.

Application code should not directly instantiate and use instances of Handler. Instead, the Handler class is a base class that defines the interface that all handlers should have and establishes some default behavior that child classes can use (or override).

Formatters

Formatter objects configure the final order, structure, and contents of the log message. Unlike the base logging.Handler class, application code may instantiate formatter classes, although you could likely subclass the formatter if your application needs special behavior. The constructor takes three optional arguments -- a message format string, a date format string and a style indicator.

logging.Formatter.__init__(fmt=None, datefmt=None, style='%')

If there is no message format string, the default is to use the raw message. If there is no date format string, the default date format is:

%Y-%m-%d %H:%M:%S

with the milliseconds tacked on at the end. The style is one of '%', '{', or '$'. If one of these is not specified, then '%' will be used.

If the style is '%', the message format string uses %(<dictionary key>)s styled string substitution; the possible keys are documented in LogRecord 屬性. If the style is '{', the message format string is assumed to be compatible with str.format() (using keyword arguments), while if the style is '$' then the message format string should conform to what is expected by string.Template.substitute().

在 3.2 版的變更: 新增 style 參數。

The following message format string will log the time in a human-readable format, the severity of the message, and the contents of the message, in that order:

'%(asctime)s - %(levelname)s - %(message)s'

Formatters use a user-configurable function to convert the creation time of a record to a tuple. By default, time.localtime() is used; to change this for a particular formatter instance, set the converter attribute of the instance to a function with the same signature as time.localtime() or time.gmtime(). To change it for all formatters, for example if you want all logging times to be shown in GMT, set the converter attribute in the Formatter class (to time.gmtime for GMT display).

Configuring Logging

Programmers can configure logging in three ways:

Creating loggers, handlers, and formatters explicitly using Python code that calls the configuration methods listed above.

Creating a logging config file and reading it using the fileConfig() function.

Creating a dictionary of configuration information and passing it to the dictConfig() function.

For the reference documentation on the last two options, see Configuration functions. The following example configures a very simple logger, a console handler, and a simple formatter using Python code:

import logging

# create logger
logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)

# create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)

# create formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')

# add formatter to ch
ch.setFormatter(formatter)

# add ch to logger
logger.addHandler(ch)

# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')

Running this module from the command line produces the following output:

$ python simple_logging_module.py
2005-03-19 15:10:26,618 - simple_example - DEBUG - debug message
2005-03-19 15:10:26,620 - simple_example - INFO - info message
2005-03-19 15:10:26,695 - simple_example - WARNING - warn message
2005-03-19 15:10:26,697 - simple_example - ERROR - error message
2005-03-19 15:10:26,773 - simple_example - CRITICAL - critical message

The following Python module creates a logger, handler, and formatter nearly identical to those in the example listed above, with the only difference being the names of the objects:

import logging
import logging.config

logging.config.fileConfig('logging.conf')

# create logger
logger = logging.getLogger('simpleExample')

# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')

Here is the logging.conf file:

[loggers]
keys=root,simpleExample

[handlers]
keys=consoleHandler

[formatters]
keys=simpleFormatter

[logger_root]
level=DEBUG
handlers=consoleHandler

[logger_simpleExample]
level=DEBUG
handlers=consoleHandler
qualname=simpleExample
propagate=0

[handler_consoleHandler]
class=StreamHandler
level=DEBUG
formatter=simpleFormatter
args=(sys.stdout,)

[formatter_simpleFormatter]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s

The output is nearly identical to that of the non-config-file-based example:

$ python simple_logging_config.py
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message

You can see that the config file approach has a few advantages over the Python code approach, mainly separation of configuration and code and the ability of noncoders to easily modify the logging properties.

警告

The fileConfig() function takes a default parameter, disable_existing_loggers, which defaults to True for reasons of backward compatibility. This may or may not be what you want, since it will cause any non-root loggers existing before the fileConfig() call to be disabled unless they (or an ancestor) are explicitly named in the configuration. Please refer to the reference documentation for more information, and specify False for this parameter if you wish.

The dictionary passed to dictConfig() can also specify a Boolean value with key disable_existing_loggers, which if not specified explicitly in the dictionary also defaults to being interpreted as True. This leads to the logger-disabling behaviour described above, which may not be what you want - in which case, provide the key explicitly with a value of False.

Note that the class names referenced in config files need to be either relative to the logging module, or absolute values which can be resolved using normal import mechanisms. Thus, you could use either WatchedFileHandler (relative to the logging module) or mypackage.mymodule.MyHandler (for a class defined in package mypackage and module mymodule, where mypackage is available on the Python import path).

In Python 3.2, a new means of configuring logging has been introduced, using dictionaries to hold configuration information. This provides a superset of the functionality of the config-file-based approach outlined above, and is the recommended configuration method for new applications and deployments. Because a Python dictionary is used to hold configuration information, and since you can populate that dictionary using different means, you have more options for configuration. For example, you can use a configuration file in JSON format, or, if you have access to YAML processing functionality, a file in YAML format, to populate the configuration dictionary. Or, of course, you can construct the dictionary in Python code, receive it in pickled form over a socket, or use whatever approach makes sense for your application.

Here's an example of the same configuration as above, in YAML format for the new dictionary-based approach:

version: 1
formatters:
  simple:
    format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
handlers:
  console:
    class: logging.StreamHandler
    level: DEBUG
    formatter: simple
    stream: ext://sys.stdout
loggers:
  simpleExample:
    level: DEBUG
    handlers: [console]
    propagate: no
root:
  level: DEBUG
  handlers: [console]

For more information about logging using a dictionary, see Configuration functions.

What happens if no configuration is provided

If no logging configuration is provided, it is possible to have a situation where a logging event needs to be output, but no handlers can be found to output the event.

The event is output using a 'handler of last resort', stored in lastResort. This internal handler is not associated with any logger, and acts like a StreamHandler which writes the event description message to the current value of sys.stderr (therefore respecting any redirections which may be in effect). No formatting is done on the message - just the bare event description message is printed. The handler's level is set to WARNING, so all events at this and greater severities will be output.

在 3.2 版的變更: For versions of Python prior to 3.2, the behaviour is as follows:

If raiseExceptions is False (production mode), the event is silently dropped.

If raiseExceptions is True (development mode), a message 'No handlers could be found for logger X.Y.Z' is printed once.

To obtain the pre-3.2 behaviour, lastResort can be set to None.

Configuring Logging for a Library

When developing a library which uses logging, you should take care to document how the library uses logging - for example, the names of loggers used. Some consideration also needs to be given to its logging configuration. If the using application does not use logging, and library code makes logging calls, then (as described in the previous section) events of severity WARNING and greater will be printed to sys.stderr. This is regarded as the best default behaviour.

If for some reason you don't want these messages printed in the absence of any logging configuration, you can attach a do-nothing handler to the top-level logger for your library. This avoids the message being printed, since a handler will always be found for the library's events: it just doesn't produce any output. If the library user configures logging for application use, presumably that configuration will add some handlers, and if levels are suitably configured then logging calls made in library code will send output to those handlers, as normal.

A do-nothing handler is included in the logging package: NullHandler (since Python 3.1). An instance of this handler could be added to the top-level logger of the logging namespace used by the library (if you want to prevent your library's logged events being output to sys.stderr in the absence of logging configuration). If all logging by a library foo is done using loggers with names matching 'foo.x', 'foo.x.y', etc. then the code:

import logging
logging.getLogger('foo').addHandler(logging.NullHandler())

should have the desired effect. If an organisation produces a number of libraries, then the logger name specified can be 'orgname.foo' rather than just 'foo'.

備註

It is strongly advised that you do not log to the root logger in your library. Instead, use a logger with a unique and easily identifiable name, such as the __name__ for your library's top-level package or module. Logging to the root logger will make it difficult or impossible for the application developer to configure the logging verbosity or handlers of your library as they wish.

備註

It is strongly advised that you do not add any handlers other than NullHandler to your library's loggers. This is because the configuration of handlers is the prerogative of the application developer who uses your library. The application developer knows their target audience and what handlers are most appropriate for their application: if you add handlers 'under the hood', you might well interfere with their ability to carry out unit tests and deliver logs which suit their requirements.

Logging Levels

The numeric values of logging levels are given in the following table. These are primarily of interest if you want to define your own levels, and need them to have specific values relative to the predefined levels. If you define a level with the same numeric value, it overwrites the predefined value; the predefined name is lost.

Level

Numeric value

CRITICAL

50

ERROR

40

WARNING

30

INFO

20

DEBUG

10

NOTSET

0

Levels can also be associated with loggers, being set either by the developer or through loading a saved logging configuration. When a logging method is called on a logger, the logger compares its own level with the level associated with the method call. If the logger's level is higher than the method call's, no logging message is actually generated. This is the basic mechanism controlling the verbosity of logging output.

Logging messages are encoded as instances of the LogRecord class. When a logger decides to actually log an event, a LogRecord instance is created from the logging message.

Logging messages are subjected to a dispatch mechanism through the use of handlers, which are instances of subclasses of the Handler class. Handlers are responsible for ensuring that a logged message (in the form of a LogRecord) ends up in a particular location (or set of locations) which is useful for the target audience for that message (such as end users, support desk staff, system administrators, developers). Handlers are passed LogRecord instances intended for particular destinations. Each logger can have zero, one or more handlers associated with it (via the addHandler() method of Logger). In addition to any handlers directly associated with a logger, all handlers associated with all ancestors of the logger are called to dispatch the message (unless the propagate flag for a logger is set to a false value, at which point the passing to ancestor handlers stops).

Just as for loggers, handlers can have levels associated with them. A handler's level acts as a filter in the same way as a logger's level does. If a handler decides to actually dispatch an event, the emit() method is used to send the message to its destination. Most user-defined subclasses of Handler will need to override this emit().

Custom Levels

Defining your own levels is possible, but should not be necessary, as the existing levels have been chosen on the basis of practical experience. However, if you are convinced that you need custom levels, great care should be exercised when doing this, and it is possibly a very bad idea to define custom levels if you are developing a library. That's because if multiple library authors all define their own custom levels, there is a chance that the logging output from such multiple libraries used together will be difficult for the using developer to control and/or interpret, because a given numeric value might mean different things for different libraries.

Useful Handlers

In addition to the base Handler class, many useful subclasses are provided:

StreamHandler instances send messages to streams (file-like objects).

FileHandler instances send messages to disk files.

BaseRotatingHandler is the base class for handlers that rotate log files at a certain point. It is not meant to be instantiated directly. Instead, use RotatingFileHandler or TimedRotatingFileHandler.

RotatingFileHandler instances send messages to disk files, with support for maximum log file sizes and log file rotation.

TimedRotatingFileHandler instances send messages to disk files, rotating the log file at certain timed intervals.

SocketHandler instances send messages to TCP/IP sockets. Since 3.4, Unix domain sockets are also supported.

DatagramHandler instances send messages to UDP sockets. Since 3.4, Unix domain sockets are also supported.

SMTPHandler instances send messages to a designated email address.

SysLogHandler instances send messages to a Unix syslog daemon, possibly on a remote machine.

NTEventLogHandler instances send messages to a Windows NT/2000/XP event log.

MemoryHandler instances send messages to a buffer in memory, which is flushed whenever specific criteria are met.

HTTPHandler instances send messages to an HTTP server using either GET or POST semantics.

WatchedFileHandler instances watch the file they are logging to. If the file changes, it is closed and reopened using the file name. This handler is only useful on Unix-like systems; Windows does not support the underlying mechanism used.

QueueHandler instances send messages to a queue, such as those implemented in the queue or multiprocessing modules.

NullHandler instances do nothing with error messages. They are used by library developers who want to use logging, but want to avoid the 'No handlers could be found for logger XXX' message which can be displayed if the library user has not configured logging. See Configuring Logging for a Library for more information.

在 3.1 版被加入: The NullHandler class.

在 3.2 版被加入: The QueueHandler class.

The NullHandler, StreamHandler and FileHandler classes are defined in the core logging package. The other handlers are defined in a sub-module, logging.handlers. (There is also another sub-module, logging.config, for configuration functionality.)

Logged messages are formatted for presentation through instances of the Formatter class. They are initialized with a format string suitable for use with the % operator and a dictionary.

For formatting multiple messages in a batch, instances of BufferingFormatter can be used. In addition to the format string (which is applied to each message in the batch), there is provision for header and trailer format strings.

When filtering based on logger level and/or handler level is not enough, instances of Filter can be added to both Logger and Handler instances (through their addFilter() method). Before deciding to process a message further, both loggers and handlers consult all their filters for permission. If any filter returns a false value, the message is not processed further.

The basic Filter functionality allows filtering by specific logger name. If this feature is used, messages sent to the named logger and its children are allowed through the filter, and all others dropped.

Exceptions raised during logging

The logging package is designed to swallow exceptions which occur while logging in production. This is so that errors which occur while handling logging events - such as logging misconfiguration, network or other similar errors - do not cause the application using logging to terminate prematurely.

SystemExit and KeyboardInterrupt exceptions are never swallowed. Other exceptions which occur during the emit() method of a Handler subclass are passed to its handleError() method.

The default implementation of handleError() in Handler checks to see if a module-level variable, raiseExceptions, is set. If set, a traceback is printed to sys.stderr. If not set, the exception is swallowed.

備註

The default value of raiseExceptions is True. This is because during development, you typically want to be notified of any exceptions that occur. It's advised that you set raiseExceptions to False for production usage.

Using arbitrary objects as messages

In the preceding sections and examples, it has been assumed that the message passed when logging the event is a string. However, this is not the only possibility. You can pass an arbitrary object as a message, and its __str__() method will be called when the logging system needs to convert it to a string representation. In fact, if you want to, you can avoid computing a string representation altogether - for example, the SocketHandler emits an event by pickling it and sending it over the wire.

最佳化

Formatting of message arguments is deferred until it cannot be avoided. However, computing the arguments passed to the logging method can also be expensive, and you may want to avoid doing it if the logger will just throw away your event. To decide what to do, you can call the isEnabledFor() method which takes a level argument and returns true if the event would be created by the Logger for that level of call. You can write code like this:

if logger.isEnabledFor(logging.DEBUG):
    logger.debug('Message with %s, %s', expensive_func1(),
                                        expensive_func2())

so that if the logger's threshold is set above DEBUG, the calls to expensive_func1 and expensive_func2 are never made.

備註

In some cases, isEnabledFor() can itself be more expensive than you'd like (e.g. for deeply nested loggers where an explicit level is only set high up in the logger hierarchy). In such cases (or if you want to avoid calling a method in tight loops), you can cache the result of a call to isEnabledFor() in a local or instance variable, and use that instead of calling the method each time. Such a cached value would only need to be recomputed when the logging configuration changes dynamically while the application is running (which is not all that common).

There are other optimizations which can be made for specific applications which need more precise control over what logging information is collected. Here's a list of things you can do to avoid processing during logging which you don't need:

What you don't want to collect

How to avoid collecting it

Information about where calls were made from.

Set logging._srcfile to None. This avoids calling sys._getframe(), which may help to speed up your code in environments like PyPy (which can't speed up code that uses sys._getframe()).

Threading information.

將 logging.logThreads 設為 False。

目前的行程 ID (os.getpid())

將 logging.logProcesses 設為 False。

Current process name when using multiprocessing to manage multiple processes.

將 logging.logMultiprocessing 設為 False。

Current asyncio.Task name when using asyncio.

將 logging.logAsyncioTasks 設為 False。

Also note that the core logging module only includes the basic handlers. If you don't import logging.handlers and logging.config, they won't take up any memory.

其他資源

也參考

logging 模組

API reference for the logging module.

logging.config 模組

Configuration API for the logging module.

logging.handlers 模組

Useful handlers included with the logging module.

A logging cookbook

Logging Cookbook

作者:

Vinay Sajip <vinay_sajip at red-dove dot com>

This page contains a number of recipes related to logging, which have been found useful in the past. For links to tutorial and reference information, please see 其他資源.

Using logging in multiple modules

Multiple calls to logging.getLogger('someLogger') return a reference to the same logger object. This is true not only within the same module, but also across modules as long as it is in the same Python interpreter process. It is true for references to the same object; additionally, application code can define and configure a parent logger in one module and create (but not configure) a child logger in a separate module, and all logger calls to the child will pass up to the parent. Here is a main module:

import logging
import auxiliary_module

# create logger with 'spam_application'
logger = logging.getLogger('spam_application')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
fh.setFormatter(formatter)
ch.setFormatter(formatter)
# add the handlers to the logger
logger.addHandler(fh)
logger.addHandler(ch)

logger.info('creating an instance of auxiliary_module.Auxiliary')
a = auxiliary_module.Auxiliary()
logger.info('created an instance of auxiliary_module.Auxiliary')
logger.info('calling auxiliary_module.Auxiliary.do_something')
a.do_something()
logger.info('finished auxiliary_module.Auxiliary.do_something')
logger.info('calling auxiliary_module.some_function()')
auxiliary_module.some_function()
logger.info('done with auxiliary_module.some_function()')

Here is the auxiliary module:

import logging

# create logger
module_logger = logging.getLogger('spam_application.auxiliary')

class Auxiliary:
    def __init__(self):
        self.logger = logging.getLogger('spam_application.auxiliary.Auxiliary')
        self.logger.info('creating an instance of Auxiliary')

    def do_something(self):
        self.logger.info('doing something')
        a = 1 + 1
        self.logger.info('done doing something')

def some_function():
    module_logger.info('received a call to "some_function"')

The output looks like this:

2005-03-23 23:47:11,663 - spam_application - INFO -
   creating an instance of auxiliary_module.Auxiliary
2005-03-23 23:47:11,665 - spam_application.auxiliary.Auxiliary - INFO -
   creating an instance of Auxiliary
2005-03-23 23:47:11,665 - spam_application - INFO -
   created an instance of auxiliary_module.Auxiliary
2005-03-23 23:47:11,668 - spam_application - INFO -
   calling auxiliary_module.Auxiliary.do_something
2005-03-23 23:47:11,668 - spam_application.auxiliary.Auxiliary - INFO -
   doing something
2005-03-23 23:47:11,669 - spam_application.auxiliary.Auxiliary - INFO -
   done doing something
2005-03-23 23:47:11,670 - spam_application - INFO -
   finished auxiliary_module.Auxiliary.do_something
2005-03-23 23:47:11,671 - spam_application - INFO -
   calling auxiliary_module.some_function()
2005-03-23 23:47:11,672 - spam_application.auxiliary - INFO -
   received a call to 'some_function'
2005-03-23 23:47:11,673 - spam_application - INFO -
   done with auxiliary_module.some_function()

Logging from multiple threads

Logging from multiple threads requires no special effort. The following example shows logging from the main (initial) thread and another thread:

import logging
import threading
import time

def worker(arg):
    while not arg['stop']:
        logging.debug('Hi from myfunc')
        time.sleep(0.5)

def main():
    logging.basicConfig(level=logging.DEBUG, format='%(relativeCreated)6d %(threadName)s %(message)s')
    info = {'stop': False}
    thread = threading.Thread(target=worker, args=(info,))
    thread.start()
    while True:
        try:
            logging.debug('Hello from main')
            time.sleep(0.75)
        except KeyboardInterrupt:
            info['stop'] = True
            break
    thread.join()

if __name__ == '__main__':
    main()

When run, the script should print something like the following:

   0 Thread-1 Hi from myfunc
   3 MainThread Hello from main
 505 Thread-1 Hi from myfunc
 755 MainThread Hello from main
1007 Thread-1 Hi from myfunc
1507 MainThread Hello from main
1508 Thread-1 Hi from myfunc
2010 Thread-1 Hi from myfunc
2258 MainThread Hello from main
2512 Thread-1 Hi from myfunc
3009 MainThread Hello from main
3013 Thread-1 Hi from myfunc
3515 Thread-1 Hi from myfunc
3761 MainThread Hello from main
4017 Thread-1 Hi from myfunc
4513 MainThread Hello from main
4518 Thread-1 Hi from myfunc

This shows the logging output interspersed as one might expect. This approach works for more threads than shown here, of course.

Multiple handlers and formatters

Loggers are plain Python objects. The addHandler() method has no minimum or maximum quota for the number of handlers you may add. Sometimes it will be beneficial for an application to log all messages of all severities to a text file while simultaneously logging errors or above to the console. To set this up, simply configure the appropriate handlers. The logging calls in the application code will remain unchanged. Here is a slight modification to the previous simple module-based configuration example:

import logging

logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
ch.setFormatter(formatter)
fh.setFormatter(formatter)
# add the handlers to logger
logger.addHandler(ch)
logger.addHandler(fh)

# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')

Notice that the 'application' code does not care about multiple handlers. All that changed was the addition and configuration of a new handler named fh.

The ability to create new handlers with higher- or lower-severity filters can be very helpful when writing and testing an application. Instead of using many print statements for debugging, use logger.debug: Unlike the print statements, which you will have to delete or comment out later, the logger.debug statements can remain intact in the source code and remain dormant until you need them again. At that time, the only change that needs to happen is to modify the severity level of the logger and/or handler to debug.

Logging to multiple destinations

Let's say you want to log to console and file with different message formats and in differing circumstances. Say you want to log messages with levels of DEBUG and higher to file, and those messages at level INFO and higher to the console. Let's also assume that the file should contain timestamps, but the console messages should not. Here's how you can achieve this:

import logging

# set up logging to file - see previous section for more details
logging.basicConfig(level=logging.DEBUG,
                    format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
                    datefmt='%m-%d %H:%M',
                    filename='/tmp/myapp.log',
                    filemode='w')
# define a Handler which writes INFO messages or higher to the sys.stderr
console = logging.StreamHandler()
console.setLevel(logging.INFO)
# set a format which is simpler for console use
formatter = logging.Formatter('%(name)-12s: %(levelname)-8s %(message)s')
# tell the handler to use this format
console.setFormatter(formatter)
# add the handler to the root logger
logging.getLogger('').addHandler(console)

# Now, we can log to the root logger, or any other logger. First the root...
logging.info('Jackdaws love my big sphinx of quartz.')

# Now, define a couple of other loggers which might represent areas in your
# application:

logger1 = logging.getLogger('myapp.area1')
logger2 = logging.getLogger('myapp.area2')

logger1.debug('Quick zephyrs blow, vexing daft Jim.')
logger1.info('How quickly daft jumping zebras vex.')
logger2.warning('Jail zesty vixen who grabbed pay from quack.')
logger2.error('The five boxing wizards jump quickly.')

When you run this, on the console you will see

root        : INFO     Jackdaws love my big sphinx of quartz.
myapp.area1 : INFO     How quickly daft jumping zebras vex.
myapp.area2 : WARNING  Jail zesty vixen who grabbed pay from quack.
myapp.area2 : ERROR    The five boxing wizards jump quickly.

and in the file you will see something like

10-22 22:19 root         INFO     Jackdaws love my big sphinx of quartz.
10-22 22:19 myapp.area1  DEBUG    Quick zephyrs blow, vexing daft Jim.
10-22 22:19 myapp.area1  INFO     How quickly daft jumping zebras vex.
10-22 22:19 myapp.area2  WARNING  Jail zesty vixen who grabbed pay from quack.
10-22 22:19 myapp.area2  ERROR    The five boxing wizards jump quickly.

As you can see, the DEBUG message only shows up in the file. The other messages are sent to both destinations.

This example uses console and file handlers, but you can use any number and combination of handlers you choose.

Note that the above choice of log filename /tmp/myapp.log implies use of a standard location for temporary files on POSIX systems. On Windows, you may need to choose a different directory name for the log - just ensure that the directory exists and that you have the permissions to create and update files in it.

Custom handling of levels

Sometimes, you might want to do something slightly different from the standard handling of levels in handlers, where all levels above a threshold get processed by a handler. To do this, you need to use filters. Let's look at a scenario where you want to arrange things as follows:

Send messages of severity INFO and WARNING to sys.stdout

Send messages of severity ERROR and above to sys.stderr

Send messages of severity DEBUG and above to file app.log

Suppose you configure logging with the following JSON:

{
    "version": 1,
    "disable_existing_loggers": false,
    "formatters": {
        "simple": {
            "format": "%(levelname)-8s - %(message)s"
        }
    },
    "handlers": {
        "stdout": {
            "class": "logging.StreamHandler",
            "level": "INFO",
            "formatter": "simple",
            "stream": "ext://sys.stdout"
        },
        "stderr": {
            "class": "logging.StreamHandler",
            "level": "ERROR",
            "formatter": "simple",
            "stream": "ext://sys.stderr"
        },
        "file": {
            "class": "logging.FileHandler",
            "formatter": "simple",
            "filename": "app.log",
            "mode": "w"
        }
    },
    "root": {
        "level": "DEBUG",
        "handlers": [
            "stderr",
            "stdout",
            "file"
        ]
    }
}

This configuration does almost what we want, except that sys.stdout would show messages of severity ERROR and only events of this severity and higher will be tracked as well as INFO and WARNING messages. To prevent this, we can set up a filter which excludes those messages and add it to the relevant handler. This can be configured by adding a filters section parallel to formatters and handlers:

{
    "filters": {
        "warnings_and_below": {
            "()" : "__main__.filter_maker",
            "level": "WARNING"
        }
    }
}

and changing the section on the stdout handler to add it:

{
    "stdout": {
        "class": "logging.StreamHandler",
        "level": "INFO",
        "formatter": "simple",
        "stream": "ext://sys.stdout",
        "filters": ["warnings_and_below"]
    }
}

A filter is just a function, so we can define the filter_maker (a factory function) as follows:

def filter_maker(level):
    level = getattr(logging, level)

    def filter(record):
        return record.levelno <= level

    return filter

This converts the string argument passed in to a numeric level, and returns a function which only returns True if the level of the passed in record is at or below the specified level. Note that in this example I have defined the filter_maker in a test script main.py that I run from the command line, so its module will be __main__ - hence the __main__.filter_maker in the filter configuration. You will need to change that if you define it in a different module.

With the filter added, we can run main.py, which in full is:

import json
import logging
import logging.config

CONFIG = '''
{
    "version": 1,
    "disable_existing_loggers": false,
    "formatters": {
        "simple": {
            "format": "%(levelname)-8s - %(message)s"
        }
    },
    "filters": {
        "warnings_and_below": {
            "()" : "__main__.filter_maker",
            "level": "WARNING"
        }
    },
    "handlers": {
        "stdout": {
            "class": "logging.StreamHandler",
            "level": "INFO",
            "formatter": "simple",
            "stream": "ext://sys.stdout",
            "filters": ["warnings_and_below"]
        },
        "stderr": {
            "class": "logging.StreamHandler",
            "level": "ERROR",
            "formatter": "simple",
            "stream": "ext://sys.stderr"
        },
        "file": {
            "class": "logging.FileHandler",
            "formatter": "simple",
            "filename": "app.log",
            "mode": "w"
        }
    },
    "root": {
        "level": "DEBUG",
        "handlers": [
            "stderr",
            "stdout",
            "file"
        ]
    }
}
'''

def filter_maker(level):
    level = getattr(logging, level)

    def filter(record):
        return record.levelno <= level

    return filter

logging.config.dictConfig(json.loads(CONFIG))
logging.debug('A DEBUG message')
logging.info('An INFO message')
logging.warning('A WARNING message')
logging.error('An ERROR message')
logging.critical('A CRITICAL message')

And after running it like this:

python main.py 2>stderr.log >stdout.log

We can see the results are as expected:

$ more *.log
::::::::::::::
app.log
::::::::::::::
DEBUG    - A DEBUG message
INFO     - An INFO message
WARNING  - A WARNING message
ERROR    - An ERROR message
CRITICAL - A CRITICAL message
::::::::::::::
stderr.log
::::::::::::::
ERROR    - An ERROR message
CRITICAL - A CRITICAL message
::::::::::::::
stdout.log
::::::::::::::
INFO     - An INFO message
WARNING  - A WARNING message

Configuration server example

Here is an example of a module using the logging configuration server:

import logging
import logging.config
import time
import os

# read initial config file
logging.config.fileConfig('logging.conf')

# create and start listener on port 9999
t = logging.config.listen(9999)
t.start()

logger = logging.getLogger('simpleExample')

try:
    # loop through logging calls to see the difference
    # new configurations make, until Ctrl+C is pressed
    while True:
        logger.debug('debug message')
        logger.info('info message')
        logger.warning('warn message')
        logger.error('error message')
        logger.critical('critical message')
        time.sleep(5)
except KeyboardInterrupt:
    # cleanup
    logging.config.stopListening()
    t.join()

And here is a script that takes a filename and sends that file to the server, properly preceded with the binary-encoded length, as the new logging configuration:

#!/usr/bin/env python
import socket, sys, struct

with open(sys.argv[1], 'rb') as f:
    data_to_send = f.read()

HOST = 'localhost'
PORT = 9999
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('connecting...')
s.connect((HOST, PORT))
print('sending config...')
s.send(struct.pack('>L', len(data_to_send)))
s.send(data_to_send)
s.close()
print('complete')

Dealing with handlers that block

Sometimes you have to get your logging handlers to do their work without blocking the thread you're logging from. This is common in web applications, though of course it also occurs in other scenarios.

A common culprit which demonstrates sluggish behaviour is the SMTPHandler: sending emails can take a long time, for a number of reasons outside the developer's control (for example, a poorly performing mail or network infrastructure). But almost any network-based handler can block: Even a SocketHandler operation may do a DNS query under the hood which is too slow (and this query can be deep in the socket library code, below the Python layer, and outside your control).

One solution is to use a two-part approach. For the first part, attach only a QueueHandler to those loggers which are accessed from performance-critical threads. They simply write to their queue, which can be sized to a large enough capacity or initialized with no upper bound to their size. The write to the queue will typically be accepted quickly, though you will probably need to catch the queue.Full exception as a precaution in your code. If you are a library developer who has performance-critical threads in their code, be sure to document this (together with a suggestion to attach only QueueHandlers to your loggers) for the benefit of other developers who will use your code.

The second part of the solution is QueueListener, which has been designed as the counterpart to QueueHandler. A QueueListener is very simple: it's passed a queue and some handlers, and it fires up an internal thread which listens to its queue for LogRecords sent from QueueHandlers (or any other source of LogRecords, for that matter). The LogRecords are removed from the queue and passed to the handlers for processing.

The advantage of having a separate QueueListener class is that you can use the same instance to service multiple QueueHandlers. This is more resource-friendly than, say, having threaded versions of the existing handler classes, which would eat up one thread per handler for no particular benefit.

An example of using these two classes follows (imports omitted):

que = queue.Queue(-1)  # no limit on size
queue_handler = QueueHandler(que)
handler = logging.StreamHandler()
listener = QueueListener(que, handler)
root = logging.getLogger()
root.addHandler(queue_handler)
formatter = logging.Formatter('%(threadName)s: %(message)s')
handler.setFormatter(formatter)
listener.start()
# The log output will display the thread which generated
# the event (the main thread) rather than the internal
# thread which monitors the internal queue. This is what
# you want to happen.
root.warning('Look out!')
listener.stop()

which, when run, will produce:

MainThread: Look out!

備註

Although the earlier discussion wasn't specifically talking about async code, but rather about slow logging handlers, it should be noted that when logging from async code, network and even file handlers could lead to problems (blocking the event loop) because some logging is done from asyncio internals. It might be best, if any async code is used in an application, to use the above approach for logging, so that any blocking code runs only in the QueueListener thread.

在 3.5 版的變更: Prior to Python 3.5, the QueueListener always passed every message received from the queue to every handler it was initialized with. (This was because it was assumed that level filtering was all done on the other side, where the queue is filled.) From 3.5 onwards, this behaviour can be changed by passing a keyword argument respect_handler_level=True to the listener's constructor. When this is done, the listener compares the level of each message with the handler's level, and only passes a message to a handler if it's appropriate to do so.

在 3.14 版的變更: The QueueListener can be started (and stopped) via the with statement. For example:

with QueueListener(que, handler) as listener:
    # The queue listener automatically starts
    # when the 'with' block is entered.
    pass
# The queue listener automatically stops once
# the 'with' block is exited.

Sending and receiving logging events across a network

Let's say you want to send logging events across a network, and handle them at the receiving end. A simple way of doing this is attaching a SocketHandler instance to the root logger at the sending end:

import logging, logging.handlers

rootLogger = logging.getLogger('')
rootLogger.setLevel(logging.DEBUG)
socketHandler = logging.handlers.SocketHandler('localhost',
                    logging.handlers.DEFAULT_TCP_LOGGING_PORT)
# don't bother with a formatter, since a socket handler sends the event as
# an unformatted pickle
rootLogger.addHandler(socketHandler)

# Now, we can log to the root logger, or any other logger. First the root...
logging.info('Jackdaws love my big sphinx of quartz.')

# Now, define a couple of other loggers which might represent areas in your
# application:

logger1 = logging.getLogger('myapp.area1')
logger2 = logging.getLogger('myapp.area2')

logger1.debug('Quick zephyrs blow, vexing daft Jim.')
logger1.info('How quickly daft jumping zebras vex.')
logger2.warning('Jail zesty vixen who grabbed pay from quack.')
logger2.error('The five boxing wizards jump quickly.')

At the receiving end, you can set up a receiver using the socketserver module. Here is a basic working example:

import pickle
import logging
import logging.handlers
import socketserver
import struct

class LogRecordStreamHandler(socketserver.StreamRequestHandler):
    """Handler for a streaming logging request.

    This basically logs the record using whatever logging policy is
    configured locally.
    """

    def handle(self):
        """
        Handle multiple requests - each expected to be a 4-byte length,
        followed by the LogRecord in pickle format. Logs the record
        according to whatever policy is configured locally.
        """
        while True:
            chunk = self.connection.recv(4)
            if len(chunk) < 4:
                break
            slen = struct.unpack('>L', chunk)[0]
            chunk = self.connection.recv(slen)
            while len(chunk) < slen:
                chunk = chunk + self.connection.recv(slen - len(chunk))
            obj = self.unPickle(chunk)
            record = logging.makeLogRecord(obj)
            self.handleLogRecord(record)

    def unPickle(self, data):
        return pickle.loads(data)

    def handleLogRecord(self, record):
        # if a name is specified, we use the named logger rather than the one
        # implied by the record.
        if self.server.logname is not None:
            name = self.server.logname
        else:
            name = record.name
        logger = logging.getLogger(name)
        # N.B. EVERY record gets logged. This is because Logger.handle
        # is normally called AFTER logger-level filtering. If you want
        # to do filtering, do it at the client end to save wasting
        # cycles and network bandwidth!
        logger.handle(record)

class LogRecordSocketReceiver(socketserver.ThreadingTCPServer):
    """
    Simple TCP socket-based logging receiver suitable for testing.
    """

    allow_reuse_address = True

    def __init__(self, host='localhost',
                 port=logging.handlers.DEFAULT_TCP_LOGGING_PORT,
                 handler=LogRecordStreamHandler):
        socketserver.ThreadingTCPServer.__init__(self, (host, port), handler)
        self.abort = 0
        self.timeout = 1
        self.logname = None

    def serve_until_stopped(self):
        import select
        abort = 0
        while not abort:
            rd, wr, ex = select.select([self.socket.fileno()],
                                       [], [],
                                       self.timeout)
            if rd:
                self.handle_request()
            abort = self.abort

def main():
    logging.basicConfig(
        format='%(relativeCreated)5d %(name)-15s %(levelname)-8s %(message)s')
    tcpserver = LogRecordSocketReceiver()
    print('About to start TCP server...')
    tcpserver.serve_until_stopped()

if __name__ == '__main__':
    main()

First run the server, and then the client. On the client side, nothing is printed on the console; on the server side, you should see something like:

About to start TCP server...
   59 root            INFO     Jackdaws love my big sphinx of quartz.
   59 myapp.area1     DEBUG    Quick zephyrs blow, vexing daft Jim.
   69 myapp.area1     INFO     How quickly daft jumping zebras vex.
   69 myapp.area2     WARNING  Jail zesty vixen who grabbed pay from quack.
   69 myapp.area2     ERROR    The five boxing wizards jump quickly.

Note that there are some security issues with pickle in some scenarios. If these affect you, you can use an alternative serialization scheme by overriding the makePickle() method and implementing your alternative there, as well as adapting the above script to use your alternative serialization.

Running a logging socket listener in production

To run a logging listener in production, you may need to use a process-management tool such as Supervisor [http://supervisord.org/]. Here is a Gist [https://gist.github.com/vsajip/4b227eeec43817465ca835ca66f75e2b] which provides the bare-bones files to run the above functionality using Supervisor. It consists of the following files:

檔案

目的

prepare.sh

A Bash script to prepare the environment for testing

supervisor.conf

The Supervisor configuration file, which has entries for the listener and a multi-process web application

ensure_app.sh

A Bash script to ensure that Supervisor is running with the above configuration

log_listener.py

The socket listener program which receives log events and records them to a file

main.py

A simple web application which performs logging via a socket connected to the listener

webapp.json

A JSON configuration file for the web application

client.py

A Python script to exercise the web application

The web application uses Gunicorn [https://gunicorn.org/], which is a popular web application server that starts multiple worker processes to handle requests. This example setup shows how the workers can write to the same log file without conflicting with one another --- they all go through the socket listener.

To test these files, do the following in a POSIX environment:

Download the Gist [https://gist.github.com/vsajip/4b227eeec43817465ca835ca66f75e2b] as a ZIP archive using the Download ZIP button.

Unzip the above files from the archive into a scratch directory.

In the scratch directory, run bash prepare.sh to get things ready. This creates a run subdirectory to contain Supervisor-related and log files, and a venv subdirectory to contain a virtual environment into which bottle, gunicorn and supervisor are installed.

Run bash ensure_app.sh to ensure that Supervisor is running with the above configuration.

Run venv/bin/python client.py to exercise the web application, which will lead to records being written to the log.

Inspect the log files in the run subdirectory. You should see the most recent log lines in files matching the pattern app.log*. They won't be in any particular order, since they have been handled concurrently by different worker processes in a non-deterministic way.

You can shut down the listener and the web application by running venv/bin/supervisorctl -c supervisor.conf shutdown.

You may need to tweak the configuration files in the unlikely event that the configured ports clash with something else in your test environment.

The default configuration uses a TCP socket on port 9020. You can use a Unix Domain socket instead of a TCP socket by doing the following:

In listener.json, add a socket key with the path to the domain socket you want to use. If this key is present, the listener listens on the corresponding domain socket and not on a TCP socket (the port key is ignored).

In webapp.json, change the socket handler configuration dictionary so that the host value is the path to the domain socket, and set the port value to null.

Adding contextual information to your logging output

Sometimes you want logging output to contain contextual information in addition to the parameters passed to the logging call. For example, in a networked application, it may be desirable to log client-specific information in the log (e.g. remote client's username, or IP address). Although you could use the extra parameter to achieve this, it's not always convenient to pass the information in this way. While it might be tempting to create Logger instances on a per-connection basis, this is not a good idea because these instances are not garbage collected. While this is not a problem in practice, when the number of Logger instances is dependent on the level of granularity you want to use in logging an application, it could be hard to manage if the number of Logger instances becomes effectively unbounded.

Using LoggerAdapters to impart contextual information

An easy way in which you can pass contextual information to be output along with logging event information is to use the LoggerAdapter class. This class is designed to look like a Logger, so that you can call debug(), info(), warning(), error(), exception(), critical() and log(). These methods have the same signatures as their counterparts in Logger, so you can use the two types of instances interchangeably.

When you create an instance of LoggerAdapter, you pass it a Logger instance and a dict-like object which contains your contextual information. When you call one of the logging methods on an instance of LoggerAdapter, it delegates the call to the underlying instance of Logger passed to its constructor, and arranges to pass the contextual information in the delegated call. Here's a snippet from the code of LoggerAdapter:

def debug(self, msg, /, *args, **kwargs):
    """
    Delegate a debug call to the underlying logger, after adding
    contextual information from this adapter instance.
    """
    msg, kwargs = self.process(msg, kwargs)
    self.logger.debug(msg, *args, **kwargs)

The process() method of LoggerAdapter is where the contextual information is added to the logging output. It's passed the message and keyword arguments of the logging call, and it passes back (potentially) modified versions of these to use in the call to the underlying logger. The default implementation of this method leaves the message alone, but inserts an 'extra' key in the keyword argument whose value is the dict-like object passed to the constructor. Of course, if you had passed an 'extra' keyword argument in the call to the adapter, it will be silently overwritten.

The advantage of using 'extra' is that the values in the dict-like object are merged into the LogRecord instance's __dict__, allowing you to use customized strings with your Formatter instances which know about the keys of the dict-like object. If you need a different method, e.g. if you want to prepend or append the contextual information to the message string, you just need to subclass LoggerAdapter and override process() to do what you need. Here is a simple example:

class CustomAdapter(logging.LoggerAdapter):
    """
    This example adapter expects the passed in dict-like object to have a
    'connid' key, whose value in brackets is prepended to the log message.
    """
    def process(self, msg, kwargs):
        return '[%s] %s' % (self.extra['connid'], msg), kwargs

which you can use like this:

logger = logging.getLogger(__name__)
adapter = CustomAdapter(logger, {'connid': some_conn_id})

Then any events that you log to the adapter will have the value of some_conn_id prepended to the log messages.

Using objects other than dicts to pass contextual information

You don't need to pass an actual dict to a LoggerAdapter - you could pass an instance of a class which implements __getitem__ and __iter__ so that it looks like a dict to logging. This would be useful if you want to generate values dynamically (whereas the values in a dict would be constant).

Using Filters to impart contextual information

You can also add contextual information to log output using a user-defined Filter. Filter instances are allowed to modify the LogRecords passed to them, including adding additional attributes which can then be output using a suitable format string, or if needed a custom Formatter.

For example in a web application, the request being processed (or at least, the interesting parts of it) can be stored in a threadlocal (threading.local) variable, and then accessed from a Filter to add, say, information from the request - say, the remote IP address and remote user's username - to the LogRecord, using the attribute names 'ip' and 'user' as in the LoggerAdapter example above. In that case, the same format string can be used to get similar output to that shown above. Here's an example script:

import logging
from random import choice

class ContextFilter(logging.Filter):
    """
    This is a filter which injects contextual information into the log.

    Rather than use actual contextual information, we just use random
    data in this demo.
    """

    USERS = ['jim', 'fred', 'sheila']
    IPS = ['123.231.231.123', '127.0.0.1', '192.168.0.1']

    def filter(self, record):

        record.ip = choice(ContextFilter.IPS)
        record.user = choice(ContextFilter.USERS)
        return True

if __name__ == '__main__':
    levels = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, logging.CRITICAL)
    logging.basicConfig(level=logging.DEBUG,
                        format='%(asctime)-15s %(name)-5s %(levelname)-8s IP: %(ip)-15s User: %(user)-8s %(message)s')
    a1 = logging.getLogger('a.b.c')
    a2 = logging.getLogger('d.e.f')

    f = ContextFilter()
    a1.addFilter(f)
    a2.addFilter(f)
    a1.debug('A debug message')
    a1.info('An info message with %s', 'some parameters')
    for x in range(10):
        lvl = choice(levels)
        lvlname = logging.getLevelName(lvl)
        a2.log(lvl, 'A message at %s level with %d %s', lvlname, 2, 'parameters')

which, when run, produces something like:

2010-09-06 22:38:15,292 a.b.c DEBUG    IP: 123.231.231.123 User: fred     A debug message
2010-09-06 22:38:15,300 a.b.c INFO     IP: 192.168.0.1     User: sheila   An info message with some parameters
2010-09-06 22:38:15,300 d.e.f CRITICAL IP: 127.0.0.1       User: sheila   A message at CRITICAL level with 2 parameters
2010-09-06 22:38:15,300 d.e.f ERROR    IP: 127.0.0.1       User: jim      A message at ERROR level with 2 parameters
2010-09-06 22:38:15,300 d.e.f DEBUG    IP: 127.0.0.1       User: sheila   A message at DEBUG level with 2 parameters
2010-09-06 22:38:15,300 d.e.f ERROR    IP: 123.231.231.123 User: fred     A message at ERROR level with 2 parameters
2010-09-06 22:38:15,300 d.e.f CRITICAL IP: 192.168.0.1     User: jim      A message at CRITICAL level with 2 parameters
2010-09-06 22:38:15,300 d.e.f CRITICAL IP: 127.0.0.1       User: sheila   A message at CRITICAL level with 2 parameters
2010-09-06 22:38:15,300 d.e.f DEBUG    IP: 192.168.0.1     User: jim      A message at DEBUG level with 2 parameters
2010-09-06 22:38:15,301 d.e.f ERROR    IP: 127.0.0.1       User: sheila   A message at ERROR level with 2 parameters
2010-09-06 22:38:15,301 d.e.f DEBUG    IP: 123.231.231.123 User: fred     A message at DEBUG level with 2 parameters
2010-09-06 22:38:15,301 d.e.f INFO     IP: 123.231.231.123 User: fred     A message at INFO level with 2 parameters

Use of contextvars

Since Python 3.7, the contextvars module has provided context-local storage which works for both threading and asyncio processing needs. This type of storage may thus be generally preferable to thread-locals. The following example shows how, in a multi-threaded environment, logs can populated with contextual information such as, for example, request attributes handled by web applications.

For the purposes of illustration, say that you have different web applications, each independent of the other but running in the same Python process and using a library common to them. How can each of these applications have their own log, where all logging messages from the library (and other request processing code) are directed to the appropriate application's log file, while including in the log additional contextual information such as client IP, HTTP request method and client username?

Let's assume that the library can be simulated by the following code:

# webapplib.py
import logging
import time

logger = logging.getLogger(__name__)

def useful():
    # Just a representative event logged from the library
    logger.debug('Hello from webapplib!')
    # Just sleep for a bit so other threads get to run
    time.sleep(0.01)

We can simulate the multiple web applications by means of two simple classes, Request and WebApp. These simulate how real threaded web applications work - each request is handled by a thread:

# main.py
import argparse
from contextvars import ContextVar
import logging
import os
from random import choice
import threading
import webapplib

logger = logging.getLogger(__name__)
root = logging.getLogger()
root.setLevel(logging.DEBUG)

class Request:
    """
    A simple dummy request class which just holds dummy HTTP request method,
    client IP address and client username
    """
    def __init__(self, method, ip, user):
        self.method = method
        self.ip = ip
        self.user = user

# A dummy set of requests which will be used in the simulation - we'll just pick
# from this list randomly. Note that all GET requests are from 192.168.2.XXX
# addresses, whereas POST requests are from 192.16.3.XXX addresses. Three users
# are represented in the sample requests.

REQUESTS = [
    Request('GET', '192.168.2.20', 'jim'),
    Request('POST', '192.168.3.20', 'fred'),
    Request('GET', '192.168.2.21', 'sheila'),
    Request('POST', '192.168.3.21', 'jim'),
    Request('GET', '192.168.2.22', 'fred'),
    Request('POST', '192.168.3.22', 'sheila'),
]

# Note that the format string includes references to request context information
# such as HTTP method, client IP and username

formatter = logging.Formatter('%(threadName)-11s %(appName)s %(name)-9s %(user)-6s %(ip)s %(method)-4s %(message)s')

# Create our context variables. These will be filled at the start of request
# processing, and used in the logging that happens during that processing

ctx_request = ContextVar('request')
ctx_appname = ContextVar('appname')

class InjectingFilter(logging.Filter):
    """
    A filter which injects context-specific information into logs and ensures
    that only information for a specific webapp is included in its log
    """
    def __init__(self, app):
        self.app = app

    def filter(self, record):
        request = ctx_request.get()
        record.method = request.method
        record.ip = request.ip
        record.user = request.user
        record.appName = appName = ctx_appname.get()
        return appName == self.app.name

class WebApp:
    """
    A dummy web application class which has its own handler and filter for a
    webapp-specific log.
    """
    def __init__(self, name):
        self.name = name
        handler = logging.FileHandler(name + '.log', 'w')
        f = InjectingFilter(self)
        handler.setFormatter(formatter)
        handler.addFilter(f)
        root.addHandler(handler)
        self.num_requests = 0

    def process_request(self, request):
        """
        This is the dummy method for processing a request. It's called on a
        different thread for every request. We store the context information into
        the context vars before doing anything else.
        """
        ctx_request.set(request)
        ctx_appname.set(self.name)
        self.num_requests += 1
        logger.debug('Request processing started')
        webapplib.useful()
        logger.debug('Request processing finished')

def main():
    fn = os.path.splitext(os.path.basename(__file__))[0]
    adhf = argparse.ArgumentDefaultsHelpFormatter
    ap = argparse.ArgumentParser(formatter_class=adhf, prog=fn,
                                 description='Simulate a couple of web '
                                             'applications handling some '
                                             'requests, showing how request '
                                             'context can be used to '
                                             'populate logs')
    aa = ap.add_argument
    aa('--count', '-c', type=int, default=100, help='How many requests to simulate')
    options = ap.parse_args()

    # Create the dummy webapps and put them in a list which we can use to select
    # from randomly
    app1 = WebApp('app1')
    app2 = WebApp('app2')
    apps = [app1, app2]
    threads = []
    # Add a common handler which will capture all events
    handler = logging.FileHandler('app.log', 'w')
    handler.setFormatter(formatter)
    root.addHandler(handler)

    # Generate calls to process requests
    for i in range(options.count):
        try:
            # Pick an app at random and a request for it to process
            app = choice(apps)
            request = choice(REQUESTS)
            # Process the request in its own thread
            t = threading.Thread(target=app.process_request, args=(request,))
            threads.append(t)
            t.start()
        except KeyboardInterrupt:
            break

    # Wait for the threads to terminate
    for t in threads:
        t.join()

    for app in apps:
        print('%s processed %s requests' % (app.name, app.num_requests))

if __name__ == '__main__':
    main()

If you run the above, you should find that roughly half the requests go into app1.log and the rest into app2.log, and the all the requests are logged to app.log. Each webapp-specific log will contain only log entries for only that webapp, and the request information will be displayed consistently in the log (i.e. the information in each dummy request will always appear together in a log line). This is illustrated by the following shell output:

~/logging-contextual-webapp$ python main.py
app1 processed 51 requests
app2 processed 49 requests
~/logging-contextual-webapp$ wc -l *.log
  153 app1.log
  147 app2.log
  300 app.log
  600 total
~/logging-contextual-webapp$ head -3 app1.log
Thread-3 (process_request) app1 __main__  jim    192.168.3.21 POST Request processing started
Thread-3 (process_request) app1 webapplib jim    192.168.3.21 POST Hello from webapplib!
Thread-5 (process_request) app1 __main__  jim    192.168.3.21 POST Request processing started
~/logging-contextual-webapp$ head -3 app2.log
Thread-1 (process_request) app2 __main__  sheila 192.168.2.21 GET  Request processing started
Thread-1 (process_request) app2 webapplib sheila 192.168.2.21 GET  Hello from webapplib!
Thread-2 (process_request) app2 __main__  jim    192.168.2.20 GET  Request processing started
~/logging-contextual-webapp$ head app.log
Thread-1 (process_request) app2 __main__  sheila 192.168.2.21 GET  Request processing started
Thread-1 (process_request) app2 webapplib sheila 192.168.2.21 GET  Hello from webapplib!
Thread-2 (process_request) app2 __main__  jim    192.168.2.20 GET  Request processing started
Thread-3 (process_request) app1 __main__  jim    192.168.3.21 POST Request processing started
Thread-2 (process_request) app2 webapplib jim    192.168.2.20 GET  Hello from webapplib!
Thread-3 (process_request) app1 webapplib jim    192.168.3.21 POST Hello from webapplib!
Thread-4 (process_request) app2 __main__  fred   192.168.2.22 GET  Request processing started
Thread-5 (process_request) app1 __main__  jim    192.168.3.21 POST Request processing started
Thread-4 (process_request) app2 webapplib fred   192.168.2.22 GET  Hello from webapplib!
Thread-6 (process_request) app1 __main__  jim    192.168.3.21 POST Request processing started
~/logging-contextual-webapp$ grep app1 app1.log | wc -l
153
~/logging-contextual-webapp$ grep app2 app2.log | wc -l
147
~/logging-contextual-webapp$ grep app1 app.log | wc -l
153
~/logging-contextual-webapp$ grep app2 app.log | wc -l
147

Imparting contextual information in handlers

Each Handler has its own chain of filters. If you want to add contextual information to a LogRecord without leaking it to other handlers, you can use a filter that returns a new LogRecord instead of modifying it in-place, as shown in the following script:

import copy
import logging

def filter(record: logging.LogRecord):
    record = copy.copy(record)
    record.user = 'jim'
    return record

if __name__ == '__main__':
    logger = logging.getLogger()
    logger.setLevel(logging.INFO)
    handler = logging.StreamHandler()
    formatter = logging.Formatter('%(message)s from %(user)-8s')
    handler.setFormatter(formatter)
    handler.addFilter(filter)
    logger.addHandler(handler)

    logger.info('A log message')

Logging to a single file from multiple processes

Although logging is thread-safe, and logging to a single file from multiple threads in a single process is supported, logging to a single file from multiple processes is not supported, because there is no standard way to serialize access to a single file across multiple processes in Python. If you need to log to a single file from multiple processes, one way of doing this is to have all the processes log to a SocketHandler, and have a separate process which implements a socket server which reads from the socket and logs to file. (If you prefer, you can dedicate one thread in one of the existing processes to perform this function.) This section documents this approach in more detail and includes a working socket receiver which can be used as a starting point for you to adapt in your own applications.

You could also write your own handler which uses the Lock class from the multiprocessing module to serialize access to the file from your processes. The stdlib FileHandler and subclasses do not make use of multiprocessing.

Alternatively, you can use a Queue and a QueueHandler to send all logging events to one of the processes in your multi-process application. The following example script demonstrates how you can do this; in the example a separate listener process listens for events sent by other processes and logs them according to its own logging configuration. Although the example only demonstrates one way of doing it (for example, you may want to use a listener thread rather than a separate listener process -- the implementation would be analogous) it does allow for completely different logging configurations for the listener and the other processes in your application, and can be used as the basis for code meeting your own specific requirements:

# You'll need these imports in your own code
import logging
import logging.handlers
import multiprocessing

# Next two import lines for this demo only
from random import choice, random
import time

#
# Because you'll want to define the logging configurations for listener and workers, the
# listener and worker process functions take a configurer parameter which is a callable
# for configuring logging for that process. These functions are also passed the queue,
# which they use for communication.
#
# In practice, you can configure the listener however you want, but note that in this
# simple example, the listener does not apply level or filter logic to received records.
# In practice, you would probably want to do this logic in the worker processes, to avoid
# sending events which would be filtered out between processes.
#
# The size of the rotated files is made small so you can see the results easily.
def listener_configurer():
    root = logging.getLogger()
    h = logging.handlers.RotatingFileHandler('mptest.log', 'a', 300, 10)
    f = logging.Formatter('%(asctime)s %(processName)-10s %(name)s %(levelname)-8s %(message)s')
    h.setFormatter(f)
    root.addHandler(h)

# This is the listener process top-level loop: wait for logging events
# (LogRecords)on the queue and handle them, quit when you get a None for a
# LogRecord.
def listener_process(queue, configurer):
    configurer()
    while True:
        try:
            record = queue.get()
            if record is None:  # We send this as a sentinel to tell the listener to quit.
                break
            logger = logging.getLogger(record.name)
            logger.handle(record)  # No level or filter logic applied - just do it!
        except Exception:
            import sys, traceback
            print('Whoops! Problem:', file=sys.stderr)
            traceback.print_exc(file=sys.stderr)

# Arrays used for random selections in this demo

LEVELS = [logging.DEBUG, logging.INFO, logging.WARNING,
          logging.ERROR, logging.CRITICAL]

LOGGERS = ['a.b.c', 'd.e.f']

MESSAGES = [
    'Random message #1',
    'Random message #2',
    'Random message #3',
]

# The worker configuration is done at the start of the worker process run.
# Note that on Windows you can't rely on fork semantics, so each process
# will run the logging configuration code when it starts.
def worker_configurer(queue):
    h = logging.handlers.QueueHandler(queue)  # Just the one handler needed
    root = logging.getLogger()
    root.addHandler(h)
    # send all messages, for demo; no other level or filter logic applied.
    root.setLevel(logging.DEBUG)

# This is the worker process top-level loop, which just logs ten events with
# random intervening delays before terminating.
# The print messages are just so you know it's doing something!
def worker_process(queue, configurer):
    configurer(queue)
    name = multiprocessing.current_process().name
    print('Worker started: %s' % name)
    for i in range(10):
        time.sleep(random())
        logger = logging.getLogger(choice(LOGGERS))
        level = choice(LEVELS)
        message = choice(MESSAGES)
        logger.log(level, message)
    print('Worker finished: %s' % name)

# Here's where the demo gets orchestrated. Create the queue, create and start
# the listener, create ten workers and start them, wait for them to finish,
# then send a None to the queue to tell the listener to finish.
def main():
    queue = multiprocessing.Queue(-1)
    listener = multiprocessing.Process(target=listener_process,
                                       args=(queue, listener_configurer))
    listener.start()
    workers = []
    for i in range(10):
        worker = multiprocessing.Process(target=worker_process,
                                         args=(queue, worker_configurer))
        workers.append(worker)
        worker.start()
    for w in workers:
        w.join()
    queue.put_nowait(None)
    listener.join()

if __name__ == '__main__':
    main()

A variant of the above script keeps the logging in the main process, in a separate thread:

import logging
import logging.config
import logging.handlers
from multiprocessing import Process, Queue
import random
import threading
import time

def logger_thread(q):
    while True:
        record = q.get()
        if record is None:
            break
        logger = logging.getLogger(record.name)
        logger.handle(record)

def worker_process(q):
    qh = logging.handlers.QueueHandler(q)
    root = logging.getLogger()
    root.setLevel(logging.DEBUG)
    root.addHandler(qh)
    levels = [logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
              logging.CRITICAL]
    loggers = ['foo', 'foo.bar', 'foo.bar.baz',
               'spam', 'spam.ham', 'spam.ham.eggs']
    for i in range(100):
        lvl = random.choice(levels)
        logger = logging.getLogger(random.choice(loggers))
        logger.log(lvl, 'Message no. %d', i)

if __name__ == '__main__':
    q = Queue()
    d = {
        'version': 1,
        'formatters': {
            'detailed': {
                'class': 'logging.Formatter',
                'format': '%(asctime)s %(name)-15s %(levelname)-8s %(processName)-10s %(message)s'
            }
        },
        'handlers': {
            'console': {
                'class': 'logging.StreamHandler',
                'level': 'INFO',
            },
            'file': {
                'class': 'logging.FileHandler',
                'filename': 'mplog.log',
                'mode': 'w',
                'formatter': 'detailed',
            },
            'foofile': {
                'class': 'logging.FileHandler',
                'filename': 'mplog-foo.log',
                'mode': 'w',
                'formatter': 'detailed',
            },
            'errors': {
                'class': 'logging.FileHandler',
                'filename': 'mplog-errors.log',
                'mode': 'w',
                'level': 'ERROR',
                'formatter': 'detailed',
            },
        },
        'loggers': {
            'foo': {
                'handlers': ['foofile']
            }
        },
        'root': {
            'level': 'DEBUG',
            'handlers': ['console', 'file', 'errors']
        },
    }
    workers = []
    for i in range(5):
        wp = Process(target=worker_process, name='worker %d' % (i + 1), args=(q,))
        workers.append(wp)
        wp.start()
    logging.config.dictConfig(d)
    lp = threading.Thread(target=logger_thread, args=(q,))
    lp.start()
    # At this point, the main process could do some useful work of its own
    # Once it's done that, it can wait for the workers to terminate...
    for wp in workers:
        wp.join()
    # And now tell the logging thread to finish up, too
    q.put(None)
    lp.join()

This variant shows how you can e.g. apply configuration for particular loggers - e.g. the foo logger has a special handler which stores all events in the foo subsystem in a file mplog-foo.log. This will be used by the logging machinery in the main process (even though the logging events are generated in the worker processes) to direct the messages to the appropriate destinations.

使用 concurrent.futures.ProcessPoolExecutor

If you want to use concurrent.futures.ProcessPoolExecutor to start your worker processes, you need to create the queue slightly differently. Instead of

queue = multiprocessing.Queue(-1)

you should use

queue = multiprocessing.Manager().Queue(-1)  # also works with the examples above

and you can then replace the worker creation from this:

workers = []
for i in range(10):
    worker = multiprocessing.Process(target=worker_process,
                                     args=(queue, worker_configurer))
    workers.append(worker)
    worker.start()
for w in workers:
    w.join()

to this (remembering to first import concurrent.futures):

with concurrent.futures.ProcessPoolExecutor(max_workers=10) as executor:
    for i in range(10):
        executor.submit(worker_process, queue, worker_configurer)

Deploying Web applications using Gunicorn and uWSGI

When deploying Web applications using Gunicorn [https://gunicorn.org/] or uWSGI [https://uwsgi-docs.readthedocs.io/en/latest/] (or similar), multiple worker processes are created to handle client requests. In such environments, avoid creating file-based handlers directly in your web application. Instead, use a SocketHandler to log from the web application to a listener in a separate process. This can be set up using a process management tool such as Supervisor - see Running a logging socket listener in production for more details.

Using file rotation

Sometimes you want to let a log file grow to a certain size, then open a new file and log to that. You may want to keep a certain number of these files, and when that many files have been created, rotate the files so that the number of files and the size of the files both remain bounded. For this usage pattern, the logging package provides a RotatingFileHandler:

import glob
import logging
import logging.handlers

LOG_FILENAME = 'logging_rotatingfile_example.out'

# Set up a specific logger with our desired output level
my_logger = logging.getLogger('MyLogger')
my_logger.setLevel(logging.DEBUG)

# Add the log message handler to the logger
handler = logging.handlers.RotatingFileHandler(
              LOG_FILENAME, maxBytes=20, backupCount=5)

my_logger.addHandler(handler)

# Log some messages
for i in range(20):
    my_logger.debug('i = %d' % i)

# See what files are created
logfiles = glob.glob('%s*' % LOG_FILENAME)

for filename in logfiles:
    print(filename)

The result should be 6 separate files, each with part of the log history for the application:

logging_rotatingfile_example.out
logging_rotatingfile_example.out.1
logging_rotatingfile_example.out.2
logging_rotatingfile_example.out.3
logging_rotatingfile_example.out.4
logging_rotatingfile_example.out.5

The most current file is always logging_rotatingfile_example.out, and each time it reaches the size limit it is renamed with the suffix .1. Each of the existing backup files is renamed to increment the suffix (.1 becomes .2, etc.) and the .6 file is erased.

Obviously this example sets the log length much too small as an extreme example. You would want to set maxBytes to an appropriate value.

Use of alternative formatting styles

When logging was added to the Python standard library, the only way of formatting messages with variable content was to use the %-formatting method. Since then, Python has gained two new formatting approaches: string.Template (added in Python 2.4) and str.format() (added in Python 2.6).

Logging (as of 3.2) provides improved support for these two additional formatting styles. The Formatter class been enhanced to take an additional, optional keyword parameter named style. This defaults to '%', but other possible values are '{' and '$', which correspond to the other two formatting styles. Backwards compatibility is maintained by default (as you would expect), but by explicitly specifying a style parameter, you get the ability to specify format strings which work with str.format() or string.Template. Here's an example console session to show the possibilities:

>>> import logging
>>> root = logging.getLogger()
>>> root.setLevel(logging.DEBUG)
>>> handler = logging.StreamHandler()
>>> bf = logging.Formatter('{asctime} {name} {levelname:8s} {message}',
...                        style='{')
>>> handler.setFormatter(bf)
>>> root.addHandler(handler)
>>> logger = logging.getLogger('foo.bar')
>>> logger.debug('This is a DEBUG message')
2010-10-28 15:11:55,341 foo.bar DEBUG    This is a DEBUG message
>>> logger.critical('This is a CRITICAL message')
2010-10-28 15:12:11,526 foo.bar CRITICAL This is a CRITICAL message
>>> df = logging.Formatter('$asctime $name ${levelname} $message',
...                        style='$')
>>> handler.setFormatter(df)
>>> logger.debug('This is a DEBUG message')
2010-10-28 15:13:06,924 foo.bar DEBUG This is a DEBUG message
>>> logger.critical('This is a CRITICAL message')
2010-10-28 15:13:11,494 foo.bar CRITICAL This is a CRITICAL message
>>>

Note that the formatting of logging messages for final output to logs is completely independent of how an individual logging message is constructed. That can still use %-formatting, as shown here:

>>> logger.error('This is an%s %s %s', 'other,', 'ERROR,', 'message')
2010-10-28 15:19:29,833 foo.bar ERROR This is another, ERROR, message
>>>

Logging calls (logger.debug(), logger.info() etc.) only take positional parameters for the actual logging message itself, with keyword parameters used only for determining options for how to handle the actual logging call (e.g. the exc_info keyword parameter to indicate that traceback information should be logged, or the extra keyword parameter to indicate additional contextual information to be added to the log). So you cannot directly make logging calls using str.format() or string.Template syntax, because internally the logging package uses %-formatting to merge the format string and the variable arguments. There would be no changing this while preserving backward compatibility, since all logging calls which are out there in existing code will be using %-format strings.

There is, however, a way that you can use {}- and $- formatting to construct your individual log messages. Recall that for a message you can use an arbitrary object as a message format string, and that the logging package will call str() on that object to get the actual format string. Consider the following two classes:

class BraceMessage:
    def __init__(self, fmt, /, *args, **kwargs):
        self.fmt = fmt
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        return self.fmt.format(*self.args, **self.kwargs)

class DollarMessage:
    def __init__(self, fmt, /, **kwargs):
        self.fmt = fmt
        self.kwargs = kwargs

    def __str__(self):
        from string import Template
        return Template(self.fmt).substitute(**self.kwargs)

Either of these can be used in place of a format string, to allow {}- or $-formatting to be used to build the actual "message" part which appears in the formatted log output in place of "%(message)s" or "{message}" or "$message". It's a little unwieldy to use the class names whenever you want to log something, but it's quite palatable if you use an alias such as __ (double underscore --- not to be confused with _, the single underscore used as a synonym/alias for gettext.gettext() or its brethren).

The above classes are not included in Python, though they're easy enough to copy and paste into your own code. They can be used as follows (assuming that they're declared in a module called wherever):

>>> from wherever import BraceMessage as __
>>> print(__('Message with {0} {name}', 2, name='placeholders'))
Message with 2 placeholders
>>> class Point: pass
...
>>> p = Point()
>>> p.x = 0.5
>>> p.y = 0.5
>>> print(__('Message with coordinates: ({point.x:.2f}, {point.y:.2f})',
...       point=p))
Message with coordinates: (0.50, 0.50)
>>> from wherever import DollarMessage as __
>>> print(__('Message with $num $what', num=2, what='placeholders'))
Message with 2 placeholders
>>>

While the above examples use print() to show how the formatting works, you would of course use logger.debug() or similar to actually log using this approach.

One thing to note is that you pay no significant performance penalty with this approach: the actual formatting happens not when you make the logging call, but when (and if) the logged message is actually about to be output to a log by a handler. So the only slightly unusual thing which might trip you up is that the parentheses go around the format string and the arguments, not just the format string. That's because the __ notation is just syntax sugar for a constructor call to one of the XXXMessage classes.

If you prefer, you can use a LoggerAdapter to achieve a similar effect to the above, as in the following example:

import logging

class Message:
    def __init__(self, fmt, args):
        self.fmt = fmt
        self.args = args

    def __str__(self):
        return self.fmt.format(*self.args)

class StyleAdapter(logging.LoggerAdapter):
    def log(self, level, msg, /, *args, stacklevel=1, **kwargs):
        if self.isEnabledFor(level):
            msg, kwargs = self.process(msg, kwargs)
            self.logger.log(level, Message(msg, args), **kwargs,
                            stacklevel=stacklevel+1)

logger = StyleAdapter(logging.getLogger(__name__))

def main():
    logger.debug('Hello, {}', 'world!')

if __name__ == '__main__':
    logging.basicConfig(level=logging.DEBUG)
    main()

The above script should log the message Hello, world! when run with Python 3.8 or later.

Customizing LogRecord

Every logging event is represented by a LogRecord instance. When an event is logged and not filtered out by a logger's level, a LogRecord is created, populated with information about the event and then passed to the handlers for that logger (and its ancestors, up to and including the logger where further propagation up the hierarchy is disabled). Before Python 3.2, there were only two places where this creation was done:

Logger.makeRecord(), which is called in the normal process of logging an event. This invoked LogRecord directly to create an instance.

makeLogRecord(), which is called with a dictionary containing attributes to be added to the LogRecord. This is typically invoked when a suitable dictionary has been received over the network (e.g. in pickle form via a SocketHandler, or in JSON form via an HTTPHandler).

This has usually meant that if you need to do anything special with a LogRecord, you've had to do one of the following.

Create your own Logger subclass, which overrides Logger.makeRecord(), and set it using setLoggerClass() before any loggers that you care about are instantiated.

Add a Filter to a logger or handler, which does the necessary special manipulation you need when its filter() method is called.

The first approach would be a little unwieldy in the scenario where (say) several different libraries wanted to do different things. Each would attempt to set its own Logger subclass, and the one which did this last would win.

The second approach works reasonably well for many cases, but does not allow you to e.g. use a specialized subclass of LogRecord. Library developers can set a suitable filter on their loggers, but they would have to remember to do this every time they introduced a new logger (which they would do simply by adding new packages or modules and doing

logger = logging.getLogger(__name__)

at module level). It's probably one too many things to think about. Developers could also add the filter to a NullHandler attached to their top-level logger, but this would not be invoked if an application developer attached a handler to a lower-level library logger --- so output from that handler would not reflect the intentions of the library developer.

In Python 3.2 and later, LogRecord creation is done through a factory, which you can specify. The factory is just a callable you can set with setLogRecordFactory(), and interrogate with getLogRecordFactory(). The factory is invoked with the same signature as the LogRecord constructor, as LogRecord is the default setting for the factory.

This approach allows a custom factory to control all aspects of LogRecord creation. For example, you could return a subclass, or just add some additional attributes to the record once created, using a pattern similar to this:

old_factory = logging.getLogRecordFactory()

def record_factory(*args, **kwargs):
    record = old_factory(*args, **kwargs)
    record.custom_attribute = 0xdecafbad
    return record

logging.setLogRecordFactory(record_factory)

This pattern allows different libraries to chain factories together, and as long as they don't overwrite each other's attributes or unintentionally overwrite the attributes provided as standard, there should be no surprises. However, it should be borne in mind that each link in the chain adds run-time overhead to all logging operations, and the technique should only be used when the use of a Filter does not provide the desired result.

Subclassing QueueHandler and QueueListener- a ZeroMQ example

Subclass QueueHandler

You can use a QueueHandler subclass to send messages to other kinds of queues, for example a ZeroMQ 'publish' socket. In the example below,the socket is created separately and passed to the handler (as its 'queue'):

import zmq   # using pyzmq, the Python binding for ZeroMQ
import json  # for serializing records portably

ctx = zmq.Context()
sock = zmq.Socket(ctx, zmq.PUB)  # or zmq.PUSH, or other suitable value
sock.bind('tcp://*:5556')        # or wherever

class ZeroMQSocketHandler(QueueHandler):
    def enqueue(self, record):
        self.queue.send_json(record.__dict__)

handler = ZeroMQSocketHandler(sock)

Of course there are other ways of organizing this, for example passing in the data needed by the handler to create the socket:

class ZeroMQSocketHandler(QueueHandler):
    def __init__(self, uri, socktype=zmq.PUB, ctx=None):
        self.ctx = ctx or zmq.Context()
        socket = zmq.Socket(self.ctx, socktype)
        socket.bind(uri)
        super().__init__(socket)

    def enqueue(self, record):
        self.queue.send_json(record.__dict__)

    def close(self):
        self.queue.close()

Subclass QueueListener

You can also subclass QueueListener to get messages from other kinds of queues, for example a ZeroMQ 'subscribe' socket. Here's an example:

class ZeroMQSocketListener(QueueListener):
    def __init__(self, uri, /, *handlers, **kwargs):
        self.ctx = kwargs.get('ctx') or zmq.Context()
        socket = zmq.Socket(self.ctx, zmq.SUB)
        socket.setsockopt_string(zmq.SUBSCRIBE, '')  # subscribe to everything
        socket.connect(uri)
        super().__init__(socket, *handlers, **kwargs)

    def dequeue(self):
        msg = self.queue.recv_json()
        return logging.makeLogRecord(msg)

Subclassing QueueHandler and QueueListener- a pynng example

In a similar way to the above section, we can implement a listener and handler using pynng [https://pypi.org/project/pynng/], which is a Python binding to NNG [https://nng.nanomsg.org/], billed as a spiritual successor to ZeroMQ. The following snippets illustrate -- you can test them in an environment which has pynng installed. Just for variety, we present the listener first.

Subclass QueueListener

# listener.py
import json
import logging
import logging.handlers

import pynng

DEFAULT_ADDR = "tcp://localhost:13232"

interrupted = False

class NNGSocketListener(logging.handlers.QueueListener):

    def __init__(self, uri, /, *handlers, **kwargs):
        # Have a timeout for interruptability, and open a
        # subscriber socket
        socket = pynng.Sub0(listen=uri, recv_timeout=500)
        # The b'' subscription matches all topics
        topics = kwargs.pop('topics', None) or b''
        socket.subscribe(topics)
        # We treat the socket as a queue
        super().__init__(socket, *handlers, **kwargs)

    def dequeue(self, block):
        data = None
        # Keep looping while not interrupted and no data received over the
        # socket
        while not interrupted:
            try:
                data = self.queue.recv(block=block)
                break
            except pynng.Timeout:
                pass
            except pynng.Closed:  # sometimes happens when you hit Ctrl-C
                break
        if data is None:
            return None
        # Get the logging event sent from a publisher
        event = json.loads(data.decode('utf-8'))
        return logging.makeLogRecord(event)

    def enqueue_sentinel(self):
        # Not used in this implementation, as the socket isn't really a
        # queue
        pass

logging.getLogger('pynng').propagate = False
listener = NNGSocketListener(DEFAULT_ADDR, logging.StreamHandler(), topics=b'')
listener.start()
print('Press Ctrl-C to stop.')
try:
    while True:
        pass
except KeyboardInterrupt:
    interrupted = True
finally:
    listener.stop()

Subclass QueueHandler

# sender.py
import json
import logging
import logging.handlers
import time
import random

import pynng

DEFAULT_ADDR = "tcp://localhost:13232"

class NNGSocketHandler(logging.handlers.QueueHandler):

    def __init__(self, uri):
        socket = pynng.Pub0(dial=uri, send_timeout=500)
        super().__init__(socket)

    def enqueue(self, record):
        # Send the record as UTF-8 encoded JSON
        d = dict(record.__dict__)
        data = json.dumps(d)
        self.queue.send(data.encode('utf-8'))

    def close(self):
        self.queue.close()

logging.getLogger('pynng').propagate = False
handler = NNGSocketHandler(DEFAULT_ADDR)
# Make sure the process ID is in the output
logging.basicConfig(level=logging.DEBUG,
                    handlers=[logging.StreamHandler(), handler],
                    format='%(levelname)-8s %(name)10s %(process)6s %(message)s')
levels = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
          logging.CRITICAL)
logger_names = ('myapp', 'myapp.lib1', 'myapp.lib2')
msgno = 1
while True:
    # Just randomly select some loggers and levels and log away
    level = random.choice(levels)
    logger = logging.getLogger(random.choice(logger_names))
    logger.log(level, 'Message no. %5d' % msgno)
    msgno += 1
    delay = random.random() * 2 + 0.5
    time.sleep(delay)

You can run the above two snippets in separate command shells. If we run the listener in one shell and run the sender in two separate shells, we should see something like the following. In the first sender shell:

$ python sender.py
DEBUG         myapp    613 Message no.     1
WARNING  myapp.lib2    613 Message no.     2
CRITICAL myapp.lib2    613 Message no.     3
WARNING  myapp.lib2    613 Message no.     4
CRITICAL myapp.lib1    613 Message no.     5
DEBUG         myapp    613 Message no.     6
CRITICAL myapp.lib1    613 Message no.     7
INFO     myapp.lib1    613 Message no.     8
(and so on)

In the second sender shell:

$ python sender.py
INFO     myapp.lib2    657 Message no.     1
CRITICAL myapp.lib2    657 Message no.     2
CRITICAL      myapp    657 Message no.     3
CRITICAL myapp.lib1    657 Message no.     4
INFO     myapp.lib1    657 Message no.     5
WARNING  myapp.lib2    657 Message no.     6
CRITICAL      myapp    657 Message no.     7
DEBUG    myapp.lib1    657 Message no.     8
(and so on)

In the listener shell:

$ python listener.py
Press Ctrl-C to stop.
DEBUG         myapp    613 Message no.     1
WARNING  myapp.lib2    613 Message no.     2
INFO     myapp.lib2    657 Message no.     1
CRITICAL myapp.lib2    613 Message no.     3
CRITICAL myapp.lib2    657 Message no.     2
CRITICAL      myapp    657 Message no.     3
WARNING  myapp.lib2    613 Message no.     4
CRITICAL myapp.lib1    613 Message no.     5
CRITICAL myapp.lib1    657 Message no.     4
INFO     myapp.lib1    657 Message no.     5
DEBUG         myapp    613 Message no.     6
WARNING  myapp.lib2    657 Message no.     6
CRITICAL      myapp    657 Message no.     7
CRITICAL myapp.lib1    613 Message no.     7
INFO     myapp.lib1    613 Message no.     8
DEBUG    myapp.lib1    657 Message no.     8
(and so on)

As you can see, the logging from the two sender processes is interleaved in the listener's output.

An example dictionary-based configuration

Below is an example of a logging configuration dictionary - it's taken from the documentation on the Django project [https://docs.djangoproject.com/en/stable/topics/logging/#configuring-logging]. This dictionary is passed to dictConfig() to put the configuration into effect:

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'verbose': {
            'format': '{levelname} {asctime} {module} {process:d} {thread:d} {message}',
            'style': '{',
        },
        'simple': {
            'format': '{levelname} {message}',
            'style': '{',
        },
    },
    'filters': {
        'special': {
            '()': 'project.logging.SpecialFilter',
            'foo': 'bar',
        },
    },
    'handlers': {
        'console': {
            'level': 'INFO',
            'class': 'logging.StreamHandler',
            'formatter': 'simple',
        },
        'mail_admins': {
            'level': 'ERROR',
            'class': 'django.utils.log.AdminEmailHandler',
            'filters': ['special']
        }
    },
    'loggers': {
        'django': {
            'handlers': ['console'],
            'propagate': True,
        },
        'django.request': {
            'handlers': ['mail_admins'],
            'level': 'ERROR',
            'propagate': False,
        },
        'myproject.custom': {
            'handlers': ['console', 'mail_admins'],
            'level': 'INFO',
            'filters': ['special']
        }
    }
}

For more information about this configuration, you can see the relevant section [https://docs.djangoproject.com/en/stable/topics/logging/#configuring-logging] of the Django documentation.

Using a rotator and namer to customize log rotation processing

An example of how you can define a namer and rotator is given in the following runnable script, which shows gzip compression of the log file:

import gzip
import logging
import logging.handlers
import os
import shutil

def namer(name):
    return name + ".gz"

def rotator(source, dest):
    with open(source, 'rb') as f_in:
        with gzip.open(dest, 'wb') as f_out:
            shutil.copyfileobj(f_in, f_out)
    os.remove(source)

rh = logging.handlers.RotatingFileHandler('rotated.log', maxBytes=128, backupCount=5)
rh.rotator = rotator
rh.namer = namer

root = logging.getLogger()
root.setLevel(logging.INFO)
root.addHandler(rh)
f = logging.Formatter('%(asctime)s %(message)s')
rh.setFormatter(f)
for i in range(1000):
    root.info(f'Message no. {i + 1}')

After running this, you will see six new files, five of which are compressed:

$ ls rotated.log*
rotated.log       rotated.log.2.gz  rotated.log.4.gz
rotated.log.1.gz  rotated.log.3.gz  rotated.log.5.gz
$ zcat rotated.log.1.gz
2023-01-20 02:28:17,767 Message no. 996
2023-01-20 02:28:17,767 Message no. 997
2023-01-20 02:28:17,767 Message no. 998

A more elaborate multiprocessing example

The following working example shows how logging can be used with multiprocessing using configuration files. The configurations are fairly simple, but serve to illustrate how more complex ones could be implemented in a real multiprocessing scenario.

In the example, the main process spawns a listener process and some worker processes. Each of the main process, the listener and the workers have three separate configurations (the workers all share the same configuration). We can see logging in the main process, how the workers log to a QueueHandler and how the listener implements a QueueListener and a more complex logging configuration, and arranges to dispatch events received via the queue to the handlers specified in the configuration. Note that these configurations are purely illustrative, but you should be able to adapt this example to your own scenario.

Here's the script - the docstrings and the comments hopefully explain how it works:

import logging
import logging.config
import logging.handlers
from multiprocessing import Process, Queue, Event, current_process
import os
import random
import time

class MyHandler:
    """
    A simple handler for logging events. It runs in the listener process and
    dispatches events to loggers based on the name in the received record,
    which then get dispatched, by the logging system, to the handlers
    configured for those loggers.
    """

    def handle(self, record):
        if record.name == "root":
            logger = logging.getLogger()
        else:
            logger = logging.getLogger(record.name)

        if logger.isEnabledFor(record.levelno):
            # The process name is transformed just to show that it's the listener
            # doing the logging to files and console
            record.processName = '%s (for %s)' % (current_process().name, record.processName)
            logger.handle(record)

def listener_process(q, stop_event, config):
    """
    This could be done in the main process, but is just done in a separate
    process for illustrative purposes.

    This initialises logging according to the specified configuration,
    starts the listener and waits for the main process to signal completion
    via the event. The listener is then stopped, and the process exits.
    """
    logging.config.dictConfig(config)
    listener = logging.handlers.QueueListener(q, MyHandler())
    listener.start()
    if os.name == 'posix':
        # On POSIX, the setup logger will have been configured in the
        # parent process, but should have been disabled following the
        # dictConfig call.
        # On Windows, since fork isn't used, the setup logger won't
        # exist in the child, so it would be created and the message
        # would appear - hence the "if posix" clause.
        logger = logging.getLogger('setup')
        logger.critical('Should not appear, because of disabled logger ...')
    stop_event.wait()
    listener.stop()

def worker_process(config):
    """
    A number of these are spawned for the purpose of illustration. In
    practice, they could be a heterogeneous bunch of processes rather than
    ones which are identical to each other.

    This initialises logging according to the specified configuration,
    and logs a hundred messages with random levels to randomly selected
    loggers.

    A small sleep is added to allow other processes a chance to run. This
    is not strictly needed, but it mixes the output from the different
    processes a bit more than if it's left out.
    """
    logging.config.dictConfig(config)
    levels = [logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
              logging.CRITICAL]
    loggers = ['foo', 'foo.bar', 'foo.bar.baz',
               'spam', 'spam.ham', 'spam.ham.eggs']
    if os.name == 'posix':
        # On POSIX, the setup logger will have been configured in the
        # parent process, but should have been disabled following the
        # dictConfig call.
        # On Windows, since fork isn't used, the setup logger won't
        # exist in the child, so it would be created and the message
        # would appear - hence the "if posix" clause.
        logger = logging.getLogger('setup')
        logger.critical('Should not appear, because of disabled logger ...')
    for i in range(100):
        lvl = random.choice(levels)
        logger = logging.getLogger(random.choice(loggers))
        logger.log(lvl, 'Message no. %d', i)
        time.sleep(0.01)

def main():
    q = Queue()
    # The main process gets a simple configuration which prints to the console.
    config_initial = {
        'version': 1,
        'handlers': {
            'console': {
                'class': 'logging.StreamHandler',
                'level': 'INFO'
            }
        },
        'root': {
            'handlers': ['console'],
            'level': 'DEBUG'
        }
    }
    # The worker process configuration is just a QueueHandler attached to the
    # root logger, which allows all messages to be sent to the queue.
    # We disable existing loggers to disable the "setup" logger used in the
    # parent process. This is needed on POSIX because the logger will
    # be there in the child following a fork().
    config_worker = {
        'version': 1,
        'disable_existing_loggers': True,
        'handlers': {
            'queue': {
                'class': 'logging.handlers.QueueHandler',
                'queue': q
            }
        },
        'root': {
            'handlers': ['queue'],
            'level': 'DEBUG'
        }
    }
    # The listener process configuration shows that the full flexibility of
    # logging configuration is available to dispatch events to handlers however
    # you want.
    # We disable existing loggers to disable the "setup" logger used in the
    # parent process. This is needed on POSIX because the logger will
    # be there in the child following a fork().
    config_listener = {
        'version': 1,
        'disable_existing_loggers': True,
        'formatters': {
            'detailed': {
                'class': 'logging.Formatter',
                'format': '%(asctime)s %(name)-15s %(levelname)-8s %(processName)-10s %(message)s'
            },
            'simple': {
                'class': 'logging.Formatter',
                'format': '%(name)-15s %(levelname)-8s %(processName)-10s %(message)s'
            }
        },
        'handlers': {
            'console': {
                'class': 'logging.StreamHandler',
                'formatter': 'simple',
                'level': 'INFO'
            },
            'file': {
                'class': 'logging.FileHandler',
                'filename': 'mplog.log',
                'mode': 'w',
                'formatter': 'detailed'
            },
            'foofile': {
                'class': 'logging.FileHandler',
                'filename': 'mplog-foo.log',
                'mode': 'w',
                'formatter': 'detailed'
            },
            'errors': {
                'class': 'logging.FileHandler',
                'filename': 'mplog-errors.log',
                'mode': 'w',
                'formatter': 'detailed',
                'level': 'ERROR'
            }
        },
        'loggers': {
            'foo': {
                'handlers': ['foofile']
            }
        },
        'root': {
            'handlers': ['console', 'file', 'errors'],
            'level': 'DEBUG'
        }
    }
    # Log some initial events, just to show that logging in the parent works
    # normally.
    logging.config.dictConfig(config_initial)
    logger = logging.getLogger('setup')
    logger.info('About to create workers ...')
    workers = []
    for i in range(5):
        wp = Process(target=worker_process, name='worker %d' % (i + 1),
                     args=(config_worker,))
        workers.append(wp)
        wp.start()
        logger.info('Started worker: %s', wp.name)
    logger.info('About to create listener ...')
    stop_event = Event()
    lp = Process(target=listener_process, name='listener',
                 args=(q, stop_event, config_listener))
    lp.start()
    logger.info('Started listener')
    # We now hang around for the workers to finish their work.
    for wp in workers:
        wp.join()
    # Workers all done, listening can now stop.
    # Logging in the parent still works normally.
    logger.info('Telling listener to stop ...')
    stop_event.set()
    lp.join()
    logger.info('All done.')

if __name__ == '__main__':
    main()

Inserting a BOM into messages sent to a SysLogHandler

RFC 5424 [https://datatracker.ietf.org/doc/html/rfc5424.html] requires that a Unicode message be sent to a syslog daemon as a set of bytes which have the following structure: an optional pure-ASCII component, followed by a UTF-8 Byte Order Mark (BOM), followed by Unicode encoded using UTF-8. (See the relevant section of the specification [https://datatracker.ietf.org/doc/html/rfc5424.html#section-6].)

In Python 3.1, code was added to SysLogHandler to insert a BOM into the message, but unfortunately, it was implemented incorrectly, with the BOM appearing at the beginning of the message and hence not allowing any pure-ASCII component to appear before it.

As this behaviour is broken, the incorrect BOM insertion code is being removed from Python 3.2.4 and later. However, it is not being replaced, and if you want to produce RFC 5424 [https://datatracker.ietf.org/doc/html/rfc5424.html]-compliant messages which include a BOM, an optional pure-ASCII sequence before it and arbitrary Unicode after it, encoded using UTF-8, then you need to do the following:

Attach a Formatter instance to your SysLogHandler instance, with a format string such as:

'ASCII section\ufeffUnicode section'

The Unicode code point U+FEFF, when encoded using UTF-8, will be encoded as a UTF-8 BOM -- the byte-string b'\xef\xbb\xbf'.

Replace the ASCII section with whatever placeholders you like, but make sure that the data that appears in there after substitution is always ASCII (that way, it will remain unchanged after UTF-8 encoding).

Replace the Unicode section with whatever placeholders you like; if the data which appears there after substitution contains characters outside the ASCII range, that's fine -- it will be encoded using UTF-8.

The formatted message will be encoded using UTF-8 encoding by SysLogHandler. If you follow the above rules, you should be able to produce RFC 5424 [https://datatracker.ietf.org/doc/html/rfc5424.html]-compliant messages. If you don't, logging may not complain, but your messages will not be RFC 5424-compliant, and your syslog daemon may complain.

Implementing structured logging

Although most logging messages are intended for reading by humans, and thus not readily machine-parseable, there might be circumstances where you want to output messages in a structured format which is capable of being parsed by a program (without needing complex regular expressions to parse the log message). This is straightforward to achieve using the logging package. There are a number of ways in which this could be achieved, but the following is a simple approach which uses JSON to serialise the event in a machine-parseable manner:

import json
import logging

class StructuredMessage:
    def __init__(self, message, /, **kwargs):
        self.message = message
        self.kwargs = kwargs

    def __str__(self):
        return '%s >>> %s' % (self.message, json.dumps(self.kwargs))

_ = StructuredMessage   # optional, to improve readability

logging.basicConfig(level=logging.INFO, format='%(message)s')
logging.info(_('message 1', foo='bar', bar='baz', num=123, fnum=123.456))

If the above script is run, it prints:

message 1 >>> {"fnum": 123.456, "num": 123, "bar": "baz", "foo": "bar"}

Note that the order of items might be different according to the version of Python used.

If you need more specialised processing, you can use a custom JSON encoder, as in the following complete example:

import json
import logging

class Encoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, set):
            return tuple(o)
        elif isinstance(o, str):
            return o.encode('unicode_escape').decode('ascii')
        return super().default(o)

class StructuredMessage:
    def __init__(self, message, /, **kwargs):
        self.message = message
        self.kwargs = kwargs

    def __str__(self):
        s = Encoder().encode(self.kwargs)
        return '%s >>> %s' % (self.message, s)

_ = StructuredMessage   # optional, to improve readability

def main():
    logging.basicConfig(level=logging.INFO, format='%(message)s')
    logging.info(_('message 1', set_value={1, 2, 3}, snowman='\u2603'))

if __name__ == '__main__':
    main()

When the above script is run, it prints:

message 1 >>> {"snowman": "\u2603", "set_value": [1, 2, 3]}

Note that the order of items might be different according to the version of Python used.

Customizing handlers with dictConfig()

There are times when you want to customize logging handlers in particular ways, and if you use dictConfig() you may be able to do this without subclassing. As an example, consider that you may want to set the ownership of a log file. On POSIX, this is easily done using shutil.chown(), but the file handlers in the stdlib don't offer built-in support. You can customize handler creation using a plain function such as:

def owned_file_handler(filename, mode='a', encoding=None, owner=None):
    if owner:
        if not os.path.exists(filename):
            open(filename, 'a').close()
        shutil.chown(filename, *owner)
    return logging.FileHandler(filename, mode, encoding)

You can then specify, in a logging configuration passed to dictConfig(), that a logging handler be created by calling this function:

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'default': {
            'format': '%(asctime)s %(levelname)s %(name)s %(message)s'
        },
    },
    'handlers': {
        'file':{
            # The values below are popped from this dictionary and
            # used to create the handler, set the handler's level and
            # its formatter.
            '()': owned_file_handler,
            'level':'DEBUG',
            'formatter': 'default',
            # The values below are passed to the handler creator callable
            # as keyword arguments.
            'owner': ['pulse', 'pulse'],
            'filename': 'chowntest.log',
            'mode': 'w',
            'encoding': 'utf-8',
        },
    },
    'root': {
        'handlers': ['file'],
        'level': 'DEBUG',
    },
}

In this example I am setting the ownership using the pulse user and group, just for the purposes of illustration. Putting it together into a working script, chowntest.py:

import logging, logging.config, os, shutil

def owned_file_handler(filename, mode='a', encoding=None, owner=None):
    if owner:
        if not os.path.exists(filename):
            open(filename, 'a').close()
        shutil.chown(filename, *owner)
    return logging.FileHandler(filename, mode, encoding)

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'default': {
            'format': '%(asctime)s %(levelname)s %(name)s %(message)s'
        },
    },
    'handlers': {
        'file':{
            # The values below are popped from this dictionary and
            # used to create the handler, set the handler's level and
            # its formatter.
            '()': owned_file_handler,
            'level':'DEBUG',
            'formatter': 'default',
            # The values below are passed to the handler creator callable
            # as keyword arguments.
            'owner': ['pulse', 'pulse'],
            'filename': 'chowntest.log',
            'mode': 'w',
            'encoding': 'utf-8',
        },
    },
    'root': {
        'handlers': ['file'],
        'level': 'DEBUG',
    },
}

logging.config.dictConfig(LOGGING)
logger = logging.getLogger('mylogger')
logger.debug('A debug message')

To run this, you will probably need to run as root:

$ sudo python3.3 chowntest.py
$ cat chowntest.log
2013-11-05 09:34:51,128 DEBUG mylogger A debug message
$ ls -l chowntest.log
-rw-r--r-- 1 pulse pulse 55 2013-11-05 09:34 chowntest.log

Note that this example uses Python 3.3 because that's where shutil.chown() makes an appearance. This approach should work with any Python version that supports dictConfig() - namely, Python 2.7, 3.2 or later. With pre-3.3 versions, you would need to implement the actual ownership change using e.g. os.chown().

In practice, the handler-creating function may be in a utility module somewhere in your project. Instead of the line in the configuration:

'()': owned_file_handler,

you could use e.g.:

'()': 'ext://project.util.owned_file_handler',

where project.util can be replaced with the actual name of the package where the function resides. In the above working script, using 'ext://__main__.owned_file_handler' should work. Here, the actual callable is resolved by dictConfig() from the ext:// specification.

This example hopefully also points the way to how you could implement other types of file change - e.g. setting specific POSIX permission bits - in the same way, using os.chmod().

Of course, the approach could also be extended to types of handler other than a FileHandler - for example, one of the rotating file handlers, or a different type of handler altogether.

Using particular formatting styles throughout your application

In Python 3.2, the Formatter gained a style keyword parameter which, while defaulting to % for backward compatibility, allowed the specification of { or $ to support the formatting approaches supported by str.format() and string.Template. Note that this governs the formatting of logging messages for final output to logs, and is completely orthogonal to how an individual logging message is constructed.

Logging calls (debug(), info() etc.) only take positional parameters for the actual logging message itself, with keyword parameters used only for determining options for how to handle the logging call (e.g. the exc_info keyword parameter to indicate that traceback information should be logged, or the extra keyword parameter to indicate additional contextual information to be added to the log). So you cannot directly make logging calls using str.format() or string.Template syntax, because internally the logging package uses %-formatting to merge the format string and the variable arguments. There would be no changing this while preserving backward compatibility, since all logging calls which are out there in existing code will be using %-format strings.

There have been suggestions to associate format styles with specific loggers, but that approach also runs into backward compatibility problems because any existing code could be using a given logger name and using %-formatting.

For logging to work interoperably between any third-party libraries and your code, decisions about formatting need to be made at the level of the individual logging call. This opens up a couple of ways in which alternative formatting styles can be accommodated.

Using LogRecord factories

In Python 3.2, along with the Formatter changes mentioned above, the logging package gained the ability to allow users to set their own LogRecord subclasses, using the setLogRecordFactory() function. You can use this to set your own subclass of LogRecord, which does the Right Thing by overriding the getMessage() method. The base class implementation of this method is where the msg % args formatting happens, and where you can substitute your alternate formatting; however, you should be careful to support all formatting styles and allow %-formatting as the default, to ensure interoperability with other code. Care should also be taken to call str(self.msg), just as the base implementation does.

Refer to the reference documentation on setLogRecordFactory() and LogRecord for more information.

Using custom message objects

There is another, perhaps simpler way that you can use {}- and $- formatting to construct your individual log messages. You may recall (from Using arbitrary objects as messages) that when logging you can use an arbitrary object as a message format string, and that the logging package will call str() on that object to get the actual format string. Consider the following two classes:

class BraceMessage:
    def __init__(self, fmt, /, *args, **kwargs):
        self.fmt = fmt
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        return self.fmt.format(*self.args, **self.kwargs)

class DollarMessage:
    def __init__(self, fmt, /, **kwargs):
        self.fmt = fmt
        self.kwargs = kwargs

    def __str__(self):
        from string import Template
        return Template(self.fmt).substitute(**self.kwargs)

Either of these can be used in place of a format string, to allow {}- or $-formatting to be used to build the actual "message" part which appears in the formatted log output in place of “%(message)s” or “{message}” or “$message”. If you find it a little unwieldy to use the class names whenever you want to log something, you can make it more palatable if you use an alias such as M or _ for the message (or perhaps __, if you are using _ for localization).

Examples of this approach are given below. Firstly, formatting with str.format():

>>> __ = BraceMessage
>>> print(__('Message with {0} {1}', 2, 'placeholders'))
Message with 2 placeholders
>>> class Point: pass
...
>>> p = Point()
>>> p.x = 0.5
>>> p.y = 0.5
>>> print(__('Message with coordinates: ({point.x:.2f}, {point.y:.2f})', point=p))
Message with coordinates: (0.50, 0.50)

Secondly, formatting with string.Template:

>>> __ = DollarMessage
>>> print(__('Message with $num $what', num=2, what='placeholders'))
Message with 2 placeholders
>>>

One thing to note is that you pay no significant performance penalty with this approach: the actual formatting happens not when you make the logging call, but when (and if) the logged message is actually about to be output to a log by a handler. So the only slightly unusual thing which might trip you up is that the parentheses go around the format string and the arguments, not just the format string. That’s because the __ notation is just syntax sugar for a constructor call to one of the XXXMessage classes shown above.

Configuring filters with dictConfig()

You can configure filters using dictConfig(), though it might not be obvious at first glance how to do it (hence this recipe). Since Filter is the only filter class included in the standard library, and it is unlikely to cater to many requirements (it's only there as a base class), you will typically need to define your own Filter subclass with an overridden filter() method. To do this, specify the () key in the configuration dictionary for the filter, specifying a callable which will be used to create the filter (a class is the most obvious, but you can provide any callable which returns a Filter instance). Here is a complete example:

import logging
import logging.config
import sys

class MyFilter(logging.Filter):
    def __init__(self, param=None):
        self.param = param

    def filter(self, record):
        if self.param is None:
            allow = True
        else:
            allow = self.param not in record.msg
        if allow:
            record.msg = 'changed: ' + record.msg
        return allow

LOGGING = {
    'version': 1,
    'filters': {
        'myfilter': {
            '()': MyFilter,
            'param': 'noshow',
        }
    },
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
            'filters': ['myfilter']
        }
    },
    'root': {
        'level': 'DEBUG',
        'handlers': ['console']
    },
}

if __name__ == '__main__':
    logging.config.dictConfig(LOGGING)
    logging.debug('hello')
    logging.debug('hello - noshow')

This example shows how you can pass configuration data to the callable which constructs the instance, in the form of keyword parameters. When run, the above script will print:

changed: hello

which shows that the filter is working as configured.

A couple of extra points to note:

If you can't refer to the callable directly in the configuration (e.g. if it lives in a different module, and you can't import it directly where the configuration dictionary is), you can use the form ext://... as described in Access to external objects. For example, you could have used the text 'ext://__main__.MyFilter' instead of MyFilter in the above example.

As well as for filters, this technique can also be used to configure custom handlers and formatters. See User-defined objects for more information on how logging supports using user-defined objects in its configuration, and see the other cookbook recipe Customizing handlers with dictConfig() above.

Customized exception formatting

There might be times when you want to do customized exception formatting - for argument's sake, let's say you want exactly one line per logged event, even when exception information is present. You can do this with a custom formatter class, as shown in the following example:

import logging

class OneLineExceptionFormatter(logging.Formatter):
    def formatException(self, exc_info):
        """
        Format an exception so that it prints on a single line.
        """
        result = super().formatException(exc_info)
        return repr(result)  # or format into one line however you want to

    def format(self, record):
        s = super().format(record)
        if record.exc_text:
            s = s.replace('\n', '') + '|'
        return s

def configure_logging():
    fh = logging.FileHandler('output.txt', 'w')
    f = OneLineExceptionFormatter('%(asctime)s|%(levelname)s|%(message)s|',
                                  '%d/%m/%Y %H:%M:%S')
    fh.setFormatter(f)
    root = logging.getLogger()
    root.setLevel(logging.DEBUG)
    root.addHandler(fh)

def main():
    configure_logging()
    logging.info('Sample message')
    try:
        x = 1 / 0
    except ZeroDivisionError as e:
        logging.exception('ZeroDivisionError: %s', e)

if __name__ == '__main__':
    main()

When run, this produces a file with exactly two lines:

28/01/2015 07:21:23|INFO|Sample message|
28/01/2015 07:21:23|ERROR|ZeroDivisionError: division by zero|'Traceback (most recent call last):\n  File "logtest7.py", line 30, in main\n    x = 1 / 0\nZeroDivisionError: division by zero'|

While the above treatment is simplistic, it points the way to how exception information can be formatted to your liking. The traceback module may be helpful for more specialized needs.

Speaking logging messages

There might be situations when it is desirable to have logging messages rendered in an audible rather than a visible format. This is easy to do if you have text-to-speech (TTS) functionality available in your system, even if it doesn't have a Python binding. Most TTS systems have a command line program you can run, and this can be invoked from a handler using subprocess. It's assumed here that TTS command line programs won't expect to interact with users or take a long time to complete, and that the frequency of logged messages will be not so high as to swamp the user with messages, and that it's acceptable to have the messages spoken one at a time rather than concurrently, The example implementation below waits for one message to be spoken before the next is processed, and this might cause other handlers to be kept waiting. Here is a short example showing the approach, which assumes that the espeak TTS package is available:

import logging
import subprocess
import sys

class TTSHandler(logging.Handler):
    def emit(self, record):
        msg = self.format(record)
        # Speak slowly in a female English voice
        cmd = ['espeak', '-s150', '-ven+f3', msg]
        p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
        # wait for the program to finish
        p.communicate()

def configure_logging():
    h = TTSHandler()
    root = logging.getLogger()
    root.addHandler(h)
    # the default formatter just returns the message
    root.setLevel(logging.DEBUG)

def main():
    logging.info('Hello')
    logging.debug('Goodbye')

if __name__ == '__main__':
    configure_logging()
    sys.exit(main())

When run, this script should say "Hello" and then "Goodbye" in a female voice.

The above approach can, of course, be adapted to other TTS systems and even other systems altogether which can process messages via external programs run from a command line.

Buffering logging messages and outputting them conditionally

There might be situations where you want to log messages in a temporary area and only output them if a certain condition occurs. For example, you may want to start logging debug events in a function, and if the function completes without errors, you don't want to clutter the log with the collected debug information, but if there is an error, you want all the debug information to be output as well as the error.

Here is an example which shows how you could do this using a decorator for your functions where you want logging to behave this way. It makes use of the logging.handlers.MemoryHandler, which allows buffering of logged events until some condition occurs, at which point the buffered events are flushed - passed to another handler (the target handler) for processing. By default, the MemoryHandler flushed when its buffer gets filled up or an event whose level is greater than or equal to a specified threshold is seen. You can use this recipe with a more specialised subclass of MemoryHandler if you want custom flushing behavior.

The example script has a simple function, foo, which just cycles through all the logging levels, writing to sys.stderr to say what level it's about to log at, and then actually logging a message at that level. You can pass a parameter to foo which, if true, will log at ERROR and CRITICAL levels - otherwise, it only logs at DEBUG, INFO and WARNING levels.

The script just arranges to decorate foo with a decorator which will do the conditional logging that's required. The decorator takes a logger as a parameter and attaches a memory handler for the duration of the call to the decorated function. The decorator can be additionally parameterised using a target handler, a level at which flushing should occur, and a capacity for the buffer (number of records buffered). These default to a StreamHandler which writes to sys.stderr, logging.ERROR and 100 respectively.

Here's the script:

import logging
from logging.handlers import MemoryHandler
import sys

logger = logging.getLogger(__name__)
logger.addHandler(logging.NullHandler())

def log_if_errors(logger, target_handler=None, flush_level=None, capacity=None):
    if target_handler is None:
        target_handler = logging.StreamHandler()
    if flush_level is None:
        flush_level = logging.ERROR
    if capacity is None:
        capacity = 100
    handler = MemoryHandler(capacity, flushLevel=flush_level, target=target_handler)

    def decorator(fn):
        def wrapper(*args, **kwargs):
            logger.addHandler(handler)
            try:
                return fn(*args, **kwargs)
            except Exception:
                logger.exception('call failed')
                raise
            finally:
                super(MemoryHandler, handler).flush()
                logger.removeHandler(handler)
        return wrapper

    return decorator

def write_line(s):
    sys.stderr.write('%s\n' % s)

def foo(fail=False):
    write_line('about to log at DEBUG ...')
    logger.debug('Actually logged at DEBUG')
    write_line('about to log at INFO ...')
    logger.info('Actually logged at INFO')
    write_line('about to log at WARNING ...')
    logger.warning('Actually logged at WARNING')
    if fail:
        write_line('about to log at ERROR ...')
        logger.error('Actually logged at ERROR')
        write_line('about to log at CRITICAL ...')
        logger.critical('Actually logged at CRITICAL')
    return fail

decorated_foo = log_if_errors(logger)(foo)

if __name__ == '__main__':
    logger.setLevel(logging.DEBUG)
    write_line('Calling undecorated foo with False')
    assert not foo(False)
    write_line('Calling undecorated foo with True')
    assert foo(True)
    write_line('Calling decorated foo with False')
    assert not decorated_foo(False)
    write_line('Calling decorated foo with True')
    assert decorated_foo(True)

When this script is run, the following output should be observed:

Calling undecorated foo with False
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
Calling undecorated foo with True
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
about to log at ERROR ...
about to log at CRITICAL ...
Calling decorated foo with False
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
Calling decorated foo with True
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
about to log at ERROR ...
Actually logged at DEBUG
Actually logged at INFO
Actually logged at WARNING
Actually logged at ERROR
about to log at CRITICAL ...
Actually logged at CRITICAL

As you can see, actual logging output only occurs when an event is logged whose severity is ERROR or greater, but in that case, any previous events at lower severities are also logged.

You can of course use the conventional means of decoration:

@log_if_errors(logger)
def foo(fail=False):
    ...

Sending logging messages to email, with buffering

To illustrate how you can send log messages via email, so that a set number of messages are sent per email, you can subclass BufferingHandler. In the following example, which you can adapt to suit your specific needs, a simple test harness is provided which allows you to run the script with command line arguments specifying what you typically need to send things via SMTP. (Run the downloaded script with the -h argument to see the required and optional arguments.)

import logging
import logging.handlers
import smtplib

class BufferingSMTPHandler(logging.handlers.BufferingHandler):
    def __init__(self, mailhost, port, username, password, fromaddr, toaddrs,
                 subject, capacity):
        logging.handlers.BufferingHandler.__init__(self, capacity)
        self.mailhost = mailhost
        self.mailport = port
        self.username = username
        self.password = password
        self.fromaddr = fromaddr
        if isinstance(toaddrs, str):
            toaddrs = [toaddrs]
        self.toaddrs = toaddrs
        self.subject = subject
        self.setFormatter(logging.Formatter("%(asctime)s %(levelname)-5s %(message)s"))

    def flush(self):
        if len(self.buffer) > 0:
            try:
                smtp = smtplib.SMTP(self.mailhost, self.mailport)
                smtp.starttls()
                smtp.login(self.username, self.password)
                msg = "From: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n" % (self.fromaddr, ','.join(self.toaddrs), self.subject)
                for record in self.buffer:
                    s = self.format(record)
                    msg = msg + s + "\r\n"
                smtp.sendmail(self.fromaddr, self.toaddrs, msg)
                smtp.quit()
            except Exception:
                if logging.raiseExceptions:
                    raise
            self.buffer = []

if __name__ == '__main__':
    import argparse

    ap = argparse.ArgumentParser()
    aa = ap.add_argument
    aa('host', metavar='HOST', help='SMTP server')
    aa('--port', '-p', type=int, default=587, help='SMTP port')
    aa('user', metavar='USER', help='SMTP username')
    aa('password', metavar='PASSWORD', help='SMTP password')
    aa('to', metavar='TO', help='Addressee for emails')
    aa('sender', metavar='SENDER', help='Sender email address')
    aa('--subject', '-s',
       default='Test Logging email from Python logging module (buffering)',
       help='Subject of email')
    options = ap.parse_args()
    logger = logging.getLogger()
    logger.setLevel(logging.DEBUG)
    h = BufferingSMTPHandler(options.host, options.port, options.user,
                             options.password, options.sender,
                             options.to, options.subject, 10)
    logger.addHandler(h)
    for i in range(102):
        logger.info("Info index = %d", i)
    h.flush()
    h.close()

If you run this script and your SMTP server is correctly set up, you should find that it sends eleven emails to the addressee you specify. The first ten emails will each have ten log messages, and the eleventh will have two messages. That makes up 102 messages as specified in the script.

Formatting times using UTC (GMT) via configuration

Sometimes you want to format times using UTC, which can be done using a class such as UTCFormatter, shown below:

import logging
import time

class UTCFormatter(logging.Formatter):
    converter = time.gmtime

and you can then use the UTCFormatter in your code instead of Formatter. If you want to do that via configuration, you can use the dictConfig() API with an approach illustrated by the following complete example:

import logging
import logging.config
import time

class UTCFormatter(logging.Formatter):
    converter = time.gmtime

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'utc': {
            '()': UTCFormatter,
            'format': '%(asctime)s %(message)s',
        },
        'local': {
            'format': '%(asctime)s %(message)s',
        }
    },
    'handlers': {
        'console1': {
            'class': 'logging.StreamHandler',
            'formatter': 'utc',
        },
        'console2': {
            'class': 'logging.StreamHandler',
            'formatter': 'local',
        },
    },
    'root': {
        'handlers': ['console1', 'console2'],
   }
}

if __name__ == '__main__':
    logging.config.dictConfig(LOGGING)
    logging.warning('The local time is %s', time.asctime())

When this script is run, it should print something like:

2015-10-17 12:53:29,501 The local time is Sat Oct 17 13:53:29 2015
2015-10-17 13:53:29,501 The local time is Sat Oct 17 13:53:29 2015

showing how the time is formatted both as local time and UTC, one for each handler.

Using a context manager for selective logging

There are times when it would be useful to temporarily change the logging configuration and revert it back after doing something. For this, a context manager is the most obvious way of saving and restoring the logging context. Here is a simple example of such a context manager, which allows you to optionally change the logging level and add a logging handler purely in the scope of the context manager:

import logging
import sys

class LoggingContext:
    def __init__(self, logger, level=None, handler=None, close=True):
        self.logger = logger
        self.level = level
        self.handler = handler
        self.close = close

    def __enter__(self):
        if self.level is not None:
            self.old_level = self.logger.level
            self.logger.setLevel(self.level)
        if self.handler:
            self.logger.addHandler(self.handler)

    def __exit__(self, et, ev, tb):
        if self.level is not None:
            self.logger.setLevel(self.old_level)
        if self.handler:
            self.logger.removeHandler(self.handler)
        if self.handler and self.close:
            self.handler.close()
        # implicit return of None => don't swallow exceptions

If you specify a level value, the logger's level is set to that value in the scope of the with block covered by the context manager. If you specify a handler, it is added to the logger on entry to the block and removed on exit from the block. You can also ask the manager to close the handler for you on block exit - you could do this if you don't need the handler any more.

To illustrate how it works, we can add the following block of code to the above:

if __name__ == '__main__':
    logger = logging.getLogger('foo')
    logger.addHandler(logging.StreamHandler())
    logger.setLevel(logging.INFO)
    logger.info('1. This should appear just once on stderr.')
    logger.debug('2. This should not appear.')
    with LoggingContext(logger, level=logging.DEBUG):
        logger.debug('3. This should appear once on stderr.')
    logger.debug('4. This should not appear.')
    h = logging.StreamHandler(sys.stdout)
    with LoggingContext(logger, level=logging.DEBUG, handler=h, close=True):
        logger.debug('5. This should appear twice - once on stderr and once on stdout.')
    logger.info('6. This should appear just once on stderr.')
    logger.debug('7. This should not appear.')

We initially set the logger's level to INFO, so message #1 appears and message #2 doesn't. We then change the level to DEBUG temporarily in the following with block, and so message #3 appears. After the block exits, the logger's level is restored to INFO and so message #4 doesn't appear. In the next with block, we set the level to DEBUG again but also add a handler writing to sys.stdout. Thus, message #5 appears twice on the console (once via stderr and once via stdout). After the with statement's completion, the status is as it was before so message #6 appears (like message #1) whereas message #7 doesn't (just like message #2).

If we run the resulting script, the result is as follows:

$ python logctx.py
1. This should appear just once on stderr.
3. This should appear once on stderr.
5. This should appear twice - once on stderr and once on stdout.
5. This should appear twice - once on stderr and once on stdout.
6. This should appear just once on stderr.

If we run it again, but pipe stderr to /dev/null, we see the following, which is the only message written to stdout:

$ python logctx.py 2>/dev/null
5. This should appear twice - once on stderr and once on stdout.

Once again, but piping stdout to /dev/null, we get:

$ python logctx.py >/dev/null
1. This should appear just once on stderr.
3. This should appear once on stderr.
5. This should appear twice - once on stderr and once on stdout.
6. This should appear just once on stderr.

In this case, the message #5 printed to stdout doesn't appear, as expected.

Of course, the approach described here can be generalised, for example to attach logging filters temporarily. Note that the above code works in Python 2 as well as Python 3.

A CLI application starter template

Here's an example which shows how you can:

Use a logging level based on command-line arguments

Dispatch to multiple subcommands in separate files, all logging at the same level in a consistent way

Make use of simple, minimal configuration

Suppose we have a command-line application whose job is to stop, start or restart some services. This could be organised for the purposes of illustration as a file app.py that is the main script for the application, with individual commands implemented in start.py, stop.py and restart.py. Suppose further that we want to control the verbosity of the application via a command-line argument, defaulting to logging.INFO. Here's one way that app.py could be written:

import argparse
import importlib
import logging
import os
import sys

def main(args=None):
    scriptname = os.path.basename(__file__)
    parser = argparse.ArgumentParser(scriptname)
    levels = ('DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL')
    parser.add_argument('--log-level', default='INFO', choices=levels)
    subparsers = parser.add_subparsers(dest='command',
                                       help='Available commands:')
    start_cmd = subparsers.add_parser('start', help='Start a service')
    start_cmd.add_argument('name', metavar='NAME',
                           help='Name of service to start')
    stop_cmd = subparsers.add_parser('stop',
                                     help='Stop one or more services')
    stop_cmd.add_argument('names', metavar='NAME', nargs='+',
                          help='Name of service to stop')
    restart_cmd = subparsers.add_parser('restart',
                                        help='Restart one or more services')
    restart_cmd.add_argument('names', metavar='NAME', nargs='+',
                             help='Name of service to restart')
    options = parser.parse_args()
    # the code to dispatch commands could all be in this file. For the purposes
    # of illustration only, we implement each command in a separate module.
    try:
        mod = importlib.import_module(options.command)
        cmd = getattr(mod, 'command')
    except (ImportError, AttributeError):
        print('Unable to find the code for command \'%s\'' % options.command)
        return 1
    # Could get fancy here and load configuration from file or dictionary
    logging.basicConfig(level=options.log_level,
                        format='%(levelname)s %(name)s %(message)s')
    cmd(options)

if __name__ == '__main__':
    sys.exit(main())

And the start, stop and restart commands can be implemented in separate modules, like so for starting:

# start.py
import logging

logger = logging.getLogger(__name__)

def command(options):
    logger.debug('About to start %s', options.name)
    # 在這裡實際執行命令處理 ...
    logger.info('Started the \'%s\' service.', options.name)

and thus for stopping:

# stop.py
import logging

logger = logging.getLogger(__name__)

def command(options):
    n = len(options.names)
    if n == 1:
        plural = ''
        services = '\'%s\'' % options.names[0]
    else:
        plural = 's'
        services = ', '.join('\'%s\'' % name for name in options.names)
        i = services.rfind(', ')
        services = services[:i] + ' and ' + services[i + 2:]
    logger.debug('About to stop %s', services)
    # 在這裡實際執行命令處理 ...
    logger.info('Stopped the %s service%s.', services, plural)

and similarly for restarting:

# restart.py
import logging

logger = logging.getLogger(__name__)

def command(options):
    n = len(options.names)
    if n == 1:
        plural = ''
        services = '\'%s\'' % options.names[0]
    else:
        plural = 's'
        services = ', '.join('\'%s\'' % name for name in options.names)
        i = services.rfind(', ')
        services = services[:i] + ' and ' + services[i + 2:]
    logger.debug('About to restart %s', services)
    # 在這裡實際執行命令處理 ...
    logger.info('Restarted the %s service%s.', services, plural)

If we run this application with the default log level, we get output like this:

$ python app.py start foo
INFO start Started the 'foo' service.

$ python app.py stop foo bar
INFO stop Stopped the 'foo' and 'bar' services.

$ python app.py restart foo bar baz
INFO restart Restarted the 'foo', 'bar' and 'baz' services.

The first word is the logging level, and the second word is the module or package name of the place where the event was logged.

If we change the logging level, then we can change the information sent to the log. For example, if we want more information:

$ python app.py --log-level DEBUG start foo
DEBUG start About to start foo
INFO start Started the 'foo' service.

$ python app.py --log-level DEBUG stop foo bar
DEBUG stop About to stop 'foo' and 'bar'
INFO stop Stopped the 'foo' and 'bar' services.

$ python app.py --log-level DEBUG restart foo bar baz
DEBUG restart About to restart 'foo', 'bar' and 'baz'
INFO restart Restarted the 'foo', 'bar' and 'baz' services.

And if we want less:

$ python app.py --log-level WARNING start foo
$ python app.py --log-level WARNING stop foo bar
$ python app.py --log-level WARNING restart foo bar baz

In this case, the commands don't print anything to the console, since nothing at WARNING level or above is logged by them.

A Qt GUI for logging

A question that comes up from time to time is about how to log to a GUI application. The Qt [https://www.qt.io/] framework is a popular cross-platform UI framework with Python bindings using PySide2 [https://pypi.org/project/PySide2/] or PyQt5 [https://pypi.org/project/PyQt5/] libraries.

The following example shows how to log to a Qt GUI. This introduces a simple QtHandler class which takes a callable, which should be a slot in the main thread that does GUI updates. A worker thread is also created to show how you can log to the GUI from both the UI itself (via a button for manual logging) as well as a worker thread doing work in the background (here, just logging messages at random levels with random short delays in between).

The worker thread is implemented using Qt's QThread class rather than the threading module, as there are circumstances where one has to use QThread, which offers better integration with other Qt components.

The code should work with recent releases of any of PySide6, PyQt6, PySide2 or PyQt5. You should be able to adapt the approach to earlier versions of Qt. Please refer to the comments in the code snippet for more detailed information.

import datetime
import logging
import random
import sys
import time

# Deal with minor differences between different Qt packages
try:
    from PySide6 import QtCore, QtGui, QtWidgets
    Signal = QtCore.Signal
    Slot = QtCore.Slot
except ImportError:
    try:
        from PyQt6 import QtCore, QtGui, QtWidgets
        Signal = QtCore.pyqtSignal
        Slot = QtCore.pyqtSlot
    except ImportError:
        try:
            from PySide2 import QtCore, QtGui, QtWidgets
            Signal = QtCore.Signal
            Slot = QtCore.Slot
        except ImportError:
            from PyQt5 import QtCore, QtGui, QtWidgets
            Signal = QtCore.pyqtSignal
            Slot = QtCore.pyqtSlot

logger = logging.getLogger(__name__)

#
# Signals need to be contained in a QObject or subclass in order to be correctly
# initialized.
#
class Signaller(QtCore.QObject):
    signal = Signal(str, logging.LogRecord)

#
# Output to a Qt GUI is only supposed to happen on the main thread. So, this
# handler is designed to take a slot function which is set up to run in the main
# thread. In this example, the function takes a string argument which is a
# formatted log message, and the log record which generated it. The formatted
# string is just a convenience - you could format a string for output any way
# you like in the slot function itself.
#
# You specify the slot function to do whatever GUI updates you want. The handler
# doesn't know or care about specific UI elements.
#
class QtHandler(logging.Handler):
    def __init__(self, slotfunc, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.signaller = Signaller()
        self.signaller.signal.connect(slotfunc)

    def emit(self, record):
        s = self.format(record)
        self.signaller.signal.emit(s, record)

#
# This example uses QThreads, which means that the threads at the Python level
# are named something like "Dummy-1". The function below gets the Qt name of the
# current thread.
#
def ctname():
    return QtCore.QThread.currentThread().objectName()

#
# Used to generate random levels for logging.
#
LEVELS = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
          logging.CRITICAL)

#
# This worker class represents work that is done in a thread separate to the
# main thread. The way the thread is kicked off to do work is via a button press
# that connects to a slot in the worker.
#
# Because the default threadName value in the LogRecord isn't much use, we add
# a qThreadName which contains the QThread name as computed above, and pass that
# value in an "extra" dictionary which is used to update the LogRecord with the
# QThread name.
#
# This example worker just outputs messages sequentially, interspersed with
# random delays of the order of a few seconds.
#
class Worker(QtCore.QObject):
    @Slot()
    def start(self):
        extra = {'qThreadName': ctname() }
        logger.debug('Started work', extra=extra)
        i = 1
        # Let the thread run until interrupted. This allows reasonably clean
        # thread termination.
        while not QtCore.QThread.currentThread().isInterruptionRequested():
            delay = 0.5 + random.random() * 2
            time.sleep(delay)
            try:
                if random.random() < 0.1:
                    raise ValueError('Exception raised: %d' % i)
                else:
                    level = random.choice(LEVELS)
                    logger.log(level, 'Message after delay of %3.1f: %d', delay, i, extra=extra)
            except ValueError as e:
                logger.exception('Failed: %s', e, extra=extra)
            i += 1

#
# Implement a simple UI for this cookbook example. This contains:
#
# * A read-only text edit window which holds formatted log messages
# * A button to start work and log stuff in a separate thread
# * A button to log something from the main thread
# * A button to clear the log window
#
class Window(QtWidgets.QWidget):

    COLORS = {
        logging.DEBUG: 'black',
        logging.INFO: 'blue',
        logging.WARNING: 'orange',
        logging.ERROR: 'red',
        logging.CRITICAL: 'purple',
    }

    def __init__(self, app):
        super().__init__()
        self.app = app
        self.textedit = te = QtWidgets.QPlainTextEdit(self)
        # Set whatever the default monospace font is for the platform
        f = QtGui.QFont('nosuchfont')
        if hasattr(f, 'Monospace'):
            f.setStyleHint(f.Monospace)
        else:
            f.setStyleHint(f.StyleHint.Monospace)  # for Qt6
        te.setFont(f)
        te.setReadOnly(True)
        PB = QtWidgets.QPushButton
        self.work_button = PB('Start background work', self)
        self.log_button = PB('Log a message at a random level', self)
        self.clear_button = PB('Clear log window', self)
        self.handler = h = QtHandler(self.update_status)
        # Remember to use qThreadName rather than threadName in the format string.
        fs = '%(asctime)s %(qThreadName)-12s %(levelname)-8s %(message)s'
        formatter = logging.Formatter(fs)
        h.setFormatter(formatter)
        logger.addHandler(h)
        # Set up to terminate the QThread when we exit
        app.aboutToQuit.connect(self.force_quit)

        # Lay out all the widgets
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(te)
        layout.addWidget(self.work_button)
        layout.addWidget(self.log_button)
        layout.addWidget(self.clear_button)
        self.setFixedSize(900, 400)

        # Connect the non-worker slots and signals
        self.log_button.clicked.connect(self.manual_update)
        self.clear_button.clicked.connect(self.clear_display)

        # Start a new worker thread and connect the slots for the worker
        self.start_thread()
        self.work_button.clicked.connect(self.worker.start)
        # Once started, the button should be disabled
        self.work_button.clicked.connect(lambda : self.work_button.setEnabled(False))

    def start_thread(self):
        self.worker = Worker()
        self.worker_thread = QtCore.QThread()
        self.worker.setObjectName('Worker')
        self.worker_thread.setObjectName('WorkerThread')  # for qThreadName
        self.worker.moveToThread(self.worker_thread)
        # This will start an event loop in the worker thread
        self.worker_thread.start()

    def kill_thread(self):
        # Just tell the worker to stop, then tell it to quit and wait for that
        # to happen
        self.worker_thread.requestInterruption()
        if self.worker_thread.isRunning():
            self.worker_thread.quit()
            self.worker_thread.wait()
        else:
            print('worker has already exited.')

    def force_quit(self):
        # For use when the window is closed
        if self.worker_thread.isRunning():
            self.kill_thread()

    # The functions below update the UI and run in the main thread because
    # that's where the slots are set up

    @Slot(str, logging.LogRecord)
    def update_status(self, status, record):
        color = self.COLORS.get(record.levelno, 'black')
        s = '<pre><font color="%s">%s</font></pre>' % (color, status)
        self.textedit.appendHtml(s)

    @Slot()
    def manual_update(self):
        # This function uses the formatted message passed in, but also uses
        # information from the record to format the message in an appropriate
        # color according to its severity (level).
        level = random.choice(LEVELS)
        extra = {'qThreadName': ctname() }
        logger.log(level, 'Manually logged!', extra=extra)

    @Slot()
    def clear_display(self):
        self.textedit.clear()

def main():
    QtCore.QThread.currentThread().setObjectName('MainThread')
    logging.getLogger().setLevel(logging.DEBUG)
    app = QtWidgets.QApplication(sys.argv)
    example = Window(app)
    example.show()
    if hasattr(app, 'exec'):
        rc = app.exec()
    else:
        rc = app.exec_()
    sys.exit(rc)

if __name__=='__main__':
    main()

Logging to syslog with RFC5424 support

Although RFC 5424 [https://datatracker.ietf.org/doc/html/rfc5424.html] dates from 2009, most syslog servers are configured by default to use the older RFC 3164 [https://datatracker.ietf.org/doc/html/rfc3164.html], which hails from 2001. When logging was added to Python in 2003, it supported the earlier (and only existing) protocol at the time. Since RFC5424 came out, as there has not been widespread deployment of it in syslog servers, the SysLogHandler functionality has not been updated.

RFC 5424 contains some useful features such as support for structured data, and if you need to be able to log to a syslog server with support for it, you can do so with a subclassed handler which looks something like this:

import datetime
import logging.handlers
import re
import socket
import time

class SysLogHandler5424(logging.handlers.SysLogHandler):

    tz_offset = re.compile(r'([+-]\d{2})(\d{2})$')
    escaped = re.compile(r'([\]"\\])')

    def __init__(self, *args, **kwargs):
        self.msgid = kwargs.pop('msgid', None)
        self.appname = kwargs.pop('appname', None)
        super().__init__(*args, **kwargs)

    def format(self, record):
        version = 1
        asctime = datetime.datetime.fromtimestamp(record.created).isoformat()
        m = self.tz_offset.match(time.strftime('%z'))
        has_offset = False
        if m and time.timezone:
            hrs, mins = m.groups()
            if int(hrs) or int(mins):
                has_offset = True
        if not has_offset:
            asctime += 'Z'
        else:
            asctime += f'{hrs}:{mins}'
        try:
            hostname = socket.gethostname()
        except Exception:
            hostname = '-'
        appname = self.appname or '-'
        procid = record.process
        msgid = '-'
        msg = super().format(record)
        sdata = '-'
        if hasattr(record, 'structured_data'):
            sd = record.structured_data
            # This should be a dict where the keys are SD-ID and the value is a
            # dict mapping PARAM-NAME to PARAM-VALUE (refer to the RFC for what these
            # mean)
            # There's no error checking here - it's purely for illustration, and you
            # can adapt this code for use in production environments
            parts = []

            def replacer(m):
                g = m.groups()
                return '\\' + g[0]

            for sdid, dv in sd.items():
                part = f'[{sdid}'
                for k, v in dv.items():
                    s = str(v)
                    s = self.escaped.sub(replacer, s)
                    part += f' {k}="{s}"'
                part += ']'
                parts.append(part)
            sdata = ''.join(parts)
        return f'{version} {asctime} {hostname} {appname} {procid} {msgid} {sdata} {msg}'

You'll need to be familiar with RFC 5424 to fully understand the above code, and it may be that you have slightly different needs (e.g. for how you pass structural data to the log). Nevertheless, the above should be adaptable to your speciric needs. With the above handler, you'd pass structured data using something like this:

sd = {
    'foo@12345': {'bar': 'baz', 'baz': 'bozz', 'fizz': r'buzz'},
    'foo@54321': {'rab': 'baz', 'zab': 'bozz', 'zzif': r'buzz'}
}
extra = {'structured_data': sd}
i = 1
logger.debug('Message %d', i, extra=extra)

How to treat a logger like an output stream

Sometimes, you need to interface to a third-party API which expects a file-like object to write to, but you want to direct the API's output to a logger. You can do this using a class which wraps a logger with a file-like API. Here's a short script illustrating such a class:

import logging

class LoggerWriter:
    def __init__(self, logger, level):
        self.logger = logger
        self.level = level

    def write(self, message):
        if message != '\n':  # avoid printing bare newlines, if you like
            self.logger.log(self.level, message)

    def flush(self):
        # doesn't actually do anything, but might be expected of a file-like
        # object - so optional depending on your situation
        pass

    def close(self):
        # doesn't actually do anything, but might be expected of a file-like
        # object - so optional depending on your situation. You might want
        # to set a flag so that later calls to write raise an exception
        pass

def main():
    logging.basicConfig(level=logging.DEBUG)
    logger = logging.getLogger('demo')
    info_fp = LoggerWriter(logger, logging.INFO)
    debug_fp = LoggerWriter(logger, logging.DEBUG)
    print('An INFO message', file=info_fp)
    print('A DEBUG message', file=debug_fp)

if __name__ == "__main__":
    main()

When this script is run, it prints

INFO:demo:An INFO message
DEBUG:demo:A DEBUG message

You could also use LoggerWriter to redirect sys.stdout and sys.stderr by doing something like this:

import sys

sys.stdout = LoggerWriter(logger, logging.INFO)
sys.stderr = LoggerWriter(logger, logging.WARNING)

You should do this after configuring logging for your needs. In the above example, the basicConfig() call does this (using the sys.stderr value before it is overwritten by a LoggerWriter instance). Then, you'd get this kind of result:

>>> print('Foo')
INFO:demo:Foo
>>> print('Bar', file=sys.stderr)
WARNING:demo:Bar
>>>

Of course, the examples above show output according to the format used by basicConfig(), but you can use a different formatter when you configure logging.

Note that with the above scheme, you are somewhat at the mercy of buffering and the sequence of write calls which you are intercepting. For example, with the definition of LoggerWriter above, if you have the snippet

sys.stderr = LoggerWriter(logger, logging.WARNING)
1 / 0

then running the script results in

WARNING:demo:Traceback (most recent call last):

WARNING:demo:  File "/home/runner/cookbook-loggerwriter/test.py", line 53, in <module>

WARNING:demo:
WARNING:demo:main()
WARNING:demo:  File "/home/runner/cookbook-loggerwriter/test.py", line 49, in main

WARNING:demo:
WARNING:demo:1 / 0
WARNING:demo:ZeroDivisionError
WARNING:demo::
WARNING:demo:division by zero

As you can see, this output isn't ideal. That's because the underlying code which writes to sys.stderr makes multiple writes, each of which results in a separate logged line (for example, the last three lines above). To get around this problem, you need to buffer things and only output log lines when newlines are seen. Let's use a slightly better implementation of LoggerWriter:

class BufferingLoggerWriter(LoggerWriter):
    def __init__(self, logger, level):
        super().__init__(logger, level)
        self.buffer = ''

    def write(self, message):
        if '\n' not in message:
            self.buffer += message
        else:
            parts = message.split('\n')
            if self.buffer:
                s = self.buffer + parts.pop(0)
                self.logger.log(self.level, s)
            self.buffer = parts.pop()
            for part in parts:
                self.logger.log(self.level, part)

This just buffers up stuff until a newline is seen, and then logs complete lines. With this approach, you get better output:

WARNING:demo:Traceback (most recent call last):
WARNING:demo:  File "/home/runner/cookbook-loggerwriter/main.py", line 55, in <module>
WARNING:demo:    main()
WARNING:demo:  File "/home/runner/cookbook-loggerwriter/main.py", line 52, in main
WARNING:demo:    1/0
WARNING:demo:ZeroDivisionError: division by zero

How to uniformly handle newlines in logging output

Usually, messages that are logged (say to console or file) consist of a single line of text. However, sometimes there is a need to handle messages with multiple lines - whether because a logging format string contains newlines, or logged data contains newlines. If you want to handle such messages uniformly, so that each line in the logged message appears uniformly formatted as if it was logged separately, you can do this using a handler mixin, as in the following snippet:

# Assume this is in a module mymixins.py
import copy

class MultilineMixin:
    def emit(self, record):
        s = record.getMessage()
        if '\n' not in s:
            super().emit(record)
        else:
            lines = s.splitlines()
            rec = copy.copy(record)
            rec.args = None
            for line in lines:
                rec.msg = line
                super().emit(rec)

You can use the mixin as in the following script:

import logging

from mymixins import MultilineMixin

logger = logging.getLogger(__name__)

class StreamHandler(MultilineMixin, logging.StreamHandler):
    pass

if __name__ == '__main__':
    logging.basicConfig(level=logging.DEBUG, format='%(asctime)s %(levelname)-9s %(message)s',
                        handlers = [StreamHandler()])
    logger.debug('Single line')
    logger.debug('Multiple lines:\nfool me once ...')
    logger.debug('Another single line')
    logger.debug('Multiple lines:\n%s', 'fool me ...\ncan\'t get fooled again')

The script, when run, prints something like:

2025-07-02 13:54:47,234 DEBUG     Single line
2025-07-02 13:54:47,234 DEBUG     Multiple lines:
2025-07-02 13:54:47,234 DEBUG     fool me once ...
2025-07-02 13:54:47,234 DEBUG     Another single line
2025-07-02 13:54:47,234 DEBUG     Multiple lines:
2025-07-02 13:54:47,234 DEBUG     fool me ...
2025-07-02 13:54:47,234 DEBUG     can't get fooled again

If, on the other hand, you are concerned about log injection [https://owasp.org/www-community/attacks/Log_Injection], you can use a formatter which escapes newlines, as per the following example:

import logging

logger = logging.getLogger(__name__)

class EscapingFormatter(logging.Formatter):
    def format(self, record):
        s = super().format(record)
        return s.replace('\n', r'\n')

if __name__ == '__main__':
    h = logging.StreamHandler()
    h.setFormatter(EscapingFormatter('%(asctime)s %(levelname)-9s %(message)s'))
    logging.basicConfig(level=logging.DEBUG, handlers = [h])
    logger.debug('Single line')
    logger.debug('Multiple lines:\nfool me once ...')
    logger.debug('Another single line')
    logger.debug('Multiple lines:\n%s', 'fool me ...\ncan\'t get fooled again')

You can, of course, use whatever escaping scheme makes the most sense for you. The script, when run, should produce output like this:

2025-07-09 06:47:33,783 DEBUG     Single line
2025-07-09 06:47:33,783 DEBUG     Multiple lines:\nfool me once ...
2025-07-09 06:47:33,783 DEBUG     Another single line
2025-07-09 06:47:33,783 DEBUG     Multiple lines:\nfool me ...\ncan't get fooled again

Escaping behaviour can't be the stdlib default , as it would break backwards compatibility.

Patterns to avoid

Although the preceding sections have described ways of doing things you might need to do or deal with, it is worth mentioning some usage patterns which are unhelpful, and which should therefore be avoided in most cases. The following sections are in no particular order.

Opening the same log file multiple times

On Windows, you will generally not be able to open the same file multiple times as this will lead to a "file is in use by another process" error. However, on POSIX platforms you'll not get any errors if you open the same file multiple times. This could be done accidentally, for example by:

Adding a file handler more than once which references the same file (e.g. by a copy/paste/forget-to-change error).

Opening two files that look different, as they have different names, but are the same because one is a symbolic link to the other.

Forking a process, following which both parent and child have a reference to the same file. This might be through use of the multiprocessing module, for example.

Opening a file multiple times might appear to work most of the time, but can lead to a number of problems in practice:

Logging output can be garbled because multiple threads or processes try to write to the same file. Although logging guards against concurrent use of the same handler instance by multiple threads, there is no such protection if concurrent writes are attempted by two different threads using two different handler instances which happen to point to the same file.

An attempt to delete a file (e.g. during file rotation) silently fails, because there is another reference pointing to it. This can lead to confusion and wasted debugging time - log entries end up in unexpected places, or are lost altogether. Or a file that was supposed to be moved remains in place, and grows in size unexpectedly despite size-based rotation being supposedly in place.

Use the techniques outlined in Logging to a single file from multiple processes to circumvent such issues.

Using loggers as attributes in a class or passing them as parameters

While there might be unusual cases where you'll need to do this, in general there is no point because loggers are singletons. Code can always access a given logger instance by name using logging.getLogger(name), so passing instances around and holding them as instance attributes is pointless. Note that in other languages such as Java and C#, loggers are often static class attributes. However, this pattern doesn't make sense in Python, where the module (and not the class) is the unit of software decomposition.

Adding handlers other than NullHandler to a logger in a library

Configuring logging by adding handlers, formatters and filters is the responsibility of the application developer, not the library developer. If you are maintaining a library, ensure that you don't add handlers to any of your loggers other than a NullHandler instance.

Creating a lot of loggers

Loggers are singletons that are never freed during a script execution, and so creating lots of loggers will use up memory which can't then be freed. Rather than create a logger per e.g. file processed or network connection made, use the existing mechanisms for passing contextual information into your logs and restrict the loggers created to those describing areas within your application (generally modules, but occasionally slightly more fine-grained than that).

其他資源

也參考

logging 模組

API reference for the logging module.

logging.config 模組

Configuration API for the logging module.

logging.handlers 模組

Useful handlers included with the logging module.

基礎教學

進階教學

如何使用正規表示式

作者:

A.M. Kuchling <amk@amk.ca>

摘要

此文件為如何在 Python 中使用 re 模組來撰寫正規表示式的入門指導。進階使用及參考文件請見函式庫參考一章。

簡介

正規表示式 (也稱為 REs、regexes 或 regex patterns) 是一個輕量且高專業化的程式語言。在 Python 中可透過內建的 re 模組直接使用。你可以使用此輕量化的語言針對想要匹配的一組字串撰寫規則，這組字串可能包含了英語句子、e-mail 地址、TeX 命令或任何東西。你可以檢查如「這組字串是否匹配這個規則？」或「這組字串中是否有任一處匹配這個規則？」。除此之外，你也可以使用 REs 來修改或是切割字串。

Regular expression patterns are compiled into a series of bytecodes which are then executed by a matching engine written in C. For advanced use, it may be necessary to pay careful attention to how the engine will execute a given RE, and write the RE in a certain way in order to produce bytecode that runs faster. Optimization isn't covered in this document, because it requires that you have a good understanding of the matching engine's internals.

The regular expression language is relatively small and restricted, so not all possible string processing tasks can be done using regular expressions. There are also tasks that can be done with regular expressions, but the expressions turn out to be very complicated. In these cases, you may be better off writing Python code to do the processing; while Python code will be slower than an elaborate regular expression, it will also probably be more understandable.

Simple Patterns

We'll start by learning about the simplest possible regular expressions. Since regular expressions are used to operate on strings, we'll begin with the most common task: matching characters.

For a detailed explanation of the computer science underlying regular expressions (deterministic and non-deterministic finite automata), you can refer to almost any textbook on writing compilers.

Matching Characters

Most letters and characters will simply match themselves. For example, the regular expression test will match the string test exactly. (You can enable a case-insensitive mode that would let this RE match Test or TEST as well; more about this later.)

There are exceptions to this rule; some characters are special metacharacters, and don't match themselves. Instead, they signal that some out-of-the-ordinary thing should be matched, or they affect other portions of the RE by repeating them or changing their meaning. Much of this document is devoted to discussing various metacharacters and what they do.

Here's a complete list of the metacharacters; their meanings will be discussed in the rest of this HOWTO.

. ^ $ * + ? { } [ ] \ | ( )

The first metacharacters we'll look at are [ and ]. They're used for specifying a character class, which is a set of characters that you wish to match. Characters can be listed individually, or a range of characters can be indicated by giving two characters and separating them by a '-'. For example, [abc] will match any of the characters a, b, or c; this is the same as [a-c], which uses a range to express the same set of characters. If you wanted to match only lowercase letters, your RE would be [a-z].

Metacharacters (except \) are not active inside classes. For example, [akm$] will match any of the characters 'a', 'k', 'm', or '$'; '$' is usually a metacharacter, but inside a character class it's stripped of its special nature.

You can match the characters not listed within the class by complementing the set. This is indicated by including a '^' as the first character of the class. For example, [^5] will match any character except '5'. If the caret appears elsewhere in a character class, it does not have special meaning. For example: [5^] will match either a '5' or a '^'.

Perhaps the most important metacharacter is the backslash, \. As in Python string literals, the backslash can be followed by various characters to signal various special sequences. It's also used to escape all the metacharacters so you can still match them in patterns; for example, if you need to match a [ or \, you can precede them with a backslash to remove their special meaning: \[ or \\.

Some of the special sequences beginning with '\' represent predefined sets of characters that are often useful, such as the set of digits, the set of letters, or the set of anything that isn't whitespace.

Let's take an example: \w matches any alphanumeric character. If the regex pattern is expressed in bytes, this is equivalent to the class [a-zA-Z0-9_]. If the regex pattern is a string, \w will match all the characters marked as letters in the Unicode database provided by the unicodedata module. You can use the more restricted definition of \w in a string pattern by supplying the re.ASCII flag when compiling the regular expression.

The following list of special sequences isn't complete. For a complete list of sequences and expanded class definitions for Unicode string patterns, see the last part of Regular Expression Syntax in the Standard Library reference. In general, the Unicode versions match any character that's in the appropriate category in the Unicode database.

\d

Matches any decimal digit; this is equivalent to the class [0-9].

\D

Matches any non-digit character; this is equivalent to the class [^0-9].

\s

Matches any whitespace character; this is equivalent to the class [ \t\n\r\f\v].

\S

Matches any non-whitespace character; this is equivalent to the class [^ \t\n\r\f\v].

\w

Matches any alphanumeric character; this is equivalent to the class [a-zA-Z0-9_].

\W

Matches any non-alphanumeric character; this is equivalent to the class [^a-zA-Z0-9_].

These sequences can be included inside a character class. For example, [\s,.] is a character class that will match any whitespace character, or ',' or '.'.

The final metacharacter in this section is .. It matches anything except a newline character, and there's an alternate mode (re.DOTALL) where it will match even a newline. . is often used where you want to match "any character".

Repeating Things

Being able to match varying sets of characters is the first thing regular expressions can do that isn't already possible with the methods available on strings. However, if that was the only additional capability of regexes, they wouldn't be much of an advance. Another capability is that you can specify that portions of the RE must be repeated a certain number of times.

The first metacharacter for repeating things that we'll look at is *. * doesn't match the literal character '*'; instead, it specifies that the previous character can be matched zero or more times, instead of exactly once.

For example, ca*t will match 'ct' (0 'a' characters), 'cat' (1 'a'), 'caaat' (3 'a' characters), and so forth.

Repetitions such as * are greedy; when repeating a RE, the matching engine will try to repeat it as many times as possible. If later portions of the pattern don't match, the matching engine will then back up and try again with fewer repetitions.

A step-by-step example will make this more obvious. Let's consider the expression a[bcd]*b. This matches the letter 'a', zero or more letters from the class [bcd], and finally ends with a 'b'. Now imagine matching this RE against the string 'abcbd'.

Step

Matched

Explanation

1

a

The a in the RE matches.

2

abcbd

The engine matches [bcd]*, going as far as it can, which is to the end of the string.

3

Failure

The engine tries to match b, but the current position is at the end of the string, so it fails.

4

abcb

Back up, so that [bcd]* matches one less character.

5

Failure

Try b again, but the current position is at the last character, which is a 'd'.

6

abc

Back up again, so that [bcd]* is only matching bc.

6

abcb

Try b again. This time the character at the current position is 'b', so it succeeds.

The end of the RE has now been reached, and it has matched 'abcb'. This demonstrates how the matching engine goes as far as it can at first, and if no match is found it will then progressively back up and retry the rest of the RE again and again. It will back up until it has tried zero matches for [bcd]*, and if that subsequently fails, the engine will conclude that the string doesn't match the RE at all.

Another repeating metacharacter is +, which matches one or more times. Pay careful attention to the difference between * and +; * matches zero or more times, so whatever's being repeated may not be present at all, while + requires at least one occurrence. To use a similar example, ca+t will match 'cat' (1 'a'), 'caaat' (3 'a's), but won't match 'ct'.

There are two more repeating operators or quantifiers. The question mark character, ?, matches either once or zero times; you can think of it as marking something as being optional. For example, home-?brew matches either 'homebrew' or 'home-brew'.

The most complicated quantifier is {m,n}, where m and n are decimal integers. This quantifier means there must be at least m repetitions, and at most n. For example, a/{1,3}b will match 'a/b', 'a//b', and 'a///b'. It won't match 'ab', which has no slashes, or 'a////b', which has four.

You can omit either m or n; in that case, a reasonable value is assumed for the missing value. Omitting m is interpreted as a lower limit of 0, while omitting n results in an upper bound of infinity.

The simplest case {m} matches the preceding item exactly m times. For example, a/{2}b will only match 'a//b'.

Readers of a reductionist bent may notice that the three other quantifiers can all be expressed using this notation. {0,} is the same as *, {1,} is equivalent to +, and {0,1} is the same as ?. It's better to use *, +, or ? when you can, simply because they're shorter and easier to read.

Using Regular Expressions

Now that we've looked at some simple regular expressions, how do we actually use them in Python? The re module provides an interface to the regular expression engine, allowing you to compile REs into objects and then perform matches with them.

Compiling Regular Expressions

Regular expressions are compiled into pattern objects, which have methods for various operations such as searching for pattern matches or performing string substitutions.

>>> import re
>>> p = re.compile('ab*')
>>> p
re.compile('ab*')

re.compile() also accepts an optional flags argument, used to enable various special features and syntax variations. We'll go over the available settings later, but for now a single example will do:

>>> p = re.compile('ab*', re.IGNORECASE)

The RE is passed to re.compile() as a string. REs are handled as strings because regular expressions aren't part of the core Python language, and no special syntax was created for expressing them. (There are applications that don't need REs at all, so there's no need to bloat the language specification by including them.) Instead, the re module is simply a C extension module included with Python, just like the socket or zlib modules.

Putting REs in strings keeps the Python language simpler, but has one disadvantage which is the topic of the next section.

The Backslash Plague

As stated earlier, regular expressions use the backslash character ('\') to indicate special forms or to allow special characters to be used without invoking their special meaning. This conflicts with Python's usage of the same character for the same purpose in string literals.

Let's say you want to write a RE that matches the string \section, which might be found in a LaTeX file. To figure out what to write in the program code, start with the desired string to be matched. Next, you must escape any backslashes and other metacharacters by preceding them with a backslash, resulting in the string \\section. The resulting string that must be passed to re.compile() must be \\section. However, to express this as a Python string literal, both backslashes must be escaped again.

Characters

Stage

\section

Text string to be matched

\\section

Escaped backslash for re.compile()

"\\\\section"

Escaped backslashes for a string literal

In short, to match a literal backslash, one has to write '\\\\' as the RE string, because the regular expression must be \\, and each backslash must be expressed as \\ inside a regular Python string literal. In REs that feature backslashes repeatedly, this leads to lots of repeated backslashes and makes the resulting strings difficult to understand.

The solution is to use Python's raw string notation for regular expressions; backslashes are not handled in any special way in a string literal prefixed with 'r', so r"\n" is a two-character string containing '\' and 'n', while "\n" is a one-character string containing a newline. Regular expressions will often be written in Python code using this raw string notation.

In addition, special escape sequences that are valid in regular expressions, but not valid as Python string literals, now result in a DeprecationWarning and will eventually become a SyntaxError, which means the sequences will be invalid if raw string notation or escaping the backslashes isn't used.

Regular String

Raw string

"ab*"

r"ab*"

"\\\\section"

r"\\section"

"\\w+\\s+\\1"

r"\w+\s+\1"

Performing Matches

Once you have an object representing a compiled regular expression, what do you do with it? Pattern objects have several methods and attributes. Only the most significant ones will be covered here; consult the re docs for a complete listing.

方法/屬性

Purpose

match()

Determine if the RE matches at the beginning of the string.

search()

Scan through a string, looking for any location where this RE matches.

findall()

Find all substrings where the RE matches, and returns them as a list.

finditer()

Find all substrings where the RE matches, and returns them as an iterator.

match() and search() return None if no match can be found. If they're successful, a match object instance is returned, containing information about the match: where it starts and ends, the substring it matched, and more.

You can learn about this by interactively experimenting with the re module.

This HOWTO uses the standard Python interpreter for its examples. First, run the Python interpreter, import the re module, and compile a RE:

>>> import re
>>> p = re.compile('[a-z]+')
>>> p
re.compile('[a-z]+')

Now, you can try matching various strings against the RE [a-z]+. An empty string shouldn't match at all, since + means 'one or more repetitions'. match() should return None in this case, which will cause the interpreter to print no output. You can explicitly print the result of match() to make this clear.

>>> p.match("")
>>> print(p.match(""))
None

Now, let's try it on a string that it should match, such as tempo. In this case, match() will return a match object, so you should store the result in a variable for later use.

>>> m = p.match('tempo')
>>> m
<re.Match object; span=(0, 5), match='tempo'>

Now you can query the match object for information about the matching string. Match object instances also have several methods and attributes; the most important ones are:

方法/屬性

Purpose

group()

Return the string matched by the RE

start()

Return the starting position of the match

end()

Return the ending position of the match

span()

Return a tuple containing the (start, end) positions of the match

Trying these methods will soon clarify their meaning:

>>> m.group()
'tempo'
>>> m.start(), m.end()
(0, 5)
>>> m.span()
(0, 5)

group() returns the substring that was matched by the RE. start() and end() return the starting and ending index of the match. span() returns both start and end indexes in a single tuple. Since the match() method only checks if the RE matches at the start of a string, start() will always be zero. However, the search() method of patterns scans through the string, so the match may not start at zero in that case.

>>> print(p.match('::: message'))
None
>>> m = p.search('::: message'); print(m)
<re.Match object; span=(4, 11), match='message'>
>>> m.group()
'message'
>>> m.span()
(4, 11)

In actual programs, the most common style is to store the match object in a variable, and then check if it was None. This usually looks like:

p = re.compile( ... )
m = p.match( 'string goes here' )
if m:
    print('Match found: ', m.group())
else:
    print('No match')

Two pattern methods return all of the matches for a pattern. findall() returns a list of matching strings:

>>> p = re.compile(r'\d+')
>>> p.findall('12 drummers drumming, 11 pipers piping, 10 lords a-leaping')
['12', '11', '10']

The r prefix, making the literal a raw string literal, is needed in this example because escape sequences in a normal "cooked" string literal that are not recognized by Python, as opposed to regular expressions, now result in a DeprecationWarning and will eventually become a SyntaxError. See The Backslash Plague.

findall() has to create the entire list before it can be returned as the result. The finditer() method returns a sequence of match object instances as an iterator:

>>> iterator = p.finditer('12 drummers drumming, 11 ... 10 ...')
>>> iterator
<callable_iterator object at 0x...>
>>> for match in iterator:
...     print(match.span())
...
(0, 2)
(22, 24)
(29, 31)

模組層級函式

You don't have to create a pattern object and call its methods; the re module also provides top-level functions called match(), search(), findall(), sub(), and so forth. These functions take the same arguments as the corresponding pattern method with the RE string added as the first argument, and still return either None or a match object instance.

>>> print(re.match(r'From\s+', 'Fromage amk'))
None
>>> re.match(r'From\s+', 'From amk Thu May 14 19:12:10 1998')
<re.Match object; span=(0, 5), match='From '>

Under the hood, these functions simply create a pattern object for you and call the appropriate method on it. They also store the compiled object in a cache, so future calls using the same RE won't need to parse the pattern again and again.

Should you use these module-level functions, or should you get the pattern and call its methods yourself? If you're accessing a regex within a loop, pre-compiling it will save a few function calls. Outside of loops, there's not much difference thanks to the internal cache.

Compilation Flags

Compilation flags let you modify some aspects of how regular expressions work. Flags are available in the re module under two names, a long name such as IGNORECASE and a short, one-letter form such as I. (If you're familiar with Perl's pattern modifiers, the one-letter forms use the same letters; the short form of re.VERBOSE is re.X, for example.) Multiple flags can be specified by bitwise OR-ing them; re.I | re.M sets both the I and M flags, for example.

Here's a table of the available flags, followed by a more detailed explanation of each one.

旗標

含義

ASCII, A

Makes several escapes like \w, \b, \s and \d match only on ASCII characters with the respective property.

DOTALL, S

Make . match any character, including newlines.

IGNORECASE, I

Do case-insensitive matches.

LOCALE, L

Do a locale-aware match.

MULTILINE, M

Multi-line matching, affecting ^ and $.

VERBOSE, X (for 'extended')

Enable verbose REs, which can be organized more cleanly and understandably.

re.I

re.IGNORECASE

Perform case-insensitive matching; character class and literal strings will match letters by ignoring case. For example, [A-Z] will match lowercase letters, too. Full Unicode matching also works unless the ASCII flag is used to disable non-ASCII matches. When the Unicode patterns [a-z] or [A-Z] are used in combination with the IGNORECASE flag, they will match the 52 ASCII letters and 4 additional non-ASCII letters: 'İ' (U+0130, Latin capital letter I with dot above), 'ı' (U+0131, Latin small letter dotless i), 'ſ' (U+017F, Latin small letter long s) and 'K' (U+212A, Kelvin sign). Spam will match 'Spam', 'spam', 'spAM', or 'ſpam' (the latter is matched only in Unicode mode). This lowercasing doesn't take the current locale into account; it will if you also set the LOCALE flag.

re.L

re.LOCALE

Make \w, \W, \b, \B and case-insensitive matching dependent on the current locale instead of the Unicode database.

Locales are a feature of the C library intended to help in writing programs that take account of language differences. For example, if you're processing encoded French text, you'd want to be able to write \w+ to match words, but \w only matches the character class [A-Za-z] in bytes patterns; it won't match bytes corresponding to é or ç. If your system is configured properly and a French locale is selected, certain C functions will tell the program that the byte corresponding to é should also be considered a letter. Setting the LOCALE flag when compiling a regular expression will cause the resulting compiled object to use these C functions for \w; this is slower, but also enables \w+ to match French words as you'd expect. The use of this flag is discouraged in Python 3 as the locale mechanism is very unreliable, it only handles one "culture" at a time, and it only works with 8-bit locales. Unicode matching is already enabled by default in Python 3 for Unicode (str) patterns, and it is able to handle different locales/languages.

re.M

re.MULTILINE

(^ and $ haven't been explained yet; they'll be introduced in section More Metacharacters.)

Usually ^ matches only at the beginning of the string, and $ matches only at the end of the string and immediately before the newline (if any) at the end of the string. When this flag is specified, ^ matches at the beginning of the string and at the beginning of each line within the string, immediately following each newline. Similarly, the $ metacharacter matches either at the end of the string and at the end of each line (immediately preceding each newline).

re.S

re.DOTALL

Makes the '.' special character match any character at all, including a newline; without this flag, '.' will match anything except a newline.

re.A

re.ASCII

Make \w, \W, \b, \B, \s and \S perform ASCII-only matching instead of full Unicode matching. This is only meaningful for Unicode patterns, and is ignored for byte patterns.

re.X

re.VERBOSE

This flag allows you to write regular expressions that are more readable by granting you more flexibility in how you can format them. When this flag has been specified, whitespace within the RE string is ignored, except when the whitespace is in a character class or preceded by an unescaped backslash; this lets you organize and indent the RE more clearly. This flag also lets you put comments within a RE that will be ignored by the engine; comments are marked by a '#' that's neither in a character class or preceded by an unescaped backslash.

For example, here's a RE that uses re.VERBOSE; see how much easier it is to read?

charref = re.compile(r"""
 &[#]                # Start of a numeric entity reference
 (
     0[0-7]+         # Octal form
   | [0-9]+          # Decimal form
   | x[0-9a-fA-F]+   # Hexadecimal form
 )
 ;                   # Trailing semicolon
""", re.VERBOSE)

Without the verbose setting, the RE would look like this:

charref = re.compile("&#(0[0-7]+"
                     "|[0-9]+"
                     "|x[0-9a-fA-F]+);")

In the above example, Python's automatic concatenation of string literals has been used to break up the RE into smaller pieces, but it's still more difficult to understand than the version using re.VERBOSE.

More Pattern Power

So far we've only covered a part of the features of regular expressions. In this section, we'll cover some new metacharacters, and how to use groups to retrieve portions of the text that was matched.

More Metacharacters

There are some metacharacters that we haven't covered yet. Most of them will be covered in this section.

Some of the remaining metacharacters to be discussed are zero-width assertions. They don't cause the engine to advance through the string; instead, they consume no characters at all, and simply succeed or fail. For example, \b is an assertion that the current position is located at a word boundary; the position isn't changed by the \b at all. This means that zero-width assertions should never be repeated, because if they match once at a given location, they can obviously be matched an infinite number of times.

|

Alternation, or the "or" operator. If A and B are regular expressions, A|B will match any string that matches either A or B. | has very low precedence in order to make it work reasonably when you're alternating multi-character strings. Crow|Servo will match either 'Crow' or 'Servo', not 'Cro', a 'w' or an 'S', and 'ervo'.

To match a literal '|', use \|, or enclose it inside a character class, as in [|].

^

Matches at the beginning of lines. Unless the MULTILINE flag has been set, this will only match at the beginning of the string. In MULTILINE mode, this also matches immediately after each newline within the string.

For example, if you wish to match the word From only at the beginning of a line, the RE to use is ^From.

>>> print(re.search('^From', 'From Here to Eternity'))
<re.Match object; span=(0, 4), match='From'>
>>> print(re.search('^From', 'Reciting From Memory'))
None

To match a literal '^', use \^.

$

Matches at the end of a line, which is defined as either the end of the string, or any location followed by a newline character.

>>> print(re.search('}$', '{block}'))
<re.Match object; span=(6, 7), match='}'>
>>> print(re.search('}$', '{block} '))
None
>>> print(re.search('}$', '{block}\n'))
<re.Match object; span=(6, 7), match='}'>

To match a literal '$', use \$ or enclose it inside a character class, as in [$].

\A

Matches only at the start of the string. When not in MULTILINE mode, \A and ^ are effectively the same. In MULTILINE mode, they're different: \A still matches only at the beginning of the string, but ^ may match at any location inside the string that follows a newline character.

\z

Matches only at the end of the string.

\Z

The same as \z. For compatibility with old Python versions.

\b

Word boundary. This is a zero-width assertion that matches only at the beginning or end of a word. A word is defined as a sequence of alphanumeric characters, so the end of a word is indicated by whitespace or a non-alphanumeric character.

The following example matches class only when it's a complete word; it won't match when it's contained inside another word.

>>> p = re.compile(r'\bclass\b')
>>> print(p.search('no class at all'))
<re.Match object; span=(3, 8), match='class'>
>>> print(p.search('the declassified algorithm'))
None
>>> print(p.search('one subclass is'))
None

There are two subtleties you should remember when using this special sequence. First, this is the worst collision between Python's string literals and regular expression sequences. In Python's string literals, \b is the backspace character, ASCII value 8. If you're not using raw strings, then Python will convert the \b to a backspace, and your RE won't match as you expect it to. The following example looks the same as our previous RE, but omits the 'r' in front of the RE string.

>>> p = re.compile('\bclass\b')
>>> print(p.search('no class at all'))
None
>>> print(p.search('\b' + 'class' + '\b'))
<re.Match object; span=(0, 7), match='\x08class\x08'>

Second, inside a character class, where there's no use for this assertion, \b represents the backspace character, for compatibility with Python's string literals.

\B

Another zero-width assertion, this is the opposite of \b, only matching when the current position is not at a word boundary.

Grouping

Frequently you need to obtain more information than just whether the RE matched or not. Regular expressions are often used to dissect strings by writing a RE divided into several subgroups which match different components of interest. For example, an RFC-822 header line is divided into a header name and a value, separated by a ':', like this:

From: author@example.com
User-Agent: Thunderbird 1.5.0.9 (X11/20061227)
MIME-Version: 1.0
To: editor@example.com

This can be handled by writing a regular expression which matches an entire header line, and has one group which matches the header name, and another group which matches the header's value.

Groups are marked by the '(', ')' metacharacters. '(' and ')' have much the same meaning as they do in mathematical expressions; they group together the expressions contained inside them, and you can repeat the contents of a group with a quantifier, such as *, +, ?, or {m,n}. For example, (ab)* will match zero or more repetitions of ab.

>>> p = re.compile('(ab)*')
>>> print(p.match('ababababab').span())
(0, 10)

Groups indicated with '(', ')' also capture the starting and ending index of the text that they match; this can be retrieved by passing an argument to group(), start(), end(), and span(). Groups are numbered starting with 0. Group 0 is always present; it's the whole RE, so match object methods all have group 0 as their default argument. Later we'll see how to express groups that don't capture the span of text that they match.

>>> p = re.compile('(a)b')
>>> m = p.match('ab')
>>> m.group()
'ab'
>>> m.group(0)
'ab'

Subgroups are numbered from left to right, from 1 upward. Groups can be nested; to determine the number, just count the opening parenthesis characters, going from left to right.

>>> p = re.compile('(a(b)c)d')
>>> m = p.match('abcd')
>>> m.group(0)
'abcd'
>>> m.group(1)
'abc'
>>> m.group(2)
'b'

group() can be passed multiple group numbers at a time, in which case it will return a tuple containing the corresponding values for those groups.

>>> m.group(2,1,2)
('b', 'abc', 'b')

The groups() method returns a tuple containing the strings for all the subgroups, from 1 up to however many there are.

>>> m.groups()
('abc', 'b')

Backreferences in a pattern allow you to specify that the contents of an earlier capturing group must also be found at the current location in the string. For example, \1 will succeed if the exact contents of group 1 can be found at the current position, and fails otherwise. Remember that Python's string literals also use a backslash followed by numbers to allow including arbitrary characters in a string, so be sure to use a raw string when incorporating backreferences in a RE.

For example, the following RE detects doubled words in a string.

>>> p = re.compile(r'\b(\w+)\s+\1\b')
>>> p.search('Paris in the the spring').group()
'the the'

Backreferences like this aren't often useful for just searching through a string --- there are few text formats which repeat data in this way --- but you'll soon find out that they're very useful when performing string substitutions.

Non-capturing and Named Groups

Elaborate REs may use many groups, both to capture substrings of interest, and to group and structure the RE itself. In complex REs, it becomes difficult to keep track of the group numbers. There are two features which help with this problem. Both of them use a common syntax for regular expression extensions, so we'll look at that first.

Perl 5 is well known for its powerful additions to standard regular expressions. For these new features the Perl developers couldn't choose new single-keystroke metacharacters or new special sequences beginning with \ without making Perl's regular expressions confusingly different from standard REs. If they chose & as a new metacharacter, for example, old expressions would be assuming that & was a regular character and wouldn't have escaped it by writing \& or [&].

The solution chosen by the Perl developers was to use (?...) as the extension syntax. ? immediately after a parenthesis was a syntax error because the ? would have nothing to repeat, so this didn't introduce any compatibility problems. The characters immediately after the ? indicate what extension is being used, so (?=foo) is one thing (a positive lookahead assertion) and (?:foo) is something else (a non-capturing group containing the subexpression foo).

Python supports several of Perl's extensions and adds an extension syntax to Perl's extension syntax. If the first character after the question mark is a P, you know that it's an extension that's specific to Python.

Now that we've looked at the general extension syntax, we can return to the features that simplify working with groups in complex REs.

Sometimes you'll want to use a group to denote a part of a regular expression, but aren't interested in retrieving the group's contents. You can make this fact explicit by using a non-capturing group: (?:...), where you can replace the ... with any other regular expression.

>>> m = re.match("([abc])+", "abc")
>>> m.groups()
('c',)
>>> m = re.match("(?:[abc])+", "abc")
>>> m.groups()
()

Except for the fact that you can't retrieve the contents of what the group matched, a non-capturing group behaves exactly the same as a capturing group; you can put anything inside it, repeat it with a repetition metacharacter such as *, and nest it within other groups (capturing or non-capturing). (?:...) is particularly useful when modifying an existing pattern, since you can add new groups without changing how all the other groups are numbered. It should be mentioned that there's no performance difference in searching between capturing and non-capturing groups; neither form is any faster than the other.

A more significant feature is named groups: instead of referring to them by numbers, groups can be referenced by a name.

The syntax for a named group is one of the Python-specific extensions: (?P<name>...). name is, obviously, the name of the group. Named groups behave exactly like capturing groups, and additionally associate a name with a group. The match object methods that deal with capturing groups all accept either integers that refer to the group by number or strings that contain the desired group's name. Named groups are still given numbers, so you can retrieve information about a group in two ways:

>>> p = re.compile(r'(?P<word>\b\w+\b)')
>>> m = p.search( '(((( Lots of punctuation )))' )
>>> m.group('word')
'Lots'
>>> m.group(1)
'Lots'

Additionally, you can retrieve named groups as a dictionary with groupdict():

>>> m = re.match(r'(?P<first>\w+) (?P<last>\w+)', 'Jane Doe')
>>> m.groupdict()
{'first': 'Jane', 'last': 'Doe'}

Named groups are handy because they let you use easily remembered names, instead of having to remember numbers. Here's an example RE from the imaplib module:

InternalDate = re.compile(r'INTERNALDATE "'
        r'(?P<day>[ 123][0-9])-(?P<mon>[A-Z][a-z][a-z])-'
        r'(?P<year>[0-9][0-9][0-9][0-9])'
        r' (?P<hour>[0-9][0-9]):(?P<min>[0-9][0-9]):(?P<sec>[0-9][0-9])'
        r' (?P<zonen>[-+])(?P<zoneh>[0-9][0-9])(?P<zonem>[0-9][0-9])'
        r'"')

It's obviously much easier to retrieve m.group('zonem'), instead of having to remember to retrieve group 9.

The syntax for backreferences in an expression such as (...)\1 refers to the number of the group. There's naturally a variant that uses the group name instead of the number. This is another Python extension: (?P=name) indicates that the contents of the group called name should again be matched at the current point. The regular expression for finding doubled words, \b(\w+)\s+\1\b can also be written as \b(?P<word>\w+)\s+(?P=word)\b:

>>> p = re.compile(r'\b(?P<word>\w+)\s+(?P=word)\b')
>>> p.search('Paris in the the spring').group()
'the the'

Lookahead Assertions

Another zero-width assertion is the lookahead assertion. Lookahead assertions are available in both positive and negative form, and look like this:

(?=...)

Positive lookahead assertion. This succeeds if the contained regular expression, represented here by ..., successfully matches at the current location, and fails otherwise. But, once the contained expression has been tried, the matching engine doesn't advance at all; the rest of the pattern is tried right where the assertion started.

(?!...)

Negative lookahead assertion. This is the opposite of the positive assertion; it succeeds if the contained expression doesn't match at the current position in the string.

To make this concrete, let's look at a case where a lookahead is useful. Consider a simple pattern to match a filename and split it apart into a base name and an extension, separated by a .. For example, in news.rc, news is the base name, and rc is the filename's extension.

The pattern to match this is quite simple:

.*[.].*$

Notice that the . needs to be treated specially because it's a metacharacter, so it's inside a character class to only match that specific character. Also notice the trailing $; this is added to ensure that all the rest of the string must be included in the extension. This regular expression matches foo.bar and autoexec.bat and sendmail.cf and printers.conf.

Now, consider complicating the problem a bit; what if you want to match filenames where the extension is not bat? Some incorrect attempts:

.*[.][^b].*$

The first attempt above tries to exclude bat by requiring that the first character of the extension is not a b. This is wrong, because the pattern also doesn't match foo.bar.

.*[.]([^b]..|.[^a].|..[^t])$

The expression gets messier when you try to patch up the first solution by requiring one of the following cases to match: the first character of the extension isn't b; the second character isn't a; or the third character isn't t. This accepts foo.bar and rejects autoexec.bat, but it requires a three-letter extension and won't accept a filename with a two-letter extension such as sendmail.cf. We'll complicate the pattern again in an effort to fix it.

.*[.]([^b].?.?|.[^a]?.?|..?[^t]?)$

In the third attempt, the second and third letters are all made optional in order to allow matching extensions shorter than three characters, such as sendmail.cf.

The pattern's getting really complicated now, which makes it hard to read and understand. Worse, if the problem changes and you want to exclude both bat and exe as extensions, the pattern would get even more complicated and confusing.

A negative lookahead cuts through all this confusion:

.*[.](?!bat$)[^.]*$

The negative lookahead means: if the expression bat doesn't match at this point, try the rest of the pattern; if bat$ does match, the whole pattern will fail. The trailing $ is required to ensure that something like sample.batch, where the extension only starts with bat, will be allowed. The [^.]* makes sure that the pattern works when there are multiple dots in the filename.

Excluding another filename extension is now easy; simply add it as an alternative inside the assertion. The following pattern excludes filenames that end in either bat or exe:

.*[.](?!bat$|exe$)[^.]*$

Modifying Strings

Up to this point, we've simply performed searches against a static string. Regular expressions are also commonly used to modify strings in various ways, using the following pattern methods:

方法/屬性

Purpose

split()

Split the string into a list, splitting it wherever the RE matches

sub()

Find all substrings where the RE matches, and replace them with a different string

subn()

Does the same thing as sub(), but returns the new string and the number of replacements

Splitting Strings

The split() method of a pattern splits a string apart wherever the RE matches, returning a list of the pieces. It's similar to the split() method of strings but provides much more generality in the delimiters that you can split by; string split() only supports splitting by whitespace or by a fixed string. As you'd expect, there's a module-level re.split() function, too.

.split(string[, maxsplit=0])

Split string by the matches of the regular expression. If capturing parentheses are used in the RE, then their contents will also be returned as part of the resulting list. If maxsplit is nonzero, at most maxsplit splits are performed.

You can limit the number of splits made, by passing a value for maxsplit. When maxsplit is nonzero, at most maxsplit splits will be made, and the remainder of the string is returned as the final element of the list. In the following example, the delimiter is any sequence of non-alphanumeric characters.

>>> p = re.compile(r'\W+')
>>> p.split('This is a test, short and sweet, of split().')
['This', 'is', 'a', 'test', 'short', 'and', 'sweet', 'of', 'split', '']
>>> p.split('This is a test, short and sweet, of split().', 3)
['This', 'is', 'a', 'test, short and sweet, of split().']

Sometimes you're not only interested in what the text between delimiters is, but also need to know what the delimiter was. If capturing parentheses are used in the RE, then their values are also returned as part of the list. Compare the following calls:

>>> p = re.compile(r'\W+')
>>> p2 = re.compile(r'(\W+)')
>>> p.split('This... is a test.')
['This', 'is', 'a', 'test', '']
>>> p2.split('This... is a test.')
['This', '... ', 'is', ' ', 'a', ' ', 'test', '.', '']

The module-level function re.split() adds the RE to be used as the first argument, but is otherwise the same.

>>> re.split(r'[\W]+', 'Words, words, words.')
['Words', 'words', 'words', '']
>>> re.split(r'([\W]+)', 'Words, words, words.')
['Words', ', ', 'words', ', ', 'words', '.', '']
>>> re.split(r'[\W]+', 'Words, words, words.', 1)
['Words', 'words, words.']

Search and Replace

Another common task is to find all the matches for a pattern, and replace them with a different string. The sub() method takes a replacement value, which can be either a string or a function, and the string to be processed.

.sub(replacement, string[, count=0])

Returns the string obtained by replacing the leftmost non-overlapping occurrences of the RE in string by the replacement replacement. If the pattern isn't found, string is returned unchanged.

The optional argument count is the maximum number of pattern occurrences to be replaced; count must be a non-negative integer. The default value of 0 means to replace all occurrences.

Here's a simple example of using the sub() method. It replaces colour names with the word colour:

>>> p = re.compile('(blue|white|red)')
>>> p.sub('colour', 'blue socks and red shoes')
'colour socks and colour shoes'
>>> p.sub('colour', 'blue socks and red shoes', count=1)
'colour socks and red shoes'

The subn() method does the same work, but returns a 2-tuple containing the new string value and the number of replacements that were performed:

>>> p = re.compile('(blue|white|red)')
>>> p.subn('colour', 'blue socks and red shoes')
('colour socks and colour shoes', 2)
>>> p.subn('colour', 'no colours at all')
('no colours at all', 0)

Empty matches are replaced only when they're not adjacent to a previous empty match.

>>> p = re.compile('x*')
>>> p.sub('-', 'abxd')
'-a-b--d-'

If replacement is a string, any backslash escapes in it are processed. That is, \n is converted to a single newline character, \r is converted to a carriage return, and so forth. Unknown escapes such as \& are left alone. Backreferences, such as \6, are replaced with the substring matched by the corresponding group in the RE. This lets you incorporate portions of the original text in the resulting replacement string.

This example matches the word section followed by a string enclosed in {, }, and changes section to subsection:

>>> p = re.compile('section{ ( [^}]* ) }', re.VERBOSE)
>>> p.sub(r'subsection{\1}','section{First} section{second}')
'subsection{First} subsection{second}'

There's also a syntax for referring to named groups as defined by the (?P<name>...) syntax. \g<name> will use the substring matched by the group named name, and \g<number> uses the corresponding group number. \g<2> is therefore equivalent to \2, but isn't ambiguous in a replacement string such as \g<2>0. (\20 would be interpreted as a reference to group 20, not a reference to group 2 followed by the literal character '0'.) The following substitutions are all equivalent, but use all three variations of the replacement string.

>>> p = re.compile('section{ (?P<name> [^}]* ) }', re.VERBOSE)
>>> p.sub(r'subsection{\1}','section{First}')
'subsection{First}'
>>> p.sub(r'subsection{\g<1>}','section{First}')
'subsection{First}'
>>> p.sub(r'subsection{\g<name>}','section{First}')
'subsection{First}'

replacement can also be a function, which gives you even more control. If replacement is a function, the function is called for every non-overlapping occurrence of pattern. On each call, the function is passed a match object argument for the match and can use this information to compute the desired replacement string and return it.

In the following example, the replacement function translates decimals into hexadecimal:

>>> def hexrepl(match):
...     "Return the hex string for a decimal number"
...     value = int(match.group())
...     return hex(value)
...
>>> p = re.compile(r'\d+')
>>> p.sub(hexrepl, 'Call 65490 for printing, 49152 for user code.')
'Call 0xffd2 for printing, 0xc000 for user code.'

When using the module-level re.sub() function, the pattern is passed as the first argument. The pattern may be provided as an object or as a string; if you need to specify regular expression flags, you must either use a pattern object as the first parameter, or use embedded modifiers in the pattern string, e.g. sub("(?i)b+", "x", "bbbb BBBB") returns 'x x'.

Common Problems

Regular expressions are a powerful tool for some applications, but in some ways their behaviour isn't intuitive and at times they don't behave the way you may expect them to. This section will point out some of the most common pitfalls.

Use String Methods

Sometimes using the re module is a mistake. If you're matching a fixed string, or a single character class, and you're not using any re features such as the IGNORECASE flag, then the full power of regular expressions may not be required. Strings have several methods for performing operations with fixed strings and they're usually much faster, because the implementation is a single small C loop that's been optimized for the purpose, instead of the large, more generalized regular expression engine.

One example might be replacing a single fixed string with another one; for example, you might replace word with deed. re.sub() seems like the function to use for this, but consider the replace() method. Note that replace() will also replace word inside words, turning swordfish into sdeedfish, but the naive RE word would have done that, too. (To avoid performing the substitution on parts of words, the pattern would have to be \bword\b, in order to require that word have a word boundary on either side. This takes the job beyond replace()'s abilities.)

Another common task is deleting every occurrence of a single character from a string or replacing it with another single character. You might do this with something like re.sub('\n', ' ', S), but translate() is capable of doing both tasks and will be faster than any regular expression operation can be.

In short, before turning to the re module, consider whether your problem can be solved with a faster and simpler string method.

match() versus search()

The match() function only checks if the RE matches at the beginning of the string while search() will scan forward through the string for a match. It's important to keep this distinction in mind. Remember, match() will only report a successful match which will start at 0; if the match wouldn't start at zero, match() will not report it.

>>> print(re.match('super', 'superstition').span())
(0, 5)
>>> print(re.match('super', 'insuperable'))
None

On the other hand, search() will scan forward through the string, reporting the first match it finds.

>>> print(re.search('super', 'superstition').span())
(0, 5)
>>> print(re.search('super', 'insuperable').span())
(2, 7)

Sometimes you'll be tempted to keep using re.match(), and just add .* to the front of your RE. Resist this temptation and use re.search() instead. The regular expression compiler does some analysis of REs in order to speed up the process of looking for a match. One such analysis figures out what the first character of a match must be; for example, a pattern starting with Crow must match starting with a 'C'. The analysis lets the engine quickly scan through the string looking for the starting character, only trying the full match if a 'C' is found.

Adding .* defeats this optimization, requiring scanning to the end of the string and then backtracking to find a match for the rest of the RE. Use re.search() instead.

Greedy versus Non-Greedy

When repeating a regular expression, as in a*, the resulting action is to consume as much of the pattern as possible. This fact often bites you when you're trying to match a pair of balanced delimiters, such as the angle brackets surrounding an HTML tag. The naive pattern for matching a single HTML tag doesn't work because of the greedy nature of .*.

>>> s = '<html><head><title>Title</title>'
>>> len(s)
32
>>> print(re.match('<.*>', s).span())
(0, 32)
>>> print(re.match('<.*>', s).group())
<html><head><title>Title</title>

The RE matches the '<' in '<html>', and the .* consumes the rest of the string. There's still more left in the RE, though, and the > can't match at the end of the string, so the regular expression engine has to backtrack character by character until it finds a match for the >. The final match extends from the '<' in '<html>' to the '>' in '</title>', which isn't what you want.

In this case, the solution is to use the non-greedy quantifiers *?, +?, ??, or {m,n}?, which match as little text as possible. In the above example, the '>' is tried immediately after the first '<' matches, and when it fails, the engine advances a character at a time, retrying the '>' at every step. This produces just the right result:

>>> print(re.match('<.*?>', s).group())
<html>

(Note that parsing HTML or XML with regular expressions is painful. Quick-and-dirty patterns will handle common cases, but HTML and XML have special cases that will break the obvious regular expression; by the time you've written a regular expression that handles all of the possible cases, the patterns will be very complicated. Use an HTML or XML parser module for such tasks.)

Using re.VERBOSE

By now you've probably noticed that regular expressions are a very compact notation, but they're not terribly readable. REs of moderate complexity can become lengthy collections of backslashes, parentheses, and metacharacters, making them difficult to read and understand.

For such REs, specifying the re.VERBOSE flag when compiling the regular expression can be helpful, because it allows you to format the regular expression more clearly.

The re.VERBOSE flag has several effects. Whitespace in the regular expression that isn't inside a character class is ignored. This means that an expression such as dog | cat is equivalent to the less readable dog|cat, but [a b] will still match the characters 'a', 'b', or a space. In addition, you can also put comments inside a RE; comments extend from a # character to the next newline. When used with triple-quoted strings, this enables REs to be formatted more neatly:

pat = re.compile(r"""
 \s*                 # Skip leading whitespace
 (?P<header>[^:]+)   # Header name
 \s* :               # Whitespace, and a colon
 (?P<value>.*?)      # The header's value -- *? used to
                     # lose the following trailing whitespace
 \s*$                # Trailing whitespace to end-of-line
""", re.VERBOSE)

This is far more readable than:

pat = re.compile(r"\s*(?P<header>[^:]+)\s*:(?P<value>.*?)\s*$")

Feedback

Regular expressions are a complicated topic. Did this document help you understand them? Were there parts that were unclear, or Problems you encountered that weren't covered here? If so, please send suggestions for improvements to the author.

The most complete book on regular expressions is almost certainly Jeffrey Friedl's Mastering Regular Expressions, published by O'Reilly. Unfortunately, it exclusively concentrates on Perl and Java's flavours of regular expressions, and doesn't contain any Python material at all, so it won't be useful as a reference for programming in Python. (The first edition covered Python's now-removed regex module, which won't help you much.) Consider checking it out from your library.

Socket 程式設計指南

作者:

Gordon McMillan

摘要

Sockets 在各處都被廣泛使用，但卻是一項被誤解最嚴重的技術之一。這是一篇對 sockets 的概論介紹。這並不是一個完整的教學指南 - 你還需要做許多準備才能讓 sockets 正常運作。這篇文章也沒有包含細節（其中有非常多的細節），但我希望這篇文章能夠讓你有足夠的背景知識，以便開始正確的使用 sockets 程式設計。

Sockets

我只會討論關於 INET（例如：IPv4）的 sockets，但它們涵蓋了幾乎 99% 的 sockets 使用場景。而我也將僅討論關於 STREAM（比如：TCP）類型的 sockets - 除非你真的知道你在做什麼（在這種情況下，這份指南可能不適合你），使用 STREAM 類型的 socket 會獲得比其他 sockets 類型更好的表現和性能。我將會嘗試解釋 socket 是什麼，以及如何使用阻塞 (blocking) 和非阻塞 (non-blocking) sockets 的一些建議。但首先我會先談論阻塞 sockets。在處理非阻塞 sockets 之前，你需要了解它們的工作原理。

要理解這些東西的困難點之一在於 "scoket" 可以代表多種具有些微差異的東西，這主要取決於上下文。所以首先，讓我們先區分「用戶端 (client)」socket 和「伺服器端 (server)」socket 的差別，「用戶端」socket 表示通訊的一端，「伺服器端」socket 更像是一個電話總機接線員。用戶端應用程式（例如：你的瀏覽器）只能使用「用戶端」socket; 它所連接的網路伺服器則同時使用「伺服器端」socket 和 「用戶端」socket 來進行通訊。

歷史

在各種形式的 IPC 中，sockets 是最受歡迎的。在任何特定的平台上，可能會存在其他更快速的 IPC 形式，但對於跨平台通訊來說，sockets 是唯一的選擇。

Sockets 作為 Unix 的 BSD 分支的一部分在 Berkeley 被發明出來。它們隨著網際網路的普及而迅速蔓延開來。這是有很好的理由 — sockets 和 INET 的結合讓世界各地任何的機器之間的通訊變得非常簡單（至少與其它方案相比是如此）。

建立一個 Socket

大致上來說，當你點擊了帶你來到這個頁面的連結時，你的瀏覽器做了以下的操作：

# create an INET, STREAMing socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# now connect to the web server on port 80 - the normal http port
s.connect(("www.python.org", 80))

當 connect 完成時，這個 socket s 可以用來發送請求來取得頁面的文本。同一個 socket 也會讀取回傳值，然後再被銷毀。是的，會被銷毀。用戶端 socket 通常只用來做一次交換（或是一小組連續交換）。

網路伺服器 (web server) 的運作就稍微複雜一點。首先，網路伺服器會建立一個「伺服器端 socket」：

# create an INET, STREAMing socket
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# bind the socket to a public host, and a well-known port
serversocket.bind((socket.gethostname(), 80))
# become a server socket
serversocket.listen(5)

有幾件事需要注意：我們使用了 socket.gethostname()，這樣 socket 才能對外部網路可見。如果我們使用了 s.bind(('localhost', 80)) 或 s.bind(('127.0.0.1', 80))，我們會得到一個「伺服器端」socket，但是只能在同一台機器內可見。s.bind(('', 80)) 指定 socket 可以透過機器的任何地址存取。

第二個要注意的是：數字小的連接埠 (port) 通常保留給「廣為人知的」服務（HTTP、SNMP等）。如果你只是想執行程式，可以使用一個數字較大的連接埠（4 位數字）。

最後，listen 引數告訴 socket 函式庫 (library)，我們希望在佇列 (queue) 中累積達 5 個（正常的最大值）連線請求後再拒絕外部連線。如果其餘的程式碼編寫正確，這應該足夠了。

現在我們有一個監聽 80 連接埠的「伺服器端」socket 了，我們可以進入網路伺服器的主迴圈了：

while True:
    # accept connections from outside
    (clientsocket, address) = serversocket.accept()
    # now do something with the clientsocket
    # in this case, we'll pretend this is a threaded server
    ct = make_client_thread(clientsocket)
    ct.start()

事實上，有三種方法可以讓這個迴圈運作 - 分配一個執行緒 (thread) 來處理 clientsocket 、建立一個新行程 (process) 來處理 clientsocket，或者將這個程式重新改寫成使用非阻塞 socket，並使用 select 在我們的「伺服器端」socket 和任何有效的 clientsocket 之間進行多工處理。稍後將會更詳細的介紹。現在最重要的是理解：這就是「伺服器端」socket 做的所有 事情。它不會發送任何資料、也不接收任何資料，它只會建立「伺服器端」socket。每個 clientsocket 都是為了回應某些其他 connect() 到我們綁定的主機上的「用戶端」socket。一但 clientsocket 建立完成，就會繼續監聽更多的連線請求。兩個「用戶端」可以隨意的通訊 - 它們使用的是一些動態分配的連接埠，會在通訊結束的時候被回收並重新利用。

IPC

如果你需要在一台機器上的兩個行程間進行快速的行程間通訊 (IPC)，你應該考慮使用管道 (pipes) 或共享記憶體 (shared memory)。如果你確定要使用 AF_INET sockets，請將「伺服器端」socket 綁定到 'localhost'。在大多數平台上，這樣將會繞過幾個網路程式碼層，並且速度會更快一些。

也參考

multiprocessing 將跨平台行程間通訊整合到更高層的 API 中。

使用一個 Socket

首先需要注意，網頁瀏覽器的「用戶端」socket 和網路伺服器的「用戶端」socket 是非常類似的。也就是說，這是一個「點對點 (peer to peer)」的通訊方式，或者也可以說作為設計者，你必須決定通訊的規則。通常情況下，connect 的 socket 會透過發送一個請求或者信號來開始一次通訊。但這屬於設計決策，而不是 socket 的規則。

現在有兩組可供通訊使用的動詞。你可以使用 send 和 recv，或者可以將用戶端 socket 轉換成類似檔案的形式，並使用 read 和 write。後者是 Java 中呈現 socket 的方式。我不打算在這裡討論它，只是提醒你需要在 socket 上使用 flush。這些是緩衝的「檔案」，一個常見的錯誤是使用 write 寫入某些內容，然後直接 read 回覆。如果不使用 flush，你可能會一直等待這個回覆，因為請求可能還在你的輸出緩衝中。

現在我們來到 sockets 的主要障礙 - send 和 recv 操作的是網路緩衝區。他們不一定會處理你提供給它們的所有位元組（或者是你期望它處理的位元組），因為它們主要的重點是處理網路緩衝區。一般來說，它們會在關聯的網路衝區已滿 (send) 或已清空 (recv) 時回傳，然後告訴你它們處理了多少位元組。你 的責任是一直呼叫它們直到你所有的訊息處理完成。

當 recv 回傳「零位元組 (0 bytes)」時，就表示另一端已經關閉（或著正在關閉）連線。你再也不能從這個連線上取得任何資料了。你可能還是可以成功發送資料；我稍後會對此進行更詳細的解釋。

像 HTTP 這樣的協定只使用一個 socket 進行一次傳輸，用戶端發送一個請求，然後讀取一個回覆。就這樣，然後這個 socket 就會被銷毀。這表示者用戶端可以透過接收「零位元組」來檢測回覆的結束。

但是如果你打算在之後的傳輸中重新利用 socket 的話，你需要明白socket 中是不存在 EOT （傳輸結束）。重申一次：如果一個 socket 的 send 或 recv 處理了「零位元組」後回傳，表示連線已經斷開。如果連線沒有 斷開，你可能會永遠處於等待 recv 的狀態，因為（就目前來說）socket 不會 告訴你沒有更多資料可以讀取了。現在，如果你稍微思考一下，你就會意識到 socket 的一個基本事實：訊息要麼是一個固定的長度（不好的做法），要麼是可以被分隔的（普通的做法），要麼是指定其長度（更好地做法），要麼透過關閉連線來結束。完全由你來決定要使用哪種方式（但有些方法比其他方法來的更好）。

假設你不想結束連線，最簡單的方式就是使用固定長度的訊息：

class MySocket:
    """demonstration class only
      - coded for clarity, not efficiency
    """

    def __init__(self, sock=None):
        if sock is None:
            self.sock = socket.socket(
                            socket.AF_INET, socket.SOCK_STREAM)
        else:
            self.sock = sock

    def connect(self, host, port):
        self.sock.connect((host, port))

    def mysend(self, msg):
        totalsent = 0
        while totalsent < MSGLEN:
            sent = self.sock.send(msg[totalsent:])
            if sent == 0:
                raise RuntimeError("socket connection broken")
            totalsent = totalsent + sent

    def myreceive(self):
        chunks = []
        bytes_recd = 0
        while bytes_recd < MSGLEN:
            chunk = self.sock.recv(min(MSGLEN - bytes_recd, 2048))
            if chunk == b'':
                raise RuntimeError("socket connection broken")
            chunks.append(chunk)
            bytes_recd = bytes_recd + len(chunk)
        return b''.join(chunks)

發送部分的程式碼幾乎可用於任何訊息的傳送方式 - 在 Python 中你發送一個字串，可以用 len() 來確認他的長度（即使字串包含了 \0 字元）。在這裡，主要是接收的程式碼變得更複雜一些。（在 C 語言中，情況沒有變得更糟，只是如果訊息中包含了 \0 字元，你就不能使用 strlen 函式。）

最簡單的改進方法是將訊息的第一個字元表示訊息的類型，並根據訊息的類型來決定訊息的長度。現在你需要使用兩次 recv - 第一次用於接收（至少）第一個字元來得知長度，第二次用於在迴圈中接收剩下的訊息。如果你決定使用分隔符號的方式，你將會以某個任意的區塊大小進行接收（4096 或 8192 通常是網路緩衝區大小的良好選擇），並在收到的內容中掃描分隔符號。

需要注意的一個複雜情況是，如果你的通訊協定允許連續發送多個訊息（沒有任何回應），並且你傳遞給 recv 函式一個任意的區塊大小，最後有可能讀取到下一條訊息的開頭。你需要將其放在一旁並保留下來，直到需要使用的時候。

使用長度作為訊息的前綴（例如，使用 5 個數字字元表示）會變得更複雜，因為（信不信由你）你可能無法在一次 recv 中獲得所有 5 個字元。在一般使用下，可能不會有這個狀況，但在高負載的網路下，除非使用兩個 recv （第一個用於確定長度，第二個用於取得訊息的資料部分），否則你的程式碼很快就會出現錯誤。這令人非常頭痛。同樣的情況也會讓你發現 send 並不總能在一次傳輸中完全清除所有內容。儘管已經閱讀了這篇文章，但最終還是無法解決！

為了節省篇幅、培養你的技能（並保持我的競爭優勢），這些改進方法留給讀者自行練習。現在讓我們開始進行清理工作。

二進位資料

使用 socket 傳輸二進位資料完全是可行的。最主要的問題在於不同機器使用不同的二進位資料格式。例如，網路二進位順序 [https://en.wikipedia.org/wiki/Endianness#Networking] 採用的是「大端序 big-endian」，所以一個值為 1 的 16 位元整數會表示成兩個 16 進位的位元組 00 01。然而大多數常見的處理器 (x86/AMD64，ARM，RISC-V) 採用的是「小端序 little-endian」，所以相同的 1 會被表示成 01 00。（譯者注：將一個多位數的低位放在較小的位址處，高位放在較大的位址處，則稱小端序；反之則稱大端序。）

Socket 函式庫提供了用於轉換 16 位元和 32 位元整數的函式 - ntohl, htonl, ntohs, htons，其中 "n" 表示 network，"h" 表示 host，"s" 表示 short，"l" 表示 long。當網路的位元組順序和主機位元組順序相同時，這些函式不會做任何操作，但當主機的位元組順序相反時，這些函式會適當的交換位元組順序。

在現今的 64 位元機器中，二進位資料的 ASCII 表示通常會比二進位表示要小，這是因為在很多情況下，大多數整數的值為 0 或者 1。例如，字串形式的 "0" 是兩個位元組，而完整的 64 位元整數則是 8 個位元組。當然，這對固定長度的訊息來說不太適合，需要自行決定。

結束連線

嚴格來說，在關閉 socket 前，你應該使用 shutdown 函式。shutdown 函式是發送給 socket 另一端的一個提醒。根據你傳遞的引數，它可以表示「我不會再發送任何訊息了，但我仍然會持續監聽」，或者是「我不會再繼續監聽了，真讚！」。然而，大多數的 socket 函式庫或程式設計師都習慣忽略這種禮節，因為通常情況下 close 跟 shutdown(); close() 是一樣的。所以在大多數情況下，不需要再特地使用 shutdown 了。

有效使用 shutdown 的一種方式是在類似 HTTP 的交換中，用戶端發送請求後，然後使用 shutdown(1)。這告訴伺服器「這個用戶端已經發送完成，但仍可以接收」。伺服器可以透過接收「零位元組」來檢測 "EOF"。這樣它就可以確定已經接收到完整的請求。伺服器發送回覆，如果 send 成功完成，那麼用戶端確實在持續接收。

Python 更進一步地採取自動關閉的步驟，並且當 socket 被垃圾回收機制回收時，如果需要的話，他會自動執行 close。但依賴這個機制是一個非常不好的習慣，如果你的 socket 在沒有 close 的情況下消失了，那麼另一端的 socket 可能會認為你只是慢了一步，而無期限的等待。請務必 在使用完畢後使用 close 關閉你的 sockets。

Sockets 何時銷毀

使用阻塞式 socket 最糟糕的地方可能是在另一端突然強制關閉（未執行 close）的情況下會發生什麼？你的 socket 很可能會處於阻塞狀態。TCP 是一種可靠的協定，它在放棄連線之前會等待很長很長的時間。如果你正在使用執行緒，整個執行緒基本上已經無法使用。在這方面，你無法做太多事情。只要你不做一些愚蠢的事情，比如在執行阻塞式讀取時持有一個鎖，那麼執行緒並不會消耗太多資源。不要試圖終止執行緒 - 執行緒比行程更有效的部分原因是它們避免了與自動回收資源相關的開銷。換句話說，如果你確實設法終止了執行緒，整個行程可能會出現問題。

非阻塞的 Sockets

如果你已經理解了前面的內容，你已經知道了大部分關於使用 sockets 的機制的所需知識，你仍然會以非常相似的方式使用相同的函式。就這樣而已，如果你做的對，你的程式就會是近乎完美的。

在 Python 中可以使用 socket.setblocking(False) 來設定為非阻塞。在 C 的作法更為複雜（例如，你需要在 BSD 風格的 O_NONBLOCK 和幾乎沒有區別的 POSIX 風格的 O_NDELAY 之間做出選擇，這與 TCP_NODELAY 完全不同），但基本思想是一樣的，你要在建立 socket 後但在使用它之前執行此操作。（實際上，如果你願意的話，你甚至可以來回切換。）

主要的機制差異在於 send、recv、connect 和 accept 可能在沒有執行任何操作的情況下就回傳了。你當然有多種選擇。你可以檢查回傳值和錯誤代碼，但這些操作通常會讓自己抓狂。如果你不相信我，不妨試試看。你的應用程式會變得臃腫、錯誤百出，並且占用 CPU。所以，讓我們跳過無腦的解決方案，使用正確的方式。

使用 select。

在 C 中，編寫 select 是非常複雜的，但在 Python 中，這很簡單，並與 C 的版本非常類似，如果你理解了 Python 中的 select，在 C 中處理它時也不會有太大的困難：

ready_to_read, ready_to_write, in_error = \
               select.select(
                  potential_readers,
                  potential_writers,
                  potential_errs,
                  timeout)

你傳遞給 select 三個列表：第一個列表包含你可能想要嘗試讀取的所有 sockets；第二個包含所有你可能想要嘗試寫入的 sockets，最後一個（通常為空）包含你想要檢查錯誤的 sockets。你應該注意，一個 socket 可以同時存在於多個列表中。select 呼叫是阻塞的，但你可以設置超時。通常這是一個明智的做法 - 除非有充分的理由，否則給它一個很長的超時（比如一分鐘）。

作為回傳，你將獲得三個列表。它們包含實際上可讀取、可寫入和出錯的 sockets。這些列表中的每一個都是你傳入的相應列表的子集（可能為空）。

如果一個 socket 在輸出的可讀列表中，你可以幾乎確定，在這個業務中我們能夠得到的最接近確定的事情是，對該 socket 的 recv 呼叫將會回傳一些內容。對於可寫列表，也是同樣的想法。你將能夠發送一些 內容。也許不是全部，但一些內容總比什麼都沒有好。（實際上，任何比較正常的 socket 都會以可寫的方式回傳 - 這只是意味者「外送網路 (outbound network)」的緩衝空間是可用的。）

如果你有一個「伺服器端」socket，請將其放在 potential_readers 列表中，如果它在可讀列表中出現，你的 accept 呼叫（幾乎可以確定）會成功。如果你建立了一個新的 socket 去 connect 到其他地方，請將它放在 potential_writers 列表中，如果它在可寫列表中出現，那麼他有可能已經連接上了。

實際上，即使是使用阻塞式 socket 的情況下，select 也很方便。這是一種判斷是否會被阻塞的方法之一 - 當緩衝區中有某些內容時， socket 會回傳為可讀。然而，這仍然無法解決判斷另一端是否完成，或者只是忙於其他事情的問題。

可移植性警告：在 Unix 上，select 同時適用於 sockets 和文件。但請不要在 Windows 上嘗試這麼做，在 Windows 上，select 只適用於 sockets。同時，請注意，在 C 語言中，許多更進階的 socket 選項在 Windows 上有不同的實現方式。實際上，在 Windows 上，我通常會使用執行緒（這非常，非常有效）與我的 sockets 一起使用。

排序技法

作者:

Andrew Dalke 和 Raymond Hettinger

Python 的串列有一個內建的 list.sort() 方法可以原地 (in-place) 排序該串列，也有一個內建的 sorted() 函式可以排序可疊代物件 (iterable) 並建立一個新的排序好的串列。

在這份文件裡，我們探索使用 Python 排序資料的各種方法。

基礎排序

單純的升冪排序很容易做到：只要呼叫 sorted() 函式，它會回傳一個新的串列：

>>> sorted([5, 2, 3, 1, 4])
[1, 2, 3, 4, 5]

你也可以使用 list.sort() 方法，它會原地排序串列（並回傳 None 以避免混淆）。它通常會比 sorted() 來得不方便——但如果你不需要保留原始串列的話，它會稍微有效率一點。

>>> a = [5, 2, 3, 1, 4]
>>> a.sort()
>>> a
[1, 2, 3, 4, 5]

另一個差異是 list.sort() 方法只有定義在串列上，而 sorted() 函式可以接受任何可疊代物件。

>>> sorted({1: 'D', 2: 'B', 3: 'B', 4: 'E', 5: 'A'})
[1, 2, 3, 4, 5]

鍵函式 (key functions)

list.sort() 方法和 sorted()、min()、max()、heapq.nsmallest() 及 heapq.nlargest() 函式都有一個參數 key 可以指定一個函式（或其它可呼叫物件 (callable)），其會在每個串列元素做比較前被呼叫。

例如使用 str.casefold() 來做不區分大小寫的字串比對：

>>> sorted("This is a test string from Andrew".split(), key=str.casefold)
['a', 'Andrew', 'from', 'is', 'string', 'test', 'This']

參數 key 的值必須是一個函式（或其它可呼叫物件），且這個函式接受單一引數並回傳一個用來排序的鍵。因為對每個輸入來說鍵函式只會被呼叫一次，所以這個做法是快速的。

一個常見的模式是在排序複雜物件的時候使用一部分物件的索引值當作鍵，例如：

>>> student_tuples = [
...     ('john', 'A', 15),
...     ('jane', 'B', 12),
...     ('dave', 'B', 10),
... ]
>>> sorted(student_tuples, key=lambda student: student[2])   # 依照年齡排序
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

相同的做法也適用在有命名屬性的物件，例如：

>>> class Student:
...     def __init__(self, name, grade, age):
...         self.name = name
...         self.grade = grade
...         self.age = age
...     def __repr__(self):
...         return repr((self.name, self.grade, self.age))

>>> student_objects = [
...     Student('john', 'A', 15),
...     Student('jane', 'B', 12),
...     Student('dave', 'B', 10),
... ]
>>> sorted(student_objects, key=lambda student: student.age)   # 依照年齡排序
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

具有命名屬性的物件可以如上方的方式使用一個常規的類別建立，或是他們可以是 dataclass 的實例或是一個 named tuple。

Operator 模組函式以及部份函式 (partial function) 評估

上述的鍵函式模式非常常見，所以 Python 提供了方便的函式讓物件存取更簡單且快速。operator 模組裡有 itemgetter()、attrgetter() 及 methodcaller() 函式可以使用。

使用這些函式讓上面的範例變得更簡單且快速：

>>> from operator import itemgetter, attrgetter

>>> sorted(student_tuples, key=itemgetter(2))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

>>> sorted(student_objects, key=attrgetter('age'))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

operator 模組的函式允許多層的排序，例如先用 grade 排序再用 age 排序：

>>> sorted(student_tuples, key=itemgetter(1,2))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]

>>> sorted(student_objects, key=attrgetter('grade', 'age'))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]

模組 functools 提供了另一個製作鍵函式的好用工具。partial() 函式可以減少多引數函式的引數數目 [https://en.wikipedia.org/wiki/Arity]，使其更適合作為鍵函式使用。

>>> from functools import partial
>>> from unicodedata import normalize

>>> names = 'Zoë Åbjørn Núñez Élana Zeke Abe Nubia Eloise'.split()

>>> sorted(names, key=partial(normalize, 'NFD'))
['Abe', 'Åbjørn', 'Eloise', 'Élana', 'Nubia', 'Núñez', 'Zeke', 'Zoë']

>>> sorted(names, key=partial(normalize, 'NFC'))
['Abe', 'Eloise', 'Nubia', 'Núñez', 'Zeke', 'Zoë', 'Åbjørn', 'Élana']

升冪與降冪

list.sort() 和 sorted() 都有一個 boolean 參數 reverse 用來表示是否要降冪排序。例如將學生資料依據 age 做降冪排序：

>>> sorted(student_tuples, key=itemgetter(2), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]

>>> sorted(student_objects, key=attrgetter('age'), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]

排序穩定性與複合排序

排序保證是穩定的 [https://en.wikipedia.org/wiki/Sorting_algorithm#Stability]，意思是當有多筆資料有相同的鍵，它們會維持原來的順序。

>>> data = [('red', 1), ('blue', 1), ('red', 2), ('blue', 2)]
>>> sorted(data, key=itemgetter(0))
[('blue', 1), ('blue', 2), ('red', 1), ('red', 2)]

可以注意到有兩筆資料的鍵都是 blue，它們會維持本來的順序，即 ('blue', 1) 保證在 ('blue', 2) 前面。

這個美妙的特性讓你可以用一連串的排序來作出複合排序。例如對學生資料用 grade 做降冪排序再用 age 做升冪排序，你可以先用 age 排序一遍再用 grade 排序一遍：

>>> s = sorted(student_objects, key=attrgetter('age'))     # 依照次要鍵排序
>>> sorted(s, key=attrgetter('grade'), reverse=True)       # 現在依照主要鍵降冪排序
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

這可以抽出一個包裝函式 (wrapper function)，接受一個串列及多個欄位及升降冪的元組為引數，來對這個串列排序多遍。

>>> def multisort(xs, specs):
...     for key, reverse in reversed(specs):
...         xs.sort(key=attrgetter(key), reverse=reverse)
...     return xs

>>> multisort(list(student_objects), (('grade', True), ('age', False)))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

Python 裡使用的 Timsort [https://en.wikipedia.org/wiki/Timsort] 演算法，因為能利用資料集裡已經有的順序，可以有效率地做多次排序。

裝飾-排序-移除裝飾 (decorate-sort-undecorate)

這個用語的來源是因為它做了以下三件事情：

首先，原始串列會裝飾 (decorated) 上新的值用來控制排序的順序。

接下來，排序裝飾過的串列。

最後，裝飾會被移除，並以新的順序產生一個只包含原始值的串列。

例如用上面說的方式來以 grade 排序學生資料：

>>> decorated = [(student.grade, i, student) for i, student in enumerate(student_objects)]
>>> decorated.sort()
>>> [student for grade, i, student in decorated]               # 移除裝飾
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]

這個方式會有效是因為元組是依照字典順序 (lexicographically) 來比較，先比較第一個項目，如果一樣再比較第二個項目，並依此類推。

在所有情況下都把索引 i 加入已裝飾的串列並不是絕對需要的，但這樣做會有兩個好處：

排序會是穩定的 -- 如果兩個項目有相同的鍵，它們在排序好的串列中會保持原來的順序。

原始項目不需要是可以比較的，因為最多只會用到前兩個項目就能決定裝飾過的元組的順序。例如原始串列可以包含不能直接用來排序的複數。

這個用語的另一個名字是 Schwartzian transform [https://en.wikipedia.org/wiki/Schwartzian_transform]，是由於 Randal L. Schwartz 讓這個方法在 Perl 程式設計師間普及。

而因為 Python 的排序提供了鍵函式，已經不太需要用到這個方法了。

比較函式 (comparison functions)

不像鍵函式回傳一個用來排序的值，比較函式計算兩個輸入間的相對順序。

例如天秤 [https://upload.wikimedia.org/wikipedia/commons/1/17/Balance_à_tabac_1850.JPG]比較兩邊樣本並給出相對的順序：較輕、相同或較重。同樣地，像是 cmp(a, b) 這樣的比較函式會回傳負數代表小於、0 代表輸入相同或正數代表大於。

當從其它語言翻譯演算法的時候常看到比較函式。有些函式庫也會提供比較函式作為其 API 的一部份，例如 locale.strcoll() 就是一個比較函式。

為了滿足這些情境，Python 提供 functools.cmp_to_key 來包裝比較函式，讓其可以當作鍵函式來使用：

sorted(words, key=cmp_to_key(strcoll))  # 理解語系的排序順序

Strategies For Unorderable Types and Values

A number of type and value issues can arise when sorting. Here are some strategies that can help:

Convert non-comparable input types to strings prior to sorting:

>>> data = ['twelve', '11', 10]
>>> sorted(map(str, data))
['10', '11', 'twelve']

This is needed because most cross-type comparisons raise a TypeError.

Remove special values prior to sorting:

>>> from math import isnan
>>> from itertools import filterfalse
>>> data = [3.3, float('nan'), 1.1, 2.2]
>>> sorted(filterfalse(isnan, data))
[1.1, 2.2, 3.3]

This is needed because the IEEE-754 standard [https://en.wikipedia.org/wiki/IEEE_754] specifies that, "Every NaN shall compare unordered with everything, including itself."

Likewise, None can be stripped from datasets as well:

>>> data = [3.3, None, 1.1, 2.2]
>>> sorted(x for x in data if x is not None)
[1.1, 2.2, 3.3]

This is needed because None is not comparable to other types.

Convert mapping types into sorted item lists before sorting:

>>> data = [{'a': 1}, {'b': 2}]
>>> sorted(data, key=lambda d: sorted(d.items()))
[{'a': 1}, {'b': 2}]

This is needed because dict-to-dict comparisons raise a TypeError.

Convert set types into sorted lists before sorting:

>>> data = [{'a', 'b', 'c'}, {'b', 'c', 'd'}]
>>> sorted(map(sorted, data))
[['a', 'b', 'c'], ['b', 'c', 'd']]

This is needed because the elements contained in set types do not have a deterministic order. For example, list({'a', 'b'}) may produce either ['a', 'b'] or ['b', 'a'].

雜項說明

要處理能理解本地語系 (locale aware) 的排序可以使用 locale.strxfrm() 當作鍵函式，或 locale.strcoll() 當作比較函式。這樣做是必要的，因為在不同文化中就算是相同的字母，按「字母順序」排序的結果也各不相同。

reverse 參數依然會維持排序穩定性（即有相同鍵的資料會保持原來順序）。有趣的是，不加這個參數也可以模擬這個效果，只要使用內建的 reversed() 函式兩次：

>>> data = [('red', 1), ('blue', 1), ('red', 2), ('blue', 2)]
>>> standard_way = sorted(data, key=itemgetter(0), reverse=True)
>>> double_reversed = list(reversed(sorted(reversed(data), key=itemgetter(0))))
>>> assert standard_way == double_reversed
>>> standard_way
[('red', 1), ('red', 2), ('blue', 1), ('blue', 2)]

排序時會使用 < 來比較兩個物件，因此要在類別裡面加入排序順序比較規則是簡單的，只要透過定義 __lt__() 方法：

>>> Student.__lt__ = lambda self, other: self.age < other.age
>>> sorted(student_objects)
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

然而，請注意，當 __lt__() 沒有被實作時，< 可以回退 (fall back) 使用 __gt__()（有關技術上的細節資訊請看 object.__lt__() ）。為了避免意外發生，PEP 8 [https://peps.python.org/pep-0008/] 建議所有六種的比較函式都需要被實作。裝飾器 total_ordering() 被提供用來讓任務更為簡單。

鍵函式不需要直接依賴用來排序的物件。鍵函式也可以存取外部資源，例如如果學生成績儲存在字典裡，它可以用來排序一個單獨的學生姓名串列：

>>> students = ['dave', 'john', 'jane']
>>> newgrades = {'john': 'F', 'jane':'A', 'dave': 'C'}
>>> sorted(students, key=newgrades.__getitem__)
['jane', 'dave', 'john']

部份排序

有些應用程式只需要排序部份的資料。基礎函式庫提供相較做完整排序更為輕鬆的多項工具：

min() 以及 max() 會分別回傳最小值及最大值。這些函式會將輸入資料進行一次傳遞且幾乎無須輔助記憶體。

heapq.nsmallest() 以及 heapq.nlargest() 會分別回傳 n 個最小值及最大值。這些函式會將資料進行一次傳遞且一次只會保留 n 個元素在記憶體中。對於相對於輸入數量較小的 n 個值，這些函式進行的比較比完整排序要少得多。

heapq.heappush() 和 heapq.heappop() 會建立並維持一個部份排序的資料排列，將最小的元素保持在位置 0。這些函式適合用來實作常用於任務排程的優先佇列。

Unicode HOWTO

發佈版本:

1.12

This HOWTO discusses Python's support for the Unicode specification for representing textual data, and explains various problems that people commonly encounter when trying to work with Unicode.

Introduction to Unicode

定義

Today's programs need to be able to handle a wide variety of characters. Applications are often internationalized to display messages and output in a variety of user-selectable languages; the same program might need to output an error message in English, French, Japanese, Hebrew, or Russian. Web content can be written in any of these languages and can also include a variety of emoji symbols. Python's string type uses the Unicode Standard for representing characters, which lets Python programs work with all these different possible characters.

Unicode (https://www.unicode.org/) is a specification that aims to list every character used by human languages and give each character its own unique code. The Unicode specifications are continually revised and updated to add new languages and symbols.

A character is the smallest possible component of a text. 'A', 'B', 'C', etc., are all different characters. So are 'È' and 'Í'. Characters vary depending on the language or context you're talking about. For example, there's a character for "Roman Numeral One", 'Ⅰ', that's separate from the uppercase letter 'I'. They'll usually look the same, but these are two different characters that have different meanings.

The Unicode standard describes how characters are represented by code points. A code point value is an integer in the range 0 to 0x10FFFF (about 1.1 million values, the actual number assigned [https://www.unicode.org/versions/latest/#Summary] is less than that). In the standard and in this document, a code point is written using the notation U+265E to mean the character with value 0x265e (9,822 in decimal).

The Unicode standard contains a lot of tables listing characters and their corresponding code points:

0061    'a'; LATIN SMALL LETTER A
0062    'b'; LATIN SMALL LETTER B
0063    'c'; LATIN SMALL LETTER C
...
007B    '{'; LEFT CURLY BRACKET
...
2167    'Ⅷ'; ROMAN NUMERAL EIGHT
2168    'Ⅸ'; ROMAN NUMERAL NINE
...
265E    '♞'; BLACK CHESS KNIGHT
265F    '♟'; BLACK CHESS PAWN
...
1F600   '😀'; GRINNING FACE
1F609   '😉'; WINKING FACE
...

Strictly, these definitions imply that it's meaningless to say 'this is character U+265E'. U+265E is a code point, which represents some particular character; in this case, it represents the character 'BLACK CHESS KNIGHT', '♞'. In informal contexts, this distinction between code points and characters will sometimes be forgotten.

A character is represented on a screen or on paper by a set of graphical elements that's called a glyph. The glyph for an uppercase A, for example, is two diagonal strokes and a horizontal stroke, though the exact details will depend on the font being used. Most Python code doesn't need to worry about glyphs; figuring out the correct glyph to display is generally the job of a GUI toolkit or a terminal's font renderer.

Encodings

To summarize the previous section: a Unicode string is a sequence of code points, which are numbers from 0 through 0x10FFFF (1,114,111 decimal). This sequence of code points needs to be represented in memory as a set of code units, and code units are then mapped to 8-bit bytes. The rules for translating a Unicode string into a sequence of bytes are called a character encoding, or just an encoding.

The first encoding you might think of is using 32-bit integers as the code unit, and then using the CPU's representation of 32-bit integers. In this representation, the string "Python" might look like this:

   P           y           t           h           o           n
0x50 00 00 00 79 00 00 00 74 00 00 00 68 00 00 00 6f 00 00 00 6e 00 00 00
   0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

This representation is straightforward but using it presents a number of problems.

It's not portable; different processors order the bytes differently.

It's very wasteful of space. In most texts, the majority of the code points are less than 127, or less than 255, so a lot of space is occupied by 0x00 bytes. The above string takes 24 bytes compared to the 6 bytes needed for an ASCII representation. Increased RAM usage doesn't matter too much (desktop computers have gigabytes of RAM, and strings aren't usually that large), but expanding our usage of disk and network bandwidth by a factor of 4 is intolerable.

It's not compatible with existing C functions such as strlen(), so a new family of wide string functions would need to be used.

Therefore this encoding isn't used very much, and people instead choose other encodings that are more efficient and convenient, such as UTF-8.

UTF-8 is one of the most commonly used encodings, and Python often defaults to using it. UTF stands for "Unicode Transformation Format", and the '8' means that 8-bit values are used in the encoding. (There are also UTF-16 and UTF-32 encodings, but they are less frequently used than UTF-8.) UTF-8 uses the following rules:

If the code point is < 128, it's represented by the corresponding byte value.

If the code point is >= 128, it's turned into a sequence of two, three, or four bytes, where each byte of the sequence is between 128 and 255.

UTF-8 has several convenient properties:

It can handle any Unicode code point.

A Unicode string is turned into a sequence of bytes that contains embedded zero bytes only where they represent the null character (U+0000). This means that UTF-8 strings can be processed by C functions such as strcpy() and sent through protocols that can't handle zero bytes for anything other than end-of-string markers.

A string of ASCII text is also valid UTF-8 text.

UTF-8 is fairly compact; the majority of commonly used characters can be represented with one or two bytes.

If bytes are corrupted or lost, it's possible to determine the start of the next UTF-8-encoded code point and resynchronize. It's also unlikely that random 8-bit data will look like valid UTF-8.

UTF-8 is a byte oriented encoding. The encoding specifies that each character is represented by a specific sequence of one or more bytes. This avoids the byte-ordering issues that can occur with integer and word oriented encodings, like UTF-16 and UTF-32, where the sequence of bytes varies depending on the hardware on which the string was encoded.

References

The Unicode Consortium site [https://www.unicode.org] has character charts, a glossary, and PDF versions of the Unicode specification. Be prepared for some difficult reading. A chronology [https://www.unicode.org/history/] of the origin and development of Unicode is also available on the site.

On the Computerphile Youtube channel, Tom Scott briefly discusses the history of Unicode and UTF-8 [https://www.youtube.com/watch?v=MijmeoH9LT4] (9 minutes 36 seconds).

To help understand the standard, Jukka Korpela has written an introductory guide [https://jkorpela.fi/unicode/guide.html] to reading the Unicode character tables.

Another good introductory article [https://www.joelonsoftware.com/2003/10/08/the-absolute-minimum-every-software-developer-absolutely-positively-must-know-about-unicode-and-character-sets-no-excuses/] was written by Joel Spolsky. If this introduction didn't make things clear to you, you should try reading this alternate article before continuing.

Wikipedia entries are often helpful; see the entries for "character encoding [https://en.wikipedia.org/wiki/Character_encoding]" and UTF-8 [https://en.wikipedia.org/wiki/UTF-8], for example.

Python's Unicode Support

Now that you've learned the rudiments of Unicode, we can look at Python's Unicode features.

The String Type

Since Python 3.0, the language's str type contains Unicode characters, meaning any string created using "unicode rocks!", 'unicode rocks!', or the triple-quoted string syntax is stored as Unicode.

The default encoding for Python source code is UTF-8, so you can simply include a Unicode character in a string literal:

try:
    with open('/tmp/input.txt', 'r') as f:
        ...
except OSError:
    # 'File not found' error message.
    print("Fichier non trouvé")

Side note: Python 3 also supports using Unicode characters in identifiers:

répertoire = "/tmp/records.log"
with open(répertoire, "w") as f:
    f.write("test\n")

If you can't enter a particular character in your editor or want to keep the source code ASCII-only for some reason, you can also use escape sequences in string literals. (Depending on your system, you may see the actual capital-delta glyph instead of a u escape.)

>>> "\N{GREEK CAPITAL LETTER DELTA}"  # Using the character name
'\u0394'
>>> "\u0394"                          # Using a 16-bit hex value
'\u0394'
>>> "\U00000394"                      # Using a 32-bit hex value
'\u0394'

In addition, one can create a string using the decode() method of bytes. This method takes an encoding argument, such as UTF-8, and optionally an errors argument.

The errors argument specifies the response when the input string can't be converted according to the encoding's rules. Legal values for this argument are 'strict' (raise a UnicodeDecodeError exception), 'replace' (use U+FFFD, REPLACEMENT CHARACTER), 'ignore' (just leave the character out of the Unicode result), or 'backslashreplace' (inserts a \xNN escape sequence). The following examples show the differences:

>>> b'\x80abc'.decode("utf-8", "strict")
Traceback (most recent call last):
    ...
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 0:
  invalid start byte
>>> b'\x80abc'.decode("utf-8", "replace")
'\ufffdabc'
>>> b'\x80abc'.decode("utf-8", "backslashreplace")
'\\x80abc'
>>> b'\x80abc'.decode("utf-8", "ignore")
'abc'

Encodings are specified as strings containing the encoding's name. Python comes with roughly 100 different encodings; see the Python Library Reference at 標準編碼 for a list. Some encodings have multiple names; for example, 'latin-1', 'iso_8859_1' and '8859' are all synonyms for the same encoding.

One-character Unicode strings can also be created with the chr() built-in function, which takes integers and returns a Unicode string of length 1 that contains the corresponding code point. The reverse operation is the built-in ord() function that takes a one-character Unicode string and returns the code point value:

>>> chr(57344)
'\ue000'
>>> ord('\ue000')
57344

Converting to Bytes

The opposite method of bytes.decode() is str.encode(), which returns a bytes representation of the Unicode string, encoded in the requested encoding.

The errors parameter is the same as the parameter of the decode() method but supports a few more possible handlers. As well as 'strict', 'ignore', and 'replace' (which in this case inserts a question mark instead of the unencodable character), there is also 'xmlcharrefreplace' (inserts an XML character reference), backslashreplace (inserts a \uNNNN escape sequence) and namereplace (inserts a \N{...} escape sequence).

The following example shows the different results:

>>> u = chr(40960) + 'abcd' + chr(1972)
>>> u.encode('utf-8')
b'\xea\x80\x80abcd\xde\xb4'
>>> u.encode('ascii')
Traceback (most recent call last):
    ...
UnicodeEncodeError: 'ascii' codec can't encode character '\ua000' in
  position 0: ordinal not in range(128)
>>> u.encode('ascii', 'ignore')
b'abcd'
>>> u.encode('ascii', 'replace')
b'?abcd?'
>>> u.encode('ascii', 'xmlcharrefreplace')
b'&#40960;abcd&#1972;'
>>> u.encode('ascii', 'backslashreplace')
b'\\ua000abcd\\u07b4'
>>> u.encode('ascii', 'namereplace')
b'\\N{YI SYLLABLE IT}abcd\\u07b4'

The low-level routines for registering and accessing the available encodings are found in the codecs module. Implementing new encodings also requires understanding the codecs module. However, the encoding and decoding functions returned by this module are usually more low-level than is comfortable, and writing new encodings is a specialized task, so the module won't be covered in this HOWTO.

Unicode Literals in Python Source Code

In Python source code, specific Unicode code points can be written using the \u escape sequence, which is followed by four hex digits giving the code point. The \U escape sequence is similar, but expects eight hex digits, not four:

>>> s = "a\xac\u1234\u20ac\U00008000"
... #     ^^^^ two-digit hex escape
... #         ^^^^^^ four-digit Unicode escape
... #                     ^^^^^^^^^^ eight-digit Unicode escape
>>> [ord(c) for c in s]
[97, 172, 4660, 8364, 32768]

Using escape sequences for code points greater than 127 is fine in small doses, but becomes an annoyance if you're using many accented characters, as you would in a program with messages in French or some other accent-using language. You can also assemble strings using the chr() built-in function, but this is even more tedious.

Ideally, you'd want to be able to write literals in your language's natural encoding. You could then edit Python source code with your favorite editor which would display the accented characters naturally, and have the right characters used at runtime.

Python supports writing source code in UTF-8 by default, but you can use almost any encoding if you declare the encoding being used. This is done by including a special comment as either the first or second line of the source file:

#!/usr/bin/env python
# -*- coding: latin-1 -*-

u = 'abcdé'
print(ord(u[-1]))

The syntax is inspired by Emacs's notation for specifying variables local to a file. Emacs supports many different variables, but Python only supports 'coding'. The -*- symbols indicate to Emacs that the comment is special; they have no significance to Python but are a convention. Python looks for coding: name or coding=name in the comment.

If you don't include such a comment, the default encoding used will be UTF-8 as already mentioned. See also PEP 263 [https://peps.python.org/pep-0263/] for more information.

Unicode Properties

The Unicode specification includes a database of information about code points. For each defined code point, the information includes the character's name, its category, the numeric value if applicable (for characters representing numeric concepts such as the Roman numerals, fractions such as one-third and four-fifths, etc.). There are also display-related properties, such as how to use the code point in bidirectional text.

The following program displays some information about several characters, and prints the numeric value of one particular character:

import unicodedata

u = chr(233) + chr(0x0bf2) + chr(3972) + chr(6000) + chr(13231)

for i, c in enumerate(u):
    print(i, '%04x' % ord(c), unicodedata.category(c), end=" ")
    print(unicodedata.name(c))

# Get numeric value of second character
print(unicodedata.numeric(u[1]))

When run, this prints:

0 00e9 Ll LATIN SMALL LETTER E WITH ACUTE
1 0bf2 No TAMIL NUMBER ONE THOUSAND
2 0f84 Mn TIBETAN MARK HALANTA
3 1770 Lo TAGBANWA LETTER SA
4 33af So SQUARE RAD OVER S SQUARED
1000.0

The category codes are abbreviations describing the nature of the character. These are grouped into categories such as "Letter", "Number", "Punctuation", or "Symbol", which in turn are broken up into subcategories. To take the codes from the above output, 'Ll' means 'Letter, lowercase', 'No' means "Number, other", 'Mn' is "Mark, nonspacing", and 'So' is "Symbol, other". See the General Category Values section of the Unicode Character Database documentation [https://www.unicode.org/reports/tr44/#General_Category_Values] for a list of category codes.

Comparing Strings

Unicode adds some complication to comparing strings, because the same set of characters can be represented by different sequences of code points. For example, a letter like 'ê' can be represented as a single code point U+00EA, or as U+0065 U+0302, which is the code point for 'e' followed by a code point for 'COMBINING CIRCUMFLEX ACCENT'. These will produce the same output when printed, but one is a string of length 1 and the other is of length 2.

One tool for a case-insensitive comparison is the casefold() string method that converts a string to a case-insensitive form following an algorithm described by the Unicode Standard. This algorithm has special handling for characters such as the German letter 'ß' (code point U+00DF), which becomes the pair of lowercase letters 'ss'.

>>> street = 'Gürzenichstraße'
>>> street.casefold()
'gürzenichstrasse'

A second tool is the unicodedata module's normalize() function that converts strings to one of several normal forms, where letters followed by a combining character are replaced with single characters. normalize() can be used to perform string comparisons that won't falsely report inequality if two strings use combining characters differently:

import unicodedata

def compare_strs(s1, s2):
    def NFD(s):
        return unicodedata.normalize('NFD', s)

    return NFD(s1) == NFD(s2)

single_char = 'ê'
multiple_chars = '\N{LATIN SMALL LETTER E}\N{COMBINING CIRCUMFLEX ACCENT}'
print('length of first string=', len(single_char))
print('length of second string=', len(multiple_chars))
print(compare_strs(single_char, multiple_chars))

When run, this outputs:

$ python compare-strs.py
length of first string= 1
length of second string= 2
True

The first argument to the normalize() function is a string giving the desired normalization form, which can be one of 'NFC', 'NFKC', 'NFD', and 'NFKD'.

The Unicode Standard also specifies how to do caseless comparisons:

import unicodedata

def compare_caseless(s1, s2):
    def NFD(s):
        return unicodedata.normalize('NFD', s)

    return NFD(NFD(s1).casefold()) == NFD(NFD(s2).casefold())

# Example usage
single_char = 'ê'
multiple_chars = '\N{LATIN CAPITAL LETTER E}\N{COMBINING CIRCUMFLEX ACCENT}'

print(compare_caseless(single_char, multiple_chars))

This will print True. (Why is NFD() invoked twice? Because there are a few characters that make casefold() return a non-normalized string, so the result needs to be normalized again. See section 3.13 of the Unicode Standard for a discussion and an example.)

Unicode Regular Expressions

The regular expressions supported by the re module can be provided either as bytes or strings. Some of the special character sequences such as \d and \w have different meanings depending on whether the pattern is supplied as bytes or a string. For example, \d will match the characters [0-9] in bytes but in strings will match any character that's in the 'Nd' category.

The string in this example has the number 57 written in both Thai and Arabic numerals:

import re
p = re.compile(r'\d+')

s = "Over \u0e55\u0e57 57 flavours"
m = p.search(s)
print(repr(m.group()))

When executed, \d+ will match the Thai numerals and print them out. If you supply the re.ASCII flag to compile(), \d+ will match the substring "57" instead.

Similarly, \w matches a wide variety of Unicode characters but only [a-zA-Z0-9_] in bytes or if re.ASCII is supplied, and \s will match either Unicode whitespace characters or [ \t\n\r\f\v].

References

Some good alternative discussions of Python's Unicode support are:

Processing Text Files in Python 3 [https://python-notes.curiousefficiency.org/en/latest/python3/text_file_processing.html], by Nick Coghlan.

Pragmatic Unicode [https://nedbatchelder.com/text/unipain.html], a PyCon 2012 presentation by Ned Batchelder.

The str type is described in the Python library reference at Text Sequence Type --- str.

unicodedata 模組的文件。

codecs 模組的文件。

Marc-André Lemburg gave a presentation titled "Python and Unicode" (PDF slides) [https://downloads.egenix.com/python/Unicode-EPC2002-Talk.pdf] at EuroPython 2002. The slides are an excellent overview of the design of Python 2's Unicode features (where the Unicode string type is called unicode and literals start with u).

Reading and Writing Unicode Data

Once you've written some code that works with Unicode data, the next problem is input/output. How do you get Unicode strings into your program, and how do you convert Unicode into a form suitable for storage or transmission?

It's possible that you may not need to do anything depending on your input sources and output destinations; you should check whether the libraries used in your application support Unicode natively. XML parsers often return Unicode data, for example. Many relational databases also support Unicode-valued columns and can return Unicode values from an SQL query.

Unicode data is usually converted to a particular encoding before it gets written to disk or sent over a socket. It's possible to do all the work yourself: open a file, read an 8-bit bytes object from it, and convert the bytes with bytes.decode(encoding). However, the manual approach is not recommended.

One problem is the multi-byte nature of encodings; one Unicode character can be represented by several bytes. If you want to read the file in arbitrary-sized chunks (say, 1024 or 4096 bytes), you need to write error-handling code to catch the case where only part of the bytes encoding a single Unicode character are read at the end of a chunk. One solution would be to read the entire file into memory and then perform the decoding, but that prevents you from working with files that are extremely large; if you need to read a 2 GiB file, you need 2 GiB of RAM. (More, really, since for at least a moment you'd need to have both the encoded string and its Unicode version in memory.)

The solution would be to use the low-level decoding interface to catch the case of partial coding sequences. The work of implementing this has already been done for you: the built-in open() function can return a file-like object that assumes the file's contents are in a specified encoding and accepts Unicode parameters for methods such as read() and write(). This works through open()'s encoding and errors parameters which are interpreted just like those in str.encode() and bytes.decode().

Reading Unicode from a file is therefore simple:

with open('unicode.txt', encoding='utf-8') as f:
    for line in f:
        print(repr(line))

It's also possible to open files in update mode, allowing both reading and writing:

with open('test', encoding='utf-8', mode='w+') as f:
    f.write('\u4500 blah blah blah\n')
    f.seek(0)
    print(repr(f.readline()[:1]))

The Unicode character U+FEFF is used as a byte-order mark (BOM), and is often written as the first character of a file in order to assist with autodetection of the file's byte ordering. Some encodings, such as UTF-16, expect a BOM to be present at the start of a file; when such an encoding is used, the BOM will be automatically written as the first character and will be silently dropped when the file is read. There are variants of these encodings, such as 'utf-16-le' and 'utf-16-be' for little-endian and big-endian encodings, that specify one particular byte ordering and don't skip the BOM.

In some areas, it is also convention to use a "BOM" at the start of UTF-8 encoded files; the name is misleading since UTF-8 is not byte-order dependent. The mark simply announces that the file is encoded in UTF-8. For reading such files, use the 'utf-8-sig' codec to automatically skip the mark if present.

Unicode filenames

Most of the operating systems in common use today support filenames that contain arbitrary Unicode characters. Usually this is implemented by converting the Unicode string into some encoding that varies depending on the system. Today Python is converging on using UTF-8: Python on MacOS has used UTF-8 for several versions, and Python 3.6 switched to using UTF-8 on Windows as well. On Unix systems, there will only be a filesystem encoding. if you've set the LANG or LC_CTYPE environment variables; if you haven't, the default encoding is again UTF-8.

The sys.getfilesystemencoding() function returns the encoding to use on your current system, in case you want to do the encoding manually, but there's not much reason to bother. When opening a file for reading or writing, you can usually just provide the Unicode string as the filename, and it will be automatically converted to the right encoding for you:

filename = 'filename\u4500abc'
with open(filename, 'w') as f:
    f.write('blah\n')

Functions in the os module such as os.stat() will also accept Unicode filenames.

The os.listdir() function returns filenames, which raises an issue: should it return the Unicode version of filenames, or should it return bytes containing the encoded versions? os.listdir() can do both, depending on whether you provided the directory path as bytes or a Unicode string. If you pass a Unicode string as the path, filenames will be decoded using the filesystem's encoding and a list of Unicode strings will be returned, while passing a byte path will return the filenames as bytes. For example, assuming the default filesystem encoding is UTF-8, running the following program:

fn = 'filename\u4500abc'
f = open(fn, 'w')
f.close()

import os
print(os.listdir(b'.'))
print(os.listdir('.'))

will produce the following output:

$ python listdir-test.py
[b'filename\xe4\x94\x80abc', ...]
['filename\u4500abc', ...]

The first list contains UTF-8-encoded filenames, and the second list contains the Unicode versions.

Note that on most occasions, you should can just stick with using Unicode with these APIs. The bytes APIs should only be used on systems where undecodable file names can be present; that's pretty much only Unix systems now.

Tips for Writing Unicode-aware Programs

This section provides some suggestions on writing software that deals with Unicode.

The most important tip is:

Software should only work with Unicode strings internally, decoding the input data as soon as possible and encoding the output only at the end.

If you attempt to write processing functions that accept both Unicode and byte strings, you will find your program vulnerable to bugs wherever you combine the two different kinds of strings. There is no automatic encoding or decoding: if you do e.g. str + bytes, a TypeError will be raised.

When using data coming from a web browser or some other untrusted source, a common technique is to check for illegal characters in a string before using the string in a generated command line or storing it in a database. If you're doing this, be careful to check the decoded string, not the encoded bytes data; some encodings may have interesting properties, such as not being bijective or not being fully ASCII-compatible. This is especially true if the input data also specifies the encoding, since the attacker can then choose a clever way to hide malicious text in the encoded bytestream.

Converting Between File Encodings

The StreamRecoder class can transparently convert between encodings, taking a stream that returns data in encoding #1 and behaving like a stream returning data in encoding #2.

For example, if you have an input file f that's in Latin-1, you can wrap it with a StreamRecoder to return bytes encoded in UTF-8:

new_f = codecs.StreamRecoder(f,
    # en/decoder: used by read() to encode its results and
    # by write() to decode its input.
    codecs.getencoder('utf-8'), codecs.getdecoder('utf-8'),

    # reader/writer: used to read and write to the stream.
    codecs.getreader('latin-1'), codecs.getwriter('latin-1') )

Files in an Unknown Encoding

What can you do if you need to make a change to a file, but don't know the file's encoding? If you know the encoding is ASCII-compatible and only want to examine or modify the ASCII parts, you can open the file with the surrogateescape error handler:

with open(fname, 'r', encoding="ascii", errors="surrogateescape") as f:
    data = f.read()

# make changes to the string 'data'

with open(fname + '.new', 'w',
          encoding="ascii", errors="surrogateescape") as f:
    f.write(data)

The surrogateescape error handler will decode any non-ASCII bytes as code points in a special range running from U+DC80 to U+DCFF. These code points will then turn back into the same bytes when the surrogateescape error handler is used to encode the data and write it back out.

References

One section of Mastering Python 3 Input/Output [https://pyvideo.org/video/289/pycon-2010--mastering-python-3-i-o], a PyCon 2010 talk by David Beazley, discusses text processing and binary data handling.

The PDF slides for Marc-André Lemburg's presentation "Writing Unicode-aware Applications in Python" [https://downloads.egenix.com/python/LSM2005-Developing-Unicode-aware-applications-in-Python.pdf] discuss questions of character encodings as well as how to internationalize and localize an application. These slides cover Python 2.x only.

The Guts of Unicode in Python [https://pyvideo.org/video/1768/the-guts-of-unicode-in-python] is a PyCon 2013 talk by Benjamin Peterson that discusses the internal Unicode representation in Python 3.3.

致謝

The initial draft of this document was written by Andrew Kuchling. It has since been revised further by Alexander Belopolsky, Georg Brandl, Andrew Kuchling, and Ezio Melotti.

Thanks to the following people who have noted errors or offered suggestions on this article: Éric Araujo, Nicholas Bastin, Nick Coghlan, Marius Gedminas, Kent Johnson, Ken Krugler, Marc-André Lemburg, Martin von Löwis, Terry J. Reedy, Serhiy Storchaka, Eryk Sun, Chad Whitacre, Graham Wideman.

如何使用 urllib 套件取得網路資源

作者:

Michael Foord [https://agileabstractions.com/]

簡介

Related Articles

以下這些與 Python 有關的文章說不定能幫到你:

Basic Authentication [https://web.archive.org/web/20201215133350/http://www.voidspace.org.uk/python/articles/authentication.shtml]

以 Python 為例的 Basic Authentication 教學。

urllib.request 是一個用來從 URLs (Uniform Resource Locators) 取得資料的Python模組。它提供一個了非常簡單的介面能接受多種不同的協定，urlopen 函式。也提供了較複雜的介面用於處理一些常見的狀況，例如：基本的 authentication、cookies、proxies 等等，這些都可以由 handler 或 opener 物件操作。

urllib.request supports fetching URLs for many "URL schemes" (identified by the string before the ":" in URL - for example "ftp" is the URL scheme of "ftp://python.org/") using their associated network protocols (e.g. FTP, HTTP). This tutorial focuses on the most common case, HTTP.

一般情形下 urlopen 是非常容易使用的，但當你遇到錯誤或者較複雜的情況下，你可能需要對超文本協定 (HyperText Transfer Protocol) 有一定的了解。最完整且具參考價值的是 RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html]，不過它是一份技術文件並不容易閱讀，以下的教學會提供足夠的 HTTP 知識來幫助你使用 urllib。這份教學並非要取代 urllib.request 這份文件，你還是會需要它。

從 URL 取得資源

以下是使用 urllib.request 最簡單的方法:

import urllib.request
with urllib.request.urlopen('http://python.org/') as response:
   html = response.read()

If you wish to retrieve a resource via URL and store it in a temporary location, you can do so via the shutil.copyfileobj() and tempfile.NamedTemporaryFile() functions:

import shutil
import tempfile
import urllib.request

with urllib.request.urlopen('http://python.org/') as response:
    with tempfile.NamedTemporaryFile(delete=False) as tmp_file:
        shutil.copyfileobj(response, tmp_file)

with open(tmp_file.name) as html:
    pass

Many uses of urllib will be that simple (note that instead of an 'http:' URL we could have used a URL starting with 'ftp:', 'file:', etc.). However, it's the purpose of this tutorial to explain the more complicated cases, concentrating on HTTP.

HTTP is based on requests and responses - the client makes requests and servers send responses. urllib.request mirrors this with a Request object which represents the HTTP request you are making. In its simplest form you create a Request object that specifies the URL you want to fetch. Calling urlopen with this Request object returns a response object for the URL requested. This response is a file-like object, which means you can for example call .read() on the response:

import urllib.request

req = urllib.request.Request('http://python.org/')
with urllib.request.urlopen(req) as response:
   the_page = response.read()

Note that urllib.request makes use of the same Request interface to handle all URL schemes. For example, you can make an FTP request like so:

req = urllib.request.Request('ftp://example.com/')

In the case of HTTP, there are two extra things that Request objects allow you to do: First, you can pass data to be sent to the server. Second, you can pass extra information ("metadata") about the data or about the request itself, to the server - this information is sent as HTTP "headers". Let's look at each of these in turn.

Data

Sometimes you want to send data to a URL (often the URL will refer to a CGI (Common Gateway Interface) script or other web application). With HTTP, this is often done using what's known as a POST request. This is often what your browser does when you submit a HTML form that you filled in on the web. Not all POSTs have to come from forms: you can use a POST to transmit arbitrary data to your own application. In the common case of HTML forms, the data needs to be encoded in a standard way, and then passed to the Request object as the data argument. The encoding is done using a function from the urllib.parse library.

import urllib.parse
import urllib.request

url = 'http://www.someserver.com/cgi-bin/register.cgi'
values = {'name' : 'Michael Foord',
          'location' : 'Northampton',
          'language' : 'Python' }

data = urllib.parse.urlencode(values)
data = data.encode('ascii') # data should be bytes
req = urllib.request.Request(url, data)
with urllib.request.urlopen(req) as response:
   the_page = response.read()

Note that other encodings are sometimes required (e.g. for file upload from HTML forms - see HTML Specification, Form Submission [https://www.w3.org/TR/REC-html40/interact/forms.html#h-17.13] for more details).

If you do not pass the data argument, urllib uses a GET request. One way in which GET and POST requests differ is that POST requests often have "side-effects": they change the state of the system in some way (for example by placing an order with the website for a hundredweight of tinned spam to be delivered to your door). Though the HTTP standard makes it clear that POSTs are intended to always cause side-effects, and GET requests never to cause side-effects, nothing prevents a GET request from having side-effects, nor a POST requests from having no side-effects. Data can also be passed in an HTTP GET request by encoding it in the URL itself.

This is done as follows:

>>> import urllib.request
>>> import urllib.parse
>>> data = {}
>>> data['name'] = 'Somebody Here'
>>> data['location'] = 'Northampton'
>>> data['language'] = 'Python'
>>> url_values = urllib.parse.urlencode(data)
>>> print(url_values)  # The order may differ from below.
name=Somebody+Here&language=Python&location=Northampton
>>> url = 'http://www.example.com/example.cgi'
>>> full_url = url + '?' + url_values
>>> data = urllib.request.urlopen(full_url)

Notice that the full URL is created by adding a ? to the URL, followed by the encoded values.

Headers

We'll discuss here one particular HTTP header, to illustrate how to add headers to your HTTP request.

Some websites [1] dislike being browsed by programs, or send different versions to different browsers [2]. By default urllib identifies itself as Python-urllib/x.y (where x and y are the major and minor version numbers of the Python release, e.g. Python-urllib/2.5), which may confuse the site, or just plain not work. The way a browser identifies itself is through the User-Agent header [3]. When you create a Request object you can pass a dictionary of headers in. The following example makes the same request as above, but identifies itself as a version of Internet Explorer [4].

import urllib.parse
import urllib.request

url = 'http://www.someserver.com/cgi-bin/register.cgi'
user_agent = 'Mozilla/5.0 (Windows NT 6.1; Win64; x64)'
values = {'name': 'Michael Foord',
          'location': 'Northampton',
          'language': 'Python' }
headers = {'User-Agent': user_agent}

data = urllib.parse.urlencode(values)
data = data.encode('ascii')
req = urllib.request.Request(url, data, headers)
with urllib.request.urlopen(req) as response:
   the_page = response.read()

The response also has two useful methods. See the section on info and geturl which comes after we have a look at what happens when things go wrong.

Handling Exceptions

urlopen raises URLError when it cannot handle a response (though as usual with Python APIs, built-in exceptions such as ValueError, TypeError etc. may also be raised).

HTTPError is the subclass of URLError raised in the specific case of HTTP URLs.

The exception classes are exported from the urllib.error module.

URLError

Often, URLError is raised because there is no network connection (no route to the specified server), or the specified server doesn't exist. In this case, the exception raised will have a 'reason' attribute, which is a tuple containing an error code and a text error message.

例如：

>>> req = urllib.request.Request('http://www.pretend_server.org')
>>> try: urllib.request.urlopen(req)
... except urllib.error.URLError as e:
...     print(e.reason)
...
(4, 'getaddrinfo failed')

HTTPError

Every HTTP response from the server contains a numeric "status code". Sometimes the status code indicates that the server is unable to fulfil the request. The default handlers will handle some of these responses for you (for example, if the response is a "redirection" that requests the client fetch the document from a different URL, urllib will handle that for you). For those it can't handle, urlopen will raise an HTTPError. Typical errors include '404' (page not found), '403' (request forbidden), and '401' (authentication required).

See section 10 of RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html] for a reference on all the HTTP error codes.

The HTTPError instance raised will have an integer 'code' attribute, which corresponds to the error sent by the server.

Error Codes

Because the default handlers handle redirects (codes in the 300 range), and codes in the 100--299 range indicate success, you will usually only see error codes in the 400--599 range.

http.server.BaseHTTPRequestHandler.responses is a useful dictionary of response codes that shows all the response codes used by RFC 2616 [https://datatracker.ietf.org/doc/html/rfc2616.html]. An excerpt from the dictionary is shown below

responses = {
    ...
    <HTTPStatus.OK: 200>: ('OK', 'Request fulfilled, document follows'),
    ...
    <HTTPStatus.FORBIDDEN: 403>: ('Forbidden',
                                  'Request forbidden -- authorization will '
                                  'not help'),
    <HTTPStatus.NOT_FOUND: 404>: ('Not Found',
                                  'Nothing matches the given URI'),
    ...
    <HTTPStatus.IM_A_TEAPOT: 418>: ("I'm a Teapot",
                                    'Server refuses to brew coffee because '
                                    'it is a teapot'),
    ...
    <HTTPStatus.SERVICE_UNAVAILABLE: 503>: ('Service Unavailable',
                                            'The server cannot process the '
                                            'request due to a high load'),
    ...
    }

When an error is raised the server responds by returning an HTTP error code and an error page. You can use the HTTPError instance as a response on the page returned. This means that as well as the code attribute, it also has read, geturl, and info, methods as returned by the urllib.response module:

>>> req = urllib.request.Request('http://www.python.org/fish.html')
>>> try:
...     urllib.request.urlopen(req)
... except urllib.error.HTTPError as e:
...     print(e.code)
...     print(e.read())
...
404
b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n\n\n<html
  ...
  <title>Page Not Found</title>\n
  ...

Wrapping it Up

So if you want to be prepared for HTTPError or URLError there are two basic approaches. I prefer the second approach.

Number 1

from urllib.request import Request, urlopen
from urllib.error import URLError, HTTPError
req = Request(someurl)
try:
    response = urlopen(req)
except HTTPError as e:
    print('The server couldn\'t fulfill the request.')
    print('Error code: ', e.code)
except URLError as e:
    print('We failed to reach a server.')
    print('Reason: ', e.reason)
else:
    # everything is fine

備註

The except HTTPError must come first, otherwise except URLError will also catch an HTTPError.

Number 2

from urllib.request import Request, urlopen
from urllib.error import URLError
req = Request(someurl)
try:
    response = urlopen(req)
except URLError as e:
    if hasattr(e, 'reason'):
        print('We failed to reach a server.')
        print('Reason: ', e.reason)
    elif hasattr(e, 'code'):
        print('The server couldn\'t fulfill the request.')
        print('Error code: ', e.code)
else:
    # everything is fine

info and geturl

The response returned by urlopen (or the HTTPError instance) has two useful methods info() and geturl() and is defined in the module urllib.response.

geturl - this returns the real URL of the page fetched. This is useful because urlopen (or the opener object used) may have followed a redirect. The URL of the page fetched may not be the same as the URL requested.

info - this returns a dictionary-like object that describes the page fetched, particularly the headers sent by the server. It is currently an http.client.HTTPMessage instance.

Typical headers include 'Content-length', 'Content-type', and so on. See the Quick Reference to HTTP Headers [https://jkorpela.fi/http.html] for a useful listing of HTTP headers with brief explanations of their meaning and use.

Openers and Handlers

When you fetch a URL you use an opener (an instance of the perhaps confusingly named urllib.request.OpenerDirector). Normally we have been using the default opener - via urlopen - but you can create custom openers. Openers use handlers. All the "heavy lifting" is done by the handlers. Each handler knows how to open URLs for a particular URL scheme (http, ftp, etc.), or how to handle an aspect of URL opening, for example HTTP redirections or HTTP cookies.

You will want to create openers if you want to fetch URLs with specific handlers installed, for example to get an opener that handles cookies, or to get an opener that does not handle redirections.

To create an opener, instantiate an OpenerDirector, and then call .add_handler(some_handler_instance) repeatedly.

Alternatively, you can use build_opener, which is a convenience function for creating opener objects with a single function call. build_opener adds several handlers by default, but provides a quick way to add more and/or override the default handlers.

Other sorts of handlers you might want to can handle proxies, authentication, and other common but slightly specialised situations.

install_opener can be used to make an opener object the (global) default opener. This means that calls to urlopen will use the opener you have installed.

Opener objects have an open method, which can be called directly to fetch urls in the same way as the urlopen function: there's no need to call install_opener, except as a convenience.

Basic Authentication

To illustrate creating and installing a handler we will use the HTTPBasicAuthHandler. For a more detailed discussion of this subject -- including an explanation of how Basic Authentication works - see the Basic Authentication Tutorial [https://web.archive.org/web/20201215133350/http://www.voidspace.org.uk/python/articles/authentication.shtml].

When authentication is required, the server sends a header (as well as the 401 error code) requesting authentication. This specifies the authentication scheme and a 'realm'. The header looks like: WWW-Authenticate: SCHEME realm="REALM".

例如

WWW-Authenticate: Basic realm="cPanel Users"

The client should then retry the request with the appropriate name and password for the realm included as a header in the request. This is 'basic authentication'. In order to simplify this process we can create an instance of HTTPBasicAuthHandler and an opener to use this handler.

The HTTPBasicAuthHandler uses an object called a password manager to handle the mapping of URLs and realms to passwords and usernames. If you know what the realm is (from the authentication header sent by the server), then you can use a HTTPPasswordMgr. Frequently one doesn't care what the realm is. In that case, it is convenient to use HTTPPasswordMgrWithDefaultRealm. This allows you to specify a default username and password for a URL. This will be supplied in the absence of you providing an alternative combination for a specific realm. We indicate this by providing None as the realm argument to the add_password method.

The top-level URL is the first URL that requires authentication. URLs "deeper" than the URL you pass to .add_password() will also match.

# create a password manager
password_mgr = urllib.request.HTTPPasswordMgrWithDefaultRealm()

# Add the username and password.
# If we knew the realm, we could use it instead of None.
top_level_url = "http://example.com/foo/"
password_mgr.add_password(None, top_level_url, username, password)

handler = urllib.request.HTTPBasicAuthHandler(password_mgr)

# create "opener" (OpenerDirector instance)
opener = urllib.request.build_opener(handler)

# use the opener to fetch a URL
opener.open(a_url)

# Install the opener.
# Now all calls to urllib.request.urlopen use our opener.
urllib.request.install_opener(opener)

備註

In the above example we only supplied our HTTPBasicAuthHandler to build_opener. By default openers have the handlers for normal situations -- ProxyHandler (if a proxy setting such as an http_proxy environment variable is set), UnknownHandler, HTTPHandler, HTTPDefaultErrorHandler, HTTPRedirectHandler, FTPHandler, FileHandler, DataHandler, HTTPErrorProcessor.

top_level_url is in fact either a full URL (including the 'http:' scheme component and the hostname and optionally the port number) e.g. "http://example.com/" or an "authority" (i.e. the hostname, optionally including the port number) e.g. "example.com" or "example.com:8080" (the latter example includes a port number). The authority, if present, must NOT contain the "userinfo" component - for example "joe:password@example.com" is not correct.

Proxies

urllib will auto-detect your proxy settings and use those. This is through the ProxyHandler, which is part of the normal handler chain when a proxy setting is detected. Normally that's a good thing, but there are occasions when it may not be helpful [5]. One way to do this is to setup our own ProxyHandler, with no proxies defined. This is done using similar steps to setting up a Basic Authentication handler:

>>> proxy_support = urllib.request.ProxyHandler({})
>>> opener = urllib.request.build_opener(proxy_support)
>>> urllib.request.install_opener(opener)

備註

Currently urllib.request does not support fetching of https locations through a proxy. However, this can be enabled by extending urllib.request as shown in the recipe [6].

備註

HTTP_PROXY will be ignored if a variable REQUEST_METHOD is set; see the documentation on getproxies().

Sockets and Layers

The Python support for fetching resources from the web is layered. urllib uses the http.client library, which in turn uses the socket library.

As of Python 2.3 you can specify how long a socket should wait for a response before timing out. This can be useful in applications which have to fetch web pages. By default the socket module has no timeout and can hang. Currently, the socket timeout is not exposed at the http.client or urllib.request levels. However, you can set the default timeout globally for all sockets using

import socket
import urllib.request

# timeout in seconds
timeout = 10
socket.setdefaulttimeout(timeout)

# this call to urllib.request.urlopen now uses the default timeout
# we have set in the socket module
req = urllib.request.Request('http://www.voidspace.org.uk')
response = urllib.request.urlopen(req)

註腳

This document was reviewed and revised by John Lee.

[1]

Google for example.

[2]

Browser sniffing is a very bad practice for website design - building sites using web standards is much more sensible. Unfortunately a lot of sites still send different versions to different browsers.

[3]

The user agent for MSIE 6 is 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)'

[4]

For details of more HTTP request headers, see Quick Reference to HTTP Headers [https://jkorpela.fi/http.html].

[5]

In my case I have to use a proxy to access the internet at work. If you attempt to fetch localhost URLs through this proxy it blocks them. IE is set to use the proxy, which urllib picks up on. In order to test scripts with a localhost server, I have to prevent urllib from using the proxy.

[6]

urllib opener for SSL proxy (CONNECT method): ASPN Cookbook Recipe [https://code.activestate.com/recipes/456195-urrlib2-opener-for-ssl-proxy-connect-method/].

ipaddress 模組介紹

作者:

Peter Moody

作者:

Nick Coghlan

總攬

這份文件旨在為 ipaddress 模組提供一個初步介紹。文件主要針對那些不熟悉 IP 網路術語的使用者，但對想要了解 ipaddress 模組如何表示 IP 網址概念的網路工程師也可能有用。

建立 Address/Network/Interface 物件

由於 ipaddress 是一個用於檢查和操作 IP 位址的模組，你首先會想要做的事情是建立一些物件。你可以使用 ipaddress 從字串和整數建立物件。

關於 IP 版本的說明

對於不太熟悉 IP 位址的讀者來說，重要的是要知道網際網路協定 (Internet Protocol, IP) 目前正在從協定的第 4 版過渡到第 6 版。這個轉換主要是因為協定的第 4 版無法提供足夠的位址來處理全世界的需求，特別是考慮到直接連接到網際網路的裝置數量不斷增加。

解釋這兩個版本協定之間差異的細節超出了本文介紹的範圍，但讀者至少需要知道這兩個版本的存在，而且有時候會需要強制使用其中一個版本。

IP 主機位址

位址，通常被稱為「主機位址」，是處理 IP 位址時最基本的單位。建立位址最簡單的方法是使用 ipaddress.ip_address() 工廠函式，它會根據傳入的值自動判斷要建立 IPv4 還是 IPv6 位址：

>>> ipaddress.ip_address('192.0.2.1')
IPv4Address('192.0.2.1')
>>> ipaddress.ip_address('2001:DB8::1')
IPv6Address('2001:db8::1')

位址也可以直接從整數建立。符合 32 位元以內的值會被假定為 IPv4 位址：

>>> ipaddress.ip_address(3221225985)
IPv4Address('192.0.2.1')
>>> ipaddress.ip_address(42540766411282592856903984951653826561)
IPv6Address('2001:db8::1')

要強制使用 IPv4 或 IPv6 位址，可以直接呼叫相關的類別。這對於強制為小整數建立 IPv6 位址特別有用：

>>> ipaddress.ip_address(1)
IPv4Address('0.0.0.1')
>>> ipaddress.IPv4Address(1)
IPv4Address('0.0.0.1')
>>> ipaddress.IPv6Address(1)
IPv6Address('::1')

定義網路

主機位址通常會被分組到 IP 網路中，因此 ipaddress 提供了一種建立、檢查和操作網路定義的方法。IP 網路物件是從定義該網路所包含之主機位址範圍的字串建構而成。這些資訊最簡單的形式是「網路位址/網路前綴」配對，其中前綴定義了用於比較的前導位元數量，以判斷位址是否屬於該網路的一部分，而網路位址則定義了這些位元的預期值。

至於位址，提供了一個工廠函式可以自動判斷正確的 IP 版本：

>>> ipaddress.ip_network('192.0.2.0/24')
IPv4Network('192.0.2.0/24')
>>> ipaddress.ip_network('2001:db8::0/96')
IPv6Network('2001:db8::/96')

網路物件不能設定任何主機位元。這樣做的實際效果是 192.0.2.1/24 並不描述一個網路。這類定義被稱為介面物件，因為 ip-on-a-network 標記法通常用於描述電腦在給定網路上的網路介面，並將在下一節中進一步說明。

預設情況下，嘗試建立帶有主機位元設定的網路物件會導致引發 ValueError。若要求將額外的位元強制轉換為零，可以在建構子中傳遞旗標 strict=False：

>>> ipaddress.ip_network('192.0.2.1/24')
Traceback (most recent call last):
   ...
ValueError: 192.0.2.1/24 has host bits set
>>> ipaddress.ip_network('192.0.2.1/24', strict=False)
IPv4Network('192.0.2.0/24')

雖然字串形式提供了更大的靈活性，但網路也可以像主機位址一樣使用整數來定義。在這種情況下，網路被認為僅包含由該整數識別的單一位址，因此網路前綴包含了整個網路位址：

>>> ipaddress.ip_network(3221225984)
IPv4Network('192.0.2.0/32')
>>> ipaddress.ip_network(42540766411282592856903984951653826560)
IPv6Network('2001:db8::/128')

與位址一樣，可以透過直接呼叫類別建構子而非使用工廠函式，來強制建立特定類型的網路。

主機介面

如上所述，如果你需要描述特定網路上的位址，位址類別和網路類別都不足以滿足需求。像 192.0.2.1/24 這樣的標記法通常被網路工程師以及編寫防火牆和路由器工具的人用作「網路 192.0.2.0/24 上的主機 192.0.2.1」的簡寫。因此，ipaddress 提供了一組混合類別，將位址與特定網路關聯起來。建立介面的方式與定義網路物件相同，只是位址部分不受限於必須是網路位址。

>>> ipaddress.ip_interface('192.0.2.1/24')
IPv4Interface('192.0.2.1/24')
>>> ipaddress.ip_interface('2001:db8::1/96')
IPv6Interface('2001:db8::1/96')

可以接受整數輸入（如同網路一樣），並且可以透過直接呼叫相關的建構子來強制使用特定的 IP 版本。

檢視 Address/Network/Interface 物件

你費心建立了 IPv(4|6)(Address|Network|Interface) 物件，所以你可能想要取得關於它的資訊。ipaddress 試圖讓這件事變得簡單且直觀。

提取 IP 版本：

>>> addr4 = ipaddress.ip_address('192.0.2.1')
>>> addr6 = ipaddress.ip_address('2001:db8::1')
>>> addr6.version
6
>>> addr4.version
4

從介面取得網路：

>>> host4 = ipaddress.ip_interface('192.0.2.1/24')
>>> host4.network
IPv4Network('192.0.2.0/24')
>>> host6 = ipaddress.ip_interface('2001:db8::1/96')
>>> host6.network
IPv6Network('2001:db8::/96')

找出網路中有多少個別位址：

>>> net4 = ipaddress.ip_network('192.0.2.0/24')
>>> net4.num_addresses
256
>>> net6 = ipaddress.ip_network('2001:db8::0/96')
>>> net6.num_addresses
4294967296

迭代網路上「可用的」位址：

>>> net4 = ipaddress.ip_network('192.0.2.0/24')
>>> for x in net4.hosts():
...     print(x)
192.0.2.1
192.0.2.2
192.0.2.3
192.0.2.4
...
192.0.2.252
192.0.2.253
192.0.2.254

取得網路遮罩（即對應於網路前綴的設定位元）或主機遮罩（任何不屬於網路遮罩的位元）：

>>> net4 = ipaddress.ip_network('192.0.2.0/24')
>>> net4.netmask
IPv4Address('255.255.255.0')
>>> net4.hostmask
IPv4Address('0.0.0.255')
>>> net6 = ipaddress.ip_network('2001:db8::0/96')
>>> net6.netmask
IPv6Address('ffff:ffff:ffff:ffff:ffff:ffff::')
>>> net6.hostmask
IPv6Address('::ffff:ffff')

展開或壓縮位址：

>>> addr6.exploded
'2001:0db8:0000:0000:0000:0000:0000:0001'
>>> addr6.compressed
'2001:db8::1'
>>> net6.exploded
'2001:0db8:0000:0000:0000:0000:0000:0000/96'
>>> net6.compressed
'2001:db8::/96'

雖然 IPv4 不支援展開或壓縮，但相關的物件仍然提供了相關屬性，使得版本中立的程式碼可以輕鬆地確保 IPv6 位址使用最簡潔或最詳細的形式，同時仍能正確處理 IPv4 位址。

作為位址串列的網路

有時將網路視為串列是很有用的。這意味著可以像這樣對它們進行索引：

>>> net4[1]
IPv4Address('192.0.2.1')
>>> net4[-1]
IPv4Address('192.0.2.255')
>>> net6[1]
IPv6Address('2001:db8::1')
>>> net6[-1]
IPv6Address('2001:db8::ffff:ffff')

這也意味著網路物件適合使用串列成員測試語法，像這樣：

if address in network:
    # 做某些事情

msgstr "可以根據網路前綴有效率地檢查是否包含： ::"

>>> addr4 = ipaddress.ip_address('192.0.2.1')
>>> addr4 in ipaddress.ip_network('192.0.2.0/24')
True
>>> addr4 in ipaddress.ip_network('192.0.3.0/24')
False

比較

ipaddress 提供了一些簡單且希望是直觀的方法來比較物件，只要這樣做有道理：

>>> ipaddress.ip_address('192.0.2.1') < ipaddress.ip_address('192.0.2.2')
True

如果你嘗試比較不同版本或不同類型的物件，會引發 TypeError 例外。

與其他模組一起使用 IP 位址

其他使用 IP 位址的模組（例如 socket）通常不會直接接受來自此模組的物件。相反地，它們必須被強制轉換為其他模組能接受的整數或字串：

>>> addr4 = ipaddress.ip_address('192.0.2.1')
>>> str(addr4)
'192.0.2.1'
>>> int(addr4)
3221225985

在實例建立失敗時取得更多細節

當使用版本無關的工廠函式建立位址/網路/介面物件時，任何錯誤都會以 ValueError 回報，並附帶一個通用的錯誤訊息，簡單地說明傳入的值未被識別為該類型的物件。缺乏具體錯誤的原因是，為了提供更多關於為何被拒絕的細節，需要知道該值應該是 IPv4 還是 IPv6。

為了支援需要存取這些額外細節的使用情境，個別類別建構子實際上會引發 ValueError 的子類別 ipaddress.AddressValueError 和 ipaddress.NetmaskValueError，以明確指出定義的哪個部分無法正確解析。

當直接使用類別建構子時，錯誤訊息會詳細得多。例如：

>>> ipaddress.ip_address("192.168.0.256")
Traceback (most recent call last):
  ...
ValueError: '192.168.0.256' does not appear to be an IPv4 or IPv6 address
>>> ipaddress.IPv4Address("192.168.0.256")
Traceback (most recent call last):
  ...
ipaddress.AddressValueError: Octet 256 (> 255) not permitted in '192.168.0.256'

>>> ipaddress.ip_network("192.168.0.1/64")
Traceback (most recent call last):
  ...
ValueError: '192.168.0.1/64' does not appear to be an IPv4 or IPv6 network
>>> ipaddress.IPv4Network("192.168.0.1/64")
Traceback (most recent call last):
  ...
ipaddress.NetmaskValueError: '64' is not a valid netmask

然而，這兩個模組特定的例外都以 ValueError 作為它們的父類別，因此如果你不關心特定類型的錯誤，你仍然可以撰寫如下的程式碼：

try:
    network = ipaddress.IPv4Network(address)
except ValueError:
    print('address/netmask is invalid for IPv4:', address)

使用 DTrace 和 SystemTap 檢測 CPython

作者:

David Malcolm

作者:

Łukasz Langa

DTrace 和 SystemTap 都是監測工具，各自都提供了一種檢查電腦系統之行程 (process) 正在執行什麼操作的方法。它們都使用了領域限定 (domain-specific) 的語言，允許使用者編寫以下腳本：

過濾要觀察的行程

收集來自感興趣之行程的資料

以這些資料產生報告

從 Python 3.6 開始，CPython 可以使用嵌入式「標記 (marker)」（也稱為「探針 (probe)」）建置，可以透過 DTrace 或 SystemTap 腳本進行觀察，從而更輕鬆地監視系統之 CPython 行程正在執行的操作。

DTrace 標記是 CPython 直譯器的實作細節。不保證 CPython 版本之間的探針相容性。更改 CPython 版本時，DTrace 腳本可能會停止運作或錯誤地運作，而不會發出警告。

啟用靜態標記

macOS 內建了對 DTrace 的支援。在 Linux 上，為了建置帶有 SystemTap 嵌入標記的 CPython，必須安裝 SystemTap 開發工具。

在 Linux 機器上，這可以透過以下方式完成：

$ yum install systemtap-sdt-devel

或是：

$ sudo apt-get install systemtap-sdt-dev

然後 CPython 必須使用配置 --with-dtrace 選項：

checking for --with-dtrace... yes

在 macOS 上，你可以透過在後台運行 Python 行程並列出 Python 發布者 (provider) 所提供的所有可用探針，以列出可用的 DTrace 探針：

$ python3.6 -q &
$ sudo dtrace -l -P python$!  # 或 dtrace -l -m python3.6

   ID   PROVIDER            MODULE                          FUNCTION NAME
29564 python18035        python3.6          _PyEval_EvalFrameDefault function-entry
29565 python18035        python3.6             dtrace_function_entry function-entry
29566 python18035        python3.6          _PyEval_EvalFrameDefault function-return
29567 python18035        python3.6            dtrace_function_return function-return
29568 python18035        python3.6                           collect gc-done
29569 python18035        python3.6                           collect gc-start
29570 python18035        python3.6          _PyEval_EvalFrameDefault line
29571 python18035        python3.6                 maybe_dtrace_line line

在 Linux 上，你可以透過查看二進位建置檔案中是否包含 ".note.stapsdt" 部分來驗證 SystemTap 靜態標記是否存在。

$ readelf -S ./python | grep .note.stapsdt
[30] .note.stapsdt        NOTE         0000000000000000 00308d78

如果你已將 Python 建置為共享函式庫（使用 --enable-shared 配置選項），則需要在共享函式庫中查找。例如：

$ readelf -S libpython3.3dm.so.1.0 | grep .note.stapsdt
[29] .note.stapsdt        NOTE         0000000000000000 00365b68

足夠現代化的 readelf 可以印出元資料 (metadata)：

$ readelf -n ./python

Displaying notes found at file offset 0x00000254 with length 0x00000020:
    Owner                 Data size          Description
    GNU                  0x00000010          NT_GNU_ABI_TAG (ABI version tag)
        OS: Linux, ABI: 2.6.32

Displaying notes found at file offset 0x00000274 with length 0x00000024:
    Owner                 Data size          Description
    GNU                  0x00000014          NT_GNU_BUILD_ID (unique build ID bitstring)
        Build ID: df924a2b08a7e89f6e11251d4602022977af2670

Displaying notes found at file offset 0x002d6c30 with length 0x00000144:
    Owner                 Data size          Description
    stapsdt              0x00000031          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: gc__start
        Location: 0x00000000004371c3, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6bf6
        Arguments: -4@%ebx
    stapsdt              0x00000030          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: gc__done
        Location: 0x00000000004374e1, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6bf8
        Arguments: -8@%rax
    stapsdt              0x00000045          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: function__entry
        Location: 0x000000000053db6c, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6be8
        Arguments: 8@%rbp 8@%r12 -4@%eax
    stapsdt              0x00000046          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: function__return
        Location: 0x000000000053dba8, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6bea
        Arguments: 8@%rbp 8@%r12 -4@%eax

上述元資料包含 SystemTap 的資訊，描述了它如何修補策略性放置的機器碼指令以啟用 SystemTap 腳本使用的追蹤 hook。

靜態 DTrace 探針

以下範例示範 DTrace 腳本可用於顯示 Python 腳本的呼叫/回傳階層結構，僅在名為 "start" 的函式的呼叫內進行追蹤。換句話說，引入時的函式呼叫不會被列出：

self int indent;

python$target:::function-entry
/copyinstr(arg1) == "start"/
{
        self->trace = 1;
}

python$target:::function-entry
/self->trace/
{
        printf("%d\t%*s:", timestamp, 15, probename);
        printf("%*s", self->indent, "");
        printf("%s:%s:%d\n", basename(copyinstr(arg0)), copyinstr(arg1), arg2);
        self->indent++;
}

python$target:::function-return
/self->trace/
{
        self->indent--;
        printf("%d\t%*s:", timestamp, 15, probename);
        printf("%*s", self->indent, "");
        printf("%s:%s:%d\n", basename(copyinstr(arg0)), copyinstr(arg1), arg2);
}

python$target:::function-return
/copyinstr(arg1) == "start"/
{
        self->trace = 0;
}

可以這樣呼叫：

$ sudo dtrace -q -s call_stack.d -c "python3.6 script.py"

輸出如下所示：

156641360502280  function-entry:call_stack.py:start:23
156641360518804  function-entry: call_stack.py:function_1:1
156641360532797  function-entry:  call_stack.py:function_3:9
156641360546807 function-return:  call_stack.py:function_3:10
156641360563367 function-return: call_stack.py:function_1:2
156641360578365  function-entry: call_stack.py:function_2:5
156641360591757  function-entry:  call_stack.py:function_1:1
156641360605556  function-entry:   call_stack.py:function_3:9
156641360617482 function-return:   call_stack.py:function_3:10
156641360629814 function-return:  call_stack.py:function_1:2
156641360642285 function-return: call_stack.py:function_2:6
156641360656770  function-entry: call_stack.py:function_3:9
156641360669707 function-return: call_stack.py:function_3:10
156641360687853  function-entry: call_stack.py:function_4:13
156641360700719 function-return: call_stack.py:function_4:14
156641360719640  function-entry: call_stack.py:function_5:18
156641360732567 function-return: call_stack.py:function_5:21
156641360747370 function-return:call_stack.py:start:28

靜態 SystemTap 標記

使用 SystemTap 整合的低階方法是直接使用靜態標記。這會需要你明確聲明包含它們的二進位檔案。

例如，此 SystemTap 腳本可用於顯示 Python 腳本的呼叫/回傳階層結構：

probe process("python").mark("function__entry") {
     filename = user_string($arg1);
     funcname = user_string($arg2);
     lineno = $arg3;

     printf("%s => %s in %s:%d\\n",
            thread_indent(1), funcname, filename, lineno);
}

probe process("python").mark("function__return") {
    filename = user_string($arg1);
    funcname = user_string($arg2);
    lineno = $arg3;

    printf("%s <= %s in %s:%d\\n",
           thread_indent(-1), funcname, filename, lineno);
}

可以這樣呼叫：

$ stap \
  show-call-hierarchy.stp \
  -c "./python test.py"

輸出如下所示：

11408 python(8274):        => __contains__ in Lib/_abcoll.py:362
11414 python(8274):         => __getitem__ in Lib/os.py:425
11418 python(8274):          => encode in Lib/os.py:490
11424 python(8274):          <= encode in Lib/os.py:493
11428 python(8274):         <= __getitem__ in Lib/os.py:426
11433 python(8274):        <= __contains__ in Lib/_abcoll.py:366

其中的行 (column) 是：

自腳本開始以來的時間（以微秒為單位）

可執行檔案的名稱

行程的 PID

其餘部分表示腳本執行時的呼叫/回傳階層結構。

對於以 --enable-shared 建置的 CPython，標記被包含在 libpython 共享函式庫中，並且探針的帶點路徑 (dotted path) 需要反映這一點。例如，上面範例中的這一列：

probe process("python").mark("function__entry") {

應該改為讀取：

probe process("python").library("libpython3.6dm.so.1.0").mark("function__entry") {

（假設 CPython 3.6 的除錯建置版本）

可用的靜態標記

function__entry(str filename, str funcname, int lineno)

該標記表示 Python 函式的執行已經開始。它僅針對純 Python（位元組碼）函式觸發。

檔案名稱、函式名稱和列號作為位置引數提供給追蹤腳本，必須使用 $arg1、$arg2、$arg3 來存取：

$arg1 : (const char *) 檔案名稱，可使用 user_string($arg1) 存取

$arg2 ：(const char *) 函式名稱，可使用 user_string($arg2) 存取

$arg3 : int 列號

function__return(str filename, str funcname, int lineno)

該標記與 function__entry() 相反，表示 Python 函式的執行已結束（透過 return 或透過例外）。它僅針對純 Python（位元組碼）函式觸發。

引數與 function__entry() 相同

line(str filename, str funcname, int lineno)

該標記表示一列 Python 即將被執行。它相當於使用 Python 分析器來逐行追蹤。它不在 C 函式內觸發。

引數與 function__entry() 相同。

gc__start(int generation)

當 Python 直譯器開始垃圾回收 (garbage collection) 週期時觸發。arg0 是要掃描的一代 (generation)，如 gc.collect()。

gc__done(long collected)

當 Python 直譯器完成垃圾回收週期時觸發。arg0 是收集到的物件數量。

import__find__load__start(str modulename)

在 importlib 嘗試查找並載入模組之前觸發。arg0 是模組名稱。

在 3.7 版被加入.

import__find__load__done(str modulename, int found)

在呼叫 importlib 的 find_and_load 函式後觸發。 arg0 是模組名稱，arg1 代表模組是否已成功載入。

在 3.7 版被加入.

audit(str event, void *tuple)

當呼叫 sys.audit() 或 PySys_Audit() 時觸發。arg0 是 C 字串形式的事件名稱，arg1 是指向元組 (tuple) 物件的 PyObject 指標。

在 3.8 版被加入.

SystemTap Tapsets

使用 SystemTap 整合的高階方法是使用 "tapset"：SystemTap 相當於一個函式庫，它隱藏了靜態標記的一些低階詳細資訊。

這是一個 tapset 檔案，是基於 CPython 的非共享建置版本：

/*
   提供一個更高階、在 function__entry 和 function__return 標記上的包裝：
 \*/
probe python.function.entry = process("python").mark("function__entry")
{
    filename = user_string($arg1);
    funcname = user_string($arg2);
    lineno = $arg3;
    frameptr = $arg4
}
probe python.function.return = process("python").mark("function__return")
{
    filename = user_string($arg1);
    funcname = user_string($arg2);
    lineno = $arg3;
    frameptr = $arg4
}

如果此檔案是安裝在 SystemTap 的 tapset 目錄中（例如 /usr/share/systemtap/tapset），則這些額外的探測點將可被使用：

python.function.entry(str filename, str funcname, int lineno, frameptr)

該探測點表示 Python 函式的執行已經開始。它僅針對純 Python（位元組碼）函式觸發。

python.function.return(str filename, str funcname, int lineno, frameptr)

這個探測點與 python.function.return 相反，表示 Python 函式的執行已經結束（透過 return 或者透過例外）。它僅針對純 Python（位元組碼）函式觸發。

範例

此 SystemTap 腳本使用上面的 tapset 來更清晰地實作上面給出的追蹤 Python 函式呼叫階層結構的範例，而無需直接命名靜態標記：

probe python.function.entry
{
  printf("%s => %s in %s:%d\n",
         thread_indent(1), funcname, filename, lineno);
}

probe python.function.return
{
  printf("%s <= %s in %s:%d\n",
         thread_indent(-1), funcname, filename, lineno);
}

以下腳本使用上面的 tapset 來提供所有正在運行之 CPython 程式碼的近乎最高層視角，顯示整個系統中每秒最常被進入的 20 個位元組碼幀 (bytecode frame)：

global fn_calls;

probe python.function.entry
{
    fn_calls[pid(), filename, funcname, lineno] += 1;
}

probe timer.ms(1000) {
    printf("\033[2J\033[1;1H") /* clear screen \*/
    printf("%6s %80s %6s %30s %6s\n",
           "PID", "FILENAME", "LINE", "FUNCTION", "CALLS")
    foreach ([pid, filename, funcname, lineno] in fn_calls- limit 20) {
        printf("%6d %80s %6d %30s %6d\n",
            pid, filename, lineno, funcname,
            fn_calls[pid, filename, funcname, lineno]);
    }
    delete fn_calls;
}

Python 對 Linux perf 分析器的支援

作者:

Pablo Galindo

Linux 性能分析器 (Linux perf profiler) [https://perf.wiki.kernel.org] 是一個非常強大的工具，可讓你分析並取得有關應用程式的性能資訊。perf 還擁有一個非常活躍的工具生態系統，有助於分析其生成的資料。

在 Python 應用程式中使用 perf 分析器的主要問題是 perf 僅取得有關原生符號的資訊，即用 C 編寫的函式和程式的名稱。這表示程式碼中的 Python 函式名稱和檔案名稱不會出現在 perf 的輸出中。

從 Python 3.12 開始，直譯器可以在特殊模式下執行，該模式允許 Python 函式出現在 perf 分析器的輸出中。啟用此模式後，直譯器將在執行每個 Python 函式之前插入 (interpose) 一小段動態編譯的程式碼，並使用 perf map 檔案來告訴 perf 這段程式碼與相關聯的 Python 函式間的關係。

備註

目前對 perf 分析器的支援僅適用於 Linux 的特定架構上。檢查 configure 建構步驟的輸出或檢查 python -m sysconfig | grep HAVE_PERF_TRAMPOLINE 的輸出來查看你的系統是否支援。

例如，參考以下腳本：

def foo(n):
    result = 0
    for _ in range(n):
        result += 1
    return result

def bar(n):
    foo(n)

def baz(n):
    bar(n)

if __name__ == "__main__":
    baz(1000000)

我們可以執行 perf 以 9999 赫茲取樣 CPU 堆疊追蹤 (stack trace)：

$ perf record -F 9999 -g -o perf.data python my_script.py

然後我們可以使用 perf report 來分析資料：

$ perf report --stdio -n -g

# Children      Self       Samples  Command     Shared Object       Symbol
# ........  ........  ............  ..........  ..................  ..........................................
#
    91.08%     0.00%             0  python.exe  python.exe          [.] _start
            |
            ---_start
            |
                --90.71%--__libc_start_main
                        Py_BytesMain
                        |
                        |--56.88%--pymain_run_python.constprop.0
                        |          |
                        |          |--56.13%--_PyRun_AnyFileObject
                        |          |          _PyRun_SimpleFileObject
                        |          |          |
                        |          |          |--55.02%--run_mod
                        |          |          |          |
                        |          |          |           --54.65%--PyEval_EvalCode
                        |          |          |                     _PyEval_EvalFrameDefault
                        |          |          |                     PyObject_Vectorcall
                        |          |          |                     _PyEval_Vector
                        |          |          |                     _PyEval_EvalFrameDefault
                        |          |          |                     PyObject_Vectorcall
                        |          |          |                     _PyEval_Vector
                        |          |          |                     _PyEval_EvalFrameDefault
                        |          |          |                     PyObject_Vectorcall
                        |          |          |                     _PyEval_Vector
                        |          |          |                     |
                        |          |          |                     |--51.67%--_PyEval_EvalFrameDefault
                        |          |          |                     |          |
                        |          |          |                     |          |--11.52%--_PyLong_Add
                        |          |          |                     |          |          |
                        |          |          |                     |          |          |--2.97%--_PyObject_Malloc
...

如你所見，Python 函式未顯示在輸出中，僅顯示 _Py_Eval_EvalFrameDefault （為 Python 位元組碼 (bytecode) 求值的函式）。不幸的是，這不是很有用，因為所有 Python 函式都使用相同的 C 函式來替位元組碼求值，因此我們無法知道哪個 Python 函式是對應於哪個位元組碼計算函式。

作為替代，如果我們在啟用 perf 支援的情況下執行相同的實驗，我們會得到：

$ perf report --stdio -n -g

# Children      Self       Samples  Command     Shared Object       Symbol
# ........  ........  ............  ..........  ..................  .....................................................................
#
    90.58%     0.36%             1  python.exe  python.exe          [.] _start
            |
            ---_start
            |
                --89.86%--__libc_start_main
                        Py_BytesMain
                        |
                        |--55.43%--pymain_run_python.constprop.0
                        |          |
                        |          |--54.71%--_PyRun_AnyFileObject
                        |          |          _PyRun_SimpleFileObject
                        |          |          |
                        |          |          |--53.62%--run_mod
                        |          |          |          |
                        |          |          |           --53.26%--PyEval_EvalCode
                        |          |          |                     py::<module>:/src/script.py
                        |          |          |                     _PyEval_EvalFrameDefault
                        |          |          |                     PyObject_Vectorcall
                        |          |          |                     _PyEval_Vector
                        |          |          |                     py::baz:/src/script.py
                        |          |          |                     _PyEval_EvalFrameDefault
                        |          |          |                     PyObject_Vectorcall
                        |          |          |                     _PyEval_Vector
                        |          |          |                     py::bar:/src/script.py
                        |          |          |                     _PyEval_EvalFrameDefault
                        |          |          |                     PyObject_Vectorcall
                        |          |          |                     _PyEval_Vector
                        |          |          |                     py::foo:/src/script.py
                        |          |          |                     |
                        |          |          |                     |--51.81%--_PyEval_EvalFrameDefault
                        |          |          |                     |          |
                        |          |          |                     |          |--13.77%--_PyLong_Add
                        |          |          |                     |          |          |
                        |          |          |                     |          |          |--3.26%--_PyObject_Malloc

如何啟用 perf 分析支援

要啟用 perf 分析支援，可以在一開始就使用環境變數 PYTHONPERFSUPPORT 或使用 -X perf 選項，也可以使用 sys.activate_stack_trampoline() 和 sys.deactivate_stack_trampoline() 來動態啟用。

sys 函式優先於 -X 選項、-X 選項優先於環境變數。

例如，使用環境變數：

$ PYTHONPERFSUPPORT=1 perf record -F 9999 -g -o perf.data python my_script.py
$ perf report -g -i perf.data

例如，使用 -X 選項：

$ perf record -F 9999 -g -o perf.data python -X perf my_script.py
$ perf report -g -i perf.data

例如，在 example.py 檔案中使用 sys API：

import sys

sys.activate_stack_trampoline("perf")
do_profiled_stuff()
sys.deactivate_stack_trampoline()

non_profiled_stuff()

...然後：

$ perf record -F 9999 -g -o perf.data python ./example.py
$ perf report -g -i perf.data

如何獲得最佳結果

為了獲得最佳結果，應使用 CFLAGS="-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer" 來進行 Python 編譯，因為這能允許分析器僅使用 frame 指標而不是 DWARF 除錯資訊來解析 (unwind)。這是因為，由於插入以允許 perf 支援的程式碼是動態生成的，因此它沒有任何可用的 DWARF 除錯資訊。

你可以透過執行以下指令來檢查你的系統是否已使用此旗標進行編譯：

$ python -m sysconfig | grep 'no-omit-frame-pointer'

如果你沒有看到任何輸出，則表示你的直譯器尚未使用 frame 指標進行編譯，因此它可能無法在 perf 的輸出中顯示 Python 函式。

How to work without frame pointers

If you are working with a Python interpreter that has been compiled without frame pointers, you can still use the perf profiler, but the overhead will be a bit higher because Python needs to generate unwinding information for every Python function call on the fly. Additionally, perf will take more time to process the data because it will need to use the DWARF debugging information to unwind the stack and this is a slow process.

To enable this mode, you can use the environment variable PYTHON_PERF_JIT_SUPPORT or the -X perf_jit option, which will enable the JIT mode for the perf profiler.

備註

Due to a bug in the perf tool, only perf versions higher than v6.8 will work with the JIT mode. The fix was also backported to the v6.7.2 version of the tool.

Note that when checking the version of the perf tool (which can be done by running perf version) you must take into account that some distros add some custom version numbers including a - character. This means that perf 6.7-3 is not necessarily perf 6.7.3.

When using the perf JIT mode, you need an extra step before you can run perf report. You need to call the perf inject command to inject the JIT information into the perf.data file.:

$ perf record -F 9999 -g -k 1 --call-graph dwarf -o perf.data python -Xperf_jit my_script.py
$ perf inject -i perf.data --jit --output perf.jit.data
$ perf report -g -i perf.jit.data

或使用環境變數：

$ PYTHON_PERF_JIT_SUPPORT=1 perf record -F 9999 -g --call-graph dwarf -o perf.data python my_script.py
$ perf inject -i perf.data --jit --output perf.jit.data
$ perf report -g -i perf.jit.data

perf inject --jit command will read perf.data, automatically pick up the perf dump file that Python creates (in /tmp/perf-$PID.dump), and then create perf.jit.data which merges all the JIT information together. It should also create a lot of jitted-XXXX-N.so files in the current directory which are ELF images for all the JIT trampolines that were created by Python.

警告

When using --call-graph dwarf, the perf tool will take snapshots of the stack of the process being profiled and save the information in the perf.data file. By default, the size of the stack dump is 8192 bytes, but you can change the size by passing it after a comma like --call-graph dwarf,16384.

The size of the stack dump is important because if the size is too small perf will not be able to unwind the stack and the output will be incomplete. On the other hand, if the size is too big, then perf won't be able to sample the process as frequently as it would like as the overhead will be higher.

The stack size is particularly important when profiling Python code compiled with low optimization levels (like -O0), as these builds tend to have larger stack frames. If you are compiling Python with -O0 and not seeing Python functions in your profiling output, try increasing the stack dump size to 65528 bytes (the maximum):

$ perf record -F 9999 -g -k 1 --call-graph dwarf,65528 -o perf.data python -Xperf_jit my_script.py

Different compilation flags can significantly impact stack sizes:

Builds with -O0 typically have much larger stack frames than those with -O1 or higher

Adding optimizations (-O1, -O2, etc.) typically reduces stack size

Frame pointers (-fno-omit-frame-pointer) generally provide more reliable stack unwinding

註釋 (annotation) 最佳實踐

作者:

Larry Hastings

摘要

本文件旨在封裝 (encapsulate) 使用註釋字典 (annotations dicts) 的最佳實踐。如果你寫 Python 程式碼並在調查 Python 物件上的 __annotations__ ，我們鼓勵你遵循下面描述的準則。

本文件分為四個部分：在 Python 3.10 及更高版本中存取物件註釋的最佳實踐、在 Python 3.9 及更早版本中存取物件註釋的最佳實踐、適用於任何Python 版本 __annotations__ 的最佳實踐，以及 __annotations__ 的奇異之處。

請注意，本文件是特別說明 __annotations__ 的使用，而非如何使用註釋。如果你正在尋找如何在你的程式碼中使用「型別提示 (type hint)」的資訊，請查閱模組 (module) typing。

在 Python 3.10 及更高版本中存取物件的註釋字典

Python 3.10 在標準函式庫中新增了一個新函式：inspect.get_annotations()。在 Python 3.10 到 3.13，呼叫此函式是存取任何支援註釋的物件的註釋字典的最佳實踐。此函式也可以為你「取消字串化 (un-stringize)」字串化註釋。

In Python 3.14, there is a new annotationlib module with functionality for working with annotations. This includes a annotationlib.get_annotations() function, which supersedes inspect.get_annotations().

若由於某種原因 inspect.get_annotations() 對你的場合不可行，你可以手動存取 __annotations__ 資料成員。 Python 3.10 中的最佳實踐也已經改變：從 Python 3.10 開始，保證 o.__annotations__ 始終適用於 Python 函式、類別 (class) 和模組。如果你確定正在檢查的物件是這三個特定物件之一，你可以簡單地使用 o.__annotations__ 來取得物件的註釋字典。

但是，其他型別的 callable（可呼叫物件）（例如，由 functools.partial() 建立的 callable）可能沒有定義 __annotations__ 屬性 (attribute)。當存取可能未知的物件的 __annotations__ 時，Python 3.10 及更高版本中的最佳實踐是使用三個參數呼叫 getattr()，例如 getattr(o, '__annotations__', None)。

在 Python 3.10 之前，存取未定義註釋但具有註釋的父類別的類別上的 __annotations__ 將傳回父類別的 __annotations__。在 Python 3.10 及更高版本中，子類別的註釋將會是一個空字典。

在 Python 3.9 及更早版本中存取物件的註釋字典

在 Python 3.9 及更早版本中，存取物件的註釋字典比新版本複雜得多。問題出在於這些舊版 Python 中有設計缺陷，特別是與類別註釋有關的設計缺陷。

存取其他物件（如函式、其他 callable 和模組）的註釋字典的最佳實踐與 3.10 的最佳實踐相同，假設你沒有呼叫 inspect.get_annotations()：你應該使用三個：參數 getattr() 來存取物件的 __annotations__ 屬性。

不幸的是，這不是類別的最佳實踐。問題是，由於 __annotations__ 在類別上是選填的 (optional)，並且因為類別可以從其基底類別 (base class) 繼承屬性，所以存取類別的 __annotations__ 屬性可能會無意中回傳基底類別的註釋字典。舉例來說：

class Base:
    a: int = 3
    b: str = 'abc'

class Derived(Base):
    pass

print(Derived.__annotations__)

這將印出 (print) 來自 Base 的註釋字典，而不是 Derived。

如果你正在檢查的物件是一個類別 (isinstance(o, type))，你的程式碼將必須有一個單獨的程式碼路徑。在這種情況下，最佳實踐依賴 Python 3.9 及之前版本的實作細節 (implementation detail)：如果一個類別定義了註釋，它們將儲存在該類別的 __dict__ 字典中。由於類別可能定義了註釋，也可能沒有定義，因此最佳實踐是在類別字典上呼叫 get() 方法。

總而言之，以下是一些範例程式碼，可以安全地存取 Python 3.9 及先前版本中任意物件上的 __annotations__ 屬性：

if isinstance(o, type):
    ann = o.__dict__.get('__annotations__', None)
else:
    ann = getattr(o, '__annotations__', None)

運行此程式碼後，ann 應該是字典或 None。我們鼓勵你在進一步檢查之前使用 isinstance() 仔細檢查 ann 的型別。

請注意，某些外來 (exotic) 或格式錯誤 (malform) 的型別物件可能沒有 __dict__ 屬性，因此為了額外的安全，你可能還希望使用 getattr() 來存取 __dict__。

手動取消字串化註釋

在某些註釋可能被「字串化」的情況下，並且你希望評估這些字串以產生它們表示的 Python 值，最好呼叫 inspect.get_annotations() 來為你完成這項工作。

如果你使用的是 Python 3.9 或更早版本，或者由於某種原因你無法使用 inspect.get_annotations()，則需要複製其邏輯。我們鼓勵你檢查目前 Python 版本中 inspect.get_annotations() 的實作並遵循類似的方法。

簡而言之，如果你希望評估任意物件 o 上的字串化註釋：

如果 o 是一個模組，則在呼叫 eval() 時使用 o.__dict__ 作為全域變數。

如果 o 是一個類別，當呼叫 eval() 時，則使用 sys.modules[o.__module__].__dict__ 作為全域變數，使用 dict(vars(o)) 作為區域變數。

如果 o 是使用 functools.update_wrapper()、functools.wraps() 或 functools.partial() 包裝的 callable ，請依據需求，透過存取 o.__wrapped__ 或 o.func 來疊代解開它，直到找到根解包函式。

如果 o 是 callable（但不是類別），則在呼叫 eval() 時使用 o.__globals__ 作為全域變數。

然而，並非所有用作註釋的字串值都可以透過 eval() 成功轉換為 Python 值。理論上，字串值可以包含任何有效的字串，並且在實踐中，型別提示存在有效的用例，需要使用特定「無法」評估的字串值進行註釋。例如：

在 Python 3.10 支援 PEP 604 [https://peps.python.org/pep-0604/] 聯合型別 (union type) | 之前使用它。

Runtime 中不需要的定義，僅在 typing.TYPE_CHECKING 為 true 時匯入。

如果 eval() 嘗試計算這類型的值，它將失敗並引發例外。因此，在設計使用註釋的函式庫 API 時，建議僅在呼叫者 (caller) 明確請求時嘗試評估字串值。

任何 Python 版本中 __annotations__ 的最佳實踐

你應該避免直接指派給物件的 __annotations__ 成員。讓 Python 管理設定 __annotations__。

如果你直接指派給物件的 __annotations__ 成員，則應始終將其設為 dict 物件。

You should avoid accessing __annotations__ directly on any object. Instead, use annotationlib.get_annotations() (Python 3.14+) or inspect.get_annotations() (Python 3.10+).

如果直接存取物件的 __annotations__ 成員，則應確保它是字典，然後再嘗試檢查其內容。

你應該避免修改 __annotations__ 字典。

你應該避免刪除物件的 __annotations__ 屬性。

__annotations__ 奇異之處

在 Python 3 的所有版本中，如果沒有在該物件上定義註釋，則函式物件會延遲建立 (lazy-create) 註釋字典。你可以使用 del fn.__annotations__ 刪除 __annotations__ 屬性，但如果你隨後存取 fn.__annotations__，該物件將建立一個新的空字典，它將作為註釋儲存並傳回。在函式延遲建立註釋字典之前刪除函式上的註釋將拋出 AttributeError；連續兩次使用 del fn.__annotations__ 保證總是拋出 AttributeError 。

上一段的所有內容也適用於 Python 3.10 及更高版本中的類別和模組物件。

在 Python 3 的所有版本中，你可以將函式物件上的 __annotations__ 設定為 None。但是，隨後使用 fn.__annotations__ 存取該物件上的註釋將根據本節第一段的內容延遲建立一個空字典。對於任何 Python 版本中的模組和類別來說，情況並非如此；這些物件允許將 __annotations__ 設定為任何 Python 值，並且將保留設定的任何值。

如果 Python 為你字串化你的註釋（使用 from __future__ import annotations），並且你指定一個字串作為註釋，則該字串本身將被引用。實際上，註釋被引用了兩次。例如：

from __future__ import annotations
def foo(a: "str"): pass

print(foo.__annotations__)

這會印出 {'a': "'str'"}。這不應該被認為是一個「奇異的事」，他在這裡被簡單提及，因為他可能會讓人意想不到。

If you use a class with a custom metaclass and access __annotations__ on the class, you may observe unexpected behavior; see 749 [https://peps.python.org/pep-0749/#pep749-metaclasses] for some examples. You can avoid these quirks by using annotationlib.get_annotations() on Python 3.14+ or inspect.get_annotations() on Python 3.10+. On earlier versions of Python, you can avoid these bugs by accessing the annotations from the class's __dict__ (for example, cls.__dict__.get('__annotations__', None)).

In some versions of Python, instances of classes may have an __annotations__ attribute. However, this is not supported functionality. If you need the annotations of an instance, you can use type() to access its class (for example, annotationlib.get_annotations(type(myinstance)) on Python 3.14+).

隔離擴充模組

摘要

Traditionally, state belonging to Python extension modules was kept in C static variables, which have process-wide scope. This document describes problems of such per-process state and shows a safer way: per-module state.

The document also describes how to switch to per-module state where possible. This transition involves allocating space for that state, potentially switching from static types to heap types, and—perhaps most importantly—accessing per-module state from code.

Who should read this

This guide is written for maintainers of C-API extensions who would like to make that extension safer to use in applications where Python itself is used as a library.

背景

An interpreter is the context in which Python code runs. It contains configuration (e.g. the import path) and runtime state (e.g. the set of imported modules).

Python supports running multiple interpreters in one process. There are two cases to think about—users may run interpreters:

in sequence, with several Py_InitializeEx()/Py_FinalizeEx() cycles, and

in parallel, managing "sub-interpreters" using Py_NewInterpreter()/Py_EndInterpreter().

Both cases (and combinations of them) would be most useful when embedding Python within a library. Libraries generally shouldn't make assumptions about the application that uses them, which include assuming a process-wide "main Python interpreter".

Historically, Python extension modules don't handle this use case well. Many extension modules (and even some stdlib modules) use per-process global state, because C static variables are extremely easy to use. Thus, data that should be specific to an interpreter ends up being shared between interpreters. Unless the extension developer is careful, it is very easy to introduce edge cases that lead to crashes when a module is loaded in more than one interpreter in the same process.

Unfortunately, per-interpreter state is not easy to achieve. Extension authors tend to not keep multiple interpreters in mind when developing, and it is currently cumbersome to test the behavior.

Enter Per-Module State

Instead of focusing on per-interpreter state, Python's C API is evolving to better support the more granular per-module state. This means that C-level data should be attached to a module object. Each interpreter creates its own module object, keeping the data separate. For testing the isolation, multiple module objects corresponding to a single extension can even be loaded in a single interpreter.

Per-module state provides an easy way to think about lifetime and resource ownership: the extension module will initialize when a module object is created, and clean up when it's freed. In this regard, a module is just like any other PyObject*; there are no "on interpreter shutdown" hooks to think—or forget—about.

Note that there are use cases for different kinds of "globals": per-process, per-interpreter, per-thread or per-task state. With per-module state as the default, these are still possible, but you should treat them as exceptional cases: if you need them, you should give them additional care and testing. (Note that this guide does not cover them.)

Isolated Module Objects

The key point to keep in mind when developing an extension module is that several module objects can be created from a single shared library. For example:

>>> import sys
>>> import binascii
>>> old_binascii = binascii
>>> del sys.modules['binascii']
>>> import binascii  # 建立一個新的模組物件
>>> old_binascii == binascii
False

As a rule of thumb, the two modules should be completely independent. All objects and state specific to the module should be encapsulated within the module object, not shared with other module objects, and cleaned up when the module object is deallocated. Since this just is a rule of thumb, exceptions are possible (see Managing Global State), but they will need more thought and attention to edge cases.

While some modules could do with less stringent restrictions, isolated modules make it easier to set clear expectations and guidelines that work across a variety of use cases.

Surprising Edge Cases

Note that isolated modules do create some surprising edge cases. Most notably, each module object will typically not share its classes and exceptions with other similar modules. Continuing from the example above, note that old_binascii.Error and binascii.Error are separate objects. In the following code, the exception is not caught:

>>> old_binascii.Error == binascii.Error
False
>>> try:
...     old_binascii.unhexlify(b'qwertyuiop')
... except binascii.Error:
...     print('boo')
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
binascii.Error: Non-hexadecimal digit found

This is expected. Notice that pure-Python modules behave the same way: it is a part of how Python works.

The goal is to make extension modules safe at the C level, not to make hacks behave intuitively. Mutating sys.modules "manually" counts as a hack.

Making Modules Safe with Multiple Interpreters

Managing Global State

Sometimes, the state associated with a Python module is not specific to that module, but to the entire process (or something else "more global" than a module). For example:

The readline module manages the terminal.

A module running on a circuit board wants to control the on-board LED.

In these cases, the Python module should provide access to the global state, rather than own it. If possible, write the module so that multiple copies of it can access the state independently (along with other libraries, whether for Python or other languages). If that is not possible, consider explicit locking.

If it is necessary to use process-global state, the simplest way to avoid issues with multiple interpreters is to explicitly prevent a module from being loaded more than once per process—see Opt-Out: Limiting to One Module Object per Process.

Managing Per-Module State

To use per-module state, use multi-phase extension module initialization. This signals that your module supports multiple interpreters correctly.

Set PyModuleDef.m_size to a positive number to request that many bytes of storage local to the module. Usually, this will be set to the size of some module-specific struct, which can store all of the module's C-level state. In particular, it is where you should put pointers to classes (including exceptions, but excluding static types) and settings (e.g. csv's field_size_limit) which the C code needs to function.

備註

Another option is to store state in the module's __dict__, but you must avoid crashing when users modify __dict__ from Python code. This usually means error- and type-checking at the C level, which is easy to get wrong and hard to test sufficiently.

However, if module state is not needed in C code, storing it in __dict__ only is a good idea.

If the module state includes PyObject pointers, the module object must hold references to those objects and implement the module-level hooks m_traverse, m_clear and m_free. These work like tp_traverse, tp_clear and tp_free of a class. Adding them will require some work and make the code longer; this is the price for modules which can be unloaded cleanly.

An example of a module with per-module state is currently available as xxlimited [https://github.com/python/cpython/blob/master/Modules/xxlimited.c]; example module initialization shown at the bottom of the file.

Opt-Out: Limiting to One Module Object per Process

A non-negative PyModuleDef.m_size signals that a module supports multiple interpreters correctly. If this is not yet the case for your module, you can explicitly make your module loadable only once per process. For example:

// A process-wide flag
static int loaded = 0;

// Mutex to provide thread safety (only needed for free-threaded Python)
static PyMutex modinit_mutex = {0};

static int
exec_module(PyObject* module)
{
    PyMutex_Lock(&modinit_mutex);
    if (loaded) {
        PyMutex_Unlock(&modinit_mutex);
        PyErr_SetString(PyExc_ImportError,
                        "cannot load module more than once per process");
        return -1;
    }
    loaded = 1;
    PyMutex_Unlock(&modinit_mutex);
    // ... rest of initialization
}

If your module's PyModuleDef.m_clear function is able to prepare for future re-initialization, it should clear the loaded flag. In this case, your module won't support multiple instances existing concurrently, but it will, for example, support being loaded after Python runtime shutdown (Py_FinalizeEx()) and re-initialization (Py_Initialize()).

Module State Access from Functions

Accessing the state from module-level functions is straightforward. Functions get the module object as their first argument; for extracting the state, you can use PyModule_GetState:

static PyObject *
func(PyObject *module, PyObject *args)
{
    my_struct *state = (my_struct*)PyModule_GetState(module);
    if (state == NULL) {
        return NULL;
    }
    // ... rest of logic
}

備註

PyModule_GetState may return NULL without setting an exception if there is no module state, i.e. PyModuleDef.m_size was zero. In your own module, you're in control of m_size, so this is easy to prevent.

Heap Types

Traditionally, types defined in C code are static; that is, static PyTypeObject structures defined directly in code and initialized using PyType_Ready().

Such types are necessarily shared across the process. Sharing them between module objects requires paying attention to any state they own or access. To limit the possible issues, static types are immutable at the Python level: for example, you can't set str.myattribute = 123.

CPython 實作細節： Sharing truly immutable objects between interpreters is fine, as long as they don't provide access to mutable objects. However, in CPython, every Python object has a mutable implementation detail: the reference count. Changes to the refcount are guarded by the GIL. Thus, code that shares any Python objects across interpreters implicitly depends on CPython's current, process-wide GIL.

Because they are immutable and process-global, static types cannot access "their" module state. If any method of such a type requires access to module state, the type must be converted to a heap-allocated type, or heap type for short. These correspond more closely to classes created by Python's class statement.

For new modules, using heap types by default is a good rule of thumb.

Changing Static Types to Heap Types

Static types can be converted to heap types, but note that the heap type API was not designed for "lossless" conversion from static types—that is, creating a type that works exactly like a given static type. So, when rewriting the class definition in a new API, you are likely to unintentionally change a few details (e.g. pickleability or inherited slots). Always test the details that are important to you.

Watch out for the following two points in particular (but note that this is not a comprehensive list):

Unlike static types, heap type objects are mutable by default. Use the Py_TPFLAGS_IMMUTABLETYPE flag to prevent mutability.

Heap types inherit tp_new by default, so it may become possible to instantiate them from Python code. You can prevent this with the Py_TPFLAGS_DISALLOW_INSTANTIATION flag.

Defining Heap Types

Heap types can be created by filling a PyType_Spec structure, a description or "blueprint" of a class, and calling PyType_FromModuleAndSpec() to construct a new class object.

備註

Other functions, like PyType_FromSpec(), can also create heap types, but PyType_FromModuleAndSpec() associates the module with the class, allowing access to the module state from methods.

The class should generally be stored in both the module state (for safe access from C) and the module's __dict__ (for access from Python code).

Garbage-Collection Protocol

Instances of heap types hold a reference to their type. This ensures that the type isn't destroyed before all its instances are, but may result in reference cycles that need to be broken by the garbage collector.

To avoid memory leaks, instances of heap types must implement the garbage collection protocol. That is, heap types should:

Have the Py_TPFLAGS_HAVE_GC flag.

Define a traverse function using Py_tp_traverse, which visits the type (e.g. using Py_VISIT(Py_TYPE(self))).

Please refer to the documentation of Py_TPFLAGS_HAVE_GC and tp_traverse for additional considerations.

The API for defining heap types grew organically, leaving it somewhat awkward to use in its current state. The following sections will guide you through common issues.

tp_traverse in Python 3.8 and lower

The requirement to visit the type from tp_traverse was added in Python 3.9. If you support Python 3.8 and lower, the traverse function must not visit the type, so it must be more complicated:

static int my_traverse(PyObject *self, visitproc visit, void *arg)
{
    if (Py_Version >= 0x03090000) {
        Py_VISIT(Py_TYPE(self));
    }
    return 0;
}

Unfortunately, Py_Version was only added in Python 3.11. As a replacement, use:

PY_VERSION_HEX, if not using the stable ABI, or

sys.version_info (via PySys_GetObject() and PyArg_ParseTuple()).

Delegating tp_traverse

If your traverse function delegates to the tp_traverse of its base class (or another type), ensure that Py_TYPE(self) is visited only once. Note that only heap type are expected to visit the type in tp_traverse.

For example, if your traverse function includes:

base->tp_traverse(self, visit, arg)

...and base may be a static type, then it should also include:

if (base->tp_flags & Py_TPFLAGS_HEAPTYPE) {
    // a heap type's tp_traverse already visited Py_TYPE(self)
} else {
    if (Py_Version >= 0x03090000) {
        Py_VISIT(Py_TYPE(self));
    }
}

It is not necessary to handle the type's reference count in tp_new and tp_clear.

定義 tp_dealloc

If your type has a custom tp_dealloc function, it needs to:

call PyObject_GC_UnTrack() before any fields are invalidated, and

decrement the reference count of the type.

To keep the type valid while tp_free is called, the type's refcount needs to be decremented after the instance is deallocated. For example:

static void my_dealloc(PyObject *self)
{
    PyObject_GC_UnTrack(self);
    ...
    PyTypeObject *type = Py_TYPE(self);
    type->tp_free(self);
    Py_DECREF(type);
}

The default tp_dealloc function does this, so if your type does not override tp_dealloc you don't need to add it.

Not overriding tp_free

The tp_free slot of a heap type must be set to PyObject_GC_Del(). This is the default; do not override it.

避免使用 PyObject_New

GC-tracked objects need to be allocated using GC-aware functions.

If you use PyObject_New() or PyObject_NewVar():

Get and call type's tp_alloc slot, if possible. That is, replace TYPE *o = PyObject_New(TYPE, typeobj) with:

TYPE *o = typeobj->tp_alloc(typeobj, 0);

Replace o = PyObject_NewVar(TYPE, typeobj, size) with the same, but use size instead of the 0.

If the above is not possible (e.g. inside a custom tp_alloc), call PyObject_GC_New() or PyObject_GC_NewVar():

TYPE *o = PyObject_GC_New(TYPE, typeobj);

TYPE *o = PyObject_GC_NewVar(TYPE, typeobj, size);

Module State Access from Classes

If you have a type object defined with PyType_FromModuleAndSpec(), you can call PyType_GetModule() to get the associated module, and then PyModule_GetState() to get the module's state.

To save a some tedious error-handling boilerplate code, you can combine these two steps with PyType_GetModuleState(), resulting in:

my_struct *state = (my_struct*)PyType_GetModuleState(type);
if (state == NULL) {
    return NULL;
}

Module State Access from Regular Methods

Accessing the module-level state from methods of a class is somewhat more complicated, but is possible thanks to API introduced in Python 3.9. To get the state, you need to first get the defining class, and then get the module state from it.

The largest roadblock is getting the class a method was defined in, or that method's "defining class" for short. The defining class can have a reference to the module it is part of.

Do not confuse the defining class with Py_TYPE(self). If the method is called on a subclass of your type, Py_TYPE(self) will refer to that subclass, which may be defined in different module than yours.

備註

The following Python code can illustrate the concept. Base.get_defining_class returns Base even if type(self) == Sub:

class Base:
    def get_type_of_self(self):
        return type(self)

    def get_defining_class(self):
        return __class__

class Sub(Base):
    pass

For a method to get its "defining class", it must use the METH_METHOD | METH_FASTCALL | METH_KEYWORDS calling convention and the corresponding PyCMethod signature:

PyObject *PyCMethod(
    PyObject *self,               // object the method was called on
    PyTypeObject *defining_class, // defining class
    PyObject *const *args,        // C array of arguments
    Py_ssize_t nargs,             // length of "args"
    PyObject *kwnames)            // NULL, or dict of keyword arguments

Once you have the defining class, call PyType_GetModuleState() to get the state of its associated module.

舉例來說：

static PyObject *
example_method(PyObject *self,
        PyTypeObject *defining_class,
        PyObject *const *args,
        Py_ssize_t nargs,
        PyObject *kwnames)
{
    my_struct *state = (my_struct*)PyType_GetModuleState(defining_class);
    if (state == NULL) {
        return NULL;
    }
    ... // rest of logic
}

PyDoc_STRVAR(example_method_doc, "...");

static PyMethodDef my_methods[] = {
    {"example_method",
      (PyCFunction)(void(*)(void))example_method,
      METH_METHOD|METH_FASTCALL|METH_KEYWORDS,
      example_method_doc}
    {NULL},
}

Module State Access from Slot Methods, Getters and Setters

備註

This is new in Python 3.11.

Slot methods—the fast C equivalents for special methods, such as nb_add for __add__ or tp_new for initialization—have a very simple API that doesn't allow passing in the defining class, unlike with PyCMethod. The same goes for getters and setters defined with PyGetSetDef.

To access the module state in these cases, use the PyType_GetModuleByDef() function, and pass in the module definition. Once you have the module, call PyModule_GetState() to get the state:

PyObject *module = PyType_GetModuleByDef(Py_TYPE(self), &module_def);
my_struct *state = (my_struct*)PyModule_GetState(module);
if (state == NULL) {
    return NULL;
}

PyType_GetModuleByDef() works by searching the method resolution order (i.e. all superclasses) for the first superclass that has a corresponding module.

備註

In very exotic cases (inheritance chains spanning multiple modules created from the same definition), PyType_GetModuleByDef() might not return the module of the true defining class. However, it will always return a module with the same definition, ensuring a compatible C memory layout.

Lifetime of the Module State

When a module object is garbage-collected, its module state is freed. For each pointer to (a part of) the module state, you must hold a reference to the module object.

Usually this is not an issue, because types created with PyType_FromModuleAndSpec(), and their instances, hold a reference to the module. However, you must be careful in reference counting when you reference module state from other places, such as callbacks for external libraries.

Open Issues

Several issues around per-module state and heap types are still open.

Discussions about improving the situation are best held on the discuss forum under c-api tag [https://discuss.python.org/c/core-dev/c-api/30].

Per-Class Scope

It is currently (as of Python 3.11) not possible to attach state to individual types without relying on CPython implementation details (which may change in the future—perhaps, ironically, to allow a proper solution for per-class scope).

Lossless Conversion to Heap Types

The heap type API was not designed for "lossless" conversion from static types; that is, creating a type that works exactly like a given static type.

計時器檔案描述器 (timerfd) 指南

發佈版本:

1.13

此篇指南探討 Python 對 Linux 計時器檔案描述器的支援。

範例

以下範例顯示如何使用計時器檔案描述器來每秒執行函式兩次：

# 實際腳本應該使用非阻塞計時器，
# 在這裡為了簡單起見我們使用阻塞計時器。
import os, time

# 建立計時器檔案描述器
fd = os.timerfd_create(time.CLOCK_REALTIME)

# 在 1 秒後開始計時器，間隔為半秒
os.timerfd_settime(fd, initial=1, interval=0.5)

try:
    # 處理計時器事件四次。
    for _ in range(4):
        # read() 會阻塞直到計時器到期
        _ = os.read(fd, 8)
        print("Timer expired")
finally:
    # 記得關閉計時器檔案描述器！
    os.close(fd)

為了避免由 float 型別造成的精度損失，計時器檔案描述器允許使用函式的 _ns 變體以整數奈秒為單位指定初始到期時間和間隔。

此範例展示如何將 epoll() 與計時器檔案描述器一起使用，用於等待檔案描述器直到它準備好讀取：

import os, time, select, socket, sys

# 建立 epoll 物件
ep = select.epoll()

# 在此範例中，使用回送位址 (loopback address) 向伺服器發送 "stop" 命令。
#
# $ telnet 127.0.0.1 1234
# Trying 127.0.0.1...
# Connected to 127.0.0.1.
# Escape character is '^]'.
# stop
# Connection closed by foreign host.
#
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(("127.0.0.1", 1234))
sock.setblocking(False)
sock.listen(1)
ep.register(sock, select.EPOLLIN)

# 以非阻塞模式建立計時器檔案描述器。
num = 3
fds = []
for _ in range(num):
    fd = os.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
    fds.append(fd)
    # 為讀取事件註冊計時器檔案描述器
    ep.register(fd, select.EPOLLIN)

# 使用 os.timerfd_settime_ns() 以奈秒為單位啟動計時器。
# 計時器 1 每 0.25 秒觸發一次；計時器 2 每 0.5 秒觸發一次；以此類推
for i, fd in enumerate(fds, start=1):
    one_sec_in_nsec = 10**9
    i = i * one_sec_in_nsec
    os.timerfd_settime_ns(fd, initial=i//4, interval=i//4)

timeout = 3
try:
    conn = None
    is_active = True
    while is_active:
        # 等待計時器在 3 秒內到期。
        # epoll.poll() 回傳一個 (fd, event) 配對的串列。
        # fd 是檔案描述器。
        # sock 和 conn[=socket.accept() 的回傳值] 是 socket 物件，不是檔案描述器。
        # 所以要使用 sock.fileno() 和 conn.fileno() 來取得檔案描述器。
        events = ep.poll(timeout)

        # 如果同時有多個計時器檔案描述器準備好讀取，
        # epoll.poll() 會回傳一個 (fd, event) 配對的串列。
        #
        # 在此範例設定中，
        #    第 1 個計時器在 0.25 秒內每 0.25 秒觸發一次。(0.25, 0.5, 0.75, 1.0, ...)
        #    第 2 個計時器在 0.5 秒內每 0.5 秒觸發一次。(0.5, 1.0, 1.5, 2.0, ...)
        #    第 3 個計時器在 0.75 秒內每 0.75 秒觸發一次。(0.75, 1.5, 2.25, 3.0, ...)
        #
        #    在 0.25 秒時，只有第 1 個計時器觸發。
        #    在 0.5 秒時，第 1 個計時器和第 2 個計時器同時觸發。
        #    在 0.75 秒時，第 1 個計時器和第 3 個計時器同時觸發。
        #    在 1.5 秒時，第 1、2、3 個計時器同時觸發。
        #
        # 如果計時器檔案描述器自上次 os.read() 呼叫以來被觸發多次，
        # os.read() 會以主機類別位元組順序回傳被觸發次數。
        print(f"Signaled events={events}")
        for fd, event in events:
            if event & select.EPOLLIN:
                if fd == sock.fileno():
                    # 檢查是否有連線請求。
                    print(f"Accepting connection {fd}")
                    conn, addr = sock.accept()
                    conn.setblocking(False)
                    print(f"Accepted connection {conn} from {addr}")
                    ep.register(conn, select.EPOLLIN)
                elif conn and fd == conn.fileno():
                    # 檢查是否有資料要讀取。
                    print(f"Reading data {fd}")
                    data = conn.recv(1024)
                    if data:
                        # 為了安全起見，你應該捕獲 UnicodeDecodeError 例外。
                        cmd = data.decode()
                        if cmd.startswith("stop"):
                            print(f"Stopping server")
                            is_active = False
                        else:
                            print(f"Unknown command: {cmd}")
                    else:
                        # 沒有更多資料，關閉連線
                        print(f"Closing connection {fd}")
                        ep.unregister(conn)
                        conn.close()
                        conn = None
                elif fd in fds:
                    print(f"Reading timer {fd}")
                    count = int.from_bytes(os.read(fd, 8), byteorder=sys.byteorder)
                    print(f"Timer {fds.index(fd) + 1} expired {count} times")
                else:
                    print(f"Unknown file descriptor {fd}")
finally:
    for fd in fds:
        ep.unregister(fd)
        os.close(fd)
    ep.close()

此範例展示如何將 select() 與計時器檔案描述器一起使用，用於等待檔案描述器直到它準備好讀取：

import os, time, select, socket, sys

# 在此範例中，使用回送位址向伺服器發送 "stop" 命令。
#
# $ telnet 127.0.0.1 1234
# Trying 127.0.0.1...
# Connected to 127.0.0.1.
# Escape character is '^]'.
# stop
# Connection closed by foreign host.
#
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(("127.0.0.1", 1234))
sock.setblocking(False)
sock.listen(1)

# 以非阻塞模式建立計時器檔案描述器。
num = 3
fds = [os.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
       for _ in range(num)]
select_fds = fds + [sock]

# 使用 os.timerfd_settime() 以秒為單位啟動計時器。
# 計時器 1 每 0.25 秒觸發一次；計時器 2 每 0.5 秒觸發一次；以此類推
for i, fd in enumerate(fds, start=1):
   os.timerfd_settime(fd, initial=i/4, interval=i/4)

timeout = 3
try:
    conn = None
    is_active = True
    while is_active:
       # 等待計時器在 3 秒內到期。
       # select.select() 回傳檔案描述器或物件的串列。
       rfd, wfd, xfd = select.select(select_fds, select_fds, select_fds, timeout)
       for fd in rfd:
           if fd == sock:
               # 檢查是否有連線請求。
               print(f"Accepting connection {fd}")
               conn, addr = sock.accept()
               conn.setblocking(False)
               print(f"Accepted connection {conn} from {addr}")
               select_fds.append(conn)
           elif conn and fd == conn:
               # 檢查是否有資料要讀取。
               print(f"Reading data {fd}")
               data = conn.recv(1024)
               if data:
                   # 為了安全起見，你應該捕獲 UnicodeDecodeError 例外。
                   cmd = data.decode()
                   if cmd.startswith("stop"):
                       print(f"Stopping server")
                       is_active = False
                   else:
                       print(f"Unknown command: {cmd}")
               else:
                   # 沒有更多資料，關閉連線
                   print(f"Closing connection {fd}")
                   select_fds.remove(conn)
                   conn.close()
                   conn = None
           elif fd in fds:
               print(f"Reading timer {fd}")
               count = int.from_bytes(os.read(fd, 8), byteorder=sys.byteorder)
               print(f"Timer {fds.index(fd) + 1} expired {count} times")
           else:
               print(f"Unknown file descriptor {fd}")
finally:
    for fd in fds:
       os.close(fd)
    sock.close()
    sock = None

Python 2.3 方法解析順序

備註

這是一份歷史文件，作為正式文件的附錄提供。此處討論的方法解析順序 (Method Resolution Order) 是在 Python 2.3 中 引入 的，但仍在後續版本中使用，包括 Python 3。

作者：Michele Simionato [https://www.phyast.pitt.edu/~micheles/]。

摘要:

此文件適用於想要了解 Python 2.3 中使用的 C3 方法解析順序的 Python 程式設計師。雖然它不是為初學者準備的，但透過許多實際範例進行教學。我沒找到其他具有相同範圍的公開文件，因此這應該很有用。

免責聲明：

我根據 Python 2.3 授權條款將此文件捐贈給 Python 軟體基金會。如同往常，我警告讀者，以下內容 *應該 是正確的，但我不提供任何保證。使用時風險自負！*

致謝：

感謝 Python 郵件列表中所有給予我支持的人。Paul Foley 指出了各種不精確之處，並促使我加入了區域優先順序（local precedence ordering）的部分。David Goodger 協助 reStructuredText 的格式化。David Mertz 協助編輯。最後，Guido van Rossum 熱情地將此文件加入到 Python 2.3 官方首頁。

開端

Felix qui potuit rerum cognoscere causas -- Virgilius

一切始於 Samuele Pedroni 向 Python 開發郵件列表發表的貼文 [1]。在他的貼文中，Samuele 指出 Python 2.2 的方法解析順序不具單調性（monotonic），並提議以 C3 方法解析順序來取代。Guido 同意他的論點，因此 Python 2.3 現在使用 C3。C3 方法本身與 Python 無關，因為它是由研究 Dylan 語言的人所發明，並在一篇針對 Lisp 程式設計師的論文 [2] 中描述。本文為想要了解此變更原因的 Python 程式設計師提供了 C3 演算法（希望是）易讀的討論。

首先讓我指出，我要說的僅適用於 Python 2.2 中引入的 新式類別（new style classes）：經典類別（classic classes） 維持其舊有的方法解析順序，即深度優先然後由左至右。因此，經典類別的舊程式碼不會受到影響；即使原則上 Python 2.2 新式類別的程式碼可能會受影響，但實際上 C3 解析順序與 Python 2.2 方法解析順序不同的情況極為罕見，因此預期不會真正破壞程式碼。因此：

別怕！

此外，除非你大量使用多重繼承且有複雜的類別階層，否則你無需了解 C3 演算法，可以輕鬆跳過本文。另一方面，如果你真的想知道多重繼承如何運作，那麼本文就是為你準備的。好消息是，事情並不像你想像的那樣複雜。

讓我從一些基本定義開始。

給定複雜多重繼承階層中的類別 C，要指定方法被覆寫（override）的順序並非易事，也就是要指定 C 的祖先順序。

類別 C 的祖先串列（包含類別本身），從最近的祖先到最遠的祖先排序，稱為類別優先串列（class precedence list）或 C 的線性化（linearization）。

方法解析順序 (Method Resolution Order, MRO) 是建構線性化的一組規則。在 Python 文獻中，習慣用語「C 的 MRO」也是 C 類別線性化的同義詞。

例如，在單一繼承階層的情況下，如果 C 是 C1 的子類別，而 C1 是 C2 的子類別，那麼 C 的線性化就是串列 [C, C1, C2]。然而，在多重繼承階層中，線性化的建構更加複雜，因為要建構一個遵守區域優先順序（local precedence ordering） 和單調性（monotonicity） 的線性化更加困難。

我將在稍後討論區域優先順序，但可以在此給出單調性的定義。當以下條件為真時，MRO 具有單調性：如果 C1 在 C 的線性化中先於 C2，那麼 C1 在 C 的任何子類別的線性化中也先於 C2。否則，衍生新類別這個看似無害的操作可能會改變方法的解析順序，進而引入非常微妙的錯誤。稍後將展示發生這種情況的範例。

並非所有類別都能進行線性化。在複雜的階層結構中，有些情況下無法衍生出一個類別，使其線性化遵守所有所需的屬性。

以下是這種情況的範例。考慮以下階層結構

>>> O = object
>>> class X(O): pass
>>> class Y(O): pass
>>> class A(X,Y): pass
>>> class B(Y,X): pass

可以用以下繼承圖來表示，其中我用 O 標示 object 類別，這是新式類別的任何階層結構的起點：

 -----------
|           |
|    O      |
|  /   \    |
 - X    Y  /
   |  / | /
   | /  |/
   A    B
   \   /
     ?

在這種情況下，不可能從 A 和 B 衍生出新的類別 C，因為 X 在 A 中先於 Y，但 Y 在 B 中先於 X，因此 C 的方法解析順序會產生歧義。

Python 2.3 在這種情況下會引發例外（TypeError: MRO conflict among bases Y, X），防止程式設計師建立有歧義的階層結構。Python 2.2 則不會引發例外，而是選擇 ad hoc 順序（在這種情況下為 CABXYO）。

C3 方法解析順序

讓我介紹一些簡單的符號標示法，這對以下討論很有用。我將使用簡寫符號：

C1 C2 ... CN

用來表示類別串列 [C1, C2, ... , CN]。

串列的 head（頭部）是其第一個元素：

head = C1

而 tail（尾部）是串列的其餘部分：

tail = C2 ... CN.

我還將使用以下符號：

C + (C1 C2 ... CN) = C C1 C2 ... CN

標示串列的和 [C] + [C1, C2, ..., CN]。

現在我就可以繼續解釋 MRO 在 Python 2.3 中的運作方式。

考慮多重繼承階層結構中的類別 C，C 從基底類別 B1、B2、...、BN 繼承。我們想計算類別 C 的線性化 L[C]。規則如下：

C 的線性化是 C 加上父類別線性化的合併以及父類別串列的和。

用符號標示：

L[C(B1 ... BN)] = C + merge(L[B1] ... L[BN], B1 ... BN)

特別是如果 C 是沒有父類別的 object 類別，那麼線性化是簡單的：

L[object] = object.

然而，一般來說必須根據以下規則來計算合併：

取第一個串列的頭部，即 L[B1][0]；如果此頭部不在其他任何串列的尾部中，那麼將它加入到 C 的線性化中，並從合併中的所有串列移除它；否則查看下一個串列的頭部，如果它是一個好的頭部就取它。然後重複此操作，直到所有類別都被移除或無法找到好的頭部。在後面這種情況下，無法建構合併，Python 2.3 將拒絕建立類別 C 並引發例外。

此規則確保合併操作保留順序（如果順序可以被保留）。另一方面，如果無法保留順序（如上面討論的嚴重順序分歧的範例），則無法計算合併。

如果 C 只有一個父類別（單一繼承），則合併的計算是微不足道的。在這種情況下：

L[C(B)] = C + merge(L[B],B) = C + L[B]

但是，在多重繼承的情況下，事情更加複雜，我不指望你能在沒有幾個範例的情況下理解這個規則 ;-)

範例

第一個例子，請參考以下階層結構：

>>> O = object
>>> class F(O): pass
>>> class E(O): pass
>>> class D(O): pass
>>> class C(D,F): pass
>>> class B(D,E): pass
>>> class A(B,C): pass

在這種情況下，繼承圖可以繪製為：

                          6
                         ---
Level 3                 | O |                  （更廣泛）
                      /  ---  \
                     /    |    \                      |
                    /     |     \                     |
                   /      |      \                    |
                  ---    ---    ---                   |
Level 2        3 | D | 4| E |  | F | 5                |
                  ---    ---    ---                   |
                   \  \ _ /       |                   |
                    \    / \ _    |                   |
                     \  /      \  |                   |
                      ---      ---                    |
Level 1            1 | B |    | C | 2                 |
                      ---      ---                    |
                        \      /                      |
                         \    /                      \ /
                           ---
Level 0                 0 | A |                （更專精）
                           ---

O、D、E 和 F 的線性化很簡單：

L[O] = O
L[D] = D O
L[E] = E O
L[F] = F O

B 的線性化可以計算為：

L[B] = B + merge(DO, EO, DE)

我們看到 D 是一個好的頭部，因此我們取它，並將其簡化為 merge(O,EO,E)。現在 O 不是一個好的頭部，因為它位於序列 EO 的尾部。在這種情況下，規則說我們必須跳到下一個序列。然後我們看到 E 是一個好的頭部；我們取它，並簡化為計算 merge(O, O) 得出 O。因此：

L[B] =  B D E O

使用相同的程序可以發現：

L[C] = C + merge(DO,FO,DF)
     = C + D + merge(O,FO,F)
     = C + D + F + merge(O,O)
     = C D F O

現在我們可以計算出：

L[A] = A + merge(BDEO,CDFO,BC)
     = A + B + merge(DEO,CDFO,C)
     = A + B + C + merge(DEO,DFO)
     = A + B + C + D + merge(EO,FO)
     = A + B + C + D + E + merge(O,FO)
     = A + B + C + D + E + F + merge(O,O)
     = A B C D E F O

在此範例中，線性化是根據繼承層級以相當不錯的方式排序的，因為較低層級（即更專精的類別）具有更高的優先級（請參見繼承圖）。但是這不是一般情況。

第二個範例的線性化之計算我留給讀者當作練習：

>>> O = object
>>> class F(O): pass
>>> class E(O): pass
>>> class D(O): pass
>>> class C(D,F): pass
>>> class B(E,D): pass
>>> class A(B,C): pass

與上一個範例的唯一區別是 B(D,E) --> B(E,D) 的變化；但是即使是這樣小小的修改，也完全改變了階層結構的順序：

                           6
                          ---
Level 3                  | O |
                       /  ---  \
                      /    |    \
                     /     |     \
                    /      |      \
                  ---     ---    ---
Level 2        2 | E | 4 | D |  | F | 5
                  ---     ---    ---
                   \      / \     /
                    \    /   \   /
                     \  /     \ /
                      ---     ---
Level 1            1 | B |   | C | 3
                      ---     ---
                       \       /
                        \     /
                          ---
Level 0                0 | A |
                          ---

請注意，階層結構的第二層中的類別 E，先於階層結構第一層的類別 C，即 E 比 C 更專精，即使它處於更高層。

懶惰的程式設計師可以直接從 Python 2.2 取得 MRO，因為在這種情況下，它與 Python 2.3 線性化一致。呼叫類別 A 的 mro() 方法就足夠了：

>>> A.mro()
[<class 'A'>, <class 'B'>, <class 'E'>,
<class 'C'>, <class 'D'>, <class 'F'>,
<class 'object'>]

最後，讓我考慮第一部分中討論的範例，涉及嚴重的順序分歧。在這種情況下，計算 O、X、Y、A 和 B 的線性化是很簡單的：

L[O] = 0
L[X] = X O
L[Y] = Y O
L[A] = A X Y O
L[B] = B Y X O

但是，我們不可能計算出從 A 和 B 繼承的類別 C 的線性化：

L[C] = C + merge(AXYO, BYXO, AB)
     = C + A + merge(XYO, BYXO, B)
     = C + A + B + merge(XYO, YXO)

在這一點上，我們無法合併串列 XYO 和 YXO，因為 X 位於 YXO 的尾部，而 Y 則位於 XYO 的尾部：因此，沒有好的頭部，C3 演算法停止。Python 2.3 會引發錯誤而拒絕建立類別 C。

不良的方法解析順序

當 MRO 打破諸如區域優先順序和單調性之類的基本屬性時，MRO 是不良的。在本節中，我將證明經典類別的 MRO 和 Python 2.2 的新式類別的 MRO 都是不好的。

從區域優先順序開始更容易。考慮以下範例：

>>> F=type('Food',(),{'remember2buy':'spam'})
>>> E=type('Eggs',(F,),{'remember2buy':'eggs'})
>>> G=type('GoodFood',(F,E),{}) # under Python 2.3 this is an error!

包含繼承圖

             O
             |
(buy spam)   F
             | \
             | E   (buy eggs)
             | /
             G

      (buy eggs or spam ?)

我們看到類別 G 從 F 和 E 繼承，F 在 E 之前：因此，我們希望屬性 G.remember2buy 被 F.remember2buy 繼承，而不是 E.remember2buy：儘管如此，Python 2.2 給出

>>> G.remember2buy
'eggs'

這是區域優先順序的破壞，因為區域優先串列中的順序，即 G 的父類別串列，在 Python 2.2 的 G 的線性化中不被保留：

L[G,P22]= G E F object   # F *跟隨* E

有人可能會說，F 在 Python 2.2 線性化中跟隨 E 的原因是 F 比 E 特化程度較低，因為 F 是 E 的超類別；然而，局部優先順序的破壞非常不直覺且容易出錯。尤其如此，因為它與舊式類別不同：

>>> class F: remember2buy='spam'
>>> class E(F): remember2buy='eggs'
>>> class G(F,E): pass
>>> G.remember2buy
'spam'

在這種情況下，MRO 是 GFEF 並且保留區域優先順序。

通常應避免諸如上一個等階層結構，因為尚不清楚 F 是否應覆蓋 E 或反過來。 Python 2.3 透過在建立類別 G 時引發例外來解決歧義，從而有效地阻止程式設計師產生模棱兩可的階層結構。原因是當這樣合併時 C3 演算法會失敗：

merge(FO,EFO,FE)

無法計算，因為 F 在 EFO 的尾部，而 E 在 FE 的尾部。

真正的解決方案是設計一個非歧義的階層結構，即源自 E 和 F（更具體的第一）而不是 F 和 E；在這種情況下，MRO 毫無疑問是 GEF。

           O
           |
           F (spam)
         / |
(eggs)   E |
         \ |
           G
             (eggs, no doubt)

Python 2.3 迫使程式設計師要編寫良好（或至少較不易於出錯）的階層結構。

與之相關的是，我指出 Python 2.3 演算法足夠聰明，可以識別出明顯的錯誤，例如父類別串列中類別的重複：

>>> class A(object): pass
>>> class C(A,A): pass # error
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: duplicate base class A

在這種情況下，Python 2.2（無論是經典類別還是新式類別）不會引發任何例外。

最後，我想指出我們從這個範例中學到的兩個教訓：

儘管名稱如此，但不僅是方法的解析順序，MRO 也決定了屬性的解析順序；

Pythonistas 的預設食物是 spam！（但是你已經知道 ;-)

在討論了區域優先順序的問題之後，現在讓我考慮單調性問題。我的目標是表明經典類別的 MRO 或 Python 2.2 新式類別都不是單調的。

為了證明經典類別的 MRO 是非單調的，查看鑽石圖就足夠了：

   C
  / \
 /   \
A     B
 \   /
  \ /
   D

可以很容易地辨別出這種不一致：

L[B,P21] = B C        # B 優先於 C：B 的方法勝出
L[D,P21] = D A C B C  # B 跟隨 C：C 的方法勝出！

另一方面，Python 2.2 和 2.3 MRO 沒有問題，它們兩個都給出了：

L[D] = D A B C

Guido 在他的文章 [3] 中指出，經典的 MRO 在實踐中還不錯，因為通常可以避開經典類別的鑽石圖。但是所有新式類別都從 object 繼承，因此鑽石圖是不可避免的，並且在每個多重繼承圖中都出現了不一致之處。

Python 2.2 的 MRO 讓打破單調性變得困難，但並非不可能。以下最初由 Samuele Pedroni 提供的範例展示 Python 2.2 的 MRO 是非單調的：

>>> class A(object): pass
>>> class B(object): pass
>>> class C(object): pass
>>> class D(object): pass
>>> class E(object): pass
>>> class K1(A,B,C): pass
>>> class K2(D,B,E): pass
>>> class K3(D,A):   pass
>>> class Z(K1,K2,K3): pass

以下是根據 C3 MRO 的線性化（讀者應練習驗證這些線性化並繪製繼承圖 ;-) ：

L[A] = A O
L[B] = B O
L[C] = C O
L[D] = D O
L[E] = E O
L[K1]= K1 A B C O
L[K2]= K2 D B E O
L[K3]= K3 D A O
L[Z] = Z K1 K2 K3 D A B C E O

Python 2.2 給出了 A、B、C、D、E、K1、K2 和 K3 完全相同的線性化，但是 Z 的線性化卻不同：

L[Z,P22] = Z K1 K3 A K2 D B C E O

顯然，這種線性化是錯誤的，因為 A 在 D 之前，而在 K3 的線性化中，A 在 D 之後。換句話說，在 K3 中由 D 衍生的方法會覆寫由 A 衍生的方法，但在 Z 中（它仍然是 K3 的子類別），由 A 衍生的方法卻覆寫由 D 衍生的方法！這是對單調性的違反。此外，Z 的 Python 2.2 線性化也與局部優先順序不一致，因為類別 Z 的局部優先串列是 [K1, K2, K3]（K2 先於 K3），但在 Z 的線性化中 K2 跟隨 K3。這些問題解釋了為什麼 2.2 規則被摒棄而採用 C3 規則。

結語

本節適用於那些不耐煩、所有先前部分都跳過並直接滑到最後的讀者，也適用於懶得鍛鍊大腦的程式設計師。最後，這也是針對一些自負的程式設計師，不然她/他也不會想閱讀有關多重繼承階層中 C3 方法解析順序的文章；-)擁有這三種美德（注意是同時擁有，不是分開）就值得獲得獎品：獎品是一個簡短的 Python 2.2 腳本，可以幫你計算 2.3 MRO 而不用傷腦筋。只需更改最後一行就可以試跑我在本文中討論的各種範例。

#<mro.py>

"""Samuele Pedroni 撰寫的 C3 演算法（由我改善了可讀性）。"""

class __metaclass__(type):
    "所有類別都會被神奇地修改以便美觀地列印"
    __repr__ = lambda cls: cls.__name__

class ex_2:
    "嚴重的順序分歧" # 來自 Guido
    class O: pass
    class X(O): pass
    class Y(O): pass
    class A(X,Y): pass
    class B(Y,X): pass
    try:
        class Z(A,B): pass # 在 Python 2.2 中會建立 Z(A,B)
    except TypeError:
        pass # 在 Python 2.3 中無法建立 Z(A,B)

class ex_5:
    "我的第一個範例"
    class O: pass
    class F(O): pass
    class E(O): pass
    class D(O): pass
    class C(D,F): pass
    class B(D,E): pass
    class A(B,C): pass

class ex_6:
    "我的第二個範例"
    class O: pass
    class F(O): pass
    class E(O): pass
    class D(O): pass
    class C(D,F): pass
    class B(E,D): pass
    class A(B,C): pass

class ex_9:
    "Python 2.2 MRO 與 C3 的差異" # 來自 Samuele
    class O: pass
    class A(O): pass
    class B(O): pass
    class C(O): pass
    class D(O): pass
    class E(O): pass
    class K1(A,B,C): pass
    class K2(D,B,E): pass
    class K3(D,A): pass
    class Z(K1,K2,K3): pass

def merge(seqs):
    print '\n\nCPL[%s]=%s' % (seqs[0][0],seqs),
    res = []; i=0
    while 1:
      nonemptyseqs=[seq for seq in seqs if seq]
      if not nonemptyseqs: return res
      i+=1; print '\n',i,'round: candidates...',
      for seq in nonemptyseqs: # 在序列頭部中尋找合併候選者
          cand = seq[0]; print ' ',cand,
          nothead=[s for s in nonemptyseqs if cand in s[1:]]
          if nothead: cand=None # 拒絕候選者
          else: break
      if not cand: raise "不一致的階層結構"
      res.append(cand)
      for seq in nonemptyseqs: # 移除候選者
          if seq[0] == cand: del seq[0]

def mro(C):
    "根據 C3 計算類別優先串列 (mro)"
    return merge([[C]]+map(mro,C.__bases__)+[list(C.__bases__)])

def print_mro(C):
    print '\nMRO[%s]=%s' % (C,mro(C))
    print '\nP22 MRO[%s]=%s' % (C,C.mro())

print_mro(ex_9.Z)

#</mro.py>

就這樣，各位，

祝使用愉快！

資源

[1]

Samuele Pedroni 發起的 python-dev 主題討論：https://mail.python.org/pipermail/python-dev/2002-October/029035.html

[2]

論文 A Monotonic Superclass Linearization for Dylan: https://doi.org/10.1145/236337.236343

[3]

Guido van Rossum 的文章 Unifying types and classes in Python 2.2：https://web.archive.org/web/20140210194412/http://www.python.org/download/releases/2.2.2/descrintro

Python 自由執行緒的支援

Starting with the 3.13 release, CPython has support for a build of Python called free threading where the global interpreter lock (GIL) is disabled. Free-threaded execution allows for full utilization of the available processing power by running threads in parallel on available CPU cores. While not all software will benefit from this automatically, programs designed with threading in mind will run faster on multi-core hardware.

Some third-party packages, in particular ones with an extension module, may not be ready for use in a free-threaded build, and will re-enable the GIL.

This document describes the implications of free threading for Python code. See 支援自由執行緒的 C API 擴充 for information on how to write C extensions that support the free-threaded build.

也參考

PEP 703 [https://peps.python.org/pep-0703/] – Making the Global Interpreter Lock Optional in CPython for an overall description of free-threaded Python.

安裝

Starting with Python 3.13, the official macOS and Windows installers optionally support installing free-threaded Python binaries. The installers are available at https://www.python.org/downloads/.

For information on other platforms, see the Installing a Free-Threaded Python [https://py-free-threading.github.io/installing-cpython/], a community-maintained installation guide for installing free-threaded Python.

When building CPython from source, the --disable-gil configure option should be used to build a free-threaded Python interpreter.

Identifying free-threaded Python

To check if the current interpreter supports free-threading, python -VV and sys.version contain "free-threading build". The new sys._is_gil_enabled() function can be used to check whether the GIL is actually disabled in the running process.

The sysconfig.get_config_var("Py_GIL_DISABLED") configuration variable can be used to determine whether the build supports free threading. If the variable is set to 1, then the build supports free threading. This is the recommended mechanism for decisions related to the build configuration.

The global interpreter lock in free-threaded Python

Free-threaded builds of CPython support optionally running with the GIL enabled at runtime using the environment variable PYTHON_GIL or the command-line option -X gil.

The GIL may also automatically be enabled when importing a C-API extension module that is not explicitly marked as supporting free threading. A warning will be printed in this case.

In addition to individual package documentation, the following websites track the status of popular packages support for free threading:

https://py-free-threading.github.io/tracking/

https://hugovk.github.io/free-threaded-wheels/

執行緒安全

The free-threaded build of CPython aims to provide similar thread-safety behavior at the Python level to the default GIL-enabled build. Built-in types like dict, list, and set use internal locks to protect against concurrent modifications in ways that behave similarly to the GIL. However, Python has not historically guaranteed specific behavior for concurrent modifications to these built-in types, so this should be treated as a description of the current implementation, not a guarantee of current or future behavior.

備註

It's recommended to use the threading.Lock or other synchronization primitives instead of relying on the internal locks of built-in types, when possible.

已知限制

This section describes known limitations of the free-threaded CPython build.

不滅化 (Immortalization)

In the free-threaded build, some objects are immortal. Immortal objects are not deallocated and have reference counts that are never modified. This is done to avoid reference count contention that would prevent efficient multi-threaded scaling.

As of the 3.14 release, immortalization is limited to:

Code constants: numeric literals, string literals, and tuple literals composed of other constants.

Strings interned by sys.intern().

Frame objects

It is not safe to access frame.f_locals from a frame object if that frame is currently executing in another thread, and doing so may crash the interpreter.

疊代器

It is generally not thread-safe to access the same iterator object from multiple threads concurrently, and threads may see duplicate or missing elements.

單執行緒效能

The free-threaded build has additional overhead when executing Python code compared to the default GIL-enabled build. The amount of overhead depends on the workload and hardware. On the pyperformance benchmark suite, the average overhead ranges from about 1% on macOS aarch64 to 8% on x86-64 Linux systems.

Behavioral changes

This section describes CPython behavioural changes with the free-threaded build.

Context variables

In the free-threaded build, the flag thread_inherit_context is set to true by default which causes threads created with threading.Thread to start with a copy of the Context() of the caller of start(). In the default GIL-enabled build, the flag defaults to false so threads start with an empty Context().

Warning filters

In the free-threaded build, the flag context_aware_warnings is set to true by default. In the default GIL-enabled build, the flag defaults to false. If the flag is true then the warnings.catch_warnings context manager uses a context variable for warning filters. If the flag is false then catch_warnings modifies the global filters list, which is not thread-safe. See the warnings module for more details.

支援自由執行緒的 C API 擴充

Starting with the 3.13 release, CPython has support for running with the global interpreter lock (GIL) disabled in a configuration called free threading. This document describes how to adapt C API extensions to support free threading.

Identifying the Free-Threaded Build in C

The CPython C API exposes the Py_GIL_DISABLED macro: in the free-threaded build it's defined to 1, and in the regular build it's not defined. You can use it to enable code that only runs under the free-threaded build:

#ifdef Py_GIL_DISABLED
/* code that only runs in the free-threaded build */
#endif

備註

On Windows, this macro is not defined automatically, but must be specified to the compiler when building. The sysconfig.get_config_var() function can be used to determine whether the current running interpreter had the macro defined.

模組初始化

Extension modules need to explicitly indicate that they support running with the GIL disabled; otherwise importing the extension will raise a warning and enable the GIL at runtime.

There are two ways to indicate that an extension module supports running with the GIL disabled depending on whether the extension uses multi-phase or single-phase initialization.

Multi-Phase Initialization

Extensions that use multi-phase initialization (i.e., PyModuleDef_Init()) should add a Py_mod_gil slot in the module definition. If your extension supports older versions of CPython, you should guard the slot with a PY_VERSION_HEX check.

static struct PyModuleDef_Slot module_slots[] = {
    ...
#if PY_VERSION_HEX >= 0x030D0000
    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
#endif
    {0, NULL}
};

static struct PyModuleDef moduledef = {
    PyModuleDef_HEAD_INIT,
    .m_slots = module_slots,
    ...
};

單一階段初始化 (Single-Phase Initialization)

Extensions that use single-phase initialization (i.e., PyModule_Create()) should call PyUnstable_Module_SetGIL() to indicate that they support running with the GIL disabled. The function is only defined in the free-threaded build, so you should guard the call with #ifdef Py_GIL_DISABLED to avoid compilation errors in the regular build.

static struct PyModuleDef moduledef = {
    PyModuleDef_HEAD_INIT,
    ...
};

PyMODINIT_FUNC
PyInit_mymodule(void)
{
    PyObject *m = PyModule_Create(&moduledef);
    if (m == NULL) {
        return NULL;
    }
#ifdef Py_GIL_DISABLED
    PyUnstable_Module_SetGIL(m, Py_MOD_GIL_NOT_USED);
#endif
    return m;
}

General API Guidelines

Most of the C API is thread-safe, but there are some exceptions.

Struct Fields: Accessing fields in Python C API objects or structs directly is not thread-safe if the field may be concurrently modified.

Macros: Accessor macros like PyList_GET_ITEM, PyList_SET_ITEM, and macros like PySequence_Fast_GET_SIZE that use the object returned by PySequence_Fast() do not perform any error checking or locking. These macros are not thread-safe if the container object may be modified concurrently.

Borrowed References: C API functions that return borrowed references may not be thread-safe if the containing object is modified concurrently. See the section on borrowed references for more information.

容器執行緒安全性

Containers like PyListObject, PyDictObject, and PySetObject perform internal locking in the free-threaded build. For example, the PyList_Append() will lock the list before appending an item.

PyDict_Next

A notable exception is PyDict_Next(), which does not lock the dictionary. You should use Py_BEGIN_CRITICAL_SECTION to protect the dictionary while iterating over it if the dictionary may be concurrently modified:

Py_BEGIN_CRITICAL_SECTION(dict);
PyObject *key, *value;
Py_ssize_t pos = 0;
while (PyDict_Next(dict, &pos, &key, &value)) {
    ...
}
Py_END_CRITICAL_SECTION();

借用參照

Some C API functions return borrowed references. These APIs are not thread-safe if the containing object is modified concurrently. For example, it's not safe to use PyList_GetItem() if the list may be modified concurrently.

The following table lists some borrowed reference APIs and their replacements that return strong references.

借用參照 API

強參照 API

PyList_GetItem()

PyList_GetItemRef()

PyList_GET_ITEM()

PyList_GetItemRef()

PyDict_GetItem()

PyDict_GetItemRef()

PyDict_GetItemWithError()

PyDict_GetItemRef()

PyDict_GetItemString()

PyDict_GetItemStringRef()

PyDict_SetDefault()

PyDict_SetDefaultRef()

PyDict_Next()

none (see PyDict_Next)

PyWeakref_GetObject()

PyWeakref_GetRef()

PyWeakref_GET_OBJECT()

PyWeakref_GetRef()

PyImport_AddModule()

PyImport_AddModuleRef()

PyCell_GET()

PyCell_Get()

Not all APIs that return borrowed references are problematic. For example, PyTuple_GetItem() is safe because tuples are immutable. Similarly, not all uses of the above APIs are problematic. For example, PyDict_GetItem() is often used for parsing keyword argument dictionaries in function calls; those keyword argument dictionaries are effectively private (not accessible by other threads), so using borrowed references in that context is safe.

Some of these functions were added in Python 3.13. You can use the pythoncapi-compat [https://github.com/python/pythoncapi-compat] package to provide implementations of these functions for older Python versions.

Memory Allocation APIs

Python's memory management C API provides functions in three different allocation domains: "raw", "mem", and "object". For thread-safety, the free-threaded build requires that only Python objects are allocated using the object domain, and that all Python objects are allocated using that domain. This differs from the prior Python versions, where this was only a best practice and not a hard requirement.

備註

Search for uses of PyObject_Malloc() in your extension and check that the allocated memory is used for Python objects. Use PyMem_Malloc() to allocate buffers instead of PyObject_Malloc().

Thread State and GIL APIs

Python provides a set of functions and macros to manage thread state and the GIL, such as:

PyGILState_Ensure() 和 PyGILState_Release()

PyEval_SaveThread() 和 PyEval_RestoreThread()

Py_BEGIN_ALLOW_THREADS 和 Py_END_ALLOW_THREADS

These functions should still be used in the free-threaded build to manage thread state even when the GIL is disabled. For example, if you create a thread outside of Python, you must call PyGILState_Ensure() before calling into the Python API to ensure that the thread has a valid Python thread state.

You should continue to call PyEval_SaveThread() or Py_BEGIN_ALLOW_THREADS around blocking operations, such as I/O or lock acquisitions, to allow other threads to run the cyclic garbage collector.

Protecting Internal Extension State

Your extension may have internal state that was previously protected by the GIL. You may need to add locking to protect this state. The approach will depend on your extension, but some common patterns include:

Caches: global caches are a common source of shared state. Consider using a lock to protect the cache or disabling it in the free-threaded build if the cache is not critical for performance.

Global State: global state may need to be protected by a lock or moved to thread local storage. C11 and C++11 provide the thread_local or _Thread_local for thread-local storage [https://en.cppreference.com/w/c/language/storage_duration].

Critical Sections

In the free-threaded build, CPython provides a mechanism called "critical sections" to protect data that would otherwise be protected by the GIL. While extension authors may not interact with the internal critical section implementation directly, understanding their behavior is crucial when using certain C API functions or managing shared state in the free-threaded build.

What Are Critical Sections?

Conceptually, critical sections act as a deadlock avoidance layer built on top of simple mutexes. Each thread maintains a stack of active critical sections. When a thread needs to acquire a lock associated with a critical section (e.g., implicitly when calling a thread-safe C API function like PyDict_SetItem(), or explicitly using macros), it attempts to acquire the underlying mutex.

Using Critical Sections

The primary APIs for using critical sections are:

Py_BEGIN_CRITICAL_SECTION and Py_END_CRITICAL_SECTION - For locking a single object

Py_BEGIN_CRITICAL_SECTION2 and Py_END_CRITICAL_SECTION2 - For locking two objects simultaneously

These macros must be used in matching pairs and must appear in the same C scope, since they establish a new local scope. These macros are no-ops in non-free-threaded builds, so they can be safely added to code that needs to support both build types.

A common use of a critical section would be to lock an object while accessing an internal attribute of it. For example, if an extension type has an internal count field, you could use a critical section while reading or writing that field:

// read the count, returns new reference to internal count value
PyObject *result;
Py_BEGIN_CRITICAL_SECTION(obj);
result = Py_NewRef(obj->count);
Py_END_CRITICAL_SECTION();
return result;

// write the count, consumes reference from new_count
Py_BEGIN_CRITICAL_SECTION(obj);
obj->count = new_count;
Py_END_CRITICAL_SECTION();

How Critical Sections Work

Unlike traditional locks, critical sections do not guarantee exclusive access throughout their entire duration. If a thread would block while holding a critical section (e.g., by acquiring another lock or performing I/O), the critical section is temporarily suspended—all locks are released—and then resumed when the blocking operation completes.

This behavior is similar to what happens with the GIL when a thread makes a blocking call. The key differences are:

Critical sections operate on a per-object basis rather than globally

Critical sections follow a stack discipline within each thread (the "begin" and "end" macros enforce this since they must be paired and within the same scope)

Critical sections automatically release and reacquire locks around potential blocking operations

Deadlock Avoidance

Critical sections help avoid deadlocks in two ways:

If a thread tries to acquire a lock that's already held by another thread, it first suspends all of its active critical sections, temporarily releasing their locks

When the blocking operation completes, only the top-most critical section is reacquired first

This means you cannot rely on nested critical sections to lock multiple objects at once, as the inner critical section may suspend the outer ones. Instead, use Py_BEGIN_CRITICAL_SECTION2 to lock two objects simultaneously.

Note that the locks described above are only PyMutex based locks. The critical section implementation does not know about or affect other locking mechanisms that might be in use, like POSIX mutexes. Also note that while blocking on any PyMutex causes the critical sections to be suspended, only the mutexes that are part of the critical sections are released. If PyMutex is used without a critical section, it will not be released and therefore does not get the same deadlock avoidance.

Important Considerations

Critical sections may temporarily release their locks, allowing other threads to modify the protected data. Be careful about making assumptions about the state of the data after operations that might block.

Because locks can be temporarily released (suspended), entering a critical section does not guarantee exclusive access to the protected resource throughout the section's duration. If code within a critical section calls another function that blocks (e.g., acquires another lock, performs blocking I/O), all locks held by the thread via critical sections will be released. This is similar to how the GIL can be released during blocking calls.

Only the lock(s) associated with the most recently entered (top-most) critical section are guaranteed to be held at any given time. Locks for outer, nested critical sections might have been suspended.

You can lock at most two objects simultaneously with these APIs. If you need to lock more objects, you'll need to restructure your code.

While critical sections will not deadlock if you attempt to lock the same object twice, they are less efficient than purpose-built reentrant locks for this use case.

When using Py_BEGIN_CRITICAL_SECTION2, the order of the objects doesn't affect correctness (the implementation handles deadlock avoidance), but it's good practice to always lock objects in a consistent order.

Remember that the critical section macros are primarily for protecting access to Python objects that might be involved in internal CPython operations susceptible to the deadlock scenarios described above. For protecting purely internal extension state, standard mutexes or other synchronization primitives might be more appropriate.

Building Extensions for the Free-Threaded Build

C API extensions need to be built specifically for the free-threaded build. The wheels, shared libraries, and binaries are indicated by a t suffix.

pypa/manylinux [https://github.com/pypa/manylinux] supports the free-threaded build, with the t suffix, such as python3.13t.

pypa/cibuildwheel [https://github.com/pypa/cibuildwheel] supports the free-threaded build on Python 3.13 and 3.14. On Python 3.14, free-threaded wheels will be built by default. On Python 3.13, you will need to set CIBW_ENABLE to cpython-freethreading [https://cibuildwheel.pypa.io/en/stable/options/#enable].

Limited C API and Stable ABI

The free-threaded build does not currently support the Limited C API or the stable ABI. If you use setuptools [https://setuptools.pypa.io/en/latest/setuptools.html] to build your extension and currently set py_limited_api=True you can use py_limited_api=not sysconfig.get_config_var("Py_GIL_DISABLED") to opt out of the limited API when building with the free-threaded build.

備註

You will need to build separate wheels specifically for the free-threaded build. If you currently use the stable ABI, you can continue to build a single wheel for multiple non-free-threaded Python versions.

Windows

Due to a limitation of the official Windows installer, you will need to manually define Py_GIL_DISABLED=1 when building extensions from source.

也參考

Porting Extension Modules to Support Free-Threading [https://py-free-threading.github.io/porting/]: A community-maintained porting guide for extension authors.

遠端偵錯附加協定

此協定使外部工具能夠附加到正在執行的 CPython 行程並遠端執行 Python 程式碼。

大多數平台上都會需要更高的權限才能附加到另一個 Python 行程。

停用遠端偵錯

要停用遠端偵錯支援，請使用以下任一方法：

在啟動直譯器之前，將 PYTHON_DISABLE_REMOTE_DEBUG 環境變數設為 1。

使用 -X disable_remote_debug 命令列選項。

使用 --without-remote-debug 建置旗標來編譯 Python。

權限需求

在大多數平台上，附加到正在執行的 Python 行程進行遠端偵錯需要更高的權限。具體要求和疑難排解步驟會取決於你的作業系統：

Linux

執行追蹤的行程 (tracer process) 必須具有 CAP_SYS_PTRACE 功能或同等權限。你只能追蹤你擁有且可以發送訊號的行程。如果行程已經被追蹤，或者它以 set-user-ID 或 set-group-ID 執行，則追蹤可能會失敗。像 Yama 這樣的安全模組可能會進一步限制追蹤。

要暫時放寬 ptrace 限制（直到重新開機），請執行：

echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope

備註

停用 ptrace_scope 會降低系統安全性，應僅在受信任的環境中執行此操作。

如果在容器內執行，請使用 --cap-add=SYS_PTRACE 或 --privileged，並在需要時以 root 身分執行。

嘗試使用提升後的權限重新執行命令：

sudo -E !!

macOS

要附加到另一個行程，你通常需要以提升過的權限來執行偵錯工具。這可以透過使用 sudo 或以 root 身分執行來完成。

即使附加到你擁有的行程，macOS 也可能會阻止偵錯，除非偵錯器以 root 權限執行，這是由於系統安全限制。

Windows

要附加到另一個行程，你通常需要以系統管理員權限執行偵錯工具。以系統管理員身分啟動命令提示字元或終端機。

即使具有系統管理員權限，某些行程仍可能無法存取，除非你啟用了 SeDebugPrivilege 權限。

要解決檔案或資料夾存取問題，請調整安全權限：

右鍵點擊檔案或資料夾並選擇 Properties。

前往 Security 分頁以檢視具有存取權限的使用者和群組。

點擊 Edit 以修改權限。

選擇你的使用者帳戶。

在 Permissions 中，視需要勾選 Read 或 Full control。

點擊 Apply，然後點擊 OK 來確認。

備註

在繼續之前，請確保你已滿足所有 權限需求。

本節描述了低階協定，使外部工具能夠在正在執行的 CPython 行程中注入並執行 Python 腳本。

此機制構成了 sys.remote_exec() 函式的基礎，該函式指示遠端 Python 行程執行 .py 檔案。但本節不記錄該函式的用法，而是提供底層協定的詳細說明，該協定以目標 Python 行程的 pid 和要執行的 Python 原始檔路徑作為輸入。此資訊支援該協定的獨立重新實作，無論使用何種程式語言。

警告

注入腳本的執行取決於直譯器是否到達安全執行點 (safe evaluation point)。因此，執行可能會根據目標行程的 runtime 狀態而延遲。

一旦注入，腳本將在下次到達安全執行點時會由目標行程內的直譯器執行。這種方法使遠端執行功能成為可能，而不需修改正在執行的 Python 應用程式的行為或結構。

後續章節提供了協定的逐步描述，包括在記憶體中定位直譯器結構、安全存取內部欄位以及觸發程式碼執行的技術。在適用的情況下會註明平台特有的變化，並包含範例實作以闡明每個操作。

定位 PyRuntime 結構

CPython 將 PyRuntime 結構放置在專用的二進位區段（section）中，以幫助外部工具在 runtime 找到它。此區段的名稱和格式因平台而異。例如，ELF 系統使用 .PyRuntime、macOS 使用 __DATA,__PyRuntime。工具可以透過檢查磁碟上的二進位檔案來找到此結構的偏移量。

PyRuntime 結構包含 CPython 的全域直譯器狀態，並可存取其他內部資料，包括直譯器清單、執行緒狀態和偵錯器支援欄位。

要與遠端 Python 行程協作，偵錯器必須首先找到目標行程中 PyRuntime 結構的記憶體位址。此位址無法寫死或從符號名稱計算出，因為它取決於作業系統載入二進位檔案的位置。

尋找 PyRuntime 的方法取決於平台，但步驟大致相同：

找到目標行程中 Python 二進位檔案或共享函式庫被載入的基底位址。

使用磁碟上的二進位檔案來定位 .PyRuntime 區段的偏移量。

將區段偏移量加到基底位址以計算記憶體中的位址。

以下各節說明如何在每個支援的平台上執行此操作，並包含範例程式碼。

Linux (ELF)

在 Linux 上尋找 PyRuntime 結構：

讀取行程的記憶體對映（例如 /proc/<pid>/maps）以找到 Python 可執行檔位址或 libpython 被載入的位址。

剖析二進位檔案中的 ELF 區段標頭以取得 .PyRuntime 區段的偏移量。

將該偏移量加到步驟 1 的基底位址以取得 PyRuntime 的記憶體位址。

以下是一個範例實作：

def find_py_runtime_linux(pid: int) -> int:
    # 步驟 1：嘗試在記憶體中找到 Python 可執行檔
    binary_path, base_address = find_mapped_binary(
        pid, name_contains="python"
    )

    # 步驟 2：如果找不到可執行檔，則改用共享函式庫
    if binary_path is None:
        binary_path, base_address = find_mapped_binary(
            pid, name_contains="libpython"
        )

    # 步驟 3：剖析 ELF 標頭以取得 .PyRuntime 區段偏移量
    section_offset = parse_elf_section_offset(
        binary_path, ".PyRuntime"
    )

    # 步驟 4：計算 PyRuntime 在記憶體中的位址
    return base_address + section_offset

在 Linux 系統上，有兩種主要方法可以從另一個行程讀取記憶體。第一種是透過 /proc 檔案系統，特別是從 /proc/[pid]/mem 讀取，這提供了對行程記憶體的直接存取。這需要適當的權限 - 要麼與目標行程是同一使用者，要麼就要擁有 root 存取權限。第二種方法是使用 process_vm_readv() 系統呼叫，它提供了在行程之間複製記憶體的更有效方式。雖然 ptrace 的 PTRACE_PEEKTEXT 操作也可以用來讀取記憶體，但它明顯較慢，因為它一次只讀取一個字，並且需要追蹤器和被追蹤行程之間的多次情境切換。

對於剖析 ELF 區段，該過程涉及從磁碟上的二進位檔案讀取並解釋 ELF 檔案格式結構。ELF標頭包含指向區段標頭表的指標。每個區段標頭包含關於區段的中介資料，包括其名稱（儲存在單獨的字串表中）、偏移量和大小。要找到像 .PyRuntime 這樣的特定區段，你需要遍歷這些標頭並匹配區段名稱。然後區段標頭會提供該區段在檔案中存在的偏移量，當二進位檔案載入到記憶體時，可以用它來計算 runtime 位址。

你可以在 ELF 規範 [https://en.wikipedia.org/wiki/Executable_and_Linkable_Format]中閱讀更多關於 ELF 檔案格式的資訊。

macOS (Mach-O)

在 macOS 上找 PyRuntime 結構：

呼叫 task_for_pid() 以取得目標行程的 mach_port_t 任務埠 (task port)。此控制代碼 (handle) 用於使用像 mach_vm_read_overwrite 和 mach_vm_region 這樣的 API 來讀取記憶體。

掃描記憶體區域以找到包含 Python 可執行檔或 libpython 的區域。

從磁碟載入二進位檔案並剖析 Mach-O 標頭以找到 __DATA 程式段（segment）中名為 PyRuntime 的區段。在 macOS 上，符號名稱會自動加上底線前綴，因此 PyRuntime 符號在符號表中顯示為 _PyRuntime，但區段名稱不受影響。

以下是一個範例實作：

def find_py_runtime_macos(pid: int) -> int:
    # 步驟 1：取得對行程記憶體的存取權限
    handle = get_memory_access_handle(pid)

    # 步驟 2：嘗試在記憶體中找到 Python 可執行檔
    binary_path, base_address = find_mapped_binary(
        handle, name_contains="python"
    )

    # 步驟 3：如果找不到可執行檔，則改用 libpython
    if binary_path is None:
        binary_path, base_address = find_mapped_binary(
            handle, name_contains="libpython"
        )

    # 步驟 4：剖析 Mach-O 標頭以取得 __DATA,__PyRuntime 區段偏移量
    section_offset = parse_macho_section_offset(
        binary_path, "__DATA", "__PyRuntime"
    )

    # 步驟 5：計算 PyRuntime 在記憶體中的位址
    return base_address + section_offset

在 macOS 上，存取另一個行程的記憶體需要使用 Mach-O 特定的 API 和檔案格式。第一步是透過 task_for_pid() 取得 task_port 控制代碼，它提供對目標行程記憶體空間的存取。此控制代碼透過像 mach_vm_read_overwrite() 這樣的 API 啟用記憶體操作。

可以使用 mach_vm_region() 掃描虛擬記憶體空間來檢查行程記憶體，而 proc_regionfilename() 幫助識別在每個記憶體區域載入了哪些二進位檔案。當找到 Python 二進位檔案或函式庫時，需要剖析其 Mach-O 標頭以定位 PyRuntime 結構。

Mach-O 格式將程式碼和資料組織成程式段和區段。PyRuntime 結構位於 __DATA 程式段內名為 __PyRuntime 的區段中。實際的 runtime 位址計算涉及找到作為二進位檔案基底位址的 __TEXT 程式段，然後定位包含我們目標區段的 __DATA 程式段。最終位址是透過將基底位址與來自 Mach-O 標頭的適當區段偏移量組合來計算的。

請注意，在 macOS 上存取另一個行程的記憶體通常需要提升過後的權限 - 要麼是 root 存取權限，要麼是授予偵錯行程的特殊安全授權。

Windows (PE)

在 Windows 上找 PyRuntime 結構：

使用 ToolHelp API 來列舉目標行程中載入的所有模組。這是使用諸如 CreateToolhelp32Snapshot [https://learn.microsoft.com/en-us/windows/win32/api/tlhelp32/nf-tlhelp32-createtoolhelp32snapshot]、Module32First [https://learn.microsoft.com/en-us/windows/win32/api/tlhelp32/nf-tlhelp32-module32first] 和 Module32Next [https://learn.microsoft.com/en-us/windows/win32/api/tlhelp32/nf-tlhelp32-module32next] 等函式來完成的。

識別對應於 python.exe 或 pythonXY.dll 的模組，其中 X 和 Y 是Python 版本的主要和次要版本號，並記錄其基底位址。

定位 PyRuntim 區段。由於 PE 格式對區段名稱有 8 個字元的限制（定義為 IMAGE_SIZEOF_SHORT_NAME），所以原始名稱 PyRuntime 會被截斷。此區段包含 PyRuntime 結構。

檢索區段的相對虛擬位址 (RVA, relative virtual address) 並將其加到模組的基底位址。

以下是一個範例實作：

def find_py_runtime_windows(pid: int) -> int:
    # 步驟 1：嘗試在記憶體中找到 Python 可執行檔
    binary_path, base_address = find_loaded_module(
        pid, name_contains="python"
    )

    # 步驟 2：如果找不到可執行檔，則改用共享函式庫 pythonXY.dll
    if binary_path is None:
        binary_path, base_address = find_loaded_module(
            pid, name_contains="python3"
        )

    # 步驟 3：剖析 PE 區段標頭以取得 PyRuntime 區段的 RVA。
    # 由於 PE 格式 (IMAGE_SIZEOF_SHORT_NAME) 有8 字元的限制，
    # 區段名稱顯示為 "PyRuntim"。
    section_rva = parse_pe_section_offset(binary_path, "PyRuntim")

    # 步驟 4：計算 PyRuntime 在記憶體中的位址
    return base_address + section_rva

在 Windows 上，存取另一個行程的記憶體需要使用像 CreateToolhelp32Snapshot() 和 Module32First()/Module32Next() 這樣的 Windows API 函式來列舉載入的模組。OpenProcess() 函式提供一個控制代碼來存取目標行程的記憶體空間，並透過 ReadProcessMemory() 啟用記憶體操作。

可以透過列舉載入的模組來檢查行程記憶體，以找到 Python 二進位檔案或 DLL。找到後，需要剖析其 PE 標頭以定位 PyRuntime 結構。

PE 格式將程式碼和資料組織成區段。PyRuntime 結構位於名為 "PyRuntim" 的區段中（由於 PE 的 8 字元名稱限制，從 "PyRuntime" 截斷）。實際的 runtime 位址計算涉及從模組項目中找到模組的基底位址，然後在 PE 標頭中定位我們的目標區段。最終位址是透過將基底位址與 PE 區段標頭中的區段虛擬位址組合來計算的。

請注意，在 Windows 上存取另一個行程的記憶體通常需要適當的權限 - 要麼是系統管理員存取權限，要麼是授予偵錯行程的 SeDebugPrivilege 權限。

讀取 _Py_DebugOffsets

一旦確定了 PyRuntime 結構的位址，下一步就是讀取位於 PyRuntime 區塊開頭的 _Py_DebugOffsets 結構。

此結構提供了安全讀取直譯器和執行緒狀態記憶體所需的版本特定欄位偏移量。這些偏移量在不同的 CPython 版本之間有所不同，必須在使用前檢查以確保它們相容。

要讀取並檢查偵錯偏移量，請按照以下步驟操作：

從目標行程中的 PyRuntime 位址開始讀取記憶體，涵蓋與 _Py_DebugOffsets 結構相同的位元組數。此結構位於 PyRuntime 記憶體區塊的最開始處。其佈局 (layout) 在 CPython 的內部標頭中定義，並在給定的次要版本中維持不變，但在主要版本中可能會更改。

檢查結構是否包含有效資料：

cookie 欄位必須匹配預期的偵錯標記。

version 欄位必須匹配偵錯器使用的 Python 直譯器版本。

如果偵錯器或目標行程使用的是預發行版本（例如 alpha、beta 或候選版本），版本必須完全匹配。

free_threaded 欄位在偵錯器和目標行程中必須具有相同的值。

如果結構有效，其中包含的偏移量可用於定位記憶體中的欄位。如果任何檢查失敗，偵錯器應停止操作以避免以錯誤的格式讀取記憶體。

以下是一個讀取並檢查 _Py_DebugOffsets 的範例實作：

def read_debug_offsets(pid: int, py_runtime_addr: int) -> DebugOffsets:
    # 步驟 1：在 PyRuntime 位址從目標行程讀取記憶體
    data = read_process_memory(
        pid, address=py_runtime_addr, size=DEBUG_OFFSETS_SIZE
    )

    # 步驟 2：將原始位元組反序列化為 _Py_DebugOffsets 結構
    debug_offsets = parse_debug_offsets(data)

    # 步驟 3：驗證結構的內容
    if debug_offsets.cookie != EXPECTED_COOKIE:
        raise RuntimeError("Invalid or missing debug cookie")
    if debug_offsets.version != LOCAL_PYTHON_VERSION:
        raise RuntimeError(
            "Mismatch between caller and target Python versions"
        )
    if debug_offsets.free_threaded != LOCAL_FREE_THREADED:
        raise RuntimeError("Mismatch in free-threaded configuration")

    return debug_offsets

警告

建議暫停行程

為了避免競態條件 (race conditions) 並確保記憶體一致性，強烈建議在執行任何讀取或寫入內部直譯器狀態的操作之前暫停目標行程。Python runtime 可能在正常執行期間同時變更直譯器資料結構 - 例如建立或銷毀執行緒。這可能導致無效的記憶體讀取或寫入。

偵錯器可以透過使用 ptrace 附加到行程或發送 SIGSTOP 訊號來暫停執行。只有在偵錯器端的記憶體操作完成後才應恢復執行。

備註

一些工具，例如分析器 (profilers) 或基於取樣的偵錯器，可能在不暫停的情況下對正在執行的行程進行操作。在這種情況下，工具必須明確設計為能夠處理部分更新或不一致的記憶體。對於大多數偵錯器實作來說，暫停行程仍然是最安全可靠的方法。

定位直譯器和執行緒狀態

在可以於遠端 Python 行程中注入並執行程式碼之前，偵錯器必須選擇一個用於排程執行的執行緒。這是必要的，因為用於執行遠端程式碼注入的控制欄位位於 _PyRemoteDebuggerSupport 結構中，該結構嵌入在 PyThreadState 物件中。偵錯器會修改這些欄位以請求執行注入的腳本。

PyThreadState 結構代表在 Python 直譯器內執行的執行緒。它維護執行緒的求值情境 (evaluation context)，並包含偵錯器協調所需的欄位。因此，定位有效的 PyThreadState 是遠端觸發執行的關鍵前提。

通常根據執行緒的角色或 ID 來選擇執行緒。在大多數情況下會使用主執行緒，但某些工具可能會透過其原生執行緒 ID 來定位特定執行緒。一旦選擇了目標執行緒，偵錯器必須在記憶體中定位直譯器和相關的執行緒狀態結構。

相關的內部結構定義如下：

PyInterpreterState 代表一個隔離的 Python 直譯器實例。每個直譯器維護自己的一組已引入模組、內建狀態和執行緒狀態串列。雖然大多數 Python 應用程式使用單一直譯器，但 CPython 支援在同一行程中使用多個直譯器。

PyThreadState 代表在直譯器內運行的執行緒。它包含執行狀態和偵錯器使用的控制欄位。

要定位執行緒：

使用偏移量 runtime_state.interpreters_head 來取得 PyRuntime 結構中第一個直譯器的位址。這是活動直譯器鏈結串列的進入點。

使用偏移量 interpreter_state.threads_main 來存取與所選直譯器相關的主執行緒狀態。這通常是最可靠的目標執行緒。

可選地使用偏移量 interpreter_state.threads_head 來遍歷所有執行緒狀態的鏈結串列。每個 PyThreadState 結構包含一個 native_thread_id 欄位，可以將其與目標執行緒 ID 進行比較以找到特定執行緒。

一旦找到有效的 PyThreadState，其位址可以在協定的後續步驟中使用，例如寫入偵錯器控制欄位和排程執行。

以下是一個定位主執行緒狀態的範例實作：

def find_main_thread_state(
    pid: int, py_runtime_addr: int, debug_offsets: DebugOffsets,
) -> int:
    # 步驟 1：從 PyRuntime 讀取 interpreters_head
    interp_head_ptr = (
        py_runtime_addr + debug_offsets.runtime_state.interpreters_head
    )
    interp_addr = read_pointer(pid, interp_head_ptr)
    if interp_addr == 0:
        raise RuntimeError("No interpreter found in the target process")

    # 步驟 2：從直譯器讀取 threads_main 指標
    threads_main_ptr = (
        interp_addr + debug_offsets.interpreter_state.threads_main
    )
    thread_state_addr = read_pointer(pid, threads_main_ptr)
    if thread_state_addr == 0:
        raise RuntimeError("Main thread state is not available")

    return thread_state_addr

以下範例示範如何透過原生執行緒 ID 來定位執行緒：

def find_thread_by_id(
    pid: int,
    interp_addr: int,
    debug_offsets: DebugOffsets,
    target_tid: int,
) -> int:
    # 從 threads_head 開始並遍歷鏈結串列
    thread_ptr = read_pointer(
        pid,
        interp_addr + debug_offsets.interpreter_state.threads_head
    )

    while thread_ptr:
        native_tid_ptr = (
            thread_ptr + debug_offsets.thread_state.native_thread_id
        )
        native_tid = read_int(pid, native_tid_ptr)
        if native_tid == target_tid:
            return thread_ptr
        thread_ptr = read_pointer(
            pid,
            thread_ptr + debug_offsets.thread_state.next
        )

    raise RuntimeError("Thread with the given ID was not found")

一旦定位到有效的執行緒狀態，偵錯器就可以繼續修改其控制欄位並排程執行，如下一節所述。

寫入控制資訊

一旦識別出有效的 PyThreadState 結構，偵錯器就可以修改其中的控制欄位以排程執行指定的 Python 腳本。直譯器會定期檢查這些控制欄位，當正確設定時，它們會在求值迴圈中的安全點觸發遠端程式碼的執行。

每個 PyThreadState 都包含一個 _PyRemoteDebuggerSupport 結構，能用於偵錯器和直譯器之間的通訊。其欄位的位置由 _Py_DebugOffsets 結構定義，包括以下內容：

debugger_script_path：一個固定大小的緩衝區，用於保存 Python 原始檔（.py）的完整路徑。觸發執行時，目標行程必須能夠存取和讀取此檔案。

debugger_pending_call：一個整數旗標。將其設定為 1 會告訴直譯器腳本已準備好執行。

eval_breaker：直譯器在執行期間檢查的欄位。在此欄位中設定位元 5（_PY_EVAL_PLEASE_STOP_BIT，值 1U << 5）會導致直譯器暫停並檢查偵錯器活動。

要完成注入，偵錯器必須執行以下步驟：

將完整的腳本路徑寫入 debugger_script_path 緩衝區。

將 debugger_pending_call 設定為 1。

讀取 eval_breaker 目前的值，設定位元 5（_PY_EVAL_PLEASE_STOP_BIT）並將更新後的值寫回。這會向直譯器發出檢查偵錯器活動的訊號。

以下是一個範例實作：

def inject_script(
    pid: int,
    thread_state_addr: int,
    debug_offsets: DebugOffsets,
    script_path: str
) -> None:
    # 計算 _PyRemoteDebuggerSupport 的基底偏移量
    support_base = (
        thread_state_addr +
        debug_offsets.debugger_support.remote_debugger_support
    )

    # 步驟 1：將腳本路徑寫入 debugger_script_path
    script_path_ptr = (
        support_base +
        debug_offsets.debugger_support.debugger_script_path
    )
    write_string(pid, script_path_ptr, script_path)

    # 步驟 2：將 debugger_pending_call 設定為 1
    pending_ptr = (
        support_base +
        debug_offsets.debugger_support.debugger_pending_call
    )
    write_int(pid, pending_ptr, 1)

    # 步驟 3：在 eval_breaker 中設定 _PY_EVAL_PLEASE_STOP_BIT（位元 5，值為 1 << 5）
    eval_breaker_ptr = (
        thread_state_addr +
        debug_offsets.debugger_support.eval_breaker
    )
    breaker = read_int(pid, eval_breaker_ptr)
    breaker |= (1 << 5)
    write_int(pid, eval_breaker_ptr, breaker)

一旦設定了這些欄位，偵錯器就可以恢復行程（如果它先被暫停了）。直譯器將在下一個安全執行點處理請求、從磁碟載入腳本並執行它。

偵錯器有責任確保腳本檔案在執行期間仍然存在且可供目標行程存取。

備註

腳本執行是非同步的。注入後不能立即刪除腳本檔案。偵錯器應等到注入的腳本產生可觀察的效果後再刪除檔案。此效果取決於腳本被設計要執行的操作。例如，偵錯器可能會等到遠端行程連回通訊端後再刪除腳本。一旦觀察到這種效果，就可以安全地假設不再需要該檔案。

摘要

要在遠端行程中注入並執行 Python 腳本：

在目標行程的記憶體中定位 PyRuntime 結構。

讀取並驗證 PyRuntime 開頭的 _Py_DebugOffsets 結構。

使用偏移量來定位有效的 PyThreadState。

將 Python 腳本的路徑寫入 debugger_script_path。

將 debugger_pending_call 旗標設定為 1。

在 eval_breaker 欄位中設定 _PY_EVAL_PLEASE_STOP_BIT。

恢復行程（如果已暫停）。腳本將在下一個安全執行點執行。

Python 常見問題

一般的 Python 常見問答集

程式開發常見問答集

設計和歷史常見問答集

函式庫和擴充功能的常見問題

擴充/嵌入常見問題集

在 Windows 使用 Python 的常見問答集

圖形使用者介面常見問答集

「為什麼 Python 被安裝在我的機器上？」常見問答集

一般的 Python 常見問答集

目錄

一般的 Python 常見問答集

一般資訊

什麼是 Python？

什麼是 Python 軟體基金會？

使用 Python 時有任何版權限制嗎？

當初為什麼 Python 會被創造出來？

什麼是 Python 擅長的事情？

Python 的版本編號系統是如何運作的？

我要如何得到 Python 的原始碼複本？

我要如何取得 Python 的說明文件？

我從來沒有寫過程式，有沒有 Python 的教學？

有沒有 Python 專屬的新聞群組或郵件討論群？

如何取得 Python 的 beta 測試版本？

如何提交 Python 的錯誤報告和修補程式？

是否有關於 Python 的任何已出版文章可供參考？

有沒有關於 Python 的書？

www.python.org 的真實位置在哪裡？

為什麼要取名為 Python？

我需要喜歡「Monty Python 的飛行馬戲團」嗎？

在真實世界中的 Python

Python 的穩定性如何？

有多少人在使用 Python？

有沒有任何重要的專案使用 Python 完成開發？

Python 未來預期會有哪些新的開發？

對 Python 提出不相容的變更建議是否適當？

Python 對於入門的程式設計師而言是否為好的語言？

一般資訊

什麼是 Python？

Python 是一種直譯的、互動的、物件導向的程式設計語言。它結合了模組、例外、動態型別 (dynamic typing)、非常高階的動態資料型別，以及 class（類別）。它能支援物件導向程式設計之外的多種程式設計典範，例如程序式 (procedural) 和函式語言 (functional) 程式設計。Python 結合了卓越的功能與非常清晰的語法。它有許多系統呼叫和函式庫的介面，以及各種視窗系統的介面，並且在 C 或 C++ 中可以擴充。它還可以作為一種擴充語言，使用於需要可程式化介面 (programmable interface) 的應用程式。最後，Python 是可攜的 (portable)：它能運行在許多 Unix 的變體上，包括 Linux 和 macOS，也能運行在 Windows 上。

要尋找更多內容，請從 Python 教學開始。Python 初學者指南 [https://wiki.python.org/moin/BeginnersGuide]可連結到其他介紹式教學以及學習 Python 的資源。

什麼是 Python 軟體基金會？

Python 軟體基金會 (Python Software Foundation) 是一個獨立的非營利性組織，它擁有 Python 2.1 版與之後各版本的版權。PSF 的使命在於推展 Python 程式設計語言相關的開放原始碼技術，以及宣傳 Python 的使用。PSF 首頁的網址是 https://www.python.org/psf/。

在美國捐款給 PSF 是免稅的。如果你使用了 Python 且發現它很有用，請至 PSF 捐款頁面 [https://www.python.org/psf/donations/]為它做出貢獻。

使用 Python 時有任何版權限制嗎？

你可以對原始碼做任何你想做的事情，只要你保留版權，並且在你製作的任何關於 Python 的說明文件中顯示這些版權即可。如果你遵守版權規則，就可以將 Python 用於商業用途，以原始碼或二進制形式（修改或未修改）銷售 Python 的複本，或者以某種形式銷售內含 Python 的產品。當然，我們仍然會想要知道所有的 Python 商業用途。

請參閱 授權頁面 [https://docs.python.org/3/license.html]，查詢更深入的說明和 PSF 授權全文的連結。

Python 標誌是註冊商標，在某些情況下需要許可才能使用它。請參閱商標使用政策 [https://www.python.org/psf/trademarks/]以取得更多資訊。

當初為什麼 Python 會被創造出來？

以下是由 Guido van Rossum 所撰寫，關於這一切如何開始的非常簡短的摘要：

我在 CWI 的 ABC 小組中擁有實作直譯語言方面的豐富經驗，而透過與該小組的合作，我學到了很多關於語言設計的知識。這是許多 Python 功能的起源，包括使用縮排進行陳述式分組以及納入非常高階的資料型別（儘管在 Python 中的細節都已經不同）。

我對 ABC 語言有一些牢騷，但我也喜歡它的許多功能。想要擴充 ABC 語言（或其實作）來去除我的抱怨是不可能的。事實上，缺乏可擴充性就是它最大的問題之一。我有一些使用 Modula-2+ 的經驗，也與 Modula-3 的設計者交談過，並閱讀了 Modula-3 的報告。Modula-3 就是用於例外及另外一些 Python 功能的語法和語義的起源。

我當時正在 CWI 的 Amoeba 分散式作業系統小組工作。我們需要一種比編寫 C 程式或 Bourne shell 腳本更好的方法來進行系統管理，因為 Amoeba 有自己的系統呼叫介面，而它無法簡單地從 Bourne shell 進行存取。我在 Amoeba 中處理錯誤的經驗，使我深切地意識到例外作為程式設計語言功能的重要性。

我突然想到，一種具有類似 ABC 的語法但可以存取 Amoeba 系統呼叫的腳本語言將能滿足該需求。我了解編寫 Amoeba 專用語言是愚蠢的，所以我決定，我需要一種可以廣泛擴充的語言。

在 1989 年的聖誕節假期，我有很多自由時間，所以我決定來嘗試一下。在接下來的一年裡，雖然我大部分時間仍然在為此而努力，但 Python 在 Amoeba 專案中的使用得到了越來越多的成功，且同事們的回饋也使我為它增加了許多早期的改進。

在 1991 年 2月，經過一年多的發展，我決定將它發表到 USENET。其他的記錄都在 Misc/HISTORY 檔案中。

什麼是 Python 擅長的事情？

Python 是一種高階的、用途廣泛的程式設計語言，可以用來解決許多不同類型的問題。

這個語言提供了一個大型的標準函式庫，涵蓋了字串處理（正規表示式、Unicode、檔案之間的差異計算）、網際網路協定（HTTP、FTP、SMTP、XML-RPC、POP、IMAP）、軟體工程（單元測試、日誌記錄、效能分析、剖析 Python 程式碼）以及作業系統介面（系統呼叫、檔案系統、TCP/IP 插座 (socket)）等領域。請查看 Python 標準函式庫 (Standard Library) 的目錄，以了解可用的函式。此外，還有各式各樣的第三方擴充。請查詢 Python 套件索引 (Python Package Index) [https://pypi.org] 來尋找你有興趣的套件。

Python 的版本編號系統是如何運作的？

Python 各版本會被編號為 "A.B.C" 或 "A.B"：

A 為主要版本編號 -- 它只會在語言中有真正重大的變更時才會增加。

B 為次要版本編號 -- 只有在影響範圍較小的變更出現時增加。

C 為微小版本編號 —- 會在每個錯誤修正發布 (bugfix release) 增加。

並非所有的發布版本都是錯誤修正發布版本。在一個新功能發布版本的準備階段，會發布一系列開發版本，標示為 alpha、beta 或候選發布版本 (release candidate)。Alpha 是介面尚未最終化的早期發布版本；看到兩個 alpha 發布版本之間的介面變更並不會令人意外。Beta 則更為穩定，保留了現有的介面，但可能會增加新的模組，而候選發布版本會被凍結，除了需要修正關鍵錯誤之外，不會再進行任何變更。

Alpha、beta 和候選發布版本都有一個額外的後綴：

Alpha 版本的後綴是 "aN"，其中 N 是某個較小的數字。

Beta 版本的後綴是 "bN"，其中 N 是某個較小的數字。

候選發布版本的後綴是 "rcN"，其中 N 是某個較小的數字。

換句話說，所有標記為 2.0aN 的版本都在標記為 2.0bN 的版本之前，而 2.0bN 版本都在標記為 2.0rcN 的版本之前，而它們都是在 2.0 版之前。

你還可以找到帶有「+」後綴的版本編號，例如「2.2+」。這些是未發布的版本，直接從 CPython 的開發儲存庫被建置。實際上，在每一次的最終次要版本發布完成之後，版本編號將會被增加到下一個次要版本，並成為「a0」版，例如「2.4a0」。

請參閱開發人員指南 [https://devguide.python.org/developer-workflow/development-cycle/]以獲得更多關於開發週期的資訊，並參閱 PEP 387 [https://peps.python.org/pep-0387/] 以瞭解更多關於 Python 的向後相容性政策。另外，也請查看 sys.version、sys.hexversion 和 sys.version_info 的說明文件。

我要如何得到 Python 的原始碼複本？

最新的 Python 原始碼發行版永遠可以從 python.org 取得，在 https://www.python.org/downloads/。最新的開發中原始碼可以在 https://github.com/python/cpython/ 取得。

原始碼發行版是一個以 gzip 壓縮的 tar 檔，它包含完整的 C 原始碼、Sphinx 格式的說明文件、Python 函式庫模組、範例程式，以及幾個好用的可自由發行軟體。該原始碼在大多數 UNIX 平台上，都是可以立即編譯及運行的。

關於取得和編譯原始碼的詳細資訊，請參閱 Python 開發人員指南中的 "Getting Started" 段落 [https://devguide.python.org/setup/]。

我要如何取得 Python 的說明文件？

Python 目前穩定版本的標準說明文件可在 https://docs.python.org/3/ 找到。EPUB、純文字和可下載的 HTML 版本也可在 https://docs.python.org/3/download.html 找到。

說明文件是以 reStructuredText 格式編寫，並由 Sphinx 說明文件工具 [https://sphinx-doc.org/]處理。說明文件的 reStructuredText 原始碼是 Python 原始碼發行版的一部分。

我從來沒有寫過程式，有沒有 Python 的教學？

有許多可用的教學和書籍。標準說明文件包括 Python 教學。

要尋找 Python 程式設計初學者的資訊，包括教學資源列表，請參閱初學者指南 [https://wiki.python.org/moin/BeginnersGuide]。

有沒有 Python 專屬的新聞群組或郵件討論群？

有一個新聞群組 (newsgroup)，comp.lang.python，也有一個郵件討論群 (mailing list)，python-list [https://mail.python.org/mailman/listinfo/python-list]。新聞群組和郵件討論群是彼此相通的——如果你能閱讀新聞，則無需加入郵件討論群。comp.lang.python 的流量很高，每天會收到數百篇文章，而 Usenet 的讀者通常較能夠處理這樣的文章數量。

新的軟體發布版本及事件的通知，可以在 comp.lang.python.announce 中找到，這是一個低流量的精選討論群，每天收到大約五篇文章。它也能從 python-announce 郵件討論群 [https://mail.python.org/mailman3/lists/python-announce-list.python.org/]的頁面中訂閱。

關於其他郵件討論群和新聞群組的更多資訊，可以在 https://www.python.org/community/lists/ 中找到。

如何取得 Python 的 beta 測試版本？

Alpha 和 beta 發布版本可以從 https://www.python.org/downloads/ 取得。所有的發布版本都會在 comp.lang.python 和 comp.lang.python.announce 新聞群組上宣布，也會在 Python 首頁 https://www.python.org/ 中宣布；RSS 新聞摘要也是可使用的。

你也可以藉由 Git 來存取 Python 的開發版本。更多詳細資訊，請參閱 Python 開發人員指南 [https://devguide.python.org/]。

如何提交 Python 的錯誤報告和修補程式？

要回報一個錯誤 (bug) 或提交一個修補程式 (patch)，請使用於 https://github.com/python/cpython/issues 的問題追蹤系統。

關於如何開發 Python 的更多資訊，請參閱 Python 開發人員指南 [https://devguide.python.org/]。

是否有關於 Python 的任何已出版文章可供參考？

也許最好是引用你最喜歡的關於 Python 的書。

最早討論 Python 的文章 [https://ir.cwi.nl/pub/18204]是在 1991 年寫的，但現在來看已經過時了。

Guido van Rossum 和 Jelke de Boer，「使用 Python 程式設計語言互動式測試遠端伺服器」，CWI 季刊，第 4 卷，第 4 期（1991 年 12 月），阿姆斯特丹，第 283–303 頁。

有沒有關於 Python 的書？

有，很多書已經出版，也有更多正在出版中的書。請參閱 python.org 的 wiki 在 https://wiki.python.org/moin/PythonBooks 頁面中的書目清單。

你也可以在網路書店搜尋關鍵字「Python」，並過濾掉 Monty Python 的結果；或者可以搜尋「Python」和「語言」。

www.python.org 的真實位置在哪裡？

Python 專案的基礎建設遍佈世界各地，由 Python 基礎建設團隊管理。詳細資訊在此 [https://infra.psf.io]。

為什麼要取名為 Python？

當 Guido van Rossum 開始實作 Python 時，他也正在閱讀 1970 年代 BBC 喜劇節目「Monty Python 的飛行馬戲團」 [https://en.wikipedia.org/wiki/Monty_Python]的出版劇本。Van Rossum 認為他需要一個簡短、獨特且略帶神秘的名字，因此他決定將該語言稱為 Python。

我需要喜歡「Monty Python 的飛行馬戲團」嗎？

不需要，但它有幫助。:)

在真實世界中的 Python

Python 的穩定性如何？

非常穩定。自從 1991 年開始，大約每隔 6 到 18 個月都會發布新的穩定版本，而且這看起來會繼續進行。從 3.9 版開始，Python 每隔 12 個月將會釋出一個新功能發行版本 (PEP 602 [https://peps.python.org/pep-0602/])。

開發人員會釋出針對先前版本的錯誤修正發布版本，因此現有發布版本的穩定性會逐漸提高。錯誤修正發布版本是由版本編號的第三個部分表示（例如 3.5.3，3.6.2），這些版本會被用於改善穩定性；在錯誤修正發布版本中，只會包含針對已知問題的修正，並且會保證介面在一系列的錯誤修正發布版本中維持不變。

最新的穩定發布版本隨時都可以在 Python 下載頁面 [https://www.python.org/downloads/]上找到。Python 3.x 是推薦的版本，並且被大多數廣泛使用的函式庫所支援。Python 2.x 已不再被維護 [https://peps.python.org/pep-0373/]。

有多少人在使用 Python？

可能有幾百萬個使用者，但實際的數量是難以確定的。

Python 是可以免費下載的，所以不會有銷售數據，而且它可以從許多不同的網站取得，並與許多 Linux 發行版套裝在一起，所以下載次數的統計也無法反映完整的情況。

comp.lang.python 新聞群組非常活躍，但並非所有 Python 使用者都會在該群組發表文章或甚至閱讀它。

有沒有任何重要的專案使用 Python 完成開發？

要查看使用 Python 的專案清單，請參閱 https://www.python.org/about/success。藉由查詢過去的 Python 會議記錄 [https://www.python.org/community/workshops/]可以看見來自許多不同公司和組織的貢獻。

備受矚目的 Python 專案包括 Mailman 郵件討論群管理員 [https://www.list.org]和 Zope 應用程式伺服器 [https://www.zope.dev]。有一些 Linux 發行版，最著名的是 Red Hat [https://www.redhat.com]，已經用 Python 編寫了部分或全部的安裝程式及系統管理軟體。內部使用 Python 的公司包括 Google、Yahoo 和 Lucasfilm Ltd。

Python 未來預期會有哪些新的開發？

請至 https://peps.python.org/ 參閱 Python 增強提案 (Python Enhancement Proposal, PEP)。PEP 是用來描述一項被建議的 Python 新功能的設計文件，它提供了簡潔的技術規範及基本原理。請尋找一篇名為「Python X.Y Release Schedule（發布時程表）」的 PEP，其中 X.Y 是一個尚未公開發布的版本。

新的開發會在 python-dev 郵件討論群 [https://mail.python.org/mailman3/lists/python-dev.python.org/]中討論。

對 Python 提出不相容的變更建議是否適當？

一般來說，不適當。全世界已經有數百萬行 Python 程式碼，因此在語言中的任何變更，若會使現有程式的一小部分成為無效，它都是不被允許的。即使你可以提供轉換程式，仍然會有需要更新全部說明文件的問題；市面上已經有很多介紹 Python 的書，而我們不想一下子就把它們都變為無效。

如果一項功能必須被變更，那麼一定要提供逐步升級的路徑。PEP 5 [https://peps.python.org/pep-0005/] 描述了要引進反向不相容 (backward-incompatible) 的變更，同時也要對使用者的擾亂最小化，所需遵循的程序。

Python 對於入門的程式設計師而言是否為好的語言？

是的。

學生們仍然普遍地會從一種程序語言和靜態型別語言 (statically typed language) 開始入門，這些語言像是 Pascal、C，或是 C++ 或 Java 的某個子集。透過學習 Python 作為他們的第一個語言，學生們可能會學得更好。Python 具有非常簡單且一致的語法和一個大型的標準函式庫，最重要的是，在入門程式設計課程中使用 Python 可以讓學生專注於重要的程式設計技巧，例如問題的分解和資料型別的設計。使用 Python，可以快速地向學生介紹基本觀念，例如迴圈和程序。他們甚至可能在第一堂課中就學到使用者自訂的物件。

對於以前從未進行過程式設計的學生來說，使用靜態型別語言似乎是不自然的。它使學生必須掌握額外的複雜性，並減慢了課程的節奏。學生們正在試圖學著像電腦一樣思考、分解問題、設計一致的介面，並封裝資料。雖然從長遠來看，學習使用靜態型別語言很重要，但在學生的第一堂程式設計課程中，它不一定是最好的課程主題。

Python 的許多其他面向使它成為一種很好的第一語言。像 Java 一樣，Python 有一個大型的標準函式庫，因此學生可以在課程的早期就被指派程式設計的專案，且這些專案能夠做一些事情。指派的內容不會侷限於標準的四功能計算機和平衡檢驗程式。透過使用標準函式庫，學生可以在學習程式設計基礎知識的同時，獲得處理真實應用程式的滿足感。使用標準函式庫還可以教導學生程式碼再使用 (code reuse) 的課題。像是 PyGame 等第三方模組也有助於延伸學生的學習領域。

Python 的互動式直譯器使學生能夠在程式設計時測試語言的功能。他們可以開著一個運行直譯器的視窗，同時在另一個視窗中輸入他們的程式原始碼。如果他們不記得 list（串列）的 method（方法），他們可以像這樣做：

>>> L = []
>>> dir(L)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
'__dir__', '__doc__', '__eq__', '__format__', '__ge__',
'__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__',
'__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__',
'__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
'__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__',
'__sizeof__', '__str__', '__subclasshook__', 'append', 'clear',
'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove',
'reverse', 'sort']
>>> [d for d in dir(L) if '__' not in d]
['append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

>>> help(L.append)
Help on built-in function append:

append(...)
    L.append(object) -> None -- append object to end

>>> L.append(1)
>>> L
[1]

有了直譯器，當學生正在程式設計時，說明文件永遠都不會遠離他們。

Python 也有很好的 IDE。IDLE 是 Python 的一個跨平臺 IDE，它以 Python 編寫並使用 Tkinter。Emacs 使用者會很高興知道 Emacs 有一個非常好的 Python 模式。這些程式設計環境全部都能提供語法突顯 (syntax highlighting)、自動縮排，以及在編寫程式時存取互動式直譯器。要查看 Python 編輯環境的完整清單，請參閱 Python wiki [https://wiki.python.org/moin/PythonEditors]。

如果你想討論 Python 在教育領域中的使用，你可能會有興趣加入 edu-sig 郵件討論群 [https://www.python.org/community/sigs/current/edu-sig]。

程式開發常見問答集

目錄

程式開發常見問答集

常見問題

是否有可以使用在程式碼階段,具有中斷點,步驟執行等功能的除錯器？

有沒有工具能夠幫忙找 bug 或執行靜態分析？

如何從 Python 腳本建立獨立的二進位檔案？

Python 程式碼是否有編碼標準或風格指南？

核心語言

為什麼當變數有值時，我仍得到錯誤訊息 UnboundLocalError？

Python 的區域變數和全域變數有什麼規則？

為什麼以不同的值在迴圈中定義的 lambda 都回傳相同的結果？

如何跨模組共享全域變數？

在模組中使用 import 的「最佳實踐」有哪些？

為什麼物件之間共享預設值？

How can I pass optional or keyword parameters from one function to another?

引數 (arguments) 和參數 (parameters) 有什麼區別？

為什麼更改串列 'y' 也會更改串列 'x'？

如何編寫帶有輸出參數的函式（透過傳參照呼叫 (call by reference)）？

你如何在 Python 中建立高階函式？

如何在 Python 中複製物件？

如何找到物件的方法或屬性？

我的程式碼如何發現物件的名稱？

逗號運算子的優先級是什麼？

是否有等效於 C 的 "?:" 三元運算子？

Is it possible to write obfuscated one-liners in Python?

函式參數串列中的斜線 (/) 是什麼意思？

數字和字串

如何指定十六進位和八進位整數？

為什麼 -22 // 10 回傳 -3？

How do I get int literal attribute instead of SyntaxError?

如何將字串轉換為數字？

如何將數字轉換為字串？

如何原地修改字串？

如何使用字串呼叫函式/方法？

Is there an equivalent to Perl's chomp() for removing trailing newlines from strings?

Is there a scanf() or sscanf() equivalent?

What does UnicodeDecodeError or UnicodeEncodeError error mean?

Can I end a raw string with an odd number of backslashes?

效能

我的程式太慢了。我該如何加快速度？

What is the most efficient way to concatenate many strings together?

序列（元組/串列）

如何在元組和串列之間進行轉換？

什麼是負索引？

How do I iterate over a sequence in reverse order?

如何從串列中刪除重複項？

How do you remove multiple items from a list?

How do you make an array in Python?

如何建立多維度串列？

如何將方法或函式應用於物件序列？

為什麼 a_tuple[i] += ['item'] 做加法時會引發例外？

我想做一個複雜的排序：你能用 Python 做一個 Schwartzian 變換嗎？

如何根據另一個串列中的值對一個串列進行排序？

物件

什麼是類別 (class)？

什麼是方法 (method)？

什麼是 self？

如何檢查物件是否是給定類別的實例或其子類別的實例？

什麼是委派 (delegation)？

How do I call a method defined in a base class from a derived class that extends it?

我可以如何組織我的程式碼以使得更改基底類別變的更容易？

如何建立靜態類別資料和靜態類別方法？

如何在 Python 中多載 (overload) 建構函式（或方法）？

我嘗試使用 __spam，但收到有關 _SomeClassName__spam 的錯誤。

我的類別定義了 __del__ 但是當我刪除物件時它沒有被呼叫。

我該如何取得給定類別的所有實例的串列？

為什麼 id() 的結果看起來不唯一？

我什麼時候可以依靠 is 運算子進行識別性測試？

子類別如何控制不可變實例中儲存的資料？

如何快取方法呼叫？

模組

如何建立 .pyc 檔案？

如何找到目前模組名稱？

要怎樣才能擁有相互引入的模組？

__import__('x.y.z') 回傳 <module 'x'>，那我怎麼得到 z？

當我編輯需要引入的模組並重新引入它時，更動沒有反應出來。為什麼會這樣？

常見問題

是否有可以使用在程式碼階段,具有中斷點,步驟執行等功能的除錯器？

有的。

下面描述了幾個 Python 除錯器，內建函式 breakpoint() 允許你進入其中任何一個。

pdb 模組是一個簡單但足夠的 Python 控制台模式除錯器。它是標準 Python 函式庫的一部分，並記錄在函式庫參考手冊中。你也可以參考 pdb 的程式碼作為範例來編寫自己的除錯器。

IDLE 交互式開發環境，它是標準 Python 發行版的一部分（通常作為 Tools/scripts/idle3 [https://github.com/python/cpython/blob/main/Tools/scripts/idle3] 提供），包括一個圖形除錯器。

PythonWin 是一個 Python IDE，它包含一個基於 pdb 的 GUI 除錯器。 PythonWin 除錯器為斷點著色並具有許多很酷的功能，例如除錯非 PythonWin 程式。 PythonWin 作為 pywin32 [https://github.com/mhammond/pywin32] 專案的一部分和作為 ActivePython [https://www.activestate.com/products/python/] 的一部分發佈。

Eric [https://eric-ide.python-projects.org/] 是一個基於 PyQt 和 Scintilla 編輯元件所建構的 IDE。

trepan3k [https://github.com/rocky/python3-trepan/] 是一個類似 gdb 的除錯器。

Visual Studio Code [https://code.visualstudio.com/] 是一個整合了版本控制軟體與除錯工具的 IDE。

有數個商業化Python整合化開發工具包含圖形除錯功能。這些包含：

Wing IDE [https://wingware.com/]

Komodo IDE [https://www.activestate.com/products/komodo-ide/]

PyCharm [https://www.jetbrains.com/pycharm/]

有沒有工具能夠幫忙找 bug 或執行靜態分析？

有的。

Pylint [https://pylint.pycqa.org/en/latest/index.html] 和 Pyflakes [https://github.com/PyCQA/pyflakes] 進行基本檢查以幫助你儘早抓出錯誤。

靜態型別檢查器，例如 Mypy [https://mypy-lang.org/]、Pyre [https://pyre-check.org/] 和 Pytype [https://github.com/google/pytype] 可以檢查 Python 原始碼中的型別提示。

如何從 Python 腳本建立獨立的二進位檔案？

如果你想要的只是一個使用者可以下載並執行而無需先安裝 Python 發行版的獨立程式，則不需要將 Python 編譯為 C 程式碼的能力。有許多工具可以判斷程式所需的模組集，並將這些模組與 Python 二進位檔案綁定在一起以產生單個可執行檔。

一種是使用 freeze 工具，它位於 Python 原始碼樹中的 Tools/freeze [https://github.com/python/cpython/tree/main/Tools/freeze]。它將 Python 位元組碼轉換為 C 陣列；使用 C 編譯器，你可以將所有模組嵌入到一個新程式中，然後將其與標準 Python 模組連結。

It works by scanning your source recursively for import statements (in both forms) and looking for the modules in the standard Python path as well as in the source directory (for built-in modules). It then turns the bytecode for modules written in Python into C code (array initializers that can be turned into code objects using the marshal module) and creates a custom-made config file that only contains those built-in modules which are actually used in the program. It then compiles the generated C code and links it with the rest of the Python interpreter to form a self-contained binary which acts exactly like your script.

以下套件可以幫助建立 console 和 GUI 可執行檔案：

Nuitka [https://nuitka.net/]（跨平台）

PyInstaller [https://pyinstaller.org/]（跨平台）

PyOxidizer [https://pyoxidizer.readthedocs.io/en/stable/]（跨平台）

cx_Freeze [https://marcelotduarte.github.io/cx_Freeze/]（跨平台）

py2app [https://github.com/ronaldoussoren/py2app]（僅限 macOS）

py2exe [https://www.py2exe.org/]（僅限 Windows）

Python 程式碼是否有編碼標準或風格指南？

是的。標準函式庫模組所需的編碼風格稱為 PEP 8 [https://peps.python.org/pep-0008/]。

核心語言

為什麼當變數有值時，我仍得到錯誤訊息 UnboundLocalError？

It can be a surprise to get the UnboundLocalError in previously working code when it is modified by adding an assignment statement somewhere in the body of a function.

這段程式碼:

>>> x = 10
>>> def bar():
...     print(x)
...
>>> bar()
10

可以執行,但是這段程式:

>>> x = 10
>>> def foo():
...     print(x)
...     x += 1

導致 UnboundLocalError：

>>> foo()
Traceback (most recent call last):
  ...
UnboundLocalError: local variable 'x' referenced before assignment

This is because when you make an assignment to a variable in a scope, that variable becomes local to that scope and shadows any similarly named variable in the outer scope. Since the last statement in foo assigns a new value to x, the compiler recognizes it as a local variable. Consequently when the earlier print(x) attempts to print the uninitialized local variable and an error results.

在上面的範例中，你可以透過將其聲明為全域變數來存取外部範圍變數：

>>> x = 10
>>> def foobar():
...     global x
...     print(x)
...     x += 1
...
>>> foobar()
10

This explicit declaration is required in order to remind you that (unlike the superficially analogous situation with class and instance variables) you are actually modifying the value of the variable in the outer scope:

>>> print(x)
11

你可以使用 nonlocal 關鍵字在巢狀作用域內做類似的事情：

>>> def foo():
...    x = 10
...    def bar():
...        nonlocal x
...        print(x)
...        x += 1
...    bar()
...    print(x)
...
>>> foo()
10
11

Python 的區域變數和全域變數有什麼規則？

In Python, variables that are only referenced inside a function are implicitly global. If a variable is assigned a value anywhere within the function's body, it's assumed to be a local unless explicitly declared as global.

Though a bit surprising at first, a moment's consideration explains this. On one hand, requiring global for assigned variables provides a bar against unintended side-effects. On the other hand, if global was required for all global references, you'd be using global all the time. You'd have to declare as global every reference to a built-in function or to a component of an imported module. This clutter would defeat the usefulness of the global declaration for identifying side-effects.

為什麼以不同的值在迴圈中定義的 lambda 都回傳相同的結果？

假設你使用 for 迴圈來定義幾個不同的 lambda（甚至是普通函式），例如：

>>> squares = []
>>> for x in range(5):
...     squares.append(lambda: x**2)

這會提供一個包含五個計算 x**2 的 lambda 串列。你可能會預期在呼叫它時，它們會分別回傳 0、1、4、9 和 16，然而當你實際嘗試你會發現它們都回傳 16：

>>> squares[2]()
16
>>> squares[4]()
16

發生這種情況是因為 x 不是 lambda 的局部變數，而是在外部作用域中定義的，且是在呼叫 lambda 時才會存取它，並非於定義時就會存取。在迴圈結束時，x 的值為 4，因此所有函式都回傳 4**2，即為 16。你還可以透過更改 x 的值來驗證這一點，並查看 lambda 運算式的結果如何變化：

>>> x = 8
>>> squares[2]()
64

為了避免這種情況，你需要將值保存在 lambda 的局部變數中，這樣它們就不會依賴於全域 x 的值：

>>> squares = []
>>> for x in range(5):
...     squares.append(lambda n=x: n**2)

Here, n=x creates a new variable n local to the lambda and computed when the lambda is defined so that it has the same value that x had at that point in the loop. This means that the value of n will be 0 in the first lambda, 1 in the second, 2 in the third, and so on. Therefore each lambda will now return the correct result:

>>> squares[2]()
4
>>> squares[4]()
16

請注意，此行為並非 lambda 所特有，也適用於常規函式。

如何跨模組共享全域變數？

The canonical way to share information across modules within a single program is to create a special module (often called config or cfg). Just import the config module in all modules of your application; the module then becomes available as a global name. Because there is only one instance of each module, any changes made to the module object get reflected everywhere. For example:

config.py：

x = 0   # 'x' 配置設定的預設值

mod.py：

import config
config.x = 1

main.py：

import config
import mod
print(config.x)

請注意，出於同樣的原因，使用模組也是實作單例設計模式的基礎。

在模組中使用 import 的「最佳實踐」有哪些？

In general, don't use from modulename import *. Doing so clutters the importer's namespace, and makes it much harder for linters to detect undefined names.

Import modules at the top of a file. Doing so makes it clear what other modules your code requires and avoids questions of whether the module name is in scope. Using one import per line makes it easy to add and delete module imports, but using multiple imports per line uses less screen space.

It's good practice if you import modules in the following order:

標準函式庫模組 —— 例如 sys、os、argparse、re

third-party library modules (anything installed in Python's site-packages directory) -- e.g. dateutil, requests, PIL.Image

本地開發的模組

It is sometimes necessary to move imports to a function or class to avoid problems with circular imports. Gordon McMillan says:

Circular imports are fine where both modules use the "import <module>" form of import. They fail when the 2nd module wants to grab a name out of the first ("from module import name") and the import is at the top level. That's because names in the 1st are not yet available, because the first module is busy importing the 2nd.

In this case, if the second module is only used in one function, then the import can easily be moved into that function. By the time the import is called, the first module will have finished initializing, and the second module can do its import.

It may also be necessary to move imports out of the top level of code if some of the modules are platform-specific. In that case, it may not even be possible to import all of the modules at the top of the file. In this case, importing the correct modules in the corresponding platform-specific code is a good option.

Only move imports into a local scope, such as inside a function definition, if it's necessary to solve a problem such as avoiding a circular import or are trying to reduce the initialization time of a module. This technique is especially helpful if many of the imports are unnecessary depending on how the program executes. You may also want to move imports into a function if the modules are only ever used in that function. Note that loading a module the first time may be expensive because of the one time initialization of the module, but loading a module multiple times is virtually free, costing only a couple of dictionary lookups. Even if the module name has gone out of scope, the module is probably available in sys.modules.

為什麼物件之間共享預設值？

這種類型的錯誤通常會困擾新手程式員。像是這個函式：

def foo(mydict={}):  # 危險：所有呼叫共享對字典的參照
    ... 計算一些東西 ...
    mydict[key] = value
    return mydict

第一次呼叫此函式時， mydict 包含一個項目。第二次後 mydict 包含兩個項目，因為當 foo() 開始執行時，mydict 以其中已有的項目開始。

It is often expected that a function call creates new objects for default values. This is not what happens. Default values are created exactly once, when the function is defined. If that object is changed, like the dictionary in this example, subsequent calls to the function will refer to this changed object.

By definition, immutable objects such as numbers, strings, tuples, and None, are safe from change. Changes to mutable objects such as dictionaries, lists, and class instances can lead to confusion.

由於這個特性，不使用可變物件作為預設值是一個很好的程式設計習慣，而是應使用 None 作為預設值，並在函式內部檢查參數是否為 None，再建立一個新的串列/字典/或其他東西。例如，不要這樣寫：

def foo(mydict={}):
    ...

而是寫成：

def foo(mydict=None):
    if mydict is None:
        mydict = {}  # 為區域命名空間建立一個新字典

This feature can be useful. When you have a function that's time-consuming to compute, a common technique is to cache the parameters and the resulting value of each call to the function, and return the cached value if the same value is requested again. This is called "memoizing", and can be implemented like this:

# 呼叫者只能提供兩個參數，並選擇性地透過關鍵字傳遞 _cache
def expensive(arg1, arg2, *, _cache={}):
    if (arg1, arg2) in _cache:
        return _cache[(arg1, arg2)]

    # Calculate the value
    result = ... expensive computation ...
    _cache[(arg1, arg2)] = result           # 將結果儲存在快取中
    return result

你可以使用包含字典的全域變數而不是預設值；這取決於喜好。

How can I pass optional or keyword parameters from one function to another?

Collect the arguments using the * and ** specifiers in the function's parameter list; this gives you the positional arguments as a tuple and the keyword arguments as a dictionary. You can then pass these arguments when calling another function by using * and **:

def f(x, *args, **kwargs):
    ...
    kwargs['width'] = '14.3c'
    ...
    g(x, *args, **kwargs)

引數 (arguments) 和參數 (parameters) 有什麼區別？

參數由出現在函式定義中的名稱定義，而引數是呼叫函式時實際傳遞給函式的值。參數定義函式可以接受的引數種類。例如，給定以下函式定義：

def func(foo, bar=None, **kwargs):
    pass

foo、bar 和 kwargs 是 func 的參數。然而當呼叫 func 時，例如：

func(42, bar=314, extra=somevar)

42、314 和 somevar 是引數。

為什麼更改串列 'y' 也會更改串列 'x'？

如果你寫了像這樣的程式碼：

>>> x = []
>>> y = x
>>> y.append(10)
>>> y
[10]
>>> x
[10]

你可能想知道為什麼將一個元素附加到 y 時也會改變 x。

產生這個結果的原因有兩個：

Variables are simply names that refer to objects. Doing y = x doesn't create a copy of the list -- it creates a new variable y that refers to the same object x refers to. This means that there is only one object (the list), and both x and y refer to it.

list 是 mutable，這意味著你可以變更它們的內容。

After the call to append(), the content of the mutable object has changed from [] to [10]. Since both the variables refer to the same object, using either name accesses the modified value [10].

如果我們改為賦予一個不可變物件給 x：

>>> x = 5  # 整數為不可變的
>>> y = x
>>> x = x + 1  # 5 不可變，在這邊會建立一個新物件
>>> x
6
>>> y
5

we can see that in this case x and y are not equal anymore. This is because integers are immutable, and when we do x = x + 1 we are not mutating the int 5 by incrementing its value; instead, we are creating a new object (the int 6) and assigning it to x (that is, changing which object x refers to). After this assignment we have two objects (the ints 6 and 5) and two variables that refer to them (x now refers to 6 but y still refers to 5).

Some operations (for example y.append(10) and y.sort()) mutate the object, whereas superficially similar operations (for example y = y + [10] and sorted(y)) create a new object. In general in Python (and in all cases in the standard library) a method that mutates an object will return None to help avoid getting the two types of operations confused. So if you mistakenly write y.sort() thinking it will give you a sorted copy of y, you'll instead end up with None, which will likely cause your program to generate an easily diagnosed error.

However, there is one class of operations where the same operation sometimes has different behaviors with different types: the augmented assignment operators. For example, += mutates lists but not tuples or ints (a_list += [1, 2, 3] is equivalent to a_list.extend([1, 2, 3]) and mutates a_list, whereas some_tuple += (1, 2, 3) and some_int += 1 create new objects).

換句話說：

If we have a mutable object (list, dict, set, etc.), we can use some specific operations to mutate it and all the variables that refer to it will see the change.

If we have an immutable object (str, int, tuple, etc.), all the variables that refer to it will always see the same value, but operations that transform that value into a new value always return a new object.

If you want to know if two variables refer to the same object or not, you can use the is operator, or the built-in function id().

如何編寫帶有輸出參數的函式（透過傳參照呼叫 (call by reference)）？

請記住，在 Python 中引數是透過賦值傳遞的。由於賦值只是建立對物件的參照，因此呼叫者和被呼叫者的引數名稱之間沒有別名，因此本身沒有傳參照呼叫。你可以透過多種方式實作所需的效果。

透過回傳結果的元組：

>>> def func1(a, b):
...     a = 'new-value'        # a 和 b 為區域名稱
...     b = b + 1              # 賦值到新物件
...     return a, b            # 回傳新值
...
>>> x, y = 'old-value', 99
>>> func1(x, y)
('new-value', 100)

這幾乎都會是最清楚的方案。

透過使用全域變數。這不是執行緒安全的，所以不推薦。

透過傳遞一個可變的（可於原地 (in-place) 改變的）物件：

>>> def func2(a):
...     a[0] = 'new-value'     # 'a' 參照一個可變的串列
...     a[1] = a[1] + 1        # 改變共享的物件
...
>>> args = ['old-value', 99]
>>> func2(args)
>>> args
['new-value', 100]

透過傳入一個發生改變的字典：

>>> def func3(args):
...     args['a'] = 'new-value'     # args 是可變字典
...     args['b'] = args['b'] + 1   # 原地改變它
...
>>> args = {'a': 'old-value', 'b': 99}
>>> func3(args)
>>> args
{'a': 'new-value', 'b': 100}

或者在類別實例中捆綁值：

>>> class Namespace:
...     def __init__(self, /, **args):
...         for key, value in args.items():
...             setattr(self, key, value)
...
>>> def func4(args):
...     args.a = 'new-value'        # args 是可變命名空間
...     args.b = args.b + 1         # 原地改變物件
...
>>> args = Namespace(a='old-value', b=99)
>>> func4(args)
>>> vars(args)
{'a': 'new-value', 'b': 100}

幾乎不會有要讓事情變得如此複雜的充分理由。

你最好的選擇是回傳一個包含多個結果的元組。

你如何在 Python 中建立高階函式？

你有兩種選擇：可以使用巢狀作用域，也可以使用可呼叫物件。例如，假設你想定義 linear(a,b)，它會回傳 a*x+b 計算值的函式 f(x)。使用巢狀作用域：

def linear(a, b):
    def result(x):
        return a * x + b
    return result

或者使用可呼叫物件：

class linear:

    def __init__(self, a, b):
        self.a, self.b = a, b

    def __call__(self, x):
        return self.a * x + self.b

在這兩種情況下：

taxes = linear(0.3, 2)

給定一個可呼叫物件，其中 taxes(10e6) == 0.3 * 10e6 + 2。

The callable object approach has the disadvantage that it is a bit slower and results in slightly longer code. However, note that a collection of callables can share their signature via inheritance:

class exponential(linear):
    # __init__ inherited
    def __call__(self, x):
        return self.a * (x ** self.b)

物件可以封裝多個方法的狀態：

class counter:

    value = 0

    def set(self, x):
        self.value = x

    def up(self):
        self.value = self.value + 1

    def down(self):
        self.value = self.value - 1

count = counter()
inc, dec, reset = count.up, count.down, count.set

這裡的 inc()、dec() 和 reset() 就像共享相同計數變數的函式一樣。

如何在 Python 中複製物件？

In general, try copy.copy() or copy.deepcopy() for the general case. Not all objects can be copied, but most can.

Some objects can be copied more easily. Dictionaries have a copy() method:

newdict = olddict.copy()

序列可以透過切片 (slicing) 複製：

new_l = l[:]

如何找到物件的方法或屬性？

For an instance x of a user-defined class, dir(x) returns an alphabetized list of the names containing the instance attributes and methods and attributes defined by its class.

我的程式碼如何發現物件的名稱？

Generally speaking, it can't, because objects don't really have names. Essentially, assignment always binds a name to a value; the same is true of def and class statements, but in that case the value is a callable. Consider the following code:

>>> class A:
...     pass
...
>>> B = A
>>> a = B()
>>> b = a
>>> print(b)
<__main__.A object at 0x16D07CC>
>>> print(a)
<__main__.A object at 0x16D07CC>

Arguably the class has a name: even though it is bound to two names and invoked through the name B the created instance is still reported as an instance of class A. However, it is impossible to say whether the instance's name is a or b, since both names are bound to the same value.

Generally speaking it should not be necessary for your code to "know the names" of particular values. Unless you are deliberately writing introspective programs, this is usually an indication that a change of approach might be beneficial.

在 comp.lang.python 中，Fredrik Lundh 曾針對這個問題給出了一個極好的比喻：

就像你在門廊上發現的那隻貓的名字一樣：貓（物件）本身不能告訴你它的名字，它也不關心 - 所以找出它叫什麼的唯一方法是詢問所有鄰居（命名空間）是否是他們的貓（物件）...

....如果你發現它有很多名字，或者根本沒有名字，請不要感到驚訝！

逗號運算子的優先級是什麼？

Comma is not an operator in Python. Consider this session:

>>> "a" in "b", "a"
(False, 'a')

Since the comma is not an operator, but a separator between expressions the above is evaluated as if you had entered:

("a" in "b"), "a"

而不是：

"a" in ("b", "a")

The same is true of the various assignment operators (=, += etc). They are not truly operators but syntactic delimiters in assignment statements.

是否有等效於 C 的 "?:" 三元運算子？

有的，語法如下：

[on_true] if [expression] else [on_false]

x, y = 50, 25
small = x if x < y else y

Before this syntax was introduced in Python 2.5, a common idiom was to use logical operators:

[expression] and [on_true] or [on_false]

However, this idiom is unsafe, as it can give wrong results when on_true has a false boolean value. Therefore, it is always better to use the ... if ... else ... form.

Is it possible to write obfuscated one-liners in Python?

Yes. Usually this is done by nesting lambda within lambda. See the following three examples, slightly adapted from Ulf Bartelt:

from functools import reduce

# Primes < 1000
print(list(filter(None,map(lambda y:y*reduce(lambda x,y:x*y!=0,
map(lambda x,y=y:y%x,range(2,int(pow(y,0.5)+1))),1),range(2,1000)))))

# First 10 Fibonacci numbers
print(list(map(lambda x,f=lambda x,f:(f(x-1,f)+f(x-2,f)) if x>1 else 1:
f(x,f), range(10))))

# Mandelbrot set
print((lambda Ru,Ro,Iu,Io,IM,Sx,Sy:reduce(lambda x,y:x+'\n'+y,map(lambda y,
Iu=Iu,Io=Io,Ru=Ru,Ro=Ro,Sy=Sy,L=lambda yc,Iu=Iu,Io=Io,Ru=Ru,Ro=Ro,i=IM,
Sx=Sx,Sy=Sy:reduce(lambda x,y:x+y,map(lambda x,xc=Ru,yc=yc,Ru=Ru,Ro=Ro,
i=i,Sx=Sx,F=lambda xc,yc,x,y,k,f=lambda xc,yc,x,y,k,f:(k<=0)or (x*x+y*y
>=4.0) or 1+f(xc,yc,x*x-y*y+xc,2.0*x*y+yc,k-1,f):f(xc,yc,x,y,k,f):chr(
64+F(Ru+x*(Ro-Ru)/Sx,yc,0,0,i)),range(Sx))):L(Iu+y*(Io-Iu)/Sy),range(Sy
))))(-2.1, 0.7, -1.2, 1.2, 30, 80, 24))
#    \___ ___/  \___ ___/  |   |   |__ lines on screen
#        V          V      |   |______ columns on screen
#        |          |      |__________ maximum of "iterations"
#        |          |_________________ range on y axis
#        |____________________________ range on x axis

孩子們，不要在家裡嘗試這個！

函式參數串列中的斜線 (/) 是什麼意思？

A slash in the argument list of a function denotes that the parameters prior to it are positional-only. Positional-only parameters are the ones without an externally usable name. Upon calling a function that accepts positional-only parameters, arguments are mapped to parameters based solely on their position. For example, divmod() is a function that accepts positional-only parameters. Its documentation looks like this:

>>> help(divmod)
Help on built-in function divmod in module builtins:

divmod(x, y, /)
    Return the tuple (x//y, x%y).  Invariant: div*y + mod == x.

參數串列最後的斜線表示兩個參數都是僅限位置參數。因此使用關鍵字引數呼叫 divmod() 會導致錯誤：

>>> divmod(x=3, y=4)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: divmod() takes no keyword arguments

數字和字串

如何指定十六進位和八進位整數？

To specify an octal digit, precede the octal value with a zero, and then a lower or uppercase "o". For example, to set the variable "a" to the octal value "10" (8 in decimal), type:

>>> a = 0o10
>>> a
8

Hexadecimal is just as easy. Simply precede the hexadecimal number with a zero, and then a lower or uppercase "x". Hexadecimal digits can be specified in lower or uppercase. For example, in the Python interpreter:

>>> a = 0xa5
>>> a
165
>>> b = 0XB2
>>> b
178

為什麼 -22 // 10 回傳 -3？

It's primarily driven by the desire that i % j have the same sign as j. If you want that, and also want:

i == (i // j) * j + (i % j)

那麼整數除法必須回傳向下取整的結果。 C 還要求保留​​該識別性，然後截斷 i // j 的編譯器需要使 i % j 具有與 i 相同的符號。

There are few real use cases for i % j when j is negative. When j is positive, there are many, and in virtually all of them it's more useful for i % j to be >= 0. If the clock says 10 now, what did it say 200 hours ago? -190 % 12 == 2 is useful; -190 % 12 == -10 is a bug waiting to bite.

How do I get int literal attribute instead of SyntaxError?

嘗試以正常方式查找 int 字面值屬性會給出一個 SyntaxError，因為句點被視為小數點：

>>> 1.__class__
  File "<stdin>", line 1
  1.__class__
   ^
SyntaxError: invalid decimal literal

解決方式是用空格或圓括號將字面值與句點分開。

>>> 1 .__class__
<class 'int'>
>>> (1).__class__
<class 'int'>

如何將字串轉換為數字？

For integers, use the built-in int() type constructor, e.g. int('144') == 144. Similarly, float() converts to a floating-point number, e.g. float('144') == 144.0.

By default, these interpret the number as decimal, so that int('0144') == 144 holds true, and int('0x144') raises ValueError. int(string, base) takes the base to convert from as a second optional argument, so int( '0x144', 16) == 324. If the base is specified as 0, the number is interpreted using Python's rules: a leading '0o' indicates octal, and '0x' indicates a hex number.

Do not use the built-in function eval() if all you need is to convert strings to numbers. eval() will be significantly slower and it presents a security risk: someone could pass you a Python expression that might have unwanted side effects. For example, someone could pass __import__('os').system("rm -rf $HOME") which would erase your home directory.

eval() also has the effect of interpreting numbers as Python expressions, so that e.g. eval('09') gives a syntax error because Python does not allow leading '0' in a decimal number (except '0').

如何將數字轉換為字串？

To convert, e.g., the number 144 to the string '144', use the built-in type constructor str(). If you want a hexadecimal or octal representation, use the built-in functions hex() or oct(). For fancy formatting, see the f-string（f 字串） and 格式化文字語法 sections, e.g. "{:04d}".format(144) yields '0144' and "{:.3f}".format(1.0/3.0) yields '0.333'.

如何原地修改字串？

這沒辦法做到，因為字串是不可變的。在大多數情況下，你應以要拿來組裝的各個部分建構出一個新字串。但是如果你需要一個能夠原地修改 unicode 資料的物件，請嘗試使用 io.StringIO 物件或 array 模組：

>>> import io
>>> s = "Hello, world"
>>> sio = io.StringIO(s)
>>> sio.getvalue()
'Hello, world'
>>> sio.seek(7)
7
>>> sio.write("there!")
6
>>> sio.getvalue()
'Hello, there!'

>>> import array
>>> a = array.array('w', s)
>>> print(a)
array('w', 'Hello, world')
>>> a[0] = 'y'
>>> print(a)
array('w', 'yello, world')
>>> a.tounicode()
'yello, world'

如何使用字串呼叫函式/方法？

有各式各樣的技法。

The best is to use a dictionary that maps strings to functions. The primary advantage of this technique is that the strings do not need to match the names of the functions. This is also the primary technique used to emulate a case construct:

def a():
    pass

def b():
    pass

dispatch = {'go': a, 'stop': b}  # Note lack of parens for funcs

dispatch[get_input()]()  # Note trailing parens to call function

使用內建函式 getattr()：

import foo
getattr(foo, 'bar')()

請注意 getattr() 適用於任何物件，包括類別、類別實例、模組等。

這在標準函式庫中的幾個地方被使用，如：

class Foo:
    def do_foo(self):
        ...

    def do_bar(self):
        ...

f = getattr(foo_instance, 'do_' + opname)
f()

使用 locals() 解析函式名稱：

def myFunc():
    print("hello")

fname = "myFunc"

f = locals()[fname]
f()

Is there an equivalent to Perl's chomp() for removing trailing newlines from strings?

You can use S.rstrip("\r\n") to remove all occurrences of any line terminator from the end of the string S without removing other trailing whitespace. If the string S represents more than one line, with several empty lines at the end, the line terminators for all the blank lines will be removed:

>>> lines = ("line 1 \r\n"
...          "\r\n"
...          "\r\n")
>>> lines.rstrip("\n\r")
'line 1 '

Since this is typically only desired when reading text one line at a time, using S.rstrip() this way works well.

Is there a scanf() or sscanf() equivalent?

Not as such.

For simple input parsing, the easiest approach is usually to split the line into whitespace-delimited words using the split() method of string objects and then convert decimal strings to numeric values using int() or float(). split() supports an optional "sep" parameter which is useful if the line uses something other than whitespace as a separator.

For more complicated input parsing, regular expressions are more powerful than C's sscanf and better suited for the task.

What does UnicodeDecodeError or UnicodeEncodeError error mean?

請參閱 Unicode HOWTO。

Can I end a raw string with an odd number of backslashes?

A raw string ending with an odd number of backslashes will escape the string's quote:

>>> r'C:\this\will\not\work\'
  File "<stdin>", line 1
    r'C:\this\will\not\work\'
    ^
SyntaxError: unterminated string literal (detected at line 1)

There are several workarounds for this. One is to use regular strings and double the backslashes:

>>> 'C:\\this\\will\\work\\'
'C:\\this\\will\\work\\'

Another is to concatenate a regular string containing an escaped backslash to the raw string:

>>> r'C:\this\will\work' '\\'
'C:\\this\\will\\work\\'

It is also possible to use os.path.join() to append a backslash on Windows:

>>> os.path.join(r'C:\this\will\work', '')
'C:\\this\\will\\work\\'

Note that while a backslash will "escape" a quote for the purposes of determining where the raw string ends, no escaping occurs when interpreting the value of the raw string. That is, the backslash remains present in the value of the raw string:

>>> r'backslash\'preserved'
"backslash\\'preserved"

Also see the specification in the language reference.

效能

我的程式太慢了。我該如何加快速度？

That's a tough one, in general. First, here are a list of things to remember before diving further:

Performance characteristics vary across Python implementations. This FAQ focuses on CPython.

Behaviour can vary across operating systems, especially when talking about I/O or multi-threading.

You should always find the hot spots in your program before attempting to optimize any code (see the profile module).

Writing benchmark scripts will allow you to iterate quickly when searching for improvements (see the timeit module).

It is highly recommended to have good code coverage (through unit testing or any other technique) before potentially introducing regressions hidden in sophisticated optimizations.

That being said, there are many tricks to speed up Python code. Here are some general principles which go a long way towards reaching acceptable performance levels:

Making your algorithms faster (or changing to faster ones) can yield much larger benefits than trying to sprinkle micro-optimization tricks all over your code.

Use the right data structures. Study documentation for the 內建型別 and the collections module.

When the standard library provides a primitive for doing something, it is likely (although not guaranteed) to be faster than any alternative you may come up with. This is doubly true for primitives written in C, such as builtins and some extension types. For example, be sure to use either the list.sort() built-in method or the related sorted() function to do sorting (and see the 排序技法 for examples of moderately advanced usage).

Abstractions tend to create indirections and force the interpreter to work more. If the levels of indirection outweigh the amount of useful work done, your program will be slower. You should avoid excessive abstraction, especially under the form of tiny functions or methods (which are also often detrimental to readability).

If you have reached the limit of what pure Python can allow, there are tools to take you further away. For example, Cython [https://cython.org] can compile a slightly modified version of Python code into a C extension, and can be used on many different platforms. Cython can take advantage of compilation (and optional type annotations) to make your code significantly faster than when interpreted. If you are confident in your C programming skills, you can also write a C extension module yourself.

也參考

有個 wiki 頁面專門介紹效能改進小提示 [https://wiki.python.org/moin/PythonSpeed/PerformanceTips]。

What is the most efficient way to concatenate many strings together?

str and bytes objects are immutable, therefore concatenating many strings together is inefficient as each concatenation creates a new object. In the general case, the total runtime cost is quadratic in the total string length.

To accumulate many str objects, the recommended idiom is to place them into a list and call str.join() at the end:

chunks = []
for s in my_strings:
    chunks.append(s)
result = ''.join(chunks)

(another reasonably efficient idiom is to use io.StringIO)

To accumulate many bytes objects, the recommended idiom is to extend a bytearray object using in-place concatenation (the += operator):

result = bytearray()
for b in my_bytes_objects:
    result += b

序列（元組/串列）

如何在元組和串列之間進行轉換？

型別建構函式 tuple(seq) 將任何序列（實際上是任何可疊代物件）轉換為具有相同順序的相同項的元組。

For example, tuple([1, 2, 3]) yields (1, 2, 3) and tuple('abc') yields ('a', 'b', 'c'). If the argument is a tuple, it does not make a copy but returns the same object, so it is cheap to call tuple() when you aren't sure that an object is already a tuple.

The type constructor list(seq) converts any sequence or iterable into a list with the same items in the same order. For example, list((1, 2, 3)) yields [1, 2, 3] and list('abc') yields ['a', 'b', 'c']. If the argument is a list, it makes a copy just like seq[:] would.

什麼是負索引？

Python sequences are indexed with positive numbers and negative numbers. For positive numbers 0 is the first index 1 is the second index and so forth. For negative indices -1 is the last index and -2 is the penultimate (next to last) index and so forth. Think of seq[-n] as the same as seq[len(seq)-n].

Using negative indices can be very convenient. For example S[:-1] is all of the string except for its last character, which is useful for removing the trailing newline from a string.

How do I iterate over a sequence in reverse order?

Use the reversed() built-in function:

for x in reversed(sequence):
    ...  # do something with x ...

This won't touch your original sequence, but build a new copy with reversed order to iterate over.

如何從串列中刪除重複項？

請參閱 Python Cookbook 以得到有關執行此操作的各種方法的詳細討論：

https://code.activestate.com/recipes/52560/

如果你不介意重新排序串列，可以對其進行排序，然後從串列末尾開始掃描，同時刪除重複項：

if mylist:
    mylist.sort()
    last = mylist[-1]
    for i in range(len(mylist)-2, -1, -1):
        if last == mylist[i]:
            del mylist[i]
        else:
            last = mylist[i]

如果串列的所有元素都可以做為集合的鍵（即它們都必須是 hashable），那這通常會更快：

mylist = list(set(mylist))

這會將串列轉換為一個集合，從而刪除重複項，然後再轉換回串列。

How do you remove multiple items from a list?

As with removing duplicates, explicitly iterating in reverse with a delete condition is one possibility. However, it is easier and faster to use slice replacement with an implicit or explicit forward iteration. Here are three variations:

mylist[:] = filter(keep_function, mylist)
mylist[:] = (x for x in mylist if keep_condition)
mylist[:] = [x for x in mylist if keep_condition]

The list comprehension may be fastest.

How do you make an array in Python?

Use a list:

["this", 1, "is", "an", "array"]

Lists are equivalent to C or Pascal arrays in their time complexity; the primary difference is that a Python list can contain objects of many different types.

The array module also provides methods for creating arrays of fixed types with compact representations, but they are slower to index than lists. Also note that NumPy [https://numpy.org/] and other third party packages define array-like structures with various characteristics as well.

To get Lisp-style linked lists, you can emulate cons cells using tuples:

lisp_list = ("like",  ("this",  ("example", None) ) )

If mutability is desired, you could use lists instead of tuples. Here the analogue of a Lisp car is lisp_list[0] and the analogue of cdr is lisp_list[1]. Only do this if you're sure you really need to, because it's usually a lot slower than using Python lists.

如何建立多維度串列？

你可能會這樣建立一個多維度陣列：

>>> A = [[None] * 2] * 3

如果你印出它，這看起來是正確的：

>>> A
[[None, None], [None, None], [None, None]]

但是當你賦予一個值時，它會出現在多個地方：

>>> A[0][0] = 5
>>> A
[[5, None], [5, None], [5, None]]

原因是複製帶有 * 的串列不會建立副本，它只會建立對現有物件的參照。*3 建立一個串列，其中包含 3 個對長度為 2 的相同串列的參照。對其中一列的變更也將顯示在所有其他列中，而這幾乎不會是你想要的。

建議的方法是先建立所需長度的串列，然後用新建立的串列填充每個元素：

A = [None] * 3
for i in range(3):
    A[i] = [None] * 2

這會產生一個包含 3 個長度為 2 的不同串列的串列。你也可以使用串列綜合運算式：

w, h = 2, 3
A = [[None] * w for i in range(h)]

或者你也可以使用提供矩陣資料型別的擴充套件；NumPy [https://numpy.org/] 是其中最著名的一個。

如何將方法或函式應用於物件序列？

To call a method or function and accumulate the return values is a list, a list comprehension is an elegant solution:

result = [obj.method() for obj in mylist]

result = [function(obj) for obj in mylist]

To just run the method or function without saving the return values, a plain for loop will suffice:

for obj in mylist:
    obj.method()

for obj in mylist:
    function(obj)

為什麼 a_tuple[i] += ['item'] 做加法時會引發例外？

This is because of a combination of the fact that augmented assignment operators are assignment operators, and the difference between mutable and immutable objects in Python.

This discussion applies in general when augmented assignment operators are applied to elements of a tuple that point to mutable objects, but we'll use a list and += as our exemplar.

如果你寫了：

>>> a_tuple = (1, 2)
>>> a_tuple[0] += 1
Traceback (most recent call last):
   ...
TypeError: 'tuple' object does not support item assignment

The reason for the exception should be immediately clear: 1 is added to the object a_tuple[0] points to (1), producing the result object, 2, but when we attempt to assign the result of the computation, 2, to element 0 of the tuple, we get an error because we can't change what an element of a tuple points to.

這個增強賦值陳述式在背後大致是做這些事情：

>>> result = a_tuple[0] + 1
>>> a_tuple[0] = result
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment

It is the assignment part of the operation that produces the error, since a tuple is immutable.

當你寫這樣的東西時：

>>> a_tuple = (['foo'], 'bar')
>>> a_tuple[0] += ['item']
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment

The exception is a bit more surprising, and even more surprising is the fact that even though there was an error, the append worked:

>>> a_tuple[0]
['foo', 'item']

To see why this happens, you need to know that (a) if an object implements an __iadd__() magic method, it gets called when the += augmented assignment is executed, and its return value is what gets used in the assignment statement; and (b) for lists, __iadd__() is equivalent to calling extend() on the list and returning the list. That's why we say that for lists, += is a "shorthand" for list.extend():

>>> a_list = []
>>> a_list += [1]
>>> a_list
[1]

這等價於：

>>> result = a_list.__iadd__([1])
>>> a_list = result

The object pointed to by a_list has been mutated, and the pointer to the mutated object is assigned back to a_list. The end result of the assignment is a no-op, since it is a pointer to the same object that a_list was previously pointing to, but the assignment still happens.

因此，在我們的元組範例中，發生的事情等同於：

>>> result = a_tuple[0].__iadd__(['item'])
>>> a_tuple[0] = result
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment

The __iadd__() succeeds, and thus the list is extended, but even though result points to the same object that a_tuple[0] already points to, that final assignment still results in an error, because tuples are immutable.

我想做一個複雜的排序：你能用 Python 做一個 Schwartzian 變換嗎？

The technique, attributed to Randal Schwartz of the Perl community, sorts the elements of a list by a metric which maps each element to its "sort value". In Python, use the key argument for the list.sort() method:

Isorted = L[:]
Isorted.sort(key=lambda s: int(s[10:15]))

如何根據另一個串列中的值對一個串列進行排序？

將它們合併到一個元組疊代器中，對結果的串列進行排序，然後挑選出你想要的元素。

>>> list1 = ["what", "I'm", "sorting", "by"]
>>> list2 = ["something", "else", "to", "sort"]
>>> pairs = zip(list1, list2)
>>> pairs = sorted(pairs)
>>> pairs
[("I'm", 'else'), ('by', 'sort'), ('sorting', 'to'), ('what', 'something')]
>>> result = [x[1] for x in pairs]
>>> result
['else', 'sort', 'to', 'something']

物件

什麼是類別 (class)？

A class is the particular object type created by executing a class statement. Class objects are used as templates to create instance objects, which embody both the data (attributes) and code (methods) specific to a datatype.

A class can be based on one or more other classes, called its base class(es). It then inherits the attributes and methods of its base classes. This allows an object model to be successively refined by inheritance. You might have a generic Mailbox class that provides basic accessor methods for a mailbox, and subclasses such as MboxMailbox, MaildirMailbox, OutlookMailbox that handle various specific mailbox formats.

什麼是方法 (method)？

A method is a function on some object x that you normally call as x.name(arguments...). Methods are defined as functions inside the class definition:

class C:
    def meth(self, arg):
        return arg * 2 + self.attribute

什麼是 self？

Self 只是方法第一個引數的約定名稱。對於所定義類別的某個實例 x，一個定義為 meth(self, a, b, c) 的方法應該以 x.meth(a, b, c) 形式來呼叫；被呼叫的方法會認為它是以 meth(x, a, b, c) 來呼叫的。

另請參閱 為何「self」在方法 (method) 定義和呼叫時一定要明確使用？。

如何檢查物件是否是給定類別的實例或其子類別的實例？

Use the built-in function isinstance(obj, cls). You can check if an object is an instance of any of a number of classes by providing a tuple instead of a single class, e.g. isinstance(obj, (class1, class2, ...)), and can also check whether an object is one of Python's built-in types, e.g. isinstance(obj, str) or isinstance(obj, (int, float, complex)).

請注意，isinstance() 還會檢查來自抽象基底類別 (abstract base class) 的虛擬繼承。因此對已註冊類別的檢驗會回傳 True，即使沒有直接或間接繼承自它。要測試「真正繼承」，請掃描該類別的 MRO：

from collections.abc import Mapping

class P:
     pass

class C(P):
    pass

Mapping.register(P)

>>> c = C()
>>> isinstance(c, C)        # 直接
True
>>> isinstance(c, P)        # 間接
True
>>> isinstance(c, Mapping)  # 虛擬
True

# 實際的繼承鏈結
>>> type(c).__mro__
(<class 'C'>, <class 'P'>, <class 'object'>)

# 「真正繼承」的檢驗
>>> Mapping in type(c).__mro__
False

Note that most programs do not use isinstance() on user-defined classes very often. If you are developing the classes yourself, a more proper object-oriented style is to define methods on the classes that encapsulate a particular behaviour, instead of checking the object's class and doing a different thing based on what class it is. For example, if you have a function that does something:

def search(obj):
    if isinstance(obj, Mailbox):
        ...  # 搜尋信箱的程式碼
    elif isinstance(obj, Document):
        ...  # 搜尋文件的程式碼
    elif ...

更好的方法是在所有類別上定義一個 search() 方法然後呼叫它：

class Mailbox:
    def search(self):
        ...  # 搜尋信箱的程式碼

class Document:
    def search(self):
        ...  # 搜尋文件的程式碼

obj.search()

什麼是委派 (delegation)？

委派是一種物件導向的技法（也稱為設計模式）。假設你有一個物件 x 並且只想更改其中一個方法的行為。你可以建立一個新類別，它提供你想改變的那個方法的新實作，並將所有其他方法委派給 x 的相應方法。

Python 程式設計師可以輕鬆地實作委派。舉例來說，以下類別實作了一個行為類似檔案的類別，但將所有寫入的資料轉換為大寫：

class UpperOut:

    def __init__(self, outfile):
        self._outfile = outfile

    def write(self, s):
        self._outfile.write(s.upper())

    def __getattr__(self, name):
        return getattr(self._outfile, name)

Here the UpperOut class redefines the write() method to convert the argument string to uppercase before calling the underlying self._outfile.write() method. All other methods are delegated to the underlying self._outfile object. The delegation is accomplished via the __getattr__() method; consult the language reference for more information about controlling attribute access.

Note that for more general cases delegation can get trickier. When attributes must be set as well as retrieved, the class must define a __setattr__() method too, and it must do so carefully. The basic implementation of __setattr__() is roughly equivalent to the following:

class X:
    ...
    def __setattr__(self, name, value):
        self.__dict__[name] = value
    ...

許多 __setattr__() 的實作會呼叫 object.__setattr__() 以設定 self 的屬性，而不會導致無限遞迴。

class X:
    def __setattr__(self, name, value):
        # 自訂邏輯放在這裡...
        object.__setattr__(self, name, value)

Alternatively, it is possible to set attributes by inserting entries into self.__dict__ directly.

How do I call a method defined in a base class from a derived class that extends it?

使用內建的 super() 函式：

class Derived(Base):
    def meth(self):
        super().meth()  # 呼叫 Base.meth

In the example, super() will automatically determine the instance from which it was called (the self value), look up the method resolution order (MRO) with type(self).__mro__, and return the next in line after Derived in the MRO: Base.

我可以如何組織我的程式碼以使得更改基底類別變的更容易？

You could assign the base class to an alias and derive from the alias. Then all you have to change is the value assigned to the alias. Incidentally, this trick is also handy if you want to decide dynamically (e.g. depending on availability of resources) which base class to use. Example:

class Base:
    ...

BaseAlias = Base

class Derived(BaseAlias):
    ...

如何建立靜態類別資料和靜態類別方法？

Python 支援靜態資料和靜態方法（在 C++ 或 Java 的意義上）。

對於靜態資料，只需定義一個類別屬性即可。要為屬性分配新值，你必須在分配中顯式使用類別名稱：

class C:
    count = 0   # C.__init__ 被呼叫的次數

    def __init__(self):
        C.count = C.count + 1

    def getcount(self):
        return C.count  # 或回傳 self.count

c.count 還指代任何 c 的 C.count 使得 isinstance(c, C) 成立，除非被 c 本身或某些人覆蓋從 c.__class__ 回到 C 的基底類別搜尋路徑上的類別。

Caution: within a method of C, an assignment like self.count = 42 creates a new and unrelated instance named "count" in self's own dict. Rebinding of a class-static data name must always specify the class whether inside a method or not:

C.count = 314

靜態方法是可能的：

class C:
    @staticmethod
    def static(arg1, arg2, arg3):
        # 沒有 'self' 參數！
        ...

However, a far more straightforward way to get the effect of a static method is via a simple module-level function:

def getcount():
    return C.count

If your code is structured so as to define one class (or tightly related class hierarchy) per module, this supplies the desired encapsulation.

如何在 Python 中多載 (overload) 建構函式（或方法）？

這個答案實際上適用於所有方法，但這個問題通常會先出現在建構函式的情境中。

在 C++ 中你會寫成

class C {
    C() { cout << "No arguments\n"; }
    C(int i) { cout << "Argument is " << i << "\n"; }
}

在 Python 中，你必須編寫一個建構函式來捕獲所有使用預設引數的情況。例如：

class C:
    def __init__(self, i=None):
        if i is None:
            print("No arguments")
        else:
            print("Argument is", i)

這並不完全等價，但在實際情況中已夠接近。

你也可以嘗試長度可變的引數串列，例如：

def __init__(self, *args):
    ...

相同的手段適用於所有方法的定義。

我嘗試使用 __spam，但收到有關 _SomeClassName__spam 的錯誤。

帶有雙前導底線的變數名會被「破壞 (mangled)」以做為提供定義類別私有變數的一個簡單但有效的方法。__spam 形式的任何識別字（至少兩個前導底線，最多一個尾隨底線）在文字上會被替換為 _classname__spam，其中 classname 是目前類別之所有前導底線被去除的名稱。

The identifier can be used unchanged within the class, but to access it outside the class, the mangled name must be used:

class A:
    def __one(self):
        return 1
    def two(self):
        return 2 * self.__one()

class B(A):
    def three(self):
        return 3 * self._A__one()

four = 4 * A()._A__one()

In particular, this does not guarantee privacy since an outside user can still deliberately access the private attribute; many Python programmers never bother to use private variable names at all.

也參考

The private name mangling specifications for details and special cases.

我的類別定義了 __del__ 但是當我刪除物件時它沒有被呼叫。

這有幾個可能的原因。

del 陳述式不一定會呼叫 __del__() -- 它只是減少物件的參照計數，如果達到零則呼叫 __del__()。

If your data structures contain circular links (e.g. a tree where each child has a parent reference and each parent has a list of children) the reference counts will never go back to zero. Once in a while Python runs an algorithm to detect such cycles, but the garbage collector might run some time after the last reference to your data structure vanishes, so your __del__() method may be called at an inconvenient and random time. This is inconvenient if you're trying to reproduce a problem. Worse, the order in which object's __del__() methods are executed is arbitrary. You can run gc.collect() to force a collection, but there are pathological cases where objects will never be collected.

Despite the cycle collector, it's still a good idea to define an explicit close() method on objects to be called whenever you're done with them. The close() method can then remove attributes that refer to subobjects. Don't call __del__() directly -- __del__() should call close() and close() should make sure that it can be called more than once for the same object.

Another way to avoid cyclical references is to use the weakref module, which allows you to point to objects without incrementing their reference count. Tree data structures, for instance, should use weak references for their parent and sibling references (if they need them!).

最後，如果你的 __del__() 方法引發例外，則會將一條警告訊息印出到 sys.stderr。

我該如何取得給定類別的所有實例的串列？

Python 不會追蹤類別（或內建型別）的所有實例。你可以將類別的建構函式進行改寫，以透過保留對每個實例之弱參照串列來追蹤所有實例。

為什麼 id() 的結果看起來不唯一？

The id() builtin returns an integer that is guaranteed to be unique during the lifetime of the object. Since in CPython, this is the object's memory address, it happens frequently that after an object is deleted from memory, the next freshly created object is allocated at the same position in memory. This is illustrated by this example:

>>> id(1000)
13901272
>>> id(2000)
13901272

The two ids belong to different integer objects that are created before, and deleted immediately after execution of the id() call. To be sure that objects whose id you want to examine are still alive, create another reference to the object:

>>> a = 1000; b = 2000
>>> id(a)
13901272
>>> id(b)
13891296

我什麼時候可以依靠 is 運算子進行識別性測試？

is 運算子測試物件識別性。測試 a is b 等同於 id(a) == id(b) 。

識別性測試最重要的屬性是物件始終與自身相同， a is a 總是回傳 True 。識別性測試通常比相等性測試更快。與相等性測試不同，識別性測試保證回傳布林值 True 或 False 。

然而，只有當物件識別性得到保證時，識別性測試才能代替相等性測試。一般來說，保證識別性的情況有以下三種：

Assignments create new names but do not change object identity. After the assignment new = old, it is guaranteed that new is old.

Putting an object in a container that stores object references does not change object identity. After the list assignment s[0] = x, it is guaranteed that s[0] is x.

If an object is a singleton, it means that only one instance of that object can exist. After the assignments a = None and b = None, it is guaranteed that a is b because None is a singleton.

在大多數其他情況下，識別性測試是不可取的，相等性測試是首選。特別是，識別性測試不應用於檢查常數，例如不能保證是單例的 int 和 str：

>>> a = 1000
>>> b = 500
>>> c = b + 500
>>> a is c
False

>>> a = 'Python'
>>> b = 'Py'
>>> c = b + 'thon'
>>> a is c
False

同樣地，可變容器的新實例永遠不會相同：

>>> a = []
>>> b = []
>>> a is b
False

在標準函式庫程式碼中，你將看到幾種正確使用識別性測試的常見模式：

正如 PEP 8 [https://peps.python.org/pep-0008/] 所推薦的，識別性測試是檢查 None 的首選方法。這在程式碼中讀起來像簡單的英語，並避免與其他可能具有評估為 false 的布林值的物件混淆。

Detecting optional arguments can be tricky when None is a valid input value. In those situations, you can create a singleton sentinel object guaranteed to be distinct from other objects. For example, here is how to implement a method that behaves like dict.pop():

_sentinel = object()

def pop(self, key, default=_sentinel):
    if key in self:
        value = self[key]
        del self[key]
        return value
    if default is _sentinel:
        raise KeyError(key)
    return default

容器實作有時需要透過識別性測試來增強相等性測試。這可以防止程式碼被諸如 float('NaN') 之類的不等於自身的物件所混淆。

例如，以下是 collections.abc.Sequence.__contains__() 的實作：

def __contains__(self, value):
    for v in self:
        if v is value or v == value:
            return True
    return False

子類別如何控制不可變實例中儲存的資料？

When subclassing an immutable type, override the __new__() method instead of the __init__() method. The latter only runs after an instance is created, which is too late to alter data in an immutable instance.

所有這些不可變類別都具有與其父類別不同的簽名：

from datetime import date

class FirstOfMonthDate(date):
    "總是選擇每個月的第一天"
    def __new__(cls, year, month, day):
        return super().__new__(cls, year, month, 1)

class NamedInt(int):
    "允許一些數字的文字名稱"
    xlat = {'zero': 0, 'one': 1, 'ten': 10}
    def __new__(cls, value):
        value = cls.xlat.get(value, value)
        return super().__new__(cls, value)

class TitleStr(str):
    "將 str 轉換成適合作為 URL 路徑的名稱"
    def __new__(cls, s):
        s = s.lower().replace(' ', '-')
        s = ''.join([c for c in s if c.isalnum() or c == '-'])
        return super().__new__(cls, s)

這些類別可以像這樣使用：

>>> FirstOfMonthDate(2012, 2, 14)
FirstOfMonthDate(2012, 2, 1)
>>> NamedInt('ten')
10
>>> NamedInt(20)
20
>>> TitleStr('Blog: Why Python Rocks')
'blog-why-python-rocks'

如何快取方法呼叫？

The two principal tools for caching methods are functools.cached_property() and functools.lru_cache(). The former stores results at the instance level and the latter at the class level.

The cached_property approach only works with methods that do not take any arguments. It does not create a reference to the instance. The cached method result will be kept only as long as the instance is alive.

The advantage is that when an instance is no longer used, the cached method result will be released right away. The disadvantage is that if instances accumulate, so too will the accumulated method results. They can grow without bound.

lru_cache 方法適用於具有可雜湊引數的方法。除非特別努力傳遞弱參照，否則它會建立對實例的參照。

The advantage of the least recently used algorithm is that the cache is bounded by the specified maxsize. The disadvantage is that instances are kept alive until they age out of the cache or until the cache is cleared.

這個例子展示了各種技術：

class Weather:
    "Lookup weather information on a government website"

    def __init__(self, station_id):
        self._station_id = station_id
        # The _station_id is private and immutable

    def current_temperature(self):
        "Latest hourly observation"
        # Do not cache this because old results
        # can be out of date.

    @cached_property
    def location(self):
        "Return the longitude/latitude coordinates of the station"
        # Result only depends on the station_id

    @lru_cache(maxsize=20)
    def historic_rainfall(self, date, units='mm'):
        "Rainfall on a given date"
        # Depends on the station_id, date, and units.

The above example assumes that the station_id never changes. If the relevant instance attributes are mutable, the cached_property approach can't be made to work because it cannot detect changes to the attributes.

To make the lru_cache approach work when the station_id is mutable, the class needs to define the __eq__() and __hash__() methods so that the cache can detect relevant attribute updates:

class Weather:
    "Example with a mutable station identifier"

    def __init__(self, station_id):
        self.station_id = station_id

    def change_station(self, station_id):
        self.station_id = station_id

    def __eq__(self, other):
        return self.station_id == other.station_id

    def __hash__(self):
        return hash(self.station_id)

    @lru_cache(maxsize=20)
    def historic_rainfall(self, date, units='cm'):
        'Rainfall on a given date'
        # Depends on the station_id, date, and units.

模組

如何建立 .pyc 檔案？

When a module is imported for the first time (or when the source file has changed since the current compiled file was created) a .pyc file containing the compiled code should be created in a __pycache__ subdirectory of the directory containing the .py file. The .pyc file will have a filename that starts with the same name as the .py file, and ends with .pyc, with a middle component that depends on the particular python binary that created it. (See PEP 3147 [https://peps.python.org/pep-3147/] for details.)

One reason that a .pyc file may not be created is a permissions problem with the directory containing the source file, meaning that the __pycache__ subdirectory cannot be created. This can happen, for example, if you develop as one user but run as another, such as if you are testing with a web server.

Unless the PYTHONDONTWRITEBYTECODE environment variable is set, creation of a .pyc file is automatic if you're importing a module and Python has the ability (permissions, free space, etc...) to create a __pycache__ subdirectory and write the compiled module to that subdirectory.

Running Python on a top level script is not considered an import and no .pyc will be created. For example, if you have a top-level module foo.py that imports another module xyz.py, when you run foo (by typing python foo.py as a shell command), a .pyc will be created for xyz because xyz is imported, but no .pyc file will be created for foo since foo.py isn't being imported.

如果你需要為 foo 建立一個 .pyc 檔案 —— 也就是說，要為一個未引入的模組建立一個 .pyc 檔案 —— 你可以使用 py_compile 和 compileall 模組。

py_compile 模組允許手動編譯任何模組。其中一種方法是在該模組中以交互方式使用 compile() 函式：

>>> import py_compile
>>> py_compile.compile('foo.py')

這會將 .pyc 寫入與 foo.py 相同位置的 __pycache__ 子目錄（或者你可以使用可選參數 cfile 覆蓋它）。

You can also automatically compile all files in a directory or directories using the compileall module. You can do it from the shell prompt by running compileall.py and providing the path of a directory containing Python files to compile:

python -m compileall .

如何找到目前模組名稱？

A module can find out its own module name by looking at the predefined global variable __name__. If this has the value '__main__', the program is running as a script. Many modules that are usually used by importing them also provide a command-line interface or a self-test, and only execute this code after checking __name__:

def main():
    print('Running test...')
    ...

if __name__ == '__main__':
    main()

要怎樣才能擁有相互引入的模組？

假設你有以下模組：

foo.py：

from bar import bar_var
foo_var = 1

bar.py：

from foo import foo_var
bar_var = 2

問題是直譯器將執行以下步驟：

主要引入 foo

建立了 foo 的空全域變數

foo 被編譯並開始執行

foo 引入 bar

建立了 bar 的空全域變數

bar 已被編譯並開始執行

bar 引入 foo（這是一個空操作，因為已經有一個名為 foo 的模組）

引入機制嘗試從 foo 全域變數中讀取 foo_var，以設定 bar.foo_var = foo.foo_var

最後一步失敗了，因為 Python 還沒有完成對 foo 的直譯，而 foo 的全域符號字典仍然是空的。

The same thing happens when you use import foo, and then try to access foo.foo_var in global code.

此問題有（至少）三種可能的解決方法。

Guido van Rossum recommends avoiding all uses of from <module> import ..., and placing all code inside functions. Initializations of global variables and class variables should use constants or built-in functions only. This means everything from an imported module is referenced as <module>.<name>.

Jim Roskind 建議在每個模組中按以下順序執行各個步驟：

exports (globals, functions, and classes that don't need imported base classes)

import 陳述式

活躍程式碼（包括從引入值初始化的全域變數）。

Van Rossum 不太喜歡這種方法，因為引入出現在一個奇怪的地方，但它確實有效。

Matthias Urlichs 建議重組 (restructuring) 你的程式碼，以便打從一開始就不需要遞迴引入。

這些方案並不衝突。

__import__('x.y.z') 回傳 <module 'x'>，那我怎麼得到 z？

Consider using the convenience function import_module() from importlib instead:

z = importlib.import_module('x.y.z')

當我編輯需要引入的模組並重新引入它時，更動沒有反應出來。為什麼會這樣？

For reasons of efficiency as well as consistency, Python only reads the module file on the first time a module is imported. If it didn't, in a program consisting of many modules where each one imports the same basic module, the basic module would be parsed and re-parsed many times. To force re-reading of a changed module, do this:

import importlib
import modname
importlib.reload(modname)

警告：此技術並非 100% 萬無一失。尤其是包含像這樣陳述式的模組：

from modname import some_objects

will continue to work with the old version of the imported objects. If the module contains class definitions, existing class instances will not be updated to use the new class definition. This can result in the following paradoxical behaviour:

>>> import importlib
>>> import cls
>>> c = cls.C()                # 建立一個 C 的實例
>>> importlib.reload(cls)
<module 'cls' from 'cls.py'>
>>> isinstance(c, cls.C)       # isinstance 為 false？！？
False

如果印出類別物件的「識別性」，問題的本質就很清楚了：

>>> hex(id(c.__class__))
'0x7352a0'
>>> hex(id(cls.C))
'0x4198d0'

設計和歷史常見問答集

目錄

設計和歷史常見問答集

為什麼 Python 使用縮排將陳述式進行分組？

為什麼我會從簡單的數學運算得到奇怪的結果？

為何浮點數運算如此不精確？

為什麼 Python 字串不可變動？

為何「self」在方法 (method) 定義和呼叫時一定要明確使用？

為何我不能在運算式 (expression) 中使用指派運算？

為何 Python 對於一些功能實作使用方法（像是 list.index()），另一些使用函式（像是 len(list)）？

為何 join() 是字串方法而非串列 (list) 或元組 (tuple) 方法？

例外處理有多快？

為什麼 Python 內沒有 switch 或 case 陳述式？

為何不能在直譯器上模擬執行緒，而要使用作業系統的特定實作方式？

為何 lambda 運算式不能包含陳述式？

Python 可以被編譯成機器語言、C 語言或其他種語言嗎？

Python 如何管理記憶體？

為何 CPython 不使用更多傳統的垃圾回收機制？

當 CPython 結束時，為何所有的記憶體不會被釋放？

為何要把元組 (tuple) 和串列 (list) 分成兩個資料型別？

串列 (list) 在 CPython 中是怎麼實作的？

字典 (dictionaries) 在 CPython 中是怎麼實作的？

為何字典的鍵一定是不可變的？

為何 list.sort() 不是回傳排序過的串列？

如何在 Python 中指定和強制使用一個介面規範 (interface spec)？

為何沒有 goto 語法？

為何純字串 (r-string) 不能以反斜線結尾？

為何 Python 沒有屬性賦值的 with 陳述式？

為何產生器 (generator) 不支援 with 陳述式？

為何 if、while、def、class 陳述式裡需要冒號？

為何 Python 允許在串列和元組末端加上逗號？

為什麼 Python 使用縮排將陳述式進行分組？

Guido van Rossum 相信使用縮排來分組超級優雅，並且對提高一般 Python 程式的清晰度有許多貢獻。許多人在學習一段時間之後就愛上了這個功能。

因為沒有開始/結束括號，因此剖析器和人類讀者感知到的分組就不存在分歧。偶爾 C 語言的程式設計師會遇到這樣的程式碼片段：

if (x <= y)
        x++;
        y--;
z++;

如果條件為真，只有 x++ 陳述式會被執行，但縮排會讓很多人對他有不同的理解。即使是資深的 C 語言開發者有時也會盯著他許久，思考為何即便 x > y，但 y 還是減少了。

因為沒有開頭與結尾的括號，Python 比起其他語言會更不容易遇到程式碼風格的衝突。在 C 語言中，有多種不同的方法來放置花括號。在習慣讀寫特定風格後，去讀（或是必須去寫）另一種風格會覺得不太舒服。

很多程式碼風格會把 begin/end 獨立放在一行。這會讓程式碼很長且浪費珍貴的螢幕空間，要概覽程式時也變得較為困難。理想上來說，一個函式應該要佔一個螢幕（大概 20 至 30 行）。20 行的 Python 程式碼比起 20 行的 C 程式碼可以做更多事。雖然沒有開頭與結尾的括號並非單一原因（沒有變數宣告及高階的資料型別同樣有關），但縮排式的語法確實給了幫助。

為什麼我會從簡單的數學運算得到奇怪的結果？

請見下一個問題。

為何浮點數運算如此不精確？

使用者時常對這樣的結果感到驚訝：

>>> 1.2 - 1.0
0.19999999999999996

然後認為這是 Python 的 bug，但這並不是。這跟 Python 幾乎沒有關係，而是和底層如何處理浮點數有關係。

CPython 的 float 型別使用了 C 的 double 型別來儲存。一個 float 物件的值會以固定的精度（通常為 53 位元）存為二進制浮點數，Python 使用 C 來運算浮點數，而他的結果會依處理器中的硬體實作方式來決定。這表示就浮點數運算來說，Python 和 C、Java 等很多受歡迎的語言有一樣的行為。

很多數字可以簡單地寫成十進位表示，但卻無法簡單地以二進制浮點數表示。比方說，在以下程式碼執行後：

>>> x = 1.2

x 裡的值是一個（很接近）1.2 的估計值，但並非精確地等於 1.2。以一般的電腦來說，他實際儲存的值是：

1.0011001100110011001100110011001100110011001100110011 (binary)

而這個值正是：

1.1999999999999999555910790149937383830547332763671875 (decimal)

53 位元的精度讓 Python 可以有 15 至 16 小數位的準確度。

要更完全的解釋可以查閱在 Python 教學的浮點運算一章。

為什麼 Python 字串不可變動？

有許多優點。

其一是效能：知道字串不可變動後，我們就可以在創造他的時候就分配好空間，而後他的儲存空間需求就是固定不變的。這也是元組 (tuple) 和串列 (list) 相異的其中一個原因。

另一個優點是在 Python 中，字串和數字一樣「基本」。沒有任何行為會把 8 這個數值改成其他數值；同理，在 Python 中也沒有任何行為會修改字串「eight」。

為何「self」在方法 (method) 定義和呼叫時一定要明確使用？

此構想從 Modula-3 而來。因為許多原因，他可以說是非常實用。

第一，這樣可以更明顯表現出你在用方法 (method) 或是實例 (instance) 的屬性，而非一個區域變數。即使不知道類別 (class) 的定義，當看到 self.x 或 self.meth()，就會很清楚地知道是正在使用實例的變數或是方法。在 C++ 裡，你可以藉由沒有區域變數宣告來判斷這件事 ── 但在 Python 裡沒有區域變數宣告，所以你必須去看類別的定義來確定。有些 C++ 和 Java 的程式碼規格要求要在實例屬性的名稱加上前綴 m_，所以這種明確性在那些語言也是很好用的。

第二，當你想明確地使用或呼叫在某個類別裡的方法的時候，你不需要特殊的語法。在 C++ 裡，如果你想用一個在繼承類別時被覆寫的基底類別方法，必須要用 :: 運算子 -- 但在 Python 裡，你可以直接寫成 baseclass.methodname(self, <argument list>)。這在 __init__() 方法很好用，特別是在一個繼承的類別要擴充基底類別的方法而要呼叫他時。

最後，他解決了關於實例變數指派的語法問題：因為區域變數在 Python 是（定義為）在函式內被指派值的變數（且沒有被明確宣告成全域），所以會需要一個方法來告訴直譯器這個指派運算是針對實例變數，而非針對區域變數，這在語法層面處理較好（為了效率）。C++ 用宣告解決了這件事，但 Python 沒有，而為了這個原因而引入變數宣告機制又略嫌浪費。但使用明確的 self.var 就可以把這個問題圓滿解決。同理，在用實例變數的時候必須寫成 self.var 即代表對於在方法中不特定的名稱不需要去看實例的內容。換句話說，區域變數和實例變數存在於兩個不同的命名空間 (namespace)，而你需要告訴 Python 要使用哪一個。

為何我不能在運算式 (expression) 中使用指派運算？

從 Python 3.8 開始，你可以這麼做了！

指派運算式使用海象運算子 := 來在運算式中指派變數值：

while chunk := fp.read(200):
   print(chunk)

更多資訊請見 PEP 572 [https://peps.python.org/pep-0572/]。

為何 Python 對於一些功能實作使用方法（像是 list.index()），另一些使用函式（像是 len(list)）？

如 Guido 所說：

（一） 對一些運算來說，前綴寫法看起來會比後綴寫法好 ── 前綴（和中綴！）運算在數學上有更久遠的傳統，這些符號在視覺上幫助數學家們更容易思考問題。想想把 x*(a+b) 這種式子展開成 x*a + x*b 的簡單，再比較一下古老的圈圈符號記法的笨拙就知道了。

（二） 當我看到一段程式碼寫著 len(x)，我知道他要找某個東西的長度。這告訴了我兩件事：結果是一個整數、參數是某種容器。相對地，當我看到 x.len()，我必須先知道 x 是某種容器，並實作了一個介面或是繼承了一個有標準 len() 的類別。遇到一個沒有實作對映 (mapping) 的類別卻有 get() 或 keys() 方法，或是不是檔案但卻有 write() 方法時，我們偶爾會覺得困惑。

—https://mail.python.org/pipermail/python-3000/2006-November/004643.html

為何 join() 是字串方法而非串列 (list) 或元組 (tuple) 方法？

自 Python 1.6 之後，字串變得很像其他標準的型別，也在此時，一些可以和字串模組的函式有相同功能的方法也被加入。大多數的新方法都被廣泛接受，但有一個方法似乎讓一些程式人員不舒服：

", ".join(['1', '2', '4', '8', '16'])

結果是：

"1, 2, 4, 8, 16"

通常有兩個反對這個用法的論點。

第一項這麼說：「用字串文本 (string literal) （字串常數）看起來真的很醜」，也許真的如此，但字串文本就只是一個固定值。如果方法可以用在值為字串的變數上，那沒道理字串文本不能被使用。

第二個反對意見通常是：「我是在叫一個序列把它的成員用一個字串常數連接起來」。但很遺憾地，你並不是在這樣做。因為某種原因，把 split() 當成字串方法比較簡單，因為這樣我們可以輕易地看到：

"1, 2, 4, 8, 16".split(", ")

這是在叫一個字串文本回傳由指定的分隔符號（或是預設為空白）分出的子字串的指令。

join() 是一個字串方法，因為在用他的時候，你是告訴分隔字串去走遍整個字串序列，並將自己插入到相鄰的兩項之間。這個方法的參數可以是任何符合序列規則的物件，包括自己定義的新類別。在 bytes 和 bytearray 物件也有類似的方法可用。

例外處理有多快？

如果沒有例外被丟出，一個 try/except 區塊是非常有效率的。事實上，抓捕例外要付出昂貴的代價。在 Python 2.0 以前，這樣使用是相當常見的：

try:
    value = mydict[key]
except KeyError:
    mydict[key] = getvalue(key)
    value = mydict[key]

這只有在你預料這個字典大多數時候都有鍵的時候才合理。如果並非如此，你應該寫成：

if key in mydict:
    value = mydict[key]
else:
    value = mydict[key] = getvalue(key)

單就這個情況來說，你也可以用 value = dict.setdefault(key, getvalue(key))，不過只有在 getvalue() 代價不大的時候才能用，畢竟他每次都會被執行。

為什麼 Python 內沒有 switch 或 case 陳述式？

In general, structured switch statements execute one block of code when an expression has a particular value or set of values. Since Python 3.10 one can easily match literal values, or constants within a namespace, with a match ... case statement. An older alternative is a sequence of if... elif... elif... else.

如果可能性很多，你可以用字典去對映要呼叫的函式。舉例來說：

if key in mydict:
    value = mydict[key]
else:
    value = mydict[key] = getvalue(key)

對於呼叫物件裡的方法，你可以利用內建用來找尋特定方法的函式 getattr() 來做進一步的簡化：

class MyVisitor:
    def visit_a(self):
        ...

    def dispatch(self, value):
        method_name = 'visit_' + str(value)
        method = getattr(self, method_name)
        method()

我們建議在方法名稱加上前綴，以這個例子來說是 像是 visit_。沒有前綴的話，一旦收到從不信任來源的值，攻擊者便可以隨意呼叫在你的專案內的方法。

Imitating switch with fallthrough, as with C's switch-case-default, is possible, much harder, and less needed.

為何不能在直譯器上模擬執行緒，而要使用作業系統的特定實作方式？

答案一：很不幸地，直譯器對每個 Python 的堆疊框 (stack frame) 會推至少一個 C 的堆疊框。同時，擴充套件可以隨時呼叫 Python，因此完整的實作必須要支援 C 的執行緒。

答案二：幸運地，無堆疊 (Stackless) Python [https://github.com/stackless-dev/stackless/wiki] 完全重新設計了直譯器迴圈，並避免了 C 堆疊。

為何 lambda 運算式不能包含陳述式？

Python 的 lambda 運算式不能包含陳述式是因為 Python 的語法框架無法處理包在運算式中的陳述式。然而，在 Python 裡這並不是一個嚴重的問題。不像在其他語言中有獨立功能的 lambda，Python 的 lambda 只是一個在你懶得定義函式時可用的一個簡寫表達法。

函式已經是 Python 裡的一級物件 (first class objects)，而且可以在區域範圍內被宣告。因此唯一用 lambda 而非區域性的函式的優點就是你不需要多想一個函式名稱 — 但這樣就會是一個區域變數被指定成函式物件（和 lambda 運算式的結果同類）！

Python 可以被編譯成機器語言、C 語言或其他種語言嗎？

Cython [https://cython.org/] 可以編譯一個調整過有選擇性註解的 Python 版本。Nuitka [https://nuitka.net/] 是一個有潛力編譯器，可以把 Python 編譯成 C++，他的目標是支援完整的 Python 語言。

Python 如何管理記憶體？

Python 記憶體管理的細節取決於實作。Python 的標準實作 CPython 使用參照計次 (reference counting) 來偵測不再被存取的物件，並用另一個機制來收集參照循環 (reference cycle)、定期執行循環偵測演算法來找不再使用的循環並刪除相關物件。 gc 模組提供了可以執行垃圾收集、抓取除錯統計數據和調整收集器參數的函式。

然而，在其他實作（像是 Jython [https://www.jython.org] 或 PyPy [https://pypy.org]）中，會使用像是成熟的垃圾收集器等不同機制。如果你的 Python 程式碼的表現取決於參照計次的實作，這個相異處會導致一些微小的移植問題。

在一些 Python 實作中，下面這段程式碼（在 CPython 可以正常運作）可能會把檔案描述子 (file descriptor) 用盡：

for file in very_long_list_of_files:
    f = open(file)
    c = f.read(1)

實際上，使用 CPython 的參照計次和解構方案 (destructor scheme)，每個對 f 的新指派都會關閉前面打開的檔案。然而用傳統的垃圾回收 (GC) 的話，這些檔案物件只會在不固定且有可能很長的時間後被收集（並關閉）。

如果你希望你的程式碼在任何 Python 實作版本中都可以運作，那你應該清楚地關閉檔案或是使用 with 陳述式，如此一來，不用管記憶體管理的方法，他也會正常運作：

for file in very_long_list_of_files:
    with open(file) as f:
        c = f.read(1)

為何 CPython 不使用更多傳統的垃圾回收機制？

第一，這並不是 C 的標準功能，因此他的可攜性低。（對，我們知道 Boehm GC 函式庫。他有可相容於大多數平台的組合語言程式碼，但依然不是全部，而即便它大多數是通透的，也並不完全，要讓它跟 Python 相容還是需要做一些修補。）

傳統的垃圾收集 (GC) 在 Python 被嵌入其他應用程式時也成了一個問題。在獨立的 Python 程式裡當然可以把標準的 malloc() 和 free() 換成 GC 函式庫提供的其他版本；但一個嵌著 Python 的應用程式可能想用自己的 malloc() 和 free() 替代品，而不是用 Python 的。以現在來說，CPython 和實作 malloc() 和 free() 的程式相處融洽。

當 CPython 結束時，為何所有的記憶體不會被釋放？

當離開 Python 時，從 Python 模組的全域命名空間來的物件並非總是會被釋放。在有循環引用的時候，這可能會發生。有些記憶體是被 C 函式庫取用的，他們不可能被釋放（例如：像是 Purify 之類的工具會抱怨）。然而，Python 在關閉的時候會積極清理記憶體並嘗試刪除每個物件。

如果你想要強迫 Python 在釋放記憶體時刪除特定的東西，你可以用 atexit 模組來執行會強制刪除的函式。

為何要把元組 (tuple) 和串列 (list) 分成兩個資料型別？

串列和元組在很多方面相當相似，但通常用在完全不同的地方。元組可以想成 Pascal 的 record 或是 C 的 struct，是一小群相關聯但可能是不同型別的資料集合，以一組為單位進行操作。舉例來說，一個笛卡兒坐標系可以適當地表示成一個有二或三個值的元組。

另一方面，串列更像是其他語言的陣列 (array)。他可以有不固定個同類別物件，且為逐項操作。舉例來說，os.listdir('.') 回傳當下目錄裡的檔案，以包含字串的串列表示。如果你新增了幾個檔案到這個目錄，一般來說操作結果的函式也會正常運作。

元組則是不可變的，代表一旦元組被建立，你就不能夠改變裡面的任何一個值。而串列可變，所以你可以改變裡面的元素。只有不可變的元素可以成為字典的鍵，所以只能把元組當成鍵，而串列則不行。

串列 (list) 在 CPython 中是怎麼實作的？

CPython 的串列 (list) 事實上是可變長度的陣列 (array)，而不是像 Lisp 語言的鏈接串列 (linked list)。實作上，他是一個連續的物件參照 (reference) 陣列，並把指向此陣列的指標 (pointer) 和陣列長度存在串列的標頭結構內。

因此，用索引來找串列特定項 a[i] 的代價和串列大小或是索引值無關。

當新物件被新增或插入時，陣列會被調整大小。為了改善多次加入物件的效率，我們有用一些巧妙的方法，當陣列必須變大時，會多收集一些額外的空間，接下來幾次新增時就不需要再調整大小了。

字典 (dictionaries) 在 CPython 中是怎麼實作的？

CPython 的字典是用可調整大小的雜湊表 (hash table) 實作的。比起 B 樹 (B-tree)，在搜尋（目前為止最常見的操作）方面有更好的表現，實作上也較為簡單。

字典利用內建 hash() 函式，對每個鍵做雜湊計算。雜湊結果依據鍵的值和個別執行緒 (processes) 的種子而有相當大的差距。例如，'Python' 的雜湊是 -539294296，而只差一個字的 'python' 則是 1142331976。雜湊結果接著被用來計算值在內部陣列儲存的位置。假設你存的鍵都有不同的雜湊值，那字典只需要常數時間 — 用大 O 表示法 (Big-O notation) 就是 O(1) — 來找任意一個鍵。

為何字典的鍵一定是不可變的？

實作字典用的雜湊表是根據鍵的值做計算從而找到鍵的。如果鍵可變的話，他的值就可以改變，則雜湊的結果也會一起變動。但改變鍵的物件的人無從得知他被用來當成字典的鍵，所以無法修改字典的內容。然後，當你嘗試在字典中尋找這個物件時，因為雜湊值不同的緣故，你找不到他。而如果你嘗試用舊的值去尋找，也一樣找不到，因為他的雜湊結果和原先物件不同。

如果你想要用串列作為字典的索引，把他轉換成元組即可。tuple(L) 函式會建立一個和串列 L 一樣內容的元組。而元組是不可變的，所以可以用來當成字典的鍵。

也有人提出一些不能接受的方法：

用串列的記憶體位址（物件 id）來雜湊。這不會成功，因為你如果用同樣的值建立一個新的串列，是找不到的。舉例來說：

mydict = {[1, 2]: '12'}
print(mydict[[1, 2]])

這將會導致 KeyError 例外，因為 [1, 2] 的 id 在第一行和第二行是不同的。換句話說，字典的鍵應該要用 == 來做比較，而不是用 is。

複製一個串列作為鍵。這一樣不會成功，因為串列是可變的，他可以包含自己的參照，所以複製會形成一個無窮迴圈。

允許串列作為鍵，但告訴使用者不要更動他。當你不小心忘記或是更動了這個串列，會產生一種難以追蹤的 bug。他同時也違背了一項字典的重要定則：在 d.keys() 的每個值都可以當成字典的鍵。

一旦串列被當成鍵，把他標記成只能讀取。問題是，這不只要避免最上層的物件改變值，就像用元組包含串列來做為鍵。把一個物件當成鍵，需要將從他開始可以接觸到的所有物件都標記成只能讀取 — 所以再一次，自己參照自己的物件會導致無窮迴圈。

如果你需要的話，這裡有個小技巧可以幫你，但請自己承擔風險：你可以把一個可變物件包裝進一個有 __eq__() 和 __hash__() 方法的類別實例。只要這種包裝物件還存在於字典（或其他類似結構）中，你就必須確定在字典（或其他用雜湊為基底的結構）中他們的雜湊值會保持恆定。

class ListWrapper:
    def __init__(self, the_list):
        self.the_list = the_list

    def __eq__(self, other):
        return self.the_list == other.the_list

    def __hash__(self):
        l = self.the_list
        result = 98767 - len(l)*555
        for i, el in enumerate(l):
            try:
                result = result + (hash(el) % 9999999) * 1001 + i
            except Exception:
                result = (result % 7777777) + i * 333
        return result

請注意，雜湊的計算可能變得複雜，因為有串列成員不可雜湊 (unhashable) 和算術溢位的可能性。

此外，不管物件是否在字典中，如果 o1 == o2（即 o1.__eq__(o2) is True），則 hash(o1) == hash(o2)（即 o1.__hash__() == o2.__hash__()），這個事實必須要成立。如果無法滿足這項限制，那字典和其他用雜湊為基底的結構會出現不正常的行為。

至於 ListWrapper，只要這個包裝過的物件在字典中，裡面的串列就不能改變以避免不正常的事情發生。除非你已經謹慎思考過你的需求和無法滿足條件的後果，不然請不要這麼做。請自行注意。

為何 list.sort() 不是回傳排序過的串列？

在重視效能的情況下，把串列複製一份有些浪費。因此，list.sort() 直接在串列裡做排序。為了提醒你這件事，他不會回傳排序過的串列。這樣一來，當你需要排序過和未排序過的串列時，你就不會被誤導而不小心覆蓋掉串列。

如果你想要他回傳新的串列，那可以改用內建的 sorted()。他會用提供的可疊代物件 (iterable) 來排序建立新串列，並回傳之。例如，以下這個範例會說明如何有序地疊代字典的鍵：

for key in sorted(mydict):
    ...  # do whatever with mydict[key]...

如何在 Python 中指定和強制使用一個介面規範 (interface spec)？

像是 C++ 和 Java 等語言提供了模組的介面規範，他描述了該模組的方法和函式的原型。很多人認為這種在編譯時強制執行的介面規範在建構大型程式時十分有幫助。

Python 2.6 加入了 abc 模組，讓你可以定義抽象基底類別 (Abstract Base Class, ABC)。你可以使用 isinstance() 和 issubclass() 來確認一個實例或是類別是否實作了某個抽象基底類別。而 collections.abc 模組定義了一系列好用的抽象基底類別，像是 Iterable、Container 和 MutableMapping。

對 Python 來說，很多介面規範的優點可以用對元件適當的測試規則來達到。

一個針對模組的好測試套件提供了迴歸測試 (regression testing)，並作為模組介面規範和一組範例。許多 Python 模組可以直接當成腳本執行，並提供簡單的「自我測試」。即便模組使用了複雜的外部介面，他依然可以用外部介面的簡單的「樁」(stub) 模擬來獨立測試。doctest 和 unittest 模組或第三方的測試框架可以用來建構詳盡徹底的測試套件來測試模組裡的每一行程式碼。

就像介面規範一樣，一個適當的測試規則在建造大型又複雜的 Python 應用程式時可以幫上忙。事實上，他可能可以有更好的表現，因為介面規範無法測試程式的特定屬性。舉例來說，list.append() 方法應該要在某個內部的串列最後面加上新的元素，而介面規範沒辦法測試你的 list.append() 是不是真的有正確的實作，但這在測試套件裡是件很簡單的事。

撰寫測試套件相當有幫助，而你會像要把程式碼設計成好測試的樣子。測試驅動開發 (test-driven development) 是一個越來越受歡迎的設計方法，他要求先完成部分的測試套件，再去撰寫真的要用的程式碼。當然 Python 也允許你草率地不寫任何測試。

為何沒有 goto 語法？

在 1970 年代，人們了解到沒有限制的 goto 會導致混亂、難以理解和修改的「義大利麵」程式碼 ("spaghetti" code)。在高階語言裡，這也是不需要的，因為有方法可以做邏輯分支（以 Python 來說，用 if 陳述式和 or、and 及 if/else 運算式）和迴圈（用 while 和 for 陳述式，可能會有 continue 和 break）。

我們也可以用例外來做「結構化的 goto」，這甚至可以跨函式呼叫。很多人覺得例外可以方便地模擬在 C、Fortran 和其他語言裡各種合理使用的 go 和 goto。例如：

class label(Exception): pass  # declare a label

try:
    ...
    if condition: raise label()  # goto label
    ...
except label:  # where to goto
    pass
...

這依然不能讓你跳進迴圈內，這通常被認為是對 goto 的濫用。請小心使用。

為何純字串 (r-string) 不能以反斜線結尾？

更精確地來說，他不能以奇數個反斜線結尾：尾端未配對的反斜線會使結尾的引號被轉義 (escapes)，變成一個未結束的字串。

設計出純字串是為了提供有自己反斜線跳脫處理的處理器（主要是正規表示式）一個方便的輸入方式。這種處理器會把未配對的結尾反斜線當成錯誤，所以純字串不允許如此。相對地，他讓你用一個反斜線跳脫引號。這些規則在他們預想的目的上正常地運作。

如果你嘗試建立 Windows 的路徑名稱，請注意 Windows 系統指令也接受一般斜線：

f = open("/mydir/file.txt")  # works fine!

如果你嘗試建立 DOS 指令的路徑名稱，試試看使用以下的範例：

dir = r"\this\is\my\dos\dir" "\\"
dir = r"\this\is\my\dos\dir\ "[:-1]
dir = "\\this\\is\\my\\dos\\dir\\"

為何 Python 沒有屬性賦值的 with 陳述式？

Python 的 with 陳述式包裝了一區塊程式的執行，在進入和離開該區塊時執行程式碼。一些語言會有像如下的結構：

with obj:
    a = 1               # equivalent to obj.a = 1
    total = total + 1   # obj.total = obj.total + 1

但在 Python，這種結構是模糊的。

在其他語言裡，像是 Object Pascal、Delphi 和 C++，使用的是靜態型別，所以我們可以清楚地知道是哪一個成員被指派值。這是靜態型別的重點 — 在編譯的時候，編譯器永遠都知道每個變數的作用域 (scope)。

Python 使用的是動態型別。所以我們不可能提前知道在執行時哪個屬性會被使用到。成員屬性可能在執行時從物件中被新增或移除。這使得如果簡單來看的話，我們無法得知以下哪個屬性會被使用：區域的、全域的、或是成員屬性？

以下列不完整的程式碼為例：

def foo(a):
    with a:
        print(x)

這段程式碼假設 a 有一個叫做 x 的成員屬性。然後，Python 裡並沒有任何跡象告訴直譯器這件事。在假設「a」是一個整數的話，那會發生什麼事？如果有一個全域變數稱為 x，那在這個 with 區塊會被使用嗎？如你所見，Python 動態的天性使得這種選擇更加困難。

然而 with 陳述式或類似的語言特性（減少程式碼量）的主要好處可以透過賦值來達成。相較於這樣寫：

function(args).mydict[index][index].a = 21
function(args).mydict[index][index].b = 42
function(args).mydict[index][index].c = 63

應該寫成這樣：

ref = function(args).mydict[index][index]
ref.a = 21
ref.b = 42
ref.c = 63

這也有提升執行速度的副作用，因為 Python 的名稱綁定解析會在執行的時候發生，而第二版只需要執行解析一次即可。

類似的提案包括引入語法以進一步減少程式碼量，例如使用「前導點 (leading dot)」，但這些提案已被捨棄，以維持程式的明確性（參閱 https://mail.python.org/pipermail/python-ideas/2016-May/040070.html）。

為何產生器 (generator) 不支援 with 陳述式？

出於技術原因，把產生器直接用作情境 (context) 管理器會無法正常運作。因為通常來說，產生器是被當成疊代器 (iterator)，到最後完成時不需要被手動關閉。但如果你需要的話，你可以在 with 陳述式裡用 contextlib.closing(generator) 來包裝他。

為何 if、while、def、class 陳述式裡需要冒號？

需要冒號主要是為了增加可讀性（由 ABC 語言的實驗得知）。試想如下範例：

if a == b
    print(a)

以及：

if a == b:
    print(a)

注意第二個例子稍微易讀一些的原因。可以更進一步觀察，一個冒號是如何放在這個 FAQ 答案的例子裡的，這是標準的英文用法。

另一個小原因是冒號會使編輯器更容易做語法突顯，他們只需要看冒號的位置就可以決定是否需要更多縮排，而不用做更多繁複精密的程式碼剖析。

為何 Python 允許在串列和元組末端加上逗號？

Python 允許你在串列、元組和字典的結尾加上逗號：

[1, 2, 3,]
('a', 'b', 'c',)
d = {
    "A": [1, 5],
    "B": [6, 7],  # last trailing comma is optional but good style
}

這有許多原因可被允許。

當你要把串列、元組或字典的值寫成多行時，這樣做會讓你新增元素時較為方便，因為你不需要在前一行加上逗號。這幾行的值也可以被重新排序，而不會導致語法錯誤。

不小心遺漏了逗號會導致難以發現的錯誤，例如：

x = [
  "fee",
  "fie"
  "foo",
  "fum"
]

這個串列看起來有四個元素，但他其實只有三個：「fee」、「fiefoo」、「fum」。永遠記得加上逗號以避免這種錯誤。

允許結尾逗號也讓生成的程式碼更容易產生。

函式庫和擴充功能的常見問題

目錄

函式庫和擴充功能的常見問題

常見函式問題

我如何找到執行任務 X 的模組或應用程式？

哪裡可以找到 math.py (socket.py, regex.py, 等...) 來源檔案？

我如何使 Python script 執行在 Unix？

是否有適用於 Python 的 curses/termcap 套件？

Python 中是否有等同於 C 的 onexit() 的函式？

為什麼我的訊號處理程式不起作用？

常見課題

如何測試 Python 程式或元件？

如何從文件字串建立文件？

How do I get a single keypress at a time?

執行緒

如何使用執行緒編寫程式？

我的執行緒似乎都沒有運行：為什麼？

How do I parcel out work among a bunch of worker threads?

什麼樣的全域值變化是執行緒安全的？

不能擺脫全域直譯器鎖嗎？

輸入與輸出

如何刪除檔案？（以及其他檔案問題...）

如何複製檔案？

如何讀取（或寫入）二進位制資料？

我似乎無法在用 os.popen() 建立的 pipe 上使用 os.read()；為什麼？

如何存取序列 (RS232) 連接埠？

為什麼關閉 sys.stdout (stdin, stderr) 並沒有真正關閉它？

網路 (Network)/網際網路 (Internet) 程式

Python 有哪些 WWW 工具？

我應該使用什麼模組來輔助產生 HTML？

如何從 Python 腳本發送郵件？

如何避免阻塞 socket 的 connect() 方法？

資料庫

Python 中是否有任何資料庫套件的介面？

你如何在 Python 中實作持久性物件？

數學和數值

如何在 Python 中生成隨機數？

常見函式問題

我如何找到執行任務 X 的模組或應用程式？

查看函式庫參照以了解是否有相關的標準函式庫模組。 （當你熟悉標準函式庫中的內容後就可以能跳過這一步。）

對於第三方套件，搜尋 Python 套件索引 [https://pypi.org]或嘗試使用 Google [https://www.google.com] 或其他網路搜尋引擎。搜尋 "Python" 加上你感興趣主題的一兩個關鍵字，通常能夠找到有用的東西。

哪裡可以找到 math.py (socket.py, regex.py, 等...) 來源檔案？

If you can't find a source file for a module it may be a built-in or dynamically loaded module implemented in C, C++ or other compiled language. In this case you may not have the source file or it may be something like mathmodule.c, somewhere in a C source directory (not on the Python Path).

有（至少）三種 Python 模組：

以 Python 編寫的模組 (.py)；

用 C 編寫並動態載入的模組（.dll、.pyd、.so、.sl 等）；

用 C 編寫並與直譯器鏈接的模組；要獲得這些 list，請輸入：

import sys
print(sys.builtin_module_names)

我如何使 Python script 執行在 Unix？

You need to do two things: the script file's mode must be executable and the first line must begin with #! followed by the path of the Python interpreter.

第一個是透過執行 chmod +x scriptfile 或者可能是 chmod 755 scriptfile 來完成的。

第二個則可以透過多種方式完成。最直接的方法是寫：

#!/usr/local/bin/python

作為檔案的第一行，使用 Python 直譯器安裝在你的平台上的路徑名稱。

If you would like the script to be independent of where the Python interpreter lives, you can use the env program. Almost all Unix variants support the following, assuming the Python interpreter is in a directory on the user's PATH:

#!/usr/bin/env python

不要對 CGI 腳本執行此操作。CGI 腳本的 PATH 變數通常非常小，因此你需要使用直譯器的實際絕對路徑名稱。

Occasionally, a user's environment is so full that the /usr/bin/env program fails; or there's no env program at all. In that case, you can try the following hack (due to Alex Rezinsky):

#! /bin/sh
""":"
exec python $0 ${1+"$@"}
"""

次要缺點是這定義了腳本的 __doc__ 字串。但是你可以透過新增下面這一行來解決這個問題：

__doc__ = """...Whatever..."""

是否有適用於 Python 的 curses/termcap 套件？

For Unix variants: The standard Python source distribution comes with a curses module in the Modules [https://github.com/python/cpython/tree/3.14/Modules] subdirectory, though it's not compiled by default. (Note that this is not available in the Windows distribution -- there is no curses module for Windows.)

The curses module supports basic curses features as well as many additional functions from ncurses and SYSV curses such as colour, alternative character set support, pads, and mouse support. This means the module isn't compatible with operating systems that only have BSD curses, but there don't seem to be any currently maintained OSes that fall into this category.

Python 中是否有等同於 C 的 onexit() 的函式？

atexit 模組提供了一個類似於 C onexit() 的註冊函式。

為什麼我的訊號處理程式不起作用？

最常見的問題是訊號處理程式是用錯誤的引數串列聲明的。它以以下形式來呼叫：

handler(signum, frame)

所以它應該用兩個參數聲明：

def handler(signum, frame):
    ...

常見課題

如何測試 Python 程式或元件？

Python comes with two testing frameworks. The doctest module finds examples in the docstrings for a module and runs them, comparing the output with the expected output given in the docstring.

unittest 模組是一個更炫目的測試框架，它以 Java 和 Smalltalk 測試框架為模型。

To make testing easier, you should use good modular design in your program. Your program should have almost all functionality encapsulated in either functions or class methods -- and this sometimes has the surprising and delightful effect of making the program run faster (because local variable accesses are faster than global accesses). Furthermore the program should avoid depending on mutating global variables, since this makes testing much more difficult to do.

The "global main logic" of your program may be as simple as

if __name__ == "__main__":
    main_logic()

at the bottom of the main module of your program.

Once your program is organized as a tractable collection of function and class behaviours, you should write test functions that exercise the behaviours. A test suite that automates a sequence of tests can be associated with each module. This sounds like a lot of work, but since Python is so terse and flexible it's surprisingly easy. You can make coding much more pleasant and fun by writing your test functions in parallel with the "production code", since this makes it easy to find bugs and even design flaws earlier.

"Support modules" that are not intended to be the main module of a program may include a self-test of the module.

if __name__ == "__main__":
    self_test()

Even programs that interact with complex external interfaces may be tested when the external interfaces are unavailable by using "fake" interfaces implemented in Python.

如何從文件字串建立文件？

The pydoc module can create HTML from the doc strings in your Python source code. An alternative for creating API documentation purely from docstrings is epydoc [https://epydoc.sourceforge.net/]. Sphinx [https://www.sphinx-doc.org] can also include docstring content.

How do I get a single keypress at a time?

對於 Unix 變體有幾種解決方案。使用 curses 執行此操作很直觀，但 curses 是一個學習成本較大的模組。

執行緒

如何使用執行緒編寫程式？

Be sure to use the threading module and not the _thread module. The threading module builds convenient abstractions on top of the low-level primitives provided by the _thread module.

我的執行緒似乎都沒有運行：為什麼？

As soon as the main thread exits, all threads are killed. Your main thread is running too quickly, giving the threads no time to do any work.

一個簡單的修復方式是在程式末尾新增一個足夠長的 sleep，讓所有執行緒都完成：

import threading, time

def thread_task(name, n):
    for i in range(n):
        print(name, i)

for i in range(10):
    T = threading.Thread(target=thread_task, args=(str(i), i))
    T.start()

time.sleep(10)  # <---------------------------!

But now (on many platforms) the threads don't run in parallel, but appear to run sequentially, one at a time! The reason is that the OS thread scheduler doesn't start a new thread until the previous thread is blocked.

一個簡單的修復方式是在運行函式的開頭新增一個小 sleep：

def thread_task(name, n):
    time.sleep(0.001)  # <--------------------!
    for i in range(n):
        print(name, i)

for i in range(10):
    T = threading.Thread(target=thread_task, args=(str(i), i))
    T.start()

time.sleep(10)

Instead of trying to guess a good delay value for time.sleep(), it's better to use some kind of semaphore mechanism. One idea is to use the queue module to create a queue object, let each thread append a token to the queue when it finishes, and let the main thread read as many tokens from the queue as there are threads.

How do I parcel out work among a bunch of worker threads?

The easiest way is to use the concurrent.futures module, especially the ThreadPoolExecutor class.

Or, if you want fine control over the dispatching algorithm, you can write your own logic manually. Use the queue module to create a queue containing a list of jobs. The Queue class maintains a list of objects and has a .put(obj) method that adds items to the queue and a .get() method to return them. The class will take care of the locking necessary to ensure that each job is handed out exactly once.

這是一個簡單的例子：

import threading, queue, time

# The worker thread gets jobs off the queue.  When the queue is empty, it
# assumes there will be no more work and exits.
# (Realistically workers will run until terminated.)
def worker():
    print('Running worker')
    time.sleep(0.1)
    while True:
        try:
            arg = q.get(block=False)
        except queue.Empty:
            print('Worker', threading.current_thread(), end=' ')
            print('queue empty')
            break
        else:
            print('Worker', threading.current_thread(), end=' ')
            print('running with argument', arg)
            time.sleep(0.5)

# Create queue
q = queue.Queue()

# Start a pool of 5 workers
for i in range(5):
    t = threading.Thread(target=worker, name='worker %i' % (i+1))
    t.start()

# Begin adding work to the queue
for i in range(50):
    q.put(i)

# Give threads time to run
print('Main thread sleeping')
time.sleep(5)

運行時，這將產生以下輸出：

Running worker
Running worker
Running worker
Running worker
Running worker
Main thread sleeping
Worker <Thread(worker 1, started 130283832797456)> running with argument 0
Worker <Thread(worker 2, started 130283824404752)> running with argument 1
Worker <Thread(worker 3, started 130283816012048)> running with argument 2
Worker <Thread(worker 4, started 130283807619344)> running with argument 3
Worker <Thread(worker 5, started 130283799226640)> running with argument 4
Worker <Thread(worker 1, started 130283832797456)> running with argument 5
...

Consult the module's documentation for more details; the Queue class provides a featureful interface.

什麼樣的全域值變化是執行緒安全的？

A global interpreter lock (GIL) is used internally to ensure that only one thread runs in the Python VM at a time. In general, Python offers to switch among threads only between bytecode instructions; how frequently it switches can be set via sys.setswitchinterval(). Each bytecode instruction and therefore all the C implementation code reached from each instruction is therefore atomic from the point of view of a Python program.

In theory, this means an exact accounting requires an exact understanding of the PVM bytecode implementation. In practice, it means that operations on shared variables of built-in data types (ints, lists, dicts, etc) that "look atomic" really are.

For example, the following operations are all atomic (L, L1, L2 are lists, D, D1, D2 are dicts, x, y are objects, i, j are ints):

L.append(x)
L1.extend(L2)
x = L[i]
x = L.pop()
L1[i:j] = L2
L.sort()
x = y
x.field = y
D[x] = y
D1.update(D2)
D.keys()

這些不是：

i = i+1
L.append(L[-1])
L[i] = L[j]
D[x] = D[x] + 1

Operations that replace other objects may invoke those other objects' __del__() method when their reference count reaches zero, and that can affect things. This is especially true for the mass updates to dictionaries and lists. When in doubt, use a mutex!

不能擺脫全域直譯器鎖嗎？

The global interpreter lock (GIL) is often seen as a hindrance to Python's deployment on high-end multiprocessor server machines, because a multi-threaded Python program effectively only uses one CPU, due to the insistence that (almost) all Python code can only run while the GIL is held.

With the approval of PEP 703 [https://peps.python.org/pep-0703/] work is now underway to remove the GIL from the CPython implementation of Python. Initially it will be implemented as an optional compiler flag when building the interpreter, and so separate builds will be available with and without the GIL. Long-term, the hope is to settle on a single build, once the performance implications of removing the GIL are fully understood. Python 3.13 is likely to be the first release containing this work, although it may not be completely functional in this release.

The current work to remove the GIL is based on a fork of Python 3.9 with the GIL removed [https://github.com/colesbury/nogil] by Sam Gross. Prior to that, in the days of Python 1.5, Greg Stein actually implemented a comprehensive patch set (the "free threading" patches) that removed the GIL and replaced it with fine-grained locking. Adam Olsen did a similar experiment in his python-safethread [https://code.google.com/archive/p/python-safethread] project. Unfortunately, both of these earlier experiments exhibited a sharp drop in single-thread performance (at least 30% slower), due to the amount of fine-grained locking necessary to compensate for the removal of the GIL. The Python 3.9 fork is the first attempt at removing the GIL with an acceptable performance impact.

The presence of the GIL in current Python releases doesn't mean that you can't make good use of Python on multi-CPU machines! You just have to be creative with dividing the work up between multiple processes rather than multiple threads. The ProcessPoolExecutor class in the new concurrent.futures module provides an easy way of doing so; the multiprocessing module provides a lower-level API in case you want more control over dispatching of tasks.

Judicious use of C extensions will also help; if you use a C extension to perform a time-consuming task, the extension can release the GIL while the thread of execution is in the C code and allow other threads to get some work done. Some standard library modules such as zlib and hashlib already do this.

減少 GIL 影響的另一種方法是將 GIL 設置為直譯器各自狀態的鎖 (per-interpreter-state lock)，而不是真正的全域鎖。這在 Python 3.12 中首次實現，並且可於 C API 中使用。預計 Python 3.13 將會提供其 Python 介面。目前主要的限制可能是第三方擴充模組，因為實作時必須考慮到多個直譯器才能使用，因此許多舊的擴充模組將無法使用。

輸入與輸出

如何刪除檔案？（以及其他檔案問題...）

Use os.remove(filename) or os.unlink(filename); for documentation, see the os module. The two functions are identical; unlink() is simply the name of the Unix system call for this function.

To remove a directory, use os.rmdir(); use os.mkdir() to create one. os.makedirs(path) will create any intermediate directories in path that don't exist. os.removedirs(path) will remove intermediate directories as long as they're empty; if you want to delete an entire directory tree and its contents, use shutil.rmtree().

要重新命名檔案，請使用 os.rename(old_path, new_path)。

To truncate a file, open it using f = open(filename, "rb+"), and use f.truncate(offset); offset defaults to the current seek position. There's also os.ftruncate(fd, offset) for files opened with os.open(), where fd is the file descriptor (a small integer).

shutil 模組還包含許多用於檔案處理的函式，包括 copyfile()、copytree() 和 rmtree()。

如何複製檔案？

The shutil module contains a copyfile() function. Note that on Windows NTFS volumes, it does not copy alternate data streams [https://en.wikipedia.org/wiki/NTFS#Alternate_data_stream_(ADS)] nor resource forks [https://en.wikipedia.org/wiki/Resource_fork] on macOS HFS+ volumes, though both are now rarely used. It also doesn't copy file permissions and metadata, though using shutil.copy2() instead will preserve most (though not all) of it.

如何讀取（或寫入）二進位制資料？

To read or write complex binary data formats, it's best to use the struct module. It allows you to take a string containing binary data (usually numbers) and convert it to Python objects; and vice versa.

For example, the following code reads two 2-byte integers and one 4-byte integer in big-endian format from a file:

import struct

with open(filename, "rb") as f:
    s = f.read(8)
    x, y, z = struct.unpack(">hhl", s)

The '>' in the format string forces big-endian data; the letter 'h' reads one "short integer" (2 bytes), and 'l' reads one "long integer" (4 bytes) from the string.

For data that is more regular (e.g. a homogeneous list of ints or floats), you can also use the array module.

備註

To read and write binary data, it is mandatory to open the file in binary mode (here, passing "rb" to open()). If you use "r" instead (the default), the file will be open in text mode and f.read() will return str objects rather than bytes objects.

我似乎無法在用 os.popen() 建立的 pipe 上使用 os.read()；為什麼？

os.read() is a low-level function which takes a file descriptor, a small integer representing the opened file. os.popen() creates a high-level file object, the same type returned by the built-in open() function. Thus, to read n bytes from a pipe p created with os.popen(), you need to use p.read(n).

如何存取序列 (RS232) 連接埠？

對於 Win32、OSX、Linux、BSD、Jython、IronPython：

pyserial [https://pypi.org/project/pyserial/]

對於 Unix，請參閱 Mitch Chapman 的 Usenet 貼文：

https://groups.google.com/groups?selm=34A04430.CF9@ohioee.com

為什麼關閉 sys.stdout (stdin, stderr) 並沒有真正關閉它？

Python 檔案物件是低階 C 檔案描述器的高階抽象層。

For most file objects you create in Python via the built-in open() function, f.close() marks the Python file object as being closed from Python's point of view, and also arranges to close the underlying C file descriptor. This also happens automatically in f's destructor, when f becomes garbage.

But stdin, stdout and stderr are treated specially by Python, because of the special status also given to them by C. Running sys.stdout.close() marks the Python-level file object as being closed, but does not close the associated C file descriptor.

To close the underlying C file descriptor for one of these three, you should first be sure that's what you really want to do (e.g., you may confuse extension modules trying to do I/O). If it is, use os.close():

os.close(stdin.fileno())
os.close(stdout.fileno())
os.close(stderr.fileno())

或者你可以分別使用數字常數 0、1 和 2。

網路 (Network)/網際網路 (Internet) 程式

Python 有哪些 WWW 工具？

See the chapters titled 網路協定 (Internet protocols) 及支援 and 網際網路資料處理 in the Library Reference Manual. Python has many modules that will help you build server-side and client-side web systems.

Paul Boddie 有在 https://wiki.python.org/moin/WebProgramming維護可用框架的摘要。

我應該使用什麼模組來輔助產生 HTML？

你可以在 "網頁程式維基頁面 <https://wiki.python.org/moin/WebProgramming>" 上找到一組有用的鏈接。

如何從 Python 腳本發送郵件？

使用標準函式庫模組 smtplib。

Here's a very simple interactive mail sender that uses it. This method will work on any host that supports an SMTP listener.

import sys, smtplib

fromaddr = input("From: ")
toaddrs  = input("To: ").split(',')
print("Enter message, end with ^D:")
msg = ''
while True:
    line = sys.stdin.readline()
    if not line:
        break
    msg += line

# The actual mail send
server = smtplib.SMTP('localhost')
server.sendmail(fromaddr, toaddrs, msg)
server.quit()

使用 sendmail 是僅適用於 Unix 的替代方案。sendmail 程式的位置會因系統而異；有時是 /usr/lib/sendmail，有時是 /usr/sbin/sendmail。sendmail 使用手冊將能夠幫助你。這是一些範例程式碼：

import os

SENDMAIL = "/usr/sbin/sendmail"  # sendmail location
p = os.popen("%s -t -i" % SENDMAIL, "w")
p.write("To: receiver@example.com\n")
p.write("Subject: test\n")
p.write("\n")  # blank line separating headers from body
p.write("Some text\n")
p.write("some more text\n")
sts = p.close()
if sts != 0:
    print("Sendmail exit status", sts)

如何避免阻塞 socket 的 connect() 方法？

select 模組通常用於幫助處理 socket 上的非同步 I/O。

To prevent the TCP connect from blocking, you can set the socket to non-blocking mode. Then when you do the connect(), you will either connect immediately (unlikely) or get an exception that contains the error number as .errno. errno.EINPROGRESS indicates that the connection is in progress, but hasn't finished yet. Different OSes will return different values, so you're going to have to check what's returned on your system.

You can use the connect_ex() method to avoid creating an exception. It will just return the errno value. To poll, you can call connect_ex() again later -- 0 or errno.EISCONN indicate that you're connected -- or you can pass this socket to select.select() to check if it's writable.

備註

asyncio 模組提供了一個通用的單執行緒並發非同步函式庫，可用於編寫非阻塞網路程式碼。第三方 Twisted [https://twisted.org/] 函式庫是一種流行且功能豐富的替代方案。

資料庫

Python 中是否有任何資料庫套件的介面？

有的。

Interfaces to disk-based hashes such as DBM and GDBM are also included with standard Python. There is also the sqlite3 module, which provides a lightweight disk-based relational database.

Support for most relational databases is available. See the DatabaseProgramming wiki page [https://wiki.python.org/moin/DatabaseProgramming] for details.

你如何在 Python 中實作持久性物件？

The pickle library module solves this in a very general way (though you still can't store things like open files, sockets or windows), and the shelve library module uses pickle and (g)dbm to create persistent mappings containing arbitrary Python objects.

數學和數值

如何在 Python 中生成隨機數？

標準模組 random 實作了一個隨機數生成器。用法很簡單：

import random
random.random()

這將回傳 [0, 1) 範圍內的隨機浮點數。

該模組中還有許多其他專用生成器，例如：

randrange(a, b) 會選擇 [a, b) 範圍內的一個整數。

uniform(a, b) 會選擇 [a, b) 範圍內的浮點數。

normalvariate(mean, sdev) 對常態（高斯）分佈進行取樣 (sample)。

一些更高階的函式會直接對序列進行操作，例如：

choice(S) 會從給定序列中選擇一個隨機元素。

shuffle(L) 會原地 (in-place) 打亂 list，即隨機排列它。

還有一個 Random 類別，你可以將它實例化以建立多個獨立的隨機數生成器。

擴充/嵌入常見問題集

目錄

擴充/嵌入常見問題集

我可以在 C 中建立自己的函式嗎？

我可以在 C++ 中建立自己的函式嗎？

寫 C 很難；還有其他選擇嗎？

如何從 C 執行任意 Python 陳述式？

如何計算來自 C 的任意 Python 運算式？

如何從 Python 物件中提取 C 值？

如何使用 Py_BuildValue() 建立任意長度的元組？

如何從 C 呼叫物件的方法？

我如何捕捉 PyErr_Print() 的輸出（或任何印出到 stdout/stderr 的東西）？

如何從 C 存取用 Python 編寫的模組？

我如何從 Python 介接到 C++ 物件？

我使用安裝檔案新增了一個模組，但 make 失敗了；為什麼？

如何為擴充套件除錯？

我想在我的 Linux 系統上編譯一個 Python 模組，但是缺少一些檔案。為什麼？

如何從「無效輸入」區分出「不完整輸入」？

如何找到未定義的 g++ 符號 __builtin_new 或 __pure_virtual？

我可以用一些用 C 實作的方法和用 Python 實作的其他方法（例如透過繼承）建立一個物件類別嗎？

我可以在 C 中建立自己的函式嗎？

是的，你可以在 C 中建立包含函式、變數、例外甚至新型別的內建模組，擴充和嵌入 Python 直譯器 文件中有相關說明。

大多數中級或進階 Python 書籍也會涵蓋這個主題。

我可以在 C++ 中建立自己的函式嗎？

是的，可使用 C++ 中的 C 相容性功能。將 extern "C" { ... } 放在 Python 引入檔案周圍，並將 extern "C" 放在每個將由 Python 直譯器呼叫的函式之前。但具有構造函式的全域或靜態 C++ 物件可能不是一個好主意。

寫 C 很難；還有其他選擇嗎？

There are a number of alternatives to writing your own C extensions, depending on what you're trying to do. Recommended third party tools offer both simpler and more sophisticated approaches to creating C and C++ extensions for Python.

如何從 C 執行任意 Python 陳述式？

執行此操作的最高階函式是 PyRun_SimpleString()，它接受一個要在模組 __main__ 的情境中執行的單一字串引數，成功時回傳 0，發生例外（包括 SyntaxError）時回傳 -1。如果你想要更多控制，請使用 PyRun_String()；請參閱 Python/pythonrun.c 中 PyRun_SimpleString() 的原始碼。

如何計算來自 C 的任意 Python 運算式？

呼叫前一個問題中的 PyRun_String() 函式，並使用起始符號 Py_eval_input；它會剖析一個運算式，計算它並回傳它的值。

如何從 Python 物件中提取 C 值？

這取決於物件的型別。如果它是一個元組，PyTuple_Size() 會回傳它的長度，PyTuple_GetItem() 則回傳指定索引的項目。串列具有類似的函式 PyList_Size() 和 PyList_GetItem()。

對於位元組，PyBytes_Size() 會回傳它的長度，PyBytes_AsStringAndSize() 則提供指向該值與該長度的指標。請注意，Python 位元組物件可能包含空位元組，因此不應使用 C 的 strlen()。

要測試物件的型別，首先確保它不是 NULL，然後再使用 PyBytes_Check()、PyTuple_Check()、PyList_Check() 等函式。

還有一個針對 Python 物件的高階 API，它由所謂的「抽象」介面所提供 —— 請閱讀 Include/abstract.h 以了解更多詳細資訊。它允許使用 PySequence_Length()、PySequence_GetItem() 等函式的呼叫以及許多其他有用的協定，例如數值（PyNumber_Index() 等）和 PyMapping API 中的對映，來與任何類型的 Python 序列做介接。

如何使用 Py_BuildValue() 建立任意長度的元組？

這無法做到。請改用 PyTuple_Pack()。

如何從 C 呼叫物件的方法？

PyObject_CallMethod() 函式可用於呼叫物件的任意方法。參數是物件、要呼叫的方法名稱、與 Py_BuildValue() 一起使用的格式字串，以及引數值：

PyObject *
PyObject_CallMethod(PyObject *object, const char *method_name,
                    const char *arg_format, ...);

這適用於任何具有方法的物件 —— 無論是內建的還是使用者定義的。你負責最終為回傳值來 Py_DECREF()。

例如，使用引數 10、0 呼叫檔案物件的 "seek" 方法（假設檔案物件指標為 "f"）：

res = PyObject_CallMethod(f, "seek", "(ii)", 10, 0);
if (res == NULL) {
        ... 發生一個例外 ...
}
else {
        Py_DECREF(res);
}

請注意，由於 PyObject_CallObject() 總是需要一個元組作為引數列表，若要呼叫一個不帶引數的函式，要傳遞 "()" 作為格式，並呼叫一個帶有一個引數的函式，將引數括起來在括號中，例如 "(i)"。

我如何捕捉 PyErr_Print() 的輸出（或任何印出到 stdout/stderr 的東西）？

在 Python 程式碼中定義一個支援 write() 方法的物件。將此物件分配給 sys.stdout 和 sys.stderr。呼叫 print_error，或者只允許標準的回溯機制起作用。然後，輸出將會傳送到你的 write() 方法所指定的位置。

最簡單的方法是使用 io.StringIO 類別：

>>> import io, sys
>>> sys.stdout = io.StringIO()
>>> print('foo')
>>> print('hello world!')
>>> sys.stderr.write(sys.stdout.getvalue())
foo
hello world!

執行相同操作的自訂物件如下所示：

>>> import io, sys
>>> class StdoutCatcher(io.TextIOBase):
...     def __init__(self):
...         self.data = []
...     def write(self, stuff):
...         self.data.append(stuff)
...
>>> import sys
>>> sys.stdout = StdoutCatcher()
>>> print('foo')
>>> print('hello world!')
>>> sys.stderr.write(''.join(sys.stdout.data))
foo
hello world!

如何從 C 存取用 Python 編寫的模組？

你可以取得指向模組物件的指標，如下所示：

module = PyImport_ImportModule("<modulename>");

如果模組還沒有被引入（即它還沒有出現在 sys.modules 中），這會初始化模組；否則它只回傳 sys.modules["<modulename>"] 的值。請注意，它不會將模組輸入任何命名空間——它只會確保它已被初始化並儲存在 sys.modules 中。

然後你可以存取模組的屬性（即模組中定義的任何名稱），如下所示：

attr = PyObject_GetAttrString(module, "<attrname>");

呼叫 PyObject_SetAttrString() 來分配模組中的變數也有效。

我如何從 Python 介接到 C++ 物件？

根據你的要求不同而有多種不同方法。要手動執行此操作，請先閱讀「擴充和嵌入」說明文件。對於 Python run-time 系統，C 和 C++ 之間並沒有太多區別 —— 因此圍繞 C 結構（指標）型別來構建新 Python 型別的策略也適用於 C++ 物件。

對於 C++ 函式庫，請參閱 寫 C 很難；還有其他選擇嗎？。

我使用安裝檔案新增了一個模組，但 make 失敗了；為什麼？

安裝程式必須以換行符結尾，如果那裡沒有換行符，構建過程將失敗。（解決這個問題需要一些醜陋的 shell 腳本 hackery，而且這個錯誤很小，似乎不值得付出努力。）

如何為擴充套件除錯？

將 GDB 與動態載入的擴充一起使用時，在載入擴充之前不能在擴充中設定斷點。

在你的 .gdbinit 檔案中（或交互地），新增命令：

br _PyImport_LoadDynamicModule

然後，當你運行 GDB 時：

$ gdb /local/bin/python
gdb) run myscript.py
gdb) continue # repeat until your extension is loaded
gdb) finish   # so that your extension is loaded
gdb) br myfunction.c:50
gdb) continue

我想在我的 Linux 系統上編譯一個 Python 模組，但是缺少一些檔案。為什麼？

大多數打包版本的 Python 省略了編譯 Python 擴充所需的一些檔案。

在 Red Hat 上，請安裝 python3-devel RPM 來取得必要的檔案。

對於 Debian，運行 apt-get install python3-dev。

如何從「無效輸入」區分出「不完整輸入」？

有時你會想模擬 Python 交互式直譯器的行為，當輸入不完整時（例如，當你輸入了 "if" 陳述式的開頭或者你沒有關閉你的括號或三重字串引號）它會給你一個繼續提示字元，但是當輸入無效時，它會立即為你提供語法錯誤訊息。

在 Python 中，你可以使用 codeop 模組，它充分模擬了剖析器 (parser) 的行為。像是 IDLE 就有使用它。

在 C 中執行此操作的最簡單方法是呼叫 PyRun_InteractiveLoop()（可能是在單獨的執行緒中）並讓 Python 直譯器為你處理輸入。你還可以將 PyOS_ReadlineFunctionPointer() 設定為指向你的自訂輸入函式。有關更多提示，請參閱 Modules/readline.c 和 Parser/myreadline.c。

如何找到未定義的 g++ 符號 __builtin_new 或 __pure_virtual？

要動態載入 g++ 擴充模組，你必須重新編譯 Python，並使用 g++ 重新鏈接它（更改 Python 模組 Makefile 中的 LINKCC），且使用 g++ 鏈接你的擴充模組（例如，g++ -shared -o mymodule.so mymodule.o）。

我可以用一些用 C 實作的方法和用 Python 實作的其他方法（例如透過繼承）建立一個物件類別嗎？

是的，你可以繼承內建類別，例如 int、list、dict 等。

Boost Python 函式庫（BPL，https://www.boost.org/libs/python/doc/index.html）提供了一種從 C++ 執行此操作的方法（即你可以使用 BPL 來繼承用 C++ 編寫的擴充類別）。

在 Windows 使用 Python 的常見問答集

目錄

在 Windows 使用 Python 的常見問答集

如何在 Windows 作業系統裡運行 Python 程式？

如何使 Python 腳本可以執行？

為什麼 Python 有時需要這麼長的時間才能開始？

如何從 Python 腳本製作可執行檔？

*.pyd 檔是否與 DLL 相同？

如何將 Python 嵌入 Windows 應用程式中？

如何防止編輯器在我的 Python 原始碼中插入 tab？

如何在不阻塞的情況下檢查 keypress？

如何解決遺漏 api-ms-win-crt-runtime-l1-1-0.dll 的錯誤？

如何在 Windows 作業系統裡運行 Python 程式？

這個問題的答案可能有點複雜。如果你經常使用「命令提示字元」執行程式，那這對你來說不會是什麼難事。如果不然，那就需要更仔細的說明了。

除非你使用某種整合開發環境，否則你最終將會在所謂的「命令提示字元視窗」中 打字輸入 Windows 命令。通常，你可以透過從搜尋欄中搜尋 cmd 來建立這樣的視窗。你應該能夠認出何時已啟動這樣的視窗，因為你將看到 Windows「命令提示字元」，它通常看起來像這樣：

C:\>

第一個字母可能不一樣，且後面也可能還有其他內容，因此你可能會很容易看到類似以下的文字：

D:\YourName\Projects\Python>

取決於你的電腦如何被設置，以及你最近對它所做的其他操作。一旦你啟動了這樣一個視窗，你就即將可以運行 Python 程式了。

你需要了解，你的 Python 腳本必須被另一個稱為 Python 直譯器的程序來處理。直譯器會讀取你的腳本，將其編譯為位元組碼，然後執行該位元組碼以運行你的程式。那麼，你要如何安排直譯器來處理你的 Python 呢？

首先，你需要確保你的命令視窗會將單字 "py" 識別為啟動直譯器的指令。如果你已經開啟一個命令視窗，則你應該試試輸入命令 py 並按下 return 鍵：

C:\Users\YourName> py

然後，你應該看到類似下面的內容：

Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

你已經啟動直譯器中的「互動模式」。這表示你能夠以互動方式輸入 Python 陳述式或運算式，並在等待時執行或計算它們。這是 Python 最強大的功能之一。輸入你所選的幾個運算式並查看結果，可以檢驗此功能：

>>> print("Hello")
Hello
>>> "Hello" * 3
'HelloHelloHello'

許多人將互動模式作為方便但可高度程式化的計算機。如果你要結束互動式 Python 對話，請呼叫 exit() 函式或是按住 Ctrl 鍵再輸入 Z，然後按下 "Enter" 鍵以返回 Windows 命令提示字元。

你可能還會發現你有一個開始功能表項目，像是：開始 ‣ 所有程式 ‣ Python 3.x ‣ Python（命令行），它會讓你在一個新視窗中看到 >>> 提示字元。如果是這樣，該視窗將在你呼叫 exit() 函式或輸入 Ctrl-Z 字元後消失；Windows 正在該視窗中運行單一個「python」命令，並在你終止直譯器時將其關閉。

現在我們知道 py 命令已被識別，而你可以將你的 Python 腳本提供給它。你必須為 Python 腳本給定絕對路徑或相對路徑。假設你的 Python 腳本位於桌面上，並被命名為 hello.py，且你的命令提示字元在你的家目錄 (home directory) 中順利地被開啟，那麼你就會看到類似以下的內容：

C:\Users\YourName>

因此，現在你將透過鍵入 py 加上腳本路徑，來使用 py 命令將你的腳本提供給 Python：

C:\Users\YourName> py Desktop\hello.py
hello

如何使 Python 腳本可以執行？

在 Windows 上，標準的 Python 安裝程式已將 .py 副檔名與一種檔案類型 (Python.File) 進行關聯，並為該檔案類型提供一個開啟命令來運行直譯器 (D:\Program Files\Python\python.exe "%1" %*)。這足以使腳本能以類似 'foo.py' 的形式從命令提示字元被執行。如果你希望能夠簡單地輸入 'foo' 來執行腳本，而不用加上副檔名，則需要將 .py 新增至 PATHEXT 環境變數中。

為什麼 Python 有時需要這麼長的時間才能開始？

通常 Python 在 Windows 上啟動得非常快，但偶爾會有一些錯誤報告，內容是 Python 突然開始需要很長的時間才能啟動。這種情形更令人費解，因為 Python 在其他 Windows 系統上可以正常工作，而那些系統似乎也有相同的配置。

這個問題可能是由發生此問題的電腦上的病毒檢查軟體配置錯誤所引起的。目前已知某些病毒掃描程式，在它們被配置為監視來自檔案系統的所有讀取時，會引入兩個數量級的啟動負擔。請試著檢查你系統上的病毒掃描軟體配置，以確保它們的配置確實相同。當 McAfee 被配置為掃描所有檔案系統的讀取活動時，它是一個特定的違規者。

如何從 Python 腳本製作可執行檔？

請參閱如何從 Python 腳本建立獨立的二進位檔案？該章節列出了用於製作可執行檔的工具清單。

*.pyd 檔是否與 DLL 相同？

是的，.pyd 檔類似於 dll，但也有一些區別。如果你有一個名為 foo.pyd 的 DLL，則它必須具有函式 PyInit_foo()。接著你可以將 "import foo" 寫入 Python 腳本，Python 將會搜尋 foo.pyd（以及 foo.py、foo.pyc），如果 Python 找到它，將會嘗試呼叫 PyInit_foo() 來將它初始化。你並不會將你的 .exe 與 foo.lib 連結 (link)，因為這會導致 Windows 要求 DLL 的存在。

請注意，foo.pyd 的搜尋路徑是 PYTHONPATH，與 Windows 用於搜尋 foo.dll 的路徑不同。此外，foo.pyd 不需存在即可運行你的程式，然而如果你將程式連結了一個 dll，則該 dll 會是必要的。當然，如果你想要 import foo，foo.pyd 就是必要的。在 DLL 中，連結是以 __declspec(dllexport) 在原始碼中被宣告。在 .pyd 中，連結是在一個可用函式的 list（串列）中被定義。

如何將 Python 嵌入 Windows 應用程式中？

在 Windows 應用程式中嵌入 Python 直譯器的過程可以總結如下：

不要直接將 Python 建置到你的 .exe 檔中。在 Windows 上，Python 必須是一個 DLL 來處理模組的 import，而那些模組本身也是 DLL。（這是第一個未正式記載的關鍵事實。）請改為連結到 pythonNN.dll；它通常被安裝在 C:\Windows\System 中。NN 是 Python 版本，例如 "33" 就是指 Python 3.3。

你可以透過兩種不同的方式連結到 Python。載入時連結 (load-time linking) 表示要連結到 pythonNN.lib，而執行環境連結 (run-time linking) 表示要連結到 pythonNN.dll。（一般註解：pythonNN.lib 是 pythonNN.dll 相對應的所謂 "import lib"。它只會為鏈接器定義符號。）

執行環境連結大大簡化了連結選項；所有事情都會發生在執行環境。你的程式碼必須使用 Windows LoadLibraryEx() 常式 (routine) 來載入 pythonNN.dll。該程式碼也必須用 Windows GetProcAddress() 常式所取得的指標，來使用 pythonNN.dll 中的（即為 Python C API 的）存取常式和資料。對於任何呼叫 Python C API 常式的 C 程式碼，巨集可以讓使用這些指標的過程透明化。

如果你使用 SWIG，則可輕鬆地建立一個 Python 「擴充模組」，該模組將使應用程式的資料和 method（方法）可供 Python 使用。SWIG 會為你處理幾乎所有的繁瑣細節。結果就是，你會將 C 程式碼連結到你的 .exe 檔裡（！）你不必建立 DLL 檔，而這也簡化了連結。

SWIG 將建立一個 init 函式（一個 C 函式），其名稱取決於擴充模組的名稱。例如，如果模組的名稱是 leo，則該 init 函式會命名為 initleo()。如果你使用 SWIG shadow class（類別），則 init 函式會命名為 initleoc()。這會初始化被 shadow class 所用的大多數隱藏的 helper class。

你可以將步驟 2 中的 C 程式碼連結到 .exe 檔中的原因是，呼叫初始化函式就等效於 import 模組進 Python！（這是第二個未正式記載的關鍵事實。）

簡而言之，你可以使用以下程式碼，以你的擴充模組初始化 Python 直譯器。

#include <Python.h>
...
Py_Initialize();  // 初始化 Python。
initmyAppc();  // 初始化（引入）幫助類別。
PyRun_SimpleString("import myApp");  // 引入 shadow 類別。

Python 的 C API 有兩個問題，如果你使用 MSVC（用於建置 pythonNN.dll 的編譯器）以外的編譯器，這些問題將會變得明顯。

問題 1：使用 FILE * 引數的所謂「非常高階」的函式，在多編譯器 (multi-compiler) 的環境中會無法作用，因為每個編譯器對 struct FILE 的概念不同。從實作的觀點來看，這些都是非常_低階_的函式。

問題 2：SWIG 在為 void 函式產生包裝函式 (wrapper) 時會產生以下程式碼：

Py_INCREF(Py_None);
_resultobj = Py_None;
return _resultobj;

唉，Py_None 是一個巨集，它會延伸到一個參照，指向 pythonNN.dll 內部的一種稱為 _Py_NoneStruct 的複雜資料結構。同樣的，此程式碼在多編譯器環境中將會失效。請將此類程式碼替換為：

return Py_BuildValue("");

有可能可以使用 SWIG 的 %typemap 命令以自動進行程式碼變更，雖然我未曾這樣正常運作過（我是一個完全的 SWIG 新手）。

使用 Python shell 腳本從你的 Windows 應用程式內部建造一個 Python 直譯器視窗不是一個好主意；該視窗將會獨立於你的應用程式視窗系統。與其如此，你（或 wxPythonWindow class）應該要建立一個「本機」直譯器視窗。將該視窗連接到 Python 直譯器是很容易的。你可以將 Python 的 i/o 重定向 (redirect) 到可支援讀取和寫入的任何物件，因此你只需要一個包含 read() 和 write() method 的 Python 物件（在你的擴充模組中被定義）就可以了。

如何防止編輯器在我的 Python 原始碼中插入 tab？

FAQ 不建議使用 tab，且 Python 風格指南 PEP 8 [https://peps.python.org/pep-0008/] 建議在分散式 Python 程式碼使用 4 個空格；這也是 Emacs 的 python 模式預設值。

在任何編輯器下，將 tab 和空格混合都是一個壞主意。MSVC 在這方面也是一樣，且可以輕鬆配置為使用空格：選擇工具 ‣ 選項 ‣ Tabs，然後對於「預設」檔案類型，將「Tab 大小」和「縮排大小」設定為 4，然後選擇「插入空格」單選鈕。

如果混合 tab 和空格造成前導空白字元出現問題，則 Python 會引發 IndentationError 或 TabError。你也可以運行 tabnanny 模組，在批次模式下檢查目錄樹。

如何在不阻塞的情況下檢查 keypress？

使用 msvcrt 模組。這是一個標準的 Windows 專用擴充模組。它定義了一個函式 kbhit()，該函式會檢查是否出現鍵盤打擊 (keyboard hit)，以及函式 getch()，該函式會取得一個字元且不會將其印出。

如何解決遺漏 api-ms-win-crt-runtime-l1-1-0.dll 的錯誤？

使用 Windows 8.1 或更早版本時，若尚未安裝所有的更新，則可能會在 Python 3.5 以上的版本發生這種情況。首先要確保你的作業系統仍受支援並且是最新的，如果這無法解決問題，請造訪 Microsoft 支援頁面 [https://support.microsoft.com/en-us/help/3118401/]以取得關於手動安裝 C Runtime 更新的指南。

圖形使用者介面常見問答集

目錄

圖形使用者介面常見問答集

圖形使用者介面 (GUI) 的常見問題

Python 有哪些 GUI 套件？

Tkinter 的問答

如何凍結 Tkinter 應用程式？

是否可以在等待 I/O 時處理 Tk 事件？

我無法讓鍵繫結 (key binding) 在 Tkinter 中作用：為什麼？

圖形使用者介面 (GUI) 的常見問題

Python 有哪些 GUI 套件？

Python 的標準版本會包含一個 Tcl/Tk 小工具集 (widget set) 的物件導向介面，稱為 tkinter。這可能是最容易安裝（因為它已包含在 Python 的大多數二進制發行版本 [https://www.python.org/downloads/]中）和使用的。有關 Tk 的詳細資訊（包含指向原始碼的指標），請參閱 Tcl/Tk 首頁 [https://www.tcl.tk]。Tcl/Tk 在 macOS、Windows 和 Unix 平台上是完全可攜 (portable) 的。

根據你要使用的平台，還有其他幾種選擇。在 python wiki 上可以找到一份跨平台的 [https://wiki.python.org/moin/GuiProgramming#Cross-Platform_Frameworks]以及各平台專屬的 [https://wiki.python.org/moin/GuiProgramming#Platform-specific_Frameworks] GUI 框架清單。

Tkinter 的問答

如何凍結 Tkinter 應用程式？

凍結 (freeze) 是一個能建立獨立應用程式的工具。在凍結 Tkinter 應用程式時，該應用程式不是真正的獨立，因為該應用程式仍然需要 Tcl 和 Tk 函式庫。

將應用程式與 Tcl 和 Tk 函式庫一併發送是一種解決方法，並在執行環境 (run-time) 使用 TCL_LIBRARY 和 TK_LIBRARY 環境變數來指向該函式庫。

各種第三方凍結函式庫，例如 py2exe 和 cx_Freeze，都有內建了對 Tkinter 應用程式的處理。

是否可以在等待 I/O 時處理 Tk 事件？

在 Windows 以外的平台上是可以的，你甚至不需要執行緒！但是，你必須稍微調整你的 I/O 程式碼。Tk 具有等效於 Xt 的 XtAddInput() 的函式呼叫，它能讓你記錄一個回呼 (callback) 函式，當 I/O 在一個檔案描述符 (file descriptor) 上可進行時，該函式將會從 Tk mainloop 被呼叫。請參閱檔案處理常式。

我無法讓鍵繫結 (key binding) 在 Tkinter 中作用：為什麼？

一個經常聽到的抱怨是，儘管事件處理程式 (event handler) 已經繫結到帶有 bind() method 的事件，但在按下相應的鍵時，該事件也沒有被處理。

最常見的原因是，繫結到的小工具並沒有「鍵盤焦點 (keyboard focus)」。請查看 Tk 說明文件中關於焦點命令的敘述。通常，點擊一個小工具，會讓它得到鍵盤焦點（但不適用於標籤；請參閱 takefocus 選項）。

「為什麼 Python 被安裝在我的機器上？」常見問答集

什麼是 Python？

Python 是一種程式語言。它被使用於不同種類的應用程式中。因為 Python 屬於容易學習的語言，它在一些高中和大學課程中被用作介紹程式語言的工具；但它也被專業的軟體開發人員所使用，例如 Google、美國太空總署與盧卡斯電影公司。

若你想學習更多關於 Python 的知識，可以先從 Python 初學者指引 [https://wiki.python.org/moin/BeginnersGuide]開始閱讀。

為什麼 Python 被安裝在我的機器上?

若你發現曾安裝 Python 於系統中，但不記得何時安裝過，那有可能是透過以下幾種途徑安裝的。

也許其他使用此電腦的使用者想要學習撰寫程式並且安裝了 Python；你需要回想一下誰曾經使用此機器且可能進行安裝。

安裝於機器的第三方應用程式可能以 Python 語言撰寫並且安裝了 Python。這樣的應用程式並不少，從 GUI 程式到網路伺服器和管理者腳本都有。

一些安裝 Windows 的機器也被安裝 Python。截至撰寫此文件的當下，我們得知 HP 與 Compaq 出廠的機器都預設安裝 Python。顯然的 HP 與 Compaq 部分的管理工具程式是透過 Python 語言所撰寫。

許多相容於 Unix 系統，例如 macOS 和一些 Linux 發行版本預設安裝 Python；它被包含在基礎安裝內。

我能夠自行刪除 Python 嗎？

需要依據 Python 的安裝方式決定。

若有人是有意地安裝 Python，你可自行移除移除它，這不會造成其他影響。Windows 作業系統中，請於控制台 (Control Panel) 中尋找新增/移除程式來解除安裝。

若 Python 是透過第三方應用程式安裝時，你也可自行移除，不過該應用程式將無法正常執行。你應該使用應用程式解除安裝功能而非直接刪除 Python。

當作業系統預設安裝 Python，不建議移除它。對你而言某些工具程式是重要不可或缺的，若自行移除它，透過 Python 撰寫的工具程式將無法正常執行。重新安裝整個系統，才能再次解決這些問題。

已棄用項目

Python 3.15 中待移除的項目

引入系統 (import system)：

在模組上設定 __cached__ 而沒有設定 __spec__.cached 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __cached__。(gh-97879 [https://github.com/python/cpython/issues/97879])

在模組上設定 __package__ 而沒有設定 __spec__.parent 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __package__。(gh-97879 [https://github.com/python/cpython/issues/97879])

ctypes：

自 Python 3.13 起，未記錄的 ctypes.SetPointerType() 函式已被棄用。

http.server：

過時且很少使用的 CGIHTTPRequestHandler 自 Python 3.13 起已被棄用。不存在直接的替代。任何東西都比 CGI 更好地將 Web 伺服器與請求處理程序介接起來。

自 Python 3.13 起，python -m http.server 命令列介面的 --cgi 旗標已被棄用。

importlib：

load_module() method：請改用 exec_module()。

locale：

getdefaultlocale() 已在 Python 3.11 中被棄用，原本計劃在 Python 3.13 中移除 (gh-90817 [https://github.com/python/cpython/issues/90817])，但被延後至 Python 3.15。請改用 getlocale()、setlocale() 和 getencoding()。 (由 Hugo van Kemenade 於 gh-111187 [https://github.com/python/cpython/issues/111187] 貢獻。)

pathlib：

PurePath.is_reserved() 已自 Python 3.13 被棄用。請用 os.path.isreserved() 來偵測 Windows 上的保留路徑。

platform：

自 Python 3.13 起，java_ver() 已被棄用。此函式僅對 Jython 支援有用，具有令人困惑的 API，基本上未經測試。

sysconfig：

sysconfig.is_python_build() 的 check_home 引數自 Python 3.12 起已被棄用。

threading：

RLock() 在 Python 3.15 中將不接受任何引數。自 Python 3.14 起，傳遞任何引數的用法已被棄用，因為 Python 版本不允許任何引數，但 C 版本允許任意數量的位置或關鍵字引數，並忽略每個引數。

types：

types.CodeType：自 3.10 起，存取 co_lnotab 已在 PEP 626 [https://peps.python.org/pep-0626/] 中被棄用，並計劃在 3.12 中移除，但只在 3.12 中於適當時發出 DeprecationWarning。可能在 3.15 中移除。（由 Nikita Sobolev 於 gh-101866 [https://github.com/python/cpython/issues/101866] 貢獻。）

typing：

用於建立 NamedTuple 類別的未以文件記錄之關鍵字引數語法 (Point = NamedTuple("Point", x=int, y=int)) 已自 Python 3.13 棄用。請改用基於類別的語法或函式語法 (functional syntax)。

當使用 TypedDict 的函式語法時，未傳遞值給 fields 參數 (TD = TypedDict("TD")) 或傳遞 None (TD = TypedDict("TD", None)) 的做法自 Python 3.13 起已被棄用。請使用 class TD(TypedDict): pass 或 TD = TypedDict("TD", {}) 來建立具有零個欄位的 TypedDict。

自 Python 3.13 起，typing.no_type_check_decorator() 裝飾器函式已被棄用。在 typing 模組中使用了八年之後，它尚未得到任何主要型別檢查器的支援。

wave：

已棄用 Wave_read 和 Wave_write 類別的 getmark()、setmark() 和 getmarkers() 方法自 Python 3.13 被棄用。

zipimport：

load_module() 自 Python 3.10 被棄用。請改用 exec_module()。（由 Jiahao Li 於 gh-125746 [https://github.com/python/cpython/issues/125746] 貢獻。）

Python 3.16 中待移除的項目

引入系統 (import system)：

在模組上設定 __loader__ 而沒有設定 __spec__.loader 的做法將於 Python 3.16 被棄用。在 Python 3.16 中，引入系統或標準函式庫將不再設定或考慮 __loader__。

array：

自 Python 3.3 起，'u' 格式碼 (wchar_t) 在文件中已被棄用，自 Python 3.13 起在 runtime 已被棄用。請使用 'w' 格式碼 (Py_UCS4) 來取代 Unicode 字元。

asyncio：

asyncio.iscoroutinefunction() 已被棄用並將在 Python 3.16 中移除；請改用 inspect.iscoroutinefunction()。（由 Jiahao Li 和 Kumar Aditya 於 gh-122875 [https://github.com/python/cpython/issues/122875] 貢獻。）

asyncio 策略系統已被棄用並將在 Python 3.16 中移除。特別是以下類別和函式已被棄用：

asyncio.AbstractEventLoopPolicy

asyncio.DefaultEventLoopPolicy

asyncio.WindowsSelectorEventLoopPolicy

asyncio.WindowsProactorEventLoopPolicy

asyncio.get_event_loop_policy()

asyncio.set_event_loop_policy()

使用者應該使用 asyncio.run() 或 asyncio.Runner 搭配 loop_factory 來使用所需的事件迴圈實作。

例如在 Windows 上使用 asyncio.SelectorEventLoop：

import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

（由 Kumar Aditya 於 gh-127949 [https://github.com/python/cpython/issues/127949] 貢獻。）

builtins：

自 Python 3.12 起，布林型別的位元反轉 ~True 或 ~False 已被棄用，因為它會產生不預期且不直觀的結果（-2 和 -1）。使用 not x 代替布林值的邏輯否定。在極少數情況下，你需要對底層的整數進行位元反轉，請明確轉換為 ~int(x) (~int(x))。

functools：

自 Python 3.14 起，使用 function 或 sequence 關鍵字引數呼叫 functools.reduce() 的 Python 實作已被棄用。

logging：

對具有 strm 引數的自訂日誌記錄處理函式的支援已被棄用，並計劃在 Python 3.16 中移除。請改用 stream 引數。（由 Mariusz Felisiak 於 gh-115032 [https://github.com/python/cpython/issues/115032] 貢獻。）

mimetypes：

有效的副檔名以 '.' 開頭或對 mimetypes.MimeTypes.add_type() 為空字串。未加點的副檔名已被棄用，並將在 Python 3.16 中引發 ValueError。（由 Hugo van Kemenade 於 gh-75223 [https://github.com/python/cpython/issues/75223] 貢獻。）

shutil：

自 Python 3.14 起，ExecError 例外已被棄用。自 Python 3.4 以來，它尚未被 shutil 中的任何函式使用，現在是 RuntimeError 的別名。

symtable：

自 Python 3.14 起，Class.get_methods 方法已被棄用。

sys：

自 Python 3.13 起，_enablelegacywindowsfsencoding() 函式已被棄用。請改用 PYTHONLEGACYWINDOWSFSENCODING 環境變數。

sysconfig：

自 Python 3.14 起，sysconfig.expand_makefile_vars() 函式已被棄用。請改用 sysconfig.get_paths() 的 vars 引數。

tarfile：

自 Python 3.13 起，未以文件記錄和未被使用的 TarFile.tarfile 屬性已被棄用。

Python 3.17 中待移除的項目

collections.abc：

collections.abc.ByteString 預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

typing：

在 Python 3.14 之前，舊式聯集是使用私有類別 typing._UnionGenericAlias 實作的。這個類別不再被需要，但為了向後相容性而保留，並計劃將在 Python 3.17 中移除。使用者應該改用文件中記錄的內省輔助函式，例如 typing.get_origin() 和 typing.get_args()，或者依賴私有實作細節。

typing.ByteString 自 Python 3.9 起已被棄用，預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

Python 3.18 中待移除的項目

decimal：

非標準且無文件記載的 Decimal 格式說明符號 'N'，僅在 decimal 模組的 C 實作中被支援，自 Python 3.13 起已被棄用。（由 Serhiy Storchaka 於 gh-89902 [https://github.com/python/cpython/issues/89902] 中貢獻。）

Python 3.19 中待移除的項目

ctypes：

在非 Windows 平台上，透過設定 _pack_ 而沒有設定 _layout_ 來隱式地切換到與 MSVC 相容的結構佈局。

未來版本中的待移除項目

以下 API 將在未來被移除，雖然目前尚未安排移除日期。

argparse：

巢狀引數群組和巢狀互斥群組已被棄用。

將未以文件記錄的關鍵字引數 prefix_chars 傳遞給 add_argument_group() 的做法現在已被棄用。

argparse.FileType 型別轉換器已被棄用。

builtins：

產生器：throw(type, exc, tb) 和 athrow(type, exc, tb) 簽名已被棄用：請改用 throw(exc) 和 athrow(exc)，為單引數簽名。

目前 Python 接受數值字面值後面立即接關鍵字，例如 0in x、1or x、0if 1else 2。它讓運算式模糊且容易混淆，如 [0x1for x in y]（可以解釋為 [0x1 for x in y] 或 [0x1f or x in y]）。如果數值字面值後立即接 and、else、for、if、in、is 和 or 之一的關鍵字，則會引發語法警告。在未來版本中，它將被更改為語法錯誤。(gh-87999 [https://github.com/python/cpython/issues/87999])

__index__() 和 __int__() 方法回傳非 int 型別的支援：這些方法將需要回傳 int 的嚴格子類別實例。

回傳 float 嚴格子類別 __float__() 方法的支援：這些方法將需要回傳 float 的實例。

回傳 complex 嚴格子類別 __complex__() 方法的支援：這些方法將需要回傳 complex 的實例。

將 int() 委派給 __trunc__() 方法。

在 complex() 建構子中將複數作為 real 或 imag 引數傳遞現在已被棄用；它應該只作為單個位置引數傳遞。 (由 Serhiy Storchaka 於 gh-109218 [https://github.com/python/cpython/issues/109218] 貢獻。)

calendar：calendar.January 和 calendar.February 常數已被棄用並被 calendar.JANUARY 和 calendar.FEBRUARY 取代。 (由 Prince Roshan 於 gh-103636 [https://github.com/python/cpython/issues/103636] 貢獻。)

codecs：請改用 open() 而非 codecs.open()。(gh-133038 [https://github.com/python/cpython/issues/133038])

codeobject.co_lnotab：請改用 codeobject.co_lines() 方法。

datetime：

utcnow()：請改用 datetime.datetime.now(tz=datetime.UTC)。

utcfromtimestamp()：請改用 datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)。

gettext：複數值必須是整數。

importlib：

cache_from_source() debug_override 參數已被棄用：請改用 optimization 參數。

importlib.metadata：

EntryPoints 元組介面。

回傳值上的隱式 None。

logging：自 Python 3.3 起，warn() 方法已被棄用，請改用 warning()。

mailbox：已棄用 StringIO 輸入和文本模式，請改用 BytesIO 和二進位模式。

os：在多執行緒行程中呼叫 os.register_at_fork()。

pydoc.ErrorDuringImport：exc_info 參數的元組值已被棄用，請用例外實例。

re：現在對正規表示式中的數值群組參照和群組名稱用了更嚴格的規則。現在只有 ASCII 數碼序列被接受作為數值參照。位元組模式和替換字串中的群組名稱現在只能包含 ASCII 字母、數碼和底線。（由 Serhiy Storchaka 於 gh-91760 [https://github.com/python/cpython/issues/91760] 貢獻。）

sre_compile、sre_constants 和 sre_parse 模組。

shutil：rmtree() 的 onerror 參數在 Python 3.12 中已被棄用；請改用 onexc 參數。

ssl 選項和協定：

不帶協定引數的 ssl.SSLContext 已被棄用。

ssl.SSLContext：set_npn_protocols() 和 selected_npn_protocol() 已被棄用：請改用 ALPN。

ssl.OP_NO_SSL* 選項

ssl.OP_NO_TLS* 選項

ssl.PROTOCOL_SSLv3

ssl.PROTOCOL_TLS

ssl.PROTOCOL_TLSv1

ssl.PROTOCOL_TLSv1_1

ssl.PROTOCOL_TLSv1_2

ssl.TLSVersion.SSLv3

ssl.TLSVersion.TLSv1

ssl.TLSVersion.TLSv1_1

threading 方法：

threading.Condition.notifyAll()：請用 notify_all()。

threading.Event.isSet()：請用 is_set()。

threading.Thread.isDaemon()、threading.Thread.setDaemon()：請用 threading.Thread.daemon 屬性。

threading.Thread.getName()、threading.Thread.setName()：請用 threading.Thread.name 屬性。

threading.currentThread()：請用 threading.current_thread()。

threading.activeCount()：請用 threading.active_count()。

typing.Text (gh-92332 [https://github.com/python/cpython/issues/92332])。

內部類別 typing._UnionGenericAlias 不再用於實作 typing.Union。為了保持與此私有類別使用者的相容性，直到至少 Python 3.17 都將提供一個相容性 shim。（由 Jelle Zijlstra 於 gh-105499 [https://github.com/python/cpython/issues/105499] 貢獻。）

unittest.IsolatedAsyncioTestCase：從測試案例中回傳非 None 的值已被棄用。

urllib.parse 已棄用函式：請改用 urlparse()。

splitattr()

splithost()

splitnport()

splitpasswd()

splitport()

splitquery()

splittag()

splittype()

splituser()

splitvalue()

to_bytes()

wsgiref：SimpleHandler.stdout.write() 不應該進行部分寫入。

xml.etree.ElementTree：已棄用對 Element 的真值測試。在未來版本中，它將始終回傳 True。請改用明確的 len(elem) 或 elem is not None 測試。

sys._clear_type_cache() 已被棄用：請改用 sys._clear_internal_caches()。

C API 的棄用項目

Python 3.15 中待移除的項目

PyImport_ImportModuleNoBlock()：請改用 PyImport_ImportModule()。

PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT()：請改用 PyWeakref_GetRef()。可以使用 pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]來為 Python 3.12 和更早版本取得 PyWeakref_GetRef()。

Py_UNICODE 型別與 Py_UNICODE_WIDE 巨集：請改用 wchar_t。

PyUnicode_AsDecodedObject()：請改用 PyCodec_Decode()。

PyUnicode_AsDecodedUnicode()：請改用 PyCodec_Decode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 str 的型別，例如 bytes。

PyUnicode_AsEncodedObject()：請改用 PyCodec_Encode()。

PyUnicode_AsEncodedUnicode()：請改用 PyCodec_Encode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 bytes 的型別，例如 str。

Python 初始化函式，自 Python 3.13 起已被棄用：

Py_GetPath()：請改用 PyConfig_Get("module_search_paths") (sys.path)。

Py_GetPrefix()：請改用 PyConfig_Get("base_prefix") (sys.base_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("prefix") (sys.prefix)。

Py_GetExecPrefix()：請改用 PyConfig_Get("base_exec_prefix") (sys.base_exec_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("exec_prefix") (sys.exec_prefix)。

Py_GetProgramFullPath()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetProgramName()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetPythonHome()：請改用 PyConfig_Get("home") 或 PYTHONHOME 環境變數。

pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/] 可以用來為 Python 3.13 和更早版本取得 PyConfig_Get()。

用於配置 Python 初始化的函式，自 Python 3.11 起已被棄用：

PySys_SetArgvEx()：請改用 PyConfig.argv。

PySys_SetArgv()：請改用 PyConfig.argv。

Py_SetProgramName()：請改用 PyConfig.program_name。

Py_SetPythonHome()：請改用 PyConfig.home。

PySys_ResetWarnOptions()：請改為清除 sys.warnoptions 和 warnings.filters。

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API。

全域配置變數：

Py_DebugFlag：請改用 PyConfig.parser_debug 或 PyConfig_Get("parser_debug")。

Py_VerboseFlag：請改用 PyConfig.verbose 或 PyConfig_Get("verbose")。

Py_QuietFlag：請改用 PyConfig.quiet 或 PyConfig_Get("quiet")。

Py_InteractiveFlag：請改用 PyConfig.interactive 或 PyConfig_Get("interactive")。

Py_InspectFlag：請改用 PyConfig.inspect 或 PyConfig_Get("inspect")。

Py_OptimizeFlag：請改用 PyConfig.optimization_level 或 PyConfig_Get("optimization_level")。

Py_NoSiteFlag：請改用 PyConfig.site_import 或 PyConfig_Get("site_import")。

Py_BytesWarningFlag：請改用 PyConfig.bytes_warning 或 PyConfig_Get("bytes_warning")。

Py_FrozenFlag：請改用 PyConfig.pathconfig_warnings 或 PyConfig_Get("pathconfig_warnings")。

Py_IgnoreEnvironmentFlag：請改用 PyConfig.use_environment 或 PyConfig_Get("use_environment")。

Py_DontWriteBytecodeFlag：請改用 PyConfig.write_bytecode 或 PyConfig_Get("write_bytecode")。

Py_NoUserSiteDirectory：請改用 PyConfig.user_site_directory 或 PyConfig_Get("user_site_directory")。

Py_UnbufferedStdioFlag：請改用 PyConfig.buffered_stdio 或 PyConfig_Get("buffered_stdio")。

Py_HashRandomizationFlag：請改用 PyConfig.use_hash_seed 和 PyConfig.hash_seed 或 PyConfig_Get("hash_seed")。

Py_IsolatedFlag：請改用 PyConfig.isolated 或 PyConfig_Get("isolated")。

Py_LegacyWindowsFSEncodingFlag：請改用 PyPreConfig.legacy_windows_fs_encoding 或 PyConfig_Get("legacy_windows_fs_encoding")。

Py_LegacyWindowsStdioFlag：請改用 PyConfig.legacy_windows_stdio 或 PyConfig_Get("legacy_windows_stdio")。

Py_FileSystemDefaultEncoding、Py_HasFileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding 或 PyConfig_Get("filesystem_encoding")。

Py_FileSystemDefaultEncodeErrors：請改用 PyConfig.filesystem_errors 或 PyConfig_Get("filesystem_errors")。

Py_UTF8Mode：請改用 PyPreConfig.utf8_mode 或 PyConfig_Get("utf8_mode")。（請參閱 Py_PreInitialize()）

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API 來設定這些選項。或者也可以使用 PyConfig_Get() 在執行時取得這些選項。

Python 3.18 中待移除的項目

以下私有函式已被棄用，並計劃在 Python 3.18 中移除：

_PyBytes_Join()：請改用 PyBytes_Join()。

_PyDict_GetItemStringWithError()：請改用 PyDict_GetItemStringRef()。

_PyDict_Pop()：請改用 PyDict_Pop()。

_PyLong_Sign()：請改用 PyLong_GetSign()。

_PyLong_FromDigits() 和 _PyLong_New()：請改用 PyLongWriter_Create()。

_PyThreadState_UncheckedGet()：請改用 PyThreadState_GetUnchecked()。

_PyUnicode_AsString()：請改用 PyUnicode_AsUTF8()。

_PyUnicodeWriter_Init()：將 _PyUnicodeWriter_Init(&writer) 替換為 writer = PyUnicodeWriter_Create(0)。

_PyUnicodeWriter_Finish()：將 _PyUnicodeWriter_Finish(&writer) 替換為 PyUnicodeWriter_Finish(writer)。

_PyUnicodeWriter_Dealloc()：將 _PyUnicodeWriter_Dealloc(&writer) 替換為 PyUnicodeWriter_Discard(writer)。

_PyUnicodeWriter_WriteChar()：將 _PyUnicodeWriter_WriteChar(&writer, ch) 替換為 PyUnicodeWriter_WriteChar(writer, ch)。

_PyUnicodeWriter_WriteStr()：將 _PyUnicodeWriter_WriteStr(&writer, str) 替換為 PyUnicodeWriter_WriteStr(writer, str)。

_PyUnicodeWriter_WriteSubstring()：將 _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) 替換為 PyUnicodeWriter_WriteSubstring(writer, str, start, end)。

_PyUnicodeWriter_WriteASCIIString()：將 _PyUnicodeWriter_WriteASCIIString(&writer, str) 替換為 PyUnicodeWriter_WriteASCII(writer, str)。

_PyUnicodeWriter_WriteLatin1String()：將 _PyUnicodeWriter_WriteLatin1String(&writer, str) 替換為 PyUnicodeWriter_WriteUTF8(writer, str)。

_PyUnicodeWriter_Prepare()：（無替代方案）。

_PyUnicodeWriter_PrepareKind()：（無替代方案）。

_Py_HashPointer()：請改用 Py_HashPointer()。

_Py_fopen_obj()：請改用 Py_fopen()。

可以使用 pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] 來取得這些於 Python 3.13 及更早版本的新公開函式。（由 Victor Stinner 在 gh-128863 [https://github.com/python/cpython/issues/128863] 貢獻）

未來版本中的待移除項目

下列 API 已被棄用並將會被移除，不過目前尚未訂定移除日期。

Py_TPFLAGS_HAVE_FINALIZE：自 Python 3.8 起不再需要

PyErr_Fetch()：請改用 PyErr_GetRaisedException()。

PyErr_NormalizeException()：請改用 PyErr_GetRaisedException()。

PyErr_Restore()：請改用 PyErr_SetRaisedException()。

PyModule_GetFilename()：請改用 PyModule_GetFilenameObject()。

PyOS_AfterFork()：請改用 PyOS_AfterFork_Child()。

PySlice_GetIndicesEx()：請改用 PySlice_Unpack() 和 PySlice_AdjustIndices()。

PyUnicode_READY()：自 Python 3.12 起不再需要

PyErr_Display()：請改用 PyErr_DisplayException()。

_PyErr_ChainExceptions()：請改用 _PyErr_ChainExceptions1。

PyBytesObject.ob_shash 成員：請改為呼叫 PyObject_Hash()。

執行緒局部儲存 (Thread Local Storage, TLS) API：

PyThread_create_key()：請改用 PyThread_tss_alloc()。

PyThread_delete_key()：請改用 PyThread_tss_free()。

PyThread_set_key_value()：請改用 PyThread_tss_set()。

PyThread_get_key_value()：請改用 PyThread_tss_get()。

PyThread_delete_key_value()：請改用 PyThread_tss_delete()。

PyThread_ReInitTLS()：自 Python 3.7 起不再需要。

術語表

>>>

互動式 shell 的預設 Python 提示字元。常見於能在直譯器中以互動方式被執行的程式碼範例。

...

可以表示：

在一個被縮排的程式碼區塊、在一對匹配的左右定界符（delimiter，例如括號、方括號、花括號或三引號）內部，或是在指定一個裝飾器 (decorator) 之後，要輸入程式碼時，互動式 shell 顯示的預設 Python 提示字元。

The three dots form of the Ellipsis object.

abstract base class（抽象基底類別）

抽象基底類別（又稱為 ABC）提供了一種定義介面的方法，作為 duck-typing（鴨子型別）的補充。其他類似的技術，像是 hasattr()，則顯得笨拙或是帶有細微的錯誤（例如使用魔術方法 (magic method)）。ABC 採用虛擬的 subclass（子類別），它們並不繼承自另一個 class（類別），但仍可被 isinstance() 及 issubclass() 辨識；請參閱 abc 模組的說明文件。Python 有許多內建的 ABC，用於資料結構（在 collections.abc 模組）、數字（在 numbers 模組）、串流（在 io 模組）及 import 尋檢器和載入器（在 importlib.abc 模組）。你可以使用 abc 模組建立自己的 ABC。

annotate function（註釋函式）

A function that can be called to retrieve the annotations of an object. This function is accessible as the __annotate__ attribute of functions, classes, and modules. Annotate functions are a subset of evaluate functions.

annotation（註釋）

一個與變數、class 屬性、函式的參數或回傳值相關聯的標籤。照慣例，它被用來作為 type hint（型別提示）。

在 runtime 的區域變數註釋無法被存取，但全域變數、類別屬性和函式的註釋，分別能夠以對模組、類別和函式呼叫 annotationlib.get_annotations() 來取得。

請參閱 variable annotation、function annotation、PEP 484 [https://peps.python.org/pep-0484/]、PEP 526 [https://peps.python.org/pep-0526/] 和 PEP 649 [https://peps.python.org/pep-0649/]，這些章節皆有此功能的說明。關於註釋的最佳實踐方法也請參閱 註釋 (annotation) 最佳實踐。

argument（引數）

呼叫函式時被傳遞給 function（或 method）的值。引數有兩種：

關鍵字引數 (keyword argument)：在函式呼叫中，以識別字（identifier，例如 name=）開頭的引數，或是以 ** 後面 dictionary（字典）內的值被傳遞的引數。例如，3 和 5 都是以下 complex() 呼叫中的關鍵字引數：

complex(real=3, imag=5)
complex(**{'real': 3, 'imag': 5})

位置引數 (positional argument)：不是關鍵字引數的引數。位置引數可在一個引數列表的起始處出現，和（或）作為 * 之後的 iterable（可疊代物件）中的元素被傳遞。例如，3 和 5 都是以下呼叫中的位置引數：

complex(3, 5)
complex(*(3, 5))

引數會被指定給函式主體中的附名區域變數。關於支配這個指定過程的規則，請參閱Calls章節。在語法上，任何運算式都可以被用來表示一個引數；其評估值會被指定給區域變數。

另請參閱術語表的 parameter（參數）條目、常見問題中的引數和參數之間的差異，以及 PEP 362 [https://peps.python.org/pep-0362/]。

asynchronous context manager（非同步情境管理器）

一個可以控制 async with 陳述式中所見環境的物件，而它是透過定義 __aenter__() 和 __aexit__() method（方法）來控制的。由 PEP 492 [https://peps.python.org/pep-0492/] 引入。

asynchronous generator（非同步產生器）

一個會回傳 asynchronous generator iterator（非同步產生器疊代器）的函式。它看起來像一個以 async def 定義的協程函式 (coroutine function)，但不同的是它包含了 yield 運算式，能生成一系列可用於 async for 迴圈的值。

這個術語通常用來表示一個非同步產生器函式，但在某些情境中，也可能是表示非同步產生器疊代器 (asynchronous generator iterator)。萬一想表達的意思不夠清楚，那就使用完整的術語，以避免歧義。

一個非同步產生器函式可能包含 await 運算式，以及 async for 和 async with 陳述式。

asynchronous generator iterator（非同步產生器疊代器）

一個由 asynchronous generator（非同步產生器）函式所建立的物件。

這是一個 asynchronous iterator（非同步疊代器），當它以 __anext__() method 被呼叫時，會回傳一個可等待物件 (awaitable object)，該物件將執行非同步產生器的函式主體，直到遇到下一個 yield 運算式。

每個 yield 會暫停處理程序，並記住執行狀態（包括區域變數及擱置中的 try 陳述式）。當非同步產生器疊代器以另一個被 __anext__() 回傳的可等待物件有效地回復時，它會從停止的地方繼續執行。請參閱 PEP 492 [https://peps.python.org/pep-0492/] 和 PEP 525 [https://peps.python.org/pep-0525/]。

asynchronous iterable（非同步可疊代物件）

一個物件，它可以在 async for 陳述式中被使用。必須從它的 __aiter__() method 回傳一個 asynchronous iterator（非同步疊代器）。由 PEP 492 [https://peps.python.org/pep-0492/] 引入。

asynchronous iterator（非同步疊代器）

一個實作 __aiter__() 和 __anext__() method 的物件。__anext__() 必須回傳一個 awaitable（可等待物件）。async for 會解析非同步疊代器的 __anext__() method 所回傳的可等待物件，直到它引發 StopAsyncIteration 例外。由 PEP 492 [https://peps.python.org/pep-0492/] 引入。

atomic operation

An operation that appears to execute as a single, indivisible step: no other thread can observe it half-done, and its effects become visible all at once. Python does not guarantee that high-level statements are atomic (for example, x += 1 performs multiple bytecode operations and is not atomic). Atomicity is only guaranteed where explicitly documented. See also race condition and data race.

attached thread state

A thread state that is active for the current OS thread.

When a thread state is attached, the OS thread has access to the full Python C API and can safely invoke the bytecode interpreter.

Unless a function explicitly notes otherwise, attempting to call the C API without an attached thread state will result in a fatal error or undefined behavior. A thread state can be attached and detached explicitly by the user through the C API, or implicitly by the runtime, including during blocking C calls and by the bytecode interpreter in between calls.

On most builds of Python, having an attached thread state implies that the caller holds the GIL for the current interpreter, so only one OS thread can have an attached thread state at a given moment. In free-threaded builds of Python, threads can concurrently hold an attached thread state, allowing for true parallelism of the bytecode interpreter.

attribute（屬性）

一個與某物件相關聯的值，該值大多能透過使用點分隔運算式 (dotted expression) 的名稱被參照。例如，如果物件 o 有一個屬性 a，則該屬性能以 o.a 被參照。

如果一個物件允許，給予該物件一個名稱不是由Names (identifiers and keywords)所定義之識別符 (identifier) 的屬性是有可能的，例如使用 setattr()。像這樣的屬性將無法使用點分隔運算式來存取，而是需要使用 getattr() 來取得它。

awaitable（可等待物件）

一個可以在 await 運算式中被使用的物件。它可以是一個 coroutine（協程），或是一個有 __await__() method 的物件。另請參閱 PEP 492 [https://peps.python.org/pep-0492/]。

BDFL

Benevolent Dictator For Life（終身仁慈獨裁者），又名 Guido van Rossum [https://gvanrossum.github.io/]，Python 的創造者。

binary file（二進位檔案）

一個能夠讀取和寫入 bytes-like objects（類位元組串物件）的 file object（檔案物件）。二進位檔案的例子有：以二進位模式（'rb'、'wb' 或 'rb+'）開啟的檔案、sys.stdin.buffer、sys.stdout.buffer，以及 io.BytesIO 和 gzip.GzipFile 實例。

另請參閱 text file（文字檔案），它是一個能夠讀取和寫入 str 物件的檔案物件。

borrowed reference（借用參照）

在 Python 的 C API 中，借用參照是一個對物件的參照，其中使用該物件的程式碼並不擁有這個參照。如果該物件被銷毀，它會成為一個迷途指標 (dangling pointer)。例如，一次垃圾回收 (garbage collection) 可以移除對物件的最後一個 strong reference（強參照），而將該物件銷毀。

對 borrowed reference 呼叫 Py_INCREF() 以將它原地 (in-place) 轉換為 strong reference 是被建議的做法，除非該物件不能在最後一次使用借用參照之前被銷毀。Py_NewRef() 函式可用於建立一個新的 strong reference。

bytes-like object（類位元組串物件）

一個支援緩衝協定 (Buffer Protocol)且能夠匯出 C-contiguous 緩衝區的物件。這包括所有的 bytes、bytearray 和 array.array 物件，以及許多常見的 memoryview 物件。類位元組串物件可用於處理二進位資料的各種運算；這些運算包括壓縮、儲存至二進位檔案和透過 socket（插座）發送。

有些運算需要二進位資料是可變的。說明文件通常會將這些物件稱為「可讀寫的類位元組串物件」。可變緩衝區的物件包括 bytearray，以及 bytearray 的 memoryview。其他的運算需要讓二進位資料被儲存在不可變物件（「唯讀的類位元組串物件」）中；這些物件包括 bytes，以及 bytes 物件的 memoryview。

bytecode（位元組碼）

Python 的原始碼會被編譯成位元組碼，它是 Python 程式在 CPython 直譯器中的內部表示法。該位元組碼也會被暫存在 .pyc 檔案中，以便第二次執行同一個檔案時能夠更快速（可以不用從原始碼重新編譯為位元組碼）。這種「中間語言 (intermediate language)」據說是運行在一個 virtual machine（虛擬機器）上，該虛擬機器會執行與每個位元組碼對應的機器碼 (machine code)。要注意的是，位元組碼理論上是無法在不同的 Python 虛擬機器之間運作的，也不能在不同版本的 Python 之間保持穩定。

位元組碼的指令列表可以在 dis 模組的說明文件中找到。

callable（可呼叫物件）

一個 callable 是可以被呼叫的物件，呼叫時可能以下列形式帶有一組引數（請見 argument）：

callable(argument1, argument2, argumentN)

一個 function 與其延伸的 method 都是 callable。一個有實作 __call__() 方法的 class 之實例也是個 callable。

callback（回呼）

作為引數被傳遞的一個副程式 (subroutine) 函式，會在未來的某個時間點被執行。

class（類別）

一個用於建立使用者定義物件的模板。Class 的定義通常會包含 method 的定義，這些 method 可以在 class 的實例上進行操作。

class variable（類別變數）

一個在 class 中被定義，且應該只能在 class 層次（意即不是在 class 的實例中）被修改的變數。

closure variable（閉包變數）

從外部作用域中定義且從巢狀作用域參照的自由變數，不是於 runtime 從全域或內建命名空間解析。可以使用 nonlocal 關鍵字明確定義以允許寫入存取，或者如果僅需讀取變數則隱式定義即可。

例如在下面程式碼中的 inner 函式中，x 和 print 都是自由變數，但只有 x 是閉包變數：

def outer():
    x = 0
    def inner():
        nonlocal x
        x += 1
        print(x)
    return inner

由於 codeobject.co_freevars 屬性（儘管名稱如此，但它僅包含閉包變數的名稱，而不是列出所有參照的自由變數），當預期含義是特指閉包變數時，有時候甚至也會使用更通用的自由變數一詞。

complex number（複數）

一個我們熟悉的實數系統的擴充，在此所有數字都會被表示為一個實部和一個虛部之和。虛數就是虛數單位（-1 的平方根）的實數倍，此單位通常在數學中被寫為 i，在工程學中被寫為 j。Python 內建了對複數的支援，它是用後者的記法來表示複數；虛部會帶著一個後綴的 j 被編寫，例如 3+1j。若要將 math 模組內的工具等效地用於複數，請使用 cmath 模組。複數的使用是一個相當進階的數學功能。如果你沒有察覺到對它們的需求，那麼幾乎能確定你可以安全地忽略它們。

concurrency（並行性）

The ability of a computer program to perform multiple tasks at the same time. Python provides libraries for writing programs that make use of different forms of concurrency. asyncio is a library for dealing with asynchronous tasks and coroutines. threading provides access to operating system threads and multiprocessing to operating system processes. Multi-core processors can execute threads and processes on different CPU cores at the same time (see parallelism).

concurrent modification

When multiple threads modify shared data at the same time. Concurrent modification without proper synchronization can cause race conditions, and might also trigger a data race, data corruption, or both.

context（情境）

This term has different meanings depending on where and how it is used. Some common meanings:

The temporary state or environment established by a context manager via a with statement.

The collection of keyvalue bindings associated with a particular contextvars.Context object and accessed via ContextVar objects. Also see context variable.

一個 contextvars.Context 物件。另請參閱 current context。

context management protocol（情境管理協定）

由 with 陳述式所呼叫的 __enter__() 和 __exit__() 方法。另請參閱 PEP 343 [https://peps.python.org/pep-0343/]。

context manager（情境管理器）

An object which implements the context management protocol and controls the environment seen in a with statement. See PEP 343 [https://peps.python.org/pep-0343/].

context variable（情境變數）

A variable whose value depends on which context is the current context. Values are accessed via contextvars.ContextVar objects. Context variables are primarily used to isolate state between concurrent asynchronous tasks.

contiguous（連續的）

如果一個緩衝區是 C-contiguous 或是 Fortran contiguous，則它會確切地被視為是連續的。零維 (zero-dimensional) 的緩衝區都是 C 及 Fortran contiguous。在一維 (one-dimensional) 陣列中，各項目必須在記憶體中彼此相鄰地排列，而其索引順序是從零開始遞增。在多維的 (multidimensional) C-contiguous 陣列中，按記憶體位址的順序瀏覽各個項目時，最後一個索引的變化最快。然而，在 Fortran contiguous 陣列中，第一個索引的變化最快。

coroutine（協程）

協程是副程式 (subroutine) 的一種更為廣義的形式。副程式是在某個時間點被進入並在另一個時間點被退出。協程可以在許多不同的時間點被進入、退出和回復。它們能夠以 async def 陳述式被實作。另請參閱 PEP 492 [https://peps.python.org/pep-0492/]。

coroutine function（協程函式）

一個回傳 coroutine（協程）物件的函式。一個協程函式能以 async def 陳述式被定義，並可能會包含 await、async for 和 async with 關鍵字。這些關鍵字由 PEP 492 [https://peps.python.org/pep-0492/] 引入。

CPython

Python 程式語言的標準實作 (canonical implementation)，被發布在 python.org [https://www.python.org] 上。「CPython」這個術語在必要時被使用，以區分此實作與其它語言的實作，例如 Jython 或 IronPython。

current context

The context (contextvars.Context object) that is currently used by ContextVar objects to access (get or set) the values of context variables. Each thread has its own current context. Frameworks for executing asynchronous tasks (see asyncio) associate each task with a context which becomes the current context whenever the task starts or resumes execution.

cyclic isolate

A subgroup of one or more objects that reference each other in a reference cycle, but are not referenced by objects outside the group. The goal of the cyclic garbage collector is to identify these groups and break the reference cycles so that the memory can be reclaimed.

data race

A situation where multiple threads access the same memory location concurrently, at least one of the accesses is a write, and the threads do not use any synchronization to control their access. Data races lead to non-deterministic behavior and can cause data corruption. Proper use of locks and other synchronization primitives prevents data races. Note that data races can only happen in native code, but that native code might be exposed in a Python API. See also race condition and thread-safe.

deadlock

A situation in which two or more tasks (threads, processes, or coroutines) wait indefinitely for each other to release resources or complete actions, preventing any from making progress. For example, if thread A holds lock 1 and waits for lock 2, while thread B holds lock 2 and waits for lock 1, both threads will wait indefinitely. In Python this often arises from acquiring multiple locks in conflicting orders or from circular join/await dependencies. Deadlocks can be avoided by always acquiring multiple locks in a consistent order. See also lock and reentrant.

decorator（裝飾器）

一個函式，它會回傳另一個函式，通常它會使用 @wrapper 語法，被應用為一種函式的變換 (function transformation)。裝飾器的常見範例是 classmethod() 和 staticmethod()。

裝飾器語法只是語法糖。以下兩個函式定義在語義上是等效的：

def f(arg):
    ...
f = staticmethod(f)

@staticmethod
def f(arg):
    ...

Class 也存在相同的概念，但在那裡比較不常用。關於裝飾器的更多內容，請參閱函式定義和 class 定義的說明文件。

descriptor（描述器）

任何定義了 __get__()、__set__() 或 __delete__() method 的物件。當一個 class 屬性是一個描述器時，它的特殊連結行為會在屬性查找時被觸發。通常，使用 a.b 來取得、設定或刪除某個屬性時，會在 a 的 class 字典中查找名稱為 b 的物件，但如果 b 是一個描述器，則相對應的描述器 method 會被呼叫。對描述器的理解是深入理解 Python 的關鍵，因為它們是許多功能的基礎，這些功能包括函式、method、屬性 (property)、class method、靜態 method，以及對 super class（父類別）的參照。

關於描述器 method 的更多資訊，請參閱實作描述器或描述器使用指南。

dictionary（字典）

一個關聯陣列 (associative array)，其中任意的鍵會被對映到值。鍵可以是任何帶有 __hash__() 和 __eq__() method 的物件。在 Perl 中被稱為雜湊 (hash)。

dictionary comprehension（字典綜合運算）

一種緊密的方法，用來處理一個可疊代物件中的全部或部分元素，並將處理結果以一個字典回傳。results = {n: n ** 2 for n in range(10)} 會產生一個字典，它包含了鍵 n 對映到值 n ** 2。請參閱Displays for lists, sets and dictionaries。

dictionary view（字典檢視）

從 dict.keys()、dict.values() 及 dict.items() 回傳的物件被稱為字典檢視。它們提供了字典中項目的動態檢視，這表示當字典有變動時，該檢視會反映這些變動。若要強制將字典檢視轉為完整的 list（串列），須使用 list(dictview)。請參閱字典視圖物件。

docstring（說明字串）

一個在 class、函式或模組中，作為第一個運算式出現的字串文本。雖然它在套件執行時會被忽略，但它會被編譯器辨識，並被放入所屬 class、函式或模組的 __doc__ 屬性中。由於說明字串可以透過內省 (introspection) 來瀏覽，因此它是物件的說明文件存放的標準位置。

duck-typing（鴨子型別）

一種程式設計風格，它不是藉由檢查一個物件的型別來確定它是否具有正確的介面；取而代之的是，method 或屬性會單純地被呼叫或使用。（「如果它看起來像一隻鴨子而且叫起來像一隻鴨子，那麼它一定是一隻鴨子。」）因為強調介面而非特定型別，精心設計的程式碼能讓多形替代 (polymorphic substitution) 來增進它的靈活性。鴨子型別要避免使用 type() 或 isinstance() 進行測試。（但是請注意，鴨子型別可以用抽象基底類別 (abstract base class) 來補充。）然而，它通常會採用 hasattr() 測試，或是 EAFP 程式設計風格。

dunder（雙底線）

一個非正式的縮寫，代表「雙底線 (double underscore)」，當談論到特殊方法時使用。例如，__init__ 通常被叫做 "dunder init"。

EAFP

Easier to ask for forgiveness than permission.（請求寬恕比請求許可更容易。）這種常見的 Python 編碼風格會先假設有效的鍵或屬性的存在，並在該假設被推翻時再捕獲例外。這種乾淨且快速的風格，其特色是存在許多的 try 和 except 陳述式。該技術與許多其他語言（例如 C）常見的 LBYL 風格形成了對比。

evaluate function（求值函式）

A function that can be called to evaluate a lazily evaluated attribute of an object, such as the value of type aliases created with the type statement.

expression（運算式）

一段可以被評估並求值的語法。換句話說，一個運算式就是文字、名稱、屬性存取、運算子或函式呼叫等運算式元件的累積，而這些元件都能回傳一個值。與許多其他語言不同的是，並非所有的 Python 語言構造都是運算式。另外有一些 statement（陳述式）不能被用作運算式，例如 while。賦值 (assignment) 也是陳述式，而不是運算式。

extension module（擴充模組）

一個以 C 或 C++ 編寫的模組，它使用 Python 的 C API 來與核心及使用者程式碼進行互動。

f-string（f 字串）

f-strings（f 字串）

以 f 或 F 為前綴的字串文本通常被稱為「f 字串」，它是格式化的字串文本的縮寫。另請參閱 PEP 498 [https://peps.python.org/pep-0498/]。

file object（檔案物件）

一個讓使用者透過檔案導向 (file-oriented) API（如 read() 或 write() 等 method）來操作底層資源的物件。根據檔案物件被建立的方式，它能夠協調對真實磁碟檔案或是其他類型的儲存器或通訊裝置（例如標準輸入／輸出、記憶體內緩衝區、socket（插座）、管線 (pipe) 等）的存取。檔案物件也被稱為類檔案物件 (file-like object) 或串流 (stream)。

實際上，有三種檔案物件：原始的二進位檔案、緩衝的二進位檔案和文字檔案。它們的介面在 io 模組中被定義。建立檔案物件的標準方法是使用 open() 函式。

file-like object（類檔案物件）

file object（檔案物件）的同義字。

filesystem encoding and error handler（檔案系統編碼和錯誤處理函式）

Python 所使用的一種編碼和錯誤處理函式，用來解碼來自作業系統的位元組，以及將 Unicode 編碼到作業系統。

檔案系統編碼必須保證能成功解碼所有小於 128 的位元組。如果檔案系統編碼無法提供此保證，則 API 函式會引發 UnicodeError。

sys.getfilesystemencoding() 和 sys.getfilesystemencodeerrors() 函式可用於取得檔案系統編碼和錯誤處理函式。

filesystem encoding and error handler（檔案系統編碼和錯誤處理函式）會在 Python 啟動時由 PyConfig_Read() 函式來配置：請參閱 filesystem_encoding，以及 PyConfig 的成員 filesystem_errors。

另請參閱 locale encoding（區域編碼）。

finder（尋檢器）

一個物件，它會嘗試為正在被 import 的模組尋找 loader（載入器）。

有兩種類型的尋檢器：元路徑尋檢器 (meta path finder) 會使用 sys.meta_path，而路徑項目尋檢器 (path entry finder) 會使用 sys.path_hooks。

請參閱 尋檢器 (Finder) 與載入器 (Loader) 和 importlib 以了解更多細節。

floor division（向下取整除法）

向下無條件捨去到最接近整數的數學除法。向下取整除法的運算子是 //。例如，運算式 11 // 4 的計算結果為 2，與 float（浮點數）真除法所回傳的 2.75 不同。請注意，(-11) // 4 的結果是 -3，因為是 -2.75 被向下無條件捨去。請參閱 PEP 238 [https://peps.python.org/pep-0238/]。

free threading（自由執行緒）

為一種執行緒模型，多個執行緒可以在同一直譯器中同時運行 Python 位元組碼。這與全域直譯器鎖形成對比，後者一次只允許一個執行緒執行 Python 位元組碼。請參閱 PEP 703 [https://peps.python.org/pep-0703/]。

free variable（自由變數）

Formally, as defined in the language execution model, a free variable is any variable used in a namespace which is not a local variable in that namespace. See closure variable for an example. Pragmatically, due to the name of the codeobject.co_freevars attribute, the term is also sometimes used as a synonym for closure variable.

function（函式）

一連串的陳述式，它能夠向呼叫者回傳一些值。它也可以被傳遞零個或多個引數，這些引數可被使用於函式本體的執行。另請參閱 parameter（參數）、method（方法），以及函式定義章節。

function annotation（函式註釋）

函式參數或回傳值的一個 annotation（註釋）。

函式註釋通常被使用於型別提示：例如，這個函式預期會得到兩個 int 引數，並會有一個 int 回傳值：

def sum_two_numbers(a: int, b: int) -> int:
   return a + b

函式註釋的語法在函式定義章節有詳細解釋。

請參閱 variable annotation 和 PEP 484 [https://peps.python.org/pep-0484/]，皆有此功能的描述。關於註釋的最佳實踐方法，另請參閱 註釋 (annotation) 最佳實踐。

__future__

future 陳述式：from __future__ import <feature>，會指示編譯器使用那些在 Python 未來的發布版本中將成為標準的語法或語義，來編譯目前的模組。而 __future__ 模組則記錄了 feature（功能）可能的值。透過 import 此模組並對其變數求值，你可以看見一個新的功能是何時首次被新增到此語言中，以及它何時將會（或已經）成為預設的功能：

>>> import __future__
>>> __future__.division
_Feature((2, 2, 0, 'alpha', 2), (3, 0, 0, 'alpha', 0), 8192)

garbage collection（垃圾回收）

當記憶體不再被使用時，將其釋放的過程。Python 執行垃圾回收，是透過參照計數 (reference counting)，以及一個能夠檢測和中斷參照循環 (reference cycle) 的循環垃圾回收器 (cyclic garbage collector) 來完成。垃圾回收器可以使用 gc 模組對其進行控制。

generator（產生器）

一個會回傳 generator iterator（產生器疊代器）的函式。它看起來像一個正常的函式，但不同的是它包含了 yield 運算式，能產生一系列的值，這些值可用於 for 迴圈，或是以 next() 函式，每次檢索其中的一個值。

這個術語通常用來表示一個產生器函式，但在某些情境中，也可能是表示產生器疊代器。萬一想表達的意思不夠清楚，那就使用完整的術語，以避免歧義。

generator iterator（產生器疊代器）

一個由 generator（產生器）函式所建立的物件。

每個 yield 會暫停處理程序，並記住執行狀態（包括區域變數及擱置中的 try 陳述式）。當產生器疊代器回復時，它會從停止的地方繼續執行（與那些每次呼叫時都要重新開始的函式有所不同）。

generator expression（產生器運算式）

一個會回傳疊代器的運算式。它看起來像一個正常的運算式，後面接著一個 for 子句，該子句定義了迴圈變數、範圍以及一個選擇性的 if 子句。該組合運算式會為外層函式產生多個值：

>>> sum(i*i for i in range(10))         # 平方之和 0, 1, 4, ... 81
285

generic function（泛型函式）

一個由多個函式組成的函式，該函式會對不同的型別實作相同的運算。呼叫期間應該使用哪種實作，是由調度演算法 (dispatch algorithm) 來決定。

另請參閱 single dispatch（單一調度）術語表條目、functools.singledispatch() 裝飾器和 PEP 443 [https://peps.python.org/pep-0443/]。

generic type（泛型型別）

一個能夠被參數化 (parameterized) 的 type（型別）；通常是一個 容器型別，像是 list 和 dict。它被用於型別提示和註釋。

詳情請參閱泛型別名型別、PEP 483 [https://peps.python.org/pep-0483/]、PEP 484 [https://peps.python.org/pep-0484/]、PEP 585 [https://peps.python.org/pep-0585/] 和 typing 模組。

GIL

請參閱 global interpreter lock（全域直譯器鎖）。

global interpreter lock（全域直譯器鎖）

CPython 直譯器所使用的機制，用以確保每次都只有一個執行緒能執行 Python 的 bytecode（位元組碼）。透過使物件模型（包括關鍵的內建型別，如 dict）自動地避免並行存取 (concurrent access) 的危險，此機制可以簡化 CPython 的實作。鎖定整個直譯器，會使直譯器更容易成為多執行緒 (multi-threaded)，但代價是會犧牲掉多處理器的機器能夠提供的一大部分平行性 (parallelism)。

然而，有些擴充模組，無論是標準的或是第三方的，它們被設計成在執行壓縮或雜湊等計算密集 (computationally intensive) 的任務時，可以解除 GIL。另外，在執行 I/O 時，GIL 總是會被解除。

從 Python 3.13 開始可以使用 --disable-gil 建置設定來停用 GIL。使用此選項建立 Python 後，必須使用 -X gil=0 來執行程式碼，或者設定 PYTHON_GIL=0 環境變數後再執行程式碼。此功能可以提高多執行緒應用程式的效能，並使多核心 CPU 的高效使用變得更加容易。有關更多詳細資訊，請參閱 PEP 703 [https://peps.python.org/pep-0703/]。

In prior versions of Python's C API, a function might declare that it requires the GIL to be held in order to use it. This refers to having an attached thread state.

global state

Data that is accessible throughout a program, such as module-level variables, class variables, or C static variables in extension modules. In multi-threaded programs, global state shared between threads typically requires synchronization to avoid race conditions and data races.

hash-based pyc（雜湊架構的 pyc）

一個位元組碼 (bytecode) 暫存檔，它使用雜湊值而不是對應原始檔案的最後修改時間，來確定其有效性。請參閱Cached bytecode invalidation。

hashable（可雜湊的）

如果一個物件有一個雜湊值，該值在其生命週期中永不改變（它需要一個 __hash__() method），且可與其他物件互相比較（它需要一個 __eq__() method），那麼它就是一個可雜湊物件。比較結果為相等的多個可雜湊物件，它們必須擁有相同的雜湊值。

可雜湊性 (hashability) 使一個物件可用作 dictionary（字典）的鍵和 set（集合）的成員，因為這些資料結構都在其內部使用了雜湊值。

大多數的 Python 不可變內建物件都是可雜湊的；可變的容器（例如 list 或 dictionary）並不是；而不可變的容器（例如 tuple（元組）和 frozenset），只有當它們的元素是可雜湊的，它們本身才是可雜湊的。若物件是使用者自定 class 的實例，則這些物件會被預設為可雜湊的。它們在互相比較時都是不相等的（除非它們與自己比較），而它們的雜湊值則是衍生自它們的 id()。

IDLE

Python 的 Integrated Development and Learning Environment（整合開發與學習環境）。IDLE --- Python 編輯器與 shell 是一個基本的編輯器和直譯器環境，它和 Python 的標準發行版本一起被提供。

immortal（不滅）

不滅物件 (Immortal objects) 是 PEP 683 [https://peps.python.org/pep-0683/] 引入的 CPython 實作細節。

如果一個物件是不滅的，它的參照計數永遠不會被修改，因此在直譯器運行時它永遠不會被釋放。例如，True 和 None 在 CPython 中是不滅的。

Immortal objects can be identified via sys._is_immortal(), or via PyUnstable_IsImmortal() in the C API.

immutable（不可變物件）

一個具有固定值的物件。不可變物件包括數字、字串和 tuple（元組）。這類物件是不能被改變的。如果必須儲存一個不同的值，則需要建立一個新的物件。它們在需要恆定雜湊值的地方扮演重要的角色，例如 dictionary 中的一個鍵。不可變物件本質上是執行緒安全的，因為它們的狀態在建立後無法被修改，從而消除了對不當同步的並行修改的疑慮。

import path（引入路徑）

一個位置（或路徑項目）的列表，而那些位置就是在 import 模組時，會被 path based finder（基於路徑的尋檢器）搜尋模組的位置。在 import 期間，此位置列表通常是來自 sys.path，但對於子套件 (subpackage) 而言，它也可能是來自父套件的 __path__ 屬性。

importing（引入）

一個過程。一個模組中的 Python 程式碼可以透過此過程，被另一個模組中的 Python 程式碼使用。

importer（引入器）

一個能夠尋找及載入模組的物件；它既是 finder（尋檢器）也是 loader（載入器）物件。

interactive（互動的）

Python 有一個互動式直譯器，這表示你可以在直譯器的提示字元輸入陳述式和運算式，立即執行它們並且看到它們的結果。只要啟動 python，不需要任何引數（可能藉由從你的電腦的主選單選擇它）。這是測試新想法或檢查模組和包的非常強大的方法（請記住help(x)）。更多互動式模式相關資訊請見 互動模式。

interpreted（直譯的）

Python 是一種直譯語言，而不是編譯語言，不過這個區分可能有些模糊，因為有位元組碼 (bytecode) 編譯器的存在。這表示原始檔案可以直接被運行，而不需明確地建立另一個執行檔，然後再執行它。直譯語言通常比編譯語言有更短的開發／除錯週期，不過它們的程式通常也運行得較慢。另請參閱 interactive（互動的）。

interpreter shutdown（直譯器關閉）

當 Python 直譯器被要求關閉時，它會進入一個特殊階段，在此它逐漸釋放所有被配置的資源，例如模組和各種關鍵內部結構。它也會多次呼叫垃圾回收器 (garbage collector)。這能夠觸發使用者自定的解構函式 (destructor) 或弱引用的回呼 (weakref callback)，並執行其中的程式碼。在關閉階段被執行的程式碼會遇到各種例外，因為它所依賴的資源可能不再有作用了（常見的例子是函式庫模組或是警告機制）。

直譯器關閉的主要原因，是 __main__ 模組或正被運行的腳本已經執行完成。

iterable（可疊代物件）

一種能夠一次回傳一個其中成員的物件。可疊代物件的例子包括所有的序列型別（像是 list、str 和 tuple）和某些非序列型別，像是 dict、檔案物件，以及你所定義的任何 class 物件，只要那些 class 有實作 sequence（序列）語意的 __iter__() 或是 __getitem__() method，該物件就是可疊代物件。

可疊代物件可用於 for 迴圈和許多其他需要一個序列的地方 (zip()、map()...)。當一個可疊代物件作為引數被傳遞給內建函式 iter() 時，它會為該物件回傳一個疊代器。此疊代器適用於針對一組值進行一遍 (one pass) 運算。使用疊代器時，通常不一定要呼叫 iter() 或自行處理疊代器物件。for 陳述式會自動地為你處理這些事，它會建立一個暫時性的未命名變數，用於在迴圈期間保有該疊代器。另請參閱 iterator（疊代器）、sequence（序列）和 generator（產生器）。

iterator（疊代器）

一個表示資料流的物件。重複地呼叫疊代器的 __next__() method（或是將它傳遞給內建函式 next()）會依序回傳資料流中的各項目。當不再有資料時，則會引發 StopIteration 例外。此時，該疊代器物件已被用盡，而任何對其 __next__() method 的進一步呼叫，都只會再次引發 StopIteration。疊代器必須有一個 __iter__() method，它會回傳疊代器物件本身，所以每個疊代器也都是可疊代物件，且可以用於大多數適用其他可疊代物件的場合。一個明顯的例外，是嘗試多遍疊代 (multiple iteration passes) 的程式碼。一個容器物件（像是 list）在每次你將它傳遞給 iter() 函式或在 for 迴圈中使用它時，都會產生一個全新的疊代器。使用疊代器嘗試此事（多遍疊代）時，只會回傳在前一遍疊代中被用過的、同一個已被用盡的疊代器物件，使其看起來就像一個空的容器。

在疊代器型別文中可以找到更多資訊。

CPython 並不是始終如一地都會檢查「疊代器有定義 __iter__()」這個規定。另請注意，free-threading（自由執行緒） CPython 不保證疊代器操作的執行緒安全 行為。

key function（鍵函式）

鍵函式或理序函式 (collation function) 是一個可呼叫 (callable) 函式，它會回傳一個用於排序 (sorting) 或定序 (ordering) 的值。例如，locale.strxfrm() 被用來產生一個了解區域特定排序慣例的排序鍵。

Python 中的許多工具，都接受以鍵函式來控制元素被定序或分組的方式。它們包括 min()、max()、sorted()、list.sort()、heapq.merge()、heapq.nsmallest()、heapq.nlargest() 和 itertools.groupby()。

有幾種方法可以建立一個鍵函式。例如，str.casefold() method 可以作為不分大小寫排序的鍵函式。或者，一個鍵函式也可以從 lambda 運算式被建造，例如 lambda r: (r[0], r[2])。另外，operator.attrgetter()、operator.itemgetter() 和 operator.methodcaller() 為三個鍵函式的建構函式 (constructor)。關於如何建立和使用鍵函式的範例，請參閱如何排序。

keyword argument（關鍵字引數）

請參閱 argument（引數）。

lambda

由單一 expression（運算式）所組成的一個匿名行內函式 (inline function)，於該函式被呼叫時求值。建立 lambda 函式的語法是 lambda [parameters]: expression

LBYL

Look before you leap.（三思而後行。）這種編碼風格會在進行呼叫或查找之前，明確地測試先決條件。這種風格與 EAFP 方式形成對比，且它的特色是會有許多 if 陳述式的存在。

在一個多執行緒環境中，LBYL 方式有在「三思」和「後行」之間引入競爭條件 的風險。例如以下程式碼 if key in mapping: return mapping[key]，如果另一個執行緒在測試之後但在查找之前，從 mapping 中移除了 key，則該程式碼就會失效。這個問題可以用鎖或使用 EAFP 編碼方式來解決。另請參閱執行緒安全。

lexical analyzer（詞法分析器）

tokenizer 的正式名稱；請參閱 token。

list（串列）

一個 Python 內建的 sequence （序列）。儘管它的名字是 list，它其實更類似其他語言中的一個陣列 (array) 而較不像一個鏈結串列 (linked list)，因為存取元素的時間複雜度是 O(1)。

list comprehension（串列綜合運算）

一種用來處理一個序列中的全部或部分元素，並將處理結果以一個 list 回傳的簡要方法。result = ['{:#04x}'.format(x) for x in range(256) if x % 2 == 0] 會產生一個字串 list，其中包含 0 到 255 範圍內，所有偶數的十六進位數 (0x..)。if 子句是選擇性的。如果省略它，則 range(256) 中的所有元素都會被處理。

lock（鎖）

A synchronization primitive that allows only one thread at a time to access a shared resource. A thread must acquire a lock before accessing the protected resource and release it afterward. If a thread attempts to acquire a lock that is already held by another thread, it will block until the lock becomes available. Python's threading module provides Lock (a basic lock) and RLock (a reentrant lock). Locks are used to prevent race conditions and ensure thread-safe access to shared data. Alternative design patterns to locks exist such as queues, producer/consumer patterns, and thread-local state. See also deadlock, and reentrant.

loader（載入器）

一個能夠載入模組的物件。它必須定義 exec_module() 和 create_module() 方法以實作 Loader 介面。載入器通常是被 finder（尋檢器）回傳。更多細節請參閱：

尋檢器 (Finder) 與載入器 (Loader)

importlib.abc.Loader

PEP 302 [https://peps.python.org/pep-0302/]

locale encoding（區域編碼）

在 Unix 上，它是 LC_CTYPE 區域設定的編碼。它可以用 locale.setlocale(locale.LC_CTYPE, new_locale) 來設定。

在 Windows 上，它是 ANSI 碼頁（code page，例如 "cp1252"）。

在 Android 和 VxWorks 上，Python 使用 "utf-8" 作為區域編碼。

locale.getencoding() 可以用來取得區域編碼。

也請參考 filesystem encoding and error handler。

magic method（魔術方法）

special method（特殊方法）的一個非正式同義詞。

mapping（對映）

一個容器物件，它支援任意鍵的查找，且能實作 abstract base classes（抽象基底類別）中，collections.abc.Mapping 或 collections.abc.MutableMapping 所指定的 method。範例包括 dict、collections.defaultdict、collections.OrderedDict 和 collections.Counter。

meta path finder（元路徑尋檢器）

一種經由搜尋 sys.meta_path 而回傳的 finder（尋檢器）。元路徑尋檢器與路徑項目尋檢器 (path entry finder) 相關但是不同。

關於元路徑尋檢器實作的 method，請參閱 importlib.abc.MetaPathFinder。

metaclass（元類別）

一種 class 的 class。Class 定義過程會建立一個 class 名稱、一個 class dictionary（字典），以及一個 base class（基底類別）的列表。Metaclass 負責接受這三個引數，並建立該 class。大多數的物件導向程式語言會提供一個預設的實作。Python 的特別之處在於它能夠建立自訂的 metaclass。大部分的使用者從未需要此工具，但是當需要時，metaclass 可以提供強大且優雅的解決方案。它們已被用於記錄屬性存取、增加執行緒安全性、追蹤物件建立、實作單例模式 (singleton)，以及許多其他的任務。

更多資訊可以在Metaclasses章節中找到。

method（方法）

一個在 class 本體內被定義的函式。如果 method 作為其 class 實例的一個屬性被呼叫，則它將會得到該實例物件成為它的第一個 argument（引數）（此引數通常被稱為 self）。請參閱 function（函式）和 nested scope（巢狀作用域）。

method resolution order（方法解析順序）

方法解析順序是在查找某個成員的過程中，base class（基底類別）被搜尋的順序。關於 Python 自 2.3 版直譯器所使用的演算法細節，請參閱 Python 2.3 方法解析順序。

module（模組）

一個擔任 Python 程式碼的組織單位 (organizational unit) 的物件。模組有一個命名空間，它包含任意的 Python 物件。模組是藉由 importing 的過程，被載入至 Python。

另請參閱 package（套件）。

module spec（模組規格）

一個命名空間，它包含用於載入模組的 import 相關資訊。它是 importlib.machinery.ModuleSpec 的一個實例。

另請參閱 模組規格。

MRO

請參閱 method resolution order（方法解析順序）。

mutable（可變物件）

An object with state that is allowed to change during the course of the program. In multi-threaded programs, mutable objects that are shared between threads require careful synchronization to avoid race conditions. See also immutable, thread-safe, and concurrent modification.

named tuple（附名元組）

術語「named tuple（附名元組）」是指從 tuple 繼承的任何型別或 class，且它的可索引 (indexable) 元素也可以用附名屬性來存取。這些型別或 class 也可以具有其他的特性。

有些內建型別是 named tuple，包括由 time.localtime() 和 os.stat() 回傳的值。另一個例子是 sys.float_info：

>>> sys.float_info[1]                   # 以索引存取
1024
>>> sys.float_info.max_exp              # 以欄位名稱存取
1024
>>> isinstance(sys.float_info, tuple)   # 屬於 tuple 型別
True

有些 named tuple 是內建型別（如上例）。或者，一個 named tuple 也可以從一個正規的 class 定義來建立，只要該 class 是繼承自 tuple，且定義了附名欄位 (named field) 即可。這類的 class 可以手工編寫、可以繼承自 typing.NamedTuple 來建立，也可以使用工廠函式 (factory function) collections.namedtuple() 來建立。後者技術也增加了一些額外的 method，這些 method 可能是在手寫或內建的 named tuple 中，無法找到的。

namespace（命名空間）

變數被儲存的地方。命名空間是以 dictionary（字典）被實作。有區域的、全域的及內建的命名空間，而在物件中（在 method 中）也有巢狀的命名空間。命名空間藉由防止命名衝突，來支援模組化。例如，函式 builtins.open 和 os.open() 是透過它們的命名空間來區分彼此。命名空間也藉由明確地區分是哪個模組在實作一個函式，來增進可讀性及可維護性。例如，寫出 random.seed() 或 itertools.islice() 明確地表示，這些函式分別是由 random 和 itertools 模組在實作。

namespace package（命名空間套件）

一個 package（套件），它只能作為子套件 (subpackage) 的一個容器。命名空間套件可能沒有實體的表示法，而且具體來說它們不像是一個 regular package（正規套件），因為它們並沒有 __init__.py 這個檔案。

命名空間套件允許數個可獨立安裝的套件擁有一個共同的父套件。除此之外，建議使用 regular package。

更多資訊，請參閱 PEP 420 [https://peps.python.org/pep-0420/] 和 命名空間套件。

另請參閱 module（模組）。

native code

Code that is compiled to machine instructions and runs directly on the processor, as opposed to code that is interpreted or runs in a virtual machine. In the context of Python, native code typically refers to C, C++, Rust or Fortran code in extension modules that can be called from Python. See also extension module.

nested scope（巢狀作用域）

能夠參照外層定義 (enclosing definition) 中的變數的能力。舉例來說，一個函式如果是在另一個函式中被定義，則它便能夠參照外層函式中的變數。請注意，在預設情況下，巢狀作用域僅適用於參照，而無法用於賦值。區域變數能在最內層作用域中讀取及寫入。同樣地，全域變數是在全域命名空間中讀取及寫入。nonlocal 容許對外層作用域進行寫入。

new-style class（新式類別）

一個舊名，它是指現在所有的 class 物件所使用的 class 風格。在早期的 Python 版本中，只有新式 class 才能使用 Python 較新的、多樣的功能，像是 __slots__、描述器 (descriptor)、屬性 (property)、__getattribute__()、class method（類別方法）和 static method（靜態方法）。

non-deterministic

Behavior where the outcome of a program can vary between executions with the same inputs. In multi-threaded programs, non-deterministic behavior often results from race conditions where the relative timing or interleaving of threads affects the result. Proper synchronization using locks and other synchronization primitives helps ensure deterministic behavior.

object（物件）

具有狀態（屬性或值）及被定義的行為（method）的任何資料。它也是任何 new-style class（新式類別）的最終 base class（基底類別）。

optimized scope（最佳化作用域）

A scope where target local variable names are reliably known to the compiler when the code is compiled, allowing optimization of read and write access to these names. The local namespaces for functions, generators, coroutines, comprehensions, and generator expressions are optimized in this fashion. Note: most interpreter optimizations are applied to all scopes, only those relying on a known set of local and nonlocal variable names are restricted to optimized scopes.

optional module（可選模組）

An extension module that is part of the standard library, but may be absent in some builds of CPython, usually due to missing third-party libraries or because the module is not available for a given platform.

See 可選模組的需求 for a list of optional modules that require third-party libraries.

package（套件）

一個 Python 的 module（模組），它可以包含子模組 (submodule) 或是遞迴的子套件 (subpackage)。技術上而言，套件就是具有 __path__ 屬性的一個 Python 模組。

另請參閱 regular package（正規套件）和 namespace package（命名空間套件）。

parallelism

Executing multiple operations at the same time (e.g. on multiple CPU cores). In Python builds with the global interpreter lock (GIL), only one thread runs Python bytecode at a time, so taking advantage of multiple CPU cores typically involves multiple processes (e.g. multiprocessing) or native extensions that release the GIL. In free-threaded Python, multiple Python threads can run Python code simultaneously on different cores.

parameter（參數）

在 function（函式）或 method 定義中的一個命名實體 (named entity)，它指明該函式能夠接受的一個 argument（引數），或在某些情況下指示多個引數。共有有五種不同的參數類型：

positional-or-keyword（位置或關鍵字）：指明一個可以按照位置或是作為關鍵字引數被傳遞的引數。這是參數的預設類型，例如以下的 foo 和 bar：

def func(foo, bar=None): ...

positional-only（僅限位置）：指明一個只能按照位置被提供的引數。在函式定義的參數列表中包含一個 / 字元，就可以在該字元前面定義僅限位置參數，例如以下的 posonly1 和 posonly2：

def func(posonly1, posonly2, /, positional_or_keyword): ...

keyword-only（僅限關鍵字）：指明一個只能以關鍵字被提供的引數。在函式定義的參數列表中，包含一個任意數量位置參數 (var-positional parameter) 或是單純的 * 字元，就可以在其後方定義僅限關鍵字參數，例如以下的 kw_only1 和 kw_only2：

def func(arg, *, kw_only1, kw_only2): ...

var-positional（任意數量位置）：指明一串能以任意序列被提供的位置引數（在已被其他參數接受的任何位置引數之外）。這類參數是透過在其參數名稱字首加上 * 來定義的，例如以下的 args：

def func(*args, **kwargs): ...

var-keyword（任意數量關鍵字）：指明可被提供的任意數量關鍵字引數（在已被其他參數接受的任何關鍵字引數之外）。這類參數是透過在其參數名稱字首加上 ** 來定義的，例如上面範例中的 kwargs。

參數可以指明引數是選擇性的或必需的，也可以為一些選擇性的引數指定預設值。

另請參閱術語表的 argument（引數）條目、常見問題中的引數和參數之間的差異、inspect.Parameter class、函式定義章節，以及 PEP 362 [https://peps.python.org/pep-0362/]。

path entry（路徑項目）

在 import path（引入路徑）中的一個位置，而 path based finder （基於路徑的尋檢器）會參考該位置來尋找要 import 的模組。

path entry finder（路徑項目尋檢器）

被 sys.path_hooks 中的一個可呼叫物件 (callable)（意即一個 path entry hook）所回傳的一種 finder，它知道如何以一個 path entry定位模組。

關於路徑項目尋檢器實作的 method，請參閱 importlib.abc.PathEntryFinder。

path entry hook（路徑項目鉤）

在 sys.path_hooks 列表中的一個可呼叫物件 (callable)，若它知道如何在一個特定的 path entry 中尋找模組，則會回傳一個 path entry finder（路徑項目尋檢器）。

path based finder（基於路徑的尋檢器）

預設的元路徑尋檢器 (meta path finder) 之一，它會在一個 import path 中搜尋模組。

path-like object（類路徑物件）

一個表示檔案系統路徑的物件。類路徑物件可以是一個表示路徑的 str 或 bytes 物件，或是一個實作 os.PathLike 協定的物件。透過呼叫 os.fspath() 函式，一個支援 os.PathLike 協定的物件可以被轉換為 str 或 bytes 檔案系統路徑；而 os.fsdecode() 及 os.fsencode() 則分別可用於確保 str 及 bytes 的結果。由 PEP 519 [https://peps.python.org/pep-0519/] 引入。

PEP

Python Enhancement Proposal（Python 增強提案）。PEP 是一份設計說明文件，它能為 Python 社群提供資訊，或是描述 Python 的一個新功能或該功能的程序和環境。PEP 應該要提供簡潔的技術規範以及被提案功能的運作原理。

PEP 的存在目的，是要成為重大新功能的提案、社群中關於某個問題的意見收集，以及已納入 Python 的設計決策的記錄，這些過程的主要機制。PEP 的作者要負責在社群內建立共識並記錄反對意見。

請參閱 PEP 1 [https://peps.python.org/pep-0001/]。

portion（部分）

在單一目錄中的一組檔案（也可能儲存在一個 zip 檔中），這些檔案能對一個命名空間套件 (namespace package) 有所貢獻，如同 PEP 420 [https://peps.python.org/pep-0420/] 中的定義。

positional argument（位置引數）

請參閱 argument（引數）。

provisional API（暫行 API）

暫行 API 是指，從標準函式庫的向後相容性 (backwards compatibility) 保證中，故意被排除的 API。雖然此類介面，只要它們被標示為暫行的，理論上並不會有重大的變更，但如果核心開發人員認為有必要，也可能會出現向後不相容的變更（甚至包括移除該介面）。這種變更並不會無端地產生——只有 API 被納入之前未察覺的嚴重基本缺陷被揭露時，它們才會發生。

即使對於暫行 API，向後不相容的變更也會被視為「最後的解決方案」——對於任何被發現的問題，仍然會盡可能找出一個向後相容的解決方案。

這個過程使得標準函式庫能隨著時間不斷進化，而避免耗費過長的時間去鎖定有問題的設計錯誤。請參閱 PEP 411 [https://peps.python.org/pep-0411/] 了解更多細節。

provisional package（暫行套件）

請參閱 provisional API（暫行 API）。

Python 3000

Python 3.x 系列版本的暱稱（很久以前創造的，當時第 3 版的發布是在遙遠的未來。）也可以縮寫為「Py3k」。

Pythonic（Python 風格的）

一個想法或一段程式碼，它應用了 Python 語言最常見的慣用語，而不是使用其他語言常見的概念來實作程式碼。例如，Python 中常見的一種習慣用法，是使用一個 for 陳述式，對一個可疊代物件的所有元素進行迴圈。許多其他語言並沒有這種類型的架構，所以不熟悉 Python 的人有時會使用一個數值計數器來代替：

for i in range(len(food)):
    print(food[i])

相較之下，以下方法更簡潔、更具有 Python 風格：

for piece in food:
    print(piece)

qualified name（限定名稱）

一個「點分隔名稱」，它顯示從一個模組的全域作用域到該模組中定義的 class、函式或 method 的「路徑」，如 PEP 3155 [https://peps.python.org/pep-3155/] 中的定義。對於頂層的函式和 class 而言，限定名稱與其物件名稱相同：

>>> class C:
...     class D:
...         def meth(self):
...             pass
...
>>> C.__qualname__
'C'
>>> C.D.__qualname__
'C.D'
>>> C.D.meth.__qualname__
'C.D.meth'

當用於引用模組時，完全限定名稱 (fully qualified name) 是表示該模組的完整點分隔路徑，包括任何的父套件，例如 email.mime.text：

>>> import email.mime.text
>>> email.mime.text.__name__
'email.mime.text'

race condition

A condition of a program where the its behavior depends on the relative timing or ordering of events, particularly in multi-threaded programs. Race conditions can lead to non-deterministic behavior and bugs that are difficult to reproduce. A data race is a specific type of race condition involving unsynchronized access to shared memory. The LBYL coding style is particularly susceptible to race conditions in multi-threaded code. Using locks and other synchronization primitives helps prevent race conditions.

reference count（參照計數）

對於一個物件的參照次數。當一個物件的參照計數下降到零時，它會被解除配置 (deallocated)。有些物件是「不滅的 (immortal)」並擁有不會被改變的參照計數，也因此永遠不會被解除配置。參照計數通常在 Python 程式碼中看不到，但它卻是 CPython 實作的一個關鍵元素。程式設計師可以呼叫 getrefcount() 函式來回傳一個特定物件的參照計數。

在 CPython 中，參照計數不被視為穩定或明確定義的值；對物件的參照數量，以及該數量如何受到 Python 程式碼的影響，在不同版本之間可能會有所不同。

regular package（正規套件）

一個傳統的 package（套件），例如一個包含 __init__.py 檔案的目錄。

另請參閱 namespace package（命名空間套件）。

reentrant

A property of a function or lock that allows it to be called or acquired multiple times by the same thread without causing errors or a deadlock.

For functions, reentrancy means the function can be safely called again before a previous invocation has completed, which is important when functions may be called recursively or from signal handlers. Thread-unsafe functions may be non-deterministic if they're called reentrantly in a multithreaded program.

For locks, Python's threading.RLock (reentrant lock) is reentrant, meaning a thread that already holds the lock can acquire it again without blocking. In contrast, threading.Lock is not reentrant - attempting to acquire it twice from the same thread will cause a deadlock.

另請參閱 lock 和 deadlock。

REPL

「read-eval-print 迴圈 (read–eval–print loop)」的縮寫，是互動式直譯器 shell 的另一個名稱。

__slots__

在 class 內部的一個宣告，它藉由預先宣告實例屬性的空間，以及消除實例 dictionary（字典），來節省記憶體。雖然該技術很普遍，但它有點難以正確地使用，最好保留給那種在一個記憶體關鍵 (memory-critical) 的應用程式中存在大量實例的罕見情況。

sequence（序列）

一個 iterable（可疊代物件），它透過 __getitem__() special method（特殊方法），使用整數索引來支援高效率的元素存取，並定義了一個 __len__() method 來回傳該序列的長度。一些內建序列型別包括 list、str、tuple 和 bytes。請注意，雖然 dict 也支援 __getitem__() 和 __len__()，但它被視為對映 (mapping) 而不是序列，因為其查找方式是使用任意的 hashable 鍵，而不是整數。

抽象基底類別 (abstract base class) collections.abc.Sequence 定義了一個更加豐富的介面，並不僅止於 __getitem__() 和 __len__()，還增加了 count()、index()、__contains__() 和 __reversed__()。實作此擴充介面的型別，可以使用 register() 被明確地註冊。更多關於序列方法的文件，請見常見序列操作。

set comprehension（集合綜合運算）

一種緊密的方法，用來處理一個可疊代物件中的全部或部分元素，並將處理結果以一個 set 回傳。results = {c for c in 'abracadabra' if c not in 'abc'} 會產生一個字串 set：{'r', 'd'}。請參閱Displays for lists, sets and dictionaries。

single dispatch（單一調度）

generic function（泛型函式）調度的一種形式，在此，實作的選擇是基於單一引數的型別。

slice（切片）

一個物件，它通常包含一段 sequence（序列）的某一部分。建立一段切片的方法是使用下標符號 (subscript notation) []，若要給出多個數字，則在數字之間使用冒號，例如 variable_name[1:3:5]。在括號（下標）符號的內部，會使用 slice 物件。

soft deprecated（軟性棄用）

被軟性棄用的 API 代表不應再用於新程式碼中，但在現有程式碼中繼續使用它仍會是安全的。API 仍會以文件記錄並會被測試，但不會被繼續改進。

與正常棄用不同，軟性棄用沒有刪除 API 的規劃，也不會發出警告。

請參閱 PEP 387：軟性棄用 [https://peps.python.org/pep-0387/#soft-deprecation]。

special method（特殊方法）

一種會被 Python 自動呼叫的 method，用於對某種型別執行某種運算，例如加法。這種 method 的名稱會在開頭和結尾有兩個下底線。Special method 在Special method names中有詳細說明。

標準函式庫

包含套件、模組和擴充模組的集合，它們是作為官方 Python 直譯器套件的一部分來發行。該集合的成員可能會因平台、可用的系統函式庫或其他條件而有所不同。相關文件可以在 Python 標準函式庫 (Standard Library) 中找到。

請參閱 sys.stdlib_module_names 以取得所有可能的標準函式庫模組名稱的列表。

statement（陳述式）

陳述式是一個套組（suite，一個程式碼「區塊」）中的一部分。陳述式可以是一個 expression（運算式），或是含有關鍵字（例如 if、while 或 for）的多種結構之一。

static type checker（靜態型別檢查器）

會讀取 Python 程式碼並分析的外部工具，能夠找出錯誤，像是使用了不正確的型別。另請參閱型別提示 (type hints) 以及 typing 模組。

stdlib（標準函式庫）

standard library 的縮寫。

strong reference（強參照）

在 Python 的 C API 中，強參照是對物件的參照，該物件為持有該參照的程式碼所擁有。建立參照時透過呼叫 Py_INCREF() 來獲得強參照、刪除參照時透過 Py_DECREF() 釋放強參照。

Py_NewRef() 函式可用於建立一個對物件的強參照。通常，在退出強參照的作用域之前，必須在該強參照上呼叫 Py_DECREF() 函式，以避免洩漏一個參照。

另請參閱 borrowed reference（借用參照）。

synchronization primitive

A basic building block for coordinating (synchronizing) the execution of multiple threads to ensure thread-safe access to shared resources. Python's threading module provides several synchronization primitives including Lock, RLock, Semaphore, Condition, Event, and Barrier. Additionally, the queue module provides multi-producer, multi-consumer queues that are especially useful in multithreaded programs. These primitives help prevent race conditions and coordinate thread execution. See also lock.

t-string（t 字串）

t-strings（t 字串）

以 t 或 T 為前綴的字串文本通常被稱為「t 字串」，它是模板化的字串文本的縮寫。

text encoding（文字編碼）

Python 中的字串是一個 Unicode 編碼位置 (code point) 的序列（範圍在 U+0000 -- U+10FFFF 之間）。若要儲存或傳送一個字串，它必須被序列化為一個位元組序列。

將一個字串序列化為位元組序列，稱為「編碼」，而從位元組序列重新建立該字串則稱為「解碼 (decoding)」。

有多種不同的文字序列化編解碼器 (codecs)，它們被統稱為「文字編碼」。

text file（文字檔案）

一個能夠讀取和寫入 str 物件的一個 file object（檔案物件）。通常，文字檔案實際上是存取位元組導向的資料流 (byte-oriented datastream) 並會自動處理 text encoding（文字編碼）。文字檔案的例子有：以文字模式（'r' 或 'w'）開啟的檔案、sys.stdin、sys.stdout 以及 io.StringIO 的實例。

另請參閱 binary file（二進位檔案），它是一個能夠讀取和寫入類位元組串物件 (bytes-like object) 的檔案物件。

thread state

The information used by the CPython runtime to run in an OS thread. For example, this includes the current exception, if any, and the state of the bytecode interpreter.

Each thread state is bound to a single OS thread, but threads may have many thread states available. At most, one of them may be attached at once.

An attached thread state is required to call most of Python's C API, unless a function explicitly documents otherwise. The bytecode interpreter only runs under an attached thread state.

Each thread state belongs to a single interpreter, but each interpreter may have many thread states, including multiple for the same OS thread. Thread states from multiple interpreters may be bound to the same thread, but only one can be attached in that thread at any given moment.

See Thread State and the Global Interpreter Lock for more information.

thread-safe

A module, function, or class that behaves correctly when used by multiple threads concurrently. Thread-safe code uses appropriate synchronization primitives like locks to protect shared mutable state, or is designed to avoid shared mutable state entirely. In the free-threaded build, built-in types like dict, list, and set use internal locking to make many operations thread-safe, although thread safety is not necessarily guaranteed. Code that is not thread-safe may experience race conditions and data races when used in multi-threaded programs.

token

原始碼的小單位，由 詞法分析器 （也稱為 tokenizer）產生。名稱、數字、字串、運算子、換行符號等都以 token 表示。

tokenize 模組公開了 Python 的詞法分析器。token 模組包含各種 token 類型的資訊。

triple-quoted string（三引號內字串）

由三個雙引號 (") 或單引號 (') 的作為邊界的一個字串。雖然它們並沒有提供異於單引號字串的任何額外功能，但基於許多原因，它們仍是很有用的。它們讓你可以在字串中包含未跳脫 (unescaped) 的單引號和雙引號，而且它們不需使用連續字元 (continuation character) 就可以跨越多行，這使得它們在編寫說明字串時特別有用。

type（型別）

一個 Python 物件的型別決定了它是什麼類型的物件；每個物件都有一個型別。一個物件的型別可以用它的 __class__ 屬性來存取，或以 type(obj) 來檢索。

type alias（型別別名）

一個型別的同義詞，透過將型別指定給一個識別符 (identifier) 來建立。

型別別名對於簡化型別提示 (type hint) 很有用。例如：

def remove_gray_shades(
        colors: list[tuple[int, int, int]]) -> list[tuple[int, int, int]]:
    pass

可以寫成這樣，更具有可讀性：

Color = tuple[int, int, int]

def remove_gray_shades(colors: list[Color]) -> list[Color]:
    pass

請參閱 typing 和 PEP 484 [https://peps.python.org/pep-0484/]，有此功能的描述。

type hint（型別提示）

一種 annotation（註釋），它指定一個變數、一個 class 屬性或一個函式的參數或回傳值的預期型別。

型別提示是選擇性的，而不是被 Python 強制的，但它們對靜態型別檢查器 (static type checkers)很有用，並能協助 IDE 完成程式碼的補全 (completion) 和重構 (refactoring)。

全域變數、class 屬性和函式（不含區域變數）的型別提示，都可以使用 typing.get_type_hints() 來存取。

請參閱 typing 和 PEP 484 [https://peps.python.org/pep-0484/]，有此功能的描述。

universal newlines（通用換行字元）

一種解譯文字流 (text stream) 的方式，會將以下所有的情況識別為一行的結束：Unix 行尾慣例 '\n'、Windows 慣例 '\r\n' 和舊的 Macintosh 慣例 '\r'。請參閱 PEP 278 [https://peps.python.org/pep-0278/] 和 PEP 3116 [https://peps.python.org/pep-3116/]，以及用於 bytes.splitlines() 的附加用途。

variable annotation（變數註釋）

一個變數或 class 屬性的 annotation（註釋）。

註釋變數或 class 屬性時，賦值是選擇性的：

class C:
    field: 'annotation'

變數註釋通常用於型別提示 (type hint)：例如，這個變數預期會取得 int（整數）值：

count: int = 0

變數註釋的語法在註釋賦值陳述式章節有詳細的解釋。

請參閱 function annotation（函式註釋）、PEP 484 [https://peps.python.org/pep-0484/] 和 PEP 526 [https://peps.python.org/pep-0526/]，皆有此功能的描述。關於註釋的最佳實踐方法，另請參閱 註釋 (annotation) 最佳實踐。

virtual environment（虛擬環境）

一個協作隔離 (cooperatively isolated) 的執行環境，能讓 Python 的使用者和應用程式得以安裝和升級 Python 發佈套件，而不會對同一個系統上運行的其他 Python 應用程式的行為產生干擾。

另請參閱 venv。

virtual machine（虛擬機器）

一部完全由軟體所定義的電腦 (computer)。Python 的虛擬機器會執行由 bytecode（位元組碼）編譯器所發出的位元組碼。

walrus operator（海象運算子）

A light-hearted way to refer to the assignment expression operator := because it looks a bit like a walrus if you turn your head.

Zen of Python（Python 之禪）

Python 設計原則與哲學的列表，其內容有助於理解和使用此語言。此列表可以透過在互動式提式字元後輸入「import this」來找到它。

關於這份說明文件

Python 說明文件是透過使用 Sphinx [https://www.sphinx-doc.org/]（一個原為 Python 而生的文件產生器、目前是以獨立專案形式來維護）將使用 reStructuredText [https://docutils.sourceforge.io/rst.html] 撰寫的原始檔轉換而成。

如同 Python 自身，透過自願者的努力下產出文件與封裝後自動化執行工具。若想要回報臭蟲，請見 處理錯誤 (Bug) 頁面，內含相關資訊。我們永遠歡迎新的自願者加入！

致謝：

Fred L. Drake, Jr.，原始 Python 文件工具集的創造者以及一大部份內容的作者；

創造 reStructuredText 和 Docutils 工具組的 Docutils [https://docutils.sourceforge.io/] 專案；

Fredrik Lundh 先生，Sphinx 從他的 Alternative Python Reference 計劃中獲得許多的好主意。

Python 文件的貢獻者們

許多人都曾為 Python 這門語言、Python 標準函式庫和 Python 說明文件貢獻過。Python 所發佈的原始碼中含有部份貢獻者的清單，請見 Misc/ACKS [https://github.com/python/cpython/tree/3.14/Misc/ACKS] 。

正因為 Python 社群的撰寫與貢獻才有這份這麼棒的說明文件 -- 感謝所有貢獻過的人們！

處理錯誤 (Bug)

Python 已經是一個以穩定著稱的成熟程式語言。為了維持「穩定」的信譽，開發者們想知道任何你在 Python 中發現的缺失。

有時候自己直接修復錯誤並且送出一個修正給 Python 會比較快，因為這樣會加速流程而且不會困擾到太多人。學習如何貢獻給 Python。

說明文件的錯誤

如果你在這份說明文件中發現了錯誤並想要提出改進方案，請將錯誤報告提交到錯誤追蹤系統 (issue tracker)。如果你有相應的修正建議，請一併提交。（譯者註：如果是繁體中文說明文件翻譯相關的錯誤，請提交到 https://github.com/python/python-docs-zh-tw/issues。）

如果錯誤或建議的改進涉及此文件的翻譯，請將報告提交到翻譯存儲庫 [https://github.com/python/python-docs-zh-tw]。

你也可以在我們的說明文件 Discourse 討論區 [https://discuss.python.org/c/documentation/26]中新增一個討論事項。

如果你發現文件主題 (HTML / CSS / JavaScript) 中存在錯誤，請在 python-doc-theme 問題追蹤系統 [https://github.com/python/python-docs-theme]上提交錯誤報告。

也參考

說明文件錯誤 [https://github.com/python/cpython/issues?q=is%3Aissue+is%3Aopen+label%3Adocs]

一系列已被提交至 Python 問題追蹤系統的有關說明文件的錯誤。

問題追蹤系統 [https://devguide.python.org/tracker/]

在追蹤系統上回報改進建議的過程簡介。

貢獻說明文件 [https://devguide.python.org/docquality/#helping-with-documentation]

給有意成為 Python 說明文件貢獻者的綜合指南。

說明文件翻譯 [https://devguide.python.org/documentation/translating/]

一份 GitHub 網頁的清單，裡面有各個說明文件翻譯團隊的連結，以及他們的主要聯絡人。

使用 Python 問題追蹤系統

對於 Python 本身的問題報告，應該透過 GitHub 問題追蹤系統 (https://github.com/python/cpython/issues) 提交。這個 GitHub 問題追蹤系統提供了一個網頁表單，可以輸入並提交相關資訊給開發者。

填寫報告的第一步，是確認該問題是否已經被回報過了。這樣做的好處，除了可以節省開發者的時間，也能讓你了解目前關於該問題的處理進度；有可能已經在下一個發行版本中修正了這個問題，也有可能需要更詳細的資訊（在這種情況下，如果可以，非常歡迎你提供資訊！）。要確認是否重複回報，請使用頁面頂端的搜尋框來搜尋追蹤系統。

如果你想回報的問題還沒有在問題列表出現過，請登入 GitHub。如果你還沒有 GitHub 帳戶，請點選「Sign up」連結來建立一個新的帳戶。你無法以匿名方式提交錯誤報告。

如果已經登入，那你就可以提交問題了。請點選列表頂端區域的「New issue」按鈕，來回報一個新的問題。

提交的表單中有兩個欄位，「Title」及「Comment」。

在「Title」欄位，輸入對該問題非常簡短的描述；最好少於十個單字。

在「Comment」欄位，請詳細描述該問題，包括你預期發生的情況和實際發生的情況。請確定說明中包含了涉及到的任何擴充模組，以及你當時所使用的硬體和軟體平台（視情況而定，可以附上版本資訊）。

每一份問題報告都會被一位開發人員查核，並由他決定要做出什麼變更來修正這個問題。每當該問題有修正動作時，你會收到更新回報。

也參考

如何有效地回報錯誤 [https://www.chiark.greenend.org.uk/~sgtatham/bugs.html]

這篇文章詳細說明如何建立一份有用的錯誤報告。它描述了什麼樣的資訊是有用的，以及這些資訊為什麼有用。

錯誤撰寫指南 [https://bugzilla.mozilla.org/page.cgi?id=bug-writing.html]

撰寫一份優良錯誤報告的相關資訊。部分的文章內容是針對 Mozilla 專案，但它也描述了通用的好習慣。

開始讓自己貢獻 Python

除了只是回報你所發現的錯誤之外，同樣也歡迎你提交修正它們的修補程式 (patch)。你可以在 Python 開發者指南 [https://mail.python.org/mailman3/lists/core-mentorship.python.org/]中找到如何開始修補 Python 的更多資訊。如果你有任何問題，核心導師郵寄清單 [https://devguide.python.org/]是一個友善的地方，你可以在那裡得到，關於 Python 修正錯誤的過程中，所有問題的答案。

版權宣告

Python 和這份說明文件的版權：

Copyright © 2001 Python 軟體基金會。保留所有權利。

Copyright © 2000 BeOpen.com 保留所有權利。

Copyright © 1995-2000 Corporation for National Research Initiatives 保留所有權利。

Copyright © 1991-1995 Stichting Mathematisch Centrum 保留所有權利。

完整的授權條款資訊請參見沿革與授權。

沿革與授權

軟體沿革

Python 是由荷蘭數學和計算機科學研究學會（CWI，見 https://www.cwi.nl）的 Guido van Rossum 於 1990 年代早期所創造，目的是作為一種稱為 ABC 語言的後繼者。儘管 Python 包含了許多來自其他人的貢獻，Guido 仍是其主要作者。

1995 年，Guido 在維吉尼亞州雷斯頓的國家創新研究公司（CNRI，見 https://www.cnri.reston.va.us）繼續他在 Python 的工作，並在那裡發佈了該軟體的多個版本。

2000 年五月，Guido 和 Python 核心開發團隊轉移到 BeOpen.com 並成立了 BeOpen PythonLabs 團隊。同年十月，PythonLabs 團隊轉移到 Digital Creations，後來成為 Zope Corporation。2001 年，Python 軟體基金會（PSF，見 https://www.python.org/psf/）成立，這是一個專為擁有 Python 相關的智慧財產權而創立的非營利組織。Zope Corporation 過去是 PSF 的一個贊助會員。

所有的 Python 版本都是開源的（有關開源的定義，參閱 https://opensource.org）。歷史上，大多數但非全部的 Python 版本，也是 GPL 相容的；以下表格總結各個版本的差異。

發佈版本

源自

年份

擁有者

GPL 相容性？ (1)

0.9.0 至 1.2

不適用

1991-1995

CWI

是

1.3 至 1.5.2

1.2

1995-1999

CNRI

是

1.6

1.5.2

2000

CNRI

否

2.0

1.6

2000

BeOpen.com

否

1.6.1

1.6

2001

CNRI

是 (2)

2.1

2.0+1.6.1

2001

PSF

否

2.0.1

2.0+1.6.1

2001

PSF

是

2.1.1

2.1+2.0.1

2001

PSF

是

2.1.2

2.1.1

2002

PSF

是

2.1.3

2.1.2

2002

PSF

是

2.2 以上

2.1.1

2001 至今

PSF

是

備註

GPL 相容並不表示我們是在 GPL 下發佈 Python。不像 GPL，所有的 Python 授權都可以讓你發佈修改後的版本，但不一定要使你的變更成為開源。GPL 相容的授權使得 Python 可以結合其他在 GPL 下發佈的軟體一起使用；但其它的授權則不行。

根據 Richard Stallman 的說法，1.6.1 不是 GPL 相容的，因為其授權有一個法律選擇條款。然而根據 CNRI 的說法，Stallman 的律師告訴 CNRI 的律師，1.6.1 與 GPL「不相容」。

感謝許多的外部志工，在 Guido 指導下的付出，使得這些版本的發佈成為可能。

關於存取或以其他方式使用 Python 的合約條款

Python 軟體和說明文件的授權是基於 Python 軟體基金會授權第二版 (Python Software Foundation License Version 2)。

從 Python 3.8.6 開始，說明文件中的範例、程式庫和其他程式碼，是被雙重授權 (dual licensed) 於 PSF 授權第二版以及 Zero-Clause BSD 授權。

有些被納入 Python 中的軟體是基於不同的授權。這些授權將會與其授權之程式碼一起被列出。關於這些授權的不完整清單，請參閱被收錄軟體的授權與致謝。

PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2

1. This LICENSE AGREEMENT is between the Python Software Foundation ("PSF"), and
   the Individual or Organization ("Licensee") accessing and otherwise using this
   software ("Python") in source or binary form and its associated documentation.

2. Subject to the terms and conditions of this License Agreement, PSF hereby
   grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
   analyze, test, perform and/or display publicly, prepare derivative works,
   distribute, and otherwise use Python alone or in any derivative
   version, provided, however, that PSF's License Agreement and PSF's notice of
   copyright, i.e., "Copyright © 2001 Python Software Foundation; All Rights
   Reserved" are retained in Python alone or in any derivative version
   prepared by Licensee.

3. In the event Licensee prepares a derivative work that is based on or
   incorporates Python or any part thereof, and wants to make the
   derivative work available to others as provided herein, then Licensee hereby
   agrees to include in any such work a brief summary of the changes made to Python.

4. PSF is making Python available to Licensee on an "AS IS" basis.
   PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF
   EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
   WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE
   USE OF PYTHON WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
   FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
   MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON, OR ANY DERIVATIVE
   THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.

6. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

7. Nothing in this License Agreement shall be deemed to create any relationship
   of agency, partnership, or joint venture between PSF and Licensee.  This License
   Agreement does not grant permission to use PSF trademarks or trade name in a
   trademark sense to endorse or promote products or services of Licensee, or any
   third party.

8. By copying, installing or otherwise using Python, Licensee agrees
   to be bound by the terms and conditions of this License Agreement.

BEOPEN.COM LICENSE AGREEMENT FOR PYTHON 2.0

BEOPEN PYTHON OPEN SOURCE LICENSE AGREEMENT VERSION 1

1. This LICENSE AGREEMENT is between BeOpen.com ("BeOpen"), having an office at
   160 Saratoga Avenue, Santa Clara, CA 95051, and the Individual or Organization
   ("Licensee") accessing and otherwise using this software in source or binary
   form and its associated documentation ("the Software").

2. Subject to the terms and conditions of this BeOpen Python License Agreement,
   BeOpen hereby grants Licensee a non-exclusive, royalty-free, world-wide license
   to reproduce, analyze, test, perform and/or display publicly, prepare derivative
   works, distribute, and otherwise use the Software alone or in any derivative
   version, provided, however, that the BeOpen Python License is retained in the
   Software, alone or in any derivative version prepared by Licensee.

3. BeOpen is making the Software available to Licensee on an "AS IS" basis.
   BEOPEN MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF
   EXAMPLE, BUT NOT LIMITATION, BEOPEN MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
   WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE
   USE OF THE SOFTWARE WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

4. BEOPEN SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF THE SOFTWARE FOR
   ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF USING,
   MODIFYING OR DISTRIBUTING THE SOFTWARE, OR ANY DERIVATIVE THEREOF, EVEN IF
   ADVISED OF THE POSSIBILITY THEREOF.

5. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

6. This License Agreement shall be governed by and interpreted in all respects
   by the law of the State of California, excluding conflict of law provisions.
   Nothing in this License Agreement shall be deemed to create any relationship of
   agency, partnership, or joint venture between BeOpen and Licensee.  This License
   Agreement does not grant permission to use BeOpen trademarks or trade names in a
   trademark sense to endorse or promote products or services of Licensee, or any
   third party.  As an exception, the "BeOpen Python" logos available at
   http://www.pythonlabs.com/logos.html may be used according to the permissions
   granted on that web page.

7. By copying, installing or otherwise using the software, Licensee agrees to be
   bound by the terms and conditions of this License Agreement.

CNRI LICENSE AGREEMENT FOR PYTHON 1.6.1

1. This LICENSE AGREEMENT is between the Corporation for National Research
   Initiatives, having an office at 1895 Preston White Drive, Reston, VA 20191
   ("CNRI"), and the Individual or Organization ("Licensee") accessing and
   otherwise using Python 1.6.1 software in source or binary form and its
   associated documentation.

2. Subject to the terms and conditions of this License Agreement, CNRI hereby
   grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
   analyze, test, perform and/or display publicly, prepare derivative works,
   distribute, and otherwise use Python 1.6.1 alone or in any derivative version,
   provided, however, that CNRI's License Agreement and CNRI's notice of copyright,
   i.e., "Copyright © 1995-2001 Corporation for National Research Initiatives; All
   Rights Reserved" are retained in Python 1.6.1 alone or in any derivative version
   prepared by Licensee.  Alternately, in lieu of CNRI's License Agreement,
   Licensee may substitute the following text (omitting the quotes): "Python 1.6.1
   is made available subject to the terms and conditions in CNRI's License
   Agreement.  This Agreement together with Python 1.6.1 may be located on the
   internet using the following unique, persistent identifier (known as a handle):
   1895.22/1013.  This Agreement may also be obtained from a proxy server on the
   internet using the following URL: http://hdl.handle.net/1895.22/1013".

3. In the event Licensee prepares a derivative work that is based on or
   incorporates Python 1.6.1 or any part thereof, and wants to make the derivative
   work available to others as provided herein, then Licensee hereby agrees to
   include in any such work a brief summary of the changes made to Python 1.6.1.

4. CNRI is making Python 1.6.1 available to Licensee on an "AS IS" basis.  CNRI
   MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF EXAMPLE,
   BUT NOT LIMITATION, CNRI MAKES NO AND DISCLAIMS ANY REPRESENTATION OR WARRANTY
   OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF
   PYTHON 1.6.1 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

5. CNRI SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 1.6.1 FOR
   ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
   MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 1.6.1, OR ANY DERIVATIVE
   THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.

6. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

7. This License Agreement shall be governed by the federal intellectual property
   law of the United States, including without limitation the federal copyright
   law, and, to the extent such U.S. federal law does not apply, by the law of the
   Commonwealth of Virginia, excluding Virginia's conflict of law provisions.
   Notwithstanding the foregoing, with regard to derivative works based on Python
   1.6.1 that incorporate non-separable material that was previously distributed
   under the GNU General Public License (GPL), the law of the Commonwealth of
   Virginia shall govern this License Agreement only as to issues arising under or
   with respect to Paragraphs 4, 5, and 7 of this License Agreement.  Nothing in
   this License Agreement shall be deemed to create any relationship of agency,
   partnership, or joint venture between CNRI and Licensee.  This License Agreement
   does not grant permission to use CNRI trademarks or trade name in a trademark
   sense to endorse or promote products or services of Licensee, or any third
   party.

8. By clicking on the "ACCEPT" button where indicated, or by copying, installing
   or otherwise using Python 1.6.1, Licensee agrees to be bound by the terms and
   conditions of this License Agreement.

CWI LICENSE AGREEMENT FOR PYTHON 0.9.0 THROUGH 1.2

Copyright © 1991 - 1995, Stichting Mathematisch Centrum Amsterdam, The
Netherlands.  All rights reserved.

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided that
the above copyright notice appear in all copies and that both that copyright
notice and this permission notice appear in supporting documentation, and that
the name of Stichting Mathematisch Centrum or CWI not be used in advertising or
publicity pertaining to distribution of the software without specific, written
prior permission.

STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE FOR ANY SPECIAL, INDIRECT
OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

ZERO-CLAUSE BSD LICENSE FOR CODE IN THE PYTHON DOCUMENTATION

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

被收錄軟體的授權與致謝

本節是一個不完整但持續增加的授權與致謝清單，對象是在 Python 發佈版本中所收錄的第三方軟體。

Mersenne Twister

random 模組底下的 _random C 擴充程式包含了以 http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html 的下載內容為基礎的程式碼。以下是原始程式碼的完整聲明：

A C-program for MT19937, with initialization improved 2002/1/26.
Coded by Takuji Nishimura and Makoto Matsumoto.

Before using, initialize the state by using init_genrand(seed)
or init_by_array(init_key, key_length).

Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

 1. Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

 2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

 3. The names of its contributors may not be used to endorse or promote
    products derived from this software without specific prior written
    permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Any feedback is very welcome.
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)

Sockets

socket 模組使用 getaddrinfo() 和 getnameinfo() 函式，它們在 WIDE 專案（https://www.wide.ad.jp/）內，於不同的原始檔案中被編碼：

Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. Neither the name of the project nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.

非同步 socket 服務

test.support.asynchat 和 test.support.asyncore 模組包含以下聲明：

Copyright 1996 by Sam Rushing

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of Sam
Rushing not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Cookie 管理

http.cookies 模組包含以下聲明：

Copyright 2000 by Timothy O'Malley <timo@alum.mit.edu>

               All Rights Reserved

Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of
Timothy O'Malley  not be used in advertising or publicity
pertaining to distribution of the software without specific, written
prior permission.

Timothy O'Malley DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS, IN NO EVENT SHALL Timothy O'Malley BE LIABLE FOR
ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

執行追蹤

trace 模組包含以下聲明：

portions copyright 2001, Autonomous Zones Industries, Inc., all rights...
err...  reserved and offered to the public under the terms of the
Python 2.2 license.
Author: Zooko O'Whielacronx
http://zooko.com/
mailto:zooko@zooko.com

Copyright 2000, Mojam Media, Inc., all rights reserved.
Author: Skip Montanaro

Copyright 1999, Bioreason, Inc., all rights reserved.
Author: Andrew Dalke

Copyright 1995-1997, Automatrix, Inc., all rights reserved.
Author: Skip Montanaro

Copyright 1991-1995, Stichting Mathematisch Centrum, all rights reserved.

Permission to use, copy, modify, and distribute this Python software and
its associated documentation for any purpose without fee is hereby
granted, provided that the above copyright notice appears in all copies,
and that both that copyright notice and this permission notice appear in
supporting documentation, and that the name of neither Automatrix,
Bioreason or Mojam Media be used in advertising or publicity pertaining to
distribution of the software without specific, written prior permission.

UUencode 與 UUdecode 函式

uu 編解碼器包含以下聲明：

Copyright 1994 by Lance Ellinghouse
Cathedral City, California Republic, United States of America.
                       All Rights Reserved
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of Lance Ellinghouse
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.
LANCE ELLINGHOUSE DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS, IN NO EVENT SHALL LANCE ELLINGHOUSE CENTRUM BE LIABLE
FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Modified by Jack Jansen, CWI, July 1995:
- Use binascii module to do the actual line-by-line conversion
  between ascii and binary. This results in a 1000-fold speedup. The C
  version is still 5 times faster, though.
- Arguments more compliant with Python standard

XML 遠端程序呼叫

xmlrpc.client 模組包含以下聲明：

    The XML-RPC client interface is

Copyright (c) 1999-2002 by Secret Labs AB
Copyright (c) 1999-2002 by Fredrik Lundh

By obtaining, using, and/or copying this software and/or its
associated documentation, you agree that you have read, understood,
and will comply with the following terms and conditions:

Permission to use, copy, modify, and distribute this software and
its associated documentation for any purpose and without fee is
hereby granted, provided that the above copyright notice appears in
all copies, and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of
Secret Labs AB or the author not be used in advertising or publicity
pertaining to distribution of the software without specific, written
prior permission.

SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.

test_epoll

test.test_epoll 模組包含以下聲明：

Copyright (c) 2001-2006 Twisted Matrix Laboratories.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Select kqueue

select 模組對於 kqueue 介面包含以下聲明：

Copyright (c) 2000 Doug White, 2006 James Knight, 2007 Christian Heimes
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.

SipHash24

Python/pyhash.c 檔案包含 Marek Majkowski' 基於 Dan Bernstein 的 SipHash24 演算法的實作。它包含以下聲明：

<MIT License>
Copyright (c) 2013  Marek Majkowski <marek@popcount.org>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
</MIT License>

Original location:
   https://github.com/majek/csiphash/

Solution inspired by code from:
   Samuel Neves (supercop/crypto_auth/siphash24/little)
   djb (supercop/crypto_auth/siphash24/little2)
   Jean-Philippe Aumasson (https://131002.net/siphash/siphash24.c)

strtod 與 dtoa

Python/dtoa.c 檔案提供了 C 的 dtoa 和 strtod 函式，用於將 C 的雙精度浮點數和字串互相轉換。該檔案是衍生自 David M. Gay 建立的同名檔案，後者現在可以從 https://web.archive.org/web/20220517033456/http://www.netlib.org/fp/dtoa.c 下載。於 2009 年 3 月 16 日所檢索的原始檔案包含以下版權與授權聲明：

/****************************************************************
 *
 * The author of this software is David M. Gay.
 *
 * Copyright (c) 1991, 2000, 2001 by Lucent Technologies.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHOR NOR LUCENT MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 *
 ***************************************************************/

OpenSSL

如果 OpenSSL 函式庫可被作業系統使用，則 hashlib、posix、ssl 模組會使用它來提升效能。此外，因為 Windows 和 macOS 的 Python 安裝程式可能包含 OpenSSL 函式庫的副本，所以我們也在此收錄 OpenSSL 授權的副本。對於 OpenSSL 3.0 版本以及由此衍生的更新版本則適用 Apache 許可證 v2：

                              Apache License
                        Version 2.0, January 2004
                     https://www.apache.org/licenses/

TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

1. Definitions.

   "License" shall mean the terms and conditions for use, reproduction,
   and distribution as defined by Sections 1 through 9 of this document.

   "Licensor" shall mean the copyright owner or entity authorized by
   the copyright owner that is granting the License.

   "Legal Entity" shall mean the union of the acting entity and all
   other entities that control, are controlled by, or are under common
   control with that entity. For the purposes of this definition,
   "control" means (i) the power, direct or indirect, to cause the
   direction or management of such entity, whether by contract or
   otherwise, or (ii) ownership of fifty percent (50%) or more of the
   outstanding shares, or (iii) beneficial ownership of such entity.

   "You" (or "Your") shall mean an individual or Legal Entity
   exercising permissions granted by this License.

   "Source" form shall mean the preferred form for making modifications,
   including but not limited to software source code, documentation
   source, and configuration files.

   "Object" form shall mean any form resulting from mechanical
   transformation or translation of a Source form, including but
   not limited to compiled object code, generated documentation,
   and conversions to other media types.

   "Work" shall mean the work of authorship, whether in Source or
   Object form, made available under the License, as indicated by a
   copyright notice that is included in or attached to the work
   (an example is provided in the Appendix below).

   "Derivative Works" shall mean any work, whether in Source or Object
   form, that is based on (or derived from) the Work and for which the
   editorial revisions, annotations, elaborations, or other modifications
   represent, as a whole, an original work of authorship. For the purposes
   of this License, Derivative Works shall not include works that remain
   separable from, or merely link (or bind by name) to the interfaces of,
   the Work and Derivative Works thereof.

   "Contribution" shall mean any work of authorship, including
   the original version of the Work and any modifications or additions
   to that Work or Derivative Works thereof, that is intentionally
   submitted to Licensor for inclusion in the Work by the copyright owner
   or by an individual or Legal Entity authorized to submit on behalf of
   the copyright owner. For the purposes of this definition, "submitted"
   means any form of electronic, verbal, or written communication sent
   to the Licensor or its representatives, including but not limited to
   communication on electronic mailing lists, source code control systems,
   and issue tracking systems that are managed by, or on behalf of, the
   Licensor for the purpose of discussing and improving the Work, but
   excluding communication that is conspicuously marked or otherwise
   designated in writing by the copyright owner as "Not a Contribution."

   "Contributor" shall mean Licensor and any individual or Legal Entity
   on behalf of whom a Contribution has been received by Licensor and
   subsequently incorporated within the Work.

2. Grant of Copyright License. Subject to the terms and conditions of
   this License, each Contributor hereby grants to You a perpetual,
   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
   copyright license to reproduce, prepare Derivative Works of,
   publicly display, publicly perform, sublicense, and distribute the
   Work and such Derivative Works in Source or Object form.

3. Grant of Patent License. Subject to the terms and conditions of
   this License, each Contributor hereby grants to You a perpetual,
   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
   (except as stated in this section) patent license to make, have made,
   use, offer to sell, sell, import, and otherwise transfer the Work,
   where such license applies only to those patent claims licensable
   by such Contributor that are necessarily infringed by their
   Contribution(s) alone or by combination of their Contribution(s)
   with the Work to which such Contribution(s) was submitted. If You
   institute patent litigation against any entity (including a
   cross-claim or counterclaim in a lawsuit) alleging that the Work
   or a Contribution incorporated within the Work constitutes direct
   or contributory patent infringement, then any patent licenses
   granted to You under this License for that Work shall terminate
   as of the date such litigation is filed.

4. Redistribution. You may reproduce and distribute copies of the
   Work or Derivative Works thereof in any medium, with or without
   modifications, and in Source or Object form, provided that You
   meet the following conditions:

   (a) You must give any other recipients of the Work or
       Derivative Works a copy of this License; and

   (b) You must cause any modified files to carry prominent notices
       stating that You changed the files; and

   (c) You must retain, in the Source form of any Derivative Works
       that You distribute, all copyright, patent, trademark, and
       attribution notices from the Source form of the Work,
       excluding those notices that do not pertain to any part of
       the Derivative Works; and

   (d) If the Work includes a "NOTICE" text file as part of its
       distribution, then any Derivative Works that You distribute must
       include a readable copy of the attribution notices contained
       within such NOTICE file, excluding those notices that do not
       pertain to any part of the Derivative Works, in at least one
       of the following places: within a NOTICE text file distributed
       as part of the Derivative Works; within the Source form or
       documentation, if provided along with the Derivative Works; or,
       within a display generated by the Derivative Works, if and
       wherever such third-party notices normally appear. The contents
       of the NOTICE file are for informational purposes only and
       do not modify the License. You may add Your own attribution
       notices within Derivative Works that You distribute, alongside
       or as an addendum to the NOTICE text from the Work, provided
       that such additional attribution notices cannot be construed
       as modifying the License.

   You may add Your own copyright statement to Your modifications and
   may provide additional or different license terms and conditions
   for use, reproduction, or distribution of Your modifications, or
   for any such Derivative Works as a whole, provided Your use,
   reproduction, and distribution of the Work otherwise complies with
   the conditions stated in this License.

5. Submission of Contributions. Unless You explicitly state otherwise,
   any Contribution intentionally submitted for inclusion in the Work
   by You to the Licensor shall be under the terms and conditions of
   this License, without any additional terms or conditions.
   Notwithstanding the above, nothing herein shall supersede or modify
   the terms of any separate license agreement you may have executed
   with Licensor regarding such Contributions.

6. Trademarks. This License does not grant permission to use the trade
   names, trademarks, service marks, or product names of the Licensor,
   except as required for reasonable and customary use in describing the
   origin of the Work and reproducing the content of the NOTICE file.

7. Disclaimer of Warranty. Unless required by applicable law or
   agreed to in writing, Licensor provides the Work (and each
   Contributor provides its Contributions) on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
   implied, including, without limitation, any warranties or conditions
   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
   PARTICULAR PURPOSE. You are solely responsible for determining the
   appropriateness of using or redistributing the Work and assume any
   risks associated with Your exercise of permissions under this License.

8. Limitation of Liability. In no event and under no legal theory,
   whether in tort (including negligence), contract, or otherwise,
   unless required by applicable law (such as deliberate and grossly
   negligent acts) or agreed to in writing, shall any Contributor be
   liable to You for damages, including any direct, indirect, special,
   incidental, or consequential damages of any character arising as a
   result of this License or out of the use or inability to use the
   Work (including but not limited to damages for loss of goodwill,
   work stoppage, computer failure or malfunction, or any and all
   other commercial damages or losses), even if such Contributor
   has been advised of the possibility of such damages.

9. Accepting Warranty or Additional Liability. While redistributing
   the Work or Derivative Works thereof, You may choose to offer,
   and charge a fee for, acceptance of support, warranty, indemnity,
   or other liability obligations and/or rights consistent with this
   License. However, in accepting such obligations, You may act only
   on Your own behalf and on Your sole responsibility, not on behalf
   of any other Contributor, and only if You agree to indemnify,
   defend, and hold each Contributor harmless for any liability
   incurred by, or claims asserted against, such Contributor by reason
   of your accepting any such warranty or additional liability.

END OF TERMS AND CONDITIONS

expat

除非在建置 pyexpat 擴充時設定為 --with-system-expat，否則該擴充會用一個內含 expat 原始碼的副本來建置：

Copyright (c) 1998, 1999, 2000 Thai Open Source Software Center Ltd
                               and Clark Cooper

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

libffi

除非在建置 ctypes 模組底下 _ctypes 擴充程式時設定為 --with-system-libffi，否則該擴充會用一個內含 libffi 原始碼的副本來建置：

Copyright (c) 1996-2008  Red Hat, Inc and others.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

zlib

如果在系統上找到的 zlib 版本太舊以致於無法用於建置 zlib 擴充，則該擴充會用一個內含 zlib 原始碼的副本來建置：

Copyright (C) 1995-2011 Jean-loup Gailly and Mark Adler

This software is provided 'as-is', without any express or implied
warranty.  In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
   claim that you wrote the original software. If you use this software
   in a product, an acknowledgment in the product documentation would be
   appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

3. This notice may not be removed or altered from any source distribution.

Jean-loup Gailly        Mark Adler
jloup@gzip.org          madler@alumni.caltech.edu

cfuhash

tracemalloc 使用的雜湊表 (hash table) 實作，是以 cfuhash 專案為基礎：

Copyright (c) 2005 Don Owens
All rights reserved.

This code is released under the BSD license:

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the following
    disclaimer in the documentation and/or other materials provided
    with the distribution.

  * Neither the name of the author nor the names of its
    contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
OF THE POSSIBILITY OF SUCH DAMAGE.

libmpdec

除非在建置 decimal 模組底下 _decimal C 擴充程式時設定為 --with-system-libmpdec，否則該模組會用一個內含 libmpdec 函式庫的副本來建置：

Copyright (c) 2008-2020 Stefan Krah. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.

W3C C14N 測試套件

test 程式包中的 C14N 2.0 測試套件 (Lib/test/xmltestdata/c14n-20/) 是從 W3C 網站 https://www.w3.org/TR/xml-c14n2-testcases/ 被檢索，且是基於 3-clause BSD 授權被發佈：

Copyright (c) 2013 W3C(R) (MIT, ERCIM, Keio, Beihang),
All Rights Reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

* Redistributions of works must retain the original copyright notice,
  this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the original copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
* Neither the name of the W3C nor the names of its contributors may be
  used to endorse or promote products derived from this work without
  specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

mimalloc

MIT 授權：

Copyright (c) 2018-2021 Microsoft Corporation, Daan Leijen

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

asyncio

asyncio 模組的部分內容是從 uvloop 0.16 [https://github.com/MagicStack/uvloop/tree/v0.16.0] 中收錄過來，其基於 MIT 授權來發佈：

Copyright (c) 2015-2021 MagicStack Inc.  http://magic.io

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Global Unbounded Sequences (GUS)

The file Python/qsbr.c is adapted from FreeBSD's "Global Unbounded Sequences" safe memory reclamation scheme in subr_smr.c [https://github.com/freebsd/freebsd-src/blob/main/sys/kern/subr_smr.c]. The file is distributed under the 2-Clause BSD License:

Copyright (c) 2019,2020 Jeffrey Roberson <jeff@FreeBSD.org>

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice unmodified, this list of conditions, and the following
   disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Zstandard bindings

Zstandard bindings in Modules/_zstd and Lib/compression/zstd are based on code from the pyzstd library [https://github.com/Rogdham/pyzstd/], copyright Ma Lin and contributors. The pyzstd code is distributed under the 3-Clause BSD License:

Copyright (c) 2020-present, Ma Lin and contributors.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Python 模組索引

_ | a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | z

| _ |
| __future__ | Future statement definitions
| __main__ | The environment where top-level code is run. Covers command-line interfaces, import-time behavior, and ``__name__ == '__main__'``.
| _thread | Low-level threading API.
| _tkinter | A binary module that contains the low-level interface to Tcl/Tk.
| a |
| abc | Abstract base classes according to :pep:`3119`.
| aifc | 已棄用: Removed in 3.13.
| annotationlib | Functionality for introspecting annotations
| argparse | Command-line option and argument parsing library.
| array | Space efficient arrays of uniformly typed numeric values.
| ast | Abstract Syntax Tree classes and manipulation.
| asynchat | 已棄用: Removed in 3.12.
| asyncio | Asynchronous I/O.
| asyncore | 已棄用: Removed in 3.12.
| atexit | Register and execute cleanup functions.
| audioop | 已棄用: Removed in 3.13.
| b |
| base64 | RFC 4648: Base16, Base32, Base64 Data Encodings; Base85 and Ascii85
| bdb | Debugger framework.
| binascii | Tools for converting between binary and various ASCII-encoded binary representations.
| bisect | Array bisection algorithms for binary searching.
| builtins | The module that provides the built-in namespace.
| bz2 | Interfaces for bzip2 compression and decompression.
| c |
| calendar | Functions for working with calendars, including some emulation of the Unix cal program.
| cgi | 已棄用: Removed in 3.13.
| cgitb | 已棄用: Removed in 3.13.
| chunk | 已棄用: Removed in 3.13.
| cmath | Mathematical functions for complex numbers.
| cmd | Build line-oriented command interpreters.
| code | Facilities to implement read-eval-print loops.
| codecs | Encode and decode data and streams.
| codeop | Compile (possibly incomplete) Python code.
- | collections | Container datatypes
|     collections.abc | Abstract base classes for containers
| colorsys | Conversion functions between RGB and other color systems.
| compileall | Tools for byte-compiling all Python source files in a directory tree.
- | compression |
|     compression.zstd | Low-level interface to compression and decompression routines in the zstd library.
- | concurrent |
|     concurrent.futures | Execute computations concurrently using threads or processes.
|     concurrent.interpreters | Multiple interpreters in the same process
| configparser | Configuration file parser.
| contextlib | Utilities for with-statement contexts.
| contextvars | Context Variables
| copy | Shallow and deep copy operations.
| copyreg | Register pickle support functions.
| cProfile |
| crypt | 已棄用: Removed in 3.13.
| csv | Write and read tabular data to and from delimited files.
| ctypes | A foreign function library for Python.
- | curses (Unix) | An interface to the curses library, providing portable terminal handling.
|     curses.ascii | Constants and set-membership functions for ASCII characters.
|     curses.panel | A panel stack extension that adds depth to curses windows.
|     curses.textpad | Emacs-like input editing in a curses window.
| d |
| dataclasses | Generate special methods on user-defined classes.
| datetime | Basic date and time types.
- | dbm | Interfaces to various Unix "database" formats.
|     dbm.dumb | Portable implementation of the simple DBM interface.
|     dbm.gnu (Unix) | GNU database manager
|     dbm.ndbm (Unix) | The New Database Manager
|     dbm.sqlite3 (All) | SQLite backend for dbm
| decimal | Implementation of the General Decimal Arithmetic Specification.
| difflib | Helpers for computing differences between objects.
| dis | Disassembler for Python bytecode.
| distutils | 已棄用: Removed in 3.12.
| doctest | Test pieces of code within docstrings.
| e |
- | email | Package supporting the parsing, manipulating, and generating email messages.
|     email.charset | Character Sets
|     email.contentmanager | Storing and Retrieving Content from MIME Parts
|     email.encoders | Encoders for email message payloads.
|     email.errors | The exception classes used by the email package.
|     email.generator | Generate flat text email messages from a message structure.
|     email.header | Representing non-ASCII headers
|     email.headerregistry | Automatic Parsing of headers based on the field name
|     email.iterators | Iterate over a message object tree.
|     email.message | The base class representing email messages.
|     email.mime | Build MIME messages.
|     email.mime.application |
|     email.mime.audio |
|     email.mime.base |
|     email.mime.image |
|     email.mime.message |
|     email.mime.multipart |
|     email.mime.nonmultipart |
|     email.mime.text |
|     email.parser | Parse flat text email messages to produce a message object structure.
|     email.policy | Controlling the parsing and generating of messages
|     email.utils | Miscellaneous email package utilities.
- | encodings | Encodings package
|     encodings.idna | Internationalized Domain Names implementation
|     encodings.mbcs | Windows ANSI codepage
|     encodings.utf_8_sig | UTF-8 codec with BOM signature
| ensurepip | Bootstrapping the "pip" installer into an existing Python installation or virtual environment.
| enum | Implementation of an enumeration class.
| errno | Standard errno system symbols.
| f |
| faulthandler | Dump the Python traceback.
| fcntl (Unix) | The fcntl() and ioctl() system calls.
| filecmp | Compare files efficiently.
| fileinput | Loop over standard input or a list of files.
| fnmatch | Unix shell style filename pattern matching.
| fractions | Rational numbers.
| ftplib | FTP protocol client (requires sockets).
| functools | Higher-order functions and operations on callable objects.
| g |
| gc | Interface to the cycle-detecting garbage collector.
| getopt | Portable parser for command line options; support both short and long option names.
| getpass | Portable reading of passwords and retrieval of the userid.
| gettext | Multilingual internationalization services.
| glob | Unix shell style pathname pattern expansion.
| graphlib | Functionality to operate with graph-like structures
| grp (Unix) | The group database (getgrnam() and friends).
| gzip | Interfaces for gzip compression and decompression using file objects.
| h |
| hashlib | Secure hash and message digest algorithms.
| heapq | Heap queue algorithm (a.k.a. priority queue).
| hmac | Keyed-Hashing for Message Authentication (HMAC) implementation
- | html | Helpers for manipulating HTML.
|     html.entities | Definitions of HTML general entities.
|     html.parser | A simple parser that can handle HTML and XHTML.
- | http | HTTP status codes and messages
|     http.client | HTTP and HTTPS protocol client (requires sockets).
|     http.cookiejar | Classes for automatic handling of HTTP cookies.
|     http.cookies | Support for HTTP state management (cookies).
|     http.server | HTTP server and request handlers.
| i |
| idlelib | Implementation package for the IDLE shell/editor.
| imaplib | IMAP4 protocol client (requires sockets).
| imghdr | 已棄用: Removed in 3.13.
| imp | 已棄用: Removed in 3.12.
- | importlib | The implementation of the import machinery.
|     importlib.abc | Abstract base classes related to import
|     importlib.machinery | Importers and path hooks
|     importlib.metadata | Accessing package metadata
|     importlib.resources | Package resource reading, opening, and access
|     importlib.resources.abc | Abstract base classes for resources
|     importlib.util | Utility code for importers
| inspect | Extract information and source code from live objects.
| io | Core tools for working with streams.
| ipaddress | IPv4/IPv6 manipulation library.
| itertools | Functions creating iterators for efficient looping.
| j |
- | json | Encode and decode the JSON format.
|     json.tool | A command-line interface to validate and pretty-print JSON.
| k |
| keyword | Test whether a string is a keyword in Python.
| l |
| linecache | Provides random access to individual lines from text files.
| locale | Internationalization services.
- | logging | Flexible event logging system for applications.
|     logging.config | Configuration of the logging module.
|     logging.handlers | Handlers for the logging module.
| lzma | A Python wrapper for the liblzma compression library.
| m |
| mailbox | Manipulate mailboxes in various formats
| mailcap | 已棄用: Removed in 3.13.
| marshal | Convert Python objects to streams of bytes and back (with different constraints).
| math | Mathematical functions (sin() etc.).
| mimetypes | Mapping of filename extensions to MIME types.
| mmap | Interface to memory-mapped files for Unix and Windows.
| modulefinder | Find modules used by a script.
| msilib | 已棄用: Removed in 3.13.
| msvcrt (Windows) | Miscellaneous useful routines from the MS VC++ runtime.
- | multiprocessing | Process-based parallelism.
|     multiprocessing.connection | API for dealing with sockets.
|     multiprocessing.dummy | Dumb wrapper around threading.
|     multiprocessing.managers | Share data between process with shared objects.
|     multiprocessing.pool | Create pools of processes.
|     multiprocessing.shared_memory | Provides shared memory for direct access across processes.
|     multiprocessing.sharedctypes | Allocate ctypes objects from shared memory.
| n |
| netrc | Loading of .netrc files.
| nis | 已棄用: Removed in 3.13.
| nntplib | 已棄用: Removed in 3.13.
| numbers | Numeric abstract base classes (Complex, Real, Integral, etc.).
| o |
| operator | Functions corresponding to the standard operators.
| optparse | Command-line option parsing library.
- | os | Miscellaneous operating system interfaces.
|     os.path | Operations on pathnames.
| ossaudiodev | 已棄用: Removed in 3.13.
| p |
- | pathlib | Object-oriented filesystem paths
|     pathlib.types | pathlib types for static type checking
| pdb | The Python debugger for interactive interpreters.
| pickle | Convert Python objects to streams of bytes and back.
| pickletools | Contains extensive comments about the pickle protocols and pickle-machine opcodes, as well as some useful functions.
| pipes | 已棄用: Removed in 3.13.
| pkgutil | Utilities for the import system.
| platform | Retrieves as much platform identifying data as possible.
| plistlib | Generate and parse Apple plist files.
| poplib | POP3 protocol client (requires sockets).
| posix (Unix) | The most common POSIX system calls (normally used via module os).
| pprint | Data pretty printer.
| profile | Python source profiler.
| pstats | Statistics object for use with the profiler.
| pty (Unix) | Pseudo-Terminal Handling for Unix.
| pwd (Unix) | The password database (getpwnam() and friends).
| py_compile | Generate byte-code files from Python source files.
| pyclbr | Supports information extraction for a Python module browser.
| pydoc | Documentation generator and online help system.
| q |
| queue | A synchronized queue class.
| quopri | Encode and decode files using the MIME quoted-printable encoding.
| r |
| random | Generate pseudo-random numbers with various common distributions.
| re | Regular expression operations.
| readline (Unix) | GNU readline support for Python.
| reprlib | Alternate repr() implementation with size limits.
| resource (Unix) | An interface to provide resource usage information on the current process.
| rlcompleter | Python identifier completion, suitable for the GNU readline library.
| runpy | Locate and run Python modules without importing them first.
| s |
| sched | General purpose event scheduler.
| secrets | Generate secure random numbers for managing secrets.
| select | Wait for I/O completion on multiple streams.
| selectors | High-level I/O multiplexing.
| shelve | Python object persistence.
| shlex | Simple lexical analysis for Unix shell-like languages.
| shutil | High-level file operations, including copying.
| signal | Set handlers for asynchronous events.
| site | Module responsible for site-specific configuration.
| sitecustomize |
| smtpd | 已棄用: Removed in 3.12.
| smtplib | SMTP protocol client (requires sockets).
| sndhdr | 已棄用: Removed in 3.13.
| socket | Low-level networking interface.
| socketserver | A framework for network servers.
| spwd | 已棄用: Removed in 3.13.
| sqlite3 | A DB-API 2.0 implementation using SQLite 3.x.
| ssl | TLS/SSL wrapper for socket objects
| stat | Utilities for interpreting the results of os.stat(), os.lstat() and os.fstat().
| statistics | Mathematical statistics functions
- | string | Common string operations.
|     string.templatelib | Support for template string literals.
| stringprep | String preparation, as per RFC 3453
| struct | Interpret bytes as packed binary data.
| subprocess | Subprocess management.
| sunau | 已棄用: Removed in 3.13.
| symtable | Interface to the compiler's internal symbol tables.
- | sys | Access system-specific parameters and functions.
|     sys.monitoring | Access and control event monitoring
| sysconfig | Python's configuration information
| syslog (Unix) | An interface to the Unix syslog library routines.
| t |
| tabnanny | Tool for detecting white space related problems in Python source files in a directory tree.
| tarfile | Read and write tar-format archive files.
| telnetlib | 已棄用: Removed in 3.13.
| tempfile | Generate temporary files and directories.
| termios (Unix) | POSIX style tty control.
- | test | Regression tests package containing the testing suite for Python.
|     test.regrtest | Drives the regression test suite.
|     test.support | Support for Python's regression test suite.
|     test.support.bytecode_helper | Support tools for testing correct bytecode generation.
|     test.support.import_helper | Support for import tests.
|     test.support.os_helper | Support for os tests.
|     test.support.script_helper | Support for Python's script execution tests.
|     test.support.socket_helper | Support for socket tests.
|     test.support.threading_helper | Support for threading tests.
|     test.support.warnings_helper | Support for warnings tests.
| textwrap | Text wrapping and filling
| threading | Thread-based parallelism.
| time | Time access and conversions.
| timeit | Measure the execution time of small code snippets.
- | tkinter | Interface to Tcl/Tk for graphical user interfaces
|     tkinter.colorchooser (Tk) | Color choosing dialog
|     tkinter.commondialog (Tk) | Tkinter base class for dialogs
|     tkinter.dnd (Tk) | Tkinter drag-and-drop interface
|     tkinter.filedialog (Tk) | Dialog classes for file selection
|     tkinter.font (Tk) | Tkinter font-wrapping class
|     tkinter.messagebox (Tk) | Various types of alert dialogs
|     tkinter.scrolledtext (Tk) | Text widget with a vertical scroll bar.
|     tkinter.simpledialog (Tk) | Simple dialog windows
|     tkinter.ttk | Tk themed widget set
| token | Constants representing terminal nodes of the parse tree.
| tokenize | Lexical scanner for Python source code.
| tomllib | Parse TOML files.
| trace | Trace or track Python statement execution.
| traceback | Print or retrieve a stack traceback.
| tracemalloc | Trace memory allocations.
| tty (Unix) | Utility functions that perform common terminal control operations.
| turtle | An educational framework for simple graphics applications
| turtledemo | A viewer for example turtle scripts
| types | Names for built-in types.
| typing | Support for type hints (see :pep:`484`).
| u |
| unicodedata | Access the Unicode Database.
- | unittest | Unit testing framework for Python.
|     unittest.mock | Mock object library.
- | urllib |
|     urllib.error | Exception classes raised by urllib.request.
|     urllib.parse | Parse URLs into or assemble them from components.
|     urllib.request | Extensible library for opening URLs.
|     urllib.response | Response classes used by urllib.
|     urllib.robotparser | Load a robots.txt file and answer questions about fetchability of other URLs.
| usercustomize |
| uu | 已棄用: Removed in 3.13.
| uuid | UUID objects (universally unique identifiers) according to RFC 9562
| v |
| venv | Creation of virtual environments.
| w |
| warnings | Issue warning messages and control their disposition.
| wave | Provide an interface to the WAV sound format.
| weakref | Support for weak references and weak dictionaries.
| webbrowser | Easy-to-use controller for web browsers.
| winreg (Windows) | Routines and objects for manipulating the Windows registry.
| winsound (Windows) | Access to the sound-playing machinery for Windows.
- | wsgiref | WSGI Utilities and Reference Implementation.
|     wsgiref.handlers | WSGI server/gateway base classes.
|     wsgiref.headers | WSGI response header tools.
|     wsgiref.simple_server | A simple WSGI HTTP server.
|     wsgiref.types | WSGI types for static type checking
|     wsgiref.util | WSGI environment utilities.
|     wsgiref.validate | WSGI conformance checker.
| x |
| xdrlib | 已棄用: Removed in 3.13.
- | xml | Package containing XML processing modules
|     xml.dom | Document Object Model API for Python.
|     xml.dom.minidom | Minimal Document Object Model (DOM) implementation.
|     xml.dom.pulldom | Support for building partial DOM trees from SAX events.
|     xml.etree.ElementInclude |
|     xml.etree.ElementTree | Implementation of the ElementTree API.
|     xml.parsers.expat | An interface to the Expat non-validating XML parser.
|     xml.parsers.expat.errors |
|     xml.parsers.expat.model |
|     xml.sax | Package containing SAX2 base classes and convenience functions.
|     xml.sax.handler | Base classes for SAX event handlers.
|     xml.sax.saxutils | Convenience functions and classes for use with SAX.
|     xml.sax.xmlreader | Interface which SAX-compliant XML parsers must implement.
- | xmlrpc | Server and client modules implementing XML-RPC.
|     xmlrpc.client | XML-RPC client access.
|     xmlrpc.server | Basic XML-RPC server implementations.
| z |
| zipapp | Manage executable Python zip archives
| zipfile | Read and write ZIP-format archive files.
| zipimport | Support for importing Python modules from ZIP archives.
| zlib | Low-level interface to compression and decompression routines compatible with gzip.
| zoneinfo | IANA time zone support

Python 3.14 中待移除的項目

PyDictObject 中的 ma_version_tag 欄位，用於擴充模組 (PEP 699 [https://peps.python.org/pep-0699/]；gh-101193 [https://github.com/python/cpython/issues/101193])。

使用可變基底建立不可變型別 (gh-95388 [https://github.com/python/cpython/issues/95388])。

Python 3.15 中待移除的項目

PyImport_ImportModuleNoBlock()：請改用 PyImport_ImportModule()。

PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT()：請改用 PyWeakref_GetRef()。可以使用 pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/]來為 Python 3.12 和更早版本取得 PyWeakref_GetRef()。

Py_UNICODE 型別與 Py_UNICODE_WIDE 巨集：請改用 wchar_t。

PyUnicode_AsDecodedObject()：請改用 PyCodec_Decode()。

PyUnicode_AsDecodedUnicode()：請改用 PyCodec_Decode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 str 的型別，例如 bytes。

PyUnicode_AsEncodedObject()：請改用 PyCodec_Encode()。

PyUnicode_AsEncodedUnicode()：請改用 PyCodec_Encode()；請注意某些編解碼器（例如 "base64"）可能會回傳非 bytes 的型別，例如 str。

Python 初始化函式，自 Python 3.13 起已被棄用：

Py_GetPath()：請改用 PyConfig_Get("module_search_paths") (sys.path)。

Py_GetPrefix()：請改用 PyConfig_Get("base_prefix") (sys.base_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("prefix") (sys.prefix)。

Py_GetExecPrefix()：請改用 PyConfig_Get("base_exec_prefix") (sys.base_exec_prefix)。如果需要處理虛擬環境，請改用 PyConfig_Get("exec_prefix") (sys.exec_prefix)。

Py_GetProgramFullPath()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetProgramName()：請改用 PyConfig_Get("executable") (sys.executable)。

Py_GetPythonHome()：請改用 PyConfig_Get("home") 或 PYTHONHOME 環境變數。

pythoncapi-compat 專案 [https://github.com/python/pythoncapi-compat/] 可以用來為 Python 3.13 和更早版本取得 PyConfig_Get()。

用於配置 Python 初始化的函式，自 Python 3.11 起已被棄用：

PySys_SetArgvEx()：請改用 PyConfig.argv。

PySys_SetArgv()：請改用 PyConfig.argv。

Py_SetProgramName()：請改用 PyConfig.program_name。

Py_SetPythonHome()：請改用 PyConfig.home。

PySys_ResetWarnOptions()：請改為清除 sys.warnoptions 和 warnings.filters。

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API。

全域配置變數：

Py_DebugFlag：請改用 PyConfig.parser_debug 或 PyConfig_Get("parser_debug")。

Py_VerboseFlag：請改用 PyConfig.verbose 或 PyConfig_Get("verbose")。

Py_QuietFlag：請改用 PyConfig.quiet 或 PyConfig_Get("quiet")。

Py_InteractiveFlag：請改用 PyConfig.interactive 或 PyConfig_Get("interactive")。

Py_InspectFlag：請改用 PyConfig.inspect 或 PyConfig_Get("inspect")。

Py_OptimizeFlag：請改用 PyConfig.optimization_level 或 PyConfig_Get("optimization_level")。

Py_NoSiteFlag：請改用 PyConfig.site_import 或 PyConfig_Get("site_import")。

Py_BytesWarningFlag：請改用 PyConfig.bytes_warning 或 PyConfig_Get("bytes_warning")。

Py_FrozenFlag：請改用 PyConfig.pathconfig_warnings 或 PyConfig_Get("pathconfig_warnings")。

Py_IgnoreEnvironmentFlag：請改用 PyConfig.use_environment 或 PyConfig_Get("use_environment")。

Py_DontWriteBytecodeFlag：請改用 PyConfig.write_bytecode 或 PyConfig_Get("write_bytecode")。

Py_NoUserSiteDirectory：請改用 PyConfig.user_site_directory 或 PyConfig_Get("user_site_directory")。

Py_UnbufferedStdioFlag：請改用 PyConfig.buffered_stdio 或 PyConfig_Get("buffered_stdio")。

Py_HashRandomizationFlag：請改用 PyConfig.use_hash_seed 和 PyConfig.hash_seed 或 PyConfig_Get("hash_seed")。

Py_IsolatedFlag：請改用 PyConfig.isolated 或 PyConfig_Get("isolated")。

Py_LegacyWindowsFSEncodingFlag：請改用 PyPreConfig.legacy_windows_fs_encoding 或 PyConfig_Get("legacy_windows_fs_encoding")。

Py_LegacyWindowsStdioFlag：請改用 PyConfig.legacy_windows_stdio 或 PyConfig_Get("legacy_windows_stdio")。

Py_FileSystemDefaultEncoding、Py_HasFileSystemDefaultEncoding：請改用 PyConfig.filesystem_encoding 或 PyConfig_Get("filesystem_encoding")。

Py_FileSystemDefaultEncodeErrors：請改用 PyConfig.filesystem_errors 或 PyConfig_Get("filesystem_errors")。

Py_UTF8Mode：請改用 PyPreConfig.utf8_mode 或 PyConfig_Get("utf8_mode")。（請參閱 Py_PreInitialize()）

應改用帶有 PyConfig 的 Py_InitializeFromConfig() API 來設定這些選項。或者也可以使用 PyConfig_Get() 在執行時取得這些選項。

Python 3.16 中待移除的項目

libmpdecimal 的打包副本 (bundled copy)。

Python 3.18 中待移除的項目

以下私有函式已被棄用，並計劃在 Python 3.18 中移除：

_PyBytes_Join()：請改用 PyBytes_Join()。

_PyDict_GetItemStringWithError()：請改用 PyDict_GetItemStringRef()。

_PyDict_Pop()：請改用 PyDict_Pop()。

_PyLong_Sign()：請改用 PyLong_GetSign()。

_PyLong_FromDigits() 和 _PyLong_New()：請改用 PyLongWriter_Create()。

_PyThreadState_UncheckedGet()：請改用 PyThreadState_GetUnchecked()。

_PyUnicode_AsString()：請改用 PyUnicode_AsUTF8()。

_PyUnicodeWriter_Init()：將 _PyUnicodeWriter_Init(&writer) 替換為 writer = PyUnicodeWriter_Create(0)。

_PyUnicodeWriter_Finish()：將 _PyUnicodeWriter_Finish(&writer) 替換為 PyUnicodeWriter_Finish(writer)。

_PyUnicodeWriter_Dealloc()：將 _PyUnicodeWriter_Dealloc(&writer) 替換為 PyUnicodeWriter_Discard(writer)。

_PyUnicodeWriter_WriteChar()：將 _PyUnicodeWriter_WriteChar(&writer, ch) 替換為 PyUnicodeWriter_WriteChar(writer, ch)。

_PyUnicodeWriter_WriteStr()：將 _PyUnicodeWriter_WriteStr(&writer, str) 替換為 PyUnicodeWriter_WriteStr(writer, str)。

_PyUnicodeWriter_WriteSubstring()：將 _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) 替換為 PyUnicodeWriter_WriteSubstring(writer, str, start, end)。

_PyUnicodeWriter_WriteASCIIString()：將 _PyUnicodeWriter_WriteASCIIString(&writer, str) 替換為 PyUnicodeWriter_WriteASCII(writer, str)。

_PyUnicodeWriter_WriteLatin1String()：將 _PyUnicodeWriter_WriteLatin1String(&writer, str) 替換為 PyUnicodeWriter_WriteUTF8(writer, str)。

_PyUnicodeWriter_Prepare()：（無替代方案）。

_PyUnicodeWriter_PrepareKind()：（無替代方案）。

_Py_HashPointer()：請改用 Py_HashPointer()。

_Py_fopen_obj()：請改用 Py_fopen()。

可以使用 pythoncapi-compat project [https://github.com/python/pythoncapi-compat/] 來取得這些於 Python 3.13 及更早版本的新公開函式。（由 Victor Stinner 在 gh-128863 [https://github.com/python/cpython/issues/128863] 貢獻）

未來版本中的待移除項目

下列 API 已被棄用並將會被移除，不過目前尚未訂定移除日期。

Py_TPFLAGS_HAVE_FINALIZE：自 Python 3.8 起不再需要

PyErr_Fetch()：請改用 PyErr_GetRaisedException()。

PyErr_NormalizeException()：請改用 PyErr_GetRaisedException()。

PyErr_Restore()：請改用 PyErr_SetRaisedException()。

PyModule_GetFilename()：請改用 PyModule_GetFilenameObject()。

PyOS_AfterFork()：請改用 PyOS_AfterFork_Child()。

PySlice_GetIndicesEx()：請改用 PySlice_Unpack() 和 PySlice_AdjustIndices()。

PyUnicode_READY()：自 Python 3.12 起不再需要

PyErr_Display()：請改用 PyErr_DisplayException()。

_PyErr_ChainExceptions()：請改用 _PyErr_ChainExceptions1。

PyBytesObject.ob_shash 成員：請改為呼叫 PyObject_Hash()。

執行緒局部儲存 (Thread Local Storage, TLS) API：

PyThread_create_key()：請改用 PyThread_tss_alloc()。

PyThread_delete_key()：請改用 PyThread_tss_free()。

PyThread_set_key_value()：請改用 PyThread_tss_set()。

PyThread_get_key_value()：請改用 PyThread_tss_get()。

PyThread_delete_key_value()：請改用 PyThread_tss_delete()。

PyThread_ReInitTLS()：自 Python 3.7 起不再需要。

Python 3.13 中待移除的項目

模組（請見 PEP 594 [https://peps.python.org/pep-0594/]）：

aifc

audioop

cgi

cgitb

chunk

crypt

imghdr

mailcap

msilib

nis

nntplib

ossaudiodev

pipes

sndhdr

spwd

sunau

telnetlib

uu

xdrlib

其他模組：

lib2to3 和 2to3 程式 (gh-84540 [https://github.com/python/cpython/issues/84540])

API：

configparser.LegacyInterpolation (gh-90765 [https://github.com/python/cpython/issues/90765])

locale.resetlocale() (gh-90817 [https://github.com/python/cpython/issues/90817])

turtle.RawTurtle.settiltangle() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.findTestCases() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.getTestCaseNames() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.makeSuite() (gh-50096 [https://github.com/python/cpython/issues/50096])

unittest.TestProgram.usageExit() (gh-67048 [https://github.com/python/cpython/issues/67048])

webbrowser.MacOSX (gh-86421 [https://github.com/python/cpython/issues/86421])

classmethod 描述器鏈接 (gh-89519 [https://github.com/python/cpython/issues/89519])

Python 3.14 中待移除的項目

argparse：argparse.BooleanOptionalAction 的 type、choices 和 metavar 參數已被棄用，將在 3.14 中移除。 (由 Nikita Sobolev 於 gh-92248 [https://github.com/python/cpython/issues/92248] 貢獻。)

ast：自 Python 3.8 起，下列功能已在文件中被棄用，現在在存取或使用時會於 runtime 發出 DeprecationWarning，並將在 Python 3.14 中移除：

ast.Num

ast.Str

ast.Bytes

ast.NameConstant

ast.Ellipsis

請改用 ast.Constant。（由 Serhiy Storchaka 於 gh-90953 [https://github.com/python/cpython/issues/90953] 貢獻。）

asyncio：

已棄用並將在 Python 3.14 中移除的 child watcher 類別：asyncio.MultiLoopChildWatcher、asyncio.FastChildWatcher、asyncio.AbstractChildWatcher 和 asyncio.SafeChildWatcher。 (由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。)

asyncio.set_child_watcher()、asyncio.get_child_watcher()、asyncio.AbstractEventLoopPolicy.set_child_watcher() 和 asyncio.AbstractEventLoopPolicy.get_child_watcher() 已被棄用並將在 Python 3.14 中移除。（由 Kumar Aditya 於 gh-94597 [https://github.com/python/cpython/issues/94597] 貢獻。）

預設事件迴圈策略的 get_event_loop() 方法現在會在沒有設定目前事件迴圈且決定建立一個時發出 DeprecationWarning。 (由 Serhiy Storchaka 和 Guido van Rossum 於 gh-100160 [https://github.com/python/cpython/issues/100160] 貢獻。)

email：已棄用 email.utils.localtime() 中的 isdst 參數。（由 Alan Williams 於 gh-72346 [https://github.com/python/cpython/issues/72346] 貢獻。）

importlib.abc 的已棄用類別：

importlib.abc.ResourceReader

importlib.abc.Traversable

importlib.abc.TraversableResources

請改用 importlib.resources.abc 類別：

importlib.resources.abc.Traversable

importlib.resources.abc.TraversableResources

（由 Jason R. Coombs 和 Hugo van Kemenade 貢獻於 gh-93963 [https://github.com/python/cpython/issues/93963]。）

itertools 有不以文件記錄、效率低下、過去常有 bug 且不一致的 copy、deepcopy 和 pickle 操作支援。將在 3.14 中移除以大幅減少程式碼量和維護負擔。 (由 Raymond Hettinger 於 gh-101588 [https://github.com/python/cpython/issues/101588] 貢獻。)

multiprocessing：預設的啟動方法將在 Linux、BSD 和其他非 macOS POSIX 平台上更改為更安全的 方法，目前 'fork' 是預設值 (gh-84559 [https://github.com/python/cpython/issues/84559])。對此增加一個 runtime 警告被認為太過擾人，因為 大多數程式碼不會在意。請使用 get_context() 或 set_start_method() API 來明確指定你的程式碼何時需要 'fork'。請參閱 Contexts and start methods。

pathlib：已棄用 is_relative_to() 和 relative_to()：額外引數的傳遞已被棄用。

pkgutil：pkgutil.find_loader() 和 pkgutil.get_loader() 現在會引發 DeprecationWarning；請改用 importlib.util.find_spec()。 (由 Nikita Sobolev 於 gh-97850 [https://github.com/python/cpython/issues/97850] 貢獻。)

pty：

master_open()：請用 pty.openpty()。

slave_open()：請用 pty.openpty()。

sqlite3：

version 和 version_info。

execute() 和 executemany()，如果使用 named placeholders 且 parameters 是序列而不是 dict。

urllib：urllib.parse.Quoter 已被棄用：它並非預期的公開 API。(由 Gregory P. Smith 於 gh-88168 [https://github.com/python/cpython/issues/88168] 貢獻。)

Python 3.15 中待移除的項目

引入系統 (import system)：

在模組上設定 __cached__ 而沒有設定 __spec__.cached 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __cached__。(gh-97879 [https://github.com/python/cpython/issues/97879])

在模組上設定 __package__ 而沒有設定 __spec__.parent 的做法已被棄用。在 Python 3.15 中，引入系統或標準函式庫將不再設定或考慮 __package__。(gh-97879 [https://github.com/python/cpython/issues/97879])

ctypes：

自 Python 3.13 起，未記錄的 ctypes.SetPointerType() 函式已被棄用。

http.server：

過時且很少使用的 CGIHTTPRequestHandler 自 Python 3.13 起已被棄用。不存在直接的替代。任何東西都比 CGI 更好地將 Web 伺服器與請求處理程序介接起來。

自 Python 3.13 起，python -m http.server 命令列介面的 --cgi 旗標已被棄用。

importlib：

load_module() method：請改用 exec_module()。

locale：

getdefaultlocale() 已在 Python 3.11 中被棄用，原本計劃在 Python 3.13 中移除 (gh-90817 [https://github.com/python/cpython/issues/90817])，但被延後至 Python 3.15。請改用 getlocale()、setlocale() 和 getencoding()。 (由 Hugo van Kemenade 於 gh-111187 [https://github.com/python/cpython/issues/111187] 貢獻。)

pathlib：

PurePath.is_reserved() 已自 Python 3.13 被棄用。請用 os.path.isreserved() 來偵測 Windows 上的保留路徑。

platform：

自 Python 3.13 起，java_ver() 已被棄用。此函式僅對 Jython 支援有用，具有令人困惑的 API，基本上未經測試。

sysconfig：

sysconfig.is_python_build() 的 check_home 引數自 Python 3.12 起已被棄用。

threading：

RLock() 在 Python 3.15 中將不接受任何引數。自 Python 3.14 起，傳遞任何引數的用法已被棄用，因為 Python 版本不允許任何引數，但 C 版本允許任意數量的位置或關鍵字引數，並忽略每個引數。

types：

types.CodeType：自 3.10 起，存取 co_lnotab 已在 PEP 626 [https://peps.python.org/pep-0626/] 中被棄用，並計劃在 3.12 中移除，但只在 3.12 中於適當時發出 DeprecationWarning。可能在 3.15 中移除。（由 Nikita Sobolev 於 gh-101866 [https://github.com/python/cpython/issues/101866] 貢獻。）

typing：

用於建立 NamedTuple 類別的未以文件記錄之關鍵字引數語法 (Point = NamedTuple("Point", x=int, y=int)) 已自 Python 3.13 棄用。請改用基於類別的語法或函式語法 (functional syntax)。

當使用 TypedDict 的函式語法時，未傳遞值給 fields 參數 (TD = TypedDict("TD")) 或傳遞 None (TD = TypedDict("TD", None)) 的做法自 Python 3.13 起已被棄用。請使用 class TD(TypedDict): pass 或 TD = TypedDict("TD", {}) 來建立具有零個欄位的 TypedDict。

自 Python 3.13 起，typing.no_type_check_decorator() 裝飾器函式已被棄用。在 typing 模組中使用了八年之後，它尚未得到任何主要型別檢查器的支援。

wave：

已棄用 Wave_read 和 Wave_write 類別的 getmark()、setmark() 和 getmarkers() 方法自 Python 3.13 被棄用。

zipimport：

load_module() 自 Python 3.10 被棄用。請改用 exec_module()。（由 Jiahao Li 於 gh-125746 [https://github.com/python/cpython/issues/125746] 貢獻。）

Python 3.16 中待移除的項目

引入系統 (import system)：

在模組上設定 __loader__ 而沒有設定 __spec__.loader 的做法將於 Python 3.16 被棄用。在 Python 3.16 中，引入系統或標準函式庫將不再設定或考慮 __loader__。

array：

自 Python 3.3 起，'u' 格式碼 (wchar_t) 在文件中已被棄用，自 Python 3.13 起在 runtime 已被棄用。請使用 'w' 格式碼 (Py_UCS4) 來取代 Unicode 字元。

asyncio：

asyncio.iscoroutinefunction() 已被棄用並將在 Python 3.16 中移除；請改用 inspect.iscoroutinefunction()。（由 Jiahao Li 和 Kumar Aditya 於 gh-122875 [https://github.com/python/cpython/issues/122875] 貢獻。）

asyncio 策略系統已被棄用並將在 Python 3.16 中移除。特別是以下類別和函式已被棄用：

asyncio.AbstractEventLoopPolicy

asyncio.DefaultEventLoopPolicy

asyncio.WindowsSelectorEventLoopPolicy

asyncio.WindowsProactorEventLoopPolicy

asyncio.get_event_loop_policy()

asyncio.set_event_loop_policy()

使用者應該使用 asyncio.run() 或 asyncio.Runner 搭配 loop_factory 來使用所需的事件迴圈實作。

例如在 Windows 上使用 asyncio.SelectorEventLoop：

import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

（由 Kumar Aditya 於 gh-127949 [https://github.com/python/cpython/issues/127949] 貢獻。）

builtins：

自 Python 3.12 起，布林型別的位元反轉 ~True 或 ~False 已被棄用，因為它會產生不預期且不直觀的結果（-2 和 -1）。使用 not x 代替布林值的邏輯否定。在極少數情況下，你需要對底層的整數進行位元反轉，請明確轉換為 ~int(x) (~int(x))。

functools：

自 Python 3.14 起，使用 function 或 sequence 關鍵字引數呼叫 functools.reduce() 的 Python 實作已被棄用。

logging：

對具有 strm 引數的自訂日誌記錄處理函式的支援已被棄用，並計劃在 Python 3.16 中移除。請改用 stream 引數。（由 Mariusz Felisiak 於 gh-115032 [https://github.com/python/cpython/issues/115032] 貢獻。）

mimetypes：

有效的副檔名以 '.' 開頭或對 mimetypes.MimeTypes.add_type() 為空字串。未加點的副檔名已被棄用，並將在 Python 3.16 中引發 ValueError。（由 Hugo van Kemenade 於 gh-75223 [https://github.com/python/cpython/issues/75223] 貢獻。）

shutil：

自 Python 3.14 起，ExecError 例外已被棄用。自 Python 3.4 以來，它尚未被 shutil 中的任何函式使用，現在是 RuntimeError 的別名。

symtable：

自 Python 3.14 起，Class.get_methods 方法已被棄用。

sys：

自 Python 3.13 起，_enablelegacywindowsfsencoding() 函式已被棄用。請改用 PYTHONLEGACYWINDOWSFSENCODING 環境變數。

sysconfig：

自 Python 3.14 起，sysconfig.expand_makefile_vars() 函式已被棄用。請改用 sysconfig.get_paths() 的 vars 引數。

tarfile：

自 Python 3.13 起，未以文件記錄和未被使用的 TarFile.tarfile 屬性已被棄用。

Python 3.17 中待移除的項目

collections.abc：

collections.abc.ByteString 預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

typing：

在 Python 3.14 之前，舊式聯集是使用私有類別 typing._UnionGenericAlias 實作的。這個類別不再被需要，但為了向後相容性而保留，並計劃將在 Python 3.17 中移除。使用者應該改用文件中記錄的內省輔助函式，例如 typing.get_origin() 和 typing.get_args()，或者依賴私有實作細節。

typing.ByteString 自 Python 3.9 起已被棄用，預計在 Python 3.17 中移除。

使用 isinstance(obj, collections.abc.Buffer) 來測試 obj 是否在 runtime 實作了緩衝區協定。在型別註解的使用中，請用 Buffer 或明確指定你的程式碼所支援型別的聯集（例如 bytes | bytearray | memoryview）。

ByteString 最初被設計為一個抽象類別，以作為 bytes 和 bytearray 的超型別 (supertype)。然而由於 ABC 從未擁有任何方法，知道一個物件是 ByteString 的實例從未真正告訴你任何關於該物件的有用資訊。其他常見的緩衝區型別如 memoryview 也從未被理解為 ByteString 的子型別（無論是在 runtime 還是由靜態型別檢查器）。

更多細節請見 PEP 688 [https://peps.python.org/pep-0688/#current-options]。（由 Shantanu Jain 於 gh-91896 [https://github.com/python/cpython/issues/91896] 貢獻。）

Python 3.18 中待移除的項目

decimal：

非標準且無文件記載的 Decimal 格式說明符號 'N'，僅在 decimal 模組的 C 實作中被支援，自 Python 3.13 起已被棄用。（由 Serhiy Storchaka 於 gh-89902 [https://github.com/python/cpython/issues/89902] 中貢獻。）

Python 3.19 中待移除的項目

ctypes：

在非 Windows 平台上，透過設定 _pack_ 而沒有設定 _layout_ 來隱式地切換到與 MSVC 相容的結構佈局。

未來版本中的待移除項目

以下 API 將在未來被移除，雖然目前尚未安排移除日期。

argparse：

巢狀引數群組和巢狀互斥群組已被棄用。

將未以文件記錄的關鍵字引數 prefix_chars 傳遞給 add_argument_group() 的做法現在已被棄用。

argparse.FileType 型別轉換器已被棄用。

builtins：

產生器：throw(type, exc, tb) 和 athrow(type, exc, tb) 簽名已被棄用：請改用 throw(exc) 和 athrow(exc)，為單引數簽名。

目前 Python 接受數值字面值後面立即接關鍵字，例如 0in x、1or x、0if 1else 2。它讓運算式模糊且容易混淆，如 [0x1for x in y]（可以解釋為 [0x1 for x in y] 或 [0x1f or x in y]）。如果數值字面值後立即接 and、else、for、if、in、is 和 or 之一的關鍵字，則會引發語法警告。在未來版本中，它將被更改為語法錯誤。(gh-87999 [https://github.com/python/cpython/issues/87999])

__index__() 和 __int__() 方法回傳非 int 型別的支援：這些方法將需要回傳 int 的嚴格子類別實例。

回傳 float 嚴格子類別 __float__() 方法的支援：這些方法將需要回傳 float 的實例。

回傳 complex 嚴格子類別 __complex__() 方法的支援：這些方法將需要回傳 complex 的實例。

將 int() 委派給 __trunc__() 方法。

在 complex() 建構子中將複數作為 real 或 imag 引數傳遞現在已被棄用；它應該只作為單個位置引數傳遞。 (由 Serhiy Storchaka 於 gh-109218 [https://github.com/python/cpython/issues/109218] 貢獻。)

calendar：calendar.January 和 calendar.February 常數已被棄用並被 calendar.JANUARY 和 calendar.FEBRUARY 取代。 (由 Prince Roshan 於 gh-103636 [https://github.com/python/cpython/issues/103636] 貢獻。)

codecs：請改用 open() 而非 codecs.open()。(gh-133038 [https://github.com/python/cpython/issues/133038])

codeobject.co_lnotab：請改用 codeobject.co_lines() 方法。

datetime：

utcnow()：請改用 datetime.datetime.now(tz=datetime.UTC)。

utcfromtimestamp()：請改用 datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)。

gettext：複數值必須是整數。

importlib：

cache_from_source() debug_override 參數已被棄用：請改用 optimization 參數。

importlib.metadata：

EntryPoints 元組介面。

回傳值上的隱式 None。

logging：自 Python 3.3 起，warn() 方法已被棄用，請改用 warning()。

mailbox：已棄用 StringIO 輸入和文本模式，請改用 BytesIO 和二進位模式。

os：在多執行緒行程中呼叫 os.register_at_fork()。

pydoc.ErrorDuringImport：exc_info 參數的元組值已被棄用，請用例外實例。

re：現在對正規表示式中的數值群組參照和群組名稱用了更嚴格的規則。現在只有 ASCII 數碼序列被接受作為數值參照。位元組模式和替換字串中的群組名稱現在只能包含 ASCII 字母、數碼和底線。（由 Serhiy Storchaka 於 gh-91760 [https://github.com/python/cpython/issues/91760] 貢獻。）

sre_compile、sre_constants 和 sre_parse 模組。

shutil：rmtree() 的 onerror 參數在 Python 3.12 中已被棄用；請改用 onexc 參數。

ssl 選項和協定：

不帶協定引數的 ssl.SSLContext 已被棄用。

ssl.SSLContext：set_npn_protocols() 和 selected_npn_protocol() 已被棄用：請改用 ALPN。

ssl.OP_NO_SSL* 選項

ssl.OP_NO_TLS* 選項

ssl.PROTOCOL_SSLv3

ssl.PROTOCOL_TLS

ssl.PROTOCOL_TLSv1

ssl.PROTOCOL_TLSv1_1

ssl.PROTOCOL_TLSv1_2

ssl.TLSVersion.SSLv3

ssl.TLSVersion.TLSv1

ssl.TLSVersion.TLSv1_1

threading 方法：

threading.Condition.notifyAll()：請用 notify_all()。

threading.Event.isSet()：請用 is_set()。

threading.Thread.isDaemon()、threading.Thread.setDaemon()：請用 threading.Thread.daemon 屬性。

threading.Thread.getName()、threading.Thread.setName()：請用 threading.Thread.name 屬性。

threading.currentThread()：請用 threading.current_thread()。

threading.activeCount()：請用 threading.active_count()。

typing.Text (gh-92332 [https://github.com/python/cpython/issues/92332])。

內部類別 typing._UnionGenericAlias 不再用於實作 typing.Union。為了保持與此私有類別使用者的相容性，直到至少 Python 3.17 都將提供一個相容性 shim。（由 Jelle Zijlstra 於 gh-105499 [https://github.com/python/cpython/issues/105499] 貢獻。）

unittest.IsolatedAsyncioTestCase：從測試案例中回傳非 None 的值已被棄用。

urllib.parse 已棄用函式：請改用 urlparse()。

splitattr()

splithost()

splitnport()

splitpasswd()

splitport()

splitquery()

splittag()

splittype()

splituser()

splitvalue()

to_bytes()

wsgiref：SimpleHandler.stdout.write() 不應該進行部分寫入。

xml.etree.ElementTree：已棄用對 Element 的真值測試。在未來版本中，它將始終回傳 True。請改用明確的 len(elem) 或 elem is not None 測試。

sys._clear_type_cache() 已被棄用：請改用 sys._clear_internal_caches()。

發布 Python 模組

備註

有關發布 Python 模組和套件的資訊和指南已移至 Python Packaging User Guide [https://packaging.python.org/]，而相關教學已經移至 packaging Python projects [https://packaging.python.org/en/latest/tutorials/packaging-projects/]。

Argument Clinic 指南

備註

Argument Clinic 操作方法已移至「Python 開發人員指南 [https://devguide.python.org/development-tools/clinic/]」。

如何將 Python 2 的程式碼移植到 Python 3

作者:

Brett Cannon

Python 2 reached its official end-of-life at the start of 2020. This means that no new bug reports, fixes, or changes will be made to Python 2 - it's no longer supported: see PEP 373 [https://peps.python.org/pep-0373/] and status of Python versions [https://devguide.python.org/versions].

If you are looking to port an extension module instead of pure Python code, please see 遷移延伸模組到 Python 3.

The archived python-porting [https://mail.python.org/pipermail/python-porting/] mailing list may contain some useful guidance.

Since Python 3.11 the original porting guide was discontinued. You can find the old guide in the archive [https://docs.python.org/3.10/howto/pyporting.html].

Third-party guides

There are also multiple third-party guides that might be useful:

Guide by Fedora [https://portingguide.readthedocs.io]

PyCon 2020 tutorial [https://www.youtube.com/watch?v=JgIgEjASOlk]

Guide by DigitalOcean [https://www.digitalocean.com/community/tutorials/how-to-port-python-2-code-to-python-3]

Guide by ActiveState [https://www.activestate.com/blog/how-to-migrate-python-2-applications-to-python-3]

aifc --- 讀寫 AIFF 與 AIFC 檔案

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 aifc 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/aifc.html]。

asynchat --- 非同步 socket 指令/回應處理函式

自從版本 3.6 後不推薦使用，已從版本 3.12 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.6 中被棄用，並已在 Python 3.12 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

應用程式應改用 asyncio 模組。

最後提供 asynchat 模組的 Python 版本是 Python 3.11 [https://docs.python.org/3.11/library/asynchat.html]。

asyncore --- 非同步 socket 處理函式

自從版本 3.6 後不推薦使用，已從版本 3.12 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.6 中被棄用，並已在 Python 3.12 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

應用程式應改用 asyncio 模組。

最後提供 asyncore 模組的 Python 版本是 Python 3.11 [https://docs.python.org/3.11/library/asyncore.html]。

audioop --- 操作原始聲音檔案

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 audioop 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/audioop.html]。

cgi --- 通用閘道器介面支援

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

可以改用 PyPI 上的模組 fork：legacy-cgi [https://pypi.org/project/legacy-cgi/]。這是 cgi 模組的一個副本，不再由 Python 核心團隊維護或支援。

最後提供 cgi 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/aifc.html]。

cgitb --- CGI 腳本的回溯管理器 (traceback manager)

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

可以改用 PyPI 上的模組 fork：legacy-cgi [https://pypi.org/project/legacy-cgi/]。這是 cgi 模組的一個複本，不再由 Python 核心團隊維護或支援。

最後提供 cgitb 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/cgitb.html]。

chunk --- 讀取 IFF 分塊資料

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 chunk 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/chunk.html]。

crypt --- 用於檢查 Unix 密碼的函式

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

應用程式可以改用標準函式庫中的 hashlib 模組。其他可能的替代方案是 PyPI 上的第三方庫：legacycrypt [https://pypi.org/project/legacycrypt/]、bcrypt [https://pypi.org/project/bcrypt/] 或 argon2-cffi [https://pypi.org/project/argon2-cffi/]。這些函式庫並不受 Python 核心團隊支援或維護。

最後提供 crypt 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/crypt.html]。

distutils --- 建置與安裝 Python 模組

自從版本 3.10 後不推薦使用，已從版本 3.12 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.10 中被棄用，並已在 Python 3.12 中被移除。它的移除是在 PEP 632 [https://peps.python.org/pep-0632/] 中決定的，該 PEP 附有遷移建議 [https://peps.python.org/pep-0632/#migration-advice]。

最後提供 distutils 模組的 Python 版本是 Python 3.11 [https://docs.python.org/3.11/library/distutils.html]。

程式框架

此章節不再維護，所包含的模組已移至各自的主題文件中。

cmd — 命令列介面函式庫

shlex — Unix 特定服務

turtle — 使用 Tk 的圖形化使用者介面

imghdr --- 判定圖片種類

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

可能的替代方案是 PyPI 上的第三方函式庫：filetype [https://pypi.org/project/filetype/]、puremagic [https://pypi.org/project/puremagic/] 或 python-magic [https://pypi.org/project/python-magic/]。它們並不受 Python 核心團隊支援或維護。

最後提供 imghdr 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/imghdr.html]。

imp --- 存取引入系統內層

自從版本 3.4 後不推薦使用，已從版本 3.12 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.4 中被棄用，並已在 Python 3.12 中被移除。

其移除通知包含了從 imp 遷移至 importlib 的指引。

最後提供 imp 模組的 Python 版本是 Python 3.11 [https://docs.python.org/3.11/library/imp.html]。

mailcap --- Mailcap 檔案處理

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 mailcap 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/mailcap.html]。

msilib --- 讀寫 Microsoft Installer 檔案

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 msilib 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/msilib.html]。

nis --- Sun NIS (Yellow Pages) 介面

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 nis 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/nis.html]。

nntplib --- NNTP 協定用戶端

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 nntplib 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/nntplib.html]。

ossaudiodev --- 對 OSS 相容聲音裝置的存取

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 ossaudiodev 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/ossaudiodev.html]。

pipes --- shell pipelines 介面

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

應用程式應改用 subprocess 模組。

最後提供 pipes 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/pipes.html]。

smtpd --- SMTP 伺服器

自從版本 3.6 後不推薦使用，已從版本 3.12 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.6 中被棄用，並已在 Python 3.12 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

一個可能的替代方案是第三方 aiosmtpd [https://pypi.org/project/aiosmtpd/] 函式庫。這個函式庫並不是由 Python 核心團隊維護或支援。

最後提供 smtpd 模組的 Python 版本是 Python 3.11 [https://docs.python.org/3.11/library/smtpd.html]。

sndhdr --- 判定聲音檔案的種類

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

可能的替代方案是 PyPI 上的第三方模組：filetype [https://pypi.org/project/filetype/]、puremagic [https://pypi.org/project/puremagic/] 或 python-magic [https://pypi.org/project/python-magic/]。它們並不受 Python 核心團隊支援或維護。

最後提供 sndhdr 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/sndhdr.html]。

spwd --- shadow 密碼資料庫

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

可能的替代方案是 PyPI 上的第三方函式庫：python-pam [https://pypi.org/project/python-pam/]。這並不受 Python 核心團隊支援或維護。

最後提供 spwd 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/spwd.html]。

sunau --- 讀寫 Sun AU 檔案

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 sunau 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/sunau.html]。

telnetlib --- Telnet 用戶端

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

可能的替代方案是 PyPI 上的第三方函式庫：telnetlib3 [https://pypi.org/project/telnetlib3/] 或 Exscript [https://pypi.org/project/Exscript/]。它們並不受 Python 核心團隊支援或維護。

最後提供 telnetlib 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/telnetlib.html]。

uu --- uuencode 檔案的編碼與解碼

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 uu 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/uu.html]。

xdrlib --- XDR 資料的編碼與解碼

自從版本 3.11 後不推薦使用，已從版本 3.13 中移除。.

這個模組已不再是 Python 標準函式庫的一部分。它在 Python 3.11 中被棄用，並已在 Python 3.13 中被移除。它的移除是在 PEP 594 [https://peps.python.org/pep-0594/] 中決定的。

最後提供 xdrlib 模組的 Python 版本是 Python 3.12 [https://docs.python.org/3.12/library/xdrlib.html]。